Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries

Bibliographic Details
Title: Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries
Authors: Zixin Fan, Xiaoyu Chen, Jingjing Shi, Hui Nie, Xiaoming Zhang, Xingping Zhou, Xiaolin Xie, Zhigang Xue
Source: Nano-Micro Letters, Vol 17, Iss 1, Pp 1-38 (2025)
Publisher Information: SpringerOpen, 2025.
Publication Year: 2025
Collection: LCC:Technology
Subject Terms: Separators, Polymer electrolytes, Lithium batteries, Electrochemical performances, Functionalization, Technology
More Details: Highlights The commonly used modification methods for separator of lithium batteries are summarized, which include surface coating, in situ modification and grafting modification. The adhesion of coating materials with the separators and wettability of the modified separators prepared from the three methods are compared. The challenges and future directions of separator modification are provided.
Document Type: article
File Description: electronic resource
Language: English
ISSN: 2311-6706
2150-5551
Relation: https://doaj.org/toc/2311-6706; https://doaj.org/toc/2150-5551
DOI: 10.1007/s40820-024-01596-x
Access URL: https://doaj.org/article/ee4fa3e847054ca9bab7c0da04938147
Accession Number: edsdoj.4fa3e847054ca9bab7c0da04938147
Database: Directory of Open Access Journals
Full text is not displayed to guests.
FullText Links:
  – Type: pdflink
    Url: https://content.ebscohost.com/cds/retrieve?content=AQICAHjPtM4BHU3ZchRwgzYmadcigk49r9CVlbU7V5F6lgH7WwGaBh-bxatxOFb2zJzSvon6AAAA4jCB3wYJKoZIhvcNAQcGoIHRMIHOAgEAMIHIBgkqhkiG9w0BBwEwHgYJYIZIAWUDBAEuMBEEDFzZmR3Gd63pwOmi2QIBEICBmlDUzreqrw34h05ZR8Fyw-tn9mlGJGBLlkGi3_f11yhVHTttYeHvIhc8vR9QcsW98-_11_JW39iTj2DCf6S8AaDrAzRBSN2miRF8LOsoBKTMDQCSHieNem3gQNqyTlXD7OwZgsmpq99A2VuUh1TK7LFRuQraz4Q2GaMLyGdqTIPtnD3SeQ2-uhbDtwfppnbWgz0XO9edSJ1vKpM=
Text:
  Availability: 1
  Value: <anid>AN0182798912;[b2o9]05feb.25;2025Feb07.04:55;v2.2.500</anid> <title id="AN0182798912-1">Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries </title> <p>Highlights: The commonly used modification methods for separator of lithium batteries are summarized, which include surface coating, in situ modification and grafting modification. The adhesion of coating materials with the separators and wettability of the modified separators prepared from the three methods are compared. The challenges and future directions of separator modification are provided.</p> <p>The growing demands for energy storage systems, electric vehicles, and portable electronics have significantly pushed forward the need for safe and reliable lithium batteries. It is essential to design functional separators with improved mechanical and electrochemical characteristics. This review covers the improved mechanical and electrochemical performances as well as the advancements made in the design of separators utilizing a variety of techniques. In terms of electrolyte wettability and adhesion of the coating materials, we provide an overview of the current status of research on coated separators, in situ modified separators, and grafting modified separators, and elaborate additional performance parameters of interest. The characteristics of inorganics coated separators, organic framework coated separators and inorganic–organic coated separators from different fabrication methods are compared. Future directions regarding new modified materials, manufacturing process, quantitative analysis of adhesion and so on are proposed toward next-generation advanced lithium batteries.</p> <p>Keywords: Separators; Polymer electrolytes; Lithium batteries; Electrochemical performances; Functionalization; Chemical Sciences Physical Chemistry (incl. Structural) Engineering Materials Engineering</p> <p>Graph</p> <hd id="AN0182798912-2">Introduction</hd> <p>For a more sustainable society, it is now critical to develop renewable, clean energy as well as effective energy conversion and storage systems. Because of their high energy density and low redox potential, lithium batteries as one type of Secondary batteries are widely utilized in energy storage systems [[<reflink idref="bib1" id="ref1">1</reflink>]]. Lithium-ion batteries were first developed and commercialized by Sony in 1991 [[<reflink idref="bib2" id="ref2">2</reflink>]]. However, the energy density of the state-of-the-art lithium-ion batteries, which use graphite anodes and insertion compound cathodes, has achieved its maximum (~ 150 Wh kg<sups>−1</sups>) [[<reflink idref="bib3" id="ref3">3</reflink>]]. Theoretically, lithium metal batteries offer a more appealing and higher energy density. The unstable solid electrolyte interphase (SEI) of the lithium anodes and severe lithium dendrite growth readily lead to short circuits and rapid, uncontrolled discharge of the battery, causing a series of safety issues [[<reflink idref="bib4" id="ref4">4</reflink>]]. Lithium-sulfide batteries and lithium-oxygen batteries also form multiple lithium sulfides and lithium oxide intermediate products during the cycling process, which seriously passivates the lithium anodes, resulting in a decline in cycle efficiency and battery performance [[<reflink idref="bib5" id="ref5">5</reflink>]]. In addition, the overheating of lithium batteries causes fire and explosion accidents. For instance, fast charging and rapid heating might cause the liquid electrolyte to burn, which is extremely dangerous for human life and health. Although extending the energy density and cycle life of lithium batteries is a popular objective, cost and safety are also receiving a lot of attention. Improving the physical and chemical characteristics of battery components proves to be a successful and efficient route.</p> <p>Until now, tremendous advances have been made in optimization of electrodes for improved performance of lithium metal batteries, including the creation of artificial SEI, modulation of the anode's three-dimensional structure, and control of the cathode's surface structure. Recently, there has been a greater focus on the role separators play in regulating ion transport and, consequently, the behavior of lithium deposition. Uniform and fast transport of Li<sups>+</sups> through separators is essential to reduce the risk of local overcharge and growth of lithium dendrite [[<reflink idref="bib6" id="ref6">6</reflink>]]. Ion flux distribution is greatly influenced by the chemical composition and pore structure of the separators [[<reflink idref="bib7" id="ref7">7</reflink>]], and micro-channels within the separators facilitate the migration of Li<sups>+</sups>. It has been demonstrated that separators can significantly increase the cycle life of lithium batteries. Lithium battery separators have advanced quickly since the turn of the twenty-first century due to the widespread use of lithium batteries. Figure 1 illustrates the increase in pertinent research publications as well as papers on different separators used in battery systems.</p> <p>Graph: Fig. 1 a Research papers from September 1995 to September 2024 with the keywords of "lithium battery separator" "functionalized" or "lithium battery separator" "modified" searching on Clarivate. b Papers on various separators in battery systems. Figures were prepared in September 2024</p> <p>At present, there are reviews on different types of separators [[<reflink idref="bib1" id="ref8">1</reflink>], [<reflink idref="bib8" id="ref9">8</reflink>]], their fabrication technologies [[<reflink idref="bib1" id="ref10">1</reflink>], [<reflink idref="bib9" id="ref11">9</reflink>]], safety issues [[<reflink idref="bib9" id="ref12">9</reflink>]] and functional design [[<reflink idref="bib1" id="ref13">1</reflink>]], but the impact of various modification techniques on the performance of functional separators has not been particularly investigated. Thus, this paper aims to present a comprehensive and concise review of the latest development of functional separators based on different modification methods. We will explore the influence of different modified separators on the battery performance from the perspective of coating, in-situ, and grafting functionalization methods. Emphasis is generally placed on electrolyte wettability and adhesion of the coating materials of the functional separators, and additional performance parameters of interest will be elaborated. We hope to provide guidance for the future design of new functional separators.</p> <hd id="AN0182798912-3">Basic of Separators</hd> <p>The separator, one of the most critical components of lithium battery, is placed between the positive and negative electrodes. It plays the following important roles: (<reflink idref="bib1" id="ref14">1</reflink>) prevent contact between the positive electrode and negative electrode and thus avoid short circuits of the battery; (<reflink idref="bib2" id="ref15">2</reflink>) provide channels for rapid Li<sups>+</sups> transport [[<reflink idref="bib1" id="ref16">1</reflink>], [<reflink idref="bib8" id="ref17">8</reflink>], [<reflink idref="bib10" id="ref18">10</reflink>], [<reflink idref="bib11" id="ref19">11</reflink>]–[<reflink idref="bib12" id="ref20">12</reflink>]]. The currently used separators are usually classified into three types, microporous polyolefin separators, non-woven separators, and inorganic composite separators [[<reflink idref="bib13" id="ref21">13</reflink>]]. Microporous polyolefin separators, such as polyethylene (PE), polypropylene (PP) separators, and three-layer composite separators composed of PE and PP, are the mostly used commercialized separators due to their high mechanical properties and excellent dimensional stability. The non-woven separator is composed of randomly arranged fibers [[<reflink idref="bib14" id="ref22">14</reflink>]]. Cellulose [[<reflink idref="bib15" id="ref23">15</reflink>]], polyvinylidene fluoride (PVDF) [[<reflink idref="bib17" id="ref24">17</reflink>]], aramid nanofiber (ANF) [[<reflink idref="bib18" id="ref25">18</reflink>]], poly(acrylonitrile) (PAN) [[<reflink idref="bib19" id="ref26">19</reflink>]], polyimide (PI) [[<reflink idref="bib21" id="ref27">21</reflink>]], polyetherimide (PEI) [[<reflink idref="bib23" id="ref28">23</reflink>]], poly(ether ether ketone) (PEEK) [[<reflink idref="bib24" id="ref29">24</reflink>]], polybenzimidazole (PBI) [[<reflink idref="bib25" id="ref30">25</reflink>]] and other materials [[<reflink idref="bib26" id="ref31">26</reflink>]] have been exploited to form fibrous membranes through electrospinning and melt-blowing. By integrating inorganic particles into a polymer matrix, the formed inorganic composite separator combines the characteristics of both materials. The relevant data of the commonly used separators that have been industrialized is shown in Table 1.</p> <p>Table 1 Summary of characteristics of some representative commonly used separators that have been industrialized</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Brand</p></th><th align="left"><p>Thickness (μm)</p></th><th align="left"><p>Porosity (%)</p></th><th align="left"><p>Pore size (μm)</p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th></tr></thead><tbody><tr><td align="left"><p>PP</p></td><td align="left"><p>Celgard 2400</p></td><td align="left"><p>25</p></td><td align="left"><p>41</p></td><td char="." align="char"><p>0.043</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td></tr><tr><td align="left"><p>PP</p></td><td align="left"><p>Celgard 2500</p></td><td align="left"><p>25</p></td><td align="left"><p>55</p></td><td char="." align="char"><p>0.091</p></td><td align="left"><p> > 90°</p></td><td char="." align="char"><p>–</p></td></tr><tr><td align="left"><p>PE</p></td><td align="left"><p>Hipore</p></td><td align="left"><p>16</p></td><td align="left"><p>41</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.61</p></td></tr><tr><td align="left"><p>PE</p></td><td align="left"><p>Senior</p></td><td align="left"><p>9</p></td><td align="left"><p>43</p></td><td char="." align="char"><p>0.045</p></td><td align="left"><p> > 50°</p></td><td char="." align="char"><p>1.04</p></td></tr><tr><td align="left"><p>Cellulose</p></td><td align="left"><p>Cellulion</p></td><td align="left"><p>20</p></td><td align="left"><p>63</p></td><td char="." align="char"><p>2.44</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.90</p></td></tr><tr><td align="left"><p>PI</p></td><td align="left" /><td align="left"><p>20</p></td><td align="left"><p>91</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>10°</p></td><td char="." align="char"><p>1.71</p></td></tr></tbody></table> </ephtml> </p> <p>One aspect that affects the uniformity of ions transport through the separator is wetting ability [[<reflink idref="bib6" id="ref32">6</reflink>]]. Separators must possess high porosity and good wettability toward liquid electrolytes (LEs) to increase their uptake and retention rate [[<reflink idref="bib27" id="ref33">27</reflink>]]. The separator with good wettability is conducive to rapid electrolyte permeation, to fill the pores of the separator and establish an efficient and fast lithium-ion transport channel [[<reflink idref="bib14" id="ref34">14</reflink>], [<reflink idref="bib28" id="ref35">28</reflink>], [<reflink idref="bib30" id="ref36">30</reflink>], [<reflink idref="bib31" id="ref37">31</reflink>]–[<reflink idref="bib32" id="ref38">32</reflink>]], as shown in Fig. 2a, which minimizes the ion transfer resistance, enhances the ionic conductivity and suppresses the lithium dendrites growth [[<reflink idref="bib33" id="ref39">33</reflink>]]. Incomplete filling of the pore space blocks the transport path of the pore network and decreases the lithium-ion transport capacity of the separator, as shown in Fig. 2b [[<reflink idref="bib6" id="ref40">6</reflink>]]. The interlayer or functional separator with high porosity and excellent wettability toward LEs regulates the transport behavior of Li<sups>+</sups> to the greatest extent so that lithium-ion is uniformly deposited on the surface of the lithium metal anode, thus inhibiting the lithium dendrites growth and realizing homogeneous ionic transport for long-cycling lithium batteries [[<reflink idref="bib7" id="ref41">7</reflink>], [<reflink idref="bib35" id="ref42">35</reflink>]].</p> <p>Graph: Fig. 2 a, b Schematic illustration of the influence of separator wettability toward electrolyte on Li+ transportation. c, d Schematic illustration of the adhesion between the matrix film and the modified layer</p> <p>However, the commercial polyolefin separators contain abundant nonpolar –CH<subs>2</subs> and –CH<subs>3</subs> groups, resulting in poor affinity for electrolytes [[<reflink idref="bib13" id="ref43">13</reflink>], [<reflink idref="bib36" id="ref44">36</reflink>]]. Inorganic composite separators have the problem of uneven mixing of inorganic particles with matrix, which leads to low structural integrity, reduced porosity and ionic conductivity [[<reflink idref="bib37" id="ref45">37</reflink>], [<reflink idref="bib38" id="ref46">38</reflink>]–[<reflink idref="bib39" id="ref47">39</reflink>]]. Numerous nonwoven-based separators have excellent wettability and have been used in lithium batteries due to their high porosity and specific surface area, but their other properties such as mechanical strength still need to be optimized [[<reflink idref="bib11" id="ref48">11</reflink>], [<reflink idref="bib14" id="ref49">14</reflink>]]. Based on this, the researchers modify the separator using a variety of materials, such as inorganic nanoparticles and polymers with abundant polar groups [[<reflink idref="bib13" id="ref50">13</reflink>], [<reflink idref="bib40" id="ref51">40</reflink>]]. The modified separator exhibits good wettability with LEs due to its polar structures and porous structures. For surface-modified separators, the adhesion between the matrix film and the modified layer is particularly important (Fig. 2c, d), which refers to the dimension stability of the separators. The separators modified by coating, in situ and grafting functionalization methods can not only improve the wettability but also improve the adhesion step by step. The differences between the three functionalization methods are also compared, as shown in Fig. 3. Except for electrolyte wetting ability and adhesive properties of coating materials, chemical stability, thickness, porosity, pore size, mechanical strength, thermal stability and electrochemical stability of the separators are also important parameters affecting the performance of batteries [[<reflink idref="bib41" id="ref52">41</reflink>], [<reflink idref="bib43" id="ref53">43</reflink>], [<reflink idref="bib44" id="ref54">44</reflink>]–[<reflink idref="bib45" id="ref55">45</reflink>]].</p> <p>Graph: Fig. 3 Schematic showing three commonly used modification methods for separators of lithium batteries and their advantages and disadvantages</p> <hd id="AN0182798912-4">Coated Separators</hd> <p>The coating can facilely introduce functional layers, which have high polarity and good compatibility with LEs on the surface of separators. The commonly used methods include blast-coating, vacuum filtration and dip-coating. These methods enable large-scale and low-cost production of surface functionalized membranes.</p> <hd id="AN0182798912-5">Inorganics–Coated Separators</hd> <p>Inorganic ceramics, carbon-based nanomaterials, metal nitrides and metal sulfides are largely exploited for surface coating of separators. These inorganic modification layers always feature excellent wettability for LEs due to (a) increased surface roughness and/or surface energy and (b) uniform size at the nanoscale [[<reflink idref="bib46" id="ref56">46</reflink>]]. Meanwhile, the inorganic coated layers also improve the thermal stability of the separators to a certain extent. The characteristics and electrochemical performance of inorganic-coated separators and their assembled lithium batteries are summarized in Table 2.</p> <p>Table 2 Summary of characteristics and electrochemical performance of the inorganic-coated separators</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness (μm)</p></th><th align="left"><p>Porosity<sup>a</sup></p></th><th align="left"><p>Coating mass fraction</p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left" colspan="9"><p><italic>Inorganic ceramics</italic></p></td></tr><tr><td align="left"><p>PE/WCDA-SiO<sub>2</sub></p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>310%</p></td><td char="." align="char"><p>0.32</p></td><td align="left"><p>73.3% after 100 cycles at 0.5C (original) 81.6% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr47">47</xref>]</p></td></tr><tr><td align="left"><p>PP/SiO<sub>2</sub></p></td><td align="left"><p>6</p></td><td align="left"><p>–</p></td><td align="left"><p>20%</p></td><td align="left"><p> < 10°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr48">48</xref>]</p></td></tr><tr><td align="left"><p>PE/SiO<sub>2</sub></p></td><td align="left"><p>10</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.61</p></td><td align="left"><p>73% after 200 cycles at 0.5C (original) 77% after 200 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr49">49</xref>]</p></td></tr><tr><td align="left"><p>PP/SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>120%</p></td><td char="." align="char"><p>0.78</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr50">50</xref>]</p></td></tr><tr><td align="left"><p>PP/SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>21.7° (H<sub>2</sub>O)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>64.7% after 400 cycles at 1C (original) 90.9% after 400 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr51">51</xref>]</p></td></tr><tr><td align="left"><p>PIC/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>1.64</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr52">52</xref>]</p></td></tr><tr><td align="left"><p>PP/SiO<sub>2</sub></p></td><td align="left"><p>6</p></td><td align="left" /><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>346%</p></td><td char="." align="char"><p>0.63</p></td><td align="left"><p>80.6% after 100 cycles at 1C (original) 87.4% after 100 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr53">53</xref>]</p></td></tr><tr><td align="left"><p>PP/Al(OH)<sub>3</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>84%</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>127%</p></td><td char="." align="char"><p>1.00</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr54">54</xref>]</p></td></tr><tr><td align="left"><p>PE/AlOOH</p></td><td align="left"><p>1.15</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>6.56</p></td><td align="left"><p>94.6% after 100 cycles at 1C (original) 96.3% after 100 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr55">55</xref>]</p></td></tr><tr><td align="left"><p>PE/N-SiO<sub>2</sub></p></td><td align="left"><p>2.5</p></td><td align="left" /><td align="left"><p>–</p></td><td align="left"><p>51.3° (H<sub>2</sub>O)</p></td><td align="left"><p>195%</p></td><td char="." align="char"><p>0.81</p></td><td align="left"><p>88.5% after 200 cycles at 0.1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr56">56</xref>]</p></td></tr><tr><td align="left"><p>PVDF/SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>0.2</p></td><td align="left"><p>68.1%</p></td><td align="left"><p>–</p></td><td align="left"><p>18.9°</p></td><td align="left"><p>468%</p></td><td char="." align="char"><p>2.24</p></td><td align="left"><p>71.6% after 100 cycles at 0.2C (PP) 86.4% after 100 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr57">57</xref>]</p></td></tr><tr><td align="left"><p>PVDF/Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>61.8%</p></td><td align="left"><p>–</p></td><td align="left"><p>18.3°</p></td><td align="left"><p>366%</p></td><td char="." align="char"><p>2.06</p></td><td align="left"><p>78.4% after 100 cycles at 0.5C (PE) 81.3% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr58">58</xref>]</p></td></tr><tr><td align="left"><p>PI/SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>5</p></td><td align="left"><p>89.8%</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>519%</p></td><td char="." align="char"><p>2.92</p></td><td align="left"><p>95.58% after 250 cycles at 5C (PP) 98.76% after 250 cycles at 5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr59">59</xref>]</p></td></tr><tr><td align="left"><p>PE/Al<sub>2</sub>O<sub>3</sub>/HNTs</p></td><td align="left"><p>3</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>9°</p></td><td align="left"><p>281%</p></td><td char="." align="char"><p>0.67</p></td><td align="left"><p>84.4% after 200 cycles at 0.2C (original) 83.4% after 200 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr60">60</xref>]</p></td></tr><tr><td align="left"><p>PE/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>3</p></td><td align="left"><p>31.7%</p></td><td align="left"><p>–</p></td><td align="left"><p>4.21°</p></td><td align="left"><p>170%</p></td><td char="." align="char"><p>1.16</p></td><td align="left"><p>82.2% after 100 cycles at 0.5C (original) 91.5% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr61">61</xref>]</p></td></tr><tr><td align="left"><p>PP/Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub></p></td><td align="left"><p>10</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>15°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr62">62</xref>]</p></td></tr><tr><td align="left"><p>PET/LLZO</p></td><td align="left"><p>–</p></td><td align="left"><p>50%</p></td><td align="left"><p>87%</p></td><td align="left"><p>19.6°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>2.80</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr63">63</xref>]</p></td></tr><tr><td align="left"><p>PVA/ZrO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>73%</p></td><td align="left"><p>–</p></td><td align="left"><p>21.6°</p></td><td align="left"><p>420%</p></td><td char="." align="char"><p>2.19</p></td><td align="left"><p>90% after 200 cycles at 0.2C (PE) 97% after 200 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr64">64</xref>]</p></td></tr><tr><td align="left"><p>PE/SnO<sub>2</sub></p></td><td align="left"><p>2.7</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>46.5° (H<sub>2</sub>O)</p></td><td align="left"><p>119%</p></td><td char="." align="char"><p>0.72</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr65">65</xref>]</p></td></tr><tr><td align="left"><p>PP/Zeolite 4A</p></td><td align="left"><p>10</p></td><td align="left"><p>58%</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>270%</p></td><td char="." align="char"><p>2.25</p></td><td align="left"><p>83.4% after 100 cycles at 0.5C (original) 96.2% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr66">66</xref>]</p></td></tr><tr><td align="left"><p>PE/Si–O-Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>269%</p></td><td char="." align="char"><p>0.68</p></td><td align="left"><p>16.0% after 400 cycles at 0.5C (original) 54.1% after 1000 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr67">67</xref>]</p></td></tr><tr><td align="left" colspan="9"><p><italic>Carbon-based nanomaterials</italic></p></td></tr><tr><td align="left"><p>PP/DLC</p></td><td align="left"><p>2.9</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>29°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.69</p></td><td align="left"><p>71% after 1000 cycles at 5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr68">68</xref>]</p></td></tr><tr><td align="left"><p>PP/LNS/CB</p></td><td align="left"><p>3.5</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.59</p></td><td align="left"><p>86% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr69">69</xref>]</p></td></tr><tr><td align="left"><p>PP/GO</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>15° (H<sub>2</sub>O)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.60</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr70">70</xref>]</p></td></tr><tr><td align="left"><p>PP/SFGS</p></td><td align="left"><p>20</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>54.4° (H<sub>2</sub>O)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr71">71</xref>]</p></td></tr><tr><td align="left"><p>ANF/rGOF</p></td><td align="left"><p>15 ~ 20</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>89.07% after 2000 cycles at 50 C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr72">72</xref>]</p></td></tr><tr><td align="left"><p>PP/rGO/BNNSs</p></td><td align="left"><p>9.5</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>10.97°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>92.3% after 500 cycles at 4 C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr73">73</xref>]</p></td></tr><tr><td align="left"><p>PP/rGO/Li-Al-LDH</p></td><td align="left"><p>12</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>233%</p></td><td char="." align="char"><p>0.74</p></td><td align="left"><p>95.76% after 250 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr74">74</xref>]</p></td></tr><tr><td align="left"><p>PP/Fe<sub>3</sub>N@NG</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>5.23°</p></td><td align="left"><p>116%</p></td><td char="." align="char"><p>0.70</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr75">75</xref>]</p></td></tr><tr><td align="left"><p>PP/CFs</p></td><td align="left"><p>15</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>48.7% after 500 cycles at 0.5C (original) 64.5% after 500 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr76">76</xref>]</p></td></tr><tr><td align="left"><p>ANF/ NiFe<sub>2</sub>O<sub>4</sub>-OCNT</p></td><td align="left"><p>1.6</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>17.6°</p></td><td align="left"><p>253%</p></td><td char="." align="char"><p>2.21</p></td><td align="left"><p>72% after 1000 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr77">77</xref>]</p></td></tr><tr><td align="left" colspan="9"><p><italic>Others</italic></p></td></tr><tr><td align="left"><p>PP/CuS/graphene</p></td><td align="left"><p>20</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>62.1% after 200 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr78">78</xref>]</p></td></tr><tr><td align="left"><p>PP/h-BN</p></td><td align="left"><p>2</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>15.7°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr79">79</xref>]</p></td></tr><tr><td align="left"><p>PI/hBN</p></td><td align="left"><p>3</p></td><td align="left"><p>44.5%</p></td><td align="left"><p>–</p></td><td align="left"><p>7.2°</p></td><td align="left"><p>63%</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>73% after 300 cycles at 1C (PP) 79% after 300 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr80">80</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–" means not mentioned</p> <hd id="AN0182798912-6">Inorganic Ceramics</hd> <p>Inorganic ceramic materials generally refer to a class of inorganic non-metallic materials made of natural or synthetic compounds by forming and sintering at high temperature. With the help of binder, SiO<subs>2</subs> [[<reflink idref="bib48" id="ref57">48</reflink>], [<reflink idref="bib50" id="ref58">50</reflink>]–[<reflink idref="bib51" id="ref59">51</reflink>]], Al<subs>2</subs>O<subs>3</subs> [[<reflink idref="bib52" id="ref60">52</reflink>], [<reflink idref="bib61" id="ref61">61</reflink>], [<reflink idref="bib81" id="ref62">81</reflink>]] and other derivatives [[<reflink idref="bib54" id="ref63">54</reflink>], [<reflink idref="bib63" id="ref64">63</reflink>]] are commonly used inorganic ceramics for surface coated separators with improved electrolyte uptake and ionic conductivity [[<reflink idref="bib82" id="ref65">82</reflink>]].</p> <p>For example, the surface coating of SiO<subs>2</subs> can be achieved either by uniformly coating slurry containing the commercially available SiO<subs>2</subs> on the separator surface [[<reflink idref="bib49" id="ref66">49</reflink>]], or directly hydrolyzing tetraethyl orthosilicate to deposit SiO<subs>2</subs> on the separator [[<reflink idref="bib48" id="ref67">48</reflink>]] (Fig. 4a). Through the latter method, the coating thickness (lower than the directly coated SiO<subs>2</subs> [[<reflink idref="bib49" id="ref68">49</reflink>]]) and specific surface area of the ceramic coating layer could be easily controlled by adjusting the solution concentration and deposition time, and a contact angle of less than 10° was achieved. The coated separators showed significant electrolyte uptake and improved battery performance. The amino-functionalized SiO<subs>2</subs> (N-SiO<subs>2</subs>) coating layer with a thin coating thickness of 2.5 μm (compared to 6 μm in [[<reflink idref="bib48" id="ref69">48</reflink>]]) was fabricated on PE separator, which exhibited higher ionic conductivity of 0.81 mS cm<sups>–1</sups> (compared to 0.61 mS cm<sups>–1</sups> in [[<reflink idref="bib49" id="ref70">49</reflink>]]), and excellent electrolyte wettability. The contact angle decreased from 96.3° to 51.3° (Fig. 4b). Interestingly, N-SiO<subs>2</subs> particles also played a role as a HF scavenger, which effectively inhibited electrolyte decomposition at high temperatures and realized stable cycling of battery (88.5% capacity retention after 200 cycles at 0.1C) [[<reflink idref="bib56" id="ref71">56</reflink>]]. Mixed coating of two different ceramic materials on the polyolefin separator can further improve the electrolyte wettability [[<reflink idref="bib51" id="ref72">51</reflink>], [<reflink idref="bib60" id="ref73">60</reflink>]]. Coating slurry with mixture of SiO<subs>2</subs> and Al<subs>2</subs>O<subs>3</subs> on the PVDF fibrous membrane led to separators with excellent electrolyte uptake (more than 350%) and remarkable ionic conductivity (more than 2 mS cm<sups>–1</sups>), as shown in Fig. 4c. Impressively, capacity retention of more than 80% after 100 cycles could be achieved for the assembled cells [[<reflink idref="bib57" id="ref74">57</reflink>]]. Figure 4d showed separators coated with both Al<subs>2</subs>O<subs>3</subs> and halloysite nanotubes (HNTs) had better wettability than those coated with Al<subs>2</subs>O<subs>3</subs> alone. The HNTs with hollow structure not only reduced the weight increase, but also provided fast ion transport channels for the modified separators. Meanwhile, the positive charge on the surface of HNT could adsorb anions and promote the Li<sups>+</sups> movement. The assembled cells achieved capacity retention rate of 83.4% after 200 cycles at 0.2C. This demonstrated the more abundant polar functional groups in the coating layer, the better affinity with polar electrolytes. Fortunately, the multi-material coating didn't significantly increase the separator thickness and presented a loosely stacked porous structure [[<reflink idref="bib60" id="ref75">60</reflink>]]. Currently, ceramic-coated separators based on SiO<subs>2</subs> and Al<subs>2</subs>O<subs>3</subs> are widely used in commercial lithium batteries.</p> <p>Graph: Fig. 4 a Schematic illustration of the SiO2 coated PE separator and their contact angles [[<reflink idref="bib56" id="ref76">56</reflink>]].</p> <p>Generally, inorganic ceramics-coated separators suffer from some shortcomings such as uneven separator thickness, blockage of separator pores, interface incompatibility, and brittleness. In addition, the binders melt or decompose with the rising of temperatures, leading to the detachment of the coating materials. Zhang et al. [[<reflink idref="bib61" id="ref77">61</reflink>]] fabricated Al<subs>2</subs>O<subs>3</subs> ceramic-coated separators using an organic–inorganic composite binder composed of polyvinyl alcohol-phosphate inorganic (PVA-PIB). The organic binder has poor thermal resistance and easily melts at high temperatures, leading to the shrinkage of the separator. The inorganic binder has poor compatibility with the polyolefin matrix, resulting in poor adhesion. Thus, the PVA-PIB organic–inorganic composite binder overcame the above shortcomings simultaneously, and the assembled cells had improved electrochemical performance. Luo et al. [[<reflink idref="bib83" id="ref78">83</reflink>]] prepared a raspberry microparticle polymer (RMP) binder with a soft inner core and hard outer sphere. With this binder, the Al<subs>2</subs>O<subs>3</subs> could be firmly attached to the PE separator. Meanwhile, the pore blockage was avoided. Na et al. [[<reflink idref="bib84" id="ref79">84</reflink>]] activated the surface of polyolefin separator by ultraviolet ozone (UVO) plasma treatment. Then through silane hybridization, SiO<subs>2</subs> nanoparticles were coated on the separator surface. This work demonstrated the fabrication of SiO<subs>2</subs>-modified separator without polymer binder for the first time. In general, the ceramic and the binder content of slurry for coating needs to be optimized to prevent the plugging of separator pores. Also, molecular and morphological designs of inorganic coatings have impact on the separator's wettability and thus battery performance. Firmly attachment of ceramic coatings on the surface of separator with enhanced wettability is a huge challenge.</p> <hd id="AN0182798912-7">Inorganic Carbon-Based Nanomaterials</hd> <p>Inorganic carbon-based nanomaterials are widely used in the field of clean energy storage and conversion because of their unique crystal structure, rich chemical bond types and good environmental adaptability, including graphene [[<reflink idref="bib70" id="ref80">70</reflink>], [<reflink idref="bib73" id="ref81">73</reflink>]], carbon fiber (CFs) [[<reflink idref="bib76" id="ref82">76</reflink>]], carbon nanotubes (CNTs) [[<reflink idref="bib77" id="ref83">77</reflink>], [<reflink idref="bib85" id="ref84">85</reflink>]] and other graphitic carbons. On the one hand, carbon-based coatings can greatly enhance surface-wetting properties by changing the separator morphology and surface polarity without reducing the lithium-ion transport flux. On the other hand, their small pore sizes can decrease the local current density and lithium surface reaction to inhibit lithium dendrite formation. Meanwhile, carbon-based nanomaterials can synergistically improve the performance of other additives [[<reflink idref="bib70" id="ref85">70</reflink>]].</p> <p>When the two-dimensional graphene oxide (GO) nanomaterial was exploited as a coating material, good electrolyte wettability (contact angle 15°) could be achieved for the coated separator [[<reflink idref="bib70" id="ref86">70</reflink>]]. The coated separator could be further functionalized for improved performance. Kown et al. [[<reflink idref="bib71" id="ref87">71</reflink>]] designed a GO-coated separator functionalized with polyacrylic acid (PAA), which showed better electrolyte wettability (the contact angle decreasing from 68° to 54.4°), improved ionic conductivity, and more homogeneous Li<sups>+</sups> flux than the only GO-coated separator. When GO was doped with other inorganic materials and applied as coating materials, the obtained composite separator exhibited excellent wettability (contact angle no exceeding 10°) [[<reflink idref="bib73" id="ref88">73</reflink>], [<reflink idref="bib74" id="ref89">74</reflink>]–[<reflink idref="bib75" id="ref90">75</reflink>]], high ionic conductivity (no less than 0.7 mS cm<sups>–1</sups>) [[<reflink idref="bib74" id="ref91">74</reflink>]] and remarkable battery cycling performance. Yang et al. [[<reflink idref="bib73" id="ref92">73</reflink>]] creatively designed B/N co-doping reduced graphene oxide/boron nitride nanosheet, and exploited it for separator coating. This coated separator assembled lithium-sulfur batteries showed capacity retention of 92.3% after 500 cycles at a current density of 4C. The Laponite nanosheets and carbon black coated Celgard separator had good thermal stability at 160 °C, amazing electrolyte wettability (contact angle of nearly 0°), high ion conductivity (0.59 mS cm<sups>–1</sups>) and good flexibility [[<reflink idref="bib69" id="ref93">69</reflink>]]. In addition, the carbon material-modified separator showed promise in inhibition of lithium dendrite growth. The fabricated GO fibers were filtered on aramid paper, which were bonded together by hydrogen bonding. The rGO-coated aramid nanofiber (ANF) separator induced the formation of LiF, thus stabilizing the SEI layer, as shown in Fig. 5a [[<reflink idref="bib72" id="ref94">72</reflink>]]. The rGOF was able to capture of F<sups>−</sups> produced by the decomposition of LiPF<subs>6</subs> electrolyte, and promoted the formation of LiF rich SEI. The rGO/Li-Al-LDH composite nanosheets coating could not only improve the wettability of the LEs of the separator (contact angle of nearly 0°), but also provided additional ion channels, thus endowing more efficient lithium-ion transport characteristics for the separator [[<reflink idref="bib74" id="ref95">74</reflink>]]. The Fe<subs>3</subs>N-doped GO-coated separator inhibited the growth of lithium dendrites by accelerating Li<sups>+</sups> transport and adjusting Li<sups>+</sups> flux, as shown in Fig. 5b [[<reflink idref="bib75" id="ref96">75</reflink>]]. The CNT-modified ANF separator also has excellent wettability [[<reflink idref="bib77" id="ref97">77</reflink>]]. Meanwhile, its conductive and catalytic characteristics with NiFe<subs>2</subs>O<subs>4</subs> modification can efficiently enhance the conversion of lithium polysulfides, as shown in Fig. 5c.</p> <p>Graph: Fig. 5 a Schematic illustration of ANF/rGOF separator [[<reflink idref="bib72" id="ref98">72</reflink>]].</p> <hd id="AN0182798912-8">Other Inorganic Materials</hd> <p>Except for ceramic nanoparticles and inorganic carbon materials, some nitrides and sulfides are also exploited for separator modification due to their unique characteristics, such as high thermal stability and thermal conductivity. Thermal conductive separators can be fabricated by surface coating of hexagonal boron nitride (h-BN). In addition, the h-BN coated polypropylene (PP) separator induced the formation of SEI with more inorganic species and improved the cycling performance of battery [[<reflink idref="bib79" id="ref99">79</reflink>]].</p> <hd id="AN0182798912-9">Summary</hd> <p>Introducing inorganic materials on the surface of separators effectively improves the electrolyte wettability and ionic conductivity. However, inorganic materials still show some shortcomings. Firstly, the coating thickness of separator can hardly be tuned and can easily reach several micrometers, which greatly increases the weight of separators and decreases the specific energy density of batteries. Secondly, the polymer binders tend to block the pores of separators, which sacrifice the ionic conductivity and power capability of batteries. Lastly, the polarity difference and the weak adhesion between the matrix separator and the coating layers make the shedding problem difficult to ignore, which affects the battery cycling life.</p> <hd id="AN0182798912-10">Organic Framework Coated Separator</hd> <p>Metal–organic frameworks (MOFs) and covalent-organic frameworks (COFs) have attracted tremendous attention in various areas due to their structural adjustability, extensive specific surface area, and well-organized pores [[<reflink idref="bib86" id="ref100">86</reflink>]]. Compared with the above inorganic nanomaterials, the porous structures of organic frameworks are more regular and uniform, and their pore size is more controllable [[<reflink idref="bib87" id="ref101">87</reflink>]]. When MOFs and COFs are coated on separators, their abundant and ordered nanopores and relatively large specific surface areas increases the contact area with electrolyte. Meanwhile, the nanopores can retain the electrolyte for a longer time, resulting in good electrolyte wettability and retention capability. In addition, this structural characteristic enables selective transport and uniform deposition of Li<sups>+</sups> while improves the wettability and ionic conductivity of the separators [[<reflink idref="bib87" id="ref102">87</reflink>], [<reflink idref="bib89" id="ref103">89</reflink>], [<reflink idref="bib90" id="ref104">90</reflink>]–[<reflink idref="bib91" id="ref105">91</reflink>]]. The characteristics and electrochemical performances of some representative organic framework-coated separators developed in recent years are summarized in Table 3.</p> <p>Table 3 Partial summary of characteristics and electrochemical performance of organic framework coated separators</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness (μm)</p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Li<sup>+</sup> transference number</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PP/MOFs</p></td><td align="left"><p>–<sup>a</sup></p></td><td align="left"><p>15.88°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.26</p></td><td char="." align="char"><p>0.68</p></td><td align="left"><p>98.1% after 50 cycles at 2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr92">92</xref>]</p></td></tr><tr><td align="left"><p>PP/UIO-SOLi</p></td><td align="left"><p>4</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.11</p></td><td char="." align="char"><p>0.82</p></td><td align="left"><p>66.7% after 170 cycles at 0.1C (original) 97.0% after 640 cycles at 0.1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr93">93</xref>]</p></td></tr><tr><td align="left"><p>PP/Cr-MOFs</p></td><td align="left"><p>22</p></td><td align="left"><p>9.52°</p></td><td align="left"><p>250%</p></td><td char="." align="char"><p>3.50</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr94">94</xref>]</p></td></tr><tr><td align="left"><p>PE/COF-C16</p></td><td align="left"><p>1.4</p></td><td align="left"><p>16.02°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>90.0% after 800 cycles at 1C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr95">95</xref>]</p></td></tr><tr><td align="left"><p>PP/COF-COOH</p></td><td align="left"><p>10</p></td><td align="left"><p>13.98°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.64</p></td><td char="." align="char"><p>0.70</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr96">96</xref>]</p></td></tr><tr><td align="left"><p>PP/COF-F</p></td><td align="left"><p> < 10</p></td><td align="left"><p>12°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.76</p></td><td char="." align="char"><p>0.87</p></td><td align="left"><p>80.1% after 2000 cycles at 5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr97">97</xref>]</p></td></tr><tr><td align="left"><p>PP/COF</p></td><td align="left"><p>5</p></td><td align="left"><p>26.9°</p></td><td align="left"><p>224%</p></td><td char="." align="char"><p>0.24</p></td><td char="." align="char"><p>0.65</p></td><td align="left"><p>88.5% after 200 cycles at 1C (original) 97.8% after 200 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr98">98</xref>]</p></td></tr><tr><td align="left"><p>PP/PA-COF</p></td><td align="left"><p>8.2</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td char="." align="char"><p>0.87</p></td><td align="left"><p>93.6% after 200 cycles at 0.5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr99">99</xref>]</p></td></tr><tr><td align="left"><p>PE/HC-CTF</p></td><td align="left"><p>1.5</p></td><td align="left"><p>41.2°</p></td><td align="left"><p>124%</p></td><td char="." align="char"><p>0.67</p></td><td char="." align="char"><p>0.60</p></td><td align="left"><p>16.8% after 300 cycles at 1C (original) 45.4% after 1000 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr100">100</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "–"means not mentioned</p> <p>A large number of C, O, and N atoms in the framework structure provides active sites for further modification [[<reflink idref="bib89" id="ref106">89</reflink>]], and some polar negatively charged groups such as − SO<subs>3</subs>H, − COOH, and − F ions have been successfully attached to the framework structure. Commonly, these frameworks have been used for surface coating of the commercial polyolefin separator. Hao et al. [[<reflink idref="bib92" id="ref107">92</reflink>]] carefully designed MOFs containing both − NH<subs>2</subs> and − SO<subs>3</subs><sups>−</sups> groups. It showed good cation-selectivity and excellent electrolyte wettability with contact angle of 15.88°, as shown in Fig. 6a. The intrinsic nanochannels and negatively charged intergranular channels in the MOF structure limited the free migration of anions, and the rapid and uniform deposition of Li<sups>+</sups> inhibited the lithium dendrites growth. The capacity retention ratio reached 98.08% after 50 cycles at 2C. The composite separator coated with TpPa-2SO<subs>3</subs>H COFs had both neatly arranged nanochannels and rich functional groups. It possessed a suitable porous structure, high electrolyte absorption and improved electrolyte wettability, providing rich pathways for rapid Li<sups>+</sups> transport, as shown in Fig. 6b, c [[<reflink idref="bib93" id="ref108">93</reflink>], [<reflink idref="bib98" id="ref109">98</reflink>]]. An et al. [[<reflink idref="bib94" id="ref110">94</reflink>]] designed a covalent organic framework modified with lithium-philic carbonyl and carboxy groups (COF-COOH) and coated it on PP (Fig. 6d). The COF-COOH presented a crystalline two-dimensional structure with abundant pores and a large number of lipophilic groups, which was conducive to improving the electrolyte wettability (contact angle 13.98°) and endowing high ionic conductivity (0.64 mS cm<sups>–1</sups>) of the separator. At the same time, the presence of negative charge sites in COF-COOH inhibited the diffusion of anions in lithium salts through electrostatic interaction, and Li<sups>+</sups> transference number increased to 0.70. Yao et al. [[<reflink idref="bib98" id="ref111">98</reflink>]] used a cationic COF and weakly bonded fluoride ion (F<sups>−</sups>) for separator modification, which not only improved the electrolyte's wettability but also constructed a robust LiF-rich SEI, as shown in Fig. 6e. Interestingly, the highly ordered crystalline covalent triazine frameworks (CTF) also contributed to selective and fast transport of Li<sups>+</sups>, as shown in Fig. 6f [[<reflink idref="bib100" id="ref112">100</reflink>]].</p> <p>Graph: Fig. 6 a, b Schematic illustration of PP/MOF separators mechanism and static electrolyte contact angle [[<reflink idref="bib92" id="ref113">92</reflink>]].</p> <hd id="AN0182798912-11">Inorganic–Organic Coated Separators</hd> <p>Introducing hydrophilic polymers on the surface of separators can enhance their surface energy. Hydrophilic functional groups in polymers improve electrolyte wettability to accelerate Li-ion conduction. Moreover, polymer coatings can introduce highly electronegative functional groups, such as carboxyl and sulfonates, and endue a net negative surface charge on the surface of separators. It can not only retard the migration of anions by electrostatic repulsive but also enable the rapid transport of Li<sups>+</sups>, thus efficiently suppressing the growth of lithium dendrites [[<reflink idref="bib101" id="ref114">101</reflink>]]. Poly-<emph>p</emph>-phenylene terephthamide (PPTA) could be coated on the commercial PP separator without binders. The electrolyte wettability was greatly improved and the electrolyte contact angle was reduced from 50° to 15° after coating [[<reflink idref="bib102" id="ref115">102</reflink>]]. Polymers such as polytetrafluoroethylene (PVDF) [[<reflink idref="bib103" id="ref116">103</reflink>]] and poly(ethylene oxide) (PEO) [[<reflink idref="bib105" id="ref117">105</reflink>]] have also been used to modify separators for improved wettability. However, the thickness of the polymer coating is difficult to control, and thick coating easily causes blockage of the separator pores and reduction of ionic conductivity. The ionic conductivity of polymers such as polydopamine [[<reflink idref="bib106" id="ref118">106</reflink>]] is also low, and the mechanical properties are poor, which affects the battery cycle performance. The characteristics and electrochemical performance of some representative polymer-coated separators are summarized in Table 4.</p> <p>Table 4 Summary of characteristics and electrochemical performance of polymer-coated separators</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness (μm)</p></th><th align="left"><p>Porosity<sup>a</sup></p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PE/PVDF-HFP</p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>140%</p></td><td char="." align="char"><p>0.44</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr103">103</xref>]</p></td></tr><tr><td align="left"><p>PE/PMMA</p></td><td align="left"><p>2 ~ 3</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>200%</p></td><td char="." align="char"><p>0.52</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr107">107</xref>]</p></td></tr><tr><td align="left"><p>PE/PDA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>39°</p></td><td align="left"><p>126%</p></td><td char="." align="char"><p>0.41</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr27">27</xref>]</p></td></tr><tr><td align="left"><p>PE/EC</p></td><td align="left"><p>2 ~ 3</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.68</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr108">108</xref>]</p></td></tr><tr><td align="left"><p>PE/AN-<italic>co</italic>-MMA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>150%</p></td><td char="." align="char"><p>2.06</p></td><td align="left"><p>83.0% after 50 cycles at 0.2C (original) 86.3% after 50 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr109">109</xref>]</p></td></tr><tr><td align="left"><p>PP/PDA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p> < 20° (water)</p></td><td align="left"><p>290%</p></td><td char="." align="char"><p>1.30</p></td><td align="left"><p>94.2% after 100 cycles at 0.2C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr110">110</xref>]</p></td></tr><tr><td align="left"><p>Cellulose/PVDF-HFP</p></td><td align="left"><p>–</p></td><td align="left"><p>65%</p></td><td align="left"><p>55°</p></td><td align="left"><p>280%</p></td><td char="." align="char"><p>1.04</p></td><td align="left"><p>71.0% after 100 cycles at 0.5C (PP) 83.0% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr111">111</xref>]</p></td></tr><tr><td align="left"><p>PE/PDA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>39°</p></td><td align="left"><p>112%</p></td><td char="." align="char"><p>0.30</p></td><td align="left"><p>94.9% after 100 cycles at 0.5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr40">40</xref>]</p></td></tr><tr><td align="left"><p>PE/PEO</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>76%</p></td><td char="." align="char"><p>1.00</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr105">105</xref>]</p></td></tr><tr><td align="left"><p>PP/PI</p></td><td align="left"><p>8.16</p></td><td align="left"><p>53.05%</p></td><td align="left"><p>5°</p></td><td align="left"><p>208%</p></td><td char="." align="char"><p>0.34</p></td><td align="left"><p>75.4% after 200 cycles at 1C (original) 80.1% after 200 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr112">112</xref>]</p></td></tr><tr><td align="left"><p>PE/PBI</p></td><td align="left"><p>4</p></td><td align="left"><p>54%</p></td><td align="left"><p>10°</p></td><td align="left"><p>225%</p></td><td char="." align="char"><p>0.60</p></td><td align="left"><p>93.9% after 100 cycles at 0.5C (original) 97.7% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr113">113</xref>]</p></td></tr><tr><td align="left"><p>PE/PI</p></td><td align="left"><p>–</p></td><td align="left"><p>60%</p></td><td align="left"><p>0°</p></td><td align="left"><p>400%</p></td><td char="." align="char"><p>1.34</p></td><td align="left"><p>96.4% after 100 cycles at 1C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr114">114</xref>]</p></td></tr><tr><td align="left"><p>PVDF/PMIA</p></td><td align="left"><p>–</p></td><td align="left"><p>83.97%</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.81</p></td><td align="left"><p>84.3% after 100 cycles at 0.2C 93.1% after 100 cycles at 0.2C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr115">115</xref>]</p></td></tr><tr><td align="left"><p>PEEK/PMMA</p></td><td align="left"><p>–</p></td><td align="left"><p>64.1%</p></td><td align="left"><p>0°</p></td><td align="left"><p>173%</p></td><td char="." align="char"><p>1.03</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr116">116</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–" means not mentioned</p> <p>To solve the shortcomings of inorganic material-coated and polymer-coated separators, researchers devoted much efforts to developing inorganic–organic composite-coated separators. The composite coatings can effectively improve the overall performance of the separators in high-energy storage batteries. The characteristics and electrochemical performance of inorganic–organic composite coated separators are summarized in Table 5.</p> <p>Table 5 Summary of characteristics and electrochemical performance of inorganic–organic coated separators</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness (μm)</p></th><th align="left"><p>Porosity<sup>a</sup></p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PE/Al<sub>2</sub>O<sub>3</sub>/DLSS</p></td><td align="left"><p>6</p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>63.11°</p></td><td align="left"><p>100%</p></td><td char="." align="char"><p>0.85</p></td><td align="left"><p>89.2% after 400 cycles at 0.5C 93.6% after 400 cycles at 0.5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr117">117</xref>]</p></td></tr><tr><td align="left"><p>PP/GO-<italic>g</italic>-PAM</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>430%</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr118">118</xref>]</p></td></tr><tr><td align="left"><p>PE/Al<sub>2</sub>O<sub>3</sub>/PHC</p></td><td align="left"><p>1.5</p></td><td align="left"><p>42.7%</p></td><td align="left"><p>–</p></td><td align="left"><p>92%</p></td><td char="." align="char"><p>0.93</p></td><td align="left"><p>83.4% after 350 cycles at 1C (original) 87.6% after 350 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr119">119</xref>]</p></td></tr><tr><td align="left"><p>PP/SiO<sub>2</sub>-PVA</p></td><td align="left"><p>–</p></td><td align="left"><p>50.5%</p></td><td align="left"><p>12.7°</p></td><td align="left"><p>201%</p></td><td char="." align="char"><p>1.26</p></td><td align="left"><p>73.6% after 100 cycles at 0.5C (original) 91.0% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr120">120</xref>]</p></td></tr><tr><td align="left"><p>PE/Al<sub>2</sub>O<sub>3</sub>/PDA</p></td><td align="left"><p>4</p></td><td align="left"><p>35.3%</p></td><td align="left"><p>0°</p></td><td align="left"><p>70%</p></td><td char="." align="char"><p>0.71</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr121">121</xref>]</p></td></tr><tr><td align="left"><p>PE/PVDF-EC-A-SiO<sub>2</sub></p></td><td align="left"><p>2</p></td><td align="left"><p>–</p></td><td align="left"><p>23.2°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.79</p></td><td align="left"><p>91.7% after 200 cycles at 0.5C (original) 95.7% after 200 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr122">122</xref>]</p></td></tr><tr><td align="left"><p>PE/SiO<sub>2</sub>-PMMA</p></td><td align="left"><p>5</p></td><td align="left"><p>–</p></td><td align="left"><p>6.1°</p></td><td align="left"><p>90%</p></td><td char="." align="char"><p>1.08</p></td><td align="left"><p>94.6% after 100 cycles at 1C (original) 95.4% after 100 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr123">123</xref>]</p></td></tr><tr><td align="left"><p>PE/ZrO<sub>2</sub>@PI</p></td><td align="left"><p>4</p></td><td align="left"><p>54.28%</p></td><td align="left"><p>0°</p></td><td align="left"><p>164%</p></td><td char="." align="char"><p>0.68</p></td><td align="left"><p>75.1% after 200 cycles at 1C (original) 84.4% after 200 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr124">124</xref>]</p></td></tr><tr><td align="left"><p>PE/SiO<sub>2</sub>-PZS</p></td><td align="left"><p>1.5</p></td><td align="left"><p>–</p></td><td align="left"><p>13.4°</p></td><td align="left"><p>155%</p></td><td char="." align="char"><p>1.04</p></td><td align="left"><p>80.0% after 100 cycles at 2C (original) 81.7% after 100 cycles at 2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr125">125</xref>]</p></td></tr><tr><td align="left"><p>PP/PDA@AlN</p></td><td align="left"><p>18</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.75</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr106">106</xref>]</p></td></tr><tr><td align="left"><p>PP/PDA/Gr-CMC</p></td><td align="left"><p>21</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>58.0% after 1000 cycles at 1C (original) 93.3% after 1000 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr126">126</xref>]</p></td></tr><tr><td align="left"><p>PVDF/PAN/Al<sub>2</sub>O<sub>3</sub>/NC</p></td><td align="left"><p>5</p></td><td align="left"><p>–</p></td><td align="left"><p>0° (H<sub>2</sub>O)</p></td><td align="left"><p>395%</p></td><td char="." align="char"><p>1.49</p></td><td align="left"><p>57.1% after 120 cycles at 0.5C (original) 65.9% after 120 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr127">127</xref>]</p></td></tr><tr><td align="left"><p>PPS/SiO<sub>2</sub>/PVDF-HFP</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>230%</p></td><td char="." align="char"><p>1.02</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr128">128</xref>]</p></td></tr><tr><td align="left"><p>PP/PI/Al<sub>2</sub>O<sub>3</sub></p></td><td align="left"><p>2.5</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.95</p></td><td align="left"><p>100% after 350 cycles at 0.5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr129">129</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–" means not mentioned</p> <p>Coating slurries with both inorganic and organic materials on the surface of the separator is a commonly used method [[<reflink idref="bib127" id="ref119">127</reflink>]]. For example, when polymeric surfactant disodium laureth sulfosuccinate (DLSS) was introduced into the Al<subs>2</subs>O<subs>3</subs> slurry, the polymer with both hydrophilic and hydrophobic groups not only enabled the coating with water-based slurry, but also greatly improved the electrolyte wettability (contact angle decreasing from 199.27° to 63.11°) and electrolyte uptake (100%) [[<reflink idref="bib117" id="ref120">117</reflink>]]. Li et al. [[<reflink idref="bib118" id="ref121">118</reflink>]] grafted GO onto polyacrylamide (PAM), while Zhang et al. [[<reflink idref="bib120" id="ref122">120</reflink>]] fabricated covalently bonded ceramic nanoparticles-poly(vinyl alcohol) (PVA) composites, and then coated it on the separator. On the one hand, the polar groups on the surface of the separator were increased, on the other hand, the coating materials had tight adhesion and uniformity of the coating materials was achieved. Combined with high electrolyte wettability and ionic conductivity, the cycling performance of the battery was largely improved, as shown in Fig. 7a. Wang et al. [[<reflink idref="bib124" id="ref123">124</reflink>]] prepared ZrO<subs>2</subs>@PI hollow core–shell microspheres and coated it on the polyolefin separator, as shown in Fig. 7b. The separator has excellent wettability and ionic conductivity (0.68 mS cm<sups>–1</sups>), and the hollow microspheres reduced the surface weight density of the separator, resulting in a high overall energy density of the battery. Fu et al. [[<reflink idref="bib125" id="ref124">125</reflink>]] coated core–shell structured SiO<subs>2</subs>-PZS (silica-poly (cyclotriphosphazene-<emph>co</emph>-4,4′-sulfonyldiphenol)) nanoparticles on the separator, and the hydroxyl groups and N, O atoms on the surface could coordinate with Li<sups>+</sups> to enhance the dissociation of lithium salt (LiPF<subs>6</subs>), thus further enhancing the ionic conductivity (1.04 mS cm<sups>–1</sups>) and showing higher wettability. Different from firstly fabrication of inorganic and organic composites and then coating on matrix separator, Tang et al. [[<reflink idref="bib106" id="ref125">106</reflink>]] coated the inorganic material AlN on the separator at first, and then grew polydopamine (PDA) in situ on the coating, as shown in Fig. 7c. The combination of rigidity and flexibility of the separator was realized by optimization of the modification sequence. The integration of the two materials with different characteristics provided another strategy to enable fast ion transport and enhanced wettability, benefiting for uniform lithium deposition. Kim et al. [[<reflink idref="bib126" id="ref126">126</reflink>]] first deposited organic polydopamine (PDA) on the PP separator, and then modified the inorganic graphene (Gr) nanosheets. The prepared three-layer separator had excellent electrolyte wettability, enhanced coulombic efficiency and increased capacity of lithium storage with 93.3% capacity retention after 1000 cycles at 1C. With this separator, the interfacial impedance between the electrode and the separator was significantly reduced, as shown in Fig. 7d.</p> <p>Graph: Fig. 7 a Schematic illustration of the synthesis of GO-g-PAM molecular brushes and lithium deposition on anode using GO-g-PAM/PP separator [[<reflink idref="bib120" id="ref127">120</reflink>]].</p> <hd id="AN0182798912-12">Section Summary</hd> <p>A variety of inorganic and organic materials can be easily modified on the separator by surface coating. The adhesion of inorganic materials on the commonly used polyolefin is weak, and the binder tends to melt resulting in the blockage of the pores. In some cases, the inorganic materials can be coated without binder by preprocessing of the matrix separator, such as ultraviolet electron beam irradiation. The thickness of the polymer coating is not controllable, and the falling-off problem still exists. It is expected that in situ modification or grafting should be better strategies for polymer coating. The coating of inorganic–organic composite can combine the functions of both materials to a certain extent, and has obvious improvement in wettability and ion conductivity of the separators. In addition, the adhesion of coating layer with the matrix separator and the dimensional stability of the coated separator also increased, leading to highly improved cycling stability of the assembled batteries.</p> <hd id="AN0182798912-13">In Situ Modified Separator</hd> <p>While surface coating is indeed a straightforward approach that enhances wettability with electrolytes, thereby improving electrochemical performance, its effectiveness is constrained by the limited adhesion between the coating and the base separator, as noted in previous studies [[<reflink idref="bib130" id="ref128">130</reflink>], [<reflink idref="bib132" id="ref129">132</reflink>], [<reflink idref="bib133" id="ref130">133</reflink>]–[<reflink idref="bib134" id="ref131">134</reflink>]]. In contrast, in situ modification emerges as a superior alternative. This strategy not only achieves a comparable level of surface wettability akin to surface coating but also ensures a robust bond between the coating materials and the base separator. Furthermore, surface coating typically covers only the outer surface of the base separator. Conversely, coatings formed through in situ modification can permeate the entire surface, both external and internal, of the separator [[<reflink idref="bib135" id="ref132">135</reflink>]]. Crucially, the uniformity of the in situ-grown coating significantly minimizes interfacial resistance and facilitates the homogeneous distribution of Li<sups>+</sups>. Additionally, in situ modification has the advantage of producing thin coatings while preserving the pore structure of the base separator, as evidenced in various studies [[<reflink idref="bib137" id="ref133">137</reflink>], [<reflink idref="bib139" id="ref134">139</reflink>]–[<reflink idref="bib140" id="ref135">140</reflink>]].</p> <hd id="AN0182798912-14">In Situ Formed Inorganic Modification Materials</hd> <p>Inorganic materials such as SiO<subs>2</subs> [[<reflink idref="bib56" id="ref136">56</reflink>]], ZrO<subs>2</subs> [[<reflink idref="bib141" id="ref137">141</reflink>]] and Al<subs>2</subs>O<subs>3</subs> [[<reflink idref="bib142" id="ref138">142</reflink>]], among others, are widely favored as modification materials owing to their notable enhancements in wettability and thermal stability. Nevertheless, their weak interaction with the base separator necessitates the use of organic binders to bolster adhesion. Furthermore, the incorporation of ceramic particles can result in an unwanted increase in both the thickness and weight of the separator [[<reflink idref="bib112" id="ref139">112</reflink>], [<reflink idref="bib143" id="ref140">143</reflink>], [<reflink idref="bib144" id="ref141">144</reflink>]–[<reflink idref="bib145" id="ref142">145</reflink>]]. In situ modification can solve these problems because the inorganic coating via in situ growth distributes uniformly and adheres tightly to the base separator while not significantly affecting the pore structure and separator thickness [[<reflink idref="bib146" id="ref143">146</reflink>]]. The characteristics and electrochemical performance of in situ modified separators by inorganic materials are listed in Table 6.</p> <p>Table 6 The characteristics and electrochemical performance of in situ modified separators by inorganic materials</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness</p></th><th align="left"><p>Porosity<sup>a</sup> (%)</p></th><th align="left"><p>Coating mass fraction (%)</p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PP/Al<sub>2</sub>O<sub>3</sub> (ALD)</p></td><td align="left"><p>6 nm</p></td><td align="left"><p>44</p></td><td char="." align="char"><p>40.1</p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>80% after 1000 cycles at 4C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr148">148</xref>]</p></td></tr><tr><td align="left"><p>PVDF/Al<sub>2</sub>O<sub>3</sub> (ALD)</p></td><td align="left"><p>10 nm</p></td><td align="left"><p>87</p></td><td char="." align="char"><p>-</p></td><td align="left"><p>22°</p></td><td align="left"><p>350%</p></td><td char="." align="char"><p>3.1</p></td><td align="left"><p>91% after 100 cycles at 0.2C (original) 100% after 100 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr149">149</xref>]</p></td></tr><tr><td align="left"><p>PE/PP/PE/Al<sub>2</sub>O<sub>3</sub> (ALD)</p></td><td align="left"><p>5 nm</p></td><td align="left"><p>49</p></td><td char="." align="char"><p>8.5</p></td><td align="left"><p>34.5°</p></td><td align="left"><p>260%</p></td><td char="." align="char" /><td align="left"><p>75% after 100 cycles at 1C (original) 85% after 100 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr150">150</xref>]</p></td></tr><tr><td align="left"><p>PP/TiO<sub>2</sub> (ALD)</p></td><td align="left"><p>1 nm</p></td><td align="left"><p>41</p></td><td char="." align="char"><p>3.5</p></td><td align="left"><p>38.4°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>91% after 100 cycles at 5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr151">151</xref>]</p></td></tr><tr><td align="left"><p>PI/SiO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>61</p></td><td char="." align="char"><p>14.3</p></td><td align="left"><p>6.8°</p></td><td align="left"><p>264%</p></td><td char="." align="char" /><td align="left"><p>88% after 100 cycles at 1C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr152">152</xref>]</p></td></tr><tr><td align="left"><p>PI/ZrO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>83</p></td><td char="." align="char"><p>7.65</p></td><td align="left"><p>18°</p></td><td align="left"><p>345%</p></td><td char="." align="char"><p>3.73</p></td><td align="left"><p>100% after 100 cycles at 1C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr153">153</xref>]</p></td></tr><tr><td align="left"><p>CNFs/Sn-MoS<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>-</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>51% after 500 cycles at 2C (original) 73% after 500 cycles at 2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr154">154</xref>]</p></td></tr><tr><td align="left"><p>PP/CoSO<sub>2</sub></p></td><td align="left"><p>12.1 μm</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>-</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>46% after 500 cycles at 1C (original) 62% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr155">155</xref>]</p></td></tr><tr><td align="left"><p>PP/GDY</p></td><td align="left"><p> < 2 μm</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>-</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p> < 10% after 500 cycles at 1C (original) 53% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr156">156</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–" means not mentioned</p> <p>Atomic layer deposition (ALD) technology is a method for depositing layers on the substrate surface in the form of single atomic films. This method allows for the creation of ultra-thin and conformal coating layers, which exhibit precise thickness control and exceptional uniformity. By utilizing ALD, inorganic materials can grow conformally within the internal microstructure of the substrate. [[<reflink idref="bib157" id="ref144">157</reflink>], [<reflink idref="bib159" id="ref145">159</reflink>]–[<reflink idref="bib160" id="ref146">160</reflink>]]. For instance, Jung et al. [[<reflink idref="bib148" id="ref147">148</reflink>]] deposited the atomic layers of Al<subs>2</subs>O<subs>3</subs> on the surface of PP separator by utilizing trimethylaluminium (TMA) and H<subs>2</subs>O as precursors. As shown in Fig. 8a, the pore structure was almost unchanged because of the slow growth rate of Al<subs>2</subs>O<subs>3</subs> on PP (increasing 1.2 Å per cycle). The Al<subs>2</subs>O<subs>3</subs> ALD coating significantly enhanced the wettability and the LiPF<subs>6</subs> in pure propylene carbonate (PC) could completely infiltrate the modified separator (after 50 and 100 ALD cycles). Therefore, the nano-Li<subs>4</subs>Ti<subs>5</subs>O<subs>12</subs> (LTO, anode)/LiFePO<subs>4</subs> (LFP, cathode) half-cell with after 50 ALD cycles separator showed excellent cycling stability (a high-capacity retention of 80% at 4C after 1000 charge–discharge cycles). The ALD technology can precisely control the thickness and uniformity of coating layers at the angstrom level, but the required test device is expensive. Besides, a pristine PP separator surface usually requires large numbers of ALD cycles [[<reflink idref="bib161" id="ref148">161</reflink>]]. Therefore, its large-scale application is limited.</p> <p>Graph: Fig. 8 a Thin Al2O3 ALD coating (a few nm) on the PP separator [[<reflink idref="bib148" id="ref149">148</reflink>]].</p> <p>In situ hydrolysis of inorganic material precursor on the nonwoven separator is also commonly used, forming a unique core–shell structure to improve the wettability and mechanical properties of nanofibers. For instance, Wu et al. [[<reflink idref="bib152" id="ref150">152</reflink>]] proposed a novel idea of in situ nano-encapsulation hydrolysis method to prepare uniform silica nanolayers on polyimide (PI) nanofibers (Fig. 8b). First, they prepared PI nanofibers through electrospinning, and then immersed it in the silica precursor solution. After heating and hydrolysis, the silicon grew uniformly and densely in situ on the surface of the PI nanofiber and formed a core–shell structure. This method can effectively encapsulate inorganic materials on the inner and outer surfaces of the separator without a significant increase in thickness. Due to the coverage of hydrophilic silica on the surface, the wettability of the separator (contact angle of only 6.8°) and the rate of electrolyte absorption (absorbing liquid electrolyte completely in 5 s) are significantly improved. The in-situ generated silica effectively improves the wettability of the separator, which has a positive impact on improving the transmission capacity and efficiency of Li<sups>+</sups>. The NCM811/Li half-cell with modified separator showed a high capacity of 146 mAh g<sups>−1</sups> at 5C, and a 10% increase was achieved when compared with the PI separator. Furthermore, the battery with PI/SiO<subs>2</subs> nanofiber separator maintained a high-capacity retention rate of 88% after 100 cycles at 1C. Similarly, Dong et al. [[<reflink idref="bib153" id="ref151">153</reflink>]] reported a zirconium dioxide (ZrO<subs>2</subs>)-armored polymeric separator by in situ hydrolysis of ZrOCl<subs>2</subs> on PI nanofibers, forming a core–shell structure. The introduction of ZrO<subs>2</subs> shell layers promoted the wettability (contact angle of 18°) of the separator and rate capability (128.6 mAh g<sups>−1</sups> at 5C) of the assembled batteries.</p> <p>Some special inorganic materials can be grown in situ on separators through methods such as the hydrothermal reaction. For instance, Lu et al. [[<reflink idref="bib155" id="ref152">155</reflink>]] prepared CoSO<subs>4</subs> hydrate nano-architecture in situ on the surface of the PP separator through the hydrothermal reaction (Fig. 8c). The polar CoSO<subs>4</subs> can catalyze the conversion of polysulfide during charging and discharging, thus improving the utilization of sulfur. Besides, Rich adsorption sites ensure sufficient Li<sups>+</sups> transport while suppressing shuttle effects. Therefore, the cell with the modified separator showed a high initial specific capacity of 807.7 mAh g<sups>−1</sups> and maintained a capacity retention rate of 62.5% after 500 cycles at 1C.</p> <p>Generally speaking, inorganic materials can significantly enhance the wettability, thermal stability, and mechanical properties of separators. However, there is a scarcity of reports on the in situ modification of separators using inorganic materials, potentially due to the intricate nature of their in situ preparation process.</p> <hd id="AN0182798912-15">In Situ Formed Organic Framework Materials</hd> <p>When compared to other methods [[<reflink idref="bib163" id="ref153">163</reflink>], [<reflink idref="bib165" id="ref154">165</reflink>], [<reflink idref="bib166" id="ref155">166</reflink>]–[<reflink idref="bib167" id="ref156">167</reflink>]], the in situ formation of MOF and COF materials on the separator offers several advantages: it enhances adhesion to mitigate stripping defects, reduces interfacial resistance, and enables the attainment of thinner, more uniform coatings, thereby augmenting energy density. The characteristics and electrochemical performance of in situ modified separators by MOF as well as COF are listed in Table 7.</p> <p>Table 7 The characteristics and electrochemical performance of in situ modified separators by MOF as well as COF</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness</p></th><th align="left"><p>Porosity<sup>a</sup> (%)</p></th><th align="left"><p>Electrolyte contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PEN/PDA + ZIF-67</p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>450%</p></td><td char="." align="char"><p>1.57</p></td><td align="left"><p>83% after 240 cycles at 0.5C (original) 96% after 240 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr168">168</xref>]</p></td></tr><tr><td align="left"><p>GO-PAN/MOF</p></td><td align="left"><p> < 10 nm</p></td><td align="left"><p>–</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>63% after 100 cycles at 1C (original) 81% after 600 cycles at 5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr169">169</xref>]</p></td></tr><tr><td align="left"><p>PP/Ni<sub>3</sub>(HITP)<sub>2</sub></p></td><td align="left"><p>340 nm</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>-</p></td><td align="left"><p>38% after 100 cycles at 0.2C (original) 84.1% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr170">170</xref>]</p></td></tr><tr><td align="left"><p>PVDF-PMIA/ZIF-8</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>15.8°</p></td><td align="left"><p>1908%</p></td><td char="." align="char"><p>1.66</p></td><td align="left"><p>75% after 300 cycles at 0.2C (original) 73% after 300 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr171">171</xref>]</p></td></tr><tr><td align="left"><p>PP/COF-SO<sub>3</sub>H</p></td><td align="left"><p>127 nm</p></td><td align="left" /><td align="left"><p>16.4°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.18</p></td><td align="left"><p>67% after 500 cycles at 1C (original) 75% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr136">136</xref>]</p></td></tr><tr><td align="left"><p>CNT/COF-2S</p></td><td align="left"><p>–</p></td><td align="left"><p>49</p></td><td align="left"><p>0°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>53% after 500 cycles at 1C (original) 84% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr172">172</xref>]</p></td></tr><tr><td align="left"><p>PP/PDA + SWCNT + COF</p></td><td align="left"><p>669 nm</p></td><td align="left"><p>–</p></td><td align="left"><p>14.8°</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.53</p></td><td align="left"><p>43% after 500 cycles at 1C (original) 74% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr173">173</xref>]</p></td></tr><tr><td align="left"><p>PAN/CTP + LLZTO</p></td><td align="left"><p>100 nm</p></td><td align="left"><p>65.8</p></td><td align="left"><p>8.5°</p></td><td align="left"><p>385%</p></td><td char="." align="char"><p>0.64</p></td><td align="left"><p>33% after 500 cycles at 0.5C (original) 70.3% after 500 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr140">140</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–" means not mentioned</p> <p>MOF was considered to be more effective candidates for regulating Li<sups>+</sups> distribution and inhibiting lithium dendrites [[<reflink idref="bib174" id="ref157">174</reflink>], [<reflink idref="bib176" id="ref158">176</reflink>]–[<reflink idref="bib177" id="ref159">177</reflink>]]. For instance, the Zeolitic imidazolate framework (ZIF), as a MOF subclass, features zeolite topologies generated from metal ions and imidazolate ligands. Because of its high porosity, good thermal and chemical stabilities, the feasibility of in situ growth on polymer substrates as well as anion trapping capacity, ZIF had been selected as a representative MOF to modify the separator [[<reflink idref="bib178" id="ref160">178</reflink>], [<reflink idref="bib179" id="ref161">179</reflink>]–[<reflink idref="bib180" id="ref162">180</reflink>]]. Lin et al. [[<reflink idref="bib168" id="ref163">168</reflink>]] prepared a functional separator, which ZIF-67 grew in situ on both sides of the dopamine (DA) pretreated polyarylene ether nitrile (PEN) separator (PEN@PDA) shown in Fig. 9a. Specifically, based on the self-polymerization of DA and the π-π interaction between PDA and PEN, PDA tightly adhered to the surface of PEN while introducing abundant reactive groups to couple with Co<sups>2+</sups> and 2-methylimidazole ligands. As a result of the stronger negative charge of the PEN@PDA separator, it effectively adsorbed Co<sups>2+</sups> and formed active sites for ZIF-67 layer growth, which facilitated the stable fixation of a homogeneous and defect-free coating on the outer and inner surface of the separator. As a highly porous material, the in situ growth of ZIF-67 increased significantly the porosity and overall specific surface area of the separator. Therefore, the contact angle between the electrolyte and modified separator was almost 0°. The electrolyte absorption rate of the separator reached 450%. After being treated at 50 °C for 500 min, 70 wt% of the electrolyte within the separator can be maintained. The above abilities of separator enabled its greatly improved ionic conductivity compared with the base separator (from 0.86 to 1.57 mS cm<sups>−1</sups>). Besides, ZIF-67 endowed the separator with a uniform sub-nano/nanoporous structure and ability to adsorb anions, which homogenized the concentration of electrolyte at the electrode interface and guided uniform Li<sups>+</sups> diffusion. It ultimately resulted in a stable SEI with high ionic conductivity. Hence, the cell with the modified PEN separator showed a high <emph>t</emph><subs>Li</subs><sups>+</sups> of 0.81, superior rate capability, and cycle stability (specific capacity of 152 mAh g<sups>−1</sups> and capacity retention of 96.3% after 240 cycles at 0.5C).</p> <p>Graph: Fig. 9 a Schematic for construction of sandwich-structured MOF/PDA-PEN/MOF hybrid separators [[<reflink idref="bib168" id="ref164">168</reflink>]].</p> <p>COF is a framework material with regular pores or holes connected by organic units with covalent bonds [[<reflink idref="bib88" id="ref165">88</reflink>], [<reflink idref="bib181" id="ref166">181</reflink>]]. Zhao et al. [[<reflink idref="bib136" id="ref167">136</reflink>]] prepared a COF modified PP separator by in situ interfacial polymerization, which not only avoided significant increases in thickness and volume of the separator but also reduced the interfacial resistance (Fig. 9b). The PP separator was placed at the interface of the dichloromethane (DCM) phase and the water phase, then 1,3,5-triformylphloroglucinol (Tp) molecules in the DCM phase and 2,5-diaminobenzene sulfonic acid (Pa-SO<subs>3</subs>H) molecules in the water phase met at the PP separator with the diffusion of liquid flow. The COF consisted of Tp and Pa-SO<subs>3</subs>H units grew in situ on both the inner and outer surfaces of the separator. The introduction of lipophilic groups-sulfonic groups inhibits the shuttle of soluble polysulfides by Coulomb repulsion while promoting lithium-ion migration. Besides, sulfonic groups enhanced the wettability with electrolyte (contact angle decreasing from 42.7° to 16.4°), which resulted in a lower interfacial resistance and higher ionic conductivity. With sulfonic groups and regular channels of TpPa-SO<subs>3</subs>H COF, the modified separator showed better electrochemical performance and battery performance than that of PP separator. The initial specific capacity of the cell with modified separator was 863.97 mAh g<sups>−1</sups> at 1C, increasing by 56% compared with the PP separator (551.84 mAh g<sups>−1</sups>). Moreover, it was able to steadily work for 500 cycles with a high-capacity retention of 75%.</p> <p>In summary, MOF and COF are excellent modification materials. Their regular channels regulate Li<sups>+</sups> transport, and ultra-high specific surface areas improve wettability as well as electrolyte absorption rate. The flexible structural design expands the application range. Besides, in situ growth of MOFs and COFs overcomes the problem of poor adhesion.</p> <hd id="AN0182798912-16">In Situ Formed Organic Modification Materials</hd> <p>To address the issue of poor wettability in commercial polyolefin separators, numerous hydrophilic polymers, including PEO [[<reflink idref="bib183" id="ref168">183</reflink>]], polymethyl methacrylate (PMMA) [[<reflink idref="bib184" id="ref169">184</reflink>]], PVDF [[<reflink idref="bib185" id="ref170">185</reflink>]], and PI [[<reflink idref="bib186" id="ref171">186</reflink>]], have been investigated. Most of these polymers are applied to the separator surface through solution-based coating processes. However, these methods often result in a reduction in porosity due to pore blockage and limited control over coating thickness, ultimately leading to a decrease in energy density [[<reflink idref="bib45" id="ref172">45</reflink>], [<reflink idref="bib107" id="ref173">107</reflink>]]. In situ modification emerges as a promising alternative strategy, as it preserves the porous structure while enhancing the adhesion between the coating and the base separator. The characteristics and electrochemical performance of in situ modified separators by organic modification materials are in Table 8.</p> <p>Table 8 The characteristics and electrochemical performance of in situ modified separators by organic modification materials</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness</p></th><th align="left"><p>Porosity<sup>a</sup> (%)</p></th><th align="left"><p>Coating mass fraction (%)</p></th><th align="left"><p>Contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PE/PDA</p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>39° (H<sub>2</sub>O)</p></td><td align="left"><p>126%</p></td><td char="." align="char"><p>0.41</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr27">27</xref>]</p></td></tr><tr><td align="left"><p>PVDF/PDA</p></td><td align="left"><p> < 1 μm</p></td><td align="left"><p>72.8</p></td><td char="." align="char"><p>11.7</p></td><td align="left"><p>0° (electrolyte)</p></td><td align="left"><p>254%</p></td><td char="." align="char"><p>1.40</p></td><td align="left"><p>98.8% after 100 cycles at 1C (original) 99.1% after 100 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr187">187</xref>]</p></td></tr><tr><td align="left"><p>CP/PDA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>0° (electrolyte)</p></td><td align="left"><p>320%</p></td><td char="." align="char"><p>1.29</p></td><td align="left"><p> < 50% after 600 cycles at 5C (original) > 80% after 600 cycles at 5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr188">188</xref>]</p></td></tr><tr><td align="left"><p>PP/TA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>72° (H<sub>2</sub>O)</p></td><td align="left"><p>125%</p></td><td char="." align="char"><p>0.46</p></td><td align="left"><p>91% after 200 cycles at 1C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr189">189</xref>]</p></td></tr><tr><td align="left"><p>PP/PA</p></td><td align="left"><p>800 nm</p></td><td align="left"><p>41</p></td><td char="." align="char"><p>1.8</p></td><td align="left"><p>54.7° (H<sub>2</sub>O)</p></td><td align="left"><p>129%</p></td><td char="." align="char"><p>0.57</p></td><td align="left"><p>91.6% after 200 cycles at 1C (original) 97.7% after 200 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr190">190</xref>]</p></td></tr><tr><td align="left"><p>PP/PEI + PDA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>46.3° (H<sub>2</sub>O)</p></td><td align="left"><p>144%</p></td><td char="." align="char"><p>0.58</p></td><td align="left"><p>65% after 200 cycles at 0.2C (original) 80% after 200 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr191">191</xref>]</p></td></tr><tr><td align="left"><p>PP/PEI + TA</p></td><td align="left"><p>–</p></td><td align="left"><p>61.6</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>12.7° (electrolyte)</p></td><td align="left"><p>140%</p></td><td char="." align="char"><p>0.95</p></td><td align="left"><p>69.3% after 200 cycles at 1C (original) 90.9% after 200 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr192">192</xref>]</p></td></tr><tr><td align="left"><p>PP/PDA + PPFPA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>36.5° (electrolyte)</p></td><td align="left"><p>209%</p></td><td char="." align="char"><p>0.83</p></td><td align="left"><p>52% after 700 cycles at 1C (original) 83% after 700 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr193">193</xref>]</p></td></tr><tr><td align="left"><p>PP/NCMP</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p> < 5° (electrolyte)</p></td><td align="left"><p>116%</p></td><td char="." align="char"><p>1.10</p></td><td align="left"><p>40% after 400 cycles at 0.2C (original) 76% after 800 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr135">135</xref>]</p></td></tr><tr><td align="left"><p>PP/Al-CPP</p></td><td align="left"><p>800 nm</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>22.6° (electrolyte)</p></td><td align="left"><p>124%</p></td><td char="." align="char"><p>0.51</p></td><td align="left"><p>40% after 500 cycles at 1C (original) 61% after 500 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr194">194</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–"means not mentioned</p> <p>Inspired by mussels that exhibit superior adhesion in nature, researchers found that dopamine (DA) with both catechol and amine groups can be used as the basis for strong adhesion [[<reflink idref="bib195" id="ref174">195</reflink>], [<reflink idref="bib196" id="ref175">196</reflink>]–[<reflink idref="bib197" id="ref176">197</reflink>]]. For instance, Choi et al. [[<reflink idref="bib27" id="ref177">27</reflink>]] reported a kind of separator modified by polydopamine (PDA) in situ by self-polymerization of DA in the buffered aqueous solution at pH 8.5 (Fig. 10a). In this way, a very thin coating could be obtained, which would not cause pore clogging. Due to the hydrophilic nature of PDA, the wettability (the contact angle with water droplets decreasing from 108° to 39°) and the electrolyte uptake (increasing from 96% to 126%) of modified separator was significantly improved, which led to a 78% increase in ionic conductivity (from 0.23 to 0.41 mS cm<sups>−1</sups>). Besides, the exceptionally strong adhesion between the PDA and basement separator was beneficial for long-term battery operation. Shi et al. [[<reflink idref="bib187" id="ref178">187</reflink>]] prepared a thin PDA layer in situ on the surface of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) nano-fibers, forming a unique core–shell structure. The modified separator had contact angle with electrolyte of almost 0° and high electrolyte uptake (254%). The ionic conductivity of modified separator was 1.40 mS cm<sups>−1</sups> which was much higher than the PP separator (0.80 mS cm<sups>−1</sups>). Similarly, Zhou et al. [[<reflink idref="bib188" id="ref179">188</reflink>]] reported a novel separator with well electrochemical and mechanical properties by in situ modification of virgin cellulose paper (CP) with PDA, thus reducing the contact angle from 37° to 0°. Due to the sufficient hydrophilic functional groups and their affinity for electrolytes on the modified separator, it exhibited a much higher electrolyte uptake of 320 wt%. Therefore, it showed a higher ionic conductivity (1.29 mS cm<sups>−1</sups>) and excellent cycling stability without significant capacity decay after 600 cycles at 5C. However, the DA is not suitable for practical applications because it is too expensive. Therefore, more coating materials similar to DA were developed, such as tannic acid (TA) and pyrogallic acid (PA) (Fig. 10b), which could be directly extracted from natural materials [[<reflink idref="bib198" id="ref180">198</reflink>]]. For instance, Wang et al. [[<reflink idref="bib190" id="ref181">190</reflink>]] prepared PA coating on the surface of PP separator by its in situ self-polymerization, successfully enhancing the hydrophilicity and electrochemical performance. Similarly, Pan et al. [[<reflink idref="bib189" id="ref182">189</reflink>]] coated TA on PP separator by its in situ self-polymerization in weak alkaline aqueous solution, enhancing the wettability (the contact angle with water droplets decreasing from 120° to 73°) and liquid electrolyte uptake while maintaining the original pore structure.</p> <p>Graph: Fig. 10 a Schematic illustration of the PDA on PE [[<reflink idref="bib27" id="ref183">27</reflink>]].</p> <p>Although the DA or similar materials (TA, PA) have been used for modification of the separator surface and achieved good results in improving wettability, they easily form aggregates or depositions due to non-covalent interaction including hydrogen bond and π-π staking among oligomers, which causes uneven surface and inhomogeneous deposition of Li<sups>+</sups> on the surface of the lithium anode [[<reflink idref="bib200" id="ref184">200</reflink>]]. Besides, this process takes a long time, not conducive to large-scale application. Li et al. [[<reflink idref="bib189" id="ref185">189</reflink>]] found that the co-deposition of DA and polyethyleneimine (PEI, 600 Da) decreased the non-covalent interaction. The PP separator was soaked in Tris–HCl buffer solution (pH = 8.5, 50 mM) including polyethyleneimine and dopamine with a mass ratio of 1:1 for 1 h. This strategy not only destroyed the formation of aggregates but also formed the thinner and more uniform coating with short coating time (Fig. 10c). The contact angles with water droplets of PP, PP-DA, and PP-DA/PEI separators were 114.4°, 58.7°, and 46.3°, respectively, indicating that the introduction of PEI further improved the surface hydrophilicity due to its higher nitrogen content. The enhanced wettability brought a high electrolyte uptake, contributing to increasing ionic conductivity and capacity. Coincidentally, Zhang et al. [[<reflink idref="bib192" id="ref186">192</reflink>]] prepared a thin and uniform hydrophilic coating in situ through the layer-by-layer assembly of TA/PEI (Fig. 10d). Immersing the separator in solutions of TA and PEI in sequence, the self-assembly of TA and PEI by hydrogen bonding interaction and oxidation polymerization ensured the adhesion of the coating. In addition, it controlled over the thickness of the coating at a molecular level. The modified separator showed improved wettability with electrolyte (the contact angle decreasing from 45° to 12.7°), higher electrolyte uptake (increasing 42% compared with the PP separator), and faster penetration rate. Besides, the nitrogen atoms could break off the solvation sheath of lithium-ion to promote migration, increasing the <emph>t</emph><subs>Li</subs><sups>+</sups> from 0.28 to 0.44.</p> <p>DA can self-polymerize on the inert substrate surface to form PDA, and it is considered as an excellent surface modification material. Therefore, active sites can be introduced on the surface of the base separator through its self-polymerization without damaging the base separator structure. The active sites further triggered subsequent modification of the separator. Zheng et al. [[<reflink idref="bib193" id="ref187">193</reflink>]] reported an electronegative poly (pentafluorophenyl acrylate) (PPFPA) polymer brush-grafted PP separator by a PDA-assisted surface-initiated atom transfer radical polymerization (SI-ATRP) strategy (Fig. 11a). Concretely, DA containing 2-bromoisobutyryl bromide (DA-Br) was introduced to PP separator by bio-inspired self-polymerization to produce the uniform coating layer containing initiator. Afterward, the Br atom on the surface of coating induced the ATRP reaction, thus achieving high-density PPFPA polymer brushes. The polar PPFPA polymer chains contained abundant F and O atoms to improve the wettability with electrolyte (the contact angle decreasing from 62.6° to 36.5°). Besides, uniform PPFPA polymer brushes could shape highly directed 1D Li<sups>+</sups> flux paths to induce rapid diffusion and uniform deposition of Li<sups>+</sups>. The ionic conductivity of modified separator was significantly improved (twice the ionic conductivity of PP). It thus contributed to the uniform nucleation and deposition of Li metal and effectively maintained the structural integrity of SEI in both ether and carbonate electrolytes. Moreover, the LiFePO<subs>4</subs>/Li half-cell assembled with the modified separator also exhibited a high discharge capacity of 150.2 mAh g<sups>−1</sups> (increasing 21% compared with the PP separator) and a high-capacity retention rate of 83% after 700 cycles at 1C.</p> <p>Graph: Fig. 11 a Schematic illustration of PDA-assisted surface-initiated ATRP (SI-ATRP) strategy to in situ grow electronegative PPFPA polymer brushes on the Celgard separator [[<reflink idref="bib193" id="ref188">193</reflink>]].</p> <p>Expect organic materials like DA, conjugated microporous polymers (CMPs) can also modify separators through in-situ polymerization. Yang et al. [[<reflink idref="bib135" id="ref189">135</reflink>]] proposed a strategy of in-situ modification of polyolefin separator using an N-rich conjugated microporous polymer (NCMP), which generated ultra-thin NCMP coating on the entire outer and inner surface of PP (Fig. 11b). The NCMP coating had rich N-containing groups (-NH<subs>2</subs> and -N =), uniform nanopores (12.294 Å) and π-conjugated structure, effectively suppressing LiPS shuttle, molecular sieve effects and Coulomb interactions. At the same time, the NCMP-PP separator has good electrolyte wettability (the contact angle with electrolyte < 5°) and high electrolyte absorption capacity. The nanopores of NCMP with abundant N-containing groups were larger than twice the Debye length of Li<sups>+</sups> (3.0 Å), which facilitated the passage of Li<sups>+</sups>. Meanwhile, the highly electronegative π-electron cloud of the NCMP repelled the passage of TFSI<sups>–</sups> (7.9 Å) via the Coulombic interaction. This modified separator was able to generate a uniform Li<sups>+</sups> flux between the separator and the surface of the lithium metal anode, forming a stable SEI layer and smooth lithium anode without dendrite. The assembled lithium symmetric cells thus showed long-term cycling performance with a current density of 1 mA cm<sups>−2</sups>. Therefore, Li–S battery exhibited excellent rate performance (674 mAh g<sups>−1</sups>, 3C), high cycle stability (0.028% capacity degradation per cycle at 0.2C for 800 cycles), and ultra-low self-discharge (3.4% capacity degradation within 10 days).</p> <p>The polymer electrolyte obtained by the separator-assisted in situ process can also be regarded as a special process of in situ modification of the separator. In this process, a less viscous precursor in the liquid state consisting of low molecular weight monomers, Li salt, initiator, or catalyst is added to the base separator and assembled into a cell, thus the precursor polymerized inside the sealed cell, which can be seen that the polymer modification coating is formed in situ on the separator without adding liquid electrolyte. This method can not only form a well contact between electrolyte and electrode but also avoid organic solvent leakage and spontaneous combustion for high [[<reflink idref="bib202" id="ref190">202</reflink>], [<reflink idref="bib204" id="ref191">204</reflink>]–[<reflink idref="bib205" id="ref192">205</reflink>]]. For instance, Guo et al. [[<reflink idref="bib206" id="ref193">206</reflink>]] prepared a block copolymer electrolyte (BCPE) consisting of RAFT polymerization of poly (ethylene glycol) methyl ether acrylate (PEGA) and carboxylic acid-catalyzed ROP of caprolactone (CL), which were fabricated in situ in cellulose separator. The block structure balanced the ability of Li salt dissociation and Li<sups>+</sups> coordination while reducing the crystallinity of polymer, thus showing high ionic conductivity (0.185 mS cm<sups>−1</sups>) and high <emph>t</emph><subs>Li</subs><sups>+</sups> (0.59). Besides, the compatibility between electrolyte and electrode was also improved, promoting the rapid transport and uniform deposition of Li<sups>+</sups>. Therefore, it exhibited excellent cycling performances, with a retention rate of 92% after 400 cycles at 1C.</p> <p>In summary, in situ formation of organic materials represents an environmentally friendly, efficient, straightforward, and widely adopted modification method. Organic compounds, such as dopamine (DA), are among the most prevalent organic modification materials owing to their robust self-polymerization capabilities and excellent adhesion properties. Furthermore, they possess the ability to introduce active sites conducive to additional modifications, including self-assembly and ATRP polymerization.</p> <hd id="AN0182798912-17">Section Summary</hd> <p>Overall, compared with coating modification, in situ modification has the following advantages: it enhances adhesion, facilitates the creation of thinner and more uniform coatings, preserves the pore structure, and reduces interface impedance. However, its application is currently constrained by the limited availability of polymerization materials and the complexity of the processes involved.</p> <hd id="AN0182798912-18">Grafting Modified Separators</hd> <p>While in situ modification has indeed effectively improved adhesion, the coating and the base separator are still primarily bound through non-covalent interactions, resulting in adhesion that is somewhat limited. Grafting modification offers a solution by enabling the formation of chemical bonds between the coating and the base separator, thereby achieving stronger adhesion while simultaneously enhancing wettability [[<reflink idref="bib8" id="ref194">8</reflink>], [<reflink idref="bib207" id="ref195">207</reflink>]]. The characteristics and electrochemical performance of grafting modified separators by inorganic modification materials are in Table 9.</p> <p>Table 9 The characteristics and electrochemical performance of grafting modified separators by inorganic modification materials</p> <p> <ephtml> <table frame="hsides" rules="groups"><thead><tr><th align="left"><p>Separator</p></th><th align="left"><p>Coating thickness (μm)</p></th><th align="left"><p>Porosity<sup>a</sup> (%)</p></th><th align="left"><p>Coating mass fraction (%)</p></th><th align="left"><p>Contact angle</p></th><th align="left"><p>Electrolyte uptake</p></th><th align="left"><p>Ionic conductivity (mS cm<sup>–1</sup>) at RT</p></th><th align="left"><p>Cyclic performance</p></th><th align="left"><p>References</p></th></tr></thead><tbody><tr><td align="left"><p>PE/TiO<sub>2</sub></p></td><td align="left"><p>–<sup>b</sup></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>89° (H<sub>2</sub>O)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.50</p></td><td align="left"><p> > 90% after 100 cycles at 0.2C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr209">209</xref>]</p></td></tr><tr><td align="left"><p>PE/SiO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>79° (H<sub>2</sub>O)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.45</p></td><td align="left"><p> > 90% after 100 cycles at 0.2C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr210">210</xref>]</p></td></tr><tr><td align="left"><p>PP/FeOOH</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>19.7° (electrolyte)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>80.5% after 500 cycles at 5C</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr211">211</xref>]</p></td></tr><tr><td align="left"><p>PP/AA</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>75° (H<sub>2</sub>O)</p></td><td align="left"><p>280%</p></td><td char="." align="char"><p>–</p></td><td align="left"><p>78% after 50 cycles at 0.2C (original) > 90% after 50 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr212">212</xref>]</p></td></tr><tr><td align="left"><p>PP/CFP</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>26.5°(electrolyte)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.99</p></td><td align="left"><p>53% after 800 cycles at 1C (original) 87.6% after 800 cycles at 1C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr213">213</xref>]</p></td></tr><tr><td align="left"><p>PP/PAM + SiO<sub>2</sub></p></td><td align="left"><p>3</p></td><td align="left"><p>45</p></td><td align="left"><p>–</p></td><td align="left"><p>37° (H<sub>2</sub>O)</p></td><td align="left"><p>436%</p></td><td char="." align="char"><p>1.43</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr214">214</xref>]</p></td></tr><tr><td align="left"><p>PP/PE/PP/SiO<sub>2</sub> + TEOS</p></td><td align="left"><p>0.6</p></td><td align="left"><p>–</p></td><td align="left"><p>28</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>0.16</p></td><td align="left"><p>91% after 65 cycles at 0.2C (original) 96% after 65 cycles at 0.2C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr215">215</xref>]</p></td></tr><tr><td align="left"><p>PP-S/PPS + CTS</p></td><td align="left"><p>0.73</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>7.4° (electrolyte)</p></td><td align="left"><p>–</p></td><td char="." align="char"><p>1.01</p></td><td align="left"><p>52% after 300 cycles at 0.5C (original) 94.5% after 300 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr216">216</xref>]</p></td></tr><tr><td align="left"><p>PE/PEI + SiO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>47.6</p></td><td align="left"><p>–</p></td><td align="left"><p>24.6° (H<sub>2</sub>O)</p></td><td align="left"><p>398%</p></td><td char="." align="char"><p>0.49</p></td><td align="left"><p>79% after 100 cycles at 0.5C (original) 90.1% after 100 cycles at 0.5C (modified)</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr217">217</xref>]</p></td></tr><tr><td align="left"><p>PE/PAA + ZrO<sub>2</sub></p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>–</p></td><td align="left"><p>39° (H<sub>2</sub>O)</p></td><td align="left"><p>325%</p></td><td char="." align="char"><p>0.51</p></td><td align="left"><p>–</p></td><td align="left"><p>[<xref ref-type="bibr" rid="bibr218">218</xref>]</p></td></tr></tbody></table> </ephtml> </p> <p> <sups>a</sups> "Porosity" is the entire separator's, instead of the coating's. <sups>b</sups> "–" means not mentioned</p> <hd id="AN0182798912-19">Chemical Grafting Modification</hd> <p>Chemical grafting techniques can generate active sites on the inert surface of separators through pre-treatments such as UV radiation, plasma treatment, and chemical initiator decomposition [[<reflink idref="bib219" id="ref196">219</reflink>], [<reflink idref="bib221" id="ref197">221</reflink>], [<reflink idref="bib222" id="ref198">222</reflink>]–[<reflink idref="bib223" id="ref199">223</reflink>]]. These active sites facilitate the formation of chemical bonds between modification materials and the separator, leading to a robust and secure binding. Additionally, the coating layers formed through these methods are extremely thin, ensuring that the pore structure of the separator remains well-preserved. [[<reflink idref="bib224" id="ref200">224</reflink>]]. The inorganic modification materials (e.g., SiO<subs>2</subs>, TiO<subs>2</subs>, Al<subs>2</subs>O<subs>3</subs>) show excellent ability to improve wettability and reduce the risk of coating detachment during battery assembly and charge/discharge by the chemical grafting method. For instance, Zhu et al. [[<reflink idref="bib209" id="ref201">209</reflink>]] prepared a new TiO<subs>2</subs> ceramic-grafted polyethylene (TiO<subs>2</subs>-grafted PE) separator by electron beam radiation (Fig. 12a). The study indicated that the TiO<subs>2</subs>-grafted PE separator not only showed improved wettability (the contact angle with H<subs>2</subs>O decreasing from 112° to 89°) and ionic conductivity (increasing from 0.32 to 0.5 mS cm<sups>−1</sups>), but also exhibited highly enhanced thermal stability. Besides, the thickness and pore structure of modified PE separator were similar to original PE. Except for inorganic modification materials, the organic modification materials can also significantly improve wettability by introducing polar groups (e.g., C = O, COOH, NH<subs>2</subs>). For instance, Yin et al. [[<reflink idref="bib212" id="ref202">212</reflink>]] grafted acrylic acid (AA) onto the surface of PP separator by an atmospheric pressure glow discharge plasma jet (APGD-PJ) while retaining the pore structure of the base separator. The introduction of AA enhanced wettability, thus reducing the contact angle with H<subs>2</subs>O (decreasing from 112° to 75°), and the electrolyte uptake of modified separator increased nearly 4 times compared with the original PP separator. Furthermore, the cyclic stability, discharge specific capacity, and Coulombic efficiency of LiFePO<subs>4</subs>/Li half-cells assembled with modified PP separators increased noticeably. Besides, the organic/inorganic hybrid strategy was utilized to enhance the thermal dimensional stability, wetting ability, and electrochemical properties of separators. As shown in Fig. 12b, Liu et al. [[<reflink idref="bib214" id="ref203">214</reflink>]] grafted acrylamide (AM) onto the PP separator by initiator decomposition, then reacted with tetraethylorthosilicate (TEOS) to obtain SiO<subs>2</subs> particles and ultimately prepared a novel SiO<subs>2</subs>/PAM-grafted PP separator. As a result, the modified separator demonstrated superior wettability (the contact angle with H<subs>2</subs>O decreasing from 105° to 37°) and better thermal stability compared with the unmodified separator.</p> <p>Graph: Fig. 12 a Preparation process of the TiO2-grafted PE separator by electron beam radiation [[<reflink idref="bib209" id="ref204">209</reflink>]].</p> <hd id="AN0182798912-20">Further Modification after Chemical Grafting</hd> <p>After chemically grafting active groups on the surface of the base separator, further modification is feasible. For instance, Yang et al. [[<reflink idref="bib216" id="ref205">216</reflink>]] prepared a multifunctional layered separator by grafting the SO<subs>3</subs><sups>−</sups> group to induce self-assembly (Fig. 12c). This study introduced the SO<subs>3</subs><sups>−</sups> group on the surface of the PP separator first. Then, the strong electrostatic interaction between SO<subs>3</subs><sups>−</sups> groups and NH<subs>3</subs><sups>+</sups> groups caused chitosan to tightly adhere to the surface of the separator. Similarly, polystyrene sulfonate (PSS) adhered to the surface of chitosan layer relying on the electrostatic interaction and finally formed the nanoscale self-assembled functional layers with nanoscale thickness. The grafting layers significantly decreased the contact angle from 46° to 7.4°. More importantly, the assembled Li-LiNi<subs>0.8</subs>Co<subs>0.15</subs>Al<subs>0.05</subs> full cells with modified separator showed excellent cycling stability with a high-capacity retention of 94.5% after 300th cycles at 0.5C under an ultra-lean electrolyte condition of 4.8 g A h<sups>−1</sups>. Coincidentally, Wang et al. [[<reflink idref="bib217" id="ref206">217</reflink>]] demonstrated a self-assembly process of oppositely charged polymer polyethyleneimine (PEI) and inorganic oxide SiO<subs>2</subs> for the construction of an ultrathin layer on the surface of PE separator (Fig. 12d). They treated PE separator by CO<subs>2</subs>-plasma to give rise to carboxyl-activated surface, and constructed PEI/SiO<subs>2</subs> ultra-thin layer on the surface of carboxylated PE separator. Through the imidization between carboxyl groups and amino groups, the interlayer cross-linking happened. The electrolyte wettability of the modified separator was significantly improved without obviously increasing in separator thickness or blocking the original micropores (contact angle with H<subs>2</subs>O decreasing from 124° to 24.6°). Meanwhile, the modified separator demonstrated better cycle performance for working about 100 cycles with a high-capacity retention (90.1%) compared to the unmodified one (79.0%).</p> <hd id="AN0182798912-21">Section Summary</hd> <p>In general, grafting modification is an effective method that not only enhances the wettability of separators but also addresses the issue of weak adhesion between the coating and the base separator. However, most pre-treatments, such as UV radiation, plasma treatment, and high-energy radiation, necessitate complex and costly equipment, making it challenging to achieve large-scale production. Excessive pre-treatment can also lead to significant damage to the porous structure, resulting in decreased ion conductivity and mechanical strength. Additionally, this damage to the pore structure causes a reduction in the porosity of the modified separator [[<reflink idref="bib226" id="ref207">226</reflink>], [<reflink idref="bib228" id="ref208">228</reflink>], [<reflink idref="bib229" id="ref209">229</reflink>]–[<reflink idref="bib230" id="ref210">230</reflink>]]. These limitations hinder the further application of surface modification techniques (Fig. 13).</p> <p>Graph: Fig. 13 The outlook for the development direction of separators</p> <hd id="AN0182798912-22">Conclusions and Outlook</hd> <p></p> <hd id="AN0182798912-23">Conclusions</hd> <p>In lithium batteries, the separator plays a crucial role as it acts as a physical barrier between the positive and negative electrodes while also facilitating ion transport. Various properties of the separator, such as its thickness, pore structure, wettability, mechanical properties, and dimensional thermal stability, significantly impact the battery's performance. Given that traditional separators cannot meet the demands of more advanced lithium batteries, the improvement of existing separators and the development of new separators are urgent priorities. Researchers have made numerous attempts to optimize traditional separators, and in this review, we have summarized the three most commonly utilized modification methods, focusing on enhancing wettability and adhesion.</p> <p>Firstly, we discussed the coating modification of the separator and introduced different coating materials. Coating modification is a simple and effective method to improve electrochemical performance, and thus large-scale production has been realized in industry. However, the weak adhesion between the coating and the base separator, as well as the uncontrollable coating thickness, lead to compromised battery performance. Then, in situ modification was proposed as an alternative strategy. Enhancement of adherence is accompanied by a thinner and more uniform coating. As a result, the performance of the battery was satisfactorily improved. However, limited polymerization materials and sophisticated processes limited its application. Lastly, several chemical grafting modification strategies were listed. Although the adhesion produced by this method was the strongest among the three modification methods, it usually required complex and costly instruments, as well as destroyed the separator structure.</p> <p>In summary, a detailed comparison is made of the properties, such as wettability and adhesion, of modified separators and the assembled batteries. The enhancement of wettability can be directly observed in the improved electrochemical performance. Notably, separators prepared through in situ modification exhibit superior cyclic performance compared to other methods, which may be attributed to their lower interface impedance. However, it is evident that there is a lack of quantitative analysis on the adhesion of coatings in many studies. Additionally, there are also some sophisticated modification methods that do not fall within the three categories discussed here, such as the combination of multiple different modification techniques. methods.</p> <hd id="AN0182798912-24">Outlook</hd> <p>Based on the three modification methods of separator, the following future directions are proposed toward future advanced lithium batteries:</p> <p> <bold>(<reflink idref="bib1" id="ref211">1</reflink>) New modified materials.</bold> At present, polyolefin separators and coated polyolefin separators (coating materials including Al<subs>2</subs>O<subs>3</subs>, SiO<subs>2</subs>, boehmite, PVDF, aramid fiber, etc.) are still the mostly used commercial separators. Although further improvements are expected for these separators, other modification materials usually stay in the laboratory stage due to cost. Therefore, low-cost and high-powered materials must be developed to promote the commercialization of advanced modified separators. For instance, poly(ε-caprolactone) (PCL) is a popular polymer in the field of electrolytes with stable electrochemical window (~ 5 V), high dielectric constant, weak interaction with Li<sups>+</sups>, low-cost and environmentally friendly features. Few studies have used PCL as coating materials to modify separators. Ye et al. [[<reflink idref="bib231" id="ref212">231</reflink>]] innovatively used blended of PCL and PEO as coating materials to modify the PP separator, significantly promoting the cycle stability of battery. New functional coating materials are expected to be developed.</p> <p> <bold>(<reflink idref="bib2" id="ref213">2</reflink>) New manufacturing process.</bold> In addition to the development of new materials, the new manufacturing process also needs to be considered, which has a significant effect on coating thickness and adhesion. At present, the thickness of commercial coated separators is about 20 μm, which means large quantity of coating material and reduced energy density of the battery. Besides, the coating materials are also at risk of peeling. Therefore, developing new manufacturing processes to decrease coating thickness and improve adhesion is conducive to the development of advanced lithium batteries. In the laboratory, researchers are no longer limited to single modification methods, but prefer the combination of multiple modification approaches. It can be predicted that the combination of multiple methods and materials may be the development trend.</p> <p> <bold>(<reflink idref="bib3" id="ref214">3</reflink>) Functional separators.</bold> In addition to the basic role of the separator in transporting ions and preventing short circuits, it is also expected to acquire other functions such as inhibiting lithium dendrites, forming stable SEI and capturing side reaction products. The non-uniform lithium flux in lithium metal batteries is the main reason for the growth of lithium dendrites. Therefore, the separator with the function of promoting the uniform distribution of Li<sups>+</sups> can effectively inhibit the growth of lithium dendrites. Materials with uniform nanochannels, including COF, MOF, brush polymer, inorganic and organic porous materials, contribute to the uniform distribution of Li<sups>+</sups>, and thus they are used as modified materials to endow the separators with lithium dendrites inhibition ability. Besides, imparting the separator with cation selectivity is also an innovative strategy, which greatly promotes the migration of Li<sups>+</sups> and inhibits anion diffusion, achieving smooth lithium deposition [[<reflink idref="bib232" id="ref215">232</reflink>], [<reflink idref="bib233" id="ref216">233</reflink>]–[<reflink idref="bib234" id="ref217">234</reflink>]]. The side reaction between lithium metal and electrolyte results in the formation of SEI. However, unstable SEI would cause the unreacted lithium metal to be exposed to the electrolyte, resulting in continuous decomposition of the electrolyte and ultimately a decrease in battery life. Functional separator can be designed to construct a stable SEI by sustained-release strategy and form artificial SEI. Traditional separators can be used as substrates to release active substances such as inorganic salt and transition metal oxides, which slowly dissolve in the electrolyte during the cycle and react with lithium metal to form stable SEI. Another strategy is to prepare reactive separators with the function of constructing artificial SEI. In this method, the coating on the surface of the separator that can react with lithium metal, such as organic (lignosulfonate) and inorganic salt (boehmite, SnS<subs>2</subs>). This in situ artificial SEI layer can protect the lithium anode from electrolyte side reactions and inhibit the degradation of liquid electrolytes. In the process of charge and discharge, some by-products are inevitably produced (HF, transition metal ion, polysulfide), which shuttle in the battery causing capacity attenuation and battery life decline. They can be suppressed by introducing specific groups or coatings on the separator surface to inhibit or capture these products.</p> <p> <bold>(<reflink idref="bib4" id="ref218">4</reflink>) Quantitative analysis of adhesion.</bold> Adhesion of coating is an important parameter in industry that deeply affects the safety and cycle stability of batteries. The coating with poor adhesion may fall off from the separator, generating cracks between the separator and the electrodes, thus resulting in increased internal impedance of the battery, uneven current density distribution, inhomogeneous deposition of lithium and lithium dendrite growth, seriously affecting the performance of the battery. At present, few researchers have conducted quantitative analysis of adhesion, and most of them use qualitative methods, such as observing whether the coating falls off by folding and bending the separator. Therefore, we expect more studies to characterize adhesion through quantitative analysis techniques (such as 180° peel test).</p> <p> <bold>(<reflink idref="bib5" id="ref219">5</reflink>) Security.</bold> With the rapid development of high-energy density batteries, safety issues have become one of the great challenges to be solved. Flammable organic solvents in liquid electrolytes are one of the main factors affecting the safety of batteries. Solid polymer electrolyte (SPE) is considered as a good solution strategy due to the absence of traditional organic solvents. In particular, the polymer electrolyte is prepared by the separator-assisted in situ process to effectively enhance the efficient Li<sups>+</sups> transport between anodes and cathodes [[<reflink idref="bib235" id="ref220">235</reflink>]]. Although there is a gap in electrochemical performance between the SPE and liquid electrolyte, SPE is considered as a promising development direction for high-safety lithium-ion batteries in the future.</p> <hd id="AN0182798912-25">Acknowledgements</hd> <p>We are grateful to the Center of Lithium Battery Membrane Materials jointly established by School of Chemistry and Chemical Engineering of Huazhong University of Science and Technology and Shenzhen Senior Technology Material Co. Ltd., the National Natural Science Foundation of China (52020105012, 52303084), and the Young Scientists Fund of Natural Science Foundation of Hubei Province (2023AFB220) for the support of this work.</p> <hd id="AN0182798912-26">Author Contributions</hd> <p>Zixin Fan, Xiaoyu Chen: Investigation, original draft writing. Jingjing Shi, Xiaoming Zhang: Investigation, visualization. Xiaolin Xie: Conceptualization, review. Hui Nie, Xingping Zhou, Zhigang Xue: Visualization, funding acquisition, supervision.</p> <hd id="AN0182798912-27">Declarations</hd> <p></p> <hd id="AN0182798912-28">Conflict of Interest</hd> <p>The authors declare no interest conflict. They have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.</p> <hd id="AN0182798912-29">Publisher's Note</hd> <p>Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.</p> <ref id="AN0182798912-30"> <title> References </title> <blist> <bibl id="bib1" idref="ref1" type="bt">1</bibl> <bibtext> Yang Y, Wang W, Meng G, Zhang J. Function-directed design of battery separators based on microporous polyolefin membranes. J. Mater. Chem. A. 2022; 10; 27: 14137-14170. 10.1039/D2TA03511A. 1524.94042</bibtext> </blist> <blist> <bibl id="bib2" idref="ref2" type="bt">2</bibl> <bibtext> Liu K, Liu Y, Lin D, Pei A, Cui Y. Materials for lithium-ion battery safety. Sci. Adv. 2018; 4; 6: eaas9820. 10.1126/sciadv.aas9820. 1237.37028</bibtext> </blist> <blist> <bibl id="bib3" idref="ref3" type="bt">3</bibl> <bibtext> Niu C, Lee H, Chen S, Li Q, Du J. High-energy lithium metal pouch cells with limited anode swelling and long stable cycles. Nat. Energy. 2019; 4; 7: 551-559. 10.1038/s41560-019-0390-6</bibtext> </blist> <blist> <bibl id="bib4" idref="ref4" type="bt">4</bibl> <bibtext> You J, Wang Q, Wei R, Deng L, Hu Y. Boosting high-voltage practical lithium metal batteries with tailored additives. Nano-Micro Lett. 2024; 16: 257. 10.1007/s40820-024-01479-1</bibtext> </blist> <blist> <bibl id="bib5" idref="ref5" type="bt">5</bibl> <bibtext> Shen J, Xu X, Liu J, Wang Z, Zuo S. Unraveling the catalytic activity of Fe–based compounds toward Li2Sx in Li-S chemical system from d-p bands. Adv. Energy Mater. 2021; 11: 2100673. 10.1002/aenm.202100673</bibtext> </blist> <blist> <bibl id="bib6" idref="ref6" type="bt">6</bibl> <bibtext> Lagadec MF, Zahn R, Wood V. Characterization and performance evaluation of lithium-ion battery separators. Nat. energy. 2019; 4; 1: 16-25. 10.1038/s41560-018-0295-9. 1326.81135</bibtext> </blist> <blist> <bibl id="bib7" idref="ref7" type="bt">7</bibl> <bibtext> Jia H, Zeng C, Lim H-S, Simmons A, Zhang Y. Important role of ion flux regulated by separators in lithium metal batteries. Adv. Mater. 2024; 36; 19: 2311312. 10.1002/adma.202311312</bibtext> </blist> <blist> <bibl id="bib8" idref="ref9" type="bt">8</bibl> <bibtext> Lingappan N, Lee W, Passerini S, Pecht M. A comprehensive review of separator membranes in lithium-ion batteries. Renew. Sust. Energ. Rev. 2023; 187. 10.1016/j.rser.2023.113726113726</bibtext> </blist> <blist> <bibl id="bib9" idref="ref11" type="bt">9</bibl> <bibtext> Waqas M, Ali S, Feng C, Chen D, Han J. Recent development in separators for high-temperature lithium-ion batteries. Small. 2019; 15; 33: 1901689. 10.1002/smll.201901689</bibtext> </blist> <blist> <bibtext> Seh ZW, Sun Y, Zhang Q, Cui Y. Designing high-energy lithium-sulfur batteries. Chem. Soc. Rev. 2016; 45; 20: 5605-5634. 10.1039/C5CS00410A</bibtext> </blist> <blist> <bibtext> Lu W, Yuan Z, Zhao Y, Zhang H, Zhang H. Porous membranes in secondary battery technologies. Chem. Soc. Rev. 2017; 46; 8: 2199-2236. 10.1039/C6CS00823B. 07947637</bibtext> </blist> <blist> <bibtext> Arora P, Zhang Z. Battery separators. Chem. Rev. 2004; 104; 10: 4419-4462. 10.1021/cr020738u</bibtext> </blist> <blist> <bibtext> Su M, Huang G, Wang S, Wang Y, Wang H. High safety separators for rechargeable lithium batteries. Sci. China-Chem. 2021; 64; 7: 1131-1156. 10.1007/s11426-021-1011-9. 1197.34010</bibtext> </blist> <blist> <bibtext> Yu Y, Liu M, Chen Z, Zhang Z, Qiu T. Advances in nonwoven-based separators for lithium-ion batteries. Adv. Fiber Mater. 2023; 5; 6: 1827-1851. 10.1007/s42765-023-00322-3. 1381.35213</bibtext> </blist> <blist> <bibtext> Kim H, Mattinen U, Guccini V, Liu H, Salazar-Alvarez G. Feasibility of chemically modified cellulose nanofiber membranes as lithium-ion battery separators. ACS Appl. Mater. Interfaces. 2020; 12; 37: 41211-41222. 10.1021/acsami.0c08820</bibtext> </blist> <blist> <bibtext> Lv D, Chai J, Wang P, Zhu L, Liu C. Pure cellulose lithium-ion battery separator with tunable pore size and improved working stability by cellulose nanofibrils. Carbohydr. Polym. 2021; 251. 10.1016/j.carbpol.2020.116975116975</bibtext> </blist> <blist> <bibtext> Hwang K, Kwon B, Byun H. Preparation of PVDF nanofiber membranes by electrospinning and their use as secondary battery separators. J. Membr. Sci. 2011; 378; 1: 111-116. 10.1016/j.memsci.2011.06.005</bibtext> </blist> <blist> <bibtext> Yang B, Wang L, Zhang M, Li W, Zhou Q. Advanced separators based on aramid nanofiber (ANF) membranes for lithium-ion batteries: a review of recent progress. J. Mater. Chem. A. 2021; 9; 22: 12923-12946. 10.1039/D1TA03125B. 1464.76200</bibtext> </blist> <blist> <bibtext> Dong T, Arifeen WU, Choi J, Yoo K, Ko T. Surface-modified electrospun polyacrylonitrile nano-membrane for a lithium-ion battery separator based on phase separation mechanism. Chem. Eng. J. 2020; 398. 10.1016/j.cej.2020.125646125646</bibtext> </blist> <blist> <bibtext> Fu X, Shang C, Yang M, Akinoglu EM, Wang X. An ion-conductive separator for high safety Li metal batteries. J. Power Sources. 2020; 475. 10.1016/j.jpowsour.2020.228687228687</bibtext> </blist> <blist> <bibtext> Ding Y, Hou H, Zhao Y, Zhu Z, Fong H. Electrospun polyimide nanofibers and their applications. Prog. Polym. Sci. 2016; 61: 67-103. 10.1016/j.progpolymsci.2016.06.006. 0979.90048</bibtext> </blist> <blist> <bibtext> Wang Y, Wang S, Fang J, Ding L-X, Wang H. A nano-silica modified polyimide nanofiber separator with enhanced thermal and wetting properties for high safety lithium-ion batteries. J. Membr. Sci. 2017; 537: 248-254. 10.1016/j.memsci.2017.05.023. 1458.93130</bibtext> </blist> <blist> <bibtext> Li D, Zhang H, Li X. Porous polyetherimide membranes with tunable morphology for lithium-ion battery. J. Membr. Sci. 2018; 565: 42-49. 10.1016/j.memsci.2018.08.011. 1162.16310</bibtext> </blist> <blist> <bibtext> Li D, Shi D, Feng K, Li X, Zhang H. Poly (ether etherketone) (PEEK) porous membranes with super high thermal stability and high rate capability for lithium-ion batteries. J. Membr. Sci. 2017; 530: 125-131. 10.1016/j.memsci.2017.02.027. 1199.20022</bibtext> </blist> <blist> <bibtext> Li D, Shi D, Xia Y, Qiao L, Li X. Superior thermally stable and nonflammable porous polybenzimidazole membrane with high wettability for high-power lithium-ion batteries. ACS Appl. Mater. Interfaces. 2017; 9; 10: 8742-8750. 10.1021/acsami.6b16316. 1376.52014</bibtext> </blist> <blist> <bibtext> Yu Y, Jia G, Zhao L, Xiang H, Hu Z. Flexible and heat-resistant polyphenylene sulfide ultrafine fiber hybrid separators for high-safety lithium-ion batteries. Chem. Eng. J. 2023; 452. 10.1016/j.cej.2022.139112139112</bibtext> </blist> <blist> <bibtext> Ryou M-H, Lee YM, Park J-K, Choi JW. Mussel-inspired polydopamine-treated polyethylene separators for high-power Li-ion batteries. Adv. Mater. 2011; 23; 27: 3066-3070. 10.1002/adma.201100303</bibtext> </blist> <blist> <bibtext> Liu K, Zhuo D, Lee H-W, Liu W, Lin D. Extending the life of lithium-based rechargeable batteries by reaction of lithium dendrites with a novel silica nanoparticle sandwiched separator. Adv. Mater. 2017; 29; 4: 1603987. 10.1002/adma.201603987</bibtext> </blist> <blist> <bibtext> Wang Y. Separator wettability enhanced by electrolyte additive to boost the electrochemical performance of lithium metal batteries. Nano-Micro Lett. 2021; 13: 210. 10.1007/s40820-021-00731-2. 1526.92008</bibtext> </blist> <blist> <bibtext> Pfleging W, Pröll J. A new approach for rapid electrolyte wetting in tape cast electrodes for lithium-ion batteries. J. Mater. Chem. A. 2014; 2; 36: 14918-14926. 10.1039/C4TA02353F</bibtext> </blist> <blist> <bibtext> Jeong H-S, Choi E-S, Lee S-Y, Kim JH. Evaporation-induced, close-packed silica nanoparticle-embedded nonwoven composite separator membranes for high-voltage/high-rate lithium-ion batteries: advantageous effect of highly percolated, electrolyte-philic microporous architecture. J. Membr. Sci. 2012; 415–416: 513-519. 10.1016/j.memsci.2012.05.038</bibtext> </blist> <blist> <bibtext> Chen J, Wang S, Cai D, Wang H. Porous SiO2 as a separator to improve the electrochemical performance of spinel LiMn2O4 cathode. J. Membr. Sci. 2014; 449: 169-175. 10.1016/j.memsci.2013.08.028. 1337.74046</bibtext> </blist> <blist> <bibtext> Huang J, Liu J, He J, Wu M, Qi S. Optimizing electrode/electrolyte interphases and Li-ion flux/solvation for lithium-metal batteries with qua-functional heptafluorobutyric anhydride. Angew. Chem. Int. Ed. 2021; 60; 38: 20717-20722. 10.1002/anie.202107957</bibtext> </blist> <blist> <bibtext> Wang Z, Pan R, Xu C, Ruan C, Edström K. Conducting polymer paper-derived separators for lithium metal batteries. Energy Storage Mater. 2018; 13: 283-292. 10.1016/j.ensm.2018.02.006</bibtext> </blist> <blist> <bibtext> Xiao J. How lithium dendrites form in liquid batteries. Science. 2019; 366; 6464: 426-427. 10.1126/science.aay8672. 0881.35062</bibtext> </blist> <blist> <bibtext> Zhang M, Wang L, Xu H, Song Y, He X. Polyimides as promising materials for lithium-ion batteries: a review. Nano-Micro Lett. 2023; 15; 1: 135. 10.1007/s40820-023-01104-7. 1435.93077</bibtext> </blist> <blist> <bibtext> Waqas M, Tan C, Lv W, Ali S, Boateng B. A highly-efficient composite separator with strong ligand interaction for high-temperature lithium-ion batteries. ChemElectroChem. 2018; 5; 19: 2722-2728. 10.1002/celc.201800800. 1231.34063</bibtext> </blist> <blist> <bibtext> Zhang SS, Xu K, Jow TR. An inorganic composite membrane as the separator of Li-ion batteries. J. Power. Sources. 2005; 140; 2: 361-364. 10.1016/j.jpowsour.2004.07.034. 1026.91039</bibtext> </blist> <blist> <bibtext> Kango S, Kalia S, Celli A, Njuguna J, Habibi Y. Surface modification of inorganic nanoparticles for development of organic-inorganic nanocomposites—a review. Prog. Polym. Sci. 2013; 38; 8: 1232-1261. 10.1016/j.progpolymsci.2013.02.003</bibtext> </blist> <blist> <bibtext> Ryou M-H, Lee DJ, Lee J-N, Lee YM, Park J-K. Excellent cycle life of lithium-metal anodes in lithium-ion batteries with mussel-inspired polydopamine-coated separators. Adv. Energy Mater. 2012; 2; 6: 645-650. 10.1002/aenm.201100687. 0626.57020</bibtext> </blist> <blist> <bibtext> Chen Z, Zhao W, Liu Q, Xu Y, Wang Q. Janus quasi-solid electrolyte membranes with asymmetric porous structure for high-performance lithium-metal batteries. Nano-Micro Lett. 2024; 16: 114. 10.1007/s40820-024-01325-4. 07803924</bibtext> </blist> <blist> <bibtext> Liang Y, Zhao C-Z, Yuan H, Chen Y, Zhang W. A review of rechargeable batteries for portable electronic devices. InfoMat. 2019; 1; 1: 6-32. 10.1002/inf2.12000. 1313.91067</bibtext> </blist> <blist> <bibtext> Huang X. A lithium-ion battery separator prepared using a phase inversion process. J. Power. Sources. 2012; 216: 216-221. 10.1016/j.jpowsour.2012.05.019. 0541.16028</bibtext> </blist> <blist> <bibtext> Tong B, Li X. Towards separator safety of lithium-ion batteries: a review. Mat. Chem. Front. 2024; 8; 2: 309-340. 10.1039/D3QM00951C. 1357.35221</bibtext> </blist> <blist> <bibtext> Lee H, Yanilmaz M, Toprakci O, Fu K, Zhang X. A review of recent developments in membrane separators for rechargeable lithium-ion batteries. Energy Environ. Sci. 2014; 7; 12: 3857-3886. 10.1039/C4EE01432D</bibtext> </blist> <blist> <bibtext> Takemura D, Aihara S, Hamano K, Kise M, Nishimura T. A powder particle size effect on ceramic powder based separator for lithium rechargeable battery. J. Power. Sources. 2005; 146; 1: 779-783. 10.1016/j.jpowsour.2005.03.159. 1186.03051</bibtext> </blist> <blist> <bibtext> Chen W, Shi L, Zhou H, Zhu J, Wang Z. Water-based organic-inorganic hybrid coating for a high-performance separator. ACS Sustain. Chem. Eng. 2016; 4; 7: 3794-3802. 10.1021/acssuschemeng.6b00499. 1469.35039</bibtext> </blist> <blist> <bibtext> Fu D, Luan B, Argue S, Bureau MN, Davidson IJ. Nano SiO2 particle formation and deposition on polypropylene separators for lithium-ion batteries. J. Power. Sources. 2012; 206: 325-333. 10.1016/j.jpowsour.2011.10.130</bibtext> </blist> <blist> <bibtext> Jeong H-S, Lee S-Y. Closely packed SiO2 nanoparticles/poly(vinylidene fluoride-hexafluoropropylene) layers-coated polyethylene separators for lithium-ion batteries. J. Power Sources. 2011; 196; 16: 6716-6722. 10.1016/j.jpowsour.2010.11.037</bibtext> </blist> <blist> <bibtext> Liu H, Xu J, Guo B, He X. Effect of Al2O3/SiO2 composite ceramic layers on performance of polypropylene separator for lithium-ion batteries. Ceram. Int. 2014; 40; 9: 14105-14110. 10.1016/j.ceramint.2014.05.142. 1371.20035</bibtext> </blist> <blist> <bibtext> Kennedy S, Kim J-T, Kim J, Lee YM, Phiri I. Synergistic effect of dual-ceramics for improving the dispersion stability and coating quality of aqueous ceramic coating slurries for polyethylene separators in Li secondary batteries. Batteries. 2022; 8; 8: 82. 10.3390/batteries8080082. 06902821</bibtext> </blist> <blist> <bibtext> Wang Z, Xiang H, Wang L, Xia R, Nie S. A paper-supported inorganic composite separator for high-safety lithium-ion batteries. J. Membr. Sci. 2018; 553: 10-16. 10.1016/j.memsci.2018.02.040. 1409.92267</bibtext> </blist> <blist> <bibtext> Feng G, Li Z, Mi L, Zheng J, Feng X. Polypropylene/hydrophobic-silica-aerogel-composite separator induced enhanced safety and low polarization for lithium-ion batteries. J. Power Sources. 2018; 376: 177-183. 10.1016/j.jpowsour.2017.11.086. 1304.35666</bibtext> </blist> <blist> <bibtext> Yeon D, Lee Y, Ryou M-H, Lee YM. New flame-retardant composite separators based on metal hydroxides for lithium-ion batteries. Electrochim. Acta. 2015; 157: 282-289. 10.1016/j.electacta.2015.01.078. 1410.94013</bibtext> </blist> <blist> <bibtext> Yang C, Tong H, Luo C, Yuan S, Chen G. Boehmite particle coating modified microporous polyethylene membrane: a promising separator for lithium ion batteries. J. Power. Sources. 2017; 348: 80-86. 10.1016/j.jpowsour.2017.02.078. 1156.28307</bibtext> </blist> <blist> <bibtext> Cho J, Jung Y-C, Lee YS, Kim D-W. High performance separator coated with amino-functionalized SiO2 particles for safety enhanced lithium-ion batteries. J. Membr. Sci. 2017; 535: 151-157. 10.1016/j.memsci.2017.04.042. 1323.93056</bibtext> </blist> <blist> <bibtext> Yu Z, Wu S, Ji C, Tang F, Zhang L. Enhancing the β phase of poly(vinylidene fluoride) nanofibrous membranes for thermostable separators in lithium-ion batteries. ACS Appl. Nano Mater. 2023; 6; 12: 10340-10350. 10.1021/acsanm.3c01267</bibtext> </blist> <blist> <bibtext> Wu S, Ning J, Jiang F, Shi J, Huang F. Ceramic nanoparticle-decorated melt-electrospun PVDF nanofiber membrane with enhanced performance as a lithium-ion battery separator. ACS Omega. 2019; 4; 15: 16309-16317. 10.1021/acsomega.9b01541</bibtext> </blist> <blist> <bibtext> Liang X, Yang Y, Jin X, Huang Z, Kang F. The high performances of SiO2/Al2O3-coated electrospun polyimide fibrous separator for lithium-ion battery. J. Membr. Sci. 2015; 493: 1-7. 10.1016/j.memsci.2015.06.016</bibtext> </blist> <blist> <bibtext> Su M, Chen Y, Wang S, Wang H. Bifunctional separator with high thermal stability and lithium dendrite inhibition toward high safety lithium-ion batteries. Chin. Chem. Lett. 2023; 34; 5. 10.1016/j.cclet.2022.05.067. 1529.93053107553</bibtext> </blist> <blist> <bibtext> Zhang Y, Du S, Pang Y, Gao X, Luo D. Enhanced thermostability and electrochemical performance of separators based on an organic-inorganic composite binder composed of polyvinyl alcohol and inorganic phosphate for lithium ion batteries. J. Alloys Compd. 2022; 895. 10.1016/j.jallcom.2021.162646162646</bibtext> </blist> <blist> <bibtext> Parikh D, Jafta CJ, Thapaliya BP, Sharma J, Meyer HM. Al2O3/TiO2 coated separators: roll-to-roll processing and implications for improved battery safety and performance. J. Power Sources. 2021; 507. 10.1016/j.jpowsour.2021.230259230259</bibtext> </blist> <blist> <bibtext> Cheng EJ, Nishikawa K, Abe T, Kanamura K. Polymer-in-ceramic flexible separators for Li-ion batteries. Ionics. 2022; 28; 11: 5089-5097. 10.1007/s11581-022-04752-8</bibtext> </blist> <blist> <bibtext> Xiao W, Song J, Huang L, Yang Z, Qiao Q. PVA-ZrO2 multilayer composite separator with enhanced electrolyte property and mechanical strength for lithium-ion batteries. Ceram. Int. 2020; 46; 18: 29212-29221. 10.1016/j.ceramint.2020.08.095</bibtext> </blist> <blist> <bibtext> Xiang Y, Zhu W, Qiu W, Guo W, Lei J. SnO2 functionalized polyethylene separator with enhanced thermal stability for high performance lithium ion battery. ChemistrySelect. 2018; 3; 3: 911-916. 10.1002/slct.201702529</bibtext> </blist> <blist> <bibtext> Shekarian E, Jafari Nasr MR, Mohammadi T, Bakhtiari O, Javanbakht M. Preparation of 4A zeolite coated polypropylene membrane for lithium-ion batteries separator. J. Appl. Polym. Sci. 2019; 136; 32: 47841. 10.1002/app.47841</bibtext> </blist> <blist> <bibtext> Qiu Z, Yuan S, Wang Z, Shi L, Jo JH. Construction of silica-oxygen-borate hybrid networks on Al2O3-coated polyethylene separators realizing multifunction for high-performance lithium ion batteries. J. Power Sources. 2020; 472. 10.1016/j.jpowsour.2020.228445228445</bibtext> </blist> <blist> <bibtext> Li S, Lin J, Ding Y, Xu P, Guo X. Defects engineering of lightweight metal-organic frameworks-based electrocatalytic membrane for high-loading lithium-sulfur batteries. ACS Nano. 2021; 15; 8: 13803-13813. 10.1021/acsnano.1c05585</bibtext> </blist> <blist> <bibtext> Yang Y, Zhang J. Highly stable lithium-sulfur batteries based on laponite nanosheet-coated celgard separators. Adv. Energy Mater. 2018; 8; 25: 1801778. 10.1002/aenm.201801778</bibtext> </blist> <blist> <bibtext> Kim JY, Shin DO, Kim KM, Oh J, Kim J. Graphene oxide induced surface modification for functional separators in lithium secondary batteries. Sci. Rep. 2019; 9; 1: 2464. 10.1038/s41598-019-39237-8. 1441.94100</bibtext> </blist> <blist> <bibtext> Kwon K, Kim J, Roh K, Kim PJ, Choi J. Towards high performance Li metal batteries: surface functionalized graphene separator with improved electrochemical kinetics and stability. Electrochem. Commun. 2023; 157. 10.1016/j.elecom.2023.107598. 1537.74335107598</bibtext> </blist> <blist> <bibtext> Gong YJ, Heo JW, Lee H, Kim H, Cho J. Nonwoven rGO fiber-aramid separator for high-speed charging and discharging of Li metal anode. Adv. Energy Mater. 2020; 10; 27: 2001479. 10.1002/aenm.202001479</bibtext> </blist> <blist> <bibtext> Yang J, Cao C, Qiao W, Qiao J, Tang C. B/N co-doping rGO/BNNSs heterostructure with synergistic adsorption-electrocatalysis function enabling enhanced electrochemical performance of lithium-sulfur batteries. Chem. Eng. J. 2023; 467. 10.1016/j.cej.2023.143377143377</bibtext> </blist> <blist> <bibtext> Yang L, Sheng L, Gao X, Xie X, Bai Y. rGO/Li-Al-LDH composite nanosheets modified commercial polypropylene (PP) separator to suppress lithium dendrites for lithium metal battery. Electrochim. Acta. 2022; 430. 10.1016/j.electacta.2022.141073141073</bibtext> </blist> <blist> <bibtext> Zhang X, Ma F, Srinivas K, Yu B, Chen X. Fe3N@N-doped graphene as a lithiophilic interlayer for highly stable lithium metal batteries. Energy Storage Mater. 2022; 45: 656-666. 10.1016/j.ensm.2021.12.010. 07486814</bibtext> </blist> <blist> <bibtext> Zheng B, Yu L, Zhao Y, Xi J. Ultralight carbon flakes modified separator as an effective polysulfide barrier for lithium-sulfur batteries. Electrochim. Acta. 2019; 295: 910-917. 10.1016/j.electacta.2018.11.145. 1390.93716</bibtext> </blist> <blist> <bibtext> Pei H, Guan X, Chen X, Chen Y, Yang Y. Multifunctional tri-layer aramid nanofiber composite separators for high-energy-density lithium-sulfur batteries. Nano Energy. 2024; 126. 10.1016/j.nanoen.2024.109680109680</bibtext> </blist> <blist> <bibtext> Li H, Sun L, Zhao Y, Tan T, Zhang Y. A novel CuS/graphene-coated separator for suppressing the shuttle effect of lithium/sulfur batteries. Appl. Surf. Sci. 2019; 466: 309-319. 10.1016/j.apsusc.2018.10.046</bibtext> </blist> <blist> <bibtext> Sheng J, Zhang Q, Liu M, Han Z, Li C. Stabilized solid electrolyte interphase induced by ultrathin boron nitride membranes for safe lithium metal batteries. Nano Lett. 2021; 21; 19: 8447-8454. 10.1021/acs.nanolett.1c03106. 1471.35292</bibtext> </blist> <blist> <bibtext> Liu J, Cao D, Yao H, Liu D, Zhang X. Hexagonal boron nitride-coated polyimide ion track etched separator with enhanced thermal conductivity and high-temperature stability for lithium-ion batteries. ACS Appl. Energ. Mater. 2022; 5; 7: 8639-8649. 10.1021/acsaem.2c01163. 1217.26039</bibtext> </blist> <blist> <bibtext> Lee J, Lee C-L, Park K, Kim I-D. Synthesis of an Al2O3-coated polyimide nanofiber mat and its electrochemical characteristics as a separator for lithium ion batteries. J. Power Sources. 2014; 248: 1211-1217. 10.1016/j.jpowsour.2013.10.056. 1370.68074</bibtext> </blist> <blist> <bibtext> Choi J-A, Kim SH, Kim D-W. Enhancement of thermal stability and cycling performance in lithium-ion cells through the use of ceramic-coated separators. J. Power Sources. 2010; 195; 18: 6192-6196. 10.1016/j.jpowsour.2009.11.020. 1262.11020</bibtext> </blist> <blist> <bibtext> Luo H, Ma S, Liu J, Luo Y, Gao X. Raspberry-like micro-size polymer with high spherical shape-retention capability and adhesion as binder for ceramic separators. Eur. Polym. J. 2023; 194. 10.1016/j.eurpolymj.2023.112184. 1540.11050112184</bibtext> </blist> <blist> <bibtext> Na W, Koh KH, Lee AS, Cho S, Ok B. Binder-less chemical grafting of SiO2 nanoparticles onto polyethylene separators for lithium-ion batteries. J. Membr. Sci. 2019; 573: 621-627. 10.1016/j.memsci.2018.12.039</bibtext> </blist> <blist> <bibtext> Song Y-M, Qiu S-X, Feng S-X, Zuo R, Zhang Y-T. The role of carbon nanotubes in modern electrochemical energy storage: a comprehensive review. New Carbon Mater. 2024; 39: 1-38. 10.1016/S1872-5805(24)60878-4. 1184.92032</bibtext> </blist> <blist> <bibtext> Ye Z, Jiang Y, Li L, Wu F, Chen R. Rational design of MOF-based materials for next-generation rechargeable batteries. Nano-Micro Lett. 2021; 13; 1: 203. 10.1007/s40820-021-00726-z. 1206.65237</bibtext> </blist> <blist> <bibtext> Yang Y, Sun Z, Wu Y, Liang Z, Li F. Porous organic framework materials (MOF, COF, and HOF) as the multifunctional separator for rechargeable lithium metal batteries. Small. 2024; 20: 2401457. 10.1002/smll.202401457</bibtext> </blist> <blist> <bibtext> Zhu D, Xu G, Barnes M, Li Y, Tseng C-P. Covalent organic frameworks for batteries. Adv. Funct. Mater. 2021; 31; 32: 2100505. 10.1002/adfm.202100505</bibtext> </blist> <blist> <bibtext> Lu Y, Oh K-S, Seo J-M, Qin W, Lee S. A solvent-free covalent organic framework single-ion conductor based on ion-dipole interaction for all-solid-state lithium organic batteries. Nano-Micro Lett. A. 2024; 16: 265. 10.1007/s40820-024-01485-3</bibtext> </blist> <blist> <bibtext> Lu Y, Zhou R, Wang N, Yang Y, Zheng Z. Engineer nanoscale defects into selective channels: MOF-enhanced Li+ separation by porous layered double hydroxide membrane. Nano-Micro Lett. 2023; 15; 1: 147. 10.1007/s40820-023-01101-w</bibtext> </blist> <blist> <bibtext> Lu J, Zhang H, Hou J, Li X, Hu X. Efficient metal ion sieving in rectifying subnanochannels enabled by metal-organic frameworks. Nat. Mater. 2020; 19; 7: 767-774. 10.1038/s41563-020-0634-7</bibtext> </blist> <blist> <bibtext> Hao Z, Wu Y, Zhao Q, Tang J, Zhang Q. Functional separators regulating ion transport enabled by metal-organic frameworks for dendrite-free lithium metal anodes. Adv. Funct. Mater. 2021; 31; 33: 2102938. 10.1002/adfm.202102938</bibtext> </blist> <blist> <bibtext> Li J, Chen L, Wang F, Qin Z, Zhang Y. Anionic metal-organic framework modified separator boosting efficient Li-ion transport. Chem. Eng. J. 2023; 451. 10.1016/j.cej.2022.138536138536</bibtext> </blist> <blist> <bibtext> Li X, Zhang F, Zhang M, Zhou Z, Zhou X. Chromium-based metal-organic framework coated separator for improving electrochemical performance and safety of lithium-ion battery. J. Energy Storage. 2023; 59. 10.1016/j.est.2022.106473. 1297.68208106473</bibtext> </blist> <blist> <bibtext> Bian S, Huang G, Xuan Y, He B, Liu J. Pore surface engineering of covalent organic framework membrane by alkyl chains for lithium based batteries. J. Membr. Sci. 2023; 669. 10.1016/j.memsci.2022.121268121268</bibtext> </blist> <blist> <bibtext> An Q, Wang H-E, Zhao G, Wang S, Xu L. Understanding dual-polar group functionalized COFs for accelerating Li-ion transport and dendrite-free deposition in lithium metal anodes. Energy Envion. Mater. 2023; 6; 2. 10.1002/eem2.12345e12345</bibtext> </blist> <blist> <bibtext> Yao S, Yang Y, Liang Z, Chen J, Ding J. A dual-functional cationic covalent organic frameworks modified separator for high energy lithium metal batteries. Adv. Funct. Mater. 2023; 33; 13: 2212466. 10.1002/adfm.202212466</bibtext> </blist> <blist> <bibtext> Wang C, Li W, Jin Y, Liu J, Wang H. Functional separator enabled by covalent organic frameworks for high-performance Li metal batteries. Small. 2023; 19; 28: 2300023. 10.1002/smll.202300023. 1543.83040</bibtext> </blist> <blist> <bibtext> Li G-H, Yang Y, Cai J-C, Wen T, Zhuang L-C. Lithiophilic aromatic sites and porosity of COFs for a stable lithium metal anode. ACS Appl. Energ. Mater. 2022; 5; 11: 13554-13561. 10.1021/acsaem.2c02233</bibtext> </blist> <blist> <bibtext> Wang Y, Sun R, Chen Y, Wang X, Yang Y. Highly crystalline covalent triazine frameworks modified separator for lithium metal batteries. Energy Mater. 2024; 4; 5: 400056. 10.20517/energymater.2023.133. 1544.74086</bibtext> </blist> <blist> <bibtext> Liu Y, Tao X, Wang Y, Jiang C, Ma C. Self-assembled monolayers direct a LiF-rich interphase toward long-life lithium metal batteries. Science. 2022; 375; 6582: 739-745. 10.1126/science.abn1818. 1546.90083</bibtext> </blist> <blist> <bibtext> He L, Qiu T, Xie C, Tuo X. A phase separation method toward PPTA-polypropylene nanocomposite separator for safe lithium ion batteries. J. Appl. Polym. Sci. 2018; 135; 39: 46697. 10.1002/app.46697</bibtext> </blist> <blist> <bibtext> Kim KJ, Kim J-H, Park M-S, Kwon HK, Kim H. Enhancement of electrochemical and thermal properties of polyethylene separators coated with polyvinylidene fluoride-hexafluoropropylene co-polymer for Li-ion batteries. J. Power Sources. 2012; 198: 298-302. 10.1016/j.jpowsour.2011.09.086. 1262.80026</bibtext> </blist> <blist> <bibtext> Lee H, Alcoutlabi M, Watson JV, Zhang X. Electrospun nanofiber-coated separator membranes for lithium-ion rechargeable batteries. J. Appl. Polym. Sci. 2013; 129; 4: 1939-1951. 10.1002/app.38894</bibtext> </blist> <blist> <bibtext> Kim D-W, Ko J-M, Chun J-H, Kim S-H, Park J-K. Electrochemical performances of lithium-ion cells prepared with polyethylene oxide-coated separators. Electrochem. Commun. 2001; 3; 10: 535-538. 10.1016/S1388-2481(01)00214-4. 1418.94076</bibtext> </blist> <blist> <bibtext> Tang W, Zhao T, Wang K, Yu T, Lv R. Dendrite-free lithium metal batteries enabled by coordination chemistry in polymer-ceramic modified separators. Adv. Funct. Mater. 2024; 34; 18: 2314045. 10.1002/adfm.202314045</bibtext> </blist> <blist> <bibtext> Park J-H, Park W, Kim JH, Ryoo D, Kim HS. Close-packed poly(methyl methacrylate) nanoparticle arrays-coated polyethylene separators for high-power lithium-ion polymer batteries. J. Power Sources. 2011; 196; 16: 7035-7038. 10.1016/j.jpowsour.2010.09.102. 07493965</bibtext> </blist> <blist> <bibtext> Xiong M, Tang H, Wang Y, Pan M. Ethylcellulose-coated polyolefin separators for lithium-ion batteries with improved safety performance. Carbohydr. Polym. 2014; 101: 1140-1146. 10.1016/j.carbpol.2013.10.073. 1147.35054</bibtext> </blist> <blist> <bibtext> Rao MM, Liu JS, Li WS, Liang Y, Zhou DY. Preparation and performance analysis of PE-supported P(AN-co-MMA) gel polymer electrolyte for lithium ion battery application. J. Membr. Sci. 2008; 322; 2: 314-319. 10.1016/j.memsci.2008.06.004. 1340.05156</bibtext> </blist> <blist> <bibtext> Zhang C, Liang H-Q, Pi J-K, Wu G-P, Xu Z-K. Polypropylene separators with robust mussel-inspired coatings for high lithium-ion battery performances. Chin. J. Polym. Sci. 2019; 37; 10: 1015-1022. 10.1007/s10118-019-2310-4</bibtext> </blist> <blist> <bibtext> Zhang J, Liu Z, Kong Q, Zhang C, Pang S. Renewable and superior thermal-resistant cellulose-based composite nonwoven as lithium-ion battery separator. ACS Appl. Mater. Interfaces. 2013; 5; 1: 128-134. 10.1021/am302290n</bibtext> </blist> <blist> <bibtext> Yu J, Dong N, Liu B, Tian G, Qi S. A newly-developed heat-resistance polyimide microsphere coating to enhance the thermal stability of commercial polyolefin separators for advanced lithium-ion battery. Chem. Eng. J. 2022; 442. 10.1016/j.cej.2022.136314136314</bibtext> </blist> <blist> <bibtext> Li D, Shi D, Yuan Z, Feng K, Zhang H. A low cost shutdown sandwich-like composite membrane with superior thermo-stability for lithium-ion battery. J. Membr. Sci. 2017; 542: 1-7. 10.1016/j.memsci.2017.07.051. 1413.65352</bibtext> </blist> <blist> <bibtext> Shi C, Zhang P, Huang S, He X, Yang P. Functional separator consisted of polyimide nonwoven fabrics and polyethylene coating layer for lithium-ion batteries. J. Power Sources. 2015; 298: 158-165. 10.1016/j.jpowsour.2015.08.008</bibtext> </blist> <blist> <bibtext> Zhai Y, Wang N, Mao X, Si Y, Yu J. Sandwich-structured PVDF/PMIA/PVDF nanofibrous separators with robust mechanical strength and thermal stability for lithium ion batteries. J. Mater. Chem. A. 2014; 2; 35: 14511-14518. 10.1039/C4TA02151G</bibtext> </blist> <blist> <bibtext> Li Z, Xiong Y, Sun S, Zhang L, Li S. Tri-layer nonwoven membrane with shutdown property and high robustness as a high-safety lithium ion battery separator. J. Membr. Sci. 2018; 565: 50-60. 10.1016/j.memsci.2018.07.094. 1400.37072</bibtext> </blist> <blist> <bibtext> Jeon H, Yeon D, Lee T, Park J, Ryou M-H. A water-based Al2O3 ceramic coating for polyethylene-based microporous separators for lithium-ion batteries. J. Power Sources. 2016; 315: 161-168. 10.1016/j.jpowsour.2016.03.037. 1412.62073</bibtext> </blist> <blist> <bibtext> Li C, Liu S, Shi C, Liang G, Lu Z. Two-dimensional molecular brush-functionalized porous bilayer composite separators toward ultrastable high-current density lithium metal anodes. Nat. Commun. 2019; 10; 1: 1363. 10.1038/s41467-019-09211-z. 1165.76058</bibtext> </blist> <blist> <bibtext> Deng Y, Song X, Ma Z, Zhang X, Shu D. Al2O3/PVDF-HFP-CMC/PE separator prepared using aqueous slurry and post-hot-pressing method for polymer lithium-ion batteries with enhanced safety. Electrochim. Acta. 2016; 212: 416-425. 10.1016/j.electacta.2016.07.016</bibtext> </blist> <blist> <bibtext> Zhang Z, Yuan W, Li L. Enhanced wettability and thermal stability of nano-SiO2/poly(vinyl alcohol)-coated polypropylene composite separators for lithium-ion batteries. Particuology. 2018; 37: 91-98. 10.1016/j.partic.2017.10.001</bibtext> </blist> <blist> <bibtext> Shi C, Dai J, Li C, Shen X, Peng L. A modified ceramic-coating separator with high-temperature stability for lithium-ion battery. Polymers. 2017; 9; 5: 159. 10.3390/polym9050159. 1060.68029</bibtext> </blist> <blist> <bibtext> Zuo X, Wu J, Ma X, Deng X, Cai J. A poly(vinylidene fluoride)/ethyl cellulose and amino-functionalized nano-SiO2 composite coated separator for 5V high-voltage lithium-ion batteries with enhanced performance. J. Power. Sources. 2018; 407: 44-52. 10.1016/j.jpowsour.2018.10.056</bibtext> </blist> <blist> <bibtext> Yang P, Zhang P, Shi C, Chen L, Dai J. The functional separator coated with core–shell structured silica-poly(methyl methacrylate) sub-microspheres for lithium-ion batteries. J. Membr. Sci. 2015; 474: 148-155. 10.1016/j.memsci.2014.09.047</bibtext> </blist> <blist> <bibtext> Wang Z, Li X, Dong N, Liu B, Tian G. Novel ZrO2@polyimde nano-microspheres-coated polyethylene separators for high energy density and high safety Li-ion battery. Mater. Today Energy. 2022; 30. 10.1016/j.mtener.2022.101155101155</bibtext> </blist> <blist> <bibtext> Fu W, Xu R, Zhang X, Tian Z, Huang H. Enhanced wettability and electrochemical performance of separators for lithium-ion batteries by coating core-shell structured silica-poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) particles. J. Power. Sources. 2019; 436. 10.1016/j.jpowsour.2019.226839226839</bibtext> </blist> <blist> <bibtext> Kim PJ, Pol VG. High performance lithium metal batteries enabled by surface tailoring of polypropylene separator with a polydopamine/graphene layer. Adv. Energy Mater. 2018; 8; 36: 1802665. 10.1002/aenm.201802665</bibtext> </blist> <blist> <bibtext> Shin D-M, Son H, Park KU, Choi J, Suk J. Al2O3 ceramic/nanocellulose-coated non-woven separator for lithium-metal batteries. Coatings. 2023; 13; 5: 916. 10.3390/coatings13050916</bibtext> </blist> <blist> <bibtext> Luo D, Chen M, Xu J, Yin X, Wu J. Polyphenylene sulfide nonwoven-based composite separator with superior heat-resistance and flame retardancy for high power lithium ion battery. Compos. Sci. Technol. 2018; 157: 119-125. 10.1016/j.compscitech.2018.01.023</bibtext> </blist> <blist> <bibtext> Lee Y, Lee H, Lee T, Ryou M-H, Lee YM. Synergistic thermal stabilization of ceramic/co-polyimide coated polypropylene separators for lithium-ion batteries. J. Power Sources. 2015; 294: 537-544. 10.1016/j.jpowsour.2015.06.106. 1055.76510</bibtext> </blist> <blist> <bibtext> Li X, Sun X. Interface design and development of coating materials in lithium-sulfur batteries. Adv. Funct. Mater. 2018; 28; 30: 1801323. 10.1002/adfm.201801323</bibtext> </blist> <blist> <bibtext> Sun F, He X, Jiang X, Osenberg M, Li J. Advancing knowledge of electrochemically generated lithium microstructure and performance decay of lithium ion battery by synchrotron X-ray tomography. Mater. Today. 2019; 27: 21-32. 10.1016/j.mattod.2018.11.003</bibtext> </blist> <blist> <bibtext> Ali S, Waqas M, Chen N, Chen D, Han Y. Three-dimensional twisted fiber composite as high-loading cathode support for lithium sulfur batteries. Compos. Pt. B-Eng. 2019; 174. 10.1016/j.compositesb.2019.107025. 1487.26033107025</bibtext> </blist> <blist> <bibtext> Cha H, Lee Y, Kim J, Park M, Cho J. Flexible 3D interlocking lithium-ion batteries. Adv. Energy Mater. 2018; 8; 30: 1801917. 10.1002/aenm.201801917</bibtext> </blist> <blist> <bibtext> Yue W, Li X, Zhao J, Gao Y, Gao N. Ultra-small ferromagnetic Fe3O4 nanoparticles modified separator for high-rate and long cycling lithium-sulfur batteries. Batteries Supercaps. 2022; 5; 5. 10.1002/batt.202200020. 1488.05135e202200020</bibtext> </blist> <blist> <bibtext> Yang Y, Mu P, Li B, Li A, Zhang J. In situ separator modification with an N-rich conjugated microporous polymer for the effective suppression of polysulfide shuttle and Li dendrite growth. ACS Appl. Mater. Interfaces. 2022; 14; 43: 49224-49232. 10.1021/acsami.2c15812. 1477.35172</bibtext> </blist> <blist> <bibtext> Zhao J, Yan G, Zhang X, Feng Y, Li N. In situ interfacial polymerization of lithiophilic COF@PP and POP@PP separators with lower shuttle effect and higher ion transport for high-performance Li-S batteries. Chem. Eng. J. 2022; 442. 10.1016/j.cej.2022.136352136352</bibtext> </blist> <blist> <bibtext> Zhang L, Wan F, Wang X, Cao H, Dai X. Dual-functional graphene carbon as polysulfide trapper for high-performance lithium sulfur batteries. ACS Appl. Mater. Interfaces. 2018; 10; 6: 5594-5602. 10.1021/acsami.7b18894. 1351.35154</bibtext> </blist> <blist> <bibtext> Vijayakumar V, Anothumakkool B, Kurungot S, Winter M, Nair JR. In situpolymerization process: an essential design tool for lithium polymer batteries. Energy Environ. Sci. 2021; 14; 5: 2708-2788. 10.1039/d0ee03527k</bibtext> </blist> <blist> <bibtext> Cao Y, Wu H, Li G, Liu C, Cao L. Ion selective covalent organic framework enabling enhanced electrochemical performance of lithium-sulfur batteries. Nano Lett. 2021; 21; 7: 2997-3006. 10.1021/acs.nanolett.1c00163. 1479.05003</bibtext> </blist> <blist> <bibtext> Wu S, Yao Y, Nie X, Yu Z, Yu Y. Interfacial engineering of binder-free janus separator with ultra-thin multifunctional layer for simultaneous enhancement of both metallic Li anode and sulfur cathode. Small. 2022; 18; 28: 2202651. 10.1002/smll.202202651</bibtext> </blist> <blist> <bibtext> Das M, Ghosh K, Raja MW. Flexible ceramic based 'paper separator' with enhanced safety for high performance lithium-ion batteries: probing the effect of ceramics impregnation on electrochemical performances. J. Power Sources. 2024; 606. 10.1016/j.jpowsour.2024.234573234573</bibtext> </blist> <blist> <bibtext> Gong J, Shi S, Cheng S, Yang K, Zheng P. High-performance and safe lithium-ion battery with precise ultrathin Al2O3-coated polyethylene separator. Appl. Surf. Sci. 2024; 659. 10.1016/j.apsusc.2024.159918159918</bibtext> </blist> <blist> <bibtext> Huang X. Separator technologies for lithium-ion batteries. J. Solid State Electrochem. 2010; 15; 4: 649-662. 10.1007/s10008-010-1264-9. 0729.73280</bibtext> </blist> <blist> <bibtext> Jeon H, Choi J, Ryou M-H, Lee YM. Comparative study of the adhesion properties of ceramic composite separators using a surface and interfacial cutting analysis system for lithium-ion batteries. ACS Omega. 2017; 2; 5: 2159-2164. 10.1021/acsomega.7b00493. 0954.76507</bibtext> </blist> <blist> <bibtext> Liu Y, Zhang R, Wang J, Wang Y. Current and future lithium-ion battery manufacturing. iScience. 2021; 24; 4: 102332. 10.1016/j.isci.2021.102332. 1488.90088</bibtext> </blist> <blist> <bibtext> Kong L, Wang Y, Yu H, Liu B, Qi S. In situ armoring: A robust, high-wettability, and fire-resistant hybrid separator for advanced and safe batteries. ACS Appl. Mater. Interfaces. 2018; 11; 3: 2978-2988. 10.1021/acsami.8b17521. 1490.35226</bibtext> </blist> <blist> <bibtext> Dong G, Liu B, Kong L, Wang Y, Tian G. Neoteric polyimide nanofiber encapsulated by the TiO2 armor as the tough, highly wettable, and flame-retardant separator for advanced lithium-ion batteries. ACS Sustain. Chem. Eng. 2019; 7; 21: 17643-17652. 10.1021/acssuschemeng.9b03525</bibtext> </blist> <blist> <bibtext> Jung YS, Cavanagh AS, Gedvilas L, Widjonarko NE, Scott ID. Improved functionality of lithium-ion batteries enabled by atomic layer deposition on the porous microstructure of polymer separators and coating electrodes. Adv. Energy Mater. 2012; 2; 8: 1022-1027. 10.1002/aenm.201100750</bibtext> </blist> <blist> <bibtext> Wang W, Yuan Y, Wang J, Zhang Y, Liao C. Enhanced electrochemical and safety performance of lithium metal batteries enabled by the atom layer deposition on PVDF-HFP separator. ACS Appl. Energ. Mater. 2019; 2; 6: 4167-4174. 10.1021/acsaem.9b00383. 1426.93151</bibtext> </blist> <blist> <bibtext> Lee JW, Soomro AM, Waqas M, Khalid MAU, Choi KH. A highly efficient surface modified separator fabricated with atmospheric atomic layer deposition for high temperature lithium ion batteries. Int. J. Energy Res. 2020; 44; 8: 7035-7046. 10.1002/er.5371</bibtext> </blist> <blist> <bibtext> Chen H, Lin Q, Xu Q, Yang Y, Shao Z. Plasma activation and atomic layer deposition of TiO2 on polypropylene membranes for improved performances of lithium-ion batteries. J. Membr. Sci. 2014; 458: 217-224. 10.1016/j.memsci.2014.02.004</bibtext> </blist> <blist> <bibtext> Wu D, Dong N, Wang R, Qi S, Liu B. In situ construction of high-safety and non-flammable polyimide "ceramic" lithium-ion battery separator via SiO2 nano-encapsulation. Chem. Eng. J. 2021; 420. 10.1016/j.cej.2021.129992129992</bibtext> </blist> <blist> <bibtext> Dong N, Wang J, Chen N, Liu B, Tian G. In situ reinforcing: ZrO2-armored hybrid polyimide separators for advanced and safe lithium-ion batteries. ACS Sustain. Chem. Eng. 2021; 9; 18: 6250-6257. 10.1021/acssuschemeng.0c08818</bibtext> </blist> <blist> <bibtext> Liu X, Chen P, Wang W, Li W, Rao Y. In situ reduction growth Sn-MoS2 on CNFs as advanced separator coating for improved-performance lithium sulfur batteries. J. Alloys Compd. 2024; 979. 10.1016/j.jallcom.2024.173432173432</bibtext> </blist> <blist> <bibtext> Lu X, Wang H, Liu X, Song Z, Jiang N. Functional separators prepared via in-situ growth of hollow CoSO4 hydrate arrays on pristine polypropylene membrane for high performance lithium-sulfur batteries. J. Alloys Compd. 2020; 838. 10.1016/j.jallcom.2020.155618155618</bibtext> </blist> <blist> <bibtext> Wang J, Wang K, Yang Z, Li X, Gao J. Effective stabilization of long-cycle lithium-sulfur batteries utilizing in situ prepared graphdiyne-modulated separators. ACS Sustain. Chem. Eng. 2019; 8; 4: 1741-1750. 10.1021/acssuschemeng.9b04970. 1418.60077</bibtext> </blist> <blist> <bibtext> Ali K, Ali J, Mehdi SM, Choi K-H, An YJ. Rapid fabrication of Al2O3 encapsulations for organic electronic devices. Appl. Surf. Sci. 2015; 353: 1186-1194. 10.1016/j.apsusc.2015.07.032. 1350.65141</bibtext> </blist> <blist> <bibtext> Xu Q, Yang Y, Wang X, Wang Z, Jin W. Atomic layer deposition of alumina on porous polytetrafluoroethylene membranes for enhanced hydrophilicity and separation performances. J. Membr. Sci. 2012; 415–416: 435-443. 10.1016/j.memsci.2012.05.031. 1260.93114</bibtext> </blist> <blist> <bibtext> Xu Q, Yang Y, Yang J, Wang X, Wang Z. Plasma activation of porous polytetrafluoroethylene membranes for superior hydrophilicity and separation performances via atomic layer deposition of TiO2. J. Membr. Sci. 2013; 443: 62-68. 10.1016/j.memsci.2013.04.061. 1262.42017</bibtext> </blist> <blist> <bibtext> George SM. Atomic layer deposition: an overview. Chem. Rev. 2010; 110; 1: 111-131. 10.1021/cr900056b. 0971.60004</bibtext> </blist> <blist> <bibtext> Jin Y, Yu H, Liang X. Understanding the roles of atomic layer deposition in improving the electrochemical performance of lithium-ion batteries. Appl. Phys. Rev. 2021; 8; 3. 10.1063/5.0048337031301</bibtext> </blist> <blist> <bibtext> Wang X, Yushin G. Chemical vapor deposition and atomic layer deposition for advanced lithium ion batteries and supercapacitors. Energy Environ. Sci. 2015; 8; 7: 1889-1904. 10.1039/c5ee01254f. 1338.34124</bibtext> </blist> <blist> <bibtext> Cao S, Tan J, Ma L, Liu Y, He Q. Covalent organic frameworks-based functional separators for rechargeable batteries: design, mechanism, and applications. Energy Storage Mater. 2024; 66; 25. 10.1016/j.ensm.2024.103232103232</bibtext> </blist> <blist> <bibtext> Huang W, Li X, Yang X, Zhang X, Wang H. The recent progress and perspectives on metal- and covalent-organic framework based solid-state electrolytes for lithium-ion batteries. Mat. Chem. Front. 2021; 5; 9: 3593-3613. 10.1039/d0qm00936a. 07497689</bibtext> </blist> <blist> <bibtext> Chen P, Ren H, Yan L, Shen J, Wang T. Metal-organic frameworks enabled high-performance separators for safety-reinforced lithium ion battery. ACS Sustain. Chem. Eng. 2019; 7; 19: 16612-16619. 10.1021/acssuschemeng.9b03854</bibtext> </blist> <blist> <bibtext> Zhu T, Kong Y, Lyu B, Cao L, Shi B. 3D covalent organic framework membrane with fast and selective ion transport. Nat. Commun. 2023; 14; 1: 5926. 10.1038/s41467-023-41555-5. 1525.93117</bibtext> </blist> <blist> <bibtext> Banerjee R, Phan A, Wang B, Knobler C, Furukawa H. High-throughput synthesis of zeolitic imidazolate frameworks and application to CO2 capture. Science. 2008; 319; 5865: 939-943. 10.1126/science.1152516</bibtext> </blist> <blist> <bibtext> Lin G, Jia K, Bai Z, Liu C, Liu S. Metal-organic framework sandwiching porous super-engineering polymeric membranes as anionphilic separators for dendrite-free lithium metal batteries. Adv. Funct. Mater. 2022; 32; 47: 2207969. 10.1002/adfm.202207969</bibtext> </blist> <blist> <bibtext> Zhou C, He Q, Li Z, Meng J, Hong X. A robust electrospun separator modified with in situ grown metal-organic frameworks for lithium-sulfur batteries. Chem. Eng. J. 2020; 395. 10.1016/j.cej.2020.124979124979</bibtext> </blist> <blist> <bibtext> Zang Y, Pei F, Huang J, Fu Z, Xu G. Large-area preparation of crack-free crystalline microporous conductive membrane to upgrade high energy lithium-sulfur batteries. Adv. Energy Mater. 2018; 8; 31: 1802052. 10.1002/aenm.201802052</bibtext> </blist> <blist> <bibtext> Liu J, Wang J, Zhu L, Chen X, Yi G. In situ grown MOFs and PVDF-HFP co-modified aramid gel nanofiber separator for high-safety lithium-sulfur batteries. J. Mater. Chem. A. 2022; 10; 26: 14098-14110. 10.1039/d2ta03301a</bibtext> </blist> <blist> <bibtext> Li M, Yan G, Zou P, Ji H, Wang H. Dynamic disulfide bonds contained covalent organic framework modified separator as efficient inhibit polysulfide shuttling in Li-S batteries. ACS Sustain. Chem. Eng. 2022; 10; 41: 13638-13649. 10.1021/acssuschemeng.2c03498</bibtext> </blist> <blist> <bibtext> Han L, Yang Y, Sun S, Yue J, Li J. Polydopamine-assisted in situ formation of a covalent organic framework on single-walled carbon nanotubes to multifunctionalize separators for advanced lithium-sulfur batteries. ACS Sustain. Chem. Eng. 2023; 11; 23: 8431-8441. 10.1021/acssuschemeng.2c07568</bibtext> </blist> <blist> <bibtext> Yu J, Mu C, Yan B, Qin X, Shen C. Nanoparticle/MOF composites: preparations and applications. Mater. Horizons. 2017; 4; 4: 557-569. 10.1039/c6mh00586a. 1105.90113</bibtext> </blist> <blist> <bibtext> Wen H, Li B, Yuan D, Wang H, Yildirim T. A porous metal-organic framework with an elongated anthracene derivative exhibiting a high working capacity for the storage of methane. J. Mater. Chem. A. 2014; 2; 29: 11516-11522. 10.1039/c4ta01860e. 1525.91035</bibtext> </blist> <blist> <bibtext> Zhao Y, Song Z, Li X, Sun Q, Cheng N. Metal organic frameworks for energy storage and conversion. Energy Storage Mater. 2016; 2: 35-62. 10.1016/j.ensm.2015.11.005. 1531.81030</bibtext> </blist> <blist> <bibtext> Jahan M, Bao Q, Yang J-X, Loh KP. Structure-directing role of graphene in the synthesis of metal-organic framework nanowire. J. Am. Chem. Soc. 2010; 132; 41: 14487-14495. 10.1021/ja105089w</bibtext> </blist> <blist> <bibtext> Yao J, He M, Wang K, Chen R, Zhong Z. High-yield synthesis of zeolitic imidazolate frameworks from stoichiometric metal and ligand precursor aqueous solutions at room temperature. CrystEngComm. 2013; 15; 18: 3601-3606. 10.1039/c3ce27093a</bibtext> </blist> <blist> <bibtext> Park KS, Ni Z, Côté AP, Choi JY, Huang R. Exceptional chemical and thermal stability of zeolitic imidazolate frameworks. Proc. Natl. Acad. Sci. U.S.A. 2006; 103; 27: 10186-10191. 10.1073/pnas.0602439103</bibtext> </blist> <blist> <bibtext> Phan A, Doonan CJ, Uribe-Romo FJ, Knobler CB, O'Keeffe M. Synthesis, structure, and carbon dioxide capture properties of zeolitic imidazolate frameworks. Acc. Chem. Res. 2010; 43; 1: 58-67. 10.1021/ar900116g</bibtext> </blist> <blist> <bibtext> Yang Y, Yao S, Wu Y, Ding J, Liang Z. Hydrogen-bonded organic framework as superior separator with high lithium affinity C=N bond for low N/P ratio lithium metal batteries. Nano Lett. 2023; 23: 5061-5069. 10.1021/acs.nanolett.3c00801</bibtext> </blist> <blist> <bibtext> Yoo J, Cho S-J, Jung GY, Kim SH, Choi K-H. COF-net on CNT-net as a molecularly designed, hierarchical porous chemical trap for polysulfides in lithium-sulfur batteries. Nano Lett. 2016; 16; 5: 3292-3300. 10.1021/acs.nanolett.6b00870. 1360.68282</bibtext> </blist> <blist> <bibtext> Chen Y, Wang K, Zhang L, Guo W, Li M. Oriented carbon fiber/PEO functional modified polyethylene separator for high-performance lithium metal batteries. Mater. Lett. 2023; 332. 10.1016/j.matlet.2022.133511133511</bibtext> </blist> <blist> <bibtext> Sohn J-Y, Im J-S, Shin J, Nho Y-C. PVDF-HFP/PMMA-coated PE separator for lithium ion battery. J. Solid State Electrochem. 2011; 16; 2: 551-556. 10.1007/s10008-011-1379-7. 1368.68131</bibtext> </blist> <blist> <bibtext> Wang Y, Yin C, Song Z, Wang Q, Lan Y. Application of PVDF organic particles coating on polyethylene separator for lithium ion batteries. Materials. 2019; 12; 19: 3125. 10.3390/ma12193125. 1504.57047</bibtext> </blist> <blist> <bibtext> Song J, Ryou M-H, Son B, Lee J-N, Lee DJ. Co-polyimide-coated polyethylene separators for enhanced thermal stability of lithium ion batteries. Electrochim. Acta. 2012; 85: 524-530. 10.1016/j.electacta.2012.06.078. 1137.76653</bibtext> </blist> <blist> <bibtext> Shi C, Dai J, Huang S, Li C, Shen X. A simple method to prepare a polydopamine modified core-shell structure composite separator for application in high-safety lithium-ion batteries. J. Membr. Sci. 2016; 518: 168-177. 10.1016/j.memsci.2016.06.046</bibtext> </blist> <blist> <bibtext> Zhou M, Zhang Z, Xu J, Wei J, Yu J. PDA modified commercial paper separator engineering with excellent lithiophilicity and mechanical strength for lithium metal batteries. J. Electroanal. Chem. 2020; 868. 10.1016/j.jelechem.2020.114195114195</bibtext> </blist> <blist> <bibtext> Pan L, Wang H, Wu C, Liao C, Li L. Tannic-acid-coated polypropylene membrane as a separator for lithium-ion batteries. ACS Appl. Mater. Interfaces. 2015; 7; 29: 16003-16010. 10.1021/acsami.5b04245</bibtext> </blist> <blist> <bibtext> Wang H, Pan L, Wu C, Gao D, Chen S. Pyrogallic acid coated polypropylene membranes as separators for lithium-ion batteries. J. Mater. Chem. A. 2015; 3; 41: 20535-20540. 10.1039/c5ta06381g</bibtext> </blist> <blist> <bibtext> Li J, Bi S, Li M, Xian Y, Shui Y. Rapid homogenization preparation of the mussel-inspired hydrophilic separator for high power lithium-ion batteries. J. Appl. Polym. Sci. 2020; 137; 36. 10.1002/app.49052. 0988.05506e49052</bibtext> </blist> <blist> <bibtext> Zhang Y, Yuan J, Song Y, Yin X, Sun C. Tannic acid/polyethyleneimine-decorated polypropylene separators for Li-ion batteries and the role of the interfaces between separator and electrolyte. Electrochim. Acta. 2018; 275: 25-31. 10.1016/j.electacta.2018.03.099</bibtext> </blist> <blist> <bibtext> Zheng S, Mo L, Chen K, Chen A, Zhang X. Precise control of Li+ directed transport via electronegative polymer brushes on polyolefin separators for dendrite-free lithium deposition. Adv. Funct. Mater. 2022; 32; 41: 2201430. 10.1002/adfm.202201430. 1492.35253</bibtext> </blist> <blist> <bibtext> Guan X, Zhao Y, Pei H, Zhao M, Wang Y. Metalloporphyrin conjugated porous polymer in-situ grown on a celgard separator as multifunctional polysulfide barrier and catalyst for high-performance Li-S batteries. Chem. Eng. J. 2023. 10.1016/j.cej.2023.144733. 0925.81391</bibtext> </blist> <blist> <bibtext> Kang SM, You I, Cho WK, Shon HK, Lee TG. One-step modification of superhydrophobic surfaces by a mussel-inspired polymer coating. Angew. Chem. Int. Ed. 2010; 49; 49: 9401-9404. 10.1002/anie.201004693. 1377.30041</bibtext> </blist> <blist> <bibtext> Lee H, Lee BP, Messersmith PB. A reversible wet/dry adhesive inspired by mussels and geckos. Nature. 2007; 448; 7151: 338-341. 10.1038/nature05968. 0790.16019</bibtext> </blist> <blist> <bibtext> Lee H, Dellatore SM, Miller WM, Messersmith PB. Mussel-inspired surface chemistry for multifunctional coatings. Science. 2007; 318; 5849: 426-430. 10.1126/science.1147241</bibtext> </blist> <blist> <bibtext> Novak I, Šeruga M, Komorsky-Lovrić Š. Square-wave and cyclic voltammetry of epicatechin gallate on glassy carbon electrode. J. Electroanal. Chem. 2009; 631; 1–2: 71-75. 10.1016/j.jelechem.2009.03.005</bibtext> </blist> <blist> <bibtext> Chen J, Bai J. Chemiluminescence flow sensor with immobilized reagent for the determination of pyrogallol based on potassium hexacyanoferrate (III) oxidation. Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. 2008; 71; 3: 989-992. 10.1016/j.saa.2008.02.022. 1466.90052</bibtext> </blist> <blist> <bibtext> Bieker G, Winter M, Bieker P. Electrochemical in situ investigations of SEI and dendrite formation on the lithium metal anode. PCCP. 2015; 17; 14: 8670-8679. 10.1039/c4cp05865h. 1531.11044</bibtext> </blist> <blist> <bibtext> Yang H, Wu M, Li Y, Chen Y, Wan L. Effects of polyethyleneimine molecular weight and proportion on the membrane hydrophilization by codepositing with dopamine. J. Appl. Polym. Sci. 2016; 133; 32: 43792. 10.1002/app.43792</bibtext> </blist> <blist> <bibtext> Tang S, Guo W, Fu Y. Advances in composite polymer electrolytes for lithium batteries and beyond. Adv. Energy Mater. 2020; 11; 2: 2000802. 10.1002/aenm.202000802. 1103.35340</bibtext> </blist> <blist> <bibtext> Luo J, Zhang Q. In situ polymer gel electrolyte in boosting scalable fibre lithium battery applications. Nano-Micro Lett. 2024; 16: 230. 10.1007/s40820-024-01451-z. 1476.90022</bibtext> </blist> <blist> <bibtext> Zou S, Yang Y, Wang J, Zhou X, Wan X. In situ polymerization of solid-state polymer electrolytes for lithium metal batteries: a review. Energy Environ. Sci. 2024; 17: 4426-4460. 10.1039/D4EE00822G. 1416.76234</bibtext> </blist> <blist> <bibtext> Li J, Cai Y, Wu H, Yu Z, Yan X. Polymers in lithium-ion and lithium metal batteries. Adv. Energy Mater. 2021; 11; 15: 2003239. 10.1002/aenm.202003239. 1406.74229</bibtext> </blist> <blist> <bibtext> Guo K, Wang J, Shi Z, Wang Y, Xie X. One-step in situ polymerization: a facile design strategy for block copolymer electrolytes. Angew. Chem. Int. Ed. 2023; 62; 9. 10.1002/anie.202213606e202213606</bibtext> </blist> <blist> <bibtext> Zhou D, Tang X, Guo X, Li P, Shanmukaraj D. Polyolefin-based janus separator for rechargeable sodium batteries. Angew. Chem. Int. Ed. 2020; 59; 38: 16725-16734. 10.1002/anie.202007008</bibtext> </blist> <blist> <bibtext> Zhang L, Li X, Yang M, Chen W. High-safety separators for lithium-ion batteries and sodium-ion batteries: Advances and perspective. Energy Storage Mater. 2021; 41: 522-545. 10.1016/j.ensm.2021.06.033. 1482.86022</bibtext> </blist> <blist> <bibtext> Zhu X, Jiang X, Ai X, Yang H, Cao Y. TiO2 ceramic-grafted polyethylene separators for enhanced thermostability and electrochemical performance of lithium-ion batteries. J. Membr. Sci. 2016; 504: 97-103. 10.1016/j.memsci.2015.12.059</bibtext> </blist> <blist> <bibtext> Zhu X, Jiang X, Ai X, Yang H, Cao Y. A highly thermostable ceramic-grafted microporous polyethylene separator for safer lithium-ion batteries. ACS Appl. Mater. Interfaces. 2015; 7; 43: 24119-24126. 10.1021/acsami.5b07230</bibtext> </blist> <blist> <bibtext> Wang X, Jia X, Liang Q, Yang J, Li Y. Building polysulfides shuttle barrier with unblocked Li+ transit channels via in-situ grown FeOOH modified separator for Li-S batteries. Appl. Surf. Sci. 2022; 606. 10.1016/j.apsusc.2022.154903154903</bibtext> </blist> <blist> <bibtext> Yin M, Huang J, Yu J, Chen G, Qu S. The polypropylene membrane modified by an atmospheric pressure plasma jet as a separator for lithium-ion button battery. Electrochim. Acta. 2018; 260: 489-497. 10.1016/j.electacta.2017.12.119</bibtext> </blist> <blist> <bibtext> Cao S, He X, Chen M, Han Y, Wang K. A CF4 plasma functionalized polypropylene separator for dendrite-free lithium metal anodes. J. Mater. Chem. A. 2023; 11; 14: 7545-7555. 10.1039/d2ta09763j. 1527.93225</bibtext> </blist> <blist> <bibtext> Liu M, Zhang P, Gou L, Hou Z. B, Huang, Enhancement on the thermostability and wettability of lithium-ion batteries separator via surface chemical modification. Mater. Lett. 2017; 208: 98-101. 10.1016/j.matlet.2017.05.031</bibtext> </blist> <blist> <bibtext> Zhao P, Yang J, Shang Y, Wang L, Fang M. Surface modification of polyolefin separators for lithium ion batteries to reduce thermal shrinkage without thickness increase. J. Energy Chem. 2015; 24; 2: 138-144. 10.1016/S2095-4956(15)60294-7. 1327.62313</bibtext> </blist> <blist> <bibtext> Min Yang K, Yang K, Cho M, Kim S, Lee Y. Self-assembled functional layers onto separator toward practical lithium metal batteries. Chem. Eng. J. 2023; 454: 140191. 10.1016/j.cej.2022.140191</bibtext> </blist> <blist> <bibtext> Wang Z, Guo F, Chen C, Shi L, Yuan S. Self-assembly of PEI/SiO2 on polyethylene separators for Li-ion batteries with enhanced rate capability. ACS Appl. Mater. Interfaces. 2015; 7; 5: 3314-3322. 10.1021/am508149n. 1202.37054</bibtext> </blist> <blist> <bibtext> Xu W, Wang Z, Shi L, Ma Y, Yuan S. Layer-by-layer deposition of organic-inorganic hybrid multilayer on microporous polyethylene separator to enhance the electrochemical performance of lithium-ion battery. ACS Appl. Mater. Interfaces. 2015; 7; 37: 20678-20686. 10.1021/acsami.5b05457</bibtext> </blist> <blist> <bibtext> Na W, Lee AS, Lee JH, Hwang SS, Kim E. Lithium dendrite suppression with UV-curable polysilsesquioxane separator binders. ACS Appl. Mater. Interfaces. 2016; 8; 20: 12852-12858. 10.1021/acsami.6b02735. 1014.94538</bibtext> </blist> <blist> <bibtext> Laurita R, Zaccaria M, Gherardi M, Fabiani D, Merlettini A. Plasma processing of electrospun Li-ion battery separators to improve electrolyte uptake. Plasma Process. Polym. 2015; 13; 1: 124-133. 10.1002/ppap.201500145</bibtext> </blist> <blist> <bibtext> Wang Z, Zhu H, Yang L, Wang X, Liu Z. Plasma modified polypropylene membranes as the lithium-ion battery separators. Plasma Sci. Technol. 2016; 18; 4: 424-429. 10.1088/1009-0630/18/4/16. 1067.32014</bibtext> </blist> <blist> <bibtext> Li B, Li Y, Dai D, Chang K, Tang H. Facile and nonradiation pretreated membrane as a high conductive separator for Li-ion batteries. ACS Appl. Mater. Interfaces. 2015; 7; 36: 20184-20189. 10.1021/acsami.5b05718. 1266.65090</bibtext> </blist> <blist> <bibtext> Song M-K, Cho J-Y, Cho BW, Rhee H-W. Characterization of UV-cured gel polymer electrolytes for rechargeable lithium batteries. J. Power Sources. 2002; 110; 1: 209-215. 10.1016/S0378-7753(02)00258-6. 1008.68645</bibtext> </blist> <blist> <bibtext> Jiang X, Zhu X, Ai X, Yang H, Cao Y. Novel ceramic-grafted separator with highly thermal stability for safe lithium-ion batteries. ACS Appl. Mater. Interfaces. 2017; 9; 31: 25970-25975. 10.1021/acsami.7b05535. 1432.65033</bibtext> </blist> <blist> <bibtext> Jiang Q, Li Z, Wang S, Zhang H. A separator modified by high efficiency oxygen plasma for lithium ion batteries with superior performance. RSC Adv. 2015; 5; 113: 92995-93001. 10.1039/c5ra18457f</bibtext> </blist> <blist> <bibtext> Gao K, Hu X, Yi T, Dai C. PE-g-MMA polymer electrolyte membrane for lithium polymer battery. Electrochim. Acta. 2006; 52; 2: 443-449. 10.1016/j.electacta.2006.05.049</bibtext> </blist> <blist> <bibtext> Kim JY, Lee Y, Lim DY. Plasma-modified polyethylene membrane as a separator for lithium-ion polymer battery. Electrochim. Acta. 2009; 54; 14: 3714-3719. 10.1016/j.electacta.2009.01.055. 1171.90449</bibtext> </blist> <blist> <bibtext> Kim KJ, Park M-S, Yim T, Yu J-S, Kim Y-J. Electron-beam-irradiated polyethylene membrane with improved electrochemical and thermal properties for lithium-ion batteries. J. Appl. Electrochem. 2014; 44; 3: 345-352. 10.1007/s10800-014-0661-7. 1372.70010</bibtext> </blist> <blist> <bibtext> Li J, Huang Y, Zhang S, Jia W, Wang X. Decoration of silica nanoparticles on polypropylene separator for lithium-sulfur batteries. ACS Appl. Mater. Interfaces. 2017; 9; 8: 7499-7504. 10.1021/acsami.7b00065. 1199.37052</bibtext> </blist> <blist> <bibtext> Jin SY, Manuel J, Zhao X, Park WH, Ahn J-H. Surface-modified polyethylene separator via oxygen plasma treatment for lithium ion battery. J. Ind. Eng. Chem. 2017; 45: 15-21. 10.1016/j.jiec.2016.08.021. 07370648</bibtext> </blist> <blist> <bibtext> Ye W, Fan Z, Zhou X, Xue Z. Functionalized polypropylene separator coated with polyether/polyester blend for high-performance lithium metal batteries. Energy Mater. 2024; 4; 4: 400049. 10.20517/energymater.2023.129</bibtext> </blist> <blist> <bibtext> Xiang H, Zhang F, Zou B, Hou Q, Cheng C. High-performance lithium batteries achieved by electrospun MXene-enhanced cation-selective membranes. J. Membr. Sci. 2024; 704. 10.1016/j.memsci.2024.122867122867</bibtext> </blist> <blist> <bibtext> Li Z, Pan Q, Yang P, Jiang S, Zheng Z. Enhancing the cycle performance of lithium–sulfur batteries by coating the separator with a cation-selective polymer layer. Chem. Eur. J. 2023; 29. 10.1002/chem.202302334e202302334</bibtext> </blist> <blist> <bibtext> Zhao Q, Zhou R, Wang C, Kang J, Zhang Q. Anion immobilization enabled by cation-selective separators for dendrite-free lithium metal batteries. Adv. Funct. Mater. 2022; 32: 2112711. 10.1002/adfm.202112711</bibtext> </blist> <blist> <bibtext> Wang L, Xu S, Wang Z, Yang E, Jiang W. A nano fiber-gel composite electrolyte with high Li+ transference number for application in quasi-solid batteries. eScience. 2023; 3; 2: 100090. 10.1016/j.esci.2022.100090. 1398.35234</bibtext> </blist> </ref> <aug> <p>By Zixin Fan; Xiaoyu Chen; Jingjing Shi; Hui Nie; Xiaoming Zhang; Xingping Zhou; Xiaolin Xie and Zhigang Xue</p> <p>Reported by Author; Author; Author; Author; Author; Author; Author; Author</p> </aug> <nolink nlid="nl1" bibid="bib10" firstref="ref18"></nolink> <nolink nlid="nl2" bibid="bib11" firstref="ref19"></nolink> <nolink nlid="nl3" bibid="bib12" firstref="ref20"></nolink> <nolink nlid="nl4" bibid="bib13" firstref="ref21"></nolink> <nolink nlid="nl5" bibid="bib14" firstref="ref22"></nolink> <nolink nlid="nl6" bibid="bib15" firstref="ref23"></nolink> <nolink nlid="nl7" bibid="bib17" firstref="ref24"></nolink> <nolink nlid="nl8" bibid="bib18" firstref="ref25"></nolink> <nolink nlid="nl9" bibid="bib19" firstref="ref26"></nolink> <nolink nlid="nl10" bibid="bib21" firstref="ref27"></nolink> <nolink nlid="nl11" bibid="bib23" firstref="ref28"></nolink> <nolink nlid="nl12" bibid="bib24" firstref="ref29"></nolink> <nolink nlid="nl13" bibid="bib25" firstref="ref30"></nolink> <nolink nlid="nl14" bibid="bib26" firstref="ref31"></nolink> <nolink nlid="nl15" bibid="bib27" firstref="ref33"></nolink> <nolink nlid="nl16" bibid="bib28" firstref="ref35"></nolink> <nolink nlid="nl17" bibid="bib30" firstref="ref36"></nolink> <nolink nlid="nl18" bibid="bib31" firstref="ref37"></nolink> <nolink nlid="nl19" bibid="bib32" firstref="ref38"></nolink> <nolink nlid="nl20" bibid="bib33" firstref="ref39"></nolink> <nolink nlid="nl21" bibid="bib35" firstref="ref42"></nolink> <nolink nlid="nl22" bibid="bib36" firstref="ref44"></nolink> <nolink nlid="nl23" bibid="bib37" firstref="ref45"></nolink> <nolink nlid="nl24" bibid="bib38" firstref="ref46"></nolink> <nolink nlid="nl25" bibid="bib39" firstref="ref47"></nolink> <nolink nlid="nl26" bibid="bib40" firstref="ref51"></nolink> <nolink nlid="nl27" bibid="bib41" firstref="ref52"></nolink> <nolink nlid="nl28" bibid="bib43" firstref="ref53"></nolink> <nolink nlid="nl29" bibid="bib44" firstref="ref54"></nolink> <nolink nlid="nl30" bibid="bib45" firstref="ref55"></nolink> <nolink nlid="nl31" bibid="bib46" firstref="ref56"></nolink> <nolink nlid="nl32" bibid="bib48" firstref="ref57"></nolink> <nolink nlid="nl33" bibid="bib50" firstref="ref58"></nolink> <nolink nlid="nl34" bibid="bib51" firstref="ref59"></nolink> <nolink nlid="nl35" bibid="bib52" firstref="ref60"></nolink> <nolink nlid="nl36" bibid="bib61" firstref="ref61"></nolink> <nolink nlid="nl37" bibid="bib81" firstref="ref62"></nolink> <nolink nlid="nl38" bibid="bib54" firstref="ref63"></nolink> <nolink nlid="nl39" bibid="bib63" firstref="ref64"></nolink> <nolink nlid="nl40" bibid="bib82" firstref="ref65"></nolink> <nolink nlid="nl41" bibid="bib49" firstref="ref66"></nolink> <nolink nlid="nl42" bibid="bib56" firstref="ref71"></nolink> <nolink nlid="nl43" bibid="bib60" firstref="ref73"></nolink> <nolink nlid="nl44" bibid="bib57" firstref="ref74"></nolink> <nolink nlid="nl45" bibid="bib83" firstref="ref78"></nolink> <nolink nlid="nl46" bibid="bib84" firstref="ref79"></nolink> <nolink nlid="nl47" bibid="bib70" firstref="ref80"></nolink> <nolink nlid="nl48" bibid="bib73" firstref="ref81"></nolink> <nolink nlid="nl49" bibid="bib76" firstref="ref82"></nolink> <nolink nlid="nl50" bibid="bib77" firstref="ref83"></nolink> <nolink nlid="nl51" bibid="bib85" firstref="ref84"></nolink> <nolink nlid="nl52" bibid="bib71" firstref="ref87"></nolink> <nolink nlid="nl53" bibid="bib74" firstref="ref89"></nolink> <nolink nlid="nl54" bibid="bib75" firstref="ref90"></nolink> <nolink nlid="nl55" bibid="bib69" firstref="ref93"></nolink> <nolink nlid="nl56" bibid="bib72" firstref="ref94"></nolink> <nolink nlid="nl57" bibid="bib79" firstref="ref99"></nolink> <nolink nlid="nl58" bibid="bib86" firstref="ref100"></nolink> <nolink nlid="nl59" bibid="bib87" firstref="ref101"></nolink> <nolink nlid="nl60" bibid="bib89" firstref="ref103"></nolink> <nolink nlid="nl61" bibid="bib90" firstref="ref104"></nolink> <nolink nlid="nl62" bibid="bib91" firstref="ref105"></nolink> <nolink nlid="nl63" bibid="bib92" firstref="ref107"></nolink> <nolink nlid="nl64" bibid="bib93" firstref="ref108"></nolink> <nolink nlid="nl65" bibid="bib98" firstref="ref109"></nolink> <nolink nlid="nl66" bibid="bib94" firstref="ref110"></nolink> <nolink nlid="nl67" bibid="bib100" firstref="ref112"></nolink> <nolink nlid="nl68" bibid="bib101" firstref="ref114"></nolink> <nolink nlid="nl69" bibid="bib102" firstref="ref115"></nolink> <nolink nlid="nl70" bibid="bib103" firstref="ref116"></nolink> <nolink nlid="nl71" bibid="bib105" firstref="ref117"></nolink> <nolink nlid="nl72" bibid="bib106" firstref="ref118"></nolink> <nolink nlid="nl73" bibid="bib127" firstref="ref119"></nolink> <nolink nlid="nl74" bibid="bib117" firstref="ref120"></nolink> <nolink nlid="nl75" bibid="bib118" firstref="ref121"></nolink> <nolink nlid="nl76" bibid="bib120" firstref="ref122"></nolink> <nolink nlid="nl77" bibid="bib124" firstref="ref123"></nolink> <nolink nlid="nl78" bibid="bib125" firstref="ref124"></nolink> <nolink nlid="nl79" bibid="bib126" firstref="ref126"></nolink> <nolink nlid="nl80" bibid="bib130" firstref="ref128"></nolink> <nolink nlid="nl81" bibid="bib132" firstref="ref129"></nolink> <nolink nlid="nl82" bibid="bib133" firstref="ref130"></nolink> <nolink nlid="nl83" bibid="bib134" firstref="ref131"></nolink> <nolink nlid="nl84" bibid="bib135" firstref="ref132"></nolink> <nolink nlid="nl85" bibid="bib137" firstref="ref133"></nolink> <nolink nlid="nl86" bibid="bib139" firstref="ref134"></nolink> <nolink nlid="nl87" bibid="bib140" firstref="ref135"></nolink> <nolink nlid="nl88" bibid="bib141" firstref="ref137"></nolink> <nolink nlid="nl89" bibid="bib142" firstref="ref138"></nolink> <nolink nlid="nl90" bibid="bib112" firstref="ref139"></nolink> <nolink nlid="nl91" bibid="bib143" firstref="ref140"></nolink> <nolink nlid="nl92" bibid="bib144" firstref="ref141"></nolink> <nolink nlid="nl93" bibid="bib145" firstref="ref142"></nolink> <nolink nlid="nl94" bibid="bib146" firstref="ref143"></nolink> <nolink nlid="nl95" bibid="bib157" firstref="ref144"></nolink> <nolink nlid="nl96" bibid="bib159" firstref="ref145"></nolink> <nolink nlid="nl97" bibid="bib160" firstref="ref146"></nolink> <nolink nlid="nl98" bibid="bib148" firstref="ref147"></nolink> <nolink nlid="nl99" bibid="bib161" firstref="ref148"></nolink> <nolink nlid="nl100" bibid="bib152" firstref="ref150"></nolink> <nolink nlid="nl101" bibid="bib153" firstref="ref151"></nolink> <nolink nlid="nl102" bibid="bib155" firstref="ref152"></nolink> <nolink nlid="nl103" bibid="bib163" firstref="ref153"></nolink> <nolink nlid="nl104" bibid="bib165" firstref="ref154"></nolink> <nolink nlid="nl105" bibid="bib166" firstref="ref155"></nolink> <nolink nlid="nl106" bibid="bib167" firstref="ref156"></nolink> <nolink nlid="nl107" bibid="bib174" firstref="ref157"></nolink> <nolink nlid="nl108" bibid="bib176" firstref="ref158"></nolink> <nolink nlid="nl109" bibid="bib177" firstref="ref159"></nolink> <nolink nlid="nl110" bibid="bib178" firstref="ref160"></nolink> <nolink nlid="nl111" bibid="bib179" firstref="ref161"></nolink> <nolink nlid="nl112" bibid="bib180" firstref="ref162"></nolink> <nolink nlid="nl113" bibid="bib168" firstref="ref163"></nolink> <nolink nlid="nl114" bibid="bib88" firstref="ref165"></nolink> <nolink nlid="nl115" bibid="bib181" firstref="ref166"></nolink> <nolink nlid="nl116" bibid="bib136" firstref="ref167"></nolink> <nolink nlid="nl117" bibid="bib183" firstref="ref168"></nolink> <nolink nlid="nl118" bibid="bib184" firstref="ref169"></nolink> <nolink nlid="nl119" bibid="bib185" firstref="ref170"></nolink> <nolink nlid="nl120" bibid="bib186" firstref="ref171"></nolink> <nolink nlid="nl121" bibid="bib107" firstref="ref173"></nolink> <nolink nlid="nl122" bibid="bib195" firstref="ref174"></nolink> <nolink nlid="nl123" bibid="bib196" firstref="ref175"></nolink> <nolink nlid="nl124" bibid="bib197" firstref="ref176"></nolink> <nolink nlid="nl125" bibid="bib187" firstref="ref178"></nolink> <nolink nlid="nl126" bibid="bib188" firstref="ref179"></nolink> <nolink nlid="nl127" bibid="bib198" firstref="ref180"></nolink> <nolink nlid="nl128" bibid="bib190" firstref="ref181"></nolink> <nolink nlid="nl129" bibid="bib189" firstref="ref182"></nolink> <nolink nlid="nl130" bibid="bib200" firstref="ref184"></nolink> <nolink nlid="nl131" bibid="bib192" firstref="ref186"></nolink> <nolink nlid="nl132" bibid="bib193" firstref="ref187"></nolink> <nolink nlid="nl133" bibid="bib202" firstref="ref190"></nolink> <nolink nlid="nl134" bibid="bib204" firstref="ref191"></nolink> <nolink nlid="nl135" bibid="bib205" firstref="ref192"></nolink> <nolink nlid="nl136" bibid="bib206" firstref="ref193"></nolink> <nolink nlid="nl137" bibid="bib207" firstref="ref195"></nolink> <nolink nlid="nl138" bibid="bib219" firstref="ref196"></nolink> <nolink nlid="nl139" bibid="bib221" firstref="ref197"></nolink> <nolink nlid="nl140" bibid="bib222" firstref="ref198"></nolink> <nolink nlid="nl141" bibid="bib223" firstref="ref199"></nolink> <nolink nlid="nl142" bibid="bib224" firstref="ref200"></nolink> <nolink nlid="nl143" bibid="bib209" firstref="ref201"></nolink> <nolink nlid="nl144" bibid="bib212" firstref="ref202"></nolink> <nolink nlid="nl145" bibid="bib214" firstref="ref203"></nolink> <nolink nlid="nl146" bibid="bib216" firstref="ref205"></nolink> <nolink nlid="nl147" bibid="bib217" firstref="ref206"></nolink> <nolink nlid="nl148" bibid="bib226" firstref="ref207"></nolink> <nolink nlid="nl149" bibid="bib228" firstref="ref208"></nolink> <nolink nlid="nl150" bibid="bib229" firstref="ref209"></nolink> <nolink nlid="nl151" bibid="bib230" firstref="ref210"></nolink> <nolink nlid="nl152" bibid="bib231" firstref="ref212"></nolink> <nolink nlid="nl153" bibid="bib232" firstref="ref215"></nolink> <nolink nlid="nl154" bibid="bib233" firstref="ref216"></nolink> <nolink nlid="nl155" bibid="bib234" firstref="ref217"></nolink> <nolink nlid="nl156" bibid="bib235" firstref="ref220"></nolink>
CustomLinks:
  – Url: https://resolver.ebsco.com/c/xy5jbn/result?sid=EBSCO:edsdoj&genre=article&issn=23116706&ISBN=&volume=17&issue=1&date=20250201&spage=1&pages=1-38&title=Nano-Micro Letters&atitle=Functionalized%20Separators%20Boosting%20Electrochemical%20Performances%20for%20Lithium%20Batteries&aulast=Zixin%20Fan&id=DOI:10.1007/s40820-024-01596-x
    Name: Full Text Finder (for New FTF UI) (s8985755)
    Category: fullText
    Text: Find It @ SCU Libraries
    MouseOverText: Find It @ SCU Libraries
  – Url: https://doaj.org/article/ee4fa3e847054ca9bab7c0da04938147
    Name: EDS - DOAJ (s8985755)
    Category: fullText
    Text: View record from DOAJ
    MouseOverText: View record from DOAJ
Header DbId: edsdoj
DbLabel: Directory of Open Access Journals
An: edsdoj.4fa3e847054ca9bab7c0da04938147
RelevancyScore: 1082
AccessLevel: 3
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 1081.56311035156
IllustrationInfo
Items – Name: Title
  Label: Title
  Group: Ti
  Data: Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Zixin+Fan%22">Zixin Fan</searchLink><br /><searchLink fieldCode="AR" term="%22Xiaoyu+Chen%22">Xiaoyu Chen</searchLink><br /><searchLink fieldCode="AR" term="%22Jingjing+Shi%22">Jingjing Shi</searchLink><br /><searchLink fieldCode="AR" term="%22Hui+Nie%22">Hui Nie</searchLink><br /><searchLink fieldCode="AR" term="%22Xiaoming+Zhang%22">Xiaoming Zhang</searchLink><br /><searchLink fieldCode="AR" term="%22Xingping+Zhou%22">Xingping Zhou</searchLink><br /><searchLink fieldCode="AR" term="%22Xiaolin+Xie%22">Xiaolin Xie</searchLink><br /><searchLink fieldCode="AR" term="%22Zhigang+Xue%22">Zhigang Xue</searchLink>
– Name: TitleSource
  Label: Source
  Group: Src
  Data: Nano-Micro Letters, Vol 17, Iss 1, Pp 1-38 (2025)
– Name: Publisher
  Label: Publisher Information
  Group: PubInfo
  Data: SpringerOpen, 2025.
– Name: DatePubCY
  Label: Publication Year
  Group: Date
  Data: 2025
– Name: Subset
  Label: Collection
  Group: HoldingsInfo
  Data: LCC:Technology
– Name: Subject
  Label: Subject Terms
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Separators%22">Separators</searchLink><br /><searchLink fieldCode="DE" term="%22Polymer+electrolytes%22">Polymer electrolytes</searchLink><br /><searchLink fieldCode="DE" term="%22Lithium+batteries%22">Lithium batteries</searchLink><br /><searchLink fieldCode="DE" term="%22Electrochemical+performances%22">Electrochemical performances</searchLink><br /><searchLink fieldCode="DE" term="%22Functionalization%22">Functionalization</searchLink><br /><searchLink fieldCode="DE" term="%22Technology%22">Technology</searchLink>
– Name: Abstract
  Label: Description
  Group: Ab
  Data: Highlights The commonly used modification methods for separator of lithium batteries are summarized, which include surface coating, in situ modification and grafting modification. The adhesion of coating materials with the separators and wettability of the modified separators prepared from the three methods are compared. The challenges and future directions of separator modification are provided.
– Name: TypeDocument
  Label: Document Type
  Group: TypDoc
  Data: article
– Name: Format
  Label: File Description
  Group: SrcInfo
  Data: electronic resource
– Name: Language
  Label: Language
  Group: Lang
  Data: English
– Name: ISSN
  Label: ISSN
  Group: ISSN
  Data: 2311-6706<br />2150-5551
– Name: NoteTitleSource
  Label: Relation
  Group: SrcInfo
  Data: https://doaj.org/toc/2311-6706; https://doaj.org/toc/2150-5551
– Name: DOI
  Label: DOI
  Group: ID
  Data: 10.1007/s40820-024-01596-x
– Name: URL
  Label: Access URL
  Group: URL
  Data: <link linkTarget="URL" linkTerm="https://doaj.org/article/ee4fa3e847054ca9bab7c0da04938147" linkWindow="_blank">https://doaj.org/article/ee4fa3e847054ca9bab7c0da04938147</link>
– Name: AN
  Label: Accession Number
  Group: ID
  Data: edsdoj.4fa3e847054ca9bab7c0da04938147
PLink https://login.libproxy.scu.edu/login?url=https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&scope=site&db=edsdoj&AN=edsdoj.4fa3e847054ca9bab7c0da04938147
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1007/s40820-024-01596-x
    Languages:
      – Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 38
        StartPage: 1
    Subjects:
      – SubjectFull: Separators
        Type: general
      – SubjectFull: Polymer electrolytes
        Type: general
      – SubjectFull: Lithium batteries
        Type: general
      – SubjectFull: Electrochemical performances
        Type: general
      – SubjectFull: Functionalization
        Type: general
      – SubjectFull: Technology
        Type: general
    Titles:
      – TitleFull: Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries
        Type: main
  BibRelationships:
    HasContributorRelationships:
      – PersonEntity:
          Name:
            NameFull: Zixin Fan
      – PersonEntity:
          Name:
            NameFull: Xiaoyu Chen
      – PersonEntity:
          Name:
            NameFull: Jingjing Shi
      – PersonEntity:
          Name:
            NameFull: Hui Nie
      – PersonEntity:
          Name:
            NameFull: Xiaoming Zhang
      – PersonEntity:
          Name:
            NameFull: Xingping Zhou
      – PersonEntity:
          Name:
            NameFull: Xiaolin Xie
      – PersonEntity:
          Name:
            NameFull: Zhigang Xue
    IsPartOfRelationships:
      – BibEntity:
          Dates:
            – D: 01
              M: 02
              Type: published
              Y: 2025
          Identifiers:
            – Type: issn-print
              Value: 23116706
            – Type: issn-print
              Value: 21505551
          Numbering:
            – Type: volume
              Value: 17
            – Type: issue
              Value: 1
          Titles:
            – TitleFull: Nano-Micro Letters
              Type: main
ResultId 1