possess safety issues, such as thermal runaway and have limitations in numerous cell designs due to their liquid organic solvent. [5,6] To resolve these concerns, solidstate electrolytes are being considered as an alternative for combustible liquid electrolytes because they provide not only good thermal stability and safety from solution leakage but also the possibility to use Li metal anodes with a promising high capacity. [7-11] However, the prerequisite is minimal cell performance and mechanical strength at ambient temperatures. Therefore, achieving ionic conductivity comparable to that of liquid electrolytes is a key feature for the success of solid electrolytebased LIBs. Gel polymer electrolytes (GPEs) are regarded as promising substitutes for liquid electrolytes due to their excellent ionic conductivity, effective encapsulation of organic solvents in cells, good interfacial adhesion to electrodes, high flexibility, and light weight. [8,10,12] However, GPEs have a limited mechanical strength because the organic liquid electrolyte is confined in a small fraction of the polymer network. Cross-linking of linear polymer or oligomer chains is one of the facile and effective ways to enhance the mechanical toughness of GPEs while maintaining their ionic conductivity. [12,13] In particular, GPEs prepared by the UV (ultraviolet)-curing method have been employed to induce cross-linking of polymer matrixes. [14-20] Inherently, the ionic conductivity of solid electrolytes, including GPEs, is inversely proportional to their mechanical properties because high liquid contents that improve the ionic conductivity soften the solid electrolyte. To solve this problem, composite gel polymer electrolytes (CGPEs), which are organic polymers mixed with inorganic fillers, have been extensively researched and found to improve the ionic conductivity and enhance the stability of polymer electrolytes. [7,21-23] Montmorillonite (MMT), a well-known group of smectite clays that are 2:1 type phyllosilicates composed of octahedral sheets sandwiched between two silica tetrahedral sheets, is an attractive and nextgeneration inorganic filler. [22,23] This is because they are not only abundant in the crust of the Earth but also sustainable and procurable materials that can be continuously generated by weathering. [22,24-26] In addition, they are dielectric materials with a high aspect ratio and large interfacial area that can Commercialized lithium-ion batteries (LIBs) with a liquid electrolyte have a high potential for combustion or explosion. The use of solid electrolytes in LIBs is a promising way to overcome the drawbacks of conventional liquid electrolyte-based systems, but they generally have a lower ionic conductivity and lithium ion mobility. Here, a UV-crosslinked composite polymer-clay electrolyte (U-CPCE) that is composed of a durable semi-interpenetrating polymer network (semi-IPN) ion transportive matrix (ETPTA/PVdF-HFP) and 2D ultrathin clay nanosheets that are fabricated by a one-step in situ UV curing method, are reported. The U-...

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Nonflammable lithium‐ion batteries (LIBs) are developed by adapting polymer solid electrolytes, but their insufficient electrochemical performance has not been fully addressed to date. Crosslinked polymer gel electrolytes with minimal organic solvents (hard gels) are proven to be nonflammable electrolytes, but their lithium metal battery performance is not comparable to those of conventional liquid electrolyte‐based systems. Here, a semi‐interpenetrating polymer network (semi‐IPN) ion‐transporting solid film that comprises a UV‐curable crosslinked polymer and tailored linear pyrrolidinium‐polyethylene glycol copolyester ion channels (named PNPEG), is reported. PNPEG can solvate Li+ effectively with the help of carbonate solvents. Molecular dynamics (MD) simulations confirm that Li+ transportation is accelerated due to the weaker interaction between PNPEG and Li+ ions than between the solvents and ions. The semi‐IPN electrolyte with PNPEG exhibits a flexible, nonflammable nature with an ionic conductivity of 4.2 × 10−1 mS cm−1 and Li+ transference number of 0.51. The individual pyrrolidinium‐Bis(trifluoromethanesulfonyl)imide (pyrrolidinium‐Tf2N) monomer and PEG chain ratios in PNPEG strongly affect battery performance, and the optimized semi‐IPN‐based lithium metal half cells with LiCoO2 cathodes show greatly improved discharge capacity retention at high c‐rate conditions owing to effective Li+ transportation and excellent cycling performance (93.8% capacity retention after 200 cycles at 0.5 C).

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