Quasi-solid electrolyte membranes based on poly(ionic liquids) and MOF confinement for lithium-metal batteries

Safe and high-performance electrolyte membranes are critical for lithium-metal batteries operating under elevated temperatures. Herein, a quasi-solid polymer electrolyte membrane based on a poly(ionic liquid) poly(IL)-integrated metal–organic framework (MOF)/PVDF-HFP matrix is fabricated via a facile solution-casting approach. An ionic-liquid-electrolyte-confined ZIF-8 (ILE@ZIF-8) filler and a poly(IL) component are uniformly incorporated into the polymer matrix to regulate membrane microstructure and ion-transport behavior. The optimized membrane (MSPE-10) exhibits a room-temperature ionic conductivity of 1.38 × 10 −3 S·cm −1 and a Li + transference number of 0.53. Structural analysis reveals that the incorporation of ILE@ZIF-8 effectively suppresses polymer crystallinity while generating interconnected nanochannels and abundant Lewis-acidic sites. Consequently, the electrolyte membrane demonstrates an expanded electrochemical stability window up to 5.0 V versus Li + /Li and enhanced interfacial stability toward lithium metal, leading to suppressed dendrite growth. The LiFePO 4 |MSPE-10|Li full cell incorporated with the optimized membrane delivers a discharge capacity of 159.6 mAh·g −1 at 0.1C and 25 °C with > 99% capacity retention over 200 cycles, and maintains 156.1 mAh·g −1 at 1C and 50 °C with 62.6% capacity retention after 1000 cycles. This work demonstrates that integrating MOF-confined ionic liquids with poly(IL) chemistry provides an effective strategy for designing thermally stable quasi-solid electrolyte membranes for advanced lithium-metal batteries.