Composite Gel Electrolytes with Ion‐Mediated Compatibilization and Matrix‐Assisted Conduction for Wide‐Temperature Lithium Metal Batteries

Gel polymer electrolytes (GPEs) with solvent‐in‐polymer structure typically encounter a trade‐off between ionic conductivity and mechanical properties. This challenge has not been adequately addressed by conventional single‐material, miscible polymers, or polymer/ceramic composite electrolytes. Herein, the phase consistency of composite GPE matrix, which contains polymer blends of “soft” poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVHF) and “hard” polyether‐ether‐ketone (PEEK), is enhanced by ion‐mediated compatibilization through the incorporation of lithium sulfonate groups. In addition, the electrolyte's ionic environment is optimized by the pendent lithium sulfonate positioned at the interface between polymer‐rich and solvent‐rich domains, thus achieving high ionic conductivity of 1.87 mS cm −1 at 20 °C and 1.28 mS cm −1 at −20 °C via the matrix‐assisted conduction. As a consequence, the composite gel electrolyte confers the Li||LiFePO 4 battery with high discharge capacity of 157.0 mAh g −1 at 1 C and capacity retention of 90.7% after 1500 cycles, and superior electrochemical performance under harsh conditions, including high rate of 5 C (96.0% capacity retention after 1000 cycles), extreme temperatures from −20 °C to 80 °C, and in conjunction with 30‐µm lithium metal anode. This work advances the development of high‐performance gel polymer electrolytes through innovative nanostructure and molecule design.