Organic–Inorganic Covalently Crosslinked Electrolyte Fabricated In Situ via Multifunctional Fillers for High‐Performance Solid‐State Lithium Metal Batteries

Abstract In‐situ polymerization of poly(1,3‐dioxolane) electrolyte can avert from the interface problem for solid‐state batteries. However, its limited compatibility with lithium metal, insufficient mechanical strength, and reduced ionic conductivity caused by crystallization present challenges. Herein, an organic–inorganic covalently crosslinked electrolyte is developed via InF 3 ‐based filler functionalized with 𝛾‐(2,3‐epoxypropoxy) propyl‐trimethoxy‐silane (KH560) silane coupling agent (KH560@InF 3 ). The composite filler provides integrated functions: not only suppressing polymer crystallization and enhancing mechanical properties, but also catalytically initiating in‐situ polymerization and promoting stability of solid electrolyte interphase (SEI). The epoxy groups of KH560@InF 3 and 1,3‐dioxolane copolymerize via the ring‐opening reaction to form the organic–inorganic covalently crosslinked networks, thus enabling uniform dispersion of the filler and excellent mechanical properties. Moreover, KH560@InF 3 can undergo interfacial chemical reactions with lithium metal to form a stable SEI enriched with LiF and LiIn, which facilitates rapid Li⁺ migration, thereby suppressing overpotential, homogenizing Li⁺ flux, and promoting uniform lithium deposition. The corresponding Li/LiFePO 4 cell exhibits stable high‐rate performance: even at 10C, it has a capacity retention rate of 83.6% after 800 cycles. Such an organic–inorganic covalently crosslinked electrolyte achieves a triple synergistic enhancement in mechanical robustness, ionic conductivity, and interfacial electrochemical stability, providing a viable approach to develop practical solid‐state lithium‐metal batteries.