Rapidly In Situ Cross-Linked Poly(butylene oxide) Electrolyte Interface Enabling Halide-Based All-Solid-State Lithium Metal Batteries

Halide-based solid-state halide electrolytes (SSEs) were recently revived as promising candidates for next-generation all-solid-state batteries due to their superionic conductivity, direct compatibility with high-voltage cathodes, and scalable production. However, the incompatibility between halide SSEs and lithium metal anodes remains a main challenge to achieve high energy density. Herein, we demonstrate a thin cross-linked poly(butylene oxide) solid polymer electrolyte (xPBO SPE) interlayer on the superionic Li₃InCl₆ SSE to enable lithium metal compatibility. A rapid and solvent-free in situ cross-linking process is developed by reaction between a 0.5 s pulse of trimethylaluminum vapor and the hydroxyl terminal groups of poly(butylene oxide). The Li–Li symmetric cells using xPBO-SPE@Li₃InCl₆ demonstrate a highly stable cycling performance over 1100 h and up to 1.0 mA cm^–2 and 1.0 mAh cm^–2. All-solid-state lithium metal battery (ASSLMB) performance with a LiCoO₂ cathode is presented. This new rapid cross-linking strategy shall inspire more possibilities for lithium metal anode integration in ASSLMBs.