Stabilizing Halide Electrolytes against Lithium Metal with a Self-Limiting Layer for All-Solid-State Lithium Metal Batteries

Halide solid-state electrolytes (SSEs) with high ionic conductivity and high-voltage stability have attracted significant interest for application in all-solid-state batteries. However, they are not chemically stable against the lithium (Li) metal anode due to continuous side reduction reactions, hindering the application of halide SSEs in high-energy-density all-solid-state Li metal batteries (ASSLMBs). Here, we report a self-limiting layer (SLL) composed of InF₃ and Li₂ZrCl₆ (LZC) to stabilize the halide SSEs and Li metal anode interface, where the in situ generated LiF-rich layer serves as a passivation layer to suppress ensuing reactions and kinetically stabilize the interface between LZC and Li metal anode. As a result, Li metal symmetric cells with LZC protected by the SLL exhibit excellent cycling performance for over 3000 h. The ASSLMBs with SLL achieve 99.2% capacity retention over 100 cycles at 0.5 C and 83.5% capacity retention after 250 cycles at 2 C. Density functional theory-computed thermodynamic data and postcycling experimental characterizations confirm the forming of a LiF-rich passivation layer between the SLL and the Li anode, which effectively prevents continuous side reactions. This self-limiting interface protection offers a feasible kinetical passivation strategy for halide SSEs and the Li metal anode toward high-performance ASSLMBs.