Halide Layer Cathodes for Compatible and Fast‐Charged Halides‐Based All‐Solid‐State Li Metal Batteries

A lithium intercalation chemistry in layered VX₃ (X=Cl, Br, I) enabled by compatible halide-based solid electrolytes was explored for the first time. The electrode-electrolyte interfacial stability can be achieved in a thermodynamic manner instead of by passivation, ensured by the good chemical stability between the VX₃ cathode and halide electrolytes as well as the wide electrochemical stability windows.

Abstract

Insertion-type compounds based on oxides and sulfides have been widely identified and well-studied as cathode materials in lithium-ion batteries. However, halides have rarely been used due to their high solubility in organic liquid electrolytes. Here, we reveal the insertion electrochemistry of VX₃ (X=Cl, Br, I) by introducing a compatible halide solid-state electrolyte with a wide electrochemical stability window. X-ray absorption near-edge structure analyses reveal a two-step lithiation process and the structural transition of typical VCl₃. Fast Li⁺ insertion/extraction in the layered VX₃ active materials and favorable interface guaranteed by the compatible electrode-electrolyte design enables high rate capability and stable operation of all-solid-state Li-VX₃ batteries. The findings from this study will contribute to developing intercalation insertion electrochemistry of halide materials and exploring novel electrode materials in viable energy storage systems.

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