Interfacial Stabilization Mechanism of Zirconium‐Based Halide and Li–In Alloy Anode in All‐Solid‐State Lithium Batteries

Abstract The interfacial stability between halide solid‐state electrolytes and anodes directly affects their application in commercial all‐solid‐state lithium batteries, especially for low‐cost zirconium‐based halides. However, few research are done on interfacial reactions. This study elucidates the dynamic processes of the interface between Li₂ZrCl₆ and Li–In alloy, that is, indium atoms are oxidized and incorporated into Li₂ZrCl₆, while zirconium atoms are partially reduced to balance the charge changes, resulting in an ion‐conductive interface stabilization layer of Li₂(Zr⁴⁺_aZr³⁺_bZr²⁺_c)^(4‐3x)+In³⁺_xCl₆ (0 < x < 1/3, a + b + c = 1). Based on this mechanism, the LiCoO₂│Li₂ZrCl₆│Li–In cell with single‐layer halide solid‐state electrolyte is constructed for the first time, showing satisfying electrochemical performance with an initial Coulombic efficiency of 97.1% and a capacity retention rate of 78.7% after 300 cycles. Compared with the common LiCoO₂│Li₂ZrCl₆│Li₆PS₅Cl│Li–In cell with halide and sulfide dual‐layer solid‐state electrolyte, the gravimetric and volumetric energy densities of the all‐solid‐state lithium pouch batteries are increased by 6.7% and 9%, respectively.