Anion-Engineering Toward High-Voltage-Stable Halide Superionic Conductors for All-Solid-State Lithium Batteries

Halide solid electrolytes (SEs) are attracting strong attention as one of the compelling candidates for the next-generation of inorganic SEs due to their high ionic conductivity. Nevertheless, unsatisfactory high-voltage stability restricts the further applications of halide SEs. Herein, the anion-engineering of F⁻/O²⁻ is evolved to construct the high-voltage stable zirconium-based halide superionic conductors (Li_2.5ZrCl₅F_0.5O_0.5, LZCFO). Benefiting from the thermodynamic/kinetic high-voltage stability of F-containing SE and the disordered localized structure introduced by O²⁻, LZCFO displays a practical electrochemical limit of 4.87 V versus Li/Li⁺ and an ionic conductivity of 1.17 mS cm⁻¹ at 30 °C. With LZCFO and NCM955, the all-solid-state lithium battery exhibits a high discharge capacity of 207.1 mAh g⁻¹ at 0.1C and a capacity retention of 81.2% after 500 cycles at 0.5C. The interfacial characterization further demonstrates the formation of the F-rich cathode–electrolyte interphase (CEI), which inhibits side reactions between the cathode and the SE and boosts excellent cycling stability. This work affords fresh insights on the engineering of SEs with high-voltage stability, high ionic conductivity, and stable CEI in all-solid-state lithium batteries.