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 (Li2.5ZrCl5F0.5O0.5, 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 degrees 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. The high-voltage stable halide superionic conductor LZCFO is synthesized based on anion-engineering of F-/O2-. F-rich CEI promotes high-voltage stability and is attributed to the long cycle lifespan, while the amorphous electrolyte design enhances the ionic conductivity for achieving excellent rate performance. image