Simultaneously Enhance Humidity Tolerance and Ionic Conductivity of Halide Electrolytes by Cation–Anion Co‐Doping

Halide solid-state electrolytes (SSEs) with high ionic conductivity and oxidation stability show significant potentials for the commercialization of all-solid-state batteries (ASSBs). However, their practical applications are limited by poor humidity tolerance and decreased ionic conductivity. Herein, the Li_3/3- _xIn_1- _xM_xCl_5.6F_0.4 (M = Hf, Zr, Fe, and Y; x = 0.015, 0.02, 0.025, 0.075, 0.1, 0.125, and 0.15) are synthesized by co-doping Li₃InCl₆ with M and F ions for high-performance ASSBs. Li_2.98In_0.98Hf_0.02Cl_5.6F_0.4 achieves the highest ionic conductivity of 1.04 mS cm^-1 at room temperature and good humidity tolerance of 87.96% conductivity retention after 24 h exposure. The analysis of experiments combining BVSE and AIMD simulations indicates that it benefits from the enhanced rigid structure that is thermodynamically stable to water caused by Cl^- doping with F^- and higher Li⁺ vacancies concentration that facilitates Li⁺ conduction generated by In³⁺ doping with Hf⁴⁺. Moreover, an all-solid-state battery ensembled with Li_2.98In_0.98Hf_0.02Cl_5.6F_0.4, LiCoO₂ and Li-In alloy, exhibits a high discharge capacity of 83.6 mAh g^-1 and 78.6% capacity retention after 100 cycles under 0.5 C at 25 °C. This work provides a reliable strategy for designing advanced halide SSEs for commercial applications in ASSBs by cation-anion co-doping.