Multifunctional Dual‐Doping Strategy Improving Halide‐Based Solid‐State Electrolyte

Abstract For the enhanced energy density and safety of lithium batteries, the development of solid‐state electrolytes (SSEs) compatible with high‐voltage cathode materials has become a primary objective. In this study, a halide‐based solid‐state electrolyte with a Li 3 InCl 6 (LIC) structure is engineered through a dual‐doping strategy, which enables its application with LiCoO 2 (LCO) and LiNi 0.5 Mn 1.5 O 4 (LNMO) cathodes. Fluorine doping is introduced into the LIC SSE to widen its electrochemical stability window. However, this modification leads to a reduction in ionic conductivity. To address this issue, a small amount of Zr 4+ is co‐doped to partially substitute In 3+ , which introduces lithium vacancies that facilitate Li + diffusion and enhance ionic conductivity. The optimized composition, Li 2.9 In 0.9 Zr 0.1 Cl 5.2 F 0.8 (LIZCF), exhibits the best balance of high ionic conductivity (1.37 x 10 −3 S cm −1 ) and a wide electrochemical stability window. When applied in high‐voltage cathode‐based cells, fluorine doping is found to improve cycling stability, while Zr co‐doping effectively reduces the overpotential during operation. Furthermore, partial density of states (PDOS) calculations confirm that the dual‐doping strategy suppresses side reactions. These findings demonstrate the strong potential of the dual‐doping approach for the development of next‐generation high‐energy solid‐state battery systems.