Local Bonding and Reconstruction Enhancing Ion Transport in Li ₃ InCl ₆

ABSTRACT

Developing solid‐state electrolytes with high ionic conductivity has been recognized as crucial for advancing all‐solid‐state batteries. Enhancing the ionic conductivity of solid‐state electrolytes crucially depends on establishing the relationship between microstructure and ion transport. This study employs the aliovalent Nb ⁵⁺ doping strategy to successfully create a favorable microstructural environment in the halide solid‐state electrolyte Li ₃ InCl ₆ that facilitates rapid Li ⁺ transport. The introduction of Nb ⁵⁺ is found to significantly optimize the Li ⁺ migration pathways by triggering a local structural distortion. Further electronic structure analysis reveals that the formation of strong Nb─Cl bonds concurrently weaken the Li─Cl interactions, which is crucial for enhancing ionic conductivity. This synergistic microstructural optimization enables the optimal composition, Li _2.84 In _0.92 Nb _0.08 Cl ₆ , to achieve a room‐temperature ionic conductivity of 1.03 mS cm ⁻¹ and an activation energy of 0.305 eV. Furthermore, Nb ⁵⁺ doping effectively suppresses the electronic conductivity and mitigates side reactions between the electrolyte and Li metal, thereby enabling all‐solid‐state batteries to exhibit exceptional long‐term cycling stability. This work elucidates the regulation mechanism of local bond reorganization through cation doping, thereby providing important insights for the rational design of high‐performance halide solid‐state electrolytes.