Local Bonding and Reconstruction Enhancing Ion Transport in Li3InCl6.

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 Nb5+ doping strategy to successfully create a favorable microstructural environment in the halide solid-state electrolyte Li3InCl6 that facilitates rapid Li+ transport. The introduction of Nb5+ 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, Li2.84In0.92Nb0.08Cl6, to achieve a room-temperature ionic conductivity of 1.03 mS cm-1 and an activation energy of 0.305 eV. Furthermore, Nb5+ 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.