Dual substitution in cationic and anionic sublattices of lithium indium chloride for high-performance solid-state lithium metal batteries

Abstract

The compatibility of solid-state electrolytes with high-voltage cathodes and their electrochemical stability make them promising candidates for solid-state lithium-metal batteries. Metal-based lithium chlorides were proposed as superionic conducting electrolytes; however, further enhancements are required regarding their room-temperature ionic conductivity, interfacial stability with lithium metal anodes, and moisture sensitivity. The proposed strategy targets synergistic improvement of these properties by enhancement of the Li₃InCl₆ crystal structure, as a model compound, through dual substitution in its cationic and anionic sublattices. The study reveals that singly doped Li₃In_1−xZr_xCl₆ (0 ≤ x < 0.6) electrolytes possess enhanced ionic conductivity, while fluorine-substituted Li₃InCl_6−yF_y (0 ≤ y < 0.6) electrolytes have improved oxidation stability at the electrolyte–lithium metal interfaces. The dual substitution results in an optimized Li_2.6In_0.6Zr_0.4Cl_5.9F_0.1 electrolyte with synergistically combined superior properties compared to undoped and single-doped derivatives. Solid-state electrochemical cells with the Li_2.6In_0.6Zr_0.4Cl_5.9F_0.1 electrolyte deliver a high specific capacity of 216 mA h g⁻¹ at 0.1C, a volumetric energy density of 419.1 W h cm⁻³, and a gravimetric energy density of 723.3 W h kg⁻¹. The dual-doping strategy enhances the properties of inorganic solid-state electrolytes, provides critical insights into lithium-ion transport at interfaces, and reveals key transformations in structure–property relationships with progressing from undoped to singly doped and further to dual-doped superionic conductors for next-generation energy storage systems.