Water-Mediated Synthesis of a Superionic Halide Solid Electrolyte

To promote the development of solid-state batteries, polymer-, oxide-, and sulfide-based solid-state electrolytes (SSEs) have been extensively investigated. However, the disadvantages of these SSEs, such as high-temperature sintering of oxides, air instability of sulfides, and narrow electrochemical windows of polymers electrolytes, significantly hinder their practical application. Therefore, developing SSEs that have a high ionic conductivity (>10^-3 S cm^-1 ), good air stability, wide electrochemical window, excellent electrode interface stability, low-cost mass production is required. Herein we report a halide Li⁺ superionic conductor, Li₃ InCl₆ , that can be synthesized in water. Most importantly, the as-synthesized Li₃ InCl₆ shows a high ionic conductivity of 2.04×10^-3 S cm^-1 at 25 °C. Furthermore, the ionic conductivity can be recovered after dissolution in water. Combined with a LiNi_0.8 Co_0.1 Mn_0.1 O₂ cathode, the solid-state Li battery shows good cycling stability.