A Novel Ethanol-Mediated Synthesis of Superionic Halide Electrolytes for High-Voltage All-Solid-State Lithium–Metal Batteries

Halide electrolytes are rising stars among inorganic solid-state electrolytes due to their high ionic conductivity and good compatibility with high-voltage electrodes. However, their traditional synthesis methods including ball-milling annealing are usually energy-intensive and time-consuming compared with liquid-mediated routes. What's more, the only method in aqueous solution is not perfect considering detrimental effect of trace water for battery performances. Here, we propose a novel ethanol-mediated synthesis route for superionic Li₃InCl₆ electrolyte via energy-friendly dissolution and post-treatment. The organics in ethanol-mediated precursor disappear in form of light gas during post-treatment. And Li₃InCl₆ with best thermal stability and ionic conductivity (0.79 mS cm^-1, 20 °C) can be successfully prepared after postheating for 3 h at 200 °C. Besides, it is also found that the ionic conductivity of Li₃InCl₆ is positively correlated with peak intensity ratio of (131) plane/(001) plane since crystal plane and preferred orientation can directly affect polyhedrons through which lithium ions migrate in crystalline conductors. The assembled LiNi_0.8Co_0.1Mn_0.1O₂/Li₃InCl₆/Li₁₀GeP₂S₁₂/Li-In cell presents high initial charge capacity of 174.8 mAh g^-1 at 0.05 C and a good rate performance of 122.9 mAh g^-1 at 1 C. Especially, the retention rate of charge capacity can reach 94.8% after 200 cycles. The ethanol-mediated synthesized Li₃InCl₆ is a novel promising electrolyte which can be coupled with high-voltage cathode for the application of all-solid-state lithium-metal batteries.