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 Li 3 InCl 6 electrolyte via energy-friendly dissolution and post-treatment. The organics in ethanol-mediated precursor disappear in form of light gas during post-treatment. And Li 3 InCl 6 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 Li 3 InCl 6 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 0.8 Co 0.1 Mn 0.1 O 2 /Li 3 InCl 6 /Li 10 GeP 2 S 12 /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 Li 3 InCl 6 is a novel promising electrolyte which can be coupled with high-voltage cathode for the application of all-solid-state lithium-metal batteries.