Fundamental air stability in solid-state electrolytes: principles and solutions

Solid-state electrolytes (SSEs) have been put forward as excellent alternatives to liquid electrolytes owing to their good thermal stability, non-flammability, and good compatibility with lithium anodes. Their air stability is one of the most important factors towards large-scale synthesis and applications. Unfortunately, few reviews focus on outlining the effects of air stability buried in SSEs. Herein, to replenish this deficiency, we summarize the principles of the atmospheric instability, including the moisture-induced emission of H2S, H+/Li+ ionic exchange, surface oxidation and expansion of contaminants. Current solutions developed to improve the atmospheric stability are also sorted and introduced with respect to doping, surface modification, and applying other physical approaches. Finally, we also introduce possible approaches to improve the air stability of SSEs based on our insights into the air stability of SSEs.