Evidencing Phase Transformations of Li₆PS₅Cl Argyrodite under Ambient Air and Dry Room Exposure

All-solid-state electrolytes have been extensively studied for the last years in order to achieve high conductivities and improved safety among lithium-ion technologies. Sulfide electrolytes, such as argyrodites (Li₆PS₅X, X = Cl, Br, and I), succeed to show high performances despite their poor chemical stability. As a matter of fact, argyrodite reactivity to water is known as a common drawback for easy implementation and requires the use of dry room for cell preparation. The understanding of argyrodite degradation under ambient air exposure is a key for the development of stable electrolytes, coatings, and processes and has been incompletely explored until now. This study brings unreported elements of comprehension around the degradation mechanisms of Li₆PS₅Cl solid electrolyte using transmission electron microscopy (TEM) and complementary spectroscopic techniques.