Understanding on the effects of chemical reaction at cathode-electrolyte interface in sulfide based all-solid-state batteries

Driven by a paradigm shift from conventional liquid-based systems to all-solid-state batteries (ASSBs), the chemo-mechanical behavior of the solid-solid interface is of growing importance for understanding the intricate interfacial phenomena of ASSBs. At the interfaces, various degradation factors of the cells during electrochemical cycling are complexly intertwined such as electrochemically driven volume changes of active materials and formation of highly reactive cathode. Moreover, chemical reactions at the interface between the solid materials involving the diffusion of chemical species at the junction that occur immediately after the cell assembly are also correlated to the cell performance. However, the individual effects on electrochemistry are vaguely understood. In this study, we investigate the independent effect of chemical reaction between a cathode and a sulfide-based electrolyte. We reveal that chemical degradation products are different from those commonly observed after electrochemical cycling and they induce sluggish kinetics on ionic conduction at grain boundary. We also find physical contact-loss between cathode and electrolyte, implying that chemically driven mechanical degradations occurred simultaneously. Our research provides an insight into the complex behaviors at the solid-solid interface in sulfide-based ASSBs.