Asymmetric Contact Loss Dynamics during Plating and Stripping in Solid‐State Batteries

Abstract Solid‐state batteries (SSBs) hold the potential to improve energy density and offer enhanced safety when compared to lithium‐ion batteries. However, the development of practical SSBs faces major challenges, such as filament growth and void formation, which necessitate a comprehensive understanding of the intrinsic solid–solid interfaces and limiting mechanisms. In this work, the underpinning asymmetry in the mechanistic interplay and resulting interface dynamics during Li plating and stripping is demonstrated, illustrating the critical effect of reaction heterogeneity on the contact loss behavior. With increasing stripping rates, the manifestation of solid–solid point contacts is identified as a key descriptor that signifies a transition in electrochemical response from a regime of continuous contact decay to current constriction. It is revealed that contact loss can also occur during plating at the Li/Li 6 PS 5 Cl interface; this severity scales with the reaction heterogeneity and is identified as an important challenge toward achieving faster charging rates in SSBs. The distinct nature of competing electrochemical–mechanical interactions that govern void formation during plating/stripping are delineated in this work. Coupled with these intrinsic mechanisms, non‐uniformities in external pressure and temperature fields drastically alter the contact dynamics, resulting in disparate void localization patterns.