Stack pressure effects and viscoplastic deformation in argyrodite solid-state electrolyte

Lithium metal dendrite penetration and interfacial instabilities are critical challenges that hinder the widespread adoption of all-solid-state batteries (ASSBs). In this work, we systematically investigate the impact of viscoplastic deformation on these mechanisms, using Li₆PS₅Cl electrolyte as an example. This study focuses on evaluating rate-dependent behavior by applying moderate stack pressures with custom-designed electrochemical cycling protocols that employ zero-current holds and sinusoidal-like cycling. The highest critical current density achieved in our study was 4.8 mA/cm². Our analysis indicates that relatively slow lithium creep mitigates interfacial void formation and enhances the critical current density and cycle life. It also indicates that the stresses in the vicinity of these voids are well above the reported yield stress for lithium metal. The overall findings highlight the critical role of mechanical properties in the stability of the electrolyte-metal interface and demonstrate that leveraging viscoplasticity can substantially enhance the sulfide-based ASSB cycling performance.