Modeling of Void-Mediated Cracking and Lithium Penetration in All-Solid-State Batteries

All-solid-state batteries (ASSBs) are expected to have an exceptional energy density and safety owing to the possibilities of direct usage of lithium as an anode and the suppression of dendrites by a solid-state electrolyte (SSE). However, recent experiments unveil discharging-induced voids in lithium-SSE interfaces and charging-induced cracks in SSE, wherein lithium penetration occurs. To avoid such cell failures, a theoretical model rendering high-credibility simulations is needed to assist ASSB designs. Herein, such a model coupling the electrochemical processes and mechanical responses of an ASSB are proposed, in which the kinetics of voids and cracks are the key ingredients. Numerical simulations based on the model reveal that void growth is the result of stripping with disparate diffusivity in the surface layer and the bulk of lithium. They bring about the non-uniform distribution of Li⁺ during electroplating, a damage zone near the interface, SSE cracking, and then lithium plating in the cracks. It is noted that the cracks and lithium dendrites revealed by the simulations are very similar to those observed in in situ experiments and that a high stack pressure cannot inhibit cracking and lithium penetration. Instead, suitable lateral compressive stresses can prevent SSE from cracking and therefore inhibit lithium dendrites.