Electro-chemo-mechanics interplays caused by solid electrolyte-lithium anode interface roughness in all-solid-state batteries

Solid-to-solid interfacial issues are one of the most intractable problems hindering the practical application of all-solid-state batteries (ASSBs). The interfacial instability behaviors caused by the rough interface between lithium anode and solid electrolyte (SE) involve complicated electro-chemo-mechanics interplays and their quantitative relationships still remain unclear. The three-dimensional electro-chemo-mechanical coupled model with randomly generated rough lithium-SE interface is developed in this study to investigate the effects of interface roughness on the interfacial failure behaviors. Results demonstrate that the existence of a rough lithium-SE interface causes the highly concentrated strain, GPa-level stress, and localized current density at the protruding tips, probably inducing dendrite formation and interface cracking. The interface roughness effect is much more pronounced in lithium anode than graphite anode due to their different Li storage mechanisms, i.e., surface deposition and Li intercalation. Excessive stack pressure (>50 MPa) magnifies the stress effect on overpotential to enlarge the current density localization and deteriorate the interfacial instability issues. Reducing interface roughness through surface treatment, together with regulation of external operation conditions, can effectively improve interfacial stability performance. The results provide an in-depth understanding of the underlying electro-chemo-mechanical coupling mechanism caused by the rough anode-SE interface and bring more insights into further improvement of ASSBs’ enhanced reliability and longevity.