How Does the Creep Stress Regulate Void Formation at the Lithium‐Solid Electrolyte Interface during Stripping?

Interfacial instability from void formation at the solid–solid interface is one of the crucial challenges in solid‐state batteries. However, the fundamental mechanism as to how stress is generated in lithium and thus impacts void formation has not been established. A general creep/contact electro‐chemo‐mechanical model is herein developed to reveal the mechanisms of void formation at the Li/solid electrolyte (SE) interface during stripping. Li stress calculation is achieved by presuming that the strain‐rate‐dependent creep deformation of Li metal acts like that of an incompressible viscous fluid flow. The results demonstrate that the dominant mechanism that impedes void formation is the creep‐induced flux enhancement of vacancies, which are transported into Li metal for a non‐ideal Li/SE interface with pre‐existing interfacial defects. This contrasts with previous simulations on an ideal flat Li/SE interface in which the vacancy diffusion away from the interface is shown to govern whether voids are formed. The mechanism of void formation at the Li/solid‐electrolyte interface is revealed through the creep/contact electro‐chemo‐mechanical model. The dominant mechanism that impedes void formation is the creep stress‐induced flux enhancement of vacancies, which are transported into Li‐metal for a non‐ideal interface with defects. This contrasts with the mechanism on an ideal flat interface in which vacancies diffusing away from the interface govern void formation.