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

摘要

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.