The Lithium Metal Electrochemical-Mechanical Evolution Mechanism of Void Defects for Interface Mechanical Failure in Solid-State Lithium Metal Batteries

Solid state lithium metal batteries are the most promising candidates for high-energy density battery systems due to their high energy density and safety characteristics. However, the incomplete smooth solid–solid interface between the solid electrolyte and the lithium metal anode leads to poor interface contact, resulting in uneven lithium plating and lithium dendrite penetration, which in turn causes mechanical failure of the interface. Herein, the effect mechanism of lithium metal evolution on interface mechanical failure in solid electrolyte void defects was investigated by establishing a two-dimensional electrochemical mechanical multiphysics coupling model. The lithium metal at the interface void defect of LLZO with high ionic conductivity exhibits small Von Mises stress, which is conducive to suppressing the growth of lithium dendrites perpendicular to the interface direction. The LLZO interface void defect with low ionic conductivity exhibits large local equivalent strain, and the damage area parallel to the interface direction inside the void is narrower, which is more conducive to protecting the solid electrolyte. Moreover, when the interface reaction is at a low reaction rate and high diffusion rate, corresponding to R ≥ 1, stable deposition is formed at the interface. By regulating the stacking pressure to 30–60 MPa, it can effectively deflect and prevent the growth of lithium dendrites. This work provides scientific theoretical guidance for interface engineering of solid-state lithium metal batteries.