Filament-Induced Failure in Lithium-Reservoir-Free Solid-State Batteries

Lithium-reservoir-free solid-state batteries can fail due to electrical shorting as a result of fracture and lithium metal filament formation. Mechanical stress at the solid electrolyte surface can induce fractures, which promote lithium filament growth. This stress arises from both electrochemical sources, due to lithium electrodeposition, and mechanical sources, such as external stack pressure. Solid electrolyte surface roughness and the applied stack pressure together affect stress development. This study combines electrochemical experiments, 3D synchrotron imaging, and mesoscale modeling to explore how stack pressure influences failure mechanisms in lithium free solid-state batteries. At low stack pressure, irregular lithium plating and the resulting high local current density drive failure. At higher stack pressure, uniform lithium plating is favored; however, notch-like features in the surface of the solid electrolyte experience high tensile stress, leading to fractures that cause premature short-circuiting.