Disconnected Lithium Metal Damages Solid-State Electrolytes

Solid-state batteries with a lithium-metal anode are energy-storage devices that promise increased energy density and improved safety compared to liquid systems. Despite significant developments, the chemomechanical degradation of solid-state batteries represents a significant challenge to their widespread adoption. Specifically, Li-filled cracks (called 'dendrites') and electronically isolated Li inclusions ('dead' Li) are key defects resulting from coupled electrochemical-mechanical degradation during cycling. In this study, we use a symmetrical Li|LLZO|Li cell with a single-crystal electrolyte and demonstrate that an electronically isolated Li-metal inclusion exhibits bipolarity under an external electrical field, which leads to further crack expansion. We suggest that this process of 'dead' metal activation accelerates chemomechanical degradation in solid-state batteries with alkali anodes.