Critical Currents of Lithium Anode Solid-State Batteries with Ceramic Electrolytes

Solid-state batteries using a lithium anode and a ceramic electrolyte promise to improve the energy density and safety of cells. However, there are significant challenges to cycling lithium anode solid-state batteries at practical current densities of several mA cm^-2. Critical currents occur on discharge (stripping) above which cells fail due to voiding at the Li/solid electrolyte interface. Such voiding depends on Li creep rates, which depend on temperature and stack pressure. Dendrites (Li filaments) penetrate the solid electrolyte on charge (plating). Using X-ray computed tomography we have followed in detail how Li dendrites crack Li₆PS₅Cl electrolytes and how the dendrite-cracks propagate across the solid electrolyte. We model the process based on our observations including the process of dry crack propagation. The relationship between cycling conditions, stack pressure and the properties of the solid electrolyte will be discussed. The findings help to inform routes for realising solid-state batteries that avoid short-circuits.