Dendrite Growth in Lithium Metal Solid-State Batteries

Solid-state batteries which combine both a lithium anode and ceramic solid electrolytes promise a step change in cell energy density. However, there are significant challenges to charging and discharging these cells at high current densities in the range of several mA cm^-2. At high rates of charge, dendrites (filaments of lithium metal) are observed to crack through ceramic electrolytes, leading to critical failure of the cell. The realisation of solid-state batteries with lithium metal anodes therefore depends on understanding how a soft metal such as Li can induce fracture of a stiff ceramic electrolyte.<br/>Using a combination of X-ray computed tomography and FIB-SEM we have made observations which reveal both how Li dendrites crack Li₆PS₅Cl electrolytes and how these dendrite-cracks propagate across the solid electrolyte. We have made the finding that dendrite-cracks propagate whilst partially filled, driven by Li at the back of the crack not the tip. This has enabled advances in understanding dendrites in ceramics and the factors that influence then and their progression to a short-circuit.