A critical current density on stripping (CCS) is identified that results in dendrite formation on plating and cell failure. When the stripping current density removes lithium from the interface faster than it can be replenished, voids form in the lithium at the interface and accumulate on cycling increasing the local current density at the interface and ultimately leading to dendrite formation on plating, short-circuit and cell death. This occurs even when the overall current density is significantly below the threshold for dendrite formation on plating. For the Li / Li6PS5Cl / Li cell, this is 0.2 and 1 mA•cm -2 at 3 and 7 MPa pressure respectively, compared with a critical current for plating of 2 mA•cm -2 at both 3 and 7 MPa. The pressure dependence on stripping indicates creep rather than Li diffusion is the dominant mechanism transporting Li to the interface. The critical stripping current is a major factor limiting the power density of lithium anode solid state cells. Significant pressure may be required to achieve even modest power densities in solid state cells.

Lithium dendrite (filament) propagation through ceramic electrolytes, leading to short-circuits at high rates of charge, is one of the greatest barriers to realising high energy density all-solidstate lithium anode batteries. Utilising in-situ X-ray computed tomography coupled with spatially mapped X-ray diffraction, the propagation of cracks and the propagation of lithium dendrites through the solid electrolyte have been tracked in a Li/Li6PS5Cl/Li cell as a function of the charge passed. On plating, cracking initiates with spallation, conical "pothole"-like cracks that form in the ceramic electrolyte near the surface with the plated electrode. The spallations form predominantly at the lithium electrode edges where local fields are high. Transverse cracks then propagate from the spallations across the electrolyte from the plated to the stripped electrode. Lithium ingress drives the propagation of the spallation and transverse cracks by widening the crack from the rear, i.e. the crack front propagates ahead of the Li. As a result, cracks traverse the entire electrolyte before the Li arrives at the other electrode and therefore before a short-circuit occurs.

A novel templating method to create 3D bicontinuous structured hybrid electrolytes with improved mechanical properties for all-solid-state lithium batteries.