Modeling storage particle delamination and electrolyte cracking in cathodes of solid state batteries

Interface delamination between storage particles and solid electrolytes contributes to greater impedance for Li transfer and capacity loss in solid-state batteries. Electrolyte cracking would cause degradation of the ionic or electronic conductivity of electrolytes. The occurrence of interface delamination and electrolyte cracking is commonly ascribed to mechanical stress, which evolves from inhomogeneous shrinkage and swelling of storage particles confined by the surrounding solid electrolytes when lithium is extracted or inserted. Here, a coupled model of Li diffusion, ionic conduction, interfacial reaction, mechanical stress and a phase field fracture approach is applied to investigate defect-initiated interface delamination and how cracks nucleate in electrolytes in a full 3D dynamical description for the first time. We find that unstable interface delamination is a very likely event during extraction. On the other hand, homogeneous delamination where the whole interface delaminates simultaneously, can happen for smaller interfacial defects with larger particle sizes and higher applied current densities. Larger interfacial defects delay the onset of delamination due to damage dependent interfacial reaction. More particle storage capacity can be utilized for smaller particle sizes and smaller interfacial defects prior to delamination. We further demonstrate electrolyte cracking can happen quite readily, and the electrolyte can break into several parts in only one insertion half cycle and even the appearance of full delamination.