The role of elasto-plastic deformation in solid electrolytes on the electrode-electrolyte interfacial stresses of all-solid-state batteries

Lithium all-solid-state batteries (ASSBs) represent a cutting-edge technology for future battery development. Recent research interest in ASSBs stems from their potential to outperform traditional lithium-ion batteries. ASSBs offer several advantages, particularly higher energy density and enhanced safety. However, several issues hinder the commercialization of ASSBs. One of the major problems is the complex nature of solid-solid interfaces. Composite cathodes are one of the critical areas where solid-solid interfaces play a vital role. These cathodes rely on a densely packed architecture of active material particles surrounded by a conductive solid electrolyte to facilitate ionic transport, along with additional additives for electronic conduction. During ion intercalation/deintercalation, the active material particles undergo volumetric expansion and contraction. In the confined environment of the all-solid-state architecture, this can lead to the generation of high stresses. In this work, we investigated the impact of nonlinear deformation of solid electrolytes on the active materials/solid electrolytes interfacial stress state using a simple 1D spherical model. Assuming an incompressible elastic-perfectly plastic material for the solid electrolytes, we examined the stress resulting from the volumetric change during lithium-ion deintercalation/intercalation (completing one full cycle). Analytical expressions for the stress state were obtained as the plastic region propagates during de-lithiation, and reverse yielding occurs during lithiation. These analytical solutions can serve as a preliminary estimate for assessing interfacial stress in solid electrolyte materials beyond the linear elasticity range.