Electro-chemo-mechanical finite-element model of single-crystal and polycrystalline NMC cathode particles embedded in an argyrodite solid electrolyte

All-solid-state batteries (ASSB) are emerging as a high-performance alternative to Li-ion batteries. However, some technical challenges need to be overcome before commercialization. Understanding and improving the chemo-mechanical behavior is considered one of the fundamental challenges in the development of ASSB. This work develops a continuum-level, two-dimensional finite-element model that predicts electro-chemo-mechanical responses of a cathode particle in contact with, and surrounded by, solid electrolyte. The model incorporates physics such as structural anisotropy, intergranular particle fracture, cathode embrittlement upon lithiation and cycling, and intragranular separation at cathode-electrolyte interfaces. The model results compare electrochemical performance between single-crystal and randomly oriented polycrystalline cathode particles. Additionally, performance is predicted at several operating pressures. The manuscript considers LiXNi0.8Mn0.1Co0.1O2 (NMC811) electrode particles surrounded by Li6PS5Cl (LPSC) solid-state electrolyte. The model aims to inform the design of microstructures and operating conditions that limit or prevent mechanical damage during electrochemical cycling of all-solid-state batteries. The results indicate the superior performance of single-crystal NMC811 particles with smaller sizes and higher applied pressure. The highest degradation is predicted in the first cycle. Particle size is identified as a critical parameter for composite electrode performance.