Mechanism of silicon fragmentation in all-solid-state battery evaluated by discrete element method

Abstract

Silicon (Si) alloy provides a high charge capacity as the active material (AM) in anodes of all-solid-state batteries (ASSBs); however, it may expand by up to 300% during charging, which causes capacity losses associated with fragmentation and contact losses. Herein, a simulation framework including fabrication and intercalation of Si anode in an ASSB using the discrete element method (DEM) is proposed. AM particles were simulated as pre-aggregated primary particles. The Li distribution within the AM particles in the intercalation simulation was obtained by calculating the diffusion of Li between primary particles. The damage inflicted on both AM and solid electrolyte (SE) during intercalation expansion was determined by calculating breakage of fusion bonds. Diffusion limitation caused uneven expansion of AM particles, resulting in high stress and breakage of AM aggregates. The simulation was performed with different stack pressure, C-rate, and AM fraction values. Structural properties such as porosity and the AM–SE contact area were significantly affected by stack pressure. Moreover, C-rate had a significant impact on Li concentration gradient and damage to AM particles because of diffusion limitation. This study provides insights on interactions between reaction, diffusion, intercalation expansion, and damage in ASSBs and the development of improved battery designs.