Simulation of All-Solid-State Lithium-Ion Batteries With Fastening Stress and Volume Expansion

The volume expansion of anode active materials in all-solid-state lithium-ion batteries strongly affects the dynamic change in the electrode structure and its activity in electrochemical reactions and mass transport. Thus, understanding the mechanisms and internal phenomena during the charging process with volume expansion is important. In addition, clarifying these phenomena contributes to the selection of the active material when creating the electrode structure. This study aimed to verify the effect of volume expansion of the active material in a porous electrode layer on the charging performance using a numerical simulation. In this calculation, for the electrochemical reaction transport analysis, equations were applied based on the porous electrode theory; for the structural deformation due to expansion, we expressed the change by controlling the structural parameters and built a model for simulation. From the simulation results, when the fastening pressure was small, the active material with a large volume expansion ratio exhibited a larger capacity. However, for a large fastening pressure, active materials with a large volume expansion ratio seemed not to be used. Although the volume expansion of the active material should be suppressed from the viewpoint of ion conduction network rupture, these results demonstrate that the influence of volume expansion effectively depends on the electrode creation conditions. This model will help to optimize the design of all-solid-state batteries and can be the key to further performance improvement.