Investigation on damage mechanism and optimization strategy of the LiCoO2 composite cathode in All-Solid-State Lithium Battery

Solid-state composite electrodes play a crucial role in all-solid-state lithium batteries (ASSLBs). However, strain mismatch between the active material (AM) and matrix volume changes during discharge/charge cycles induce diffusion-induced stresses, resulting in the degradation of the solid composite cathode. In this study, we develop a particle-level geometric model to investigate the damage evolution in the solid electrolyte (SE) caused by ion/electron migration in the SE matrix, material transfer in the active particles, the interaction between the SE matrix and active particles, and the local current density at the SE/AM interface. We simulate the effect of mechanical damage on the electrochemical properties by coupling the damage variables and the ionic conductivity of the SE matrix. Our research results indicate that at higher discharge rates, the capacity decline caused by mechanical damage worsens. Furthermore, an increase in the volume ratio of active particles leads to additional damage in this model. Therefore, while maintaining an appropriate volume ratio, we propose a larger particle LS (larger particle near separator) dual-gradient near the separator, which will increase the discharge capacity by 8.5% at a discharge rate of 2C.