Numerical Investigation on Diffusion-Induced Cracking in Solid Electrolyte of Composite Electrode and Its Impact on the Li-Ion Conductivity

Abstract

In this paper, the cracking of the solid electrolyte (SE) and its impacts on the effective Li-ion conductivity of composite electrodes of all-solid-state lithium-ion batteries (ASSLIBs) are investigated numerically. A two-dimensional finite element (2D FEM) model was developed for composite electrodes in which active material particles (AM particles) are embedded in the solid electrolyte. The 2D FEM model can successfully calculate and simulate the diffusion-induced stress, the generation of solid electrolyte cracks (SE cracks), and the Li-ion transport. The degradation of Li-ion conductivity for cracked composite electrodes is calculated with the homogenization method. It is revealed that the diffusion-induced volume variation in AM particles can generate significant stress and thus SE cracking in composite electrodes of ASSLIBs. The calculated results suggest that swelling AM particles are more favorable than shrinking AM particles for the structural stability of composite electrodes. It is also demonstrated that the evolution of the conductivity with the propagation of SE cracking is consistent with the percolation theory. The fundamental understating of the SE cracking and its impact in this paper may benefit the design of novel ASSLIBs with more stable performance and a longer lifespan.