Inhomogeneous stress development at the multiparticle electrode of lithium-ion batteries

Abstract

The active particle at the electrode of Li-ion batteries is surrounded by other particles and binders. During the lithiation/delithiation process, these surrounding materials mechanically constrain expansion and contraction of the particle. Since electrochemical and mechanical responses mutually influence each other, the constraining condition can finally affect cell performance. In this paper, we investigate the mechanical and electrochemical responses at the particle and cell levels with consideration of the coupling effect of electrochemistry and mechanics. To study the effect of mechanical constraints on cell performance, we carry out numerical simulations with a particle network electrode model, where binders connect the multi-sized particles that are enclosed in a binder layer. The simulations show that the constraint from neighboring particles generates nonsymmetric lithium concentration and stress distribution. Stress-potential coupling in the battery model reduces the stress level by a maximum of 8.4% in the small particles and 30% in the large particles. However, due to the constraint of the binder and connected particles, the reduction in stress is not uniform. The maximum stress difference between the interacting point and the free surface is 13.6%. Besides, the results depict that considering the stress-potential coupling effect results in increased discharge capacity of the cell by 13.4%. Our study suggests that to design robust electrodes, understanding the mechanical-electro-chemo coupled behavior is essential. Highlights We establish a fully coupled chemo-mechanical multiparticle model. Stress-potential coupling alleviates concentration and stress gradients inside active particles. Particle-particle and particle-binder interactions cause stress inhomogeneity. Increasing binder modulus enhances stress nonuniformity.