Mechanical-Electrochemical Modeling of Agglomerate Particles in Lithium-Ion Battery Electrodes

Abstract

Many electrode materials for lithium-ion battery applications are composed of secondary particles. Such an active material particle is not a solid particle, but consists of many fine primary particles. This work presents a coupled mechanical and electrochemical model to predict the intercalation-induced stress in a secondary particle with an agglomerate structure. In this model the electrochemical and transport processes are accounted for at both the secondary and primary particle levels. For mechanical analysis the secondary particle is treated as a continuum with stress calculated through lithium concentration and elastic deformation. With this model we revealed several important factors that affect stresses in secondary particles. Our simulations show that a stronger dependence of the open circuit potential of the active material on lithium-ion concentration reduces the stress level. A larger magnitude of over-potential at the surface of a secondary particle causes larger stresses. A larger primary particle size helps to reduce the stresses in the secondary particle as long as the secondary particle is a continuum containing many primary particles. Finally, a comparison between a porous secondary particle and a solid particle of the same size shows that the stress level in a porous secondary particle is much smaller.