PHASE-FIELD COHESIVE MODELING OF FRACTURE IN STORAGE PARTICLES OF LITHIUM-ION BATTERIES

During charging and discharging of lithium-ion batteries (LIBs), lithium extraction and insertion induce inhomogeneous volume changes of storage particles, resulting in significant mechanical stresses. Dependent on the size and shape of storage particles as well as the recharging-charging rate, the diffusion-induced stress may lead to crack nucleation, propagation and even fracture of storage particles, yielding detrimental effects on the capacity and cycle life of LIBs. Aiming to simulate and predict the failure process of storage particles in LIBs, this work addresses a chemo-mechanically coupled phase-field cohesive zone model (PF-CZM) within the framework of the unified phase-field theory for damage and fracture. The numerical algorithm and computational implementation are also presented in the context of the multi-field finite element method, with applications to the modeling of mechanical failure of two-dimensional cylindrical and three-dimensional spherical storage particles in LIBs. As it intrinsically incorporates the strength-based nucleation criterion, the fracture energy-based propagation criterion and the variational principle based path chooser, the proposed PF-CZM applies not only to fracture analyses of pre-notched storage particles, but also to the simulation of the complete failure process of intact ones with no pre-defined defects. Extensive numerical results demonstrate that the proposed model is able to capture arbitrary crack configurations in storage particles due to evolution of Li-ion concentration, to predict the resulting mechanical failure of LIBs, and is useful for the optimal design of commercial LIBs.