Modeling of diffusion-induced inter-/transgranular cracking in polycrystal NCM particles: Effects of external force and boundary constraints

Experimental results have evidenced that appropriate external forces can mitigate structural degradation and damage of active particles during electrochemical cycling of metal-ion batteries. Currently, there are few studies on structural degradation and damage of active particles under concurrent action of diffusion and external loading. Using finite-discrete element method (FDEM), we analyze diffusion-induced cracking in a polycrystal NCM (lithium nickel manganese cobalt oxide) particle under three different configurations: traction-free boundary, rigid confinement to opposite ends, and external loading to opposite ends under constant influx. The numerical results illustrate that appropriate external loading can suppress the nucleation and propagation of cracks induced by the diffusion of solute atoms and retard structural degradation/damage of polycrystal NCM particles. Increasing the amount of solute atoms and applying excessive external loading can promote the nucleation and propagation of cracks in polycrystal NCM particles due to large contact deformation and the deformation induced by the diffusion of solute atoms, which escalates structural degradation/damage of the electrodes in metal-ion batteries.