Chemo-mechanical model predicted critical SOCs for the mechanical stability of electrode materials in lithium-ion batteries

Abstract

The electrochemical performance and capacity retention of lithium-ion batteries significantly depend on the structural integrity of electrode materials. Understanding of the mechanical failure mechanisms in the active and inactive material phases of the electrode is critical to predict safe operation conditions, and to design next generation electrodes. The mechanical failure of the electrode can be effectively avoided by tailoring the lithiation kinetics and the size of the active and inactive materials. To predict the critical state of charges (SOCs) for mechanical failures, we develop a fully coupled chemo-mechanical model, and examine the effect of stress-concentration coupling on the maximum stored capacity. We focus on three types of mechanical failures: particle fracture, binder yielding, and debonding at the particle-binder interface. The simulations show that the medium-sized particles achieve larger capacity with no mechanical failure. Moreover, the simulation results reveal that as the binder modulus and charge rates increase, the safe zone shrinks considerably, while the binder thickness imposes no significant effect. These findings provide a fundamental insight into providing optimized charging protocols for minimum capacity retention due to mechanical failures at the electrode.