Dislocation Based Stress Developments in Lithium-Ion Batteries

It has been suggested that structural failures are the primary factor responsible for the observed rate-capacity fade of lithium-ion batteries. In the present study, we report three different lithium intercalation-induced dislocation mechanisms explaining experimentally observed cracks. We use the theory of elasticity and the superposition method to investigate stress and force fields between multiple dislocations. In most cases, dislocations are not perfectly parallel to one specific axis. Therefore, stress variations for arbitrary Burger's vectors are investigated. The stress fields manifesting between dislocations are numerically calculated and anisotropic material properties of electrodes are employed. The result shows that multiple dislocations are likely to be orthogonal to each other to reduce the total energy. In addition, studies have shown that when the discharging rate is increased, the capacity decreases due to the buildup of the internal elastic/plastic energy. Therefore, the stress fields of dislocation interactions in our study could be used to deduce and suggest the most feasible modes of crack formation and to provide insights into the lost of capacity in LiFePO4. Thus, the current study provide links between stress fields and the observed structural failure in lithium-ion batteries.