Effect of Misfit Dislocation on Li Diffusion and Stress in a Phase Transforming Spherical Electrode

The Li-ion battery electrode materials generally experience significant volume change during lithium diffusion. These volume changes lead to diffusion induced stress. Diffusion induced stress(DIS) will cause fracture and nucleation in the electrode. Many electrode materials undergo formation of two or more phases during lithium insertion. By analyzing the process of lithiation, the DIS in phase transforming electrodes using a core-shell model structural is investigated. The new model considering the misfit dislocation effect is established to analyze the stress distribution in the nanoparticle electrode. We observe that the magnitude of DIS can be affected by the misfit dislocation. In addition, the concentration jumps is also affected by the misfit at phase boundaries that result in stress discontinuities, which in turn can cause cracking. The influence of the mechanical properties of the two phases on stress evolution, stress discontinuity, and misfit dislocation effect are clarified. What's more, the Tresca stress is also expounded in the Li-ion battery. The effect of misfit dislocation and the phase transforming on the Tresca stress is clarified. The trends obtained with the model may be used to help tune electrode materials with appropriate interfacial and the misfit dislocation so as to increase the durability of battery electrodes. (C) The Author(s) 2015. Published by ECS. All rights reserved.