Analysis of large-deformed electrode of lithium-ion battery: Effects of defect evolution and solid reaction

In this work, we analyze the diffusion-induced deformation in a spherical Sn (tin) particle during lithiation in the framework of chemo-mechanics, taking into account finite elasto-viscoplastic deformation and solid reaction (alloying). A viscoplastic constitutive relationship, which is based on the evolution of defects similar to dislocation mechanics, is used in the analysis. The contribution of solute atoms (lithium) to the mass transport in a deforming electrode consists of two parts; one is from “mobile” solute atoms associated with diffusion and local convection, and the other is from “immobile” solute atoms associated with local solid reaction. Finite element method is used to calculate the deformation of the spherical Sn particle with traction-free condition and galvanostatic charging during lithiation. The numerical results show that the local solid reaction increases the concentration gradient of mobile atoms, leading to the increase of the radial and hoop stress components. Plastic flow can significantly reduce the magnitudes of the stresses, likely preventing the Sn electrode from mechanical degradation and improving the structural durability of lithium-ion battery.