Effect of plasticity on voltage decay studied by a stress coupled phase field reaction model

Abstract

Many promising candidate electrode materials suffer from severe voltage decay, which is detrimental to lithium ion battery performance. Recently, the relationship between stress-mediated chemical potential and voltage variation has received much attention. While, how the plastic deformation affects the voltage variation remains unclear. A stress coupled phase field reaction model is employed to reveal the mechanism for the stress-related voltage decay accompanied by plastic deformation, wherein different lithiation behaviors under electrochemical reactions are considered. It is demonstrated that hydrostatic compression on the surface is responsible for the stress-induced voltage decay, and the plastic deformation can mitigate the voltage decay via not only relaxing the hydrostatic compression, but also changing hydrostatic compression on the surface to be hydrostatic tension under the small yield stress. In addition, under the same yield stress, two-phase lithiation process is prone to trigger the plastic deformation compared to the single phase lithiation process, facilitating to elevate the output voltage. Further, compared to the circular particle, the interconnected particle can improve the output voltage through the favorable transition from hydrostatic compression to hydrostatic tension at the interconnected region and the surface with large curvature.