An Electrochemical-Mechanical Phase Field Model for Lithium Dendrite

Lithium metal is considered a holy grail anode material for high theoretical energy batteries. However, lithium dendrite associated with interface instability has severely derailed efforts to commercialize safe and high-capacity lithium batteries. Here, we propose an electrochemical-mechanical phase field model by incorporating the elastic energy into the Gibbs free energy to reveal the role of stress in lithium dendrites. It is found that the compressive stress associated with lithium electroplating gradually concentrates near the nucleation site, acting as a driving force for dendrite formation. The surface energy plays a critical role in determining the dendrite morphology, the higher the surface energy the higher the curvature of the dendrite. A phase diagram of four types of morphologies is identified in terms of the interface energy density and charging rate. Our analysis suggests that a low charging rate or improving the interfacial Li ⁺ diffusion ability is beneficial to maintaining interface stability.