Phase-field study of dendritic morphology in lithium metal batteries

Abstract

Lithium metal is a promising anode candidate for high-energy-density secondary batteries due to its high theoretical capacity and low electrochemical potential, but the uncontrolled lithium dendrite growth causing the poor cycling performance and safety concerns becomes the main drawback in the lithium metal batteries (LMBs). This study presents a phase-field method for modeling the lithium dendrite formation in LMBs. In this model, the electrochemical kinetics is described by a modified Butler–Volmer equation for deposition non-uniformity, and the Nernst–Planck equations and charge neutrality condition are used to solve the electric potential field and the ionic concentration fields. Our simulation results show that this model is able to accurately describe the growth of mossy dendrites, which is missing in previous phase-field works. We found that the lithium dendrite growth is strongly affected by the deposition non-uniformity originated from the competition of SEI growth and lithium growth and the charge conditions. Under high deposition rates, the depletion of the lithium ionic concentration takes place near the anode, and the dendrite growth undergoes a transition from the reaction-limited mossy growth to the diffusion-limited fractal growth.