Influence of concentration-dependent diffusivity on lithium plating: Polarization, stability, and dendrite formation in phase-field simulations

Lithium dendrite issues significantly impede the development of high -energy -density secondary batteries with a lithium anode. The widely -used classical Sand's limiting current density, predicting lithium dendrite formation during plating, relies on constant diffusivity. However, overlooking realistic ion transport dynamics, like concentration -influenced diffusivity, often results in discrepancies between analytical predictions and experiments. To better understand the origin of the observed inconsistency, our study presents a phase -field method for solving the dynamics of ion transport in electrolytes during anode surface migration in plating. The model integrates the Stewart-Newman diffusivity for concentration -influenced ion transport dynamics and the Butler-Volmer equation for electrochemical kinetics at the anode -electrolyte interface. In addition to phase -field simulations, we performed a steady-state analysis of the concentration distribution in electrolytes, determining the limiting current density. Verification confirms strong agreement between the phase -field model and analytical predictions. Our two-dimensional phase -field simulations further reveal that the varying diffusivity, dependent on concentration, plays a crucial role in plating stability and the resulting lithium morphology. Results of this study provides valuable insights for resolving the observed discrepancies in the onset of lithium dendrite formation between experiments and the classical Sand's formula.