Phase-field simulation tending to depict practical electrodeposition process in lithium-based batteries

Lithium dendrite growth due to uneven electrodeposition usually leads to the potential hazard of internal short circuit and shorter lifetime of lithium-based batteries. Extensive efforts have been devoted to explore the effects of single or two factors on dendrite growth, involving the diffusion coefficient, exchange current density, electrolyte concentration, temperature, and applied voltage. However, these factors interrelate during battery operation, signifying that a understanding of how they jointly influence the electrodeposition is of paramount importance for the effective suppression of dendrites. Here, we incorporate the dependent relationships among key factors into the phase-field model to capture their synergistic effects on electrodeposition. All the simulations are implemented in our self-written MATLAB code under a unified modeling framework. Following this, five groups of experimentally common dendrite patterns are reproduced and the corresponding electrodeposition driving forces are identified. Unexpectedly, we find that with the decrease of the ratio of exchange current density(or applied voltage) to diffusion coefficient, the electrodeposition morphology changes from needle-like dendrites to columnar dendrites and to uniform deposition. The present phase-field simulation tends to depict the practical electrodeposition process, providing important insights into synergistic regulation to suppress dendrite growth.

Understanding the separator pore size inhibition effect on lithium dendrite via phase-field simulations

Dendrite growth in lithium-ion batteries may bring thermal run-away especially at high current densities,which remains the major bottleneck to implement safe and fast charging for portable electronic devices or electronical vehicles.Designing dendrite inhibition separators with proper pore size is considered to be one of the most promising strategies to guarantee the battery safety.However,due to the impossible observation of lithium-ion distribution under separator by experiments,the underlying dendrite inhibition mechanism is still not fully understood.Here,we apply the phase-field model,which takes the separator phase into account to construct the electrochemical system total free energy,to study the ion re-distribution behavior of porous separator and understand the pore size inhibition effect on lithium dendrite.The numerical results indicate that separator with smaller pore size is beneficial to smoother electrodeposition,since the lithium-ion concentration on the electrode surface is more uniform under denser separator pores,when their sizes is larger than the critical nucleus.The proposed model could capture the physicochemical process of electrodeposition under multiphase structures,so it could also be used to explore dendrite growth under composite electrodes and composite solid electrolytes.