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

Abstract

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.