Phase Field Method And Numerical Simulations Of Improving Lithium Dendritic Growth

Lithium metal anodes is one of the most attractive and promising electrodes in the energy storage field.However,the uncontrollable growth of lithium dendrites limits its commercial application,so it is necessary to study the impact factors about lithium deposition,further effective improving the growth of lithium dendrites.In this paper,a nonlinear phase field model is established to simulate and study the growth of lithium dendrites,and two main approaches are proposed to improve the growth of lithium dendrites.(1)Firstly,some major factors are considered into the phase field model to study their influences on the growth of lithium dendrites,including the anisotropy strength,applied voltage,and nucleation spacing.The results revealed that as the anisotropy strength increases,the growth rate of the tip of the lithium dendrite increases and dendrites grow obviously along the main branch direction,while the radius of the tip decreases;as the applied voltage increases,the morphology of lithium dendrites becomes complex and the lithium dendrite is much larger;when the nucleation spacing is small,lithium dendrites tend to be needle-like,and as the nucleation spacing become larger,the growth of the lateral branches is more obvious and lithium dendrites tend to be branch-like.(2)Based on the established nonlinear phase field model,the effect of pulse charge on the growth of lithium dendrites was thoroughly investigated.Lithium ions preferentially deposited on the tip of lithium dendrites under constant-voltage charging,which will be effectively alleviated by adopting the pulse-voltage charging method to improve lithium deposition.The formed lithium dendrites under pulse-voltage charging is smaller than that under constant-voltage charging.Such results provide insight on suppressing the undesired growth of lithium dendrites.(3)Fabricating the structured lithium metal anode is an effective and easily operable method to improving the poor cycling performance and severe safety problem of the lithium metal anode.In this paper,based on the nonlinear phase field model,the mechanism of porosity and pore distribution’s influences on lithium deposition is studied and the non-uniform lithium deposition in structured lithium metal anodes is simulated.Finally,the porosity-gradient structure is fabricated to significantly facilitate homogeneous lithium deposition and increase the lithium deposition amount.This result provides a new sight for the further design of high-performance lithium metal anodes.