Study On The Growth Characteristics Of Lithium Dendrites In The Negative Side Of Lithium Metal Batteries

Lithium metal batteries are considered as one of the most promising candidates for nextgeneration power batteries due to their high energy density.However,the uncontrolled growth of lithium dendrites during the charging process severely restricts the practical application of lithium metal batteries.Understanding the growth mechanism of lithium dendrites is thus key to developing the suppression strategies for lithium dendrites.In this paper,the dynamic growth process of lithium dendrites in lithium metal electrodes during the charging process is simulated using a nonlinear phase-field method.The different patterns of lithium dendrites observed in experiments,including dendritic,mossy,and needle-like dendritic structures,are simulated by adjusting the simulation parameters in the model and the effects of various internal and external factors on dendrite growth are investigated,respectively.A number of factors influence the growth of lithium dendrites.A larger strength of interfacial anisotropy is more likely to cause the gradient fluctuation of electrolyte concentration near the interface and promote the formation of more secondary dendrites.A rougher electrode surface will reduce the local surface current density and lower the ion mobility,effectively inhibiting the lateral growth of lithium dendrites.The use of a skeleton structure can also effectively slow down the growth of lithium dendrites and promote the uniform deposition of lithium.Moreover,the random porous skeleton is more helpful in inhibiting the dendrite growth than the uniform porous structure due to higher tortuosity and higher growth path and resistance.The growth of lithium dendrites is also affected by various external factors,such as temperature,voltage,current density,and pressure.Higher voltages and current densities will generate larger overpotentials and promote the deposition reaction.The growth rate of lithium deposition is inversely proportional to the temperature,and the lithium dendrites are smoother and have fewer secondary crystal arms when working at high temperatures.The effects of external pressure and lithium affinity of the electrode surface on lithium dendrite growth are also analyzed.The results show that the increase of external pressure causes the electrolyte to squeeze inward,which strengthens the internal stress,weakens the deposition reaction rate,and inhibits the dendrite growth.The lithium-friendly electrode surface can also effectively inhibit dendrite growth with the influence of the wetting potential.A full lithium metal battery model is further developed based on the proposed half cell to study the lithium metal plating process on the graphite negative side.The results show that more solid-phase lithium is deposited near the separator during charging,and the accumulated lithium deposition will finally contact and pierce the separator,resulting in irreversible damage to the battery.This study is of great significance for understanding the deposition mechanism of lithium metal anode charging process and provides a rich theoretical basis for developing strategies to suppress lithium dendrites.