Analysis of the lithium electrodeposition behavior in the charge process of lithium metal battery associated with overpotential

Abstract

The Li dendrite growth with non-uniform electrodeposition on negative electrode surface needs to be reduced in lithium metal batteries (LMB). Coupling Butler-Volmer equation and extended Ohm's law with species transport and heat transfer equations, the effects of electrode solid-phase volume fraction and lithium active material amount in porous positive electrode, Li+ ion concentration in electrolyte and protrusion size under different operating temperatures and charging current densities on the performances of LMB with protrusion on negative electrode surface are numerically analyzed during charging. The higher solid-phase volume fraction and more lithium active materials in positive electrode enlarge LMB specific capacity, and the larger exchange current density and Li+ ion concentration in electrolyte cause higher cell overpotential. The protrusion including its size and number on negative electrode surface influence the electrochemical behaviors in cell during charging, in which the higher operating temperature benefits uniform electrodeposition distribution. The comparisons of deposition height, Li+ ion concentration in electrolyte and electrode overpotential are conducted between under constant current and forward or reverse pulse currents in charging. By applying a reverse pulse current (RPC) and reducing forward current duty cycle, more uniform electrodeposition occurs. All results can be utilized to obtain high-performance operation in LMB.