Phase Field Modeling of Lithium Electrodeposition in Lithium-Ion Batteries
In high energy Li-ion batteries, Li deposits formed on the anode surface during cell charging can cause poor cycling and sever safety problem. The formation of Li deposits leads to a large decrease of reversible capacity and worst a short-circuiting phenomenon as deposits grow towards to the cathode. Even for the graphite anode instead of lithium metal there is still a great chance for lithium to be deposited when Li-ion batteries undergo a high rate charge. During lithium electrodeposition processes, it is believed that the morphology and growth of electrodeposits are mainly determ ined by the kinetics of the heterogeneous electrode reaction, electrode surface states, Ohmic potential drop and mass species transports inside the bulk materials.
In this talk, I will present a nonlinear phase field model for predicting electrode-electrolyte interface motion and microstructure evolution during the electrochemical deposition involving highly nonequilibrium processes. Without considering the solid-electrolyte interface (SEI) layer effect, this model is able to simulate and predict the lithium deposits formation and growth in Li-ion batteries during charging operations. The electrodeposition rate implicitly follows the Butler-Volmer kinetic with a diffuse electrode-electrolyte interface description. The consuming of Li+ concentration and electric potential drop across the interface is correlated to the electrochemical reaction kinetic. The local variations of ion concentration and overpotential cause the instability of electrode surface which eventually produce fiber-like lithium deposits growth. The effects of charged current density and reaction rate constant on the deposits morphology are discussed in details.