Electrolytes, SEI and Charge Discharge Kinetics of Li-ion Batteries

Charge discharge kinetics of Li-ion batteries is dominated by the lithium ion (Li+) charge transfer kinetics, which involves the process of transporting the solvated Li+ in the electrolyte to the insertion of Li+ and the accepting of an electron at the same time in the electrode active materials. The importance of electrolytes and recent studies of Li+ charge transfer kinetics were briefly reviewed. Using 3-electrode cells and a DC Pulse Current Impedance method, we examined the charge discharge kinetics of the anode and the cathode in the same electrolyte at the same time. We observed a slower kinetics at the graphitic carbon anode as indicated by higher activation energy than that at the lithium nickel cobalt aluminum mixed oxide (LiNi0.80Co0.15Al0.05O2) cathode. While desolvation is a dominating step as concluded in recent studies on the Li+ charge transfer kinetics, this study suggests that the nature of SEIs and electrode materials play crucial roles on Li+ charge discharge kinetics.