Impedance Based Electrode Diagnostics of Charge-Discharge Kinetics in Li-Ion Pouch Cells

Abstract

The electrochemical reactions inside a Li-ion cell is a result of complex interplay among different physicochemical processes occurring at anode and cathode. In order to fundamentally understand the charge/discharge kinetics at each electrode, an impedance based in-situ diagnostics is presented within a three-electrode pouch cell configuration. This allows identifying the factors that influence the Li-ion cell performance at different temperatures over a range depths of discharge. The resistances and the activation energies of different processes, such as charge-transfer and diffusion, are determined for individual electrodes. It was found that at low temperatures, the effect of intercalation induced staging in a graphite anode affects the pore ionic resistance, diffusion resistance and the double layer capacitance.