Electrochemical impedance study of LiCoO2 cathode reactions in a lithium ion cell incorporating a reference electrode

Kinetic characteristics of LiCoO2 cathode materials are studied using a Li-ion secondary cell incorporating a reference electrode. By carrying out electrochemical impedance spectroscopy (EIS) measurements at different state of charges (SOCs) and temperatures and obtaining dQ/dE vs. E curves, the activation energy, pre-exponential factor, and reaction rate constant of Li-ion insertion/deinsertion reactions are analyzed as a function of cathode potential. The kinetic behavior of Li-ion conduction, Li-ion solvation/desolvation, and charge transfer reactions of LiCoO2 and its dependency on the structural changes of LiCoO2 are studied. The charge transfer, Li-ion conduction, and Li-ion solvation/desolvation reactions exhibited a dependency on the structural changes of the cathode material.