Electrochemical Impedance Spectroscopy (EIS) Study of LiNi1/3Co1/3Mn1/3O2 for Li-ion Batteries

Electrochemical impedance spectroscopy (EIS) is employed to investigate the electrochemical properties of LiNi1/3Co1/3Mn1/3O2 cathode. The Nyquist plots at initial state, 40%SOC, 80%SOC and 100%SOC at first cycle, second cycle and 10th cycle, respectively, are investigated. The information of electrolyte resistance, surface film resistance and charge transfer resistance are obtained by modeling with two different equivalent circuits according with the Nyquist plots with different shape. The comparison between LiCoO2 and LiNi1/3Co1/3Mn1/3O2 is also investigated in this study. It can be speculated that both the passivating film on the surface of LiNi1/3Co1/3Mn1/3O2 cathode and the channels for lithium ion transfer in LiNi1/3Co1/3Mn1/3O2 cathode are mostly formed during the first charge/discharge process. Both diffusion coefficient of lithium ion in LiNi1/3Co1/3Mn1/3O2 cathode and exchange current density are in accord with the analysis of the Nyquist plots of electrochemical impedance spectra, indicating the rationality of the speculation.