Investigation of layered LiNi1/3Co1/3Mn1/3O2 cathode of lithium ion battery by electrochemical impedance spectroscopy

The present study applies electrochemical impedance spectra (EIS) to study the interfacial processes of lithium ion batteries (LIBs) and determine the corresponding kinetic parameters. The EIS of the insertion and extraction of lithium ions in layered LiNi1/3Co1/3Mn1/3O2 materials as cathode of LIBs are obtained at different potentials during the first charge/discharge cycle and at different temperatures after 10 charge/discharge cycles. The EIS spectra exhibit three semicircles and a slightly inclined line that appear successively along with decrease in frequency. The high-frequency, the middle-frequency, and the low-frequency semicircles can be attributed respectively to the migration of the lithium ions through the SEI film, the electronic properties of the material and the charge transfer step. The slightly inclined line arises from the solid state diffusion process. The electrical conductivity of the layered LiNi1/3Mn1/3Co1/3O2 changes dramatically at early delithiation as a result of an insulator-to-metal transition. In an electrolyte solution of 1 mol L-1 LiPF6-EC(ethylene carbonate): DEC(diethyl carbonate): DMC(dimethyl carbonate), the activation energy of the ion jump which is related to the migration of the lithium ions through the SEI film, the thermal activation energy of the electrical conductivity and the activation energy of the intercalation/deintercalation reaction are determined 23.1, 44.0 and 66.5 kJ mol(-1), respectively. (C) 2012 Elsevier B.V. All rights reserved.