Abstract Variations of impedance spectra, electronic resistance, and the resistances of the SEI film and the charge transfer reaction of LiCoO2 electrode in the 1M LiPF6-EC:DEC:DMC and 1M LiPF6-PC:DMC+5%VC electrolyte solutions with the temperature in the range 0~30℃, had been investigated by electrochemical impedance spectroscopy (EIS). It is found that, the common EIS features of LiCoO2 electrode in the 1M LiPF6-EC:DEC:DMC and 1M LiPF6-PC:DMC+5%VC electrolyte solutions are related to the temperature, a straight line reflecting solid state Li ion diffusion in the bulk of active mass appears at 10 and 20℃ respectively. The energy barrier for the ion jump related to migration of lithium ions through the SEI film of LiCoO2 electrode in the 1M LiPF6-EC:DEC:DMC and 1M LiPF6-PC:DMC+5%VC electrolyte solutions is 37.74 and 26.55 KJ/mol, the thermal active energy of the electronic conductivity is 39.08 and 53.81 KJ/mol, and the intercalation-deintercalation reaction energy is 68.97and 73.73 KJ/mol, respectively.

Key words: lithium-ion batteries, LiCoO2, SEI film, electronic resistance, charge transfer reaction resistance