Two-and three-electrode impedance spectroscopic studies of graphite electrode in the first lithiation

The first lithiation of graphite electrode was investigated by electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) in a two-electrode button cell and a three-electrode glass cell. The results demonstrate that the study of the variation of EIS feature of the graphite electrode in the two-electrode button cell with electrode polarization potential decreasing in the first lithiation cannot be used to investigate the formation mechanism of the solid electrolyte interphase (SEI) film. However, the formation and growth process of the SEI film can be acquired by investigating the variation of EIS features of the graphite electrode in the three-electrode glass cell with the decrease of electrode po-larization potential in the first lithiation. Moreover, the results also point out that the SEI film on graph-ite electrode is mainly formed between 1.0 and 0.6 V in the first lithiation.