Interpretation of voltammograms of lithium ion at pyrolytic graphite electrode

Peak currents and potentials of voltammograms of lithium ion at the pyrolytic graphite electrode were obtained under the conventionally voltammetric conditions except for addition of supporting electrolyte. They were interpreted on the basis of the voltammetric concept in order to estimate rate-determining steps and redox potentials at zero current. The cathodic wave at concentrations less than 10 mM was controlled by diffusion and migration of lithium ion in the solution, whereas that at higher concentrations was by the intercalation kinetics. The anodic wave was caused by the deintercalation, and behaved like an adsorption wave. The cathodic charge evaluated from the integration of the voltammogram was larger by 30% than the anodic one because of side reaction of acetonitrile or impurities. The anodic and the cathodic peak potentials extrapolated to zero current were, respectively, −1.58 and −2.11 V vs. Ag|AgCl, which can be regarded as universal values. The crystallinity of graphite electrode was investigated by Raman spectroscopy.