ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY OF INTERCALATED ELECTRODES

Electrochemical impedance Spectra of graphite in contact with H2SO4 at various steps of intercalation were analyzed by means of transmission line models. The thorough knowledge of both the crystallographic and geometric features of HOPG samples enables us to discuss quantitatively the nature of the low-frequency resistance and capacitance and of the diffusion factor l2/3RC, expressed as (rhoC)-1, where l is sample width, R is resistance, C is capacitance and rho is resistivity. It is shown that these electrodes can be considered either as porous blocking electrodes or as solid mixed conductors.