Study of the Properties of Soft Carbons and Graphite by Electrochemical Impedance Spectroscopy. Analysis of the Distribution Function of Relaxation Times

Changes in the electrochemical impedance spectra of lithium–carbon cells during cathodic polarization of a carbon electrode were analyzed using the distribution of relaxation times (DRT) function. The carbon materials included soft carbon and graphite. An analysis of the electrochemical impedance spectra of lithium–carbon cells using the DRT function allows us to establish the number of electrochemical cells and calculate their parameters. The use of DRT functions for modeling electrochemical impedance showed that a lithium–carbon cell contains eight electrochemical elements and allowed quantification of their parameters. The results are in good agreement with theoretical concepts about the structure of carbon materials and electrochemical processes during their polarization. Analysis of the electrochemical impedance spectra of lithium–carbon cells using the DRT function is a more objective method compared to the equivalent electrical circuit (EEC) method.