Time-difference impedance spectroscopy of growing films containing a single mobile charge carrier, with application to surface films on Li electrodes

A new approach to analyze the electrochemical impedance spectroscopy (EIS) data for electrodes covered by passivating surface films that grow in time is reported. The time-difference impedance spectra (DIS), which is the difference between two complex impedance curves, Z(omega, T1)-Z(omega, t2) measured after different period of storage, t1and t2 as a function of frequency provide an useful tool for characterizing the nature of the growing passivating films.