Electrochemical Impedance Spectroscopy (EIS) and non-linear harmonic analysis (NHA) of Li-SOCl2/SO2Cl2 batteries

Abstract

Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for characterizing primary lithium batteries. Before fitting the spectrum, the so-called Kramers-Kronig(KK) method has to be checked for the reliability and accuracy of the EIS spectrum. The decision to further fit and analyze the spectrum for physical events in the system is made after checking the KK compatibility of the spectrum. In this paper, we propose further confirmation of the reliability and the accuracy of the EIS spectrum by using the Non-linear harmonic analysis (NHA) of the measurement. The study shows that the KK-compatible EIS spectrum shows homogeneous higher harmonics results where one can further verify the spectrum. The phase of the excitation signal and its effects on the NHA are discussed. A measurement method for measuring Li/SOCl2 and SO2Cl2 batteries to obtain the KK-compatible EIS spectrum is introduced.