Reduced artifacts in dynamic electrochemical impedance spectroscopy applied to battery degradation analysis

Lithium-ion batteries (LIBs) degradation can be classified into capacity reduction and increase of the internal resistance. Accurate estimation of degradation is important to determine the economic value and the remaining useful life of the battery. This paper adopts dynamic electrochemical impedance spectroscopy (EIS) to evaluate degradation while charging the battery, without requiring additional time for the analysis. A new method is proposed to remove the artifacts arising from the time-variance of the system during the measurement. The validity of the method is confirmed by comparing it with the results obtained by static EIS measurements at equilibrium. The spectra are fitted to an equivalent circuit containing three resistances ( R 0 , R 1 , R 2 ). The method is applied to data obtained before and after aging cycles performed at 1.4C charge and 2.0C discharge rates, at 25 °C, 10 °C and −5 °C. The resistance of the films ( R 1 ), which is obtained from the semicircle at high frequencies in the EIS spectrum, has proved to be the key indicator of aging, and linearly depends on the SoC. The increase of R 1 dominates among all the resistances, particularly at higher temperatures. Dynamic EIS is considered a powerful tool to diagnose LIBs in practical applications. • Analysis of degradation based on dynamic electrochemical impedance spectroscopy. • The proposed model corrects the artifact caused by the variation of SoC while measuring. • The method is applied on cells aged with fast charging at 25 °C, 10 °C and −5 °C. • Films and charge transfer resistances dominate the battery aging at higher temperatures. • The resistance associated with the films, R 1 , is a key indicator of degradation and SoC.