Parameter Identification of Fractional-order Models of Battery Cells Utilizing Impedance Spectroscopy

In this paper the parameter estimation of five fractional-order models of a battery cell is performed. Real measurements obtained by electrochemical impedance spectroscopy on a lithium cobalt oxide graphite cell are utilized, although the method can be applied to cells of various battery types. Optimal parameter values are determined by minimizing the sum of squared residuals, where the residual is defined as the distance between measured and estimated impedance values in the complex plane for a specified frequency, with the Levenberg-Marquardt algorithm employed. The obtained results are compared and analyzed. This approach could be part of a broader process aimed at improving the performance of individual battery cells of various battery types and, consequently, the overall battery.