Analysis of Lithium-Ion Battery Models Based on Electrochemical Impedance Spectroscopy

Abstract

This work is an overview of various equivalent circuits (ECs) containing various degrees of detail. The ECs are evaluated in terms of model accuracy and parameterization time for the systematic assignment of an equivalent circuit to application fields. For this purpose, impedance spectra were measured using electrochemical impedance spectroscopy at different states of charge, health and temperatures. Then the parameters of the EC were extracted using the least-squares method and the Levenberg–Marquardt algorithm. After comparing the simulated to the measured impedance spectrum, a review and assignment of equivalent circuits for potential applications is given. Simple equivalent circuits with a series resistor and a maximum of two resistance–capacitance (RC) elements are ideal for simulations with lower dynamics. Equivalent circuits with up to five RC elements or even a constant-phase element (CPE) are promising for simulating highly dynamic processes. By using RCPE elements the impedance spectrum can be modeled with the highest accuracy, which is why this type of model should be used for diagnostic purposes.