A simplification of the time-domain equivalent circuit model for lithium-ion batteries based on low-frequency electrochemical impedance spectra

Abstract

The traditional time-domain equivalent circuit model (ECM) for Li-ion batteries may achieve high accuracy by identifying model parameters through limited dynamic conditions. However, the traditional ECM (TECM) parameter matching techniques based on time-domain may have the problem of adaptability of working conditions. To solve the problem of dependence on time-domain working conditions and improve the stability of the full-cycle modeling of lithium batteries, it is critical to establish the ECM based on the principle of electrochemical impedance spectroscopy (EIS). However, the full-frequency domain ECM structures (FECM) and the corresponding parameters based on the whole frequency ranges of the EIS employ too many resources for on-line estimation. In this paper, we firstly analyze the frequency region of the standard operating conditions of electric vehicles and theoretically discuss the rationality of the Simplified ECM base on the low-frequency region of the EIS. The proposed low-frequency domain ECM (LECM) simplifies the elements that describe the medium-high frequency regions of the EIS. It only uses the low-frequency region of the EIS to identify the model parameters. The results show that the accuracy of the proposed LECM is almost the same as that of FECM, and saves an average of 40% of the calculation load.