Fast State of Charge Estimation for Lithium-ion Battery Based on Electrochemical Impedance Spectroscopy Frequency Feature Extraction

A fast state of charge (SOC) estimation method is proposed based on simplified electrochemical model in this article. Firstly, the solution-phase and solid-phase lithium-ion diffusion models are stripped from the simplified electrochemical model to characterize the lithium-ion concentration. Then, based on the correlation analysis between the solution-phase lithium-ion concentration, the solid-phase surface lithium-ion stoichiometry and the obtained electrochemical impedance spectroscopy (EIS) data, key frequency features for SOC estimation are extracted through the established five feature extraction principles. Finally, the proposed SOC estimation method is expanded to consider the influences of ambient temperature. Experimental study indicates that the integration of lithium-ion diffusion process can significantly improve the accuracy of SOC estimation and reduce the computational time compared with the traditional broadband domain method and the fractional-order equivalent circuit model (FOECM).