State Estimation of Lithium-Ion Battery using Radius of Curvature based on Electrochemical Impdance Spectroscopy

Monitoring state of lithium-ion battery (LIB) is important to prevent energy storage system (ESS)-related accidents. One of the most common methods for LIB state estimation is analysis of electrochemical impedance spectroscopy (EIS). This method analyzes chemical structure of LIB by electrochemical equivalent circuit. But EIS measurement has a limit in generating input current due to limit of voltage and difficulty in sweeping the frequency of current source. In this paper, the new state estimation method of LIB by replacing the current source used in conventional EIS device with voltage source is used. Also, the new EIS analysis method with radius of curvature (ROC) is introduced. The proposed method estimates impedance for LIB with a different aging cycle and compares the result with EIS measurement result. Also, by analyzing the radius of curvature of the Nyquist plot of EIS, it can be confirmed that the aging effect can be measured equally with EIS device data and proposed method.