Impedance Spectra Investigation and Parameter Analysis of Traction LiFePO₄ Battery

This paper focuses on the performance of traction lithium-ion batteries. The kinetic process of battery electrode system was analyzed by fitting the measured electrochemical impedance curve with equivalent circuit. The parameters of equivalent circuit model in different SOC ranges were selected to analyze the different AC impedance components and the influence on battery charging and discharging characteristics. The results show that the parameters of equivalent circuit model obtained with impedance spectra test can get battery charge transfer impedance and diffusion impedance in higher accuracy respectively. The distinction between electrochemical polarization and concentration polarization is helpful to analyze the battery charging and discharging performance in different temperatures and SOC.