Development of Electro‐Thermal Circuit Model of Lithium‐Ion Battery through Electrochemical Impedance Spectroscopy and Distribution of Relaxation Times Method†

In this study, a coupled electrical and thermal circuit model of a lithium‐ion battery (LIB) was developed to analyze the temperature and the voltage transient response during charging and discharging. The electrical circuit was determined by separating the impedance measured by the electrochemical impedance spectroscopy for each elementary process component using the distribution of relaxation times analysis, and different temperature dependence was confirmed for each elementary process component. The thermal circuit based on a lumped model of LIB was designed considering heat generation in the battery, convective heat transfer on the battery surface, and heat loss to conducting wires. Measurements and simulations were carried out by using current patterns of pulsed charging/discharging and simplified Federal Urban Driving Schedule to examine the validity of the electro‐thermal circuit model developed in this study. Good agreement of accuracy was found between simulations and experiments in environments where flow velocities from 0.2 to 1.0 m/s were applied. The results of the heat generation analysis showed that the irreversible heat generation has a large influence on the battery temperature in this study. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.