Simultaneous and continuous characterization of reversible and irreversible heat of lithium-ion battery using wavelet transform technique

Abstract

Entropy coefficient and internal resistance of lithium-ion batteries are the key thermal properties needed for an optimal design of thermal management systems. Currently, these two parameters are measured separately with either potentiometric or calorimetric method and electrochemical impedance spectroscopy (EIS) or hybrid pulse power characterization (HPPC) method, respectively, which requires different equipment and extra experimental time. In addition, both results are discrete at given state of charge (SOC) points, which does not provide the values in-betweens. In this paper, we proposed a fast and highly efficient calorimetric method based on an isothermal calorimeter that allows for simultaneous and continuous characterization of these two parameters. The method is developed using the wavelet analysis technique, where a sinusoidal AC current with a small DC current offset is used as an input for battery and the heat generation rate is measured as an output using the calorimeter. Then, the two parameters are determined simultaneously in time-frequency domain. The results are compared with those measured by the potentiometric method and EIS analysis, respectively with respect to measurement time and accuracy. The saved time is 95%, and the proposed method maintains the accuracy. In addition, the obtained parameters are used to calculate the total heat generation, which shows a good agreement with the experimental measured one both in the shape and tendency.