Numerical investigation on the thermal behavior of cylindrical lithium-ion batteries based on the electrochemical-thermal coupling model

Abstract

• HET model and LET model are proposed. • Radial temperature gradient of cylindrical LIB is non-negligible. • Inhomogeneous discharge due to non-uniform temperature distribution inside cylindrical LIB is investigated. • This work provides insights to choose appropriate electrochemical-thermal coupling models. In this paper, a one-dimensional electrochemical model and a three-dimensional axisymmetric heat transfer model are coupled to simulate the electrochemical and thermal behavior of cylindrical lithium-ion batteries (LIBs). The model is verified against the experimental data of discharge voltage and surface temperature of LIBs under different discharge rates. First, the holistic electrochemical-thermal coupling (HET) model and the layered electrochemical-thermal coupling (LET) model are established. In contrast to the traditional HET model, the advantage of the LET model is that it can realize the investigation on the inhomogeneous discharge and aging induced by the non-uniform temperature distribution inside the battery. We demonstrate the radially inhomogeneous discharge of cylindrical LIBs with a 4-layer LET model in this work. It is also found that the HET model can provide desirable simulation accuracy in temperature with less computational cost. This provides insights for researchers to choose more appropriate electrochemical-thermal coupling models in accordance with the different scenarios. Second, the thermal behavior of cylindrical LIBs at different discharge rates is studied by analyzing the heat generation rate and heat dissipation characteristics during the discharge process. The study reveals that, unlike pouch LIBs, there is a significant temperature gradient in the radial direction of cylindrical LIBs. Finally, the factors that affect the temperature uniformity of the battery, such as cooling conditions, ambient temperature, discharge rate, radial dimension, and radial thermal conductivity are analyzed in detail. Meanwhile, some suggestions are provided to improve the temperature uniformity. The findings in this work are of benefit to obtain profound understading of thermal behavior in cylindrical LIBs. Besides, they also have potential applications in improving the prediction accuracy of the temperature signal in the battery thermal management system of LIBs.