Numerical study on thermal characteristics comparison between charge and discharge process for lithium ion battery

The comparison of thermal characteristics between charge and discharge processes for lithium ion battery is usually neglected but has a strongly effect on its performance and safety. In this paper, an electrochemical-thermal cycling model is presented for a 5 Ah LiNi1/3Co1/3Mn1/3 26650 type lithium ion battery to evaluate and compare the thermal characteristics, includes the temperature distribution, heat generation and contribution during charge and discharge processes. The model is validated during cycling by experiment firstly. The results show that the constant current charge process displays a shorter duration, a higher peak temperature, and a quicker temperature rise rate compared with the corresponding discharge process. The heat generated at charge process is larger than that at discharge of lower rate (0.5 C and 1 C), while that of discharge accounts for 52.97%, exceeding the charge process at 1.5 C. The constant current charge ends at state of charge of 91.31%, 84.62% and 78.06% for 0.5 C, 1 C and 1.5 C, respectively, which means that more capacity is charged and more heat is generated during constant voltage charge at higher rate. Moreover, the dominant heat generation in charge process is the polarization heat of negative electrode, while the dominant heat generation in discharge process is the polarization heat of positive electrode.