An Electrochemical-Thermal Model for Lithium-Ion Battery Packs during Driving of Battery Electric Vehicles

In this study, an electrochemical–thermal coupled model is proposed to predict phenomena in battery packs that consist of lithium-ion battery cells during the driving of battery electric vehicles (BEVs). The model considers the cycle degradation and internal short circuits per cell and can quantitatively evaluate the temperature, loss capacity, and internal resistance per cell. Using this model, simulations are performed focusing on the three impacts of (i) the short-circuit object electric resistance, (ii) number of runs, and (iii) environmental temperature. When the short-circuit object resistance is 5 Ω, the temperature rise in the first run is 6.0 times higher and the loss capacity is 1.7 times higher than that in the non-shorted condition, and it is also confirmed that the risk of thermal runaway is high because the short-circuit object reaches a maximum of 114.2 °C. If there are no short-circuited cells, in repeated runs at an environmental temperature of 40 °C, the driving range at the 300th run is 17 % lower than that of the first run. The loss of the driving range is 3.5 times larger than that at 20 °C, which indicates that the cycle degradation progresses approximately 3.5 times faster.