Numerical study on tab dimension optimization of lithium-ion battery from the thermal safety perspective

Highlights: • An electrochemical-thermal coupling model is developed for a pouch cell. • The temperature distribution is investigated at four discharge rates. • Tab dimensions are optimized for 4 C discharge rate. • The heat generation mechanism and characteristics are discussed for the optimized tab dimension. Tab is related to the safety of the whole battery, it is crucial to optimize the tab dimension to reduce the battery temperature and improve the safety performance. An electrochemical-thermal coupling model for an 18.5 Ah pouch cell is proposed and the model is validated with experimental data. Using this model, the temperature distribution is investigated at four discharge rates of 0.5 C, 1 C, 2 C and 4 C, respectively. It is found that heat will be accumulated at the positive tab at high discharge rate. Then the thermal behavior is analyzed with different tab dimensions for 4 C discharge rate to determine an optimized tab dimension. The results indicate that widening and thickening the tab appropriately can significantly reduce the battery temperature and lead to more uniform temperature distribution. Eventually the tab with thickness of 0.2 mm, width of 35 mm and height of 20 mm are selected as the optimized tab design for this battery. Afterwards, the heat generation mechanism and characteristics are discussed at the optimized tab dimension, which indicates that the irreversible heat, especially the positive irreversible heat occupies an increasingly dominant position in the total heat generation rate with the increase of the discharge rate.