Thermal management of 21700 Li-ion battery packs: Experimental and numerical investigations

Due to its increased cell size, LIB 21700 (Lithium-ion battery) format has surpassed the existing formats as it offers larger capacity and higher energy density. However, the battery pack's extended life and appropriate performance greatly relies on the temperature. Therefore, the thermal performance assessment of LIBS is quite essential. In line with this, the objective of this study is to investigate the heat generation inside the 21,700 battery or battery pack experimentally and numerically. The numerical analysis is carried out at different discharge rates by the lumped model, and two distinct arrangement designs of 5 x 6 and 2 x 15 are compared in the battery pack. The numerical results at each discharge rate in the 5 x 6 battery pack are completely matched with the experimental data, and this thermal model is used to predict the temperature distribution at several discharge rates in the 2 x 15 battery pack. The results indicated that 5 x 6 battery pack offers greater heat dissipation performance at the battery's entrance and exit. However, at the center, the temperature surpasses the working temperature range due to the tight arrangement, resulting in a substantial temperature difference between the 5 x 6 battery pack's batteries. It was also found that both battery packs operate under 40 degrees C only for 1C discharge rate while for discharge rates of 2C and 5C, internal temperature of battery is greater than 50 degrees C and 94 degrees C, respectively.