Heat generation quantification of high-specific-energy 21700 battery cell using average and variable specific heat capacities

The electrical performance, safety and life of a battery are closely related to its operating temperature; therefore, a thermal management system is necessary to ensure that the battery operates within its most suitable temperature range. Accurately testing the heat generation of a battery is necessary for the design of a thermal management system. Specific heat capacity is one of the most important parameters of thermophysical properties, and its accurate measurement is a prerequisite for the quantitative analysis of battery heat generation. In the literature on battery heat generation tests, the average specific heat capacity is usually used to calculate the battery heat generation. Thus, the change in the specific heat capacity of the battery is not considered. Considering the high-specific-energy 21700 battery made with a nickel-cobalt-manganese (NCM)/graphite material system, this paper compares for the first time the difference between using the average specific heat capacity and variable specific heat capacity to calculate the instantaneous heat generation of a battery. The experimental results showed that the specific heat capacity in the target temperature range during the actual use of power batteries (i.e., a low temperature range of 25-35 degrees C) had a more significant impact on the heat generation power calculation error, and the relative error could reach 30%. In addition, based on the obtained variable specific heat capacity, the heat generation characteristics of the 21700 battery under different operating conditions were analysed. The results showed that this battery has a higher specific volume heat generation power compared with the pouch-type batteries reported in the literature. This article provides guidance for battery cell thermal simulation, more accurate quantitative measurement of battery heat generation and thermal management system design.

Automated summary

The thermal management of a battery is crucial for its performance and lifespan; accurate measurement of specific heat capacity is essential for the design of a thermal management system. This study compares for the first time the use of average specific heat capacity versus variable specific heat capacity in calculating battery heat generation, showing a significant impact of specific heat capacity on the calculation of instantaneous heat generation. The results provide guidance for battery cell thermal simulation and design of a more accurate thermal management system.