Quantitative measurement of thermal performance of a cylindrical lithium-ion battery.

• Presents a method to measure heat generation of a cylindrical lithium ion battery. • Effects of high and low temperature rises on battery heat generation is revealed. • Falling temperature and ascending discharge rate increase battery heat generation. • This study profits the thermal design of electric vehicle battery pack. Measuring the thermal performance of lithium-ion battery cells is a critical task in the thermal design of electric vehicle battery packs. This study introduces a quantitative method to assess the thermal performance of cylindrical 21,700 cells considering heat loss, under conditions of both high and low temperature-rises. By supervising the cell's outgoing heat-flux (heat loss), we thoroughly analyzed the differences in cell heat generation rates between high temperature-rise (HTR) and low temperature-rise (LTR) conditions. The results show that under LTR conditions, the cell heat generation exhibits a "fast-slow-fast" increasing trend, while under HTR conditions, it displays a U-shaped pattern. Notably, the mean cell heat generation rate increases with decreasing temperatures and increasing discharge rates, especially under LTR conditions, where it significantly outperforms that under HTR conditions. This method provides valuable insights for optimizing the thermal design of battery packs. [ABSTRACT FROM AUTHOR]