Experimental Study on Cycle Aging Life of 21700 Cylindrical Batteries Under Different Heat Exchange Conditions

Lithium-ion batteries are widely used in energy storage systems, and temperature is an important factor that affects the battery aging performance. Battery aging tests have been conducted in environmental chambers in numerous studies. The ambient temperature is usually regarded as an indicator that affects the battery aging performance. However, with the same ambient temperature but different heat exchange conditions, the battery cycle aging life can still vary. In this study, a side face temperature control device and end faces temperature control device for a cylindrical battery were designed and made. Together with the environmental chamber, three types of heat exchange conditions were used to conduct cycle aging tests for the 21700 cylindrical battery. Based on the aging results of batteries under different heat exchange conditions, the battery aging mechanisms were analyzed. At the end of the battery’s life, the maximum loss rate of the active anode material is close to 20%, and the loss rate of the lithium inventory of most test groups is approximately 10%. The internal resistance growth rate of the aged battery can exceed 50%. During the battery aging process, battery temperature data were monitored, and the cumulative time-averaged surface temperature (CTAT) was proposed as a new metric to assess the temperature level for the long-term operating battery. The aging results of the 21700 cylindrical batteries show that within the temperature range of this study, the lower the CTAT, the faster the battery capacity degrades. The correlation between the battery temperature level and aging performance was also analyzed, which can be used to predict the battery cycle life. The analysis of battery aging mechanisms and the proposed temperature metric in this study provide guidance for research on battery life sustainability, as well as the thermal management strategy design of the battery.