A calorimeter for analyzing ejected and non-ejected heat during Li-ion battery thermal runaway

Thermal runaway in lithium-ion battery cells poses significant safety risks due to rapid heat generation and potential thermal propagation within a battery system. This study investigates the total heat released and the fraction of energy contained in gas and particles ejected during thermal runaway using a purpose-built calorimeter setup. The results show that the fraction of ejected heat is significantly influenced by the state of charge (SOC) and cell mass loss. Notably, the non-ejected heat was higher at 75% SOC compared to 100% SOC due to higher fraction of ejected heat at high SOC. This will have implications in thermal propagation scenarios. Additionally, the study compares the results with accelerating rate calorimetry tests, highlighting the limitations of the latter in measuring the total heat released during thermal runaway. The findings show the need for comprehensive testing methods that can improve thermal management and safety in battery systems.