Study on the combustion behaviors and thermal stability of aging lithium-ion batteries with different states of charge at low pressure

Currently, there are many application scenarios for lithium-ion batteries (LIBs) in high-temperature environments, such as large-scale energy storage, electric vehicles, aviation and so on. However, the fire and explosion risks of LIBs will pose a serious threat to transportation, industry applications, and environment. In this work, hence, considering the influence of ambient pressure, a series of experiments are performed to study the characteristics of thermal runaway (TR) for commercial LIBs with different states of charge (SOCs). Relative to past research on fresh batteries, aging LIBs whether at 100 % SOC condition or at lower SOCs, did not particularly exhibit significant spark ejection. The simultaneous burning flame was vertically upwards and no petal-shaped flame appeared. And the maximum flame temperature of LIBs during TR are 394 degrees C, 368 degrees C, 469 degrees C and 508 degrees C from 30 % SOC to 100 % SOC, respectively. The maximum flame temperature and average mass loss rate of LIBs show a correlation with SOC. Given that the combustions of gases and most ejected combustibles are significantly affected by the environmental pressure, the modified energy balance equation of the battery during the entire TR process is established to quantitative the relationship between the cell surface temperature and SOC under different environmental conditions. These results will help to further identify the risk of the TR process of LIBs with different SOCs after high-temperature aging, and provide a scientific basis for the transportation and use of batteries.