Toxicity and Explosive Hazards of Thermal Runaway Gases in Aged Batteries under Different States of Charge

The safety performance of lithium-ion batteries (LIBs) significantly deteriorates with aging. Furthermore, the extent of aging influences the composition and quantity of gases released during the thermal runaway (TR) process. Consequently, conducting in-depth research on the gas generation characteristics during TR of aged LIBs and performing quantitative assessments of the toxicity and explosion hazards posed by these TR gases are crucial for enhancing battery safety. This study employs an experimental approach combined with empirical formulations to evaluate both the toxicity and explosion hazards of TR gases generated by aged LIBs. The results demonstrate that NCA batteries subjected to 120 aging cycles initiate TR gas release 156 s earlier than their new counterparts under identical conditions. After 120 cycles of aging, the peak values of the battery’s TR gases were 30.64 for FED, 7143.03 for FIC, and 22 for the lethality factor LFED. These parameters significantly exceeded their respective critical thresholds, indicating severe toxic hazards. In addition, as the state of charge (SOC) of the battery increases, the lower explosive limit (LEL) of the TR gas released from aging batteries decreases, while the maximum explosion index gradually increases.