Effects of carbonates on explosion characteristics of lithium-ion batteries venting gases

The electrolyte is a critical component of lithium-ion batteries (LIBs). The electrolyte commonly consists of carbonate mixture and lithium salt. During thermal runaway, the carbonate mixture is vented into the environment along with LIBs venting gases, potentially leading to fire or explosion incidents. In this study, in an 8 - L stainless steel cylindrical explosion vessel, the explosion characteristics of carbonates (dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC)), and LIBs venting gases were identified, and the mutual influences between different carbonates were also clarified, and the effects of carbonate mixture on explosion characteristics of LIBs venting gases were investigated, such as the overpressure, the rate of pressure rise, lower flammability limits (LFL) and limiting oxygen concentrations (LOC). The results indicated that the explosion severity of carbonate mixture (DMC and EMC) increased with the increasing EMC content. As the carbonate mixture content increased in mixtures of carbonates and LIBs venting gases, the maximum overpressure, the maximum rate of pressure rise and LOC increased, while LFL showed a decrease trend. Furthermore, the LOC prediction method of NFPA 69 (A standard offers a method for estimating the LOC for fuels) can predict LOC well on LIBs venting mixtures. The LFL of the mixture of carbonates and gases vented from LIBs was calculated by using CHEMKIN. The results showed that the calculated values were good agreement with the experimental data. Moreover, the changes in the concentration of intermediate products during the combustion of the mixture were analyzed. It was found that introducing EMC and DMC mixtures into the gases vented by LIBs caused an increase in the concentrations of H2, CO and C2H4 in the reactants. The underlying causes of this phenomenon were sufficiently analyzed and discussed. The findings of this research contribute to a deeper understanding of the risks associated with mixtures vented from LIBs and offer valuable insights for designing explosion-proof transport containers and LIBs energy storage stations.