Study of combustion characteristics of linear carbonates (DMC/DEC/EMC) and cyclic carbonate (EC): Laminar burning velocity and chemical reaction kinetics modeling

Experimental and chemical kinetics studies on the combustion of linear and cyclic carbonates are essential for gaining insight into the complex chemical reaction processes associated with thermal runaway in lithium-ion batteries (LIBs). In a constant-volume combustion chamber, experiments were conducted at initial temperatures of 403/473/543 K, initial pressures of 1/2/3 atm, and equivalence ratios ranging from 0.7 to 1.5. Laminar burning velocities (LBV) were measured for commonly used linear carbonates, including dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and a cyclic carbonate, ethyl carbonate (EC), which are frequently used in LIBs. The results indicate that the gas-phase reactivity of these carbonates under the same experimental conditions can be summarized as DEC = EMC > DMC > EC. The obtained LBV data have been utilized to validate a new comprehensive chemical kinetics mechanism (CEL) for both linear and cyclic carbonates. CEL places particular emphasis on accurately describing fuel-specific reactions and the CH₂CO sub-model. Throughout the entire scope of this study, the predictions made by CEL align well with the experimental data. A detailed kinetics analysis using CEL has revealed that the differences in reaction activity among the four carbonate species primarily arise from variations in the concentrations of active radical species such as H and OH, as well as differences in the initial oxidation reactions that control fuel consumption. All four carbonates generate CO₂ from two main sources: one is the CO₂ elimination reactions from intermediate species, and the other is the oxidation of CO.