High-temperature decomposition and oxidation of dimethyl carbonate: A lithium-ion battery electrolyte solvent

Accurate fire-risk assessment of lithium-ion batteries (LiBs) is an increasingly urgent challenge due to the rapid growth of LiB-powered devices and large-scale energy storage systems. The electrolytes used in LiBs commonly consist of mixtures of flammable carbonate esters such as dimethyl carbonate (DMC). During thermal runaway, these electrolytes undergo rapid high-temperature decomposition and oxidation; understanding their reaction kinetics is therefore essential for improving predictive fire-safety models. In this study, DMC pyrolysis and oxidation were investigated using shock-tube experiments coupled with laser absorption spectroscopy. Time histories of CO and CO₂ were measured at near-atmospheric pressure, over a temperature range of 1200–1800 K, and over equivalence ratios from ultra-lean (φ = 0.25) to ultra-rich (φ = 3.0). The measurements obtained were then compared with predictions of several modern kinetic mechanisms, revealing discrepancies between the predictions and the experimental data. Among the mechanisms evaluated, the Gregoire et al. [57] and Yu et al. [62] mechanisms exhibited the closest agreement with CO and CO₂ profiles, respectively. A statistical assessment highlighted a complementary predictive behavior between these two mechanisms. To investigate this behavior, sensitivity and pathway analyses were performed, identifying key reactions in each mechanism and revealing notable discrepancies in their respective DMC oxidation pathways. To the best of the authors’ knowledge, this study reports the first measured CO₂ time histories during the high-temperature DMC reactions. The experimental data reported herein provide a valuable foundation for refining kinetic mechanisms of LiB electrolytes, which is essential for improving fire-safety modeling of battery thermal runaway scenarios.