Experimental study of ethylene carbonate (EC) pyrolysis and oxidation in jet-stirred reactor by SVUV-PIMS

Abstract

Ethylene carbonate (EC) is a major component of the widely used lithium-ion battery (LIB) electrolytes, therefore it is of great importance for the risk assessment of LIB fires. In this work, the pyrolysis and oxidation of EC (equivalence ratio of 0.5) was investigated in a jet-stirred reactor (JSR) coupled to synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and gas chromatography at atmospheric pressure, with initial EC mole fraction of 0.0021 and residence time of 2 s. The mole fraction profiles of reaction products measured in this work, including hydrogen, water, carbon monoxide, carbon dioxide, C₁C₂ hydrocarbons, formaldehyde, acetaldehyde, ketene and etc., were utilized to validate the recently proposed electrolyte surrogate models in the literatures. The results showed that the prediction of ketene yield in EC pyrolysis, as well as the prediction of EC reactivity in EC oxidation, are poor using the previous models. Therefore, based on reaction pathway analysis and sensitivity analysis in JSR, the kinetic model of EC in the literature was improved by updating and tuning the rate constants of some key reactions related to the formation and consumption of formyl methyl radical (ĊH₂CHO) and ketene. The updated model could predict EC consumption and the yield of major species better than those predicted by models in the literatures. In addition, from the oxidation results of EC, we found that the reactivity of EC could be significantly enhanced by hydroxyl radical (ȮH) produced by the reaction of formyl methyl radical with oxygen.