Towards a micro-kinetic model of Li-ion battery thermal runaway — Reaction network analysis of dimethyl carbonate thermal decomposition

Thermal runaway (TR), a major safety concern for Li-ion batteries (LIBs), involves a complex network of chemical reactions leading to the production of flammable and toxic gases. Computational modelling of LIB TR continues to aid safer battery design. But to improve the capability of TR simulations, here we apply micro-kinetic modelling to describe the kinetics of LIB TR at a mechanistic level. We focused on developing a micro-kinetic model for the thermal decomposition of dimethyl carbonate, an important electrolyte component. Comparing two reaction networks for this process, (1) not involving radical pathways and (2) involving radical pathways, we show that radical reaction pathways are important for the decomposition of DMC at low temperatures in the region of TR onset. Further, this second network is important for the accurate prediction of off-gas species. This work forms the basis of being able to predict hazardous species production. With further work to develop a reaction network for the decomposition of the entire electrolyte and electrode-electrolyte reactions, predictive capabilities can be extended to allow for detailed risk assessment of LIBs.