Evaluation of combustion properties of vent gases from Li-ion batteries

Fire incidents involving Li-ion batteries is an increasing concern as the use of battery electric vehicles is increasing. Abuse conditions such as heating can result in ejection of flammable and toxic gases, presenting a health risk and risk of explosion or fire. The purpose of the present work is to increase the understanding of combustion of gas mixtures vented from Li-ion batteries. The investigation uses a new merged kinetic mechanism including hydrocarbons, hydrogen, carbon oxides, carbonates and fluorinated compounds. Seven typical Li-ion vent gas mixtures were selected based on published studies, and ignition and laminar flames were simulated. Modeling reveal a large variation in laminar burning velocity, flame temperature and heat release. Determining factors for laminar flames are the relative content of the carbonates and hydrogen gas, and the inert carbon dioxide. Gases from highly charged battery cells have the shortest ignition time at high temperatures and the fastest laminar burning velocity. The results can be used as input in computational fluid dynamics or safety engineering modeling. In addition, the versatile kinetic model can be used for fundamental studies of the combustion process and for generation of combustion characteristics such as laminar burning velocities for other vent gas mixtures.