Investigation on the explosion characteristics of typical lithium-ion battery vent gas

Abstract

Thermal runaway (TR) events in lithium-ion batteries (LIBs) pose significant safety hazards, particularly in energy storage systems (ESS). The release of flammable and toxic battery vent gases (BVGs) during TR can lead to catastrophic explosions. To investigate the explosion characteristics of these BVGs, this study developed a detailed chemical kinetics-based model. The model was employed to analyze the effects of battery type, state of charge (SOC), dilution, and component interactions on BVG explosion behavior under common thermodynamic conditions. Results revealed that lithium iron phosphate (LFP) batteries exhibit a higher explosion propensity than Nickel Cobalt Aluminum (NCA) batteries, primarily attributed to higher concentrations of ethylene and ethane. The explosion tendency of LFP BVGs increases nonlinearly with SOC, peaking at SOC between 50 % and 100 %. Nitrogen in ambient air exerts a dilution effect that becomes more pronounced at higher SOCs. Among individual BVG components, ethylene is the most hazardous, and carbon monoxide is the least prone to explode. Ethane exhibits unique explosion behavior due to its sensitivity to temperature and pressure variations, stemming from competing reaction pathways involving the C₂H₅O₂ radical. BVG mixtures exhibit nonlinear explosion behaviors that cannot be predicted by simple linear combinations of their individual component properties. Furthermore, small additions of hydrocarbons like ethylene or methane to carbon monoxide significantly enhance ignition propensity by enriching the radical pool, although this enhancing effect diminishes at higher hydrocarbon concentrations. The controlling mechanism of H₂/CO synergistic effect is also revealed.