Research on the effect of thermal runaway gas components and explosion limits of lithium-ion batteries under different charge states

•Provide data support for the initial energy of the domino effect of the thermal runaway of multi-cell lithium-ion batteries.•Study the relationship between the explosion limit of pyrolysis gas and battery SOC.•Provide suggestions for lithium-ion batteries storage power. The combustion and explosion of thermal runaway gases from lithium-ion batteries may accelerate the propagation of thermal runaway from lithium-ion batteries and pose a serious threat to surrounding people and property. Therefore, the research of thermal runaway gas composition and explosion limits of lithium-ion batteries is of great significance for the prevention and control of thermal runaway of lithium-ion batteries. In this paper, we use experiments combined with empirical formulas to investigate the composition of gases generated by the thermal runaway and the explosion limit of 18,650 lithium-ion batteries. The analysis of the thermal runaway gas components of lithium-ion batteries by using gas chromatography-mass spectrometry (GC-MS) shows that as the SOC increases, the number of thermal runaway gases increases. With the increase of SOC, the change of lower explosion limit (LEL) shows the same trend as that in alkanes content, which increases and then decreases; while the change of upper explosion limit (UEL) shows the same trend as that in unsaturated hydrocarbons content, which decreases and then increases. In addition, 50% SOC battery shows the lowest exhausted gas combustion explosion danger.