Combustion characteristics of gases released from thermal runaway batteries under methane atmosphere

The gases released during thermal runaway of lithium-ion batteries (BRGs) pose explosion risks, yet their combustion behavior in methane-rich environments remains poorly understood. This study systematically explored the laminar burning velocity (LBV) and ignition delay time (IDT) of BRGs in methane atmospheres for the first time through numerical simulations. It was found that the addition of methane reduced the LBV and prolonged the IDT of BRG because methane lowered combustion temperatures and hampered combustion reactions involving H2 and CO. Moreover, an increase in methane concentration had a minimal impact on the overall activation energy of the reaction but significantly reduced the generation rate and concentration of key reactive radicals (H, OH, O), thereby inhibiting combustion efficiency. It was determined that the impact of CH4 addition on LBV and IDT could be primarily attributed to the following four key reactions through sensitivity analysis: OH + CH4 <=> CH3+H2O, H + O2+H2O<=>HO2+H2O, H + CH4 <=> CH3+H2, and H + CH3 (+M) <=> CH4 (+M), which decrease the concentration of free radicals and reduce the peaks of H and OH radicals. These findings bridged a critical gap in lithium-ion batteries' safety research in methane-rich environments.