Impact of Air and N2 Atmospheres on Thermal Runaway and Gas Emissions in 21700 Lithium-Ion Batteries

This study investigates the thermal runaway (TR) behavior, gas emissions, heat release, and explosion risks of 21700 lithium-ion batteries (LIBs) under varying atmospheric conditions, including air, nitrogen (N2), and hypoxic environments (11% O2). The experiments analyzed the impact of different oxygen concentrations on gas production and TR characteristics, with a focus on aviation battery transport safety. Gas chromatography (GC) and a Siemens Calomat analyzer were employed to measure key emissions, including CO2, CO, hydrocarbons, and hydrogen. The lower and upper explosive limits (LEL and UEL) of emitted gases were calculated to assess explosion risks, and the total heat release (THR) was quantified to understand the thermal impact of TR under each condition. Results demonstrated that the air facilitated more complete combustion, resulting in lower gas volumes, reduced heat release, and a decreased explosion risk. In contrast, the nitrogen conditions led to higher flammable gas production, elevated hydrogen levels, increased heat release, and greater hazards due to incomplete combustion. The hypoxic environment produced intermediate results between the air and N₂ cases. These findings highlight critical safety considerations for transporting LIBs in oxygen-limited environments, such as airplane cargo holds, where gas buildup and combustion risks must be carefully managed.