Laminar burning velocity of Lithium-ion battery vent gas during thermal runaway

In the energy storage and transportation sectors, the use of lithium-ion (LIB) battery technology is growing rapidly. However, the potential for fire and explosion raises safety concerns. Thermal runaway (TR) events can occur in LIBs, releasing flammable gases and posing fire and explosion risks. However, there are limited data available on the flammability characteristics of gases released during a thermal failure event. This paper evaluates an important safety characteristic, the laminar burning velocity (Su), using experimental data and modelling approach to assess the influence of cell chemistry on LIB behaviour. Commercial cylindrical cells with various chemistries, i.e., Lithium Nickel Cobalt Aluminium Oxide (NCA) and Lithium Nickel Manganese Cobalt Oxide (NMC), were tested at 100 % SoC. The gas released from the cell was analysed by heating the cell at a constant heating rate of 5 °C/min in a laboratory scale apparatus equipped with an on-line FT-IR spectrometer coupled with a mass spectrometer for continuous gas analysis. H2, CH4, CO, CO2, HF and vapours of electrolyte compounds, such as dimethyl carbonate (DMC), diethyl carbonate (DEC) and ethylene carbonate (EC), were the main components of the battery vent gas (BVG) produced during TR. Su was calculated using the 1-D laminar premixed flame model in the CHEMKIN software. Due to the continuous monitoring of the released gas, different compositions of the BVG were considered for the Su calculation. Depending on the cell chemistry, the most critical BVG composition is released during the TR phase (NCA) or during the venting phase (NMC). The main reason of this behaviour is related to the H2 emission. Finally, the effect of temperature reached during the TR on the Su was evaluated, so the simulations were carried out at 25 °C, 150 °C, 300 °C, and 500 °C at 1 atm.