Thermal Runaway Propagation in Li-ion Battery Packs Due to Combustion of Vent Gases

Accurate understanding of propagation of thermal runaway is of much importance for developing safe battery pack designs. Combustion of vent gases emerging from a trigger cell undergoing thermal runaway has not been studied in sufficient detail, even though the additional heat generated during combustion likely plays an important role in thermal runaway propagation. This work presents comprehensive numerical modeling and simulations of thermal runaway propagation in a pack of cylindrical cells. The model accounts for multiple coupled non-linear phenomena, including vent gas flow and combustion, radiation and thermal runaway. Non-premixed combustion of venting gas is modeled using k - ε turbulence model and finite rate chemical kinetics. Simulation results are shown to be in good agreement with experimental data for a benchmark turbulent non-premixed jet flame. Simulations show that hot combustion products are rapidly transported in gaps between cells, potentially leading to self-sustained thermal runaway propagation to adjacent cells. Results demonstrate the critical importance of combustion in determining the nature of propagation of thermal runaway. The vent hole location is identified as an important parameter that influences whether and the extent to which thermal runaway propagation occurs. This work contributes towards the practical understanding of thermal runaway safety of Li-ion battery packs.