Effect of flame heating on thermal runaway propagation of lithium-ion batteries in confined space

As the thermal runaway (TR) of lithium-ion batteries (LIBs) may be induced in enclosed systems, thermal hazards from the ceiling fire contribute to the TR propagation in battery module. However, the characteristic of TR propagation in confined space, especially the heating effect of battery flame, is still unclear. To fill the knowledge gaps, a refined study has been conducted with LiFePO4 battery modules in a confined space. The TR propagation behavior, battery temperature, propagation time and the heat transfer are analyzed quantitatively with different plate heights and heating modes. The results show the TR propagation occurs at 2, 5 and 10 cm plate height while no propagation at higher height. The lower height leads to the increasing of flame heating effect and decreasing of TR propagation time. The flame heating reduces the demand of the heat transferred through the conduction for TR propagation. Further, the heat from ceiling flame has little change with different heights as it is mainly depended on the combustion time. Finally, the heating power of ceiling flame is analyzed and the maximum increases from 1400.3 to 2594.6 W when height decreases from 15 to 2 cm, while it is higher with continuous heating. •The thermal runaway propagation under different ceiling heights is investigated.•Thermal runaway will propagate when the ceiling height decreases to 10 cm below.•Fire propagation only occurs with continuous heating and low ceiling height.•Fire contribution to thermal runaway propagation is quantized.