Effects of heating position on the thermal runaway propagation of a lithium-ion battery module in a battery enclosure

In practice, lithium-ion batteries (LIBs) are usually placed in a battery enclosure (BE). The heat source that triggers thermally induced failures of LIBs may be located inside or outside the BE, and its effects on the thermal runaway (TR) propagation characteristics have not been revealed. In this study, this research gap was investigated via thermal abuse experiments of a LIB module. The results show that the first TR in the module is significantly delayed when the heater is outside the BE; however, the TR propagation speed, maximum cell temperature, and mass loss are all higher than those when the heater is inside the BE. In addition, more heat conduction energy is required between cells to maintain TR propagation when the heater is inside the BE. The presence of a jet flame intensifies the TR propagation and reduces the need for heat conduction energy. The no-return temperature of the cell in the BE was calculated for the first time, and the effect of the BE thermal conductivity on the TR propagation of LIBs was analyzed. This study deepens the understanding of the TR propagation behavior in practical applications and provides a reference for the safe design of LIBs.