Lithium-Ion Battery Thermal Runaway Propagation Characteristics Under 20 kPa with Different Airflow Rates

As a common safety issue, thermal runaway (TR) of lithium-ion batteries (LIBs) may propagate to adjacent batteries and grow into a large-scale fire, in a multi-cell array or pack. A dynamic pressure chamber was developed to investigate the effect of airflow rates on TR propagation among pouch LIBs under the ambient pressures of 95 kPa and 20 kPa. The results indicate that the ununiform heating and asynchronous trigger of TR between two side of battery are occurred when the TR propagated from TR battery with high temperature over 800°C. The TR propagation can be slowed down under low ambient pressure, e.g., propagation time under 20 kPa is 83 s slightly slower than 73 s under 95 kPa with same airflow rate of 60 L/s. As the increase of airflow rate under 20 kPa from 60 L/s to 150 L/s, peak heat release rate and total heat release increase from 6.1 kW to 29 kW, and from 287 kJ to 872 kJ, and TR fire behaviours also are intensified, which can further shorten the TR propagation time from 83 s to 71 s, through heat feedback from TR combustion fire. The release of toxic/flammable or potentially explosive gases, such as 3620 ppm for total hydrocarbons, 0.97% for CO under 20 kPa during TR propagation needs to be paid attentions especially with low airflow rate. Airflow rate under low pressure condition of 20 kPa has a great impact on the TR propagation, and some mitigation measures and protection design about the LIB module used under low pressure environments should be taken.