Inhibition effect of different interstitial materials on thermal runaway propagation in the cylindrical lithium-ion battery module

With the growing demand for high specific energy density of lithium-ion battery pack in electric vehicle to relieve range anxiety, thermal stability in abused conditions is becoming increasingly important in battery pack safety design. Most of the fire accidents are resulted from the thermal runaway (TR) of a single cell and then propagate to the battery modules and entire pack. This study focuses on the safety enhancement methods for battery module, which is filled with different interstitial materials. The basic safety unit is composed of 11 commercial 18,650 cylindrical cells, which is isolated from the electric vehicle pack as the test module. The test modules were intentionally triggered into TR by heating wire to evaluate the TR propagation resistance. A model based on finite volume method was established to simulate the TR propagation. The results of both simulation and experiments show that the protection of neighboring cells from different interstitial materials varies significantly. Graphite composite sheet and Al extrusion as interstitial materials could effectively suppress TR propagation. The results also indicate that for safety design of battery pack, thermal path should be effectively controlled, and particularly the combustion of expelled electrolyte must be directed away from adjacent cells.