Non-uniform phase change material strategy for directional mitigation of battery thermal runaway propagation

Thermal runaway propagation of the power battery pack is an essential factor affecting the safety of electric vehicles. The commonly adopted propagation inhibition methods mainly include adding heat insulation materials and enlarging battery spacing, which could cause problematic heat dissipation and lower the system energy density. Herein, an innovative battery thermal management system composed of non-uniform thermal conductivity phase change materials and assisted liquid cooling is proposed. Combining the phase change materials with high and low thermal conductivity balances heat transfer and heat insulation requirements. The cooling performance and the ability of thermal runaway propagation mitigation of the proposed schemes are numerically studied. The results show that the proposed strategy can meet the heat dissipation requirements under normal operation and control the thermal runaway in a safe range by transferring the heat generated from the battery thermal runaway in the set direction. The maximum battery temperature and the temperature difference are 38.1 °C and 2.1 °C, respectively, under 3C discharge. Under thermal runaway conditions, the strategy successful confines the thermal runaway propagation within the middle row. The maximum battery temperature in other rows can be controlled under the irreversible thermal runaway reaction temperature of 200 °C. Further study found that increased thermal conductivity benefits the battery heat dissipation and reduces the risk of thermal runaway. However, it propagates faster and broader once the thermal runaway is triggered. In comparison, the decrease of thermal conductivity is beneficial to the mitigation of propagation but may reduce the overall heat dissipation of the battery module. This study can provide a new way to solve the contradiction between battery temperature control and thermal runaway spread suppression.