Experimental study of Li-ion battery thermal management based on the liquid-vapor phase change in direct contact with the cells

One of the significant challenges in using lithium-ion batteries is their thermal management. Hence, to this end, different thermal management systems were proposed. In the present study, the battery pack cooling was experimentally examined through using the liquid-vapor phase change in direct contact with the cells. The impact of changes in refrigerant height, ambient temperature, and pack compartment pressure on maximum temperature was assessed. The results revealed that the increased refrigerant height and the decreased compartment pressure decrease the pack's maximum temperature. Moreover, increasing the refrigerant height decreases the temperature difference between the cells and the temperature difference inside each cell. Furthermore, the increased ambient temperature leads to the increased maximum temperature of the pack. At a temperature close to the refrigerant boiling point, the maximum pack temperature increases because of the earlier onset of refrigerant phase change. Also, the results show that a 16 degrees C increase in the ambient temperature is associated with a 0.9 degrees C decrease in the temperature difference between the cells. Besides, the performance of this system was examined in sequential charging and discharging processes. The results suggested that in these conditions, the temperature is well controlled. In addition, it was revealed that the high heat absorption potential in the phase change process declines the battery pack's maximum temperature. The maximum temperature decreased 30.8 degrees C, reaching from 71.2 degrees C to 40.5 degrees C in the 4C discharge rate in 100 % immersion condition compared to the condition without cooling. Moreover, the maximum temperature difference of the battery pack declined from 11.6 degrees C in the non-cooling condition to 2 degrees C in the 100 % immersion condition. Finally, the outcomes indicate that the temperature difference between the cells do not change when the pack pressure is decreased.