Thermal performance of direct two-phase refrigerant cooling for lithium-ion batteries in electric vehicles

The lithium-ion battery has been considered as a power source of electric vehicles (EVs). An efficient battery thermal management system is essential for lithium-ion batteries with high cooling performance and long lifetime. The objective of this study is to investigate the performance improvement of a novel direct two-phase refrigerant cooling over a conventional liquid cooling for traction batteries of EVs. Based on full-scale experiments under actual vehicle conditions, the thermal performance of the two-phase refrigerant cooling is compared with that of the conventional liquid cooling with the same outer size. The two-phase refrigerant cooling satisfies the maximum cell temperature limit of 45 °C even under harsh environmental conditions. During aging, the two-phase refrigerant cooling provides 16.1% higher battery capacity and 15.0% lower internal resistance compared with the liquid cooling under harsh environmental conditions. Overall, the two-phase refrigerant cooling is considered a preferred alternative to the conventional liquid cooling owing to its reliable performance even with a simple and lightweight structure.