Numerical Simulation of Low-Temperature Thermal Management of Lithium-Ion Batteries Based on Composite Phase Change Material

Phase change materials (PCMs) have attracted greater attention in battery thermal management systems (BTMS) applications due to their compact structure and excellent thermal storage performance. This work developed a BTMS model based on composite phase change material (CPCM) for a cylindrical lithium-ion battery pack. The initial state of the CPCM was set as a liquid phase, and the insulating performance of the BTMS was investigated numerically, considering the CPCM solidifying from liquid phase to solid phase in a low-temperature environment. The numerical model was built, and calculations were performed using Ansys Fluent 19.2. The research results showed that a CPCM effectively can extend the time that the battery pack remains above 0°C by releasing a large amount of latent heat during the solidification process in a low-temperature environment. As the convective heat transfer coefficient increased, the insulation effect provided by CPCM to lithium-ion battery packs decreased, exacerbating the temperature inhomogeneity inside the low-temperature thermal management system. Increasing the thermal conductivity of the CPCM ensured that the maximum temperature difference of the battery pack during operation remained within a safe range. Finally, the simulation results indicated that adding different thicknesses of insulation materials at the periphery of the low-temperature thermal management system effectively can improve the insulation effect. However, it also is necessary to select the appropriate thickness of insulation materials in combination with the actual demand.