Abstract: In order to control the maximum temperature better and improve temperature uniformity within battery packs, this study developed a hydrated salt-based flexible phase change material (PCM) and applied it to the thermal management of lithium-ion batteries. The results demonstrated that with the addition of 40% silicone rubber, the flexible PCM exhibited a phase change temperature of 45.3 ℃, a phase change enthalpy of 123.2 J/g, and a thermal conductivity of 0.35 W/(m·K), alongside excellent anti-leakage properties, thermal stability, and flexibility. Compared to air cooling, the PCM-based cooling approach reduced the maximum temperature of a single battery under a 2C discharge rate at room temperature (25 ℃) to 58.61 ℃, representing a 7.52 ℃ decrease. For the battery pack, the maximum temperature dropped by 13.48 ℃, and the maximum temperature difference decreased by 7.82 ℃. Furthermore, under high-rate discharge conditions, the PCM-based cooling exhibited superior thermal management performance compared to low-rate discharge scenarios. By using hydrated salt phase change material as a protective layer, the maximum temperature of thermal runaway in the battery adjacent to the heating plate was reduced by 440.8 ℃, effectively blocking the spread of thermal runaway in the battery. The mechanism of phase change materials in battery thermal management and thermal runaway propagation barrier was explored, mainly due to the multiple heat absorption of hydrated salt phase change materials and the formation of porous insulation layers.

Key words: flexible phase change materials, battery thermal management, phase change cooling, maximum temperature, maximum temperature difference