Preparation of methyl stearate phase change emulsion and its application in the thermal management system of a lithium-ion battery pack

• Methyl stearate phase change emulsion (M-PCE) was firstly prepared for the thermal management system of a lithium-ion battery pack. • The M-PCE has a peak specific heat capacity of 8.33 J/(g·K) and good stability after 120 heating and cooling cycles. • The electrical conductivity of M-PCE complies with the Chinese National Standard for Motor Vehicle Coolant—Part 1: Fuel Vehicle Engine Coolant. • At a discharge rate of 6C, the T max and ΔT max of M-PCE are 26.68 °C and 1.39 °C, respectively. Phase change emulsion (PCE), a promising latent heat functional fluid, enhances heat transfer efficiency and the temperature control capability of thermal management system for lithium-ion batteries. In this work, the methyl stearate phase change emulsion (M-PCE) sample was prepared at an HLB value of 12, an emulsifier mass fraction of 5 wt%, a methyl stearate mass fraction of 15 wt%, and an ultrasonic time of 10 min. The M-PCE sample demonstrates good stability with a phase separation rate of 3.33% after 60 days storage, a high thermal conductivity of 0.5832 W/(m·K), and a low electrical conductivity of 74.8 μS/cm. The maximum peak specific heat capacity is 8.33 J/(g·K), which is 1.99 times that of water. Meanwhile, the M-PCE sample was employed as the coolant in the thermal management system of a lithium-ion battery pack, the maximum temperature of the battery pack is 26.68 °C and the maximum temperature difference is 1.39 °C at a discharge rate of 6C, which are lower than those of water. The M-PCE sample shows significant potential applications in the field of thermal management systems.