Exploring a preheating strategy for lithium-ion battery pack using graphene-enhanced microencapsulated phase change materials

Lithium-ion batteries (LIBs) are fundamental to the operation of electric vehicles due to their superior energy density and extended cycle life. However, the performance of LIBs deteriorates significantly in subzero temperatures. This study investigates the potential of graphene-enhanced microencapsulated phase change materials (G-MEPCM) as a solution to improve the preheating performance of LIBs in cold environments. Numerical analysis has been conducted to evaluate the thermal performance of the LIB/G-MEPCM system under varying conditions, including different graphene contents, ambient temperatures, heat transfer coefficients, and heating power levels. Results indicate that higher graphene content within MEPCM improves thermal uniformity and reduces internal temperature differences, with 4 wt% graphene content identified as optimal for achieving a balance between rapid heating and temperature uniformity. Besides, increasing the heat transfer coefficient decreases the average temperature and increases the temperature difference of the battery pack. On the contrary, increasing ambient temperature increases the average temperature and decreases the temperature difference of the battery pack. When ambient temperature equals to −25 °C, the temperature difference of battery pack is 21.4 % higher than that when ambient temperature equals to −10 °C. Furthermore, both the average temperature and temperature difference of the battery back increase with the increases of the heating power. • A coupled battery/graphene-enhanced microencapsulated PCM system is proposed. • Pure PCM and microencapsulated PCM on preheating performance are compared. • Various factors on the effects of preheating performance are examined. • The average temperature and temperature difference are used to assess the performance.