Aloe vera-inspired boron nitride/expanded graphite/melamine phosphate polymer composites for battery temperature management

With the rapid development of electric vehicles (EVs), the thermal management of lithium-ion batteries (LIBs) has become a critical issue in ensuring driving safety and prolonging battery lifespan. Polymer-based composite materials are expected to become promising candidates for battery thermal management systems (BTMS) due to their lightweight nature and flexibility. However, conventional polymer composites typically suffer from low intrinsic thermal conductivity and high flammability. In this study, a novel high-thermal-conductivity, flexible, and flame-retardant polymer composite material with polydimethylsiloxane (PDMS), boron nitride (BN), expanded graphite (EG), and melamine phosphate (MP) is developed. Experimental results show that when the component ratio of PDMS:BN:EG:MP is optimized at 10:3:3:1 (i.e., PDMS/BN/EG/MP5), the composite achieves the best overall performance and maintains good flexibility, shape stability, and thermal uniformity despite long-term exposure to high temperatures. PDMS/BN/EG/MP5 has a limiting oxygen index (LOI) of 43.2 % and a thermal conductivity of 1.16 W/(m·K). The electrical conductivity of PDMS/BN/EG/MP composite is within the range of ∼10−15-10−14 S cm−1. Moreover, 18650 LIBs are employed as the research object to confirm the thermal management performance of PDMS/BN/EG/MP5. The maximum temperature only reaches 45.43 °C at 3C, which is 22.73 °C lower than that of a bare battery. Additionally, the temperature gradient across the battery surface is effectively minimized, with a maximum temperature difference maintained within 4 °C, and increasing the thickness of the coating layer further reduces the maximum temperature of the LIBs. Therefore, the PDMS/BN/EG/MP5 composite provides a promising solution for improving the thermal safety of battery modules in EVs.