Smart Integration of Expandable Graphite in Composite Phase Change Materials for Optimized Electric Vehicle Battery Thermal Management

Abstract

Conventional battery thermal management systems in electric vehicles often face critical limitations, such as excessive system weight, low thermal conductivity of phase change materials, poor thermal contact resistance, slow response to transient loads, inadequate flame resistance, and inefficient utilization of latent heat storage. These shortcomings result in uneven heat dissipation, thermal hotspots, and reduced battery lifespan and safety. To overcome these limitations, this study introduces an advanced composite solution incorporating expandable graphite (EG) into paraffin (PA)-based materials. Expandable graphite, recognized for its excellent thermal stability and flame-retardant properties, is strategically blended with paraffin wax to significantly boost both thermal conductivity and fire resistance. As a result, the composite achieves a thermal conductivity of (27.10 W/mK) over 100 times greater than that of pure paraffin (0.24 W/mK) and enhances mechanical strength with tensile and compressive limits reaching 9.0 MPa and 39.4 MPa, respectively. Additionally, the system effectively reduces battery surface temperatures to below 42°C during high-load operation, compared to over 52°C in conventional setups. This study uniquely combines the integration of expandable graphite into paraffin with optimization of its distribution using a novel biased random-key elk herd optimizer algorithm. This approach achieves over 100-fold improvement in thermal conductivity while reducing system weight without compromising performance or safety. Optimization using a Biased Random-Key Elk Herd Optimizer (BRKEHO) further refines expandable graphite distribution for balanced weight, efficiency, and safety. Python-based simulations and experiments validate that expandable graphite enhanced composites offer a promising path toward lightweight, efficient, and fire-safe battery thermal management systems designs for future electric vehicle applications.