Flexible and highly thermally conductive phase change materials with hierarchical dual network for thermal management

Phase Change Materials (PCMs), known for their exceptional thermal storage capability and consistent phase change temperature, have shown immense potential for enabling energy-efficient thermal management of electronic devices. However, conventional organic PCMs face several limitations, including leakage, intrinsic rigidity, and unsatisfied synchronized enhancement of thermal conductivity in both perpendicular and parallel directions. Addressing these challenges, we developed a shape-stable, flexible, and highly thermally conductive composite PCMs by integrating flexible olefin block copolymers (OBC) with a hierarchical bi-network of graphene nanoplates (GNPs), spanning nano- and micro-scales. The strategic incorporation of paraffin (PA) within the phase-segregated OBC matrix ensures both flexibility and shape stability, while the bi-continuous thermal network of GNPs provides dual encapsulation and significantly enhances both through-plane (kappa(perpendicular to), 5.42 W/mK) and in-plane (kappa(parallel to), 6.46 W/mK) thermal conductivity. This results in efficient heat distribution whether faced with concentrated point heat sources or uniform planar heat fluxes. When conformed to the contours of Li-ion batteries, thanks to superior thermal conductivity enhancement and phase transition temperatures (similar to 47degree celsius) aligned with safe battery operation, the prepared PCMs lowers the operating temperature by 21degree celsius during 3C rapid charging, thus mitigating thermal runaway risks compared to an unmodified battery pack. This study charts a path toward the development of composite PCMs that excel in thermal management applications.