Carbonization welding graphene architecture for thermally conductive phase change composites with solar/electric-to-heat conversion ability

Graphene-based porous architectures are promising in addressing the poor thermal conductivity, leakage, shape stability problems of organic phase change materials (PCMs), meanwhile endowing them with excellent solar/electric-to-heat conversion ability, but they are still limited by the high interfacial thermal/electrical resistance in architectures caused by organic “binders”. In this work, in view of the excellent gel ability of aramid nanofibers (ANF) and its highly ordered conjugate molecular structure, a promising graphene porous architecture assisted by ANF was constructed by unidirectional freeze casting coupled with carbonization welding technique. Due to the similar graphite lattice structure of ANF-derived carbonization and graphene, the interfacial thermal/electrical resistance in highly vertically oriented graphene architecture was greatly reduced. As a result, the PCMs composite encapsulated by the graphene architecture carbonizing at 1500 °C exhibited an outstanding thermal conductivity of as high as 4.85 W/mK at only 4.26 vol%, which enables a rapid heat transfer and storage in PCM composite. The honeycomb porous graphene architecture with high porosity can accommodate sufficient PCMs for energy storage, showing a high latent heat enthalpy of 149.7 J/g with excellent shape stability during phase change process. More importantly, the graphene architecture endows PCM composites with excellent solar/electric-to-thermal conversion capacities, which not only expands the types of energy stored by PCMs, but is also promising in the thermal management application requiring a continuous and stable temperature environment.