Shape-stabilized, thermally conductive phase-change composites for thermal energy storage

Abstract

Phase-change materials (PCMs) with three-dimensional thermally conductive skeletons show promise for thermal energy storage, but they have poor stability. Therefore, based on hydrogen bonding between graphene oxide and polyvinyl alcohol, a shape-stable thermally conductive graphene oxide/graphene nanoplates/polyvinyl alcohol (GO/GNP/PVAs) 3D porous skeleton was prepared by a simple vacuum freeze–drying method in this paper. To further improve the thermal conductivity of the GO/GNP/PVAs 3D porous skeleton, so carbonization is applied on it. After encapsulating polyethylene glycol (PEG) in the skeleton, a thermally conductive phase-change composite with good shape stability was obtained, even at a PEG loading as high as 96.1%. The carbonized C-GO/GNP/PVAs/PEG phase-change composites exhibited higher thermal conductivity (1.57 W m⁻¹ K⁻¹) than uncarbonized GO/GNP/PVAs/PEG phase-change composites (0.52 W m⁻¹ K⁻¹). This was mainly due to the low thermal conductivity GO annealing into high thermal conductivity reduced graphene oxide (rGO), which formed a conductive three-dimensional network. Meanwhile, the formation of a carbon skeleton by PVA chains after annealing also improved the thermal conductivity of the composites. The C-GO/GNP/PVAs/PEG phase-change composites also showed excellent solar-to-heat conversion properties.