Interlayer spacing control strategy to construct the rapid thermal conductivity channel in the molten salt phase change materials

Abstract

With the goal of improving the thermal conductivity of inorganic salt PCMs without significantly affecting the thermal energy storage density, a functionalized modification strategy to regulate the layer spacing of nano two-dimensional (2D) materials was proposed to construct a thermal conduction pathway in phase change materials (PCMs). In the instance of graphene, we proposed hydroxylation to increase the lamellar spacing between graphene, improve its dispersion in molten salt PCMs, and speed heat transfer of graphene composite molten salt. When compared to pure graphene, the addition of hydroxylated graphene (GOH) improved the thermal conductivity of PCMs significantly. The thermal conductivity model demonstrated that the thermal conductivity pathway can be constructed by equally dispersing enough GOH to further increase the thermal conductivity. When the GOH percentage was 0.8 %, the composite's thermal conductivity was 2.60 W/(m·K), which was 118.5 % greater than the graphene composite with the same content. When the melting point was 240.00 °C, the composite material had a high latent heat of 355.52 J/g. The morphology characterization and thermal conductivity model analysis show that adjusting the layer spacing can improve graphene dispersion, facilitating the construction of thermal conduction pathway in PCMs, accelerating heat transfer, and essentially maintaining PCMs' original thermal energy storage density. Therefore, the strategy of regulating the layer spacing of 2D materials in this study has the potential to extend the application of other 2D materials used in PCMs to improve the heat storage properties.