Preparation and Thermal Properties of Novel Chloride Salts/Forsterite Composite Phase Change Materials for Thermal Energy Storage

The improvement of composite phase change materials in energy storage density and thermal conductivity is significant for the efficient use of energy. This study proposed novel composite materials based on forsterite with high specific heat as matrix materials, chloride salts (NaCl-KCl) with high latent heat as phase change materials and SiO 2 nanoparticles as fillers. The results indicated that forsterite and chloride salts exhibited excellent chemical compatibility, and the composite materials containing 40% (in weight) chloride salts achieved an energy storage density of 882.5 J/g within the range of 100°C to 800°C, a latent heat of 108.1 J/g, and a thermal conductivity of 0.68–0.81 W/(m·K) at 300°C–500°C. Furthermore, the addition of SiO 2 enhanced the thermal conductivity and energy storage density of composite materials due to the formation of unique nanostructures. More importantly, the removal of structural water during heat-treatment process resulted in the formation of micropores and increased specific surface area of forsterite particles, which facilitated the adsorption and stabilization of molten chloride salts. Combined with the stabilization effect of forsterite and synergistic effect of SiO 2 nanoparticles, the obtained composite materials with 2.0% (in weight) SiO 2 nanoparticles exhibited good thermal stability with 1.80% weight loss and 2.34% reduction in latent heat after 150 cycles, indicating a promising application in high-temperature thermal energy storage.