High-performance aluminum phase change macrocapsules coated with mechanically reinforced ceramic shells for high-temperature solar thermal energy storage

To develop mechanically robust and scalable phase-change macrocapsules for high-temperature solar thermal energy storage, Al-based macrocapsules with reinforced ceramic shells were fabricated using a rolling coating process combined with a paraffin sacrificial-layer strategy. In this work, Al(H 2 PO 4 ) 3 was introduced as a sintering aid to promote the bonding and densification of the Al 2 O 3 shell, while Al 2 O 3 fibers were incorporated to improve shell toughness and suppress crack formation. The optimized Al@Al 2 O 3 -F5P30 macrocapsules exhibited an average fracture load of 135 N, approximately six times higher than that of the unmodified Al@Al 2 O 3 capsules. After 150 melting-solidification cycles in air, the capsules remained intact without leakage, and the fracture load was retained at approximately 120 N. The phase-change temperature and latent heat of the Al core remained nearly unchanged after cycling, indicating good thermal stability. Within 600–700 ℃, the 20 mm@2 mm macrocapsules achieved a gravimetric heat storage density of 351.37 kJ/kg and a volumetric heat storage density of 964.47 J/cm 3 . These results suggest that the rolling coating strategy provides a feasible route for fabricating mechanically reinforced metal PCM macrocapsules for potential high-temperature solar thermal energy storage applications.