High-temperature metallic phase change materials (PCMs) are promising thermal storage materials, which can play important roles in high-temperature thermal storage systems, such as solar thermal power generation. The high-temperature metallic materials have the advantages of high thermal storage density and high thermal conductivity, but the volume expansion during the high-temperature phase change process and the melting corrosion of the container have limited their further development. Therefore, it is important to develop reasonable encapsulation technology to solve the problems of leakage and high-temperature corrosion of metallic PCMs. In this paper, we report a new method to encapsulate Al to form macrocapsules of Al@Al₂O₃ for thermal energy storage. The capsules contain pores inside the core, which can act as the buffer space to accommodate the volume expansion of Al core during heating and melting, thereby avoid the cracking of Al₂O₃ shell. Under optimal preparation conditions, the Al core of the macrocapsule has a high latent density of 343.0 J/g and a melting temperature of 655.4 °C. In the temperature range of 400-900°C, the large capsules have a high thermal storage density up to 702.8 J/g. The macrocapsules also show good cyclic thermal stability as investigated by the 50 times of melting and solidification. This study provides an approach to further development of metallic base phase change macrocapsules using encapsulation techniques for promising application in high temperature thermal storage.

thermal energy storage, phase change materials, thermal management, phase change capsules, heat storage