Fabrication of Sn@SiO2 core-shell microcapsules with high durability for medium-temperature thermal energy storage

Phase change materials (PCMs) using metals/alloys have been concerned for medium temperature solar thermal storage and waste heat recovery. However, the PCMs may leak due to the solid-liquid phase change, which greatly limits the use of metallic PCMs. In this study, we report the synthesis of microencapsulated PCMs (MEPCMs) using metallic Sn as PCM core and a sol-gel coated SiO 2 as shell. The as-coated microcapsules are further undergone a high temperature heat treatment at oxygen/nitrogen atmosphere. Due to the self-repairing effect, the cracked microcapsules can be sealed and stabilized, thereby forming high stabilized MEPCMs over 100 cycles. The melting point and latent heat of the Sn@SiO 2 –O 2 microcapsules were around 233 °C and 56 J g -1 respectively, while the values were around 233 °C and 58 J g -1 for Sn@SiO 2 –N 2 microcapsules, similar to the theoretical values of metallic Sn. The successfully prepared Sn@SiO 2 MEPCMs could find wide applications in medium temperature thermal energy storage .