Preparation and Characterization of Graphite-SiO₂ Composites for Thermal Storage Cement-Based Materials

Thermal storage cement-based materials, formed by integrating phase change materials into cementitious materials, exhibit significant potential as energy storage materials. However, poor thermal conductivity severely limits the development and application of these materials. In this study, an amorphous SiO₂ shell is encapsulated on a graphite surface to create a novel thermally modified admixture (C@SiO₂). This material exhibits excellent thermal conductivity, and the surface-encapsulated amorphous SiO₂ enhances its bond with cement. Further, C@SiO₂ was added to the thermal storage cement-based materials at different volume ratios. The effects of C@SiO₂ were evaluated by measuring the fluidity, thermal conductivity, phase change properties, temperature change, and compressive strength of various thermal storage cement-based materials. The results indicate that the newly designed thermal storage cement-based material with 10 vol% C@SiO₂ increases the thermal conductivity coefficient by 63.6% and the latent heat of phase transition by 11.2% compared to common thermal storage cement-based materials. Moreover, C@SiO₂ does not significantly impact the fluidity and compressive strength of the thermal storage cement-based material. This study suggests that C@SiO₂ is a promising additive for enhancing thermal conductivity in thermal storage cement-based materials. The newly designed thermal storage cement-based material with 10 vol% C@SiO₂ is a promising candidate for energy storage applications.