Microscale homogeneous refinement of CaO/Ca(OH)2 particles for enhancing thermochemical energy storage performance

Abstract

Thermochemical energy storage technology based on the Ca(OH)₂/CaO dehydration–hydration reaction is considered as a promising strategy for addressing the transient storage of renewable energy due to high thermal storage density, long cycle characteristics, and safety. However, this technology suffers from drawbacks like agglomeration and sintering at high temperatures, along with poor cycling stability. In this study, the “dynamic” doping of Ca(OH)₂ with C₃N₄ was introduced to optimize the microstructure of particles, which enhanced thermal performance, elevated the conversion rate, and improved cycling stability, without reducing thermal storage density. In-depth characterization revealed that C₃N₄ transformed Ca(OH)₂ from a flake-like structure to uniform spherical particles, approximately 10 μm in size. In particular, when the doping amount reached 30 wt%, the thermal storage density increased by 11.10% in contrast to pure Ca(OH)₂, the peak reaction temperature decreased by 13.98 °C, and the conversion rate improved to 91.22%. Simultaneously, the material exhibited excellent anti-caking properties, maintaining a thermal storage density of 776.46 J g⁻¹ after 20 cycles, representing a 27% augmentation compared to the unmodified sample. The microscale effect of the material was retained. In summary, this outcome showcases outstanding comprehensive properties, advancing thermochemical energy storage materials towards practical scenarios.