CaO-based materials store and release thermal energy through reversible carbonation/calcination reactions. They are promising candidates for high-temperature thermochemical energy storage due to their high energy-storage density and low cost. However, their practical application is hindered by sintering-induced capacity decay, particle fragmentation, and challenges in large-scale manufacturing. This study aims to improve the CO₂ adsorption/desorption performance and cyclic stability of CaO-based materials through reaction condition optimization, material doping, and micro/nanostructure engineering. A series of composite CaO-based materials were prepared by wet mixing and mechanical ball milling. Their cyclic energy-storage performance is evaluated in pressurized fixed-bed and bubbling fluidized-bed reactors. Pressurized carbonation increases the energy-storage performance by 1.8 times compared with atmospheric-pressure operation. This improvement results from suppressed CaO grain growth under elevated pressure, which maintains smaller grain sizes and enhances resistance to sintering and cyclic deactivation. In addition, a micron-scale tubular structure significantly increases the specific surface area and porosity, reducing the optimal inert dopant loading by 50%. To overcome the poor flowability of CaO-based particles, a nanoscale coating strategy improves their flowability at high temperatures by up to 59-fold. Kilogram-scale CaO-based particles are successfully produced through extrusion and spheronization, exhibiting less than 3% energy-storage capacity loss over 100 cycles. Furthermore, honeycomb CaO-based monoliths maintain their structural integrity without visible cracks after more than 20 cycles. Overall, pressurization, micro/nanostructure engineering, and granulation improve the performance and durability of CaO-based materials, supporting their large-scale production.
 

Calcium looping, thermochemical energy storage, micro-nano structures