High-performance Al-doped CaO pellets fabricated via template-based tableting method for thermochemical energy storage

To address the self-sintering property of CaO-based materials for thermochemical energy storage and intensified deactivation of CaO-based pellets manufactured via traditional granulation process, a template-assisted granulation approach to yield highly effective morph-genetic Al-doped CaO pellets was reported here. The effects of preparation conditions on energy storage performance and mechanical properties were examined, alongside the kinetic enhancement mechanism of the hollow tubular pore structure. Results show that the morph-genetic Al-doped CaO pellets with the tableting pressure of 0.4 t and Ca/Al molar ratio of 100:10 exhibit staggered hollow tubular pores. This pore structure reduces CO 2 diffusion resistance, and the generated Ca 12 Al 14 O 33 stabilizes the hollow structure, thereby improving the energy storage density and cyclic stability of the pellets. The optimized pellets achieve remarkable energy storage density of 1610 kJ/kg after 50 cycles, the cumulative energy storage density of 99.23 MJ/kg and the crushing strength of 1.58 N. Even under CO 2 -rich calcination conditions (950 °C, 50 % CO 2 /N 2 balance), their energy storage efficiency is 20 % higher than that of non-templated CaO-based pellets. The optimized pellets combine the advantages of the hierarchical porous biostructure derived from the template and improved mechanical strength, reaching a leading level in the energy storage performance of granular CaO-based pellets. • Morph-genetic Al-doped CaO pellet was prepared by template-based tableting method. • Optimal pellets exhibit staggered hollow micro-tubular pores inside. • The hollow tubular structure is stabilized by the support of Ca 12 Al 14 O 33 . • The hollow tubular structure enhances the reaction kinetics of optimal pellets. • Energy storage performance and mechanical properties of optimal pellets are improved.