Research on High-Temperature Thermochemical Energy Storage Material: Co-Based Metal Oxide

Metal oxides, particularly the $\mathrm{Co}_{3} \mathrm{O}_{4} / \mathrm{CoO}$ system, have emerged as promising thermochemical energy storage materials due to their superior properties, including high operating temperatures, high energy density, ambient storage without time limitations, and suitability for long-distance transportation. These attributes make them ideal for large-scale applications such as renewable energy storage, power generation, and even household energy systems. However, their technical readiness level (TRL) is currently limited to 1–4, lagging behind sensible and latent thermal energy storage technologies, which are already commercialized with TRLs of 6–9. The primary challenge lies in achieving a balance between thermochemical performance and mechanical integrity during scale-up. This entails enhancing mechanical stability while maintaining an appropriate reaction temperature, reaction rate, and energy storage density. In this study, the $\mathrm{Co}_{3} \mathrm{O}_{4} / \mathrm{CoO}$ metal oxide pair for thermochemical energy storage is systematically investigated. Pure $\mathrm{Co}_{3} \mathrm{O}_{4} / \mathrm{CoO}$ is optimized by doping with varying amounts of Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (5 wt% to 20 wt%). The microstructure and morphologies of the materials are analyzed, alongside their thermochemical properties and mechanical strength. The results indicate that $\mathrm{Co}_{3} \mathrm{O}_{4} / \mathrm{CoO}$ with 10 wt% Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> achieves a favorable balance, exhibiting a significant enthalpy change, improved mechanical stability, high porosity, and a well-preserved specific surface area. Furthermore, cycling experiments confirm the advantages of the developed materials, demonstrating their potential for enhanced performance and durability in thermochemical energy storage applications.