CaCo_0.05Mn_0.95O_3-δ: A Promising Perovskite Solid Solution for Solar Thermochemical Energy Storage.

Area of Science:

• Materials Science
• Energy Storage
• Thermochemistry

Background:

• Thermochemical energy storage (TCES) using redox cycles of doped CaMnO3-δ is a cost-effective high-temperature solution for concentrating solar power.
• Dopants enhance thermal stability and TCES density of CaMnO3-δ materials.
• CaMnO3-δ exhibits promising redox properties for energy storage applications.

Purpose of the Study:

• To investigate Co-doped CaMnO3-δ (CaCoₓMn₁₋ₓO₃₋δ) as a novel TCES material.
• To evaluate the impact of Co doping on phase composition, redox capacity, TCES density, reaction rates, and redox chemistry.
• To understand the role of doping in improving material performance for high-temperature energy storage.

Main Methods:

• Synthesis and characterization of Co-doped CaMnO3-δ perovskites (x = 0-0.5).
• Experimental analysis of phase composition, redox capacity, TCES density, and reaction kinetics.
• Theoretical calculations to elucidate redox chemistry and doping effects.

Main Results:

• CaCo₀.₀₅Mn₀.₉₅O₃₋δ demonstrated excellent redox capacity at 1000 °C (p<0xE2><0x82><0x92>O₂ = 10⁻⁵ bar) without decomposition.
• The highest TCES density reported to date (∼571 kJ kg⁻¹) was achieved with CaCo₀.₀₅Mn₀.₉₅O₃₋δ.
• Co doping increased B-site cation valence and facilitated oxygen diffusion, enhancing redox performance.

Conclusions:

• Co-doped CaMnO3-δ perovskites are highly promising for high-temperature TCES applications.
• Optimized doping (CaCo₀.₀₅Mn₀.₉₅O₃₋δ) significantly boosts TCES density and redox capacity.
• Understanding the influence of cooling rates on microstructure is crucial for efficient TCES system design and operation.