Investigation of Zr-doped CaMnO3 perovskite solid solution for high-temperature solar thermochemical energy storage

CaMnO3 perovskite oxide, composed of earth-abundant and cost-effective elements, could store and release heat by the redox reactions over a wide range of temperatures and partial pressures of oxygen (p(O2)). CaMnO3 perovskite oxide has been regarded as a promising candidate for thermochemical heat storage in concentrated solar power plants. However, CaMnO3 perovskite oxide is partially decomposed during the high-temperature reduction process, resulting in the incomplete reoxidation of the material, which severely limits its thermochemical energy storage performance. Herein, Zr-doped CaMnO3 has been proposed as a novel thermochemical energy storage material. Moreover, its phase structure, redox capability, energy storage performance, and solar spectral absorption properties have been thoroughly investigated through experimental and theoretical calculations. The results demonstrated that the CaZr0.1Mn0.9O3 perovskite solid solution could achieve a fully reversible redox cycle while effectively inhibiting decomposition during reduction. However, with the further increase in the Zr doping ratio, the produced side phases would significantly reduce the redox performance of the material. The thermochemical energy storage density of CaZr0.1Mn0.9O3 could reach 390.6±32.8 kJ/kg at 1000°C and p(O2)=10−5 atm, and the effective doping of Zr could enhance the spectral absorption of CaMnO3 in the near-infrared region. According to the calculation of density functional theory, the effective doping of Zr could enhance the B–O chemical bond strength of ABO3 oxides, thus strengthening the structural stability and improving the thermochemical energy storage density. This study provides guidance for the development of perovskites for thermochemical energy storage. © 2022 Chinese Academy of Sciences. All rights reserved.