Sr and Co Co-doping on Thermochemical Energy Storage Properties of CaMnO3−δ

The successful commercialization of concentrated solar power (CSP) plants necessitates the development of efficient energy storage systems to ensure the on-demand power generation during solar transients. In recent years, the redox cycling of doped CaMnO3−δ has emerged as a promising approach for thermochemical energy storage (TCES) in CSP applications. This study aims to enhance the thermochemical energy storage capability of CaMnO3−δ by co-doping with Sr and Co at the A- and B-sites, respectively, forming (SrxCa1–x)(CoxMn1–x)O3–δ. Two doping levels (x = 0.05 and 0.10) were investigated. XRD and SEM–EDS analyses confirmed that Sr and Co were homogeneously incorporated into the perovskite lattice, yielding porous microstructures in both compositions. Notably, evaluation of the thermochemical energy storage (TCES) densities of these codoped perovskites under diverse thermal energy storage conditions revealed that although the two materials exhibited different heat storage processes, comparable TCES densities were ultimately achieved. In particular, under favorable thermochemical energy storage conditions (1100 °C, pO2 = 10–5 atm), the thermochemical energy storage densities of Sr0.05Ca0.95Co0.05Mn0.95O3–δ and Sr0.10Ca0.90Co0.10Mn0.90O3–δ achieved 459 kJ/kgABO3 and 470 kJ/kgABO3, respectively. However, in the subsequent redox cycle tests, Sr0.10Ca0.90Co0.10Mn0.90O3–δ demonstrated a stronger reoxidation capability compared to Sr0.05Ca0.95Co0.05Mn0.95O3–δ. Compared to the undoped material, both co-doped samples exhibited significant improvements in the TCES density and thermal stability. Moreover, the isothermal redox reaction rate measurements and the analysis revealed the rapid redox reaction rate in both materials, providing valuable insights for the development of advanced perovskite-based thermochemical energy storage systems.