Li-modified BaCoO3−δ for thermochemical energy storage: enhanced reaction performance and modification mechanism

Abstract

Perovskite materials are promising candidates for thermochemical energy storage, yet conventional substitutional doping has not effectively increased their reactivity at lower temperatures (600–900 °C), limiting practical applications. This study synthesized Li-modified BaCoO_3−δ to enhance gas–solid reaction activity by introducing structural defects. XRD and ICP analyses confirmed the incorporation of Li into the BaCoO_3−δ lattice. TG and DSC experiments demonstrated that Li doping significantly improved the redox activity of the material within the 600–900 °C range, increasing the thermochemical storage density by approximately 75% from 199.1 kJ kg⁻¹ to 348.4 kJ kg⁻¹. Van't Hoff analysis indicates that Li doping increases the entropy and enthalpy of the thermochemical reactions. Cycling experiments showed stable performance enhancement, retaining over 95% (and even up to 99%) of activity after 450 cycles, still significantly outperforming fresh BaCoO_3−δ. DFT calculations, XPS, and EPR analysis revealed that Li doping stabilizes surface oxygen vacancy structures, increasing surface defect oxygen content and enabling stronger redox reactions at lower temperatures. This study elucidates how Li doping enhances the thermochemical heat storage performance of BaCoO_3−δ, providing valuable insights for designing perovskite materials.