Encapsulation and coupling of brownmillerite-structured active oxides with metallic phase change materials for multiModal heat storage and air separation

Abstract

The development of integrated thermal energy storage and oxygen production systems represents a critical pathway toward sustainable energy solutions. The brownmillerite-structured Ca₂AlMnO₅ (CAMO) material demonstrates remarkable potential for chemical looping applications owing to its outstanding redox activity, achieving a thermochemical energy density of 150.67 J g⁻¹. To address the mechanical limitations of powders without compromising reactivity, we designed composite macrocapsules featuring a CAMO shell and a metallic Al–Si phase-change core. This innovative architecture provides robust containment for molten Al–Si while maintaining efficient oxygen transport pathways. The optimal single-shell configuration exhibits a total heat storage density of 483.92 J g⁻¹, representing a 205% improvement over conventional Al₂O₃ ceramic balls and positioning this system as a leading candidate in this temperature window. The macrocapsules maintain excellent cycling stability over hundreds of thermal cycles without structural degradation or performance decay, while showing superior sintering resistance compared to monolithic CAMO balls and consistently preserving approximately 2.50 wt% oxygen storage capacity. This work demonstrates a viable strategy for high-performance thermal energy storage that effectively bridges advanced thermal management with carbon-neutral technologies, enabling simultaneous enhancement of energy storage density and on-demand oxygen production for sustainable energy systems.