Subunits controlled synthesis of α-Fe2O3 multi-shelled core–shell microspheres and their effects on lithium/sodium ion battery performances

Abstract

Two kinds of Fe₂O₃ core–shell microspheres were synthesized. The Fe₂O₃ sample obtained using ethanol (E–Fe₂O₃) contains a shell and a core assembled by nanoparticles with a diameter of ∼150 nm and the surface is fairly smooth. Fe₂O₃ with optimized subunits was produced using water (W–Fe₂O₃). The core is assembled by smaller nanoparticles of ∼50 nm. The thicker shell and exterior surface possess porous nanorods. These peculiar subunits endow W–Fe₂O₃ with a higher specific surface area, more pore volume and larger nanopores. W–Fe₂O₃ displayed 733.1 mA h g⁻¹ at 6000 mA g⁻¹, which is more than two times that of E–Fe₂O₃ (306.5 mA h g⁻¹). Encouragingly, W–Fe₂O₃ also expressed relatively promising sodium ion battery performances. The significantly different performances between E–Fe₂O₃ and W–Fe₂O₃ can be almost entirely attributed to their distinctive subunits. The study demonstrated that enhanced lithium/sodium ion storage properties can be achieved by adjusting the subunits.