Controllable formation of multi-layered SnO₂@Fe₂O₃ sandwich cubes as a high-performance anode for Li-ion batteries

The design and controllable synthesis of hollow multi-layered "sandwich" nanostructures offer opportunities for metal oxides to buffer the volume expansion and aggregation due to coalescence into bulk structures, while realizing improved tap density and superior ion transport. We report the intentional construction of Fe₂O₃ nanorod-assembled layers to cover and fill the surface and interlayer of double-shelled SnO₂ hollow nanocubes (HNCs) to form multi-layered SnO₂@Fe₂O₃ sandwich nanocubes (SNCs). The crystallinity and morphological characteristics confirm that the dense well-aligned Fe₂O₃ nanorods vertically cover all surfaces of the SnO₂ layers. When used as the anode active material for lithium-ion batteries (LIBs), these sandwich hetero-nanostructures demonstrate evidently improved Li ion storage performances compared to pure SnO₂, with higher specific capacity and cyclability (750.8 mA h g^-1 after 200 cycles at a current density of 500 mA g^-1) due to the synergistic effect of the hollow multi-layered nanostructure and uniform Fe₂O₃ hetero-coating.