Robust hollow Bowl-like α-Fe₂O₃ nanostructures with enhanced electrochemical lithium storage performance

The design and synthesis of hollow-nanostructured transition metal oxide-based anodes is of great importance for long-term operation of lithium ion batteries (LIBs). Herein, a special hollow bowl-like α-Fe₂O₃ nanostructure is controllably synthesized through a facile hydrothermal technique and exhibits great electrochemical lithium storage performance when used as LIBs anode. Under a facile hydrothermal condition, α-Fe₂O₃ nanostructures evolve from solid pie-like structure to hollow bowl-like structure and finally α-Fe₂O₃ nanorings through the regulation of HPO₄^- derived from ionized Na₃PO₄·12H₂O and Ostwald ripening process. The designed hollow bowl-like α-Fe₂O₃ nanostructure not only has the merits of hollow structure, which can accelerate the diffusion of lithium ions and electrons, but also shows great mechanical strength to disperse stress when compared to solid pie-like and ring-like α-Fe₂O₃ nanostructures, which would avoid collapse during charge/discharge process. As a result, the as-synthesized hollow bowl-like α-Fe₂O₃ nanostructure displays an initial reversible capacity of 1616 mAh g^-1 at a current density of 1 A g^-1, an excellent cycling performance with a reversible capacity of 1018 mAh g^-1 after 500 cycles and an outstanding rate capability (68.1% capacity retention at current densities from 100 to 2000 mA g^-1). This work provides not only a novel hollow bowl-like α-Fe₂O₃ nanostructure with high specific surface area and stable structure as potential electrode materials for energy storage, but also a facile self-templated strategy free of any surfactants and templates for hollow nanostructures.