Mesoporous Fe₂O₃ flakes of high aspect ratio encased within thin carbon skeleton for superior lithium-ion battery anodes

Reticulated mesoporous Fe2O3@C flakes, consisting of nanocrystalline α-Fe2O3 encased within a thin carbon skeleton, were synthesized using ferrocene as iron and carbon sources and a novel reaction agent of ammonium sulphate via a facile two-step heating route. Those flakes, which were several nanometers thick and 1–2 μm in diameter, showed high capacity, excellent cyclic stability and rate capability as an anode material for lithium-ion batteries (LIBs). An initial reversible capacity of 910 mA h g−1 at a discharge/charge current of 0.1 A g−1 was obtained, and the capacity showed a gradual increase during cycling, reaching a high capacity of 1080 mA h g−1 after 120 cycles. An in situ lithiation study by transmission electron microscopy showed that the reticulated mesopores and the ultrathin feature of the Fe2O3@C flakes can largely accommodate the mechanical stresses and volume expansion of Fe2O3 during lithiation and hence maintain their integrity and provide excellent properties. The thin carbon skeleton not only facilitates the electronic conduction, but also inhibits the aggregation of nanocrystalline Fe2O3 flakes. The facile fabrication method and the unique structure of the mesoporous Fe2O3@C flakes offer high performance for LIB anodes and great potential for other applications of Fe2O3.