Mesoporous Fe<inf>2</inf>O<inf>3</inf> flakes of high aspect ratio encased within thin carbon skeleton for superior lithium-ion battery anodes

Abstract

© The Royal Society of Chemistry 2015. Reticulated mesoporous Fe<inf>2</inf>O<inf>3</inf>@C flakes, consisting of nanocrystalline α-Fe<inf>2</inf>O<inf>3</inf> 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 Fe<inf>2</inf>O<inf>3</inf>@C flakes can largely accommodate the mechanical stresses and volume expansion of Fe<inf>2</inf>O<inf>3</inf> 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 Fe<inf>2</inf>O<inf>3</inf> flakes. The facile fabrication method and the unique structure of the mesoporous Fe<inf>2</inf>O<inf>3</inf>@C flakes offer high performance for LIB anodes and great potential for other applications of Fe<inf>2</inf>O<inf>3</inf>.