Flame synthesis of 26-faceted maghemite polyhedrons grown via 14-faceted polyhedrons and their carbon composites for Li-ion battery application

Abstract

26-faceted truncated cuboctahedrons of maghemite (γ-Fe₂O₃) nanocrystals are grown via 14-faceted truncated octahedrons through simple and effective flame pyrolysis method by direct burning of ferrocene in different solvents in an alcohol lamp. Systematic investigations showed that the solvent plays an important role in the formation and development of the polyhedral maghemite nanocrystals. The maghemite polyhedral structures are characterized by XRD, TEM and HR-SEM analysis in detail and on the basis of these, the crystal growth mechanism is discussed. Some solvents generated maghemite–carbon composites by encapsulation of maghemite polyhedron by graphene-like layered carbon surrounded by amorphous carbon shell. The as-prepared maghemite–carbon composite showed superior storage performance when tested for Li-ion battery applications. Compared to pure maghemite, the carbon composite exhibited a stable discharge capacity of ∼400 mA h g⁻¹ even after 50 cycles, while the discharge capacities of bare maghemite dropped to ∼100 mA h g⁻¹ after 20 cycles.