Nanoporous iron oxide@carbon composites with low carbon content as high-performance anodes for lithium-ion batteries

Abstract

A composite of nanoporous iron oxide (Fe₂O₃) nanoparticles coated with a thin layer of carbon (designated as nanoporous Fe₂O₃@C) is synthesized using a convenient one-pot solvothermal method. Although the thickness of the carbon framework is only 6 nm on average, which is very small compared to the size of Fe₂O₃ nanoparticles, the carbon framework significantly enhances the electrochemical performance of nanoporous Fe₂O₃@C composites when they are used as an anode material for lithium-ion batteries. Thanks partly to the relatively low carbon content of 6.7 wt%, the nanoporous Fe₂O₃@C anodes exhibit a high reversible capacity of 767 mA h g⁻¹ after 100 cycles at a current density of 500 mA g⁻¹ and 545 mA h g⁻¹ even at a higher current density of 2 A g⁻¹. In comparison to commercial Fe₂O₃ nanoparticles and bare nanoporous Fe₂O₃ nanoparticles, the nanoporous Fe₂O₃@C anodes show superior cycle life. The nanoporous structure offers void space for volume change of Fe₂O₃ nanoparticles, while the thin carbon framework improves the stability of structures and SEI (solid electrolyte interphase) films during the continuous intercalation/deintercalation processes of Li ions.