MOF-derived Fe3O4/carbon octahedral nanostructures with enhanced performance as anode materials for lithium-ion batteries

Abstract

Fe₃O₄/carbon (C) nanocomposites with octahedral structure have been successfully prepared as anode materials for lithium-ion batteries (LIBs) by carbonizing hexagonal dipyramid Fe–metal organic frameworks (MOFs) under N₂ directly. The prepared Fe–MOFs and Fe₃O₄/C octahedral nanostructures were carefully characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, thermogravimetric analysis, N₂ adsorption/desorption isotherms and electrochemical techniques. The results showed that octahedral Fe₃O₄ was encapsulated by carbon layers to form porous Fe₃O₄/C octahedral nanostructures. Benefiting from the high electrical conductivity of the carbon matrix and the porous structure of Fe₃O₄/C nanocomposites, the Fe₃O₄/C octahedral nanostructures demonstrated a lithium storage capacity of 861 mA h g⁻¹ after 100 cycles at a specific current of 100 mA g⁻¹, as anode for lithium ion batteries (LIBs), which is much higher than that of spindle-like Fe₂O₃ obtained via direct carbonization of Fe–MOFs under an air atmosphere (merely 603 mA h g⁻¹ under identical conditions) and commercial Fe₃O₄. The elaborate and well-defined configuration also delivered a high rate capability and long cycling stability. Hence, the combination of Fe₃O₄ crystals with an octahedral nanostructure and the random doping of carbon could offer a valid method for the development of anode materials for high-performance LIBs.