Facile synthesis of porous iron oxide rods coated with carbon as anode of high energy density lithium ion battery

Highlights: • A novel composite, Fe₂O₃@C, was synthesized via template-free hydrothermal method. • Fe₂O₃@C has a configuration consisting of Fe₂O₃ nanoparticles coated with carbon. • Fe₂O₃@C exhibits excellent rate capability and cyclic stability. - Abstract: A novel composite of Fe₂O₃ and carbon (Fe₂O₃@C) was synthesized hydrothermally without using any template and evaluated as anode of high energy density lithium ion battery. Physical characterizations, from XRD, FESEM, TEM, HRTEM, TGA, XPS, and Raman spectroscopy, demonstrate that the resulting Fe₂O₃@C takes a morphology of porous rods, which is composed of 100 nm Fe₂O₃ particles that are coated uniformly with a layer of amorphous carbon. Charge/discharge tests indicate that the resulting Fe₂O₃@C delivers a reversible discharge capacity of 907 mAh g⁻¹ at 100 mA g⁻¹ and 420 mAh g⁻¹ at 5000 mA g⁻¹, and maintains a discharge capacity of 639 mAh g⁻¹ after 300 cycles at 500 mA g⁻¹. These performances can be attributed to the unique configuration of the Fe₂O₃@C rods. The nanoparticles in the rods shorten the path of lithium ion diffusion and increase the reaction sites for lithium insertion/extraction, the pores in the rods provide space to accommodate the volume change yielded during charge/discharge process and the carbon coating preserves the structural integrity of Fe₂O₃.