Study of TiO2-Coated α-Fe2O3Composites and the Oxygen-Defects Effect on the Application as the Anode Materials of High-Performance Li-Ion Batteries

TiO2-coated Fe2O3 composites exhibiting high electrochemical stability with oxygen defects were synthesized as the anode materials of Li-ion batteries using an easy sol-gel method. The industrial submicron-sized Fe2O3 with no special shape and commercial tetrabutyl titanate were adopted as raw materials. The phase structures, morphologies, and elements distribution on the surface were characterized by X-ray diffraction analysis, electron paramagnetic resonance, scanning electron microscopy, X-ray photoelectron spectroscopy, and so forth. Results indicated that TiO2 was well coated on the surface of raw Fe2O3 with an average thickness of 5.5 nm, and the oxygen defects were successfully introduced into the composites with the reduction treatment. Electrochemical characterization indicated that TiO2 coating was beneficial to the cycle performance of Fe2O3. The coating layer significantly improved the electronic conductivity and cycling stability of the Fe2O3 anode material, as theoretically supported by the density functional theory calculation. Moreover, the introduction of oxygen defects in samples resulted in more excellent cycling stability compared to that in samples without reduction. The reduced Fe2O3@0.2TiO2 sample exhibited a specific discharge capacity of 405.6 mA h·g-1 after 150 cycles, which effectively improved the intrinsic cycling performance of Fe2O3, and a corresponding discharge capacity of 50 mA h·g-1 after 30 cycles.