A Simple and Low-Cost Method to Synthesize Cr-Doped alpha-Fe2O3 Electrode Materials for Lithium-Ion Batteries

Chromium-doped alpha-Fe2O3 samples are successfully synthesized by using a ball-milling-assisted rheological phase method combined with heat treatment. The electronic properties of undoped alpha-Fe2O3 and 4.0 at% Cr-doped alpha-Fe2O3 are investigated by first-principles calculations. The calculation results show that Cr doping can reduce the band gap and impurity levels that appear in the band gap. The structure and morphology of the samples are evaluated by X-ray diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The Cr-doped alpha-Fe2O3 electrode delivers a higher reversible capacity and outstanding rate capability as the anode of a lithium-ion battery compared with the undoped alpha-Fe2O3 electrode. The initial discharge/charge capacities of the 4.0 at% Cr-doped alpha-Fe2O3 electrode can reach 1624/1065.9 mAh g(-1), respectively, and exhibit an excellent reversible capacity of 971.3 mAh g(-1) after 150 cycles at a current density of 0.1 A g(-1). Even after 200 cycles, the capacity can remain as high as 758.1 mAh g(-1) at a current density of 0.5 A g(-1), far beyond than that of the undoped alpha-Fe2O3 electrode (376.5 mAh g(-1)).