Electrochemical performance of hematite nanoparticles derived from spherical maghemite and elongated goethite particles

We report here an interesting observation on the electrochemical performance of hematite nanoparticles derived from cubic maghemite nanoparticles and hexagonal goethite rods prepared by a sonochemical process. We prepared hematite (α-Fe₂O₃) particles by annealing the as-prepared spherical cubic maghemite (γ-Fe₂O₃) nanoparticles and rod shaped hexagonal goethite (α-FeOOH) particles at 600 °C in air and investigated their performance as a Li-ion battery anode. Interestingly, annealing of spherical maghemite particles resulted in the formation of plate like interconnected hematite particles exhibiting unimodal pore distribution whereas rod shaped goethite has resulted in the formation of irregularly shaped porous hematite particles having a wide and multimodal pore distribution. The plate like α-Fe₂O₃ cells delivered a reversible capacity of ∼1160 and the porous α-Fe₂O₃ nanoparticles exhibited a slightly lower capacity of ∼1100 mAh g^-1. The test cells rendered a reversible capacity of ∼926 and ∼841 mAh g^-1 for nanoparticles derived from maghemite and goethite, respectively, after 40 galvanostatic cycles and a capacity of 611 and 522 mAh g^-1 at 0.1C rate after 100 cycles. In other words, the investigated α-Fe₂O₃ nanomaterials retained a reversible capacity of ∼80 and 75%, respectively after 40 galvanostatic cycles. The basic difference in the electrochemical performance of the studied hematite particles have been attributed to the difference in the porosity of the samples. Moreover, the adopted synthesis technique is very simple and easily up scalable compared to most of the methods available in the literature for the synthesis of hematite nanoparticles.