Porous CoO Nanostructure Arrays Converted from Rhombic Co(OH)F and Needle-like Co(CO3)0.5(OH)·0.11H2O and Their Electrochemical Properties

Novel CoO nanostructure arrays on nickel foam with needle-like and rhombic morphologies have been prepared by using urea and hexamethylenetetramine as hydrolysis agents through fluoride-assisted hydrothermal method, respectively. The possible formation mechanism and effect factors of the novel arrays were systematically investigated by X-ray diffraction, scanning and transmission electron microscopies, N 2 sorption, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The precursor Co(CO 3 ) 0.5 (OH)·0.11H 2 O or Co(OH)F plays a crucial role in the formation of needle-like or rhombic arrays. As-prepared precursor arrays can be further converted to corresponding CoO arrays by annealing at 450 °C for 2 h without signification alteration of one-dimensional (1D) morphology. When tested as anodes for lithium ion batteries (LIBs) without the addition of other ancillary materials (carbon black and binder), the synthesized CoO arrays with needle-like and rhombic morphologies deliver ultrahigh initial discharge capacities of 1973.3 and 1447.9 mAh g –1, respectively. In addition, they also maintain high reversible capacities of 710 and 719 mAh g –1 at 0.2 C after 50 cycles, respectively.