Synthesis, Electronic Structure, and Electrochemical Properties of the Cubic MgMnO Spinel with Porous-Spongy Structure.

MgMnO nanoparticles with cubic spinel structure were synthesized by the sol-gel method using polyvinyl alcohol (PVA) as a chelating agent. X-ray powder diffraction, infrared spectrum (IR), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to characterize the crystalline phase and particle size of as-synthesized nanoparticles. The electronic structure of MgMnO spinel was studied by X-ray photoelectron spectroscopy (XPS). The results showed that pure cubic MgMnO spinel nanoparticles were obtained when the annealing temperature was 500-700 °C. The samples had a porous-spongy structure assembled by nanoparticles. XPS studies indicated that MgMnO nanoparticles were mixed spinel structures and the degree of cation inversion decreased with increasing annealing temperature. Furthermore, the performance of MgMnO as lithium anode material was studied. The results showed that MgMnO samples had good cycle stability except for the slight decay in the capacity at 50 cycles. The coulombic efficiency (ratio of discharge and charge capacity) in most cycles was near 100%. The sample annealed at 600 °C exhibited good electrochemical properties, the first discharge capacity was 771.5 mAh/g, and the capacity remained 340 mAh/g after 100 cycles. The effect of calcination temperature on the charge-discharge performance of the samples was studied and discussed.