Preparation and electrochemical performance of spinel LiNi0.5-xMn1.5+xO4 (x=0, 0.05, 0.1) hollow microspheres as cathode materials for lithium-ion batteries

摘要

The spinel LiNi0.5-xMn1.5+xO4 (x= 0, 0.05, 0.1) including LiNi0.5Mn1.5O4, LiNi0.45Mn1.55O4, and LiNi0.4Mn1.6O4 hollow microspheres has been prepared by adjusting the stoichiometric ratios of Ni and Mn with an impregnation method followed by a simple solid-state reaction. They are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, and electrochemical tests. The results show that LiNi0.5Mn1.5O4 is the ordered with the space group of P4(3)32, but LiNi0.45Mn1.55O4 and LiNi0.4Mn1.6O4 are the disordered with the space group of Fd3m. All the three types of hollow microspheres have the similar primary particles. Compared to LiNi0.5Mn1.5O4, partial Ni atoms are substituted by Mn atoms in LiNi0.45Mn1.55O4 and LiNi0.4Mn1.6O4 lattices along with incorporation of small amounts of Mn3+. Although the ordered LiNi0.5Mn1.5O4 hollow microspheres deliver the highest capacity of 128.5 mAh/g at 1 C among the three types of spinel materials, the disordered LiNi0.45Mn1.55O4 hollow microspheres exhibit the highest capacity of 96.8 mAh/g at 10 C. The superior rate capability of LiNi0.45Mn1.55O4 hollow microspheres is attributed to the combination of the increased electronic conductivity and Li+-ion diffusion by moderate Mn3+ incorporation, along with the hierarchical structure.