Preparation-microstructure-performance relationship of Li-rich transition metal oxides microspheres as cathode materials for lithium ion batteries

Highlights: • The relationship among preparing condition, microstructure, and performance. • The obtained LLNMO have a diameter of ∼5 μm and hollow inner structure. • The obtained LLNMO exhibit excellent cycling stability and rate performance. - Abstract: We report the preparation and characterization of Li_1.2Ni_0.2Mn_0.6O₂ (=0.5Li₂MnO₃·0.5LiNi_0.5Mn_0.5O₂) microspheres as cathode materials for lithium ion batteries. These microspheres were synthesized by carbonate co-precipitation and calcination with lithium salt. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma-atomic emission spectrometer, and nitrogen adsorption. It is found that the synthesized samples, of spherical morphology with primary nanoparticles assembled in secondary microparticles, have a diameter of ∼5 μm. When used as the cathode materials for lithium ion batteries, the sample prepared at aging time of 9 h with ammonia concentration of 0.6 mol L⁻¹ shows excellent electrochemical performance. Their charge capacities are 274 mAh g⁻¹ at the current density of 20 mA g⁻¹, much higher than those of the commercial LiCoO₂ and LiFePO₄. More importantly, they exhibit excellent rate performances with a capacity of 165 and 144 mAh g⁻¹ at the current densities of 600 and 1000 mA g⁻¹, respectively, superior to those of other reported Li-rich cathode materials. This work illustrates the relation among synthesis condition, inner structure and electrochemical performance, which has a positive effect on industry production.