Synthesis and characterization of a Li-rich layered cathode material Li-1.15[(Mn1/3Ni1/3Co1/3)(0.5)(Ni1/4Mn3/4)(0.5)](0.85)O-2 with spherical core-shell structure

A Li-rich layered cathode material Li-1.15[(Ni1/3Co1/3Mn1/3)(0.5)(Ni1/4Mn3/4)(0.5)](0.85)O-2 with a spherical core-shell structure was firstly synthesized by a co-precipitation route. In this material, the Li-1.15[Ni1/3Co1/3Mn1/3](0.85)O-2 core was completely encapsulated by a Li-1.15[Ni1/4Mn3/4](0.85)O-2 shell. The structure and morphology of the as-prepared core-shell structured material were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results indicate that the core-shell structured material has a typical layered structure with the existence of a Li2MnO3-type integrated component. Spherical morphologies with an inner core and outer shell layer are clearly observed by SEM. A half cell using the core-shell structured cathode material showed a high capacity of 242 mA h g(-1) at a rate of 0.1 C in a voltage range of 2.0-4.8 V. Especially, the core-shell structured cathode material represents excellent lithium intercalation stability compared to the Li-1.15[Mn1/3Co1/3Mn1/3](0.85)O-2 core, and an improved rate capability compared to the Li-1.15[Ni1/4Mn3/4](0.85)O-2 shell. A synergetic effect of the positive attributes of the two materials is achieved by the formation of the core-shell architecture. Therefore, the as-prepared core-shell structured Li-1.15[(Mn1/3Ni1/3Co1/3)(0.5)(Ni1/4Mn3/4)(0.5)](0.85)O-2 is very effective for improving the electrochemical behavior of Li-rich layered cathode materials in the high-performance lithium ion batteries.