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A Li-rich layered cathode material Li 1.15 [(Ni 1/3 Co 1/3 Mn 1/3 ) 0.5 (Ni 1/4 Mn 3/4 ) 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 [Ni 1/3 Co 1/3 Mn 1/3 ] 0.85 O 2 core was completely encapsulated by a Li 1.15 [Ni 1/4 Mn 3/4 ] 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 Li 2 MnO 3 -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 À1 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 [Mn 1/3 Co 1/3 -Mn 1/3 ] 0.85 O 2 core, and an improved rate capability compared to the Li 1.15 [Ni 1/4 Mn 3/4 ] 0.85 O 2 shell. A synergetic effect of the positive attributes of the two materials is achieved by the formation of the coreshell architecture. Therefore, the as-prepared core-shell structured Li 1.15 [(Mn 1/3 Ni 1/3 Co 1/3 ) 0.5 -(Ni 1/4 Mn 3/4 ) 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.

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