A Li-rich layered cathode material Li_1.15[(Ni_1/3Co_1/3Mn_1/3)_0.5(Ni_1/4Mn_3/4)_0.5]_0.85O₂ with a spherical core–shell structure was firstly synthesized by a co-precipitation route. In this material, the Li_1.15[Ni_1/3Co_1/3Mn_1/3]_0.85O₂ core was completely encapsulated by a Li_1.15[Ni_1/4Mn_3/4]_0.85O₂ 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[Mn_1/3Co_1/3Mn_1/3]_0.85O₂ core, and an improved rate capability compared to the Li_1.15[Ni_1/4Mn_3/4]_0.85O₂ 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[(Mn_1/3Ni_1/3Co_1/3)_0.5(Ni_1/4Mn_3/4)_0.5]_0.85O₂ is very effective for improving the electrochemical behavior of Li-rich layered cathode materials in the high-performance lithium ion batteries.