Lithium-rich layered oxide is recognized as prospective cathode material for next-generation batteries thanks to its high theoretical specific capacities. They, however, suffer from voltage decay, and capacity fades upon a long cycling process. Herein, a facile supercritical carbon dioxide (scCO2)-assisted method, for the first time, was applied to prepare the layered cathode material. As-prepared Li1.2Mn0.52Ni0.20Co0.08O2 cathode material exhibits a rock-like spherical morphology along with a well-developed hexagonal layered structure. The electrochemical results of Li1.2Mn0.52Ni0.20Co0.08O2 exhibit good discharge capacity and rate performance: delivering an initial discharge capacity of 235.06 mAh.g(-1) at C/20, 201.60 mAh.g(-1) at C/3 and 139.82 mAh.g(-1) at 3C, which are better than that of the same sample prepared without scCO2. The high discharge capacity and improved ratecapability are attributed to superior well-distributed morphology and a highly crystalline layered structure. The novel synthesis strategy reported here offers several advanced Li-rich layered materials that could be further utilized in high-performance Li-ion batteries.