Different morphologies of Li-rich layered oxides, Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO), were synthesised using a rapid nucleation and post-solvothermal method followed by calcination. After the process of rapid nucleation, the as-prepared mixture of M(OH)2 using NaOH as the precipitator showed nanoplate aggregation, while the mixture of MCO3 using (NH4)2CO3 as the precipitator presented a spherical morphology. After subsequent solvothermal processing and calcination, Li1.2Mn0.54Co0.13Ni0.13O2 samples with uniform nanoplate particles (LMNCO-P) and spherical particles (LMNCO-S) were obtained. The as-prepared LMNCO-P and LMNCO-S samples exhibited excellent electrochemical performance and delivered high initial discharge capacities of 282 and 278mA h g−1, respectively, at 0.1C with a cut-off voltage in the range 2.0–4.8V. The LMNCO-S cathode material exhibited outstanding cycling performance with capacity retention ratios of 88%, 89%, and 92% at 1, 2, and 5C, respectively, after 100 cycles. Furthermore, after a stepped pre-cycling treatment, the capacity retention of the LMNCO-S cathode material reached 79% after 500 cycles at 5C. The superior cycling performance can be ascribed to the spherical morphology with a small surface area, which decreased side reactions with the electrolyte and enhanced the crystal structure stability after the pre-cycling treatment.