Fine powders of Li1.2Ni0.2Mn0.6−xMoxO2 (x=0, 0.002, 0.005, 0.01, 0.05) are prepared by a thermopolymerization method. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements are carried out to characterize these samples. The maximum Mo-doping level to obtain a pure layered phase is 0.005. The Mo-doped samples show a great improvement in rate performance and cycling stability. For the optimal composition Li1.2Ni0.2Mn0.59Mo0.01O2, it exhibits a discharge capacity of 245 and 110mAhg−1 at 0.1C and 5C, respectively. It retains a capacity of 229mAhg−1 at 0.1C after 204 cycles with a capacity retention of 93.2%. This study suggests that the partial substitution of Mn4+ with Mo6+ can improve both the rate capability and cycle performance of this high-capacity cathode material.