The Mo-doped LiNi0.5Mn1.5O4 cathodes are successfully synthesized by citric acid-assisted sol–gel method. The result demonstrates that the Mo-doped LiMn1.4Ni0.55Mo0.05O4 cathodes present the improved electrochemical performance over pristine LiNi0.5Mn1.5O4. At the 2 C rate after 80 cycles, the discharge capacities are 68.5 mAh g−1 for the pristine LiNi0.5Mn1.5O4 material (53.9% of the capacity at 0.1 C), 107.4 mAh g−1 for the LiMn1.425Ni0.5Mo0.05O4 material (82.1% at 0.1 C), and 122.7 mAh g−1 for the LiMn1.4Ni0.55Mo0.05O4 material (90.5% at 0.1 C). Mo-doping is favorable for reducing the electrode polarization, suggesting that Mo-doped LiNi0.5Mn1.5O4 electrodes have faster lithium insertion/extraction kinetics during cycling. Mo-doped LiNi0.5Mn1.5O4 electrodes show lower charge-transfer resistance and higher lithium diffusion coefficients. In addition, LiMn1.4Ni0.55Mo0.05O4 cathode exhibits the smallest particle size, the lowest charge-transfer resistance and the highest lithium diffusion coefficient among all samples, indicating that it has a high reversibility and good rate capability.