Lithium-rich manganese-based (Li-rich Mn-based) cathode materials possess high specific capacity, low self-discharge rate and steady working voltage, but cycle performance and rate performance need to be further improved. In this study, cathode materials Li_1.2Mn_0.54Ni_0.13Co_0.13O_2-xF_x (x = 0, 0.02, 0.05, 0.08) are synthesized by the co-precipitation method with the two-step calcination process. And the F-doping effects on the microstructure and the electrochemical performance are investigated in the cathode materials Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. The results indicate that among all the F-doped cathode materials, the crystal lattice parameters are increased, order degree and stability of the layered structure are improved. As for x = 0.05, cathode material Li_1.2Mn_0.54Ni_0.13Co_0.13O_1.95F_0.05 (LMO-F_0.05) shows the best cycle performance and rate performance with its capacity retention rate 87.7% after 100 cycles at 0.2 C and discharge capacity 117 mAh g⁻¹ at 5 C high power. It can be seen that F doping is a simple and crucial strategy to promote the Li ion diffusion and develop high performance layered cathode materials.