The cobalt cation and fluorine anion co-doped cathode materials of Li_1+δNi_1-xCo_xO_2-yF_y (0≤δ≤0.2, 0≤x≤0.5, 0≤y≤0.1) were synthesized by solid state reaction method at 650～750℃ under air atmosphere, and characterized by XRD, SEM, TEM, BET, laser particle-size distribution measurement and electrochemical performance testing. The effects of different nickel sources on the properties of as-synthesized cathode materials were investigated. The results demonstrated that the materials of Li_1+δNi_1-xCo_xO_2-yF_y have complete layered structure, uniform surface morphology and better particle-size distribution as well as excellent electrochemical performances. At 20～25℃, 0.15～0.25 mA charge and discharge current, 4.25～2.70 V cut-off voltage, 0.2～0.5C charge and discharge rate and 0.2～0.5 mA/cm² current density, the cathode material of LiNi_0.8Co_0.2O_1.95F_0.05 has higher initial charge and discharge capacity and better cyclic properties, which can be mainly attributed to the doping of the higher electronegative fluorine which improves the structural stability and the synergistic reaction of cobalt and fluorine ions co-doped in the cathode materials. Under the above conditions, the initial charge and discharge capacity of LiNi_0.8-Co_0.2O_1.95F_0.05 are 165.70 mAh/g and 146.10 mAh/g, respectively. After 50 cycles, it keeps more than 140 mAh/g of discharge capacity and displays potential application.

Key words: lithium-ion rechargeable battery, cathode material, Li_1+δNi_1-xCo_xO_2-yF_y, synthesis, LiF, co-doping