Abstract: MgF2-coated LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by impregnation method.The effects of amounts of MgF2 coating on the structure，morphology，and electrochemical properties of LiNi1/3Co1/3Mn1/3O2  were analyzed by XRD，SEM，charge-discharge tests，and electrochemical impedance spectra（EIS），respectively.Results showed that the uncrystalline MgF2 uniformly distributed on the surface of the LiNi1/3Co1/3Mn1/3O2  particles.The sample with 3%（amount-of-substance frac- tion，same below） MgF2 coating showed excellent electrochemical properties.Between 3.0~4.6 V，at 0.1C，the sample of above-mentioned exhibited a initial discharge capacity of 196.3 mA·h/g.At 1C，it maintained 95.7% of the initial capacity af- ter 50 cycles，and 93.3% capacity retention after 50 cycles at 55 ℃.

Key words: lithium ion batteries, cathode material, LiNi1/3Co1/3Mn1/3O2, MgF2, coating