关键词: 锂离子电池, 正极材料, 富锂层状氧化物, YF3包覆, 倍率

Abstract: The Li(Li_0.22Ni_0.17Mn_0.61)O₂ was prepared with oxalic co-precipitation and coated with an YF₃ layer by a chemical deposition method. The as-prepared and YF₃-coated Li-rich materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results demonstrate that the as-prepared and YF₃-coated Li(Li_0.22Ni_0.17Mn_0.61)O₂ materials have a typical layered structure and are composed of sphere-like particles with a diameter of 100~200 nm. Galvanostatic charge-discharge tests show that the discharge capacity of the YF₃-coated Li(Li_0.22Ni_0.17Mn_0.61)O₂ is obviously improved. At the low current density of 60 mA.g^-1, the discharge capacity reaches 240 mAh.g^-1, and remains 220 mAh.g^-1 after 30 cycles. At the high current density of 1500 mA.g^-1, the discharge capacity still keeps 150 mAh.g^-1, showing an excellent high-rate capability. Electrochemical impedance spectra (EIS) reveal that the YF₃-coated Li(Li_0.22Ni_0.17Mn_0.61)O₂ shows lower charge-transfer resistance and diffusion impedance as compared with the as-prepared Li(Li_0.22Ni_0.17Mn_0.61)O₂.

Key words: Li-ion batteries, cathode material, Li-rich layered oxides, YF3-coated, high-rate capability