Excellent high rate capability and high voltage cycling stability of Y2O3-coated LiNi0.5Co0.2Mn0.3O2

Y2O3-coated LiNi0.5Co0.2Mn0.3O2 cathode materials show excellent cycling stability and higher rate capability than the bare LiNi0.5Co0.2Mn0.3O2 at higher cut-off voltages of 4.6 V and 4.8 V. The thickness of Y2O3-coating layer is about 5-15 nm, and the original structure of the LiNi0.5Co0.2Mn0.3O2 isn't influenced by Y2O3 coating layer. The 2 wt% Y2O3-coated LiNi0.5Co0.2Mn0.3O2 can deliver 114.5 mAh g(-1) (76.3% of its initial discharge capacity) after 100 cycles at 10C (1800 mA g(-1)) between 2.8 and 4.6 V, while the bare LiNi0.5Co0.2Mn0.3O2 delivers only 11.5 mAh g(-1) with 83% capacity retention left. When the high cut-off voltage increases to 4.8 V, the capacity retention of 2 wt% Y2O3-coated sample is 49.0%, which is much higher than that of the bare sample (5.9%) at 10C after 100 cycles. The rate capabilities of 2 wt% Y2O3-coated LiNi0.5Co0.2Mn0.3O2 are also improved significantly, especially at high rates (10C and 20C). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are carried out to confirm the existence of Y2O3 layer on the LiNi0.5Co0.2Mn0.3O2 surface. Electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM) are applied to analyze the role of Y2O3-coating layer on the long cycling life and high rate capability. (C) 2014 Elsevier B.V. All rights reserved.