Powder Technology, Vol.381, 269-279, 2021
Improved electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2 cathode material with Li-conductive Li3PO4 coating and F- doping double modifications
Different contents of Li3PO4 coated Li-1.20[Mn0.54Ni0.13Co0.13]O1.95F0.05 were successfully synthesized by the combination of a sol-gel method with hydrothermal process. Rietveld refinement of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to observe and compare the microstructure and particle morphology of cathode after Li3PO4 coating and F- doping. The results revealed that the cathode active particle was surrounded by a continuous covering film with the thickness of 10-30 nm and F- element was distributed in the cathode uniformly. Besides the Li3PO4 coated and F- doped samples demonstrated the superior electrochemical properties when compared to the bare cathode, and the 2 wt% Li3PO4 coated Li-1.20[Mn0.54Ni0.13Co0.13]O1.95F0.05 delivered the optimal performance among the five cathode materials. By comparison, the 2 wt% Li3PO4 coated Li-1.20[Mn0.54Ni0.13Co0.13]O1.95F0.05 could express a large discharge capacity of 143.6mA h g(-1) at 5C rate, which was 51.0 mAhg(-1) higher than the bare one. Meanwhile, the 2 wt% Li3PO4 coated Li-1.20[Mn0.54Ni0.13Co0.13]O1.95F0.05 remained a capacity retention of 91.2% after 300 cycles at 45 degrees C. While the bare cathode delivered an initial discharge capacity of 199.5 mA h g(-1) at 45 degrees C, then dramatically attenuated to 160.8 mA h g(-1) at 300th cycle with the capacity retention of 80.6%. The electrochemical impedance spectroscopy (EIS) analysis further indicated the F- doping and Li3PO4 coating played a significant role on suppressing the increasing of charge transfer resistance, which greatly contributed to enhancing the rate capability and maintaining the cycling stability during cycling. (C) 2020 Elsevier B.V. All rights reserved.