Mo-doping for improving the ZrF4 coated-Li[Li0.20Mn0.54Ni0.13Co0.13]O-2 as high performance cathode materials in lithium-ion batteries

摘要

The different amounts of Mo6+ and the 2 wt% ZrF4 coating layer have been co-modified the Li[Li0.20Mn0.54Ni0.13Co0.13]O-2 cathode material via using the carbonate co-precipitation method and wet coating process. And the influences of Mo6+ doping and ZrF4 surface coating on the cathode crystal structure, morphology and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), Transmission Electron Microscope (TEM) and galvanostatic charge-discharge tests. The 2 wt% ZrF4 coated-Li[Li0.20Mn0.52Ni0.13Co0.13Mo0.02]O-2 demonstrated the lower cation mixing and a thickness of 15-35 nm film coated on the surface of cathode particles. Compared with the pristine cathode, the samples after ZrF4 coating and Mo6+ doping exhibited the less irreversible capacity loss, better high rate capability and superior cyclic performance owing to the lower impedance for Li+ migration across the SEI film and the faster Li+ migration speed in the cathode bulk. Among all samples, the 2 wt% ZrF4 coated-Li[Li0.20Mn0.52Ni0.13Co0.13Mo0.02]O-2 showed the optimum electrochemical properties, with a high capacity retention of 88.7% after 100 cycles at 55 degrees C, much higher than that (82.9%) of the pristine cathode. Besides, when the electric current increased to 5C high rate, the pristine Li[Li0.20Mn0.54Ni0.13Co0.13]O-2 delivered a discharge capacity of 21.9 mAh g(-1) lower than that of 2 wt% ZrF4 coated-Li[Li0.20Mn0.52Ni0.13Co0.13Mo0.02]O-2. (C) 2018 Elsevier B.V. All rights reserved.