Effect of heat-treatment on Li2ZrO3-coated LiNi1/3Co1/3Mn1/3O2 and its high voltage electrochemical performance

The surface of LiNi1/3Co1/3Mn1/3O2 particles was modified by Li2ZrO3. Influences of heat-treatment were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The results show that Li2ZrO3 is well-crystallized and successfully coated on the surface of LiNi1/3Co1/3Mn1/3O2 after heated at 700 degrees C. Electrochemical tests demonstrate that the coated sample exhibits excellent cycling performances with 89.0% (25 degrees C) and 84.9% (55 degrees C) capacity retention at 1C after 100 cycles under the high cut-off voltage of 4.6 V, which are much higher than 82.7% (25 degrees C) and 62.5% (55 degrees C) for the pristine one. Meanwhile, the rate capability of the coated sample is dramatically improved even under the high current densities, and the capacities are delivered as high as 168.7 mAh g(-1) and 155.2 mAh g(-1) at 5C and 10C respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses reveal that coating with Li2ZrO3 could decrease electrode polarization and diminish the charge transfer impedance. Moreover, XRD and SEM characterizations of cycled electrodes evidence that the coating layer of Li2ZrO3 plays an important role in alleviating structural damage of LiNi1/3Co1/3Mn1/3O2 and protecting LiNi1/3Co1/3Mn1/3O2 from electrolyte during the charge/discharge processes. (C) 2015 Elsevier B.V. All rights reserved.