Enhanced cycling stability and rate performance of Li[Ni0.5Co0.2Mn0.3] O2 by CeO2 coating at high cut-off voltage

A rough coating structure of CeO2@Li[Ni0.5Co0.2Mn0.3]O-2 can be formed via a wet chemical method. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM) equipped with an energy dispersive spectroscope (EDS) are carried out to study the structures and morphologies, which all confirm the existence of CeO2 coating layer on the Li[Ni0.5Co0.2Mn0.3]O-2 surface. The 2 wt.% CeO2-coated Li[Ni0.5Co0.2Mn0.3]O-2 can deliver 97.4 mAh g(-1) at 10 C and 59.2 mAh g(-1) at 20 C after 100 cycles in the voltage range of 2.8-4.6 V, while the pristine Li[Ni0.5Co0.2Mn0.3]O-2 can deliver only 23.5 mAh g(-1) at 10 C and 9.0 mAh g(-1) at 20 C. The discharge capacities of CeO2-coated Li[Ni0.5Co0.2Mn0.3]O-2 samples at high discharge rates are much higher than those of the pristine Li[Ni0.5Co0.2Mn0.3]O-2. Meanwhile, the CeO2-coated Li[Ni0.5Co0.2Mn0.3]O-2 sample shows better rate performance at different rates. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements reveal that the improved electrochemical performance can be attributed to the reduced interfacial polarization and stabilized structure of Li[Ni0.5Co0.2Mn0.3]O-2 by CeO2 coating. Transmission electron microscope (TEM) is applied to analyze the role of CeO2 coating layer on the long cycling life. (C) 2015 Elsevier B.V. All rights reserved.