Improve the structure and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathode material by nano-Al2O3 ultrasonic coating

The LiNi0.6Co0.2Mn0.2O2 powder was coated with nano-Al2O3 particles via ultrasonic coating, and its electrochemical performances were improved greatly. The X-ray diffraction, scanning electron microscopy, transmission electron microscope and energy dispersive spectroscopy were employed to research the structure variation, surface appearance and coating status. The results show that the nano-Al2O3 particles are successfully coated and the thickness of coating layer is about 20-25 nm. The XRD test results indicate that appropriate amount of Al2O3 coated is beneficial to form a better layered structure with smaller cation disorder. The charge-discharge results show that LiNi0.6Co0.2Mn0.2O2 coated with Al2O3 of 1.0 wt.% has initial discharge capacity of 197.1 mA h g (1), initial coulombic efficiency of 91.2% at 0.2 C over 2.8-4.5 V and capacity retention of 91.0% much more than the pristine one of 82.9.0% after 30 cycles at 1 C. Especially, the rate capability of 1.0 wt.% Al2O3-coated sample is improved evidently, it shows a high discharge capacity of 153.5 mA h g (1) after 5 cycles under a 10 C rate, whereas the pristine one is only 126.3 mA h g (1) under the same conditions. The electrochemical impedance spectroscopy tests results also show that the impedance of LiNi0.6Co0.2Mn0.2O2 is significantly reduced by Al2O3 coating during the cycling. (C) 2014 Elsevier B. V. All rights reserved.