SnO2-coated LiCoO2 cathode material for high-voltage applications in lithium-ion batteries

In order to improve the electrochemical performances of LiCoO2 cathode in high voltage cycling range (3.0-4.5 V), SnO2 thin film has been deposited on the surface of electrode material by an electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD). Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns confirm the presence of SnO2 thin layers on the tape-casted electrode composed of nanocrystalline structure with agglomerated grain size ranging from 30 to 40 nm. The electrochemical tests show that the SnO2 coating layer significantly enhances the cycling performance of LiCoO2 cathode material. While the bare LiCoO2 cell does not work after 370 cycles, the surface-modified electrode exhibits the extended performance over 500 cycles with excellent capacity retention. In addition, it is also observed that 5'102 coating material is able to amplify the initial discharge capacity of bare LiCoO2 from 172 tol 83 mAhg-1 at 1 degrees degrees C and effectively increase the coulombic efficiency of pristine LiCoO2 cathode. We conclude that these electrochemical improvements are strongly due to the suppression of charge transfer resistance and prevention of side reactions during the charge/discharge process via surface coating of electrodes. (C) 2014 Elsevier B.V. All rights reserved.