Preparation and characterization of conducting polyaniline-coated LiVPO4F nanocrystals with core-shell structure and its application in lithium-ion batteries

In this paper, the electrochemical performance of the pure LiVPO4F electrode is significantly improved by coating it with the conducting polyaniline via sol-gel method followed by a self-assembly process. X-ray diffraction (XRD) results indicate that the as-prepared sample crystallized in a triclinic LiVPO4F phase. Scanning and transmission electron microscopy images show that the particle size of the composite is about hundreds of nanometer and the conducting layer of polyaniline is uniformly coated on the surface of LiVPO4F particles. Electrochemical tests reveal that the polyaniline-coated LiVPO4F composite exhibits superior capacity and cycle stability, delivering an initial discharge capacity of 149.3 mAh g(-1) at 0.1 degrees C in the voltage range of 3.0-4.5 V. Even at high current rates, it can still present discharge capacities of 146.7, 140.1, 131.9 and 121.5 mAh g(-1) at 0.2, 1, 2 and 5 degrees C, respectively. The superior electrochemical performance of the electrode could be attributed to the uniform conducting polymer layer, which improves the electronic conductivity and Li-ions diffusion of LiVPO4F. Therefore, it can be drawn a conclusion that the remarkable electrochemical performance of the polyaniline-coated LiVPO4F makes this 4 V-class electrode a promising alternative for next-generation lithium-ion batteries. (C) 2015 Elsevier Ltd. All rights reserved.