Long-life and high-rate LiVPO4F/C nanocrystals modified with graphene as cathode material for lithium-ion batteries

Graphene modified LiVPO4F/C nanocomposite has been firstly investigated as cathode material for lithium-ion batteries. The LiVPO4F/C nanocrystals embedded on reduced graphene oxide sheets are synthesized via a sol-gel method. The obtained sample of graphene modified LiVPO4F/C is studied comparatively with LiVPO4F/C by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra and various electrochemical tests. The results reveal that the modification of LiVPO4F/C nanocrystals with graphene can form an effective conducting network, which can greatly improve the electronic conductivity and lithium ion transport. Thus, the as-synthesized nanocomposite exhibits excellent high-rate capability and cycling stability. In the voltage range of 3.0-4.5 V, the graphene modified LiVPO4F/C delivers a reversible discharge capacity of 151.6 (nearly to its theoretical capability of 156 mAhg(-1)) and 147.8 mAhg(-1) at 0.1 and 0.5 C, respectively. It also achieves an improved cyclability with capacity retention ratio of 91.4% after 300 cycles at a higher rate of 10 C. Therefore, it is of great potential use as a cathode material in rechargeable lithium-ion batteries for hybrid-electric vehicles and electric vehicles. (C) 2014 Elsevier B.V. All rights reserved.