Enhanced electrochemical performance of graphene modified LiFePO$_4$ as a cathode material for lithium ion batteries

We synthesized LiFePO$_4$/graphene nano-composites using a sol-gel method by adding water dispersed graphene oxide to the LiFePO$_4$ precursors during the synthesis. The graphene oxide was subsequently reduced to graphene by annealing the composite which was confirmed by Raman spectroscopy and X-ray Photoelectron spectroscopy. The electronic conductivity of the composite was found to be six orders of magnitude higher than that of pure LiFePO$_4$ Scanning Electron microscopy and Transmission electron microscopy images show LiFePO$_4$ particles are wrapped in uniformly distributed graphene sheets throughout the material forming a three dimensional conducting network. At low currents, (C/3), the capacity of the composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene wrapped LiFePO$_4$ shows a dramatically improved rate capability up to 27C, and excellent charge-discharge cycle stability over 500 stable cycles as compared to the pure LiFePO$_4$.