Study of LiFePO4 cathode modified by graphene sheets for high-performance lithium ion batteries

Here three kinds of graphene preparation strategies, namely, chemical vapor deposition (CVD), Wurtz-type reductive coupling reaction and chemical exfoliation, respectively, have been developed to synthesize large-scale high-quality graphene for improving the electrochemical properties of LiFePO4 (LFP) cathodes. The flexible graphene sheets as effective conduction channels possess larger surface area to load more LFP nanoparticles (NPs). The amount of the 5 wt% graphene additive greatly reduces the contact resistance between LFP NPs, and dramatically enhances the electrical conductivity and electrochemical performances of the cathodes. Particularly, when the large-size, defect-free and highly crystalline CVD graphene sheets are used to modify LFP cathodes, the capacities reach up to 132 mA h g−1 and 80 mA h g−1 at 1C and 20C discharge rates, and the corresponding capacity decay rates are 3.1% and 6.5% after 100 cycles, respectively. The excellent performance shows that the graphene-modified LFP is promising cathodes for high rate lithium ion batteries.

► Three kinds of graphene preparation strategies have been synthesized large-scale graphene.
► The graphene electrical conductivities are significantly superior to carbon black additive.
► The flexible graphene sheets possess larger surface area to load more LiFePO4 nanoparticles.
► Graphene additive dramatically enhances the electrochemical performances of the cathodes.