Effect of graphene nanosheets content on the morphology and electrochemical performance of LiFePO4 particles in lithium ion batteries

Few layers graphene nanosheets (GS) are obtained by the reduction of graphite oxide (GO) via Lithium aluminium tetrahydride (LiAlH4) and Phosphorus tribromide (PBr3) as the deoxidizer. The LiFePO4/GS composite is prepared using a solution phase method followed by a calcination process with only 2 h at 600 °C. The effect of the GS content in LiFePO4/GS on the morphology and electrochemical performance of LiFePO4 particles is extensively investigated. Results show that the optimized amount of GS in LiFePO4/GS is 5%. The primary particle size of LiFePO4/5%GS is 100∼150 nm which are wrapped and connected homogeneously and loosely by GS with ∼4 layers. The GS can restrict the growth of LiFePO4 particle and construct an effective conductive network LiFePO4/GS composite, which all can enhance the conductivity of LiFePO4 particle. The LiFePO4/5%GS composite delivers a capacity of 155.4 mAhg−1 at 0.2 C, which is much higher than pure LiFePO4 (125.3 mAhg−1). Even at high rate of 5 C, a specific capacity of 124.3 mAhg−1 is achievable, with no obvious capacity fading after 100 cycles.