Enhanced electrochemical performance in LiFePO4/graphene nanocomposite cathode material for lithium ion batteries

We synthesized LiFePO$_{4}$/graphene nano-composite employing a sol-gel method, where graphene oxide solution was added to the LiFePO$_{4}$ precursors during the synthesis. Electrical measurement reveals that the addition of 10{\%} graphene (by weight) to LiFePO$_{4}$ increases its conductivity by 5 orders of magnitude. SEM images of the composite show that the material consists of LiFePO$_{4}$ nanoparticles (with a mean particle size $\sim $ 50 nm) homogeneously mixed with graphene sheets; the latter provides a three-dimensional conducting network for Li+ ion and electron transport. A large specific capacity of 170 mAh/g was observed at a discharge rate of C/2. To further increase the conductivity and inhibit particle size growth of LiFePO$_{4}$ (thus to increase the rate capacity), we coated the nanoparticles with a thin carbon layer by adding 0.25M lauric acid as precursor in addition to graphene oxide during the synthesis. The respective roles of graphene and lauric-acid-induced carbon coating in the specific capacity and charge-discharge rate of the LiFePO$_{4}$ cathode material will be discussed.