The Preparation And Performance Of Graphene/LiFepO₄Composite Cathode Materials

Abstract:As graphene has excellent electric conductivity, high specific surface area, and high crystallinity, in this paper, it was applied to preparing the precursor of LiFePO4cathode materials to improve its electrochemical performance.The flocculent FePO4·2H2O precursor were prepared by homogeneous precipitation method with Fe(NO3)3·9H2O, NaH2PO4·2H2O and HC1, and the round graphene/FePO4·2H2O composite precursor were prepared by adding in graphene oxide in the same way. Results showed that, graphene oxide had been mainly reduced to graphene. Then concentrated the round precursor by filtration, and dropped raw materials in it to make the round precursor regrowth. The final precursor was spherical. D50of the above precursors were13.76,2.817,4.220μm, and the tap density were0.70,1.10,1.31g/cm3, respectively. This showed that the partical size would be decreased by graphene oxide, and the shape would be more regular by regrowth. And the tap density would be improved by both of them.The first discharge capacity of LiFePO4and graphene/LiFePO4before regrowth was149.63mAh/g and160.13mAh/g at0.1C rate, it indicated that the conductivity could be obviously improved by graphene oxide, which was not suitable for graphene/LiFePO4after regrowth. After3C rate discharging, the electric capacity retention of LiFePO4and graphene/LiFePO4before and after regrowth were88.74%,103.03%, and109.16%, respectively. This had important application value for the preparation of high ratio cathode materials.By means of adding graphene oxide in both bottom and dropped liquids, the round precursor were coated entirely by graphene. And the first discharge capacity of graphene/LiFePO4was163.59mAh/g at0.1C rate, this might be due to the conductive network formed by graphene.