Study On Preparation Of Graphene And Modified Natural Graphite Anode Materials

In this paper, based on investigations of a large amount of literature and followed the steps with international researches in the field. The influence of different synthesis conditions of graphene-coated natural graphite was surveyed and contrasted by a series of experiments systematically. The electrochemical performance of the products was evaluated by galvanostatic charge/discharge technique, cyclic voltammograms (CV), and electrochemical impedance spectroscopy (EIS), etc. The research focuses on three aspects and conclusions are as follows:Natural graphite as the main raw materials, in the experimental process the graphene oxide and natural graphite precursor material will be mixed, after using mechanical milling and ultrasonic dispersed graphene oxide, by high temperature carbon thermal reduction modification in prepared a series of different graphene content of the graphene/natural graphite from the composite anode material.And then use X-ray diffraction (XRD), and scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), constant current charge discharge and cyclic voltammetry test method graphene/natural graphite composite materials structure, morphology and electrochemical performance of influence were studied systema-tically.Graphene oxide coated composite material graphene oxide/natural respectively at 600℃,700℃,750℃,800℃,850℃ different temperature of carbothermal reduction graphene/natural graphite composite and at 0.1C current density,0.005-3V voltage range of constant current charge discharge tested.The results show that the composite material has higher specific capacity and better cycle performance than the graphite graphene/natural obtained after the temperature reduction at 800℃. The first discharge and charge specific capacity can reach 413mAh/g and 410mAh/g higher than the reduction of the ratio of the capacity at other temperatures,the coulombic efficiency of 99.5%.After 30 cycles. Its discharge specific capacity can still reach 404 mAh/g,The retention rate of capacity is 98.3%. The physical examination results of SEM and XRD show that the synthesized graphite graphene/natural composites have the standard core shell structure. The CV and EIS tests showed that the polarization of the composites was small, the diffusion rate and conductivity of Li+ were increased, and the specific capacity and cycling performance were enhanced.Composite materials obtained from the different temperature reduction.The effect of different content (0,1%,2%,3%,4%) of graphene on the properties of graphene/natural composites was studied,at the current density of 0.1C,0.005-3V voltage range of constant current charge discharge tested. The study found that the graphene/natural material with 3% graphene content has higher specific capacity and better cycle performance, It’s initial discharge and charge specific capacity were 412mAh/g and 407mAh/g higher than 364mAh/g and 349mAh/g of natural graphite, It’s Kulun efficiency reached 98.8%. After 30 cycles, the discharge specific capacity can still reach 396mAh/g, and the retention rate of the capacity is up to 99.4%.Graphene coating can improve the capacity and cycle performance of graphite materials. And compared with the pure natural graphite, graphene coated natural graphite materials show excellent rate capability in high rate condition, that graphene coated layer is conducive to enhance the natural graphite nanosheets layer between the longitudinal electron conductivity.