Synthesis And Electrochemical Performance Of Hydrothermal/Solvothermal Reduced Graphene Oxide And Itsanthraquinone Composite

With the rapid development of renewable energy storage and electric vehicles, the betterperformance of lithium-ion batteries is required. With its unique structure and excellentproperties, the graphene oxide (GO) based carbon material has become one of the mostpromising new clean cathode materials for energy storage battery. It is of great scientificsignificance to study GO based carbon material and its composites.In this thesis, GO, reduced graphene oxide (RGO) and reduced grapheneoxide/anthraquinone composite (RGO/AQ) were successfully prepared. Subsequently, theirelectrochemical properties were studied and then their charge/discharge mechanism wasinvestigated and discussed. The main results are summarized as follows:(1) GO was synthesis by Hummers method. The composition, thermostability,morphology and electrochemical properties of the as-prepared GO were characterized usingX-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermogravimetry(TG), scanning electron microscope (SEM), galvanostatic charge-discharge cycling techniqueand cyclic voltammetry (CV). The results show that, the as-prepared GO possesses a lot ofoxygen-containing groups, but its thermal stability is not good. Both the fist charge anddischarge curves had a platform，and at25mA g-1the fist discharge and charge capacitieswere282and314mAh g-1, respectively. However, the cycling performance was not verysatisfactory, and the discharge capacity was just about126mAh g-1after ten cycles.(2) Two kinds of RGO were successfully prepared based on the aforementioned GO byhydrothermal and mixed-solvothermal methods, respectively. FTIR, TG, galvanostaticcharge-discharge cycling technique and CV were used to characterize the hydrothermalreduced GO (HRGO) and the mixed-solvothermal reduced GO (MRGO). The reductiondegree of HRGO samples increased with the increase of reduction temperature, but theirelectrochemical properties did not show much difference to each other. At25mA g-1the firstdischarge capacities of HRGO samples were just about20mAh g-1, but gradually increased toa stable value of122.6(HRGO-140),113.9(HRGO-160) and115(HRGO-180) mAh g-1withthe increase of cycle numbers, respectively. The reduction degree of MRGO was higher thanthat of HRGO prepared at the same temperature. At25and100mA g-1, the capacities ofMRGO-160were165and123mAh g-1, respectively. However, the high rate performances ofHRGO and MRGO were not good enough. All of the CV curves of GO, HRGO and MRGOshowed a pair of broadening redox peaks. We speculate that the redox reaction between lithium ions and epoxide/carbonyl/carboxyl groups are reversible, while that of hydroxyl isirreversible. In addition, double layer capacitance is one of the main energy storagemechanisms.(3) MRGO/AQ composite was fabricated on the basis of the mixed-solvothermal methodand was further characterized by FTIR, galvanostatic charge-discharge cycling technique andCV. The results show that, AQ and MRGO can be firmly bonded together by π-π stackinginteraction to form MRGO/AQ composite. The content ofAQ is low.