Preparation And Properties Studies Of Manganese Oxide-Based Electrode Materials For Supercapacitor

Over the past few years, supercapacitors have attracted a great deal of attention due to their advantages such as high power density, environmental friendliness and long service life, and shown a bright, promising prospect in areas like new electronic and renewable energy system, which were thought to be one of the most promissing elctrochemical energy storage devices. The composite of carbon-based materials and transition matel oxides has been the research hotspot for several years because of their abundance, low cost, environmental friendliness and good electrochemical performance.Among them, graphene and manganese oxide composite material was most studied by researchers worldwide. However, the preparation of graphene materials was the crux of the research, because the graphene tend to agglomerate during the process of reduction which makes the obtained materials lost the excellent properties of graphene. In this dissertation, we take certain measures to control the agglomeration of graphene, and prepare the composite of graphene-based materials and manganese oxide, then test the electrochemical properties of composite materials.The graphene-carbon black composite was prepared by the addition of carbon black before the reduction of graphene oxide. Comparing SEM and Raman spectra of materials prepared by adding carbon black before the reduction of graphene oxide with those of materials prepared by adding carbon black after the reduction of graphene oxide, it was found out that the addition of carbon black must be carried out before the reduction of graphene oxide, or it would not able to inhibit the agglomeration of graphene. And the best ratio of graphite oxide and carbon black is 10: 1.Among the electrode materials prepared by the redox reaction between KMnO₄ and graphene-carbon black composites, the maximum specific capacitance at current density of 1 A/g and 0.5 F/g was 118 F/g and 146.7 F/g, respectively. Impurities were generated at 120? and 150?. With the increase of KMnO₄ concentration, Mn₃O₄ would gradually agglomerate, which would lead to the decrease of the specific capacitance.Among the electrode materials prepared by the redox reaction between KMnO₄ and ethylene glycol, the maximum specific capacitance at current density of 1 A/g and0.5 F/g was 62.1 F/g and 77.9 F/g, respectively. Pure Mn₃O₄ could not bring into play its excellent pseudocapacitance due to its poor electrical conductivity. The graphene-carbon black composite on one hand improve electrical conductivity of Mn₃O₄, on the other hand refine Mn₃O₄ structure, whitch increase the contact between electrolyte and Mn₃O₄, leading to an increase in the specific capacitance.Comparing the two method, it was found out that the in-situ one-pot hydrothermal method was a much more better and pactical method.