Preparation Of MnO_x/C Composites By Electrochemical Methods And Its Capacitance Performance Research

Supercapacitor is widely used in the electric automobile, aviation, aerospace, communication, consumer electronics etc. due to its large power density, high energy density, long cycle life, fast charge-discharge and environmental friendness. The manganese oxide has many advantages, such as natural abundant, low cost and high specific capacitance, but the practical application in supercapacitors has been limited by its low electronic conductivity and poor cycling performance. Whereas, the carbon-based material has benefits of high specific surface area and high electronic conductivity. Therefore, it has become the focus that how to combine with MnOx and carbon. Herein, we reported an easy and fast approach to synthesis MnOx/C composites by electrochemical method and explored its electrochemical performance. The main research contents as follow:(1) Graphene/Mn3O4 composite electrode with 3D porous stainless steel substrate was prepared by electrophoretic deposition in the electrolyte contain liquid phase exfoliated graphene with manganous nitrate. The morphology, structure and content of the electrode were characterized by SEM, TEM, Raman, XRD and TG. The results showed that graphene sheets were covered by Mn3O4 with loading of 80.8wt% in the graphene/Mn3O4 (GM) composites electrode. A relatively high specific capacitance of 357.2 F/g at a scan rate of 5mV/s is obtained by means of cyclic voltammetry. And the galvanostatic charge-discharge test show that the composite display the specific capacitance as high as 281.6 F/g at a current density of 1A/g, which is almost 2.6 times higher than that of pure Mn3O4. The cycling measurements showed that its capacity retention is 99.4% after 1000 cycles at a current density of 1A/g.(2) Graphite crystallite/MnO2 composite was prepared by electrochemical method with the liquid phase NMP contain manganous nitrate as electrolyte.The morphology and structure of the composites with various voltages and different concentration of manganous nitrate was characterized by TEM, Raman, EDX and FTIR. The composite prepared with optimized conditions has good reversibility and excellent electrochemical performance. Cyclic voltammetry revealed that the composite has a specific capacitance of 206.8F/g at a scan rate of 5mV/s. Galvanostatic charge-discharge discharge showed that the composite has a specific capacitance of 78.4F/g at a current density of 1A/g.