Preparation And Electrochemical Performance Of Electrode Material For Supercapacitors

Supercapacitors play an increasing important role in the aspect of modern energy storage due to their long cycle life, good stability, high capacitance and power density. From a materials science point of view, the storage capacity of supercapacitor is depend on the electrode materials. Conductive polymers (polypyrrole (PPy), polyaniline (PANI)) possess the characteristics of specific doping/dedoping property, good electrical conductivity, simple synthesis, and low cost. However, the poor electrochemical utilization and rapid capacity decay severely limit their application and development.The combination of conductive polymers and graphene oxide (GO) or graphene (GN) which as nano-filler. The performance of the electrode active material may improve significantly owing to the synergistic effect of the two components. In addition, the preparation of conductive polymers with special morphology and structure is also an approach to improve the overall performance of materials. Porous carbon materials with high specific surface area have the characteristics of simple synthesis, low cost, good cycle stability. The modification of carbon material can improve its electrochemical properties. The electrode materials of carbon materials have been paid much attention recently due to good prospects for development.The main content of this paper is introduced as follows:1. The layered PPy-GO-sodium dodecylbenzene sulfonate (PPyGO-SDBS) nanocomposites were facilely fabricated via an in situ emulsion polymerization method with the assistance of SDBS as dopant and stabilizer. SEM, TEM, FTIR, XRD and electrochemical performance were employed to analyze the structure and the characteristics of the composites. The results showed that the SDBS played an important role in improving the electrochemical performance of the PPyGO-SDBS, by dispersing the PPy between the layers of the GO. The obtained PPyGO-SDBS exhibited remarkable performance as an electrode material for supercapacitors mainly due to the synergistic effect between the PPy and the GO and the dispersion of the PPy induced by the SDBS.2. PPy was synthesized on GN sheets which was reduced from graphene oxide by microwave irradiation in N-methyl-2-pyrrolidinone (NMP) and dispersed very well in β-naphthalene sulfonic acid solution. Homogeneous PPy/GN (PGN) composites had been successfully prepared via an in situ emulsion polymerization method and showed better electrochemical performance including high specific capacitance, rate characteristic and cycling stability compared with PPy/GO (PGO) composites. The NMP molecules entered into GN which was helpful for PPy deposition on the GN sheets evenly. The good electrochemical performance of PGN composites is mainly attributed to its uniform structure, the N doping, and the synergistic effects between the two components.3. Novel hollow tetragonal starlike PANI (HTS-PANI) doped with citric acid has been successfully synthesized by hydrothermal method for the first time. SEM, TEM, UV-vis, FT-IR, and XRD were employed to analysis the morphology and structure of the obtained PANI. The results show that the HTS-PANI is highly crystallized, accompanied with good thermal stability. According to the galvanostatic charge-discharge analysis, the specific capacitance of the sample is up to 460 F/g at a current density of 0.2 A/g in 1 M KC1 electrolyte, and retains about 58% after 1000 charge-discharge processes at a current density of 5 A/g.4. Hollow melamine resin-based carbon spheres (HMCS) clad in GN sheets brought an unique three-dimensional (3D) network architecture after the pyrolysis of the melamine-formaldehyde (MF) resin spheres/GO composite under argon. Polyvinyl alcohol plays an important role in controlling the size and the structure of the MF resin spheres and can induce the formation of hollow nitrogen-containing carbon spheres to produce the HMCS/GN composite after anneal treatment. The diameter of the HMCS can be tuned by changing the carbonization temperature. The HMCS/GN annealed at 600℃ exhibits excellent electrochemical performance making it an ideal electrode material for supercapacitors. High specific capacitance of 720 F/g at a current density of 0.2 A/g,560 F/g at 5 A/g and 420 F/g at 20 A/g can be achieved which indicates ideal rate capability. The specific capacitance retains 80.3% after 10000 charge-discharge processes at a current density of 20 A/g. The excellent electrochemical performance of the HMCS/GN is ascribed to its unique 3D network architecture constructed by the hollow carbon spheres intercalated in GN sheets and the high nitrogen content of the composite.