Investigations On Graphene/polyaniline Composites And The Electrochemical Performance For Supercapacitors

As a kind of new green energy storage devices, the supercapacitor due to its advantages of high power density, fast charge and discharge and the long cycle life, has become the most widely studied energy storage devices. The performance of supercapacitor mainly depends on the electrode materials. Graphene, owning to its good thermal stability, conductivity and high specific surface area, has become one of the most promising candidate materials for supercapacitor. Polyaniline, benefits from its advantages of low cost, easy synthesis, high conductivity, is considered to be one of the most promising electrode materials. Due to its irreversible agglomeration, the capacitor performance of graphene is not ideal. This paper focuses on the chemical doping, the preparation of composite and the material structure design to overcome this disadvantage. The main research contents are as follows:In this part, graphene oxide(GO) was synthesized from naturalflake graphite by modified Hummers method. Graphene nanosheets(GNs) were exfoliated by microwave irradiation assisted. N-doping graphene(N-GNs) was prepared by high temperature sintering the precursor, which is synthesis by hydrothermal method. The N2 adsorption results showed that the specific surface area and pore volume of N-GNs were 280.78 m2/g and 1.25 cm2/g, which are much larger than that of GNs(83.70 m2/g and 0.35 cm2/g). The electrochemical results showed that the N-GNs exhibited better electrochemical property with the specific capacity of 169 F g-1 at the current density of 0.1 A/g.Due to its good dispersion and hydrophilic resulted from a large number of functional groups, two-dimensional GO was elected as flexible base material. Polyaniline(PANI) was in-situ polymerized on the surface of GO to form PANI encapsulating GO composite. The microstructure analysis indicates that the PANI nanoparticles homogeneously deposits on the surface of GO to form a film-like structure. The morphology of PANI particles and its dispersion have been effectively improved. The GO/PANI exhibited a specific capacity of 162 F g-1 at the current density of 0.1 A/g. After 2000 cycles, the composite remains capacity of 142 F g-1(capacity retention ratio up to 87.9 %).Papillae-like PANI nanocones arrays oriented on GNs were synthesized by in situ polymerization with the assistant of ethanol as a dispersant. The microstructure analysis indicates that papillae-like PANI nanocones arrays are oriented uniformly on the flexible two-dimensional GNs. Electrochemical tests showed that GNs/PANI exhibited better electrochemical performances than the bare individual components. GNs/PANI electrode delivered not only a remarkable specific capacitance of 372 F g-1 at a current density of 0.1 A/g but also an excellent cycle life along with ~86.0 % capacitance retention over 3,000 cycles.