Research Of Electrochemical Capacitance Based On Conducting Polymer Composites

As a new energy storage device, electrochemical supercapacitor has a promisingfuture for its high specific capacitance, high power density, long cycle life,environmental friendly and maintenance-free properties. Carbon-based materials,transition metal oxides and conducting polymers have been extensively studied aselectrode materials. It’s urgent to find a way to improve the electrochemicalperformance of supercapacitor electrode materials. In this paper, in order to improvethe specific capacitance, tailored carbon nanotubes were used to modify polyanilineand polypyrrole to get nanocomposites with special construction. The main studies areas follows:1. Oxidized tailored carbon nanotubes were prepared by tailoring multi-walledcarbon nanotubes through a modified Hummers method. In the presence of oxidizedtailored carbon nanotubes, polyaniline was synthesized by in-situ chemicalpolymerization to get polyaniline/oxidized tailored carbon nanotubes nanocomposites.After that, hydrazine monohydrate was used to reduce polyaniline/oxidized tailoredcarbon nanotubes to polyaniline/tailored carbon nanotubes. Compared to purepolyaniline, higher specific capacitance, wider potential window, better response ofcurrent, higher power density and longer cycle life were achieved for thepolyaniline/tailored carbon nanotubes. At a current density of0.5A g-1, the specificcapacitance of polyaniline/tailored carbon nanotubes is as high as373.5F g-1, and itsenergy density reachs up to51.9W h kg-1. Meanwhile, the specific capacitance ofpolyaniline/tailored carbon nanotubes retains61.7%after1000cycles. This is a greatchange for the stability of polyaniline.2. Hydrazine monohydrate was used to reduce oxidized tailored carbonnanotubes to tailored carbon nanotubes. Polypyrrole/tailored carbon nanotubescomposites were prepared via in situ polymerization of pyrrole monomers in thepresence of tailored carbon nanotubes. The study on the electrochemical performanceof composites with different mass ratios of polypyrrole to tailored carbon nanotubesshows that5:1is the optimal mass ratio for good electrochemical performance. Thespecific capacitance of composite with the optimal mass ratio is463.89F g-1and itsenergy density is34.75W h kg-1at0.5A g-1. The composite retains93%capacityafter1000cycles at a scan rate of50mV s1, which shows its super long cycle life. 3. The electrochemical property of asymmetric supercapacitor usingpolyaniline/tailored carbon nanotubes as positive electrode material and graphene asnegative electrode material was studied. The results indicate that the workingpotential window of asymmetric supercapacitor with good specific capacitance wasgreatly broadened to1.8V. From-0.9to0.9V, the specific capacitance of asymmetricelectrode is77.22F g-1and the energy density is as high as34.75W h kg-1at0.2A g-1.Meanwhile, the asymmetric supercapacitor has good cycle life. Its specificcapacitance retains69.8%after700cycles.