Construction Of Metal Oxide / Polyaniline / Carbon Ternary Composites And Its Application In Supercapacitor

Supercapacitors as a new type of energy storage device have both possess higher power density, energy density and a long repeat service life compared to traditional batteries and capacitors. Therefore, they have been widely used in the fields of electronic communication, electric vehicle and national defense science and technology to date. The main electrode materials of supercapacitors are composed of carbon-based materials, metal oxide and conducting polymer. In this work, new ternary composite of metal oxide, polyaniline and carbon materials were successfully synthesized by two-step method. The as-prepared nano composites were fully characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and ultraviolet visible spectra (UV-vis) to for further verifying the structure mode of new termary composite. The electrochemical capacitor performance of the composite electrodes were further investigated by cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS), and Galvanostatic charge-discharge (GCD). The main content includes the following several aspects:(1) In this paper, a new class of ternary coaxial hierarchical nanofibers was fabricated by two-step strategy. Conducting polymer polyaniline (PANI) was coated on the outer surface of multiwalled carbon nanotubes (MWCNT) to form PANI/MWCNT composite nanofibers. Then, manganese dioxide (MnO2) in-situ grows on PANI/MWCNT nanofibers to obtain ternary hierarchical nanofibers MnO2/PANI/MWCNT by in-situ chemical reaction between PANI/MWCNT and KMnO4 under mild conditions. The electrochemical performance of MnO2/PANI/MWCNT is investigated by using cyclic voltammetry (CV), galvanostatic charge-discharge measurement, and electrochemical impedance spectroscopy (EIS). The results showed that as-prepared ternary hierarchical nanofibers are all typical pseudo-capacitance capacitors. In comparison with MWCNT, PANI nanofibers, and PANI/MWCNT composite nanofibers, the specific capacitance of MnO2/PANI/MWCNT composites displays the highest capacitance of 348.5 F·g-1 at 1 A·g-1, and 88.2% retention of which can still be maintained after 2000 consecutive cycles. The electrochemical measurements demonstrate that PANI layer and nanoflaky MnO2 can increase the specific capacitance of MWCNT. More important, MnO2 in-situ growth on PANI layer can effectively retain the structure of composites and improve the long-term cycle stability. Thus, the as-prepared ternary coaxial hierarchical nanostructure of MnO2/PANI/MWCNT is an excellent electrode material for supercapacitor, which is helpful in developing new kinds of portable energy storage devices.(2) The sandwich structure of MnO2/PANI/RGO nanosheets was prepared by a two-step method. Conducting polymer polyaniline (PANI) is coated on reduced graphene oxide (RGO) to form PANI/RGO hybrid nanosheets. Then, nanoflaky manganese dioxide (MnO2) in-situ grows on PANI/RGO hybrid nanosheets to obtain ternary hierarchical nanosheets MnO2/PANI/RGO by simply mixing PANI/RGO and KMnO4 under mild condition. In comparison with RGO, PANI, and PANI/RGO hybrid nanosheets, MnO2/PANI/RGO composites display the highest specific capacitance of 1090.2 F·g-1 at 0.5 A·g-1. They maintain 86.1% initial capacitance after 2000 consecutive cycles at 1 A·g-1. Thus, the sandwich-like ternary hierarchical nanosheets of MnO2/PANI/RGO are excellent electrode material in supercapacitor with high specific capacitance and the long-term cycle stability.(3) The ternary composite Fe2O3/PANI/RGO nanosheets were prepared by a two-step method. Firstly, conducting polymer polyaniline (PANI) is coated on reduced graphene oxide (RGO) to form PANI/RGO hybrid nanosheets. Using K2FeO4 as iron source, the ternary composite of Fe2O3/PANI/RGO was obtained by stirring the mixture of K2FeO4 and PANI/RGO at a certain mass ratio under mild condition. The results obtained from electrochemical tests indicating that the ternary composites Fe2O3/PANI/RGO have the largest specific capacitance. Fe2O3/PANI/RGO composites display the specific capacitance of 520.5 F·g-1 at 1 A·g-1. The specific capacitances of Fe2O3/PANI/RGO maintain 93.21% initial capacitance after charging and discharging circulation for 2000 times at 1 A·g-1. Fe2O3/PANI/RGO has a potential application as a supercapacitor electrode material.