Preparation And Electrochemical Properties Of Composite Electrode Materials For Supercapacitors

The supercapacitor called electrochemical capacitor is a new type storage equipment between electrostatic capacitors and batteries, which has high power density, high energy density, short charge and discharge time, long cycle life, broad operating temperature range, safety, friendly to environment and wide potential application. In this paper, ternary composite materials including carbon material, metal oxide and conducting polymer were fabricated for electrode material. The ternary composites may have good electrochemical properties due to the synergistic effects of each component in the composite. The main results are as follows:(1) Novel carbazole-based polymers, poly[(2,5-di-phenyl-1,3,4-oxadiazole)-4-diylvinylene-alt-3,6-(N-butyl-carbazolenevinylene)] (POXA-CAR), poly[N-butyl-3,6-carbazolevinylene-alt-(2,5-dioctyloxy)-p-phenylenevinylene] (PPH-CAR) were synthesized via Wittig reaction. The structure and property of the polymers were characterized by Fourier transform infrared (FTIR),1H nuclear magnetic resonance (’HNMR), Thermal gravimetric analysis (TGA), UV-vis and electrochemical analysis. The results showed that these polymers had good thermal stability. CV test indicated the polymers possess good hole and electron transporting ability.(2) A simple two-step method was developed to fabricate GO/MnO2 /POXA-CAR ternary nanocomposite. The structure and morphology of the composite were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM) and the electrochemical performance was tested by cycle voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectrometry (EIS). Electrochemical test showed the specific capacitance of GO/MnO2/POXA-CAR was 310 Fg-1, which was 150% increase over GO/MnO2 (125 Fg-1) at a current density of 2.5 mA/cm2. The specific capacitance of GO/MnO2/POXA-CAR after 1000 cycles did not decrease at the current density of 5 mA/cm2 during the cycling test indicting good cycling stability.(3) A simple two-step method was used to fabricate RGO/MnO2/PPH-CAR ternary nanocomposite. The structure and morphology of the composite were characterized by XRD, XPS, FE-SEM, TEM and the electrochemical performance was tested by CV, galvanostatic charge-discharge and EIS. When the content of PPH-CAR was 5%, the ternary composite had better electrochemical behavior. Electrochemical test showed the specific capacitance of RGO/MnO2/PPH-CAR was 175 Fg’1, which was 46% increase over RGO/MnO2 at a current density of 2.5 mA/cm2. The composite electrode maintained more than 90% capacitance after 1000 cycles demonstrating very cycle stability.