Modification Of Pani And Its Application For Supercapacitor

With the rapid growth of population and rapid development of socio-economic, resources and energy are hard up day by day, the environment is deteriorating, and human beings will be more dependent on the new clean and renewable energy. Supercapacitor (also known as electrochemical capacitors) is a new type electrochemical energy storage device between the traditional dielectric capacitor and the battery. Compared with the conventional capacitor, supercapacitor has a larger capacity and higher energy density, its capacity can be Farah (F) or even thousands of Farah, but the capacity of the traditional capacitor is only microfarads (μF). Compared with the battery, supercapacitor has higher power density and longer cycle life, can realize high-current charging and discharging. Electrode material is one of the important factors in affecting the performance and cost of supercapacitor. Electrode material mainly includes carbon material, metal oxide and conducting polymer. Among the conductive polymer, polyaniline (PANI) is a focus due to raw material readily available, easy synthesis, low cost, good chemical stability and electrical conductivity, high pseudo-capacitance energy storage and other characteristics.In this dissertation, PANI, PANI-CNTs and PANI-Co3O4 composite were prepared by chemical in-situ polymerization using manganese dioxide (MnO2) as the oxidant. In addition, PANI nano-materils with different morphology have been synthesized successfully by interfacial polymerization with FeCl3 as oxidant and different concentrations HCOOH as dopant. The electrochemical performances of the PANI, PANI-CNTs and PANI-Co3O4 in acidic media have been studied. The main points of this dissertion are summarized as follows:(1) PANI was prepared by chemical in-situ polymerization at ambient temperature, using MnO2 or ammonium persulphate (APS) as the oxidant. The morphology and structure of PANI were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The electrochemical performances of the supercapacitor assembled with PANI were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge. These results show that the specific capacitance of the M-PANI electrode prepared by MnO2 was about 260 F/g at the charge-discharge current density of 5 mA/cm2. After 500 charge-discharge cycles the specific capacitance of the M-PANI electrode was about 188 F/g and its capacitance retention is 72.3%. For comparison, M-PANI has better cycle performance and higher capacity than N-PANI, which was prepared by APS.(2) PANI-CNTs (abbr.M-PC) were prepared by chemical in-situ polymerization at ambient temperature, using MnO2 as the oxidant. The morphology and structure of M-PC were characterized by SEM, FTIR and XRD. The electrochemical performances of the supercapacitor assembled with M-PC were investigated by CV and galvanostatic charge-discharge. These results of galvanostatic charge-discharge experiment show that the specific capacitance of the M-PC decreases as the charge-discharge current density increases. The specific capacitance of the M-PC electrode is about 355 F/g at the charge-discharge current density of 5 mA/cm2. After 500 charge-discharge cycles the specific capacitance of the M-PC electrode is about 306 F/g and its capacitance retention is 86.2%. For comparison, M-PC has better cycle performance and higher capacity than N-PC, which was prepared by APS.(3) Co3O4 nanocubes were synthesized by solvothermal method in water and n-butanol solution, which polyethylene glycol was used as dispersant. PANI-Co3O4 composite material was prepared by chemical in-situ polymerization at ambient temperature, using MnO2 as the oxidant. The morphology and structure of PANI-Co3O4 were characterized by SEM, FTIR, and XRD. The electrochemical performances of the supercapacitor assembled with PANI-Co3O4 were investigated by cyclic voltammetry, and galvanostatic charge-discharge. These results show that the specific capacitance of the composite material of PANI-oO3O4 electrode was about 287 F/g at the charge-discharge current density of 5 mA/cm2. After 500 charge-discharge cycles the specific capacitance of the PANI-Co3O4 electrode was about 271 F/g. and its capacitance retention is 94.4%. For comparison, PANI-Co3O4 has better cycle performance and higher capacity than M-PANI.(4) Formic acid-doped PANI nanomaterils with different morphology had been synthesized successfully by interfacial polymerization with FeCl3 as oxidant and HCOOH as dopant. The morphology and structure of PANI were characterized by SEM, FTIR and XRD. Symmetric redox supercapacitor was assembled with the PANI as active electrode material and 1 mol/L H2SO4 aqueous solution as electrolyte. The electrochemical performances of the supercapacitor were investigated by CV and galvanostatic charge-discharge. These results show that PANI with different morphology depends on the concentration of HCOOH. PANI with fiber morphology has better power characteristic and cycle performance in the application of supercapacitor, whose specific capacitance is about 292 F/g at the current density of 15 mA/cm2. After 500 charge-discharge cycles its specific capacitance was about 201 F/g and its capacitance retention is 68.8%.