Preparation And Capacitive Properties Of Porous Polyaniline And Its Derivatives Electrode Materials

With the rapid development of the economy in the21st century, people have to meet aseries of severe problems, such as climate warming, available resources depleted and so on,which require the people to develop clean and renewable energy to meet the increasing needs.In this case, people invented the supercapacitor and found it is an important energy storageequipment. In an advanced supercapacitor device, an active electrode material with excellentelectrochemical performance is indispensable. Therefore, in this dissertation, we usedtemplate method to prepare conductive polymer electrode material with pesudocapacitiveproperty, i.e. polyaniline (PANI). At the same time, we used it as precursor to prepare theelectrode material with the electric double layer property after carbonization and activation,i.e. porous nitrogen-containing carbon material. On this basis, AC/MnO2composites wereprepared using the resulting nitrogen-containing carbon material as the substrate. Themorphology and microstructure of the samples were examined by X-ray diffraction (XRD),scanning electron microscopy (SEM), transition electron microscopy (TEM), Raman spectraand X-ray photoelectron spectroscopy (XPS). The effects of preparation process, theproportion of the raw materials, the composition and microstructure of the materials on theelectrochemical properties were investigated in detail. At last, the asymmetric supercapacitorswere assembled by the suitable electrode materials, and the electrochemical properties werecharacterized by cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemicalimpedance spectroscopy (EIS) and cycle life. The research content and results aresummarized as follows:In this dissertation, we prepared PANI with different morphology by template methoduseing spherical silica (SiO2) with the diameter of20nm as the template. The content of SiO2had an influence on the morphology of the prepared PANI. The obtained PANI wasnano-lamellar structure without SiO2. When the content of SiO2was less than2:1, theobtained PANI was nano-lamellar structure with porous. Once the content of SiO2was higherthan10:1, the obtained PANI was a three-dimensional crosslinked spherical shell structure.The results showed that the microstructure of the PANI had a significantly influence on itselectrochemical performance. Because there was high specific surface area and the space forthe electrolyte in the spherical shell (SiO2:PANI=10:1), which could shorten the distance of the ion transfer, the material had excellent electrochemical properties. At the same time, theshell structure could restrain the fracture of the PANI material in a certain extent due to therepeated doping/dedoping in the charge storage process, which was beneficial to theimprovement of the cycle stability.The porous PANI was an excellent electrode material and it was a good precursor of theporous carbon material, therefore, we used the prepared PANI samples as the precursors toprepare porous nitrogen-containing carbon materials through carbonization and activationprocesses. The results showed that the porous structure was well preserved after the processesof carbonization and activation, and there were also numerous micropores in the pore walls,which effectively increased the surface area of the materials. The flaky porousnitrogen-containing carbon material had excellent electrochemical performance with a highcapacity, an intriguing capacity retention rate in large charge/discharge current density andimpressive cycle stability.On this basis, we managed to synthesize AC/MnO2composite electrode materials bymicrowave method using prepared porous nitrogen-containing carbon materials（A-SiO2:PANI=2:1）as the substrate. These materials had the advantages of electric doublelayer capacitor and pseudocapacitor. The effect of the content of MnO2on the compositecapacity and capacitance retention was investigated in detail. During the optimization ofmaterials’ properties, we assembled a AC/84.69%-MnO2//A-SiO2:PANI=2:1asymmetricsupercapacitor which used AC/84.69%-MnO2and A-SiO2:PANI=2:1as positive and negativeelectrode materials, respectively. This asymmetric supercapacitor was measured in neutralelectrolyte solution (1mol·L-1Na2SO4) and the voltage could reach1.8V, so this asymmetricsupercapacitor had high energy density and high power density. After1500consecutive cycles,the capacitance retention of AC/84.69%-MnO2//A-SiO2:PANI=2:1asymmetric supercapacitorstill kept86.2%of its initial capacitance, indicating that this material owned a good cyclestability.