Synthesis Of Conductive Polymer Composites And Their Application In Electrode Materials Of Supercapacitor

Supercapacitor is a new type of energy storage devices, which combines theadvantages of both dielectric capacitors that can deliver high power within a verysmall period and conventional rechargeable batteries that have high energy densities.Therefore, supercapacitors have become one of new chemical power sources. Now,the investigations about supercapacitors are focused on the electrode materials, whichinclude carbon-based materials with electric double layer properties andpseudo-capacitive materials （e.g., transition metal oxides and conductive polymers）.Among them, the conductive polymer with unique structure and excellent physicaland chemical properties has attracted wide attention, but its weakness is poorcirculation performance. For this reason, conductive polymers often combine withcarbon-based materials to prepare composite electrode materials which achieve theenhanced capacitive performance for supercapacitors due to the positive synergisticeffect between different materials. In this work, we have prepared conductive polymercomposites which can be used as electrode materials of supercapacitor, characterizedstructure and morphology of the resultant composites and estimated theirelectrochemical performance in detail. The main content is as follows:1. Polypyrrole/graphite oxide composites （PPy/GO） with different mass ratioswere prepared by in situ polymerization and then reduced by NaBH4to formpolypyrrole/reduced graphene oxide （PPy/RGO）. The morphology and structure of thecomposites were characterized by X-ray diffraction （XRD）, Fourier transform infraredspectroscopy （FT-IR） and field emission scanning electron microscopy （FESEM）. Theelectrochemical performances of the composites were investigated by cyclicvoltammetry, galvanostatic charge/discharge and electrochemical impedancetechniques. The experimental results showed that the composites with the mass ratioof Py to GO up to95︰5reached the specific capacitances of401.5and314.5F/gbefore and after reduction at the current density of0.5A/g, respectively, which weremuch higher in comparison with pristine GO （34.8F/g） and PPy （267.5F/g）. Thecapacitance retention is about62.5%for PPy/RGO after1200cycles, which is much better than those of16.8%for PPy and46.4%for PPy/GO, indicating that thePPy/RGO has a high cycle stability and potential as electrode material forsupercapacitors.2. We used a two-step method to prepare SnO₂/RGO with a homogeneousdispersion, and then the resultant SnO₂/RGO served as a template to obtainSnO₂/RGO/PPy ternary composites by in-situ chemical oxidative polymerization ofpyrrole. Their morphologies and structures were characterized by Fourier transforminfrared spectrometer （FT-IR） analysis, X-ray diffraction （XRD） analysis, Fieldemission scanning electron microscopy （FESEM）. The electrochemical properties ofthe ternary composites for electrochemical capacitors were investigated by cyclicvoltammogram （CV）, galvanostatic charge/discharge tests and electrochemicalimpedance techniques. The results showed that the ternary composites gave a goodcharge/discharge cycle performance and a maximum specific capacitance of305.3F/g,which is greater than that of SnO₂/RGO binary composite. Furthermore, the specificcapacitance of samples increases with increasing amount of PPy in the ternarycomposites. The layered structure of composites with high surface area and thepositive synergy effect between components might enhance the capacitiveperformance.3. The SnO₂/RGO/PANI ternary composites are prepared by means of a two-stepmethod which includes the synthesis of well-dispersed SnO₂/RGO and the in-situchemical oxidative polymerization of aniline. The morphologies and microstructuresof the resulting product are characterized by Fourier transform infrared （FT-IR）spectrometer, X-ray diffraction （XRD） and Field emission scanning electronmicroscopy （FESEM）. The electrochemical behaviors of the ternary composites as asingle electrode of supercapacitors are investigated by cyclic voltammogram （CV）,galvanostatic charge/discharge tests and electrochemical impedance techniques. Theresults show that the ternary composites exhibit a maximum specific capacitance of424.8F/g, which is greater in comparison with the specific capacitance of SnO₂/RGObinary composite. Furthermore, the specific capacitance of samples increases withincreasing amount of PANI in the ternary composites. The positive synergy effectbetween components might enhance the capacitive performance.