| Electrochemical supercapacitor is a new type of energy storage device between traditional capacitors and rechargeable batteries. Because of its high specific power and long life and other outstanding advantages, in recent years, supercapacitors have attracted great interest in energy storage applications. The electrode materials are one of the key factors to determine capacitive properties of electrochemical capacitors, as the focus of the study. Flexible Pillared Graphene-Paper Electrodes are of both scientifical interest and technological importance to design and fabricate novel electrode materials with a revolutionary architectures for cell assembly that are highly flexible, mechanically robust, and ultralight weight without additives or current collectors, which can deliver a high specific gravimetric and volumetric capacitance. The main points of this thesis are summarized as follows:(1) The dispersion of MoS2nanosheet was prepared by a mixed-solvent strategy under ultrasound stripping. The materials were characterized by various electrochemical methods in combination with powder X-ray diffraction(XRD), Scanning Electron Microscope(SEM), Transmission Electron Microscopic(TEM) and electrochemical measurements. The effects of structure, impurity and electrochemical performance were studied. It was found that the dispersed MoS2showed a good lamellar structure, and the MoS2nanosheet was consisted of four to five layers. The MoS2nanosheet showed the maximum specific capacitance of127F-g-1in saturated sodium sulfate solution. The impedance phase angle of the MoS2nanosheet capacitor reached-45°at～2500Hz, that is to say its RC time constants were less than0.4milliseconds which would be comparable to good filtering capacitors.(2) Graphene oxide was prepared by an improved method of Hummers’ method, and its dispersibility in different solvents, surface morphology, and electrochemical performance were studied. The results showed that GO were well dispersed, and the thickness of single-atom layer GO was hundreds of nano or so. The GO showed the maximum specific capacitance of184F·g-1in saturated sodium sulfate solution, and it exhibited exhibits cycling stability with the6.7%specific capacitance decreased after 1000cycles. The capacitance of GO almost had no change at1.25A·g-1and5A·g-1, which proved GO had good stability as an electrode material. By control of the volume ratio of GO and MoS2solution as1:1, Pillared GO/MoS2-Paper Electrodes were prepared with a simple vacuum filtration method. The electrodes acted out highly flexible and mechanically robust nature. The electrodes showed the maximum specific capacitance of119F·g-1at0.17A·g-1in saturated sodium sulfate solution. EIS measurement showed that the electrodes had big charge-transfer resistance, and the capacitance and charge-transfer resistance increased along with cycle numbers increasing because of collapse and loose of the electrode. It’s important to realize that by constant current charging and discharging test, GO/MoS2-Paper proved clear characteristic of battery.(3) CO3O4microspheres were synthesized by a simple hydrothermal reaction, then RGO/Co3O4(RC) and CTAB-RGO/Co3O4(CRC) were prepared by Physical mix method and chemical mix method with surfactant, respectively. XRD showed that all diffraction peak observed in all materials were still in good accordance with those of cubic spinel CO3O4. Through electrochemical measurements, the specific capacitance of Co3O4, RC and CRC are calculated to be289F·g-1,486F·g-1,776.3F·g-1, respectively. In2M KOH solution, CRC showed the maximum specific capacitance of643.5F·g-1,690.2F·g-1,776.3F·g-1at1.5A·g-1,0.5A·g-1,0.15A·g-1, respectively.CRC exhibited exhibits cycling stability with the17%specific capacitance increased after1000cycles, but the RC and Co3O4exhibited worse cycling stability in the same condition. In especial, the capacitance of Co3O4decreased by20%. These proved that CRC had the best stability in chemical and needed more time to perform its potential of capacitive character. EIS measurement showed that the CRC had the smallest charge-transfer resistance, and RC had the biggest. All materials had good super capacitive. |
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