Study Of Hierarchical Porous Carbon And Ni₃（NO₃）₂（OH）₄as Electrode Materials For Supercapacitors

The research status of supercapacitors and the recent progress of the electrode materials were reviewed in this thesis. First, we synthesized hierarchical porous carbons and Ni3(NO3)2(OH)4successfully. Then, the microstructures and compositions of these materials were investigated by X-ray diffraction measurements (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Brunauer Emmett Teller (BET). The electrochemical performance has been evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectra (EIS). Besides, the factors that influence the electrochemical performance were discussed. The main content is the following:1. In order to synthesize hierarchical porous carbons, first, we prepared the molecular sieves with different pore size and wall thickness, using TMB as an expanding agent. In synthetic process, two carbon sources, that is furfuryl alcohol and sucrose, were studied. With furfuryl alcohol as carbon source, we prepared a series of hierarchical porous carbons with two pore size distributions by regulating the concentration of furfuryl alcohol. The structural characterization and electrochemical performance test results show that the unique hierarchical porous carbon pore size distributions, not only maintain the good performance of the electric double layer, but also enhance the rate capability of hierarchical porous carbons. Hierarchical porous carbon electrode materials have high specific surface area, and the maximum specific capacitance (SC) can reach143F/g at5mA/cm2current density. Specially, the SC at200mA/cm2current density, can still maintain51.90%of SC at5mA/cm2current density. With sucrose as carbon source, the hierarchical porous carbons can also be synthesized successfully, with the maximum SC of155.63F/g. In addition, the rational relation between electrochemical properties and pore size distributions, was discussed in this thesis.2. Flower-like Ni3(NO3)2(OH)4was successfully synthesized by a facile solvothermal method without adding any surfactant. The results indicate that the flower-like structure has profound impacts on electrode performance at high discharge capacity. A maximum specific capacitance (SC) of2212.5F/g at the current density of5mA/cm2could be achieved in a half-cell setup configuration for the Ni3(NO3)2(OH)4electrode, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Besides, charge-discharge cycle data illustrate that the prepared Ni3(NO3)2(OH)4has good electrochemical stability. The capacitance value of1511.6F/g can be remained after continuous1000cycles. Furthermore, the effects of Ni(NO3)2-6H2O concentration and temperature on the microstructure and SC of prepared Ni3(NO3)2(OH)4have also been systematically studied. The results show that flower-like structure can be formed when the concentration is0.02M,while the temperature has just little effect on its electrochemical properties. After direct thermal decomposition at320℃, Ni3(NO3)2(OH)4can be converted to NiO. The structural characterization showed that, the structure of NiO was damaged greatly after thermal decomposition, and the electrochemical performance is not well. Specifically, the maximum SC at5mA/cm2current density is only reach254.7F/g.