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Supercapacitor Performance Studies Of Hierarchical Porous Carbons And Their Derivatives

Posted on:2017-05-20Degree:MasterType:Thesis
Country:ChinaCandidate:Y L WangFull Text:PDF
GTID:2272330482480899Subject:Applied Chemistry
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As a new type of high-efficient energy storage/conversion devices, supercapacitors possess a variety of advantages including high power/energy density, fast charging-discharging ability and long cycling life, which endow them extensive applications in the fields of electric vehicles, memory back-up systems, small electronic products and energy managements. In terms of the difference of energy-storage mechanism, supercapacitors can be divided into electric double-layer capacitors(EDLCs) and pesudocapacitors. EDLCs store charge in the interfacial double-layer between electrode and electrolyte and they have excellent electric conductivity as well as outstanding cycleability. Pesudocapacitors, which are associated to rapid surface redox reactions, exhibit much higher specific capacitance than EDLCs whereas their poor cycle stability still cannot be ignored. Porous carbon materials are the most widely used electrode materials of EDLCs for their easily availability, less weight, good chemical stability and environmental friendliness. Regardless of their large surface area, numerous micropores in commercial activated carbon may limit the diffusion of electrolyte ions onto inner pore wall, and large amounts of surface areas of micropores cannot participate in the charge-storage process of EDLCs, resulting in an unsatisfied capacitive performance of electrode materials. Mesopores can provide suitable pore channels and relatively high specific surface area. Macroporous structure facilitates the rapid transport of electrolyte ions in electrodes, whereas the surface area of electrode is severely limited in macroporous carbons. Therefore, the current researches have focused on designing and synthesizing hierarchical porous carbon electrode material with high specific surface area, uniform pore size distribution and large pore volume. In this dissertation, hierarchical porous carbon material has been used as research object to prepare a series of hierarchical porous carbons and their derivative materials via different methods. Meanwhile, the prepared materials were characterized by SEM, TEM, N2 adsorption-desorption technique and so on. Their electrochemical performance was investigated using an electrochemical workstation. The detailed works were summarized as follows:1. Porous NiO electrode material with high specific surface area and developed porosity was prepared by a synthesis route including hydrothermal synthesis of carbon nanospheres using glucose as carbon source, porous carbon nanosphere synthesized by ZnCl2 activation, preparation of porous NiO via hard template method. This electrode material exhibited ultrahigh specific capacitance for supercapacitor application.2. Mesoporous activated carbon nanospheres with high specific surface area, uniform pore size distribution and large pore volume were prepared by one-step Zn Cl2-activation method using resorcinol formaldehyde resin as carbon source. The electrochemical properties including gravimetric specific capacitance, rate performance and cycle stability were studied.3. N-doped activated carbon sheets were prepared by a melamine-assisted chemical blowing synthesis method. Melamine simultaneously acts as nitrogen source and blowing agent, KOH as activating agent. The obtained material possesses microscale sheet-like morphology, high specific surface area, superior hierarchical micro/mesoporous structure and high nitrogen content. Electrochemical measurements demonstrated its outstanding capacity performance both in three-electrode system and two-electrode system.
Keywords/Search Tags:supercapacitor, carbon material, hierarchical structure, ZnCl2 activation, nitrogen-doped carbon material
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