Three Dimensional Porous Materials Fabricated By Self-assembly Of Two Dimensional Macromolecules For Potential Application In High Performance Electrochemical Capacitors

As one of the most potential energy storage devices in recent years,electrochemical capacitors?ECs?has attracted considerable interests for its highlighted traits such as high power density,faster charge/discharge rates and excellent cycling stability.Since the performance of ECs is strongly governed by the nature of the electrode materials,the development of electrochemical materials with desired structures and high activity has been the research focus over the past decade,and researchers have been developing vairous chemical and/or physical methods to fabricate three dimensional?3D?materials with new structures as electrode materials.In this thesis,based on self-assembly behavior oftwo dimensional?2D?materials,we prepared structure-controlled 3D porous materials as potential electrodes in ECs.?1?Nitrogen-enriched hierarchically porous carbon materials fabricated by graphene aerogel templated Schiff-base chemistry for high performance electrochemical capacitors:In hydrothermal process,2D graphene oxides?GOs?were partly reduced to form 3D graphene aerogels?GAs?spontaneously by?-?interaction between GO sheets,1,3-diaminopropane was used to modify GA with amino groups,then the aminated GAs?AGAs?were made as a 3D macroporous template for the Schiff-base polymerization of melamine and 1,4-phthalaldehyde,through which the 3D graphene-coupled Schiff-base hierarchically porous polymers?3D GS-HPPs?were obtained.3D nitrogen-enriched hierarchically porous carbons?N-HPCs?were prepared by pyrolysis of 3D GS-HPPs under nitrogen atmosphere.Such composite material not only maintains the 3D framework with macropores,but also possesses a high nitrogen content and a large specific area.The N-HPC samples show high specific capacitance of up to 335 F g^-1 at 0.1 A g^-1 in 6 M KOH,good capacitance retention with increasing current density,and outstanding cycling stability.?2?3D Ni foam coated with vertical Polypyrrole?PPy?nanosheets is prepared as the active electrode of flexible all-solid-state supercapacitor,this material coupled with commecial actived carbon was assembled into flexible all-solid-state asymmetric supercapacitor,the performance of which has been intensively studied.The clean Ni foam was soaked in a mixed solution containing deionic water,ethanol and pyrrole?Py?monomer,then phase separation of water and Py after the volatilization of ethanol led to the formation of a film with“sea-island”morphology on the hydrophobic surface of Ni foam when solvent evaporates.Ammonium peroxydisulfate?APS?was used to initate the polymerization of Py on the surface of Ni foam,which yielded the vertically aligned PPy nanosheets on Ni foam.This method of preparing vertical nanosheets shows advantages of easy synthesis,environmental protection and no need of expensive instruments.A flexible all-solid-state asymmetric supercapacitor—PPy-Ni?AC-Ni was fabricated by using our PPy-Ni as the flexible positive electrode and commercial actived carbon as negative electrode.The PPy-Ni?AC-Ni shows 38F g^-1 specific capacitance at 0.2A g^-1,and the energy density of 14W h kg^-1 at the power density of 3.0 kW kg^-1,which is higher than those of most commercial supercapacitors(5¹0W h kg^-1).The device could retain 82%specific capacitance after 2000cycles at 1A g^-1,which shows good cyclical stability when compared with electrode materials composed of pseudo-capacitance materials.