Preparations And Electrochemical Capacitance Behaviors Of Nano-Carbon Materials And Their Composites

Nano-carbon material has larger surface area due to the unique nano-size advantageand good conductivity, which making it has great application prospects in electrodematerial of electrochemical capacitor and conductive additives. Carbon nanofibers （CNF）,carbon nanotubes （CNT） and graphene （GR） are the typical representative of nano-carbonmaterials. The three kinds of nano-carbon materials and their composites were studied aselectrode materials of electrochemical capacitor in this paper, and the paper is divided intosix chapters, including the following aspects:The first chapter reviewed the status of basic research about electrochemical capacitors,the applications of nano-carbon materials in electrochemical capacitors, and the researchstatus of flexible electrode materials in electrochemical capacitor.The second chapter introduced the preparation of porous carbon nanofibers byelectrospinning, followed by in situ growth carbon nanotubes to prepare porous carbonnanofibers/carbon nanotube composites, and their electrochemical capacitance behaviorswere also studied. It had shown that it could effectively improve the material surface areaand electrochemical capacitance performance through making pores by adding inorganicsalts in electrospinning precursor and the capacitance could get to265F.g^-1; It couldimprove electrical conductivity of the porous carbon fibers through growing CNT, while thecapacitance was lower than before growing CNT because of electrolyte infiltrating decline.It could improve the electrical conductivity and specific capacitance of the porous carbonfibers that dispersed single-walled carbon nanotubes （SWCNT） in the electrospinningsolution to make SWCNT compound with in the porous CNF. The specific capacitance ofnew material could get to417F.g^-1.Some flexible composites were built with CNT paper as basis in the third chapter.Manganese dioxide （MnO₂） nanocrystalline was deposited on the CNT paper networkthrough electrochemical deposition technology and the influence of MnO₂morphology andstructure to electrochemical capacitance were also studied. Then CNT/MnO₂/graphenepaper was prepared using a simple process of soaking the graphene solution, which couldimprove the electrical conductivity of MnO₂. The ternary composite of CNT/MnO₂/graphene could exhibit huge pseudo-capacitance characteristics of MnO₂fully and givebetter electrochemical cycle life than CNT/MnO₂. It was found that the capacitance ofCNT/MnO₂/graphene could get to561.1F.g^-1(125mA.g^-1) and the capacitance could keep92.8%of first cycle capacitance after800cycles.The fouth chapter followed research ideas of the third chapter. A ternary compositepaper of CNT/polyaniline （PANI）/graphene had been prepared in order to play thecapacitor performance of PANI fully. It found that the ternary materials was with betterelectrochemical cycle life and higher current capacitance characteristics than CNT/PANIbinary material. It was found that the capacitance of CNT/PANI/graphene could get to415F.g^-1(0.5A.g^-1) and the capacitance could keep173F.g^-1at high current density of10A.g^-1.The fifth chapter mainly introduced the performances of electrochemical capacitorassembled with the materials prepared in Chapter2⁴. An important element was how tooptimize the electrode match. It has shown that asymmetric capacitor constructed withporous carbon nanofiber/SWCNTs as negative electrode and CNT/MnO₂as positiveelectrode （porous carbon nanofiber/SWCNT//CNT/MnO₂） could work in1.8V voltagestable in aqueous electrolyte and energy density could get to37.5Wh.kg^-1, which could becomparable to similar works perfectly; Besides, the capacitor constructed with CNT/MnO₂/graphene as positive electrode and CNT/PANI as negative electrode （CNT/PANI//CNT/MnO₂/graphene） exhibited good flexibility and good electrochemicalcapacitance performance. The energy density and power density were24.82Wh.kg^-1and2234W.kg^-1, respectively.At last, summary of all works in full text could be seen from chapter six. Besides,some advices based on works experience and problems also were given in this chapter.