Preparation And Property Of Supercapacitor Electrodes Based On Carbon Nanotube-graphene-ni Foam Three-dimensional Composite Structures

Supercapacitors as a new energy techonology have attracted great attention due to their wideapplication in electronic products and vehicle energy supply. Electrode materials are the keycomponent for devices, which is of great importance for the development of supercapacitors.Carbon materials are a class of ideal electrode materials for electrochemical capacitors becauseof their high surface area, electrical conductivity, and low cost. In recent years, with the discoveryof fullerenes, carbon nanotubes and graphene, carbon nanomaterials have become the hotspot in thisfield. Among them, carbon nanotube (CNT)-graphene hybrid structure owns excellent surfaciallyelectrical charge transport properties, and maintains the individual characteristics of the originalbuilding blocks. In addition, This hybrid structure could effectively resolve the directiondependence of one-dimensional CNTs and two-dimensional graphene in heat and electrontransportation as well as the low surface conductivity, demonstating an excellent synergy and greatpotential in new energy materials. Recently, we have synthesized a three-dimensional (3D)CNT-graphene-Ni foam hybrid by two-step chemical vapor deposition route， and roughlyinvestigate the chemical properties of the surface, electrochemical properties and potentialapplications. Based on this type of electrode platform, in this thesis, MnO2and PANI were selectedas Faradic materials and loaded on the CNT-graphene-Ni hybrids by a mild chemical deposition andelectrochemical deposition, respectively. Such a hiratical structure composed of metal oxide orconductive polymer, CNT and graphene was prepared and optimized by adjusting the loadingamount and nanosture of MnO2and PANI. Some good progresses are obtained and summarized asfollows:We have developed a simple route to synthesize3D CNTs/G/NF seamless hybrids bysequentially growing CNTs and graphene on Ni foam (NF) substrate with ethanol through two stepsof CVD.1. We have develop a two-step CVD process to synthesize3D CNT-graphen-Ni hybrids bysequentially growing CNTs and graphene on Ni foam (NF) substrate with ethanol. Then MnO2nanoflakes were immobilized onto CNTs by a mild chemical deposition, thus forming3DMnO2–CNT–graphene–Ni hybrid foams. The as-prepared hybrid materials maintain the highconductivity and high surface-to-volume ratio of CNTs, large pseudocapacitance of MnO2nanoflakes and high porosity provided by the framework of Ni foam. In aqueous electrolytes, the3D MnO2–CNT–graphene–Ni based prototype supercapacitors show specific capacitancesof~251F/g with good cycling stability at a current density of1.0A/g. In addition, these3Dhybrids could be feasibly assembled into all-solid-sate devices and light a lightemitting diode(LED) after charging, demonstrating their potential in flexible supercapacitors.2. In addition to use metal oxides to increase the capacitance of carbon materials, here conductivepolymer with high capacitance was also incorporated. On the CNT–graphene–Ni electrodeplatform,(PANI) was deposited onto CNTs by electrochemical route, thus formingthree-dimensional PANI–CNT–graphene–Ni composities. We investigated the effects ofdifferent deposition time on the structures and properties of the composites. Three-electrodesupercapacitor cells constructed with the composites yield higher values of gravimetriccapacitance with aqueous electrolyte. The PANI-CNT-graphene-Ni electrodes present a specificcapacitance of219F/g at the current density of2.0A/g.