Study Of Supercapacitors Based On Nanomaterials Of Novel Architectures

The extensive dependence on fossil fuels has caused significant environmental pollution as well as energy resource crisis. Sustainable exploration and use of energy source depend on discovery of new energy source and development of novel energy devices. As a kind of energy storage device, supercapacitors have many advantages over conventional batteries:high power density, long cycling stability, fast charge-discharge rate and being environment friendly. Wide research of nanoscale materials has promoted flourish of advanced energy storage technology. However, common problems involved with nanomaterials such as bad structural continuity, conglomeration and structural instability have restricted their application in supercapacitors. This work introduces strategies based on design of porous materials with high area aiming at improve the performance of the supercapacitors. We have conducted the design, synthesis and performance research of the electrode materials containing:the composite of porous metal materials with transition metal oxide and conducting polymers, one dimensional structural composite and macroporous metal/metal oxide hybrid materials. We demonstrate the above composite materials have wide prospect for application in the supercapacitors as well as other similar fields.1. Controllable synthesis of MnO2/polyaniline nanocomposite and its electrochemical capacitive property.Polyaniline (PANI) and MnO2/PANI composites are simply and controllably fabricated by one-step interfacial polymerization at various pH. The morphologies and components of MnO2/PANI composites are modulated by changing pH of the solution. Formation procedure and capacitive property of the products are investigated by XRD,FTIR, TEM and electrochemical techniques. We demonstrate that MnO2as an intermedia material plays a key role in the formation of sample structures. The MnO2/PANI composites exhibit good cycling stability as well as a high capacitance close to207F g-1. Samples fabricated with the facile one-step method are also expected to be adopted in other field such as catalysis, lithium ion battery and biosensor.2. Sub-micrometer-thick all-solid-state supercapacitors with high power and energy densities.Fast development of portable and miniature electrics desires compatible energy conversion and storage devices. A flexible NPG-PPy composite film was fabricated using a convenient dealloying and electro-polymerization process. The bicontinuous pore/ligament structure provides high electric conductivity as well as improved ionic transferring channels, which increases the efficiency of the active materials. All-solid-state supercapacitors were designed with NPG-PPy films as both electrodes and PVA as both the separator and electrolyte. The symmetric supercapacitor thus-produced offers large specific capacitance, power density and energy density (296kW kg-1and27Wh kg-1), and exhibits almost identical performance at various curvatures, which suggests its wide application prospect in powering wearable/miniaturized electronics.3. Electrochemical capacitive behavior of metal oxide and nanoporous gold hybrid structure.Cobalt oxide and nanoporous gold (NPG) hybrid films are fabricated by a facile electrochemical technique. Structural morphology, composition and capacitive behavior of the sample have been investigated. The composite film has a sandwich like structure containing NPG film as the inside layer and cobalt oxide films as outside layers. NPG, as a3dimensional interconnected skeleton, can afford electron and ion transfer channels thus improve the efficiency of cobalt oxide. The hybrid films provide high volumetric (598F cm-3) and gravimetric capacitances (563F g-1), additionally exhibit good stibility.To improve the apparent capacitance of the supercapacitors, we chose the ideal capacitive material RuO2as the active electrode material. NPG/RuO2composites are synthesized by CV method using NPG as the substrate and the corrent collectors. The gravimetric capacitance of RuO2achieves502F g-1, and the volumetric capacitance of the composite is close to1.5F g-1.4. MnOx Nanowires aligned on the macroporous structures with high volumetric electrochemical capacitance.Because of their high power densities, long lifespan and safe operation, supercapacitors have been used in the areas of hybrid vehicles, digital telecommunication systems, uninterrupted backup energy systems and pulsed laser techniques. The fast development of electronic techniques such as portable electronics or stationary energy storage devices poses new challenges for the design and fabrication of compatible energy devices with large amount of energy stored per area as well as energy per mass. For this work, we propose a facile hydrothermal synthesis method for MnOx nanowires aligned on Ni foam. As prepared porous nanostructures can provide fast electronic transferring channels and reduce ionic diffusion distance with enlarged electrode/electrolyte contact area. The entangled MnOx nanowires provide high pseudocapacitance, and the porous Ni foam serves as substrate and current collectors. The capacitance per mass and area are estimated as high as576F g-1and7.6F cm-2.