Study Of Carbon-Nickel Hydroxide Composite Eletrode Materials And Their Application In The Asymmetric Supercapacitors

Expanding energy demand, increasingly severe environmental situation as well asefficient utilization of renewably clean energies have become three major issues in themodern society. The demand for energies is increasing as the population expanding, andso are the exploitation of the traditional energies and the number of energy-consumptionequipment, resulting in series of consequences as follows. On one hand, people willenhance the depriving of conventional energies, on the other hand much pressure hasdumped on the environment’s shoulders. Therefore, it is urgent to solve the aboveproblems in an effective way, so as to alleviate the demand for natural resources and tominimize the pollution and destruction on the environment, for which reason the new andclean energy storage materials are gradually becoming the mainstreamed energy sourcesand the driving force for the new energy times. New types of equipment used forenvironmental protection and energy storage, such as lithium ion battery, solar battery,fuel cell, supercapacitors, etc., in this background emerge, and gradually have a footholdin today’s society. Among them, the supercapacitors akin to a kind of new and greenenergy storage device, with the high power density approach to conventional capacitorsand large energy density close to rechargeable batteries, have the advantages of quickcharge-discharge efficiency, long service life, wide working temperature range, portable,maintainance free and environment friendly, etc., which leads to a broad applicationprospect in the human lives and varieties of industries.Carbonaceous materials used for supercapacitor electrodes have quite a few advantagessuch as high specific surface area and electrical conductivity, strong chemical tolerance,wide working potential window, excellent utilization rate per quality and outstandingelectrochemical performance. Meanwhile, pesudocapaeitor electrode materials, especiallythe nickel hydroxide have showed the excellent properties of low cost, high theoreticallyspecific capacitance, strong redox activity, etc. If the two types of materials can beincorporated into each other with the advantages of both, by coupling that with someunique preparation methods and innovative thinking method, good results could obtain.During the process, the collector, carbon materials and nickel hydroxide are combined automatically without additional agents. To make the specific avenue come true, uniquemeasures can be summarized as the following: First of all, Ni foam as the substrate andcollector with porous structure and excellent electric conductivity is used. Then, throughthe in situ growth method (the growth of carbon materials is accomplished on the collectorsubstrate directly, without adding the conductive and binder agents), carbonaceousmaterials with excellent morphologic characteristics and good electrical conductivity areprepared. Finally, the growth of nickel hydroxide is completed on the as-produced highsurface area basements (carbonaceous materials on Ni foam substrate), which in thesystem act as the intermediate buffer layer and the overall conductive agent. In general, thecarbonaceous materials as the substrates not only increase the electric conductivity of theintegral system, but also ensure the terrific bonding of the active materials anchoring onthe substrates, which can well realize the effectively functioning of the composite anodesin the supercapacitors. Last but not least, we apply the as-produced composite materials inthe button-type asymmetric supercapacitors and probe into its electrochemicalperformance.In order to achieve the above goals, we have carried out the concrete experimental planand design. Firstly, a variety of carbonaceous materials as the substrates are prepared byusing the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. By adjustingthe reaction parameters, such as the type of collectors, the composition of reaction gas, gasflow ratio, systematic pressure, reaction temperature and time, etc., the preparation ofdifferent morphologic carbonaceous substrates can be achieved. Secondly, throughapplying the constant current cathodic electrochemical deposition method, the activematerials namely nickel hydroxide can be deposited on all kinds of carbon materials,finally, forming the carbon-nickel hydroxide composite anodes followed by the subsequentperformance characterization to find out the comprehensively best properties of the anodematerials for the application in supercapacitors. Finally, we respectively accomplished theassembly and explored their electrochemical properties and temperature characteristics ofthe button-type asymmetric supercapacitors with the as-produced composite materials,single nickel hydroxide materials as anodes and the active carbon as cathodes forcomparison. Through the analysis of the samples by the relevant techniques, we found that theelectrochemical performance of the composite electrode materials is excellent. Forinstance, the generally high specific capacitance of the samples is able to reach more than1500F/g, and the stability is also good comparatively. As for the assembled button-typeasymmetric supercapacitors, their specific capacitances can reach80F/g (under thecharge-discharge current density of0.5mA/cm~2) to the maximum, which shows anexcellent electrochemical performance. Especially, the preparation method is simpler andquicker than the conventionally chemical synthesis route, without introducing extraaddtional ingredients such as conductive agent, binder, etc., therefore, reducing the as-usedweight within the system and strengthening the binding force between the electrodematerials and the substrates, which provides a certain reference and theoretical support forthe optimization of supercapacitors’ performance, upgrades the pertinent technology andhas a certain significance in the research and the application facets.