Synthesis And Property Test Of The Manganese/cobalt Oxidc Electrodes Flor Super-capacitiors

The exponential-growth needs of the portable electronic devices together with the electric automobiles have raised an ever-increasing demand for light-weight and compact electric power sources with high energy as well as high power density. Among them, pseudocapacitors (a kind of electrochemical capacitors or supercapacitors), as advanced and clean energy storage and management devices, offering extremely high powers as well as possible high energy densities, are expected to play a crucial role where superior power performance is required. While, existing pseudocapacitors always suffer from limited cycle life and low energy density, due to the phase changes caused by redox reactions when energy is stored/released on the surface or subsurface of the electrode. To emerge as an important energy storage technology in the future, hence, advanced electrode materials for supercapacitor are required to be equipped with higher operating voltage and higher energy and power delivery, while maintaining high cyclability.Transition-metal oxides, i.e. RuO2, MnOx, NiO, CoO, Fe3O4, VOx and MnOx-RuO2, are one kind of the most promising electrochemical supercapacitor materials, which are attracting widely interest owing to their relative high specific capacitance and high energy density, compared with carboneous materials and conducting-metal polymers. Among these materials, amorphous hydrated ruthenium oxide exhibits remarkably high specific capacitance and excellent reversibility because of the ideal solid-state pesudofaradaic reaction. However, the high cost, low porosity and toxic nature of RuO2limit its practical application. Therefore, some cheap and environmentally friendly metal oxides have received more and more attention. Manganese oxide, Cobalt oxide materials, as promising candidates for electrochemical supercapacitors, satisfy these fundamental requirements, low cost, environment friendly and reasonable high specific capacitance, whose theoretical value is of about1500F/g, gets more and more attention. In the work reported here, we made carbon fiber paper (CFP) supported nano-structured MnOx and Co3O4as electrodes for symmetric cells, respectivily. Both of these two kind of active materials can achieve eery high specific capacitance of over1000F/g, superior stability (more than5,000CV cycles, as good as carbon based electrodes) and high reaction rate (high rate capability), rectangular shapes even at a CV scan rate of100mv/s at an operating voltage window of0-0.8V in1M Na2SO4aqueous solution with the loading amount of～mg·cm-2, by preparing nano-structure metal oxide with rather simple chemical solution methods, followed by heat treatment.Scanning electron microscope (SEM Leo/Zeiss1530), the high resolution transmission electron microscope (JEOL4000EX) and Synchrotron-based X-ray analysis (Diffraction XRD and Absorption XANES) were employed to collect the morphology and phase information of the active materials. To characterize their electrochemical performance as super-capacitors, cyclic voltammetry (CV) curves and galvanostatic charge-discharge curves were recorded at room temperature in a symmetric-cell configuration containing1M Na2SO4,1M Ca(NO3)2, or1M H2SO4electrolyte solution. The potential and current were controlled by an Electrochemical Interface (Solartron, SI1286) and the electrochemical impedance spectroscopy (EIS) analysis was conducted using a Frequency Response Analyzer (Solartron SI1255) and SI1286with an applied ac voltage of10mV in the frequency range of0.001Hz to1MHz.