Preparation And Performance Of Manganese Oxide Electrode Materials

Energy is always a priority issue for human being. The high-energy, high-power energy storage devices are widely investigated, owing to the decreasing availability of fossil and climate change. Although electrochemical capacitor has a high power density as a promising energy storage device, it cannot content the market demands due to its low energy density compared with other energy storage devices (e. g. lithium-ion batteries). Consequently, Choosing effective technology and low costing to prepare electrode materials with excellent electrochemical performance has become critical issue.Manganese dioxide (MnO2) is an important transition oxide, of particular interest for its potential applications in energy storage devices, such as lithium-ion batteries and supercapacitors, on account of its high theoretical capacitance, low cost and environmental friendliness. We used mild chemical bath route at 60-80℃to synthesize MnO2, which was confirmed as a mixed phase of bothα- andδ-phases. Pureα-,δ-, and y-phase MnO2 can also be chemically prepared in the same solution system by adjusting reaction parameters slightly. The crystallographic structure of MnO2 was found to be determined by the chemical bath reaction temperature, pH value and time. The electrochemical test results indicate that mixed-phase MnO2 have better capacitance properties than other pure phase MnO2. The mixed-phase MnO2 possessing lots of phase interface can provide extra electrochemically active boundaries and is propitious to electron/ionic transmission. In the current work, we not only purposefully designed the optimum reaction parameters to synthesize high performance mixed-phase MnO2 through mild chemical bath route, but also provides an effectives approach to enhance the capacitance of powder-based electrodes.MnO2 microrod arrays and nanowall arrays were prepared through two template-free cathodic electrodeposition processes. The experiment results indicate that the etching effect of F- is a key factor to form microrod arrays and the growth of nanowall arrays is based on the electrolysis of water. MnO2 nanowall arrays have a larger specific capacitance as electrode materials. Moreover, the template-free synthesis methods are simple in preparation, which provide a referential example for electrodeposition of micro/nano-array materials.