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Shape-Controllable Synthesis and Electrochemical Properties of Nano-Structured Manganese Dioxides

Author: WangYuZuo
Tutor: LiWenCui
School: Dalian University of Technology
Course: Chemical processes
Keywords: Nano - manganese dioxide Supercapacitor Controllable Preparation Cyclic voltammetry Charge-discharge
CLC: O614.711
Type: Master's thesis
Year: 2011
Downloads: 207
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Abstract


Supercapacitor is a new energy storage element in the range between the batteries and electrostatic capacitors, and has a wide operating temperature range, long cycle life, and be able to meet the electric car start to accelerate high-power output. The preparation of high energy density of the water phase asymmetric capacitor can not only improve the energy density of the capacitor can also reduce costs, and is also conducive to environmental protection, research hotspot in recent years. Supercapacitor is mainly concentrated in the electrode material, manganese dioxide as a common manganese oxide because of its environment-friendly, low price and excellent performance caused great concern, and the incorporation of manganese dioxide The asymmetric capacitor voltage can broaden the scope to improve the capacity of the capacitors, and therefore is considered to be the most potential for development of electrochemical capacitor electrode material one. Manganese dioxide is widely used in chemical power, separation and catalysis. Study prove its nanoparticle morphology, crystal type, size, and number of dimensions and other factors varying degrees of impact on the electrical, optical and magnetic properties of nanomaterials. Thus, through the use of a certain method to control the directional growth of the nano-manganese dioxide, thus achieving the regulation of nanomaterials morphology, crystal structure and size is useful important significance. Full-text including literature review and experimental. The main contents and results are as follows: KMnO4 for manganese, vitamin C as a reducing agent or structure-directing agent by liquid redox reaction synthesis of three-dimensional network morphology of manganese oxide nanomaterials. The results show that: the manganese dioxide having a porous three-dimensional mesh structure, to provide a smooth channel for the movement of ions in the electrolyte solution, to improve the utilization of materials. The high power density of the high energy density of 10.4 Wh kg-1 and 14.7kW kg-1, the material composition of the asymmetric capacitors even after 1200 cycles. With KMnO4 as the manganese source, and ethylene glycol as a reducing agent, a series of high ratio table prepared by redox reaction occurs in the presence of an acid environment, the Nanoflower shaped MnO2 · while manganese oxide crystal is proposed with the increase in the amount of acid phase transition and the growth mechanism of the acid-soluble. The electrochemical tests show that adding acid, manganese dioxide capacity increased by 11% after 250 cycles, without the acid treatment electrode capacity fading 18%. Manganese sulfate and ammonium thiosulfate hydrothermal system twelve alkyl sulfate (SDS), the short rod manganese oxide nanorods (80 nm) can be obtained. Experimental results show that: adjusting the added amount of the surface active agent is able to control the aspect ratio of the product. Electrochemical test shows that compared to shorten the longitudinal dimension of the manganese oxide electrode material with 400 nm-long rod manganese oxide plus SDS obtained magnification characteristics improved. The paper also examines the alkaline electrolyte concentration on the electrochemical performance. The conclusion is obtained in the high-concentration alkaline electrolyte capacitor low. Wide potential window a low concentration of the alkaline electrolyte, the capacitance value is high, good stability, the KOH concentration is then low due to the conductivity decreased lead capacitance value has dropped, so considering 1MKOH optimum concentration.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > The Ⅶ group metal elements and their compounds > The manganese Vice Family ( VII B group metal elements) > Manganese Mn
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