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Hydrothemal Synthesis,morphological Characterization, and Studies on Electrochemical Properties of Manganese Oxides

Author: ChenYuJuan
Tutor: HangYiPing；RuanXiangYuan
School: South China University of Technology
Course: Analytical Chemistry
Keywords: Manganese dioxide Hydrothermal method Doping Electrochemical properties Lithium battery
CLC: O614.711
Type: Master's thesis
Year: 2010
Downloads: 379
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Abstract


Series of different crystal structure and morphology of manganese dioxide powder materials prepared by hydrothermal synthesis. X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry - differential thermal analysis Yee (TG-DTA), field emission scanning electron microscope ( FESEM) and electrochemical workstation technology, and by changing the type of divalent manganese salt reactant and doped lanthanum element of the structure, morphology and electrochemical properties of the material in-depth research. KMnO4 and MnSO4 reactants by hydrothermal method to prepare nano MnO2 powder. Prepared by changing the reaction conditions such as temperature, time and pH of the hydrothermal reaction, the α crystal type MnO2 nanorods. The study showed that: the hydrothermal reaction time and temperature on the crystal structure of MnO2 little effect, but the degree of crystallinity of MnO2 increases with the reaction time. Maintaining the reaction time and temperature constant, with increasing the pH of the solution of the reaction system, and manganese dioxide product structure by the α-MnO2-type amorphous MnO2 conversion, i.e., under alkaline conditions, more conducive to the formation of the amorphous manganese dioxide . With AUTOLab electrochemical workstation test under different conditions of α-MnO2 discharge performance. When the hydrothermal reaction time is 24 hours, the hydrothermal reaction temperature is 140 ° C, a solution of pH 1.5 is generated when the α-MnO2 discharge capacity of 150mAh / g. MnSO4, Mn (NO3) 2 and MnCl2 reducing agent, with KMnO4 response. Research anion of the crystal structure of the product, morphological and electrochemical properties. The study showed that: easy to form a γ-MnO2, NO3-or Cl-divalent manganese salt solution containing divalent manganese salt solution containing SO42-, favor the formation of an α-MnO2. The same charge and discharge conditions, the α-MnO2 powder containing γ-MnO2 electrode materials, the first discharge capacity is higher than the capacity of the single-phase α-MnO2, up to 203 mAh / g. In order to improve the circulation of the α-MnO2 charge-discharge performance, La Doping modified α-MnO2. When La / Mn molar ratio of 0.0029, which can effectively improve the α-MnO2 cycle charge-discharge characteristics, the initial discharge capacity of 122.7 mAh / g, the the cycle discharge up to 28 times, the discharge capacity was 101 mAh / g, the attenuation capacity attributable first 17.7% of the discharge capacity of the times, α-MnO2 electrode material, far lower than the non-doped La its attenuation capacity 66.4%. The first discharge capacity of La-doped α-MnO2 decreased with increasing La / Mn molar ratio. Studies have shown that doped with La elements, can effectively improve the the MnO2 cycle discharge performance, effectively inhibited MnO2 attenuation capacity, able to meet the requirements of the battery materials.

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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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