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Preparation and Applications Studies of Co3O4 Ultra-fine Powder

Author: WuDaoMing
Tutor: ChenFanCai
School: Hunan University
Course: Applied Chemistry
Keywords: Co3O4 ultra-fine powder electrochemical method reverse microemulsion method doped Zr specific capacitance
CLC: O614.812
Type: Master's thesis
Year: 2011
Downloads: 69
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Abstract


More and more researchers committed to develop a kind of device, which can achieve efficient storage and transformation of energy, with intensified crisis of energy sources. Lithium-ion battery and super capacitor are such devices, which are commonly used. The performance of Co3O4 ultra-fine powder is excellent, it can be used as the main raw material to make lithium-ion battery and super capacitor, and the performance of Co3O4 ultra-fine powder can directly affect the performance of lithium-ion battery and super capacitor, so it is very important to prepare qualified Co3O4 powder to make lithium-ion battery and super capacitor.Co3O4 ultra-fine powder, which was expected to be used as the main raw material for lithium-ion battery, was successfully prepared by electrochemical method. The precursor Co（OH）2 basiclly converted to Co3O4 when calcination temperature was 400℃and calcinations time was 2 hours. The influence of parameters on the distribution of particle size of Co3O4 powder was studied, the parameters included the concentration of Co（NO3）2、current density、the kinds and concentration of additive、reaction temperature and reaction time. The optimal parameters was that the concentration of Co（NO3）2 was 0.3mol·L-1, current density was 600A·m-2, the additive was NH4H2PO4 and its concentration was 0.03mol·L-1 , reaction temperature was 35℃, reaction time was 2 hours. The result of XRD showed that the crystal of the product was face centered cubic phase. The result of SEM showed that the range of the particle size of the product was 4μm to 8μm, the morphology was tetrahedron, and it had good dispersion.Co3O4 ultra-fine powder, which was expected to be used as the main raw material for super capacitor, was successfully prepared by reverse microemulsion method.The components of reverse microemulsion could affect solubilization capacity, the components included the kinds of S、O and AS. The optimal components of reverse microemulsion was that S was TritonX-100, O was cyclohexane, AS was butanol. The influence of parameters on the regional area of reverse microemulsion was studied, the parameters included the mass ratio of AS to S、the concentration of CoCl2、the concentration of ammonia、temperature.The optimal parameters was that the mass ratio of AS to S was 1, the concentration of CoCl2 was 0.5mol·L-1, the concentration of ammonia was 5%, temperature was 25℃. Conductivity test showed that the reaction was basically completed when time was 2 hours. The result of SEM showed that the particle size and the morphology of the product would change when the value of R was changed. The result of XRD showed that that the crystal of the product was face centered cubic phase. The result of SEM showed that the particle size of the product was 190nm, and the morphology was sphere. galvanostatic current charge and discharge test showed that the maximum specific capacitance was 216F·g-1.Zr doped Co3O4 ultra-fine powder was successfully prepared by reverse microemulsion method. The influence of doping Zr on the morphology, phase composition, electrochemical properties of the products was studied. The result of SEM showed that the particle size of the product was to be smaller with doping Zr to some extent, the morphology of all products was sphere.The result of XRD showed that doping Zr could not change the crystal of the product, the crystal of all products were face centered cubic phase, and it would appear characteristic peak of monoclinic phase ZrO2 with high doping amount. Cyclic voltammetry （CV）、electrochemical impedance spectrometry （EIS） and galvanostatic charge-discharge tests indicated that the charge transfer resistance was to be smaller, the reversible was enhanced, the specific capacitance was increased, and the cycle life was improved with doping certain amount of Zr. The specific capacitance of the undoped product was 216F·g-1, The highest specific capacitance of 451F·g-1 was obtained when the molar ratio of Zr to Co was 5 to 95, which was 67% higher than that of the undoped product. After 800 charge-discharge cycles, the specific capacitance was only decreased 4.21%, while the specific capacitance of the undoped product was decreased 22.2%.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > First Ⅷ group metal elements and their compounds > Iron metal element > Cobalt Co
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