The Preparation And Electrochemical Properties Research Of Sphere And Nano-Structure Nickel Hydroxide

This thesis has involved in the synthesis ofβ-Ni(OH)2 andα-Ni(OH)2by adopting complex method, and the prepared samples have aslo been characterized by XRD, FSEM and IR. The electrochemical properties ofβ-Ni(OH)2 andα-Ni(OH)2 were investigated. The conclusions are shown as follows:(1) The nanostructured sphericalβ-Ni(OH)2 has been prepared by adopting complex method. We have obtained the optimal conditions of preparingβ-Ni(OH)2 and the affecting order of factors on the electrochemical properties ofβ-Ni(OH)2 through the orthogonal experiments and single factor experiments. The optical conditions are:cNH3=3.0 mol/l,pH=11.45, cNi2+=1.2 mol/l,cOH-=2.4 mol/l,T=50℃.The order of affecting factors is:cNH3> pH> CNi2+> T. XRD and FSEM analysis has shown that the sample is 8-20μm in diameter. In the electrochemical properties, the charge and discharge performance was tested at different current densities. After comparing the experimental results, we have decided to use 2000 mA/g for the current density in our research. Constant current charge-discharge test in 2000 mA/g of the sample indicates that the sample has good fast charge and discharge performance. The high-pressure section of the discharge specific capacity is up to 219～277 mAh/g. Cyclic voltammetry test shows that the reversibility of theβ-Ni(OH)2 sample is good.(2) Al-substitutedα-Ni(OH)2 in which the content of Al is 17mol% has been prepared. The sample not only has a good spherical structure, but also has a developed nano-second structure which displays the excellent electrochemical properties. The constant current charge-discharge experiments have demonstrated that the discharge specific capacity is 354 mAh/g at current density of 250mA/g, which is much higher than the theoretical discharge specific capacity ofβ-Ni(OH)2(289 mAh/g). After 200 cycles, the discharge capacity can still retains 238 mAh/g, which shows a good charge and discharge performance. In addition, we have investigated the influence of the dropping speed of the reaction solution to the electrochemical performance. The results of experiments indicate that when the dropping speed is much too high, the discharge specific capacity will be significantly weakened. Therefore, appropriate dropping speed should be controlled in the preparation ofα-Ni(OH)2.(3) The spherical Al(OH)3 which has a good chemical activity has been prepared. The Al(OH)3 mentioned above andβ-Ni(OH)2 have been used to prepare the Al-doppedα-Ni(OH)2at the appropriate conditions of temperature, pH and molar ratio. XRD spectra has illustrated that the products acquired by this method are the mixture of a-Ni(OH)2 andβ-Ni(OH)2.