| The microstructures of spherical Ni(OH)2 was studied, and the preparation, the structure, and the relationships between them were carefully and systematically discussed. The growth processes and the structure formation mechanisms for the spherical Ni(OH)2 were penetrated. The causes to affect the electrochemical activities and the kinetics of the polarization processes of the electrodes for spherical Ni(OH)2 were also explored. It is important for the dissertation to develop the manufacture, the electrochemical performance, and the understanding of the relevant industry crystallization for spherical Ni(OH)2.When the low impeller of the reactor for preparing the spherical Ni(OH)2 is of turbine, the products show stable performance and high tap density. When the stirring strength is enhanced, the tap density and the average particle size increase.Two methods—impressing and cutting were successfully applied to attain the inner intersection samples in order to characterize the unique microstructures for spherical Ni(OH)2 particles. The spherical Ni(OH)2 with radial three-dimensional reticulate structure is disordered and badly crystallized with structure disfigurements showing the characteristics of βbc-Ni(OH)2. Its structural formula should be: Ni0.85(2H)0.15(OH)2.It was found by Electron Microscopy, X-Ray Diffraction and thermal analysis that the crystallites size decreases, and the disfigurements increase when the crystallites' morphologies on the surface of the sphere change with the sequence: piled platelets or thick planks, spindles or toothpicks, string of beads, clear grains and vague grains. The corresponding thermal decomposition temperature decreases and the thermal decomposition rate increases with the above sequence. So it was indicated that the corresponding structural regularity decreases.The formation mechanism of the unique microstructures for thespherical Ni(OH)2 was studied, and the Screen Growth Model was put forward to explain the interface growth of the aggregates. The aggregation is the main mechanism for the particles to grow up, and the recrystallization is the important cause of irreversible agglomeration. When either of two neighboring particles grows, the other shrinks and tends to disappear with the crystal interface moving. In this way the close radiate structure is formed.According to the effect on the structure of the crystallites decreasing for the spherical Ni(OH)2, the technical parameters follow the sequence: temperature, pH value and ammonia content. The structural regularity is improved with the temperature and ammonia content increasing and the pH value decreasing.Different kinds of work electrodes were prepared for different kinds of measurement methods: galvastatic charge/discharge, cyclic voltammetry (CV) and electrochemical impedance spectrum(EIS) to characterize the electrochemical performance of the spherical Ni(OH)2 electrodes. The polarization processes of the spherical Ni(OH)2 electrodes were analysed and modeled with R(Qi(RQ2)) equivalent circuit by EIS measurements. The charge transfer resistance slowly increases and proton diffusion impedance drastically decreases when the state of charge(SOC) of the spherical Ni(OH)2 electrode is enhanced. The proton diffusion rate at high SOC is higher than that at low SOC. The discharge capacity is negatively related to the charge transfer resistance and proton diffusion impedance, and the relativity to the former is higher than that to the latter.The electrochemical performance of the spherical Ni(OH)2 electrode characterized with discharge capacity is generally improved by enhancing the crystallization extent and the size of the crystallites on the surface of the spherical Ni(OH)2 particles, but perfect crystallization restrains the electrochemical activities and reduces the discharge capacity. The technical parameters of preparation influence the electrochemical performance through the microstructures. Too low and too high pH valuehave disadvantage to the discharge capacity, and the tap density decreases when the pH value is enhanced. When ammonia content increases, the tap density and the electrochemical performance of the products are enhanced.The unique microstructure of the spherical Ni(OH)2 is very stable and affords long cycle life. The crannies and holes in the crystallites and cleaves not only shorten the proton diffusion roads and speed the diffusion, but also facilitate the phase transform of electrochemical reaction. Therefore the spherical Ni(OH)2 shows much better integrated electrochemical performance than the normal Ni(OH)2.
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