Study On Anodic Materials For Nikel-Zinc Secondary Cells

Advanced rechargeable batteries have long been recognized for the capacity to efficiently convert and store electrical energy, which is now used in a myriad of devices, such as electronic product and electric vehicles. The worldwide market for batteries is expected to grow along with our increasing use of electricity and electrical devices. Much of the recent research and development on advanced rechargeable batteries has been driven by such applications, and Ni-Zn alkaline secondary batteries is the leading candidates for the same reason, which has remarkable advantages of high specific energy and power, good low-temperature performance, low cost and environmental toxicity. However, widespread commercialization of Ni-Zn alkaline secondary batteries has been with some shortcomings and we must always endeavour to improve it. This problem has been derived from the redistribution of Zn active material such as shape change and the formation of unwanted Zn electrode morphologies during recharge, which is mainly dendrites, and the high solubility of zinc discharge products in the electrolyte. Increasing efforts have been devoted to overcome these difficulties, including:(1) additives to the anode and the electrolytes;(2) development and improvement of separators;(3) miscellaneous techniques such as pulse charging. Base on these points, the present work discussed the effects on the electrochemical properties of different morphology of ZnO as anode materials for Ni/Zn secondary batteries. The method of preparing calcium zincate as unearthly perfect electrode materials was improved. Besides, the electrochemistry performances of ZnAl-CO3-LDHs as a novel anode material for Ni-Zn secondary cells were also discussed.The hollow fusiform ZnO and hexagonal taper-like ZnO have been prepared by hydrothermal method. The synthetic materials have been characterized by XRD, and SEM, which is shown that the samples had evenly distuibuted sizes, good crystallization. As anode materials for Ni/Zn cells, the hollow fusiform ZnO and hexagonal taper-like ZnO on electrochemical performance have been investigated by cyclic voltammetry (CV), and galvanostatic charge-discharge measurement. The hollow fusiform ZnO and hexagonal taper-like ZnO have shown better cycle stability and higher discharge plateau. The better electrochemical performance is attributed to higher electrochemical activity, which is ascribed to the novel initial shape and size of as-prepared ZnO active material. The original morphology unchanges essentially and the zinc dendrite are suppressed effectively, which result in the improvement of cycle stability of Ni/Zn secondary cells.As a novel anode material for Ni-Zn secondary cells, ZnAl-CO3layered double hydroxides (LDHs) were prepared by the constant pH coprecipitation method. The Fourier Transform Infrared Spectroscopy (FTIR) spectra, X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images shown that the sample was well-crystallized and had the plate-like morphology. Cyclic voltammetry (CV) was utilized to inspect the electrochemical performance of ZnAl-hydrotalcites as a novel anode material for Ni-Zn secondary cells. The results show that the reversibility of the electrode reaction became obviously better in the alkaline system, good cyclical stability and the higher rate of capacity retention, which was attributed to the lamellar structure of ZnAl-CO3-LDHs and the trivalent aluminum ions. However, from the average internal resistance curves, it can be found that the internal resistance of the cell was comparatively large so that this novel anodic material need to be further improved. Furthermore, the electrochemistry performances of ZnAl-CO3-LDHs with different Zn/Al molar ratio were discussed. The results show that the ZnAl-CO3-LDH with Zn/Al (molar ratio)=4/1) had a better electrochemical performance than others.The calcium zincate were prepared in the different alcoholic solutions. The X-ray diffraction(XRD) patterns, scanning electron microscopy(SEM) images and Fourier Transform Infrared Spectroscopy (FTIR) spectra shown that the sample was well-crystallized and had regular morphology. It is indicated that this method could be used for calcium zincate preparation. But the samples were different. In the ethanol solution, the calcium zincate sample had good crystallization and uniformity and integrated morphology. There is ZnO impurity in the samples that were prepared in the isopropanol and normal butanol solutions, which is indicated that the synthetic reactions are incomplete. Furthermore, the electrochemical performance of zinc electrode of Ni-Zn battery was greatly changed, which was confirmed by CV and EIS. From the galvanostatic charge-discharge measurement, the higher charge transferred resistance of the calcium zincate electrodes have no effect on cycle performance, but the samples that prepared in different alcoholic solution have some difference with electrochemical activity, which is put down to ZnO impurity content. The calcium zincate that were prepared in the ethanol solution has good electrochemical behavior.