| Summary: | 碩士 === 明志科技大學 === 化工與材料工程研究所 === 97 === The purpose of this work is to improve the life-cycle of a Zn electrode on a secondary Ni/Zn battery. As we know, the application of the secondary Zn electrode on the rechargeable Ni/Zn battery is still limited because of the dendritic growth, the shape change, and the high solubility in a concentrated KOH solution for the Zn electrode. The calcium zincate powders used as active materials (so-called CP-ZnCa) for the secondary Zn electrode were prepared by a chemical co-precipitation (CP) method. The preparation condition of CP-ZnCa active materials was at 60oC and pH=12. Moreover, the CP-ZnCa powders show higher surface area (28.66 m2 g-1) and smaller particle size, and the chemical uniformity of the CP-ZnCa powers was extremely good. The characteristic properties of CP-ZnCa powders were systematically examined by thermal gravimetric analysis (TGA), X-ray diffraction (XRD) analysis, Brunauer-Emmett-Teller (BET) measurement, Transmission electron microscope (TEM), and micro-Raman spectroscopy. As a result, the electrochemical performance of CP-ZnCa powders was much better than that of BM-ZnCa powders.
In order to avoid the dendritic growth of the secondary Zn electrode, the zinc electrodes generally need a suitable micro-porous polymer membrane during the charge/discharge process. In this work, we prepared two types of new micro-porous polymer membranes, namely, the micro-porous PVA/PVC and PVA/PEO composite polymer membranes, for the secondary zinc electrode. The secondary zinc electrode by using CP-ZnCa powders coated on the brass screen wrapped with the micro-porous PVA/PVC or PVA/PEO composite polymer membranes was prepared and studied. Using cycle voltammetry to examine the cycle-life of the secondary zinc electrode, it was found that it exhibited at least 200 life-cycle. In addition, the secondary Ni/Zn battery was prepared and examined by using galvanostatic test method at the C/5 charge and the C/5 discharge rates. The experimental result revealed that the secondary Ni/Zn battery showed at least 50 life-cycle; moreover, the current and energy efficiencies of the Ni/Zn battery were about 80% and 70%, respectively.
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