Electrodeposition of zinc for applications in zinc-air cell /
Porous zinc electrodes are prepared from an acidic, chloride electrolytic bath for application in zinc-air microbattery. The aim is to produce a high specific surface area zinc coating in order to obtain high storage capacity and high limiting current density of the microbattery. The correlation bet...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kulliyyah of Engineering, International Islamic University Malaysia,
2012
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | Porous zinc electrodes are prepared from an acidic, chloride electrolytic bath for application in zinc-air microbattery. The aim is to produce a high specific surface area zinc coating in order to obtain high storage capacity and high limiting current density of the microbattery. The correlation between the physical properties of zinc electrodeposits and zinc-air cell discharge performance is also studied. The electrolytic bath consists of zinc chloride as the metal source and ammonium chloride as the supporting electrolyte. The concentration of the supporting electrolyte is varied from 0 to 4 M, while the concentration of zinc chloride is fixed at 2 M. The electrodeposition is performed at a constant current density of 100 mAcm-2 for duration of 90 minutes. No electrolyte agitation is attempted. Zinc electrodeposits are characterized according to their X-ray diffraction (XRD) patterns, Scanning Electron Microscopy (SEM) observation, electronic densimeter measurement, and specific surface area and pore volume density determinations from the nitrogen physisorption isotherms at 77 K. X-ray diffractograms and supported by SEM observations are used as main instruments to identify variation in the zinc electrodeposits characteristics. SEM micrographs reveal unique porous network morphology of zinc electrodeposits. As the ammonium chloride concentration increases, flake microstructure appeared and later becomes predominant. High surface area and porous zinc electrodeposits have been prepared by electrodeposition; the BET surface area is in excess of 330 m2 g-1 and the electrode porosity is at least 60 %. Alkaline zinc-air microbattery, 1 cm2 area x ca. 305 μm thick, is fabricated utilizing the zinc electrodeposits prepared from all electrolytic bath formulations and characterized according to its limiting current density and discharge capacity. The cell is able to deliver a maximum limiting current density of 55 mA cm-2 and produce an optimum discharge capacity of 34.5 mAh rated at 20 mA. It is discovered that the variation in limiting current density matches that of BET surface area and the trend for discharge capacity resembles that of pore volume density. These results suggest that zinc-air electrochemical system or metal-air electrochemical system in general can be utilized to gauge porous electrode properties. It is further supported by the fact that since oxygen is not stored within the system and is consumed directly from the ambient air, any variation in the metal-air electrochemical cell performance can be attributed almost exclusively on the metal anode properties or porous electrode properties in this context. Though it might not be a quantitative method, this technique is particularly useful for rapid screening or defect detection purposes. Other advantages include easy test cell assembly, do not require special sample preparation such as degassing, ambient temperature measurement, immediate data interpretation, quick results and low cost. |
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| Item Description: | Abstract in English and Arabic. "A thesis submitted in fulfilment of the requirement for the degree of Master of Science (Materials Engineering)."--On t.p. |
| Physical Description: | xiv, 95 leaves : ill. charts ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 73-78). |