Publication: Zinc-air batteries employi ng tapioca binder in porous zinc anode
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Date
2009-05-01
Authors
Ng, Chai Yan
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Abstract
A zinc-air (Zn-air) battery was fabricated using the porous Zn anode, air cathode and sago gel electrolyte. The porous Zn anode has been fabricated from Zn powder using tapioca as a binder. Tapioca is biodegradable, non-hazardous, low cost and highly available. The tapioca binder concentrations were varied to obtain the best electrode composition. The electrode performance was evaluated from the Zn-air battery galvanostatic discharge capability and cyclic voltammetry (CV) characterization. The Zn-air battery employing 80 mg cm-3 of the tapioca binder in the porous Zn anode exhibited the best discharge performance compared to 60, 100 and 120 mg cm-3. The battery with 80 mg cm-3 of the tapioca binder has the cell capacity of 2002 mAh, specific capacity of 500.5 mAh g-1 and nominal voltage of 1.047 V. At this concentration, the binder is able to shield some portion of the Zn powder and provide a good binding between the Zn powders. Besides that, the binder is also not too viscous to encapsulate the Zn powder. For the CV characterization of the porous Zn anode, there were only three anodic peaks formed with the absence of the cathodic peak. The electrode degradation after discharge cycling was characterized by microstructural and structural methods. The analyses shown that the electrode failure was due to the formation of zinc oxide (ZnO) insulating layer on the electrode surface. The oxide layer blocked the utilization of the porous Zn anode and was identified as a cause for the failure of the battery.