아연 전극의 성능에 미치는 전해질 첨가제의 영향

Abstract

The zinc electrode is one of the most widely used as an anode material in alkaline battery systems, and the silver-zinc system has the highest gravimetric energy density and the highest volumetric energy density among all of the rechargeable batteries. Some rechargeable lithium batteries are reported to have better performances. They are, however, still in reserach stage having several defects, for example small size, limited rate capability, moreover, being considered as an obstacle eventual use due to the safety problem and the environmental concern. The advantage of using zinc electrode are low cost, good electrochemical equivalent (820 Ah/Kg) and high open-circuit voltages (OCVs) in most of battery systems. But its cycle life as secondary battery is very short, because the shape change is occurred by the replacement of zinc active material and the dendrite growth causing undesirable morphology .

Generally the methods of improvement of zinc electrode's characteristic are mixing Hg, Cd, As with zinc active materials in manufacturing process, changing their separator or adding small amount of additives into alkaline electrolyte.

In this study, four kinds of experiments were performed in order to investicat the effects of additives by adding four types additives which have been reported to show an effect on improving the performance of silver-zinc secondary battery systems with zinc anode, and Pb₃O₄ to inhibit the dissolution of zinc into KOH electrolyte.

Firstly, the potential versus submerged time as to the variation of the quantity of additives was measured in order to select the most appropriate quantity of Pb₃O₄.

Secondly, executed potentiodynamic polarization test was performed in order to measure the degree of corrosion of zinc electrode.

Thirdly, conducted charge-discharge cycle life test was performed.

And finely the morphology of the surface of zinc electrode was analyzed through SEM (Scanning Electron Microscope) photographs.

The results of this study are as follows :

1) The result of potential vs. submerging time for 21days showed that potential of Zn electrode contained its properties in case of 0.5 wt.% of Pb₃O₄ when Zn electrode was set in 40 wt.% of KOH as to the quantity of Pb₃O₄ 0.5, 1.0 and 2.0 wt.% and four types additives .

2) The result of polarization test in case of 40 wt.% KOH electrolyte with 0.5 wt.% of Pb₃O₄ and the four types additives was that the protection property of Pb₃O₄ showed the best performance and then followed by tartrate. In case that nothing was added(here in after referred to No Addition), it showed the worst performance.

3) The result of charge-discharge cycle life test showed that the property of charge and discharge, when the additives were added, was better case of No Addition. Especially the discharge property of tartrate showed the best result, and the charge property was good also.

4) The result of SEM analysis showed that the shape change and the dendrite growth of Zn electrode surface was noticed with the lowest amount in case of adding tartrate and Pb₃O₄ showed fair performance for three days.