아연-산화은 2차 전지의 아연극에 미치는 첨가제의 영향

Abstract

Zn electrode is being widely used as an anode material in alkaline battery systems. It was well known that Zn electrode is comparatively low cost and has a good electrochemical equivalent (820 Ah/Kg) and high open-circuit voltages (OCVs) in many kinds of battery systems.

When Zn electrode was used in highly concentrated KOH electrolyte, however it has a high dissolution rate and a rapid electrochemical reaction. And shape change is often occurred due to the replacement of active material of zinc and the undesirable morphology caused by dendrite growth, so that the cycle life of Zinc electrode as a secondary battery is significantly shortened rather than that of other electrodes.

Therefore, in order to the undesirable characteristics of Zn electrode modification, lots of studies have been carried out such as Zn electrode mixed with Hg, Cd and As etc., replacement of seperator surrounding Zn electrode and adding inhibitor in alkaline electrolyte to decrease corrosion rate of Zn electrode.

In this study, corrosion resistance and charging/discharging characteristics of the Zn electrode were investigated with adding Pb3O4 as well as some additives such as Ca(OH)2, citrate, tartrate and gluconate to electrolyte.

To examine the electrochemical behavior on the Zn electrode were such as various experimental methods measurement of variation of corrosion potential as submerged time, Tafel analysis obtained by potentiodynamic polarization curves, cyclic voltammetry, accelerated cycle life test, and SEM photographs etc. were performed.

Experimental procedures are composed of three parts.

1. 0.5 wt. % Pb3O4 and 4 types additives as electrolyte additives showed a good effect on the electrochemical behavior of Zn electrode. Especially tartrate had a best effect among those additives.

2. Zn electrode with addition of Pb3O4 improved not only the corrosion resistance but also properties of charging/discharging voltage.

3. 5 wt. % Pb3O4 was the optimum amount adding to Zn electrode to increase the corrosion resistance.

4. Tartrate among those additives had the best effect compared to other additives on the pure Zn electrode as well as Zn electrode with addition of 5 wt. % Pb3O4.

1. The corrosion potential of Zn electrode added with Pb3O4 showed more positive potential than the value of the pure Zn electrode and its potential has a tendency to descend as additives were added.

2. The corrosion potential of both the Zn electrode mixed with Pb3O4 and the electrode in solution added with additives were generally stable even though time goes by and the corrosion current density also had a tendency of decreasing in general. When the tartrate was added the lowest corrosion current density was obtained at the 7 th day compared to other additives.

3. For the 50th cyclic voltammetric test, both the activity limit current density and the reduction current density have a comparatively large value when tartrate was added.

4. In the charge/discharge cyclic test, dropping range of discharging voltage and charging voltage in the presence of additives were smaller comparing with the case of the pure Zn electrode as numbers of cycle were being increased.

5. In the SEM photographs particle sizes were increased bigger pattern as additives were added. When tartrate was added, the crystal particles were smaller than those of other additives, so dense surface patterns were also obtained.

6. In the result of this study, it was shown that corrosion resistance could be improved with adding Pb3O4 to the Zn electrode. And it was considered that the corrosion resistance and charge/discharge capacity together coubld be also improved predominantly when some additives were added. Especially, when tartrate was added, the result has the best effect.

And the summary of the results are as follows

1. Zn electrode added with Pb3O4 showed more positive potential than that of pure Zn electrode.

2. In case of 3 and 5 wt. % Pb3O4 addition to Zn electrode, their corrosion potentials were comparatively stable and also corrosion current densities were decreased rater than that of no addition of Pb3O4.

3. Variation of charging / discharging voltage with increasing of cycle life test numbers of the Zn electrode with addition of Pb3O4 was smaller than that of pure Zn electrode.

4. 5 wt. % Pb3O4 addition showed the considerably improved corrosion resistance as well as improved charging and discharging characteristics rather than any other adding amount of Pb3O4.

Chpater 5 is to examine the corrosion resistance and charging / discharging characteristics of the Zn electrode mixed with 5 wt. % Pb3O4 as the other additives were added to 40 wt. % KOH electrolyte at 25℃. Especially their comparative evaluation of each other effect was investigated with electrochemical methods.

The results obtained were as follows

1. Corrosion potential was shifted to positive direction with increasing of addition of Pb3O4, however the addition of 0.5 wt. % Pb3O4 indicated comparatively stable potential not arising corrosion potential.

2. The addition of Pb3O4 increased the corrosion resistance compared to no addition, however, in case of mixed with some additives to Pb3O4 its resistance was decreased more or less than that of no addition.

3. In the SEM photographs, the addition of tartrate showed the fine morphology similar to only Pb3O4 addition while some additives (Ca(OH)2, citrate and gluconate )indicated dendrite growth.

4. It was well known that tartrate addition has a good effect not only improvement of corrosion resistance but also improvement of charging / discharging characteristics.

Chpater 4 is to investigate the effect of Pb3O4 on the corrosion resistance of Zn electrode when Pb3O4 was mixed to Zn material.

The results obtained were as follows.

Chaper 3 is to confirm the optimum amount of Pb3O4 and the effect of additives when they are added to KOH 40 wt. % electrolyte.

The results obtained were as follows