JPH0275160A - Zinc electrode - Google Patents

Abstract

PURPOSE:To provide a Zn electrode with high anti-corrosiveness, long lifetime, and less self-discharge by using alloy of Cu and Sn as electricity collecting material. CONSTITUTION:A plate-shaped electricity collecting body of 0.5mm thick and with an aperture ratio of approx. 50% is formed from Cu-Sn alloy for ex. containing 62wt.% Cu and 38wt.% Sn, and thereupon a sheet-shaped Zn active substance layer is molded fast under pressure to form a Zn electrode. This electricity collecting material made of Cu-Sn alloy has a high hydrogen over- voltage and excellent anti-corrosiveness. Inclusion of a metal with high hydrogen over-voltage, for ex. Cd, in a minute amount does not influence the performance. This Zn electrode may be used for both primary battery and secondary battery.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is applicable to the use of zinc in the negative electrode of nickel-zinc batteries, nickel-zinc batteries, etc. This invention relates to an alkaline zinc secondary battery that uses electrodes and mainly uses an alkaline solution as the electrolyte.

Conventional technology and its problems As current collector materials for alkaline zinc electrodes, silver or copper metal nets, expanded metals, pan-thousand metals, etc. are known, and iron, copper, zinc, tin, cadmium, lead, etc. It is known to plate metals with high hydrogen overvoltage, such as thallium, indium, and mercury. Furthermore, brass is also known as an example of using an alloy. Silver is more expensive than zinc, which is an active material, and poses a cost problem. On the other hand, copper is relatively cheap and has excellent electrical conductivity, but when steel is used as a current collector, copper oxides are formed on the surface of the current collector during electrode plate manufacture, and these oxides are deposited inside the battery. Dissolve with. Furthermore, when using a battery, if a deep discharge is reversed, or if the battery is left unattended with a load connected, electrochemical corrosion of the current collector material occurs, and copper oxidizes and dissolves. Alternatively, the surface of copper is covered with copper oxide, reducing electrical conductivity.

Moreover, the copper ions eluted at this time are reprecipitated on the negative electrode by charging. This deposited copper has a large surface area and reduces the hydrogen overvoltage of the zinc electrode, which tends to cause self-discharge of the zinc.

Furthermore, in sealed batteries, the hydrogen gas generated during self-discharge is known to suppress the pressure rise inside the cell and cause leakage, but iron has a low hydrogen overvoltage, and iron alone has a low hydrogen overvoltage. It had the disadvantages of self-discharge, making it unusable, and poor electrochemical corrosion resistance.To compensate for these disadvantages, a method of surface coating by plating with the aforementioned metal with high hydrogen overvoltage was proposed. be.

However, with this surface treatment, the thickness of the coating is uneven, and furthermore, scratches may occur after the treatment, exposing the base metal such as the saw or iron. This causes self-discharge and a decrease in capacity of the sub-K) pole. ＠In paulownia, cadmium, mercury, thallium, etc. are highly toxic, and their use must be avoided as much as possible from the viewpoint of non-pollution.

Although tin exhibits fairly good characteristics initially, it has the disadvantage that the surface coating gradually peels off and the base metal is gradually exposed when repeated deep discharges or when used in a heating device connected to the negative electrode.

Furthermore, when brass is used as a current collector using a metal alloy, there are disadvantages such as not only copper being oxidized due to corrosion of the current collector, but also only zinc in the alloy being leached out, weakening the strength of the current collector. Ta.

OBJECTS OF THE INVENTION It is an object of the invention to provide a zinc electrode with improved corrosion resistance of a current collector material, excellent life performance, and reduced self-discharge.

Structure of the Invention In order to achieve the above object, the present invention uses copper as a current collector,
This is a zinc electrode characterized by using a tin alloy.

Example Hereinafter, the details of the present invention will be explained using one example.

One example of various copper-tin alloys produced as the metal material used for the current collector was shown.

Copper metal is melted in advance, and metal tin is added and melted to form copper 6.
A copper-tin alloy containing 2 wt% and 38 wt% tin was produced.

This was made into a plate-like current collector with a thickness of 0.5 tntrr and a porosity of cotton of 50%. The electrochemical corrosion properties of this current collector material were investigated using constant potential electrolysis method.

The result was approximately 10% less than conventionally used copper.
It was found that it has 0 times the corrosion resistance.

Furthermore, an improvement of approximately 50 mV in hydrogen overvoltage was introduced.

Using this current collector, sheet-like zinc active material layers produced by a calendar roll method were pressure-molded on both sides. A zinc electrode with a length of 50 x 30 x thickness was obtained.

The bird oil material may also be applied by a pasting method.

The four zinc electrodes thus obtained and the six nickel electrodes of the same size were stacked alternately with separators made of a microporous film, a cellophane membrane, and a nylon nonwoven fabric interposed in between to form a battery of the present invention with a battery capacity of 3AH. zinc! A nickel-zinc storage battery (G) using electrodes was created. In addition, as a comparison, a current collector material for a battery using a conventionally known collection material: silver, (
C) Current collecting material: Copper, ■) Taking the hammer: Sparrow on the hook, (G)
) Current collector: Sparrow on iron, σ) Current collector: Sparrow on nickel.

Using these batteries, we conducted a charge/discharge cycle test with a deep discharge depth using a long-term continuous load connection method, which is a usage condition where electrochemical corrosion is likely to occur. The test conditions are 0 charge
．． The discharge was carried out at 1OA for 12 hours, and the discharge was repeated for 20 hours at a load resistance equivalent to 0.10. The results are shown in Figure 1.

As can be seen from FIG. 1, among the conventionally used current collector materials, battery 03) using silver has the best characteristics. It can be seen that the battery (4) using the current collector of the present invention has almost the same performance as the battery ω) using silver. Batteries () to (g) are made of copper, iron, and nickel coated with tin plating, respectively, and all of the batteries exhibited fairly good characteristics during the initial several dozen cycles, but rapidly deteriorated.

This is because the tin coated on the surface with plating is oxidized and peeled off due to electrochemical corrosion. The reason why nickel and iron are so bad is that the hydrogen overvoltage of nickel and iron exposed on the surface due to tin peeling is low, which deteriorates the self-discharge performance and charge acceptance of the zinc electrode. The present invention eliminates peeling, which is a drawback of tin pricking, by using an alloy of copper and tin, and provides a current collecting side that is resistant to overdischarge.

The current collecting side used in the zinc W electrode of the present invention aims to improve performance especially when used at a deep discharge depth, and the performance required of the current collecting material is that hydrogen overvoltage must be high to prevent self-discharge. , and is required to have excellent corrosion resistance against electrochemical corrosion. A current collector made of a copper-tin alloy has a high hydrogen overvoltage and excellent corrosion resistance. Moreover, in terms of cost, it is very cheap compared to silver.

Furthermore, even if metals with high hydrogen overvoltage, such as cadmium, indium, thallium, bismuth, zinc, mercury, and silver, are mixed into the copper-tin alloy, the above-mentioned performance will not be affected.

Furthermore, the other battery N and the pole of the present invention can be used not only as a secondary battery but also as a primary battery.

Effects of the Invention As mentioned above, the present invention is a collection! Since it is possible to provide a zinc electrode with improved phase corrosion resistance, excellent life performance, and stagnant self-discharge, its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram comparing the charge/discharge cycle test characteristics of a battery using a zinc electrode of the present invention and a battery using a zinc electrode using a conventional current collector.

Claims (1)

[Claims] A zinc electrode characterized by using an alloy of copper and tin as a current collector.