JPS636747A - Zince alkaline battery - Google Patents

Abstract

PURPOSE:To decrease amalgamation ratio of negative zinc by containing a specified amount of indium and at least one element selected from lead, cadmium, bismuth, and tellurium, and barium in a zinc alloy to form a negative active material. CONSTITUTION:0.001-0.5wt% indium, 0.01-0.5wt% at least one element selected from lead, cadmium, bismuth, and tellurium, and 0.001-0.5 wt% barium are contained in a zinc alloy to form a negative electrode 2 as a negative active material. The negative electrode 2 is combined with a positive electrode 5 such as silver oxide, and a separator 4 to form a zinc alkaline battery. Corrosion resistant effect is increased by hydrogen overvoltage increasing capability of indium, segregation capability of lead and cadmium in the vicinity of grain boundary of zinc alloy, and affinity of barium with mercury. Therefore, amalgamation ratio is decreased and the battery having low environmental pollution and high performance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses zinc as a negative electrode active material, an alkaline electrolyte as an electrolyte, and manganese dioxide, silver oxide, or silver oxide as a positive electrode active material.
This invention relates to improvements in negative electrodes for zinc-alkaline batteries using mercury oxide, oxygen, nickel hydroxide, etc.

2. Prior Art Conventionally, a common problem with this type of zinc-alkaline battery is corrosion of the negative electrode zinc by the electrolyte during storage. Conventionally, it has been adopted as an industrial method to increase the hydrogen overvoltage by using frozen zinc powder, which is made by adding 5 to 10% by weight of mercury to zinc, and to suppress corrosion to a level that causes no practical problems. .

However, in recent years, there has been an increasing social need to reduce the amount of mercury contained in batteries in order to reduce pollution, and various studies have been conducted. For example, lead in zinc.

A method has been proposed to improve corrosion resistance and reduce the hydration rate by using an alloy powder to which cadmium, indium, gallium, etc. are added. These corrosion-inhibiting effects are not only due to the single additive element, but also due to the combined effect of multiple additive elements.Conventionally, indium and lead, or gallium added to these, and zinc alloys with gallium and lead added, etc. , has been proposed as a promising system.

In addition, zinc alloys in which gallium and silver are added to lead and cadmium (Japanese Unexamined Patent Publication No. 78062/1982), zinc alloys in which aluminum is added to gallium and thallium (Japanese Unexamined Patent Application Publication No. 1982-78062),
1-78061), and a zinc alloy in which one or more of silver, gallium, thallium, and cadmium are added to aluminum and lead (Japanese Patent Application Laid-Open No. 1982-78059).

Problems to be Solved by the InventionAlthough all of the zinc alloys proposed above can be expected to have a certain degree of corrosion resistance and a certain degree of reduction in the rate of icing, the effects of the combination of these elements are currently insufficient. Elucidating the alloy composition based on the effective combination K remains a future challenge.

The present invention solves these problems, and reduces the hydration rate without deteriorating the corrosion resistance of negative electrode zinc, resulting in low pollution and excellent overall performance such as discharge performance, storage performance, and leakage resistance. The object of the present invention is to provide a zinc-alkaline battery with a high temperature.

Means for Solving the Problems The present invention uses a zinc alloy containing 0.001 to 0.5% by weight of indium (In), lead (PB), cadmium (Cd), and bismuth as a negative electrode active material. As a result, the amount of mercury contained in zinc-alkaline batteries has been reduced.

Function Although the mechanism of action of each additive element in the zinc alloy of the present invention is unclear, the synergistic effect regarding corrosion prevention is inferred as follows.

First, since In has the effect of increasing hydrogen overvoltage and has a high affinity with mercury, In has the effect of increasing hydrogen overvoltage and has a high affinity for mercury. It is thought that Pb, Cd
etc., which tend to segregate near the grain boundaries of zinc alloys, and when zinc alloys are hydrated from the surface, they suppress the diffusion of mercury in the surface layer into the zinc alloy through the grain boundaries, reducing the mercury concentration on the surface. This is thought to contribute to maintaining a high level. Furthermore, since Ba has a high affinity with mercury, it is expected to have a similar anticorrosion effect to that of In, and is presumed to play a role in supplementing the effect of In.

As described above, the zinc alloy used in the present invention has a complex anti-corrosion effect in which each element complements each other with its unique action in order to maintain a high mercury concentration on the surface of the zinc alloy by hydrating it with a small amount of mercury. It is thought that this was effective. The present invention has experimentally investigated the combination of additive elements in this zinc alloy and their content, and has developed a low-pollution, highly practical zinc-alkaline battery that has a low hydration rate, sufficient corrosion resistance, and discharge performance. We have completed an effective means to achieve this.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Examples Various zinc alloys were prepared by adding the various elements shown in the following table to a zinc ingot with a purity of 99.997%, melted at about SOO°C, and powdered by spraying with compressed air. ~15
The particles were sieved in a particle size range of 0 mesh. Next, the above powder was put into a 10% by weight aqueous solution of caustic potash, and a predetermined amount of mercury was added dropwise while stirring to hydrate it. Thereafter, it was washed with water, replaced with acetone, and dried to produce a zinc hydrate alloy powder.

Further, frozen zinc powder or hydrated zinc alloy powder other than the examples of the present invention were also prepared in the same manner as comparative examples.

Using these hydrated powders, the button-shaped silver oxide battery shown in the figure was manufactured. In the figure, reference numeral 1 denotes a sealing plate made of stainless steel, the inner surface of which is plated with copper 1'. 2 is a zinc negative electrode prepared by gelling an electrolytic solution in which a 40% by weight aqueous solution of caustic potassium is saturated with zinc oxide with carboxymethylcellulose, and dispersing zinc hydrate alloy powder in this gel. 3 is a cellulose-based liquid retaining material, 4 is a porous polypropylene separator, 6 is a positive electrode made of a mixture of silver oxide and graphite and pressure molded, 6 is a positive electrode ring made of nickel-plated iron, and 7 is an inner and outer surface. This is a positive electrode can made of stainless steel with nickel plating. A polypropylene gasket 8 is compressed between the positive electrode can 7 and the sealing plate 1 by bending the opening of the positive electrode can 7 . The prototype battery has a diameter of 11
．． 6M, height 6.4, weight of frozen powder of negative electrode 19
The amount of mercury added (hydration rate) was 1.0% by weight based on the zinc alloy powder.

The following table shows the composition of the zinc alloy of the prototype battery, the changes in discharge performance and total battery height after storage at 60°C for one month, and the number of leaking batteries as determined by visual inspection. Discharge performance is 20°C
It is expressed as the discharge duration when discharged with a 51C1 load and a final voltage of 0.9V.

In this table, the total battery height generally decreases over time after the battery is sealed until the stress relationship between each battery component becomes stable. but,
In a battery in which a large amount of hydrogen gas is generated due to corrosion of the zinc negative electrode, there is a strong tendency to increase the total battery height due to an increase in battery internal pressure that counteracts the above-mentioned decrease in the total battery height. Therefore, the corrosion resistance of the zinc negative electrode can be evaluated by the increase or decrease in the total height of the battery due to storage. In addition, batteries with insufficient corrosion resistance will not only increase the total height of the battery, but also have their leakage resistance deteriorate due to an increase in battery internal pressure, and zinc will be depleted due to corrosion.

The formation of an oxide film on the zinc surface, the inhibition of the discharge reaction due to the presence of hydrogen gas, etc. cause the discharge performance to deteriorate significantly, and both the leakage resistance and the discharge duration greatly depend on the corrosion resistance of the zinc negative electrode.

As seen in this table, Ivy 1 which also added In alone
4 in which Pb or Cd or Bi or To was co-existing.
2, 3, and 4.6 all have good corrosion resistance, especially p
The combined effect of b is large. However, these are all 1.0
At a water conversion rate as low as % by weight, practically satisfactory properties are not obtained, and corrosion resistance cannot be said to be sufficient.

In contrast to these conventional examples, In, Pb, Cd, and Bi.

Among 6 to 32, in which one or more types of Te and Ba are co-existed, those with an appropriate content of each additional element exhibit excellent characteristics, which is due to the combination of Ba and other elements. This is due to the combined effect of f2 and JFL9, for example.
This is clear from the comparison between 3 and 422, f4 and 425, and f6 and &28. In addition, the appropriate content of each element is
In is 0.001 to 0.5% by weight, Pb, Cd, Bi,
The sum of the contents of one or more elements selected from 7e is 0.0
A zinc alloy containing 1 to 0.5% by weight and 0.001 to 0.5% by weight of Ba is effective, and if the content of each additional element is excessive or insufficient than the above, It shows characteristic values that are not much different from the conventional example or have the opposite effect. As described above, the present invention uses In and Ba as essential additive elements, and further includes P)1. At least one of Cd, Te, and Bi is an essential additive element, and in addition, Pb, Cd, Te, and Bi are added.
By using a negative electrode containing one or more of these as essential additives and a zinc alloy containing appropriate amounts of each element, we have achieved excellent practical performance such as discharge performance, storage performance, and leakage resistance with a low water conversion rate. This is a completed low-pollution zinc-alkaline battery.

In the examples, the method of adding additive elements was to add them to the molten zinc base metal, but when adding In or Ba, which easily forms into amalgam, the additive elements should be dissolved in advance and added to the molten zinc ingot. It is also possible to adopt a method of adding at the same time as oxidation. In addition, when adding In, which has a smaller ionization tendency than zinc, it can be precipitated on the surface of the zinc alloy through a substitution reaction with Zn in a solution such as indium chloride to form an alloy. Also, the same effects as the present invention can be obtained and are included in the embodiments of the present invention.

In addition, in the example, a battery using a 1.0% by weight frozen zinc negative electrode was explained, but if very strict storage performance or leakage resistance is required, the upper limit is about 3% by weight, and 1.0% by weight is used. There are cases in which it is appropriate to apply a freezing rate of 0% by weight or more.On the other hand, in air batteries equipped with an exhaust device or sealed zinc-alkaline batteries equipped with a hydrogen absorption mechanism, hydrogen gas is generated. Since the allowable amount is relatively large, LO weight%
It is also possible to carry out the process with an unhydrated ice rate, or in some cases, with anhydrous conditions.

Effects of the Invention As described above, the present invention can lower the hydration rate of negative electrode zinc,
It is extremely effective for obtaining low-pollution zinc-alkaline batteries.

[Brief explanation of the drawing]

The figure is a partially sectional side view of a button-shaped silver oxide battery used in an example of the present invention. 2...Zinc negative electrode, 4...Separator,
5...Silver oxide positive electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person2-
--t, -Koragemari Li-1 Paleta 5--Ichishundai Ginmi Tadashi

Claims (1)

[Claims] 0.001 to 0.5% by weight of indium and 0.01 to 0.5% by weight of one or more of lead, cadmium, bismuth, and tellurium.
A zinc-alkaline battery using a zinc alloy containing 6% by weight and 0.001 to 0.5% by weight of barium as a negative electrode active material.