JPS63178451A - Zinc alkaline battery - Google Patents

Abstract

PURPOSE:To increase the corrosion resistance of a zinc alloy used in a negative electrode to obtain a zinc alkaline battery having low environmental pollution and high practicality by utilizing a synergetic effect produced by the combination of added elements. CONSTITUTION:A zinc alloy containing 0.01-0.5 wt.% thallium, 0.01-0.2 wt.% aluminum, and 0.01-0.2 wt.% at least one of calcium, magnesium, and strontium is used as a negative active material. Thallium has a high effect on increasing hydrogen overvoltage, is well alloyed with mercury at room temperature, and increases hydrogen overvoltage on the surface of zinc. Addition of aluminium is related to the particle shape of atomized zinc powder. The particle of zinc is made globular and the surface of particle is made smooth. This reduces the surface area conducting corrosion reaction of zinc powder with electrolyte and increases corrosion resistance. By adding calcium, magnesium, or strontium together with aluminum, corrosion resistance is further increased. Therefore, a zinc alkaline battery whose amalgamation rate is low but practicality is high 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.
In zinc alkaline batteries using mercury oxide, oxygen, nickel hydroxide, etc., the present invention particularly relates to improvements in negative electrodes.

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. For some time now, it has been adopted as an industrial method to increase the hydrogen overvoltage by using zinc hydrate powder, which is made by adding about 5 to 10 parts by weight of mercury to zinc, and to suppress corrosion to the extent that there is no practical problem. There is.

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, zinc.

A method has been proposed in which t-alloy powder is added with cadmium, indium, gallium, etc. to improve corrosion resistance and reduce the rate of icing. These corrosion-inhibiting effects can be achieved not only by the effect of a single additive element but also by the combined effect of multiple additive elements, and indium and lead, or zinc alloys in which gallium is added to these, have been proposed as promising systems.

In addition, zinc alloys in which gallium and silver are added to lead and cadmium (JP-A No. 61-78062) and zinc alloys in which aluminum is added to gallium and thallium (JP-A-61-78062).
No. 78061), and zinc alloys made of aluminum and lead with one or more of silver, gallium, thallium, and cadmium added (Japanese Unexamined Patent Publication No. 78059/1983).

Problems to be Solved by the Invention Although all of these conventional zinc alloys can be expected to have some degree of corrosion resistance and can reduce the hydration rate to some extent, the effects of the combination of these elements are not sufficient at present. Elucidating the alloy composition based on effective combinations is 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. In order to provide the zinc negative electrode with the desired characteristics, the purpose is to select additive elements and appropriately combine their contents.

Means for Solving the Problem In order to solve this problem, the present invention provides thallium with 0.
01-0.5 wt%, aluminum o, 01-0.2
This is a zinc-alkaline battery using a zinc alloy containing 0.01 to 0.2 weight percent of at least one of calcium, magnesium, and strontium as a negative electrode active material.

EffectThe mechanism of action of each additive element in this configuration is not clear, but
The synergistic effect regarding corrosion prevention is inferred as follows.

First, thallium is highly effective in increasing the hydrogen overpotential and is well alloyed with mercury at room temperature, increasing the hydrogen overpotential on the zinc surface.

Zinc used in alkaline batteries is in the form of so-called atomized zinc powder, which is made by spraying and solidifying molten zinc with compressed air or the like. The addition of aluminum affects the particle shape of the atomized zinc powder, making the particles spherical and smoothing the surface, which reduces the surface area where corrosion reactions occur when the zinc powder comes into contact with the electrolyte, increasing corrosion resistance. can.

Adding calcium, magnesium, and strontium at the same time as aluminum has the effect of making the atomized zinc powder more spherical in shape and smoothing its surface, thereby further improving corrosion resistance.

It has been confirmed in basic corrosion resistance experiments that the above-mentioned additive elements, when added alone, have poor corrosion resistance, or rather have the opposite effect. It is thought that the combined addition reduces adverse effects due to the corrosion resistance of each additive alloy, and has a synergistic effect.

The present invention experimentally investigated the combination of additive elements and their contents in zinc alloys, and realized a low-pollution, highly practical zinc-alkaline battery that has a low hydration rate, sufficient corrosion resistance, and discharge performance. This is an effective means to accomplish this. This will be explained in detail below using examples.

Examples Various zinc alloys were prepared by adding various elements as shown in the table below to zinc ingots with a purity of 99. , sieved to a particle size range of 50 to 150 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, zinc hydrate alloy powders other than the examples of the present invention were also prepared in the same manner as comparative examples.

Using these hydrated powders, we fabricated the cylindrical alkaline manganese battery shown in the figure. In the figure, reference numeral 1 denotes a positive electrode case made of nickel-plated iron; inside is a positive electrode 2 made of a mixture of manganese dioxide and graphite that is pressure-molded; and a separator 3 made of polypropylene nonwoven fabric. Cellulose bottom plate 4. It houses a gel-like negative electrode 6 in which various frozen zinc alloys are dispersed in an electrolyte of aqueous caustic potassium solution gelled with carboxymethyl cellulose. 6 is a sealing plate made of polypropylene which seals the opening of the case 1, and a negative electrode current collector 7 made of brass is fixed in the center thereof. 8 is a negative terminal plate, 9 is a positive terminal plate, 10.11 is an insulating ring, 12 is a heat-shrinkable resin tube, and 13 is a metal outer can.

The prototype friend battery was an AA alkaline manganese battery, and the weight of the frozen zinc alloy powder used for the negative electrode was unified to 2.80y, and the amount of mercury added (hydration rate) was 2wt to the zinc alloy. %
And so. After storing the prototype battery at 60℃ for 1 month,
Continuous discharge performance under a 1Ω load and leakage resistance were evaluated in c. The breakdown of the zinc alloy used in the negative electrode and the test results are shown in the table below.

In batteries with insufficient corrosion resistance, the leakage resistance deteriorates due to an increase in the battery internal pressure, and the zinc is consumed due to corrosion, an oxide film is formed on the zinc surface, and the discharge reaction is inhibited due to the internal pressure of hydrogen gas. The discharge performance does not deteriorate significantly, and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode.

Muds 1 to 3 listed as comparative examples of the present invention in the table above
The corrosion resistance and discharge performance of the zinc negative electrode are better when added alone (&1, 2), when two types of elements are added (f;, 3), and when three types of elements are added. It has been improved somewhat.

However, an example of the present invention in which Tl, Al, Ca, Mg, and Sr were coexisting in an appropriate combination and in an appropriate content (
&es.

6.7,8,11. 12, 13, 16, 1, 18
In the case of 21.22, 23, 25, 26, 27, 28, 29.30), the corrosion resistance and discharge performance are even better than in the comparative example, and the combined effect of the added elements is remarkable. On the other hand, even when three elements coexist, there is an excess or deficiency in their content (4, 9, 10, 14° 16.19, 20.24
), there is no significant difference from the comparative example, and the combined effect is poor.

In line with the above, the present invention is based on T1. Al, Ca, Mg,
By appropriately combining Sr and using a zinc alloy coexisting at an appropriate content as shown in the example for the negative electrode, we succeeded in achieving a low aging rate. has Tl of 0.01 to 0.5% by weight and aluminum of 0.0% by weight.
It is appropriate that the total amount of calcium, magnesium, and strontium be 1 to 0.2% by weight, and the sum of at least one of calcium, magnesium, and strontium be 0.01 to 0.2% by weight.

As described above, the present invention has discovered that the corrosion resistance of zinc alloys used for negative electrodes is improved due to the synergistic effect of the combination of the above-mentioned additive elements, and by determining the appropriate content, zinc alloys with low pollution and excellent practicality have been developed. This is the realization of an alkaline battery. In the example, a battery using a zinc hydrate negative electrode was explained, but in open air batteries and sealed zinc-alkaline batteries equipped with a hydrogen absorption mechanism, the allowable amount of hydrogen gas generated is relatively large. Therefore, when the present invention is applied to such a case, it can be carried out with a lower rate of water retention, and in some cases, with anhydrous state.

Effects of the Invention As described above, according to the present invention, the freezing rate of negative electrode zinc can be reduced, and a zinc-alkaline battery with low pollution can be provided.

[Brief explanation of the drawing]

The figure is a half-sectional view of an alkaline manganese battery used in an example of the present invention. 2... Positive electrode, 3... Separator, 5...
...Zinc negative electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person2-
- Kazumasa Yuu 3---Ceno x Lator 5---H, supply and negative electrode

Claims (1)

[Claims] 0.01 to 0.5% by weight of thallium, 0% of aluminum
．． 0.01-0.2% by weight, 0.01-0.2% by weight of one or more of calcium, magnesium, and strontium
A zinc-alkaline battery that uses a zinc alloy as the negative electrode active material.