JPH0622119B2 - Zinc alkaline battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide as a positive electrode active material.
The present invention relates to improvement of the negative electrode of a zinc-alkaline battery using mercury oxide, oxygen, nickel hydroxide, etc.

2. Description of the Related Art A common problem with zinc alkaline batteries is corrosion of the negative electrode zinc during storage by the electrolytic solution. Conventionally, it has been adopted as an industrial method to add about 5 to 10% by weight of mercury to zinc to suppress corrosion to the extent that there is no practical problem. However, in recent years, reducing the amount of mercury contained in a battery has become a social need to reduce pollution, and various studies have been made. For example, lead in zinc,
There has been proposed a method of improving corrosion resistance and reducing the conversion rate by using an alloy powder to which cadmium, indium, gallium, etc. are added. In addition to the effect of a single additive element, these corrosion inhibition effects have a large composite effect of multiple additive elements. Indium and lead, or those in which gallium is further added, and zinc alloys in which gallium and lead are added, etc. Conventionally, it has been proposed as a promising system.

All of these can be expected to have a certain degree of corrosion resistance, and although it is possible to expect a reduction in the degree of conversion to a certain extent, it is necessary to search for alloy systems with even better corrosion resistance.

In addition, there is a proposal that using a zinc alloy obtained by adding indium to zinc or a zinc alloy to the negative electrode has a great anticorrosion effect mainly for the purpose of improving a manganese dry battery (Japanese Patent Publication No. 33-3204).

Problems to be Solved by the Invention In the above proposals, Fe, Cd, Cr, Pb, Ca, Hg, Bi, Sb and A are used as elements in the zinc alloy in addition to indium.
Although it is described that it includes 1 or 2 or more as impurities or additives such as l, Ag, Mg, Si, Ni, Mn, etc., it is not effective when indium and lead are used in combination as additive elements. In, the classification of whether each of the above-mentioned miscellaneous elements is included as an impurity or added as an effective element is not clearly indicated, and it is not clear even which element is effective for anticorrosion. There is no description other than indium and lead.

It is still a future subject to investigate the effect of the combination of these elements, and further to investigate this in a zinc alkaline battery to obtain an effective alloy composition.

INDUSTRIAL APPLICABILITY The present invention reduces the corrosion rate of the negative electrode zinc without degrading the discharge performance, the discharge performance, the storability, and the low pollution.
It is an object of the present invention to provide a zinc-alkaline battery having excellent overall performance such as leakage resistance.

Means for Solving the Problems The present invention is directed to an electrolytic solution containing an alkaline aqueous solution containing caustic potash or caustic soda as a main component, a negative electrode active material containing zinc, and a positive electrode active material containing manganese dioxide, silver oxide, oxygen, and oxidation. For a negative electrode of a so-called zinc alkaline battery using mercury or the like, zinc is a main component, indium is 0.005 to 0.5% by weight, strontium is 0.005 to 0.2% by weight, aluminum,
0.005 for one or more of calcium and magnesium
It is characterized in that a zinc alloy containing 0.2 to 0.2% by weight is used as a negative electrode active material.

In the present invention, an experiment was conducted paying attention to Sr as an additive element to a zinc alloy, and a zinc alloy containing Sr alone has a poor anticorrosion property, but has a large composite effect with other additive elements. It has been completed by finding that a very remarkable composite anticorrosive effect can be obtained when an appropriate amount is contained in combination with the element.

The mechanism of action for the anti-corrosion effect by addition of each element and the combined effect of these elements is unclear, but it is presumed as follows. First, since Sr has a high affinity with mercury, it is considered that it has an action of facilitating uniform grading when grading the surface of the zinc alloy. Further, it has a function of eliminating "wrinkles" on the surface of the zinc alloy powder pulverized by spraying the molten zinc alloy and smoothing it. However, since Sr has an electrochemically base potential lower than that of zinc, it is more likely to corrode preferentially than zinc, and addition of this alone does not provide a sufficient anticorrosion effect. In addition, In is conventionally known as an additive element having a large anticorrosion effect, and is effective in increasing the hydrogen overvoltage of a zinc alloy and being easily compatible with mercury. Therefore, it is effective in homogenizing the surface state by grading. It is also expected to have a role of fixing mercury on the surface and grain boundaries of Al to keep the mercury concentration on the surface high. Further, Al, Ca, and Mg all have a low affinity with mercury, and thus suppress the diffusion of mercury into the zinc alloy to maintain the mercury concentration on the surface and, like Sr, are obtained by the injection method. It has the effect of smoothing the surface of the zinc alloy powder and reducing the surface area. However, since it has a base potential similar to that of Sr, sufficient addition of the anticorrosion effect cannot be obtained by adding it alone, and excessive addition will impair the anticorrosion property.

As described above, it is considered that each additive element has a different action. However, although the addition of any elements other than In has a poor anticorrosion effect, the addition of elements in the combination of the present invention yields a zinc alloy having much better corrosion resistance than the addition of In alone. This is because the above-mentioned elements complement each other's strengths and weaknesses, and by adding a small amount of mercury, the hydrogen overvoltage on the surface of the zinc alloy powder is maintained for a long time and the surface condition is made uniform, further reducing the surface area. It is thought that this is due to the result. The present invention thus realizes a corrosion-resistant zinc negative electrode with a low selection rate,
It provides a low-pollution zinc-alkaline battery with excellent storage properties.

Hereinafter, detailed description will be given with reference to examples.

Example Various zinc alloys were prepared by adding various elements shown in the following table to a zinc ingot having a purity of 99.997%, melted at about 500 ° C. and sprayed with compressed air to be powdered, 150
It was sieved to the particle size range of the mesh. Then, 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 effect hydration. Then wash with water,
It was replaced with acetone and dried to prepare a zinc fluoride alloy powder. Further, zinc fluorinated powder or zinc hydride alloy powder other than the examples of the present invention was prepared by the same method as a comparative example.

A button type silver oxide battery shown in the figure was produced using these selected powders. In the figure, 1 is a stainless steel sealing plate, the inner surface of which is plated with copper 1 '. Reference numeral 2 is a zinc negative electrode in which a 40 wt% aqueous solution of caustic potash was used to gel an electrolytic solution saturated with zinc oxide by carboxymethyl cellulose, and a zinc halide alloy powder was dispersed in the gel. 3 is a cellulosic liquid-retaining material, 4 is a separator made of porous polypropylene, 5 is a positive electrode formed by mixing silver oxide with graphite and pressure-molded, 6 is a positive electrode ring made of iron plated with nickel, and 7 is stainless steel Although not shown, the inner and outer surfaces of the positive electrode can are made of nickel. A polypropylene gasket 8 is compressed between the positive electrode can and the sealing plate by bending the positive electrode can.

The prototype battery has a diameter of 11.6 mm and a height of 5.4 mm.
The weight of the selective powder of the negative electrode was unified to 193 mg, and the amount of mercury added (selective rate) was 2% by weight based on the zinc alloy powder.

The following table shows the composition of the zinc alloy of the prototype battery, and the changes in discharge performance and total battery height after storage at 60 ° C. for 1 month. The discharge performance was expressed as the discharge duration when discharged at 20 ° C. with 510Ω as the final voltage of 0.9V.

In addition, after leaving for 1 month at a temperature of 60 ° C. and a humidity of 90%, the state of liquid leakage was visually determined, and the number of leaked batteries was also shown.

Regarding the change in the total battery height in this table, it is customary that the total battery height decreases after the battery is sealed until the stress relationship between the battery constituent elements stabilizes over time.
However, 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 the internal pressure of the battery, which opposes the above-described force of reducing the total battery height. Therefore, the corrosion resistance of the zinc negative electrode can be evaluated by increasing or decreasing the total height of the battery due to storage. In addition, in the case of batteries with insufficient corrosion resistance, the total height of the battery increases and the leakage resistance deteriorates due to an increase in the internal pressure of the battery.
The discharge performance is significantly deteriorated due to the formation of an oxide film on the zinc surface and the inhibition of the discharge reaction due to the internal presence of hydrogen gas, and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode.

Now, in the table, No. 1 given as a comparative example of the present invention
~ 8 when the additional element is added alone (No. 1, 2,
When two elements are added (No. 3, 4, 5) (No.
6, 7, and 8) are somewhat improved in corrosion resistance and discharge performance of the zinc negative electrode.

However, Examples of the present invention (No. 10, 11, 1) in which In, Sr, Al, Ca, and Mg are coexisted in a proper combination in a proper content.
2, 15, 16, 17, 20, 21, 23, 24, 25, 26, 27, 28, 2
In the case of (9, 30), compared with the above comparative example, corrosion resistance is further improved,
The discharge performance is excellent and the combined effect of the additional elements is remarkable. On the other hand, even when the three elements are coexistent, when there is an excess or deficiency in the content (NO. 9, 13, 14, 18, 19, 22, 31, 32), there is not much difference from the comparative example, and the combined effect is poor.

As described above, the present invention uses a proper combination of In, Sr, Al, Ca, and Mg, for example, a zinc alloy having a proper content as shown in (No. 27, 28, 29, 30) as a negative electrode. By using it, the reduction rate has been successfully reduced, and the content of each element is such that In is 0.005 to 0.5% by weight and Sr is 0.005 to 0.5% by weight.
0.2 wt% and the sum of one or more of Al, Ca, and Mg are 0.005-0.2 wt%.

As described above, the present invention has found that the corrosion resistance of the zinc alloy used for the negative electrode is improved by the synergistic effect of the combination of the above-mentioned additive elements, and it is possible to determine an appropriate content to obtain a low-pollution zinc alkaline excellent in practical performance. It is a battery implementation. In the examples, the battery using the zinc hydride negative electrode was described, but in the open type air battery and the sealed zinc alkaline battery provided with the hydrogen absorption mechanism,
Since the allowable generation amount of hydrogen gas is comparatively large, when the present invention is applied to such a case, it can be carried out with a low reduction rate, or in some cases, without reduction.

Effects of the Invention As described above, the present invention can reduce the conversion rate of negative electrode zinc,
It is extremely effective in obtaining a low-pollution zinc alkaline battery.

[Brief description of drawings]

The figure is a side view in which a button-shaped silver oxide battery used in an example of the present invention is partially sectioned. 2 ... Zinc negative electrode, 4 ... Separator, 5 ... Silver oxide positive electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ryoji Okazaki Ryoji Okazaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 652-15 Takehara-cho, Takehara-shi, Hiroshima Prefecture

Claims (1)

[Claims] 1. Indium is 0.005-0.5% by weight,
0.005 to 0.2% by weight of strontium, and one or more of aluminum, calcium, and magnesium in an amount of 0.
A zinc alkaline battery using a zinc alloy containing 005 to 0.2 wt% as a negative electrode active material.