JPH0682551B2 - Zinc alkaline battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to zinc as a negative electrode active material, an alkaline electrolyte as an electrolytic solution, and manganese dioxide, silver oxide as a positive electrode active material.
The present invention particularly relates to the improvement of the negative electrode in zinc-alkaline batteries using mercury oxide, oxygen, nickel hydroxide, etc.

2. Description of the Related Art Conventionally, a common problem of this type of zinc alkaline battery is corrosion of the negative electrode zinc during storage by an electrolytic solution. Hitherto, it has been adopted as an industrial method to increase hydrogen overvoltage by using zinc fluoride powder in which about 5 to 10% by weight of mercury is added to zinc to suppress corrosion to the extent that there is no practical problem.

However, in recent years, reduction of the mercury contained in the battery has become a social need to reduce pollution, and various studies have been conducted. For example, a method has been proposed in which an alloy powder obtained by adding lead, cadmium, indium, gallium, or the like to zinc is used to improve the corrosion resistance and reduce the conversion rate. These corrosion inhibition effects are largely due to the combined effect of multiple additive elements in addition to the effect of the additive element alone. Indium and lead, or those in which gallium is added, and zinc alloys in which gallium and lead are added are conventionally used. , Has been proposed as a promising system.

Further, a zinc alloy in which gallium and silver are added to lead and gadmium (JP-A-61-78062), and a zinc alloy in which aluminum is added to gallium and thallium (JP-A-61-7806).
No. 1), a zinc alloy containing one or more of aluminum, lead, silver, gallium, thallium, and cadmium (Japanese Patent Laid-Open No. 61-78059).

Problems to be Solved by the Invention The zinc alloys of the above proposals can be expected to have corrosion resistance to some extent, and a reduction in the conversion rate can be expected to some extent, but the effect of the combination of these elements is not sufficient at present. , Elucidation of alloy composition by effective combination is still a future subject.

The present invention solves such a problem, and reduces deterioration rate without deteriorating the corrosion resistance of the negative electrode zinc, and is excellent in overall performance such as discharge performance, storage performance and liquid leakage resistance with low pollution. Another object of the present invention is to provide a zinc negative electrode.

MEANS FOR SOLVING THE PROBLEMS The present invention is directed to an electrolytic solution containing an alkaline aqueous solution containing caustic potash, caustic soda, etc. as a main component, zinc as a negative electrode active material, and manganese dioxide, silver oxide, mercury oxide as a positive electrode active material. In the negative electrode of a so-called zinc alkaline battery using oxygen or the like, zinc is the main component, indium is 0.001 to 0.5 wt% as an additive element, and at least one of the group consisting of aluminum, calcium and magnesium is 0.001 to 0.3 wt%, 0.00 barium
A zinc alloy containing 1 to 0.5% by weight is used.

The present invention is used in combination with In, which is known to have a relatively large anticorrosion effect, and the anticorrosion effect is poor when added alone.
By adding an element selected from l, Ca, Mg and Ba,
It was found that a zinc alloy that is several steps better than the zinc alloy added alone was obtained, and it was completed by experimentally examining the combination of addition elements and the addition ratio.

Action The action mechanism of each additional element in the zinc alloy according to the present invention is unclear, but the synergistic effect on corrosion protection is presumed as follows.

First, since In has the effect of increasing the hydrogen overvoltage and has a high affinity with mercury, the mercury added for the purpose of fixation is fixed on the surface and grain boundaries of the zinc alloy, and a small amount of mercury is added to the surface of the zinc alloy. It is considered that there is a large anticorrosion effect due to the action of maintaining a high mercury concentration at the grain boundaries and grain boundaries. Further, the effect of adding Al, Ca, and Mg is to reduce the surface area of the zinc alloy powder used for the negative electrode by pulverizing it to suppress corrosion of the zinc alloy. That is,
The zinc alloy powder normally used for the negative electrode is an atomized powder produced by spray-solidifying a molten zinc alloy with high-pressure gas, and the surface of ordinary zinc or zinc alloy atomized powder is covered with fine wrinkles generated during solidification. Al, C
When a and Mg are added, the wrinkles are reduced, the surface of the particles can be smoothed, and the surface area for the corrosion reaction by contact with the electrolytic solution can be reduced to increase the corrosion resistance.

Furthermore, since Ba has a high affinity for mercury, it is expected to have a similar action effect to the anticorrosion action of In, and it is presumed that it plays a role of supplementing the action of In. As described above, since the zinc alloy used in the present invention can be maintained with a high mercury concentration on the surface of the zinc alloy by using a small amount of mercury, and the surface area of the zinc alloy powder can be reduced, the corrosion resistance is extremely excellent. It is considered to be a thing. The present invention experimentally examines the combination of additive elements and the content thereof in such a zinc alloy, and realizes a low-pollution and highly-practical zinc-alkaline battery having both low corrosion rate and sufficient corrosion resistance and discharge performance. It has been completed the effective means. 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., sprayed with compressed air to be powdered, and 50 to 150 mesh. It screened in the particle size range of. Then 10% by weight of caustic potash
The above-mentioned powder was put into an aqueous solution, and a predetermined amount of mercury was dropped to the solution while agitating it. Then, it was washed with water, replaced with acetone and dried to prepare a zinc hydride 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 manufactured 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 nickel plated on iron, and 7 is nickel plated It is a positive electrode can made of stainless steel. 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 11.6 mm and a height.
At 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 1.0% by weight with respect to the zinc alloy powder.

The following table shows the composition of the zinc alloy of the prototype battery, the change in discharge performance and total battery height after storage at 60 ° C for 1 month, and the number of leakage batteries by visual judgment. Discharge performance at 20 ℃
It was expressed as the discharge duration when discharged at a termination voltage of 0.9 V at 510 Ω.

In this table, the change in the total battery height generally indicates that the total battery height decreases with time in the period after the sealing of the battery and until the relation of the stress between the battery constituent elements is stabilized. However, in a battery in which a large amount of hydrogen gas is generated due to corrosion of the zinc negative electrode, the increase in the battery internal pressure against the above-described decrease in the battery total height increases the tendency to increase the battery total 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 the increase in the battery internal pressure, and zinc consumption due to corrosion, formation of an oxide film on the zinc surface, and discharge due to the internal hydrogen gas Due to reaction inhibition, etc.
The discharge performance is significantly deteriorated, and both the leakage resistance and the discharge duration depend largely on the corrosion resistance of the zinc negative electrode.

As can be seen in this table, in the case of No. 1 battery in which In was added alone, Al, Ca, and Ag were co-existed in No. 2, 3, and 4, all were No. 1 Corrosion resistance is better than other batteries, especially Ca, A
The combined effect of l is large. However, these do not have practically satisfactory characteristics at a low weight reduction rate of 1.0% by weight, and thus cannot be said to have sufficient corrosion resistance.

In contrast to these conventional examples, In and Al, Ca, one or more of Mg, coexisting, in addition to Ba No. 5 ~ 27, the content of each additive element is appropriate, further, It shows excellent properties, which is due to the combined effect of Ba and other elements.For example, No.2 and No.10, No.3 and No.15, No.4 and No.1
This is clear from the contrast of 8. Further, a suitable content of each element is 0.001 to 0.5 wt% In, the total content of one or more elements selected from Al, Ca, Mg is 0.001 to 0.3 wt%, Ba 0.001 to The zinc alloys each contained in the range of 0.5% by weight are effective, and when the content of each additive element is excessive or insufficient from the above, it is not much different from the conventional example or shows the characteristic value of the opposite effect. As described above, the present invention, In, Ba as an essential additive element, further, Al, Ca, as an essential additive element of one or more of Mg, by using a zinc alloy containing an appropriate amount of each for the negative electrode We have completed a low-pollution zinc-alkaline battery with low practicality, excellent discharge performance, storability, and leakage resistance.

In the examples, as a method for adding the additional element,
Although the method of adding into the molten zinc ingot is adopted, when adding In or Ba that easily forms an amalgam, it is also possible to dissolve the additive element in advance and add it at the same time as the selective conversion. Further, in the case of adding In, which has a smaller ionization tendency than zinc, for example, in a solution of indium chloride or the like, it can be deposited on the surface of a zinc alloy by a substitution reaction with Zn to form an alloy, and any method is adopted. However, the same effects as those of the present invention can be obtained and are included in the embodiments of the present invention.

Further, in the examples, a battery using a 1.0 wt% zinc hydride load was described, but when extremely strict storage performance and liquid leakage resistance are required, the upper limit is about 3 wt% and 1.0 wt% In some cases, it is appropriate to apply the above conversion rates, and conversely, in an air battery equipped with an exhaust device or a sealed zinc alkaline battery equipped with a hydrogen absorption mechanism, the allowable hydrogen gas generation amount is Since the amount is relatively large, it is possible to carry out the treatment with a reduction ratio of less than 1.0% by weight, and 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 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Megumi City, Hiroshima Prefecture Takehara City, Takehara Town 652-15 (72) Inventor Nobuyoshi Kasahara 1531-45 Takehara Town, Takehara City, Hiroshima Prefecture

Claims (1)

[Claims] 1. Indium is 0.001 to 0.5% by weight, at least one of the group consisting of aluminum, calcium and magnesium is 0.001 to 0.3% by weight, and barium is 0.001 to 0.5% by weight.
A zinc alkaline battery using the contained zinc alloy as a negative electrode active material.