JPH0622120B2 - 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. Heretofore, it has been adopted as an industrial method to increase hydrogen overvoltage by using zinc fluoride powder obtained by adding about 5 to 10% by weight of mercury to zinc to suppress corrosion to such an 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, 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. 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, 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. For a negative electrode of a so-called zinc alkaline battery using oxygen or the like, zinc is a main component, and at least 0.001 to 0.5% by weight of indium and 0.01 to 0.5% by weight of lead are essential addition elements. 0.001 to 0.3% by weight of gallium and 0.001 to 0.2% by weight of at least one of the group consisting of magnesium, calcium, barium and strontium.
The zinc alloy contained is used.

In the present invention, among the additional elements in the above-mentioned conventional zinc alloy and other elements, the addition of a single element has a poor anticorrosion effect, but it is added in combination with an element having a relatively large anticorrosion effect such as In, Ga and Pb. Then, attention was paid to Mg, Ca, Ba, and Sr as elements exhibiting a complex anticorrosion effect, and the addition ratios thereof were experimentally examined and completed.

Operation The mechanism of action of the additive elements of the present invention is not clear, but it is considered that the action of each additive element exerted a synergistic effect and significantly improved the corrosion resistance, and is speculated as follows.

In is known as one of the most effective elements among all elements as an additional element for anticorrosion,
In addition to having the effect of increasing the hydrogen overvoltage, it has a high affinity with mercury, so the mercury added for grading is fixed on the surface and grain boundaries of the zinc alloy to suppress the diffusion inside the crystal and inside the zinc alloy. However, it is considered that a large anticorrosion effect can be obtained because the mercury concentration on the surface and grain boundaries can be maintained high by adding a small amount of mercury. Pb is easily segregated in the vicinity of the grain boundaries of the zinc alloy, and when it is screened from the surface of the zinc alloy, it suppresses the diffusion of mercury in the surface layer into the zinc alloy through the grain boundaries of the surface of the zinc alloy. It seems to contribute to maintaining a high mercury concentration. Further, since Ga has a relatively high affinity with mercury, it is possible that Ga existing in the crystal grain boundaries fixes mercury that has been screened from the surface of the zinc alloy to the crystal grain boundaries and diffuses from the surface layer into the crystals. It is considered that the effect of suppressing and maintaining a high surface concentration of mercury is synergistically exerted with the action of In and Pb.

Further, the effect of adding Mg, Ca, Ba, and Sr is to reduce the surface area of the zinc alloy powder used for the negative electrode and to suppress corrosion of the zinc alloy. That is, normally, the zinc alloy powder used for the negative electrode is an atomized powder produced by spray-solidifying a molten zinc alloy with a high-pressure gas, and the surface of the atomized powder of a normal zinc or zinc alloy is a fine powder produced during solidification. It is covered with wrinkles, but when Mg, Ca, Ba, Sr is added, the wrinkles disappear, the surface of the particles can be smoothed, and the true surface area for the corrosion reaction due to contact with the electrolytic solution is reduced. , The corrosion resistance can be increased. As described above, the present invention increases the hydrogen overvoltage of the zinc alloy itself by the synergistic effect of coexisting In, Pb, and Ga, and maintains the mercury concentration on the surface of the zinc alloy powder at a high level by adding a small amount of mercury. This makes it possible to make the surface state uniform and to further increase the hydrogen overvoltage.
By the addition of at least one of g, Ca, Ba and Sr, the combined action of reducing the surface area of the zinc alloy powder,
The anticorrosion property is remarkably improved.

Hereinafter, the present invention will be described in detail 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 7 and the sealing plate 1 by bending the positive electrode can 7.

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 0.5% by weight based on the zinc alloy powder.

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

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, the total battery height tends to increase due to the increase in the battery internal pressure that 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 battery height increases, and the leakage resistance deteriorates due to the increase in battery internal pressure, as well as zinc consumption due to corrosion, the formation of an oxide film on the zinc surface, and the internal presence of hydrogen gas. Discharge performance will be significantly deteriorated due to the inhibition of discharge reaction,
The liquid leakage resistance and the discharge duration also largely depend on the corrosion resistance of the zinc negative electrode.

As can be seen in this table, no.
Among 1, 2, 3, and 5, to 8, the effect of adding In is large, and then Ga and Pb also have some effects, and M
In the case of g, Ca, Ba and Sr, the corrosion resistance and the discharge performance are inferior to the others. In addition, In, Pb, Ga, which has been attracting attention as one of the zinc alloys with the highest corrosion resistance,
No. 4 which coexisted with No. 1 is the best among No. 1 to No. 8, but 0.5% by weight in discharge performance and leakage resistance.
It cannot be said to have sufficient practical performance at such a low reduction rate. In contrast to these conventional examples, In, Pb, Ga, and Sr
Among Nos. 9 to 28, in which Co. coexisted, those with appropriate content of each additive element showed superior performance to No. 4, and the composite anticorrosion effect by addition of Sr was confirmed. . That is, 0.001 to 0.5% by weight of In, 0.01 to 0.5% by weight of Pb, 0.001 to 0.3% by weight of Ga, and 0.001 to 0.3% by weight of Sr. Within the range, the zinc alloys contained are effective, and when the content of each additional element is excessive or insufficient than the above, it is not much different from No. 4 or shows the performance value of the opposite effect. Also, instead of Sr, Co or M
Similar effects are also observed in Nos. 29 to 34 to which g or Ba is added and Nos. 35 and 36 in which these are coexisted. As described above, the present invention uses In, Pb, and Ga as essential additive elements, and one or more of Sr, Ca, Mg, and Ba as essential additive elements, and a zinc alloy containing an appropriate amount of each is used as the negative electrode. By using it, it is possible to construct a zinc-alkali battery with a low reduction rate and excellent practical performance. In the above embodiment, In, Pb, Ga, and Sr or Ca, Mg,
Or, only the essential addition element of Ba in the present invention is described, but as additional non-essential addition elements, Tl, C
d, Sn, Bi, Ag, Al, Hi, Na, K, Rb, Cu, T
Even when any one of e, Ta, Si, and Ti was added to No. 10 in the above table in an amount of 0.1% by weight, performance values substantially equal to those of No. 10 were obtained. Therefore, even if the above-mentioned non-essential additive element is added within the limit after containing a predetermined amount of the essential additive element in the present invention, as in the case of the present invention example in which only the essential element is added, it is essentially The same effect can be obtained. In addition, in the examples, a battery using a zinc hydride negative electrode was described, but in an open type air battery or a sealed zinc alkaline battery provided with a hydrogen absorbing mechanism,
Since the permissible generation amount of hydrogen gas is relatively large, the present invention can be carried out with a further lowering rate, or in some cases with no reduction.

Further, in the present embodiment, a case has been described where a zinc alloy as a zinc alloy is added with an additional element to form an alloy and then pulverized. However, as an alternative method, an addition element such as In or Ga that easily forms an amalgam is added. A method of preliminarily containing a metal in mercury used for hydration and adding the zinc alloy simultaneously with hydration, or a zinc alloy by a substitution reaction with zinc in a solution in which a hydroxide or salt of Pb, In, Ga is dissolved. A method of precipitating the above element on the surface and alloying it can also be adopted.

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. 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 in an amount of 0.001 to 0.5% by weight,
0.01 to 0.5% by weight of lead and 0.001 to 0.001 of gallium
A zinc alkaline battery using, as a negative electrode active material, a zinc alloy containing 0.3% by weight and 0.001 to 0.2% by weight of at least one selected from the group consisting of magnesium, calcium, barium and strontium.