JPS6290857A - Zinc alkaline cell - Google Patents

Abstract

PURPOSE:To obtain an overall efficiency of excellent discharge, preservation, and antileakage properties and the like with little environmental pollution, by applying a zinc alloy containing Zn as the main component, and specific ratio of Ni, In, Tl, and Ba as a negative electrode. CONSTITUTION:For a negative electrode 2 of a zinc alkaline type cell, a zinc alloy containing n as the main component, 0.01-0.5wt% of Ni, 0.001-0.5wt% of at least either In or Tl, and 0.001-0.3wt% of Ba is used as an active substance. In such a composition, by composing the functions of Ni, In or Tl, and Ba, a higher hydrogen supervoltage, a smaller surface area, and a high mercury density on surface through mercurating by small amount mercury are maintained, and an even surface condition of zinc alloy powder is obtained. By applying such a zinc zlloy as a zinc alkaline cell, a cell of excellent preservation, antileakage, and discharge properties with small amount of mercury content can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses zinc as a negative electrode active material, an alkaline aqueous solution 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.

A common problem with conventional zinc-alkaline batteries is corrosion of the negative electrode zinc by the electrolyte during storage.

Conventionally, 5~IO weight for zinc? It has been adopted as an industrial method to increase the hydrogen overvoltage by using zinc hydride powder to which about 6% of mercury is added 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 research on mercury is being conducted. For example, lead in zinc,
cadmium.

A method has been proposed in which alloy powders containing indium, gallium, etc. are used to improve corrosion resistance and reduce the hydration rate. These corrosion-inhibiting effects are not only due to the single additive element, but also due to the combined effect of multiple additive elements. has been proposed as a promising system.

Although all of these can be expected to have a certain degree of corrosion resistance and to reduce the hydration rate to some extent, it is necessary to search for an alloy system with even better corrosion resistance.

In addition, with the aim of mainly improving manganese dry batteries, there is a proposal that using zinc or a zinc alloy with indium added to the zinc alloy for the negative electrode would have a great anti-corrosion effect (Special Publication No. 33-320 = No. 1). .

Point a that the invention seeks to solve Among the above proposals, in addition to indium, Fe, Cd, Cr, Pb, Ca, and H are used as elements in the zinc alloy.
g.

Bi, Sb, AI, Ag, Mg, Si, N
The description includes the case of containing one or more types of impurities or additives such as i, IVin, etc., but apart from the effectiveness of using indium and lead together as additive elements, there are various miscellaneous effects mentioned above. It is not clear whether an element is added as an impurity or an effective element, and it is not even clear which element is effective for corrosion prevention, and the appropriate amount of addition is unknown.

There is no description of anything outside the lead layer.

It remains a challenge for the future to study the effects of the combination of these elements in zinc-alkaline batteries and to find an effective alloy composition.

The present invention reduces the hydration rate without deteriorating the corrosion resistance and discharge performance of negative electrode zinc, and improves discharge performance, storage stability, and low pollution.
The purpose is to provide a zinc-alkaline battery with excellent overall performance such as leakage resistance.

Means for Solving the Problems The present invention uses an alkaline aqueous solution containing caustic potash, caustic soda, etc. as the main components for the electrolyte, zinc for the negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, etc. for the positive electrode active material. The negative electrode of a so-called zinc-alkaline battery that uses oxygen etc. has zinc as its main component and nickel (Ni) of 0.01 to 0.5! fi%,
Indium (In>.

At least one type of thallium (TI>) in the range of 0.001 to 0.
It is characterized by using a zinc alloy containing 5% by weight and 0.001 to 0.3% by weight of barium (Ba).

The present invention focused on the fact that among the additive elements or impurities in the conventional zinc alloy, Ni is an element that is inexpensive and has no concern about environmental pollution, and as a result of conducting experiments on the effect of adding Ni, it was found that Ni Zinc alloys containing I alone have poor corrosion protection, but I, which has been known as an effective additive element,
It was discovered that when Ba coexists with n and TI, the anticorrosive effect can be enhanced, and when Ba coexists with these, an even more complex anticorrosive effect can be obtained.

Function The mechanism of action regarding the anticorrosion effect of each additive element and the combined effect of these elements is largely unclear, but it is inferred as follows. First, although Ni has a low meltability with respect to zinc, the cooling rate when molten zinc alloy is blown into powder by the injection method is extremely high, on the order of approximately 103°C/sec, so it is not suitable for use in the examples described below. If the zinc alloy powder has a content of ff1 (0.01 to 0.5% by weight), there is a possibility that Ni and zinc will become a solution. Therefore, when hydration occurs from the surface of a zinc alloy, Ni, which has a small affinity for mercury (11), is expected to suppress the diffusion of mercury into the crystals and contribute to maintaining a high mercury concentration on the surface of the zinc alloy. Ru. On the other hand, there is a concern that the adhesion of mercury to the zinc alloy surface may become worse, and Ni
A great anticorrosive effect cannot be obtained by adding only one. In addition, In and TI have long been known as additive elements with great anti-corrosion effects, and as they easily mix with mercury when increasing the hydrogen overvoltage of zinc alloys, they are effective in making the surface condition uniform through hydration. It is also thought to play a role in fixing mercury on the surface and grain boundaries of the zinc alloy. Moreover, Ba has the effect of smoothing the surface of the zinc alloy powder obtained by the injection method and reducing the surface area.

In other words, zinc, which is usually used in the negative electrode of zinc-alkaline batteries,
Alternatively, zinc alloy is a so-called atomized powder obtained by spraying and solidifying molten metal with high-pressure gas. This atomized powder is usually covered with many fine wrinkles that form during solidification. However, when Ba is added, the formation of wrinkles is suppressed, the specific surface area of the zinc alloy powder is reduced, and the corrosion rate due to contact with the alkaline electrolyte can be reduced. The present invention has a large hydrogen overvoltage, a small surface tank, and a high mercury concentration on the surface due to the combination of the effects of Ni, In or TI, and Ba. 11 to obtain zinc alloy powder with a uniform surface condition, and by using this as the negative electrode of a zinc-alkaline battery, a battery with low mercury content and excellent storage stability, leakage resistance, and discharge performance was completed. This is what I did.

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 zinc ingot with a purity of 99.997%, melted at about 500°C, and pulverized by spraying with compressed air. 50-15
The particles were sieved to a particle size range of 0 mesh. Next, the above powder was put into an aqueous solution of caustic potash at IO weight i%, 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.

Furthermore, hydrated zinc powder or zinc hydrated 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 coated with copper plating 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 separator made of porous polypropylene, 5 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 stainless steel. The positive electrode can is made of aluminum, and its inner and outer surfaces are nickel-plated.

A polypropylene gasket 8 is compressed between the positive electrode can 7 and the sealing plate 1 when the positive electrode can 7 is bent.

The prototype battery had a diameter of 11.6 mm and a height of 5.4 m, the weight of the hydrated powder of the negative electrode was unified to 193 mg, and the amount of mercury added (hydration rate) was the same as that of the zinc alloy powder. 1
It was bound in weight%.

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 one month, and the number of leaking batteries as determined by visual inspection. The discharge performance was expressed as the discharge duration when discharging at 510Ω at 20° C. with a final voltage of 0.9V.

Regarding changes in the total battery height in this table, it is normal that the total battery height decreases during the period after the battery is sealed until the stress relationship between each battery component becomes stable over time.

However, in a battery where a large amount of hydrogen gas is generated due to corrosion of the zinc negative electrode, the overall battery height tends to increase due to an increase in battery internal pressure that counteracts the above-mentioned force for reducing the total battery height. Therefore,
The corrosion resistance of the zinc negative electrode can be evaluated by the change in total battery height due to storage. In addition, in batteries with insufficient corrosion resistance, the total height of the battery increases, the leakage resistance deteriorates due to an increase in battery internal pressure, and the zinc is consumed due to corrosion, the formation of an oxide film on the zinc surface, and the presence of hydrogen gas. The discharge performance is significantly deteriorated due to inhibition of the discharge reaction, etc., and the leakage resistance and discharge duration are also largely dependent on the corrosion resistance of the zinc negative electrode.

As seen in this table, No. added with a single element,
Among i~4, the effect of addition of In and Tl is relatively seen, but all of the above battery characteristics have problems, and Ni and Ba
is even worse than these.

Also, Nos. 5 to 7 are I where In or TI and Ni coexist.
It is superior to the case where N or T1 is added alone, and N
A compound effect is observed due to the addition of i, but in discharge performance and leakage resistance it is 1? A water conversion rate as low as 6 cannot be said to have sufficient practical performance.

Regarding the performance values in these cases, in addition to Ni and In, Ba
Among Nos. 8 to 23, which coexisted with Ba, those with appropriate contents of each additive element showed better performance than Nos. 15 to 7, confirming the composite anticorrosion effect of the addition of Ba. . That is, In is 0.001 to 0.5% by weight, N+ is 0.01 to 0.5% by weight, and Ba is 0.001% by weight.
A zinc alloy containing in the range of ~0.3% by weight is effective, and if the content of each additional element is in excess or in shortage of the above, then No.

5 to 7, it shows a performance value that is not much different or has the opposite effect. In addition, No. 24.25 in which TI was added instead of In
．． And (n, No. 26°27 in which TI coexists also shows better performance than No. 95-7. As described above, the present invention uses N1°Ba as the basic cold power n element. Furthermore, by using a zinc alloy containing appropriate amounts of In and TI as essential additive elements for the negative electrode, discharge performance, storage performance, and ifi liquid resistance are achieved with a low water conversion rate. This is a completed zinc-alkaline battery with excellent practical performance.

In the examples, only Ni, Ba, In, or TI, which are essential addition elements in the present invention, are described, but Cd is added as an additional non-essential element.

Sn, Pb, Co, Ga, Ag, Te, Bi, AI M
g.

Ca, Ta, Si, Ti, Sr, Li, Na, Rb
.

Even when 0.1% by weight of Cu was added to No. 1O of the former husband, almost the same performance value as No. 10 was obtained. Therefore, even when a predetermined amount of the essential additive elements of the present invention is contained and an appropriate amount of the above-mentioned non-essential additive elements is added, the same effects as those of the present invention can be obtained. In addition, in the examples, a battery using a zinc hydrate negative electrode was explained, but in an open air battery or a sealed zinc alkaline battery equipped with a hydrogen absorption mechanism, the permissible amount of hydrogen gas generated is Since the amount is relatively large, the present invention can be carried out with a lower hydration rate, and in some cases, with anhydration as it is.

Furthermore, in this example, a case was explained in which additive elements were added to molten zinc to form a zinc alloy, alloyed, and then powdered. However, as an alternative method, among the additive elements, In, which is an additive metal that is easily amalgamated, .

There is a method in which TI is pre-contained in the mercury used for hydration and added at the same time as the zinc alloy is hydrated.

Almost the same effect can be obtained by using a method in which the above elements are precipitated on the surface of a zinc alloy by a substitution reaction with zinc in a solution containing TI hydroxide or salt to form an alloy.

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

[Brief explanation of drawings]

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.

Claims (1)

[Claims] A zinc alloy containing 0.01 to 0.5% by weight of nickel, 0.001 to 0.5% by weight of at least one of indium and thallium, and 0.001 to 0.3% by weight of barium is used as a negative electrode active material. Zinc alkaline battery.