JPS6290854A - 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 In, Cd, Co, Ni, Al, Ca, and Sr respectively as a negative electrode. CONSTITUTION:For a negative electrode 2 of a zinc alkaline type cell, a zinc alloy containing Zn as the main component, 0.005-0.5wt% of In, 0.01-0.5wt% of at least either Pb or Cd, 0.01-0.5wt% of at least either Co or Ni, and 0.005-0.5wt% of at lest one of Al, Mg, Ca, and Sr is used as an active substance. Such an element is not effective or sometimes less effective to anticorrosion when used separately. However, by setting the combination of elements and their amounts adequately to supplement their merits and demerits each other, the anticorrosive property of the zinc alloy for the negative electrode 2 can be improved, and a zinc alkaline cell of excellent discharge and preservative properties with little environmental pollution 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 aqueous solution as an electrolyte, and manganese dioxide, silver oxide, or silver oxide as a positive electrode active material.
This invention relates to improving the negative fi of zinc alkaline batteries using mercury oxide, oxygen, nickel hydroxide, etc.

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

Conventionally, it has been adopted as an industrial method to add about 5 to IO weight % of mercury to zinc to suppress corrosion to a practically acceptable level. 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, a method has been proposed to improve corrosion resistance and reduce the hydration rate by using an alloy powder in which lead, cadmium, indium, gallium, etc. are added to zinc. These corrosion-inhibiting effects are not only due to the single additive element, but also due to the combined effect of multiple additive elements. It has been proposed as a promising system.

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

Furthermore, with the aim of mainly improving manganese dry batteries, there has been a proposal that using zinc or a zinc alloy in which indium is added to a zinc alloy for the negative electrode is highly effective in preventing corrosion (Japanese Patent Publication No. 33-3204).

Problems to be Solved by the Invention 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, A1. Although it is described including the case where one or more types of Ag, Mg, Si, Ni, M etc. are included as impurities or additives, there is no effect other than the effectiveness when indium and lead are used together as additive elements. It is not clear whether the above miscellaneous elements are added as impurities or added as effective elements, and it is not even clear which elements are effective for corrosion prevention. .

There is no mention of anything other than lead.

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 of the present invention is to provide a zinc-alkaline battery with excellent overall performance including B liquid resistance.

Means for Solving the Problems The present invention uses an alkaline aqueous solution containing caustic potash, caustic soda, etc. as its main components as an electrolyte, zinc as a negative electrode active material, and manganese dioxide, silver oxide, and oxygen as a positive electrode active material.

The negative electrode of a so-called zinc-alkaline battery that uses mercury oxide etc. contains zinc as the main component and indium from 0.005 to 0.
．． 5ffii%, 0.01 to 0.5% by weight of at least one of lead and cadmium, 0.01 to 0.5% by weight of at least one of cobalt and nickel, and a group consisting of aluminum, magnesium, calcium, and strontium. It is characterized by using a zinc alloy containing 0.005 to 0.5% by weight of at least one of these.

The present invention has conducted experiments focusing on Ni and Co among additive elements, impurities, and other elements in zinc alloys, and has
Zinc alloys to which o is added alone have poor corrosion protection, but the combined effect with other additive elements is large, and especially when the appropriate amount is added in combination with the above elements, extremely remarkable composite corrosion protection can be achieved. It was completed after discovering that it was effective.

Effect The mechanism of action of the anticorrosive effect of the addition of each element and the combined effect of these elements is unclear, but it is inferred as follows. First, although the solubility of Ni and Co in zinc is small, the cooling rate when pulverizing molten zinc alloy by the injection method is on the order of 102°C/see, which is extremely high, so it is not suitable for the examples described later. In a zinc alloy powder with a content of 10%, there is a possibility that Ni and Co will be solutionized with zinc. Therefore, when a zinc alloy is hydrated from the surface, Ni and Co, which have a low affinity for mercury, suppress the diffusion of mercury into the crystal and contribute to maintaining a high concentration of mercury on the surface of the zinc alloy. Conceivable. However, on the other hand, there is also a concern that it may actually worsen the compatibility of mercury with the surface of the zinc alloy. Also, pb and C
d tends to segregate near the grain boundaries of zinc alloys, and contributes to maintaining a high mercury concentration on the surface by suppressing mercury in the surface layer of the zinc hydrate alloy from diffusing into the interior through the grain boundaries. Seem.

In addition, In increases the hydrogen overvoltage of zinc alloys and is easily compatible with mercury, so when zinc alloys are hydrated, it is effective in making the surface condition uniform by hydration. It is also expected to play a role in fixing mercury at grain boundaries. Also, AI, Mg.

Both Ca and Sr, like Ni, have a low affinity for mercury, so they suppress the diffusion of mercury into the interior of the zinc alloy, and as a unique function, the molten zinc alloy is pulverized by the injection method. It is thought that this method eliminates the wrinkles on the surface of the zinc alloy powder, smooths it, reduces the surface area, and improves the anti-corrosion effect. However, since these elements are base metals than zinc, they are more likely to corrode than zinc in the electrolyte.
It is necessary to maintain a balance with the expected anticorrosion effect, and excessive addition will actually impair the anticorrosion properties.

As described above, each additive element is expected to have a different effect. However, each element alone is not necessarily effective in preventing corrosion, and the effect may be poor in some cases. The present invention was completed by experimentally determining the appropriate combination and content of elements that complement the strengths and weaknesses of these additive elements, and it is possible to reduce the hydrogen overvoltage on the surface of zinc alloy powder by adding a small amount of mercury. By maintaining a high corrosion resistance over a long period of time, making the surface uniform, and further reducing the surface area, the corrosion resistance of the zinc alloy used in the negative electrode is significantly improved. This creates a corrosion-resistant zinc negative electrode with a low hydration rate and excellent discharge performance.

The present invention provides a low-pollution zinc-alkaline battery with excellent storage performance.

Hereinafter, it will be explained in detail using 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 powdered by spraying with compressed air. 150
It was sieved into a mesh particle size range. 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. Then wash with water,
The mixture was replaced with acetone and dried to produce 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, ■ is a sealing plate made of stainless steel, and its inner surface 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. This is a positive electrode can made of nickel, and its inner and outer surfaces are nickel-plated (not shown). 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 ms+, the weight of the hydrated powder of the negative electrode is unified to 193 mg, and the amount of mercury added (hydration rate) is 0 for the zinc alloy powder. .5% by weight.

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 one month. The discharge performance was expressed by the discharge duration when discharging at 510Ω at 20° C. with a final voltage of 0.9V.

Also, after leaving it for one month at a temperature of 60℃ and humidity of 90%,
The state of leakage was visually determined, and the number of batteries leaking was also indicated.

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, there is a strong tendency to increase the total battery height due to an increase in battery internal pressure that counteracts the above-described force for decreasing the total battery height. Therefore, the corrosion resistance of the zinc negative electrode can be evaluated by the increase or decrease in the total height of the battery due to storage. In addition, batteries with insufficient corrosion resistance will not only increase the total height of the battery, but also deteriorate leakage resistance due to an increase in battery internal pressure, as well as depletion of zinc due to corrosion, formation of an oxide film on the surface of zinc, and the presence of hydrogen gas. This results in a significant deterioration of discharge performance due to inhibition of the discharge reaction, etc., and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode.

In the above table, No. 1 listed as a comparative example of the present invention
When an additional element is added alone among 8 to 8 (No, 1.
2), when two elements are added (No, 3.4
), when three more elements are added (No, 5.6,
7.8) Both the corrosion resistance and discharge performance of the zinc negative electrode are somewhat improved.

However, In, Cd, Pb, Co, Ni, A1
．． Mg.

Example of the present invention (No, 10.11.12. Is
, 16°19, 20.23.25.26.27.28
．． 29.30.31.32゜33, 34.35.36.
In the case of 37), the corrosion resistance is much higher than that of the above comparative example.
The discharge performance is excellent, and the combined effect of the added elements is remarkable. - When there is excess or deficiency in the content even when crab elements are present together (No.

9, 13.14.18.21.22.24> are not much different from the comparative example, and the composite effect is poor.

As mentioned above, the present invention includes In, Cd, Pb, Co,
Ni.

A1. By appropriately combining Mg, Ca, and Sr and using a zinc alloy in the appropriate content as shown in the example for the negative electrode, we succeeded in reducing the wood reduction rate. 0.005-0.5% by weight, Pb, Cd
The sum of one or two of these is 0.001 to 0.5% by weight, Co
, the sum of one or two types of Ni is 0.01 to 0.5% by weight
, AI, Mg, Ca.

It is appropriate that the sum of one or more types of Sr is 0.005 to 0.5% by weight.

As described above, the present invention has discovered that the corrosion resistance of the zinc alloy used for the negative electrode is improved due to the synergistic effect of the combination of the above-mentioned additive elements, and has determined the appropriate content to create a zinc-alkaline alloy with low pollution and excellent practical performance. This is the realization of a battery. 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,
Since the permissible amount of hydrogen gas to be generated is relatively large, when the present invention is applied to such a case, it is possible to carry out the process with the reduction of trees, and in some cases, with the dehydration.

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. Name of agent: Patent attorney Toshio Nakao and 1 other person 2-4 lead
Winding 4 --- (] 1 router 5-monoacid fti eyes positive rabbit

Claims (1)

[Claims] 0.005-0.5% by weight of indium, 0.01-0.5% by weight of at least one of lead and cadmium, and 0.01-0.0% of at least one of cobalt and nickel.
．． 5% by weight, 0 at least one member from the group consisting of aluminum, magnesium, calcium, and strontium
．． A zinc alkaline battery using a zinc alloy containing 0.005 to 0.5% by weight as a negative electrode active material.