JPS6290852A - 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, Ni, Ca, Sr, and Mg 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 Ni, and 0.05-0.2wt% of one or more of Ca, Sr, and Mg is used as an active substance. Ni has a less affinity with mercury and restricts the expansion of mercury into the crystals of the zinc alloy, resulting in maintaining a high mercury density over the surface of zinc alloy. In is an additive element for a high anticorrosion, while Ca, Sr, or Mg functions to smooth the surface of the zinc alloy powder. By combining adequate amounts of those elements for aditives, an anticorrosive zinc anode with a low mercurating rate is realized, 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 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, it has been adopted as an industrial method to add about 5 to 10 weight Q6 of mercury to zinc to suppress corrosion to an extent that poses no problem in practice. 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 extensive research is being carried out. 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, such as indium and lead, or a combination of indium and lead with gallium added thereto, and a zinc alloy with gallium and lead added. It has been proposed as a promising system.

All of these are expected to have some degree of corrosion resistance, and although a reduction in hydration rate can be expected to some extent, it is necessary to search for an alloy system with even better corrosion resistance.

Furthermore, with the aim of improving manganese dry batteries, there has been a proposal that using zinc or a zinc alloy with indium added to the zinc alloy for the negative electrode would have a significant anti-corrosion effect (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.
l.

The description includes cases in which one or more types of Bi, Sb, AI, Ag, Mg, Si, Ni, Mn, etc. are included as impurities or additives, but when indium and lead are used together as additive elements. Other than the effectiveness of these elements, there is no clear distinction as to whether they are included as impurities or added as effective elements, and it is unclear whether these elements are effective for corrosion prevention. Indium is the most important additive.

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 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 is made of zinc as the main component and indium of 0°005 to 0.
．． It is characterized by using a zinc alloy containing 5% by weight of nickel, 0.01 to 0.5% by weight of nickel, and 0.005 to 0.2mm% of one or more of calcium, strontium, and magnesium.

The present invention conducted experiments focusing on Ni among the additive elements to zinc alloys, and found that zinc alloys with Ni added alone have poor corrosion resistance, but the combined effect with other additive elements is large, and in particular, the above-mentioned This work was completed after discovering that a very significant anticorrosion effect can be obtained when the appropriate amount is contained in combination with the following elements.

Effect The mechanism of action of the anticorrosive effect of the addition of each element and the combined effect of these elements is unclear, or may be surmised as follows. First, although the solubility of Ni in zinc is small, the cooling rate when pulverizing molten zinc alloy by the injection method is on the order of 102°C/sec, which is extremely high. There is a possibility that Ni may be dissolved in the zinc alloy powder. Therefore, when a zinc alloy is hydrated from the surface, it is thought that Ni, which has a low affinity for mercury, suppresses the diffusion of mercury into the zinc alloy crystals and contributes to maintaining a high mercury concentration on the zinc alloy surface. It will be done. However, on the other hand, there is a concern that it may actually worsen the conformability of the zinc alloy surface, and it is thought that the anticorrosion effect is small when added alone.

In addition, In has long been known as an additive element with a large anticorrosion effect, increasing the hydrogen overvoltage of zinc alloys, and being compatible with mercury, it is effective in making the surface condition uniform through hydration. It is also expected to play a role in maintaining a high mercury concentration on the surface by fixing mercury on the surface and grain boundaries. Further, Ca, Sr, and Mg have the effect of eliminating wrinkles and smoothing the surface of the zinc alloy powder, which is pulverized by spraying molten zinc alloy, thereby reducing the surface roughness. However, since all of these additive elements are electrochemically more base than zinc, they are more likely to corrode than zinc, and are ineffective when added alone, and have the opposite effect when added in excess.

As mentioned above, each additive element has a different effect, and In
Addition of elements other than JJ alone is insufficiently effective, or by adding elements in combination according to the present invention, a zinc alloy with corrosion resistance far superior to that obtained by adding In alone can be obtained. This is because each of the above-mentioned elements takes advantage of each other's strengths and complements each other's weaknesses, allowing a high concentration of mercury to be maintained on the surface of the zinc alloy powder over a long period of time with the addition of a small amount of mercury, resulting in a uniform surface condition. ? This is thought to be due to the fact that a large hydrogen overvoltage was obtained and the surface tsubaki force was small.

The present invention thereby realizes a corrosion-resistant zinc negative electrode with a low hydration rate, and provides a low-pollution zinc-alkaline battery with excellent discharge performance and storage stability.

Hereinafter, this will be explained in detail using examples.

Examples Various zinc alloys were prepared by adding the various elements shown in the following table to a zinc ingot with a hardness of 99.9972 g, melted at about 500°C, and powdered by spraying with compressed air. 15
The particles were sieved to a particle size range of 0 mesh. 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. Thereafter, it was washed with water, replaced with acetone, and dried to produce zinc carbide 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 carbide 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 mm, the weight of the negative electrode carbonized powder is unified to 193 Trur, and the amount of mercury added (water ratio) is 1 weight per 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 one month. The discharge performance was expressed as 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 determined visually, 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. The discharge performance is significantly deteriorated due to inhibition of the discharge reaction by the zinc negative electrode, and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode.

Now, in the table, No. listed as a comparative example of the present invention,
When the additive element is added alone among 1 to 8 (No, 1
．． However, the corrosion resistance and discharge performance of the zinc negative electrode were improved somewhat when two elements were added (No, 6.7.8) than in the case of In, Ni, Ca, and 2.3, 4.5).
Examples of the present invention (No. 10.11.12.
15.16.17.20.21.23.24゜25,2
In the case of 6.27.28.29.30), the corrosion resistance and discharge performance are even better than in the above-mentioned comparative example, and the combined effects of the added elements are clearly exhibited. - Even if crab elements coexist, there is an excess or deficiency in the content (No, 9, 1
3.14.18.19.22.31.32) are not much different from the comparative example, and the combined effect is poor.

As mentioned above, the present invention includes In, Ni, Ca, Sr,
8=Ig in appropriate combination, e.g. (No, 27.28
．． As shown in 29.30), by using a zinc alloy in the negative electrode in an appropriate amount, the reduction in shrub size was successfully achieved. The content of each element is In: 0.005 to 0
．． 5% by weight, Ni 0.01-0.5% by weight, Ca, S
r, the sum of one or more types of Mg is 0°005 to 0.
A suitable amount is 2% 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 an unformed zinc 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 in such a case, the water ratio can be lowered, and depending on the case, it can be carried out without any water.

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] 0.005-0.5% by weight of indium, 0% of nickel
．． 01-0.5% by weight, calcium, strontium,
A zinc alkaline battery using a zinc alloy containing 0.005 to 0.2% by weight of one or more types of magnesium as a negative electrode active material.