JPS5846453B2 - Method for producing silver peroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silver peroxide which has particularly low self-discharge properties and is excellent for use in batteries.

Silver peroxide for batteries needs to have a long life so as to be suitable for batteries used in watches and the like, and for this purpose, it is required to have stability, that is, low self-discharge properties.

During battery storage, silver peroxide gradually decomposes in the alkaline electrolyte and releases oxygen; however, if the stability of silver peroxide is poor, decomposition progresses during storage, reducing the usable power. In addition, the pressure of oxygen produced by decomposition causes deformation and damage to the airtight cell.

A commonly used method for producing silver peroxide is to precipitate silver peroxide by adding silver nitrate and an oxidizing agent to an alkaline hydroxide solution.

As a measure of the stability of silver peroxide for batteries, there is a specific value called the gas generation rate or oxygen generation rate.

For example, this is expressed as the amount of oxygen generated in a certain period of time from 1 g of silver peroxide present in a 40% sodium hydroxide or 9 um hydroxide solution at 40°C under conditions more severe than normal usage conditions. .

Silver peroxide batteries generally use sodium hydroxide as the electrolyte, but for applications that require a large current at one time, it is necessary to use potassium hydroxide as the electrolyte.

Usually obtained silver peroxide is much less stable in a potassium hydroxide electrolyte than in a sodium hydroxide electrolyte. This is thought to be due to reaction with the electrolyte, and to eliminate this drawback, US Pat. No. 3,017.
It is described in the specification of No. 448.

In this method, 0.1 to 5 parts by weight of lead, lead oxide, lead hydroxide, or sodium malite fine powder is mixed with silver peroxide, and the mixture is reacted in an alkaline electrolyte to form silver peroxide particles. This method generates lead acid silver on the surface.

In addition, JP-A-54-132732 or JP-A-54-
No. 132734 discloses Zn and Cd, respectively, to improve the stability of silver peroxide.

There is a description that A4 is added, and it is roughly V.

It is known that the addition of Cr or the like has some effect.

However, the effect of these additives is that the amount of oxygen generated is reduced to 40% compared to when no additives are used.
℃, 35μt/in 40% potassium hydroxide solution.
El・48 hours or more.

The applicant had previously filed a patent application for the same purpose in 1984-1031.
No. 2 and Japanese Patent Application No. 54-84427 disclose the effects of adding lead and tellurium, lead and aluminum, respectively, and in particular in the latter case even in potassium hydroxide solution where the instability is greater than that of sodium hydroxide. It was reported that silver peroxide with unprecedented stability could be obtained.

As a result of intensive research into ways to further dramatically reduce the amount of oxygen generated, the inventors have found that the amount of oxygen generated by silver peroxide can be reduced by coating the surface of silver peroxide with both cadmium and tellurium. The present invention was achieved by discovering that the amount of carbon dioxide is significantly reduced.

That is, this invention relates to a method for producing silver peroxide in which an alkali hydroxide, silver nitrate, and an oxidizing agent are reacted, which is generally used as a method for producing silver peroxide for batteries. The structure is such that it contains tellurium in an amount of at least 0.01% by weight and at least 0.01% by weight, and a Cd /Te ratio of 0.5 or more.

Even when this invention is applied to silver peroxide products produced by other conventionally known methods, such as silver halide oxidation method, electrolytic oxidation method, etc., there are some variations in the effectiveness, but in all cases, the stability is improved. can be improved and gas generation rate reduced.

To make silver peroxide contain cadmium and tellurium components, for example, alkali hydroxide, silver nitrate, and an oxidizing agent are reacted, and the resulting silver peroxide is poured into a slurry before over-drying to add cadmium and tellurium components. Although it is convenient to add and mix silver peroxide and overdry it in the wake, it is also possible to redisperse the once dried silver peroxide in a dispersion medium and add the same components of cadmium and tellurium. The same components of cadmium and tellurium may be mechanically mixed into this as is.

Further, in the process of manufacturing an anode for a battery using silver peroxide, the same effect can be obtained by adding the same components of cadmium and tellurium to a granulated product of silver peroxide and molding the product.

The cadmium component and the tellurium component contained in the silver peroxide must contain 0.03% by weight or more of cadmium, 0.01% by weight or more of tellurium, and 0.5% or more of CdTeO3 as metals.

Even when using a combination of 0.03% by weight of cadmium, which is the lower limit addition amount of the same component, and 0.01% by weight of tellurium, the stabilizing effect of silver peroxide is significantly improved compared to the conventional technique in which cadmium is used alone.

In order to obtain the same effect, it is necessary to use cadmium in a weight capacity of 0.3 or more, so it is thought that a synergistic effect is clearly exhibited by using the same component.

Of course, the effect of reducing the amount of oxygen generated when using cadmium and tellurium in combination is more effective than the sample without additives, but
If each content is below the above-mentioned lower limit addition amount, the effect will be insufficiently significant.

Furthermore, it is necessary to maintain the Cd/Te ratio to be contained at 0.5 or more, and if the ratio is 0.5 or less, that is, the amount of tellurium is more than twice the amount of cadmium, the effect will be reduced. So I don't like it.

The upper limit of the amount of these components used is preferably about 10 parts by weight in total of cadmium and tellurium, and using an excessive amount will lower the purity of silver peroxide, leading to a reduction in the amount of electricity generated.

However, when used as an extender for forming an anode of a battery, it is possible to add 10% by weight or more, and even in this case, the stability will not deteriorate.

Examples of cadmium components used include cadmium oxide,
Examples include cadmium hydroxide, metal cadmium powder, cadmium sulfide, cadmium sulfate, cadmium nitrate, cadmium stearate, cadmium formate, and cadmium selenide, which may be used alone or in combination.

Examples of tellurium components used include tellurium dioxide,
There are tellurium trioxide, metal tellurium powder, telluric acid, tellurite acid, or alkali salts thereof, and these can be used alone or in combination.

Compounds and alloys containing both cadmium and tellurium, such as CdTeO31CdTe04. Cd-Te alloy powder can also be added.

When metal powder is used as a cadmium source or tellurium source to be contained in silver peroxide, it is preferable that the metal powder has a smaller particle size because the specific surface area becomes larger and the effective surface area in contact with silver peroxide increases. It is preferable that most of the particles are 50μ or less.

This invention will be described below with reference to embodiments.

Example 1 Dried silver peroxide 10 (L9) synthesized using silver nitrate and potassium persulfate in an alkaline solution was poured into 10100O pure water and stirred to disperse it well.

In this, CdO is used as a cadmium source, and T is used as a tellurium source.
Using eO2, a predetermined amount of each was added as an aqueous dispersion, stirred for 10 minutes, and then filtered and dried.

For each product, the gas generation rate at 40° C. in a 40% aqueous solution of 9 ram hydroxide and the contents of cadmium and tellurium in the silver oxide product were measured.

The results are shown in Table 1.

Tests A1 to A3 are comparative examples that do not contain cadmium or tellurium at all, or contain only one of them.

In Tests 44 to 7, both cadmium and tellurium were added, but the amount added was below the lower limit of this invention, so the gas generation rate was not sufficiently reduced.

Tests/168 to 19 were products according to the present invention, and all showed a remarkable decrease in gas generation rate.

However, test/1619 is not preferable because the amount of additives relative to silver peroxide is large, resulting in a decrease in the amount of electricity generated.

Tests A20 to A22 are examples in which the Cd/Te ratio is 0.5 or less, and all of them show unfavorable results of 5.

Example 2 Dried silver peroxide 101 synthesized using silver nitrate and potassium persulfate in an alkaline solution and predetermined amounts of a cadmium source and a tellurium source were manually mixed in a dry state in a beaker with a capacity of 50 QmA'. , and further stirred for 15 parts using a blender.

For each product, the gas generation rate was measured at 40°C using potassium hydroxide or sodium hydroxide at a concentration of 40°C.

The results are shown in Table 2.

As shown in Tests A23 to A27, similar effects were observed even when various cadmium sources and tellurium sources were used, although there were some variations in the results.

Tests A28-30 are examples in which a compound or alloy containing both cadmium and tellurium was used.

Also, in the test, %31-33 is NaOH for gas generation rate test.
The results using 1. %31 and A33 are comparative examples.

Example 3: Silver peroxide synthesized using silver nitrate and potassium permanganate in an alkaline solution was wet mixed with a cadmium source and a tellurium source in the same manner as in Example 1, and the gas generation rate was adjusted to 40°C and 40°C.
% potassium hydroxide aqueous solution.

The results are shown in Table 3. Tests/1634 to 36 show that even if the oxidizing agent used in the production of silver peroxide is different, if a cadmium source and a tellurium source are added, the gas generation rate is similarly reduced.

Test A37-3 Example 4 20g of silver chloride 9 is a comparative example.

Repulp in 0ml of water, add 50g of NaOH crystals, maintain the temperature at 758C after dissolving, add 30g of persulfate little by little, and react with stirring for 3 hours.

After washing and drying, silver peroxide was obtained.

This silver peroxide had an AgO content of 98.1% by weight.

As in Example 1, predetermined amounts of CdO and TeO2 were added to this in a wet manner and dried.

The gas evolution rate at 40° C. in a 40% KOH aqueous solution was measured for each product.

The results are shown in Table 4. Test A40 is a comparative example in which no cadmium source or tellurium source is added, and Tests 41 to 44 show that even if the production method of silver peroxide is different, the gas generation rate similarly decreases when a cadmium source or tellurium source is added. ing.

Claims (1)

[Claims] 1. In a method for producing silver peroxide for batteries, the produced silver peroxide contains 0.03% by weight or more of a cadmium component and 0.01% by weight or more of a tellurium component as metals, and Cd/T.
A method for producing silver peroxide, comprising containing e in an amount such that the content ratio is 0°5 or more.