JPS605528B2 - 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 add a silver nitrate solution and an oxidizing agent to an alkaline hydroxide solution to precipitate silver peroxide.

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

This is expressed, for example, as the amount of oxygen generated in a given time from silver peroxide present in a 40% sodium hydroxide or potassium hydroxide solution at 4 pi . 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. The commonly obtained filtered silver oxide is much less stable in potassium hydroxide electrolytes than in sodium hydroxide electrolytes. The reason why silver peroxide becomes unstable is thought to be due to the high activity of silver peroxide, which reacts with the alkaline electrolyte that comes into contact with it. coating is described in US Pat. No. 3,017,448.

In this method, 0.1 to 5% 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. This Ikebo Kaisho 5
Publication No. 4-132732 or Tsubaki Sekisho 54-13273
Publication No. 4 describes the addition of Zn, Cd, and AI to improve the stability of silver peroxide, and it is also known that the addition of V, Cr, etc. has some effect. There is. However, the effect of these additives is that the amount of oxygen generated is 1/2 to 1/2 compared to when no additives are used.
In the 40 qo, 40% potassium hydroxide solution, it was more than 3 times per evening and 4 times in the morning. The applicant had previously applied for the same purpose under the Special Order No. 54-103.
No. 1 and Japanese Patent Application No. 1984-84427 disclose the effects of adding lead and tellurium, and lead and aluminum, respectively, and especially in the latter case, the instability in potassium hydroxide solution is greater than that of sodium hydroxide. It was reported that silver peroxide with excellent stability unparalleled in the past could be obtained. The inventors researched a method to further dramatically reduce the amount of oxygen generated, and added 0.0% by weight of cadmium as a metal to silver peroxide once generated.
and the tellurium component is 0.01% by weight or more, and C
A method of adding d-Te so that the content ratio becomes 0.5 or more was filed as Tokuiso Sho 55-83974. Furthermore, as a result of intensive research into the method of adding cadmium and tellurium components, the inventors found that instead of adding cadmium to tellurium components to silver peroxide once produced, they could be added to the reaction raw materials for silver peroxide or during the reaction process. The present invention was achieved by discovering that the stability of silver peroxide was similarly improved. That is, this invention relates to a manufacturing method for producing silver peroxide for batteries, for example, in which alkali hydroxide, silver nitrate, and an oxidizing agent are reacted, which is generally used. A cadmium component and a tellurium component are added in advance and reacted to produce silver peroxide containing cadmium and tellurium, or during the reaction process of silver peroxide, that is, a neutralization process, an oxidation process, and an alkali washing process. Silver peroxide containing cadmium and tellurium is produced by adding cadmium and tellurium components to either the Shino process or the like, and the cadmium component is removed as a metal in silver peroxide.
．． 03% by weight or more, and tellurium component by 0.01% by weight
and the content ratio of Cd/Te is 0.5 or more.

Further, one of the cadmium component and the tellurium component may be added to the reaction raw material and the other during the reaction process, or may be added to both the reaction raw material and the reaction process.

Even when this invention is applied to other conventionally known manufacturing methods, such as silver halide oxidation method and ozone oxidation method, the effectiveness varies slightly, but all of them improve the stability and reduce the gas generation rate. Can be reduced.

The cadmium component and tellurium component contained in silver peroxide are metals such that cadmium is 0.0% by weight or more, tellurium is 0.01% by weight or more, and the Cd/Te ratio is 0.5.
The above is necessary. Even when using a combination of 0.03% by weight of cadmium and 0.01% by weight of tellurium, which is the lower limit addition amount of both components, the stabilizing effect of silver peroxide is significantly improved compared to the conventional technique in which cadmium is used alone. To obtain the same effect, cadmium should be added to 0. Since it is necessary to use more than % by weight, it is considered that the use of both components clearly shows a synergistic effect. Of course, the effect of reducing the amount of oxygen generated when using cadmium and tellurium in combination is sufficiently effective compared to samples without additives, but if the content of each is below the above lower limit addition amount, the effect may not be sufficiently noticeable. Become. Furthermore, it is necessary to maintain the Cd/Te ratio to be contained at 0.5 or more; 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. Undesirable.

The upper limit of the amount of both components used is preferably about 1% by weight for the total of cadmium and tellurium; using too much will lower the purity of silver peroxide, leading to a decrease in the amount of electricity generated. However, when used as an extender for forming an anode of a battery, it is possible to add 1.0% by weight or more, and even in this case, the stability of silver peroxide will not decrease. Examples of cadmium components to be added include cadmium oxide, 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. Ru.

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 CdTe03, CdT
e04, Cd-Te alloy powder can also be added.

In the case of the tellurium component, it is dissolved in the caustic aqueous solution, so the entire amount added does not remain in the silver peroxide.
Depending on the addition conditions, the performance may be quite poor.

In such a case, it is necessary to predict the yield rate of the tellurium component in advance and add the amount in excess. Further, in order to improve the growth rate of tellurium, it is preferable to add it to the alkali refining step after the reaction is completed. This invention will be described below with reference to embodiments.

Example 1 Pot A: 1/2, pH 2.0 silver nitrate aqueous solution 1000'
Add cadmium and tellurium components to Cd(OH)2, Te
Add the specified amount in the form of 02, shake well and heat to 80℃*, add 400mL of sodium hydroxide/250mL of an aqueous solution, then add 150mL of potassium persulfate, and react for 30 minutes. After that, wash the forehead thoroughly and wash the rice bran.
Potassium hydroxide 4 was used as a sample of filtered and dried silver peroxide.
The gas generation rate per night of Ago at 40 qo in a 0% aqueous solution and the contents of cadmium and tellurium in the silver peroxide product were measured.

The results are shown in Table 1. Table 1 Test No. Comparative Examples 1 to 3 do not contain cadmium or tellurium at all, or contain only one of them.

Test No. Although both 4-cadmium and tellurium are added, the amount of addition is below the lower limit of this invention, so the gas generation rate is not sufficiently reduced. Test No. No. 59 is a product according to the present invention, and all of them show a remarkable decrease in gas generation rate. Test No. 9
This is the case when the amount added is large, but it shows that there is a limit to the effect even if added more than this. Test No. 10-14
Test No. 1 is an example in which the Cd/Te ratio is 0.5 or less, and the amount of cadmium added is almost the same. Even when compared with Test Nos. 6 to 8, the effect is no longer noticeable, especially in Test No. 1
As shown in No. 4, when the amounts of Cd and Te added are large, the problem becomes significant. Example 2 A predetermined amount of a cadmium source was added to 100 liters of the NaOH aqueous solution, simmered well, and 160 quarts of potassium persulfate was added to it, and the mixture was made to overflow to 75 quarts, containing 0.00 liters of A-chicken. Add 165% of an aqueous silver nitrate solution and allow to react for 40 minutes.

After the reaction was completed, a predetermined amount of tellurium source was added, and the reaction was carried out for 10 minutes at 80 oo of saline, followed by washing, washing, and filtering.
The gas generation rate per evening was measured. The results are shown in Table 2. Table 2 Test No. As shown in 15 to 18, similar effects were observed even when various cadmium sources and tellurium sources were used, although there were some variations in the results.

Test No. 19 and 20 show the results of using NaOH in the gas generation rate test. The Cd/Te ratio is 2 in both cases.
．． It was 0 or more. Example 3 100% of the sodium chloride aqueous solution 500% *C
Add a predetermined amount of d○, Te02, gradually add 33 yen silver nitrate crystals while holding a light to make silver chloride, and add 50 ml of silver chloride to this.
After dissolving the solution, add NaOH crystals to adjust the concentration to 75 quarts, then add 30 quarts of potassium persulfate powder little by little, and let the mixture react for 3 hours while stirring.

The product was refined, passed through the oven, and dried for 2 hours at 660°C to produce Example 2.
The gas generation rate was measured in the same manner. The results are shown in Table 3.
From the results shown in Table 3 above, it can be seen that even when the present invention is applied to the production process of silver peroxide via silver chloride, it shows great effects.

Claims (1)

[Claims] 1. A method for producing silver peroxide for batteries, which consists of adding a cadmium component and a tellurium component during the reaction raw material or reaction process of silver peroxide, at which time 0.03 weight of the cadmium component as a metal is added to the silver peroxide. % or more and a tellurium component in an amount of 0.01% by weight or more and a Cd/Te content ratio of 0.5 or more.