JPS5924496B2 - Manufacturing method of positive electrode for silver oxide batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides silver divalent oxide Ag0 or monovalent silver oxide Ag0 and monovalent silver oxide Ag0.
The present invention relates to an improvement in the positive electrode of a silver oxide battery in which a mixture with No. 20 is used as a positive electrode active material and, for example, zinc is used as a negative electrode active material.

Mercury batteries or silver oxide batteries are conventional power sources for small devices.

And with the recent increase in electronic devices that have become even more compact,
The size of batteries has been limited, and there has been a demand for smaller and higher output batteries. Therefore, the active material of conventional silver oxide batteries is i].

For silver oxide Ag2O, the capacity per weight is 1.
Silver divalent oxide (Ag0) is attracting attention because it can extract 86 times the capacity and 1.93 times the capacity per volume. However, this Ag0 is unstable in an alkaline solution and generates oxygen gas when decomposed from Ag0 to Ag2O as shown in 2AgO→Ag3O+1/20|, so there was a problem that it could not be used as a sealed battery.

Therefore, in order to obtain stable Ag0, production methods such as anodic oxidation of silver salt in an alkaline solution, electrolysis of silver nitrate solution, or ozone oxidation of silver salt have been proposed, but these methods cannot be used as a sealed battery. Stable Ag0 has not been obtained.

In addition, there is a method of mixing lead oxide PbO powder into AgO to use as a positive electrode active material, and by making lead ions exist in the alkaline electrolyte in the battery structure and injecting that electrolyte into the battery, it is possible to suppress the generation of oxygen gas from AgO. Attempts are being made to do so.

However, in the former method, the effect is not sufficiently recognized, and in the latter method, sharp ions in the electrolytic solution react with zinc of the negative electrode active material, causing self-discharge of the zinc electrode, so it is not suitable. A common problem with both is that AgO powder itself has very poor moldability, and it is difficult to form a molded body unless some kind of binder is mixed into the powder. Normally, 1 to 5% by weight of fluororesin is added, but even in this case, sufficient strength is not obtained, resulting in cracks in the molded product and chipping at the edges.
The present invention is based on the discovery that by treating Ag0 with an alkaline solution containing lead acid ions, gas generation due to decomposition of Ag0 can be effectively suppressed and the formability of the positive electrode can be improved. .

The present invention will be explained below with reference to Examples.

A solution is prepared by dissolving silver nitrate AgNO35O9 in 100TrL1 of water.

Next, an alkaline solution containing 709 NaOH dissolved in water 11 was kept at a temperature of 80'C, and potassium persulfate K2S2
At the same time as the addition of O8729 is completed, the above AgNO3 solution is added dropwise for about 10 minutes. At this time, the reaction vessel (flask)
Inside, use a stirrer to continue stirring at a constant speed until the synthesis is complete. After dropping the AgNO3 solution, the temperature was raised to 90°C for about 15 minutes.
and kept at the same temperature for 20 minutes to finish converting AgNO3 into AgO.

Next, the supernatant liquid in the reaction vessel is discarded, and water 11 is newly added, and after stirring for 5 minutes, the supernatant liquid is discarded again. Then 3 mol/IO
Add a solution of 0.79 lead oxide dissolved in KOH or HaOH aqueous solution 11 to the above container, stir at room temperature for 2 hours, then discard the supernatant, then add water 1' and stir for 5 minutes, then discard the supernatant. Repeat the operation 6 times.

The product is then filtered and dried under reduced pressure at a temperature of 50° C. for 15 hours. A with a silver lead acid compound formed on the surface in this way
Obtain gO. On the other hand, by electrochemical method. To obtain AgO, a silver net is used as a current collector, and on both sides, an average particle size of 30
Electrodes are made by press-molding micron silver powder using a force of about 2000K9A.

Using this electrode as an anode and a nickel or silver plate as the counter electrode,
5 mol/F. Anodize in KOH or HaOH aqueous solution. The molded electrode made into AgO was washed with water and KOH
Or NaO} {remove and dry, then crush, AgO
) to obtain a powder. Next, a silver lead acid compound is generated on the surface of the AgO powder by the same method as described above. Next, AgO(a) obtained by the above chemical oxidation method, AgO powder also obtained by the chemical oxidation method, and 2 weight? The results of comparing the characteristics of (b) a mixture of PbO powder and (c) a mixture of silver lead acid compound 2 on the surface of AgO obtained by a chemical oxidation method will be explained.

First, each sample 19 was taken and molded at a pressure of 2000 K7 using a cylindrical mold with an inner diameter of 10.6 mm.The molding thickness and moldability were as shown in Table 1. Also, 2 weights 70 for each sample.
Table 2 shows the average rate of gas generation when pellets formed in the same manner as above with the addition of fluororesin powder as a binder were immersed in a 10 mol/IKOH aqueous solution at a temperature of 70'C for 4 hours. It was hot. Next, the above pellet was used as a positive electrode,
An alkaline battery with an actual capacity of 160 mAh was constructed using a molded body of amalgamated granular zinc as a negative electrode, and after being stored at a temperature of 45°C for 1 month, the battery capacity was compared when it was discharged with a resistance of 1 KΩ as a load. It looked like Table 3.

As is clear from the above, chemically synthesized AgO,
By processing in an alkaline solution containing lead acid ions, gas generation due to decomposition in an alkali can be reduced.

Furthermore, as a result of the improved moldability, it has become possible to assemble the battery easily and improve the volumetric efficiency of the battery. In addition, as shown in Table 3, batteries using chemically synthesized A and a silver lead acid compound as the positive electrode showed discharge capacity as designed, but AgO mixed with PbO powder Batteries using AgO and chemically synthesized AgO
In a battery using PbO as an active material and injecting an electrolyte in which PbO was dissolved, the discharge capacity was lower than the designed value.

This is thought to be due to self-discharge of the negative electrode zinc. Note that the same applies to AgO obtained electrochemically instead of chemically synthesized AgO.

Next, curve 1 in the figure shows the relationship between the concentration of PbO dissolved in an alkaline solution for forming silver lead oxide on chemically synthesized AgO and the gas generation rate under the same conditions as in Table 2 above. shows. Curve 2 in the same figure is Pb against AgO powder.
The relationship between the amount of O(7) added and the gas generation rate is shown. In the method of the present invention, most of the lead content in the PbO dissolved in the alkaline solution for Ag(6) treatment is added to AgO by the AgO treatment, so the PbO concentration in the alkali is determined by the addition of PbO to AgO. Shown as quantity.

From curve 1 in the figure, in the method of the present invention, the amount of PbO is A
10f for gOlOO9! Although the gas generation rate is slowest in the vicinity, the utilization rate as an active material decreases due to the production of silver lead acid compounds, so 0.5 to 59Pb0/Ag
Approximately OLOO9 is appropriate.

The silver lead acid compound produced on the AgO surface by the method of the present invention was mainly Ag5PbO6. In the above embodiment, an example was shown in which AgO alone was used as the positive electrode active material, but even with the treatment according to the present invention, it is difficult to completely eliminate gas generation. Therefore, it is advantageous to mix this with Ag and O in an appropriate ratio to form a positive electrode active material, especially in reducing the expansion of the battery when stored at high temperatures. Table 4 shows that batteries using positive electrodes with different mixing ratios (weight ratios) of AgO powder forming a silver lead acid compound and Ag, O powders were aged at 45°C for 12 hours and then tested at 20°C for 60Ω and 1KΩ
A comparison of the discharge capacity when continuously discharging is shown.

The same table also shows the degree of expansion of the battery when stored at a temperature of 60°C as a change in the height of the battery.

Note that this battery is a button type battery with a diameter of 11.2 mm and a height of 4.0 mm. As is clear from Table 4 on the back side, when AgO according to the present invention is mixed with Ag2O in an appropriate proportion, it can be used to reduce battery expansion and provide a practical battery with a larger capacity than a battery using Ag and O alone. A silver oxide battery can be obtained.

[Brief explanation of the drawing]

The drawing shows the relationship between the amount of PbO added to AgO and the gas generation rate of AgO in an alkaline solution.

Claims (1)

[Claims] 1. A method for producing a positive electrode for a silver oxide battery, comprising the step of treating silver divalent oxide with an alkaline solution containing lead acid ions to form a silver lead acid compound on the surface.