JPS5924495B2 - Manufacturing method of silver oxide positive electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the positive electrode of an alkaline battery using silver divalent oxide AgO as a positive electrode active material and, for example, zinc as a negative electrode active material.

Batteries with higher capacity are being sought as power sources for small electronic devices, and among these, silver-zinc oxide batteries, which use divalent silver oxide as the positive electrode active material, have excellent battery performance and high capacity. It is also a particularly excellent battery in terms of compatibility.

Compared to the currently used monovalent silver oxide A920,
A9O is 1.86 times more powerful per unit weight and 1.86 times more powerful per unit weight.
The energy density is 93 times higher. However, there are problems when using it as a battery positive electrode active material. The problem is that AgO is unstable in alkaline solution, and 2Ag0→AI2O+XO
As the decomposition reaction progresses, it changes to stable A920 and at the same time releases oxygen gas. Therefore, when a sealed battery is constructed, the internal pressure of the battery increases, which ultimately leads to expansion of the battery, leakage, etc., and the high energy density characteristic of A90 cannot be utilized. In addition, the nature of AgO is that it is very unstable thermally, and the above decomposition reaction occurs at a considerable rate even at around 100°C, resulting in silver oxide and A9O.
(A silver oxide with an intermediate composition of 5Ag2O is produced. Therefore, in wet manufacturing methods such as chemical oxidation method and electrochemical oxidation method, it is necessary to dry the UO produced in the final process, but drying at high temperature is not possible. Therefore, it is possible to use methyl alcohol or ethyl alcohol just before drying, but since A90 is a very strong oxidizing agent, the alcohol acts as a reducing agent and the A90 Changes to A92O.

Furthermore, even with acetone which is stable against oxidation, some amount of A90 is inevitably generated. The present inventors oxidize silver salt or silver powder in an alkaline aqueous solution with an oxidizing agent such as potassium persulfate, potassium permanganate, or hypochlorite, or
In a method for obtaining A90 by electrochemical oxidation of an aqueous solution of a silver salt or a molded body of silver powder, it has been found that by treating the obtained AgO with tetrahydrofuran, the rate of gas generation in an alkaline solution can be significantly suppressed.

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

An alkaline solution of caustic soda 729 dissolved in 1 ton of distilled water is maintained at a temperature of 85°C, and potassium persulfate 759 is added to the solution.
At the same time as adding some distilled water to make a paste, add silver nitrate Af! to 100ml of distilled water! NO3
A solution in which 5l9 was dissolved was added dropwise over about 10 minutes, and then the temperature was raised to 90°C and the reaction was allowed to proceed for 20 minutes.

Meanwhile, the reaction solution is stirred at a constant speed. After the reaction is complete, the AjO produced in the solution is precipitated and the supernatant liquid is discarded.
Add approximately 1 ton of distilled water, stir for 5 minutes, and discard the supernatant liquid again. This operation is repeated until the pH of the supernatant liquid reaches 9.5, and the final washing liquid is filtered to obtain A9O. When obtaining MO from silver powder, it is sufficient to add silver powder instead of silver nitrate, or to form a molded body of silver powder and anodize it in an alkaline solution using it as an electrode.Then, it is necessary to wash it with distilled water and remove the alkali solution. except for. Next, Af obtained by oxidizing silver nitrate with potassium persulfate in an alkaline solution as described above.
! After immersing O in various organic solvents with water still attached and stirring, the temperature was 30°C and -7601! I! It was dried under a reduced pressure of 1 liter, and the time required for it to reach its desired mass was determined.

At the same time, this dried A9O was heated to 10NK0H at a temperature of 70°C.
The average gas generation rate was measured when immersed in an aqueous solution for 4 hours. These results are shown in the table below. As is clear from the above results, when A9O is treated with an organic solvent, the gas generation rate is generally reduced, but when treated with ethyl alcohol, as mentioned above, divalent silver oxide is converted to silver oxide. has increased, and as a result, the gas generation rate has apparently decreased.
Furthermore, in the case of acetone, the rate of gas generation was only slightly reduced as a result of the silver oxide A92O formation progressing to some extent. On the other hand, those treated with tetrahydrofuran had Af! Although there is no change in the zero state, the gas generation suppressing effect is observed.
The effect of suppressing gas generation was the same when A9O was dried and then treated with tetrahydrofuran.

As described above, according to the present invention, A9O with less gas generation
This enables a sealed battery using MO as the positive electrode active material.

Claims (1)

[Claims] 1. A silver oxide positive electrode comprising a step of obtaining divalent silver oxide by oxidizing a silver salt or silver powder in an aqueous alkaline solution using an oxidizing agent or electrochemical oxidation, and a step of treating this silver oxide with tetrahydrofuran. manufacturing method.