JPS58163152A - Manufacture of silver (2) oxide cell - Google Patents

Abstract

PURPOSE:To obtain a silver (II) oxide cell with less increase of the internal resistance during storage by forming a lead-dioxide layer on the surface of a positive electrode shaped body, in the neutral aqueous solution. CONSTITUTION:260mg. of the mixture consisting of 47.5 parts of silver (II) oxide powder and 47.5 parts of silver (I) oxide powder is press-molded under 5t/ cm<2> pressure to a shaped body having a diameter of 9mm. and a thickness of 0.7mm.. Said shaped body is immersed for 60min into the aqueous solution containing 1.5gr. of lead nitrate dissolved into 1,000ml, water allowing lead dioxide to be deposited onto the surface, and then washed and dried. The amount of lead dioxide deposited onto the positive electrode thus formed is 0.3mg, and the results that the absorption rate for carbon dioxide is exceedingly small and the increase of the internal resistance during storage is little are shown in the figure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the manufacturing method of a silver oxide battery, and an object of the present invention is to provide a silver oxide battery whose internal resistance increases less during storage.

In silver oxide batteries, if phosphorescent graphite or carbon plaque, which is often used in silver oxide batteries, is used as a conductive agent, the oxidizing power of the silver oxide is too strong, so these will not be oxidized. It turns into carbon dioxide and loses its conductivity, and the generated carbon dioxide reacts with the electrolyte and consumes the electrolyte, so it is necessary to add conductivity with something other than phosphorous graphite or carbon plaque. No.

Therefore, the surface layer of the press-molded product of silver oxide is reduced to form a layer of ferrous oxide around the ferrous oxide layer, and the surface layer of the ferrous oxide layer is further reduced to 1. A silver layer is formed around the ferrous oxide layer to impart electrical conductivity and to prevent the two-stage discharge characteristic of ferric oxide batteries.

However, batteries using a positive electrode with a three-layer structure consisting of a silver oxide layer, a silver oxide layer, and a silver layer suffer from the problem that the silver layer on the surface disappears during storage (2) the internal resistance of the battery increases. There is.

Therefore, the present inventors conducted various studies on the causes of the disappearance of the silver layer, and found that the disappearance of the silver layer occurs when the surface silver layer and the internal silver oxide layer have ionic contact with each other in the same electrolytic solution. Because it exists in the system, the following formulas (1) and m) 2Ago+H20-t-2e-+Ag20+ are present in the positive electrode.
20H- (T)2Ag+20H-→Ag
It has been found that a type of battery reaction using silver oxide as the positive electrode and silver as the negative electrode, as shown by 20+H20+2C-(+t), occurs when silver is oxidized to become silver oxide1- is.

Based on such findings, the present inventors have conducted extensive research to provide conductivity to the positive electrode using a substance other than silver in order to suppress the increase in internal resistance during storage, and as a result, have developed the following. They discovered that by forming a layer of lead dioxide on the surface of the positive electrode, a silver oxide battery with little increase in internal resistance during storage could be obtained, and the present invention was completed.

That is, the present invention immerses a molded body containing ferric oxide in an alkaline aqueous solution in which lead ions are dissolved, oxidizes the lead ions using the oxidizing power of the ferric oxide, deposits lead dioxide on the surface of the molded body, and makes the molded body conductive. This invention relates to a method for manufacturing a silver oxide battery, characterized in that it is used as a positive electrode.

To explain the present invention in more detail, when a molded article containing silver oxide is immersed in a neutral aqueous solution in which lead ions are dissolved, 2 parts gO + Pb2++2 as shown in the following formula 010.
0H-→A, O+PbO2+H20 (Ill) Lead ions are oxidized to become lead dioxide, which is tetravalent lead, and deposited on the surface of the molded body.

By the way, lead dioxide is an oxide in the highest oxidation state, so it cannot be oxidized any further, so it has extremely good oxidation resistance, good alkali resistance, and has good electrical conductivity comparable to that of metals. If a layer of lead dioxide is formed on the surface of the positive electrode as in N1 above, this battery will have a small internal resistance and can be put to practical use, and the increase in internal resistance will be small during storage. Become.

Furthermore, since lead dioxide has extremely high oxidation resistance, it will not be oxidized and disappear like silver, and will continue to function as a conductive layer whenever it is used, so its thickness should be kept to the minimum necessary. be able to. Therefore, in comparison with conventional batteries, where the thickness of the silver layer was changed depending on the storage period, and the silver layer had to be made thicker when the storage period was long, the manufacturing process was simplified, and the oxidation Since the two silver layers can be made larger, the discharge capacity is improved. Further, since lead dioxide acts as an active material after the reaction of ferric oxide and silver oxide, it is possible to increase the discharge capacity from this point of view as well.

By the way, the present inventors previously immersed the positive electrode molded body in an alkaline aqueous solution in which lead ions were dissolved, oxidized the lead ions with the oxidizing power of silver oxide, and deposited lead dioxide on the surface of the molded body. They discovered that conductivity can be imparted to the positive electrode7 and have already applied for a patent17. Although this method is excellent from the perspective of imparting conductivity, it is difficult to perform alkali cleaning treatment after forming the lead dioxide layer. In addition, there is a problem that the positive electrode active material easily absorbs carbon dioxide when it is alkaline, resulting in a decrease in the amount of discharged electricity. The present invention solves the above-mentioned drawbacks by forming the lead dioxide layer using a neutral aqueous solution.

The molded article containing silver oxide used in the present invention can be produced by pressure molding a mixture of silver oxide and silver oxide, or by thermally decomposing the surface layer of silver oxide powder. It is obtained by pressure molding a ferric oxide powder having a layer of ferric oxide on the surface of the particles reduced to ferric oxide. Alternatively, it may be formed by pressure molding only silver oxide. Furthermore, in order to improve moldability, these active materials may be pressure-molded with a small amount of a binder such as polytetrafluoroethylene added thereto.

A neutral aqueous solution in which lead ions are dissolved for dipping the molded body can be obtained by dissolving, for example, lead nitrate, lead acetate, etc. in water. Although the concentration of lead ions is not particularly limited, a concentration close to saturation is usually selected. In the present invention, a neutral aqueous solution in which lead ions are dissolved refers to an aqueous solution that dissolves lead ions and has a pH in the range of 5 to 9.

The thickness of the lead dioxide layer formed on the surface of the molded product is usually 10 μm.
A certain degree of conductivity can be ensured. The immersion time varies depending on the concentration of the liquid and other factors, but is usually about 80 to 120 minutes.

Next, the present invention will be explained with reference to Examples.

Example: 5 tons of 260 parts of a mixture consisting of 47.5 parts (by weight, the same applies hereinafter) of ferric oxide powder and 47.5 parts of ferric oxide powder
Pressure molded in 7 m2 parts, diameter 9sm, thickness 0.7ff
A molded body was produced.

Next, this molded body was mixed with lead nitrate of 1.59? Water 100077
A molded body was obtained by immersing the molded body in an aqueous solution dissolved in Jl and changing the immersion time to vary the amount of lead dioxide deposited on the surface of the molded body. FIG. 1 shows the relationship between the amount of lead dioxide deposited on this molded body and the electrical resistance of the molded body.

As shown in FIG. 1, if the amount of lead dioxide deposited is 0.2 cap, the electrical resistance of the molded body can be reduced to a desirable level.

Based on the above experimental results, a battery was assembled as shown below using a molded body to which 0.3 cap of lead dioxide was attached as a positive electrode.

That is, the above-mentioned positive electrode (1) is inserted into the positive electrode can (4) into which a part of the electrolytic solution is injected, and the seven filters (5) and the electrolytic solution absorber (6) are placed on the positive electrode (1). They were placed sequentially.

Next, an annular gas is attached to the periphery of the positive electrode can (4) f in this state.
7 pieces) (7) f*combined, 7. Wow. Ah, ka4
I, engineering. Oh.

Fit the negative electrode terminal plate (8) containing the negative electrode (9) as the electrode active material and the remaining half of the electrolyte, and tighten the opening of the positive electrode can (4) inward by bending it. A button-shaped ferric oxide battery having the structure shown in FIG. 2 was manufactured by pressing the inner peripheral surface of the battery against an annular gasket (7) and sealing the battery.

In FIG. 2, (2) constituting the positive electrode (1) is a layer containing ferric oxide, and in this example, it is formed by pressure molding a mixture of ferric oxide and ferric oxide. It is something that (3) is the lead dioxide layer formed as described above.

Comparative example Pressure molded silver oxide powder 260 cape to a diameter of 9 mg.

A molded body having a thickness of 0.71 nI was produced.

This molded body was immersed for 60 minutes in a mixed solution of 30% potassium hydroxide aqueous solution and ethyl alcohol in a container ratio of 9=1.
It is reduced to a partially fully oxidized argonium oxide with a thickness of about 100 μm from the surface, and then it is dissolved in a 1% alcohol solution of hydrazine for 1 hour.
The sample was immersed for 0 minutes, and the silver oxide in a portion approximately 50 μm thick from the surface was reduced to silver.

A button-shaped ferric oxide battery was manufactured in the same manner as in the example except that the positive electrode having a three-layer structure consisting of the second @ oxide layer, the ferrous oxide layer, and the silver layer thus prepared was used.

The battery of the example and the battery of the comparative example manufactured as described above were stored at 60°C for a predetermined period of time, and changes in internal resistance at that time were examined. The results are shown in FIG.

As shown in FIG. 3, the increase in internal resistance due to storage in the battery of the example is smaller than that of the battery of the comparative example.

Next, Table 1 shows the difference in carbon dioxide absorption rate between the positive electrode a in the present invention and the positive electrode in which a lead dioxide layer was formed using an alkaline solution.

The positive electrode a in the present invention contains 5 parts of a mixture of 47.5 parts of ferric oxide powder and 47.5 parts of ferrous oxide powder.
A molded body having a diameter of 9 m and a thickness of 0.7 bait molded under pressure at t/cm2 was immersed in an aqueous solution of 1.5 f of lead nitrate dissolved in 1000 m of water for 60 minutes to deposit lead dioxide on the surface, and then washed with water. , made by drying. The positive electrode is a pressure molded product similar to the above f80% potassium hydroxide aqueous solution 20
The molded body was made by immersing it in a solution of 1f lead monoxide dissolved in 0ml for 60 minutes to deposit lead dioxide on the surface of the molded body, washing with water, and drying. In each case, 100 molded bodies with lead dioxide layers formed thereon were placed in 200 ml of water, and the molded bodies were washed by gently shaking the molded bodies. The number of times of water washing was 5 for both. The amount of lead dioxide deposited was o and aMg in both cases, and the carbon dioxide absorption rate was measured after leaving the positive electrode in the atmosphere for 24 hours.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of lead dioxide deposited and the electrical resistance of the molded body, FIG. 2 is a cross-sectional view of a ferric oxide battery manufactured according to an embodiment of the present invention, and FIG. 3 is a diagram of the present invention. FIG. 3 is a diagram illustrating changes in internal resistance due to storage of a battery according to the conventional method and a battery according to the conventional method. (1)...Positive electrode, (2)...Layer containing ferric oxide, (3)...Lead dioxide layer Patent applicant Hitachi Maxell Co., Ltd. Representative Patent Attorney Tetsuo Miwa Wholesaler 1□Pasho, 1 ano 1st figure 0 0.1 0.2 0.3
0.4 0.5 Adhesive amount of lead dioxide (mP) Figure 2

Claims (1)

[Claims] 1. A positive electrode is produced by immersing a molded body containing ferric oxide in a neutral aqueous solution in which lead ions are dissolved, and oxidizing the lead ions using the oxidizing power of the ferric oxide to deposit lead dioxide on the surface of the molded body. A method for producing a ferric oxide battery, characterized by: