JPS5832463B2 - silver oxide battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvement of the positive electrode active material in a silver oxide battery, and an object of the present invention is to provide a battery with good storage stability.

In recent years, various studies have been made on the use of ferric oxide (Age) as an anode active material.

This is silver oxide (Ag20), which has been commonly used for a long time.
Discharge capacity per unit volume of 1680 mAH/cri
L is E, whereas ferric oxide is about 3330 mAH
This is because it has a discharge capacity of about 2.0 times that of /- and is promising as an anode active material.

However, ferric oxide easily decomposes in alkaline electrolyte, resulting in significant performance deterioration during storage, and the oxygen gas generated during decomposition (thus promoting leakage of electrolyte and causing deformation and rupture of the battery). There are drawbacks to doing so.

In order to overcome these drawbacks, it has been proposed to form a coating of metallic silver or silver oxide on the surface of the ferric oxide particles, but no satisfactory results have been obtained.

As a result of various studies on the decomposition of silver oxide in an alkaline electrolyte, the present inventors found that the decomposition of silver oxide was suppressed by forming a gold film on the surface of the silver oxide. I discovered that.

Methods for forming a gold film on the surface of ferric oxide include direct plating using a method such as evaporation of ferric oxide powder, or gold plating on the surface of metallic silver, and then oxidizing the metallic silver. There is a method of metamorphosing it into silver oxide with a gold coating, but
The latter is more effective in suppressing the decomposition of silver oxide in an alkaline solution.

Details of the manufacturing method in which the surface of metallic silver is plated with gold and then oxidized to form a gold coating (secondary silver oxide) (This will be explained in the examples, but the method of plating metallic silver with gold is, for example, electrolytic plating. There are various methods of oxidizing gold-plated metallic silver (for example, anodizing method, ozone oxidation method, chemical oxidation method, etc.), and the present invention can be manufactured by a combination of all of these methods. .

Example 1: Silver powder with a particle size of about 50 μm or less is gold-plated using a chemical plating method, and then it is heated to 50 to 95 degrees Celsius in one pot of an alkaline solution such as sodium hydroxide or potassium hydroxide. Add an oxidizing agent such as potassium persulfate or sodium persulfate while stirring.
The gold-plated silver powder is chemically oxidized, then washed with water, collected and dried.

In the battery E of the present invention manufactured by the above method, 1 g each of the used silver oxide particles A and the conventionally used 2 g silver oxide particles B were kept at 38°C. Figure 1 shows the amount of gas accumulated when the sample was immersed in 10ml of solution.

The amount of gold coating on the second silver oxide used in the battery of the present invention is about 1% by weight based on 1 piece of silver.

As is clear from this figure, the amount of gas accumulated in the battery of the present invention (the amount of gas accumulated in the silver oxide particles used in this case is smaller than the amount of gas accumulated in the conventional silver oxide particles); Decomposition of ferric silver is suppressed.

As a conductive agent for the anode, it has good conductivity, low bulk density, and lubricating effect (this makes it easy to remove the formed anode from the mold).
Phosphorous graphite is commonly used for reasons such as its ability to be released from molds. It was found that the decomposition of ferric silver was accelerated.

This tendency is shown in Figure 2. An anode was made by mixing 0.5 g of phosphorous graphite in various proportions with 0.5 g of silver oxide and press-molding it. The graph shows the change in discharge capacity of the anode after being moistened with an electrolytic solution consisting of an aqueous IJum solution and stored at 60° C. for 40 days.

As is clear from this figure, as the amount of phosphorous graphite added increases (therefore, the decomposition of silver oxide is promoted, the discharge capacity decreases significantly after storage).

Therefore, it is more effective to form an anode by pressure-molding a positive electrode active material made of silver oxide without containing phosphorous graphite in terms of suppressing the decomposition of silver oxide.

The present inventors further attempted to increase the discharge capacity by increasing the packing density of the anode in order to obtain a stable anode with a large discharge capacity.

Figure 3 shows the relationship between the filling density of the anode and the discharge performance. Anodes with various packing densities were made by pressure molding, and the changes in discharge capacity were measured when the anodes were moistened with an electrolyte consisting of a 25% by weight aqueous sodium hydroxide solution and stored at 60°C for 40 days. It is something.

As is clear from this figure (the packing density of the anode is approximately 5g)
/- or more have a large discharge capacity with less decomposition of the active material, while if the packing density is less than about 5 g/-, the alkaline electrolyte will easily penetrate into the anode, and during storage]
Decomposition of silver oxide is occurring.

In addition, when the packing density of silver oxide is 5 g/- or more, most of the silver oxide particles have a plate-like shape, so when compression molding, sliding between the particles occurs, causing fine particles on the anode E. However, when using second oxide particles with a gold coating on the surface, the gaps between the particles are suppressed by the gold on the surface, which adversely affects storage performance. There is little impact.

[Next] Example 1 of the present invention will be explained.

About 100 g of silver powder with a particle size of about 1 to 20 microns, preferably about 5 to 15 microns, is mixed with about 2 ml of chloroauric acid (HAnCl 4-4H20).
Pour gold into 200 ml of a weak nitric acid solution in which 100 g was dissolved, and stir to chemically plate the gold onto the surface of the silver powder.

This silver powder was mixed with a sodium hydroxide aqueous solution (temperature change: 80°
While stirring the liquid under pressure with carbon, potassium persulfate 54 (Bi'), which is an oxidizing agent, is added to chemically oxidize the gold-plated silver powder.

After reacting with stirring for about 2 hours, high-purity silver oxide with a gold coating was obtained, which was then washed with water (to remove unreacted alkali, oxidizing agent, etc.), collected with a glass filter, and dried under reduced pressure. Thus, silver oxide on which a filter film was formed was obtained for use in the present invention.

In addition, in the examples, the amount of gold is about 1% by weight relative to silver,
A range of about 0.05 to 2% by weight is effective, preferably about 0.2 to 1.5% by weight.

The surface synthesized by the above method (using silver oxide with a gold coating formed thereon, and without adding phosphorous graphite)
Pressure molded at a pressure of ton/- to approximately 5.6j; l/-
An anode 1 having a packing density of .

Figure 4 shows a silver oxide battery using this anode 1, in which a small amount of alkaline electrolyte consisting of a 25% by weight sodium hydroxide solution is injected into the bottom of the anode can 2, and then the anode 1 Insert the anode 1 and moisten the anode 1 with the electrolyte.
A microporous film 3 made of polyolefin, a semipermeable membrane 4 made of cellophane, and a liquid-absorbing paper 5 made of vinylon-rayon mixed paper are sequentially placed on top of the film.

A cathode terminal plate 8 filled with a cathode agent 7 made of a mixture of zinc powder and a gelled alkaline electrolyte is fitted into the opening of the anode can 2 (here, a cathode terminal plate 8 is fitted through a gasket 6 made of synthetic resin and having an angular cross-section). Then, by bending the opening edge of the anode can 2 inward, the battery is sealed.

The present invention has the above-mentioned configuration, and uses silver oxide with a gold coating on the surface, does not contain phosphorous graphite, and has a packing density of about 5 g/cd or more. (Thus, these synergistic effects can be exerted, effectively suppressing the decomposition of the positive electrode active material mainly composed of silver oxide, and providing a silver oxide battery with good storage stability.

The G-12 type silver oxide battery C of this example and the conventionally used silver oxide were compression molded to increase the packing density of the anode to 4.
．． The packing density of the anode was made by compression molding the ferric oxide battery with 5 g/Cr1L and the ferric oxide to make the packing density of the anode 5 to 6 g/cyi.
Table 1 shows the storage characteristics of a silver oxide battery E with a temperature of t and a silver oxide battery F with a positive electrode packing density of 5.6 g/cIrL by adding silver oxide (gold powder).

In addition, the discharge duration in the table is the discharge time when the terminal voltage reaches 1.3 Vl when each sample battery (6.5) is discharged at 20°C with a load resistor of 12 connected. What is 6
Storage at 0°C for 20 days. ■ is the discharge duration after storage at 60°C for 40 days.

As is clear from this table, the battery of the present invention has superior storage stability compared to the conventional battery.

[Brief explanation of drawings]

Figure 1 is a relationship between the storage time of silver oxide and the amount of gas accumulated, Figure 2 is a relationship between the addition rate of phosphorous graphite and electrode performance,
FIG. 3 is a diagram showing the relationship between the packing density of the anode and the electrode performance, and FIG. 4 is a cross-sectional view of the ferric oxide battery according to the present invention. 1... Anode.

Claims (1)

[Claims] 1 A silver oxide battery that uses silver oxide as the main anode active material and an alkaline solution as the electrolyte (in this case, the surface of the anode active material particles made of silver oxide (a gold coating is formed on the surface of the anode active material particles) 1. A ferric oxide battery characterized in that positive electrode active material particles are molded without containing a conductive aid such as phosphorous graphite, and the packing density thereof is approximately 5 g/- or more.