JPS5999679A - Silver (ii) oxide cell - Google Patents

Abstract

PURPOSE:To prevent the internal short-circuit from occurring by containing silver (II) oxide as a main active material and lead dioxide as a conductive auxiliary in a positive electrode black mix and forming a gold-plated layer on the inner surface of a positive electrode can where at least the black mix is brought into contact. CONSTITUTION:Silver (II) oxide as a main active material and lead dioxide as a conductive auxiliary are contained in a positive electrode black mix 1, and a gold-plated layer 8 is formed on the inner surface of a positive electrode can where at least the black mix 1 is brought into contact. For example, a positive electrode black mix made of silver (II) oxide of 47.5wt%, silver ( I ) oxide of 47.5wt%, and lead dioxide of 5wt% is pressurized and molded at 5t/cm<2> to obtain a molded positive electrode black mix 1. Then, this black mix 1, a positive electrode can 2 formed with a gold-plated layer 8 with a thickness of 0.3mum on its whole inner surface, an alkaline electrolyte, and a negative electrode 6 using amalgamated zinc as an active material, etc. are used to produce a button- type silver (II) oxide cell.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferric oxide battery using ferric oxide (Age) as an anode material and lead dioxide (Pb02) as a conductive agent.

Conventionally, in this type of battery, an active material consisting of ferric oxide and usually a predetermined amount of silver oxide (Ag20) is mixed with lead dioxide as a conductive agent, and this is pressure-formed to form an anode can. However, batteries made using this method generate a lot of oxygen gas during storage, which damages the separator, resulting in a relatively high rate of internal short circuits in the battery. Ta.

As a result of studying the above-mentioned problem, the inventors found that direct contact between silver oxide in the anode mixture and lead dioxide, which has excellent conductivity, causes the potential of the silver oxide to directly change to an anode with a low cumulative overvoltage. It was discovered that gas is generated due to the application of gas to the gas, and as a result of further study based on this knowledge, the present invention was completed.

That is, in this invention, the anode mixture contains lead dioxide as a conductive additive along with ferric oxide as a living substance, and generally has a thickness of 0.05 to 1 μm on at least the inner surface of the anode can that the above mixture comes into contact with. This invention relates to a silver oxide battery characterized by forming a gold plating layer with a certain thickness.

As described above, in this invention, since a gold plating layer is formed on the inner wall surface of the anode can, the acid-based overvoltage of this gold plating layer is lower than that of an anode can (generally made of stainless steel or iron-nickel plating). Since the oxidation potential is extremely high, even if a potential difference is applied to the anode mixture, no oxygen gas is generated, and the rate of occurrence of internal short circuits during storage can be greatly reduced.

The gold plating layer is formed on the inner surface of the anode can, which is in contact with the anode mixture, but may be formed over the entire inner surface, including the surface with which the separator and sealing gasket come into contact, if necessary. In addition, a pedestal is often used when press-molding the anode mixture, and this pedestal is housed in the battery together with the anode mixture so that it comes into contact with the inner surface of the anode can. , if this is the case, please use the above pedestal (
A gold plating layer similar to that on the inside of the anode can should be formed on the inner surface of the can that comes into contact with the anode mixture.

The present invention will be explained below based on examples.

Example: 47.5% by weight of opaque silver oxide and 47.5% by weight of silver oxide
and 5% by weight of lead dioxide.
Pressure molded at ton/d, diameter 9 mm, thickness 0.7 rr
A molded anode mixture of vt+ was obtained. Using this mixture, batteries as shown in FIGS. 1 and 2 were produced by the following method.

First, a part of alkaline electrolyte is injected into the anode can 2 which has a gold plating layer 8 of 0.3 μm thickness formed on the entire inner surface, the above-mentioned molded anode mixture 1 is inserted, and a separator is placed on top of this mixture 1. 3 and electrolyte absorber 4 were placed in order.

Next, the anode can 2 in this state is fitted with an annular gasket 7 around its periphery, and a cathode terminal plate containing a cathode 6 containing 75 mg of amalgamated zinc as an active material and most of the remaining alkaline electrolyte is inserted. 5, the opening of the anode can 2 is tightened and bent inward, and its inner circumferential surface is pressed against the annular gasket 7 and sealed at °C to form the anode shown in FIGS. 1 and 2. A button-shaped ferric oxide battery with the following configuration was fabricated.

The anode can 2 used before the gold plating layer was formed was made of iron and had its surface plated with nickel, and the cathode terminal plate 5 was made of a copper-stainless steel-nickel clad plate. As separator 3, graft film (
A composite membrane laminated with a graft film obtained by graft-polymerizing methacrylic acid onto a crosslinked low-density polyethylene film is used, and the electrolyte absorber 4 is made of a polypropylene nonwoven fabric. As the alkaline electrolyte, a 25% by weight aqueous solution of caustic soda in which zinc oxide was dissolved was used. The battery (button type) has a diameter of 9.5 mm and a height of 2.7 rrvn.

When the silver oxide battery thus obtained was stored at 60° C., the relationship between the number of storage days and the rate of occurrence of internal short circuits was investigated, and the results were as follows.

The following comparative example is a test result of a battery manufactured in the same manner as in the above example except that no gold plated layer was formed on the inner surface of the anode can made of iron-nickel plating.

Further, the internal short circuit occurrence rate is expressed as the number of internal short circuits occurring out of 100 tests, and the internal short circuit here means that the open circuit voltage is lower than 1.5V.

Example product Comparative product After 40 days of storage 0 pieces θ After 60 days of storage 0 pieces 3 After 100 days of storage
0 廚 15 As is clear from the above test results, it can be seen that the silver oxide battery of the present invention has good battery performance in which the occurrence of internal short circuits is suppressed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a silver oxide battery according to the present invention, and FIG. 2 is an enlarged view of the section ■ in FIG. ■...Anode mixture, 2...Anode can.

Claims (1)

[Claims] (1) The anode mixture contains ferric oxide as a living substance and lead dioxide as a conductive additive, and a gold plating layer is formed on at least the inner surface of the anode can that comes into contact with the above mixture. Silver oxide battery.