JPS5840306B2 - alkaline battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to alkaline batteries such as silver oxide batteries and manganese dioxide batteries that use an alkaline electrolyte as an electrolyte.

Generally, when sealing a battery, &'! A gasket made of synthetic resin such as polyethylene or polypropylene or rubber is placed in the opening part of the anode can, and by tightening this gasket inward of the anode can, the cathode current collector such as the cathode lead body or cathode terminal plate is removed. By pressing the contact surfaces between the anode can, the gasket, and the cathode current collector into close contact with each other, leakage of the electrolyte from these contact surfaces is prevented.

However, batteries that use an alkaline electrolyte such as caustic potash tend to have low leakage resistance despite the above-mentioned sealing means, and for this reason, until now, the shape of the cathode terminal plate has been designed to improve leakage resistance. In addition, the contact surface between the gasket and the anode can and cathode current collector is
Many proposals have been made, such as interposing a liquid backing such as fluorine oil, but even these proposed methods do not necessarily provide the high degree of leakage resistance required for use in wristwatches, electronic exposure meters, etc. I'm sure you've gotten it too.

By the way, electrolyte leakage in alkaline batteries is generally more likely to occur from the contact surface between the cathode current collector and the gasket than from the contact surface between the anode can and the gasket.

The reason for this is that most of the alkaline electrolyte is injected into the cathode side in order to improve discharge characteristics.
It is thought that this is mainly due to the electrochemical leap phenomenon peculiar to the cathode current collector.

That is, when the electrolyte is electrochemically reduced at the rising edge from the cathode agent layer in the cathode current collector, that is, at the boundary where the contact between the current collector and the cathode agent layer is broken, and OH- is generated,
The alkali concentration is locally high (and the surrounding electrolyte migrates to the above-mentioned rising part due to the concentration difference, but as a result of this migration being influenced by electrochemistry, it gradually changes over time along the current collector surface. L. Appears as an upward creep phenomenon.

In addition, the cathode current collector is typically made of steel or copper at least on the side of the current collector that comes into contact with the cathode agent, to prevent the formation of local batteries with amalgamated zinc powder, which is common as a cathode active material. Although it is composed of an alloy, the relatively large potential difference between this metal and zinc, which is an active material, is also a cause of the electrochemical leap phenomenon mentioned above.

In light of the above circumstances, it is an object of the present invention to improve the leakage resistance of the battery as a whole by suppressing leakage of electrolyte from the interface between the cathode current collector and the gasket as much as possible. As a result of intensive studies by the inventors for this purpose, it was found that when a specific anti-rust coating is formed on the surface of the copper alloy of the cathode current collector, the leakage resistance is greatly improved. was realized and was done.

An embodiment of the present invention will be described below based on the drawings. In FIGS. 1 and 2, 1 is an anode active material such as silver oxide, manganese dioxide, ferric oxide, or mercury oxide. , carbon fuzuzu An anode mixture containing a conductive agent such as phosphor graphite and partially impregnated with an alkaline electrolyte, 2 is the mixture 1 and a metal fixed to the periphery of the mixture. A separator that is in contact with the annular base 3 and is made of, for example, a hydrophilically treated microporous film 4, a cellophane film 5, and a liquid absorbing layer 6 such as vinylon-rayon mixed paper; I is an amalgamated zinc activated It is a cathode material that contains a substance and a glue such as sodium polyacrylate, carboxymethylcellulose, or starch, and is made by injecting most of the alkaline electrolyte into this.

8 is an anode can such as a nickel-plated iron can containing an anode mixture 1 and a separator 2, and a cathode terminal plate 9 as a cathode current collector with a cathode agent 7 filled in the opening of the can; An annular gasket 10 made of various resins such as polyethylene, polypropylene, etc. or rubber is interposed and fitted, and the anode can 8 is tightened inward to form a sealed structure inside the battery.

The cathode terminal plate 9 has a nickel layer 12 on the outer surface of a steel plate 11 to give an aesthetic appearance and satisfy corrosion resistance, and a copper layer 13 on the inner surface to prevent the formation of local batteries with the zinc active material. Usually, a clad plate consisting of a steel plate 11, a nickel layer 12, and a copper layer 13 is formed into a shape having a peripheral folded part 14 by drawing, or the edges of the steel plate 11 are formed in advance by a similar means. After forming, a nickel layer 12 and a copper layer 13 are formed by plating.

The surface 15 of the peripheral folded portion 14 of the terminal plate 9 and the copper layer 13 in the vicinity thereof that is brought into contact with the annular gasket 10
A rust preventive coating 16 is provided on the surface of the copper layer 13 by coating and drying a rust preventive agent containing benzothiazole or its derivative as a main component. It is strongly chemically bonded to the surface.

Here, the benzothiazole derivative refers to a compound represented by the general formula (wherein R represents a substituent such as a halogen or an alkyl group), and representative examples thereof include methylbenzothiazole and ethylbenzothiazole.

These benzothiazoles or their derivatives are usually dissolved in an alcoholic solvent such as methanol or ethanol at a concentration of about 0.02%.
Dissolve to a concentration of ~2 weight, preferably about 0.3 weight φ, apply this to the peripheral folded portion 14 of the cathode terminal plate 9 and the contact surface 15 of the copper layer 13 in the vicinity with the annular gasket 10, and dry. This makes it possible to form a film that adheres easily and is strong.

Nao, in forming this anti-rust coating, the contact surface 15
After removing oil etc. from the surface, it is made smooth by chemical polishing etc., and then a rust preventive film is formed on this smooth surface.The leakage resistance can be further improved significantly, and the surface roughness is The center line average roughness according to JISB0601 is about 3μ or less, preferably 0.5 to 3μ, and L.

In the above-mentioned embodiment, when the antirust coating 16 mainly composed of benzothiazole or its derivative is formed on the surface 15 in contact with the annular gasket 10 of the peripheral folded portion 14 of the cathode terminal plate 9 and the copper layer 13 in the vicinity thereof, the coating 16 improves the adhesion between the terminal plate 9 and the gasket 10, and further brings about an increase in water repellency and adhesion strength to the contact surface 15 due to the chemical bond between the benzothiazole or its derivative and the copper layer 13, Furthermore, the function unique to the anti-corrosion film is to prevent the formation of an oxide film on the surface of the copper layer 13, and the synergistic effect of these factors suppresses the leakage of electrolyte from the contact surface 15, which is mainly caused by the electrochemical leak phenomenon. Show effectiveness.

Such a leak-preventing effect cannot be achieved with common water-repellent resins such as fluorine resins, silicone resins, and polyamide resins, which are merely physically applied to the surface of the copper or copper alloy to be coated. It is something that cannot be obtained.

The following table shows the leakage resistance ( 45° C., 90% RH) in comparison with button-type batteries B and C having a different configuration from that of the present invention.

Note that battery B has a water-repellent resin coating 16 made of fluororesin formed on the contact surface 15 of the cathode terminal plate 9 with the gasket 10, and battery C has no coating formed on the contact surface 15 at all. The numerical values in the table are the number of batteries in which electrolyte leakage was observed when 100 batteries were tested.

From this table, it can be clearly seen that the battery A of the present invention has superior leakage resistance compared to the other batteries B and C.

FIGS. 3 and 4 show other embodiments of the present invention, in which an anti-rust coating 16 is formed on the contact surface 15 of the cathode terminal plate 9 with the gasket 10 in a button type battery. On the other hand, the gasket 10 of the cathode lead body 17 made of brass, which is an alloy of copper and zinc, in a cylindrical battery.
A rust-preventive coating 16 containing the benzothiazole or its derivative as a main component is formed on the contact surface 15 with L.

In the figure, the same numbers are given to those having the same composition and function as the previous example (・However, the anode can 8 is the inner can 8a and the outer can 8b
It consists of

Generally speaking, the contact surface 15 of the cathode lead body 17 with the gasket 10 is considered to be very important in terms of electrolyte leakage in a cylindrical alkaline battery. Accordingly, leakage of the electrolytic solution mainly due to electrochemical leakage along the lead body 17 can be effectively suppressed for the same reason as in the case of the button-type battery described above.

As described in detail above, this invention provides a method for making copper L-
A rust-preventing coating mainly composed of benzothiazole or its derivative is formed on at least the surface of the copper alloy that is in contact with the gasket. According to this, the surface of the copper alloy that contacts the gasket Since leakage of the electrolyte from the battery can be prevented, the leakage resistance of the battery as a whole is greatly improved.

Further, in the present invention, if a liquid backing such as pitch or silicone oil is further interposed between the anti-rust coating and the gasket, the leakage resistance can be further improved.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a button-type alkaline battery showing an embodiment of the present invention, Fig. 2 is an enlarged view of the part ■ in Fig. 1, and Fig. 3
The figure is a cross-sectional view of a cylindrical alkaline battery showing another embodiment of the present invention, and FIG. 4 is an enlarged view of the part (■) in FIG. 9.17... Cathode current collector, 10... Gasket, 1
5... Surface to be brought into contact, 16... Antirust coating.

Claims (1)

[Claims] 1 Antirust coating 1 containing benzothiazole or a derivative thereof as a main component on at least the surface 15 of the copper or copper alloy surface of the cathode current collectors 9 and 17 that is in contact with the gasket 10
An alkaline battery characterized by forming 6.