JPS5837946B2 - 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 rubber gasket made of synthetic resin such as polyethylene or polypropylene is placed at the opening of the anode can, and this gasket is tightened inward to the anode can to seal the cathode lead body and the cathode. By pressing against a cathode current collector such as a terminal plate to bring 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 alkaline electrolytes such as caustic potash tend to have low leakage resistance despite the above-mentioned sealing methods, and for this reason, until now, the shape of the cathode terminal plate has been modified to improve leakage resistance. We have improved the shape, and added pitch and
Many proposals have been made, such as using liquid packing 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. have not been obtained either.

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 an electrochemical creep phenomenon peculiar to the cathode current collector.

That is, when the electrolytic solution is electrochemically reduced at the rising part 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,
When the alkali concentration locally increases, the surrounding electrolyte moves to the above-mentioned rising part due to the concentration difference, but as a result of this migration being influenced by electrochemistry, it creeps up along the current collector surface over time. It appears as a creep phenomenon.

In addition, the cathode current collector is usually made of copper 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 above-mentioned electrochemical creep phenomenon.

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 or copper alloy of the cathode current collector, the leakage resistance is greatly improved. It has been done.

An embodiment of the present invention will be described below based on the drawings.
In FIG. 1 and FIG. 2, 1 is an anode active material such as ferrous oxide, manganese dioxide, ferric oxide, or mercury oxide;
An anode mixture containing a conductive additive such as carbon black and phosphorescent graphite and partially impregnated with an alkaline electrolyte; 2 is a metal annular mixture fixed to the mixture 1 and the periphery of the mixture; A separator 7 is made of a hydrophilically treated microporous film 4, a cellophane film 5, and a liquid absorption layer 6 such as Pinilon-rayon mixed paper, which is in contact with the base 3. 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 in which an anode mixture 1 and a separator 2 are filled, and a cathode terminal plate 9 as a cathode current collector with a cathode agent 7 filled in the opening of the can is made of polyethylene. An annular gasket 10 with an L-shaped cross section made of various resins such as polypropylene 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 structure in which a nickel layer 12 is provided on the outer surface of a steel plate 11 to satisfy aesthetics and corrosion resistance, and a copper layer 13 is provided 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 drawn into a shape having a peripheral folded part 14, or the steel plate 11 is
Only the nickel layer 12 and the copper layer 13 were formed in advance by a similar method, and then a nickel layer 12 and a copper layer 13 were formed by plating.

The surface 15 of the folded portion 14 around the terminal plate 90 and the copper layer 13 in the vicinity of which the annular gasket 10 comes into contact
If penzotriazole 《 is its derivative and the general formula g
-(OR)3 (wherein R represents a phenyl group or an alkyl group with or without a substituent)
A rust-preventing coating 16 is provided by coating and drying a rust-preventing agent containing a mixture of organic phosphorus compounds as a main component, and this coating 16 has a strong activity against copper of the mixture. Strongly chemically bonded.

Here, the term "penzotriazole derivative" refers to a penzotriazole compound represented by the general formula (in which R represents a substituent such as a halogen or an alkyl group), and representative examples thereof include methylbenzotriazole, These include chlorbenzotriazole.

Representative examples of organic phosphorus compounds include tributyl phosphite, triphenyl phosphite, tris(2-bromoethyl) phosphite, tris(2-chloroethyl) phosphite, and tridecyl phosphite.

When used, usually penzotriazole or its derivative and an organic phosphorus compound are mixed in an alcoholic solvent such as methanol or ethanol, and the former is usually 0.01 to 0.0%.
5 parts by weight, preferably about 0.2 parts by weight, and the latter usually from 0.1 to 3 parts by weight, preferably about 1 part by weight.
The solution is melted to a concentration of 100% by weight and applied to the folded portion 14 around the cathode terminal plate 90 and the contact surface 15 of the copper layer 13 in the vicinity with the annular gasket 10, and is dried to easily adhere and become robust. It is possible to judge the appearance of the membrane.

In addition, in forming this anti-rust coating, the contact surface 15
After removing oil etc. from the 0 surface, it is made smooth by chemical polishing etc., and then a rust preventive coating is formed on this smooth surface.The leakage resistance can be further improved significantly, and the surface roughness is The centerline average roughness according to JISBO601 is preferably about 3μ or less, usually 0.5 to 3μ.

In the above-mentioned embodiment, the mixture of penzotriazole or its derivative and an organic phosphorus compound is used as a main component on the contact surface 15 of the cathode terminal plate 90 peripheral folded portion 14 and the copper layer 13 in the vicinity thereof with the annular gasket 10. When the anti-rust coating 16 is formed, the coating 16 improves the adhesion between the terminal plate 9 and the gasket 10, and furthermore, due to the chemical bond between the mixture and the copper layer 13, water repellency and the contact surface 15 are improved.
In addition, it has a function unique to the anti-rust coating, that is, prevents the formation of an oxide film on the surface of the copper layer 13, and the synergistic effect of these factors causes the contact surface 15 to be mainly affected by electrochemical creep phenomenon. It shows the effect of suppressing leakage of electrolyte from.

Such a leakage prevention effect cannot be achieved with general water-repellent resins such as fluororesins, silicone resins, and polyamide resins, which are simply physically applied to the surface of the copper or copper alloy to be adhered. It is something that cannot be done.

The following table shows the leakage resistance of button type batteries A and B having the above configuration of the present invention, in which silver oxide is used as the anode active material, amalgamated zinc powder is used as the cathode active material, and a caustic potassium aqueous solution is used as the electrolyte. The temperature (45° C., 90% RH) is compared with button-type batteries C, D, E, and F having different configurations from those of the present invention.

In the table, battery A uses a mixture of penzotriazole and tributyl phosphite as a rust preventive agent, battery B uses a mixture of methylbenzotriazole and tributyl phosphite, and batteries C: D and E each use penzotriazole and tributyl phosphite. Battery F uses zotriazole, methylbeizotriazole, and tributyl phosphite.Battery F uses a water-repellent resin made of fluororesin.The values in the table are the electrolysis values when 100 batteries were tested This is the number of batteries that were found to have leaked fluid.

From this table, it can be clearly seen that Batteries A and B of the present invention have superior leakage resistance compared to Batteries C, D, and E, which use each component alone, and Batteries F of another construction.

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.
Rust-preventive coating 16 mainly composed of a mixture of penzotriazole or its derivative and an organic phosphorus compound on the contact surface 15 with
is formed.

In the figure, parts having the same composition or function as the previous example are given the same numbers, and the anode can 8 is composed of an inner can 8a and an outer can 8b.

Generally, it is said that the contact surface 15 of the cathode lead body 17 with the gasket 10 is important for electrolyte leakage in cylindrical alkaline batteries. Leakage of the electrolyte mainly due to electrochemical creep along the body 17 can be effectively suppressed for the same reason as in the case of the button-type battery described above.

As detailed above, the present invention involves forming a rust-preventive coating mainly composed of penzotriazole or a mixture of its derivatives and an organic phosphorus compound on at least the surface of the copper or copper alloy surface of the cathode aggregate that is in contact with the gasket. According to this, leakage of the electrolyte from the contact surface between the cathode current collector and the gasket can be prevented, so that the leakage resistance of the battery as a whole is greatly improved.

Furthermore, in the present invention, if a liquid packing such as pitch or silicone oil is further interposed between the anticorrosive 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. Penzotriazole or a derivative thereof and a compound of the general formula
) 3 (in the formula, R represents a phenyl group or an alkyl group with or without a substituent) Rust-preventive coating 1 whose main component is a mixture with an organic phosphorus compound
An alkaline battery characterized by forming 6.