JPS5841627B2 - 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.

In general, when sealing a battery, a gasket made of synthetic resin such as polyethylene or polypropylene or rubber is placed at the opening of the anode can, and this gasket is tightened inward of the anode can to remove the cathode lead body, cathode terminal plate, etc. By pressing the contact surfaces of the anode can, the gasket, and the cathode current collector against the cathode current collector, the electrolyte is prevented from leaking from these contact surfaces.

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. However, leakage of electrolyte 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 electronic conduction or leap phenomenon peculiar to the cathode current collector.

In other words, when the electrolytic solution is electronically reduced to produce OH- 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, the alkali concentration increases. As the electrolyte becomes locally high, 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 electron conduction, it creeps up along the current collector surface over time as a creep phenomenon. appear.

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 a cause of the above-mentioned electronic conduction and leap 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, when the surface of the copper or copper alloy surface of the cathode current collector that the gasket contacts is made smooth and a specific anti-corrosion coating is formed on this smooth surface. This was done after finding that the leakage resistance was greatly improved.

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 consisting of, for example, a hydrophilically treated microporous film 4, a cellophane film 5, and a liquid absorption layer 6 such as vinylon-rayon mixed paper, which is in contact with the base 3Vc; This is a cathode material that contains sodium acrylate, carboquine methyl cellulose, and a glue such as starch, into which most of the alkaline electrolyte is poured.

Reference numeral 8 denotes 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 I filled in the opening of the can. An annular gasket 10 made of various resins such as polyethylene or polypropylene or rubber and having an angular cross section 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. The clad plate is usually formed by drawing a clad plate consisting of a steel plate 11, a nickel layer 12, and a copper layer 13 into a shape having a peripheral folded portion 14.

Further, at least the peripheral folded portion 14 of this terminal plate 9 with which the gasket 10 comes into contact and the copper layer 1 in the vicinity thereof
Three sides are polished in advance to make them smooth.

In general, the surface of the terminal plate 90 becomes rough due to the above-mentioned drawing force, and in particular, the surface roughness of the copper layer near the folded portion 14 before processing is about 1 μm or less, but the surface roughness is usually about 4 to 7 μm. It is recognized that it can deteriorate to

Therefore, after this molding process, it is polished by any means such as mechanical polishing, electrolytic polishing, and chemical polishing to smooth the surface preferably to a surface roughness of about 3 microns or less, usually 0.5 to 3 microns.

It is preferable to carry out this polishing process using a chemical polishing method that uses an abrasive that has an oxidizing ability, such as a hydrogen peroxide and sulfuric acid type abrasive.This method ensures that the required areas are smoothed uniformly and reliably. It is possible and has excellent workability.

Note that surface roughness in this specification is defined by JISBO601.
means center line average roughness.

The surface of the copper layer 13 smoothed by such polishing treatment is further provided with a rust preventive coating 15, which is formed by coating and drying a rust preventive agent containing benzotriazole or a triazole compound as a main component. 15 is strongly chemically bonded to the surface of the copper layer 13 due to the strong activity of benzotriazole or a triazole compound toward copper.

Typical triazole compounds are 1.2.3 triazole, l-methyltriazole, 1-amino-1°2.4
-) There are various compounds such as lyazole.

Commercially available rust preventives containing benzotriazole include Ryoe Chemical Products C, B, and Bright.

As is clear from this configuration, the surface of the copper layer 13, which is in contact with the gasket 10 in the vicinity of the folded portion 14 around the cathode terminal plate 90, is a smooth surface, and this smooth surface contains benzotriazole or a triazole-based compound as a main component. Since the anti-rust coating 15 is formed, when the gasket 10 is pressed against the terminal plate 9 by tightening the anode can 8 inward, the adhesion between the terminal plate 9 and the gasket 10 is very good. The chemical bond between the benzotriazole or triazole compound and the copper layer 13 imparts a kind of water-repellent function to the coating 15, and the copper layer 13
The adhesion strength to the surface is also increased, and the anti-rust coating function, that is, the function of preventing the formation of an oxide film on the surface of the copper layer before or after battery assembly, is exerted, and these factors work synergistically. The contact surface 1 with the gasket 10 in the cathode terminal plate 9 which is mainly composed of electron conduction and leaps.
Leakage of electrolyte from 6 is effectively suppressed.

In addition, if the anti-rust coating 15 has a leakage prevention effect and is lightning resistant, it may be different from the anti-rust coating 15 described above, for example, depending on a general water-repellent resin coating made of fluororesin, silicone resin, polyamide resin, etc., as described above. It is impossible to obtain a sufficient leakage prevention effect.

In terms of examples, such a coating is merely physically applied and does not form a chemical bond with the copper layer, so it has inferior adhesion to the copper layer compared to the anti-rust coating 15.
In addition, due to this poor adhesion and lack of rust prevention function, oxidation of the surface of the copper layer cannot be effectively prevented, and the surface condition is likely to be damaged due to the formation of an uneven oxide film, resulting in problems such as electron conduction and leakage. This is because the leakage prevention effect of the electrolyte, which is the main component, is reduced.

The following table shows the leakage resistance (45%) of button-type battery A having the above-described configuration of the present invention, using silver oxide as an anode active material, amalgamated zinc powder as a cathode active material, and a caustic potassium aqueous solution as an electrolyte. ℃, 90% RH) in comparison with button-type batteries B and C having different configurations from those of the present invention.

Battery A according to the present invention uses a hydrogen peroxide solution containing 4 weight φ of sulfuric acid as an etching agent and is immersed in this solution for about 5 to 10 seconds, followed by pickling with sulfuric acid and washing with water to smooth the surface. Battery B uses a cathode terminal plate with a rust-preventive coating made of benzotriazole formed on its surface.
In battery C, a water-repellent resin coating made of fluororesin was formed on the surface of the cathode terminal plate that was not polished and in contact with the gasket, and in battery C, an untreated cathode terminal plate was used.

The numerical values in the table are the number of batteries in which electrolyte leakage was observed when each ioo battery was tested.

From this table, it can be seen that the battery A according to the present invention can further improve the leakage resistance compared to the battery B.

Figures 4 and 5 show other embodiments of the present invention, in which at least the contact surface of the cathode terminal plate with the gasket in a button-type battery was smoothed to form a rust-preventive coating. In contrast, in a cylindrical battery, at least the surface 16 in contact with the gasket 10 of the cathode lead body 17 made of brass, which is an alloy of copper and zinc, is polished in advance and the main component is benzotriazole or a triazole-based compound. The inside of the battery is sealed by forming a rust-preventive coating.

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.

According to this example, the adhesion between the cathode lead body 17 and the gasket 10 is improved for the same reason as mentioned above, and the contact surface 16 along the lead body 17 also has good electron conductivity due to the unique function of the antirust coating 15. It is possible to effectively prevent leakage of the electrolyte mainly composed of leaps.

As detailed above, the present invention is such that at least the surface of the copper or copper alloy surface of the two cathode current collectors that comes into contact with the gasket is smoothed, and a specific anti-rust coating is formed on the smooth surface of the bracket. According to the method, leakage of the electrolytic solution 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 can be greatly improved.

Further, in the present invention, if a liquid backing such as pitch or silicone oil is further interposed between the anticorrosion 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 one embodiment of the present invention, Fig. 2 is an enlarged view of the ■ part in Fig. 1, and Fig. 3 is a cylindrical type alkaline battery showing another embodiment of the invention. A sectional view of the alkaline battery, FIG. 4, is an enlarged view of the ■ part in FIG. 3. 9.17... Cathode conductor, 10... Gasket, 15... Antirust coating, 16...
・Let it come into contact.

Claims (1)

[Claims] 1. At least the surface 16 of the copper or copper alloy surface of the cathode current collectors 9, 17 that contacts the gasket 10 is polished and smoothed, and benzotriazole or a triazole-based compound is applied as a main component to this smooth surface. An alkaline battery characterized by being provided with a rust-preventing coating 15. 2. The alkaline battery according to claim 1, wherein the contact surface 16 is smoothed to a surface roughness of 3 μ or less. 3. The alkaline battery according to claim 1 or 2, wherein the contact surface 16 is made smooth by chemical polishing using an abrasive having oxidizing ability.