JPS6151378B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing alkaline batteries such as silver oxide batteries and manganese oxide batteries that use an alkaline electrolyte as the electrolyte. Generally, when sealing a battery, a gasket made of synthetic resin such as polyethylene or polypropylene or rubber is placed in the opening of the anode can, and this gasket is tightened inward of the anode can to seal the cathode lead body, cathode terminal plate, etc. By pressing the anode can, gasket, and cathode current collector against the cathode current collector, the contact surfaces between the anode can, the gasket, and the cathode current collector are brought into close contact with each other, thereby preventing electrolyte from leaking from these contact surfaces. However, batteries that use alkaline electrolytes 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 modified to improve leakage resistance. Many proposals have been made, such as improving the gasket, interposing liquid packing such as pitch or fluorine oil on the contact surfaces of the gasket, anode can, and cathode current collector. However, the high degree of leakage resistance required for use in wristwatches, electronic exposure meters, etc., is not necessarily achieved. 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, but it is thought to be mainly due to the electron conductive creep phenomenon unique to the cathode current collector. There is. In other words, the electrolyte is electronically 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.
When OH ^- is generated, the alkali concentration locally increases and the surrounding electrolyte migrates to the above-mentioned rising part due to the concentration difference, but as this migration is affected by electron conduction, the current collector surface This appears as a creep phenomenon that creeps up over time. 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, in order to prevent the formation of local batteries with amalcamized 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 electron conductive creep phenomenon. In addition, this creep phenomenon is accelerated when oxygen is supplied, but there is usually a thin oxide film on the surface of the copper or copper alloy, and this oxide film acts as a source of oxygen and accelerates the creep phenomenon. When did it become so noticeable? In light of the above circumstances, the purpose of the present invention is to improve the leakage resistance of the battery as a whole by suppressing leakage of electrolyte from the contact surface between the cathode current collector and the gasket as much as possible. It is something. As a basic idea for improving this leakage resistance, it has been proposed to increase the adhesion between the cathode current collector and the gasket. That is, it has been reported that after the cathode terminal plate is formed, it is smoothed by mechanical polishing such as diamond cutting or electrolytic polishing (Japanese Patent Publication No. 42290/1983). However, according to the findings of the inventors who investigated the industrial usefulness of this method, there are cases in which either method shows almost no improvement in leakage resistance despite such treatment. . The reason for this is probably that when a cathode terminal plate has a complicated curved surface after molding, a metal oxide film remains in the recesses of the polished surface even after smoothing by mechanical polishing. This is thought to be due to the fact that the oxide film promotes the creep phenomenon as described above. On the other hand, in smoothing treatment by electrolytic polishing, the oxide film is removed, but a chemically formed film by electrolytic polishing is formed on the polished surface. The reason why almost no improvement in leakage resistance is observed in the smoothing treatment by electrolytic polishing is thought to be due to this chemically formed film as well as the above-mentioned reason. That is, although the reason is not clear, it is thought that this chemically formed film promotes the creep phenomenon. In place of mechanical polishing and electrolytic polishing, which have these drawbacks and are inherently disadvantageous in terms of workability and equipment, the inventors proposed a current collector such as a cathode terminal plate with a complicated shape. We searched for a method that could uniformly and stably smoothen the polished surface easily and quickly, as well as completely remove the oxide film and obtain a clean metal surface without forming the chemical film mentioned above. It was discovered that a specific chemical polishing method was suitable for the purpose, and the present invention was gradually completed. An embodiment of the present invention will be described below based on the drawings. In FIG. 1, first, a cathode terminal plate having a predetermined shape, which is a type of cathode current collector, is made. FIG. 1A shows a metal plate 1 used in this method, which includes, for example, a copper plate 2 with a nickel layer 3 on one side that satisfies aesthetics and corrosion resistance, and a local battery with a zinc active material on the other side. It has a structure in which a copper layer 4 is provided to prevent the formation of .The copper layer 4 usually has a thickness of about 15 to 50 microns. This metal plate 1 is drawn into a shape having a peripheral folded portion 5 by drawing so that the copper layer 4 is on the inner surface side (see FIG. 1B). During this molding process, the surfaces of the nickel layer 3 and the copper layer 4 became extremely rough at several bends and near the folded portions.
In particular, the surface roughness of the copper layer 4 near the folded portion 5 before processing (center line average roughness according to JISB0601; hereinafter the same) was approximately 1μ or less, whereas it is usually 4 to 7μ.
The surface roughness deteriorates to about μ. Therefore, after this molding process, a chemical polishing treatment, which is a feature of the present invention, is performed. This treatment is usually carried out by immersing the entire molded body in a polishing solution, but the purpose of polishing is to make the surface 16 that contacts the gasket during battery assembly smooth and clean. Further, it is also possible to immerse only the vicinity of the folded portion 5 having the above-mentioned surface roughness, which corresponds to the surface 16 to be cleaned, into the polishing liquid. The polishing liquid used here can be broadly used as long as it is an etching agent with oxidizing ability, and specific examples include hydrogen peroxide-acid etching agents and polishing agents mainly based on nitric acid. Preferred is a hydrogen peroxide-acid type etching agent. More desirable is a hydrogen peroxide-nitric acid based abrasive using sulfuric acid as the acid. When immersed in such a polishing liquid, the protrusions on the polished surface are first oxidized to form metal oxides, which gradually dissolve into the polishing liquid. In order to aid this elution, it is generally desirable to perform acid cleaning with sulfuric acid or the like after immersion in a polishing solution, as in the case of ordinary chemical polishing. According to this oxidation and elution mechanism, the portion immersed in the polishing liquid can be smoothed uniformly and with good reproducibility. After polishing in this manner, the copper layer 4 at least near the folded portion 5 is washed thoroughly with water and dried.
A cathode terminal plate 6 according to the present invention as shown in FIG. 1B is obtained, the surface of which is uniformly adjusted to a surface roughness of usually about 1 to 3 μm or less, and which is free from oxide films or chemically formed films and is clean. It will be done. Figures 2 and 3 show a button-type battery manufactured using this cathode terminal plate 6, and 7 is an anode active material such as ferrous oxide, manganese dioxide, ferric oxide, or mercury oxide. and a conductive additive such as carbon black or phosphorous graphite, and a part of the alkaline electrolyte is impregnated into the anode mixture; 3.
For example, a hydrophilically treated microporous film 10 and a cellophane film 11 are in contact with the mixture 7 and the metal annular pedestal 9 fixed to the periphery of the mixture.
and a liquid-absorbing layer 1 like vinylon-rayon mixed paper.
2, and 13 is a cathode material containing an amalgamated zinc active material and a sizing agent such as sodium polyacrylate, carboxymethyl cellulose, and starch, into which most of the alkaline electrolyte is injected. . 14 is an anode can such as a nickel-plated iron can containing an anode mixture 7 and a separator 8;
The peripheral folded portion 5 of the cathode terminal plate 6 containing the cathode mixture 13 in the can opening is fitted with an annular gasket 15 having an L-shaped cross section made of various resins such as polyethylene, polypropylene, or rubber. Then, the anode can 14 is tightened inward and the gasket 15 is pressed against the surface of the copper layer 4 in the vicinity of the peripheral folded portion 5 of the cathode terminal plate 6, thereby creating a sealed structure inside the battery (see FIG. 3). According to this configuration, the four surfaces of the copper layer in the vicinity of the peripheral folded portion 5 of the cathode terminal plate 6 are chemically polished with an etching agent having oxidizing ability, and the copper layer is polished by mechanical polishing or electrolytic polishing as described above. Since the local defects in the gasket 15 are made into a uniform and stable smooth surface with no variation between lots, this smooth surface has good adhesion with the gasket 15, and furthermore, this smooth surface is coated with oxide films, chemical coatings, etc. As a result, leakage of electrolyte from the contact surface 16 between the cathode terminal plate 6 and the gasket 15, which is mainly caused by electronic conductive creep, impairs battery performance. It is suppressed more reliably without any damage. The following table shows the leakage resistance of button-type battery A having the above-described configuration of the present invention, in which silver oxide is used as an anode active material, amalgamated zinc powder is used as a cathode active material, and a charged potassium aqueous solution is used as an electrolyte. (45℃, 90%
RH) is shown in comparison with button-type batteries B and C having a different configuration from that of the present invention.

[Table] Battery A according to the present invention was chemically polished by immersing it in a hydrogen peroxide solution containing 4% by weight of sulfuric acid as an abrasive for about 30 to 120 seconds, followed by pickling with sulfuric acid and washing with water. Battery B uses a cathode terminal plate that has been smoothed by electrolytic polishing using a known phosphoric acid bath, and Battery C uses a cathode terminal plate that has been smoothed by electrolytic polishing using a known phosphoric acid bath. A cathode terminal plate is used, and the numbers 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 seen that battery A according to the present invention can more reliably improve leakage resistance than battery B. FIG. 4 shows another embodiment of the present invention. In the previous example, at least the contact surface of the cathode terminal plate with the gasket in a button-type battery was smoothed, whereas in a cylindrical battery, the contact surface with the gasket was smoothed. Cathode lead body 17 made of brass, which is an alloy of copper and zinc.
At least the contact surface 16 with the gasket 15 in
The inside of the battery is sealed by chemical polishing using an etching agent with oxidizing ability. In the figure, parts having the same composition or function as the previous example are given the same numbers, and the anode can 14 is composed of an inner can 14a and an outer can 14b. According to this example, the adhesion between the cathode lead body 17 and the gasket 15 is improved for the same reason as described above, and the contact surface 16 between the cathode lead body 17 and the gasket 15 is a clean surface free from a film that promotes the creep phenomenon. Therefore, it is possible to reliably prevent leakage of the electrolytic solution mainly due to electron conductive creep from the contact surface along the lead body 17. As described in detail above, the present invention applies a specific chemical polishing treatment to at least the surface of the cathode current collector that contacts the gasket, and according to this, from the contact surface of the cathode current collector and gasket electrolyte leakage without deteriorating battery performance.
Furthermore, it can be prevented more reliably than mechanical polishing or electrolytic polishing, and the leakage resistance of the battery as a whole can be greatly improved.

[Brief explanation of the drawing]

1A and 1B are explanatory diagrams showing the process of making a cathode terminal plate according to the present invention, FIG. 2 is a partial sectional view showing an example of a button-type battery manufactured according to the present invention, and FIG. FIG. 4, an enlarged partial view, is a sectional view showing an example of a cylindrical battery manufactured according to the present invention. 6, 17... Cathode current collector, 15... Gasket, 16... Surface to be brought into contact.

Claims (1)

[Claims] 1. At least the gasket 15 on the copper or copper alloy surface of the formed cathode current collector 6, 17
A method for manufacturing an alkaline battery, which comprises chemically polishing the surface 16 that is brought into contact with the abrasive agent in advance using an abrasive having oxidizing ability. 2. The method for producing an alkaline battery according to claim 1, wherein a hydrogen peroxide-acid based abrasive is used as the abrasive having oxidizing ability.