JP3681798B2 - Manufacturing method for negative electrode case of button type alkaline battery - Google Patents

Description

【００２９】
上記の表１中の数値は、各電池１００個につき試験したときの、１カ月後に電解液の漏出が認められた電池個数である。この表１の結果から明らかなように、本発明の電池Ａによれば、従来構成の電池Ｂに比べて、より確実に耐漏液性を向上できるものであることが理解できる。
【００３０】
【発明の効果】
以上のように、本発明によれば、負極ケ―スの周辺折り返し部に対して、負極ケ―スの内面側の水素過電圧の大きい金属層に亀裂が生じないように整形を施したことにより、上記の金属層の脱落などが防止され、その結果、電池性能を十分確保しつつ、耐漏液性の向上を図ることができる。また、上記整形手段として、負極ケ―スをプレス成形する際に金型を用いて周辺折り返し部を押圧するようにしたので、工程数を増やすことなく、周辺折り返し部の金属層に亀裂が生じないように容易に整形することができる。
【図面の簡単な説明】
【図１】本発明のボタン型アルカリ電池の一例を示す半截縦断面図である。
【図２】同ボタン型アルカリ電池の負極ケ―スを製作するための金属板を示す縦断面図である。
【図３】同金属板をプレス加工して得られた負極ケ―スを一部拡大して示す縦断面図である。
【図４】本発明のボタン型アルカリ電池の負極ケ―ス製作用の金型の要部を示す縦断面図である。
【図５】従来の負極ケ―ス製作用の金型の要部を示す縦断面図である。
【符号の説明】
１ 正極缶
１ａ 正極缶の開口端部
３ 負極ケ―ス
３ａ 周辺折り返し部
４ 負極活物質
１０ 金属板
１１ 基板
１３ 水素過電圧の高い金属層
Ｎ 金型[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a negative electrode case for a button-type alkaline battery using anhydrous silver zinc as a negative electrode active material.
[0002]
[Prior art]
In button-type alkaline batteries, in general, when zinc is used as a negative electrode active material as it is, zinc dissolves while generating hydrogen gas in an alkaline aqueous solution, so-called self-corrosion, so that amalgamated zinc that can suppress self-corrosion Is generally used as a negative electrode active material.
[0003]
However, recently, there has been a strong demand for dehydration of batteries due to environmental problems, and zinc having low self-corrosion has been developed even in the case of anhydrous silver, and has already been put to practical use in dry batteries and the like (Japanese Patent Laid-Open No. Sho 62-62). No. 40163). The button-type alkaline battery is also being studied for the application of such anhydrous zinc, but has the disadvantage of causing battery blistering and capacity deterioration due to the generation of hydrogen gas.
[0004]
For this reason, as disclosed in JP-A-6-163026, the inner surface of the negative electrode case is covered with a metal layer having a high hydrogen overvoltage such as indium, lead, tin and zinc, or an alloy thereof. Thus, attempts have been made to effectively suppress the generation of hydrogen gas and prevent battery blistering and capacity deterioration.
[0005]
[Problems to be solved by the invention]
However, as described above, it was found that, in the case where the metal layer having a high hydrogen overvoltage was formed on the inner surface of the negative electrode case, the liquid leakage resistance tended to decrease even though the capacity deterioration could be suppressed to some extent. The reason for this is that the surface state of the peripheral folded portion of the negative electrode case, which is most likely to affect the liquid leakage resistance, was covered with a metal layer with a high hydrogen overvoltage, so that the electrolyte was easily exposed and extremely rough. This is probably due to the change to the surface state.
[0006]
In the sealing of a button-type alkaline battery, a synthetic resin such as polyethylene or polypropylene or a rubber gasket is usually arranged between the peripheral folded portion of the negative electrode case and the open end of the positive electrode can. The opening end of each part is deformed inward and is crimped to the peripheral folded part of the negative electrode case via a gasket, thereby preventing leakage of the electrolyte from the contact surface of each part.
[0007]
However, in a battery using an alkaline electrolyte such as potassium hydroxide, the leakage resistance tends to be lowered despite the above-described sealing means. Therefore, the shape of the negative electrode case has a reduced leakage resistance. Many proposals have been made such as improving the shape so that it can be improved, or interposing liquid packing such as pitch or fluorine oil on the contact surface between the gasket, the positive electrode can and the negative electrode case. However, even with these methods, it has been found that, when anhydrous silver zinc is used as the negative electrode active material, it is difficult to ensure sufficient leakage resistance.
[0008]
In addition, leakage of the electrolyte in a button-type alkaline battery is generally more likely to occur from the contact surface between the negative electrode case and the gasket than from the contact surface between the positive electrode can and the gasket. This is due to the fact that most of the alkaline electrolyte is injected into the negative electrode side in order to improve discharge characteristics, etc., but according to the study by the inventors, anhydrous silver is used as the negative electrode active material. Since zinc is used, cracks are generated in the above metal layer by press working on the surface of the peripheral folded portion of the negative electrode case whose inner surface is coated with a metal layer having a high hydrogen overvoltage. As a result of gas generation due to the formation of a local battery with the base metal which is the substrate of the gas, it is considered that the internal pressure rises and the electrolyte is easily leaked.
[0009]
Due to the presence of this crack, the capillary phenomenon also promotes the rising of the liquid, the leakage of the electrolyte becomes even more pronounced, reducing the leakage resistance of the battery, and required for use in watches, electronic exposure meters, etc. However, there is a problem that the high liquid leakage resistance cannot be obtained.
[0010]
The present invention has been made in view of the above circumstances, and can suppress the generation of hydrogen gas to prevent the battery from blistering. The button-type alkaline battery with improved capacity, excellent capacity retention and storage characteristics, and the negative electrode case for this battery can be manufactured without increasing the number of manufacturing steps and eliminating the need for peripheral folding. An object of the present invention is to provide the above-described method that can be shaped into a cracked state.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention uses an anhydrous silver zinc as a negative electrode active material, and a metal plate in which a metal layer having a high hydrogen overvoltage is formed on one side of a substrate is a state in which the gold layer is on the inner surface side. In a button-type alkaline battery comprising a negative electrode case that is formed by press-molding and having a folded portion that is crimped to the opening end of the positive electrode can through a gasket at the periphery. The metal layer is shaped so as to be crack-free.
[0012]
Further, the present invention provides a method for producing a negative electrode case for a button-type alkaline battery having the above-described configuration, wherein a tensile force acts on the metal layer by using a mold at the time of the press molding. It is pressed so as not to be shaped. Here, in order to press the metal layer so that no tensile force acts on the metal layer, for example, the inner peripheral corner portion of the mold corresponding to the peripheral folded portion is closely attached to the peripheral folded portion. A curved tensile force restraining surface portion may be formed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a half-longitudinal longitudinal sectional view showing an example of a button-type alkaline battery of the present invention.
[0014]
In the figure, reference numeral 1 denotes an iron positive electrode can whose surface is nickel-plated, and a positive electrode mixture 2 is loaded therein. This positive electrode mixture 2 is formed by press-molding a mixed powder of a positive electrode active material such as silver oxide, manganese dioxide, nickel hydroxide and a conductive aid such as carbon black, graphite, graphite into a disk shape, This molded body is constituted by impregnating a part of an alkaline electrolyte.
[0015]
Reference numeral 3 denotes a negative electrode case that contains the negative electrode active material 4 and covers the opening side of the positive electrode can 1. The negative electrode active material 4 comprises an anhydrous silver zinc powder and a gelling agent such as polyacrylic acid soda or carboxymethyl cellulose which is added as necessary. The amount of being injected.
[0016]
Reference numeral 5 denotes a separator disposed between the positive electrode mixture 2 and the negative electrode active material 4. For example, a microporous film 6 that is hydrophilically treated and contacts the positive electrode mixture 2, and It is composed of a liquid absorbing layer 8 such as vinylon / rayon mixed paper disposed on one side via a cellophane film 7.
[0017]
Between the peripheral folded portion 3a formed on the negative electrode case 3 and the open end 1a of the positive electrode can 1, an annular gasket 9 having an L-shaped cross section made of various synthetic resins such as polyethylene and polypropylene or rubber is interposed. The inside of the battery is hermetically sealed by deforming the open end 1a of the positive electrode can 1 inward and tightening the gasket 9 so as to be crimped to the peripheral folded portion 3a of the negative electrode case 3.
[0018]
The negative electrode case 3 is manufactured from the metal plate 10 shown in FIG.
In FIG. 2, a metal plate 10 is a negative case substrate, for example, a stainless steel plate (SUS304) 11, and a nickel plate 12 that is clad to provide corrosion resistance on one side of the stainless steel plate 11 for beauty. And a tin layer 13 formed by electrolytic method plating as a metal having a high hydrogen overvoltage for preventing the generation of hydrogen gas on the surface opposite to the nickel plate 12. The tin layer 13 is preferably set to a thickness of 1 to 50 μm, for example, and is within 15%, preferably 1 to 5% of the thickness of the metal plate 10. Is good.
[0019]
Further, in this example, a copper layer 14 is interposed between the stainless steel plate 11 and the tin layer 13 as a metal layer for improving the adhesion between the both 11 and 13. The copper layer 14 is made of, for example, a thin copper plate, and is clad on the stainless steel plate 11 prior to the formation of the tin layer 13 on the stainless steel plate 11. May be hot.
[0020]
The metal plate 10 having such a structure is molded to a predetermined size, and is pressed to form a tin layer 13 on the inner surface side as shown in FIG. 3, and the peripheral folded portion 3a is formed. By forming, the negative electrode case 3 is manufactured. Here, the peripheral folded portion 3a is shaped using a specific molding die N (FIG. 4) described later so that the tin layer 13 is not cracked during press molding.
[0021]
The negative electrode case of a button-type alkaline battery is a cup-type, unlike a cylinder-type rod, so a metal with excellent extensibility and workability is required. However, most of the practical metal with high hydrogen overvoltage has insufficient strength to go through the pressing process, and when forming so that the metal layer with high hydrogen overvoltage is on the inner surface side by drawing process consisting of multiple steps, Cracks will occur on the surface of the folded part. If such cracks exist, the effect of preventing leakage of the electrolytic solution is not sufficiently exerted, and the electrolytic solution is likely to leak through the surface of the negative electrode case during storage or use of the battery.
[0022]
This point will be described in more detail. A metal having a high hydrogen overvoltage such as the tin layer 13 has high stretchability but is flexible and therefore tends to have low tensile strength. In this case, when the metal plate 10 is press-molded using the conventional first to third molds M, N, and W as shown in FIG. 5, the second gold corresponding to the peripheral folded portion 3a. A corner portion on the inner peripheral side of the mold N exists as a void G. For this reason, since the tensile force acts on the tin layer 13 on the surface of the peripheral folded portion 3a (the inner peripheral surface of the negative electrode case), it is stretched, so that it is very thin compared to other portions. Even if the tin layer 13 is thickened, the increase in volume due to processing increases, and conversely, cracks become conspicuous, and the tin layer 13 falls off.
[0023]
On the other hand, in the present invention, the peripheral folded portion 3a is not deformed by natural bending as in the prior art, but is bent while being pressed by a mold. That is, among the molds M, N, and W shown in FIG. 4, the concave curved tensile force restraining surface portion Na that is in close contact with the peripheral folded portion 3 a is formed at the inner peripheral corner portion of the second mold N. According to this, the tensile force applied to the tin layer 13 at the time of press molding is suppressed, and the peripheral folded portion 3a is formed so as to be expanded, so that the tin layer 13 can be cracked without increasing the number of steps. It can be easily molded to be in a state. Therefore, the negative electrode case 3 in which the tin layer 13 is well held as shown in the enlarged portion of FIG. 3 can be obtained even after the press molding process.
[0024]
As a result, in the button-type alkaline battery of FIG. 1, the generation of hydrogen gas is suppressed by the tin layer 13 on the inner surface of the negative electrode case 3, and the battery can be prevented from blistering. The sealability between the portion 3a and the gasket 9 can be improved, and a local battery is not formed between the base plate and the stainless steel plate 11, and the leakage resistance can be improved.
[0025]
In the above embodiment, when the metal plate 10 is press-molded against the tin layer 13 of the peripheral folded portion 3a, the peripheral folded portion 3a is pressed by the second mold N so as to be shaped without cracks. However, in some cases, after forming the negative electrode case 3, the tin layer 13 may be shaped in the same manner as described above. In addition, tin is used as a metal having a large hydrogen overvoltage, but other materials such as indium, lead and zinc, or alloys thereof can be appropriately selected.
[0026]
Table 1 shows that a copper layer of a nickel / stainless steel plate (SUS304) / copper is coated with a tin layer having a thickness of about 5 μm by electrolytic method plating, and this is punched out with a press to have a predetermined shape. The button-type alkaline batteries A and B having the above-described structure using silver oxide as a positive electrode active material, anhydrous silver zinc powder as a negative electrode active material, and an aqueous potassium hydroxide solution as an electrolyte solution. (45 ° C., 90% RH).
[0027]
The battery A is a product of the present invention, and uses a negative electrode case punched out by a press using a second mold N having a shape capable of pressing the peripheral folded portion. Battery B is a comparative product using a negative electrode case pressed by a conventional method.
[0028]

[0029]
The numerical values in Table 1 above are the number of batteries in which leakage of the electrolyte was observed after one month when 100 batteries were tested. As is apparent from the results in Table 1, it can be understood that according to the battery A of the present invention, the leakage resistance can be improved more reliably than the battery B having the conventional configuration.
[0030]
【The invention's effect】
As described above, according to the present invention, the peripheral folded portion of the negative electrode case is shaped so as not to cause a crack in the metal layer having a large hydrogen overvoltage on the inner surface side of the negative electrode case. The above metal layer is prevented from falling off, and as a result, the leakage resistance can be improved while sufficiently ensuring the battery performance. In addition, as the shaping means, when the negative electrode case is press-molded, the peripheral folded portion is pressed using a mold, so that the metal layer of the peripheral folded portion is cracked without increasing the number of steps. It can be shaped easily so that there is no.
[Brief description of the drawings]
FIG. 1 is a semi-longitudinal longitudinal sectional view showing an example of a button-type alkaline battery of the present invention.
FIG. 2 is a longitudinal sectional view showing a metal plate for manufacturing a negative electrode case of the button-type alkaline battery.
FIG. 3 is a longitudinal sectional view showing a partially enlarged negative electrode case obtained by pressing the metal plate.
FIG. 4 is a longitudinal sectional view showing a main part of a mold for producing a negative electrode case of the button-type alkaline battery of the present invention.
FIG. 5 is a longitudinal sectional view showing a main part of a conventional mold for producing a negative electrode case.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Positive electrode can 1a Opening edge part 3 of positive electrode can 3 Negative electrode case 3a Peripheral folding | turning part 4 Negative electrode active material 10 Metal plate 11 Board | substrate 13 Metal layer N with a high hydrogen overvoltage Mold

Claims (1)

  Anhydrous zinc is used as the negative electrode active material, and a metal plate with a metal layer with high hydrogen overvoltage formed on one side of the substrate is press-molded so that the metal layer is on the inner surface side. In the above-described negative electrode case manufacturing method for a button-type alkaline battery comprising a negative electrode case formed with a folded portion that is crimped via a gasket at the end, a mold is used during the above press molding. A method for manufacturing a negative electrode case, wherein the peripheral folded portion is pressed and shaped so that a tensile force does not act on the metal layer.

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