JPS6157658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an annular pedestal attached to a shaped anode such as a button type battery.

Generally, in button-type batteries, an anode active material such as silver oxide or manganese oxide is pressure-formed into a disk shape before being stored in the battery. A metal annular pedestal is fixed, and this is housed inside the battery as it is, and the pressure applied during sealing is stopped by the pedestal, thereby preventing the molded anode from deforming or collapsing due to the sealing pressure.

However, when manufacturing such a molded anode with a pedestal, an annular pedestal is usually placed in a predetermined mold, filled with an anode active material, a conductive additive, etc., and then pressure-molded from above. When taken out, the molded product generally tends to stretch in the radial direction or thickness direction due to the residual stress between the powders, causing a so-called spillback phenomenon.

In this case, the outward stretching force in the radial direction is stopped by the annular pedestal that is fixed at the same time as the molding, and the spring stress due to the pedestal being made of metal also acts. The central part of the molded anode 61 is curved so that the anode 61 is curved, causing problems such as cracks or fractures occurring at the curved part 62, or the annular pedestal 63 falling off.

By the way, conventional button batteries generally have a battery life of about 1.8
Molded anodes with a thickness of approximately 1 mm are used, and the above problems do not occur as much with this thickness. However, as batteries have become thinner in recent years, the thickness of molded anodes has become even thinner. For example, in silver oxide batteries, the thickness of 1 mm or less is desirable. There is a demand for the thickness to be 0.5 mm or less, and in this case, the above-mentioned problem becomes very noticeable, so how to solve this problem becomes an extremely important issue.

In view of these circumstances, the inventors conducted extensive studies and found that the annular pedestal attached to the molded anode is generally made by cutting a metal plate such as stainless steel into an L-shaped cross section. The metal plates used in this process usually have large internal distortions that occur during the cold rolling process, and as a result of this internal distortion becoming even larger during the drawing process, the resulting annular pedestal has very high hardness and low tensile strength. It has been found that the elongation rate is small and the so-called spring elasticity is large, and that this promotes problems such as cracks or cracks in the center of the anode caused by the spinning back phenomenon.

The inventors succeeded in overcoming this problem by specifying the material of the metal plate to be used, and the present invention will be described below with reference to the drawings.

FIG. 1A shows a metal plate 1 mainly composed of nickel and/or iron used in the present invention, and this metal plate 1 has a Vickers hardness of 175 Hv or less, which has a smaller internal strain than conventional metal plates. , tensile strength in tensile creep test is 75
Kg/mm ² or more and elongation rate is set to 40% or more.

Incidentally, the commercially available SUS304 used conventionally has a Bitkers hardness of 180 to 210 Hv, a tensile strength of 60 to 65 Kg/mm ² or less, and an elongation rate of 20 to 30%. When this commercially available product is heated to a high temperature of about 700 to 1000 degrees Celsius for about several minutes and then gradually cooled down, so-called annealing treatment, the internal distortion is reduced and each characteristic value is kept within the above-mentioned range according to the present invention. be able to.

In addition, what is Bitkers hardness in this specification?
JIS-B-7725 by JIS-Z-2244 test method
In addition, the tensile strength and elongation rate in the tensile creep test are measured using the test method according to JIS-Z-2241 on the test piece specified in JIS-Z-2201. The elongation rate refers to the permanent elongation.

The thickness of the metal plate 1 varies depending on the thickness of the molded anode, but in general, from the viewpoint of increasing the amount of active material and reducing the spring elasticity, it is within a range that can maintain the mechanical strength necessary for the pedestal to perform its original function. It is desirable to make it as thin as possible; for example, in the case of stainless steel, it is about 0.1 to 0.12 mm, and in the case of nickel alone, it is 0.2 mm.
It is enough to do it to a certain extent.

Such a metal plate 1 is then squeezed according to a conventional method to form a cross section L having an opening 2 as shown in FIG. 1B and consisting of a horizontal portion 3 and a vertical portion 4. The annular pedestal 5 is shaped like a letter. The pedestal height h is usually about 0.7 to 0.9 times the thickness of the molded anode; if it is too high, the mold may be damaged when making the molded anode, or the amount of active material filled cannot be increased. undesirable from.

The resulting annular pedestal 5 has the Vickers hardness, tensile strength, and elongation rate of the metal plate set within the above-mentioned ranges, so internal distortion occurs during forming such as squeezing, resulting in an increase in hardness, tensile strength, and elongation. Even if this is accompanied by a decrease in the elasticity, the spring elasticity will not be as great as in the past, and the property of being easily plastically deformed before molding will generally be maintained.

In FIG. 2, the annular pedestal 5 made in this way is set in the underframe 6 and cylinder frame 7 of the mold, and ferrous oxide, ferric oxide, manganese oxide, mercury oxide, and nickel peroxide are added thereto. A molded anode 9 with a pedestal having an anode thickness of 1 mm or less is filled with an anode active material such as (NiOOH) and a conductive additive such as carbon black if necessary, and pressurized from above the upper frame 8.
shall be.

When this anode 9 is taken out from the mold, a spilling phenomenon occurs depending on the type of active material and molding pressure, but the annular pedestal 5 fixed to the periphery of the anode 9 has weak spring elasticity and is easily deformed plastically. As shown in FIG.
It extends slightly outward following the elongation of. Therefore, even when the thickness of the anode 9 is as thin as 1 mm or less, as described above, problems such as cracks or cracks in the center of the anode and detachment of the pedestal 5 do not occur.

Figure 4 shows the production number of 100 pieces of a molded anode with a pedestal when ferrous oxide is used as the anode active material.
The number of pieces in which the above-mentioned problem occurs is defined as the defect rate, and the relationship between this and the wall thickness of the molded anode is shown. When commercially available SUS304 is annealed using the method described above to give it a Bitkers hardness of 170Hv, a tensile strength of 76Kg/ ^mm2 , and an elongation rate of 45%, and the resulting annular pedestal is used,
Curve b shows the case where commercially available SUS304, which is not based on the present invention, is used as a metal plate and an annular pedestal obtained by this is used.

As is clear from this figure, the thickness of the molded anode is smaller in the case of using an annular pedestal different from this invention.
When it becomes less than 1.0mm, the defect rate gradually increases,
While the failure rate reached 70% with 0.5 mm, it can be seen that when the annular pedestal of the present invention is used, such failure rate is significantly reduced.

FIG. 5 shows a state in which such a molded anode with a pedestal is housed inside a battery. A molded anode 9 with a pedestal is placed inside the anode can 10 so that the annular pedestal 5 is positioned upward, and a vinylon, for example, is placed on top of the molded anode 9. - A separator 11 consisting of a rayon liquid-absorbing layer, a cellophane layer, and a hydrophilically treated polypropylene layer is provided, and contains a cathode active material such as zinc amalgam and a sizing agent such as sodium polyacrylate or carboxymethyl cellulose, and an alkaline electrolyte is added to the separator 11. Cathode 1 made by adding
2 is inserted into the anode can 1.
0 through an annular gasket 14, and tightens the anode can 10 inward to seal the inside of the battery.

According to this battery, a molded anode with a pedestal 9 is used.
Since it has no cracks or cracks in the center and has excellent adhesion to the pedestal, it not only provides good results in battery characteristics, but also allows the pedestal to perform its original function, that is, to hold the anode can 10 inward. The function of preventing mechanical deformation or collapse of the anode 9 by absorbing the sealing pressure applied when tightening can be fully exhibited.

[Brief explanation of the drawing]

Figures 1A and B are cross-sectional views for explaining the manufacturing method of the present invention, Figure 2 is a cross-sectional view showing a state in which an anode is formed using the annular pedestal according to the present invention, and Figure 3 is a metal A cross-sectional view showing the state taken out after pressure molding in a mold, FIG. 4 is a characteristic diagram showing the relationship between the thickness of the molded anode and the defective rate, and FIG. 5 is a molded anode with an annular pedestal according to the method of this invention. FIG. 6 is a sectional view showing a molded anode with a pedestal according to a conventional method. 1... Metal plate, 5... Annular pedestal, 9... Molded anode.

Claims (1)

[Claims] 1. In the manufacturing method of the annular pedestal 5 with an L-shaped cross section attached to the periphery of the molded anode 9 with a thickness of 1 mm or less, the Vickers hardness is 175 Hv or less and the tensile strength in the tensile creep test is 75 Kg, which is mainly composed of iron and/or nickel. 1. A method for manufacturing an annular pedestal attached to a molded anode, characterized in that a metal plate 1 having a thickness of /mm ² or more and an elongation rate of 40% or more is molded into the above-described shape.