JPS5953665B2 - Method for manufacturing an annular pedestal attached to a molded anode - 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 residual stress between the powders, causing a so-called springback phenomenon.

In this case, the radially outward stretching force 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, so if the thickness of the molded anode is thin, the center of the molded anode There are problems such as cracks or fractures occurring in the curved portion, or the annular pedestal separating.

By the way, since a conventional button-type battery generally uses a molded anode of about 1.8 mm, the above-mentioned problem does not occur as much with this thickness.

However, as batteries have become thinner in recent years, the thickness of molded anodes has also become thinner.For example, in silver oxide batteries, the failure rate is 70%.
There is a request to reduce the thickness to approximately 0.5 mm or less, which reaches more than %.
Therefore, in this case, how to solve the above problem becomes an extremely important issue. In view of these circumstances, the inventors conducted extensive research and found that by annealing the annular pedestal attached to the molded anode, even if the thickness of the molded anode is reduced, cracks or cracks will not occur or the pedestal will come off. We have already discovered that it can suppress problems such as separation. It is true that this already proposed method is a good method that does not cause defects such as bending, cracks, or cracks in the formed anode even when the thickness of the formed anode layer is less than one matrix, especially less than 0.5 mm. This is a method for manufacturing an annular pedestal attached to a molded anode, but on the other hand, metal oxides and carbides may adhere to the surface of the annular pedestal, and electrically poor conductors such as oxides may adhere to the surface of the pedestal. Incorporating a molded anode into a button-type battery or the like with substances adhered to it causes deterioration of battery characteristics such as increased internal resistance and poor anode current collection ability, which is not preferred.

Therefore, the inventors continued to research and as a result of intensive consideration, they first annealed the molded pedestal, and after this annealing treatment, the pedestal was post-treated with a specific acid to remove the metal oxide on the pedestal surface. By removing metal carbides, etc.
We have completed a method for manufacturing an annular pedestal attached to a molded anode that does not cause bending, cracking, or cracking of the anode even when the layer thickness of the molded anode is 1 mm or less, and does not cause deterioration of battery characteristics such as increased internal resistance. We have arrived at this invention.

That is, in manufacturing an annular pedestal with an L-shaped cross section to be attached to the periphery of a molded anode with a thickness of 1 mm or less from a metal plate 1 whose main component is iron and/or nickel, the present invention involves forming the metal plate 1. The present invention relates to a method for producing an annular pedestal attached to a shaped anode, which comprises post-annealing and further post-treatment with mineral acid after the annealing to remove metal oxides, metal carbides, etc. on the surface of the pedestal.

The drawings schematically show one embodiment of the present invention, and the following description will be made based on the drawings.

Figure 1A shows the nickel and/or materials used in this invention.
Alternatively, it shows a metal plate 1 whose main component is iron, and the thickness of this plate varies depending on the thickness of the molded anode, but in general, from the viewpoint of increasing the amount of active material and decreasing the spring elasticity, the original function of the pedestal is exhibited. It is desirable to make the material as thin as possible within a range that maintains the mechanical strength necessary for this purpose; for example, in the case of stainless steel, the thickness may be approximately 0.1 to 0.12 mm, and in the case of nickel alone, the thickness may be approximately 0.2 mm. .

This metal plate 1 is then squeezed in a conventional manner to form an L-shaped cross section having an opening 2 and consisting of a horizontal part 3 and a vertical part 4 as shown in FIG. 1B. Molded into a shape,
After this forming process, the annular pedestal 5 of the present invention is obtained by performing a so-called annealing process in which it is heated to a high temperature of about 700 to 1000 DEG C. for about several minutes and then gradually cooled down.

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 This is undesirable because it prevents you from being able to do much. When the above-mentioned annealing treatment is performed after forming, the distortion inside the metal that occurs before the treatment, such as the distortion that occurs during the cold rolling process when forming a metal plate and the process of forming this metal plate into a pedestal shape. As a result, the strain before treatment was strong with high hardness and low tensile strength or elongation rate due to internal strain, whereas after treatment, the hardness decreased and the tensile strength or elongation rate decreased. As a result of the increase in , the property is modified to have weak spring elasticity and easy plastic deformation.

After this annealing treatment, the pedestal 5 is post-treated with mineral acid to remove metal oxides or metal carbides adhering to the pedestal surface.

Here, since the electrically poor conductive material that adheres to the surface of the pedestal 5 differs depending on the material of the metal plate 1 used to form the pedestal 5, the type of mineral acid used in the post-processing process also depends on this poor conductive material. depending on the situation, usually HC]. HNO3, H2SO4
, H3PO4, or a mixed acid of two or more of these are preferably used for removing metal oxides.

In addition, if the metal plate 1 is made of stainless steel, Gr3c2, C
Since metal carbides such as r5c3 and Cr4c may also adhere to the surface of the pedestal 5, the pedestal surface is treated with HCl as a primary treatment to remove these metal carbides.
It is then desirable to use H2SO4, HNO3, or the like as a secondary treatment to remove metal oxides.
The method of post-treating the pedestal using these mineral acids is to immerse the pedestal in mineral acid diluted to about 1/4 normal for about 3 to 8 minutes, and then wash the mineral acid remaining on the surface with water. Bye.

Furthermore, it is desirable to perform this immersion treatment under heating because it shortens the treatment time, but it is undesirable to perform this immersion treatment at too high a temperature because it causes changes in the concentration of mineral acids and deterioration of the working environment, which is usually 80 to 90°C. The following may be used.

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. An anode active material such as (NiOOH) and a conductive additive such as carbon black are filled as necessary, and pressure is applied from above the upper frame 8 to form a molded anode 9 with a pedestal having an anode thickness of 1 mm or less.

When this anode 9 is taken out from the mold, a springback phenomenon occurs depending on the type of active material and the molding pressure, but the annular pedestal 5 fixed to the periphery of the anode 9 has weak spring elasticity and is easily deformed plastically. Therefore, even when a radially outward stretching force is applied, the vertical portion 4 of the pedestal 5 slightly extends outward following the expansion of the anode 9, as shown in FIG.

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 as in the prior art no longer occur.

FIG. 4 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 consisting of a rayon liquid-absorbing layer, a cellophane layer, and a hydrophilically treated polypropylene layer], which contains a cathode active material such as zinc amalgam and a sizing agent such as sodium polyacrylate or carboxymethylcellulose, which is subjected to alkaline electrolysis. A cathode terminal plate 13 filled with a cathode 12 formed by adding a liquid is fitted into the anode can 10 via an annular gasket 14, and the anode can 10 is tightened inward to seal the inside of the battery. .

According to this battery, the molded anode 9 with a pedestal used has no cracks or cracks in the center, and the thickness of the anode can be reduced to 0.5 mm or less, which has been required in recent years, and has excellent adhesion to the pedestal. In particular, since the pedestal itself has low electrical resistance or excellent anode current collecting ability, it not only can bring good results to the battery characteristics, but also the original function of the pedestal, that is, the anode can 10. The function of preventing mechanical deformation or collapse of the anode 9 by absorbing the sealing pressure applied when the anode 9 is tightened inward can be fully exerted.

This result is also clear from the test examples of this invention described below.

Test Example A SUS3O4 (stainless steel plate) with a thickness of 0.12 mm was made to a height of HO. 37mm, layer thickness 0.5
A pedestal for a molded anode of mm was manufactured (pedestal A).

This pedestal was heated in the air at 900° C. for 10 minutes, and then cooled slowly to room temperature to perform a so-called annealing treatment (pedestal B).

C After further immersing this pedestal in 1/4N HCl for 5 minutes, it became 80-9
After being immersed in 1/4N HNO3 at 0° C. for 5 minutes, it was washed with water to remove oxides and carbides on the surface of the pedestal (pedestal C). Using these three types of pedestals, Ag2O, carbon black, silver,
Three types of molded anodes (molded anodes A, B, and C) were obtained by filling and press-molding an anode mixture such as the following into this pedestal.

Note that molded anodes A, B, and C use pedestals A, B, and C, respectively. Using this type of pedestal, it was measured whether the electrical resistance value was within the range of 10 to 50 mΩ normally required for an alkaline battery pedestal. In addition, after taking out the three types of molded anodes from the molding frame, one of the same type of anodes
We investigated how many defective products such as curves and cracks occur among 00 products. The results are summarized in Tables 1 and 2 below.
As is clear from the above results, the pedestal (pedestal C) obtained by the method of the present invention has a low electrical resistance value and is an excellent pedestal for attaching to a molded anode with almost no occurrence of defective products.

[Brief explanation of drawings]

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 FIG. 4 is a cross-sectional view showing a state in which the molded anode with an annular pedestal according to the method of the present invention is housed inside a battery. 1... Metal plate, 5... Annular pedestal, 9...
...Molded anode.

Claims (1)

[Claims] 1. When manufacturing an annular pedestal 5 having an L-shaped cross section to be attached to the periphery of a molded anode 9 having a thickness of 1 mm or less from a metal plate 1 whose main components are iron and/or nickel, the metal plate 1 described above is used.
A method for manufacturing an annular pedestal to be attached to a shaped anode, characterized by forming and annealing the anode, and further post-treating with a mineral acid after the annealing to remove metal oxides, metal carbides, etc. on the surface of the pedestal 5.