JPS627660B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to button-type batteries such as silver oxide batteries and manganese oxide batteries.

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 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 acts. There are problems such as the curved portion causing cracks or fractures, or the annular pedestal coming off.

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.
As you can understand from c, the thickness of the molded anode is 1.0 mm.
Below that, the defectiveness rate gradually increases, and this increase is particularly noticeable near 0.6mm, reaching a 70% defectiveness rate at 0.5mm, for example.

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 at this thickness. However, as batteries have become thinner in recent years, the thickness of the molded anode has also become thinner.For example, in silver oxide batteries, there is a demand for the thickness to be less than 0.6 mm or 0.5 mm, which increases the rate of failure. How to solve the above problem becomes an extremely important issue.

It is obvious that a molded anode with cracks or cracks will not be able to obtain the desired discharge characteristics, and if the pedestal comes off after molding, it will interfere with the assembly of the electrode and it will be difficult for the pedestal to fully perform its original function. Because it will be.

In view of these circumstances, the inventors conducted extensive research and found that generally, annular pedestals are made from a metal plate such as stainless steel, and are machined into an L-shaped cross section. The annular pedestal made in this way has internal distortion that occurs during the cold rolling process when forming the metal plate and the process of forming the metal plate into the pedestal form, and this internal distortion results in high hardness and low tensile strength or elongation. Since the spring tends to be small and has strong spring elasticity, we tried reducing the thickness of the metal plate used as a means to weaken this spring elasticity as much as possible. It has been found that even when the thickness of the molded anode is reduced, problems such as the occurrence of cracks or cracks and detachment of the pedestal can be suppressed, leading to the completion of this invention.

An embodiment of the present invention will be described below based on the drawings.

FIG. 1A shows a metal plate 1 used for manufacturing the annular pedestal according to the present invention, and the metal plate 1 is made of various types of stainless steel and has a thickness of 0.05~
It is set to 0.1mm. On the other hand, in conventional metal plates for manufacturing pedestals, the thickness of the formed anode is
Since the thickness was around 1.8 mm, the plate thickness was usually around 0.15 mm to 0.2 mm to ensure sufficient mechanical strength.

The inventors have discovered that the 0.6 mm
When making a molded anode with the following thickness, we considered it necessary to make the thickness of the conventional metal plate as thin as possible within the range that allows the pedestal to perform its original function, also in relation to the overall thickness of the battery. However, in addition to this, as mentioned above, by considering how much plate thickness should be used in relation to spring elasticity, we found that if the plate thickness is set to 0.1 mm or less, cracks and cracks during anode forming will be reduced. It has been found that if the thickness is too thin than 0.05 mm, the pedestal cannot perform its original function as described above, and furthermore, it becomes difficult to form the metal plate itself.

The reason why the material of the metal plate 1 is limited to stainless steel is mainly because other metal plates such as nickel cannot maintain mechanical strength when the thickness is within the above range, and the spring elasticity decreases due to thinning. This is because the effect of suppressing cracks or cracks during anode molding cannot be sufficiently obtained.

Next, this metal plate 1 is 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.
An annular pedestal 5 according to the present invention formed into a character shape
shall be. This pedestal 5 has a property of being susceptible to plastic deformation with weak spring elasticity depending on the initial plate thickness, even if internal distortion during forming may cause an increase in hardness or a decrease in tensile strength or elongation. It is something.

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 0.6 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 if a stretching force is applied outward in the radial direction, the vertical portion 4 of the pedestal 5 will not reach the anode 9 as shown in FIG.
It extends slightly outward following the elongation of.

Therefore, the thickness of the anode 9 is 0.6 mm as mentioned above.
Even if the anode is as thin as below, problems such as cracks or cracks in the center of the anode and detachment of the pedestal 5 are less likely to occur. Curves a and b in Fig. 4 show the failure rate when the annular pedestal according to the present invention is used.
Moreover, curve-b is the one in which the thickness of the stainless steel plate is 0.12 mm. From this, the thickness of stainless steel
A curve using a conventional metal plate made of 0.18mm.
It can be seen that the defectiveness rate is very low compared to the case b, and it is possible to reduce the thickness of the anode using ferrous oxide as an active material to 0.6 mm to 0.5 mm or less, which has been recently demanded in this industry.

FIG. 5 shows an example of a button-type battery of the present invention in which such a molded anode with a pedestal is housed inside the battery. A molded anode 9 is placed thereon, and a separator 11 made of, for example, a vinylon-rayon absorbent layer, a cellophane layer, and a hydrophilized polypropylene layer is provided, and a cathode active material such as zinc amalgam, sodium polyacrylate, or carboxymethyl cellulose is disposed on the anode 9. A cathode terminal plate 13 containing a cathode 12 made of a glue and an alkaline electrolyte is fitted into the anode can 10 through an annular gasket 14, and the anode can 10 is inserted into the anode can 10. Tighten 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]

1A and 1B are cross-sectional views for explaining the method for manufacturing an annular pedestal according to the present invention, FIG. Figure 3 is a cross-sectional view showing the state taken out after pressure molding in a mold, Figure 4 is a characteristic diagram showing the relationship between the thickness of the molded anode and the failure rate, and Figure 5 is a button type battery of the present invention. It is a sectional view showing an example. 5... Annular pedestal, 9... Molded anode.

Claims (1)

[Claims] 1. The material of the annular pedestal 5 having an L-shaped cross section attached to the periphery of the molded anode 9 having a thickness of 0.6 mm or less is stainless steel, and the plate thickness of this stainless steel is 0.05 to 0.10 mm.
button type battery.