JPH0441573Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a flat battery, particularly one having a current collector made of a metal net.

In flat batteries, in order to ensure good and reliable electrical connection between the active material of the positive or negative electrode and the terminal, a current collector may be interposed between the active material and the terminal. It is done. Furthermore, this current collector bites into the active material of the positive electrode or negative electrode and is tightly bonded to the active material, thereby greatly contributing to lowering the internal resistance of the battery.
Expanded metal or metal nets are often used as current collectors. In particular, since metal nets are lower in cost than expanded metals, they are often used in, for example, non-aqueous electrolyte batteries or alkaline batteries.

A current collector made of a metal net can be easily obtained by punching out a metal net, which is a base material, into a circular shape, for example, as shown in FIG. However, as shown in FIG. 1, after the current collector 28 obtained by punching out a metal net is punched into a predetermined contour shape, a part of the wire 30 constituting the net becomes scraps 30a. The particles 30a detach or fall off, or even partially fall off, and these particles 30a get mixed into the inside of the battery, causing internal short circuits or other defects or failures. Furthermore, the residue 30a may cause failure of the manufacturing equipment.

Therefore, the metal net as described above is used as the current collector 28.
Conventional flat batteries have not always been reliable in terms of reliability.

In this case, for example, as disclosed in Japanese Utility Model Application Publication No. 57-2573, it is conceivable to weld all the lattice portions of the metal net. However, when such a configuration is adopted, the degree of freedom of the wires constituting the metal net is lost, so the degree to which the metal net digs into the active material side is reduced, resulting in insufficient electrical connection between the active material and the metal net. Become.

This idea was created in view of the above-mentioned conventional problems, and its purpose is to maintain a good electrical connection between the current collector and the active material while using a metal net. In particular, it is an object of the present invention to provide a flat battery that can prevent a decrease in reliability caused by this problem.

In order to achieve the above object, this invention provides a flat battery in which the current collector is made of a metal net punched into a predetermined contour shape, and the metal net is
It is characterized in that only the lattice portions along the outline of the punched shape are spot welded in advance.

Hereinafter, preferred embodiments of this invention will be described based on the drawings.

Note that the same or corresponding parts in each figure are indicated by the same reference numerals.

FIG. 2 shows the process of forming a current collector 28 used in a flat battery according to an embodiment of this invention.

First, in FIGS. 2a and 2b, only the lattice portions along the outline of the punched shape of the base material 32 made of metal net are spot welded. Specifically, figure b
As shown in FIG. 3, the base material 32 is spot welded into a donut shape using an annular spot welding electrode 40 having a predetermined width. As a result, a region R1 is formed in which the grid portions located along the donut-shaped portion are spot welded.

Next, as shown in FIG. 2C, a circular punch is punched out along the donut-shaped spot welding region R1. The punching contour R2 at this time is made to fall within the donut-shaped portion of the spot welding region R1.

In the manner described above, a current collector 28 made of a circularly punched metal net is obtained as shown in FIG. 4D. This current collector 28 has spot welds 34 formed in the grid portion along its contour. This spot weld 34 is formed in the process shown in FIG. .

Therefore, the edges of the current collector 28 punched out in a circular shape are stably fixed, and there is almost no possibility that a part of the wire forming the net will come off or fall off. Section 34 is
Since it is formed only on the part that follows the contour,
The degree of freedom of the wire rod other than this is ensured. On the other hand, since the base material 32 after the current collector 28 is punched out is also spot welded along the punched portion, there is almost no scum generated there.

The current collector 28 configured as described above can continue to maintain its current state even after subsequent handling without some of the wires coming off or falling off. As a result, a flat battery configured using the current collector 28 is significantly less susceptible to defects such as internal short circuits or failures, compared to the conventional battery described above. In other words, the reliability of the battery is greatly improved.

On the other hand, since some of the wires constituting the net do not become detached or fall off as debris, failures on the battery manufacturing equipment side can also be prevented. Since the current collector 28 is made of a metal net, the cost of the battery can be kept low.

FIG. 3 shows an example of a flat battery constructed using the above-described current collector 28.

In the flat battery shown in the figure, a power generating element 16 is hermetically sealed within a flat battery case 24. The battery case 24 is composed of a metal negative terminal 18 forming the negative side portion of the case, a metal positive electrode can 20 also serving as a positive terminal, and a sealing gasket 22. The power generation element 16 is constructed by arranging in layers a negative electrode active material 10 made of a light metal such as lithium, a separator 12 impregnated with a non-aqueous electrolyte, and a positive electrode active material 14 mainly made of manganese dioxide. . And positive electrode active material 1
The above-mentioned current collector 28 is interposed between the positive electrode can 20 and the positive electrode can 20 .

Here, the current collector 28 is press-bonded in advance to the positive electrode active material 14 side, and thereby bites into the positive electrode active material 14 to obtain an electrically tight bonding state.

By the way, first of all, the wire diameter of the metal net constituting the current collector 28 is 30 mm.
It is desirable that the thickness be in the range of ~200 μm. this is,
This is because if the thickness is less than 30 μm or more than 200 μm, it is difficult to form a good spot weld in the lattice portion of the net. In particular, if the wire is less than 30 μm, the wire tends to be partially fused during spot welding. Furthermore, if the thickness is 200 μm or more, there is a risk that the welded portion may peel off during the punching process.

Furthermore, it is desirable that the metal net constituting the current collector 28 has a mesh size of 120 meshes or more. If a metal net with a mesh size of 120 mesh or less is used, the ends of the wire will not be securely attached and fixed, and there is a risk that the ends of the wire will bend and become loose, causing an internal short circuit. Ikuru.

As mentioned above, the flat battery according to this invention is
By using a metal net with only the lattice part pre-spot welded along the contour as a current collector, the reliability of the battery as a battery can be increased while maintaining low cost without reducing the degree of penetration into the active material side. can significantly improve gender.

[Brief explanation of the drawing]

Figure 1 is a one-sided view showing an example of a current collector used in a conventional flat battery, Figure 2 a, b,
3c and d are diagrams showing the process of forming a current collector used in a flat battery according to an embodiment of this invention, and FIG. 3 is a side view showing an embodiment of a flat battery according to this invention. 10... Negative electrode active material, 12... Separator, 1
4... Positive electrode active material, 10... Power generation element, 18...
Negative electrode terminal, 20... Positive electrode can, 22... Gasket, 24... Battery case, 28... Current collector made of metal net, 30... Wire constituting the metal net, 30a... Scrap, 32... Mother Material, 34...Spot welding part, 40...Annular spot welding electrode, R1...Spot welding area, R2...Punching contour.

Claims (1)

[Claims for Utility Model Registration] (1) In a flat battery in which the current collector is made of a metal net punched into a predetermined contour shape, the metal net is pre-spotted only in the lattice portion along the contour of the punched shape. A flat battery characterized by being welded. (2) The wire diameter of the above metal net is 30 to 200 μm.
A flat battery according to claim 1 of the utility model registration claim, which is characterized in that: (3) The flat battery according to claim 1 or 2, wherein the metal net has a mesh of 120 or more meshes.