JPS594447Y2 - flat battery - Google Patents

Description

[Detailed Description of the Invention] An object of the present invention is to provide a flat battery with excellent leakage resistance.

BACKGROUND ART Recently, as electronic devices have become smaller and thinner, power batteries have also become thinner, and flat batteries have been developed.

One of the drawbacks of this flat battery is that it has poor leakage resistance, which causes inconveniences such as deterioration of battery performance and damage to equipment due to leaked electrolyte.

In conventional flat batteries, especially batteries that use alkaline electrolyte, the power generation element is usually housed in a metal container, a metal sealing plate is placed through a synthetic resin gasket, and the container is caulked to close the battery. It was sealed.

In this method, the seal is made by caulking metal, so caulking cannot be done with a thin foil-like metal plate, and the battery thickness is approximately 1 mm.
The limit is about 0 to 1.5 mm, and it is difficult to manufacture even thinner batteries.

Further, with caulking type sealing, it is impossible to completely close the extremely small gap between the metal container or metal lid and the synthetic resin gasket, and leakage resistance is not necessarily sufficient.

Therefore, in order to obtain an even thinner flat battery, a thin metal plate is coated with a synthetic resin layer to form a sealing material (container), for example, two sheets of the sealing material are prepared, and a power generating element is housed between them. Some synthetic resins are welded and sealed together by thermal welding at the overlapped portions.

20 In the heat welding method, the sealing part is formed by welding synthetic resin, so it has improved leakage resistance compared to the metal container caulking method described above, but it uses an alkaline electrolyte that is particularly prone to leakage. Batteries that do this are not enough.

FIG. 2 shows an example of a conventional heat welding method.

8 is a metal foil, both sides of which are covered with a polypropylene film 9, and this composite sheet serves as a sealing material.

10 is a positive electrode, 11 is a negative electrode, and 12 is a separator impregnated with an electrolyte.

13 is a positive electrode 1 by removing a part of the polypropylene film.
0 and is taken out to the outside as a positive terminal, and 14 is a negative terminal having a similar configuration.

The overlapped portion 15 of the two polypropylene films is welded together by heating and pressure to form a sealed portion.

It is difficult to completely prevent electrolyte leakage in this sealed portion.

There are two types of leakage paths in this conventional heat welding method: one is the heat weld, and the other is the current collector terminal, for example 14.
This is a path for leakage to the outside through between the inner resin films.

The latter is particularly noticeable in the case of alkaline electrolytes.

Although it is not a heat welding method, it has been proposed to wrap the battery around the battery with a U-shaped frame to improve leakage resistance when constructing the unit cell of a laminated battery. Since a synthetic resin rod is used, there is a limit to how flat it can be, and since the leakage prevention measure is simply a film rather than heat welding, it does not necessarily have sufficient leakage resistance.

The present invention is an improvement on the conventional product and significantly improves the leakage resistance of the flat battery.

This will be explained below using examples.

In FIG. 1, numeral 1 is a nickel plate with thicknesses Q and Q5 mm, both sides of which are covered with polyethylene films 2 and 2' with a thickness of 0.02 mm.

This composite sheet made of a nickel plate and polyethylene film becomes a sealing material, and between the two sealing materials, a sheet-like positive electrode 3 made of silver oxide as the main active material, a sheet-like negative electrode 4 made of zinc, and cellophane and microporous polyethylene are placed between the two sheets of sealing material. A power generation element made of a composite separator 5 made of film is housed.

The ends of the sealing material are stacked together and pressurized by a heated mold to weld the polyethylene films that are in contact with each other.

This welded portion becomes the first sealing portion.

Then, a polyethylene resin thin plate 6 is further arranged on the outer surface of this sealing part so as to have a U-shaped cross section, and is pressurized with a heated mold in the same manner as described above, and is welded to the polyethylene resin 2 on the outer surface.
A seal is formed.

Before forming the second sealed portion, it is effective to further improve leakage resistance by applying a water repellent agent 7 such as asphalt pitch or polybutene that suppresses permeation of the electrolytic solution.

Note that the thickness l' of the second sealed part is the thickness l of the battery in other parts.
Must be equal to or less than.

Note that the nickel inner surface of the negative electrode terminal portion is tin-plated.

A leakage resistance test was conducted on the battery thus produced.

In the test, the device was left in an atmosphere with a temperature of 45° C. and a humidity of 90%, and leakage was investigated.

There are three types of batteries: A, a product of the present invention with a water repellent applied between the first and second sealing parts, B, a product without water repellent, and a conventional product C shown in Figure 2. , 50 cells each.

As a result of the test, the number of cells that leaked is shown in the table below.

As is clear from the table above, the first of the 11 inventions. Batteries A and B having the second sealed portion have significantly improved leakage resistance compared to conventional product C.

Among them, A has two sealed parts, a first sealed part and a second sealed part, and a water repellent is interposed between the sealed parts. The leakage resistance is extremely good because the intrusion of the electrolyte can be suppressed and the leakage of the electrolyte to the outside of the jacket can be sufficiently prevented by the two sealing parts.

The key point of the present invention is the second sealed part, and as mentioned above, the thickness l' of this second sealed part should be equal to or less than the other battery thickness part l, so that the thickness of the second sealed part is equal to or less than that of the other battery thickness part l. Design to ensure thinness.

The present invention can be applied not only to the silver-zinc alkaline electrolyte battery described in the above embodiment, but also to other batteries.

That is, other batteries using alkaline electrolytes, such as mercury-zinc type, manganese dioxide-zinc type, nickel-cadmium type, nickel-zinc type, as well as manganese dioxide-zinc type using neutral salts, and even organic electrolytes. It can also be applied to, for example, lithium batteries.

For these various types of batteries, a harmless sealing material and water repellent may be used for each battery.

For example, as the sealing material, polypropylene can be used for organic electrolyte batteries, and polyamide, polyethylene, etc. can be used in addition to polypropylene for alkaline electrolytes and neutral salts.

In addition to the asphalt pitch and polybutene mentioned above, polyamide adhesives can be used as water repellents for alkaline electrolytes, and epoxy resins can be used for neutral salt solutions.

As described above, the present invention provides a flat battery with excellent leakage resistance.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view showing an embodiment of the battery of the present invention, and FIG. 2 is a partially cutaway side view of a conventional example. 1...Thin metal plate, 2,2'...Synthetic resin film, 3...Positive electrode, 4...Negative electrode, 5...Curved separator J... Curved water damage agent.

Claims (1)

[Scope of utility model registration request] In a flat battery in which a power generating element is housed in a battery sealing material made of a thin metal plate covered with a synthetic resin layer on both sides, a first sealing part heat-welded at the overlapping part of the sealing material; A second sealing part is formed by heat-welding another sealing material in contact with the outer surface of the sealing part, and a water repellent is interposed between the first and second sealing parts, and the second sealing material is heat-welded. A flat battery characterized in that one part of the battery has a height that is equal to or less than the height of other parts of the battery.