JP2001084971A - Sealed battery and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a battery and improve electrical characteristics and safety by providing a heat sealing tube penetrating a fused sealing part of the peripheral part of a package accommodating a power generating element and sealed at the outside end part. SOLUTION: Package films are fused together and sealed at a peripheral part 2 of a film-like package 1. A heat-sealing tube 3 penetrates through the fused part of the peripheral part 2 of the film-like package 1. The heat-sealing tube 3 is fused with the package film, and a hole of the heat sealing tube 3 is compressed to fuse a wall in the hole, and the hole of the heat sealing tube 3 is sealed. A positive electrode 4 and a negative electrode 5 are connected to a positive electrode and a negative electrode of an inner group of electrodes, respectively, and are also fused with the package film. Constituent materials of the film-like package 1 are aluminum foil of superior barrier property as a core, a layer of resin such as a polyester or a polyamide of superior mechanical strength in outer face, and a layer of a heat-sealing resin such as denatured polyethylene maleate as an inner face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery housed in a film package. Further, the present invention provides a sealed battery which is excellent in electric characteristics, high in safety and inexpensive.

[0002]

2. Description of the Related Art In recent years, with the great progress in electronic technology, portable devices for general users have been reduced in size and weight.
There is an increasing demand for batteries with good electrical properties, safety and low cost.

[0003] Taking the non-aqueous electrolyte type sealed battery as an example, the movement of miniaturization and lightening from the viewpoint of the package of the battery shows that in the case of a molded product, heavy materials such as iron and stainless steel are replaced by aluminum. There is a switch to lighter materials such as. As a more recent movement, there has been adopted a laminate film in which an aluminum foil is used as a core material and a synthetic resin layer is disposed on both sides thereof. The laminated film generally has a protective layer made of a resin layer having excellent mechanical strength such as polyester or polyamide resin on the outer surface and a modified polyolefin resin layer made of an inner surface having excellent adhesion to aluminum. Examples of the modified polyolefin include maleic acid-modified polypropylene and the same modified polyethylene. This package system
For example, it is proposed in Japanese Utility Model Publication No. 2-9498 and Japanese Utility Model Publication No. 3-39883.

[0004] In the case of a sealed battery housed in a film-like package, usually, the package films are fused and sealed at the periphery. The electrode group was previously impregnated with the electrolytic solution. After the electrode group was housed in the package, the periphery was fused and sealed, for example, under reduced pressure.

[0005] The electrolytic solution has high hygroscopicity and high volatility of the solvent. In a conventional battery, the electrode group containing the electrolyte is exposed to the surrounding atmosphere until it is sealed in a package. During this time, moisture absorption of the electrode group and volatilization of the solvent occur simultaneously in parallel.

[0006] When the electrolyte absorbs moisture, a resistive film that inhibits the movement of lithium ions is formed on the electrode, which causes an increase in the internal impedance of the battery. In addition, gas generated by reacting with lithium accumulates at the interface between the electrode and the electrolyte, which reduces the working area of the battery and may lower the battery performance. Further, when the solvent volatilizes, the viscosity of the electrolytic solution is increased, and the movement of ions is reduced. Also,
Since the solubility in the lithium salt is reduced, the conductivity of the electrolytic solution is reduced, which causes an increase in the internal impedance of the battery.

In order to suppress moisture absorption and volatilization of the electrolyte solvent during the assembling process, an electrode group containing no electrolyte is inserted in advance into a package having an open end, and the electrolyte is injected from the open end and then released. There is a method of fusing and sealing the ends.

However, in this method, since the modified polyolefin resin used on the inner surface of the film-like package has high affinity with the electrolyte, once the electrolyte adheres to the sealing portion, the resin surface is contaminated, and the molten resin is fused. There is a disadvantage that the attachment is likely to be incomplete and the reliability of the sealing portion is not sufficient.

Further, since the electrolyte is in a flowable state until the injected electrolyte is absorbed by the electrode group,
When the battery is tilted and the open end is directed sideways or downward, there is a disadvantage that the electrolyte spills out.

Also, from the viewpoint of safety, it is difficult to locally provide a battery with a weak peel strength for releasing pressure.

Further, since the electrode group holding the electrolyte is liable to slip at the interface between the separator and the electrode, the electrode group is likely to be displaced particularly when the electrode group is sealed in a package, and handling in the manufacturing process is difficult.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an inexpensive battery with further improved electrical characteristics and safety.

[0013]

According to the present invention, there is provided a battery in which a power generating element is housed in a film-like package. A sealed battery comprising a heat-fusible tube having a sealed portion. Further, the peel strength between the inner surface of the film package and the outer surface of the heat-fusible tube and / or the peel strength between the inner surfaces of the holes of the sealed heat-fusible tube is a fusion force between the film packages. The sealed battery is characterized by having a smaller peel strength than the sealed battery. Further, the pressure inside the package is reduced via the heat-fusible tube, and then the electrolyte is injected from the tube, and then the end of the tube is fusion-sealed. Is the way.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail, but the technical scope of the present invention is not limited by the following description.

First, the configuration of the battery of the present invention will be described.

The material of the synthetic resin film constituting the film package 1 is required to be a material which can be fused and does not deteriorate even when it comes into contact with an electrode or an electrolytic solution. In the case of a non-aqueous electrolyte battery, specifically, polypropylene and polyethylene are preferred. The thickness of the film is preferably 20 to several tens μm.

The material of the heat-fusible tube 3 is preferably a resin having a higher melting point, for example, high-density polypropylene than the fusible resin layer on the inner surface of the film package 1. Accordingly, the peel strength between the inner surface of the film package 1 and the outer surface of the heat-fusible tube 3 and / or the inner surface of the holes of the heat-fusible tube 3 are compared with the peel strength of the fused portion between the film packages 1. Peel strength can be reduced. When gas is generated inside due to misuse or the like and the internal pressure of the battery rises abnormally, the fusion portion between the outer surface of the heat-fusible tube 3 and the inner surface of the film-like package 1 and / or the hole of the heat-fusible tube 3 may be damaged. Since it functions as a pressure relief valve, it is possible to avoid the danger that an unexpected portion of the battery package will burst and destroy the equipment.

The electrolyte to be injected may contain a liquid monomer which can be polymerized by heat or actinic rays. After the battery is completely sealed, the monomer can be polymerized by heat treatment, electron beam irradiation, or the like, and the electrolytic solution can be made into a gel state.

The electrode group can be in a state in which a plurality of electrode pairs each including a positive electrode, a separator, and a negative electrode are stacked, or in a state in which a long electrode pair is wound.

FIG. 1 is an external view showing an example of the battery of the present invention. In the peripheral portion 2 of the film-shaped package 1, the package films are fused and sealed. A heat-fusible tube 3 penetrates the fused portion of the peripheral portion 2 of the package film 1 and communicates with the inside of the package. The heat-fusible tube 3 is fused to the package film 1, and at the same time, the hole is compressed and the inner wall of the hole is fused to seal the hole of the heat-fusible tube 3. The positive electrode terminal 4 and the negative electrode terminal 5 are connected to the positive electrode and the negative electrode of the internal electrode group, respectively.
It is fused to the package film 1.

The film-shaped package is made of aluminum foil having a good barrier property as a core material, the outer surface is made of a resin layer of polyester or polyamide having excellent mechanical strength, and the inner surface is made of maleic acid-modified polyethylene or maleic acid-modified polypropylene. Is a layer of a heat-fusible resin.

FIG. 2 is a sectional view of a battery including a heat-fusible tube penetrating portion. Inside the package 1 is a positive electrode 6,
Negative electrode 7, separator 8, positive electrode lead 9, negative electrode lead 10
Is stored.

FIG. 3 is a sectional view of the positive electrode terminal penetrating portion.
The positive electrode terminal 4 is connected to a positive electrode lead 9, and is fused to the inner surface of the film-shaped package 1 at the peripheral portion 2 of the film-shaped package 1.

The heat-fusible tube 3 is pressed at the peripheral edge 2 of the film-like package 1, the hole is crushed and sealed, and the outer surface of the heat-fusible tube is fused to the package film 1.

Next, a method for manufacturing the battery of the present invention will be described.

FIG. 4 is a view showing a process of fusing and sealing the package 1 at the peripheral edge 2 and simultaneously fusing the outer surface of the heat-fusible tube 3 to the inner surface of the film package 1. Non-adhesive pins 12 are previously inserted into the holes of the heat-fusible tube 3 for the heat-fusible tube 3, and a hot plate 11 heated to 150 to 180 ° C. is pressed from above and below to form a peripheral portion. The inner surface 2 and the outer surface of the heat-fusible tube 3 are simultaneously fused. After fusion, the pin 12 is pulled out to secure a hole.

As the material of the pin 12, for example, a metal material such as titanium or aluminum, or a material whose surface is coated with Teflon or silicon resin is suitable. The cross-sectional shape of the heat-fusible tube 3 is preferably elliptical for both the outer surface and the hole. If it is made into an elliptical shape, the outer surface of the heat-fusible tube 3 and the package film 1
Of the inner surface of the substrate and the sealing of the holes in the subsequent step are completed.

FIG. 5 is a view showing a step of reducing the pressure inside the package and a step of injecting the electrolytic solution. Heat-fusible tube 3
Is connected to the pipe 13 connected to the vacuum device 14 and the electrolyte injection device 15.

First, the valve 17 is opened so as to be connected to the vacuum device 14, and the pressure inside the package is reduced.

Next, the valve 17 is closed, and the valve 16 is opened so as to be connected to the electrolyte injection device 15 to perform pressure injection. After the completion of the injection, the heat-fusible tube 3 to the pipe 13
Remove. Unlike the conventional acid-modified polyolefin, the material of the heat-fusible tube 3 has a low affinity for the electrolytic solution, so that the inner surface of the heat-fusible tube 3 is extremely unlikely to be contaminated by the adhered electrolytic solution. Therefore, the reliability of the seal when the heat-fusible tube 3 is sealed by fusion in the next step is much higher than that of the conventional battery. Further, even if the battery is tilted after the injection, the injected electrolyte is not spilled because the injection hole is pressed by the atmospheric pressure.

After injecting the electrolytic solution, as shown in FIG.
The hot plate 11 heated to about 200 ° C. is pressed to seal the holes of the heat-fusible tube 3 by fusion. Next, as shown in FIG. 7, the protruding portion of the heat-fusible tube 3 is cut off with a cutter 18 to complete the battery of the present invention.

[0032]

As described above, according to the present invention, since the liquid is injected using a tube, the peripheral portion is not contaminated, a highly reliable sealing can be performed, and the moisture absorption of the electrolyte and the volatilization of the solvent can be prevented. Can be suppressed. Further, since the electrode group is injected after being sealed in the package, displacement during handling is less likely to occur. As described above, since the manufacturing is easy, the product yield is high and the cost is low. Further, since the internal pressure release mechanism is provided, safety is high.

[Brief description of the drawings]

FIG. 1 is an external view of a battery of the present invention.

FIG. 2 is a cross-sectional view of a heat-fusible tube penetrating portion of the battery of the present invention.

FIG. 3 is a sectional view of a positive electrode terminal penetration portion of the battery of the present invention.

FIG. 4 is a view showing a step of fusing the outer surface of the heat-fusible tube to the inner surface of the package film.

FIG. 5 is a view showing a step of reducing the pressure inside the package and an electrolyte injection step.

FIG. 6 is a view showing a step of fusing and sealing a hole of the heat-fusible tube.

FIG. 7 is a view showing a step of cutting off a protruding portion of the heat-fusible tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film-shaped package 2 Peripheral part 3 Heat-fusible tube

Claims (3)

[Claims] 1. A battery in which a power generating element is housed in a film-shaped package, comprising a heat-fusible tube that penetrates a fusion-sealing portion of a package peripheral edge and has an outer end sealed. A sealed battery characterized by the above. 2. The peel strength between the inner surface of the film package and the outer surface of the heat-fusible tube and / or the peel strength between the inner surfaces of the holes of the sealed heat-fusible tube is smaller than that of the film packages. 2. The sealed battery according to claim 1, wherein the sealed battery has a smaller peeling strength than the fused portion. 3. The pressure inside the package is reduced via the heat-fusible tube, and after the electrolyte is injected from the tube, the end of the tube is fusion-sealed. 3. The method for producing a sealed battery according to 1 or 2.