JP4069565B2 - Sealed battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin sealed battery, and more particularly to a sealed battery sealed by a bag-shaped package made of a flexible film.
[0002]
[Prior art]
With recent reductions in size and weight of various portable devices, there is an increasing demand for higher energy and smaller and lighter batteries used in these devices. Development of thin secondary batteries such as secondary batteries is rapidly progressing.
[0003]
The trend of reducing the size and weight of the battery package in such a thin secondary battery will be described. In the thin secondary battery, when the sealing property of the battery package is lowered, the battery performance is remarkably deteriorated due to volatilization or leakage of the electrolyte constituting the power generation element, or moisture entering from the outside. Therefore, the conventional battery package is mainly a metal molded product having a long-term reliability in a sealing function, in which a change from a heavy material such as iron or stainless steel to a thin material such as aluminum has been attempted. However, metal molded products have problems in that they are limited in weight reduction, are limited in size due to limitations in processing technology, are expensive in molds, are complicated in process, and are expensive. Therefore, in recent years, it has become common to further reduce the weight by adopting a laminate film in which an aluminum foil is used as a core material and synthetic resin layers are disposed on both surfaces thereof. The structure of a thin secondary battery using such a film material will be described below with reference to FIG.
[0004]
FIG. 4 shows a schematic configuration of a thin secondary battery having a metal resin composite film as a battery package. 4A is an external perspective view, and FIG. 4B is an XX ′ cross-sectional view of FIG. It consists of a metal resin composite film 111 formed by laminating an inner layer 112 made of a heat-fusible resin, a core layer 113 made of aluminum foil, etc., and an outer layer 114 made of a rigid resin such as polyethylene terephthalate, in order from the inner surface. Inside the battery package 110, a thin power generation element 120 including a positive electrode 121 including a positive electrode layer 122 and a positive electrode current collector 123, a separator 124, and a negative electrode 125 including a negative electrode layer 126 and a negative electrode current collector 127 is housed. Has been. A positive electrode terminal 131 and a negative electrode terminal 132 connected to the positive electrode current collector 123 and the negative electrode current collector 127 are exposed from the edge 115 of the metal resin composite film 111 to the outside. In the edge portion 115, the inner layers 112 made of heat-fusible resin are heat-sealed to each other, whereby the thin power generation element 120 is sealed in the battery package 110.
[0005]
In the thin secondary battery as described above, when gas is generated inside due to overcharge or the like, the internal pressure of the battery rises, and the battery package 110 made of the metal resin composite film 111 expands to compress the storage portion. There is a risk of damaging the equipment. Furthermore, if the sealing portion is broken, combustible gas is released, which may cause a dangerous situation.
[0006]
In a lithium ion battery using a battery case of a metal molded product, as shown in, for example, Japanese Patent Laid-Open No. 1-189855, when the opening is closed with a thin film and the internal pressure rises, A structure in which a thin film is broken with a cutting blade arranged in the above is generally used. However, in a lithium ion battery using a battery package made of a metal resin composite film, since the battery package itself is flexible, it is difficult to install such an internal pressure release valve. Therefore, for example, Japanese Patent Laid-Open Nos. 11-86823, 11-102673, and 10-208720 disclose methods for preventing such a flexible battery package from bursting.
[0007]
First, in Japanese Patent Application Laid-Open No. 11-86823, the battery package 110 shown in FIG. 4 has a structure in which a part of the inner layer 112 thermally fused to each other has a lower peeling strength than the other part, and the internal pressure rises. When the battery package 110 expands due to the above, it is possible to prevent the battery package 110 from being ruptured at a high pressure by preferentially opening such a portion having a weak peel strength as a gas discharge port. Yes.
[0008]
In Japanese Patent Application Laid-Open No. 11-102673, a hole or notch is provided in a part of a battery package (metal resin composite film), and the hole or notch is closed from the inner surface of the metal resin composite film. A structure for disposing the foil is disclosed, and the hole or the cut portion is easily broken when the internal pressure rises, and gas is released from this, thereby preventing the battery package from bursting at high pressure. It is described that it is possible.
[0009]
Further, in Japanese Patent Laid-Open No. 10-208720, by providing a sharp protrusion inside the battery case that houses the battery package, a through hole is formed by this protrusion on the battery package that has expanded when the battery internal pressure rises. It is described that it is possible to release gas from here.
[0010]
[Problems to be solved by the invention]
However, the above technique has the following problems. First of all, the techniques described in JP-A-11-86823 and JP-A-11-102673 all weaken the strength of a part of the battery package (metal resin composite film), and this part is reduced when the internal pressure increases. It is intended to release gas by preferential destruction, and it can be said that it is extremely unreliable from the viewpoint of securing the sealing property of the battery. In other words, it was impossible to satisfy both contradictory demands of securing strength for hermeticity and lowering strength for gas release.
[0011]
The technique described in Japanese Patent Application Laid-Open No. 10-208720 does not intentionally reduce the strength of the battery package, and thus the above-described problems have been solved. However, since a considerable amount of expansion is required in the entire battery package before the through hole is formed by the protrusion, the reliability of the operation is inferior, and there is room for improvement in terms of ensuring safety against battery rupture. It was.
[0012]
Accordingly, an object of the present invention is to provide a highly safe sealed battery, particularly a thin secondary battery, which has excellent sealing properties and can reliably prevent rupture due to an increase in internal pressure.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, a sealed battery according to the present invention is a sealed battery in which a power generation element is sealed inside a battery package, and has a local expansion allowance that expands due to an increase in battery internal pressure, and the expansion allowance expands. In this case, the battery package of this portion is provided with a punching means for punching a through hole. Thereby, a through-hole is reliably formed at the expansion margin when the battery internal pressure rises, and the battery package is prevented from rupturing under high pressure. In addition, the strength of the battery package is not inferior, and the reliability of the product is ensured.
[0014]
Further, the sealed battery of the present invention is characterized by comprising a pressure-resistant plate that comes into contact with the battery package. Thereby, the portion of the expansion allowance expands more preferentially, and the internal pressure is reliably released.
[0015]
In the present invention, the internal pressure of the battery is released by perforating the battery package as in JP-A-10-208720. However, the present invention has the greatest feature in that it provides a local expansion allowance that expands in preference to the expansion of the entire battery package, and is therefore excellent in that the internal pressure release is performed at an earlier stage and more reliably. . In addition, since the portion having inferior strength is not provided for the battery package, the reliability of the battery as a product is simultaneously ensured.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
A first embodiment of the present invention is shown below. FIG. 1 is an example of a sealed battery according to the present invention, in which (a) is a top view and (b) is a partial cross-sectional view. In the sealed battery 100, a positive electrode layer 122 and a positive electrode current collector 123 are formed inside a battery package 110 made of a metal-resin film 111 formed by laminating an inner layer 112, a core layer 113, and an outer layer 114. A thin power generation element 120 including a positive electrode 121, a separator 124, and a negative electrode 125 including a negative electrode layer 126 and a negative electrode current collector 127 is housed. A positive electrode terminal 131 and a negative electrode terminal 132 connected to the positive electrode current collector 123 and the negative electrode current collector 127 are exposed from the edge 115 of the metal resin composite film 111 to the outside. The inner layers 112 are in close contact with each other at the edge 115, and the thin power generation element 120 is sealed in the battery package 110 under reduced pressure.
[0017]
As a specific example of the configuration of the metal resin composite film 111, a heat-fusible resin having a thickness of about 50 to 100 μm, for example, acid-modified polypropylene or acid-modified polyethylene is used as the inner layer 112, and this is heat-sealed. Battery sealing is ensured. The core layer 113 may be an aluminum foil having a thickness of about 30 to 50 μm, and the outer layer 114 may be a resin having a thickness of about 10 to 50 μm and rigidity, such as polyethylene terephthalate, polyamide, or polyimide.
[0018]
Now, the margin 115 is formed with a bulge allowance 140 in which the two metal resin composite films 111 are not thermally fused. At this time, a sufficient adhesion strength of the battery package 110 can be secured by keeping the width of the edge portion 115 wide for the portion A forming the swelling allowance 140. Further, a cutting blade 150 is fixedly installed at a position facing the expansion allowance 140, for example, in the battery storage space inner wall of the device or inside the hard battery case. When the sealed battery 100 is operating normally, the battery package 110 does not contact the cutting blade 150 because the entire battery package 110 is in close contact with the thin power generation element 120.
[0019]
Next, the operation until the internal pressure is released when gas is generated in the battery package 110 of the sealed battery 100 in the overcharge or overdischarge state will be described with reference to the partial cross-sectional view of FIG. Due to the gas generated inside the battery package 110, the expansion of the expansion allowance 140 occurs in preference to the expansion of the entire battery package 110. The expanded swelling margin 140 contacts the cutting edge 150. As a result, a through hole is formed in the metal resin composite film 111 in the swelling margin 140 portion, and the internal gas is released from this portion. Accordingly, since the internal pressure is released before the entire package swells and compresses the device, it is possible to prevent device damage and battery rupture accidents. In the present embodiment, the battery package 110 is perforated using the cutting blade 150. However, the present invention is not limited to this. For example, a pin that has a sharp tip or the like can be reliably perforated.
[0020]
(Embodiment 2)
A second embodiment of the present invention will be described below. In addition, description is abbreviate | omitted about the part which overlaps with 1st embodiment, and only a different part is demonstrated. FIG. 3 is a partial cross-sectional view showing an example of the sealed battery of the present invention. In the present embodiment, the pressure plate 310 is provided in a portion other than the expansion allowance 140 in the battery package 110. By adopting such a configuration, it is possible to preferentially generate expansion with respect to the expansion allowance 140. Therefore, the sensitivity to the increase in internal pressure can be increased.
[0021]
Note that the pressure plate 210 is not a separate component, and members constituting the wall of the battery storage space of the device can also serve as the pressure plate 310.
[0022]
【The invention's effect】
As described above, according to the present invention, a sealed battery having high reliability with respect to sealing and high safety against overcharge and overdischarge is obtained.
[Brief description of the drawings]
FIG. 1 is a top view and a partial cross-sectional view showing a first embodiment of a sealed battery according to the present invention.
FIG. 2 is a partial cross-sectional view for explaining the operation in the first embodiment of the sealed battery according to the present invention.
FIG. 3 is a partial cross-sectional view showing a second embodiment of the sealed battery of the present invention.
4A and 4B are an external perspective view and a cross-sectional view showing the structure of a conventional sealed battery.
[Explanation of symbols]
100 Sealed battery 110 Battery package 111 Metal resin composite film 112 Inner layer 113 Core layer 114 Outer layer 115 Edge 120 Thin power generation element 121 Positive electrode 122 Positive electrode layer 123 Positive electrode current collector 124 Separator 125 Negative electrode 126 Negative electrode layer 127 Negative electrode current collector 131 Positive electrode Terminal 132 Negative terminal 133 Conductor 140 Blow allowance 150 Cutting blade 310 Pressure plate

Claims (1)

A pressure-resistant plate is brought into contact with a flat surface of a thin sealed battery in which a power generation element is sealed inside a flexible battery package , and a part of the edge of the sealed battery expands locally due to an increase in battery internal pressure. A sealed battery comprising: a swellable margin; and a piercing means for piercing a through-hole in the battery package at this portion when the swellable portion expands.

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