JP2001196036A - Bag for thin battery and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bag for a thin battery that gives no leak of electrolyte or the like even in storage for a long time and its manufacturing method. SOLUTION: Inner face of this bag for a thin battery is composed of aluminum laminate film 1 coated with sealant resin, and a chromate coating 3 is formed between aluminum foil 2 and the sealant resin coat layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin battery bag for accommodating a power generating element for a thin battery such as a lithium ion secondary battery (LIB) and a method for producing the same.

[0002]

2. Description of the Related Art With the recent development of various electronic devices, there has been an increasing need for downsizing and space saving of electronic devices, and further thinning of thin batteries (sheet batteries) used for these devices is required. Have been. In order to meet such needs, a lithium ion secondary battery using a gel polymer electrolyte is entering a stage of practical use.

FIGS. 3 and 4 show structural examples of a lithium ion secondary battery using a gel polymer electrolyte of this kind. In these figures, 31 is a positive electrode current collector made of an aluminum foil, 32 is a positive electrode made of a lithium-containing composite oxide such as lithium cobalt oxide, 33 is a separator made of a gel polymer electrolyte plasticized with a solvent, 34 Is a negative electrode made of a carbon material, 35 is a negative electrode current collector made of a copper foil,
These constitute a power generation element. The power generating element is stored in the bag 36 to form a thin battery.
Here, the bag 36 is configured as follows. In other words, in an aluminum laminate film obtained by laminating a thermoplastic resin coating layer for a sealant on an aluminum foil, two sheets of the film are prepared, and the thermoplastic resin coating layers for a sealant are stacked with the two facing each other, and the peripheral portion is heated. It is configured in a sealed bag shape. 36a is a heat seal portion,
37 is an electrode. In some cases, sealing with an adhesive is performed instead of or together with the heat sealing.

[0004]

However, in the thin battery using the bag 36 as described above, the phenomenon that the electrolyte leaks due to long-term storage or the like occurs.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin battery bag which does not leak electrolyte and the like even during long-term storage and the like, and a method for manufacturing the same.

[0006]

According to the present invention, there is provided a bag comprising an aluminum laminate film having an inner surface coated with a sealant resin, wherein the bag comprises an aluminum foil and a sealant resin coating layer. A first aspect of the present invention is a method for manufacturing a thin battery bag in which a thin film is formed by a chromate treatment, wherein at least one surface of the aluminum foil is coated with a chromate treatment solution. Forming a laminate film by forming a sealant resin coating layer made of a thermoplastic resin on the surface on which the above-mentioned treatment is performed, and heat-sealing the sealant resin coating layers of the laminate film to form a laminate film The method of manufacturing a thin battery bag comprising the steps of:

The inventors of the present invention have studied the cause of the leakage of the electrolyte and the like as described above. As a result, the leakage is caused by the hermeticity of the heat seal portion where the electrode 37 extends outside the thin battery. I guessed that it would do so, and continued further research. As a result, the above-mentioned portion of the above-mentioned bag body 36 may be slightly opened during long-term storage or the like, and moisture in the air enters therefrom, and this reacts with the electrolytic solution of the power generating element to generate hydrofluoric acid (gaseous). Fluoric acid penetrates the sealant resin coating layer of the aluminum laminate film and acts on the aluminum foil, causing peeling of the aluminum foil and the sealant resin coating layer and causing corrosion of the aluminum foil itself. Was.

That is, the present inventors have made a series of studies on the corrosion resistance to hydrofluoric acid, and as a result, have found that a film formed by chromate treatment (hereinafter referred to as “chromate film”).
Has excellent gas barrier properties and excellent adhesion to aluminum foil and sealant resin coating layer.Hydrofluoric acid permeated through sealant resin coating layer is blocked by this chromate film and does not act on aluminum foil. Have been achieved, and the present invention has been achieved.

Next, the present invention will be described in detail.

The thin battery bag according to the present invention comprises an aluminum laminated film whose inner surface is coated with a sealant resin.
A chromate film is formed between the aluminum foil and the sealant resin coating layer. This chromate film is obtained, for example, by applying a chromate treatment solution to one surface of an aluminum foil, as described later.

As the above-mentioned aluminum foil, an aluminum foil made of aluminum or an aluminum alloy, obtained by rolling, electrolysis or the like is used. And the thickness is 5-100
It is preferable to set it in the range of μm. The above thickness is 5μ
If it is less than m, pinholes and the like are likely to be generated in the metal foil layer, and if it is more than 100 μm, it is disadvantageous for thinning and flexibility of the thin battery bag.

As the sealant resin coating layer, polypropylene, polyethylene, polyester, polyacrylonitrile, ethylene vinyl acetate copolymer (EV
A), polyvinyl alcohol (PVA), modified polypropylene, modified polyethylene, polyvinyl acetate, polyvinyl acetate, and the like are used. These are formed into a film shape, laminated on an aluminum foil, heat-sealed and integrated (laminated), or coated on an aluminum foil in a resin liquid state to form a resin coating layer. In particular, from the viewpoint of gas barrier properties and chemical resistance, among the above materials, polypropylene and polyethylene are preferable. The thickness is preferably set in the range of 5 to 1000 μm. If the thickness is less than 5 μm, the sealing property of the electrode seal portion and the reliability of the insulation between the electrode and the metal layer are reduced. If the thickness is more than 1000 μm, it is disadvantageous for thinning the thin battery bag. .

The above-mentioned chromate film is formed by treating an aluminum foil with a coating type or a chemical-washing type chromate treatment solution, and the chromate treatment used depends on these treatment methods. The liquid is also different.

As the coating type chromate treatment liquid, for example, an aqueous solution containing dichromic acid, phosphoric acid, silicate and the like can be mentioned.
It is preferable to set in the range of 0 g / l. That is,
If it is less than 5 g / l, it is 10 mg / m in terms of metallic chromium.
^It is not preferable because it is difficult to form ^two or more chromate films.
This is because it is difficult to form a chromate film of g / m ² or less, which is not preferable. The chromium ions contained in the chromate treatment solution have a trivalent / hexavalent chromium ion ratio of 0.1.
Those having a weight ratio of 25 to 1.5 are preferred. That is, if it is less than 0.25, the elution resistance of chromium in the phosphate treatment step is not sufficient, which is not preferable.
It is because when it exceeds, the corrosion resistance is insufficient, which is not preferable. In order to set the total chromium ion and trivalent / hexavalent chromium ion ratio in a predetermined range, as described above,
It can be carried out by blending trivalent chromium ions in the range of 3 to 50 g / l and trivalent chromium ions in the range of 2 to 40 g / l. Further, the phosphate ion in the above chromate treatment solution is set in the range of 1 to 100 g / l, and the phosphate ion with respect to the total chromium ion is set in the range of 0.1 to 1.2 in terms of weight ratio, so that it is effective. Chromium elution resistance can be improved. The silicate is arbitrarily added to the above-mentioned chromate treatment liquid, and the content thereof is adjusted to 0.1 to 1.2 in terms of the weight ratio with respect to all chromium ions, thereby further improving the adhesion to the application surface of the chromate film. Can be done. The coating type chromate film is formed by applying such a chromate treatment liquid to an aluminum foil or the like by a roll coating method or the like, and then drying it.

The above-mentioned chemical-water-washing type chromate treatment liquid is, for example, 0.4 to 10 g / l as chromic acid, 1.5 to 50 g / l as phosphoric acid, and 0.1 to 50 g / l as hydrofluoric acid.
An aqueous solution containing three kinds of acids of 0.5 to 5 g / l, or 0.4 to 10 g / l as chromic acid and 0.1 to 0.1 as nitric acid
An aqueous solution containing 10 g / l and three kinds of acids of 0.05 to 5 g / l as hydrofluoric acid is exemplified. Chromic acid concentration less than 0.4 g / l, phosphoric acid concentration less than 1.5 g / l,
If the hydrofluoric acid concentration is less than 0.05 g / l, the weight of the formed chromate film is 10
It takes time to reach 150 mg / m ² , which is not preferable. Also, the chromic acid concentration is less than 0.4 g / l, the nitric acid concentration is less than 0.1 g / l, and the hydrofluoric acid concentration is less than 0.0 g / l.
The same applies to the case of less than 5 g / l. And chemical
The water-washable chromate film is formed by dipping an aluminum foil in such a chromate treatment liquid, then pulling it up, thoroughly washing with water, and drying.

[0016] As described above, regardless of whether the treatment is carried out using a chromate treatment solution of a coating type or a chemical conversion-washing type, 10 to 1000 mg / metal chromium equivalent.
m ² is preferable. That is, if the amount is less than 10 mg / m ² , the corrosion resistance is insufficient, which is not preferable.
If it exceeds 00 mg / m ² , the corrosion resistance performance is saturated.
It is not economical. An adhesive layer may be provided on such a chromate film. However, since the chromate film has a high adhesive strength to a resin, a thermoplastic resin film can be directly laminated on the chromate film.
Usually, the thickness of the above chromate film is 0.01 to 10 μm
It is preferably about 0.05 to 2 μm.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partial sectional view showing one embodiment of an aluminum laminated film constituting a thin battery bag according to the present invention. In this embodiment, the aluminum laminated film 1 has a chromate film 3 formed on one surface of an aluminum foil 2, a polypropylene sealant resin coating layer 4 laminated on the chromate film 3, and the aluminum foil 2 A polyethylene terephthalate (PET) resin layer 6 is laminated on the other surface of the substrate with an adhesive layer 5 interposed therebetween. To form the bag, the sealant resin coating layer 4 is used as the inner surface, and the resin layers are heat-sealed by heat sealing. At this time,
The PET resin layer 6 is on the outside (outer surface) of the bag. With the above configuration, it is possible to form a bag having excellent thermal stability and chemical resistance and high physical strength. In addition,
As shown in FIG. 2, an adhesive layer 7 may be provided between the chromate film 3 and the sealant resin coating layer 4.

The formation of the thin battery bag of the present invention will be described in more detail. The thin battery bag of the present invention can be produced, for example, as follows. That is,
Two aluminum laminate films 1 cut into a substantially square shape are prepared, overlapped, and heat-sealed or the like while leaving a part of the periphery thereof to form a bottomed cylindrical body. Then, the thin battery power generating element is accommodated therein, and the positive electrode lead and the negative electrode lead extended from the thin battery power generating element are made to exit from the opening of the bottomed cylindrical body. A thin battery can be obtained by heat sealing the opening of the bottomed cylindrical body. Since the bag body has the sealant resin coating layer 4 of the aluminum laminate film 1 on the inner surface, as described above, hydrofluoric acid is generated inside the bag body due to infiltration of moisture or the like, and the hydrofluoric acid is converted into the hydrofluoric acid. Even when the film passes through the sealant resin coating layer 4 on the inner surface of the bag, since the chromate film 3 is formed between the sealant resin coating layer 4 and the aluminum foil 2, the hydrofluoric acid is blocked by the film 3 and the aluminum foil 2 can be prevented.

The size of the power generating element for a thin battery accommodated in the thin battery bag is usually 40 mm × 80 m.
It is about mx 2 mm (thickness). Other configurations are the same as those of the related art shown in FIGS. 3 and 4, and thus illustration and description are omitted.

Next, examples will be described together with comparative examples.

[0022]

Example 1 [Preparation of base material] A 12 μm thick aluminum foil (aluminum foil 8021, manufactured by Toyo Aluminum Co., Ltd.) was placed on a 20 μm thick aluminum foil via a commercially available urethane adhesive (2 μm thick).
m of corona surface-treated PET film (Lumirror, manufactured by Toray Industries, Inc.). And PE of the above aluminum foil
On the side opposite to the side where the T film was laminated,
A degreaser (containing 1 g of water and 20 g of a degreaser (Fine Cleaner 4377A, manufactured by Nippon Parkerizing Co., Ltd.)) in a warm bath (60 ° C. × 10
Sec), and then the aluminum foil surface was washed with water to perform a degreasing treatment.

[Chromate treatment] A chromate treatment solution (Parchrome R-282, manufactured by Nippon Parkerizing Co., Ltd.) is applied to the surface of the aluminum foil subjected to the degreasing treatment at room temperature.
Was coated with a bar coater and dried at 100 ° C. for 2 minutes. The thickness of the chromate film formed at this time is approximately 1
５5 μm.

[Formation of Sealant Resin Coating Layer] Using a laminator, a 50 μm thick
m maleic anhydride-modified polypropylene (Modick P
502, manufactured by Mitsubishi Chemical Corporation).
At this time, the laminator was set at a roll temperature of 160 ° C., a linear pressure of 2.7 kg / cm, and a roll linear speed of 1 m / min.

[Preparation of Thin Battery Bag (for Testing)] In the aluminum laminate film thus obtained, both edges of the aluminum laminate film are lifted with the sealant resin coating layer being on the inner surface. The sealant resin coating layers are heat-sealed (seal width 5 mm) to form a flat cylinder as a whole, and the bottom and upper openings are heat-sealed (seal width 5 mm).
mm), the whole was sealed and a flat bag body (the bag portion was 4 cm × 9 cm) was produced.

[0026]

Example 2 The same base material as in Example 1 was prepared, and the surface of an aluminum foil subjected to degreasing was treated with a chromate treatment solution (Alchrome-713, manufactured by Nippon Parkerizing Co., Ltd.) at a temperature of 60 ° C. Immersion treatment for 2 seconds, then thoroughly wash this surface with tap water and pure water,
Thereafter, the aluminum foil was dried at 100 ° C. for 2 minutes. Then, a sealant resin coating layer similar to that of Example 1 was formed on the chromate film formed on the aluminum foil surface, and then a bag similar to that of Example 1 was formed using the obtained aluminum laminate film. The body was made.

[0027]

Comparative Example 1 A base material similar to that of Example 1 was prepared, and a sealant resin coating layer similar to that of Example 1 was formed on the degreasing-treated aluminum foil surface without performing chromate treatment. Then, a bag similar to that of Example 1 was produced from the aluminum laminate film obtained as described above.

[0028]

Comparative Example 2 A base material similar to that of Example 1 was prepared, and a degreasing-treated aluminum foil surface was not subjected to a chromate treatment, but via a commercially available urethane resin, and a sealant resin similar to that of Example 1 was used. A covering layer was formed, and then a bag similar to that of Example 1 was produced from the aluminum laminate film obtained as described above.

A solution of the same kind as the electrolytic solution {propylene carbonate: ethylene carbonate: dimethyl carbonate: diethyl carbonate =
A mixture of LiPF ₆ 1 mol / l in a 1: 1: 1: 1 (weight ratio) solvent was injected with a syringe needle. Further, about 0.5 g of water was injected into the bag, and the bag was sealed after the injection. Then, the bags of the example product and the comparative example product
It was left in an autoclave set at 0 ° C. for 7 days to perform an aging test. Then, in the bag body before and after performing this test, the aluminum laminated film at the center of the bag other than the heat-sealed portion was cut off, and the adhesive force between the aluminum foil and the sealant resin coating layer was pulled by aluminum foil. 180 ° peel test (measuring speed: 50mm / mi)
m, 10 mm width).

As a result, in Example 1, the measured value before the test (initial) was 1.1 kg / cm, and the measured value after the test was 1.0 kg / cm. It was confirmed that. Also in Example 2, the measured value before the test was 1.3 kg / cm and the measured value after the test was 1.2 kg / cm, so that almost no change was observed as in Example 1. However,
In Comparative Example 1, the measured value before the test was 1.0 kg / c.
After the test, peeling was already confirmed between the aluminum foil and the sealant resin coating layer (0.1 m).
kg / cm). Similarly, in Comparative Example 2, the measured value before the test was 1.3 kg / cm, but delamination was confirmed after the test. When the aluminum surface of the peeled comparative product was confirmed by an electron microscope, irregularities presumably due to corrosion were observed on the aluminum surface. Further, elemental analysis of the portion revealed that fluorine was detected, so that the cause of the peeling was presumed to be the corrosion of aluminum by hydrofluoric acid.

[0031]

As described above, the thin battery bag according to the present invention comprises an aluminum laminated film whose inner surface is coated with a sealant resin. In this aluminum laminated film, an aluminum foil and a sealant resin coating layer are formed. A chromate film is formed between them. Therefore, even if the electrolyte solution and the water inside the bag react with each other due to infiltration of the water, hydrofluoric acid is generated inside the bag, and the hydrofluoric acid permeates the sealant resin coating layer on the inner surface of the bag, Hydrofluoric acid is blocked by the chromate film formed between the sealant resin coating layer and the aluminum foil, so that the aluminum foil can be prevented from being attacked. Therefore, battery performance can be maintained for a long period of time without causing electrolyte leakage due to delamination or corrosion of the aluminum foil itself.

Also, as in the production method of the present invention, a chromate film is formed on at least one surface of an aluminum foil, and a thermoplastic resin film is laminated on the film surface to form a sealant resin coating layer. When the formed laminated film is formed into a bag by heat-sealing the sealant resin coating layers with each other without using an adhesive, it is not necessary to provide an adhesive layer at a sealing portion to form the bag. Because of the advantages, the thin battery bag of the present invention can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing an embodiment of an aluminum laminated film constituting a thin battery bag of the present invention.

FIG. 2 is a partial cross-sectional view showing another embodiment of the aluminum laminated film constituting the thin battery bag of the present invention.

FIG. 3 is a perspective view showing a conventional lithium ion secondary battery.

FIG. 4 is a sectional view taken along line A-A 'of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aluminum laminated film 2 Aluminum foil 3 Chromate film 4 Sealant resin coating layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H011 AA17 BB04 CC02 CC06 CC10 CC23 DD23 5H029 AJ13 AJ15 AL12 BJ04 DJ02 EJ01 EJ12

Claims (2)

[Claims] 1. A bag made of an aluminum laminate film having an inner surface coated with a sealant resin, wherein a film is formed between the aluminum foil and the sealant resin coating layer by a chromate treatment. Thin battery bag. 2. The method for producing a thin battery bag according to claim 1, wherein a step of forming a film on at least one surface of the aluminum foil by a treatment with a chromate treatment solution, and Forming a laminate film by forming a sealant resin coating layer made of a thermoplastic resin; and heat-sealing the sealant resin coating layers of the laminate film to form a laminate film in a bag shape. Method for manufacturing a thin battery bag.