JP2002157980A - Sealing bag for nonaqueous electrolyte battery and nonaqueous electrolyte battery using this bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing bag capable of housing a large electrode without a dead space, effective in increasing capacitance of battery, and using a laminated sheet by applying drawing process treatment, and to provide a nonaqueous electrolyte battery excellent in sealing reliability by using this sealing bag. SOLUTION: At least one treatment of formation treatment and anodic oxidation treatment is applied to a surface being at least the electrolyte side of metallic foil for constituting the laminated sheet of the sealing bag of the battery, a heat seal layer is formed on this treated metallic foil surface by a heat laminate without using an adhesive to be formed as the laminated sheet, the two laminated sheets of these same kinds are superposed by putting a surface having the heat seal layer on the inside, and the periphery is heat-sealed as a housing port for housing an electrode, a diaphragm, and an electrolyte by leaving a part to be formed as the sealing bag. After housing the electrode, the diaphragm, and the electrolyte in the sealing bag from the housing port, the housing port is heat-sealed in a state of taking out a lead wire from the electrode to the outside to be formed as this nonaqueous electryte battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed bag for a non-aqueous electrolyte battery, and a non-aqueous electrolyte battery in which a positive electrode, a negative electrode, a diaphragm, an electrolyte, and the like are stored in the sealed bag.

[0002]

2. Description of the Related Art Along with miniaturization of electronic equipment, demands for miniaturization and weight reduction of batteries as power sources are increasing. on the other hand,
There is also a demand for higher energy density and higher energy efficiency for batteries, and expectations for secondary batteries such as Li-ion batteries are increasing. For these requests, for example,
As seen in JP-A-61-240564, an electrode group is inserted into a bag made of an acid-resistant thermoplastic resin, and a large number of the electrode groups are made of a film-shaped, sheet-shaped or tube-shaped synthetic resin. Attempts have been made to wrap it in a bag-like outer package to make it a sealed lead-acid battery. Also, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 2447 and Japanese Patent Application Laid-Open No. 57-115820, a metal layer is interposed between a plastic film and a sheet used for forming an enclosing bag for accommodating an electrode, a diaphragm, and an electrolyte. There is also an attempt to improve the sealing performance as a sandwiched structure.

[0003]

SUMMARY OF THE INVENTION As described above,
By providing the metal layer between the plastic films, the sealing property of the laminated sheet used for the enclosing bag is significantly improved in the sense of preventing the volatilization of the electrolyte. However, it is very difficult to completely prevent intrusion of moisture from the outside through the interface between the metal layer and the plastic in the heat seal portion around the enclosing bag. When moisture enters from the heat seal portion, the moisture reacts with the electrolyte to generate hydrofluoric acid in the sealed bag. When hydrofluoric acid is generated, this hydrofluoric acid penetrates the plastic film layer used for the sheet of the enclosing bag, and corrodes the metal layer bonded to the film layer, or causes the metal layer and the plastic layer to intersect. It may cause peeling. There is known a method of using an acid-modified polyolefin for a heat seal layer in order to improve the sealing property of a heat seal portion. However, even if an acid-denatured polyolefin is used for the heat seal layer, if a bonded sheet that has been subjected to a drawing process is used,
Sealability decreases.

Here, the drawing process means that a flat concave portion is formed inside by using a mold while leaving a heat seal portion having a predetermined width for heat sealing along the periphery of the sheet. Is formed. By bonding the drawn sheets together to form an enclosing bag, it is possible to secure a space for the electrodes and the like in advance. That is, when an enclosing bag is formed using a sheet that has been subjected to a drawing process, a predetermined bulge that matches the shape of the electrode to be enclosed in the enclosing bag can be given to the sheet in advance. As a result, using a sealed bag having the same size at the peripheral portion, the largest possible electrode can be inserted without any dead space between the electrode and the inner surface of the sealed bag, which is effective in increasing the electric capacity of the battery. . FIG. 2 shows an example of a laminated sheet subjected to a drawing process. In FIG. 2, reference numeral 6 denotes a heat seal portion, and reference numeral 7 denotes a flat concave portion. As described above, creating an enclosing bag for a non-aqueous electrolyte battery using the bonded sheet subjected to the drawing processing is effective in increasing the electric capacity of the battery, but the drawing processing is not effective for the bonded sheet. There is a problem that the sealing reliability of the encapsulating bag is reduced probably because the interface between the metal layer and the plastic is adversely affected.

According to the present invention, an electrode as large as possible can be inserted therein without dead space, and as a result, a non-encapsulated bag using a drawn laminated sheet is effective for increasing the capacity of a battery. An object of the present invention is to provide a non-aqueous electrolyte battery which is a water electrolyte battery and whose sealing reliability does not decrease.

[0006]

The features of the present invention are as follows. At least one of a chemical conversion treatment and an anodic oxidation treatment has been performed on at least the surface of the metal foil constituting the bonded sheet of the encapsulating bag containing the electrodes, the diaphragm, the electrolyte and the like of the nonaqueous electrolyte battery. A heat seal layer is formed on the surface of the treated metal foil by heat lamination without using an adhesive to form a bonded sheet. Two bonded sheets of the same type are bonded to the surface having the heat seal layer. , And heat sealing the periphery except for a part as a storage port for storing an electrode, a diaphragm, an electrolyte, etc., to form a battery enclosing bag. After storing electrodes, diaphragms, electrolytes, etc. from the storage port left without heat sealing,
With the lead wire from the electrode taken out, the storage opening is heat-sealed to obtain a non-aqueous electrolyte battery.
As described above, a bag for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery using the same, in which the sealing reliability does not decrease even when a sheet obtained by subjecting the bonded sheet to a drawing process, were obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. As a non-aqueous electrolyte battery of a type in which electrodes, electrolytes, diaphragms, and the like are housed in an enclosing bag, for example, FIG.
(A) has a structure as shown in cross section.
In the non-electrolyte battery shown in FIG. 3A, the encapsulation bag is formed by arranging two bonded sheets formed by bonding a metal foil and a plastic film so that the heat seal layer 15 faces each other. When the shape of the bonded sheet is rectangular, the three sides of the rectangle are attached to the sides,
5 are heat-sealed with each other. Then, as shown in FIG. 3B, the remaining one side not heat-sealed is used as a storage port, as schematically shown in FIG.
A positive electrode 11, a negative electrode 13, a diaphragm 12, and an electrolyte (not shown) are stored in the enclosing bag 10. FIG.
FIG. 7 is an enlarged cross-sectional view including a lead wire of the remaining one side of the heat-sealed part 0 which is not heat-sealed. As shown in FIG. 4, the battery is formed by taking out the lead wire 8 to the outside and heat-sealing the fourth side of the rectangle left without being heat-sealed when forming the bag into a bag shape.

The positive and negative electrode plates have a structure in which an active material layer is formed on a metal substrate called a current collector, such as a metal foil or expanded metal. The method of connecting the lead wire, the positive electrode, and the negative electrode is not particularly limited, but a method of connecting the metal base of the electrode plate and the conductor of the lead wire by spot welding or ultrasonic welding is preferably used. Is done.

Since a high voltage is applied to the positive electrode, the material of the conductor of the lead wire connected to the positive electrode is preferably a material that is difficult to dissolve even at a high potential. Therefore, as the conductor of the lead wire connected to the positive electrode, aluminum, titanium,
Alternatively, it is preferable to use alloys of these metals. In the vicinity of the negative electrode, lithium is deposited due to overcharging,
Over-discharge may increase the potential. Therefore, the material of the conductor of the lead wire connected to the negative electrode is preferably a material that hardly forms an alloy with lithium and that is difficult to dissolve at a high potential. Therefore, as the conductor of the lead wire connected to the negative electrode,
It is preferable to use nickel or copper, or an alloy of these metals.

Although the shape of the conductor of the lead wire is not particularly limited, a rectangular conductor is preferred. In the case of a rectangular conductor, it is possible to cope with an increase in the electric capacity of the battery by increasing the width without increasing the thickness. If the thickness of the conductor is small, it is easy to maintain the reliability of the heat seal at the portion where the lead wire is taken out. In connection with external circuits and electrodes, rectangular conductors can have a larger contact area and can be spot welded or ultrasonically welded.
A more reliable connection can be made.

The electrolyte includes propylene carbonate, γ
-Butyrolactone, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, organic solvent such as tetrahydrofuran, Li
_{ClO 4, LiBF 4, LiPF 6} , LiAsF aqueous electrolyte and plus such _6, such as a lithium-ion conductive solid electrolyte can be used.

The major reason why the present invention is effective is in the structure of the enclosing bag. In the enclosing bag according to the present invention, the laminated sheet used as the wall is formed by sandwiching a metal foil with a plastic sandwich. Then, at least one of a chemical conversion treatment and an anodic oxidation treatment is performed on at least a surface of the metal foil on the side of the electrolyte, and a heat seal layer is formed on the treated metal foil surface with a urethane-based adhesive or the like. Without heat treatment and by heat lamination. The surface opposite to the electrolyte side of the metal foil surface does not necessarily require a treatment such as a chemical conversion treatment or an anodic oxidation treatment. The plastic for protecting the metal surface on this side may be formed by thermal lamination, or may be bonded using an adhesive or the like. The encapsulation bag, two bonded sheets created as described above, facing the side of the heat sealing layer side, leaving a part as a storage port for storing an electrode, a diaphragm, an electrolyte, and the like, The periphery is formed by heat sealing. After the electrodes, the diaphragm, the electrolyte, and the like are stored in the storage bag from the storage opening, the storage opening is heat-sealed with the lead wire from the electrode taken out to form a nonaqueous electrolyte battery. As described above, the laminated sheet used for the enclosing bag according to the present invention is obtained by subjecting the metal foil surface to at least one of a chemical conversion treatment and an anodic oxidation treatment. It is made by directly bonding plastic with heat lamination and bonding metal foil and plastic together. Therefore, even if the above-mentioned drawing process is performed on the bonded sheet, the sealing reliability of the enclosing bag is reduced. A major feature is that they do not.

The chemical conversion treatment on the surface of the metal foil includes a chromate treatment and a boehmite treatment. As the chromate treatment, a method in which a metal foil is immersed in a chromic acid solution or a chromic acid solution (for example, Surfcoat manufactured by Nippon Paint Co., Ltd.)
Is applied to the metal foil surface with a bar coater and dried. The boehmite treatment is, for example, a method in which 0.1% aqueous ammonia is heated to 90 ° C. and a metal foil is immersed therein. Further, as the anodic oxidation treatment, for example, 20
The metal foil is immersed in 10% sulfuric acid at
There is a method such as energizing for minutes.

After performing the above-described treatment on the surface of the metal foil,
As a heat sealing layer, for example, an acid-modified polyethylene, an acid-modified polypropylene, an ionomer, or the like is directly adhered by heat lamination without using an adhesive, and the sealing bag of the battery is formed so that this surface is on the inside. Shall be.

To the inner heat seal layer, one or several inorganic fillers selected from the group consisting of hydrotalcites and magnesium sulfate, which have been calcined to remove water of crystallization, are added to the above-mentioned polymer. It can also have a water permeation prevention function. Further, a metal carboxylate or a metal oxide may be added to the above-mentioned polymer in the heat seal layer on the inner side to have an acid permeation preventing function. In addition, one heat seal layer may have both a water permeation prevention function and an acid permeation prevention function, and a heat seal layer having each function may be attached to the heat seal layer to perform both functions as a whole. You can also have it.

One of the chemical conversion treatment and the anodic oxidation treatment may be performed on the surface of the metal foil opposite to the electrolyte side.
The opposite side is not required, as it does not come into contact with the electrolyte. On the opposite side, it is sufficient to attach a PET film or a nylon film using an adhesive so that the surface of the metal foil can be protected from external damage.

[0017]

The contents of the present invention will be described below with reference to examples. The sealing performance of the encapsulation bag is determined by enclosing only the electrolyte for which the sealing performance is a problem, instead of actually preparing the battery by enclosing the electrodes and the like, and placing the electrolyte in an 85 ° C. constant temperature bath. After heating for one day, the electrolyte was examined by a method of measuring the weight loss rate.

FIG. 1 shows a cross-sectional structure of a laminated sheet used for an enclosing bag according to the present invention. In the bonded sheet of FIG. 1, a 25 μm-thick nylon film 2 as an external protective layer is bonded to one side of an aluminum foil 1 having a thickness of 40 μm via a urethane-based adhesive, and the other side is heat-sealed. A layer was formed. The heat-seal layer was, in order from the aluminum foil side, a heat-seal A layer 3 having a thickness of 20 μm and a thickness of 20 μm.
Heat seal B layer 4, heat seal C having a thickness of 20 μm
It is composed of three layers of layer 5 and is bonded to an aluminum foil by heat lamination without using an adhesive. The heat-sealing A layer 4 is made of an acid-modified LDPE, and the heat-sealing B layer is made of a resin composition obtained by adding 30 parts by weight of magnesium sulfate and 10 parts by weight of calcium carbonate to 100 parts by weight of an acid-modified LDPE. As the C layer 5, an acid-modified LDPE was used.

The enclosing bag is made from the above-mentioned laminated sheet in a length of one.
Cut out into a rectangle of 20 mm and a width of 60 mm, and two of them are overlapped with the heat sealing layer facing each other.
It was prepared by heat sealing only the side width 3 mm. The electrolyte is sealed by taking the remaining one side of the two superposed rectangular sheets, which is not heat-sealed, as the storage port, storing the electrolyte from the storage port, and heat-sealing the storage port also by 3 mm in width. I went.

The aluminum foil has a thickness of 40 μm, and is untreated, chromate-treated,
A comparison was made using four types: those with boehmite treatment and those with anodization treatment. The conditions for each treatment were as follows. Chromate treatment: Chromic acid solution is applied with a bar coater. Boehmite treatment: Dipped in 0.1% aqueous ammonia heated to 90 ° C. for 5 minutes. Anodizing treatment: immersion in 10% sulfuric acid at 20 ° C, voltage 10
Energized with V for 1 minute.

When neither of the two bonded sheets constituting the enclosing bag was subjected to the drawing process using a mold, the result of the sealing test was the same even if the aluminum foil was used without being processed. Has a good sealing property with a weight reduction rate of the electrolyte of 0.3% or less, but the electrolyte is sealed on one side using a sheet that has been subjected to a drawing process with a depth of 3 mm using a mold. In this case, when the aluminum foil was used without any treatment, the weight reduction rate of the electrolyte was increased to 0.45%.

On the other hand, on the aluminum foil surface,
A 3 mm deep drawing process is performed on a laminated sheet using aluminum foil treated with a mold, and the encapsulation is made with the laminated sheet and a similar laminated sheet that has not been subjected to the drawing process. In the case of a bag, the electrolyte was sealed. The results of the sealing test were as follows: the chromate treatment resulted in a 0.15% electrolyte weight loss, the boehmite treatment resulted in a 0.14% electrolyte weight loss, and anodization. In the case of the treatment, the weight loss rate of the electrolyte was 0.21%. That is, the sealing bags for non-electrolyte batteries according to the present invention all had good sealing properties.

[0023]

As described above, the encapsulating bag for a non-aqueous electrolyte battery of the present invention is obtained by subjecting a metal foil such as an aluminum foil to at least one of the above-mentioned chemical conversion treatment and anodic oxidation treatment. A heat sealing layer is directly formed on the treated metal foil surface by heat lamination to form a bonded sheet, and the two bonded sheets are placed on the side of the heat sealing layer inside to form an electrode and a diaphragm. The non-aqueous electrolyte battery of the present invention is formed by heat sealing the periphery except for a part serving as a storage port for storing the electrolyte and the like. After storing the diaphragm, electrolyte, etc., with the lead wire from the electrode taken out,
Since the storage opening is formed by heat sealing, even if a sheet subjected to the drawing process is used for the bonded sheet, the sealing reliability does not decrease, and the drawing process is performed in the sealed bag. This can be performed according to the shape of the electrode or the diaphragm to be housed, and the dead space can be reduced in the enclosing bag. As a result, it is useful to increase the capacity of the battery, so that the industrial use value is remarkable.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a laminated sheet used for an enclosing bag of the present invention.

FIG. 2 is a perspective view showing a laminated sheet subjected to drawing processing.

FIG. 3A is a side cross-sectional view showing a nonaqueous electrolyte battery using a sealed bag. (B) Front sectional view of a nonaqueous electrolyte battery using an enclosing bag.

FIG. 4 is an enlarged cross-sectional view of a lead wire extraction portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal foil 2 External protective layer 3 Heat seal A layer 4 Heat seal B layer 5 Heat seal C layer 6 Heat seal part 7 Flat recessed part 8 Lead wire conductor 9 Lead wire insulation 10 Encapsulation bag 11 Positive electrode 12 Diaphragm 13 Negative electrode 14 Electrolyte 15 Heat seal layer 16 Metal foil 17 External protective layer

Continued on the front page (72) Inventor Satoshi Sukushima 1-3-1 Shimaya, Konohana-ku, Osaka City Inside the Osaka Works, Sumitomo Electric Industries, Ltd. (72) Inventor Kosuke Tanaka 1-3-1 Shimaya, Konohana-ku, Osaka City Sumitomo Electric Industries, Ltd. Osaka Works F-term (reference) 5H011 AA03 AA17 CC02 CC10 DD05 DD13 EE04 FF04 GG09 HH02 HH13 JJ25 5H029 AJ03 AJ15 AM03 AM07 CJ01 CJ02 CJ14 CJ16 DJ03 DJ05 EJ01

Claims (4)

[Claims] At least one of a chemical conversion treatment and an anodic oxidation treatment is performed on at least the surface of the metal foil constituting the bonded sheet of the encapsulating bag containing the electrodes, the diaphragm, the electrolyte and the like of the nonaqueous electrolyte battery. A heat-sealing layer is formed on the metal foil surface which has been processed by heat lamination without using an adhesive to form a bonded sheet, and two bonded sheets of the same type are subjected to the above-described processing. An encapsulation bag for a non-aqueous electrolyte battery, characterized in that the heat-sealing layer is stacked with the surface with the heat seal layer inside, and the periphery is heat-sealed except for a part as a storage port for storing an electrode, a diaphragm, an electrolyte and the like. 2. The sealed bag for a non-aqueous electrolyte battery according to claim 1, wherein at least one of the two bonded sheets has been subjected to a drawing process. 3. At least one of a chemical conversion treatment and an anodic oxidation treatment is performed on at least the surface of the metal foil constituting the bonded sheet of the sealing bag containing the electrodes, the diaphragm, the electrolyte and the like of the non-aqueous electrolyte battery on the electrolyte side. A heat-seal layer is formed on the treated metal foil surface by heat lamination without using an adhesive to form a bonded sheet.
By laminating two sheets of the same kind of laminated sheets with the surface with the heat seal layer inside, as a storage port for storing electrodes, diaphragms, electrolytes, etc., heat-sealing the periphery except a part, Form an enclosing bag, in the enclosing bag, from the storage port left without heat sealing, electrodes, diaphragm,
A non-aqueous electrolyte battery characterized in that the storage opening is heat-sealed with the lead wire from the electrode taken out of the encapsulating bag after storing the electrolyte and the like. 4. The non-aqueous electrolyte battery according to claim 3, wherein at least one of the two bonded sheets has been subjected to a drawing process.