JPH1186808A - Sealing bag for nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a metal layer from being corroded through an electrolyte by forming a sealing bag sealing a positive electrode, a negative electrode, and the electrolyte with a sheet constituted of the metallic layer and a plastic layer, and heat-laminating the plastic layer to the face on the electrolyte side of the metallic layer with acid denatured polyethylene to directly stick them together. SOLUTION: A sealing bag for sealing a positive electrode, a negative electrode, and an electrolyte and extracting the lead wires of the positive electrode and the negative electrode to the outside is formed with a material stuck together with plastic layers inserted with a metal layer, such as an aluminum foil and a metal deposition layer into a sandwich shape, a PET film is stuck to the outer face side of the metallic layer, and a thermoplastic resin such as polyethylene is stuck to the inner face side. A composition mainly made of acid denatured polyethylene, acid denatured polypropylene, or ionomer is used for a plastic layer stuck to the face on the electrolyte side of the metallic layer, and it is directly heat-laminated and stuck to the metallic layer for providing a moisture permeation preventing function and an acid permeation preventing function.

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 used for a power source of an electronic device. More specifically, it has a structure in which the positive electrode, the negative electrode, and the electrolyte are sealed, and the lead wires of the positive electrode and the negative electrode are respectively taken out to the outside, and has a highly reliable structure for sealing the electrolyte. The present invention relates to a sealed bag for a non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art Along with the miniaturization of electronic devices, there is an increasing demand for miniaturization and weight reduction of batteries as power sources. On the other hand, batteries are also required to have higher energy density and higher energy efficiency, and expectations for secondary batteries such as Li-ion batteries are increasing. In response to such demands, for example, as seen in JP-A-61-240564, a group of electrode plates is inserted into a bag made of an acid-resistant thermoplastic resin, and a large number of the electrode groups are formed into a film or sheet. There has been proposed an attempt to form a sealed lead-acid battery by enclosing it in a bag-like outer body made of a tubular or tubular synthetic resin. Also, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 2447 and Japanese Patent Application Laid-Open No. 57-115820, there is also an attempt to improve the sealing performance by forming a structure in which a metal layer is sandwiched between plastic films in a sheet of an enclosing bag.

[0003]

The provision of a metal layer greatly improves the sealing performance, but does not completely prevent the penetration of moisture from the sealing portion. When moisture enters, it reacts with the electrolytic solution to generate hydrofluoric acid, and this hydrofluoric acid may permeate the plastic film layer and corrode the metal layer, or may cause separation between the metal layer and the plastic layer. This peeling was also caused by the use of a urethane-based adhesive or the like as an anchor coat material for bonding the metal layer and the plastic layer. The present invention prevents the invasion of moisture as much as possible, and does not corrode the metal layer or cause peeling between the metal layer and the plastic film layer even if moisture invades and generates hydrofluoric acid. An object of the present invention is to provide a sealed bag for a non-aqueous electrolyte battery.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, as a plastic,
Acid-modified polyethylene or acid-modified polypropylene,
Alternatively, if an ionomer is used to create a bonded sheet of metal and plastic directly bonded to the metal layer by thermal lamination, and this plastic surface is used as the electrolyte side to form a battery encapsulation bag, the above-mentioned purpose can be achieved. I found what I could achieve. Further, preferably, the plastic layer has a function of preventing water permeation and a function of preventing permeation of acid, so that the function of preventing moisture intrusion can be remarkably improved. It has been found that even if is generated, the metal layer is not corroded and no peeling occurs between the metal layer and the plastic film layer.

Hereinafter, the present invention will be described in detail with reference to the drawings. In a battery of a type in which an electrode, an electrolyte, a diaphragm, and the like are inserted into an encapsulation bag, as shown in FIG. 3, the encapsulation is performed by fusing the innermost heat seal layer 10 inside the encapsulation bag in direct contact. A bag has been made. Then, as shown in FIG. 2, the positive electrode, the negative electrode, the diaphragm, and the electrolytic solution are stored in the encapsulation bag, and as shown in FIG. 4, the encapsulation bag and the lead wire are connected to the heat seal layer 10 of the encapsulation bag. The insulator 2 of the lead wire is integrated by fusing, the lead wire is taken out, and the lead wire is connected to the positive and negative electrode plates inside the enclosing bag. The lead wire and the electrode are connected in advance and sealed in a sealing bag.

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 an expanded metal. The method of connecting the lead wire to the positive and negative electrode plates is not particularly limited, but a method of connecting the metal base material of the electrode plate and the conductor of the lead wire by spot welding, ultrasonic welding, or the like can be preferably used.

Since a very high potential is applied to the lead wire conductor for connecting the positive electrode, a material that does not melt at a high potential is desirable. Aluminum for that,
Alternatively, titanium or an alloy of these metals can be preferably used. For the connection of the negative electrode, lithium is deposited by overcharging, and in overdischarge, the potential is high, so the shape is not easily changed when lithium is deposited. A material that is difficult to work is preferable. From the above viewpoints, nickel or copper, or an alloy of these metals can be preferably used as the material of the conductor.

As for the shape of the conductor, a single wire of a round shape or a rectangular conductor can be preferably used. However, in the case of a round shape, the diameter of the round shape increases when the battery capacity is large. Since the thickness of the lead wire interposed between the heat seal layers 10 becomes large, a gap is easily generated in a fusion portion between the insulator 2 as the outermost layer of the lead wire and the heat seal layer 10 as the innermost layer of the encapsulating bag. As a result, there is a problem that the reliability of sealing at the fusion portion between the lead wire and the sealing bag is lowered. On the other hand, when a rectangular conductor is used, it is possible to increase the cross-sectional area by increasing the width of the conductor without increasing the thickness of the conductor to increase the battery capacity. There is no reduction in the reliability with respect to the sealing of the fused portion of the lead wire sandwiched between the layer 10 and the insulator 2. Further F
When connecting to an external circuit using a PC (flexible printed circuit board) or the like, or to the electrode plate, the rectangular conductor has a larger contact area, and more reliable connection can be performed by spot welding or ultrasonic welding. It becomes possible.

The electrolyte includes propylene carbonate, γ
LiCl in organic solvents such as butyrolactone, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1.2-dimethoxyethane, tetrahydrofuran, etc.
A non-aqueous electrolyte such as l04, LiBF4, LiPF6, LiAsF6, and a lithium ion conductive solid electrolyte can be used.

The encapsulating bag is preferably made of a material that is bonded to a metal foil such as an aluminum foil or a plastic in which a metal deposition layer is inserted in a sandwich shape. At least the inner plastic must not dissolve in the electrolyte. .

An important feature of the present invention resides in the material of the plastic layer constituting the enclosing bag. As an example of the configuration of the enclosing bag, there can be cited one in which a PET film is attached to the outer surface of an aluminum foil and a thermoplastic resin such as polyethylene is attached to the inner surface. The PET on the outer surface is provided to protect aluminum from external damage, and the polyethylene on the inner surface is provided for heat sealing. When such a conventionally devised material is used, moisture gradually penetrates during long-term storage even when heat-sealing, and the water reacts with the electrolyte solution sealed in the bag. To produce hydrofluoric acid. This hydrofluoric acid has a problem in that it permeates polyethylene and the like and peels off the adhesive interface between aluminum and polyethylene, which is one of the factors that make such a bag-type battery container not practical. In order to solve this problem, the inventors of the present invention have used an acid-modified polyethylene, an acid-modified polypropylene, or an ionomer for the plastic layer constituting the encapsulation bag, and heat-laminated the metal layer with no adhesive. Came up with a direct connection. Further, they have found that it is preferable to provide the plastic layer with a moisture permeation preventing function and an acid permeation preventing function.

In order to provide the plastic layer with a function of preventing moisture permeation, the resin used as the plastic layer must be
A mixture of one or more inorganic fillers selected from the group consisting of hydrotalcites and magnesium sulfate from which water of crystallization has been removed by firing can be used.

In order to provide the plastic layer with an acid permeation preventing function, a resin used as a plastic layer mixed with a metal carboxylate or a metal oxide can be used. Carboxylic acid metal salts, as metal oxides calcium carbonate, magnesium oxide, hydrotalcites, calcium stearate and the like are preferred,
Other stabilizers for polyvinyl chloride are also effective.

It is possible to provide both the function of preventing water permeation and the function of preventing acid permeation by providing both functions in one plastic layer, or to provide a function of preventing water permeation. It can also be obtained by laminating a plastic layer and a plastic layer having an acid permeation preventing function.

As the resin for the plastic layer of the present invention, an acid modified product of polyethylene, an acid modified product of polypropylene, an ionomer and the like which are not easily attacked by the electrolytic solution are preferable. Can be used if a resin layer hardly eroded by the electrolyte is provided.

[0016]

The embodiments will be described below. First, Li
100 parts by weight of CoO2 powder (manufactured by Nippon Chemical Industry), 10 parts by weight of graphite and 10 parts by weight of polyvinylidene fluoride were mixed and dissolved in N-methyl-2-pyrrolidone.
Paste. Next, this paste was applied to a thickness of 20 μm.
Was coated on one side of an aluminum foil, dried and then roller-pressed. Thus, an electrode plate having a thickness of 0.1 mm, a width of 50 mm, and a length of 105 mm (5 mm is an uncoated portion) was prepared and used as a positive electrode.

Next, 20 parts by weight of polyvinylidene fluoride was mixed with 100 parts by weight of phosphorous natural graphite powder, dissolved in N-methyl-2-pyrrolidone, and then made into a paste. This paste was applied on both sides of a copper foil having a thickness of 20 μm, dried, and then roller-pressed. Thus, an electrode plate (5 mm thick, 50 mm wide, 105 mm long)
mm is an uncoated part) to prepare a negative electrode.

An aluminum foil (positive electrode) on which an active material layer of an electrode plate is not coated is sandwiched by a 25 μm-thick polypropylene fine and porous film fusion film sandwiched between the positive electrode and the negative electrode thus obtained. Each of the foils (negative electrodes) was connected to the conductor of the lead wire by ultrasonic welding, inserted into a sealed bag as shown in FIG. 2, injected with 8 cc of an electrolytic solution, impregnated under reduced pressure, and then inserted into the sealed bag. The inner layer of the sealed bag and the insulator outside the lead wire were heat-sealed (sealing width: 10 mm) with a sealing machine at 200 ° C. for 5 seconds to form a test battery. As the electrolytic solution, a solution obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 and dissolving lithium hexafluorophosphate at 1 mol / liter was used.

The method for producing the sealed bag is as follows. That is, the sheet having the configuration shown in Table 1 was formed into a rectangular shape (70 mm × 1
35 mm), and the two sheets were faced to each other with the PET surface facing outward, and three sides of the rectangle were heat-sealed with a width of 3 mm to obtain a sealed bag.

Each of the sheets was prepared as follows. First, a 20 μm acid-modified LDPE was extruded and coated on the aluminum foil surface of a PET film and aluminum foil bonded together via a urethane-based adhesive.
A sheet common to all was obtained by directly laminating by heat lamination. Next, various heat seal layer films were bonded to the obtained sheet by heat lamination.

The heat seal layer film was prepared by molding various resin mixtures shown in Table 2 obtained by roll mixing into a film having a predetermined thickness using a T-die extruder.

[0022]

[Table 1]

[0023]

[Table 2]

In the configuration of the encapsulation bag shown in Table 1, a test battery was produced using an encapsulation bag in which the heat seal layer Y and the heat seal layer Z were variously changed. The composition of the resin used for the heat seal layer is shown in Table 3, and the respective intentions are shown below.

Example 1 Calcined hydrotalcite 30 (parts by weight) was used as an acid trapping agent, and magnesium sulfate (30 parts by weight) was used as a moisture trapping agent.

(Example 2) In Example 1, the acid trapping agent was changed to calcium carbonate (10 parts).

(Example 3) In Example 1, the acid trapping agent was changed to magnesium oxide (5 parts).

Example 4 The amount of the acid trapping agent (magnesium oxide) in Example 3 was changed to 100 parts.

Example 5 In Example 2, the amount of the moisture trapping agent (magnesium sulfate) was changed to 10 parts.

Example 6 The amount of the water trapping agent (magnesium sulfate) in Example 2 was changed to 100 parts.

Example 7 The calcined hydrotalcite (30 parts) served as both a moisture trapping agent and an acid trapping agent.

Example 8 One layer was prepared by mixing magnesium sulfate (30 parts) as a water trapping agent and calcium carbonate (10 parts) as an acid trapping agent.

Comparative Example 1 No trapping agent was added.

Comparative Example 2 In Example 2, the amount of the moisture trapping agent (magnesium sulfate) was changed to 120 parts.

Comparative Example 3 An acid trap layer was not provided.

Comparative Example 4 No water trap layer was provided.

Comparative Example 5 The amount of the acid trapping agent (magnesium oxide) in Example 3 was changed to 120 parts.

Comparative Example 6 A laminated film of PET (12 μm) / urethane adhesive (5 μm) / aluminum foil (9 μm), acid-modified LDPE (20 μm), and Example 7
A three-layer film was prepared by laminating the heat seal layers Y and Z having the structure described above, and the aluminum foil surface and the acid-modified LDPE surface were adhered via a urethane-based anchor coat material to obtain a film for an enclosing bag.

[0039]

[Table 3]

Comparative Examples 2 and 5 could not be formed into a film having a thickness of 100 μm or less, probably because the amount of the filler was too large. In addition, in Examples 1 to 8 and Comparative Examples 1, 3, and 4, test batteries could be manufactured, and the reliability tests described below could be performed.

[0041]

The effects of the present invention were confirmed by conducting a reliability test using the above-described test battery as follows. That is, the test battery was placed in a 60 ° C., 95% RH
After standing for 1000 hours, the concentration of hydrofluoric acid in the internal electrolytic solution was measured, and the appearance was further confirmed. The concentration was determined by titration with a hydrofluoric acid concentration of 0.1 mol / liter sodium hydroxide solution. Table 4 shows the results of the reliability test.

[0042]

[Table 4]

In Comparative Examples 1 and 4 using an encapsulating bag without a moisture trapping agent, the hydrofluoric acid concentration was drastically increased. In particular, in Comparative Example 1 having no acid trapping layer, the aluminum in the encapsulating bag was made of hydrofluoric acid. Corrosion and delamination of the aluminum-heat seal layer were caused. Also, in Comparative Example 4, slight delamination between aluminum and the heat seal layer was recognized, indicating that the effect of the hydrofluoric acid trapping agent was weakened. Furthermore, Comparative Example 3 containing no hydrofluoric acid trapping agent was also made of aluminum
It was found that delamination of the heat seal layer was recognized, and that it was affected by hydrofluoric acid which was slightly generated. Comparative Example 6
Because of the use of a urethane-based adhesive, slight peeling was observed.

In contrast, none of the samples using the sealed bags of Examples 1 to 8 affected the appearance even after 1000 hours. However, the hydrofluoric acid concentration slightly increased, and it was not possible to prevent 100% moisture penetration. However, at this time, the acid trapping agent adsorbs the hydrofluoric acid formed by the reaction between the slightly invaded moisture and the electrolyte, preventing the corrosion of the aluminum in the sealed bag or the separation between the aluminum and the heat seal layer. Thus, a remarkable effect of maintaining the battery performance was confirmed.

[Brief description of the drawings]

FIG. 1 shows a non-aqueous electrolyte battery using a sealed bag and a lead wire of the present invention.

FIG. 2 schematically shows the inside of an enclosing bag.

FIG. 3 shows a cross section of an enclosing bag.

FIG. 4 is an enlarged view of a heat sealing portion of the enclosing bag.

[Explanation of symbols]

 1, 1 ': conductor of lead wire 2, 2': insulation of lead wire 3: sealed bag 4: sealed portion of sealed bag (example) 5, 5 ': electrode 6: diaphragm 7: positive electrode current collector 7': Negative electrode current collector 8: Positive electrode active material 8 ': Negative electrode active material 9: Aluminum foil 10: Heat seal layer 11: PET layer

Continuation of front page (72) Inventor Takehiro Hosokawa 1-3-1 Shimaya, Konohana-ku, Osaka-shi, Osaka Sumitomo Electric Industries, Ltd. Osaka Works

Claims (7)

[Claims] 1. A non-aqueous electrolyte battery having a structure in which a positive electrode, a negative electrode, an electrolytic solution and the like are sealed in an enclosing bag and a lead of the positive electrode and a negative electrode are respectively taken out of the bag. It is composed of laminated sheets of layers,
The plastic layer adhered to the electrolyte side of the metal layer is acid-modified polyethylene, or acid-modified polypropylene,
Alternatively, an encapsulating bag for a non-aqueous electrolyte battery, comprising a composition mainly composed of an ionomer, wherein a metal layer and a plastic layer are directly bonded by thermal lamination. 2. A plastic layer having an acid permeation preventing function,
The sealing bag for a non-aqueous electrolyte battery according to claim 1, wherein the sealing bag has both functions of preventing water permeation. 3. A means for imparting an acid and water permeation preventing function is to use a multilayer plastic layer, one of which has an acid permeation preventing function, and the other has a water permeation preventing function. 3. The sealed bag for a non-aqueous electrolyte battery according to claim 2, wherein: 4. A means for imparting an acid and water permeation preventing function, wherein one or more plastic layers are used, and one of the layers has both an acid permeation preventing function and a water permeation preventing function. The sealing bag for a non-aqueous electrolyte battery according to claim 2, characterized in that: 5. A resin layer containing 100 parts by weight or less of a metal carboxylate or a metal oxide with respect to 100 parts by weight of a thermoplastic resin as a layer having a function of preventing permeation of acid. As a layer to have, a resin layer containing one or more mixtures selected from the group consisting of hydrotalcites and magnesium sulfate from which 100 parts by weight or less of thermoplastic resin has been calcined to remove water of crystallization by firing. The encapsulating bag for a non-aqueous electrolyte battery according to claim 3, characterized in that: 6. A layer having an acid permeation prevention function and a water permeation prevention function is 100 parts by weight per 100 parts by weight of the thermoplastic resin.
Not more than part by weight of a metal carboxylate or metal oxide;
1 selected from the group consisting of hydrotalcites and magnesium sulfate from which crystallization water has been removed by calcination of 100 parts by weight or less
The encapsulating bag for a non-aqueous electrolyte battery according to claim 4, wherein the encapsulating bag contains a resin layer containing one or more kinds of mixtures. 7. The metal carboxylate or metal oxide is one or more of a mixture selected from the group consisting of calcium carbonate, magnesium oxide and hydrotalcite. The sealed bag for a non-aqueous electrolyte battery according to 1.