JP3240965B2 - Enclosure bag for non-aqueous electrolyte battery and method of manufacturing the same - Google Patents

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 as a power source for electronic equipment. More specifically, the positive electrode, the negative electrode, the electrolyte is sealed, and has a structure to take out the lead wires of the positive electrode and the negative electrode, respectively,
Also, the present invention relates to a sealed bag for a non-aqueous electrolyte battery having a highly reliable structure for sealing an electrolyte and a method for manufacturing the same.

[0002]

2. Description of the Related Art Along with miniaturization of electronic equipment, there is an increasing demand for miniaturization and weight reduction of a battery as a power supply. 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]

A structure in which an electrode and an electrolytic solution are put into an encapsulation bag and a lead wire is taken out of the encapsulation bag. When heat sealing the end portion of the encapsulation bag, a large amount of "heat fusion" can be obtained. For example, heat sealing with high sealing reliability can be performed. On the other hand, there is a demand that the size of the battery be as small as possible, and it is necessary to make the "heat fusion margin" as small as possible.

When trying to reduce the "heat fusion margin",
Due to wrinkles during heat sealing, poor sealing is likely to occur. If sealing failure occurs, electrolyte leakage may occur. Also, even if the electrolyte does not leak, moisture penetrates and reacts with the electrolyte to generate hydrofluoric acid,
This hydrofluoric acid may corrode the metal layer constituting the enclosing bag, and may promote a decrease in sealing performance.

[0005]

In order to respond to the demand for miniaturization of the battery, the present inventors have proposed a method for reducing the "heat fusion margin" of the heat seal as much as possible and not reducing the sealing reliability. Various studies were made. As a result, the present inventors have found that the above-mentioned problems can be solved by previously providing a "shape" so that the electrodes and the lead wires can be accommodated in the bonding sheet for the enclosing bag, and completed the present invention.

[0006] As a method of giving a “shape habit” to a bonded sheet, a method called embossing is used to press a male and female mold as shown in FIG. 5, and as shown in FIG. There are a method of pressing the mold with pressurized air, and a method of absorbing and depressurizing using a female mold. In addition, it has been found that it is preferable to use an iron-aluminum alloy for the metal layer constituting the bonded sheet in order to prevent the bonded sheet from "breaking" during embossing.

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 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 connection to the positive electrode, a material which 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, or in overdischarge, the potential is high, so the shape is not easily changed when lithium is deposited, that is, it is difficult to form an alloy with lithium, and at a relatively high potential. A material that is difficult to dissolve 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.

Regarding the shape of the conductor, a single wire of a round shape or a flat 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, the cross-sectional area can be increased by increasing the width without increasing the thickness of the conductor even when the battery capacity is increased. There is no reduction in the reliability of the sealing of the fused portion of the lead wire sandwiched between the heat seal layer 10 and the insulator 2. Furthermore, when connecting to an external circuit using FPC (flexible printed circuit board) or the like or an electrode plate, a rectangular conductor has a larger contact area, and a more reliable connection can be made by spot welding or ultrasonic welding. Becomes possible.

The electrolyte includes propylene carbonate, γ
LiCl in organic solvents such as butyrolactone, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1.2-dimethoxyethane and tetrahydrofuran
A non-aqueous electrolyte such as 10 ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ or a solid electrolyte having lithium ion conductivity can be used.

The encapsulating bag preferably uses a material bonded to a plastic in which a metal layer is inserted in a sandwich shape, and it is necessary that at least the inner plastic does not dissolve in the electrolytic solution. Examples of the metal layer include a metal foil such as an aluminum foil and a metal deposition layer, and an iron-aluminum alloy foil is preferable. The plastic layer on the side in contact with the electrolytic solution is preferably polyethylene, polypropylene, an acid-modified product thereof, an ionomer, or the like, which is hardly attacked by the electrolytic solution. In addition, these resins may be used as a plastic layer in which one or more inorganic fillers selected from the group consisting of hydrotalcites and magnesium sulfate, from which water is removed and sintered to remove water of crystallization, are removed. Can be. Further, a resin mixed with a metal carboxylate or a metal oxide can be used in order to provide the plastic layer with an acid permeation preventing function.

An important feature of the present invention is that at least one of the bonded sheets is embossed to a depth such that an electrode or a lead wire can enter therein before heat-sealing the bonded sheet in the enclosing bag. . By doing so, even if the "heat fusion margin" is small, it is possible to perform heat sealing with high sealing reliability without wrinkles or the like.

[0015]

The embodiments will be described below. First, Li
100 parts by weight of CoO ₂ 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. In this way, 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 were 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 the active material layer of the electrode plate is not coated is sandwiched between a fine and porous film of polypropylene having a thickness of 25 μm 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.

Table 1 shows the structure of the laminated sheet for the enclosing bag.
And was produced as follows. First, P
20 μm acid-modified LD on the metal foil surface of a film obtained by bonding an ET film and a metal foil via a urethane-based adhesive
The sheet was obtained by extrusion coating PE. Then, a heat seal layer film was bonded to the obtained sheet by heat lamination. The heat seal layer film is
The resin mixture shown in Table 2 obtained by roll mixing was formed into a film having a predetermined thickness using a T-die extruder.

[0019]

[Table 1]

[0020]

[Table 2]

Example 1 A laminated sheet having the structure shown in Table 1 and using an aluminum foil as a metal foil was cut into a rectangular shape (70 mm × 135 mm) and cut into a rectangular shape (60 m
m × 120 mm) using a press die, the PET surface side becomes convex, 5 mm wide on three sides of the rectangle, and 10 mm on the top side of the rectangle.
Embossing was performed to a maximum depth of 1 mm so that a peripheral portion having a width of mm was left.

(Example 2) Using a bonded sheet having a structure shown in Table 1 using an aluminum alloy foil containing 1% iron as a metal foil, embossing to a maximum depth of 2 mm was performed in the same manner as in Example 1. gave.

Comparative Example 1 An embossing process was not performed on a laminated sheet having the structure shown in Table 1 using an aluminum foil as a metal foil.

(Comparative Example 2) An embossing process having a maximum depth of 2 mm was performed in the same manner as in Example 1 on a bonded sheet having the structure shown in Table 1 using an aluminum foil as a metal foil. (Example 1) (Example 2) (Comparative Example 1) (Comparative Example 2) Two bonded sheets were faced each other with the PET surface facing outward, and three sides of the rectangle were each 3 mm wide. Tosir. Next, an electrode, an electrolyte, and the like were put into these sealed bags, and a lead wire was taken out from the upper side, and the upper side was heat-sealed to produce a test battery.

[0025]

The effects of the present invention were confirmed by conducting a reliability test using the test battery as described below. That is, the test battery was placed in a constant temperature / humidity bath at 60 ° C. and 95% RH , and allowed to stand for 1000 hours. Then, the concentration of hydrofluoric acid in the internal electrolytic solution was measured, and the appearance was further confirmed. Hydrofluoric acid concentration was determined by titration with sodium hydroxide solution 0.1 mol / liter. Table 3 shows the results of the reliability test.

[0025]

The effects of the present invention were confirmed by conducting a reliability test using the test battery as described below. That is, the test battery was placed in a constant temperature / humidity bath at 60 ° C. and 95% RH, and allowed to stand for 1000 hours. Then, the concentration of hydrofluoric acid in the internal electrolytic solution was measured, and the appearance was further confirmed. The hydrofluoric acid concentration was measured by titration with a 0.1 mol / liter sodium hydroxide solution. Table 3 shows the results of the reliability test.

[0026]

[Table 3]

In Comparative Example 1 in which no embossing was performed, the heat-sealed portion had many wrinkles, moisture entered from the wrinkled portions, and the hydrofluoric acid concentration increased. In Comparative Example 2, during the embossing, the aluminum was torn and moisture entered from the part,
Hydrofluoric acid concentration increased sharply. In contrast, in the case of Examples 1 and 2, the appearance did not change even after 1000 hours, and the hydrofluoric acid concentration did not change significantly, indicating that the sealing reliability of the present invention was excellent.

[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.

FIG. 5 shows a method of embossing by press molding.

FIG. 6 shows a method of embossing by pressurized air.

FIG. 7 shows a cross section of a non-aqueous electrolyte battery using a bonded sheet having one side embossed.

[Explanation of symbols]

 1, 1 ': Conductor of lead wire 2, 2': Insulation of lead wire 3: Sealing bag 4: Sealing portion of sealing bag (example) 5, 5 ': Electrode 6: Diaphragm 7: Positive electrode 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 12: Laminated sheet 13: Die 14: Molding end R 15: Pressurized air 16: Laminated sheet with emboss processing 17: Laminated sheet without emboss processing

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-208708 (JP, A) JP-A-10-106531 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/02-2/08

Claims (5)

(57) [Claims] A positive electrode, a negative electrode, and a non-aqueous electrolyte battery,
A bag for enclosing an electrolyte or the like, taking out the lead wires of the positive electrode and the negative electrode respectively, and enclosing these lead wires at the outlet, wherein the metal layer is sandwiched.
From the material pasted with the plastic inserted into the
Mixed with a material that removes moisture from the plastic layer
Further, it is provided with a function of preventing acid permeation, wherein at least one side of the bag is embossed on the bonded sheet, and the sheet is sealed at a side portion of the sheet. For non-aqueous electrolyte batteries. 2. A positive electrode, a negative electrode, and a non-aqueous electrolyte battery constituting a non-aqueous electrolyte battery.
A positive electrode and a negative electrode lead wire are respectively taken out to the outside by enclosing an electrolyte and the like, and a plastic layer in which a metal layer for enclosing these lead wires is inserted in a sandwich shape at a take-out opening.
A method for producing a bag made of a material to be bonded to a plastic , wherein a material for removing moisture is mixed with the plastic layer.
And, which it has to have a permeation prevention function of acid, prior to heat-sealing, in advance, stiffness facilities embossing on at least a bag one surface of the bonded sheet, the sheet at the edge portion of the sheet seal A method for producing a sealed bag for a non-aqueous electrolyte battery. 3. The method for producing a sealed bag for a non-aqueous electrolyte battery according to claim 2, wherein aluminum containing iron is used as a metal layer constituting the bonded sheet to be embossed. 4. A resin constituting the plastic layer
Is polyethylene, polypropylene or their
It is an acid modified product and an ionomer that removes moisture from the resin.
As a material to be removed, hydro-
One selected from the group of talcites and magnesium sulfate
Or plastics mixed with multiple inorganic fillers
The non-aqueous electrolyte battery according to claim 1, wherein
Enclosure bag. 5. The plastic layer has an acid permeation preventing function.
Carboxylic acid metal salt or metal oxide to have
2. The resin according to claim 1, wherein
A sealed bag for a non-aqueous electrolyte battery according to the above.