JPH1140114A - Non-aqueous electrolyte battery - Google Patents

Abstract

(57) Abstract: 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, having a structure in which lead wires of the positive electrode and the negative electrode are respectively taken out, and It is another object of the present invention to provide a non-aqueous electrolyte battery having a structure in which these lead wires are also sealed and which can maintain sealing reliability even when used for a long time. SOLUTION: A protective film layer is provided on a heat sealing portion of an enclosing bag. It is also characterized in that the plastic layer constituting the protective film layer has a function of preventing water permeation and / or a function of preventing acid permeation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to 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 in an encapsulating bag, and has a structure in which the lead wires of the positive electrode and the negative electrode are respectively taken out,
In addition, it has a highly reliable structure for sealing the electrolyte.

[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,
The hydrofluoric acid reacts with the electrolytic solution to generate hydrofluoric acid. The hydrofluoric acid may penetrate the plastic film layer and corrode the metal layer, or may cause separation between the metal layer and the plastic layer. The present invention substantially prevents corrosion of the metal layer of the encapsulating bag or peeling between the metal layer and the plastic film layer by greatly controlling the intrusion of moisture from the seal portion and reducing the generation of hydrofluoric acid. An object of the present invention is to provide a non-aqueous electrolyte battery using a sealed bag having the function of (1).

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above-mentioned object, and as a result, by providing a specific protective film layer on the heat seal portion of the sealed bag,
The penetration of moisture from the sealing part can be greatly restricted, and as a result, the generation of hydrofluoric acid is reduced, and the function of substantially preventing corrosion of the metal layer of the encapsulating bag or preventing peeling between the metal layer and the plastic film layer. The present inventors have found that they can be held in an enclosing bag and completed the present invention.

Hereinafter, an enclosed bag type battery according to the present invention will be described in detail with reference to the drawings. Electrodes, electrolytes,
For batteries of the type in which a septum or the like is inserted in an enclosure bag,
As shown in FIG. 3, the encapsulation bag is produced by fusing the innermost heat seal layer 10 inside the encapsulation bag which is in direct contact. And, as shown in FIG. 2,
A positive electrode, a negative electrode, a diaphragm, and an electrolytic solution are stored in the encapsulating bag. As shown in FIG. 4, the encapsulating bag and the lead wire are formed by fusing the heat seal layer 10 of the encapsulating bag and the insulator 2 of the lead wire. The lead wires are integrated and taken out to the outside, and the lead wires are connected to the positive and negative electrode plates, respectively, 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 precipitated by overcharging, or in overdischarge, the potential is high, so that when lithium is deposited, the shape is hard to change, 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.

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 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 metal foil such as an aluminum foil or a plastic in which a metal deposition layer is inserted in a sandwich shape. It is necessary that at least the inner plastic does not dissolve in the electrolyte. .

The battery of the type in which the electrodes, the electrolyte, the diaphragm, and the like are inserted into the sealed bag is as described above. 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 using such a conventionally invented material,
Even if heat sealing is performed, moisture gradually invades during long-term storage, and the water reacts with the electrolyte solution sealed in the bag to generate 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.

As a means for solving this problem, the present inventors have found that it is effective to provide a specific protective film layer on the heat-sealed portion of the enclosing bag. For example, a one-layer or plural-layer plastic film, or a laminated film of this and a metal layer can be used. A commercially available foil such as aluminum or copper can be used as the metal layer to be bonded, and a plastic layer that can be thermally bonded to the encapsulating bag is appropriate. For example, if the outermost layer of the encapsulating bag is a PET film layer, a polyester hot melt resin or a silane graft EEA that can be thermally bonded to PET is used.
Resins such as (ethylene-ethyl acrylate) are suitable.

Further, more effective results can be obtained by providing the protective film layer with a moisture permeation preventing function or an acid permeation preventing function or both functions.

The resin used as the plastic layer of the protective film layer is selected from the group consisting of hydrotalcites and magnesium sulfate, which are calcined to remove water of crystallization, so that the protective film layer has a function of preventing moisture permeation. A mixture of one or more inorganic fillers can be used.

In order to provide the protective film layer with an acid permeation preventing function, a resin obtained by mixing a metal carboxylate or a metal oxide with a resin used as a plastic layer of the protective film layer can be used. As the carboxylate metal salt and metal oxide, calcium carbonate, magnesium oxide, hydrotalcites, calcium stearate and the like are preferable, but 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 formed by laminating a plastic layer and a plastic layer having an acid permeation preventing function.

The resin for obtaining the plastic layer having such a function is preferably polyethylene, polypropylene, or an acid modified product thereof or an ionomer which is hardly affected by the electrolytic solution. Even if it is a material, it can be used if it has a configuration in which a resin layer which is hardly eroded by the electrolytic solution is provided on its inner surface.

[0018]

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. 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 phosphorus-like natural graphite powder, dissolved in N-methyl-2-pyrrolidone, and then formed 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 obtained in this manner. Each foil (negative electrode) was connected to the conductor portion 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 used encapsulating bag was obtained as follows. First, the sheet having the structure shown in Table 1 was cut into two rectangular shapes (70 mm x 135 mm), the PET surfaces were faced outward, and the three sides of the rectangular shape were heat-sealed with a width of 3 mm and sealed. I got The sheet was made of a 100 μm acid-modified LDP on the aluminum surface of a film in which a PET film and an aluminum foil were bonded via a urethane-based adhesive.
E was obtained by extrusion coating.

[0022]

[Table 1]

A test battery was manufactured using the thus obtained sealed bag. Then, a sample in which the sealing portion of the test battery was covered with various protective films and heat-sealed was prepared, and subjected to a test of the battery sealing reliability.

As the structure of the protective film, a film shown in Table 2 which was slit to a width of 3 mm was used.

[0025]

[Table 2]

The plastic film of the protective film had the composition shown in Table 3.

[0027]

[Table 3]

Protective film A: A protective film having the composition shown in Table 2 and using A in Table 3 as the composition of the plastic layer. Protective film B: Similarly, B used in Table 3 was used. Protective film C: similarly using C in Table 3. Protective film D: Similarly, D in Table 3 was used.

(Example 1) Protective film A having a width of 3 mm
Was cut to the length of the heat-sealed portion of the test battery, and the heat-sealed portion was covered as shown in FIG.
Heat sealing was performed for 5 seconds.

Example 2 The same operation as in Example 1 was performed using the protective film B.

Example 3 The same operation as in Example 1 was performed using the protective film C.

Example 4 The same operation as in Example 1 was performed using the protective film D.

(Comparative Example 1) No protective film was attached.

The battery samples of Examples 1 to 4 and Comparative Example 1 prepared as described above were subjected to 60 ° C., 95% R
After being placed in an H constant temperature and humidity chamber and left for 1000 hours, 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.

[0035]

The test results of the sealing reliability are shown in Table 4, and the effect of the protective film of the present invention is remarkably exhibited. That is, the samples using the sealed bags of Examples 1 to 4 did not affect the appearance even after the elapse of 1000 hours, and the increase in the concentration of hydrofluoric acid was extremely small. In particular, those using C and D showed almost no increase. On the other hand, in the sample of Comparative Example 1 without the protective film, the hydrofluoric acid concentration was increased, and furthermore, although slightly, peeling was observed between the aluminum and the heat seal layer.

[0036]

[Table 4]

In the above, an example in which the heat-sealed portion is covered with the protective film is shown. However, the sealed bag-type test battery in which the heat-sealed plastic film according to Formulation C or Formulation D in Table 3 was sandwiched between the heat-sealed portions. Also, good sealing reliability test results were obtained.

[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 state where the heat sealing portion is covered with a protective film.

[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: Active material of positive electrode 8 ': Active material of negative electrode 9: Aluminum foil 10: Heat seal layer 11: PET layer 12: Heat seal portion 13: Protective film

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

Claims (2)

[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 a sealed bag, wherein a protective film layer is provided on a heat-sealed portion of the sealed bag. battery. 2. The non-aqueous electrolyte battery according to claim 1, wherein the plastic layer constituting the protective film has a function of preventing water permeation and / or a function of preventing acid permeation.