JP3379417B2 - Enclosure bag for non-aqueous electrolyte batteries - Google Patents

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

[0002]

2. Description of the Related Art 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, 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. To meet such requirements, for example, as shown in JP-A-61-240564, an electrode plate group is inserted into a bag made of an acid-resistant thermoplastic resin, and a large number of this electrode plate group is formed into a film or sheet. It has been proposed to wrap it in a bag-shaped exterior body made of synthetic resin having a tubular shape or a tubular shape to form a sealed lead-acid battery. In addition, JP-A-3-6
There is also an attempt to improve the hermeticity by using a structure in which a metal layer is sandwiched between plastic films on a sheet of an enclosure bag as seen in 2447 and JP-A-57-115820.

[0003]

By providing the metal layer, the sealing property is significantly improved, but it is not possible to completely prevent the intrusion of water from the sealed portion. When water enters, it reacts with the electrolytic solution to generate hydrofluoric acid, which may penetrate the plastic film layer to corrode the metal layer or cause peeling between the metal layer and the plastic layer. This peeling was also due to the use of an adhesive such as urethane as an anchor coat material for the purpose of adhering 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 to generate hydrofluoric acid. An object is to provide a sealed bag for a non-aqueous electrolyte battery.

[0004]

Means for Solving the Problems As a result of intensive investigations by the present inventors to achieve the above-mentioned object, as a plastic,
Acid-modified polyethylene or acid-modified polypropylene,
Alternatively, if an ionomer is used, a laminated sheet of metal and plastic that is directly adhered to the metal layer by thermal lamination is created, and the plastic surface is used as the electrolyte side to form an enclosing bag for the battery. I found that I could achieve it. Further, preferably, the plastic layer is provided with a water permeation preventing function and an acid permeation preventing function, whereby the water permeation preventing function can be markedly improved, and even if water permeates into the hydrofluoric acid, It was found that, even if the metal was generated, it did not corrode the metal layer and did not cause peeling between the metal layer and the plastic film layer.

The present invention will be described in detail below with reference to the drawings. In a battery of a type in which an electrode, an electrolyte, a diaphragm, etc. are inserted in a sealing bag, as shown in FIG. 3, the innermost heat seal layer 10 inside the sealing bag which is in direct contact is fused and sealed. The bag is made. The positive electrode, the negative electrode, the diaphragm, and the electrolytic solution are housed in the encapsulating bag as shown in FIG. 2, and the encapsulating bag and the lead wire are the heat-sealing layer 10 of the encapsulating bag as shown in FIG. The lead wire insulators 2 are integrated by fusing and the lead wires are taken out to the outside, and the lead wires are connected to the positive and negative electrode plates inside the enclosing bag, respectively. The lead wire and the electrode are connected in advance and sealed in a sealing bag.

The positive electrode plate and the negative electrode plate have a structure in which an active material layer is formed on a metal base material such as a metal foil or expanded metal called a current collector. The method of connecting the lead wire to the positive electrode and the negative electrode plate 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.

It is desirable that the material of the lead wire conductor is a material that does not melt at a high potential because a very high potential is applied to it for connecting the positive electrode. For that purpose,
Alternatively, titanium or an alloy of these metals can be preferably used. Lithium is deposited by overcharging for negative electrode connection, or the potential is increased by overdischarging, so the shape is unlikely to change when lithium is deposited, that is, it is difficult to form an alloy with lithium and melt at a relatively high potential. A material that is difficult to do is preferable. From the above viewpoint, nickel, copper, or an alloy of these metals can be preferably used as the material of the conductor.

Regarding the shape of the conductor, a round wire or a single wire of a rectangular conductor can be preferably used. However, in the case of the round shape, the diameter of the round shape becomes large when the battery capacity is large, so that the innermost layer of the enclosing bag is formed. Since the thickness of the lead wire sandwiched between the heat seal layers 10 becomes large, a gap is apt to be formed at the fusion-bonded portion between the outermost insulator 2 of the lead wire and the innermost heat seal layer 10 of the enclosing bag. Therefore, there is a problem that the reliability of the sealing at the fusion portion of the lead wire and the sealing bag becomes low. On the other hand, when a rectangular conductor is used, the cross-sectional area can be increased by increasing the width without increasing the conductor thickness even if the battery capacity is increased. The reliability of the sealing of the fused portion of the lead wire sandwiched between the layer 10 and the insulator 2 does not decrease. Further F
Even when connecting to an external circuit using a PC (flexible printed circuit board) or an electrode plate, the rectangular conductor has a larger contact area, and spot welding or ultrasonic welding can provide more reliable connection. It will be possible.

As the electrolyte, propylene carbonate, γ
-LiC in an organic solvent such as ptyrolactone, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1.2-dimethoxyethane or tetrahydrofuran.
A nonaqueous electrolytic solution such as 10 4, LiBF 4, LiPF 6, LiAsF 6 or a lithium ion conductive solid electrolyte can be used.

The enclosing bag is preferably made of a metal foil such as an aluminum foil or a bonding material with a plastic in which a metal vapor deposition layer is inserted in a sandwich form, and at least the plastic inside is required to be insoluble in the electrolyte. .

An important feature of the present invention lies in the material of the plastic layer constituting the enclosing bag. As an example of the structure of the enclosing bag, there may be mentioned 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 the aluminum from external damage, and the polyethylene on the inner surface is provided to perform heat sealing. When such a conventionally devised material is used, even if it is heat-sealed, moisture gradually enters during storage for a long time, and the water reacts with the electrolytic solution enclosed in the bag. To generate hydrofluoric acid. This hydrofluoric acid has a problem in that it penetrates polyethylene and the like and peels off the adhesive interface between aluminum and polyethylene, which is one of the factors that prevent such bag-type battery containers from being put to practical use. In order to solve this problem, the inventors of the present invention have used an acid-modified polyethylene or an acid-modified polypropylene or an ionomer for a plastic layer forming a sealing bag to form a thermal laminate with a metal layer without an adhesive. I came up with a direct connection. Further, it has been found that it is preferable that the plastic layer has a moisture permeation preventing function and an acid permeation preventing function.

In order to give the plastic layer a water permeation preventing function, the resin used as the plastic layer is
It is possible to use a mixture of one or several kinds of inorganic fillers selected from the group of hydrotalcites and magnesium sulfate, which are calcined to remove water of crystallization.

In order to give the plastic layer a function of preventing the permeation of acid, the resin used as the plastic layer should be carbonated.
It is possible to use a mixture of lucium or a metal oxide. As the metal oxide, magnesium oxide, hydrotalcites and the like are preferable.

It is possible to provide both the water permeation prevention function and the acid permeation prevention function by providing both functions in one plastic layer, and also to have the water permeation prevention function. It is also possible to attach a plastic layer and a plastic layer having a function of preventing acid permeation.

The resin for the plastic layer of the present application is preferably a polyethylene acid-modified product, a polypropylene acid-modified product, an ionomer, or the like which is not easily corroded by the electrolytic solution, but even if the material is corroded by the electrolytic solution, its inner surface It can be used if a resin layer that is not easily attacked by the electrolyte is provided.

[0016]

EXAMPLES Examples will be described below. First, Li
100 parts by weight of CoO2 powder (manufactured by Nippon Kagaku Kogyo Co., Ltd.) was mixed with 10 parts by weight of graphite and 10 parts by weight of polyvinylidene fluoride and dissolved in N-methyl-2-pyrrolidone.
Made into a paste. Next, this paste is 20 μm thick
The aluminum foil was coated on one side, dried, and then roller pressed. Thus, an electrode plate (5 mm is an uncoated part) having a thickness of 0.1 mm, a width of 50 mm and a length of 105 mm was prepared and used as a positive electrode.

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

Between the positive electrode and the negative electrode thus obtained, a fine polypropylene film having a thickness of 25 μm and a fused film of a porous film were sandwiched, and an aluminum foil (positive electrode) not coated with the active material layer of the electrode plate and copper Each of the foils (negative electrodes) was connected to the conductor of the lead wire by ultrasonic welding, inserted into the encapsulating bag as shown in FIG. 2, and then 8 cc of electrolyte was injected and impregnated under reduced pressure. The test piece was sandwiched between them, and the inner layer of the enclosing bag and the insulator on the outer side of the lead wire were heat-sealed (seal width: 10 mm) with a sealing machine under the conditions of 200 ° C. and 5 seconds to obtain a test battery. As the electrolytic solution, a solution prepared 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), the two pieces were faced with the PET surface facing outward, and the three sides of the rectangle were heat-sealed with a width of 3 mm to obtain a sealed bag.

Each sheet was manufactured as follows. First, 20 μm of acid-modified LDPE is extrusion-coated on the aluminum foil surface of a film obtained by bonding a PET film and an aluminum foil with a urethane adhesive,
Directly laminated by heat lamination to obtain a sheet common to all. Next, various heat seal layer films were attached 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 by a T-die extruder.

[0022]

[Table 1]

[0023]

[Table 2]

An attempt was made to fabricate a test battery using the enclosure bag shown in Table 1 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 intention of each is shown below.

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

Example 2 The acid trap agent in Example 1 was changed to calcium carbonate (10 parts).

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

(Example 4) In Example 3, the amount of the acid trap agent (magnesium oxide) was changed to 100 parts.

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

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

Example 7 Calcined hydrotalcite (30 parts) was made to function as both a water trap agent and an acid trap agent.

Example 8 A mixture of magnesium sulfate (30 parts) as a moisture trap agent and calcium carbonate (10 parts) as an acid trap agent was used for one layer.

Comparative Example 1 No trapping agent was added.

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

Comparative Example 3 The acid trap layer was not provided.

(Comparative Example 4) A moisture trap layer was not provided.

Comparative Example 5 In Example 3, the amount of acid trap agent (magnesium oxide) 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 in which the heat-sealing layers Y and Z having the above structure were laminated was prepared, 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 a sealed bag.

[0039]

[Table 3]

In Comparative Examples 2 and 5, a film having a thickness of 100 μm or less could not be formed probably because the amount of the filler was too large, and a test battery could not be prepared. Other Examples 1 to 8 and Comparative Example 1, Comparative Example 3, and Comparative Example 4 were able to produce test batteries, and the reliability test described below could be carried out.

[0041]

The effect of the present invention was confirmed by carrying out a reliability test using the test battery as described below. That is, put the test battery in a constant temperature and humidity chamber at 60 ° C. and 95% RH,
After standing for 1000 hours, the concentration of hydrofluoric acid in the internal electrolytic solution was measured to further confirm the appearance. , Hydrofluoric acid concentration was measured by titration with a 0.1 mol / liter sodium hydroxide solution. Table 4 shows the results of the reliability test.

[0042]

[Table 4]

The concentration of hydrofluoric acid in Comparative Examples 1 and 4 using the enclosing bag without the water trapping agent was drastically increased, and in Comparative Example 1 in which the acid trap layer was not provided, the aluminum of the enclosing bag was changed by hydrofluoric acid. It caused corrosion and delamination of the aluminum-heat seal layer. Further, in Comparative Example 4 as well, some delamination between the aluminum and the heat seal layer was observed, which shows that the effect of the hydrofluoric acid trapping agent has diminished. Furthermore, in Comparative Example 3 containing no hydrofluoric acid trapping agent, aluminum-
It can be seen that delamination of the heat-seal layer was observed, and it was slightly affected by hydrofluoric acid. Comparative Example 6
Since a urethane-based adhesive was used, peeling was observed although it was slight.

On the other hand, the samples using the sealed bags of Examples 1 to 8 have no influence on the appearance even after 1000 hours. However, the concentration of hydrofluoric acid was slightly increased, and it was not possible to prevent 100% moisture intrusion. However, at this time, the acid trap agent adsorbs the hydrofluoric acid formed by the reaction of the slightly invading water and the electrolytic solution, and prevents the aluminum in the enclosing bag from corroding or peeling between the aluminum and the heat seal layer. It was confirmed that the battery performance could be maintained.

[Brief description of drawings]

FIG. 1 shows a non-aqueous electrolyte battery using an enclosure bag and lead wires of the present invention.

FIG. 2 schematically shows the inside of a sealed bag.

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

FIG. 4 shows an enlarged view of the heat-sealing portion of the sealed bag.

[Explanation of symbols]

1,1 ': Lead wire conductor 2, 2 ': Lead wire insulation 3: Enclosed bag 4: Seal part of the enclosed 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 the front page (72) Inventor Takehiro Hosokawa 1-3-1, Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Electric Industries, Ltd. (56) Reference JP-A-3-34267 (JP, A) ) JP-A-62-61268 (JP, A) JP-A-11-7921 (JP, A) JP-A-10-255731 (JP, A) JP-A-10-208709 (JP, A) JP-A-9- 288998 (JP, A) JP-A-9-283101 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 2/02-2/08

Claims (2)

(57) [Claims] 1. A positive electrode, a negative electrode, electrolyte and the like is sealed encapsulating bag, a for a non-aqueous electrolyte battery is taken out of the lead of the said cathode negative respectively outside the encapsulating bag and a metal layer 1 consists of a bonded sheet layers or plastic layers made of multilayer, the metal layer of the electrolyte side of the laminated to the surface together the said plastic layer is acid-modified polyethylene or acid-modified polypropylene, or a composition mainly comprising ionomer from become those with the gold <br/> genus layer and the plastic layer which gave are bonded directly, and permeation prevention function of acid to the plastic layer, both the transmission function of preventing water by heat lamination As a means for providing the above-mentioned acid and water permeation preventive function,
Wherein the plastic layer is composed of a plurality of layers, to have an acid permeation prevention function one layer of them, a different one layer to have a water permeation prevention function, heat as a layer having a permeation prevention function of the acid Plastic resin 1
100 parts by weight or less of calcium carbonate based on 00 parts by weight
Alternatively, a resin layer containing a metal oxide is used as a layer having the above-mentioned water permeation-preventing function, and hydrotalcites or sulfuric acid obtained by removing 100% by weight or less of crystal water by baking with respect to 100 parts by weight of the thermoplastic resin. An encapsulating bag for a non-aqueous electrolyte battery, which contains a resin layer containing one kind or a mixture of several kinds selected from the group of magnesium. 2. A positive electrode, a negative electrode, electrolyte and the like is sealed encapsulating bag, a for a non-aqueous electrolyte battery is taken out of the lead of the said cathode negative respectively outside the encapsulating bag and a metal layer 1 consists of a bonded sheet layers or plastic layers made of multilayer, the metal layer of the electrolyte side of the laminated to the surface together the said plastic layer is acid-modified polyethylene or acid-modified polypropylene, or a composition mainly comprising ionomer from become those with the gold <br/> genus layer and the plastic layer which gave are bonded directly, and permeation prevention function of acid to the plastic layer, both the transmission function of preventing water by heat lamination As a means for providing the above-mentioned acid and water permeation preventive function,
One of the plastic layers is provided with both an acid permeation prevention function and a water permeation prevention function, and as a layer having both the acid permeation prevention function and the water permeation prevention function with respect to 100 parts by weight of the thermoplastic resin. 100 parts by weight or less
Of calcium carbonate or metal oxide of 100 parts by weight or less to remove water of crystallization by baking, and a resin layer containing one or several mixtures selected from the group of hydrotalcites and magnesium sulfate. An encapsulating bag for a non-aqueous electrolyte battery, which is characterized in that