JP3141021B1 - Battery - Google Patents

Abstract

The present invention provides a battery having improved sealing properties by enhancing the adhesion between an external lead terminal extending from positive and negative electrodes of a power generating element and an exterior film. A power generating element having a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an external lead terminal electrically connected to the positive and negative electrodes, respectively, is provided. The outer periphery of the outer film is stored and sealed, and the external lead terminals and the outer film are adhered to each other and the ends of the outer lead terminals are extended out of the outer film. In the battery, among the external lead terminals, at least the entire peripheral surface of the external lead terminal on the positive electrode side sealed with the exterior film has a porous oxide film formed on the surface by a chemical treatment. Features.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery having a structure in which a power generation element is sealed with an exterior film interposed with a metal foil as a barrier material in the middle.

[0002]

2. Description of the Related Art With the progress of electronic devices such as mobile phones and personal computers, there has been a constant demand for batteries used in these devices to be smaller, lighter, larger in capacity, higher in performance and lower in cost. For this reason, batteries have been improved by changing the electrode materials such as the positive electrode active material and the negative electrode active material to those with higher energy density, making the separator thinner, and replacing the battery can with an aluminum can instead of an iron can. Has been planned.

However, these improvements have not yet reached a satisfactory level, and further miniaturization, weight reduction, large capacity, high performance, and cost reduction have been demanded.
Gel electrolyte, solid polymer electrolyte, etc. are included in the power generation element, and sealed with an exterior film consisting of a plastic laminate film sandwiched between aluminum foil as a barrier material, making it thinner, smaller, and lighter. The thin battery which aimed at is beginning to be marketed.

In the thin battery, specifically, a power generating element in which a positive electrode and a negative electrode are interposed, and an external lead terminal is connected to each of the positive and negative electrodes is housed in an exterior film.
The open peripheral portion of the exterior film is heat-sealed and sealed, and is bonded to each of the external lead terminals to extend their ends to the outside of the exterior film, and further contains an electrolytic solution in the exterior film. It has the following structure.

The exterior film is generally made of a thin aluminum foil having a small specific gravity, which can prevent the permeation of an electrolytic solution or gas, is used as a barrier material, and a thin polymer film is bonded to both sides of the aluminum foil.
On the surface side of the exterior film, a film exhibiting mechanical structural characteristics is arranged. In addition, a film (sealant film) having heat sealability is attached to the inner layer side or the back surface of the exterior film.

As the organic resin film on the outer side of the exterior film, typically, oriented polyethylene (PE) is used.
Polyolefin film such as polypropylene and polypropylene (PP), polyethylene terephthalate (PET) film,
A polyamide (PA) film is used. Aluminum foil is generally used as the barrier material. As the sealant film on the inner side of the outer film, a polyolefin-based film such as polypropylene (PP) that has not been mainly stretched is used.

[0007]

However, in the case of a thin battery using the above-mentioned outer film, the adhesive strength between the sealant film inside the outer film and the external lead terminal made of metal is low. There is a risk of seeping out through the adhesive interface between the terminal and the exterior film. For example, when a hydrofluoric acid-based electrolyte is used, when the electrolyte leaks out, the electrolyte in the electrolyte reacts with the moisture in the air to generate hydrofluoric acid, corroding the metal of the external lead terminals and disconnecting. There was a risk of developing into an accident. In particular, aluminum used for the positive electrode reacts with hydrofluoric acid to react with AlF ₃ .3H ₂ O, AlF (OH) ₂ , AlO
(OH) etc. are generated and corroded. In addition, there was a problem that the characteristics of the battery deteriorated with a decrease in the electrolytic solution.

An object of the present invention is to provide a battery having an improved sealing property by enhancing the adhesion between an external lead terminal of a power generating element (particularly, an external lead terminal on the positive electrode side made of aluminum or an aluminum alloy) and an exterior film. Things.

An object of the present invention is to provide a battery in which the adhesion between an external lead terminal extending from a positive electrode and a negative electrode of a power generation element and an exterior film is further enhanced to improve the sealing property.

[0010]

A battery according to the present invention has a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and external lead terminals respectively electrically connected to the positive and negative electrodes. A power generation element is provided, the power generation element is housed in an exterior film, and the open peripheral portion of the exterior film is sealed, and each of the external lead terminals and the exterior film are adhered to each other to form a tip of the external lead terminal. in the battery of the extending out was a structure to the outside of the casing film, the external lead terminals of the positive electrode side, aluminum also
An aluminum alloy, and at least the outer film said sealed with the positive electrode side porous formed by chemical treatment of the entire peripheral surface is the surface of the external lead terminals of Al
It has an oxide film made of mina .

In the battery according to the present invention, it is preferable that an adhesive insulating film is interposed between the external lead terminals of the positive and negative electrodes and the exterior film.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery (for example, a thin non-aqueous electrolyte secondary battery) according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a perspective view showing a thin non-aqueous electrolyte secondary battery, and FIG. 2 is a sectional view taken along the line II-II in FIG.

As shown in FIGS. 1 and 2, the power generating element 1 has a positive electrode 4 having a positive electrode active material layer 2 containing, for example, an active material and a binder carried on both surfaces of a current collector 3, a separator 5 and an active material. The negative electrode active material layer 6 containing the binder and the negative electrode 8 supported on both surfaces of the current collector 7 and the separator 5 are spirally wound, and further formed into a flat and rectangular shape. External lead terminals 9 and 10 connected to the positive and negative electrodes 4 and 8, respectively, extend outside from the same side surface of the power generating element 1. Of these external lead terminals, the external lead terminal 9 on the positive electrode side made of aluminum or an aluminum alloy has a porous oxide film formed by chemical treatment on the entire peripheral surface in contact with an exterior film described later.

As shown in FIG. 1, the power generating element 1 has a bent portion in which the external lead terminals 9 and 10 of the power generating element 1 extend into a cup 12 of a two-fold cup-shaped exterior film 11, for example. It is wrapped so that it is located on the side surface opposite to the side surface. As shown in FIG. 2, this exterior film 11 is a sealant film 1 located on the inner surface side.
3. It has a structure in which an aluminum or aluminum alloy foil 14 and a rigid organic resin film 15 are laminated in this order. Three side portions corresponding to two long side surfaces and one short side surface of the power generating element 1 excluding the bent portion in the exterior film 11 are seals extending in the horizontal direction by heat sealing the sealant films 13 to each other. Parts 16a, 16b and 16c are formed, and the power generating element 1 is sealed by these seal parts 16a, 16b and 16c. The external terminals 9 and 10 connected to the positive and negative electrodes 4 and 8 of the power generating element 1 extend to the outside through the seal portion 16b on the side opposite to the bent portion. A non-aqueous electrolyte is impregnated and contained in the power generation element 1 and the exterior film 11 sealed by the seal portions 16a, 16b, 16c.

Next, the positive electrode 4, the separator 5, the negative electrode 8, the non-aqueous electrolyte, the external lead terminals 9, 10 and the exterior film 11 will be described.

The positive electrode 4 has a structure in which, for example, a positive electrode active material layer 2 containing an active material and a binder is supported on both surfaces of a current collector 3. Note that the positive electrode may have a structure in which a positive electrode active material layer is supported on one surface of a current collector.

Examples of the current collector include an aluminum, nickel, or stainless steel plate, and an aluminum, nickel, or stainless steel mesh.

The active material is preferably a lithium composite oxide having a high energy density. Specifically, LiC
oO ₂ , LiNiO ₂ , Li _x Ni _y Co _{1 -y} O ₂ (where x and y vary depending on the state of charge of the battery, and usually 0 <x
<1, 0.7 <y <1.0. ), Li _x Co _y Sn
_z O ₂ (where x, y and z are each 0.05 ≦ x ≦ 1.1
0, 0.85 ≦ y ≦ 1.00, 0.001 ≦ z ≦ 0.1
Represents the number 0. ). Lithium composite oxide is obtained by mixing and grinding lithium carbonate, nitrate, oxide or hydroxide and carbonate, nitrate, oxide or hydroxide such as cobalt, manganese or nickel with a predetermined composition, It can be obtained by firing at a temperature of 600 to 1000 ° C. in an atmosphere. Among them, Li
_x Co _y Sn _z O ₂ (provided that, x, y, z are each 0.05 ≦
x ≦ 1.10, 0.85 ≦ y ≦ 1.00, 0.001 ≦
represents the number z ≦ 0.10. In the case of ()), the addition of a small amount of Sn makes the particle size of the lithium-containing compound small and uniform, so that a battery having excellent cycle characteristics can be obtained. 0.001
The reason why ≦ z ≦ 0.10 is that when z is less than 0.001, it is difficult to sufficiently control the particle size. On the other hand, z
Is more than 0.1, the capacity is reduced.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR). it can.

The positive electrode active material layer is allowed to contain a conductive agent such as acetylene black, carbon black, and graphite.

The separator 5 is made of, for example, a microporous membrane made of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, or a woven or non-woven fabric having fibers of these materials.

The negative electrode 8 has a structure in which a negative electrode active material layer 6 containing an active material and a binder is supported on both surfaces of a current collector 7. Note that the negative electrode may have a structure in which a negative electrode active material layer is supported on one surface of a current collector.

Examples of the current collector include a copper or nickel plate or mesh.

The active material may be any material capable of doping and dedoping lithium, such as graphites, cokes (petroleum coke, pitch coke, needle coke, etc.), pyrolytic carbons, and calcination of organic polymer compounds. (A phenol resin or the like fired at an appropriate temperature and carbonized) or lithium metal, polyacetylene, polypyrrole, or the like.

The binder preferably contains, for example, a binder such as polytetrafluoroethylene, polyvinylidene fluoride, ethylene-propylene-diene copolymer, styrene-butadiene rubber, and carboxymethyl cellulose.

The non-aqueous electrolyte has a composition in which an electrolyte is dissolved in a non-aqueous solvent.

As the electrolyte, for example, lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiB
F ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), LiN (CF
₃ SO ₂ ) ₂ , lithium bis [5-fluoro-2-orato-
1-benzene-sulfonato (2-)] borate and the like can be used.

Examples of the non-aqueous solvent include γ-butyrolactone, ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolan, Methylsulfolane, acetonitrile, propylnitrile,
Anisole, acetate, propionate and the like can be used, and two or more kinds may be used in combination.

The concentration of the electrolyte in the non-aqueous solvent is as follows:
It is preferable to set it to 0.5 mol / L or more.

In particular, the higher the viscosity of the electrolyte in the power generating element, the less likely it is for the electrolyte to ooze out. However, the higher the viscosity, the greater the drop in capacity generally at low temperatures. The electrolyte solution composed of ethylene carbonate (hereinafter referred to as EC), γ-butyrolactone (hereinafter referred to as γ-BL) and LiBF ₄ has relatively high viscosity but excellent discharge characteristics at low temperatures, so that the electrolyte solution seeps out. A battery that is difficult to perform can be obtained. EC has a higher viscosity than γ-BL, and has a smaller capacity at low temperatures. Therefore, as the amount of EC increases, the bleeding of the electrolytic solution is less likely to occur, but the low-temperature characteristics deteriorate. Conversely, the higher the γ-BL, the better the low-temperature characteristics, but the more easily the electrolyte oozes out. Further, γ-BL easily reacts with the negative electrode carbon at high temperature, and the capacity decrease at high temperature becomes large.
Therefore, the mixing ratio of EC / γ-BL is 2/1 to 1/5.
(Volume ratio) is good. Further, in order to improve the cycleability, for example, a small amount (0.2 to 10% by weight) of an additive such as vinylene carbonate or catechol carbonate may be added. By adding these additives, a stable solid electrolyte interface (SEI) is formed on the surface of the negative electrode, and cycle deterioration due to repeated charge and discharge and capacity reduction due to high-temperature discharge are less likely to occur. If the amount is less than 0.2% by weight, this effect cannot be sufficiently exerted. On the other hand, if the amount exceeds 10% by weight, the formation of a stable SEI film is hindered by an excessive additive, and the energy density per film weight may be reduced. The amount of LiBF ₄ added was 0.1% based on the total amount of the solvent.
Preferably it is 75 to 2 mol / L. If it is less than 0.75 mol / L, a desired large capacity may not be obtained. On the other hand, if it exceeds 2 mol / L, cycle deterioration is likely to occur, and the electrolyte may be expensive.

In addition to the above-mentioned electrolyte, a polymer gel electrolyte impregnated with the electrolyte or an all-solid polymer solid electrolyte containing no solvent may be used.

The polymer used as the polymer gel electrolyte is not particularly limited, but includes polyacrylonitrile resin, polyethylene oxide resin, polyether resin, polyester resin, polyacrylate resin, and fluorine resin. And the like.

Examples of the material of the external lead terminal include aluminum for the positive electrode, nickel and copper for the negative electrode. Here, since aluminum and copper are easily corroded by the electrolytic solution, and nickel is hardly corroded, nickel is suitable as the material of the external lead terminal. However, when copper or nickel is used as the material of the external lead terminal on the positive electrode side, it elutes into the electrolytic solution. Also, SUS2942 made of titanium or stainless steel
Does not elute in the electrolyte, but these metals are not suitable because they increase the impedance of the battery.

Therefore, aluminum or an aluminum alloy must be used as the external lead terminal material on the positive electrode side.

It is preferable to use nickel as the external lead terminal material on the negative electrode side for the above-mentioned reason. Since nickel is hardly corroded by the electrolytic solution, an external lead terminal on the negative electrode side not subjected to surface treatment with a chemical solution may be used. Of course, the negative electrode lead terminal may be subjected to a surface treatment with a chemical solution to make the battery more reliable.

A porous oxide film is formed by a chemical treatment on the entire peripheral surface of the external lead terminal on the positive electrode side made of aluminum or an aluminum alloy which is in contact with the exterior film. It is desirable that the thickness of this oxide film be 5 nm or more, more preferably 10 to 1000 nm.

Examples of such a chemical treatment method include (1) anodization at 10 V in a 100 g / L phosphoric acid aqueous solution, (2) anodization at 15 V in a 100 g / L sulfuric acid aqueous solution, and (3) 75 g. / L anodic oxidation at 20 V in chromic acid aqueous solution, (4) Surface treatment by immersion in 140 g / L caustic soda water, (5) Aqueous solution of sodium dichromate / sulfuric acid / water at a mass ratio of 3/30/100 Surface treatment by dipping at a temperature of 60 to 70 ° C.

By the chemical treatment using these chemicals, the surface of the positive external lead terminal made of aluminum or aluminum alloy has a contact angle with pure water of 40 ° or less.
In addition, the surface of the external lead terminal on the positive electrode side made of aluminum or aluminum alloy has a height of several nm to several thousand n.
An oxide film made of porous alumina having an opening shape and having a large number of protrusions of about m is formed.

The sealant film of the exterior film 11 seals the power generation element by thermocompression bonding between the sealant films, between the sealant film and the external lead terminals, and between the sealant film and an adhesive insulating film described later. . This sealant film is preferably a non-stretched film that does not dissolve or swell in the electrolytic solution. For example, unstretched polypropylene (P
P) and other polyolefin polymers, ethylene / vinyl acetate (EVA) copolymer, ionomer (IO), polyamide (PA), nylon (Ny), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PV
A), ethylene-vinyl alcohol (EVOH), polycarbonate (PC), polystyrene (PS), polyacrylonitrile (PAN), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (E
MMA), ethylene / methyl acrylate copolymer (E
MA), ethylene / methyl methacrylate copolymer (E
MMA), ethylene / ethyl acrylate copolymer (E
EA), a resin film made of polymethylpentene (PMP) or the like can be used. In particular, in order to increase the adhesiveness to a metal, it is preferable to use one of these resins as a base polymer and graft-polymerize an acid anhydride such as maleic anhydride.

The above-mentioned sealant film makes the battery small,
From the viewpoint of weight reduction, it is desirable to reduce the thickness as much as possible. However, it is necessary to secure a sufficient thickness so that the sealant resin can sufficiently flow around the external lead terminals of the positive and negative electrodes. For this reason, the thickness of the sealant film is
When the adhesive insulating film described below is not used, it is preferable that the thickness of the external lead terminals of the positive and negative electrodes be D / 2 to D / 2. When an adhesive insulating film described later is used, the thickness of the sealant film is preferably D / 7 to D, where D is the thickness of the external lead terminals of the positive and negative electrodes.

The aluminum or aluminum alloy foil functions as a barrier for preventing the permeation of the electrolyte or gas.

The organic resin film having the rigidity of the exterior film has a function of protecting the aluminum or aluminum alloy foil and maintaining the mechanical structural characteristics of the battery. As this organic resin film, for example, biaxially stretched polyethylene (P
E), polyolefin polymers such as polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA), and polyvinylidene chloride (PVDC) coated films thereof.

In the battery according to the present invention, as shown in FIG. 3, an adhesive insulating film 17 is allowed to be interposed between the positive and negative external lead terminals 9 and 10 and the sealant film 13 of the exterior film 11. I do.

As the adhesive insulating film, an organic polymer having a melting point of 115 to 175 ° C., having good adhesion between the metal of the external lead terminal and the sealant film of the exterior film while having the same properties and moldability as the sealant. May be used. Specifically, a resin obtained by adding a few percent of an acid anhydride to a polyolefin resin such as polyethylene or polypropylene is preferable. In particular, a film obtained by grafting a few percent of maleic anhydride to polypropylene (hereinafter referred to as a maleated PP film) Is preferred.

It is preferable that the thickness of the adhesive insulating film be at least half the thickness of the external lead terminals.

Preferably, the adhesive insulating film is interposed between the external lead terminals of the positive and negative electrodes and the exterior film so as to protrude from the end of the sealing portion of the exterior film by 0.1 to 5 mm outside. . By interposing the adhesive insulating film in such a state, the distance (insulation distance) between the aluminum or aluminum alloy foil disposed in the middle of the exterior film and the external lead terminal can be increased. Short circuit with the negative electrode can be prevented. Moreover, since the bending stress of the external lead terminal can be reduced by the adhesive insulating film, an effect of suppressing breakage due to repeated bending of the external lead terminal at the end of the exterior film can be exhibited. If the protruding length of the adhesive insulating film is less than 0.1 mm, it is difficult to sufficiently exert the effect of extending the insulation distance. On the other hand, if the protruding length of the adhesive insulating film exceeds 5 mm, it may be an obstacle to packaging the battery.

Although the adhesive insulating film and the sealant film may be different from each other, if the same type or the same material is used, the periphery of the external lead terminals of the positive and negative electrodes is uniform and highly reliable. A sealing structure can be realized.

Next, a method of manufacturing the above-mentioned thin non-aqueous electrolyte secondary battery will be described.

First, a positive electrode in which a positive electrode active material layer containing an active material and a binder is supported on, for example, both surfaces of a current collector, a negative electrode active material layer containing an active material and a binder is provided on, for example, both surfaces of the current collector. The supported negative electrode and separator are spirally wound to produce a substantially cylindrical power generating element. At the time of this winding, external lead terminals are connected to the positive and negative electrodes by, for example, welding.

Next, the obtained cylindrical power generating element is formed into a flat shape. Subsequently, a two-fold cup-shaped exterior film material having a dimension slightly longer than the long side of the power generating element and having a length, for example, twice as long as the short side thereof, is prepared.
As shown in FIG.
The flat power-generating element 1 is housed in the battery 2 such that a side surface of the power-generating element 1 opposite to the external lead terminals 9 and 10 is located at a bent portion of the material. At this time, if necessary, an adhesive insulating film may be interposed at a contact portion between the exterior film material and the external lead terminal. Subsequently, the left end of the material 18 corresponding to the long side of the power generating element 1 and the end of the material 18 corresponding to the extension side of the external lead terminals 9 and 10 are heat-sealed to form a seal portion. Thereafter, a non-aqueous electrolyte is injected through the unsealed portion of the exterior film material, the unsealed portion is heat-sealed, and the excess exterior film material is cut and removed. Manufacture secondary batteries.

The heat sealing of the exterior film material is 18
By performing at 0 ° C. to 240 ° C., the outer lead terminal and the sealant film and the sealant film can be completely adhered to each other without the outer film such as nylon of the exterior film material being welded to the press head used at the time of heat sealing. Sufficient sealing without exudation of the electrolyte can be achieved. When the heat sealing temperature is lower than 180 ° C., the sealant film and the adhesive insulating film are not sufficiently melted, and it is difficult to perform sufficient heat sealing. On the other hand, if the heat sealing temperature exceeds 240 ° C., the flow of the sealant film or the adhesive insulating film becomes too large, and the exterior film may be welded to the press head, or the resin film of the exterior film may be melted.

The thin nonaqueous electrolyte secondary battery shown in FIGS. 1 and 2 uses a power generating element obtained by winding a positive electrode, a separator, and a negative electrode and forming them into a flat shape. May be used.

The exterior film is not limited to the cup type, but may be a pouch or pillow structure.

As described above, the battery of the present invention is a power generating element having a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and external lead terminals respectively electrically connected to the positive and negative electrodes. The power generating element is housed in an exterior film, and the open peripheral portion of the exterior film is heat-sealed and sealed, and is bonded to each of the external lead terminals to extend their ends to the outside of the exterior film. In the battery having the structure as described above, of the external lead terminals, at least the entire peripheral surface of the external lead terminal on the positive electrode side that is in contact with the exterior film has a porous oxide film formed on the surface by a chemical treatment. Have.

According to such a configuration, for example, the height of the external lead terminal on the positive electrode side is at least several nm to several thousand n on at least the entire peripheral surface that comes into contact with the exterior film.
Since an open porous oxide film having a large number of protrusions of about m is formed, the adhesive strength between the external lead terminal and the sealant film of the exterior film can be improved in the sealing portion of the exterior film, The power generation element and the electrolyte inside the exterior film can be sealed well.
As a result, it is possible to prevent the electrolyte solution from seeping out from the sealing portion of the exterior film from which the external lead terminals are extended, so that corrosion of the external lead terminals can be prevented and a high-performance battery can be obtained.

Examples of the surface treatment include a chemical treatment such as etching and anodic oxidation with a chemical solution, and a physical treatment such as a blast treatment for colliding particles with an external lead terminal to roughen the surface. It is optimal to form an oxide film made of porous alumina by chemical treatment with a chemical solution. This is when the exterior film is thermocompressed,
This is because the viscosity of the melt of the sealant film or the adhesive insulating film of the exterior film is high, and it is difficult to wet the entire metal surface of the external lead terminal with a rough surface formed by physical treatment.

When a thin metal plate such as a positive or negative external lead terminal is physically subjected to a surface treatment, a wide surface can be treated, but a rectangular lead terminal has a particle cross section in the thickness direction. Is not easy, and the processing itself is difficult. On the other hand, according to the chemical treatment using a chemical solution as in the present invention, a uniform porous oxide film can be formed over the entire circumference even for a thin and small cross section such as an external lead terminal. Becomes possible. In addition, the surface irregularities are at most several hundred nm order as described above, and form an active interface, so that the wettability with the melt of the sealant film is good and strong adhesion to external lead terminals is achieved. Structure can be obtained.

Further, by interposing an adhesive insulating film between the external lead terminals of the positive and negative electrodes and the exterior film, the sealant film of the exterior film and the external lead terminals were directly adhered during thermocompression bonding. As compared with the case, the meltability of the adhesive insulating film around the external lead terminal is improved, so that it is possible to prevent a void portion from being formed around the external lead terminal. as a result,
Since the exterior film can be more firmly adhered to the external lead terminals, it is possible to prevent corrosion of the external lead terminals and deterioration of battery performance due to leakage of the electrolyte.

In particular, the melting point of the adhesive insulating film is set to 115
To 175 ° C, and by setting the temperature of the press head at the time of sealing higher than this, the melt can be easily poured into a large gap where the melt cannot flow only with the sealant film located on the inner surface of the exterior film. Since the sealing is performed more completely by flowing the electrolyte, it is possible to provide a more reliable battery in which the oozing of the electrolytic solution is prevented.

In order to fill a large void only with the sealant film, the sealant film must be thickened. As a result, the thickness of the outer film is increased, which is disadvantageous in reducing the thickness and weight of the battery. Also, in order to sufficiently seal the external lead terminals of the positive and negative electrodes, when heating and pressing with a large load, the sealant film flows too much, the sealant film becomes too thin, and the external lead terminals of the positive and negative electrodes and the aluminum Or it comes in contact with aluminum alloy foil and short circuit occurs. The disadvantage can be solved by interposing an adhesive insulating film between the external lead terminals of the positive and negative electrodes and the exterior film as in the present invention.

[0062]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below in detail with reference to the drawings.

Example 1 <Preparation of Positive Electrode> Li having an average particle size of 3 μm was used as a positive electrode active material.
89 parts by weight of CoSn _0.02 O _2, 6 parts by weight of graphite (KS6 manufactured by Lonza) as a conductive filler, and polyvinylidene fluoride (brand name; # 110 manufactured by Kureha Chemical Co., Ltd.) as a binder
0) 3 parts by weight was added to 25 parts by weight of N-methylpyrrolidone as a solvent, and after uniform shear stirring, dispersed using a bead mill to prepare a positive electrode slurry. The apparent viscosity of this slurry was 7,500 mPa · s. Subsequently, the positive electrode slurry was uniformly applied to both surfaces of a 20 μm-thick strip-shaped aluminum foil as a current collector, the solvent was dried, and the mixture was pressure-formed by a roll press. The obtained positive electrode raw material was cut into a predetermined size to produce a belt-shaped positive electrode. An aluminum external lead terminal on the positive electrode side was attached to one end of the positive electrode current collector by welding. This external lead terminal has a thickness of 0.1 mm, a width of 5 mm, and a length of 50 mm.
mm aluminum plate (1N3 of JIS H 4160)
0 material) in a 100 g / L phosphoric acid aqueous solution at 24 ° C.
It has a configuration in which a porous oxide film is formed on the surface by a chemical treatment of anodizing at 10 V for 25 minutes, washing with water and drying.

<Preparation of Negative Electrode> 50 parts by weight of flaky graphite was dispersed in 1.5 parts by weight of carboxymethylcellulose to prepare a carbon master batch paint. To this dispersion, 50 parts by weight of a fibrous carbon material was added, similarly shear-dispersed, 2.4 parts by weight of styrene-butadiene rubber latex was further added, and the mixture was uniformly mixed and stirred to prepare a negative electrode slurry. The apparent viscosity of this slurry was 4500 mPa · s. Subsequently, this negative electrode slurry was applied to a thickness of 1 as a current collector.
It was uniformly applied to both sides of a 0 μm strip-shaped copper foil, the solvent was dried, and then pressure-molded with a roll press. The obtained negative electrode raw material was cut into a predetermined size to produce a strip-shaped negative electrode 8. One end of the current collector of the negative electrode has a thickness of 0.1 m.
A nickel external lead terminal having a length of m, a width of 5 mm and a length of 50 mm was attached by welding.

Next, the strip-shaped positive electrode and the strip-shaped negative electrode were formed to have a thickness of 25 μm, a porosity of 40%, and an air permeability of 500 seconds.
/ Polymer laminated in the order of positive electrode / separator / negative electrode / separator through a separator composed of 100 cc polyethylene microporous membrane, spirally wound with a core having an elliptical cross section, and further compressed and formed by a hydraulic press. Thus, a flat power generating element was manufactured.

Next, a stretched nylon film having a thickness of 25 μm and an aluminum foil having a thickness of 40 μm (JIS H4
160 8079 material) and 70 μm thick maleated PP
A film (sealant film) was laminated and bonded in this order via a urethane-based adhesive to the exterior film material, which was heated and pressed from the maleated PP film side using a forming punch and a forming die to form a cup. The melting point of the maleated PP film is 138 ° C. Next, this is cut into strips and the maleated PP
A 180 ° bend was formed at the short-side molded end of the cup made of the exterior film material so that the film surfaces face each other on the inside. As shown in FIG. 4 described above, the cup 1 of the exterior film material 18 is used.
The flat power generating element 1 manufactured in the above-described manner in 2 and previously dried by heating at 60 ° C. under vacuum to remove water to 300 ppm or less is connected to the positive and negative external lead terminals 9 and 10 outside the external film material 18. Housed so as to stick out. Press head heated to 210 ° C in this state (not shown)
And pressurized for 4 seconds to apply positive and negative external lead terminals 9.10
And the maleated PP film, and the maleated PP film were adhered to each other to form a seal portion 16b. The long side of the exterior film material 18 where the positive and negative external lead terminals 9 and 10 are not present is also pressed for 4 seconds by a press head (not shown) heated to 210 ° C.
The seal portions 16a were formed by bonding the P films together.
These heat sealing sequences may be performed simultaneously or first.

The electrolyte was injected and impregnated under vacuum through the open long side portion of the exterior film material 18. As the electrolytic solution, EC / γ-BL = 1/3 (volume ratio)
Was used to which 1.5 mol / L of LiBF ₄ was added to the solvent, and 0.5 wt% of vinylene carbonate was further added. Thereafter, the unsealed portion was pressed for 4 seconds by a press head (not shown) in which the unsealed portion was heated to 210 ° C., and the maleated PP films were adhered to each other to form a seal portion 1.
1c is formed, and the external dimensions shown in FIGS. 1 and 2 are 3.6 mm thick, 35 mm wide, 62 mm high, and have a capacity of 530 mAh (0.2 C (Discharge) thin battery was manufactured.

(Example 2) An aluminum plate (JIS 41) similar to that of Example 1 was used as an external lead terminal on the positive electrode side.
60 1N30 material) in a 100 g / L aqueous sulfuric acid solution at 24 ° C., anodized at 15 V for 25 minutes, washed with water and dried to form a porous oxide film on the surface. A thin battery similar to that of Example 1 was manufactured except for using the same.

(Example 3) As an external lead terminal on the positive electrode side, an aluminum plate (JIS 41) similar to that of Example 1 was used.
60 1N30 material) in a 75 g / L aqueous solution of chromic acid at 24 ° C. and anodized at 20 V for 25 minutes,
A thin battery similar to that of Example 1 was manufactured except that a porous oxide film was formed on the surface by a chemical treatment of washing with water and drying.

(Example 4) An aluminum plate (JIS 41) similar to that of Example 1 was used as an external lead terminal on the positive electrode side.
60 1N30 material) was immersed in 140 g / L of caustic soda water at 30 ° C., washed with water, and dried to form a porous oxide film on the surface.
A thin battery similar to that of Example 1 was manufactured.

(Example 5) An aluminum plate (JIS 41) similar to that of Example 1 was used as an external lead terminal on the positive electrode side.
60 1N30 materials), sodium bichromate / sulfuric acid /
A mass of water is used to form a 3/30/100 aqueous solution at a temperature of 65 ° C., immersed in this aqueous solution for 20 minutes, washed with water and dried to form a porous oxide film on the surface by chemical treatment. A thin battery similar to that of Example 1 was manufactured except for using the same.

Comparative Example 1 An untreated aluminum plate (1N30 of JIS H 4160) having a thickness of 0.1 mm, a width of 5 mm and a length of 50 mm was used as an external lead terminal on the positive electrode side.
Except for the use of the same material as in Example 1, a thin battery was manufactured.

(Comparative Example 2) As an external lead terminal on the positive electrode side, alumina powder having an average particle size of 37 μm was applied to an aluminum plate (1N30 material of JIS H 4160) having a thickness of 0.1 mm, a width of 500 mm, and a length of 50 mm. After spraying using an air gun and roughening the surface, width 5 mm, length 50 mm
A thin battery was manufactured in the same manner as in Example 1 except that the cut battery was used.

The obtained Examples 1 to 5 and Comparative Examples 1 and 2
The angle of contact when pure water was dropped on the external lead terminal on the positive electrode side used for the measurement was measured with a contact angle meter (CA manufactured by Kyowa Interface Science Co., Ltd.).
-P type). The results are shown in Table 1 below.

In each of Examples 1 to 5 and Comparative Examples 1 and 2, the bonding strength between the external lead terminal on the positive electrode side and the maleated PP film was measured for the peeling adhesive strength in accordance with JIS K 6854 T peeling. Was. Table 1 shows the results.

Further, Examples 1 to 5 and Comparative Examples 1 and 2
For the thin battery of Example 1, the corrosion state and the change in capacity after being left in a 90% RH atmosphere at 65 ° C. for one week were examined. Table 1 shows the results.

[0077]

[Table 1]

As is clear from Table 1, the first embodiment in which a porous oxide film was formed on the surface by performing a chemical treatment with a chemical solution.
The external lead terminals on the positive electrode side of Nos. 5 to 5 each have a smaller contact angle of 40 ° or less than the untreated and positive external lead terminals of Comparative Examples 1 and 2 blasted with alumina particles, and an active surface is formed. It can be seen that the wettability was improved.

As is clear from the above Table 1, the peeling adhesive strength was highest for the external lead terminal on the positive electrode side blasted with the alumina particles of Comparative Example 2, and for the positive electrode chemically treated with the chemicals of Examples 1 to 5. Side external lead terminals follow this,
It can be seen that the untreated positive external lead terminal of Comparative Example 1 is the lowest.

Further, as is apparent from Table 1, the thin battery of Comparative Example 1 having an untreated positive external lead terminal and the thin battery of Comparative Example 2 having a positive external lead terminal blasted with alumina particles were used. A white precipitate was observed on the aluminum surface of the external lead terminal on the positive electrode side protruding from the exterior film, indicating that corrosion had occurred and the capacity was reduced.

On the other hand, in the thin batteries of Examples 1 to 5 having the positive electrode side external lead terminals on the surface of which a porous oxide film was formed by chemical treatment with a chemical solution, no corrosion occurred and the capacity decreased. Had hardly happened.

From the above results, the untreated positive external lead terminal used in Comparative Example 1 did not have sufficient adhesion, and the electrolyte was sewn on the interface between the sealant film of the exterior film and the aluminum of the positive external lead terminal. It seems to have oozed out. Also, the positive electrode side external lead terminal which has been subjected to surface treatment by colliding inorganic particles with the surface used in Comparative Example 2 can improve the adhesive strength, but does not have the effect of preventing seepage of the electrolytic solution. This is due to the fact that the surface treatment of the thin cross section has not been completed, the surface roughness is too large, and the melt of the sealant film that constitutes the exterior film cannot flow, resulting in the generation of minute voids. It is considered that the electrolyte solution oozes out of these portions.

(Examples 6 to 10) The constituent material of the exterior film was changed, an adhesive insulating film was used, and the sealing temperature (heat sealing) condition of the portion where the external lead terminals were interposed was set at 210 ° C. to 230 ° C. Examples 1 to 5 except that
A thin battery as shown in FIG. 4 was manufactured in the same manner as described above.

That is, the exterior film was a PET film having a thickness of 16 μm and an aluminum foil having a thickness of 40 μm (JI
SH4160 (8079 material) and a 30 μm-thick unstretched polypropylene (CPP) [sealant film] film in this order via a urethane-based adhesive.
What was adhered was used. The melting point of CPP is 168 ° C.
It is.

Further, a maleated PP film (adhesive insulating film) having a thickness of 70 μm and a melting point of 168 ° C. is protruded 2 mm outside the end of the exterior film between the exterior film and the external lead terminals of the positive and negative electrodes. Inserted.

Comparative Example 3 A thin battery was manufactured in the same manner as in Examples 6 to 10 except that the same external lead terminals as in Comparative Example 1 were used.

Comparative Example 4 A thin battery was manufactured in the same manner as in Examples 6 to 10, except that the same external lead terminal as in Comparative Example 2 was used.

The obtained Examples 6 to 10 and Comparative Examples 3,
4 for 1 h at -25 ° C and 1 h at + 60 ° C
After repeating the holding heat cycle 100 times, 65
The corrosion state and the change in capacity after one week at 90 ° C. in a 90% RH atmosphere were examined. Table 2 shows the results.

[0089]

[Table 2]

As is clear from Table 2, the thin battery of Comparative Example 3 having an untreated positive external lead terminal and the thin battery of Comparative Example 4 having a positive external lead terminal blasted with alumina particles had an outer package. A white precipitate was observed on the aluminum surface of the positive electrode side external lead terminal protruding from the film, indicating that corrosion had occurred and the capacity had decreased.

On the other hand, a positive electrode-side external lead terminal having a porous oxide film formed on the surface by chemical treatment with a chemical solution is provided, and an adhesive insulating film is provided between the external film and the external lead terminal. In the thin batteries of Examples 6 to 10 interposed, no corrosion occurred and no capacity reduction occurred even after the heat cycle test and the moisture absorption test were performed under the severe conditions described above. This is because, by inserting the adhesive insulating film into the external lead terminal, at the time of heat sealing, the melt of the adhesive insulating film flows and fills in a large gap formed between the external lead terminal and the sealant film of the exterior film, This is because sufficient sealing without oozing out of the electrolytic solution can be performed. The reason why the capacity retention rate after the test was high was that sealing was sufficient and that deterioration by the test was small by using appropriate positive electrodes, negative electrodes, electrolytes, and separators.

(Examples 11 to 15) A maleated PP film having a thickness of 30 μm and 70 μm and a melting point of 168 ° C. was used as a sealant film and an adhesive insulating film of an exterior film, and an external lead terminal was interposed. The sealing temperature (heat sealing) condition of the place is changed from 210 ° C. to 2
A thin battery shown in FIG. 4 was manufactured in the same manner as in Examples 1 to 5, except that the temperature was changed to 30 ° C. The adhesive insulating film was inserted between the exterior film and the external lead terminals of the positive and negative electrodes so as to protrude 2 mm outside the edge of the exterior film.

Comparative Example 5 A thin battery was manufactured in the same manner as in Examples 11 to 15, except that the same external lead terminals as in Comparative Example 1 were used.

Comparative Example 6 A thin battery was manufactured in the same manner as in Examples 11 to 15, except that the same external lead terminals as in Comparative Example 2 were used.

The heat cycle of holding the obtained thin batteries of Examples 11 to 15 and Comparative Examples 5 and 6 at −25 ° C. for 1 hour and at + 60 ° C. for 1 hour was repeated 100 times.
The corrosion state and the change in the capacity after being left in a 90% RH atmosphere at 65 ° C. for one week were examined. Table 3 shows the results.

[0096]

[Table 3]

As is evident from Table 3, the positive electrode-side external lead terminal having a porous oxide film formed on the surface by chemical treatment with a chemical solution is provided, and the external lead terminal is bonded between the outer film and the external lead terminal. Example 1 with a conductive insulating film interposed
In the thin batteries of Nos. 1 to 15, no corrosion occurred even after the heat cycle test and the moisture absorption test were performed under the severe conditions, and the capacity retention rate was improved as compared with the thin batteries of Examples 6 to 10. You can see that. This is probably because the adhesive insulating film and the sealant film were made of the same material, so that a stronger sealing could be performed.

[0098]

As described above, according to the present invention, the external lead terminal on the positive electrode side is chemically treated with a chemical solution to form a porous oxide film on the surface, so that the external lead terminal can be bonded to the exterior film. The battery can be improved and the electrolyte solution in the exterior film can be prevented from seeping out, so that a battery having excellent performance with a high capacity retention rate can be provided without causing corrosion of the external lead terminal on the positive electrode side, and furthermore, no disconnection accident.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a thin battery of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view of a main part showing another thin battery of the present invention.

FIG. 4 is a perspective view showing a manufacturing process of the thin battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power generation element, 4 ... Positive electrode, 8 ... Negative electrode, 9 ... Positive side external lead terminal, 10 ... Negative side external lead terminal, 11 ... Outer film, 12 ... Cup, 13 ... Sealant film, 16a, 16b, 16c ... Seal Part, 17 ... adhesive insulating film.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-10-312788 (JP, A) JP-A-3-179662 (JP, A) JP-A-11-86842 (JP, A) JP-A-10-108 302756 (JP, A) JP-A-61-161652 (JP, A) JP-A-60-257069 (JP, A) Japanese Utility Model Application Sho-61-99965 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) H01M 2/20-2/34 H01M 2/02-2/08 H01M 4/58 H01M 10/40

Claims (17)

(57) [Claims] 1. A power generating element having a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an external lead terminal electrically connected to the positive and negative electrodes, respectively. And sealing the open peripheral portion of the exterior film, bonding each of the external lead terminals and the exterior film, and extending the tips of the external lead terminals to the outside of the exterior film. In the battery, the external lead terminal on the positive electrode side is made of aluminum or an aluminum alloy, and at least the entire peripheral surface of the external lead terminal on the positive electrode side sealed with the exterior film is formed by a surface chemical treatment. A battery comprising an oxide film made of porous alumina. 2. An oxide film comprising the porous alumina.
Is an open porous oxide film with many protrusions.
The battery according to claim 1, wherein: 3. The projection has a height of several nm to several thousand nm.
The battery according to claim 2, comprising: 4. The battery according to claim 1, wherein the external lead terminal on the positive electrode side is surface-treated by immersion in an aqueous solution comprising sodium dichromate and sulfuric acid. 5. The external lead terminal on the positive electrode side is made of aluminum or an aluminum alloy, and is subjected to a surface treatment so that a contact angle with pure water is 40 ° or less. Batteries. 6. The exterior film is a polyethylene terephthalate film or a nylon film /
The battery according to claim 1, wherein the battery has a three-layer structure of an aluminum foil or an aluminum alloy foil / a resin film obtained by adding an acid anhydride to a polyolefin resin. 7. The exterior film is a polyethylene terephthalate film or a nylon film /
The battery according to claim 1, wherein the battery has a three-layer structure of aluminum foil or aluminum alloy foil / unstretched polyethylene film or polypropylene film. 8. The battery according to claim 1, wherein an adhesive insulating film is interposed between the external lead terminals of the positive and negative electrodes and the exterior film. 9. The melting point of the adhesive insulating film is 11
9. The battery according to claim 8, wherein the temperature is 5C to 175C. 10. The battery according to claim 8, wherein the adhesive insulating film is made of a resin obtained by adding an acid anhydride to a polyolefin resin. 11. The battery according to claim 8, wherein the material of the innermost layer film of the exterior film and the material of the adhesive insulating film are the same. 12. The adhesive insulating film is attached to the external lead terminal by 0.1 to 5 mm from an end of the exterior film.
The battery according to claim 8, wherein the battery is formed so as to protrude outside. 13. An electrolytic solution having a composition in which an electrolyte of lithium tetrafluoroborate is dissolved in a non-aqueous solvent of ethylene carbonate and γ-butyrolactone is contained in the exterior film. The battery according to 1. 14. The battery according to claim 13, wherein the electrolyte further contains vinylene carbonate or catechol carbonate in an amount of 0.2 to 10% by weight based on the total amount of the non-aqueous solvent. 15. The battery according to claim 1, wherein the positive electrode contains a lithium-containing compound as an active material, and the negative electrode contains a lithium-doped carbonaceous material as an active material. 16. The lithium-containing compound is LixC
oySnzO2 (where x, y, and z are each 0.05 ≦
x ≦ 1.10, 0.85 ≦ y ≦ 1.00, 0.001 ≦
The battery according to claim 15, wherein z ≤ 0.10. 17. The battery according to claim 1, wherein the power generation element sealed in the exterior film has a water content of 300 ppm or less.