JP2002198013A - Packing material of cell, and secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell with good durability of which, a cell packing body is composed of a compound material of metal and resin in order to make the cell small, light, and thin, and the metal and the resin hardly exfoliate form each other. SOLUTION: The packing material of the cell is composed of a metal layer, an olefinic resin layer containing acid accepting agent, and a denatured olefinic resin layer containing acid receiving agent laid between the metal layer and the olefinic resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a battery packaging material and a secondary battery.

[0002]

At present, mobile communication devices,
Miniaturization of electronic devices such as notebook computers, palmtop computers, integrated video cameras, portable CD players, headphone stereos, and cordless telephones.
Lighter and more portable, secondary batteries have been widely used as power supplies.

As secondary batteries, lead secondary batteries and nickel-cadmium batteries are well known.

Further, non-aqueous electrolyte secondary batteries using a material capable of doping and undoping lithium metal, a lithium alloy, or lithium ion as a negative electrode active material have been actively studied as being capable of obtaining a high energy density. Have been.

[0005] As a non-aqueous electrolyte secondary battery of this type, initially, a strip of positive and negative electrodes wound spirally through a separator was loaded in a cylindrical or prismatic metal case. It was of the type.

A secondary battery of a type in which a power generating element including a positive electrode, a negative electrode, an electrolyte, and the like is loaded in a cylindrical or prismatic metal case is limited in its size, weight, and thickness. It is said.

Therefore, recently, it has been proposed to construct a battery case (also referred to as a package, a sealed bag, or an outer package) using a composite material in which a metal foil and a resin film are laminated. I have.

For example, in Japanese Patent Application Laid-Open No. 9-288997, a positive electrode, a negative electrode, and an electrolytic solution are sealed in a sealing bag, and a lead bag for a positive electrode and a negative electrode is taken out to the outside. A laminated sheet of a metal layer and a plastic or the like, wherein an insulating layer having excellent electrolyte barrier properties is provided between the innermost heat-sealing plastic layer and the metal layer. An enclosure bag for a water electrolyte battery has been proposed. The bonding sheet of the metal layer of the nonaqueous electrolyte battery encapsulating bag and a plastic or the like is specifically made of PET (polyethylene terephthalate) having a thickness of 12 μm / acid-modified LDPE (low density polyethylene) having a thickness of 15 μm. / Aluminum foil with a thickness of 10 μm / acid-modified LDPE with a thickness of 50 μm / ethylene-vinyl alcohol copolymer with a thickness of 20 μm / acid-modified LDPE with a thickness of 50 μm or PET with a thickness of 12 μm / thickness Fifteen
μm acid-modified LDPE / aluminum foil having a thickness of 10 μm / nylon having a thickness of 25 μm / acid-modified LDPE having a thickness of 50 μm.

In Japanese Patent Application Laid-Open No. 11-67166,
A packaging material for a polymer battery, comprising aluminum / maleic anhydride-modified polypropylene or aluminum / heat lamination polypropylene / maleic anhydride-modified polypropylene, has been proposed.

In Japanese Patent Application Laid-Open No. 11-162420, (A) a polyolefin layer, (B) a metal foil layer, and (C)
Hydrotalcites compounds, aluminum oxide, magnesium oxide, calcium oxide, a laminated film consisting of at least three layers obtained by sequentially laminating a polyolefin layer containing at least one acid acceptor selected from the group consisting of lead oxide, There has been proposed an outer package for a battery in which the (C) layer is processed into a bag shape on the inside.

When a battery package is made of a multilayer laminate as described above, it is required that there be no peeling between the aluminum foil (metal layer) and the olefin-based resin film.

That is, even when a solid electrolyte such as a conductive polymer is used as an electrolyte, for example, propylene carbonate (PC), diethylene carbonate (DE
C), a solvent such as ethylene carbonate (EC) is used, and the adhesive force between the aluminum foil and the olefin-based resin film is reduced by these electrolytic solutions.

Further, for example, when LiPF ₆ is used as an electrolyte substance, hydrofluoric acid is generated by a reaction between the LiPF ₆ and water. This hydrofluoric acid passes through the olefin-based resin film, reaches the aluminum foil, and causes corrosion of the aluminum foil. For this reason, the adhesive strength between the aluminum foil and the olefin-based resin film is significantly reduced.

The above-mentioned problem cannot be solved by the above-mentioned proposed multilayer laminate.

[0015] Accordingly, the problem to be solved by the present invention is that when the battery package is made of a composite material of a metal and a resin for the purpose of miniaturization, weight reduction, and thinning, a problem arises between the metal and the resin. An object of the present invention is to provide a battery which is hardly peeled off and has high durability.

As a result of diligent research into solving the above-mentioned problems, the present inventor has found that a metal layer such as an aluminum foil and an olefin-based resin layer such as a polypropylene film can be used. In the composite material having, by interposing a modified olefin resin layer containing an acid acceptor between the metal layer and the olefin resin layer, and also an acid acceptor in the olefin resin layer PC, DEC, EC
It was found that the olefin-based resin layer was hardly peeled off even when encountering a solvent such as fluoric acid. In particular, they have found that by including an acid acceptor in both the olefin-based resin layer and the modified olefin-based resin layer, deterioration due to aging is extremely small.

The present invention has been accomplished on the basis of the knowledge obtained, and the above-mentioned problems have been solved by the present invention in that a metal layer, an olefin-based resin layer containing an acid acceptor, and an olefin-based resin layer between the metal layer and the olefin-based resin layer are provided. And a modified olefin-based resin layer containing an acid acceptor provided in the above.

Basically, the packaging material of the present invention may have the above configuration. However, when a packaging body is formed using this packaging material so that an olefin-based resin layer exists on the inner surface side, the metal layer is exposed on the outer surface side of the packaging body. For this reason, from the viewpoint of appearance and prevention of damage to the metal layer (for example, aluminum foil), it is preferable that a protective layer is provided on the metal layer on which the olefin-based resin layer is not provided. Examples of the protective layer include a resin film and a coating film. The coating film is obtained by applying and drying a predetermined paint. The resin film can be provided on the surface of the metal layer with an adhesive such as a urethane resin adhesive. Any film may be used as the resin film. However, from the viewpoint of the battery package of the present invention,
A heat-resistant biaxially stretched film having a thickness of 10 to 50 μm, particularly a biaxially stretched film of a polyester resin or a nylon resin is preferred.

The metal layer in the packaging material of the present invention is made of a metal foil such as a stainless steel foil or an aluminum foil. From the viewpoint of the battery package of the present invention (weight reduction, processability into a package), it is preferable to use aluminum foil. The aluminum foil may be soft or hard. or,
A degreasing treatment or a base treatment may be performed. The aluminum foil has a thickness of 10 to 200 μm, and more preferably 20 to 100 μm.
μm, particularly preferably 30 to 50 μm. this is,
If the thickness is too small, the mechanical strength of the battery package decreases, and if it is too large, it is difficult to achieve a reduction in weight and thickness.

The olefin resin layer in the packaging material of the present invention preferably has heat sealing properties. That is, if the package has heat sealing properties, the package can be easily formed by heat sealing. As the olefin resin, for example, polyethylene, polypropylene,
Examples include homopolymers or copolymers such as polybutene, polypentene, and polyhexene. Among them, polypropylene, particularly unstretched polypropylene, is preferred. The thickness of the olefin-based resin layer such as polypropylene is preferably 10 to 100 μm, particularly preferably 20 to 60 μm. 10 to 100 μm in thickness, especially 20 to
When the thickness is set to 60 μm, if the thickness is less than 10 μm, the solvent and the like easily pass through, and the barrier property is inferior. If the thickness is more than 100 μm, the thickness becomes too large.
This is because it is difficult to achieve a reduction in thickness.

As the modified olefin resin in the modified olefin resin layer of the packaging material of the present invention, acid-modified olefin resins, especially acid anhydride-modified olefin resins, especially maleic anhydride, phthalic anhydride, itaconic anhydride, An acid anhydride-modified olefin resin obtained by copolymerizing or graft-polymerizing an unsaturated carboxylic anhydride such as endic acid anhydride and acrylic acid anhydride, for example, a maleic acid-modified olefin resin. The degree of modification with these acids, that is, the ratio of the acid in the modified olefin resin, is about 0.001 to 10% by weight. As the olefin resin in the modified olefin resin, the same olefin resin as described above is used. Therefore, as a modified olefin resin, for example, maleic anhydride is 0.001 to
A typical example is polypropylene graft-polymerized by about 10% by weight. In the present invention, the reason for providing the modified olefin-based resin layer is to increase the adhesive strength with the olefin-based resin layer. That is, even if the solvent contained in the electrolyte permeates, the olefin-based resin layer is difficult to peel off.

The olefin resin layer and the modified olefin resin layer contain an acid acceptor. For example, it contains at least one acid acceptor selected from the group consisting of hydrotalcite compounds, aluminum oxide, magnesium oxide, calcium oxide, and lead oxide. That is, by containing an acid acceptor in both the olefin-based resin layer and the modified olefin-based resin layer, the barrier function against hydrofluoric acid is greatly enhanced. That is, even if hydrofluoric acid generated from the electrolyte contained therein passes through the olefin-based resin layer, it is hindered by the modified olefin-based resin layer, and hydrofluoric acid cannot reach the metal layer (the aluminum foil surface).
Therefore, the metal layer is hardly corroded. Therefore, the adhesiveness with the olefin resin layer is not impaired. In order to sufficiently exert the above-mentioned barrier function against hydrofluoric acid, the content of the acid acceptor is 0.0
1-30 wt%, especially 0.1-15 wt% is preferable.

The modified olefin resin layer is formed by applying a coating containing the above modified olefin resin, an acid acceptor, and a solvent by a coating means such as gravure coating or roll coating to a thickness of 1 to 20 μm, especially 2 to 20 μm. It is provided by coating so as to have a thickness of 7 μm.

[0023] A secondary battery characterized by comprising a package made of the packaging material having the above-described structure, and a positive electrode, a negative electrode, and an electrolyte provided in the case, has a high durability. In addition, a reduction in size, weight, and thickness can be achieved. Moreover, it can be obtained at low cost.

In particular, a package formed by heat-sealing the olefin-based resin layer in the packaging material having the above structure, and a positive electrode, a negative electrode provided in the case body,
And a secondary battery characterized by comprising an electrolyte,
It is highly durable, and can be reduced in size, weight, and thickness. Moreover, it can be obtained at low cost.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery packaging material according to the present invention comprises a metal layer, an olefin resin layer containing an acid acceptor, and an acid receiving layer provided between the metal layer and the olefin resin layer. And a modified olefin-based resin layer containing the agent (modified olefin-based resin adhesive layer).

Further, a protective layer is provided on the metal layer on which the olefin resin layer is not provided. The protective layer is formed by providing a resin film such as a heat-resistant biaxially stretched film (for example, a biaxially stretched film of a polyester resin or a nylon resin) having a thickness of 10 to 50 μm with an adhesive such as a urethane resin adhesive. It was done. Alternatively, it is a coating film provided by a coating means.

The metal layer in the above packaging material is made of a metal foil such as a stainless steel foil or an aluminum foil. It is made of soft or hard, especially soft aluminum foil. Aluminum foil has a thickness of 10 to 200 μm, especially 20 to 200 μm.
100 μm, and more preferably 30 to 50 μm.

The olefin resin layer in the above packaging material is
For example, it is composed of a homopolymer or copolymer film such as polyethylene, polypropylene, polybutene, polypentene, and polyhexene. It is made of a material having heat sealing properties. Above all, it is composed of a film of polypropylene, particularly unstretched polypropylene. The thickness of these films is 10 to 100 μm, and more preferably 20 to 6 μm.
0 μm, especially 30 to 50 μm.

The modified olefin resin in the modified olefin resin layer of the above-mentioned packaging material is preferably an acid-modified olefin resin, especially an acid anhydride-modified olefin resin, especially maleic anhydride, phthalic anhydride, itaconic anhydride, ene anhydride. An acid anhydride-modified olefin resin obtained by copolymerizing or graft-polymerizing an unsaturated carboxylic anhydride such as Dick acid and acrylic anhydride, for example, a maleic acid-modified olefin resin is used. The degree of modification with these acids, that is, the ratio of the acid in the modified olefin resin, is about 0.001 to 10% by weight. As the olefin resin in the modified olefin resin, the same olefin resin as described above is used. Therefore, as a modified olefin resin, for example, maleic anhydride is 0.001 to
A typical example is polypropylene polymerized by about 10% by weight.

The olefin resin layer and the modified olefin resin layer contain an acid acceptor. For example, it contains at least one acid acceptor selected from the group consisting of hydrotalcite compounds, aluminum oxide, magnesium oxide, calcium oxide, and lead oxide. The content of acid acceptor is 0.01 ~ 30wt
%, Particularly preferably 0.1 to 15 wt%.

The thickness of the modified olefin resin layer after drying is 1 to 20 μm, especially 2 to 2 μm, by applying a coating containing the above modified olefin resin, an acid acceptor and a solvent with a coating means such as gravure coat or roll coat. It is provided by coating so as to have a thickness of 7 μm.

The battery packaging material according to the present invention is made of a modified olefin resin, an acid acceptor, and a solvent by using a coating device equipped with a drying facility on an aluminum foil having the above-mentioned characteristics and having no dirt or residual oil on the surface. Is applied at a thickness of 1 to 20 μm, and dried at 150 to 300 ° C. for 5 to 30 seconds.

Then, an olefin resin film, such as a polypropylene film, which constitutes the olefin resin layer containing the acid acceptor sent out from another roll is overlaid on the above-mentioned modified olefin resin layer containing the acid acceptor. A thermocompression bonding is performed at 150 to 250 ° C. with a pressing roll to obtain a composite material including aluminum foil / acid-accepting agent-containing modified olefin resin layer / olefin resin layer.

Thereafter, for protection of the outer surface, a protective film is bonded to the surface of the aluminum foil with a urethane adhesive, and the outer protective layer / adhesive layer / aluminum foil / modified olefin resin layer containing an acid acceptor / olefin resin A composite consisting of layers is obtained. A battery (secondary battery) according to the present invention includes a package formed of the above-described packaging material, and a positive electrode, a negative electrode, and an electrolyte provided in the case.
In particular, a package configured by heat sealing the olefin-based resin layer in the packaging material having the above configuration,
A positive electrode, a negative electrode, and an electrolyte provided in the case body. The positive electrode is formed by providing a coating containing a positive electrode active material and a binder on a metal foil such as an aluminum foil. As the positive electrode active material, any material can be used as long as it can dope and dedope lithium ions, for example. For example, Li _x Co _y Mz O ₂ (M is at least one selected from Al, In, and Sn, and x, y, and z are 0 <x ≦
1.1, 0.5 <a number satisfying y ≦ 1, z ≦ 0.1), L
_{i x CoO 2 (0 <x} ≦ 1), Li x Co y Ni z O 2
(X, y, z are positive numbers satisfying 0 <x ≦ 1, y + z = 1), Li _x MnO ₂ (0 <x ≦ 1), Li _x Mn ₂ O
₄ (0 <x ≦ 1), LiCo _x Mn _2-x O ₄ (0 <x ≦ 1)
_{0.5), Lix Cr 3 O 8} (0 <x ≦ 1), LiCr
O ₂ , Li _x V ₂ O ₅ (0 <x ≦ 1), Li _x V ₆ O ₁₃
(0 <x ≦ 1), Li _{1 + x} V ₃ O ₈ (0 <x ≦ 1), L
i _x MoO ₃ (0 <x ≦ 1), Li _x MoS ₂ (0 <x
≦ 1), Li _x Ti ₂ O ₄ (0 <x ≦ 1), Li _x Ti
₂ S ₂ (0 <x ≦ 1). Examples of the binder include polysaccharides such as starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, and styrene butadiene rubber. One or a mixture of two or more selected from thermoplastic resins such as fluorine rubber and polyethylene oxide, and polymers having rubber elasticity are used. Then, a paint containing 0.1 to 20 parts by weight of a binder with respect to 100 parts by weight of the active material is coated with a paint having a thickness of 15 to 20 parts.
Apply to μm aluminum foil. The coating thickness (thickness after drying) is 30 to 300 μm per side, particularly 70 to 1 μm.
30 μm. In the coating film, if necessary, graphite such as natural graphite or synthetic graphite, carbon black, acetylene black, carbon fiber, metal powder, metal fiber, or a polyphenylene derivative, a conductive agent such as a conductive polymer, Further, it contains an olefin-based polymer such as polypropylene or polyethylene, or a filler such as glass fiber.

A negative electrode is formed in the same manner as described above or by a known method.

A separator is provided between the positive electrode and the negative electrode. As the separator, for example, a single film of a microporous film of polyolefin such as polyethylene or polypropylene, or a laminated film of two or more kinds can be used. or,
Non-woven fabrics such as polyolefin, polyester, polyamide, and cellulose can be used alone or in combination with the microporous membrane.

The negative electrode, the separator, and the positive electrode are loaded into a package made of the above-described packaging material, and one end of a negative electrode lead is attached to the negative electrode in order to collect the negative electrode. In order to collect current, one end of the positive electrode lead is attached to the positive electrode, a solid electrolyte in which a lithium salt such as LiPF ₆ is dissolved in an organic solvent (PC, DEC or EC, etc.) is put in the package, and the opening is opened. Sealing was performed by heat sealing to produce a secondary battery according to the present invention.

Hereinafter, a more specific description will be given.

[0039]

Example 1 A metal layer was formed of a soft aluminum foil having a thickness of 40 μm.

The olefin resin layer was composed of a 50 μm thick polypropylene film. In addition, this polypropylene film contains hydrotalcite as an acid acceptor in an amount of 0.1%.
25 wt% is contained.

The modified olefin resin layer was coated with maleic anhydride-modified polypropylene (MP-7, manufactured by Toyo Morton Co., Ltd.).
8HB71). The modified olefin-based resin layer contained 2.5 wt% of hydrotalcite as an acid acceptor.
contains.

The outer surface protective layer was composed of a polyester film having a thickness of 12 μm.

First, a coating containing an acid acceptor and a modified polypropylene was applied to a thickness of 5 μm on a soft aluminum foil having a thickness of 40 μm, and dried at 230 ° C. for 20 seconds.

Next, a polypropylene film having a thickness of 50 μm was overlaid on the modified polypropylene layer,
Pressure was applied by a heat roll heated to ℃, and they were bonded together.

Thereafter, a polyester film having a thickness of 12 μm was laminated on a soft aluminum foil with a urethane-based adhesive, and the polyester film / urethane-based adhesive layer / soft aluminum foil / hydrotalcite-containing modified polypropylene adhesive layer / hydro- A composite material comprising the talcite-containing polypropylene film was obtained.

Then, the composite material is formed into a bag shape so that the polypropylene film is on the inside, and the positive electrode, the negative electrode, and the electrolyte (LiPF ₆ ) are placed in the bag-shaped package, and sealed by heat sealing. A lithium secondary battery was constructed.

[0047]

Example 2 Example 1 was repeated except that calcium oxide was used instead of hydrotalcite.

[0048]

Example 3 The procedure of Example 1 was repeated, except that aluminum oxide was used instead of hydrotalcite.

[0049]

Example 4 The procedure of Example 1 was repeated except that magnesium oxide was used instead of hydrotalcite.

[0050]

Example 5 The same procedure was performed as in Example 1, except that lead oxide was used instead of hydrotalcite.

[0051]

Comparative Example 1 The same procedure was performed as in Example 1 except that hydrotalcite was not used.

[0052]

Comparative Example 2 In Example 1, the content of hydrotalcite in the olefin resin layer was set to 0.5 wt%,
The same operation was performed except that the content of hydrotalcite in the modified olefin-based resin layer was set to 0 wt%.

[0053]

Comparative Example 3 The same procedure as in Example 1 was carried out except that the content of hydrotalcite in the olefin resin layer was changed to 0 wt% and the content of hydrotalcite in the modified olefin resin layer was changed to 5 wt%.

[0054]

[Characteristics] The composite material obtained in each of the above examples was subjected to EC: PC: DEC.
= 1: 1: 1 immersed in a mixed solvent, left at 60 ° C,
The adhesion between the aluminum foil and the polypropylene film was examined, and the results are shown in Table 1.

Further, the composite material obtained in each of the above examples was heat-sealed to produce a pouch, 0.2% hydrofluoric acid was sealed therein, and the mixture was allowed to stand at 60 ° C. to form an aluminum foil and a polypropylene film. Table 2 shows the results.
Shown in

Table 1 Adhesive strength between foil and film gf / 15 mm (180 ° peel) Initial 1 day 3 days 6 days 10 days Example 1 1630 1620 1600 Example 2 1540 1520 1520 Example 3 1500 1490 1480 Example 4 1480 1450 1440 Example 5 1490 1460 1450 Comparative Example 1 1560 1240 1180 Comparative Example 2 1600 1600 1200 1190 Comparative Example 3 1630 1230 1220 1190 Table-2 Adhesive strength between foil and film gf / 15 mm (180 ° peel) Initially 1 After 3 days After 6 days After 10 days Example 1 1630 1610 1590 Example 2 1540 1520 1500 Example 3 1500 1490 1470 Example 4 1480 1450 1430 Example 5 1490 1450 1 40 Comparative Example 1 1560 1050 0 Comparative Example 2 1600 1600 1580 700 400 Comparative Example 3 1630 1300 1000 900

According to the present invention, the olefin resin layer is hardly peeled off by the solvent or by the hydrofluoric acid generated from the electrolyte substance. Therefore, when the battery case (package) is made of the packaging material of the present invention, not only miniaturization, weight reduction, and thinning are achieved, but also the durability is enhanced.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ken Narita 520 Imazato, Susono City, Shizuoka Pref. AM07 BJ04 DJ02 DJ08 EJ01 EJ05 EJ12 HJ04

Claims (10)

[Claims] A metal layer, an olefin resin layer containing an acid acceptor, and a modified olefin resin layer containing an acid acceptor provided between the metal layer and the olefin resin layer. A packaging material for a battery, comprising: 2. The battery packaging material according to claim 1, wherein a protective layer is provided on the metal layer on which the olefin-based resin layer is not provided. 3. The battery packaging material according to claim 1, wherein the metal layer is an aluminum foil. 4. The olefin-based resin layer has heat-sealing properties.
Any battery packaging material. 5. An olefin resin layer having a thickness of 10 to 10
The battery packaging material according to claim 1, wherein the battery packaging material has a thickness of 0 μm. 6. The battery packaging material according to claim 1, wherein the modified olefin resin is an acid-modified olefin resin. 7. The modified olefin resin layer has a thickness of 1-2.
The battery packaging material according to claim 1, wherein the battery packaging material has a thickness of 0 μm. 8. The method according to claim 1, wherein the acid acceptor is at least one selected from the group consisting of hydrotalcite compounds, aluminum oxide, magnesium oxide, calcium oxide, and lead oxide. Item 7. A battery packaging material according to any one of Items 7. 9. A battery comprising: a package comprising the battery packaging material according to claim 1; a positive electrode, a negative electrode, and an electrolyte provided in the package. Next battery. 10. A package formed by heat-sealing an olefin-based resin layer in a packaging material for a battery according to any one of claims 1 to 8, a positive electrode, a negative electrode, and an electrolyte provided in the package. A secondary battery comprising: