JP2015156403A - Exterior material for lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exterior material for a lithium ion battery having excellent moldability.

SOLUTION: In an exterior material 1 for a lithium ion battery, a base material layer 11, an adhesive layer 12, a metal foil layer 13, a corrosion protection processing layer 14, an adhesive resin layer 15, and a sealant layer 16 are laminated sequentially, and the stress at 20% elongation (the amount of displacement of 7 mm) are 61.5-71.5 MPa in both the MD direction and the TD direction in the tensile test (specimen width of 6 mm, gauge length of 35 mm, and tensile rate of 300 mm/min).

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a packaging material for a lithium ion battery.

  Nickel-metal hydride and lead-acid batteries are known as secondary batteries, but lithium ion with high energy density is indispensable due to downsizing of secondary batteries due to downsizing of portable devices and installation space restrictions. Batteries are attracting attention. Conventionally, metal cans have been used as exterior materials used in lithium ion batteries, but multilayer films that are lightweight, have high heat dissipation properties, and can be handled at low cost are being used.

The electrolyte of the lithium ion battery is composed of an aprotic solvent such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and an electrolyte. Further, lithium salts such as LiPF _6, LiBF ₄ is used as a lithium salt as the electrolyte. However, these lithium salts generate hydrofluoric acid by a hydrolysis reaction with moisture, which may cause corrosion of the metal surface of the battery member and decrease of the laminate strength between the respective layers of the exterior material made of the multilayer film. Therefore, an exterior material made of a multilayer film is generally provided with an aluminum foil layer inside to suppress moisture from entering from the surface of the multilayer film. For example, a packaging material for a lithium ion battery in which a heat-resistant base material layer / adhesive layer / aluminum foil layer / corrosion prevention treatment layer / adhesive resin layer / sealant layer for preventing corrosion due to hydrofluoric acid is sequentially laminated is known. ing. A lithium ion battery using such a packaging material for a lithium ion battery is called an aluminum laminate type lithium ion battery.

  Lithium-ion battery exterior materials made of laminated films are roughly classified into two types depending on the type of the adhesive resin layer. That is, it can be roughly divided into a dry laminate configuration using an adhesive for dry lamination for the adhesive resin layer and a thermal laminate configuration using a thermoplastic material such as acid-modified polyolefin resin for the adhesive resin layer. Since the adhesive used in the dry laminate configuration has a highly hydrolyzable bond such as an ester group or a urethane group, hydrolysis reaction with hydrofluoric acid is likely to occur. Therefore, the exterior material for lithium ion batteries having a heat laminate configuration is used for applications that require higher reliability.

  An aluminum laminate type lithium ion battery is formed, for example, by forming a recess in a part of the outer packaging material for a lithium ion battery of a multilayer film by cold molding, and placing a positive electrode, a separator, a negative electrode, an electrolyte, etc. in the recess, and the rest It is formed by folding back the part and heat-sealing the edge part. In recent years, in order to efficiently store more contents and increase the energy density, a lithium ion battery in which concave portions are formed on both sides of a bonding material for a lithium ion battery to be bonded is also manufactured.

As a method of further increasing the energy density of the lithium ion battery, there is a method of deepening the recess formed by cold forming and increasing the amount of contents accommodated in the recess. However, the deeper the recess, the more likely the pinholes and breaks occur at the sides and corners of the recess, which is a portion with a high stretch rate, during molding with a mold. The following are known as exterior materials for lithium ion batteries that can increase the molding depth of the recesses.
(1) As a base material layer, a polyamide film or a polyester film having a tensile strength of 150 N / mm ² or more in all four directions of 0 °, 45 °, 90 °, and 135 ° with respect to the stretching direction and an elongation of 80% or more. The exterior material used.
However, since it is required to further improve the energy density of the lithium ion battery, further improvement of the moldability of the exterior material for the lithium ion battery is desired.

Japanese Patent No. 3567230

  An object of this invention is to provide the exterior material for lithium ion batteries which has the outstanding moldability.

The present invention employs the following configuration in order to solve the above problems.
[1] A lithium ion battery exterior material in which an adhesive layer, a metal foil layer, a corrosion prevention treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of a base material layer, A monolayer film made of a biaxially stretched polyamide film, or a layer formed of a laminated film in which a biaxially stretched polyamide film and a biaxially stretched polyethylene terephthalate film are laminated from the metal foil layer side, and the adhesive layer is A layer formed of polyurethane adhesive, the metal foil layer is a layer formed of aluminum foil, the adhesive resin layer is a layer formed of acid-modified polyolefin resin, and the sealant layer Is a layer formed of a film made of polyolefin resin, and M in a tensile test (sample width 6 mm, distance between gauge points 35 mm, tensile speed 300 mm / min). Lithium ion battery exterior material, characterized in that at 20% stretch in the direction and the TD direction stress values (displacement amount 7 mm) is both 61.5MPa than 71.5MPa or less.
[2] A lithium ion battery exterior material in which a molding improving layer, a metal foil layer, a corrosion prevention treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of the base material layer, Is a layer formed of a monolayer film made of a biaxially stretched polyamide film or a laminated film in which a biaxially stretched polyamide film and a biaxially stretched polyethylene terephthalate film are laminated from the metal foil layer side, and the molding improving layer Is a layer formed of a mixture in which a coupling agent is mixed with an adhesive, the metal foil layer is a layer formed of an aluminum foil, and the adhesive resin layer is formed of an acid-modified polyolefin resin. The sealant layer is a layer formed of a film made of polyolefin resin, and is subjected to a tensile test (sample width 6 mm, distance between gauge points 35 mm, tensile speed). 300 mm / min) Exterior material for lithium ion batteries, characterized in that the stress value at 20% stretch in the MD direction and the TD direction (amount of displacement 7 mm) is both 61.5MPa than 71.5MPa or less in.
[3] The base material layer is a layer formed of the laminated film, and the laminated film is obtained by laminating the biaxially stretched polyamide film and the biaxially stretched polyethylene terephthalate film via a polyurethane adhesive. The exterior material for a lithium ion battery according to [1] or [2], which is a laminated film.
[4] The base material layer is a layer formed of the laminated film, and the laminated film is a laminated film in which a polyamide film and a polyethylene terephthalate film are laminated by a coextrusion method and biaxially stretched. [1] or [2], a packaging material for a lithium ion battery.
[5] The exterior packaging material for a lithium ion battery according to any one of [1] to [4], wherein the sealant layer is laminated by sandwich lamination on the corrosion prevention treatment layer side of the metal foil layer.

  The exterior material for a lithium ion battery of the present invention has excellent moldability.

It is sectional drawing which showed an example of the exterior material for lithium ion batteries of this invention. It is sectional drawing which showed the other example of the exterior material for lithium ion batteries of this invention.

Hereinafter, an example of an embodiment of the outer packaging material for a lithium ion battery of the present invention will be shown and described in detail.
[First Embodiment]
As shown in FIG. 1, an exterior material 1 for a lithium ion battery according to the present embodiment (hereinafter referred to as “exterior material 1”) has an adhesive layer 12, a metal foil layer 13, This is a laminate in which the corrosion prevention treatment layer 14, the adhesive resin layer 15, and the sealant layer 16 are sequentially laminated.

(Base material layer 11)
The base material layer 11 provides heat resistance in a sealing process when manufacturing a lithium ion battery, and plays a role of suppressing generation of pinholes that may occur during processing and distribution.
The base material layer 11 is preferably a resin layer that improves the moldability when producing a lithium ion battery. Examples of the resin layer include stretched or unstretched films such as polyamide film, polyester film, and polypropylene film. Of these, a biaxially stretched polyamide film and a biaxially stretched polyester film are preferable from the viewpoint of improving moldability and heat resistance.

The base material layer 11 may be a single layer film or a laminated film in which two or more layers are laminated. The laminated film may be a laminate of two films via an adhesive for dry lamination, or may be a laminate of two films by a coextrusion method. As the adhesive for dry lamination, the same adhesive as that used in the adhesive layer 12 described later can be used.
When the laminated film is formed by a coextrusion method, an adhesive resin which is a thermoplastic material mentioned in the adhesive resin layer 15 described later can be used, and an acid-modified polyolefin resin added with an acid-modified styrene elastomer resin can be used. . In the present specification, the acid-modified polyolefin resin means a polyolefin resin modified by graft copolymerization of an acid. The acid-modified styrene elastomer resin means a styrene elastomer resin modified by graft copolymerization of an acid. The adhesive resin is preferably a maleic anhydride-modified polyolefin resin graft-modified with maleic anhydride to which a maleic anhydride-modified styrene elastomer resin graft-modified with maleic anhydride is added.

  As the laminated film, a laminated film in which a biaxially stretched polyamide film and a biaxially stretched polyester film are laminated in order from the metal foil layer 13 side is preferable because the moldability is improved. The laminated film may be a biaxially stretched film after laminating a polyamide film and a polyester film by a co-extrusion method.

  As the base material layer 11, a single layer film made of a biaxially stretched polyamide film or a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyamide film, and a biaxially stretched polyethylene terephthalate film are dry because the puncture strength and impact strength are improved. It is preferable that the laminated film, the biaxially stretched polyamide film and the biaxially stretched polyethylene terephthalate film laminated via an adhesive for laminating are any of laminated films laminated by a coextrusion method.

  6-40 micrometers is preferable and, as for the thickness of the base material layer 11, 10-25 micrometers is more preferable. When the thickness of the base material layer 11 is 6 μm or more, the pinhole resistance and the insulation are improved. If the thickness of the base material layer 11 is 40 μm or less, the moldability is improved. The said thickness is the whole thickness, when the base material layer 11 is a multilayer film.

(Adhesive layer 12)
The adhesive layer 12 is a layer that bonds the base material layer 11 and the metal foil layer 13 together.
As an adhesive constituting the adhesive layer 12, a two-component curable polyurethane system in which a bifunctional or higher functional aromatic or aliphatic isocyanate is allowed to act as a curing agent on a main component such as polyester polyol, polyether polyol, and acrylic polyol. An adhesive is preferred.
The polyurethane adhesive is subjected to aging for 4 days or more after application, for example, at 40 ° C., whereby the reaction between the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds to enable strong adhesion. 1-10 are preferable and, as for the molar ratio (NCO / OH) of the isocyanate group which the hardening | curing agent has with respect to the hydroxyl group which a main ingredient has, 2-5 are more preferable.

  The thickness of the adhesive layer 12 made of the polyurethane adhesive is preferably 1 to 10 μm, and more preferably 3 to 7 μm, from the viewpoints of adhesive strength, followability, workability, and the like.

(Metal foil layer 13)
As the metal foil layer 13, various metal foils such as aluminum and stainless steel can be used, and aluminum foil is preferable from the viewpoint of workability such as moisture resistance and spreadability and cost. A general soft aluminum foil can be used as the aluminum foil. Especially, the layer using the aluminum foil containing iron is preferable from the point which can provide pinhole resistance and the extensibility at the time of shaping | molding.
In this case, the content of iron in the aluminum foil (100% by mass) is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass. When the iron content is 0.1% by mass or more, pinhole resistance and spreadability are improved. If the iron content is 9.0% by mass or less, flexibility is improved.

  The thickness of the metal foil layer 13 is preferably 9 to 200 μm, more preferably 15 to 100 μm, from the viewpoint of barrier properties, pinhole resistance, and workability.

(Corrosion prevention treatment layer 14)
The corrosion prevention treatment layer 14 improves the role of suppressing the corrosion of the metal foil layer 13 due to the hydrofluoric acid generated by the reaction between the electrolytic solution and moisture and the interaction with the metal foil layer 13 to improve the interaction with the adhesive resin layer 15. Plays a role in improving the adhesion of the.
The corrosion prevention treatment layer 14 is preferably a coating film formed by a coating type or immersion type acid resistant corrosion prevention treatment agent. If the corrosion prevention treatment layer 14 is the coating film, the effect of preventing corrosion of the metal foil layer 13 with respect to acid is improved. Furthermore, by forming an anchor on the metal foil layer 13, the adhesion between the metal foil layer 13 and the adhesive resin layer 15 becomes stronger, and resistance to contents such as an electrolytic solution is improved.

The coating film is, for example, chromate treatment with a corrosion prevention treatment agent composed of chromate, phosphate, fluoride and various thermosetting resins, and oxides that are rare earth elements (for example, cerium oxide, zircon oxide, etc.). It can be formed by ceriazol treatment with a corrosion prevention treatment agent comprising phosphate, phosphate and various thermosetting resins.
The corrosion prevention treatment layer 14 is not limited to the coating film formed by the above treatment as long as the corrosion resistance of the metal foil layer 13 is sufficiently obtained. For example, you may form by a phosphate process, a boehmite process, etc.

The corrosion prevention treatment layer 14 may be a single layer or a plurality of layers. In addition, an additive such as a silane coupling agent may be added to the corrosion prevention treatment layer 14.
The thickness of the corrosion prevention treatment layer 14 is preferably 10 nm to 5 μm, more preferably 20 nm to 500 nm, from the viewpoint of the corrosion prevention function and the function as an anchor.

(Adhesive resin layer 15)
Examples of the component constituting the adhesive resin layer 15 include an acid-modified polyolefin resin.
Examples of the acid-modified polyolefin resin include a polyolefin resin graft-modified with a carboxylic acid, an epoxy compound, or the like.
Examples of polyolefin resins include low density, medium density, and high density polyethylene; ethylene-α olefin copolymer, homo, block or random polypropylene, propylene-α olefin copolymer; acrylic acid, methacrylic acid, etc. And a polymer such as a cross-linked polyolefin. These polyolefin resin may be used individually by 1 type, and may use 2 or more types together.
The component constituting the adhesive resin layer 15 is preferably a maleic anhydride-modified polyolefin resin graft-modified with maleic anhydride.

In addition, an acid-modified styrene-based elastomer resin may be dispersed in the acid-modified polyolefin-based resin according to desired characteristics. As the acid-modified styrene elastomer resin, a maleic anhydride-modified styrene elastomer resin graft-modified with maleic anhydride is preferable.
The adhesive resin layer 15 can be formed, for example, by extruding these adhesive resins with an extrusion device.

(Sealant layer 16)
The sealant layer 16 is a layer that imparts sealing properties by heat sealing in the exterior material 1.
Examples of the sealant layer 16 include a polyolefin resin or a film made of an acid-modified polyolefin resin obtained by graft-modifying an acid such as maleic anhydride to a polyolefin resin.
Examples of the polyolefin resin include low density, medium density, and high density polyethylene; ethylene-α olefin copolymer; homo, block, or random polypropylene; propylene-α olefin copolymer. These polyolefin resin may be used individually by 1 type, and may use 2 or more types together.

The sealant layer 16 may be a single layer film or a multilayer film, and may be selected according to a required function. For example, in terms of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cycloolefin copolymer or polymethylpentene is interposed may be used.
Further, the sealant layer 16 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.
10-100 micrometers is preferable and, as for the thickness of the sealant layer 16, 20-60 micrometers is more preferable.

  The exterior material 1 is preferably one in which the adhesive resin layer 15 is made of an acid-modified polyolefin resin and the sealant layer 16 is laminated by sandwich lamination from the viewpoint of improving adhesiveness.

The exterior material 1 is a stress at the time of 20% stretching (displacement amount 7 mm) in the MD (Machine Direction) direction and the TD (Transverse Direction) direction in a tensile test (sample width 6 mm, distance between gauge points 35 mm, tensile speed 300 mm / min). Both values are 61.5 MPa or more and 71.5 MPa or less. If the stress value in the tensile test in the MD direction and the TD direction of the exterior material 1 is within the above range, excellent moldability can be obtained, and cold at a deeper molding depth without causing pinholes or breakage. Can be molded. 62.5 MPa or more and 71.0 MPa or less are preferable and, as for the stress value at the time of the said 20% extending | stretching of the exterior material 1, 63.0 MPa or more and 68.0 MPa or less are more preferable.
The stress value at the time of 20% stretching can be adjusted by stretching conditions at the time of film formation of the film used for the base material layer 11.

(Production method)
Hereinafter, the manufacturing method of the exterior material 1 is demonstrated. However, the manufacturing method of the exterior material 1 is not limited to the following method.
As a manufacturing method of the exterior material 1, the method which has the following process (I-1)-(III-1) is mentioned, for example.
(I-1) A step of forming a corrosion prevention treatment layer 14 on the metal foil layer 13.
(II-1) The process of bonding the base material layer 11 through the contact bonding layer 12 to the opposite side to the side in which the corrosion prevention process layer 14 in the metal foil layer 13 was formed.
(III-1) A step of bonding the sealant layer 16 to the corrosion prevention treatment layer 14 side of the metal foil layer 13 via the adhesive resin layer 15.

Step (I-1):
A corrosion prevention treatment agent is applied to one surface of the metal foil layer 13 and dried to form a corrosion prevention treatment layer 14. Examples of the corrosion prevention treatment agent include the above-described corrosion prevention treatment agent for chromate treatment, and a corrosion prevention treatment agent for ceriazole treatment.
The coating method of the corrosion inhibitor is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating, and bar coating can be employed.

Step (II-1):
The base material layer 11 is bonded to the side of the metal foil layer 13 opposite to the side on which the anticorrosion treatment layer 14 is formed using an adhesive that forms the adhesive layer 12 by a technique such as dry lamination. When the base material layer 11 is a laminated film, the lamination of the film forming the laminated film and the lamination of the metal foil layer 13 and the base material layer 11 are performed using the same dry laminating adhesive. Also good.
In step (II-1), an aging treatment may be performed in the range of room temperature to 100 ° C. in order to promote adhesion.

Step (III-1):
Adhesive resin for forming an adhesive resin layer 15 by extrusion lamination on the corrosion prevention treatment layer 14 side of the laminate in which the base material layer 11, the adhesive layer 12, the metal foil layer 13, and the corrosion prevention treatment layer 14 are laminated in this order. The sealant layer 16 is pasted through. The lamination of the sealant layer 16 is preferably performed by sandwich lamination.

The packaging material 1 is obtained by the steps (I-1) to (III-1) described above.
In addition, the manufacturing method of the exterior material 1 is not limited to the method of implementing the said process (I-1)-(III-1) sequentially. For example, step (I-1) may be performed after performing step (II-1). Moreover, you may provide a corrosion prevention process layer on both surfaces of a metal foil layer. Moreover, you may perform a process (II-1) after performing a process (III-1).

[Second Embodiment]
Next, a lithium ion battery exterior material 2 (hereinafter referred to as “exterior material 2”), which is another example of the lithium ion battery exterior material of the present invention, will be described. In the exterior material 2, the same parts as those of the exterior material 1 are denoted by the same reference numerals and description thereof is omitted.
As shown in FIG. 2, the exterior material 2 of the present embodiment has a molding improving layer 17, a metal foil layer 13, a corrosion prevention treatment layer 14, an adhesive resin layer 15, and a sealant layer 16 on one surface of the base material layer 11. Is a laminated body sequentially laminated.

(Molding improvement layer)
The molding improvement layer 17 is a layer that plays a role of improving the moldability of the exterior material 2.
The components constituting the molding improvement layer 17 include polyolefin resin, polyether resin, polyester resin, polyurethane resin, polyvinyl resin, polystyrene resin, polyacrylic resin, phenolic resin, polyamide resin, melamine One or more selected from the group consisting of epoxy resins, epoxy resins, unsaturated polyester resins, silicone resins, polysulfone resins, polycarbonate resins, polyallyl resins and ionomer resins, or silane coupling agents, One or more selected from the group consisting of titanate coupling agents, aluminate coupling agents and zirconate coupling agents can be mentioned. The above-mentioned resin may use a modified product thereof. In addition, any of the above-described resins and coupling agents may be used alone or in combination.

Examples of the polyolefin resin used for the molding improvement layer 17 include polyethylene, polypropylene, polybutene, α-polyolefin, and polymethylpentene.
Examples of polyether resins include polyether ketone and polyether ether ketone.
Examples of the polyester resin include polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polybutylene naphthalate.
Examples of the polyurethane resin include poly-n-butyl isocyanate, poly-n-hexyl isocyanate, and 2-6-polyurethane.
Examples of the polyvinyl resin include ethylene / vinyl acetate copolymer, polyvinyl chloride, styrene vinyl, and vinyl acetate.
Examples of polystyrene resins include styrene / acrylonitrile copolymers, acrylonitrile / butadiene / styrene resins, and impact-resistant polystyrene.
Examples of the polyacrylic resin include polymethyl methacrylate, ethylene / methyl methacrylate copolymer, and polycarboxylic acid.
Examples of the phenolic resin include random novolak type, high ortho novolak type, alkali resol type, ammonia resol type, benzyl ether resol type resin and the like.
Examples of the polyamide resin include nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, and the like.
Examples of melamine resins include guanamine and aniline.
Examples of the epoxy resin include resins of glycidyl ester type, glycidyl amine type, and cycloaliphatic type.
Examples of the unsaturated polyester resin include orthophthalic acid, isophthalic acid, terephthalic acid, dicyclo, fatty saturated acid, and bisphenol resins.
Examples of the silicone resin include polydimethylsiloxane, polydiethylsiloxane, and polymethylphenylsiloxane.
Examples of the polysulfone-based resin include polyether sulfone, polysulfone, polyallyl sulfone, and allyl polyphenyl sulfone.
Polycarbonate resins include polytetramethylene carbonate, polypentamethylene carbonate, polyhexamethylene carbonate, and the like.
Examples of polyallyl resins include polyallylamine, polyallylamide, polyallyl ether, polyallyl ether ketone, and the like.
Examples of the ionomer resin include those obtained by polymerizing an ethylene-based, styrene-based or elastomer-based resin or an ethylene carboxylic acid copolymer with an ion source such as Na, K, Li, or Zn.

Examples of the silane coupling agent used for the molding improvement layer 17 include trimethoxysilane, tetramethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane.
Examples of titanate coupling agents include trimethoxy titanate, tetramethoxy titanate, tetrapropoxy titanate, chlorotrimethoxy titanate, methyl triethoxy titanate, diethyl diethoxy titanate, and phenyl trimethoxy titanate.
Examples of the aluminate coupling agent include trimethoxy aluminate, triethoxy aluminate, tripropoxy aluminate, and tetraethoxy aluminate.
Examples of the zirconate coupling agent include trimethoxy zirconate, tetramethoxy zirconate, tetrapropoxy zirconate, chlorotriethoxy zirconate, ethyl trimethoxy zirconate, and phenyl trimethoxy zirconate.

Among the components described above, a silane coupling agent is preferable as the component constituting the molding improvement layer 17 because the adhesion strength is improved.
The molding improvement layer 17 may be a single layer or two or more layers.
When the exterior material 2 has the molding improvement layer 17, the adhesion strength between the base material layer 11 and the metal foil layer 13 is improved, and tensile and compressive stress is applied to the exterior material 2 during molding. Also, the adhesion between the base material layer 11 and the metal foil layer 13 can be secured more stably. Since the exterior material 2 has the molding improvement layer 17, the moldability is further superior to the exterior material 1 due to the above effect.
Moreover, the molding improvement layer 17 of this example has adhesiveness and also serves as an adhesive layer. As a form which makes the shaping | molding improvement layer 17 serve as an adhesive bond layer, the form which uses heat-adhesive resin, such as polyolefin resin, among the said resin, and the form which contains an adhesive agent are mentioned, for example. Examples of the adhesive contained in the molding improving layer 17 include the dry laminating adhesive mentioned in the adhesive layer 12.

  The thickness of the molding improvement layer 17 is preferably 20 nm to 50 μm. If the thickness of the molding improvement layer 17 is 20 nm or more, it is easy to suppress the occurrence of film peeling, unevenness, etc., and the effects of the molding improvement layer 17 can be sufficiently exhibited. If the thickness of the molding improvement layer 17 is 50 μm or less, excellent moldability is easily obtained.

Stress during 20% stretching (displacement 7 mm) in the MD (Machine Direction) direction and TD (Transverse Direction) direction in the tensile test for the exterior material 2 (sample width 6 mm, distance between gauge points 35 mm, tensile speed 300 mm / min) Both values are 61.5 MPa or more and 71.5 MPa or less for the same reason as the exterior material 1. The stress value in the MD direction and the TD direction in the tensile test of the exterior material 2 is preferably 62.5 MPa or more and 71.0 MPa or less, and more preferably 63.0 MPa or more and 68.0 MPa or less.
The exterior material 2 is preferable to the exterior material 1 in that the moldability is improved by the molding improvement layer 17.

(Production method)
Hereinafter, the manufacturing method of the exterior material 2 is demonstrated. However, the manufacturing method of the exterior material 2 is not limited to the following method.
As a manufacturing method of the exterior material 2, the method which has the following process (I-2)-(III-2) is mentioned, for example.
(I-2) A step of forming the corrosion prevention treatment layer 14 on the metal foil layer 13.
(II-2) A step of bonding the base material layer 11 to the opposite side of the metal foil layer 13 from the side on which the corrosion prevention treatment layer 14 is formed via the molding improvement layer 17.
(III-2) A step of bonding the sealant layer 16 to the corrosion prevention treatment layer 14 side of the metal foil layer 13 via the adhesive resin layer 15.

Step (I-2):
The step (I-2) can be performed in the same manner as the step (I-1) in the method for manufacturing the exterior material 1.

Step (II-2):
Using a mixture containing an adhesive for dry laminating and at least one of the resin and coupling agent forming the molding improving layer 17, opposite to the side of the metal foil layer 13 on which the corrosion prevention treatment layer 14 is formed. The base material layer 11 is bonded to the side by a technique such as dry lamination.
In step (II-2), an aging treatment (curing) may be performed in the range of room temperature to 100 ° C. in order to promote adhesion.

Step (III-2):
The step (III-2) can be performed in the same manner as the step (III-1) in the method for manufacturing the exterior material 1.

The exterior material 2 is obtained by the steps (I-2) to (III-2) described above.
In addition, the manufacturing method of the exterior material 2 is not limited to the method of implementing the said process (I-2)-(III-2) sequentially. For example, the step (I-2) may be performed after performing the step (II-2). Moreover, you may provide a corrosion prevention process layer on both surfaces of a metal foil layer. Moreover, you may perform a process (II-2) after performing a process (III-2).

  The exterior material for a lithium ion battery of the present invention described above has excellent moldability because the stress value in the MD direction and the TD direction in the tensile test described above is 61.5 MPa or more and 71.5 MPa or less. Deeper deep drawing can be performed without causing pinholes or breakage.

In addition, the exterior material for lithium ion batteries of this invention is not limited to the exterior materials 1 and 2 mentioned above. For example, in the exterior materials 1 and 2, the corrosion prevention treatment layer 14 is provided on the surface of the metal foil layer 13 on the side of the adhesive resin layer 15, that is, on the side that may come into contact with hydrofluoric acid generated by the reaction between the electrolytic solution and moisture. However, if necessary, a corrosion prevention treatment layer may also be provided on the surface of the metal foil layer 13 on the base material layer 11 side.
In the exterior material 2, the molding improvement layer 17 also serves as an adhesive layer. However, the form having the molding improvement layer in the exterior material for a lithium ion battery of the present invention is not limited to this form, and is bonded separately from the molding improvement layer. An adhesive layer formed using an agent may be provided. For example, an exterior material in which a base material layer / molding improvement layer / adhesion layer / metal foil layer / corrosion prevention treatment layer / adhesive resin layer / sealant layer are sequentially laminated, base material layer / adhesion layer / mold improvement layer / metal foil layer And / or an exterior material in which a corrosion prevention treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated.

A lithium ion battery using the outer packaging material for a lithium ion battery of the present invention can be produced by a known method except that the outer packaging material for a lithium ion battery of the present invention is used. For example, it is obtained as follows. A recess is formed in a part of the outer packaging material for a lithium ion battery of the present invention by cold molding, and a positive electrode, a separator, and a negative electrode are placed inside the concave portion, and another outer packaging material for a lithium ion battery of the present invention is placed. Are stacked so that the sealant layer 16 faces each other, and the three sides are heat-sealed. Thereafter, in a vacuum state, an electrolyte is injected from the remaining one side, and the remaining one side is heat-sealed and sealed to obtain a lithium ion battery.
In addition, the lithium ion battery using the exterior material for lithium ion batteries of this invention is not limited to what was manufactured by the said method.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Materials used]
The materials used in this example are shown below.
(Base material layer 11)
Base material A-1: Biaxially stretched polyamide film (thickness 25 μm).
Base material A-2: Biaxially stretched polyamide film (thickness 25 μm).
Base material A-3: Biaxially stretched polyamide film (thickness 25 μm).
Base material A-4: Biaxially stretched polyethylene terephthalate film (thickness 12 μm).

(Adhesive layer 12, molding improvement layer 17)
Adhesive B-1: Polyurethane adhesive (trade name “A525 / A50”, manufactured by Mitsui Chemicals Polyurethanes).
Adhesive B-2: A mixture obtained by mixing 2% by mass of a silane coupling agent with a polyurethane adhesive (trade name “A525 / A50”, manufactured by Mitsui Chemicals Polyurethanes).

(Metal foil layer 13)
Metal foil C-1: Soft aluminum foil 8079 material (Toyo Aluminum Co., Ltd., thickness 40 μm).

(Corrosion prevention treatment layer 14)
Treatment agent D-1: Treatment agent for coating chromate treatment mainly composed of trivalent chromium, phosphoric acid, and acrylic resin.

(Adhesive resin layer 15)
Adhesive resin E-1: Polypropylene resin graft-modified with maleic anhydride (trade name Admer, Mitsui Chemicals).

(Sealant layer 16)
Film SL-1: A film obtained by corona-treating the surface to be the inner surface of an unstretched polypropylene film (thickness: 40 μm).

[Creation of exterior materials for lithium ion batteries]
(1) Coating material D-1 was applied to one surface of metal foil C-1 to be a metal foil layer 13 and the base material layer was a single layer film. The corrosion prevention treatment layer 14 was formed by drying. Next, the base material layer 11 was formed by laminating the base material having the structure shown in Table 1 on the opposite surface of the metal foil layer 13 to the corrosion prevention treatment layer 14 by the dry laminating method using the adhesive B-1. Thereafter, aging was performed at 60 ° C. for 6 days. Next, the adhesive resin E-1 was extruded to the corrosion prevention treatment layer 14 side of the obtained laminate by an extrusion device, the film SL-1 was bonded, and sandwich lamination was performed to form the sealant layer 16. Then, the obtained laminate, 160 ° C., was created exterior material by heat pressing at 4kg ^/ cm 2, 2m ^/ min conditions.

(2) Coating material D-1 was applied to one surface of the metal foil C-1 that becomes the metal foil layer 13 as a base material layer, and the corrosion prevention treatment layer 14 was formed. Next, the base material of the structure shown in Table 1 was laminated | stacked in order by the dry lamination method on the opposite surface of the corrosion prevention process layer 14 in the metal foil layer 13. FIG. The laminated film is formed by first laminating a film on the metal foil layer 13 using the adhesives B-1 and B-2 to be the adhesive layer 12 or the molding improving layer 17, and then, on the film, the adhesive B- This was performed by laminating a second film by a dry laminating method using 1. After film lamination, aging was performed at 60 ° C. for 6 days. Next, the adhesive resin E-1 was extruded to the corrosion prevention treatment layer 14 side of the obtained laminate by an extrusion device, the film SL-1 was bonded, and sandwich lamination was performed to form the sealant layer 16. Then, the obtained laminate, 160 ° C., was created exterior material by heat pressing at 4kg ^/ cm 2, 2m ^/ min conditions.

[Measurement of stress value during 20% stretching]
About the exterior material obtained in each example, a tensile test (sample width: 6 mm, distance between gauge points: 35 mm, tensile speed: 300 mm / min) was performed with Tensilon, and when stretched by 20% in the MD direction and the TD direction (displacement amount: 7 mm). Stress values were evaluated.

[Evaluation of moldability]
The exterior material obtained in each example was cut into a blank shape of 150 mm × 190 mm, cold-molded while changing the molding depth, and the moldability was evaluated. A punch having a shape of 100 mm × 150 mm, a punch corner R (RCP) of 1.5 mm, a punch shoulder R (RP) of 0.75 mm, and a die shoulder R (RD) of 0.75 mm was used. Evaluation was performed according to the following criteria.
“A”: Deep drawing with a molding depth of 7 mm or more was possible without causing breakage and cracks.
“◯”: Deep drawing with a molding depth of 5 mm or more and less than 7 mm was possible without causing breakage and cracks.
“×”: Breaking and cracking occurred in deep drawing with a molding depth of less than 5 mm.

[Examples 1 to 5 and Comparative Example 1]
The exterior material of the structure shown in Table 1 was created by the said creation method.
The results are shown in Table 1. In addition, "A-4 / A-1" in Table 1 is a laminated film obtained by laminating each substrate so that the substrate A-4 is on the outside of the substrate layer 11 and A-1 is on the metal foil layer 13 side. The same applies to other notations.

As shown in Table 1, the exterior materials of Examples 1 to 5 in which the stress value during 20% stretching in the tensile test is 61.5 MPa or more and 71.5 MPa or less in both the MD direction and the TD direction are deep at a deep molding depth. It was able to be drawn and was excellent in moldability. In particular, the exterior material of Example 1 can be deep-drawn without breaking or cracking even at a molding depth of 8 mm, and the exterior material of Example 2 can be fractured or cracked even at a molding depth of 8.5 mm. Deep drawing was possible. Furthermore, since the exterior material of Example 3 was provided with the molding improvement layer 17, the moldability was superior to the exterior material of Example 5 having the same stress value when stretched by 20% in the MD direction and the TD direction.
On the other hand, the exterior material of Comparative Example 1 in which the stress value during 20% stretching in the MD direction was less than 61.5 MPa was broken at a molding depth of 5 mm.

DESCRIPTION OF SYMBOLS 1, 2 Lithium ion battery exterior material 11 Base material layer 12 Adhesive layer 13 Metal foil layer 14 Corrosion prevention treatment layer 15 Adhesive resin layer 16 Sealant layer 17 Molding improvement layer

Claims (5)

A lithium ion battery exterior material in which an adhesive layer, a metal foil layer, a corrosion prevention treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of the base material layer,
The base material layer is a single layer film made of a biaxially stretched polyamide film, or a layer formed of a laminated film in which a biaxially stretched polyamide film and a biaxially stretched polyethylene terephthalate film are laminated from the metal foil layer side,
The adhesive layer is a layer formed of a polyurethane adhesive,
The metal foil layer is a layer formed of aluminum foil,
The adhesive resin layer is a layer formed of an acid-modified polyolefin resin,
The sealant layer is a layer formed of a film made of polyolefin resin,
In the tensile test (sample width: 6 mm, distance between gauge points: 35 mm, tensile speed: 300 mm / min), the stress values at the time of 20% stretching in the MD direction and TD direction (displacement amount: 7 mm) are both 61.5 MPa and 71.5 MPa. A packaging material for a lithium ion battery. A lithium ion battery exterior material in which a molding improvement layer, a metal foil layer, a corrosion prevention treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one surface of a base material layer,
The base material layer is a single layer film made of a biaxially stretched polyamide film, or a layer formed of a laminated film in which a biaxially stretched polyamide film and a biaxially stretched polyethylene terephthalate film are laminated from the metal foil layer side,
The molding improvement layer is a layer formed of a mixture obtained by mixing a coupling agent with an adhesive,
The metal foil layer is a layer formed of aluminum foil,
The adhesive resin layer is a layer formed of an acid-modified polyolefin resin,
The sealant layer is a layer formed of a film made of polyolefin resin,
In the tensile test (sample width: 6 mm, distance between gauge points: 35 mm, tensile speed: 300 mm / min), the stress values at the time of 20% stretching in the MD direction and TD direction (displacement amount: 7 mm) are both 61.5 MPa and 71.5 MPa. A packaging material for a lithium ion battery. The base material layer is a layer formed of the laminated film;
The exterior material for lithium ion batteries according to claim 1 or 2, wherein the laminated film is a laminated film in which the biaxially stretched polyamide film and the biaxially stretched polyethylene terephthalate film are laminated via a polyurethane-based adhesive. . The base material layer is a layer formed of the laminated film;
The exterior material for a lithium ion battery according to claim 1 or 2, wherein the laminated film is a laminated film in which a polyamide film and a polyethylene terephthalate film are laminated by a co-extrusion method and biaxially stretched.   The exterior material for a lithium ion battery according to any one of claims 1 to 4, wherein the sealant layer is laminated by sandwich lamination on the corrosion prevention treatment layer side of the metal foil layer.

Images