JP2011076735A - Packaging material for lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging material for a lithium ion battery capable of suppressing occurrence of crack and breakage even if molding depth is made deeper when forming a recessed part by cold molding and having excellent moldability. <P>SOLUTION: In the packaging material 1 for a lithium ion battery having a first adhesive layer 12, an aluminum foil layer 13, a second adhesive layer 14 and a base material layer 15A laminated in this order on one surface of a sealant layer 11, the base material layer 15A is a polymer film (A) having a displacement amount of 2.0-10.0% at 0.2% distortion in a tension testing in each of a flow direction (MD) and a vertical direction (TD) under a condition of a sample width 15 mm, a distance between gauge marks 50 mm/min and a tension speed 30 mm/min, and moreover, a yield point elongation is 0-2.0%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Nickel metal hydride and lead acid batteries have been widely used as secondary batteries. However, due to the demand for downsizing of secondary batteries due to downsizing of portable devices and limitations on installation space, lithium ion batteries with high energy density are attracting attention. Conventionally, metal cans have been used as packaging materials used in lithium ion batteries, but multilayer films are used because they are lightweight, have high heat dissipation, low cost, and high degree of freedom in shape. It is becoming.

As an electrolytic solution of the lithium ion battery, a solution obtained by dissolving an electrolyte in an aprotic solvent such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate is used. As the electrolyte lithium salt, LiPF ₆ , LiBF ₄ or the like is used. However, the lithium salt generates hydrofluoric acid by hydrolysis. Hydrofluoric acid causes corrosion of the metal surface and a decrease in the laminate strength between the layers in the multilayer film. Therefore, by providing an aluminum foil layer inside the multilayer film, moisture from the surface of the multilayer film is prevented from entering. Thus, a lithium battery using a multilayer film having an aluminum foil layer therein is called an aluminum laminate type lithium ion battery.

As a packaging material for a lithium ion battery having an aluminum foil layer, for example, a sealant layer is laminated on one surface of the aluminum foil layer via a first adhesive layer, and a second adhesive layer is interposed on the other surface. The multilayer film which laminated | stacked the base material layer is mentioned. The lithium ion battery packaging material is roughly classified into two types: a dry laminate structure in which the first adhesive layer is made of an adhesive resin layer for dry laminate and a thermal laminate structure in which the first adhesive layer is made of a thermoplastic material. Is done. Since the adhesive of the dry laminate product has a highly hydrolyzable bond portion such as an ester group or a urethane group, hydrolysis reaction with hydrofluoric acid is likely to occur. Therefore, a thermal laminate configuration is used for applications where reliability is required.
A laminate-type lithium ion battery can be obtained by processing such a multilayer film into a bag shape, and sealing it with a positive electrode, a separator, a negative electrode, an electrolytic solution, a tab, and the like.

  In addition, in order to further increase the energy density, the lithium ion battery employs a form in which more battery contents are accommodated by forming a concave portion in which the multilayer film is concaved by cold molding. In recent years, in order to store the contents more efficiently, a form in which the volume is increased by bonding two concave multilayer films to increase the energy density is also used. However, in such cold forming of a multilayer film, the multilayer film is likely to break at sides and corners, which are parts having a high stretch ratio, during molding with a mold. In particular, in the case of a heat-laminated product, the crystallized state of the sealant layer changes due to high-temperature processing, and therefore breakage easily occurs. Therefore, there is a demand for a multilayer film that can suppress cracks and breaks in the film during the cold molding and can increase the molding depth even for a heat-laminated product.

The following lithium ion battery packaging materials are shown as packaging materials excellent in moldability that can increase the molding depth.
(1) A stretched polyamide film or a stretched polyester film having a tensile strength of 150 N / mm ² or more and an elongation of 80% or more in all four directions of 0 °, 45 °, 90 °, and 135 ° is applied to the base material layer. Used lithium ion battery packaging material (Patent Document 1).

Japanese Patent No. 3567230

However, in a lithium ion battery in which a recess is formed with a multilayer film, it is desired to further increase the moldability of the packaging material for lithium ion batteries, for example, it is required to further increase the molding depth. Yes.
Accordingly, an object of the present invention is to provide a packaging material for a lithium ion battery having better moldability.

The present invention employs the following configuration in order to solve the above problems.
[1] In a lithium ion battery packaging material in which at least a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a base material layer are sequentially laminated on one surface of the sealant layer, the base material layer includes: A packaging material for a lithium ion battery comprising the following polymer film (A).
Polymer film (A): 0.2% strain in a tensile test under the conditions of a sample width of 15 mm, a distance between gauge points of 50 mm / min, and a tensile speed of 30 mm / min for each of the flow direction (MD) and the vertical direction (TD) A polymer film having an hourly displacement of 2.0 to 10.0% and a yield point elongation of 0 to 2.0%.
[2] The packaging material for a lithium ion battery according to [1], wherein the polymer film (A) includes one or both of a biaxially stretched nylon film and a biaxially stretched polyethylene terephthalate film.
[3] The base material layer is composed of a laminated film having the polymer film (A) and another polymer film (B), and the outermost layer on the second adhesive layer side of the laminated film is a polymer. The packaging material for a lithium ion battery according to [1] or [2], which is a film (A).
[4] The first adhesive layer is an adhesive resin layer containing an acid-modified polyolefin resin, and the second adhesive layer is made of an adhesive capable of bonding the aluminum foil layer and the base material layer by dry lamination. The packaging material for a lithium ion battery according to any one of [1] to [3], which is an adhesive layer.

  The packaging material for a lithium ion battery of the present invention can suppress the occurrence of cracks and breaks in the film even when the molding depth is increased, and has excellent moldability.

It is sectional drawing which showed an example of embodiment of the packaging material for lithium ion batteries of this invention. It is a figure explaining the displacement amount at the time of 0.2% distortion in the tension test of a polymer film. It is a figure explaining the yield point elongation in the tensile test of a polymer film. It is sectional drawing which showed the other embodiment example of the packaging material for lithium ion batteries of this invention.

  In the lithium ion battery packaging material of the present invention, at least a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a base material layer are sequentially laminated on one surface of the sealant layer. Has a polymer film (A) having specific physical properties. Hereinafter, the present invention will be described in detail by showing an example of an embodiment of a packaging material for a lithium ion battery of the present invention.

[First Embodiment]
As shown in FIG. 1, the packaging material 1 for a lithium ion battery of the present embodiment has at least a first adhesive layer 12 (hereinafter simply referred to as “adhesive layer 12”), aluminum on one surface of a sealant layer 11. The foil layer 13, the second adhesive layer 14 (hereinafter simply referred to as “adhesive layer 14”), and the base material layer 15A are sequentially laminated.

(Sealant layer 11)
The sealant layer 11 is a layer made of a heat-weldable film that is an inner layer of the packaging material 1 for a lithium ion battery in a lithium ion battery. The sealant layer 11 may be made of a single layer film or a laminated film in which a plurality of films are laminated.
Examples of the component constituting the sealant layer 11 include a polyolefin resin and an acid-modified polyolefin resin obtained by graft-modifying a polyolefin resin with maleic anhydride or the like. Among these, an acid-modified polyolefin resin obtained by graft-modifying maleic anhydride or the like on a polyolefin resin is preferable.
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 resins may be used individually by 1 type, and may use 2 or more types together.

For the sealant layer 11, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene is interposed may be used as necessary for the purpose of imparting moisture resistance.
Moreover, the sealant layer 11 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 11, 20-50 micrometers is more preferable. When the sealant layer 11 is a multilayer film, the thickness is the total thickness.

(Adhesive layer 12)
The adhesive layer 12 is a layer that adheres the sealant layer 11 and the aluminum foil layer 13.
The component constituting the adhesive layer 12 preferably includes an acid-modified polyolefin resin, and more preferably a mixed resin obtained by adding an acid-modified styrene elastomer resin to the acid-modified polyolefin resin. 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.
Examples of the polyolefin resin are the same as those mentioned in the sealant layer 11. As the acid-modified polyolefin resin, a maleic anhydride-modified polyolefin resin graft-modified with maleic anhydride is preferable.

  Styrenic elastomer resin is a resin that has a hard segment represented by polystyrene and a soft segment represented by ethylene and butadiene. Etc. can be modified to improve compatibility with various resins and adhesion with various substrates. The acid-modified styrene elastomer resin is preferably a maleic anhydride-modified styrene elastomer resin graft-modified with maleic anhydride.

(Aluminum foil layer 13)
As a material of the aluminum foil layer 13, a known soft aluminum foil can be used, and an aluminum foil containing iron is preferable from the viewpoint of excellent pinhole resistance and extensibility during molding.
0.1-9.0 mass% is preferable with respect to the total mass of 100 mass% of aluminum foil, and, as for iron content in this aluminum foil, 0.5-2.0 mass% is more preferable. 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.
Moreover, you may use the aluminum foil which performed the degreasing process and the corrosion-resistant process.
The thickness of the aluminum foil layer 13 is preferably 9 to 200 μm and more preferably 15 to 100 μm from the viewpoint of barrier properties, pinhole resistance, and workability.

(Adhesive layer 14)
The adhesive layer 14 is a layer that adheres the aluminum foil layer 13 and the base material layer 15A.
As the adhesive constituting the adhesive layer 14, an adhesive capable of adhering the aluminum foil layer 13 and the base material layer 15A by dry lamination is preferable, and a polyol such as polyester polyol, polyether polyol, acrylic polyol or the like as a main ingredient is aromatic. More preferred are two-component curable polyurethane adhesives that use a polyisocyanate or an aliphatic isocyanate as a curing agent. The adhesive is subjected to an aging treatment for 4 days or more at 40 ° C. after coating, whereby the OH group of the main polyol and the NCO group of the curing agent isocyanate react to form the aluminum foil layer 13 and the base material layer 15A. And firmly adhere.
1-10 are preferable and, as for the molar ratio (NCO / OH) of the NCO group of the hardening | curing agent with respect to OH group of a main ingredient, 2-5 are more preferable.
The thickness of the adhesive layer 12 is preferably 1 to 10 μm, and more preferably 3 to 7 μm, from the viewpoint of adhesive strength, followability, workability, and the like.

(Base material layer 15A)
The base material layer 15A is a layer made of a single layer film. As the film, the sample width is 15 mm, the distance between gauge points is 50 mm / min, and the tensile speed is 30 mm / min for each of the flow direction (MD) and the vertical direction (TD). A polymer film (A) having a displacement amount of 0.2 to 10.0% in a tensile test under the conditions of 2.0 to 10.0% and a yield point elongation of 0 to 2.0% was used. Is a layer.

Hereinafter, the displacement amount at the time of 0.2% strain will be described. FIG. 2 shows a general relationship between the amount of displacement (unit:%) and the stress (unit: MPa) when a tensile test is performed on the polymer film.
When a tensile test is performed on the polymer film, as shown in FIG. 2, the stress increases linearly in proportion to the amount of displacement (deformation) at the initial stage of tension. The region where the stress increases linearly is an elastic region, and the slope is the Young's modulus E. In the elastic region, when the stress is removed, the polymer film returns to its original length, that is, no distortion. On the other hand, when the displacement amount is further increased, the displacement amount and the stress are not proportional, and the increase amount of the stress with respect to the displacement amount decreases. In this region, the deformation of the polymer film changes from elastic deformation to plastic deformation. In the region where plastic deformation occurs, the polymer film does not return to its original length even when the stress is removed, and is in a strained state (permanent elongation). “At 0.2% strain” means that the elongation of a film having this strain is 0.2% with respect to the original length of the film (the displacement a in FIG. 2 is 0.2%). Time). The “displacement amount at 0.2% strain” is a displacement amount that causes a strain of 0.2%, and the slope passing through the point a corresponding to the 0.2% strain is the Young's modulus E. This is the displacement c at the intersection b (inelastic region) between the straight line α and the curve actually measured in the tensile test.
It can be said that the larger the displacement at 0.2% strain, the wider the elastic region. In general, in a tensile test of steel or the like, stress at 0.2% strain (0.2% yield strength) is evaluated in order to grasp the elastic limit stress.

  The displacement amount (%) at the time of 0.2% strain of the polymer film (A) is 2.0 to 10.0%, preferably 2.5 to 5.0%. If the displacement at the time of 0.2% strain is within the above range, cracks and fractures may occur even when the molding depth is increased when the packaging material 1 for lithium ion battery is cold-molded to form a recess. Is suppressed, and excellent moldability is obtained.

Next, yield point elongation (unit:%) will be described with reference to FIG.
When a polymer film is subjected to a tensile test, depending on the polymer film, there is an area where the stress (MPa) linearly increases according to the displacement (%) and then the stress decreases as the displacement increases. is there. This phenomenon is called yielding, the vertex of stress is called the upper yield point (point d in FIG. 3), and the trough of stress is called the falling yield point (point e in FIG. 3). Further, depending on the polymer film, there is a region f in which the stress does not change even when the amount of displacement further increases from the lower yield point (point e), and this region f is called the yield point elongation. Yield point elongation indicates plastic deformation. That is, the yield point elongation (%) means the amount of displacement in the region f (the amount of displacement from point e to point g in FIG. 3).

  The yield point elongation (%) of the polymer film (A) is 0 to 2.0%, preferably 0 to 1.0%. If the elongation at yield of the polymer film (A) is 2.0% or less, when forming the recess by cold forming the packaging material 1 for lithium ion batteries, cracks and fractures occur even if the molding depth is increased. Is suppressed, and excellent moldability is obtained.

The polymer film (A) of the base layer 15A is preferably a resin film that can be easily improved in moldability during the production of a lithium ion battery. For example, a stretched or unstretched film such as a polyamide film, a polyester film, or a polyolefin film is used. Can be mentioned. Examples of the polyamide film include a nylon film and an aramid film. Examples of the polyester film include a polyethylene terephthalate film and a polybutylene terephthalate film. As a polyolefin film, a polypropylene film etc. are mentioned, for example.
The polymer film (A) is preferably a biaxially stretched polyamide film or a biaxially stretched polyester film, more preferably a biaxially stretched nylon film or a biaxially stretched polyethylene terephthalate film, from the viewpoint of excellent moldability and heat resistance.

(Production method)
Hereinafter, the manufacturing method of the packaging material 1 for lithium ion batteries is demonstrated. However, the manufacturing method of the packaging material 1 for lithium ion batteries is not limited to the method shown below. The manufacturing method of the packaging material 1 for lithium ion batteries has the following process (I-1) and process (II-1).
Step (I-1): A base material layer 15 </ b> A is laminated on one surface of the aluminum foil layer 13 via an adhesive layer 14.
Step (II-1): The sealant layer 11 is laminated on the other surface of the aluminum foil layer 13 via the adhesive layer 12.

Step (I-1):
A polymer film (A) is bonded onto the aluminum foil layer 13 to laminate a base material layer 15A. Examples of the bonding method include a dry laminating method using the adhesive (polyurethane adhesive, etc.) for forming the adhesive layer 14. Thereby, the laminated body by which the aluminum foil layer 13, the contact bonding layer 14, and 15 A of base material layers were laminated | stacked one by one is obtained.

Step (II-1):
The sealant layer 11 is laminated on the surface of the laminated body opposite to the base material layer 15 </ b> A of the aluminum foil layer 13 via the adhesive layer 12. Examples of the lamination method include a dry process and a wet process (coating as a dispersion).
In the case of a dry process, the adhesive resin layer 12 is formed on the aluminum foil layer 13 of the laminate by extrusion lamination using pellets made of an adhesive resin forming the adhesive layer 12, and further obtained by an inflation method or a cast method. A sealant layer 11 is laminated. Alternatively, the adhesive layer 12 may be laminated by extrusion lamination, and the sealant layer may be laminated by heat lamination. Alternatively, a multilayer film of the adhesive resin layer 12 and the sealant layer 11 may be formed by an inflation method or a cast method, and the multilayer film may be laminated on the laminate by thermal lamination.

In the case of a wet process, a dispersion containing an adhesive resin for forming the adhesive layer 12 is applied on the aluminum foil layer 13 of the laminate, and the solvent is volatilized at a temperature equal to or higher than the melting point of the adhesive resin. Bake by melting and softening the adhesive resin. Then, the packaging material 1 for lithium batteries is obtained by laminating the sealant layer 11 by heat treatment such as thermal lamination.
A known method is used as the dispersion coating method, and examples thereof include a gravure coater, a gravure reverse coater, a roll coater, a reverse roll coater, a die coater, a bar coater, a kiss coater, and a comma coater.

[Second Embodiment]
Next, the packaging material 2 for lithium ion batteries which is the other embodiment of the packaging material for lithium ion batteries of this invention is demonstrated. In the lithium ion battery packaging material 2, the same parts as those in the lithium ion battery packaging material 1 are denoted by the same reference numerals and description thereof is omitted.
As shown in FIG. 4, the lithium ion battery packaging material 2 has at least an adhesive layer 12, an aluminum foil layer 13, an adhesive layer 14, and a base material layer 15 </ b> B sequentially laminated on one surface of the sealant layer 11. That is, the lithium ion battery packaging material 2 is the same as the lithium ion battery packaging material 1 except for the base material layer 15B.

(Base material layer 15B)
The base material layer 15B is a layer made of a laminated film in which a polymer film 15a and a polymer film 15b are laminated via an adhesive layer 15c.
The polymer films 15a and 15b may both be a polymer film (A), and the polymer film 15b may be another polymer film (B), but both are polymer films (A). Is preferably used. As the base material layer 15B, from the viewpoint of moldability, as the polymer film 15a, the displacement amount at the time of 0.2% strain is 2.0 to 10.0%, and the yield point elongation is 0 to 2.0%. A biaxially stretched polyamide film is used, and the amount of displacement at 0.2% strain is 2.0 to 10.0% and the yield point elongation is 0 to 2.0% as the polymer film 15b. It is particularly preferable to use an axially stretched polyester film.

When the polymer film (A) and another polymer film (B) are used in combination, the outermost layer on the adhesive layer 14 side of the base material layer 15B, that is, the polymer film 15a is high from the viewpoint of moldability. The molecular film (A) is preferred.
The other polymer film (B) is, for example, a resin film of the same type as the polymer film (A), and either or both of the displacement amount at 0.2% strain and the elongation at yield point are both polymer films. Examples thereof include a film that does not satisfy the specified value of (A).
As the adhesive constituting the adhesive layer for adhering the polymer film 15a and the polymer film 15b, for example, the same adhesive as the adhesive mentioned in the adhesive layer 14 can be used. For example, a polyurethane adhesive or the like Is mentioned.

(Production method)
Hereinafter, although the manufacturing method of the packaging material 2 for lithium ion batteries is demonstrated, a manufacturing method is not limited to the method as described below. The manufacturing method of the packaging material 2 for lithium ion batteries has the following process (I-2) and process (II-2).
Step (I-2): The base material layer 15 </ b> B is laminated on one surface of the aluminum foil layer 13 via the adhesive layer 14.
Step (II-2): The sealant layer 11 is laminated on the other surface of the aluminum foil layer 13 via the adhesive layer 12.

Step (I-1):
A polymer film 15 a is bonded onto the aluminum foil layer 13 via an adhesive layer 14. Examples of the bonding method include a dry laminating method using the adhesive (polyurethane adhesive, etc.) for forming the adhesive layer 14. Furthermore, the polymer film 15b is bonded onto the polymer film 15a via the adhesive layer 15c. Examples of the method for laminating the polymer film 15b include a dry laminating method using a polyurethane-based adhesive or the like, as in the method for laminating the polymer film 15a. Thereby, the laminated body in which the aluminum foil layer 13, the adhesive layer 14, and the base material layer 15B (the polymer film 15a, the adhesive layer 15c, and the polymer film 15b) are sequentially laminated is obtained.

Step (II-2):
In the same manner as in the step (II-1) of the first embodiment, the sealant layer 11 is laminated on the aluminum foil layer 13 of the laminate through the adhesive layer 12, and the packaging material 2 for a lithium ion battery is obtained. obtain.

The lithium ion battery packaging material of the present invention can be used, for example, as follows to obtain a lithium ion battery.
The aforementioned multilayer film is embossed to form a recess, and a positive electrode, a separator, a negative electrode, and a tab are placed inside the recess, and then the two multilayer films are overlaid with the sealant layer 11 facing each other. Seal 3 sides. Thereafter, an electrolyte is injected from the remaining one side in a vacuum state, the remaining one side is finally sealed, and the inside is sealed to produce a lithium ion battery.

The above-described packaging material for lithium ion batteries of the present invention uses, as a base material layer, a polymer film (A) in which a displacement amount at 0.2% strain and a yield point elongation are defined within a predetermined range. When forming the recess by cold molding, even if the molding depth is increased, the occurrence of cracks and breakage is suppressed, and excellent moldability is obtained.
In addition, the packaging material for lithium ion batteries of this invention is not limited to the packaging materials 1 and 2 for lithium ion batteries mentioned above. For example, the base material layer may be a layer having three or more laminated films including the polymer film (A).

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.
The raw materials used in this example are shown below.
[Base material layer]
Table 1 shows polymer films used for the base material layer. However, “biaxially stretched Ny” in Table 1 means “biaxially stretched nylon film”, and “biaxially stretched PET” means “biaxially stretched polyethylene terephthalate film”.

[Second adhesive layer]
C-1: Polyurethane adhesive (trade name “A525 / A50”, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) (4 μm).

[Aluminum foil layer]
D-1: Soft aluminum foil 8079 material (40 μm).

[First adhesive layer]
E-1: Maleic anhydride-modified polypropylene resin (20 μm).
E-2: Polyurethane adhesive (4 μm).

[Sealant layer]
F-1: An unstretched polypropylene film (25 μm) obtained by corona-treating the surface on the inner surface of the packaging material.

[Example 1]
A heat-resistant polymer film A-1 as a base material layer was laminated on the aluminum foil layer D-1 by a dry laminating method using an adhesive C-1. Thereafter, aging was performed at 60 ° C. for 6 days. Next, the adhesive resin E-1 is extruded on the opposite side of the surface of the aluminum foil layer D-1 on which the base material layer is laminated, and a laminate F is obtained by sandwiching a film F-1 serving as a sealant layer. Obtained. Thereafter, the laminate was thermocompression bonded at 160 ° C. under the conditions of 4 kg / cm ² and 2 m / min to prepare a lithium ion battery packaging material (manufacturing method (i); thermal laminating method).

[Example 2]
A packaging material for a lithium ion battery was prepared in the same manner as in Example 1 except that the polymer film A-2 was used instead of the polymer film A-1.

[Example 3]
The polymer film A-1 is laminated on the aluminum foil D-1, and the polymer film B-2 is further formed on the polymer film A-1 by a dry laminating method using the same adhesive as the adhesive C-1. After laminating, a packaging material for a lithium ion battery was produced in the same manner as in Example 1 except that aging was performed at 60 ° C. for 6 days (manufacturing method (ii); thermal laminating method).

[Comparative Example 1]
The polymer film B-1 is used in place of the polymer film A-1, and the film F-1 is formed on the opposite side of the surface on which the base layer of the aluminum foil layer D-1 is laminated using the adhesive E-2. A packaging material for a lithium ion battery was prepared in the same manner as in Example 1 except that a sealant layer was provided by aging at 60 ° C. for 6 days (production method (iii); dry lamination method).

[Comparative Example 2]
A packaging material for a lithium ion battery was prepared in the same manner as in Comparative Example 1 except that the polymer film B-2 was used instead of the polymer film B-1.

[Comparative Example 3]
A packaging material for a lithium ion battery was prepared in the same manner as in Example 1 except that the polymer film B-3 was used instead of the polymer film A-1.

[Evaluation methods]
The packaging material for lithium ion batteries obtained in each example was cut into a blank shape (150 mm × 190 mm), and the moldability (molding depth at which breakage and cracks do not occur) was evaluated according to the following criteria. 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.
◯: Molding was possible at a molding depth of 7 mm or more without breaking or cracking.
(Triangle | delta): If it was the shaping | molding depth of 5 mm or more and less than 7 mm, it was moldable without a fracture | rupture and a crack producing.
X: Breaking and cracking occurred at a molding depth of 5 mm or more.
Table 2 shows the evaluation results in Examples and Comparative Examples.

In Example 1 in which the polymer film A-1 was used as the base material layer, it was possible to mold without breaking or cracking even at a molding depth of 9 mm regardless of the thermal laminating method, and the moldability was excellent. It was. Similarly, in Example 2 using the polymer film A-2, it was possible to mold without breaking or cracking even at a molding depth of 7 mm, regardless of the thermal laminating method.
Moreover, even in Example 3 using the laminated film of the polymer film A-1 and the polymer film B-2 whose adhesive layer side is the polymer film A-1, the fracture was caused even at a molding depth of 9 mm regardless of the thermal laminating method. It was possible to mold without cracking.

On the other hand, in Comparative Example 1 using the polymer film B-1 having a displacement amount of less than 2.0% when the MD is strained at 0.2%, fracture occurs at a molding depth of 7 mm even in the dry lamination method. The moldability was inferior to the examples.
Moreover, even in Comparative Example 2 using the polymer film B-2 in which the displacement amount at 0.2% strain is less than 2.0% for both MD and TD, even in the dry laminate method, the fracture is caused at a molding depth of 5 mm. occured.
In Comparative Example 3 using the polymer film B-3 in which the displacement amount at 0.2% strain exceeds 2.0% for both MD and TD but the elongation at yield point exceeds 2.0%, the molding depth Breakage occurred at 5 mm, and the moldability was poor.

  As described above, by using a polymer film in which the displacement amount at 0.2% strain is 2.0 to 10.0% for both MD and TD and the elongation at yield point is 0 to 2.0%, Even if the depth is increased, cracks and breakage are suppressed, and a packaging material for a lithium ion battery having excellent moldability is obtained. That is, in the molding process, the base material layer plays an important role in suppressing the breakage and cracking of the aluminum foil layer. Protection became possible.

  DESCRIPTION OF SYMBOLS 1, 2 Lithium ion battery packaging material 11 Sealant layer 12 1st contact bonding layer 13 Aluminum foil layer 14 2nd contact bonding layer 15A, 15B Base material layer

Claims (4)

In the lithium ion battery packaging material in which at least the first adhesive layer, the aluminum foil layer, the second adhesive layer, and the base material layer are sequentially laminated on one surface of the sealant layer,
The said base material layer has the following polymer film (A), The packaging material for lithium ion batteries characterized by the above-mentioned.
Polymer film (A): 0.2% strain in a tensile test under the conditions of a sample width of 15 mm, a distance between gauge points of 50 mm / min, and a tensile speed of 30 mm / min for each of the flow direction (MD) and the vertical direction (TD) A polymer film having an hourly displacement of 2.0 to 10.0% and a yield point elongation of 0 to 2.0%.   The packaging material for a lithium ion battery according to claim 1, comprising one or both of a biaxially stretched nylon film and a biaxially stretched polyethylene terephthalate film as the polymer film (A).   The base material layer is composed of a laminated film having the polymer film (A) and another polymer film (B), and the outermost layer on the second adhesive layer side of the laminated film is a polymer film (A 3) The packaging material for a lithium ion battery according to claim 1 or 2. The first adhesive layer is an adhesive resin layer containing an acid-modified polyolefin resin;
The lithium ion battery packaging according to any one of claims 1 to 3, wherein the second adhesive layer is an adhesive layer made of an adhesive capable of adhering the aluminum foil layer and the base material layer by dry lamination. Wood.

Images