JP2008130436A - Package material for battery case, and case for the battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a package material for a battery case capable of securing superior moldability, even if it is not coated with slipperiness-imparting component and of obtaining the sufficient volume/capacity ratio. <P>SOLUTION: In the package material for the battery case, containing a heat-resistant resin stretched film 2 as the outer layer, a thermoplastic resin-unstreched film layer 3 as the inner layer, and an aluminum foil layer 4 arranged and installed between both these film layers, as the heat resistant resin stretched film, the heat resistant resin stretched film is used, of which the refractive index range is 1.40 to 1.70. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a packaging material for a case of a battery such as a lithium ion secondary battery.

  In this specification, the term “aluminum” is used to include aluminum and its alloys.

  Lithium ion secondary batteries are widely used as power sources for notebook computers, video cameras, mobile phones, electric vehicles, and the like. As this lithium ion secondary battery, one having a configuration in which the periphery of the battery body is surrounded by a case is used. As this packaging material for a case, for example, a structure in which an outer layer made of a stretched polyamide film, an aluminum foil layer, and an inner layer made of an unstretched polypropylene film are bonded and integrated in this order is known (see Patent Document 1).

Since such a battery case packaging material is formed into an arbitrary battery shape, it is required to have high deep drawability. Conventionally, for example, the surface of the outer layer film is coated with a fatty acid amide-based slipperiness-imparting component in order to impart high deep drawability, and the material slips into the mold during molding (patented) Reference 2) and a configuration in which the thickness of the outer layer film is increased with respect to the thickness of the aluminum foil layer have been adopted.
JP 20016631 A JP 2002-216714 A

  However, the structure in which the surface of the outer layer film is coated with a fatty acid amide-based slipperiness imparting component has to be provided with a step of coating the slipperiness imparting component, resulting in low productivity. Furthermore, the slipperiness-imparting component evaporates when the battery is degassed or sealed, and the evaporated component adheres to the processing equipment, which requires a cleaning operation to remove it, further reducing productivity. There was a problem to do.

  In addition, in the configuration in which the thickness of the outer layer film is increased with respect to the thickness of the aluminum foil layer, there is a problem that the volumetric volume ratio of the battery decreases because the overall thickness of the packaging material increases.

  The present invention has been made in view of such a technical background, and is capable of ensuring excellent moldability without coating a slipperiness-imparting component, and for a battery case capable of obtaining a sufficient volume-volume ratio. An object is to provide a packaging material and a battery case.

  In order to achieve the above object, as a result of intensive studies, the present inventor has found a new finding that the refractive index of the heat-resistant resin stretched film layer, which is the outer layer of the packaging material, affects the moldability of the packaging material. The present invention has been completed. That is, the present invention provides the following means.

[1] In a battery case packaging material including a heat-resistant resin stretched film layer as an outer layer, a thermoplastic resin unstretched film layer as an inner layer, and an aluminum foil layer disposed between these two film layers,
A battery case packaging material, wherein a stretched heat resistant resin film having a refractive index of 1.40 to 1.70 is used as the stretched heat resistant resin film.

[2] In a battery case packaging material including a heat-resistant resin stretched film layer as an outer layer, a thermoplastic resin unstretched film layer as an inner layer, and an aluminum foil layer disposed between these two film layers,
As the heat-resistant resin stretched film layer, a biaxially stretched polyamide film having a refractive index of 1.40 to 1.70, a biaxially stretched polyethylene naphthalate film having a refractive index of 1.40 to 1.70, or a refractive index of 1. A battery case packaging material using a biaxially stretched polyethylene terephthalate film of 40 to 1.70.

  [3] The battery case packaging material according to item 1 or 2, wherein the stretched film has a refractive index of 1.50 to 1.60.

  [4] A battery case obtained by deep-drawing or stretch-molding the battery case packaging material according to any one of items 1 to 3.

  In the invention of [1], since a heat resistant resin stretched film having a refractive index of 1.40 to 1.70 is used as the heat resistant resin stretched film layer constituting the outer layer, deep drawing molding, stretch molding, etc. This makes it possible to form a sharp shape with a deep molding height. Thus, since excellent moldability can be secured without coating the slipperiness imparting component, it is not necessary to provide a step of coating the slipperiness imparting component as in the prior art, and the productivity is excellent. Moreover, since it is not necessary to make the thickness of the outer layer film particularly thick with respect to the thickness of the aluminum foil layer as in the prior art, a sufficient volume volume ratio can be obtained.

  In the invention of [2], as the heat-resistant resin stretched film layer constituting the outer layer, a biaxially stretched polyamide film having a refractive index of 1.40 to 1.70, a biaxial having a refractive index of 1.40 to 1.70. Since a stretched polyethylene naphthalate film or a biaxially stretched polyethylene terephthalate film having a refractive index of 1.40 to 1.70 is used, it is particularly excellent in moldability such as deep drawing and stretch molding, and is sharper and Molding with a deep molding height is possible. Thus, since excellent moldability can be secured without coating the slipperiness imparting component, it is not necessary to provide a step of coating the slipperiness imparting component as in the prior art, and the productivity is excellent. Moreover, since it is not necessary to make the thickness of the outer layer film particularly thick with respect to the thickness of the aluminum foil layer as in the prior art, a sufficient volume volume ratio can be obtained.

  In the invention of [3], since the refractive index of the stretched film is 1.50 to 1.60, the moldability such as deep drawing molding and overhang molding is further improved, and molding with a deeper molding height is possible. It becomes.

  In the invention of [4], it is possible to provide a battery case having a sharp shape and a deep molding height.

  One embodiment of a battery case packaging material (1) according to the present invention is shown in FIG. This packaging material is used as a packaging material for a lithium ion secondary battery case. In the battery case packaging material (1), a heat resistant resin stretched film layer (outer layer) (2) is laminated and integrated on the upper surface of the aluminum foil layer (4) via the first adhesive layer (5). In addition, the thermoplastic resin unstretched film layer (inner layer) (3) is laminated and integrated on the lower surface of the aluminum foil layer (4) via the second adhesive layer (6).

  The heat-resistant resin stretched film layer (outer layer) (2) is a member mainly responsible for ensuring good moldability as a packaging material, that is, the role of preventing breakage due to necking of the aluminum foil during molding. It is what you bear. In this invention, it is necessary to use a heat resistant resin stretched film having a refractive index of 1.40 to 1.70 as the heat resistant resin stretched film layer (2). When the refractive index is less than 1.40, the shrinkage of the film becomes high, and peeling occurs between the heat-resistant resin stretched film layer (2) and the aluminum foil layer (4) after molding. On the other hand, when the refractive index exceeds 1.70, the packaging material is broken or cracked when molding such as deep drawing molding or stretch molding is performed. Especially, it is preferable to use a heat resistant resin stretched film having a refractive index of 1.50 to 1.60 as the heat resistant resin stretched film.

  Further, as the heat-resistant resin stretched film layer (2), a biaxially stretched polyamide film having a refractive index of 1.40 to 1.70, a biaxially stretched polyethylene naphthalate (PEN) having a refractive index of 1.40 to 1.70. It is preferable to use a biaxially stretched polyethylene terephthalate (PET) film having a refractive index of 1.40 to 1.70. In this case, it is possible to further improve the formability such as deep drawing and overhang forming, and it is possible to form a shape that is sharper and has a higher forming height.

  The “refractive index” is a refractive index measured using an Abbe refractometer in accordance with JIS K7142-1996. That is, the “refractive index” is the light in the refraction phenomenon that occurs at the interface between the two when the test piece (20 mm × 8 mm) of the stretched heat-resistant resin film (2) is placed on the prism of the Abbe refractometer. It is the ratio (sin α / sin β) between the sine of the incident angle α and the sine of the refraction angle β.

  The refractive index of the heat resistant resin stretched film (2) can be controlled, for example, by adjusting the heat setting temperature during stretching. It is also possible to change the orientation of the resin crystals by selecting a stretching method (simultaneous biaxial stretching method in which the longitudinal direction and the transverse direction are stretched simultaneously, sequential biaxial stretching method in which the longitudinal direction and the transverse direction are sequentially stretched, etc.). Can be controlled.

  The thickness of the heat-resistant resin stretched film layer (2) is preferably set to 12 to 50 μm.

  The thermoplastic resin unstretched film layer (inner layer) (3) has excellent chemical resistance against highly corrosive electrolytes used in lithium ion secondary batteries, etc. It plays a role of imparting heat sealability.

  The thermoplastic resin unstretched film layer (3) is not particularly limited, but is at least one selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers. It is preferably composed of an unstretched film made of a thermoplastic resin.

  The thickness of the unstretched thermoplastic resin film layer (3) is preferably set to 20 to 80 μm. When the thickness is 20 μm or more, pinholes can be sufficiently prevented from being generated, and by setting the thickness to 80 μm or less, the amount of resin used can be reduced, and the cost can be reduced. Especially, it is especially preferable that the thickness of the said thermoplastic resin unstretched film layer (3) is set to 30-50 micrometers.

  In addition, both the said heat resistant resin stretched film layer (2) and the said thermoplastic resin unstretched film layer (3) may be a single layer, and may be a multilayer.

  The said aluminum foil layer (4) bears the role which provides the gas barrier property which prevents the penetration | invasion of oxygen and a water | moisture content to a packaging material. As said aluminum foil (4), the foil of thickness 5-50 micrometers which consists of pure Al or an Al-Fe type-alloy is used suitably.

  Although it does not specifically limit as said 1st adhesive bond layer (5), For example, a urethane type adhesive layer, an acrylic adhesive layer, etc. are mentioned. Especially, it is preferable that the said 1st adhesive bond layer (5) is a urethane type adhesive layer formed with the urethane type two-component reaction type adhesive agent, and it becomes possible to perform still more shaping | molding by this.

  The second adhesive layer (6) is not particularly limited. For example, in addition to acid-modified polyolefins such as maleic anhydride-modified polyethylene and maleic anhydride-modified polypropylene, urethane resins, acrylic resins, Examples include an adhesive layer formed of a resin containing a thermoplastic elastomer. These second adhesive layers (6) are formed, for example, by laminating an adhesive resin film (such as an acid-modified polyolefin film) on one surface of the thermoplastic resin unstretched film layer (3).

  In addition, in the said embodiment, although the structure which provided the 1st adhesive bond layer (5) and the 2nd adhesive bond layer (6) is employ | adopted, both these layers (5) (6) are essential. Instead of the constituent layers, it is also possible to adopt a configuration in which these are not provided.

  The battery case packaging material (1) of the present invention is suitably used as a packaging material for a lithium ion secondary battery case that requires a high volumetric energy density, but is not particularly limited to such applications.

  A battery case can be obtained by molding the battery case packaging material (1) of the present invention (deep drawing molding, stretch molding, etc.).

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
As shown in FIG. 2, while coextruding a maleic anhydride-modified polypropylene layer (21) having a thickness of 3 μm and an unmodified polypropylene layer (22) having a thickness of 12 μm, an aluminum foil having a thickness of 40 μm (AA8079- While supplying O material (4), a 30 μm-thick unstretched film (3) made of polypropylene is supplied from the right side of the drawing, and maleic anhydride-modified coextruded between (3) and (4) The polypropylene layer (21) and the unmodified polypropylene layer (22) were sandwiched between a pair of heat and pressure rolls and heat laminated.

  Next, the urethane resin adhesive (5) is applied to the surface of the aluminum foil (4) of the obtained laminated film with a gravure roll, dried to some extent by heating, and then the adhesive surface is made of nylon. A biaxially stretched film (2) having a thickness of 25 μm and a refractive index of 1.55 was laminated to obtain a battery case packaging material.

  The biaxially stretched nylon film (2) having a refractive index of 1.55 was obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature during the stretching to 210 ° C. Is.

<Example 2>
The same procedure as in Example 1 was performed except that a biaxially stretched film made of nylon having a thickness of 15 μm and a refractive index of 1.60 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. Thus, a packaging material for a battery case was obtained.

  The biaxially stretched nylon film having a refractive index of 1.60 is obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature during the stretching to 220 ° C. .

<Example 3>
The same procedure as in Example 1 was performed except that a biaxially stretched film made of nylon having a thickness of 15 μm and a refractive index of 1.51 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. Thus, a packaging material for a battery case was obtained.

  The biaxially stretched nylon film having a refractive index of 1.51 is obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature during the stretching to 200 ° C. .

<Comparative Example 1>
The same procedure as in Example 1 was performed except that a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.38 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. Thus, a packaging material for a battery case was obtained.

  The biaxially stretched nylon film having a refractive index of 1.38 is obtained by stretching using a sequential biaxial stretching method and setting the heat setting temperature during the stretching to 190 ° C. .

<Comparative example 2>
The same procedure as in Example 1 was used except that a biaxially stretched film having a thickness of 25 μm and a refractive index of 1.75 was used instead of a biaxially stretched film having a thickness of 25 μm and a refractive index of 1.55. Thus, a packaging material for a battery case was obtained.

  The biaxially stretched nylon film having a refractive index of 1.75 is obtained by stretching using a sequential biaxial stretching method and setting the heat setting temperature during the stretching to 230 ° C. .

<Example 4>
Example except that a biaxially stretched film made of polyethylene terephthalate (PET) having a thickness of 12 μm and a refractive index of 1.62 was used instead of the biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. In the same manner as in Example 1, a battery case packaging material was obtained.

  The biaxially stretched PET film having a refractive index of 1.62 is obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature during the stretching to 230 ° C. .

<Example 5>
Example except that a biaxially stretched film made of polyethylene terephthalate (PET) having a thickness of 20 μm and a refractive index of 1.45 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. In the same manner as in Example 1, a battery case packaging material was obtained.

  The biaxially stretched PET film having a refractive index of 1.45 was obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature at 210 ° C. during the stretching process. .

<Example 6>
Example except that a biaxially stretched film made of polyethylene terephthalate (PET) having a thickness of 12 μm and a refractive index of 1.52 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. In the same manner as in Example 1, a battery case packaging material was obtained.

  The biaxially stretched PET film having a refractive index of 1.52 was obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature at the time of stretching to 220 ° C. .

<Comparative Example 3>
Example except that a biaxially stretched film made of polyethylene terephthalate (PET) having a thickness of 12 μm and a refractive index of 1.35 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. In the same manner as in Example 1, a battery case packaging material was obtained.

  The biaxially stretched PET film having a refractive index of 1.35 is obtained by stretching using a sequential biaxial stretching method and setting the heat setting temperature during the stretching to 200 ° C. .

<Comparative Example 4>
Example except that a biaxially stretched film made of polyethylene terephthalate (PET) having a thickness of 12 μm and a refractive index of 1.72 was used instead of the biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. In the same manner as in Example 1, a battery case packaging material was obtained.

  The biaxially stretched PET film having a refractive index of 1.72 was obtained by stretching using a sequential biaxial stretching method and setting the heat setting temperature at the time of stretching to 240 ° C. .

<Example 7>
Implementation was performed except that a biaxially stretched film made of polyethylene naphthalate (PEN) having a thickness of 25 μm and a refractive index of 1.55 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. A battery case packaging material was obtained in the same manner as in Example 1.

  The biaxially stretched PEN film having a refractive index of 1.55 was obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature during the stretching to 220 ° C. .

<Example 8>
Implementation was carried out except that a biaxially stretched film made of polyethylene naphthalate (PEN) having a thickness of 15 μm and a refractive index of 1.68 was used instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. A battery case packaging material was obtained in the same manner as in Example 1.

  The biaxially stretched PEN film having a refractive index of 1.68 was obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature during the stretching to 230 ° C. .

<Example 9>
Except for using a biaxially stretched film made of polyethylene naphthalate (PEN) instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55, a biaxially stretched film having a refractive index of 1.43 was used. A battery case packaging material was obtained in the same manner as in Example 1.

  The biaxially stretched PEN film having a refractive index of 1.43 is obtained by stretching using a simultaneous biaxial stretching method and setting the heat setting temperature at 210 ° C. during the stretching process. .

<Comparative Example 5>
Except for using a biaxially stretched film made of polyethylene naphthalate (PEN) and a biaxially stretched film having a refractive index of 1.38 instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55. A battery case packaging material was obtained in the same manner as in Example 1.

  The biaxially stretched PEN film having a refractive index of 1.38 is obtained by sequentially stretching using a biaxial stretching method and setting the heat setting temperature at 210 ° C. during the stretching process. .

<Comparative Example 6>
Except for using a biaxially stretched film made of polyethylene naphthalate (PEN) instead of a biaxially stretched film made of nylon having a thickness of 25 μm and a refractive index of 1.55, a biaxially stretched film having a refractive index of 1.75 was used. A battery case packaging material was obtained in the same manner as in Example 1.

  The biaxially stretched PEN film having a refractive index of 1.75 is obtained by sequentially stretching using a biaxial stretching method and setting the heat setting temperature during the stretching to 240 ° C. .

  Performance evaluation was performed based on the following evaluation method with respect to each battery case packaging material obtained as described above.

<Formability evaluation method>
The packaging material was made into a blank shape of 110 × 180 mm, and deep drawing one-step molding was performed with a straight mold having a molding height of 6 mm, and the moldability was evaluated. “◎” indicates that no cracks occurred, “○” indicates that cracks occurred in a small part but almost none, “△” indicates that cracks occurred in a substantial part, and cracks almost entirely What occurred was marked "x". The punch shape of the mold used was 60 mm long side, 45 mm short side, corner R: 1-2 mm, punch shoulder R: 1-2 mm, and die shoulder R: 0.5 mm.

<Evaluation of presence / absence of peeling of outer surface>
The molded product obtained by the deep drawing single-stage molding was allowed to stand at 80 ° C. for 3 hours in a dryer, and then visually observed for delamination (peeling) on the outer surface layer.

  As is apparent from the table, the battery case packaging materials of Examples 1 to 9 of the present invention are excellent in moldability, can be molded with a sharper and deeper shape, and the outer surface. No delamination occurred.

  On the other hand, in Comparative Examples 1, 3, and 5 in which the refractive index of the stretched film of the outer layer was less than 1.40, peeling of the outer surface layer occurred. Moreover, in Comparative Examples 2, 4, and 6 in which the refractive index of the stretched film of the outer layer exceeded 1.70, the moldability was insufficient.

  The battery case packaging material of the present invention is used as a packaging material for battery cases such as lithium ion secondary batteries.

It is sectional drawing which shows one Embodiment of the packaging material for battery cases of this invention. It is a figure which shows an example of the manufacturing method of the packaging material for battery cases of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery case packaging material 2 ... Outer layer (heat-resistant resin stretched film layer)
3. Inner layer (thermoplastic resin unstretched film layer)
4 ... Aluminum foil layer

Claims (4)

In a battery case packaging material comprising a heat-resistant resin stretched film layer as an outer layer, a thermoplastic resin unstretched film layer as an inner layer, and an aluminum foil layer disposed between these two film layers,
A battery case packaging material, wherein a stretched heat resistant resin film having a refractive index of 1.40 to 1.70 is used as the stretched heat resistant resin film. In a battery case packaging material comprising a heat-resistant resin stretched film layer as an outer layer, a thermoplastic resin unstretched film layer as an inner layer, and an aluminum foil layer disposed between these two film layers,
As the heat-resistant resin stretched film layer, a biaxially stretched polyamide film having a refractive index of 1.40 to 1.70, a biaxially stretched polyethylene naphthalate film having a refractive index of 1.40 to 1.70, or a refractive index of 1. A battery case packaging material using a biaxially stretched polyethylene terephthalate film of 40 to 1.70.   The packaging material for battery cases according to claim 1 or 2, wherein the stretched film has a refractive index of 1.50 to 1.60.   A battery case formed by deep-drawing or stretch-molding the battery case packaging material according to claim 1.

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