JP2018073648A - Exterior material for power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exterior material for a power storage device, which has good shapability even if it is arranged in a thin layer form.SOLUTION: An exterior material for a power storage device comprises at least a base material layer, a metal foil layer, a sealant adhesive layer and a sealant layer in this order. According to a tensile test (JIS K 7127 with a tensile speed of 50 mm/min, under the measurement environment of 23°C and 50%RH, and the sample type-5), the base material layer has a tensile strength of 20-70 MPa in both of MD direction and TD direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exterior material for an electricity storage device.

  As a battery exterior material for mobile devices such as smart phones that are made thinner, for example, a laminated film including an epoxy resin layer, a metal foil layer, and a heat-adhesive resin layer in this order has been proposed (for example, see Patent Document 1). .

JP 2001-176465 A

  However, in accordance with the material and the manufacturing method described in Patent Document 1, if an exterior material having a thin layer is manufactured to some extent and an attempt is made to form a deep recess, the exterior material may break.

  In view of the above circumstances, an object of the present invention is to provide an exterior material for an electricity storage device that has good moldability even if it is thinned.

  The present invention includes at least a base material layer, a metal foil layer, a sealant adhesive layer, and a sealant layer in this order, and a tensile test (JIS K 7127: tensile speed 50 mm / min, measurement environment 23 ° C., 50% RH). The external packaging material for electrical storage devices in which the tensile strength of MD direction and TD direction in sample type-5) is both 20-70 MPa.

  If it is the exterior material of this invention, even if it is made thin, it can have favorable moldability.

  In this invention, it is preferable that a base material layer is formed from at least 1 sort (s) selected from the group which consists of a water dispersion type polyester resin and a water dispersion type urethane resin. Thereby, a tough base material layer is easily formed and it becomes easy to maintain moldability.

  In this invention, it is preferable that the thickness of a base material layer is 2-15 micrometers. Moreover, it is preferable that the thickness of an exterior material is 40-60 micrometers. Thereby, a thin-layer exterior material can be provided while maintaining barrier properties and insulating properties.

  In this invention, it is preferable that a metal foil layer has a corrosion prevention layer on both surfaces. Thereby, electrolyte solution tolerance can be improved more.

  In the present invention, the sealant adhesive layer is preferably made of an acid-modified polyolefin resin. Thereby, it becomes easy to obtain the slipperiness of the inner layer side.

  ADVANTAGE OF THE INVENTION According to this invention, even if it makes it thin, the exterior material for electrical storage devices which has favorable moldability can be provided.

It is sectional drawing which shows the exterior | packing material for electrical storage devices which concerns on one Embodiment of this invention.

<Exterior materials for electricity storage devices>
An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an electricity storage device exterior material (hereinafter simply referred to as “exterior material”) 1 of the present embodiment.

  The exterior material of the present embodiment includes a first corrosion prevention layer and a base material layer in this order on the first surface of the metal foil layer, and a second corrosion prevention layer on the second surface of the metal foil layer, A sealant adhesive layer and a sealant layer are provided in this order. That is, as shown in FIG. 1, the exterior material 1 includes a metal foil layer 11 that exhibits a barrier function, a first corrosion prevention layer 12 and a base material that are sequentially formed on the first surface of the metal foil layer 11. A layer 13, a second corrosion prevention layer 14 formed on the second surface of the metal foil layer 11, and a sealant adhesive layer 15 and a sealant layer 16 sequentially formed on the second corrosion prevention layer 14. ing. When forming an electrical storage device using the exterior material 1, the base material layer 13 becomes an outermost layer, and the sealant layer 16 becomes an innermost layer.

  The thickness of the exterior material 1 is preferably 40 to 60 μm, and more preferably 45 to 55 μm, from the viewpoint of maintaining moldability even if it is thinned.

[Metal foil layer]
As the metal foil layer 11, various metal foils made of aluminum, copper, copper alloy, stainless steel, nickel, iron, magnesium, titanium, and the like can be used, and among these, workability such as moisture resistance and ductility can be used. From the surface, aluminum foil, copper foil, and stainless steel foil are preferable. Furthermore, an aluminum foil is more preferable from the viewpoint of cost. A general soft aluminum foil can be used as the aluminum foil. Among these, 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 and, as for content of iron in the aluminum foil (100 mass%) containing iron, 0.5-2.0 mass% is more preferable. When the iron content is 0.1% by mass or more, the exterior material 1 is more excellent in pinhole resistance and spreadability. If the iron content is 9.0% by mass or less, the exterior material 1 is more excellent in flexibility.

  The thickness of the metal foil layer 11 is preferably 9 to 40 μm and more preferably 15 to 30 μm from the viewpoints of barrier properties, pinhole resistance, workability, and the like.

[Base material layer]
The base material layer 13 provides heat resistance in the sealing process when manufacturing the electricity storage device, and electrolyte resistance that does not change even when the electrolyte is attached to the exterior material 1 and can be a pin that can occur during processing and distribution. It plays a role in suppressing the generation of holes.

  The base material layer 13 is formed of a resin, and is preferably formed directly on the first corrosion prevention layer 12 formed on the first surface of the metal foil layer 11, preferably without an adhesive layer. In addition, the base material layer 13 formed by coating can also be called a coating layer.

  The tensile strength in the MD direction and the TD direction of the base material layer 13 in the tensile test (JIS K 7127: tensile speed 50 mm / min, measurement environment 23 ° C., 50% RH, sample type-5) is 20 to 70 MPa. If the tensile strength is 20 MPa or more, a sufficiently strong base material layer can be obtained, and if the tensile strength is 70 MPa or less, appropriate stretchability of the base material layer can be ensured. Thereby, even if the exterior material of the present embodiment is thinned, it is possible to maintain good moldability. From this viewpoint, the tensile strength is preferably 30 to 65 MPa, and more preferably 40 to 60 MPa.

  In addition, the test sample for the tensile test of the base material layer 13 is obtained by, for example, immersing the exterior material in a sodium hydroxide solution, dissolving the metal foil layer 11 made of aluminum foil, and separating the base material layer 13. .

  The base material layer 13 can be formed using various resins such as polyester resin, urethane resin, fluororesin, epoxy resin, amino resin, acrylic resin, phenol resin, alkyd resin, and polyvinyl alcohol. From the viewpoint of stretchability, polyester resins and urethane resins are preferred.

  As the polyester resin, there are a solvent-soluble type and a water-dispersed type. Examples of the solvent-soluble type include those obtained by replacing a part of raw material polyalcohol ethylene glycol or the like with cyclohexanedimethanol or neopentyl glycol. The water-dispersed type is, for example, a polyester obtained by polycondensation of a carboxylic acid component composed of a divalent or higher polyvalent carboxylic acid compound and an alcohol component composed of a divalent or higher polyhydric alcohol compound, a sulfonic acid metal base, Examples thereof include those in which a hydrophilic polar group such as a carboxyl group or a phosphate group is introduced and dispersed in water.

  Examples of the urethane resin include a two-component curing type and a water dispersion type. The two-component curing type is, for example, a TDI, MDI, XDI, IPDI, or HDI system that mainly contains acrylic polyol, polyester polyol, polyether polyol, etc. having a hydroxyl group in the molecule and has a partial NCO structure in the molecule. Is added as a curing agent to obtain a coating solution. After the coating, the solvent is dried, and in order to promote the reaction between the hydroxyl group and the isocyanate, for example, an aging treatment is performed at 60 ° C. for 5 days to form a coating layer. The water dispersion type is, for example, a TDI type, MDI type, XDI type, IPDI type, HDI type or the like having a polyol component such as polyether diol, polyester diol, and polycarbonate diol having a hydroxyl group in the molecule and an NCO partial structure in the molecule. A product obtained by introducing a hydrophilic group (self-emulsifying type) into a reaction product with isocyanate and dispersing in water.

  It is preferable to form the base material layer using a water-dispersed polyester resin or a water-dispersible urethane resin because the molecular weight can be increased and thereby a tough base material layer can be easily obtained.

  The thickness of the base material layer 13 is preferably 2 to 15 μm and more preferably 4 to 10 μm from the viewpoint of maintaining insulation and stretchability. Since the base material layer 13 can be directly formed on the first corrosion prevention layer 12 formed on the first surface of the metal foil layer 11, by making the thickness of the base material layer 13 15 μm or less, It is also easy to make the structure thinner than the outer packaging material.

[Corrosion prevention layer]
The first corrosion prevention layer 12 and the second corrosion prevention layer 14 (hereinafter referred to as “corrosion prevention layer”) prevent corrosion of the metal foil layer 11 by the electrolytic solution or hydrofluoric acid generated by the reaction between the electrolytic solution and moisture. Play a role to suppress. Moreover, it plays the role which raises the adhesive force of the base material layer 13 and the metal foil layer 11, and the metal foil layer 11 and the sealant contact bonding layer 15.

  Examples of the corrosion prevention layer include a coating film formed by a coating type or immersion type acid-resistant corrosion prevention treatment agent, and a metal oxide layer derived from a metal element constituting the metal foil layer 11. Such a coating film or layer is excellent in the effect of preventing corrosion against acid. As the coating film, for example, a ceriazol-treated coating film, a chromate salt, a phosphate salt, a fluoride, and various thermosetting resins with a corrosion prevention treatment agent composed of cerium oxide, phosphate and various thermosetting resins. Examples thereof include a chromate-treated coating film with a preventive treatment agent. In addition, if it is a coating film from which the corrosion resistance of the metal foil layer 11 is fully obtained, it will not be limited to what was mentioned above. For example, a coating film formed by phosphate treatment, boehmite treatment, or the like may be used. On the other hand, examples of the metal oxide layer derived from the metal element constituting the metal foil layer 11 include layers according to the metal foil layer 11 used. For example, when an aluminum foil is used as the metal foil layer 11, the aluminum oxide layer functions as a corrosion prevention layer. These corrosion prevention layers can be used in a single layer or in combination of a plurality of layers. Further, the first corrosion prevention layer 12 and the second corrosion prevention layer 14 may have the same configuration or different configurations. Further, an additive such as a silane coupling agent may be added to the corrosion prevention layer.

  The thickness of the corrosion prevention layer is preferably 10 nm to 5 μm, more preferably 20 to 500 nm, from the viewpoint of the corrosion prevention function and the function as an anchor.

[Sealant adhesive layer]
The sealant adhesive layer 15 is a layer that bonds the metal foil layer 11 on which the second corrosion prevention layer 14 is formed and the sealant layer 16. The exterior material 1 is roughly divided into two, a thermal laminate configuration and a dry laminate configuration, depending on the adhesive component that forms the sealant adhesive layer 15.

  In the case of a thermal laminate configuration, the adhesive component for forming the sealant adhesive layer 15 is preferably an acid-modified polyolefin resin obtained by graft-modifying a polyolefin resin with an acid such as maleic anhydride. Since the acid-modified polyolefin-based resin is one in which a polar group is introduced into a part of the non-polar polyolefin-based resin, for example, a non-polar layer formed of a polyolefin-based resin film or the like as the sealant layer 16 is used. Further, when a layer having polarity is used as the second corrosion prevention layer 14, it is possible to firmly adhere to both of these layers. In addition, by using an acid-modified polyolefin resin, resistance to contents such as an electrolytic solution is improved, and even if hydrofluoric acid is generated inside the battery, it is easy to prevent a decrease in adhesion due to deterioration of the sealant adhesive layer 15. . The acid-modified polyolefin resin used for the sealant adhesive layer 15 may be one type or two or more types.

  Examples of the polyolefin resin used for the acid-modified polyolefin resin include low density, medium density or high density polyethylene; ethylene-α olefin copolymer; homo, block or random polypropylene; propylene-α olefin copolymer. Can be mentioned. In addition, a copolymer obtained by copolymerizing a polar molecule such as acrylic acid or methacrylic acid with the aforementioned one, a polymer such as a crosslinked polyolefin, and the like can also be used. Examples of the acid that modifies the polyolefin-based resin include carboxylic acid and acid anhydride, and maleic anhydride is preferable.

  In the case of a thermal laminate configuration, the sealant adhesive layer 15 can be formed by extruding the adhesive component with an extrusion device.

  In the case of a dry laminate configuration, as an adhesive component of the sealant adhesive layer 15, for example, a bifunctional or higher functional aromatic or aliphatic isocyanate compound acts as a curing agent on a main component such as polyester polyol, polyether polyol, or acrylic polyol. And a two-component curable polyurethane adhesive. However, since the polyurethane-based adhesive has a highly hydrolyzable bond such as an ester group or a urethane group, a thermal laminate configuration is preferable for applications that require higher reliability.

  The sealant adhesive layer 15 having a dry laminate structure can be formed by applying an adhesive component on the second corrosion prevention layer 14 and then drying it. If a polyurethane adhesive is used, after coating, for example, by aging at 40 ° C. for 4 days or more, the reaction of the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds to enable strong adhesion. It becomes.

  The thickness of the sealant adhesive layer 15 is preferably 2 to 50 μm and more preferably 3 to 20 μm from the viewpoints of adhesiveness, followability, workability, and the like.

  When the sealant adhesive layer 15 has a dry laminate configuration, the lubricant contained in the sealant layer 16 or the lubricant applied on the sealant layer 16 is trapped by the sealant adhesive layer 15 and the slipperiness of the sealant layer 16 is reduced. Tend. Therefore, from the viewpoint of maintaining the slipperiness of the sealant layer 16, the sealant adhesive layer 15 is preferably formed by forming an acid-modified polyolefin resin with an extrusion apparatus and laminating with a heat laminate.

[Sealant layer]
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 resin film made of an acid-modified polyolefin resin obtained by graft-modifying a polyolefin resin with an acid such as maleic anhydride.

  Examples of the polyolefin resin include low density, medium density or 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.

  Examples of the acid that modifies the polyolefin resin include the same acids as those described in the description of the sealant adhesive layer 15.

  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-cyclic olefin copolymer or polymethylpentene is interposed can be used.

  The sealant layer 16 may contain various additives such as a flame retardant, a lubricant, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

  The thickness of the sealant layer 16 is preferably 5 to 50 μm and more preferably 10 to 30 μm from the viewpoint of ensuring insulation.

  The exterior material 1 may be one in which the sealant layer 16 is laminated by dry lamination. From the viewpoint of the slipperiness of the sealant layer 16, the sealant adhesive layer 15 is an acid-modified polyolefin resin, sandwich lamination, or coextrusion method. It is preferable that the sealant layer 16 is laminated.

<Method for manufacturing exterior material for power storage device>
Hereinafter, the manufacturing method of the exterior material 1 of this embodiment is demonstrated. Specifically, although the method which has the following process (1)-(3) is mentioned as the manufacturing method, the following content is an example and the manufacturing method of the exterior | packing material 1 is not limited to the following content.

  Process 1: The process of forming the 1st corrosion prevention layer 12 and the 2nd corrosion prevention layer 14 on both surfaces (1st surface and 2nd surface) of the metal foil layer 11. FIG.

  Process 2: The process of forming the base material layer 13 on the 1st corrosion prevention layer 12 formed in the 1st surface of the metal foil layer 11 using the raw material (resin material) for base material layers.

  Process 3: The process of bonding the sealant layer 16 on the 2nd corrosion prevention layer 14 formed in the 2nd surface of the metal foil layer 11 via the sealant adhesive layer 15.

(Process 1)
For example, a corrosion prevention treatment agent is applied to both surfaces of the metal foil layer 11 and dried to form the first corrosion prevention layer 12 and the second corrosion prevention layer 14. Examples of the corrosion prevention treatment agent include the above-described corrosion prevention treatment agent for ceriazole treatment and corrosion prevention treatment agent for chromate 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. Alternatively, by oxidizing the surface of the metal foil layer 11, metal oxide layers derived from the metal elements constituting the metal foil layer 11 on both surfaces of the metal foil layer 11 (the first corrosion prevention layer 12 and the second corrosion prevention layer 12). A corrosion protection layer 14) is formed. Note that one surface of the metal foil layer 11 may be treated with a corrosion preventing treatment agent and the other surface may be oxidized.

(Process 2)
On the first corrosion prevention layer 12 formed on the first surface of the metal foil layer 11, a substrate layer raw material (resin material) serving as a substrate layer is applied and dried to form a substrate layer 13. Form. The application method is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating, and bar coating can be employed. After coating, for example, curing acceleration can be obtained by aging treatment at 60 ° C. for 7 days.

(Process 3)
A sealant adhesive layer 15 is formed on the second corrosion prevention layer 14 of the laminate in which the base material layer 13, the first corrosion prevention layer 12, the metal foil layer 11, and the second corrosion prevention layer 14 are laminated in this order. Then, the laminate and the resin film forming the sealant layer 16 are bonded together. At this time, the sealant adhesive layer 15 and the sealant layer 16 can be coextruded to be laminated on the laminate.

  The exterior material 1 is obtained by the steps (1) to (3) described above. In addition, the process sequence of the manufacturing method of the cladding | exterior_material 1 is not limited to the method of implementing process (1)-(3) sequentially. For example, step (2) may be performed after performing step (3).

  The two exterior materials 1 obtained in this way are prepared and the sealant layers 16 are opposed to each other, or the exterior material 1 is folded back so that the sealant layers 16 are opposed to each other, and become power generation elements and terminals inside. By arranging a tab member or the like and joining the peripheral edges by heat sealing, a cell of an electricity storage device using the exterior material 1 is completed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.

[Materials used]
The material used for preparation of the exterior material of an Example and a comparative example is shown below.

表中、引張強度は、引張試験（ＪＩＳ Ｋ ７１２７：引張速度５０ｍｍ／分、測定環境２３℃、５０％ＲＨ、試料 ｔｙｐｅ−５）に準じて測定した。試験用試料は、作製した外装材を所定の溶液に浸漬して金属箔層を溶かし、基材層を分離することで得た。 (Base material layer)

In the table, the tensile strength was measured according to a tensile test (JIS K 7127: tensile speed 50 mm / min, measurement environment 23 ° C., 50% RH, sample type-5). The test sample was obtained by immersing the prepared exterior material in a predetermined solution to dissolve the metal foil layer and separating the base material layer.

(Base layer side corrosion prevention layer: first corrosion prevention layer)
Corrosion prevention layer B-1: Cerium oxide layer (layer thickness: 100 nm)
Corrosion prevention layer B-2: Chromium oxide layer (layer thickness 100 nm)
Corrosion prevention layer B-3: Aluminum oxide layer (layer thickness 100 nm)

(Metal foil layer)
Metal foil C-1: Soft aluminum foil 8021 material (Toyo Aluminum Co., Ltd., thickness 25 μm)
Metal foil C-2: Soft aluminum foil 8021 (Toyo Aluminum Co., Ltd., thickness 20 μm)
Metal foil C-3: Copper foil (Fukuda Metal Foil Powder Co., Ltd., thickness 25 μm)
Metal foil C-4: Stainless steel foil (Nippon Metals Co., Ltd., thickness 25 μm)

(Sealant layer side corrosion prevention layer: Second corrosion prevention layer)
Corrosion prevention layer D-1: Cerium oxide layer (layer thickness 100 nm)

(Sealant adhesive layer)
Adhesive resin E-1: Polypropylene resin graft-modified with maleic anhydride (trade name “Admer”, Mitsui Chemicals, layer thickness 10 μm)

(Sealant layer)
Thermal fusion resin F-1: Polypropylene resin (trade name “Prime Polypro”, manufactured by Prime Polymer Co., Ltd., layer thickness 10 μm)

(Preparation of exterior materials)
Corrosion prevention layer D-1 was formed by direct gravure coating on one surface of metal foil C-1, C-2, C-3 or C-4. Next, the corrosion prevention layer B-1, B-2 or B-3 is formed on the other surface of the metal foil C-1, C-2, C-3 or C-4 where the corrosion prevention layer D-1 is not formed. Was formed by direct gravure coating. In Examples, the base layer raw material A is formed on the surface of the metal foil C-1, C-2, C-3 or C-4 on which the corrosion prevention layer B-1, B-2 or B-3 is formed. -1 (Example 1) to A-7 (Example 12) were applied to form a base material layer (coating layer).

  On the other hand, in the comparative example, the base layer raw material A-8 (Comparative Example 1) or A-9 (Comparative Example 2) is applied to the surface of the metal foil C-1 on which the corrosion prevention layer B-1 is formed. To form a base material layer.

  Next, the adhesive resin E-1 and the heat-sealing resin F-1 are coextruded with an extrusion apparatus on the corrosion prevention layer D-1 side of the laminates of the obtained examples and comparative examples, and a sealant adhesive layer is formed. A sealant layer was formed. The exterior material of each Example and the comparative example was produced through the above process.

[Various evaluations]
Various evaluations were performed according to the following methods. The evaluation results are shown in Table 2.

[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 in a molding environment with a room temperature of 23 ° C. and a dew point temperature of −35 ° C., 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. The evaluation criteria were as follows.
“A”: Deep drawing with a molding depth of 3 mm or more was possible without causing breakage and cracks.
"B": Deep drawing with a molding depth of 2 mm or more and less than 3 mm was possible without causing breakage or cracks.
“C”: Breaking and cracking occurred in deep drawing with a molding depth of less than 2 mm.

[Evaluation of insulation]
A part of the base material layer of the packaging material obtained in each example was peeled off, and the other terminal was brought into contact with the metal foil with one terminal of the tester exposed. The insulation of the base material layer was evaluated by applying a voltage of 25 V for 30 minutes and measuring the insulation resistance value. The evaluation criteria were as follows.
“A”: The insulation resistance value was 25 GΩ or more.
“B”: The insulation resistance value was less than 25 GΩ.

  In the example having the configuration of the present invention, it was possible to provide an exterior material for an electricity storage device having good moldability even when the layer was thinned.

  DESCRIPTION OF SYMBOLS 1 ... Exterior material (exterior material) for electrical storage devices, 11 ... Metal foil layer, 12 ... 1st corrosion prevention layer, 13 ... Base material layer, 14 ... 2nd corrosion prevention layer, 15 ... Sealant adhesion layer, 16 ... Sealant layer.

Claims (6)

At least a base material layer, a metal foil layer, a sealant adhesive layer and a sealant layer are provided in this order,
The tensile strength in the MD direction and TD direction in the tensile test (JIS K 7127: tensile speed 50 mm / min, measurement environment 23 ° C., 50% RH, sample type-5) is 20 to 70 MPa. Exterior material for electricity storage devices.   The power storage device exterior material according to claim 1, wherein the base material layer is formed of at least one selected from the group consisting of a water-dispersible polyester resin and a water-dispersible urethane resin.   The power storage device exterior material according to claim 1 or 2, wherein the base material layer has a thickness of 2 to 15 µm.   The exterior | packing material for electrical storage devices as described in any one of Claims 1-3 whose thickness is 40-60 micrometers.   The exterior | packing material for electrical storage devices as described in any one of Claims 1-4 with which the said metal foil layer has a corrosion prevention layer on both surfaces.   The power storage device exterior material according to any one of claims 1 to 5, wherein the sealant adhesive layer is made of an acid-modified polyolefin resin.

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