JP6492402B2 - Power storage device exterior materials - Google Patents

Description

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

  Conventionally, nickel-metal hydride and lead-acid batteries are known as secondary battery and other power storage devices, but the energy density is often low because downsizing of portable devices and installation space are limited. High lithium-ion batteries are attracting attention. Conventionally, metal cans have been used as exterior materials for lithium-ion batteries (hereinafter sometimes referred to simply as “exterior materials”), but they are lightweight, have high heat dissipation, and can be handled at low cost. Many possible multilayer films have been 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. As the electrolyte, lithium salts such as LiPF ₆ and LiBF ₄ are used. However, these lithium salts generate hydrofluoric acid by a hydrolysis reaction. Hydrofluoric acid 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, the exterior material made of a multilayer film is provided with a barrier layer made of a metal foil or the like inside to prevent moisture from entering from the surface of the multilayer film. For example, a packaging material is known in which a base material layer having heat resistance / first adhesive layer / barrier layer / corrosion prevention treatment layer for preventing corrosion due to hydrofluoric acid / second adhesive layer / sealant layer are sequentially laminated. Aluminum is often used as the material of the metal foil.

  As a type of lithium ion battery, a recess is formed in a part of the exterior material by cold forming, and the battery contents such as a positive electrode, a separator, a negative electrode, and an electrolytic solution are accommodated in the recess, and the remaining portion of the exterior material is One that is folded and sealed with a heat seal is known. Such a battery is also called an embossed type lithium ion battery. In recent years, for the purpose of increasing the energy density, an embossed type lithium ion battery has also been manufactured in which recesses are formed on both sides of an exterior material to be bonded to accommodate more battery contents.

  The energy density of a lithium ion battery increases as the recesses formed by cold forming become deeper. However, in particular, when the barrier layer is made of aluminum, the deeper the concave portion to be formed, the easier it is for pinholes and breaks during molding of the exterior material. Then, protecting metal foil using the biaxially stretched polyamide film for the base material layer of exterior material is performed. (For example, refer to Patent Document 1).

JP2013-65556A

  In the technique of Patent Document 1, the poor formability of the barrier layer is compensated by the base material layer, but this method has a limit in improving the moldability. In an embossed type lithium ion battery, since the upper limit of the battery capacity is defined by the amount of drawing, an exterior material for an electricity storage device that is further excellent in moldability is required.

  In light of the above circumstances, an object of the present invention is to provide an exterior material for an electricity storage device that is more excellent in moldability.

The present invention provides an electricity storage device packaging material covering a battery element of an electricity storage device, a metal foil layer made of copper, an adhesive layer formed on the metal foil layer, and a sealant layer formed on the adhesive layer, with a thickness of the metal foil layer state, and are more 40μm or less 10 [mu] m, even on the metal foil layer, on a surface thereof opposite to the adhesive layer is formed faces, a second adhesive layer, A coating layer that is bonded to the metal foil layer via the second adhesive layer is provided, the second adhesive layer is a two-component curable urethane adhesive, and the thickness of the second adhesive layer is Ru der above 10μm or less 1μm as an exterior material for a power storage device.

Thickness before Symbol coating layer may be 10μm or more 30μm or less.

  According to the exterior device for an electricity storage device of the present invention, it can be made more excellent in moldability.

It is sectional drawing which shows the exterior | packing material for electrical storage devices which concerns on 1st embodiment of this invention. It is sectional drawing which shows the exterior | packing material for electrical storage devices which concerns on 2nd embodiment of this invention.

A first 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.
As shown in FIG. 1, the exterior material 1 includes a metal foil layer 11 made of copper, and an adhesive layer 12 and a sealant layer 13 sequentially laminated on the metal foil layer 11. When forming the electricity storage device using the exterior material 1, the sealant layer 13 becomes the innermost layer.

  Since the metal foil layer 11 is formed of copper foil, the metal foil layer 11 has excellent extensibility and has good moldability in drawing. In addition, it has high corrosion resistance.

  The thickness of the metal foil layer 13 is preferably 5 μm or more and 100 μm or less, but more preferably 10 μm or more and 80 μm or less from the viewpoint of moldability. Furthermore, from a viewpoint of weight reduction and thin film formation, it is more preferable that they are 10 micrometers or more and 40 micrometers or less. Since the metal foil layer of the present invention is excellent in extensibility as compared with an aluminum metal foil layer, even if it has the same thickness, formation of breakage, pinholes, etc. is hardly caused. As a result, it can be formed thinner than a metal foil layer made of aluminum.

The metal foil layer 13 can be subjected to corrosion prevention treatment as necessary.
The corrosion prevention treatment plays a role of suppressing corrosion of the metal foil layer 11 due to the electrolytic solution or hydrofluoric acid generated by the reaction between the electrolytic solution and moisture. Further, it plays a role of increasing the adhesion between the metal foil layer 11 and the adhesive layer 12.
As the corrosion prevention treatment, a coating film formed by a coating type or immersion type acid-resistant corrosion prevention treatment agent is preferable. Such a coating film is excellent in the effect of preventing corrosion of the metal foil layer 11 with respect to acid. Further, since the adhesion between the metal foil layer 11 and the adhesive layer 12 is further strengthened by the anchor effect, excellent resistance to contents such as an electrolytic solution can be obtained.

Corrosion prevention treatment includes, for example, a coating film formed by ceriazol treatment with a corrosion prevention treatment agent comprising cerium oxide, phosphate and various thermosetting resins, chromate, phosphate, fluoride and various thermosetting For example, a coating film formed by chromate treatment with a corrosion-inhibiting treatment agent made of a conductive resin.
The corrosion prevention treatment is not limited to the above-described one as long as the corrosion resistance of the metal foil layer 11 is sufficiently obtained. For example, a coating film formed by phosphate treatment, boehmite treatment, or the like may be used.

The coating film formed as the corrosion prevention treatment may be a single layer or a plurality of layers. When it consists of a plurality of layers, it may be a material that exhibits a function different from the function of each layer due to the interaction between the layers. Moreover, additives, such as a silane coupling agent, may be added to the material of a coating film.
The thickness of the coating film is preferably 10 nm or more and 5 μm or less, and more preferably 20 nm or more and 500 nm or less from the viewpoint of the corrosion prevention function and the function as an anchor.
In addition, the said coating film may be further provided between the coating layer 32 and the metal foil layer 11 according to the function required.

The adhesive layer 12 is a layer that bonds the metal foil layer 11 and the sealant layer 13 together. When an acid-modified polyolefin resin obtained by modifying a polyolefin resin with an acid is selected as an adhesive component for forming the adhesive layer 12, heat lamination is performed. The acid-modified polyolefin resin is a non-polar polyolefin resin. Since a polar group is introduced into a part of the sealant layer 13, it can be firmly adhered to the nonpolar sealant layer 13 formed of a polyolefin resin film or the like, and the sealant layer 13 and the metal foil can be used even when the electrolytic solution penetrates. This is particularly preferable because the adhesion with the layer 11 can be easily maintained.
The acid-modified polyolefin resin used for the adhesive layer 12 may be one type or two or more types.
On the other hand, as an adhesive component for forming the adhesive layer 12 in a dry laminate configuration, two-component curing using polyester polyol, polyether polyol, acrylic polyol, polyolefin or the like as a main agent and aromatic or aliphatic isocyanate as a curing agent. A mold adhesive can be mentioned. The adhesive has a molar ratio (NCO / OH (or COOH group)) of the NCO group of the curing agent to the OH group (or COOH group) of the main agent, preferably from 1 to 10, and more preferably from 2 to 5.

Examples of the polyolefin resin used for the acid-modified polyolefin resin include low density, medium density, and high density polyethylene; ethylene-α olefin copolymer; homo, block or random polypropylene; propylene-α olefin copolymer. Can be mentioned.
Examples of the acid that modifies the polyolefin-based resin include carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and acid anhydrides, mono- and diesters, amides, imides, and the like. preferable.

  The adhesive layer 12 may contain a styrene-based or olefin-based elastomer. Thereby, it is easy to suppress that the adhesive layer 12 is cracked and whitened during cold forming.

  The thickness of the adhesive layer 12 is preferably 2 μm or more and 50 μm or less from the viewpoint of adhesiveness and suppression of water vapor intrusion from the end. Moreover, when producing by a dry laminate structure, it is preferable that they are 1 micrometer or more and 10 micrometers or less from a viewpoint of adhesiveness and water vapor | steam barrier property.

The sealant layer 13 is a layer that imparts a sealing property by heat sealing in the exterior material 1. Examples of the material for the sealant layer 13 include polyolefin resins, acid-modified polyolefin resins, and the like.
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.
Examples of the acid-modified polyolefin resin include the same ones as mentioned in the description of the adhesive layer 12.

Moreover, the sealant layer 13 may be blended with various additives such as a flame retardant, slip agent, anti-blocking agent, antioxidant, light stabilizer, and tackifier.
The thickness of the sealant layer 13 is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 80 μm or less from the viewpoint of adhesiveness and suppression of water vapor intrusion from the end.

Prepare two outer packaging materials 1 so that the sealant layers 13 face each other, or fold one outer packaging material 1 so that the sealant layers 13 face each other, and arrange a tab member or the like to be a power generation element or terminal inside. The periphery is joined by heat sealing. Further, when an insulating coating or the like is applied to the surface of the metal foil layer 11 to provide insulation to the outer surface, a cell of an electricity storage device using the exterior material 1 is completed.
The provision of insulation may be performed after the exterior material is manufactured and before the sealant layer 13 is joined.

  As described above, according to the packaging material 1 of the present embodiment, the metal foil layer 11 is made of copper, so that the moldability can be improved. Therefore, in order to increase the capacity of the battery cell to be manufactured, the metal foil layer 11 is suitably stretched and molded while suitably maintaining the barrier function even if deep drawing molding or the like for forming the recess is performed. be able to.

  A second embodiment of the present invention will be described with reference to FIG. The difference between the exterior material 31 of the present embodiment and the exterior material 1 of the first embodiment is that a coating layer is further provided. In the following description, the same components as those already described are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 2 is a cross-sectional view of the exterior material 31. On the surface of the metal foil layer 11 opposite to the surface on which the adhesive layer 12 is formed, a coating layer 33 made of a resin is provided via a second adhesive layer 32. Hereinafter, the details of the second adhesive layer 32 and the covering layer 33 will be described.

The second adhesive layer 32 is a layer that adheres the covering layer 33 and the metal foil layer 11.
As the adhesive constituting the second adhesive layer 32, a two-component curable type in which a bifunctional or higher functional aromatic or aliphatic isocyanate compound is allowed to act as a curing agent on a main component such as polyester polyol, polyether polyol, and acrylic polyol. The urethane adhesive is preferable.
The thickness of the second adhesive layer 32 is preferably 1 to 10 μm and more preferably 3 to 7 μm from the viewpoints of adhesive strength, followability, workability, and the like.

  The covering layer 33 has a function of imparting insulation to the outermost surface of the exterior material and further improving moldability. Moreover, it also has a role of imparting heat resistance in the sealing process when manufacturing the electricity storage device and suppressing the generation of pinholes that may occur during processing and distribution. As the covering layer 33, a film made of polyester resin, polyamide resin or the like can be used. Although the thickness of the coating layer 33 can be set as appropriate, it is preferably 6 μm or more and 40 μm or less, and more preferably 10 μm or more and 30 μm or less. When the thickness of the coating layer 33 is equal to or greater than the lower limit value, the pinhole resistance, the insulating property, and the moldability become better. If the thickness of the coating layer 33 is equal to or less than the upper limit value, the expansion and contraction of the portion stretched by the molding process is suppressed, and the shape after the molding process can be maintained.

Similarly to the exterior material 1 of the first embodiment, the exterior material 31 of the present embodiment can be molded while suitably maintaining the barrier function as a result of improved moldability.
Moreover, since the coating layer 33 which covers the metal foil layer 11 is provided, the metal foil layer 11 is suitably protected and an insulation process such as coating is not required.

  The packaging material and secondary battery of the present invention will be further described using examples and comparative examples. However, the present invention is not limited to the specific contents of the examples.

It shows below about the layer structure of the exterior material of an Example and a comparative example. The numerical value in parentheses indicates the thickness.
Example 1
Metal foil layer: copper foil (40 μm) / adhesive layer: acid-modified polyolefin adhesive (3 μm) / sealant layer: polypropylene film (80 μm)
(Example 2)
Covering layer: polyamide film (12 μm) / second adhesive layer: urethane resin adhesive (3 μm) / metal foil layer: copper foil (40 μm) / adhesive layer: acid-modified polyolefin adhesive (3 μm) / sealant layer: polypropylene Film (80μm)
(Example 3)
Coating layer: polyamide film (25 μm) / second adhesive layer: urethane resin adhesive (3 μm) / metal foil layer: copper foil (40 μm) / adhesive layer: acid-modified polyolefin adhesive (3 μm) / sealant layer: polypropylene Film (80μm)
Example 4
Metal foil layer: copper foil (20 μm) / adhesive layer: acid-modified polyolefin adhesive (3 μm) / sealant layer: polypropylene film (80 μm)
(Example 5)
Coating layer: polyamide film (12 μm) / second adhesive layer: urethane resin adhesive (3 μm) / metal foil layer: copper foil (20 μm) / adhesive layer: acid-modified polyolefin adhesive (3 μm) / sealant layer: polypropylene Film (80μm)
(Comparative Example 1)
Aluminum foil (40 μm) / acid-modified polyolefin adhesive (3 μm) / polypropylene film (80 μm)
(Comparative Example 2)
Polyamide film (12 μm) / urethane resin adhesive (3 μm) / aluminum foil (40 μm) / acid-modified polyolefin adhesive (3 μm) / polypropylene film (80 μm)
(Comparative Example 3)
Polyamide film (25 μm) / urethane resin adhesive (3 μm) / aluminum foil (40 μm) / acid-modified polyolefin adhesive (3 μm) / polypropylene film (80 μm)

Using the packaging materials of the examples and comparative examples, the moldability was evaluated by the following procedure.
(Preparation of molding sample)
The exterior material was cut into a 150 × 190 mm size blank shape, stored in a room temperature 23 ° C./room dew point temperature−35 ° C. environment for 24 hours, and then cold-formed in the same environment. The molding depth was 4 steps of 4 mm, 5 mm, 6 mm, and 7 mm, and three molding samples were prepared for each molding depth. 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 of moldability)
About the molding sample of each example, the presence or absence of a fracture | rupture and a crack was confirmed visually, and the three-stage evaluation was performed on the following references | standards.
“Good”: Neither fracture nor crack occurs at all molding depths.
“◯ (fair)”: Neither fracture nor crack occurs in the sample having a molding depth of 5 mm or less.
“× (insufficient)”: Samples of all molding depths were broken or cracked.

  The moldability evaluation results are shown in Table 1.

表１に示すように、銅箔を金属箔層に用いた各実施例では、被覆層の有無にかかわらず、成型深さ５ｍｍまでの深絞り成型を破断およびクラックを生じさせずに行うことができた。被覆層を設けた実施例では、さらに成型性が向上しており、成型深さが６ｍｍ以上の深絞り成型でも破断およびクラックを生じなかった。

As shown in Table 1, in each example in which a copper foil is used for a metal foil layer, deep drawing up to a molding depth of 5 mm can be performed without causing breakage and cracking regardless of the presence or absence of a coating layer. did it. In the example in which the coating layer was provided, the moldability was further improved, and no breakage or cracking occurred even in deep drawing with a molding depth of 6 mm or more.

  The embodiments and examples of the present invention have been described above. However, the technical scope of the present invention is not limited to the above-described embodiments, and combinations of components may be changed without departing from the spirit of the present invention. Various changes can be added to or deleted from each component.

DESCRIPTION OF SYMBOLS 1, 31 Power storage device exterior material 11 Metal foil layer 12 Adhesive layer 13 Sealant layer 33 Coating layer

Claims (2)

In the exterior device for the electricity storage device that covers the battery element of the electricity storage device,
A metal foil layer made of copper;
An adhesive layer formed on the metal foil layer;
A sealant layer formed on the adhesive layer;
With
The thickness of the metal foil layer is 10 μm or more and 40 μm or less,
On the surface of the metal foil layer opposite to the surface on which the adhesive layer is formed,
A second adhesive layer;
A coating layer bonded to the metal foil layer via the second adhesive layer;
Is provided,
The second adhesive layer is a two-component curable urethane adhesive, and the thickness of the second adhesive layer is 1 μm or more and 10 μm or less. The packaging material for an electricity storage device according to claim 1 , wherein the coating layer has a thickness of 10 μm or more and 30 μm or less.

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