JP6492526B2 - Power storage device exterior material and power storage device - Google Patents

Description

  The present invention relates to an exterior material for a power storage device and a power storage device.

  As power storage devices, for example, secondary batteries such as lithium ion batteries, nickel metal hydride batteries, and lead storage batteries, and electric double layer capacitors are known. There is a demand for further miniaturization of power storage devices due to miniaturization of portable devices or limitations on installation space, and lithium ion batteries with high energy density are attracting attention. The lithium ion battery employs a configuration in which the entire battery is covered with an exterior material including an aluminum foil layer in order to prevent moisture from entering the inside. This is called an aluminum laminate type lithium ion battery. In an aluminum laminate type lithium ion battery, for example, a recess is formed in a part of the exterior material by cold molding, and battery elements (positive electrode, separator, negative electrode, electrolyte, etc.) are accommodated in the recess, and the remainder of the exterior material is stored. The edge portion is folded and the edge portion is bonded by heat sealing, thereby forming an embossed type lithium ion battery.

The energy density of a lithium ion battery can be increased as the recess formed by cold forming is deepened. However, the deeper the recesses are formed, the easier it is for pinholes and fractures to occur in the outer packaging material at the time of molding, resulting in lower moldability. Then, protecting metal foils, such as aluminum foil, is performed using the stretched polyamide film etc. for the base material layer of exterior material. As an example, for example, in Patent Document 1, the base material layer has a tensile strength of 150 N / mm ² or more up to four directions of break at 0 °, 45 °, 90 ° and 135 ° in the tensile test, and It has been proposed to use a film having an elongation in four directions of 80% or more.

JP 2000-123800 A

  However, when a film having a strong tensile strength as described above is used for the base material layer and deep drawing is performed to form a recess in the exterior material, the exterior material after molding is warped toward the base material layer side. Problems arise. If the amount of warping of the exterior material after the molding process is large, the transportability of the exterior material and the handling property at the time of heat sealing after accommodating the battery element are hindered.

  The present invention has been made in view of the above circumstances, and is capable of reducing the amount of warpage after molding while maintaining excellent moldability, and the power storage device It is an object of the present invention to provide a power storage device including an exterior material.

  In order to solve the above-described problem, an exterior material for a power storage device according to one aspect of the present invention includes a base material layer including a biaxially stretched film, a metal foil layer disposed on the base material layer, and a metal foil layer. And an inner layer sandwiching a metal foil layer between the base material layer and the base material layer, and the base material layer includes at least one of a biaxially stretched polyester film and a biaxially stretched polyamide film as a biaxially stretched film. The inner layer includes at least one biaxially stretched polyolefin film.

  In the power storage device exterior material, the base material layer includes at least one of a biaxially stretched polyester film and a biaxially stretched polyamide film. In this case, since the base material layer protects the metal foil layer and can prevent the metal foil layer from being broken during the molding process, excellent moldability can be maintained. Moreover, in the said exterior material for electrical storage devices, the inner layer contains the biaxially stretched polyolefin film. In this case, the upper yield point strength in the tensile test of the inner layer provided on the battery element side can be increased to approach the upper yield point strength of the base material layer. Thus, by bringing the upper yield point strength of the base material layer and the inner layer close to each other, when the layers of the exterior material stretched by the molding process try to return to the state before stretching, the balance of force is lost and warping occurs. This can be suppressed, and the amount of warping of the exterior material after molding can be reduced.

  In the power storage device exterior material, a stretching ratio of the biaxially stretched polyolefin film may be 3 to 10 times in both the longitudinal direction and the lateral direction. If the draw ratio is 3 times or more, the inner layer can obtain a sufficient upper yield strength, and the amount of warpage after molding can be reduced. Moreover, if a draw ratio is 10 times or less, the excessive molecular orientation of an inner layer can be avoided and generation | occurrence | production of the microcrack by the extending | stretching at the time of a shaping | molding process can be prevented.

  In the power storage device exterior material, the stretch ratio of the biaxially stretched polyolefin film may be larger than the stretch ratio of the biaxially stretched film of the base material layer. In this case, the upper yield point strength of the inner layer can be made closer to the upper yield point strength of the base material layer, and the amount of warpage after molding can be more reliably reduced.

In the power storage device exterior material, the upper yield point strength of the biaxially stretched polyolefin film may be 40 N / mm ² or more. In this case, the upper yield point strength of the inner layer can be brought close to the upper yield point strength of the base material layer, and the amount of warpage after molding can be reduced.

  In the power storage device exterior material, the biaxially stretched polyolefin film may be thicker than the base material layer. In this case, the upper yield point strength of the inner layer can be made closer to the upper yield point strength of the base material layer, and the amount of warpage to the base material layer side after molding can be more reliably reduced.

  In the power storage device exterior material, the base material layer may have a thickness of 15 μm to 35 μm, and the biaxially stretched polyolefin film may have a thickness of 20 μm to 50 μm. When the thickness of the base material layer is 15 μm or more, it is difficult to break even when stress is applied by molding, and the moldability of the exterior material can be further improved. Moreover, the curvature amount to the base material layer side after a shaping | molding process can be reduced because the thickness of a base material layer is 35 micrometers or less. Moreover, when the thickness of the biaxially stretched polyolefin film is 20 μm or more, the amount of warpage toward the base material layer after the molding process can be reduced. Moreover, when the thickness of the biaxially stretched polyolefin film is 50 μm or less, the amount of warpage to the inner layer side after molding can be reduced.

  In the above power storage device exterior material, the inner layer may further include a heat sealable sealant layer, and the biaxially stretched polyolefin film may be disposed between the sealant layer and the metal foil layer. In this case, since the sealant layer can provide heat-sealing sealing performance to the power storage device exterior material, the intermediate layer does not need to have heat-fusibility, and the choice of materials can be expanded.

  In the power storage device exterior material, the biaxially stretched polyolefin film may be thicker than the sealant layer. In this case, it is easy to increase the upper yield strength of the inner layer while suppressing the total thickness of the power storage device exterior material.

  In the power storage device exterior material, the biaxially stretched polyolefin film may be a biaxially stretched polypropylene film, and the sealant layer may be formed of a polypropylene resin. In this case, since the intermediate layer and the sealant layer are formed of the same material, the adhesion between them can be improved.

  The present invention also relates to a power storage device as another aspect. This power storage device is the above-described power storage device exterior material, which is folded so that the inner layers are thermally fused together, and a battery disposed inside the folded power storage device exterior material And an element. In this power storage device, the power storage device exterior material is provided, and for the reasons described above, the power storage device exterior material maintains excellent moldability and reduces the amount of warping after molding. The handling property at the time of heat sealing can be improved.

  In the above power storage device, the power storage device exterior material may have a recess, and the battery element may be accommodated in the recess. In this case, the battery element can be accommodated to have a higher energy density.

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage apparatus provided with the exterior material for electrical storage devices which reduces the curvature amount after a shaping | molding process, and the said electrical storage device exterior material can be provided, maintaining the outstanding moldability.

It is a schematic sectional drawing of the exterior material for electrical storage apparatuses which concerns on one Embodiment of this invention. It is a figure which shows the exterior material after a shaping | molding process typically, (a) is the perspective view, (b) followed the bb line | wire of the exterior material after the shaping | molding process shown to (a). It is sectional drawing. It is a perspective view which shows the process of manufacturing a secondary battery using an exterior material, (a) shows the state which prepared the exterior material for electrical storage apparatuses, (b) is the electrical storage apparatus shape-processed by the emboss type The state which prepared the exterior material for a battery and the battery element is shown, (c) shows the state which folded the part of the exterior material for electrical storage devices, and heat-sealed the peripheral part.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment.

[Exterior Material 10 for Power Storage Device]
First, a power storage device exterior material 10 according to the present embodiment (hereinafter also simply referred to as “exterior material 10”) will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of a power storage device exterior material according to an embodiment of the present invention. The exterior material 10 covers battery elements such as a positive electrode, a separator, a negative electrode, and an electrolyte solution to prevent moisture from entering into the battery, or a substance generated inside (for example, hydrofluoric acid generated by moisture penetration) ) To prevent leakage to the outside. As shown in FIG. 1, the exterior material 10 includes a base material layer 11 including a biaxially stretched film, a metal foil layer 13 disposed on the base material layer 11, and a metal foil layer 13. The inner layer 18 which sandwiches the metal foil layer 13 with the layer 11 is provided as a basic configuration. In the exterior material 10, a base material adhesive layer 12 may be disposed between the base material layer 11 and the metal foil layer 13. That is, the base material adhesive layer 12 disposed on the base material layer 11 may be further provided, and the metal foil layer 13 may be disposed on the base material layer 11 via the base material adhesive layer 12.

  In the exterior material 10, a corrosion prevention treatment layer 14 and / or an inner layer adhesive layer 15 may be disposed between the metal foil layer 13 and the inner layer 18. That is, the exterior material 10 further includes a corrosion prevention treatment layer 14 and / or an inner layer adhesion layer 15 disposed on the metal foil layer 13, and the inner layer 18 is interposed via the corrosion prevention treatment layer 14 and / or the inner layer adhesion layer 15. It may be arranged on the metal foil layer 13. When both the corrosion prevention treatment layer 14 and the inner layer adhesion layer 15 are arranged, the corrosion prevention treatment layer 14 is arranged on the metal foil layer 13 side, and the inner layer adhesion layer 15 is arranged on the inner layer 18 side.

  Further, the inner layer 18 includes at least one intermediate layer (biaxially stretched polyolefin film) 16. The inner layer 18 may further include a sealant layer 17 having heat fusion properties. That is, the inner layer 18 is a laminated structure of the intermediate layer 16 and the sealant layer 17, and the biaxially stretched polyolefin film of the intermediate layer 16 may be disposed between the sealant layer 17 and the metal foil layer 13. . In the exterior material 10, the base material layer 11 may be the outermost layer, and the sealant layer 17 may be the innermost layer. That is, the packaging material 10 may be a container for a power storage device, and may contain the battery element of the power storage device with the base material layer 11 on the outside and the sealant layer 17 on the inside.

  Next, each layer constituting the exterior material 10 will be described in more detail.

[Base material layer 11]
The base material layer 11 is a layer for imparting heat resistance to the exterior material 10 in a pressurization heat fusion process, which will be described later when manufacturing the power storage device, to suppress the generation of pinholes that may occur during processing or distribution. It is. The base material layer 11 includes at least one layer of a biaxially stretched polyester film and a biaxially stretched polyamide film as a biaxially stretched film. When the base material layer 11 includes at least one of a biaxially stretched polyester film and a biaxially stretched polyamide film, the metal foil layer 13 is protected at the time of molding and the breakage is suppressed. Further, from the viewpoint of excellent puncture strength or impact strength, the biaxially stretched polyester film is more preferably a biaxially stretched polyethylene terephthalate (PET) film, and the biaxially stretched polyamide film is a biaxially stretched nylon (ONy) film. It is more preferable. In addition, the base material layer 11 may be comprised including both layers of the biaxially stretched polyester film and the biaxially stretched polyamide film.

  The thickness of the base material layer 11 is preferably 15 μm to 35 μm, for example, and more preferably 20 μm to 30 μm. When the thickness of the base material layer 11 is 15 μm or more, the protective effect of the metal foil layer 13 is improved, and even if stress is applied by the molding process, it is difficult to break, and more excellent moldability can be obtained. When the thickness of the base material layer 11 is 35 μm or less, it is possible to reduce the amount of warpage particularly toward the base material layer 11 after the molding process. Moreover, 1.5 to 3.5 times is preferable and, as for the draw ratio of the base material layer 11, 2 to 3 times is more preferable. If the draw ratio is 1.5 times or more, sufficient strength can be obtained in the molding process. If the draw ratio is 3.5 times or less, sufficient ductility can be obtained in the molding process.

Further, the upper yield strength in a tensile test of the base layer 11 is preferably 70N / mm ² or more 150 N / mm ² or less, more preferably 90 N / mm ² or more 130N / mm ² or less. If the upper yield point strength is 70 N / mm ² or more, sufficient strength can be obtained in the molding process. If the upper yield point strength is 150 N / mm ² or less, the amount of warpage after molding can be reduced.

[Base Adhesive Layer 12]
The substrate adhesive layer 12 is a layer that bonds the substrate layer 11 and the metal foil layer 13 together. The adhesive constituting the substrate adhesive layer 12 is a two-component curable polyurethane adhesive containing a main agent such as polyester polyol, polyether polyol, and acrylic polyol, and a curing agent such as aromatic polyisocyanate. Is preferred. The base material adhesive layer 12 is a two-component curable aromatic polyester urethane adhesive containing a main component made of polyester polyol and a curing agent made of aromatic polyisocyanate from the viewpoint of increasing the tensile elongation of the exterior material 10. It is more preferable that After applying the urethane adhesive, for example, by aging for 4 days or more at 40 ° C., the reaction of the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds, and the base layer 11 and the metal foil layer 13 Can be firmly bonded.

  The thickness of the base adhesive layer 12 is preferably, for example, 1 μm to 10 μm, and more preferably 3 μm to 7 μm, from the viewpoint of adhesive strength, followability, workability, and the like.

[Metal foil layer 13]
The metal foil layer 13 is made of, for example, an aluminum foil from the viewpoint of workability such as moisture resistance and spreadability and cost. The aluminum foil preferably contains iron from the viewpoint of excellent pinhole resistance and extensibility during molding. As content of iron in aluminum foil, it is preferred that it is 0.5 mass%-5.0 mass%, and it is more preferred that it is 0.7 mass%-2.0 mass%.

  The thickness of the metal foil layer 13 is preferably, for example, 20 μm to 60 μm, and more preferably 30 μm to 50 μm, from the viewpoint of barrier properties, pinhole resistance, and moldability.

[Corrosion prevention treatment layer 14]
The corrosion prevention treatment layer 14 suppresses the corrosion of the metal foil layer 13 due to the electrolytic solution or hydrofluoric acid generated by the reaction between the electrolytic solution and moisture, and increases the adhesion between the metal foil layer 13 and the inner adhesive layer 15. Play a role.

  The corrosion prevention treatment layer 14 is preferably a coating film formed by a coating type or immersion type acid resistant corrosion prevention treatment agent. This coating film is excellent in the effect of preventing corrosion of the metal foil layer 13 with respect to acid. Moreover, since the adhesive force between the metal foil layer 13 and the inner layer adhesive layer 15 is further strengthened by the anchor effect, excellent resistance to power storage device elements such as an electrolytic solution can be obtained. Moreover, the corrosion prevention process layer 14 may be added between the base-material adhesive layer 12 and the metal foil layer 13 according to the function required.

  The coating film of the corrosion inhibitor is, for example, ceriazol treatment with a corrosion inhibitor consisting of cerium oxide, phosphate and various thermosetting resins, and chromate, phosphate, fluoride and various thermosets. Formed by a chromate treatment with a corrosion prevention treatment agent composed of a conductive resin. The corrosion prevention treatment layer 14 is not limited to the above-described coating film as long as the corrosion resistance of the metal foil layer 13 is sufficiently obtained. The corrosion prevention treatment layer 14 may be a coating film formed by, for example, a phosphate treatment and a boehmite treatment.

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

[Inner layer adhesive layer 15]
The inner layer adhesive layer 15 is a layer for bonding the metal foil layer 13 on which the corrosion prevention treatment layer 14 is formed and the inner layer 18. The exterior material 10 is roughly divided into a thermal laminate configuration and a dry laminate configuration depending on the adhesive component forming the inner layer adhesive layer 15.

  The adhesive component constituting the inner adhesive layer 15 in the thermal laminate configuration is preferably an acid-modified polyolefin resin or an epoxy-modified polyolefin resin obtained by graft-modifying a polyolefin resin with an acid or an epoxy compound. Since the acid-modified polyolefin resin has a polar group introduced into a part of the non-polar polyolefin resin, the acid-modified polyolefin resin has a polarity with the inner layer 18 when it is composed of a non-polar polyolefin resin film or the like. It is possible to firmly adhere to both of the corrosion prevention treatment layers 14 having a large amount. In addition, the use of the acid-modified polyolefin-based resin improves the resistance of the exterior material 10 to the power storage device element such as the electrolyte, and even if hydrofluoric acid is generated inside the battery, the adhesion due to the deterioration of the inner layer adhesive layer 15 is improved. Easy to prevent decline.

  Examples of the polyolefin resin used in the production of the acid-modified polyolefin resin include low density, medium density and high density polyethylene; ethylene-α olefin copolymer; polypropylene; and propylene-α olefin copolymer. Can be mentioned. In the case of the copolymer, the polyolefin resin may be a block copolymer or a random copolymer.

  Examples of the acid-modifying method in the polyolefin-based resin include a method of graft-modifying with an acid and a method of copolymerizing an acid-containing monomer. Examples of the acid that modifies the polyolefin resin include carboxylic acid and acid anhydride, and the acid is preferably maleic anhydride. The inner adhesive layer 15 preferably contains maleic anhydride-modified polyolefin resin, and more preferably contains maleic anhydride-modified polypropylene. By including the maleic anhydride-modified polyolefin-based resin in the inner layer adhesive layer 15, it becomes easy to maintain the adhesive force between the inner layer 18 and the metal foil layer 13 even when the electrolytic solution penetrates.

  The modification rate of the polyolefin resin by acid (for example, the mass of the portion derived from maleic anhydride relative to the total mass of maleic anhydride-modified polypropylene) is preferably 0.1% by mass to 20% by mass, More preferably, the content is from 5% by mass to 5% by mass.

  The inner adhesive layer 15 having a heat laminate structure preferably further contains a styrene-based or olefin-based elastomer. Thereby, it is easy to suppress that the inner layer adhesive layer 15 is cracked and whitened during cold molding, and it can be expected that the adhesion is improved by improving the wettability and the film forming property is improved by reducing the anisotropy. These elastomers are preferably dispersed in a nanometer order in a polyolefin resin or compatible with the polyolefin resin.

  The polyolefin resin may constitute the inner layer adhesive layer 15 alone, or may constitute the inner layer adhesive layer 15 by combining two or more kinds.

  The inner adhesive layer 15 having a heat laminate structure can be manufactured by extruding the adhesive component with an extrusion device. The melt flow rate (MFR) of the adhesive component of the inner layer adhesive layer 15 having a heat laminate structure is preferably 4 to 30 g / 10 min under the conditions of 230 ° C. and a load of 2.16 kgf. The thickness of the inner adhesive layer 15 having a heat laminate structure is preferably 5 μm to 40 μm, for example.

  Examples of the adhesive component in the inner-layer adhesive layer 15 having a dry laminate structure include the same two-component curable polyurethane adhesive as that described for the base adhesive layer 12. Since the inner layer adhesive layer 15 having a dry laminate structure has a highly hydrolyzable bonding portion such as an ester group and a urethane group, the inner layer adhesive layer 15 has a heat laminate structure for applications requiring higher reliability. Preferably there is.

[Intermediate layer 16]
The intermediate layer 16 increases the upper yield point strength in the tensile test of the inner layer 18, approaches the upper yield point strength of the base material layer 11, and reduces the amount of warpage particularly toward the base material layer 11 after the molding process. Is a layer. The intermediate layer 16 is made of a biaxially stretched polyolefin film, which is a biaxially stretched film made of a polyolefin resin. Examples of the polyolefin-based resin include low density, medium density and high density polyethylene; ethylene-α olefin copolymer; polypropylene; and propylene-α olefin copolymer. In the case of the copolymer, the polyolefin resin may be a block copolymer or a random copolymer.

The upper yield strength in the tensile test of the biaxially stretched polyolefin film of the intermediate layer 16 is preferably 20 N / mm ² or more and 100 N / mm ² or less, and more preferably 40 N / mm ² or more and 80 N / mm ² or less. preferable. If the upper yield point strength is 20 N / mm ² or more, the amount of warping after molding can be reduced. If the upper yield point strength is 100 N / mm ² or less, excessive molecular orientation can be avoided, and the occurrence of microcracks in the intermediate layer 16 due to stretching during molding can be suppressed. The difference between the upper yield point strength and the upper yield point strength in the tensile test of the base material layer 11 is preferably within 50 N / mm ² .

  The intermediate layer 16 may be a single layer film or a multilayer film, and may be selected according to a required function. Moreover, the intermediate | middle layer 16 may contain various additives, such as a flame retardant, a slip agent, an antiblocking agent, antioxidant, a light stabilizer, and a tackifier. Further, the intermediate layer 16 may be installed as a sealant layer, and the sealant layer 17 may be omitted if it also functions as a sealant layer.

  The intermediate layer 16 has high strength both in the vertical direction and in the horizontal direction by being biaxially stretched. The stretching ratio of the intermediate layer 16 is preferably 3 to 10 times, and more preferably 4 to 8 times. If the draw ratio is 3 times or more, a sufficient upper yield strength can be obtained, and the amount of warpage after molding can be reduced. Moreover, if a draw ratio is 10 times or less, excessive molecular orientation can be avoided and generation | occurrence | production of the microcrack by the extending | stretching at the time of a shaping | molding process can be prevented.

  The stretching ratio of the biaxially stretched polyolefin film of the intermediate layer 16 is preferably larger than the stretching ratio of the biaxially stretched film of the base material layer 11. That is, the draw ratio of the biaxially stretched polyolefin film of the intermediate layer 16 is preferably 1 or more times the stretch ratio of the biaxially stretched film of the base material layer 11. The stretching ratio of the biaxially stretched polyolefin film of the intermediate layer 16 is, for example, 3 to 10 times, whereas the stretching ratio of the biaxially stretched film of the base layer 11 is, for example, 2 to 3 times. Is done.

  The thickness of the biaxially stretched polyolefin film constituting the intermediate layer 16 is preferably 20 μm to 50 μm, for example, and more preferably 30 μm to 40 μm. When the thickness of the intermediate layer 16 is 20 μm or more, the amount of warpage toward the base material layer 11 after the molding process can be reduced. Moreover, when the thickness of the intermediate layer 16 is 50 μm or less, the amount of warpage toward the inner layer 18 after the molding process can be reduced. The intermediate layer 16 is preferably thicker than the base material layer 11. Even if the polyolefin is biaxially stretched, the upper yield point strength tends to be insufficient with respect to the upper yield point strength of the base material layer 11. By adjusting the thickness of the intermediate layer 16, the upper yield point strength of the intermediate layer 16 can be made closer to the upper yield point strength of the base material layer 11. Can be more reliably reduced.

[Sealant layer 17]
The sealant layer 17 is a layer that imparts sealing properties to the exterior material 10 by heat sealing. Examples of the sealant layer 17 include a resin film made of a polyolefin resin or an acid-modified polyolefin resin obtained by graft-modifying a polyolefin resin with an acid such as maleic anhydride. Examples of the polyolefin-based resin include low density, medium density and high density polyethylene; ethylene-α olefin copolymer; polypropylene; and propylene-α olefin copolymer. In the case of the copolymer, the polyolefin resin may be a block copolymer or a random copolymer. Examples of the acid-modified polyolefin-based resin include those similar to those exemplified in the inner layer adhesive layer 15.

  The sealant layer 17 may be a single layer film or a multilayer film, and may be selected according to a required function. The sealant layer 17 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

  If the sealant layer 17 is formed of the same material as that of the intermediate layer 16, the adhesion between the sealant layer 17 and the intermediate layer 16 is increased and it is difficult to peel off. For example, when the biaxially stretched polyolefin film of the intermediate layer 16 is a biaxially stretched polypropylene film, such an effect can be obtained by forming the sealant layer 17 from a polypropylene resin.

  The sealant layer 17 is preferably thinner than the intermediate layer 16. The thickness of the sealant layer 17 may be a thickness that is necessary for exhibiting the performance of imparting sealing properties to the exterior material 10 by heat sealing, and the necessity of increasing the thickness further is low. On the other hand, the thickness of the intermediate layer 16 is preferably increased in order to balance the inner layer 18 with the base material layer 11. Therefore, the sealant layer 17 is made thinner than the intermediate layer 16 to suppress the total thickness of the exterior material 10, and the intermediate layer 16 is made thicker than the sealant layer 17 to increase the upper yield strength of the inner layer 18. Is preferred.

[Method for Manufacturing Exterior Material 10]
Next, the manufacturing method of the exterior material 10 is demonstrated. However, the manufacturing method of the exterior material 10 is not limited to the following method.

As a manufacturing method of the exterior material 10, the method which has following process S11-S14 is mentioned, for example.
Step S11: A step of forming the corrosion prevention treatment layer 14 on one surface of the metal foil layer 13.
Step S12: A step of forming the base material layer 11 on the other surface of the metal foil layer 13 via the base material adhesive layer 12.
Step S13: A step of forming the intermediate layer 16 on the corrosion prevention treatment layer 14 via the inner layer adhesive layer 15.
Step S14: A step of forming the sealant layer 17 on the intermediate layer 16.

[Step S11]
The corrosion prevention treatment layer 14 is formed on one surface of the metal foil layer 13 by applying a corrosion prevention treatment agent on one surface of the metal foil layer 13 and drying, for example. Examples of the anti-corrosion treatment agent include the above-described anti-corrosion treatment agent for ceriazole treatment, and anti-corrosion 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.

[Step S12]
The base material layer 11 is bonded to the other surface of the metal foil layer 13 by a technique such as dry lamination using an adhesive that forms the base material adhesive layer 12. Formed on the other surface. In order to improve the adhesion between the base material layer 11 and the metal foil layer 13, the laminate after the base material layer 11 is formed may be aged (cured) in the range of room temperature to 100 ° C. The aging time is, for example, 1 to 10 days.

[Step S13]
An intermediate layer 16 is formed via an inner layer adhesive layer 15 on the corrosion prevention treatment layer 14 side of the laminate in which at least the metal foil layer 13 and the corrosion prevention treatment layer 14 are laminated. The intermediate layer 16 may be laminated by dry lamination, sandwich lamination, or the like. The intermediate layer 16 is more preferably laminated by sandwich lamination, for example, from the viewpoint of improving adhesiveness.

[Step S14]
A sealant layer 17 is formed on the intermediate layer 16. The sealant layer 17 is preferably formed by extrusion molding. In addition, thermal lamination may be performed after the extrusion to enhance the adhesion.

  The exterior material 10 can be obtained by the steps S11 to S14 described above. In addition, the process sequence of the manufacturing method of the cladding | exterior_material 10 is not limited to the method of implementing said process S11-S14 sequentially. For example, step S11 may be performed after performing step S12, step S13, or step S14.

[Power storage device]
Next, a power storage device including the exterior material 10 as a container will be described. The power storage device includes a power storage device exterior material 10 that is folded so that the inner layers 18 are heat-sealed, and a battery element 1 that is disposed inside the folded power storage device exterior material 10 (FIG. 3). The power storage device exterior material 10 has a recess, and the battery element 1 is accommodated in the recess. The container may be obtained by stacking two exterior members 10 with the inner layers 18 facing each other, and heat-sealing the peripheral portions of the stacked exterior members 10. It may be obtained by folding back and overlapping in the vicinity of the part, and similarly heat-sealing the peripheral part of the exterior material 10. Examples of the power storage device include secondary batteries such as lithium ion batteries, nickel metal hydride batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors.

  Next, a method for manufacturing a power storage device using the exterior material 10 described above will be described with reference to FIGS. Here, the case where the secondary battery 40 is manufactured using the embossed type exterior material 30 as an example of the exterior material 10 after the molding process will be described.

  The embossed type exterior member 30 has a molding process area 32 as a concave portion having a rectangular shape in plan view. As shown in FIG. 3A and FIG. 3B, the molding area 32 presses a pressing member having, for example, a rectangular pressure surface against a part of the exterior material 10 in the thickness direction. Formed with. Further, the pressing position, that is, the molding process area 32 is formed at a position biased to one end portion in the longitudinal direction of the exterior material 10 from the center S of the exterior material 10 cut into a rectangle. As a result, the other end side where the molding area 32 is not formed after the molding process can be folded back to form the lid 34.

  After performing such a molding process, the secondary battery 40 is manufactured by performing the following steps on the embossed type exterior member 30. That is, after forming the molding process area 32 as a recess as in the above-described process, the battery element 1 is disposed in the recess as shown in FIGS. The material 30 is folded and overlapped so that the inner layers 18 face each other, more specifically, the sealant layers 17 face each other. The stacked embossed type exterior member 30 is heat-sealed at the two sides of the peripheral portion with the tab lead 2 extending from the battery element 1 being sandwiched. Thereafter, in a vacuum state, an electrolyte is injected from the remaining one side, and the remaining one side is heat-sealed and sealed to obtain the secondary battery 40. The power storage device using the power storage device exterior material of the present invention is not limited to the one manufactured by the above method.

  According to such an exterior material 10, the intermediate layer 16 of the inner layer 18 is formed of a biaxially stretched polyolefin while maintaining excellent moldability by making the base material layer 11 a biaxially stretched polyester film or a biaxially stretched polyamide film. By using a film, it is possible to reduce the amount of warping after molding. That is, in the exterior material 10, since the base material layer 11 includes at least one of a biaxially stretched polyester film and a biaxially stretched polyamide film, the base material layer 11 protects the metal foil layer 13 during molding, Since breakage of the metal foil layer 13 can be suppressed, excellent moldability can be maintained. Moreover, in the exterior material 10, since the inner layer 18 includes the biaxially stretched polyolefin film, the upper yield point strength in the tensile test of the inner layer 18 provided on the battery element 1 side is increased, and the upper yield point of the base material layer 11 is increased. Can be close to strength. Thus, by bringing the upper yield point strengths of the base material layer 11 and the inner layer 18 close to each other, the balance of force is warped when each layer of the exterior material 10 stretched by the molding process returns to the state before stretching. Can be suppressed, and the amount of warpage of the exterior material 10 after molding can be reduced.

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

[Preparation of materials used]
First, the following were prepared as materials for the exterior material 10 (Example and Comparative Example) having the configuration shown in FIG. Specifically, the base materials A-1 to A-7 for the base material layer 11, the adhesive for the base material adhesive layer 12, the metal foil layer 13, the treatment agent for the corrosion prevention treatment layer 14, the inner layer adhesive layer 15 Resin, films F-1 to F-10 for intermediate layer 16, and resin for sealant layer 17 were prepared.
(Base material layer 11)
Base material A-1: Biaxially stretched nylon (Ny) film (thickness 25 μm, stretch ratio 2.5 times, upper yield strength 2.25 N / mm (90 N / mm ² ))
Base material A-2: Biaxially stretched nylon (Ny) film (thickness 15 μm, stretch ratio 2.5 times, upper yield strength 1.35 N / mm (90 N / mm ² ))
Base material A-3: Biaxially stretched polyethylene terephthalate (PET) film (thickness 25 μm, stretch ratio 2.5 times, upper yield strength 2.25 N / mm (90 N / mm ² ))
Base material A-4: Biaxially stretched nylon (Ny) film (thickness 15 μm, stretch ratio 2.5 times) + interlayer adhesive layer (thickness 8 μm) + biaxially stretched polyethylene terephthalate (PET) film (thickness 12 μm) , Draw ratio 2.5 times), total thickness 35 μm, upper yield strength 2.8 N / mm (80 N / mm ² )
Base material A-5: Biaxially stretched polyethylene terephthalate (PET) film (thickness 12 μm, stretch ratio 2.5 times, upper yield strength 1.08 N / mm (90 N / mm ² ))
Base material A-6: Biaxially stretched nylon (Ny) film (thickness 25 μm, stretch ratio 2.5 times) + interlayer adhesive layer (thickness 8 μm) + biaxially stretched polyethylene terephthalate (PET) film (thickness 12 μm) , Draw ratio 2.5 times), total thickness 45 μm, upper yield point strength 3.825 N / mm (85 N / mm ² )
Base material A-7: Unstretched nylon (Ny) film (thickness 30 μm, upper yield point strength 0.15 N / mm (5 N / mm ² ))
Here, the draw ratio mentioned above is the same value in both the vertical direction and the horizontal direction. The upper yield point strength is the upper yield point strength (N / mm) per 1 mm width, and the values in parentheses are the upper yield point strength (N / mm ² ) per 1 mm width and 1 mm thickness.
(Base material adhesive layer 12)
-Adhesive B-1: Polyester urethane adhesive (metal foil layer 13)
Metal foil C-1: Soft aluminum foil 8079 material (Toyo Aluminum Co., Ltd., thickness 40 μm)
(Corrosion prevention treatment layer 14)
Treatment agent D-1: Treatment agent for coating-type ceriazole treatment mainly composed of cerium oxide, phosphoric acid, and acrylic resin (inner layer adhesive layer 15)
Adhesive resin E-1: Polypropylene resin graft-modified with maleic anhydride (trade name “Admer”, manufactured by Mitsui Chemicals)
(Intermediate layer 16)
Film F-1: Biaxially stretched polypropylene film (thickness 35 μm, stretch ratio 6 times, upper yield point strength 2.205 N / mm (63 N / mm ² ))
Film F-2: Biaxially stretched polypropylene film (thickness 20 μm, stretch ratio 6 times, upper yield point strength 1.26 N / mm (63 N / mm ² ))
Film F-3: Biaxially stretched polypropylene film (thickness 50 μm, stretch ratio 6 times, upper yield point strength 3.15 N / mm (63 N / mm ² ))
Film F-4: Biaxially stretched polypropylene film (thickness 35 μm, stretch ratio 3 times, upper yield strength 1.4 N / mm (40 N / mm ² ))
Film F-5: Biaxially stretched polypropylene film (thickness 35 μm, stretch ratio 10 times, upper yield strength 3.15 N / mm (90 N / mm ² ))
Film F-6: Biaxially stretched polypropylene film (thickness 10 μm, stretch ratio 6 times, upper yield strength 0.63 N / mm (63 N / mm ² ))
Film F-7: Biaxially stretched polypropylene film (thickness 60 μm, stretch ratio 6 times, upper yield strength 3.78 N / mm (63 N / mm ² ))
Film F-8: Biaxially stretched polypropylene film (thickness 35 μm, stretch ratio 2 times, upper yield strength 1.05 N / mm (30 N / mm ² ))
Film F-9: Biaxially stretched polypropylene film (thickness 35 μm, stretch ratio 11 times, upper yield point strength 3.5 N / mm (100 N / mm ² ))
Film F-10: unstretched polypropylene film (thickness 35 μm, upper yield strength 0.175 N / mm (5 N / mm ² ))
Here, the draw ratio is the same value in both the vertical direction and the horizontal direction. The upper yield point strength is the upper yield point strength (N / mm) per 1 mm width, and the values in parentheses are the upper yield point strength (N / mm ² ) per 1 mm width and 1 mm thickness.
(Sealant layer 17)
Extruded resin G-1: Polypropylene resin (thickness 20 μm)

[Creation of exterior material 10]
The treatment agent D-1 was applied to one surface of the metal foil C-1 to be the metal foil layer 13 and dried to form a corrosion prevention treatment layer 14. Next, on the surface of the metal foil layer 13 opposite to the corrosion prevention treatment layer 14, the base materials A-1 to A-7 are formed by a dry laminating method using the adhesive B-1 as the base material adhesive layer 12. Any one was bonded, and then aging was performed at 60 ° C. for 6 days. Here, the base material A-4 and the base material A-6 were laminated with a biaxially stretched nylon (Ny) film and the metal foil layer 13 via an adhesive B-1, and then laminated biaxially stretched nylon ( Ny) A biaxially stretched polyethylene terephthalate (PET) film was bonded to the film as an interlayer adhesive layer (thickness 8 μm) using adhesive B-1, and aging was performed.

  Next, an adhesive resin E-1 is extruded by an extrusion device to the corrosion prevention treatment layer 14 side of the obtained laminate to form an inner layer adhesive layer 15, and films F-1 to F-10 are bonded together to sandwich lamination. Thus, the intermediate layer 16 was formed. Thereafter, the extrusion resin G-1 was extruded on the intermediate layer 16 by an extrusion device to form the sealant layer 17, and the exterior material 10 was created by thermocompression bonding at 190 ° C. to the obtained laminate.

Examples 1 to 14 and Comparative Examples 1 and 2 of the exterior material 10 thus created were configured as shown in Table 1 below. The thickness of the base material layer 11 is indicated by the total thickness.

[Evaluation of warpage after molding]
Next, each exterior material 10 of Examples 1 to 14 and Comparative Examples 1 to 2 is cut into a blank shape of 120 mm × 260 mm, and placed in a molding apparatus so that the sealant layer 17 faces upward, and the room temperature is 23 ° C. The molding depth was set to 3 mm under a molding environment with a dew point temperature of −35 ° C., and cold molding was performed from the sealant layer 17 side. A punch having a shape of 70 mm × 80 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 clearance between the punch and the die was 0.2 mm. Moreover, in the state which put the shaping | molding process area 32 in the one end part of the longitudinal direction of a blank shape so that it may become 25 mm from one edge part of the longitudinal direction of a blank shape, and both ends of a transversal direction, respectively. Formed.

Subsequently, for each of the molded exterior materials 10, the sample warped to the base material layer 11 side has the base material layer 11 side as an upper surface, and the sample warped to the sealant layer 17 side has the sealant layer 17 side as an upper surface. Then, it was allowed to stand for 60 minutes in an environment having a room temperature of 23 ° C. and a dew point temperature of −35 ° C., and the amount of warping (distance from the stationary surface) of the edge of the unmolded area was measured. Evaluation criteria were performed according to the following.
“◎”: The amount of warpage was less than 50 mm.
“◯”: The amount of warpage was 50 mm or more and less than 100 mm.
“×”: The amount of warpage was 100 mm or more.

[Evaluation of molding depth]
Moreover, each exterior material 10 of Examples 1-14 and Comparative Examples 1-2 is cut into a blank shape of 150 mm × 190 mm, and is placed in a molding apparatus so that the sealant layer 17 faces upward, at room temperature of 23 ° C., While changing the molding depth in a molding environment having a dew point temperature of -35 ° C., cold molding was performed from the sealant layer 17 side, 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 clearance between the punch and the die was 0.2 mm.

Evaluation criteria were performed according to the following.
“A”: Deep drawing with a molding depth of 6 mm or more is possible without causing breakage and cracks.
“◯”: Deep drawing with a molding depth of 4 mm or more and less than 6 mm is possible without causing breakage or cracks.
“X”: Breaking and cracking occur in deep drawing with a molding depth of less than 4 mm.

[Evaluation of microcracks after molding]
Moreover, each exterior material 10 of Examples 1-14 and Comparative Examples 1-2 is cut into a blank shape of 120 mm × 260 mm, and is placed in a molding apparatus so that the sealant layer 17 faces upward, at room temperature of 23 ° C., The molding depth was set to 3 mm under a molding environment with a dew point temperature of −35 ° C., and cold molding was performed from the sealant layer 17 side. A punch having a shape of 70 mm × 80 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 clearance between the punch and the die was 0.2 mm. In addition, the molding area is formed in a state of being brought to one end portion in the longitudinal direction of the blank shape so that it is 25 mm from one end portion in the longitudinal direction of the blank shape and both ends in the lateral direction. went.

  After forming the molding process area 32, the exterior material 10 was folded back and overlapped so that the sealant layer 17 faced, and the two sides were heat-sealed. Among them, a tab lead 2 was interposed on one side. Thereafter, in a vacuum state, an electrolytic solution was injected from the remaining one side, and the remaining one side was heat-sealed and sealed to prepare a sample for evaluation. The electrolytic solution was in contact with the intervening tab lead 2 so that the inside of the molding processing area 32 and the outside were connected via the tab lead 2.

In the evaluation, the tab lead 2 and the metal foil of the exterior material 10 were connected to a terminal, a voltage of 25 V was applied for 30 minutes, and the insulation resistance value was measured to evaluate the insulation degradation due to microcracks. Evaluation criteria were performed according to the following.
“◎”: Insulation resistance value is 2.5 GΩ or more “O”: Insulation resistance value is 200 MΩ or more and less than 2.5 GΩ “×”: Insulation resistance value is less than 200 MΩ

Table 2 below shows the evaluation results of the warp direction, the warp amount, the molding depth, and the microcracks in each of the exterior materials of Examples 1 to 14 and Comparative Examples 1 and 2.

  As shown in Table 2, the base material layer 11 includes at least one of a biaxially stretched nylon (Ny) film and a biaxially stretched polyethylene terephthalate (PET) film, and has a total thickness (thickness) of 15 μm or more and 35 μm or less. In Examples 1 to 8 using a biaxially stretched polypropylene film having a thickness of 20 μm or more and 50 μm or less and a stretching ratio of 3 times or more and 10 times or less for the intermediate layer 16, the amount of warpage after the molding process was greatly increased It was confirmed that it could be reduced. Moreover, in Examples 1 to 8, it was possible to perform deep-drawing with a molding depth of 6 mm or more and to confirm that the moldability was excellent because there was no decrease in insulating properties due to the intermediate layer microcracks. .

  In Example 13 in which a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 12 μm was used for the base material layer 11, the amount of warpage after molding could be reduced. However, due to insufficient thickness of the base material layer 11, the effect of reducing the amount of warpage did not reach that of Examples 1 to 8. Further, in terms of molding depth, the moldability did not reach Examples 1-8. In Example 13, there was no tendency for the insulation to decrease due to microcracks.

  In Example 14 using a biaxially stretched nylon (Ny) film (25 μm) + interlayer adhesive layer (8 μm) + biaxially stretched polyethylene terephthalate (PET) film (12 μm) having a total thickness of 45 μm as the base material layer 11, The amount of warping after molding could be reduced. However, since the base material layer 11 was thick and the upper yield point strength of the base material layer 11 was increased, the effect of reducing the amount of warp did not reach that of Examples 1-8. In Example 14, deep drawing with a molding depth of 6 mm or more was possible, and there was no tendency for the insulation to decrease due to microcracks.

  In Example 11 in which a biaxially stretched polypropylene film having a stretch ratio of 2 was used for the intermediate layer 16, the amount of warpage after molding could be reduced. However, since the draw ratio of the intermediate layer 16 was low and the upper yield point strength of the intermediate layer 16 was not sufficiently obtained, the effect of reducing the amount of warp did not reach Examples 1-8. In Example 11, deep drawing with a molding depth of 6 mm or more was possible, and there was no tendency for the insulation to decrease due to microcracks.

  In Example 12 in which a biaxially stretched polypropylene film having a stretch ratio of 11 times was used for the intermediate layer 16, the amount of warpage after molding could be reduced. However, since the stretch ratio of the intermediate layer 16 was high and the polypropylene was strongly molecularly oriented, microcracks were generated by stretching in the molding process, resulting in a decrease in the insulating properties of the inner layer 18. In Example 12, deep drawing with a molding depth of 6 mm or more was possible.

  Further, in Example 9 in which a biaxially stretched polypropylene film having a thickness of 10 μm was used for the intermediate layer 16, the amount of warpage after the molding process could be reduced. However, since the thickness of the intermediate layer 16 is thin and the upper yield point strength of the intermediate layer 16 cannot be obtained sufficiently, the effect of reducing the amount of warp did not reach that of Examples 1-8. In Example 9, deep drawing with a molding depth of 6 mm or more was possible, and there was no tendency for the insulation to decrease due to microcracks.

  Further, in Example 10 in which a biaxially stretched polypropylene film having a thickness of 60 μm was used for the intermediate layer 16, the amount of warpage after the molding process could be reduced. However, since the thickness of the intermediate layer 16 was thick and the upper yield point strength of the intermediate layer 16 was too high, the effect of reducing the amount of warp did not reach Examples 1-8. In Example 10, deep drawing with a molding depth of 6 mm or more was possible, and there was no tendency for the insulation to decrease due to microcracks.

  On the other hand, in Comparative Example 1 in which an unstretched nylon (Ny) film was used for the base material layer 11, the upper yield point strength of the base material layer 11 was not obtained, and the amount of warping after the molding process was greatly increased. Moreover, since the protective effect of the metal foil layer 13 was not obtained, the moldability was greatly deteriorated in terms of the molding depth.

  Moreover, in the comparative example 2 which used the unstretched polypropylene film for the intermediate | middle layer 16, the upper yield point intensity | strength of the intermediate | middle layer 16 was not obtained, and the curvature amount after a shaping | molding process became large significantly.

  From the above, if a film including at least one of a biaxially stretched nylon (Ny) film and a biaxially stretched polyethylene terephthalate (PET) film is used for the base material layer 11, and a biaxially stretched polypropylene film is used for the intermediate layer 16, It was found that the amount of warpage after molding could be reduced while maintaining excellent moldability.

DESCRIPTION OF SYMBOLS 1 ... Battery element, 10 ... Exterior material for electrical storage devices, 11 ... Base material layer, 13 ... Metal foil layer, 16 ... Intermediate layer (biaxially stretched polyolefin film), 17 ... Sealant layer, 18 ... Inner layer, 30 ... Embossed type Exterior material (exterior material for power storage device), 32... Molding area (recessed portion), 40... Secondary battery (power storage device).

Claims (11)

A base material layer comprising a biaxially stretched film;
A metal foil layer disposed on the substrate layer;
An inner layer disposed on the metal foil layer and sandwiching the metal foil layer with the base material layer,
The base material layer includes at least one of a biaxially stretched polyester film and a biaxially stretched polyamide film as the biaxially stretched film,
The inner layer, at least one layer saw including a biaxially oriented polyolefin film,
The value obtained by subtracting the upper yield point strength of the biaxially oriented polyolefin film from the upper yield point strength of the base material layer is −1.53 N / mm or more and 1.62 N / mm or less ,
Exterior material for power storage devices.   The power storage device exterior material according to claim 1, wherein a stretching ratio of the biaxially stretched polyolefin film is 3 times or more and 10 times or less in both the vertical direction and the horizontal direction.   The packaging material for a power storage device according to claim 1 or 2, wherein a stretch ratio of the biaxially stretched polyolefin film is larger than a stretch ratio of the biaxially stretched film of the base material layer. The packaging material for a power storage device according to any one of claims 1 to 3, wherein an upper yield point strength of the biaxially stretched polyolefin film is 40 N / mm ² or more.   The power storage device exterior material according to any one of claims 1 to 4, wherein the biaxially stretched polyolefin film is thicker than the base material layer. The thickness of the base material layer is 15 μm or more and 35 μm or less,
The packaging material for a power storage device according to any one of claims 1 to 5, wherein a thickness of the biaxially stretched polyolefin film is 20 µm or more and 50 µm or less. The inner layer further includes a sealant layer having heat-fusibility,
The power storage device exterior material according to any one of claims 1 to 6, wherein the biaxially stretched polyolefin film is disposed between the sealant layer and the metal foil layer.   The power storage device exterior material according to claim 7, wherein the biaxially stretched polyolefin film is thicker than the sealant layer. The biaxially stretched polyolefin film is a biaxially stretched polypropylene film,
The power storage device exterior material according to claim 7 or 8, wherein the sealant layer is formed of a polypropylene resin. The power storage device exterior material according to any one of claims 1 to 9, wherein the power storage device exterior material is bent so that the inner layers are heat-sealed.
A battery element disposed inside the folded outer packaging material for a power storage device;
A power storage device comprising: The power storage device exterior material has a recess,
The power storage device according to claim 10, wherein the battery element is accommodated in the recess.

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