Exterior material for energy storage device

Abstract

This exterior material for an electric storage device is provided at least with a base material protection layer, a base material layer, an adhesive layer, a metal foil layer, and a sealant layer in this sequence from the external surface side, wherein: the base material protection layer is formed by hardening a curable resin which has blended therein multiple types of particles having different average particle diameters; the curable resin is composed of a material that contains a polyol component as a main agent and a polyisocyanate component as a curative agent; when, of the multiple types of particles, the particles having larger average particle diameters are defined as a large filler, while the particles having smaller average particle diameters are defined as a small filler, the large filler has an average particle diameter of at least 10 μm, while the small filler has an average particle diameter of at least 1 μm, and the blended amount of the large filler and the blended amount of the small filler in the base material protection layer are at least 3 mass% and at least 5 mass%, respectively.

Description

Technical Field

[0001] The present disclosure relates to an exterior material for a power storage device.

Background Art

[0002] As power storage devices, for example, secondary batteries such as lithium ion batteries, nickel metal hydride batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors are known. Further miniaturization of power storage devices is required due to miniaturization of portable devices or limitation of installation space, and lithium ion batteries with high energy density have attracted attention. As an exterior material used for lithium ion batteries, a metal can has been conventionally used, but a film-like exterior material that is lightweight, has high heat dissipation, and can be manufactured at low cost is now being used.

[0003] This film-like exterior material serves to prevent moisture from entering the lithium ion battery. For this reason, a film having a multilayer structure including a metal foil in its layer structure is used as this film-like exterior material. Then, the film-like exterior material is cold-formed to form a recess, the battery contents are accommodated in the recess, and the remaining portion of the exterior material is folded back and the edge portion is heat-sealed to constitute the above lithium ion battery (see Patent Document 1).

[0004] By the way, in order to prevent contamination during the manufacturing process of such a film-like exterior material having a multilayer structure, a lightly adhesive protective film that can be easily peeled off may be attached to the outside thereof for manufacturing. Among them, in the exterior material of a lithium ion battery having a matte outer surface, a base material protective layer formed by mixing particles to have a matte shape is disposed on the outer surface. When an electrolytic solution for a battery or the like adheres to the surface of this base material protective layer, the appearance may change. Therefore, it is normal to manufacture such an exterior material having a matte outer surface by attaching a protective film for protecting the base material protective layer.

[0005] Note that this protective film is peeled off and removed during the battery manufacturing process or after the battery is manufactured. When the lightly adhesive protective film is peeled off and removed in this way, the adhesive used for the protective film must not remain on the outer surface of the exterior material.

[0006] On the other hand, when using the lithium-ion battery manufactured in this way, it is adhesively fixed to the electrical device using a strongly adhesive double-sided tape (PSA tape). When adhesively fixing to the electrical device in this way, the PSA tape must adhere firmly to the outer surface of the exterior material.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Thus, although both the protective film and the PSA tape are adhesive films or adhesive tapes, one of them (the protective film) needs to be peelable without leaving an adhesive residue on the outer surface of the exterior material, and the other (the PSA tape) must adhere firmly to the outer surface of the exterior material.

[0009] Therefore, an object of the present disclosure is to provide an exterior material for a power storage device that can peel off and remove the above-mentioned protective film used during the manufacturing process from the outer surface of the exterior material without leaving an adhesive residue, and moreover, can firmly adhere a PSA tape to the outer surface of the exterior material thus exposed.

Means for Solving the Problems

[0010] To achieve the above object, the present disclosure provides the following invention. [1] An exterior material for a power storage device, comprising, in order from at least the outer surface side, a base material protective layer, a base material layer, an adhesive layer, a metal foil layer, and a sealant layer, wherein the base material protective layer is formed by curing a curable resin containing a plurality of types of particles having different average particle diameters, the curable resin is composed of a polyol component as a main agent and a polyisocyanate component as a curing agent, when the particles having a large average particle diameter among the plurality of types of particles are used as large fillers and the particles having a small average particle diameter are used as small fillers, the average particle diameter of the large fillers is 10 μm or more, the average particle diameter of the small fillers is 1 μm or more, and the blending amount of the large fillers in the base material protective layer is 3% by mass or more, and the blending amount of the small fillers is 5% by mass or more.

[0011] [2] The exterior material for a power storage device according to [1] above, wherein the average particle diameter of the large fillers is 30 μm or less, the average particle diameter of the small fillers is 5 μm or less, and the blending amount of the large fillers is 25% by mass or less.

[0012] [3] The exterior material for a power storage device according to [1] or [2] above, wherein at least a part of the polyisocyanate component is composed of an alicyclic polyisocyanate.

[0013] [4] The exterior material for a power storage device according to any one of [1] to [3] above, wherein at least a part of the polyisocyanate component is composed of an aliphatic polyisocyanate or an aromatic polyisocyanate, the blending amount of the large fillers is 25% by mass or less, and the total blending amount of the large fillers and the small fillers is 50% by mass or less.

[0014] [5] The exterior material for a power storage device according to any one of [1] to [4] above, wherein the large fillers contain particles of an organic substance.

[0015] [6] The exterior material for a power storage device according to [5] above, wherein the large fillers contain particles of a thermoplastic organic substance, and the thickness of the base material protective layer is 10 μm or less.

[0016] [7] The exterior material for a power storage device according to any one of [1] to [6] above, wherein the large filler contains inorganic particles.

[0017] [8] The exterior material for a power storage device according to any one of [1] to [7] above, wherein a coloring pigment is blended in the adhesive layer.

Advantages of the Invention

[0018] As can be seen from the experimental examples described later, according to the invention described in [1] above, a lightly adhesive protective film can be peeled off and removed from the outer surface of the exterior material without leaving an adhesive residue, and moreover, a strongly adhesive PSA tape can be firmly adhered to the outer surface of the exterior material.

[0019] In addition, according to the invention described in [2] above, its outer surface can be formed into a uniform and dense matte shape. Therefore, an exterior material with an excellent appearance without a rough feeling on the appearance can be obtained.

[0020] Also, according to the invention described in [3] above, a lightly adhesive protective film can be peeled off and removed from the outer surface of the exterior material without leaving an adhesive residue, and moreover, a strongly adhesive PSA tape can be adhered more firmly to the outer surface of the exterior material.

[0021] Also, according to the invention described in [4] above, cold forming can be performed without causing cracks or peeling to form a battery element accommodation recess. From the viewpoint of obtaining such an effect more sufficiently, a part of the polyisocyanate component may be composed of an alicyclic polyisocyanate and a part may be composed of an aliphatic polyisocyanate or an aromatic polyisocyanate.

[0022] Also, according to the invention described in [5] above, it becomes easier to adjust the thickness of the base material protective layer, and while ensuring the peelability of the protective film and the adhesiveness of the PSA tape, the thickness of the base material protective layer can be reduced. By reducing the thickness of the base material protective layer, the process management when cold-forming the exterior material for a power storage device becomes easy. At this time, by setting the thickness of the base material protective layer within the range described in [6] above, the above effects can be obtained more sufficiently.

[0023] Also, according to the invention described in [7] above, it is possible to perform cold forming while maintaining a uniform and dense matte outer surface without any change in the gloss of the outer surface due to cold forming.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0025] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0026] [Exterior Material for Power Storage Device] FIG. 1 is a cross-sectional view schematically showing an embodiment of the exterior material for a power storage device of the present disclosure. As shown in FIG. 1, the exterior material (exterior material for a power storage device) 10 of this embodiment is formed by laminating a base material protective layer 12, a base material layer 11, a metal foil layer 14, and a sealant layer 17 in this order. Corrosion prevention treatment layers 15a and 15b are provided on both surfaces of the metal foil layer 14. Further, the base material layer 11 and the metal foil layer 14 are adhered via an adhesive layer 13, and the metal foil layer 14 and the sealant layer 17 are adhered via a sealant adhesive layer 16. Note that this exterior material 10 is used with the base material protective layer 12 as the outer surface of the power storage device and the sealant layer 17 as the inner surface of the power storage device. Hereinafter, each layer will be described.

[0027] (Base material layer 11) The base material layer 11 plays a role of imparting heat resistance in the sealing process when manufacturing the power storage device and suppressing the occurrence of pinholes that may occur during molding and distribution. Further, scratch resistance, chemical resistance, insulation, etc. can also be imparted.

[0028] The base material layer 11 is preferably a layer made of a resin film formed of an insulating resin. Examples of the resin film include stretched or unstretched films such as a polyester film, a polyamide film, and a polypropylene film. The base material layer 11 may be a single-layer film composed of any of these resin films, or may be a laminated film composed of two or more of these resin films.

[0029] Among these films, as the base material layer 11, a polyamide film is preferable and a biaxially stretched polyamide film is more preferable because of its excellent moldability. Examples of the polyamide resin for forming the polyamide film include nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), nylon 11, nylon 12, and the like. Among these, nylon 6 (ONy) is preferable from the viewpoints of heat resistance, puncture strength, and impact strength.

[0030] (Base material protective layer 12) The base material protective layer 12 is located on the outer surface of the exterior material 10 for the power storage device, protects the base material layer 11, adheres a lightly adhesive protective film used in the battery manufacturing process, and has the function of being easily peelable and removable without leaving adhesive residues when peeling and removing this protective film. Further, the base material protective layer 12 has the role of firmly adhering and fixing a strongly adhesive double-sided tape (PSA tape) when adhering and fixing this exterior material 10 for the power storage device to an electric device.

[0031] In order to fulfill these roles, this base material protective layer 12 needs to be composed of a cured resin obtained by curing a curable resin blended with a plurality of types of particles having different average particle diameters.

[0032] This curable resin has a polyol component as the main agent and a polyisocyanate component as the curing agent.

[0033] The polyol component may be any polyol. For example, polyester polyol, acrylic polyol, or polyether polyol can be used. A mixture of a plurality of types of polyols may also be used. From the viewpoints of chemical resistance, adhesion to the base material layer 11, or coating film suitability, polyester polyol or acrylic polyol can preferably be used.

[0034] A single type of polyisocyanate can be used as the polyisocyanate component, or a plurality of types of polyisocyanates can be blended and used. In any case, the polyisocyanate component may contain an alicyclic polyisocyanate, may contain an aliphatic polyisocyanate or an aromatic polyisocyanate, but it is preferable to contain an alicyclic polyisocyanate. Desirably, a part of the polyisocyanate component is composed of an alicyclic polyisocyanate, and the remainder is composed of an aliphatic polyisocyanate or an aromatic polyisocyanate, and these alicyclic polyisocyanate and aliphatic polyisocyanate or aromatic polyisocyanate are blended to form the above polyisocyanate component.

[0035] As can be understood from the experimental examples described later, when the polyisocyanate component contains an alicyclic polyisocyanate, compared with the case where it does not contain an alicyclic polyisocyanate, when the exterior material 10 for a power storage device is adhesively fixed to an electric device, if a PSA tape with strong adhesiveness is used, this PSA tape can be adhesively fixed more firmly. On the other hand, even when it does not contain an aliphatic polyisocyanate or an aromatic polyisocyanate, the above PSA tape can be adhesively fixed firmly, but cracks may occur when the exterior material 10 for a power storage device is cold-formed.

[0036] Examples of the alicyclic polyisocyanate include methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, etc. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, etc. Examples of the aromatic polyisocyanate include xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, etc.

[0037] Next, among the plurality of types of the above particles having different average particle diameters, when the particles with a large average particle diameter are used as large fillers and the particles with a small average particle diameter are used as small fillers, the large fillers form large irregularities on the surface of the substrate protective layer 12, adhesively bond the weakly adhesive protective film in a point contact manner, and can be easily peeled off and removed without leaving the adhesive used for this protective film on the surface of the substrate protective layer 12. For such reasons, the average particle diameter of the large fillers needs to be 10 μm or more. When the average particle diameter of the large fillers is smaller than this, when the above protective film is peeled off and removed, the adhesive used for this protective film may remain on the surface of the substrate protective layer 12, that is, on the outer surface of the exterior material 10 for a power storage device, and may inhibit the adhesive fixation of the above double-sided tape.

[0038] Also, the average particle size of the large filler is desirably 30 μm or less. If the average particle size of the large filler is larger than this, the surface appearance of the base material protective layer 12 will not be a uniform and dense matte.

[0039] In addition, the compounding amount of the large filler in the base material protective layer 12 needs to be 3% by mass or more. If the compounding amount of the large filler is less than this, when the protective film is peeled off, the adhesive used for the protective film may remain on the surface of the base material protective layer 12.

[0040] Also, the compounding amount of the large filler in the base material protective layer 12 is desirably 25% by mass or less. If the compounding amount of the large filler is more than this, the surface appearance of the base material protective layer 12 will not be a uniform and dense matte.

[0041] On the other hand, the small filler forms small irregularities on the surface of the base material protective layer 12, enabling the PSA tape to be firmly adhered and fixed. For this reason, the average particle size of the small filler needs to be 1 μm or more. If the average particle size of the small filler is smaller than this, the surface appearance of the base material protective layer 12 will not be a uniform and dense matte, and since the irregularities are few, the PSA tape cannot be firmly adhered and fixed.

[0042] Also, the average particle size of the small filler is desirably 5 μm or less. If the average particle size of the small filler is larger than this, the surface appearance of the base material protective layer 12 will not be a uniform and dense matte.

[0043] In addition, the compounding amount of the small filler in the base material protective layer 12 needs to be 5% by mass or more. If the compounding amount of the small filler is less than this, the surface appearance of the base material protective layer 12 will not be a uniform and dense matte, and since the irregularities are few, the PSA tape cannot be firmly adhered and fixed.

[0044] Also, the compounding amount of the small filler in the base material protective layer 12 is desirably 45% by mass or less. If the compounding amount of the small filler is more than this, the surface appearance of the base material protective layer 12 will not become a uniform and dense matte shape, and also the base material protective layer 12 will become brittle and cracks may occur during cold forming.

[0045] In addition, the total compounding amount of these large fillers and small fillers is desirably 50% by mass or less. This is because when the total compounding amount is more than this, the base material protective layer 12 becomes brittle and cracks or the like are likely to occur in the base material protective layer during cold forming. Also, this total compounding amount is desirably 8% by mass or more.

[0046] The materials of such large fillers and small fillers may be arbitrary. For example, organic particles (particles of organic substances) or inorganic particles (particles of inorganic substances) can be used. Examples of the organic particles include polyolefin particles such as polyethylene particles, acrylic particles, urethane particles, polyester particles, and the like. Also, examples of the inorganic particles include silica particles, alumina particles, barium sulfate particles, calcium carbonate particles, titanium oxide particles, and the like.

[0047] In addition, inorganic particles may be used as the large filler. When organic particles are used, this large filler may be crushed during cold forming, resulting in a change in gloss on the surface of the base material protective layer 12, that is, the outer surface of the exterior material 10 for the power storage device. On the other hand, when inorganic particles are used, it is possible to suppress a change in gloss on the outer surface of the exterior material 10 for the power storage device due to cold forming.

[0048] In addition, organic particles may be used as the large filler. When organic particles are used, if the exterior material 10 for the power storage device is manufactured through a lamination process, the organic particles can be crushed to reduce the thickness of the base material protective layer 12. By using thermoplastic organic particles among the organic particles, it becomes easier to control the thickness of the exterior material for the power storage device during production. As the thermoplastic organic particles, for example, polyolefin particles such as polyethylene particles can be used. By reducing the thickness of the base material protective layer 12, process management during cold forming or the like becomes easier. Further, even when the organic particles are crushed and the contact area with the protective film increases, the organic particles (especially polyethylene particles etc.) do not have an excessive increase in the adhesion force with the weakly adhesive protective film, and can be easily peeled off and removed without leaving the adhesive used for the protective film on the surface of the base material protective layer 12.

[0049] This base material protective layer 12 can be formed by dissolving or dispersing each component constituting it in a solvent to form a coating solution, and applying this coating solution to the base material layer 11.

[0050] For example, the above polyol component can be dissolved in a solvent to form a varnish, and the large filler and the small filler can be blended into this varnish, and the above polyisocyanate component can be blended to obtain the above coating solution. Also, the above polyol component can be dissolved in a solvent to form a varnish, while the large filler and the small filler are dispersed in a solvent to produce a slurry, and this slurry can be blended into the above varnish, and the above polyisocyanate component can be blended to obtain the above coating solution.

[0051] In addition, additives such as a flame retardant, a lubricant, an antioxidant, a light stabilizer, an adhesion promoter, a leveling agent, an antifoaming agent, a catalyst, and a reaction retarder may be blended into this coating solution. Examples of the lubricant include fatty acid amides such as oleic acid amide, erucic acid amide, stearic acid amide, behenic acid amide, ethylene bisoleic acid amide, and ethylene biserucic acid amide. Also, acetylacetone can be exemplified as the reaction retarder.

[0052] In addition, as the coating method, a gravure direct coating method, a gravure reverse coating method, a micro gravure coating method, etc. can be used.

[0053] The thickness of the base material protective layer 12 may be 0.5 μm or more, 1.0 μm or more, or 1.5 μm or more, and may be 50 μm or less, 30 μm or less, 15 μm or less, or 10 μm or less. When this thickness is below the above lower limit value, the function of protecting the base material layer 11, the function of being easily peeled off without leaving adhesive residue when peeling off the lightly adhesive protective film, and the function of firmly adhering and fixing the strongly adhesive PSA tape can be obtained more sufficiently. Also, when the thickness is below the above upper limit value, the thickness of the entire exterior material 10 for the power storage device can be reduced, and the process management during cold forming of the exterior material 10 for the power storage device becomes easy. In addition, when the base material protective layer 12 contains thermoplastic organic particles as a large filler, in the laminating process when manufacturing the exterior material 10 for the power storage device, the organic particles tend to be crushed and the thickness of the base material protective layer 12 tends to become thinner. Therefore, when the large filler contains thermoplastic organic particles or consists only of thermoplastic organic particles, the thickness of the base material protective layer 12 may be 10 μm or less, 8 μm or less, or 6 μm or less.

[0054] (Adhesive layer 13) The adhesive layer 13 is a layer that adheres the base material layer 11 and the metal foil layer 14. The adhesive layer 13 has the adhesive strength necessary to firmly adhere the base material layer 11 and the metal foil layer 14, and also has followability (the performance to surely form the adhesive layer 13 on the member without peeling even if the member is deformed and expanded or contracted) to suppress the metal foil layer 14 from being broken by the base material layer 11 during cold forming.

[0055] As the adhesive constituting the adhesive layer 13, for example, a two-component curable polyurethane-based adhesive having a main component composed of a polyol such as polyester polyol, polyether polyol, acrylic polyol, etc., and a curing agent composed of an isocyanate such as aromatic or aliphatic can be used. In the above adhesive, the molar ratio of the isocyanate group of the curing agent to the hydroxyl group of the main component (= NCO / OH) is preferably 1 to 50, more preferably 2 to 30.

[0056] After the above polyurethane-based adhesive is applied, for example, by aging at 40°C or higher for 4 days or more, the reaction between the hydroxyl group of the main component and the isocyanate group of the curing agent proceeds, enabling stronger adhesion between the base material layer 11 and the metal foil layer 14.

[0057] In addition, a coloring pigment can also be blended into this adhesive. For example, it is a black pigment. By blending a coloring pigment into the adhesive to form the adhesive layer 13, the exterior material 10 for the power storage device is colored in this color, and the appearance of the power storage device using this exterior material 10 for the power storage device is also colored in this color, enhancing its designability.

[0058] (Metal foil layer 14) Examples of the metal foil layer 14 include various metal foils such as aluminum and stainless steel. From the viewpoints of workability such as moisture resistance and ductility, and cost, the metal foil layer 14 is preferably an aluminum foil. The aluminum foil may be a general soft aluminum foil, but from the viewpoints of excellent pinhole resistance and ductility during molding, it is preferably an aluminum foil containing iron.

[0059] (Corrosion prevention treatment layers 15a, 15b) The corrosion prevention treatment layers 15a and 15b serve to suppress the corrosion of the metal foil layer 14 by the electrolytic solution or hydrofluoric acid generated by the reaction of the electrolytic solution and moisture. Further, the corrosion prevention treatment layer 15a serves to enhance the adhesion between the metal foil layer 14 and the adhesive layer 13. Also, the corrosion prevention treatment layer 15b serves to enhance the adhesion between the metal foil layer 14 and the sealant adhesive layer 16. The corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b may be layers having the same configuration or layers having different configurations.

[0060] These corrosion prevention treatment layers 15a and 15b can be formed by subjecting the metal foil layer 14 to, for example, degreasing treatment, hot water conversion treatment, anodizing treatment, chemical conversion treatment, a coating type corrosion prevention treatment of applying a coating agent having corrosion prevention ability, or a corrosion prevention treatment combining these treatments.

[0061] (Sealant adhesive layer 16) The sealant adhesive layer 16 is a layer that adheres the metal foil layer 14 on which the corrosion prevention treatment layer 15b is formed to the sealant layer 17. This sealant adhesive layer 16 may be composed of an adhesive for dry lamination or a molten adhesive resin. A general adhesive for adhering the metal foil layer 14 and the sealant layer 17 can be used for this sealant adhesive layer 16. As a lamination method of the metal foil layer 14 and the sealant layer 17 via the sealant adhesive layer 16, for example, a dry lamination method using an adhesive for dry lamination such as a polyurethane-based adhesive, or an extrusion lamination method or a sand lamination method using an acid-modified polyolefin can be used.

[0062] (Sealant layer 17) The sealant layer 17 is a layer that imparts heat-sealing properties to the exterior material 10 for a power storage device, and is a layer that is disposed inside and heat-sealed during the assembly of the power storage device. 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 an acid such as maleic anhydride onto a polyolefin resin. Among these, a polyolefin resin that can improve the barrier property against water vapor and can form the shape of the power storage device without being excessively crushed by heat sealing is preferable, and polypropylene is particularly preferable.

[0063] (Method for manufacturing the exterior material 10 for a power storage device) Next, a method for manufacturing the exterior material 10 for a power storage device will be described. Note that the manufacturing method is not limited to the following method.

[0064] As a method for manufacturing the exterior material 10 for a power storage device, for example, there is a method having the following steps S11 to S14 and manufacturing in the order of S11, S12, S13, and S14. Step S11: A step of forming a corrosion prevention treatment layer 15a on one surface of the metal foil layer 14 and forming a corrosion prevention treatment layer 15b on the other surface of the metal foil layer 14. Step S12: A step of bonding the surface of the corrosion prevention treatment layer 15a opposite to the metal foil layer 14 and the base material layer 11 via the adhesive layer 13. Step S13: A step of applying and forming a base material protection layer 12 on the surface of the base material layer 11 opposite to the adhesive layer 13. Step S14: A step of forming a sealant layer 17 via a sealant adhesive layer 16 on the surface of the corrosion prevention treatment layer 15b opposite to the metal foil layer 14.

[0065] [Method for manufacturing a power storage device] Next, a method for manufacturing a power storage device using the exterior material 10 for a power storage device will be described. FIGS. 3(a) to (d) are perspective views showing the manufacturing process of a single-sided formed battery. Note that FIG. 2 shows the exterior material 10 for a power storage device cold-formed.

[0066] The secondary battery 20, which is a single-sided formed battery, can be manufactured, for example, by the following steps S21 to S28. The secondary battery 20 manufactured through this process can be firmly adhered and fixed to an electric device via a strong adhesive double-sided tape (PSA tape). Step S21: A step of preparing an exterior material 10 for a power storage device, a battery element 1 including electrodes, and a lead 2 extending from the above electrodes. Step S22: A step of cold-forming a recess 10a for arranging the battery element 1 on one side of the exterior material 10 for a power storage device (see FIGS. 3(a) and 3(b)). Step S23: The battery element 1 is arranged in the recess 10a of the exterior material 10 for a power storage device in which the recess 10a is formed, and the exterior material 10 for a power storage device is folded and overlapped so that the lid portion 10b covers the recess 10a, and one side of the exterior material 10 for a power storage device is pressure heat-sealed so as to sandwich the lead 2 extending from the battery element 1 (see FIGS. 3(b) and 3(c)). Step S24: A step of attaching a protective film to the exterior material 10 for a power storage device. Step S25: Leaving one side other than the side sandwiching the lead 2, heat-sealing the other sides under pressure, then injecting an electrolytic solution from the remaining side, and heat-sealing the remaining side under pressure in a vacuum state to manufacture the battery 20 (see FIG. 3(c)). Step S26: A step of performing charge and discharge under predetermined conditions such as current value, voltage value, and environmental temperature to cause a chemical change. Step S27: A step of peeling and removing the protective film from the exterior material 10 for a power storage device. Step S28: A step of cutting the ends of the pressure heat-sealed sides other than the side sandwiching the lead 2 and bending them toward the recess 10a side (see FIG. 3(d)).

Example

[0067] Hereinafter, the present disclosure will be described by way of examples and comparative examples. For the sake of convenience of explanation, all of these will be referred to as experimental examples without distinction between examples and comparative examples.

[0068] These experimental examples can be distinguished into the first to the twenty-first experimental example groups. Therefore, they will be described for each experimental example group, considerations will be added for each experimental example group, and finally, the considerations of these individual experimental examples will be organized.

[0069] In these experimental examples, a nylon film was used as the base material layer 11. Also, aluminum with a thickness of 35 μm provided with corrosion prevention treatment layers 15a and 15b on both sides was used as the metal foil layer 14. Further, a polypropylene film with a thickness of 35 μm was used as the sealant layer 17. The base material protective layer 12 will be described later.

[0070] First, the base material layer 11 and the metal foil layer 14 were bonded together with a heat-sensitive adhesive (step S12).

[0071] Next, the base material protective layer 12 was applied and formed on the surface of the base material layer 11 (step S13).

[0072] Next, the sealant adhesive layer 16 and the sealant layer 17 were formed on the metal foil layer 14 by coextrusion to manufacture the exterior material 10 for the power storage device (step S14).

[0073] Next, prior to describing the base material protective layer 12 of each experimental example, the evaluation methods of these experimental examples will be described. These experimental examples were evaluated from the following four viewpoints.

[0074] <Evaluation Method> (Appearance of the Coating Film) After the base material protective layer 12 was applied and formed (the above step S13), the appearance of the base material protective layer 12 was observed with the naked eye. Those with a non-gritty, uniform, and dense matte appearance were evaluated as "A", and those with a smooth appearance and those with a gritty feeling were evaluated as "F".

[0075] (PSA Adhesion) In the obtained exterior material, a double-sided tape with strong adhesiveness was attached to the sealant layer 17, and it was attached to the metal plate through this double-sided tape. Next, a PSA tape with a width of 10 mm was attached onto the base material protection layer 12, and an aluminum foil was attached through this PSA tape. Then, after leaving it standing at room temperature for 2 hours, using a tensile testing machine, 180-degree peeling was performed under the condition of a speed of 300 mm / min, and the peel strength between the base material protection layer 12 and the PSA tape was measured.

[0076] Those with a peel strength of 5 N / 10 mm or more were evaluated as "A", those with a peel strength of less than 2.5 N / 10 mm and less than 5 N / 10 mm were evaluated as "B", and those with a peel strength of less than 2.5 N / 10 mm were evaluated as "F".

[0077] (Residual adhesive of protective film) A double-sided tape with strong adhesiveness was attached to the sealant layer 17 of the obtained exterior material 10, and it was attached to the metal plate through this double-sided tape. Next, a protective film with weak adhesiveness was attached to the base material protection layer 12. Then, it was stored under the temperature condition of 85°C for 6 hours, allowed to cool and return to room temperature, and using a tensile testing machine, 180-degree peeling was performed between the base material protection layer 12 and the protective film under the condition of a speed of 300 mm / min, and it was confirmed whether the adhesive of the protective film remained on the surface of the base material protection layer 12. Those in which no residual adhesive was observed were evaluated as "A", and those in which residual adhesive was observed were evaluated as "F".

[0078] (Appearance after molding) A recess 10a was cold-formed on the exterior material 10 for the power storage device (the above step S22). The depth of this recess 10a was 3.5 mm. Then, with the naked eye, the presence or absence of cracks and the presence or absence of gloss change generated in the base material protection layer 12 were evaluated. Those without cracks and with the gloss also maintaining the state before cold-forming were evaluated as "A". Those without cracks but with a change in gloss and a terry feeling (increase in gloss) occurring in a part of it were evaluated as "B". Also, those with cracks in the base material protection layer 12 were evaluated as "F".

[0079] (Film thickness) The film thickness of the base material protective layer 12 in the obtained exterior material 10 was measured using a contact thickness measuring device (trade name: Peacock, manufactured by Ozaki Manufacturing Co., Ltd.). The difference between the thickness of the obtained exterior material 10 and the thickness of the exterior material sample without the base material protective layer 12 was defined as the film thickness of the base material protective layer 12.

[0080] <First Experimental Example Group and Its Consideration> The first experimental example group consists of Experimental Examples 1-1 to 1-5. In this experimental example group, the main agent is polyester polyol and the curing agent is hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Note that HDI is an aliphatic polyisocyanate and IPDI is an alicyclic polyisocyanate. And the mixing ratio of HDI and IPDI is 9:1 by mass ratio of HDI:IPDI.

[0081] Also, in this experimental example group, silica particles with an average particle size of 15 μm were used as the large filler, and this was blended at 10% by mass with respect to the base material protective layer 12.

[0082] Also, in this experimental example group, silica particles were used as the small filler, and this silica particle was blended at 20% by mass with respect to the base material protective layer 12.

[0083] And by using small fillers with different average particle sizes for each experimental example, the relationship between the average particle size of this small filler and each of the above evaluation items was investigated. The results are shown in Table 1.

[0084]

Table 1

[0085] (Appearance of Coating Film) From these results, it can be seen that under the above conditions, when the average particle size of the small filler is 1 to 5 μm, a non-grainy, uniform and dense matte base material protection layer can be formed. In Experimental Examples 1-4, since the average particle size of the small filler was smaller than this, the unevenness on the surface of the base material protection layer was small and it did not become matte. Also, in Experimental Example 1-5, although the surface of the base material protection layer became matte, since the average particle size of the small filler was large, the unevenness was large and it did not become a uniform and dense matte.

[0086] (PSA adhesion) From these results, it can be seen that under the above conditions, when the average particle size of the small filler is 1 μm or more, the PSA tape adheres firmly.

[0087] (Residual protective film adhesive) Under the above conditions, it can be understood that the average particle size of the small filler has nothing to do with the residual protective film adhesive, and no adhesive residue occurs at any average particle size.

[0088] (Appearance after molding) Under the above conditions, it can be seen that the average particle size of the small filler has nothing to do with the appearance after molding, and no cracks occur in the base material protection layer at any average particle size, and also no change in gloss occurs.

[0089] <The Second Experimental Example Group and Its Consideration> The second experimental example group is composed of Experimental Example 2-1. This second experimental example group used large fillers with a small average particle size, and by comparing with the first experimental example group, the relationship between the average particle size of the large filler and the above-mentioned various evaluation items was investigated. That is, the average particle size of the large filler used in Experimental Example 2-1 was 5 μm. Except for this, the exterior material 10 for a power storage device was manufactured in the same manner as in Experimental Example 1-2, and the above-mentioned various evaluation items were investigated. The results are shown in Table 2.

[0090]

Table 2

[0091] (Appearance of coating film) From these results, it can be seen that even when the average particle size of the large filler is 5 μm, the appearance of the coating film does not change. That is, similar to Experimental Example 1-2, there is no rough feeling, and a uniform and dense matte base material protection layer can be formed.

[0092] (PSA adhesion) It can be understood that even when the average particle size of the large filler is 5 μm, the PSA tape adheres firmly, similar to Experimental Example 1-2.

[0093] (Adhesive residue of protective film) When the large filler is made smaller and its average particle size is 5 μm, different from Experimental Example 1-2, the adhesive of the protective film remains on the surface of the base material protection layer 12. Therefore, it can be understood that the average particle size of the large filler is related to the adhesive residue of the protective film, and under the above conditions, in order to prevent the adhesive residue, the average particle size of the large filler may be set to 15 μm (Experimental Example 1-3).

[0094] (Appearance after molding) It can be seen that even when the average particle size of the large filler is 5 μm, no cracks occur in the base material protection layer, and no change in gloss occurs, similar to Experimental Example 1-2.

[0095] <The third experimental example group and its discussion> In the first experimental example group with the average particle size of the large filler being 15 μm, no adhesive residue of the protective film occurred, and in the second experimental example group with the average particle size of the large filler being 5 μm, adhesive residue of the protective film occurred. Therefore, in the third experimental example group, the relationship between the average particle size of the large filler having an average particle size between them and the above respective evaluation items was investigated. That is, the average particle size of the large filler used in this third experimental example group is 10 μm.

[0096] Also, by using small fillers with different average particle sizes for each experimental example, the relationship between the average particle size of the small filler and the above respective evaluation items was investigated when using a large filler with an average particle size of 10 μm.

[0097] In the first experimental example group, when the average particle size of the small filler was 0.1 μm (Experimental Examples 1-4) and 10 μm (Experimental Example 1-5), the evaluation of the coating film appearance and PSA adhesion was poor. Therefore, except for these cases, for the cases where the average particle size of the small filler was 5 μm (Experimental Example 3-1), 3 μm (Experimental Example 3-2), and 1 μm (Experimental Example 3-3), the exterior material 10 for the power storage device was manufactured, and each of the above evaluation items was examined. The results are shown in Table 3.

[0098]

Table 3

[0099] (Coating film appearance) From these results, it can be seen that even when the average particle size of the large filler is 10 μm, the appearance of the coating film does not change, and there is no rough feeling as in the first experimental example group, and a uniform and dense matte base material protection layer can be formed. Moreover, the average particle size of the small filler is irrelevant.

[0100] (PSA adhesion) It can be understood that even when the average particle size of the large filler is 10 μm, the PSA tape adheres firmly as in the first experimental example group. The average particle size of the small filler is irrelevant.

[0101] (Residual glue of the protective film) Even when the average particle size of the large filler is 10 μm, no residual glue occurs. The average particle size of the small filler is irrelevant.

[0102] Considering the results of this third experimental example group in addition to the results of the first experimental example group and the second experimental example group, it can be understood that in order to prevent residual glue, the average particle size of the large filler should be 10 μm or more.

[0103] (Appearance after molding) It can be seen that even when the average particle size of the large filler is 10 μm, cracks do not occur in the base material protection layer and there is no change in gloss as in the first experimental example group. The average particle size of the small filler is irrelevant.

[0104] <Example Group 4 and Its Considerations> The fourth experimental example group increased the average particle size of the large filler and investigated the relationship between the average particle size of this large filler and each of the above evaluation items. That is, the average particle size of the large filler used in this fourth experimental example group is 30 μm.

[0105] Also, by using small fillers with different average particle sizes for each experimental example, the relationship between the average particle size of the small filler and each of the above evaluation items was investigated when using a large filler with an average particle size of 30 μm. The average particle sizes of the small fillers are 5 μm (Experimental Example 4-1), 3 μm (Experimental Example 4-2), and 1 μm (Experimental Example 4-3), respectively.

[0106] The results of each of the above evaluation items are shown in Table 4.

[0107]

Table 4

[0108] (Appearance of Coating Film) From these results, it can be seen that even when the average particle size of the large filler is 30 μm, the appearance of the coating film does not change, and like the first experimental example group, there is no roughness, and a uniform and dense matte-like substrate protection layer can be formed. The average particle size of the small filler is irrelevant.

[0109] (PSA Adhesion) It can be understood that even when the average particle size of the large filler is 30 μm, the PSA tape adheres firmly, just like the first experimental example group. The average particle size of the small filler is irrelevant.

[0110] (Residual Adhesive of Protection Film) No adhesive residue occurs even when the average particle size of the large filler is 30 μm. The average particle size of the small filler is irrelevant.

[0111] (Appearance after Molding) Even when the average particle size of the large filler is 30 μm, it can be seen that cracks do not occur in the substrate protective layer and the gloss does not change, similar to the first experimental example group. The average particle size of the small filler is irrelevant.

[0112] <The Fifth Experimental Example Group and Its Consideration> The fifth experimental example group further increased the average particle size of the large filler and examined the relationship between the average particle size of this large filler and the above-mentioned evaluation items. That is, the average particle size of the large filler used in this fifth experimental example group is 50 μm.

[0113] This fifth experimental example group is composed of Experimental Example 5-1. That is, the average particle size of the large filler used in Experimental Example 5-1 is 50 μm. Except for this, the exterior material 10 for the power storage device was manufactured in the same manner as in Experimental Example 1-2, and the above-mentioned evaluation items were examined. The results are shown in Table 5.

[0114]

Table 5

[0115] (Appearance of Coating Film) From these results, it can be seen that when the average particle size of the large filler is 50 μm, there is no roughness, and a uniform and dense matte substrate protective layer cannot be formed. That is, because the average particle size of the large filler is large, the surface of the substrate protective layer becomes a matte surface with a rough feeling.

[0116] Therefore, in order to form a uniform and dense matte substrate protective layer without roughness, in addition to setting the average particle size of the small filler to 1 to 5 μm (refer to the consideration of the first experimental example group), it can be understood that the average particle size of the large filler should be 30 μm or less.

[0117] (PSA Adhesion) Even when the average particle size of the large filler is 50 μm, it can be understood that the PSA tape adheres firmly in the same manner as in Experimental Example 1-2.

[0118] (Residual Paste of Protective Film) Even if the average particle size of the large filler is 50 μm, no paste residue occurs as in Experimental Example 1-2.

[0119] (Appearance after molding) Even if the average particle size of the large filler is 50 μm, it can be seen that no cracks occur in the substrate protective layer and no change in gloss occurs, as in Experimental Example 1-2.

[0120] (The Sixth Experimental Example Group and Its Consideration) The sixth experimental example group changed the blending amount of the large filler and investigated the relationship between the blending amount of this large filler and the above-mentioned respective evaluation items. That is, in the sixth experimental example group, the blending amounts of the large filler in the substrate protective layer are 1% by mass (Experimental Example 6-1), 3% by mass (Experimental Example 6-2), 25% by mass (Experimental Example 6-3), and 30% by mass (Experimental Example 6-4), respectively. Except for this, the exterior material 10 for the power storage device was manufactured in the same manner as in Experimental Example 1-2, and the above-mentioned respective evaluation items were investigated. The results are shown in Table 6.

[0121] [Table 6]

[0122] (Appearance of the coating film) In Experimental Example 6-4, since the blending amount of the large filler was too large, the surface of the substrate protective layer became a matte state with a rough feeling. From this result, in addition to setting the average particle size of the small filler to 1 to 5 μm and the average particle size of the large filler to 30 μm or less (refer to the consideration of the first and fifth experimental example groups), it was understood that the blending amount of the large filler should be 25% by mass or less.

[0123] (PSA adhesion) It can be understood that if the blending amount of the large filler is within the range of 1 to 30% by mass, the PSA tape adheres firmly as in Experimental Example 1-2.

[0124] (Paste residue of the protective film) In Experimental Example 6-4, since the blending amount of the large filler is too small, the adhesive of the protective film remains on the surface of the base material protective layer 12. From this result, in order to prevent the adhesive residue of the protective film, in addition to setting the average particle diameter of the large filler to 10 μm or more (refer to the consideration of the third experimental example group), it can be understood that the blending amount may be set to 3 mass% or more.

[0125] (Appearance after molding) If the blending amount of the large filler is within the range of 1 to 30 mass%, it can be seen that cracks do not occur in the base material protective layer and the gloss does not change, similar to Experimental Examples 1-2.

[0126] <The Seventh Experimental Example Group and Its Consideration> The seventh experimental example group set the blending amount of the large filler to 30 mass% and changed the blending amount of the small filler to examine the relationship between the total blending amount of the large filler and the small filler and each of the above evaluation items.

[0127] In this experimental example group, the average particle diameter of the large filler is simultaneously changed, and the average particle diameters are 10 μm and 15 μm. As can be seen from the consideration of the first to sixth experimental example groups described above, the difference in the average particle diameter to this extent does not affect the results of each evaluation item.

[0128] In addition, experimental examples in which the blending amount of the large filler is less than 30 mass% and the blending amount of the small filler is changed to examine the relationship between the total blending amount and each of the above evaluation items will be described later as the eighth to ninth experimental example groups.

[0129] That is, in Experimental Example 7-1, the average particle diameter of the large filler used was 15 μm, the blending amount was 30 mass%, and the blending amount of the small filler was 30 mass%. The total blending amount was 60 mass%. Except for this, the exterior material 10 for a power storage device was manufactured in the same manner as in Experimental Examples 1-2.

[0130] In addition, in Experimental Example 7-2, the average particle diameter of the large filler used was 10 μm, the blending amount was 20 mass%, and the blending amount of the small filler was 30 mass%. The total blending amount was 50 mass%.

[0131] The results of the above evaluation items are shown in Table 7.

[0132]

Table 7

[0133] (Appearance of coating film) Since the blending amount of the large filler was too large, the surface of the substrate protective layer became a matte surface with a rough feeling in both Experimental Example 7-1 and Experimental Example 7-2. The relationship between the total blending amount and the appearance of the coating film cannot be evaluated in this experimental example group.

[0134] (PSA adhesion) It can be understood that even when the total blending amount is 50 to 60% by mass, the PSA tape adheres firmly as in Experimental Example 1-2.

[0135] (Adhesive residue of protective film) It can be understood that even when the total blending amount is 50 to 60% by mass, no adhesive residue of the protective film occurs as in Experimental Example 1-2.

[0136] (Appearance after molding) In Experimental Example 7-1 in which the blending amount of the small filler was 30% by mass and the total blending amount was 60% by mass, cracks occurred in the substrate protective layer after cold molding. Regarding whether the reason is that the blending amount of the small filler is too large or the total blending amount is too large, it is not clear in this seventh experimental example group. However, by considering together with the eighth to ninth experimental example groups described below, it can be found that the cause of the poor appearance after molding is mainly in the total blending amount.

[0137] <Eighth Experimental Example Group and Its Consideration> The eighth experimental example group investigated the relationship between the total blending amount of the large filler and the small filler and the above evaluation items by changing the blending amount of the small filler while setting the average particle diameter of the large filler to 15 μm and its blending amount to 3% by mass. And except for this, the exterior material 10 for a power storage device was manufactured in the same manner as in Experimental Example 1-2.

[0138] The results of the above evaluation items are shown in Table 8.

[0139]

Table 8

[0140] (Appearance of coating film) In Experimental Example 8-1, since the blending amount of the small filler was small (2% by mass) and the total blending amount was also small (5% by mass), the appearance of the base material protective layer 12 did not become a uniform and dense matte shape but became smooth. In the experimental examples where the blending amount of the small filler was 5% by mass or more and the total blending amount was 8% by mass or more, there was no roughness and it had a uniform and dense matte shape. Therefore, it can be understood that in order to make the appearance of the base material protective layer 12 a uniform and dense matte shape, the blending amount of the small filler should be 5% by mass or more and the total blending amount should be 8% by mass or more. Regarding whether the reason for the smooth appearance of the base material protective layer 12 lies in the blending amount of the small filler or the total blending amount, it is not clear in this group of experimental examples.

[0141] (PSA adhesion) Similarly, in Experimental Example 8-1, since the blending amount of the small filler was small (2% by mass) and the total blending amount was also small (5% by mass), the PSA tape did not adhere firmly. Since the experimental examples where the blending amount of the small filler was 5% by mass or more and the total blending amount was 8% by mass or more showed high peel strength, in addition to making the average particle size of the small filler 1 μm or more (refer to the discussion of the first group of experimental examples) in order to firmly adhere the PSA tape to the base material protective layer 12, it can be understood that the blending amount should be 5% by mass or more and the total blending amount should be 8% by mass or more. Regarding whether the reason lies in the blending amount of the small filler or the total blending amount, it is not clear in this group of experimental examples.

[0142] (Adhesive residue of protective film) It can be understood that even when the total blending amount is 2 to 53% by mass, no adhesive residue of the adhesive of the protective film occurs.

[0143] (Appearance after molding) In Experimental Example 8-6 where the blending amount of the small filler was 50% by mass and the total blending amount was 53% by mass, cracks occurred in the base material protective layer after cold forming. Regarding whether the reason lies in the fact that the blending amount of the small filler is too large or the total blending amount is too large, this is not clarified even in this eighth group of experimental examples.

[0144] <The Ninth Group of Experimental Examples and Considerations Thereof> The ninth group of experimental examples was to investigate the relationship between the total blending amount of the large filler and the small filler and each of the above evaluation items by setting the average particle diameter of the large filler to 15 μm and its blending amount to 25% by mass and varying the blending amount of the small filler. And except for this, the exterior material 10 for the power storage device was manufactured in the same manner as in Experimental Examples 1-2.

[0145] The results of each of the above evaluation items are shown in Table 9.

[0146]

Table 9

[0147] (Appearance of Coating Film) In Experimental Example 9-1, since the blending amount of the small filler was small (2% by mass), the appearance of the base material protective layer 12 did not become a uniform and dense matte state but became smooth. In addition, in this Experimental Example 9-1, since the total blending amount was 27% by mass, considering it together with the aforementioned eighth group of experimental examples, it can be inferred that the reason for the smoothness of the base material protective layer 12 is mainly due to the blending amount of the small filler.

[0148] On the other hand, in the experimental examples where the blending amount of the small filler was 5% by mass or more, there was no roughness and it became a uniform and dense matte state. Therefore, it can be inferred that the blending amount of the small filler should be 5% by mass or more.

[0149] (PSA Adhesion) Similarly, in Experimental Example 9-1, since the blending amount of the small filler was small (2% by mass), the PSA tape did not adhere firmly. Also, it can be inferred that the reason is mainly due to the blending amount of the small filler.

[0150] In addition, in the experimental examples where the compounding amount of the small filler is 5% by mass or more, since high peel strength is exhibited, in order to firmly adhere the PSA tape to the base material protective layer 12, in addition to setting the average particle diameter of the small filler to 1 μm or more (refer to the consideration of the first experimental example group), it can be inferred that the compounding amount of the small filler may be set to 5% by mass or more.

[0151] (Residual adhesive of protective film) It can be understood that even when the total compounding amount is 27 to 75% by mass, no residual adhesive of the adhesive of the protective film occurs. Considering this together with the aforementioned eighth experimental example group, it is considered that the total compounding amount has little relation to the residual adhesive of the adhesive of the protective film.

[0152] (Appearance after molding) In Experimental Example 9-6 where the compounding amount of the small filler is 45% by mass and the total compounding amount is 70% by mass, cracks occurred in the base material protective layer after cold molding. In the aforementioned Experimental Example 8-5, although the compounding amount of the small filler was 45% by mass, no cracks occurred in the base material protective layer, and no change in gloss occurred either. Therefore, it can be understood that the cause of the cracks lies in the total compounding amount.

[0153] And in the experimental examples where this total compounding amount is 50% by mass or less, no cracks occur, and no change in gloss occurs either. Therefore, it can be understood that in order to obtain a good appearance after molding, the total compounding amount of the large filler and the small filler may be set to 50% by mass or less.

[0154] <The Tenth Experimental Example Group and Its Consideration> The tenth experimental example group changed the polyisocyanate component of the curable resin and investigated the relationship between the type of this polyisocyanate component and the above-mentioned respective evaluation items. And except for this, the exterior material 10 for a power storage device was manufactured in the same manner as in Experimental Example 1-1. In Experimental Example 10-1, the mixing ratio of tolylene diisocyanate (TDI) and IPDI is 9:1 in terms of mass ratio.

[0155] The results of the above-mentioned respective evaluation items are shown in Table 10.

[0156]

Table 10

[0157] (Appearance of coating film) As can be seen from these results, the appearance of the coating film does not depend on the type of polyisocyanate component.

[0158] (PSA adhesion) In Experimental Example 10-2 using only aliphatic polyisocyanate (HDI) and Experimental Example 10-4 using only aromatic polyisocyanate (TDI) as the polyisocyanate component, a decrease in the peel strength of the PSA tape was observed. It does not adhere firmly. In contrast, in Experimental Examples 10-1 and 10-3 using alicyclic polyisocyanate (IPDI) as at least a part of the polyisocyanate component, since a high peel strength is shown, in order to firmly adhere the PSA tape to the substrate protective layer 12, in addition to setting the average particle diameter of the small filler to 1 μm or more and its blending amount to 5 mass% or more (refer to the discussion of the 1st and 9th experimental example groups), it can be understood that it is important to use alicyclic polyisocyanate as at least a part of the polyisocyanate component.

[0159] (Adhesive residue of protective film) It can be understood that the adhesive residue of the protective film does not depend on the type of polyisocyanate component.

[0160] (Appearance after molding) In Experimental Example 10-3 using only alicyclic polyisocyanate (IPDI) as the polyisocyanate component, cracks occurred in the substrate protective layer after cold molding. In contrast, in Experimental Examples 1-1, 1-2, and 1-4 using aliphatic polyisocyanate (HDI) or aromatic polyisocyanate (TDI) as at least a part of the polyisocyanate component, cracks did not occur in the substrate protective layer, and also no change in gloss occurred. Therefore, it can be seen that in order to obtain a good appearance after molding, it is sufficient to use aliphatic polyisocyanate or aromatic polyisocyanate as at least a part of the polyisocyanate component.

[0161] <Example Group 11 of Experiments and Considerations Thereof> The 11th experimental example group changed the materials of the large filler and the small filler and examined the relationship between the materials of these fillers and each of the above evaluation items. Except for this, the exterior material 10 for the power storage device was manufactured in the same manner as in Experimental Example 1-1. In Experimental Example 11-1, organic particles (urethane particles) were used as the large filler and the small filler. In Experimental Example 11-2, inorganic particles (silica particles) were used as the large filler and organic particles (urethane particles) were used as the small filler. In Experimental Example 11-3, conversely, organic particles (urethane particles) were used as the large filler and inorganic particles (silica particles) were used as the small filler.

[0162] The results of each of the above evaluation items are shown in Table 11.

[0163]

Table 11

[0164] (Appearance of Coating Film) As can be seen from these results, the appearance of the coating film does not depend on the materials of these fillers.

[0165] (PSA Adhesion) The adhesive strength of the PSA tape also does not vary significantly depending on the materials of these fillers.

[0166] (Residue of Protective Film Adhesive) The residue of the adhesive of the protective film also does not depend on the materials of these fillers.

[0167] (Appearance after Molding) In Experimental Examples 11-1 and 11-3 where organic particles (urethane particles) were used as the large filler, this large filler was crushed during cold molding, resulting in gloss (terry feeling) on the substrate protective layer 12. In contrast, such gloss (terry feeling) does not occur in Experimental Example 11-2 where inorganic particles (silica particles) were used as the large filler or in the aforementioned Experimental Example Group 1.

[0168] Therefore, it can be understood that in order to prevent the gloss change due to cold forming, inorganic particles may be used as the large filler.

[0169] <Experimental Example Groups 12 to 21 and Their Considerations> The experimental example groups 12 to 21 are those obtained by repeating the experimental example groups 1 to 11, with the polyol component of the curable resin being a polyacrylic polyol having a glass transition temperature of 50 to 60°C. The results of the above respective evaluation items are shown in Tables 12 to 21.

[0170]

Table 12

[0171]

Table 13

[0172]

Table 14

[0173]

Table 15

[0174]

Table 16

[0175]

Table 17

[0176]

Table 18

[0177]

Table 19

[0178]

Table 20

[0179]

Table 21

[0180] The results of the above evaluation items are the same as those of the 1st to 11th experimental example groups. Therefore, it can be understood that for any evaluation item, it does not depend on the type of polyol component.

[0181] <The 22nd Experimental Example Group and Its Discussion> The 22nd experimental example group used polyethylene (PE) particles, which are organic particles, as the large filler, and changed their particle size and compounding amount to investigate the relationship between the material, particle size, and compounding amount of the large filler and the above evaluation items. And except for this, the exterior material 10 for the power storage device was manufactured in the same manner as in Experimental Example 18-1.

[0182] The results of the above evaluation items are shown in Table 22.

[0183]

Table 22

[0184] (Appearance of Coating Film) From this result, it can be seen that even when PE particles are used as the large filler, if the average particle size is 50 μm, a rough feeling does not occur, and a uniform and dense matte-like substrate protection layer cannot be formed. That is, because the average particle size of the large filler is large, the surface of the substrate protection layer becomes a matte-like with a rough feeling.

[0185] (PSA Adhesion) It can be understood that the adhesion of the PSA tape does not vary significantly depending on the material, particle size, and compounding amount of the large filler.

[0186] (Adhesive residue on the protective film) In Experimental Example 22-6, since the blending amount of the large filler was too small, the adhesive of the protective film remained on the surface of the base material protective layer 12. From this result, it was understood that in order to prevent the adhesive residue of the protective film, even when PE particles were used as the large filler, the blending amount should be 3% by mass or more.

[0187] (Appearance after molding) In Experimental Example 22-4, since the blending amount of the large filler was 25% by mass and the total blending amount of the large filler and the small filler was too much at 55% by mass, gloss (terry feeling) occurred on the base material protective layer after cold molding.

[0188] (Film thickness) In the 1st to 21st experimental example groups, the film thickness of the base material protective layer 12 was about the same as the particle size of the large filler. However, in the 22nd experimental example group using PE particles as the large filler, the film thickness of the base material protective layer 12 was clearly smaller than the particle size of the large filler. This is because the PE particles were deformed by heat in the laminating process when manufacturing the exterior material 10 for the power storage device. Even in this case, PSA adhesion and adhesive residue on the protective film were good except for Experimental Example 22-6. Also, the appearance of the coating film was good except for Experimental Example 22-7. Furthermore, no cracks were observed in the appearance after molding in any of the experimental examples.

[0189] <Summary of discussion> The above results can be summarized as follows.

[0190] (Appearance of the coating film) In order to obtain a base material protective layer with a non-granular, uniform and dense matte appearance, the following Conditions 1-1 to 1-4 may be satisfied. Condition 1-1: The average particle size of the small filler is 1 to 5 μm. Condition 1-2: The blending amount of the small filler is 5% by mass or more. Condition 1-3: The average particle size of the large filler is 30 μm or less. Condition 1-4: The compounding amount of the large filler shall be 25% by mass or less.

[0191] (PSA adhesion) When a PSA tape is attached to the base material protective layer, in order to firmly adhere the two, the following Conditions 2-1 to 2-3 may be satisfied. In order to obtain stronger adhesion, Condition 2-4 may be further satisfied. Condition 2-1: The average particle size of the small filler shall be 1 μm or more. Condition 2-2: The compounding amount of the large filler shall be 1% by mass or more. Condition 2-3: The compounding amount of the small filler shall be 5% by mass or more. Condition 2-4: An alicyclic polyisocyanate shall be used as at least part of the polyisocyanate component.

[0192] (Adhesive residue of protective film) When a protective film is attached to the base material protective layer and then peeled off, in order to prevent the adhesive of the protective film from remaining on the surface of the base material protective layer, the following Conditions 3-1 and 3-2 may be satisfied. Condition 3-1: The average particle size of the large filler shall be 10 μm or more. Condition 3-2: The compounding amount of the large filler shall be 3% by mass or more.

[0193] (Appearance after molding) When the exterior material for a power storage device is cold-formed, in order to prevent cracks from occurring in the base material protective layer, the following Conditions 4-1 and 4-2 may be satisfied.

[0194] Also, at this time, in order to maintain the gloss in the state before cold forming, the following Condition 4-3 or Condition 4-4 may be satisfied. Condition 4-1: The total compounding amount of the large filler and the small filler shall be 50% by mass or less. Condition 4-2: An aliphatic polyisocyanate or an aromatic polyisocyanate shall be used as at least part of the polyisocyanate component. Condition 4-3: Inorganic particles shall be used as the large filler. Condition 4-4: Use polyethylene particles as the large filler.

Explanation of symbols

[0195] 1… Battery element, 2… Lead, 10… Exterior material, 10a… Recess, 10b… Cover part, 11… Base material layer, 12… Base material protection layer, 13… Adhesive layer, 14… Metal foil layer, 15a… Corrosion prevention treatment layer, 15b… Corrosion prevention treatment layer, 16… Adhesive layer, 17… Sealant layer, 20… Secondary battery.

Claims

1. An exterior material for a power storage device, comprising, in order from at least the outer surface side, a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, and a sealant layer, wherein the substrate protective layer is formed by curing a curable resin containing a plurality of types of particles having different average particle diameters, the curable resin is composed of a polyol component as a main agent and a polyisocyanate component as a curing agent, when the particles having a large average particle diameter among the plurality of types of particles are defined as large fillers and the particles having a small average particle diameter are defined as small fillers, the average particle diameter of the large fillers is 10 μm or more, and the average particle diameter of the small fillers is 1 μm or more, and the blending amount of the large fillers in the substrate protective layer is 3% by mass or more, and the blending amount of the small fillers is 5% by mass or more, the exterior material for a power storage device, wherein the large fillers contain inorganic particles (however, excluding the case where the substrate protective layer contains polymer wax particles made of a non-crosslinked polymer).

2. An exterior material for a power storage device, comprising, in order from at least the outer surface side, a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, and a sealant layer, wherein the substrate protective layer is formed by curing a curable resin containing a plurality of types of particles having different average particle diameters, the curable resin is composed of a polyol component as a main agent and a polyisocyanate component as a curing agent, when the particles having a large average particle diameter among the plurality of types of particles are defined as large fillers and the particles having a small average particle diameter are defined as small fillers, the average particle diameter of the large fillers is 10 μm or more, and the average particle diameter of the small fillers is 1 μm or more, and the blending amount of the large fillers in the substrate protective layer is 3% by mass or more, and the blending amount of the small fillers is 5% by mass or more, the exterior material for a power storage device (however, excluding the case where the substrate protective layer contains polymer wax particles made of a non-crosslinked polymer, and the case where the substrate protective layer contains aggregates of a plurality of the large fillers).

3. The exterior material for a power storage device according to claim 2, wherein the large fillers contain inorganic particles.

4. The exterior material for a power storage device according to any one of claims 1 to 3, wherein the average particle diameter of the large fillers is 30 μm or less, the average particle diameter of the small fillers is 5 μm or less, and the blending amount of the large fillers is 25% by mass or less.

5. The exterior material for a power storage device according to any one of claims 1 to 4, wherein at least a part of the polyisocyanate component is composed of an alicyclic polyisocyanate.

6. At least a part of the polyisocyanate component is composed of an aliphatic polyisocyanate or an aromatic polyisocyanate, The compounding amount of the large filler is 25% by mass or less, and the total compounding amount of the large filler and the small filler is 50% by mass or less. The exterior material for a power storage device according to any one of claims 1 to 5.

7. The exterior material for a power storage device according to any one of claims 1 to 6, wherein the large filler contains particles of an organic substance.

8. The exterior material for a power storage device according to claim 7, wherein the large filler contains particles of a thermoplastic organic substance, and the thickness of the base material protective layer is 10 μm or less.

9. The exterior material for a power storage device according to any one of claims 1 to 8, wherein a coloring pigment is compounded in the adhesive layer.

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