JP7403208B2 - Exterior material for power storage devices - Google Patents

Description

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

As power storage devices, for example, secondary batteries such as lithium ion batteries, nickel hydride batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors are known. BACKGROUND ART Due to the miniaturization of portable devices and the limitations on installation space, there is a demand for further miniaturization of power storage devices, and lithium ion batteries with high energy density are attracting attention. Conventionally, metal cans have been used as the exterior material for lithium-ion batteries, but multilayer films (for example, base material layer/metal foil layer/ A film with a structure similar to a sealant layer) is now being used.

In a lithium ion battery that uses the multilayer film described above as an exterior material, a configuration is adopted in which the battery contents are covered with an exterior material that includes an aluminum foil layer as a metal foil layer in order to prevent moisture from entering the battery. A lithium ion battery employing such a configuration is called an aluminum laminate type lithium ion battery. The contents of a lithium ion battery include a positive electrode, a negative electrode, a separator, and a lithium salt as an electrolyte in an aprotic solvent with penetrating power such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. An electrolyte layer consisting of a dissolved electrolyte or a polymer gel impregnated with the electrolyte is included.

For example, in an aluminum laminate type lithium-ion battery, a recess is formed in a part of the exterior material by cold molding, the battery contents are stored in the recess, and the remaining part of the exterior material is folded back and the edges are heated. Embossed type lithium ion batteries sealed with a seal are known. The exterior materials that make up such lithium-ion batteries are required to exhibit stable sealing properties through heat sealing, and to be resistant to deterioration in the lamination strength between the aluminum foil layer and the sealant layer due to the electrolyte in the battery contents. ing.

In addition, with the miniaturization of power storage devices, the base material layer, metal foil layer, and sealant layer of the exterior material for power storage devices are becoming thinner. This has become a problem.

Therefore, for example, in Patent Document 1, by providing a heat sealing layer (sealant layer) containing an adhesive polymethylpentene layer, the barrier layer of the exterior body and the tab are stabilized without shorting due to the heat and pressure of heat sealing. Exterior materials that can be sealed have been proposed.

Japanese Patent Application Publication No. 2002-245983

In the conventional exterior material as described in Patent Document 1, measures are taken to prevent the insulation from decreasing due to contact between the tab lead and the metal foil layer. However, it is thought that there are other factors contributing to the decrease in insulation properties. In order to store energy as a lithium ion battery, it is necessary to charge and discharge the battery under predetermined conditions such as current value, voltage value, and environmental temperature to cause a chemical change (chemical formation). This chemical conversion step is performed in a temporary battery state in which an electrolyte is injected. The battery is then opened once to remove the gases generated by chemical formation and to replenish the electrolyte, and then a final seal is applied to complete the battery. This final seal seals the part once immersed in the electrolyte, so it becomes a degassing seal (degassing heat seal) that performs heat sealing while the electrolyte is trapped.

The present inventors' past verifications have revealed that deterioration in insulation is often caused by destruction of the sealant layer due to degassing and heat sealing, and that countermeasures against this are extremely important. Patent Document 1 does not consider destruction of the sealant layer due to degassing heat sealing.

In degassing heat sealing, when heat sealing the exterior material containing the battery contents, the electrolyte is bitten into the heat seal, which may cause the electrolyte to foam and destroy the sealant layer. . It is thought that the electrolytic solution enters through the destroyed portion of the sealant layer and comes into contact with the metal layer, resulting in a decrease in insulation.

Furthermore, the reduction in insulation properties caused by the destruction of the sealant layer due to degassing and heat sealing is susceptible to thinning of the sealant layer, so measures will need to be taken in the future to improve insulation properties.

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide an exterior material for a power storage device that can sufficiently maintain insulation properties after degassing and heat sealing.

The present invention provides an exterior packaging material for a power storage device that includes at least a base material layer, a metal foil layer provided with a corrosion prevention treatment layer on one or both surfaces, and a sealant layer in this order.

In the above exterior material, the sealant layer includes a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin, and the content of the incompatible component (B) is as follows. The amount is 1 to 40% by mass based on the total amount of the sealant layer. Furthermore, the above-mentioned exterior materials stacked so that the above-mentioned sealant layers face each other are heat-sealed at a temperature of 190°C and a pressure of 0.5 MPa for 3 seconds, and the bonded portion is sealed from one end to the other. In the graph showing the relationship between the displacement from the one end and the seal strength when the seal strength is continuously measured, the maximum seal strength _SM is 35 N/15 mm or more, and the following (1) or (2) ) satisfies the conditions.
(1) A stable region of seal strength exists after the displacement at which the maximum seal strength S _M is obtained, and the ratio S _S /S _M of the seal strength S _S to the maximum seal strength S _M in the stable region is 0. It is 3 or more.
(2) The above stable region does not exist, and the ratio S _A /S _M of the average seal strength S _A to the above maximum seal strength S _M at the displacement from the displacement where the above maximum seal strength S _M was obtained to the above other end is It is 0.3 or more.

According to the exterior material for a power storage device having the above configuration, even when the sealant layer is thinned, the insulation properties after degassing and heat sealing can be sufficiently maintained. The present inventors speculate that the reason why the above-mentioned exterior material for a power storage device has such an effect is as follows. The sealant layer of the exterior material for a power storage device is prone to defects during power storage device manufacturing processes such as heat sealing, degassing heat sealing, and molding. In particular, due to the thinning of the sealant layer, in degassing heat sealing in which heat sealing is performed with electrolyte trapped, the deformation of the sealant layer, which is thought to be due to volatilization (foaming) of the electrolyte, becomes large, resulting in poor insulation properties. tends to decline. A possible reason for the deterioration of insulation properties due to the deformation is that the vicinity of the metal foil layer is likely to be exposed due to foaming, and the electrolytic solution comes into contact with the exposed portion. In the present invention, the maximum seal strength S _M is 35 N/15 mm or more, and the exterior material satisfies the conditions (1) or (2) above. It is thought that this provides a strong cohesive force of the sealant resin, making it difficult to form voids even when the electrolytic solution foams. As a result, deterioration in insulation properties is less likely to occur.

In the above graph, it is preferable that the maximum seal strength S _M is 40 N/15 mm or more, and the ratio S _S /S _M or the ratio S _A /S _M is 0.6 or more. This makes it easier to suppress a decrease in insulation properties.

Since the sealant layer contains a polypropylene resin (A) and an incompatible component (B) that is not compatible with the polypropylene resin, a sea-island structure is formed in the sealant layer. By forming this sea-island structure, impact resistance can be imparted to the sealant layer, and seal strength can be improved.

It is preferable that the incompatible component (B) contains a compound (B1) having a compatible portion with the polypropylene resin (A). The present inventors considered that when foaming of the electrolytic solution occurs during degassing heat sealing, voids are likely to be formed starting from this sea-island interface. Therefore, in the sealant layer, the incompatible component (B) contains a compound (B1) having a compatible portion with the polypropylene resin (A), thereby improving the adhesion strength of the sea-island interface. Since the formation of voids due to foaming of the electrolytic solution is suppressed, the insulation properties can be further improved. Further, by improving the adhesion strength of the sea-island interface by the compound (B1), the seal strength S _M , _SS or S _A can also be improved.

The sealant layer may be composed of a plurality of layers, in which case at least one layer contains the polypropylene resin (A) and the incompatible component (B) that is incompatible with the polypropylene resin. , and the incompatible component (B) may be a layer containing the compound (B1).

The incompatible component (B) may contain an ethylene-α olefin copolymer. Further, the sealant layer may further include a compatible elastomer (C) that is compatible with the polypropylene resin (A), and the compatible elastomer (C) may contain a propylene-α olefin copolymer. Can be done.

The thickness of the sealant layer may be 10-45 μm. Even if the sealant layer is made thinner, sufficient insulation properties can be maintained after degassing and heat sealing.

According to the present invention, it is possible to provide an exterior material for a power storage device that can sufficiently maintain insulation properties after degassing and heat sealing.

FIG. 1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of the exterior material after the exterior materials are stacked one on top of the other so that the sealant layers face each other and heat-sealed. It is a graph showing an example of the measurement result of continuously measuring the seal strength of the adhesive part of the exterior material from one end to the other, and is a graph showing the relationship between the displacement from one end of the adhesive part and the seal strength. This is a graph showing another example of the measurement results of continuous measurement of the seal strength of the adhesive part of the exterior material from one end to the other, and is a graph showing the relationship between the displacement from one end of the adhesive part and the seal strength. be. FIG. 1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example.

Hereinafter, preferred embodiments of the present invention 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 redundant explanations will be omitted. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

[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 according to the present embodiment. As shown in FIG. 1, the exterior material (exterior material for power storage device) 10 of this embodiment includes a base material layer 11 and an adhesive layer 12 (a first adhesive layer) formed on one surface of the base material layer 11. ), a metal foil layer 13 formed on the surface of the first adhesive layer 12 opposite to the base layer 11 , and a first adhesive layer 12 of the metal foil layer 13 . A corrosion prevention treatment layer 14 formed on the surface opposite to the adhesive layer 12 and an adhesive layer 17 (second adhesive layer) formed on the surface of the corrosion prevention treatment layer 14 opposite to the metal foil layer 13. This is a laminate in which a sealant layer 16 formed on the surface of the second adhesive layer 17 opposite to the corrosion prevention treatment layer 14 is sequentially laminated. In the exterior material 10, the base material layer 11 is the outermost layer, and the sealant layer 16 is the innermost layer. That is, the exterior material 10 is used with the base layer 11 facing the outside of the power storage device and the sealant layer 16 facing the inside of the power storage device.

The exterior material 10 is stacked so that the sealant layers 16 face each other, and by heat-sealing them using a seal bar, the sealant layers 16 are thermally fused and adhered to each other. FIG. 2 is a cross-sectional view of the exterior material after heat-sealing, and the heat-sealed portion _PH shows the portion directly heat-sealed by the seal bar. Further, FIG. 2 shows a state in which a part of the sealant layer 16 melted by heating moves from the heat-sealed part _PH to form a sealant-fused part _16M . Due to the formation of the sealant fused portion _16M , the exterior materials 10 are bonded to each other even in the fused portion _PM that has not been heat sealed. That is, the exterior material 10 is bonded to each other at the heat-sealed portion P _H and the fused portion P _M (also referred to as the adhesive portion). The heat seal strength of the exterior material 10 bonded in this way is measured as the load per unit width required when peeling off one exterior material 10 that has been adhered to the other exterior material 10. The bonded exterior material 10 is used as a sample for heat-sealing strength measurement in the form of a strip including a fused part _PM on the side where the electrolyte is injected and a heat-sealed part _PH with the width direction of the heat seal as the longitudinal direction. is cut off. FIG. 3 is a graph showing an example of the measurement results of continuous measurement of the seal strength of the adhesive part of the exterior material from one end to the _other . It is a graph showing the relationship between displacement and seal strength. In the graph of FIG. 3, the left end indicates one end in the width direction of the bonded portion, and the point where the seal strength decreased indicates the other end. In the graph of FIG. 3, the curve rises from one end of the bonded portion, indicating the maximum seal strength. Peeling of the exterior material 10 first accompanies the destruction of the sealant fused part _16M at one end of this bonded part, and since a large force is required to destroy the sealant fused part _16M , the above maximum value in the graph is obtained. it is conceivable that. Since the maximum value in the graph is considered to be caused by the destruction of the sealant fused portion _16M , it is sometimes referred to as burst strength or the like. Usually, the maximum value of this seal strength is the maximum seal strength _SM . In this embodiment, the maximum sealing strength S _M is 35 N/15 mm or more, preferably 40 N/15 mm or more, and more preferably It is 50N/15mm or more.

In the graph of FIG. 3, the seal strength gradually stabilizes after the displacement at which the maximum value is obtained. In this specification, the region in the above graph in which the seal strength is stabilized is referred to as a stable region. The stable region is defined as a region in which the variation in seal strength during measurement is ±3 N/15 mm or less and has a length of 5 mm or more. In this embodiment, if a stable region exists in the above graph, the exterior material 10 satisfies the following condition (1).
(1) When heat sealing is performed under the conditions of temperature 190° C., pressure 0.5 MPa, and 3 seconds, the ratio S _S /S _M of the seal strength S _S to the maximum seal strength S _M in the above stable range is 0.3 or more. It is.

The ratio S _S /S _M is preferably 0.5 or more, more preferably 0.6 or more. When the maximum seal strength S _M is 35 N/15 mm or more and the ratio S _S /S _M is 0.3 or more, insulation properties after degassing heat sealing can be sufficiently maintained. Note that the seal strength _S is the average value of the seal strength in the above-mentioned stable region.

On the other hand, although the graph of FIG. 3 exemplifies the measurement results in the case where a stable region exists, there may be cases where the stable region does not exist. FIG. 4 is a graph showing another example of the measurement results of continuous measurement of the seal strength of the adhesive part of the exterior material from one end to the other, and shows the displacement and seal strength when peeled from the end of the adhesive part. It is a graph showing the relationship between In the graph of FIG. 4, there is no stable region after the displacement at which the maximum value of the seal strength is obtained. In this embodiment, if there is no stable region in the graph showing the measurement results of seal strength, the exterior material 10 satisfies the following condition (2).
(2) Average seal strength _S A maximum seal strength S _M at the displacement from the displacement where the maximum value was obtained to the other end when heat sealing was performed under the conditions of temperature 190°C, pressure 0.5 MPa, and 3 seconds. The ratio S _A /S _M is 0.3 or more.

The ratio S _A /S _M is preferably 0.5 or more, more preferably 0.6 or more. When the maximum sealing strength S _M is 35 N/15 mm or more and the ratio S _A /S _M is 0.3 or more, insulation properties after degassing heat sealing can be sufficiently maintained. The average seal strength S _A is the seal strength for every 1 mm of displacement after the displacement at which the maximum value is obtained (for example, the seal strength S ₁ , S ₂ , S ₃ , S ₄ , S ₅ , S ₆ in the graph of FIG. 4). ) and calculate their average value.

In this embodiment, a stable region may exist in the graph as shown in FIG. 3, or may not exist as shown in FIG. It is preferable that a stable region exists in the above graph. If the stable region exists in the graph, the exterior material 10 satisfies the condition (1) above, and if the stable region does not exist in the graph, the exterior material 10 satisfies the condition (2) above.

An improvement in the seal strength when the exterior material 10 is heat-sealed usually means an improvement in both the seal strength S _M and the seal strength S _S or the seal strength _SA . However, particularly the value of the maximum seal strength S _M varies depending on the size and strength of the sealant fused portion 16 _M formed at the end of the bonded portion. Therefore, the value of the maximum sealing strength S _M varies depending on, for example, the melt flow rate (MFR), crystallinity, thickness, etc. of the sealant layer 16, and also depends on the heat sealing conditions (temperature, pressure, time). Change. By controlling the maximum seal strength S _M with respect to the seal strengths _{S S} and _SA , the ratio S _S /S _M and the ratio S _A /S _M can also be controlled. Each layer constituting the exterior material 10 will be specifically described below.

<Base material layer 11>
The base material layer 11 is provided for the purpose of imparting heat resistance in the sealing process during the production of the power storage device and as a countermeasure against pinholes that may occur during processing and distribution, and it is preferable to use an insulating resin layer. As such a resin layer, for example, a stretched or unstretched film such as a polyester film, a polyamide film, a polypropylene film, etc. can be used as a single layer or a multilayer film in which two or more layers are laminated. It is also possible to use a coextruded multilayer stretched film in which a polyethylene terephthalate film (PET) and a nylon film (Ny) are coextruded using an adhesive resin and then subjected to a stretching treatment.

The base material layer 11 may be provided by directly coating on the metal foil layer 13 described later. In this case, the first adhesive layer 12 described later is unnecessary. As a method for forming the base material layer by coating, a method can be adopted in which a resin coating liquid such as urethane resin, acrylic resin, or polyester resin is applied and cured by ultraviolet irradiation, high temperature heating, aging treatment, etc. The coating method is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating, and bar coating can be employed.

The thickness of the base layer 11 is preferably 3 to 40 μm, more preferably 5 to 25 μm. When the thickness of the base material layer 11 is 3 μm or more, there is a tendency that the pinhole resistance and insulation properties of the exterior material 10 for a power storage device can be improved.

<First adhesive layer 12>
The first adhesive layer 12 is a layer that adheres the base material layer 11 and the metal foil layer 13. Specifically, the material constituting the first adhesive layer 12 is, for example, polyurethane made by reacting a bifunctional or more functional isocyanate compound with a base material such as polyester polyol, polyether polyol, acrylic polyol, carbonate polyol, etc. Examples include resin.

The various polyols mentioned above can be used alone or in combination of two or more types depending on the function and performance required of the exterior material.

Further, depending on the performance required of the adhesive, various other additives and stabilizers may be added to the above-mentioned polyurethane resin.

The thickness of the first adhesive layer 12 is not particularly limited, but from the viewpoint of obtaining desired adhesive strength, trackability, workability, etc., it is preferably 1 to 10 μm, and 3 to 7 μm, for example. More preferred.

<Metal foil layer 13>
The metal foil layer 13 has water vapor barrier properties that prevent moisture from entering the interior of the power storage device. Further, the metal foil layer 13 has ductility in order to be deep drawn. As the metal foil layer 13, various metal foils such as aluminum, stainless steel, copper, etc. can be used, and aluminum foil is preferable in terms of mass (specific gravity), moisture resistance, workability, and cost.

As the aluminum foil, a soft aluminum foil that has been subjected to an annealing treatment is preferably used because it can impart the desired ductility during molding, but it can also impart further pinhole resistance and ductility during molding. For this purpose, it is more preferable to use aluminum foil containing iron. The iron content in the aluminum foil is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass based on 100% by mass of the aluminum foil. When the iron content is 0.1% by mass or more, it is possible to obtain the exterior material 10 having better pinhole resistance and spreadability. When the iron content is 9.0% by mass or less, it is possible to obtain the exterior material 10 with more excellent flexibility.

The thickness of the metal foil layer 13 is not particularly limited, but it is preferably 9 to 200 μm, more preferably 15 to 100 μm, considering barrier properties, pinhole resistance, and workability. .

When aluminum foil is used for the metal foil layer 13, untreated aluminum foil may be used, but it is preferable to use degreased aluminum foil in order to impart electrolyte resistance.

In addition, when degreasing the aluminum foil, the degreasing treatment may be performed on only one side of the aluminum foil, or the degreasing treatment may be performed on both sides.

<Corrosion prevention treatment layer 14>
The corrosion prevention treatment layer 14 is a layer provided to prevent the metal foil layer 13 from being corroded by the electrolyte or hydrofluoric acid generated by the reaction between the electrolyte and water. The corrosion prevention treatment layer 14 is formed by, for example, degreasing treatment, hydrothermal conversion treatment, anodic oxidation treatment, chemical conversion treatment, or a combination of these treatments.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of acid degreasing include a method using an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, or hydrofluoric acid alone or a mixture thereof. For acid degreasing, an acid degreasing agent prepared by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the above-mentioned inorganic acid can be used to degrease aluminum, especially when aluminum foil is used for the metal foil layer 13. Not only is this effective, it also forms a passive aluminum fluoride, which is effective in terms of hydrofluoric acid resistance. Examples of alkaline degreasing include a method using sodium hydroxide or the like.

Examples of the hydrothermal conversion treatment include boehmite treatment in which the aluminum foil is immersed in boiling water to which triethanolamine is added.

Examples of the anodizing treatment include alumite treatment.

Examples of chemical conversion treatment include dipping type and coating type. Examples of immersion type chemical conversion treatments include chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, and various chemical conversion treatments consisting of a mixed phase thereof. It will be done. On the other hand, examples of the coating type chemical conversion treatment include a method of coating the metal foil layer 13 with a coating agent having anti-corrosion properties.

When forming at least a portion of the corrosion prevention treatment layer by any of these corrosion prevention treatments, hydrothermal conversion treatment, anodization treatment, and chemical conversion treatment, it is preferable to perform the above-mentioned degreasing treatment in advance. Note that when a degreased metal foil, such as a metal foil that has undergone an annealing process, is used as the metal foil layer 13, it is not necessary to perform the degreasing process again when forming the corrosion prevention treatment layer 14.

The coating agent used in the paint-on type chemical conversion treatment preferably contains trivalent chromium. Moreover, the coating agent may contain at least one kind of polymer selected from the group consisting of cationic polymers and anionic polymers described below.

Furthermore, among the above treatments, particularly in hydrothermal conversion treatment and anodization treatment, the surface of the aluminum foil is dissolved by a treatment agent to form an aluminum compound (boehmite, alumite) having excellent corrosion resistance. Therefore, since a co-continuous structure is formed from the metal foil layer 13 using aluminum foil to the corrosion prevention treatment layer 14, the above treatment is included in the definition of chemical conversion treatment. On the other hand, as will be described later, it is also possible to form the corrosion prevention treatment layer 14 using only a pure coating method, which is not included in the definition of chemical conversion treatment. For this method, for example, a sol of rare earth element oxide such as cerium oxide with an average particle size of 100 nm or less is used as a material that has an inhibitory effect on aluminum and is also suitable from an environmental standpoint. Examples of methods used include: By using this method, it is possible to impart a corrosion-inhibiting effect to metal foil such as aluminum foil even with a general coating method.

Examples of the above rare earth element oxide sols include sols using various solvents such as aqueous, alcohol, hydrocarbon, ketone, ester, and ether solvents. Among these, water-based sols are preferred.

In order to stabilize the dispersion, the rare earth element oxide sol usually contains an inorganic acid or its salt such as nitric acid, hydrochloric acid, phosphoric acid, or an organic acid such as acetic acid, malic acid, ascorbic acid, or lactic acid to stabilize the dispersion. Used as a curing agent. Among these dispersion stabilizers, phosphoric acid in particular is used in the exterior material 10 to (1) stabilize dispersion of the sol, (2) improve adhesion to the metal foil layer 13 by utilizing the aluminum chelating ability of phosphoric acid. , (3) imparting electrolyte resistance by capturing aluminum ions eluted under the influence of hydrofluoric acid (forming passivity); (4) providing corrosion prevention treatment layer 14 (because dehydration condensation of phosphoric acid is likely to occur even at low temperatures); This is expected to improve the cohesive force of the oxide layer).

Examples of the phosphoric acid or its salt include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, and alkali metal salts and ammonium salts thereof. Among these, condensed phosphoric acids such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, or alkali metal salts or ammonium salts thereof are preferable for realizing functions in the exterior material 10. In addition, when considering the dry film forming property (drying ability, amount of heat) when forming the corrosion prevention treatment layer 14 made of rare earth element oxide by various coating methods using the above rare earth element oxide sol, it is necessary to Sodium salts are more preferred because they have excellent dehydration condensation properties. As the phosphate, water-soluble salts are preferred.

The blending ratio of phosphoric acid (or its salt) to the rare earth element oxide is preferably 1 to 100 parts by mass based on 100 parts by mass of the rare earth element oxide. If the above-mentioned compounding ratio is 1 part by mass or more with respect to 100 parts by mass of the rare earth element oxide, the rare earth element oxide sol will become more stable and the function of the exterior material 10 will become better. The above blending ratio is more preferably 5 parts by mass or more based on 100 parts by mass of the rare earth element oxide. Moreover, if the above-mentioned compounding ratio is 100 parts by mass or less with respect to 100 parts by mass of the rare earth element oxide, the function of the rare earth element oxide sol will be enhanced and the performance of preventing corrosion of the electrolytic solution will be excellent. The above blending ratio is more preferably 50 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the rare earth element oxide.

Since the corrosion prevention treatment layer 14 formed from the rare earth element oxide sol is an aggregate of inorganic particles, the cohesive force of the layer itself may be reduced even after the dry curing process. Therefore, the corrosion prevention treatment layer 14 in this case is preferably composited with an anionic polymer or a cationic polymer described below in order to supplement the cohesive force.

Examples of the anionic polymer include polymers having a carboxyl group, such as poly(meth)acrylic acid (or a salt thereof) or a copolymer copolymerized with poly(meth)acrylic acid as a main component. The copolymerization components of this copolymer include alkyl (meth)acrylate monomers (alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, (t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide (alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxy (meth)acrylamide, N,N-dialkoxy Amide group-containing monomers such as (meth)acrylamide, (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), N-methylol (meth)acrylamide, and N-phenyl (meth)acrylamide; 2- Hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; Glycidyl group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; (meth)acryloxypropyltrimethoxysilane, (meth) Examples include silane-containing monomers such as acryloxypropyltriethoxylane; and isocyanate group-containing monomers such as (meth)acryloxypropyl isocyanate.

These anionic polymers play a role of improving the stability of the corrosion prevention treatment layer 14 (oxide layer) obtained using the rare earth element oxide sol. This is due to the effect of protecting the hard and brittle oxide layer with the acrylic resin component and the effect of trapping ionic contamination (especially sodium ions) derived from phosphates contained in the rare earth element oxide sol (cation catcher). achieved. In other words, if alkali metal ions such as sodium or alkaline earth metal ions are contained in the corrosion prevention treatment layer 14 obtained using the rare earth element oxide sol, corrosion will be prevented starting from the location containing these ions. The treated layer 14 is likely to deteriorate. Therefore, by immobilizing sodium ions and the like contained in the rare earth element oxide sol with the anionic polymer, the resistance of the corrosion prevention treatment layer 14 is improved.

The corrosion prevention treatment layer 14, which is a combination of an anionic polymer and rare earth element oxide sol, has the same corrosion prevention performance as the corrosion prevention treatment layer 14 formed by subjecting aluminum foil to chromate treatment. The anionic polymer preferably has a crosslinked structure of essentially water-soluble polyanionic polymer. Examples of the crosslinking agent used to form this structure include compounds having an isocyanate group, a glycidyl group, a carboxy group, and an oxazoline group.

Examples of the compound having an isocyanate group include diisocyanates such as tolylene diisocyanate, xylylene diisocyanate or a hydrogenated product thereof, hexamethylene diisocyanate, 4,4' diphenylmethane diisocyanate or a hydrogenated product thereof, isophorone diisocyanate; or these isocyanates. polyisocyanates such as adducts obtained by reacting these with polyhydric alcohols such as trimethylolpropane, biurets obtained by reacting with water, or isocyanurates which are trimers; Examples include blocked polyisocyanates in which isocyanates are blocked with alcohols, lactams, oximes, etc.

Examples of compounds having a glycidyl group include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, Epoxy compounds made by reacting epichlorohydrin with glycols such as neopentyl glycol; Epoxy compounds made by reacting epichlorohydrin with polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, and sorbitol; phthalic acid, terephthal Examples include epoxy compounds made by reacting dicarboxylic acids such as oxalic acid and adipic acid with epichlorohydrin.

Examples of the compound having a carboxy group include various aliphatic or aromatic dicarboxylic acids. Further, poly(meth)acrylic acid or an alkali (earth) metal salt of poly(meth)acrylic acid may be used.

As the compound having an oxazoline group, for example, when using a low molecular weight compound having two or more oxazoline units, or a polymerizable monomer such as isopropenyloxazoline, (meth)acrylic acid, (meth)acrylic acid alkyl ester , those copolymerized with acrylic monomers such as hydroxyalkyl (meth)acrylate.

In addition, the anionic polymer and the silane coupling agent are reacted, and more specifically, the carboxyl group of the anionic polymer and the functional group of the silane coupling agent are selectively reacted, and the crosslinking point is also converted into a siloxane bond. good. In this case, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ -Mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, etc. can be used. Among these, epoxysilane, aminosilane, and isocyanatesilane are preferable, especially considering the reactivity with anionic polymers or copolymers thereof.

The ratio of these crosslinking agents to the anionic polymer is preferably 1 to 50 parts by weight, more preferably 10 to 20 parts by weight, based on 100 parts by weight of the anionic polymer. If the ratio of the crosslinking agent is 1 part by mass or more with respect to 100 parts by mass of the anionic polymer, a crosslinked structure is sufficiently likely to be formed. If the ratio of the crosslinking agent is 50 parts by mass or less with respect to 100 parts by mass of the anionic polymer, the pot life of the coating liquid will be improved.

The method of crosslinking the anionic polymer is not limited to the above-mentioned crosslinking agent, but may also be a method of forming ionic crosslinks using titanium or zirconium compounds.

Examples of cationic polymers include polymers containing amines, such as polyethyleneimine, ionic polymer complexes made of polyethyleneimine and a polymer containing carboxylic acid, primary amine-grafted acrylic resins in which a primary amine is grafted onto an acrylic main skeleton, Examples include cationic polymers such as polyallylamine or derivatives thereof, and aminophenol. Examples of the polyallylamine include homopolymers and copolymers of allylamine, allylamine amide sulfate, diallylamine, dimethylallylamine, and the like. These amines may be free amines or stabilized with acetic acid or hydrochloric acid. Moreover, maleic acid, sulfur dioxide, etc. may be used as a copolymer component. Furthermore, a type in which thermal crosslinkability is imparted by partially methoxylating a primary amine can also be used, and aminophenol can also be used. Particularly preferred is allylamine or a derivative thereof.

The cationic polymer is preferably used in combination with a crosslinking agent having a functional group capable of reacting with an amine/imine, such as a carboxy group or a glycidyl group. As a crosslinking agent used in combination with a cationic polymer, a polymer having a carboxylic acid that forms an ionic polymer complex with polyethyleneimine can also be used, such as a polycarboxylic acid (salt) such as polyacrylic acid or an ionic salt thereof, or Copolymers in which a comonomer is introduced, polysaccharides having carboxy groups such as carboxymethylcellulose or ionic salts thereof, and the like.

In this embodiment, a cationic polymer is also described as one component constituting the corrosion prevention treatment layer 14. The reason for this is that as a result of extensive research using various compounds to provide the electrolyte resistance and hydrofluoric acid resistance required for exterior materials for power storage devices, the cationic polymer itself has also achieved electrolyte resistance and hydrofluoric acid resistance. This is because it was found to be a compound that can be applied. The reason for this is presumed to be that damage to the aluminum foil is suppressed by trapping fluorine ions with cationic groups (anion catcher).

Cationic polymers are more preferred materials in terms of improved adhesion. Further, since the cationic polymer is also water-soluble like the anionic polymer, it is more preferable to form a crosslinked structure to impart water resistance. As the crosslinking agent for forming a crosslinked structure in the cationic polymer, the crosslinking agents explained in the section of the anionic polymer can be used. When a rare earth element oxide sol is used as the corrosion prevention treatment layer 14, a cationic polymer may be used as the protective layer instead of the anionic polymer described above.

Corrosion prevention treatment layer by chemical conversion treatment, typified by chromate treatment, forms a graded structure with aluminum foil. The aluminum foil is then treated with chromium or a non-chromium compound to form a chemical conversion layer on the aluminum foil. However, since the above-mentioned chemical conversion treatment uses an acid as a chemical conversion treatment agent, it is accompanied by deterioration of the working environment and corrosion of the coating equipment. On the other hand, unlike the chemical conversion treatment typified by chromate treatment, the coating type corrosion prevention treatment layer 14 described above does not require forming a sloped structure on the metal foil layer 13 using aluminum foil. Therefore, the properties of the coating agent are not limited by acidity, alkalinity, neutrality, etc., and a good working environment can be realized. In addition, a coating type corrosion prevention treatment layer 14 is preferable from the viewpoint of environmental hygiene and the need for an alternative to chromate treatment using a chromium compound.

From the above, examples of combinations of the above-mentioned coating type corrosion prevention treatments are: (1) Rare earth element oxide sol only, (2) Anionic polymer only, (3) Cationic polymer only, (4) Rare earth element Oxide sol + anionic polymer (laminated composite), (5) Rare earth element oxide sol + cationic polymer (laminated composite), (6) (Rare earth element oxide sol + anionic polymer: laminated composite) / Examples include cationic polymer (multilayer), (7) (rare earth element oxide sol + cationic polymer: laminated composite)/anionic polymer (multilayer), and the like. Among them, (1) and (4) to (7) are preferred, and (4) to (7) are particularly preferred. However, this embodiment is not limited to the above combination. For example, as an example of selecting a corrosion prevention treatment, a cationic polymer is a highly preferable material in that it has good adhesion with the modified polyolefin resin mentioned in the explanation of the second adhesive layer or sealant layer described later. Therefore, when the second adhesive layer or sealant layer is composed of a modified polyolefin resin, a cationic polymer is provided on the surface in contact with the second adhesive layer or sealant layer (for example, configuration (5) and (6) and other configurations) are possible.

Further, the corrosion prevention treatment layer 14 is not limited to the layer described above. For example, it may be formed using a treatment agent containing a resin binder (such as aminophenol) mixed with phosphoric acid and a chromium compound, as in the case of coating type chromate, which is a known technique. By using this treatment agent, it is possible to obtain a layer that has both corrosion prevention function and adhesion. In addition, although it is necessary to consider the stability of the coating liquid, it is possible to achieve both corrosion prevention function and adhesion by using a coating agent that is made of rare earth element oxide sol and polycationic polymer or polyanionic polymer in advance. It can be made into a layer that has both.

The mass per unit area of the corrosion prevention treatment layer 14 is preferably 0.005 to 0.200 g/m ² , more preferably 0.010 to 0.100 g/m ² regardless of whether it has a multilayer structure or a single layer structure. preferable. If the mass per unit area is 0.005 g/m ² or more, it is easy to provide the metal foil layer 13 with a corrosion prevention function. Moreover, even if the mass per unit area exceeds 0.200 g/m ² , the corrosion prevention function does not change much. On the other hand, when a rare earth element oxide sol is used, if the coating film is thick, curing due to heat during drying may be insufficient, which may lead to a decrease in cohesive force. Note that the thickness of the corrosion prevention treatment layer 14 can be calculated from its specific gravity.

The corrosion prevention treatment layer 14 facilitates maintaining adhesion between the sealant layer and the metal foil layer, prevents the generation of starting points for foaming of the electrolytic solution, and further facilitates suppressing deterioration of insulation properties after degassing and heat sealing. From the viewpoint of The metal foil layer 13 may be formed by subjecting it to a chemical conversion treatment, or it may be formed by subjecting the metal foil layer 13 to a chemical conversion treatment and containing a cationic polymer.

<Second adhesive layer 17>
The second adhesive layer 17 is a layer that adheres the sealant layer 16 to the metal foil layer 13 on which the corrosion prevention treatment layer 14 is formed. For the second adhesive layer 17, a general adhesive for bonding a metal foil layer and a sealant layer can be used.

When the corrosion prevention treatment layer 14 has a layer containing at least one kind of polymer selected from the group consisting of the above-mentioned cationic polymer and anionic polymer, the second adhesive layer 17 is included in the corrosion prevention treatment layer 14. The layer preferably contains a compound (hereinafter also referred to as "reactive compound") that is reactive with the above-mentioned polymer.

For example, if the corrosion prevention treatment layer 14 includes a cationic polymer, the second adhesive layer 17 includes a compound that is reactive with the cationic polymer. When the corrosion prevention treatment layer 14 contains an anionic polymer, the second adhesive layer 17 contains a compound that is reactive with the anionic polymer. Furthermore, when the corrosion prevention treatment layer 14 contains a cationic polymer and an anionic polymer, the second adhesive layer 17 contains a compound that is reactive with the cationic polymer and a compound that is reactive with the anionic polymer. . However, the second adhesive layer 17 does not necessarily need to contain the above two types of compounds, and may contain a compound that is reactive with both the cationic polymer and the anionic polymer. Here, "having reactivity" means forming a covalent bond with a cationic polymer or anionic polymer. Moreover, the second adhesive layer 17 may further contain an acid-modified polyolefin resin.

Examples of the compound having reactivity with the cationic polymer include at least one compound selected from the group consisting of polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxy group, and compounds having an oxazoline group.

Examples of these polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group include the polyfunctional isocyanate compounds, glycidyl compounds, and carboxy groups exemplified above as crosslinking agents for making a cationic polymer into a crosslinked structure. Examples include compounds having an oxazoline group and compounds having an oxazoline group. Among these, polyfunctional isocyanate compounds are preferred because they have high reactivity with cationic polymers and are easy to form crosslinked structures.

Examples of the compound having reactivity with the anionic polymer include at least one compound selected from the group consisting of glycidyl compounds and compounds having an oxazoline group. Examples of these glycidyl compounds and oxazoline group-containing compounds include the glycidyl compounds and oxazoline group-containing compounds exemplified above as crosslinking agents for forming a cationic polymer into a crosslinked structure. Among these, glycidyl compounds are preferred because of their high reactivity with anionic polymers.

When the second adhesive layer 17 includes an acid-modified polyolefin resin, the reactive compound preferably also has reactivity with the acidic groups in the acid-modified polyolefin resin (that is, forms a covalent bond with the acidic groups). This further enhances the adhesion with the corrosion prevention treatment layer 14. In addition, the acid-modified polyolefin resin has a crosslinked structure, and the solvent resistance of the exterior material 10 is further improved.

The content of the reactive compound is preferably from an equivalent amount to 10 times the amount of acidic groups in the acid-modified polyolefin resin. If the amount is equal to or more, the reactive compound sufficiently reacts with the acidic group in the acid-modified polyolefin resin. On the other hand, if the amount exceeds 10 times the equivalent amount, the crosslinking reaction with the acid-modified polyolefin resin has reached sufficient saturation, so unreacted substances exist, and there is a concern that various performances may deteriorate. Therefore, for example, the content of the reactive compound is preferably 5 to 20 parts by mass (solid content ratio) per 100 parts by mass of the acid-modified polyolefin resin.

Acid-modified polyolefin resin is a polyolefin resin in which acidic groups are introduced. Examples of the acidic group include a carboxy group, a sulfonic acid group, an acid anhydride group, and particularly preferred are a maleic anhydride group and a (meth)acrylic acid group. As the acid-modified polyolefin resin, for example, the same one as that described later as the modified polyolefin resin (a) used for the first sealant layer 16a can be used.

The second adhesive layer 17 may contain various additives such as flame retardants, slip agents, anti-blocking agents, antioxidants, light stabilizers, and tackifiers.

The second adhesive layer 17 is made of, for example, acid-modified polyolefin, a polyfunctional isocyanate compound, a glycidyl compound, etc., from the viewpoint of suppressing a decrease in laminate strength when an electrolytic solution is involved and further suppressing a decrease in insulation properties. , a compound having a carboxyl group, a compound having an oxazoline group, and at least one curing agent selected from the group consisting of a carbodiimide compound. In addition, examples of the carbodiimide compound include N,N'-di-o-tolylcarbodiimide, N,N'-diphenylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N,N'-bis (2,6-diisopropylphenyl)carbodiimide, N,N'-dioctyldecylcarbodiimide, N-triyl-N'-cyclohexylcarbodiimide, N,N'-di-2,2-di-t-butylphenylcarbodiimide, N- Triyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide, N,N'-di-p-aminophenylcarbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, N,N '-di-cyclohexylcarbodiimide, N,N'-di-p-tolylcarbodiimide, and the like.

Further, as the adhesive forming the second adhesive layer 17, for example, a polyurethane adhesive containing a polyester polyol made of a hydrogenated dimer fatty acid and a diol and a polyisocyanate can be used.

The thickness of the second adhesive layer 17 is not particularly limited, but from the viewpoint of obtaining desired adhesive strength and processability, it is preferably 1 to 10 μm, more preferably 3 to 7 μm.

<Sealant layer 16>
The sealant layer 16 is a layer that provides sealing properties to the exterior material 10 by heat sealing. In the graph of FIG. 2, the sealant layer 16 is configured such that the maximum seal strength S _M is 35 N/15 mm or more, and the ratio S _S /S _M or the ratio S _A /S _M is 0.3 or more. Ru. An example of configuring the sealant layer 16 will be described below.

The sealant layer 16 includes a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin. The sealant layer 16 may further contain a compatible elastomer (C) that is compatible with the polypropylene resin (A). Hereinafter, in some cases, the polypropylene resin (A) will be referred to as "component (A)", and the incompatible component (B) that is incompatible with component (A) will be referred to as "component (B)", A compatible elastomer (C) that is compatible with the above component (A) may be referred to as a "compatible elastomer (C)" or "component (C)." Here, "not compatible with component (A)" and "incompatible with component (A)" (incompatible system) mean that the polypropylene resin constituting component (A) is This means that the dispersed phase size is 200 nm or more and less than 50 μm. In addition, "compatible with component (A)" and "having compatibility with component (A)" (compatible system) mean that the dispersed phase size in the polypropylene resin constituting component (A) is 1 nm or more and 200 nm. means to disperse less than

In the sealant layer 16, the incompatible component (B) preferably contains a compound (B1) having a compatible portion with the polypropylene resin (A). Hereinafter, the compound (B1) having a compatible moiety with component (A) may be referred to as "compound (B1)" or "component (B1)" depending on the case. The incompatible component (B) may consist only of the compound (B1).

When the sealant layer 16 contains the component (A) and the component (B), a sea-island structure is formed in the sealant layer 16, and the seal strength after heat sealing can be improved. When the sealant layer 16 further contains the above component (C), the sealant layer 16 can be provided with further flexibility. Since the sealant layer 16 has flexibility, it is possible to impart functions such as suppressing mold whitening, and it is possible to provide an exterior material with further improved functionality.

An example of the sealant layer 16 will be described below.

(Polypropylene resin (A))
The polypropylene resin (A) is a resin obtained from a polymerized monomer containing propylene. Examples of the polypropylene resin (A) include homopolypropylene and random polypropylene. The polypropylene resin (A) is preferably random polypropylene, more preferably a propylene-ethylene random copolymer, from the viewpoint of basic performance of the exterior material such as heat seal strength. A propylene-ethylene random copolymer has excellent heat-sealing properties at low temperatures and can improve sealing properties involving electrolyte.

In the propylene-ethylene random copolymer, the ethylene content is preferably 0.1 to 10% by mass, more preferably 1 to 7% by mass, and even more preferably 2 to 5% by mass. When the ethylene content is 0.1% by mass or more, the effect of lowering the melting point by copolymerizing ethylene can be sufficiently obtained, and the sealing properties involving the electrolyte can be further improved, as well as impact resistance can be obtained. , there is a tendency that seal strength and molding whitening resistance can be improved. When the ethylene content is 10% by mass or less, the melting point can be prevented from falling too much, and the maximum seal strength _SM can be prevented from becoming too high (that is, the ratio S _S /S _M can be increased). Tend. Note that the ethylene content can be calculated from the mixing ratio of monomers during polymerization.

The melting point of the propylene-ethylene random copolymer is preferably 120 to 145°C, more preferably 125 to 140°C. When the melting point is 120° C. or higher, there is a tendency that the maximum sealing strength S _M can be prevented from becoming too high (that is, the ratio S _S /S _M can be increased). When the melting point is 145° C. or lower, there is a tendency that the sealing properties involving the electrolyte can be further improved.

The propylene-ethylene random copolymer may be acid-modified, for example, an acid-modified propylene-ethylene random copolymer obtained by graft-modifying maleic anhydride. By using an acid-modified propylene-ethylene random copolymer, it is possible to maintain adhesion to the tab reed even without a tab sealant.

Propylene-ethylene random copolymers can be used alone or in combination of two or more.

In the sealant layer 16, the content of component (A) may be 50 to 99% by mass, 50 to 95% by mass, 50 to 85% by mass, based on the total solid content of the sealant layer 16. It may be mass %. When the content of component (A) is 50% by mass or more, the sealing properties can be improved due to the effect of using component (A) itself. In addition, by setting the content of component (A) to 50% by mass or more, it is possible to prevent component (B) from being present in excess, thereby suppressing a decrease in heat resistance and cohesive force of the sealant layer 16. . On the other hand, by setting the content of component (A) to 99% by mass or less, component (B) can be contained at 1% by mass or more, so that the seal strength and insulation properties of component (B) can be improved. can.

(Incompatible component (B))
Examples of the incompatible component (B) include graft copolymers, block copolymers, and random copolymers. These copolymers have at least a portion that is incompatible with component (A).

The incompatible component (B) preferably contains a compound (B1) having a compatible portion with the polypropylene resin (A). By containing the compound (B1) in the incompatible component (B), it is possible to improve the adhesion strength of the sea-island interface of the sea-island structure formed by the components (A) and (B). Since the formation of voids due to foaming of the liquid is suppressed, insulation properties can be further improved. Further, by improving the adhesion strength of the sea-island interface by the compound (B1), the above-mentioned seal strength S _M , S _S or S _A can also be improved. Such a compound (B1) can be obtained, for example, when the incompatible component (B) is a graft copolymer or a block copolymer. Graft copolymers suitable as compound (B1) include graft copolymers consisting of a main chain of polyolefin and side chains of polystyrene, and graft copolymers consisting of a main chain of polyolefin and side chains of styrene-acrylonitrile copolymer. etc. As the above-mentioned graft copolymer, for example, "Modiper" manufactured by NOF Corporation is suitable.

Suitable block copolymers as compound (B1) include block copolymers having a block composed of styrene units and a block composed of ethylene-butylene units, and block copolymers having blocks composed of styrene units and ethylene-butylene units. A block copolymer having a block composed of a unit and a block composed of a crystalline olefin unit, a block copolymer having a block composed of a crystalline ethylene unit and a block composed of an ethylene-butylene unit , a block copolymer having a block composed of ethylene and a block composed of ethylene-octene 1, and a block copolymer having a block composed of propylene units and a block composed of ethylene units, etc. can be mentioned. For example, a block composed of propylene units is a part compatible with the component (A), and a block composed of ethylene units is a part incompatible with the component (A). Suitable examples of the block copolymer include "DYNARON" manufactured by JSR, "INTUNE" and "INFUSE" manufactured by DOW.

The incompatible component (B) may contain an incompatible elastomer. Examples of the incompatible elastomer include polyolefin elastomers containing α-olefin as a comonomer. In particular, by using an ethylene-α olefin copolymer, there is a tendency that functionality can be imparted to the sealant layer 16 without reducing the strength of the electrolyte laminate or the strength of various seals related to the electrolyte. The ethylene-α-olefin copolymer is a copolymer of ethylene and at least one α-olefin selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. An ethylene-butene-1 random copolymer obtained by copolymerizing ethylene with 1-butene can be preferably used. As the ethylene-α olefin copolymer, "Tafmer" manufactured by Mitsui Chemicals, "Exelen" manufactured by Sumitomo Chemical, etc. are suitable.

The sealant layer 16 is prepared by preparing a dispersion in which the incompatible component (B) is dispersed in the polypropylene resin (A), and using the dispersion, the polypropylene resin (A) and the incompatible component (B) are prepared. May contain. Such a dispersion includes a dispersion in which an elastomer is finely dispersed in a polypropylene resin. When the sealant layer 16 contains a dispersion in which the incompatible component (B) is dispersed in the polypropylene resin (A) in advance, the insulation properties and seal strength tend to be further improved. The incompatible component (B) in the dispersion preferably contains a graft copolymer or a block copolymer. When the incompatible component (B) in the dispersion contains a graft copolymer or a block copolymer, there is a tendency that the adhesion at the sea-island interface can be further improved.

An example of a dispersion in which an incompatible component (B) is dispersed in a polypropylene resin (A) and in which the incompatible component (B) contains a graft copolymer is (using peroxide). Examples include dynamically crosslinked PP elastomer (TPV). Dynamically crosslinked PP elastomer (TPV) is a dispersion in which a crosslinked elastomer is finely dispersed in polypropylene, and the crosslinked elastomer is grafted, and the grafted portion forms an interface with the polypropylene. It is a dispersion with In the dynamically crosslinked PP elastomer (TPV), polypropylene corresponds to component (A), and the grafted elastomer corresponds to compound (B1). Moreover, block polypropylene etc. are mentioned as an example of the dispersion in which the incompatible component (B) is dispersed in the polypropylene resin (A). Block polypropylene is composed of homopolypropylene and an ethylene-based elastomer component that is incompatible therewith. In block polypropylene, homopolypropylene corresponds to component (A), and the ethylene elastomer component corresponds to component (B). Further, examples of the dispersion in which an elastomer is finely dispersed in a polypropylene resin include reactor type TPO and the like. In the reactor type TPO, the polypropylene resin corresponds to the (A) component, and the elastomer corresponds to the (B) component. Suitable reactor type TPOs include, for example, "Zelas" manufactured by Mitsubishi Chemical Corporation, "Cataroy" manufactured by Montell, "Wellnex" manufactured by Nippon Polypropylene, and "Prime TPO" manufactured by Prime Polymer.

Although olefin-based and styrene-based materials have been described above as the incompatible component (B), from the viewpoint of electrolyte resistance, it is preferable that the incompatible component (B) is an olefin-based material.

(Compatible elastomer (C))
Examples of the compatible elastomer (C) include propylene-α olefin copolymer. By using the propylene-α olefin copolymer, functionality can be imparted to the sealant layer 16 without reducing the strength of the electrolyte laminate or the strength of various seals related to the electrolyte. The propylene-α-olefin copolymer is a compound obtained by copolymerizing propylene with an α-olefin selected from 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. A propylene-butene-1 random copolymer obtained by copolymerizing 1-butene can be preferably used.

The melting point of the polyolefin elastomer is preferably 150°C or lower, but from the viewpoint of improving the ratio S _S /S _M , suppressing mold whitening, and improving sealing properties related to the electrolyte, it is 60 to 120°C. The temperature is preferably 65 to 90°C, more preferably 65 to 90°C. By having a melting point of 150° C. or less, it is possible to improve the sealing properties involving the electrolyte, especially the degassing heat seal strength. Further, a melting point of 60° C. or higher is advantageous from the viewpoint of improving the ratio S _S /S _M.

The polyolefin elastomers can be used alone or in combination of two or more.

In the sealant layer 16, the content of component (B) is 1 to 40% by mass, preferably 5 to 25% by mass, based on the total solid content of the sealant layer 16. When the content of component (B) is 1% by mass or more, impact resistance can be imparted to the sealant layer 16, and seal strength and insulation properties can be improved. On the other hand, by setting the content of component (B) to 40% by mass or less, the cohesive force of the entire sealant layer 16 can be improved, and the seal strength and insulation properties can be improved. For convenience, a dispersion in which an elastomer is finely dispersed in a polypropylene resin is described as an incompatible component (B), but the elastomer part in the above dispersion is classified as a component (B), and the polypropylene resin is classified as an incompatible component (A). ) are classified as components.

When the sealant layer 16 contains the (C) component, the content of the (C) component in the sealant layer 16 is 5 to 30% by mass, based on the total solid content of the sealant layer 16, and 10 to 25% by mass. It is preferable that there be. When the content of component (C) is 5% by mass or more, flexibility of the sealant layer 16 can be easily obtained, and functions such as suppressing mold whitening can be imparted to the exterior material with improved functionality. can be provided. On the other hand, by setting the content of component (C) to 30% by mass or less, the cohesive force of the entire sealant layer 16 can be improved, and the seal strength and insulation properties can be improved.

In addition, the content ratio (M _C /M _B ) of the compatible elastomer (C) to the incompatible component (B) is preferably 0.2 to 3.0 in terms of mass ratio, and 0.3 to 2 More preferably, it is .0. When the content ratio (M _C /M _B ) is within the above range, the maximum seal strength S _M and the seal strengths S _S and _SA can be improved in a well-balanced manner.

When the incompatible component (B) contains the compound (B1), the content of the compound (B1) in the sealant layer 16 is preferably 1 to 40% by mass, based on the total amount of the sealant layer, and preferably 2 to 40% by mass. More preferably, it is 25% by mass. When the content of compound (B1) is 1% by mass or more, it becomes easier to improve the adhesion strength of the sea-island interface, and it becomes easier to obtain the effect of improving seal strength and insulation. On the other hand, by setting the content of the compound (B1) to 40% by mass or less, it becomes easier to suppress a decrease in the cohesive force, seal strength, and insulation properties of the sealant layer 16 as a whole.

(Additional ingredients)
The sealant layer 16 may further contain components other than the components (A) to (C) described above. As other components other than components (A) to (C), other resins such as LDPE (low density polyethylene) may be added, for example, in order to improve take-up properties and processability. The content of other resin components to be added is preferably 10 parts by mass or less when the total mass of the sealant layer 16 is 100 parts by mass. In addition, examples of components other than resins include slip agents, anti-blocking agents, antioxidants, light stabilizers, flame retardants, and the like. The content of components other than these resins is preferably 5 parts by mass or less when the total mass of the sealant layer 16 is 100 parts by mass.

The presence of α-olefin in the sealant layer 16 can be confirmed by attribution using FT-IR (Fourier transform infrared spectrophotometer). The content of α-olefin can be determined using a calibration curve based on the transmittance or absorbance of the characteristic absorption bands of components (A) to (C) using a sealant layer 16 containing a known amount of elastomer containing a known amount of α-olefin. This can be confirmed by creating . Furthermore, the α-olefin content of each of the incompatible component (B) and the compatible elastomer (C) was similarly imaged using the characteristic absorption band of FT-IR, and microscopic FT-IR (transmission method) ) can be confirmed by mapping the absorption band caused by butene-1. In addition to FT-IR, it is also possible to confirm the presence and content of butene-1 by measuring the sealant layer 16 by NMR.

The thickness of the sealant layer 16 is, for example, 5 to 100 μm. Due to the demand for miniaturization of power storage devices, the thickness may be 10 to 80 μm, 10 to 60 μm, 10 to 45 μm, or 30 μm or less. Even with such a thin film configuration, the exterior material for a power storage device according to the present embodiment can suppress a decrease in insulation properties after heat sealing, molding, and degassing heat sealing.

Although the preferred embodiment of the exterior material for a power storage device according to the present embodiment has been described above in detail, the present invention is not limited to such specific embodiment, and the present invention is described within the scope of the claims. Various modifications and changes are possible within the scope of the gist.

For example, although FIG. 1 shows a case where the corrosion prevention treatment layer 14 is formed on the surface of the metal foil layer 13 on the second adhesive layer 17 side, the corrosion prevention treatment layer 14 is formed on the surface of the metal foil layer 13 on the second adhesive layer 17 side. It may be formed on the surface of the first adhesive layer 12 side, or may be formed on both surfaces of the metal foil layer 13. When the corrosion prevention treatment layer 14 is formed on both sides of the metal foil layer 13, the structure of the corrosion prevention treatment layer 14 formed on the first adhesive layer 12 side of the metal foil layer 13 and the structure of the metal foil layer 13 are different. The structure of the corrosion prevention treatment layer 14 formed on the second adhesive layer 17 side may be the same or different.

Although FIG. 1 shows the case where the metal foil layer 13 and the sealant layer 16 are laminated using the second adhesive layer 17, the exterior material 20 for power storage device shown in FIG. 5 and the power storage device shown in FIG. The sealant layer 16 may be formed directly on the metal foil layer 13 without intervening the second adhesive layer 17 like the device exterior material 30. On the other hand, the power storage device exterior material 20 shown in FIG. 5 and the power storage device exterior material 30 shown in FIG. 6 can also include a second adhesive layer 17 between the metal foil layer 13 and the sealant layer 16. .

Although FIG. 1 shows a case in which the sealant layer 16 is formed from a single layer, the sealant layer 16 can be formed by a power storage device exterior material 20 shown in FIG. 5 and a power storage device exterior material 30 shown in FIG. It may be formed from two or more layers. The composition of each of the multiple layers forming the sealant layer 16 may be the same or different. In addition, when the sealant layer 16 is multilayered, at least one of the layers contains a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin, and the incompatible component (B) is preferably a layer containing compound (B1).

In the exterior material 20 for a power storage device shown in FIG. 5, the sealant layer 16 includes a first sealant layer 16a and a second sealant layer 16b. Here, the first sealant layer 16a is the outermost layer of the sealant layer, and the second sealant layer 16b is the innermost layer of the sealant layer. At least one layer selected from the group consisting of the first sealant layer 16a and the second sealant layer 16b contains a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin, and It is preferable that the incompatible component (B) is a layer containing the compound (B1).

The second sealant layer 16b (innermost layer) can be formed using, for example, the same components as the sealant layer 16 in the exterior material 10 described above. In the second sealant layer 16b, when the incompatible component (B) contains the compound (B1), a decrease in insulation properties is easily suppressed.

Furthermore, in the second sealant layer 16b, the incompatible component (B) does not need to contain the compound (B1).

The thickness of the second sealant layer 16b may be, for example, 5 to 100 μm, 10 to 60 μm, 10 to 40 μm, 10 to 30 μm, for example. The thickness may be 20 μm or less.

The first sealant layer 16a (outermost layer, metal foil side layer) may be formed using, for example, the same components as the second sealant layer 16b, but in the first sealant layer 16a, for example, In place of the same constituent components as those of the second sealant layer 16b, it is preferable to use an adhesive constituent component containing an additive component as necessary in consideration of aluminum treatment and adhesive properties. By using the adhesive component described above as the first sealant layer 16a, the sealant layer can be formed on the metal foil layer without using an adhesive layer. Like the second sealant layer 16b, the first sealant layer 16a contains components corresponding to the above-mentioned components (A) and (B), and the first sealant layer 16a forms a sea-island structure, and In the first sealant layer 16a, when the incompatible component (B) contains the compound (B1), the adhesion of the sea-island interface can be improved, and the adhesion between the sealant layer and the metal foil layer can be improved. It tends to be easier to hold, to prevent the generation of voids due to foaming of the electrolytic solution, and to further suppress the decrease in insulation properties after degassing and heat sealing.

The adhesive components in the first sealant layer 16a are not particularly limited, but include a modified polypropylene resin (i) component as the (A) component, and a macrophase-separated thermoplastic elastomer (ii) as the (B) component. ) components. Further, the additive component preferably contains polypropylene having an atactic structure or a propylene-α olefin copolymer (iii) having an atactic structure. Each component will be explained below.

(Modified polypropylene resin (i))
The modified polypropylene resin (i) is a polypropylene resin in which an unsaturated carboxylic acid derivative component derived from an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, or an ester of an unsaturated carboxylic acid is graft-modified onto a polypropylene resin. It is preferable that the resin is made of a resin.

Examples of the polypropylene resin include homopolypropylene and random polypropylene.

Compounds used for graft modification of these polypropylene resins include unsaturated carboxylic acid derivative components derived from unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and unsaturated carboxylic acid esters. It will be done.

Specifically, unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo[2,2,1]hept-2-ene-5, Examples include 6-dicarboxylic acid.

Examples of unsaturated carboxylic acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, and bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic anhydride. Examples include acid anhydrides of unsaturated carboxylic acids such as carboxylic acids.

Examples of esters of unsaturated carboxylic acids include methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citraconate, and tetrahydrophthalic anhydride. Examples include esters of unsaturated carboxylic acids such as dimethyl and dimethyl bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylate.

The modified polypropylene resin (i) is obtained by graft polymerization (graft modification) of 0.2 to 100 parts by mass of the above-mentioned unsaturated carboxylic acid derivative component to 100 parts by mass of the base polypropylene resin in the presence of a radical initiator. It can be manufactured by The reaction temperature for graft modification is preferably 50 to 250°C, more preferably 60 to 200°C. The reaction time is appropriately set depending on the production method, but for example, in the case of melt graft polymerization using a twin-screw extruder, it is preferably within the residence time of the extruder, specifically 2 to 30 minutes, and 5 to 10 minutes. minutes is more preferred. Incidentally, the graft modification can be carried out under either normal pressure or pressurized conditions.

Examples of radical initiators used for graft modification include organic peroxides such as alkyl peroxides, aryl peroxides, acyl peroxides, ketone peroxides, peroxyketals, peroxycarbonates, peroxyesters, and hydroperoxides. It will be done.

These organic peroxides can be appropriately selected and used depending on the conditions of the reaction temperature and reaction time mentioned above. For example, in the case of melt graft polymerization using a twin-screw extruder, alkyl peroxides, peroxyketals, and peroxy esters are preferred, and specifically di-t-butyl peroxide, 2,5-dimethyl-2,5-dimethyl -t-butylperoxy-hexyne-3, dicumyl peroxide and the like are preferred.

The modified polypropylene resin (i) is preferably modified with maleic anhydride, and suitable examples include "Admer" manufactured by Mitsui Chemicals, "Modic" manufactured by Mitsubishi Chemical, and the like. Such modified polypropylene resin (i) has excellent reactivity with various metals and polymers having various functional groups, so it is possible to use this reactivity to impart adhesion to the first sealant layer 16a. It is possible to improve electrolyte resistance.

(Macro phase separated thermoplastic elastomer (ii))
The macrophase-separated thermoplastic elastomer (ii) forms a macrophase-separated structure in the modified polypropylene resin (i) with a dispersed phase size in a range of more than 200 nm and 50 μm or less.

Since the first sealant layer 16a contains the macrophase-separated thermoplastic elastomer (ii), this occurs when laminating the modified polypropylene resin (i), etc., which can be the main component of the first sealant layer 16a. It is possible to release the residual stress caused by this, and it is possible to impart viscoelastic adhesiveness to the first sealant layer 16a. Therefore, the adhesion of the first sealant layer 16a is further improved, and an exterior material 20 with better electrolyte resistance can be obtained. By containing the macrophase-separated thermoplastic elastomer (ii) in the first sealant layer 16a, impact resistance can be imparted to the sealant layer 16, and seal strength and insulation properties can be improved.

The macrophase-separated thermoplastic elastomer (ii) exists in the form of sea islands in the modified polypropylene resin (i), but when the dispersed phase size is 200 nm or less, it is difficult to improve viscoelastic adhesion. It becomes difficult. On the other hand, when the dispersed phase size exceeds 50 μm, the modified polypropylene resin (i) and the macrophase-separated thermoplastic elastomer (ii) are essentially incompatible, so lamination suitability (processability) is significantly reduced. At the same time, the physical strength of the first sealant layer 16a tends to decrease. From the above, the dispersed phase size is preferably 500 nm to 10 μm.

Such a macrophase-separated thermoplastic elastomer (ii) is, for example, a combination of ethylene and an α-olefin selected from 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. Examples include polymerized polyethylene thermoplastic elastomers.

Furthermore, as the macro phase-separated thermoplastic elastomer (ii), commercially available products can be used, such as "Tafmer" manufactured by Mitsui Chemicals, "Xelas" manufactured by Mitsubishi Chemical, and "Cataroy" manufactured by Montell. etc. are suitable.

In the first sealant layer 16a, the content of the macrophase-separated thermoplastic elastomer (ii) relative to the modified polypropylene resin (i) is 1 to 40 parts by mass based on 100 parts by mass of the modified polypropylene resin (i). The amount is preferably 5 to 30 parts by mass, and more preferably 5 to 30 parts by mass. Here, if the content of the macrophase-separated thermoplastic elastomer (ii) is less than 1 part by mass, improvement in the adhesion of the first sealant layer cannot be expected. On the other hand, if the content of the macrophase-separated thermoplastic elastomer (ii) exceeds 40 parts by mass, the modified polypropylene resin (i) and the macrophase-separated thermoplastic elastomer (ii) are inherently low in compatibility and cannot be processed. Sexuality tends to deteriorate significantly. Furthermore, since the macrophase-separated thermoplastic elastomer (ii) is not a resin that exhibits adhesive properties, the adhesion of the first sealant layer 16a to other layers such as the second sealant layer 16b and the corrosion prevention treatment layer 14 is reduced. It becomes easier.

(Atactic structure polypropylene or atactic structure propylene-α olefin copolymer (iii))
The first sealant layer 16a preferably contains polypropylene having an atactic structure or a propylene-α olefin copolymer having an atactic structure (hereinafter simply referred to as "component (iii)") as an additive component. Here, component (iii) is a completely amorphous resin component. By including the component (iii) in the first sealant layer 16a, flexibility can be imparted to the sealant layer 16. The flexibility of the sealant layer 16 allows the exterior material 10 to have functions such as suppressing mold whitening, thereby providing an exterior material with improved functionality.

The first sealant layer 16a contains, as an additive component, a propylene-α olefin copolymer having an isotactic structure corresponding to the component (C) in addition to the component (iii) mentioned above for imparting flexibility. It may further contain.

In the first sealant layer 16a, the total mass of the components (i) and (ii) may be, for example, 60% by mass or more and 95% by mass or less, based on the total mass of the first sealant layer 16a. , 70% by mass or more and 90% by mass or less.

In the first sealant layer 16a, the mass of component (iii) is, for example, 5% by mass or more and 40% by mass or less, based on the total mass of components (i), (ii), and (iii). is preferred. If the mass of component (iii) is 5% by mass or more based on the total mass of component (i), component (ii), and component (iii), the effect of adding the additive as described above will be reduced. They tend to be easier to obtain. On the other hand, if the mass of component (iii) is 40% by mass or less based on the total mass of components (i), (ii), and (iii), the second sealant layer 16b or the corrosion prevention treatment layer The adhesion of the first sealant layer 16a to other layers such as the first sealant layer 16a tends to decrease easily. From these viewpoints, in the first sealant layer 16a, the total mass of component (i) and component (ii) is based on the total mass of component (i), component (ii), and component (iii), for example, It is preferably 60 to 95% by mass.

In addition, as a method for analyzing the component (iii) which is an additive component in the first sealant layer 16a, it is possible to quantify it by stereoregularity evaluation using nuclear magnetic resonance spectroscopy (NMR), for example.

The first sealant layer 16a includes, in addition to adhesive components (i.e., modified polypropylene resin (i) and macrophase-separated thermoplastic elastomer (ii)) and additive components (i.e., component (iii)), necessary Depending on the situation, various additives such as flame retardants, slip agents, anti-blocking agents, antioxidants, light stabilizers, tackifiers, etc. may be included.

The thickness of the first sealant layer 16a is not particularly limited, but from the viewpoint of stress relaxation and moisture/electrolyte permeation, it is preferably the same or less than the thickness of the second sealant layer 16b.

Also, in the exterior material 20 for a power storage device, from the viewpoint of thinning the film, the thickness of the sealant layer 16 (total thickness of the first sealant layer 16a and the second sealant layer 16b) is 10 to 80 μm. It may be 10 to 60 μm, 10 to 45 μm, or 30 μm or less. Even with such a thin film configuration, the exterior material for a power storage device according to the present embodiment can suppress a decrease in insulation properties after heat sealing, molding, and degassing heat sealing.

Although FIG. 5 shows a case where the sealant layer 16 is formed of two layers, the sealant layer 16 may be formed of three layers like the exterior material 30 for a power storage device shown in FIG. 6. In the power storage device exterior material 30 shown in FIG. 5, the sealant layer 16 includes a first sealant layer 16a, a second sealant layer 16b, and a third sealant layer 16c. Here, the first sealant layer 16a is the outermost layer (metal foil side layer) of the sealant layers, the third sealant layer 16c is an intermediate layer of the sealant layers, and the second sealant layer 16b is the outermost layer of the sealant layers. It is the innermost layer. At least one layer selected from the group consisting of these three layers contains a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin, and the incompatible component (B) is a compound. It is preferable that the layer contains (B1).

Examples and preferred forms of the material constituting the first sealant layer 16a of the exterior material 30 for a power storage device are the same as those for the first sealant layer 16a of the exterior material 20 for a power storage device.

Examples and preferred forms of the materials constituting the second sealant layer 16b and third sealant layer 16c of the power storage device exterior packaging material 30 are the same as those for the second sealant layer 16b of the power storage device exterior packaging material 20.

In the exterior material 30 for a power storage device, the thickness of the first sealant layer 16a may be, for example, 2 to 30 μm, 5 to 20 μm, or 8 to 10 μm, The thickness of the third sealant layer 16b may be, for example, 5 to 80 μm, 13 to 40 μm, or 15 to 20 μm, and the thickness of the third sealant layer 16c may be, for example, , 2 to 30 μm, 5 to 20 μm, or 8 to 10 μm.

Also in the power storage device exterior material 30, from the viewpoint of thinning the film, the thickness of the sealant layer 16 (the total thickness of the first sealant layer 16a, second sealant layer 16b, and third sealant layer 16c) is , 30 μm or less. Even with such a thin film configuration, the exterior material for a power storage device according to the present embodiment can suppress a decrease in insulation properties after heat sealing, molding, and degassing heat sealing.

Similarly, when the sealant layer is composed of multiple layers like the exterior materials 20 and 30 for power storage devices, the content of the incompatible component (B) in the sealant layer 16 is based on the total amount of the sealant layer 16. The content is 1 to 40% by weight, preferably 1 to 35% by weight, and more preferably 2 to 25% by weight. The content of the component in each layer is adjusted so that the content of the component (B) in the entire sealant layer 16 is within the above range.

When the sealant layer is composed of multiple layers like the exterior materials 20 and 30 for power storage devices, in the first sealant layer 16a closest to the metal foil layer 13, the incompatible component (B) combines the compound (B1). It is preferable to contain. In the first sealant layer 16a, since the incompatible component (B) contains the compound (B1), the adhesion strength of the sea-island interface can be improved, and the formation of voids due to foaming of the electrolytic solution can be suppressed. Therefore, there is a tendency that the insulation properties after degassing heat sealing can be further improved. Foaming of the electrolytic solution during degassing heat sealing often occurs in a portion of the sealant layer 16 close to the metal foil layer 13, and in the layer closest to the metal foil layer 13, the incompatible component (B) is By containing (B1), there is a tendency to more efficiently suppress a decrease in insulation properties. In the first sealant layer 16a, when the incompatible component (B) contains a compound (B1), the content of the compound (B1) is 1 to 40% by mass based on the total amount of the first sealant layer 16a. parts by weight, and more preferably from 2 to 25 parts by weight.

When the content of the compound (B1) in the first sealant layer 16a is 1 part by mass or more, sealing strength and insulation properties can be easily obtained. Moreover, when the content of the compound (B1) is 40 parts by mass or less, it becomes easier to suppress a decrease in the cohesive force, seal strength, and insulation properties of the entire sealant layer.

Moreover, in the second sealant layer 16b or the third sealant layer 16c, the incompatible component (B) may contain the compound (B1). Since the second sealant layer 16b or the third sealant layer 16c contains the compound (B1), it is possible to improve the adhesion strength of the sea-island interface formed by the components (A) and (B), Since the formation of voids due to foaming of the electrolytic solution is suppressed, insulation properties can be further improved. In the second sealant layer 16b, when the incompatible component (B) contains the compound (B1), the content of the compound (B1) in the second sealant layer 16b is Based on the total amount, the amount is preferably 1 to 40 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 2 to 15 parts by weight.

The content of the compound (B1) in the third sealant layer 16c is preferably 1 to 40 parts by mass, and preferably 2 to 20 parts by mass, based on the total amount of the third sealant layer 16c. More preferably, the amount is 2 to 15 parts by mass.

In addition, whether the sealant layer is composed of a single layer or multiple layers, the content of the compound (B1) in the sealant layer can be adjusted while maintaining other properties. From the viewpoint of suppressing a decrease in insulation properties after heat sealing, the amount is preferably 1 to 40 parts by mass, more preferably 2 to 20 parts by mass, and 2 to 15 parts by mass, based on the total amount of the sealant layer. It is more preferable that

[Manufacturing method of exterior material]
Next, an example of a method for manufacturing the exterior material 10 shown in FIG. 1 will be described. Note that the method for manufacturing the exterior material 10 is not limited to the following method.

The manufacturing method of the exterior material 10 of this embodiment includes a step of laminating a corrosion prevention treatment layer 14 on a metal foil layer 13, a step of laminating the base material layer 11 and the metal foil layer 13, and a step of laminating a second adhesive layer. It is generally configured to include a step of further laminating a sealant layer 16 via a sealant layer 17 to produce a laminate, and a step of subjecting the obtained laminate to an aging treatment, if necessary.

(Lamination process of corrosion prevention treatment layer 14 on metal foil layer 13)
This step is a step of forming a corrosion prevention treatment layer 14 on the metal foil layer 13. As described above, examples of the method include subjecting the metal foil layer 13 to degreasing treatment, hydrothermal conversion treatment, anodizing treatment, chemical conversion treatment, and applying a coating agent having corrosion prevention performance. .

In addition, when the corrosion prevention treatment layer 14 is multi-layered, for example, a coating liquid (coating agent) constituting the corrosion prevention treatment layer on the lower layer side (metal foil layer 13 side) is applied to the metal foil layer 13 and baked. After forming one layer, a coating liquid (coating agent) constituting the upper corrosion prevention treatment layer may be applied to the first layer and baked to form a second layer.

For degreasing treatment, use the spray method or dipping method. For hydrothermal conversion treatment and anodizing treatment, use the dipping method. For chemical conversion treatment, select the dipping method, spray method, coating method, etc. depending on the type of chemical conversion treatment. Just do it.

Various methods such as gravure coating, reverse coating, roll coating, and bar coating can be used to coat the coating agent with corrosion prevention performance.

As mentioned above, various treatments may be applied to either both sides or one side of the metal foil, but in the case of single-sided treatment, it is preferable that the treated side is applied to the side on which the second adhesive layer 17 is laminated. Note that the above-mentioned treatment may also be applied to the surface of the base material layer 11, as required.
Further, the coating amount of the coating agent for forming the first layer and the second layer is preferably 0.005 to 0.200 g/m ² , more preferably 0.010 to 0.100 g/m ² .

Furthermore, if dry curing is required, it can be carried out at a base material temperature in the range of 60 to 300° C. depending on the drying conditions of the corrosion prevention treatment layer 14 used.

(Bonding process of base material layer 11 and metal foil layer 13)
This step is a step in which the metal foil layer 13 provided with the corrosion prevention treatment layer 14 and the base material layer 11 are bonded together via the first adhesive layer 12. As a bonding method, dry lamination, non-solvent lamination, wet lamination, or the like is used, and the two are bonded together using the material constituting the first adhesive layer 12 described above. The first adhesive layer 12 is provided with a dry coating amount in the range of 1 to 10 g/m ² , more preferably in the range of 3 to 7 g/m ² .

(Lamination step of second adhesive layer 17 and sealant layer 16)
This step is a step of bonding the sealant layer 16 to the corrosion prevention treatment layer 14 side of the metal foil layer 13 via the second adhesive layer 17. Examples of bonding methods include wet process and dry lamination.

In the case of a wet process, a solution or dispersion of the adhesive constituting the second adhesive layer 17 is applied onto the corrosion prevention treatment layer 14 and heated to a predetermined temperature (if the adhesive contains an acid-modified polyolefin resin). The solvent is evaporated at a temperature higher than the melting point of the film to form a dry film, or a baking treatment is performed as necessary after drying to form a film. Thereafter, the sealant layer 16 is laminated to manufacture the exterior material 10. Examples of the coating method include the various coating methods exemplified above.

(Aging treatment process)
This step is a step of aging (curing) the laminate. By aging the laminate, it is possible to promote adhesion between the metal foil layer 13/corrosion prevention treatment layer 14/second adhesive layer 17/sealant layer 16. The aging treatment can be performed at a temperature ranging from room temperature to 100°C. The aging time is, for example, 1 to 10 days. Further, in order to bond the second adhesive layer 17/sealant layer 16, heat treatment can be performed at a temperature equal to or higher than the melting point of the second adhesive layer 17. Examples of the heat treatment include, but are not limited to, oven heating, sandwiching between heated rolls (thermal lamination), and winding around heated rolls.

In this way, the exterior material 10 of this embodiment as shown in FIG. 1 can be manufactured.

Next, an example of a method for manufacturing the exterior material 20 shown in FIG. 2 will be described. Note that the method for manufacturing the exterior material 20 is not limited to the following method.

The manufacturing method of the exterior material 20 of this embodiment includes a step of laminating the corrosion prevention treatment layer 14 on the metal foil layer 13, a step of laminating the base material layer 11 and the metal foil layer 13, and a step of laminating the first sealant layer 16a. It is generally configured to include a step of further laminating a second sealant layer 16b to produce a laminate, and a step of heat-treating the obtained laminate, if necessary. Note that the steps up to the step of bonding the base material layer 11 and the metal foil layer 13 together can be performed in the same manner as the method for manufacturing the exterior material 10 described above.

(Lamination step of first sealant layer 16a and second sealant layer 16b)
This step is a step of forming a first sealant layer 16a and a second sealant layer 16b on the corrosion prevention treatment layer 14 formed in the previous step. Examples of this method include a method of sand-laminating the first sealant layer 16a and the second sealant layer 16b using an extrusion laminating machine. Furthermore, the first sealant layer 16a and the second sealant layer 16b can be laminated by a tandem lamination method or a coextrusion method in which the first sealant layer 16a and the second sealant layer 16b are extruded. In forming the first sealant layer 16a and the second sealant layer 16b, for example, each component is blended so as to satisfy the above-described configurations of the first sealant layer 16a and the second sealant layer 16b.

Through this step, as shown in FIG. A laminate in which each layer is laminated is obtained.

The first sealant layer 16a may be formed by directly laminating dry blended materials using an extrusion laminator so that the material composition is as described above, or by laminating the first sealant layer 16a in advance using a single-screw extruder or twin-screw extruder. The first sealant layer 16a, which is granulated after being melt-blended using a melt-kneading device such as a Brabender mixer, may be laminated using an extrusion laminating machine.

The second sealant layer 16b may be formed by directly laminating materials dry-blended to have the above-mentioned material composition as constituent components for forming the sealant layer using an extrusion laminator, or by laminating them in advance using a single-screw extruder. , a twin-screw extruder, a Brabender mixer, or other melt-blending device is used to melt-blend the granulated product, and an extrusion laminating machine is used to extrude the first sealant layer 16a and the second sealant layer 16b. Lamination may be performed by a tandem lamination method or a coextrusion method. Alternatively, a single sealant film may be formed in advance as a cast film using the constituent components for forming the sealant layer, and this film may be laminated with an adhesive resin by sand lamination, or by using an adhesive. They may be laminated by a dry lamination method.

(Heat treatment process)
This step is a step of heat-treating the laminate. By heat-treating the laminate, the adhesion between the metal foil layer 13/corrosion prevention treatment layer 14/first sealant layer 16a/second sealant layer 16b is improved, resulting in better electrolyte resistance and resistance. Hydrofluoric acid properties can be imparted. As for the heat treatment method, it is preferable to perform the treatment at a temperature at least equal to or higher than the melting point of the first sealant layer 16a.

In this way, the exterior material 20 of this embodiment as shown in FIG. 5 can be manufactured.

Next, an example of a method for manufacturing the exterior material 30 shown in FIG. 6 will be described. Note that the method for manufacturing the exterior material 30 is not limited to the following method.

The manufacturing method of the exterior material 30 of this embodiment includes a step of laminating the corrosion prevention treatment layer 14 on the metal foil layer 13, a step of laminating the base material layer 11 and the metal foil layer 13, and a step of laminating the first sealant layer 16a. , a step of further laminating a third sealant layer 16c and a second sealant layer 16b to produce a laminate, and, if necessary, a step of heat-treating the obtained laminate. .

(Lamination step of first sealant layer 16a, third sealant layer 16c, and second sealant layer 16b)
This step is a step of forming a first sealant layer 16a, a third sealant layer 16c, and a second sealant layer 16b on the corrosion prevention treatment layer 14. Examples of the method include a tandem lamination method in which the first sealant layer 16a, third sealant layer 16c, and second sealant layer 16b are extruded using an extrusion laminating machine, and a coextrusion method. In this case, dry-blended materials having the above-mentioned material composition as components for forming the sealant layer may be directly laminated using an extrusion laminator, or alternatively, they may be laminated in advance using a single-screw extruder or twin-screw extruder. The granules are melt-blended using a melt-kneading device such as a Brabender mixer, and then the first sealant layer 16a, third sealant layer 16c, and second sealant layer 16b are formed using an extrusion laminating machine. Lamination may be performed by an extrusion tandem lamination method or a coextrusion method.

The third sealant layer 16c and the second sealant layer 16b may be formed by coextrusion, and then laminated by a method of sand laminating these films together with the constituent components for forming the first sealant layer 16a.

In this way, the exterior material 30 of this embodiment as shown in FIG. 6 can be manufactured.

Although the preferred embodiments of the exterior material for power storage devices of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and the present invention described within the scope of the claims Various modifications and changes are possible within the scope of the gist. For example, when manufacturing an exterior material for a power storage device that does not have the first adhesive layer 12, a resin material capable of forming the base layer 11 is applied or coated on the metal foil layer 13, as described above. By this, the base material layer 11 may be formed.

The exterior material for power storage devices of the present invention is suitable as, for example, exterior materials for power storage devices such as secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries, and electrochemical capacitors such as electric double layer capacitors. Can be used. Among these, the exterior material for a power storage device of the present invention is suitable as an exterior material for a lithium ion battery.

EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

[Materials used]
The materials used in Examples and Comparative Examples are shown below.
<Base material layer (thickness 15 μm)>
A nylon film (Ny) (manufactured by Toyobo Co., Ltd.) was used.

<First adhesive layer (thickness 4 μm)>
A polyurethane adhesive (manufactured by Toyo Ink Co., Ltd.) containing a polyester polyol base resin and a tolylene diisocyanate adduct curing agent was used.

<First corrosion prevention treatment layer (base material layer side) and second corrosion prevention treatment layer (sealant layer side)>
(CL-1): Distilled water was used as a solvent, and "sodium polyphosphate stabilized cerium oxide sol" adjusted to a solid content concentration of 10% by mass was used. Note that the sodium polyphosphate stabilized cerium oxide sol was obtained by blending 10 parts by mass of Na salt of phosphoric acid with 100 parts by mass of cerium oxide.
(CL-2): 90% by mass of "polyallylamine (manufactured by Nittobo Co., Ltd.)" which was adjusted to a solid content concentration of 5% by mass using distilled water as a solvent, and "polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation)" A composition consisting of 10% by mass was used.
(CL-3): Using a 1% by mass phosphoric acid aqueous solution as a solvent, chromium fluoride (CrF ₃ ) was added to a water-soluble phenol resin (manufactured by Sumitomo Bakelite Co., Ltd.) whose solid content was adjusted to 1% by mass. The concentration of the chemical conversion treatment agent was adjusted so that the amount of Cr present in the dried film was 10 mg/m ² .

<Metal foil layer (thickness 35 μm)>
A soft aluminum foil (manufactured by Toyo Aluminum Co., Ltd., "8079 material") that had been annealed and degreased was used.

<Second adhesive layer (thickness 3 μm)>
The following adhesives a and b were prepared as adhesives for forming the second adhesive layer.
Adhesive a: An adhesive in which 10 parts by mass (solid content ratio) of a polyisocyanate compound having an isocyanurate structure is blended with 100 parts by mass of an acid-modified polyolefin resin dissolved in toluene.
Adhesive b: A polyurethane adhesive containing a polyester polyol consisting of a hydrogenated dimer fatty acid and a diol and a polyisocyanate at a molar ratio (NCO/OH) of 2.

<Sealant layer>
[Base resin composition]
As a base resin composition for forming a sealant layer, resins RC1 to RC9 were prepared at the mass ratios shown in Tables 1 and 2. The details of the terms used in Tables 1 and 2 are as follows.
((A) component)
Acid-modified PP: acid-modified polypropylene.
Random PP: Propylene-ethylene random copolymer.
((B) component)
Ethylene-α-olefin copolymer: An ethylene-propylene copolymer elastomer that is incompatible with acid-modified PP (component (A)).
Ethylene-butene-1 random copolymer: An ethylene-butene-1 random copolymer elastomer that has no compatibility with random PP (component (A)).
Reactor type TPO: A dispersion in which ethylene rubber is finely dispersed in polypropylene.
Dynamically crosslinked PP elastomer (TPV) (using peroxide): A dispersion in which a crosslinked elastomer is finely dispersed in polypropylene, the crosslinked elastomer is grafted, and the grafted portion is The dispersion that makes up the interface.
Block copolymer 1: A block copolymer composed of crystalline ethylene units and ethylene-butylene units and not compatible with random PP (component (A)).
Block copolymer 2: A block copolymer composed of propylene units and ethylene units and having no compatibility with random PP (component (A)).
Graft copolymer: A graft copolymer consisting of a main chain of polyolefin and a side chain of polystyrene and having no compatibility with random PP (component (A)).
((C) component)
Atactic structure copolymer: A propylene-α olefin copolymer with an atactic structure that is compatible with acid-modified PP (component (A)).
Propylene-butene-1 random copolymer: A propylene-butene-1 random copolymer elastomer that is compatible with random PP (component (A)).

Note that the reactor type TPO and the dynamically crosslinked PP elastomer are those in which the (B) component is dispersed in the (A) component. For convenience, in Table 1, for example, reactor type TPO is classified and described as component (B), but the mass ratio (10.0) of reactor type TPO shown in Table 1 is ) Indicates the amount of the component corresponding to the component. The amount of the component corresponding to component (A) in the reactor type TPO is included in the mass ratio (70.0) of random PP. Similarly, the mass ratio (10.0) of the dynamically crosslinked PP elastomer shown in Table 1 also indicates the amount of the component corresponding to component (B) in the dynamically crosslinked PP elastomer. The amount of the component corresponding to component (A) is included in the mass ratio (70.0) of random PP.

[Example 1]
First, first and second anti-corrosion treated layers were provided on the metal foil layer using the following procedure. That is, (CL-1) was applied to both surfaces of the metal foil layer by microgravure coating at a dry coating amount of 70 mg/m ² , and baked at 200° C. in a drying unit. Next, by applying (CL-2) on the obtained layer by microgravure coating at a dry coating amount of 20 mg/m ² , a composite consisting of (CL-1) and (CL-2) was formed. The layers were formed as first and second anti-corrosion treated layers. This composite layer exhibits corrosion prevention performance by combining two types, (CL-1) and (CL-2).

Next, the first corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is bonded using a polyurethane adhesive (first adhesive layer) using a dry lamination method. Attached to the material layer. This is set in the unwinding section of an extrusion laminating machine, and the material for the sealant layer is coextruded onto the second corrosion-prevention treatment layer at 270°C and 100 m/min processing conditions. A layer (hereinafter also referred to as "AL side layer") (thickness: 8.3 μm) and an innermost layer (thickness: 16.7 μm) were laminated in this order. Note that for the AL side layer and the innermost layer, compounds of various materials were prepared in advance using a twin-screw extruder, and the compounds were used in the above-mentioned extrusion laminate through a water cooling and pelletizing process. Resin RC1 was used to form the AL side layer. Resin RC3 was used to form the innermost layer (corresponding to the sealant layer 16b).

The thus obtained laminate was heat-treated so that the maximum temperature of the laminate was 190°C, and the exterior material of Example 1 (base layer/first adhesive layer/first adhesive layer) A laminate of the first corrosion prevention treated layer/metal foil layer/second corrosion prevention treatment layer/AL side layer (sealant layer 16a)/innermost layer (sealant layer 16b) was manufactured.

[Example 2]
The exterior material of Example 2 was manufactured in the same manner as Example 1 except that the material used to form the innermost layer (sealant layer 16b) was changed to resin RC4.

[Example 3]
The exterior material of Example 3 was manufactured in the same manner as Example 1 except that the material used to form the innermost layer (sealant layer 16b) was changed to resin RC5.

[Example 4]
The exterior material of Example 4 was manufactured in the same manner as Example 2, except that the material used for forming the AL side layer (sealant layer 16a) was changed to resin RC8.

[Example 5]
The exterior material of Example 5 was manufactured in the same manner as Example 2, except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC6.

[Example 6]
The exterior material of Example 6 was manufactured in the same manner as Example 3, except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC8.

[Example 7]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC6, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC9. The exterior material of Example 7 was manufactured in the same manner as Example 1.

[Example 8]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC7, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC10. The exterior material of Example 8 was manufactured in the same manner as Example 1.

[Example 9]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC8, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC11. The exterior material of Example 9 was manufactured in the same manner as Example 1.

[Example 10]
The exterior material of Example 10 was manufactured in the same manner as Example 1 except that the material used for forming the AL side layer (sealant layer 16a) was changed to resin RC6.

[Example 11]
The exterior material of Example 11 was manufactured in the same manner as Example 1, except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC8.

[Example 12]
The exterior material of Example 12 was manufactured in the same manner as Example 1 except that the material used to form the innermost layer (sealant layer 16b) was changed to resin RC9.

[Example 13]
The exterior material of Example 13 was manufactured in the same manner as in Example 1, except that the material used to form the innermost layer (sealant layer 16b) was changed to resin RC11.

[Example 14]
The exterior material of Example 14 was manufactured in the same manner as Example 7 except that the material used for forming the AL side layer (sealant layer 16a) was changed to resin RC2.

[Example 15]
First, first and second anti-corrosion treated layers were provided on the metal foil layer using the following procedure. That is, (CL-3) was applied to both surfaces of the metal foil layer by microgravure coating at a dry coating amount of 30 mg/m ² , and baked at 200° C. in a drying unit. Next, by applying (CL-2) on the obtained layer by microgravure coating at a dry coating amount of 20 mg/m ² , a composite consisting of (CL-3) and (CL-2) was formed. The layers were formed as first and second anti-corrosion treated layers. This composite layer exhibits corrosion prevention performance by combining two types, (CL-3) and (CL-2). The exterior material of Example 15 was manufactured in the same manner as Example 7 except that the metal foil layer provided with the first and second corrosion prevention treatment layers was used in this manner.

[Example 16]
In the same manner as in Example 1, first and second anti-corrosion treated layers were provided on the metal foil layer. The first corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is attached to the base material layer using a polyurethane adhesive (first adhesive layer) using a dry lamination method. Pasted it. Next, the second corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is dry laminated using adhesive a (second adhesive layer) to form a sealant layer 16. (innermost layer) (thickness: 25 μm) to produce the exterior material of Example 16. A mixture with resin RC9 was used to form the innermost layer (sealant layer 16).

[Example 17]
In the same manner as in Example 1, first and second anti-corrosion treated layers were provided on the metal foil layer. The first corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is attached to the base material layer using a polyurethane adhesive (first adhesive layer) using a dry lamination method. Pasted it. Next, the second corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is dry laminated using adhesive b (second adhesive layer) to form a sealant layer 16. (innermost layer) (thickness: 25 μm) to produce the exterior material of Example 17. A mixture with resin RC9 was used to form the innermost layer (sealant layer 16).

[Example 18]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC6, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC12. The exterior material of Example 18 was manufactured in the same manner as Example 1.

[Example 19]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC8, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC13. The exterior material of Example 19 was manufactured in the same manner as Example 1.

[Example 20]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC8, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC14. The exterior material of Example 20 was manufactured in the same manner as Example 1.

[Example 21]
Example 7 was carried out in the same manner as in Example 7, except that the thickness of the AL side layer (sealant layer 16a) was changed to 3.3 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 6.7 μm. , the exterior material of Example 21 was manufactured.

[Example 22]
Example 9 was carried out in the same manner as in Example 9, except that the thickness of the AL side layer (sealant layer 16a) was changed to 3.3 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 6.7 μm. , the exterior material of Example 22 was manufactured.

[Example 23]
Example 23 was carried out in the same manner as in Example 5, except that the thickness of the AL side layer (sealant layer 16a) was changed to 15 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 30 μm. manufactured exterior materials.

[Example 24]
Example 24 was carried out in the same manner as in Example 6, except that the thickness of the AL side layer (sealant layer 16a) was changed to 15 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 30 μm. manufactured exterior materials.

[Example 22]
Example 25 was carried out in the same manner as Example 9, except that the thickness of the AL side layer (sealant layer 16a) was changed to 15 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 30 μm. manufactured exterior materials.

[Example 26]
Example 26 was carried out in the same manner as in Example 5, except that the thickness of the AL side layer (sealant layer 16a) was changed to 20 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 40 μm. manufactured exterior materials.

[Example 27]
Example 27 was carried out in the same manner as in Example 6, except that the thickness of the AL side layer (sealant layer 16a) was changed to 20 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 40 μm. manufactured exterior materials.

[Example 28]
Example 28 was conducted in the same manner as Example 9, except that the thickness of the AL side layer (sealant layer 16a) was changed to 20 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 40 μm. manufactured exterior materials.

[Example 29]
Example 5 was carried out in the same manner as in Example 5, except that the thickness of the AL side layer (sealant layer 16a) was changed to 26.7 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 53.3 μm. , the exterior material of Example 29 was manufactured.

[Example 30]
Example 6 was carried out in the same manner as in Example 6, except that the thickness of the AL side layer (sealant layer 16a) was changed to 26.7 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 53.3 μm. , the exterior material of Example 30 was manufactured.

[Example 31]
The same procedure as in Example 9 was carried out, except that the thickness of the AL side layer (sealant layer 16a) was changed to 26.7 μm, and the thickness of the innermost layer (sealant layer 16b) was changed to 53.3 μm. , the exterior material of Example 31 was manufactured.

[Example 32]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC15, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC13. The exterior material of Example 32 was manufactured in the same manner as Example 1.

[Comparative example 1]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC16, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC18. An exterior material of Comparative Example 1 was manufactured in the same manner as Example 1.

[Comparative example 2]
Except that the material used to form the AL side layer (sealant layer 16a) was changed to resin RC17, and the material used to form the innermost layer (sealant layer 16b) was changed to resin RC19. An exterior material of Comparative Example 2 was manufactured in the same manner as Example 1.

The main conditions of each example and comparative example are shown in Tables 3 and 4.

<Evaluation>
The following evaluation tests were conducted on the exterior materials obtained in Examples and Comparative Examples.

(Seal strength)
A sample of the exterior material cut to 60 mm x 120 mm was folded in half with the sealant layer inside, and one side was heat-sealed with a 10 mm wide seal bar at 190°C, 0.5 MPa, and 3 seconds to form an adhesive part. did. After storing at room temperature for 24 hours, cut the first side of the heat seal to a width of 15 mm (see Figure 7), and measure the seal strength (T-shaped peel strength) from one end of the adhesive part in the width direction to the other end using a testing machine. (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at 23° C. in a 50% RH atmosphere at a peeling rate of 50 mm/min. In the graph (see FIG. 3) showing the relationship between the displacement from one end of the adhesive part and the seal strength, the first maximum value of the load after the start of peeling was defined as the maximum seal strength S _M (N/15 mm). In addition, in the above graph, if there is a stable region of seal strength with respect to displacement (mm) (a region where the variation in seal strength of ±3 N/15 mm or less continues for 5 mm or more), calculate the average seal strength _S in this stable region. Then, the ratio S _S /S _M of the average seal strength S _S to the maximum seal strength S _M was determined. In addition, in the above graph, if the above stable region does not exist, measure the seal strength every 1 mm from the displacement where the maximum seal strength was obtained to the other end of the heat seal part (see Fig. 4), and The average seal strength _SA was calculated by averaging the values. The ratio S _A /S _M of the calculated average seal strength S _A to the maximum seal strength S _M was determined.

(Electrolyte laminate strength)
A Teflon (registered trademark) container is filled with an electrolytic solution prepared by adding LiPF ₆ to 1M in a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio), and the exterior material is placed in it. A sample cut to 15 mm x 100 mm was placed in the container, and the container was sealed and stored at 85° C. for 24 hours. Thereafter, it was co-washed, and the lamination strength (T-peel strength) between the metal foil layer and the sealant layer was measured using a testing machine (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at 23° C. in a 50% RH atmosphere at a peeling rate of 50 mm/min. Based on the results, evaluation was made using the following criteria.
A: Lamination strength is more than 7N/15mm B: Lamination strength is 6N/15mm or more and 7N/15mm or less C: Lamination strength is 5N/15mm or more and less than 6N/15mm D: Lamination strength is less than 5N/15mm

(Electrolyte heat seal strength)
A sample of the exterior material cut to 60 mm x 120 mm was folded in half with the sealant layer inside, and one side was heat-sealed using a 10 mm wide seal bar at 190°C, 0.5 MPa, and 3 seconds to form a heat-sealed part. did. After that, the remaining two sides were also heat-sealed, and LiPF ₆ was added to the mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio) to 1M to the bag-shaped exterior material. After storing the pouch in which 2ml of the electrolyte was injected for 24 hours at 60°C, cut the first side of the heat-sealed part to a width of 15 mm (see Figure 8), and cut one end of the heat-sealed part (the end that was in contact with the electrolyte) The seal strength (T-peel strength) was continuously measured using a tester (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at 23° C. in a 50% RH atmosphere at a peeling rate of 50 mm/min. Based on the results of the maximum seal strength and ratio obtained in the same manner as the "Seal strength" item, evaluation was made according to the following criteria.
S: Maximum seal strength is 50 N/15 mm or more A: Maximum seal strength is 45 N/15 mm or more, less than 50 N/15 mm B: Maximum seal strength is 35 N/15 mm or more, less than 45 N/15 mm C: Maximum seal strength is 25 N/15 mm or more , Less than 35N/15mm D: Maximum seal strength is less than 25N/15mm

(Degassing heat seal strength (Degassing heat seal strength))
After cutting a sample of the exterior material to 75 mm x 150 mm and folding it in half to 37.5 mm x 150 mm with the sealant layer inside (see Figure 9(a)), heat seal one of the 150 mm side and the 37.5 mm side. Then, bags were made. After that, 5 ml of an electrolyte solution prepared by adding LiPF ₆ to 1M to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio) was poured into the pouch, and the electrolyte was poured into the pouch, and the electrolyte solution was poured into the pouch. The other side was heat-sealed to obtain a pouch sealed by the seal portion DS1. Next, after storing this pouch at 60°C for 24 hours, the center of the pouch containing the electrolyte was heat-sealed using a 10mm wide seal bar at 190°C, 0.3 MPa, and 2 seconds (degassing heat sealing). section DS2, see FIG. 9(b)). In order to stabilize the sealed part, after storing it at room temperature for 24 hours, the area including the degassing heat-sealed part DS2 was cut to a width of 15 mm (see Figure 9(c)), and one end of the degassing heat-sealed part ( The seal strength (T-peel strength) was measured from the end that was in contact with the electrolytic solution using a tester (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at 23° C. in a 50% RH atmosphere at a peeling rate of 50 mm/min. Based on the results of the maximum seal strength and ratio obtained in the same manner as the "Seal strength" item, evaluation was made according to the following criteria.
S: Maximum seal strength is 45 N/15 mm or more A: Maximum seal strength is 40 N/15 mm or more, less than 45 N/15 mm B: Maximum seal strength is 30 N/15 mm or more, less than 40 N/15 mm C: Maximum seal strength is 20 N/15 mm or more , Less than 30N/15mm D: Maximum seal strength is less than 20N/15mm

(Insulation properties after degassing heat sealing (degas insulation))
Sample 40, which was made by cutting the exterior material into 120 mm x 200 mm, was set in a cold molding mold so that the sealant layer was in contact with the convex part of the molding machine, and deep drawing was performed to 2.0 mm at a molding speed of 15 mm/sec. After forming the deep drawn part 41, it was folded in two to 120 mm x 100 mm (see FIG. 10(a)). Next, the 100 mm top side 44 was heat-sealed with the tab 42 and tab sealant 43 sandwiched between them (see FIG. 10(b)), and then the 120 mm side side 45 was heat-sealed to form a bag. (See Figure 10(c)). Thereafter, in order to bring the electrode into contact, a part of the outer layer of the sample 40 was shaved off to form an exposed portion 46 of the metal foil layer (see FIG. 10(d)). Next, 5 ml of an electrolytic solution prepared by adding LiPF ₆ to 1 M to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio) was poured into the pouch, and the lower side of 100 mm was poured into the pouch. 47 was sealed with a heat seal (see FIG. 10(e)). Thereafter, this pouch was left lying flat at 60°C for 24 hours, and the inner part 48 of the heat-sealed lower side 47 was heated to 190°C with a surface pressure of 0.3 MPa (surface pressure ), and degassed and heat-sealed for 2 seconds (see FIG. 10(f)). Next, the electrodes 49a and 49b are connected to the tab 42 and the exposed part 46 of the metal foil layer, and 25V is applied using a withstand voltage/insulation resistance tester (manufactured by KIKUSUI, "TOS9201"), and the resistance value at that time is measured. was measured (see Figure 10(g)). For samples whose resistance value was less than 15 MΩ, 25 V was subsequently applied for 2 hours to identify locations where the insulation had deteriorated. By applying the voltage for a long time, a reaction product between the metal foil and the electrolytic solution is precipitated from the location where the insulation is degraded, so the location where the insulation is degraded can be identified. The mold used had a molding area of 80 mm x 70 mm (square tube type) and a punch corner radius (RCP) of 1.0 mm. Based on the results, evaluation was made using the following criteria.
A: Resistance value is more than 200MΩ B: Resistance value is 100MΩ or more and 200MΩ or less C: Resistance value is 15MΩ or more and less than 100MΩ D: Resistance value is less than 15MΩ

(Total quality)
The results of each of the above evaluations are shown in Tables 5 and 6. In Tables 5 and 6 below, if there is no D rating in each evaluation result, it can be said that the overall quality is excellent.

In all the exterior materials obtained in the Examples and Comparative Examples, there was a stable region in the graph for seal strength evaluation. As is clear from the results shown in Tables 5 and 6, it was confirmed that the exterior materials of Examples 1 to 31 had excellent insulation properties after degassing and heat sealing. Furthermore, it was confirmed that the exterior materials of Examples 1 to 31 had sufficient performance in terms of electrolyte lamination strength, electrolyte heat seal strength, and degassing heat seal strength. On the other hand, it was confirmed that the exterior materials of Comparative Examples 1 and 2 were inferior in seal strength and insulation properties.

Comparing Examples 1 to 3, it is found that by using reactor type TPO in which elastomer is finely dispersed or dynamically crosslinked PP elastomer to which elastomer is grafted as the incompatible component (B) in the innermost layer, the sea-island interface is It can be confirmed that the adhesion was improved, and the seal strength and insulation properties were improved.

Comparing Examples 21 to 31, it can be confirmed that when the sealant layer was made thicker, both the maximum seal strength S _M and the ratio S _S /S _M were improved, and even better seal strength and insulation properties were obtained. . On the other hand, it can be confirmed that even if the sealant layer was made thinner, sealing strength and insulation properties that were satisfactory as an exterior material were obtained.

DESCRIPTION OF SYMBOLS 10, 20, 30... Exterior material for power storage device, 11... Base material layer, 12... First adhesive layer, 13... Metal foil layer, 14... Corrosion prevention treatment layer, 16... Sealant layer, 16a... First Sealant layer, 16b...Second sealant layer, 16c...Third sealant layer, 17...Second adhesive layer, DS1...Seal part, DS2...Degassing heat seal part.

Claims (6)

An exterior packaging material for a power storage device comprising at least a base material layer, a metal foil layer provided with a corrosion prevention treatment layer on one or both surfaces, and a sealant layer, in this order,
The sealant layer includes a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin,
The incompatible component (B) is a compound having a compatible portion with the polypropylene resin (A), and is composed of a graft copolymer or a block composed of a crystalline ethylene unit and an ethylene-butylene unit. A block copolymer having a block composed of ethylene and a block composed of ethylene-octene 1, or a block composed of a block composed of propylene units and an ethylene unit Contains a compound (B1) containing a block copolymer,
The content of the incompatible component (B) is 1 to 40% by mass based on the total amount of the sealant layer,
The exterior material stacked so that the sealant layers face each other is heat-sealed under the conditions of a temperature of 190°C, a pressure of 0.5 MPa, and 3 seconds, and the seal strength from one end to the other of the bonded part is determined. In a graph showing the relationship between the displacement from the one end and the seal strength when continuously measured,
An exterior material for a power storage device that has a maximum seal strength S _M of 35 N/15 mm or more and satisfies the following conditions (1) or (2) ( however, at least the base material layer, the first adhesive layer, the barrier layer, A laminate film for a battery exterior in which a second adhesive layer and a sealant layer are laminated in this order, the sealant layer being formed of a compound containing the following components (A) and (B): Excludes battery exterior laminate films characterized by having at least one layer I).
Component (A): polyethylene with a density of 0.930 g/cm ³ or more and 0.950 g/cm ³ or less produced using a metallocene catalyst
Component (B): a polypropylene elastomer in which rubber is dispersed in a polypropylene matrix) .
(1) A stable region of seal strength exists after the displacement at which the maximum seal strength S _M is obtained, and the ratio S _S /S _M of the seal strength S _S to the maximum seal strength S _M in the stable region is 0. It is 3 or more.
(2) The stable region does not exist and the ratio S A /S M of the average seal strength S _A to the maximum seal strength S _M at the displacement from the displacement where the maximum seal strength S _M is obtained to the other end is S _A /S _M It is 0.3 or more. In the graph,
The exterior material for a power storage device according to claim 1, wherein the maximum seal strength S _M is 40 N/15 mm or more, and the ratio S _S /S _M or the ratio S _A /S _M is 0.6 or more. The sealant layer is composed of a plurality of layers, at least one of which contains the polypropylene resin (A) and the incompatible component (B) that is incompatible with the polypropylene resin, and The exterior material for a power storage device according to claim 1 or 2, wherein component (B) is a layer containing the compound (B1). The exterior material for a power storage device according to any one of claims 1 to 3, wherein the incompatible component (B) contains an ethylene-α olefin copolymer. The sealant layer further includes a compatible elastomer (C) that is compatible with the polypropylene resin (A),
The exterior material for a power storage device according to any one of claims 1 to 4, wherein the compatible elastomer (C) contains a propylene-α olefin copolymer. The exterior material for a power storage device according to any one of claims 1 to 5, wherein the sealant layer has a thickness of 10 to 45 μm.

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