JP6812633B2 - Exterior material for power storage device and power storage device using it - Google Patents

Description

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

As the power storage device, for example, a secondary battery such as a lithium ion battery, a nickel hydrogen battery, and a lead storage battery, and an electrochemical capacitor such as an electric double layer capacitor are known. In recent years, there is a demand for further miniaturization of power storage devices due to miniaturization of mobile devices or restrictions on installation space, and lithium ion batteries having a high energy density are attracting attention. Conventionally, metal cans have been used as exterior materials used in lithium-ion batteries, but multilayer films that are lightweight, have high heat dissipation, and can be produced at low cost are now being used.

In a lithium ion battery using the above-mentioned multilayer film as an exterior material, in order to prevent moisture from entering the inside, the battery contents (positive electrode, separator, negative electrode, electrolytic solution, etc.) are covered with an exterior material containing an aluminum foil layer. It has been adopted. A lithium-ion battery adopting such a configuration is called an aluminum laminate type lithium-ion battery.

In an aluminum laminate type lithium-ion battery, for example, a recess is formed in a part of the exterior material by cold molding, the battery contents are housed in the recess, and the remaining part of the exterior material is folded back to heat the edge portion. An embossed lithium-ion battery sealed with a seal is known. (See, for example, Patent Document 1). In such a lithium-ion battery, the deeper the recess formed by cold molding, the more battery contents can be accommodated, so that the energy density can be increased.

Japanese Unexamined Patent Publication No. 2013-101765

When the power storage device is applied to an application that requires high reliability such as a car or an electric motorcycle, a compression test for compressing a battery cell is performed as a harsh test. Here, even if the exterior material does not show a difference in performance in other evaluation items, a difference in the result of the compression test may be seen for some reason.

Therefore, an object of the present invention is to provide an exterior material for a power storage device that shows good results in a compression test of a battery cell, and a power storage device using the same.

The present invention is an exterior material for a power storage device having a structure in which a coating layer, a barrier layer, a sealant adhesive layer, and a sealant layer are laminated in this order, and the barrier layer is an aluminum foil layer and an aluminum foil layer. It has a corrosion prevention treatment layer provided on the sealant layer side and facing the sealant adhesive layer, and the surface of the aluminum foil layer on the sealant layer side has a 60 ° glossiness in the MD direction and a 60 ° glossiness in the TD direction. Provided are exterior materials for power storage devices, all of which are 690 or less and the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction is 100 or less.

According to the study of the present inventor, when the battery cell bursts in the compression test, the interface between the barrier layer and the sealant adhesive layer is easily peeled off, and the glossiness of the aluminum foil layer of the barrier layer is different. It was found that the adhesion of the sealant adhesive layer changed. The glossiness of the aluminum foil layer is considered to reflect the surface roughness of the aluminum foil layer. If the surface roughness is different, the strength of the anchor effect based on this is also different, and it is presumed that this is the cause of the change in the adhesion of the sealant adhesive layer. When the difference in glossiness and glossiness on the sealant layer side of the aluminum foil layer facing the sealant adhesive layer satisfies the above numerical range, the surface roughness of the aluminum foil layer is reflected on the surface of the corrosion prevention treatment layer. The compression test of the battery cell made of the exterior material for the power storage device of the present invention shows good results.

Here, both the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the surface of the aluminum foil layer on the sealant layer side may be 150 or less, and the 60 ° glossiness in the MD direction The difference from the 60 ° glossiness in the TD direction may be 50 or less. Even in this case, the effect of the present invention is sufficiently exhibited.

Further, the present invention is an exterior material for a power storage device having a structure in which a coating layer, a barrier layer, a sealant adhesive layer, and a sealant layer are laminated in this order, and the barrier layer is an aluminum foil layer. It has a corrosion prevention treatment layer provided on the sealant layer side of the aluminum foil layer and facing the sealant adhesive layer, and has a 60 ° glossiness in the MD direction of the aluminum foil layer in the state where the corrosion prevention treatment layer is provided, and Provided is an exterior material for a power storage device, wherein the 60 ° glossiness in the TD direction is 590 or less, and the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction is 100 or less.

According to the study of the present inventor, when the battery cell bursts in the compression test, the interface between the barrier layer and the sealant adhesive layer is easily peeled off, and the aluminum foil layer provided with the corrosion prevention treatment layer in the barrier layer. It was found that the adhesion of the sealant adhesive layer changed depending on the glossiness of the sealant. It is considered that the glossiness of the aluminum foil layer in the state where the corrosion prevention treatment layer is provided reflects the surface roughness of the aluminum foil layer. If the surface roughness is different, the strength of the anchor effect based on this is also different, and it is presumed that this is the cause of the change in the adhesion of the sealant adhesive layer. When the difference in glossiness and glossiness of the aluminum foil layer in the state where the corrosion prevention treatment layer facing the sealant adhesive layer satisfies the above numerical range, the battery cell produced by the exterior material for the power storage device of the present invention The compression test shows good results.

Here, the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the aluminum foil layer in the state where the corrosion prevention treatment layer is provided may both be 120 or less, and 60 in the MD direction. The difference between the ° glossiness and the 60 ° glossiness in the TD direction may be 40 or less. Even in this case, the effect of the present invention is sufficiently exhibited.

Further, the present invention includes a battery element including an electrode, a reed extending from the electrode, and a container for accommodating the battery element. The container has a sealant layer inside from any of the above-mentioned exterior materials for a power storage device. Provided is a power storage device formed so as to become. This power storage device shows good results in the compression test of the battery cell.

According to the present invention, it is possible to provide an exterior material for a power storage device that shows good results in a compression test of a battery cell, and a power storage device using the same.

It is the schematic sectional drawing of the exterior material for a power storage device which concerns on one Embodiment of this invention. It is a figure which shows the embossing type exterior material obtained by using the exterior material for a power storage device which concerns on one Embodiment of this invention, (a) is the perspective view, (b) is the embossing shown in (a). It is a vertical cross-sectional view along the line IIb-IIb of the type exterior material. It is a perspective view which shows the process of manufacturing a secondary battery using the exterior material for a power storage device which concerns on one Embodiment of this invention, (a) shows the state which prepared the exterior material for a power storage device, (b). Indicates a state in which an embossed exterior material for a power storage device and a battery element are prepared, and (c) shows a state in which a part of the exterior material for a power storage device is folded back and the end portion is melted. ) Indicates a state in which both sides of the folded portion are folded upward.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

[Exterior material for power storage device]
FIG. 1 is a cross-sectional view schematically showing an embodiment of an exterior material for a power storage device of the present invention. As shown in FIG. 1, the exterior material (exterior material for a power storage device) 10 of the present embodiment includes a coating layer 21, a barrier layer 22 provided on one surface side of the coating layer 21, and the barrier layer 22. The sealant adhesive layer 16 provided on the side opposite to the coating layer 21 and the sealant layer 17 provided on the side opposite to the barrier layer 22 of the sealant adhesive layer 16 are sequentially laminated.

The coating layer 21 has a base material layer 11 and an adhesive layer 13, and the adhesive layer 13 faces the barrier layer 22. The barrier layer 22 has an aluminum foil layer 14 and corrosion prevention treatment layers 15a and 15b provided on both sides thereof. Here, the corrosion prevention treatment layer 15a is provided so as to face the adhesive layer 13, and the corrosion prevention treatment layer 15b is provided so as to face the sealant adhesive layer 16. Here, "face-to-face" means that the faces are in direct contact with each other.

In the exterior material 10, the base material layer 11 is the outermost layer and the sealant layer 17 is the innermost layer. That is, the exterior material 10 is used with the base material layer 11 facing the outside of the power storage device and the sealant layer 17 facing the inside of the power storage device. Hereinafter, each layer will be described.

(Base material layer 11)
When the power storage device is manufactured, the base material layer 11 imparts heat resistance in the pressure heat fusion step described later and electrolytic solution resistance to the electrolytic solution leaked from the other power storage device to the exterior material 10 for processing. Alternatively, it is a layer for suppressing the occurrence of pinholes that may occur during distribution. The base material layer 11 is a layer made of a polyamide film.

The base material layer 11 is preferably a layer made of a biaxially stretched polyamide film from the viewpoint of obtaining more excellent deep drawing moldability.

Examples of the polyamide resin constituting the biaxially stretched polyamide film include nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, and polymethaxylylene adipamide (MXD6). , Nylon 11, nylon 12, and the like. Among these, nylon 6 (ONy) is preferable from the viewpoint of excellent heat resistance, piercing strength and impact strength.

Examples of the stretching method in the biaxially stretched film include a sequential biaxial stretching method, a tubular biaxial stretching method, and a simultaneous biaxial stretching method. The biaxially stretched film is preferably stretched by the tubular biaxial stretching method from the viewpoint of obtaining more excellent deep drawing moldability.

The thickness of the base material layer 11 is preferably 6 to 40 μm, more preferably 10 to 30 μm. When the thickness of the base material layer 11 is 6 μm or more, the pinhole resistance and the insulating property of the exterior material 10 for the power storage device tend to be improved. If the thickness of the base material layer 11 exceeds 40 μm, the total thickness of the exterior material 10 for the power storage device becomes large, and the electric capacity of the battery may have to be reduced.

(Adhesive layer 13)
The adhesive layer 13 is a layer that adheres the base material layer 11 and the barrier layer 22. The adhesive layer 13 has an adhesive force necessary for firmly adhering the base material layer 11 and the barrier layer 22, and the base material layer 11 breaks the barrier layer 22 during cold molding. It also has followability for suppressing (performance for reliably forming the adhesive layer 13 on the member without peeling even if the member is deformed or expanded / contracted).

The adhesive constituting the adhesive layer 13 is a two-component adhesive having, for example, a main agent composed of a polyol such as a polyester polyol, a polyether polyol, and an acrylic polyol, and a curing agent composed of an aromatic-based or aliphatic-based isocyanate. A curable polyurethane adhesive can be used. In the above adhesive, the molar ratio (= NCO / OH) of the isocyanate group of the curing agent to the hydroxyl group of the main agent is preferably 1 to 10, and more preferably 2 to 5.

After coating, the polyurethane adhesive is aged at 40 ° C. for 4 days or more, so that the reaction between the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds, and the base material layer 11 and the barrier layer 22 Allows for stronger adhesion.

The thickness of the adhesive layer 13 is preferably 1 to 10 μm, more preferably 2 to 6 μm, from the viewpoint of obtaining desired adhesive strength, followability, processability, and the like.

(Aluminum foil layer 14)
The aluminum foil layer 14 is excellent in terms of workability such as moisture resistance and ductility as a metal foil, and cost. The aluminum foil may be a general soft aluminum foil, but is preferably an aluminum foil containing iron from the viewpoint of excellent pinhole resistance and ductility during molding.

In the aluminum foil containing iron (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass. When the iron content is 0.1% by mass or more, the exterior material 10 having more excellent pinhole resistance and ductility can be obtained. When the iron content is 9.0% by mass or less, the exterior material 10 having more excellent flexibility can be obtained.

Further, as the aluminum foil, a soft aluminum foil that has been annealed (for example, an aluminum foil made of 8021 material or 8079 material according to JIS standards) is more preferable from the viewpoint of imparting a desired ductility during molding.

The aluminum foil used for the aluminum foil layer 14 is preferably subjected to, for example, a degreasing treatment in order to obtain a desired electrolytic solution resistance. Further, in order to simplify the manufacturing process, the aluminum foil is preferably one whose surface is not etched. As the degreasing treatment, for example, a wet type degreasing treatment or a dry type degreasing treatment can be used, but a dry type degreasing treatment is preferable from the viewpoint of simplifying the manufacturing process.

Examples of the dry type degreasing treatment include a method of performing the degreasing treatment by lengthening the treatment time in the step of annealing the aluminum foil. Sufficient electrolytic solution resistance can be obtained even with the degreasing treatment that is performed at the same time as the annealing treatment that is performed to soften the aluminum foil.

Further, as the dry type degreasing treatment, treatments such as frame treatment and corona treatment, which are treatments other than the annealing treatment, may be used. Further, as the dry type degreasing treatment, for example, a degreasing treatment for oxidatively decomposing and removing contaminants by active oxygen generated when an aluminum foil is irradiated with ultraviolet rays having a specific wavelength may be used.

As the wet type degreasing treatment, for example, treatments such as acid degreasing treatment and alkaline degreasing treatment can be used. As the acid used for the acid degreasing treatment, for example, an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, or hydrofluoric acid can be used. One of these acids may be used alone, or two or more of these acids may be used in combination. Further, as the alkali used for the alkali degreasing treatment, for example, sodium hydroxide having a high etching effect can be used. Further, the alkaline degreasing treatment may be performed using a weak alkaline material and a material containing a surfactant or the like. The wet type degreasing treatment described above can be performed by, for example, a dipping method or a spraying method.

The 60 ° glossiness of the aluminum foil layer 14 in the MD direction (extruding direction during rolling) and the 60 ° glossiness in the TD direction (direction perpendicular to the MD direction) are both 690 or less, preferably 680. The following, more preferably 670 or less. The glossiness of the aluminum foil layer 14 is considered to reflect the surface roughness of the aluminum foil layer 14. If the surface roughness is different, the strength of the anchor effect based on this is also different, so that it is considered that the adhesion between the aluminum foil layer 14 and the sealant adhesive layer 16 changes. When all of the above glossiness is 690 or less, the compression test of the battery cell produced by the exterior material 10 for the power storage device shows good results.

Generally, in the manufacturing stage of the aluminum foil, scratches parallel to the MD direction are generated, so that there is a difference in glossiness between the TD direction and the MD direction of the aluminum foil. The difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the aluminum foil layer 14 is 100 or less, preferably 80 or less, and more preferably 65 or less. When the difference between the two glossinesses is 100 or less, the surface roughness of the aluminum foil layer 14 is well-balanced regardless of the in-plane direction, and good adhesion to the sealant adhesive layer 16 can be obtained. When the difference between the two glossiness exceeds 100, the anisotropy of the surface roughness becomes strong, and the load tends to be concentrated locally in the compression test of the battery cell made of the exterior material 10 for the power storage device. Therefore, in this case, the durability of the exterior material 10 for the power storage device tends to decrease.

The aluminum foil usually has a glossy surface having a high glossiness and an erasing surface having a low glossiness. Generally, when the exterior material for a power storage device is manufactured, the erasing surface is usually directed to the base material layer 11 side, but the erasing surface may be directed to the sealant layer 17 side. In this case, the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction may both be 150 or less, preferably 140 or less, and more preferably 130 or less. Further, in this case, the difference between the two glossinesses may be 50 or less, preferably 45 or less, and more preferably 35 or less.

The glossiness of the aluminum foil layer 14 can also be measured in a state where the corrosion prevention treatment layer 15b, which will be described later, is provided. The 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the aluminum foil layer 14 in the state where the corrosion prevention treatment layer 15b is provided are both 590 or less, preferably 580 or less. , More preferably, both are 570 or less. It is considered that the glossiness of the aluminum foil layer 14 in the state where the corrosion prevention treatment layer 15b is provided reflects the surface roughness of the aluminum foil layer 14. If the surface roughness is different, the strength of the anchor effect based on this is also different, so that it is considered that the adhesion between the aluminum foil layer 14 provided with the corrosion prevention treatment layer 15b and the sealant adhesive layer 16 changes. When all of the above glossiness is 590 or less, the compression test of the battery cell produced by the exterior material 10 for the power storage device shows good results.

Further, the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the aluminum foil layer 14 in the state where the corrosion prevention treatment layer 15b is provided is 100 or less, preferably 70 or less. More preferably, it is 55 or less. When the difference between the two glossinesses is 100 or less, the surface roughness of the aluminum foil layer 14 is well-balanced regardless of the in-plane direction, and good adhesion to the sealant adhesive layer 16 can be obtained. When the difference between the two glossiness exceeds 100, the anisotropy of the surface roughness becomes strong, and the load tends to be concentrated locally in the compression test of the battery cell made of the exterior material 10 for the power storage device. Therefore, in this case, the durability of the exterior material 10 for the power storage device tends to decrease.

The aluminum foil usually has a glossy surface having a high glossiness and an erasing surface having a low glossiness. Generally, when the exterior material for a power storage device is manufactured, the erasing surface is usually directed to the base material layer 11 side, but the erasing surface may be directed to the sealant layer 17 side. In this case, the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction may both be 120 or less, preferably 110 or less, and more preferably 100 or less. Further, in this case, the difference between the two glossinesses may be 40 or less, preferably 35 or less, and more preferably 30 or less.

The glossiness described above is the glossiness as a material before producing the exterior material 10, and is a value measured using a gloss meter.

The thickness of the aluminum foil layer 14 is preferably 9 to 200 μm, more preferably 15 to 150 μm, and further preferably 15 to 100 μm from the viewpoint of barrier property, pinhole resistance and processability. preferable. When the thickness of the aluminum foil layer 14 is 9 μm or more, it is difficult to break even if stress is applied by the molding process. When the thickness of the aluminum foil layer 14 is 200 μm or less, the increase in the mass of the exterior material can be reduced, and the decrease in the weight energy density of the power storage device can be suppressed.

(Corrosion prevention treatment layers 15a, 15b)
The corrosion prevention treatment layers 15a and 15b play a role of suppressing corrosion of the aluminum foil layer 14 due to the electrolytic solution or hydrofluoric acid generated by the reaction between the electrolytic solution and water. Further, the corrosion prevention treatment layer 15a plays a role of enhancing the adhesion between the aluminum foil layer 14 and the adhesive layer 13. Further, the corrosion prevention treatment layer 15b plays a role of enhancing the adhesion between the aluminum foil layer 14 and the sealant adhesive layer 16. The corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b may have the same structure or may have different structures.

The corrosion prevention treatment layers 15a and 15b are coating agents having, for example, degreasing treatment, hydrothermal transformation treatment, anodizing treatment, chemical conversion treatment, and corrosion prevention ability for the layers serving as the base material of the corrosion prevention treatment layers 15a and 15b. It can be formed by carrying out a coating type corrosion prevention treatment or a corrosion prevention treatment combining these treatments.

Of the above-mentioned treatments, the degreasing treatment, the hydrothermal transformation treatment, the anodizing treatment, particularly the hydrothermal modification treatment and the anodizing treatment dissolve the surface of the metal foil (aluminum foil) with a treatment agent and are excellent in corrosion resistance. This is a process for forming an aluminum compound (boehmite, alumite). Therefore, such a treatment may be included in the definition of chemical conversion treatment in order to obtain a structure forming a co-continuous structure from the aluminum foil layer 14 to the corrosion prevention treatment layers 15a and 15b.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of the acid degreasing include a method using acid degreasing obtained by using the above-mentioned inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid alone or in combination thereof. Further, as the acid degreasing, by using an acid degreasing agent in which a fluorine-containing compound such as monosodium ammonium difluoride is dissolved in the above-mentioned inorganic acid, not only the degreasing effect of the aluminum foil layer 14 but also the immobile metal fluoride is used. It is possible to form, and it is effective in terms of resistance to fluorine acidity. Examples of the alkaline degreasing include a method using sodium hydroxide and the like.

As the hydrothermal transformation treatment, for example, a boehmite treatment obtained by immersing the aluminum foil layer 14 in boiling water to which triethanolamine is added can be used. As the anodizing treatment, for example, an alumite treatment can be used. Further, as the chemical conversion treatment, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or a treatment in which two or more of these are combined is used. be able to. In these hot water transformation treatments, anodizing treatments, and chemical conversion treatments, it is preferable to perform the above-mentioned degreasing treatment in advance.

The chemical conversion treatment is not limited to the wet method, and for example, a method in which a treatment agent used for these treatments is mixed with a resin component and applied may be used. Further, as the corrosion prevention treatment, a coating type chromate treatment is preferable from the viewpoint of maximizing the effect and waste liquid treatment.

The coating agent used for the coating type corrosion prevention treatment for applying a coating agent having anticorrosion performance contains at least one selected from the group consisting of rare earth element oxide sol, anionic polymer, and cationic polymer. Coating agents can be mentioned. In particular, a method using a coating agent containing a rare earth element oxide sol is preferable.

The method using a coating agent containing a rare earth element oxide sol is a pure coating type corrosion prevention treatment, and by using this method, the aluminum foil layer 14 is provided with a corrosion prevention effect even with a general coating method. It is possible. Further, the layer formed by using the rare earth element oxide sol has a corrosion preventing effect (inhibitor effect) of the aluminum foil layer 14, and is also an environmentally suitable material.

In the rare earth element oxide sol, fine particles of the rare earth element oxide (for example, particles having an average particle diameter of 100 nm or less) are dispersed in a liquid dispersion medium. Examples of the rare earth element oxide include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide. Of these, cerium oxide is preferable. Thereby, the adhesion between the aluminum foil layer 14 and the aluminum foil layer 14 can be further improved. As the liquid dispersion medium of the rare earth element oxide sol, for example, various solvents such as water, alcohol-based solvent, hydrocarbon-based solvent, ketone-based solvent, ester-based solvent, and ether-based solvent can be used. Of these, water is preferable. The rare earth element oxides contained in the corrosion prevention treatment layers 15a and 15b can be used alone or in combination of two or more.

The rare earth element oxide sol is an inorganic acid such as nitric acid, hydrochloric acid, and phosphoric acid, and an organic acid such as acetic acid, malic acid, ascorbic acid, and lactic acid as a dispersion stabilizer in order to stabilize the dispersion of the rare earth element oxide particles. It is preferable to contain acids, salts thereof and the like. Of these dispersion stabilizers, it is particularly preferable to use phosphoric acid or phosphate. As a result, not only the dispersion stabilization of the rare earth element oxide particles, but also the improvement of the adhesion with the aluminum foil layer 14 by utilizing the chelating ability of phosphoric acid in the use of the exterior material for lithium ion batteries, and the addition of phosphoric acid. It can be expected to have effects such as imparting electrolyte resistance by capturing metal ions eluted by the influence (passivation formation), and improving the cohesiveness of the rare earth element oxide layer by easily causing dehydration condensation of phosphoric acid even at low temperatures. Examples of the phosphoric acid or phosphate used as the dispersion stabilizer include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, alkali metal salts thereof, ammonium salts and the like. Of these, condensed phosphoric acids such as trimetaphosphoric acid, tetramethaphosphoric acid, hexametaphosphoric acid, and ultramethaphosphoric acid, or alkali metal salts and ammonium salts thereof are preferable for exhibiting functions as exterior materials for lithium ion batteries. In particular, considering the dry film-forming property (drying capacity, calorific value) when forming a layer containing a rare earth oxide by various coating methods using a coating composition containing a rare earth element oxide sol, reactivity at a low temperature is taken into consideration. A sodium salt is preferable because it is excellent in dehydration condensation property at low temperature. As the phosphate, a water-soluble salt is preferable. The phosphoric acid or phosphate contained in the corrosion prevention treatment layers 15a and 15b may be used alone or in combination of two or more.

The blending amount of phosphoric acid or a salt thereof in the rare earth element oxide sol is preferably 1 part by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the rare earth element oxide. When it is 1 part by mass or more, the sol is well stabilized and it is easy to satisfy the function as an exterior material for a lithium ion battery. The upper limit of the amount of phosphoric acid or a salt thereof with respect to 100 parts by mass of the rare earth element oxide may be a range that does not cause functional deterioration of the rare earth element oxide sol, and 100 parts by mass or less with respect to 100 parts by mass of the rare earth element oxide. It is preferably 50 parts by mass or less, more preferably 20 parts by mass or less.

However, since the layer formed from the above-mentioned rare earth element oxide sol is an aggregate of inorganic particles, the cohesive force of the layer itself is low even after the drying cure step. Therefore, in order to supplement the cohesive force of this layer, it is preferable to combine it with an anionic polymer.

Examples of the anionic polymer include polymers having a carboxy group, and examples thereof include poly (meth) acrylic acid (or a salt thereof) and a copolymer obtained by copolymerizing poly (meth) acrylic acid as a main component. The copolymerization component of the copolymer includes an alkyl (meth) acrylate-based monomer (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, etc. 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, etc.) n-Pulch pill 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 (meth) acrylamide, (as the alkoxy group, methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide and other amide group-containing monomers; Hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; glycidyl group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; (meth) acryloxypropyltrimethoxysilane, ( Examples thereof include silane-containing monomers such as meta) acryloxypropyltrier xylan; and isociane group-containing monomers such as (meth) acryloxypropyl isocyane. Also, styrene, α-methylstyrene, vinylmethyl ether, vinylethyl ether, maleic acid, alkylmalic acid monoester, fumaric acid, alkylfumaric acid monoester, itaconic acid, alkylitaconic acid monoester, (meth) acrylonitrile, chloride. Examples thereof include vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate and butadiene.

The anionic polymer plays a role of improving the stability of the corrosion prevention treatment layers 15a and 15b (oxide layers) obtained by using the rare earth element oxide sol. This is due to the effect of protecting the hard and brittle oxide layer with an acrylic resin component and the effect of capturing ion contamination (particularly sodium ions) derived from phosphate contained in the rare earth oxide sol (cation catcher). Achieved. That is, when the corrosion prevention treatment layers 15a and 15b obtained by using the rare earth element oxide sol contain alkali metal ions such as sodium or alkaline earth metal ions, the starting point is the place containing the ions. The corrosion prevention treatment layers 15a and 15b are likely to deteriorate. Therefore, the resistance of the corrosion prevention treatment layers 15a and 15b is improved by immobilizing sodium ions and the like contained in the rare earth oxide sol with the anionic polymer.

The corrosion prevention treatment layers 15a and 15b in which the anionic polymer and the rare earth element oxide sol are combined have the same corrosion prevention performance as the corrosion prevention treatment layers 15a and 15b formed by subjecting the aluminum foil layer 14 to a chromate treatment. The anionic polymer preferably has a structure in which an essentially water-soluble polyanionic polymer is crosslinked. Examples of the cross-linking agent used for forming the structure include compounds having an isociane group, a glycidyl group, a carboxy group, and an oxazoline group. Furthermore, it is also possible to introduce a crosslinked site having a siloxane bond by using a silane coupling agent.

Examples of the compound having an isocyanate group include diisocyanate such as tolylene diisocyanate, xylylene diisocyanate or a hydrogenated product thereof, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate or a hydrogenated product thereof, and isophorone diisocyanate. Kind; or poly such as an adduct compound obtained by reacting these isocyanate compounds with a polyhydric alcohol such as trimethylolpropane, a burette compound obtained by reacting these isocyanates with water, or a trimeric isocyanurate compound. Isocyanates; or blocked polyisocyanates obtained by blocking these polyisocyanates with alcohols, lactams, oximes, and the like.

Examples of the compound having a glycidyl group include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, and 1,6-hexanediol. Epoxy compounds in which glycols such as neopentyl glycol were allowed to act on epic mouth luhydrin, polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, and sorbyl were allowed to act on epic mouth ruhydrin. Examples thereof include an epoxy compound, an epoxy compound in which a dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid, and adipic acid is allowed to act with epichlorohydrin.

Examples of the compound having a carboxy group include various aliphatic or aromatic dicarboxylic acids, and it is also possible to use an alkali (earth) metal salt of poly (meth) acrylic acid and poly (meth) acrylic acid. is there.

As the compound having an oxazoline group, for example, when a low molecular weight compound having two or more oxazoline units or a polymerizable monomer such as isopropenyl oxazoline is used, (meth) acrylic acid or (meth) acrylic acid alkyl ester , (Meta) A compound obtained by copolymerizing an acrylic monomer such as hydroxyalkyl acrylate.

Examples of the silane coupling agent include γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-chloropropylmethoxysilane. Vinyl trichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, and especially anion Considering the reactivity with the sex polymer, epoxysilane, aminosilane, and isocyanatesilane are preferable.

The amount of the cross-linking agent blended is preferably 1 to 50 parts by mass, more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the anionic polymer. When the ratio of the cross-linking agent is 1 part by mass or more with respect to 100 parts by mass of the anionic polymer, the cross-linked structure is easily sufficiently formed. When the ratio of the cross-linking 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 is improved.

The method for cross-linking the anionic polymer is not limited to the above-mentioned cross-linking agent, and may be a method for forming an ionic cross-link using a titanium or zirconium compound. Further, as these materials, a coating composition for forming the corrosion prevention treatment layer 15a may be applied.

In the corrosion prevention treatment layers 15a and 15b described above, the corrosion prevention treatment layers 15a and 15b by chemical conversion treatment represented by chromate treatment form an inclined structure with the aluminum foil layer 14, and therefore, particularly hydrofluoric acid, hydrochloric acid and nitrate. The aluminum foil layer 14 is treated with a chemical conversion treatment agent containing hydrochloric acid or salts thereof, and then a chromium-based or non-chromate-based compound is allowed to act to form the chemical conversion treatment layer on the aluminum foil layer 14. However, since the chemical conversion treatment uses an acid as the chemical conversion treatment agent, the working environment is deteriorated and the coating device is corroded.

On the other hand, the coating type corrosion prevention treatment layers 15a and 15b described above do not need to form an inclined structure with respect to the aluminum foil layer 14 unlike the chemical conversion treatment typified by chromate treatment. Therefore, the properties of the coating agent are not restricted by acidity, alkalinity, neutrality, etc., and a good working environment can be realized. In addition, for the chromate treatment using a chromium compound, coating type corrosion prevention treatment layers 15a and 15b are preferable from the viewpoint that alternatives are required in terms of environmental hygiene.

If necessary, the corrosion prevention treatment layers 15a and 15b may have a laminated structure in which a cationic polymer is further laminated. Examples of the cationic polymer include polyethyleneimine, an ionic polymer complex composed of polyethyleneimine and a polymer having a carboxylic acid, a primary amine graft acrylic resin in which a primary amine is graphed on the acrylic main skeleton, polyallylamine or a derivative thereof. , Aminophenol resin and the like.

Examples of the "polymer having a carboxylic acid" that forms an ionic polymer complex include polycarboxylic acid (salt), a copolymer in which a comonomer is introduced into the polycarboxylic acid (salt), and a polysaccharide having a carboxy group. Be done. Examples of the polycarboxylic acid (salt) include polyacrylic acid or an ionic salt thereof. Examples of the polysaccharide having a carboxy group include carboxymethyl cellulose or an ionic salt thereof. Examples of the ionic salt include alkali metal salts and alkaline earth metal salts.

The primary amine graph acrylic resin is a resin in which a primary amine is graphed on the acrylic main skeleton. Examples of the acrylic main skeleton include various monomers used in the above-mentioned acrylic polyols such as poly (meth) acrylic acid. Examples of the primary amine to be graphed on the acrylic main skeleton include ethyleneimine.

As the polyallylamine or a derivative thereof, homopolymers or copolymers such as allylamine, allylamine amide sulfate, diallylamine, and dimethylallylamine can be used, and further, these amines may be free amines or may be made of acetic acid or hydrochloric acid. Stabilized products can also be used. Further, it is also possible to use maleic acid, sulfur dioxide or the like as the copolymer component. Furthermore, it is also possible to use a type in which thermal crosslinkability is imparted by partially methoxylating a primary amine. These cationic polymers may be used alone or in combination of two or more. Among the above, as the cationic polymer, at least one selected from the group consisting of polyallylamine and its derivatives is preferable.

The cationic polymer is preferably used in combination with a cross-linking agent having a functional group capable of reacting with an amine / imine such as a carboxy group and a glycidyl group. As the cross-linking agent used in combination with the cationic polymer, a polymer having a carboxylic acid that forms an ionic polymer complex with polyethyleneimine can also be used, and for example, a polycarboxylic acid (salt) such as polyacrylic acid or an ionic salt thereof, or a polycarboxylic acid (salt) thereof. Examples thereof include a copolymer in which a comonomer is introduced into the polymer, a polysaccharide having a carboxy group such as carboxymethyl cellulose or an ionic salt thereof, and the like.

In the present embodiment, the cationic polymer is also described as one component constituting the corrosion prevention treatment layers 15a and 15b. The reason for this is that as a result of diligent studies using various compounds to impart the electrolyte resistance and hydrofluoric acid resistance required for exterior materials for lithium-ion batteries, the cationic polymer itself also has electrolyte resistance and hydrofluoric acid resistance. This is because it was found to be a compound capable of imparting acidity. It is presumed that this factor is because the aluminum foil layer 14 is suppressed from being damaged by capturing fluorine ions with a cationic group (anion catcher). The cationic polymer is also very preferable in terms of improving the adhesiveness between the corrosion prevention treatment layer 15b and the sealant adhesive layer 16. Further, since the cationic polymer is water-soluble like the anionic polymer described above, water resistance can be improved by forming a crosslinked structure using the above-mentioned crosslinking agent. As described above, since the crosslinked structure can be formed even by using the cationic polymer, when the rare earth oxide sol is used for forming the corrosion prevention treatment layers 15a and 15b, the anionic polymer is used as the protective layer thereof. A cationic polymer may be used instead.

From the above, as examples of the combination of coating type corrosion prevention treatments described above, (1) rare earth oxide sol only, (2) anionic polymer only, (3) cationic polymer only, (4) rare earth oxide Sol + anionic polymer (laminated composite), (5) rare earth oxide sol + cationic polymer (laminated composite), (6) (rare earth oxide sol + anionic polymer: laminated composite) / cationic polymer ( Multilayering), (7) (rare earth oxide sol + cationic polymer: laminated composite) / anionic polymer (multilayering), and the like. Among them, (1) and (4) to (7) are preferable, and (4) to (7) are more preferable. Further, in the case of the corrosion prevention treatment layer 15a, (6) is particularly preferable because the corrosion prevention effect and the anchor effect (adhesion improving effect) can be realized in one layer. Further, in the case of the corrosion prevention treatment layer 15b, (6) and (7) are particularly preferable because it becomes easier to maintain the electrolytic solution resistance on the sealant layer 17 side. However, this embodiment is not limited to the above combination. For example, as an example of selection of the corrosion prevention treatment, the cationic polymer is a very preferable material in that it has good adhesion to the modified polyolefin resin described in the description of the sealant adhesive layer 16 described later, and therefore the sealant is bonded. When the layer 16 is made of a modified polyolefin resin, it is possible to design such that a cationic polymer is provided on the surface in contact with the sealant adhesive layer 16 (for example, the configurations (5) and (6)).

However, the corrosion prevention treatment layers 15a and 15b are not limited to the above-mentioned layers. For example, it may be formed by using an agent in which a phosphoric acid and a chromium compound are mixed in a resin binder (aminophenol resin or the like), such as coating type chromate which is a known technique. By using the treatment agent, it is possible to form a layer having both a corrosion prevention function and adhesion. Further, in order to improve the adhesion to the above-mentioned chemical conversion treatment layer (layer formed by degreasing treatment, hydrothermal transformation treatment, anodizing treatment, chemical conversion treatment, or a combination of these treatments), the above-mentioned cationic property It is also possible to perform complex treatments with polymers and / or anodized polymers, or to laminate cationic and / or anodized polymers as a multilayer structure for a combination of these treatments. In addition, although it is necessary to consider the stability of the coating liquid, the corrosion prevention function is performed by using a coating agent obtained by preliminarily liquefying the rare earth oxide sol and the cationic polymer or the anionic polymer described above. It can be a layer that has both adhesion and adhesion.

Corrosion treatment layer 15a, the mass per unit area of 15b is preferably in a range of 0.005~0.200g / ^{m 2,} the range of 0.010~0.100g / ^{m 2} is more preferable. If it is 0.005 g / m ² or more, it is easy to impart a corrosion prevention function to the aluminum foil layer 14. Further, even if the mass per unit area exceeds 0.200 g / m ² , the corrosion prevention function is saturated and does not change much. On the other hand, when a rare earth oxide sol is used, if the coating film is thick, the cure due to heat during drying becomes insufficient, and the cohesive force may decrease. In the above content, the mass per unit area is described, but if the specific gravity is known, the thickness can be converted from it.

The thickness of the corrosion prevention treatment layers 15a and 15b is preferably, for example, 10 nm to 5 μm, and more preferably 20 nm to 500 nm from the viewpoint of the corrosion prevention function and the function as an anchor. The thickness of the corrosion prevention treatment layer 15b on the sealant layer 17 side is preferably such that the unevenness of the surface roughness of the aluminum foil layer 14 is not filled, and is formed on the surface of the aluminum foil layer 14. The thickness is preferably 0.1 to 10% of the unevenness height, and more preferably 0.5 to 5%.

(Sealant adhesive layer 16)
The sealant adhesive layer 16 is a layer for adhering the aluminum foil layer 14 on which the corrosion prevention treatment layer 15b is formed and the sealant layer 17. The exterior material 10 is roughly divided into a heat-laminated structure and a dry-laminated structure depending on the adhesive component forming the sealant adhesive layer 16.

The adhesive component forming the sealant adhesive layer 16 in the heat-laminated structure is preferably an acid-modified polyolefin-based resin obtained by graft-modifying a polyolefin-based resin with an acid. Since the acid-modified polyolefin-based resin has a polar group introduced into a part of the non-polar polyolefin-based resin, it has polarity with the sealant layer 17 when it is composed of a non-polar polyolefin-based resin film or the like. It can firmly adhere to both of the corrosion prevention treatment layer 15b, which is often the case. Further, by using the acid-modified polyolefin resin, the resistance of the exterior material 10 to the contents such as the electrolytic solution is improved, and even if hydrofluoric acid is generated inside the battery, the adhesive force is lowered due to the deterioration of the sealant adhesive layer 16. Is easy to prevent.

Examples of the polyolefin-based resin of the acid-modified polyolefin-based resin include low-density, medium-density and high-density polyethylene; ethylene-α-olefin copolymer; polypropylene; and propylene-α-olefin copolymer. When it is a copolymer, the polyolefin resin may be a block copolymer or a random copolymer. Further, as the polyolefin resin, a copolymer obtained by copolymerizing the above-mentioned one with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as crosslinked polyolefin can also be used. Examples of the acid for modifying the polyolefin resin include carboxylic acids, epoxy compounds and acid anhydrides, and maleic anhydride is preferable. The acid-modified polyolefin resin used for the sealant adhesive layer 16 may be one type or two or more types.

The sealant adhesive layer 16 having a heat-laminated structure can be formed by extruding the adhesive component with an extrusion device. The thickness of the sealant adhesive layer 16 having a heat-laminated structure is preferably 2 to 50 μm.

Examples of the adhesive component forming the sealant adhesive layer 16 having a dry laminate structure include the same adhesives as those mentioned in the adhesive layer 13. In this case, in order to suppress swelling due to the electrolytic solution and hydrolysis due to hydrofluoric acid, it is possible to design the composition of the adhesive so that it is the main component of the skeleton that is difficult to hydrolyze and the crosslink density can be improved. preferable.

When improving the cross-linking density, for example, dimer fatty acid, ester or hydrogenated dimer fatty acid, reduced glycol of dimer fatty acid, ester of dimer fatty acid or reduced glycol of hydrogenated material may be added to the adhesive. The dimer fatty acid is an acid obtained by dimerizing various unsaturated fatty acids, and examples of its structure include an acyclic type, a monocyclic type, a polycyclic type, and an aromatic ring type.

The fatty acid that is the starting material of the dimer fatty acid is not particularly limited. Further, a dibasic acid as used in a normal polyester polyol may be introduced with such a dimer fatty acid as an essential component. As a curing agent for the main agent constituting the sealant adhesive layer 16, for example, an isocyanate compound that can also be used as a chain extender for a polyester polyol can be used. As a result, the crosslink density of the adhesive coating film is increased, leading to improvement in solubility and swelling property, and an increase in urethane group concentration is expected to improve substrate adhesion.

Since the sealant adhesive layer 16 having a dry-laminated structure has highly hydrolyzable bonding portions such as an ester group and a urethane group, the sealant adhesive layer 16 has a heat-laminated structure for applications requiring higher reliability. It is preferable to use the adhesive component of. For example, an acid-modified polyolefin resin is dissolved or dispersed in a solvent such as toluene or methylcyclohexane (MCH), and various curing agents described above are mixed with the coating liquid, and the sealant adhesive layer 16 is formed by coating and drying. To do.

When the sealant adhesive layer 16 is formed by extrusion molding, the adhesive resin tends to be oriented in the MD direction (extrusion direction) due to stress generated during extrusion molding or the like. In this case, an elastomer may be added to the sealant adhesive layer 16 in order to alleviate the anisotropy of the sealant adhesive layer 16. As the elastomer to be blended in the sealant adhesive layer 16, for example, an olefin-based elastomer, a styrene-based elastomer, or the like can be used.

The average particle size of the elastomer is preferably a particle size capable of improving the compatibility between the elastomer and the adhesive resin and improving the effect of alleviating the anisotropy of the sealant adhesive layer 16. Specifically, the average particle size of the elastomer is preferably 200 nm or less, for example.

The average particle size of the elastomer can be determined by, for example, taking an enlarged photograph of the cross section of the elastomer composition with an electron microscope and then measuring the average particle size of the dispersed crosslinked rubber components by image analysis. .. The above elastomer may be used alone or in combination of two or more.

When the elastomer is blended in the sealant adhesive layer 16, the blending amount of the elastomer added in the sealant adhesive layer 16 (100% by mass) is, for example, preferably 1 to 25% by mass, more preferably 10 to 20% by mass. By setting the blending amount of the elastomer to 1% by mass or more, the compatibility with the adhesive resin tends to be improved, and the effect of alleviating the anisotropy of the sealant adhesive layer 16 tends to be improved. Further, by setting the blending amount of the elastomer to 25% by mass or less, the effect of suppressing the swelling of the sealant adhesive layer 16 by the electrolytic solution tends to be improved.

As the sealant adhesive layer 16, for example, a dispersion type adhesive resin liquid in which an adhesive resin is dispersed in an organic solvent may be used.

The thickness of the sealant adhesive layer 16 is preferably 8 μm or more and 50 μm or less, and more preferably 20 μm or more and 40 μm or less in the case of a heat-laminated structure. When the thickness of the sealant adhesive layer 16 is 8 μm or more, it is easy to obtain sufficient adhesive strength between the aluminum foil layer 14 provided with the corrosion prevention treatment layer 15b and the sealant layer 17, and when it is 50 μm or less, it is easy to obtain. It is possible to easily reduce the amount of water that penetrates into the internal battery element from the end face of the exterior material. The thickness of the sealant adhesive layer 16 is preferably 1 μm or more and 5 μm or less in the case of a dry laminate structure. When the thickness of the sealant adhesive layer 16 is 1 μm or more, it is easy to obtain sufficient adhesive strength between the aluminum foil layer 14 provided with the corrosion prevention treatment layer 15b and the sealant layer 17, and when it is 5 μm or less, it is easy to obtain. The occurrence of cracks in the sealant adhesive layer 16 can be suppressed.

(Sealant layer 17)
The sealant layer 17 is a layer that imparts sealing properties to the exterior material 10 by heat sealing, and is a layer that is arranged inside when the power storage device is assembled and is heat-sealed. Examples of the sealant layer 17 include a polyolefin-based resin or a resin film made of an acid-modified polyolefin-based resin obtained by graft-modifying an acid such as maleic anhydride to the polyolefin-based resin. Of these, polyolefin-based resins that improve the barrier property of water vapor and can form the form of the power storage device without being excessively crushed by heat sealing are preferable, and polypropylene is particularly preferable.

Examples of the polyolefin-based resin include low-density, medium-density and high-density polyethylene; ethylene-α-olefin copolymer; polypropylene; and propylene-α-olefin copolymer. When it is a copolymer, the polyolefin resin may be a block copolymer or a random copolymer. One type of these polyolefin resins may be used alone, or two or more types may be used in combination.

In addition, each of the above types of polypropylene, that is, random polypropylene, homopolypropylene, and block polypropylene, includes a low-crystalline ethylene-butene copolymer, a low-crystalline propylene-butene copolymer, and ethylene, butene, and propylene. An anti-blocking agent (AB agent) such as a tarpolymer composed of a component copolymer, silica, zeolite, or acrylic resin beads, a fatty acid amide-based slip agent, or the like may be added.

Examples of the acid-modified polyolefin-based resin include those similar to those mentioned in the sealant adhesive layer 16.

The sealant layer 17 may be a single-layer film or a multilayer film, and may be selected according to a required function. For example, in terms of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer and polymethylpentene is interposed can be used.

Further, the sealant layer 17 may contain various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer and a tackifier.

When a heat-weldable film formed by extrusion molding is used as the sealant layer 17, there is a tendency for the heat-weldable film to be oriented in the extrusion direction. Therefore, from the viewpoint of alleviating the anisotropy of the sealant layer 17 due to orientation, an elastomer may be added to the heat-weldable film. As a result, it is possible to prevent the sealant layer 17 from whitening when the exterior material 10 for a power storage device is cold-molded to form a recess.

As the elastomer constituting the sealant layer 17, for example, the same material as the material exemplified as the elastomer constituting the sealant adhesive layer 16 can be used. When the sealant layer 17 has a multilayer film structure, at least one of the plurality of layers constituting the multilayer film structure may be configured to contain an elastomer. For example, in the case of a three-layer laminated structure including the laminated random polypropylene layer / block polypropylene layer / random polypropylene layer as the sealant layer 17, the elastomer may be blended only in the block polypropylene layer or only in the random polypropylene layer. It may be blended, or it may be blended in both the random polypropylene layer and the block polypropylene layer.

In addition, a lubricant may be contained in order to impart slipperiness to the sealant layer 17. As described above, when the sealant layer 17 contains the lubricant to form a recess in the power storage device exterior material 10 by cold molding, the side or corner of the recess having a high stretch ratio in the power storage device exterior material 10 is formed. It is possible to prevent the portion to be stretched more than necessary. As a result, it is possible to prevent the aluminum foil layer 14 and the sealant adhesive layer 16 from peeling off, and the sealant layer 17 and the sealant adhesive layer 16 from being broken or whitened due to cracks.

When the sealant layer 17 contains a lubricant, the content of the lubricant in the sealant layer 17 (100% by mass) is preferably 0.001% by mass to 0.5% by mass. When the content of the lubricant is 0.001% by mass or more, whitening of the sealant layer 17 tends to be more suppressed during cold molding. Further, when the content of the lubricant is 0.5% by mass or less, there is a tendency that the decrease in the adhesion strength between the surface of the sealant layer 17 and the surface of another layer in contact with the sealant layer 17 can be suppressed.

The thickness of the sealant layer 17 is preferably 10 to 100 μm, more preferably 20 to 60 μm. When the thickness of the sealant layer 17 is 20 μm or more, sufficient heat seal strength can be obtained, and when it is 90 μm or less, the amount of water vapor infiltrated from the end portion of the exterior material can be reduced.

[Manufacturing method of exterior materials]
Next, a method of manufacturing the exterior material 10 will be described. The method for manufacturing the exterior material 10 is not limited to the following method.

Examples of the method for manufacturing the exterior material 10 include a method having the following steps S11 to S13.
Step S11: A step of forming a corrosion prevention treatment layer 15a on one surface of the aluminum foil layer 14 and forming a corrosion prevention treatment layer 15b on the other surface of the aluminum foil layer 14.
Step S12: A step of bonding the surface of the corrosion prevention treatment layer 15a on the side opposite to the side on which the aluminum foil layer 14 is laminated and the surface of the base material layer 11 via the adhesive layer 13.
Step S13: A step of forming a sealant layer 17 via a sealant adhesive layer 16 on a surface of the corrosion prevention treatment layer 15b opposite to the side on which the aluminum foil layer 14 is laminated.

(Step S11)
In step S11, the corrosion prevention treatment layer 15a is formed on one surface of the aluminum foil layer 14, and the corrosion prevention treatment layer 15b is formed on the other surface of the aluminum foil layer 14. The corrosion prevention treatment layers 15a and 15b may be formed separately, or both may be formed at the same time. Specifically, for example, a corrosion prevention treatment agent (base material of the corrosion prevention treatment layer) is applied to both surfaces of the aluminum foil layer 14, and then drying, curing, and baking are sequentially performed to prevent the corrosion treatment layer. 15a and 15b are formed at once. Further, an anticorrosion treatment agent is applied to one surface of the aluminum foil layer 14, and drying, curing, and baking are sequentially performed to form the corrosion prevention treatment layer 15a, and then the other surface of the aluminum foil layer 14 is similarly subjected to the same procedure. The corrosion prevention treatment layer 15b may be formed. The order of forming the corrosion prevention treatment layers 15a and 15b is not particularly limited. Further, as the corrosion prevention treatment agent, different ones may be used for the corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b, or the same one may be used. As the corrosion prevention treatment agent, for example, a corrosion prevention treatment agent for coating type chromate treatment can be used. The method of applying the corrosion prevention treatment agent is not particularly limited, and for example, a method such as a gravure coating method, a gravure reverse coating method, a roll coating method, a reverse roll coating method, a die coating method, a bar coating method, a kiss coating method, and a comma coating method. Can be used. As the aluminum foil layer 14, an untreated aluminum foil layer may be used, or an aluminum foil layer that has been degreased by a wet type degreasing treatment or a dry type degreasing treatment may be used.

(Step S12)
In step S12, the surface of the corrosion prevention treatment layer 15a opposite to the side on which the aluminum foil layer 14 is laminated and the surface of the base material layer 11 are dry-laminated or the like using an adhesive forming the adhesive layer 13. It is pasted by the method of. In step S12, an aging (curing) treatment may be performed in the range of room temperature to 100 ° C. in order to promote adhesiveness. The aging time is, for example, 1 to 10 days.

(Step S13)
After the step S12, among the laminated bodies in which the base material layer 11, the adhesive layer 13, the corrosion prevention treatment layer 15a, the aluminum foil layer 14 and the corrosion prevention treatment layer 15b are laminated in this order, the aluminum foil layer 14 of the corrosion prevention treatment layer 15b The sealant layer 17 is formed via the sealant adhesive layer 16 on the surface opposite to the side on which the sealants are laminated. The sealant layer 17 may be laminated by dry lamination, sandwich lamination or the like, or may be laminated together with the sealant adhesive layer 16 by a coextrusion method. From the viewpoint of improving the adhesiveness, the sealant layer 17 is preferably laminated by, for example, sandwich lamination, or is laminated together with the sealant adhesive layer 16 by a coextrusion method, and more preferably by sandwich lamination.

The exterior material 10 is obtained by the steps S11 to S13 described above. The process order of the method for manufacturing the exterior material 10 is not limited to the method in which the above steps S11 to S13 are sequentially performed. For example, the order of the steps to be performed may be changed as appropriate, such as performing step S13 and then performing step S12.

[Power storage device]
Next, a power storage device including the exterior material 10 as a container will be described. The power storage device includes a battery element 1 including an electrode, a lead 2 extending from the electrode, and a container for accommodating the battery element 1. The container has a sealant layer 17 inside from the exterior material 10 for the power storage device. Is formed to be. The container may be obtained by stacking two exterior materials with the sealant layers 17 facing each other and heat-sealing the peripheral edges of the stacked exterior materials 10, or by folding back one exterior material. It may be obtained by superimposing and heat-sealing the peripheral edge portion of the exterior material 10 in the same manner. Further, the power storage device may include the exterior material 20 as a container. Examples of the power storage device include a secondary battery such as a lithium ion battery, a nickel hydrogen battery, and a lead storage battery, and an electrochemical capacitor such as an electric double layer capacitor.

The reed 2 is sandwiched and sealed by an exterior material 10 that forms a container with the sealant layer 17 inside. The reed 2 may be sandwiched by the exterior material 10 via the tab sealant.

[Manufacturing method of power storage device]
Next, a method of manufacturing a power storage device using the above-mentioned exterior material 10 will be described. Here, a case where the secondary battery 40 is manufactured by using the embossed type exterior material 30 will be described as an example. FIG. 2 is a diagram showing the embossed type exterior material 30. 3 (a) to 3 (d) are perspective views showing a manufacturing process of a one-sided molded battery using the exterior material 10. The secondary battery 40 is a double-sided molded battery manufactured by providing two exterior materials such as the embossed type exterior material 30 and laminating such exterior materials while adjusting the alignment. May be good. Further, the embossed type exterior material 30 may be formed by using the exterior material 20.

The secondary battery 40, which is a one-side molded processed battery, can be manufactured, for example, by the following steps S21 to S25.
Step S21: A step of preparing the exterior material 10, the battery element 1 including the electrode, and the lead 2 extending from the electrode.
Step S22: A step of forming a recess 32 for arranging the battery element 1 on one side of the exterior material 10 (see FIGS. 3 (a) and 3 (b)).
Step S23: The battery element 1 is arranged in the molding processing area (recess 32) of the embossed type exterior material 30, the embossed exterior material 30 is folded back and overlapped so that the lid 34 covers the recess 32, and extends from the battery element 1. A step of pressurizing and heat-sealing one side of the embossed type exterior material 30 so as to sandwich the lead 2 (see FIGS. 3 (b) and 3 (c)).
Step S24: One side other than the side holding the reed 2 is left, and the other side is pressure-heat fused. Then, the electrolytic solution is injected from the remaining side, and the one side remaining in the vacuum state is pressure-heat-sealed. Step to perform (see FIG. 3C).
Step S25: A step of cutting the end of the pressure heat fusion side other than the side holding the reed 2 and bending it toward the molding processing area (recess 32) (see FIG. 3D).

(Step S21)
In step S21, the exterior material 10, the battery element 1 including the electrodes, and the reed 2 extending from the electrodes are prepared. The exterior material 10 is prepared based on the above-described embodiment. The battery element 1 and the lead 2 are not particularly limited, and known battery elements 1 and the lead 2 can be used.

(Step S22)
In step S22, a recess 32 for arranging the battery element 1 is formed on the sealant layer 17 side of the exterior material 10. The planar shape of the recess 32 is a shape that matches the shape of the battery element 1, for example, a rectangular shape in a plan view. The recess 32 is formed by, for example, pressing a pressing member having a rectangular pressure surface against a part of the exterior material 10 in the thickness direction thereof. Further, the pressing position, that is, the recess 32 is formed at a position biased toward one end in the longitudinal direction of the exterior material 10 from the center of the exterior material 10 cut out in a rectangular shape. As a result, the other end side on which the recess 32 is not formed after the molding process can be folded back to form a lid (lid portion 34).

More specifically, as a method of forming the concave portion 32, a molding process using a mold (deep drawing molding) can be mentioned. As a molding method, a method of using a female mold and a male mold arranged so as to have a gap equal to or larger than the thickness of the exterior material 10 and pushing the male mold together with the exterior material 10 into the female mold. Can be mentioned. By adjusting the pushing amount of the male die, the depth (deep drawing amount) of the recess 32 can be adjusted to a desired amount. The embossed type exterior material 30 can be obtained by forming the recess 32 in the exterior material 10. The embossed type exterior material 30 has a shape as shown in FIG. 2, for example. Here, FIG. 2A is a perspective view of the embossed type exterior material 30, and FIG. 2B is a vertical cross section of the embossed type exterior material 30 shown in FIG. 2A along the line bb. It is a figure.

(Step S23)
In step S23, the battery element 1 composed of a positive electrode, a separator, a negative electrode, and the like is arranged in the molding processing area (recess 32) of the embossed type exterior material 30. Further, the leads 2 extending from the battery element 1 and joined to the positive electrode and the negative electrode, respectively, are pulled out from the molding processing area (recessed portion 32). After that, the embossed type exterior material 30 is folded back at substantially the center in the longitudinal direction, the sealant layers 17 are stacked so as to be inside, and one side of the embossed type exterior material 30 holding the lead 2 is pressure-heat fused. To. Pressurized heat fusion is controlled under three conditions of temperature, pressure and time, and is appropriately set. The temperature of the pressure heat fusion is preferably equal to or higher than the temperature at which the sealant layer 17 is melted.

The thickness of the sealant layer 17 before heat fusion is preferably 40% or more and 80% or less with respect to the thickness of the lead 2. When the thickness of the sealant layer 17 is at least the above lower limit value, the heat-sealing resin tends to sufficiently fill the two ends of the reed, and when it is at least the above upper limit value, the exterior material 10 of the secondary battery 40 The thickness of the end portion can be appropriately suppressed, and the amount of water infiltrated from the end portion of the exterior material 10 can be reduced.

(Step S24)
In step S24, pressure heat fusion is performed on the other side, leaving one side other than the side holding the lead 2. After that, the electrolytic solution is injected from the remaining side, and the remaining side is pressurized and heat-sealed in a vacuum state. The conditions for pressure heat fusion are the same as in step S23.

(Step S25)
The peripheral edge pressure heat fusion side end portion other than the side sandwiching the reed 2 is cut, and the sealant layer 17 protruding from the end portion is removed. After that, the peripheral pressure heat-sealing portion is folded back toward the molding processing area 32 to form the folded-back portion 42, whereby the secondary battery 40 is obtained.

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

For example, in the above embodiment, the base layer 11 is adhered to the barrier layer 22 by the adhesive layer 13, but the base layer 11 may be provided by applying the base layer 11 to the barrier layer 22. In this case, the material resin of the base material layer 11 may be applied and dried as it is, or may be dissolved in an appropriate solvent and applied and dried. In this case, the coating layer 21 is composed of only the base material layer 11 and does not have the adhesive layer 13.

Further, in the above embodiment, the barrier layer 22 has the corrosion prevention treatment layers 15a and 15b, but the barrier layer 22 may not have at least one of the corrosion prevention treatment layers 15a and 15b.

Hereinafter, the contents of the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

<Material>
The materials constituting the exterior material for the power storage device are as follows.

(Base layer)
A co-pressed biaxially stretched film of PET having a thickness of 5 μm and Ny (nylon 6) having a thickness of 25 μm.

(Adhesive layer)
Polyurethane adhesive.

(Aluminum foil layer)
Soft aluminum foil with different gloss (8079 material, thickness 40 μm, manufactured by Toyo Aluminum K.K.).

(Corrosion prevention treatment layer)
Corrosion prevention treatment layer A: A composition composed of 90% by mass of "cerium oxide sol" adjusted to a solid content concentration of 10% by mass and 10% by mass of condensed Na phosphate salt is used as a base using distilled water as a solvent. On this base, a treated layer of a composition composed of "polyallylamine polymer" / "glycidyl compound" = 90/10 adjusted to a final solid content concentration of 5% by mass using distilled water as a solvent is provided.
Corrosion treatment layer B: the resin composition consisting of polyacrylic acid and oxazoline group-containing acrylic resin, CrF ₃ and coating type chemical conversion treatment agent obtained by blending a phosphate (final solids concentration of 5 wt%) Use as a base. On this base, a treated layer of a composition composed of "polyallylamine polymer" / "glycidyl compound" = 90/10 adjusted to a final solid content concentration of 5% by mass using distilled water as a solvent is provided.

(Sealant adhesive layer)
An adhesive composition obtained by blending 10 parts by mass (solid content ratio) of a polyisocyanate compound with 100 parts by mass of a toluene solution of a maleic anhydride-modified polyolefin resin. For dry laminating.

(Sealant layer)
A multilayer film of 2 types and 3 layers composed of random propylene / blocked propylene / random propylene (thickness 80 μm, manufactured by Okamoto Co., Ltd.).

<Measurement / evaluation>
(Glossiness)
The 60 ° glossiness of the aluminum foil layer alone and the 60 ° glossiness of the aluminum foil layer with the corrosion prevention treatment layer provided are measured in each of the TD direction and the MD direction. The measurement is performed by arranging the incident surfaces of the light source light of the gloss meter so as to coincide with each other in the TD direction and the MD direction.

(Compression test)
The prepared dummy cells are placed between the flat plates of the press. Gradually apply pressure, stop pressurizing when the target pressure is reached, and hold at that pressure for 3 minutes.
-Evaluation of compression test ◯: The battery cell did not burst from the inside when a pressure of 2.2 MPa was applied.
X: The battery cell burst from the inside when a pressure of 2.2 MPa was applied.
・ Comprehensive evaluation ○: Can withstand practical use as a lithium-ion battery.
X: Cannot withstand practical use as a lithium-ion battery.

<Example 1>
(Manufacturing of exterior materials for power storage devices)
First, a soft aluminum foil 8079 material (manufactured by Toyo Aluminum K.K. Co., Ltd.) having a thickness of 40 μm was prepared as an aluminum foil layer, and the 60 ° glossiness of the surface on the sealant layer side was measured. The 60 ° glossiness in the MD direction was 77.1, and the 60 ° glossiness in the TD direction was 110.3.

Next, the base material of the corrosion prevention treatment layer A or the corrosion prevention treatment layer B was applied to both sides of the aluminum foil layer by gravure coating.

Next, after the applied base material was dried, a baking treatment was sequentially performed to form a corrosion prevention treatment layer. At this time, the baking conditions were a temperature of 150 ° C. and a processing time of 30 seconds.

Next, one side of the PET / Ny co-pressed biaxially stretched film as the base material layer was corona-treated.

Next, a polyurethane-based adhesive as an adhesive layer was applied to one side of the corrosion prevention treatment layer provided on the aluminum foil layer. Then, the aluminum foil layer and the corona-treated surface of the base material layer were adhered to each other via the adhesive layer by the dry laminating method. Then, the structure composed of the base material layer, the adhesive layer, the corrosion prevention treatment layer, the aluminum foil layer, and the corrosion prevention treatment layer was left for 6 days in an atmosphere at a temperature of 60 ° C. for aging treatment.

Next, an adhesive composition as a raw material for the sealant adhesive layer was applied to the surface of the aluminum foil layer opposite to the side on which the base material layer was provided. Next, by a dry laminating method, a multilayer film of two types and three layers made of random propylene / blocked propylene / random propylene to be the sealant layer 17 was adhered to the aluminum foil layer via the sealant adhesive layer. Then, the structure composed of the base material layer, the adhesive layer, the corrosion prevention treatment layer, the aluminum foil layer, the corrosion prevention treatment layer, the sealant adhesive layer, and the sealant layer is left to stand in an atmosphere at a temperature of 40 ° C. for 6 days. , Aged. As a result, an exterior material for a power storage device was produced.

(Making a lithium-ion battery dummy cell)
The exterior material for the power storage device was cut out and molded so as to have a cell size of 6 mm (height) × 51 mm × 43 mm in consideration of the seal portion (in the region where the recess 32 in FIG. 2 corresponds to the molded cell size). is there). An aluminum foil wound so as to have a size of 6 mm × 51 mm × 43 mm was prepared as the content, placed in the molded exterior material, and sealed leaving one side. Next, 12 ml of water was injected instead of the electrolytic solution, and the remaining one side was sealed to prepare a dummy cell.

Five of these battery cells were prepared and compression tests were performed on each of them. The results of the compression test are shown in Table 1. In Table 1, "n" indicates the sample number used in the compression test.

<Examples 2 to 8 and Comparative Examples 1 to 8>
An exterior material for a power storage device and a lithium ion battery dummy cell were produced in the same manner as in Example 1 except that the glossiness on the sealant layer side and the corrosion prevention treatment layer used variously different aluminum foils as shown in Table 1. , A compression test was performed. The glossiness here is the glossiness measured as a single aluminum foil layer.

According to these results, the aluminum foil layer used for producing the lithium ion battery dummy cell has a 60 ° glossiness in the MD direction and a 60 ° glossiness in the TD direction as a single aluminum foil layer of 690 or less. It can be seen that the result of the compression test is good when the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction is 100 or less.

<Examples 9 to 16, Comparative Examples 9 to 16>
An exterior material for a power storage device and a lithium ion battery dummy cell were produced in the same manner as in Example 1 except that the glossiness on the sealant layer side and the corrosion prevention treatment layer used different aluminum foils as shown in Table 2. , A compression test was performed. The glossiness here is a value as an "aluminum foil layer in a state where the corrosion prevention treatment layer is provided" measured at the time when the corrosion prevention treatment layer is formed. The aluminum foils used in Examples 9 to 16 and Comparative Examples 9 to 16 were of the same lot as the aluminum foils used in Examples 1 to 8 and Comparative Examples 1 to 8, respectively.

According to these results, the aluminum foil layer used for producing the lithium ion battery dummy cell has a 60 ° glossiness in the MD direction and a TD direction as the aluminum foil layer in the state where the corrosion prevention treatment layer is provided. When the 60 ° glossiness in the above is 590 or less and the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction is 100 or less, the result of the compression test is good. I understand.

1 ... Battery element, 2 ... Lead, 10 ... Exterior material (exterior material for power storage device), 11 ... Base material layer, 13 ... Adhesive layer, 14 ... Aluminum foil layer, 15a, 15b ... Corrosion prevention treatment layer, 16 ... Sealant Adhesive layer, 17 ... Sealant layer, 30 ... Embossed type exterior material, 32 ... Molding area (recess), 34 ... Lid, 40 ... Secondary battery.

Claims (5)

An exterior material for a power storage device having a structure in which a coating layer, a barrier layer, a sealant adhesive layer, and a sealant layer are laminated in this order.
The barrier layer has an aluminum foil layer and a corrosion prevention treatment layer provided on the sealant layer side of the aluminum foil layer and facing the sealant adhesive layer.
The 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the surface of the aluminum foil layer on the sealant layer side are both 690 or less.
An exterior material for a power storage device, wherein the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction is 61.4 or more and 100 or less. An exterior material for a power storage device having a structure in which a coating layer, a barrier layer, a sealant adhesive layer, and a sealant layer are laminated in this order.
The barrier layer has an aluminum foil layer and a corrosion prevention treatment layer provided on the sealant layer side of the aluminum foil layer and facing the sealant adhesive layer.
The 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the surface of the aluminum foil layer on the sealant layer side are both 150 or less.
The difference between the 60 ° glossiness of 60 ° glossiness and the TD direction in the MD direction is 50 or less than 33.2, a charge reservoir for the outer package. An exterior material for a power storage device having a structure in which a coating layer, a barrier layer, a sealant adhesive layer, and a sealant layer are laminated in this order.
The barrier layer has an aluminum foil layer and a corrosion prevention treatment layer provided on the sealant layer side of the aluminum foil layer and facing the sealant adhesive layer.
The 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the aluminum foil layer with the corrosion prevention treatment layer provided are both 590 or less.
An exterior material for a power storage device, wherein the difference between the 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction is 52.2 or more and 100 or less. An exterior material for a power storage device having a structure in which a coating layer, a barrier layer, a sealant adhesive layer, and a sealant layer are laminated in this order.
The barrier layer has an aluminum foil layer and a corrosion prevention treatment layer provided on the sealant layer side of the aluminum foil layer and facing the sealant adhesive layer.
The 60 ° glossiness in the MD direction and the 60 ° glossiness in the TD direction of the aluminum foil layer in the state where the corrosion prevention treatment layer is provided are both 120 or less.
Wherein the 60 ° gloss in the MD direction difference between the 60 ° gloss in the TD direction is 28.2 or more 40 or less, a charge reservoir for the outer package. A battery element including an electrode, a reed extending from the electrode, and a container for accommodating the battery element are provided.
The container is formed from the exterior material for a power storage device according to any one of claims 1 to 4 so that the sealant layer is on the inside.

Images