JP6728579B2 - Secondary battery exterior material - Google Patents

Description

The present invention relates to a secondary battery exterior material.

2. Description of the Related Art In recent years, mobile devices such as mobile phones, smartphones, and music playback mobile devices, hybrid electric vehicles, and electric vehicles have become widespread. A secondary battery typified by a nickel-hydrogen battery or a lithium-ion battery is used as a battery for supplying electricity, which is a power source and a power source. Rechargeable batteries are required to be lightweight and compact for mobile devices, and are connected in parallel and in series to increase energy and output in vehicle applications, and are being connected in multiple layers to make them more lightweight and compact. It has been demanded.

By the way, as for the secondary battery, a metal can and a laminated film exterior material are used properly depending on the application and use environment, but the laminated film exterior material is drawing attention from the viewpoint of weight reduction and freedom of shape.

In order to prevent the entry of moisture from the outside of the secondary battery, a metal foil typified by an aluminum foil or a stainless steel foil is generally used for the barrier layer in the laminate film exterior material. Among the metal foils, an aluminum foil laminated film having an aluminum foil as a barrier layer is often used because of its light weight, spreadability, and material cost.

The aluminum foil laminate film is a laminate of aluminum foil and resin, and generally, a sealant layer, an adhesive layer, a corrosion prevention treatment layer, an aluminum foil layer, a corrosion prevention treatment layer, and a substrate in order from the inner layer close to the battery element. It has an adhesive layer and a base material layer (nylon, PET, etc.).

For example, as a battery element of a lithium ion secondary battery, a positive electrode material, a negative electrode material, and a separator for preventing contact between the electrodes, aproton such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of the organic solvent include an electrolytic solution in which an electrolyte (lithium salt) is dissolved, or an electrolytic layer made of a polymer gel impregnated with the electrolytic solution. Electric power stored in these battery elements is supplied to a metal terminal (hereinafter, tab lead). And) to the outside of the battery.

It is important to reduce the thickness of such a laminated film exterior material in order to make a secondary battery that is lightweight, compact, and has a higher capacity.However, if the innermost sealant layer is too thin, it will be used as a barrier layer. The metal foil and the tab lead may come into contact with each other and the secondary battery may be short-circuited.

As a method of preventing such a short circuit of the secondary battery end portion, for example, as described in Patent Document 1, by providing an intermediate layer between the barrier layer and the sealant layer, the film thickness of the heat seal portion There has been proposed a method of maintaining the above-mentioned property and preventing contact (occurrence of short circuit) between the tab lead and the metal foil used for the barrier layer.

JP2011-138793A

However, in the method described in Patent Document 1, although it is possible to prevent a short circuit between the tab lead and the metal foil used as the barrier layer of the exterior material, the film thickness increases due to the addition of one intermediate layer. I will end up.

Lithium-ion secondary batteries, which have become widespread in recent years, have the risk of deterioration of battery performance due to lack of electrical insulation, heat generation, and fire. Required. On the other hand, on the other hand, it is a fact that an effective means for preventing a short circuit between the tab lead and the secondary battery outer packaging material has not yet been sufficiently obtained while thinning the outer packaging material.

In view of the above problems, it is an object of the present invention to provide an exterior material for a secondary battery that can achieve both sufficient thinness and excellent electrical insulation.

The present invention comprises at least a base material layer, a barrier layer and a sealant layer in this order, the barrier layer is made of a metal foil, the barrier layer has a corrosion prevention treatment layer at least on the sealant layer side, The sealant layer is directly formed on the corrosion-preventing layer, the sealant layer has a thickness of 5 to 30 μm, and the sealant layer contains a high melting point substance, to provide a secondary battery exterior material.

Thus, a sealant layer is directly provided on the corrosion prevention treatment layer on the first surface of the barrier layer without an adhesive, the sealant layer has a thickness of 5 to 30 μm, and a high melting point substance is contained in the sealant layer. Thus, it is possible to provide an exterior material for a secondary battery, which has excellent electrical insulation even with a thin film.

In the secondary battery exterior material of the present invention, the sealant layer is preferably formed of an acid-modified polyolefin-based resin.

By forming the sealant layer using an acid-modified polyolefin resin, the sealant layer and the barrier layer can be firmly adhered. In addition, the sealant layer of the secondary battery exterior material is formed into a bag with the sealant layer inside and heat-sealed, so that the sealant layers can be more firmly adhered to each other.

In the secondary battery exterior material of the present invention, the sealant layer is preferably formed of a resin having a melting point of 100 to 165°C.

When the melting point of the sealant resin is 100 to 165°C, more stable heat sealing characteristics can be obtained.

In the exterior material for a secondary battery of the present invention, the average particle diameter of the high melting point substance is preferably 30 to 80% of the thickness of the sealant layer.

Since the sealant layer contains a high melting point substance having a particle size of 30 to 80% with respect to the thickness of the sealant layer, the thickness of the sealant layer in the heat-sealed portion can be easily maintained and no short circuit occurs. It becomes easy to obtain excellent electrical insulation.

In the packaging material for a secondary battery of the present invention, it is preferable that the high melting point substance has a melting point of 220° C. or higher.

When the melting point of the high-melting point substance is 220° C. or higher, the high-melting point substance is difficult to melt even if heat sealing is performed, the layer thickness of the sealant layer is maintained, and it becomes easy to obtain excellent electric insulation without short circuit.

In the secondary battery exterior material of the present invention, it is preferable that the number of high melting point substances is 1 to 15 million pieces/cm ³ per unit volume of the sealant layer.

When the number of high-melting point substances is 1 to 15 million pieces/cm ³ per unit volume of the sealant layer, the high-melting point substances are evenly dispersed, and stable and excellent electric insulating properties are easily obtained.

ADVANTAGE OF THE INVENTION According to this invention, the exterior material for secondary batteries which can satisfy|fill sufficient thinness and the outstanding electrical insulation property can be provided. Specifically, according to the secondary battery exterior material of the present invention, even if the sealant layer is thinned, a short circuit with the tab lead can be suppressed and excellent electrical insulation can be maintained.

FIG. 1 is a cross-sectional view showing a secondary battery casing material according to an embodiment of the present invention. FIG. 3 is a perspective view showing a secondary battery obtained by using the secondary battery casing material according to the embodiment of the present invention.

<Exterior material for secondary battery>
Hereinafter, an exterior material for a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. First, as shown in FIG. 1, the secondary battery outer packaging material 1 of the present embodiment includes at least a base material layer 15, a barrier layer 13, and a sealant layer 11 in this order, and the barrier layer 13 is made of a metal foil. The barrier layer 13 has the corrosion prevention treatment layer 12 at least on the sealant layer 11 side, and the sealant layer 11 has a configuration directly formed on the corrosion prevention treatment layer 12. That is, the exterior material 1 for a secondary battery of the present embodiment is formed of a laminated body in which one surface (second surface) of the barrier layer 13 has at least the base material layer 15, and the side opposite to the base material layer 15 is formed. The other surface (first surface) of the above is constituted by a laminate in which the sealant layer 11 is directly formed on the corrosion prevention treatment layer 12 formed on the barrier layer 13 without an adhesive layer. As shown in the figure, the corrosion prevention treatment layer 12 may be provided also on the base layer side of the barrier layer 13, and the base layer 15 and the barrier layer 13 via the base adhesive layer 14. It may be adhered.

In the secondary battery exterior material 1, the base material layer 15 is the outermost layer and the sealant layer 11 is the innermost layer. That is, the secondary battery exterior material 1 is used with the base material layer 15 on the outside of the secondary battery and the sealant layer 11 on the inside of the secondary battery. Hereinafter, the details of each layer constituting the exterior material 1 for a secondary battery will be described.

[Sealant layer 11]
The sealant layer 11 is a layer that imparts hermeticity by heat sealing in the secondary battery exterior material 1. The sealant layer 11 is formed of a predetermined resin, and is directly formed on the corrosion prevention treatment layer 12 on the surface (first surface) of the barrier layer 13 opposite to the base material layer 15 without using an adhesive or the like. .. The sealant layer 11 can be formed by applying or coating a resin material for the sealant layer 11 on the corrosion prevention treatment layer 12 formed on the barrier layer 13.

Examples of the resin used to form the sealant layer 11 include polyolefin resins. However, in order to further improve the adhesion with the barrier layer 13 which is the barrier layer, an acid-modified polyolefin resin obtained by graft-modifying an acid such as an unsaturated carboxylic acid or an anhydride thereof to the polyolefin resin is preferably used. Examples of the polyolefin resin include low density, medium density, and high density polyethylene, homo, block, or random polypropylene. As the resin used for forming the sealant layer 11, polypropylene having heat resistance is particularly preferable.

Polypropylene is different from propylene in terms of other α-olefins such as ethylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-. 1-pentene, 2-methyl-1-pentene, 1-heptene, etc. are randomly copolymerized at 1 to 10 mol %. Examples of the unsaturated carboxylic acid or an anhydride thereof to be grafted include unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraniconic acid, allylsuccinic acid, mesaconic acid, glutaconic acid, and nadic acid. Unsaturated dicarboxylic acids such as acids, methyl nadic acid, tetrahydrophthalic acid, methyl hexahydrophthalic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, allyl succinic anhydride, glutaconic anhydride, nadic acid anhydride, methyl nadic anhydride Examples thereof include unsaturated dicarboxylic acid anhydrides such as acids, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. A mixture of two or more of these components may be used for the graft modification. Of these unsaturated carboxylic acids or their acid anhydrides, maleic acid, maleic anhydride, nadic acid or nadic acid anhydride is preferably used.

A well-known method can be adopted as the method of graft modification. For example, it is carried out by adding the polypropylene, the unsaturated carboxylic acid and the like, and further a radical initiator to a predetermined solvent and heating to a high temperature.

The resin used for the sealant layer 11 is preferably a resin that does not open the heat seal portion even when the battery element housed in the secondary battery is heated and can secure good heat sealability. .. From this point of view, the sealant layer is preferably formed of a resin having a melting point (measured by differential thermal analysis) of 100 to 165°C. From the viewpoint of further improving high heat resistance and productivity, the melting point is more preferably 120 to 160°C.

The sealant layer 11 may contain various additives such as slip agents, anti-blocking agents, antistatic agents, nucleating agents, pigments and dyes. These additives may be used alone or in combination of two or more.

The resin (coating liquid) used for the sealant layer 11 is the above-mentioned polyolefin resin dispersed in an organic solvent in a solid state. Examples of the organic solvent that can be used include aromatic hydrocarbons such as toluene and xylene, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, and aliphatic hydrocarbons such as hexane, heptane, and decane. Further, in order to achieve stable storage, poor solvents such as alcohols, ketones, ethers, acid anhydrides, esters and cellosolves can be added. Examples of the poor solvent include methanol, ethanol, propanol, butanol, pentanol, hexanol, propanediol, phenol, water, diethyl ether, dipropyl ether, dibutyl ether, anisole, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, methyl isobutyl ketone. , Bentanone, hexanone, isophorone, acetophenone, acetic anhydride, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate, ethyl cellosolve, methyl cellosolve and the like can be used.

The sealant layer 11 is provided on the corrosion prevention treatment layer 12 on the surface (first surface) of the barrier layer 13 opposite to the surface on which the base material layer 15 is laminated, but is not particularly limited to direct gravure coating, offset gravure coating, and bar coating. It is directly formed by a known coating method such as a coater without using an adhesive layer. The secondary battery casing material 1 thus obtained is folded back to the sealant layer 11 side so that the sealant layers 11 face each other, and the end portions of the sealant layer 11 are heat-sealed at a melting temperature or higher, whereby the secondary battery The battery element can be sealed.

The thickness of the sealant layer 11 is 5 to 30 μm. When the layer thickness is thin, there is a tendency that pinholes are easily generated in the sealant layer 11 or that the electrical insulating property is deteriorated and the adhesion is poor at the time of heat sealing. On the other hand, if the layer thickness is too thick, the material cost will increase. From such a viewpoint, the thickness is preferably 7 to 20 μm.

[High melting point substance 16]
As shown in FIG. 1, the sealant layer 11 contains a high melting point substance 16. In FIG. 1, the shape of the high melting point substance 16 is typically spherical, but the shape is not necessarily limited to spherical. Examples of the material of the high melting point substance 16 include filler, glass fiber, non-woven fabric and the like, and the filler is preferable from the viewpoint of shape and size, dispersibility in the sealant resin and the like.

As the high melting point substance 16, inorganic particles such as aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), magnesium oxide (MgO) and glass, and organic particles (heat resistant particles) such as nylon and epoxy resin are used. To be Among these, aluminum oxide particles are preferable from the viewpoint of cost.

The high melting point substance 16 is not particularly specified as long as it is a substance that does not melt at the time of heat sealing, but a substance having a melting point of 220° C. or higher is preferable. It is more preferable that the melting point is 250° C. or higher in order to suppress melting due to heat sealing temperature conditions. The upper limit of the melting point is not particularly limited, but may be about 2050°C.

The high-melting point substance 16 can be surface-treated with a silane coupling agent or the like in order to enhance the adhesion with the resin forming the sealant layer.

If the average particle size of the high-melting point substance 16 is too small, the film thickness of the sealant layer 11 cannot be ensured during heat sealing, and the electrical insulating property is deteriorated. If the average particle size is too large, the heat-sealing property is ensured. Therefore, it is necessary to increase the film thickness of the sealant layer 11, which is disadvantageous in reducing the film thickness. Therefore, the average particle diameter is preferably 30 to 80%, and more preferably 40 to 70% with respect to the thickness of the sealant layer. Alternatively, the average particle diameter is preferably 1.5 to 24 μm, and more preferably 2.8 to 14 μm. The average particle diameter of the high melting point substance 16 can be measured by, for example, a laser diffraction method or a scattering method.

If the number (content) of the high-melting point substances 16 per unit volume of the sealant layer 11 is less than 100 pieces/cm ³ , the electrical insulating property of the heat-sealed end portion is deteriorated, which may cause a short circuit, resulting in 15 million pieces/cm ^3. If it exceeds, there is a risk that the heat sealing force will decrease. Therefore, per unit volume of the sealant layer 11, preferably the number of high-melting material 16 is from 100 to 15,000,000 cells / cm ^3, more preferably from 10,000 to 10,000,000 pieces / cm ^3. The number of high melting point substances 16 per unit volume of the sealant layer 11 can be measured using X-ray CT. Specifically, the sealant layer 11 of the coated laminated film is cut out at a thickness of 10 mm ² × the coating film thickness and converted into a three-dimensional image by X-ray CT imaging, and the three-dimensional image is binarized with respect to the high melting point substance and the coating resin. I do. Then, the number of the high melting point substances 16 can be measured by extracting only the high melting point substances from the binarized data, counting the number, and calculating the number per unit volume.

[Corrosion prevention treatment layer]
The anticorrosion treatment layer 12 is formed on at least the sealant layer 11 side of the barrier layer 13. In the lithium ion secondary battery, for example, the corrosion prevention treatment layer 12 needs to be formed on the sealant layer 11 side in order to prevent the corrosion of the surface of the barrier layer 13 due to hydrofluoric acid generated by the reaction between the electrolyte and water.

The corrosion prevention treatment layer 12 may be formed on the base material layer 15 side of the barrier layer 13 if necessary. In this case, the corrosion prevention treatment layer 12 functions not only as a corrosion prevention function but also as an anchor layer for the sealant layer 11 and the base material adhesive layer 14.

The corrosion prevention treatment layer 12 is formed, for example, by chromate treatment using a corrosion prevention treatment agent composed of chromate, phosphate, fluoride and various thermosetting resins, cerium oxide which is an oxide of a rare earth element. A ceria sol treatment using a corrosion prevention treatment agent composed of phosphate and various thermosetting resins can be used. The corrosion prevention treatment layer 12 is not limited to the coating film formed by the above treatment as long as it is a coating film that satisfies the corrosion resistance of the barrier layer 13, and, for example, phosphate treatment, boehmite treatment or the like may be used. Further, the anticorrosion treatment layer 12 is not limited to a single layer, and even if a structure having two or more layers having corrosion resistance is adopted, such as coating a resin having an anticorrosion function with a resin as an overcoat agent. Good.

The thickness of the anticorrosion treatment layer 12 is preferably 5 nm to 11 μm, more preferably 10 to 200 nm, from the viewpoint of the corrosion prevention function and the function as an anchor.

[Barrier layer 13]
The barrier layer 13 is formed between the base material layer 15 (or the base material adhesive layer 14 provided as necessary) and the sealant layer 11. The barrier layer 13 is required to have functions such as high water vapor barrier property and stretchability in order to prevent water from entering the battery.

As the barrier layer 13, various metal foils such as aluminum, stainless steel, and copper can be used, but from the viewpoint of weight (specific gravity), moisture resistance, and cost, aluminum foil is preferable. A known soft aluminum foil can be used as the aluminum foil, and an iron-containing aluminum foil is preferable from the viewpoint of pinhole resistance and spreadability during molding. The content of iron in the aluminum foil is preferably 0.1 to 9.0 mass%, more preferably 0.5 to 2.0 mass%. If the iron content is at least the lower limit, the pinhole resistance and stretchability will tend to improve, and if it is at most the upper limit, the flexibility will tend to improve.

The thickness of the barrier layer 13 is preferably 10 to 100 μm, more preferably 15 to 80 μm, from the viewpoint of barrier properties, pinhole resistance, and workability.

An untreated metal foil may be used for the barrier layer 13, but a degreased metal foil is preferably used. The degreasing treatment can be roughly classified into a wet type and a dry type.

Examples of the wet type degreasing treatment include acid degreasing and alkaline degreasing. Examples of the acid used for acid degreasing include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid. These acids may be used alone or in combination of two or more. Further, from the viewpoint of improving the etching effect of the metal foil, various metal salts serving as a supply source of iron (III) ions, cerium (III) ions and the like may be blended if necessary. Examples of the alkali used for alkali degreasing include strong etching type alkalis such as sodium hydroxide. Moreover, you may use the thing which mix|blended a weak alkaline type|system|group or a surfactant. The wet type degreasing treatment is performed by a dipping method or a spray method.

Examples of the dry type degreasing treatment include a method of performing degreasing treatment by lengthening the treatment time in the step of annealing the aluminum when the barrier layer is an aluminum foil. In addition to the degreasing treatment, flame treatment, corona treatment and the like can be mentioned. Further, a degreasing treatment for oxidatively decomposing/removing pollutants with active oxygen generated by irradiating ultraviolet rays of a specific wavelength may be adopted.

[Base material adhesive layer 14]
The base adhesive layer 14 is formed between the base layer 15 and the barrier layer 13 as needed. The base material adhesive layer 14 has an adhesive force necessary to firmly bond the base material layer 15 and the barrier layer 13. To form the base adhesive layer 14, it is possible to use a two-component curable adhesive containing a polyester polyol, a polyether polyol, an acrylic polyol, etc. as a main component and an aromatic or aliphatic isocyanate as a curing agent. it can. A thermoplastic elastomer, a tackifier, a filler, a pigment, a dye, or the like can be added to the base adhesive layer 14.

The thickness of the base adhesive layer 14 is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm from the viewpoint of adhesive strength, conformability, workability, and the like.

[Base material layer 15]
The base material layer 15 is formed on the barrier layer 13 with the base material adhesive layer 14 interposed therebetween in some cases. The base material layer 15 imparts heat resistance in a sealing step when manufacturing a secondary battery, and plays a role of suppressing generation of pinholes that may occur during processing or distribution. It also plays a role of preventing breakage of the barrier layer 13 at the time of molding, and electrical insulating property of preventing contact between the barrier layer 13 and another metal.

The base material layer 15 may be formed by laminating a stretched film or the like on the barrier layer 13 via the base material adhesive layer 14, or by applying a liquid resin on the barrier layer 13. It may be directly formed (coating layer). The method for forming the base material layer 15 is not particularly limited to either of these. For example, in the case of the former, the deep drawability is good, and in the case of the latter, the total thickness of the secondary battery case 1 is large. Since the battery can be made thinner, there is a tendency that a thinner battery can be made.

Examples of the stretched film and the like include stretched and unstretched films of polyester resin, polyamide resin, polyolefin resin and the like. Among them, biaxially stretched polyamide and biaxially stretched polyester are preferable from the viewpoint of improving moldability, heat resistance, puncture resistance and electric insulation. One of these films may be used alone or two or more of them may be used as a composite film.

Examples of the liquid resin (coating liquid resin) include polyester resin, polyurethane resin, fluororesin, polyimide resin, polyamideimide resin, polyetherimide resin, epoxy resin and melamine resin. Among them, polyester resin is preferable from the viewpoint of mechanical properties, chemical resistance, insulation, and cost. The crosslinking method may be crosslinking with a known curing agent such as isocyanate or baking with melamine or epoxy, and the crosslinking method is not particularly limited.

Additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer, a tackifier, and an antistatic agent may be dispersed inside or applied to the surface of the base material layer 15. Examples of the slip agent include fatty acid amides (eg, oleic acid amide, erucic acid amide, stearic acid amide, behenic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide). As the antiblocking agent, various filler antiblocking agents such as silica are preferable. The additives may be used alone or in combination of two or more.

The thickness of the base material layer 15 is preferably 6 to 50 μm, more preferably 10 to 40 μm from the viewpoint of puncture resistance, electrical insulation, molding processability, and the like.

An uneven shape can be formed on the surface of the base material layer 15 in order to improve scratch resistance and slipperiness.

<Method for manufacturing exterior material for secondary battery>
Hereinafter, a method for manufacturing the secondary battery exterior material 1 will be described with reference to an example of an embodiment. The following content is an example, and the manufacturing method of the secondary battery case 1 is not limited to the following content.

Examples of the method for manufacturing the secondary battery casing material 1 include a method including the following steps (I) to (III). In the following, a case where a base resin film is used as the base layer 15 will be described.
Step I: A step of forming the corrosion prevention treatment layer 12 on one surface (first surface) of the barrier layer 13.
Step II: A step of attaching the base material layer 15 to the surface (second surface) opposite to the first surface of the barrier layer 13 via the base material adhesive layer 14.
Step III: A step of forming the sealant layer 11 using a sealant resin material on the corrosion prevention treatment layer 12 formed on the barrier layer 13.

[Step I]
A corrosion prevention treatment agent is applied to the first surface of the barrier layer 13 and dried to form the corrosion prevention treatment layer 12. At this time, the corrosion prevention treatment layer 12 may be similarly formed on the second surface of the barrier layer 13 in some cases. Examples of the anticorrosion treatment agent include the anticorrosion treatment agent for ceriasol treatment and the anticorrosion treatment agent for chromate treatment described above. The method of applying the anticorrosion treatment agent is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating and bar coating can be adopted.

[Step II]
On the second surface of the barrier layer 13, a base resin film that forms the base layer 15 via the base adhesive layer 14 is attached by a dry lamination method to form the base layer 15. After lamination, for example, aging treatment at 60° C. for 7 days is performed to obtain a laminate including the corrosion prevention treatment layer 12, the barrier layer 13, the base material adhesive layer 14, and the base material layer 15.

[Step III]
Applying and drying a resin material to be a sealant layer on the corrosion prevention treatment layer 12 of a laminate in which the base material layer 15, the base material adhesive layer 14, the barrier layer 13 and the corrosion prevention treatment layer 12 are laminated in this order. Then, the sealant layer 11 is formed on the first surface of the barrier layer 13. The coating method is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating and bar coating can be adopted.

By carrying out the steps (I) to (III) described above, the secondary battery casing material 1 is obtained. Note that the order of steps in the method of manufacturing the secondary battery case 1 is not limited to the method of sequentially performing the above (I) to (III). For example, when the corrosion prevention treatment layer 12 is not formed on the second surface of the barrier layer 13, the step (II) may be performed before the step (I).

<Method for manufacturing secondary battery>
Hereinafter, a method for manufacturing the secondary battery 2 will be described. Examples of the method of manufacturing the secondary battery 2 include a method including the following steps (I) to (III).
Step I: a step of forming a molding portion for arranging the battery element in a half region of the secondary battery case 1.
Step II: A battery element is arranged in the molded portion of the secondary battery exterior material 1. Then, the other half region of the secondary battery exterior material 1 is folded back so that the sealant layer 11 is the inner surface and the three sides are overlapped, and only one side that sandwiches the tab made of the lead and the tab sealant is heated by heat. The process of fusing.
Step III: One side of the remaining two sides is left and pressure heat fusion is performed. Then, a step of injecting an electrolytic solution from the remaining one side and pressurizing and heat-sealing in a vacuum state.

The secondary battery 2 is obtained by performing the steps (I) to (III) described above. However, the manufacturing method of the secondary battery 2 is not limited to the method described above.

The secondary battery 2 of the present embodiment thus obtained, as shown in FIG. 2, accommodates an electricity storage device element by a secondary battery exterior material 21 and is connected to the positive electrode and the negative electrode of the electricity storage device element, respectively. In addition, a tab 24 composed of the lead 22 and the tab sealant 23 is sandwiched between the pressure heat-sealing portions 25.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like within a range not departing from the gist of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited by the following description.

[Materials used]
The materials used for the preparation of the exterior materials for secondary batteries of Examples and Comparative Examples are shown below.

(Sealant layer)

(Corrosion prevention treatment layer)
Acid value cerium (thickness 100 nm)

(Barrier layer)
Soft aluminum foil 8079 material (thickness 30 μm)

(Base material adhesive layer)
Polyurethane adhesive (thickness 3 μm)

(Base material layer)
Nylon film (thickness 25 μm)

(High melting point substance)
Aluminum oxide filler

[Evaluation]
The following evaluations were performed for the secondary battery casing materials of Examples and Comparative Examples.

(Evaluation of electrical insulation)
The secondary battery case 1 of each Example and Comparative Example was cut into a size of 120 mm×60 mm and folded in half so that the sealant layer was on the inside. Next, with the folded portion as the bottom, the left and right ends were heat-sealed at 190° C./0.5 MPa/3 sec at a width of 5 mm to produce a pouch on the bag. From the remaining side, ethylene carbonate/diethyl carbonate/dimethyl carbonate (1/1/1:weight ratio) and a mixed solution of LiPF ₆ Li salt mixed into the electrolyte were injected, and the thickness was 50 μm, the width was 12 mm, and the length was 12 mm. A tab lead wire of 50 mm size is sandwiched and heat-sealed to a width of 10 mm under two conditions of "190°C/0.5 MPa/3 sec" or "200°C/0.5 MPa/3 sec" to produce a sample for electrical insulation evaluation. did. Using this sample, electrical insulation was evaluated by an AC/DC withstand voltage/insulation resistance tester (Kikusui Electronics Co., Ltd.).

(Electrical insulation evaluation standard)
Electrodes were placed on the tab lead of the sample and the barrier layer of the exterior material, and the electrical insulation was evaluated according to the following criteria. The results are shown in Table 2.
Reference: A voltage of 25 V was applied for 5 seconds. If the measured value was 25Ω or more, it was OK, and if it was less than 25Ω, it was NG.
"A": 190°C: OK, 200°C: OK
"B": 190°C: OK, 200°C: NG
"C": 190°C: NG, 200°C: NG

(Heat seal strength evaluation)
The secondary battery exterior material 1 obtained by the above-described manufacturing method was cut into a size of 120 mm×60 mm, folded in half so that the sealant layer was on the inside, and the end opposite to the folded part was 190° C./0. It was heat-sealed at a width of 10 mm at 5 MPa/3 sec. Then, the central portion in the longitudinal direction of the heat-sealed portion was cut out with a width of 15 mm and a length of 300 mm to produce a heat-sealing strength measurement sample. Using this sample, heat seal strength evaluation was performed using a tensile tester (manufactured by Shimadzu Corporation).

(Heat seal strength evaluation standard)
The heat-sealed portion of the sample was subjected to a T-shaped peeling test under the condition of a pulling speed of 50 mm/min and evaluated according to the following criteria. The results are shown in Table 2.
"A": Heat seal strength is 120 N or more "B": Heat seal strength is 90 N or more and less than 120 N "C": Heat seal strength is less than 90 N

In this example, it was found that both sufficient thinness and excellent electrical insulation can be achieved. Moreover, in this example, it was found that the heat seal strength was not impaired even if the sealant layer was thinned.

DESCRIPTION OF SYMBOLS 1... Exterior material for secondary batteries, 11... Sealant layer, 12... Corrosion prevention processing layer, 13... Barrier layer, 14... Base material adhesive layer, 15... Base material layer, 16... High melting point material, 2... Secondary Battery, 21... Secondary battery exterior material, 22... Lead, 23... Tab sealant, 24... Tab, 25... Pressurized heat-bonding portion.

Claims (6)

At least a base material layer, a base material adhesive layer, a barrier layer and a sealant layer are provided in this order,
The barrier layer is made of a metal foil, the barrier layer has a corrosion prevention treatment layer at least on the sealant layer side,
The sealant layer is directly formed on the corrosion prevention treatment layer, the sealant layer has a thickness of 5 to 30 μm, the sealant layer is formed of a single polyolefin resin layer, and the sealant layer has a melting point. Contains particles of a high melting point substance having a melting point of 220° C. or higher,
The average particle diameter of the particles of the refractory material, Ri 40% to 70% der thickness of the sealant layer, the refractory material, aluminum oxide, silicon oxide, magnesium oxide, glass, nylon, and epoxy resin Including at least one selected from the group consisting of
Exterior material for secondary batteries. The exterior material for a secondary battery according to claim 1, wherein the sealant layer is formed of a single acid-modified polyolefin resin layer. The exterior material for a secondary battery according to claim 1, wherein the sealant layer is formed of a resin having a melting point of 100 to 165° C. 4. The packaging material for a secondary battery according to any one of claims 1 to 3, wherein the number of the high melting point substances is 1 to 15 million pieces/cm ³ per unit volume of the sealant layer. The exterior battery packaging material according to any one of claims 1 to 4, wherein particles of the high-melting-point substance are uniformly dispersed in the sealant layer. It is a manufacturing method of the exterior material for secondary batteries according to any one of claims 1 to 5,
A step of forming the corrosion prevention treatment layer on at least one surface of the barrier layer,
On the surface opposite to the one surface of the barrier layer, a step of bonding the base material layer via a base material adhesive layer,
Forming a sealant layer by applying and drying a sealant resin material on the corrosion prevention treatment layer formed on the barrier layer.

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