KR20160100604A - An Aluminium pouch film and the Secondary Battery comprising the same - Google Patents

Abstract

The present invention relates to an aluminum layer; An intermediate layer formed on the first surface of the aluminum layer; An inner layer formed on the intermediate layer; And an outer layer formed on a second surface of the aluminum layer, wherein the intermediate layer comprises a copolymer of a polyolefin or a polyolefin having at least one chlorine (Cl) atom in its main chain .

Description

An aluminum pouch film and a secondary battery comprising the same,

The present invention relates to an aluminum pouch film, and more particularly to an aluminum pouch film which forms an intermediate layer on an aluminum layer.

The secondary battery generally refers to a lithium secondary battery, which is a battery having a polymer electrolyte and generating a current by the movement of lithium ions. A pouch for a secondary battery is used as a casing for packaging the secondary battery. Such a pouch for a secondary battery has a structure of an outer layer, an adhesive layer, an aluminum layer, an adhesive layer and an inner layer.

Such pouch type secondary battery may be damaged for various reasons in various processes. For example, in the process of storing the electrode assembly in the pouch, protruding portions such as electrode tabs and electrode leads may crack cracks and the like, and the aluminum layer can be exposed by such damage.

In addition, when the pouch is sealed, heat is applied from the outside. Due to such heat, fine pinholes may be generated, or a crack may be generated in the internal adhesive layer due to the pouch internal cavity, so that the aluminum layer may be exposed to an electrolyte or the like. Also, the adhesive layer formed in the form of a thin film may be damaged by falling, impact, pressure, or pressing, and the aluminum layer is exposed to the electrolyte through the damaged portion of the adhesive layer.

The aluminum layer exposed to the electrolytic solution may be corroded by causing a chemical reaction with oxygen or moisture, which is penetrated or diffused into the inside of the battery, and a corrosive gas is generated, thereby causing a swelling phenomenon There is a problem that will occur. More specifically, LiPF ₆ reacts with water and oxygen to produce hydrofluoric acid (HF), which is a corrosive gas. Such hydrofluoric acid may react with aluminum to cause a rapid exothermic reaction. When the aluminum is adsorbed on the aluminum surface due to the secondary reaction and penetrates into the inside of the structure, the brittleness of the structure is increased and cracks of the pouch film occur even in a fine impact. The reaction between lithium and the atmosphere may cause ignition.

In order to prevent such a problem, various improvement techniques have been studied. Specifically, as disclosed in Korean Patent Laid-Open No. 10-2001-0006042, a multi-layered laminate sheet has been developed.

However, since the capacity of the secondary battery is gradually increasing in capacity in recent years, there is a limitation in solving the above-mentioned problems with the conventional technology, and an aluminum pouch film for a secondary battery excellent in heat resistance, chemical resistance and durability, There is a continuing need for an aluminum pouch film for a secondary battery that can prevent the penetration of a substance such as HF in an electrolytic solution.

KR 10-2001-0006042 A

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

It is an object of the present invention to provide a secondary battery for a secondary battery, which is excellent in moldability, insulation, electrolyte resistance, and barrier properties even when the battery is exposed to physical, chemical, or stress from the outside, And to provide a pouch film.

The present invention relates to an aluminum layer; An intermediate layer formed on the first surface of the aluminum layer; An inner layer formed on the intermediate layer; And an outer layer formed on a second surface of the aluminum layer, wherein the intermediate layer comprises a copolymer of a polyolefin or a polyolefin having at least one chlorine (Cl) atom in its main chain .

The present invention also provides a secondary battery comprising the aluminum pouch film for the secondary battery.

When the aluminum pouch film according to the present invention is used in a secondary battery, not only the formability, the insulating property and the electrolytic solution resistance but also the gas barrier property are remarkably improved, so that even if exposed to physical or chemical shock, Cracking of the adhesive layer can be suppressed and a gas such as an aluminum layer and HF can be prevented from causing a chemical reaction, so that the risk of explosion of the secondary battery can be reduced.

1 is a view showing an embodiment of an aluminum pouch film of the present invention.

The aluminum pouch film for a secondary battery of the present invention comprises an aluminum layer (1) as shown in Fig. 1, an intermediate layer (2) formed on a first surface of the aluminum layer, And an inner layer (3) formed on the intermediate layer (2); And an outer layer (4) on the second surface of the aluminum layer (1).

An adhesive layer can be formed between the aluminum layer 1 and the intermediate layer 2, between the intermediate layer 2 and the inner layer 3, and between the aluminum layer 1 and the outer layer 4 to hold each layer.

Hereinafter, each constitution of the aluminum pouch film for a secondary battery of the present invention will be described in detail.

Aluminum layer

In the aluminum pouch film for a secondary battery of the present invention, preferably, the aluminum layer may be a soft aluminum foil, more preferably an aluminum foil containing iron Can be used. In the aluminum foil containing the iron, the content of iron may include preferably from 0.1 to 9.0 mass%, more preferably from 0.5 to 2.0 mass%, based on 100 mass% of the entire aluminum foil have. If the content of iron is less than 0.1% by mass based on 100% by mass of the total aluminum foil, ductility of the aluminum layer is deteriorated. If the content of aluminum exceeds 9.0% by mass, moldability is deteriorated.

The thickness of the aluminum layer is preferably 10 to 100 占 퐉, more preferably 30 to 50 占 퐉, in view of the hole filling property, workability, oxygen and moisture barrier properties. If the above range is not satisfied, if it is less than 10 탆, it easily tears and deteriorates the electrolytic resistance and insulation property, and if it exceeds 100 탆, the moldability becomes poor.

As the aluminum foil used for the aluminum layer, an untreated aluminum foil may be used. However, it is more desirable to use an aluminum foil subjected to degreasing treatment in terms of imparting electrolytic solution resistance and electrolyte resistance. Examples of the degreasing treatment method include wet type and dry type treatment methods.

Examples of the wet type degreasing include sapphire and alkali degreasing. The acid used for acid degreasing includes, for example, inorganic acids such as sulfuric acid, acetic acid, phosphoric acid, and hydrofluoric acid. These acids may be used singly or in combination. Further, in order to improve the etching effect of the aluminum foil, various metal salts may be blended if necessary. The alkali used for alkali degreasing includes, for example, strong alkali such as sodium hydroxide, and a weak alkaline compound or a surfactant may be blended together.

An example of a dry type degreasing treatment is a step of annealing aluminum at a high temperature, and a degreasing treatment is performed.

Middle layer

In the aluminum pouch film for a secondary battery of the present invention, as the intermediate layer, a resin containing a copolymer of a polyolefin or a polyolefin having at least one chlorine (Cl) atom in its main chain can be used, preferably polyvinylidene chloride PVDC, polyvinylidene chloride) may be used as the polyolefin or polyolefin.

In the present invention, any one or more of polyethylene and polypropylene may be used as the polyolefin. Examples of the polyethylene (PE) include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), ultra high density polyethylene (UHDPE) And mPE (metallocene polyethylene). The polypropylene (PP) may be any one selected from the group consisting of homo polypropylene, block polypropylene, and random polypropylene These can be used singly or in combination.

The intermediate layer is used to improve the gas barrier property of the aluminum pouch film for a secondary battery of the present invention. When an aluminum pouch film is applied to a secondary battery, LiPF ₆ in the electrolyte in the aluminum pouch film reacts with water and oxygen to produce hydrofluoric acid (HF), which is a corrosive gas. Such hydrofluoric acid may react with aluminum to cause a rapid exothermic reaction. When the aluminum is adsorbed on the aluminum surface due to the secondary reaction and penetrates into the inside of the structure, the brittleness of the structure is increased and cracks of the pouch film occur even in a fine impact. In the present invention, when an intermediate layer containing a copolymer of a polyolefin or a polyolefin containing at least one chlorine (Cl) atom is separately formed as in the present invention, lithium fluoride (HF) gas is blocked by the intermediate layer, so that the hydrofluoric acid (HF) gas does not react with the aluminum layer.

The thickness of the intermediate layer is preferably 2 to 20 占 퐉 and preferably 5 to 10 占 퐉 in consideration of moldability, insulation, electrolyte resistance and gas barrier properties. If the above range is not satisfied, the moldability, the insulating property, the electrolyte resistance and the gas barrier property become insufficient and a problem may arise.

Inner layer

In the aluminum pouch film for a secondary battery of the present invention, a polyolefin such as polyethylene (PE) or polypropylene (PP) or a copolymer thereof may be used as the inner layer. When polyolefin such as PE or PP or a copolymer thereof is used for the polymer layer, not only the physical properties required as a packaging material for a secondary battery such as good heat-seizing property, moisture-proofing property and heat resistance, but also good workability such as lamination Do.

The thickness of the polymer layer of the inner layer is preferably 20 to 60 占 퐉, more preferably 30 to 50 占 퐉 in consideration of moldability, insulation, electrolyte resistance, and the like. If the above range is not satisfied, there may arise a problem that moldability, insulation, and electrolytic solution resistance are deteriorated.

Outer layer

In the aluminum pouch film for a secondary battery of the present invention, since the outer layer corresponds to a portion directly contacting the hardware, it is preferably a resin having an insulating property. Therefore, it is preferable to use a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate or the like or nylon film as the resin used as the outer layer And it is particularly preferable to use a nylon film. The nylon film is excellent in heat resistance, cold resistance and mechanical strength as well as excellent in rupture strength, pinhole property, gas barrier property and the like, and thus is mainly used as packaging film. Specific examples of the nylon film include polyamide resins such as nylon 6, nylon 66, copolymers of nylon 6 and nylon 66, nylon 610, and polymetaxylene imine amide (MXD6).

When the outer layer is laminated, the thickness of the laminated outer layer is preferably 10 to 30 탆 or more, particularly preferably 12 to 25 탆. If it is less than 10 탆, the physical property tends to be lost and tear easily. If it is more than 30 탆, the moldability is deteriorated.

When the outer layer is laminated, there is no particular limitation, but it is possible to laminate the outer layer by lamination using a dry lamination method or an extrusion lamination method.

Adhesive layer

In the aluminum pouch film for a secondary battery of the present invention, an adhesive layer may be formed to hold the respective constituent layers. Specifically, the aluminum layer 1 and the intermediate layer 2, the intermediate layer 2 and the inner layer 3, An adhesive layer may be formed between the layer (1) and the outer layer (4).

As the adhesive layer, for example, an adhesive commonly used in the related art can be used. For example, a polyurethane, an acid-modified (polyurethane) Polyolefin resin, epoxy resin, etc. may be used. Specific examples thereof include maleic anhydride polypropylene (MAHPP) and the like.

Between the aluminum layer (1) and the outer layer (4), a polyurethane adhesive containing a polyol component as a main component and further containing an isocyanate compound or a derivative thereof as a curing agent component may be used.

The adhesive layer can be formed in consideration of adhesiveness with each structure, thickness after molding, and the like. The thickness of the adhesive layer is preferably 2 to 30 탆, more preferably 3 to 15 탆. If the thickness is less than 2 탆, the adhesiveness is poor, and if it exceeds 30 탆, cracks may occur.

When an adhesive layer is formed on each of the above-described structures and laminated, there is no particular limitation, but lamination can be preferably performed by using a dry lamination method or an extrusion lamination method.

A method for manufacturing an aluminum pouch film for a secondary battery of the present invention comprises the steps of: a) preparing an aluminum layer; b) forming an intermediate layer on the first surface of the aluminum layer, the intermediate layer comprising a copolymer of a polyolefin or a polyolefin having at least one chlorine (Cl) atom in the main chain; c) forming an inner layer on the intermediate layer; And d) forming an outer layer on the second surface of the aluminum layer.

The present invention also provides a secondary battery comprising the aluminum pouch film for the secondary battery.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the embodiments of the present invention described below are illustrative only and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated in the claims, and moreover, includes all changes within the meaning and range of equivalency of the claims. In the following Examples and Comparative Examples, "%" and "part" representing the content are on a mass basis unless otherwise specified.

Example  1 and Comparative Example  1: Fabrication of aluminum pouch film

[Example 1]

On the aluminum foil (40 탆 thick, A8021 or A8079 material), a multilayer polyolefin film including an interlayer and an adhesive resin layer for adhesion to aluminum was heat laminated using a heating roll. In order to prevent changes in numerical value and physical properties due to residual heat, the multilayered laminated film was passed through a cooling roll and rapidly cooled at a cooling rate of 10 ° C / sec or more to prevent deformation.

The multilayer laminated film used here was composed of an adhesive layer composed of an acid-modified polyolefin and an intermediate layer composed of a copolymer of polyvinylidene chloride and polypropylene (Hanse Micron) and a polymer of polypropylene (Hanse Micron) A film was formed using the constituted sealant layer as an inner layer. At this time, the total thickness of the multilayer film was set to 40 μm, and the thickness ratio of the adhesive layer, the gas barrier layer and the inner layer was 3: 1: 4.

Thereafter, a 4 탆 thick polyurethane adhesive resin (HiChem) was applied, and then a nylon 6 having a thickness of 25 탆 (Hyosung Co., Ltd.) was subjected to dry lamination to laminate nylon on the aluminum layer.

Further, in order to increase the bonding strength between the aluminum foil and the adhesive layer and to remove the residual solvent, the multilayer laminated film was stored in a reflux oven at 80 DEG C for 96 hours and then stored at room temperature for 48 hours to remove the residual heat history An aluminum pouch film for a secondary battery was obtained.

[Comparative Example 1]

An aluminum pouch film was produced in the same manner as in Example 1, except that the intermediate layer was formed.

Electrolytic solution resistance  evaluation

Each of the aluminum pouch films for secondary batteries according to Example 1 and Comparative Example 1 was cut into 2 cm x 4 cm pieces. The test pieces were sealed with a LiPF ₆ electrolyte solution (manufactured by RICHM Co.) The films were collected every 4 hours until the elapsed time, and the peeling between films was visually observed to evaluate the electrolyte resistance.

4 hours 8 hours 12 hours 16 hours 20 hours 24 hours Comparative Example 1 O O O △ △ △ Example 1 O O O O O O

O: No peeling occurred

DELTA: Partial peeling occurred

X: Peeling occurred

Insulation evaluation

The aluminum pouch film for a secondary battery according to Example 1 and Comparative Example 1 was molded into a 3 cm x 5 cm x 0.62 cm (width x length x thickness), and an electrode assembly of a positive electrode, a separation membrane and a negative electrode and a LiPF ₆ electrolyte After filling and sealing, it was stored at 85 ° C for 24 hours, and then the electrode and the aluminum layer on the upper surface were artificially exposed to measure electrical insulation (1 MΩ or more).

Insulation evaluation Comparative Example 1 > 1 MΩ Example 1 > 1 MΩ

Barrier  Character rating

The oxygen permeability of the film was measured in accordance with ASTM D-3985 using the OX-TRAN 2/21 (manufactured by MOCON) of the intermediate layer and the inner layer (Example 1) and the inner layer (Comparative Example 1) in the aluminum pouch film for secondary battery according to Example 1 and Comparative Example 1 .

Oxygen permeability Comparative Example 1 1,500 cc / m ² day atm Example 1 0.07cc / m ² day atm

As described above, it was found that the film of Example 1, which is the pouch film of the present invention, was excellent in electrolyte resistance and insulation as well as barrier properties as compared with the film of Comparative Example 1. [

Claims (9)

An aluminum layer;
An intermediate layer formed on the first surface of the aluminum layer;
An inner layer formed on the intermediate layer; And
And an outer layer formed on a second surface of the aluminum layer,
Wherein the intermediate layer comprises a copolymer of a polyolefin or a polyolefin having at least one chlorine (Cl) atom in its main chain. The method according to claim 1,
Wherein the intermediate layer comprises a copolymer of polyolefin or polyolefin comprising polyvinylidene chloride (PVDC). The method according to claim 1,
Wherein the outer layer is selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, polycarbonate and nylon film. The method according to claim 1,
Wherein the inner layer is formed from a copolymer of a polyolefin or a polyolefin. The method according to claim 1,
Wherein the polyolefin is polyethylene (PE) or polypropylene (PP). The method of claim 4,
Wherein the polyolefin is polyethylene (PE) or polypropylene (PP). The method according to claim 1,
Wherein the thickness of the intermediate layer is 2 to 20 占 퐉. A packaging material comprising an aluminum pouch film for a secondary battery according to any one of claims 1 to 7. A secondary battery comprising the aluminum pouch film for a secondary battery according to any one of claims 1 to 7.

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