KR20210105483A - Sealant film for cell pouch having gradient composition type barrier properties, cell pouch including the same and method for preparing the same - Google Patents

Abstract

Disclosed are a sealant film for a gradient composition type cell pouch in which the elastomer content of each sealant layer is gradually different as a sealant film having a sealant layer with a multilayer structure of two or more, a cell pouch including the same, and a manufacturing method thereof. In order to prevent the disadvantages of lower crystallinity and chemical resistance when applying elastomer to the sealant layer of the cell pouch, the sealant layer is composed of multiple layers and the amount of elastomer is gradually adjusted in each layer to improve chemical resistance, thereby enabling to improve insulation resistance. In addition, it is possible to implement high sealing properties and high barrier properties with excellent thermal bonding strength and barrier layer adhesion properties.

Description

Sealant film for cell pouch having gradient composition type barrier properties, cell pouch including same, and method for manufacturing the same

The present specification relates to a polyolefin sealant film for a cell pouch having a gradient composition type barrier property, insulation resistance property and excellent thermal adhesive strength, a cell pouch including the same, and a method for manufacturing the same.

Lithium secondary batteries (LiBs) are being applied to many applications based on various advantages such as high energy density and excellent output.

The cell pouch is a packaging material that surrounds the electrode group and the electrolyte of such a secondary battery, and it must satisfy the required characteristics such as adhesion between the metal thin film and the polymer layer, thermal fusion strength, electrolyte resistance, airtightness, moisture permeability, and moldability.

1 is a schematic diagram showing a layer configuration of a cell pouch according to an exemplary embodiment of the present invention.

1, the cell pouch is composed of an outer layer, a barrier layer, and a sealant layer of an inner layer. Usually, the outer layer or outermost layer is composed of nylon or a mixed material of nylon and PET (polyethylene terephthalate), OPP (stretched polypropylene), polyethylene, and the like. As the required characteristics of the outer layer or the outermost layer, heat resistance, pinhole resistance, chemical resistance, moldability, insulation, and the like are required.

The barrier layer is required to formability together with barrier properties to water vapor or other gases. In this respect, a moldable metal such as aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), etc. is used for the barrier layer, and aluminum is currently the most used.

In the sense that the sealant layer of the inner layer is a layer in contact with the electrolyte along with thermal adhesion and moldability, electrolyte resistance and insulation resistance are required.

However, since the conventional sealant film or other polymer films constituting the sealant layer contain an excessive amount of copolymer and elastomer, thermal adhesion properties are excellent, but insulation properties due to electrolyte swelling are lowered, which may cause insulation failure. Nevertheless, conventional sealant films have a limitation in that copolymer and elastomer raw materials must be used in order to maintain thermal adhesion properties.

Japanese Patent No. 6595634

In exemplary embodiments of the present invention, in one aspect, a gradient composition type barrier property having excellent chemical resistance and insulation resistance properties by improving problems such as low insulation properties due to excessive use of the elastomer and copolymer of the conventional sealant layer An object of the present invention is to provide a sealant film for a cell pouch, a cell pouch including the same, and a method for manufacturing the same.

In exemplary embodiments of the present invention, in another aspect, a sealant film for a cell pouch having a gradient composition type barrier property of high sealing property and high barrier property having excellent thermal adhesive strength and barrier layer adhesion properties, a cell pouch comprising the same, and a cell pouch comprising the same It is intended to provide a manufacturing method.

Exemplary embodiments of the present invention provide a sealant film for a gradient composition type cell pouch having a sealant layer having a multilayer structure of two or more layers, wherein the elastomer content of each sealant layer is different.

Exemplary embodiments of the present invention also provide a cell pouch including the sealant film.

In exemplary embodiments of the present invention, there is also a method for manufacturing a cell pouch, comprising: manufacturing a sealant film to have a sealant layer having a multi-layered structure of two or more layers, wherein the elastomer content of each sealant layer is different; A method of making a pouch is provided.

In exemplary embodiments of the present invention, there is also provided a method for improving the insulation properties of a cell pouch, comprising: preparing a sealant film to have a sealant layer having a multi-layered structure of two or more layers, wherein the elastomer content of each sealant layer is different; It provides a method for improving the insulation properties of a cell pouch comprising a.

According to exemplary embodiments of the present invention, in order to prevent the disadvantage that crystallinity and chemical resistance are lowered when the elastomer is applied to the sealant layer of the cell pouch, the sealant layer is composed of multiple layers and the amount of the elastomer is gradually adjusted in each layer. . In particular, it is possible to improve the insulation resistance by improving chemical resistance by adding a minimum amount to the inner layer that is in contact with the electrolyte. In addition, by adding an excessive amount of an elastomer to the sealant layer, which is the adhesive surface of the barrier layer, high sealing properties and high barrier properties having excellent thermal adhesive strength and barrier layer adhesion properties can be realized.

1 is a schematic diagram showing a typical cell pouch layer structure.
2 is a schematic diagram showing a sealant film having a multilayer structure according to an exemplary embodiment of the present invention.
3 is a schematic view showing the cell pouch sealant film layer configuration according to Example 1 (FIG. 3A) and Comparative Example 1 (FIG. 3B) of the present invention.

In the present specification, the gradient composition type means that in two or more sealant layers, the content of the elastomer in each layer is gradually different (gradient).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Exemplary embodiments of the present invention provide a sealant film for a gradient composition type cell pouch, which has a sealant layer having a multilayer structure of two or more layers, wherein the elastomer content of each sealant layer is different.

2 is a schematic diagram showing the construction of a multilayer sealant film according to an exemplary embodiment of the present invention.

In an exemplary embodiment, as shown in FIG. 2 , the multi-layered sealant layer is, for example, a three-layer sealant layer having a core layer, a sealant layer, and skin layers on both sides. That is, it is composed of a first skin layer that is a sealant layer in contact with the barrier layer (metal layer), a sealant layer that is a core layer, and a second skin layer that is a sealant layer that is in direct contact with the electrolyte. The first skin layer is required to have electrolyte resistance, hydrofluoric acid resistance, and insulation properties as well as adhesiveness with a metal, which is a barrier layer. The core layer requires heat resistance and thermal adhesion, as well as electrolyte resistance, hydrofluoric acid resistance, and insulation. The second skin layer is required to have thermal adhesion, electrolyte resistance, and insulation as well as slip properties and stenosis adhesion.

In an exemplary embodiment, the elastomer content of the first skin layer is greater than the elastomer content of the core layer, and the elastomer content of the core layer is greater than the elastomer content of the second skin layer.

In an exemplary embodiment, the first skin sealant layer on the barrier layer side is Random PP [R PP] or Ter PP [TER PP], or Block PP 50 of the total composition of the skin layer. It can be used in ~90% by weight. If the PP layer corresponding to the matrix is used in excess of 90% by weight, whitening may occur during pouch stretching and thus may not be used alone. The performance is improved, but the high temperature stability and chemical resistance can be greatly reduced.

Meanwhile, in the first skin sealant layer, the elastomer may be used in a total amount of 40 to 70% by weight of the total composition of the skin layer. If the elastomer is prescribed lower than the corresponding range in the first skin layer, whitening and sealing properties may be deteriorated.

In an exemplary embodiment, the sealant layer, which is the core layer, may use both homo PP and block PP. If TER PP or random PP of the core layer is used, it is vulnerable to swelling caused by electrolyte, so homo PP and block PP must be used for the matrix layer. The content ratio of the components should not exceed the maximum of 50% of the homo PP content. If the content is too high, the elastic modulus of the product rises, causing whitening and poor formability.

On the other hand, the elastomer may be used in a total amount of 10 to 40% by weight of the total composition of the core layer. When the amount of elastomer in the core layer is used in less than 10% by weight, whitening occurs and sealing properties are deteriorated, and when used in excess of 40% by weight, dispersibility and chemical resistance may be deteriorated.

In one exemplary embodiment, the sealant layer, which is the innermost second skin layer in contact with the electrolyte, comprises a homo PP and a block PP. Random PP and terrestrial PP can be used together, and the content of homo PP should not exceed 50% at most. Since this second skin layer is a layer in contact with the electrolyte, it must have the best chemical resistance, so it is necessary to secure chemical resistance by adding up to 90% of PP content. That is, it is important to maintain the PP matrix content to the maximum, but to prescribe the minimum elastomer for moldability. The PP matrix uses homo PP and block PP like the core in consideration of electrolyte resistance, and the elastomer content is prescribed within 10% by weight.

In a non-limiting example, the elastomer may be used in a total amount of 1 to 10% by weight of the total composition of the second skin layer. When an excessive amount of the elastomer is added in the second skin layer, the penetration of the electrolyte into the skin layer is deepened, and insulation resistance may be greatly reduced.

In an exemplary embodiment, the elastomer includes thermoplastic polyolefin elastomer (TPO), RTPO (reactor made thermoplastic olefin), such as ethylene propylene rubber (EPR), ethylene butane rubber (EBR, ethylene butane rubber), LLDPE-based elastomer, etc. , an elastomer such as thermoplastic polyurethane (TPU, thermoplastic polyurethane) can be used.

As described above, although the elastomer imparting the sealing effect is used, the amount of the elastomer is gradually adjusted in order to prevent the disadvantages of lowering the crystallinity and chemical resistance due to the addition of the elastomer. In particular, a minimum amount is added to the second skin layer, which is the innermost layer that is in contact with the electrolyte, to improve chemical resistance to improve insulation resistance. To achieve high sealing properties and high barrier properties with adhesive properties.

In an exemplary embodiment, the second skin layer, the sealant layer, preferably has a thickness corresponding to about 10 to 20% of the total sealant layer, and preferably has a thickness of at least 3 to 10 μm. If it is too thin, the adhesion between the sealant layer stenosis and the electrolyte resistance may be deteriorated, and if it is too thick, the thermal adhesion may be deteriorated.

Since slip property is required for the second skin layer, it is preferable to include at least one additive such as an anti-blocking agent and a slip agent (eg, amide-based). As the anti-blocking agent, inorganic particles such as zeolite and silicon particles are added, and by containing the anti-blocking agent, it is made to protrude on the film surface. On the other hand, the slip agent uses erucamide, behen-amide, oleamide, silicone oil, etc., and by containing the slip agent, the film surface can be made slippery.

On the other hand, the sealant layer, which is the core layer, preferably has a thickness corresponding to 50 to 80% of the total sealant layer, and is preferably at least 10 to 40 μm or more. Since most of the properties required for the sealant layer can be realized from this core layer, it should be thicker than the skin layers.

In such a core layer, it is preferable that the melting point (Tm) of the raw material for the intermediate layer is 150° C. or higher for heat resistance, and in this respect, the melting point of the intermediate layer material is 160° C. or more, so as to include homo PP. The homo PP has thermal stability and dimensional stability.

In addition, the first skin layer, which is the barrier layer contact layer, preferably has a thickness corresponding to 10 to 20% of the total sealant layer for metal adhesion and electrolyte resistance.

Meanwhile, exemplary embodiments of the present invention provide a cell pouch including the above-described sealant film and a secondary battery external to the cell pouch. Such a secondary battery may typically be a lithium secondary battery, and in particular, may be a medium or large secondary battery such as an electric vehicle (EV) or an energy storage system (ESS).

In an exemplary embodiment, the cell pouch may include, for example, an outer layer including nylon, a barrier layer including aluminum, and the sealant film.

In an exemplary embodiment, the cell pouch may further include an outermost layer including polyethylene terephthalate (PET) as an outermost layer of the outer layer. As described above, the configuration further including PET as the outermost layer may be particularly applied to a medium or large-sized secondary battery.

In exemplary embodiments of the present invention, in the above-described cell pouch manufacturing method, the cell pouch sealant film is prepared to have a sealant layer having a multilayer structure of two or more layers, but the elastomer content of each sealant layer is different. It provides a method for manufacturing a cell pouch comprising;

In addition, in exemplary embodiments of the present invention, as a method for improving the insulation properties of a cell pouch, a cell pouch sealant film is prepared to have a sealant layer having a multilayer structure of two or more layers, but the elastomer content of each sealant layer is different It provides a method for improving the insulation properties of a cell pouch comprising the;

Exemplary embodiments of the present invention are described in more detail through the following examples. The embodiments disclosed in this specification are illustrated for the purpose of explanation only, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described herein.

As a configuration common to the pouches of Examples and Comparative Examples, the outermost PET layer was 12 μm, the outer layer NY (nylon) 15 μm, the barrier layer Al 40 μm, and the inner layer, a sealant film, were 50 μm.

embodiment configuration

As shown in Figure 3a, in the embodiment, the first skin layer is composed of Random PP, Ter PP, and Block PP, and EPR (ethylene propylene rubber)-based elastomer is used as the second skin layer. It was constituted by using a total of 40% by weight of the total composition. For the core layer, homo PP and block PP were used together, and the elastomer was used in a total of 15% by weight of the total composition of the core layer. For the second skin layer, homo PP and block PP were used together, and the elastomer was used in a total amount of 5% by weight of the total composition of the second skin layer.

Comparative example configuration

As shown in FIG. 3B , in the comparative example, the composition of the first skin layer polymer is the same as in Example 1. That is, it was composed of Random PP, Ter PP, and Block PP, and an elastomer was added. The core layer was composed of block PP and an EPR (ethylene propylene rubber)-based elastomer was added. The second skin layer was configured in the same manner as the first skin layer. In the first skin layer, the core layer, and the second skin layer, the elastomer content was prescribed at 15 wt% for both skin layers, and 50 wt% for the core layer.

heat bonding strength

The thermal adhesive strength was measured by applying a load of 30 kgf at 2000 degrees using an adhesive strength measuring device (AGS-1kNX model manufactured by SHIMADZU, Japan).

moisture permeability

The moisture permeability test of the sealing film itself was measured using the US MOCON's moisture permeability measuring equipment (PEMATRAN_W 3/33 MA model).

Insulation Resistance

Insulation resistance was measured by applying a voltage of 500V to the Al layer after manufacturing the DUMMY cell and using an insulation resistance measuring device of Megger of the United States.

The above test results are shown in Table 1 below.

comparative example Example sealant film
thickness 50 50 thermal bonding strength
(N/15mm) 13 12 Moisture permeability (mg/m ² ·day) 10 8 Insulation resistance (gigaohms) 30 100

As described above, it was confirmed that the Example of the present invention has better thermal bonding strength and insulation resistance compared to the Comparative Example. In addition, as a result of measuring the moisture permeability of the film itself, it was confirmed that the barrier properties (water vapor permeability) of the sealant film were excellent.

Although non-limiting and exemplary embodiments of the present invention have been described above, the technical spirit of the present invention is not limited to the accompanying drawings or the above description. It will be apparent to those skilled in the art that various types of modifications are possible within the scope of the present invention without departing from the spirit of the present invention, and also, such modifications will fall within the scope of the claims of the present invention.

Claims (14)

A sealant film having a sealant layer having a multilayer structure of two or more layers,
A sealant film for a gradient composition type cell pouch, characterized in that the elastomer content of each sealant layer is different.
The method of claim 1,
The sealant film is a sealant film for a gradient composition type cell pouch, characterized in that it is composed of a sealant layer that is a first skin layer in contact with the barrier layer, a sealant layer that is a core layer, and a sealant layer that is a second skin layer that is in contact with the electrolyte.
3. The method of claim 2,
The elastomer content of the first skin layer is greater than the elastomer content of the core layer,
A sealant film for a gradient composition type cell pouch, characterized in that the content of the elastomer in the core layer is higher than the content of the elastomer in the second skin layer.
4. The method of claim 3,
The core layer is a sealant film for a gradient composition type cell pouch, characterized in that it contains Homer PP.
5. The method of claim 4,
The first skin layer includes random PP, Ter PP and block PP,
The core layer comprises Homer PP and Block PP;
The second skin layer is a sealant film for a gradient composition type cell pouch, characterized in that it comprises Homer PP and Block PP.
6. The method of claim 5,
The first skin layer comprises 40 to 70% by weight of the elastomer based on the total weight of the layer composition,
The core layer comprises 10 to 40% by weight of the elastomer based on the total weight of the layer composition,
The second skin layer is a sealant film for a gradient composition type cell pouch, characterized in that it contains 1 to 10% by weight of the elastomer based on the total weight of the layer composition.
A cell pouch comprising the sealant film of any one of claims 1 to 6.
8. The method of claim 7,
The cell pouch comprises an outer layer comprising nylon, a barrier layer comprising aluminum, and the sealant film.
9. The method of claim 8,
The cell pouch further comprises an outermost layer comprising polyethylene terephthalate (PET) as an outermost layer of the outer layer.
A secondary battery, characterized in that it is externally covered with the cell pouch of claim 7.
11. The method of claim 10,
The secondary battery is a secondary battery, characterized in that the lithium secondary battery.
11. The method of claim 10,
The secondary battery is a secondary battery, characterized in that for an electric vehicle or an energy storage device.
The method for manufacturing the cell pouch of claim 7,
A method for manufacturing a cell pouch, comprising: preparing a cell pouch sealant film to have a sealant layer having a multi-layered structure of two or more layers, wherein the elastomer content of each sealant layer is different.
A method for improving the insulation properties of a cell pouch, comprising:
A method for improving insulation properties of a cell pouch, comprising: preparing a cell pouch sealant film to have a sealant layer having a multi-layered structure of two or more layers, wherein the elastomer content of each sealant layer is different.

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