KR20230000022A - Sealant film for cell pouch having barrier properties using hygroscopicity of inorganic materals, cell pouch including the same and method for preparing the same - Google Patents

Abstract

Disclosed is a sealant film having a sealant layer in a multilayer structure that has 2 or more layers, a cell pouch including the same, and a preparation method thereof, wherein the content of an elastomer in each sealant layer becomes gradually different and an inorganic adhesive is contained in the sealant layer in contact with a barrier layer. In order to prevent a disadvantage that the inclusion of the elastomer into the sealant layer of the cell pouch decreases crystallinity and chemical resistance, the sealant layer is configured to have multiple layers and the amount of added elastomer is gradually adjusted in each layer. In particular, the minimum amount is added to an inner layer touched by an inner electrolyte to improve chemical resistance, thereby enhancing insulation resistance. In addition, an excessive amount of the elastomer and an inorganic additive are added to the sealant layer that comes in planar contact with the barrier layer to impart excellent thermal adhesion strength and properties of adhering to the barrier layer and improve moisture permeability, thereby achieving improved sealing performance and barrier performance.

Description

Sealant film for cell pouch having barrier properties using inorganic hygroscopicity, cell pouch including the same, and manufacturing method thereof

The present specification relates to a sealant film for a cell pouch having barrier properties using inorganic hygroscopicity, a cell pouch including the same, and a manufacturing method thereof.

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

The cell pouch is an exterior material that surrounds the electrode group and electrolyte of such a secondary battery, and must satisfy required properties such as adhesion between metal thin films and polymer layers, thermal fusion strength, electrolyte resistance, airtightness, moisture permeability, and moldability.

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

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

The barrier layer requires moldability as well as barrier properties against water vapor or other gases. In this respect, formable metals such as aluminum (Al), iron (Fe), copper (Cu), and nickel (Ni) are used for the barrier layer, and aluminum is currently used most often.

Since 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.

By the way, the conventional sealant film contains an excessive amount of copolymer and elastomer, so it has excellent thermal bonding properties, but due to low crystallinity, the free volume of the polymer is high, so the moisture permeability is high and the moisture permeability is poor. Battery failure may occur due to hydrofluoric acid generation.

In order to improve the inherent moisture permeability of polypropylene, which is an existing sealant film, crystallinity should be maximized, but there is a limit to improving this because copolymer and elastomer raw materials must be used.

Japanese Patent No. 6595634

In exemplary embodiments of the present invention, in one aspect, excellent chemical resistance and insulation resistance properties, especially high-temperature insulation properties, are improved by improving problems such as low insulation properties due to excessive use of elastomers and copolymers in conventional sealant layers. It is intended to provide a sealant film for a cell pouch, a cell pouch including the same, and a manufacturing method thereof.

In exemplary embodiments of the present invention, on the other hand, a sealant film for a cell pouch capable of achieving further improved sealing and barrier properties by further improving moisture permeability while having excellent thermal bonding strength and barrier layer adhesive properties, It is intended to provide a cell pouch containing and a method for manufacturing the same.

In exemplary embodiments of the present invention, a sealant film having a sealant layer having a multi-layer structure of two or more layers, each sealant layer having a different elastomer content, and a sealant layer contacting a barrier layer containing an inorganic additive, a sealant for a cell pouch. provide film.

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

In exemplary embodiments of the present invention, as a cell pouch manufacturing method, a 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, and the sealant in contact with the barrier layer Provides a method for manufacturing a cell pouch comprising: providing an inorganic additive to the layer.

In exemplary embodiments of the present invention, as a method for improving high-temperature insulation resistance properties of a cell pouch, a sealant film is prepared to have a sealant layer having a multi-layer structure of two or more layers, but the elastomer content of each sealant layer is different, Provides a method for improving the insulating properties of a cell pouch including providing an inorganic additive to a sealant layer in contact with the barrier layer.

According to exemplary embodiments of the present invention, in order to prevent the disadvantages of lowering crystallinity and chemical resistance when elastomer is applied to the sealant layer of the cell pouch, the sealant layer is composed of multiple layers and the amount of elastomer added is gradually adjusted in each layer. . In particular, by adding a minimum amount to the inner layer that comes into contact with the internal electrolyte solution, chemical resistance can be improved and insulation resistance can be improved. In addition, by adding an excessive amount of elastomer to the sealant layer, which is the adhesive surface of the barrier layer, and containing a predetermined amount of inorganic additives, it has excellent thermal bonding strength and barrier layer adhesive properties, and has improved moisture permeability, so that more improved sealing and barrier properties can be implemented. .

1 is a schematic diagram showing a general 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.
Figure 3 is a schematic diagram showing the composition of the cell pouch sealant film layer according to Comparative Example 1 (Fig. 3a), Comparative Example 2 (Fig. 3b) and Example 1 (Fig. 3a) of the present invention.

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

In this specification, in the high temperature insulation resistance characteristics, the high temperature is above 60°C.

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

In exemplary embodiments of the present invention, a sealant film for a gradient composition-type cell pouch is provided as a sealant film having two or more multi-layered sealant layers, the elastomer content of each sealant layer being different, and the corresponding gradient composition-type cell In the sealant film for a pouch, a predetermined inorganic additive may be added to the skin layer in contact with the barrier layer (usually a metal layer) to further increase sealing properties and improve moisture permeability.

2 is a schematic diagram showing a multi-layer sealant film configuration according to an exemplary embodiment of the present invention.

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

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

More specifically, in order to prevent the disadvantages of lowering the crystallinity and chemical resistance of the elastomer addition, the amount of elastomer added is gradually adjusted, and the chemical resistance is improved by adding a minimum amount of elastomer to the second skin layer in contact with the electrolyte to improve insulation resistance. and an excessive amount of elastomer is added to the first skin layer, which is the adhesive surface of the barrier layer (usually a metal layer), so as to have excellent thermal bonding strength and barrier layer adhesive properties. Furthermore, by adding an inorganic additive with high absorbency to the first skin layer, it is possible to achieve an effect of blocking moisture generated in the battery cell, thereby achieving further improved sealing and high barrier properties.

In an exemplary embodiment, the inorganic additive may use, for example, one or more of CaCO ₃ , BaSO ₄ , TiO ₂ , zeolite, and silica as a porous inorganic additive, and the effective content is the corresponding skin of the sealant film. It is preferred to add from 1% to 10% by weight based on the weight of the layer. When added at less than 1% by weight, the hygroscopic effect is insufficient, and when it exceeds 10% by weight, problems may occur in the appearance of the product.

In an exemplary embodiment, the first skin layer on the barrier layer side uses Random PP [R PP], Ter PP [TER PP], or Block PP as 50 to 50 of the total composition of the skin layer. It can be used at 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, making it impossible to use it alone. Although performance is improved, high-temperature stability and chemical resistance may be greatly reduced.

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

In one exemplary embodiment, the sealant film core layer may use both homo PP and block PP. If TER PP and random PP are used in the core layer, they are vulnerable to the swelling phenomenon caused by the electrolyte, so the matrix layer must use Homo PP and block PP. The content ratio of components is such that the content of homo PP does not exceed a maximum of 50%. If the content is too high, the modulus of elasticity of the product increases, resulting in whitening and poor formability.

Meanwhile, 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 elastomer is used in an amount of less than 10% by weight in the core layer, whitening occurs and sealing property is deteriorated, and when it is used in an amount exceeding 40% by weight, dispersibility and chemical resistance may be deteriorated.

In an exemplary embodiment, the sealant layer, which is the innermost second skin layer in contact with the electrolyte solution, includes homo PP and block PP. Random PP and random PP can be used together, and the content of homo PP is configured so that the maximum does not exceed 50%. 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 injecting up to 90% of PP content. That is, it is important to keep the PP matrix content to the maximum but to minimize the elastomer prescription for moldability. Considering the electrolyte resistance, the PP matrix uses homo PP and block PP like the core, 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 elastomer is added in the second skin layer, penetration of the electrolyte solution into the skin layer is intensified, and insulation resistance may be greatly reduced.

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

In this way, an elastomer imparting a sealing effect is used, but the addition amount of the elastomer is gradually adjusted in order to prevent the deterioration of crystallinity and chemical resistance due to the addition of the elastomer. In particular, a minimum amount is added to the second skin layer, the innermost layer that comes into contact with the electrolyte, to improve chemical resistance and insulation resistance, and an excessive amount of elastomer is added to the adhesive surface of the barrier layer made of aluminum to achieve excellent thermal bonding strength and barrier layer To achieve high sealability and high barrier properties with adhesive properties. Furthermore, by adding a porous inorganic additive with high absorptivity to the first skin layer in contact with the barrier layer (usually a metal layer), moisture generated in the battery cell is further blocked to improve moisture permeability, and further improved sealing and high barrier properties can be achieved. there is.

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

Since the second skin layer requires slip properties, it is preferable to include one or more additives 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 the anti-blocking agent is contained so that the film surface protrudes. On the other hand, the slip agent uses Erucamide, Behen-amide, Oleamide, silicone oil, etc., and the film surface can be made slippery by containing the slip agent.

Meanwhile, the sealant layer, which is the core layer, preferably has a thickness corresponding to 50 to 80% of the total sealant layer, and preferably has a thickness of at least 10 to 40 μm. Since most of the properties required in the sealant layer can be implemented from this core layer, it should be thicker than the skin layers.

In this core layer, it is preferable that the melting point (Tm) of the intermediate layer material is 150° C. or more for heat resistance, and in this respect, homo PP having a melting point of 160° C. or more is included. Such homo PP has thermal stability and dimensional stability.

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

Meanwhile, in exemplary embodiments of the present invention, a cell pouch including the above-described sealant film and a secondary battery external to the cell pouch are provided. 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 one exemplary embodiment, the cell pouch may further include an outermost layer including polyethylene terephthalate (PET) as an outermost layer of the outer layer. In this way, a configuration further including PET as an outermost layer may be particularly applied to medium or large-sized secondary batteries.

In exemplary embodiments of the present invention, in the cell pouch manufacturing method described above, 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, Provides a cell pouch manufacturing method comprising: providing an inorganic additive to a sealant layer in contact with the barrier layer.

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 multi-layer structure of two or more layers, but the elastomer content of each sealant layer is different, , Providing an inorganic additive to the sealant layer in contact with the barrier layer; provides a method for improving the insulating properties of a cell pouch including.

Exemplary embodiments of the present invention are described in more detail through the following examples. Embodiments disclosed herein are illustrated for purposes of explanation only, and embodiments of the present invention may be implemented 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 below, the outermost layer of PET was 12 μm, the outer layer of NY (nylon) was 15 μm, the barrier layer of Al was 40 μm, and the sealant film of the inner layer was 50 μm.

[Experiment 1]

Comparative Example 1 Configuration

As shown in FIG. 3A, in Comparative Example 1, the polymer composition of 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 corresponding agent. One skin layer was added in a total of 15% by weight of the total composition. No inorganic additives were used.

The core layer was composed of block PP and EPR (ethylene propylene rubber)-based elastomer was added.

The second skin layer was configured in the same way as the first skin layer. The elastomer content in the first skin layer, the core layer, and the second skin layer was equally prescribed at 15% by weight on both sides of the skin layer, and 50% by weight in the core layer.

Comparative Example 2 Configuration

As shown in FIG. 3B, in Comparative Example 2, the first skin layer was composed of Random PP, Ter PP, and Block PP, and EPR (ethylene propylene rubber)-based elastomer was used as the first skin layer. It was constituted by using a total of 40% by weight of the total composition of the layer. 11% by weight of an inorganic additive (Zeolite) was added to the first skin layer.

For the core layer, both homo PP and block PP were used, 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, both homo PP and block PP were used, and the elastomer was used in a total amount of 5% by weight of the total composition of the second skin layer.

Example 1 Configuration

As shown in FIG. 3C, in Example 1, the first skin layer is composed of Random PP, Ter PP, and Block PP, and EPR (ethylene propylene rubber)-based elastomer is used in the first skin layer. It was added in a total of 40% by weight of the total composition of the skin layer. The inorganic additive (Zeolite) was composed of 5% by weight of the total composition of the first skin layer.

The core layer and the second skin layer were configured in the same manner as in Comparative Example 2.

heat seal strength

Thermal bonding strength was measured using a UTM measuring device (AGS-1kNX model manufactured by SHIMADZU, Japan) by applying a load of 30 kgf at 200 degrees for 2 sec to the thermal bonding machine.

moisture permeability

The moisture permeability test of the sealing film itself was measured using a moisture permeability measuring device (PEMATRAN_W 3/33 MA model) from MOCON, USA.

Insulation Resistance

Insulation resistance was measured by applying a 500V voltage to the Al layer after manufacturing the DUMMY CELL and using an insulation resistance measuring device from Megger, USA.

The high-temperature insulation resistance was measured by the number of cells destroyed by hydrofluoric acid gas when the DUMMYCELL was aged for 1 day at room temperature and left for 5 days after manufacturing the DUMMYCELL.

The above test results are shown in Table 1 below.

Item unit Comparative Example 1 Comparative Example 2 Example 1
(Elastomer+
inorganic additives) inorganic additives wt% 0wt% 11wt%
(more than 10%) 5wt% Thermal bonding strength
(weight) N/15mm 80N 110N 100N moisture permeability mg/cc.day 9.0 6.5 7.0 formability mm 10 N.G (below 6) 10 Isolation
resistance normal temperature NG out of 10
(less than 1G)
Count 8/10 1/10 1/10 High temperature 10/10 7/10 2/10

*N.G: Not Good

As described above, in the case of the embodiment of the present invention, unlike Comparative Example 1, it was confirmed that the moisture permeability and insulation resistance characteristics were improved. That is, as a result of measuring the moisture permeability of the film itself, it was confirmed that the sealant film had excellent barrier properties (water vapor transmission rate). The moisture permeability was good in both Example 1 and Comparative Example 2, but Example 1 was particularly excellent in the evaluation of high-temperature insulation resistance due to moisture inside the cell. On the other hand, when the content of inorganic additives exceeds 10wt%, the moldability is measured as 6mm (max forming depths) or less, and the moldability at the commercialization level is not obtained.

Although non-limiting and exemplary implementations of the present invention have been described above, the technical idea of the present invention is not limited to the accompanying drawings or the above description. It is obvious to those skilled in the art that various types of modifications are possible within the scope of the technical spirit of the present invention, and also, these types of 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 cell pouch, characterized in that each sealant layer has a different elastomer content and an inorganic additive is contained in the sealant layer in contact with the barrier layer.
According to claim 1,
The sealant film is a sealant film for a cell pouch, characterized in that composed of a sealant layer as a first skin layer in contact with the barrier layer, a sealant layer as a core layer, and a sealant layer as a second skin layer in contact with the electrolyte.
According to 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 cell pouch, characterized in that the elastomer content of the core layer is greater than the elastomer content of the second skin layer.
According to claim 3,
The core layer is a sealant film for a cell pouch, characterized in that it comprises Homer PP.
According to claim 4,
The first skin layer includes random PP, Ter PP, and block PP,
The core layer includes Homer PP and block PP,
The second skin layer is a sealant film for a cell pouch, characterized in that it comprises Homer PP and block PP.
According to claim 5,
The first skin layer includes 40 to 70% by weight of an elastomer based on the total weight of the first skin layer composition, and 1 to 10% by weight of the inorganic additive based on the total weight of the first skin layer composition,
The core layer contains an elastomer in an amount of 10 to 40% by weight based on the total weight of the core layer composition,
The sealant film for a cell pouch, characterized in that the second skin layer contains an elastomer in an amount of 1 to 10% by weight based on the total weight of the second skin layer composition.
According to claim 1,
The inorganic additive is a sealant film for a cell pouch, characterized in that at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , TiO ₂ , zeolite, and silica.
A cell pouch comprising the sealant film of any one of claims 1 to 7.
According to claim 8,
The cell pouch includes an outer layer containing at least one of nylon and polyethylene terephthalate (PET), a barrier layer containing aluminum, and the sealant film.
A secondary battery characterized in that it is exteriorized with the cell pouch of claim 8.
According to claim 10,
The secondary battery, characterized in that the secondary battery is a lithium secondary battery.
According to claim 10,
The secondary battery, characterized in that for an electric vehicle or an energy storage device.
In the cell pouch manufacturing method of claim 8,
manufacturing a cell pouch sealant film to have two or more multi-layered sealant layers, making the elastomer content of each sealant layer different, and providing an inorganic additive to the sealant layer in contact with the barrier layer; A method for manufacturing a cell pouch.
A method for improving the high temperature insulation resistance of a cell pouch,
manufacturing a cell pouch sealant film to have two or more multi-layered sealant layers, making the elastomer content of each sealant layer different, and providing an inorganic additive to the sealant layer in contact with the barrier layer; A method for improving the insulation properties of a cell pouch.

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