KR20220059712A - Lead tab film, manufacturing method thereof, and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a film for a lead tab, a manufacturing method thereof, and a secondary battery including the same, wherein the film for a lead tab is manufactured by thermally laminating: a first film of co-extruded triple layers, which sequentially consists of a random polypropylene layer (A layer), a block polypropylene layer (B layer) and a first tertiary polypropylene layer (C1 layer); and a second film of a single layer which consists of a second tertiary polypropylene layer (C2 layer).

Description

Lead tab film, manufacturing method thereof, and secondary battery including same

The present invention relates to a film for a lead tab, a manufacturing method thereof, and a secondary battery including the same.

Recently, as technology development and demand for mobile devices increase, the demand for secondary batteries is also increasing. Among these secondary batteries, the demand for lithium secondary batteries having particularly high energy density and discharge voltage is rapidly increasing.

In general, lithium secondary batteries are classified into lithium ion secondary batteries, lithium ion polymer batteries, lithium polymer batteries, and the like according to the type of electrolyte. Furthermore, depending on the external appearance, it is largely classified into a cylindrical secondary battery, a prismatic secondary battery, and a pouch-type secondary battery.

Among them, the demand for thin prismatic secondary batteries and pouch-type secondary batteries is increasing in line with the trend of miniaturization of mobile devices. .

Such a pouch-type secondary battery is attracting attention as a power source for a battery vehicle or a hybrid electric vehicle because it is advantageous for weight reduction and miniaturization compared to a cylindrical or prismatic secondary battery.

Most pouch-type secondary batteries have a lead tab drawn out from the electrode group, and the lead tab and the exterior material (pouch) are sealed through a lead tab film (or a sealing film). Such a film for a lead tab is manufactured as a three-layer film having a structure of an outer layer/middle layer/inner layer through a three-layer coextrusion method, and the inner layer is adhered to the lead tab to seal the pouch.

On the other hand, in order to provide a high-performance secondary battery with improved capacity, the thickness of the lead tab tends to become thicker, and in order to completely seal it, the thickness of the inner layer attached to the lead tab becomes thicker. There are difficulties in making changes.

Accordingly, there is a need to develop a triple-layer film for a lead tab that does not cause delamination while increasing the thickness of the inner layer without changing the three-layer co-extrusion facility.

As a similar prior document for this, Republic of Korea Patent Publication No. 10-2089415 is presented.

Republic of Korea Patent Publication No. 10-2089415 (2020.03.10.)

In order to solve the above problems, an object of the present invention is to provide a film for a lead tab that does not cause delamination and a method for manufacturing the same while increasing the thickness of the inner layer without changing the three-layer co-extrusion facility.

Another object of the present invention is to provide a secondary battery including the film for the lead tab.

However, the above purpose is illustrative, and the technical spirit of the present invention is not limited thereto.

One aspect of the present invention for achieving the above object is a first film of the co-extruded triple layer; and a second film of a single layer; a film for lead tabs manufactured by thermal lamination, wherein the first film is sequentially a random polypropylene layer (layer A), a block polypropylene layer (layer B) and a first ter polypropylene layer ( C1 layer), the second film is composed of a second tertiary polypropylene layer (C2 layer), and the first tertiary polypropylene layer (C1 layer) of the first film and the second tertiary polypropylene layer of the second film It relates to a film for lead tabs, characterized in that the polypropylene layer (C2 layer) is thermally laminated so as to be in contact with each other.

In one aspect, the film for the lead tab has a random polypropylene layer (layer A): a block polypropylene layer (layer B): a thickness ratio of the terpolypropylene layer (layer C1 + layer C2) of 1:1 to 2:2 It may be characterized in that it is 3 to 3.

In the above aspect, the tertiary polypropylene layer (C1 layer + C2 layer) has a thickness ratio of the first tertiary polypropylene layer (C1 layer): the second tertiary polypropylene layer (C2 layer) is 1:1 to 10. may be characterized.

In addition, another aspect of the present invention is a random polypropylene (r-PP), block polypropylene (B-PP) and first ter-polypropylene (ter-PP) by co-extrusion sequentially random polypropylene layer (A layer) ), preparing a first film of a triple layer consisting of a block polypropylene layer (B layer) and a first ter polypropylene layer (C1 layer); and preparing a film for a lead tab by thermally laminating a second film of a single layer consisting of the first film and the second tertiary polypropylene layer (C2 layer); including, the first tertiary polypropylene layer of the first film (C1 layer) and the second tertiary polypropylene layer (C2 layer) of the second film, it relates to a method for producing a film for a lead tab, characterized in that the thermal lamination so as to be in contact with each other.

In another aspect, the film for the lead tab has a random polypropylene layer (layer A): a block polypropylene layer (layer B): a thickness ratio of the ter polypropylene layer (layer C1 + layer C2) 1: 1 to 2: It may be characterized in that it is 2-3.

In the other aspect, the tertiary polypropylene layer (C1 layer + C2 layer) has a thickness ratio of the first tertiary polypropylene layer (C1 layer): the second tertiary polypropylene layer (C2 layer) is 1:1 to 10. It may be characterized by

In the other aspect, in the method for manufacturing the film for the lead tab, the tension applied to the first film is controlled to 9 to 21 N, and the tension applied to the second film is controlled to 3 to 13 N to heat It may be amalgamation.

In the other aspect, the method for manufacturing the film for the lead tab may be to control the tension applied to each film to satisfy the following Relational Expression 1 or Relational Expression 2.

[Relational Expression 1]

8 ≤ T ₁ ≤ 11

[Relational Expression 2]

3 ≤ T ₂ ≤ 11

(In the above relation 1, T ₁ is the tension (N) applied to the second film when the tension applied to the first film is controlled to be less than 9 to 18 N,

In Relation 2, T ₂ is the tension (N) applied to the second film when the tension applied to the first film is controlled to be 18 to 21 N.)

In addition, another aspect of the present invention relates to a secondary battery including the film for the lead tab described above, wherein the secondary battery may be a pouch-type secondary battery.

In another aspect, the film for the lead tab may be thermally bonded to the lead tab of the secondary battery.

The film for lead tab according to the present invention is formed by thermally laminating the co-extruded triple-layered first film and single-layered second film to form an inner terpolypropylene layer (C layer, C1 + C2). The thickness of the inner layer can be adjusted as desired without changing the

In addition, since the first ter polypropylene layer (C1 layer) and the second ter polypropylene layer (C2 layer), which are the same material, are thermally laminated so that they come into contact with each other, delamination does not easily occur even after thermal lamination. It has the advantage of being able to seal more effectively.

1 is a schematic view briefly showing a method of manufacturing a film for a lead tab according to an embodiment of the present invention.

Hereinafter, a film for a lead tab according to the present invention, a method for manufacturing the same, and a secondary battery including the same will be described in detail. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used, it has the meaning commonly understood by those of ordinary skill in the art to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted.

The film for lead tabs according to the present invention is composed of a random polypropylene layer (layer A) as an outer layer, a block polypropylene layer (layer B) as an intermediate layer, and a terpolypropylene layer (layer C) as an inner layer, wherein the inner layer is a pouch-type secondary It may be a layer that is adhered to the lead tab of the battery to seal the pouch.

More specifically, the film for a lead tab according to an embodiment of the present invention includes a co-extruded triple-layered first film; and a second film of a single layer; a film for lead tabs manufactured by thermal lamination, wherein the first film is sequentially a random polypropylene layer (layer A), a block polypropylene layer (layer B) and a first ter polypropylene layer ( C1 layer), the second film is composed of a second tertiary polypropylene layer (C2 layer), and the first tertiary polypropylene layer (C1 layer) of the first film and the second tertiary polypropylene layer of the second film It may be characterized in that the polypropylene layer (C2 layer) is thermally laminated to be in contact with each other.

As such, the film for lead tab according to the present invention is formed by thermally laminating the co-extruded triple-layered first film and single-layered second film to form an inner terpolypropylene layer (C layer, C1 + C2). The thickness of the inner layer can be adjusted as desired without changing the extrusion equipment, and the cost can be reduced because the co-extrusion equipment may not be changed.

In addition, since the first ter polypropylene layer (C1 layer) and the second ter polypropylene layer (C2 layer), which are the same material, are thermally laminated so that they come into contact with each other, delamination does not easily occur even after thermal lamination. It has the advantage of being able to seal more effectively.

Hereinafter, each component of the film for lead tabs according to an example of the present invention will be described in more detail.

First, the random polypropylene layer (layer A) which is an outer layer is demonstrated.

In one example of the present invention, the random polypropylene layer is a layer made of a random copolymer of a propylene monomer and another olefin monomer, for example, a layer made of a propylene-ethylene random copolymer or a propylene-1-butene random copolymer. and, preferably, in terms of improving tensile strength, it may be a layer made of a propylene-ethylene random copolymer. As a more specific example, the propylene-ethylene random copolymer may have a molecular weight distribution (Mw/Mn) of 4.0 to 15.0, preferably 4.5 to 9.0. In addition, the propylene-ethylene random copolymer may have a melt index (MI, 230° C., 2.16 kg load) of 3 to 10 g/10 min, and more preferably, a melt index (MI, 230° C., 2.16 kg load) It may be 4 to 7 g/10min, but is not necessarily limited thereto.

Next, the block polypropylene layer (B layer) which is an intermediate|middle layer is demonstrated.

In one embodiment of the present invention, the block polypropylene layer is a layer made of a block copolymer of a propylene monomer and another olefin monomer, for example, a layer made of a propylene-ethylene block copolymer or a propylene-1-butene block copolymer. It may be, preferably, a layer made of a propylene-ethylene block copolymer in terms of improving tensile strength. As a more specific example, the propylene-ethylene block copolymer may have a molecular weight distribution (Mw/Mn) of 4.0 to 8.0, and more preferably 4.5 to 7.5. In addition, the propylene-ethylene block copolymer may have a melt index (MI, 230°C, 2.16kg load) of 1 to 10 g/10min, and more preferably, a melt index (MI, 230°C, 2.16kg load) It may be 1 to 5 g/10min, but is not necessarily limited thereto.

Next, the terpolypropylene layer (C layer) which is an inner layer is demonstrated.

As described above, the ter polypropylene layer (C layer) is a thermal lamination process of the first ter polypropylene layer (C1 layer) of the first film and the second ter polypropylene layer (C2 layer) of the second film As a layer laminated together through

As a specific example, the terpolypropylene layer (C layer) may be a layer made of a propylene-ethylene-1-butene random triple copolymer, and in a more specific example, the propylene-ethylene-1-butene random triple copolymer may have a molecular weight distribution (Mw/Mn) of 2.0 to 9.5, and more preferably 2.5 to 9.0. In addition, the propylene-ethylene-1-butene random triple copolymer may have a melt index (MI, 230° C., 2.16 kg load) of 3 to 10 g/10 min, and more preferably, a melt index (MI, 230° C., 2.16kg load) may be 4 to 7 g/10min, but is not necessarily limited thereto.

On the other hand, as described in the background art, the thickness of the lead tab tends to increase in order to provide a high-performance secondary battery with improved capacity. However, in order to increase the thickness of the inner layer only through three-layer co-extrusion, there is a problem in that the existing three-layer co-extrusion equipment needs to be changed, resulting in excessive cost.

Accordingly, the present inventors have repeatedly studied a method for increasing the thickness of the inner layer while using the existing equipment as it is, after repeatedly studying a random polypropylene layer (A layer), a block polypropylene layer (B layer) and a first tertiary polypropylene layer ( Prepare the first film of the co-extruded triple layer consisting of layer C1), and laminate the first film and the second film of a single layer (second ter polypropylene layer (C2 layer)) through a thermal lamination process to form the inner layer It was possible to develop a film for lead tabs that does not easily cause delamination while increasing the thickness of the terpolypropylene layer (layer C).

Specifically, the film for the lead tab may have a total film thickness of 80 to 150 μm, more preferably 90 to 130 μm, and even more preferably 95 to 110 μm. In the above thickness conditions, it is particularly important to properly control the thickness ratio of each layer. If the thickness of the inner layer among the total thickness of the film is too thin, the area of the gap between the end region of the lead tab and the film for the lead tab may be widened. , if the thickness of the inner layer is too thick, mechanical properties such as tensile strength of the film itself are lowered, so it may be difficult to sufficiently protect the lead tab.

As a preferred example, the film for the lead tab has a thickness ratio of random polypropylene layer (layer A): block polypropylene layer (layer B): terpolypropylene layer (layer C1 + layer C2) of 1:1 to 2:2 to 3, more preferably 1: 1.2 to 1.8: 2.2 to 2.8, and most preferably 1: 1.4 to 1.6: 2.4 to 2.6. In such a range, it is possible to effectively seal the lead tab, which is thicker than the existing ones, because the inner layer is thick enough while having excellent mechanical properties such as tensile strength.

In addition, in the tertiary polypropylene layer (C1 layer + C2 layer), the thickness ratio of the first tertiary polypropylene layer (C1 layer): the second tertiary polypropylene layer (C2 layer) may be 1:1 to 10, and better is 1: 2 to 8, more preferably 1: 3 to 5 may be characterized. In this range, the thickness of the inner layer can be adjusted according to the target without changing the existing equipment, and the first ter polypropylene layer (C1 layer) and the second tertiary polypropylene layer (C2 layer) are effectively laminated well during the thermal lamination process. It may not delaminate easily.

As such, the film for the lead tab can be manufactured by thermally laminating the co-extruded first film of the triple layer and the second film of the single layer as described above, and specifically, the method of manufacturing the film for the lead tab is random polypropylene (r- PP), a block polypropylene (B-PP), and a first ter polypropylene (ter-PP) are co-extruded to sequentially a random polypropylene layer (A layer), a block polypropylene layer (B layer) and a first ter poly Preparing a triple-layered first film consisting of a propylene layer (C1 layer); and preparing a film for a lead tab by thermally laminating a second film of a single layer consisting of the first film and the second tertiary polypropylene layer (C2 layer); including, the first tertiary polypropylene layer of the first film (C1 layer) and the second tertiary polypropylene layer (C2 layer) of the second film may be characterized in that it is thermally laminated so as to be in contact with each other.

Through this, it is possible to effectively manufacture a film for a lead tab having a desired thickness, that is, a thicker inner layer, without changing the existing co-extrusion equipment.

First, a random polypropylene (r-PP), a block polypropylene (B-PP) and a first ter-polypropylene (ter-PP) are co-extruded to sequentially a random polypropylene layer (A layer), a block polypropylene layer ( B layer) and the first tertiary polypropylene layer (C1 layer) can perform the step of manufacturing the first film of the triple layer, in this case, the polymer material used for each layer is the same as described above, so the overlapping description is Omitted, and their co-extrusion may be performed under conditions commonly used in the art.

Next, the first film and the second tertiary polypropylene layer (C2 layer) may be thermally laminated to prepare a film for a lead tab by thermally laminating the second film, wherein the second film is made of a ter polypropylene material. It may be prepared by single extrusion.

Referring to Figure 1, the first film wound on the upper roll and the second film wound on the lower roll are laminated on each other at the unwinding unit, and then sent to the heating unit to perform thermal lamination, which is cooled by the cooling unit and wound up at the winding unit. to manufacture a film for lead tabs.

In particular, a film for lead tabs with excellent quality by properly adjusting the tension applied to each film when the first film wound on the upper roll and the second film wound on the lower roll are laminated together in the unwinding unit and sent to the heating unit It is preferable to be able to manufacture

As a specific example, the first film may be thermally laminated by controlling the tension applied to the film to 9 to 21 N, and controlling the tension applied to the second film to 3 to 13 N. In this range, there is no discoloration, wrinkles are minimized, and it is good to be able to manufacture a film for a lead tab in which the thickness is hardly reduced.

More preferably, the method of manufacturing the film for the lead tab may control the tension applied to each film to satisfy the following Relational Expression 1 or Relational Expression 2.

[Relational Expression 1]

8 ≤ T ₁ ≤ 11

[Relational Expression 2]

3 ≤ T ₂ ≤ 11

(In the above relation 1, T ₁ is the tension (N) applied to the second film when the tension applied to the first film is controlled to be less than 9 to 18 N,

In Relation 2, T ₂ is the tension (N) applied to the second film when the tension applied to the first film is controlled to be 18 to 21 N.)

That is, when the tension applied to the first film is relatively small, 9 to less than 18 N, it is preferable to control the tension applied to the second film to 8 to 11 N, and the tension applied to the first film is 18 to 21 N. When N is relatively high, it is preferable to control the tension applied to the second film to 3 to 11 N. In this range, the film for lead tabs having the best quality can be manufactured.

On the other hand, the temperature during the thermal lamination process may be 100 to 150 ℃, more preferably 105 to 130 ℃, most preferably 110 to 120 ℃ may be. In such a range, the first film and the second film are effectively laminated and may not be easily delaminated.

Thereafter, the thermally laminated film for the lead tab may be cooled in the cooling unit, and the cooling may be to cool the thermally laminated film for the lead tab to a temperature of room temperature.

Finally, the cooled film for the lead tab may be wound on a roll again in the winding unit, and the tension applied to the film for the lead tab at this time may be 20 to 30 N. When the tension applied to the film for the lead tab is less than 20 N, the film for the lead tab may not be wound on the roll, and when the tension applied to the film for the lead tab exceeds 30 N, the camber phenomenon may become severe, which is not good.

On the other hand, another aspect of the present invention relates to a secondary battery including the film for the lead tab described above, wherein the secondary battery may be a pouch-type secondary battery commonly used in the art, the specific configuration of which can be understood by those skilled in the art. A detailed description of the bar will be omitted. The film for the lead tab may be thermally bonded to the lead tab of the secondary battery to completely seal the lead tab and the pouch of the secondary battery.

Hereinafter, a film for a lead tab according to the present invention, a method for manufacturing the same, and a secondary battery including the same will be described in more detail through Examples. However, the following examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention. In addition, the unit of additives not specifically described in the specification may be weight %.

[Example 1]

Random polypropylene (A, Lotte Chemical, sfc550), block polypropylene (B, Lotte Chemical, fc330), and the first ter polypropylene (C1, Lotte Chemical, bp402) were sequentially heated at 145℃, 163℃, 145℃ A first film of A/B/C1 triple layer structure (thickness of A/B/C1 = 20/30/10 μm) was prepared by co-extrusion under the conditions.

The second tertiary polypropylene (C2, Lotte Chemical, bp402) was extruded to prepare a C2 single-layered second film (C2 thickness = 40 μm).

Next, as shown in FIG. 1, after rolling the first film on the upper roll and the second film on the lower roll, the tension applied to the first film of the upper roll and the tension applied to the second film of the lower roll The thermal lamination process was performed by controlling as described in Table 1 below, wherein the thermal lamination temperature was controlled to 115 °C. At this time, in Table 1 below, the vertical dimension is the tension (0 to 22 N) applied to the first film of the upper roll, and the horizontal is the tension (0 to 14 N) applied to the second film of the lower roll.

From this, a film for a triple-layer lead tab having an A/B/C structure was prepared, and the thickness of each layer was A/B/C = 20/30/50 μm.

Then, the properties of the prepared film were evaluated, and when there was no reduction in thickness and wrinkles, ◎, when the thickness was reduced to 2 μm or less or weak wrinkles were formed ○, when clear wrinkles were formed visually, △, when the thickness was reduced to more than 2 μm The case was evaluated as ▲, and discoloration occurred as ◆.

[Table 1]

As can be seen from Table 1, it was confirmed that it is preferable to appropriately control the tension applied to each film during thermal lamination in order to manufacture a film for a triple-layer lead tab with excellent quality.

In particular, the first film (thickness of A/B/C1 = 20/30/10 μm) and the second film (thickness of C2 = 40 μm) were thermally laminated to obtain A/B/C = 20/30/50 μm. When the film for the triple-layer lead tab is manufactured, when the tension applied to the first film of the upper roll is 9 to 17 N, the film of the highest quality when the tension applied to the second film of the lower roll is controlled to 8 to 11 could be manufactured. In addition, when the tension applied to the first film of the upper roll is slightly increased to 18 to 21 N, the film of the highest quality can be manufactured when the tension applied to the second film of the lower roll is controlled to 3 to 11 N. there was.

Although the present invention has been described with reference to specific matters and limited examples as described above, these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and the present invention pertains to Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims described below, but also all of the claims and all equivalents or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

110: upper roll 120: lower roll
200: unwinding unit 300: heating unit
400: cooling unit 500: winding unit

Claims (10)

Co-extruded triple-layered first film; and a second film of a single layer; a film for lead tabs prepared by thermal lamination,
The first film is sequentially composed of a random polypropylene layer (layer A), a block polypropylene layer (layer B) and a first tertiary polypropylene layer (C1 layer), and the second film is a second tertiary polypropylene layer (C2 floor),
The film for lead tabs, characterized in that the first tertiary polypropylene layer (C1 layer) of the first film and the second tertiary polypropylene layer (C2 layer) of the second film are thermally laminated so as to be in contact with each other.
The method of claim 1,
The film for the lead tab is characterized in that the thickness ratio of the random polypropylene layer (A layer): the block polypropylene layer (B layer): the ter polypropylene layer (C1 layer + C2 layer) is 1: 1 to 2: 2 to 3 The film for the lead tab to do.
3. The method of claim 2,
The ter-polypropylene layer (C1 layer + C2 layer) is for a lead tab, characterized in that the thickness ratio of the first ter-polypropylene layer (C1 layer): the second ter-polypropylene layer (C2 layer) is 1:1 to 10. film.
Random polypropylene (r-PP), block polypropylene (B-PP) and first ter polypropylene (ter-PP) are co-extruded to sequentially form a random polypropylene layer (A layer), a block polypropylene layer (B layer) ) and a first tertiary polypropylene layer (C1 layer) for preparing a first film of a triple layer; and
Preparing a film for a lead tab by thermally laminating the second film of a single layer consisting of the first film and the second tertiary polypropylene layer (C2 layer);
A method for producing a film for lead tabs, characterized in that the first tere polypropylene layer (C1 layer) of the first film and the second tertiary polypropylene layer (C2 layer) of the second film are in contact with each other by thermal lamination.
5. The method of claim 4,
The film for the lead tab is characterized in that the thickness ratio of the random polypropylene layer (A layer): the block polypropylene layer (B layer): the ter polypropylene layer (C1 layer + C2 layer) is 1: 1 to 2: 2 to 3 The manufacturing method of the film for lead tabs to do.
6. The method of claim 5,
The ter-polypropylene layer (C1 layer + C2 layer) is for a lead tab, characterized in that the thickness ratio of the first ter-polypropylene layer (C1 layer): the second ter-polypropylene layer (C2 layer) is 1:1 to 10. A method of making a film.
5. The method of claim 4,
The method for producing the film for the lead tab is to control the tension applied to the first film to 9 to 21 N, and to control the tension applied to the second film to 3 to 13 N to perform thermal lamination, for the lead tab A method of making a film.
8. The method of claim 7,
The method for producing the film for the lead tab is to control the tension applied to each film to satisfy the following Relational Expression 1 or Relational Expression 2, a method for producing a film for a lead tab.
[Relational Expression 1]
8 ≤ T ₁ ≤ 11
[Relational Expression 2]
3 ≤ T ₂ ≤ 11
(In the above relation 1, T ₁ is the tension (N) applied to the second film when the tension applied to the first film is controlled to be less than 9 to 18 N,
In Equation 2, T ₂ is the tension (N) applied to the second film when the tension applied to the first film is controlled to be 18 to 21 N.)
A secondary battery comprising the film for a lead tab of any one of claims 1 to 3.
10. The method of claim 9,
The film for the lead tab is a secondary battery that is thermally bonded to the lead tab of the secondary battery.

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