KR20220168419A - Film for lead tab of secondary battery and manufacturing method thereof - Google Patents

Abstract

According to an embodiment of the present invention, there is provided a film for a secondary battery lead tab is a film for a secondary battery lead tab that seals a gap between a battery case of a secondary battery and an electrode lead electrically connected to a positive electrode or a negative electrode of an electrode assembly of the secondary battery. The film comprises: a first skin layer that adheres to the electrode lead; an intermediate layer that is provided on one of upper and lower surfaces of the first skin layer; and a second skin layer that is provided on one of the upper and lower surfaces of the intermediate layer, which faces the first skin layer, and adheres to the battery case, wherein at least one of the first skin layer and the second skin layer may be provided to have a greater surface area or greater adhesion than that of the other. According to the present invention, it is possible to enhance productivity and reduce production costs.

Description

Secondary battery lead tab film and its manufacturing method {FILM FOR LEAD TAB OF SECONDARY BATTERY AND MANUFACTURING METHOD THEREOF}

The present invention relates to a film for a lead tab for a secondary battery and a method for manufacturing the same, and more particularly, to a film for a lead tab for a secondary battery capable of increasing adhesion and a method for manufacturing the same.

Secondary batteries are used as power sources, energy storage devices (ESS), such as electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed as a solution to air pollution caused by conventional gasoline vehicles and diesel vehicles using fossil fuels. ) is also noted.

Typically, in terms of battery shape, there is a high demand for prismatic secondary batteries and pouch-type secondary batteries that can be applied to products such as mobile phones with a thin thickness, and in terms of materials, they have advantages such as high energy density, discharge voltage, and output stability. Demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries is high.

In addition, secondary batteries are classified according to the structure of the electrode assembly of the cathode/separator/cathode structure. Typically, a jelly structure in which long sheet-shaped cathodes and cathodes are wound with a separator interposed therebetween. -Roll (wound type) electrode assembly, a stack type (stacked) electrode assembly in which a plurality of positive and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, positive electrodes and negative electrodes of a predetermined unit with a separator interposed therebetween A stack/folding type electrode assembly having a structure in which bi-cells or full cells are stacked in one state and wound is exemplified.

Recently, a pouch-type secondary battery having a structure in which a stacked or stacked/folding type electrode assembly is embedded in a pouch-type battery case of an aluminum laminate sheet has attracted much attention due to low manufacturing cost, small weight, and easy shape deformation. and its usage is gradually increasing.

1 is an exploded perspective view showing a pouch-type secondary battery according to the prior art.

Referring to FIG. 1, a pouch-type secondary battery 1 includes an electrode assembly 3 in which a negative electrode and a positive electrode are separated and insulated by a separator, electrode tabs 4 extending from the positive and negative electrodes of the electrode assembly 3, 5), and a battery case 2 accommodating the electrode leads 6 and 7 and the electrode assembly 3 welded to the electrode tabs 4 and 5.

The electrode assembly 3 is a power generating device in which an anode and a cathode are sequentially stacked with a separator interposed therebetween, and has a stacked or stacked/folded structure. The electrode tabs 4 and 5 extend from the positive electrode and the negative electrode of the electrode assembly 3, and the electrode leads 6 and 7 include a plurality of electrode tabs 4 and 5 extending from each positive electrode and the negative electrode, For example, each is electrically connected by welding, and a part is exposed to the outside of the battery case 2.

In addition, an insulating film 8 having excellent insulating properties is attached to a part of the upper and lower surfaces of the electrode leads 6 and 7 to improve sealing performance with the battery case 2 and at the same time secure an electrical insulation state. The battery case 2 is made of an aluminum laminate sheet, provides a space for accommodating the electrode assembly 3, and has a pouch shape as a whole.

Here, the pouch-type battery case 2 may include an upper cap 20 and a lower can 30, and the upper cap 20 and the lower can 30 are made of CPP (Casting polypropylene Film; unstretched PP). It may be made of a typical three-layer structure of a representative heat sealing layer (2b)/aluminum metal layer (2c)/a protective layer (2d) represented by nylon. The electrode assembly 3 may be accommodated by being bonded to each other by heat and pressure to heat-seal layers of the sheets constituting the upper cap 20 and the lower can 30 . The upper cap 20 and the lower can 30 may be collectively referred to as a battery case.

On the other hand, the insulating film 8 has a portion that is melted when heated and adhered to the electrode leads 6 and 7, a heat-resistant portion that maintains its shape during heating, and a portion that adheres to the heat-sealing layer 2b of the battery case 2. It may have a three-layer structure including In some cases, it may have a two-layer structure in which a heat-resistant portion and a portion that adheres to the heat-sealing layer of the battery case are formed as one layer.

When the insulating film 8 has a three-layer structure, additional surface treatment is required for the adhesive layer of the insulating film to improve the adhesion performance between the electrode lead and the insulating film or between the battery case and the insulating film. Therefore, such an insulating film has disadvantages in that the production process is lengthened and the production cost is increased by performing an additional surface treatment process after the film extrusion or lamination process.

The present applicant has proposed the present invention in order to solve the above problems.

Korean Patent Registration No. 10-0815605 (registration announcement 2008.03.20.)

The present invention has been proposed to solve the above problems, and provides a film for a lead tab for a secondary battery and a method for manufacturing the same, which do not require an additional surface treatment process to improve adhesion performance.

The present invention provides a film for a lead tab for a secondary battery capable of increasing the surface area of an adhesive surface during a process in which a film having a three-layer structure is collectively formed by a co-extrusion process, and a method for manufacturing the same.

The present invention provides a film for a lead tab for a secondary battery and a method for manufacturing the same, which can improve adhesion performance by increasing the area of a surface bonded to a lead tab or a battery case.

A film for a secondary battery lead tab according to an embodiment of the present invention for achieving the above object is provided between a battery case of a secondary battery and an electrode lead electrically connected to an anode or a cathode of an electrode assembly of the secondary battery. A film for a lead tab of a secondary battery to be sealed, comprising: a first skin layer bonded to the electrode lead; an intermediate layer provided on any one of the upper and lower surfaces of the first skin layer; A second skin layer provided on one surface of the upper or lower surface of the intermediate layer facing the first skin layer and adhered to the battery case, wherein at least one of the first skin layer and the second skin layer is It can be prepared to have a larger surface area than one or a large adhesive force.

Among the first skin layer and the second skin layer, a skin layer having a large surface area or high adhesive strength may be formed to have a surface in direct contact with the electrode lead or the battery case and a surface not in contact with the battery case.

Among the first skin layer and the second skin layer, the skin layer having a large surface area or high adhesive strength may have concavo-convex or embossed or intaglio formed on a surface facing the electrode lead or the battery case.

Among the first skin layer and the second skin layer, the surface area of the skin layer having a large surface area or a large adhesive force is equal to the sum of the area of the embossed embossment, the area of the intaglio, and the area of the portion connecting the embossed and intaglio. can be formed to

The embossed and intaglios may be alternately formed, and the sum of the areas of the embossments may be greater than the sum of the areas of the intaglios.

The intaglio surface may be formed at a position 0.1 to 10 μm lower than the embossed surface.

The surface area of one of the embossments may be 25 μm ² to 10,000 μm ² .

Among the first skin layer and the second skin layer, a skin layer having a large surface area or high adhesive strength may be formed such that 50 to 200 embossments exist within a plane area of 100 mm ² .

The first skin layer, the intermediate layer, or the second skin layer may be formed of polyethylene, polypropylene, and copolymers or terpolymers thereof or polyolefin resin.

On the other hand, according to another field of the invention, the present invention is a method for manufacturing the film for a lead tab for a secondary battery, wherein the first skin layer, the intermediate layer, and the second skin layer are melted and sequentially laminated by co-extrusion. It is possible to provide a method for manufacturing a film for a secondary battery lead tab formed in a state of being formed.

The first skin layer, the intermediate layer, and the second skin layer simultaneously pass through a T-die and are cooled by a casting roller so that irregularities are formed on the surface of at least one of the first skin layer and the second skin layer. and intaglio patterns can be transferred.

The outlet of the T-Dye may have an edge portion larger than a central portion.

The film for secondary battery lead tab and its manufacturing method according to the present invention do not require an additional surface treatment process to improve the adhesion or adhesion performance between the lead tab or battery case and the film, so productivity can be increased and production costs can be reduced. .

A film for a lead tab for a secondary battery according to the present invention and a method for manufacturing the same can increase the surface area of the film by forming concavo-convex or embossed and intaglio patterns on the adhesive surface of the film during the process of collectively manufacturing the three-layer film through a co-extrusion process. there is.

The film for a lead tab for a secondary battery according to the present invention and its manufacturing method do not require a separate process for forming concavo-convex or embossed and intaglio patterns on the surface of the film while cooling the coextruded film.

A film for a lead tab for a secondary battery according to the present invention and a method for manufacturing the same can increase the surface area of the film by forming concavo-convex or embossed and intaglio patterns on the surface of the film, thereby expanding the area where the film and the lead tab or the film and the battery case are bonded. and, as a result, adhesion can be improved.

The film for a lead tab for a secondary battery according to the present invention and its manufacturing method use a method of forming a certain pattern on the surface of the film during the extrusion process to increase the surface area of the film surface to improve the adhesive force with the adherend, so that after extrusion of the film No separate process is required.

A film for a lead tab for a secondary battery according to the present invention and a method for manufacturing the same have a pattern formed on the surface of a casting roller transferred to the surface of an extruded film while the film is extruded through a T-die, thereby transferring a certain pattern to the surface of the film. As it cools down, the overall surface area of the film is increased by the surface pattern of the extruded film, so that the adhesive strength is improved by the effect of the widened surface area during adhesion with the adherend.

1 is an exploded perspective view showing a pouch-type secondary battery according to the prior art.
2 is a perspective view showing a lead tab for a pouch-type secondary battery and a film for a lead tab according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view taken along cutting lines AA and BB of FIG. 2 .
4 is a view exemplarily showing the surface of a film for a lead tab for a secondary battery according to an embodiment of the present invention.
5 is a cross-sectional view taken along the cutting line CC of FIG. 4 .
6 is a conceptual diagram of a coextrusion system for manufacturing a film for a lead tab according to FIG. 4 .
Figure 7 is a diagram showing an example of the coextrusion system according to Figure 6;
Figure 8 shows a part of the coextrusion system according to Figure 7;
Figure 9 is a view for explaining the operation of the casting roller of the co-extrusion system according to Figure 7;

Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings, but the same or similar reference numerals are given to the same or similar components, and overlapping descriptions thereof will be omitted. The suffix "part" for components used in the following description is given or used interchangeably in consideration of ease of writing the specification, and does not itself have a meaning or role distinct from each other. In addition, in describing the embodiments disclosed in this specification, if it is determined that a detailed description of a related known technology may obscure the gist of the embodiment disclosed in this specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, the technical idea disclosed in this specification is not limited by the accompanying drawings, and all changes included in the spirit and technical scope of the present invention , it should be understood to include equivalents or substitutes.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

It should be understood that when an element is referred to as being “connected” to another element, it may be directly connected to the other element, but other elements may exist in the middle.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

It is advised that the drawings are schematic and not drawn to scale. Relative dimensions and proportions of parts in the drawings are shown exaggerated or reduced in size for clarity and convenience in the drawings, and any dimensions are illustrative only and not limiting. And like structures, elements or parts appearing in two or more drawings, like reference numerals are used to indicate like features.

The embodiments of the present invention specifically represent ideal embodiments of the present invention. As a result, various modifications of the drawings are expected. Therefore, the embodiment is not limited to the specific shape of the illustrated area, and includes, for example, modification of the shape by manufacturing.

2 is a perspective view showing a lead tab and a film for a lead tab applied to a pouch-type secondary battery according to an embodiment of the present invention, FIG. 3 is a cross-sectional view taken along cutting lines A-A and B-B of FIG. 2, and FIG. 4 is an embodiment of the present invention. A view exemplarily showing the surface of a film for a lead tab for a secondary battery according to the example, FIG. 5 is a cross-sectional view taken along the cutting line C-C in FIG. 4, FIG. 6 is a conceptual diagram of a co-extrusion system for manufacturing a film for a lead tab according to FIG. 7 is a view showing an example of the coextrusion system according to FIG. 6, FIG. 8 is a view showing a part of the coextrusion system according to FIG. 7, and FIG. 9 is a view to explain the operation of the casting roller of the coextrusion system according to FIG. 7 It is a drawing for

The secondary battery lead tab film and its manufacturing method according to an embodiment of the present invention described below are used for lithium secondary batteries, and a pouch type lithium secondary battery will be described as an example, but is not limited thereto. .

Hereinafter, the secondary battery lead tab film 100 according to an embodiment of the present invention and its manufacturing method will be described in detail with reference to the drawings.

A secondary battery to which the film 100 for a secondary battery lead tab according to an embodiment of the present invention is applied is the same as the pouch-type secondary battery shown in FIG. 1 , so a repetitive description thereof will be omitted.

The secondary battery lead tab film 100 according to an embodiment of the present invention is electrically connected to the battery cases 20 and 30 of the secondary battery 1 and the positive electrode or negative electrode of the electrode assembly 3 of the secondary battery 1. It is a secondary battery lead tab film (100, hereinafter referred to as "lead tab film") that seals between the connected electrode leads 6 and 7.

2 and 3, the lead tab film 100 according to an embodiment of the present invention is provided between the battery cases 20 and 30 and the electrode leads 6 and 7, and the electrode leads 6, As a member for bonding or sealing 7) to the battery cases 20 and 30, it may be provided in the form of an insulating film.

Referring to FIGS. 2 and 3 , the film 100 for a lead tab according to an embodiment of the present invention may be adhered to or provided on the upper and lower surfaces of the electrode leads 6 and 7 , respectively. Here, the electrode leads 6 and 7 have one ends 6a and 7a connected to the electrode tabs 4 and 5 extending from the positive and negative electrodes of the electrode assembly 3 and the other ends 6b and 7b connected to external devices. can include

The lead tab film 100 should be adhered to the electrode leads 6 and 7 in a close contact state so that there is no gap or play between the electrode leads 6 and 7.

Referring to FIG. 3 , the lead tab film 100 according to an embodiment of the present invention is electrically connected to the battery cases 20 and 30 of the secondary battery and the positive electrode or negative electrode of the electrode assembly 3 of the secondary battery. A first skin layer 110 bonded to the electrode leads 6 and 7 as a film 100 for a secondary battery lead tab that seals between the connected electrode leads 6 and 7; an intermediate layer 130 provided on any one of the upper and lower surfaces of the first skin layer 110; A second skin layer 150 provided on one surface of the upper or lower surface of the intermediate layer 130 facing the first skin layer 110 and bonded to the battery cases 20 and 30; may include. Therefore, the lead tab film 100 according to an embodiment of the present invention is in the form of a film having a three-layer structure in which a first skin layer 110, an intermediate layer 130, and a second skin layer 150 are sequentially stacked. can be provided.

Referring to FIG. 3 , in the lead tab film 100 according to an embodiment of the present invention, the first skin layer 110 is bonded to the electrode leads 6 and 7, and is placed on the first skin layer 110. The intermediate layer 130 is located, and has a layered structure in which the second skin layer 150 is located on the intermediate layer 130 . Although not shown, the second skin layer 150 is bonded to the battery cases 20 and 30 .

In the case of the lead tab film 100 shown in FIG. 3 , the lowermost and uppermost surfaces of the film 100 serve as adhesive surfaces, respectively.

Here, in the lead tab film 100 according to an embodiment of the present invention, at least one of the first skin layer 110 and the second skin layer 150 is provided to have a larger surface area or greater adhesive strength than the other one. It can be. That is, either one of the surface (lower surface) of the first skin layer 110 or the surface (upper surface) of the second skin layer 150 may have a larger surface area than the other or may be formed to have greater adhesive strength. In some cases, the surface (lower surface) of the first skin layer 110 is formed to have a larger surface area than the other surface (top surface bonded to the middle layer) of the first skin layer 110, and the second skin layer 150 The surface (top surface) of ) may be formed to have a larger surface area than the other surface (bottom surface bonded to the intermediate layer) of the second skin layer 150 .

For reference, FIG. 3 does not specifically show that the surface area of the surface (lower surface) of the first skin layer 110 or the surface (upper surface) of the second skin layer 150 is formed to be wide.

The lead tab film 100 according to an embodiment of the present invention has a surface area of the first skin layer 110 or the second skin layer 150 in contact with the electrode leads 6 and 7 or the battery cases 20 and 30. It is possible to increase the adhesive force of the first skin layer 110 or the second skin layer 150 and improve the adhesive performance by widening the .

In the lead tab film 100 according to an embodiment of the present invention, the skin layer having a large surface area or high adhesive strength among the first skin layer 110 or the second skin layer 150 is the electrode lead 6 or 7 It may be provided to have a surface in direct contact with the battery cases 20 and 30 and a surface not in contact with them.

The lead tab film 100 according to an embodiment of the present invention is the first skin layer 110 or the second skin layer 105 bonded to the electrode leads 6 and 7 or the battery cases 20 and 30. The entire surface is not bonded to the electrode leads 6 and 7 or the battery cases 20 and 30, but may have greater adhesive strength because there are portions that are not directly adhered to.

To this end, in the lead tab film 100 according to an embodiment of the present invention, the skin layer having a large surface area or high adhesive strength among the first skin layer 110 and the second skin layer 150 is the electrode lead 6, 7) Alternatively, irregularities may be formed on surfaces facing the battery cases 20 and 30, that is, surfaces to be bonded, or embossed and intaglios may be formed.

4 shows the surface of the lead tab film 100 according to an embodiment of the present invention by way of example. FIG. 4 shows the surface of the second skin layer 150 of the lead tab film 100, that is, the surface bonded to the battery cases 20 and 30. Referring to FIG. 4 , it can be seen that on the surface (adhesive surface) of the second skin layer 150, a plurality of irregularities repeated in the same shape or embossed and engraved patterns are repeatedly formed. More specifically, a plurality of X-shaped intaglios P4 are formed in a diagonal direction at regular intervals, and a diamond-shaped embossed angle P3 is formed between the intaglios.

As shown in FIG. 4, on the surface (adhesive surface) of the second skin layer 150, when irregularities are formed or embossed and intaglios are formed, only the embossed (P3) portion and the battery cases 20 and 30 are formed. will be glued

Meanwhile, the shape of the surface shown in FIG. 4 may be formed on the surface of the first skin layer 110, that is, the surface (adhesive surface) bonded to the electrode leads 6 and 7. In this case, only the embossed portion P3 is bonded to the electrode leads 6 and 7.

As such, in the lead tab film 100 according to an embodiment of the present invention, the skin layer having a large surface area or high adhesive strength among the first skin layer 110 or the second skin layer 150 has irregularities or embossments (P3 ) and a pattern including the intaglio P4 may be repeatedly formed.

Here, the shape of the pattern including concavo-convex or embossed and intaglio formed on the surface (adhesive surface) of the first skin layer 110 or the second skin layer 150 is not limited to the rhombic shape as shown in FIG. It can be provided in various forms. As long as the surface area of the first skin layer 110 or the second skin layer 150 can be increased, any pattern shape of concavo-convex or embossed and intaglio patterns is possible. For example, embossed and engraved patterns are not limited to grid patterns, and may be formed in various patterns such as dots, lines, and dash-dots.

In the above, it has been described that patterns including concavo-convex or embossed and intaglio patterns are repeatedly formed on the skin layer having a large surface area or large adhesive strength among the first skin layer 110 or the second skin layer 150. The relationship between the intaglio pattern and the surface area will be explained.

5 is a cross-sectional view taken along the line C-C in FIG. 4; If the surface shown in FIG. 4 is the surface (adhesive surface) of the second skin layer 150, its cross-sectional view is as shown in FIG.

Referring to FIG. 5 , the lead tab film 100 according to an embodiment of the present invention includes a first skin layer 110 positioned at the bottom, a second skin layer 150 positioned at the top, and the first skin layer It may include an intermediate layer 130 positioned between (110) and the second skin layer (150).

As shown in FIG. 5, the surface (adhesive surface) of the second skin layer 150 has an intaglio surface (S2) formed recessed from the surface, an embossed surface (S1) formed at a higher position than the intaglio surface (S2), and an intaglio surface (S2) and the embossed surface (S1) connecting surfaces (S3, S4) may be formed. Here, the intaglio surface (S2) corresponds to the intaglio (P4) of FIG. 4, the embossed surface (S1) corresponds to the embossed (P3) in FIG. ) and the intaglio (P4).

Referring to FIG. 5, the surface area of the surface of the second skin layer 150 (adhesive surface bonded to the battery case) is the area of the embossed surface S1, the area of the intaglio surface S2, and the area of the embossed surface S1 and the intaglio. It may be formed equal to the sum of the areas of the connecting surfaces S3 and S4 connecting the surfaces S2. Therefore, the surface area of the surface on which the concavo-convex or embossed and intaglio is formed is inevitably greater than the surface area of the surface on which the concavo-convex or embossed and intaglio is not formed. Because the surface on which concavo-convex or embossed and intaglios are formed has an area corresponding to the connection surfaces S3 and S4 shown in FIG. 5, the surface area is inevitably larger. As such, a skin layer having a large surface area due to unevenness or embossing and intaglio in the first skin layer 110 or the second skin layer 150 has high adhesive strength due to the large surface area. Because the surface area increases due to irregularities or embossments and intaglios, the area bonded to the battery case or the electrode lead increases correspondingly, resulting in increased adhesion.

4 and 5 show the case where concavo-convex or embossed and intaglio patterns are formed on the surface of the second skin layer 150, but the surface of the first skin layer 110 (adhesive surface bonded to the electrode leads) is also concavo-convex. Alternatively, embossed and intaglio patterns may be repeatedly formed.

On the other hand, as shown in Figure 4, the embossed (P3) and the negative (P4) are formed alternately with each other, the sum of the areas of all the embossed (P3) can be formed greater than the sum of the areas of all the negative (P4) there is. When the surface shown in FIG. 4, that is, the surface (adhesive surface) of the second skin layer 150 is bonded to the battery case, the embossed (P3) portion is entirely bonded to the battery case, while the intaglio (P4) portion There may be parts that are bonded to the silver battery case and parts that are not bonded. However, if the total area of the embossed (P3) is smaller than the total area of the intaglio (P4), even if the embossed and intaglio are formed, it is impossible to expect an improvement in adhesive strength. Therefore, in order to improve adhesion, it is preferable that the total area of the embossed (P3) is larger than the total area of the intaglio (P4).

As described above, the concave-convex (P4) part of the unevenness shown in FIG. 4 may have a part adhered to the battery case and a part not adhered to the battery case, which may be determined by the depth of the concave-convex (P4) part.

Referring to Figure 5, the intaglio surface (S2) is located at a lower point by a certain depth (D) than the embossed surface (S1), the intaglio surface (S2) by the depression depth (D) of the intaglio surface (S2) It can be determined whether or not it adheres to the battery case.

The present inventors have repeatedly tested to determine whether a large portion of the intaglio surface S2 contributes to adhesion when the depression depth D of the intaglio surface S2 with respect to the embossed surface S1 is. As a result, the depth of the irregularities, that is, the depression depth (D) of the intaglio surface (S2) is preferably 0.1 to 10 μm, more preferably 0.2 to 5 μm, and still more preferably 0.5 to 1 μm. It was confirmed that many parts of (S2) were adhered.

If the depression depth (D) of the intaglio surface (S2) is less than 0.1 μm, the effect of increasing the surface area is nullified and the adhesive force cannot be increased, and the depression depth (D) of the intaglio surface (S2) exceeds 10 μm. In this case, voids may be generated during the thermal fusion process of the lead tab film 100, causing defects in the lead tab film 100.

Accordingly, the surface of the intaglio P4 may be formed at a position 0.1 to 10 μm lower than the surface of the embossed engraving P3.

On the other hand, it has been described above that it is preferable that the sum of the total areas of the embossments P3 is greater than the sum of the total areas of the intaglios P4, but the individual size or area of the embossments P3 affects adhesive strength or productivity. can give

Referring to FIG. 4 , each embossed mark P3 is a portion indicated by a dotted line. Here, the size (area) of one embossing (P3) may be preferably 25 μm ² to 10,000 μm ² , more preferably 100 μm ² to 5,000 μm ² , and more preferably 400 μm ² to 2,500 μm ² .

If the size (area) of one embossing (P3) is greater than 10,000 μm ² , the effect of increasing the surface area by forming embossed and engraved patterns on the surface of the first skin layer 110 or the second skin layer 150 is low do. In addition, when the size (area) of one embossment P3 is smaller than 25 μm ² , it is difficult to uniformly transfer the embossed and intaglio patterns to the surface of the lead tab film 100 .

Therefore, it is preferable that the surface area of one of the embossments P3 is 25 μm ² to 10,000 μm ² .

On the other hand, the present inventors conducted a repeated test to check whether the adhesive performance is excellent in the case of how many embossments P3 are formed in the unit area of the first skin layer 110 or the second skin layer 150. saw. Here, the unit area is defined as 100 mm ² (width 10 mm × length 10 mm). As a result, the number of reliefs P3 located within 100 mm ² may be preferably 50, more preferably 100, and still more preferably 200.

If the number of embossed points (P3) located within 100 mm ² is less than 50, the area of the embossed points (P3) becomes wider, making gap-filling of the resin difficult during thermal fusion, resulting in voids on the adhesive surface may occur. In addition, when the number of embossed points P3 located within 100 mm ² exceeds 200, the line width of the intaglio P4 becomes thin, which may cause defects in pattern formation.

Therefore, among the first skin layer 110 and the second skin layer 150, the skin layer having a large surface area or high adhesive strength is preferably formed such that 50 to 200 embossed points P3 exist within a plane area of 100 mm ² . .

In the lead tab film 100 according to an embodiment of the present invention, the first skin layer 110, the middle layer 130, or the second skin layer 150 are polyethylene, polypropylene, or copolymers thereof, or It may be formed of a polymer (Ter-polymer) or polyolefin resin.

The lead tab film 100 according to an embodiment of the present invention described above is formed by forming concavo-convex or embossed and intaglio patterns on the surface (adhesive surface) of the first skin layer 110 or the second skin layer 150. It is possible to widen the bonding area and thereby improve the bonding strength, and a separate process for forming concavo-convex or embossed and intaglio patterns is not required. In the process of co-extruding the first skin layer 110, the intermediate layer 130, and the second skin layer 150 at once, irregularities or embossed and engraved patterns may be formed. Hereinafter, a method of manufacturing the lead tab film 100 according to an embodiment of the present invention will be described.

A method for manufacturing a film 100 for a lead tab for a secondary battery according to an embodiment of the present invention is a method for manufacturing the film 100 for a lead tab for a secondary battery as described above, and includes a first skin layer 110, an intermediate layer 130 and After each of the two skin layers 150 is melted, a film for a secondary battery lead tab may be manufactured in a state in which the skin layers 150 are sequentially stacked by co-extrusion. That is, the film 100 for a lead tab for a secondary battery according to the present invention is manufactured by a three-layer co-extrusion method, and may be manufactured through a process of inputting raw materials, melting and kneading, and casting.

6 is a schematic diagram of a co-extrusion system 200 for manufacturing a film 100 for a lead tab according to an embodiment of the present invention. Referring to FIG. 6 , the coextrusion system 200 includes a hopper 210 into which the materials of the first skin layer 110, the middle layer 130, and the second skin layer 150 are put, and the materials put into the hopper 210. Cylinder 220 melted and transported, T-die 230 that thinly discharges the molten material to form a film, and casting cools the thin material discharged through the T-die 230 and forms it into a predetermined thickness It may include various rollers 253, 254, 255, 256, 257, and 258 that transport the film 100 passing through the rollers 251 and 252 and the casting rollers 251 and 252 in a stretched state or in a state in which tension is maintained. The formed film 100 is finally wound around the winding roller 259 .

In the lead tab film 100 according to an embodiment of the present invention, the first skin layer 110, the middle layer 130, and the second skin layer 150 are simultaneously co-extruded, and the lead tab film 100 has a three-layer structure. In order to manufacture, the materials of the first skin layer 110, the middle layer 130 and the second skin layer 150 must be supplied separately. Therefore, in the co-extrusion system 200 used to manufacture the lead tab film 100 according to an embodiment of the present invention, as shown in FIG. The raw materials of the first hopper 211, the first cylinder 221, and the second hopper 212, the first cylinder 222, and the second skin layer 150 into which the raw materials of the intermediate layer 130 are put and melted and transferred. It may include a third hopper 213 and a third cylinder 223 that are put in and melted and transported.

The raw material input process is a process in which raw materials forming the first skin layer 110, the intermediate layer 130, and the second skin layer 150 are input into the first to third hoppers 211, 212, and 213. At this time, the input raw material may include polyethylene (PE), polypropylene (PP) and its copolymer or ter-polymer or polyolefin resin.

On the other hand, here, the first skin layer 110 is made of a material that can adhere to the surfaces of the metal electrode leads 6 and 7 in a heated and melted state, and the second skin layer 150 is in a heated and melted state. In the battery case (20, 30) can be provided with a material that can be in close contact with the thermally fused layer (2b).

In addition, the intermediate layer 130 is preferably made of a material having excellent heat resistance. If the middle layer 130 is made of a material with poor heat resistance, when heating to bond the first skin layer 110 and the second skin layer 150, the middle layer 130 melts and the battery case 20, 30) may contact the electrode leads 6 and 7. This will cause a short circuit. Therefore, the intermediate layer 130 should also function as a heat-resistant layer capable of maintaining its shape even when heated.

Raw materials put into the first to third hoppers 211 , 212 , and 213 may be melted in the first to third cylinders 221 , 222 , and 223 , respectively, and then transported toward the T-Die 230 . Here, it is a melting and kneading process that passes through the first to third cylinders 221 , 222 , and 223 .

The melting and kneading process refers to a process in which raw materials introduced into the first to third hoppers 211, 212, and 213 are introduced into the first to third cylinders 221, 222, and 223 to be melted and kneaded. The internal temperature of is higher as it progresses from the first section to the fourth section.

Here, the temperature of the first section may be preferably determined to be 140°C or more and 220°C or less, more preferably 150°C or more and 210°C or less, and more preferably 160°C or more and 200°C or less. The temperature of the second section may be preferably determined to be 150°C or more and 230°C or less, more preferably 160°C or more and 220°C or less, and more preferably 170°C or more and 210°C or less. The temperature of the third section may be preferably determined to be 180°C or more and 240°C or less, more preferably 190°C or more and 230°C or less, and more preferably 180°C or more and 220°C or less. The temperature of the fourth section may be preferably determined to be 190°C or more and 250°C or less, more preferably 200°C or more and 240°C or less, and still more preferably 210°C or more and 230°C or less.

If the internal temperature of the preceding cylinder section is higher than the internal temperature of the succeeding cylinder section, the flowability of the molten resin is lowered and the resin cannot move within the cylinder and may become stagnant in the preceding section. In addition, when the internal temperature of the cylinder is 140 ° C or lower, the resin may not be melted and may not move inside the cylinder, and when the temperature exceeds 250 ° C, the physical properties of the lead tab film 100 are deteriorated due to deterioration of the resin. or, in severe cases, thermal decomposition of the resin may occur.

Referring to FIG. 8 , discharge ports of the first cylinder 221 to the third cylinder 223 may be commonly connected to the T die 230 .

The casting process is a process in which molten resin that has passed through the first to third cylinders 221, 222, and 223 is discharged after passing through a T-die 230 and formed into a film by a casting roller 251 and 252. It is collectively called, and is an important step in determining the thickness of the lead tab film 100.

However, in the process of cooling the molten resin by the casting rollers 251 and 252 after passing through the T-die 230, necking of the molten resin occurs, and the thickness of the edge portion of the lead tab film 100 is reduced. A phenomenon that is smaller than the middle part may occur. In order to prevent this phenomenon, the size or width of the discharge port 231 of the T-die 230 should be set larger (thicker) in the edge portion compared to the center portion. As such, it is preferable that the width of the edge portion of the outlet 231 of the T-die 230 is larger than that of the center portion.

Meanwhile, the lead tab film 100 is discharged after passing through the T-die 230 and cooled by the casting rollers 251 and 252 to finally form a film. In this process, it is formed on the surface of the casting rollers 251 and 252. The patterns P3 and P4 are transferred to the surface of the lead tab film 100 according to the patterns P1 and P2, so that the surface area of the lead tab film 100 increases.

Referring to FIG. 7 , the molten resin discharged from the T-die 230 may be cooled and transported simultaneously while passing between the first and second casting rollers 251 and 252 . Here, the first casting roller 251 functions to cool, transport and maintain the thickness of the film, while the second casting roller 252 transfers the pattern to the surface of the film in addition to the functions of cooling, transport and maintaining the thickness of the film. function to do.

As shown in FIG. 7 , the lead tab film 100 is transferred in a state of being in contact with a part of the surface of the second casting roller 252, and in this process, cooling and pattern transfer occur. In this way, in the lead tab film 100 according to an embodiment of the present invention, after the first skin layer 110, the middle layer 130, and the second skin layer 150 pass through the T-die 230 at the same time, By the casting rollers 251 and 252, irregularities may be formed on the surface of at least one of the first skin layer 110 and the second skin layer 150, or embossed and engraved patterns may be formed.

9, among the casting rollers 251 and 252 of the co-extrusion system 200 used for manufacturing the film 100 for a lead tab according to an embodiment of the present invention, a first part of the casting roller 251 and 252 is in contact with the film 100 for a lead tab. 2 On the surface of the casting roller 252, the same pattern (P1 , P2) is formed. Therefore, while the lead tab film 100 discharged from the T-die 230 passes through the first and second casting rollers 251 and 252, at least one of the first skin layer 110 and the second skin layer 150 On the surface of the second casting roller 252, patterns formed on the surface of the second casting roller 252, such as irregularities or reliefs P1 and intaglios P2, may be transferred. That is, the irregularities formed on the surface of the second casting roller 252 or the pattern of the embossed (P1) and intaglio (P2) is transferred as it is, and is transferred to the first skin layer 110 or the second skin layer 150. It is imprinted on at least one surface.

In this way, the lead tab film 100 according to an embodiment of the present invention has uneven or embossed edges as at least one of the first skin layer 110 and the second skin layer 150 is cooled by the casting roller 252. and intaglio patterns can be transferred.

Meanwhile, the coextrusion system 200 used in the manufacture of the lead tab film 100 according to an embodiment of the present invention uses one casting capable of transferring a pattern to the lead tab film 100 instead of a pair of casting rollers. It may also include only roller 252 .

The lead tab film 100 according to an embodiment of the present invention manufactured by the method described above includes the first skin layer 110, the middle layer 130, and the second skin layer 150 by the coextrusion system 200. may be integrally formed or integrally formed. That is, after the first skin layer 110, the middle layer 130, and the second skin layer 150 are each manufactured in the form of a film, the first skin layer 110 is adhered to one surface of the middle layer 130, and the second skin The first skin layer 110, the middle layer 130, and the second skin layer 150 have a three-layer structure by forming the layer 150 integrally or collectively instead of attaching it to the other surface of the middle layer 130. will achieve Therefore, the lead tab film 100 forms a layered structure in the order of the first skin layer 110, the intermediate layer 130, and the second skin layer 150, but has a separate bonding structure (adhesive structure) between adjacent layers. does not exist

The lead tab film 100 according to an embodiment of the present invention may be formed by integrally co-extruding the first skin layer 110, the middle layer 130, and the second skin layer 150. . That is, the first skin layer 110, the intermediate layer 130, and the second skin layer 150 are not manufactured in the form of films and then attached or thermally bonded to each other, but using the co-extrusion system 200. By doing so, a film in which the first skin layer 110, the intermediate layer 130, and the second skin layer 150 are laminated can be integrally manufactured at once.

Therefore, in the lead tab film 100 according to an embodiment of the present invention, separate adhesive components are provided between the first skin layer 110 and the middle layer 130 and between the middle layer 130 and the second skin layer 150. Alternatively, even if there is no adhesive layer or adhesive structure and the lead tab film 100 is pressed in a heated state in order to adhere to the battery cases 20 and 30 and the electrode leads 6 and 7, the lead tab film 100 is interlayered. Separation (peeling) does not occur, and there is no problem that each layer is extruded from the end.

The present inventors conducted a comparative experiment on the peel strength of the lead tab film 100 according to an embodiment of the present invention, and the results are as follows.

(1) Comparative Example 1

A polypropylene film having an intermediate layer, a first skin layer, and a second skin layer was prepared through co-extrusion. The thickness of the intermediate layer was 70 μm, the first skin layer and the second skin layer were composed of 35 μm and 45 μm, respectively, and no surface treatment was performed on the surface of the film after extrusion.

The surface area of the film was measured after pretreatment at 80°C for 3 hr using a BET (specific surface area measuring instrument, Autosorb-iQ/MP model from Quantachrome inst.), and the measured specific surface area of the film was 72.36 m ² /g. appear. After cutting this film into a width of 5 mm and a length of 5 cm, it was heat-sealed with electrode leads by applying heat of 185° C. and pressure of 30 kgf for 5 seconds. Then, for each of the thermally bonded specimens, the thermal adhesive strength between the electrode lead and the sealing film was measured at a speed of 200 mm/min using UTM (SHIMADZU's AGS-500NX model), and the adhesion of the film measured in this way The strength was found to be 3 N/10 mm.

(2) Comparative Example 2

The same film as in Comparative Example 1 was used, except that the first skin layer was surface-treated with an acid anhydride.

The specific surface area measured in the same manner as in Comparative Example 1 was 71.57 m ² /g, and the adhesive strength was 15 N/mm.

(3) Comparative Example 3

After extrusion, the same film as in Comparative Example 1 was used, except that the surface of the film was subjected to corona discharge treatment.

The specific surface area of the film measured in the same manner as in Comparative Example 1 was 74.57 m ² /g, and the adhesive strength was 17 N/mm.

(4) Example

A polypropylene lead tab film 100 having an intermediate layer 130, a first skin layer 110, and a second skin layer 150 was manufactured using the coextrusion system 200 according to the present invention. During manufacturing, the lattice pattern formed on the surface of the casting roller 252 was transferred to the surface of the lead tab film 100 as it was. The thickness of the middle layer 130, the first skin layer 110, and the second skin layer 150 was prepared for a lead tab film 100 composed of 70 μm, 35 μm, and 45 μm, respectively. 100) did not proceed with any surface treatment.

The surface area of the film was measured after pretreatment at 80°C for 3 hr using a BET (specific surface area measuring instrument, Autosorb-iQ/MP model from Quantachrome inst.), and the measured specific surface area of the film was 92.83 m ² /g. appear. After cutting this film into a width of 5 mm and a length of 5 cm, it was heat-sealed with electrode leads by applying heat of 185° C. and pressure of 30 kgf for 5 seconds. Then, for each of the thermally bonded specimens, the thermal bonding strength between the electrode lead and the lead tab film was measured at a speed of 200 mm/min using UTM (SHIMADZU's AGS-500NX model), and the film measured in this way. The adhesive strength of was 23 N/10mm.

The lead tab film 100 according to an embodiment of the present invention has a specific surface area improved by about 30% compared to the comparative example, and as a result, the peel strength with the electrode lead increased by 40% or more.

As described above, the embodiments of the present invention have been described with specific details such as specific components and limited embodiments and drawings, but these are provided only to help a more general understanding of the present invention, and the present invention is limited to the above embodiments. It is not, and those skilled in the art can make various modifications and variations from these descriptions. Therefore, the spirit of the present invention should not be limited to the described embodiments and should not be determined, and all things equivalent or equivalent to the claims as well as the following claims belong to the scope of the present invention.

1: pouch type secondary battery 3: electrode assembly
6,7: electrode lead 20,30: battery case
100: lead tab film 110: first skin layer
130: middle layer 150: second skin layer
200: co-extrusion system 230: T-die
252: casting roller

Claims (12)

A secondary battery lead tab film that seals between a battery case of a secondary battery and an electrode lead electrically connected to an anode or a cathode of the electrode assembly of the secondary battery,
a first skin layer bonded to the electrode lead;
an intermediate layer provided on any one of the upper and lower surfaces of the first skin layer;
A second skin layer provided on one surface of the upper or lower surface of the intermediate layer facing the first skin layer and adhered to the battery case,
A film for a secondary battery lead tab, wherein at least one of the first skin layer and the second skin layer is provided to have a larger surface area or greater adhesive strength than the other skin layer.
According to claim 1,
Among the first skin layer and the second skin layer, the skin layer having a large surface area or high adhesive strength has a surface in direct contact with the electrode lead or the battery case and a surface not in contact with the secondary battery lead tab film, characterized in that .
According to claim 2,
The skin layer having a large surface area or high adhesive strength among the first skin layer or the second skin layer has irregularities formed on a surface facing the electrode lead or the battery case, or embossed and intaglio formed therein. Film for lead tabs.
According to claim 3,
Among the first skin layer and the second skin layer, the surface area of the skin layer having a large surface area or a large adhesive force is equal to the sum of the area of the relief, the area of the intaglio, and the area of the portion connecting the embossment and the intaglio. A film for a secondary battery lead tab, characterized in that.
According to claim 4,
The film for a lead tab for a secondary battery, characterized in that the embossed and intaglios are alternately formed, and the sum of the areas of the embossments is greater than the sum of the areas of the intaglios.
According to claim 5,
The film for a secondary battery lead tab, characterized in that the intaglio surface is formed at a position 0.1 to 10 μm lower than the embossed surface.
According to claim 6,
A film for a secondary battery lead tab, characterized in that the surface area of one of the embossed edges is formed to be 25 μm ² to 10,000 μm ² .
According to claim 7,
Among the first skin layer and the second skin layer, the skin layer having a large surface area or high adhesive strength is formed so that 50 to 200 embossments exist within a plane area of 100 mm ² . Film for lead tabs for secondary batteries.
According to any one of claims 1 to 8,
The first skin layer, the intermediate layer, or the second skin layer is a film for a secondary battery lead tab, characterized in that formed of polyethylene, polypropylene, copolymers or terpolymers thereof, or polyolefin resin.
A method of manufacturing the film for a lead tab for a secondary battery according to claim 9,
The method of manufacturing a film for a secondary battery lead tab, characterized in that the first skin layer, the intermediate layer, and the second skin layer are formed in a laminated state in order by co-extrusion after melting, respectively.
According to claim 10,
The first skin layer, the intermediate layer, and the second skin layer simultaneously pass through a T-die and are cooled by a casting roller so that irregularities are formed on the surface of at least one of the first skin layer and the second skin layer. and a method of manufacturing a film for a secondary battery lead tab, characterized in that the intaglio pattern is transferred.
According to claim 11,
The method of manufacturing a film for a secondary battery lead tab, characterized in that the discharge port of the T-die is formed with a width of an edge portion larger than a width of a central portion.

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