KR101638472B1 - Pacing Film for Battery Pack and Battery Pack Comprising the Same - Google Patents

Abstract

The present invention relates to an external film comprising a top coat layer (a), a transparent polymer resin layer (b) as an outermost layer, and an adhesive layer (d) adhered to a pack case as an innermost layer and having a thickness of 24 micrometers to 40 micrometers The thickness of the exterior film can be reduced while maintaining the same quality of the battery pack, thereby improving the capacity of the battery and reducing the cost, thereby improving the efficiency in the manufacturing process.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an external film for manufacturing a battery pack,

The present invention relates to an outer film for manufacturing a battery pack and a battery pack including the same, which can improve the capacity of a battery and exhibit excellent manufacturing efficiency.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

The lithium secondary battery is classified into a cylindrical battery, a prismatic battery, a pouch-type battery, and the like depending on the outer shape thereof, and may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of electrolyte.

In addition, the secondary battery is generally classified into an external battery pack (hard pack) and an internal battery pack (inner pack) according to the form in which the secondary battery is mounted on the case. Since the external battery pack forms part of the external shape of the external device to which the external battery pack is attached, it is easy to mount the external battery pack to an external device in use. However, since the case must be designed in accordance with the type of the external device, And has a problem of low compatibility.

On the other hand, the built-in battery pack has a disadvantage in that it is relatively troublesome to install the battery pack because it covers the cover forming part of the external device in the state of being mounted inside the external device, but it is easy to design, Have.

A prismatic battery and a pouch-shaped battery are often used as a battery cell that is the main body of the built-in battery pack. The prismatic battery is a battery in which an electrode assembly is built in a battery can such as aluminum or stainless steel, and the pouch-

A battery in which an electrode assembly is built in a pouch-shaped battery case of a mineral sheet. In recent years, there is an increasing demand for a pouch-type battery which is low in weight, low in cost, and easy to deform in accordance with capacity and output.

1 is an exploded perspective view of a built-in battery pack according to a prior art including a pouch-shaped battery cell.

1, the battery pack 30 includes a pouch-shaped battery cell 31 in which an electrode assembly of an anode, a cathode, and a separator, and an electrolyte are embedded in a sealed state, an inside And an upper case 33 which is coupled to the lower case 32 in which the battery cells 31 are accommodated and seals the battery cells 31. [ A double-sided tape (not shown) is interposed between the battery cell 31 and the upper and lower cases 32 and 33 to stably fix the battery cell 31 in the inner space of the cases 32 and 33. In order to further increase the coupling force between the cases 32 and 33 after the upper case 33 is coupled to the lower case 32 in which the battery cells 31 are housed and to prevent the foreign substances from entering the coupling part or the case, And wrapped with a film 35. The upper case 33 and the lower case 32 are assembled by mutual coupling by ultrasonic welding.

On the other hand, since ultrasonic welding between the upper and lower cases with a small thickness has a relatively low bonding force, it is necessary to secure a bonding force necessary for use as a battery pack and to prevent foreign substances from flowing into the battery pack It is required to constitute the outer surface of the battery pack with a film-like outer film.

In addition, the exterior film supports the fixed state of the battery cell with respect to the frame member, acts to protect the battery cell from the outside, and functions as a label indicating the configuration of the battery pack, the method of use, and the source.

As the material of such an exterior film, for example, a polymer resin material such as PE, PP, PET (polyethylene terephthalate), or a thin metal material may be used, and among them, a polymer resin material is more preferable.

Such an exterior film based on a polymer resin can be made very light and thin as compared with a metal material of a thin film, is resistant to impact, can be added to any shape, for example, a curved area, Because of its advantages, its use is expanding.

2 schematically shows a cross-sectional structure of a conventional exterior film generally used in manufacturing a battery pack.

2, the envelope film 10 includes a transparent polymer resin layer 11, a second adhesive layer 15, an ink layer 12, a metal vapor-deposited polymer resin layer 13 as an outermost layer, and a pack And a first adhesive layer 14 attached to the case are stacked in order.

A heat-shrinkable film such as a polyethylene terephthalate (PET) film in which a stretching process is mainly performed in one direction is used as the metal vapor-deposited polymer resin layer 13 as the base material of the outer film. The metal vapor-deposited polymer resin layer 13 generally has a thin metal vapor deposition layer formed on one surface. The metal vapor deposition layer basically shields the inside of the metal vapor deposition polymer layer 13, and provides a metallic luster and improves the aesthetics of the battery pack. And also enhances the rigidity of the exterior film.

The ink layer 12 formed on one surface of the metal vapor-deposited polymer resin layer 13 is generally applied by a printing method widely known using a UV curable ink.

The transparent polymer resin layer 11 as an outermost layer is required to have excellent tensile strength, weather resistance, transparency, dimensional stability, water resistance, solvent resistance, heat resistance and the like, A lot of films are being used.

A first adhesive layer 14 which is applied to the other surface of the metal vapor-deposited polymer resin layer 13 which is the base of the cover film 10 and serves to attach the cover film 10 to the outer surface of the pack case, The second adhesive layer 15 formed on the transparent polymer resin layer 11 for bonding the first adhesive layer 12 to the second adhesive layer 15 is a layer coated with a known adhesive or a pressure sensitive adhesive, It is also added in the form of a layer.

In such an exterior film, it is possible to improve the capacity and quality of the battery in comparison with the same standard, and to prevent the battery pack from being stably coated on the outer surface of the battery pack due to the adhering process to the pack case or the occurrence of the curling phenomenon in the attached state There is a high need for technology.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments. As described later, when using an exterior film including predetermined layers, the thickness of the exterior film is reduced while maintaining the same quality of the battery pack The capacity of the battery can be improved and the cost can be reduced, thereby increasing the efficiency in the manufacturing process. Thus, the present invention has been accomplished.

Therefore, the covering film according to the present invention comprises a top coating layer (a), a transparent polymer resin layer (b) as an outermost layer, and an adhesive layer (d) attached to the pack case as an innermost layer, Of the thickness.

The external film according to the present invention can maximize the effect by organically bonding the constituent elements. Therefore, when the battery pack is used, the thickness of the external film is further reduced in response to the demand for reduction in weight and thickness of the battery pack, The capacity of the contrast cell can be improved.

That is, conventionally, an external film having a thickness of 45 micrometers or more has been used. However, the thickness of the external film according to the present invention may be 24 to 40 micrometers, more specifically, 26 to 33 micrometers, More specifically, the thickness of the external film can be reduced to a maximum of 40 micrometers or less, which can solve the problem of adhering to the pack case and the curling phenomenon that may occur in the attached state. When the thickness of the exterior film is less than 24 micrometers, the durability against external impact may be weakened, and efficiency in the manufacturing process may deteriorate.

On the outer surface of the top coat layer (a), a print layer (a ') for selectively displaying information may be additionally provided. This printing layer a 'can be used together with the colored coating layer c to be described below when information is to be displayed. In some cases, the printing layer a' or the colored coating layer c can be used alone have.

For example, desired information contents can be selectively displayed on the print layer (a ') to display information. In order to more effectively express the contents of the label of the pack case, thickness of the external film, Can be displayed in various forms in consideration of the above.

The printing layer (a ') may be formed by applying ink onto a topcoat layer (a) or a predetermined paper by using a known printing method such as relieflower printing, silk screen printing, or gravure printing, And the thickness of this print layer (a ') may vary depending on the use of the label, but may be, for example, 4 micrometers to 6 micrometers, and in particular 5 micrometers. If the thickness of the print layer (a ') is less than 4 micrometers, the efficiency of the manufacturing process is lowered. If the thickness of the print layer (a') is greater than 6 micrometers, the thickness of the external film becomes too thick.

The printing ink of the printing layer (a ') may have a chroma of 4 degrees to 6 degrees, and more specifically, a chroma of 5 degrees. Such printing inks are suitably used in accordance with the printing method, and any kind of conventional solvent-based or solvent-free ink can be used. In general, air-hardening (oxidative polymerization), UV-hardening, and electron beam hardening Ink may be used.

As the air-curing ink, a so-called drying oil such as tung oil, linseed oil, and boiling oil is used as a binder and a curing catalyst, a dye for ink, a pigment and the like are used as a main component. Examples of the UV curable ink include a photosensitizer, a photopolymerization initiator, a dye for ink, and a pigment as main components, using acrylic monomer, acryl oligomer, polyester acryl, epoxy acryl, polyurethane acryl or the like as a binder, And UVA series (trade name) of Advance. Examples of the electron beam curable ink include an acrylic monomer, an acryl oligomer, a polyester acryl, an epoxy acryl, a polyurethane acryl, and the like as a binder and a dye for ink and a pigment are blended. In addition, even when a sensitizer and a photopolymerization initiator are not blended, There are features to cure by.

In the present invention, the top coating layer (a) may be, for example, a metal coating layer of a thin film. Such a metal coating layer exhibits shielding properties and imparts a high aesthetic and high metallic luster. In some cases, it has a function of preventing the inflow or outflow of foreign substances such as gas and moisture, and a function of improving the strength of the pack case. Generally, aluminum, nickel or silver can be used. The metal coating layer can be appropriately selected within a range not to impair the mechanical strength, handling property of the label, etc., and can be formed by vacuum vapor deposition, It is possible.

The thickness of the top coating layer (a) may be from 0.5 micrometer to 2 micrometers, and more specifically from 1 micrometer to 1.5 micrometer.

When the thickness of the top coat layer (a) is less than 0.5 micrometer, it does not exhibit the desired characteristics, and when the thickness of the top coat layer (a) is larger than 2 micrometer, the thickness of the outer film may become thick.

In one example, in order to prevent the problem of the electrochemical reaction of the surface of the battery can and the metal of the surface of the electrode terminal due to the metal coating layer being eluted by external impact, May be preferably used, and as such metal, silver (Ag) particles may be included.

The transparent polymer resin layer (b) transmits information displayed on the colored coating layer (c) so as to be exposed to the outside, and covers the pack case to protect the battery pack from the outside. Although a transparent resin such as a vinyl-based, acrylic-based or phenol-based resin can be used for the transparent polymer resin layer (b), it is required to have excellent resistance to external environment and thus to have excellent tensile strength and weatherability relative to thickness, In terms of giving high gloss, a PET film can be preferably used. The thickness of the transparent polymer resin layer (b) can be appropriately selected within a range not to impair the mechanical strength, and in detail, it may be from 11 micrometers to 15 micrometers, more specifically from 12 micrometers to 14 micrometers, More specifically, it may be 13 micrometers. If the thickness of the transparent polymer resin layer (b) is less than 11 micrometers, the efficiency of the manufacturing process may deteriorate. If the thickness of the transparent polymer resin layer (b) is greater than 15 micrometers, It is not desirable because it can be difficult.

The colored coating layer (c) is not particularly limited as long as it is a color capable of clearly displaying information, and may be formed of a black coating layer or a white coating layer, which is generally used as a color of a label. . The thickness of the colored coating layer (c) may be, for example, 1 to 3 micrometers.

Such a structure can be used in various combinations of the colors of the colored coating layer (c) and the printing layer (a ') so that the contents of the label can be expressed more effectively and variously, and in some cases, ') May be used.

An adhesive layer (d) attached to the pack case is bonded to one surface of the colored coating layer (c). The type of the adhesive layer (d) is not limited as long as it can be coated with known pressure sensitive adhesives or adhesives such as rubber, acrylic, and resin, and can be adhered without damaging the battery pack. Generally, a heat-sensitive adhesive is used, which is an adhesive whose surface after application and drying does not melt at room temperature, but which exhibits adhesiveness upon heating, and may be a mixture of one or more heat-melt resins and various additives. The hot molten resin may include an acrylic acid ester, an acrylic acid copolymer, an ethylenic copolymer, or a natural rubber as a main material and a tackifier. The tackifier may improve adhesiveness. Examples of the tackifier include resin acids such as rosin resins and dimers, terpene resins, terpene-phenol resins, and petroleum resins. Among them, a rosin-based resin and a terpene-based resin are preferable. The tackifier may be used alone or in combination of two or more.

In one example, in order to further improve the adhesive force with the pack case and efficiently perform the attaching operation of the cover film, the adhesive layer (d) and the pack case may be formed in an embossed structure by a mechanical or chemical method . For example, since the emulsion-type heat-sensitive adhesive agent is a dispersion liquid in which solid components are dispersed in a liquid state in a liquid, fine unevenness due to particles can be formed on the coated surface of the adhesive.

The thickness of the adhesive layer (d) can be appropriately selected in consideration of adhesiveness, appearance and cost, and if the thickness of the adhesive layer (d) is too thick, cohesive failure occurs and the required adhesive strength is not obtained , Whereas if it is too thin, a sufficient tackiness can not be obtained, it can have a thickness of from 8 micrometers to 13 micrometers, and more specifically from 10 micrometers to 13 micrometers, and more specifically, And can have the desired adhesive force without air bubbles during the bonding process

The initial adhesive strength of the adhesive layer (d) may be 800 g or more based on SUS, specifically, 1000 g or more, and more specifically, 1000 g or more and 1500 g or less.

SUS is an abbreviation of "steel use stainless" used in Japanese Industrial Standards (JIS), and is a term widely known in the art.

The outer surface of the adhesive layer (d) may be further provided with an embossed paper (e) in an embossed shape for preserving the adhesive force of the adhesive layer (d) before attaching to the pack case. As the release paper (e), a polyolefin-based film having excellent releasability, a silicone-coated paper, or the like can be used.

In the present invention, the embossed paper (e) of the emboss type is adhered to the adhesive layer (d) having the above-described structure, so that the phenomenon of the curling of the release paper and the phenomenon of the embossed marks can be minimized.

The covering ratio of the cover film according to the present invention may be 0.200% to 0.800% at a wavelength of 800 nm based on white polyethylene terephthalate (PET), more specifically 0.400% to 0.600% Lt; / RTI > This concealment rate is a unique property that each constituent element of the covering film according to the present invention is formed by organic bonding.

Further, the present invention provides a battery pack in which the above-mentioned casing film is attached to the outer surface of the pack case.

The battery pack according to the present invention may have various forms, and preferably, the pouch type battery cell may be embedded in a pack case. That is, the pack case is composed of an upper case and a lower case, and after the pouch type battery cell is housed in the lower case, it is combined with the upper case by ultrasonic welding or the like, and then coated with an external film.

The detailed structure of the battery pack and the manufacturing method thereof and the like are well known in the art, and a detailed description thereof will be omitted in this specification.

As described above, the external film according to the present invention minimizes the thickness, and the capacity of the battery pack manufactured using the battery pack can be relatively increased, and the cost can be reduced. In addition to the process of attaching the pack case, It is possible to prevent the curling phenomenon even after a considerable time has elapsed since the attachment, so that the efficiency in the manufacturing process can be maximized.

1 is an exploded perspective view of a built-in battery pack according to a related art including a pouch-shaped battery cell;
2 is a cross-sectional schematic diagram of a prior art envelope film;
Figure 3 is a schematic cross-sectional view of an envelope film, according to one embodiment of the present invention;
4 is a cross-sectional schematic diagram of an envelope film further comprising a printing layer and a release paper in the structure of Fig. 3, according to another embodiment of the present invention;
5 is a schematic cross-sectional view of an envelope film further comprising a colored coating layer in the structure of FIG. 4, according to another embodiment of the present invention;
6 is a photograph showing the results of the print abrasion resistance test of the cell with the exterior film according to Example 1;
7 is a photograph showing the results of the chemical resistance test in the printed battery of the cell with the exterior film according to Example 1;
8 is a photograph showing the S / N abrasion resistance test result of the battery with the exterior film according to Example 1;
9 is a photograph showing the results of a pressure-sensitive adhesive transfer test of a battery with a casing film according to Example 1;
10 is a photograph showing a result of a high-temperature and high-humidity test of a battery with a casing film according to Example 1; And
11 is a graph showing a test result of a concealment rate measurement test of a cell to which a casing film according to the first embodiment is attached.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

FIG. 3 schematically shows a cross-sectional structure of the cover film 100 according to one embodiment of the present invention.

3, a top film layer (a) 110 is disposed as an outermost layer, a transparent polymer resin layer (b) 130, and an adhesive layer (d: 140) ) Are stacked in this order.

The top coating layer (a) 110 may be formed of, for example, a thin film containing silver particles on one side

The transparent polymer resin layer (b) 130 is made of, for example, a 13-micrometer transparent PET film having high tensile strength and weather resistance capable of stably protecting the pack case (not shown) against the external environment.

The adhesive layer (d) 140 has a thickness of, for example, 11 micrometers and has adhesiveness because it forms the inside of the envelope film as a portion that engages with a battery pack (not shown).

4 shows a cross-sectional schematic diagram of an envelope film 102 which further includes a print layer (a ') 150 and an embossed release paper (e) 120 in the structure of FIG.

4, a 5 micrometer printed layer (a ') 150 is laminated on the outer surface of a top coating layer (a) 110, and an embossed release paper (e: 120) 3, except that it is placed on the outer surface of the housing.

That is, the print film a ': 150, the top coat layer a: 110, the transparent polymer resin layer b: 130, the adhesive layer d 140, and the embossed paper e : 120) are stacked in this order.

The print layer (a ') 150 selectively displays information.

The embossed paper (e) 120 in the embossed form is made of, for example, a polyolefin-based film and preserves the adhesive strength of the adhesive layer before attachment to the pack case.

FIG. 5 is a schematic cross-sectional view showing a color coating layer (c: 160) for displaying information between a transparent polymer resin layer (b) 130 and an adhesive layer (d) And is an outer film 104 that is formed of a film.

Such an exterior film can have a thickness of 30 micrometers, which can improve manufacturing processability while minimizing the thickness of the exterior film.

≪ Example 1 >

An exterior film according to the above-described FIG. 3 was produced.

<Experimental Example>

The test for the exterior film according to Example 1 was carried out as follows.

<Print Abrasion Resistance Test>

After attaching the outer film to the battery cell, the rubber eraser was reciprocated 20 times on the surface of the outer film to measure whether or not the letters printed on the print layer of the outer film were erased.

According to FIG. 6, it can be seen that there is almost no influence on the printed characters in both of the tests (a and b), so that the cover film according to the present invention has excellent print abrasion resistance.

<Print chemical resistance test>

After attaching the outer film to the battery cell, methyl alcohol was applied to the surface of the outer film, and the rubber eraser was reciprocated 20 times to measure whether or not the letters printed on the print layer of the outer film were erased.

According to FIG. 7, it can be seen that there is almost no influence on the characters printed in both of the tests (a and b), so that the cover film according to the present invention has excellent chemical resistance in printing.

<S / N Abrasion Resistance Test>

After attaching the cover film to the battery cell, the rubber eraser was reciprocated 250 times on the surface of the cover film to measure whether or not the characters printed on the print layer of the cover film were erased.

According to FIG. 8, it can be seen that there is almost no influence on the printed characters in both of the tests (a and b), and therefore it can be seen that the cover film according to the present invention is excellent in the S / N abrasion resistance test.

<Adhesion Test>

After attaching the outer film to the battery cell, the initial adhesion was measured 3 times (samples a, b, c) and the average value was calculated. The average value was measured by using a 2 kg compression rubber roller at a speed of 300 mm / After a lapse of 30 minutes, the sample was pulled 180 degrees to measure the late adhesive force 3 times (samples a, b, c), and the average value was calculated.

Battery cell Elapsed time Result (kg) Battery cell Elapsed time Result (kg) Sample a 30 ' 1.1 Sample a 30 ' 1.2 Sample b 30 ' 1.2 Sample b 30 ' 1.2 Sample c 30 ' 1.1 Sample c 30 ' 1.1 Initial adhesion average value 1.12 Late adhesion average value 1.40

&Lt; Tensile transfer test >

When the exterior film was attached to the battery cell using a load of 2 kg and then peeled off after the elapse of 96 hours, the transfer state of the pressure-sensitive adhesive was confirmed and is shown in FIG.

According to FIG. 9, it can be confirmed that even when the exterior film is removed, the adhesive does not transfer to the surface of the battery cell.

<High temperature and high humidity test>

(A) When the exterior film was attached to the battery cell and then peeled off after a lapse of 96 hours under conditions of a temperature of 65 ° C and a humidity of 90%, (b) the lifting of the label was confirmed and shown in FIG.

According to FIG. 10, it can be seen that lifting of the label hardly occurs.

<Concealment rate measurement test>

After the outer film was attached to the battery cell, the release film of the outer film was removed, and the cover ratio was measured by increasing the wavelength up to 800 nm on the basis of white polyethylene terephthalate (PET) .

According to FIG. 11, it can be seen that the light transmittance is 0.571% at a wavelength of 800 nm.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (17)

Characterized in that it comprises a top coating layer (a), a transparent polymer resin layer (b) as an outermost layer and an adhesive layer (d) adhering to the pack case as an innermost layer and having a thickness of 26 micrometers to 33 micrometers film. delete The exterior film according to claim 1, further comprising a printed layer (a ') on the outer surface of the topcoat layer (a) for selectively displaying information. 4. The sheathing film according to claim 3, wherein the thickness of the print layer (a ') is 4 micrometers to 6 micrometers. The exterior film according to claim 3, wherein the printing layer (a ') has a chroma of 4 to 6 degrees. The facing film of claim 1, wherein the top coating layer (a) is made of aluminum, nickel, or silver. 4. The sheathing film according to claim 3, wherein the top coating layer (a) has a thickness of 0.5 micrometer to 2 micrometers. The sheathing film according to claim 1, wherein the transparent polymer resin layer (b) is a transparent PET film of 11 micrometers to 15 micrometers. The exterior film according to claim 1, further comprising a colored coating layer (c) interposed between the transparent polymer resin layer (b) and the adhesive layer (d). The exterior film of claim 9, wherein the colored coating layer (c) is a white or black coating layer of 1 micrometer to 3 micrometers. The exterior film of claim 10, wherein the colored coating layer (c) is a white coating layer. The sheeting film of claim 1, wherein the adhesive layer (d) is between 8 micrometers and 13 micrometers. The exterior film according to claim 1, wherein the adhesive strength of the adhesive layer (d) is 800 g or more based on SUS. The exterior film according to claim 1, wherein an embossed release paper (e) is attached to the outer surface of the adhesive layer (d). 15. The covering film according to claim 14, wherein the release paper (e) is a polyolefin-based film and / or a silicon-coated paper. The covering film according to claim 1, wherein the cover film has a concealment ratio of 0.200 to 0.800% at a wavelength of 800 nm based on white polyethylene terephthalate (PET). The battery pack according to claim 1, wherein the outer film is attached to an outer surface of the battery pack case.

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