KR100870458B1 - Packing Film for Battery Pack and Method for Preparation of the Same - Google Patents

Abstract

The present invention is an outer film used in the manufacture of a battery pack, a high tensile strength and weather resistance transparent polymer resin layer (a) as the outermost layer, an ink layer (b) for displaying information, a polymer resin layer for shielding the inside ( c) and an adhesive layer (d) attached to the pack case as the innermost layer, wherein the transparent polymer resin layer (a) and the shielding polymer resin layer (c) are heated in a state where the ink layer (c) is partially interposed. Provided is an exterior film composed of mutual bonding by fusion, a method of manufacturing the same, and a battery pack using the same. This outer film significantly reduces the thickness, ultimately improves the battery capacity, prevents the curling phenomenon of the outer film by bonding by heat fusion, and further separate or warp the outer film and the pack case due to external shock and vibration, etc. The phenomenon can be prevented and structural stability can be maintained even at the time of temperature rise or volume expansion by gas generation.

Description

Packing film for battery pack and method for preparation of the same

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

2 is a schematic cross-sectional view of an exterior film according to the prior art;

3 is a schematic cross-sectional view of an exterior film according to one embodiment of the present invention.

<Description of Major Symbols in Drawing>

10, 100: exterior film

11, 110: transparent polymer resin layer

12, 120: ink layer

13, 130: polymer resin layer

14, 140: adhesive layer

The present invention relates to an outer film for battery pack manufacturing, a so-called label, and more particularly, a transparent polymer resin layer (a) having high tensile strength and weather resistance as an outermost layer, an ink layer (b) for displaying information, and an interior thereof. A polymer resin layer (c) for shielding and an adhesive layer (d) attached to the pack case as the innermost layer, wherein the transparent polymer resin layer (a), the ink layer (b) and the polymer resin layer for shielding (c) The present invention relates to a battery pack manufacturing exterior film, a manufacturing method of the exterior film, and a battery pack attached to an outer surface of a case using the exterior film. The exterior film according to the present invention may be manufactured in a thinner thickness according to the tendency of the small size of the battery pack, it is possible to prevent the curling (curling) that can be caused when attached to the pack case.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches have been conducted and commercialized and widely used for lithium secondary batteries with high energy density and discharge voltage. It is used.

Lithium secondary batteries are largely classified into cylindrical batteries, square batteries, pouch-type batteries, and the like according to their appearance, and may be classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, and the like depending on the type of electrolyte.

In addition, according to the form in which the secondary battery is mounted in the case, it is generally classified into an external battery pack (hard pack) and an internal battery pack (inner pack). The external battery pack has a merit that it forms an external part of the external device to which it is mounted, so it is easy to be mounted on the external device when it is used, but it is relatively expensive because the case must be designed according to the type of the external device with the battery cell embedded therein. There is a less compatible problem.

On the other hand, since the built-in battery pack covers a cover that forms part of the external device in a state of being mounted inside the external device, mounting is relatively cumbersome, but it is easy to design, inexpensive, and has compatibility advantages. .

As a battery cell of a built-in battery pack, a square battery and a pouch-type battery are frequently used. A rectangular battery is a battery in which an electrode assembly is embedded in a battery can such as aluminum or stainless steel, and a pouch type battery is a battery in which an electrode assembly is embedded in a pouch type battery case of an aluminum laminate sheet. In recent years, there is an increasing demand for pouch-type batteries which are light in weight, low in price, and easily deformable according to capacity and output.

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

Referring to FIG. 1, the battery pack 30 may include a pouch-type battery cell 31 and a battery cell 31 in which the electrode assembly of the positive electrode, the negative electrode, and the separator and the electrolyte are sealed. A lower case 32 having a space and an upper case 33 coupled to the lower case 32 in which the battery cells 31 are housed are sealed to the battery cells 31. In addition, a double-sided tape 34 is interposed between the battery cells 31 and the upper and lower cases 32 and 33 to stably fix the battery cells 31 in the spaces inside the cases 32 and 33. After the upper case 31 is coupled to the lower case 32 in which the battery cells 31 are accommodated, the outer case 31 further enhances the coupling force between the cases 31 and 32 and prevents foreign substances from entering the coupling part or the case. Wrapped with a film 35. The upper case 33 and the lower case 32 are assembled by mutual coupling by ultrasonic welding.

Ultrasonic welding between the thin upper and lower cases is relatively inferior in bonding force, thereby securing the bonding force necessary for use as a battery pack, and preventing the inflow of foreign matter into the battery pack through the coupling part or therethrough. It is desired to apply the outer surface of the battery pack with the outer packaging film.

In addition, the exterior film supports the fixing state of the battery cell to the frame member, and serves to protect the battery cell from the outside, and also serves as a label for displaying the configuration and use method, source, etc. of the battery pack.

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

The exterior film based on such a polymer resin has various advantages such as being extremely light and thin compared to a thin metal material, being resistant to impact, being able to be molded into an arbitrary shape, for example, curved surface and increasing transparency. Its use is getting wider.

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

Referring to FIG. 2, the exterior film 10 is packed as the outermost layer with a transparent polymer resin layer 11, a second adhesive layer 15, an ink layer 12, a metal deposited polymer resin layer 13, and an innermost layer. The first adhesive layer 14 attached to the case is laminated in order.

As the base material of the exterior film, the polymer resin layer 13 is mainly a heat-shrinkable film such as a polyethylene terephthalate (PET) film which has been stretched in one direction.

The metal deposition polymer resin layer 13 generally has a metal deposition layer formed on one side of a thin film, and the metal deposition layer basically serves to shield the inside, to impart metal gloss and improve aesthetics of the battery pack. It also serves to increase the rigidity of the exterior film.

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

As the outermost layer of the transparent polymer resin layer 11 serves to protect the battery from the outside, excellent tensile strength and weather resistance, transparency, dimensional stability, water resistance, solvent resistance, heat resistance, etc. to thickness are required, and polyester, in particular, transparent PET Films are used a lot.

The first adhesive layer 14 and the ink layer 12, which are formed on the other surface of the polymer resin layer 13, which is a base material of the exterior film 10, serve to attach the exterior film 10 to the outer surface of the pack case. The second adhesive layer 15 formed on the transparent polymer resin layer 11 is a layer coated with a known adhesive or a pressure-sensitive adhesive to bond the adhesive, and the second adhesive layer 15 may be an embossed layer in some cases. Sometimes added in the form of.

In such an exterior film, the thickness of the battery pack is further reduced in response to the demand of lightening or thinning the battery pack, thereby ultimately improving the capacity of the battery compared to the same standard, and also the curling phenomenon in the attaching process or the attached state to the pack case. It is very important to prevent this from happening stably applied to the outer surface of the battery pack.

In order to prevent curling in such an exterior film, Japanese Patent Application Laid-Open No. 2005-183093 discloses a heat shrinkable film having a heat shrinkage of 10% or more in the main stretching direction, and an adhesive layer having 10 ethylene copolymers and total solids. Techniques for using emulsion type thermal adhesives comprising ˜30% tackifier have been presented. However, the exterior film produced by the above method is relatively expensive, it is difficult to reduce the thickness compared to the conventional exterior film, it was confirmed that problems such as curling phenomenon can not be solved.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

The inventors of the present application after various experiments and in-depth studies, the transparent polymer resin layer and the shielding polymer resin layer by heat fusion without using a separate adhesive layer in the state of interposing the ink layer during the manufacture of the outer film By mutually reducing the thickness of the outer film, it is possible to ultimately improve the battery capacity, prevent the curling phenomenon of the outer film by thermal fusion, furthermore, the outer film and pack case The present invention has been completed to prevent the phenomenon of dissociation or twisting and to maintain structural stability even when the temperature rises or the volume expansion due to gas generation.

Accordingly, the outer film for manufacturing a battery pack according to the present invention includes a transparent polymer resin layer (a) having high tensile strength and weather resistance as an outermost layer, an ink layer (b) for displaying information, and a polymer resin layer for shielding the inside ( c) and an adhesive layer (d) attached to the pack case as the innermost layer, wherein the transparent polymer resin layer (a) and the shielding polymer resin layer (c) are partially interposed with the ink layer (b). It consists of mutually bonding by heat fusion.

The exterior film for manufacturing a battery pack of the present invention omits the adhesive layer inserted between the ink layer and the transparent polymer resin layer of the outermost layer, and mutually couples the two polymer resin layers by thermal fusion in the state where the ink layer is partially interposed. By reducing the thickness of the exterior film by about 40% or more, the battery capacity is relatively thin and the battery capacity can be increased, and also the curling phenomenon of the exterior film can be prevented and applied to the pack case stably.

The polymer resin layer (c) as a substrate of the exterior film is required to have excellent tensile and durability, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate polyester resins such as (polydethylene naphthalate; PEN), polyolefin resins such as polyethylene and polypropylene, polystyrene resins such as polystyrene, polyvinyl chloride resins, and polyvinylidene chloride resins. These materials can be used individually or in mixture of 2 or more types. Among them, polyester resins, polystyrene resins, and polyvinyl chloride resins are preferable, and poly PET having excellent strength and toughness is particularly preferable.

Such a polymer resin layer may preferably be composed of a heat-shrinkable film subjected to an stretching treatment. The heat-shrinkable film may be formed by uniaxial stretching or biaxial stretching, and by this stretching treatment, the label substrate has orientation and large heat shrinkability in the stretching direction. Therefore, when the film is wound around the circumference of the pack case, it may exhibit high adhesion due to large shrinkage in the circumferential direction of the battery.

A thin metal coating layer is formed on one or both surfaces of the polymer resin layer, and the metal coating layer exhibits a shielding property and gives a high metallic luster with excellent psychological properties. In some cases, it also functions to prevent inflow or leakage of foreign substances such as gas and moisture, and to improve the strength of the pack case. In general, aluminum, nickel, or silver may be used, and the metal coating layer may be formed by, for example, vacuum deposition to a thickness of about 0.01 to 0.1 μm, or may be laminated as a separate metal layer.

In one preferred embodiment, the metal coating layer is eluted by an external impact to prevent the electrochemical reaction with the metal on the surface of the battery outer can or the electrode terminal surface, an electric potential equal to or higher than that of nickel, which is mainly employed in the battery complex. A metal having a compound may be preferably used, and it is particularly preferable that a silver (Ag) layer is coated on one or both surfaces of the polymer resin layer (c).

The thickness of such a polymer resin layer can be appropriately selected within a range that does not impair mechanical strength, handleability of a label, or the like, preferably 10 to 200 µm, and more preferably 20 to 30 µm.

An ink layer for displaying information is stacked on one surface of the polymer resin layer. In the present invention, "the ink layer (b) is partially interposed between the transparent polymer resin layer (a) and the shielding polymer resin layer (c)" means that the ink is a polymer for the purpose of displaying information. By coating the resin layer (c) in the form of letters, figures, or the like, there is a portion where ink is not applied, and the transparent polymer resin layer (a) and the shielding polymer resin layer (c) are in contact with each other at such an uncoated portion. That means you can. Therefore, such an uncoated area of ink enables direct thermal fusion of the transparent polymer resin layer and the shielding polymer resin layer.

The ink layer (b) may be formed by applying an ink on the polymer resin layer using a known printing method such as relief rotary printing, silk screen printing, gravure printing, or the like, and curing the same. The thickness of the printing ink layer may vary depending on the use of the label, but is usually about 0.5 to 15 μm.

The ink for the printing of the ink layer may be any kind of conventional solvent type, solvent free ink, such as ink according to the printing method, and is generally easy to handle, such as air curing type (oxidation polymerization type), UV curing type, And electron beam curable inks are used.

As the air curable ink, a so-called dry oil such as tung oil, linseed oil or voile oil is used as a binder, and a curing catalyst, a dye for ink and a pigment are mainly used as the UV curable ink, and an acrylic monomer, an acrylic oligomer, It is made of polyester acrylic, epoxy acrylic, polyurethane acrylic, etc. as a binder, and is mainly composed of a photosensitizer, a photopolymerization initiator, a dye pigment for ink, and specific examples include Seiko Advans' UVA series (trade name). Examples of the electron beam curable ink include acrylic monomers, acrylic oligomers, polyester acrylics, epoxy acrylics, polyurethane acrylics, etc. as binders, and dyes and pigments for inks are blended. Although there is a characteristic to cure, UV curable inks are generally used as electron beam curable inks. .

In one preferred embodiment, in order to prevent the heat-sensitive adhesive layer is activated or the polymer resin layer (c) is damaged by heat during heat shrinkage, the UV curable ink having excellent heat resistance may be used.

As the outermost layer, the transparent polymer resin layer (a) is laminated on the ink layer to protect the ink layer from the outside, while transmitting the information represented by it so that it can be seen from the outside, and the metal is eluted from the metal coating layer, so that the battery pack and the electric It also serves to prevent chemical contact. Vinyl, acrylic or phenol-based transparent resin may be used as the transparent polymer resin layer, but should have excellent resistance from the external environment, it is necessary to have excellent tensile strength and weather resistance to thickness, and protect the ink layer and high gloss In terms of imparting a PET film may be preferably used. Such transparent polymer resin layer thickness can be suitably selected in the range which does not impair mechanical strength, Preferably it is 10-200 micrometers, More preferably, it is 10-20 micrometers.

The transparent polymer resin layer is bonded to each other by thermal fusion with the transparent polymer resin layer in a state where the ink layer is interposed, and the heat fusion is achieved by applying heat at least partially melting.

Therefore, there is no need to stack an adhesive layer separately in order to bond the ink layer and the transparent polymer resin layer, so that the thickness of the exterior film can be reduced, thereby ultimately increasing the battery capacity. In addition, it is possible to prevent the curling phenomenon of the outer film by being bonded by the thermal fusion method, and to prevent the phenomenon such as separation or warpage of the battery pack and the outer film due to external shock and vibration, etc. Structural stability can be maintained even when volume expansion occurs.

The other surface of the polymer resin layer is bonded to the adhesive layer (d) attached to the pack case as the innermost layer. The adhesive layer may be coated with a known adhesive or an adhesive such as rubber, acrylic, resin, and the like, as long as the adhesive layer may be bonded without damaging the battery pack. In general, a thermal adhesive is used, which is an adhesive in which the adhesive surface after application and drying does not melt at room temperature, but exhibits adhesiveness upon heating, and may be a mixture of one or more hot melt resins and various additives. The hot melt resin may be an acrylic ester, an acrylic acid copolymer, an ethylene copolymer, or a natural rubber, and may include a tackifier. The tackifier improves adhesiveness, and examples thereof include rosin resins, resin acids such as dimers, terpene resins, terpene resins, terpene-phenol resins, and petroleum resins. Among them, rosin-based resins and terpene-based resins are preferable. A tackifier can be used individually or in combination of 2 or more types.

In one preferred example, an embossed structure can be formed by a mechanical or chemical method on the contact surface between the adhesive layer and the pack case in order to further improve the adhesion to the pack case and to efficiently attach the outer film. For example, since an emulsion type thermal adhesive agent is a dispersion liquid in which solid content was disperse | distributed in the liquid state in a liquid state, the coating surface of an adhesive agent can form the micro unevenness | corrugation resulting from a particle | grain.

The thickness of the adhesive layer can be appropriately selected in consideration of adhesiveness, appearance, cost, and the like. If the thickness of the adhesive layer is too thick, there is a problem in that cohesive failure occurs and the required adhesive strength cannot be obtained. When thin, sufficient adhesiveness cannot be obtained, and therefore it preferably has a thickness of 20 to 30 mu m.

Release paper for preserving the adhesive force of the adhesive layer may be additionally attached to the outer surface of the adhesive layer prior to attachment to the pack case. As the release paper, a polyolefin-based film, a silicone coated paper, or the like having excellent peelability can be used.

The present invention also provides a method of manufacturing the exterior film,

Partially forming an ink layer (b) for displaying information on the polymer resin layer (c) for shielding the inside;

Bonding the high tensile strength and weather resistance transparent polymer resin layer (a) to the shielding polymer resin layer (c) by thermal fusion as the outermost layer with the ink layer (b) partially interposed therebetween; And

Further forming an adhesive layer (d) attached to the pack case as an innermost layer on the shielding polymer resin layer (c);

It is configured to include.

An ink layer is formed on a polymer resin layer on which a metal deposition layer is formed as a base material of an exterior film by a known printing method, and in the state where the ink layer is interposed, a high tensile strength and weather resistance transparent polymer number as an outermost layer The ground layer is mutually bonded to the shielding polymer resin layer by thermal fusion. Then, an adhesive layer attached to the pack case as an innermost layer is further formed on the shielding polymer resin layer.

In addition, the present invention provides a battery pack having the outer film attached to the outer surface of the pack case.

The battery pack according to the present invention may be in various forms, and preferably, may be a form in which a pouch-type battery cell is embedded in a pack case. That is, the pack case is composed of an upper case and a lower case, the pouch-type battery cell is accommodated in the lower case and then combined with a method such as the upper case and ultrasonic fusion, it can be produced by applying an outer film.

Since a more detailed structure of the battery pack and a method of manufacturing the same are known in the art, a detailed description thereof will be omitted herein.

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

Figure 2 is a schematic diagram of a cross-sectional structure of the exterior film according to an embodiment of the present invention. The following ink layer is only partially formed on the polymer resin layer, but is represented as a separate layer for convenience of description.

Referring to these drawings, the exterior film 100 includes the polymer resin layer 130 in which the transparent polymer resin layer 110 is positioned as the outermost layer and the metal deposition layer 132 is formed as the base of the exterior film 100. An ink layer 120 for displaying information is coated on one surface of the structure, and the adhesive layer 140 attached to the pack case as the innermost layer is laminated on the opposite surface of the polymer resin layer (c). That is, the transparent polymer resin layer 110, the ink layer 120, the polymer resin layer 130, and the adhesive layer 140 are laminated in order from the outside.

Since the transparent polymer resin layer 110 is located on the outer surface of the outer film 100, a high tensile strength and weather resistance that can stably protect the pack case (not shown) against the external environment is required, and the outer part made of PET The coating layer 110 can satisfy this requirement.

Since the ink layer 120 is formed only partially as a layer for displaying information on the composition, usage, source, etc. of the battery pack, the transparent polymer resin layer 110 and the polymer resin layer 130 are excluded from the ink layer. ) Are brought into contact with each other by thermal fusion.

The polymer resin layer 120 serves to block the inside, and one or both surfaces of the polymer resin layer 120 are coated with a metal (not shown) having a high metallic luster and a barrier property to block gas, moisture, and the like including air. . The metallic coating is preferably coated with silver (Ag) in the form of a thin film.

Since the emboss adhesive layer 130 forms an inner side of the exterior film as a portion to be bonded to the battery pack 100, the emboss adhesive layer 130 has adhesiveness.

Although the embodiments of the present invention have been described above with reference to the drawings, those skilled in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the exterior film according to the present invention can omit the adhesive layer by mutually bonding the transparent polymer resin layer and the exterior film base layer by thermal fusion in the state where the ink layer is partially interposed, thereby reducing the thickness of the exterior film It can greatly reduce the battery capacity and ultimately improve the battery capacity, prevent the curling phenomenon of the outer film by thermal fusion, further prevent the phenomenon such as separation or warp of the outer film and the pack case due to external shock and vibration, Structural stability can be maintained even upon rise or volume expansion by gas generation.

Claims (7)

As the outermost layer, the transparent polymer resin layer (a) of the PET film, the ink layer (b) for displaying information, the polymer resin layer (c) for shielding the inside as the base material of the outer film, and the innermost layer adhere to the pack case. A battery pack having a bonding layer (d), wherein the transparent polymer resin layer (a) and the shielding polymer resin layer (c) are bonded to each other by thermal fusion in a state where the ink layer (b) is partially interposed. Exterior film for manufacturing. The exterior film of claim 1, wherein the polymer resin layer (c) is a PET film having a thickness of 20 to 30 μm and coated with silver on one or both surfaces. The exterior film of claim 1, wherein the ink layer (b) is a UV curing ink layer. The exterior film of claim 1, wherein the transparent polymer resin layer (a) is 10 to 20 μm thick. The exterior film according to claim 1, wherein the adhesive layer (d) has a thickness of 20 to 30 µm and is formed in an embossed shape. Forming an ink layer (b) for displaying information on the polymer resin layer (c) for shielding the inside; Bonding the transparent polymer resin layer (a) of the PET film to the shielding polymer resin layer (c) by thermal fusion as the outermost layer with the ink layer (b) partially interposed therebetween; And Further forming an adhesive layer (d) attached to the pack case as an innermost layer on the shielding polymer resin layer (c); Method of manufacturing an outer film for manufacturing a battery pack according to claim 1 comprising a. A battery pack having the outer film according to any one of claims 1 to 6 attached to an outer surface of a pack case.

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