Pouch film laminate and secondary battery

Abstract

The present invention relates to a pouch film laminate and a secondary battery including a pouch-type battery case manufactured using the same. The pouch-type film laminate according to the present invention includes a base layer, a gas barrier layer, and a sealant layer laminated in this order, and the melt viscosity of the sealant layer measured at 190°C is 1000 Pa·s to 3500 Pa·s.

Description

[Technical Field]

[0001] The present invention relates to a pouch film laminate and a pouch-type secondary battery produced by molding the same. [Background technology]

[0002] Secondary batteries are used in a wide range of fields, from small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes to large products that require high output such as electric and hybrid vehicles, as well as power storage devices and backup power storage devices that store surplus generated power and new renewable energy. Types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries.

[0003] Secondary batteries can be manufactured by placing an electrode assembly, in which positive and negative electrodes are alternately stacked with a separator between them, in a battery case, injecting an electrolyte, and then sealing the battery case. Secondary batteries are classified into pouch types, can types, etc., depending on the material of the case that houses the electrode assembly.

[0004] A pouch-type secondary battery can be manufactured by pressing a flexible pouch film laminate to form a cup portion, then placing an electrode assembly in the receiving space inside the cup portion and sealing the seal portion. The pouch film laminate is formed of multiple layers, including a metal gas barrier layer on one side of which a polymer film such as polyethylene terephthalate is laminated, and a sealant layer made of a thermoplastic polyolefin resin is laminated on the other side. When the pouch-type battery case is sealed, the sealant layers are thermally bonded to each other to form the seal portion.

[0005] In recent years, as the capacity of pouch-type secondary batteries has increased, the demand for pouches with excellent moldability has increased. Therefore, attempts have been made to improve the moldability of pouches by increasing the thickness of the gas barrier layer. However, when the gas barrier layer is thickened, the conventional sealant layer structure cannot ensure sufficient insulation, and the overall thickness of the pouch increases, which causes the sealant layer to melt less easily during sealing, resulting in poor sealing quality. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is intended to solve the above problems and provides a pouch film laminate having excellent sealing quality, which includes a sealant layer having a specific melt viscosity at 190°C, and a pouch-type battery including a battery case formed using the same. [Means for solving the problem]

[0007] According to one embodiment of the present invention, there is provided a pouch film laminate comprising a base layer, a gas barrier layer, and a sealant layer laminated in this order, wherein the melt viscosity of the sealant layer measured at 190°C is 1000 Pa·s to 3500 Pa·s.

[0008] The melt viscosity of the sealant layer measured at 170°C may be 1400 Pa·s to 4500 Pa·s, and the melt viscosity of the sealant layer measured at 210°C may be 500 Pa·s to 2500 Pa·s.

[0009] The melt flow rate (MFR) of the sealant layer measured under conditions of a temperature of 230°C and a load of 2.16 kg may be 1 g / 10 min to 15 g / 10 min, 1.5 g / 10 min to 15 g / 10 min, or 5 g / 10 min to 15 g / 10 min.

[0010] The sealant layer may have a thickness of 30 μm to 130 μm, the gas barrier layer may have a thickness of 40 μm to 100 μm, and the base layer may have a thickness of 5 μm to 100 μm.

[0011] The substrate layer may include a first substrate layer and a second substrate layer disposed between the first substrate layer and the gas barrier layer, and the second substrate layer may include nylon. In this case, the second substrate layer may include nylon 6.

[0012] According to another embodiment of the present invention, there is provided a pouch-type secondary battery including a pouch-type battery case accommodating an electrode assembly, the pouch-type battery case including a pouch film laminate, the pouch film laminate including a base layer, a gas barrier layer, and a sealant layer laminated in that order, and the melt viscosity of the sealant layer measured at 190°C is 1000 Pa s to 3500 Pa s.

[0013] When the pouch-type battery case is sealed for 1.6 seconds under conditions of 210°C and 1.2 MPa, the thickness of the sealant layer of the sealed portion formed on the pouch-type battery case may be 54% to 86% of the thickness of the sealant layer of the pouch film laminate. [Effects of the Invention]

[0014] The pouch film laminate according to the present invention is characterized by including a sealant layer having a melt viscosity of 1000 to 3500 Pa·s at 190°C. When the melt viscosity of the sealant layer at 190°C satisfies this range, the flow characteristics of the sealant layer are improved near the sealing temperature, allowing the seal portion to be sealed to a desired thickness within a set production time. Furthermore, sufficient sealing between the sealant layers improves the seal strength of the pouch. When a pouch-type battery case manufactured using the pouch film laminate according to the present invention is applied to a secondary battery, venting due to reduced seal strength and reduced insulation due to reduced seal thickness are suppressed, resulting in excellent safety. [Brief explanation of the drawings]

[0015] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention below, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited solely to the matters depicted in such drawings.

[0016] [Figure 1] 1 is an exploded view of a pouch-type secondary battery according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0017] The advantages and features of the present invention, as well as methods for achieving them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various different forms. The present embodiments are provided solely for the purpose of complete disclosure of the present invention and to enable those skilled in the art to fully understand the scope of the invention. The present invention is defined solely by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

[0018] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the meaning commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly defined otherwise.

[0019] The terms used in this specification are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless otherwise specified in the phrase. As used in this specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0020] In this specification, when a part is said to include a certain component, it does not mean that it may further include other components, unless otherwise specified.

[0021] In this specification, the expression "A and / or B" means A, B, or A and B.

[0022] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0023] Pouch film laminate The pouch film laminate according to the present invention comprises a base layer, a gas barrier layer, and a sealant layer laminated in this order, and the melt viscosity of the sealant layer measured at 190°C is 1000 Pa·s to 3500 Pa·s.

[0024] Hereinafter, each component of the pouch film laminate of the present invention will be described in more detail.

[0025] (1) Base material layer The substrate layer is formed as the outermost layer of the pouch film laminate to protect the secondary battery from external friction and impact. The substrate layer is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0026] The substrate layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. The substrate layer is preferably made of polyethylene terephthalate (PET), nylon, or a combination thereof, which are abrasion-resistant and heat-resistant.

[0027] The thickness of the substrate layer may be 5 μm to 100 μm, specifically 7 μm to 70 μm, more specifically 25 μm to 60 μm. When the thickness of the substrate layer satisfies the above range, the external insulation is excellent, and the thickness of the entire pouch is not large, so that the energy density relative to the volume of the secondary battery is excellent.

[0028] The substrate layer may have a single film structure made of any one material. Alternatively, the substrate layer may have a composite film structure made of two or more materials, each of which may have a layer formed thereon. In the composite film structure, an adhesive layer may be further formed between each layer.

[0029] Specifically, the substrate layer may include a first substrate layer and a second substrate layer. For example, the substrate layer may include a first substrate layer disposed on the outermost side of the pouch film laminate and a second substrate layer disposed between the first substrate layer and the gas barrier layer. The first substrate layer may include, but is not limited to, at least one polyester-based film such as polyethylene terephthalate or polybutylene terephthalate. The second substrate layer may include, but is not limited to, at least one polyamide-based film such as nylon 6, nylon 6,6, nylon MXD6, or nylon 4,10. The second substrate layer preferably includes nylon 6, which has the advantage of improving pouch formability due to the excellent stretchability of nylon 6.

[0030] (2) Gas barrier layer The gas barrier layer is laminated between the base layer and the sealant layer to ensure the mechanical strength of the pouch, block the entry and exit of gases and moisture outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type battery case.

[0031] The gas barrier layer may be formed of a metal, for example, a metal thin film containing one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel, titanium, and invar (INVAR, an Fe-Ni alloy), but is not limited thereto.

[0032] According to one embodiment of the present invention, the gas barrier layer may be formed of an aluminum alloy thin film. When an aluminum alloy thin film is used to form the gas barrier layer, it is possible to ensure a predetermined level of mechanical strength, a light weight, and the electrochemical properties of the electrode assembly and the electrolyte can be complemented, and heat dissipation can be ensured. The aluminum alloy thin film may contain at least one metal element other than aluminum (Al), such as iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0033] The thickness of the gas barrier layer may be 40 μm to 100 μm, specifically 50 μm to 90 μm, more specifically 55 μm to 85 μm. When the thickness of the gas barrier layer satisfies the above range, excellent moldability and gas barrier performance are achieved when forming the cup portion.

[0034] (3) Sealant layer The sealant layer serves to completely seal the interior of the pouch-type battery case by thermally bonding the seal portions together when the pouch-type battery case, which houses the electrode assembly inside, is sealed, and therefore may be formed of a material with excellent thermal bonding strength.

[0035] The sealant layer may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the sealant layer is in direct contact with the electrode assembly and / or electrolyte inside the pouch-type battery case, it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the sealant layer must completely seal the interior of the pouch-type battery case to prevent the transfer of materials between the inside and outside, it may be formed of a material having high sealing properties (e.g., excellent thermal adhesive strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer may be formed of a polymer material.

[0036] On the other hand, when the thickness of the gas barrier layer is increased to produce a pouch with good formability, the sealant layer does not melt easily when sealing the pouch-type battery case, and when the sealing temperature is increased to 220°C or higher to solve this problem, the base layer melts and deforms.

[0037] As a result of extensive research into solving such problems, the inventors discovered that by controlling the melt viscosity of the sealant layer of a pouch film laminate within a specific numerical range, thermal adhesion between the sealant layers can be smoothly achieved, improving the seal strength of the pouch and enabling the seal portion to be sealed to a desired thickness range within a specified production time, thereby completing the present invention.

[0038] In the present invention, the melt viscosity of the sealant layer measured at 190°C may be 1000 Pa·s to 3500 Pa·s, specifically 1000 Pa·s to 3000 Pa·s, and more specifically 1200 Pa·s to 3000 Pa·s. If the melt viscosity of the sealant layer measured at 190°C is less than 1000 Pa·s, the sealant layer will melt excessively when the pouch is sealed, resulting in a thin remaining thickness of the sealant layer in the sealed portion and insulation breakdown. If the melt viscosity of the sealant layer measured at 190°C is more than 3500 Pa·s, the sealant layer will not melt sufficiently when the pouch is sealed, resulting in insufficient thermal sealing between the sealant layers and low seal strength.

[0039] The melt viscosity of the sealant layer measured at 170°C may be 1400 Pa·s to 4500 Pa·s, specifically 1400 Pa·s to 4000 Pa·s, and more specifically 1800 Pa·s to 4000 Pa·s. When the melt viscosity of the sealant layer measured at 170°C is within the above range, the seal portion can be sealed to a desired thickness within the specified production time.

[0040] The melt viscosity of the sealant layer measured at 210°C may be 500 Pa·s to 2500 Pa·s, specifically 800 Pa·s to 2500 Pa·s, and more specifically 800 Pa·s to 2000 Pa·s. When the melt viscosity of the sealant layer measured at 210°C is within the above range, the seal portion can be sealed to a desired thickness within the specified production time.

[0041] The melt viscosity of the sealant layer may vary depending on the type and physical properties of the material constituting the sealant layer. For example, when the sealant layer is formed using a polyolefin copolymer, the melt viscosity may vary depending on the type and content of unit monomers constituting the copolymer, the weight average molecular weight of the copolymer, etc.

[0042] Meanwhile, in the present invention, the melt flow rate (MFR) of the sealant layer measured under conditions of a temperature of 230°C and a load of 2.16 kg may be 1 g / 10 min to 15 g / 10 min, 1.5 g / 10 min to 15 g / 10 min, 5 g / 10 min to 15 g / 10 min, 6 g / 10 min to 15 g / 10 min, or 6 g / 10 min to 14 g / 10 min. When the melt flow rate of the sealant layer satisfies the above numerical range, the seal portion can be sealed to a desired thickness range within a specified production time.

[0043] On the other hand, the thickness of the sealant layer may be 30 μm to 130 μm, specifically 50 μm to 120 μm, more specifically 70 μm to 100 μm. When the thickness of the sealant layer satisfies the above range, it is possible to ensure the formability of the pouch film laminate while ensuring the seal strength of the sealed portion.

[0044] The thickness of the sealant layer is preferably equal to or greater than the thickness of the gas barrier layer. Specifically, the thickness of the sealant layer may be 1 to 1.5 times, 1.1 to 1.5 times, or 1.2 to 1.5 times the thickness of the gas barrier layer. This is because if the thickness of the sealant layer is thinner than the thickness of the gas barrier layer, the insulating properties may be reduced.

[0045] The sealant layer may comprise a polyolefin resin such as polyethylene, polypropylene, polybutylene, or a copolymer thereof, a polycarbonate resin, a polyethylene terephthalate resin, a polyvinyl chloride resin, an acrylic polymer, a polyacrylonitrile resin, a polyimide resin, a polyamide resin, a cellulose resin, an aramid resin, a nylon resin, a polyester resin, polyparaphenylene benzobisoxazole, a polyarylate resin, Teflon, glass fiber, or a mixture thereof, and is preferably made of a polyolefin resin. The sealant layer is more preferably made of cast polypropylene (CPP), acid-modified polypropylene (PPA), a polypropylene-ethylene copolymer, and / or a polypropylene-butylene-ethylene terpolymer.

[0046] Meanwhile, the sealant layer according to the present invention may have a single film structure made of any one material. Alternatively, the sealant layer may have a composite film structure formed by layers of two or more materials. Specifically, the sealant layer may include a first sealant layer and a second sealant layer. In this case, the first sealant layer may be a layer disposed adjacent to the gas barrier layer, and the second sealant layer may be a layer disposed on the first sealant layer. The first sealant layer and the second sealant layer may be made of materials having different materials and / or physical properties. An interface may exist between the first sealant layer and the second sealant layer. This means that the first sealant layer and the second sealant layer are different layers and may be formed separately.

[0047] In order to ensure long-term adhesion between the gas barrier layer and the first sealant layer, it is particularly preferable that the first sealant layer is made of acid-modified polypropylene (PPa), which may be maleic anhydride polypropylene (MAH PP).

[0048] The second sealant layer may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the second sealant layer is in direct contact with the electrode assembly (160 in FIG. 1) and / or the electrolyte inside the receiving space (124 in FIG. 1), it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the second sealant layer must completely seal the inside of the battery case to prevent the transfer of materials between the inside and outside, it may be formed of a material having high sealing properties. To ensure such insulation, corrosion resistance, and sealing properties, the second sealant layer may include a polyolefin resin such as polyethylene, polypropylene, polybutylene, or a copolymer thereof, a polycarbonate resin, a polyethylene terephthalate resin, a polyvinyl chloride resin, an acrylic polymer, a polyacrylonitrile resin, a polyimide resin, a polyamide resin, a cellulose resin, an aramid resin, a nylon resin, a polyester resin, polyparaphenylene benzobisoxazole, a polyarylate resin, Teflon, glass fiber, or a mixture thereof, and is preferably made of a polyolefin resin. More preferably, the second sealant layer is made of cast polypropylene (CPP), acid-modified polypropylene (PPA), a polypropylene-ethylene copolymer, and / or a polypropylene-butylene-ethylene terpolymer.

[0049] Pouch-type secondary battery Next, the pouch-type secondary battery according to the present invention will be described.

[0050] The pouch-type secondary battery according to the present invention includes a pouch-type battery case in which an electrode assembly is housed, the pouch-type battery case including a pouch film laminate, the pouch film laminate including a base layer, a gas barrier layer, and a sealant layer laminated in that order, and the melt viscosity of the sealant layer measured at 190°C is 1000 Pa·s to 3500 Pa·s.

[0051] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to the drawings.

[0052] 1 is an exploded view of a pouch-type secondary battery 100 according to the present invention. As shown in FIG. 1, the pouch-type secondary battery 100 according to the present invention may include a pouch-type battery case 110, an electrode assembly 160, an electrode lead 180, an insulating part 190, and an electrolyte (not shown).

[0053] (1) Pouch-type battery case The pouch-type battery case 110 can house the electrode assembly 160 inside. The pouch-type battery case 110 can be manufactured by molding the pouch film laminate of the present invention described above. The detailed structure and properties of the pouch film laminate have been described above, so a detailed description thereof will be omitted.

[0054] The pouch film laminate may be drawn and stretched using a punch or the like to manufacture the pouch-type battery case 110. As a result, the pouch-type battery case 110 may include a cup portion 122 and a receiving portion 124. The receiving portion 124 is a portion that receives the electrode assembly, and may refer to a pocket-shaped receiving space formed inside the cup portion 122 by forming the cup portion 122.

[0055] According to an embodiment of the present invention, a pouch-type battery case 110 may include a first case 120 and a second case 130, as shown in FIG. 1. The first case 120 may include a receiving portion 124 that can receive an electrode assembly 160, and the second case 130 may cover the receiving portion 124 from above to prevent the electrode assembly 160 from falling out of the battery case 110. The first case 120 and the second case 130 may be manufactured with one side connected to each other as shown in FIG. 1, but the present invention is not limited thereto and may be manufactured in various forms, such as being separated from each other and separately manufactured.

[0056] According to another embodiment of the present invention, when forming cup portions in a pouch film laminate, two symmetrical cup portions 122, 132 may be adjacent to one another by drawing molding. In this case, the first case 120 and the second case 130 may be formed with the cup portions 122, 132, respectively, as shown in FIG. 1 . The electrode assembly 160 may be accommodated in the accommodation portion 124 provided in the cup portion 122 of the first case 120, and then the bridge portion 140 formed between the two cup portions 122, 132 may be folded so that the two cup portions 122, 132 face each other. In this case, the cup portion 132 of the second case 130 can accommodate the electrode assembly 160 from above. Therefore, because two cup portions 122, 132 accommodate one electrode assembly 160, a thicker electrode assembly 160 can be accommodated than if there were only one cup portion 122. In addition, since one edge of the secondary battery 100 is formed by folding the pouch-type battery case 110, the number of edges to be sealed in a subsequent sealing process is reduced, thereby improving the processing speed of the pouch-type secondary battery 100 and reducing the number of sealing processes.

[0057] The pouch-type battery case 110 may be sealed with the electrode assembly 160 housed therein so that a portion of the electrode lead 180, i.e., a terminal portion, described below, is exposed. Specifically, after the electrode lead 180 is connected to the electrode tab 170 of the electrode assembly 160 and an insulating portion 190 is formed on a portion of the electrode lead 180, the electrode assembly 160 may be housed in a housing portion 124 provided in the cup portion 122 of the first case 120, and the second case 130 may cover the housing portion 124 from above. Next, an electrolyte may be injected into the housing portion 124, and the seal portion 150 formed on the edges of the first case 120 and the second case 130 may be sealed.

[0058] The sealing portion 150 serves to seal the accommodation portion 124. Specifically, the sealing portion 150 is formed along the edge of the accommodation portion 124 to seal the accommodation portion 124. The temperature at which the sealing portion 150 is sealed may be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature is within the above range, the pouch-type battery case 110 can ensure sufficient seal strength through thermal bonding.

[0059] According to the present invention, when the sealant layers of the first case 120 and the second case 130 are stacked so as to abut against each other and then sealed for 1.6 seconds under conditions of 210°C and 1.2 MPa, the thickness of the sealant layer of the seal portion 150 formed in the pouch-type battery case 110 can be 54% to 86%, specifically 55% to 85%, and more specifically 60% to 85% of the thickness of the sealant layer of the pouch film laminate. When the thickness of the sealant layer of the seal portion 150 relative to the thickness of the sealant layer of the pouch film laminate satisfies the above numerical range, there is an effect of ensuring sufficient sealing strength while maintaining insulating properties.

[0060] (2) Electrode assembly The electrode assembly 160 may be inserted into the pouch-type battery case 110, and after an electrolyte is injected, the pouch-type battery case 110 may be sealed.

[0061] The electrode assembly 160 may be formed by stacking a positive electrode, a separator, and a negative electrode in this order. Specifically, the electrode assembly 160 may include two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate the electrodes from each other.

[0062] The positive and negative electrodes may each have a structure in which an active material slurry is applied to a metal foil or metal mesh electrode current collector containing aluminum and copper, respectively. The slurry may be formed by stirring a granular active material, an auxiliary conductor, a binder, a conductive material, and the like, in a solvent. The solvent may be removed in a subsequent process.

[0063] A slurry containing an electrode active material, a binder, and / or a conductive material is applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on either side of a separator to form a predetermined electrode assembly 160. Types of electrode assemblies 160 include, but are not limited to, a stack type, a jelly roll type, and a stack-and-fold type.

[0064] The electrode assembly 160 may include an electrode tab 170 .

[0065] The electrode tabs 170 are connected to the positive and negative electrodes of the electrode assembly 160, protrude from the electrode assembly 160, and serve as paths for electrons to move between the inside and outside of the electrode assembly 160. The electrode current collector included in the electrode assembly 160 may be composed of a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 170 may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion by ultrasonic welding or the like. As shown in FIG. 1, the electrode tabs 170 may protrude in different directions from the electrode assembly 160, but are not limited thereto. They may be formed to protrude in various directions, such as protruding in parallel from one side in the same direction.

[0066] (3) Electrode lead The electrode lead 180 can supply electricity to the outside of the secondary battery 100. The electrode lead 180 can be connected to the electrode tab 170 of the electrode assembly 160 by spot welding or the like.

[0067] The electrode lead 180 is connected to the electrode assembly 160 and may protrude to the outside of the pouch-type battery case 110 via the seal portion 150. Specifically, one end of the electrode lead 180 is connected to the electrode assembly 160, particularly to the electrode tab 170, and the other end of the electrode lead 180 may protrude to the outside of the pouch-type battery case 110.

[0068] The electrode lead 180 may include a positive electrode lead 182 having one end connected to the positive electrode tab 172 and extending in the direction in which the positive electrode tab 172 protrudes, and a negative electrode lead 184 having one end connected to the negative electrode tab 174 and extending in the direction in which the negative electrode tab 174 protrudes. The other ends of both the positive electrode lead 182 and the negative electrode lead 184 may protrude to the outside of the battery case 110. This allows electricity generated inside the electrode assembly 160 to be supplied to the outside. In addition, since the positive electrode tab 172 and the negative electrode tab 174 protrude in different directions, the positive electrode lead 182 and the negative electrode lead 184 may also extend in different directions. The positive electrode lead 182 and the negative electrode lead 184 may be made of different materials. That is, the positive electrode lead 182 may be made of aluminum (Al), the same material as the positive electrode current collector, and the negative electrode lead 184 may be made of copper (Cu), the same material as the negative electrode current collector, or copper coated with nickel (Ni). The portion of the electrode lead 180 that protrudes outside the battery case 110 serves as a terminal portion, and can be electrically connected to an external terminal.

[0069] (4) Insulation section The insulating portion 190 prevents electricity generated from the electrode assembly 160 from flowing to the battery case 110 via the electrode lead 180, thereby maintaining the sealing of the battery case 110. To this end, the insulating portion 190 may be formed of an insulator that is electrically non-conductive and does not easily conduct electricity. Generally, the insulating portion 190 is formed of a relatively thin insulating tape or film that is easily attached to the electrode lead 180, but the insulating portion 190 is not limited thereto, and any material that insulates the electrode lead 180 may be used.

[0070] The insulating portion 190 may be arranged to surround the outer peripheral surface of the electrode lead 180. Specifically, at least a portion of the electrode lead 180 may be surrounded by the insulating portion 190. In this case, the insulating portion 190 may be arranged between the electrode lead 180 and the pouch-type battery case 110. The insulating portion 190 may be located in a limited area of ​​the seal portion 150 where the first case 120 and the second case 130 of the pouch-type battery case 110 are heat-sealed, and the electrode lead 180 may be bonded to the battery case 110.

[0071] (5) Electrolyte The pouch-type secondary battery 100 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type battery case 110. The electrolyte is used to transport lithium ions generated by an electrochemical reaction of the electrodes during charge / discharge of the secondary battery 100, and may include a non-aqueous organic electrolytic solution that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. The electrolyte may also include a sulfide-based, oxide-based, or polymer-based solid electrolyte, and such a solid electrolyte may have flexibility that makes it easily deformable under external force.

[0072] Meanwhile, when pressure is applied due to external force or gas generation, peeling can occur at interfaces with relatively weak adhesive strength in a sealed battery case 110. For example, peeling can occur along the interface between sealant layers that are thermally bonded to each other. However, in the case of a battery case manufactured using the pouch film laminate of the present invention, the sealant layers, which have improved flow properties when melted, are smoothly thermally bonded to each other, thereby maintaining high adhesive strength at the interface and providing excellent seal strength.

[0073] (Examples for carrying out the invention) The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative to aid in understanding the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present description, and it is obvious that such changes and modifications are included in the scope of the appended claims.

[0074] Examples and Comparative Examples Example 1 (1) Manufacturing of pouch film laminates A 266mm wide, 50mm long, 60μm thick aluminum alloy thin film was laminated on one side with a 266mm wide, 50mm long, 3μm thick first adhesive film, a 266mm wide, 50mm long, 25μm thick nylon film, a 266mm wide, 50mm long, 3μm thick second adhesive film, and a 266mm wide, 50mm long, 12μm thick polyethylene terephthalate (PET) film. A 266mm wide, 50mm long, 80μm thick sealant layer was then formed on the other side of the aluminum alloy thin film by extruding a polypropylene-ethylene-butylene copolymer resin with a weight average molecular weight of 380,000g / mol and containing propylene:ethylene:butylene in a weight ratio of 87:9:4, to produce a pouch film laminate.

[0075] (2) Manufacturing pouch-type battery cases The pouch film laminate produced by the above method was cut to a size of 266 mm wide and 200 mm long, and then folded in half so that the sealant layer was in contact to make a size of 133 mm wide x 200 mm long.The end of the long side (200 mm) was then sealed for 1.6 seconds under conditions of a seal bar area of ​​200 mm x 8 mm, 210°C, and 1.2 MPa, thereby producing a pouch-type battery case with a sealed portion formed.

[0076] Example 2 A pouch film laminate and a pouch-type battery case were produced in the same manner as in Example 1, except that the sealant layer was formed using a polypropylene-ethylene-butylene copolymer resin having a weight average molecular weight of 360,000 g / mol and containing propylene:ethylene:butylene in a weight ratio of 92:7:1.

[0077] Example 3 A pouch film laminate and a pouch-type battery case were produced in the same manner as in Example 1, except that the sealant layer was formed using a polypropylene-ethylene-butylene copolymer resin having a weight average molecular weight of 330,000 g / mol and containing propylene:ethylene:butylene in a weight ratio of 79:11:10.

[0078] Example 4 Except that the sealant layer was formed using a polypropylene-ethylene copolymer resin having a weight average molecular weight of 440,000 g / mol and containing propylene:ethylene in a weight ratio of 97:3. A pouch film laminate and a pouch-type battery case were produced in the same manner as in Example 1.

[0079] Comparative Example 1 A pouch film laminate and a pouch-type battery case were produced in the same manner as in Example 1, except that the sealant layer was formed using a polypropylene-ethylene-butylene copolymer resin having a weight average molecular weight of 430,000 g / mol and containing propylene:ethylene:butylene in a weight ratio of 94:4:2.

[0080] Comparative Example 2 A pouch film laminate and a pouch-type battery case were produced in the same manner as in Example 1, except that the sealant layer was formed using a polypropylene-ethylene-butylene copolymer resin having a weight average molecular weight of 310,000 g / mol and containing propylene:ethylene:butylene in a weight ratio of 91:3:6.

[0081] Experimental Example 1: Evaluation of the melt properties of the sealant layer The melt properties of the sealant layers contained in the pouch film laminates produced in Examples 1 to 4 and Comparative Examples 1 and 2 were measured.

[0082] Specifically, the pouch film laminate was cut into 5 cm x 30 cm pieces, then treated with 37 wt% hydrochloric acid for 24 hours to remove the aluminum alloy thin film (gas barrier layer), and the polypropylene-containing polymer film (sealant layer) was separated and dried in a vacuum oven for 24 hours.

[0083] Three dried test pieces (3 g) were wound circumferentially and placed in an MFR measuring device (MI-40 manufactured by Gottfert), and the melt flow rate (MFR) was measured in the measurement range of 24.0 to 1.0 mm under the conditions of a temperature of 230°C and a load of 2.16 kg.

[0084] The melt viscosity of the separated polymer film (sealant layer) was also measured in frequency sweep mode at three temperatures: 170°C, 190°C, and 210°C using a rheometer (TA DHR-20). The geometry was 25 mm parallel plates, and measurements were taken in the range of 0.1 to 100 Hz under 0.1% strain. The Cox-Merz transformation was then used to measure the melt viscosity of the separated polymer film (sealant layer) at 3.5 s. -1 The values ​​were measured at a shear rate of 1000 kJ / min.

[0085] The results of the above measurements are shown in Table 1 below.

[0086] Experimental Example 2: Measurement of the thickness ratio of the sealant layer at the seal The thickness of the sealant layer included in the seal portion of each of the pouch-shaped cases produced in Examples 1 to 4 and Comparative Examples 1 and 2 was measured, and the ratio (%) of the thickness of the sealant layer in the seal portion to the thickness of the sealant layer of the pouch film laminate was calculated.

[0087] Specifically, the thickness of the sealant layer included in the seal portion was calculated by measuring the thickness of the seal portion formed on the pouch-type battery case at 9 equally spaced points using a micrometer device, and then subtracting the thicknesses of the base material layer and the gas barrier layer from the average value.

[0088] Thereafter, the ratio (%) of the thickness of the sealant layer at the sealed portion to the thickness (80 μm) of the sealant layer of the pouch film laminate in Examples 1 to 4 and Comparative Examples 1 and 2 was calculated and shown in Table 1 below.

[0089] Experimental Example 3: Evaluation of the seal strength of a pouch-type battery case The seal strength of the pouch-type battery cases produced in Examples 1 to 4 and Comparative Examples 1 and 2 was measured.

[0090] Specifically, the seal strength was calculated from the maximum tensile strength measured by cutting the seal formed on the pouch-type battery case at 15 mm intervals and then pulling it in a 180° direction at room temperature at a rate of 5 mm / min using a UTM. The results are shown in Table 1 below.

[0091] Experimental Example 4: Evaluation of insulation resistance of pouch-type battery cases The insulation resistance of the pouch-type battery cases produced in Examples 1 to 4 and Comparative Examples 1 and 2 was measured.

[0092] Specifically, the insulation resistance was measured using a resistance meter (RM3544-01) manufactured by HIOKI Corporation, by checking the resistance value after applying 100 V for 5 seconds. The measurement results are shown in Table 1 below.

[0093] [Table 1]

[0094] According to Table 1, in Examples 1 to 4, in which the melt viscosity of the sealant layer measured at 190°C was 1000 to 3500 Pa s, a seal was formed within the required sealing time (1.6 seconds) in which the thickness of the sealant layer at the sealed portion was 54 to 86% of the thickness of the sealant layer of the pouch film laminate, and the seal strength was significantly higher than in Comparative Example 1 and the insulation resistance was significantly higher than in Comparative Example 2. [Explanation of symbols]

[0095] 100 Pouch-type secondary battery 110 Pouch-type battery case 120 Case 1 122 Cup section 124 Storage unit 130 Case 2 132 Cup section 140 Bridge section 150 Seal part 160 Electrode assembly 170 Electrode Tab 172 Positive electrode tab 174 Negative electrode tab

Claims

1. The laminated film includes a base layer, a gas barrier layer, and a sealant layer, which are laminated in this order. A pouch film laminate, wherein the melt viscosity of the sealant layer measured at 190°C is 1000 Pa·s to 3500 Pa·s.

2. 2. The pouch film laminate according to claim 1, wherein the melt viscosity of the sealant layer measured at 170°C is 1400 Pa·s to 4500 Pa·s.

3. 2. The pouch film laminate according to claim 1, wherein the sealant layer has a melt viscosity measured at 210°C of 500 Pa·s to 2500 Pa·s.

4. 2. The pouch film laminate according to claim 1, wherein the sealant layer has a melt flow rate (MFR) of 1 g / 10 min to 15 g / 10 min measured at a temperature of 230° C. and a load of 2.16 kg.

5. 2. The pouch film laminate according to claim 1, wherein the sealant layer has a thickness of 30 μm to 130 μm.

6. 2. The pouch film laminate according to claim 1, wherein the gas barrier layer has a thickness of 40 μm to 100 μm.

7. The pouch film laminate according to claim 1, wherein the thickness of the base layer is 5 μm to 100 μm.

8. the substrate layer includes a first substrate layer and a second substrate layer disposed between the first substrate layer and the gas barrier layer, The pouch film laminate of claim 1 , wherein the second substrate layer comprises nylon.

9. The pouch film laminate of claim 8 , wherein the second substrate layer comprises nylon 6.

10. A pouch-type secondary battery including a pouch-type battery case in which an electrode assembly is housed, the pouch-type battery case includes a pouch film laminate; The pouch film laminate includes a base layer, a gas barrier layer, and a sealant layer, which are laminated in this order, The pouch-type secondary battery has a melt viscosity of the sealant layer measured at 190°C of 1000 Pa·s to 3500 Pa·s.

11. 11. The pouch-type secondary battery according to claim 10, wherein, when the pouch-type battery case is sealed for 1.6 seconds under conditions of 210°C and 1.2 MPa, the thickness of the sealant layer of the sealed portion formed in the pouch-type battery case is 54% to 86% of the thickness of the sealant layer of the pouch film laminate.

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