Pouch film laminate, pouch-type battery case, and pouch-type secondary battery

Abstract

The present invention relates to a pouch film laminate, in which a base layer, a gas barrier layer, and a sealant layer are sequentially laminated, wherein the base layer contains a polyester-based resin including an ethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure, and the molar ratio of the ethylene glycol-derived structure and the butylene glycol-derived structure is 95:5 to 80:20.

Description

Pouch film laminate, pouch-type battery case and pouch-type secondary battery

[0001] This invention claims the benefit of priority to Korean Patent Application Nos. 10-2024-0037462 and 10-2024-0037463, filed March 18, 2024, Korean Patent Application No. 10-2024-0196382, filed December 24, 2024, and Korean Patent Application No. 10-2025-34244, filed March 17, 2025, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a pouch film laminate and a pouch-type secondary battery, and more specifically, to a pouch film laminate, a pouch-type battery case, and a pouch-type secondary battery having excellent heat resistance and chemical resistance and improved formability.

[0003] As technological development and demand for electric vehicles and energy storage systems (ESS) increase, the demand for batteries as an energy source is rapidly increasing, and research is being conducted on batteries that can meet various needs.

[0004] These lithium secondary batteries mainly use lithium oxide as the positive electrode active material and carbon material as the negative electrode active material, and are generally classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of electrolyte used, and are also classified into cylindrical, prismatic, and pouch-type secondary batteries depending on the external shape of the battery. In terms of battery shape, there is a high demand for prismatic and pouch-type secondary batteries that can be applied to products such as mobile phones due to their thin thickness.

[0005] Among these, interest is focused on pouch-type secondary batteries, which are particularly suitable for manufacturing lightweight, thin cells as they have no restrictions on shape and size, are easy to assemble through thermal fusion, and are effective in releasing gas or liquid when abnormal behavior occurs.

[0006] A pouch-type battery case is manufactured by forming a cup portion by performing press processing on a flexible pouch film laminate. Then, once the cup portion is formed, an electrode assembly is accommodated in the cup portion's receiving space and a sealing portion is sealed to manufacture a secondary battery.

[0007] Among these press processes, drawing forming is performed by inserting a pouch film into a press device and applying pressure to the pouch film laminate with a punch to stretch the pouch film laminate. The pouch film laminate is generally formed of multiple layers, in which a polymer film, such as polyethylene terephthalate, is laminated on one side of a metal gas barrier layer, and a sealant layer is laminated on the other side.

[0008] Recently, with the increasing demand for high-capacity batteries, such as those for electric vehicles and energy storage systems (ESS), there's a growing need for technologies that increase the amount of cell material per pouch to improve energy density. To compensate for the increased weight and volume of cells, a technology has been developed that increases the thickness of the aluminum gas barrier layer to increase the formability and rigidity of the pouch, the outer material. However, this method has limitations, resulting in a lower overall energy density per volume.

[0009] The problem to be solved by the present invention is to provide a pouch film laminate that can exhibit ultra-high formability by increasing ductility while maintaining corrosion resistance and insulation properties against the external environment of the base layer.

[0010] Another problem to be solved by the present invention is to provide a pouch-shaped battery case manufactured by molding the pouch film laminate.

[0011] Another problem to be solved by the present invention is to provide a lithium secondary battery including the pouch-type battery case.

[0012] To solve the above problem, the present invention provides a pouch film laminate, a pouch-type battery case, and a lithium secondary battery.

[0013] [1] The present invention provides a pouch film laminate in which a substrate layer, a gas barrier layer, and a sealant layer are sequentially laminated, wherein the substrate layer includes a polyester resin including an ethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure, and the molar ratio of the ethylene glycol-derived structure: butylene glycol-derived structure is 95:5 to 80:20.

[0014] [2] The present invention provides a pouch film laminate according to the above [1], wherein the base layer includes a surface protection layer and a stretching auxiliary layer, the surface protection layer includes the polyester resin, and the stretching auxiliary layer includes a polyamide resin.

[0015] [3] The present invention provides a pouch film laminate according to the above [2], wherein the surface protective layer has a thickness of 20 ㎛ to 30 ㎛.

[0016] [4] The present invention provides a pouch film laminate in which the ratio of the total thickness of the pouch film laminate to the thickness of the surface protective layer is 5 to 10 in at least one of the above [2] and [3].

[0017] [5] The present invention provides a pouch film laminate, wherein the thickness of the stretching auxiliary layer is 20 µm to 30 µm in any one or more of the above [2] to [4].

[0018] [6] The present invention provides a pouch film laminate having a ratio of the thickness of the stretching auxiliary layer to the thickness of the surface protective layer of at least one of [2] to [5] above of 1.2 or less.

[0019] [7] The present invention provides a pouch film laminate, wherein the thickness of the gas barrier layer is 60 µm to 130 µm in any one or more of the above [1] to [6].

[0020] [8] The present invention provides a pouch film laminate having a thickness of the gas barrier layer of 70 µm to 90 µm in any one or more of the above [1] to [7].

[0021] [9] The present invention provides a pouch film laminate, wherein the ratio of the thickness of the gas barrier layer to the thickness of the surface protective layer is 2.5 to 3.3 in any one or more of the above [2] to [8].

[0022]

[0010] The present invention provides a pouch film laminate, wherein the total thickness of the pouch film laminate is 160 ㎛ to 280 ㎛, in any one or more of the above [1] to [9].

[0023]

[0011] The present invention provides a pouch film laminate comprising a second polymer including polypropylene (PP), wherein the sealant layer comprises at least one of [1] to

[0010] .

[0024]

[0012] The present invention provides a pouch film laminate, wherein in any one or more of the above [1] to

[0011] , the sealant layer is formed by sequentially laminating a first sealant layer, a second sealant layer, and a third sealant layer.

[0025]

[0013] The present invention provides a pouch film laminate in which the molar ratio of the ethylene glycol-derived structure: butylene glycol-derived structure is 1:0.100 to 1:0.220 in any one or more of the above [1] to

[0012] .

[0026]

[0014] The present invention provides a pouch film laminate comprising a polycondensation reaction product of at least one of the above [1] to

[0013] , wherein the polyester resin is a mixture of ethylene glycol and butylene glycol and at least one selected from the group consisting of dimethyl terephthalate and terephthalic acid.

[0027]

[0015] The present invention provides a pouch film laminate, wherein in any one or more of the above [1] to

[0014] , the gas barrier layer includes at least one selected from the group consisting of aluminum, copper, stainless steel, nickel, titanium, and INVAR.

[0028]

[0016] The present invention provides a pouch-shaped battery case manufactured by drawing and forming one or more of the pouch film laminates of [1] to

[0015] .

[0029]

[0017] The present invention provides a pouch-type secondary battery including a pouch-type battery case according to the above

[0016] ; and an electrode assembly housed in the pouch-type battery case.

[0030] The pouch film laminate according to the present invention can exhibit ultra-high formability by including a polyester resin modified with polyethylene terephthalate instead of the conventional polyethylene terephthalate in the base layer of a conventional pouch film laminate while maintaining corrosion resistance and insulation against an external environment and exhibiting improved stretchability, and thus can be usefully used in the manufacture of a pouch-type lithium secondary battery with improved pouch appearance defects.

[0031] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the contents of the invention described above, serve to further understand the technical idea of ​​the present invention. Therefore, the present invention should not be interpreted as being limited to the matters described in such drawings.

[0032] Figure 1 is a cross-sectional view of a pouch film laminate according to one embodiment of the present invention.

[0033] Figure 2 is an exploded assembly diagram of a pouch-type secondary battery according to one embodiment of the present invention.

[0034] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill 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 explicitly and specifically defined otherwise.

[0036] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0037] In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0038] In this specification, the description of “A and / or B” means A, or B, or A and B.

[0039] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0040]

[0041] Pouch film laminate

[0042]

[0043] The pouch film laminate of the present invention is a pouch film laminate in which a substrate layer, a gas barrier layer, and a sealant layer are sequentially laminated, wherein the substrate layer includes a polyester resin including an ethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure, and the molar ratio of the ethylene glycol-derived structure: butylene glycol-derived structure is 95:5 to 80:20.

[0044]

[0045] In order to increase the amount of cell material accommodated within the pouch-type battery case and thereby improve the energy density, the accommodation space of the pouch-type battery case must be increased, and for this purpose, the depth of the cup portion of the pouch-type battery case must be increased. In order to increase the depth of the cup portion of the pouch-type battery case, the barrier property can be maintained by increasing the thickness of the gas barrier layer; however, if the formability of the base layer is relatively low, cracks may occur on the exterior of the pouch-type battery case.

[0046] The pouch film laminate according to the present invention can exhibit ultra-high moldability by including a polyester resin including a polyethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure with improved elongation, instead of the polyethylene terephthalate contained in the base layer of a conventional pouch film laminate. Therefore, even when the thickness of the base layer is increased, excellent moldability can be exhibited, so that even when the molding depth of the pouch film laminate is increased, cracks do not occur and the protective effect and insulating properties exhibited by the base layer can be maintained.

[0047]

[0048] Substrate layer

[0049] The above substrate layer is formed on the outermost layer of the pouch film laminate to protect the secondary battery from friction and collision with the outside. The substrate layer is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0050]

[0051] The above-mentioned base layer includes a polyester resin including an ethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure, and the polyester resin may include an ethylene terephthalate structure and a butylene terephthalate structure in the main chain.

[0052] Polyethylene terephthalate (PET) has excellent chemical resistance and insulation properties, but its relatively low elongation limits the formability of pouch film laminates. In contrast, polybutylene terephthalate (PBT) exhibits high elongation, but its chemical and heat resistance are lower than those of polyethylene terephthalate, making it difficult to apply it alone to the substrate layer. In contrast, the substrate layer of the pouch film laminate of the present invention includes a polyester resin having an ethylene terephthalate structure and a butylene terephthalate structure in its main chain, so that the properties of polyethylene terephthalate and polybutylene terephthalate can be appropriately exhibited together, thereby maintaining excellent chemical resistance and insulation properties while exhibiting improved formability.

[0053] In one embodiment of the present invention, the molar ratio of the ethylene terephthalate structure and the butylene terephthalate structure included in the polyester resin may be 95:5 to 80:20, specifically 90:10 to 80:20, and more specifically 90.9:9.1 to 82.0:18.

[0054] The molar ratio of the ethylene terephthalate structure and the butylene terephthalate structure included in the above polyester resin may be the molar ratio of the ethylene terephthalate structure and the butylene terephthalate structure included in the remaining structures excluding the terephthalic acid-derived structure included in the above polyester resin.

[0055] When the ethylene terephthalate structure and the butylene terephthalate structure are included in the polyester resin at the molar ratio, the elongation of the base layer increases, thereby improving the formability of the pouch film laminate, while maintaining the heat resistance and chemical resistance of the pouch film laminate. When the ratio of the butylene terephthalate structure is less than the above range, it is difficult to expect an appropriate formability improvement effect, and when the ratio of the butylene terephthalate structure is greater than the above range, the formability may increase, but it is difficult to maintain the heat resistance and chemical resistance of the pouch film laminate.

[0056]

[0057] In one embodiment of the present invention, the molar ratio of the ethylene terephthalate structure and the butylene terephthalate structure included in the polyester resin may be 1:0.100 to 1:0.220, specifically 1:0.105 to 1:0.210, and even more specifically 1:0.110 to 1:0.200, when the number of moles of the ethylene terephthalate structure included in the polyester resin is 1. When the ethylene terephthalate structure and the butylene terephthalate structure are included in the polyester resin at the molar ratio, the elongation of the base layer may increase, thereby improving the formability of the pouch film laminate, while maintaining the heat resistance and chemical resistance of the pouch film laminate. If the ratio of the above butylene terephthalate structure is less than the above range, it is difficult to expect an appropriate formability improvement effect, and if the ratio of the above butylene terephthalate structure is more than the above range, the formability may increase, but it is difficult to maintain the heat resistance and chemical resistance of the pouch film laminate.

[0058] The method for producing the above polyester resin is not particularly limited, and may be produced by a method known in the art, for example, a terephthalic acid (TPA) method by reacting a mixture of ethylene glycol and butylene glycol with terephthalic acid, or a dimethyl terephthalate (DMT) method by reacting a mixture of ethylene glycol and butylene glycol with dimethyl terephthalate.

[0059] In one embodiment of the present invention, the polyester resin may be a result of an esterification reaction and a polycondensation reaction between a mixture of, for example, ethylene glycol and butylene glycol and at least one selected from the group consisting of dimethyl terephthalate and terephthalic acid.

[0060] The thickness of the above substrate layer may be 40 ㎛ to 60 ㎛, specifically 42 ㎛ to 58 ㎛, and more specifically 45 ㎛ to 55 ㎛. When the above substrate layer satisfies the above thickness range, the external insulation is excellent, and the thickness of the entire pouch is not thick, so the energy density per volume of the secondary battery can be excellent.

[0061] The above substrate layer may have a single film structure composed of a single material. Alternatively, the substrate layer may have a composite film structure composed of two or more materials formed in layers.

[0062] In one embodiment of the present invention, the substrate layer may include a surface protection layer and a stretching auxiliary layer. The surface protection layer may be a layer disposed on the outermost layer of the pouch film laminate, and may be, for example, a surface protection film, and the stretching auxiliary layer may be a layer disposed between the surface protection film and the gas barrier layer, and may be, for example, a stretching protection film. The surface protection layer and the stretching auxiliary layer may each be formed of materials having different materials and / or different physical properties. An interface may exist between the surface protection layer and the stretching auxiliary layer. This means that the surface protection layer and the stretching auxiliary layer are different layers and may be formed separately.

[0063] In one embodiment of the present invention, when the substrate layer includes a surface protection film and a stretching auxiliary film, the polyester resin including the above-described ethylene glycol-derived structure, butylene glycol-derived structure, and terephthalic acid-derived structure may be included in the surface protection film.

[0064] The thickness of the surface protection layer may be 20 ㎛ to 30 ㎛, specifically 22 ㎛ to 28 ㎛, and more specifically 24 ㎛ to 26 ㎛. The thickness of the surface protection layer is increased compared to the thickness of the surface protection layer included in a conventional pouch film laminate for a conventional pouch-type battery case. When the thickness of the surface protection layer satisfies the above numerical range, even when the molding depth of the pouch film laminate increases, the insulation and moldability of the pouch can be stably secured while effectively suppressing moisture penetration into the interior of the pouch film laminate. In addition, by ensuring that the thickness of the entire pouch film laminate is not too thick, the secondary battery can exhibit excellent energy density relative to its volume.

[0065] In one embodiment of the present invention, the ratio of the total thickness of the pouch film laminate to the thickness of the surface protection layer may be 5 to 10, specifically 6 to 10, 6 to 9, 7 to 10, or 7 to 9, and more specifically 8 to 9. The pouch film laminate according to one embodiment of the present invention includes a gas barrier layer and a surface protection layer with increased thicknesses so as to exhibit an increased forming depth, and the thickness of the surface protection layer and the total thickness of the pouch film laminate satisfy the above ratio. In contrast, a conventional pouch film laminate has a limitation in increasing the upper limit of the thickness due to the low elongation of polyethylene terephthalate included in the surface protection layer, and thus the thickness of the surface protection layer is too thin to satisfy the above ratio.

[0066] The surface protection layer may include an additive. By including an additive in the surface protection layer, the physical properties of the surface protection layer may be changed. For example, as an additive for controlling the tensile strength of the surface protection layer, at least one of carbon fiber, glass fiber, and aramid fiber may be added.

[0067] The above-mentioned stretching auxiliary layer may be a layer disposed between the surface protection layer and the gas barrier layer. In this case, the stretching auxiliary layer may play a role in improving the formability of the pouch film laminate.

[0068] The stretching auxiliary layer may include a polyamide-based resin, and may include, for example, a polyamide-based film. The stretching auxiliary layer may include, but is not limited to, at least one selected from the group consisting of nylon 6,6, nylon MXD6 (polyxylylene adipamide), nylon 4, nylon 4,6, and nylon 4,10. Specifically, in order for the stretching auxiliary layer to have a melting temperature of 240°C or higher, the stretching auxiliary layer may include nylon 6,6 and / or nylon MXD6.

[0069] The thickness of the above-mentioned stretching auxiliary layer may be 20 ㎛ to 30 ㎛, specifically 22 ㎛ to 28 ㎛, and more specifically 24 ㎛ to 26 ㎛. When the thickness of the above-mentioned stretching auxiliary layer satisfies the above-mentioned numerical range, the formability of the pouch can be secured while preventing the volumetric energy density of the secondary battery from decreasing due to the thickness of the pouch film laminate becoming excessively thick.

[0070] In one embodiment of the present invention, the ratio of the thickness of the stretching auxiliary layer to the thickness of the surface protective layer may be 1.2 or less, specifically 0.5 to 1.2, 0.6 to 1.2, 0.7 to 1.2, 0.8 to 1.2, 0.6 to 1.1, 0.7 to 1.1, or 0.8 to 1.1, and more specifically 0.9 to 1.1. Since the pouch film laminate according to one embodiment of the present invention includes a polyester resin having a high elongation as the surface protective layer, even when the ratio of the thickness of the stretching auxiliary layer to the thickness of the surface protective layer is reduced, the pouch film laminate can exhibit excellent formability. In comparison, in order to assist the low elongation of polyethylene terephthalate included in the surface protective layer, a conventional pouch film laminate needs to relatively increase the thickness of the elongation auxiliary layer to alleviate the difference in elongation with the gas barrier layer, and therefore, the thickness of the elongation auxiliary layer is too thick to satisfy the above ratio.

[0071] In one embodiment of the present invention, when an interface exists between the surface protection layer and the stretching auxiliary layer, a first adhesive layer may be disposed at the interface. For example, when the base layer according to one embodiment of the present invention includes a first adhesive layer, the stretching protection layer, the first adhesive layer, and the surface protection layer may be sequentially laminated.

[0072] The thickness of the first adhesive layer may be 1 ㎛ to 10 ㎛, specifically 2 ㎛ to 8 ㎛, and more specifically 2 ㎛ to 5 ㎛. When the thickness of the first adhesive layer satisfies the thickness range, sufficient adhesion between the surface protective layer and the stretchable protective layer can be secured, while preventing a decrease in the energy density per volume of the secondary battery due to an excessive increase in the thickness of the pouch film laminate.

[0073] The first adhesive layer may include at least one selected from the group consisting of urethane-based, epoxy-based, and acrylic-based polymers, but is not limited thereto. In one embodiment of the present invention, the first adhesive layer may include a urethane-based polymer, in which case the surface protection layer and the stretch protection layer can be sufficiently adhered by the first adhesive layer while being easy to shape and cut.

[0074]

[0075] gas barrier layer

[0076] The gas barrier layer is laminated between the substrate layer and the sealant layer to secure the mechanical strength of the pouch, block the ingress of gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type case.

[0077] The above gas barrier layer may be formed of a metal. For example, the gas barrier layer may be a metal thin film including one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and invar (INVAR), but is not limited thereto.

[0078] The above gas barrier layer may be formed of an aluminum alloy thin film. When the gas barrier layer is formed using an aluminum alloy thin film, a mechanical strength higher than a predetermined level can be secured, while being light in weight and ensuring complementary electrochemical properties and heat dissipation properties due to the electrode assembly and electrolyte. The aluminum alloy thin film may contain elements other than aluminum (Al). For example, the aluminum alloy thin film may contain at least one selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0079] The thickness of the gas barrier layer may be 60 ㎛ to 130 ㎛, specifically 60 ㎛ to 120 ㎛, 70 ㎛ to 120 ㎛, 70 ㎛ to 110 ㎛, or 70 ㎛ to 100 ㎛, and more specifically 70 ㎛ to 90 ㎛. The thickness of the gas barrier layer is increased compared to the thickness of the gas barrier layer included in a conventional pouch film laminate, and when the thickness of the gas barrier layer satisfies the above range, when the pouch film laminate is used to form a cup portion of a pouch-type battery case, it can exhibit excellent gas barrier performance while exhibiting increased formability.

[0080] In one embodiment of the present invention, the ratio of the thickness of the gas barrier layer to the thickness of the surface protection layer that may be included in the substrate layer may be 2.5 to 3.3, specifically 2.6 to 3.3, 2.7 to 3.3, 2.8 to 3.3, 2.9 to 3.3, 3.0 to 3.3, 2.80 to 3.25, 2.90 to 3.25, 3.00 to 3.25, or 3.05 to 3.25, and more specifically 3.10 to 3.25. The pouch film laminate according to one embodiment of the present invention includes the surface protection layer and the gas barrier layer each in the ranges described above, which may be increased compared to the thicknesses of each of the surface protection layer and the gas barrier layer included in a conventional pouch film laminate, and thus the ratio of the thickness of the gas barrier layer to the thickness of the surface protection layer may satisfy the above range. According to one embodiment of the present invention, a pouch film laminate can exhibit excellent formability as the ratio of the thickness of the gas barrier layer to the thickness of the surface protective layer satisfies the above range, and the surface protective layer and the gas barrier layer can appropriately and harmoniously exhibit improved elongation.

[0081]

[0082] In one embodiment of the present invention, a second adhesive layer may be disposed between the gas barrier layer and the base layer, and when the base layer includes a surface protection layer and a stretching auxiliary layer, the second adhesive layer may be disposed between the gas barrier layer and the stretching auxiliary layer. For example, in one embodiment of the present invention, the gas barrier layer, the second adhesive layer, and the stretching auxiliary layer may be sequentially laminated.

[0083] The thickness of the second adhesive layer may be 1 ㎛ to 10 ㎛, specifically 2 ㎛ to 8 ㎛, and more specifically 2 ㎛ to 5 ㎛. When the thickness of the second adhesive layer satisfies the thickness range, sufficient adhesion between the substrate layer and the gas barrier layer can be secured, while preventing a decrease in the energy density per volume of the secondary battery due to an excessive increase in the thickness of the pouch film laminate.

[0084] The second adhesive layer may include at least one selected from the group consisting of urethane-based, epoxy-based, and acrylic-based polymers, but is not limited thereto. In one embodiment of the present invention, the second adhesive layer may include a urethane-based polymer, in which case the base layer and the gas barrier layer can be sufficiently adhered by the second adhesive layer, while being easy to shape and cut.

[0085]

[0086] sealant layer

[0087] The sealant layer is intended to completely seal the interior of the pouch-shaped battery case, which houses the electrode assembly inside, by mutually thermally bonding the sealing portion when the case is sealed. To this end, the sealant layer may be formed of a material having excellent thermal bonding strength.

[0088] Since the above sealant layer is the surface that comes into contact with the electrolyte and electrode assembly after being formed into a battery case, it must have insulating and corrosion resistance properties, and since it must completely seal the inside to block material movement between the inside and the outside, it must have high sealing properties.

[0089] The above sealant layer may be made of a polymer material, and may be made of at least one selected from the group consisting of, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon, and specifically, among these, it may include polypropylene (PP) which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance.

[0090] More specifically, the sealant layer may include polypropylene, cast polypropylene (CPP), acid modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof.

[0091] The sealant layer may have a total thickness of 60 ㎛ to 100 ㎛, specifically 60 ㎛ to 90 ㎛ or 60 ㎛ to 80 ㎛, and more specifically 70 ㎛ to 90 ㎛. If the thickness of the sealant layer is too thin, the sealing durability and insulation may be reduced, and if it is too thick, the flexibility may be reduced and the total thickness of the pouch film laminate may increase, which may lower the energy density per volume.

[0092] The above sealant layer may have a single-layer structure or a multi-layer structure including two or more layers made of different polymer materials.

[0093] In one embodiment of the present invention, the sealant layer may be a first sealant layer, a second sealant layer, and a third sealant layer sequentially laminated, and for example, the first sealant layer may be in contact with and bonded to the gas barrier layer.

[0094] In one embodiment of the present invention, the first sealant layer and the third sealant layer may each be independently made of a polymer material, and may be made of, for example, at least one 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, and Teflon, and specifically, among these, the first sealant layer and the third sealant layer may include polypropylene (PP) which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance. More specifically, the first sealant layer and the third sealant layer may each independently include polypropylene, cast polypropylene (CPP), acid modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof.

[0095] In one embodiment of the present invention, the thickness of the first sealant layer may be 10 µm to 50 µm, specifically 15 µm to 50 µm or 20 µm to 40 µm, and more specifically 25 µm to 35 µm.

[0096] In one embodiment of the present invention, the thickness of the third sealant layer may be 10 µm to 40 µm, specifically 10 µm to 40 µm or 10 µm to 30 µm, and more specifically 15 µm to 30 µm.

[0097] In one embodiment of the present invention, the second sealant layer may be included as a core layer in the sealant layer, and the second sealant layer may have a lower elastic modulus than the first sealant layer and the third sealant layer. When the second sealant layer having a relatively lower elastic modulus than the first sealant layer and the third sealant layer is interposed between the first sealant layer and the third sealant layer, the sealant layer may exhibit improved ductility even when the overall thickness of the sealant layer increases.

[0098] The second sealant layer may be formed of at least one selected from the group consisting of, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, and Teflon, and specifically, among these, it may include polypropylene (PP) which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance. More specifically, the second sealant layer may include polypropylene, cast polypropylene (CPP), acid modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof.

[0099] In one embodiment of the present invention, the thickness of the second sealant layer may be 10 µm to 50 µm, specifically 15 µm to 50 µm or 20 µm to 40 µm, and more specifically 25 µm to 35 µm.

[0100] The pouch film laminate according to the present invention as described above can be manufactured using a manufacturing method for a pouch film laminate known in the art. For example, the pouch film laminate of the present invention can be manufactured using a method in which a substrate layer is attached to the upper surface of a gas barrier layer using an adhesive, and a sealant layer is formed on the lower surface of the gas barrier layer using coextrusion or an adhesive layer, but is not limited thereto.

[0101] The above pouch film laminate may have a total thickness of 160 µm to 280 µm, specifically 170 µm to 280 µm, 180 µm to 280 µm, 185 µm to 280 µm, 185 µm to 260 µm, or 190 µm to 260 µm, and more specifically 200 µm to 250 µm. When the thickness of the pouch film laminate satisfies the above range, the forming depth can be increased while minimizing a decrease in battery accommodation space, a decrease in sealing durability, etc. due to an increase in the thickness of the pouch laminate.

[0102]

[0103] Each configuration of the pouch film laminate according to the present invention will be described in more detail with reference to FIG. 1.

[0104] FIG. 1 illustrates a cross-sectional view of a pouch film laminate according to one embodiment of the present invention.

[0105] A pouch film laminate (100) according to one embodiment of the present invention includes a sequentially laminated substrate layer (110), a gas barrier layer (120), and a sealant layer (130), and the substrate layer (110) may include a stretching auxiliary film (114) disposed on the gas barrier layer (120) and a surface protection film (112) disposed on the stretching auxiliary film (114). The surface protection film (112) may be a layer disposed on the outermost layer of the pouch film laminate, and the stretching auxiliary film (114) may be a layer disposed between the surface protection film (112) and the gas barrier layer (120).

[0106]

[0107] pouch-type battery case

[0108] A pouch-shaped battery case according to one embodiment of the present invention can house an electrode assembly inside. The pouch-shaped battery case can be manufactured by molding the pouch film laminate of the present invention described above. Since the detailed configuration and physical properties of the pouch film laminate are the same as those described above, a detailed description thereof will be omitted.

[0109] The above pouch film laminate can be drawn and stretched by a punch or the like to manufacture the pouch-shaped battery case. As a result, the pouch-shaped battery case can include a cup portion and a receiving portion. The receiving portion is a place for receiving the electrode assembly, and can refer to a receiving space formed in the shape of a pocket on the inside of the cup portion as the cup portion is formed.

[0110]

[0111] lithium secondary battery

[0112] According to another embodiment of the present invention, a lithium secondary battery is provided, including the aforementioned pouch-shaped battery case; and an electrode assembly housed inside the pouch-shaped battery case.

[0113] FIG. 2 shows an exploded assembly diagram of a lithium secondary battery (200) including an electrode assembly (260) and a pouch-shaped battery case (210) containing the electrode assembly.

[0114] As illustrated in FIG. 2, a lithium secondary battery (200) according to one embodiment of the present invention may include a pouch-type battery case (210) and an electrode assembly (260) housed in the pouch-type battery case (210). The electrode assembly (260) may be formed by stacking a positive electrode, a separator, and an negative electrode, and may include an electrode tab (270), an electrode lead (280), and a lead film (290). The lithium secondary battery (200) may be manufactured by injecting an electrolyte into the inside of the pouch-type battery case (210) with the electrode assembly (260) housed therein, and then sealing the terrace portion (250).

[0115]

[0116] The pouch-type battery case (210) can house an electrode assembly (260) inside. The pouch-type battery case (210) can be manufactured by molding the pouch film laminate (100) of FIG. 1 described above. Since the detailed configuration and physical properties of the pouch film laminate (100) are the same as those described above, a detailed description thereof will be omitted.

[0117] In order to manufacture a pouch-type battery case (210), a pouch film laminate may be formed by drawing and stretching using a punch or the like, thereby forming a cup portion (240) including a pocket-shaped receiving space (241) to receive an electrode assembly (260).

[0118] As illustrated in FIG. 2, the pouch-type battery case (210) may include an upper case and a lower case. In one embodiment, the lower case may include a lower cup portion (240) formed therein to include a receiving space (241) capable of receiving an electrode assembly (260), and the upper case may cover the receiving space (241) from above to prevent the electrode assembly (260) from being separated from the outside of the battery case (210). The upper and lower cases may be manufactured such that one side thereof is connected to the other, but are not limited thereto and may be manufactured in various ways, such as being manufactured separately and separated from the other. Accordingly, the sealing portion may be formed on three sides, may be formed on all four sides, and may also be formed such that the cup portion exists only on the lower case.

[0119] The pouch-type battery case (210) can be sealed while housing the electrode assembly (260) so that a portion of the electrode lead (280), i.e., the terminal portion, is exposed. Specifically, when the electrode lead (280) is connected to the electrode tab (270) of the electrode assembly (260) and a lead film (290) is formed on a portion of the electrode lead (280), the electrode assembly (260) can be housed in the housing space (241) provided in the cup portion (240) of the lower case, and the upper case can cover the housing space (241) from above. Subsequently, an electrolyte can be injected into the interior of the housing space (241), and the terrace portions (250) formed on the edges of the upper and lower cases can be sealed. The electrolyte is intended to move lithium ions generated by an electrochemical reaction of an electrode during charging / discharging of a lithium secondary battery (200), and may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. Furthermore, the electrolyte may include a solid electrolyte of a sulfide type, oxide type, or polymer type, and such a solid electrolyte may have flexibility that allows it to be easily deformed by an external force.

[0120]

[0121] The electrode assembly (260) can be formed by alternately stacking electrodes and separators. Specifically, the electrode assembly (260) can be formed into a predetermined shape by applying a slurry containing an electrode active material, a binder, and / or a conductive material to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and stacking the slurry on both sides of a separator. The electrode assembly (260) can be inserted into a pouch-type battery case (210) and sealed by the pouch-type battery case (210) after electrolyte injection. In one embodiment, the types of the electrode assembly (260) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc.

[0122] In one embodiment of the present invention, the electrode assembly (260) may include two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to mutually insulate the electrodes. The positive electrode and the negative electrode may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry may typically be formed by stirring a granular active material, an auxiliary conductor, a binder, and a conductive agent with the addition of a solvent. The solvent may be removed in a subsequent process.

[0123]

[0124] The electrode tabs (270) are respectively connected to the positive and negative electrodes of the electrode assembly (260), and may protrude outward from the electrode assembly (260) to serve as a path for electrons to move between the inside and the outside of the electrode assembly (260). The electrode current collector of the electrode assembly (260) may be composed of a portion where an electrode active material is applied and an end portion where the electrode active material is not applied, i.e., a non-coated portion. The electrode tabs (270) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 3, the electrode tabs (270) may protrude in different directions of the electrode assembly (260), but are not limited thereto, and may be formed to protrude in various directions, such as protruding in parallel in the same direction from one side.

[0125]

[0126] An electrode lead (280) can supply electricity to the outside of a secondary battery (200). The electrode lead (280) can be connected to an electrode tab (270) of an electrode assembly (260) by spot welding, etc. At least a portion of the electrode lead (280) can be surrounded by an insulating member (290). In one embodiment, the electrode lead (280) may have one end connected to the electrode tab (270) and the other end protruding outward from the battery case (210). The electrode lead (280) may include a positive lead (282) having one end connected to a positive tab (272) and extending in a direction in which the positive tab (272) protrudes, and a negative lead (284) having one end connected to a negative tab (274) and extending in a direction in which the negative tab (374) protrudes.

[0127] Both the positive electrode lead (282) and the negative electrode lead (284) may have their other ends protruded to the outside of the pouch-type battery case (210). Therefore, electricity generated inside the electrode assembly (260) may be supplied to the outside. In addition, since the positive electrode tab (272) and the negative electrode tab (274) are formed to protrude in various directions, the positive electrode lead (282) and the negative electrode lead (284) may also extend in various directions. In one embodiment, the positive electrode lead (282) and the negative electrode lead (284) may be made of different materials. That is, the positive electrode lead (282) may be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead (284) may be made of the same copper (Cu) material as the negative electrode current collector or a nickel (Ni)-coated copper material. A portion of the electrode lead (280) protruding to the outside of the battery case (210) may serve as a terminal portion and be electrically connected to an external terminal.

[0128]

[0129] anode

[0130] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is a metal to which the positive electrode active material layer can be easily adhered, but is not reactive in the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0131]

[0132] The above positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed.

[0133] At this time, the positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 90% to 98% by weight, based on the total weight of the positive electrode active material layer.

[0134]

[0135] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.01 wt% to 10 wt%, preferably 0.1 wt% to 9 wt%, and more preferably 0.1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer.

[0136]

[0137] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer.

[0138]

[0139] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method. Specifically, a positive electrode slurry composition prepared by dissolving or dispersing a positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent, if necessary, is applied onto a positive electrode current collector, followed by drying and rolling.

[0140] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0141]

[0142] Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling the resulting film from the support, and laminating the resulting film onto a positive electrode current collector.

[0143]

[0144] membrane

[0145] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0146]

[0147] electrolyte

[0148] In addition, the electrolyte used in the present invention may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery.

[0149] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0150] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0151]

[0152] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2 can be used. The concentration of the lithium salt is preferably within the range of 0.1 M to 4.0 M, preferably 0.5 M to 3.0 M, and more preferably 1.0 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0153]

[0154] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 10.0 wt% based on the total weight of the electrolyte.

[0155]

[0156] cathode

[0157] The above negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0158] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0159]

[0160] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0161] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fibers, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch derived cokes.

[0162] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt%, 82 wt% to 99 wt%, or 84 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0163]

[0164] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0165]

[0166] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be included in an amount of 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0167]

[0168] The above negative electrode active material layer can be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support, and then laminating the obtained film by peeling it off from the support on a negative electrode current collector.

[0169]

[0170] The lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0171] In particular, to achieve longer battery life on a single charge, batteries need to be increased in capacity, and this requires large-area electrode technology. However, the process of increasing the electrode area can degrade electrode performance, and there are concerns about thermal runaway and heat propagation to other electrodes in the event of a fire.

[0172] Accordingly, according to another embodiment of the present invention, a battery module including a plurality of the lithium secondary batteries and a battery pack including a plurality of the battery modules are provided.

[0173] The above battery module refers to a battery assembly (assembly) in which a certain number of lithium secondary batteries are bundled and placed in a frame to protect them from external shocks, heat, vibration, etc. The above battery pack refers to the final form of a battery system installed in electric vehicles, etc.

[0174] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0175] The battery module and battery pack according to the present invention include a pouch-type battery case including the above-described film laminate, so that safety due to thermal propagation in the event of an actual fire is maximized, thereby enabling high capacity and large area batteries to be realized.

[0176]

[0177] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0178]

[0179] Examples 1 and 2, Comparative Examples 1 and 2

[0180] <Manufacturing of pouch film laminate>

[0181] A pouch film laminate was manufactured by sequentially laminating an 80 ㎛ thick aluminum alloy as a gas barrier layer, a 25 ㎛ thick nylon film as a stretching auxiliary film, and a 25 ㎛ thick polyester resin film as a surface protection film on one side of an 80 ㎛ thick polypropylene (PP) film as a sealant layer.

[0182] At this time, the polyester film used was a polyester film manufactured by applying the terephthalic acid (TPA) method, which is a method for manufacturing polyethylene terephthalate by reaction of ethylene glycol and terephthalic acid using ethylene glycol or a mixture of ethylene glycol and butylene glycol.

[0183]

[0184] The polyester resin film included in the pouch film laminate of Examples 1 and 2 and Comparative Examples 1 and 2 was dissolved in hexafluoroisopropanol (HFIP), 1 H-NMR and 13 The content of structures derived from each monomer was measured using C-NMR, and is shown in Table 1 below based on 100 mol% of the content of structures derived from terephthalic acid.

[0185]

[0186] Polyester resin (surface protective layer) Ethylene glycol (mol%) Butylene glycol (mol%) Terephthalic acid (mol%) Example 183.5 15.3 100 Example 288.5 10.5 100 Comparative example 195.40 100 Comparative example 279.5 18.6 100

[0187] Experimental example

[0188] (1) Measurement of maximum forming depth

[0189] When each of the manufactured pouch-type film laminates of Examples 1 and 2 and Comparative Examples 1 and 2 was cut to a width of 266 mm and a height of 200 mm and then cold-formed to form a cup portion of 90 mm width and 160 mm height, the processing depth just before the pouch film laminate was broken was defined as the maximum processing depth (unit: mm). Fifteen pouch film laminates of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared, and the above maximum processing depth measurement experiment was performed 15 times, and the average values ​​thereof are shown in Table 2 below.

[0190]

[0191] (2) Chemical resistance test

[0192] After applying 0.1 g of electrolyte to the outermost surface of the pouch film laminates of Examples 1 and 2 and Comparative Examples 1 and 2, respectively, they were stored in a chamber at 60°C for more than 1 day. Then, they were taken out again and the presence or absence of discoloration or change in appearance was compared. This was not tested with objective numbers, but was observed with the naked eye. Cases where there was no change were indicated by ○, and cases where change occurred were indicated by ×.

[0193]

[0194] (3) Heat resistance test

[0195] A heating pad was attached to the surface of each of the pouch-shaped film laminates of manufactured Examples 1 and 2 and Comparative Examples 1 and 2, and heat of 230°C was applied, and then the presence or absence of deformation of the surface protection film was confirmed. Cases where there was no deformation were indicated by ○, and cases where deformation occurred were indicated by ×.

[0196]

[0197] Maximum forming depth Chemical resistance Heat resistance Example 113.5○○ Example 212.5○○ Comparative example 110.0○○ Comparative example 214.0○×

[0198] Referring to Table 2, it can be confirmed that Examples 1 and 2 maintained chemical resistance and heat resistance while increasing the maximum molding depth compared to Comparative Example 1. However, Comparative Example 2 had a problem with heat resistance although the maximum molding depth increased. Through this, it was confirmed that when a polyester resin appropriately including a terephthalic acid-derived structure and a butylene glycol-derived structure is applied to the substrate layer, the moldability of the pouch film laminate can be improved while maintaining the chemical resistance and heat resistance required for the substrate layer of the pouch film laminate.

[0199] [Explanation of symbols]

[0200] 100: Pouch film laminate

[0201] 110: Base layer

[0202] 112: Surface protection film

[0203] 114: Extension auxiliary film

[0204] 120: Gas barrier layer

[0205] 130: Sealant layer

[0206] 200: Lithium secondary battery

[0207] 210: Pouch-type battery case

[0208] 240: Cup

[0209] 241: Reception space

[0210] 242: Flat area

[0211] 243: Slope

[0212] 250: Terrace

[0213] 251: Sealing

[0214] 260: Electrode assembly

[0215] 270: Electrode tab

[0216] 280: Electrode lead

[0217] 290: Lead Film

Claims

1. A pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are sequentially laminated, The above-mentioned substrate layer comprises a polyester resin including an ethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure, A pouch film laminate having a molar ratio of the ethylene glycol-derived structure and the butylene glycol-derived structure of 95:5 to 80:

20.

2. In paragraph 1, The above substrate layer includes a surface protection layer and an extension auxiliary layer, The above surface protective layer includes the above polyester resin, A pouch film laminate, wherein the above-mentioned extension auxiliary layer comprises a polyamide-based resin.

3. In paragraph 2, A pouch film laminate, wherein the surface protective layer has a thickness of 20 ㎛ to 30 ㎛.

4. In paragraph 2, A pouch film laminate having a ratio of the total thickness of the pouch film laminate to the thickness of the surface protective layer of 5 to 10.

5. In paragraph 2, A pouch film laminate, wherein the thickness of the above-mentioned extension auxiliary layer is 20 ㎛ to 30 ㎛.

6. In paragraph 2, A pouch film laminate having a ratio of the thickness of the stretching auxiliary layer to the thickness of the surface protective layer of 1.2 or less.

7. In paragraph 1, A pouch film laminate, wherein the thickness of the gas barrier layer is 60 ㎛ to 130 ㎛.

8. In paragraph 1, A pouch film laminate having a thickness of the gas barrier layer of 70 ㎛ to 90 ㎛.

9. In paragraph 2 A pouch film laminate, wherein the ratio of the thickness of the gas barrier layer to the thickness of the surface protective layer is 2.5 to 3.

3.

10. In paragraph 1, A pouch film laminate having a total thickness of 160 ㎛ to 280 ㎛.

11. In paragraph 1, The above sealant layer is a pouch film laminate comprising a second polymer including polypropylene (PP).

12. In paragraph 1, A pouch film laminate, wherein the sealant layer is a first sealant layer, a second sealant layer, and a third sealant layer sequentially laminated.

13. In paragraph 1, A pouch film laminate having a molar ratio of the ethylene glycol-derived structure to the butylene glycol-derived structure of 1:0.100 to 1:0.

220.

14. In paragraph 1, The above polyester resin is a pouch film laminate comprising a polycondensation reaction product of a mixture of ethylene glycol and butylene glycol and at least one selected from the group consisting of dimethyl terephthalate and terephthalic acid.

15. In paragraph 1, A pouch film laminate wherein the gas barrier layer comprises at least one selected from the group consisting of aluminum, copper, stainless steel, nickel, titanium, and INVAR.

16. A pouch-shaped battery case manufactured by drawing and molding the pouch film laminate of Article 1.

17. Pouch-type battery case according to Article 16; and A pouch-type secondary battery including an electrode assembly housed in the above pouch-type battery case.

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