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 material layer, a gas barrier layer, and a sealant layer are laminated in this order, in which the sealant layer comprises a first sealant layer comprising a polypropylene random copolymer and a second sealant layer comprising a crosslinked polypropylene, and the degree of crosslinking of the second sealant layer is in the range of 52% to 80%.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2023-0176099, filed on December 6, 2023, and Korean Patent Application No. 10-2024-0156612, filed on November 6, 2024, the disclosures of which are incorporated herein by reference.

[0004] This invention relates to pouch-film laminates, pouch-type battery boxes, and pouch-type secondary batteries, and more specifically to pouch-film laminates having excellent insulation properties while reducing the cycle time required to seal the pouch-film laminate, pouch-type battery boxes prepared by forming the pouch-film laminate, and pouch-type secondary batteries. Background Technology

[0005] Generally, secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable gaming devices, power tools, and electric bicycles, but also in large products requiring high output, such as electric and hybrid vehicles, as well as in power storage devices and backup power storage devices that store surplus electricity or renewable energy.

[0006] To fabricate these secondary batteries, firstly, an electrode active material slurry is applied to the positive and negative current collectors to prepare the positive and negative electrodes, respectively. The positive and negative electrodes are then stacked on two sides of a separator to form an electrode assembly with a predetermined shape. Next, the electrode assembly is placed in a battery case, and the battery case is sealed after electrolyte is injected.

[0007] Secondary batteries are classified into pouch-type, can-type, etc., based on the material used to house the electrode assembly. Pouch-type batteries house the electrode assembly in a pouch made of a flexible polymer material. Can-type batteries house the electrode assembly in a box made of a material such as metal or plastic.

[0008] The bag, serving as the case for a pouch-type secondary battery, is prepared by pressing a flexible pouch film laminate to form a cup-shaped portion. Once the cup-shaped portion is formed, the secondary battery can be fabricated by accommodating the electrode assembly within the internal containment space of the cup-shaped portion and sealing the sealing portion.

[0009] Typically, a bag film laminate consists of multiple layers, in which a polymer film, such as polyethylene terephthalate, is laminated on one surface of a metal gas barrier layer, and a sealant layer is laminated on the other surface of the metal gas barrier layer.

[0010] Recently, with the increasing capacity of pouch-type secondary batteries, the demand for bags with excellent formability has gradually increased. When forming a thick gas barrier layer to prepare a bag with good formability, a problem exists: the sealant layer does not easily melt during the sealing of the pouch-type battery case. Traditionally, to solve this problem, increasing the sealing temperature and / or sealing time during the sealing of the pouch-type battery case is used as a method of applying more heat.

[0011] However, increasing the sealing time to fully seal the pouch-type battery case by sufficiently melting the sealant layer during sealing results in a decrease in the productivity of the secondary batteries due to the increased time required for their fabrication. Furthermore, while increasing the sealing temperature may reduce the sealing time, defects may occur in the pouch's appearance if the base material layer deforms due to melting.

[0012] The problem arises when excessive heat is applied to the sealant layer during the sealing process of a pouch battery case. This can lead to a decrease in the insulation resistance of the pouch membrane due to excessive deformation of the sealant layer. In this case, the insulation performance of the pouch battery case may deteriorate, potentially causing the secondary battery to experience low voltage. This could result in the battery failing to maintain a steady-state voltage, posing a risk of explosion or fire due to short circuits within the battery, and potentially causing injury to the user.

[0013] Therefore, there is a need to develop a pouch-film laminate that can reduce sealing time without increasing sealing temperature when sealing pouch-type battery boxes, while ensuring the insulation performance of the pouch-type battery boxes. Summary of the Invention

[0014] Technical issues

[0015] One aspect of the present invention provides a pouch-film laminate, a pouch-shaped battery box, and a pouch-shaped secondary battery. The pouch-film laminate can improve both sealing quality and processability by reducing sealing time during the process of sealing the pouch-shaped battery box prepared from the pouch-film laminate, while preventing deformation of the sealing portion, and can fully ensure the insulation performance of the pouch-shaped battery box.

[0016] Technical solution

[0017] [1] The present invention provides a bag film laminate in which a base material layer, a gas barrier layer and a sealant layer are sequentially laminated, wherein the sealant layer includes a first sealant layer comprising a random copolymer of polypropylene and a second sealant layer comprising crosslinked polypropylene, and the degree of crosslinking of the crosslinked polypropylene is in the range of 52% to 80%.

[0018] [2] The present invention provides the bag film composite of [1] above, wherein the first sealant layer comprises at least one selected from the group consisting of ethylene-propylene random copolymer and butene-propylene random copolymer.

[0019] [3] The present invention provides a bag film composite of [1] or [2] above, wherein, based on the total weight of the first sealant layer, the ethylene monomer of the polypropylene random copolymer is included in an amount of 5% to 50% by weight.

[0020] [4] The present invention provides a bag film composite of at least one of [1] to [3] above, wherein the second sealant layer comprises cross-linked homopolymer polypropylene.

[0021] [5] The present invention provides a bag film composite of at least one of [1] to [4] above, wherein the ratio (A / B) of the thickness (A) of the first sealant layer to the thickness (B) of the second sealant layer is in the range of 0.6 to 1.5.

[0022] [6] The present invention provides a bag film composite of at least one of [1] to [5] above, wherein the thickness of the sealant layer is 30 μm to 130 μm.

[0023] [7] The present invention provides a bag film laminate of at least one of [1] to [6] above, wherein the insulation resistance of the bag film laminate is 1000 MΩ or greater when the bag film laminate is sealed at 200°C and 0.1 MPa for 3 seconds.

[0024] [8] The present invention provides a bag film composite of at least one of [1] to [7] above, wherein the melting temperature of the sealant layer is 120°C to 150°C.

[0025] [9] The present invention provides a bag film laminate of at least one of [1] to [8] above, wherein, when the two bag film laminates are sealed at 200°C and 0.1 MPa for 3 seconds, the total thickness (D) of the two bag film laminates is... S ) and the total thickness of the two bag film layers combined before sealing (D) A The ratio of (D) S / D A It is in the range of 0.2 to 0.6.

[0026]

[10] The present invention provides a bag film composite of at least one of [1] to [9] above, wherein the sealant layer may further include a third sealant layer as the outermost layer, wherein the third sealant layer comprises a random copolymer of polypropylene.

[0027]

[11] The present invention provides a bag film laminate of at least one of [1] to

[10] above, wherein the sealant layer is a sealant layer in which a first sealant layer, a second sealant layer and a third sealant layer are sequentially laminated.

[0028]

[12] The present invention provides a pouch-type battery box, which is prepared by forming a pouch-film laminate of any one of [1] to

[11] above.

[0029]

[13] The present invention provides a pouch-type secondary battery, comprising: the pouch-type battery case of

[12] above, which is prepared by forming a pouch membrane composite; and an electrode assembly, which is housed in the pouch-type battery case.

[0030] Beneficial effects

[0031] According to the present invention, since the sealant layer comprises a first sealant layer containing a random copolymer of polypropylene and a second sealant layer containing crosslinked polypropylene, and the degree of crosslinking of the second sealant layer is adjusted to a specific range, melting of the base material layer does not occur during the sealing process of the pouch battery case. Therefore, appearance defects can be improved by preventing deformation of the sealed portion, while sealing time can be reduced. Thus, the sealing quality, processability, and productivity of the pouch battery case prepared from the pouch film layer assembly of the present invention can be ensured, and the durability and lifespan characteristics of the pouch secondary battery can be improved.

[0032] Furthermore, even when excessive heat is applied to the sealant layer during the sealing process of the pouch battery box, the insulation resistance of the pouch battery box can remain above a certain level, thus ensuring its insulation performance. Therefore, since the secondary battery can operate at normal voltage, its performance will not degrade, and stability can be improved by preventing short circuits within the battery. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view illustrating the structure of a bag-film laminate according to an embodiment of the present invention.

[0034] Figure 2 This is a cross-sectional view illustrating the structure of a bag-film laminate according to another embodiment of the present invention.

[0035] Figure 3 This is an exploded assembly diagram of the pouch-type secondary battery according to the present invention. Detailed Implementation

[0036] The invention will be described in more detail below.

[0037] It should be understood that the words or terms used in the specification and claims should not be interpreted as having the meaning defined in a commonly used dictionary, and further understood that, based on the principle that the inventor may appropriately define the meaning of words or terms to best interpret the invention, the words or terms should be interpreted as having a meaning consistent with their meaning in the context of the related technology and the inventive concept.

[0038] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the invention. Unless otherwise stated, singular terms may include plural forms.

[0039] It will be further understood that the terms “comprising,” “including,” or “having” in this specification specify the presence of the stated features, number, steps, elements, or combinations thereof, but do not preclude the presence or addition of one or more other features, number, steps, elements, or combinations thereof.

[0040] In this specification, "degree of crosslinking" refers to the ratio of chemical bonds formed between polypropylene chains. The "degree of crosslinking" of crosslinked polypropylene can be measured using the method for measuring the degree of crosslinking as specified in ASTM D2765. Specifically, after a certain amount of sample is ground to prepare it into powder form and placed in a Timble Filter, and then the sample is circulated at 110°C for 12 hours using xylene contained in a reactor connected to a cooler to dissolve all uncrosslinked components, the degree of crosslinking of the crosslinked polyolefin resin can be obtained by measuring the weight of the crosslinked and undissolved sample compared to the weight of the initially added sample and then calculating it using the following equation.

[0041] [Equation 1]

[0042] Degree of crosslinking (%) = (Weight of sample not dissolved in solvent / Weight of initially added sample) × 100

[0043] The pouch-film laminate, pouch-type battery case, and lithium secondary battery according to the present invention include at least one of the following disclosed configurations, and may include any combination of technically possible configurations among the following configurations.

[0044] Extensive research has been conducted on the development of a pouch-film laminate that can prevent deformation of the sealing portion during sealing while reducing sealing time and ensuring the insulation resistance of the pouch battery box is at a certain or higher level. Therefore, the inventors have discovered that when the sealant layer comprises a first sealant layer containing a random copolymer of polypropylene and a second sealant layer containing crosslinked polypropylene, and the degree of crosslinking of the second sealant layer is in the range of 52% to 80%, the sealing time can be reduced without increasing the sealing temperature when sealing the pouch battery box prepared using the pouch-film laminate. Thus, sealing quality, productivity, and processability can be improved simultaneously. Furthermore, due to the sufficient insulation performance of the pouch battery box, battery performance and stability can also be improved, thereby leading to the completion of this invention.

[0045] The invention will be described in more detail below.

[0046] Bag film layer composite

[0047] The bag film laminate according to the present invention is a bag film laminate in which a base material layer, a gas barrier layer and a sealant layer are sequentially laminated, wherein the sealant layer comprises a first sealant layer comprising a random copolymer of polypropylene and a second sealant layer comprising crosslinked polypropylene, and the degree of crosslinking of the second sealant layer is in the range of 52% to 80%.

[0048] When the pouch-film laminate is sealed at 200°C and 0.1 MPa for 3 seconds, the insulation resistance of the pouch-film laminate can be 1000 MΩ or greater. Specifically, the insulation resistance can be 1000 MΩ or greater, 1100 MΩ or greater, 1200 MΩ or greater, 1300 MΩ or greater, 1400 MΩ or greater, 1500 MΩ or greater, 1600 MΩ or greater, or 1700 MΩ or greater. Meeting these insulation resistance ranges allows the fabricated pouch-type battery case to have sufficient insulation performance, enabling operation of secondary batteries at normal voltages, preventing short circuits in the battery, improving stability by reducing the risk of explosion or ignition, and lowering the risk of injury to the user.

[0049] The total thickness of the bag-film laminate according to the present invention can be from 120 µm to 250 µm, preferably from 140 µm to 230 µm, and more preferably from 150 µm to 215 µm. When the thickness of the bag-film laminate meets the above range, the formation depth can be increased while minimizing the reduction in sealing durability and the reduction in battery housing space caused by the increase in the thickness of the bag-film laminate.

[0050] In this case, the total thickness (D) of the two bag film layers combined when sealed at 200°C and 0.1 MPa for 3 seconds is... S ) and the total thickness of the two bag film layers combined before sealing (D) A The ratio of (D) S / D A It can be in the range of 0.2 to 0.6. Specifically, D S / D A The value can be 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.35 or greater, 0.4 or greater, or 0.4 or greater; and it can be 0.6 or less, 0.55 or less, 0.5 or less, or 0.45 or less. When these ranges are met, the sealed pouch-type battery box exhibits excellent sealing and insulation performance.

[0051] Figure 1 and Figure 2 This is a cross-sectional view illustrating the structure of a bag-film laminate according to an embodiment of the present invention.

[0052] Reference Figure 1 and Figure 2 According to an embodiment of the present invention, the bag film laminate 100 includes a base material layer 110, an air barrier layer 120 and a sealant layer 130, and the base material layer 110, the air barrier layer 120 and the sealant layer 130 can be sequentially laminated in the bag film laminate 100.

[0053] The bag-film laminate according to the present invention can be prepared by methods known in the art for preparing bag-film laminates. For example, the bag-film laminate of the present invention can be prepared by attaching a base material layer 110 to the upper surface of a gas barrier layer 120 with an adhesive and forming a sealant layer 130 on the lower surface of a gas barrier layer 120 by co-extrusion or an adhesive layer, and can be prepared by methods such as dry lamination or sandwich lamination. However, the methods for preparing the bag-film laminate are not limited to these.

[0054] In the following text, reference will be made to Figure 1 and Figure 2 Describe in detail each layer included in the bag film composite.

[0055] (1) Base material layer

[0056] The base material layer 110 is formed as the outermost layer of the bag membrane composite 100 to protect the secondary battery from friction and impact with the outside. The base material layer 110 is formed of a polymer, which allows it to electrically insulate the electrode assembly from the outside.

[0057] The base material layer 110 may be formed of at least one material selected from the group consisting of: polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyacrylate, and polytetrafluoroethylene. Preferably, the base material layer 110 may be formed of polyethylene terephthalate (PET), nylon, or a combination thereof, which have abrasion resistance and heat resistance.

[0058] The thickness of the base material layer 110 can be from 5 μm to 100 μm, particularly from 7 μm to 70 μm, and even more particularly from 10 μm to 60 μm. When the thickness of the base material layer 110 meets the above range, the energy density to volume ratio of the secondary battery can be excellent due to its excellent external insulation performance and the overall thinness of the bag.

[0059] The base material layer 110 can have a single-layer structure formed of any material. Alternatively, the base material layer 110 can have a composite layer structure formed by laminating two or more materials respectively. An adhesive layer can be additionally disposed between the individual layers in the composite layer structure.

[0060] Specifically, the base material layer 110 according to the present invention may include a first base material layer 112 and a second base material layer 114. In this case, the first base material layer 112 may be the outermost layer of the bag film composite, and the second base material layer 114 may be the layer disposed between the first base material layer 112 and the gas barrier layer 120. The first base material layer 112 and the second base material layer 114 may be formed of materials with different materials and / or physical properties. An interface may exist between the first base material layer 112 and the second base material layer 114. This means that the first base material layer 112 and the second base material layer 114 are different layers from each other and can be formed separately.

[0061] Each of the first base material layer 112 and the second base material layer 114 described above will be described in more detail below.

[0062] 1) First base material layer

[0063] The first base material layer 112 serves to prevent moisture from seeping through the outside of the bag. The first base material layer 112 can be formed of at least one material selected from the group consisting of: polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyacrylate, and polytetrafluoroethylene. Preferably, the first base material layer 112 may comprise a polyester base film with abrasion resistance and heat resistance. For example, the first base material layer 112 may comprise at least one selected from the group consisting of: polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, but is not limited thereto. The thickness of the first base material layer 112 can be from 10 μm to 50 μm, particularly from 10 μm to 40 μm, and more particularly from 12 μm to 25 μm. When the thickness of the first base material layer 112 meets the above-mentioned numerical range, moisture penetration into the interior of the bag-membrane composite can be effectively suppressed, while ensuring the bag's insulation performance and formability. Furthermore, because the entire bag is thin, the energy density to volume ratio of the secondary battery is excellent.

[0064] 2) Second base material layer

[0065] The second base material layer 114 can play a role in improving the formability of the bag. The second base material layer 114 may include a polyamide-based film. For example, the second base material layer 114 may include at least one selected from the group consisting of: nylon 6, nylon 66, nylon MXD6 (polyxylylene adipamide), nylon 4, nylon 46, and nylon 410, but is not limited thereto. Preferably, the second base material layer 114 may include nylon 6, and in this case, the excellent elongation properties of nylon 6 provide the advantage of improved bag formability. The thickness of the second base material layer 114 may be from 10 μm to 50 μm, particularly from 10 μm to 40 μm, and more particularly from 15 μm to 35 μm. When the thickness of the second base material layer 114 meets the above numerical range, a decrease in the energy density to volume ratio of the secondary battery due to excessive increase in the thickness of the bag film composite can be prevented, while ensuring the formability of the bag.

[0066] The second base material layer 114 may include metal oxide particles. The metal oxide particles can be hydroxylated by reacting with moisture introduced into the second base material layer 114 to remove moisture. The metal oxide particles may include at least one selected from the group consisting of CaO, MnO, SrO, MgO, and ZnO. Preferably, the metal oxide particles may include at least one of CaO and MgO, which is advantageous for hydroxylation with water.

[0067] The second base material layer 114 may also include additives. Adding additives to the second base material layer 114 can alter its physical properties. For example, at least one of carbon fiber, glass fiber, and aramid fiber can be added as an additive to adjust the tensile strength of the second base material layer 114.

[0068] (2) Gas barrier layer

[0069] The gas barrier layer 120 is laminated between the base material layer 110 and the sealant layer 130 to ensure the mechanical strength of the bag, prevent gas or moisture from flowing in and out of the secondary battery, and prevent electrolyte from leaking from the inside of the bag-type battery box.

[0070] The gas barrier layer 120 can be formed of a metal. For example, the gas barrier layer can be a thin film of at least one metal selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and INVAR, but is not limited thereto.

[0071] According to an embodiment of the present invention, the gas barrier layer 120 can be formed of an aluminum alloy thin film. When the gas barrier layer 120 is formed using an aluminum alloy thin film, it is lightweight while ensuring mechanical strength exceeding a predetermined level, its electrochemical performance can be compensated by the electrode assembly and electrolyte, and its heat dissipation performance can be ensured. The aluminum alloy thin film may include elements other than aluminum (Al). For example, the aluminum alloy thin film may include 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).

[0072] In another example, the gas barrier layer 120 can be formed of a stainless steel film. Specifically, the gas barrier layer 120 can be prepared by forming and / or processing a stainless steel film. Because the gas barrier layer 120 formed of stainless steel has relatively low thermal conductivity, it effectively prevents or delays heat diffusion to other cells during thermal runaway, and because the gas barrier layer 120 has relatively high toughness, it can suppress the formation of cracks in the pouch during use of the pouch battery. The stainless steel may include elements other than iron (Fe), such as at least one selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0073] The thickness of the gas barrier layer 120 can be from 20 μm to 100 μm, preferably from 30 μm to 90 μm, and more preferably from 35 μm to 85 μm. When these ranges are met, since the present invention does not cause deformation of the base material layer even when the sealing temperature is increased to allow heat transfer to the sealant layer, the gas barrier performance and formability can be improved when a cup-shaped portion is formed using a gas barrier layer that is thicker than a conventional gas barrier layer.

[0074] (3) Sealant layer

[0075] The sealant layer 130 is used to completely seal the interior of the pouch battery case by thermally bonding it to each other at the sealing portion when sealing the pouch battery case that houses the electrode assembly inside.

[0076] The thickness of the sealant layer 130 can be from 50 μm to 140 μm, particularly from 60 μm to 130 μm, and even more particularly from 70 μm to 120 μm. When the thickness of the sealant layer meets the above range, it has the effect of ensuring the sealing strength of the sealed part while ensuring the formability of the bag film layer assembly.

[0077] The sealant layer 130 according to the invention can have a composite layer structure formed by laminating two or more materials respectively. For example, the sealant layer 130 can have a multilayer structure. An adhesive layer and / or a surface layer can be provided between the individual layers of the sealant layer 130 having a composite layer structure. Since the adhesive layer and / or the surface layer have thermal adhesive properties, they can play a role in aiding the adhesion between the individual layers of the sealant layer 130. For example, the adhesive layer and / or the surface layer can include, but are not limited to, a polypropylene-based resin. Furthermore, the adhesive layer and / or the surface layer can be provided between the sealant layer 130 and the gas barrier layer 120.

[0078] Specifically, the sealant layer 130 according to the present invention includes a first sealant layer 132 and a second sealant layer 134. As another example, the sealant layer 130 may also include a third sealant layer 136 and / or a fourth sealant layer 138 in addition to the first sealant layer 132 and the second sealant layer 134. Each layer of the sealant layer 130, including the first sealant layer 132 and the second sealant layer 134, may be formed of materials with different materials and / or physical properties. Interfaces may exist between the various layers included in the sealant layer 130. This means that the individual layers are distinct from each other and can be formed independently.

[0079] Specifically, in the bag film composite according to the invention, the sealant layer includes a first sealant layer 132 comprising a random copolymer of polypropylene and a second sealant layer 134 comprising cross-linked polypropylene.

[0080] When the sealant layers of the first and second housings come into contact with each other in the sealed portion and are sealed by thermal bonding, the sealant layers must completely seal the pouch battery case to prevent the electrolyte solution inside the pouch battery case from leaking to the outside, and must protect the secondary battery from external impacts or moisture penetration. Furthermore, since the sealant layer is in direct contact with the electrode components and / or electrolyte inside the pouch battery case, it must possess insulating properties and corrosion resistance. For this purpose, the sealant layer must have excellent thermal bonding strength and insulation resistance, ensuring that the pouch battery case has sufficient sealing, insulation, and corrosion resistance.

[0081] To ensure excellent thermal bonding strength of the sealant layers, sufficient heat must be applied during sealing to allow the sealant layers to melt sufficiently and adhere tightly to each other. In this case, as a way to apply more heat when sealing pouch-type battery cases, the sealing temperature and / or sealing time can be increased.

[0082] However, with increased sealing temperature, the base material layer may deform as moisture evaporates, and thus the battery quality may be reduced due to potential defects in the appearance of the pouch-shaped battery box.

[0083] Therefore, traditionally, polypropylene homopolymers or polypropylene block copolymers are typically included in the sealant layer, and the sealing time is increased to improve the sealing strength of the pouch battery case. However, in this case, the increased sealing time leads to an increased time required for the secondary battery manufacturing process, resulting in reduced processability and productivity of the secondary battery.

[0084] Therefore, since the bag film composite according to the present invention includes a random copolymer of polypropylene instead of a homopolymer of polypropylene or a block copolymer of polypropylene in the first sealant layer, the time required for sealing is reduced, while ensuring sufficient sealing strength of the bag-type secondary battery.

[0085] However, when the sealant layer consists only of a random copolymer of polypropylene, the arrangement of the random copolymer may change as the sealant layer melts due to excessive heat applied to the sealing portion during the sealing process of the pouch-type secondary battery. This could result in a significant reduction in the thickness of the sealant layer. If the sealant layer thickness is reduced, corrosion problems may be exacerbated by electrolyte penetration into the sealant layer due to contact with it. Furthermore, as the insulation resistance of the sealing portion decreases below a certain level, the insulation performance of the pouch-type battery box deteriorates, potentially posing a risk of short circuits, explosions, or ignition within the battery, and could cause serious injury to the user.

[0086] Therefore, since the bag film composite according to the present invention includes a second sealant layer comprising cross-linked polypropylene and a first sealant layer comprising a random copolymer of polypropylene, even when the sealing portion is compressed during the sealing process of the bag-type secondary battery when a large amount of heat is applied to the sealing portion, the deformation of the polymer components and the excessive reduction of the thickness and insulation resistance of the sealant layer can be prevented. Thus, the insulation performance and corrosion resistance of the prepared bag-type battery box can be sufficiently ensured.

[0087] The first sealant layer 132 and the second sealant layer 134 may be sequentially laminated, or the second sealant layer 134 and the first sealant layer 132 may be sequentially laminated. In cases where a third sealant layer 136 is also included, the third sealant layer 136 may be located at the outermost portion of the sealant layers, and the first sealant layer 132, the second sealant layer 134, and the third sealant layer 136 may be sequentially laminated, or the second sealant layer 134, the first sealant layer 132, and the third sealant layer 136 may be sequentially laminated.

[0088] The ratio (A / B) of the thickness (A) of the first sealant layer 132 to the thickness (B) of the second sealant layer 134 can be in the range of 0.6 to 1.5. Specifically, the ratio (A / B) of the thickness (A) of the first sealant layer 132 to the thickness (B) of the second sealant layer 134 can be 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater, and can be 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, or 1.1 or less. When the above ranges are met, the prepared pouch-type battery box has excellent sealing, corrosion resistance, and insulation properties, and at the same time shortens the sealing time, thus the productivity of the secondary battery can be excellent.

[0089] Each layer of the sealant layer will be described in detail below.

[0090] 1) First sealant layer

[0091] The first sealant layer 132 comprises a polypropylene random copolymer. In this case, the polypropylene random copolymer as a copolymer component refers to a copolymer containing propylene and other copolymer components besides propylene. Specifically, the first sealant layer 132 may include at least one selected from the group consisting of ethylene-propylene random copolymers and butene-propylene random copolymers, and may preferably include an ethylene-propylene random copolymer. When the polypropylene random copolymer is included in the first sealant layer, the desired seal thickness can be achieved quickly when the same amount of heat is applied due to the high melt flow rate (MFR) and low melting point. Therefore, compared to the case of including a polypropylene homopolymer, the sealing time can be shortened and the processing time of the secondary battery can be reduced even without increasing the sealing temperature, thus improving productivity and processability. At the same time, the pouch battery box can have excellent sealing performance due to the high thermal bonding strength of the first sealant layer.

[0092] Based on the total weight of the first sealant layer 132, the ethylene monomer of the polypropylene random copolymer may be included in an amount from 5% to 50% by weight. Specifically, based on the total weight of the first sealant layer 132, the ethylene monomer of the polypropylene random copolymer may be included in an amount of 5% or more, 7% or more, 10% or more, 12% or more, 15% or more, or 17% or more, and may be included in an amount of 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, or 20% or less. For example, based on the total weight of the first sealant layer 132, the ethylene monomer of the polypropylene random copolymer may be included in an amount from 5% to 50% by weight, preferably from 10% to 30% by weight, more preferably from 12% to 25% by weight, and even more preferably from 15% to 20% by weight. If the above conditions are met, the sealing time can be shortened while maintaining excellent thermal bonding strength, since the sealant layer can be sealed by rapid melting during the sealing process.

[0093] The first sealant layer 132 may have a melting temperature of 120°C to 150°C. Specifically, the melting temperature of the first sealant layer 132 may be 120°C or higher, 125°C or higher, 130°C or higher, or 135°C or higher, and may be 150°C or lower, 145°C or lower, or 140°C or lower. When the melting temperature is met, the sealant layer can fully melt within the sealing process temperature to achieve excellent sealing performance.

[0094] The thickness of the first sealant layer 132 can be from 10 µm to 90 µm, particularly from 10 µm to 60 µm, and more particularly from 10 µm to 40 µm. When the thickness of the first sealant layer 132 meets the above range, excellent sealing strength can be achieved because the pouch-type battery box prepared from the pouch-film laminate exhibits excellent sealing durability and insulation performance. Furthermore, during the extrusion process of the pouch-film laminate, extrusion can be performed with a uniform thickness, and the problem of reduced energy density in the prepared pouch-type secondary battery can be prevented.

[0095] According to an embodiment of the present invention, the first sealant layer 132 may be a layer in direct contact with the gas barrier layer 120, or it may be a layer that is not in direct contact with the gas barrier layer 120. When the first sealant layer is in direct contact with the gas barrier layer 120, if the bag film composite 100 is co-extruded, the first sealant layer 132 can adhere directly to the gas barrier layer 120. In another example, an adhesive layer and / or a surface layer may be provided between the first sealant layer 132 and the gas barrier layer 120 to improve the adhesion between them. When the first sealant layer is not in direct contact with the gas barrier layer 120, a second sealant layer 134 may be provided between the first sealant layer 132 and the gas barrier layer 120.

[0096] 2) Second sealant layer

[0097] The second sealant layer 134 can be formed of a material with insulating, corrosion-resistant, and sealing properties. Specifically, due to the second sealant layer 134 and the accommodating space ( Figure 3 Electrode assembly inside 224) Figure 3 Since the second sealant layer 134 is in direct contact with the electrolyte (260) and / or the electrolyte, it can be formed of a material with insulating and corrosion-resistant properties. Furthermore, since the second sealant layer 134 completely seals the interior of the battery case to prevent material movement between the interior and exterior, it can be formed of a material with high sealing performance.

[0098] The second sealant layer 134 may include cross-linked polypropylene. The cross-linked polypropylene may have a structure in which the polypropylene straight chains are covalently linked to each other at multiple sites, and the cross-linked polypropylene may include partially cross-linked polypropylene. Specifically, the second sealant layer may include cross-linked homopolymer polypropylene.

[0099] In this invention, since cross-linked polypropylene is included in the second sealant layer 134, even when a large amount of heat is applied to the sealant layer during the sealing of the bag film assembly, the distance between the polypropylene chains remains within a certain range due to the covalent bonds between the polypropylene chains of the cross-linked polypropylene, even under heat and pressure. Therefore, even if sealing occurs during the sealing process of the bag film assembly, the sealant layer can maintain a certain thickness or greater, and thus, even if the sealant layer comes into contact with the electrolyte solution contained in the battery case, it can exhibit corrosion resistance. Furthermore, since the insulation resistance of the sealed bag-type battery case can be at a predetermined level or higher, insulation performance and corrosion resistance can be ensured. Therefore, the advantage lies in ensuring the stability and battery performance of the prepared bag-type secondary battery.

[0100] The degree of crosslinking of cross-linked polypropylene can range from 52% to 80%. Specifically, the degree of crosslinking of cross-linked polypropylene can be 52% or greater, 55% or greater, 57% or greater, or 60% or greater, and can be 80% or less, 75% or less, 70% or less, 65% or less, or 60% or less. When the degree of crosslinking is less than 52%, the distance between polypropylene chains may not be maintained due to the low crosslinking ability of cross-linked polypropylene when a large amount of heat is applied to the sealant layer. Therefore, the thickness of the sealant layer after sealing may be significantly reduced, and thus, the insulation performance of the pouch battery box may deteriorate. When the degree of crosslinking is greater than 80%, the thickness of the sealant layer does not decrease significantly when sealing the pouch battery box, but delamination may occur at the interface of the second sealant layer, and thus, the insulation performance, corrosion resistance, and sealing performance of the pouch battery box may be affected. Therefore, when the degree of crosslinking is within the range of 52% to 80%, the prepared pouch battery box can have excellent insulation performance while preventing delamination between the sealant layer interfaces.

[0101] By adjusting the amount of crosslinking agent added, the degree of crosslinking of crosslinked polypropylene can be adjusted to an appropriate range. Specifically, the crosslinking agent can be a tin-based compound, more specifically an organotin-based compound, and more specifically an octyltin-based compound and / or a butyltin-based compound.

[0102] The second sealant layer 134 may have a melting temperature of 120°C to 150°C. Specifically, the melting temperature of the second sealant layer 134 may be 120°C or higher, 125°C or higher, 130°C or higher, or 135°C or higher, and may be 150°C or lower, 145°C or lower, or 140°C or lower. When the melting temperature is met, the sealant layer can fully melt within the sealing process temperature to achieve excellent sealing performance.

[0103] The thickness of the second sealant layer 134 can be from 10 µm to 90 µm, particularly from 10 µm to 60 µm, and more particularly from 10 µm to 40 µm. When the thickness of the second sealant layer 134 meets the above range, excellent sealing strength can be achieved due to the excellent sealing durability and insulation performance of the pouch-type battery case prepared from the pouch-film laminate. Furthermore, during the extrusion process of the pouch-film laminate, extrusion can be performed with a uniform thickness, and the problem of reduced energy density in the prepared pouch-type secondary battery can be prevented.

[0104] According to an embodiment of the present invention, the second sealant layer 134 may be a layer in direct contact with the gas barrier layer 120, or it may be a layer that is not in direct contact with the gas barrier layer 120. When the second sealant layer is in direct contact with the gas barrier layer, if the bag film composite 100 is co-extruded, the second sealant layer 134 can be directly adhered to the gas barrier layer 120. In another example, an adhesive layer and / or a surface layer may be provided between the second sealant layer 134 and the gas barrier layer 120 to improve the adhesion between them. When the second sealant layer is not in direct contact with the gas barrier layer 120, the first sealant layer 132 may be provided between the second sealant layer 134 and the gas barrier layer 120.

[0105] The second sealant layer 134 may be configured to directly contact the first sealant layer 132, or it may be configured not to directly contact the first sealant layer 132. When the second sealant layer 134 is not in direct contact with the first sealant layer 132, the bag-film assembly may further include at least one layer disposed between the first sealant layer 132 and the second sealant layer 134. For example, an intermediate layer (not shown) may be disposed between the first sealant layer 132 and the second sealant layer 134 to improve the insulation performance of the bag-film assembly. The intermediate layer may include at least one of polypropylene and homopolymer polypropylene. The thickness of the intermediate layer may be in the range of 80 µm or less, particularly in the range of 10 µm to 60 µm, and more particularly in the range of 10 µm to 30 µm. When the thickness of the intermediate layer meets the above numerical ranges, excellent sealing strength can be ensured while improving the co-extrusion formability of the sealant layers.

[0106] 3) Third sealant layer

[0107] The sealant layer may also include a third sealant layer 136 as the outermost layer. In this case, the third sealant layer 136 may be a material with high thermal bonding strength, wherein the sealant layers are in contact with each other when the sealing bag film layers are assembled.

[0108] The third sealant layer may include a random copolymer of polypropylene. Specifically, the third sealant layer may include at least one selected from the group consisting of ethylene-propylene random copolymers and butene-propylene random copolymers, and may preferably include an ethylene-propylene random copolymer. When a random copolymer of polypropylene is included in the third sealant layer, the desired seal thickness can be achieved quickly with the same amount of heat applied due to the high melt flow rate (MFR) and low melting point. Therefore, compared to the case of including a homopolymer of polypropylene, even without increasing the sealing temperature, productivity and processability can be improved because the sealing time can be shortened and the handling time of the secondary battery can be reduced. At the same time, the pouch battery case can have excellent sealing performance due to the high thermal bond strength of the third sealant layer.

[0109] The thickness of the third sealant layer can be from 5 µm to 50 µm, particularly from 5 µm to 30 µm, and even more particularly from 7 µm to 20 µm. When the thickness of the third sealant layer meets these ranges, excellent sealing strength can be achieved due to the superior sealing durability and insulation properties of the pouch-type battery case prepared from the pouch-film composite. Furthermore, during the extrusion process of the pouch-film composite, uniform thickness can be achieved, and the problem of reduced energy density in the prepared pouch-type secondary battery can be prevented.

[0110] The third sealant layer may be configured to be in direct contact with the second sealant layer, or it may be configured not to be in direct contact with the second sealant layer. When the third sealant layer and the second sealant layer 134 are not in direct contact, the bag-film assembly may further include at least one layer disposed between the second sealant layer 134 and the third sealant layer. For example, an intermediate layer (not shown) may be disposed between the second sealant layer 134 and the third sealant layer to improve the insulation performance of the bag-film assembly. The intermediate layer may include at least one of polypropylene and homopolymer polypropylene. The thickness of the intermediate layer may be in the range of 80 µm or less, particularly in the range of 10 µm to 60 µm, and more particularly in the range of 10 µm to 30 µm. When the thickness of the intermediate layer meets the above numerical ranges, excellent sealing strength can be ensured while improving the co-extrusion formability of the sealant layers.

[0111] 4) Fourth sealant layer

[0112] The sealant layer may further include a fourth sealant layer 138 located between the gas barrier layer and the first sealant layer. In this case, the fourth sealant layer 138 may be a material with high delamination strength to serve as the interface between the gas barrier layer and the sealant layer.

[0113] The fourth sealant layer may include a polypropylene random copolymer. Specifically, the fourth sealant layer may include at least one selected from the group consisting of ethylene-propylene random copolymers and butene-propylene random copolymers, and may preferably include an ethylene-propylene random copolymer. When a polypropylene random copolymer is included in the fourth sealant layer, the delamination strength at the interface between the gas barrier layer and the sealant layer can be improved.

[0114] The thickness of the fourth sealant layer can be from 5 µm to 50 µm, particularly from 5 µm to 30 µm, and even more particularly from 7 µm to 20 µm. When the thickness of the fourth sealant layer meets these ranges, excellent sealing strength can be achieved due to the superior sealing durability and insulation properties of the pouch-type battery case prepared from the pouch-film composite. Furthermore, during the extrusion process of the pouch-film composite, uniform thickness can be achieved, and the problem of reduced energy density in the prepared pouch-type secondary battery can be prevented.

[0115] The fourth sealant layer may be configured to be in direct contact with the first sealant layer, or it may be configured not to be in direct contact with the first sealant layer. When the fourth sealant layer and the first sealant layer 132 are not in direct contact, the bag-film assembly may further include at least one layer disposed between the second sealant layer 134 and the third sealant layer. For example, an intermediate layer (not shown) may be disposed between the first sealant layer 132 and the fourth sealant layer 138 to improve the insulation performance of the bag-film assembly. The intermediate layer may include at least one of polypropylene and homopolymer polypropylene. The thickness of the intermediate layer may be in the range of 80 µm or less, particularly in the range of 10 µm to 60 µm, and more particularly in the range of 10 µm to 30 µm. When the thickness of the intermediate layer meets the above numerical ranges, excellent sealing strength can be ensured while improving the co-extrusion moldability of the sealant layers.

[0116] pouch battery box

[0117] Figure 3 This is an exploded assembly diagram of the pouch-type secondary battery 200 according to the present invention.

[0118] Reference Figure 3 The pouch-type battery case 210 can be prepared by forming the pouch-film laminate described above according to the present invention. The pouch-type battery case 210 can accommodate the electrode assembly 260 inside. Since the detailed configuration and physical properties of the pouch-film laminate are the same as those of the pouch-film laminate described above, a detailed description is omitted.

[0119] The pouch-type battery box 210 can be fabricated by drawing and stretching using a stamping press or similar method. Therefore, the pouch-type battery box 210 may include a cup-shaped portion 222 and a receiving portion 224. The receiving portion 224 is where electrode components are received; specifically, the receiving portion 224 may refer to a pocket-shaped receiving space formed inside the cup-shaped portion 222 during its formation.

[0120] According to embodiments of the present invention, such as Figure 3 As shown, the pouch-type battery case 210 may include a first housing 220 and a second housing 230. The first housing 220 includes a receiving portion 224 capable of accommodating an electrode assembly 260, and the second housing 230 can cover the receiving portion 224 from the top, such that the electrode assembly 260 cannot be detached from the outside of the battery case 210. Figure 3 As shown, the first housing 220 and the second housing 230 can be prepared by connecting one side of them to each other, but the invention is not limited thereto, and the first housing 220 and the second housing 230 can be prepared in various ways, for example, the first housing 220 and the second housing 230 can be separated from each other and prepared individually.

[0121] According to another embodiment of the invention, when the cup-shaped portions are formed on the bag film laminate, two symmetrical cup-shaped portions 222 and 232 can be drawn adjacent to each other on a bag film laminate. In this case, as Figure 3 As shown, cup-shaped portions 222 and 232 can be formed in the first housing 220 and the second housing 230, respectively. After the electrode assembly 260 is accommodated in the receiving portion 224 provided in the cup-shaped portion 222 of the first housing 220, the bridging portion 240 formed between the two cup-shaped portions 222 and 232 can be folded so that the two cup-shaped portions 222 and 232 face each other. In this case, the cup-shaped portion 232 of the second housing 230 can accommodate the electrode assembly 260 from above. Therefore, since the two cup-shaped portions 222 and 232 accommodate one electrode assembly 260, an electrode assembly 260 with a thickness greater than that accommodated when there is only one cup-shaped portion 222 can be accommodated. Furthermore, since one edge of the secondary battery 200 is formed by folding the pouch-type battery case 210, the number of edges to be sealed can be reduced when performing the sealing process later. Therefore, the processing speed of the pouch-type secondary battery 200 can be improved, and the number of sealing processes can be reduced.

[0122] The pouch-type battery case 210 can be sealed while housing the electrode assembly 260, exposing a portion of the electrode pins 280, i.e., the terminal portion, as described later. Specifically, when the electrode pins 280 are connected to the electrode contacts 270 of the electrode assembly 260 and an insulating portion 290 is formed in the portion of the electrode pins 280, the electrode assembly 260 is housed in a receiving portion 224 provided in a cup-shaped portion 222 of the first housing 220, and the second housing 230 can cover the receiving portion 224 from the top. Subsequently, electrolyte is injected into the receiving portion 224, and a sealing portion 250 formed on the edge of the first housing 220 and the second housing 230 can be sealed.

[0123] The sealing portion 250 can be used to seal the receiving portion 224. Specifically, the sealing portion 250 can seal the receiving portion 224 while being formed along its edge. The sealing temperature of the sealing portion 250 can be in the range of 180°C to 250°C, particularly in the range of 200°C to 250°C, and more particularly in the range of 210°C to 240°C. When the sealing temperature meets the above numerical range, the pouch-type battery box 210 can ensure sufficient sealing strength through thermal bonding.

[0124] pouch-type secondary batteries

[0125] Next, the pouch-type secondary battery according to the present invention will be described.

[0126] like Figure 3 As shown, the pouch-type secondary battery 200 according to the present invention may include a pouch-type battery case 210 prepared by forming the above-described pouch-film laminate and an electrode assembly 260 housed in the pouch-type battery case 210. Specifically, the pouch-type secondary battery 200 of the present invention may include a pouch-type battery case 210, an electrode assembly 260, electrode leads 280, an insulating portion 290, and an electrolyte (not shown).

[0127] In the following text, reference will be made to Figure 3 Each configuration of the pouch-type secondary battery of the present invention will be described in more detail.

[0128] (1) Pouch-type battery box

[0129] Since each component of the pouch-type battery box is the same as that of the pouch-type battery box described above, its detailed description is omitted.

[0130] (2) Electrode assembly

[0131] The electrode assembly 260 can be inserted into the pouch battery case 210 and can be sealed by the pouch battery case 210 after electrolyte is injected.

[0132] Electrode assembly 260 can be formed by sequentially stacking a positive electrode, a spacer, and a negative electrode. Specifically, electrode assembly 260 may include two types of electrodes, such as a positive electrode and a negative electrode, and a spacer disposed between the electrodes to insulate them from each other.

[0133] The positive and negative electrodes can be structures in which an active material slurry is applied to an electrode current collector in the form of a metal foil or mesh containing aluminum and copper. The slurry is typically formed by stirring granular active material, auxiliary conductors, binders, and conductive agents with a solvent added. The solvent can be removed in subsequent processes.

[0134] A slurry containing electrode active materials, binders, and / or conductive agents is applied to a positive electrode current collector and a negative electrode current collector to prepare positive and negative electrodes. The electrode assembly 260 can be prepared in a predetermined shape by stacking the positive and negative electrodes on two sides of a separator. The type of electrode assembly 260 may include, but is not limited to, stacked, wound, and stacked and folded types.

[0135] Electrode assembly 260 may include electrode tabs 270.

[0136] Electrode tab 270 is connected to each of the positive and negative electrodes of electrode assembly 260 and protrudes from the electrode assembly 260 to the outside, such that electrode tab 270 can be a path through which electrons can move between the interior and exterior of electrode assembly 260. The electrode current collector included in electrode assembly 260 may include a portion to which electrode active material is applied and an end portion to which no electrode active material is applied, i.e., an uncoated portion. Electrode tab 270 can be formed by cutting the uncoated portion, or by connecting individual conductive members to the uncoated portion via ultrasonic welding or the like. Figure 3 As shown, 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 each direction. For example, the electrode tabs 270 may protrude side by side from one side of the electrode assembly 260 in the same direction.

[0137] (3) Electrode pins

[0138] Electrode pin 280 can provide power to the external environment of secondary battery 200. Electrode pin 280 can be connected to electrode contacts 270 of electrode assembly 260 by spot welding or the like.

[0139] Electrode pins 280 are connected to electrode assembly 260 and can protrude to the outside of pouch battery case 210 via sealing portion 250. Specifically, one end of electrode pins 280 is connected to electrode assembly 260, particularly electrode tabs 270, and the other end of electrode pins 280 can protrude to the outside of pouch battery case 210.

[0140] Electrode pins 280 may include a positive pin 282 and a negative pin 284. The positive pin 282 has one end connected to the positive contact 272 and extends in the protruding direction of the positive contact 272. The negative pin 284 has one end connected to the negative contact 274 and extends in the protruding direction of the negative contact 274. The other ends of both the positive pin 282 and the negative pin 284 may protrude to the outside of the battery case 210. Therefore, the power generated inside the electrode assembly 260 can be supplied to the outside. Furthermore, since the positive contact 272 and the negative contact 274 are formed to protrude in various directions, the positive pin 282 and the negative pin 284 can also extend in various directions. The materials of the positive pin 282 and the negative pin 284 may be different from each other. In other words, the positive electrode pin 282 can be formed of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode pin 284 can be formed of the same copper (Cu) material as the negative electrode current collector or nickel-plated copper material. Since the portion of the electrode pin 280 protruding outside the battery case 210 becomes a terminal portion, it can be electrically connected to an external terminal.

[0141] (4) Insulation part

[0142] The insulating portion 290 prevents current generated by the electrode assembly 260 from flowing through the electrode pins 280 to the battery case 210 and maintains the seal of the battery case 210. For this purpose, the insulating portion 290 can be formed of a non-conductive insulator that does not conduct electricity well. Typically, insulating tapes or films that are easy to attach to the electrode pins 280 and are relatively thin are widely used as the insulating portion 290, but the invention is not limited thereto, and any component capable of insulating the electrode pins 280 can be used.

[0143] The insulating portion 290 may be configured to surround the outer peripheral surface of the electrode pin 280. Specifically, at least a portion of the electrode pin 280 may be surrounded by the insulating portion 290. In this case, the insulating portion 290 may be disposed between the electrode pin 280 and the pouch battery case 210. The insulating portion 290 may be positioned at the sealing portion 250 where the first housing 220 and the second housing 230 of the pouch battery case 210 are thermally fused, and the electrode pin 280 may be adhered to the battery case 210.

[0144] (5) Electrolytes

[0145] The pouch-type secondary battery 200 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type battery case 210. The electrolyte is used to move lithium ions generated by the electrochemical reaction of the electrodes during the charging / discharging of the secondary battery 200. The electrolyte may include a non-aqueous organic electrolyte solution as a mixture of lithium salt and organic solvent, or a polymer electrolyte. Furthermore, the electrolyte may include a sulfide-based, oxide-based, or polymer-based solid electrolyte, and the solid electrolyte may be flexible enough to be easily deformed by external forces.

[0146] Examples and Comparison Examples

[0147] Example 1: Preparation of bag-membrane composite

[0148] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film (fourth sealant layer), a 30 μm thick ethylene-propylene random copolymer film (first sealant layer), a 30 μm thick crosslinked homopolymer polypropylene film (second sealant layer), and a 10 μm thick ethylene-propylene random copolymer film (third sealant layer) are sequentially laminated by co-extrusion. In this case, ethylene monomer is included in the ethylene-propylene random copolymer film (first sealant layer) at an amount of 15% by weight, and the degree of crosslinking of the crosslinked homopolymer polypropylene in the crosslinked homopolymer polypropylene film (second sealant layer) is 60%.

[0149] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film (fourth sealant layer) / ethylene-propylene random copolymer film (first sealant layer) / crosslinked homopolymer film (second sealant layer) / ethylene-propylene random copolymer film (third sealant layer) were sequentially laminated.

[0150] Example 2: Preparation of bag-membrane composite

[0151] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film (fourth sealant layer), a 20 μm thick ethylene-propylene random copolymer film (first sealant layer), a 40 μm thick crosslinked homopolymer polypropylene film (second sealant layer), and a 10 μm thick ethylene-propylene random copolymer film (third sealant layer) are sequentially laminated by co-extrusion. In this case, ethylene monomer is included in the ethylene-propylene random copolymer film (first sealant layer) at an amount of 15% by weight, and the degree of crosslinking of the crosslinked homopolymer polypropylene in the crosslinked homopolymer polypropylene film (second sealant layer) is 60%.

[0152] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film (fourth sealant layer) / ethylene-propylene random copolymer film (first sealant layer) / crosslinked homopolymer film (second sealant layer) / ethylene-propylene random copolymer film (third sealant layer) were sequentially laminated.

[0153] Example 3: Preparation of bag-membrane composite

[0154] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film (fourth sealant layer), a 40 μm thick ethylene-propylene random copolymer film (first sealant layer), a 20 μm thick crosslinked homopolymer polypropylene film (second sealant layer), and a 10 μm thick ethylene-propylene random copolymer film (third sealant layer) are sequentially laminated by co-extrusion. In this case, ethylene monomer is included in the ethylene-propylene random copolymer film (first sealant layer) at an amount of 15% by weight, and the degree of crosslinking of the crosslinked homopolymer polypropylene in the crosslinked homopolymer polypropylene film (second sealant layer) is 60%.

[0155] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film (fourth sealant layer) / ethylene-propylene random copolymer film (first sealant layer) / crosslinked homopolymer film (second sealant layer) / ethylene-propylene random copolymer film (third sealant layer) were sequentially laminated.

[0156] Comparative Example 1: Preparation of Bag-Membrane Composite

[0157] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film, a 60 μm thick polypropylene homopolymer film, and a 10 μm thick ethylene-propylene random copolymer film are sequentially laminated by co-extrusion.

[0158] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film / polypropylene homopolymer film / ethylene-propylene random copolymer film are sequentially laminated.

[0159] Comparative Example 2: Preparation of Bag-Membrane Composite

[0160] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film, a 60 μm thick ethylene-propylene random copolymer film, and a 10 μm thick ethylene-propylene random copolymer film are sequentially laminated by co-extrusion. Ethylene monomer is included in the ethylene-propylene random copolymer films at a weight of 15%.

[0161] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film / ethylene-propylene random copolymer film / ethylene-propylene random copolymer film are sequentially laminated.

[0162] Comparative Example 3: Preparation of Bag-Film Composite

[0163] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film, a 30 μm thick ethylene-propylene random copolymer film, a 30 μm thick crosslinked homopolymer film, and a 10 μm thick ethylene-propylene random copolymer film are sequentially laminated by co-extrusion. In this case, ethylene monomer is included in the ethylene-propylene random copolymer film at a weight of 15% and the degree of crosslinking of the crosslinked homopolymer film is 50%.

[0164] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film / crosslinked homopolymer film / ethylene-propylene random copolymer film are sequentially laminated.

[0165] Comparative Example 4: Preparation of Bag-Membrane Composites

[0166] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film, a 30 μm thick ethylene-propylene random copolymer film, a 30 μm thick crosslinked homopolymer film, and a 10 μm thick ethylene-propylene random copolymer film are sequentially laminated by co-extrusion. In this case, ethylene monomer is included in the ethylene-propylene random copolymer film at an amount of 15% by weight, and the degree of crosslinking of the crosslinked homopolymer film is 85%.

[0167] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film / crosslinked homopolymer film / ethylene-propylene random copolymer film are sequentially laminated.

[0168] Comparative Example 5: Preparation of Bag-Film Composite

[0169] On one surface of a 40 μm thick aluminum film, a first adhesive film with a thickness of 3 μm, a nylon film with a thickness of 15 μm, a second adhesive film with a thickness of 3 μm, and a polyethylene terephthalate (PET) film with a thickness of 12 μm are sequentially laminated. On the other surface of the aluminum film, a 10 μm thick ethylene-propylene random copolymer film, a 30 μm thick polypropylene homopolymer film, a 30 μm thick crosslinked homopolymer film, and a 10 μm thick ethylene-propylene random copolymer film are sequentially laminated by co-extrusion. In this case, the degree of crosslinking of the crosslinked homopolymer film is 60%.

[0170] Therefore, a bag-film laminate with the following structure was prepared, wherein polyethylene terephthalate / second adhesive film / nylon film / first adhesive film / aluminum film / ethylene-propylene random copolymer film / crosslinked homopolymer film / ethylene-propylene random copolymer film are sequentially laminated.

[0171] The laminated structures of the sealant layers prepared in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1 below. In this case, in Table 1, each laminated film in the sealant layer is numbered 1 to 4 sequentially from the layer closest to the aluminum film to the outermost layer.

[0172] [Table 1]

[0173] Experimental Example 1: Evaluation of the Sealing Performance of a Pouch-Type Battery Box

[0174] After each of the bag film laminates prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was cut into dimensions of 266 mm in width and 200 mm in length and then folded into dimensions of 133 mm × 200 mm so that the sealant layers were in contact with each other, a bag-shaped battery box with a sealing portion formed therein was prepared by sealing the end of the long side (200 mm) for 1.6 seconds, 3 seconds or 5 seconds under conditions of a sealing strip area of ​​200 mm × 8 mm, 200°C and 0.1 MPa, respectively, and the sealing strength of the bag-shaped battery box was measured according to each sealing time.

[0175] Specifically, the sealing strength is calculated by the maximum tensile strength, which is measured by cutting the sealed portion formed in the pouch-type battery box at 15 mm intervals using a universal testing machine (UTM) at room temperature and pulling the sealed portion in a 180° direction at a speed of 5 mm / min.

[0176] Based on the calculated sealing strength, Table 2 below lists whether the bag-film laminates prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were sealed.

[0177] - ○: For cases where the measured seal strength is 10 kgf or greater.

[0178] - ×: The measured seal strength is less than 10 kgf.

[0179] [Table 2]

[0180] Referring to Table 2, even when the pouch-type battery box prepared using the pouch-film laminate prepared in Examples 1 to 3 is sealed for 1.6 seconds, the sealing strength is 10 kgf or greater, confirming excellent sealing performance. In contrast, for the pouch-type battery box prepared using the pouch-film laminate prepared in Comparative Examples 1, 4, and 5, the pouch-type battery box is not sealed due to insufficient sealing strength at 1.6 seconds, and it can be confirmed that sealing performance can be ensured when the sealing time is 3 seconds or longer. In particular, for the pouch-type battery box prepared using the pouch-film laminate prepared in Comparative Example 5, it is understood that the time required to ensure sufficient sealing performance increases to 5 seconds or longer. Therefore, in the case of using the pouch-film laminate prepared in Examples 1 to 3, it is understood that the sealing time can be significantly shortened compared to the case of using the pouch-film laminate prepared in Comparative Examples 1, 4, and 5.

[0181] Experimental Example 2: Evaluation of Insulation Resistance of Pocket-Type Battery Box

[0182] After each of the bag film laminates prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was cut into dimensions of 266 mm in width and 200 mm in length and then folded into dimensions of 133 mm × 200 mm so that the sealant layers were in contact with each other, a bag-shaped battery box with a sealing portion formed therein was prepared by sealing the end of the long side (200 mm) for 3 seconds under conditions of a sealing strip area of ​​200 mm × 8 mm, 200°C and 0.1 MPa.

[0183] The insulation resistance of the pouch-type battery box prepared above was measured. Specifically, the insulation resistance was measured by checking the resistance value after applying 100V for 5 seconds using a ohmmeter (RM3544-01) from HIOKIE.E.Corporation. The measurement results are shown in Table 3 below.

[0184] [Table 3]

[0185] Referring to Table 3, it can be confirmed that the pouch-type battery box prepared using the pouch-film laminate prepared in Examples 1 to 3 has better insulation resistance compared to the pouch-type battery box prepared using the pouch-film laminate prepared in Comparative Examples 1 to 5. Specifically, for the pouch-type battery box prepared using the pouch-film laminate prepared in Examples 1 to 3, where the degree of crosslinking of the crosslinked polypropylene film is in the range of 52% to 80%, it can be confirmed that the insulation resistance is significantly better than that of the pouch-type battery box prepared using the pouch-film laminate prepared in Comparative Examples 2, 3, and 4, where the degree of crosslinking does not meet this range. Furthermore, for the pouch-type battery box prepared using the pouch-film laminate prepared in Example 1, it can be confirmed that the insulation resistance is better than that of the pouch-type battery box prepared using the pouch-film laminate prepared in Examples 2 and 3, where the thicknesses of the first and second sealant layers are adjusted.

[0186] (See attached image labels)

[0187] 100: Bag film layer combination

[0188] 110: Base material layer

[0189] 112: First base material layer

[0190] 114: Second base material layer

[0191] 120: Gas barrier layer

[0192] 130: Sealant layer

[0193] 132: First sealant layer

[0194] 134: Second sealant layer

[0195] 136: Third sealant layer

[0196] 138: Fourth sealant layer

[0197] 200: Pouch-type secondary battery

[0198] 210: Bag-type box

[0199] 220: First shell

[0200] 222: Cup-shaped part

[0201] 224: Accommodation section

[0202] 230: Second shell

[0203] 232: Cup-shaped part

[0204] 240: Bridging section

[0205] 250: Sealing part

[0206] 260: Electrode assembly

[0207] 270: Electrode contacts

[0208] 272: Positive electrode connector

[0209] 274: Negative electrode connector

[0210] 280: Electrode pin

[0211] 282: Positive pin

[0212] 284: Negative pin

[0213] 290: Insulation part

Claims

1. A bag-film laminate, wherein a base material layer, a gas barrier layer, and a sealant layer are sequentially laminated in the bag-film laminate. in, The sealant layer comprises a first sealant layer containing a random copolymer of polypropylene and a second sealant layer containing cross-linked polypropylene, and The degree of crosslinking of the crosslinked polypropylene is in the range of 52% to 80%.

2. The bag-film laminate according to claim 1, wherein, The first sealant layer comprises at least one selected from the group consisting of ethylene-propylene random copolymers and butene-propylene random copolymers.

3. The bag-film laminate according to claim 1, wherein, The second sealant layer comprises cross-linked homopolymer polypropylene.

4. The bag-film laminate according to claim 1, wherein, Based on the total weight of the first sealant layer, the ethylene monomer of the polypropylene random copolymer is included in an amount of 5% to 50% by weight.

5. The bag-film laminate according to claim 1, wherein, The ratio (A / B) of the thickness (A) of the first sealant layer to the thickness (B) of the second sealant layer is in the range of 0.6 to 1.

5.

6. The bag-film laminate according to claim 1, wherein, The thickness of the sealant layer is 30 μm to 130 μm.

7. The bag-film laminate according to claim 1, wherein, When the bag-film laminate is sealed at 200°C and 0.1 MPa for 3 seconds, the insulation resistance of the bag-film laminate is 1000 MΩ or greater.

8. The bag-film laminate according to claim 1, wherein, The melting temperature of the sealant layer is 120°C to 150°C.

9. The bag-film laminate according to claim 1, wherein, The total thickness (D) of the two bag film layers when sealed at 200°C and 0.1 MPa for 3 seconds. S ) and the total thickness of the two bag film layers before sealing (D) A The ratio of (D) S / D A It is in the range of 0.2 to 0.

6.

10. The bag-film laminate according to claim 1, wherein, The sealant layer also includes a third sealant layer as the outermost layer. The third sealant layer comprises a random copolymer of polypropylene.

11. The bag-film laminate according to claim 10, wherein, The sealant layer is a sealant layer in which the first sealant layer, the second sealant layer and the third sealant layer are sequentially laminated.

12. A pouch-type battery case, which is prepared by forming a pouch-film laminate as described in any one of claims 1 to 11.

13. A pouch-type secondary battery, comprising: A pouch-type battery case, said pouch-type battery case being prepared by forming a pouch-film laminate as described in any one of claims 1 to 11; as well as An electrode assembly, which is housed in the pouch-shaped battery compartment.

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