Pouch film laminate and secondary battery

Abstract

The pouch film laminate according to the present invention comprises a base layer, a gas barrier layer, a first sealant layer and a second sealant layer laminated in this order, and the modulus of elasticity of the first sealant layer is greater than the modulus of elasticity of the second sealant layer.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0013848, filed February 1, 2023, 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 produced by molding the same. [Background technology]

[0003] Secondary batteries are used in a wide range of fields, from small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes to large products requiring high output such as electric vehicles and hybrid vehicles, as well as power storage devices and backup power storage devices for storing surplus generated electricity and new renewable energy. Types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries.

[0004] A secondary battery can be manufactured by placing an electrode assembly, in which a positive electrode, a negative electrode, and a separator interposed therebetween are alternately stacked, in a battery case, injecting an electrolyte, and sealing the battery case. Secondary batteries can be classified into pouch-type, can-type, etc. depending on the material of the case that houses the electrode assembly.

[0005] A pouch-type secondary battery can be manufactured by pressing a flexible pouch film laminate to form a cup, placing an electrode assembly in the receiving space inside the cup, and sealing the seal. The pouch film laminate is formed of multiple layers, including a metal gas barrier layer on one side of which a polymer film such as polyethylene terephthalate is laminated, and a sealant layer made of a thermoplastic polyolefin resin is laminated on the other side. When the pouch-type battery case is sealed, the sealant layers are thermally bonded to each other to form the seal.

[0006] Recently, as the capacity of pouch-type secondary batteries has increased, the amount of gas generated inside the pouch during charging and discharging has increased. If the internal pressure of the pouch increases above a certain level due to the increased amount of gas generated, the seal of the pouch-type secondary battery may vent, resulting in a decrease in the durability and safety of the battery. Therefore, it is necessary to develop a pouch-type secondary battery with high seal strength that will prevent venting even under high internal pressure. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve the above problems, and provides a pouch film laminate that can improve the seal strength of the pouch by optimizing the elastic modulus of the sealant layer, and a pouch-type battery case and a pouch-type secondary battery manufactured by molding the same. [Means for solving the problem]

[0008] According to one embodiment of the present invention, there is provided a pouch film laminate comprising a substrate layer, a gas barrier layer, a first sealant layer, and a second sealant layer laminated in that order, wherein the modulus of elasticity of the first sealant layer is greater than the modulus of elasticity of the second sealant layer.

[0009] According to the present invention, the ratio (B / A) of the modulus of elasticity (B) of the second sealant layer to the modulus of elasticity (A) of the first sealant layer can be 0.65 or more and less than 1.0.

[0010] The first sealant layer may have an elastic modulus of 600 MPa or less, and the second sealant layer may have an elastic modulus of 200 MPa or more.

[0011] According to the present invention, the first sealant layer can be in direct contact with the gas barrier layer.

[0012] In one example, the second sealant layer can be in direct contact with the first sealant layer, while in another example, the assembly can further include one or more layers disposed between the first and second sealant layers.

[0013] The thickness of the first sealant layer according to the present invention can be 10 μm to 90 μm, and the thickness of the second sealant layer can be 10 μm to 90 μm. The first sealant layer according to the present invention can contain acid-modified polypropylene (PPa), and the second sealant layer can contain polypropylene (PP).

[0014] The gas barrier layer according to the present invention may have a thickness of 30 μm to 100 μm, and may contain aluminum.

[0015] According to another embodiment of the present invention, there is provided a pouch-type battery case manufactured by molding the above-mentioned pouch film laminate.

[0016] According to another embodiment of the present invention, there is provided a pouch-type secondary battery including: a pouch-type battery case manufactured by molding the above-described pouch film laminate; and an electrode assembly housed in the pouch-type battery case. [Effects of the Invention]

[0017] In the present invention, by adjusting the elastic modulus of the first sealant layer to be higher than that of the second sealant layer, when tensile stress is applied to the seal portion of a pouch-type battery case manufactured from the pouch film laminate, deformation due to the tensile stress is not concentrated in the first sealant layer but is dispersed to the second sealant layer, thereby achieving a higher seal strength than conventional methods.As a result, even in an environment where internal pressure increases due to gas generation inside the pouch during charge and discharge of a pouch-type secondary battery, venting of the pouch is suppressed, thereby improving the durability and safety of the battery. [Brief explanation of the drawings]

[0018] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the above-described content of the invention, serve to further understand the technical concept of the present invention, and the present invention should not be interpreted as being limited solely to the matters depicted in such drawings.

[0019] [Figure 1] 1 is a cross-sectional view of a pouch film laminate according to the present invention. [Figure 2] 1 is an exploded view of a pouch-type secondary battery according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0020] The advantages and features of the present invention, as well as methods for achieving them, will become clearer with reference to the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various different forms. However, the present embodiments are provided to fully disclose the present invention and to fully convey the scope of the invention to those skilled in the art to which the present invention pertains, and the present invention is defined only by the scope of the claims. The same reference symbols refer to the same elements throughout the specification.

[0021] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the sense that can be commonly understood by a person having ordinary skill in the art to which the present invention belongs. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless they are clearly and specifically defined.

[0022] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise stated in the text. The words "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0023] In this specification, when a part is said to include a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified to the contrary.

[0024] In this specification, the phrase "A and / or B" means A, or B, or A and B.

[0025] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0026] Pouch film laminate The pouch film laminate according to the present invention comprises a base layer, a gas barrier layer, a first sealant layer and a second sealant layer laminated in this order, and the modulus of elasticity of the first sealant layer is greater than the modulus of elasticity of the second sealant layer.

[0027] Fig. 1 is a cross-sectional view of a pouch film laminate 100 according to the present invention. Each component of the pouch film laminate 100 according to the present invention will be described in more detail below with reference to Fig. 1.

[0028] (1) Base material layer The substrate layer 110 is formed as the outermost layer of the pouch film laminate 100 and serves to protect the secondary battery from external friction and impact. The substrate layer 110 is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0029] The base layer 110 may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. Among these, the base layer 110 is preferably made of polyethylene terephthalate (PET), nylon, or a combination thereof, which are abrasion-resistant and heat-resistant.

[0030] The thickness of the base material layer 110 can be 5 μm to 100 μm, specifically 7 μm to 70 μm, and more specifically 10 μm to 60 μm. When the thickness of the base material layer 110 satisfies this range, the external insulation is excellent and the overall thickness of the pouch is not large, so that the energy density relative to the volume of the secondary battery can be excellent.

[0031] The substrate layer 110 may have a single layer structure made of any one material. Alternatively, the substrate layer 110 may have a composite layer structure made of two or more materials. In the composite layer structure, an adhesive layer may be disposed between each layer.

[0032] Specifically, the substrate layer 110 according to the present invention may include a first substrate layer (not shown) and a second substrate layer (not shown). In this case, the first substrate layer may be a layer disposed as the outermost layer of the pouch film laminate, and the second substrate layer may be a layer disposed between the first substrate layer and the gas barrier layer 120. The first substrate layer and the second substrate layer may be made of materials having different materials and / or physical properties. An interface may exist between the first substrate layer and the second substrate layer. This means that the first substrate layer and the second substrate layer are different layers and may be formed separately.

[0033] The first substrate layer can serve to prevent moisture penetration from the outside of the pouch. The first substrate layer can be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. Preferably, the first substrate layer can include a polyester film having abrasion resistance and heat resistance. For example, the first substrate layer can include at least one material selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, but is not limited thereto. The thickness of the first substrate layer can be 10 μm to 50 μm, specifically 10 μm to 40 μm, and more specifically 12 μm to 25 μm. When the thickness of the first substrate layer satisfies the above numerical range, the insulation properties and formability of the pouch can be ensured and moisture penetration into the pouch film laminate can be effectively suppressed. In addition, since the overall thickness of the pouch is not large, the energy density relative to the volume of the secondary battery is excellent.

[0034] The second substrate layer can improve the formability of the pouch. The second substrate layer can include a polyamide film. For example, the second substrate layer can include at least one selected from the group consisting of nylon 6, nylon 6,6, nylon MXD6 (polyxylylene adipamide), nylon 4, nylon 4,6, and nylon 4,10, but is not limited thereto. Preferably, the second substrate layer includes nylon 6, which has the advantage of improving the formability of the pouch due to the excellent stretchability of nylon 6. The thickness of the second substrate layer can be 10 μm to 50 μm, specifically 10 μm to 40 μm, and more specifically 15 μm to 35 μm. When the thickness of the second substrate layer satisfies the above numerical range, the formability of the pouch can be ensured and 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 can be prevented.

[0035] The second substrate layer may contain metal oxide particles. The metal oxide particles may be hydroxylated by reacting with moisture introduced into the second substrate layer, thereby removing moisture from the second substrate layer. The metal oxide particles may contain at least one selected from the group consisting of CaO, MnO, SrO, MgO, and ZnO. Preferably, the metal oxide particles may contain at least one of CaO and MgO, which are advantageous for hydroxylation with moisture.

[0036] (2) Gas barrier layer The gas barrier layer 120 is laminated between the base layer 110 and the sealant layer 130 to ensure the mechanical strength of the pouch, block the entry and exit of gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type battery case.

[0037] The gas barrier layer 120 may be formed of a metal, such as, but not limited to, a thin metal film containing one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and invar.

[0038] According to one embodiment of the present invention, the gas barrier layer 120 may be formed of an aluminum alloy thin film. Forming the gas barrier layer 120 using an aluminum alloy thin film can ensure a certain level of mechanical strength, light weight, and the electrochemical properties of the electrode assembly and electrolyte, as well as heat dissipation. The aluminum alloy thin film may contain elements other than aluminum (Al). For example, the aluminum alloy thin film may contain one or more elements selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0039] In another example, the gas barrier layer 120 may be formed of a stainless steel thin film. Specifically, the gas barrier layer 120 may be manufactured by molding and / or processing a stainless steel thin film. A gas barrier layer 120 formed of stainless steel has relatively low thermal conductivity, which is effective in preventing or delaying heat diffusion to other cells during thermal runaway. Furthermore, its relatively high toughness can suppress the occurrence of cracks in the pouch during use of the pouch-type battery. The stainless steel may contain elements other than iron (Fe), such as one or more selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0040] The thickness of the gas barrier layer 120 can be 30 μm to 100 μm, specifically 30 μm to 90 μm, and more specifically 40 μm to 80 μm. When the thickness of the gas barrier layer 120 satisfies this range, excellent moldability and gas barrier performance are achieved when forming the cup portion.

[0041] (3) Sealant layer The sealant layer 130 is intended to completely seal the inside of the pouch-type battery case by being thermally bonded to each other at the seal portion when the pouch-type battery case accommodating the electrode assembly inside is sealed. For this purpose, the sealant layer 130 may be made of a material having excellent thermal adhesive strength.

[0042] The sealant layer 130 may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the sealant layer 130 is in direct contact with the electrode assembly and / or electrolyte inside the pouch-type battery case, it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the sealant layer 130 must completely seal the interior of the pouch-type battery case and prevent the transfer of materials between the inside and outside, it may be formed of a material having high sealing properties (e.g., excellent thermal adhesive strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer 130 may be formed of a polymer material.

[0043] The sealant layer 130 may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon, and is preferably made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0044] The thickness of the sealant layer 130 can be 30 μm to 130 μm, specifically 50 μm to 120 μm, and more specifically 70 μm to 100 μm. When the thickness of the sealant layer satisfies the above range, it is possible to ensure the seal strength of the sealed portion and the formability of the pouch film laminate.

[0045] Meanwhile, the sealant layer 130 according to the present invention has a composite film structure formed by layers of two or more materials. For example, the sealant layer 130 may have a multi-layer structure. An adhesive layer and / or a skin layer may be disposed between each layer of the sealant layer 130 having the composite film structure. The adhesive layer and / or the skin layer may have thermal adhesive properties and facilitate adhesion between each layer of the sealant layer 130. For example, the adhesive layer and / or the skin layer may include, but is not limited to, a polypropylene-based resin. The adhesive layer and / or the skin layer may also be disposed between the sealant layer 130 and the gas barrier layer 120.

[0046] Specifically, the sealant layer 130 according to the present invention includes a first sealant layer 132 and a second sealant layer 134. For example, the sealant layer 130 may be composed of the first sealant layer 132 and the second sealant layer 134. As another example, the sealant layer 130 may further include a third sealant layer and / or a fourth sealant layer 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 made of materials with different materials and / or physical properties. An interface may exist between each layer included in the sealant layer 130. This means that each layer is different from the other and may be formed separately.

[0047] According to the present invention, the elastic modulus of the first sealant layer 132 is greater than the elastic modulus of the second sealant layer 134. If the elastic modulus of the first sealant layer 132 is less than the elastic modulus of the second sealant layer 134, when tensile stress is applied to the seal portion of a pouch-type battery case manufactured from the pouch film laminate, deformation may be concentrated in the first sealant layer 132 adjacent to the gas barrier layer 120. As a result, peeling occurs at the interface between the gas barrier layer 120 and the first sealant layer 132 before the sealant layer 130 ruptures, which can result in a decrease in the seal strength of the pouch-type battery case.

[0048] The ratio (B / A) of the modulus of elasticity (B) of the second sealant layer 134 to the modulus of elasticity (A) of the first sealant layer 132 can be 0.65 or more and less than 1.0, specifically 0.8 or more and less than 1.0, and more specifically 0.9 or more and less than 1.0. When the ratio (B / A) of the moduli of elasticity to the sealant layer satisfies this numerical range, the possibility of delamination at the interface between the first sealant layer 132 and the second sealant layer 134 when tensile stress is applied is reduced, and deformation due to tensile stress is not concentrated in the first sealant layer 132 but is dispersed to the second sealant layer 134, which has a predetermined level of mechanical strength or higher, thereby achieving a pouch seal strength higher than conventional ones.

[0049] To adjust the physical properties of the first sealant layer 132 and / or the second sealant layer 134 to desired values, additives may be added to the polymer material forming the first sealant layer 132. Specifically, a flexibility additive may be added to reduce the modulus of elasticity of the first sealant layer 132. The flexibility additive may be, but is not limited to, one or more selected from the group consisting of linear low-density polyethylene (LLDPE), polybutene, and polyethylene (PE)-polypropylene (PP)-polybutene (PB) terpolymer. Additives for increasing the modulus of elasticity of the first sealant layer 132 may include, for example, at least one of carbon fiber, glass fiber, and aramid fiber.

[0050] To adjust the physical properties of the first sealant layer 132 and / or the second sealant layer 134 to desired values, additives may be added to the polymer material forming the first sealant layer 132 and / or the second sealant layer 134. Specifically, a flexibility additive may be added to reduce the modulus of elasticity of the first sealant layer 132 and / or the second sealant layer 134. The flexibility additive may be, but is not limited to, one or more selected from the group consisting of linear low-density polyethylene (LLDPE), polybutene, and polyethylene (PE)-polypropylene (PP)-polybutene (PB) terpolymer. Additives for increasing the modulus of elasticity of the first sealant layer 132 and / or the second sealant layer 134 may include, for example, at least one of carbon fiber, glass fiber, and aramid fiber.

[0051] Additionally, the molecular weight and / or melt flow rate (MFR) of the polymer included in the first sealant layer 132 and / or the second sealant layer 134 can be changed to adjust the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134. For example, increasing the molecular weight or decreasing the melt flow rate of the polymer included in the first sealant layer 132 and / or the second sealant layer 134 can increase the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134. Also, decreasing the molecular weight or increasing the melt flow rate of the polymer included in the first sealant layer 132 and / or the second sealant layer 134 can decrease the elastic modulus of the first sealant layer 132 and / or the second sealant layer 134.

[0052] Each of the first sealant layer 132 and the second sealant layer 134 described above will now be described in more detail.

[0053] 1) First sealant layer The first sealant layer 132 may be formed of a polymer material. Specifically, the first sealant layer 132 may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon, and preferably made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be made of solid polypropylene (CPP), acid-modified polypropylene (PPa), or polypropylene-butylene-ethylene terpolymer.

[0054] The first sealant layer 132 is particularly preferably made of acid-modified polypropylene (PPa) to ensure long-term adhesive performance between the gas barrier layer 120 and the first sealant layer 132. Here, the acid-modified polypropylene may be maleic anhydride-modified polypropylene (MAH PP).

[0055] The elastic modulus of the first sealant layer 132 may be 600 MPa or less, specifically 200 MPa to 500 MPa, and more specifically 250 MPa to 480 MPa. When the elastic modulus of the first sealant layer 132 satisfies this numerical range, the first sealant layer 132 is not easily deformed, interfacial peeling between the gas barrier layer 120 and the first sealant layer 132 is suppressed, and the first sealant layer 132 easily adheres to the gas barrier layer 120, thereby maintaining high adhesive strength between the gas barrier layer 120 and the first sealant layer 132. Furthermore, the first sealant layer 132 has appropriate flexibility and impact resistance, which allows the insulating performance of the pouch-type battery case to be maintained.

[0056] The thickness of the first sealant layer 132 can be 10 μm to 90 μm, specifically 10 μm to 60 μm, and more specifically 10 μm to 40 μm. If the thickness of the first sealant layer 132 is thinner than 10 μm, the seal durability and insulating properties of the pouch-type battery case manufactured from the pouch film laminate will decrease, and the yield strength of the first sealant layer 132 will decrease, resulting in a weakened seal strength of the pouch-type battery case. Furthermore, it will be difficult to extrude the first sealant layer 132 with a uniform thickness during the extrusion process. On the other hand, if the thickness of the first sealant layer 132 is thicker than 90 μm, the increase in the thickness of the pouch film laminate relative to the total thickness of the pouch-type secondary battery will result in a decrease in the energy density of the pouch-type secondary battery.

[0057] According to one embodiment of the present invention, the first sealant layer 132 may be a layer that directly contacts the gas barrier layer 120. In this case, when the pouch film laminate 100 is co-extruded, the first sealant layer 132 may be directly adhered to the gas barrier layer 120. In another example, an adhesive layer and / or a skin layer may be disposed between the first sealant layer 132 and the gas barrier layer 120 to improve the adhesion between the first sealant layer 132 and the gas barrier layer 120.

[0058] 2) Second sealant layer The second sealant layer 134 may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the second sealant layer 134 is in direct contact with the electrode assembly (260 in FIG. 2) and / or the electrolyte inside the receiving space (224 in FIG. 2), the second sealant layer 134 may be formed of a material having insulating properties and corrosion resistance. In addition, since the second sealant layer 134 must completely seal the interior of the battery case and prevent the transfer of materials between the inside and outside, the second sealant layer 134 may be formed of a material having high sealing properties. To ensure such insulating properties, corrosion resistance, and sealing properties, the second sealant layer 134 may be formed of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. Preferably, the second sealant layer 134 is made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be unstretched polypropylene, acid-modified polypropylene, polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer. Here, the acid-modified polypropylene may be maleic anhydride-modified polypropylene (MAH PP). More preferably, the second sealant layer may include unstretched polypropylene (CPP), which has heat-sealability and high tensile strength.

[0059] The elastic modulus of the second sealant layer 134 can be 200 MPa or greater, specifically 200 MPa to 400 MPa, and more specifically 250 MPa to 380 MPa. When the elastic modulus of the second sealant layer 134 satisfies this numerical range, interfacial peeling between the first sealant layer 132 and the second sealant layer 134 is suppressed, reducing the possibility of rupture along the pair of sealed second sealant layers 134 in a pouch-type battery case manufactured from the pouch film laminate, and ensuring the seal durability of the pouch-type battery case. Furthermore, the second sealant layer 134 has sufficient mechanical strength and can withstand stress, ensuring the seal durability of the pouch-type battery case.

[0060] The thickness of the second sealant layer 134 can be 10 μm to 90 μm, specifically 10 μm to 60 μm, and more specifically 10 μm to 50 μm. If the thickness of the second sealant layer 134 is thinner than 10 μm, the seal durability and insulation of the pouch-type battery case manufactured from the pouch film laminate will decrease, and the yield strength of the second sealant layer 134 will decrease, resulting in a weakened seal strength of the pouch-type battery case. If the thickness of the second sealant layer 134 is thicker than 90 μm, the increased thickness of the pouch film laminate relative to the total thickness of the pouch-type secondary battery will result in a reduced energy density of the pouch-type secondary battery.

[0061] The second sealant layer 134 may be disposed so as to be in direct contact with the first sealant layer 132, or may be disposed so as not to be in direct contact with the first sealant layer 132. When the second sealant layer 134 and the first sealant layer 132 are not in direct contact with each other, the pouch film laminate may further include one or more layers 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 properties of the pouch film laminate. The intermediate layer may include at least one of polypropylene and homopolypropylene. The thickness of the intermediate layer may be 80 μm or less, specifically 10 μm to 60 μm, more specifically 30 μm to 50 μm. When the thickness of the intermediate layer satisfies the above numerical range, the co-extrusion moldability of the sealant layer is improved and excellent sealing strength can be ensured.

[0062] Pouch-type secondary battery Next, the pouch-type secondary battery according to the present invention will be described.

[0063] The pouch-type secondary battery according to the present invention includes a pouch-type battery case manufactured by molding the above-mentioned pouch film laminate, and an electrode assembly housed in the pouch-type battery case. Specifically, the pouch-type secondary battery according to the present invention includes a pouch-type battery case housing an electrode assembly, the pouch-type battery case being manufactured by molding a pouch film laminate, the pouch film laminate including a base layer, a gas barrier layer, a first sealant layer, and a second sealant layer laminated in this order, and the elastic modulus of the first sealant layer is greater than the elastic modulus of the second sealant layer.

[0064] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to FIG.

[0065] 2 is an exploded view of a pouch-type secondary battery 200 according to the present invention. As shown in FIG. 2, the pouch-type secondary battery 200 according to the present invention may include a pouch-type battery case 210, an electrode assembly 260, an electrode lead 280, an insulating portion 290, and an electrolyte (not shown).

[0066] (1) Pouch-type battery case The pouch-type battery case 210 can be manufactured by molding the pouch film laminate of the present invention. The pouch-type battery case 210 can house the electrode assembly 260 inside. The detailed structure and properties of the pouch film laminate are as described above, and a detailed description thereof will be omitted.

[0067] The pouch film laminate may be drawn and stretched using a punch or the like to manufacture the pouch-type battery case 210. As a result, the pouch-type battery case 210 may include a cup portion 222 and a receiving portion 224. The receiving portion 224 is a portion that receives the electrode assembly, and may refer to a bag-shaped receiving space formed inside the cup portion 222 as the cup portion 222 is formed.

[0068] According to one embodiment of the present invention, the pouch-type battery case 210 may include a first case 220 and a second case 230, as shown in Fig. 2. The first case 220 includes a receiving portion 224 that can receive the electrode assembly 260, and the second case 230 may cover the receiving portion 224 from above to prevent the electrode assembly 260 from falling out of the battery case 210. The first case 220 and the second case 230 may be manufactured with one side connected to each other as shown in Fig. 2, but are not limited to this and may be manufactured in various ways, such as being separately manufactured.

[0069] According to another embodiment of the present invention, when forming cup portions in a pouch film laminate, two symmetrical cup portions 222, 232 may be formed adjacent to each other by drawing one pouch film laminate. In this case, as shown in FIG. 2, the first case 220 and the second case 230 may be formed with the cup portions 222, 232, respectively. After the electrode assembly 260 is accommodated in the accommodating portion 224 of the cup portion 222 of the first case 220, the bridge portion 240 formed between the two cup portions 222, 232 may be folded so that the two cup portions 222, 232 face each other. In this case, the cup portion 232 of the second case 230 may accommodate the electrode assembly 260 from above. Therefore, since two cup portions 222, 232 accommodate one electrode assembly 260, an electrode assembly 260 that is thicker than when there is only one cup portion 222 can be accommodated. In addition, folding the pouch-type battery case 210 forms one corner of the secondary battery 200, which reduces the number of corners to be sealed during the subsequent sealing process, thereby improving the processing speed of the pouch-type secondary battery 200 and reducing the number of sealing processes.

[0070] The pouch-type battery case 210 may be sealed with the electrode assembly 260 housed therein so that a portion of the electrode lead 280, i.e., a terminal portion, described below, is exposed. Specifically, after the electrode lead 280 is connected to the electrode tab 270 of the electrode assembly 260 and an insulating portion 290 is formed on a portion of the electrode lead 280, the electrode assembly 260 may be housed in the housing portion 224 provided in the cup portion 222 of the first case 220, and the second case 230 may cover the housing portion 224 from above. Next, an electrolyte may be injected into the housing portion 224, and the sealing portion 250 formed on the periphery of the first case 220 and the second case 230 may be sealed.

[0071] The sealing portion 250 may serve to seal the accommodating portion 224. Specifically, the sealing portion 250 may be formed along the periphery of the accommodating portion 224 to seal the accommodating portion 224. The temperature at which the sealing portion 250 is sealed may be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature is within this range, the pouch-type battery case 210 can ensure sufficient seal strength through thermal bonding.

[0072] (2) Electrode assembly The electrode assembly 260 can be inserted into the pouch-type battery case 210 and sealed by the pouch-type battery case 210 after the electrolyte is injected.

[0073] The electrode assembly 260 may be formed by sequentially stacking a positive electrode, a separator, and a negative electrode. Specifically, the electrode assembly 260 may include two electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate the electrodes from each other.

[0074] The positive and negative electrodes 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. The slurry may be formed by stirring a granular active material, auxiliary conductor, binder, conductive material, etc., in a solvent. The solvent may be removed in a subsequent process.

[0075] A slurry containing a mixture of an electrode active material, a binder, and / or a conductive material is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, which are then stacked on both sides of a separator to manufacture a predetermined shape of the electrode assembly 260. The electrode assembly 260 may be categorized into a stack type, a jelly roll type, a stack and folding type, etc., but is not limited thereto.

[0076] The electrode assembly 260 may include an electrode tab 270 .

[0077] The electrode tabs 270 are connected to the positive and negative electrodes of the electrode assembly 260, respectively, and protrude from the electrode assembly 260 to serve as paths for electrons to move between the inside and outside of the electrode assembly 260. The electrode current collector included in the electrode assembly 260 may be composed of a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 270 may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion by ultrasonic welding, for example. As shown in FIG. 2, the electrode tabs 270 may protrude in different directions from the electrode assembly 260, but are not limited thereto. They may protrude in various directions, such as protruding in parallel from one side in the same direction.

[0078] (3) Electrode lead The electrode lead 280 may supply electricity to the outside of the secondary battery 200. The electrode lead 280 may be connected to the electrode tab 270 of the electrode assembly 260 by spot welding or the like.

[0079] The electrode lead 280 is connected to the electrode assembly 260 and may protrude to the outside of the pouch-type battery case 210 via the sealing portion 250. Specifically, one end of the electrode lead 280 is connected to the electrode assembly 260, particularly the electrode tab 270, and the other end of the electrode lead 280 may protrude to the outside of the pouch-type battery case 210.

[0080] The electrode lead 280 may include a positive electrode lead 282 having one end connected to the positive electrode tab 272 and extending in the direction in which the positive electrode tab 272 protrudes, and a negative electrode lead 284 having one end connected to the negative electrode tab 271 and extending in the direction in which the negative electrode tab 271 protrudes. The other ends of the positive electrode lead 282 and the negative electrode lead 284 may protrude to the outside of the battery case 210. This allows electricity generated inside the electrode assembly 260 to be supplied to the outside. In addition, since the positive electrode tab 272 and the negative electrode tab 271 protrude in different directions, the positive electrode lead 282 and the negative electrode lead 284 may also extend in different directions. 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 copper material coated with nickel (Ni). A portion of the electrode lead 280 protruding outside the battery case 210 serves as a terminal portion and may be electrically connected to an external terminal.

[0081] (4) Insulation section The insulating portion 290 prevents electricity generated from the electrode assembly 260 from flowing to the battery case 210 via the electrode lead 280, thereby maintaining the seal of the battery case 210. To this end, the insulating portion 290 may be formed of an insulator having low electrical conductivity. Generally, the insulating portion 290 is formed of a relatively thin insulating tape or film that is easily attached to the electrode lead 280, but is not limited thereto, and any material that can insulate the electrode lead 280 may be used.

[0082] The insulating part 290 may be disposed to surround the outer circumferential surface of the electrode lead 280. Specifically, at least a portion of the electrode lead 280 may be surrounded by the insulating part 290. In this case, the insulating part 290 may be disposed between the electrode lead 280 and the pouch-type battery case 210. The insulating part 290 may be located only in the seal part 250 where the first case 220 and the second case 230 of the pouch-type battery case 210 are thermally sealed, and may bond the electrode lead 280 to the battery case 210.

[0083] (5) Electrolyte 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 an electrochemical reaction of the electrodes during charging / discharging of the secondary battery 200, and may include a non-aqueous organic electrolyte solution 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 sulfide-based, oxide-based, or polymer-based solid electrolyte, and such a solid electrolyte may have flexibility that makes it easily deformable under external force.

[0084] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present description, and it goes without saying that such changes and modifications are within the scope of the appended claims.

[0085] Examples and Comparative Examples Example 1: Manufacturing of a pouch film laminate A 3 μm-thick first adhesive film, a 25 μm-thick nylon film, a 3 μm-thick second adhesive film, and a 12 μm-thick polyethylene terephthalate (PET) film were laminated in this order on one side of a 60 μm-thick aluminum alloy thin film. A 40 μm-thick acid-modified polypropylene (PPa) film and a 40 μm-thick polypropylene (PP) film were co-extruded on the other side of the aluminum alloy thin film. As a result, a pouch film laminate was produced with a structure in which polypropylene film / acid-modified polypropylene film / aluminum alloy thin film / first adhesive film / nylon film / second adhesive film / polyethylene terephthalate film were laminated in this order.

[0086] Here, the polypropylene film (second sealant layer) and the acid-modified polypropylene film (first sealant layer) are sealant layers, the aluminum alloy thin film is a gas barrier layer, and the first adhesive film, nylon film, second adhesive film and polyethylene terephthalate film are base layers.

[0087] Meanwhile, to adjust the elastic modulus of the polypropylene film and acid-modified polypropylene film, linear low-density polyethylene (LLDPE) was added as a flexibility additive during the production of each film.

[0088] Example 2: Manufacturing of a pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film (first sealant layer) was increased to decrease the elastic modulus of the acid-modified polypropylene film.

[0089] Example 3: Preparation of a pouch film laminate To decrease the elastic modulus of the acid-modified polypropylene film (first sealant layer), the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased. A pouch film laminate was manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film (30 μm thick), a polypropylene film (middle layer) (30 μm thick), and a polypropylene film (20 μm thick) were co-extruded on the other side of the aluminum alloy thin film.

[0090] Example 4: Preparation of a pouch film laminate To decrease the elastic modulus of the acid-modified polypropylene film (first sealant layer), the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased. A pouch film laminate was manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film (20 μm thick), a polypropylene film (middle layer) (50 μm thick), and a polypropylene film (10 μm thick) were co-extruded on the other side of the aluminum alloy thin film.

[0091] Example 5: Preparation of a pouch film laminate To decrease the elastic modulus of the acid-modified polypropylene film (first sealant layer), the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased. A pouch film laminate was manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film (20 μm thick), a polypropylene film (middle layer) (50 μm thick), and a polypropylene film (10 μm thick) were co-extruded on the other side of the aluminum alloy thin film.

[0092] Example 6: Preparation of a pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film (first sealant layer) was increased to decrease the elastic modulus of the acid-modified polypropylene film.

[0093] Example 7: Preparation of a pouch film laminate To decrease the elastic modulus of the acid-modified polypropylene film (first sealant layer), the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased. A pouch film laminate was manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film (20 μm thick), a polypropylene film (middle layer) (50 μm thick), and a polypropylene film (10 μm thick) were co-extruded on the other side of the aluminum alloy thin film.

[0094] Example 8: Preparation of a pouch film laminate To reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer) and the polypropylene film (second sealant layer), an acid-modified polypropylene film and a polypropylene film with a high melt flow rate (MFR) were used. A pouch film laminate was manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film (30 μm thick) and the polypropylene film (50 μm thick) were co-extruded on the other side of the aluminum alloy thin film.

[0095] Example 9: Preparation of a pouch film laminate To reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer), an acid-modified polypropylene film with a high melt flow rate (MFR) was used. A pouch film laminate was manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film (30 μm thick) and a polypropylene film (50 μm thick) were co-extruded on the other side of the aluminum alloy thin film.

[0096] Comparative Example 1: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that an acid-modified polypropylene film with a high melt flow rate (MFR) was used to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer), and the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased.

[0097] Comparative Example 2: Production of pouch film laminate To decrease the elastic modulus of the acid-modified polypropylene film (first sealant layer), the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased. To increase the elastic modulus of the polypropylene film (middle layer), the amount of linear low-density polyethylene (LLDPE) added to the polypropylene film was decreased. A pouch film laminate was produced in the same manner as in Example 3, except that a polypropylene film with a low melt flow rate (MFR) was used to increase the elastic modulus of the polypropylene film (second sealant layer).

[0098] Comparative Example 3: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that an acid-modified polypropylene film with a high melt flow rate (MFR) was used to reduce the elastic modulus of the acid-modified polypropylene film (first sealant layer).

[0099] Comparative Example 4: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film (first sealant layer) was increased to decrease the elastic modulus of the acid-modified polypropylene film, and a polypropylene film with a low melt flow rate (MFR) was used to increase the elastic modulus of the polypropylene film (second sealant layer).

[0100] Comparative Example 5: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film (first sealant layer) was increased to decrease the elastic modulus of the acid-modified polypropylene film.

[0101] Comparative Example 6: Production of pouch film laminate To decrease the elastic modulus of the acid-modified polypropylene film (first sealant layer), the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film was increased. To increase the elastic modulus of the polypropylene film (middle layer), the amount of linear low-density polyethylene (LLDPE) added to the polypropylene film was decreased. A pouch film laminate was produced in the same manner as in Example 3, except that a polypropylene film with a low melt flow rate (MFR) was used to increase the elastic modulus of the polypropylene film (second sealant layer).

[0102] Comparative Example 7: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film (first sealant layer) was reduced to increase the elastic modulus of the acid-modified polypropylene film.

[0103] Comparative Example 8: Production of pouch film laminate A pouch film laminate was manufactured in the same manner as in Example 1, except that the amount of linear low-density polyethylene (LLDPE) added to the acid-modified polypropylene film (first sealant layer) and the polypropylene film (second sealant layer) was increased to decrease the elastic modulus of the acid-modified polypropylene film and the polypropylene film.

[0104] Experimental Example 1: Measurement of the elastic modulus of the sealant layer included in the pouch film laminate The elastic modulus in the thickness direction of each layer included in the sealant layer of each of the pouch film laminates produced in Examples 1 to 9 and Comparative Examples 1 to 8 was measured using a compression elastic modulus tester (micro-indenter). Specifically, the probe of the compression elastic modulus tester was used to indent one side of each layer included in the sealant layer to a depth of 10 μm at an indentation load rate of 0.1 N / min. The elastic modulus was calculated from the resulting stress-strain graph and is shown in Table 1 below.

[0105] [Table 1]

[0106] Experimental Example 2: Measuring the seal strength of a pouch-type battery case Pouch film laminates were prepared in Examples 1 to 9 and Comparative Examples 1 to 8. Each pouch film laminate was then cut to a size of 266 mm wide and 200 mm long, and then folded in half to a size of 133 mm wide x 200 mm long so that the sealant layers were in contact. The edge of the long side (200 mm) was then sealed with a seal bar (area: 200 mm x 8 mm), at 210°C, and under a surface pressure of 1.0 to 2.0 MPa for 1.6 seconds to produce a pouch-type battery case.

[0107] The pouch-type battery case was then cut to a width of 15 mm to include the seal. One end of each of the upper and lower pouch film laminates in the cut sample was folded and fastened to the upper and lower fixtures of a measuring device (UTM, manufactured by Zwick). The sample was then pulled vertically (180°) at a speed of 5 mm / min at 25°C to measure the maximum tensile strength at which the seal broke. The measurement results are shown in Table 2 below.

[0108] [Table 2]

[0109] From Tables 1 and 2, it can be seen that in Examples 1 to 9, in which the modulus of elasticity of the first sealant layer is greater than the modulus of elasticity of the second sealant layer, the seal strength measured at a temperature condition of 25°C is significantly higher than that of Comparative Examples 1 to 8. [Explanation of symbols]

[0110] 100 Pouch film laminate 110 Base material layer 120 Gas barrier layer 130 Sealant Layer 132 First sealant layer 134 Second sealant layer 200 Pouch-type secondary battery 210 Pouch-type battery case 220 Case 1 222 Cup section 224 Storage Unit 230 Case 2 232 Cup section 240 Bridge section 250 Seal part 260 Electrode assembly 270 Electrode Tab 271 Negative electrode tab 272 Positive electrode tab 280 Electrode Lead 282 Positive lead 284 Negative lead 290 Insulation

Claims

1. a substrate layer, a gas barrier layer, a first sealant layer, and a second sealant layer laminated in this order; A pouch film laminate, wherein the modulus of elasticity of the first sealant layer is greater than the modulus of elasticity of the second sealant layer.

2. 2. The pouch film laminate according to claim 1, wherein the ratio (B / A) of the modulus of elasticity (B) of the second sealant layer to the modulus of elasticity (A) of the first sealant layer is 0.65 or more and less than 1.

0.

3. The pouch film laminate according to claim 1 , wherein the first sealant layer has an elastic modulus of 600 MPa or less.

4. The pouch film laminate according to claim 1 , wherein the second sealant layer has an elastic modulus of 200 MPa or more.

5. The pouch film laminate according to claim 1 , wherein the first sealant layer is in direct contact with the gas barrier layer.

6. The pouch film laminate of claim 1 , wherein the second sealant layer is in direct contact with the first sealant layer.

7. 10. The pouch film laminate of claim 1, further comprising one or more layers disposed between the first sealant layer and the second sealant layer.

8. 2. The pouch film laminate according to claim 1, wherein the first sealant layer has a thickness of 10 μm to 90 μm.

9. 2. The pouch film laminate according to claim 1, wherein the second sealant layer has a thickness of 10 μm to 90 μm.

10. The pouch film laminate of claim 1 , wherein the first sealant layer comprises acid-modified polypropylene (PPa).

11. 10. The pouch film laminate of claim 1, wherein the second sealant layer comprises polypropylene (PP).

12. 2. The pouch film laminate according to claim 1, wherein the gas barrier layer has a thickness of 30 μm to 100 μm.

13. The pouch film laminate according to claim 1 , wherein the gas barrier layer comprises aluminum.

14. A pouch-type battery case including a formed pouch film laminate, A pouch-type battery case, wherein the pouch film laminate is the pouch film laminate according to any one of claims 1 to 13.

15. a pouch-type battery case including a molded pouch film laminate; an electrode assembly housed in the pouch-type battery case; A pouch-type secondary battery comprising: The pouch film laminate is the pouch film laminate according to any one of claims 1 to 13, wherein the pouch film laminate is a pouch-type secondary battery.

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