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

Abstract

The present invention relates to a pouch film laminate comprising a base layer, a gas barrier layer, and a sealant layer, which are sequentially laminated, wherein the base layer comprises a surface protective layer, and the thickness ratio of the pouch film laminate to the surface protective layer is 6 to 10.

Description

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

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0037462, filed March 18, 2024, Korean Patent Application No. 10-2024-0037463, filed March 18, 2024, Korean Patent Application No. 10-2024-0196382, filed December 24, 2024, and Korean Patent Application No. 10-2025-0034243, filed March 17, 2025, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a pouch film laminate, a pouch-type battery case, and a pouch-type secondary battery.

[0006]

[0007] Secondary batteries are used in a wide range of applications, from small products like digital cameras, DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, to larger, high-power products like electric and hybrid vehicles, as well as power storage devices that store surplus power or renewable energy, and as backup power storage devices. Types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries.

[0008] Secondary batteries can be manufactured by placing an electrode assembly, in which a positive electrode, a negative electrode, and a separator interposed between them are alternately laminated, in a battery case, injecting an electrolyte, and then sealing the battery case. Secondary batteries are classified into pouch types and can types, depending on the material of the case housing the electrode assembly.

[0009] The pouch, which is the case of a pouch-type secondary battery, is manufactured by performing press processing on a flexible pouch film laminate to form a cup portion. Then, once the cup portion is formed, an electrode assembly is accommodated in the receiving space of the cup portion and the sealing portion is sealed to manufacture a secondary battery.

[0010] Among these press processes, drawing forming is performed by inserting a pouch film laminate into a press device and applying pressure to the pouch film laminate with a punch to stretch the pouch film laminate. At this time, the pouch film laminate is formed by sequentially stacking multiple layers such as a substrate layer, a gas barrier layer, and a sealant layer.

[0011] This multilayer structure has a significant impact on the safety, sealing properties, and formability of the secondary battery when manufacturing the pouch film laminate into a pouch-type secondary battery case, and in particular, has a significant impact on forming the depth of the cup portion deeper to achieve high energy density.

[0012] Meanwhile, conventional technologies have attempted to deepen the depth of the pouch-type case cup by controlling only the thickness and properties of a nylon film that assists stretching or an aluminum alloy thin film used as a gas barrier layer. However, since they have not considered the problem of organic bonding and behavior of each layer within the pouch film laminate, there have been limitations in realizing excellent formability and robustness.

[0013] Accordingly, the present invention seeks to provide a pouch film laminate capable of realizing superior formability and robustness by considering not only the thickness and properties of the stretching auxiliary layer or gas barrier layer, but also the thickness ratio between layers within the pouch film laminate.

[0014]

[0015] The present invention is intended to solve the above problems, and provides a pouch film laminate, a pouch-type battery case, and a pouch-type secondary battery having excellent formability and robustness by controlling the ratio of the thickness of the pouch film laminate to the thickness of the surface protective layer within a specific range.

[0016] The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned can be clearly understood by those skilled in the art from the description below.

[0017]

[0018] [1] The present invention provides a pouch film laminate comprising a sequentially laminated substrate layer, a gas barrier layer, and a sealant layer, wherein the substrate layer includes a surface protection layer, and a ratio of the thickness of the pouch film laminate to the thickness of the surface protection layer is 6 to 10.

[0019] [2] In the present invention, in the above [1], the thickness of the substrate layer may be 45 µm to 70 µm.

[0020] [3] In the present invention, in the above [1] or [2], the thickness of the surface protective layer may be 10 µm to 35 µm.

[0021] [4] In at least one of the above [1] to [3], the surface protective layer may have a maximum peak temperature of 253°C or less in a differential scanning calorimetry (DSC) analysis graph obtained by heating from 25°C to 350°C at a heating rate of 10°C / min.

[0022] [5] In at least one of the above [1] to [4], the surface protective layer may have a friction coefficient of 0.3 or less measured at a temperature of 25°C.

[0023] [6] In at least one of the above [1] to [5], the base layer further includes a stretching auxiliary layer, and the thickness of the stretching auxiliary layer may be 20 µm to 45 µm.

[0024] [7] In at least one of the above [1] to [6], the thickness of the gas barrier layer may be 70 µm to 90 µm.

[0025] [8] In at least one of the above [1] to [7], the thickness of the sealant layer may be 70 µm to 90 µm.

[0026] [9] In at least one of the above [1] to [8], the sealant layer may include a first sealant layer arranged to be in contact with the gas barrier layer, a second sealant layer laminated on the first sealant layer, and a third sealant layer laminated on the second sealant layer.

[0027]

[0010] In at least one of the above [1] to [9], the thickness of the pouch film laminate may be 120 µm to 300 µm.

[0028]

[0011] In at least one of the above [1] to

[0010] , the ratio of the thickness of the gas barrier layer to the thickness of the surface protective layer may be 2.5 to 3.3.

[0029]

[0012] In at least one of the above [1] to

[0011] , the ratio of the thickness of the gas barrier layer to the thickness of the substrate layer may be 1.4 to 1.8.

[0030]

[0013] In at least one of the above [1] to

[0012] , the base layer further includes a stretching auxiliary layer, and the ratio of the thickness of the stretching auxiliary layer to the thickness of the surface protective layer may be 1.2 or less.

[0031]

[0014] The present invention provides a pouch-shaped battery case manufactured by drawing and forming at least one pouch film laminate among the above [1] to

[0013] .

[0032]

[0015] The present invention provides a pouch-type secondary battery including the pouch-type battery case of the above

[0014] .

[0033]

[0034] The pouch film laminate according to the present invention is characterized by preventing the occurrence of perforation or breakage during the molding of the pouch film laminate by controlling the thickness ratio of the pouch film laminate to the thickness of the surface protective layer within a specific range, while also exhibiting excellent gas barrier layer residual rates. Accordingly, the pouch film laminate can achieve an excellent maximum molding depth and excellent robustness during molding.

[0035]

[0036] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the contents of the invention described above, serve to further understand the technical idea of ​​the present invention. Therefore, the present invention should not be interpreted as being limited to the matters described in such drawings.

[0037] Fig. 1 is a cross-sectional view of a pouch film laminate according to the present invention.

[0038] Figure 2 is an exploded assembly diagram of a pouch-type secondary battery according to the present invention.

[0039] Figure 3 is a schematic diagram for explaining the edges and corners of a pouch-type battery case according to the present invention.

[0040] Figure 4 is a drawing showing the cutting position of a pouch-type battery case for evaluating robustness in Experimental Example 4.

[0041] Figure 5 is a drawing showing an example of a sample cut in Experimental Example 4.

[0042] Figure 6 is a drawing showing an example of a cross-section of a sample cut in Experimental Example 4.

[0043]

[0044] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0045] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0046] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0047] In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0048] In this specification, the description of “A and / or B” means A, or B, or A and B.

[0049] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0050] In this specification, MD direction (Machine Direction) means the longitudinal direction of the pouch film laminate, and TD direction (Transverse Direction) means the width direction of the pouch film laminate.

[0051] In this specification, the MD direction tensile strength (N / 15 mm) of the surface protection layer and the stretching auxiliary layer can be measured as the strength at which a fracture occurs when the surface protection layer and the stretching auxiliary layer are cut to have a length (MD direction) x width (TD direction) of 120 mm x 15 mm, fixed to a UTM device with a grip gap of 50 mm, and pulled at a tensile speed of 5 mm / min, and the MD direction elongation (%) of the surface protection layer and the stretching auxiliary layer can be calculated as the value obtained by dividing the grip gap at the time of fracture by the grip gap before stretching (50 mm) and multiplying by 100.

[0052] The tensile strength (N / 15 mm) of the surface protection layer and the stretching auxiliary layer according to the present invention in the TD direction can be measured as the strength at which a fracture occurs when the surface protection layer and the stretching auxiliary layer are cut to have a length (MD direction) x width (TD direction) of 15 mm x 120 mm, respectively, and then fixed to a UTM device with a grip gap of 50 mm and pulled at a tensile speed of 5 mm / min. The elongation (%) in the TD direction of the surface protection layer and the stretching auxiliary layer can be calculated as the value obtained by dividing the grip gap at the time of fracture by the grip gap before stretching (50 mm) and multiplying by 100.

[0053]

[0054] The present inventors have conducted continuous research on a pouch film laminate that can realize excellent molding depth without defects such as breakage or pinholes and also has excellent robustness, and as a result, they have found that by controlling the thickness ratio of the pouch film laminate to the thickness of the surface protective layer within a specific range, a pouch film laminate can be realized that the maximum cup molding depth is increased and robustness is improved without defects such as breakage or pinholes occurring during cup molding, and thus the present invention has been completed.

[0055]

[0056] Hereinafter, the present invention will be described in detail.

[0057] The pouch film laminate according to the present invention comprises at least one of the configurations described below, and may comprise any combination between technically possible configurations among the configurations below.

[0058]

[0059] Pouch film laminate (100)

[0060] Fig. 1 is a cross-sectional view of a pouch film laminate (100) according to the present invention. Hereinafter, each component of the pouch film laminate (100) of the present invention will be described in more detail with reference to Fig. 1.

[0061]

[0062] Referring to FIG. 1, a pouch film laminate (100) according to the present invention is a pouch film laminate (100) including a sequentially laminated substrate layer (110), a gas barrier layer (120), and a sealant layer (130), wherein the substrate layer (110) includes a surface protection layer (112), and a ratio of the thickness of the pouch film laminate (100) to the thickness of the surface protection layer (112) is 5 to 10.

[0063]

[0064] Conventional techniques have attempted to deepen the depth of the cup portion of a pouch-type battery case by controlling only the thickness and properties of a nylon film that assists stretching within a pouch film laminate or an aluminum alloy thin film used as a gas barrier layer.

[0065] However, when forming a cup portion by molding a pouch film laminate, not only the stretching of the nylon film or the gas barrier layer but also the stretching of all components included in the pouch film laminate occurs simultaneously, so there is a limit to implementing excellent formability and robustness simply by controlling the nylon film and the aluminum alloy film. In particular, the surface protection layer included in the pouch film laminate does not have an appropriate softness comparable to that of the nylon film or the aluminum alloy film, so there is a problem that the forming depth is low when molding the pouch film laminate, and if the appropriateness of the thickness ratio of the pouch film laminate to the surface protection layer is not considered, there is a problem that not only the formability but also the robustness is low.

[0066]

[0067] Accordingly, the present invention aims to provide a pouch film laminate capable of realizing superior formability and robustness by controlling the ratio of the thickness of the pouch film laminate to the thickness of the surface protective layer within a specific range.

[0068]

[0069] According to one embodiment of the present invention, the ratio of the thickness of the pouch film laminate (100) to the thickness of the surface protection layer (112) may be 6 to 10, preferably 6.0 or more, 6.5 or more, 7.5 or more, or 8.0 or more, and may be 10 or less, 9.5 or less, or 9.0 or less, and more preferably 8.0 to 9.0. When the ratio of the thickness of the pouch film laminate (100) to the thickness of the surface protection layer (112) is less than 6, there is a problem that the flexibility of the pouch film laminate (100) is reduced, so that the maximum forming depth is reduced, and there is a problem that wrinkles or cracks occur because stress is not properly distributed during cup forming, and there is a problem that the robustness is reduced. In addition, when the ratio of the thickness of the pouch film laminate (100) to the thickness of the surface protection layer (112) is greater than 10, moisture easily penetrates into the pouch film laminate (100) from the outside, the pouch film laminate (100) becomes vulnerable to external impact, and stress is concentrated on the gas barrier layer (120) in the pouch film laminate (100) during molding, so there is a problem that cracks and wrinkles are likely to occur in the cup portion, specifically, the edge and corner portion of the cup portion. Therefore, when the above range is satisfied, the ratio of the thickness of the surface protection layer (112) to the thickness of the pouch film laminate (100) is appropriate, so that tensile deformation does not easily occur, and thus the phenomenon of wrinkles occurring during the molding process can be prevented, and accordingly, the molding depth can be increased, and the robustness can be excellent. In addition, when the above conditions are satisfied, the edges and / or corners are where the most stretching occurs during pouch forming as they are areas where stretching stress is concentrated, so they are formed thinner than other areas and are vulnerable to external impacts. Therefore, the thickness of the edges and / or corners is prevented from becoming excessively thin, so that the strength can be improved.

[0070]

[0071] Below, each component is described in more detail.

[0072]

[0073] (1) Substrate layer (110)

[0074] The substrate layer (110) is formed on the outermost layer of the pouch film laminate (100) to protect the secondary battery from friction and collision with the outside. The substrate layer (110) is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0075]

[0076] According to one embodiment of the present invention, the substrate layer (110) may have a composite film structure in which two or more materials are formed in layers. An adhesive layer may be additionally formed between each layer in the composite film structure. In addition, an adhesive layer may be additionally formed between the gas barrier layer (120) described below and the substrate layer (110), and the substrate layer (110) may include an adhesive layer that adheres the gas barrier layer (120) and the substrate layer (110).

[0077]

[0078] According to one embodiment of the present invention, the substrate layer (110) may include a surface protection layer (112), and preferably may further include a stretching auxiliary layer (114), and more preferably may further include a surface protection layer (112) and a stretching auxiliary layer (114). When the above conditions are satisfied, it is preferable in that the external insulation is excellent, side reactions due to external moisture can be prevented, and the formability of the pouch film laminate can be improved.

[0079] In this case, the surface protection layer (112) may be a layer disposed on the outermost layer of the pouch film laminate, and the stretching auxiliary layer (114) may be a layer disposed between the surface protection layer (112) and a gas barrier layer (120) to be described later. The surface protection layer (112) and the stretching auxiliary layer (114) may each be formed of materials having different materials and / or different physical properties. An interface may exist between the surface protection layer (112) and the stretching auxiliary layer (114). This means that the surface protection layer (112) and the stretching auxiliary layer (114) are different layers, and may be formed separately.

[0080]

[0081] Hereinafter, the surface protection layer (112) and the stretching auxiliary layer (114) will be described in detail.

[0082]

[0083] 1) Surface protective layer (112)

[0084] The surface protection layer (112) may be a layer disposed on the outermost layer of the pouch film laminate as described above. In this case, the surface protection layer (112) may serve to prevent moisture penetration from the outside of the pouch.

[0085] According to one embodiment of the present invention, the surface protection layer (112) 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, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber. Preferably, the surface protection layer (112) may include a polyester-based film having wear resistance and heat resistance. For example, the surface protection layer (112) may include at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, but is not limited thereto.

[0086] If necessary, the surface protection layer (112) may include an additive. By including an additive in the surface protection layer (112), the physical properties of the surface protection layer (112) can be changed. For example, as an additive for controlling the tensile strength of the surface protection layer (112), at least one of carbon fiber, glass fiber, and aramid fiber can be added. When the surface protection layer includes such an additive, the mechanical strength can be increased and the elongation can be further improved.

[0087]

[0088] According to one embodiment of the present invention, the surface protection layer (112) may have a maximum peak temperature of 253°C or less in a differential scanning calorimetry (DSC) analysis graph obtained by heating from 25°C to 350°C at a heating rate of 10°C / min. Preferably, it may be 220°C or more, 225°C or more, 230°C or more, 235°C or more, 240°C or more, or 245°C or more, and may be 253°C or less, 252°C or less, 251°C or less, 250°C or less, or 249°C or less, and more preferably 245°C to 249°C. The maximum peak temperature in the differential scanning calorimetry (DSC) analysis graph of the surface protection layer (112) may be a property representing the flexibility or softness of the surface protection layer (112). When the maximum peak temperature exceeds 253°C, the surface protection layer (112) is not soft enough to match the flexibility of the nylon film or aluminum alloy thin film, which may cause cracks or pinholes to form during the forming of the pouch film laminate. Therefore, when the above range is satisfied, the surface protection layer (112) can block external moisture and appropriately prevent external impact, while at the same time having appropriate softness to realize excellent formability. In this case, the maximum peak temperature may refer to the melting peak temperature.

[0089] The maximum peak temperature in the differential scanning calorimetry (DSC) analysis graph of the surface protection layer (112) can be controlled in various ways, for example, depending on the composition of the surface protection layer (112), the type of additive included in the surface protection layer (112), etc., and preferably, by changing the composition of the surface protection layer (112), and more preferably, by appropriately adjusting the molar ratio of the ethylene glycol-derived structure and the butylene glycol-derived structure included in the surface protection layer (112).

[0090]

[0091] According to one embodiment of the present invention, the surface protective layer (112) may have a coefficient of friction measured at a temperature condition of 25°C of 0.3 or less, preferably 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, or 0.07 or more, and may be 0.3 or less, 0.25 or less, 0.20 or less, 0.15 or less, 0.13 or less, 0.11 or less, or 0.10 or less, and more preferably 0.07 to 0.10. When the above range is satisfied, excellent formability can be realized due to appropriate friction and softness.

[0092]

[0093] According to one embodiment of the present invention, the surface protection layer (112) may include a polyester film, and preferably, may include a polyester resin including an ethylene glycol-derived structure, a butylene glycol-derived structure, and a terephthalic acid-derived structure, and more preferably, the polyester resin may include an ethylene terephthalate structure and a butylene terephthalate structure in the main chain. When the above conditions are satisfied, the surface protection layer (112) may have excellent chemical resistance and heat resistance, while also improving extensibility and / or softness, thereby realizing excellent formability.

[0094]

[0095] According to one embodiment of the present invention, the molar ratio of the ethylene glycol-derived structure and the butylene glycol-derived structure included in the polyester-based resin may be 80:20 to 95:5, preferably 82:18 to 90:10, and more preferably 83:17 to 89:11. At this time, the ethylene glycol-derived structure and the butylene glycol-derived structure may be ethylene terephthalate and butylene terephthalate, respectively. When the ethylene glycol-derived structure and the butylene glycol-derived structure are included in the polyester-based resin at the molar ratio, the softness of the surface protective layer (112) increases, and the moldability of the pouch film laminate (100) may be improved, while the heat resistance and chemical resistance of the pouch film laminate (100) may be maintained.

[0096]

[0097] The method for producing the above polyester resin is not particularly limited, and may be produced by a method known in the art, for example, a terephthalic acid (TPA) method by reacting a mixture of ethylene glycol and butylene glycol with terephthalic acid, or a dimethyl terephthalate (DMT) method by reacting a mixture of ethylene glycol and butylene glycol with dimethyl terephthalate.

[0098]

[0099] In one embodiment of the present invention, the polyester resin may be a result of an esterification reaction and a polycondensation reaction between a mixture of, for example, ethylene glycol and butylene glycol and at least one selected from the group consisting of dimethyl terephthalate and terephthalic acid.

[0100]

[0101] According to one embodiment of the present invention, the surface protection layer (112) may include an additive. By including an additive in the surface protection layer (112), the physical properties of the surface protection layer (112) may be changed. For example, as an additive for controlling the tensile strength of the surface protection layer (112), at least one of carbon fiber, glass fiber, and aramid fiber may be added.

[0102]

[0103] According to one embodiment of the present invention, the thickness of the surface protection layer (112) may be 10 µm to 35 µm, preferably 20 µm to 30 µm, more preferably 22 µm to 28 µm, and even more preferably 24 µm to 26 µm. When the above range is satisfied, when the pouch film laminate (100) is formed and each layer in the pouch film laminate (100) is stretched, the mechanical properties such as tensile strength and elongation of the surface protection layer (112) are excellent, so that it can behave similarly to the stretching auxiliary layer (114), gas barrier layer (120), and / or sealant layer (130) described later, thereby realizing excellent formability, and in a structure that requires deep forming by applying pressure, durability is enhanced, so that the problem of the film being torn or wrinkled during forming can be prevented.

[0104]

[0105] 2) Extension auxiliary layer (114)

[0106] According to one embodiment of the present invention, the base layer (110) may further include a stretching auxiliary layer (114). The stretching auxiliary layer (114) may be a layer disposed between the surface protection layer (112) and the gas barrier layer (120) as described above. In this case, the stretching auxiliary layer (114) has stretching properties similar to those of the gas barrier layer (120), and thus can alleviate the difference in stretching properties between the surface protection layer (112) and the gas barrier layer (120), thereby playing a role in improving the formability of the pouch.

[0107]

[0108] According to one embodiment of the present invention, the stretching auxiliary layer (114) may include a polyamide-based film. For example, the stretching auxiliary layer (114) may include at least one selected from the group consisting of nylon 6,6, nylon MXD6 (polyxylylene adipamide), nylon 4, nylon 4,6, and nylon 4,10, but is not limited thereto. Preferably, in order for the stretching auxiliary layer (114) to have a melting temperature of 240°C or higher, the stretching auxiliary layer (114) may include nylon 6,6 and / or nylon MXD6.

[0109]

[0110] According to one embodiment of the present invention, the stretching auxiliary layer (114) may include metal oxide particles. The metal oxide particles may remove moisture within the stretching auxiliary layer (114) by being hydroxylated through a reaction with moisture introduced into the stretching auxiliary layer (114). 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 are advantageous for hydroxylation with moisture.

[0111]

[0112] According to one embodiment of the present invention, the stretching auxiliary layer (114) may further include an additive. By including an additive in the stretching auxiliary layer (114), the physical properties of the stretching auxiliary layer (114) may be changed. For example, as an additive for controlling the tensile strength of the stretching auxiliary layer (114), at least one of carbon fiber, glass fiber, and aramid fiber may be added.

[0113]

[0114] According to one embodiment of the present invention, the thickness of the stretching auxiliary layer (114) may be 20 µm to 45 µm, preferably 20 µm to 30 µm, more preferably 22 µm to 28 µm, and even more preferably 24 µm to 26 µm. When the thickness of the stretching auxiliary layer (114) satisfies the above numerical range, the mechanical properties of the stretching auxiliary layer may be similar to those of the gas barrier layer, so that a deeper forming depth may be realized when forming a pouch film laminate.

[0115]

[0116] According to one embodiment of the present invention, the ratio of the MD tensile strength of the stretching auxiliary layer (114) to the MD tensile strength of the surface protection layer (112) may be 0.9 to 1.1, preferably 0.95 to 1.05, more preferably 0.98 to 1.02. When the ratio of the MD tensile strength of the stretching auxiliary layer (114) to the surface protection layer (112) satisfies the above range, the difference in mechanical properties between the surface protection layer (112) and the stretching auxiliary layer (114) is reduced, thereby preventing the occurrence of breakage and pinholes due to the difference in properties of each layer during pouch forming, thereby improving the formability of the pouch.

[0117]

[0118] According to one embodiment of the present invention, the ratio of the TD direction tensile strength of the stretching auxiliary layer (114) to the TD direction tensile strength of the surface protection layer (112) may be 0.9 to 1.1, preferably 0.95 to 1.05, and more preferably 0.98 to 1.02. When the ratio of the TD direction tensile strength of the stretching auxiliary layer (114) to the TD direction tensile strength of the surface protection layer (112) satisfies the above range, the difference in mechanical properties between the surface protection layer (112) and the stretching auxiliary layer (114) is reduced, thereby preventing the occurrence of breakage and pinholes due to the difference in properties of each layer during pouch forming, thereby improving the formability of the pouch.

[0119]

[0120] According to one embodiment of the present invention, the ratio of the MD direction elongation of the stretching auxiliary layer (114) to the MD direction elongation of the surface protection layer (112) may be 0.9 to 1.1, preferably 0.95 to 1.05, more preferably 0.98 to 1.02. When the MD direction elongation ratio of the stretching auxiliary layer (114) to the surface protection layer (112) satisfies the above range, the difference in tensile properties between the laminated structural layers is reduced, so that both films are uniformly deformed during drawing molding, so that wrinkles due to excessive shrinkage or stretching can be prevented, and stress concentration that may occur at the film interface during molding can be reduced, so that layer delamination can be prevented.

[0121]

[0122] According to one embodiment of the present invention, the ratio of the TD direction elongation of the stretching auxiliary layer (114) to the TD direction elongation of the surface protection layer (112) may be 0.9 to 1.1, preferably 0.95 to 1.05, more preferably 0.98 to 1.02. When the ratio of the TD direction elongation of the stretching auxiliary layer (114) to the surface protection layer (112) satisfies the above range, the difference in tensile properties between the laminated structural layers is reduced, so that both films are uniformly deformed during drawing molding, so that wrinkles due to excessive shrinkage or stretching can be prevented, and stress concentration that may occur at the film interface during molding can be reduced, so that layer peeling can be prevented.

[0123]

[0124] According to one embodiment of the present invention, the MD direction tensile strength of the surface protection layer (112) may be 66 N / 15 mm to 95 N / 15 mm, preferably 70 N / 15 mm to 90 N / 15 mm, and more preferably 76 N / 15 mm to 84 N / 15 mm. When the MD direction tensile strength of the surface protection layer (112) satisfies the above range, the fatigue and puncture resistance improvement effect after cup forming can be enhanced, and even if a tensile load of a certain level or more is applied to the pouch for pouch forming, the problem of the pouch film laminate (100) being broken or pinholes being generated can be prevented.

[0125]

[0126] According to one embodiment of the present invention, the MD direction tensile strength of the stretching auxiliary layer (114) may be 70 N / 15 mm to 90 N / 15 mm, preferably 72 N / 15 mm to 88 N / 15 mm, and more preferably 75 N / 15 mm to 85 N / 15 mm. When the MD direction tensile strength of the stretching auxiliary layer (114) satisfies the above range, the fatigue and puncture resistance improvement effect after cup forming can be enhanced, and even if a tensile load of a certain level or more is applied to the pouch for pouch forming, the problem of the pouch film laminate (100) being broken or pinholes being generated can be prevented.

[0127]

[0128] According to one embodiment of the present invention, the tensile strength in the TD direction of the surface protection layer (112) may be 76 N / 15 mm to 105 N / 15 mm, preferably 81 N / 15 mm to 100 N / 15 mm, and more preferably 86 N / 15 mm to 95 N / 15 mm. When the tensile strength in the TD direction of the surface protection layer (112) satisfies the above range, the effect of improving fatigue and puncture resistance after cup forming can be enhanced, and even if a tensile load of a certain level or more is applied to the pouch for pouch forming, the problem of the pouch film laminate (100) being broken or pinholes being generated can be prevented.

[0129]

[0130] According to one embodiment of the present invention, the TD direction tensile strength of the stretching auxiliary layer (114) may be 80 N / 15 mm to 100 N / 15 mm, preferably 82 N / 15 mm to 98 N / 15 mm, and more preferably 85 N / 15 mm to 95 N / 15 mm. When the TD direction tensile strength of the stretching auxiliary layer (114) satisfies the above range, the fatigue and puncture resistance improvement effect after cup forming can be enhanced, and even if a tensile load of a certain level or more is applied to the pouch for pouch forming, the problem of the pouch film laminate (100) being broken or pinholes being generated can be prevented.

[0131]

[0132] According to one embodiment of the present invention, the MD direction elongation of the surface protection layer (112) may be 105% to 137%, preferably 110% to 130%, and more preferably 114% to 126%. When the MD direction elongation of the surface protection layer (112) satisfies the above range, the gas barrier layer is well held, thereby obtaining an effect of improving formability.

[0133]

[0134] According to one embodiment of the present invention, the MD direction elongation of the stretching auxiliary layer (114) may be 110% to 130%, preferably 112% to 127%, and more preferably 115% to 125%. When the MD direction elongation of the stretching auxiliary layer (114) satisfies the above range, the gas barrier layer is well held, thereby obtaining an effect of improving formability.

[0135]

[0136] According to one embodiment of the present invention, the TD direction elongation of the surface protection layer (112) may be 114% to 147%, preferably 120% to 140%, and more preferably 124% to 137%. When the TD direction elongation of the surface protection layer (112) satisfies the above range, the gas barrier layer is well held, thereby obtaining an effect of improving formability.

[0137]

[0138] According to one embodiment of the present invention, the TD direction elongation of the stretching auxiliary layer (114) may be 120% to 140%, preferably 122% to 138%, and more preferably 125% to 135%. When the TD direction elongation of the stretching auxiliary layer (114) satisfies the above range, the gas barrier layer is well held, thereby obtaining an effect of improving formability.

[0139]

[0140] The tensile strength and elongation in the MD and TD directions of the surface protection layer (112) and the stretching auxiliary layer (114) vary depending on the type of layer, the thickness of the layer, and / or the thickness of the adhesive layer, etc., and thus, the type of layer, the thickness of the layer, and / or the thickness of the adhesive layer, etc. can be appropriately adjusted to form the surface protection layer (112) and the stretching auxiliary layer (114) having the desired tensile strength and elongation.

[0141]

[0142] According to one embodiment of the present invention, the substrate layer (110) may have a composite film structure in which two or more materials are each formed to form layers. An adhesive layer may be additionally formed between each layer in the composite film structure. The adhesive layer may be formed by applying an adhesive commonly used in the present invention, for example, a urethane-based adhesive. For example, when the substrate layer (110) includes a surface protection layer (112) and / or a stretching auxiliary layer (114), an adhesive layer may be additionally formed between the surface protection layer (112) and the stretching auxiliary layer (114), and an adhesive layer may be additionally formed between the substrate layer (110) and the gas barrier layer (120). At this time, the thickness of the adhesive layer may be 1 µm to 8 µm, preferably 1 µm to 5 µm, and more preferably 2 µm to 4 µm.

[0143]

[0144] The thickness of the substrate layer (110) may be 45 ㎛ to 70 ㎛, preferably 45 ㎛ to 60 ㎛, and more preferably 45 ㎛ to 58 ㎛. When the thickness of the substrate layer (110) satisfies the above range, the external insulation is excellent, and the substrate layer can be prevented from being damaged during molding, thereby realizing excellent moldability. At the same time, since the entire thickness of the pouch is not thick, the energy density per volume of the secondary battery can be excellent. At this time, the thickness of the substrate layer (110) may be a thickness including an adhesive layer that may be included in the substrate layer (110), and may be a thickness including an adhesive layer that adheres the gas barrier layer (120) and the substrate layer (110). As described above, when the thickness of the substrate layer (100) includes an adhesive layer in the substrate layer (100) and an adhesive layer that adheres the gas barrier layer (120) and the substrate layer (110), a more clear effect can be realized.

[0145]

[0146] (2) Gas barrier layer (120)

[0147] The gas barrier layer (120) is laminated between the substrate layer (110) and the sealant layer (130) to secure the mechanical strength of the pouch, block the ingress of gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type battery case.

[0148] According to one embodiment of the present invention, the thickness of the gas barrier layer (120) may be 70 µm to 90 µm, preferably 75 µm to 85 µm, and more preferably 78 µm to 82 µm. When the above range is satisfied, the formability of the gas barrier layer is improved, so that when the pouch film laminate is draw-formed, the depth of the cup portion can be formed deep, the outer wall of the cup portion can become closer to vertical, and the radius of curvature of the corner of the cup portion can also be reduced. Accordingly, the volume of the receiving portion increases, so that more electrode assemblies can be laminated on the electrode assemblies accommodated therein, and the energy efficiency per volume can be increased. In addition, the thickness of the entire pouch can be kept from increasing significantly without significantly increasing the manufacturing cost and without reducing the thickness of the sealant layer, and the sealing durability can not be reduced. In addition, since the amount of gas barrier layer remaining after pouch forming is appropriate, the robustness of the pouch can be improved.

[0149]

[0150] According to one embodiment of the present invention, the gas barrier layer (120) may be formed of a metal. For example, the gas barrier layer may be a metal thin film including one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and invar (INVAR), but is not limited thereto.

[0151]

[0152] According to one embodiment of the present invention, the gas barrier layer (120) may be formed of an aluminum alloy thin film. When the gas barrier layer (120) is formed using an aluminum alloy thin film, a mechanical strength higher than a predetermined level can be secured, while being light in weight, and ensuring complementary electrochemical properties and heat dissipation properties due to the electrode assembly and electrolyte. The aluminum alloy thin film may contain elements other than aluminum (Al). For example, the aluminum alloy thin film may contain one or more selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0153] 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. The 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, and has relatively high toughness, which can suppress cracking of the pouch during use of the pouch-type battery. The stainless steel may include at least one element other than iron (Fe), for example, one or more selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0154]

[0155] (3) Sealant layer

[0156] The sealant layer (130) is intended to completely seal the interior of the pouch-shaped battery case by mutually thermally bonding the sealing portion when the pouch-shaped battery case containing the electrode assembly inside is sealed. To this end, the sealant layer (130) may be formed of a material having excellent thermal bonding strength.

[0157] According to one embodiment of the present invention, the sealant layer (130) may be formed of a material having insulating, corrosion-resistant, and sealing properties. Preferably, the sealant layer (130) may be formed of a material having insulating and corrosion-resistant properties since it is in direct contact with the electrode assembly and / or electrolyte inside the pouch-type battery case. In addition, the sealant layer (130) must completely seal the inside of the pouch-type battery case to block material movement between the inside and the outside, and thus may be formed of a material having high sealing properties (e.g., excellent thermal bonding strength). In order to secure such insulating, corrosion-resistant, and sealing properties, the sealant layer (130) may be formed of a polymer material.

[0158]

[0159] According to one embodiment of the present invention, 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, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber, and preferably may be made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of cast polypropylene (CPP), acid modified polypropylene (Acid Modified Polypropylene, PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0160]

[0161] According to one embodiment of the present invention, the thickness of the sealant layer (130) may be 70 µm to 90 µm, preferably 75 µm to 85 µm, and more preferably 78 µm to 82 µm. When the thickness of the sealant layer satisfies the above range, there is an effect of securing the sealing strength of the sealing portion while also securing the formability of the pouch film laminate.

[0162]

[0163] According to one embodiment of the present invention, the sealant layer (130) may include a first sealant layer arranged to be in contact with the gas barrier layer (120), a second sealant layer laminated on the first sealant layer, and a third sealant layer laminated on the second sealant layer.

[0164]

[0165] According to one embodiment of the present invention, the first sealant layer may include polypropylene, and preferably, to secure long-term adhesion between the gas barrier layer and the first sealant layer, may include acid-modified polypropylene (PPa). Here, the acid-modified polypropylene may be maleic anhydride polypropylene (MAH PP).

[0166]

[0167] According to one embodiment of the present invention, the second sealant layer may be formed of a material having insulating, corrosion-resistant, and sealing properties. Preferably, it 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, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber. Preferably, the second sealant layer may be formed of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of non-stretched polypropylene, acid-modified polypropylene, polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer. Here, the acid-modified polypropylene may be maleic anhydride polypropylene (MAH PP). More preferably, the second sealant layer may include cast polypropylene (CPP) having heat sealability and high tensile strength.

[0168]

[0169] According to one embodiment of the present invention, the third sealant layer may include polypropylene, preferably a polypropylene random copolymer, more preferably at least one selected from the group consisting of an ethylene-propylene random copolymer and a butene-propylene random copolymer, and even more preferably an ethylene-propylene random copolymer. When the above conditions are satisfied, the melt flow rate (MFR) is high and the melting point is low, so that when the same amount of heat is applied, the desired sealing thickness can be quickly achieved. Accordingly, even without increasing the sealing temperature, the sealing time can be shortened compared to when a polypropylene homocopolymer is included, and the process time of the secondary battery can be shortened, thereby improving productivity and processability, and at the same time having strong thermal bonding strength, so that the pouch-type battery case can have excellent sealing properties.

[0170]

[0171] According to one embodiment of the present invention, the thickness of the pouch film laminate (100) may be 120 µm to 300 µm, preferably 160 µm to 250 µm, more preferably 185 µm to 240 µm, and even more preferably 200 µm to 230 µm. When the thickness of the pouch film laminate satisfies the above range, the forming depth can be increased while minimizing a decrease in battery accommodation space, a decrease in sealing durability, etc. due to an increase in the thickness of the pouch laminate.

[0172]

[0173] According to one embodiment of the present invention, the pouch film laminate (100) has a maximum forming index A (MFI) expressed by the following equation 1 A ) can be 15 or more.

[0174] [Formula 1]

[0175] Maximum Forming Index A (MFI) A ) = (PT / AT) ⅹ TS

[0176] In the above equation 1, PT is the value of the thickness (㎛) of the surface protective layer, AT is the value of the thickness (㎛) of the pouch film laminate, and TS is the value of the tensile strength (N / 15 mm) of the pouch film laminate.

[0177] Preferably, the pouch film laminate (100) has a maximum forming index A (MFI) expressed by the above formula 1 A ) may be 15 or more, 18 or more, 20 or more, 22 or more, 24 or more, 26 or more, 27 or more, 28 or more, 29 or more, 30 or more or 30.2 or more, 51 or less, 45 or less, 40 or less, 38 or less, 37 or less, 36 or less, 35 or less or 34.0 or less, and more preferably 30.2 to 34.0. The maximum forming index (Max Forming Index A, MFI) A ) is the product of the thickness ratio of the surface protective layer to the thickness of the pouch film laminate and the tensile strength of the pouch film laminate. The maximum forming index (Max Forming Index A, MFI) A ) is controlled within an appropriate range, the thickness ratio of the surface protective layer to the total thickness of the pouch film laminate and the tensile strength of the pouch film laminate are appropriately combined, so that the cup forming depth and pouch strength can be sufficiently increased during forming. In addition, it may be desirable in that the occurrence of wrinkles during pouch forming can be suppressed.

[0178]

[0179] According to one embodiment of the present invention, the substrate layer (110) further includes a stretching auxiliary layer (114), and the pouch film laminate (100) has a maximum forming index B (MFI) expressed by the following equation 2. B ) can be 45 or more.

[0180] [Formula 2]

[0181] Maximum Forming Index B (MFI) B) = {(PT+NT) / (AT)} ⅹ TS

[0182] In the above formula 2, PT is the value of the thickness (㎛) of the surface protective layer, NT is the value of the thickness (㎛) of the stretching auxiliary layer, AT is the value of the thickness (㎛) of the pouch film laminate, and TS is the value of the tensile strength (N / 15 mm) of the pouch film laminate.

[0183] Preferably, the maximum forming index B (MFI) expressed by the above formula 2 B ) may be 45 or more, 46 or more, 47 or more, 48 or more, 50 or more, 51 or more, 52 or more, 53 or more, 54 or more, 55 or more, 56 or more, 57 or more, 58 or more, 59 or more, 60 or more or 60.3 or more, 92 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 69 or less, 68 or less or 67.0 or less, and more preferably 60.3 to 67.0. The above formula 2 is the product of the ratio of the sum of the thicknesses of the surface protective layer and the stretching auxiliary layer to the thickness of the pouch film laminate and the tensile strength of the pouch film laminate. The maximum forming index A (MFI) according to the above formula 1 A ), it may be a parameter suitable for implementing better formability as a parameter that considers the extension auxiliary layer that affects formability. If the above range is satisfied, it may be desirable in that a better maximum forming depth can be implemented.

[0184]

[0185] According to one embodiment of the present invention, the elongation of the pouch film laminate (100) may be 65% to 120%, preferably 70% to 110%, and more preferably 75% to 100%. When the above range is satisfied, the pouch elongation caused by the friction between the pouch film laminate and the molding die not slipping is not low, so the cup portion forming depth can be excellent, and the strength can be improved.

[0186]

[0187] According to one embodiment of the present invention, the tensile strength of the pouch film laminate (100) may be 225 N / 15 mm to 350 N / 15 mm, preferably 225 N / 15 mm or more, 230 N / 15 mm or more, 235 N / 15 mm or more, 240 N / 15 mm or more, or 245 N / 15 mm or more, and 350 N / 15 mm or less, 330 N / 15 mm or less, 310 N / 15 mm or less, or 290 N / 15 mm or less, and more preferably 245 N / 15 mm to 290 N / 15 mm. When the above range is satisfied, the pouch slip amount corresponding to the stress applied to the pouch during pouch forming may increase, so that breakage or pinholes may not occur during pouch forming, and the cup portion forming depth may be improved. In addition, since the tensile strength of the pouch film laminate is not excessively high, the pouch slip amount is appropriate, so that wrinkles can be suppressed during pouch forming, and since there is no excessive difference in length of the pouch film laminate before and after pouch forming, the processability can be excellent.

[0188]

[0189] The tensile strength and elongation of the aforementioned pouch film laminate can be measured by a conventional method, but specifically, can be measured using a UTM device. More specifically, a sample is manufactured by cutting the pouch film laminate to a length (MD direction) x width (TD direction) of 120) mm x 15 mm. After cutting the sample so that the length direction of the sample matches the MD direction of the pouch film laminate, the samples are fixed to the UTM device with a grip gap of 50 mm, and the strength at which the samples break is measured as the tensile strength (N / 15 mm) by pulling the samples at a tensile speed of 5 mm / min. At this time, the elongation can be measured by measuring the deformation length when breakage occurs.

[0190]

[0191] According to one embodiment of the present invention, the ratio of the thickness of the gas barrier layer (120) to the thickness of the surface protection layer (112) may be 2.5 to 3.3. Preferably, it may be 2.50 or more, 2.55 or more, 2.60 or more, 2.65 or more, 2.70 or more, 2.75 or more, 2.80 or more, 2.85 or more, 2.90 or more, 2.95 or more, or 3.00 or more, and 3.30 or less. More preferably, it may be 3.00 to 3.30. When the above range is satisfied, the thicknesses of the surface protection layer (112) and the gas barrier layer (120) are balanced, so that the tensile force is evenly distributed during the molding process, thereby facilitating deformation, thereby ensuring a high molding depth while implementing excellent toughness and surface protection performance.

[0192]

[0193] According to one embodiment of the present invention, the ratio of the thickness of the gas barrier layer (120) to the thickness of the substrate layer (110) may be 1.4 to 1.8, and preferably 1.4 to 1.7. When the above range is satisfied, cracking can be prevented during molding, thereby ensuring a high molding depth.

[0194]

[0195] According to one embodiment of the present invention, the base layer (110) further includes a stretching auxiliary layer (114), and the ratio of the thickness of the stretching auxiliary layer (114) to the thickness of the surface protection layer (112) may be 1.2 or less, preferably 1.2 or less, 1.1 or less, or 1.05 or less, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more, and more preferably 0.9 to 1.05. When the above range is satisfied, the tensile stress is uniformly distributed so that the stress is not concentrated in a specific portion, so that the film is uniformly stretched, and the adhesive force between the two films acts uniformly so that delamination between layers does not occur, thereby improving the formability, and thus ensuring a high forming depth.

[0196]

[0197] Pouch-type secondary battery (200)

[0198] Next, a pouch-type secondary battery (200) according to the present invention will be described.

[0199] A pouch-type secondary battery (200) according to the present invention includes a pouch-type battery case (210) manufactured by drawing and molding the aforementioned pouch film laminate (100), and an electrode assembly (260) housed in the pouch-type battery case (210). Preferably, the pouch-type secondary battery (200) according to the present invention includes a pouch-type battery case (210) in which an electrode assembly (260) is housed, and the pouch-type battery case (210) is manufactured by drawing and molding the pouch film laminate (100), and the pouch film laminate (100) includes a substrate layer (110) including a sequentially laminated surface protection layer (112), a gas barrier layer (120), and a sealant layer (130), and a ratio of the thickness of the pouch film laminate (100) to the thickness of the surface protection layer (112) may be 5 to 10.

[0200]

[0201] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to FIG. 2.

[0202] Fig. 2 is an exploded assembly diagram of a pouch-type secondary battery (200) according to the present invention. As illustrated in Fig. 2, the pouch-type secondary battery (200) of the present invention may include a pouch-type battery case (210), an electrode assembly (260), an electrode lead (280), an insulator (290), and an electrolyte (not shown).

[0203]

[0204] (1) Pouch-type battery case

[0205] A pouch-shaped battery case (210) can be manufactured by drawing and molding the pouch film laminate of the present invention described above. The pouch-shaped battery case (210) can accommodate an electrode assembly (260) inside. Since the detailed configuration and properties of the pouch film laminate are the same as those described above, a detailed description thereof will be omitted.

[0206] The pouch film laminate can be drawn and stretched by a punch or the like to manufacture a pouch-shaped battery case (210). As a result, the pouch-shaped battery case (210) can include a cup portion (222) and a receiving portion (224). The receiving portion (224) is a place for receiving an electrode assembly, and can mean a receiving space formed in the shape of a pocket on the inside of the cup portion (222) as the cup portion (222) is formed.

[0207]

[0208] According to one embodiment of the present invention, a pouch-type battery case (210) may include a first case (220) and a second case (230) as illustrated in FIG. 2. The first case (220) includes a receiving portion (224) capable of receiving an electrode assembly (260), and the second case (230) may cover the receiving portion (224) from above to prevent the electrode assembly (260) from being separated from the outside of the battery case (210). The first case (220) and the second case (230) may be manufactured such that one side thereof is connected to each other as illustrated in FIG. 2, but are not limited thereto and may be manufactured in various ways, such as being manufactured separately and separated from each other.

[0209] According to another embodiment of the present invention, when forming a cup portion on a pouch film laminate, two symmetrical cup portions (222, 232) can be drawn and formed adjacent to each other on one pouch film laminate. In this case, cup portions (222, 232) can be formed on the first case (220) and the second case (230) respectively, as shown in FIG. 2. After the electrode assembly (260) is accommodated in the receiving portion (224) provided in the cup portion (222) of the first case (220), the bridge portion (240) formed between the two cup portions (222, 232) can 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) can accommodate the electrode assembly (260) from above. Accordingly, since two cup portions (222, 232) accommodate one electrode assembly (260), an electrode assembly (260) having a thicker thickness can be accommodated than when there is only one cup portion (222). In addition, since one corner of the secondary battery (200) is formed by folding the pouch-type battery case (210), the number of corners to be sealed can be reduced when performing a sealing process later. Accordingly, the process speed of the pouch-type secondary battery (200) can be improved, and the number of sealing processes can be reduced.

[0210]

[0211] The pouch-type battery case (210) can be sealed while housing the electrode assembly (260) so that a portion of the electrode lead (280) described later, i.e., a terminal portion, is exposed. Specifically, when 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) can be housed in a receiving portion (224) provided in a cup portion (222) of the first case (220), and the second case (230) can cover the receiving portion (224) from above. Subsequently, an electrolyte can be injected into the interior of the receiving portion (224), and the sealing portions (250) formed on the edges of the first case (220) and the second case (230) can be sealed.

[0212] The sealing portion (250) can perform a function of sealing the receiving portion (224). Specifically, the sealing portion (250) can seal the receiving portion (224) while being formed along the edge of the receiving portion (224). The temperature at which the sealing portion (250) is sealed can be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature satisfies the above numerical range, the pouch-type battery case (210) can secure sufficient sealing strength through thermal bonding.

[0213]

[0214] A pouch-shaped battery case (210) according to the present invention may include a cup portion (222, 232) having an indented shape and a terrace portion (250) located on at least a portion of the circumference of the cup portion (222, 232).

[0215] The above cup portion (222, 232) has a receiving portion (224) for receiving an electrode assembly (260), and the terrace portion (250) means an unmolded portion of the pouch film laminate (100), i.e., the remaining area excluding the cup portion (222, 232).

[0216] Referring to FIG. 3, the cup portion (222, 232) may include a bottom surface (311) and a peripheral surface (312). The peripheral surface (312) may connect the bottom surface (311) and the terrace portion (250). A plurality of peripheral surfaces (312), more specifically, four, may be provided.

[0217] The bottom surface (311) can cover one side of the electrode assembly (260), and the peripheral surface (312) can surround the periphery of the electrode assembly (260). In addition, the cup portion (222, 232) can include a first edge (313) where the peripheral surface (312) and the terrace portion (250) meet, a second edge (314) where the bottom surface (311) and the peripheral surface (312) meet, and a third edge (315) where a pair of adjacent peripheral surfaces (312) among the plurality of peripheral surfaces (312) meet. Each edge (313), (314), (315) can be formed to be rounded so as to have a predetermined radius of curvature.

[0218] In addition, the cup portion (222, 232) may include a corner (316) where a pair of adjacent peripheral surfaces (312) among the plurality of peripheral surfaces (312) meet the bottom surface (311). That is, the corner (316) may be a portion where a pair of adjacent second edges (314) and third edges (315) overlap. The corner (316) may have a predetermined radius of curvature.

[0219] Since the cup portion (222, 232) has four peripheral surfaces (312), each edge (313), (314), (315) and corner (316) can also be formed in four numbers.

[0220]

[0221] According to one embodiment of the present invention, the pouch-type battery case (210) may have a barrier residual rate (BRR) expressed by the following equation 3 of 30% to 60%, preferably 30% to 50%, and more preferably 30% to 45%.

[0222] [Formula 3]

[0223] Barrier Residual Rate (BRR) = (LT / CT) × 100

[0224] In the above formula 1, LT is a value of the thickness (μm) of the gas barrier layer included in the corner of the cup portion in the pouch-shaped battery case, and CT is a value of the thickness (μm) of the gas barrier layer included in the terrace portion in the pouch-shaped battery case. Preferably, CT may be a value of the thickness (μm) of the gas barrier layer included in the pouch film laminate before manufacturing the pouch-shaped battery case.

[0225] The above barrier retention ratio may be the ratio of the thickness of the gas barrier layer at the corner cross-section within the cup portion of the pouch-type battery case to the thickness of the gas barrier layer included in the pouch film laminate prior to manufacturing the pouch-type battery case, and is an index that can represent the robustness of the pouch-type battery case. For example, since the pouch-type battery case is manufactured by drawing and forming the pouch film laminate, the formed portion undergoes stretching, and in particular, the corner is the portion where stretching stress is concentrated, where stretching occurs the most, and therefore is formed thinner than other portions and is vulnerable to external impact. Therefore, when the above barrier retention ratio is low, the mechanical strength of the battery case may be weakened, and there is a problem that the case may be easily broken by impact, and therefore the robustness of the pouch-type battery case can be represented by the BRR expressed by the above equation 3. When the above range is satisfied, it may be desirable in that excellent mechanical strength can be realized, while also achieving an excellent maximum forming depth, and the volume of the receiving portion (224) may not be excessively reduced, so that the energy density can be excellent.

[0226]

[0227] According to one embodiment of the present invention, the thickness of the gas barrier layer (120) of the corner (316) portion may be 25 ㎛ or more, preferably 25 ㎛ or more, 26 ㎛ or more, 27 ㎛ or more, 28 ㎛ or more, 29 ㎛ or more, 30 ㎛ or more, 48 ㎛ or less, 47 ㎛ or less, 46 ㎛ or less, 45 ㎛ or less, 43 ㎛ or less, 42 ㎛ or less, or 41 ㎛ or less, and more preferably 30 ㎛ to 41 ㎛. The corner (316) is a portion where stretching stress is concentrated during cup molding, and since the most stretching occurs, it is formed thinner than other portions, and is also the most vulnerable to external impact due to the most occurrence of cracks and pinholes. In particular, when molding two cups, since pressure is applied by two punches at a close distance, the stress concentrated on the corner increases further, which tends to further aggravate this problem. Therefore, when the above range is satisfied, crack occurrence can be suppressed and damage due to external impact can be minimized.

[0228] Meanwhile, since the terrace portion (250) is an area where no forming is performed, the thickness of the gas barrier layer (120) in this portion is almost the same as the thickness of the gas barrier layer (120) of the pouch film laminate (100) before forming. Accordingly, the thickness of the gas barrier layer (120) in the terrace portion (250) may be 70 µm to 90 µm, preferably 75 µm to 85 µm, and more preferably 78 µm to 82 µm.

[0229] Meanwhile, the radius of curvature of the corner (316) may be formed to be 0.5 to 5.0 mm, preferably 1.0 to 4.0 mm, and more preferably 2.0 to 3.5 mm. The radius of curvature of the corner (316) may be the radius of curvature of the inner surface of the corner (316). If the radius of curvature of the corner (316) is too small, it is difficult to maintain the thickness of the gas barrier layer (120) at the corner to be 30 μm or more, and if the radius of curvature is too large, the accommodation space of the cup portion may be reduced, which may lower the energy density.

[0230]

[0231] (2) Electrode assembly

[0232] The electrode assembly (260) can be inserted into a pouch-type battery case (210) and sealed by the pouch-type battery case (210) after electrolyte injection.

[0233] The electrode assembly (260) may be formed by sequentially stacking an anode, a separator, and a cathode. Specifically, the electrode assembly (260) may include two types of electrodes, an anode and a cathode, and a separator interposed between the electrodes to mutually insulate the electrodes.

[0234] 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, respectively. The slurry is typically formed by stirring granular active materials, auxiliary conductors, binders, and conductive agents with the addition of a solvent. The solvent can be removed in a subsequent process.

[0235] A slurry containing an electrode active material, a binder, and / or a conductive material is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator, thereby manufacturing an electrode assembly (260) in a predetermined shape. The types of electrode assembly (260) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc.

[0236] The electrode assembly (260) may include an electrode tab (270).

[0237] The electrode tabs (270) are respectively connected to the positive and negative electrodes of the electrode assembly (260), and may protrude outward from the electrode assembly (260) to serve as a path for electrons to move between the inside and the outside of the electrode assembly (260). The electrode current collector included in the electrode assembly (260) may be composed of a portion where an electrode active material is applied and a terminal portion where the electrode active material is not applied, i.e., a non-coated portion. The electrode tabs (270) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 2, the electrode tabs (270) may protrude in different directions of the electrode assembly (260), but are not limited thereto, and may be formed to protrude in various directions, such as protruding in parallel in the same direction from one side.

[0238]

[0239] (3) Electrode lead

[0240] The electrode lead (280) can supply electricity to the outside of the secondary battery (200). The electrode lead (280) can be connected to the electrode tab (270) of the electrode assembly (260) by spot welding, etc.

[0241] 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 to 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).

[0242] The electrode lead (280) may include a positive lead (282) having one end connected to the positive tab (272) and extending in the direction in which the positive tab (272) protrudes, and a negative lead (284) having one end connected to the negative tab (271) and extending in the direction in which the negative tab (271) protrudes. Both the positive lead (282) and the negative lead (284) may have other ends protruding outward from the battery case (210). Accordingly, electricity generated inside the electrode assembly (260) may be supplied to the outside. In addition, since the positive tab (272) and the negative tab (271) are formed to protrude in various directions, the positive lead (282) and the negative lead (284) may also extend in various directions, respectively. The positive lead (282) and the negative 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 collector, and the negative electrode lead (284) may be made of the same copper (Cu) material as the negative electrode collector or a copper material coated with nickel (Ni). A portion of the electrode lead (280) protruding outside the battery case (210) may serve as a terminal portion and be electrically connected to an external terminal.

[0243]

[0244] (4) Insulation

[0245] The insulating portion (290) prevents electricity generated from the electrode assembly (260) from flowing to the battery case (210) through the electrode lead (280) and can maintain the sealing of the battery case (210). To this end, the insulating portion (290) may be formed of a non-conductive material that does not conduct electricity well. In general, the insulating portion (290) is often formed of an insulating tape or film that is easy to attach to the electrode lead (280) and has a relatively thin thickness, but is not limited thereto, and any material capable of insulating the electrode lead (280) may be used.

[0246] The insulating portion (290) may be arranged to surround the outer circumference of the electrode lead (280). Specifically, at least a portion of the electrode lead (280) may be surrounded by the insulating portion (290). In this case, the insulating portion (290) may be arranged between the electrode lead (280) and the pouch-type battery case (210). The insulating portion (290) may be positioned limited to the sealing portion (250) where the first case (220) and the second case (230) of the pouch-type battery case (210) are thermally fused, and may adhere the electrode lead (280) to the battery case (210).

[0247]

[0248] (5) Electrolyte

[0249] The pouch-type secondary battery (200) according to the present invention may further include an electrolyte (not shown) that is poured into the pouch-type battery case (210). The electrolyte is for moving lithium ions generated by an electrochemical reaction of an electrode during charging / discharging of the secondary battery (200), and may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. Furthermore, the electrolyte may include a solid electrolyte of a sulfide type, an oxide type, or a polymer type, and such a solid electrolyte may have flexibility that is easily deformed by an external force.

[0250]

[0251] Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are merely illustrative and serve to aid understanding of the present invention and do not limit its scope. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope and technical spirit of this disclosure, and such modifications and variations are naturally within the scope of the appended claims.

[0252]

[0253] Examples and Comparative Examples

[0254] Example 1: Preparation of pouch film laminate

[0255] A sequentially laminated 25 ㎛ thick polyester film, a 3 ㎛ thick first adhesive layer, a 25 ㎛ thick nylon (Ny) film, and a 3 ㎛ thick second adhesive layer were prepared as a substrate layer, an 80 ㎛ thick aluminum alloy thin film was prepared as a gas barrier layer, and an 80 ㎛ thick sealant layer was prepared as a sealant layer. The sequentially laminated pouch film laminate was used as Example 1.

[0256] At this time, the sealant layer was sequentially laminated with a first sealant layer of an acid modified polypropylene (PPa) film of 30 μm, a second sealant layer of a non-stretched polypropylene (PP) film of 30 μm, and a third sealant layer of an ethylene-propylene random copolymer film of 20 μm, based on the layer close to the aluminum alloy thin film.

[0257] In addition, in the case of the polyester film, a polyester film manufactured with the composition shown in Table 2 below was used. The terephthalic acid (TPA) method, which is a method for manufacturing polyethylene terephthalate by reaction of ethylene glycol and terephthalic acid, was applied to manufacture the polyester resin used in the manufacture of the polyester film, and ethylene glycol or a mixture of ethylene glycol and butylene glycol was used as a raw material as shown in Table 1 below.

[0258]

[0259] Comparative Examples 1 to 3: Manufacturing of Pouch Film Laminates

[0260] As shown in Tables 1 and 2 below, pouch film laminates of Comparative Examples 1 to 3 were manufactured in the same manner as in Example 1, except that the thickness of each layer was controlled or the composition of the surface protective layer was controlled.

[0261]

[0262] Thickness of each layer within the substrate layer (㎛) Thickness of gas barrier layer (㎛) Thickness of each layer within the sealant layer (㎛) Thickness of pouch film laminate (㎛) Surface protection layer 1st adhesive layer Stretching auxiliary layer 2nd adhesive layer 1st sealant layer 2nd sealant layer 3rd sealant layer Example 125325380303020216 Comparative example 11231534040040153 Comparative example 212325360303020183 Comparative example 34032538040040231

[0263] Compound molar ratio in polyester film (surface protective layer) Ethylene terephthalate Butylene terephthalate Example 184.5 15.5 Comparative Example 11000 Comparative Example 21000 Comparative Example 384.5 15.5

[0264] Experimental Example 1: Measurement of tensile strength and elongation of pouch film laminates

[0265] The tensile strength and elongation of the pouch film laminates manufactured in Example 1 and Comparative Examples 1 to 3 were measured.

[0266] The tensile strength and elongation of the above pouch film laminate were measured using a UTM device. Specifically, the pouch film laminate was cut to a length (MD direction) x width (TD direction) of 120 mm x 15 mm to manufacture a sample. After cutting the sample so that the length direction of the sample matches the MD direction of the pouch film laminate, the samples were fixed to the UTM device with a grip gap of 50 mm, and the strength at which the samples were pulled at a tensile speed of 5 mm / min was measured as the tensile strength (N / 15 mm). At this time, the elongation was measured by measuring the deformation length when the fracture occurred.

[0267] The measured tensile strength and elongation are shown in Table 3 below.

[0268]

[0269] Surface protection layer thickness (㎛) Stretching auxiliary layer thickness (㎛) Pouch film laminate MFI A MFI BThickness (㎛) Tensile strength (N / 15mm) Elongation (%) Example 125252162877633.266.4 Comparative example 112151531428711.125.1 Comparative example 212251832177314.243.9 Comparative example 340252313008551.984.4

[0270] Experimental Example 2: Evaluation of Formability and Robustness of Pouch Film Laminates

[0271] (1) Evaluation of pouch film laminate formability

[0272] The formability of each pouch film laminate according to Example 1 and Comparative Examples 1 to 3 was evaluated.

[0273] Specifically, as a method for evaluating the formability of a pouch film laminate, each of the pouch film laminates was cut to the same size of 665 mm (MD direction) x 400 mm (TD direction), and then the forming depth was changed in a 2-cup forming device equipped with a die and a punch to find the forming depth when cracks occurred, and then the depth was lowered by 0.5 mm from that depth and confirmed that there were no defects when forming 10 times, and the depth was measured as the maximum forming depth.

[0274] At this time, the mold conditions of the 2-cup molding device are as shown in Table 4 below.

[0275]

[0276] Edge curvature (mm) Punch (corner) 0.5 (3.5) Die 0.5 Bridge 0.5 Corner curvature (mm) Punch 1.5 Die 2.5 Clearance (mm) Bridge side 1 Side side 1 Bridge (mm) Width 1 Size (mm) Punch 513ⅹ95.65ⅹ2 Die 515ⅹ97.65ⅹ2

[0277] The measured maximum forming depth is shown in Table 5 below.

[0278]

[0279] (2) Evaluation of robustness of pouch film laminate

[0280] In evaluating the formability of the above pouch film laminate, the robustness of each pouch film laminate according to Example 1 and Comparative Examples 1 to 3 was evaluated when the maximum forming depth was satisfied in the manufactured pouch-type battery case.

[0281] In detail, in the pouch-type battery case manufactured during the evaluation of the formability of the above pouch film laminate, when the maximum forming depth is satisfied, a sample is manufactured by cutting the corner at a 45 degree angle as shown in FIGS. 4 to 6, and then the cut cross-section of the sample is observed under a microscope to measure the thickness of the gas barrier layer at the corner where the bottom surface and the circumference surface of the cup part meet, and the percentage of the ratio of the thickness of the gas barrier layer at the corner part after forming the cup part to the thickness of the gas barrier layer before forming is measured.

[0282] This is expressed as a barrier survival rate (BRR) expressed in Equation 3 below and is shown in Table 5 below.

[0283] [Formula 3]

[0284] Barrier Residual Rate (BRR) = (LT / CT) × 100

[0285] In the above formula 1, LT is a value of the thickness (μm) of the gas barrier layer included in the corner of the cup portion in the pouch-type battery case, and CT is a value of the thickness (μm) of the gas barrier layer included in the pouch film laminate before manufacturing the pouch-type battery case.

[0286]

[0287] Pouch film laminate thickness (㎛) to surface protective layer thickness (㎛) Maximum forming depth (mm) Gas barrier layer thickness at the corner of the cup part (㎛) Barrier residual rate (%) Example 18.64 14.53 746 Comparative example 112.75 5.82 460 Comparative example 215.25 10.03 660 Comparative example 35.78 13.55 0 62

[0288] As described in Table 5 above, in the case of Example 1, it can be confirmed that the maximum formability and strength are superior, unlike Comparative Examples 1 to 3.

[0289]

[0290] [Explanation of symbols]

[0291] 100: Pouch film laminate

[0292] 110: Base layer

[0293] 112: Surface protection layer

[0294] 114: Extension auxiliary layer

[0295] 120: Gas barrier layer

[0296] 130: Sealant layer

[0297] 200: Pouch-type secondary battery

[0298] 210: Pouch-type battery case

[0299] 220: Case 1

[0300] 222: Cup

[0301] 224: Reception area

[0302] 230: Case 2

[0303] 232: Cup

[0304] 240: Bridge section

[0305] 250: Terrace

[0306] 260: Electrode assembly

[0307] 270: Electrode tab

[0308] 271: Negative tab

[0309] 272: Positive tab

[0310] 280: Electrode lead

[0311] 282: Positive lead

[0312] 284: Negative lead

[0313] 290: Insulation

[0314] 311: Floor

[0315] 312: Perimeter

[0316] 313: First Edge

[0317] 314: The Second Edge

[0318] 315: The Third Edge

[0319] 316: Corner

Claims

1. A pouch film laminate comprising a sequentially laminated substrate layer, a gas barrier layer, and a sealant layer, The above substrate layer includes a surface protective layer, A pouch film laminate having a ratio of the thickness of the pouch film laminate to the thickness of the surface protective layer of 6 to 10.

2. In claim 1, A pouch film laminate having a thickness of the above-mentioned substrate layer of 45 ㎛ to 70 ㎛.

3. In claim 1, A pouch film laminate having a thickness of the surface protective layer of 10 ㎛ to 35 ㎛.

4. In claim 1, The above surface protective layer is a pouch film laminate having a maximum peak temperature of 253°C or less in a differential scanning calorimetry (DSC) analysis graph obtained by heating from 25°C to 350°C at a heating rate of 10°C / min.

5. In claim 1, The above surface protective layer is a pouch film laminate having a coefficient of friction of 0.3 or less measured under temperature conditions of 25°C.

6. In claim 1, The above-mentioned substrate layer further includes an extension auxiliary layer, A pouch film laminate having a thickness of the above-mentioned extension auxiliary layer of 20㎛ to 45㎛.

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

8. In claim 1, A pouch film laminate having a thickness of the sealant layer of 70 ㎛ to 90 ㎛.

9. In claim 1, A pouch film laminate comprising a first sealant layer arranged to be in contact with the gas barrier layer, a second sealant layer laminated on the first sealant layer, and a third sealant layer laminated on the second sealant layer.

10. In claim 1, A pouch film laminate having a thickness of 120 ㎛ to 300 ㎛.

11. In claim 1, A pouch film laminate having a ratio of the thickness of the gas barrier layer to the thickness of the surface protective layer of 2.5 to 3.

3.

12. In claim 1, A pouch film laminate in which the ratio of the thickness of the gas barrier layer to the thickness of the substrate layer is 1.4 to 1.

8.

13. In claim 1, The above-mentioned substrate layer further includes an extension auxiliary layer, A pouch film laminate in which the ratio of the thickness of the stretching auxiliary layer to the thickness of the surface protective layer is 1.2 or less.

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

15. A pouch-type secondary battery comprising the pouch-type battery case of claim 14.

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