Pouch-type battery case and pouch-type secondary battery

Abstract

A pouch-type battery case according to the present invention includes a pouch film laminate and includes a cup portion having a bottom surface portion and a side surface portion, and a flat portion arranged to surround the cup portion, the side surface portion including a first curved surface portion, a second curved surface portion, and a flat portion arranged between the first curved surface portion and the second curved surface portion, the first curved surface portion being defined as between the bottom surface portion and the flat surface portion, and the second curved surface portion being defined as between the flat surface portion and the flat portion, the pouch film laminate including a base layer, a sealant layer, and a gas barrier layer arranged between the base layer and the sealant layer, the gas barrier layer comprising stainless steel, and the pouch-type battery case satisfies the following formula 1: [Formula 1] 0.01≦D / {A-(R P +R D +C)} D is the thickness of the gas barrier layer, A is the depth of the cup portion in the depth direction of the cup portion, and R P is the radius of curvature of the first curved surface portion, and R D is the radius of curvature of the second curved surface portion, and C is the length of the flat surface portion in the direction perpendicular to the depth direction of the cup portion.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0182366, filed December 22, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a pouch-type battery case and a pouch-type secondary battery including the same. [Background technology]

[0003] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, lithium-ion polymer batteries, etc. These secondary batteries are used not only in small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products requiring high output such as electric vehicles and hybrid vehicles, power storage devices for storing surplus generated power and new renewable energy, and backup power storage devices.

[0004] To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on both sides of a separator to form an electrode assembly of a predetermined shape.The electrode assembly is then placed in a battery case, an electrolyte is injected, and the battery case is sealed.

[0005] Secondary batteries are divided into pouch types and can types depending on the material of the case that houses the electrode assembly. Pouch types house the electrode assembly in a pouch made of flexible polymer material, while can types house the electrode assembly in a case made of metal or plastic.

[0006] The pouch, which is the case of a pouch-type secondary battery, is manufactured by pressing a flexible pouch film laminate to form a cup portion. Once the cup portion is formed, an electrode assembly is placed in the receiving space of the cup portion, and the seal portion is sealed to manufacture a secondary battery.

[0007] Generally, a pouch film laminate is formed of multiple layers, with a substrate layer laminated on one side of a metal gas barrier layer and a sealant layer laminated on the other side. Aluminum pouches, which use aluminum for the gas barrier layer, have the advantages of ensuring a certain level of mechanical strength, being lightweight, and providing electrochemical compatibility between the electrode assembly and electrolyte, as well as heat dissipation. However, aluminum pouches can melt or deform when the internal pressure and temperature of the cell increase due to a fire or other cause.

[0008] To prevent such problems, technology has been developed to prevent deformation due to high temperatures and pressures by using high-strength materials such as stainless steel instead of aluminum for the gas barrier layer.

[0009] However, pouch film laminates using high-strength materials as gas barrier layers have poor formability, and therefore, it is difficult to ensure sufficient forming depth when forming the cup portion, which can lead to problems such as the pouch film laminate breaking.If the pouch film laminate does not have sufficient forming depth, the number of electrode assemblies that can be housed therein is limited, making it difficult to improve the cell energy density.

[0010] Therefore, there is a need to develop a pouch film that can be durable under high temperature and high pressure conditions and has a sufficient processing depth. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention provides a pouch-type battery case and a pouch-type secondary battery that can prevent damage to the pouch and the occurrence of pinholes during molding by controlling parameters derived from the shape of the pouch cup portion within specific numerical ranges. [Means for solving the problem]

[0012] According to one embodiment of the present invention, there is provided a pouch-type battery case including a pouch film laminate. The pouch-type battery case may include a cup portion including a bottom portion and a side portion, and a flat portion arranged to surround the cup portion. The side portion may include a first curved portion, a flat portion, and a second curved portion. The pouch film laminate may include a substrate layer, a gas barrier layer, and a sealant layer laminated in this order. The gas barrier layer may include stainless steel. The pouch-type battery case may satisfy the following formula 1: [Formula 1] 0.01≦D / {A-(R P +R D +C)} In the formula 1, D is the thickness of the gas barrier layer, A is the vertical depth of the cup portion, and R P is the radius of curvature of the first curved surface portion disposed between the lower surface portion and the flat surface portion, and R D is the radius of curvature of the second curved surface portion disposed between the plane portion and the flat portion, and C is the horizontal length of the plane portion. In Equation 1, A may represent the depth of the cup portion in the depth direction of the cup portion. C may represent the length of the plane portion in the direction perpendicular to the depth direction of the cup portion.

[0013] Next, according to one embodiment of the present invention, the vertical depth A of the cup portion may be 8 mm or more.

[0014] Next, according to one embodiment of the present invention, the stainless steel may contain 10% to 20% by weight of chromium.

[0015] Next, according to one embodiment of the present invention, the stainless steel may contain 5% to 20% by weight of nickel.

[0016] Next, according to one embodiment of the present invention, the melting point of the gas barrier layer may be 1000° C. or higher.

[0017] Next, according to one embodiment of the present invention, the thickness of the gas barrier layer may be 50 μm or more.

[0018] Next, according to one embodiment of the present invention, the thickness of the base layer may be 5 μm to 150 μm.

[0019] Next, according to one embodiment of the present invention, the substrate layer may include polyethylene terephthalate (PET).

[0020] Next, according to one embodiment of the present invention, the thickness of the pouch film laminate may be 80 μm to 300 μm.

[0021] According to an embodiment of the present invention, the pouch-type battery case may include a first case and a second case facing each other, and at least one of the first case and the second case may be the above-described pouch-type battery case.

[0022] Meanwhile, according to another embodiment of the present invention, there is provided a pouch-type secondary battery including the above-mentioned pouch-type battery case.

[0023] Meanwhile, according to yet another embodiment of the present invention, a method for manufacturing a pouch-type battery case is provided. The method for manufacturing the pouch-type battery case can include the steps of preparing a pouch film laminate including a base layer, a gas barrier layer, and a sealant layer that can be stacked in order, and shaping the pouch film laminate to form a cup portion and a flat portion. The cup portion can include a bottom portion and a side portion. The flat portion can be formed to surround the cup portion. The side portion can include a first curved portion, a second curved portion, and a flat portion disposed between the first curved portion and the second curved portion. The first curved portion can be defined as between the bottom portion and the flat portion, and the second curved portion can be defined as between the flat portion and the flat portion. The gas barrier layer can include stainless steel. The pouch-type battery case can satisfy Equation 1 above.

[0024] Meanwhile, according to yet another embodiment of the present invention, a pouch-type battery case including a pouch film laminate is provided. The pouch-type battery case may include a cup portion and a flat portion arranged to surround the cup portion. The cup portion may include a bottom portion and a side portion. The side portion may be defined as a first curved portion, a second curved portion, and a flat portion arranged between the first curved portion and the second curved portion. The first curved portion may be defined by a first radius between the bottom portion and the flat portion, and the second curved portion may be defined by a second radius between the flat portion and the flat portion. The cup portion may have a depth extending along the side portion. The pouch film laminate may include a substrate layer, a sealant layer, and a gas barrier layer arranged between the substrate layer and the sealant layer. The gas barrier layer may include stainless steel. The first length of the cup portion may be defined as the sum of the first radius, the second radius, and the horizontal length of the flat portion. The thickness of the gas barrier layer may be at least 1% of the difference between the depth and the first value of the cup portion.

[0025] Next, according to yet another embodiment of the present invention, the thickness of the pouch film laminate may be 80 μm to 300 μm.

[0026] Next, according to yet another embodiment of the present invention, the depth can be at least 8 mm.

[0027] Next, according to yet another embodiment of the present invention, the stainless steel may contain 10% to 20% by weight of chromium.

[0028] Next, according to yet another embodiment of the present invention, the stainless steel may contain 5% to 20% by weight of nickel.

[0029] Next, according to yet another embodiment of the present invention, the melting point of the gas barrier layer may be 1000° C. or higher.

[0030] Next, according to yet another embodiment of the present invention, the thickness of the gas barrier layer may be 50 μm or more.

[0031] Next, according to yet another embodiment of the present invention, the thickness of the base layer may be 5 μm to 150 μm.

[0032] Next, according to yet another embodiment of the present invention, the base layer may include polyethylene terephthalate (PET). [Effects of the Invention]

[0033] The pouch-type battery case according to the present invention includes a pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are laminated in this order, the gas barrier layer including stainless steel, the pouch-type battery case including a cup portion and a flat portion, and the thickness of the gas barrier layer, the lengths of the cup portion and the flat portion, etc. are related by the formula (Formula 1, D / {A-(R P +R D+C)}) is 0.01 or more. When all of the above conditions are satisfied, the durability of the pouch-type battery case under high heat and high pressure can be improved, damage to the pouch and the occurrence of pinholes can be prevented during molding, and the forming depth of the pouch can be ensured. A pouch-type secondary battery including the pouch-type battery case has excellent durability under high heat and high pressure, has excellent mechanical strength, and can ensure sufficient forming depth, thereby increasing the cell energy density.

[0034] Furthermore, in the method for producing a pouch-type battery case according to the present invention, when forming a pouch film laminate including a gas barrier layer containing stainless steel, the thickness of the gas barrier layer, the lengths of the cup portion and the flat portion, etc. are determined based on the relationship (Equation 1, D / {A-(R P +R D +C)}) is 0.01 or more. The pouch-type battery case manufactured by the present invention incorporates a high-strength material that has excellent durability against high heat and high pressure into the pouch film laminate, and can ensure an excellent level of processing depth, making it possible to realize a pouch-type secondary battery with simultaneously improved mechanical strength and cell energy density. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is an exploded view of a pouch-type secondary battery according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view of a portion of an xz cross-sectional view of a pouch-type battery case according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] 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 embodied in various different forms. 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.

[0037] 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.

[0038] In this specification, when a part is said to include a certain component, this does not mean that it may exclude other components, but that it may further include other components, unless otherwise specified to the contrary.

[0039] In this specification, the phrase "A and / or B" means A, or B, or A and B.

[0040] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0041] Hereinafter, the configurations of the pouch-type battery case and pouch-type secondary battery of the present invention will be described in more detail with reference to the drawings.

[0042] 1 is an exploded view of a pouch-type secondary battery 100 according to the present invention. As shown in FIG. 1, the pouch-type secondary battery 100 according to the present invention includes a pouch-type battery case 110.

[0043] Pouch-type battery case The pouch-type battery case 110 according to the present invention includes a pouch film laminate and may include cup portions 122, 132 including a bottom portion 125 and side portions, and a flat portion 129 arranged to surround the cup portion 122. The side portion may include a first curved portion 126, a flat portion 127, and a second curved portion 128. The pouch film laminate may include a base layer, a gas barrier layer, and a sealant layer, which are laminated in this order. The gas barrier layer may include stainless steel. The pouch-type battery case satisfies the following formula 1:

[0044] [Formula 1] 0.01≦D / {A-(R P +R D +C)}

[0045] As best shown in FIG. 2, in Equation 1, D is the thickness of the gas barrier layer, A is the vertical depth of the cup portion measured along the vertical or depth direction, and R P is the radius of curvature of the first curved surface portion 126 disposed between the lower surface portion 125 and the flat surface portion 127, and R D is the radius of curvature of the second curved surface portion 128 disposed between the plane portion 127 and the flat portion 129, and C is the projected horizontal length of the plane portion 127.

[0046] The present invention solves the problem of reduced formability that has traditionally been an issue when using stainless steel, a high-strength material, as a component of a gas barrier layer by specifying a relationship between the thickness D of the gas barrier layer, the vertical depth A of the cup portion, the radii of curvature of the first curved portion and the second curved portion, and the horizontal length of the flat portion. Despite using stainless steel as a component of the gas barrier layer, the present invention makes it possible to realize a pouch-type battery case that has excellent formability, improved sealing quality, and sufficient processing depth for the cup portion, and thus has excellent durability and high formability. Therefore, the present invention makes it possible to realize a pouch-type secondary battery that can accommodate a large number of electrode assemblies, has an improved cell energy density, and is highly durable against high heat and high pressure.

[0047] The pouch-type battery case 110 can house the electrode assembly 160 inside. The pouch-type battery case 110 includes a pouch film laminate. Specifically, the pouch-type battery case 110 can be manufactured by drawing and stretching the pouch film laminate using a punch or the like.

[0048] 2 is an enlarged view of a portion of an xz cross-sectional view of a pouch-type battery case 110 according to the present invention. As shown in FIG. 2, the pouch-type battery case 110 may include a cup portion 122, a receiving portion 124, and a flat portion 129. Specifically, the cup portion 122, the receiving portion 124, and the flat portion 129 may be formed in the pouch-type battery case 110 by molding and stretching a pouch film laminate.

[0049] The cup portion 122 may refer to a concavely shaped portion of the pouch film laminate. As shown in FIG. 2, the cup portion 122 includes a bottom portion 125 and a side portion, and the side portion may include a first curved portion 126, a flat portion 127, and a second curved portion 128. The first curved portion 126 may be formed between the bottom portion 125 and the flat portion 127, and the second curved portion 128 may be formed between the flat portion 127 and the flat portion 129. The bottom portion 125 and the flat portion 127 may each be flat, and the first curved portion 126 and the second curved portion 128 may each be curved. Therefore, in FIG. 2, the bottom portion 125 and the flat portion 127 are each illustrated as straight lines, and the first curved portion 126 and the second curved portion 128 are each illustrated as curved lines.

[0050] The receiving portion 124 may refer to a bag-shaped receiving space formed inside the cup portion 122 by forming the cup portion 122. The receiving portion 124 may receive the electrode assembly 160.

[0051] The flat portion 129 may refer to a portion of the pouch film laminate that is not formed into a concave shape. The flat portion 129 may be disposed to surround the cup portion 122. Specifically, the flat portion 129 may be formed along the periphery of the cup portion 122. When the pouch-type battery case 110 is sealed, at least a portion of the flat portion 129 may be sealed, and the sealed area of ​​the flat portion 129 may correspond to the seal portion 150. The flat portion 129 may be planar, and therefore, in FIG. 2, the flat portion 129 is illustrated as being linear.

[0052] On the other hand, A means the vertical depth of the cup portion 122. Specifically, A may be the depth of the cup portion 122 in a direction perpendicular to the lower surface portion 125. For example, in FIG. 2, A may be the depth of the cup portion 122 in the z-axis direction. Specifically, A may be 8 mm or more.

[0053] R PR denotes the radius of curvature of the first curved surface portion 126 disposed between the lower surface portion 125 and the flat surface portion 127. p Specifically, the distance can be 0.5 mm to 10 mm, more specifically, 0.7 mm to 3 mm, and even more specifically, 1 mm to 2 mm. When the distance is within the above range, the stress applied to the first curved surface portion can be minimized, and the effect of ensuring formability according to formula 1 can be more preferably achieved.

[0054] R D R denotes the radius of curvature of the second curved surface portion 128 disposed between the plane portion 127 and the flat portion 129. p Specifically, the distance can be 0.5 mm to 3 mm, more specifically, 0.7 mm to 2.5 mm, and even more specifically, 1 mm to 2 mm. When the distance is within the above range, the stress applied to the second curved surface portion can be minimized, and the effect of ensuring formability according to formula 1 can be more preferably achieved.

[0055] C refers to the horizontal length of the flat portion 127. Specifically, C may be the length of the flat portion 127 in a direction parallel to the lower surface portion 125. For example, C may be the length of the flat portion 127 in the x-axis direction in FIG. 2. Here, C refers to the clearance of the cup portion 122. Specifically, C may be 0.5 mm to 2 mm, more specifically 0.7 mm to 1.5 mm, and even more specifically 0.8 mm to 1.2 mm. When C is within the above range, it is preferable in that the desired processing depth of the cup portion can be sufficiently ensured and the possibility of breaking the pouch film laminate can be reduced to a desirable level.

[0056] In the formula 1, A and R p , R d , and C can be achieved by, for example, adjusting the punch shape, processing, and stretching degree of the pouch forming equipment.

[0057] According to the present invention, D / {A-(R P +R D+C)} is 0.01 or more, specifically 0.01 to 0.02, more specifically 0.01 to 0.015. Here, D is the thickness of the gas barrier layer described later. The parameter D / {A-(R P +R D If the parameter D / {A-(R + C)} is less than 0.01, excessive stress is concentrated in the stretched region of the pouch film laminate (e.g., the first curved portion 126 and / or the second curved portion 128), which may result in damage to the pouch or the generation of pinholes. P +R D +C)} is 0.01 or more, a pouch can be formed without damaging the pouch film laminate within the thickness range of pouch film laminates generally used in the manufacture of medium- to large-sized batteries, and there is no need to increase the thickness of the pouch film laminate to ensure formability, which is advantageous in terms of cell energy density.

[0058] In the pouch-type battery case 110 according to the present invention, the vertical depth A of the cup portion 122 can be 8 mm or more, specifically 8 mm to 20 mm, more specifically 10 mm to 20 mm. Conventionally, when a cup portion is formed so that the vertical depth is 8 mm or more, excessive stress is concentrated on the curved surface of the cup portion, which can cause problems such as cracks in the pouch film laminate. On the other hand, in the present invention, the parameter D / {A-(R P +R D +C)} is controlled to 0.01 or more, cracks do not occur in the pouch film laminate, and the cup portion 122 can be formed so that the vertical depth A is 8 mm or more. By ensuring a sufficient forming depth of the pouch, the energy density of the pouch-type secondary battery can be increased.

[0059] The thickness of the pouch film laminate can be, for example, 80 μm to 300 μm, more specifically, 80 μm to 250 μm, even more specifically, 100 μm to 250 μm, and even more specifically, 120 μm to 230 μm. When the thickness is within this range, the pouch film laminate is relatively thin, making it easy to process the pouch. Since there is no need to increase the thickness of the substrate layer to improve formability, this is advantageous in terms of heat transfer when sealing the pouch. Furthermore, when the thickness is within this range, a greater number of electrode assemblies can be accommodated for the same cell thickness, thereby improving cell energy density.

[0060] Meanwhile, the pouch film laminate according to the present invention includes a substrate layer, a gas barrier layer, and a sealant layer. In the pouch film laminate, the substrate layer, the gas barrier layer, and the sealant layer are laminated in this order. In addition, an adhesive layer may be further disposed between each layer.

[0061] <Base material layer> The substrate layer is formed on the outermost layer of the pouch film laminate to protect the secondary battery from external friction and impact. The substrate layer is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0062] The thickness of the substrate layer can be 5 μm to 150 μm, specifically 5 μm to 80 μm, more specifically 5 μm to 60 μm. When the thickness of the substrate layer satisfies this range, the overall thickness of the pouch does not become excessively thick, the secondary battery has excellent energy density relative to its volume, and the insulating properties and chemical resistance of the pouch can be ensured.

[0063] The substrate layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber. Preferably, the substrate layer is made of polyethylene terephthalate (PET), nylon, or a combination thereof, which are abrasion-resistant and heat-resistant. More specifically, the substrate layer may include polyethylene terephthalate. Even more specifically, the substrate layer may include polyethylene terephthalate or polyethylene terephthalate and nylon.

[0064] The substrate layer may have a single film structure.

[0065] The substrate layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. The substrate layer may preferably include at least one polyester film, such as polyethylene terephthalate or polybutylene terephthalate, which has abrasion resistance and heat resistance, specifically, but is not limited to, polyethylene terephthalate.

[0066] In the present invention, the pouch film laminate may further include an adhesive layer interposed between the substrate layer and a gas barrier layer (described later). The adhesive layer may be introduced for bonding or adhering the substrate layer and the gas barrier layer, and any adhesive layer known in the art may be used without limitation.

[0067] Meanwhile, the substrate layer may have a composite membrane structure formed by layers of two or more materials, and an adhesive layer may be further formed between each layer in the composite membrane structure.

[0068] Specifically, the substrate layer according to the present invention may include a first substrate layer, a second substrate layer, and / or an adhesive layer. Here, the thickness of the substrate layer refers to the total thickness of the first substrate layer, the second substrate layer, and / or the adhesive layer. The first substrate layer may be disposed as the outermost layer of the pouch film laminate, and the second substrate layer may be disposed between the first substrate layer and the gas barrier layer. The adhesive layer may be disposed between the first substrate layer and the second substrate layer, or between the second substrate layer and the gas barrier layer. The first substrate layer, the second substrate layer, and the adhesive layer may be made of materials with different materials and / or physical properties. An interface may exist between the first substrate layer, the second substrate layer, and the adhesive layer. This means that the first substrate layer, the second substrate layer, and the adhesive layer are different layers and may be formed separately.

[0069] The first substrate layer may be the outermost layer of the pouch film laminate. In this case, the first substrate layer may serve to prevent moisture from penetrating from outside the pouch. The first substrate layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon (registered trademark), and glass fiber. Preferably, the first substrate layer may include at least one polyester film such as polyethylene terephthalate or polybutylene terephthalate, which has abrasion resistance and heat resistance, but is not limited thereto.

[0070] As described above, the second substrate layer may be a layer disposed between the first substrate layer and the gas barrier layer. In this case, the second substrate layer may serve to improve the formability of the pouch. The second substrate layer may include at least one polyamide film such as, but not limited to, nylon 6, nylon 6,6, nylon MXD6, and nylon 4,10. Preferably, the second substrate layer may include nylon 6, which has the advantage of improving the formability of the pouch due to the excellent stretchability of nylon 6.

[0071] <Gas barrier layer> The gas barrier layer is laminated between the base layer and the sealant layer to ensure the mechanical strength of the pouch, block the entry and exit of gases or moisture outside the secondary battery, and prevent electrolyte leakage from the inside of the pouch-type battery case.

[0072] The gas barrier layer according to the present invention includes stainless steel. Specifically, the gas barrier layer can be manufactured by molding and / or processing a stainless steel thin film. A gas barrier layer containing stainless steel has relatively low thermal conductivity, which is effective in preventing or delaying heat diffusion to other cells during thermal runaway. It also has relatively high toughness, which can prevent cracks from occurring in the pouch during use of the pouch battery. While stainless steel gas barrier layers can reduce the formability of the pouch film laminate, as described above, the pouch battery case of the present invention can achieve improved durability at high temperatures and pressures by adjusting the relationship between the thickness of the gas barrier layer, the vertical depth of the cup portion, the radii of curvature of the first and second curved portions, and the horizontal length of the flat portion according to a specific relationship (Equation 1). This allows for the realization of a pouch film with improved formability.

[0073] The stainless steel may contain at least one element selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), zinc (Zn), molybdenum (Mo), carbon (C), phosphorus (P), sulfur (S), and nitrogen (N) in addition to iron (Fe).

[0074] Specifically, the stainless steel may contain 10 to 20% by weight of chromium, more specifically 16 to 20% by weight, and more specifically 18 to 20% by weight. When the above numerical range is satisfied, the stainless steel has excellent corrosion resistance.

[0075] Furthermore, the stainless steel may contain 5 to 20% by weight of nickel, specifically 6 to 15% by weight, and more specifically 8 to 14% by weight. When this range is satisfied, the corrosion resistance of the stainless steel to neutral and weakly acidic conditions is further improved.

[0076] The thickness of the gas barrier layer is 50 μm or more, specifically 50 μm to 100 μm, and more specifically 60 μm to 85 μm. When the thickness of the gas barrier layer satisfies the above numerical range, the gas barrier layer is uniformly stretched, which increases the stretch ratio of the pouch film laminate, improving the formability of the pouch and ensuring a sufficient processing depth for the pouch cup portion. As a result, it is easy to realize a large-area pouch-type battery that can be used in electric vehicles.

[0077] Since the gas barrier layer according to the present invention contains stainless steel, there may be little or no change in the thickness of the gas barrier layer due to the process of forming or stretching the cup portion of the pouch film laminate. In this respect, the thickness of the gas barrier layer (or D in Equation 1) may refer to the thickness of the gas barrier layer before the formation of the cup portion, or may refer to the thickness of the gas barrier layer after the formation of the cup portion. More specifically, in this specification, the thickness of the gas barrier layer (or D in Equation 1) may refer to the thickness of the gas barrier layer at the flat portion 129.

[0078] The melting point of the gas barrier layer can be 1000° C. or higher, specifically 1200° C. to 1500° C., and more specifically 1300° C. to 1450° C. When the melting point of the gas barrier layer is within the above range, structural collapse of the pouch can be prevented even when the temperature of the pouch cell rises suddenly due to thermal runaway.

[0079] <Sealant layer> The sealant layer is used to completely seal the interior of the pouch-type battery case by being thermally bonded to the sealing portion when the pouch-type battery case containing the electrode assembly is sealed. For this purpose, the sealant layer may be made of a material having excellent thermal adhesive strength.

[0080] The sealant layer may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the sealant layer is in direct contact with the electrode assembly and / or electrolyte inside the pouch-type battery case, it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the sealant layer must completely seal the interior of the pouch-type battery case and prevent material transfer between the inside and outside, it may be formed of a material having high sealing properties (e.g., excellent thermal adhesive strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer may be formed of a polymer material.

[0081] The sealant layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon®, and glass fiber, 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.

[0082] The thickness of the sealant layer can be 30 μm to 130 μm, specifically 50 μm to 120 μm, more specifically 70 μm to 100 μm. When the thickness of the sealant layer satisfies the above range, it is possible to ensure the seal strength of the sealed portion and the formability of the pouch film laminate.

[0083] The sealant layer may have a single film structure made of any one material, or alternatively, the sealant layer may have a composite film structure made of two or more materials each formed as a layer.

[0084] Meanwhile, according to one embodiment of the present invention, as shown in Fig. 1, a pouch-type battery case may include a first case 120 and a second case 130 that face each other. Here, at least one of the first case 120 and the second case 130 may be the above-mentioned pouch-type battery case.

[0085] For example, in another embodiment, when the first case is a pouch-type battery case according to the present invention, the second case may include a pouch film laminate including a base layer, a gas barrier layer, and a sealant layer stacked in order, and may not have a cup portion. More specifically, the second case may be flat and not have a cup portion. The second case may function as a cover case that covers the first case, which houses the electrode assembly, from above. The first and second cases may be connected to each other at one side or may be manufactured separately. Here, the same description regarding the pouch film laminate applies to the second case, except that the cup portion and flat portion are not distinguished.

[0086] Meanwhile, both the first case and the second case may be the pouch-type battery case described above. Specifically, as shown in FIG. 1, the first case 120 includes a receiving portion 124 that can receive the electrode assembly 160, and the second case 130 can cover the receiving portion 124 from above to prevent the electrode assembly 160 from falling out. The first case 120 and the second case 130 may be manufactured with one side connected to each other as shown in FIG. 1, but are not limited to this and may be manufactured in various ways, such as being separated from each other and separately manufactured.

[0087] When the first case and the second case are both the pouch-type battery cases described above, two symmetrical cup portions 122, 132 may be drawn adjacent to one another from one pouch film laminate. In this case, the first case 120 and the second case 130 may each have a cup portion 122, 132, as shown in FIG. 1 . After the electrode assembly 160 is accommodated in the accommodating portion 124 of the cup portion 122 of the first case 120, the bridge portion 140 formed between the two cup portions 122, 132 may be folded so that the two cup portions 122, 132 face each other. In this case, the cup portion 132 of the second case 130 may accommodate the electrode assembly 160 from above. Therefore, because two cup portions 122, 132 accommodate one electrode assembly 160, an electrode assembly 160 that is thicker than when there is only one cup portion 122 can be accommodated. In addition, folding the pouch-type battery case 110 forms one edge of the secondary battery 100, which reduces the number of edges to be sealed during the subsequent sealing process, thereby improving the processing speed of the pouch-type secondary battery 100 and reducing the number of sealing processes.

[0088] The pouch-type battery case 110 may be sealed with the electrode assembly 160 housed therein so that a portion of the electrode lead 180, i.e., a terminal portion, described below, is exposed. Specifically, after the electrode lead 180 is connected to the electrode tab 170 of the electrode assembly 160 and an insulating portion 190 is formed on a portion of the electrode lead 180, the electrode assembly 160 may be housed in a housing portion 124 provided in the cup portion 122 of the first case 120, and the second case 130 may cover the housing portion 124 from above. Next, an electrolyte may be injected into the housing portion 124, and the first case 120 and the second case 130 may be sealed with a seal portion 150 formed on the periphery thereof.

[0089] The sealing portion 150 may serve to seal the receiving portion 124. Specifically, the sealing portion 150 may be formed along the periphery of the receiving portion 124 to seal the receiving portion 124. The temperature at which the sealing portion 150 is sealed may be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature is within this range, the pouch-type battery case 110 can ensure sufficient seal strength through thermal bonding.

[0090] Manufacturing method for pouch-type battery cases The present invention also provides a method for manufacturing a pouch-type battery case, which may be the method for manufacturing the pouch-type battery case described above.

[0091] Specifically, the method for manufacturing the pouch-type battery case includes the steps of preparing a pouch film laminate including a base material layer, a gas barrier layer, and a sealant layer laminated in that order, and molding the pouch film laminate to form a cup portion and a flat portion, wherein the cup portion includes a bottom surface portion and a side surface portion, the flat portion is formed so as to surround the cup portion, the side surface portion includes a first curved surface portion, a flat surface portion, and a second curved surface portion, and the gas barrier layer includes stainless steel, and is characterized by satisfying the following formula 1:

[0092] [Formula 1] 0.01≦D / {A-(R P +R D +C)}

[0093] (In the above formula 1, D is the thickness of the gas barrier layer, A is the vertical depth of the cup portion, and R P is the radius of curvature of the first curved surface portion disposed between the lower surface portion and the flat surface portion, and R D is the radius of curvature of the second curved surface portion disposed between the plane portion and the flat portion, and C is the horizontal length of the plane portion.

[0094] In the method for manufacturing a pouch-type battery case according to the present invention, the pouch film laminate, base material layer, gas barrier layer, sealant layer, cup portion, flat portion, bottom surface portion, side surface portion, etc. are the same as those described above for the pouch-type battery case.

[0095] According to the present invention, in a pouch film laminate using a gas barrier layer containing stainless steel, it is possible to manufacture a pouch-type battery case with excellent formability by adjusting the relationship between the thickness of the gas barrier layer, the vertical depth of the cup portion, the radii of curvature of the first curved portion and the second curved portion, and the horizontal length of the flat portion according to Formula 1. As a result, by using a high-strength material as a gas barrier layer component, it is possible to manufacture a pouch-type secondary battery that has excellent durability against high heat and high pressure and can be processed deeply, thereby improving cell energy density.

[0096] Pouch-type secondary battery The pouch-type secondary battery 100 according to the present invention includes the above-described pouch-type battery case 110. The pouch-type secondary battery 100 may also include an electrode assembly 160, an electrode lead 180, an insulating part 190, and an electrolyte (not shown).

[0097] (1) Electrode assembly The electrode assembly 160 can be inserted into the pouch-type battery case 110 and sealed by the pouch-type battery case 110 after the electrolyte is injected.

[0098] The electrode assembly 160 may be formed by sequentially stacking a positive electrode, a separator, and a negative electrode. Specifically, the electrode assembly 160 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.

[0099] The positive electrode and the negative electrode may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper. The slurry may be formed by adding a solvent to a granular active material, an auxiliary conductor, a binder, a conductive material, etc., and stirring them. The solvent may be removed in a subsequent process.

[0100] 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 160. The electrode assembly 160 may be of a stack type, a jelly roll type, a stack and folding type, or the like, but is not limited thereto.

[0101] The electrode assembly 160 may include an electrode tab 170 .

[0102] The electrode tabs 170 are connected to the positive and negative electrodes of the electrode assembly 160, protrude from the electrode assembly 160, and serve as paths for electrons to travel between the inside and outside of the electrode assembly 160. The electrode current collector included in the electrode assembly 160 may be composed of a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 170 may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion using ultrasonic welding or the like. As shown in FIG. 1, the electrode tabs 170 may protrude in different directions from the electrode assembly 160, but are not limited thereto. They may protrude in various directions, such as protruding in parallel from one side in the same direction.

[0103] (2) Electrode lead The electrode lead 180 may supply electricity to the outside of the secondary battery 200. The electrode lead 180 may be connected to the electrode tab 170 of the electrode assembly 160 by spot welding or the like.

[0104] The electrode lead 180 is connected to the electrode assembly 160 and may protrude to the outside of the pouch-type battery case 110 via the seal portion 150. Specifically, one end of the electrode lead 180 is connected to the electrode assembly 160, particularly the electrode tab 170, and the other end of the electrode lead 180 may protrude to the outside of the pouch-type battery case 110.

[0105] The electrode lead 180 may include a positive electrode lead 182 having one end connected to the positive electrode tab 172 and extending in the direction in which the positive electrode tab 172 protrudes, and a negative electrode lead 184 having one end connected to the negative electrode tab 174 and extending in the direction in which the negative electrode tab 174 protrudes. The other ends of both the positive electrode lead 182 and the negative electrode lead 184 may protrude to the outside of the battery case 110. This allows electricity generated inside the electrode assembly 160 to be supplied to the outside. In addition, since the positive electrode tab 172 and the negative electrode tab 174 protrude in different directions, the positive electrode lead 182 and the negative electrode lead 184 may also extend in different directions. The positive electrode lead 182 and the negative electrode lead 184 may be made of different materials. That is, the positive electrode lead 182 may be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead 184 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 180 protruding outside the battery case 110 serves as a terminal portion and may be electrically connected to an external terminal.

[0106] (3) Insulation section The insulating portion 190 prevents electricity generated from the electrode assembly 160 from flowing to the battery case 110 via the electrode lead 180, thereby maintaining the seal of the battery case 110. To this end, the insulating portion 190 may be formed of an insulator having non-conductivity that makes it difficult for electricity to pass through. Generally, the insulating portion 190 is formed of an insulating tape or film that is easily attached to the electrode lead 180 and has a relatively thin thickness, but is not limited thereto, and any material that can insulate the electrode lead 180 may be used.

[0107] The insulating part 190 may be disposed to surround the outer circumferential surface of the electrode lead 180. Specifically, at least a portion of the electrode lead 180 may be surrounded by the insulating part 190. In this case, the insulating part 190 may be disposed between the electrode lead 180 and the pouch-type battery case 110. The insulating part 190 may be located only in the seal part 150 where the first case 120 and the second case 130 of the pouch-type battery case 110 are thermally sealed, and may bond the electrode lead 180 to the battery case 110.

[0108] (4) Electrolyte The pouch-type secondary battery 100 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type battery case 110. The electrolyte is used to 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.

[0109] 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.

[0110] Manufacturing Example 1: Manufacturing of pouch film laminate A first adhesive film measuring 266 mm wide, 50 mm long, and 3 μm thick, and a polyethylene terephthalate (PET) film measuring 266 mm wide, 50 mm long, and 6 μm thick were laminated in this order on one side of a stainless steel thin film measuring 266 mm wide, 50 mm long, and 80 μm thick. A polypropylene (PP) film measuring 266 mm wide, 50 mm long, and 80 μm thick was laminated on the other side of the stainless steel thin film. As a result, a pouch film laminate was produced with a structure in which polypropylene film / stainless steel thin film / first adhesive film / polyethylene terephthalate film were laminated in this order.

[0111] Here, the SUS grade of the stainless steel contained in the stainless steel thin film was SUS304L.

[0112] Here, the polypropylene film is a sealant layer, the stainless steel thin film is a gas barrier layer, and the first adhesive film and the polyethylene terephthalate film are base layers.

[0113] Manufacturing Example 2: Manufacturing of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a stainless steel thin film having a thickness of 60 μm was used.

[0114] The SUS grade of the stainless steel contained in the stainless steel thin film of Production Example 2 was SUS304L.

[0115] Manufacturing Example 3: Manufacturing of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a stainless steel thin film having a thickness of 50 μm was used.

[0116] The SUS grade of the stainless steel contained in the stainless steel thin film of Production Example 3 was SUS304L.

[0117] Production Example 4: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a first adhesive film measuring 266 mm wide, 50 m long, and 3 μm thick, a nylon film measuring 266 mm wide, 50 m long, and 25 μm thick, a second adhesive film measuring 266 mm wide, 50 m long, and 3 μm thick, and a polyethylene terephthalate (PET) film measuring 266 mm wide, 50 m long, and 25 μm thick were laminated in this order on one side of a stainless steel thin film measuring 266 mm wide, 50 m long, and 80 μm thick.

[0118] The SUS grade of the stainless steel contained in the stainless steel thin film of Production Example 4 was SUS304L.

[0119] Here, the polypropylene film is a sealant layer, the stainless steel thin film is a gas barrier layer, and the first adhesive film, nylon film, second adhesive film and polyethylene terephthalate film are base layers.

[0120] Production Example 5: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that only a first adhesive film having a thickness of 3 μm and a thin stainless steel film having a thickness of 60 μm were used as the base layer.

[0121] Experimental Example 1: Formability evaluation of pouch film laminate The pouch film laminates produced in Production Examples 1 to 5 were evaluated for formability.

[0122] Specifically, the pouch film laminate was cut to a size of 266 mm wide and 200 mm long, and then the cut pouch film laminate was processed and stretched using pouch forming equipment manufactured by Gwangshin Hi-Tech to form cups measuring 90 mm wide and 160 mm long to the target forming depth. The cup formation was carried out a total of 10 times, and the pouch film laminate was visually inspected for rupture during cup formation, and formability was evaluated according to the following criteria. Examples and comparative examples were classified based on the formability evaluation results, and the results are shown in Table 1 below.

[0123] -Good: No breakage of the pouch film laminate occurs after 10 measurements - Poor: Breakage of the pouch film laminate occurred at least once during 10 measurements.

[0124] [Table 1]

[0125] According to Table 1, D / {A-(R P +R D In Examples 1 to 4, where D / {A-(R P +R D It can be confirmed that the moldability is superior to that of Comparative Examples 1 to 5 in which the value of {+C)} is less than 0.01.

[0126] Furthermore, it can be understood that Examples 1 to 4 have a greater processing depth and are superior in formability compared to the corresponding Comparative Examples 1 to 4, and therefore can accommodate a greater number of electrode assemblies in the intended pouch-type secondary battery. Therefore, it is expected that Examples 1 to 4, which satisfy Formula 1, can realize a pouch-type secondary battery that has excellent levels of mechanical strength and durability and a high cell energy density by using a high-strength material as a component of the gas barrier layer. [Explanation of symbols]

[0127] 100 Pouch-type secondary battery 110 Pouch-type battery case 120 Case 1 122 Cup section 124 Storage unit 125 Bottom part 126 1st curved surface part 127 Plane section 128 Second curved surface part 129 Flat area 130 Case 2 132 Cup section 140 Bridge section 150 Seal part 160 Electrode assembly 170 Electrode Tab 172 Positive electrode tab 174 Negative electrode tab 180 Electrode Lead 182 Positive lead 184 Negative lead 190 Insulation section

Claims

1. A pouch-type battery case including a pouch film laminate, a cup portion including a bottom surface portion and a side surface portion; a flat portion disposed so as to surround the cup portion, the side surface portion includes a first curved surface portion, a second curved surface portion, and a flat surface portion disposed between the first curved surface portion and the second curved surface portion, the first curved surface portion is defined as a portion between the lower surface portion and the flat surface portion, and the second curved surface portion is defined as a portion between the flat surface portion and the flat surface portion; the pouch film laminate includes a base layer, a sealant layer, and a gas barrier layer disposed between the base layer and the sealant layer; the gas barrier layer comprises stainless steel; The pouch-type battery case satisfies the following formula 1: [Formula 1] 0.01≦D / {A-(R Ｐ +R Ｄ +C)} D is the thickness of the gas barrier layer, A is the depth of the cup portion in the depth direction of the cup portion, and R Ｐ is the radius of curvature of the first curved surface portion, and R Ｄ is the radius of curvature of the second curved surface portion, and C is the length of the flat surface portion in a direction perpendicular to the depth direction of the cup portion.

2. 2. The pouch-type battery case according to claim 1, wherein the depth A is 8 mm or more.

3. 2. The pouch-shaped battery case according to claim 1, wherein the stainless steel contains 10% to 20% by weight of chromium.

4. 2. The pouch-shaped battery case according to claim 1, wherein the stainless steel contains 5% to 20% by weight of nickel.

5. The pouch-type battery case according to claim 1 , wherein the gas barrier layer has a melting point of 1000° C. or higher.

6. 2. The pouch-type battery case according to claim 1, wherein the gas barrier layer has a thickness of 50 μm or more.

7. 2. The pouch-type battery case according to claim 1, wherein the thickness of the substrate layer is 5 μm to 150 μm.

8. The pouch-type battery case according to claim 1 , wherein the base layer comprises polyethylene terephthalate (PET).

9. 2. The pouch-type battery case according to claim 1, wherein the thickness of the pouch film laminate is 80 μm to 300 μm.

10. the pouch-type battery case includes a first case and a second case facing each other, The pouch-type battery case according to claim 1 , wherein at least one of the first case and the second case includes the cup portion.

11. A pouch-type secondary battery comprising the pouch-type battery case according to claim 1.

12. A method for manufacturing a pouch-type battery case, comprising: providing a pouch film laminate including a substrate layer, a sealant layer, and a gas barrier layer disposed between the substrate layer and the sealant layer; and forming the pouch film laminate to form a cup portion and a flat portion; The cup portion includes a bottom surface portion and a side surface portion, The flat portion is formed to surround the cup portion, the side surface portion includes a first curved surface portion, a second curved surface portion, and a flat surface portion disposed between the first curved surface portion and the second curved surface portion, the first curved surface portion is defined as a portion between the lower surface portion and the flat surface portion, and the second curved surface portion is defined as a portion between the flat surface portion and the flat surface portion; the gas barrier layer comprises stainless steel; The method for manufacturing a pouch-type battery case, wherein the pouch-type battery case satisfies the following formula 1: [Formula 1] 0.01≦D / {A-(R Ｐ +R Ｄ +C)} D is the thickness of the gas barrier layer, A is the depth of the cup portion in the depth direction of the cup portion, and R Ｐ is the radius of curvature of the first curved surface portion, and R Ｄ is the radius of curvature of the second curved surface portion, and C is the length of the flat surface portion in a direction perpendicular to the depth direction of the cup portion.

13. A pouch-type battery case including a pouch film laminate, a cup portion and a flat portion arranged to surround the cup portion; The cup portion includes a bottom surface portion and a side surface portion, The side surface portion is defined as a first curved surface portion, a second curved surface portion, and a plane portion disposed between the first curved surface portion and the second curved surface portion, the first curved surface portion is defined by a first radius between the lower surface portion and the flat surface portion, and the second curved surface portion is defined by a second radius between the flat surface portion and the flat surface portion; the cup portion has a depth extending along the side portion; the pouch film laminate includes a base layer, a sealant layer, and a gas barrier layer disposed between the base layer and the sealant layer; the gas barrier layer comprises stainless steel; a pouch-type battery case, wherein the sum of the first radius, the second radius, and the horizontal length of the flat portion is defined as a first value of the cup portion, and the gas barrier layer has a thickness that is at least 1% of the difference between the depth and the first value of the cup portion.

14. The pouch-type battery case according to claim 13, wherein the thickness of the pouch film laminate is 80 μm to 300 μm.

15. 14. The pouch-type battery case according to claim 13, wherein the depth is at least 8 mm.

16. 14. The pouch-shaped battery case according to claim 13, wherein the stainless steel contains 10% to 20% by weight of chromium.

17. 14. The pouch-shaped battery case according to claim 13, wherein the stainless steel contains 5% to 20% by weight of nickel.

18. The pouch-type battery case according to claim 13 , wherein the gas barrier layer has a melting point of 1000° C. or higher.

19. The pouch-type battery case according to claim 13 , wherein the gas barrier layer has a thickness of 50 μm or more.

20. The pouch-type battery case according to claim 13, wherein the thickness of the substrate layer is 5 μm to 150 μm.

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