Pouch type battery case and lithium secondary battery comprising same

Abstract

A pouch-type battery case according to the present invention comprises a shrinkable pouch film laminate in which a base layer, a gas barrier layer and a sealant layer are sequentially layered and in which a shape memory resin film is disposed between the gas barrier layer and the sealant layer, and thus a pouch-type battery case having improved safety can be provided.

Description

Pouch-type battery case and lithium secondary battery including the same The present invention relates to a pouch-type battery case and a lithium secondary battery including the same, and more particularly, to a pouch-type battery case with improved safety and a lithium secondary battery including the same. Common types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These batteries are used not only in small products such as digital cameras, DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in larger products requiring high output, such as electric and hybrid vehicles, as well as in power storage devices that store surplus power or renewable energy, and as backup power storage devices. To manufacture these secondary batteries, first, an electrode active material slurry 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 to form an electrode assembly of a predetermined shape. Then, the electrode assembly is housed in a battery case, filled with electrolyte, and sealed. Secondary batteries are classified into pouch type and can type, depending on the material of the case that houses the electrode assembly. Pouch type batteries house the electrode assembly in a pouch made of a flexible polymer material. Can type batteries house the electrode assembly in a case made of materials such as metal or plastic. 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. Once the cup portion is formed, an electrode assembly can be accommodated in the inner receiving space of the cup portion and the sealing portion can be sealed to manufacture a secondary battery. Typically, pouch-type battery cases are formed by laminating a polymer film, such as polyethylene terephthalate, on one side of a metal gas barrier layer, and a sealant layer on the other side, forming multiple layers. However, in the case of such conventional pouch-type battery cases, due to the need for increased battery density and capacity, the molding depth has deepened, resulting in significant tensile stress due to swelling, which in turn increases the risk of explosion. The present invention is intended to solve the above problems, and to provide a pouch-type battery case that can suppress the swelling phenomenon by additionally arranging a shape memory resin film in the film laminate structure of a pouch-type battery case to counter the risk of explosion due to the swelling phenomenon, and that improves safety through effective energy drain in an explosion-risk situation by utilizing the function of shrinking at high temperatures. The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below. [1] A pouch-type battery case according to one embodiment of the present invention includes a shrinkable pouch film laminate in which a substrate layer, a gas barrier layer, and a sealant layer are sequentially laminated, and a shape memory resin film is disposed between the gas barrier layer and the sealant layer. [2] In the above [1], the thickness of the shape memory resin film may be 30 ㎛ to 80 ㎛. [3] In the above [1] and / or [2], the pouch-type battery case may include a cup portion having a recessed shape so that an electrode assembly can be accommodated; and a sealing portion formed along the periphery of the cup portion; and the shrinkable pouch film laminate may be provided in an area excluding the sealing portion. [4] In any one or more of the above [1] to [3], the shrinkable pouch film laminate may be provided in a cup portion spaced apart from the sealing portion by a width greater than that of the sealing portion. [5] In any one or more of the above [1] to [4], the sealing portion may be provided with a general pouch film laminate without a shape memory resin film. [6] In any one or more of the above [1] to [5], the shape memory resin film may include at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTEE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer. [7] In any one or more of the above [1] to [6], the shape memory resin film may have a shape that is memorized so that it shrinks by at least 500% based on area at 100°C or higher. [8] In any one or more of the above [1] to [7], the gas barrier layer may include aluminum. [9] In any one or more of the above [1] to [8], the shrinkable pouch film laminate may further include a shape memory resin film disposed between the substrate layer and the gas barrier layer.

[0010] In any one or more of the above [1] to [9], the substrate layer may have a multilayer structure including two or more layers made of different polymers, and a shape memory resin film may be additionally disposed between the outermost layer and the innermost layer of the composite membrane.

[0011] According to another embodiment of the present invention, a lithium secondary battery includes the aforementioned pouch-type battery case; and an electrode assembly housed inside the pouch-type battery case. In order to address the risk of explosion due to swelling phenomenon, a pouch-type battery case according to one embodiment of the present invention additionally arranges a shape memory resin film within the film laminate structure of the pouch-type battery case, thereby suppressing the swelling phenomenon by utilizing the function of shrinking at high temperatures, and significantly improving safety through effective energy drain in an explosion risk situation. The above shrinkable pouch film laminate includes a shape memory resin film, and the shape memory resin film is applied as a shape that can shrink by 500% or more at high temperatures, so that when a lithium secondary battery exhibits abnormal behavior, the battery case shrinks and energy drain can occur effectively, thereby preventing the risk of explosion and thus greatly improving safety. Figure 1 is a cross-sectional view of a general pouch film laminate. Figure 2 is a cross-sectional view of a shrinkable pouch film laminate according to the present invention. Figure 3 is a plan view of a lithium secondary battery including a pouch-type battery case. Figure 4 is an exploded assembly diagram of a lithium secondary battery according to Figure 3. Figure 5 is a plan view of a lithium secondary battery including a pouch-type battery case according to the present invention. Fig. 6 is a vertical cross-sectional view showing a pouch-type battery case when cut along the line S-S' in Fig. 5. 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. 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. 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. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. 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. In this specification, the upper portion of a drawing may be referred to as the "upper portion" or "upper side" of the configuration depicted in the drawing, and the lower portion thereof may be referred to as the "lower portion" or "lower side." Furthermore, the portion between the upper and lower portions of the configuration depicted in the drawing, or the portion excluding the upper and lower portions, may be referred to as the "side portion" or "side." Relative terms such as "upper portion" and "upper side" may be used to describe the relationship between the configurations depicted in the drawing, and the present disclosure is not limited by such terms. In this specification, the direction toward the interior space of a structure may be referred to as "inside," and the direction protruding into the open exterior space may be referred to as "outside." Relative terms such as "inside," "outside," etc. may be used to describe the relationship between components depicted in the drawings, and the present disclosure is not limited by such terms. In this specification, the description of “A and / or B” means A, or B, or A and B. In this specification, when it is said that a part is connected to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another structure in between. In this specification, each of the pouch-type battery case and the lithium secondary battery includes at least one of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways. pouch-type battery case A pouch-type battery case according to one embodiment of the present invention includes a shrinkable pouch film laminate, wherein the shrinkable pouch film laminate is characterized in that a substrate layer, a gas barrier layer, and a sealant layer are sequentially laminated, and a shape memory resin film is disposed between the gas barrier layer and the sealant layer. Hereinafter, the shrinkable pouch film laminate and each layer included in the pouch film laminate will be described in detail with reference to FIGS. 1 and 2. Figure 1 is a cross-sectional view of a general pouch film laminate (100). As illustrated in FIG. 1, a typical pouch film laminate (100) includes a substrate layer (110), a gas barrier layer (120), and a sealant layer (130). (1) Substrate layer 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. The substrate layer (110) may be made of one or more materials selected from the group consisting of, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Among them, it is particularly preferable that the substrate layer (110) be made of polyethylene terephthalate (PET), nylon, or a combination thereof, which have wear resistance and heat resistance. The substrate layer (110) may have a single film structure made of a single material. Alternatively, the substrate layer (110) may have a composite film structure formed by forming layers of two or more materials. The thickness of the substrate layer (110) may be 5 ㎛ to 50 ㎛, specifically 7 ㎛ to 50 ㎛, and more specifically 7 ㎛ to 40 ㎛. When the thickness of the substrate layer (110) satisfies the above range, the pouch film laminate may have excellent external insulation, and since the thickness of the entire pouch is not thick, the energy density per volume of the secondary battery may be excellent. (2) Gas barrier layer 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 the outside of the pouch-type battery case, and prevent electrolyte leakage from the inside of the pouch-type battery case. The gas barrier layer (120) may be formed of a metal, and specifically, may be formed of an aluminum alloy thin film. When the gas barrier layer is formed using an aluminum alloy thin film, a mechanical strength higher than a predetermined level can be secured, while being light in weight, and the electrochemical properties of the electrode assembly and the electrolyte can be supplemented and heat dissipation properties can be secured. The aluminum alloy thin film may include one or two or more metal elements other than aluminum, for example, one or more metal elements selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn). The thickness of the gas barrier layer (120) may be 40 µm to 100 µm, specifically 50 µm to 90 µm, and more specifically 55 µm to 85 µm. When the thickness of the gas barrier layer (120) satisfies the above range, the formability and gas barrier performance are excellent when forming the cup portion. (3) Sealant layer The sealant layer (130) is bonded through heat compression to seal the battery case and is located on the innermost layer of the pouch film laminate (100). The sealant layer (130) must have insulating and corrosion resistance properties because it is the surface that comes into contact with the electrolyte and electrode assembly after being formed into a battery case, and must completely seal the inside to block material movement between the inside and the outside, so it must have high sealing properties. The above sealant layer (130) may be made of a polymer material, and may be made of at least one selected from the group consisting of, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. Among these, it is particularly preferable to include polypropylene (PP), which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance. The above sealant layer (130) may include polypropylene, cast polypropylene (CPP), acid modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof. The above sealant layer (130) may have a single-layer structure or may have a multi-layer structure including two or more layers made of different polymer materials. The sealant layer may have a total thickness of 60 ㎛ to 100 ㎛, preferably 60 ㎛ to 90 ㎛, and more preferably 60 ㎛ to 80 ㎛. If the thickness of the sealant layer is too thin, the sealing durability and insulation may be reduced, and if it is too thick, the flexibility may be reduced and the total thickness of the pouch film laminate may increase, which may lower the energy density per volume. Figure 2 is a cross-sectional view of a shrinkable pouch film laminate (100a). As shown in Fig. 2, compared to a general pouch film laminate (100), the shrinkable pouch film laminate (100a) has a structure in which a shape memory resin film (140) is placed between a gas barrier layer (120) and a sealant layer (130). (4) Shape memory resin film The shape memory resin film (140) is placed between the gas barrier layer (120) and the sealant layer (130), and is placed inside the pouch with respect to the gas barrier layer (120). The shape memory resin film may be manufactured through a shape memory process using a polymer material capable of shape memory, and the shape thus remembered has the characteristic of undergoing deformation at high temperatures. The above shape memory resin film (140) can be manufactured by a method including a step of softening by applying heat at a temperature higher than the glass transition temperature (Tg) of the target resin film, a step of deforming the resin film by applying force, and a step of cooling the resin film whose shape has been deformed to a temperature lower than the glass transition temperature (Tg) of the resin film. The above shape memory resin film (140) is applied to a battery case by being included in a shrinkable pouch film laminate, and when the battery behaves abnormally, the structure of the battery case collapses due to its shrinkage at high temperatures, which may induce an early short circuit, or energy drain may easily occur, eliminating the risk of explosion due to energy condensation. The above shape memory resin film may be one whose shape is memorized so that it shrinks by at least 500% on an area basis at 100°C or higher. The shrinkage rate may be determined by the force applied in the step of deforming the resin film during the shape memory process, and may be applied according to the applied temperature. The temperature at which the shrinkage occurs through this process may be 100°C or higher, 110°C or higher, 120°C or higher, or 130°C or higher, and the shrinkage rate may be 500% or higher on an area basis, and preferably, it may have a shrinkage rate of 550% or higher, 600% or higher, 650% or higher, 700% or higher, or 750% or higher. When the shrinkage force is in the above range, energy drain through destruction of the battery case may be induced in response to abnormal behavior of the battery, and therefore, it may be desirable to impart the above shrinkage force to the shape memory resin film during the shape memory process. Meanwhile, in the case of shape memory alloys, they are heavier than shape memory resin films, resulting in a large loss in energy density. In addition, the temperature applied to the shape memory process is very high, making it difficult to manufacture. In addition, the shrinkage rate is more than 100 times lower than that of resin films, making it difficult to induce a short circuit, and thus there may be no energy drain effect. In the case where the shape memory resin film (140) is arranged on the outer surface of the pouch-type battery case based on the gas barrier layer (120), the heat inside is accumulated by the gas barrier layer (120) and then shrinkage through shape memory is applied, so that energy drain cannot occur early, and the possibility of suppressing a heat event through a swelling prevention effect can be considered. However, in general, lithium secondary batteries, especially secondary batteries for automobiles or energy storage devices, are provided in the form of modules or packs in a stacked form with multiple battery cells, so suppression of the swelling phenomenon can be prevented from the form of modules or packs, and rather, energy may be condensed, which may lead to an explosion. Therefore, the shape memory resin film (140) needs to be arranged on the inner side of the gas barrier layer (120). The thickness of the shape memory resin film (140) may be 30 ㎛ to 80 ㎛, preferably 35 ㎛ or more, 40 ㎛ or more, or 45 ㎛ or more, more preferably 50 ㎛ or more or 52 ㎛ or more, and preferably 75 ㎛ or less, 70 ㎛ or less, or 65 ㎛ or less. When the thickness is in the above range, a decrease in energy density due to an increase in the thickness of the pouch film laminate can be prevented, and the possibility of a short circuit occurring in a normal driving range can be excluded. The above shrinkable pouch film laminate (100a) is characterized in that a shape memory resin film (140) is additionally disposed between the substrate layer (110) and the gas barrier layer (120). Alternatively, the substrate layer (110) may have a multilayer structure including two or more layers made of different polymers, and a shape memory resin film may be additionally disposed between the outermost layer and the innermost layer of the multilayer structure. Alternatively, a shape memory resin film may be disposed inside the substrate layer (110), and the shape memory resin film may be disposed between the substrate layer (110) and the gas barrier layer (120). When the shrinkable pouch film laminate (100a) is provided so that the shape memory resin film (140) is disposed between the gas barrier layer (120) and the sealant layer (130), the purpose of improving safety can be achieved, and additionally, it can be applied to any part of the laminated structure within the pouch film laminate. However, when additionally disposing the shape memory resin film, it is necessary to consider all factors such as energy density, formability, short-circuit induction effect, and sealing property according to the overall thickness of the pouch-type battery case. The shape memory resin film (140) may include at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTEE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer. The above-described general pouch film laminate (100) and shrinkable pouch film laminate (100a) can be manufactured through a manufacturing method of a pouch film laminate known in the art. For example, the pouch film laminate of the present invention can be manufactured through a method of attaching a substrate layer (110) to the upper surface of a gas barrier layer (120) using an adhesive, and forming a sealant layer (130) on the lower surface of the gas barrier layer (120) using co-extrusion or an adhesive layer, but is not limited thereto. The above shrinkable pouch film laminate may have a total thickness of 160 μm to 200 μm, preferably 180 μm to 200 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 and a decrease in sealing durability due to an increase in the thickness of the pouch laminate. Hereinafter, the structure of a pouch-type battery case (210) will be described with reference to FIG. 3. FIG. 3 is a plan view of an example of a lithium secondary battery (200) including a pouch-type battery case (210). The above pouch-type battery case (210) may be provided with a cup portion (240) having a recessed shape so that an electrode assembly (260) can be accommodated therein; and a sealing portion (251) formed along the circumference of the cup portion (240). The sealing portion (251) is an area indicated by a hatched pattern in FIG. 3, is located on the terrace portion (250), and may be formed by sealing all or part of the terrace portion (250). In addition, the cup portion (240) may have a recessed shape by molding so that an electrode assembly (260) can be accommodated therein, and the electrode assembly may be electrically connected to an electrode tab, and the electrode tab may be electrically connected to an electrode lead (280) extended outward. FIG. 4 is an exploded assembly drawing of a lithium secondary battery (200) including an electrode assembly (260) according to FIG. 3 and a pouch-type battery case (210) in which the electrode assembly is housed. As illustrated in FIG. 4, a lithium secondary battery (300) according to the present invention may include a pouch-type battery case (210) and an electrode assembly (260) housed in the pouch-type battery case (210). The electrode assembly (260) may be formed by stacking a positive electrode, a separator, and an anode, and may include an electrode tab (270), an electrode lead (280), and a lead film (390). The lithium secondary battery (200) may be manufactured by injecting an electrolyte into the inside of the pouch-type battery case (210) with the electrode assembly (260) housed therein, and then sealing the terrace portion (250). The pouch-type battery case (210) can house an electrode assembly (260) inside. The pouch-type battery case (210) can be manufactured by molding the pouch film laminate (100, 100a) of FIGS. 1 and 2 described above. Since the detailed configuration and physical properties of the pouch film laminate (100, 100a) are the same as those described above, a detailed description thereof will be omitted. In order to manufacture a pouch-shaped battery case (210), a pouch-shaped film laminate (100, 100a) can be formed by drawing and stretching using a punch or the like, thereby forming a cup portion (240) including a pocket-shaped receiving space (241) to receive an electrode assembly (260). As illustrated in FIG. 4, the pouch-type battery case (210) may include an upper case and a lower case. In one embodiment, the lower case includes a receiving space (241) in which a lower cup portion (240) is formed to receive an electrode assembly (260), and the upper case may cover the receiving space (241) from above to prevent the electrode assembly (260) from falling out of the battery case (210). The upper and lower cases may be manufactured such that one side thereof is connected to the other, but are not limited thereto and may be manufactured in various ways, such as being manufactured separately and separated from the other. Accordingly, the sealing portion may be formed on three sides, may be formed on all four sides, and may also be formed such that the cup portion exists only on the lower case. The pouch-type battery case (210) can be sealed while housing the electrode assembly (260) so that a portion of the electrode lead (280), i.e., the terminal portion, is exposed. Specifically, when the electrode lead (280) is connected to the electrode tab (270) of the electrode assembly (260) and a lead film (290) is formed on a portion of the electrode lead (280), the electrode assembly (260) can be housed in the housing space (241) provided in the cup portion (240) of the lower case, and the upper case can cover the housing space (241) from above. Subsequently, an electrolyte can be injected into the interior of the housing space (241), and the terrace portions (250) formed on the edges of the upper and lower cases can be sealed. The electrolyte is intended to move lithium ions generated by an electrochemical reaction of an electrode during charging / discharging of a secondary battery (200), and may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. Furthermore, the electrolyte may include a solid electrolyte of a sulfide type, oxide type, or polymer type, and such a solid electrolyte may have flexibility that allows it to be easily deformed by an external force. According to one embodiment of the present invention, the pouch-type battery case comprises a cup portion having a recessed shape to accommodate an electrode assembly; and a sealing portion formed along the periphery of the cup portion; and the shrinkable pouch film laminate may be provided in an area excluding the sealing portion. That is, a general pouch film laminate without a shape memory resin film may be provided in the sealing portion. FIG. 5 is a plan view of a lithium secondary battery including a pouch-type battery case (210) according to one embodiment of the present invention. Referring to Fig. 5, the shrinkable pouch film laminate (shaded portion) may be formed in an area excluding the sealing portion (251), that is, a portion of the cup portion (240) and the terrace portion (250), and a general pouch film laminate may be provided in the sealing portion (251). In the case of the shrinkable pouch film laminate, since it includes a shape memory resin film, a shrinking phenomenon may occur due to the sealing temperature, and even if shrinkage does not occur, there is a concern that the sealing performance may be reduced due to the length of the sealing time due to the thickness. A shrinkable pouch film laminate according to one embodiment of the present invention may be provided in a cup portion spaced apart from the sealing portion by a width (AA”) greater than that of the sealing portion, and may be spaced apart by the spacing A-A' shown in FIG. 5. That is, the spacing A-A' may be greater than or equal to the spacing AA", and in this case, a pouch-type battery case may be provided that can maximize the energy drain effect without affecting the sealing property. FIG. 6 is a cross-sectional view showing a pouch-type battery case when cut along the line S-S' of FIG. 5. The cup portion (240) is provided with a flat portion (242) where the electrode assembly is accommodated and an inclined portion (243) that is connected from the flat portion (242) to the terrace portion (250) and formed by molding, and a part or all of the terrace portion (250) may have a sealing portion (251) formed by sealing. The shrinkable pouch film laminate may be provided from the right side of line A of FIG. 6, and may preferably be provided from a portion spaced apart at least by the distance between A and A". Accordingly, the shrinkable pouch film laminate may be provided on the terrace portion (250), the inclined portion (243), and the flat portion (242), and it is preferable that it be provided at least on the flat portion (242). Hereinafter, with reference to Fig. 4, the remaining components excluding the pouch-type battery case of the lithium secondary battery will be additionally described. The electrode assembly (260) can be formed by alternately stacking electrodes and separators. Specifically, the electrode assembly (260) can be formed into a predetermined shape by applying a slurry containing an electrode active material, a binder, and / or a conductive material to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and stacking the slurry on both sides of a separator. The electrode assembly (260) can be inserted into a pouch-type battery case (210) and sealed by the pouch-type battery case (210) after electrolyte injection. In one embodiment, the types of the electrode assembly (260) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc. The electrode assembly (260) may include two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to mutually insulate the electrodes. The positive electrode and the negative electrode may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry may typically be formed by stirring a granular active material, an auxiliary conductor, a binder, and a conductive agent with a solvent added thereto. The solvent may be removed in a subsequent process. The electrode tabs (270) are respectively connected to the positive and negative electrodes of the electrode assembly (260), and may protrude outward from the electrode assembly (260) to serve as a path for electrons to move between the inside and the outside of the electrode assembly (260). The electrode current collector of the electrode assembly (260) may be composed of a portion where an electrode active material is applied and an end portion where the electrode active material is not applied, i.e., a non-coated portion. The electrode tabs (270) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 3, the electrode tabs (270) may protrude in different directions of the electrode assembly (260), but are not limited thereto, and may be formed to protrude in various directions, such as protruding in parallel in the same direction from one side. An electrode lead (280) can supply electricity to the outside of a secondary battery (200). The electrode lead (280) can be connected to an electrode tab (270) of an electrode assembly (260) by spot welding, etc. At least a portion of the electrode lead (280) can be surrounded by an insulating member (290). In one embodiment, the electrode lead (280) may have one end connected to the electrode tab (270) and the other end protruding outward from the battery case (210). The electrode lead (280) may include a positive lead (282) having one end connected to a positive tab (272) and extending in a direction in which the positive tab (272) protrudes, and a negative lead (284) having one end connected to a negative tab (274) and extending in a direction in which the negative tab (374) protrudes. Both the positive electrode lead (282) and the negative electrode lead (284) may have their other ends protruded to the outside of the battery case (210). Therefore, electricity generated inside the electrode assembly (260) may be supplied to the outside. In addition, since the positive electrode tab (272) and the negative electrode tab (274) are formed to protrude in various directions, the positive electrode lead (282) and the negative electrode lead (284) may also extend in various directions. In one embodiment, the positive electrode lead (282) and the negative electrode lead (284) may be made of different materials. That is, the positive electrode lead (282) may be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead (284) may be made of the same copper (Cu) material as the negative electrode current collector or a nickel (Ni)-coated copper material. A portion of the electrode lead (280) protruding to the outside of the battery case (210) may serve as a terminal portion and be electrically connected to an external terminal. Examples and Comparative Examples 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. Example 1 A polyethylene terephthalate film measuring 266 mm wide, 50 m long, and 12 μm thick and a nylon film measuring 266 mm wide, 50 m long, and 25 μm thick were laminated on one side of an aluminum alloy film measuring 266 mm wide, 50 m long, and 60 μm thick, and a shape memory resin film measuring 256 mm wide, 45 m long, and 50 μm thick and a non-stretched polypropylene (CPP) film measuring 266 mm wide, 50 m long, and 50 μm thick were laminated on the other side to manufacture a pouch film laminate having a polyethylene terephthalate / nylon / aluminum alloy film / shape memory resin film / non-stretched polypropylene structure. At this time, the shape memory resin film used was polytetrafluoroethylene heated to 130°C, subjected to a stress of 2 MPa, and then cooled. Here, polyethylene terephthalate and nylon are the substrate layer, aluminum alloy film is the gas barrier layer, and non-stretched polypropylene is the sealant layer. The manufactured pouch-shaped film laminate was mounted on a two-cup molding device equipped with a die and a punch, and drawing molding was performed by lowering the punch at a pressure of 0.5 MPa and a speed of 20 mm / min so that the molding depth became 9.6 mm, thereby manufacturing a pouch-shaped battery case. Example 2 A pouch-type battery case was manufactured in the same manner as in Example 1, except that a shape memory resin film was further laminated between the nylon and aluminum alloy thin films. Comparative Example 1 A pouch-type battery case was manufactured in the same manner as in Example 1, except that the shape memory resin film was not laminated. Comparative Example 2 A pouch-type battery case was manufactured in the same manner as in Example 1, except that the shape memory resin film was not laminated between the aluminum alloy thin film and the non-stretched polypropylene, but only between the nylon and the aluminum alloy thin film. Comparative Example 3 A pouch-type battery case was manufactured in the same manner as in Example 1, except that a nickel-titanium alloy was used instead of the shape memory resin film. Here, the nickel-titanium alloy was used after heating to 130°C, applying a stress of 2 MPa, and then cooling, similar to the polytetrafluoroethylene of Example 1. Comparative Example 4 A pouch-type battery case was manufactured in the same manner as in Example 1, except that the polytetrafluoroethylene was heated to 100°C, subjected to a stress of 1 MPa, and then cooled. Experimental Example 1 The pouch-type battery cases manufactured in the above examples and comparative examples were applied to the lithium secondary batteries described below and evaluated as follows, and the results are shown in Table 1. The experimental results are shown in Table 1 below. In this case, in Table 1, the "◎" mark means very good, the "○" mark means good, the "△" mark means average, and the "X" mark means poor. Manufacturing of lithium secondary batteries A positive electrode slurry was prepared by mixing a positive electrode active material (NCM65 1520), a conductive agent (Li-435), and a PVDF binder (KF9700, AD-c01) in a weight ratio of 96.5:1.5:2.0 in N-methylpyrrolidone, and the positive electrode slurry was applied to one surface of an aluminum current collector, dried at 140°C, and then rolled to prepare a positive electrode. For the negative electrode, a negative electrode active material, conductive material, and binder were prepared by mixing natural graphite and artificial graphite in a 5:5 ratio at a weight ratio of 95.6:0.9:3.4. An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes manufactured by the above-described method, and then placed inside the battery case of the above-described examples and comparative examples, and an electrolyte was injected into the case to manufacture a battery cell. The electrolyte was manufactured by dissolving 0.7 M LiPF6 in a mixed organic solvent mixed in a volume ratio of ethylene carbonate (EC): propylene carbonate (PC): ethyl methyl carbonate (EMC) = 2:1:7. 1) Shrinkage Test: The manufactured pouch-type battery case was stored in an oven at 150°C for 30 minutes, and the effect of high-temperature shrinkage was confirmed. That is, the degree of expansion before and after storage at high temperatures was evaluated in four stages. 2) Heat propagation delay test: Five of the manufactured battery cells are assembled into a module, and heat is applied to one battery cell at a rate of 0.5°C / sec using a heating pad. The heat to adjacent cells is measured using a thermocouple, and the presence of a time delay in heat propagation is evaluated in four stages. 3) Penetration test: A nail penetration test was performed by penetrating the manufactured battery cell at a speed of 0.1 mm / s using a sharp nail type, and the test was divided into four stages and evaluated based on the time of initial ignition occurrence, the size of the flame at ignition, and the amount of smoke. Shrinkage rate (%) Heat transfer delay test Penetration test Example 1○○○ Example 2◎◎○ Comparative example 1△X△ Comparative example 2○△△ Referring to Table 1 above, it can be seen that Examples 1 and 2 show superior effects in shrinkage force, heat transfer, and penetration tests compared to Comparative Examples 1 and 2. Specifically, Comparative Example 1, which did not apply the shape memory resin film, clearly shows that the overall safety is poor, and when it is placed as the outer layer of the pouch-type battery case rather than the gas barrier layer as in Comparative Example 2, it was evaluated as worse than the Example in the penetration test due to external impact, and it can be confirmed that the time delay effect is not excellent in the heat transfer test. [Explanation of symbols] 100: General pouch film laminate 100a: Shrinkable pouch film laminate 110: Base layer 120: Gas barrier layer 130: Sealant layer 140: Shape memory resin film 200: Lithium secondary battery 210: Pouch-type battery case 240: Cup section 241: Reception space 242: Flat area 243: Sloping area 250: Terrace section 251: Ceiling section 260: Electrode assembly 270: Electrode tab 280: Electrode lead 290: Lead film

Claims

1. The substrate layer, gas barrier layer, and sealant layer are sequentially laminated. A pouch-shaped battery case comprising a shrinkable pouch film laminate in which a shape memory resin film is disposed between the gas barrier layer and the sealant layer.

2. In paragraph 1, A pouch-shaped battery case wherein the shape memory resin film has a thickness of 30 ㎛ to 80 ㎛.

3. In paragraph 1, The above pouch-type battery case, A cup portion having a recessed shape to accommodate an electrode assembly; and a sealing portion formed along the circumference of the cup portion; A pouch-type battery case in which the above shrinkable pouch film laminate is provided in an area excluding the sealing portion.

4. In paragraph 3, A pouch-type battery case in which the above shrinkable pouch film laminate is provided in a cup portion spaced apart from the sealing portion by a width greater than that of the sealing portion.

5. In paragraph 3, A pouch-type battery case in which the sealing portion is provided with a general pouch film laminate without a shape memory resin film.

6. In paragraph 1, A pouch-type battery case wherein the shape memory resin film comprises at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTEE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer.

7. In paragraph 1, A pouch-type battery case in which the shape memory resin film has a shape that is memorized so that it shrinks by at least 500% based on area at 100°C or higher.

8. In paragraph 1, A pouch-shaped battery case wherein the gas barrier layer comprises aluminum.

9. In paragraph 1, The above shrinkable pouch film laminate is a pouch-shaped battery case in which a shape memory resin film is additionally disposed between a substrate layer and a gas barrier layer.

10. In paragraph 1, A pouch-shaped battery case in which the above-mentioned substrate layer is a multilayer structure including two or more layers made of different polymers, and a shape memory resin film is additionally arranged between the outermost layer and the innermost layer of the multilayer structure.

11. A pouch-type battery case according to any one of clauses 1 to 10; and A lithium secondary battery comprising an electrode assembly housed inside the pouch-shaped battery case.

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