Pouch-type battery case and lithium rechargeable battery containing the same

Abstract

The pouch-type battery case according to the present invention includes a shrinkable pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are sequentially laminated, and a shape memory resin film is placed between the gas barrier layer and the sealant layer, thereby providing a pouch-type battery case with improved safety.

Description

Technical Field

[0001] The present invention relates to a pouch-type battery case and a lithium secondary battery including the same, and more specifically, to a pouch-type battery case with improved safety and a lithium secondary battery including the same.

Background Art

[0002] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. Such secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and electric bicycles, but also in large products that require high power such as electric vehicles and hybrid vehicles, power storage devices for storing surplus generated power and newly renewable energy, and backup power storage devices.

[0003] To manufacture such 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, an electrolyte is injected, and then sealed.

[0004] Secondary batteries can be classified into pouch type and can type according to the material of the case that houses the electrode assembly. The pouch type houses the electrode assembly in a pouch made of a flexible polymer material. The can type houses the electrode assembly in a case made of a material such as metal or plastic.

[0005] The pouch, which is the case for a pouch-type rechargeable battery, is manufactured by press-forming a flexible pouch film laminate to form a cup portion. Once the cup portion is formed, the electrode assembly is housed in the internal space of the cup portion, and the seal portion is sealed to manufacture the rechargeable battery.

[0006] Generally, pouch-type battery cases consist of multiple layers, with a metal gas barrier layer on one side laminated with a polymer film such as polyethylene terephthalate, and a sealant layer on the other side. However, with such conventional pouch-type battery cases, the need to increase the size to increase battery density and capacity requires a deeper molding depth, which generates significant tensile stress due to swelling, thus increasing the risk of explosion. [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to solve the above-mentioned problems and, in order to address the risk of explosion due to the swelling phenomenon, further arrangement of a shape memory resin film within the film laminated structure of the pouch-type battery case allows the swelling phenomenon to be suppressed using the function of shrinking at high temperatures, thereby providing a pouch-type battery case with improved safety through effective energy drainage in situations where there is a risk of explosion.

[0008] The problems that the present invention addresses are not limited to those mentioned above, and any other problems not mentioned can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] [1] A pouch-type battery case according to one embodiment of the present invention includes a shrinkable pouch film laminate in which a base layer, a gas barrier layer, and a sealant layer are laminated in order, and a shape memory resin film is disposed between the gas barrier layer and the sealant layer.

[0010] [2] In the above [1], the thickness of the shape memory resin film can be 30 μm to 80 μm.

[0011] [3] In the above [1] and / or [2], the pouch-type battery case comprises a cup portion having a recessed shape for housing 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 a region other than the sealing portion.

[0012] [4] In any one or more of the above [1] to [3], the shrinkable pouch film laminate may be provided in a cup portion that is separated from the sealing portion by a distance greater than or equal to the width of the sealing portion.

[0013] [5] In any one or more of the above [1] to [4], the sealing portion may be provided with a general-purpose pouch film laminate in which no shape memory resin film is present.

[0014] [6] In any one or more of the above [1] to [5], the shape memory resin film may include one or more selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTEE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer.

[0015] [7] In any one or more of the above [1] to [6], the shape memory resin film can be stored in a shape such that it shrinks by at least 500% in area at a temperature of 100°C or higher.

[0016] [8] In any one or more of the above [1] to [7], the gas barrier layer may include aluminum.

[0017] [9] In any one or more of the above [1] to [8], the shrinkable pouch film laminate may further have a shape memory resin film placed between the substrate layer and the gas barrier layer.

[0018]

[10] In any one or more of the above [1] to [9], the base material layer is a multilayer structure comprising two or more layers made of different polymers, and a shape memory resin film may be further disposed between the outermost layer and the innermost layer of the multilayer structure.

[0019]

[11] Another embodiment of the present invention provides a lithium secondary battery comprising the above-described pouch-type battery case and an electrode assembly housed inside the pouch-type battery case. [Effects of the Invention]

[0020] In one embodiment of the present invention, a pouch-type battery case can suppress the swelling phenomenon by further arranging a shape memory resin film within the film laminated structure of the pouch-type battery case, utilizing its high-temperature shrinkage function. This significantly improves safety by enabling effective energy drainage in situations where there is a risk of explosion.

[0021] The shrinkable pouch film laminate includes a shape memory resin film, and the shape memory resin film used is one that is shaped to shrink by 500% or more at high temperatures. By shrinking the battery case and effectively draining energy in the event of abnormal behavior of the lithium secondary battery, the risk of explosion can be prevented, thereby greatly improving safety. [Brief explanation of the drawing]

[0022] [Figure 1] This is a cross-sectional view of a general-purpose pouch film laminate. [Figure 2] It is a cross-sectional view of a shrinkable pouch film laminate according to the present invention. [Figure 3] It is a plan view of a lithium secondary battery including a pouch-type battery case. [Figure 4] It is an exploded assembly view of the lithium secondary battery according to FIG. 3. [Figure 5] It is a plan view of a lithium secondary battery including a pouch-type battery case according to the present invention. [Figure 6] It is a vertical cross-sectional view showing the pouch-type battery case when cut along the line S-S' in FIG. 5.

Mode for Carrying Out the Invention

[0023] The advantages, features, and methods for achieving them of the present invention will become clear by referring to the embodiments described in detail hereinafter together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and can be realized in various different forms. This embodiment is provided to complete the disclosure of the present invention and to fully inform those with ordinary knowledge in the technical field to which the present invention belongs of the scope of the invention. The present invention is only defined by the scope of the claims. The same reference numerals throughout the specification refer to the same components.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification can be used in a meaning commonly understood by those with ordinary knowledge in the technical field to which the present invention belongs. Also, terms defined in commonly used dictionaries are not ideally or excessively interpreted unless specifically defined clearly.

[0025] The terms used herein are for illustrative purposes only and do not limit the invention. In this specification, singular nouns include plural nouns unless otherwise specified in the text. The terms “comprises” and / or “comprising” as used in this specification do not preclude the presence or addition of one or more other components beyond those mentioned.

[0026] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0027] In this specification, when a part is said to include a component, this means that, unless otherwise stated to the contrary, it may include other components rather than excluding them.

[0028] In this specification, the upper part of a drawing may be referred to as the “top” or “upper side” of the configuration illustrated in the drawing, and the lower part may be referred to as the “bottom” or “lower side.” The area between the top and bottom of the configuration illustrated in the drawing, or the remaining part other than the top and bottom, may be referred to as the “side” or “flank.” Such relative terms as “top” and “upper side” may be used to describe the relationship with the configuration illustrated in the drawing, and this disclosure is not limited by such terms.

[0029] In this specification, the direction toward the interior space of a structure may be referred to as "inside," and the direction protruding into an open exterior space may be referred to as "outside." Such relative terms as "inside" and "outside" may be used to describe the relationship with the configurations illustrated in the drawings, and this disclosure is not limited by such terms.

[0030] In this specification, the phrase "A and / or B" means A or B, or A and B.

[0031] In this specification, when a part is said to be connected to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another component in between.

[0032] In this specification, each of the pouch-type battery case and the lithium secondary battery includes one or more of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways.

[0033] 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 base layer, a gas barrier layer, and a sealant layer are laminated in order, and a shape memory resin film is disposed between the gas barrier layer and the sealant layer.

[0034] The shrinkable pouch film laminate and each layer contained within the pouch film laminate will be described in detail below with reference to Figures 1 and 2.

[0035] Figure 1 is a cross-sectional view of a general-purpose pouch film laminate 100.

[0036] As illustrated in Figure 1, a typical pouch film laminate 100 includes a base layer 110, a gas barrier layer 120, and a sealant layer 130.

[0037] (1) Base material layer The base layer 110 is formed on the outermost layer of the pouch film laminate 100 and is intended to protect the secondary battery from friction and impact with the outside. The base layer 110 is made of a polymer and can electrically insulate the electrode assembly from the outside. The base layer 110 can be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyarylate, Teflon®, and glass fiber. In particular, the base layer 110 is preferably made of polyethylene terephthalate (PET), nylon, or a combination thereof, which has abrasion resistance and heat resistance.

[0038] The base layer 110 may have a single film structure composed of any one of the following materials. Alternatively, the base layer 110 may have a composite film structure formed by two or more materials, each forming a layer.

[0039] The thickness of the base material layer 110 can be 5 μm to 50 μm, specifically 7 μm to 50 μm, and more specifically 7 μm to 40 μm. When the thickness of the base material layer 110 satisfies the above range, the pouch film laminate can have excellent external insulation properties, the overall thickness of the pouch does not increase, and it can have an excellent energy density relative to the volume of the secondary battery.

[0040] (2) Gas barrier layer The gas barrier layer 120 is laminated between the substrate layer 110 and the sealant layer 130 to ensure the mechanical strength of the pouch, block the intrusion of gases or moisture from outside the pouch-type battery case, and prevent electrolyte leakage from inside the pouch-type battery case.

[0041] The gas barrier layer 120 can be made of a metal, specifically an aluminum alloy thin film. When the gas barrier layer is made using an aluminum alloy thin film, it is possible to ensure mechanical strength above a certain level, while also ensuring light weight, complementarity with the electrochemical properties of the electrode assembly and electrolyte, and heat dissipation. The aluminum alloy thin film may contain one or more metallic elements other than aluminum, for example, one or more selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0042] The thickness of the gas barrier layer 120 can 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 moldability and gas barrier performance are excellent during the molding of the cup portion.

[0043] (3) Sealant layer The sealant layer 130 is bonded by heat and pressure to seal the battery case and is located in the innermost layer of the pouch film laminate 100.

[0044] The sealant layer 130, after being molded into the battery case, is the surface that comes into contact with the electrolyte and electrode assembly, and therefore needs to have insulating and corrosion-resistant properties. It also needs to have high sealing properties because it must completely seal the inside and block the transfer of mass between the inside and outside.

[0045] The sealant layer 130 can be made of a polymer material, for example, one or more selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), 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, abrasion resistance, and heat resistance, as well as excellent chemical properties such as corrosion resistance.

[0046] The sealant layer 130 may include polypropylene, cast polypropylene (CPP), acid-modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof.

[0047] The sealant layer 130 may be a single layer or a multilayer structure comprising two or more layers made of different polymer materials.

[0048] The sealant layer may have a total thickness of 60 μm to 100 μm, preferably 60 μm to 90 μm, and more preferably 60 μm to 80 μm. If 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, the total thickness of the pouch film laminate may increase, and the energy density relative to volume may decrease.

[0049] Figure 2 is a cross-sectional view of the shrinkable pouch film laminate 100a.

[0050] As shown in Figure 2, compared to a typical pouch film laminate 100, the shrinkable pouch film laminate 100a has a structure in which a shape memory resin film 140 is placed between the gas barrier layer 120 and the sealant layer 130.

[0051] (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 positioned on the inside of the pouch with respect to the gas barrier layer 120. The shape-memory resin film can be manufactured using a polymer material capable of shape memory, and is characterized in that the shape thus memorized deforms at high temperatures.

[0052] The shape memory resin film 140 can be manufactured by a method that includes the steps of: applying heat at a temperature above the glass transition temperature (Tg) of the target resin film to soften it; applying force to deform the resin film; and cooling the deformed resin film to a temperature below the glass transition temperature (Tg) of the resin film.

[0053] The shape memory resin film 140, when included in a shrinkable pouch film laminate, is applied to a battery case. Due to its property of shrinking at high temperatures during abnormal battery behavior, the structure of the battery case collapses, inducing a short circuit early on, or energy drainage is easily performed, eliminating the risk of explosion due to energy condensation.

[0054] The shape memory resin film can be shaped so as to shrink by at least 500% of its area at a temperature of 100°C or higher. The shrinkage rate can be determined according to the force applied in the step of deforming the resin film during the shape memory process, and can be applied according to the temperature at which it is applied. The temperature at which it shrinks through such a process can be 100°C or higher, 110°C or higher, 120°C or higher, or 130°C or higher, and the shrinkage rate can be 500% or higher based on the area, preferably 550% or higher, 600% or higher, 650% or higher, 700% or higher, or 750% or higher. When the shrinkage force is within the range described above, it is possible to induce energy drain through the destruction of the battery case in response to abnormal battery behavior, and it is preferable to apply such a shrinkage force when the shape is shaped into the shape memory resin film.

[0055] On the other hand, shape memory alloys are heavier than shape memory resin films, have greater energy density losses, and the temperature applied to the shape memory process is very high, which presents disadvantages in the manufacturing process. Furthermore, their shrinkage rate is more than 100 times lower than that of resin films, making it impossible to induce short circuits, and there is a possibility that they do not have an energy drain effect.

[0056] When the shape memory resin film 140 is placed on the outer surface of a pouch-type battery case with respect to the gas barrier layer 120, the gas barrier layer 120 causes internal heat to accumulate, and then the shrinkage due to shape memory acts to prevent the early generation of energy drain. It is possible that the shape memory resin film 140 may suppress heat problems due to its swelling prevention effect, but generally, lithium secondary batteries, especially secondary batteries for automobiles or energy storage devices, are provided in the form of modules or packs with multiple battery cells stacked together. Therefore, the suppression of the swelling phenomenon can be prevented from the form of modules or packs, and conversely, energy may condense, potentially leading to an explosion. For this reason, the shape memory resin film 140 needs to be placed inside the gas barrier layer 120.

[0057] The thickness of the shape memory resin film 140 can be 30 μm to 80 μm, preferably 35 μm or more, 40 μm or more, or 45 μm or more, more preferably 50 μm or more or 52 μm or more, and preferably 75 μm or less, 70 μm or less, or 65 μm or less. When the thickness is within the above range, it is possible to prevent a decrease in energy density due to an increase in the thickness of the pouch film laminate and eliminate the possibility of short circuits occurring in the normal driving region.

[0058] The shrinkable pouch film laminate 100a is characterized in that a shape memory resin film 140 is further disposed between the base layer 110 and the gas barrier layer 120. Alternatively, the base layer 110 may be a multilayer structure including two or more layers made of different polymers, with a shape memory resin film further disposed between the outermost and innermost layers of the multilayer structure. Alternatively, the shape memory resin film may be disposed inside the base layer 110, with a shape memory resin film disposed between the base layer 110 and the gas barrier layer 120.

[0059] If the shrinkable pouch film laminate 100a is provided such that the shape memory resin film 140 is positioned between the gas barrier layer 120 and the sealant layer 130, the objective of improving safety can be achieved, and it can be further applied to a part of the laminated structure within the pouch film laminate. However, when additional shape memory resin films are placed, it is necessary to consider all factors such as the energy density, moldability, short-circuit induction effect, and sealing properties based on the total thickness of the pouch-type battery case.

[0060] The shape memory resin film 140 may contain one or more materials selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTEE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer.

[0061] The general-purpose pouch film laminate 100 and the shrink-type pouch film laminate 100a can be manufactured by methods for manufacturing pouch film laminates that are well known in the art. For example, the pouch film laminate of the present invention can be manufactured by attaching a base material layer 110 to the upper surface of a gas barrier layer 120 via an adhesive, and forming a sealant layer 130 on the lower surface of the gas barrier layer 120 via co-extrusion or an adhesive layer, but is not limited thereto.

[0062] The shrinkable pouch film laminate can have a total thickness of 160 μm to 200 μm, preferably 180 μm to 200 μm. When the thickness of the pouch film laminate is within this range, it is possible to minimize the reduction in battery housing space and the decrease in sealing durability due to an increase in the thickness of the pouch laminate, while also increasing the molding depth.

[0063] The structure of the pouch-type battery case 210 will be described below with reference to Figure 3. Figure 3 is a plan view showing an example of a lithium secondary battery 200 including the pouch-type battery case 210.

[0064] The pouch-type battery case 210 may include a cup portion 240 having a recessed shape to accommodate the electrode assembly 260, and a sealing portion 251 formed along the periphery of the cup portion 240. The sealing portion 251 is the area shown by the diagonal pattern in Figure 3, is located on the terrace portion 250, and can be formed by sealing all or part of the terrace portion 250. The cup portion 240 may also have a recessed shape formed by molding to accommodate the electrode assembly 260, the electrode assembly may be electrically connected to electrode tabs, and the electrode tabs may be electrically connected to electrode leads 280 that are drawn out to the outside.

[0065] Figure 4 is an exploded view of a lithium secondary battery 200, including the electrode assembly 260 shown in Figure 3 and a pouch-type battery case 210 in which the electrode assembly is housed.

[0066] As illustrated in Figure 4, the 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 a negative electrode, and may include an electrode tab 270, an electrode lead 280, and a lead film 290. The lithium secondary battery 200 can be manufactured by injecting an electrolyte with the electrode assembly 260 housed inside the pouch-type battery case 210, and then sealing the terrace portion 250.

[0067] The pouch-type battery case 210 can house the electrode assembly 260 inside. The pouch-type battery case 210 can be manufactured by molding the pouch film laminates 100 and 100a shown in Figures 1 and 2 above. The detailed configuration and physical properties of the pouch film laminates 100 and 100a are as described above, and a detailed explanation is omitted.

[0068] To manufacture the pouch-type battery case 210, the pouch film laminates 100, 100a can be formed by drawing and stretching using a punch or the like to create a cup portion 240 that includes a bag-shaped storage space 241 to accommodate the electrode assembly 260.

[0069] As illustrated in Figure 4, the pouch-type battery case 210 may include an upper case and a lower case. In one embodiment, the lower case includes a housing space 241 in which a lower cup portion 240 is formed and which can accommodate an electrode assembly 260, and the upper case can cover the housing space 241 from above to prevent the electrode assembly 260 from detaching from the outside of the battery case 210. The upper and lower cases may be manufactured connected on one side, but are not limited to this, and can be manufactured separately or in various other ways. As a result, the sealing portion may be formed on three sides, on all four sides, or the cup portion may be present only on the lower case.

[0070] The pouch-type battery case 210 can be sealed with the electrode assembly 260 housed inside, such that a portion of the electrode leads 280, i.e., the terminal portion, is exposed. Specifically, the electrode leads 280 are connected to the electrode tabs 270 of the electrode assembly 260, and a lead film 290 is formed on a portion of the electrode leads 280. The electrode assembly 260 is then housed in a 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. Next, an electrolyte is injected into the housing space 241, and the terrace portions 250 formed on the periphery of the upper and lower cases can be sealed. The electrolyte is for moving lithium ions generated by the electrochemical reaction of the electrodes during charging / discharging of the secondary battery 200, and can include a non-aqueous organic electrolyte which is a mixture of lithium salts and organic solvents, or a polymer using a polymer electrolyte. Furthermore, the electrolyte can include sulfide-based, oxide-based, or polymer-based solid electrolytes, and such solid electrolytes can have flexibility that allows them to be easily deformed by external forces.

[0071] According to one embodiment of the present invention, the pouch-type battery case comprises a cup portion having a recessed shape for housing an electrode assembly, and a sealing portion formed along the periphery of the cup portion, and the shrinkable pouch film laminate can be provided in a region other than the sealing portion. That is, the sealing portion can be provided with a general-purpose pouch film laminate that does not contain a shape memory resin film.

[0072] Figure 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.

[0073] Referring to Figure 5, the shrinkable pouch film laminate (shaded portion) can be formed in areas other than the sealing portion 251, i.e., in a part of the cup portion 240 and the terrace portion 250, and the sealing portion 251 can be provided with a general-purpose pouch film laminate. In the case of the shrinkable pouch film laminate, since it contains a shape memory resin film, shrinkage may occur depending on the sealing temperature, or even if shrinkage does not occur, the sealing time may be prolonged due to the thickness, potentially reducing the sealing performance.

[0074] A shrinkable pouch film laminate according to one embodiment of the present invention can be provided in a cup portion that is separated from the sealing portion by a distance greater than or equal to the width of the sealing portion (A-A''), and the distance can be as far as the distance A-A' shown in Figure 5. That is, the distance A-A' can be greater than or equal to the distance A-A'', and in this case, a pouch-type battery case can be provided that does not affect the sealing performance and can maximize the energy drain effect.

[0075] Figure 6 is a cross-sectional view showing a pouch-type battery case cut along the line S-S' in Figure 5. The cup portion 240 has a flat portion 242 in which the electrode assembly is housed, and an inclined portion 243 formed by molding that is connected from the flat portion 242 to the terrace portion 250. A sealing portion 251 can be formed on part or all of the terrace portion 250 by sealing. The shrinkable pouch film laminate can be provided from the right side of line A in Figure 6, and preferably from a portion separated by at least the distance between A and A''. Thus, the shrinkable pouch film laminate can be provided on the terrace portion 250, on the inclined portion 243, and on the flat portion 242, and preferably on at least the flat portion 242.

[0076] The remaining components of the lithium secondary battery, other than the pouch-type battery case, will be further explained below with reference to Figure 4.

[0077] The electrode assembly 260 can be formed by alternately stacking electrodes and separators. Specifically, the electrode assembly 260 can be formed by manufacturing positive and negative electrodes by applying a slurry of electrode active material and binder and / or conductive material to positive and negative electrode current collectors, and then stacking these on both sides of a separator to form a predetermined shape. The electrode assembly 260 can be inserted into a pouch-type battery case 210, injected with an electrolyte, and then sealed by the pouch-type battery case 210. In one embodiment, the types of electrode assembly 260 may include, but are not limited to, stack type, jelly roll type, and stack-and-fold type.

[0078] The electrode assembly 260 may include two electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate them from each other. The positive and negative electrodes may each be constructed by coating an active material slurry onto an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry can typically be formed by stirring granular active material, auxiliary conductors, binders, and conductive materials with a solvent. The solvent can be removed in a subsequent step.

[0079] The electrode tabs 270 are connected to the positive and negative electrodes of the electrode assembly 260, respectively, and protrude outward from the electrode assembly 260, becoming pathways through which electrons can move between the inside and outside of the electrode assembly 260. The electrode current collector of the electrode assembly 260 can consist of a portion coated with electrode active material and an end portion not coated with electrode active material, i.e., a plain portion. The electrode tabs 270 can be formed by cutting the plain portion or by connecting another conductive member to the plain portion by ultrasonic welding or the like. As illustrated in Figure 3, the electrode tabs 270 can protrude in different directions from the electrode assembly 260, but are not limited to this, and can be formed to protrude in various directions, such as protruding parallel to the same direction from one side.

[0080] The electrode lead 280 can supply electricity to the outside of the secondary battery 200. The electrode lead 280 can be connected to the electrode tab 270 of the electrode assembly 260 by spot welding or the like. At least a portion of the electrode lead 280 can be surrounded by a lead film 290. In one embodiment, one end of the electrode lead 280 can be connected to the electrode tab 270 and the other end can protrude to the outside of the battery case 210. The electrode lead 280 may include a positive electrode lead 282, one end of which is connected to the positive electrode tab 272 and extends in the direction in which the positive electrode tab 272 protrudes, and a negative electrode lead 284, one end of which is connected to the negative electrode tab 274 and extends in the direction in which the negative electrode tab 274 protrudes.

[0081] Both the positive lead 282 and the negative lead 284 can have their other ends protruding outside the battery case 210. Therefore, electricity generated inside the electrode assembly 260 can be supplied to the outside. Also, since the positive tab 272 and the negative tab 274 are formed to protrude in various directions, the positive lead 282 and the negative lead 284 can also extend in various directions. In one embodiment, the positive lead 282 and the negative lead 284 can be made of different materials. That is, the positive lead 282 can be made of the same aluminum (Al) material as the positive current collector, and the negative lead 284 can be made of the same copper (Cu) material as the negative current collector or nickel (Ni) coated copper material. A portion of the electrode lead 280 that protrudes outside the battery case 210 can become a terminal and be electrically connected to an external terminal.

[0082] Examples and Comparative Examples The present invention will be described in more detail below with reference to specific examples. However, the following examples are illustrative to aid in understanding the present invention and do not limit the scope of the invention. It will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the described scope and technical concept, and it goes without saying that such variations and modifications fall within the scope of the appended claims.

[0083] Example 1 A pouch film laminate with a polyethylene terephthalate / nylon / aluminum alloy thin film / shape memory resin film / unoriented polypropylene structure was manufactured by laminating a polyethylene terephthalate / nylon / aluminum alloy thin film / shape memory resin film / unoriented polypropylene onto one side of an aluminum alloy thin film measuring 266 mm wide, 50 m long, and 60 μm thick, and 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. On the other side, a shape memory resin film measuring 256 mm wide, 45 m long, and 50 μm thick, and unoriented polypropylene (CPP) were laminated.

[0084] Here, the shape memory resin film used was made by heating polytetrafluoroethylene to 130°C, applying a stress of 2 MPa, and then cooling it.

[0085] Here, polyethylene terephthalate and nylon are the base layer, the aluminum alloy thin film is the gas barrier layer, and the unoriented polypropylene is the sealant layer.

[0086] The manufactured pouch-type film laminate was mounted in a two-cup molding machine equipped with a die and a punch. The punch was lowered at a pressure of 0.5 MPa and a speed of 20 mm / min to perform deep drawing to produce a pouch-type battery case with a molding depth of 9.6 mm.

[0087] 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 nylon and aluminum alloy thin films.

[0088] Comparative Example 1 A pouch-type battery case was manufactured using the same method as in Example 1, except that a shape-memory resin film was not laminated.

[0089] Comparative Example 2 A pouch-type battery case was manufactured using the same method as in Example 1, except that the shape memory resin film was not laminated between the aluminum alloy thin film and the unoriented polypropylene, but only between the nylon and the aluminum alloy thin film.

[0090] 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 a shape-memory resin film.

[0091] Here, the nickel-titanium alloy used was prepared by heating it to 130°C, applying a stress of 2 MPa, and then cooling it, similar to the polytetrafluoroethylene used in Example 1.

[0092] 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 before being applied.

[0093] Experimental Example 1 The pouch-type battery cases manufactured in the above examples and comparative examples were applied to the following lithium secondary batteries and evaluated as follows, and the results are shown in Table 1. Here, the experimental results are shown in Table 1 below. Here, in Table 1, "◎" indicates very good, "○" indicates good, "△" indicates average, and "×" indicates poor.

[0094] Manufacturing of lithium-ion batteries A positive electrode slurry was prepared by mixing a positive electrode active material (NCM65 1520), a conductive material (Li-435), and a PVDF binder (KF9700, AD-c01) in N-methylpyrrolidone in a weight ratio of 96.5:1.5:2.0. The positive electrode slurry was then applied to one surface of an aluminum current collector, dried at 140°C, and then rolled to produce a positive electrode.

[0095] For the negative electrode, the negative electrode active material, conductive material, and binder were manufactured in a weight ratio of 95.6:0.9:3.4, using a mixture of natural graphite and artificial graphite in a 5:5 ratio.

[0096] After manufacturing an electrode assembly by interposing a separator between the positive electrode and negative electrode manufactured by the method described above, the assembly was placed inside the battery case of the above example and comparative example, and then an electrolyte was injected into the case to manufacture a battery cell. The electrolyte was prepared by dissolving 0.7 M LiPF6 in a mixed organic solvent of ethylene carbonate (EC):propylene carbonate (PC):ethyl methyl carbonate (EMC) = 2:1:7 by volume.

[0097] 1) Contraction 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. Specifically, the degree of expansion before and after high-temperature storage was evaluated in four steps.

[0098] 2) Heat propagation delay test Five of the manufactured battery cells were used as one module, and heat was applied to one battery cell at a rate of 0.5°C / sec using a heating pad. The heat transferred to adjacent cells was measured using thermocouples, and the time delay in heat transfer was evaluated in four steps.

[0099] 3) Nail piercing test The manufactured battery cells were subjected to a nail-piercing experiment using a sharp nail type at a speed of 0.1 mm / s. The initial ignition time, flame size, and smoke volume were evaluated in four steps.

[0100] [Table 1]

[0101] Referring to Table 1 above, it can be seen that Examples 1 and 2 show superior effects in shrinkage force, heat transfer, and nail penetration tests compared to Comparative Examples 1 and 2. Specifically, Comparative Example 1, which does not use a shape memory resin film, clearly shows that its safety is inferior overall. In the case of Comparative Example 2, where it is placed on the outer layer of the pouch-type battery case rather than the gas barrier layer, it is evaluated as inferior to the examples in the nail penetration test due to external impact, and it can be confirmed that it does not have a superior time delay effect in the heat transfer test. [Explanation of symbols]

[0102] 100 General-purpose pouch film laminate 100a Shrink-type pouch film laminate 110 Base material layer 120 Gas barrier layer 130 sealant layer 140 Shape memory resin film 200 Lithium-ion rechargeable batteries 210 Pouch-type Battery Cases 240 cup section 241 Containment space 242 Flat area 243 Slope 250 Terrace section 251 Sealing section 260 Electrode assembly 270 electrode tabs 280 electrode leads 290 Lead Film

Claims

1. A base layer, a gas barrier layer, and a sealant layer are laminated in order. A pouch-type 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. The pouch-type battery case according to claim 1, wherein the thickness of the shape-memory resin film is 30 μm to 80 μm.

3. The aforementioned pouch-type battery case is It comprises a cup portion having a recessed shape to accommodate the electrode assembly, and a sealing portion formed along the periphery of the cup portion, The pouch-type battery case according to claim 1, wherein the shrinkable pouch film laminate is provided in a region other than the sealing portion.

4. The pouch-type battery case according to claim 3, wherein the shrinkable pouch film laminate is provided in a cup portion that is spaced at a distance greater than or equal to the width of the sealing portion from the sealing portion.

5. The pouch-type battery case according to claim 3, wherein the sealing portion is provided with a general-purpose pouch film laminate in which no shape memory resin film is present.

6. The pouch-type battery case according to claim 1, wherein the shape-memory resin film comprises one or more selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTEE), polyolefin (Polyolefin), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluororubber (Fluoropolymer Elastomer).

7. The pouch-type battery case according to claim 1, wherein the shape-memory resin film is stored in a shape such that it shrinks by at least 500% based on its area at a temperature of 100°C or higher.

8. The pouch-type battery case according to claim 1, wherein the gas barrier layer comprises aluminum.

9. The pouch-type battery case according to claim 1, wherein the shrinkable pouch film laminate further comprises a shape memory resin film disposed between the substrate layer and the gas barrier layer.

10. The pouch-type battery case according to claim 1, wherein the base material layer has a multilayer structure comprising two or more layers made of different polymers, and a shape memory resin film is further disposed between the outermost layer and the innermost layer of the multilayer structure.

11. A pouch-type battery case according to any one of claims 1 to 10, A lithium secondary battery, including an electrode assembly housed inside the aforementioned pouch-type battery case.

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