Pouch-type secondary battery

Abstract

A pouch-type secondary battery according to the present invention includes an electrode assembly, a pouch-type case including a housing that houses the electrode assembly and a sealing part that seals the housing, an electrode lead connected to the electrode assembly and protruding to the outside of the pouch-type case via the sealing part, a lead film disposed between the electrode lead and the pouch-type case, and a gas guide disposed between the electrode lead and the lead film, wherein the gas guide includes a first layer that contacts the electrode lead and a second layer disposed on the first layer, and the first layer includes a modified polyolefin-based resin.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0159794, filed November 24, 2022, Korean Patent Application No. 10-2022-0175297, filed December 14, 2022, and Korean Patent Application No. 10-2023-0164467, filed November 23, 2023, and all contents disclosed in the documents of these Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a pouch-type secondary battery, and more particularly to a pouch-type secondary battery including a gas guide portion. [Background technology]

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

[0004] A secondary battery can be manufactured by placing an electrode assembly, in which positive electrodes, negative electrodes, and separators interposed therebetween are alternately stacked, in a battery case, injecting an electrolyte, and sealing the battery case. Secondary batteries can be classified into pouch types and can types depending on the material of the case that houses the electrode assembly. Among these, a pouch-type battery can be manufactured by pressing a flexible pouch film laminate to form a cup, placing the electrode assembly in the inner space of the cup, and sealing the sealing portion.

[0005] Pouch-type secondary batteries can generate gas inside the pouch when operated at high temperatures, overcharged, or when a short circuit occurs. High gas pressure inside the pouch can lead to venting, which can result in an explosion or fire. To address this issue, a gas guide has been provided at the junction between the electrode lead and the pouch-type film laminate, which are made of different materials. When the internal pressure of the pouch increases, the interface between the gas guide and the lead film opens, allowing the gas to escape to the outside of the pouch. However, when the interface opens, the adhesive strength between the gas guide and the electrode lead weakens, causing the gas guide to detach from the electrode lead and be pushed out of the pouch. Alternatively, the electrode lead may be corroded by electrolyte leaking from the inside of the pouch, resulting in a decrease in the durability and safety of the pouch. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and provides a pouch-type secondary battery capable of improving the adhesive strength between a gas guide portion and an electrode lead. [Means for solving the problem]

[0007] According to one embodiment of the present invention, there is provided a pouch-type secondary battery comprising: an electrode assembly; a pouch-type case including a receiving portion that receives the electrode assembly and a sealing portion that seals the receiving portion; an electrode lead connected to the electrode assembly and protruding to the outside of the pouch-type case through the sealing portion; a lead film disposed between the electrode lead and the pouch-type case; and a gas guide disposed between the electrode lead and the lead film, wherein the gas guide includes a first layer that contacts the electrode lead and a second layer disposed on the first layer, and the first layer comprises a modified polyolefin-based resin. [Effects of the Invention]

[0008] The pouch-type secondary battery according to the present invention is characterized in that the first layer of the gas guide, which contacts the electrode lead, contains a modified polyolefin resin, thereby improving the adhesive strength between the gas guide and the electrode lead. Therefore, even when the pouch-type secondary battery is stored in a high-temperature electrolyte environment, the gas guide is prevented from detaching from the electrode lead or being pushed out of the pouch, causing leakage of the electrolyte inside the pouch. Therefore, the pouch-type secondary battery according to the present invention is prevented from corrosion of the electrode lead due to the electrolyte and / or gas, and has excellent durability and stability. [Brief explanation of the drawings]

[0009] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the above-described content of the invention, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited solely to the matters depicted in such drawings.

[0010] [Figure 1] 1 is an exploded view of a pouch-type secondary battery according to the present invention; [Figure 2] FIG. 2 is a cross-sectional view of a sealed pouch-type secondary battery. [Figure 3] 1 is a cross-sectional view of an example of a pouch-type secondary battery before the pouch-type case is opened. [Figure 4] 1 is an example of a cross-sectional view of a pouch-type secondary battery when the pouch-type case is opened. [Figure 5] 10 is another example of a cross-sectional view of a pouch-type secondary battery before the pouch-type case is opened. [Figure 6] 10 is another example of a cross-sectional view of a pouch-type secondary battery before the pouch-type case is opened. [Figure 7] FIG. 2 is a top perspective view of a sealing portion according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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. Therefore, 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. The present invention is defined only by the scope of the claims. The same reference symbols refer to the same elements throughout the specification.

[0012] 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.

[0013] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise stated in the phrase. The words "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0014] 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.

[0015] In this specification, the phrase "A and / or B" means A, B, or A and B.

[0016] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0017] A pouch-type secondary battery according to the present invention includes an electrode assembly, a pouch-type case including a housing that houses the electrode assembly and a sealing part that seals the housing, an electrode lead connected to the electrode assembly and protruding to the outside of the pouch-type case via the sealing part, a lead film disposed between the electrode lead and the pouch-type case, and a gas guide disposed between the electrode lead and the lead film, wherein the gas guide includes a first layer that contacts the electrode lead and a second layer disposed on the first layer, and the first layer includes a modified polyolefin-based resin.

[0018] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to the drawings.

[0019] Fig. 1 is an exploded view of a pouch-type secondary battery 100 according to the present invention, and Fig. 2 is a cross-sectional view of the sealed pouch-type secondary battery 100. In Fig. 2, some of the components of the pouch-type secondary battery 100 are omitted for ease of understanding. As shown in Figs. 1 and 2, the pouch-type secondary battery 100 according to the present invention includes a pouch-type case 110, an electrode assembly 160, electrode leads 180, a lead film 190, and a gas guide 200.

[0020] (1) Pouch-type case The pouch-type case 110 can house the electrode assembly 160 inside. The pouch-type case 110 can be manufactured by molding a pouch film laminate. In this case, the pouch film laminate can include a base layer, a gas barrier layer, and a sealant layer. In the pouch film laminate, the base layer, the gas barrier layer, and the sealant layer can be laminated in this order.

[0021] 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.

[0022] 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.

[0023] The substrate layer may have a single film structure made of any one material, or alternatively, the substrate layer may have a composite film structure made of two or more materials each formed as a layer.

[0024] The thickness of the substrate layer can be 5 μm to 50 μm, specifically 7 μm to 40 μm, more specifically 25 μm to 38 μm. When the thickness of the substrate layer satisfies this range, the external insulation is excellent and the overall thickness of the pouch is not large, so that the energy density relative to the volume of the secondary battery can be excellent.

[0025] 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 gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type case.

[0026] The gas barrier layer may be formed of a metal, specifically, an aluminum alloy thin film. When an aluminum alloy thin film is used to form the gas barrier layer, it can ensure a certain level of mechanical strength, be lightweight, and ensure electrochemical compatibility between the electrode assembly and the electrolyte, as well as heat dissipation. The aluminum alloy thin film may contain at least one metal element other than aluminum (Al), such as iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0027] The thickness of the gas barrier layer can be 40 μm to 100 μm, specifically 50 μm to 90 μm, more specifically 55 μm to 85 μm. When the thickness of the gas barrier layer satisfies this range, excellent moldability and gas barrier performance are achieved when the cup portion is formed.

[0028] The sealant layer is thermally bonded to the sealing portion when the pouch-shaped case accommodating the electrode assembly therein is sealed, thereby completely sealing the inside of the pouch-shaped case. For this purpose, the sealant layer may be made of a material having excellent thermal adhesive strength.

[0029] 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 case, it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the sealant layer must completely seal the inside of the pouch-type case to prevent the transfer of materials between the inside and outside, it may be formed of a material having high sealing properties (e.g., excellent thermal adhesive strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer may be formed of a polymer material.

[0030] 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.

[0031] 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 sealing strength of the sealed portion and the formability of the pouch film laminate.

[0032] Meanwhile, the pouch film laminate may be drawn and stretched using a punch or the like to manufacture the pouch-type case 110. As a result, the pouch-type case 110 may include a cup portion 122 and a receiving portion 124. The receiving portion 124 is a location for receiving the electrode assembly, and may refer to a bag-shaped receiving space formed inside the cup portion 122 as the cup portion 122 is formed.

[0033] According to an embodiment of the present invention, the pouch-type case 110 may include a first case 120 and a second case 130, 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 of the battery case 110. 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 manufactured separately.

[0034] According to another embodiment of the present invention, when forming cup portions in a pouch film laminate, two symmetrical cup portions 122, 132 may be formed adjacent to each other by drawing one pouch film laminate. In this case, as shown in FIG. 1, the first case 120 and the second case 130 may be formed with the cup portions 122, 132, respectively. 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 case 110 forms one corner of the secondary battery 100, which reduces the number of corners to be sealed during subsequent sealing processes, thereby improving the processing speed of the pouch-type secondary battery 100 and reducing the number of sealing processes.

[0035] The pouch-type case 110 may be sealed with the electrode assembly 160 housed therein such that a portion, i.e., a terminal portion, of the electrode lead 180 (described below) is exposed. Specifically, when the electrode lead 180 is connected to the electrode tab 170 of the electrode assembly 160 and a lead film 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 sealing portions 150 formed on the peripheries of the first case 120 and the second case 130 may be sealed.

[0036] The sealing part 150 may serve to seal the receiving part 124. Specifically, the sealing part 150 may be formed along the periphery of the receiving part 124 to seal the receiving part 124.

[0037] The temperature for sealing the sealing part 150 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 the above range, the pouch-type case 110 can be thermally bonded to ensure sufficient sealing strength.

[0038] (2) Electrode assembly The electrode assembly 160 may be inserted into the pouch-type case 110 and sealed by the pouch-type case 110 after the electrolyte is injected.

[0039] 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.

[0040] The positive and negative electrodes may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry may be formed by stirring a granular active material, a supplemental conductor, a binder, a conductive material, and the like in a solvent. The solvent may be removed in a subsequent process.

[0041] 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.

[0042] The electrode assembly 160 may include an electrode tab 170 .

[0043] The electrode tabs 170 are connected to the positive and negative electrodes of the electrode assembly 160, respectively, and protrude from the electrode assembly 160 to serve as paths for electrons to move 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 by ultrasonic welding, for example. 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 side by side in the same direction from one side.

[0044] (3) Electrode lead The electrode lead 180 may supply electricity to the outside of the secondary battery 100. The electrode lead 180 may be connected to the electrode tab 170 of the electrode assembly 160 by spot welding or the like.

[0045] The electrode lead 180 is connected to the electrode assembly 160 and may protrude to the outside of the pouch-type case 110 through the sealing portion 150. Specifically, one end of the electrode lead 180 is connected to the electrode assembly 160, particularly to the electrode tab 170, and the other end of the electrode lead 180 may protrude to the outside of the pouch-type case 110.

[0046] 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.

[0047] The surface of the electrode lead 180 that is in direct contact with the lead film 190 and / or the gas guide 200 may be coated with at least one material selected from the group consisting of chromium (Cr), nickel (Ni), aluminum oxide (Al2O3), zirconium (Zr)-based anhydrous oxide salts, and titanium (Ti)-based anhydrous oxide salts. In this case, corrosion resistance to the electrolyte and adhesion to the lead film 190 and / or the gas guide 200 can be ensured.

[0048] (4) Lead film The lead film 190 prevents electricity generated from the electrode assembly 160 from flowing to the battery case 110 via the electrode lead 180, thereby maintaining the sealing of the battery case 110. To this end, the lead film 190 may be formed of an insulator that is electrically non-conductive and does not easily pass electricity. Typically, the lead film 190 is made of a relatively thin insulating tape that is easily attached to the electrode lead 180 and / or the gas guide 200, but is not limited thereto, and any material that can insulate the electrode lead 180 may be used.

[0049] The lead film 190 according to an embodiment of the present invention may be a gas-permeable film and may be disposed to wrap the outer periphery of the electrode lead 180 and the gas guide 200. Specifically, the electrode lead 180 and the gas guide 200 may contact each other on one side, and at least a portion of the electrode lead 180 and the gas guide 200 may be surrounded by the lead film 190. The lead film 190 may be positioned only in the sealing portion 150 where the first case 120 and the second case 130 of the pouch-type case 110 are heat-sealed, and may bond the electrode lead 180 and the gas guide 200 to the battery case 110.

[0050] A lead film 190 may be disposed between the electrode lead 180 and / or gas guide 200 and the pouch-type case 110. For example, as shown in Fig. 2, a lower case 110, a lead film 190, an electrode lead 180, a gas guide 200, a lead film 190, and an upper case 110 may be disposed in a stacked state in the region of the sealing unit 150. Although not shown in the drawings, in another example, a lower case, a lead film, a gas guide, an electrode lead, a lead film, and an upper case may be disposed in a stacked state in this order, or in yet another example, a lower case, a lead film, a gas guide, an electrode lead, a gas guide, a lead film, and an upper case may be disposed in a stacked state in this order.

[0051] According to an embodiment of the present invention, one end of the lead film 190 protruding outward from the pouch-type case 110 may be disposed so as to directly contact the electrode lead 180 rather than the gas guide 200, as shown in Fig. 3 or 5. When one end of the lead film 190 is disposed so as to directly contact the electrode lead 180, i.e., so as to extend further than the gas guide 200 disposed on the electrode lead 180, when gas is discharged and the lead film 190 on the gas guide 200 is opened, an area through which gas can pass through the lead film 190 can be easily secured. Furthermore, compared to when the lead film 190 is not disposed so as to extend, the adhesion between the lead film 190 and the electrode lead 180 can minimize a decrease in durability due to opening of the lead film 190.

[0052] According to another embodiment of the present invention, as shown in FIG. 3 or 6, the first layer 210 of the gas guide portion 200 may be formed longer toward the outside of the pouch-type case 110 than the second layer 220, and one end of the lead film 190 protruding toward the outside of the pouch-type case 110 may be positioned so as to directly contact the first layer 210 rather than the second layer 220.

[0053] In particular, as shown in FIG. 3, when one end of the lead film 190 protrudes further in the protruding direction of the electrode lead to contact the electrode lead 180, and the second layer 220 of the gas guide unit 200 extends further than the first layer 210 so that a portion of the lead film 190 contacts the second layer 220, the adhesive strength between the lead film 190 and the electrode lead 180, as well as the adhesive strength between the lead film 190 and the gas guide unit 200, can be maintained strong, and a synergistic effect can be achieved in the adhesive strength between the electrode lead 180 and the gas guide unit 200, resulting in a gas exhaust component with excellent durability.

[0054] Meanwhile, the lead film 190 may include one or more layers, specifically, the lead film 190 may include a metal adhesive layer, a core layer, and a pouch adhesive layer, which are laminated in order.

[0055] The metal adhesive layer may be in direct contact with the electrode lead 180 and serve to adhere the lead film 190 to the electrode lead 180. The metal adhesive layer may include any material that easily adheres to the electrode lead 180. Specifically, the metal adhesive layer may include acid-modified polyolefin. For example, the metal adhesive layer may include at least one of PPa (acid modified polypropylene), PEa (acid modified polyethylene), and plasma-treated PP (plasma-treated polypropylene), but is not limited thereto. The thickness may be 50 μm to 80 μm, specifically 50 μm to 75 μm, and more specifically 60 μm to 75 μm. When the thickness of the metal adhesive layer satisfies the above numerical range, it is effective in preventing pinholes and leaks at the edges when the electrode lead and the lead film are fused together.

[0056] The core layer may be a layer located at the center of the lead film 190. The core layer may include, but is not limited to, polypropylene, polyolefin elastomer (POE), and / or additives such as colorants. For example, the polymer included in the core layer may be a homopolymer. When the core layer includes a homopolymer, the melting point of the core layer can be controlled within a desired range, minimizing thermal deformation and ensuring insulation. As another example, the polymer included in the core layer may be polytetrafluoroethylene, which is a fluorine-based polyolefin, or a mixture of polytetrafluoroethylene and polypropylene. In the case of a mixture, the mixture may be mixed in a weight ratio of 9:1 to 1:9. In this case, better gas permeability may be achieved than when gas permeates the lead film 190 through the gas guide 200. The thickness of the core layer may be 40 μm to 70 μm, specifically 50 μm to 70 μm, more specifically 60 μm to 70 μm. When the thickness of the core layer satisfies the above range, deformation due to heat applied during fusion and sealing is prevented, and a robust design effect is achieved in terms of ensuring insulation.

[0057] The pouch adhesive layer may be a layer that directly contacts the battery case 110, specifically, the sealant layer of the pouch film laminate. The pouch adhesive layer may include, but is not limited to, polypropylene or polyolefin elastomer (POE). In particular, the polymer included in the pouch adhesive layer may be a copolymer. When the pouch adhesive layer includes a copolymer, the melting point of the pouch adhesive layer can be controlled within a desired range, and since the copolymer has a melting point similar to that of the polymer in the sealant layer of the pouch film laminate, this is advantageous for ensuring the sealing process. The thickness of the pouch adhesive layer may be 40 μm to 100 μm, specifically 40 μm to 80 μm, and more specifically 40 μm to 60 μm. When the thickness of the pouch adhesive layer satisfies the above range, it is effective in ensuring a sufficient polymer (e.g., polypropylene) remaining rate to ensure strength when sealing the electrode lead and the pouch film laminate.

[0058] (5) Gas induction section The gas guide 200 serves to form a path for discharging gas from the inside to the outside of the pouch-type case 110. As shown in Fig. 2, the gas guide 200 of the present invention may be disposed between the electrode lead 180 and the lead film 190. In this case, the electrode lead 180 and the lead film 190 may not be in direct contact with each other in the region between the electrode lead 180 and the lead film 190 where the gas guide 200 is disposed, but may be in direct contact with each other in the region where the gas guide 200 is not disposed.

[0059] The gas guide 200 of the present invention will be described in more detail below with reference to Figures 3 and 4. Figure 3 is a cross-sectional view of the pouch-type secondary battery before the pouch-type case is opened, and Figure 4 is a cross-sectional view of the pouch-type secondary battery when the pouch-type case is opened.

[0060] 3 and 4, the interface between the gas guide unit 200 and the lead film 190 is normally left unopened, and when the internal pressure of the pouch-type case 110 increases, the interface between the gas guide unit 200 and the lead film 190 is opened, forming a gas exhaust path 300. Gas inside the pouch-type case 110 moves along the gas exhaust path 300 and then passes through the lead film 190 to be exhausted to the outside of the pouch. As a result, the internal pressure of the pouch-type case 110 is reduced, and explosion or fire of the pouch-type case 110 can be prevented.

[0061] Meanwhile, as shown in FIGS. 3 and 4, the gas guide 200 of the present invention includes a first layer 210 in contact with the electrode lead 180 and a second layer 220 disposed on the first layer 210.

[0062] The first layer 210 may be in contact with the electrode lead 180 and serve to bond the gas guide 200 to the electrode lead 180 .

[0063] The first layer 210 may include any material that can be easily bonded to the electrode lead 180. Specifically, the first layer 210 is characterized by including a modified polyolefin resin. As the internal pressure of the pouch-type case 110 increases, the interface between the lead film 190 and the gas guide 200 opens, forming a gas exhaust path 300. The gas generated inside the pouch-type case 110 can be exhausted through this path, thereby reducing the pressure in the case 110. However, the surface of the gas guide 200 that is bonded to the electrode lead 180 is the first layer 210. If the adhesive strength between the first layer 210 and the electrode lead 180 is insufficient, the gas guide 200 may detach from the electrode lead 180 or be pushed outward, resulting in leakage of the electrolyte.

[0064] Therefore, when the first layer 210 that fixes the gas guide portion 200 to the electrode lead 180 contains a modified polyolefin resin as in the present invention, the adhesive strength between the gas guide portion 200 and the electrode lead 180 is improved, and even when the pouch-type secondary battery is stored in a high-temperature environment, the above-mentioned problems of the gas guide portion 200 detaching from the electrode lead 180 and the leakage of the internal electrolyte can be prevented.

[0065] According to one embodiment of the present invention, the first layer 210 may have a structure in which it protrudes further outward from the end of the second layer 220 toward the outside of the case 110 and contacts the lead film 190, as described above. In this case, the adhesion between the electrode lead 180, the gas guide 200, and the lead film 190 is excellent, which can help improve durability.

[0066] The modified polyolefin resin contained in the first layer 210 may include at least one of an acid-modified polyolefin and a silane-modified polyolefin.

[0067] Acid-modified polyolefin refers to a polyolefin resin graft-modified with an acid. For example, acid-modified polyolefin can be a polyolefin resin that is graft-modified by reacting an unsaturated carboxylic acid with the polyolefin resin to introduce a carboxyl group. In this case, the term "unsaturated carboxylic acid" includes the concept of a carboxylic acid anhydride, and the term "carboxyl group" includes the concept of a carboxylic acid anhydride group. The unsaturated carboxylic acid reacted with the polyolefin resin can include, but is not limited to, one or more selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, and tetrahydrophthalic anhydride. Among these, maleic anhydride is preferably used to improve the adhesive strength between the gas guide 200 and the electrode lead 180. The acid-modified polyolefin may include, but is not limited to, one or more selected from the group consisting of PPa (acid modified polypropylene) and PEa (acid modified polyethylene).

[0068] Silane-modified polyolefin refers to a polyolefin resin graft-modified with an unsaturated silane compound. The silane-modified polyolefin may have a structure in which an unsaturated silane compound is graft-copolymerized onto a polyolefin resin main chain. The silane-modified polyolefin resin may include, but is not limited to, one or more selected from the group consisting of silane-modified polypropylene resin and silane-modified ethylene-vinyl acetate copolymer.

[0069] The first layer 210 may be modified, and examples of the modification include ion implantation, plasma treatment, radiation irradiation, and heat treatment, with a treatment that changes the bonding structure of the polymer layer being preferred. These modification treatments may be performed singly or in combination of two or more. The modified first layer 210 may include, but is not limited to, plasma-treated polypropylene (PP).

[0070] The thickness of the first layer 210 may be 5 μm to 130 μm, specifically 30 μm to 120 μm, and more specifically 30 μm to 80 μm. When the thickness of the first layer 210 satisfies this range, the first layer 210 can be melted within a predetermined production time (tact time), thereby easily fusing the gas guide 200 and the electrode lead 180.

[0071] Meanwhile, according to one embodiment of the present invention, the first layer 210 may include a ceramic filler. The ceramic filler may be included in an amount of 1 wt % to 19 wt %, specifically 5 wt % to 15 wt %, and more specifically 5 wt % to 12 wt %, based on the total weight of the first layer 210. When the content of the ceramic filler satisfies this range, the adhesive strength between the electrode lead 180 and the gas guide 200, which is intended to be obtained through the first layer 210, is not affected, and the ceramic filler adsorbs gases such as HF generated by various side reactions, preventing corrosion of the electrode lead 180 and significantly improving durability.

[0072] The average particle diameter D of the ceramic filler 50 The average particle size D can be 1 μm to 20 μm, specifically 1 μm to 10 μm, and more specifically 1 μm to 6 μm. 50 If the thickness satisfies the above range, the extrusion processability can be maintained at an excellent level when manufacturing the first layer 210, and problems with film adhesion, such as peeling of the first layer 210 and the second layer 220 of the gas guide portion 200 or peeling from the electrode lead 180, can be prevented.

[0073] On the other hand, the content of the ceramic filler is 1% by weight to 19% by weight with respect to the total weight of the lead film 190, and the average particle diameter D 50 When the thickness is 1 μm to 20 μm, the gas generated inside the pouch can be easily adsorbed, preventing the problem of corrosion caused by gas at the joint between the electrode lead and the pouch-shaped film laminate, and achieving high durability.

[0074] The ceramic filler may include at least one selected from the group consisting of CaCO3, Ca(OH)2, CaCl2, CaO, KOH, NaOH, and Na2CO. Preferably, the ceramic filler may include at least one of CaCO3 and Ca(OH)2, which are inexpensive and easily adsorb gases such as hydrofluoric acid (HF).

[0075] Furthermore, the first layer 210 may further include an additive other than the above-mentioned ceramic filler. By including an additive in the first layer 210, it is possible to change the physical properties of the first layer 210. For example, at least one of carbon fiber, glass fiber, and aramid fiber may be further added as an additive to adjust the tensile strength of the first layer 210.

[0076] The second layer 220 can be the layer that contacts the lead film 190 .

[0077] The second layer 220 may include at least one of, but is not limited to, polytetrafluoroethylene (PTFE) and polyimide (PI). In particular, if the second layer 220 includes polyimide, the adhesive strength between the second layer 220 and the lead film 190 is reduced, and a gas exhaust path 300 may be formed when the internal pressure of the case 110 increases.

[0078] The thickness of the second layer 220 may be 40 μm to 100 μm, specifically 40 μm to 90 μm, and more specifically 45 μm to 75 μm. When the thickness of the second layer 220 is within this range, the second layer 220 does not melt during the sealing process, and when the internal pressure of the case 110 increases, the interface between the second layer 220 and the lead film 190 opens, forming a gas exhaust path 300.

[0079] Meanwhile, the ratio D1 / D2 of the thickness D1 of the first layer to the thickness D2 of the second layer may be 0.4 to 2.0, specifically 0.4 to 1.5, and more specifically 0.4 to 1.0. When the ratio D1 / D2 satisfies the above numerical range, when the internal pressure of the case 110 increases, the interface between the second layer 220 and the lead film 190 opens, forming a gas discharge path and improving the adhesive strength between the gas guide 200 and the electrode lead 180.

[0080] (6) Electrolyte The pouch-type secondary battery 100 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type case 110. The electrolyte is used to transport lithium ions generated by an electrochemical reaction of the electrodes during charging / discharging of the secondary battery 100, 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.

[0081] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative for the purpose of facilitating understanding of the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope of the present description and technical concept, and it goes without saying that such changes and modifications fall within the scope of the appended claims.

[0082] Examples and Comparative Examples Example 1 (1) Manufacturing pouch-type cases A polyethylene terephthalate (PET) 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 thin film measuring 266 mm wide, 50 m long, and 60 μm thick, and a polypropylene film measuring 266 mm wide, 50 m long, and 80 μm thick was laminated on the other side to produce a pouch film laminate with a polyethylene terephthalate / nylon / aluminum alloy thin film / polypropylene film structure.

[0083] Here, the polyethylene terephthalate film and nylon film are the base layer, the aluminum alloy thin film is the gas barrier layer, and the polypropylene film is the sealant layer.

[0084] The pouch film laminate was molded to prepare a pouch-type case including a receiving portion and a sealing portion.

[0085] (2) Manufacturing of pouch-type secondary batteries The negative and positive electrodes and a porous polyethylene separator were stacked and then laminated to prepare an electrode assembly, and then an electrode lead was attached to the electrode assembly.

[0086] An electrolyte was prepared by dissolving LiPF6 in a solvent (volume ratio of EC:EMC:DMC = 3:3:4) to a concentration of 1.0 M. With the tip of the electrode lead extended to the outside, the electrode assembly was placed in the pouch-type case, and the electrolyte was poured into it.

[0087] A gas guide portion was formed by laminating an acid-modified polypropylene film (first layer) having a thickness of 40 μm and a polyimide film (second layer) having a thickness of 50 μm in this order on the upper surface of the electrode lead.

[0088] Next, a 200 μm thick lead film was laminated on the lower surface of the electrode lead and the upper surface of the gas guide, respectively. The lead film included a 75 μm thick metal adhesive layer containing copolymer polypropylene and acid-modified polypropylene, a 65 μm thick core layer containing homopolymer polypropylene, and a 60 μm thick pouch adhesive layer containing copolymer polypropylene.

[0089] Next, the sealing portion of the pouch-type case was sealed for 2 seconds with a seal bar area of ​​200 mm x 10 mm under conditions of 220°C and 0.27 MPa, and then left for 4 hours at 60°C to manufacture a pouch-type secondary battery. Here, the portion of the sealing portion where the lead film was formed had a structure in which the lower case / lead film / electrode lead / gas guide / lead film / upper case were laminated in this order.

[0090] Example 2 A pouch-type case and a secondary battery were manufactured in the same manner as in Example 1, except that the thickness of the acid-modified polypropylene film applied to the first layer was 10 μm and the thickness of the polyimide film applied to the second layer was 50 μm.

[0091] Example 3 A pouch-type case and a secondary battery were manufactured in the same manner as in Example 1, except that the thickness of the acid-modified polypropylene film applied to the first layer was 120 μm and the thickness of the polyimide film applied to the second layer was 50 μm.

[0092] Example 4 A pouch-type case and a secondary battery were produced in the same manner as in Example 1, except that an acid-modified polyethylene film was used in place of the acid-modified polypropylene film for the first layer.

[0093] Example 5 A pouch-type case and a secondary battery were produced in the same manner as in Example 1, except that a polytetrafluoroethylene film was used in place of the polyimide film for the second layer.

[0094] Example 6 When manufacturing the acid-modified polypropylene film applied to the first layer, CaCO3 (average particle size D 50 A pouch-type case and a secondary battery were manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film was prepared by mixing the acid-modified polypropylene film (2.8 μm) in an amount of 7 wt % of the total weight of the film.

[0095] Example 7 When manufacturing the acid-modified polypropylene film applied to the first layer, CaCO3 (average particle size D 50 A pouch-type case and a secondary battery were manufactured in the same manner as in Example 1, except that the acid-modified polypropylene film was prepared by mixing the acid-modified polypropylene film (2.8 μm) in an amount of 11% by weight based on the total weight of the film.

[0096] Comparative Example 1 A pouch-type case and a secondary battery were manufactured in the same manner as in Example 1, except that the gas guide 200 did not include the acid-modified polypropylene film (first layer) (was a single layer).

[0097] Comparative Example 2 A pouch-type case and a secondary battery were produced in the same manner as in Example 1, except that an unmodified polypropylene film was used in the first layer instead of the acid-modified polypropylene film.

[0098] Comparative Example 3 A pouch-type case and a secondary battery were produced in the same manner as in Example 1, except that a polyimide film was used as the first layer and an acid-modified polypropylene film was used as the second layer.

[0099] Experimental example 1: Durability evaluation For each of the pouch-type secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 3, the length of the gas guide portion peeled off from the electrode lead was measured, and the adhesive strength between the electrode lead and the gas guide portion, as well as the adhesive strength under the electrolyte, were measured, and the reduction rate of the adhesive strength was calculated.

[0100] 1) Storage stability in electrolyte (mm)During the manufacturing process of the pouch-type secondary battery, HF was poured into the pouch-type case, which was then sealed and stored in a chamber at 60°C for 5 days. After the storage period, the length of time that at least a portion of the gas guide and lead film had peeled from the electrode lead was measured. The results are shown in Table 1 below.

[0101] 7 is a top perspective view of a sealing unit according to an embodiment of the present invention. As shown in FIG. 7, the sealing unit 150 includes an electrode lead 180, a gas guide 200, and a lead film 190 laminated in this order. The gas guide 200 may include a first region 230 and a second region 240.

[0102] If the gas guide 200 and the lead film 190 are not durable enough against the electrolyte, they may be peeled from the inside to the outside of the pouch. Here, the length of the gas guide 200 and / or the lead film 190 peeled from the electrode lead 180 refers to the length A from the end of the second region 240 facing the inside of the pouch to the peeled portion.

[0103] 2) Adhesion strength between electrode lead and lead film (N / cm) : In the manufacturing process of pouch-type secondary batteries, a gas-generating material is placed inside the pouch-type case, and then the pouch-type case is sealed, generating CO2 gas inside the pouch and increasing the internal pressure of the pouch.

[0104] After storing the lead assembly in a 60°C chamber for 5 days, both ends of the lead assembly were cut from the inner edge of the sealing portion, i.e., the portion 10 mm away from the inner edge of the portion between the second regions 240 in Figure 7, and attached to the lower and upper jigs of the UTM. The lead assembly was then pulled 30 mm in a 180° direction at a speed of 50 mm / min, and the average value (N / 10 mm) of the flat section of the measured adhesive strength graph was calculated. The results are shown in Table 1 below.

[0105] 3) Adhesion strength (N / cm) and decrease rate of adhesion strength (%) under electrolyteAfter extracting the lead assembly as in 2), it was immersed in an electrolyte containing 1.0M LiPF6 lithium salt and an organic solvent consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethylene carbonate (DMC) mixed in a volume ratio of 3:3:4 at 60°C for 24 hours. The adhesive strength in the electrolyte was measured in the same manner as in 2), and the rate of decrease in adhesive strength before and after the electrolyte immersion was calculated.

[0106] [Table 1]

[0107] According to Table 1, in Examples 1 to 7, in which the first layer of the gas guide portion contains a modified polyolefin resin, the length of the peeled (or extruded) gas guide portion and / or lead film is significantly shorter than in Comparative Examples 1 to 3, demonstrating superior durability. Also, the adhesive strength between the lead film and the electrode lead in Examples 1 to 7 and the adhesive strength after electrolyte impregnation are significantly higher than in Comparative Examples 1 and 2. In Comparative Example 3, the adhesive completely peeled off after electrolyte impregnation, making it impossible to measure the strength, indicating a significant decrease in durability under electrolyte. [Explanation of symbols]

[0108] 100 Pouch-type secondary battery 110 Pouch-type case 120 Case 1 122 Cup section 124 Storage unit 130 Case 2 132 Cup section 140 Bridge section 150 sealing 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 Lead Film 200 Gas induction section 210 1st layer 220 2nd layer 300 Gas Exhaust Route

Claims

1. an electrode assembly; a pouch-type case including a receiving portion for receiving the electrode assembly and a sealing portion for sealing the receiving portion; an electrode lead connected to the electrode assembly and protruding to the outside of the pouch-type case through the sealing portion; a lead film disposed between the electrode lead and the pouch-shaped case; a gas guide portion disposed between the electrode lead and the lead film, the gas guide portion includes a first layer in contact with the electrode lead and a second layer disposed on the first layer; The first layer is a pouch-type secondary battery containing a modified polyolefin resin.

2. 2. The pouch-type secondary battery according to claim 1, wherein when the pressure inside the pouch-type case increases, the interface between the lead film and the first layer opens, forming a gas release path.

3. The pouch-type secondary battery according to claim 1 , wherein the first layer includes an acid-modified polyolefin.

4. The pouch-type secondary battery according to claim 3 , wherein the acid-modified polyolefin includes at least one selected from the group consisting of PPa (acid modified polypropylene) and PEa (acid modified polyethylene).

5. 2. The pouch-type secondary battery according to claim 1, wherein a ratio D1 / D2 of the thickness D1 of the first layer to the thickness D2 of the second layer is 0.4 to 2.

0.

6. The pouch-type secondary battery according to claim 1 , wherein the second layer includes at least one of polyimide (PI) and polytetrafluoroethylene (PTFE).

7. 2. The pouch-type secondary battery according to claim 1, wherein the first layer has a thickness of 5 μm to 130 μm.

8. 2. The pouch-type secondary battery according to claim 1, wherein the second layer has a thickness of 40 μm to 100 μm.

9. The pouch-type secondary battery according to claim 1 , wherein the second layer is in direct contact with the lead film.

10. The first layer has an average particle size D ５０ The pouch-type secondary battery according to claim 1, further comprising a ceramic filler having a particle size of 1 μm to 20 μm.

11. The ceramic filler is CaCO ３ , Ca(OH) ２ , CaCl ２ , CaO, KOH, NaOH and Na ２ CO ３ The pouch-type secondary battery according to claim 10, comprising at least one selected from the group consisting of:

12. The pouch-type secondary battery according to claim 10, wherein the ceramic filler is contained in an amount of 1% by weight to 19% by weight based on the total weight of the first layer.

13. The pouch-type secondary battery according to claim 1 , wherein the electrode lead, the first layer, the second layer, and the lead film are laminated in this order.

14. One surface of the electrode lead is made of chromium (Cr), nickel (Ni), and aluminum oxide (Al ２ O ３ 2. The pouch-type secondary battery according to claim 1, wherein the pouch-type secondary battery is coated with at least one selected from the group consisting of an anhydrous oxide salt of zirconium (Zr) and an anhydrous oxide salt of titanium (Ti).

15. 2. The pouch-type secondary battery according to claim 1, wherein one end of the lead film protruding outward from the pouch-type case protrudes further than one end of the gas guide portion protruding outward from the pouch-type case and is positioned so as to be in direct contact with the electrode lead.

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