Pouch-type secondary battery

Abstract

The pouch-type secondary battery according to the present invention comprises: an electrode assembly; an outer portion including an accommodating unit for accommodating the electrode assembly and a platform unit formed along a circumference of the accommodating unit and having a sealing unit in which a portion of a width is sealed; an electrode lead electrically connected to the electrode assembly and protruding to the outside of the outside; a lead film disposed between the electrode lead and the outside; a gas induction unit disposed between the electrode lead and the lead film, and including a transfer unit disposed outside the sealing unit and at least one gas flow path extending from the transfer unit toward the electrode assembly via the sealing unit; and a reinforcing film disposed on the lead film to cover at least a portion of the transfer unit, in which the reinforcing film has a single-layer structure.

Description

Technical Field

[0001] The present invention relates to a pouch-type secondary battery, and more particularly, to a pouch-type secondary battery including a gas guide portion for discharging gas inside the battery. Background Art

[0002] Secondary batteries are used in a variety of categories, including small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable gaming devices, power tools, and electric bicycles, as well as large products requiring high power, such as electric vehicles and hybrid vehicles, power storage devices for storing surplus power or renewable energy, and backup power storage devices. Secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries.

[0003] Secondary batteries can be prepared by accommodating an electrode assembly in which positive electrodes, negative electrodes, and separators interposed therebetween are alternately stacked in a battery case, injecting an electrolyte, and then sealing the battery case. Depending on the material of the case that accommodates the electrode assembly, secondary batteries are divided into pouch-type secondary batteries and can-type secondary batteries. In particular, pouch-type batteries can be manufactured by pressing a flexible pouch film laminate to form a cup-shaped portion, then accommodating the electrode assembly in a receiving space inside the cup-shaped portion, and sealing the sealing portion.

[0004] When a pouch-type secondary battery is operated at high temperature, overcharged, or short-circuited, gas may be generated inside the pouch. When the gas pressure inside the pouch increases, the pouch may vent and explode or ignite.

[0005] To overcome the above limitations, different types of gas exhaust components have been studied, and there is an increasing demand for gas exhaust components designed to manage gas exhaust, external moisture intrusion, and electrolyte leakage, gas exhaust components with high internal pressure tolerance but low operating pressure, and gas exhaust components that exhibit high durability. Summary of the Invention

[0006] Technical issues

[0007] The present invention is designed to overcome the above-mentioned limitations, and therefore, in terms of a secondary battery provided with a gas guide portion, one aspect of the present invention provides a pouch-type secondary battery and a battery pack including the pouch-type secondary battery, the pouch-type secondary battery including a reinforcing film, the reinforcing film being applied to the gas guide portion to prevent deformation, thereby maintaining an appropriate gas discharge rate, and solving moisture intrusion and electrolyte leakage caused by stretching of the film portion through which gas permeates during gas discharge.

[0008] In terms of the above-mentioned secondary battery, another aspect of the present invention provides a pouch-type secondary battery and a battery pack including the pouch-type secondary battery, wherein the pouch-type secondary battery is provided with a gas guide portion having a reinforcing film with a single-layer structure applied to prevent deformation, thereby preventing interlayer delamination by minimizing the interface between the films and improving durability while maintaining gas emission performance.

[0009] Technical Solution

[0010] [1] According to one aspect of the present invention, a pouch-type secondary battery is provided, comprising: an electrode assembly; an outer shell, the outer shell comprising a receiving portion and a platform portion, the receiving portion being for receiving the electrode assembly, the platform portion being formed along a periphery of the receiving portion and having a sealing portion in which a portion of the width of the platform portion is sealed; an electrode lead, the electrode lead being electrically connected to the electrode assembly and protruding outward from the outer shell; a lead film, the lead film being arranged between the electrode lead and the outer shell; a gas guide portion, the gas guide portion being arranged between the electrode lead and the lead film and comprising a permeable portion arranged on the outside of the sealing portion and at least one gas channel extending from the permeable portion via the sealing portion toward the electrode assembly; and a reinforcement film, the reinforcement film being arranged on the lead film to cover at least a portion of the permeable portion, wherein the reinforcement film has a single-layer structure.

[0011] [2] The present invention provides a pouch-type secondary battery according to [1] above, wherein the secondary battery can be configured so that the interface between the lead film and the gas guide film opens along the gas channel due to an increase in the internal pressure of the housing, thereby providing a gas discharge path.

[0012] [3] The present invention provides the pouch-type secondary battery according to [1] and / or [2] above, wherein the reinforcement film may be provided on the lead film to cover the entire portion of the permeable portion.

[0013] [4] The present invention provides a pouch-type secondary battery according to at least one of [1] to [3] above, wherein the pouch-type secondary battery may include an insertion portion occupying a portion of the width of the sealing portion, and the insertion portion may be an area in which one end portion of the reinforcement film extends inwardly of the outer shell and is inserted between the outer shell of the sealing portion and the lead film.

[0014] [5] The present invention provides a pouch-type secondary battery according to at least one of [1] to [4] above, wherein the reinforcement film may include an insertion portion occupying a portion of the width of the sealing portion, the insertion portion may be an area in which one end of the reinforcement film extends inwardly of the outer shell and is inserted between the outer shell of the sealing portion and the lead film, and the ratio of the length of the insertion portion to the width of the sealing portion may be in the range of 0.05 to 0.90.

[0015] [6] The present invention provides the pouch-type secondary battery according to at least one of [1] to [5] above, wherein the reinforcement film may have a thickness of 60 μm to 150 μm.

[0016] [7] The present invention provides the pouch-type secondary battery according to at least one of [1] to [6] above, wherein the reinforcement film may have a melting temperature (Tm) of 110° C. to 170° C.

[0017] [8] The present invention provides the pouch-type secondary battery according to at least one of [1] to [7] above, wherein the reinforcement film may have a tensile strength of 3.5 MPa to 5.5 MPa at 60°C.

[0018] [9] The present invention provides the pouch-type secondary battery according to at least one of [1] to [8] above, wherein the reinforcement film may include a modified polyolefin-based resin.

[0019]

[10] The present invention provides a pouch-type secondary battery according to at least one of [1] to [9] above, wherein the reinforcement film may include a modified polyolefin-based resin, and the modified polyolefin-based resin may include at least one selected from acid-modified polypropylene and acid-modified polyethylene.

[0020]

[11] The present invention provides the pouch-type secondary battery according to at least one of [1] to

[10] above, wherein the gas guide portion may include an adhesive resin layer in contact with the electrode lead and a permeable resin layer in contact with the lead film.

[0021]

[12] The present invention provides the pouch-type secondary battery according to

[11] above, wherein, in the adhesive resin layer, one end portion protruding in the outward direction of the outer case can protrude further than one end portion protruding in the outward direction of the outer case of the permeable resin layer.

[0022]

[13] The present invention provides a pouch-type secondary battery according to

[11] and / or

[12] above, wherein, in the lead film, one end portion protruding in the outward direction of the outer shell can protrude further than one end portion of the permeable resin layer protruding in the outward direction of the outer shell.

[0023]

[14] According to another aspect of the present invention, a battery pack is provided, which includes a plurality of pouch-type secondary batteries and a package for accommodating the secondary batteries, wherein the pouch-type secondary batteries include: an electrode assembly; an outer shell, the outer shell including a accommodating portion and a platform portion, the accommodating portion being used to accommodate the electrode assembly, the platform portion being formed along a periphery of the accommodating portion and having a sealing portion in which a portion of the width of the platform portion is sealed; an electrode lead, the electrode lead being electrically connected to the electrode assembly and protruding outward from the outer shell; a lead film, the lead film being arranged between the electrode lead and the outer shell; a gas guide portion, the gas guide portion being arranged between the electrode lead and the lead film and including a permeable portion arranged on the outside of the sealing portion and at least one gas channel extending from the permeable portion via the sealing portion toward the electrode assembly; and a reinforcement film, the reinforcement film being arranged on the lead film to cover at least a portion of the permeable portion, wherein the reinforcement film has a single-layer structure.

[0024] Beneficial effects

[0025] In one aspect of the present specification, a pouch-type secondary battery and a battery pack provide the following benefits by introducing a reinforcing film covering the permeable portion of the gas guide portion: preventing whitening caused by continuous tensile force applied to the lead film during gas discharge, solving electrolyte leakage, and also reducing the possibility of moisture intrusion in the long term.

[0026] On the other hand of the present specification, a pouch-type secondary battery and a battery pack introduce a reinforcement film that covers the permeable portion of the gas guide portion, while inserting a portion of the reinforcement film into the sealing area, so that the portion of the reinforcement film and the sealing area are sealed together, and thus exhibit excellent sealing strength even when the process of opening the interface between the gas guide portion and the lead film during gas discharge is repeated, and thus prevents the film from being pushed open.

[0027] Furthermore, by adopting a single-layer structure, the interfaces between the films can be minimized, thus preventing the disintegration of the sealing structure caused by delamination between the layers of the multilayer film. Furthermore, the operating pressure and discharge rate can be maintained at levels that are not significantly different from those of conventional operating pressures and discharge rates, thereby also preventing the degradation of gas emission performance. As a result, the pouch-type secondary battery exhibits improved durability and maintains satisfactory gas emission performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is an exploded view of a pouch-type secondary battery;

[0029] Figure 2 is a cross-sectional view of a sealed pouch-type secondary battery;

[0030] Figure 3 yes Figure 2An example of an enlarged cross-sectional view of a portion of frame A showing a state before the interface between the lead film and the gas guide portion is opened;

[0031] Figure 4 yes Figure 2 An example of an enlarged cross-sectional view of a portion of frame A showing a state in which the interface between the lead film and the gas guide portion is opened;

[0032] Figure 5 yes Figure 2 Another example of an enlarged cross-sectional view of a portion of frame A, which shows a state before the interface between the lead film and the gas guide film is opened;

[0033] Figure 6 yes Figure 2 Still another example of an enlarged cross-sectional view of a portion of frame A, which shows a state before the interface between the lead film and the gas guide film is opened; and

[0034] Figure 7 yes Figure 2 An example of a top perspective view of a portion of frame A in direction B. DETAILED DESCRIPTION

[0035] The advantages and features of the present disclosure and the methods for implementing the present disclosure may be more readily understood by referring to the detailed description of the following embodiments and the accompanying drawings. However, the present disclosure may be implemented in different forms, and these embodiments are provided only to make the present disclosure thorough and complete and to fully convey the scope of the present disclosure to those skilled in the art, and therefore the present disclosure is limited only by the scope of the appended claims. Throughout the specification, the same reference numerals represent the same elements.

[0036] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. Unless explicitly and specifically defined, terms defined in commonly used dictionaries should not be idealized or over-interpreted.

[0037] The terms used herein are not intended to limit the inventive concept, but rather to describe embodiments. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. As used herein, the meaning of "comprise" and / or "comprising" does not exclude the presence or addition of one or more other components in addition to the components described.

[0038] As used herein, unless explicitly described otherwise, when an element “includes” components, it may indicate that the element does not exclude other components but may also include other components.

[0039] As used herein, the description "A and / or B" means A or B, or A and B.

[0040] As used herein, "%" means % by weight unless otherwise specified.

[0041] The pouch-type secondary battery described herein may include at least one of technical components to be described later, and may include any combination of technically feasible components among the following technical components.

[0042] On the one hand, a pouch-type secondary battery includes: an electrode assembly; a shell, the shell including a accommodating portion for accommodating the electrode assembly and a platform portion formed along a periphery of the accommodating portion; an electrode lead, the electrode lead is connected to the electrode assembly and protrudes outward from the shell via the platform portion; a lead film, the lead film is arranged between the electrode lead and the shell; a gas guide portion, the gas guide portion is arranged between the electrode lead and the lead film; and a reinforcement film, the reinforcement film is arranged on the lead film.

[0043] In addition, in a pouch-type secondary battery, the platform portion is provided with a sealing portion by sealing a portion of the width of the platform portion along a periphery of the accommodating portion, the gas guide portion includes a permeable portion provided on the outside of the sealing portion and at least one gas channel provided so that the permeable portion and the inner portion of the outer shell are connected via the sealing portion, and the reinforcing film covers the entire surface of the permeable portion of the gas guide portion, has a single-layer structure with a thickness of 60 μm to 150 μm, and includes a modified polyolefin-based resin.

[0044] First, each component of the pouch-type secondary battery is briefly described with reference to the accompanying drawings.

[0045] Figure 1 is an exploded view of the pouch-type secondary battery 100, and Figure 2 is a cross-sectional view of a sealed pouch-type secondary battery 100. Figure 2 In the figure, some components of the pouch-type secondary battery 100 are not provided for ease of understanding. Figure 1 and Figure 2 As shown in , a pouch-type secondary battery 100 includes a case 110 , an electrode assembly 160 , an electrode lead 180 , a lead film 190 , a gas guide portion 200 , and a reinforcement film 300 .

[0046] (1) Housing

[0047] In one aspect, the housing 110 can house the electrode assembly 160. The housing 110 can be manufactured by molding a bag film laminate. In this case, the bag film laminate can include a base layer, a gas barrier layer, and a sealant layer. In the bag film laminate, the base layer, the gas barrier layer, and the sealant layer can be stacked in sequence.

[0048] The base layer is formed on the outermost layer of the pouch film laminate to protect the secondary battery from external friction and impact. The base layer is made of a polymer and can thus electrically insulate the electrode assembly from the outside.

[0049] The base layer can be made of at least one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic acid-based polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Preferably, the base layer can be made of polyethylene terephthalate (PET), nylon, or a combination thereof having wear resistance and heat resistance.

[0050] The base layer may have a single film structure made of any one material. Alternatively, the base layer may have a composite film structure in which two or more materials are respectively formed into layers.

[0051] The base layer may have a thickness of 5 μm to 50 μm, particularly 7 μm to 40 μm, more particularly 25 μm to 38 μm. When the thickness of the base layer satisfies the above range, external insulation is excellent, and the entire bag is not thick, and therefore, the energy density to volume ratio of the secondary battery can be excellent.

[0052] The gas barrier layer is stacked between the base layer and the sealant layer to ensure mechanical strength of the pouch, block entry and exit of gas or moisture outside the secondary battery, and prevent leakage of the electrolyte from the inside of the case.

[0053] The gas barrier layer can be formed of a metal, and specifically, can be formed of an aluminum alloy film. When the gas barrier layer is formed using an aluminum alloy film, the gas barrier layer can have a mechanical strength above a predetermined level and be lightweight, and can complement the electrochemical performance caused by the electrode assembly and the electrolyte and achieve heat dissipation. The aluminum alloy film may include a metal element other than aluminum (Al), for example, it may include at least one selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0054] The gas barrier layer may have a thickness of 40 to 100 μm, particularly 50 to 90 μm, and more particularly 55 to 85 μm. When the thickness of the gas barrier layer satisfies the above range, moldability and gas barrier properties are excellent when the cup-shaped portion is molded.

[0055] When the outer shell containing the electrode assembly is sealed so that the interior of the outer shell is completely sealed, the sealant layer is thermally bonded together at the sealed portion. For this purpose, the sealant layer may be formed of a material having excellent heat sealing strength.

[0056] The sealant layer can be formed of a material having insulation, corrosion resistance and sealing properties. Specifically, the sealant layer is in direct contact with the electrode assembly and / or the electrolyte inside the housing, and therefore can be formed of a material having insulation and corrosion resistance. In addition, the sealant layer should completely seal the interior of the housing and prevent material movement between the interior and the exterior, and therefore can be formed of a material with high sealing properties (e.g., excellent heat sealing strength). In order to ensure such insulation, corrosion resistance and sealing properties, the sealant layer can be formed of a polymer material.

[0057] The sealant layer may be made of at least one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aromatic polyamide, nylon, polyester, polyphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber, and may preferably be formed of a polyolefin-based resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be provided with cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0058] The sealant layer may have a thickness of 30 to 130 μm, particularly 50 to 120 μm, and more particularly 70 to 100 μm. When the thickness of the sealant layer satisfies the above range, both the sealing strength of the sealed portion and the formability of the bag film laminate are ensured.

[0059] The pouch film laminate may be drawn, molded, or stretched by a punching machine, etc. to manufacture the housing 110. Therefore, the housing 110 may include a cup-shaped portion 122 and a receiving portion 124. The receiving portion 124 is a place for storing the electrode assembly and may indicate a receiving space formed in a pocket shape inside the cup-shaped portion 122 when the cup-shaped portion 122 is formed.

[0060] In one aspect, the housing 110 may include Figure 1 The first case 120 and the second case 130 are shown in FIG. The first case 120 may include a receiving portion 124 capable of receiving the electrode assembly 160, and the second case 130 may cover the receiving portion 124 from above to prevent the electrode assembly 160 from being separated from the outside of the battery case 110. The first case 120 and the second case 130 may be as shown in FIG. Figure 1As shown in FIG, one side of the first box 120 and one side of the second box 130 may be manufactured in a manner of being connected to each other, but embodiments of the present invention are not limited thereto, and the first box 120 and the second box 130 may be manufactured differently, for example, individually by being separated from each other.

[0061] On the other hand, when the cup-shaped portion is formed in the bag film laminate, two symmetrical cup-shaped portions 122 and 132 can be drawn and molded adjacent to each other in one bag film laminate. In this case, the cup-shaped portions 122 and 132 can be formed in the first box 120 and the second box 130, respectively, as shown in FIG. Figure 1 As shown in . After the electrode assembly 160 is accommodated in the accommodating portion 124 provided in the cup-shaped portion 122 of the first box 120, the bridging portion 140 formed between the two cup-shaped portions 122 and 132 can be folded out so that the two cup-shaped portions 122 and 132 face each other. In this case, the cup-shaped portion 132 of the second box 130 can accommodate the electrode assembly 160 from above. Therefore, the two cup-shaped portions 122 and 132 accommodate one electrode assembly 160, and therefore can accommodate a thicker electrode assembly 160 than when there is only one cup-shaped portion 122. In addition, an edge of the secondary battery 100 is formed by folding the outer shell 110, and therefore, when the sealing process is performed later, the number of edges to be sealed can be reduced. Therefore, the processing speed of the pouch-type secondary battery 100 can be increased, and the number of sealing processes can be reduced.

[0062] The housing 110 can be sealed while accommodating the electrode assembly 160 so that a portion of the electrode lead 180, that is, the terminal portion, is exposed. Specifically, when the electrode lead 180 is connected to the electrode tab 170 of the electrode assembly 160 and the lead film 190 is formed on a portion of the electrode lead 180, the electrode assembly 160 can be accommodated in the accommodating portion 124 provided in the cup-shaped portion 122 of the first cartridge 120, and the second cartridge 130 can cover the accommodating portion 124 from above. Then, the electrolyte is injected into the accommodating portion 124, and a portion of the platform portion 150 formed along the periphery of the first cartridge 120 and the second cartridge 130 can be sealed to form a sealing portion (not shown).

[0063] The sealing portion may be used to seal the receiving portion 124. Specifically, the sealing portion may seal the receiving portion 124 by being formed on a platform portion 150 formed along a circumference of the receiving portion 124.

[0064] The temperature at which the sealing portion is sealed may be 180 to 250° C., particularly 200 to 250° C., and more particularly 210 to 240° C. When the sealing temperature satisfies the above numerical range, the housing 110 may ensure sufficient sealing strength through thermal bonding.

[0065] (2) Electrode assembly

[0066] In one aspect, the electrode assembly 160 may be inserted into the case 110 and sealed by the case 110 after electrolyte injection.

[0067] The positive electrode, the separator, and the negative electrode may be sequentially stacked to form the electrode assembly 160. Specifically, the electrode assembly 160 may include two types of electrodes, ie, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate the electrodes from each other.

[0068] The positive and negative electrodes can have a structure in which active material slurries are applied to electrode current collectors in the form of metal foil or metal mesh including aluminum and copper, respectively. Typically, particulate active material, auxiliary conductor, binder, and conductive material are stirred with an added solvent to form a slurry. The solvent can be removed in subsequent processing.

[0069] A slurry mixed with an electrode active material, a binder, and / or a conductive material is applied to a positive electrode collector and a negative electrode collector to manufacture a positive electrode and a negative electrode, and the positive electrode and the negative electrode are stacked on both sides of a separator, and thus, the electrode assembly 160 can be manufactured into a predetermined shape. Types of the electrode assembly 160 may include a stacking type, a winding type, and a stacked folding type, but are not limited thereto.

[0070] The electrode assembly 160 may include an electrode tab 170 .

[0071] The electrode tab 170 is connected to each of the positive electrode and the negative electrode of the electrode assembly 160 and protrudes outward from the electrode assembly 160, and thus can serve as a path for electrons to move between the inside and the outside of the electrode assembly 160. The electrode current collector included in the electrode assembly 160 can be provided with a portion where an electrode active material is applied and an end portion where the electrode active material is not applied, that is, an uncoated portion. The electrode tab 170 can be formed by cutting the uncoated portion, or by connecting a separate conductive member to the uncoated portion by ultrasonic welding or the like. Figure 1 As shown in FIG, the electrode tabs 170 may protrude from the electrode assembly 160 in different directions, but are not limited thereto and may be formed to protrude in various directions, such as protruding side by side in the same direction from one side.

[0072] (3) Electrode leads

[0073] In one aspect, the electrode lead 180 may supply power 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.

[0074] The electrode lead 180 may be connected to the electrode assembly 160 and may protrude to the outside of the housing 110 via the sealing portion 150. Specifically, one end of the electrode lead 180 may be connected to the electrode assembly 160, in particular, the electrode tab 170, and the other end of the electrode lead 180 may protrude to the outside of the housing 110 via the platform portion 150.

[0075] The electrode lead 180 may include a positive lead 182 and a negative lead 184, wherein the positive lead 182 has one end connected to the positive electrode tab 172 and extends in the direction in which the positive electrode tab 172 protrudes, and the negative lead 184 has one end connected to the negative electrode tab 174 and extends in the direction in which the negative electrode tab 174 protrudes. The other ends of the positive lead 182 and the negative lead 184 may protrude to the outside of the battery case 110. Therefore, the electricity generated inside the electrode assembly 160 can be supplied to the outside. In addition, the positive electrode tab 172 and the negative electrode tab 174 are each formed to protrude in various directions, and therefore, the positive lead 182 and the negative lead 184 may also extend in various directions. The positive lead 182 and the negative lead 184 may be made of different materials from each other. 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) or nickel (Ni)-coated copper material as the negative electrode current collector. The portion of the electrode lead 180 protruding to the outside of the battery case 110 may serve as a terminal portion and be electrically connected to an external terminal.

[0076] The side of the electrode lead 180 that is in direct contact with the lead film 190 and / or the gas guide portion 200 may be coated with at least one 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 solution and adhesion to the lead film 190 and / or the gas guide portion 200 can be ensured.

[0077] (4) Lead film

[0078] On the one hand, the lead film 190 can prevent the electricity generated by the electrode assembly 160 from flowing to the battery case 110 through the electrode lead 180, and allows the battery case 110 to be sealed. For this purpose, the lead film 190 can be formed of a non-conductor having a non-conductive property, and electricity cannot flow well in a non-conductor. Generally, with respect to the lead film 190, a relatively thin insulating tape that is easily attached to the electrode lead 180 and / or the gas guide portion 200 is widely used, but the embodiments of the present invention are not limited thereto, and therefore any member capable of insulating the electrode lead 180 can be used.

[0079] Lead film 190 may be provided to surround the outer peripheral surface of electrode lead 180 and gas guide portion 200. Specifically, electrode lead 180 and gas guide portion 200 are in contact with each other on one side, and in this case, at least a portion of electrode lead 180 and gas guide portion 200 may be surrounded by lead film 190. Lead film 190 may be positioned to be confined within sealing portion 150 to which first case 120 and second case 130 of outer case 110 are thermally fused, and may allow electrode lead 180 and gas guide portion 200 to adhere to battery case 110.

[0080] The lead film 190 may be provided between the electrode lead 180 and / or the gas guide portion 200 and the housing 110. For example, Figure 2 As shown in FIG, the lower case 110, the lead film 190, the electrode lead 180, the gas guide portion 200, the lead film 190, and the upper case 110 may be stacked and disposed in this order in the platform portion 150.

[0081] Meanwhile, the lead film 190 may include at least one layer. Specifically, the lead film 190 may include a metal adhesive layer, a core layer, and a bag adhesive layer stacked sequentially.

[0082] The metal adhesive layer is in direct contact with the electrode lead 180 and can be used 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 a modified polyolefin-based resin, such as an acid-modified polyolefin. For example, the metal adhesive layer may include at least one of acid-modified polypropylene (PPa), acid-modified polyethylene (PEa) and plasma-treated polypropylene (PP), but is not limited thereto. The metal adhesive layer may have a thickness of 50 μm to 80 μm, particularly 50 μm to 75 μm, and more particularly 60 μm to 75 μm. When the thickness of the metal adhesive layer meets the above numerical range, there is an effect that during fusion between the electrode lead and the lead film, penetration holes and leakage at the edge portion are prevented.

[0083] Acid-modified polyolefin refers to a polyolefin resin modified by acid grafting. For example, the acid-modified polyolefin can be obtained by reacting an unsaturated carboxylic acid with a polyolefin resin to introduce a carboxyl group (graft modification). In this case, the unsaturated carboxylic acid may include the concept of a carboxylic anhydride, and the carboxyl group may include the concept of a carboxylic anhydride group. The unsaturated carboxylic acid reacted with the polyolefin resin may include at least one 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, nadic anhydride and tetrahydrophthalic anhydride, but is not limited thereto.

[0084] The core layer may be a layer disposed at the center of the lead film 190. The core layer may include an unmodified polyolefin-based resin, and may, for example, include additives such as polypropylene resin, polyolefin elastomer (POE) and / or a colorant, but is not limited thereto. Among them, the core layer may include, for example, a polypropylene homopolymer. When the polypropylene homopolymer is included in the core layer, the melting point of the core layer can be controlled within the above numerical range, and deformation caused by heat can be minimized, which helps to better ensure insulation. The core layer may have a thickness of 40 μm to 70 μm, particularly 50 μm to 70 μm, and more particularly 60 μm to 70 μm. When the thickness of the core layer meets the above numerical range, deformation caused by the heat applied during fusion and sealing can be prevented to bring about a robust design effect in ensuring insulation.

[0085] The bag adhesive layer can be a layer that is in direct contact with the battery case 110, in particular the sealant layer of the bag film laminate. The bag adhesive layer may include an unmodified polyolefin-based resin, and may, for example, include additives such as polypropylene resin and polyolefin elastomer (POE), but is not limited thereto. Among them, the bag adhesive layer may include a polypropylene copolymer, such as a polypropylene random copolymer or a polypropylene block copolymer. The melting point of the bag adhesive layer including the above-mentioned copolymer can be controlled within the above-mentioned numerical range, and the bag adhesive layer has a melting point similar to that of the polymer in the sealant layer of the bag film laminate, which helps to better ensure the sealing processability. The bag adhesive layer may have a thickness of 40 μm to 100 μm, in particular 40 μm to 80 μm, and more particularly 40 μm to 60 μm. When the thickness of the bag adhesive layer meets the above numerical range, there is an effect of ensuring that the residual rate of the polymer (e.g., polypropylene) is sufficient to obtain the sealing strength between the electrode lead and the bag film laminate.

[0086] (5) Gas guide part

[0087] In one aspect, the gas guide portion 200 is configured to discharge gas from the interior of the housing 110 to the outside, and may include a permeable portion 230 disposed outside the housing 110 and at least one gas channel 240 extending from the permeable portion 230 toward the electrode assembly 160 via the sealing portion.

[0088] like Figure 2 As shown in , the gas guide portion 200 of the present invention may be provided between the electrode lead 180 and the lead film 190. In this case, in the region between the electrode lead 180 and the lead film 190 where the gas guide portion 200 is provided, the electrode lead 180 and the lead film 190 may not be in direct contact, whereas in the region where the gas guide portion 200 is not provided, the electrode lead 180 and the lead film 190 may be in direct contact.

[0089] In the following, reference will be made to Figure 3 and Figure 4 The gas guide portion 200 of the present invention will be described in more detail. Figure 3 is a cross-sectional view of a pouch-type secondary battery before the interface between the gas guide portion 200 and the lead film 190 is opened, and Figure 4 is a cross-sectional view of the pouch-type secondary battery after the interface between the gas guide portion 200 and the lead film 190 is opened.

[0090] like Figure 3 and Figure 4 As shown in FIG, the interface between gas guide portion 200 and lead film 190 may be normally closed, and when the pressure inside housing 110 increases, the interface between gas guide portion 200 and lead film 190 is opened along gas channel 240, thereby forming gas discharge path 250. Gas inside housing 110 may move along gas discharge path 250 on gas channel 240 to permeable portion 230, and in this case, an air pocket is formed on permeable portion 230, and thus the gas may pass through lead film 190 and be discharged to the outside of housing 110. As a result, the pressure inside housing 110 may be reduced to prevent the secondary battery from exploding or igniting.

[0091] like Figure 3 and Figure 4 As shown in FIG, gas guide portion 200 includes an adhesive resin layer 210 in contact with electrode lead 180 and a permeable resin layer 220 disposed on adhesive resin layer 210. Adhesive resin layer 210 is in contact with electrode lead 180 and may serve to adhere gas guide portion 200 to electrode lead 180.

[0092] On the one hand, as Figure 3, the adhesive resin layer 210 of the gas guide portion 200 may be formed so that the end portion in the outward direction E of the housing is longer than the permeable resin layer 220. Therefore, a structure in which the adhesive resin layer 210 directly contacts the lead film 190 at the end portion in the outward direction E of the gas guide portion 200 may be formed.

[0093] Separately, the end portion of the lead film 190 protruding in the outward direction E of the housing protrudes further in the outward direction E than the end portion of the adhesive resin layer 210 in the same direction and thus may be disposed to directly contact the electrode lead 180 .

[0094] In addition, separately, the end portion of the lead film 190 protruding in the outward direction E of the housing may be provided to protrude further in the outward direction E than the end portion of the permeable resin layer 220 in the same direction.

[0095] When the adhesive resin layer 210 is formed to protrude further in the outward direction E of the outer shell than the permeable resin layer 220, or when the lead film 190 is formed to protrude further in the outward direction of the outer shell than one end of the permeable resin layer 220 and / or the adhesive resin layer 210, the bonding strength between the electrode lead 180 and the gas guide portion 200 and between the electrode lead 180 and the lead film 190 can be excellent, and thus durability degradation caused by an increase in internal pressure can be prevented, and the area of ​​the permeable portion 230 on the permeable resin layer 220 can be easily ensured, thereby allowing stable gas discharge.

[0096] On the other hand, Figure 5 , lead film 190 is formed so that one end portion protruding in the outward direction E of the box further protrudes than the end portion of gas guide portion 200 in the outward direction E of the box, and thus can be provided to directly contact electrode lead 180. Separately, the ends of the two layers of gas guide portion 200 in the outward direction E can be formed to overlap.

[0097] On the other hand, Figure 6 , the adhesive resin layer 210 may be formed so that one end portion protruding in the outward direction E of the cartridge further protrudes than an end portion of the permeable resin layer 220 in the outward direction E, and the end portion of the adhesive resin layer 210 in the outward direction E may coincide with an end portion of the lead film 190 in the outward direction E. In this case, the lead film 190 may have a structure in which the lead film 190 contacts the adhesive resin layer 210 instead of directly contacting the electrode lead 180.

[0098] In terms of ensuring durability and the area of ​​the permeable portion 230, as Figure 3 、 Figure 5 or Figure 6The case where the arrangement structure of the lead film 190, the electrode lead 180, and the gas guide portion 200 is formed is more advantageous than the case where the lead film 190 is not provided so that one end protrudes further outward from the housing 110 than the gas guide portion 200, but is provided on the permeable resin layer 220 of the gas guide portion 200. Most preferably, the arrangement may be as follows Figure 3 Same as in Figure 5 or Figure 6 The structure of may also be applicable depending on the situation, and either structure may be optionally applied.

[0099] Adhesive resin layer 210 may include any material that easily adheres to electrode lead 180. For example, adhesive resin layer 210 may include a modified polyolefin-based resin, and may include at least one of an acid-modified polyolefin or a silane-modified polyolefin. When adhesive resin layer 210 includes a modified polyolefin-based resin, the adhesive strength between gas guide portion 200 and electrode lead 180 is improved. As a result, even when the pouch-type secondary battery is stored in a high-temperature environment, gas guide portion 220 may be prevented from detaching from electrode lead 180 and being pushed out of the pouch, or electrolyte leakage within the pouch may be prevented.

[0100] Acid-modified polyolefin refers to a polyolefin resin modified by acid grafting. For example, the acid-modified polyolefin can be obtained by reacting an unsaturated carboxylic acid with a polyolefin resin to introduce a carboxyl group (graft modification). In this case, the unsaturated carboxylic acid can include the concept of a carboxylic anhydride, and the carboxyl group can include the concept of a carboxylic anhydride group. The unsaturated carboxylic acid reacted with the polyolefin resin can include at least one 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, nadic anhydride and tetrahydrophthalic acid, but is not limited thereto. In particular, the application of maleic anhydride is preferred to improve the adhesion between the gas guide portion 200 and the electrode lead 180. The acid-modified polyolefin can include at least one selected from the group consisting of acid-modified polypropylene (PPa) and acid-modified polyethylene (PEa), but is not limited thereto.

[0101] 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 as a main chain. The silane-modified polyolefin-based resin may include at least one selected from the group consisting of a silane-modified polypropylene resin and a silane-modified ethylene-vinyl acetate copolymer, but is not limited thereto.

[0102] The adhesive resin layer 210 may be subjected to a modification process, and examples of the modification process include ion implantation, plasma treatment, irradiation treatment, heat treatment, and the like, and preferably a process that changes the bond structure of the polymer layer. These modification processes may be performed individually or in combination of two or more types. The modified adhesive resin layer 210 may include plasma-treated polypropylene (PP), but is not limited thereto.

[0103] The adhesive resin layer 210 may have a thickness of 5 μm to 130 μm, particularly 30 μm to 120 μm, and more particularly 30 μm to 80 μm. When the thickness of the adhesive resin layer 210 satisfies the above numerical range, the adhesive resin layer 210 melts within a specified production time (takt time), and thus, the gas guide portion 200 and the electrode lead 180 can be easily fused.

[0104] The permeable resin layer 220 may be a layer in contact with the lead film 190. The permeable resin layer 220 may include at least one of polytetrafluoroethylene (PTFE) or polyimide (PI). The permeable resin layer 220 is preferable because it does not have high adhesion to the lead film 190, and therefore, even when the relevant portion is sealed, when the pressure inside the box 110 increases, the interface with the lead film 190 may be opened, and thus, a gas exhaust path 250 may be formed.

[0105] The thickness of the permeable resin layer 220 may be 40 μm to 100 μm, more particularly 40 μm to 90 μm, and more particularly 45 μm to 75 μm. When the thickness of the permeable resin layer 220 satisfies the above range, the permeable resin layer 220 does not melt during the sealing process, and when the pressure inside the cartridge 110 increases, the interface between the permeable resin layer 220 and the lead film 190 may be opened to form the gas exhaust path 250.

[0106] At the same time, the ratio (D1 / D2) of the thickness (D1) of the adhesive resin layer to the thickness (D2) of the permeable resin layer 220 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, after the pressure inside the cartridge 110 increases, the interface between the permeable resin layer 220 and the lead film 190 is lifted to form a gas discharge path, and the adhesive strength between the gas guide portion 200 and the electrode lead 180 may also be improved.

[0107] The permeable resin layer 220 and the adhesive resin layer 210 may be laminated by thermal compression and may be combined after forming an adhesive layer between the permeable resin layer 220 and the adhesive resin layer 210, or may be combined after removing a release film in a tape form having an adhesive applied to one side of the permeable resin layer 220 or the adhesive resin layer 210 and a release film attached to the adhesive. The method of laminating the permeable resin layer 220 and the adhesive resin layer 210 is not particularly limited, and any method other than the above method may be applied as long as the two layers can be well adhered to each other.

[0108] (6) Enhanced membrane

[0109] In one aspect, the reinforcement film 300 is disposed on the lead film 190 to cover at least a portion of the permeable portion 230 of the gas guide portion 200 , thereby preventing whitening and electrolyte leakage.

[0110] The pouch-type secondary battery 100 has a series of mechanisms in which, as the internal pressure increases, the interface between the gas guide portion 200 and the lead film 190 is opened, and only in the portion where the gas guide portion 200 is provided, the laminate including the lead film 190 and the outer shell 110 thereon is lifted upward, thereby forming a gas discharge path 250, and via the formed gas discharge path, the internal gas is discharged to the outside through the lead film 190 passing through the permeable portion 230.

[0111] When this gas discharge mechanism is repeated, the lead film 190 located on the gas permeable portion, that is, the permeable portion 230 of the gas guide portion 200, is continuously subjected to a tensile force, and as the internal pressure increases, the tensile force applied to the lead film 190 increases, causing whitening of the corresponding portion. The whitening phenomenon may occur in a portion where the molecular structure inside the film is deformed due to the continuous stretching of the lead film 190, the internal stress increases due to the deformation, and the bonding force between molecules is correspondingly reduced.

[0112] At the same time, when the gas is discharged and the internal pressure is reduced again, that is, when a series of charge / discharge reactions are completed and the internal gas is completely discharged while being stored, the possibility of electrolyte leakage to the outside is minimized only when the lifted lead film 190 returns to its original state and the gas discharge path 250 is accordingly closed again. However, as described above, a portion where the bonding force between molecules is reduced is generated inside the lead film 190, and the electrolyte may penetrate through this portion, which may manifest as a phenomenon of electrolyte leakage in the permeable portion 230 of the gas guide portion 200 on the lead film 190, or in severe cases, may cause leakage, and after the electrolyte leakage or leakage occurs once, the possibility of moisture penetration from the outside also increases. In addition, when the above phenomenon is repeated, the electrode lead 180 may be corroded, and the increase in internal pressure may cause degassing around the portion of the lead film 190 where the bonding force is reduced.

[0113] Therefore, on one hand, the inventors of the present invention have attempted to overcome the above-mentioned limitations by introducing a reinforcement film 300 on the permeable portion 230 of the gas guide portion 200, i.e., the area where gas permeates to the lead film 190 of the pouch-type secondary battery 100, and this can achieve durability by suppressing the deterioration of the gas guide portion 200 and the lead film 190 caused by continuous gas discharge.

[0114] On the one hand, the reinforced membrane 300 has a single-layer structure. Due to this structure, after sealing, even when sealing is performed under optimal conditions, delamination between layers within the membrane itself having a multi-layer structure can be fundamentally eliminated, and since the operating pressure and gas discharge rate do not deteriorate significantly, the expected gas discharge performance can also be maintained.

[0115] In one aspect, the thickness of the reinforcement film 300 may be 60 μm to 150 μm, preferably 70 μm or more, 75 μm or more, 80 μm or more, 85 μm or more, 90 μm or more, or 95 μm or more, and may also be 140 μm or less, 130 μm or less, 120 μm or less, or 115 μm or less. When the thickness is designed to be within the range of 60 μm to 150 μm, it is expected that the effects of preventing whitening and improving supply and demand stability or unit price competitiveness by improving film forming processability can be achieved.

[0116] Reference Figure 3 and Figure 4, the gas guide portion 200 is provided on the electrode lead 180, the lead film 190 is provided on the gas guide portion 200, and the reinforcement film 300 is provided on the lead film 190, and can cover at least a portion of the permeable portion 230 of the gas guide portion 200, and preferably, can cover the entire surface of the permeable portion 230. It is possible that when the reinforcement film 300 covers the entire surface of the permeable portion 230, the gas discharge rate may be relatively slow compared to when the reinforcement film 300 covers a portion of the permeable portion 230, but considering that significant improvements in preventing whitening and improving durability can compensate for the deterioration of gas discharge performance, this design can be applied with appropriate modifications according to the application of the secondary battery.

[0117] In the reinforcement membrane 300, the area about the outer circumference of the reinforcement membrane 300 may be 100% to 500% of the area of ​​the permeable portion 230 of the gas guide portion 200. That is, the reinforcement membrane 300 may be provided to cover at least the entire area of ​​the permeable portion 230, and may be provided to cover at most the area (S) of the permeable portion 230. A ). Designing the reinforcement membrane 300 to cover the entire permeable portion 230 does not pose a particular problem, but it may not be advantageous in terms of design considerations such as the sealing process and the thickness of the sealed platform portion. Therefore, it may be desirable to design it to meet the above range. In addition, to effectively suppress electrolyte leakage and prevent whitening caused by stretching, it is desirable to design the area of ​​the reinforcement membrane 300 to be at least 110%, at least 130%, or at least 150% of the area of ​​the permeable portion 230.

[0118] When designing the area in which the reinforcement membrane 300 covers the permeable portion 230 , a reinforcement membrane portion larger than the area of ​​the permeable portion 230 may also be provided to cover a portion of the gas channel 240 .

[0119] That is, since the tensile force applied to the lead film 190 at the portion where the permeable portion 230 of the gas guide portion 200 and the gas channel 240 meet is relatively large, in order to effectively prevent electrolyte leakage and whitening caused by stretching, when the reinforcement film 300 is designed to be larger than the area of ​​the permeable portion 230 of the gas guide portion 200, it may be desirable to design the reinforcement film 300 to be wide in the width direction of the electrode lead 180 and long in the length direction of the electrode lead 180, and preferably, the reinforcement film 300 may be configured to cover both the permeable portion 230 and the gas channel 240.

[0120] In one aspect, reinforcement film 300 includes an insertion portion 301 that occupies a portion of the width of sealing portion 151. Insertion portion 301 may refer to a region where one end of reinforcement film 300 extends inwardly (I) of the housing and is inserted between the housing of sealing portion 151 and the lead film. In this case, the sealing strength can be improved, and thus, even when the interface between lead film 190 and gas guide portion 200 is repeatedly opened, the sealing strength can be maintained, thereby improving durability and preventing accidental gas discharge.

[0121] The sealing width (W) of the inserting portion 301 of the reinforcement film 300 relative to the sealing portion 151 S ) can have a length ratio of 0.05 to 0.90. When the insertion portion 301 is formed so that the above length ratio meets the corresponding range, it can be expected that the sealing strength can be ensured to be at a level that does not damage the workability of the sealing process. That is, when the reinforcement film 300 is deeply inserted into the sealing width so that the insertion portion 301 covers the entire part of the sealing portion 151, peeling may occur at the interface between the reinforcement films 300 with a multilayer structure. Therefore, by ensuring that the end of the reinforcement film 300 in the inward direction I of the shell only covers a part of the sealing width so that the reinforcement film 300 is covered by the sealing portion 151, peeling of the interface as described above can also be prevented. In order to further achieve this effect, preferably, the length ratio can be 0.07 or greater, 0.09 or greater, 0.10 or greater or 0.11 or greater, and can also be 0.85 or less, 0.83 or less, 0.80 or less, 0.79 or less or 0.78 or less.

[0122] In one aspect, the reinforcement film 300 may include a modified polyolefin-based resin. Preferably, the reinforcement film 300 contacts the lead film 190 at the lower portion and contacts the housing 110 at the upper portion, and thus preferably has similarity to the materials of the films in contact with the upper and lower portions, and is preferably applied in consideration of thermal properties that play a major role in the sealing process, and therefore, a modified polyolefin-based resin is suitable.

[0123] In the case of including a modified polyolefin-based resin, it is expected that a strong adhesive strength with the lead film and the housing can be achieved. The modified polyolefin-based resin can be an acid-modified polyolefin or a plasma-treated polyolefin, and can include, for example, at least one of acid-modified polypropylene (PPa), acid-modified polyethylene (PEa) or plasma-treated polypropylene. Acid-modified polyolefin refers to a polyolefin resin modified by acid grafting. For example, acid-modified polyolefin can be obtained by reacting an unsaturated carboxylic acid with a polyolefin resin to introduce a carboxyl group (graft modification). The unsaturated carboxylic acid reacted with the polyolefin resin can include at least one 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, nadic anhydride and tetrahydrophthalic anhydride, but is not limited thereto. In particular, maleic anhydride is preferably applied to improve adhesion between the gas discharge portion 200 and the electrode lead 180 .

[0124] The reinforcement film 300 may include a modified polyolefin-based resin and, in some cases, may also include an unmodified polyolefin-based resin. The unmodified polyolefin-based resin may also include, for example, a polypropylene copolymer, such as a polypropylene random copolymer or a polypropylene block copolymer. In addition, the unmodified polyolefin-based resin may be a cast polyolefin, and the cast polyolefin-based resin is manufactured by a casting method, is not stretched in a specific direction during the manufacturing or processing process, and is more flexible than a stretched polyolefin-based resin, does not have the problem of tearing in a specific direction, and may be relatively easy to process. When the unmodified polyolefin-based resin is included in the reinforcement film, it may be desirable to achieve a stronger sealing strength during sealing, and in terms of gas permeation, it is expected that the resistance at the interface with the lead film 190 can be minimized, thereby preferably solving the deterioration of gas emission performance.

[0125] In one aspect, the reinforcement film 300 may have a tensile strength of 3.5 MPa to 5.5 MPa at 60°C. In this context, the tensile strength is the maximum value of the force applied when a 15 mm wide and 90 mm long specimen cut from the reinforcement film is inserted into a jig 20 mm apart at each end using a UTM, and then stretched 20 mm at 60°C at a rate of 1 mm / min. The tensile strength of the reinforcement film may vary depending on the layer structure, the material of each layer, the thickness of each layer, and the like. A person skilled in the art can easily prepare or obtain a reinforcement film 300 having a specific tensile strength.

[0126] The tensile strength of the reinforcement film 300 can preferably be applied to a level that prevents the lead film 190 from being deformed due to the tensile force, thereby suppressing whitening, and blocking the opening of the interface between the lead film 190 and the gas guide part 200 when the gas is discharged, thereby preventing the operating pressure from increasing, and when the above range is met, the above effect is likely to be achieved, and the tensile strength of the reinforcement film 300 can preferably be 3.7 MPa or greater, 3.9 MPa or greater, 4.0 MPa or greater or 4.5 MPa or greater, and can also be 5.4 MPa or less, 5.3 MPa or less, 5.2 MPa or less or 5.0 MPa or less.

[0127] The reinforcing film 300 may have a melting temperature (Tm) of 110°C to 170°C. Controlling the melting temperature range may be preferable because a high temperature may be temporarily applied to the electrode lead portion, such as in a fast charge, and the ease of the sealing process may need to be considered in view of the heat applied during the sealing process. In this regard, the melting temperature of the resin included in the reinforcing film may preferably be 120°C or higher, 130°C or higher, 140°C or higher, and 165°C or lower, 160°C or lower, or 158°C or lower.

[0128] (7) Electrolytes

[0129] The pouch-type secondary battery 100 according to the present invention may further include an electrolyte (not shown) injected into the outer shell 110. The electrolyte is used to move lithium ions generated by the electrochemical reaction of the electrodes when the secondary battery 100 is charged / discharged, 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. In addition, the electrolyte may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a polymer-based solid electrolyte, and such a solid electrolyte may have flexibility and thus be easily deformed under external force.

[0130] battery pack

[0131] In one aspect, a battery pack may include a pouch-type secondary battery. In this case, the secondary battery 3 may be provided in plurality. The battery pack may include an enclosure that internally houses the plurality of pouch-type secondary batteries. The enclosure may be configured to protect the pouch-type secondary batteries from external impact or contamination. Herein, the description of the pouch-type secondary batteries may be omitted as they have already been described above.

[0132] The package may be provided as a box-shaped structure. The package may be made of metal or plastic having a predetermined rigidity. The package may have a structure in which a plurality of plates are combined.

[0133] The shape or structure of the package can be modified as needed. For example, at least a portion of the package can have a curved shape. In addition, the package can be provided with other additional components. For example, the package can be provided with a bus bar electrically connected to multiple secondary batteries and / or a vent component connecting the interior and exterior of the package.

[0134] Hereinafter, the present invention will be described in more detail by way of specific embodiments. However, the following examples are provided for the purpose of understanding the present invention only, and the scope of the inventive concept is not limited thereto. It will be apparent to those skilled in the art that various modifications and alterations may be made within the scope and technical scope of the present invention, and that these modifications and alterations fall within the scope of the claims included herein.

[0135] Examples and Comparisons

[0136] Example 1

[0137] (1) Manufacturing of the housing

[0138] A polyethylene terephthalate (PET) film having a width of 266 mm, a length of 50 m and a thickness of 12 μm and a nylon film having a width of 266 mm, a length of 50 m and a thickness of 25 μm are stacked on one side of an aluminum alloy film having a width of 266 mm, a length of 50 m and a thickness of 60 μm, and a polypropylene film having a width of 266 mm, a length of 50 m and a thickness of 80 μm is stacked on the other side to prepare a bag film laminate having a structure of polyethylene terephthalate / nylon / aluminum alloy film / polypropylene film.

[0139] In this case, the polyethylene terephthalate film and the nylon film are the base layer, the aluminum alloy thin film is the gas barrier layer, and the polypropylene film is the sealant layer.

[0140] The bag film laminate is molded to produce an enclosure including a containment portion and a sealing portion.

[0141] (2) Manufacturing of pouch-type secondary batteries

[0142] The negative electrode, the positive electrode, and the porous polyethylene separator are assembled using a stacking method, and then the negative electrode, the positive electrode, and the porous polyethylene separator are laminated to manufacture an electrode assembly. Thereafter, an electrode lead is connected to the electrode assembly.

[0143] LiPF6 was dissolved in a solvent (EC:EMC:DMC=3:3:4 volume ratio) to 1.0 M to prepare an electrolyte. The electrode assembly was housed in a case with the front end portion of the electrode lead protruding to the outside, and the electrolyte was injected.

[0144] A 43 μm thick acid-modified polypropylene film (adhesive resin layer) and a 50 μm thick polytetrafluoroethylene tape (permeable resin layer) were attached to the upper surface of the electrode lead to form a gas guide portion.

[0145] Then, a 200 μm thick lead film was stacked on each of the lower surface of the electrode lead and the upper surface of the gas guide portion. The lead film may include a 75 μm thick metal adhesive layer containing a polypropylene random copolymer and an acid-modified polypropylene, a 65 μm thick core layer containing a polypropylene homopolymer, and a 60 μm thick bag adhesive layer containing a polypropylene copolymer.

[0146] Finally, the reinforcement film was placed on the upper surface of the lead film where the gas guide portion was formed in such a manner as to be inserted into about 80% of the sealing width in the inward direction of the box and to cover the entire surface of the permeable portion in the outward direction.

[0147] The reinforcement film is made of 93 μm thick acid-modified polypropylene applied to the upper surface of the lead film, has a melting temperature of 143° C., and has a tensile strength of 5.0 MPa at 60° C. In this case, the tensile strength is the maximum value of the force applied when a 15 mm wide and 90 mm long specimen cut from the reinforcement film is inserted into a jig 20 mm at each end using a UTM and then stretched 20 mm at a rate of 1 mm / min at 60° C.

[0148] Thereafter, under the conditions of a sealing bar area of ​​200 mm×10 mm, 220° C., and 0.27 MPa, the sealing portion of the outer case was sealed for 2 seconds and then left at 60° C. for 4 hours to manufacture a pouch type secondary battery.

[0149] Example 2

[0150] A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that a reinforcement film having a melting temperature of 157° C. and a tensile strength of 4.5 MPa at 60° C. was used.

[0151] Comparative Example 1

[0152] A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that the reinforcement film was not formed.

[0153] Comparative Example 2

[0154] A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that a 200 μm lead film (a three-layer structure consisting of a 75 μm thick film containing a polypropylene random copolymer and an acid-modified polypropylene, a 65 μm thick film containing a polypropylene homopolymer, and a 60 μm thick film containing a polypropylene copolymer, Tm: 160°C, and tensile strength: 6.0 MPa at 60°C) was used as a reinforcing film.

[0155] Test Example 1: Measurement of gas discharge rate

[0156] The gas discharge rates of the pouch-type secondary batteries each manufactured in the example and the comparative example were measured.

[0157] Specifically, CO 2 was injected into the pouch-type secondary battery using a pressure device of ITS Corporation to increase the pressure inside the pouch to 1.5 atm, and the amount of gas discharged for 24 hours was measured, and the results are shown in Table 1 below.

[0158] Test Example 2: Measurement of the operating pressure of the gas guide section

[0159] The internal pressure at the start of degassing was measured for each of the pouch-type secondary batteries manufactured in the example and the comparative example.

[0160] Specifically, CO2 was injected into the pouch-type secondary battery using a pressure device from ITS Corporation, the pressure inside the pouch was increased in units of 0.1 atm, the battery was placed at each pressure for 24 hours, and the pressure was measured at the time point when the permeable portion of the gas guide portion was completely deformed (when the interface between the lead film of the permeable portion and the gas guide portion was completely opened), and the results are shown in Table 1 below.

[0161] Test Example 3: Membrane deformation and electrolyte leakage

[0162] For each of the pouch-type secondary batteries manufactured in the examples and comparative examples, the electrolyte was filled with 0.1% by weight of a penetrant (mega-check, MAGNAFLUX). CO₂ (dry ice) was injected into the pouch-type secondary batteries to increase the pressure inside the pouch to 2.0 atm. The batteries were then heated at 60°C for 5 days to inspect for deformation of the lead film at the edges of the gas-inducing section and for electrolyte leakage.

[0163] Test Example 4: Measurement of seal strength

[0164] For each of the pouch-type secondary batteries manufactured in the examples and comparative examples, the seal portion was cut into 15mm intervals, and then the electrode leads were attached to the lower jig of the UTM, and the outer case was attached to the upper jig. The sample was then pulled at a rate of 5mm / min at a 180° angle at room temperature, and the average value of the 8mm section, starting from the point where the seal strength exceeded 4.5kgf / 15mm in the measured seal strength graph, was calculated to determine the low-speed seal strength.

[0165] Table 1

[0166]

[0167] According to Table 1 above, it was confirmed that in Examples 1 and 2, when a film having an appropriate thickness and a high-temperature tensile strength within an appropriate range was applied as a reinforcement film, gas emission started early and at a satisfactory rate, with no issues regarding seal strength. In contrast, it can be seen that Comparative Example 1, which did not apply a reinforcement film, exhibited a rapid emission rate but showed membrane deformation and electrolyte leakage, indicating that commercialization was unsuitable, while Comparative Example 2, which applied a thick film, showed a late start of gas emission and a slow rate, indicating issues with emission performance. Therefore, it was confirmed that when a reinforcement film is applied, applying a reinforcement film having a single-layer structure can achieve excellent performance in terms of gas emission performance and membrane deformation.

[0168] Reference numerals

[0169] 100: Pouch-type secondary battery

[0170] 110: Shell

[0171] 120: First box

[0172] 122: cup-shaped part

[0173] 124: Accommodation

[0174] 130: Second box

[0175] 132: cup-shaped part

[0176] 140: Bridging section

[0177] 150: Platform part

[0178] 151: Sealing part

[0179] 160: Electrode assembly

[0180] 170: Electrode tab

[0181] 172: Positive terminal

[0182] 174: Negative terminal

[0183] 180: Electrode lead

[0184] 182: Positive lead

[0185] 184: Negative lead

[0186] 190: Lead film

[0187] 200: Gas guide part

[0188] 210: Adhesive resin layer

[0189] 220: Permeable resin layer

[0190] 230: Permeable part

[0191] 240: Gas channel

[0192] 250: Gas emission path

[0193] 300: Enhanced film

[0194] 301: Insert part

Claims

1. A pouch-type secondary battery, comprising: electrode assembly; a housing including a receiving portion and a platform portion, the receiving portion being configured to receive the electrode assembly, the platform portion being formed along a periphery of the receiving portion and having a sealing portion in which a portion of a width of the platform portion is sealed; an electrode lead electrically connected to the electrode assembly and projecting outwardly from the housing; a lead film, the lead film being disposed between the electrode lead and the housing; a gas guide portion disposed between the electrode lead and the lead film and comprising a permeable portion disposed outside the sealing portion and at least one gas channel extending from the permeable portion toward the electrode assembly via the sealing portion; as well as a reinforcement film provided on the lead film to cover at least a portion of the permeable portion, Wherein, the reinforcement film has a single-layer structure.

2. The pouch-type secondary battery according to claim 1, wherein The secondary battery is configured such that an interface between the lead film and the gas guide film opens along the gas passage due to an increase in internal pressure of the housing, thereby providing a gas exhaust path.

3. The pouch-type secondary battery according to claim 1, wherein The reinforcement film is provided on the lead film to cover an entire portion of the permeable portion.

4. The pouch-type secondary battery according to claim 1, wherein The reinforcement film includes an insert portion occupying a portion of the width of the sealing portion, and The insertion portion is a region in which one end portion of the reinforcement film extends in an inward direction of the outer case and is inserted between the outer case of the sealing portion and the lead film.

5. The pouch type secondary battery according to claim 1, comprising an insertion portion occupying a portion of a width of the sealing portion, in, The insertion portion is a region in which one end portion of the reinforcement film extends in an inward direction of the outer shell and is inserted between the outer shell of the sealing portion and the lead film, and A ratio of a length of the insertion portion to a width of the sealing portion is in a range of 0.05 to 0.

90.

6. The pouch-type secondary battery according to claim 1, wherein The reinforcement film has a thickness of 60 μm to 150 μm.

7. The pouch-type secondary battery according to claim 1, wherein The reinforcement film includes a resin having a melting temperature (Tm) of 110°C to 170°C.

8. The pouch-type secondary battery according to claim 1, wherein The reinforced film has a tensile strength of 3.5 MPa to 5.5 MPa at 60°C.

9. The pouch-type secondary battery according to claim 1, wherein The reinforcement film includes a modified polyolefin-based resin.

10. The pouch-type secondary battery according to claim 1, wherein The reinforcement film includes a modified polyolefin-based resin, and The modified polyolefin-based resin includes at least one selected from the group consisting of acid-modified polypropylene and acid-modified polyethylene.

11. The pouch-type secondary battery according to claim 1, wherein The gas guide portion includes an adhesive resin layer in contact with the electrode lead and a permeable resin layer in contact with the lead film.

12. The pouch-type secondary battery according to claim 11, wherein In the adhesive resin layer, One end portion protruding in an outward direction of the outer shell protrudes further than one end portion of the permeable resin layer protruding in the outward direction of the outer shell.

13. The pouch-type secondary battery according to claim 11, wherein In the lead film, One end portion protruding in an outward direction of the outer shell protrudes further than one end portion of the permeable resin layer protruding in the outward direction of the outer shell.

14. A battery pack comprising: a plurality of pouch-type secondary batteries; as well as a package for accommodating the secondary battery, Wherein, the pouch-type secondary battery comprises: electrode assembly; a housing including a receiving portion and a platform portion, the receiving portion being configured to receive the electrode assembly, the platform portion being formed along a periphery of the receiving portion and having a sealing portion in which a portion of a width of the platform portion is sealed; an electrode lead electrically connected to the electrode assembly and projecting outwardly from the housing; a lead film, the lead film being disposed between the electrode lead and the housing; a gas guide portion provided between the electrode lead and the lead film and including a permeable portion provided outside the sealing portion and at least one gas channel extending from the permeable portion toward the electrode assembly via the sealing portion; and a reinforcement film provided on the lead film to cover at least a portion of the permeable portion, and The reinforcement film has a single-layer structure.

Images