Soft package type secondary battery

Abstract

A pouch-type secondary battery according to the present disclosure comprises: an electrode assembly; a pouch-type case including an accommodating portion that accommodates the electrode assembly and a sealing portion that seals the accommodating portion; an electrode lead connected to the electrode assembly and protruding to the outside of the pouch-type case via the sealing portion; a lead film provided between the electrode lead and the pouch case; and a gas guide portion provided between the electrode lead and the lead film, in which the gas guide portion includes: a first layer in contact with the electrode lead; and a second layer disposed on the first layer, and the first layer including a modified polyolefin resin.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application Nos. 10 - 2022 - 0159794, filed on November 24, 2022, 10 - 2022 - 0175297, filed on December 14, 2022, and 10 - 2023 - 0164467, filed on November 23, 2023, with the Korean Intellectual Property Office, the entire disclosures of the foregoing Korean patent applications being incorporated herein by reference in their entireties.

[0004] The present disclosure relates to a pouch - type secondary battery, and more particularly, to a pouch - type secondary battery including a gas guiding part. Background Art

[0005] Secondary batteries are used in various categories, including: small products such as digital cameras, P - DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and electric bicycles, and large products that require 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.

[0006] A secondary battery can be manufactured by accommodating an electrode assembly in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are alternately laminated in a battery case, injecting an electrolyte, and then sealing the battery case. Secondary batteries are classified into pouch - type secondary batteries and can - type secondary batteries according to the material of the case accommodating the electrode assembly. In particular, a pouch - type battery can be manufactured by performing a pressing process on a flexible pouch film laminate to form a cup part, then accommodating the electrode assembly in the accommodation space inside the cup part and sealing the sealing part.

[0007] When operating at high temperatures, over - charging, or short - circuiting, a pouch - type secondary battery may generate gas inside the pouch. When the air pressure inside the pouch increases, the pouch may exhaust and explode or catch fire. To overcome the above problems, generally, a gas guiding part is provided at the connection part between the electrode lead containing different types of materials and the pouch - type film laminate to increase the pressure inside the pouch. Thus, the interface between the gas guiding part and the lead film is opened, and the gas is discharged to the outside of the pouch. However, when the interface is opened, the adhesion strength between the gas guiding part and the electrode lead decreases, so the gas guiding part detaches from the electrode lead and is pushed out to the outside of the pouch, or the electrode lead is corroded by the electrolyte leaking from the inside of the pouch, resulting in a reduction in the durability and safety of the pouch. Summary of the Invention

[0008] Technical problem

[0009] One aspect of the present disclosure provides a pouch-type secondary battery capable of improving the adhesion strength between a gas guide portion and an electrode lead.

[0010] Technical solution

[0011] According to one aspect of the present disclosure, there is provided a pouch-type secondary battery, comprising: 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-type case; and a gas guide portion disposed between the electrode lead and the lead film, wherein the gas guide portion includes: a first layer in contact with the electrode lead; and a second layer disposed on the first layer, and the first layer includes a modified polyolefin resin.

[0012] Advantageous effects

[0013] The pouch-type secondary battery according to the present disclosure includes a modified polyolefin resin in the first layer in contact with the electrode lead in the gas guide portion, thereby improving the adhesion strength between the gas guide portion and the electrode lead. Therefore, even when the pouch-type secondary battery is stored at a high electrolyte temperature, the pouch gas guide portion is prevented from detaching from the electrode lead and being pushed out to the outside of the pouch, or the electrolyte solution inside the pouch is prevented from leaking. Therefore, the pouch-type secondary battery according to the present disclosure is prevented from having electrode lead corrosion caused by the electrolyte solution and / or gas, and thus has excellent durability and safety. Description of the drawings

[0014] The following drawings attached herein illustrate preferred examples of the present disclosure by way of example and are used to further understand the technical concept of the present disclosure together with the detailed description of the present disclosure given below. Therefore, the present disclosure should not be construed only by the content in these drawings:

[0015] Figure 1 is an exploded view of a pouch-type secondary battery according to the present disclosure.

[0016] Figure 2 is a cross-sectional view of a sealed pouch-type secondary battery.

[0017] Figure 3 is an example of a cross-sectional view of a pouch-type secondary battery before the pouch-type case is opened.

[0018] Figure 4 is an example of a cross-sectional view of a pouch-type secondary battery when the pouch-type case is opened.

[0019] Figure 5 Another example of a cross-sectional view of a pouch-type secondary battery before the pouch-type case is opened.

[0020] Figure 6 Another example of a cross-sectional view of a pouch-type secondary battery before the pouch-type case is opened; and

[0021] Figure 7 A perspective view showing the upper surface of the sealing portion according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] The advantages and features of the present disclosure and the method of implementing the same can be more easily understood with reference to the 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 of ordinary skill in the art. Therefore, the present disclosure is defined only by the scope of the appended claims. Throughout the specification, the same reference numerals denote the same elements.

[0023] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure pertains. Terms defined in commonly used dictionaries will not be interpreted ideally or excessively unless clearly and specifically defined otherwise.

[0024] The terms used herein are not intended to limit the inventive concept, but to describe embodiments. As used herein, unless the context clearly indicates otherwise, the singular forms also include the plural forms. The meanings of "comprising" and / or "including" as used herein do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0025] In this document, when an element "comprises" a component, unless there is a contrary explicit description, this may mean that the element does not exclude another component, but may also include another component.

[0026] In this document, the description "A and / or B" means A or B or A and B.

[0027] In this document, unless otherwise indicated, "%" means wt%.

[0028] The pouch-type secondary battery according to the present disclosure includes: 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 via the sealing portion, a lead film provided between the electrode lead and the pouch-type case, and a gas guiding portion provided between the electrode lead and the lead film, wherein the gas guiding portion includes a first layer in contact with the electrode lead and a second layer provided on the first layer, and the first layer includes a modified polyolefin resin.

[0029] Hereinafter, each component of the pouch-type secondary battery of the present disclosure will be described in more detail with reference to the drawings.

[0030] Figure 1 is an exploded view of a pouch-type secondary battery 100 according to the present disclosure, and Figure 2 is a cross-sectional view of the sealed pouch-type secondary battery 100. In Figure 2 order to facilitate understanding, some components of the pouch-type secondary battery 100 are not provided. As Figure 1 and Figure 2 shown, the pouch-type secondary battery 100 according to the present disclosure includes: a pouch-type case 110, an electrode assembly 160, an electrode lead 180, a lead film 190, and a gas guiding portion 200.

[0031] (1) Pouch-type case

[0032] The inside of the pouch-type case 110 can store the electrode assembly 160. 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 sequence.

[0033] The base layer is formed on the outermost layer of the pouch film laminate to protect the secondary battery from external friction and collision. Since the base layer is made of a polymer, it can electrically insulate the electrode assembly from the outside.

[0034] The base layer can be made of at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aromatic polyamide, nylon, polyester, poly(p-phenylene benzobisoxazole), polyarylate, Teflon, and glass fiber. Preferably, the base layer can be made of polyethylene terephthalate (PET), nylon having abrasion resistance and heat resistance, or a combination thereof.

[0035] The base layer can have a single-layer film structure made of any one material. Alternatively, the base layer can have a composite film structure in which two or more materials are respectively formed into layers.

[0036] The thickness of the base layer can be from 5 μm to 50 μm, specifically from 7 μm to 40 μm, and more specifically from 25 μm to 38 μm. When the thickness of the base layer satisfies the above range, the external insulation is excellent and the entire pouch is not thick, so the energy density and volume ratio of the secondary battery can be excellent.

[0037] 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 the electrolyte from leaking from the inside of the pouch-type housing.

[0038] The gas barrier layer can be made of metal. Specifically, it can be made of an aluminum alloy thin film. When an aluminum alloy thin film is used to form the gas barrier layer, the gas barrier layer can have a predetermined level of mechanical strength and is also lightweight, and can supplement the electrochemical performance caused by the electrode assembly and the electrolyte and dissipate heat. The aluminum alloy thin film can include metal elements other than aluminum (Al). For example, it can 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).

[0039] The thickness of the gas barrier layer can be from 40 μm to 100 μm, specifically from 50 μm to 90 μm, and more specifically from 55 μm to 85 μm. When the thickness of the gas barrier layer satisfies the above range, the formability and gas barrier performance are excellent when molding the cup part.

[0040] When sealing the pouch-type housing that internally houses the electrode assembly to completely seal the inside of the pouch-type housing, the sealant layers are thermally bonded together at the sealing part. For this purpose, the sealant layer can be made of a material with excellent heat-sealing strength.

[0041] The sealant layer can be made of a material with insulation, corrosion resistance, and sealing properties. Specifically, since the sealant layer is in direct contact with the electrode assembly and / or the electrolyte inside the pouch-type housing, it can be made of a material with insulation and corrosion resistance. In addition, the sealant layer should completely seal the inside of the pouch-type housing and block the material movement between the inside and the outside, so it can be made of a material with high sealing performance (e.g., excellent heat-sealing strength). To ensure obtaining such insulation, corrosion resistance, and sealing properties, the sealant layer can be made of a polymer material.

[0042] The sealant layer can be made of at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylene benzobisoxazole), polyarylate, Teflon, and glass fiber, and preferably can be made of a polyolefin-based resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene can be provided with cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butene-ethylene terpolymer.

[0043] The thickness of the sealant layer can be 30 μm to 130 μm, specifically 50 μm to 120 μm, and more specifically 70 μm to 100 μm. When the thickness of the sealant layer satisfies the above range, it has the effect of ensuring the sealing strength of the seal part and ensuring the formability of the soft package laminate.

[0044] Meanwhile, the soft package laminate can be pulled out, molded, or stretched by a punch or the like to manufacture the soft package type case 110. Therefore, the soft package type case 110 can include a cup part 122 and a receiving part 124. The receiving part 124 is a position for storing the electrode assembly, and can represent a receiving space formed in a concave shape inside the cup part 122 when the cup part 122 is formed.

[0045] According to an embodiment of the present disclosure, as Figure 1 shown, the soft package type case 110 can include a first case 120 and a second case 130. The first case 120 can include a receiving part 124 capable of accommodating the electrode assembly 160, and the second case 130 can cover the receiving part 124 from above to prevent the electrode assembly 160 from separating to the outside of the battery case 110. As Figure 1 shown, the first case 120 and the second case 130 can be manufactured in such a way that one side of the first case 120 is connected to one side of the second case 130, but the embodiments of the present disclosure are not limited thereto, and the first case 120 and the second case 130 can be manufactured differently, for example, separately manufactured separately from each other.

[0046] According to another embodiment of the present disclosure, when forming the cup part in the soft package laminate, two symmetric cup parts 122 and 132 can be stretched and molded adjacent to each other in one soft package laminate. In this case, the cup parts 122 and 132 can be respectively formed in the first case 120 and the second case 130, as Figure 1As shown. After the electrode assembly 160 is received in the receiving portion 124 provided in the cup portion 122 of the first housing 120, the bridging portion 140 formed between the two cup portions 122 and 132 can be folded so that the two cup portions 122 and 132 face each other. In this case, the cup portion 132 of the second housing 130 can receive the electrode assembly 160 from above. Therefore, the two cup portions 122 and 132 accommodate one electrode assembly 160, and thus can accommodate a thicker electrode assembly 160 than when only one cup portion 122 is present. In addition, by folding the pouch-type housing 110 to form an edge of the secondary battery 100, the number of edges to be sealed can be reduced when the sealing process is performed later. Therefore, the process speed of the pouch-type secondary battery 100 can be increased, and the number of sealing processes can be reduced.

[0047] The pouch-type housing 110 can be sealed while accommodating the electrode assembly 160 so that a part of the electrode lead 180 to be described later, 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 part of the electrode lead 180, the electrode assembly 160 can be received in the receiving portion 124 provided in the cup portion 122 of the first housing 120, and the second housing 130 can cover the receiving portion 124 from above. Then, the electrolyte is injected into the receiving portion 124, and the sealing portion 150 formed at the edges of the first housing 120 and the second housing 130 can be sealed.

[0048] The sealing portion 150 can be used to seal the receiving portion 124. Specifically, the sealing portion 150 can be formed along the edge of the receiving portion 124, and thus the receiving portion 124 can be sealed.

[0049] The temperature at which the sealing portion 150 is sealed can be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature satisfies the above numerical range, the pouch-type housing 110 can obtain sufficient sealing strength through thermal sealing.

[0050] (2) Electrode Assembly

[0051] The electrode assembly 160 can be inserted into the pouch-type housing 110 and sealed by the pouch-type housing 110 after the electrolyte is injected.

[0052] The positive electrode, the separator, and the negative electrode can be laminated in sequence to form the electrode assembly 160. Specifically, the electrode assembly 160 can include two types of electrodes (i.e., the positive electrode and the negative electrode) and a separator interposed between the electrodes to insulate the electrodes from each other.

[0053] The positive electrode and the negative electrode may have a structure in which an active material paste is respectively coated on an electrode current collector in the form of a metal foil or a metal mesh containing aluminum and copper. Generally, granular active material, auxiliary conductor, binder, and conductive material are stirred with an added solvent to form a paste. The solvent can be removed in a subsequent process.

[0054] A paste mixed with an electrode active material, a binder, and / or a conductive material is coated on the positive electrode current collector and the negative electrode current collector to manufacture the positive electrode and the negative electrode, and the positive electrode and the negative electrode are laminated on both sides of a separator. Therefore, the electrode assembly 160 can be manufactured into a predetermined shape. The types of the electrode assembly 160 may include: a laminated type, a wound type, and a laminated and folded type, but are not limited thereto.

[0055] The electrode assembly 160 may include an electrode tab 170.

[0056] The electrode tab 170 is connected to each of the positive electrode and the negative electrode of the electrode assembly 160 and protrudes to the outside of the electrode assembly 160. Therefore, it can be used as a path for electrons to move between the inside and the outside of the electrode assembly 160. The current collector included in the electrode assembly 160 may be provided with a portion coated with the electrode active material and an end portion not coated with the electrode active material, that is, a non-coated portion. The electrode tab 170 can be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding or the like. As Figure 1 shown, the electrode tab 170 may protrude from the electrode assembly 160 in different directions, but is not limited thereto, and may be formed to protrude in all directions. For example, it protrudes from one side in the same direction.

[0057] (3) Electrode lead

[0058] The electrode lead 180 can supply power to the outside of the secondary battery 100. The electrode lead 180 can be connected to the electrode tab 170 of the electrode assembly 160 by spot welding or the like.

[0059] The electrode lead 180 can be connected to the electrode assembly 160 and can protrude to the outside of the pouch-type housing 110 via the sealing portion 150. Specifically, one end of the electrode lead 180 can be connected to the electrode assembly 160, particularly to the electrode tab 170, and the other end of the electrode lead 180 can protrude to the outside of the pouch-type housing 110.

[0060] The electrode lead 180 may include: a positive electrode lead 182, one end of the positive electrode lead 182 being 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, one end of the negative electrode lead 184 being 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. Thus, the electric power generated inside the electrode assembly 160 can be supplied to the outside. In addition, each of the positive electrode tab 172 and the negative electrode tab 174 is formed to protrude in all directions, and thus, the positive electrode lead 182 and the negative electrode lead 184 can also extend in all directions. The positive electrode lead 182 and the negative electrode 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 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 current collector. A part 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.

[0061] One 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 salts, and titanium (Ti)-based anhydrous salts. In this case, corrosion resistance to the electrolyte solution and adhesiveness to the lead film 190 and / or the gas guide portion 200 can be obtained.

[0062] (4) Lead film

[0063] The lead film 190 can prevent the electric power generated from the electrode assembly 160 from flowing through the electrode lead 180 to the battery case 110 and enable the battery case 110 to be sealed. To this end, the lead film 190 may be made of a non-conductive non-conductor through which current does not flow well. Generally, as 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 embodiments of the present disclosure are not limited thereto, and thus, any member that can insulate the electrode lead 180 may be used.

[0064] According to an embodiment of the present disclosure, the lead film 190 may be a breathable film and may be disposed to surround the outer peripheral surfaces of the electrode lead 180 and the gas guiding portion 200. Specifically, the electrode lead 180 and the gas guiding portion 200 are in contact with each other on one side, and in this case, at least a part of the electrode lead 180 and the gas guiding portion 200 may be surrounded by the lead film 190. The lead film 190 may be placed and restricted within the sealing portion 150 of the first housing 120 and the second housing 130 of the heat-sealable pouch-type housing 110, and may bond the electrode lead 180 and the gas guiding portion 200 to the battery housing 110.

[0065] The lead film 190 may be disposed between the electrode lead 180 and / or the gas guiding portion 200 and the pouch-type housing 110. For example, as Figure 2 shown, the lower housing 110, the lead film 190, the electrode lead 180, the gas guiding portion 200, the lead film 190, and the upper housing 110 may be stacked in this order and disposed in the sealing portion 150. Additionally, although not shown in the figure, as another example, they may be stacked and disposed in the order of the lower housing, the lead film, the gas guiding portion, the electrode lead, the lead film, and the upper housing, and as another example, they may be stacked and disposed in the order of the lower housing, the lead film, the gas guiding portion, the electrode lead, the gas guiding portion, the lead film, and the upper housing.

[0066] According to an embodiment of the present disclosure, one end of the lead film 190 protruding to the outside of the pouch-type housing 110 may be disposed to be in direct contact with the electrode lead 180, rather than in direct contact with the gas guiding portion 200, as Figure 3 or Figure 5 shown. When one end of the lead film 190 is disposed to be in direct contact with the electrode lead 180, that is, when it is disposed to extend more than the gas guiding portion 200 disposed on the electrode lead 180, when the lead film 190 on the gas guiding portion 200 opens as gas is discharged, the area for gas to penetrate the lead film 190 can be easily ensured, and compared with the case where the lead film 190 is not extended, the bonding strength between the lead film 190 and the electrode lead 180 can minimize the reduction in durability caused by the opening of the lead film 190.

[0067] According to another embodiment of the present disclosure, as Figure 3 or Figure 6 shown, the first layer 210 of the gas guiding portion 200 may be formed to be longer than the second layer 220 in the outward direction of the pouch-type housing 110, and one end of the lead film 190 protruding to the outside of the pouch-type housing 110 may be disposed to be in direct contact with the first layer 210, rather than in direct contact with the second layer 220.

[0068] Specifically, as in the above Figure 3As shown, one end of the lead film 190 protrudes more in the direction in which the electrode lead protrudes and contacts the electrode lead 180, and the second layer 220 of the gas guiding portion 200 extends more than the first layer 210. When a part of the lead film 190 is set to contact the second layer 220, in addition to the bonding strength between the lead film 190 and the electrode lead 180, the bonding strength between the lead film 190 and the gas guiding portion 200 can be maintained strong, and even a synergistic effect is generated on the bonding strength between the electrode lead 180 and the gas guiding portion 200, so as to obtain a gas discharge portion with excellent durability.

[0069] At the same time, 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 pouch adhesive layer stacked in sequence.

[0070] The metal adhesive layer is in direct contact with the electrode lead 180 and can be used to bond the lead film 190 to the electrode lead 180. The metal adhesive layer may include any material that is easily bonded to the electrode lead 180. Specifically, the metal adhesive layer may contain acid-modified polyolefin. For example, the metal adhesive layer may include at least one of acid-modified polypropylene (PPa), acid-modified polyethylene (PEa), or plasma-treated polypropylene (PP), but is not limited thereto. The thickness of the metal adhesive layer 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 has the effect of preventing through-holes and leakage at the edge portion during the welding between the electrode lead and the lead film.

[0071] The core layer may be a layer placed in the middle of the lead film 190. The core layer may include additives such as, for example, polypropylene, polyolefin elastomer (POE), and / or colorant, but is not limited thereto. 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 the above numerical range, and deformation caused by heat can be minimized, which can better ensure insulation. As another example, the polymer included in the core layer may be a fluorinated polyolefin, which may be polytetrafluoroethylene or may be a mixture of polytetrafluoroethylene and polypropylene, and as a mixture, the components may be mixed in a weight ratio of 9:1 to 1:9. The housing can achieve greater gas permeability than when the gas penetrates the lead film 190 via the gas guiding portion 200. The thickness of the core layer may be 40 μm to 70 μm, specifically 50 μm to 70 μm, and more specifically 60 μm to 70 μm. When the thickness of the core layer satisfies the above numerical range, deformation caused by the heat applied during welding and sealing can be prevented, thereby bringing a robust design effect in ensuring insulation.

[0072] The pouch adhesive layer can be a layer that directly contacts the battery case 110 (specifically, the sealant layer of the pouch film laminate). The pouch adhesive layer can include polypropylene or polyolefin elastomer (POE), but is not limited thereto. In particular, the polymer included in the pouch adhesive layer can be a copolymer. The melting point of the pouch adhesive layer including the copolymer can be controlled within the above numerical range, and the melting point of the pouch adhesive layer is similar to that of the polymer in the sealant layer of the pouch film laminate, which is used to better ensure the sealing processability. The thickness of the pouch adhesive layer can 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 numerical range, it has the effect of ensuring that the residual rate of the polymer (such as polypropylene) is sufficient to obtain the strength for sealing between the electrode lead and the pouch film laminate.

[0073] (5) Gas guiding part

[0074] The gas guiding part 200 is used to form a path for discharging gas from the inside of the pouch-type case 110 to the outside. As Figure 2 shown, the gas guiding part 200 of the present disclosure can be disposed 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 guiding part 200 is disposed, the electrode lead 180 and the lead film 190 may not be in direct contact, while in the region where the gas guiding part 200 is not disposed, the electrode lead 180 and the lead film 190 may be in direct contact.

[0075] Hereinafter, the gas guiding part 200 of the present disclosure will be described in more detail with reference to Figure 3 and Figure 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.

[0076] As Figure 3 and Figure 4 shown, the interface between the gas guiding part 200 and the lead film 190 is generally not opened. When the pressure inside the pouch-type case 110 increases, the interface between the gas guiding part 200 and the lead film 190 is opened, thereby forming a gas discharge path 300. The gas inside the pouch-type case 110 can move along the gas discharge path 300 and then pass through the lead film 190 to be discharged to the outside of the pouch. Therefore, the pressure inside the pouch-type case 110 can be reduced to prevent the explosion or fire of the pouch-type case 110.

[0077] Meanwhile, as Figure 3 and Figure 4As shown, the gas guiding part 200 of the present disclosure includes a first layer 210 in contact with the electrode lead 180 and a second layer 220 provided on the first layer 210.

[0078] The first layer 210 is in contact with the electrode lead 180 and can be used to bond the gas guiding part 200 to the electrode lead 180.

[0079] The first layer 210 may include any material that is easily bondable to the electrode lead 180. Specifically, the first layer 210 contains a modified polyolefin resin. The increase in the pressure of the soft-pack type housing 110 can open the interface between the lead film 190 and the gas guiding part 200, thereby forming a gas discharge path 300, and through the gas discharge path 300, the gas generated inside the soft-pack type housing 110 can be discharged, resulting in a decrease in the pressure of the housing 110. However, the surface of the gas guiding part 200 bonded to the electrode lead 180 is the first layer 210, and when the bonding strength between the first layer 210 and the electrode lead 180 is insufficient, the gas guiding part 200 detaches from the electrode lead 180 or is pushed out to the outside, resulting in the leakage of the internal electrolyte.

[0080] Therefore, as in the present disclosure, when the first layer 210 that holds the gas guiding part 200 on the electrode lead 180 includes a modified polyolefin resin, the bonding strength between the gas guiding part 200 and the electrode lead 180 becomes greater. Therefore, even when the soft-pack type secondary battery is stored at a high temperature, the above problems of the gas guiding part 200 detaching from the electrode lead 180 or the leakage of the internal electrolyte can be prevented.

[0081] According to an embodiment of the present disclosure, as described above, the first layer 210 may have a structure in which the first layer 210 protrudes more in the outward direction of the housing 110 than the end of the second layer 220 and is arranged to be in contact with the lead film 190. In this case, the strong bonding holding force among the electrode lead 180, the gas guiding part 200, and the lead film 190 can contribute to improving the durability.

[0082] The modified polyolefin resin included in the first layer 210 may include at least one of an acid-modified polyolefin and a silane-modified polyolefin.

[0083] The acid-modified polyolefin refers to a polyolefin resin modified by acid grafting. For example, an 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 carboxylic anhydride, and the carboxyl group can include the concept of carboxylic anhydride group. The unsaturated carboxylic acid reacting with the polyolefin resin can include at least one selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaric acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaric anhydride, citraconic anhydride, aconitic anhydride, norbornedicarboxylic anhydride, and tetrahydrophthalic anhydride, but is not limited thereto. In particular, the application of maleic anhydride is preferred for improving the adhesion strength between the gas guiding 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.

[0084] The silane-modified polyolefin refers to a polyolefin resin graft-modified with an unsaturated silane compound. The silane-modified polyolefin can have a structure in which an unsaturated silane compound is graft-copolymerized onto a polyolefin resin as the main chain. The silane-modified polyolefin resin can include at least one selected from the group consisting of silane-modified polypropylene resin and silane-modified ethylene-vinyl acetate copolymer, but is not limited thereto.

[0085] The first layer 210 can be subjected to a modification treatment, and examples of the modification treatment include ion implantation treatment, plasma treatment, radiation treatment, heat treatment, etc., and a treatment that changes the bonding structure of the polymer layer is preferred. These modification treatments can be performed alone or in combination of two or more. The first layer 210 subjected to the modification treatment can include plasma-treated polypropylene (PP), but is not limited thereto.

[0086] The thickness of the first layer 210 can 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 the above numerical range, the first layer 210 melts within a specified production time (takt time), so that the gas guiding portion 200 and the electrode lead 180 can be easily welded.

[0087] Meanwhile, according to an embodiment of the present disclosure, the first layer 210 may include ceramic fillers. Based on the total mass of the first layer 210, the content of the ceramic fillers may be 1 wt% to 19 wt%, specifically 5 wt% to 15 wt%, and more specifically 5 wt% to 12 wt%. When the amount of the ceramic fillers satisfies the above range, without affecting the adhesion strength between the electrode lead 180 obtained through the first layer 210 and the gas guiding portion 200, the corrosion of the electrode lead 180 can be prevented by absorbing gases such as HF generated by various side reactions. Therefore, a significant improvement in durability can be expected.

[0088] In addition, the average particle size D of the ceramic fillers 50 may be 1 μm to 20 μm, specifically 1 μm to 10 μm, and more specifically 1 μm to 6 μm. When the average particle size D 50 satisfies the above range, during the manufacture of the first layer 210, the extrusion processability can be maintained at an excellent level, and concerns about film adhesion, such as the separation of the first layer 210 of the gas guiding portion 200 from the second layer 220 or the separation from the electrode lead 180, can be prevented.

[0089] Meanwhile, when based on the total weight of the lead film 190, the amount of the ceramic fillers is 1 wt% to 19 wt%, and the average particle size D of the ceramic fillers 50 is 1 μm to 20 μm, it is easy to absorb the gases generated inside the soft package to prevent the connection portion between the electrode lead and the soft package type laminate from being corroded by the gases, thereby achieving high durability.

[0090] The ceramic fillers may include at least one selected from the group consisting of CaCO3, Ca(OH)2, CaCl2, CaO, KOH, NaOH, and Na2CO. Preferably, the ceramic fillers may include at least one of CaCO3 and Ca(OH)2, which can withstand and easily absorb gases such as hydrofluoric acid (HF).

[0091] In addition, the first layer 210 may further include additives other than the above-mentioned ceramic fillers. The inclusion of additives in the first layer 210 can change the physical properties of the first layer 210. For example, as an additive for controlling the tensile strength of the first layer 210, at least any one of carbon fiber, glass fiber, and aramid fiber may also be added.

[0092] The second layer 220 may be a layer in contact with the lead film 190.

[0093] The second layer 220 may include at least one of polytetrafluoroethylene (PTFE) and polyimide (PI), but is not limited thereto. In particular, when polyimide is included in the second layer 220, the adhesion strength between the second layer 220 and the lead film 190 is reduced. Therefore, when the pressure inside the housing 110 increases, a gas discharge path 300 can be preferably formed.

[0094] 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 satisfies the above range, the second layer 220 will not melt during the sealing process, and when the pressure inside the housing 110 increases, the interface between the second layer 220 and the lead film 190 can be opened to form a gas discharge path 300.

[0095] 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 pressure inside the housing 110 rises, the interface between the second layer 220 and the lead film 190 is opened to form a gas discharge path, and the adhesion strength between the gas guiding portion 200 and the electrode lead 180 can also be improved.

[0096] (6) Electrolyte

[0097] The pouch-type secondary battery 100 according to the present disclosure may further include an electrolyte (not shown) injected into the pouch-type housing 110. The electrolyte is used to move lithium ions generated by the electrochemical reaction through the electrodes during charging and discharging of the secondary battery 100, and may include a non-aqueous organic electrolyte solution as a mixture of a lithium salt and an organic solvent or a polymer using a polymer electrolyte. Additionally, 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 be flexible and thus easily deformed under an external force.

[0098] Hereinafter, the present disclosure will be described in more detail through specific examples. However, the examples shown below are only for understanding the present disclosure, and the scope of the concept of the present disclosure is not limited thereto. It will be apparent to those skilled in the art that various modifications and changes can be made within the scope and technical scope of the present disclosure, and such modifications and changes fall within the scope of the claims included herein.

[0099] Examples and Comparative Examples

[0100] Example 1

[0101] (1) Manufacturing a pouch-type housing

[0102] A polyethylene terephthalate (PET) film with a thickness of 266 mm, a length of 50 m, and a thickness of 12 μm, and a nylon film with a width of 266 mm, a length of 50 m, and a thickness of 25 μm are laminated on one side of an aluminum alloy film with a width of 266 mm, a length of 50 m, and a thickness of 60 μm, and a polypropylene film with a width of 266 mm, a length of 50 m, and a thickness of 80 μm is laminated on the other side to prepare a soft package laminate with a polyethylene terephthalate / nylon / aluminum alloy film / polypropylene film structure.

[0103] In this case, the PET film and the nylon film are the base layers, the aluminum alloy film is the gas barrier layer, and the polypropylene film is the sealant layer.

[0104] The soft package laminate is molded to manufacture a soft package type housing including a receiving portion and a sealing portion.

[0105] (2) Manufacturing a soft package type secondary battery

[0106] The negative electrode, the positive electrode, and the porous polyethylene separator are assembled using a lamination method and then laminated to manufacture an electrode assembly. Then, the electrode leads are combined with the electrode assembly.

[0107] LiPF6 is dissolved in a solvent (EC:EMC:DMC = 3:3:4 by volume ratio) to 1.0 M to prepare an electrolyte. The electrode assembly is accommodated in the soft package type housing, the front ends of the electrode leads protrude to the outside, and the electrolyte is injected.

[0108] An acid-modified polypropylene film (first layer) with a thickness of 40 μm and a polyimide film (second layer) with a thickness of 50 μm are sequentially laminated on the upper surface of the electrode leads to form a gas guiding portion.

[0109] Then, a 200-μm-thick lead film is laminated on each of the lower surface of the electrode leads and the upper surface of the gas guiding portion. The lead film may include a 75-μm-thick metal adhesive layer containing copolymerized polypropylene and acid-modified polypropylene, a 65-μm-thick core layer containing polypropylene homopolymer, and a 60-μm-thick soft package adhesive layer containing copolymer polypropylene.

[0110] After that, under the conditions of a sealing strip area of 200 mm × 10 mm, 220 °C, and 0.27 MPa, the sealing portion of the soft package type housing is sealed for 2 seconds, and then placed at 60 °C for 4 hours to manufacture a soft package type secondary battery. In this case, in the sealing portion, the portion where the lead film is formed has a structure of lower housing / lead film / electrode lead / gas guiding portion / lead film / upper housing laminated in sequence.

[0111] Example 2

[0112] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that the thickness of the acid-modified polypropylene film coated on the first layer was 10 μm, and the thickness of the polyimide film coated on the second layer was 50 μm.

[0113] Example 3

[0114] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that the thickness of the acid-modified polypropylene film coated on the first layer was 120 μm, and the thickness of the polyimide film coated on the second layer was 50 μm.

[0115] Example 4

[0116] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that an acid-modified polyethylene film was coated on the first layer instead of the acid-modified polypropylene film.

[0117] Example 5

[0118] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that a polytetrafluoroethylene film was coated on the second layer instead of the polyimide film.

[0119] Example 6

[0120] When manufacturing the acid-modified polypropylene film coated on the first layer, except that CaCO3 (average particle size D 50 : 2.8 μm) was mixed as a ceramic filler to constitute 7 wt% of the total weight of the acid-modified polypropylene film, a pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1.

[0121] Example 7

[0122] When manufacturing the acid-modified polypropylene film coated on the first layer, except that CaCO3 (average particle size D 50 : 2.8 μm) was mixed as a ceramic filler to constitute 11 wt% of the total weight of the acid-modified polypropylene film, a pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1.

[0123] Comparative Example 1

[0124] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that the gas guiding portion 200 was not provided with an acid-modified polypropylene film (first layer) (single layer).

[0125] Comparative Example 2

[0126] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that an unmodified polyethylene film was coated on the first layer instead of the acid-modified polypropylene film.

[0127] Comparative Example 3

[0128] A pouch-type casing and a secondary battery were manufactured in the same manner as in Example 1, except that a polyimide film was coated on the first layer and an acid-modified polypropylene film was coated on the second layer.

[0129] Experimental Example 1: Evaluation of durability

[0130] For the pouch-type secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 3, the length of the gas guiding portion separated from the electrode lead was measured, and the adhesion strength between the electrode lead and the gas guiding portion and the adhesion strength under the electrolyte solution were measured, and the reduction in the adhesion strength was calculated.

[0131] 1) Storage stability under electrolyte solution (mm): In the manufacturing process of the pouch-type secondary battery, HF was introduced into the pouch-type casing, and then the pouch-type casing was sealed and stored in a chamber at 60 °C for 5 days. After the storage period, the length of at least a part of the gas guiding portion and the lead film separated from the electrode lead was measured. The results are shown in Table 1 below.

[0132] Figure 7 is a perspective view showing the upper surface of the sealing portion according to an embodiment of the present disclosure. As Figure 7 shown, the electrode lead 180, the gas guiding portion 200, and the lead film 190 are sequentially laminated on the sealing portion 150, and the gas guiding portion 200 may include a first region 230 and a second region 240.

[0133] When the gas guiding portion 200 and the lead film 190 have low durability due to the electrolyte solution, the gas guiding portion 200 and the lead film 190 may be separated from the inside of the pouch to the outside. In this case, the length of the gas guiding portion 200 and / or the lead film 190 separated from the electrode lead 180 represents the length (A) from the inner end portion of the pouch in the second region 240 to the separation portion.

[0134] 2) Adhesion strength between the electrode lead and the lead film (N / cm): In the manufacturing process of the pouch-type secondary battery, a gas generating material was introduced into the pouch-type casing, and then the pouch-type casing was sealed, so that CO2 gas was generated inside the pouch to increase the pressure inside the pouch.

[0135] After that, the obtained product was stored in a chamber at 60 °C for 5 days, and then a part of the two ends of the lead assembly at a distance of 10 mm from the inner end portion of the sealing portion was cut, that is, Figure 7 the inner end portion of the gap portion in the second region 240 in [] was connected to each of the upper and lower jigs of the UTM, and then stretched at a speed of 50 mm / min in the 180° direction for 30 mm to calculate the average value (N / 10 mm) of the flat portion in the measured adhesion strength curve graph. The results are shown in Table 1 below.

[0136] 3) Adhesive strength (N / cm) and adhesive strength reduction rate (%) under electrolyte: Extract the lead assembly as in 2) above, then immerse it in the electrolyte at 60 °C for 60 hours. In the electrolyte, an organic solvent (where ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed in a volume ratio of 3:3:4) is mixed with 1.0 M of LiPF6 lithium salt. Then, measure the adhesive strength under the electrolyte in the same manner as in 2) above, and calculate the rate of reduction in adhesive strength before and after electrolyte immersion.

[0137] [Table 1]

[0138]

[0139] From Table 1, it can be seen that the length of the separated (or pushed out) gas guiding part and / or lead film in Examples 1 to 7 including the modified polyolefin resin in the first layer of the gas guiding part is significantly shorter than that in Comparative Examples 1 to 3, indicating excellent durability. In addition, it can be seen that 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 greater than those in Comparative Examples 1 and 2, and in Comparative Example 3, it is completely separated after electrolyte impregnation, providing no measurable strength, indicating a significant reduction in durability under the electrolyte.

[0140] Description of Reference Numerals

[0141] 100: Soft-pack secondary battery

[0142] 110: Soft-pack case

[0143] 120: First case

[0144] 122: Cup part

[0145] 124: Accommodating part

[0146] 130: Second case

[0147] 132: Cup part

[0148] 140: Bridging part

[0149] 150: Sealing part

[0150] 160: Electrode assembly

[0151] 170: Electrode tab

[0152] 172: Positive electrode tab

[0153] 174: Negative electrode tab

[0154] 180: Electrode lead

[0155] 182: Positive lead

[0156] 184: Negative lead

[0157] 190: Lead film

[0158] 200: Gas guiding part

[0159] 210: First layer

[0160] 220: Second layer

[0161] 300: Gas discharge path

Claims

1. A pouch-type secondary battery, comprising: An electrode assembly; A pouch-type case, the pouch-type case including a receiving portion and a sealing portion, the receiving portion receiving the electrode assembly, and the sealing portion sealing the receiving portion; An electrode lead, the electrode lead being connected to the electrode assembly and protruding to the outside of the pouch-type case through the sealing portion; A lead film, the lead film being disposed between the electrode lead and the pouch-type case; And A gas guiding portion, the gas guiding portion being disposed between the electrode lead and the lead film, Wherein the gas guiding portion includes: a first layer, the first layer being in contact with the electrode lead; and a second layer, the second layer being disposed on the first layer, and The first layer includes a modified polyolefin resin.

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

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 acid-modified polypropylene (PPa) and acid-modified polyethylene (PEa).

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

8. The pouch-type secondary battery according to claim 1, wherein, The thickness of the second layer is 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 pouch-type secondary battery according to claim 1, wherein, The first layer further includes ceramic fillers having an average particle size D of 1 μm to 20 μm 50 .

11. The pouch-type secondary battery according to claim 10, wherein, The ceramic filler includes at least one selected from the group consisting of CaCO3, Ca(OH)2, CaCl2, CaO, KOH, NaOH, and Na2CO3.

12. The pouch-type secondary battery according to claim 10, wherein, Based on the total weight of the first layer, the content of the ceramic filler is 1 wt% to 19 wt%.

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 stacked in sequence.

14. The pouch-type secondary battery according to claim 1, wherein, One side of the electrode lead is coated with at least one selected from the group consisting of chromium (Cr), nickel (Ni), alumina (Al2O3), zirconium (Zr)-based anhydrous salts, and titanium (Ti)-based anhydrous salts.

15. The pouch-type secondary battery according to claim 1, wherein, The lead film is disposed such that one end of the lead film protruding to the outside of the pouch-type case protrudes more than one end of the gas guiding portion protruding to the outside of the pouch-type case and is in direct contact with the electrode lead.

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