Secondary battery

Abstract

A secondary battery according to an embodiment of the present application includes: an electrode assembly; an electrode lead attached to the electrode assembly; a case in which the electrode assembly is accommodated; a lead film formed to surround a portion of an outer surface of the electrode lead and interposed between the electrode lead and the case; a gas discharge region formed in at least a portion of the case; and a gas discharge member inserted into the gas discharge region and containing linear low-density polyethylene having a comonomer having a carbon atom number of 6 or more, wherein the gas discharge member has a thickness of 50 µm or more and less than 200 µm.

Description

Secondary batteries Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2021-0048823, filed on April 14, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] This disclosure relates to a secondary battery, and more specifically, to a secondary battery having a venting component. Background Technology

[0003] Rechargeable batteries are highly adaptable to a wide range of products and exhibit excellent electrical performance, such as high energy density. They are commonly used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs) powered by electric sources. Rechargeable batteries have gained attention as a new energy source for improving environmental friendliness and energy efficiency because they can significantly reduce the use of fossil fuels and produce no byproducts during energy consumption.

[0004] Currently, widely used rechargeable batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries.

[0005] Secondary batteries typically have the following structure: an electrode assembly comprising at least one cell with a positive / separator / negative electrode structure is housed in a laminated shell (in which an outer layer, a metal barrier layer, and a sealant layer are laminated in sequence), and the sealant resin of the sealant layer is fused to seal the electrode assembly.

[0006] In conventional rechargeable batteries, fires can occur due to various reasons such as internal short circuits, overcharging or over-discharging, and temperature control issues. In such cases, a rapid rise in internal temperature can occur, and heat can be transferred to adjacent cells via thermal propagation, potentially exacerbating the fire.

[0007] To minimize damage to the electrodes caused by gas during heat propagation (i.e., when the internal temperature of the secondary battery rises), directional venting characteristics are needed to ensure that the gas is discharged in one direction. However, conventional secondary batteries have the problem of difficulty in guiding the gas to be discharged in a specific direction.

[0008] Therefore, this disclosure aims to provide a secondary battery with improved safety by emitting gas in a specific direction. Summary of the Invention

[0009] Technical issues

[0010] This disclosure aims to provide a secondary battery that, while ensuring sealing performance during normal battery operation, has improved safety by guiding the gas to be discharged in a specific direction when gas is generated.

[0011] Technical solution

[0012] In one aspect of this disclosure, a secondary battery according to the following embodiments is provided.

[0013] The first embodiment provides a secondary battery, comprising:

[0014] Electrode assembly;

[0015] Electrode leads are attached to the electrode assembly;

[0016] The housing is configured to house the electrode assembly therein;

[0017] A lead film is formed as part of the outer surface surrounding the electrode lead and is inserted between the electrode lead and the housing;

[0018] An exhaust region is formed in at least a portion of the casing; and

[0019] An exhaust component, inserted into the exhaust region, comprising linear low-density polyethylene with comonomers having 6 or more carbon atoms.

[0020] The exhaust component has a thickness of 50μm or more but less than 200μm.

[0021] In the second embodiment according to the first embodiment, the exhaust component may have a thickness of 50 μm to 100 μm.

[0022] In a third embodiment according to the first or second embodiment, the exhaust component may comprise linear low-density polyethylene having a comonomer having 6 to 8 carbon atoms.

[0023] In the fourth embodiment according to any one of the first to third embodiments, the housing may include a sealing portion formed as a sealing electrode assembly, the sealing portion may contain a sealant resin, and the linear low-density polyethylene of the venting member may have a lower melting point than the sealant resin.

[0024] In the fifth embodiment according to any one of the first to fourth embodiments, the exhaust component can be melted at 100°C to 120°C to exhaust gas.

[0025] In the sixth embodiment according to the fifth embodiment, the exhaust component can exhaust gas at a pressure of 1.5 atm or higher.

[0026] In the seventh embodiment according to any one of the first to sixth embodiments, the exhaust component can have a maximum sealing strength of less than 6 kgf / 15 mm at temperatures above 100°C.

[0027] In the eighth embodiment according to any one of the first to seventh embodiments, the exhaust component can have an average sealing strength of less than 4.5 kgf / 15 mm at temperatures above 100°C.

[0028] In the ninth embodiment according to any one of the first to eighth embodiments, the exhaust component can have a maximum sealing strength of 6 kgf / 15 mm or more at room temperature to 60°C.

[0029] In the tenth embodiment according to any one of the first to ninth embodiments, the exhaust component can have an average sealing strength of 4.5 kgf / 15 mm or more at room temperature to 60°C.

[0030] In the eleventh embodiment according to any one of the first to tenth embodiments, linear low-density polyethylene can be polymerized in the presence of a metallocene catalyst.

[0031] In the twelfth embodiment according to any one of the first to eleventh embodiments, the content of comonomers with 6 or more carbon atoms based on 100% by weight of linear low-density polyethylene may be 15% by weight or less.

[0032] In the thirteenth embodiment according to any one of the first to twelfth embodiments, the linear low-density polyethylene may have a polydispersity index (PDI) of less than 4.

[0033] In the fourteenth embodiment according to any one of the fourth to thirteenth embodiments, the difference between the crystallization temperature of the sealant resin and the crystallization temperature of linear low-density polyethylene can be less than 10°C.

[0034] In the fifteenth embodiment according to the fourteenth embodiment, linear low-density polyethylene may have a crystallization temperature of 90°C to 115°C.

[0035] In the sixteenth embodiment according to any one of the first to fifteenth embodiments, the linear low-density polyethylene may have a melting point of 100°C to 130°C.

[0036] In the seventeenth embodiment according to any one of the first to sixteenth embodiments, the linear low-density polyethylene may have a weight-average molecular weight of 100,000 g / mol to 400,000 g / mol.

[0037] In the eighteenth embodiment according to any one of the first to the seventeenth embodiments, the exhaust member may have a width that narrows along the protruding direction of the electrode lead.

[0038] In the nineteenth embodiment according to any one of the first to eighteenth embodiments, the exhaust component may have any one of the shapes of a circle, an ellipse, a stepped shape, a triangle, and a trapezoid.

[0039] In the twentieth embodiment according to any one of the fourth to nineteenth embodiments, the venting area may be located in the sealing portion.

[0040] In the twenty-first embodiment according to the twenty-first embodiment, the venting area may be located in the sealing portion at the corner of the housing.

[0041] In the twenty-second embodiment according to any one of the first to twenty-first embodiments, the secondary battery may be a pouch-type secondary battery.

[0042] Beneficial effects

[0043] The secondary battery according to embodiments of this disclosure comprises linear low-density polyethylene having comonomers having 6 or more carbon atoms, and includes a venting member having a thickness of 50 μm or more and less than 200 μm to ensure sealing performance during normal battery operation and to guide gas to the venting area when gas is generated. Therefore, battery safety is improved. Attached Figure Description

[0044] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the foregoing disclosure, are intended to provide a further understanding of the technical features of the present disclosure. Therefore, the present disclosure is not to be construed as limited to the drawings.

[0045] Figure 1 is an exploded perspective view of a secondary battery according to an embodiment of the present disclosure.

[0046] Figure 2 is a plan view of a secondary battery according to an embodiment of the present disclosure.

[0047] Figure 3 is a diagram illustrating the state in which venting occurs in a secondary battery according to an embodiment of the present disclosure.

[0048] Figure 4 is a partially enlarged plan view showing the lead film and venting member of a secondary battery according to another embodiment of the present disclosure.

[0049] Figure 5 is a partially enlarged plan view showing the lead film and venting member of a secondary battery according to another embodiment of the present disclosure.

[0050] Figure 6 is a partially enlarged plan view showing the lead film and venting member of a secondary battery according to another embodiment of the present disclosure.

[0051] Figure 7 is a graph showing the maximum sealing strength of the venting member at various temperatures in the secondary batteries prepared according to Examples 1 and 2 and Comparative Examples 1 to 3.

[0052] Figure 8 is a graph showing the average sealing strength of the venting member at various temperatures in the secondary batteries prepared according to Examples 1 and 2 and Comparative Examples 1 to 3. Detailed Implementation

[0053] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before the description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but should be interpreted based on the meaning and concepts corresponding to the technical aspects of the present disclosure, in accordance with the principle that the inventors may appropriately define the terms for best interpretation.

[0054] Therefore, the description presented herein is merely a preferred example for illustrative purposes only and is not intended to limit the scope of this disclosure. It should be understood that other equivalents and modifications may be made to this disclosure without departing from its scope.

[0055] The secondary battery according to an embodiment of the present disclosure includes: an electrode assembly; electrode leads attached to the electrode assembly; a housing configured to house the electrode assembly therein; a lead film formed to surround a portion of the outer surface of the electrode leads and inserted between the electrode leads and the housing; a venting region formed in at least a portion of the housing; and a venting member inserted into the venting region and comprising linear low-density polyethylene having a comonomer having 6 or more carbon atoms, wherein the venting member has a thickness of 50 μm or more and less than 200 μm.

[0056] Figures 1 and 2 illustrate a secondary battery 10 according to an embodiment of the present disclosure.

[0057] Referring to Figures 1 and 2, the secondary battery 10 includes an electrode assembly 12 with electrode leads 11 attached, and a housing 13.

[0058] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. In the electrode assembly 12, the positive electrode plate and the negative electrode plate can be laminated sequentially, and a separator is inserted between them.

[0059] The positive electrode plate may include a positive current collector made of a thin metal film (e.g., aluminum (Al) foil) with excellent conductivity, and a layer of positive active material coated on at least one surface thereon. Furthermore, a positive electrode sheet made of a metallic material (e.g., aluminum (Al) material) may be included at one side of the positive electrode plate. The positive electrode sheet may protrude from one side of the positive electrode plate. The positive electrode sheet may be soldered to one side of the positive electrode plate, or bonded to one side of the positive electrode plate using a conductive adhesive.

[0060] The negative electrode plate may include a negative current collector made of a conductive metal film (e.g., copper (Cu) foil) and a negative active material layer coated on at least one surface thereon. Furthermore, a negative electrode sheet formed of a metallic material (e.g., nickel (Ni) material) may be included at one side of the negative electrode plate. The negative electrode sheet may protrude from one side of the negative electrode plate. The negative electrode sheet may be soldered to one side of the negative electrode plate or bonded to one side of the negative electrode plate using a conductive adhesive.

[0061] A separator is inserted between the positive and negative electrode plates to electrically insulate them from each other. The separator can be a porous membrane, allowing lithium ions to pass between the positive and negative electrode plates. For example, the separator may comprise a porous membrane made of polyethylene (PE) or polypropylene (PP) or a composite thereof.

[0062] Inorganic coatings can be applied to the surface of the partition. The inorganic coating can have a structure in which inorganic particles are bonded together by an adhesive to form interstitial volumes between the particles.

[0063] The electrode assembly 12 can be a jelly-roll (wound type) electrode assembly, a stacked (stacked type) electrode assembly, a stacked / folded type electrode assembly, etc. The jelly-roll (wound type) electrode assembly has a structure in which long sheet-shaped positive and negative electrodes are wound together with a partition inserted between them. The stacked (stacked type) electrode assembly has a structure in which multiple positive and multiple negative electrodes cut into units of a predetermined size are stacked sequentially with a partition inserted between them. The stacked / folded type electrode assembly has a structure in which a predetermined unit of positive and negative electrodes is stacked and a partition is inserted between them, and a dual-unit or full-unit winding structure is formed.

[0064] The housing 13 is used to house the electrode assembly 12.

[0065] In an embodiment of this disclosure, as shown in FIG1, the housing 13 may include a receiving portion 13a for accommodating the electrode assembly 12, and a sealing portion 13b formed to seal the electrode assembly 12.

[0066] The sealing portion 13b may include a sealant resin, and the sealant resin may be fused along the outer periphery of the receiving portion 13a to seal the electrode assembly 12.

[0067] In embodiments of this disclosure, the housing 13 may be configured as a membrane with a multilayer structure, the multilayer structure including an outer layer for preventing external impact, a metal barrier layer for blocking moisture, and a sealant layer for sealing.

[0068] The outer layer may include a polyester base film made of polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyester, polycarbonate, nylon, etc., and may be configured as a single layer or multiple layers.

[0069] Metal barrier layers can include aluminum, copper, etc.

[0070] The sealant layer may include a sealant resin and may be formed as a single layer or multiple layers.

[0071] The sealant resin may include polypropylene (PP), acid-modified polypropylene (PPa), atactic polypropylene, ethylene-propylene copolymer, or two or more thereof. Ethylene-propylene copolymer may include, but is not limited to, ethylene-propylene rubber, ethylene-propylene block copolymer, etc.

[0072] In embodiments of this disclosure, the housing 13 may be in the form of a soft package.

[0073] The soft-pack housing 13 may include an upper soft-pack and a lower soft-pack. When the housing 13 includes an upper soft-pack and a lower soft-pack, after the upper soft-pack and the lower soft-pack are arranged so that their sealant resins face each other, the facing sealant resins may be configured to fuse with each other by heat and pressure to seal the battery.

[0074] The fusion of the sealing part 13b can be thermal fusion, ultrasonic fusion, etc., but there are no particular restrictions, as long as the sealing part 13b can be fused.

[0075] In some embodiments, the sealing portion 13b can be sealed on four or three of the outer peripheral sides of the battery housing 13. In a three-sided sealing structure, after the upper and lower soft packs are formed on a soft pack sheet, the boundary surface between the upper and lower soft packs is bent such that the electrode assembly receiving portions 13a formed on the upper and lower soft packs overlap, and in this state, the edges on the other three sides are sealed except for the bent portion.

[0076] As shown in Figure 1, the electrode lead 11 can be housed in the housing 13, such that a portion of it is exposed to the outside of the battery housing 13.

[0077] The secondary battery 10 according to an embodiment of the present disclosure includes a lead film 14.

[0078] The lead film 14 surrounds a portion of the outer surface of the electrode lead 11 and is inserted between the electrode lead 11 and the housing 13. For example, in the region where the electrode lead 11 protrudes from or extends away from the housing 13, the lead film 14 can be inserted between the electrode lead 11 and the sealing portion 13b of the housing 13 to facilitate the connection between the electrode lead 11 and the housing 13.

[0079] Referring to Figures 1 and 2, the secondary battery 10 according to an embodiment of the present disclosure may include a venting region (not shown) formed in at least a portion of the housing 13, and a venting member 15 may be inserted into the venting region. In the event of heat propagation, the venting member 15 may guide gas out in a specific direction, thereby improving battery safety.

[0080] The venting member 15 can be attached to the housing 13 by heat fusion. In another example, the venting member 15 can be attached to the housing 13 by an adhesive (e.g., glue). In another example, the venting member 15 and the housing 13 can be physically bonded to each other by clips or the like. In yet another example, at least a portion of the venting member 15 can be embedded in a membrane constituting the housing 13, such as a sealant resin.

[0081] The exhaust component 15 comprises linear low-density polyethylene with comonomers having 6 or more carbon atoms. Because the exhaust component 15 comprises linear low-density polyethylene with comonomers having 6 or more carbon atoms, the sealing performance of the housing 13 is excellent in a normal temperature range, such as from room temperature to 60°C. However, at high temperatures, such as above 100°C, the exhaust sealing strength of the housing into which the exhaust component 15 is inserted may decrease, which may result in or cause exhaust.

[0082] Figure 3 is a diagram illustrating the state of venting in a secondary battery according to an embodiment of the present disclosure. Specifically, Figure 3 is a cross-sectional view showing the venting component in a secondary battery according to an embodiment of the present disclosure.

[0083] Referring to Figure 3, at the normal operating temperature of the battery, the venting member 15 serves to seal the casing from the outside. If the battery temperature rises excessively due to abnormal battery operation, the venting member 15 melts, and the sealing strength of the portion of the casing into which the venting member 15 is inserted decreases. Therefore, gas can be released into this portion. For example, as the pressure of the gas inside the battery is applied to the interface between the venting member 15 and the casing, a gap is formed between the venting member 15 and the casing, and gas can be released into this gap.

[0084] In embodiments of this disclosure, the exhaust component 15 may comprise linear low-density polyethylene having a comonomer having 6 to 8 carbon atoms.

[0085] In embodiments of this disclosure, linear low-density polyethylene having comonomers with 6 or more carbon atoms can have a lower melting point than the sealant resin. If linear low-density polyethylene having comonomers with 6 or more carbon atoms has a lower melting point than the sealant resin, then linear low-density polyethylene may melt faster than the sealant resin at high temperatures. As the sealing strength of the portion into which the venting member 15 is inserted decreases below the sealing strength of the portion of the housing containing the sealant resin, venting characteristics can be achieved more easily.

[0086] In embodiments of this disclosure, linear low-density polyethylene having comonomers with 6 or more carbon atoms can have melting points of 100°C to 130°C, 105°C to 125°C, or 110°C to 120°C. If the melting point of the linear low-density polyethylene having comonomers with 6 or more carbon atoms meets the above range, then at high temperatures, such as above 100°C, the sealing strength of the portion into which the venting member 15 of the shell is inserted can be reduced, thereby making it easier to achieve venting characteristics.

[0087] The melting point of linear low-density polyethylene with comonomers having 6 or more carbon atoms can be measured using a differential scanning calorimeter (DSC). For example, the sample temperature is increased from 30°C to 280°C at a rate of 10°C / min, held at 280°C for 10 minutes, cooled to 30°C at a rate of 10°C / min, and then held at 30°C for 10 minutes. Then, after increasing the sample temperature from 30°C to 280°C at a rate of 10°C / min, the melting point can be measured by holding the temperature at 280°C for 10 minutes.

[0088] In embodiments of this disclosure, linear low-density polyethylene having comonomers with 6 or more carbon atoms can be polymerized in the presence of a metallocene catalyst. If linear low-density polyethylene having comonomers with 6 or more carbon atoms is polymerized in the presence of a metallocene catalyst, it may be more advantageous in terms of sealing strength and performance compared to polymerization in the presence of a Ziegler-Natta catalyst.

[0089] In embodiments of this disclosure, in linear low-density polyethylene having comonomers with 6 or more carbon atoms, based on 100% by weight of linear low-density polyethylene having comonomers with 6 or more carbon atoms, the content of comonomers with 6 or more carbon atoms can be less than 15% by weight, or less than 12% by weight, or less than 11.8% by weight, or less than 10% by weight, or less than 9% by weight, or less than 8% by weight, or less than 7.6% by weight. Simultaneously, it can be more than 5% by weight, or more than 7.6% by weight, or more than 8% by weight, or more than 9% by weight, or more than 10% by weight, or more than 11.8% by weight, or more than 12% by weight. If the content of comonomers with 6 or more carbon atoms meets the above ranges, it can be easily ensured that the sealing strength does not decrease due to the decrease in the packing density between molecules during normal battery operation.

[0090] The content of comonomers with 6 or more carbon atoms can be measured using ¹H NMR. For example, after completely dissolving approximately 10 mg of sample in approximately 0.6 mL of trichloroethylene solvent using a hot gun, a sample can be taken from an NMR tube and used for NMR analysis. 1 Measurements were performed using H-NMR.

[0091] In embodiments of this disclosure, the linear low-density polyethylene having comonomers with 6 or more carbon atoms can have a weight-average molecular weight of 100,000 g / mol to 400,000 g / mol, or 200,000 g / mol to 350,000 g / mol, or 230,000 g / mol to 300,000 g / mol. If the weight-average molecular weight of the linear low-density polyethylene having comonomers with 6 or more carbon atoms meets the above range, the sealing strength with the sealant resin can be improved during normal battery operation.

[0092] In the embodiments of this disclosure, the linear low-density polyethylene having comonomers with 6 or more carbon atoms can have a polydispersity index (PDI) of 4 or less, or 3.8 or less, or 3.796 or less, or 3.5 or less, or 3.023 or less, or 3 or less, or 2.7 or less, or 2.674 or less. Alternatively, the PDI can be 1.0 or more. If the polydispersity index of the linear low-density polyethylene having comonomers with 6 or more carbon atoms meets the above ranges, the molecular weight distribution is narrow, and therefore the sealing strength and performance can be superior during normal battery operation.

[0093] The carbon number can be measured by gel permeation chromatography (GPC) under the following conditions to determine the weight-average molecular weight and polydispersity index of linear low-density polyethylene with comonomers having 6 or more carbon atoms:

[0094] Column: Tosoh, HLC-8321GPC / HT

[0095] Solvent: TCB (trichlorobenzene) + 0.04% BHT (dried with 0.1% CaCl2)

[0096] Flow rate: 1.0 ml / min

[0097] Sample concentration: 1.5 mg / ml

[0098] Dosage: 300 μL

[0099] Column temperature: 160℃

[0100] Detector: RI detector

[0101] Standard: Polystyrene (calibrated using a third-order function)

[0102] In embodiments of this disclosure, the crystallization temperature of the sealant resin and the crystallization temperature of linear low-density polyethylene having comonomers with 6 or more carbon atoms can be similar. For example, the difference between the crystallization temperature of the sealant resin and the crystallization temperature of linear low-density polyethylene having comonomers with 6 or more carbon atoms can be less than 10°C or less, or less than 5°C. Alternatively, the difference between the crystallization temperature of the sealant resin and the crystallization temperature of linear low-density polyethylene having comonomers with 6 or more carbon atoms can be 0.1°C or more. If the difference between the crystallization temperature of the sealant resin and the crystallization temperature of linear low-density polyethylene having comonomers with 6 or more carbon atoms satisfies the above range, the sealant resin and the linear low-density polyethylene having comonomers with 6 or more carbon atoms can have improved melting characteristics during normal battery operation.

[0103] In embodiments of this disclosure, linear low-density polyethylene having comonomers with 6 or more carbon atoms can have crystallization temperatures of 90°C to 115°C, 95°C to 110°C, 100°C to 110°C, or 105°C to 110°C. If the crystallization temperature of the linear low-density polyethylene having comonomers with 6 or more carbon atoms meets the above ranges, the sealant resin and the linear low-density polyethylene having comonomers with 6 or more carbon atoms can have improved melt characteristics.

[0104] In the embodiments of this disclosure, the difference between the crystallization temperature of the sealant resin and the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms can be less than 10°C, and the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms can be from 90°C to 115°C.

[0105] Crystallization temperature can be measured using a differential scanning calorimeter (DSC). For example, the sample temperature is increased from 30°C to 280°C at a rate of 10°C / min, held at 280°C for 10 minutes, cooled to 30°C at a rate of 10°C / min, and then held at 30°C for 10 minutes. Then, after increasing the sample temperature from 30°C to 280°C at a rate of 10°C / min, the crystallization temperature can be measured by holding the temperature at 280°C for 10 minutes.

[0106] The venting member 15 has a thickness of 50 μm or more and less than 200 μm. Because the thickness of the venting member 15 meets the above-mentioned range, the battery's sealing performance can be ensured during normal battery operation, for example, at temperatures ranging from room temperature to 60°C. For example, during normal battery operation, the sealing strength can be ensured to reach the level of a conventional secondary battery. In particular, the battery's sealing performance can be ensured at 60°C.

[0107] If the thickness of the venting member 15 is 200 μm or more, it is difficult to ensure the sealing performance of the battery during normal operation. In particular, it is difficult to ensure the sealing performance of the battery at 60°C. If the thickness of the venting member 15 is 200 μm or more, compared to cases where the thickness of the venting member 15 is 50 μm or more but less than 200 μm, the sealing strength of the portion into which the venting member 15 is inserted in the casing may be very low during normal battery operation, for example, at temperatures between room temperature and 60°C. In particular, the sealing strength of the portion into which the venting member is inserted in the casing may be very low at 60°C, which may make it difficult to ensure the sealing performance of the battery.

[0108] If the thickness of the exhaust component 15 is less than 50 μm, there is a risk of deformation of the exhaust component 15 during the fusion process between the exhaust component 15 and the housing 13. Therefore, the machinability of the exhaust component 15 is significantly degraded.

[0109] In embodiments of this disclosure, the thickness of the venting member 15 can be from 50 μm to 100 μm. If the thickness of the venting member 15 meets the above range, the sealing performance of the battery can be more easily guaranteed during normal operation. In particular, the sealing performance of the battery can be more easily guaranteed at 60°C.

[0110] In embodiments of this disclosure, the venting member 15 may have a structure that narrows along the protruding direction of the electrode lead 11. The width of the venting member 15 may narrow continuously or discontinuously along the protruding direction of the electrode lead 11. If the venting member 15 has a structure that narrows along the protruding direction of the electrode lead 11, the venting angle of the discharged gas is reduced to minimize the amount of gas discharged toward the side of the electrode lead 11, thereby further improving battery safety.

[0111] Figures 4 to 6 are partially enlarged views showing the lead film 14 and the venting member 15 in a secondary battery 10 according to other embodiments of the present disclosure.

[0112] Referring to Figures 4 and 5, the exhaust member 15 may have, for example, an elliptical or stepped shape. However, the shape of the exhaust member 15 may be defined as other shapes such as circles, triangles, trapezoids, etc.

[0113] As shown in Figure 6, the exhaust member 15 can be an asymmetrical stepped structure. In an asymmetrical stepped structure, an offset between the steps can be formed, minimizing direct contact between the exhaust gas and the electrode lead 11. For example, the size (exhaust angle of the exhaust gas) and position (distance from the electrode lead 11) of the exhaust end of the exhaust member 15 can be configured to minimize contact between the exhaust gas and the electrode lead (as shown in Figure 6). Therefore, reducing the size of the exhaust end of the exhaust member 15 to guide the gas away from the electrode lead 11 and arranging the exhaust end away from the electrode lead will minimize any contact between the exhaust gas and the electrode lead. In this case, the exhaust direction of the exhaust gas can be further separated from the side of the electrode lead 11 (as shown in Figure 7).

[0114] In embodiments of this disclosure, the venting member 15 can vent at a temperature of 100°C to 120°C to discharge gas from the containment or to the outside of the secondary battery. Specifically, the venting member 15 can vent at a temperature of 100°C to 120°C and a pressure of 1.5 atm or higher. Because the venting member 15 is vented within the aforementioned temperature range and / or pressure conditions, it allows the battery to be sealed during normal operation while guiding gas venting only during periods of abnormal battery operation.

[0115] In embodiments of this disclosure, the exhaust member 15 can have a maximum sealing strength of less than 6 kgf / 15 mm, less than 5 kgf / 15 mm, or less than 4.5 kgf / 15 mm at temperatures above 100°C. In embodiments of this disclosure, the exhaust member 15 can have a maximum sealing strength of less than 6 kgf / 15 mm, less than 5 kgf / 15 mm, or less than 4.5 kgf / 15 mm at temperatures between 100°C and 120°C. In embodiments of this disclosure, the exhaust member 15 can have a maximum sealing strength of less than 3 kgf / 15 mm, less than 2 kgf / 15 mm, less than 1 kgf / 15 mm, or less than 0.5 kgf / 15 mm at temperatures above 120°C. If the exhaust member 15 meets the above sealing strength requirements within the aforementioned temperature range, the sealing strength of the portion of the housing 13 into which the exhaust member 15 is inserted can be reduced at high temperatures (e.g., above 100°C), thereby easily achieving the desired exhaust characteristics.

[0116] In embodiments of this disclosure, the venting member 15 can have a maximum sealing strength of 6 kgf / 15 mm or more, or 7 kgf / 15 mm or more, or 8 kgf / 15 mm or more, or 9 kgf / 15 mm or more, or 10 kgf / 15 mm or more, at room temperature to 60°C. If the venting member 15 meets the above sealing strength within the above temperature range, then even when the venting member 15 is inserted, the inserted portion of the housing 13 during normal battery operation can still have excellent sealing strength, which can easily ensure the sealing performance of the battery.

[0117] In embodiments of this disclosure, the venting member 15 can have a maximum sealing strength of less than 6 kgf / 15 mm at temperatures above 100°C. The venting member 15 can also have a maximum sealing strength of 6 kgf / 15 mm or more at temperatures from room temperature to 60°C. If the venting member 15 meets the aforementioned sealing strength, the sealing strength of the portion of the housing 13 into which the venting member 15 is inserted can be reduced at high temperatures (e.g., above 100°C), thereby easily achieving venting characteristics. Furthermore, since the housing 13 has excellent sealing strength during normal battery operation, the sealing performance of the battery can be easily ensured.

[0118] In embodiments of this disclosure, the exhaust member 15 can have an average sealing strength of less than 4.5 kgf / 15 mm or less than 3 kgf / 15 mm at temperatures above 100°C. In embodiments of this disclosure, the exhaust member 15 can have an average sealing strength of less than 4.5 kgf / 15 mm or less than 3 kgf / 15 mm at temperatures between 100°C and 120°C. In embodiments of this disclosure, the exhaust member 15 can have an average sealing strength of less than 2 kgf / 15 mm, less than 1 kgf / 15 mm, or less than 0.5 kgf / 15 mm at temperatures above 120°C. If the exhaust member 15 meets the above sealing strength requirements within the aforementioned temperature range, the sealing strength of the portion of the housing 13 into which the exhaust member 15 is inserted can be reduced at high temperatures (e.g., above 100°C), thereby easily achieving the desired exhaust characteristics.

[0119] In embodiments of this disclosure, the venting member 15 can have an average sealing strength of 4.5 kgf / 15 mm or more, or 5 kgf / 15 mm or more, or 6 kgf / 15 mm or more, or 7 kgf / 15 mm or more, at room temperature to 60°C. If the venting member 15 meets the above sealing strength within the above temperature range, then even when the venting member 15 is inserted, the inserted portion of the venting member 15 of the housing 13 can have excellent sealing strength during normal operation of the battery, thereby easily ensuring sealing performance.

[0120] In embodiments of this disclosure, the venting member 15 can have an average sealing strength of less than 4.5 kgf / 15 mm at temperatures above 100°C. The venting member 15 can also have an average sealing strength of 4.5 kgf / 15 mm or more at temperatures from room temperature to 60°C. If the venting member 15 has the aforementioned sealing strength within the above temperature range, the sealing strength of the portion of the housing 13 into which the venting member 15 is inserted can be reduced at high temperatures (e.g., above 100°C), thereby easily achieving venting characteristics. Furthermore, since excellent sealing strength can be ensured during normal battery operation, the battery's sealing performance can be easily ensured.

[0121] The temperature-dependent sealing strength of the exhaust component 15 can be measured by cutting the portion into which the exhaust component 15 is inserted into the housing into a 15mm wide and 5cm long section, then gripping both ends with a UTM clamp while the sections are spread out to 180°, and performing a tensile test at a speed of 5mm / min.

[0122] At this point, the maximum sealing strength refers to the maximum value when the housing 13 breaks, and the average sealing strength refers to the average value when the housing 13 is stretched by 8 mm at 4.5 kgf / 15 mm when the maximum sealing strength is above 4.5 kgf / 15 mm, and the average value when the housing 13 is stretched by 8 mm at the maximum sealing strength when the maximum sealing strength is less than 4.5 kgf / 15 mm.

[0123] In embodiments of this disclosure, as shown in Figures 1 and 2, the exhaust component 15 may be located in the sealing portion.

[0124] Referring to Figure 2, the venting member 15 can be located in a sealing portion at a corner of the housing. For example, the venting member 15 can be located at a corner of the sealing portion that exposes the electrode leads 11 to the outside. Specifically, the venting member 15 can be located in a sealing portion next to the electrode leads 11, outside the area between the electrode leads 11. When the venting member 15 is located at a corner of the sealing portion that exposes the electrode leads 11 to the outside, the amount of gas discharged toward the electrode leads 11 can be minimized, thereby further improving battery safety.

[0125] In embodiments of this disclosure, when the sealing portion 13b is sealed at three sides, the curved side of the housing and one end of the venting member 15 can be in close contact.

[0126] Furthermore, the exhaust member 15 can be inserted into the housing 13, such that, depending on the design, the insertion length can be varied or the exhaust pressure and position can be controlled. Here, the insertion length of the exhaust member 15 refers to the maximum distance between one end and the other end of the exhaust member 15 based on the protruding direction of the electrode leads.

[0127] In embodiments of this disclosure, the insertion length of the exhaust member 15 may be less than the width of the sealing portion 13b. For example, the insertion length of the exhaust member 15 may be less than approximately 50% of the width of the sealing portion 13b. Here, the width of the sealing portion 13b refers to the maximum value of the distance between one end and the other end of the sealing portion 13b based on the protruding direction of the electrode lead 11.

[0128] In another embodiment of this disclosure, the insertion length of the venting member 15 may be greater than the width of the sealing portion 13b. For example, the venting member 15 may be inserted from the receiving portion 13a through the sealing portion 13b to expose the exterior of the housing 13.

[0129] In embodiments of this disclosure, the venting member 15 may further include an adhesive layer for smoother placement.

[0130] In another embodiment of this disclosure, the venting member 15 may be located in a seal other than the seal that exposes the electrode lead 11 to the outside.

[0131] In another embodiment of this disclosure, the venting member 15 may be located in a sealing portion that exposes the electrode lead 11 to the outside. For example, the venting member 15 may be arranged in a sealing portion between electrode leads 11.

[0132] In embodiments of this disclosure, the exhaust member 15 may have a membrane shape.

[0133] In the embodiments of this disclosure, the secondary battery can be a cylindrical, prismatic, or pouch-type secondary battery. Specifically, the secondary battery can be a pouch-type secondary battery.

[0134] Implementation

[0135] In the following description, the present disclosure will be illustrated in more detail with reference to exemplary embodiments. However, the present disclosure may be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Clearly, these exemplary embodiments are provided to enable the present disclosure to be complete and readily understood by those skilled in the art.

[0136] Example 1

[0137] An upper and lower soft package, each sequentially laminated with polyethylene terephthalate (PET), aluminum foil, and polypropylene resin, are placed so that the polypropylene resin faces each other, and then housed in an electrode assembly in which the positive electrode, separator, and negative electrode are stacked in sequence.

[0138] Then, a 50 μm thick layer of linear low-density polyethylene (LG Chem, Lucene) containing a comonomer with 6 carbon atoms, polymerized in the presence of a metallocene catalyst, is inserted between the polypropylene resins. TM Exhaust components (SP311).

[0139] Example 2

[0140] The secondary battery was prepared in the same manner as in Example 1, except that it contained linear low-density polyethylene (LG Chem, Lucene) with a carbon-6 comonomer polymerized in the presence of a metallocene catalyst. TM The thickness of the exhaust component (SP311) is 100μm.

[0141] Comparative Example 1

[0142] An upper and lower soft package, each sequentially laminated with polyethylene terephthalate (PET), aluminum foil, and polypropylene resin, are placed so that the polypropylene resin faces each other, and then housed in an electrode assembly in which the positive electrode, separator, and negative electrode are stacked in sequence.

[0143] Then, the polypropylene resin is thermally melted to prepare the secondary battery.

[0144] Comparative Example 2

[0145] The secondary battery was prepared in the same manner as in Example 1, except that the thickness of the exhaust component of linear low-density polyethylene (LG Chem, Lucene™, SP311) containing a comonomer with 6 carbon atoms polymerized in the presence of a metallocene catalyst was 200 μm.

[0146] Comparative Example 3

[0147] The secondary battery was prepared in the same manner as in Example 1, except that the thickness of the exhaust component of linear low-density polyethylene (LG Chem, Lucene™, SP311) containing a comonomer with 6 carbon atoms polymerized in the presence of a metallocene catalyst was 300 μm.

[0148] Evaluation Example 1: Measurement of Sealing Strength Based on Temperature

[0149] In the secondary batteries prepared in Examples 1 and 2 and Comparative Examples 2 to 3, the portion of the casing into which the venting member is inserted was cut into pieces 15 mm wide and 5 mm long at the following temperature. The two ends of the cut samples were then opened 180° and clamped using a UTM clamp, followed by a tensile test at a speed of 5 mm / min. The sealing strength of the casing at this time is shown in Table 1 and Figures 7 to 8 below.

[0150] In the secondary battery prepared in Comparative Example 1, the portion of the casing corresponding to the sealing part was cut into pieces 15 mm wide and 5 mm long at the following temperature. The two ends of the cut sample were then opened at 180° and clamped with a UTM clamp, and a tensile test was performed at a speed of 5 mm / min. The sealing strength of the casing at this time is shown in Table 1 and Figures 7 to 8 below.

[0151] At this point, the maximum sealing strength refers to the maximum value when the shell breaks, and the average sealing strength refers to the average value when the shell is stretched by 8 mm at 4.5 kgf / 15 mm when the maximum sealing strength is above 4.5 kgf / 15 mm, and the average value when the shell is stretched by 8 mm at the maximum sealing strength when the maximum sealing strength is less than 4.5 kgf / 15 mm.

[0152] Table 1

[0153]

[0154] As shown in Table 1 and Figures 7 to 8, it can be seen that in the secondary batteries prepared in Examples 1 and 2, the maximum and average sealing strength of the portion of the casing into which the venting member is inserted at room temperature to 60°C are similar to the maximum and average sealing strength of the casing of the secondary battery prepared in Comparative Example 1 at room temperature to 60°C. Furthermore, it can be seen that in the secondary batteries prepared in Examples 1 and 2, the maximum and average sealing strength of the casing with the venting member inserted at temperatures above 100°C are significantly lower than the maximum and average sealing strength of the casing of the secondary battery prepared in Comparative Example 1 at temperatures above 100°C.

[0155] Therefore, the secondary batteries with venting components prepared in Examples 1 and 2 can ensure adequate sealing strength when the battery is operating normally, and when the battery is heated to a high temperature due to abnormal phenomena, the gas can be discharged through the venting component, which weakens the sealing strength. On the other hand, the secondary battery prepared in Comparative Example 1 can ensure adequate sealing strength when the battery is operating normally, but when the battery is heated to a high temperature due to abnormal phenomena, the gas is discharged in an unspecified direction, which may lead to chain ignition of the battery.

[0156] The results showed that in the secondary batteries prepared in Comparative Examples 2 and 3, the maximum and average sealing strength of the portion of the casing into which the venting member was inserted (particularly at 60°C) were significantly lower than those of the secondary batteries prepared according to Examples 1 and 2 at the same temperature. Therefore, it can be confirmed that the secondary batteries prepared in Comparative Examples 2 and 3 cannot guarantee sufficient sealing strength during normal battery operation.

Claims

1. A secondary battery, comprising: Electrode assembly; Electrode leads are attached to the electrode assembly; A housing is configured to house the electrode assembly therein; A lead film is formed to surround a portion of the outer surface of the electrode lead and is inserted between the electrode lead and the housing; an exhaust region is formed in at least a portion of the housing; The venting member is inserted into the venting region and comprises linear low-density polyethylene having a comonomer having 6 or more carbon atoms, wherein the venting member has a thickness of 50 μm or more and less than 200 μm, wherein the venting member is an asymmetric stepped structure, wherein the housing includes a sealing portion formed to seal the electrode assembly, the sealing portion comprising a sealant resin, and the linear low-density polyethylene of the venting member having a lower melting point than the sealant resin, and wherein the venting member is inserted from the portion receiving the electrode assembly through the sealing portion to be exposed to the outside of the housing, the venting member is positioned near the electrode lead, and the venting member is positioned near a corner of the housing, the venting member is L-shaped and includes a narrow portion and a wide portion, the narrow portion facing the outside of the housing, the wide portion facing the inside of the housing, and the narrow portion being relatively further away from the electrode lead than the wide portion.

2. The secondary battery according to claim 1, wherein, The exhaust component has a thickness of 50 μm to 100 μm.

3. The secondary battery according to claim 1, wherein, The exhaust component comprises linear low-density polyethylene having comonomers with a carbon number of 6 to 8.

4. The secondary battery according to claim 1, wherein, The exhaust component is melted at 100°C to 120°C to expel gas.

5. The secondary battery according to claim 4, wherein, The exhaust component exhausts gas at a pressure of 1.5 atm or higher.

6. The secondary battery according to claim 1, wherein, The exhaust component has a maximum sealing strength of less than 6 kgf / 15 mm at temperatures above 100°C.

7. The secondary battery according to claim 1, wherein, The exhaust component has an average sealing strength of less than 4.5 kgf / 15 mm at temperatures above 100°C.

8. The secondary battery according to claim 1, wherein, The exhaust component has a maximum sealing strength of 6 kgf / 15 mm or more at room temperature to 60°C.

9. The secondary battery according to claim 1, wherein, The exhaust component has an average sealing strength of 4.5 kgf / 15 mm or more at room temperature to 60°C.

10. The secondary battery according to claim 1, wherein, The linear low-density polyethylene is polymerized in the presence of a metallocene catalyst.

11. The secondary battery according to claim 1, wherein, Based on 100% by weight of the linear low-density polyethylene, the content of the comonomer having 6 or more carbon atoms is 15% by weight or less.

12. The secondary battery according to claim 1, wherein, The linear low-density polyethylene has a polydispersity index (PDI) of less than 4.

13. The secondary battery according to claim 1, wherein, The difference between the crystallization temperature of the sealant resin and the crystallization temperature of the linear low-density polyethylene is less than 10°C.

14. The secondary battery according to claim 13, wherein, The linear low-density polyethylene has a crystallization temperature of 90°C to 115°C.

15. The secondary battery according to claim 1, wherein, The linear low-density polyethylene has a melting point of 100°C to 130°C.

16. The secondary battery according to claim 1, wherein, The linear low-density polyethylene has a weight-average molecular weight of 100,000 g / mol to 400,000 g / mol.

17. The secondary battery according to claim 1, wherein, The venting area is located within the sealing portion.

18. The secondary battery according to claim 17, wherein, The venting area is located in the sealing portion at the corner of the housing.

19. The secondary battery according to claim 1, wherein, The secondary battery is a pouch-type secondary battery.

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