Secondary batteries

Abstract

To provide a secondary battery having a vent member.SOLUTION: A secondary battery includes: an electrode assembly with an electrode lead attached thereto; a case including an accommodation portion for accommodating the electrode assembly such that a part of the electrode lead is exposed to an outside, and a sealing portion formed to seal the electrode assembly; and a lead film surrounding a part of the outer surface of the electrode lead and interposed between the electrode lead and the sealing portion of the case. The sealing portion has a vent-inducing region including a vent member containing linear low-density polyethylene having a comonomer with 6 or more carbon atoms. The width of the vent-inducing region is smaller than the width of the sealing portion other than the vent-inducing region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application claims priority based on Korean Patent Application No. 10-2021-0049398 filed on April 15, 2021, and Korean Patent Application No. 10-2022-0007212 filed on January 18, 2022.

[0002] The present invention relates to a secondary battery, and more particularly, to a secondary battery provided with a vent member.

Background Art

[0003] Secondary batteries, which can be applied to various products and have excellent electrical characteristics such as high energy density, are widely applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) powered by electricity. Such secondary batteries not only significantly reduce the use of fossil fuels but are also environmentally friendly in that no by-products are generated during the energy consumption process, and are attracting attention as a new energy source for improving energy efficiency.

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

[0005] A secondary battery generally includes an electrode assembly including at least one unit cell having a structure of a positive electrode / separator / negative electrode, and is housed in a case made of a laminate sheet in which an outer layer, a metal barrier layer, and a sealant layer are sequentially laminated, and has a structure in which the sealant resin of the sealant layer is fused to seal the electrode assembly.

[0006] Conventionally, secondary batteries can ignite due to a variety of causes, including short circuits, overcharging or over-discharging, and temperature regulation. In such cases, a thermal runaway phenomenon occurs where the internal temperature of the secondary battery rises rapidly and heat is simultaneously transferred to adjacent cells, potentially causing the fire to spread further.

[0007] When thermal runaway occurs, that is, when the internal temperature of a secondary battery rises, directional venting characteristics are required to expel gas in one direction in order to minimize electrode damage caused by gas. However, conventional secondary batteries have the problem that it is difficult to induce gas expulsion in a specific direction.

[0008] Therefore, the present invention aims to provide a secondary battery with improved safety by inducing gas discharge in a specific direction. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The problem that this invention aims to solve is to provide a secondary battery that improves safety by more easily inducing gas discharge into the vent induction region. [Means for solving the problem]

[0010] To achieve the above objectives, according to one aspect of the present invention, a secondary battery of the following embodiment is provided.

[0011] The first embodiment relates to a secondary battery comprising an electrode assembly, electrode leads attached to the electrode assembly, a case including a housing for housing the electrode assembly and a sealing portion formed to seal the electrode assembly with a sealant resin, a lead film formed to cover a part of the outer surface of the electrode leads and interposed between the electrode leads and the case, and a vent member including linear low-density polyethylene having a comonomer with 6 or more carbon atoms, wherein the sealing portion includes a vent induction region including the vent member, and the width of the vent induction region is narrower than the width of the other sealing portions excluding the vent induction region.

[0012] According to the second embodiment, in the first embodiment, the width of the vent guidance area may be 40% to 80% of the width of the other sealing parts excluding the vent guidance area.

[0013] According to the third embodiment, in the first embodiment or the second embodiment, the tape can be inserted such that the width of the vent guidance area is narrower than the width of the other sealing portion excluding the vent guidance area.

[0014] According to the fourth embodiment, in the third embodiment, the tape may contain polyimide, polyethylene terephthalate (PET), or a mixture thereof.

[0015] According to the fifth embodiment, in the first or second embodiment, resin can be inserted such that the width of the vent guidance area is narrower than the width of the other sealing portion excluding the vent guidance area.

[0016] According to the sixth embodiment, in the fifth embodiment, the resin may include a fluororesin, a silicone resin, or a mixture thereof.

[0017] According to the seventh embodiment, in any one of the first to sixth embodiments, the vent induction region can be formed in the sealing portion close to the electrode leads, excluding the region between the electrode leads.

[0018] According to the eighth embodiment, in any one of the first to seventh embodiments, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be a linear low-density polyethylene having a comonomer with 6 to 8 carbon atoms.

[0019] According to the 9th embodiment, in any one of the 1st to 8th embodiments, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may have a lower melting point than the sealant resin.

[0020] According to the 10th embodiment, in any one of the 1st to 9th embodiments, the vent member can be melted at 100°C to 120°C in order to discharge gas.

[0021] According to the 11th embodiment, in the 10th embodiment, the venting member can vent at a pressure of 1.5 atm or more.

[0022] According to the 12th embodiment, in any one of the 1st to 11th embodiments, the maximum sealing strength of the vent member at temperatures above 100°C may be less than 6 kgf / 15 mm.

[0023] According to the 13th embodiment, in any one of the 1st to 12th embodiment, the average sealing strength of the vent member at temperatures of 100°C or higher may be less than 4.5 kgf / 15 mm.

[0024] According to the 14th embodiment, in any one of the 1st to 13th embodiment, the maximum sealing strength of the vent member at room temperature to 60°C may be 6 kgf / 15 mm or more.

[0025] According to the 15th embodiment, in any one of the 1st to 14th embodiment, the average sealing strength of the vent member at room temperature to 60°C may be 4.5 kgf / 15 mm or more.

[0026] According to the 16th embodiment, in any one of the 1st to 15th embodiments, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be polymerized in the presence of a metallocene catalyst.

[0027] According to the 17th embodiment, in any one of the 1st to 16th embodiments, the content of the comonomer with 6 or more carbon atoms in the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 15% by weight or less based on 100% by weight of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms.

[0028] According to the 18th embodiment, in any one of the 1st to 17th embodiments, the polydispersity index (PDI) of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 4 or less.

[0029] According to the 19th embodiment, in any one of the 1st to 18th embodiments, 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 may be 10°C or less.

[0030] According to the 20th embodiment, in the 19th embodiment, the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 90°C to 115°C.

[0031] According to the 21st embodiment, in any one of the 1st to 20th embodiments, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may have a melting point of 100°C to 130°C.

[0032] According to the 22nd embodiment, in any one of the 1st to 21st embodiments, the weight-average molecular weight of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 100,000 g / mol to 400,000 g / mol.

[0033] According to the 23rd embodiment, in any one of the 1st to 22nd embodiments, the secondary battery may be a pouch-type secondary battery.

[0034] According to the 24th embodiment, in any one of the 1st to 23rd embodiments, the maximum sealing strength of the vent member at 100°C to 120°C may be less than 6 kgf / 15 mm.

[0035] According to the 25th embodiment, in any one of the 1st to 24th embodiment, the average sealing strength of the vent member at 100°C to 120°C may be less than 4.5 kgf / 15 mm.

[0036] According to the 26th embodiment, in any one of the 1st to 25th embodiments, the content of comonomers having 6 or more carbon atoms may be 5% to 15% by weight, based on 100% by weight of the linear low-density polyethylene.

[0037] According to the 27th embodiment, in any one of the 1st to 26th embodiments, the linear low-density polyethylene may have a polydispersity index (PDI) of 1 to 4.

[0038] According to the 28th embodiment, in any one of the 1st to 27th embodiment, the maximum sealing strength of the vent member at 120°C or higher may be less than 3 kgf / 15 mm.

[0039] According to the 29th embodiment, in any one of the 1st to 28th embodiment, the average sealing strength of the vent member at 120°C or higher may be less than 2 kgf / 15 mm. [Effects of the Invention]

[0040] In one embodiment of the present invention, a secondary battery can more easily guide gas discharge into the vent induction region by forming a narrower width of the sealing portion in the vent induction region. This improves the safety of the battery.

[0041] A secondary battery according to one embodiment of the present invention is equipped with a vent member containing linear low-density polyethylene having a comonomer with 6 or more carbon atoms in a vent induction region, which can guide gas discharge to the vent induction region. This improves the safety of the battery.

[0042] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention; therefore, the invention should not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0043] [Figure 1] This is a plan view showing a secondary battery according to one embodiment of the present invention. [Figure 2] This is a magnified view of section A in Figure 1. [Figure 3] This is a plan view of a secondary battery according to another embodiment of the present invention. [Figure 4] This is a diagram showing an enlarged view of the vent induction region in a secondary battery according to yet another embodiment of the present invention. [Figure 5] This is a cross-sectional view along line B-B' in Figure 4. [Figure 6] This is a diagram showing an enlarged view of the vent induction region in a secondary battery according to yet another embodiment of the present invention. [Figure 7] This diagram shows the state in which venting occurs in a secondary battery according to one embodiment of the present invention. [Modes for carrying out the invention]

[0044] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary and dictionary meanings, but rather in a manner corresponding to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention.

[0045] Therefore, the embodiments described herein and the configurations shown in the drawings represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the invention. It should be understood that there are various equivalents and modifications that can be substituted for these at the time of this application.

[0046] A secondary battery according to one embodiment of the present invention includes an electrode assembly to which electrode leads are attached, a case including a housing portion for housing the electrode assembly and a sealing portion formed to seal the electrode assembly with a sealant resin, a lead film formed to cover a part of the outer surface of the electrode leads and interposed between the electrode leads and the case, and a vent member including linear low-density polyethylene having a comonomer of 6 or more carbon atoms, wherein the sealing portion includes a vent induction region including the vent member, and the width of the vent induction region is narrower than the width of the other sealing portions excluding the vent induction region.

[0047] Figure 1 is a plan view showing a secondary battery according to one embodiment of the present invention.

[0048] Referring to Figure 1, the secondary battery 10 comprises an electrode assembly 12 to which electrode leads 11 are attached, and a case 13.

[0049] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator membrane. The electrode assembly 12 can be constructed by sequentially stacking the positive electrode plate and the negative electrode plate with the separator membrane in between.

[0050] The positive electrode plate may include a positive electrode current collector made of a metal sheet with excellent conductivity, such as aluminum (Al) foil, and a positive electrode active material layer coated on at least one surface thereof. The positive electrode plate may also include a positive electrode tab made of a metal material, such as aluminum (Al), at one end. The positive electrode tab may protrude from one end of the positive electrode plate. The positive electrode tab may be welded to one end of the positive electrode plate or joined using a conductive adhesive.

[0051] The negative electrode plate may include a negative electrode current collector made of a conductive metal sheet, such as copper (Cu) foil, and a negative electrode active material layer coated on at least one surface thereof. The negative electrode plate may also include a negative electrode tab formed of a metallic material, such as nickel (Ni), at one end. The negative electrode tab may protrude from one end of the negative electrode plate. The negative electrode tab may be welded to one end of the negative electrode plate or joined using a conductive adhesive.

[0052] The separation membrane is positioned between the positive electrode plate and the negative electrode plate and electrically insulates the two plates. The separation membrane may be a porous membrane that allows lithium ions to pass between the positive electrode plate and the negative electrode plate. The separation membrane may include a porous membrane using, for example, polyethylene (PE), polypropylene (PP), or a composite film thereof.

[0053] The surface of the separation membrane may be provided with an inorganic coating layer. The inorganic coating layer may have a structure in which inorganic particles are bound together by a binder, forming a porous structure (interstitial volume) between the particles.

[0054] The electrode assembly 12 may be a jelly roll type (wind-up type) electrode assembly in which a long sheet-like positive electrode and negative electrode are wound up with a separation membrane in between; a stacked type electrode assembly in which multiple positive electrodes and negative electrodes cut into units of a predetermined size are sequentially stacked with a separation membrane in between; or a stacked / foldable type electrode assembly in which a bi-cell or full-cell in which positive electrodes and negative electrodes of a predetermined unit are stacked with a separation membrane in between is wound up.

[0055] As shown in Figure 1, the case 13 includes a storage section 13a for housing the electrode assembly 12, and a sealing section 13b formed to seal the electrode assembly 12.

[0056] The sealing portion 13b may contain a sealant resin, which can fuse along the outer surface of the storage portion 13a to seal the electrode assembly 12.

[0057] In one embodiment of the present invention, the case 13 may be provided in the form of a multilayer film comprising an outer layer for protection from external impacts, a metal barrier layer for blocking moisture, and a sealant layer for sealing the case.

[0058] The outer layer may include a polyester film made of polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate, nylon, etc., and may consist of a single layer or multiple layers.

[0059] The aforementioned metal barrier layer may contain aluminum, copper, or the like.

[0060] The sealant layer may contain a sealant resin and may consist of a single layer or multiple layers.

[0061] The sealant resin may include polypropylene (PP), acid-modified polypropylene (PPa), random polypropylene, ethylene propylene copolymer, or two or more of these. The ethylene propylene copolymer may include, but is not limited to, ethylene propylene rubber, ethylene-propylene block copolymer, etc.

[0062] In one embodiment of the present invention, the case 13 may be of pouch type.

[0063] The pouch-type battery case 13 may include an upper pouch and a lower pouch. If the case 13 includes an upper pouch and a lower pouch, it may have a structure in which the upper pouch and the lower pouch are positioned so that the sealant resins face each other, and then the opposing sealant resins are fused together by heat and pressure to seal the battery.

[0064] The sealing portion 13b can be fused by heat, ultrasonic welding, or other methods, but is not particularly limited as long as the sealing portion 13b can be fused.

[0065] In some embodiments, the sealing portion 13b can be sealed on four sides or three sides around the periphery of the case 13. In the three-sided sealing structure, after forming the upper pouch and the lower pouch from a single pouch sheet, the interface between the upper pouch and the lower pouch is folded, and with the storage portions 13a formed in the upper and lower pouches overlapping, the periphery of the remaining three sides, excluding the folded portion, is sealed.

[0066] As shown in Figure 1, the electrode lead 11 can be housed in the case 13 such that a portion of the electrode lead 11 is exposed to the outside of the case 13.

[0067] A secondary battery 10 according to one embodiment of the present invention includes a lead film 14.

[0068] The lead film 14 covers a portion of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the case 13. For example, the lead film 14 can be interposed between the electrode lead 11 and the sealing portion 13b of the case 13 where the electrode lead 11 protrudes or extends from the case 13, thereby assisting in the bonding of the electrode lead 11 and the case 13.

[0069] Referring to Figure 1, the sealing portion 13b includes a vent guide region 15, and the width of the vent guide region 15 is narrower than the width of the other sealing portions 13b excluding the vent guide region.

[0070] Figure 2 is an enlarged view of section A in Figure 1.

[0071] Referring to Figure 2, the width W1 of the vent guide region 15 is narrower than the widths W2-W1 of the other sealing portions 13b excluding the vent guide region. The vent guide region 15 has a smaller sealed area compared to the other sealing portions 13b excluding the vent guide region, and as a result, the sealing performance of the vent guide region 15 is relatively weaker. Therefore, when gas is generated, pressure is applied to the sealing portions 13b, and when pressure is applied to the sealing portions 13b, the seal is released in the vent guide region 15, which has relatively weak sealing performance among the sealing portions 13b, and the gas is discharged.

[0072] In one embodiment of the present invention, the vent induction region 15 may be formed in a manner that is recessed from the outside to the inside of the case 13.

[0073] In another embodiment of the present invention, the vent guide region 15 may be formed in a manner that is recessed from the inside to the outside of the case 13. When the vent guide region 15 is formed in a manner that is recessed from the inside to the outside of the case 13, when gas is generated and pressure is applied to the sealing portion 13b, the pressure is concentrated on the inside of the vent guide region 15 that is close to the storage portion 13a, making it easier for the seal to be released in the vent guide region 15, which has relatively weak sealing properties.

[0074] The vent induction region 15 can be formed at various locations.

[0075] Referring to Figure 1, the vent induction region 15 can be formed in the sealing portion close to the electrode leads 11, except between the electrode leads 11. The vent induction region 15 can be located in the sealing portion on the corner side of the case. For example, the vent induction region 15 can be located on the corner side of the sealing portion where the electrode leads 11 are exposed to the outside. When the vent induction region 15 is located in the above position, the amount of gas discharged toward the electrode leads 11 can be minimized, further improving the safety of the battery.

[0076] Figure 3 is a plan view of a secondary battery according to another embodiment of the present invention.

[0077] Referring to Figure 3, the vent induction region 15 may be located in the sealing portion excluding the sealing portion where the electrode lead 11 is exposed to the outside.

[0078] In one embodiment of the present invention, the vent guide region 15 may be formed by first creating a sealing portion 13b having a certain width, and then cutting the sealing portion in the vent guide region 15 to make the width of the vent guide region 15 relatively narrower. In this case, the vent guide region 15 is formed in a form that is recessed from the outside to the inside of the case 13.

[0079] In yet another embodiment of the present invention, the vent guide region 15 may be formed such that the shape of the heating means (heating block or heating jig) corresponds to the vent guide region 15 to seal the sealing portion, and the width of the vent guide region 15 is narrower than the width of the other sealing portion 13b excluding the vent guide region 15. In this case, the vent guide region 15 may be formed in a form that is recessed from the inside to the outside of the case 13.

[0080] Figure 4 is a magnified view of the vent induction region 15 in a secondary battery according to yet another embodiment of the present invention.

[0081] Referring to Figure 4, the tape 17 can be inserted and the width W1 of the vent guide region 15 can be formed to be narrower than the widths W2-W1 of the other sealing portions 13b excluding the vent guide region.

[0082] The tape 17 may contain a material with better heat resistance than the sealing portion 13b. Therefore, the portion in which the tape 17 is inserted is not sealed, and only the portion excluding the portion in which the tape 17 is inserted is sealed to form the sealing portion 13b. For example, the tape 17 may contain polyimide, polyethylene terephthalate (PET), or a mixture thereof.

[0083] Figure 5 is a cross-sectional view along line B-B' in Figure 4.

[0084] Referring to Figure 5, by inserting the tape 17 between the sealant layers sealing the case in the vent guide region 15, the width W1 of the vent guide region 15 can be made narrower than the widths W2-W1 of the other sealing portions 13b excluding the vent guide region.

[0085] Figure 6 is a magnified view of the vent induction region 15 in a secondary battery according to yet another embodiment of the present invention.

[0086] Referring to Figure 6, the resin 18 is inserted, and the width W1 of the vent guide region 15 can be formed to be narrower than the widths W2-W1 of the other sealing portions 13b excluding the vent guide region. Refer to the configuration in Figure 5 for how the resin 18 is inserted.

[0087] The resin 18 is a material that does not adhere to the sealant layer. Because the resin 18 does not adhere to the sealant layer, the portion in which the resin 18 is inserted is not sealed, and only the sealant layer excluding the portion in which the resin 18 is inserted is sealed, forming a sealed portion 13b.

[0088] In one embodiment of the present invention, the resin 18 may include a fluororesin, a silicone resin, or a mixture thereof.

[0089] The aforementioned fluororesin is CH x CF y The resin may be represented by the chemical formula (x+y=4, x=0,1,2,3,4). For example, the fluororesin may contain polytetrafluoroethylene (PTFE).

[0090] The silicone resin may include, for example, polydimethylsiloxane.

[0091] In one embodiment of the present invention, the width W1 of the vent induction region 15 may be 40% to 80% or 40% to 60% of the width W2 of the other sealing portion excluding the vent induction region. When the width W1 of the vent induction region 15 satisfies the above range, when gas is generated, the seal is more likely to be released in the vent induction region 15, which has relatively weak sealing properties.

[0092] Referring to Figure 1, the vent induction region 15 includes a vent member 16. When a thermal runaway phenomenon occurs, the vent member 16 can improve the safety of the battery by inducing gas discharge in a specific direction. In particular, by including the vent member 16 in the vent induction region 15, which has relatively weak sealing properties, it becomes easier to induce gas discharge into the vent induction region 15.

[0093] The vent member 16 and the case 13 can overlap through heat fusion. As another example, the vent member 16 and the case 13 can overlap through an adhesive such as glue. As yet another example, the vent member 16 and the case 13 can be physically joined through clips or the like. As yet another example, at least a portion of the vent member 16 can be embedded in the film constituting the case 13, for example, a sealant resin.

[0094] The vent member 16 contains linear low-density polyethylene having a comonomer with 6 or more carbon atoms. Because the vent member 16 contains linear low-density polyethylene having a comonomer with 6 or more carbon atoms, the case 13 has excellent sealing performance in the normal temperature range, for example, room temperature to 60°C, and at high temperatures, for example, 100°C or higher, the sealing strength of the case into which the vent member 16 is inserted decreases, thereby achieving or inducing venting.

[0095] In one embodiment of the present invention, the vent member 16 may include linear low-density polyethylene having a comonomer with 6 to 8 carbon atoms.

[0096] Figure 7 shows a state in which venting occurs in a secondary battery according to one embodiment of the present invention. Specifically, Figure 7 is a cross-sectional view showing a venting member included in a secondary battery according to one embodiment of the present invention.

[0097] Referring to Figure 7, at the temperature at which the battery operates normally, the vent member serves to seal the case from the outside. If the battery temperature rises excessively due to abnormal operation, the vent member melts, and the sealing strength of the area where the vent member is inserted decreases. Consequently, gas is released from this area. For example, the pressure of the internal gas of the battery is applied to the interface between the vent member and the vent guide region, creating a gap between the vent member and the vent guide region, from which gas can be released.

[0098] In one embodiment of the present invention, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may have a lower melting point than the sealant resin. When the melting point of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is lower than that of the sealant resin, the linear low-density polyethylene can melt faster than the sealant resin at high temperatures. As a result, the sealing strength of the portion in which the vent member 16 is inserted is further reduced than the sealing strength of the case portion containing the sealant resin, thereby making it easier to achieve vent properties.

[0099] In one embodiment of the present invention, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may have a melting point of 100°C to 130°C, 105°C to 125°C, or 110°C to 120°C. When the linear low-density polyethylene having a comonomer with 6 or more carbon atoms satisfies the above range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted decreases at high temperatures, for example, 100°C or higher, making it easier to achieve vent properties.

[0100] The melting point of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms can be measured using a differential scanning calorimeter (DSC). For example, the sample temperature can be raised from 30°C to 280°C at a rate of 10°C / min, maintained at 280°C for 10 minutes, cooled to 30°C at a rate of 10°C / min, and maintained at 30°C for 10 minutes. After that, the sample temperature can be raised from 30°C to 280°C at a rate of 10°C / min, and the melting point can be measured by maintaining the temperature at 280°C for 10 minutes.

[0101] In one embodiment of the present invention, the vent member 16 vents at 100°C to 120°C, allowing gas to be discharged or exhausted from the storage compartment to the outside of the battery. In particular, the vent member 16 can vent at 100°C to 120°C and a pressure of 1.5 atm or higher. By venting within the above temperature range and / or pressure conditions, the battery can be sealed when it is operating normally, and gas discharge can be induced only when the battery is malfunctioning.

[0102] In one embodiment of the present invention, the vent member 16 may 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 one embodiment of the present invention, the vent member 16 may 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 one embodiment of the present invention, the vent member 16 may 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. When the vent member 16 satisfies the above sealing strengths in the above temperature ranges, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted decreases at high temperatures, for example, above 100°C, making it easier to achieve vent characteristics.

[0103] Furthermore, in one embodiment of the present invention, the vent member 16 may have a maximum sealing strength of 6 kgf / 15 mm or more, 8 kgf / 15 mm or more, or 10 kgf / 15 mm or more at room temperature to 60°C. If the vent member 16 satisfies the above-mentioned sealing strength in the above-mentioned temperature range, even if the vent member 16 is inserted, the vent guide region 15 into which the vent member 16 is inserted will have excellent sealing strength during normal operation of the battery, and the sealing performance of the battery can be easily ensured.

[0104] In one embodiment of the present invention, the vent member 16 may have a maximum sealing strength of less than 6 kgf / 15 mm at temperatures above 100°C and a maximum sealing strength of 6 kgf / 15 mm or more at room temperature to 60°C. When the vent member 16 satisfies the above-mentioned sealing strength, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted decreases at high temperatures, for example, above 100°C, and venting characteristics can be easily achieved. Furthermore, during normal operation of the battery, the vent induction region 15 has excellent sealing strength, and the sealing performance of the battery can be easily ensured.

[0105] In one embodiment of the present invention, the vent member 16 may 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 one embodiment of the present invention, the vent member 16 may 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 one embodiment of the present invention, the vent member 16 may 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. When the vent member 16 satisfies the above sealing strength in the above temperature range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted decreases at high temperatures, for example, above 100°C, making it easier to achieve vent characteristics.

[0106] In one embodiment of the present invention, the vent member 16 may have an average sealing strength of 4.5 kgf / 15 mm or more, 5 kgf / 15 mm or more, 6 kgf / 15 mm or more, or 7 kgf / 15 mm or more at room temperature to 60°C. When the vent member 16 satisfies the above-mentioned sealing strength in the above-mentioned temperature range, even when the vent member 16 is inserted, the vent guide region 15 into which the vent member 16 is inserted will have excellent sealing strength during normal operation of the battery, and the sealing performance of the battery can be easily ensured.

[0107] In one embodiment of the present invention, the vent member 16 may have an average sealing strength of less than 4.5 kgf / 15 mm at temperatures above 100°C, and an average sealing strength of 4.5 kgf / 15 mm or more at room temperature to 60°C. When the vent member 16 has the above-mentioned temperature range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted decreases at high temperatures, for example, above 100°C, making it easy to achieve vent characteristics. Furthermore, the vent induction region 15 has excellent sealing strength during normal operation of the battery, making it easy to ensure the sealing performance of the battery.

[0108] The sealing strength of the vent member 16 in relation to temperature can be measured by cutting the case 13 of the vent induction region 15 into which the vent member 16 is inserted to a width of 15 mm and a length of 5 cm, opening both ends 180° and fixing it to a UTM jig, and performing a tensile test at a speed of 5 mm / min.

[0109] In this case, the maximum sealing strength refers to the maximum value at which case 13 breaks. The average sealing strength refers to the average value when case 13 is stretched by 8 mm at 4.5 kgf / 15 mm if the maximum sealing strength is 4.5 kgf / 15 mm or more, and to the average value when case 13 is stretched by 8 mm at the maximum sealing strength if the maximum sealing strength is less than 4.5 kgf / 15 mm.

[0110] In one embodiment of the present invention, the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be polymerized in the presence of a metallocene catalyst. When the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is polymerized in the presence of a metallocene catalyst, it is more advantageous in terms of sealing strength and physical properties than when it is polymerized in the presence of a Ziegler-Natta catalyst.

[0111] In one embodiment of the present invention, the content of the comonomer having 6 or more carbon atoms in the linear low-density polyethylene having 6 or more carbon atoms may be 15% by weight or less, 12% by weight or less, 11.8% by weight or less, 10% by weight or less, 9% by weight or less, 8% by weight or less, or 7.6% by weight or less, based on 100% by weight of the linear low-density polyethylene having 6 or more carbon atoms. At the same time, the content of the comonomer having 6 or more carbon atoms may be 5% by weight or more, 7.6% by weight or more, 8% by weight or more, 9.0% by weight or more, 10% by weight or more, 11.8% by weight or more, or 12% by weight or more, based on 100% by weight of the linear low-density polyethylene having 6 or more carbon atoms. When the content of the comonomer having 6 or more carbon atoms satisfies the above range, the problem of reduced sealing strength during normal operation of the battery due to decreased intermolecular packing density can be easily prevented.

[0112] The content of the aforementioned comonomer having 6 or more carbon atoms can be measured by 1H-NMR. For example, after completely dissolving about 10 mg of the sample in about 0.6 mL of trichloroethylene solvent using a heat gun, the sample is placed in an NMR tube. 1 This can be measured using 1H-NMR.

[0113] In one embodiment of the present invention, the weight-average molecular weight of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 100,000 g / mol to 400,000 g / mol, 200,000 g / mol to 350,000 g / mol, or 230,000 g / mol to 300,000 g / mol. When the weight-average molecular weight of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms satisfies the above range, the sealing strength will be superior during normal operation of the battery.

[0114] In one embodiment of the present invention, the polydispersity index (PDI) of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 4 or less, 3.8 or less, 3.796 or less, 3.5 or less, 3.023 or less, 3 or less, 2.7 or less, or 2.674 or less. Furthermore, the polydispersity index (PDI) may be 1.0 or higher. When the polydispersity index of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms satisfies the above range, the molecular weight distribution is narrow, resulting in even better sealing strength and physical properties during normal battery operation.

[0115] The weight-average molecular weight and polydispersity index of linear low-density polyethylene having comonomers with 6 or more carbon atoms may be measured using gel permeation chromatography (GPC) under the following conditions.

[0116] - Column: Tosoh Corporation, HLC-8321 GPC / HT - Solvent: TCB (trichlorobenzene) + 0.04% BHT (dried with 0.1% CaCl2) - Flow rate: 1.0ml / min - Sample concentration: 1.5 mg / ml - Injection volume: 300μl - Column temperature: 160℃ - Detector: RI detector - Standard: Polystyrene (corrected with a cubic function)

[0117] In one embodiment of the present invention, 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 may be similar. For example, 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 may be 10°C or less, or 5°C or less. Alternatively, 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 may be 0.1°C or more. When 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 satisfies the above range, the fusion characteristics between the sealant resin and the linear low-density polyethylene having a comonomer with 6 or more carbon atoms will be superior during normal operation of the battery.

[0118] In one embodiment of the present invention, the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 90°C to 115°C, 95°C to 110°C, 100°C to 110°C, or 105°C to 110°C. When the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms satisfies the above range, the fusion properties between the sealant resin and the linear low-density polyethylene having a comonomer with 6 or more carbon atoms become superior.

[0119] In one embodiment of the present invention, 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 is 10°C or less, and the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms may be 90°C to 115°C.

[0120] The crystallization temperature can be measured using a differential scanning calorimeter (DSC). For example, the sample temperature can be raised from 30°C to 280°C at a rate of 10°C / min, maintained at 280°C for 10 minutes, cooled to 30°C at a rate of 10°C / min, and maintained at 30°C for 10 minutes. Then, the temperature can be raised from 30°C to 280°C at a rate of 10°C / min, maintained at 280°C for 10 minutes, and the crystallization temperature can be measured.

[0121] In one embodiment of the present invention, the vent member 16 may have various shapes so that the gas flows smoothly into the vent area. For example, the vent member 16 may have a film shape.

[0122] The vent member 16 may be formed to have a predetermined thickness that has already been set. Furthermore, the vent member 16 may be inserted into the vent guide region 15 in such a way that the insertion length varies or the venting pressure and position can be controlled, depending on the design. Here, the insertion length of the vent member refers to the maximum distance between one end and the other end of the vent member with respect to the protruding direction of the electrode lead.

[0123] For example, the insertion length of the vent member 16 may be smaller than the width of the vent guide region 15. For example, the insertion length of the vent member 16 may be less than approximately 50% of the width of the vent guide region 15. Here, the width of the vent guide region means the maximum distance between one end and the other end of the vent guide region 15 with respect to the protruding direction of the electrode lead 11.

[0124] Alternatively, the insertion length of the vent member 16 may be greater than the width of the vent guide region 15. For example, the vent member 16 may be inserted so as to be exposed to the outside of the case 13 through the storage portion 13a.

[0125] In one embodiment of the present invention, the vent member 16 may further include an adhesive layer for smoother arrangement.

[0126] In one embodiment of the present invention, the secondary battery may be cylindrical, prismatic, or pouch-type secondary battery. In particular, the secondary battery may be a pouch-type secondary battery.

[0127] Although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and various modifications can be carried out by persons with ordinary skill in the art to which the present invention belongs without departing from the gist of the present invention as claimed in the claims, and such modifications should not be understood individually from the technical idea or prospects of the present invention. [Explanation of symbols]

[0128] 10 Secondary battery 11 Electrode leads 12 Electrode assembly 13 cases 13a Storage compartment 13b Sealing section 14 Lead film 15. Vent induction region 16 Vent members 17 Tapes 18 resin

Claims

1. Electrode assembly and The electrode lead attached to the electrode assembly, A case including a storage section for housing the electrode assembly and a sealing section formed to seal the electrode assembly by containing a sealant resin, A lead film is formed to cover a portion of the outer surface of the electrode lead and interposed between the electrode lead and the case, A vent member containing linear low-density polyethylene having a comonomer with 6 or more carbon atoms, Includes, The sealing portion includes a venting guide region including the venting member, A secondary battery in which the width of the vent induction region is narrower than the width of the other sealing portion excluding the vent induction region, A secondary battery in which a material containing a substance with better heat resistance than the sealing portion or a material that does not adhere to the sealant layer of the sealing portion is inserted between the sealant resins, such that the width of the vent induction region is narrower than the width of the other sealing portions excluding the vent induction region.

2. The secondary battery according to claim 1, wherein the width of the vent induction region is 40% to 80% of the width of the other sealing portion excluding the vent induction region.

3. The secondary battery according to claim 1, wherein the vent induction region is formed in the sealing portion near the electrode leads, excluding the region between the electrode leads.

4. The secondary battery according to claim 1, wherein the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is linear low-density polyethylene having a comonomer with 6 to 8 carbon atoms.

5. The secondary battery according to claim 1, wherein the linear low-density polyethylene having a comonomer with 6 or more carbon atoms has a lower melting point than the sealant resin.

6. The secondary battery according to claim 1, wherein the vent member melts at 100°C to 120°C in order to discharge gas.

7. The secondary battery according to claim 6, wherein the venting member vents at a pressure of 1.5 atm or more.

8. The secondary battery according to claim 1, wherein the maximum sealing strength of the vent member at temperatures above 100°C is less than 6 kgf / 15 mm.

9. The secondary battery according to claim 1, wherein the average sealing strength of the vent member at 100°C or higher is less than 4.5 kgf / 15 mm.

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

11. The secondary battery according to claim 1, wherein the average sealing strength of the vent member at room temperature to 60°C is 4.5 kgf / 15 mm or more.

12. The secondary battery according to claim 1, wherein the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is polymerized in the presence of a metallocene catalyst.

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

14. The secondary battery according to claim 1, wherein the polydispersity index of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is 4 or less.

15. 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 having a comonomer with 6 or more carbon atoms is 10°C or less.

16. The secondary battery according to claim 15, wherein the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is 90°C to 115°C.

17. The secondary battery according to claim 1, wherein the linear low-density polyethylene having a comonomer with 6 or more carbon atoms has a melting point of 100°C to 130°C.

18. The secondary battery according to claim 1, wherein the weight-average molecular weight of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms is 100,000 g / mol to 400,000 g / mol.

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

20. The secondary battery according to claim 1, wherein the maximum sealing strength of the vent member at 100°C to 120°C is less than 6 kgf / 15 mm.

21. The secondary battery according to claim 1, wherein the average sealing strength of the vent member at 100°C to 120°C is less than 4.5 kgf / 15 mm.

22. The secondary battery according to claim 1, wherein the content of comonomers having 6 or more carbon atoms is 5% to 15% by weight, based on 100% by weight of the linear low-density polyethylene.

23. The secondary battery according to claim 1, wherein the linear low-density polyethylene has a polydispersity index of 1 to 4.

24. The secondary battery according to claim 1, wherein the maximum sealing strength of the vent member at 120°C or higher is less than 3 kgf / 15 mm.

25. The secondary battery according to claim 1, wherein the average sealing strength of the vent member at 120°C or higher is less than 2 kgf / 15 mm.

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