Secondary battery

Abstract

The present invention discloses a secondary battery having a vent member, the secondary battery including: an electrode assembly having electrode leads attached thereto; a case including a housing that houses the electrode assembly so that a portion of the electrode leads is exposed to the outside; and a sealing portion formed to seal the electrode assembly; and a lead film that encloses a portion of the outer surface of the electrode leads and is interposed between the electrode leads and the sealing portion of the case, the sealing portion including a vent induction region that includes a vent member including a linear low-density polyethylene having a comonomer having six or more carbon atoms, the width of the vent induction region being narrower than the width of the rest of the sealing portion excluding the vent induction region.

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 that 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) driven 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, in a secondary battery, ignition may occur due to various causes such as a short circuit inside the secondary battery, overcharging or over-discharging, and temperature regulation. At this time, a thermal runaway phenomenon occurs in which the internal temperature of the secondary battery rises rapidly and heat is transmitted to adjacent cells at the same time, and there is a risk that the fire will spread further.

[0007] When the thermal runaway phenomenon occurs, that is, when the internal temperature of the secondary battery rises, in order to minimize damage to the electrodes by gas, a directional venting characteristic for discharging gas in one direction is required. However, conventional secondary batteries have a problem that it is difficult to induce gas discharge in a specific direction.

[0008] Therefore, an object of the present invention is to provide a secondary battery in which gas discharge is induced in a specific direction to improve safety.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem to be solved by the present invention is to provide a secondary battery in which gas discharge to the vent induction region is more easily induced to improve safety.

Means for Solving the Problems

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

[0011] The first embodiment is an electrode assembly, an electrode lead attached to the electrode assembly, a case including a storage portion for storing the electrode assembly therein and a sealing portion formed to seal the electrode assembly including a sealing resin, a lead film formed to cover a part of the outer surface of the electrode lead and interposed between the electrode lead and the case, A vent member including linear low-density polyethylene having a comonomer with 6 or more carbon atoms, The sealing part includes a vent guiding area including the vent member, The present invention relates to a secondary battery, characterized in that the width of the vent guiding area is narrower than the width of other sealing parts excluding the vent guiding area.

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

[0013] According to a third embodiment, in the first embodiment or the second embodiment, A tape can be inserted so that the width of the vent guiding area is narrower than the width of other sealing parts excluding the vent guiding area.

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

[0015] According to a fifth embodiment, in the first embodiment or the second embodiment, A resin can be inserted so that the width of the vent guiding area is narrower than the width of other sealing parts excluding the vent guiding area.

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

[0017] According to a seventh embodiment, in any one of the first to sixth embodiments, The vent guiding area can be formed in a sealing part close to the electrode lead, excluding the area 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 the 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 ninth embodiment, in any one of the first to eighth embodiments, The linear low-density polyethylene having the comonomer with 6 or more carbon atoms may have a melting point lower than that of the sealant resin.

[0020] According to the tenth embodiment, in any one of the first to ninth embodiments, The vent member may melt at 100°C to 120°C to discharge gas.

[0021] According to the eleventh embodiment, in the tenth embodiment, The vent member may be bent at a pressure of 1.5 atm or more.

[0022] According to the twelfth embodiment, in any one of the first to eleventh embodiments, The maximum sealing strength of the vent member at 100°C or higher may be less than 6 kgf / 15 mm.

[0023] According to the thirteenth embodiment, in any one of the first to twelfth embodiments, The average sealing strength of the vent member at 100°C or higher may be less than 4.5 kgf / 15 mm.

[0024] According to the fourteenth embodiment, in any one of the first to thirteenth embodiments, 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 fifteenth embodiment, in any one of the first to fourteenth embodiments, The average sealing strength of the vent member at normal temperature to 60 °C can 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 the 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 the 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 the 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 the 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 the 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 the 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 the 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 the 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 embodiments, 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 the comonomer with 6 or more carbon atoms may be 5 wt% to 15 wt% based on 100 wt% 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 embodiments, 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 embodiments, the average sealing strength of the vent member at 120 °C or higher may be less than 2 kgf / 15 mm.

Advantages of the Invention

[0040] The secondary battery according to an embodiment of the present invention can more easily guide the gas discharge to the vent guiding region by forming the width of the sealing portion narrow in the vent guiding region. Thereby, the safety of the battery can be improved.

[0041] The secondary battery according to an embodiment of the present invention includes a vent member containing linear low-density polyethylene having a comonomer with 6 or more carbon atoms in the vent guiding region, and can guide the gas discharge to the vent guiding region. Thereby, the safety of the battery is improved.

[0042] The following drawings attached to this specification illustrate desirable embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0044] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary and dictionary meanings, and the inventors themselves should interpret them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that they can appropriately define the concept of the terms in order to explain the invention in the best way.

[0045] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, so there may be various equivalents and modifications that can replace them at the time of this application.

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

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

[0048] Referring to FIG. 1, the secondary battery 10 includes an electrode assembly 12 to which an electrode lead 11 is attached, and a case 13.

[0049] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate and the negative electrode plate can be sequentially laminated with the separator interposed therebetween.

[0050] The positive electrode plate may include a positive electrode current collector made of a metal thin plate having excellent conductivity, such as aluminum (Al) foil, and a positive electrode active material layer coated on at least one surface thereof. Further, the positive electrode plate may include a positive electrode tab made of a metal material, such as aluminum (Al) material, at one end portion. The positive electrode tab may protrude from one end portion of the positive electrode plate. The positive electrode tab may be welded to one end portion 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 thin plate, such as copper (Cu) foil, and a negative electrode active material layer coated on at least one surface thereof. Further, the negative electrode plate may include a negative electrode tab formed of a metal material, such as nickel (Ni) material, at one end portion. The negative electrode tab may protrude from one end portion of the negative electrode plate. The negative electrode tab may be welded to one end portion of the negative electrode plate or joined using a conductive adhesive.

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

[0053] An inorganic coating layer may be provided on the surface of the separator. The inorganic coating layer may have a structure in which inorganic particles are bonded to each other by a binder to form a pore structure (interstitial volume) between the particles.

[0054] The electrode assembly 12 can be a jelly roll type (winding type) electrode assembly having a structure in which a long sheet-like positive electrode and negative electrode are wound with a separator interposed therebetween, a laminated type (stack type) electrode assembly in which a plurality of positive electrodes and negative electrodes cut out in a predetermined size are sequentially laminated with a separator interposed therebetween, a laminated / folded type electrode assembly having a structure in which a bi-cell or full-cell in which a predetermined unit of positive electrode and negative electrode are laminated with a separator interposed therebetween is wound, and the like.

[0055] As shown in FIG. 1, the case 13 includes a storage portion 13a for storing the electrode assembly 12 and a sealing portion 13b formed for sealing the electrode assembly 12.

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

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

[0058] The outer layer may include a polyester-based film using polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyester, polycarbonate, nylon, etc., and can be composed of a single layer or multiple layers.

[0059] The metal barrier layer may contain aluminum, copper, etc.

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

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

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

[0063] The pouch-type battery case 13 may include an upper pouch and a lower pouch. When the case 13 includes an upper pouch and a lower pouch, after arranging the upper pouch and the lower pouch so that the sealing resins face each other, the battery may have a structure in which the opposing sealing resins are fused to each other by heat and pressure to seal the battery.

[0064] The fusion of the sealing portion 13b may be heat fusion, fusion by ultrasonic waves, etc., but is not particularly limited as long as the sealing portion 13b can be fused.

[0065] In some embodiments, the sealing portion 13b may be four-sided sealed or three-sided sealed at 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 bent, and the storage portions 13a formed in the upper pouch and the lower pouch are overlapped, and the remaining three sides of the periphery except the bent portion are sealed.

[0066] As shown in FIG. 1, a part of the electrode lead 11 may be housed in the case 13 so that a part of the electrode lead 11 is exposed outside the case 13.

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

[0068] The lead film 14 covers a part 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, and can assist in binding the electrode lead 11 and the case 13.

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

[0070] FIG. 2 is an enlarged view showing a portion A of FIG. 1.

[0071] Referring to FIG. 2, the width W1 of the vent guiding region 15 is narrower than the width W2 of the other sealing portions 13b excluding the vent guiding region. -W1 The vent guiding region 15 has a smaller sealed area compared to the other sealing portions 13b excluding the vent guiding region, so that the sealing performance of the vent guiding region 15 is relatively weak. Therefore, if gas is generated, pressure is applied to the sealing portion 13b. When pressure is applied to the sealing portion 13b, the gas is discharged while the seal is released in the vent guiding region 15 where the sealing performance is relatively weak among the sealing portions 13b.

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

[0073] In another embodiment of the present invention, the vent guiding region 15 can be formed in a form that is recessed from the inside to the outside of the case 13. When the vent guiding region 15 is formed in a form 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 guiding region 15 close to the storage portion 13a, so that the seal is easily released in the vent guiding region 15 where the sealing performance is relatively weak.

[0074] The vent guiding region 15 can be formed at various positions.

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

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

[0077] Referring to FIG. 3, the vent guiding region 15 can be located in the sealing portion excluding the sealing portion where the electrode leads 11 are exposed to the outside.

[0078] In one embodiment of the present invention, after forming the sealing portion 13b so that the vent guiding region 15 has a certain width, the sealing portion can be cut in the vent guiding region 15 to relatively narrow the width of the vent guiding region 15. In this case, the vent guiding region 15 is formed in a form recessed from the outside to the inside of the case 13.

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

[0080] FIG. 4 is a view showing an enlarged view of a vent guiding region 15 portion in a secondary battery according to still another embodiment of the present invention.

[0081] Referring to FIG. 4, the tape 17 is inserted, and the width W1 of the vent guiding region 15 can be formed to be narrower than the width W2 of the other sealing portion 13b excluding the vent guiding region. -W1

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

[0083] FIG. 5 is a cross-sectional view taken along line B-B' of FIG. 4.

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

[0085] FIG. 6 is a view showing an enlarged vent guiding region 15 portion in a secondary battery according to still another embodiment of the present invention.

[0086] Referring to FIG. 6, the resin 18 is inserted, and the width W1 of the vent guiding region 15 can be formed to be narrower than the width W2 of the other sealing portion 13b excluding the vent guiding region. For the state in which the resin 18 is inserted, refer to the configuration of FIG. 5. -W1

[0087] The resin 18 is a material that does not adhere to the sealant layer. Since the resin 18 does not adhere to the sealant layer, the portion where the resin 18 is inserted is not sealed, and only the sealant layer excluding the portion where the resin 18 is inserted can be sealed to form the sealing 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 fluororesin may be a resin represented by the chemical formula CH x CF y (where x + y = 4, and x = 0, 1, 2, 3, 4). For example, the fluororesin may include 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 guiding region 15 may be 40% - 80%, or 40% - 60% with respect to the width W2 of the other sealing portions excluding the vent guiding region. When the width W1 of the vent guiding region 15 satisfies the above-mentioned range, when gas is generated, the seal is easily released in the vent guiding region 15 where the sealing property is relatively weak.

[0092] Referring to FIG. 1, the vent guiding region 15 includes a vent member 16. When a thermal runaway phenomenon occurs, the vent member 16 can guide the gas discharge in a specific direction to improve the safety of the battery. In particular, since the vent member 16 is included in the vent guiding region 15 where the sealing property is relatively weak, it becomes easier to guide the gas discharge to the vent guiding region 15.

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

[0094] The vent member 16 includes linear low-density polyethylene having a comonomer with 6 or more carbon atoms. Since the vent member 16 includes linear low-density polyethylene having a comonomer with 6 or more carbon atoms, it has excellent sealing performance for the case 13 in the normal temperature range, for example, room temperature to 60°C. At high temperatures, for example, 100°C or higher, the sealing strength of the case into which the vent member 16 is inserted decreases, enabling venting to be realized or induced.

[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] FIG. 7 is a diagram showing a state in which venting occurs in a secondary battery according to an embodiment of the present invention. Specifically, FIG. 7 is a cross-sectional view showing a vent member included in a secondary battery according to an embodiment of the present invention.

[0097] Referring to FIG. 7, at the temperature at which the battery operates normally, the vent member serves to seal the case from the outside. When the temperature of the battery rises excessively due to abnormal operation of the battery, while the vent member melts, the sealing strength of the portion where the vent member is inserted decreases. Therefore, gas is discharged from this portion. For example, when the pressure of the internal gas of the battery is applied to the interface between the vent member and the vent guiding region, a gap is formed between the vent member and the vent guiding region, and gas can be discharged therefrom.

[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 melting point lower than that of 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 where the vent member 16 is inserted further decreases compared to the sealing strength of the case portion containing the sealant resin, making it easier to realize venting characteristics.

[0099] In one embodiment of the present invention, the linear low-density polyethylene having the 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 the comonomer with 6 or more carbon atoms satisfies the above-mentioned range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted at a high temperature, for example, 100°C or higher, decreases, and the vent characteristics can be realized more easily.

[0100] The melting point of the linear low-density polyethylene having the comonomer with 6 or more carbon atoms can be measured using a differential scanning calorimeter (DSC). For example, after raising the temperature of the sample from 30°C to 280°C at 10°C / min, maintaining it at 280°C for 10 minutes, cooling it from 280°C to 30°C at 10°C / min, and maintaining it at 30°C for 10 minutes. Then, after raising the temperature of the sample from 30°C to 280°C at 10°C / min, 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 can be bent at 100°C to 120°C to discharge or exhaust gas from the storage part to the outside of the battery. In particular, the vent member 16 can be bent at a pressure of 1.5 atm or more at 100°C to 120°C. By bending the vent member 16 under the above-mentioned temperature range and / or the above-mentioned pressure conditions, the battery can be sealed when the battery operates normally, and gas discharge can be induced only when the battery operates abnormally.

[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 100°C or higher. 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 100°C to 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 120°C or higher. When the vent member 16 satisfies the above-described sealing strength in the above-described temperature range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted at a high temperature, for example, 100°C or higher, decreases, and the vent characteristics can be more easily realized.

[0103] Also, 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 normal temperature to 60°C. When the vent member 16 satisfies the above-described sealing strength in the above-described temperature range, even when the vent member 16 is inserted, the vent induction region 15 into which the vent member 16 is inserted has 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 100°C or higher and a maximum sealing strength of 6 kgf / 15 mm or more at normal temperature to 60°C. When the vent member 16 satisfies the above-described sealing strength, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted at a high temperature, for example, 100°C or higher, decreases, and the vent characteristics can be easily realized. Also, 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 100°C or higher. 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 100°C to 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 120°C or higher. When the vent member 16 satisfies the above-described sealing strength in the above-described temperature range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted at a high temperature, for example, 100°C or higher, decreases, and the vent characteristics can be more easily realized.

[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 normal temperature to 60°C. When the vent member 16 satisfies the above-described sealing strength in the above-described temperature range, even when the vent member 16 is inserted, the vent induction region 15 into which the vent member 16 is inserted has 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 100°C or higher and an average sealing strength of 4.5 kgf / 15 mm or more at normal temperature to 60°C. When the vent member 16 has the above-described temperature range, the sealing strength of the vent induction region 15 into which the vent member 16 is inserted at a high temperature, for example, 100°C or higher, decreases, and the vent characteristics can be easily realized. Also, the vent induction region 15 has excellent sealing strength during normal operation of the battery, and the sealing performance of the battery can be easily ensured.

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

[0109] At this time, the maximum sealing strength means the maximum value when the case 13 breaks. Also, the average sealing strength means the average value when the case 13 is stretched by 8 mm at 4.5 kgf / 15 mm when the maximum sealing strength is 4.5 kgf / 15 mm or more, and means the average value when the case 13 is stretched by 8 mm at the maximum sealing strength when 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 the comonomer with 6 or more carbon atoms may be polymerized in the presence of a metallocene catalyst. When the linear low-density polyethylene having the 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 polymerized in the presence of a Ziegler-Natta catalyst.

[0111] In one embodiment of the present invention, the content of the comonomer with 6 or more carbon atoms in the linear low-density polyethylene having the comonomer with 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, 7.6% by weight or less with respect to 100% by weight of the linear low-density polyethylene having the comonomer with 6 or more carbon atoms. At the same time, the content of the comonomer with 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 with respect to 100% by weight of the linear low-density polyethylene having the comonomer with 6 or more carbon atoms. When the content of the comonomer with 6 or more carbon atoms satisfies the above-described range, it is possible to easily prevent the problem that the packing density between molecules decreases and the sealing strength decreases during normal operation of the battery.

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

[0113] In one embodiment of the present invention, the weight average molecular weight of the linear low density polyethylene having the comonomer having 6 or more carbon atoms can 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 the comonomer having 6 or more carbon atoms satisfies the above-mentioned range, the sealing strength becomes more excellent during the normal operation of the battery.

[0114] In one embodiment of the present invention, the polydispersity index (PDI) of the linear low density polyethylene having the comonomer having 6 or more carbon atoms can 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. Also, the polydispersity index (PDI) can be 1.0 or more. When the polydispersity index of the linear low density polyethylene having the comonomer having 6 or more carbon atoms satisfies the above-mentioned range, since the molecular weight distribution is narrow, more excellent sealing strength and physical properties are exhibited during the normal operation of the battery.

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

[0116] - Column: HLC-8321 GPC / HT manufactured by Tosoh Corporation - Solvent: TCB (trichlorobenzene) + 0.04% BHT (dried with 0.1% CaCl2) - Flow rate: 1.0 ml / min - Sample concentration: 1.5 mg / ml - Injection volume: 300 μl - Column temperature: 160 °C - 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 may be similar to the crystallization temperature of the linear low-density polyethylene having a comonomer with 6 or more carbon atoms. 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. Further, 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-described range, the fusion characteristics between the sealant resin and the linear low-density polyethylene having a comonomer with 6 or more carbon atoms during normal operation of the battery will be more excellent.

[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-described 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 more excellent.

[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, after raising the temperature of the sample from 30°C to 280°C at a rate of 10°C / min, maintaining it at 280°C for 10 minutes, cooling it to 30°C at a rate of 10°C / min, and maintaining it at 30°C for 10 minutes. Then, after raising the temperature from 30°C to 280°C at a rate of 10°C / min and maintaining it at 280°C for 10 minutes, the crystallization temperature can be measured.

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

[0122] The vent member 16 can be formed to have a predetermined thickness that has already been set. Also, the vent member 16 can be inserted into the vent guiding region 15 so that the insertion length can be varied or the venting pressure and position can be controlled according to the design. Here, the insertion length of the vent member means the maximum value of the distance between one end and the other end of the vent member with reference to the protruding direction of the electrode lead.

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

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

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

[0126] In one embodiment of the present invention, the secondary battery can be a cylindrical, rectangular, or pouch-type secondary battery. Among them, the secondary battery can be a pouch-type secondary battery.

[0127] As described above, the preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the specific embodiments described above, and various modifications can be made by those having ordinary knowledge in the technical field to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Such modified implementations should not be individually understood separately from the technical idea and prospect of the present invention.

Explanation of Reference Numerals

[0128] 10 Secondary battery 11 Electrode lead 12 Electrode assembly 13 Case 13a Storage part 13b Sealing part 14 Lead film 15 Vent induction area 16 Vent member 17 Tape 18 Resin

Claims

1. An electrode assembly, an electrode lead attached to the electrode assembly, a case including a storage portion for storing the electrode assembly therein and a sealing portion formed to seal the electrode assembly including a sealing resin, a lead film formed to cover a part of the outer surface of the electrode lead and interposed between the electrode lead and the case, a vent member including linear low density polyethylene having a comonomer with 6 or more carbon atoms, comprising, the sealing portion includes a vent guiding region including the vent member, a secondary battery, wherein a width of the vent guiding region is narrower than a width of other sealing portions excluding the vent guiding region, a secondary battery, in which a tape is inserted so that a width of the vent guiding region is narrower than a width of other sealing portions excluding the vent guiding region.

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

3. The secondary battery according to claim 1, wherein the tape includes polyimide, polyethylene terephthalate, or a mixture thereof.

4. An electrode assembly, an electrode lead attached to the electrode assembly, a case including a storage portion for storing the electrode assembly therein and a sealing portion formed to seal the electrode assembly including a sealing resin, a lead film formed to cover a part of the outer surface of the electrode lead and interposed between the electrode lead and the case, a vent member including linear low density polyethylene having a comonomer with 6 or more carbon atoms, comprising, the sealing portion includes a vent guiding region including the vent member, a secondary battery, wherein a width of the vent guiding region is narrower than a width of other sealing portions excluding the vent guiding region, a secondary battery, in which a resin is inserted so that a width of the vent guiding region is narrower than a width of other sealing portions excluding the vent guiding region.

5. The secondary battery according to claim 4, wherein the resin includes a fluororesin, a silicone resin, or a mixture thereof.

6. The secondary battery according to claim 1, wherein the vent guiding region is formed in a sealing portion close to the electrode lead, excluding a region between the electrode leads.

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

8. 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 lower than that of the sealing resin.

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

10. The secondary battery according to claim 9, wherein the vent member bends at a pressure of 1.5 atm or more.

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

12. 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.

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

14. 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.

15. 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.

16. The secondary battery according to claim 1, wherein 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 is 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.

17. 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.

18. An electrode assembly, an electrode lead attached to the electrode assembly, a case including a storage portion for storing the electrode assembly therein and a sealing portion formed to seal the electrode assembly including a sealing resin, a lead film formed to cover and wrap a part of the outer surface of the electrode lead and interposed between the electrode lead and the case, a vent member including a linear low-density polyethylene having a comonomer with 6 or more carbon atoms, comprising The sealing part includes a vent induction area including the vent member, The secondary battery is such that the width of the vent induction area is narrower than the width of the other sealing parts excluding the vent induction area, The secondary battery is such that 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.

19. The secondary battery according to claim 18, 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.

20. 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.

21. 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.

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

23. 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.

24. 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.

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

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

27. 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.

28. 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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