Secondary batteries

Abstract

To provide a secondary battery which is improved in safety by guiding exhaust of gas to a specific direction.SOLUTION: The present invention relates to a secondary battery having a bent member. The secondary battery may include: an electrode assembly; a case containing a housing portion that houses the electrode assembly into an internal portion; an electrode lead that is attached to the electrode assembly; and the bent member. The case may include a ceiling portion for sealing the electrode assembly in the internal portion. The ceiling portion may include a sealant resin for sealing a peripheral edge of the electrode assembly. The electrode lead may extend along a first direction from the case. The ceiling portion may include an inclination ceiling portion adjacent to the electrode lead. The inclination ceiling portion is extended along a second direction. The second direction is not orthogonal to the first direction. The bent member may be positioned at the inclination ceiling portion. The bent member may include the bent resin of which a fusion point is lower than that of the sealant resin.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery having a vent member.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0049365 filed on April 15, 2021, and Korean Patent Application No. 10-2021-0191701 filed on December 29, 2021, and the entire contents disclosed in the specifications and drawings of the relevant applications are incorporated herein by reference. [Background technology]

[0003] Secondary batteries can be applied to a variety of products and have excellent electrical properties such as high energy density. Secondary batteries are used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs) that are powered by electricity. Secondary batteries can significantly reduce the use of fossil fuels and are environmentally friendly as they do not produce by-products 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, and nickel-zinc batteries.

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

[0006] In conventional secondary batteries, a battery can catch fire due to various reasons, such as an internal short circuit, overcharging or over-discharging, temperature regulation, etc. In this case, the internal temperature of the secondary battery can rise rapidly, and thermal propagation can occur, in which heat is transferred to adjacent cells, further increasing the risk of fire.

[0007] When thermal runaway occurs, i.e., when the internal temperature of a secondary battery rises, directional venting is required to minimize damage to the electrodes caused by gas. However, conventional secondary batteries have a problem in that it is difficult to induce gas discharge in a specific direction. Summary of the Invention [Problem to be solved by the invention]

[0008] A particular object of the present invention is to provide a secondary battery with improved safety by directing gas discharge in a specific direction. [Means for solving the problem]

[0009] In order to solve the above problems, according to one aspect of the present invention, there is provided a secondary battery according to the following embodiment.

[0010] The first embodiment is an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion for sealing the electrode assembly therein, the sealing portion including a sealant resin for sealing a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin (hereinafter referred to as "vent resin") having a melting point lower than that of the sealant resin, the sealing portion includes an inclined sealing portion adjacent to the electrode lead, the inclined sealing portion extending along a second direction, the second direction not being perpendicular to the first direction; The secondary battery is characterized in that the vent member is located in the inclined sealing portion.

[0011] The second embodiment is the first embodiment, The inclined sealing portion may have an inclination angle of 10° to 80°, and the inclination angle may be an angle between the first direction and the second direction.

[0012] The third embodiment is the first or second embodiment, The vent member may include a first side extending parallel to the second direction.

[0013] The fourth embodiment is the third embodiment, A vent may be formed along a direction perpendicular to the first side of the vent member.

[0014] A fifth embodiment is any one of the first to fourth embodiments, The device may further include a lead film that surrounds the outer surface of the electrode lead and is interposed between the electrode lead and the sealing portion, and the vent member may extend through the receiving portion so that at least a portion of the vent member overlaps or contacts the lead film in the receiving portion.

[0015] The sixth embodiment is the fifth embodiment, The vent member may include a first portion and a second portion, the first portion extending along the second direction so that at least a portion of the first portion overlaps or contacts the lead film in the storage portion, and the second portion extending along a third direction perpendicular to the second direction.

[0016] The seventh embodiment is the sixth embodiment, The vent member may be L-shaped.

[0017] The eighth embodiment is the sixth embodiment, The second portion may include a tapered edge that gradually narrows as it extends along the electrode assembly into the recess.

[0018] The ninth embodiment is any one of the sixth to eighth embodiments, An outer end of the first portion may be spaced apart from an inner end of the sealing portion adjacent to the lead film, and the outer end of the first portion may be positioned in the receiving portion.

[0019] A tenth embodiment is any one of the sixth to ninth embodiments, The second portion may not overlap or contact the lead film.

[0020] An eleventh embodiment is any one of the first to tenth embodiments, The width of the vent member may vary along a direction perpendicular to the second direction.

[0021] A twelfth embodiment is any one of the first to eleventh embodiments, The vent member may have any one of a circular, elliptical, stepped, triangular, and rectangular shape.

[0022] A thirteenth embodiment is any one of the first to twelfth embodiments, The thickness of the vent member may vary along a direction perpendicular to the second direction.

[0023] A fourteenth embodiment is any one of the fifth to thirteenth embodiments, The area where the vent member overlaps or contacts the lead film may be 1% to 30% of the area where the lead film does not overlap the electrode lead.

[0024] A fifteenth embodiment is any one of the first to fourteenth embodiments, The vent resin may include linear low density polyethylene having a comonomer having six or more carbon atoms.

[0025] A sixteenth embodiment is any one of the first to fifteenth embodiments, The vent member can melt at 100°C to 120°C to vent gas from the storage portion to the outside of the secondary battery.

[0026] The seventeenth embodiment is the sixteenth embodiment, The vent member can vent gas from the storage section when the pressure in the storage section is 0.7 atm or higher.

[0027] The eighteenth embodiment is any one of the first to seventeenth embodiments, The vent member may have a maximum sealing strength of less than 6 kgf / 15 mm at 100° C. or higher.

[0028] The 19th embodiment is any one of the 1st to 18th embodiments, The vent member may have an average sealing strength of less than 4.5 kgf / 15 mm at 100° C. or higher.

[0029] A 20th embodiment is any one of the first to nineteenth embodiments, The vent member may have a maximum sealing strength of 6 kgf / 15 mm or more at room temperature to 60°C.

[0030] The 21st embodiment is any one of the 1st to 20th embodiments, The vent member may have an average sealing strength of 4.5 kgf / 15 mm or more at room temperature to 60°C.

[0031] The 22nd embodiment is any one of the 15th to 21st embodiments, The linear low-density polyethylene may be polymerized in the presence of a metallocene catalyst.

[0032] The 23rd embodiment is any one of the 15th to 22nd embodiments, The content of comonomers having 6 or more carbon atoms may be 15% by weight or less, based on 100% by weight of the linear low-density polyethylene.

[0033] A 24th embodiment is any one of the 1st to 23rd embodiments, The vent resin may have a polydispersity index (PDI) of 4 or less.

[0034] The 25th embodiment is any one of the 1st to 24th embodiments, The difference between the crystallization temperature of the sealant resin and the crystallization temperature of the vent resin may be 10° C. or less.

[0035] The 26th embodiment is any one of the 1st to 25th embodiments, The vent resin may have a melting point of 100°C to 130°C.

[0036] The 27th embodiment is any one of the 1st to 26th embodiments, The vent resin may have a weight average molecular weight of 100,000 g / mol to 400,000 g / mol.

[0037] The 28th embodiment is any one of the 1st to 27th embodiments, The secondary battery may be a pouch-type secondary battery.

[0038] The 29th embodiment is any one of the 1st to 28th embodiments, The vent member may have a maximum sealing strength at 100°C to 120°C of less than 6 kgf / 15 mm.

[0039] A 30th embodiment is any one of the 1st to 29th embodiments, The vent member may have an average sealing strength at 100°C to 120°C of less than 4.5 kgf / 15 mm.

[0040] The 31st embodiment is any one of the 15th to 30th embodiments, The content of the comonomer having 6 or more carbon atoms may be 5% to 15% by weight based on 100% by weight of the linear low-density polyethylene.

[0041] The 32nd embodiment is any one of the 1st to 31st embodiments, The vent member may have a maximum sealing strength of less than 3 kgf / 15 mm at 120° C. or higher.

[0042] The 33rd embodiment is any one of the 1st to 32nd embodiments, The vent member may have an average sealing strength of less than 2 kgf / 15 mm at 120° C. or higher.

[0043] The 34th embodiment is: an electrode assembly; a case including a housing portion for housing the electrode assembly and a sealing portion for sealing the electrode assembly therein, the sealing portion including a sealant resin for sealing a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin, the sealing portion includes a rectangular sealing portion adjacent to the electrode lead, at least one side of the rectangular sealing portion extends along a second direction, the second direction is not parallel to the first direction, The secondary battery is characterized in that at least a portion of the vent member is located in the rectangular sealing portion.

[0044] The 35th embodiment is: an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin, the sealing portion includes a convex sealing portion that bulges adjacent to the electrode lead, the convex sealing portion extends along a curve that bulges outward from the case, and the second direction is perpendicular to the first direction; The secondary battery is characterized in that the vent member is located in the convex sealing portion.

[0045] The 36th embodiment is: an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin, the sealing portion includes a recessed sealing portion recessed adjacent to the electrode lead, the recessed sealing portion extends along a curved line recessed toward an inside of the case, and the second direction is perpendicular to the first direction; The secondary battery is characterized in that the vent member is located in the recessed sealing portion.

[0046] The 37th embodiment is: an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin, the sealing portion includes a first sealing portion and a second sealing portion; the first sealing portion and the second sealing portion are partitioned to seal along an outer circumferential surface of the storage portion, the second sealing portion is disposed between adjacent first sealing portions, the outer surface of the second sealing portion is partitioned by a straight line or a curve connecting adjacent first sealing portions, and the straight line is not parallel to the first direction; The present invention relates to a secondary battery, wherein the second sealing portion includes the vent member. [Effects of the Invention]

[0047] A secondary battery according to an embodiment of the present invention includes a vent member including a vent resin having a melting point lower than that of a sealant resin, thereby guiding gas discharge toward the vent member.

[0048] A secondary battery according to one embodiment of the present invention includes a vent member in the inclined sealing portion, which can minimize the amount of gas vented to directly contact the electrode lead, thereby improving the safety of the battery.

[0049] The secondary battery according to one embodiment of the present invention includes a vent member in the inclined sealing portion, which allows for easier gas release than a battery with a vent member in a straight sealing portion.

[0050] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concept of the present invention, so the present invention should not be interpreted as being limited to the matters described in the drawings. [Brief explanation of the drawings]

[0051] [Figure 1] FIG. 1 is a plan view showing a conventional secondary battery. [Figure 2] 1 is a partial plan view of a secondary battery according to an embodiment of the present invention; [Figure 3] 1 is a schematic view illustrating the formation of a vent in a secondary battery according to an embodiment of the present invention. [Figure 4]10 is a partially enlarged plan view showing a lead film and a vent member of a secondary battery according to still another embodiment of the present invention. FIG. [Figure 5] 10 is a partially enlarged plan view showing a vent member of a secondary battery according to still another embodiment of the present invention; FIG. [Figure 6] 10 is a partially enlarged plan view showing an inclined sealing portion of a secondary battery according to still another embodiment of the present invention; FIG. [Figure 7] 10 is a partially enlarged plan view showing a rectangular sealing portion of a secondary battery according to still another embodiment of the present invention; FIG. [Figure 8] 10 is a partially enlarged plan view showing an inclined sealing portion of a secondary battery according to still another embodiment of the present invention; FIG. [Figure 9] 10 is a partially enlarged plan view showing a bulging convex sealing portion in a secondary battery according to still another embodiment of the present invention; FIG. [Figure 10] 10 is a partially enlarged plan view showing a recessed sealing portion in a secondary battery according to still another embodiment of the present invention; FIG. [Figure 11] 10 is a partially enlarged plan view showing a vent member of a secondary battery according to still another embodiment of the present invention; FIG. [Figure 12a] 3 is a cross-sectional view of a vent member taken along axis AA' of FIG. 2 according to one embodiment of the present invention. [Figure 12b] 3 is a cross-sectional view of a vent member taken along axis AA' of FIG. 2 according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0052] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain the invention.

[0053] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted for them at the time of this application.

[0054] The electrode leads are components that rapidly increase in temperature in abnormal situations such as overcharging or internal short circuits. Therefore, minimizing direct contact between the vented gas and the electrode leads can improve safety.

[0055] 1 is a plan view of a conventional secondary battery. Referring to FIG. 1, in the conventional secondary battery, the case has a rectangular shape, and the sealing portion formed along the outer periphery of the case is not inclined. Therefore, the first and second sides of the sealing portion adjacent to the corners of the sealing portion can withstand pressure caused by swelling of the battery, and it is difficult to guide gas discharge toward the corners of the sealing portion, which can minimize direct contact between the discharged gas and the electrode lead.

[0056] The inventor of the present invention discovered that providing a sloped sealing portion at the corner of the sealing portion and inserting a vent member so that it at least partially overlaps with the sloped sealing portion facilitates venting at the corner of the sealing portion, and thus completed the present invention.

[0057] A secondary battery according to one embodiment of the present invention includes an electrode assembly having an electrode lead attached thereto, a case including a housing for housing the electrode assembly, and a sealing portion including a sealant resin and formed to seal the electrode assembly, the sealing portion including sloped sealing portions at corners, and a vent member in the sloped sealing portion including a resin having a lower melting point than the sealant resin.

[0058] In some embodiments disclosed herein, the "sloped sealing portion" may refer to a region formed between an outer sloped sealing line of the sealing portion and an inner sloped sealing line of the sealing portion, where the outer sloped sealing line refers to the region farther from the electrode assembly, and the inner sloped sealing line refers to the region closer to the electrode assembly.

[0059] In some embodiments, the term "inclined" may refer to a case where the inclined sealing portion forms an acute or obtuse angle with respect to the direction of the electrode lead (first direction), i.e., an angle (second direction) that is not perpendicular to the direction of the electrode lead.

[0060] Throughout this specification, the inclusion of a vent member in the tapered sealing portion means that the tapered sealing portion and the vent member may at least partially overlap.

[0061] In describing the preferred embodiment, reference will be made to the directional nomenclature used to describe the secondary battery, noting that this nomenclature is used for convenience only and is not intended to limit the scope of the present disclosure.

[0062] 2 shows a secondary battery 10 according to one embodiment of the present invention. Referring to FIG. 2, the secondary battery 10 includes an electrode assembly 12 to which an electrode lead 11 is attached, and a case 13. The electrode assembly 12 may include a positive electrode plate, a negative electrode, and a separator (not shown). In the electrode assembly 12, the positive electrode plate and the negative electrode plate may be stacked in order with the separator sandwiched between them.

[0063] The positive electrode plate may include a positive electrode current collector made of a highly conductive metal sheet, for example, aluminum (Al) foil, and a positive electrode active material layer coated on at least one surface of the positive electrode current collector. The positive electrode plate may also include a positive electrode tab made of a metal material, for example, aluminum, at one end. The positive electrode tab protrudes from one end of the positive electrode plate and may be welded to the one end of the positive electrode plate or bonded to the one end of the positive electrode plate using a conductive adhesive.

[0064] The negative electrode plate may include a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) foil, and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. The negative electrode plate may also include a negative electrode tab formed of a metal material, for example, copper or nickel (Ni), at one end. The negative electrode tab may protrude from one end of the negative electrode plate, or may be welded to one end of the negative electrode plate or bonded to the one end of the negative electrode plate using a conductive adhesive.

[0065] The separator is interposed between the positive electrode plate and the negative electrode plate to electrically insulate them from each other. 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 be a porous membrane made of, for example, polyethylene (PE), polypropylene (PP), or a composite film thereof.

[0066] 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 bound to each other by a binder to form interstitial volume between the particles.

[0067] The electrode assembly 12 may be a jelly roll (wound type) electrode assembly having a structure in which long sheet-shaped positive and negative electrodes are wound with a separator interposed therebetween, a stack type (layered type) electrode assembly having a structure in which a plurality of positive and negative electrodes cut into units of a predetermined size are stacked in order with a separator interposed therebetween, a bi-cell or a full cell having a structure in which a predetermined unit of positive and negative electrodes is stacked with a separator interposed therebetween, or the like.

[0068] Referring to FIG. 2, the case 13 may include a receiving portion 13a for receiving the electrode assembly 12 and a sealing portion 13b containing a sealant resin and formed to seal the electrode assembly 12.

[0069] As shown in FIG. 2, the sealing portion 13b refers to a portion that is welded along the outer periphery of the receiving portion 13a to seal the electrode assembly 12. The sealing portion 13b includes an inclined sealing portion 14 at a corner of the case 13 adjacent to the electrode lead 11 extending from the battery case. The secondary battery 10 may include a lead film 15. The lead film 15 may surround at least a portion of the outer surface of the electrode lead 11 as shown in FIG. 2. The lead film 15 is interposed between the electrode lead 11 and the sealing portion 13b of the case 13 in the area protruding from the battery case, thereby facilitating attachment of the electrode lead 11 to the sealing portion 13b of the battery case 13.

[0070] 2, the tapered sealing portion 14 includes a vent member 16. Specifically, at least a portion of the vent member 16 may overlap or be located within the tapered sealing portion 14. The vent member 16 includes a vent resin having a lower melting point than the sealant resin of the sealing portion 13b.

[0071] The vent member 16 contains a vent resin with a lower melting point than the sealant resin of the sealing portion 13b, and melts before the sealant resin at high temperatures. The sealing strength of the portion where the vent member 16 is inserted at high temperatures is lower than the sealing strength of the case portion containing the sealant resin, making it easy to realize vent characteristics. This allows gas to be guided in a specific direction in the event of a thermal runaway phenomenon, improving the safety of the battery.

[0072] 3 is a schematic diagram illustrating the formation of a vent in a secondary battery according to an embodiment of the present invention, specifically, a cross-sectional view illustrating a vent member in a secondary battery according to an embodiment of the present invention.

[0073] 3, at a temperature at which the battery normally operates, the vent member 16 serves to seal the case 13 from the outside. When the battery temperature rises due to abnormal battery behavior, the vent member 16 melts, reducing the sealing strength of the portion where the vent member 16 is inserted. As a result, the sealing strength of the portion where the vent member 16 is inserted is reduced, and a vent can be formed at that position to allow gas to be released from the storage compartment. For example, the pressure of the gas inside the battery can concentrate at the interface between the vent member 16 and the sloped sealing portion 14, forming a gap or vent between the vent member 16 and the sloped sealing portion 14, allowing gas to be released.

[0074] The vent member 16 and the sloped sealing portion 14 may be overlapped or connected to one another by heat welding or other means. In yet another example, the vent member 16 and the sloped sealing portion 14 may be overlapped or connected to one another by adhesive such as glue or other similar means. In yet another example, the vent member 16 and the sloped sealing portion 14 may be physically joined by clips or the like. In yet another example, a portion of the vent member 16 may be embedded in the film that makes up the sloped sealing portion 14.

[0075] By positioning the vent member 16 at the inclined sealing portion 14, the amount of gas that comes into direct contact with the electrode lead 11, i.e., that is vented toward the side of the electrode lead 11, can be minimized, thereby further improving the safety of the battery.

[0076] Furthermore, because the vent member 16 is located on the sloped sealing portion 14, i.e., because the inner end of the sloped sealing portion 14 is sloped, the area of ​​the inner end of the sloped sealing portion 14 exposed to the storage portion 13a is smaller than if the adjacent sealing portions 13b formed orthogonal corners. This makes it easier for pressure applied when the battery swells to concentrate on the sloped sealing portion 14 at the corners of the sealing portion, thereby guiding gas to be more easily discharged toward the corners of the sealing portion. Here, the inner end of the sloped sealing portion 14 refers to the end of the sloped sealing portion 14 closest to the storage portion 13a.

[0077] Referring to FIG. 2, the inclined sealing portion may have an inclination angle of 10° to 80°, 20° to 60°, or 40° to 50°. Here, the inclination angle refers to the angle between a first direction defined by the extended electrode lead and a second direction defined by the direction in which the inclined sealing portion extends. When the inclination angle of the inclined sealing portion satisfies this range, the amount of gas that directly contacts the electrode lead 11, i.e., that is vented from the side of the electrode lead 11, can be further minimized, thereby further improving the safety of the battery. As the arrow in FIG. 2 indicates the direction in which gas is exhausted from the secondary battery, exhaust gas can be guided in a direction away from the electrode lead 11.

[0078] 2, the vent member 16 may be parallel to a second direction. As shown in FIG. 2, the vent member 16 includes a first side that extends parallel to the second direction, and the second direction is not perpendicular to the first direction.

[0079] In one embodiment of the present invention, the vent may be formed in a direction perpendicular to the direction of the vent member. As shown in FIG. 2, the vent may be formed along a direction perpendicular to the first side of the vent member 16. In this case, the amount of gas that comes into direct contact with the electrode lead 11, i.e., that is vented at the side of the electrode lead 11, can be minimized, thereby further improving the safety of the battery.

[0080] In one embodiment of the present invention, the vent member 16 may be located in the sloped sealing portion 14. In yet another embodiment of the present invention, the vent member 16 may extend through the storage portion 13a. In yet another embodiment of the present invention, the vent member 16 may be located so as to be exposed to the outside of the case 13 through the sloped sealing portion 14 (not shown).

[0081] In one embodiment of the present invention, the vent member 16 does not need to overlap with the lead film 15 .

[0082] In yet another embodiment of the present invention, the vent member 16 may partially overlap the lead film 15, as shown in FIG. 4. When the vent member 16 at least partially overlaps the lead film 15, the position of the vent member 16 can be consistently and easily fixed. The vent member 16 may extend through the receiving portion 13a so that the vent member 16 at least partially overlaps or contacts the lead film 15 in the receiving portion 13a. For example, when the vent member 16 is inserted and then welded, a portion of the vent member 16 overlaps the lead film 15, allowing the vent member 16 to be inserted and then welded in place.

[0083] The vent member 16 may be positioned at a predetermined distance from the electrode lead 11. This can easily minimize the amount of gas vented in a direction that may come into direct contact with the electrode lead 11, i.e., at the side of the electrode lead 11, thereby further improving the safety of the battery.

[0084] In one embodiment of the present invention, the vent member 16 may be spaced apart from the lead film 15 at the sealing portion 13b (14) and may at least partially overlap or contact the lead film 15 at the receiving portion 13a. By not overlapping or contacting the lead film 15 at the sealing portion 13b (14), i.e., by positioning the vent member 16 away from the electrode lead 11, the amount of gas vented at the side of the electrode lead 11 can be minimized, further improving the safety of the battery.

[0085] In one embodiment of the present invention, the outer sealing line and the inner sealing line of the inclined sealing portion 14 may be formed of one or more straight lines. Referring to Fig. 2, the inclined sealing portion 14 may be a rectangular area formed by connecting the end of the inclined straight sealing line on the outside of the inclined sealing portion and the end of the inclined straight sealing line on the inside of the inclined sealing portion.

[0086] 2, the inclined sealing portion 14 may have an inclination angle of 10° to 80°, or 20° to 60°, or 40° to 50°. When the inclination angle of the inclined sealing portion 14 is within this range, gas can be more easily guided in a direction that minimizes direct contact with the electrode lead.

[0087] In yet another embodiment of the present invention, the sealing portion may include a first sealing portion 13b and a second sealing portion 14. The first sealing portion 13b is a sealing portion that seals along the outer periphery of the storage portion. The second sealing portion 14 is located between adjacent first sealing portions 13b. The second sealing portion 14 is a sealing portion that is connected by a straight line (e.g., see FIG. 2) or a curved line (e.g., see FIGS. 9 and 10) so that the extension lines of two adjacent first sealing portions 13b do not cross each other at right angles. That is, the outside of the second sealing portion 14 may be defined by a straight line or a curved line connecting adjacent sides of the first sealing portions 13b. The straight line does not have to be parallel to the first direction. The second sealing portion 14 may include a vent member containing a resin ("vent resin") with a lower melting point than the sealant resin.

[0088] In a secondary battery according to an embodiment of the present invention, when the secondary battery includes a second sealing portion 14, the inner edge of the second sealing portion is inclined or curved, so that the area of ​​the inner edge of the second sealing portion exposed to the storage compartment is smaller than the area of ​​the inner edge of the sealing portion forming the perpendicular corner exposed to the storage compartment, and therefore pressure is more easily concentrated on the inner edge of the second sealing portion. Here, the inner edge of the second sealing portion refers to the end of the second sealing portion that is closest to the storage compartment.

[0089] 4 is a partially enlarged view of a vent member 16 in a secondary battery according to yet another embodiment of the present invention. Referring to FIG. 4, the vent member 16 may include a first portion 16b and a second portion 16a. The first portion 16b extends along the second direction between the lead film 15 and the second portion 16a, forming a bridge portion between the second portion and the lead film. The second portion 16a extends along a third direction perpendicular to the second direction.

[0090] In one embodiment of the present invention, the vent member 16 may be L-shaped as shown in FIG.

[0091] Here, venting may occur substantially in the second portion 16a, and venting may not occur substantially in the first portion 16b.

[0092] In one embodiment of the present invention, the first portion 16b may have a rectangular shape, with the long side of the first portion positioned in the third direction and the short side of the first portion positioned in the second direction.

[0093] In one embodiment of the present invention, the second portion 16a may have a rectangular shape, for example, a short side of the second portion may be located in the third direction and a long side of the second portion may be located in the second direction.

[0094] Referring to FIG. 4 , the first portion 16b may at least partially overlap or contact the lead film 15. A portion of the first portion 16b and a portion of the lead film 15 may be overlapped or contacted by thermal welding. In another example, a portion of the first portion 16b and a portion of the lead film 15 may be overlapped or contacted by an adhesive such as glue. In another example, a portion of the first portion 16b and a portion of the lead film 15 may be physically connected by a clip or the like. In another example, a portion of the first portion 16b may be embedded in a film that constitutes the lead film 15.

[0095] 4, the second portion 16a of the vent member 16 and the lead film 15 may not overlap or contact each other. For example, the second portion 16a and the lead film 15 may not overlap or contact each other at the sealing portion 13b and / or the sloped sealing portion 14. When the second portion 16a of the vent member 16 and the lead film 15 do not overlap or contact each other, the amount of gas vented from the side of the electrode lead 11 is minimized, further improving the safety of the battery.

[0096] In one embodiment of the present invention, the area where the vent member overlaps or contacts the lead film may be 1% to 30%, or 1.3% to 23%, or 1.5% to 12%, or 2% to 9% of the area where the lead film does not overlap with the electrode lead. Here, the area where the lead film does not overlap with the electrode lead means the sum of the areas of the electrode lead and the lead film where the lead film does not overlap.

[0097] As shown in FIG. 4, the outer end of the first portion 16b may be spaced apart from the inner end of the sloped sealing portion 14. Here, the "outer end of the first portion of the vent member" refers to the end of the first portion 16b closest to the sealing portion. The "inner end of the sloped sealing portion" refers to the end of the sloped sealing portion farthest from the outside of the battery. When the outer end of the first portion 16b is spaced apart from the inner end of the sloped sealing portion 14, the entire first portion 16b is positioned within the storage portion 13a. This exposes the gap or space between the first portion 16b and the sloped sealing portion 14 to the storage portion 13a. As a result, gas pressure concentrates in this gap or space, enabling faster venting in an emergency.

[0098] FIG. 5 is a partially enlarged view of a vent member 16 in a secondary battery according to yet another embodiment of the present invention. The vent member 16 shown in FIG. 5 is substantially similar to the vent member 16 shown in FIG. 4. For example, as shown in FIG. 5, the vent member 16 may include a first portion 16b and a second portion 16a. However, as best shown in FIG. 5, the second portion 16b of the vent member 16 may include a tapered edge whose width gradually narrows as it extends along the electrode assembly 12 toward the receiving portion 13a. As the width of the edge gradually narrows, the vent member can easily be parallel to the side of the electrode assembly 12, allowing for convenient and appropriate placement of the vent member within the battery case. This also makes it easier to prevent contact between the electrode assembly 12 and the inner end of the second portion 16a within the receiving portion 13a.

[0099] Referring to FIG. 6, the inclined sealing portion may be a rectangular area connecting an end of an inclined straight sealing line on the outside of the sealing portion and an end of an inclined straight sealing line on the inside of the sealing portion.

[0100] Specifically, in the outer sealing line including a first straight portion 14a perpendicular to the first direction, an inclined portion 14b extending from the first straight portion 14a inclined toward the electrode lead 11, and a second straight portion 14c extending from the inclined portion 14b to one end of the case 13 that contacts the lead film 15, the area formed by connecting one side end and the other side end of the inclined portion 14b to one side end and the other side end of the inclined portion of the inner sealing line, respectively, can be called the inclined sealing portion.

[0101] The inclination angle of the inclined sealing portion may be 10° to 80°, or 20° to 60°, or 40° to 50°. When the inclination angle of the inclined sealing portion is within the above range, gas can be more easily guided to a direction that minimizes direct contact with the electrode lead.

[0102] 7, at least a portion of the vent member 16 may be located within a rectangular sealing portion. The rectangular sealing portion may be defined as a rectangular area formed by connecting an end of a straight sealing line parallel to the first direction on the outside of the sealing portion with an end of a straight sealing line parallel to the first direction on the inside of the sealing portion, as shown in FIG.

[0103] Specifically, in an outer sealing line including a first linear portion 14a perpendicular to the first direction, a second linear portion 14b extending from the first linear portion 14a at a right angle to the first linear portion 14a, and a third linear portion 14c extending from the second linear portion 14b at a right angle to one end of the case 13 that contacts the lead film 15, an area where one end and the other end of the second linear portion 14b are connected to one end and the other end of an inner sealing line parallel to the first direction, respectively, may be referred to as a rectangular sealing portion.

[0104] 7, at least a portion of the vent member 16 may be located within the rectangular sealing portion, which allows gas to be more easily guided in a direction that minimizes direct contact with the electrode lead.

[0105] Referring to FIG. 8, the inclined sealing portion may refer to an octagonal or multiple quadrangular area formed by connecting the end of an inclined straight sealing line on the outside of the sealing portion with the end of an inclined straight sealing line on the inside of the sealing portion.

[0106] Specifically, in the outer sealing line including a first inclined portion 14d extending from an end of the sealing portion 13b and inclined toward the electrode lead 11, a first straight portion 14e extending from the first inclined portion 14d and perpendicular to the first direction, a second inclined portion 14f extending from the first straight portion 14e and inclined toward the electrode lead 11, and a second straight portion 14g extending from the second inclined portion 14f to one end of the case 13 with which the lead film 15 comes into contact, the region where one side end of the first inclined portion 14d and the other side end of the second inclined portion 14f are connected to one side end of the inclined portion extending from the sealing portion 13b and inclined toward the electrode lead 11 and the other side end of the inner sealing line extending from the inner sealing line overlapping the lead film 15 and extending toward the sealing portion 13b, respectively, can be referred to as the inclined sealing portion.

[0107] Referring to FIG. 8, venting may occur in a direction perpendicular to the inclination angle of the first inclined portion 14d and / or the second inclined portion 14f.

[0108] The inclination angles of the first inclined portion 14d and the second inclined portion 14f may be the same or different.

[0109] The inclination angle of the first inclined portion 14d and / or the second inclined portion 14f may be 10° to 80°, or 20° to 60°, or 40° to 50°. When the inclination angle of the inclined sealing portion satisfies the above range, gas can be easily guided to a direction that minimizes direct contact with the electrode lead.

[0110] In yet another embodiment of the present invention, the outer and inner sealing lines of the sloped sealing portion 14 may be comprised of one or more curved lines.

[0111] 9, the curved outer and inner sealing lines define a curved sealing portion 14 that bulges outward from the case 13. That is, the curved sealing portion 14 may refer to the area formed by connecting the end of the outer curved sealing line of the sealing portion and the end of the inner curved sealing line of the sealing portion.

[0112] 10, the curved outer and inner sealing lines define a curved sealing portion 14 having a concave or recessed shape toward the inside of the case 13. That is, the curved sealing portion 14 may refer to the area connecting the end of the outer curved sealing line of the sealing portion and the end of the inner curved sealing line of the sealing portion.

[0113] In yet another embodiment of the present invention, the outer and inner sealing lines of the curved sealing portion 14 may be formed of two or more continuous curves, each having a different radius of curvature.

[0114] In yet another embodiment of the present invention, the outer and inner sealing lines of the inclined sealing portion 14 may be comprised of one or more straight lines and one or more curved lines.

[0115] In one embodiment of the present invention, the vent member 16 vents at 100° C. to 120° C., and gas can be discharged from the storage portion 13a to the outside of the battery through the vent member 16.

[0116] Because at least a portion of the vent member 16 overlaps or is positioned on the sloped sealing portion 14, venting can occur at a lower pressure than in conventional secondary batteries including a sealing portion without a sloped sealing portion, a rectangular sealing portion, or a curved sealing portion. For example, the vent member 16 can vent at a pressure of 0.7 atm or more at 100°C to 120°C.

[0117] The vent member 16 vents within the above temperature range and / or pressure conditions, so that the battery is sealed when the battery is operating normally and gas can be released only when the battery is behaving abnormally.

[0118] 11, the vent member 16 may have a structure in which its width tapers in a direction perpendicular to the second direction of the sloped sealing portion 14. The width of the vent member 16 may taper continuously or discontinuously along the direction perpendicular to the second direction of the sloped sealing portion 14. The vented gas is guided away from the electrode lead 11, thereby further improving the safety of the battery.

[0119] In one embodiment of the present invention, the vent member 16 may have a circular, oval, triangular, or rectangular shape.

[0120] As shown in FIG. 11 , the vent member 16 may have an asymmetrical stepped structure. In the asymmetrical stepped structure, an offset may be formed between the steps to minimize direct contact between the vented gas and the electrode lead 11. For example, the size (exhaust angle of the vented gas) and position (distance from the electrode lead 11) of the discharge end of the vent member 16 may be configured to minimize contact between the vented gas and the electrode lead, as best shown in FIG. 11 . Thus, reducing the size of the discharge end of the vent member to direct the gas away from the electrode lead 11 and positioning the discharge end farther from the electrode lead minimizes contact between the vented gas and the electrode lead. In this case, the discharge direction of the vented gas may be further away from the side of the electrode lead 11.

[0121] In one embodiment of the present invention, the thickness of the vent member 16 may decrease continuously or discontinuously along a direction perpendicular to the second direction of the tapered sealing portion 14 .

[0122] Figures 12a and 12b are cross-sectional views taken along axis A-A' of Figure 2. The thickness of the vent member 16 may decrease discontinuously along the step, as shown in Figure 12a, or may decrease continuously as shown in Figure 12b.

[0123] In one embodiment of the present invention, the vent resin having a lower melting point than the sealant resin may include linear low density polyethylene having a comonomer having 6 or more carbon atoms.

[0124] The vent resin, which has a lower melting point than the sealant resin, contains linear low-density polyethylene with a comonomer having six or more carbon atoms, which provides excellent sealing with the sealant resin within the normal temperature range. However, at high temperatures, the sealing strength of the sealing portion 13b including the vent member 16 decreases, allowing venting to be achieved.

[0125] In one embodiment of the present invention, the vent resin having a melting point lower than that of the sealant resin may include a linear low-density polyethylene having a comonomer having 6 to 8 carbon atoms.

[0126] In one embodiment of the present invention, the vent resin having a lower melting point than the sealant resin may have a melting point of 100° C. to 130° C., 105° C. to 125° C., or 110° C. to 120° C. When the melting point of the vent resin having a lower melting point than the sealant resin falls within the above-mentioned range, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, for example, above 100° C., making it easier to realize venting characteristics.

[0127] The melting point of the vent resin, which has a lower melting point than the sealant resin, can be measured using a differential scanning calorimeter (DSC). For example, the temperature of a sample is increased from 30°C to 280°C at 10°C / min, maintained at 280°C for 10 minutes, cooled to 30°C at 10°C / min, and maintained at 30°C for 10 minutes. The temperature of the sample is then increased from 30°C to 280°C at 10°C / min, and maintained at 280°C for 10 minutes to measure the melting point.

[0128] 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 another 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. If the vent member satisfies the above-described sealing strength requirements within the above-described temperature ranges, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, for example, above 100°C, making it easier to achieve venting characteristics.

[0129] In addition, in one embodiment of the present invention, the vent member 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 satisfies the above-mentioned sealing strength within the above-mentioned temperature range, it will have excellent sealing strength during normal battery operation, making it easier to ensure the hermeticity of the battery.

[0130] In one embodiment of the present invention, the vent member may have a maximum sealing strength of less than 6 kgf / 15 mm at temperatures above 100°C, and the vent member 16 may have a maximum sealing strength of 6 kgf / 15 mm or more at room temperature to 60°C. When the vent member satisfies the above-mentioned sealing strength, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, making it easier to achieve venting characteristics. Furthermore, during normal battery operation, the vent member has excellent sealing strength, making it easier to ensure the hermeticity of the battery.

[0131] 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. If the vent member 16 satisfies the above-described sealing strength requirements within the above-described temperature ranges, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, making it easier to achieve venting characteristics.

[0132] In one embodiment of the present invention, the vent member may have an average sealing strength of 4.5 kgf / 15 mm or more, or 5 kgf / 15 mm or more, or 6 kgf / 15 mm or more, or 7 kgf / 15 mm or more at room temperature to 60° C. If the vent member satisfies the above-mentioned sealing strength within the above-mentioned temperature range, it will have excellent sealing strength during normal battery operation, making it easier to ensure the hermeticity of the battery.

[0133] In one embodiment of the present invention, the vent member 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 has the above-mentioned sealing strength within the above-mentioned temperature range, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, making it easier to realize venting characteristics. In addition, the vent member has excellent sealing strength during normal battery operation, making it easier to ensure the hermeticity of the battery.

[0134] The sealing strength of the vent member 16 as a function of temperature can be measured by cutting a portion of the case into which the vent member 16 has been inserted to a width of 15 mm and a length of 5 cm, opening both ends 180°, placing the cut piece in a UTM jig, and then conducting a tensile test at a rate of 5 mm / min.

[0135] In this case, the maximum sealing strength means the maximum value at which the case breaks, and the average sealing strength means the average value when the battery case is stretched 8 mm at 4.5 kgf / 15 mm if the maximum sealing strength is 4.5 kgf / 15 mm or more, or means the average value when the battery case is stretched 8 mm at the maximum sealing strength if the maximum sealing strength is less than 4.5 kgf / 15 mm.

[0136] In one embodiment of the present invention, the linear low-density polyethylene having a comonomer having 6 or more carbon atoms may be polymerized in the presence of a metallocene catalyst. When the linear low-density polyethylene having a comonomer having 6 or more carbon atoms is polymerized in the presence of a metallocene catalyst, it may be more advantageous in terms of sealing strength and physical properties than when polymerized in the presence of a Ziegler-Natta catalyst.

[0137] 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 a comonomer having 6 or more carbon atoms may be 15 wt% or less, 12 wt% or less, 11.8 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, or 7.6 wt% or less, based on 100 wt% of the linear low-density polyethylene having a comonomer having 6 or more carbon atoms. At the same time, the content of the comonomer having 6 or more carbon atoms may be 5 wt% or more, 7.6 wt% or more, 8 wt% or more, 9.0 wt% or more, 10 wt% or more, 11.8 wt% or more, or 12 wt% or more, based on 100 wt% of the linear low-density polyethylene having a comonomer having 6 or more carbon atoms. When the content of the comonomer having 6 or more carbon atoms is within the above-mentioned range, the problem of reduced intermolecular packing density and reduced sealing strength during normal battery operation can be more easily prevented.

[0138] The content of the comonomer having 6 or more carbon atoms can be measured by H-NMR. For example, about 10 mg of a sample is completely dissolved in about 0.6 mL of trichloroethylene solvent using a heat gun, and then sampled into an NMR tube.1 H-NMR or 13 It can be measured using C-NMR.

[0139] In one embodiment of the present invention, the resin having a melting point lower than that of the sealant resin may have a weight average molecular weight of 100,000 g / mol to 400,000 g / mol, or 200,000 g / mol to 350,000 g / mol, or 230,000 g / mol to 300,000 g / mol. When the weight average molecular weight of the resin having a melting point lower than that of the sealant resin satisfies the above range, the sealing strength with the sealant resin during normal operation of the battery can be further improved.

[0140] In one embodiment of the present invention, the resin having a lower melting point than the sealant resin may have a polydispersity index (PDI) of 4 or less, or 3.8 or less, or 3.796 or less, or 3.5 or less, or 3.023 or less, or 3 or less, or 2.7 or less, or 2.674 or less. The polydispersity index (PDI) may also be 1.0 or more. When the polydispersity index of the resin having a lower melting point than the sealant resin is within the above range, the molecular weight distribution becomes narrow, and the sealing strength and physical properties with the sealant resin during normal operation of the battery are further improved.

[0141] The weight average molecular weight and polydispersity index of the vent resin having a melting point lower than that of the sealant resin may be measured by gel permeation chromatography (GPC) under the following conditions. - Column: Tosoh HLC-8321 GPC / HT - Solvent: Trichlorobenzene (TCB) + 0.04% BHT (after drying with 0.1% CaCl2) - Flow rate: 1.0ml / min - Sample concentration: 1.5mg / ml - Injection volume: 300μl - Column temperature: 160℃ - Detector: RI detector - Standard: Polystyrene (corrected to a cubic function)

[0142] In one embodiment of the present invention, the crystallization temperature of the sealant resin may be similar to that of the vent resin having a lower melting point than the sealant resin. For example, the difference between the crystallization temperature of the sealant resin and that of the vent resin having a lower melting point than the sealant resin may be 10°C or less, or 5°C or less. Furthermore, the difference between the crystallization temperature of the sealant resin and that of the vent resin may be 0.1°C or more. When the difference between the crystallization temperature of the sealant resin and that of the vent resin having a lower melting point than the sealant resin is within the above-mentioned range, the welding characteristics of the sealant resin and the vent resin having a lower melting point than the sealant resin during normal operation of the battery can be further improved.

[0143] In one embodiment of the present invention, the crystallization temperature of the vent resin having a lower melting point than the sealant resin may be 90° C. to 115° C., or 95° C. to 110° C., or 100° C. to 110° C., or 105° C. to 110° C. When the crystallization temperature of the vent resin having a lower melting point than the sealant resin satisfies the above-mentioned range, the welding properties of the sealant resin and the vent resin having a lower melting point than the sealant resin can be further improved.

[0144] The crystallization temperature can be measured using a differential scanning calorimeter (DSC). For example, the temperature of a sample can be increased from 30°C to 280°C at 10°C / min, maintained at 280°C for 10 minutes, cooled to 30°C at 10°C / min, and maintained at 30°C for 10 minutes. The temperature of the sample can then be increased from 30°C to 280°C at 10°C / min, and maintained at 280°C for 10 minutes to measure the crystallization temperature.

[0145] In one embodiment of the present invention, the vent member 16 may have the thickness of a film. The vent member 16 may be formed to have a predetermined thickness. The vent member 16 may also be inserted into a sloped sealing portion, a square sealing portion, or a curved sealing portion 14, allowing for control of insertion length, venting pressure, and position, depending on the design.

[0146] In one embodiment of the present invention, the vent member 16 may further include an adhesive layer for further enhancing sealing between the sealant resin and a vent resin having a lower melting point than the sealant resin.

[0147] A secondary battery according to one embodiment of the present invention includes a sloped sealing portion, a rectangular sealing portion, or a curved sealing portion located at a corner of the sealing portion, which is at least partially overlapped with a vent member including a vent resin. This allows for smoother and faster directional venting, which discharges gas to one side due to a decrease in sealing strength at high temperatures when the internal temperature of the battery rises, in order to minimize damage to electrodes due to gas when a thermal runaway phenomenon occurs.

[0148] In one embodiment of the present invention, the case 13 may be in the form of a pouch.

[0149] In one embodiment of the present invention, when the battery case 13 is in the form of a pouch, the battery case 13 may include an upper pouch and a lower pouch. When the battery case 13 includes the upper pouch and the lower pouch, the upper pouch and the lower pouch may be arranged so that the sealant resins face each other, and the facing sealant resins may be welded to each other by heat and pressure to seal the battery.

[0150] The welding may be heat welding or ultrasonic welding, but is not particularly limited as long as it can weld the sealing portion.

[0151] The sealing portion 13b may be sealed on four or three sides of the battery case 13. In the three-side sealing structure, the upper and lower pouches are formed on a single pouch sheet, and then the boundary between the upper and lower pouches is folded so that the receiving portions 13a formed in the upper and lower pouches overlap, and the remaining three sides, excluding the folded portion, are sealed.

[0152] In one embodiment of the present invention, the inclined sealing portion, the square sealing portion, or the curved sealing portion may be located at a corner of the sealing portion at an edge connected to the bent portion among the three sealed peripheral edges.

[0153] In one embodiment of the present invention, the battery case 13 may be provided in the form of a film having a multi-layer structure including an outer layer for protection against external impact, a metal barrier layer for blocking moisture, and a sealant layer for sealing the battery case.

[0154] The outer layer may include a polyester film made of polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate, nylon, or the like, and may be composed of a single layer or multiple layers.

[0155] The metal barrier layer may include aluminum, copper, and the like.

[0156] The sealant layer may be composed of a single layer or multiple layers.

[0157] The sealant resin may include polypropylene (PP), acid-modified polypropylene (PPa), random polypropylene, ethylene-propylene copolymer, or two or more thereof. The ethylene-propylene copolymer may include, but is not limited to, ethylene-propylene rubber, ethylene-propylene block copolymer, etc.

[0158] In one embodiment of the present invention, the secondary battery may be a cylindrical, prismatic, or pouch-type secondary battery.

[0159] Although the preferred embodiments of the present invention have been illustrated and described above, it goes without saying that the present invention is not limited to the specific preferred embodiments described above, and that various modifications can be made by those skilled in the art to which the invention pertains 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 ideas and perspectives of the present invention. [Explanation of symbols]

[0160] 10 Secondary battery 11 Electrode Lead 12 Electrode assembly 13 Battery case 13a Storage area 13b Sealing part 14 Inclined ceiling section, curved ceiling section 14a First straight section 14b 2nd straight section 14c 3rd straight section 14d 1st slope part 14e 1st straight section 14f 2nd slope 14g 2nd straight section 15 Lead Film 16 Venting material 16a Part 2 16b Part 1

Claims

1. an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion for sealing the electrode assembly therein, the sealing portion including a sealant resin for sealing a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin; a lead film surrounding an outer surface of the electrode lead and interposed between the electrode lead and the sealing portion, the sealing portion has a first side contacting a portion of the electrode lead, a second side perpendicular to the first side, and a corner of the sealing portion where the first side and the second side intersect, and includes an inclined sealing portion at the corner of the sealing portion adjacent to the electrode lead, the inclined sealing portion extends along a second direction, the second direction is not perpendicular to the first direction, and the vent member is located at the inclined sealing portion; A secondary battery, wherein the vent member extends through the housing portion so as to overlap or contact at least a portion of the lead film in the housing portion.

2. The inclined sealing portion has an inclination angle of 10° to 80°, The secondary battery according to claim 1 , wherein the tilt angle is an angle between the first direction and the second direction.

3. The secondary battery according to claim 1 , wherein the vent member includes a first side extending parallel to the second direction.

4. The secondary battery according to claim 3 , wherein the vent is formed along a direction perpendicular to the first side of the vent member.

5. the vent member includes a first portion and a second portion; the first portion extends along the second direction so that at least a portion of the first portion overlaps or contacts the lead film in the receiving portion; The secondary battery according to claim 1 , wherein the second portion extends along a third direction perpendicular to the second direction.

6. 6. The secondary battery according to claim 5, wherein the vent member is L-shaped.

7. The secondary battery according to claim 5 , wherein the second portion includes an edge whose width gradually narrows as it extends along the electrode assembly toward the receiving portion.

8. an outer end of the first portion is spaced apart from an inner end of the sealing portion adjacent to the lead film; The secondary battery according to claim 5 , wherein an outer end of the first portion is located in the storage portion.

9. The secondary battery according to claim 5 , wherein the second portion does not overlap or contact the lead film.

10. The secondary battery of claim 1 , wherein the width of the vent member varies along a direction perpendicular to the second direction.

11. The secondary battery of claim 1 , wherein the vent member has one of a circular, elliptical, stepped, triangular, and rectangular shape.

12. The secondary battery according to claim 1 , wherein the thickness of the vent member varies along a direction perpendicular to the second direction.

13. 2. The secondary battery according to claim 1, wherein the area of ​​the vent member overlapping or contacting with the lead film is 1% to 30% of the area of ​​the lead film not overlapping with the electrode lead.

14. 2. The secondary battery according to claim 1, wherein the vent resin contains linear low-density polyethylene having a comonomer having 6 or more carbon atoms.

15. 2. The secondary battery according to claim 1, wherein the vent member melts at 100° C. to 120° C. to vent gas in the storage portion to the outside of the secondary battery.

16. The secondary battery according to claim 15, wherein the vent member vents gas from the storage portion when the pressure in the storage portion is 0.7 atm or higher.

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

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

19. 2. 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.

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

21. 15. The secondary battery of claim 14, wherein the content of the comonomer having 6 or more carbon atoms is 15% by weight or less, based on 100% by weight of the linear low-density polyethylene.

22. 2. The secondary battery according to claim 1, wherein the vent resin has a polydispersity index (PDI) of 4 or less.

23. 2. The secondary battery according to claim 1, wherein the difference between the crystallization temperature of the sealant resin and the crystallization temperature of the vent resin is 10[deg.] C. or less.

24. 2. The secondary battery according to claim 1, wherein the vent resin has a melting point of 100°C to 130°C.

25. 2. The secondary battery according to claim 1, wherein the vent resin has a weight average molecular weight of 100,000 g / mol to 400,000 g / mol.

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

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

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

29. 15. The secondary battery of claim 14, wherein the content of the comonomer having 6 or more carbon atoms is 5% to 15% by weight based on 100% by weight of the linear low-density polyethylene.

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

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

32. an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin; a lead film surrounding an outer surface of the electrode lead and interposed between the electrode lead and the sealing portion, the sealing portion has a first side in contact with a portion of the electrode lead, a second side perpendicular to the first side, and a corner of the sealing portion where the first side and the second side intersect, and includes a rectangular sealing portion at the corner of the sealing portion adjacent to the electrode lead, at least one side of the rectangular sealing portion extends along a second direction, the second direction is not parallel to the first direction, and at least a portion of the vent member is located in the rectangular sealing portion; A secondary battery, wherein the vent member extends through the housing portion so as to overlap or contact at least a portion of the lead film in the housing portion.

33. an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin, the sealing portion includes a convex sealing portion that bulges adjacent to the electrode lead, the convex sealing portion is a curve that bulges so that a tangent line changes from the first direction to a second direction, and the second direction is perpendicular to the first direction; The secondary battery, wherein the vent member is located in the convex sealing portion.

34. an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin, the sealing portion includes a recessed sealing portion recessed adjacent to the electrode lead, the recessed sealing portion being a curved line recessed such that a tangent changes from a second direction to the first direction, and the second direction is perpendicular to the first direction; The secondary battery, wherein the vent member is located in the recessed sealing portion.

35. an electrode assembly; a case including a housing portion that houses the electrode assembly and a sealing portion that seals the electrode assembly therein, the sealing portion including a sealant resin that seals a periphery of the electrode assembly; an electrode lead attached to the electrode assembly and extending from the case along a first direction; a vent member containing a vent resin having a melting point lower than that of the sealant resin; a lead film surrounding an outer surface of the electrode lead and interposed between the electrode lead and the sealing portion, the sealing portion includes a first sealing portion and a second sealing portion; the first sealing portion and the second sealing portion are sealed along an outer circumferential surface of the receiving portion and are partitioned, the second sealing portion is disposed between adjacent first sealing portions, an outer surface of the second sealing portion is partitioned by a line or a curve connecting adjacent first sealing portions, the line is not parallel to the first direction, the second sealing portion is located at a corner of the case, and the second sealing portion includes the vent member; A secondary battery, wherein the vent member extends through the housing portion so as to overlap or contact at least a portion of the lead film in the housing portion.

36. The secondary battery according to claim 1 , wherein an inner end of the inclined sealing portion is inclined or curved.

37. The secondary battery according to claim 1 , wherein at least a portion of the vent member is exposed to the outside of the case, and at least a portion of the vent member is exposed to the housing portion.

38. The secondary battery according to claim 32, wherein an inner edge of the rectangular sealing portion is inclined or curved.

39. The secondary battery according to claim 32, wherein at least a portion of the vent member is exposed to the outside of the case, and at least a portion of the vent member is exposed to the housing portion.

40. The secondary battery of claim 35, wherein an inner end of the second sealing portion is inclined or curved.

41. The secondary battery according to claim 35, wherein at least a portion of the vent member is exposed to the outside of the case, and at least a portion of the vent member is exposed to the housing portion.

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