Secondary battery

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 provided with a vent member.

[0002] This application claims priority to 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 all 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 run on 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 they 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 generally 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 laminated in that order, and the electrode assembly is sealed by welding a sealant resin in the sealant layer.

[0006] In conventional secondary batteries, the battery may 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 may rise rapidly and a thermal propagation phenomenon may occur in which heat is transferred to adjacent cells, causing the fire to become even more severe.

[0007] When a thermal runaway phenomenon occurs, i.e., when the internal temperature of a secondary battery rises, a directional venting characteristic that exhausts gas in one direction 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 exhaust 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 having 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 receiving portion for receiving 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 including 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 same as 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 electrode lead may further include a lead film surrounding an outer surface of the electrode lead and interposed between the electrode lead and the sealing portion, and the vent member may extend through the receiving portion such 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 such 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 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 a 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 is capable of venting gas from the storage compartment when the pressure in the storage compartment is 0.7 atm or greater.

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

[0030] A twenty-first embodiment is any one of the first to twentieth embodiments, The vent member may have an average sealing strength at room temperature to 60°C of 4.5 kgf / 15 mm or more.

[0031] A twenty-second embodiment is any one of the fifteenth to twenty-first 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 twenty-fourth embodiment is any one of the first to twenty-third embodiments, The vent resin may have a polydispersity index (PDI) of 4 or less.

[0034] A twenty-fifth embodiment is any one of the first to twenty-fourth 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] A 26th embodiment is any one of the first to 25th embodiments, The vent resin may have a melting point of 100°C to 130°C.

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

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

[0038] A 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 first 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% by weight to 15% by weight based on 100% by weight of the linear low density polyethylene.

[0041] A 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] A 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 receiving portion for receiving 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 including 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 present invention relates to a secondary battery, wherein 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 receiving portion for receiving 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 including a vent resin having a melting point lower than that of the sealant resin; the sealing portion includes a convex sealing portion adjacent to the electrode lead, the convex sealing portion extends along a curved line convex toward an outside of the case, and the second direction is perpendicular to the first direction; The present invention relates to a secondary battery, characterized in that the vent member is located in the protruding sealing portion.

[0045] The 36th embodiment is: An electrode assembly; a case including a receiving portion for receiving 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 including a vent resin having a melting point lower than that of the sealant resin; the sealing portion includes a recessed sealing portion adjacent to the electrode lead, the recessed sealing portion extends along a curve 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 receiving portion for receiving 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 including 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, an 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. Effect of the Invention

[0047] The 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, so that gas can be guided toward the vent member.

[0048] A secondary battery according to an embodiment of the present invention includes a vent member in a sloped 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 an embodiment of the present invention includes a vent member at the inclined sealing portion, and thus gas can be discharged more easily than when a vent member is provided at 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 ideas of the present invention. Therefore, the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief description of the drawings]

[0051] [Figure 1] FIG. 1 is a plan view showing a conventional secondary battery. [Diagram 2] 1 is a partial plan view of a secondary battery according to an embodiment of the present invention; [Diagram 3] 2 is a schematic diagram illustrating the formation of a vent in a secondary battery according to an embodiment of the present invention; FIG. [Figure 4]11 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. [Diagram 5] 11 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] 13 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] 13 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] 13 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] 13 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] 11 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] 11 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 PREFERRED EMBODIMENTS

[0052] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached 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 according 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 describe 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 lead is a part whose temperature rises quickly in abnormal situations such as overcharging or internal short circuiting. Therefore, minimizing direct contact between the vented gas and the electrode lead can improve safety.

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

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

[0057] According to one embodiment of the present invention, a secondary battery includes an electrode assembly having an electrode lead attached thereto, a case including a receiving portion for receiving the electrode assembly, and a sealing portion including a sealant resin and formed to seal the electrode assembly, the sealing portion including an inclined sealing portion at a corner, and a vent member including a resin having a lower melting point than the sealant resin at the inclined sealing portion.

[0058] The term "angled sealing portion" may refer to, in some embodiments disclosed herein, an area formed between an outer angled sealing line of the sealing portion and an inner angled sealing line of the sealing portion, the outer angled sealing line being farther from the electrode assembly and the inner angled sealing line being closer to the electrode assembly.

[0059] The term "inclined" in some embodiments may refer to the 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, with the understanding 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 an 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 sequence with the separator sandwiched therebetween.

[0063] The positive electrode plate may include a positive electrode current collector made of a metal thin plate having excellent conductivity, 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 material, at one end. The positive electrode tab protrudes from one end of the positive electrode plate and may be welded to 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 the positive electrode plate and the negative electrode plate from each other. The separator may be a porous membrane through which lithium ions can pass between the positive electrode plate and the negative electrode plate. The separator may include a porous membrane using, 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 an 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-like positive and negative electrodes are wound with a separator interposed therebetween, a stack type electrode assembly having a structure in which a plurality of positive and negative electrodes cut into a predetermined size are stacked in sequence with a separator interposed therebetween, a bi-cell having a structure in which a predetermined unit of positive and negative electrodes are stacked with a separator interposed therebetween or a full cell having a structure in which a bi-cell or full cell is wound up.

[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 formed to seal the electrode assembly 12 by containing a sealant resin.

[0069] The sealing portion 13b refers to a portion that is welded along the outer circumferential surface of the storage portion 13a to seal the electrode assembly 12, as shown in FIG. 2. 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 bonding between the electrode lead 11 and 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 that has a lower melting point than the sealant resin of the sealing portion 13b, and the vent member 16 melts before the sealant resin at high temperatures. The sealing strength of the part where the vent member 16 is inserted at high temperatures becomes lower than the sealing strength of the case part containing the sealant resin, making it easy to realize vent characteristics. As a result, when a thermal runaway phenomenon occurs, gas is guided to be discharged in a specific direction, 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 serves to seal the case 13 from the outside. When the temperature of the battery rises due to abnormal battery behavior, the vent member 16 melts and the sealing strength of the portion where the vent member 16 is inserted decreases. As a result, the sealing strength of the portion where the vent member 16 is inserted decreases, and a vent is formed at that position to allow gas to be discharged from the storage portion. For example, the pressure of the gas inside the battery is concentrated at the interface between the vent member 16 and the sloped sealing portion 14, and a gap or vent is formed between the vent member 16 and the sloped sealing portion 14, allowing gas to be discharged.

[0074] The vent member 16 and the tapered 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 tapered 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 tapered sealing portion 14 may be physically joined together 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 tapered 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] In addition, since the vent member 16 is located on the inclined sealing portion 14, i.e., the inner end of the inclined sealing portion 14 is inclined, the area of ​​the inner end of the inclined sealing portion 14 exposed to the storage portion 13a is smaller than when the adjacent sealing portions 13b form orthogonal corners. This makes it easier for pressure applied when the battery swells to concentrate on the inclined sealing portion 14 at the corners of the sealing portion, so that gas can be induced to be more easily discharged toward the corners of the sealing portion. Here, the inner end of the inclined sealing portion 14 refers to the end of the inclined sealing portion 14 that is closer to the storage portion 13a.

[0077] Referring to FIG. 2, the inclined sealing portion may have an inclination angle of 10° to 80°, or 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 the above range, 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 further minimized, thereby further improving the safety of the battery. As the direction of gas exhaust from the secondary battery is shown by an arrow in FIG. 2, the 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 a second direction, the second direction being non-orthogonal 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 at the sloped sealing portion 14. In yet another embodiment of the present invention, the vent member 16 may extend through the housing 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 have to overlap the lead film 15 .

[0082] In yet another embodiment of the present invention, the vent member 16 may be partially overlapped with the lead film 15, as shown in FIG. 4. When the vent member 16 is at least partially overlapped with the lead film 15, the position of the vent member 16 may be consistently and easily fixed. The vent member 16 may extend through the receiving portion 13a such 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 may overlap the lead film 15 so that the vent member 16 may be inserted and then welded in a predetermined position.

[0083] The vent member 16 may be located at a predetermined distance from the electrode lead 11. This makes it possible to easily minimize the amount of gas vented in a direction that may directly contact 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 separated from the lead film 15 at the sealing portion 13b(14) and at least partially overlap or contact the lead film 15 at the receiving portion 13a. Since the vent member 16 does not overlap or contact the lead film 15 at the sealing portion 13b(14), i.e., the vent member 16 is located away from the electrode lead 11, the amount of gas vented at the side of the electrode lead 11 can be minimized, and the safety of the battery can be further improved.

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

[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 the above range, gas can be more easily guided to be discharged 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 circumferential surface 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 FIG. 9 and FIG. 10) so that the extension lines of two adjacent first sealing portions 13b do not cross each other at right angles and contact each other. That is, the outside of the second sealing portion 14 may be defined by a straight line or a curved line that connects adjacent sides of the first sealing portion 13b. The straight line does not have to be parallel to the first direction. The second sealing portion 14 may include a vent member that includes a resin ("vent resin") that has a melting point lower than that of the sealant resin.

[0088] In the secondary battery according to one embodiment of the present invention, when the secondary battery includes the second sealing part 14, the inner end of the second sealing part is inclined or curved, so that the area of ​​the inner end of the second sealing part exposed to the storage part is smaller than the area of ​​the inner end of the sealing part forming the perpendicular corner exposed to the storage part, and thus pressure is more easily concentrated on the inner end of the second sealing part. Here, the inner end of the second sealing part means the end of the second sealing part that is closer to the storage part.

[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 and forms 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, for example, a long side of the first portion may be located in the third direction and a short side of the first portion may be located 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] 4, first portion 16b may at least partially overlap or contact lead film 15. A portion of first portion 16b and a portion of lead film 15 may overlap or contact by thermal welding. In another example, a portion of first portion 16b and a portion of lead film 15 may overlap or contact by an adhesive such as glue. In another example, a portion of first portion 16b and a portion of lead film 15 may be physically connected by a clip or the like. In another example, a portion of first portion 16b may be embedded in a film that constitutes 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 do not overlap or contact each other at the sealing portion 13b and / or the inclined 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 at the side of the electrode lead 11 is minimized, and the safety of the battery can be further improved.

[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 both 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 part 16b may be spaced apart from the inner end of the inclined sealing part 14. Here, the "outer end of the first part of the vent member" refers to the end of the first part 16b that is closer to the sealing part. The "inner end of the inclined sealing part" refers to the end of the inclined sealing part that is farther from the outside direction of the battery. When the outer end of the first part 16b is spaced apart from the inner end of the inclined sealing part 14, the entire first part 16b is located in the storage part 13a. As a result, the gap or space between the first part 16b and the inclined sealing part 14 is exposed to the storage part 13a, and as a result, gas pressure is concentrated in this gap or space, enabling faster venting in abnormal situations.

[0098] FIG. 5 is a partially enlarged view of a vent member 16 in a secondary battery according to another embodiment of the present invention. The vent member 16 shown in FIG. 5 is almost 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 that gradually narrows as it extends along the electrode assembly 12 to the receiving portion 13a. As the edge width gradually narrows, the vent member can be easily parallel to the side of the electrode assembly 12, so that the vent member can be conveniently and appropriately positioned within the battery case. Contact between the electrode assembly 12 and the inner end of the second portion 16a inside the receiving portion 13a can be more easily prevented.

[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 in contact with the lead film 15, an 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, may be referred to as 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 satisfies the above-mentioned range, gas can be more easily discharged in 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 and 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 straight line portion 14a perpendicular to the first direction, a second straight line portion 14b extending from the first straight line portion 14a at a right angle to the first straight line portion 14a, and a third straight line portion 14c extending from the second straight line portion 14b at a right angle to one end of the case 13 in contact with the lead film 15, an area in which one and the other ends of the second straight line portion 14b are respectively connected to one and the other ends of an inner sealing line parallel to the first direction 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 may more easily direct the gas discharge 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 rectangular area formed by connecting an end of a straight sealing line inclined on the outside of the sealing portion and an end of a straight sealing line inclined on the inside of the sealing portion.

[0106] Specifically, in an 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, a region in which 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 to the other side end of the inner sealing line extending from the inner sealing line overlapping with 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-mentioned range, gas can be easily discharged in 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 angled sealing portion 14 may be comprised of one or more curved lines.

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

[0112] 10, a curved sealing portion 14 having a concave or recessed shape toward the inside of the case 13 is defined by the curved outer and inner sealing lines. That is, the curved sealing portion 14 may refer to a region connecting an end of the outer curved sealing line of the sealing portion and an 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 composed of two or more continuous curves, each of which may have 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 through the vent member 16 to the outside of the battery.

[0116] Because at least a portion of the vent member 16 overlaps or is located on the sloped sealing portion 14, venting can occur at a lower pressure than in a conventional secondary battery 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-mentioned temperature range and / or pressure conditions, so that the battery is sealed during normal operation and gas can be released only when the battery behaves abnormally.

[0118] 11, the vent member 16 may have a structure in which its width narrows in a direction perpendicular to the second direction of the inclined sealing portion 14. The width of the vent member 16 may narrow continuously or discontinuously along the direction perpendicular to the second direction of the inclined sealing portion 14. The vented gas is guided in a direction 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 step-shaped structure. In the asymmetrical step-shaped structure, an offset may be formed between the steps so that direct contact between the vented gas and the electrode lead 11 is minimized. 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 away 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, which has a melting point lower than that of the sealant resin, may include a linear low density polyethylene having a comonomer having six or more carbon atoms.

[0124] The vent resin, which has a lower melting point than the sealant resin, contains linear low-density polyethylene having a comonomer with 6 or more carbon atoms, so that it has excellent sealing properties with the sealant resin within the normal temperature range, and at high temperatures the sealing strength of the sealing part 13b including the vent member 16 decreases, making it possible to achieve venting.

[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., or 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 is within the above-mentioned range, the sealing strength of the sealing part including the vent member 16 decreases at high temperatures, for example, above 100° C., and the vent characteristics can be more easily realized.

[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 the sample is increased from 30°C to 280°C at 10°C / min, then 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 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 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 more. When the vent member satisfies the above-mentioned sealing strength in the above-mentioned temperature range, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, for example, at 100° C. or more, and the vent characteristics can be more easily realized.

[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. When the vent member satisfies the above-mentioned sealing strength in the above-mentioned temperature range, it has excellent sealing strength during normal operation of the battery, and the hermeticity of the battery can be more easily ensured.

[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 100° C. or higher, and the vent member 16 may have a maximum sealing strength of 6 kgf / 15 mm or higher at room temperature to 60° C. When the vent member satisfies the above-mentioned sealing strength, the sealing strength of the sealing part including the vent member 16 decreases at high temperatures, making it easier to realize vent characteristics. In addition, during normal operation of the battery, the sealing strength of the battery is excellent, 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 100° C. or more. 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 more. When the vent member 16 satisfies the above-mentioned sealing strength in the above-mentioned temperature range, the sealing strength of the sealing portion including the vent member 16 decreases at high temperatures, and the venting characteristics can be more easily realized.

[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. When the vent member satisfies the above-mentioned sealing strength in the above-mentioned temperature range, it has excellent sealing strength during normal operation of the battery, and the hermeticity of the battery can be more easily ensured.

[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 of 100° C. or higher, and an average sealing strength of 4.5 kgf / 15 mm or higher 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 part including the vent member 16 decreases at high temperatures, making it easier to realize vent characteristics. In addition, the vent member has excellent sealing strength during normal operation of the battery, making it easier to ensure the hermeticity of the battery.

[0134] The sealing strength of the vent member 16 according to 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 at 180°, placing the cut portion in a UTM jig, and conducting a tensile test at a speed 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 when the maximum sealing strength is 4.5 kgf / 15 mm or more, and means the average value when the battery case is stretched 8 mm at the maximum sealing strength when 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% by weight or less, 12% by weight or less, 11.8% by weight or less, 10% by weight or less, 9% by weight or less, 8% by weight or less, or 7.6% by weight or less, based on 100% by weight of the linear low density polyethylene having 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% by weight or more, 7.6% by weight or more, 8% by weight or more, 9.0% by weight or more, 10% by weight or more, 11.8% by weight or more, or 12% by weight or more, based on 100% by weight of the linear low density polyethylene having a comonomer having 6 or more carbon atoms. When the content of the comonomer having 6 or more carbon atoms satisfies the above-mentioned range, the problem of the intermolecular packing density decreasing and the sealing strength decreasing during normal operation of the battery 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 in an NMR tube.1 H-NMR or 13 It can be measured using C-NMR.

[0139] In one embodiment of the present invention, the weight average molecular weight of the resin having a melting point lower than that of the sealant resin may be 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-mentioned 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 polydispersity index (PDI) of the resin having a melting point lower than that of the sealant resin may be 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. Also, the polydispersity index (PDI) may be 1.0 or more. When the polydispersity index of the resin having a melting point lower than that of the sealant resin satisfies the above-mentioned 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 melting point lower than that of the sealant resin. For example, the difference between the crystallization temperature of the sealant resin and that of the vent resin having a melting point lower than that of the sealant resin may be 10° C. or less, or 5° C. or less. Also, 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 melting point lower than that of the sealant resin satisfies the above-mentioned range, the adhesion characteristics of the sealant resin and the vent resin having a melting point lower than that of 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 property 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 the sample can be increased from 30°C to 280°C at 10°C / min, then 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 for 10 minutes to measure the crystallization temperature.

[0145] In one embodiment of the present invention, the vent member 16 may have a thickness of a film. The vent member 16 may be formed to have a predetermined thickness of a preset size. Also, the vent member 16 may be inserted into the inclined sealing portion, the square sealing portion, or the curved sealing portion 14 so that the insertion length, venting pressure, and position can be controlled according to 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 an embodiment of the present invention includes an inclined sealing portion, a rectangular sealing portion, or a curved sealing portion located at a corner of a sealing portion that is at least partially overlapped with a vent member including a vent resin, and thereby, when the internal temperature of the battery rises, directional venting that discharges gas in one direction due to a decrease in sealing strength at high temperatures can be more smoothly and quickly implemented 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 an upper pouch and a lower pouch, the upper pouch and the lower pouch may be arranged so that the sealant resins face each other, and then the facing sealant resins may be fused 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 pouch and the lower pouch are formed on one pouch sheet, and then the boundary surface between the upper pouch and the lower pouch is folded so that the storage portions 13a formed in the upper pouch and the lower pouch are overlapped, and the peripheries of the remaining three sides excluding the folded portion are sealed.

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

[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-based film using 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 of these. 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 having ordinary skill 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 receiving portion for receiving 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 including a vent resin having a melting point lower than that of the sealant resin; a sealing portion having 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, the corner of the sealing portion including 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, and the vent member being located at the inclined sealing 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. a lead film surrounding an outer surface of the electrode lead and interposed between the electrode lead and the sealing portion, The secondary battery according to claim 1 , wherein the vent member extends through the receiving portion so as to overlap or contact at least a portion of the lead film in the receiving portion.

6. the vent member includes a first portion and a second portion; the first portion extends along the second direction such 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 5 , wherein the second portion extends along a third direction perpendicular to the second direction.

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

8. The secondary battery of claim 6 , wherein the second portion includes an edge that narrows gradually as it extends along the electrode assembly toward the receiving portion.

9. 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 6 , wherein an outer end of the first portion is located in the storage portion.

10. The secondary battery according to claim 6 , wherein the second portion does not overlap or contact the lead film.

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

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

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

14. 6. The secondary battery according to claim 5, wherein an area of ​​the vent member overlapping or contacting the lead film is 1% to 30% of an area of ​​the lead film not overlapping with the electrode lead.

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

16. 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.

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

18. 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.

19. 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.

20. 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.

21. 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.

22. The secondary battery according to claim 15, 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.

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

24. 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.

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

26. 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.

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

28. 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.

29. 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.

30. 16. The secondary battery according to claim 15, 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.

31. 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.

32. 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.

33. An electrode assembly; a case including a receiving portion for receiving 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 including a vent resin having a melting point lower than that of the sealant resin; a sealing portion having 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, the corner of the sealing portion including a rectangular sealing portion adjacent to the electrode lead, at least one side of the rectangular sealing portion extending along a second direction, the second direction not being parallel to the first direction, and at least a portion of the vent member being located in the rectangular sealing portion.

34. An electrode assembly; a case including a receiving portion for receiving 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 including 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 curved line that bulges such that a tangent line changes from the first direction to a second direction, the second direction being perpendicular to the first direction; The secondary battery, wherein the vent member is located in the protruding sealing portion.

35. An electrode assembly; a case including a receiving portion for receiving 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 including a vent resin having a melting point lower than that of the sealant resin; the sealing portion includes a concave sealing portion that is concave adjacent to the electrode lead, the concave sealing portion being a curve that is concave such that a tangent changes from a second direction to the first direction, the second direction being perpendicular to the first direction, The secondary battery, wherein the vent member is located in the recessed sealing portion.

36. An electrode assembly; a case including a receiving portion for receiving 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 including 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, a second sealing portion that is disposed between adjacent first sealing portions and that is connected to the first sealing portion by a line or curve that connects adjacent first sealing portions, the line being not parallel to the first direction, the second sealing portion being located at a corner of the case, and the second sealing portion including the vent member.

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

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

39. The secondary battery according to claim 33, wherein an inner end of the rectangular sealing part is inclined or curved.

40. The secondary battery according to claim 33, 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 storage portion.

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

42. The secondary battery according to claim 36, 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 storage portion.

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