Secondary battery

Abstract

A secondary battery according to one embodiment of the present invention includes an electrode assembly having an electrode lead attached thereto, a case for accommodating the electrode assembly, a seal portion formed for sealing the electrode assembly in the case, and a lead film for enveloping a portion of an outer surface of the electrode lead and interposed between the electrode lead and the seal portion, wherein at least a portion of an edge region of the lead film facing the electrode assembly has a shape that is not flat.

Description

[Technical field]

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery with improved safety.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0131224 filed on October 1, 2021 and Korean Patent Application No. 10-2022-0099996 filed on August 10, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings. [Background technology]

[0003] Mobile IT devices such as mobile phones, notebook computers, and tablet PCs are closely related to modern life, and the demand for secondary batteries, which are key components, is also increasing rapidly along with the growth of the IT industry market. The secondary batteries can be used repeatedly through charging and discharging, and are an environmentally friendly battery technology that does not use harmful substances such as lead, nickel, and cadmium. They are lightweight and have high energy density that can store a large amount of energy in a small volume, making them the core of the new growth power industry of the future. In particular, lithium secondary batteries are not only the most widely used power source for mobile IT devices that are closely related to human life, but are also increasingly being used as a power source for electric vehicles and a power storage device for new renewable energy.

[0004] In general, a secondary battery is composed of a positive electrode, a negative electrode, a separator separating them, an electrolyte that transfers lithium ions through the separator, a case that contains them, and an electrode lead that serves as a path of current to the outside of the case. A lead film may also be included, which is attached to the electrode lead to prevent a short circuit between the electrode lead and the battery case and to seal the electrode lead and the battery case.

[0005] Such secondary batteries tend to be vulnerable to internal pressure caused by gases and the like generated during the operation of the battery, and so there is currently a demand for the development of secondary batteries that have sufficient rigidity to withstand such internal pressure. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide a secondary battery with improved safety. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, a secondary battery according to one embodiment of the present invention includes an electrode assembly having an electrode lead attached thereto, a case for accommodating the electrode assembly, a seal portion formed for sealing the electrode assembly in the case, and a lead film for enclosing a portion of an outer surface of the electrode lead and interposed between the electrode lead and the seal portion, wherein at least a portion of an edge portion of the lead film facing the electrode assembly has a shape that is not flat.

[0008] The edge portion of the lead film facing the electrode assembly may have a radius of curvature of approximately 50 mm to 200 mm.

[0009] The lead film may have a shape in which a center portion along a second direction perpendicular to a first direction in which the electrode leads extend is convex in a direction away from the electrode assembly.

[0010] The width of the lead film in the first direction may be approximately 20% to 150% of the width of the seal portion in the first direction.

[0011] The lead film may have a shape in which a center portion along a second direction perpendicular to a first direction in which the electrode leads extend is convex toward the electrode assembly.

[0012] The width of the lead film in the first direction may be approximately 20% to 150% of the width of the seal portion in the first direction.

[0013] The lead film may include a first lead film located relatively close to the electrode assembly and a second lead film located relatively far from the electrode assembly.

[0014] The first lead film and the second lead film may be spaced apart from each other.

[0015] The first lead film may have a shape in which a center portion along a second direction perpendicular to a first direction in which the electrode leads extend is convex toward the electrode assembly.

[0016] The width of the first lead film in the first direction may be approximately 10% to 40% of the width of the seal portion in the first direction.

[0017] The width of the interface between the first lead film and the seal portion in the first direction may be approximately 10% to 40% of the width of the seal portion in the first direction.

[0018] The second lead film may have a shape in which a center portion along a second direction perpendicular to a first direction in which the electrode leads extend is convex in a direction away from the electrode assembly.

[0019] The width of the second lead film in the first direction may be approximately 10% to 40% of the width of the seal portion in the first direction.

[0020] The width of the interface between the second lead film and the seal portion in the first direction may be approximately 10% to 40% of the width of the seal portion in the first direction.

[0021] The first lead film and the second lead film may be configured such that, when the internal pressure of the secondary battery increases, the interface between the first lead film and the sealing portion is primarily broken, and the interface between the second lead film and the sealing portion is secondarily broken.

[0022] The distance between the first lead film and the second lead film may be approximately 10% to 80% of the width of the seal portion.

[0023] The planar shape of the lead film may be a closed pool shape with a hollow center.

[0024] The lead film may have a first portion facing the electrode assembly that has a convex shape toward the electrode assembly, and a second portion located opposite the first portion that has a convex shape away from the electrode assembly.

[0025] The first portion may have a shape in which a center portion along a second direction perpendicular to a first direction, which is the extension direction of the electrode lead, is convex in a direction toward the electrode assembly, and the second portion may have a shape in which a center portion along the second direction perpendicular to the first direction, which is the extension direction of the electrode lead, is convex in a direction away from the electrode assembly.

[0026] The lead film may be configured so that when the internal pressure of the secondary battery increases, the interface between the lead film and the sealing portion in a first region where the first portion and the sealing portion are bonded together is primarily broken, and the interface between the lead film and the sealing portion in a second region where the second portion and the sealing portion are bonded together is secondarily broken.

[0027] The distance between the first region and the second region along the extension direction of the electrode lead may be approximately 10% to 80% of the width of the seal portion along the extension direction of the electrode lead.

[0028] The overall width of the lead film in the direction along the extension direction of the electrode lead may be approximately 50% to 150% of the width of the seal portion in the direction along the extension direction of the electrode lead.

[0029] The width of the first region along the extension direction of the electrode lead may be approximately 10% to 40% of the width of the seal portion along the extension direction of the electrode lead.

[0030] The width of the second region along the extension direction of the electrode lead may be approximately 10% to 40% of the width of the seal portion along the extension direction of the electrode lead.

[0031] The secondary battery may be a pouch-type secondary battery. Effect of the Invention

[0032] In the secondary battery according to an embodiment of the present invention, the contact area between the electrode lead and the lead film is increased, thereby ensuring the sealing performance of the battery.

[0033] The secondary battery according to an embodiment of the present invention can improve rigidity against internal pressure, thereby improving safety.

[0034] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical ideas of the present invention. Therefore, the present invention should not be interpreted as being limited only to the matters depicted in such drawings. [Brief description of the drawings]

[0035] [Figure 1] 2 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to an embodiment of the present invention; FIG. [Diagram 2] 6A and 6B are views showing electrode leads, lead films, and sealing portions of a secondary battery according to another embodiment of the present invention. [Diagram 3]13 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to still another embodiment of the present invention. FIG. [Figure 4] 13 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to still another embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] 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 and 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.

[0037] Therefore, it should be understood that the embodiment 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 therefor at the time of this application.

[0038] According to one aspect of the present invention, there is provided a secondary battery comprising: an electrode assembly having an electrode lead attached thereto; a case for accommodating the electrode assembly; a seal portion formed for sealing the electrode assembly in the case; and a lead film for enclosing a portion of an outer surface of the electrode lead and interposed between the electrode lead and the seal portion, wherein at least a portion of an edge portion of the lead film facing the electrode assembly has a shape that is not flat.

[0039] FIG. 1 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to one embodiment of the present invention.

[0040] Referring to FIG. 1, a secondary battery 10 according to an embodiment of the present invention includes an electrode assembly 12 to which an electrode lead 11 is attached, and a case.

[0041] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly 12 may include a positive electrode plate and a negative electrode plate stacked in this order with a separator sandwiched therebetween.

[0042] The positive electrode plate may be formed including a positive electrode current collector made of a metal thin plate having excellent electrical conductivity, for example, an aluminum (Al) foil, and a positive electrode active material layer coated on at least one side of the positive electrode current collector. The positive electrode plate may also include a positive electrode tab made of a metal material, for example, an aluminum (Al) material, at one end. The positive electrode tab may extend and protrude from one end of the positive electrode plate, or may be welded to one end of the positive electrode plate or attached using a conductive adhesive.

[0043] The negative electrode plate may be formed to 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 side of the negative electrode current collector. The negative electrode plate may also include a negative electrode tab at one end made of a metal material, for example, nickel (Ni). The negative electrode tab may extend and protrude from one end of the negative electrode plate, or may be welded to one end of the negative electrode plate or attached using a conductive adhesive.

[0044] The separator may be formed in the form of a porous membrane that is sandwiched between the positive and negative electrode plates to electrically insulate the positive and negative electrode plates from each other and allow lithium ions to pass between the positive and negative electrode plates. The separator may include, for example, a porous membrane using polyethylene (PE), polypropylene (PP), or a composite film thereof.

[0045] 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 and fixed by a binder to form a pore structure due to the interstitial volume between the particles.

[0046] Examples of the electrode assembly 12 include a jelly roll type (wound type) electrode assembly having a structure in which long sheet-like positive and negative electrode plates are wound with a separator interposed therebetween, a stack type (lamination type) electrode assembly in which a plurality of positive and negative electrode plates cut into units of a predetermined size are stacked in this order with a separator interposed therebetween, and a stack / folding type electrode assembly having a structure in which a bi-cell or full cell in which a predetermined unit of positive and negative electrode plates are stacked with a separator interposed therebetween is wound up.

[0047] The case includes a receiving portion 13 a for receiving the electrode assembly 12 and a sealing portion 13 b formed to seal the electrode assembly 12 .

[0048] The sealing portion 13b indicates, for example, a portion that is fused along the outer peripheral surface of the accommodating portion 13a in order to seal the electrode assembly 12, and the fusion may be thermal fusion, ultrasonic fusion, or the like, but is not significantly limited as long as the sealing portion can be fused.

[0049] In one embodiment of the present invention, the case may be provided in the form of a film having a multi-layer structure including an outer layer for protection from external impact, a metal barrier layer for blocking moisture, and a sealant layer for sealing the case.

[0050] The outer layer may include a polyester-based film using poly(ethylene terephthalate) (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate, nylon, etc., and may be configured as a single layer or multiple layers.

[0051] The metal barrier layer may include aluminum, copper, and the like.

[0052] The sealant layer may include a sealant resin and may be configured as a single layer or multiple layers.

[0053] In one embodiment of the present invention, 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.

[0054] In one embodiment of the present invention, the case may be in the form of a pouch.

[0055] In one embodiment of the present invention, when the case is in a pouch shape, it may include an upper pouch and a lower pouch. When the case includes an upper pouch and a lower pouch, the outer peripheries of the upper pouch and the lower pouch may be fused to each other by heat and pressure to seal the battery.

[0056] When the case is in a pouch shape, the sealing portion 13b may be four-sided sealed or three-sided sealed at the periphery of the case. The three-sided sealed structure refers to a structure in which an upper pouch and a lower pouch are formed from a single pouch sheet, and then the boundary surface between the upper pouch and the lower pouch is folded so that the electrode assembly receiving portions 13a formed in the upper pouch and the lower pouch are stacked, and the remaining three peripheries excluding the folded portion are sealed.

[0057] Referring to FIG. 1, the electrode lead 11 may be housed within a case such that a portion of the electrode lead 11 is exposed to the outside of the case.

[0058] Referring to FIG. 1, a secondary battery 10 according to an embodiment of the present invention includes a lead film 14.

[0059] The lead film 14 envelops a portion of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the seal portion 13b of the case at the portion from which the electrode lead 11 protrudes. The lead film 14 can be located on at least one surface of the electrode lead 11. The lead film 14 is interposed between the electrode lead 11 and the seal portion 13b of the case at the portion from which the electrode lead protrudes, and promotes bonding between the electrode lead 11 and the seal portion 13b of the case. Sealing of the battery occurs at the surface where the lead film 14 abuts against the seal portion 13b.

[0060] Referring to FIG. 1, in the lead film 14, a part of the edge portion facing the electrode assembly 12 has a shape that is not flat. When the lead film 14 has such a shape, the contact area between the lead film 14 and the electrode lead 11 is large. In particular, the contact area between the lead film 14 and the electrode lead 11 is increased compared to a conventional secondary battery in which the edge portion of the lead film 14 facing the electrode assembly 12 has a flat structure. This increases the adhesive strength between the electrode lead 11 and the seal portion 13b, and makes it possible to increase the seal strength between the electrode lead 11 and the seal portion 13b. By increasing the seal strength between the electrode lead 11 and the seal portion 13b, it becomes possible to increase the rigidity against the internal pressure of the battery.

[0061] Furthermore, according to such a configuration of the present invention, the contact area between the lead film 14 and the seal portion 13b can also be increased. In particular, the contact area between the lead film 14 and the seal portion 13b can be increased compared to a conventional secondary battery in which the edge portion of the lead film 14 facing the electrode assembly 12 has a flat structure. This increases the adhesive strength between the electrode lead 11 and the seal portion 13b, making it possible to increase the seal strength between the electrode lead 11 and the seal portion 13b. By increasing the seal strength between the electrode lead 11 and the seal portion 13b, it becomes possible to increase the rigidity of the battery against the internal pressure.

[0062] In another aspect, such a configuration of the present invention allows the internal pressure generated inside the battery to be transmitted uniformly throughout the entire lead film 14. This allows the internal pressure to be uniformly distributed throughout the entire lead film 14, making it possible to increase the rigidity of the battery against the internal pressure.

[0063] In one embodiment of the present invention, the edge portion of the lead film 14 facing the electrode assembly 12 may have a radius of curvature in the range of approximately 50 mm to 200 mm. When the radius of curvature of the edge portion satisfies the above-mentioned range, it is possible to increase the contact area between the lead film 14 and the electrode lead 11, and it is also easy to increase the contact area between the lead film 14 and the seal portion 13b.

[0064] Meanwhile, the lead film 14 may have a shape in which the center portion along a second direction generally perpendicular to a first direction in which the electrode leads 11 extend is convex in a direction away from the electrode assembly 12. For example, the lead film 14 may be generally arch-shaped, convex toward the outside of the case.

[0065] 1, the width h of the lead film 14 along the first direction may be approximately 20% to 150% of the width d of the seal portion 13b along the first direction. When the width h of the lead film 14 satisfies the above-mentioned range, it is possible to increase the contact area between the lead film 14 and the electrode lead 11, and it is also easy to increase the contact area between the lead film 14 and the seal portion 13b.

[0066] FIG. 2 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to another embodiment of the present invention.

[0067] 2, the lead film 14 may have a shape in which a center portion along a second direction generally perpendicular to a first direction in which the electrode leads 11 extend is convex toward the electrode assembly 12. For example, the lead film 14 may have a generally arch shape that is convex toward the electrode assembly 12.

[0068] 1, the width h of the lead film 14 along the first direction can be approximately 20% to 150% of the width d of the seal portion 13b along the first direction. When the width h of the lead film 14 satisfies the above-mentioned range, the contact area between the lead film 14 and the electrode lead 11 can be increased, and the contact area between the lead film 14 and the seal portion 13b can also be easily increased.

[0069] FIG. 3 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to still another embodiment of the present invention.

[0070] 3, the lead film 14 may include a first lead film 14a located relatively close to the electrode assembly 12 and a second lead film 14b located relatively far from the electrode assembly 12. The first lead film 14a and the second lead film 14b may be spaced apart from each other.

[0071] 3, the first lead film 14a may have a shape in which a center portion along a second direction generally perpendicular to a first direction in which the electrode leads 11 extend is convex toward the electrode assembly 12. For example, the first lead film 14a may have a generally arch shape convex toward the electrode assembly 12.

[0072] In FIG. 3, the shape of the first lead film 14a is shown to be generally arch-shaped and convex in the direction in which the electrode assembly 12 is housed, but the shape of the first lead film 14a is not limited to this.

[0073] In another embodiment of the present invention, the first lead film 14a may have a generally arch-like shape that is convex toward the outside of the case.

[0074] 3, the second lead film 14b may have a shape in which a center portion along a second direction generally perpendicular to a first direction in which the electrode lead 11 extends is convex in a direction away from the electrode assembly 12. For example, the second lead film 14b may have a generally arch shape that is convex in a direction away from the electrode assembly 12.

[0075] In FIG. 3, the shape of the second lead film 14b is shown to be generally arch-shaped and protruding toward the outside of the case, but the shape of the second lead film 14b is not limited to this.

[0076] In another embodiment of the present invention, the second lead film 14b may have a generally arch-like shape that is convex toward the direction in which the electrode assembly 12 is housed.

[0077] In the case of secondary batteries, swelling may occur due to an increase in internal pressure, which may affect the safety of the battery. If swelling occurs, breakage may occur at the interface between the lead film 14 and the seal portion 13b, where the adhesive strength is slightly weak.

[0078] When the lead film 14 includes the first lead film 14a and the second lead film 14b, the lead film 14 may be configured such that, during swelling of the battery, the interface between the first lead film 14a and the sealing portion 13b is primarily broken, and then the interface between the second lead film 14b and the sealing portion 13b is secondarily broken.

[0079] When swelling occurs, the first lead film 14a is located closer to the inside of the case than the second lead film 14b, so when swelling occurs, the first lead film 14a may break before the second lead film 14b.

[0080] When swelling occurs, the seal portion 13b facing the inside of the case receives the greatest pressure. Since the first lead film 14a is located closer to the inside of the case than the second lead film 14b, fracture occurs preferentially at the interface between the first lead film 14a located in the seal portion facing the inside of the case and the seal portion 13b, making it easier to adjust the swelling pressure. This makes it possible to prevent an increase in swelling pressure and improve the safety of the battery.

[0081] If the swelling pressure increases even after fracture occurs preferentially at the interface between the first lead film 14a and the sealing portion 13b, the increase in swelling pressure can be further prevented by fracture occurring at the interface between the second lead film 14b and the sealing portion 13b.

[0082] If the interface between the second lead film 14b and the seal portion 13b is broken, the pressure inside the battery can be discharged to the outside, making it easier to adjust the swelling pressure.

[0083] In an embodiment of the present invention, the semiconductor device may further include a sensor unit (not shown) and a controller (not shown) connected to the first lead film 14a and / or the second lead film 14b. The sensor unit measures the swelling pressure and transmits the same to the controller, and the controller may cause the first lead film 14a and / or the second lead film 14b to break when the swelling pressure exceeds a certain pressure threshold.

[0084] In one embodiment of the present invention, the first lead film 14a may be located at an end of the seal toward the inside of the case.

[0085] In one embodiment of the present invention, the second lead film 14b may be located at the end of the seal portion toward the exterior of the case.

[0086] In one embodiment of the present invention, the distance between the first lead film 14a and the second lead film 14b may be approximately 10% to 80% of the width d of the seal portion 13b. Here, the distance between the first lead film 14a and the second lead film 14b refers to the distance between the end of the first lead film 14a closest to the outside of the case and the end of the second lead film 14b closest to the inside of the case. When the distance between the first lead film 14a and the second lead film 14b satisfies the above-mentioned range, it becomes easier to adjust the breakage timing of the interface between the first lead film 14a and the seal portion 13b and the interface between the second lead film 14b and the seal portion 13b.

[0087] In one embodiment of the present invention, the radius of curvature of the first lead film 14a may be approximately 50 mm to 200 mm. When the radius of curvature of the first lead film 14a satisfies the above-mentioned range, the contact area between the first lead film 14a and the electrode lead 11 and the contact area between the first lead film 14a and the seal portion 13b can be easily increased. In addition, it becomes easier to adjust the breakage timing of the interface between the first lead film 14a and the seal portion 13b.

[0088] In one embodiment of the present invention, the radius of curvature of the second lead film 14b may be approximately 50 mm to 200 mm. When the radius of curvature of the second lead film 14b satisfies the above-mentioned range, the contact area between the second lead film 14b and the electrode lead 11 and the contact area between the second lead film 14b and the seal portion 13b can be easily increased. In addition, it becomes easier to adjust the breakage timing of the interface between the second lead film 14b and the seal portion 13b.

[0089] 3, the width h1 of the first lead film 14a along the first direction, which is the extension direction of the electrode lead 11, may be approximately 10% to 40% of the width d of the seal portion 13b along the first direction. When the width h1 of the first lead film 14a satisfies the above-mentioned range, the contact area between the first lead film 14a and the electrode lead 11 and the contact area between the first lead film 14a and the seal portion 13b can be easily increased, making it easy to ensure a sufficient seal strength during normal operation of the battery.

[0090] 3, the width h2 of the second lead film 14b along the first direction, which is the extension direction of the electrode lead 11, may be approximately 10% to 40% of the width d of the seal portion 13b along the first direction. When the width h2 of the second lead film 14b satisfies the above-mentioned range, the contact area between the second lead film 14b and the electrode lead 11 and the contact area between the second lead film 14b and the seal portion 13b can be easily increased, making it easy to ensure a sufficient seal strength during normal operation of the battery.

[0091] In one embodiment of the present invention, the width of the interface between first lead film 14a and seal portion 13b along the first direction where breakage occurs may be approximately 10% to 40% of width d of seal portion 13b. When the width of the interface between first lead film 14a and seal portion 13b satisfies the above-mentioned range, sufficient seal strength can be ensured during normal operation of the battery, while breakage is more likely to occur when swelling occurs.

[0092] In one embodiment of the present invention, the width of the interface between second lead film 14b and seal portion 13b along the first direction where breakage occurs may be approximately 10% to 40% of width d of seal portion 13b. When the width of the interface between second lead film 14b and seal portion 13b satisfies the above-mentioned range, sufficient seal strength can be ensured during normal operation of the battery, while breakage is more likely to occur when swelling occurs.

[0093] FIG. 4 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to still another embodiment of the present invention.

[0094] 4, the planar shape of the lead film 14 may be a closed loop shape with a hollow center. When the lead film 14 has such a closed loop shape, the contact area between the lead film 14 and the electrode lead 11 is large, and it becomes easier to increase the contact area between the lead film 14 and the seal portion 13b. Furthermore, the internal pressure is uniformly distributed throughout the lead film 14, making it easier to increase the rigidity of the battery against the internal pressure.

[0095] For example, the lead film 14 may be generally doughnut-shaped. In another aspect, the lead film 14 may have a shape in which a first portion facing the electrode assembly 12 is convex toward the electrode assembly 12, and a second portion located on the opposite side to the first portion is convex in a direction away from the electrode assembly 12. The first portion may have a shape in which a center portion along a second direction generally perpendicular to a first direction in which the electrode lead 11 extends is convex toward the electrode assembly 12. The second portion may have a shape in which a center portion along a second direction generally perpendicular to the first direction in which the electrode lead 11 extends is convex in a direction away from the electrode assembly 12.

[0096] In one embodiment of the present invention, when the internal pressure of the secondary battery increases, the interface between the lead film 14 and the sealing portion 13b in the first region A may be primarily broken, and then the interface between the lead film 14 and the sealing portion 13b in the second region B may be secondarily broken.

[0097] Here, the first region A refers to a region where the seal portion 13b corresponds to a portion of the donut-shaped lead film 14 located relatively closer to the side where the electrode assembly 12 is housed, and the second region B refers to a region where the seal portion 13b corresponds to a portion of the donut-shaped lead film 14 located relatively farther from the side where the electrode assembly 12 is housed.

[0098] As the internal pressure of the secondary battery increases, breakage occurs preferentially at the interface between the lead film 14 and the seal portion 13b in the first region A located toward the inside of the case, which is the area that receives the greatest pressure, making it easier to adjust the swelling pressure, thereby preventing an increase in swelling pressure and improving the safety of the battery.

[0099] If the swelling pressure increases even after fracture occurs preferentially at the interface between the lead film 14 and the sealing portion 13b in the first region A, the increase in swelling pressure can be further prevented by fracture occurring at the interface between the lead film 14 and the sealing portion 13b in the second region B.

[0100] When a fracture occurs at the interface between the lead film 14 in the second region B and the seal portion 13b, the pressure inside the battery can be discharged to the outside, making it easier to adjust the swelling pressure.

[0101] In an embodiment of the present invention, the device may further include a sensor unit (not shown) and a controller (not shown) connected to the first region A and / or the second region B. The sensor unit measures the swelling pressure and transmits the same to the controller, and the controller may cause rupture to occur in the first region A and / or the second region B when the swelling pressure exceeds a certain pressure threshold.

[0102] In one embodiment of the invention, the first region A may be located at an end of the seal towards the inside of the case.

[0103] In one embodiment of the invention, the second region B may be located at an end of the seal towards the exterior of the case.

[0104] In one embodiment of the present invention, the distance between the first region A and the second region B along the extension direction of the electrode lead 11 may be approximately 10% to 80% of the width d of the seal portion 13b along the extension direction of the electrode lead 11. Here, the distance between the first region A and the second region B refers to the shortest distance among the distances between the first region A and the second region B. When the distance between the first region A and the second region B satisfies the above-mentioned range, it becomes even easier to adjust the breakage timing between the first region A and the second region B.

[0105] In one embodiment of the present invention, the radius of curvature of the closed loop-shaped lead film 14 may be approximately 50 mm to 200 mm. When the radius of curvature of the doughnut-shaped lead film 14 satisfies the above-mentioned range, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the seal portion 13b in the first region A are easily increased. In addition, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the seal portion 13b are easily increased in the second region B. It becomes easier to adjust the breakage timing of the first region A and / or the second region B.

[0106] 4, the overall width h of the lead film 14 in the direction along the extension direction of the electrode lead 11 may be approximately 50% to 150% of the width d of the seal portion 13b in the direction along the extension direction of the electrode lead 11. When the overall width of the lead film 14 satisfies the above-mentioned range, it becomes easier to increase the contact area between the lead film 14 and the electrode lead 11 while also increasing the contact area between the lead film 14 and the seal portion 13b.

[0107] 4, the width h1 along the first direction of the first portion of the closed loop-shaped lead film 14 facing the electrode assembly 12 may be approximately 10% to 40% of the width of the seal portion 13b along the first direction. When the width h1 falls within the above-mentioned range, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the seal portion 13b can be easily increased, making it easy to ensure a sufficient seal strength during normal operation of the battery.

[0108] 4, the width h2 along the first direction of the second portion of the closed loop-shaped lead film 14, which is located on the opposite side to the first portion, may be approximately 10% to 40% of the width of the seal portion 13b along the first direction. When the width h2 falls within the above-mentioned range, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14a and the seal portion 13b can be easily increased, making it easy to ensure a sufficient seal strength during normal operation of the battery.

[0109] 4, the width of the first region A along the extension direction of the electrode lead 11 may be approximately 10% to 40% of the width d of the seal portion 13b along the extension direction of the electrode lead 11. When the width of the first region A satisfies the above-mentioned range, a sufficient seal strength can be ensured during normal operation of the battery, while breakage is likely to occur when swelling occurs.

[0110] 4, the width of the second region B along the extension direction of the electrode lead 11 may be approximately 10% to 40% of the width d of the seal portion 13b along the extension direction of the electrode lead 11. When the width of the second region B satisfies the above-mentioned range, a sufficient seal strength can be ensured during normal operation of the battery, but breakage is more likely to occur when the internal pressure of the secondary battery increases.

[0111] The secondary battery may be a cylindrical, square, or pouch-type secondary battery, and more preferably, the secondary battery may be a pouch-type secondary battery.

[0112] In the case of a pouch-type secondary battery, the strength of the pouch case is weak and the pouch case has various shapes, so that the pouch case tends to be more vulnerable to internal pressure. Therefore, when the secondary battery according to an embodiment of the present invention is a pouch-type secondary battery, it is more advantageous in terms of safety.

[0113] While preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and it goes without saying that various modifications can be made by a person having ordinary knowledge in the technical field to which the invention pertains without departing from the gist of the present invention as claimed in the claims, and these modified embodiments should not be understood individually from the technical ideas and perspectives of the present invention. [Explanation of symbols]

[0114] 10 Secondary battery 11 Electrode Lead 12 Electrode assembly 13a Storage section 13b Seal part 14 Lead Film 14a First Lead Film 14b 2nd lead film A 1st area B 2nd area

Claims

1. an electrode assembly having an electrode lead attached thereto; a case for accommodating the electrode assembly; a seal portion formed in the case for sealing the electrode assembly; a lead film that envelops a part of an outer surface of the electrode lead and is interposed between the electrode lead and the seal portion; Including, The lead film has an arch shape that is convex in a direction away from the electrode assembly along a first direction, which is the extension direction of the electrode lead, or has an arch shape that is convex in a direction toward the electrode assembly along the first direction, which is the extension direction of the electrode lead.

2. 2. The secondary battery according to claim 1, wherein the edge of the lead film facing the electrode assembly has a radius of curvature of 50 mm to 200 mm.

3. 2. The secondary battery according to claim 1, wherein a width of the lead film along a first direction, which is an extension direction of the electrode lead, is 20% to 150% of a width of the seal portion along the first direction.

4. an electrode assembly having an electrode lead attached thereto; a case for accommodating the electrode assembly; a seal portion formed in the case for sealing the electrode assembly; a lead film that envelops a part of an outer surface of the electrode lead and is interposed between the electrode lead and the seal portion; Including, The lead film is a first lead film located relatively close to the electrode assembly; a second lead film located relatively far from the electrode assembly; Including, A secondary battery, wherein the first lead film has an arch shape that is convex in a direction toward the electrode assembly along a first direction which is the extension direction of the electrode lead, and / or the second lead film has an arch shape that is convex in a direction away from the electrode assembly along the first direction which is the extension direction of the electrode lead.

5. The secondary battery according to claim 4 , wherein the first lead film and the second lead film are spaced apart from each other.

6. 5. The secondary battery according to claim 4, wherein the width of the first lead film along a first direction, which is the extension direction of the electrode lead, is 10% to 40% of the width of the sealing portion along the first direction.

7. 5. The secondary battery of claim 4, wherein a width of an interface between the first lead film and the sealing portion along a first direction, which is an extension direction of the electrode lead, is 10% to 40% of a width of the sealing portion along the first direction.

8. 5. The secondary battery according to claim 4, wherein the width of the second lead film along a first direction, which is the extension direction of the electrode lead, is 10% to 40% of the width of the sealing portion along the first direction.

9. 5. The secondary battery of claim 4, wherein a width of an interface between the second lead film and the sealing portion along a first direction which is an extension direction of the electrode lead is 10% to 40% of a width of the sealing portion along the first direction.

10. The first lead film and the second lead film are The secondary battery of claim 4, wherein when the internal pressure of the secondary battery increases, the interface between the first lead film and the sealing portion is primarily broken, and the interface between the second lead film and the sealing portion is secondarily broken.

11. 6. The secondary battery according to claim 5, wherein the distance between the first lead film and the second lead film is 10% to 80% of the width of the seal portion.

12. an electrode assembly having an electrode lead attached thereto; a case for accommodating the electrode assembly; a seal portion formed in the case for sealing the electrode assembly; a lead film that envelops a part of an outer surface of the electrode lead and is interposed between the electrode lead and the seal portion; Including, The planar shape of the lead film is It is a closed loop with an open center. The lead film is a first portion facing the electrode assembly has a shape that is convex in a direction toward the electrode assembly along a first direction that is the extension direction of the electrode lead, and a second portion located on the opposite side to the first portion has a shape that is convex in a direction away from the electrode assembly along the first direction that is the extension direction of the electrode lead.

13. The lead film is The secondary battery of claim 12, wherein when the internal pressure of the secondary battery increases, the interface between the lead film and the sealing portion in a first region where the first portion and the sealing portion are bonded together is primarily broken, and the interface between the lead film and the sealing portion in a second region where the second portion and the sealing portion are bonded together is secondarily broken.

14. 14. The secondary battery according to claim 13, wherein a distance between the first region and the second region along the extension direction of the electrode lead is 10% to 80% of a width of the seal portion along the extension direction of the electrode lead.

15. 13. The secondary battery according to claim 12, wherein the overall width of the lead film in the direction along the extension direction of the electrode lead is 50% to 150% of the width of the seal portion in the direction along the extension direction of the electrode lead.

16. 14. The secondary battery according to claim 13, wherein a width of the first region along the extension direction of the electrode lead is 10% to 40% of a width of the seal portion along the extension direction of the electrode lead.

17. 14. The secondary battery according to claim 13, wherein a width of the second region along the extension direction of the electrode lead is 10% to 40% of a width of the seal portion along the extension direction of the electrode lead.

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

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