Electrode assembly, manufacturing method thereof, and secondary battery, battery pack, and vehicle including the same

Abstract

The present invention relates to a jelly-roll-shaped electrode assembly in which a positive electrode, a separator, and a negative electrode are wound up, wherein the positive electrode includes a positive electrode edge portion adjacent to a center of the winding and a seal portion surrounding the positive electrode edge portion, and the positive electrode edge portion and the seal portion are at least partially rounded.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0048819, filed with the Korean Intellectual Property Office on April 13, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly, a manufacturing method thereof, and a secondary battery, a battery pack, and a means of transportation including the same. [Background technology]

[0003] In general, a secondary battery is a battery that can be charged and discharged, unlike a primary battery that cannot be charged. Such secondary batteries are widely used in advanced electronic devices such as phones, laptops, and camcorders.

[0004] The stability of the secondary battery can be ensured by undergoing a stability test in which one side of the secondary battery is crimped with a crimping machine and internal short circuits are measured.

[0005] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal battery case, and pouch batteries, in which the electrode assembly is housed in a pouch-type battery case made of an aluminum laminate sheet.

[0006] The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element consisting of a laminated structure of a positive electrode, a separator, and a negative electrode. It is classified into a folding type electrode assembly (jelly roll) in which a long sheet-like positive electrode and negative electrode coated with an active material are wound up with a separator interposed between them, and a stack type electrode assembly in which multiple positive electrodes and negative electrodes of a predetermined size are stacked one on top of the other with a separator interposed between them. Among these, jelly rolls have the advantages of being easy to manufacture and having a high energy density per weight.

[0007] A jelly-roll electrode assembly is formed by winding a positive electrode and a negative electrode, with a separator interposed between the positive electrode and the negative electrode. However, as charge-discharge cycles are repeated hundreds to thousands of times, the jelly-roll electrode assembly contracts and expands, causing bending deformation from the end of the positive electrode at the center, which ultimately leads to cracks, which can lead to disconnections or short circuits, significantly compromising the safety of the secondary battery. Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned problems of the prior art, the present invention provides an electrode assembly and a manufacturing method thereof that prevent the edges of the electrodes from cracking the separator and other electrode surfaces when the electrodes contract and expand due to charging / discharging of the secondary battery. [Means for solving the problem]

[0009] One embodiment of the present invention provides a jelly-roll-shaped electrode assembly in which a positive electrode, a separator, and a negative electrode are wound up, the positive electrode including a positive electrode edge portion adjacent to a center of the winding and a seal portion surrounding the positive electrode edge portion, and the positive electrode edge portion and the seal portion are at least partially rolled.

[0010] One embodiment of the present invention provides a secondary battery including the electrode assembly; a battery case having one open side and accommodating the electrode assembly; and a cap assembly coupled to the open side of the battery case.

[0011] One embodiment of the present invention provides a battery pack including the secondary battery.

[0012] One embodiment of the present invention provides a mobile device including the battery pack.

[0013] Another embodiment of the present invention provides a method for manufacturing a jelly-roll-shaped electrode assembly having a positive electrode, a separator, and a negative electrode wound up, the method including: a cutting step of cutting at least a portion of the positive electrode into a round shape; a step of supplying a seal member to a seal groove provided in a pair of sealing devices, positioning an end of the positive electrode in the seal groove, and sealing the end to form a seal portion; a step of pressing the seal portion in the longitudinal direction of the positive electrode with a pair of pressure rollers to fix the shape of the seal portion and cooling the seal portion; and a step of manufacturing an electrode assembly by winding up the positive electrode, a separator, and a negative electrode. [Effects of the Invention]

[0014] In the electrode assembly and manufacturing method thereof according to an embodiment of the present invention, the end of the positive electrode where winding begins is enclosed by a seal portion and both corners of the end are rounded, thereby preventing cracks in the negative electrode where it contacts the end of the positive electrode, thereby preventing breakage and short circuits, and improving the safety of the secondary battery. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing a positive electrode according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing an end of an electrode assembly according to an embodiment of the present invention before being wound up; [Figure 3] FIG. 2 is a perspective view showing a cut shape of a positive electrode end portion according to one embodiment of the present invention. [Figure 4] 1 is a flowchart illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 5] 1 is a cross-sectional view showing a portion of a secondary battery including an electrode assembly according to an embodiment of the present invention. [Figure 6] 1 is a perspective view showing a battery pack including a secondary battery according to an embodiment of the present invention; [Figure 7] 1 is a perspective view showing a mobile device including a battery pack according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0016] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout the specification, when a part is described as "comprising" a certain element or when a certain structure and shape is described as "feature," this means that other elements, structures, and shapes may be included, but not that other elements, structures, and shapes are excluded, unless otherwise specified.

[0017] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be presented and described in detail in the detailed description, but this is not intended to limit the content of the invention according to the embodiments, and it should be understood that the present invention includes all modifications, equivalents, and alternatives that fall within the spirit and technical scope of the present invention.

[0018] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrative purposes only and the scope of the present invention is not limited by the drawings.

[0019] FIG. 1 is a cross-sectional view showing a positive electrode 110 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an end of an electrode assembly 100 according to an embodiment of the present invention before being wound up.

[0020] The electrode assembly 100 includes a positive electrode 110, a negative electrode 120, and a separator 130 disposed between the positive electrode 110 and the negative electrode 120, and is a power generating element capable of charging and discharging.

[0021] The electrode assembly 100 may include a jelly roll structure in which a positive electrode 110, a separator 130, and a negative electrode 120 are sequentially stacked and wound. The electrode assembly 100 may further include a separator, where one of the separators may be located between the positive electrode 110 and the negative electrode 120, and the other may be located on one side of the positive electrode 110 or one side of the negative electrode 120. In other words, the electrode assembly 100 according to another embodiment may include a first separator and a second separator. The first separator may be located between the positive electrode 110 and the negative electrode 120, and the second separator may be located on one side of the positive electrode 110, i.e., on the side of the positive electrode 110 where the first separator is not located, or on one side of the negative electrode 120, i.e., on the side of the negative electrode 120 where the first separator is not located.

[0022] The positive electrode 110 may include a positive electrode current collector, a positive electrode active material portion, and a positive electrode uncoated portion. The positive electrode current collector is a thin metal plate with excellent conductivity, and may include, for example, aluminum (Al) foil.

[0023] The positive electrode 110 is a positive electrode current collector having a positive active material coated on at least one of its two surfaces, the area coated with the positive active material being the positive active material portion, and the area not coated with the positive active material being the positive electrode uncoated portion. The positive electrode uncoated portion is not coated with the positive active material, so a first electrode tab can be bonded thereto.

[0024] The positive electrode active material may include lithium cobalt oxide having a high operating voltage and excellent capacity characteristics, lithium nickel oxide having a high reversible capacity and easily realizing a large-capacity battery, lithium nickel cobalt oxide in which nickel is partially substituted with cobalt, lithium nickel cobalt metal oxide in which nickel is partially substituted with manganese, cobalt, or aluminum, inexpensive lithium manganese-based oxide having excellent thermal stability, and lithium iron phosphate having excellent stability.

[0025] The negative electrode 120 may include a negative electrode current collector, a negative electrode active material portion, and a negative electrode uncoated portion. The negative electrode current collector may include a thin metal plate having excellent conductivity, such as a copper (Cu) or nickel (Ni) foil.

[0026] The negative electrode 120 is formed by coating one or both sides of a negative electrode current collector with a negative electrode active material, and the negative electrode active material portion is formed by coating or spreading the negative electrode active material, while the negative electrode uncoated portion is a region where the negative electrode current collector is exposed without being coated or spread with the negative electrode active material. Since the negative electrode uncoated portion is not coated with the negative electrode active material, a second electrode tab can be bonded thereto.

[0027] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, or carbon fiber, or lithium metal or a lithium alloy. In this case, the negative electrode active material may further include, for example, non-graphite-based silica (SiO) or silicon carbide (SiC) for a high capacity design.

[0028] The first electrode tab and the second electrode tab transmit electrons collected by the current collector to an external circuit, and may protrude in opposite directions from the electrode assembly of the jelly roll structure.

[0029] The separator 130 prevents an internal short circuit that may occur due to contact between the positive electrode 110 and the negative electrode 120, and may include a porous material to facilitate the movement of ions between the electrodes.

[0030] In one embodiment, the separator 130 may include a substrate layer made of a porous material, such as polyethylene (PE), polystyrene (PS), polypropylene (PP), or a copolymer of polyethylene (PE) and polypropylene (PP).

[0031] In another embodiment, the separator 130 may include a safety-reinforced separator (SRS). That is, the separator 130 may include a substrate layer made of a porous material and a coating layer formed by coating the substrate layer with a mixed slurry of inorganic particles and a binder polymer. Preferably, the coating layer contains ceramic particles and has a uniform pore structure formed by the interstitial volume between the ceramic particles, which are the active layer components, as well as the pore structure contained in the separator substrate itself.

[0032] The coating layer may include ceramic particles containing at least one selected from the group consisting of alumina, silica, TiO2, SiC, and MgAl2O4. The inclusion of such a coating layer can enhance the safety of the electrode assembly. The coating layer may further include a lithium salt.

[0033] The electrode assembly 100 according to the present invention may further include a seal portion 112 at one end of the positive electrode 110 .

[0034] The positive electrode 110 may include a positive electrode edge portion 111 adjacent to the winding center of the electrode assembly 100 , i.e., the winding start portion of the positive electrode 110 , and a seal portion 112 surrounding the positive electrode edge portion 111 .

[0035] In this case, the positive electrode edge portion 111 may refer to the end portion adjacent to the winding start portion of the positive electrode 110 or the winding center portion of the electrode assembly 100, or may refer to a region at a certain distance from the end portion of the positive electrode 110 in the winding direction, i.e., in the longitudinal direction of the positive electrode 110.

[0036] The positive electrode edge portion 111 has a length of more than 0 mm and not more than 10 mm from the end of the positive electrode 110 in the longitudinal direction of the positive electrode 110. Preferably, the length of the positive electrode edge portion 111 is 1 mm to 5 mm.

[0037] 3 is a perspective view showing a cut shape of a positive electrode end portion according to one embodiment of the present invention. The positive electrode edge portion 111 may be at least partially rounded. That is, the positive electrode edge portion 111 may include a rounded portion (not shown) in which at least a portion is rounded, and the positive electrode edge portion 111 may include one or more rounded portions.

[0038] The rounded portion may be formed with a width and length that are greater than 0% and not greater than 50% of the electrode width (100%).

[0039] The radius of curvature of the rounded portion may be greater than 0% and less than or equal to 50% of the electrode width (100%). For example, when the positive electrode width is 50 mm, the radius of curvature may be 25 mm or more. In one embodiment, the radius of curvature of the rounded portion may be measured using a vision device, a 3D measuring device, or the like.

[0040] The rounded portion may include one or more radii of curvature, for example, the radius of curvature may increase from one end to the other end toward the center of the rounded portion, but decrease from the center to the other end.

[0041] As the electrode assembly 100 undergoes hundreds to thousands of repeated charge / discharge cycles, the electrode may shrink and expand, causing bending deformation in the positive electrode edge portion 111, which may lead to cracks in the electrode. However, by rounding the corners of the positive electrode edge portion 111, where stress may concentrate and damage the separator, it is possible to prevent cracks and short circuits caused by the shrinkage and expansion of the positive electrode edge portion 111 and the resulting fires. In particular, in this embodiment, it is possible to prevent cracks and short circuits from occurring on both sides of the positive electrode, rather than just on one side.

[0042] When the radius of curvature of the positive electrode edge portion 111 satisfies the above range, it is possible to prevent stress from concentrating on the corner of the positive electrode edge portion 111 without degrading the performance of the electrode assembly. That is, when the radius of curvature of the positive electrode edge portion 111 exceeds the above range, the amount of positive electrode active material decreases, which may cause a problem of degrading the performance of the electrode assembly.

[0043] 3, the end of the positive electrode edge portion 111 may be provided in any one of the following shapes: convex round, V-shaped, multiple convex round, diagonal line, and concave round. In this case, the V-shaped and diagonal line shapes refer to the overall shape of the positive electrode edge portion 111 being a V-shaped and diagonal line, or the V-shaped and diagonal line shapes with rounded corners. The multiple convex round shape refers to a concave-convex shape with rounded edges.

[0044] Such various shapes of the positive electrode edge portion 111 have the effect of preventing the edge or corner of the positive electrode edge portion 111 from becoming sharp and dispersing stress applied to the positive electrode edge portion 111.

[0045] Like the positive electrode edge portion 111, the seal portion 112 has at least one corner rounded, which prevents stress from concentrating on the corners of the positive electrode edge portion 111 and the seal portion 112, thereby preventing cracks and short circuits from occurring in the electrode.

[0046] 2 and 3 are intended to illustrate the shape of the positive electrode edge portion 111 and do not illustrate the sealing portion 112, but the positive electrode 110 according to the present invention may have a sealing portion 112 at the positive electrode edge portion 111 that is the same as or different in shape from the positive electrode edge portion 111. In this case, the sealing portion 112 may be at least partially rounded.

[0047] The seal 112 increases the frictional force between the separator on one or both sides of the positive electrode 110 and the positive electrode 110, thereby preventing the positive electrode 110 from slipping and core deformation.

[0048] The end of the seal portion 112 may be provided in any one of the shapes of a convex circle, a V-shape, multiple convex circles, oblique lines, and a concave circle, and may be provided in the same shape as the end of the positive electrode edge portion 111. For example, if the end of the positive electrode edge portion 111 is provided in a convex circle shape, the end of the seal portion 112 may also be provided in a convex circle shape.

[0049] Since the sealing portion 112 is provided in the same shape as the positive electrode edge portion 111, the cross-sectional area of ​​the sealing portion 112 in contact with the separator increases, and the frictional force of the sealing portion 112 increases, thereby preventing the positive electrode from slipping due to the expansion and contraction of the electrode assembly 100.

[0050] The sealing portion 112 may extend from one or both sides of the positive electrode edge portion to the front end of the positive electrode edge portion 111. Here, the front end of the positive electrode edge portion 111 refers to the empty space between the end of the positive electrode edge portion 111 and the center of the electrode assembly 100.

[0051] The sealing portion 112 is located on one or both sides of the positive electrode edge portion 111 and can be divided into a first portion including the positive electrode 110 between the sealing portions 112, and a second portion located at the front end of the positive electrode edge portion 111 and made of only the sealing member.

[0052] The length of the seal portion 112 may be more than 0 mm and not more than 5 mm. Preferably, the length of the seal portion 112 may be 1 mm to 3 mm. The first portion of the seal portion 112 may be located on one or both sides of the positive electrode 110, over 0% and not more than 50% of the total length of the seal portion 112 (100%). For example, if the total length of the seal portion 112 is 4 mm, the first portion may be 2 mm and the second portion may be 2 mm.

[0053] The width of the sealing portion 112 may be the same as the width of the positive electrode 110, or may be 0.5 mm to 1 mm wider than the width of the positive electrode 110. When the width of the sealing portion 112 satisfies this range, the sealing portion 112 does not affect or minimizes the effect on the height and size of the electrode assembly 100, preventing a decrease in the energy efficiency of the electrode assembly 100. That is, when the width of the sealing portion 112 exceeds this range, the height and size of the electrode assembly 100 increase, which increases the size of the secondary battery, potentially resulting in a decrease in the energy efficiency of the electrode assembly 100 and the secondary battery.

[0054] The thickness of the sealed portion 112 may decrease toward the center of the winding, in other words, in the shear direction of the positive electrode edge portion 111. Specifically, the thickness of the second portion of the sealed portion 112 may decrease from the first portion toward the center of the winding. The thickness of the sealed portion 112 may decrease gradually or in steps, and preferably may decrease gradually.

[0055] This configuration can prevent cracks and overheating that can occur from the edge of the positive electrode 110. That is, as design requirements for high energy density increase, an increase in the density of the positive electrode is unavoidable when an electrode tab (third electrode tab or in tap) is joined to the core portion C of the electrode assembly 100 or when SiO is further included in the negative electrode active material, resulting in increased stress at the positive electrode step portion. Here, the positive electrode step portion is a portion where the thickness suddenly increases to 100 μm to 200 μm due to the presence of the positive electrode at the starting point of the positive electrode, forming a physical step within the electrode assembly, and corresponds to the positive electrode edge portion 111 in the figure.

[0056] The positive electrode step portion experiences high stress, and if this portion is continuously pressed during the contraction and expansion process due to charging and discharging, the separator in contact with this portion may be damaged, resulting in a high risk of fire due to cracks and short circuits. However, according to one embodiment of the present invention, the positive electrode edge portion 111 is provided with a seal portion 112, which prevents damage to the separator at the positive electrode step portion and provides a stable buffering effect, thereby preventing cracks and short circuits caused by repeated contraction and expansion at the positive electrode end, which is subject to high stress, and thereby reducing the risk of fire.

[0057] FIG. 5 is a cross-sectional view showing a portion of a secondary battery 1 including an electrode assembly 100 according to an embodiment of the present invention.

[0058] The battery case 200 may have a columnar structure with a space formed therein. The battery case 200 may accommodate an electrode assembly 100 including electrodes and a separator, and an electrolyte (not shown) in the space. The battery case 200 may have a structure in which one side is open (hereinafter referred to as an opening) and the other side is sealed. Here, the terms "one side" and "other side" refer to the ends located at the top and bottom along the direction of gravity or the central axis of the battery case 200.

[0059] The side of the upper portion of the open battery case 200 may be provided with a beading portion 210 folded toward the center of the secondary battery 1. The battery case 200 may also be provided with a crimping portion 220 above the beading portion 210. That is, the crimping portion 220 may be located at the top of the battery case 200. Here, the upper portion refers to the region from the center of the battery case 200 toward the opening.

[0060] The battery case 200 may be made of a lightweight conductive metal material such as aluminum or an aluminum alloy.

[0061] The cap assembly 300 may be coupled to the open side of the battery case 200 and may include a top cap 310 , a safety vent 320 , and a current interrupt device 330 .

[0062] The top cap 310 may be located at the top of the cap assembly 300 and may protrude in a direction opposite to the center of the battery case 200. The top cap 310 may serve as an electrode terminal such that the protruding portion is electrically connected to the outside, for example, the top cap 310 may serve as a positive electrode terminal.

[0063] The top cap 310 may have a sealing gasket 340 bonded to the edge of the top cap 310, or the sealing gasket 340 may be located inside the crimping portion 220 of the battery case 200. The sealing gasket 340 can increase the sealing force between the top cap 310 and the battery case 200.

[0064] The top cap 310 may include a protrusion protruding upward, a rim that contacts and is coupled with the sealing gasket 340, and a first connecting portion that connects the protrusion and the rim.

[0065] The safety vent 320 may be located under the top cap 310 and electrically connected to the top cap 310. At least a portion of the surface of the safety vent 320 facing the top cap 310 may be in contact with the top cap 310. The safety vent 320 may contact the top cap 310 for a certain length from its end, and the remaining portion of the safety vent 320 may be spaced a certain distance from the top cap 310. In addition, the portion of the safety vent 320 that contacts the top cap 310 may be coupled to a sealing gasket 340.

[0066] The safety vent 320 may be spaced apart from the top cap 310 from the area in contact with the top cap 310 toward the center of the safety vent 320 .

[0067] Safety vent 320 may include a contact portion that contacts top cap 310, a central portion that is located at the center of safety vent 320 and that contacts the current interrupting element, and a second connecting portion that connects the contact portion and the central portion. Safety vent 320 may have bent portions (or notches) at the portions where the contact portion and the second connecting portion and the second connecting portion and the central portion contact each other.

[0068] In one embodiment, the safety vent 320 may have an end perpendicular to the axial direction of the battery case 200. In this case, the top cap 310 may be provided perpendicular to the axial direction of the battery case 200, just like the safety vent 320. That is, the safety vent 320 and the top cap 310 may be positioned horizontally.

[0069] In other embodiments, the safety vent 320 may be provided with a folded end that surrounds the outer periphery of the top cap 310 .

[0070] In the secondary battery 1 according to the present invention, the electrode assembly 100 housed inside the battery case 200 reacts with the electrolyte, generating gas and heat, which causes an increase in internal pressure.

[0071] When the pressure inside the secondary battery 1 increases, the safety vent 320 receives a force in the direction of the top cap 310, causing the bent portion to burst and allowing the gas inside the secondary battery 1 to be discharged.

[0072] A current interruptive device (CID) 330 may be located below the safety vent 320 and at least a portion thereof may be connected to the safety vent 320 .

[0073] When the safety vent 320 bursts due to an increase in the internal pressure of the secondary battery 1, the current interruption device 330 separates from the safety vent 320 and interrupts the current.

[0074] More specifically, the current interruption device 330 may include a central portion connected to the safety vent 320, a connecting portion protruding in the direction of the safety vent 320, a peripheral portion excluding the connecting portion, and a joining portion connecting the connecting portion and the peripheral portion. A plurality of joining portions may be provided, and the plurality of joining portions may be spaced apart from one another.

[0075] When the safety vent 320 is distorted in the direction of the top cap 310, the joint breaks and the connecting portion can be separated from the surrounding portion. That is, the connecting portion is separated in the direction of the top cap 310 while remaining connected to the safety vent 320.

[0076] The CID gasket 350 surrounds the current interrupting element 330 and can electrically isolate the surrounding portion and the joint portion of the current interrupting element 330 other than the connecting portion from the safety vent 320 .

[0077] According to an embodiment of the present invention, a battery pack including any of the above-described secondary batteries is provided.

[0078] Regarding this embodiment, referring to FIG. 6, a battery pack 3 in which a secondary battery 1 is included in a pack housing 2 is shown.

[0079] The battery pack according to this embodiment has high output and high capacity.

[0080] According to an embodiment of the present invention, there is provided a vehicle including the battery pack described above.

[0081] Regarding this embodiment, referring to FIG. 7, a vehicle V including a battery pack 3 is shown.

[0082] The vehicle according to the embodiment uses a battery pack with high output / high capacity, and is therefore excellent in terms of stability and safety.

[0083] FIG. 4 is a flowchart illustrating a method for manufacturing an electrode assembly according to one embodiment of the present invention.

[0084] The method for manufacturing an electrode assembly according to the present invention includes a cutting step S10 of rolling and cutting at least a portion of a positive electrode; a sealing step S20 of supplying a seal member to a seal groove provided in a pair of sealing devices, positioning an end of the positive electrode in the seal groove, and sealing the end to form a seal; a cooling step S30 of pressing the seal member in the longitudinal direction of the positive electrode with a pair of pressure rollers to fix the shape of the seal member and cooling the seal member; and a step of winding up the positive electrode, separator, and negative electrode to manufacture an electrode assembly.

[0085] The cutting step S10 is a step of cutting the positive electrode based on the plane of the positive electrode so that there are no sharp edges. In the cutting step S10, the corners of the winding start portion of the positive electrode, i.e., the edge portion of the positive electrode, are rounded off, thereby distributing stress applied to the edge portion of the positive electrode due to contraction and expansion of the electrode assembly over the entire surface of the edge portion of the positive electrode, thereby preventing damage to the separator and cracks in the negative electrode due to the edge portion of the positive electrode.

[0086] In the cutting step S10, at least one of two corners located on the end of the positive electrode may be cut so as to be rounded with a certain radius of curvature. Furthermore, the cutting step S10 may include cutting the end of the positive electrode into any one of a convex round, a V-shape, multiple convex rounds, a diagonal line, and a concave round shape. For example, in the cutting step S10, the end of the positive electrode may be cut into a convex round shape, and then at least one of the sharp corners may be cut to be rounded.

[0087] In the sealing step S20, the pair of sealing devices may be provided with at least one sealing groove. The sealing devices may include a first sealing device facing one side of the positive electrode and a second sealing device facing the other side of the positive electrode, and the sealing groove may be formed in the first sealing device, the second sealing device, or both the first and second sealing devices.

[0088] In one embodiment, the seal groove is formed in a rectangular shape, and may have a width that is the same as that of the positive electrode or 0.5 mm to 1 mm wider than that of the positive electrode, and a length that is greater than 0 mm and not more than 5 mm.

[0089] In another embodiment, the seal groove may be formed so that positions corresponding to the two corners of the positive electrode edge portion are rounded, and in still another embodiment, the seal groove may be formed in any one of the following shapes: a convex circle, a V-shape, multiple convex circles, oblique lines, and a concave circle.

[0090] The sealing step S20 may include the steps of heating a sealing device, positioning an end of the positive electrode in a sealing groove, applying pressure with a pair of sealing devices, and then supplying a sealing member into the sealing groove, and reducing the temperature of the sealing device to cool the sealing member.

[0091] The sealing device may include a sealing material supply unit that supplies sealing material to the sealing groove from the outside.

[0092] In the step of heating the sealing device, the temperature of the sealing device may be heated to a temperature of 150° C. or higher. In one embodiment, the sealing member comprises polypropylene (PP), and by maintaining the sealing device at a temperature above the melting point of the polypropylene, the polypropylene remains in a liquid state and can migrate along the sealing member supply section to the sealing groove.

[0093] In the step of supplying the seal material to the seal groove, the supply time of the seal material may be 5 seconds or less. If the supply time of the seal material is 5 seconds or less, a seal portion can be formed at the end of the positive electrode without damaging the positive electrode. In other words, if the supply time of the seal material exceeds 5 seconds, a problem may occur in which the positive electrode is damaged by the high-temperature seal material. Preferably, the supply time of the seal material may be 2 seconds or less.

[0094] The step of cooling the seal member is a step of cooling the seal member by primary cooling to solidify the seal member.

[0095] The cooling step S30 is a step of completely cooling the primarily cooled seal member to determine the shape of the seal portion and flatten the outer surface of the seal portion to minimize roughness of the seal portion.

[0096] When the pair of pressure rollers cooled in the cooling step S30 press the positive electrode in the longitudinal direction, the pressure may increase in the shear direction from the positive electrode to the positive electrode end. The pressure of the pair of pressure rollers may increase gradually or stepwise, preferably gradually, so that both sides of the sealing portion may form a certain angle with both sides of the positive electrode.

[0097] The temperature of the pair of pressure rollers may be 150°C or less. Preferably, the temperature of the pair of pressure rollers is 70°C to 130°C, and more preferably 90°C to 100°C. When the temperature of the pressure rollers is within this range, the seal member is completely cooled, and even if force is applied to the sealed portion due to expansion and contraction of the electrode assembly or external pressure, the shape of the cooled portion does not deform. In other words, if the temperature of the pressure rollers exceeds 150°C, the seal member is not sufficiently cooled, and when pressure is applied to the sealed portion, the shape of the sealed portion may deform, resulting in problems such as stress concentration in the sealed portion.

[0098] The pressure applied by the pair of pressure rollers may be 1 kg / cm to 15 kg / cm. Specifically, the pressure applied by the pair of pressure rollers to the seal members or seal portions located on one side and the other side of the positive electrode may be 5 kg / cm to 10 kg / cm, and the pressure applied by the pair of pressure rollers to the seal member or seal portion located on the front end of the positive electrode may be 5 kg / cm to 10 kg / cm. When the pressure applied by the pressure rollers satisfies the above range, the positive electrode and positive electrode active material are not damaged by the pressure applied by the pressure rollers, and the seal portions do not affect the size of the electrode assembly.

[0099] The pressure applied by the pair of pressure rollers can be adjusted by applying pressure to the pressure rollers from the outside, or by adjusting the distance between the pair of pressure rollers.

[0100] In one embodiment, if the thickness of the seal member before cooling is 100%, the thickness of the seal member after cooling, i.e., the seal portion, may be reduced to 35% or less. For example, if the electrode thickness is 100 μm and the thickness of the seal member is 15 μm, the seal portion may be reduced to 5 μm.

[0101] The time for which the pair of pressure rollers press the sealing member or the sealing portion may be 0.5 seconds to 5 seconds.

[0102] The method for manufacturing an electrode assembly according to the present invention may further include cutting an end of the sealing part located at the front end of the positive electrode. In this case, the end of the sealing part may be cut in the same shape as the end of the positive electrode.

[0103] While the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention as set forth in the following claims. [Explanation of symbols]

[0104] 1...Secondary battery 2-pack housing 3 Battery pack 100...electrode assembly 110...Positive electrode 111 Positive electrode edge 112 Seal part 120...Negative electrode 130...Separation membrane 200 Battery Case 210 Beading section 220 Crimping section 300 Cap Assembly 310 Top Cap 320 Safety Vent 330 Current interruption element 340 Sealing gasket 350 CID gasket V...Transportation means

Claims

1. A jelly-roll-shaped electrode assembly in which a positive electrode, a separator, and a negative electrode are wound, the positive electrode includes a positive electrode edge portion adjacent to a winding center portion and a seal portion surrounding the positive electrode edge portion, The positive electrode edge portion and the sealing portion are at least partially rounded.

2. the end of the positive electrode edge portion has any one of a convex round, a V-shape, multiple convex rounds, a diagonal line, and a concave round shape; The electrode assembly of claim 1 , wherein the V-shape and the diagonal line have rounded corners.

3. The electrode assembly according to claim 1 or 2, wherein the positive electrode edge portion has a length of more than 0 mm and not more than 10 mm from an end portion of the positive electrode adjacent to a winding center portion.

4. The electrode assembly according to claim 1 or 2, wherein an end of the sealing portion is provided in the same shape as an end of the positive electrode edge portion.

5. The electrode assembly according to claim 1 or 2, wherein the thickness of the seal portion decreases toward the winding center.

6. The electrode assembly according to claim 1 or 2, wherein the sealing portion extends from one or both surfaces of the positive electrode edge portion to a front end of the positive electrode edge portion.

7. The electrode assembly according to claim 6 , wherein the length of the seal portion is greater than 0 mm and not greater than 5 mm.

8. The electrode assembly according to claim 1 or 2; a battery case having an opening on one side and containing the electrode assembly; and a cap assembly coupled to the opening of the battery case; A secondary battery comprising:

9. A battery pack comprising the secondary battery according to claim 8 .

10. A mobile device comprising the battery pack of claim 9.

11. A method for manufacturing a jelly-roll-shaped electrode assembly in which a positive electrode, a separator, and a negative electrode are wound, comprising: a cutting step of cutting at least a portion of the positive electrode into a round shape; a sealing step of supplying a seal member to a seal groove provided in a pair of sealing devices, positioning an end of the positive electrode in the seal groove, and sealing the end to form a seal portion; a cooling step in which the sealed portion is pressed in the longitudinal direction of the positive electrode by a pair of pressure rollers to fix the shape of the sealed portion and then cooled; and and winding the positive electrode, the separator, and the negative electrode to manufacture an electrode assembly. A method for manufacturing an electrode assembly, comprising:

12. 12. The method for manufacturing an electrode assembly according to claim 11, wherein the sealing step includes the steps of: heating the sealing device; positioning an end of the positive electrode in the seal groove and applying pressure with a pair of the sealing devices, and then supplying the seal member into the seal groove; and reducing the temperature of the sealing device to cool the seal member.

13. The method of claim 12 , wherein in the heating the sealing device, the sealing device is heated to a temperature of 150° C. or higher.

14. 14. The method of manufacturing an electrode assembly according to claim 11, wherein the cutting step comprises cutting the end of the positive electrode into any one of a convex circle, a V-shape, multiple convex circles, a diagonal line, and a concave circle.

15. The method for manufacturing an electrode assembly according to claim 11, wherein the pressure applied by the pressure roller increases in a longitudinal direction of the positive electrode.

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