Electrode assembly, method for manufacturing same, and secondary battery, battery pack, and transport device including electrode assembly

Abstract

The present invention relates to a core-wound electrode assembly in which a positive electrode, a separator, and a negative electrode are wound, in which the positive electrode includes a positive electrode edge portion adjacent to a winding center portion and a sealing portion surrounding the positive electrode edge portion, and the positive electrode edge portion and the sealing portion are at least partially rounded.

Description

Technical Field

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0048819 filed in 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 method for manufacturing the same, and a secondary battery, a battery pack, and a mobile device including the electrode assembly. Background Art

[0003] In general, a secondary battery refers to a chargeable and dischargeable battery unlike a non-rechargeable primary battery, and the secondary battery is widely used in the field of high-tech electronic devices such as phones, notebook computers, and camcorders.

[0004] The stability of the secondary battery can be ensured through a stability test in which one surface is compressed with a press to measure an internal short circuit.

[0005] According to the shape of a battery case, secondary batteries are classified into cylindrical batteries and square batteries in which an electrode assembly is embedded in a cylindrical or square metal battery case, and pouch-type batteries in which an electrode assembly is embedded in a pouch-type battery case made of an aluminum laminate.

[0006] In addition, the electrode assembly embedded in the battery case is a chargeable / dischargeable power generation device having a laminated structure of a positive electrode / separator / negative electrode, and is divided into: a folding type electrode assembly (roll core) in which a long sheet of a positive electrode and a negative electrode coated with an active material are wound with a separator interposed therebetween; and a stacked type electrode assembly in which a plurality of positive electrodes and negative electrodes having a predetermined size are sequentially stacked with a separator interposed therebetween. Among them, the roll core has the advantages of being easy to manufacture and having a high energy density per unit weight.

[0007] The jellyroll-type electrode assembly can be formed by winding the positive electrode and the negative electrode, in which case the positive electrode and the negative electrode are wound with a separator interposed therebetween. However, as the charge and discharge cycles are repeated hundreds to thousands of times, the jellyroll-type electrode assembly undergoes shrinkage and expansion, resulting in bending deformation of the end portion from the center of the positive electrode, causing cracks and disconnection or short circuit, thereby greatly impairing the safety of the secondary battery. Summary of the invention

[0008] Technical issues

[0009] The present invention is directed to providing an electrode assembly and a method of manufacturing the same, which can prevent cracks from being generated in a separator and another electrode surface by an electrode end portion during electrode shrinkage and expansion caused by charge / discharge of a secondary battery.

[0010] Technical Solution

[0011] An exemplary embodiment of the present invention provides a core-wound electrode assembly in which a positive electrode, a separator, and a negative electrode are wound, wherein the positive electrode includes a positive electrode edge portion adjacent to a winding center portion and a sealing portion surrounding the positive electrode edge portion, and wherein the positive electrode edge portion and the sealing portion each have at least a portion that is rounded.

[0012] Another exemplary embodiment of the present invention provides a secondary battery including: an electrode assembly; a battery case having an opening on one surface and configured to accommodate the electrode assembly; and a cap assembly coupled to the open surface of the battery case.

[0013] Another exemplary embodiment of the present invention provides a battery pack including the secondary battery.

[0014] Another exemplary embodiment of the present invention provides a mobile device including a battery pack.

[0015] Another exemplary embodiment of the present invention provides a method for manufacturing a core-wound electrode assembly in which a positive electrode, a separator and a negative electrode are wound, the method for manufacturing a core-wound electrode assembly comprising: cutting at least a portion of the positive electrode into a circular shape; supplying a sealing member to a sealing groove provided in a pair of sealing devices, positioning an end of the positive electrode in the sealing groove, and sealing the end to form a sealing portion; fixing the shape of the sealing portion by pressing the sealing portion in a longitudinal direction of the positive electrode with a pair of pressure rollers and cooling the sealing portion; and manufacturing the electrode assembly by winding the positive electrode, the separator and the negative electrode.

[0016] Beneficial Effects

[0017] In an electrode assembly and a method for manufacturing the same according to an exemplary embodiment of the present invention, a sealing portion surrounds the end portion of the positive electrode where winding starts, and two corners of the end portion are rounded, thereby preventing the negative electrode from cracking at the portion in contact with the positive electrode terminal, and preventing disconnection or short circuit, thereby improving the safety of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a cross-sectional view showing a positive electrode according to an exemplary embodiment of the present invention.

[0019] Figure 2 is a cross-sectional view showing an end portion of an electrode assembly before winding according to an exemplary embodiment of the present invention.

[0020] Figure 3 is a perspective view showing a cut shape of a positive terminal according to an exemplary embodiment of the present invention.

[0021] Figure 4is a flowchart illustrating a method of manufacturing an electrode assembly according to an exemplary embodiment of the present invention.

[0022] Figure 5 is a cross-sectional view illustrating a portion of a secondary battery including an electrode assembly according to an exemplary embodiment of the present invention.

[0023] Figure 6 is a perspective view showing a battery pack including a secondary battery according to an exemplary embodiment of the present invention.

[0024] Figure 7 is a perspective view showing a mobile device including a battery pack according to an exemplary embodiment of the present invention.

[0025] [Explanation of Reference Numerals]

[0026] 1: Secondary battery

[0027] 2: Battery pack housing

[0028] 3: Battery Pack

[0029] 100: Electrode assembly

[0030] 110: Positive

[0031] 111: Positive electrode edge

[0032] 112: Sealing part

[0033] 120: Negative electrode

[0034] 130: Diaphragm

[0035] 200: Battery housing

[0036] 210: Edge pressing part

[0037] 220: Curling part

[0038] 300: Cap assembly

[0039] 310: Top Hat

[0040] 320: Safety exhaust

[0041] 330: Current interrupting device

[0042] 340: Sealing gasket

[0043] 350: CID pad

[0044] V: Mobile Device DETAILED DESCRIPTION

[0045] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout the specification, unless there is a clear contrary description, when a component "includes (comprising)" another component or "characterized by" having a certain structure and a certain shape, this means that other components, structures and shapes can be included but not excluded.

[0046] The present invention can be modified in various ways and can have various exemplary embodiments, and specific exemplary embodiments will be described in detail in the specific embodiments. However, the description of the exemplary embodiments is not intended to limit the content of the present invention, but it should be understood that the present invention will cover all modifications, equivalents and substitutes that fall within the spirit and technical scope of the present invention.

[0047] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, it should be noted that the accompanying drawings are provided to illustrate the present invention, and the scope of the present invention is not limited by the accompanying drawings.

[0048] Figure 1 is a cross-sectional view showing a positive electrode 110 according to an exemplary embodiment of the present invention, Figure 2 is a cross-sectional view showing an end portion of an electrode assembly 100 before being wound according to an exemplary embodiment of the present invention.

[0049] The electrode assembly 100 is a power generation element that includes a positive electrode 110 , a negative electrode 120 , and a separator 130 located between the positive electrode 110 and the negative electrode 120 and can be charged and discharged.

[0050] The electrode assembly 100 may include a roll core structure in which the positive electrode 110, the separator 130, and the negative electrode 120 are sequentially stacked and wound. The electrode assembly 100 may also include a separator, in which case one of the two separators may be located between the positive electrode 110 and the negative electrode 120, and the other may be located on one surface of the positive electrode 110 or on one surface of the negative electrode 120. In other words, the electrode assembly 100 according to another exemplary 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 surface of the positive electrode 110 (i.e., one surface of the positive electrode 110 on which the first separator is not provided), or one surface of the negative electrode 120 (i.e., one surface of the negative electrode 120 on which the first separator is not provided).

[0051] The positive electrode 110 may include a positive electrode collector, a positive electrode active material portion, and a positive electrode uncoated portion. The positive electrode collector is a metal thin plate having excellent electrical conductivity, and may include, for example, aluminum (Al) foil.

[0052] The positive electrode 110 is coated with a positive electrode active material on one or more surfaces of the two surfaces of the positive electrode current collector. The area coated with the positive electrode active material is the positive electrode active material portion, and the area not coated with the positive electrode active material is the positive electrode uncoated portion. Since the positive electrode uncoated portion is not coated with the positive electrode active material, the first electrode terminal can be connected thereto.

[0053] 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 used to easily realize a large-capacity battery, lithium nickel cobalt oxide in which a portion of the nickel is replaced by cobalt, lithium nickel cobalt metal oxide in which a portion of the nickel is replaced by manganese, cobalt or aluminum, lithium manganese-based oxide having excellent thermal stability and low cost, lithium iron phosphate having excellent stability, and the like.

[0054] 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 metal thin plate having excellent electrical conductivity, such as copper (Cu) foil or nickel (Ni) foil.

[0055] The negative electrode 120 is coated with a negative active material on one surface or both surfaces of the negative current collector. The negative active material portion is formed by coating or applying the negative active material, and the negative uncoated portion is an area where the negative active material is not coated or applied and the negative current collector is exposed. Since the negative uncoated portion is not coated with the negative active material, the second electrode terminal can be connected thereto.

[0056] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite material or carbon fiber, lithium metal, lithium alloy, etc. In this case, in order to achieve a high capacity design, the negative electrode active material may also include, for example, non-graphite-based SiO (silicon dioxide), SiC (silicon carbide), etc.

[0057] The first electrode tab and the second electrode tab serve to transfer electrons collected in the current collector to an external circuit, and may protrude in opposite directions with respect to the electrode assembly of the jellyroll structure.

[0058] The separator 130 prevents an internal short circuit that may be caused when the positive electrode 110 and the negative electrode 120 contact each other, and may include a porous material to facilitate migration of ions between the electrodes.

[0059] In an exemplary embodiment, the separator 130 may include a substrate layer made of a porous material. For example, the substrate layer may include any one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and a copolymer of polyethylene (PE) and polypropylene (PP).

[0060] In another exemplary 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 coated and formed on the substrate layer by coating a mixed slurry of inorganic particles and a binder polymer. Preferably, the coating layer includes ceramic particles and has a uniform pore structure formed by the interstitial volume between the ceramic particles as a component of the active layer in addition to the pore structure of the separator substrate itself.

[0061] The coating layer may include ceramic particles including at least one selected from the group consisting of alumina, silicon dioxide, TiO2, SiC, and MgAl2O4. Including such a coating layer enables the safety of the electrode assembly to be enhanced. The coating layer may also include a lithium salt.

[0062] The electrode assembly 100 according to the exemplary embodiment of the present invention may further include a sealing portion 112 at one end portion of the positive electrode 110 .

[0063] The positive electrode 110 may include a positive electrode edge portion 111 adjacent to a winding center portion of the electrode assembly 100 (ie, a winding start portion of the positive electrode 110 ) and a sealing portion 112 surrounding the positive electrode edge portion 111 .

[0064] In this case, the positive electrode edge portion 111 may refer to an end portion adjacent to the winding start portion of the positive electrode 110 or the winding center portion of the electrode assembly 100, or a region at a predetermined 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).

[0065] The positive electrode edge portion 111 includes a length greater than 0 mm and less than or equal to 10 mm in the longitudinal direction of the positive electrode 110 from the end of the positive electrode 110. Preferably, the length of the positive electrode edge portion 111 is 1 mm to 5 mm.

[0066] Figure 3 1 is a perspective view showing a cut shape of an end portion of a positive electrode according to an exemplary embodiment of the present invention. At least a portion of the positive electrode edge portion 111 may be rounded. That is, the positive electrode edge portion 111 includes a rounded portion (not shown) in which at least a portion of the positive electrode edge portion is rounded, and the rounded portion may include one, or include two or more.

[0067] The rounded portion may be formed to have a width and a length greater than 0% and less than or equal to 50% based on the electrode width being 100%.

[0068] Based on the electrode width being 100%, the radius of curvature of the rounded portion may be greater than 0% and less than or equal to 50%. For example, when the positive electrode width is 50 mm, the radius of curvature may be greater than 25 mm. In an exemplary embodiment, the radius of curvature of the rounded portion may be measured using a visual device, a 3D measuring device, or the like.

[0069] The rounded portion may include one or more radii of curvature. For example, the radius of curvature of the rounded portion may increase from one end toward the other end toward the center of the rounded portion, and then decrease from the center toward the other end.

[0070] As the electrode assembly 100 is subjected to repeated charge and discharge cycles of hundreds to thousands of times, the electrode may shrink and expand. As a result, bending deformation may occur at the positive electrode edge portion 111, which may cause cracks in the electrode. However, by rounding the corners where the stress of the positive electrode edge portion 111 may be concentrated and damage the separator, cracks and short circuits and fires caused by shrinkage and expansion of the positive electrode edge portion 111 can be prevented. Specifically, in this exemplary embodiment, cracks and short circuits can be prevented in the electrode (not on one surface of the positive electrode, but on either side).

[0071] When the curvature radius of the positive electrode edge portion 111 satisfies the above range, the effect of preventing stress from being concentrated at the corner of the positive electrode edge portion 111 can be achieved without reducing the performance of the electrode assembly. In other words, if the curvature radius of the positive electrode edge portion 111 exceeds the above range, the amount of positive electrode active material may be reduced, which may cause a problem of reduced performance of the electrode assembly.

[0072] In addition, refer to Figure 3 , the end of the positive electrode edge portion 111 may be formed in any one of a convex circle, a V shape, a multi-convex circle, an inclined shape, and a concave circle. In this case, in the V shape and the inclined shape, the overall shape of the positive electrode edge portion 111 is a V shape or an inclined shape, and the corners may be rounded. Multi-convex circle means that the end of an irregular body in an irregular shape is rounded.

[0073] These various shapes of the positive electrode edge portion 111 have an effect of dispersing stress applied to the positive electrode edge portion 111 by preventing an angular shape of the end portion or corner portion of the positive electrode edge portion 111 .

[0074] The sealing portion 112 has at least one corner that is rounded like the positive electrode edge portion 111 , preventing stress from being concentrated on the corners of the positive electrode edge portion 111 and the sealing portion 112 , and preventing cracks and short circuits in the electrodes.

[0075] Figure 2 and Figure 3The illustrated positive electrode 110 is provided for illustrating the shape of the positive electrode edge portion 111, and does not illustrate the sealing portion 112. However, the positive electrode 110 according to the exemplary embodiment of the present invention may have a sealing portion 112 having the same or different shape as the positive electrode edge portion 111 and located at the positive electrode edge portion 111. In this case, at least a portion of the sealing portion 112 may be provided in a rounded shape.

[0076] The sealing portion 112 may increase friction with the separator on one surface or both surfaces of the positive electrode 110 to prevent the positive electrode 110 from sliding, thereby preventing core collapse (core deformation).

[0077] The end of the sealing portion 112 may be set to any one of a convex circle, a V-shape, a multi-convex circle, an inclined shape, and a concave circle, and may be set to the same shape as the end of the positive electrode edge portion 111. For example, when the end of the positive electrode edge portion 111 is set to a convex circle, the end of the sealing portion 112 may also be set to a convex circle.

[0078] Since the sealing portion 112 is configured 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 friction of the sealing portion 112 increases, thereby preventing the positive electrode from sliding due to expansion and contraction of the electrode assembly 100 .

[0079] The sealing portion 112 may extend to the front end of the positive electrode edge portion 111 on one or both surfaces of the positive electrode edge portion. Here, the front end of the positive electrode edge portion 111 refers to an empty space between the end of the positive electrode edge portion 111 and the center portion of the electrode assembly 100.

[0080] The sealing portion 112 may be divided into a first portion located on one or both surfaces of the positive electrode edge portion 111 with the positive electrode 110 contained therebetween, and a second portion located at the front end of the positive electrode edge portion 111 and provided with only a sealing member.

[0081] The length of the sealing portion 112 may be greater than 0 mm and less than or equal to 5 mm. Preferably, the length of the sealing portion 112 may be 1 mm to 3 mm. Based on the total length 100% of the sealing portion 112, the first portion of the sealing portion 112 may be located on one surface or both surfaces of the positive electrode 110 at a rate greater than 0% and less than or equal to 50%. For example, when the total length of the sealing portion 112 is 4 mm, the first portion may be 2 mm, and the second portion may be 2 mm.

[0082] 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 the above range, the sealing portion 112 has no or minimal effect on the height and size of the electrode assembly 100, thereby preventing the energy efficiency of the electrode assembly 100 from being reduced. In other words, if the width of the sealing portion 112 exceeds the above range, the height and size of the electrode assembly 100 increase, thereby increasing the size of the secondary battery and reducing the energy efficiency of the electrode assembly 100 and the secondary battery.

[0083] The thickness of the sealing portion 112 may decrease toward the winding center portion (i.e., in the front end direction of the positive electrode edge portion 111). Specifically, the second portion of the sealing portion 112 may decrease in thickness from the first portion toward the winding center. The thickness of the sealing portion 112 may decrease gradually or stepwise, preferably gradually.

[0084] With this configuration, cracks and overheating that may occur from the end of the positive electrode 110 can be prevented. That is, as the demand for high energy density design increases, the electrode joint (third electrode joint or tap) is coupled to the core C of the electrode assembly 100 or more SiO is included in the negative electrode active material, which inevitably increases the density of the positive electrode and the stress in the step portion of the positive electrode. Here, the step portion of the positive electrode is a portion where the thickness of the positive electrode rapidly increases to 100 μm to 200 μm as the positive electrode is placed at the starting point of the positive electrode, and therefore, a physical step is formed within the electrode assembly, and corresponds to the positive electrode edge portion 111 in the drawing.

[0085] The stress increases at the step portion of the positive electrode, and therefore, when the portion is continuously pressed during the contraction and expansion caused by charging and discharging, the diaphragm at the portion in contact with the step portion is damaged, thereby increasing the risk of fire due to cracks or short circuits. However, according to an exemplary embodiment of the present invention, the sealing portion 112 is located at the positive electrode edge portion 111, preventing damage to the diaphragm at the step portion of the positive electrode, and providing a stable buffering effect, so that cracks and short circuits caused by repeated contraction and expansion at the positive terminal portion where the stress is high can be prevented, thereby reducing the risk of fire.

[0086] Figure 5 is a cross-sectional view showing a portion of a secondary battery 1 including an electrode assembly 100 according to an exemplary embodiment of the present invention.

[0087] The battery housing 200 may have a columnar structure in which a space is formed. The battery housing 200 may accommodate an electrode assembly 100 including an electrode and a separator and an electrolyte solution (not shown) in the internal space. The battery housing 200 may have a structure in which one side is open (hereinafter referred to as an opening portion) and the other side is sealed. Here, one side and the other side of the battery housing 200 refer to the ends located at the upper and lower parts along the gravity direction or the central axis of the battery housing 200.

[0088] The upper side surface of the opening of the battery case 200 may be provided with a press edge portion 210 folded toward the center of the secondary battery 1. The battery case 200 may be provided with a curling portion 220 above the press edge portion 210. That is, the curling portion 220 may be located at the uppermost side of the battery case 200. Here, the upper portion refers to an area from the center of the battery case 200 toward the opening portion.

[0089] The battery case 200 may be made of a lightweight conductive metal material such as aluminum or an aluminum alloy.

[0090] The cap assembly 300 may be coupled to the opening surface of the battery case 200 , and may include a top cap 310 , a safety vent 320 , and a current interruption device 330 .

[0091] The top cap 310 is 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 be used as an electrode terminal so that the protruding portion is electrically connected to the outside. For example, the top cap 310 may be used as a positive terminal.

[0092] The top cap 310 may be coupled with a sealing gasket 340 at an edge of the top cap 310, and the sealing gasket 340 may be located inside the curling portion 220 of the battery case 200. The sealing gasket 340 may increase a sealing force between the top cap 310 and the battery case 200.

[0093] The top cap 310 may include a protruding portion protruding upward, an edge portion contacting and coupled to the sealing gasket 340 , and a first connection portion connecting the protruding portion and the edge portion.

[0094] The safety vent 320 is located below the top cap 310 and may be electrically connected to the top cap 310. At least a portion of a 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 be in contact with the top cap 310 for a certain length from an end thereof, and a portion other than the contact length may be located at a predetermined distance from the top cap 310. The portion of the safety vent 320 in contact with the top cap 310 may be coupled to the sealing gasket 340.

[0095] The spacing distance between the safety vent 320 and the top cap 310 may increase from the area in contact with the top cap 310 toward the center of the safety vent 320 .

[0096] The safety vent 320 may include a contact portion contacting the top cap 310, a central portion located at the center of the safety vent 320 and contacting the current interruption device, and a second connection portion connecting the contact portion and the central portion. The safety vent 320 may be provided with a bent portion (or notch) at portions where the contact portion contacts the second connection portion and where the second connection portion contacts the central portion.

[0097] In an exemplary embodiment, the safety vent 320 may have an end portion perpendicular to the axial direction of the battery case 200. In this case, the top cap 310 may be disposed perpendicular to the axial direction of the battery case 200 like the safety vent 320. That is, the safety vent 320 and the top cap 310 may be placed horizontally.

[0098] In another exemplary embodiment, the safety vent 320 may have an end portion bent to surround the outer circumferential surface of the top cap 310 .

[0099] In the secondary battery 1 according to the present invention, as the electrode assembly 100 accommodated inside the battery case 200 reacts with the electrolyte solution to generate gas or generate heat, the internal pressure increases.

[0100] When the internal pressure of the secondary battery 1 increases, the safety vent 320 receives a force in the direction of the top cap 310 , and the bent portion is broken, causing the gas inside the secondary battery 1 to be discharged.

[0101] A current interrupt device (CID) 330 is located below the safety vent 320 , and at least a portion thereof may be connected to the safety vent 320 .

[0102] When the safety vent 320 is ruptured as the internal pressure of the secondary battery 1 increases, the current interrupt device 330 is separated from the safety vent 320 to interrupt current.

[0103] More specifically, the current interruption device 330 may include a connection portion connected to the safety vent 320 at a central portion and protruding in a direction in which the safety vent 320 is located, an edge portion other than the connection portion, and a coupling portion connecting the connection portion and the edge portion. The coupling portion is provided in plural, and the plural coupling portions may be positioned to be spaced apart from each other.

[0104] When the safety vent 320 is deformed in the direction where the top cap 310 is located, the coupling portion can be disconnected and the connecting portion can be separated from the edge portion. That is, the connecting portion is separated in the direction of the top cap 310 while being connected to the safety vent 320.

[0105] The CID pad 350 surrounds the edge of the current interrupt device 330 , and may electrically separate the safety vent 320 from the edge portion and the connection portion of the coupling portion and the current interrupt device 330 .

[0106] According to an exemplary embodiment of the present invention, there is provided a battery pack including any one of the above-described secondary batteries.

[0107] Regarding the above exemplary embodiments, refer to Figure 6 , a battery pack 3 including a secondary battery 1 in a battery pack casing 2 is shown.

[0108] The battery pack according to the above exemplary embodiment has high output / high capacity.

[0109] According to an exemplary embodiment of the present invention, there is provided a mobile device including the above-mentioned battery pack.

[0110] Regarding the above exemplary embodiments, refer to Figure 7 , a mobile device V including a battery pack 3 is shown.

[0111] Since the mobile device according to the above-described exemplary embodiment uses a battery pack having high output / high capacity, the mobile device is excellent in stability and safety.

[0112] Figure 4 is a flowchart illustrating a method of manufacturing an electrode assembly according to an exemplary embodiment of the present invention.

[0113] The manufacturing method of an electrode assembly according to an exemplary embodiment of the present invention includes: a cutting step (S10) of cutting at least a portion of a positive electrode into a rounded shape, a sealing step (S20) of supplying a sealing member into a sealing groove provided in a pair of sealing devices, positioning an end of the positive electrode in the sealing groove and sealing the end to form a sealing portion, a cooling step (S30) of fixing the shape of the sealing portion by pressing the sealing portion in the longitudinal direction of the positive electrode with a pair of pressure rollers and cooling the sealing portion, and a step of manufacturing an electrode assembly by winding the positive electrode, a separator and a negative electrode.

[0114] The cutting step (S10) is a step of cutting the positive electrode so that no angular shape exists based on the plane of the positive electrode. In the cutting step (S10), the winding start portion of the positive electrode (i.e., the corner of the positive electrode edge portion) is cut and rounded to disperse the stress applied to the positive electrode edge portion due to the contraction and expansion of the electrode assembly over the entire surface of the positive terminal portion, thereby preventing the separator from being damaged and cracks from being generated in the negative electrode due to the positive terminal portion.

[0115] In the cutting step (S10), at least one of the two corners located at the positive terminal end may be cut into a chamfer having a predetermined radius of curvature. In addition, the cutting step (S10) may include cutting the end of the positive electrode into any one of a convex circle, a V-shape, a multi-convex circle, an inclined shape, and a concave circle. For example, in the cutting step (S10), the end of the positive electrode may be cut into a convex circle, and then at least one of the angular corners may be cut into a chamfer.

[0116] In the sealing step (S20), at least one of the pair of sealing devices may be provided with a sealing groove. The sealing device includes a first sealing device facing one surface of the positive electrode and a second sealing device facing the other surface of the positive electrode, and the sealing groove may be formed in the first sealing device, in the second sealing device, or in the first sealing device and the second sealing device.

[0117] In an exemplary embodiment, the sealing groove may be formed in a rectangular shape and may have the same width as that of the positive electrode or 0.5 mm to 1 mm wider than that of the positive electrode and a length greater than 0 mm and less than or equal to 5 mm.

[0118] In another exemplary embodiment, the sealing groove may be rounded at positions corresponding to two corners of the positive electrode edge portion, and in yet another exemplary embodiment, the sealing groove may be formed in any one of convex, V-shaped, multi-convex, inclined, and concave shapes.

[0119] The sealing step (S20) may include heating the sealing device; positioning the end of the positive electrode in the sealing groove, pressing it with a pair of sealing devices, and supplying a sealing member to the sealing groove; and lowering the temperature of the sealing device to cool the sealing member.

[0120] The sealing device may include a sealing member supplying unit which supplies the sealing member to the sealing groove from the outside.

[0121] In the step of heating the sealing device, the temperature of the sealing device may be heated to 150° C. or higher. In an exemplary embodiment, the sealing member may include polypropylene (PP), and the sealing device may maintain a temperature equal to or higher than a melting point of polypropylene so that the polypropylene remains liquid and can move along the sealing member supply unit to the sealing groove.

[0122] In the step of supplying the sealing member to the sealing groove, the sealing member supply time can be 5 seconds or shorter. When the sealing member supply time is 5 seconds or shorter, a sealing portion can be formed at the positive terminal without damaging the positive electrode. In other words, if the sealing member supply time exceeds 5 seconds, the problem of the positive electrode being damaged by the high temperature sealing member may occur. Preferably, the sealing member supply time can be 2 seconds or shorter.

[0123] The step of cooling the sealing member is a step of preliminarily cooling the sealing member, and is a step of solidifying the sealing member by cooling the sealing member.

[0124] The cooling step ( S30 ) is a step of completely cooling the preliminarily cooled sealing member to determine the shape of the sealing portion and to flatten the outer surface of the sealing portion to minimize the roughness of the sealing portion.

[0125] When the pair of pressure rollers cooled in the cooling step (S30) are pressed in the longitudinal direction of the positive electrode, the pressure in the positive electrode can be increased in the front end direction of the positive terminal. The pressure of the pair of pressure rollers can be gradually or stepwise increased, preferably gradually increased, so that the two surfaces of the sealing portion form a predetermined angle with the two surfaces of the positive electrode.

[0126] The temperature of the pair of pressure rollers may be 150°C or lower. Preferably, the temperature of the pair of pressure rollers may be 70°C to 130°C, more preferably 90°C to 100°C. When the temperature of the pressure roller satisfies the above range, the sealing member is completely cooled, so even if a force is applied to the sealing portion due to expansion and contraction of the electrode assembly or external pressure, the shape of the cooled portion is not deformed. That is, if the temperature of the pressure roller exceeds 150°C, the sealing member is not sufficiently cooled, and when pressure is applied to the sealing portion, the shape of the sealing portion is deformed, which may cause stress concentration in the sealing portion.

[0127] The pressing force of the pair of pressure rollers may be 1kg / cm to 15kg / cm. Specifically, when the pair of pressure rollers press the sealing members or sealing portions located on one surface and the other surface of the positive electrode, the pressing force may be 5kg / cm to 10kg / cm, and when the pressure rollers press the sealing members or sealing portions located at the front end portion of the positive electrode, the pressing force may be 5kg / cm to 10kg / cm. When the pressing force of the pressure rollers satisfies the above range, the positive electrode and the positive electrode active material will not be damaged by the pressing force of the pressure rollers, and the sealing portion will not affect the size of the electrode assembly.

[0128] The pressing force of the pair of pressure rollers can be adjusted by applying pressure to the pressure rollers from the outside, or by the distance between the pair of pressure rollers.

[0129] In an exemplary embodiment, when the thickness of the sealing member before cooling is 100%, the thickness of the sealing member (i.e., the sealing portion) after cooling can be reduced to 35% or less. For example, when the electrode thickness is 100 μm and the thickness of the sealing member is 15 μm, the thickness of the sealing portion can be reduced to 5 μm.

[0130] The time during which the pair of pressure rollers press the sealing member or the sealing portion may be 0.5 seconds to 5 seconds.

[0131] The method of manufacturing an electrode assembly according to an exemplary embodiment of the present invention may further include the step of cutting an end of a sealing portion located at a front end of the positive electrode. In this case, the end of the sealing portion may be cut into the same shape as the positive terminal.

[0132] Although the present invention has been described with reference to preferred exemplary embodiments, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the technical spirit and scope of the present invention.

Claims

1. A core-wound electrode assembly, in which a positive electrode, a separator and a negative electrode are wound, in, The positive electrode includes a positive electrode edge portion adjacent to a winding center portion and a sealing portion surrounding the positive electrode edge portion, and Wherein, the positive electrode edge portion and the sealing portion each have at least a portion that is rounded.

2. The electrode assembly according to claim 1, wherein: The end of the positive electrode edge portion has any one of a convex circle, a V-shape, a multi-convex circle, an inclined shape, and a concave circle, and Wherein, both the V-shape and the inclined shape have rounded corners.

3. The electrode assembly according to claim 1, wherein: The positive electrode edge portion has a length greater than 0 mm and less than or equal to 10 mm at an end portion adjacent to the winding center portion of the positive electrode.

4. The electrode assembly according to claim 1, wherein: The end portion of the sealing portion is set to have the same shape as the end portion of the positive electrode edge portion.

5. The electrode assembly according to claim 1, wherein: The sealing portion decreases in thickness toward the winding center portion.

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

7. The electrode assembly according to claim 6, wherein: The length of the sealing portion is greater than 0 mm and less than or equal to 5 mm.

8. A secondary battery, comprising: The electrode assembly according to any one of claims 1 to 7; a battery case having an opening on one surface and configured to accommodate the electrode assembly; as well as A cap assembly is coupled to the open surface of the battery case.

9. A battery pack comprising the secondary battery according to claim 8. 10 . A mobile device comprising the battery pack according to claim 9 .

11. A method for manufacturing a jellyroll-type electrode assembly, in which a positive electrode, a separator and a negative electrode are wound, the method for manufacturing a jellyroll-type electrode assembly comprising the following steps: a cutting step of cutting at least a portion of the positive electrode into a circular shape; a sealing step of supplying a sealing member to a sealing groove provided in a pair of sealing devices, positioning an end portion of the positive electrode in the sealing groove, and sealing the end portion to form a sealing portion; a cooling step of fixing the shape of the sealing portion by pressing the sealing portion in the longitudinal direction of the positive electrode with a pair of pressure rollers and cooling the sealing portion; and The step of manufacturing the electrode assembly by winding a positive electrode, a separator, and a negative electrode.

12. The method for manufacturing a jellyroll-type electrode assembly according to claim 11, wherein: The sealing step comprises the following steps: heating the sealing device; positioning the end of the positive electrode in the sealing groove, pressing the end of the positive electrode with a pair of the sealing devices, and supplying the sealing member to the sealing groove; and lowering the temperature of the sealing device to cool the sealing member.

13. The method for manufacturing a jellyroll-type electrode assembly according to claim 12, wherein: In the step of heating the sealing device, the sealing device is heated to a temperature of 150° C. or higher.

14. The method for manufacturing a jellyroll-type electrode assembly according to claim 11, wherein: The cutting step comprises the following steps: The end portion of the positive electrode is cut into any one of a convex shape, a V shape, a multi-convex shape, an inclined shape, and a concave shape.

15. The method for manufacturing a jellyroll-type electrode assembly according to claim 11, wherein: The pressure roller applies pressure in the longitudinal direction of the positive electrode.

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