Welding device, welding method using the same, and electrode assembly manufactured by the welding method

Abstract

To provide a welding device, a welding method, and an electrode assembly that are capable of reducing tensile force to be applied to an electrode tab during a pre-welding process for forming an electrode tab bundle.SOLUTION: A welding device includes an electrode assembly 100 in which a plurality of positive electrodes 110 and a plurality of negative electrodes 120 are stacked with separators 130 interposed therebetween, a guide for reducing the tensile force of an electrode tab 111 protruding from the electrode assembly, a lower welding portion disposed at a lower portion of the electrode tab, and an upper welding portion disposed at an upper portion of the electrode tab. The guide includes a first guide 210 located at the upper portion of the electrode tab, and a second guide 220 located at the lower portion of the electrode tab, and the first guide and the second guide are configured to move to be closer to or farther from each other. The first guide and the second guide include a rotating portion having a roller shape, and the rotating portions of the first guide and the second guide rotate in a direction in which the electrode tab is pressed toward the electrode assembly such that the electrode tab is in a loose state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2021-0002822 dated January 8, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a welding apparatus, a welding method using the same, and an electrode assembly manufactured by the welding method. More specifically, the present invention relates to a welding apparatus for aligning electrode tabs in a stacked electrode assembly so as to reduce tensile force applied to the electrode tabs and welding the electrode tabs, a welding method using the same, and an electrode assembly manufactured by the welding method. [Background technology]

[0003] In order to prevent the problem of environmental pollution from accelerating with the use of fossil fuels, intensive research is being carried out to replace energy sources with atomic, solar, hydroelectric, wind, and other energy sources.

[0004] Secondary batteries have been proposed as an energy source that can replace fossil fuels. The secondary batteries can be used repeatedly through continuous charging and discharging, and have the advantage of being able to significantly reduce carbon dioxide emissions.

[0005] In addition, the secondary battery can be used as a power storage means in an energy storage system (EES), which can store idle power produced by solar, hydroelectric, wind, etc. and use the stored energy in the event of an overload, optimizing power management.

[0006] Among the secondary batteries, lithium secondary batteries are lightweight, have high energy density, and can be used as a high-output energy source, and thus the demand for them is increasing.

[0007] The lithium secondary battery is charged and discharged during the process in which lithium ions transferred from the positive electrode are reversibly inserted into and extracted from the negative electrode, and an electrode assembly is formed by stacking the positive electrode and the negative electrode with a separator interposed therebetween.

[0008] The electrode assembly is housed in a battery case together with an electrolyte to form a lithium secondary battery. Depending on the shape of the battery case, it can be classified into a pouch-type battery cell made of a laminate sheet including a resin layer and a metal layer, a prismatic battery cell including a prismatic or cylindrical battery case made of a metal material, or a cylindrical battery cell. Among these, the pouch-type battery cell is used as an energy source for various devices due to its characteristics of being easily deformed and having a high energy density.

[0009] The electrode assembly may be configured to have a stacked form with a separator interposed between one or more positive electrodes and one or more negative electrodes, and the positive electrode and the negative electrode may include a positive electrode tab and a negative electrode tab protruding outward.

[0010] The process of welding the protruding electrode tabs is called pre-welding. An electrode tab bundle is formed through the pre-welding process, and an electrode lead can be coupled to the electrode tab bundle to be used as an electrode terminal.

[0011] If welding is performed in a state where the electrode tabs are stretched taut during the process of aligning the electrode tabs to form the electrode tab bundle, the electrode tabs may easily break even if a small impact is applied to the electrode tabs.

[0012] Therefore, various attempts have been made to develop technology to improve the safety of the electrode tabs.

[0013] In this regard, Patent Document 1 discloses a method for manufacturing an electrode assembly, which includes a loading process in which, prior to a pre-welding process in which electrode tabs are gathered and welded, a pair of rods are positioned on the electrode assembly side at a welding portion where the electrode tabs are to be welded, and the pair of rods are moved in a direction facing each other to bring the pair of rods into close contact with both sides of the electrode tabs. However, Patent Document 1 uses a pair of rods for the purpose of preventing dust generated during welding in the pre-welding process from moving to the electrode assembly.

[0014] Furthermore, in the loading process of Patent Document 1, a tensile force may be applied in the direction in which the electrode tab extends, which may compromise the safety of the electrode tab.

[0015] Patent Document 2 discloses a method for manufacturing a battery cell, including the steps of preparing an electrode assembly having an electrode plate on which an electrode tab is formed, vertically crimping the electrode tab with a guide jig at a point that is separated from an end of the electrode assembly by a distance within 1 / 5 of the thickness of the electrode assembly, and pre-welding the electrode tab crimped by the guide jig to form a weld at a portion adjacent to the portion where the guide jig is located.

[0016] Patent Document 2 includes a process of crimping the electrode tab using a guide jig in a step prior to prewelding, but this process is for effectively reducing the dead space of the electrode tab welded portion and does not disclose a process for preventing damage to the electrode tab.

[0017] Therefore, there is a strong need for a technology that can reduce the tensile force applied to the electrode tabs during the pre-welding process for forming the electrode tab bundle. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] Korean Patent Publication No. 2020-0105272 [Patent Document 2] Korean Patent Publication No. 2018-0072065 Summary of the Invention [Problem to be solved by the invention]

[0019] The present invention has been made to solve the above problems, and has an object to provide a welding device that can deform the electrode tabs to a loose state in an electrode assembly in which electrode tabs are welded to form an electrode tab bundle, thereby forming a welded portion in a state in which the length of the electrode tabs extending to the welded portion is increased, a welding method using the same, and an electrode assembly manufactured by the welding method. [Means for solving the problem]

[0020] To achieve the above object, the present invention provides a welding apparatus for manufacturing an electrode assembly, the apparatus including: an electrode assembly including a plurality of positive electrodes and a plurality of negative electrodes stacked with separators interposed between them; a guide for reducing a tensile force of an electrode tab protruding from the electrode assembly; a lower welding part disposed under the electrode tab; and an upper welding part disposed over the electrode tab.

[0021] The lower weld portion may be an anvil on which the electrode tab is placed, and the upper weld portion may be a horn that applies ultrasonic waves to the electrode tabs disposed on the anvil.

[0022] The lower weld and the upper weld correspond to a single welding means, which can be any welding means for joining conventional electrode tabs, such as ultrasonic welding, which corresponds to friction welding, electron beam welding, laser welding, etc.

[0023] The guides include a first guide positioned above the electrode tabs and a second guide positioned below the electrode tabs, and the first guide and the second guide can be moved closer to or farther away from each other.

[0024] The first guide and the second guide may include a rotating portion having a roller shape or a curved portion having a curved surface, and a rotation axis of the rotating portion may be parallel to a width of the electrode tab.

[0025] The first guide and the second guide may further include a body portion having one side end to which the rotating portion or the curved portion is coupled.

[0026] The body portion may include a bending portion, and the body portion may be bent about the bending portion or rotated about a rotation axis of the bending portion.

[0027] The rotating portion of the first guide and the rotating portion of the second guide may rotate in opposite directions to each other so that the electrode tabs can be pushed toward the electrode assembly.

[0028] The rotational force of the rotating part can be imparted by a repulsive force due to a magnetic field, or can also be imparted by the rotation of a motor.

[0029] Welding by the upper and lower weld portions can be started with the electrode tabs aligned by the guide, and ultrasonic waves can be applied to the horn with the electrode tabs aligned by the guide.

[0030] The present invention also provides a welding method using the welding apparatus, comprising the steps of: (a) preparing an electrode assembly; (b) using a guide to push an electrode tab toward the electrode assembly while closely contacting the electrode tab; and (c) disposing a welding portion of the electrode tab between the upper weld portion and the lower weld portion and welding the electrode tab, the guide including a first guide positioned above the electrode tab and a second guide positioned below the electrode tab.

[0031] Meanwhile, between steps (b) and (c), a step of removing the outer portion of the welded portion from the electrode tab can be added.

[0032] The step (b) may be performed by pushing the electrode tab toward the electrode assembly while the first guide and the second guide are moved toward each other.

[0033] The step (b) may be performed by pushing the electrode tab toward the electrode assembly while the first guide and the second guide are moved toward each other.

[0034] The rotating portion of the first guide and the rotating portion of the second guide may rotate in opposite directions to each other so that the electrode tabs can be pushed toward the electrode assembly.

[0035] Step (b) allows the electrode tabs to be aligned in a loose state.

[0036] The present invention also provides an electrode assembly manufactured by the above welding method.

[0037] According to the present invention, there is provided an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are stacked with separators interposed between them, and the plurality of positive electrodes and the plurality of negative electrodes include electrode tabs protruding outward, and each of the electrode tabs includes a first point connected to an electrode plate and a second point at which a welding portion that connects the electrode tabs to form a bundle begins, and a length of the electrode tab from the first point to the second point may be greater than a minimum length between the first point and the second point.

[0038] The length of the electrode tab from the first point to the second point may be greater than 0 mm and less than 2 mm greater than the minimum length between the first point and the second point, or greater than 0.0% and less than 14.3% greater than the minimum length between the first point and the second point.

[0039] Furthermore, the present invention can also be provided in the form of a combination of various means for solving the above problems. Effect of the Invention

[0040] As described above, the present invention aligns the electrode tabs using the guide, so that pre-welding can be performed with low tensile force on the electrode tabs.

[0041] Since pre-welding is performed in a state in which the electrode tabs are loosened by the guide, it is possible to prevent or delay the electrode tabs from becoming taut even if the thickness of the electrode assembly changes due to charging and discharging.

[0042] In addition, in the present invention, by deriving the difference in the length of the extending electrode tabs, the electrode tabs are prevented from being bent or broken.

[0043] In addition, even if an external force is applied to the electrode tab and the electrode tab is deformed, the electrode tab can have a sufficient length until it is broken.

[0044] In this way, the length of the electrode tab extending from the electrode to the welding portion can be increased, so that the electrode tab can be prevented from breaking and causing disconnection. [Brief description of the drawings]

[0045] [Figure 1] 1 is a side view of an electrode assembly and welding apparatus according to the present invention; [Diagram 2] FIG. 2 is a perspective view of a guide according to the first embodiment. [Diagram 3] FIG. 11 is a perspective view of a guide according to a second embodiment. [Figure 4] FIG. 11 is a perspective view of a guide according to a third embodiment. [Diagram 5] FIG. 13 is a perspective view of a guide according to a fourth embodiment. [Figure 6] 1 is a diagram showing an example of a procedure of a welding method according to the present invention. [Figure 7] 6A to 6C are diagrams showing another example of the procedure of the welding method according to the present invention. [Figure 8] 13 is a side view showing a process of pushing an electrode tab toward an electrode assembly with the guide moved closer; FIG. [Figure 9] 13 is a side view showing a process in which the electrode tab is pushed toward the electrode assembly while the guide is moved closer; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, which are provided to enable a person having ordinary skill in the art to which the present invention pertains to easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0047] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only the case where the part is directly connected to another part, but also the case where the part is indirectly connected via another element between the two parts. In addition, when a part includes a certain component, it does not mean that the other component is excluded, but that the part may further include the other component, unless otherwise specified.

[0048] Furthermore, descriptions that limit or add specific elements are applicable to all inventions and are not limited to a particular invention unless otherwise specified.

[0049] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0050] In addition, throughout the description of the present invention and the claims, unless otherwise specified, "or" includes "and." Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0051] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0052] FIG. 1 is a side view of an electrode assembly and welding apparatus according to the present invention.

[0053] Referring to FIG. 1, the welding apparatus according to the present invention is a welding apparatus for manufacturing an electrode assembly, and can be used to arrange a plurality of electrode tabs so as to overlap each other in the thickness direction and weld the electrode tabs into a single electrode tab bundle.

[0054] In particular, the welding device may include an electrode assembly 100 in which a plurality of positive electrodes 110 and a plurality of negative electrodes 120 are stacked with a separator 130 interposed therebetween, guides 210, 220 for reducing the tensile force of a positive electrode tab 111 and a negative electrode tab protruding from the electrode assembly 100, an anvil 310 on which the electrode tabs are disposed, and a horn 320 for applying ultrasonic waves to the electrode tabs disposed on the anvil 310.

[0055] The guides 210 and 220 include a first guide 210 located on the upper portion of the electrode tab and a second guide 220 located on the lower portion of the electrode tab, and the first guide 210 and the second guide 220 can each move in a vertical direction, so that they can move closer to or farther away from each other.

[0056] When the first guide 210 and the second guide 220 move toward the electrode tabs to minimize the gap between them, they rotate in a direction that pushes the electrode tabs toward the electrode assembly, so that the first guide 210 and the second guide 220 rotate in opposite directions.

[0057] Specifically, when the electrode assembly is located on the left side and the electrode tab is located on the right side as shown in FIG. 1, the first guide 210 rotates clockwise and the second guide 220 rotates counterclockwise to push the electrode tab toward the electrode assembly.

[0058] Alternatively, when the electrode assembly is located on the right side and the electrode tab is located on the left side, the first guide 210 rotates counterclockwise and the second guide 220 rotates clockwise to push the electrode tab toward the electrode assembly.

[0059] When the electrode tab is pushed toward the electrode assembly, the electrode tab becomes loose. In this state where the electrode tab is aligned by the guide, the electrode tab is placed between the horn and the anvil, and ultrasonic waves are applied to the horn to perform pre-welding.

[0060] 1 only describes a positive electrode tab 111, the welding apparatus according to the present invention, the welding method using the same, and the electrode assembly manufactured by the welding method are similarly applicable to a negative electrode tab. Furthermore, while Fig. 1 describes ultrasonic welding using an anvil 310 and a horn 320, the present invention can be applied to all conventional means for joining electrode tabs, such as ultrasonic welding equivalent to friction welding, electron beam welding, laser welding, and the like.

[0061] The positive electrode 110 has positive electrode tabs 111 protruding toward one side, and the negative electrode 120 has negative electrode tabs protruding in the opposite direction to the positive electrode tabs 111 or protruding in the same direction as the positive electrode tabs; however, the drawings in this specification omit the negative electrode tabs for ease of explanation.

[0062] The description of the positive electrode tab described in this specification can be applied to the alignment of the negative electrode tab, securing the length of the negative electrode tab using a guide, and welding. In addition, multiple positive electrode tabs and multiple negative electrode tabs can protrude from one positive electrode laminate and one negative electrode laminate. The description of the positive electrode tab described in this specification can be applied to this as well.

[0063] The positive electrode tabs 111 may be formed at the same position on a plurality of positive electrodes and aligned to overlap in the thickness direction. Before the overlapped positive electrode tabs 111 are coupled to a positive electrode lead, a pre-welding process is performed to combine the positive electrode tabs into a positive electrode tab bundle.

[0064] 1, since only one welding portion 140 for the pre-welding is formed at the center of the electrode assembly 100 in the height direction h, the electrode tabs of the electrodes located at the top and bottom ends have the longest distances to the welding portion 140. In addition, if pre-welding is performed in a taut state, these outermost electrode tabs may easily break.

[0065] In addition, as the electrode assembly 100 expands during charging and discharging, the outermost electrode tabs become more taut as the distance to the welding portion 140 increases, so that the outermost electrode tabs are at high risk of being damaged.

[0066] Alternatively, if the connection between the electrode tab bundle and the electrode lead moves away from the electrode of the electrode assembly during use of the battery cell, all of the electrode tabs may become taut, increasing the risk of breakage.

[0067] The position of the welded portion in the electrode tab bundle according to the present invention includes not only the case where the welded portion is formed at the center portion in the height direction of the electrode assembly as in the electrode assembly shown in FIG. 1, but also the case where the welded portion is formed at the upper or lower end in the height direction of the electrode assembly, or where two or more electrode tab bundles are formed.

[0068] Specifically, when a welded portion is formed at the upper end of the electrode assembly in the height direction (y direction), the length of the electrode tabs may increase from the upper end to the lower end of the electrode assembly, and when a welded portion is formed at the lower end of the electrode assembly in the height direction (y direction), the length of the electrode tabs may decrease from the upper end to the lower end of the electrode assembly. However, regardless of the length of the electrode tabs, the tensile force of the electrode tabs located at the uppermost and lowermost ends of the electrode assembly may increase the most, and a shorter electrode tab may exert a greater tensile force than a longer electrode tab.

[0069] Therefore, the present invention provides a welding apparatus and a welding method in which the electrode tabs are arranged to overlap using a guide, and a first point 115 of the electrode tab where the electrode tab and the electrode plate are connected and a second point 116 of the electrode tab where the welding portion 140 begins are aligned in a loose state, and then pre-welding is performed.

[0070] In an electrode assembly manufactured using such welding equipment and welding method, the length of the electrode tab from the first point 115 to the second point 116 may be longer than the minimum length connecting the first point 115 and the second point 116.

[0071] The present invention recognizes that if the electrode tab is extended too much, the electrode tab may be joined during assembly, which may result in defects such as disconnection. As can be understood from the following examples, the length of the electrode tab from the first point to the second point may be greater than 0 mm and less than 2 mm longer than the minimum length between the first point and the second point, or greater than 0.0% and less than 14.3% of the minimum length between the first point and the second point.

[0072] FIG. 2 shows a perspective view of a guide according to a first embodiment.

[0073] 2, an electrode tab is disposed between a first guide 210 and a second guide 220. Although FIG. 2 shows one positive electrode 110 and positive electrode tab 111 for ease of explanation, the first guide 210 and second guide 220 may be disposed in a state in which they sandwich a plurality of electrode tabs protruding from the electrode assembly as shown in FIG.

[0074] The first guide 210 and the second guide 220 each include a roller-shaped rotating portion, and a rotation axis 230 of the rotating portion is disposed parallel to the width W of the electrode tab, which is parallel to the y-axis with reference to FIG.

[0075] The first guide 210 rotates clockwise, and the second guide 220 rotates counterclockwise, pushing the positive electrode tab 111 toward the positive electrode 110.

[0076] The first guide and the second guide according to the present invention may include a rotating portion having a roller shape or a curved portion having a curved surface. Figures 1 to 6, 8 and 9 show the rotating portion, and Figure 7 shows the curved portion. In the case of the curved portion, there is no separate roller, and the curved portion is provided at the end of the bent portion.

[0077] FIG. 3 is a perspective view of a guide according to the second embodiment.

[0078] Referring to FIG. 3, a first guide 410 and a second guide 420 can be moved up and down independently to move closer to or farther from each other, and rotating parts 411 and 421 that push the electrode tabs toward the electrodes are coupled to main body parts 412 and 422.

[0079] That is, a driving unit may be added to the body parts 412 and 422 so that the first guide 410 and the second guide 420 can move in the vertical direction, and a rotating unit 411 and 421 may be coupled to one end of the body parts 412 and 422 in a direction to contact the electrode tab.

[0080] As shown in FIG. 3, in the configuration in which the rotating part is coupled to the substantially rectangular parallelepiped main body, the rotating part can be rotated in a state in which the rotating part is pressed more strongly toward the electrode tab.

[0081] FIG. 4 shows a perspective view of a guide according to a third embodiment.

[0082] Referring to FIG. 4, the guides include a first guide 510 and a second guide 520 .

[0083] The first guide 510 and the second guide 520 include main body portions 512, 522 and rotating portions 511, 521, and the main body portions 512, 522 are bent.

[0084] Specifically, when the first guide 510 and the second guide 520 move closer to each other toward the electrode tab bundle, the main body portions 512, 522 may have a straight line shape in a side view, and after the main body portions 512, 522 come into contact with the electrode tab bundle, the main body portions 512a, 522a including the rotating portions 511, 521 may rotate in the direction of the arrow based on the rotation axis at the bent portions 513, 523.

[0085] In this way, the rotating part presses the electrode tab and deforms the electrode tab to be loose, so that the electrode tab is pressed in the direction opposite to the welded part, thereby making it possible to secure a longer length between the first point of the electrode tab and the second point of the electrode tab.

[0086] In addition, when the main body portion is bent, the rotation angle and rotation speed of the first guide and the second guide can be individually controlled depending on the position where the weld is formed in the height direction of the electrode assembly, and the use of the electrode assembly does not need to be limited to a specific shape.

[0087] In addition to the rotational movement of the rotating part, the electrode tabs can also be pushed toward the electrodes by the rotation of the main body after coming into contact with the electrode tab bundle, so a synergistic effect can be expected in deforming the electrode tabs into a loose state.

[0088] In one specific example, the guide has a shape in which a portion that contacts the electrode tab bundle does not rotate, and a bent portion is formed in the main body portion, and the guide can be rotatable based on a rotation axis of the bent portion.

[0089] Specifically, the guide includes a first guide and a second guide, and the first guide and the second guide, which are linear in side view, move toward the electrode tab bundle in a direction approaching each other, and a portion of a main body of the first guide and the second guide that comes into contact with the electrode tab bundle can rotate toward the electrode assembly based on a rotation axis of the bent portion, thereby pushing the electrode tab bundle toward the electrode assembly.

[0090] 4, the rotational force of main body parts 512a and 522a including the rotating parts can be imparted by the repulsive force of a magnetic field. That is, magnetic fields of the same polarity are formed between main body part 512a to which rotating part 511 is joined in the first guide and main body part 522a to which rotating part 521 is joined in the second guide, and the repulsive force generated between them allows them to rotate in the clockwise and counterclockwise directions, respectively.

[0091] Furthermore, in the guide according to the third embodiment, the main body parts 512a and 522a to which the rotating parts are coupled can rotate not only leftward at a positive angle but also rightward at a negative angle based on the main body parts 512b and 522b.

[0092] Therefore, when the rotating parts 511, 521 come into contact with the electrode tab bundle while the main body parts 512a, 522a are rotated at a negative angle, the main body parts 512a, 522a rotate at a positive angle, and the rotating part 511 rotates clockwise and the rotating part 521 rotates counterclockwise, thereby pushing the electrode tabs toward the electrode assembly.

[0093] FIG. 5 is a perspective view of a guide according to the fourth embodiment.

[0094] Referring to FIG. 5, the guides include a first guide 610 and a second guide 620 .

[0095] The first guide 610 and the second guide 620 include main body portions 612 and 622 and rotating portions 611 and 621 , and the main body portions 612 and 622 include bending portions 613 and 623 .

[0096] The body parts 612 and 622 are bent at the bending parts 613 and 623 so that the inner angle r formed by bending is less than 90 degrees. The first guide 610 and the second guide 620 are disposed between the electrode assembly from which the electrode tabs extend and the welding portion, so that the body parts and the rotating part bent at the bending parts are disposed to face the electrode assembly.

[0097] In this manner, when a guide including a bent portion is used, the rotating portion starts to rotate as soon as the rotating portions 611, 621 come into contact with the electrode tab bundle, and the electrode tabs can be pushed toward the electrode assembly. Also, compared to the guide shown in Fig. 3 including a linear body in side view, the electrode tab bundle can be moved a greater distance toward the electrode assembly.

[0098] The guides shown in Figures 3 to 5 show the case where the guides are applied when the electrode assembly is located on the left side and the electrode tab is located on the right side, and the rotating portion of the first guide rotates clockwise and the rotating portion of the second guide rotates counterclockwise to push the electrode tab toward the electrode.

[0099] In one embodiment, FIG. 6 shows an example of a procedure for a welding method according to the present invention.

[0100] Referring to FIG. 6 , the welding method according to the present invention includes the steps of (a) preparing an electrode assembly 100, (b) pushing a guide toward the electrode assembly 100 while closely contacting the positive electrode tab 111, (c) removing an outer portion of the welding portion 140 from the positive electrode tab 111, and (d) disposing the welding portion 140 of the positive electrode tab 111 between a horn 320 and an anvil 310 and welding the same, and the guide may include a first guide 710 located on an upper portion of the positive electrode tab 111 and a second guide 720 located on a lower portion of the positive electrode tab 111.

[0101] In step (b), the rotating portion of the first guide 710 rotates clockwise and the rotating portion of the second guide 720 rotates counterclockwise to push the electrode tabs toward the electrode assembly, so that the electrode tabs can be deformed from a taut state to a loose state and aligned.

[0102] Fig. 7 shows another example of the procedure of the welding method according to the present invention. It is similar to Fig. 6 except that the first guide 710 and the second guide 720 are replaced with a first guide 810 and a second guide 820 that include a bent portion but no rotating portion. Fig. 7 shows guides with curved portions 811, 821. Due to the inclination of the bent portion and the curved surface of the end portion, even in the case of the curved portions 811, 821 without a rotating portion, the electrode tabs can be deformed from a taut state to a loose state and aligned.

[0103] FIG. 8 is a side view showing a process of pushing the electrode tab toward the electrode assembly with the guide moved closer.

[0104] Referring to FIG. 8, the electrode tab may be pushed toward the electrode assembly while the first guide 210 and the second guide 220 are moved closer to each other.

[0105] That is, the first guide 210 and the second guide 220 move up and down toward the electrode tabs while the rotating part is not rotating, and the rotating part starts to rotate while pressing the electrode tabs.

[0106] FIG. 9 is a side view showing a process in which the electrode tab is pushed toward the electrode assembly while the guide is moving closer.

[0107] Referring to FIG. 9, the step (b) may be performed by pushing the electrode tab toward the electrode assembly while the first guide 210 and the second guide 220 are moved toward each other.

[0108] That is, when the first guide 210 and the second guide 220 come into contact with the outermost electrode tabs, the rotating part starts to rotate, and the rotating part can also rotate during the process of pressing the electrode tabs so that the first guide 210 and the second guide 220 are closest to each other.

[0109] When such a method is used, the effect of deforming the outermost electrode tabs to be loose can be enhanced.

[0110] <Comparison of the effect of extending the outermost tab length> The outermost electrode tab was extended and welded using the welding device for manufacturing an electrode assembly according to the present invention, and then an electrode lead was connected thereto and the resulting product was placed in a pouch case to complete a pouch-type battery.

[0111] The electrode assembly used here was manufactured by stacking unit cells of a positive electrode, a separator, a negative electrode, and a separator. The minimum length of the outermost tab, i.e., the length from the first point 115 to the second point 116, was 14 mm. The increased length of the outermost tab for each case is shown in Table 1 below. The increased length ratio (%) is the increased length (mm) of the outermost tab divided by the length (mm) from the first point 115 to the second point 116.

[0112] In the examples and comparative examples shown in Table 1, CT (Computerized Tomography) images were taken to confirm whether the tabs would break inside the completed pouch-type batteries. An X-ray CT device was used for CT imaging. If the tabs are too long, they may break inside the battery during assembly, which may easily lead to disconnection during the charge / discharge process due to external force during the module or pack assembly process.

[0113] Each of the Examples and Comparative Examples shown in Table 1 was subjected to 1000 charge / discharge cycles at 50°C, and the pouch-type cells were disassembled to check for breakage of the tabs. Each of the Examples and Comparative Examples was charged at a constant current of 0.5C, and after reaching 4.2V, constant voltage charging was performed, and charging was terminated when the current reached 0.05C. Discharging was performed at a constant current of 0.5C until the voltage reached 3V.

[0114] In the case of broken or broken tabs, cases that occurred after performing the test on 10 identical samples are shown in Table 1.

[0115] [Table 1]

[0116] It has been confirmed that when the length of the outermost tab is increased by more than 0 mm but less than 2 mm, or increased by more than 0.0% but less than 14.3% of the minimum length of the outermost tab using the welding apparatus for manufacturing the electrode assembly according to the present invention, the tab does not bend and the tab does not break during use of the battery.

[0117] In Comparative Example 1, the length of the outermost tab was not increased, so no tab breakage occurred, but tab breakage occurred during the battery assembly process or during subsequent use.In Comparative Examples 2 and 3, the outermost tab was increased too much, so tab breakage occurred during assembly, which can cause problems with the long-term safety and performance of the battery.

[0118] Those skilled in the art will appreciate that various applications and modifications within the scope of the present invention are possible based on the above content. [Industrial Applicability]

[0119] The present invention relates to an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are stacked with separators interposed between them, a guide for reducing a tensile force of an electrode tab protruding from the electrode assembly, an anvil on which the electrode tabs are disposed, and a welding apparatus for manufacturing the electrode assembly, the apparatus including a horn for applying ultrasonic waves to the electrode tabs disposed on the anvil, a welding method using the same, and an electrode assembly manufactured by the welding method, and thus is industrially applicable. [Explanation of symbols]

[0120] 100 electrode assembly 110 Positive electrode 111 Positive electrode tab (positive electrode tab) 115 Location 1 116 Location 2 120 negative electrode 130 Separation membrane 140 Welding Part 210, 410, 510, 610, 710, 810 First Guide 220, 420, 520, 620, 720, 820 2nd Guide 811, 821 Curved section 230 Rotational Axis 310 Anvil 320 Horn 411, 421, 511, 521, 611, 621 Rotating part 412, 422, 512, 512a, 512b, 522, 522a, 522b, 612, 622 Main body 513, 523, 613, 623 Bend part

Claims

1. A welding apparatus for manufacturing an electrode assembly, comprising: an electrode assembly including a plurality of positive electrodes and a plurality of negative electrodes stacked with a separator interposed therebetween; a guide for reducing a pulling force of an electrode tab protruding from the electrode assembly; a lower weld portion disposed below the electrode tab; an upper weld portion disposed on top of the electrode tab; 13. A welding apparatus comprising:

2. the lower weld is an anvil; 2. The welding apparatus of claim 1, wherein said upper welding portion is a horn that applies ultrasonic waves to said electrode tab disposed on said anvil.

3. The guide includes a first guide located on an upper portion of the electrode tab and a second guide located on a lower portion of the electrode tab, The welding apparatus of claim 1 or 2, wherein the first guide and the second guide are configured to move toward or away from each other.

4. The first guide and the second guide include a rotating portion having a roller shape or a curved portion having a curved surface, 4. The welding apparatus of claim 3, wherein the axis of rotation of the rotor is parallel to the width of the electrode tab.

5. The welding device according to claim 4 , wherein the first guide and the second guide further include a body portion having one side end to which the rotating portion or the curved surface portion is coupled.

6. The body portion includes a bent portion, The welding device according to claim 5 , wherein the main body portion is bent about the bent portion or is rotatable about a rotation axis of the bent portion.

7. 5. The welding apparatus of claim 4, wherein the rotating portion of the first guide and the rotating portion of the second guide rotate in opposite directions to each other so as to urge the electrode tab toward the electrode assembly.

8. The welding device according to claim 7 , wherein the rotational force of the rotating portion is applied by a repulsive force due to a magnetic field.

9. The welding device according to claim 1 , wherein welding is started by the upper welding portion and the lower welding portion with the electrode tabs aligned by the guide.

10. A welding method using the welding device according to any one of claims 1 to 9, (a) a guide pressing an electrode tab included in an electrode assembly toward the electrode assembly while closely contacting the electrode tab; (b) disposing a welding portion of the electrode tab between the upper weld portion and the lower weld portion and welding the electrode tab; Including, The guide includes a first guide positioned above the electrode tab and a second guide positioned below the electrode tab.

11. The method of claim 10, wherein step (b) is performed by pushing the electrode tab toward the electrode assembly while the first guide and the second guide are moved toward each other.

12. 11. The method of claim 10, wherein step (b) is performed by pushing the electrode tab toward the electrode assembly while the first guide and the second guide are moved toward each other.

13. The welding method according to claim 10, wherein the rotating portion of the first guide and the rotating portion of the second guide rotate in opposite directions to each other so that the electrode tab can be pushed toward the electrode assembly.

14. 14. The method of claim 10, wherein in step (b) the electrode tabs are aligned in a loose condition.

15. An electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are stacked with a separator interposed therebetween, the plurality of positive electrodes and the plurality of negative electrodes each include an electrode tab protruding outwardly; Each of the electrode tabs includes a first point that is coupled to an electrode plate and a second point at which a weld begins that joins the electrode tabs to form a bundle; An electrode assembly, wherein a length of the electrode tab from the first point to the second point is greater than a minimum length between the first point and the second point.

16. 16. The electrode assembly of claim 15, wherein a length of the electrode tab from the first point to the second point is greater than a minimum length between the first point and the second point by more than 0 mm and less than 2 mm, or greater than a minimum length between the first point and the second point by more than 0.0% and less than 14.3%.

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