Electrode assembly and manufacturing method therefor

Abstract

The present invention relates to an electrode assembly in which a plurality of electrodes, in which an electrode foil is coated with an electrode slurry, and separators are repeatedly stacked, and an electrode tab is formed at an end of each of the electrodes. The electrode tabs are characterized by comprising: a tab part which protrudes from the electrode foil and in which a first metal layer, a polymer layer, and a second metal layer are stacked, and one side along the width direction is set as a first region and the other side is set as a second region; a first extension foil of which one end is stacked on one surface among the upper surface and the lower surface of the tab part and is stacked in the first region of the tab part; and a second extension foil of which one end is stacked on the other surface among the upper surface and the lower surface of the tab part and is stacked in the second region of the tab part.

Description

Electrode assembly and method of manufacturing the same

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0172415 filed November 27, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0002] The present invention relates to an electrode assembly and a method for manufacturing the same, and more specifically, to an electrode assembly and a method for manufacturing the same that can be easily joined (welded) with an electrode lead and can reduce the thickness of the portion welded to the electrode lead (i.e., can reduce the thickness of the extension foil welded to the electrode lead).

[0003]

[0004] The demand for secondary batteries as an energy source is rapidly increasing in various fields, including personal mobile devices and electric vehicles.

[0005] While secondary batteries can be classified in various ways depending on the materials of the positive and negative electrodes and their external shape, lithium secondary batteries using lithium compound materials are widely used as a replacement for conventional nickel-cadmium secondary batteries due to their high capacity and low self-discharge rate.

[0006] In addition, the above-mentioned lithium secondary battery can be manufactured in various forms, but it is generally manufactured in typical cylinder, prismatic, and pouch types.

[0007] Among these, the pouch-type secondary battery has a structure in which an electrode assembly is embedded in a pouch, wherein each of the electrode tabs (negative tab and positive tab) of the electrode assembly is gathered and welded together with those having the same polarity, and then additionally welded to their respective electrode leads (negative lead and positive lead). Furthermore, one end of each electrode lead has a structure that protrudes outside the pouch to enable electrical connection with an external device.

[0008] Meanwhile, metallized current collectors are recently being used in electrode foils (positive or negative current collectors) to which electrode slurries (positive or negative slurries) are applied. Unlike conventional electrode foils made of a single material such as aluminum or copper, metallized current collectors used as electrode foils are manufactured in a sandwich structure in which metal layers (made of aluminum or copper) are laminated on both sides with a polymer layer in between.

[0009] The above polymer layer is manufactured based on PET (polyethylene terephthalate), PI (polyimides), PEN (polyethylene naphthalate), etc., and the metal layer is manufactured by thinly coating the surface of the polymer layer through a physical vapor deposition (PVD) process, etc.

[0010] Furthermore, composite current collectors offer higher stability and lighter weight compared to conventional electrode foils made solely of metal, and are therefore being researched and developed as next-generation materials.

[0011] However, since the positive and negative tab portions (positive tab, negative tab) of the above composite current collector used as electrode foils have metal layers (first metal layer, second metal layer) stacked on both sides of the polymer layer (12) respectively and are electrically insulated from each other, as shown in FIG. 1, each tab portion (10) has an extension foil (20) separately bonded to the first metal layer (11) and the second metal layer (13) respectively, and is bonded to the electrode lead (1) while the extension foils (20) are gathered together.

[0012] That is, when the composite current collector is used as an electrode foil according to the conventional method, as shown in FIG. 1, which depicts an extension foil (13) bonded to each of the first metal layer (11) and the second metal layer (12) of the tab portion (10), since there is a structure in which two extension foils (20) are connected per tab portion (10), the possibility of bonding failure occurring (as the number of extension foils increases) was higher, and even if bonding is successful, there was a problem that the resistance of the electrode tab itself (formed by connecting the tab portion and the extension foil) increases.

[0013]

[0014] Accordingly, the primary objective of the present invention is to provide an electrode assembly comprising an electrode tab having a reduced stacking thickness of a first foil and a second foil connected to each of a first metal layer and a second metal layer of an individual tab portion, and a method for manufacturing the same, so as to reduce the possibility of bonding defects (between the tab portion and the extension foils or between the extension foils and the electrode lead) and reduce the problem of increased resistance.

[0015]

[0016] The present invention provides an electrode assembly and a method for manufacturing the same that can achieve the aforementioned objectives.

[0017] The electrode assembly provided in the present invention comprises a plurality of electrodes coated with an electrode slurry on an electrode foil and a separator film that are repeatedly stacked, wherein an electrode tab is formed at the end of the electrode. The electrode tab comprises: a tab portion that protrudes from the electrode foil and has a first metal layer, a polymer layer, and a second metal layer stacked thereon, with one side along the width direction designated as a first region and the other side designated as a second region; a first extension foil, one end of which is stacked on either the upper or lower surface of the tab portion and stacked within the first region of the tab portion; and a second extension foil, one end of which is stacked on the other side of the upper or lower surface of the tab portion and stacked within the second region of the tab portion.

[0018] At this time, when the upper and lower surfaces are projected from the above tab portion, the portion where the first extension foil is stacked and the portion where the second extension foil is stacked do not overlap each other.

[0019] The above tab portions are stacked in multiple layers, and when either the first extension foil or the second extension foil is stacked on the lower surface of the nth layer (n is a natural number greater than or equal to 1) tab portion from bottom to top, the other one is stacked on the upper surface of the nth layer tab portion, and the (n+1)th layer tab portion is stacked on top of it, and on the upper surface of the (n+1)th layer tab portion, the same as the one stacked on the lower surface of the nth layer tab portion is stacked among the first extension foil and the second extension foil.

[0020] The width of the first extension foil and the second extension foil is formed to be 50% or less of the width of the tab portion.

[0021] When the upper and lower surfaces are projected from the n-th layer tab section, the first extension foil and the second extension foil are arranged such that a gap is formed between them.

[0022] Each of the above-mentioned first extension foil and second extension foil is formed to have the same width along the length direction.

[0023] Alternatively, each of the first extension foil and the second extension foil may comprise a tab contact portion formed with a relatively narrow width and laminated to the tab portion; and an extension portion having a relatively larger width than the tab contact portion; and the first extension foil and the second extension foil may be configured to be in contact at the extension portion.

[0024] At this time, the extension portion of the first extension foil and the extension portion of the second extension foil can be stacked alternately.

[0025] In addition, one of the extension portion of the first extension foil and the extension portion of the second extension foil may have a shorter length and the other may have a longer length, and the ones having the longer length among the extension portions of the first extension foil and the second extension foil may be configured to be gathered at the ends.

[0026] In addition, the method for manufacturing an electrode assembly provided in the present invention is a method for manufacturing an electrode assembly in which a plurality of electrodes coated with an electrode slurry on an electrode foil and a separator are repeatedly stacked, and an electrode tab is formed at the end of the electrode, and includes an electrode tab extension step for extending the length of the electrode tab, wherein the electrode tab extension step comprises: a tab portion providing step in which a tab portion is provided that protrudes from the electrode foil and has a first metal layer, a polymer layer, and a second metal layer stacked, and is provided such that one side along the width direction is designated as a first region and the other side is designated as a second region; a first stacking step in which one end of a first extension foil is stacked on either the upper surface or the lower surface within the first region of the tab portion; and a second stacking step in which one end of a second extension foil is stacked on the other side between the upper surface and the lower surface within the second region of the tab portion.

[0027] And, at this time, when the upper and lower surfaces are projected from the above tab portion, the portion where the first extension foil is stacked and the portion where the second extension foil is stacked are stacked so as not to overlap each other.

[0028] In addition, the method further includes a tab portion stacking step of additionally stacking a tab portion such that one of the upper or lower surfaces of either the first extension foil or the second extension foil contacts either of the first extension foil or the second extension foil at the upper or lower side of the tab portion where the first extension foil and the second extension foil are stacked; and an extension foil stacking step of stacking another one of the first extension foil and the second extension foil that is not in contact on the other of the upper or lower surfaces of the additionally stacked tab portion; wherein the tab portion stacking step and the extension foil stacking step are repeated alternately so that the tab portions are stacked to form multiple layers.

[0029] The method includes the step of joining the first extension foils together at the other end of each first extension foil; and the step of joining the second extension foils together at the other end of each second extension foil.

[0030] It includes a joining step of joining the portion where the first extension foil and the second extension foil come into contact in the above tab portion.

[0031]

[0032] The present invention, having the technical features described above, allows the first extension foil and the second extension foil to be divided and laminated along the width direction of the tab portion, thereby reducing the thickness at the point where the first extension foil and the second extension foil are laminated with the tab portion and at the point where the first extension foil and the second extension foil are joined with the electrode lead, which can lower the possibility of a defective bond and suppress an increase in resistance.

[0033] In addition, each of the first extension foil and the second extension foil may include an expanded portion with increased width, and accordingly, the first extension foil and the second extension foil can easily come into contact.

[0034] In addition, one of the extension portion of the first extension foil and the extension portion of the second extension foil has a shorter length and the other has a longer length, and the ones having the longer lengths among the extension portions of the first extension foil and the second extension foil are configured to be gathered at the ends, thereby reducing the thickness of the portion joined to the electrode lead.

[0035]

[0036] FIG. 1 is a drawing illustrating the appearance in which, when a composite current collector is used as an electrode foil according to a conventional method, an extension foil is bonded to each of the first metal layer and the second metal layer of the tab portion, and the extension foils are gathered and bonded to an electrode lead.

[0037] FIG. 2 is a drawing showing a first extension foil and a second extension foil alternately stacked along the stacking direction in a tab portion of an electrode assembly according to an embodiment of the present invention.

[0038] FIG. 3 is a drawing showing views from above looking down of the first extension foil and the second extension foil stacked in each of the first layer tab section and the second layer tab section.

[0039] FIG. 4 is a drawing showing the first extension foil and the second extension foil stacked on the tab portion, spaced apart along the width direction so as not to overlap each other.

[0040] FIG. 5 is a cross-sectional view of part AA in FIG. 4.

[0041] FIG. 6 is a drawing showing the first extension foil and the second extension foil being joined at the tab portion and the laminated portion.

[0042] FIG. 7 is a drawing showing the appearance when an extension portion is formed on each of the first extension foil and the second extension foil.

[0043] FIG. 8 is a drawing showing that the extension portion of the first extension foil has a relatively shorter length, and the extension portion of the second extension foil has a relatively longer length.

[0044] FIG. 9 is a drawing showing a side view when the first extension foil and the second extension foil are laminated in the state of FIG. 8.

[0045] FIG. 10 is a drawing showing that the first extension foil and the second extension foil have the same width as the conventional extension foil (where the tab contact portion is removed and composed only of the extension portion), but the extension portion of the first extension foil has a relatively shorter length and the extension portion of the second extension foil has a relatively longer length.

[0046]

[0047] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0048] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0049] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0050] The present invention relates to an electrode assembly and a method for manufacturing the same, wherein a first extension foil (20) and a second extension foil (30), having a narrower width than a conventional extension foil, are sequentially connected to the tab portion (10) so as to reduce the possibility of poor bonding between the extension foil and the tab portion (10) or between the extension foil and the electrode lead (1) and to improve the problem of increased resistance. Hereinafter, embodiments provided by the present invention will be described in more detail with reference to the attached drawings.

[0051] FIG. 2 is a drawing showing a first extension foil and a second extension foil alternately stacked along the stacking direction in an electrode assembly according to an embodiment of the present invention, FIG. 3 is a drawing showing the state in which the first extension foil and the second extension foil are stacked in each of the first layer tab portion and the second layer tab portion, viewed from above and below, FIG. 4 is a drawing showing the first extension foil and the second extension foil stacked in the tab portion spaced apart along the width direction so as not to overlap each other, and FIG. 5 is a drawing showing a cross-sectional view of the AA portion in FIG. 4.

[0052] And, FIG. 6 is a drawing showing the first extension foil and the second extension foil being joined at the tab portion and the laminated portion, FIG. 7 is a drawing showing the appearance when an extension portion is formed on each of the first extension foil and the second extension foil, and FIG. 8 is a drawing showing the extension portion of the first extension foil having a relatively shorter length and the extension portion of the second extension foil having a relatively longer length.

[0053] In addition, FIG. 9 is a side view showing the stacking of the first extension foil and the second extension foil in the state of FIG. 8, and FIG. 10 is a view showing the first extension foil and the second extension foil having the same width as the conventional extension foil (with the tab contact portion removed and composed only of the extension portion), but with the extension portion of the first extension foil having a relatively shorter length and the extension portion of the second extension foil having a relatively longer length.

[0054]

[0055] First embodiment

[0056] The present invention provides, as a first embodiment, a method for manufacturing an electrode assembly in which a plurality of electrodes (anode, cathode) coated with an electrode slurry on an electrode foil and a separator are repeatedly stacked, and an electrode tab is formed at the end of the electrode.

[0057] The method for manufacturing an electrode assembly provided in this embodiment includes an electrode tab extension step of extending the length of the tab portion (10) and conducting current to the first metal layer (11) and the second metal layer (13).

[0058] Meanwhile, prior to the electrode tab extension step, a step of manufacturing an anode by applying an anode slurry to an anode current collector (anode electrode foil) and manufacturing a cathode by applying a cathode slurry to a cathode current collector (cathode electrode foil), and a step of repeatedly stacking the cathode, separator, and anode (see FIG. 1) are performed.

[0059] At this time, at least one of the positive current collector and the negative current collector (preferably both) is used as an electrode foil, which is a composite current collector in which a first metal layer (11), a polymer layer (12), and a second metal layer (13) are laminated. Then, to allow current to flow to the outside, a portion of the uncoated portion of the electrode foil where the electrode slurry (positive slurry, negative slurry) is not coated is processed into a protruding tab portion (10) to form a part of the electrode tab.

[0060] Since the tab portion configured in this manner (anode tab portion and / or cathode tab portion) has the first metal layer (11) and the second metal layer (13) insulated, the first metal layer (11) and the second metal layer (13) are in an electrically conductive state, and an electrode tab extension step is performed to secure a sufficient length that allows welding with the electrode lead (anode lead and / or cathode lead).

[0061] The above electrode tab extension step includes a tab provision step, a first stacking step, and a second stacking step.

[0062] In the above tab portion provision step, as described above, a tab portion (10) is provided that protrudes from the electrode foil and has a first metal layer (11), a polymer layer (12), and a second metal layer (13) laminated thereon. Then, the tab portion (10) is defined with a first region (I) and a second region (II). That is, as shown in FIG. 4, in this step, the tab portion (10) is divided into two along the width direction at the end where the first extension foil (20) and the second extension foil (30) are laminated, with one side defined as the first region (I) and the other side defined as the second region (II). At this time, the first region (I) and the second region (II) may be defined so as to be in contact with each other on the boundary line as shown in the figure, or they may be defined so as to be spaced apart to form a gap between them according to the width and thickness of the first extension foil (20) and the second extension foil (30), respectively.

[0063] And, in the first stacking step, one end of the first extension foil (20) is stacked on either the upper surface or the lower surface within the first area (I) of the tab portion (10). That is, referring to FIG. 3, one end of the first extension foil (20) can be stacked in the first area (I) below the lower surface of the tab portion (10'') placed in the first layer.

[0064] Next, in the second stacking step, one end of the second extension foil (30) is stacked on the other side between the upper and lower surfaces within the second area (II) of the tab portion (10''). That is, referring to FIG. 3, one end of the second extension foil (30) is stacked in the second area (II) over the upper surface of the tab portion (10'') placed in the first layer.

[0065] At this time, in order to prevent an increase in the thickness of the portion laminated with the tab portion (10) by overlapping the first extension foil (20) and the second extension foil (30), when the upper and lower surfaces are projected from the tab portion (10), the portion where one end of the first extension foil (20) is laminated and the portion where one end of the second extension foil (30) is laminated are laminated so as not to overlap each other. Preferably, as shown in FIG. 4, the first extension foil (20) and the second extension foil (30) can be laminated so that a gap (g) of a predetermined size is formed between them so as not to overlap due to twisting or the like when the first extension foil (20) and the second extension foil (30) are laminated.

[0066] In addition, when multiple tab portions (10) are stacked, a tab portion stacking step is performed following the second stacking step. In the tab portion stacking step, an additional tab portion is stacked such that either the upper or lower surface of the first extension foil (20) and the second extension foil (30) comes into contact with one of the first extension foil (20) and the second extension foil (30) at the upper or lower side of the tab portion where the first extension foil (20) and the second extension foil (30) are stacked.

[0067] Next, an extension foil lamination step is performed. In the extension foil lamination step, another lamination is performed on the other side of the upper or lower surface of the additionally laminated tab portion that is not in contact with the first extension foil (20) and the second extension foil (30).

[0068] Referring to FIG. 3, in the second stacking step, a second extension foil (30) is stacked in the second region (II) on the upper surface of the first layer tab portion (10''). Then, in the tab portion stacking step, the second layer tab portion (10') is stacked on top of it. Accordingly, the second extension foil (30) is in contact with the lower surface of the second layer tab portion (10'). Then, in the extension foil stacking step, the first extension foil (20) is stacked in the first region (I) on the upper surface of the additionally stacked second layer tab portion (10').

[0069] In this way, after the first extension foil (20) and the second extension foil (30) are stacked on the first layer tab section (10''), the tab section stacking step and the extension foil stacking step are alternately repeated until all the stacking of the target tab sections (10) is completed, thereby forming a stacked structure of the first extension foil (20), the second extension foil (30), and the tab sections (10) as shown in FIGS. 2 and 3.

[0070] Then, a joining step is performed to join the parts where the first extension foil (20) and the second extension foil (30) come into contact with the tab portion (10), and a step of joining each of the first extension foils (20) and each of the second extension foils (30) is performed at opposite ends of each of the first extension foil (20) and the second extension foil (30).

[0071]

[0072] Second embodiment

[0073] In the present invention, an electrode assembly is provided as a second embodiment in which a plurality of electrodes coated with an electrode slurry on an electrode foil and a separator are repeatedly stacked, and an electrode tab is formed at the end of the electrode.

[0074] The electrode assembly provided in this embodiment has a structure in which a plurality of anodes, separators, and cathodes are repeatedly stacked as shown in FIG. 1, and an electrode tab (anode tab and / or cathode tab) is formed at the end of the anode or cathode, comprising a tab portion (10), a first extension foil (20) and a second extension foil (30) connected to the tab portion (10) to extend the length and conduct current to a first metal layer (11) and a second metal layer (13).

[0075] The above positive electrode is manufactured by applying a positive slurry to a positive current collector (positive electrode foil), and the above negative electrode is manufactured by applying a negative slurry to a negative current collector (negative electrode foil). At this time, at least one of the positive current collector and the negative current collector (preferably both) is a composite current collector in which a first metal layer (11), a polymer layer (12), and a second metal layer (13) are laminated and used as an electrode foil.

[0076] And, in order to allow current to flow to the outside, a portion of the uncoated portion of the electrode foil where the electrode slurry (anode slurry, cathode slurry) is not coated is formed into a protruding tab portion (10) to form a portion of the electrode tab.

[0077] That is, in this embodiment, the tab portion (10) constituting the electrode tab protrudes from the electrode foil and has a structure in which a first metal layer (11), a polymer layer (12), and a second metal layer (13) are laminated. Furthermore, the end portion where the first extension foil (20) or the second extension foil (30) is laminated on the tab portion (10) is designated as a first area (I) on one side along the width direction and a second area (II) on the other side. The first area (I) and the second area (II) do not necessarily have to have the same size, but (if the first extension foil and the second extension foil have the same width size) they are designated to have the same area as much as possible and may be designated to be in contact with or spaced apart from each other at the boundary line.

[0078] And, at the end of the tab portion (10), one of the first extension foil (20) and the second extension foil (30) is stacked below the lower surface of the tab portion (10), and the other is stacked on the upper surface of the tab portion (10). That is, one end of the first extension foil (20) is stacked on either the upper or lower surface of the tab portion (10), and is stacked within the first region (I) of the tab portion (10), and one end of the second extension foil (30) is stacked on the other end of the upper or lower surface of the tab portion (10) and is stacked within the second region (II) of the tab portion (10).

[0079] More specifically, referring to FIG. 3 and 4, when looking down from above at the tab portion (10'') of the first layer, one end of the first extension foil (20) is stacked in the first region (I) below the lower surface of the tab portion (10'') of the first layer, and one end of the second extension foil (30) is stacked in the second region (II) above the upper surface of the tab portion (10'') of the first layer.

[0080] Then, a second extension foil (30) placed on the upper surface of the first layer's tab section (10'') is placed in the second area (II) below the lower surface of the second layer's tab section (10'). Next, a first extension foil (20) is placed in the first area (I) above the upper surface of the second layer's tab section (10'), and this process is repeated so that a second extension foil (30) is placed in the second area (II) above the upper surface of the third layer's tab section.

[0081] That is, the above tab section (10) is stacked in a plurality of layers, and when either the first extension foil (20) or the second extension foil (30) is stacked on the lower surface of the nth layer (n is a natural number greater than or equal to 1) tab section (10) from bottom to top, the other one is stacked on the upper surface of the nth layer tab section (10), and the (n+1)th layer tab section (10) is stacked on top of it, and one of the first extension foil (20) or the second extension foil (30) placed on the upper surface of the nth layer tab section (10) is placed on the lower surface of the (n+1)th layer tab section (10), and on the upper surface of the (n+1)th layer tab section (10), the same as the one stacked on the lower surface of the nth layer tab section (10) is stacked among the first extension foil (20) and the second extension foil (30).

[0082] For example, when a first extension foil (20) is stacked in the first area (I) below the lower surface of the 5th layer tab section (10) from bottom to top, a second extension foil (30) is stacked in the second area (II) above the upper surface of the 5th layer tab section (10), and a 6th layer tab section (10) is stacked thereon, wherein the second extension foil (30) placed on the upper surface of the 5th layer tab section (10) is placed below the lower surface of the 6th layer tab section (10), and the same first extension foil (20) stacked below the lower surface of the 5th layer tab section (10) is stacked in the first area (I) above the upper surface of the 6th layer tab section (10).

[0083] At this time, when the upper and lower surfaces are projected from the tab portion (10), the portion where the first extension foil (20) is stacked and the portion where the second extension foil (30) is stacked do not overlap each other. That is, as shown in FIG. 4, the width size (w2) of the first extension foil (20) and the width size (w3) of the second extension foil (30) are formed to be 50% or less of the width size (w1) of the tab portion. Accordingly, a gap (g) can be formed between the first extension foil (20) and the second extension foil (30). That is, when the upper and lower surfaces are projected from the nth layer tab portion (10), the first extension foil (20) and the second extension foil (30) can be arranged so that a gap is formed between them.

[0084] As shown in FIG. 5, the electrode tab configured in this way allows the first extension foil (20) and the second extension foil (30), one end of which is placed above or below the upper surface of the tab portion (10), to be positioned at the same height, so the stacking height of the first and second extension foils (20, 30) can be reduced by half compared to the conventional structure.

[0085] And, in a state where the first electrode foil (20), the second electrode foil (30), and the tab portion (10) are stacked as described above, bonding is performed to prevent the first electrode foil (20) and the second electrode foil (30) from detaching.

[0086] That is, as illustrated in FIG. 6, a joining is performed at the portion where the first extension foil (20) and the second extension foil (30) overlap on the tab portion (10). A known joining device may be used for joining the tab portion (10), the first extension foil (20), and the second extension foil (30). For example, a roller-type ultrasonic welder including an ultrasonic vibrating roller, or a pressure-type ultrasonic welder in which a horn applies ultrasonic waves while the workpiece is supported by an anvil and the workpiece is pressed at a predetermined pressure, may be used as a joining device.

[0087] The above ultrasonic welding machine is configured to apply ultrasonic waves to the point where the tap portion (10), the first extension foil (20), and the second extension foil (30) come into contact, and welding variables such as ultrasonic frequency, welding speed, welding pressure, and ultrasonic frequency amplitude can be appropriately controlled.

[0088] Accordingly, ultrasonic welding is performed on the overlapping portions of the above-mentioned tab portion (10), first extension foil (20), and second extension foil (30). At this time, the indentation (P) formed by ultrasonic welding is determined by the size or arrangement of the protrusions formed on the welding machine, and the indentation (P) can be minimized by reducing the applied pressure and welding time.

[0089] Meanwhile, each of the first extension foil (20) and the second extension foil (30) can be formed to have the same width along the length direction as shown in FIGS. 3 and 4.

[0090] In this case, since the first extension foils (20) and the second extension foils (30) are not electrically connected to each other, the first extension foils (20) are joined so that the first extension foils (20) are electrically connected to each other, and the second extension foils (30) are joined so that the second extension foils (30) are electrically connected to each other. Then, the portion where the first extension foils (20) are joined to each other and the portion where the second extension foils (30) are joined to each other are each individually joined to the electrode lead (1).

[0091] Although the above configuration can minimize the thickness of the electrode tab, there may be a problem in that the bonding process may increase because the first extension foils (20) are bonded to each other and the second extension foils (30) are bonded to each other, and then the electrode lead (1) is also bonded individually.

[0092] In order to resolve or alleviate these problems (i.e., so that the joining of the first extension foils and the second extension foils can be done at once), each of the first extension foil (20) and the second extension foil (30) may be configured to have an extension portion (22, 32).

[0093] Referring to FIG. 7, the first extension foil (20a) and the second extension foil (30a) may each be configured to include a tab contact portion (21, 31) and an extension portion (22, 32).

[0094] The above tab contact portions (21, 31) are formed with a relatively narrow width as they are stacked on the tab portion (10). The tab contact portion (21) of the first extension foil (20a) is placed in the first region (I) of the tab portion (10), and the tab contact portion (31) of the second extension foil (30a) is stacked so as to be placed in the second region (II) of the tab portion (10).

[0095] The above extension portions (22, 32) are formed to have a relatively larger width than the tab contact portions (21, 31). The above extension portions (22, 32) have a relatively larger width, but have a width size such that an overlapping portion can be formed between the extension portion (22) of the first extension foil and the extension portion (32) of the second extension foil.

[0096] That is, since the first extension foil (20a) and the second extension foil (30a) are stacked alternately, the extension portion (22) of the first extension foil and the extension portion (32) of the second extension foil are also stacked alternately. And, at the extension portions (22, 32), the first extension foil (20a) and the second extension foil (30a) overlap and come into contact with each other.

[0097] Therefore, in this structure, the first extension foils (20a) are joined together, and the second extension foils (30a) are joined only at the portion where the extension portion (22) of the first extension foil and the extension portion (32) of the second extension foil overlap, without the need to join the second extension foils (30a) together, so that all first extension foils (20a) and all second extension foils (30a) can be connected.

[0098] However, in this structure, (although the thickness can be reduced compared to the conventional method in the part that is laminated to contact the tab part), there is a problem that the thickness of the first extension foil and the second extension foil increases at the end where the electrode lead (1) is joined.

[0099] In order to resolve or alleviate this problem (i.e., to resolve the problem of the thickness increasing at the ends of the first extension foils and the second extension foils joined to the electrode lead), one of the extension portion (22) of the first extension foil and the extension portion (32) of the second extension foil are configured to have a shorter length and the other has a longer length.

[0100] For example, as illustrated in FIG. 8, the extension portion (22) of the first extension foil (20b) may be configured to have a relatively short length, and the extension portion (32) of the second extension foil (30b) may have a relatively longer length. Accordingly, as illustrated in FIG. 9, after the extension portion (22) of the first extension foil (20b) and the extension portion (32) of the second extension foil (30b) are joined together in a stacked portion (A), the extension portions (32) of the second extension foil (30b) are gathered together in a protruding portion (B), and only that portion (B) can be joined to the electrode lead (1). In this structure, the thickness is further reduced at the portion joined to the electrode lead (1), so welding can be performed more easily and resistance increase can be suppressed.

[0101] For reference, as shown in FIG. 10, the first extension foil (20c) and the second extension foil (20c) may be composed only of extension portions so that the tab contact portion is removed and the first extension foil (20c) and the second extension foil (30c) can overlap each other. However, in this structure, stacking of the first extension foil (20c) and the second extension foil (30c) can be achieved relatively easily, but (as in FIG. 5, the first extension foil and the second extension foil cannot be placed on the same height line) and the first extension foil (20c) and the second extension foil (30c) must be arranged vertically, so a problem may occur where the stacking height increases at the part connected to the tab portion (10).

[0102]

[0103] In the present invention having the technical features described above, the first extension foil (20) and the second extension foil (30) are divided and stacked along the width direction of the tab portion (10), so the thickness at the point where the first extension foil (20) and the second extension foil (30) and the tab portion (10) are stacked, and at the point where the first extension foil (20) and the second extension foil (30) and the electrode lead (1) are joined can be reduced, thereby lowering the possibility of a defective bond and suppressing an increase in resistance.

[0104] Additionally, each of the first extension foil (20) and the second extension foil (30) may include an extended portion with increased width, and accordingly, the first extension foil and the second extension foil can easily come into contact.

[0105] In addition, one of the extension portion of the first extension foil and the extension portion of the second extension foil has a shorter length and the other has a longer length, and the ones having the longer lengths among the extension portions of the first extension foil and the second extension foil are configured to be gathered at the ends, thereby reducing the thickness of the portion joined to the electrode lead.

[0106] A person skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and various embodiments derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included within the scope of the present invention.

[0107] [Explanation of the symbol]

[0108] 1 : Electrode lead

[0109] 10 : Tab section

[0110] 11: First metal layer

[0111] 12: Polymer layer

[0112] 13: Second metal layer

[0113] 20 : 1st extension foil

[0114] 30 : 2nd extension foil

[0115] I: Area 1

[0116] II: Area 2

[0117] P: Indentation

Claims

1. An electrode assembly in which a plurality of electrodes coated with electrode slurry on electrode foils and a separator are repeatedly stacked, and an electrode tab is formed at the end of the electrode, The above electrode tab is, A tab portion protruding from the electrode foil, wherein a first metal layer, a polymer layer, and a second metal layer are laminated, and along the width direction, one side is designated as a first region and the other side is designated as a second region; A first extension foil that is laminated on either the upper or lower surface of the tab portion, and is laminated within the first region of the tab portion; and An electrode assembly comprising: a second extension foil that is laminated on one of the upper and lower surfaces of the tab portion, and is laminated within the second region of the tab portion.

2. In Paragraph 1, An electrode assembly in which, when the upper and lower surfaces are projected from the above tab portion, the portion where the first extension foil is stacked and the portion where the second extension foil is stacked do not overlap each other.

3. In Paragraph 1, The above tab portions are stacked to form multiple layers, When either the first extension foil or the second extension foil is stacked on the lower surface of the tab portion of the n-th layer (n is a natural number greater than or equal to 1) from bottom to top, the other one is stacked on the upper surface of the tab portion of the n-th layer, and An electrode assembly in which an (n+1)th layer tab portion is stacked on top thereof, wherein the same as that stacked below the lower surface of the nth layer tab portion among the first extension foil and the second extension foil is stacked on the upper surface of the (n+1)th layer tab portion.

4. In Paragraph 3, An electrode assembly formed such that the width of the first extension foil and the second extension foil is 50% or less of the width of the tab portion.

5. In Paragraph 4, An electrode assembly in which the first extension foil and the second extension foil are arranged such that a gap is formed between them when the upper and lower surfaces are projected from the n-th layer tab portion.

6. In Paragraph 3, The electrode assembly is formed such that each of the first extension foil and the second extension foil has the same width along the longitudinal direction.

7. In Paragraph 3, Each of the above-mentioned first extension foil and second extension foil is, A tab contact portion formed with a relatively narrow width and laminated to the tab portion; and Includes an extension portion having a relatively larger width than the above-mentioned tab contact portion; In the above extension portion, the first extension foil and the second extension foil are in contact with an electrode assembly.

8. In Paragraph 7, The extension portion of the first extension foil and the extension portion of the second extension foil are alternately stacked to form an electrode assembly.

9. In Paragraph 8, One of the extension portion of the first extension foil and the extension portion of the second extension foil has a shorter length and the other has a longer length, An electrode assembly in which the longer of the extension portions of the first extension foil and the second extension foil are gathered at the ends.

10. A method for manufacturing an electrode assembly in which a plurality of electrodes coated with electrode slurry on electrode foils and a separator are repeatedly stacked, and an electrode tab is formed at the end of the electrode, It includes an electrode tab extension step for extending the length of the electrode tab, and The above electrode tab extension step is, A tab portion providing step in which a tab portion is provided that protrudes from an electrode foil and has a first metal layer, a polymer layer, and a second metal layer laminated thereon, with one side along the width direction defined as a first region and the other side defined as a second region; A first stacking step of stacking one end of a first extension foil on either the upper surface or the lower surface within the first area of ​​the above-mentioned tab portion; and A method for manufacturing an electrode assembly comprising: a second lamination step of laminating one end of a second extension foil to the other of the upper and lower surfaces within the second region of the above-mentioned tab portion.

11. In Paragraph 10, A method for manufacturing an electrode assembly in which, when the upper and lower surfaces are projected from the above tab portion, the portion where the first extension foil is stacked and the portion where the second extension foil is stacked are stacked so as not to overlap each other.

12. In Paragraph 11, A tab section stacking step of additionally stacking a tab section such that either the upper surface or the lower surface of either the first extension foil or the second extension foil contacts the upper or lower surface of either the first extension foil or the second extension foil at the upper or lower side of the tab section where the first extension foil and the second extension foil are stacked; and The method further includes an extension foil lamination step of laminating the other one of the first extension foil and the second extension foil that is not in contact with the other one of the upper or lower surfaces of the additionally laminated tab portion; A method for manufacturing an electrode assembly in which the above tab layer lamination step and the extension foil lamination step are alternately repeated so that the above tab portions are laminated to form a plurality of layers.

13. In Paragraph 12, A step of joining the first extension foils together at the other end of each first extension foil; and A method for manufacturing an electrode assembly comprising the step of joining the respective second extension foils together at the other end of each second extension foil.

14. In any one of paragraphs 10 through 13, A method for manufacturing an electrode assembly comprising: a bonding step of bonding the portion where the first extension foil and the second extension foil contact the above tab portion.

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