Electrode assembly with bent tab bundle and tab bundle forming device for manufacturing the same

Abstract

The present invention relates to an electrode assembly in which a separation film is interposed between a plurality of electrodes from which electrode tabs protrude, and the electrode tabs are stacked to form a tab bundle, and the tab bundle has convex portions and concave portions formed continuously extending along the length of the electrodes. The convex portions and concave portions formed in the tab bundle ensure a length margin for the electrode tabs, thereby preventing breakage of the tabs.

Description

[Technical field]

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2022-0152082 filed on November 14, 2022, and all contents disclosed in the Korean Patent Application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly having a bent tab bundle and an electrode assembly tab bundle forming apparatus for manufacturing the same. More particularly, the present invention relates to an electrode assembly for forming a structure capable of reducing stress on electrode tabs extending from the electrode assembly and an electrode assembly tab bundle forming apparatus for manufacturing the same. [Background technology]

[0003] Lithium secondary batteries can be classified according to the type of battery case that houses the electrode assembly, including prismatic and cylindrical battery cells having a metal can-shaped battery case, and pouch-type battery cells made of a laminate sheet including a resin layer and a metal layer.

[0004] The pouch-type battery cell has the advantages of being easily deformable and having a high energy density.

[0005] In general, a pouch-type battery cell is manufactured by injecting an electrode assembly and an electrolyte into a pouch-type battery case and sealing it. An electrode tab bundle is formed in which the electrode tabs protruding from the electrode assembly extend linearly rather than in another shape, and pre-welding can be performed in this state.

[0006] In this regard, FIG. 1 is a front view of a conventional electrode assembly and a molding apparatus for molding the same.

[0007] First, in FIG. 1(a), an electrode assembly is formed by stacking a negative electrode 100 and a positive electrode 300 with a separator 200 interposed between them. The negative electrode 100 of the electrode assembly is pre-welded in a state in which electrode tabs extending from an outer periphery on one side form a tab bundle B, and then the right edge of the tab bundle B is welded to an electrode lead 400.

[0008] In this case, the electrode assembly is vulnerable to movement or stress in the longitudinal direction (X-axis direction), and if swelling of the electrode assembly occurs during charging and discharging, it expands in the thickness direction (Y-axis direction), which may cause the electrode tabs to break.

[0009] 1(b), the tab bundle can be folded using a molding device 50 composed of a first mold 51 and a second mold 52. Specifically, the first mold 51 presses the lower side of the tab bundle B, and the second mold 52 presses the upper side of the tab bundle B, so that the outermost tab of the tab bundle B can be deformed into a round shape.

[0010] In this case, safety can be improved against expansion in the thickness direction (Y-axis direction) because the outermost tab has a length margin, but against movement in the longitudinal direction (X-axis direction), there is no length margin for the inner tab, so there is still a high possibility of breakage due to movement or stress in the longitudinal direction (X-axis direction).

[0011] In this regard, Patent Document 1 relates to an electrode assembly manufacturing method and an electrode assembly manufacturing apparatus, and discloses a rod process in which a pair of rods are positioned on the electrode assembly side at a portion where an electrode tab is to be welded and the pair of rods are moved in directions facing each other to closely contact both sides of the electrode tab in order to prevent dust generated during welding before a pre-welding process from moving to the electrode assembly.

[0012] Patent Document 1 discloses a method and structure that uses a pair of rods to prevent excessive tension from being generated in an electrode tab during electrode tab welding. However, the electrode tab bending structure disclosed in Patent Document 1 is a structure that makes it difficult to ensure safety against expansion caused by swelling in the thickness direction.

[0013] Patent Document 2 relates to a method for manufacturing a secondary battery and a secondary battery using the same, in which the horn and anvil for temporarily joining the multi-tab have a protrusion that protrudes toward the anvil and the anvil has a recess corresponding to the protrusion, so that the multi-tab is configured to have a bent portion, thereby eliminating the additional bending process of the multi-tab and simplifying the process.

[0014] However, in Patent Document 2, the bent portion of the multi-tab is formed at the temporary joint, so that the structure remains vulnerable to stress and expansion in the longitudinal and thickness directions in the tab bundle of the multi-tab extending from the electrode plate, excluding the bent portion. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Korean Patent Publication No. 10-2020-0105272 [Patent Document 2] Korean Patent Publication No. 10-2016-0060221 Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electrode assembly in which electrode tabs are stacked on one another, and which can prevent breakage of the electrode tabs by ensuring length margins in the longitudinal and thickness directions of a tab bundle, and a tab bundle forming apparatus for manufacturing the electrode assembly. [Means for solving the problem]

[0017] To achieve the above object, the electrode assembly according to the present invention includes a plurality of electrodes from which electrode tabs protrude, and a separator is interposed between the electrodes, and the electrode tabs are stacked to form a tab bundle. The tab bundle may be formed with continuous protrusions and recesses extending along the length of the electrodes.

[0018] One end of the tab bundle (B) that is in close contact with the electrode lead may be a flat portion.

[0019] The flat portion may be pre-welded.

[0020] The protrusions and the recesses may be formed on the remaining portion excluding the flat portion.

[0021] All the electrode tabs constituting the tab bundle may have convex and concave portions formed continuously.

[0022] The tab bundle forming device for the electrode assembly may include a first mold located on a first surface of the tab bundle (B) and a second mold located on a second surface of the tab bundle (B), the first mold including two or more guide portions spaced apart at a regular interval, and the second mold may be positioned toward a spaced apart portion between the two or more guide portions of the first mold.

[0023] The end of the guide portion facing the first surface of the tab bundle (B) may have a bulging shape.

[0024] The end of the second mold facing the second surface of the tab bundle (B) may have a bulging shape.

[0025] The two or more guide parts of the first mold can be driven independently.

[0026] The two or more guide parts of the first mold may have an integral structure with their lower ends connected to each other.

[0027] A groove having a shape corresponding to an end of the second mold may be formed at a connecting portion of the two or more guide portions.

[0028] The end of the second mold may have a convex shape, and the groove may have a concave shape.

[0029] The method for manufacturing the electrode assembly includes a first step of forming a tab bundle (B) of the same electrodes by stacking a plurality of electrodes from which electrode tabs protrude with a separator interposed between them; a second step of positioning a first mold on a first surface of the tab bundle (B) and a second mold on a second surface of the tab bundle (B); and a third step of moving the first mold and / or the second mold toward the tab bundle (B) to bend the tab bundle (B), wherein the first mold may include two or more guide portions spaced apart at a regular interval and having a bulging shape at an end portion facing the first surface, and the second mold may have a bulging shape at an end portion toward a spaced apart portion between the two or more guides of the first mold.

[0030] The method may further include a fourth step of pre-welding the ends of the tab bundle (B).

[0031] The method may further include a fifth step of cutting the end of the tab bundle (B).

[0032] Furthermore, the present invention can be provided in various combinations of the above-mentioned problems to be solved. Effect of the Invention

[0033] As described above, the present invention has the advantage that breakage of the electrode tabs can be prevented by continuously forming convex and concave portions in a tab bundle in which electrode tabs extending from a plurality of electrodes are stacked, thereby ensuring length margins not only in the longitudinal direction but also in the thickness direction. [Brief description of the drawings]

[0034] [Figure 1]FIG. 1 is a front view of a conventional electrode assembly and a molding device for molding the electrode assembly. [Diagram 2] 1 is a perspective view of an electrode assembly according to the present invention; [Diagram 3] 1 is a perspective view of a tab bundle forming device for an electrode assembly according to a first embodiment and a second embodiment of the present invention; [Figure 4] FIG. 11 is a perspective view of a tab bundle forming device for an electrode assembly according to a third and fourth embodiment of the present invention. [Diagram 5] 4 is a flow chart of a method for manufacturing an electrode assembly according to the present invention. [Figure 6] 5A to 5C are schematic diagrams illustrating a manufacturing process of an electrode assembly according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, a detailed description will be given of an embodiment of the present invention that can be easily implemented by a person having ordinary skill in the art to which the present invention pertains, with reference to the accompanying drawings. In describing the operation principle of the embodiment of the present invention in detail, if it is determined that a detailed description of related well-known functions or configurations may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0036] Throughout the drawings, parts having similar functions and actions are designated by the same reference numerals. 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.

[0037] Descriptions that specify or limit elements are applicable to all inventions and are not limited to a particular invention unless otherwise specified.

[0038] Throughout the description and claims of this invention, the singular includes the plural unless specifically stated otherwise.

[0039] Throughout the description and claims of the present invention, "or" includes "and" unless otherwise stated. Thus, "including A or B" means the three cases of including A, including B, or including both A and B.

[0040] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0041] 2 is a perspective view of an electrode assembly according to the present invention. Referring to FIG 2, the electrode assembly according to the present invention is stacked with a separator 200 interposed between a negative electrode 100 and a positive electrode 300, and the negative electrode 100 and the positive electrode 300 include a negative electrode tab 110 and a positive electrode tab 310 protruding in opposite directions.

[0042] The negative electrode tabs 110 are stacked to form a negative electrode tab bundle B, and the positive electrode tabs 310 are stacked to form a positive electrode tab bundle B. Since the configurations of the negative electrode tab bundle B and the positive electrode tab bundle B are the same, the negative electrode tab bundle B will be mainly described.

[0043] All of the negative electrode tabs 110 constituting the negative electrode tab bundle B are formed with protrusions 111 and recesses 112 extending along the longitudinal direction (X-axis direction) of the negative electrode 100, and have flat portions 113 at their edge ends.

[0044] That is, in the electrode assembly according to the present invention, all of the negative electrode tabs 110 constituting the negative electrode tab bundle B are bent such that the convex portion 111 and the concave portion 112 are continuously formed at the remaining portions except for the flat portion 113 at the edge.

[0045] Here, the flat portion 113 is a portion to which an electrode lead, which will be described later, is coupled, and is preferably pre-welded.

[0046] For example, while FIG. 2 shows one each of a protrusion and a recess, this is merely an example, and there may be two or more each of a protrusion and a recess.

[0047] Thus, the electrode assembly according to the present invention is configured in a form that secures a length margin for the electrode tabs, that is, the electrode tab bundle is not taut but is configured in a loosely curved form. Therefore, even if the electrode assembly moves freely in the longitudinal direction (X-axis direction) or swells and expands in the Y-axis direction, disconnection of the electrode tabs can be minimized.

[0048] On the other hand, the negative electrode 100 is manufactured by applying a slurry in which a negative electrode active material and a binder are mixed to a negative electrode current collector.

[0049] Here, examples of the negative electrode active material include carbon such as graphitizable carbon and graphite-based carbon; Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Si-based materials such as Si, SiO, SiO2 alone or mixtures thereof can be used, but are not limited thereto.

[0050] Further, the positive electrode 300 is manufactured by applying a slurry in which a positive electrode active material and a binder are mixed to a positive electrode current collector.

[0051] Here, examples of the positive electrode active material include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-xLithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x Ni-site type lithium nickel oxide represented by MxO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x=0.01 to 0.3); chemical formula LiMn 2-x M x Examples of the lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by the formula LiMn2O2 (wherein M is Co, Ni, Fe, Cr, Zn, or Ta, and x is 0.01 to 0.1) or Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0052] Meanwhile, the negative electrode current collector and the positive electrode current collector include a portion coated with a slurry containing an active material and an uncoated portion where the slurry is not coated, and the uncoated portion is cut to form the tabs, more specifically, the negative electrode tab 110 and the positive electrode tab 310.

[0053] In addition, an insulating thin film having high ion permeability and mechanical strength is used as the separator 200 interposed between the positive electrode 100 and the negative electrode 300. The pore diameter of the separator is generally 0.01 μm to 10 μm, and the thickness is generally 5 μm to 300 μm. As such a separator, for example, a sheet or nonwoven fabric made of an olefin polymer such as polypropylene, glass fiber, or polyethylene, which is chemically resistant and hydrophobic, can be used, but is not limited thereto.

[0054] FIG. 3 is a perspective view of a tab bundle forming apparatus for an electrode assembly according to a first embodiment and a second embodiment of the present invention, where (a) is the tab bundle forming apparatus according to the first embodiment and (b) is the tab bundle forming apparatus according to the second embodiment.

[0055] First, referring to FIG. 2, the tab bundle forming apparatus 500 for the electrode assembly according to the first embodiment will be described. The apparatus includes a first mold 510 positioned on the first surface of the tab bundle, i.e., the lower surface of tab bundle B in FIG. 2, and a second mold 520 positioned on the upper surface of tab bundle B, which corresponds to the second surface of the tab bundle.

[0056] The first mold 510 is composed of a first guide portion 511 and a second guide portion 512 that are guide portions spaced apart at a regular interval. The second mold 520 is positioned toward the spaced apart portion between the first guide portion 511 and the second guide portion 512 of the first mold 510.

[0057] This second mold 520 is inserted into the spaced apart area between the first guide portion 511 and the second guide portion 512 and presses the tab bundle, resulting in the tab bundle being bent so that convex portions and concave portions are formed continuously.

[0058] On the other hand, it is preferable that the ends of the first guide portion 511 and the second guide portion 512 facing the first surface of the tab bundle have an upwardly bulging shape, while the end of the second mold 520 facing the second surface of the tab bundle has a downwardly bulging shape.

[0059] As described above, the ends of the first guide portion 511, the second guide portion 512 and the second mold 520 are configured to have a convex shape, thereby minimizing damage to the electrode tabs during the process of bending the tab bundle.

[0060] In the tab bundle forming apparatus for the electrode assembly according to the first embodiment, the first guide part 511 and the second guide part 512 constituting the first mold 510 may be configured to be driven independently. In other words, the first guide part 511 and the second guide part 512 may be independently movable up and down, and may be operated so that the distance between them increases or decreases. This is because various bending shapes of the tab bundle can be realized.

[0061] For example, although not shown in the drawings, the first guide part 511 and the second guide part 512 may further include a cylinder (not shown) or a drive shaft to enable the above-mentioned drive.

[0062] The tab bundle forming apparatus for an electrode assembly according to the second embodiment is similar to the tab bundle forming apparatus for an electrode assembly according to the first embodiment described above, except for the first mold 510, so only the first mold 510 will be described below.

[0063] The ends of the first guide part 511 and the second guide part 512 constituting the first mold 510 are bulging upward, and the lower ends of these parts are connected to each other to form an integrated structure. Therefore, when using this, it is difficult to adjust the height and the distance between the first guide part 511 and the second guide part 512, but since they are an integrated structure, it is possible to form a tab bundle that is bent in a uniform shape.

[0064] Of course, in the first mold 510 of the second embodiment, a groove portion 514 having a shape corresponding to the end portion bulging toward the downward side of the second mold 520 is provided at the lower end connecting portion of the first guide portion 511 and the second guide portion 512.

[0065] FIG. 4 is a perspective view of a tab bundle forming apparatus for an electrode assembly according to the third and fourth embodiments of the present invention, where (a) is the tab bundle forming apparatus according to the third embodiment, and (b) is the tab bundle forming apparatus according to the fourth embodiment.

[0066] First, the tab bundle forming apparatus 500 according to the third embodiment will be described. The first mold 510 is configured to include a first guide portion 511, a second guide portion 512 and a third guide portion 513, while the second mold 520 is configured to include a first pressing portion 521 and a second pressing portion 522 which can be driven individually or independently.

[0067] Of course, the rest is the same as the first embodiment described above, except that the first pressing portion 521 moves to the spaced apart portion between the first guide portion 511 and the second guide portion 512, and the second pressing portion 522 moves to the spaced apart portion between the second guide portion 512 and the third guide portion 513.

[0068] Next, in the tab bundle forming apparatus 500 according to the fourth embodiment, the first mold 510 includes a first guide portion 511, a second guide portion 512, and a third guide portion 513, the lower ends of which are connected to each other to form an integrated structure to form a groove portion 514, while the second mold 520 is composed of a first pressing portion 521 and a second pressing portion 522 which can be driven individually or independently, but the rest is the same as that of the second embodiment described above.

[0069] Next, a method for manufacturing an electrode assembly according to the present invention will be described below. Figure 5 is a flow chart of the method for manufacturing an electrode assembly according to the present invention, and Figure 6 is a schematic diagram showing the manufacturing process of an electrode assembly according to the present invention.

[0070] 5 and 6, a method for manufacturing an electrode assembly according to the present invention includes a first step of forming a tab bundle B of the same electrodes by stacking a plurality of electrodes from which electrode tabs protrude with a separator interposed therebetween; a second step of positioning a first mold 510 on a first surface of the tab bundle B and a second mold 520 on a second surface of the tab bundle B; a third step of moving the first mold 510 and the second mold 520 toward the tab bundle B to bend the tab bundle B; a fourth step of pre-welding an end of the tab bundle B; and a fifth step of cutting an edge of the tab bundle B.

[0071] Here, the above-mentioned first to fifth steps have been described using the tab bundle forming apparatus according to the first embodiment as an example, but it is obvious that the forming apparatus according to the second to fourth embodiments can be used for manufacture. Since the specific configuration and operating principle of the forming apparatus have already been described, a repeated description will be omitted.

[0072] Meanwhile, when the pre-welding in the fourth step is completed, the lengths of the electrode tabs at the edge of the tab bundle, i.e., one edge of the flat portion, do not match each other. Therefore, it is preferable to perform a fifth step of cutting the edges of the electrode tabs so that the edges of the electrode tabs match each other prior to connecting the electrode leads.

[0073] Meanwhile, when manufacturing a secondary battery, a sixth step of connecting an electrode lead to the pre-welded portion and a seventh step of housing the electrode assembly manufactured in the first to fifth steps in a battery case may be further performed after the fifth step described above. These sixth and seventh steps correspond to known techniques, and therefore detailed description thereof will be omitted.

[0074] Those skilled in the art will appreciate that various applications and modifications within the scope of the present invention will be possible based on the above content. [Explanation of symbols]

[0075] 100 negative electrode 110 Negative electrode tab 111 Convex 112 Recess 113 Flat area 200 Separation membrane 300 positive electrode 310 Positive tab 400 Electrode Lead 50, 500 molding equipment 51, 510 First mold 511 First guide section 512 Second guide section 513 3rd Guide Section 514 Groove 52, 520 2nd mold 521 First pressing part 522 Second pressing part B Tab bundle

Claims

1. A separator is interposed between a plurality of electrodes from which electrode tabs protrude, and the electrode tabs are stacked to form a tab bundle; an electrode assembly, wherein the tab bundle is formed with a series of protrusions and recesses extending along the length of the electrode;

2. 2. The electrode assembly according to claim 1, wherein one end of the tab bundle that is in close contact with the electrode lead is a flat portion.

3. The electrode assembly of claim 2 , wherein the flat portion is pre-welded.

4. The electrode assembly according to claim 2 , wherein the protrusions and the recesses are formed on a remaining portion excluding the flat portion.

5. 2. The electrode assembly according to claim 1, wherein all the electrode tabs constituting the tab bundle have a convex portion and a concave portion formed continuously.

6. A tab bundle forming apparatus for an electrode assembly for manufacturing the electrode assembly according to any one of claims 1 to 5, comprising: a first die positioned on a first surface of the tab bundle; a second die located on a second surface of the tab bundle; The first mold includes two or more guide portions spaced apart at a fixed interval, and the second mold is positioned toward a spaced apart portion between the two or more guide portions of the first mold.

7. 7. The tab bundle forming apparatus for an electrode assembly according to claim 6, wherein an end of the guide portion facing the first surface of the tab bundle has a convex shape.

8. 7. The tab bundle forming apparatus for an electrode assembly according to claim 6, wherein an end of the second die facing the second surface of the tab bundle has a convex shape.

9. 7. The tab bundle forming apparatus for an electrode assembly according to claim 6, wherein two or more guide portions of the first die can be driven independently.

10. 7. The tab bundle forming apparatus for an electrode assembly according to claim 6, wherein the two or more guide portions of the first mold are integrally formed with their lower ends connected to each other.

11. The tab bundle forming apparatus for an electrode assembly according to claim 10 , wherein a groove having a shape corresponding to an end of the second mold is formed in a connecting portion of the two or more guide portions.

12. 12. The tab bundle forming apparatus for an electrode assembly according to claim 11, wherein the end of the second die has a convex shape, and the groove has a concave shape.

13. A method for producing the electrode assembly according to any one of claims 1 to 5, comprising the steps of: a first step of stacking a plurality of electrodes having protruding electrode tabs therebetween with a separator interposed therebetween to form a bundle of tabs of the same electrodes; a second step of positioning a first die on a first surface of the tab bundle and a second die on a second surface of the tab bundle; and a third step of moving a first die and / or a second die toward the tab bundle to bend the tab bundle, The first mold includes two or more guide portions spaced apart at a regular interval and having a bulging shape at an end toward a first surface, and the second mold has a bulging shape at an end toward a spaced portion between the two or more guides of the first mold.

14. The method of claim 13, further comprising a fourth step of pre-welding the ends of the tab bundle.

15. The method of claim 14 further comprising a fifth step of cutting an end of the tab bundle.

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