Electrode assembly

Abstract

The present invention relates to an electrode assembly having a winding structure, and more particularly, to an electrode assembly for overcoming the problem of breakage or crack in a negative electrode by reducing stress generated in the negative electrode facing an outer end portion of a positive electrode. The electrode assembly according to the present invention has a structure in which a positive electrode, a separator, and a negative electrode are wound in a stacked state, and includes a central hole in the middle. An outer end portion of the negative electrode is disposed farther from the center hole than an outer end portion of the positive electrode. And the positive electrode comprises a positive electrode current collector and positive electrode slurry coated on the positive electrode current collector. And the negative electrode comprises a negative electrode current collector, negative electrode slurry coated on the negative electrode current collector and a negative electrode connecting piece arranged on the negative electrode current collector. The negative tab is provided on an imaginary line passing through the outer end of the positive electrode and the center point of the center hole.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority of a Korean patent application filed on Nov. 01, 2022 with Serial No. 10 - 2022 - 0144045, the entire contents of which are hereby incorporated herein by reference. Technical field

[0003] The present invention relates to an electrode assembly having a wound structure, and more particularly, to an electrode assembly for improving problems of cracks or fractures in a negative electrode by reducing stress generated in the negative electrode at an outer end portion facing the positive electrode. Technical background

[0004] Batteries for storing electrical energy can generally be classified into primary batteries and secondary batteries. Such primary batteries are disposable consumable batteries. On the other hand, such secondary batteries are rechargeable batteries manufactured by using materials in which the oxidation process and the reduction process between current and materials can be repeated.

[0005] That is, when a reduction reaction of a material is performed by current, the power source is charged, and when an oxidation reaction of the material is performed by current, the power source is discharged. Here, such charging and discharging are repeatedly performed.

[0006] Among various types of secondary batteries, lithium secondary batteries are generally manufactured by installing an electrode assembly in which a positive electrode (cathode), a separator, and a negative electrode (anode) are stacked in a case. Here, as the process of insertion and extraction of lithium ions between lithium metal oxide and the negative electrode is repeated, the lithium secondary battery is charged and discharged.

[0007] In the electrode assembly, a plurality of unit cells are stacked. In each unit cell, a negative electrode, a separator, and a positive electrode are stacked in a predetermined order, and each of the negative electrode, the separator, and the positive electrode is usually cut into a predetermined size; alternatively, independent positive electrode / separator / negative electrode are repeatedly stacked to form an electrode assembly. In addition, the electrode assembly is accommodated in a case such as a cylindrical can or a prismatic pouch.

[0008] As a method for manufacturing an electrode assembly, an electrode assembly manufactured by the following methods is known: a wound - type electrode assembly in which a separator is stacked between a negative electrode and a positive electrode and then wound to manufacture an electrode assembly; a stacked - type electrode assembly in which each of the negative electrode and the positive electrode is cut into a desired width and length, and then the negative electrode, the separator, and the positive electrode are repeatedly stacked to form an electrode assembly; and a stacked - folded - type electrode assembly in which unit cells are placed parallel to each other on a folded separator and then folded from one side to manufacture an electrode assembly.

[0009] Among these electrode assemblies, a wound (jelly-roll type) electrode assembly is manufactured by fixing a first separator to a core and sequentially placing a negative electrode, a second separator, and a positive electrode during rotation of the core (in some cases, the order of placing the separator, negative electrode, and positive electrode may be changed).

[0010] In a cylindrical battery, due to its structural characteristics, the positive electrode, negative electrode, and separator between the positive electrode and the negative electrode overlap each other, and then the positive electrode, negative electrode, and separator are wound into a cylindrical shape to manufacture a jelly-roll member, and then the jelly-roll member is placed into a metal can to manufacture a battery cell having a cylindrical shape. In the related art, when charging, the negative electrode expands, usually increasing in thickness by about 10% to 20%. Due to the structural characteristics of the cylindrical battery, the outer diameter of the jelly-roll member can increase, and the circumference of the outermost negative electrode increases, resulting in stretching of the copper current collector. In particular, when the negative electrode at the stepped portion of the end facing the positive electrode expands, if stress is severely concentrated at the stepped portion of the end of the positive electrode, there is a problem of damage to the copper foil and the negative electrode. In particular, with the recent trend of developing high-capacity cylindrical batteries, the energy density of the electrodes is designed to be higher and the thickness of the copper foil is gradually thinned, and thus, there is a problem that the risk of cracks or fractures in the negative electrode gradually increases. Summary of the Invention

[0011] Technical Problem

[0012] An object of the present invention for solving the above problems is to provide an electrode assembly in which stress generated in the negative electrode at the outer end portion facing the positive electrode is reduced to improve the problem of cracks or fractures in the negative electrode.

[0013] Technical Solution

[0014] An electrode assembly according to an embodiment of the present invention may have a structure in which a positive electrode, a separator, and a negative electrode are wound in a stacked state, and the electrode assembly includes a central hole at its center, wherein an outer end portion of the negative electrode is disposed outside an outer end portion of the positive electrode with respect to the central hole, the positive electrode includes a positive current collector and a positive electrode paste coated on the positive current collector, the negative electrode includes a negative current collector, a negative electrode paste coated on the negative current collector, and a negative electrode tab disposed on the negative current collector, wherein the negative electrode tab is disposed at a position through which a virtual line passing through a central point of the outer end portion of the positive electrode and the central hole passes.

[0015] The negative electrode tab may include: an outer negative electrode tab disposed outside an outer end portion of the positive electrode with respect to the central hole; and an inner negative electrode tab disposed inside an outer end portion of the positive electrode with respect to the central hole, wherein the outer negative electrode tab may be disposed at a position through which the virtual line passes.

[0016] The negative electrode current collector may include: a bottom surface, which is the surface facing the direction of the central hole; and a top surface, which is arranged opposite to the bottom surface.

[0017] The negative electrode paste may be coated on the top surface and the bottom surface facing the outer end of the positive electrode from the outer end of the positive electrode toward the outer end of the negative electrode for a preset length, and the negative electrode paste may not be coated from the outer end of the positive electrode until the outer end of the negative electrode after the preset length.

[0018] The outer negative electrode tab may be arranged at a position where neither the top surface nor the bottom surface is coated with the negative electrode paste.

[0019] The outer negative electrode tab may be arranged on the top surface, and a first protective tape may be attached to the bottom surface corresponding to the surface on which the outer negative electrode tab is arranged.

[0020] A second protective tape may be attached to the top surface facing the bottom surface to which the first protective tape is attached.

[0021] A separator may be arranged between the first protective tape and the second protective tape.

[0022] The first protective tape may be arranged to be longer than the outer negative electrode tab.

[0023] The first protective tape may be arranged to have the same length as the second protective tape or to be longer than the second protective tape.

[0024] The outer negative electrode tab may be arranged on the bottom surface, and a third protective tape may be attached to the top surface corresponding to the surface on which the outer negative electrode tab is arranged.

[0025] The second protective tape may be attached to the top surface facing the bottom surface to which the outer negative electrode tab is attached, and the separator may be arranged between the outer negative electrode tab and the second protective tape.

[0026] Advantageous Effects

[0027] By the embodiments of the present invention, the stress generated in the negative electrode facing the outer end of the positive electrode can be reduced, thereby improving the problems of cracks and fractures in the negative electrode. Description of the Drawings

[0028] Figure 1 is a view illustrating a state in which the separator is omitted and the positive electrode and the negative electrode are wound in an electrode assembly according to the related art.

[0029] Figure 2 is a plan view illustrating the ends of the positive electrode and the negative electrode in an electrode assembly according to the related art.

[0030] Figure 3It is a view showing a state in which a separator is omitted and a positive electrode and a negative electrode are wound in an electrode assembly according to Embodiment 1 of the present invention.

[0031] Figure 4 It is a plan view showing ends of a positive electrode and a negative electrode in an electrode assembly according to Embodiment 1 of the present invention.

[0032] Figure 5 It is a view showing a state in which a separator is omitted and a positive electrode and a negative electrode are wound in an electrode assembly according to Embodiment 2 of the present invention.

[0033] Figure 6 It is a plan view showing ends of a positive electrode and a negative electrode in an electrode assembly according to Embodiment 2 of the present invention. Detailed Embodiments

[0034] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily implement the technical concept of the present invention. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein.

[0035] To clearly describe the present invention, parts irrelevant to the description are omitted, and throughout the specification, the same reference numerals refer to the same or similar components.

[0036] In addition, the terms or words used in this specification and claims should not be construed restrictively as ordinary meanings or dictionary-based meanings, but should be construed as meanings and concepts that conform to the scope of the present invention based on the principle that the inventor can appropriately define the terms in order to best describe and explain his or her invention.

[0037] Figure 1 It is a view showing a state in which a separator is omitted and a positive electrode and a negative electrode are wound in an electrode assembly according to the related art, and Figure 2 It is a plan view showing ends of a positive electrode and a negative electrode in an electrode assembly according to the related art.

[0038] As observed in Figure 1 and Figure 2 in an electrode assembly 1 according to the related art, when the negative electrode 20 expands, stress concentrates on a stepped portion of an outer end portion 13 of the positive electrode 10, resulting in a crack problem in which the negative electrode 20 is damaged.

[0039] Hereinafter, embodiments of the electrode assembly 1 for solving this problem will be described.

[0040] Embodiment 1

[0041] Hereinafter, with reference toFigure 3 and Figure 4 Describe in detail the electrode assembly according to Embodiment 1 of the present invention.

[0042] Figure 3 is a view illustrating a state in which the separator is omitted and the positive electrode and the negative electrode are wound in the electrode assembly according to Embodiment 1 of the present invention, and Figure 4 is a plan view illustrating the ends of the positive electrode and the negative electrode in the electrode assembly according to Embodiment 1 of the present invention.

[0043] Refer to Figure 3 and Figure 4 , the electrode assembly 1 may include a positive electrode 10, a separator 40, a negative electrode 20, and a central hole 50. The positive electrode 10, the separator 40, and the negative electrode 20 of the electrode assembly 1 may have a structure in which the positive electrode 10, the separator 40, and the negative electrode 20 are wound in a stacked state. The central hole 50 may be defined at the center of the electrode assembly 1. When manufacturing the electrode assembly 1, the negative electrode 20 may be placed before the positive electrode 10 is placed, and thus, the inner end portion (not shown) of the negative electrode 20 is set closer to the central hole 50 than the inner end portion (not shown) of the positive electrode 10.

[0044] The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode paste 12. The outer end portion 13 of the positive electrode 10 may be disposed inside the outer end portion 23 of the negative electrode 20. The positive electrode 10 may be coated with the positive electrode paste 12 on both surfaces up to the outer end portion 13.

[0045] The negative electrode 20 may include a negative electrode current collector 21, a negative electrode paste 22, and a negative electrode tab 24.

[0046] The outer end portion 23 of the negative electrode 20 may be disposed outside the outer end portion 13 of the positive electrode 10 with respect to the central hole 50.

[0047] The central hole 50 may be defined due to the structure in which the negative electrode 20, the positive electrode 10, and the separator 40 are wound. The center point 51 may be disposed at the center of the central hole 50.

[0048] The negative electrode tab 24 may be disposed at a position through which a virtual line 60 passing through the outer end portion 13 of the positive electrode 10 and the center point 51 of the central hole 50 passes. The negative electrode tab 24 may include an outer negative electrode tab 241 and an inner negative electrode tab 242. The negative electrode tab 24 may be disposed at the position through which the virtual line 60 passes to support the negative electrode 20.

[0049] The outer negative electrode tab 241 may be disposed outside the outer end portion 13 of the positive electrode 10 with respect to the central hole 50. The outer negative electrode tab 241 may be disposed at the position through which the virtual line 60 passes. In order to dispose the outer negative electrode tab 241 on the virtual line 60, the negative electrode 20 may be extended longer, and thus, an additional layer of the negative electrode 20 may be provided on the outermost layer.

[0050] The inner negative electrode connecting piece 242 can be disposed inside the outer end portion 13 of the positive electrode 10 relative to the central hole 50. The inner negative electrode connecting piece 242 can be disposed on the negative electrode 20 facing the central hole 50.

[0051] The negative electrode current collector 21 can include a top surface 211 and a bottom surface 212. The bottom surface 212 of the negative electrode current collector 21 can be disposed to face the central hole 50. The top surface 211 of the negative electrode current collector 21 can be disposed on the opposite surface of the bottom surface 212. Both the top surface 211 and the bottom surface 212 of the negative electrode current collector 21 can be disposed parallel to each other.

[0052] At the negative electrode current collector 21, the negative electrode paste 22 can be coated on the top surface 211 and the bottom surface 212 facing the outer end portion 13 of the positive electrode 10 from the outer end portion 13 of the positive electrode 10 toward the outer end portion 23 of the negative electrode 20 for a preset length. It is not necessary to coat the negative electrode paste 22 on the top surface 211 and the bottom surface 212 corresponding to the portion where the positive electrode 10 is not provided. The negative electrode paste 12 may not be coated on the top surface 211 and the bottom surface 212 from the outer end portion 13 of the positive electrode 10 after the preset length until the outer end portion 23 of the negative electrode 20.

[0053] The outer negative electrode connecting piece 241 can be disposed at a point where neither the top surface 211 nor the bottom surface 212 is coated with the negative electrode paste 22. The outer negative electrode connecting piece 241 can be disposed on the top surface 211.

[0054] The electrode assembly 1 can further include a protective tape 30. The negative electrode current collector 21 can be attached with a first protective tape 31 and a second protective tape 32.

[0055] The first protective tape 31 can be attached to the bottom surface 212 corresponding to the surface on which the outer negative electrode connecting piece 241 is disposed. The first protective tape 31 can be set to be longer than the outer negative electrode connecting piece 241. When the outer negative electrode connecting piece 241 is disposed on the negative electrode 20, the first protective tape 31 can protect the portion protruding from the corresponding surface.

[0056] The second protective tape 32 can be attached to the top surface 211 facing the bottom surface 212 to which the first protective tape 31 is attached. The second protective tape 32 can be attached to the top surface 211 corresponding to the point where the negative electrode paste 22 is coated on the bottom surface 212. The second protective tape 32 can protect the top surface 211 of the negative electrode 20 on which the negative electrode paste 22 is not coated.

[0057] The separator 40 can be disposed between the first protective tape 31 and the second protective tape 32.

[0058] In Embodiment 1 of the present invention, since the external negative tab 241 is disposed on the virtual line 60 between the center point 51 of the central hole 50 and the outer end portion 13 of the positive electrode 10, the problem of cracking that occurs when the electrode assembly 1 is charged and the negative electrode may expand, causing stress to concentrate on the negative electrode 20 facing the outer end portion 13 of the positive electrode 10 and damaging the negative electrode 20, is solved. That is, when the external negative tab 241 is disposed on the virtual line 60, the gap between the housing 2 of the electrode assembly 1 and the outer end portion 23 of the negative electrode 20 becomes narrow. Therefore, when the negative electrode 20 expands during charging / discharging of the electrode assembly 1, compared with the related art, the degree of expansion of the negative electrode 20 can be reduced due to the narrowing of the gap, and thus the degree of stretching that occurs can also be reduced. This has the effect of reducing the degree of reduction in the thickness of the negative electrode 20. Since the degree of reduction in the thickness of the negative electrode 20 is reduced, even if the same stress concentrates on the negative electrode 20, compared with the related art, the risk of the negative electrode 20 breaking can be naturally reduced, thereby preventing damage to the negative electrode 20.

[0059] Embodiment 2

[0060] Hereinafter, the electrode assembly according to Embodiment 2 of the present invention will be described in detail with reference to Figure 5 and Figure 6 FIGs.

[0061] Figure 5 is a view illustrating a state in which the separator is omitted and the positive and negative electrodes are wound in the electrode assembly according to Embodiment 2 of the present invention, and Figure 6 is a plan view illustrating the end portions of the positive and negative electrodes in the electrode assembly according to Embodiment 2 of the present invention.

[0062] Embodiment 2 of the present invention is different from Embodiment 1 in the position of the external negative tab 241, and a third protection band 33 is provided. The content repeated from Embodiment 1 will be omitted as much as possible, and Embodiment 2 will be described by focusing on the differences.

[0063] The external negative tab 241 may be disposed on the bottom surface 212. The electrode assembly 1 may further include a third protection band 33.

[0064] The second protection band 32 may be attached to the top surface 211 facing the bottom surface 212 to which the external negative tab 241 is attached.

[0065] A separator 40 may be disposed between the external negative tab 241 and the second protection band 32.

[0066] In Embodiment 2 of the present invention, the outer negative electrode tab 241 may be disposed on the virtual line 60 passing through the center point 51 of the central hole 50 and the outer end portion 13 of the positive electrode 10 and on the bottom surface 212 of the negative electrode 20, so as to solve the problem of cracking in which the negative electrode 20 expands during charging / discharging of the electrode assembly 1, causing stress to concentrate on the negative electrode 20 and damaging the negative electrode 20.

[0067] Although embodiments of the present invention have been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention as defined in the appended claims.

[0068] [Reference Signs]

[0069] 1: Electrode assembly

[0070] 2: Electrode assembly housing

[0071] 10: Positive electrode

[0072] 11: Positive electrode current collector

[0073] 12: Positive electrode paste

[0074] 20: Negative electrode

[0075] 21: Negative electrode current collector

[0076] 22: Negative electrode paste

[0077] 24: Negative electrode tab

[0078] 241: Outer negative electrode tab

[0079] 242: Inner negative electrode tab

[0080] 30: Protective tape

[0081] 31: First protective tape

[0082] 32: Second protective tape

[0083] 33: Third protective tape

[0084] 40: Separator

[0085] 50: Central hole

[0086] 60: Virtual line

Claims

1. An electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are wound in a stacked state, and the electrode assembly includes a central hole at its center. Wherein, The outer end portion of the negative electrode is disposed outside the outer end portion of the positive electrode with respect to the central hole. The positive electrode includes: A positive current collector; and A positive electrode paste coated on the positive current collector. The negative electrode includes: A negative current collector; A negative electrode paste coated on the negative current collector; and A negative electrode tab disposed on the negative current collector, wherein the negative electrode tab is disposed at a position through which a virtual line passing through the outer end portion of the positive electrode and the center point of the central hole passes.

2. The electrode assembly according to claim 1, wherein, The negative electrode tab includes: An outer negative electrode tab disposed outside the outer end portion of the positive electrode with respect to the central hole; and An inner negative electrode tab disposed inside the outer end portion of the positive electrode with respect to the central hole, wherein the outer negative electrode tab is disposed at the position through which the virtual line passes.

3. The electrode assembly according to claim 2, wherein, The negative current collector includes: A bottom surface which is a surface facing the direction of the central hole; and A top surface disposed opposite to the bottom surface.

4. The electrode assembly according to claim 3, wherein, The negative electrode paste is coated on the top surface and the bottom surface facing the outer end portion of the positive electrode for a preset length from the outer end portion of the positive electrode toward the outer end portion of the negative electrode, and The negative electrode paste is not coated from the outer end portion of the positive electrode after the preset length until the outer end portion of the negative electrode.

5. The electrode assembly according to claim 4, wherein, The outer negative electrode tab is disposed at a position where the negative electrode paste is not coated on both the top surface and the bottom surface.

6. The electrode assembly according to claim 5, wherein, The outer negative electrode tab is disposed on the top surface, and A first protective tape is attached to the bottom surface corresponding to the surface on which the outer negative electrode tab is disposed.

7. The electrode assembly according to claim 6, wherein, A second protective tape is attached to the top surface facing the bottom surface to which the first protective tape is attached.

8. The electrode assembly according to claim 7, wherein, The separator is disposed between the first protective tape and the second protective tape.

9. The electrode assembly according to claim 8, wherein, The first protective tape is set to be longer than the outer negative electrode tab.

10. The electrode assembly according to claim 9, wherein, The first protective tape is set to have the same length as the second protective tape or to be longer than the second protective tape.

11. The electrode assembly according to claim 5, wherein, The outer negative electrode tab is disposed on the bottom surface, and A third protective tape is attached to the top surface corresponding to the surface on which the outer negative electrode tab is disposed.

12. The electrode assembly according to claim 11, wherein, A second protective tape is attached to the top surface facing the bottom surface to which the outer negative electrode tab is attached, and The separator is disposed between the outer negative electrode tab and the second protective tape.

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