Electrode group three-dimensional

Abstract

The present invention relates to an electrode assembly having a winding structure, and more particularly to an electrode assembly for alleviating the problem of cracks and breaks in the negative electrode by alleviating stress generated in the negative electrode facing the outer end portion of the 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 stacked and wound up, and includes a central hole in the center. The outer end of the negative electrode is disposed outward from the outer end of the positive electrode relative to the central hole. The positive electrode includes a positive electrode current collector and positive electrode slurry coated on the positive electrode current collector. The negative electrode includes a negative electrode current collector, negative electrode slurry coated on the negative electrode current collector, and a negative electrode tab disposed on the negative electrode current collector. The negative electrode tab is disposed at a location where an imaginary line passing through the outer end of the positive electrode and the center point of the central hole passes.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0144045 dated November 1, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly having a winding structure, and more particularly to an electrode assembly for alleviating the problem of cracks and breaks in the negative electrode by alleviating stress generated in the negative electrode facing the outer end portion of the positive electrode. [Background technology]

[0003] Batteries that store electrical energy can generally be divided into primary batteries and secondary batteries. Primary batteries are disposable, consumable batteries, while secondary batteries are rechargeable batteries manufactured using materials that can undergo repeated oxidation and reduction processes between electric current and substances.

[0004] That is, when a reduction reaction of the material occurs due to an electric current, the power source is charged, and when an oxidation reaction of the material occurs, the power source is discharged, and this charging and discharging can be repeated.

[0005] Among various types of secondary batteries, lithium secondary batteries are generally manufactured by mounting an electrode assembly, in which a cathode, a separator, and an anode are stacked, in a case. The lithium secondary battery is charged and discharged by repeating the process of intercalation and deintercalation of lithium ions from the lithium metal oxide of the cathode to the anode.

[0006] The electrode assembly is generally formed by stacking a plurality of unit cells, each of which has a cathode, a separator, and a cathode cut to a predetermined size and stacked in a predetermined order, or by repeatedly stacking individual cathode / separator / anode units, and is housed in a case such as a cylindrical can or a rectangular pouch.

[0007] Meanwhile, methods for manufacturing the electrode assembly include a winding type in which a separator is laminated between the negative electrode and the positive electrode and then wound up; a stacking type in which the negative electrode and the positive electrode are cut to have a required width and length, and then the negative electrode, separator, and positive electrode are stacked in an alternating pattern; and a stack-and-folding type in which unit cells are placed side by side on a folding separator and then folded from one side.

[0008] Among these, the wound type (jelly roll type) electrode assembly is manufactured by fixing a first separator to a core, and sequentially inserting a negative electrode, a second separator, and a positive electrode while the core is rotating (the order of inserting the separator, negative electrode, and positive electrode may vary depending on the case).

[0009] Meanwhile, cylindrical batteries are constructed by rolling up positive and negative electrodes with a separator between them into a cylindrical jelly roll, which is then inserted into a metal can to create a cylindrical battery cell. With conventional technology, the negative electrode expands during charging, typically increasing its thickness by 10-20%. Due to the inherent structural characteristics of cylindrical batteries, the outer diameter of the jelly roll increases, and the circumference of the outermost negative electrode increases, causing stretching of the copper current collector. In particular, when the negative electrode faces the step at the end of the positive electrode, stress is concentrated at the step when it expands. In severe cases, this can lead to cracking, damaging not only the electrode layer but also the copper foil. In particular, the recent trend toward developing high-capacity cylindrical cells has led to designs that increase the energy density of electrodes, gradually thinning the copper foil, increasing the risk of cracking or disconnection of the negative electrode. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention aims to provide an electrode assembly that alleviates the above-mentioned conventional problems by alleviating stress generated in the negative electrode facing the outer end portion of the positive electrode, thereby improving the problem of cracks and breaks in the negative electrode. [Means for solving the problem]

[0011] 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 stacked and wound, and may include a central hole in the center. An outer end of the negative electrode is disposed outward from the outer end of the positive electrode relative to the central hole. The positive electrode may include a positive electrode current collector and positive electrode slurry coated on the positive electrode current collector. The negative electrode may include a negative electrode current collector, negative electrode slurry coated on the negative electrode current collector, and a negative electrode tab disposed on the negative electrode current collector. The negative electrode tab may be disposed at a location where an imaginary line passing through the outer end of the positive electrode and a center point of the central hole passes.

[0012] The negative electrode tab may include an outer negative electrode tab disposed outward from the outer end of the positive electrode relative to the central hole, and an inner negative electrode tab disposed inward from the outer end of the positive electrode relative to the central hole, and the outer negative electrode tab may be disposed where the imaginary line passes.

[0013] The negative electrode current collector may include a lower surface facing the central hole and an upper surface opposite to the lower surface.

[0014] The upper surface and the lower surface facing the outer end of the positive electrode may be coated with the negative electrode slurry up to a predetermined length from the outer end of the positive electrode toward the outer end of the negative electrode, and the negative electrode slurry may not be coated from the predetermined length from the outer end of the positive electrode to the outer end of the negative electrode.

[0015] The outer negative electrode tab may be disposed at a point where the negative electrode slurry is not applied to either the upper surface or the lower surface.

[0016] The outer negative electrode tab may be disposed on the upper surface, and a first protective tape may be attached to the lower surface corresponding to the surface on which the outer negative electrode tab is disposed.

[0017] A second protective tape may be attached to the upper surface opposite to the lower surface to which the first protective tape is attached.

[0018] The separation film may be disposed between the first protective tape and the second protective tape.

[0019] The first protective tape may be formed to be longer than the outer negative electrode tab.

[0020] The first protective tape may be formed to be as long as or longer than the second protective tape.

[0021] The outer negative electrode tab may be disposed on the lower surface, and a third protective tape may be attached to the upper surface corresponding to the surface on which the outer negative electrode tab is disposed.

[0022] A second protective tape may be attached to the upper surface opposite to the lower surface to which the outer negative electrode tab is attached, and the separator may be disposed between the outer negative electrode tab and the second protective tape. [Effects of the Invention]

[0023] The embodiment of the present invention has the effect of alleviating stress generated in the negative electrode facing the outer end portion of the positive electrode, thereby improving the problem of cracks and breaks in the negative electrode. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a view showing a conventional electrode assembly in which a positive electrode and a negative electrode are wound up without a separator. [Figure 2] 1 is a plan view showing end portions of a positive electrode and a negative electrode in a conventional electrode assembly. [Figure 3] 1 is a view showing a state in which a positive electrode and a negative electrode are wound up, with a separator omitted, in an electrode assembly according to Example 1 of the present invention. [Figure 4] 1 is a plan view showing end portions of a positive electrode and a negative electrode in an electrode assembly according to a first embodiment of the present invention. [Figure 5] 10 is a view showing a state in which a positive electrode and a negative electrode are wound up, with a separator omitted, in an electrode assembly according to a second embodiment of the present invention. [Figure 6] FIG. 10 is a plan view showing end portions of a positive electrode and a negative electrode in an electrode assembly according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0026] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0027] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention.

[0028] FIG. 1 is a view showing a conventional electrode assembly in which a positive electrode and a negative electrode are wound up without a separator, and FIG. 2 is a plan view showing end portions of the positive electrode and the negative electrode in the conventional electrode assembly.

[0029] As shown in FIGS. 1 and 2, in the conventional electrode assembly 1, when the negative electrode 20 expands, stress is concentrated at the stepped portion of the outer end 13 of the positive electrode 10, which can cause cracks that damage the negative electrode 20.

[0030] An embodiment of the electrode assembly 1 that solves this problem will be described below.

[0031] Example 1 Hereinafter, the electrode assembly according to the first embodiment of the present invention will be described in detail with reference to FIGS.

[0032] FIG. 3 is a view illustrating a wound cathode and anode without a separator in an electrode assembly according to a first embodiment of the present invention, and FIG. 4 is a plan view illustrating end portions of the cathode and anode in the electrode assembly according to the first embodiment of the present invention.

[0033] 3 and 4, the electrode assembly 1 may include a positive electrode 10, a separator 40, a negative electrode 20, and a center hole 50. The positive electrode 10, the separator 40, and the negative electrode 20 of the electrode assembly 1 may be stacked and wound up. The center hole 50 may be formed in the center of the middle of the electrode assembly 1. When the electrode assembly 1 is manufactured, the negative electrode 20 is inserted before the positive electrode 10, so the inner end (not shown) of the negative electrode 20 may be located closer to the center hole 50 than the inner end (not shown) of the positive electrode 10.

[0034] The positive electrode 10 may include a positive electrode current collector 11 and a positive electrode slurry 12. An outer terminal end 13 of the positive electrode 10 may be located inside an outer terminal end 23 of the negative electrode 20. The positive electrode 10 may be coated with the positive electrode slurry 12 on both sides thereof up to the outer terminal end 13.

[0035] The negative electrode 20 can include a negative electrode current collector 21 , a negative electrode slurry 22 , and a negative electrode tab 24 .

[0036] The outer end 23 of the negative electrode 20 may be positioned more outward than the outer end 13 of the positive electrode 10 with respect to the central hole 50 .

[0037] The central hole 50 may be formed by a structure in which the negative electrode 20, the positive electrode 10, and the separator 40 are wound up. A central point 51 may be formed in the center of the central hole 50.

[0038] The negative electrode tab 24 may be positioned at a location where an imaginary line 60 passes through the outer end 13 of the positive electrode 10 and the center point 51 of the central hole 50. 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 positioned at the location where the imaginary line 60 passes to support the negative electrode 20.

[0039] The outer negative electrode tab 241 may be disposed outside the outer end 13 of the positive electrode 10 based on the central hole 50. The outer negative electrode tab 241 may be disposed at a location where an imaginary line 60 passes. Because the outer negative electrode tab 241 is disposed on the imaginary line 60, the negative electrode 20 may be elongated, and accordingly, an additional negative electrode 20 may be formed at the outermost position.

[0040] The inner negative electrode tab 242 may be disposed on the negative electrode 20 facing the central hole 50, inward from the outer end 13 of the positive electrode 10. The inner negative electrode tab 242 may be disposed on the negative electrode 20 facing the central hole 50.

[0041] The negative electrode current collector 21 may include an upper surface 211 and a lower surface 212. The lower surface 212 of the negative electrode current collector 21 may be formed so as to face the central hole 50. The upper surface 211 of the negative electrode current collector 21 may be formed on the opposite side of the lower surface 212. The upper surface 211 and the lower surface 212 of the negative electrode current collector 21 may be formed parallel to each other.

[0042] The upper surface 211 and the lower surface 212 of the negative electrode current collector 21 facing the outer end 13 of the positive electrode 10 may be coated with the negative electrode slurry 22 up to a predetermined length from the outer end 13 of the positive electrode 10 toward the outer end 23 of the negative electrode 20. The upper surface 211 and the lower surface 212 corresponding to the portion where the positive electrode 10 is not present do not need to be coated with the negative electrode slurry 22. The upper surface 211 and the lower surface 212 facing the outer end 13 of the positive electrode 10 do not need to be coated with the negative electrode slurry 12 from the outer end 13 of the positive electrode 10 beyond the predetermined length to the outer end 23 of the negative electrode 20.

[0043] The outer negative electrode tab 241 may be disposed at a point where the negative electrode slurry 22 is not applied to either the upper surface 211 or the lower surface 212. The outer negative electrode tab 241 may be disposed on the upper surface 211.

[0044] The electrode assembly 1 may further include a protective tape 30. A first protective tape 31 and a second protective tape 32 may be attached to the negative electrode current collector 21.

[0045] The first protective tape 31 may be attached to the lower surface 212 corresponding to the surface on which the outer negative electrode tab 241 is disposed. The first protective tape 31 may be formed to be longer than the outer negative electrode tab 241. The first protective tape 31 may protect a portion of the outer negative electrode tab 241 that protrudes from the corresponding surface due to the outer negative electrode tab 241 being disposed on the negative electrode 20.

[0046] The second protective tape 32 may be attached to the upper surface 211 opposite the lower surface 212 to which the first protective tape 31 is attached. The second protective tape 32 may be attached to the upper surface 211 at a location on the lower surface 212 where the negative electrode slurry 22 is applied. The second protective tape 32 may protect the upper surface 211 of the negative electrode 20 where the negative electrode slurry 22 is not applied.

[0047] A separation membrane 40 may be disposed between the first protective tape 31 and the second protective tape 32 .

[0048] In Example 1 of the present invention, the outer negative electrode tab 241 is positioned on an imaginary line 60 that passes through the center point 51 of the central hole 50 and the outer end 13 of the positive electrode 10. This solves the problem of stress concentration on the negative electrode 20 facing the outer end 13 of the positive electrode 10 due to expansion of the negative electrode during charging of the electrode assembly 1, resulting in cracking and damage to the negative electrode 20. That is, when the outer negative electrode tab 241 is positioned on the imaginary line 60, the distance between the case 2 of the electrode assembly 1 and the outer end 23 of the negative electrode 20 is narrowed. Therefore, when the negative electrode 20 expands during charging / discharging of the electrode assembly 1, the degree of expansion of the negative electrode 20 is reduced by the narrower distance, thereby reducing the degree of elongation. This has the effect of reducing the degree of thickness reduction of the negative electrode 20. Because the degree of thickness reduction of the negative electrode 20 is reduced, even if the same stress is concentrated on the negative electrode 20, the risk of cracking the negative electrode 20 is naturally reduced, and damage to the negative electrode 20 can be prevented.

[0049] Example 2 Hereinafter, an electrode assembly according to a second embodiment of the present invention will be described in detail with reference to FIGS.

[0050] FIG. 5 is a view illustrating a state in which a positive electrode and a negative electrode are wound up without a separator in an electrode assembly according to a second embodiment of the present invention, and FIG. 6 is a plan view illustrating end portions of a positive electrode and a negative electrode in an electrode assembly according to a second embodiment of the present invention.

[0051] Example 2 of the present invention may differ from Example 1 in that the position of the outer negative electrode tab 241 is different and the third protective tape 33 may be included. Details common to Example 1 will be omitted as much as possible, and Example 2 will be described focusing on the differences.

[0052] The outer negative electrode tab 241 may be disposed on the lower surface 212. The electrode assembly 1 may further include a third protective tape 33.

[0053] The second protective tape 32 may be attached to the upper surface 211 opposite the lower surface 212 to which the outer negative electrode tab 241 is attached.

[0054] A separator 40 may be disposed between the outer negative electrode tab 241 and the second protective tape 32 .

[0055] In the second embodiment of the present invention, the outer negative electrode tab 241 is disposed on an imaginary line 60 passing through the center point 51 of the central hole 50 and the outer end 13 of the positive electrode 10, and is disposed on the underside 212 of the negative electrode 20. This solves the problem of cracks, which occur when stress caused by expansion of the negative electrode 20 during charge / discharge of the electrode assembly 1 is concentrated on the negative electrode 20 and damages the negative electrode 20, as in the first embodiment of the present invention.

[0056] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and various embodiments can be made by a person having ordinary skill in the art to which the present invention pertains within the technical spirit of the present invention and the scope of equivalents of the claims set forth below. [Explanation of symbols]

[0057] 1 Electrode assembly 2 Electrode assembly case 10 positive electrode 11 Positive electrode current collector 12 Positive electrode slurry 20 negative electrode 21 Negative electrode current collector 22 Anode slurry 24 Negative electrode tab 241 outer negative electrode tab 242 Inner negative tab 30 protective tape 31 First protective tape 32 Second protective tape 33 Third protective tape 40 Separation membrane 50 Central Hall 60 Imaginary Line

Claims

1. An electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are stacked and wound, and including a central hole in the center, an outer end of the negative electrode is disposed outward from an outer end of the positive electrode relative to the central hole; The positive electrode is a positive electrode current collector; and a positive electrode slurry applied onto the positive electrode current collector, The negative electrode is Negative electrode current collector; a negative electrode slurry applied onto the negative electrode current collector; and a negative electrode tab disposed on the negative electrode current collector, an electrode assembly, wherein the negative electrode tab is disposed at a location where an imaginary line passing through the outer end of the positive electrode and the center point of the central hole passes;

2. The negative electrode tab is an outer negative electrode tab positioned outward from the outer end of the positive electrode relative to the central hole; and an inner negative electrode tab disposed inward from the outer end of the positive electrode with respect to the central hole; The electrode assembly of claim 1 , wherein the outer negative electrode tab is located where the imaginary line passes.

3. The negative electrode current collector is a lower surface that faces the central hole; and The electrode assembly of claim 2 , further comprising an upper surface formed opposite said lower surface.

4. The upper and lower surfaces facing the outer end of the positive electrode are The negative electrode slurry is applied from the outer end of the positive electrode to a predetermined length in a direction toward the outer end of the negative electrode, The electrode assembly of claim 3 , wherein the negative electrode slurry is not applied from a predetermined length from the outer end of the positive electrode to the outer end of the negative electrode.

5. The electrode assembly of claim 4 , wherein the outer negative electrode tab is disposed at a point on the upper surface and the lower surface where the negative electrode slurry is not applied.

6. the outer negative electrode tab is disposed on the top surface; The electrode assembly of claim 5 , wherein a first protective tape is attached to the lower surface corresponding to a surface on which the outer negative electrode tab is disposed.

7. The electrode assembly of claim 6 , wherein a second protective tape is attached to the upper surface opposite to the lower surface to which the first protective tape is attached.

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

9. The electrode assembly of claim 8 , wherein the first protective tape is longer than the outer negative electrode tab.

10. The electrode assembly of claim 9 , wherein the first protective tape is formed to be as long as or longer than the second protective tape.

11. the outer negative electrode tab is disposed on the lower surface; The electrode assembly of claim 5 , wherein a third protective tape is attached to the upper surface corresponding to a surface on which the outer negative electrode tab is disposed.

12. a second protective tape is attached to the upper surface opposite to the lower surface to which the outer negative electrode tab is attached; The electrode assembly of claim 11 , wherein the separator is disposed between the outer negative electrode tab and the second protective tape.

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