Electrode assembly 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 filed on November 1, 2022, and all the contents disclosed in the literature of the Korean patent application are included as part of this specification.

[0002] The present invention relates to an electrode assembly having a winding structure, and specifically, to an electrode assembly for relaxing stress generated in a negative electrode facing a portion of an outer terminal of a positive electrode and improving problems such as cracks and disconnection of the negative electrode.

Background Art

[0003] Batteries for storing electrical energy can generally be classified into primary batteries and secondary batteries. A primary battery is a disposable consumable battery, while a secondary battery is a rechargeable battery manufactured using a material in which the process of oxidation and reduction between current and matter can be repeated.

[0004] That is, when a reduction reaction with respect to a material is performed by current, the power source is charged, and when an oxidation reaction with respect to the material is performed, the power source is discharged, and such charging and discharging can be repeated.

[0005] Among various types of secondary batteries, a lithium secondary battery is generally manufactured by mounting an electrode assembly in which a positive electrode (Cathode), a separator, and a negative electrode (Anode) are laminated in a case, and the charging and discharging of the lithium secondary battery proceeds while the process of insertion (Intercalation) and desorption (Deintercalation) of lithium ions from the lithium metal oxide of the positive electrode to the negative electrode is repeated.

[0006] The electrode assembly is generally constructed by stacking multiple unit cells, each containing a negative electrode, a separator membrane, and a positive electrode cut to a predetermined size and stacked in a predetermined order, or by repeatedly stacking individual positive electrodes, separator membranes, and negative electrodes to form a single electrode assembly. Such electrode assemblies are then housed in cases such as cylindrical cans or rectangular pouches.

[0007] On the other hand, methods for manufacturing the electrode assembly have become known, including a winding type in which a separation membrane is laminated between the negative electrode and the positive electrode and then wound up; a laminated type in which the negative electrode, separation membrane, and positive electrode are cut to the required width and length, and then laminated in a repeating manner; and a stack-and-folding type in which unit cells are placed side by side on a folding separation membrane and then folded from one side.

[0008] Of these, the winding type (jelly roll type) electrode assembly is manufactured by fixing the first separation membrane to a winding core, and then sequentially inserting the negative electrode, the second separation membrane, and the positive electrode while the winding core rotates (the order in which the separation membrane, negative electrode, and positive electrode are inserted may vary depending on the circumstances).

[0009] On the other hand, in cylindrical batteries, due to their structural characteristics, the positive electrode, negative electrode, and separator membrane in between are rolled up in a cylindrical pattern to form a jelly roll, which is then placed in a metal can to create a cylindrical battery cell. In conventional technology, the negative electrode expands during charging, usually increasing in thickness by about 10-20%. Due to the structural characteristics inherent to 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, the negative electrode facing the step at the end of the positive electrode experiences stress concentration at the step at the end of the positive electrode during expansion, and in severe cases, this can lead to cracks that damage not only the electrode layer but also the copper foil. Especially recently, with the trend towards developing high-capacity cylindrical cells, the design is moving in a direction that increases the energy density of the electrodes, and the thickness of the copper foil is gradually decreasing, which presents a problem of increasing risk of cracks or disconnections in the negative electrode. [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention aims to provide an electrode assembly that can overcome the conventional problems described above by relieving the stress generated in the negative electrode facing the outer terminal portion of the positive electrode, thereby improving the problem of cracks and disconnections in the negative electrode. [Means for solving the problem]

[0011] An electrode assembly according to an embodiment of the present invention has a structure in which a positive electrode, a separator membrane, and a negative electrode are wound in a stacked state, and includes a central hole in the middle, the outer end of the negative electrode is positioned outside the outer end of the positive electrode with respect to the central hole, the positive electrode includes a positive electrode current collector and a positive electrode slurry applied on the positive electrode current collector, the negative electrode includes a negative electrode current collector, a negative electrode slurry applied on the negative electrode current collector, and a negative electrode tab positioned on the negative electrode current collector, the negative electrode tab may be positioned where a hypothetical line passing through the outer end of the positive electrode and the center point of the central hole passes.

[0012] The negative electrode tab includes an outer negative electrode tab positioned outside the outer end of the positive electrode with respect to the central hole, and an inner negative electrode tab positioned inside the outer end of the positive electrode with respect to the central hole, wherein the outer negative electrode tab may be positioned where the imaginary line passes.

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

[0014] The upper and lower surfaces facing the outer end of the positive electrode are coated with the negative electrode slurry up to a length already set in the direction from the outer end of the positive electrode towards the outer end of the negative electrode, but the negative electrode slurry does not need to be applied from the length already set in the direction from the outer end of the positive electrode to the outer end of the negative electrode.

[0015] The outer negative electrode tab may be positioned at a location where the negative electrode slurry is not applied to both the upper and lower surfaces.

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

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

[0018] The separation membrane may be placed between the first protective tape and the second protective tape.

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

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

[0021] The outer negative electrode tab is positioned 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 positioned.

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

[0023] Through embodiments of the present invention, it is possible to alleviate the stress generated in the negative electrode facing the outer terminal portion of the positive electrode, thereby improving the problem of cracks and disconnections in the negative electrode. [Brief explanation of the drawing]

[0024] [Figure 1] This diagram shows a conventional electrode assembly with the separation membrane omitted and the positive and negative electrodes wound together. [Figure 2] It is a plan view showing the terminal portions of the positive electrode and the negative electrode in a conventional electrode assembly. [Figure 3] FIG. 4 is a view showing a state in which the positive electrode and the negative electrode are wound up with the separator omitted in the electrode assembly according to Example 1 of the present invention. [Figure 4] FIG. 7 is a plan view showing the terminal portions of the positive electrode and the negative electrode in the electrode assembly according to Example 1 of the present invention. [Figure 5] FIG. 10 is a view showing a state in which the positive electrode and the negative electrode are wound up with the separator omitted in the electrode assembly according to Example 2 of the present invention. [Figure 6] FIG. 13 is a plan view showing the terminal portions of the positive electrode and the negative electrode in the electrode assembly according to Example 2 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0025] Hereinafter, based on the attached drawings, the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0026] To clearly explain the present invention, parts not related to the explanation are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0027] Also, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor should interpret them in accordance with the principle that the concept of the terms can be appropriately defined in order to explain his invention in the best way, and they should be construed as meanings and concepts that conform to the technical idea of the present invention.

[0028] FIG. 1 is a view showing a state in which the positive electrode and the negative electrode are wound up with the separator omitted in a conventional electrode assembly, and FIG. 2 is a plan view showing the terminal portions of the positive electrode and the negative electrode in a conventional electrode assembly.

[0029] As shown in Figures 1 and 2, in the conventional electrode assembly 1, when the negative electrode 20 expands, stress concentrates 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] The following describes an embodiment of electrode assembly 1 that solves this problem.

[0031] Example 1 In the following section, the electrode assembly according to Embodiment 1 of the present invention will be described in detail with reference to Figures 3 and 4.

[0032] Figure 3 shows the electrode assembly according to Embodiment 1 of the present invention, with the separation membrane omitted and the positive and negative electrodes wound together. Figure 4 is a plan view showing the terminal portions of the positive and negative electrodes in the electrode assembly according to Embodiment 1 of the present invention.

[0033] Referring to Figures 3 and 4, the electrode assembly 1 may include a positive electrode 10, a separator membrane 40, a negative electrode 20, and a central hole 50. The positive electrode 10, separator membrane 40, and negative electrode 20 of the electrode assembly 1 may be wound in a stacked state. A central hole 50 may be formed in the center 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 central 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. The outer end 13 of the positive electrode 10 may be located inside the outer end 23 of the negative electrode 20. Both sides of the positive electrode 10, up to the outer end 13, may be coated with the positive electrode slurry 12.

[0035] The negative electrode 20 may 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 outside the outer end 13 of the positive electrode 10 with respect to the center hole 50.

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

[0038] The negative electrode tab 24 may be positioned where a virtual line 60 passes through the outer end 13 of the positive electrode 10 and the center point 51 of the center 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 can support the negative electrode 20 by being positioned where the virtual line 60 passes through.

[0039] The outer negative electrode tab 241 may be positioned outside the outer end 13 of the positive electrode 10 with respect to the center hole 50. The outer negative electrode tab 241 may be positioned where a virtual line 60 passes. Because the outer negative electrode tab 241 is positioned on the virtual line 60, the negative electrode 20 is extended further, and consequently, another layer of the negative electrode 20 may be generated on the outermost side.

[0040] The inner negative electrode tab 242 may be positioned inside the outer end 13 of the positive electrode 10 with respect to the center hole 50. The inner negative electrode tab 242 may be positioned on the negative electrode 20 facing the center 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 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 both be formed parallel to each other.

[0042] On the upper surface 211 and lower surface 212 of the negative electrode current collector 21 facing the outer end 13 of the positive electrode 10, the negative electrode slurry 22 may be applied to a predetermined length in the direction from the outer end 13 of the positive electrode 10 to the outer end 23 of the negative electrode 20. The upper surface 211 and lower surface 212 corresponding to the portion where there is no positive electrode 10 do not need to be coated with the negative electrode slurry 22. On the upper surface 211 and lower surface 212 facing the outer end 13 of the positive electrode 10, the negative electrode slurry 12 does not need to be applied from a predetermined length from the outer end 13 of the positive electrode 10 to the outer end 23 of the negative electrode 20.

[0043] The outer negative electrode tab 241 may be positioned at a location where the negative electrode slurry 22 is not applied to the entire upper surface 211 and lower surface 212. The outer negative electrode tab 241 may be positioned on the upper surface 211.

[0044] The electrode assembly 1 may further include a protective tape 30. The first protective tape 31 and the 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 positioned. The first protective tape 31 may be formed to be longer than the outer negative electrode tab 241. The first protective tape 31 can protect the portion of the outer negative electrode tab 241 that protrudes from the corresponding surface when it is positioned on the negative electrode 20.

[0046] The second protective tape 32 may be attached to the upper surface 211 facing 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 corresponding to the point on the lower surface 212 where the negative electrode slurry 22 is applied. The second protective tape 32 can protect the upper surface 211 of the negative electrode 20 to which the negative electrode slurry 22 is not applied.

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

[0048] In Embodiment 1 of the present invention, the outer negative electrode tab 241 is positioned on a virtual line 60 passing 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 cracks that damage the negative electrode 20 when the electrode assembly 1 is charged, due to the expansion of the negative electrode causing stress to concentrate on the negative electrode 20 facing the outer end 13 of the positive electrode 10. Specifically, when the outer negative electrode tab 241 is positioned on the virtual line 60, the distance between the case 2 of the electrode assembly 1 and the outer end 23 of the negative electrode 20 is reduced. Therefore, when the negative electrode 20 expands during charging / discharging of the electrode assembly 1, the degree to which the negative electrode 20 expands is reduced compared to the conventional method due to the reduced distance, and this also reduces the degree to which stretching occurs. This has the effect of reducing the degree to which the thickness of the negative electrode 20 decreases. Since the degree to which the thickness of the negative electrode 20 decreases is reduced, even if the same stress is concentrated on the negative electrode 20, the risk of cracks in the negative electrode 20 is naturally reduced compared to before, and damage to the negative electrode 20 can be prevented.

[0049] Example 2 In the following section, the electrode assembly according to Embodiment 2 of the present invention will be described in detail with reference to Figures 5 and 6.

[0050] Figure 5 shows the electrode assembly according to Embodiment 2 of the present invention, with the separation membrane omitted and the positive and negative electrodes wound together. Figure 6 is a plan view showing the terminal portions of the positive and negative electrodes in the electrode assembly according to Embodiment 2 of the present invention.

[0051] Embodiment 2 of the present invention may differ from Embodiment 1 in that the position of the outer negative electrode tab 241 is different and the third protective tape 33 can be included. We will omit as much of the content common to Embodiment 1 as possible and describe Embodiment 2 focusing on the differences.

[0052] The outer negative electrode tab 241 may be positioned on the bottom 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 that faces the lower surface 212 to which the outer negative electrode tab 241 is attached.

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

[0055] In Embodiment 2 of the present invention, the outer negative electrode tab 241 is positioned on a virtual 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 positioned on the lower surface 212 of the negative electrode 20. This solves the problem of cracks that damage the negative electrode 20, as in Embodiment 1 of the present invention, due to the stress concentrated on the negative electrode 20 caused by the expansion of the negative electrode 20 during charging / discharging of the electrode assembly 1.

[0056] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible by persons with ordinary skill in the art to which the present invention pertains, within the equivalent scope of the technical concept of the present invention and the claims described 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 Negative electrode slurry 24 Negative Electrode Tabs 241 Outer negative terminal tab 242 Inner negative terminal tab 30 protective tapes 31. First protective tape 32. Second protective tape 33. Third protective tape 40 Separation membrane 50 Central Hall 60 virtual lines

Claims

1. An electrode assembly having a structure in which a positive electrode, a separator membrane, and a negative electrode are wound in a stacked state, and including a central hole in the middle, The outer end of the negative electrode is positioned outside the outer end of the positive electrode with respect to the central hole. The positive electrode is, Positive electrode current collector; and The positive electrode slurry is applied to the positive electrode current collector, The aforementioned negative electrode is Negative electrode current collector; A negative electrode slurry applied to the negative electrode current collector; and Includes a negative electrode tab disposed on the negative electrode current collector, The electrode assembly is such that the negative electrode tab is positioned where a hypothetical line passing through the outer end of the positive electrode and the center point of the central hole passes.

2. The aforementioned negative electrode tab is An outer negative electrode tab positioned outside the outer end of the positive electrode with respect to the central hole; and Includes an inner negative electrode tab positioned inward from the outer end of the positive electrode with respect to the central hole, The electrode assembly according to claim 1, wherein the outer negative electrode tab is positioned where the virtual line passes.

3. The aforementioned negative electrode current collector is The lower surface which is the surface viewed in the direction of the central hole; and The electrode assembly according to claim 2, including an upper surface formed opposite to the 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 the outer end of the negative electrode to a length already set, The electrode assembly according to claim 3, wherein the negative electrode slurry is not applied from a predetermined length beyond the outer end of the positive electrode to the outer end of the negative electrode.

5. The electrode assembly according to claim 4, wherein the outer negative electrode tab is positioned at a location where the negative electrode slurry is not applied to both the upper and lower surfaces.

6. The outer negative electrode tab is positioned on the upper surface, The electrode assembly according to claim 5, wherein the first protective tape is attached to the lower surface corresponding to the surface on which the outer negative electrode tab is arranged.

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

8. The electrode assembly according to claim 7, wherein the separation membrane 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 formed to be even longer than the outer negative electrode tab.

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

11. The outer negative electrode tab is positioned on the lower surface, The electrode assembly according to any one of claims 5 to 10, wherein a third protective tape is attached to the upper surface corresponding to the surface on which the outer negative electrode tab is arranged.

12. A second protective tape is attached to the upper surface facing the lower surface to which the outer negative electrode tab is attached. The electrode assembly according to claim 11, wherein the separation membrane is disposed between the outer negative electrode tab and the second protective tape.

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