Electrode assembly three-dimensional

Abstract

The present invention provides an electrode assembly having a structure in which a negative electrode, a separator, and a positive electrode are stacked and wound up, and having a center hole formed in the center, the electrode assembly including: a negative electrode wound up with a negative electrode tab joined at a predetermined position; and a positive electrode having an inner end positioned closer to the center hole and an outer end opposite the inner end and positioned farther from the center hole, the negative electrode, separator, and positive electrode being wound up such that the inner end of the negative electrode is positioned closer to the center hole than the inner end of the positive electrode, and when an imaginary line is drawn between the inner end of the positive electrode and the center point of the center hole, the imaginary line passes through the negative electrode tab.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0117482 filed on September 16, 2022, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference as part of this specification.

[0002] The present invention relates to an electrode assembly having a wound structure, and more particularly, to an electrode assembly provided to solve the problems of damage to the negative electrode and the separator due to expansion of the positive electrode, resulting in short circuits, and the loosening of the separator exposed on the inner peripheral surface at the central hole.

Background Art

[0003] Batteries for storing electrical energy are generally 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 materials in which the processes of oxidation and reduction of current and substances can be repeated.

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

[0005] Among various secondary batteries, a lithium secondary battery is usually manufactured by attaching an electrode assembly in which a cathode, a separator, and an anode are laminated to a case, and the charge and discharge of the lithium secondary battery proceed while the process of intercalation and deintercalation of lithium ions from the lithium metal oxide of the cathode to the anode is repeated.

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

[0007] On the other hand, known methods for manufacturing the electrode assembly include a winding type in which a separator is stacked between the negative electrode and the positive electrode before winding; a stacking type in which the negative electrode and positive electrode are cut to have the required width and length, and then the negative electrode, separator, and positive electrode are stacked in a repeating manner; 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] In particular, the winding type (jelly roll type) electrode assembly is manufactured by fixing a first separator to a winding core and sequentially inserting the negative electrode, second separator, and positive electrode while the winding core rotates (the order in which the separator, negative electrode, and positive electrode are inserted may vary depending on the case).

[0009] Therefore, in a conventional electrode assembly, the separator is omitted, and as shown in Figure 1a, which illustrates the shape in which the negative electrode and positive electrode are wound together, a bent portion P is formed on the negative electrode 10 at a certain point on the inner end 20a of the positive electrode 20, which is a portion that bends due to the thickness of the positive electrode 20.

[0010] However, as the secondary battery repeatedly heats up and cools down during charging and discharging, the negative electrode 10 and positive electrode 20 wound around the electrode assembly contract and expand. As a result, as is more clearly shown in Figure 1b, which shows an enlarged shape of the portion where the inner end 20a of the positive electrode 20 is located in a conventional electrode assembly, the inner end 20a of the positive electrode pressurizes the separator 30 and the bent portion P of the negative electrode 10 while it is expanding.

[0011] This expansion of the positive electrode 20 could cause localized stress concentration on the negative electrode 10, potentially leading to damage to the separator 30 placed between them, and potentially causing a short circuit between the positive electrode 20 and the negative electrode 10.

[0012] Furthermore, as shown in Figure 1c, which sequentially illustrates the shape in which the separator 30 unravels due to the expansion of the positive electrode 20, there was also a possibility that the separator 30 would unravel in the region located on the innermost side of the central hole H (forming the inner circumferential surface of the central hole) and separate from the negative electrode 10. [Overview of the project] [Problems that the invention aims to solve]

[0013] Therefore, the main objective of the present invention is to provide an electrode assembly that can prevent or minimize damage to the negative electrode and separator, and prevent the separator exposed in the central hole from unraveling, even if the positive electrode expands and its inner end moves, in order to solve the conventional problems described above. [Means for solving the problem]

[0014] To achieve the above objectives, the present invention provides an electrode assembly having a structure in which a negative electrode, a separator, and a positive electrode are wound in a stacked state, with a central hole formed in the center, comprising: a negative electrode wound with a negative electrode tab joined to a predetermined position; and a positive electrode having an inner end positioned closer to the central hole and an outer end on the opposite end of the inner end, which is positioned further away from the central hole, wherein the negative electrode, the separator, and the positive electrode are wound such that the inner end of the negative electrode is positioned closer to the central hole than the inner end of the positive electrode, and when a virtual line is drawn connecting the inner end of the positive electrode and the center point of the central hole, the virtual line passes through the negative electrode tab.

[0015] The negative electrode tab includes an inner negative electrode tab that is positioned closer to the central hole than the inner end of the positive electrode, and when a virtual line is drawn connecting the inner end of the positive electrode and the center of the central hole, the virtual line passes through the inner negative electrode tab.

[0016] The positive electrode is wound up such that only one layer of negative electrode is placed between the inner end of the positive electrode and the negative electrode tab.

[0017] The negative electrode tab has a recessed groove formed on the side facing the inner end of the positive electrode, such that the surface is recessed. The recessed groove is formed in an arc shape with a predetermined curvature.

[0018] More specifically, the recessed groove has a relatively smaller curvature (larger radius of curvature) in its middle portion, and both sides of the middle portion have a relatively larger curvature (smaller radius of curvature).

[0019] A bent portion that protrudes inward is formed in the region of the negative electrode where the inner end of the positive electrode is located, and the negative electrode tab is joined such that the recessed groove faces the bent portion.

[0020] In the negative electrode tab, the surface on which the recessed groove is formed is formed such that the recessed groove is located between a flat first planar portion and a flat second planar portion.

[0021] The negative electrode tab further includes an outer negative electrode tab that is positioned further from the central hole than the outer end of the positive electrode.

[0022] An electrode assembly having the above configuration is housed in a case such as a can and provided as a secondary battery. [Effects of the Invention]

[0023] The present invention, having the technical features described above, can prevent damage to the negative electrode and separator by having the negative electrode tab accommodate the expansion of the inner end of the positive electrode instead of the negative electrode.

[0024] The negative electrode tab is formed with recessed grooves such that its surface is concave on the side facing the inner end of the positive electrode, thereby more efficiently absorbing the expansion of the positive electrode. [Brief explanation of the drawing]

[0025] [Figure 1a] A diagram showing a shape in which a separator is omitted and a negative electrode and a positive electrode are wound in a conventional electrode assembly. [Figure 1b] A diagram showing an enlarged shape of a portion where the inner end of the positive electrode is located in a conventional electrode assembly. [Figure 1c] A diagram showing, in order, a shape in which a separator comes loose due to expansion of a positive electrode in a conventional electrode assembly. [Figure 2] A diagram showing a shape in which a negative electrode tab is located in an embodiment of the present invention. [Figure 3] A diagram showing a shape of a negative electrode tab provided in an embodiment of the present invention. [Figure 4] A diagram showing, respectively, the shape (upper side) before expansion and the shape (lower side) after expansion of the inner end of the positive electrode. [Figure 5] A diagram showing a shape in which, when a virtual line connects the inner end of the positive electrode and the center point of the center hole in an embodiment of the present invention, the virtual line passes through an inner negative electrode tab.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Hereinafter, based on the accompanying drawings, the present invention will be described in detail so that a person having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0027] 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.

[0028] Also, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary and dictionary meanings, and should be construed in a meaning and concept consistent with the technical idea of the present invention in accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way.

[0029] The present invention relates to an electrode assembly that can prevent or minimize damage to the negative electrode 10 and separator 30 even if the positive electrode 20 expands and its inner end 20a moves, and can prevent the separator 30 from unraveling in the area exposed to the central hole H. Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0030] Figure 2 shows the shape in which the negative electrode tab is located in an embodiment of the present invention, Figure 3 shows the shape of the negative electrode tab provided in an embodiment of the present invention, and Figure 4 shows the shape of the inner end of the positive electrode before expansion (upper side) and after expansion (lower side), respectively. Furthermore, Figure 5 shows the shape in which, in an embodiment of the present invention, when a virtual line is drawn connecting the inner end of the positive electrode and the center point of the central hole, the virtual line passes through the inner negative electrode tab.

[0031] The electrode assembly provided according to the embodiment of the present invention has a structure in which a negative electrode 10, a separator 30, and a positive electrode 20 are wound together in a stacked state, similar to the conventional structure. That is, it is a wound-type electrode assembly in which a first separator is fixed to a winding core (not shown), and the negative electrode, a second separator, and a positive electrode are sequentially inserted while the winding core rotates (the order in which the separator, negative electrode, and positive electrode are inserted may vary depending on the case).

[0032] Therefore, the electrode assembly provided in this embodiment has a structure in which a first separator is located on the inner circumferential surface of the central hole H, and the first separator, negative electrode, second separator, and positive electrode are wound together in a stacked state.

[0033] Furthermore, the negative electrode 10 is wound up with a negative electrode tab 40 attached at a predetermined position, and the positive electrode 20 is also wound up with a positive electrode tab (not shown) attached, and has an inner end 20a located closer to the central hole H, and an outer end 20b located on the opposite end of the inner end 20a and further away from the central hole H.

[0034] As a result, as shown in Figures 2 and 5 (for reference, in Figures 2 and 5, the separator is omitted to avoid making the drawing too complex with too many lines, and only the negative and positive electrodes are shown), a bent portion P is formed on the negative electrode 10 at the inner end 20a of the positive electrode 20, which is a portion that bends due to the thickness of the positive electrode 20.

[0035] As described above, when the electrode assembly is manufactured, the negative electrode 10 is inserted into the core before the positive electrode 20, so the inner end 10a of the negative electrode 10 is located closer to the central hole H than the inner end 20a of the positive electrode 20.

[0036] Furthermore, if the inner end 20a of the positive electrode 20 and the center point of the central hole H are connected by a virtual line X, the negative electrode tab 40 (more specifically, the inner negative electrode tab) is positioned so as to pass through the virtual line X.

[0037] In this case, as shown in Figure 5, the negative electrode tab 40 is configured to include an inner negative electrode tab 40a which is positioned closer to the central hole H than the inner end 20a of the positive electrode 20, and an outer negative electrode tab 40b which is positioned further from the central hole H than the outer end 20b of the positive electrode 20, with the inner negative electrode tab 40a being configured to pass through the virtual line X.

[0038] Only one layer of negative electrode 10 is placed between the inner end 20a of the positive electrode 20 and the inner negative electrode tab 40a. For reference, although not shown in Figures 2 and 5, it is obvious that a separator 30 is located between the positive electrode 20 and the negative electrode 10, so only one layer of negative electrode and one layer of separator are placed between the inner end 20a of the positive electrode and the negative electrode tab 40.

[0039] In addition, as another embodiment, the negative electrode tab 40 (the inner negative electrode tab among the inner and outer negative electrode tabs) provided in the present invention is provided in which a recessed groove 41 is formed.

[0040] In other words, the negative electrode tab 40 has a recessed groove 41 formed on the surface facing the inner end 20a of the positive electrode 20, such that the surface has a recessed shape.

[0041] As clearly shown in Figure 3, the recessed groove 41 formed in the negative electrode tab 40 is formed in an arc shape having a predetermined curvature.

[0042] More specifically, the recessed groove 41 has a relatively smaller curvature in the middle portion i (having a larger radius of curvature so as to be relatively flat), and both sides ii and iii of the middle portion i have a relatively larger curvature (having a smaller radius of curvature so as to have a relatively more curved shape).

[0043] Furthermore, the surface of the negative electrode tab 40 on which the recessed groove 41 is formed is formed such that the recessed groove is located between a flat first planar portion 43 and a flat second planar portion 44. The formation of the first planar portion 43 and the second planar portion 44 allows for a greater increase in the welding area when the negative electrode tab 40 is welded to the negative electrode 10.

[0044] As shown in Figure 4, a bent portion that protrudes inward is formed in the region of the negative electrode 10 where the inner end 20a of the positive electrode 20 is located, and the negative electrode tab 40 is joined so that the recessed groove 41 faces the bent portion.

[0045] When the positive electrode 20 expands due to charging or discharging, the inner end 20a of the positive electrode 20 slides. In this case, the position of the bend shifts and the amount of deformation increases depending on the length of sliding (θ). Since this behavior of the bend occurs within the recessed groove 41 formed in the negative electrode tab 40, the deformation of the negative electrode 10 caused by the inner end 20a of the positive electrode 20 can be completely contained within the negative electrode tab 40. In this case, the position of the negative electrode tab 40 may also shift slightly due to the expansion of the negative electrode 10, but it will not move to the extent that it comes out of the bend.

[0046] Therefore, in the structure of the present invention, the deformation of the negative electrode 10 due to the expansion of the positive electrode 20 is contained within the recessed groove 41 of the negative electrode tab 40. Thus, the amount of deformation of the bent portion is limited (within the size of the recessed groove), and phenomena such as the expansion of such deformation to the surrounding area, the increase in the amount of deformation causing damage to the negative electrode 10 and separator 30, and the unraveling of the separator 30 forming the inner circumferential surface of the central hole H can be prevented or minimized.

[0047] An electrode assembly having the above configuration can be housed in a case such as a can and provided as a secondary battery.

[0048] The present invention, having the technical features described above, can prevent damage to the negative electrode 10 and the separator 30 by having the negative electrode tab 40 accommodate the expansion of the inner end 20a of the positive electrode instead of the negative electrode 10.

[0049] The negative electrode tab is formed with recessed grooves such that its surface is concave on the side facing the inner end of the positive electrode, thereby more efficiently absorbing the expansion of the positive electrode.

[0050] 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 and the appended claims. [Explanation of Symbols]

[0051] 10 negative electrode 10a Inner end of negative electrode 20 positive electrode 20a Inner end of positive electrode 30 Separators 40 Negative electrode tabs (40a: inner negative electrode tab, 40b: outer negative electrode tab) H center hole X is a virtual line connecting the inner end of the positive electrode and the center point of the central hole.

Claims

1. An electrode assembly having a structure in which a negative electrode, a separator, and a positive electrode are wound in a stacked state, with a central hole formed in the center, The negative electrode is wound up with the negative electrode tab attached at a predetermined position, A positive electrode having an inner end positioned closer to the central hole, and an outer end opposite to the inner end, positioned further away from the central hole, The negative electrode, the separator, and the positive electrode are wound such that the inner end of the negative electrode is closer to the central hole than the inner end of the positive electrode. If a virtual line is drawn connecting the inner end of the positive electrode and the center point of the central hole, the virtual line passes through the negative electrode tab, The negative electrode tab has a recessed groove formed on the surface facing the inner end of the positive electrode, Electrode assembly.

2. The aforementioned negative electrode tab is It includes an inner negative electrode tab that is positioned closer to the central hole than the inner end of the positive electrode, The electrode assembly according to claim 1, wherein when a virtual line is drawn connecting the inner end of the positive electrode and the center of the central hole, the virtual line passes through the inner negative electrode tab.

3. The electrode assembly according to claim 1, wherein the assembly is wound such that only one layer of negative electrode is placed between the inner end of the positive electrode and the negative electrode tab.

4. The electrode assembly according to claim 1, wherein the recessed groove is formed in an arc shape having a predetermined curvature.

5. The electrode assembly according to claim 4, wherein the recessed groove has a relatively smaller curvature in the middle portion and a relatively larger curvature on both sides of the middle portion.

6. The electrode assembly according to claim 1, wherein a bent portion protruding inward is formed in the region of the negative electrode where the inner end of the positive electrode is located, and the negative electrode tab is joined such that the recessed groove faces the bent portion.

7. The surface on which the recessed groove is formed in the negative electrode tab is The electrode assembly according to claim 1, wherein a recessed groove is formed between a flat first planar portion and a flat second planar portion.

8. The electrode assembly according to claim 2, wherein the negative electrode tab further includes an outer negative electrode tab that is positioned further from the central hole than the outer end of the positive electrode.

9. A secondary battery comprising an electrode assembly according to any one of claims 1 to 8.

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