Electrode group 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 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 wound structure, and more particularly to an electrode assembly that is provided to solve problems of short circuits caused by damage to a negative electrode and a separator due to expansion of a positive electrode, and of the separator exposed on its inner surface at a central hole coming loose. [Background technology]

[0003] Batteries that store electrical energy are generally divided into primary and secondary batteries. Primary batteries are disposable, consumable batteries, while secondary batteries are rechargeable batteries made from materials that can undergo repeated oxidation and reduction processes with electrical current.

[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 such charging and discharging can be repeated.

[0005] Among various secondary batteries, lithium secondary batteries are generally manufactured by attaching an electrode assembly, in which a cathode, a separator, and an anode are stacked, to a case, and 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 typically formed by stacking a plurality of unit cells, each of which is composed of a negative electrode, a separator, and a positive electrode cut to a predetermined size and stacked in a predetermined order, or by repeatedly stacking individual positive electrode / separator / negative electrode units, and is housed in a case such as a cylindrical can or a prismatic 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 laminated in an alternating fashion; and a stack and fold type in which unit cells are mounted side by side on a folding separator and then folded from one side.

[0008] Among these, a wound (jelly roll) 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] Therefore, in a conventional electrode assembly, the separator is omitted, and as shown in Figure 1a, which shows the shape in which the negative electrode and positive electrode are wound up, a folding portion P is formed in the negative electrode 10 at a portion of the inner end 20a of the positive electrode 20, which is a portion that folds due to the thickness of the positive electrode 20.

[0010] However, as heat and cooling are repeated during charge and discharge of a secondary battery, contraction and expansion occur in the negative electrode 10 and positive electrode 20 wound into the electrode assembly. As a result, as shown more clearly in FIG. 1b, which shows the expanded 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 presses against the bent portion P of the separator 30 and the negative electrode 10 during expansion.

[0011] Such expansion of the positive electrode 20 may cause stress to be concentrated locally on the negative electrode 10, resulting in damage, and the separator 30 placed between them may also be damaged, potentially causing a short circuit between the positive electrode 20 and the negative electrode 10.

[0012] In addition, as shown in Figure 1c, which sequentially shows the shape of the separator 30 as it unravels due to the expansion of the positive electrode 20, there was a possibility that the separator 30 would unravel in the region located at the innermost position of the central hole H (forming the inner surface of the central hole) and become separated from the negative electrode 10. Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, a primary object of the present invention is to provide an electrode assembly that can solve the above-mentioned conventional problems, prevent or minimize damage to the negative electrode and separator even when the positive electrode expands and its inner end moves, and prevent the separator exposed at the center hole from coming loose. [Means for solving the problem]

[0014] To achieve the above-mentioned object, 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 negative electrode being wound up with a negative electrode tab attached 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, the separator, and the 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.

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

[0016] The cathode is wound so that only one layer of the anode is placed between the inner end of the cathode and the anode tab.

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

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

[0019] 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 so that the recess faces the bent portion.

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

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

[0022] The electrode assembly having the above-described structure 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 accommodating expansion of the inner end of the positive electrode with the negative electrode tab instead of the negative electrode.

[0024] The negative electrode tab has a recessed groove formed on the surface facing the inner end of the positive electrode, thereby more efficiently absorbing the expansion of the positive electrode. [Brief explanation of the drawings]

[0025] [Figure 1a] 1 is a diagram showing a conventional electrode assembly in which a separator is omitted and a negative electrode and a positive electrode are wound together. [Figure 1b] 1 is a view showing an enlarged shape of a portion where an inner end of a positive electrode is located in a conventional electrode assembly. [Figure 1c] 1A and 1B are diagrams sequentially illustrating the shape of a separator that is loosened due to expansion of a positive electrode in a conventional electrode assembly; [Figure 2] 10A and 10B are diagrams illustrating the shape of a negative electrode tab in an embodiment of the present invention. [Figure 3] 1 is a diagram showing the shape of a negative electrode tab provided in an embodiment of the present invention. [Figure 4] 1A and 1B are diagrams showing the shape of the inner end of the positive electrode before expansion (upper side) and after expansion (lower side). [Figure 5] 1 is a diagram illustrating a shape in which, when an imaginary line is drawn between the inner end of a positive electrode and the center point of a central hole, the imaginary line passes through an inner negative electrode tab in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] 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.

[0027] 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.

[0028] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary and 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.

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

[0030] Fig. 2 is a diagram showing the shape of the negative electrode tab in an embodiment of the present invention, Fig. 3 is a diagram showing the shape of the negative electrode tab provided in an embodiment of the present invention, Fig. 4 is a diagram showing the shape of the inner end of the positive electrode before expansion (top side) and after expansion (bottom side), and Fig. 5 is a diagram showing the shape of the inner negative electrode tab when an imaginary line is drawn between the inner end of the positive electrode and the center point of the central hole.

[0031] The electrode assembly 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 stacked and wound, similar to a conventional structure. That is, it is a wound-type electrode assembly, and is manufactured by fixing a first separator to a winding core (not shown), and sequentially inserting the negative electrode, second separator, and positive electrode while the winding core is rotating (the insertion order of the separator, negative electrode, and positive electrode may be changed depending on the case).

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

[0033] The negative electrode 10 is wound with a negative electrode tab 40 attached at a predetermined position, and the positive electrode 20 is also wound with a positive electrode tab (not shown) attached, and has an inner end 20a positioned closer to the center hole H and an outer end 20b opposite the inner end 20a and positioned farther from the center hole H.

[0034] As a result, as shown in Figures 2 and 5 (see, for reference, Figures 2 and 5 show only the negative electrode and positive electrode, without the separator, to avoid complicating the drawings with too many lines), a folding portion P is formed in the negative electrode 10 at the portion where the inner end 20a of the positive electrode 20 is located, which is a portion where the negative electrode 10 folds due to the thickness of the positive electrode 20.

[0035] When the electrode assembly is manufactured, as described above, the negative electrode 10 is inserted into the winding core before the positive electrode 20, so that 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, when an imaginary line X connects the inner end 20a of the positive electrode 20 and the center point of the central hole H, the negative electrode tab 40 (more specifically, the inner negative electrode tab of the negative electrode tabs) is arranged to pass through the imaginary line X.

[0037] In this case, as shown in FIG. 5 , the negative electrode tab 40 includes an inner negative electrode tab 40a disposed closer to the center hole H than the inner end 20a of the positive electrode 20, and an outer negative electrode tab 40b disposed farther from the center hole H than the outer end 20b of the positive electrode 20, and the inner negative electrode tab 40a is configured to pass through the imaginary line X.

[0038] Only one layer of the 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 placed between the positive electrode 20 and the negative electrode 10, so only one layer of the negative electrode and one layer of the separator are placed between the inner end 20a of the positive electrode and the negative electrode tab 40.

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

[0040] That is, the negative electrode tab 40 has a recessed groove 41 formed on the surface facing the inner end 20a of the positive electrode 20 so that the surface has a recessed shape.

[0041] As shown more clearly in FIG. 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 middle portion i which has a relatively smaller curvature (having a larger radius of curvature so as to be relatively flat), and both sides ii, iii of the middle portion i which have a relatively larger curvature (having a smaller radius of curvature so as to have a relatively more curved shape).

[0043] In addition, 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 flat portion 43 and a flat second flat portion 44. The formation of the first flat portion 43 and the second flat portion 44 allows the welding area to be increased when the negative electrode tab 40 is welded to the negative electrode 10.

[0044] As shown in FIG. 4, a bent portion protruding 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 and discharging, the inner end 20a of the positive electrode 20 slides. The position of the bent portion shifts depending on the length of the slide (θ), and the amount of deformation also increases. This movement of the bent portion occurs within the recessed groove 41 formed in the negative electrode tab 40, so the deformation of the negative electrode 10 due to the inner end 20a of the positive electrode 20 can be accommodated entirely within the negative electrode tab 40. While the position of the negative electrode tab 40 may also shift slightly due to the expansion of the negative electrode 10, it does not shift enough to move away from the bent portion.

[0046] Therefore, in the structure of the present invention, deformation of the negative electrode 10 due to expansion of the positive electrode 20 is accommodated within the recessed groove 41 of the negative electrode tab 40. Therefore, the amount of deformation at the bent portion is limited (within the size of the recessed groove), and the phenomenon of the deformation spreading to the surrounding area, the phenomenon of the negative electrode 10 and separator 30 being damaged due to the increased amount of deformation, and the phenomenon of the separator 30 forming the inner circumferential surface of the center hole H being unraveled can be prevented or minimized.

[0047] The electrode assembly having the above-described configuration can be housed in a case such as a can and used as a secondary battery.

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

[0049] The negative electrode tab has a recessed groove formed on the surface 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 within the technical spirit of the present invention and the scope of equivalents of the appended claims by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0051] 10 negative electrode 10a Inner end of negative electrode 20 positive electrode 20a Inner end of positive electrode 30 Separator 40 negative electrode tab (40a: inner negative electrode tab, 40b: outer negative electrode tab) H center hole X: An imaginary line connecting the inner edge of the positive electrode and the center point of the center hole

Claims

1. 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, a negative electrode wound up with a negative electrode tab joined at a predetermined position; a positive electrode having an inner end disposed closer to the central hole and an outer end opposite the inner end and disposed farther from the central hole; the negative electrode, the separator, and the positive electrode are wound such that an inner end of the negative electrode is located closer to a center hole than an inner end of the positive electrode; an imaginary line connecting an inner end of the positive electrode and a center point of the central hole passes through the negative electrode tab;

2. The negative electrode tab is an inner negative electrode tab disposed closer to the central hole than an inner end of the positive electrode; The electrode assembly according to claim 1 , wherein when an imaginary line is drawn between an inner end of the positive electrode and the center of the central hole, the imaginary line passes through the inner negative electrode tab.

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

4. The electrode assembly of claim 1 , wherein the negative electrode tab has a recessed groove formed on a surface facing an inner end of the positive electrode.

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

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

7. 5. The electrode assembly of claim 4, wherein a bent portion protruding inward is formed in a region of the negative electrode where an inner end of the positive electrode is located, and the negative electrode tab is joined so that the recessed groove faces the bent portion.

8. The surface of the negative electrode tab on which the recessed groove is formed is 5. The electrode assembly of claim 4, wherein the recessed groove is formed between the first planar surface and the second planar surface.

9. The electrode assembly of claim 2 , wherein the negative electrode tab further comprises an outer negative electrode tab disposed farther from the central hole than an outer end of the positive electrode.

10. A secondary battery comprising the electrode assembly according to claim 1 .

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