Electrode assembly

Abstract

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 state of being stacked on each other and having a center hole formed at a center of the electrode assembly, the electrode assembly comprising: a negative electrode wound in a state in which a negative electrode tab is bonded at a predetermined position; and a positive electrode having an inner end portion disposed closer to the central hole and an outer end portion disposed farther from the central hole as an opposite end portion of the inner end portion, in which the negative electrode, the separator, and the positive electrode are wound such that an inner end portion of the negative electrode is disposed closer to the central hole than the inner end portion of the positive electrode, and an outer end portion of the negative electrode is disposed farther from the central hole than the inner end portion of the positive electrode. And when the inner end portion of the positive electrode and the center point of the center hole are connected by a virtual line, the virtual line passes through the negative electrode tab.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2022-0117482, filed on September 16, 2022, which is hereby incorporated by reference in its entirety. Technical Field

[0004] The present invention relates to an electrode assembly having a wound type structure, and more particularly, to an electrode assembly configured to solve a short circuit problem occurring due to damage to a negative electrode and a separator caused by expansion of a positive electrode and release of the separator exposed to an inner peripheral surface at a central hole. Background Art

[0005] Batteries that store electrical energy can generally be divided into primary batteries and secondary batteries. The primary battery is a disposable battery. On the other hand, the secondary battery is a rechargeable battery made by using a material in which an oxidation process and a reduction process can be repeated between the current and the material.

[0006] That is, when the reduction reaction of the material is performed by the current, the power source is charged, and when the oxidation reaction of the material is performed by the current, the power source is discharged. Here, such charging and discharging are repeatedly performed.

[0007] Among various types of secondary batteries, lithium secondary batteries are generally manufactured by installing an electrode assembly in which a positive electrode (cathode), a separator, and a negative electrode (anode) are stacked in a housing. Here, as the process of lithium ions being inserted and released from lithium metal oxide to the negative electrode is repeated, the lithium secondary battery is charged and discharged.

[0008] In the electrode assembly, a plurality of unit cells are stacked, and in each unit cell, a negative electrode, a separator, and a positive electrode are stacked in a predetermined order, wherein each of the negative electrode, the separator, and the positive electrode is generally cut into a predetermined size, or a single positive electrode / separator / negative electrode is repeatedly stacked to form one electrode assembly. In addition, the electrode assembly is housed in a housing such as a cylindrical can and a prismatic bag.

[0009] As methods for manufacturing electrode assemblies, the following electrode assemblies are known: a wound electrode assembly in which a separator is stacked between a negative electrode and a positive electrode and then wound to manufacture an electrode assembly; a stacked electrode assembly in which each of the negative electrode and the positive electrode is cut into a desired width and length, and then the negative electrode, the separator, and the positive electrode are repeatedly stacked to form an electrode assembly; and a stacked folding electrode assembly in which unit cells are placed parallel to each other on a folding separator and then folded from one side to manufacture an electrode assembly.

[0010] Among them, a wound (jelly roll) electrode assembly is made by fixing a first separator to a core and sequentially introducing a negative electrode, a second separator and a positive electrode during rotation of the core (in some cases, the order of introduction of the separator, negative electrode and positive electrode may be changed).

[0011] Therefore, if Figure 1a As shown in the figure, in the electrode assembly according to the prior art, the separator is omitted, and the negative electrode and the positive electrode are wound, and in the portion where the inner end portion 20a of the positive electrode 20 is set, the negative electrode 10 has a bending portion P, which is a portion bent due to the thickness of the positive electrode 20.

[0012] However, due to repeated heating and cooling while the secondary battery is charged and discharged, the negative electrode 10 and the positive electrode 20 wound around the electrode assembly shrink and expand. Figure 1b As more clearly illustrated in Figure 1b Illustrated is an enlarged view of a portion where the inner end portion 20 a of the positive electrode 20 is disposed in an electrode assembly according to the related art, and the inner end portion 20 a of the positive electrode may press the separator 30 and the bent portion P of the negative electrode 10 during expansion.

[0013] Due to such expansion of the cathode 20 , stress may be locally concentrated in the anode 10 to cause damage, and the separator 30 disposed between the cathode 20 and the anode 10 may also be damaged to cause a short circuit between the cathode 20 and the anode 10 .

[0014] In addition, as in Figure 1c As shown in the figure, Figure 1c Sequentially illustrating the case where the separator 30 is loosened as the cathode 20 expands, the separator 30 may be loosened on a region disposed at the innermost side of the central hole H (forming the inner peripheral surface of the central hole), and thus, the anode 10 may be separated. Summary of the invention

[0015] Technical issues

[0016] Therefore, in order to solve the above-mentioned conventional problems, the main object of the present invention is to provide an electrode assembly in which damage to the negative electrode and the separator can be prevented or minimized even if the positive electrode expands and the inner end of the positive electrode moves, thereby preventing the separator exposed to the central hole from loosening.

[0017] Technical Solution

[0018] In order to achieve the above-mentioned purpose, the present invention provides an electrode assembly, which has a structure in which a negative electrode, a separator and a positive electrode are wound in a stacked state and a central hole is formed in the center of the electrode assembly, the electrode assembly comprising: a negative electrode, which is wound in a state in which a negative electrode tab is combined to a predetermined position; and a positive electrode, which has an inner end portion closer to the central hole and an outer end portion farther away from the central hole as an opposite end portion of the inner end portion, wherein the negative electrode, the separator and the positive electrode are wound so that the inner end portion of the negative electrode is arranged to be closer to the central hole than the inner end portion of the positive electrode, and when a virtual line is drawn from the inner end portion of the positive electrode to the center point of the central hole, the virtual line passes through the negative electrode tab.

[0019] The negative electrode tab may include an inner negative electrode tab disposed closer to the central hole than an inner end of the positive electrode, and when a virtual line is drawn from the inner end of the positive electrode to a center point of the central hole, the virtual line may pass through the inner negative electrode tab.

[0020] Only a single layer of negative electrode may be disposed between the inner end of the positive electrode and the negative electrode tab.

[0021] A concave groove may be defined in the negative electrode tab so that the negative electrode tab has a concave shape on a surface of an inner end portion facing the positive electrode. The concave groove may be provided in an arc shape having a predetermined curvature.

[0022] The concave groove has a relatively small curvature (having a large radius of curvature) at the middle portion, and each of two side portions of the middle portion has a relatively large curvature (having a small radius of curvature).

[0023] A bending portion protruding inward may be provided on a corresponding region of the inner end portion of the negative electrode on which the positive electrode is provided, and the negative electrode tab may be combined such that the concave groove faces the bending portion.

[0024] The surface of the negative electrode tab in which the concave groove is defined may be arranged such that the concave groove is disposed between the flat first planar portion and the flat second planar portion.

[0025] The negative electrode tab may further include an outer negative electrode tab disposed farther from the central hole than an outer end of the positive electrode.

[0026] The electrode assembly having the above-described configuration is embedded in a case such as a can and provided as a secondary battery.

[0027] Beneficial Effects

[0028] In the present invention having the above technical features, the expansion of the inner end portion of the positive electrode can be absorbed by the negative electrode tab rather than the negative electrode, thereby preventing the negative electrode and the separator from being damaged.

[0029] The negative electrode tab is formed with a concave groove having a surface-concave shape in a surface of an inner end portion of the negative electrode tab facing the positive electrode to more effectively absorb expansion of the positive electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1a is a view illustrating a state in which a separator is omitted and a negative electrode and a positive electrode are wound in an electrode assembly according to the related art.

[0031] Figure 1b is an enlarged view illustrating a portion at which an inner end portion of a positive electrode is disposed in an electrode assembly according to the related art.

[0032] Figure 1c are views sequentially illustrating a state in which loosening of a separator occurs due to expansion of a positive electrode in an electrode assembly according to the related art.

[0033] Figure 2 is a view illustrating a state in which a negative electrode tab is provided according to an embodiment of the present invention.

[0034] Figure 3 is a view illustrating a configuration of a negative electrode tab provided in an embodiment of the present invention.

[0035] Figure 4 1 and 2 are views illustrating a state before the inner end portion of the positive electrode expands (upper portion) and a state after the inner end portion of the positive electrode expands (lower portion).

[0036] Figure 5 is a view of a state in which when a virtual line is drawn from an inner end portion of a positive electrode to a center point of a central hole according to an embodiment of the present invention, the virtual line passes through an inner negative electrode tab. DETAILED DESCRIPTION

[0037] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that a person skilled in the art can easily implement the technical concept of the present invention. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments described herein.

[0038] In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or like components throughout the specification.

[0039] In addition, the terms or words used in the present specification and claims should not be restrictively interpreted as ordinary meanings or dictionary-based meanings, but should be interpreted as meanings and concepts consistent with the scope of the present invention based on the principle that the inventor can appropriately define the concepts of the terms to best describe and interpret his or her invention.

[0040] The present invention relates to an electrode assembly in which damage to the negative electrode 10 and the separator 30 can be prevented or minimized even if the positive electrode 20 expands and the inner end 20a of the positive electrode 20 moves, thereby preventing the separator 30 from loosening in the area exposed to the central hole H, and hereinafter, a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

[0041] Figure 2 is a view illustrating a state where a negative electrode tab is provided according to an embodiment of the present invention, Figure 3 is a view illustrating a configuration of a negative electrode tab provided in an embodiment of the present invention, and Figure 4 : is a view illustrating a state before the inner end portion of the positive electrode expands (upper part) and a state after the inner end portion of the positive electrode expands (lower part). Figure 5 is a view of a state in which when a virtual line is drawn from an inner end portion of a positive electrode to a center point of a central hole according to an embodiment of the present invention, the virtual line passes through an inner negative electrode tab.

[0042] The electrode assembly according to the embodiment provided by the present invention has a structure in which the negative electrode 10, the separator 30 and the positive electrode 20 are wound in a stacked state, which is similar to the structure according to the prior art. That is, the wound electrode assembly is made by fixing the first separator to the core and sequentially introducing the negative electrode, the second separator and the positive electrode during the rotation of the core (in some cases, the introduction order of the separator, the negative electrode and the positive electrode can be changed).

[0043] Therefore, the electrode assembly provided in the embodiment may have a structure in which the first separator is disposed on the inner circumferential surface of the central hole H, and the first separator, the negative electrode, the second separator, and the positive electrode are wound in a stacked state.

[0044] In addition, the negative electrode 10 is wound in a state where the negative electrode tab 40 is bonded to a predetermined position, and the positive electrode 20 is also wound in a state where a positive electrode tab (not shown) is bonded, and is provided with an inner end portion 20 a closer to the central hole H and an outer end portion 20 b which is an opposite end portion of the inner end portion 20 a and farther from the central hole H.

[0045] Therefore, if Figure 2 and Figure 5 As shown in the figure (for reference, Figure 2 and Figure 5In the figure, the separator is omitted and only the negative electrode and the positive electrode are illustrated to avoid complicating the view with numerous lines), the negative electrode 10 has a bending portion P at the portion where the inner end portion 20a of the positive electrode 20 is set, and the bending portion P is a portion bent due to the thickness of the positive electrode 20.

[0046] When manufacturing the electrode assembly, as described above, the negative electrode 10 is put into the core prior to the positive electrode 20 , and therefore, the inner end 10 a of the negative electrode 10 is disposed closer to the central hole H than the inner end 20 a of the positive electrode 20 .

[0047] In addition, when a virtual line X is drawn from the inner end portion 20 a of the positive electrode 20 to the center point of the central hole H, the negative electrode tab 40 (more specifically, an inner negative electrode tab of the negative electrode tabs) is disposed so as to be passed through the virtual line X.

[0048] Here, as in Figure 5 As illustrated in , the negative electrode tab 40 includes an inner negative electrode tab 40a disposed closer to the central hole H than the inner end 20a of the positive electrode 20 and an outer negative electrode tab 40b disposed farther from the central hole H than the outer end 20b, and the inner negative electrode tab 40a is configured to be passed through by a virtual line X.

[0049] Only the single-layer negative electrode 10 is disposed between the inner end portion 20a of the positive electrode 20 and the inner negative electrode tab 40a. Figure 2 and Figure 5 It is not shown in the figure, but it is obvious that the separator 30 is provided between the positive electrode 20 and the negative electrode 10 , and therefore, only the single-layer negative electrode and the single-layer separator are provided between the inner end portion 20 a of the positive electrode and the negative electrode tab 40 .

[0050] In addition, as another embodiment, the negative electrode tab 40 (the inner negative electrode tab among the inner negative electrode tab and the outer negative electrode tab) provided in the present invention has a structure in which the concave groove 41 is defined.

[0051] That is, the concave groove 41 is defined in the negative electrode tab 40 so that the negative electrode tab 40 has a concave shape on a surface facing the inner end portion 20 a of the positive electrode 20 .

[0052] As in Figure 3 As more clearly illustrated in FIG. 1 , the concave groove 41 defined in the negative electrode tab 40 is provided in an arc shape having a predetermined curvature.

[0053] More specifically, the concave groove 41 has a relatively small curvature (a larger radius of curvature so as to be relatively flat) at the middle portion (i), and each of the two side portions (ii, iii) of the middle portion (i) has a relatively large curvature (a smaller radius of curvature so as to have a relatively more curved shape).

[0054] In addition, the surface of the negative electrode tab 40 defining the concave groove 41 is arranged such that the concave groove is arranged between the flat first plane portion 43 and the flat second plane portion 44. Since the first plane portion 43 and the second plane portion 44 are provided, when the negative electrode tab 40 is welded to the negative electrode 10, the welding area of ​​the negative electrode tab 40 can be further increased.

[0055] As in Figure 4 As illustrated in FIG. 1 , a bent portion protruding inward is provided on a corresponding region of the negative electrode 10 on which the inner end portion 20 a of the positive electrode 20 is provided, and the negative electrode tab 40 is combined such that the concave groove 41 faces the bent portion.

[0056] When the positive electrode 20 expands due to charging or discharging, etc., the inner end portion 20a of the positive electrode 20 slides. Here, according to the sliding length θ, the position of the bent portion moves, and the amount of deformation also increases. Since the behavior of the bent portion occurs within the concave groove 41 defined in the negative electrode tab 40, the deformation of the negative electrode 10 caused by the inner end portion 20a of the positive electrode 20 can be completely accommodated within the negative electrode tab 40. Here, the position of the negative electrode tab 40 may also be slightly moved due to the expansion of the negative electrode 10, but the position of the negative electrode tab 40 will not move to the extent of being separated from the bent portion.

[0057] Therefore, in the structure of the present invention, the deformation of the negative electrode 10 caused by the expansion of the positive electrode 20 is absorbed in the concave groove 41 of the negative electrode tab 40. Therefore, the deformation amount of the bent portion is limited in size (limited within the size of the concave groove), so that the following phenomena, including the expansion of the deformation to the surrounding area, the increase in the deformation amount to damage the negative electrode 10 and the separator 30, and the loosening of the separator 30 defining the inner peripheral surface of the central hole H, can be prevented or suppressed to the minimum.

[0058] The electrode assembly having the above-described configuration may be embedded in a case such as a can and provided as a secondary battery.

[0059] In the present invention having the technical features described above, expansion of the inner end portion 20 a of the positive electrode may be absorbed by the negative electrode tab 40 instead of the negative electrode 10 , thereby preventing the negative electrode 10 and the separator 30 from being damaged.

[0060] The negative electrode tab is formed with a concave groove having a surface-concave shape in a surface of an inner end portion of the negative electrode tab facing the positive electrode to more effectively absorb expansion of the positive electrode.

[0061] While embodiments of the present invention have been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

[0062] [Description of Reference Signs]

[0063] 10: Negative electrode

[0064] 10a: Inner end of negative electrode

[0065] 20: Positive electrode

[0066] 20a: Inner end of positive electrode

[0067] 30: Separator

[0068] 40: negative electrode contact (40a: inner negative electrode contact, 40b: outer negative electrode contact)

[0069] H: Central hole

[0070] X: Virtual line drawn from the inner end of the positive electrode to 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 and a central hole is formed at the center of the electrode assembly, the electrode assembly comprising: a negative electrode wound in a state where a negative electrode tab is coupled to a predetermined position; and a positive electrode having an inner end portion closer to the central hole and an outer end portion, which is an opposite end portion to the inner end portion and farther from the central hole, wherein the negative electrode, the separator, and the positive electrode are wound such that an inner end of the negative electrode is disposed closer to the central hole than an inner end of the positive electrode, and When a virtual line is drawn from the inner end of the positive electrode to the center point of the central hole, the virtual line passes through the negative electrode tab.

2. The electrode assembly according to claim 1, wherein: The negative electrode tab includes an inner negative electrode tab disposed closer to the central hole than the inner end of the positive electrode, and When the virtual line is drawn from the inner end of the positive electrode to the center point of the central hole, the virtual line passes through the inner negative electrode tab.

3. The electrode assembly according to claim 1, wherein: Only a single layer of negative electrode is arranged between the inner end of the positive electrode and the negative electrode tab.

4. The electrode assembly according to claim 1, wherein: A concave groove is defined in the negative electrode tab so that the negative electrode tab has a concave shape on a surface facing an inner end portion of the positive electrode.

5. The electrode assembly according to claim 4, wherein: The concave groove is provided in an arc shape having a predetermined curvature.

6. The electrode assembly according to claim 5, wherein: The concave groove has a relatively small curvature at a middle portion, and each of two side portions of the middle portion has a relatively large curvature.

7. The electrode assembly according to claim 4, wherein: A bending portion protruding inward is provided on a corresponding region of the negative electrode on which the inner end portion of the positive electrode is provided, and the negative electrode tabs are combined such that the concave groove faces the bending portion.

8. The electrode assembly according to claim 4, wherein: The surface of the negative electrode tab in which the concave groove is defined is arranged such that the concave groove is disposed between a flat first planar portion and a flat second planar portion.

9. The electrode assembly according to claim 2, wherein: The negative electrode tab also includes 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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