Electrode assembly and secondary battery including the same

Abstract

The present invention suppresses deformation in the vicinity of the end portion of the positive electrode by allowing the deformable portion to deform as the time of use of the secondary battery increases, thereby preventing damage to adjacent separators. An electrode assembly according to the present invention has a structure in which a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet are wound together, in which the first electrode sheet is spaced apart from one end of the second electrode sheet in a winding direction by a certain distance, and the separator is disposed between the first electrode sheet and the second electrode sheet. And may include a deformable portion protruding toward the center based on the winding state.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2022-0132752, filed on October 14, 2022, and Korean Patent Application No. 10-2023-0137082, filed on October 13, 2023, which are hereby incorporated by reference in their entirety. Technical Field

[0004] The present invention relates to an electrode assembly and a secondary battery including the electrode assembly. Background Art

[0005] In recent years, due to the depletion of fossil fuels, energy prices have risen, concerns about environmental pollution have been amplified, and the demand for eco-friendly alternative energy is becoming an indispensable factor in future life. Therefore, research on various power generation technologies such as solar energy, wind energy, and tidal energy is continuing, and power storage devices such as batteries for more efficient use of generated electrical energy are also receiving great attention.

[0006] In addition, as technology develops and demand for electronic mobile devices and electric vehicles using batteries increases, demand for batteries as energy sources is rapidly increasing. Therefore, a lot of research has been conducted on batteries that can meet various needs.

[0007] Batteries that store electrical energy can generally be divided into primary batteries and secondary batteries. Such primary batteries are disposable consumable batteries. On the other hand, such secondary batteries are rechargeable batteries manufactured by using materials in which oxidation and reduction processes between current and materials can be repeated. That is, when a reduction reaction is performed on the material by current, the power source is charged. When an oxidation reaction is performed on the material by current, the power source is discharged. Such charge-discharge is repeatedly performed to generate electricity.

[0008] According to the shape of the battery case, secondary batteries can be classified into: cylindrical batteries in which the electrode assembly is housed in a cylindrical metal can; prismatic batteries in which the electrode assembly is built into a prismatic metal can; and pouch-type batteries in which the electrode assembly is built into a pouch-type case made of an aluminum laminate.

[0009] Among these, the cylindrical battery may have a wound-type electrode assembly in which a positive electrode, a negative electrode, and a separator are wound together and disposed inside a case.

[0010] Figure 1is a schematic cross-sectional view illustrating a modified example of an electrode assembly 1 according to the related art, and Figure 2 is a schematic side view of a negative electrode 2 constituting an electrode assembly 1 according to the related art.

[0011] According to the related art, the electrode assembly 1 provided in the cylindrical secondary battery may have a structure in which the positive electrode, the negative electrode and the separator are wound together. Here, based on the state in which the electrode assembly 1 is wound, the positive electrode may be wound later than the negative electrode, so that one end of the positive electrode is arranged outward from the central portion than one end of the negative electrode.

[0012] Reference Figure 1 , depending on the use in the secondary battery according to the related art, the shape of the electrode assembly 1 may be deformed due to the empty space defined in the central portion. In particular, the shape of the electrode assembly 1 of the cylindrical secondary battery according to the related art is deformed the most mainly at the end of the positive electrode. Therefore, there is a problem that the deformed end of the positive electrode damages the adjacent separator. In addition, therefore, there is a problem that a short circuit or the like occurs, the life of the secondary battery is reduced, and the performance of the secondary battery is deteriorated.

[0013] Reference Figure 2 , the negative electrode 2 provided in the electrode assembly 1 of the cylindrical secondary battery according to the related art may have a shape in which the negative electrode tab is arranged in a substantially plate-shaped rectangular parallelepiped. In addition, a tape may be attached to one end. Specifically, the tape may refer to an insulating tape for insulation. Here, the tape may play a role such as ensuring insulation performance and protecting the negative electrode tab. Therefore, the negative electrode 2 according to the related art does not have a structure for preventing the adjacent separator from being damaged by two deformed ends due to the use of the secondary battery.

[0014] Therefore, there is a need for an electrode assembly capable of reducing the risk of a separator being damaged by both end portions due to deformation of the electrode assembly and a secondary battery including the same. Summary of the invention

[0015] Technical issues

[0016] The present invention is designed to solve the above problems, and an object of the present invention is to provide an electrode assembly and a secondary battery including the same, which can prevent adjacent separators from being damaged due to deformation of a positive terminal to improve safety and performance.

[0017] Technical Solution

[0018] In an electrode assembly according to the present invention, in which a first electrode sheet, a second electrode sheet, and a separator arranged between the first electrode sheet and the second electrode sheet are wound together, the first electrode sheet may include a deformable portion, which is arranged to be separated from one end of the second electrode sheet by a predetermined distance in the winding direction and has a shape protruding toward the central portion relative to the winding state.

[0019] The first electrode sheet may include: an uncoated portion disposed on one end portion and having a shape in which an electrode tab is disposed on one surface of the current collector; and a coated portion having a shape in which an active material is applied on each of two surfaces of the current collector.

[0020] The second electrode sheet may be disposed at a position facing the coating portion of the first electrode sheet, wherein the separator is located between the second electrode sheet and the coating portion of the first electrode sheet.

[0021] The deformable portion may be disposed to be spaced apart from the electrode tab between the electrode tab and the coating portion in the non-coating portion.

[0022] The first electrode sheet may further include a covering portion attached to the uncoated portion, and the covering portion may have a thermosetting property.

[0023] The covering portion may be attached to be wound at least once.

[0024] The covering portion may have a thickness of 40 μm or more and 100 μm or less.

[0025] The covering portion may include: a first covering portion attached to one surface of the non-coating portion to cover a portion of the electrode tab; and a second covering portion attached to the other surface of the non-coating portion.

[0026] The first covering portion may be attached at a length that is less than a length of the second covering portion.

[0027] The first electrode sheet may further include a fixing portion attached to a surface of the deformable portion opposite to a direction in which the deformable portion protrudes.

[0028] The deformable portion may have a shape that is curved while maintaining a constant radius of curvature.

[0029] The deformable portion may have a curvature radius of greater than or equal to 0.05 mm and less than or equal to 0.8 mm.

[0030] The first electrode sheet may be caused such that a degree of deformation of the deformable portion increases with increasing use time.

[0031] A secondary battery according to the present invention may include: an electrode assembly having a structure in which a first electrode sheet, a second electrode sheet, and a separator arranged between the first electrode sheet and the second electrode sheet are wound together; and an external component configured to accommodate the electrode assembly therein, wherein the first electrode sheet includes a deformable portion, which is arranged to be separated from one end of the second electrode sheet by a predetermined distance and has a shape protruding toward a central portion relative to a wound state.

[0032] Beneficial Effects

[0033] According to the present invention, in an electrode assembly having a structure in which a first electrode sheet, a second electrode sheet, and a separator arranged between the first electrode sheet and the second electrode sheet are wound together, the first electrode sheet may include a deformable portion, which is arranged to be separated from one end of the second electrode sheet by a predetermined distance in the winding direction and has a shape protruding toward the central portion relative to the winding state.

[0034] Therefore, as the use time of the secondary battery increases, the deformable portion can be deformed to suppress deformation near the end of the positive electrode, thereby preventing the adjacent separator from being damaged.

[0035] In addition, the separator may be prevented from being damaged to improve the safety and performance of a secondary battery including the electrode assembly.

[0036] The effects of the present invention are not limited to the above description, and therefore, more various effects are included in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic cross-sectional view illustrating a modified example of an electrode assembly according to the related art.

[0038] Figure 2 is a schematic side view of a negative electrode constituting an electrode assembly according to the related art.

[0039] Figure 3 is a schematic cross-sectional view illustrating a state in which the electrode assembly according to Embodiment 1 of the present invention is wound.

[0040] Figure 4 is a schematic exploded view illustrating a state before the electrode assembly according to Embodiment 1 of the present invention is wound.

[0041] Figure 5 is a schematic side view of a first electrode sheet according to Embodiment 1 of the present invention.

[0042] Figure 6 is a schematic side view of a first electrode sheet according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0043] Hereinafter, the preferred embodiments of the present invention will 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 can be implemented in several different forms and is not limited or constrained by the following examples.

[0044] In order to explain the present invention clearly, the detailed description of the parts not related to the specification or the related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and in this specification, the reference numerals are added to the components in each figure. In this case, the same or similar reference numerals are assigned to the same or similar elements throughout the specification.

[0045] In addition, the terms or words used in the 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.

[0046] Implementation Method 1

[0047] The present invention provides an electrode assembly 10 as embodiment 1.

[0048] Figure 3 is a schematic cross-sectional view illustrating a state in which the electrode assembly 10 according to Embodiment 1 of the present invention is wound. Figure 4 is a schematic exploded view illustrating a state before the electrode assembly 10 according to Embodiment 1 of the present invention is wound, and Figure 5 FIG. 1 is a schematic side view of the first electrode sheet 100 according to Embodiment 1 of the present invention.

[0049] The electrode assembly 10 according to Embodiment 1 of the present invention may be used to manufacture a secondary battery. Here, the electrode assembly 10 may refer to an electrode assembly having a wound structure, and the secondary battery may refer to a cylindrical secondary battery.

[0050] Reference Figure 3 , the electrode assembly 10 according to the embodiment 1 of the present invention may include a first electrode sheet 100, a second electrode sheet 200, and a separator 300. Specifically, the electrode assembly 10 may have a structure in which the separator 300 is provided between the first electrode sheet 100 and the second electrode sheet 200, and the first electrode sheet 100, the second electrode sheet 200, and the separator 300 are wound together. Here, the first electrode sheet 100 may refer to a negative electrode sheet, and the second electrode sheet 200 may refer to a positive electrode sheet.

[0051] The electrode assembly 1 according to the related art has a problem that the deformation near one end of the positive electrode sheet is severely deformed as the secondary battery is used. Therefore, as an example of a configuration for preventing deformation near one end of the positive electrode sheet, the first electrode sheet 100 of the electrode assembly 10 according to the embodiment 1 of the present invention may include a deformable portion 130.

[0052] The deformable portion 130 of the first electrode sheet 100 may be disposed to be spaced a predetermined distance from one end of the second electrode sheet 200, and may have a shape that protrudes toward the central portion relative to the winding state. Specifically, the deformable portion 130 of the first electrode sheet 100 may be disposed to be spaced a predetermined distance from one end of the second electrode sheet 200 in the winding direction. The deformable portion 130 may be used to deform first to prevent one end of the second electrode sheet 200 from deforming. The first electrode sheet 100 according to embodiment 1 of the present invention may cause the degree of deformation of the deformable portion 130 to increase as the use time of the secondary battery increases. Referring to Figure 3 , it can be seen that, in the electrode assembly 10 in the wound state, the deformable portion 130 is disposed at a position spaced apart from one end of the second electrode sheet 200 in the winding direction. In this regard, when the process of deforming the electrode assembly 10 inside the cylindrical secondary battery is observed by experiment, it can be seen that the degree of deformation at the portion where the deformation occurs continues to increase. That is, as the use time increases, the deformation of the electrode assembly 10 may become more serious at the deformable portion. In the absence of the deformable portion 130, the deformation near one end of the second electrode sheet 200 may become more serious due to the use of the secondary battery, and the adjacent separator 300 may be damaged by one end of the deformed second electrode sheet 200. Therefore, the first electrode sheet 100 of the electrode assembly 10 according to embodiment 1 of the present invention may be disposed to be spaced apart from one end of the second electrode sheet 200 by a predetermined distance in the winding direction, so that other portions other than one end of the second electrode sheet 200 are severely deformed to prevent the deformation near one end of the second electrode sheet 200 from occurring. This can prevent the separator from being damaged, and prevent additional problems such as short circuits from occurring due to damage to the separator.

[0053] The shape of the deformable portion 130 of the first electrode sheet 100 may vary, but the deformable portion 130 according to the first embodiment of the present invention may have a curved shape with a constant radius of curvature. Specifically, the deformable portion 130 may have a substantially semicircular shape. Preferably, the radius of curvature of the deformable portion 130 may be greater than or equal to 0.05 mm and less than or equal to 0.8 mm.

[0054] The electrode assembly 10 disposed inside the cylindrical secondary battery may have a wound-shaped shape. In order to produce this form, the first electrode sheet 100, the second electrode sheet 200 and the separator 300 may be wound together, and each of the first electrode sheet 100, the second electrode sheet 200 and the separator 300 has an approximately sheet-like shape. Here, a core having an approximately cylindrical shape may be disposed therein for winding. When the deformable portion 130 has an approximately semicircular shape, the deformable portion 130 may be formed by a relatively simple process using the core. Specifically, before winding using the core, the deformable portion 130 may be formed by pressing a portion of the first electrode sheet 100 at a position where the deformable portion 130 will be formed using the core. This is only an example of forming the deformable portion 130, and the deformable portion 130 may be formed by other methods.

[0055] The deformable portion 130 having a substantially semicircular shape may be provided on the first electrode sheet 100 using a cylindrical rod in addition to the core. Here, the deformable portion 130 may not need to be formed too large so as not to interfere with the winding. This is because if the radius of curvature of the deformable portion 130 becomes too large, problems may arise in the winding process of forming the electrode assembly 10. In view of this problem, the deformable portion 130 may be provided with a radius of curvature that is approximately half the radius of the rod or less. In this regard, since a core having a typical radius of approximately 1.6 mm is used in the winding process, the preferred radius of curvature of the deformable portion 130 may be approximately less than or equal to 0.8 mm when the winding form is considered.

[0056] On the other hand, if the curvature radius of the deformable portion 130 is too small, the effect of the present invention may not be achieved by the deformable portion 130. Therefore, the curvature radius of the deformable portion 130 having a substantially semicircular shape may be approximately greater than or equal to 0.05 mm.

[0057] Reference Figure 4 and Figure 5 , the first electrode sheet 100 of the electrode assembly 10 according to the embodiment 1 of the present invention may include an uncoated portion 110 and a coated portion 120. Specifically, the uncoated portion 110 of the first electrode sheet 100 may be provided on one end portion, and may have a shape in which the electrode tab 103 is provided on one surface of the current collector 101, and the coated portion 120 may have a shape in which the active material 102 is applied to each of the two surfaces of the current collector 101. More specifically, a portion of the current collector 101 to which the active material 102 is not applied may be the uncoated portion 110, and a portion to which the active material 102 is applied may be the coated portion 120. Here, the current collector 101 may be a substantially thin plate-shaped negative electrode current collector and may contain copper (Cu).

[0058] In order to explain in more detail the position where the deformable portion 130 is disposed in the wound electrode assembly 10, the arrangement relationship between the components of the electrode assembly 10 will first be described as follows. Figure 4 , the second electrode sheet 200 of the electrode assembly 10 according to Embodiment 1 of the present invention may be disposed at a position facing the coating portion 120 of the first electrode sheet 100, wherein the separator 300 is located between the second electrode sheet 200 and the coating portion 120 of the first electrode sheet 100. Specifically, the first electrode sheet 100 may start to be wound first, and then the second electrode sheet 200 may be wound together.

[0059] The separator may be disposed between the first electrode sheet 100 and the second electrode sheet 200 to separate the first electrode sheet 100 and the second electrode sheet 200 from each other. In order to separate the first electrode sheet 100 and the second electrode sheet 200 from each other, the separator 300 may be additionally disposed during the winding process.

[0060] As an example of a configuration for suppressing deformation of the electrode assembly 10 , the first electrode sheet 100 according to Embodiment 1 of the present invention may further include a covering portion 140 .

[0061] Reference Figure 5 , the covering portion 140 may be attached to the uncoated portion 110 of the first electrode sheet 100 and may have a thermosetting property. Specifically, the covering portion 140 may be a thermosetting tape. Thermosetting may mean a property of hardening when heat is applied.

[0062] In addition, the covering portion 140 of the first electrode sheet 100 may have a thickness of approximately 40 μm or more and 100 μm or less. As described above, the covering portion 140 may be a thermosetting tape. The covering portion 140 having a thickness of 40 μm or more and 100 μm or less may be a thermosetting tape that can be obtained relatively easily.

[0063] In the process of manufacturing the electrode assembly 10, a process of forming a central hole using a hot object may be performed to form an empty space in the center thereof. The covering portion 140 having thermosetting properties may be hardened by the heat transferred in the process. Specifically, the covering portion 140 may be made of a material that begins to harden at a temperature of about 100 degrees Celsius.

[0064] The cover portion 140 hardened by heat may not only suppress deformation of one end portion of the second electrode sheet 200 but also suppress deformation of the electrode assembly 10 itself by enhancing the rigidity of the electrode assembly.

[0065] The covering portion 140 may be formed by attaching from one end portion of the first electrode sheet 100 , or may be formed by attaching from a point about 3 mm to 4 mm away from the one end portion for process efficiency.

[0066] As an example of a configuration for effectively suppressing deformation of the electrode assembly 10, the covering portion 140 of the first electrode sheet 100 according to the first embodiment of the present invention includes a first covering portion 141 and a second covering portion 142. The first covering portion 141 may be attached to one surface of the uncoated portion 110 to cover a portion of the electrode tab 103, and the second covering portion 142 may be attached to the other surface of the uncoated portion 110. Therefore, the first covering portion 141 and the second covering portion 142 may be attached to both surfaces of the current collector 101, respectively, wherein the current collector 101 is located between the first covering portion 141 and the second covering portion 142. Here, the first covering portion 141 may be attached to the current collector 101 with a length less than the length of the second covering portion 142.

[0067] Since the first covering portion 141 and the second covering portion 142 are provided on both surfaces, the degree to which the covering portion 140 suppresses deformation of the electrode assembly 10 may be enhanced.

[0068] As an example of a configuration for suppressing deformation of the electrode assembly 10 in a relatively wide range, the covering portion 140 of the first electrode sheet 100 according to Embodiment 1 of the present invention may be attached to be wound at least once. That is, in the wound state, the uncoated portion 110 of the first electrode sheet 100 may be wound once or more.

[0069] When the covering portion 140 is attached at least once, deformation of the electrode assembly 10 may be suppressed in a wide range.

[0070] Since the deformable portion 130 is a portion causing deformation, rather than deformation of one end portion of the second electrode sheet 200, the covering portion 140 may not be attached. Therefore, the deformable portion 130 according to the first embodiment of the present invention may be disposed between the uncoated portion 110 and the coated portion 120, so that the covering portion 140 is easily attached only to the uncoated portion 110. Specifically, referring to Figure 5, the first electrode sheet 100 may be provided in the order of the uncoated portion 110, the deformable portion 130, and the coated portion 120 from one end thereof. Here, for the sake of convenience of explanation, the portion on which the active material 102 is not applied, excluding the deformable portion 130, may be represented as the uncoated portion 110. However, more accurately, the deformable portion 130 may be a part of the uncoated portion 110. That is, the deformable portion 130 may be provided on an end of the uncoated portion 110 adjacent to the coated portion 120. Therefore, the deformable portion 130 may be provided to be spaced apart from the electrode tab 103 between the electrode tab 103 and the coated portion 120 in the uncoated portion 110.

[0071] The electrode assembly 10 according to the first embodiment of the present invention can suppress deformation near the end of the second electrode sheet 200 by allowing the deformable portion 130 to deform as the use time of the secondary battery increases, thereby preventing deformation of the adjacent separator 300. In addition, the separator 300 can be prevented from being damaged to improve the safety and performance of the secondary battery including the electrode assembly 10.

[0072] A secondary battery with improved safety and performance can be manufactured by housing the electrode assembly 10 according to Embodiment 1 of the present invention in a wound state into an external member. Here, the secondary battery may be a cylindrical secondary battery, and the external member may have a substantially cylindrical can shape.

[0073] Implementation Method 2

[0074] The present invention provides, as Embodiment 2, an electrode assembly including a first electrode sheet 100 ′ having different types.

[0075] The first electrode sheet 100 ′ of the electrode assembly according to Embodiment 2 of the present invention may be different from the first electrode sheet 100 according to Embodiment 1 in the presence or absence of the fixing portion 150 and the like.

[0076] Hereinafter, a detailed description of the same configuration as that of the electrode assembly 10 according to Embodiment 1 of the present invention will be omitted.

[0077] Figure 6 FIG. 1 is a schematic side view of a first electrode sheet 100 ′ according to Embodiment 2 of the present invention.

[0078] The first electrode sheet 100' of the electrode assembly according to the second embodiment of the present invention may further include a fixing portion 150 attached to the deformable portion 130'. Specifically, the fixing portion 150 may be attached to the surface of the deformable portion 130' opposite to the direction in which the deformable portion 130' protrudes, and may have thermosetting properties like the covering portion 140. Here, the fixing portion 150 may be a thermosetting tape. In addition, like the above-mentioned covering portion 140, the fixing portion 150 may have a thickness of approximately greater than or equal to 40 μm and less than or equal to 100 μm.

[0079] Like the covering part 140, during the process of manufacturing the electrode assembly, the fixing part 150 can be hardened by heat transferred during the process of forming the central hole using a hot object to form an empty space in the center. Specifically, the fixing part 150 can be made of a material that starts to harden at a temperature of about 100 degrees Celsius.

[0080] Reference Figure 6 , the fixing portion 150 may be attached to the concave surface of the deformable portion 130'. Therefore, the electrode assembly according to Embodiment 2 of the present invention may include the fixing portion 150 to cause deformation of the deformable portion 130' in a direction toward the convex surface.

[0081] In this regard, when the fixing portion 150 is hardened by heat in the deformable portion 130', the convex surface to which the fixing portion 150 is not attached may have a relatively same shape as the other concave surface to which the fixing portion 150 is attached, and thus, the fixing force for fixing may become weak. Therefore, the first electrode sheet may be relatively effectively caused to deform in the direction of one surface to which the deformable portion 130' is not attached.

[0082] 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.

[0083] [Description of Reference Signs]

[0084] 1: Conventional electrode assembly

[0085] 2: Conventional first electrode sheet

[0086] 10: Electrode assembly

[0087] 100, 100': first electrode sheet

[0088] 101: Current Collector

[0089] 102: Active Materials

[0090] 103: Electrode contact

[0091] 110: Uncoated part

[0092] 120: Coating part

[0093] 130, 130': Deformable part

[0094] 140: Covering part

[0095] 141: First Covering Section

[0096] 142: Second covering part

[0097] 150: Fixed part

[0098] 200: Second electrode sheet

[0099] 300: Separator

Claims

1. An electrode assembly, the electrode assembly having a structure in which a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet are wound together, in, The first electrode sheet includes a deformable portion that is disposed a predetermined distance away from one end portion of the second electrode sheet in a winding direction and has a shape that protrudes toward a center portion with respect to a wound state.

2. The electrode assembly according to claim 1, wherein: The first electrode sheet comprises: an uncoated portion provided on one end portion and having a shape in which an electrode tab is provided on one surface of the current collector; and A coating portion having a shape in which an active material is applied on each of both surfaces of the current collector.

3. The electrode assembly according to claim 2, wherein: The second electrode sheet is disposed at a position facing the coating portion of the first electrode sheet, wherein the separator is located between the second electrode sheet and the coating portion of the first electrode sheet.

4. The electrode assembly according to claim 2, wherein: The deformable portion is disposed to be spaced apart from the electrode tab between the electrode tab and the coating portion in the non-coating portion.

5. The electrode assembly according to claim 2, wherein: The first electrode sheet further includes a covering portion attached to the uncoated portion, and The covering portion has thermosetting properties.

6. The electrode assembly according to claim 5, wherein: The covering portion is attached to be wound at least once.

7. The electrode assembly according to claim 5, wherein: The covering portion has a thickness of 40 μm or more and 100 μm or less.

8. The electrode assembly according to claim 5, wherein: The covered portion includes: a first covering portion attached to one surface of the uncoated portion to cover a portion of the electrode tab; and A second covering portion is attached to the other surface of the uncoated portion.

9. The electrode assembly according to claim 8, wherein: The first covering portion is attached at a length that is less than a length of the second covering portion.

10. The electrode assembly according to claim 1, wherein: The first electrode sheet further includes a fixing portion attached to a surface of the deformable portion opposite to a direction in which the deformable portion protrudes.

11. The electrode assembly according to claim 1, wherein: The deformable portion has a shape that is curved while maintaining a constant radius of curvature.

12. The electrode assembly according to claim 11, wherein: The deformable portion has a curvature radius greater than or equal to 0.05 mm and less than or equal to 0.8 mm.

13. The electrode assembly according to claim 1, wherein: The first electrode sheet is caused so that the degree of deformation of the deformable portion increases with increasing use time.

14. A secondary battery comprising: An electrode assembly, wherein the electrode assembly has a structure in which a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet are wound together; as well as an outer member configured to accommodate the electrode assembly therein, The first electrode sheet includes a deformable portion, which is disposed at a predetermined distance from one end of the second electrode sheet and has a shape protruding toward a central portion relative to a wound state.

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