Secondary battery and battery module including the same

Abstract

The present invention relates to a secondary battery and a battery module including the same, and more particularly to a secondary battery and a battery module including the same that can relieve or support stress generated in a core portion of an internal jelly-roll-type electrode assembly during charging and discharging of the secondary battery, thereby preventing irreversible electrode deformation occurring in the core portion and collapse of the core portion that may occur due to the accumulation of such deformation.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0121207, filed September 23, 2022, and Korean Patent Application No. 10-2023-0119979, filed September 8, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a battery module including the same, and more particularly to a secondary battery and a battery module including the same that can relieve or support stress generated in a core portion of an internal jelly-roll-type electrode assembly during charging and discharging of the secondary battery, thereby preventing irreversible electrode deformation occurring in the core portion and collapse of the core portion that may occur due to the accumulation of such deformation. [Background technology]

[0003] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch batteries, in which the electrode assembly is housed in a pouch-shaped case made of an aluminum laminate sheet.

[0004] The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element having a laminated structure of a positive electrode / separator / negative electrode, and can be classified into a jelly roll structure in which a separator is interposed between long sheet-like positive and negative electrodes coated with an active material and wound up, a stack structure in which a number of positive and negative electrodes of a predetermined size are stacked in order with a separator interposed therebetween, and a stack / folding type electrode assembly having a structure in which a bicell or full cell in which a predetermined number of positive and negative electrodes are stacked with a separator interposed therebetween is wound up.

[0005] Among these, jelly-roll electrode assemblies are widely produced due to their advantages of ease of manufacture and high energy density per weight. Jelly-roll electrode assemblies are produced by assembling a laminate of long, sheet-shaped positive and negative electrodes with a separator interposed between them, and winding the laminate in the longitudinal direction of the sheet with a core in contact with one end of the electrode laminate. Such a jelly-roll electrode assembly can then be inserted into a battery case made of a cylindrical metal can to form a cylindrical secondary battery.

[0006] As technology advances, cylindrical secondary batteries are becoming increasingly high-capacity, resulting in a shortage of space available for battery elements such as electrodes. Therefore, there is a need for a solution that can effectively relieve stress at the core of cylindrical batteries, such as structural collapse caused by electrode contraction and expansion.

[0007] Fig. 1 is a cross-sectional view showing an example of a conventional cylindrical secondary battery. Referring to Fig. 1, the cylindrical secondary battery includes a jelly-roll-type electrode assembly 10 formed by alternately stacking and winding electrodes and separators, and a can case 20 that houses the jelly-roll-type electrode assembly. A core portion 11 is formed in the center of the wound jelly-roll-type electrode assembly 10. The core portion 11 is an empty space formed by winding the electrode and separator stack around a winding core to produce the jelly-roll-type electrode assembly 10, and then removing the winding core.

[0008] FIG. 2 is a cross-sectional view taken along line A-A' in FIG. 2. Referring to FIG. 2, (a) of FIG. 2 shows the initial state of the jelly-roll-type electrode assembly 10 before the core 11 collapses. When charging and discharging are performed in the state shown in (a) of FIG. 2, the electrode assembly 10 (jelly-roll-type electrode assembly 10) and the core 11 of the electrode assembly 10 repeatedly expand and contract. This causes the electrodes of the core 11 to deform or to collapse due to the accumulation of deformation. The deformation and collapse of the core 11 are shown in (b) of FIG. 2.

[0009] If deformation or collapse occurs inside the core portion 11 of the electrode assembly 10, the separator may be torn by the corners of the electrode, which poses a risk of internal short circuiting that could lead to a micro-short circuit or explosion, which is a problem. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a secondary battery and a battery module including the same that can relieve or support stress generated in a core portion of an internal jelly-roll type electrode assembly during charge and discharge of the secondary battery, thereby preventing irreversible electrode deformation generated in the core portion and collapse of the core portion that may occur due to the accumulation of such deformation.

[0011] Another object of the present invention is to provide a secondary battery that can avoid the problem of smooth winding due to the rigidity of the core of a jelly-roll type electrode assembly having a small diameter core when the electrode assembly is wound up, and a battery module including the same. [Means for solving the problem]

[0012] The secondary battery according to the present invention includes a jelly-roll-type electrode assembly formed by winding up a positive electrode, a negative electrode, and a separator, a case for accommodating the electrode assembly, and an electrolyte contained in the case together with the electrode assembly. A swelling tape that expands upon absorbing the electrolyte is attached to one surface of the separator, which is positioned so as to surround a core portion that is the center of the winding of the electrode assembly. The swelling tape includes a substrate and an adhesive layer formed on one of both surfaces of the substrate that faces the separator. The substrate includes a plurality of protruding convex portions formed on the surface opposite the surface on which the adhesive layer is formed.

[0013] The substrate can include a polymeric material.

[0014] One surface of the separator can be one of the two surfaces of the separator that faces the core portion.

[0015] The electrode assembly may have a configuration in which a first separator, a positive electrode, a second separator, and a negative electrode are stacked in order and wound up, and the swelling tape may be attached to the first separator.

[0016] The swelling tape may be attached to the separator such that the core-side edge of the separator and the core-side edge of the swelling tape coincide with each other.

[0017] The convex portion may be formed to have a shape in which the width thereof becomes narrower from the bottom to the top when viewed in a cross section of the electrode assembly cut along a plane perpendicular to the winding shaft.

[0018] The protrusions may be formed to extend in the width direction of the separator, and the plurality of protrusions may be arranged such that adjacent protrusions in the length direction of the separator are spaced apart from each other at the top and in contact with each other at the bottom.

[0019] The convex portion may be formed in a semicircular or partial circle shape based on a cross section of the electrode assembly cut along a plane perpendicular to the winding axis.

[0020] The convex portion may be formed in a trapezoidal shape based on a cross section of the electrode assembly cut along a plane perpendicular to the winding axis.

[0021] The trapezoid can be an isosceles trapezoid.

[0022] The diameter (P) of the core portion is formed to be 3.2 mm to 3.6 mm, and the thickness (t) of the substrate is formed to be 30 um to 50 um.

[0023] The length (U) of the lower side of the trapezoidal convex portion may be 0.1 mm to 0.3 mm, and the angle (θ) of the convex portion, which is the angle formed by the intersection of two straight lines formed by extending a pair of opposite sides that are not parallel to each other in the trapezoidal shape, may be 6.5 degrees to 7.9 degrees.

[0024] The length (U) of the lower side of the trapezoidal convex portion may be 0.4 mm to 0.6 mm, and the angle (θ) of the convex portion, which is the angle formed by the intersection of two straight lines formed by extending a pair of opposite sides that are not parallel to each other in the trapezoidal shape, may be 16 degrees to 20 degrees.

[0025] A battery module according to the present invention includes the above-described secondary battery according to the present invention and a housing that houses a plurality of the secondary batteries. [Effects of the Invention]

[0026] The secondary battery and the battery module including the same according to the present invention can relieve or support stress generated in the core portion of the inner jelly-roll-type electrode assembly during charging and discharging of the secondary battery, thereby preventing irreversible electrode deformation occurring in the core portion and collapse of the core portion that may occur due to the accumulation of such deformation.

[0027] In addition, the secondary battery and the battery module including the same according to the present invention can avoid the problem of the electrode assembly not being smoothly wound due to the rigidity of the core portion when a jelly-roll type electrode assembly having a small diameter is wound up. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a conventional cylindrical secondary battery. [Figure 2] FIG. 2 is a cross-sectional view taken along the line AA' in FIG. [Figure 3] 2 is a cross-sectional view of the secondary battery according to the first embodiment of the present invention taken along the same line as AA' in FIG. [Figure 4] 1 is a perspective view showing a state in which a jelly-roll type electrode assembly of a secondary battery according to a first embodiment of the present invention is unfolded and disassembled. FIG. [Figure 5] FIG. 5 is an enlarged perspective view of part B in FIG. 4. [Figure 6] 6 is a side view showing the shape as seen from the direction of arrow E in FIG. 5. [Figure 7] 1 is a side view illustrating a state in which the jelly roll-type electrode assembly begins to be wound around a core in the secondary battery according to Embodiment 1 of the present invention. FIG. [Figure 8] FIG. 8 is a side view showing another modification of the embodiment shown in FIG. 7. [Figure 9] FIG. 10 is a side view showing a state in which a swelling tape is attached to a secondary battery according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a side view showing a state in which a swelling tape is attached to a secondary battery according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand the preferred embodiments of the present invention. However, the present invention may be realized in various different forms and is not limited to the following embodiments.

[0030] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the explanation or related known technologies that may obscure the gist of the present invention will be omitted, and in this specification, when adding reference symbols to components in each drawing, the same or similar reference symbols will be used throughout the specification to refer to the same or similar components.

[0031] 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.

[0032] Embodiment 1 FIG. 1 is a cross-sectional view showing an example of a conventional cylindrical secondary battery. FIG. 2 is a cross-sectional view taken along line A-A' in FIG. 1. FIG. 3 is a cross-sectional view of a secondary battery according to embodiment 1 of the present invention, cut in the same manner as A-A' in FIG. 1. FIG. 4 is a perspective view showing a state in which a jelly-roll electrode assembly of the secondary battery according to embodiment 1 of the present invention has been unfolded and disassembled. FIG. 5 is a perspective view showing an enlarged view of portion B in FIG. 4. FIG. 6 is a side view showing the shape as viewed from the direction of arrow E in FIG. 5. FIG. 7 is a side view showing a state in which the jelly-roll electrode assembly of the secondary battery according to embodiment 1 of the present invention is started to be wound around a winding core.

[0033] Referring to Figures 3, 4, and 7, the secondary battery 100 according to the first embodiment of the present invention includes an electrode assembly 110, a case, and an electrolyte, and a swelling tape 130 is attached to a core portion 120, which is the center of the electrode assembly 110.

[0034] The electrode assembly 110 may be a jelly-roll type electrode assembly 110 formed by alternately stacking and winding a negative electrode 112, a positive electrode 114, and a separator 115. The case may be a case that houses the electrode assembly. The case may be a cylindrical can case. The electrolyte (not shown) may be a liquid housed in the case together with the electrode assembly 110.

[0035] A core portion 120 is formed in the center of the winding of the jelly roll electrode assembly 110. The core portion 120 can be an empty space formed by winding a laminate of electrodes and separators 115 around a winding core K to produce the jelly roll electrode assembly 110, and then removing the winding core K.

[0036] In the secondary battery according to the first embodiment of the present invention, a swelling tape 130 is attached to one surface of the separator 115, which is positioned to surround the core part 120, which is the winding center of the electrode assembly 110. In this case, the one surface of the separator 115 may be the surface facing the core part 120 among both surfaces of the separator 115.

[0037] Specifically, referring to FIGS. 4 and 7, the electrode assembly 110 may be provided in a form in which a first separator 111, a negative electrode 112, a second separator 113, and a positive electrode 114 are stacked in this order and wound. The swelling tape 130 may be attached to the second separator 113 of the two separators 115. This means that the swelling tape 130 is attached to the separator 115 inside the core. When the swelling tape 130 is attached to the separator 115 inside the core, it is spaced from the opposing portions between the positive and negative electrodes, so it does not affect the battery reaction, eliminating the problem of changes in battery characteristics. Furthermore, during the battery manufacturing process, the swelling tape 130 plays a supporting role when the battery is wound around the winding core K in the winding direction (W), which is more advantageous (see FIG. 7). Here, the winding core K refers to two rods that take the center of the separator 115 in order to perform the winding process. After the jelly roll-type electrode assembly 110 is formed by the winding operation while the winding core K rotates, the winding core K is removed.

[0038] Figure 8 is a side view showing another modification of the embodiment shown in Figure 7. Referring to Figure 8, as another modification of the electrode assembly, the electrode assembly 110 may be provided in a form in which a first separator 111, a positive electrode 114, a second separator 113, and a negative electrode 112 are sequentially stacked and wound. The swelling tape 130 may also be attached to the second separator 113 of the two separators 115. This is also attached to the separator 115 inside the core.

[0039] 4 and 5, the swelling tape 130 may be attached to the separator 115 so that the core-side end of the separator 115 to which the swelling tape 130 is attached coincides with the core-side end of the swelling tape 130 (specifically, the swelling tape 130 may be attached so as to coincide with the core-side end of the second separator 113). The core side is indicated by an arrow pointing in the O direction in FIG. 4. The core side may refer to the direction toward the winding center.

[0040] The swelling tape 130 may be a tape that has the property of expanding when it absorbs the electrolyte. For example, the swelling tape 130 may include a polymer material. The polymer material may be a material that has the property of absorbing the electrolyte but does not react with the electrolyte. Specifically, the swelling tape 130 may include a PU (polyurethane) material.

[0041] Specifically, the swelling tape 130 may include a substrate 131 and an adhesive layer 132. The adhesive layer 132 may be an adhesive material layer applied to one side of the substrate 131. Specifically, the substrate 131 of the swelling tape 130 may be formed to include a polymer material. Specifically, the substrate 131 may include a PU (polyurethane) material. Other materials may also be used for the substrate 131 as long as they are capable of absorbing the electrolyte and expanding. The expanded substrate 131 may cushion or absorb impacts and stresses. Alternatively, it may also serve to resist and support the impacts and stresses. The adhesive layer 132 may be formed on one of both sides of the substrate 131, that faces the separator 115.

[0042] 5 and 6, in the secondary battery according to the first embodiment of the present invention, a plurality of recesses 134 and protrusions 133 may be formed on the substrate 131. Specifically, the protrusions 133 may be formed on the side opposite to the side on which the adhesive layer 132 is formed. The recesses 134 may have a concave shape. The protrusions 133 may have a shape that is relatively higher and thicker than the recesses.

[0043] For reference, the recesses 134 and the protrusions 133 can be produced by laser etching using a method of irradiating a laser onto a tape, or by applying pressure using a mold.

[0044] In the secondary battery according to the first embodiment of the present invention, the swelling tape 130 is attached to the separator 115 located in the core portion 120, thereby dissipating or supporting stress generated in the core portion 120 of the inner jelly-roll-type electrode assembly 110 during charging and discharging of the secondary battery. This prevents irreversible electrode deformation occurring in the core portion 120 and collapse of the core portion 120 that may occur due to the accumulation of such deformation.

[0045] 3, (a) of FIG. 3 shows the shape of the core portion 120 before the electrolyte is injected and before expansion and contraction occur, and (b) of FIG. 3 shows the shape of the core portion 120 after the electrolyte is injected and after expansion and contraction occur. Referring to (b) of FIG. 3, it can be seen that the core portion 120 maintains its shape without being deformed or collapsed even after repeated expansion and contraction of the core portion 120 due to the swollen swelling tape 130.

[0046] FIG. 6 is a side view showing the shape as viewed from the direction of arrow E in FIG. 5. Referring to FIG. 6, the convex portion 133 may be formed to have a shape that narrows from bottom to top based on a cross-sectional view cut along a plane perpendicular to the winding axis of the electrode assembly 110. Also, referring to FIG. 5, the convex portion 133 may be formed to extend in the width direction (Y) of the separator 115 (113). As shown in FIG. 4, the width of the swelling tape 130 may also be the same as the width of the separator 115. Referring to FIG. 6, the length (J) of the swelling tape 130 based on the length direction (L) of the separator 115 may be formed so that it is neither too long nor too short. Specifically, the length (J) of the swelling tape 130 may be determined within a range that does not interfere with the battery reaction.

[0047] 5 and 6, the plurality of protrusions 133 may be arranged such that adjacent protrusions 133 in the length direction (L) of the separator 115 are spaced apart from each other at the top and in contact with each other at the bottom.

[0048] 6, the protrusion 133 may be formed in a trapezoidal shape based on a cross section cut along a plane perpendicular to the winding axis of the electrode assembly 110. Here, the trapezoid is most preferably an isosceles trapezoid.

[0049] By forming the convex portion 133 in this shape, when winding up a jelly roll-type electrode assembly 110 having a core portion 120 with a small diameter, the problem of the swelling tape 130 attached to the core portion 120 of the electrode assembly 110 not being able to be smoothly wound due to its rigidity can be avoided.

[0050] Specifically, the swelling tape 130 needs to have a certain degree of rigidity to prevent the core portion 120 from collapsing, but such rigidity may make it difficult for the core portion 120 to form a winding, since the rigidity of the swelling tape 130 may act to apply a force that causes the winding to unwind.

[0051] Furthermore, when the electrolyte is poured into the jelly-roll electrode assembly 110 after insertion, the volume of the swelling tape 130 expands, and this expansion of the swelling tape 130 may act as a force in the direction of unwinding. The protrusions 133 of the present invention can solve the problems of unwinding and the inability to form the tape smoothly.

[0052] Specifically, the spaces between the protrusions 133 serve to weaken the rigidity or repulsive force of the swelling tape 130, thereby solving the problems of the swelling tape 130 unwinding due to its rigidity or not being smoothly formed.

[0053] 3 and 6, in the secondary battery according to the first embodiment of the present invention, the diameter (P) of the core portion 120 may be formed to be 3.2 mm to 3.6 mm, and the thickness (t) of the substrate 131 may be formed to be 30 μm to 50 μm (unit: micrometer). In addition, the thickness of the substrate layer excluding the convex portion may be formed to be about 1 / 4 to 1 / 3 of the thickness of the entire substrate layer. This is the most advantageous thickness range for forming the convex portion without exposing the adhesive layer.

[0054] The length (U) of the bottom side of the trapezoidal projection 133 may be 0.1 mm to 0.3 mm. In this case, the angle (θ) of the projection 133, which is the angle formed by the intersection of two straight lines formed by extending a pair of opposite sides that are not parallel to each other in the trapezoidal shape, may be 6.5 degrees to 7.9 degrees.

[0055] For reference, the calculation method is as follows. When the diameter (P) of the core portion 120 is approximately 3.2 mm, the circumference of the core portion 120 is 3.2 mm x 3.14 (pi) = approximately 10 mm. Assuming that the length (U) of the bottom side of the convex portion 133 is approximately 0.2 mm, dividing 10 mm by 0.2 mm results in approximately 50 convex portions 133 being formed around the core portion 120. Therefore, dividing 360 degrees by 50 results in an angle of approximately 7.2 degrees for the convex portion 133. In this case, applying a tolerance range of approximately 10%, 7.2 - 0.7 = 6.5 degrees, or 7.2 + 0.7 = 7.9 degrees.

[0056] The length (U) of the bottom side of the trapezoidal projection 133 may be 0.4 mm to 0.6 mm. In this case, the angle (θ) of the projection 133, which is the angle formed by the intersection of two straight lines formed by extending a pair of opposite sides that are not parallel to each other in the trapezoidal shape, may be 16 degrees to 20 degrees.

[0057] The same calculation can be performed in this case. When the diameter (P) of the core portion 120 is approximately 3.2 mm, the circumference of the core portion 120 is 3.2 mm × 3.14 (pi) = approximately 10 mm. Assuming that the length (U) of the bottom side of the convex portion 133 is approximately 0.5 mm, dividing 10 mm by 0.5 mm allows approximately 20 convex portions 133 to be formed around the core portion 120. Therefore, dividing 360 degrees by 20 determines the angle of the convex portion 133 to be approximately 18 degrees. In this case, applying a tolerance range of approximately 10%, 18 - 2 = 16 degrees, or 18 + 2 = 20 degrees.

[0058] Furthermore, a battery module according to the present invention can be formed including the secondary battery according to the first embodiment of the present invention described above and a housing that houses a plurality of the secondary batteries.

[0059] Embodiment 2 FIG. 9 is a side view showing a state in which a swelling tape 230 is attached to the secondary battery according to the second embodiment of the present invention.

[0060] The second embodiment of the present invention differs from the first embodiment in that the shape of the convex portion is circular rather than trapezoidal.

[0061] The description of embodiment 2 will focus on the differences and omit as much as possible the content common to embodiment 1. In other words, it is clear that the content not explained in embodiment 2 can be supplemented by the content of embodiment 1 as necessary.

[0062] Referring to FIG. 9, in the secondary battery according to the second embodiment of the present invention, the convex portion 233 may be formed in a semicircular or partial circle shape based on a cross-sectional view cut along a plane perpendicular to the winding axis of the electrode assembly.

[0063] 9 shows that semicircular convex portions 233 are formed on a substrate. Substrate 231 on which semicircular convex portions 233 are formed is attached to one surface of separator 215 in the same manner as in embodiment 1, and adhesive layer 232 is formed on one surface of substrate 231 so that it can be adhered to separator 215.

[0064] When the convex portion is formed in this manner, it is different from a trapezoid in that it can have relatively few or no corners.

[0065] Embodiment 3 FIG. 10 is a side view showing a state in which a swelling tape is attached to a secondary battery according to the third embodiment of the present invention.

[0066] Compared with the first and second embodiments of the present invention, this embodiment differs from the first and second embodiments in that the object of the present invention is achieved by attaching a plurality of narrow swelling tapes.

[0067] The description of Embodiment 3 will focus on the differences, omitting as much as possible the content common to Embodiments 1 and 2. In other words, it is clear that the content not described in Embodiment 3 can be supplemented by the content of Embodiments 1 and 2 as necessary.

[0068] 10, the secondary battery according to the third embodiment of the present invention includes a jelly-roll-type electrode assembly 110 formed by winding a negative electrode, a positive electrode, and a separator, a case for accommodating the electrode assembly, and an electrolyte solution accommodated in the case together with the electrode assembly 110. A plurality of swelling tapes 330 that expand upon absorbing the electrolyte solution may be attached at predetermined intervals to one surface of the separator 315 positioned to surround a core portion, which is the center of the winding of the electrode assembly 110. Each swelling tape 330 may include a substrate 331 and an adhesive layer 332 formed on one surface of the substrate facing the separator.

[0069] That is, the present invention is characterized in that each swelling tape 330 has a narrow width and is attached in multiple pieces. In the first and second embodiments, the role of one protrusion 133, 233 can be performed by one swelling tape 330.

[0070] In this case, since there is no need to use a separate method such as laser etching to form the recesses and protrusions, manufacturing convenience can be achieved. That is, a separate high-precision or expensive device such as a laser etching device is not required, and only the attachment of a plurality of swelling tapes 330 is required, making manufacturing and use easier.

[0071] 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]

[0072] 100 Secondary battery 110 Electrode assembly 111 First separator 112 Negative electrode 113 Second separator 114 Positive electrode 115, 215, 315 separator 120 Core 130, 230, 330 Swelling Tape 131, 231, 331 base material 132, 232, 332 Adhesive layer 133, 233 convex part 134, 234 recess K core W Winding direction

Claims

1. a jelly-roll type electrode assembly formed by winding a positive electrode, a negative electrode, and a separator; a case for accommodating the jelly-roll type electrode assembly; an electrolyte solution accommodated in the case together with the jelly-roll type electrode assembly, a swelling tape that expands when absorbing the electrolyte is attached to one surface of the separator, the swelling tape being positioned to surround a core portion that is a winding center of the jelly roll-type electrode assembly; The swelling tape is A substrate; an adhesive layer formed on one of both surfaces of the substrate facing the separator, The substrate is formed on a surface opposite to the surface on which the adhesive layer is formed, and includes a plurality of recesses and protrusions.

2. The secondary battery according to claim 1 , wherein the substrate comprises a polymer material.

3. The secondary battery according to claim 1 , wherein the one surface of the separator is a surface of the separator that faces the core portion.

4. The jelly-roll type electrode assembly has a structure in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound, The secondary battery according to claim 3 , wherein the swelling tape is attached to the second separator.

5. The jelly-roll type electrode assembly has a structure in which a first separator, a positive electrode, a second separator, and a negative electrode are sequentially stacked and wound, The secondary battery according to claim 3 , wherein the swelling tape is attached to the second separator.

6. The secondary battery according to claim 1 , wherein the swelling tape is attached to the separator such that an edge of the separator on a core side and an edge of the swelling tape on a core side coincide with each other.

7. 2. The secondary battery of claim 1, wherein the protrusions have a width that narrows from bottom to top in a cross-sectional view of the jelly-roll-type electrode assembly taken along a plane perpendicular to a winding axis.

8. The convex portion is formed to extend in the width direction of the separator, The secondary battery according to claim 7 , wherein the plurality of protrusions are arranged such that adjacent protrusions in the longitudinal direction of the separator are spaced apart from each other on the upper side and in contact with each other on the lower side.

9. The secondary battery of claim 7 , wherein the protrusion has a semicircular or partial circle shape in a cross section taken along a plane perpendicular to a winding axis of the jelly-roll-type electrode assembly.

10. The secondary battery of claim 7 , wherein the protrusion is trapezoidal in a cross section taken along a plane perpendicular to a winding axis of the jelly-roll type electrode assembly.

11. The secondary battery according to claim 10 , wherein the trapezoid is an isosceles trapezoid.

12. The diameter of the core portion is formed to be 3.2 mm to 3.6 mm, The secondary battery according to claim 10, wherein the substrate has a thickness of 30 μm to 50 μm.

13. the length of the lower side of the trapezoidal convex portion is 0.1 mm to 0.3 mm; The secondary battery according to claim 12, wherein in the trapezoidal shape, an angle of a convex portion, which is an angle formed by the intersection of two straight lines formed by extending two opposite sides that are not parallel to each other, is 6.5 degrees to 7.9 degrees.

14. the length of the lower side of the trapezoidal convex portion is 0.4 mm to 0.6 mm; The secondary battery according to claim 12, wherein in the trapezoidal shape, an angle of a convex portion, which is an angle formed by the intersection of two straight lines formed by extending a pair of two opposite sides that are not parallel, is 16 degrees to 20 degrees.

15. a jelly-roll type electrode assembly formed by winding a negative electrode, a positive electrode, and a separator; a case for accommodating the jelly-roll type electrode assembly; an electrolyte solution accommodated in the case together with the jelly-roll type electrode assembly, A plurality of swelling tapes that expand when absorbing an electrolyte are attached at predetermined intervals to one surface of the separator, which is positioned so as to surround a core portion that is the winding center of the jelly roll type electrode assembly, Each of the plurality of swelling tapes is A substrate; an adhesive layer formed on one of both surfaces of the substrate facing the separator.

16. The secondary battery according to any one of claims 1 to 15, a housing that houses a plurality of the secondary batteries.

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