Jelly roll electrode assembly and secondary battery including the same

Abstract

According to one embodiment of the present invention, there is provided a jelly roll electrode assembly in which a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet are wound together, and a plain portion in which an active material layer is not formed on the negative electrode sheet is wound at an outermost corner of the jelly roll electrode assembly, and a swelling tape is attached to an inner surface of the plain portion of the negative electrode sheet toward a center of the jelly roll electrode assembly, and the swelling tape includes one or more perforations.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of priority based on Korean Patent Application No. 10 - 2021 - 0163386 filed on November 24, 2021 and Korean Patent Application No. 10 - 2022 - 0158762 filed on November 23, 2022, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] The present invention relates to a jelly - roll electrode assembly and a secondary battery including the same.

Background Art

[0003] With the development of technology and the increasing demand for mobile devices, the demand for secondary batteries as an energy source has been rapidly increasing. In particular, secondary batteries have received much attention as an energy source not only for mobile devices such as mobile phones, digital cameras, notebook computers, and wearable devices, but also for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

[0004] Secondary batteries are classified into cylindrical batteries in which the electrode assembly is built into a cylindrical metal can, prismatic batteries in which the electrode assembly is built into a rectangular metal can, and pouch - type batteries in which the electrode assembly is built into a pouch - type case of an aluminum laminate sheet according to the shape of the battery case. Among them, cylindrical batteries have the advantages of relatively large capacity and structural stability.

[0005] The electrode assembly incorporated in the battery case is a power generation element capable of charge and discharge, having a laminated structure of a positive electrode, a separator, and a negative electrode, and is classified into a jelly roll type, a stack type, and a stack / folding type. The jelly roll type is a form in which a separator is interposed between a long sheet-like positive electrode and a negative electrode coated with an active material and wound up. The stack type is a form in which a large number of positive electrodes and negative electrodes of a predetermined size are sequentially laminated with a separator interposed therebetween. The stack / folding type is a composite structure of the jelly roll type and the stack type. Among them, the jelly roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per unit weight.

[0006] Therefore, recently, as the need for batteries to achieve high capacity and high output has increased, in the case of cylindrical batteries, in order to put a large amount of electrodes in a limited space, optimization is in progress while changing the thickness of the current collector and the separator, and the size and shape of the can and the top cap.

[0007] As one of the methods, a method of using copper as an outer tab as a negative electrode current collector has been proposed. That is, the outer tab and the separator are removed, and the copper current collector physically contacts the cylindrical can to allow current to flow.

[0008] By such a method, the amount of the separator and the amount of the tab are reduced, and the outer diameter is slightly decreased, so that the effects of securing space and saving costs appear, and the secured space can be utilized to increase the capacity or improve the output. In addition, since the copper current collector directly contacts the can, the area for heat transfer increases, and the heat generation level can also be improved.

[0009] However, when copper is actually exposed on the outer portion, one or two locations with a large outer diameter contact the can according to the roundness of the jelly roll, and the effect is reduced compared to the existing prediction.

[0010] To improve this, the contact level was improved by utilizing a swelling tape that has the property of swelling in response to an electrolyte. However, an air trap occurred during attachment in the manufacturing process, resulting in an increase in the outer diameter and a problem of decreased productivity.

[0011] Therefore, at present, it is necessary to develop a jelly roll electrode assembly and a secondary battery technology that can solve such problems.

Summary of the Invention

Problems to be Solved by the Invention

[0012] The problem to be solved by the present invention relates to a jelly roll electrode assembly that can eliminate the increase in the outer diameter due to an air trap generated by the attachment of a swelling tape and improve productivity.

[0013] The problem to be solved by the present invention is not limited to the problems described above, and problems not mentioned will be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from this specification and the attached drawings.

Means for Solving the Problems

[0014] A jelly roll electrode assembly according to an embodiment of the present invention is a jelly roll electrode assembly in which a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet are wound together, at the outermost side of the jelly roll electrode assembly, a plain portion where an active material layer is not formed is wound on the negative electrode sheet, on the plain portion of the negative electrode sheet, a swelling tape is attached to the inner surface in the direction of the central portion of the jelly roll electrode assembly, the swelling tape is characterized by including one or more perforated holes.

[0015] The swelling tape may adhere to a part of the inner surface of the plain part of the negative electrode sheet and to a part of the holding part of the negative electrode sheet in the direction of the holding part of the negative electrode sheet from the boundary surface between the plain part of the negative electrode sheet and the holding part where the active material layer is formed.

[0016] Here, the swelling tape may cover the holding part of the negative electrode sheet in the range of 0.25% to 5% of the total area of the holding part of the negative electrode sheet.

[0017] Alternatively, the swelling tape may be formed only on a part of the inner surface of the plain part of the negative electrode sheet.

[0018] Also, the swelling tape may be formed so as to cover 10% to 90% of the total area of the inner surface of the plain part of the negative electrode sheet.

[0019] Furthermore, the plain part of the outermost side negative electrode sheet on which the swelling tape is formed can face the holding part of the negative electrode sheet located inside.

[0020] Such a swelling tape may be a single-sided or double-sided tape, and the single-sided or double-sided tape is not limited as long as it is a material having chemical resistance and voltage resistance while swelling. For example, it may be made of one or more selected from the group consisting of polyurethane (PU), polyethylene (PE), polycarbonate (PC), polypropylene (PP), and polyimide (PI).

[0021] Alternatively, specifically, the swelling tape has a structure in which an adhesive layer is formed on one or both sides of the raw material base material, and the raw material base material may be a polyolefin base material, for example, polyethylene (PE) or polypropylene (PP), and the adhesive layer may contain one or more substances selected from the group consisting of polyacrylate (PA), rubber, and styrene.

[0022] On the one hand, the diameter of the perforation holes formed in the swelling tape may be 0.1 mm to 3 mm, the swelling tape includes two or more perforation holes, and the interval between each perforation hole may be 1 mm to 10 mm.

[0023] In addition, the perforation holes may be formed so as to have an area of 10% to 60% based on the total area of the swelling tape.

[0024] The positions of such perforation holes may be formed in a row on the inner side of winding in a direction perpendicular to the winding direction of the jelly roll electrode assembly in the swelling tape, or may be formed in a row at both ends in a direction horizontal to the winding direction of the jelly roll electrode assembly, or may be formed at the center of the swelling tape.

[0025] On the one hand, according to another embodiment of the present invention, a secondary battery including the jelly roll electrode assembly is provided.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0027] Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0028] For the sake of clarity in the description of the present invention, parts that are unnecessary for the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0029] Also, the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to what is shown in the drawings. The thicknesses are shown enlarged in the drawings to clearly represent various layers and regions. And, in the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated.

[0030] Also, throughout the specification, when a certain part “includes” a certain component, this means that other components can be further included, rather than excluding other components, unless otherwise stated to the contrary.

[0031] Note that throughout the specification, when it is “on a plane”, this means when the target part is viewed from above, and when it is “in a cross-section”, this means when the cross-section obtained by vertically cutting the target part is viewed from the side.

[0032] FIG. 1 is a perspective view of a jelly roll electrode assembly according to an embodiment of the present invention.

[0033] Referring to FIG. 1, a jelly roll electrode assembly 100 according to an embodiment of the present invention has a shape in which a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet are all wound together.

[0034] At this time, a positive electrode tab 113 is formed on the positive electrode sheet, and this can later form a positive electrode terminal by making an electrical connection with a cap assembly of a cylindrical battery or the like.

[0035] On one hand, at the outermost part of the jelly roll electrode assembly 100, an uncoated portion 121 where the active material layer is not formed on the negative electrode sheet is wound. Since such an uncoated portion 121 later comes into contact with the inner wall surface of the can of the secondary battery, the uncoated portion 121 of the negative electrode sheet serves as a terminal and can be directly electrically connected to the can of the cylindrical secondary battery case, so a separate negative electrode tab is not required. side

[0036] Also, since the separation membrane is not formed at the outermost part of the jelly roll electrode assembly 100, an outer diameter reduction effect can be obtained, and thereby an internal space of the battery can be secured, the capacity can be increased, the energy density can be improved, and the battery performance effect can be improved. side

[0037] However, as described above, when the uncoated portion 121 of the negative electrode sheet is actually exposed to the outside, there is a problem that one or two portions with a larger outer diameter come into contact with the can according to the roundness of the jelly roll, and the effect is reduced compared to the existing prediction. In the present invention, in order to improve this, a swelling tape having a property of swelling by reacting with the electrolyte is applied. side

[0038] At this time, the swelling tape does not affect the capacity and has a structure attached to the inner surface in the direction of the center of the jelly roll electrode assembly 100 so that the uncoated portion 121 of the outermost negative electrode sheet can later come into contact with the cylindrical secondary battery case as a whole. side side

[0039] Therefore, such a swelling tape is not shown in FIG. 1.

[0040] On the one hand, to specifically describe the swelling tape according to the present invention, FIG. 2 shows a top view of the upper surface of the negative electrode sheet 120 before winding in the jelly roll electrode assembly 100 of FIG. 1, FIG. 3 shows a cross-sectional view of the jelly roll electrode assembly 100 of FIG. 1 before winding, FIG. 4 shows a cross-sectional view of the jelly roll electrode assembly 100 according to another embodiment before winding, and FIG. 5 shows a cross-sectional view taken along the line A-A' of the jelly roll electrode assembly 100 of FIG. 1.

[0041] First, referring to FIGS. 2 and 3, the positive electrode sheet 110 includes a holding portion where a positive electrode active material layer is formed and a plain portion where no positive electrode active material layer is formed. Such a plain portion is provided between the holding portions, and a positive electrode tab 113 is attached to the plain portion.

[0042] Also, a separator 130 is interposed between the positive electrode sheet 110 and the negative electrode sheet 120.

[0043] The negative electrode sheet 120 includes a holding portion (holding portion 122 of the negative electrode sheet) where an active material layer 123 is formed on a negative electrode current collector 124 and a plain portion 121 where no active material layer 123 is formed. At this time, the plain portion 121 is located on one side and serves as a negative electrode terminal when wound on the outermost side. side By being wound on the outermost side, it serves as a negative electrode terminal.

[0044] On the other hand, a swelling tape 125 is attached to the inner surface of the winding of the plain portion 121.

[0045] Here, the swelling tape 125 is formed in an area A' that covers 10% to 90% of the total area A of the inner surface of the plain portion 121 of the negative electrode sheet 120.

[0046] Also, the swelling tape 125 may be formed only on a part of the inner surface of the plain portion 121 so as not to overlap with the holding portion 122 of the negative electrode sheet 120.

[0047] Alternatively, referring to FIG. 4, the swelling tape 125' may be attached to a part of the inner surface of the plain portion 121' of the negative electrode sheet 120' and from the boundary surface between the plain portion 121' and the holding portion 122' of the negative electrode sheet to a part of the holding portion 122' of the negative electrode sheet 120' in the direction of the holding portion 122' of the negative electrode sheet 120'. At this time, it is formed within a range of length l that does not overlap with the active material layer of the facing positive electrode sheet 110. For example, the swelling tape may cover the holding portion of the negative electrode sheet in the range of 0.25% to 10%, specifically 0.5% to 5% of the total area of the holding portion of the negative electrode sheet.

[0048] However, in any case, the outermost side plain portion 121 of the negative electrode sheet 120 on which the swelling tape 125 is formed faces the active material layer 123 of the negative electrode sheet 120 located inside, that is, faces the holding portion 122.

[0049] Therefore, since the swelling tape 125 is formed in a portion that does not face the positive electrode of the active material layer 123, that is, a portion that does not contribute to the capacity, no capacity problem occurs. At the same time, since the swelling tape 125 is formed from the outermost side of the jelly roll electrode assembly 100 to the inside of the current collector 124 of the negative electrode sheet 120, the current collector 124 can later come into contact with the can of the cylindrical battery case as a whole, and the intended effects of the present application can be achieved without reducing the improvement of conductivity and heat generation level.

[0050] On the other hand, such a swelling tape 125 has the property of expanding in volume when it absorbs the electrolytic solution, and may be a single-sided or double-sided tape.

[0051] At this time, the single-sided or double-sided tape is not limited as long as it is a material having chemical resistance and voltage resistance while swelling. For example, it is composed of one or more selected from the group consisting of polyurethane (PU), polyethylene (PE), polycarbonate (PC), polypropylene (PP), and polyimide (PI).

[0052] Alternatively, the swelling tape 125 may have a structure in which an adhesive layer is formed on one or both sides of the base fabric substrate.

[0053] Here, the base fabric substrate is a polyolefin-based substrate, and may be, for example, polyethylene (PE) or polypropylene (PP), and the adhesive layer may contain one or more substances selected from the group consisting of polyacrylate (PA), rubber, and styrene.

[0054] On the other hand, such a swelling tape 125 includes one or more perforation holes 126.

[0055] The perforation hole 126 is a hole perforated in a form that penetrates the swelling tape 125 in the thickness direction.

[0056] Therefore, it is possible to remove the air trap that may occur while attaching the swelling tape 125 to the plain part 121, and prevent an increase in the outer diameter of the jelly roll electrode assembly 100 that will be generated thereafter, so that productivity can be improved.

[0057] The form, formation position, size, etc. of the perforation hole 126 are not greatly limited as long as they are formed in a form, formation position, and size that can remove the air trap generated when the swelling tape 125 is attached.

[0058] However, in order to more effectively remove the air trap, the formation position, size, etc. have an impact.

[0059] Specifically, in order to specifically describe the perforation hole 126 formed in the swelling tape 125, FIG. 6 shows an example of the swelling tape 125.

[0060] Referring to FIG. 6, a large number of perforated holes 126 are formed in the swelling tape 125. Specifically, the swelling tape 125 can have two or more perforated holes 126, and can be appropriately selected in consideration of the degree of air trapping and the increase in the contact area between the swelling tape 125 and the battery case.

[0061] At this time, the diameter (R) of the perforated hole 126 may be 0.1 mm to 3 mm, and specifically may be 1 mm to 3 mm.

[0062] If it is outside the above range and is excessively small, it is not easy to remove the air trap. If it is excessively large, the application effect of the swelling tape cannot be fully obtained, so it is not preferable.

[0063] Also, the interval (D) between the perforated holes 126 may be 1 mm to 10 mm, and specifically may be 3 mm to 10 mm.

[0064] If it is outside the above range and the interval is excessively small, the size of the perforated hole 126 increases while being torn between adjacent perforated holes 126, and the application effect of the swelling tape 125 cannot be fully obtained. If the interval is excessively large, it is not easy to discharge the trapped air formed therebetween, so it is not preferable.

[0065] Also, the area occupied by the perforated holes 126 may be formed at 10% to 60% based on the total area of the swelling tape 125.

[0066] If it is formed with an excessively small area outside the above range, it is not easy to discharge the trapped air. If it is excessively large, the application effect of the swelling tape 125 cannot be obtained, so it is not preferable.

[0067] On the other hand, such perforated holes 126 may be formed before, simultaneously with, or after the adhesion of the swelling tape 125, and are formed at a site where air trapping is well formed or at a site that does not overlap with the equipment used for the adhesion depending on the adhesion method.

[0068] Specifically, the perforated holes 126 can be attached to the plain portion of the negative electrode sheet in a state of being previously formed in the swelling tape 125 before attachment, or can be formed near the portion where air is trapped simultaneously with the attachment to the negative electrode sheet, and can be separately formed near the portion where air is trapped after the swelling tape 125 is attached.

[0069] On the other hand, when considering the attachment method of the swelling tape 125, the perforated holes 126 are formed in a row at both ends in a direction horizontal to the winding direction of the jelly roll electrode assembly (Fig. 6(a)), and may be formed in a row on the inner side of the winding in a direction perpendicular to the winding direction of the jelly roll electrode assembly (Fig. 6(b)), or may be formed in the central portion of the swelling tape 125 (Fig. 6(c)).

[0070] However, it is not limited to such a structure and can be formed at various positions.

[0071] Also, in the drawings, the perforated holes 126 are shown as circular, but their shape is not limited either and may be formed in a polygon.

[0072] When the swelling tape 125 includes the perforated holes 126 in this way, when the swelling tape 125 is not properly attached during attachment and torsion occurs due to the crimping of the roller, the trapped air can be effectively induced to be discharged, and an increase in the outer diameter of the jelly roll electrode assembly can be prevented, so there is an effect that productivity can be improved.

[0073] In addition, since the compositions, structures, etc. of the positive electrode sheet, negative electrode sheet, and separator constituting the jelly roll electrode assembly are known in the art, detailed descriptions are omitted in this specification.

[0074] On the other hand, the present invention provides a secondary battery including the jelly roll electrode assembly.

[0075] At this time, the secondary battery may be a cylindrical secondary battery or a rectangular secondary battery that incorporates the jelly roll electrode assembly into a can.

[0076] Such secondary batteries are also known in the art, so detailed description thereof is omitted in this specification.

[0077] As described above, the preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also belong to the scope of the present invention.

Explanation of Reference Numerals

[0078] 100: Jelly roll electrode assembly 110: Positive electrode sheet 120: Negative electrode sheet 130: Separator 113: Positive electrode tab 121: Plain portion of the negative electrode sheet 122: Holding portion of the negative electrode sheet 125: Swelling tape 126: Perforated hole

Industrial Applicability

[0079] According to the embodiment, the jelly roll electrode assembly of the present invention includes a swelling tape on the inner surface of the battery plain portion of the outermost negative electrode sheet, and by including a perforated hole through which the air trapped by the swelling tape can be discharged, an increase in the outer diameter of the jelly roll electrode assembly caused by air trapping can be prevented, so that productivity can be improved. side ​

Claims

1. A jelly roll electrode assembly in which a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet are all wound together, wherein an uncoated portion where no active material layer is formed is wound on the outermost side of the jelly roll electrode assembly, a swelling tape is attached to the inner surface of the uncoated portion of the negative electrode sheet in the direction of the central portion of the jelly roll electrode assembly, the swelling tape includes one or more perforated holes, the swelling tape is attached from a part of the inner surface of the uncoated portion of the negative electrode sheet to a part of the holding portion of the negative electrode sheet in the direction of the holding portion of the negative electrode sheet from the boundary surface between the uncoated portion of the negative electrode sheet and the holding portion where the active material layer is formed, a jelly roll electrode assembly.

2. The jelly roll electrode assembly according to claim 1, wherein the swelling tape covers the holding portion of the negative electrode sheet in the range of 0.25% to 10% of the total area of the holding portion of the negative electrode sheet.

3. The jelly roll electrode assembly according to claim 1, wherein the swelling tape is formed only on a part of the inner surface of the uncoated portion of the negative electrode sheet.

4. The jelly roll electrode assembly according to claim 1, wherein the swelling tape is formed so as to cover 10% to 90% of the total area of the inner surface of the uncoated portion of the negative electrode sheet.

5. The jelly roll electrode assembly according to claim 1, wherein the swelling tape is a single-sided or double-sided tape.

6. The jelly roll electrode assembly according to claim 5, wherein the single-sided or double-sided tape is made of one or more selected from the group consisting of polyurethane (PU), polyethylene (PE), polycarbonate (PC), polypropylene (PP), and polyimide (PI).

7. The jelly roll electrode assembly according to claim 1, wherein the swelling tape has a structure in which an adhesive layer is formed on one or both sides of a polyolefin-based substrate.

8. The jelly roll electrode assembly according to claim 7, wherein the adhesive layer contains one or more substances selected from the group consisting of polyacrylate (PA), rubber, and styrene.

9. A jelly roll electrode assembly in which a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet are all wound together, On the outermost side of the jelly roll electrode assembly, a plain portion where no active material layer is formed on the negative electrode sheet is wound. On the plain portion of the negative electrode sheet, a swelling tape is attached to the inner surface in the direction of the central portion of the jelly roll electrode assembly. The swelling tape includes one or more perforated holes. The jelly roll electrode assembly, wherein the diameter of the perforated hole is 0.1 mm to 3 mm.

10. A jelly roll electrode assembly in which a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet are wound together, On the outermost side of the jelly roll electrode assembly, a plain portion where no active material layer is formed on the negative electrode sheet is wound. On the plain portion of the negative electrode sheet, a swelling tape is attached to the inner surface in the direction of the central portion of the jelly roll electrode assembly. The swelling tape includes one or more perforated holes. The jelly roll electrode assembly, wherein the swelling tape includes two or more perforated holes, and the interval between the respective perforated holes is 1 mm to 10 mm.

11. The jelly roll electrode assembly according to claim 1, wherein the perforated hole is formed to have an area of 10% to 60% based on the total area of the swelling tape.

12. The jelly roll electrode assembly according to claim 1, wherein the perforated holes are formed in a row on the inner side in the winding direction of the jelly roll electrode assembly in a direction perpendicular to the winding direction of the swelling tape.

13. The jelly roll electrode assembly according to claim 1, wherein the perforated holes are formed in a row at both ends in a direction horizontal to the winding direction of the jelly roll electrode assembly.

14. The jelly roll electrode assembly according to claim 1, wherein the perforated hole is formed in the central portion of the swelling tape.

15. A secondary battery including the jelly roll electrode assembly according to claim 1, 9 or 10.

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