Electrode assembly and secondary battery including the same

Abstract

An electrode assembly according to an embodiment of the present invention includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the separator including a first separator disposed on one side of the positive electrode and a second separator disposed on one side of the negative electrode. The positive electrode, the first separator, the negative electrode, and the second separator are wound together to form a jelly roll structure. Based on a radial direction of the jelly roll structure, there is an area where the separator overlaps in two or more layers between an edge portion of the positive electrode and the negative electrode.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0144428 filed on October 27, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly to a jelly-roll type electrode assembly and a secondary battery including the same. [Background technology]

[0003] In recent years, the demand for portable electronic products such as laptops, video cameras, and mobile phones has increased sharply, and the development of electric vehicles, energy storage batteries, robots, satellites, and other products has progressed in earnest. As a result, research into secondary batteries, which are used as the driving power source for these products, has been actively conducted.

[0004] Secondary batteries include, for example, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, etc. Among these, lithium secondary batteries are widely used in the field of cutting-edge electronic devices due to their advantages over nickel-based secondary batteries, such as almost no memory effect, freedom in charging and discharging, a very low self-discharge rate, a high operating voltage, and a high energy density per unit weight.

[0005] Secondary batteries are classified according to the shape of the battery case into cylindrical batteries, in which an electrode assembly is housed in a cylindrical metal can, prismatic batteries, in which an electrode assembly is housed in a prismatic metal can, and pouch batteries, in which an electrode assembly is housed in a pouch-shaped case made of an aluminum laminate sheet. Among these, cylindrical batteries have the advantages of relatively large capacity and structural stability.

[0006] The electrode assembly housed in the battery case is a chargeable / dischargeable power generating element composed of a stacked structure of a positive electrode, a separator, and a negative electrode, and is classified into jelly roll, stack, and stack / folding types. The jelly roll type is a long sheet-shaped positive electrode and negative electrode coated with an active material, wound with a separator interposed between them. The stack type is a type in which multiple positive electrodes and negative electrodes of a predetermined size are stacked in sequence with a separator interposed between them. The stack / folding type is a combination of the jelly roll and stack types. Among these, the jelly roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per weight.

[0007] FIG. 1 is a perspective view of a conventional jelly roll electrode assembly.

[0008] Referring to FIG. 1, a conventional jelly roll electrode assembly 10 inserted into a secondary battery includes a positive electrode 20, a negative electrode 30, a first separator 41 located on one side of the positive electrode 20, and a second separator 42 located on one side of the negative electrode 30.

[0009] The positive electrode 20 may include a positive electrode current collector 20f and a positive electrode active material layer 20m formed by applying a positive electrode active material to the positive electrode current collector 20f. The portion of the positive electrode current collector 20f that is not coated with the positive electrode active material may be positioned upward (d2), thereby forming a current path without a separate positive electrode tab.

[0010] The negative electrode 30 may include a negative electrode current collector 30f and a negative electrode active material layer 30m formed by applying a negative electrode active material to the negative electrode current collector 30f. The portion of the negative electrode current collector 30f on which the negative electrode active material is not applied is positioned downward (d1), thereby forming a current path without a separate negative electrode tab.

[0011] As described above, a tab-less electrode assembly can be manufactured in which the positive electrode current collector 20f and the negative electrode current collector 30f are used as a current path without attaching a positive electrode tab or a negative electrode tab.

[0012] In this case, in the case of the positive electrode 20, the edge portion corresponding to the end is not composed of only the positive electrode current collector but also of the positive electrode current collector coated with the positive electrode active material, forming a so-called free edge. The jelly roll electrode assembly 10 formed by winding the positive electrode 20 and the negative electrode 30 is repeatedly charged and discharged, causing the positive electrode 20 and the negative electrode 30 to repeatedly expand and contract. At this time, the edge portion of the positive electrode 20 coated with the positive electrode active material forms a step and applies pressure to the surrounding area due to the contraction and expansion. In other words, the repeated contraction and expansion of the edge portion of the positive electrode 20 may damage the negative electrode 30, the first separator 41, and the second separator 42.

[0013] Meanwhile, an empty space is formed at the center 10C of the jelly roll electrode assembly 10, and as the positive electrode 20 and negative electrode 30 repeatedly expand and contract, deformation of this center 10C can occur. In particular, in the case of a tab-less electrode assembly (jelly roll electrode assembly 10), the problem of deformation of the center 10C can be more serious because there is no separate member, such as a positive electrode tab or a negative electrode tab, that supports the center 10C of the jelly roll electrode assembly 10. If such core deformation occurs significantly, stress is concentrated in one place, which can lead to disconnections and cracks in the positive electrode 20 or negative electrode 30.

[0014] Therefore, there is a need for technological development that can solve the above-mentioned problems that the jelly roll electrode assembly 10 has. Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention provides a jelly-roll type electrode assembly and a secondary battery including the same, which can solve problems caused by the edge of a positive electrode and problems of core deformation.

[0016] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0017] An electrode assembly according to one embodiment of the present invention includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the separator including a first separator disposed on one side of the positive electrode and a second separator disposed on one side of the negative electrode. The positive electrode, the first separator, the negative electrode, and the second separator are wound together to form a jelly roll structure. In the radial direction of the jelly roll structure, there is a region where two or more layers of the separator overlap between an edge of the positive electrode and the negative electrode.

[0018] A region where the separator is overlapped in three layers may exist between the edge of the positive electrode and the negative electrode in the radial direction of the jelly roll structure.

[0019] A first tape and a second tape may be attached to one side of the first separator and one side of the second separator, respectively. The first tape may be attached to a region between one end of the first separator and a point where the positive electrode is inserted. The second tape may be attached to a region between one end of the second separator and a point where the negative electrode is inserted.

[0020] The first tape may be attached to a region spaced apart from one end of the first separator, and the second tape may be attached to a region spaced apart from one end of the second separator.

[0021] The first tape may be attached to one of both surfaces of the first separator on a side opposite to a side on which the second separator is located.

[0022] The second tape may be attached to one surface of the second separator opposite to the first separator.

[0023] The first tape and the second tape may include an electrically insulating material.

[0024] Two layers of the first separator and one layer of the second separator may be positioned between an edge portion of the positive electrode and the negative electrode in a radial direction of the jelly roll structure.

[0025] The first separator may include a first folding portion folded in a winding direction, and the first folding portion may overlap with another portion of the first separator when wound together. The second separator may include a second folding portion folded in a winding direction, and the second folding portion may overlap with another portion of the second separator when wound together.

[0026] The separator may be overlapped in three layers between the edge portion of the positive electrode and the negative electrode in a radial direction of the jelly roll structure, and two of the three layers of the separator overlapped between the edge portion of the positive electrode and the negative electrode may be the first folding portion and the second folding portion, respectively.

[0027] In the jelly roll structure, an edge portion of the negative electrode may be located closer to the center of the jelly roll structure than an edge portion of the positive electrode.

[0028] The jelly roll structure may be in a wound state with the negative electrode, the second separator, the positive electrode, and the first separator arranged in this order.

[0029] A region where two or more layers of the separator are overlapped may be located outside an edge portion of the positive electrode in a radial direction of the jelly roll structure.

[0030] The jelly roll structure may be in a wound state with the first separator, the positive electrode, the second separator, and the negative electrode arranged in this order.

[0031] A region where two or more layers of the separator are overlapped may be located inside an edge portion of the positive electrode in a radial direction of the jelly roll structure. [Effects of the Invention]

[0032] According to an embodiment of the present invention, the separator is positioned in two or more layers near the edge of the positive electrode in the radial direction of the jelly roll structure formed by the electrode assembly, thereby solving problems of damage and core deformation caused by the edge of the positive electrode.

[0033] In addition, by attaching tape to the area of ​​each separator adjacent to the center of the jelly roll structure, structural rigidity against core deformation can be enhanced.

[0034] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a perspective view showing a conventional jelly roll electrode assembly. [Figure 2] 4 is a diagram illustrating a process of winding an electrode assembly according to an embodiment of the present invention; [Figure 3] 4 is a diagram illustrating a process of winding an electrode assembly according to an embodiment of the present invention; [Figure 4] 4 is an enlarged plan view of the central region of the electrode assembly manufactured by the process of FIGS. 2 and 3. FIG. [Figure 5] 10 is a view schematically illustrating a process of winding an electrode assembly according to another embodiment of the present invention. [Figure 6] 10 is a view schematically illustrating a process of winding an electrode assembly according to another embodiment of the present invention. [Figure 7]FIG. 7 is an enlarged plan view of the central region of the electrode assembly manufactured by the process of FIGS. 5 and 6. DETAILED DESCRIPTION OF THE INVENTION

[0036] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily carry out the embodiments.

[0037] As those skilled in the art would realize, the described embodiments may be modified in various ways, all without departing from the spirit or scope of the present invention.

[0038] In order to clearly describe the present invention, parts not necessary for the description will be omitted and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0039] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, thicknesses are exaggerated to clearly show multiple layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0040] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly above" that part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the direction opposite to gravity.

[0041] Furthermore, throughout the specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, not excluding other elements, unless otherwise specified.

[0042] Also, throughout the specification, "in a plane" means a portion of the subject matter viewed from above, and "in cross section" means a portion of the subject matter viewed from the side along a vertical cross section.

[0043] 2 and 3 are views schematically illustrating a process of winding an electrode assembly according to an embodiment of the present invention, and FIG. 4 is an enlarged plan view illustrating a central region of the electrode assembly manufactured through the process of FIGS. 2 and 3.

[0044] 2 to 4, an electrode assembly 100a according to an embodiment of the present invention includes a positive electrode 200, a negative electrode 300, and a separator 400 disposed between the positive electrode 200 and the negative electrode 300. The separator 400 includes a first separator 410 disposed on one side of the positive electrode 200 and a second separator 420 disposed on one side of the negative electrode 300. The positive electrode 200, the first separator 410, the negative electrode 300, and the second separator 420 are wound together to form a jelly roll structure. That is, the electrode assembly 100a according to this embodiment is a jelly roll-type electrode assembly.

[0045] Although the positive electrode 200 and the negative electrode 300 are not specifically illustrated, as described above, the positive electrode 200 may include a positive electrode current collector and a positive electrode active material layer formed by applying a positive electrode active material to both surfaces of the positive electrode current collector, and the negative electrode 300 may include a negative electrode current collector and a negative electrode active material layer formed by applying a negative electrode active material to both surfaces of the negative electrode current collector.

[0046] A first tape 510 and a second tape 520 may be attached to one side of the first separator 410 and one side of the second separator 420, respectively. The first tape 510 may be attached to an area between one end 410E of the first separator 410 and the point where the positive electrode 200 is inserted. The second tape 520 may be attached to an area between one end 420E of the second separator 420 and the point where the negative electrode 300 is inserted. In this specification, the one end 410E of the first separator 410 refers to the portion of the first separator 410 that is first inserted into the winding core 10W, and the one end 420E of the second separator 420 refers to the portion of the second separator 420 that is first inserted into the winding core 10W.

[0047] As shown in FIG. 2, the first separator 410 and the second separator 420 are first inserted into the winding core 10W, and then a first tape 510 and a second tape 520 are attached to one side of the first separator 410 and one side of the second separator 420, respectively. Then, as shown in FIG. 3, the first separator 410 and the second separator 420 are folded to form a first folding portion 410F and a second folding portion 420F, respectively, and the anode 300 and the cathode 200 are inserted in order to perform final winding. As described above, one end 410E of the first separator 410 and one end 420E of the second separator 420 are the portions that are inserted into the winding core 10W first. The first folding portion 10F and the second folding portion 420F will be described again below.

[0048] Although the positive electrode 200 is inserted and wound after the first separator 410, as shown in Figures 2 and 3, the first tape 510 may be attached to the first separator 410 before the positive electrode 200 is inserted. Therefore, based on the wound jelly roll structure, the first tape 510 may be attached to a region between one end 410E of the first separator 410 and the point where the positive electrode 200 is inserted. In other words, the first tape 510 may be attached to a region between one end 410E of the first separator 410 and the point on the first separator 410 corresponding to the edge portion 200E of the positive electrode 200.

[0049] As described above, the negative electrode 300 is inserted and wound after the second separator 420, but as shown in Figures 2 and 3, the second tape 520 may be attached to the second separator 420 before the negative electrode 300 is inserted. Therefore, based on the wound jelly roll structure, the second tape 520 may be attached to a region between one end 420E of the second separator 420 and the point where the negative electrode 300 is inserted. In other words, the second tape 520 may be attached to a region between one end 420E of the second separator 420 and the edge portion 300E of the negative electrode 300 and the corresponding point on the second separator 420.

[0050] If, unlike the above, the first tape 510 overlaps the point where the positive electrode 200 is inserted, or the second tape 520 overlaps the point where the negative electrode 300 is inserted, the overlapping portion will cover the separator 400, and the corresponding portion of the positive electrode 200 or negative electrode 300 will become an unreacted area, which will lead to a corresponding decrease in battery capacity.

[0051] Meanwhile, the first tape 510 may be attached to one of the two surfaces of the first separator 410 facing the opposite side to the side where the second separator 420 is located, and the second tape 520 may be attached to one of the two surfaces of the second separator 420 facing the opposite side to the side where the first separator 410 is located. That is, when the first separator 410 and the second separator 420 are introduced, the first tape 510 and the second tape 520 may be attached to the opposite sides of the first separator 410 and the second separator 420, rather than to the sides where the first separator 410 and the second separator 420 face each other. Rather than providing a separate process for attaching the first tape 510 and the second tape 520, the first tape 510 and the second tape 520 may be attached simultaneously while the first separator 410 and the second separator 420 are introduced into the core, as shown in FIG. 2. Therefore, it is preferable in terms of process that the first tape 510 and the second tape 520 are attached to the opposite surfaces of the first separator 410 and the second separator 420 rather than to the surfaces facing each other.

[0052] There is no particular limitation on the method of attaching the first tape 510 and the second tape 520. For example, the first tape 510 and the second tape 520 may be cut, then transferred to an adsorbent using vacuum or low pressure, and attached to the first separation membrane 410 and the second separation membrane 420, respectively.

[0053] The first tape 510 and the second tape 520 may include an electrically insulating material and may preferably include a material that is resistant to heat shrinkage, for example, the first tape 510 and the second tape 520 may include a polypropylene or polyethylene material.

[0054] As described above, the positive electrode 200 and the negative electrode 300 repeatedly expand and contract during the charge and discharge process, which can cause deformation of the center 100C of the jelly roll structure. Here, the center 100C of the jelly roll structure refers to the center of the circular structure when the jelly roll-shaped electrode assembly 100a is viewed from the height direction, as shown in FIG.

[0055] In particular, if the electrode assembly according to this embodiment is a tab-less electrode assembly, there is no separate member supporting the center 100C of the jelly roll structure, such as a positive electrode tab and a negative electrode tab, which can lead to a more serious center deformation problem. Also, since the first separator 410 and the second separator 420 are inserted first, the center 100C of the jelly roll structure is mainly composed of the first separator 410 and the second separator 420. However, the first separator 410 and the second separator 420 are thin membranes that do not have a sufficient strength and are therefore not structured to withstand stress.

[0056] Therefore, the electrode assembly 100a according to this embodiment aims to enhance the structural rigidity of the jelly roll structure against core deformation by attaching the first tape 510 and the second tape 520 to the regions of the first separator 410 and the second separator 420, respectively, that are adjacent to the center 100C of the jelly roll structure.

[0057] There is no particular limit to the length of attachment of the first tape 510 and the second tape 520, and they may be wound 0.5 to 4 times. If the first tape 510 and the second tape 520 are wound less than 0.5 times, they may not be able to withstand internal stress, and if they are wound more than 4 times, the attachment points may overlap with the insertion points of the positive electrode 200 and the negative electrode 300, resulting in a problem of reduced battery capacity.

[0058] 4, there is a region where the separator 400 overlaps in two or more layers between the edge portion 200E of the positive electrode 200 and the negative electrode 300 in the radial direction of the jelly roll structure. More specifically, there is a region where the separator 400 overlaps in three layers between the edge portion 200E of the positive electrode 200 and the negative electrode 300. The point where the separator 400 overlaps in three layers is indicated as L3 in FIG. 4. Unlike the structure shown in FIG. 4, either the first separator 410 or the second separator 420 may be formed relatively short to overlap in two layers, or an additional separator may be interposed to overlap in four or more layers.

[0059] In this specification, the edge portion 200E of the positive electrode 200 refers to one end of the positive electrode 200 that is first inserted for winding, and the edge portion 300E of the negative electrode 300 refers to one end of the negative electrode 300 that is first inserted for winding. In addition, the radial direction of the jelly roll structure refers to the direction from the center 100C of the jelly roll structure to the outer edge of the jelly roll structure.

[0060] In the jelly roll structure, the edge portion 300E of the negative electrode 300 can be positioned closer to the center 100C of the jelly roll structure than the edge portion 200E of the positive electrode 200. That is, as shown in FIG. 3, during the winding process, the negative electrode 300 is inserted relatively earlier than the positive electrode 200. Therefore, the edge portion 300E of the negative electrode 300 can be positioned relatively closer to the center 100C of the jelly roll structure.

[0061] During the charging process of a lithium secondary battery, lithium ions from the positive electrode 200 flow into the electrolyte and then, due to the concentration gradient, are intercalated into the negative electrode 300. Because this process involves the migration of lithium ions from the positive electrode 200 to the negative electrode 300, it is preferable that the negative electrode 300 have a larger area than the positive electrode 200. If the positive electrode 200 has a larger area than the negative electrode 300, a lithium deposition reaction may occur on the corresponding surface of the lithium ions. The deposited lithium may cause a short circuit between the positive and negative electrodes. Therefore, it is preferable that the negative electrode 300 have a larger area than the positive electrode 200, and that the negative electrode 300 be inserted before the positive electrode 200 in a jelly roll structure. Furthermore, because positive electrode active material layers are provided on both sides of the positive electrode 200, it is preferable that a corresponding negative electrode 300 be located on both sides of the positive electrode 200, as shown in FIG. 4.

[0062] At this time, as described above, a positive electrode active material portion may be formed at the edge portion 200E of the positive electrode 200, i.e., a so-called free edge may be formed. The edge portion 200E of the positive electrode 200 forms a stepped structure, and as the positive electrode 200 repeatedly expands and contracts, the edge portion 200E of the positive electrode 200 may apply pressure to nearby areas. In other words, the edge portion 200E of the positive electrode 200 may damage the separator 400 and the previously wound negative electrode 300. This may cause disconnection or cracks in the separator 400 or the negative electrode 300, and may even cause an internal short circuit between the positive electrode 200 and the negative electrode 300.

[0063] Therefore, the electrode assembly 100a according to this embodiment attempts to solve this problem by configuring the separator 400 to overlap in two or more layers, particularly three layers, in the region adjacent to the edge portion 200E of the positive electrode 200. In other words, the separator 400 is configured to cover the edge portion 200E of the positive electrode 200 with three layers, in order to protect the other separators 400 and the negative electrode 300 from the pressure induced by the edge portion 200E of the positive electrode 200.

[0064] Specifically, as shown in Fig. 3, in an electrode assembly 100a according to an embodiment of the present invention, the jelly roll structure may be wound up with the negative electrode 300, the second separator 420, the positive electrode 200, and the first separator 410 arranged in this order. Since a region where the separator 400 overlaps in three layers is formed between the edge portion 200E of the positive electrode 200 and the negative electrode 300, when the electrode assembly 100a is inserted into the winding core 10W, the positive electrode 200 may be inserted between the first separator 410 and the second separator 420, and the negative electrode 300 may be inserted above the second separator 420. This arrangement may correspond to an arrangement when the winding core 10W is wound clockwise.

[0065] More specifically, when manufacturing the electrode assembly 100a in a form in which the anode 300, the second separator 420, the cathode 200, and the first separator 410 are arranged in this order and wound, the first folding portion 410F and the second folding portion 420F may be formed by folding the first separator 410 and the second separator 420 in the winding direction, as shown in Fig. 3. In this case, the winding direction may be the direction in which the winding core 10W rotates, for example, clockwise as shown in Fig. 3.

[0066] The first separator 410 may be folded clockwise around the first boundary 410B to form the first folding portion 410F. The first boundary 410B corresponds to the boundary where the first separator 410 bends after passing between the winding cores 10W, and the first folding portion 410F corresponds to the region between the first boundary 410B and one end 410E of the first separator 410. That is, the first separator 410 may include the first folding portion 410F folded in the winding direction, and the first folding portion 410F may overlap with other portions of the first separator 410 when wound together.

[0067] Similarly, the second separator 420 may be folded clockwise around the second boundary 420B to form the second folding portion 420F. The second boundary 420B corresponds to the boundary where the second separator 420 bends after passing between the winding cores 10W, and the second folding portion 420F corresponds to the region between the second boundary 420B and one end 420E of the second separator 420. That is, the second separator 420 may include the second folding portion 420F folded in the winding direction, and the second folding portion 420F may be wound up together with the other portion of the second separator 420 while overlapping it.

[0068] 4, two layers of first separator 410 and one layer of second separator 420 may be positioned between edge portion 200E of positive electrode 200 and negative electrode 300 in the radial direction of the jelly roll structure. That is, a total of three layers of separator 400 may be positioned in this configuration. More specifically, of the three layers of separator 400 overlapping between edge portion 200E of positive electrode 200 and negative electrode 300, two layers may be first folding portion 410F and second folding portion 420F, respectively. The remaining layer may not be the first folding portion 410F but may be the region of first separator 410.

[0069] Meanwhile, in the electrode assembly 100a manufactured in this manner, a region where the separator 400 is overlapped in two or more layers, particularly three layers, may be located outside the edge portion 200E of the positive electrode 200 in the radial direction of the jelly roll structure. The point indicated by L3 is located outside the edge portion 200E of the positive electrode 200 in the radial direction of the jelly roll structure. In other words, the region where the separator 400 is overlapped in three layers may be located between the edge portion 200E of the positive electrode 200 and the negative electrode 300, and may be located farther from the center 100C of the jelly roll structure than the edge portion 200E of the positive electrode 200.

[0070] A positive electrode active material layer is formed on both sides of the positive electrode 200, and the side of the positive electrode 200 facing the center 100C of the jelly roll structure corresponds to the back surface, and the opposite side corresponds to the top surface. The electrode assembly 100a according to this embodiment corresponds to a top surface reinforcement design of the positive electrode 200, in which the region where three layers of the separator 400 are overlapped is located on the top surface of the positive electrode 200.

[0071] Meanwhile, the first tape 510 may be attached to a region spaced apart from one end 410E of the first separator 410, and the second tape 520 may be attached to a region spaced apart from one end 420E of the second separator 420. More specifically, as shown in FIG. 4, the first tape 510 and the second tape 520 may be attached to regions spaced apart by a predetermined distance from one end 410E of the first separator 410 and one end 420E of the second separator 420, respectively, so that the first tape 510 and the second tape 520 do not attach to a portion (denoted as L3) of the separator 400 that covers the edge portion 200E of the positive electrode 200. Preferably, the first tape 510 and the second tape 520 are not present between the edge portion 200E of the positive electrode 200 and the negative electrode 300 thereon, and only the separator 400 is located therebetween.

[0072] If the first tape 510 or the second tape 520 were attached to cover the edge portion 200E of the positive electrode 200, the portion of the positive electrode 200 where the first tape 510 or the second tape 520 is attached would be an unreacted region, resulting in a decrease in battery capacity. In contrast, the electrode assembly 100a according to this embodiment prevents the first tape 510 or the second tape 520 from being attached to the two or more layers of separator 400 that cover the edge portion 200E of the positive electrode 200, thereby forming the top surface of the positive electrode 200 as a reaction region, thereby increasing capacity.

[0073] Hereinafter, an electrode assembly according to another embodiment of the present invention will be described in detail with reference to Figures 5 to 7. However, descriptions of parts that overlap with the above description will be omitted.

[0074] 5 and 6 are views schematically illustrating a process of winding an electrode assembly according to another embodiment of the present invention, and FIG. 7 is an enlarged plan view illustrating a central region of the electrode assembly manufactured through the process of FIGS.

[0075] 4 to 7, an electrode assembly 100b according to another embodiment of the present invention includes a positive electrode 200, a negative electrode 300, and a separator 400 positioned between the positive electrode 200 and the negative electrode 300. The separator 400 includes a first separator 410 positioned on one side of the positive electrode 200 and a second separator 420 positioned on one side of the negative electrode 300. The positive electrode 200, the first separator 410, the negative electrode 300, and the second separator 420 are wound together to form a jelly roll structure. A first tape 510 and a second tape 520 may be attached to one side of the first separator 410 and one side of the second separator 420, respectively. The attachment method of the first tape 510 and the second tape 520 is omitted as it is the same as that described above.

[0076] Based on the radial direction of the jelly roll structure, there is a region where two or more layers of separator 400 overlap between edge portion 200E of positive electrode 200 and negative electrode 300. In Figure 7, the point where three layers of separator 400 overlap is indicated as L3.

[0077] 6, in an electrode assembly 100b according to an embodiment of the present invention, the jelly roll structure may be wound with the first separator 410, the positive electrode 200, the second separator 420, and the negative electrode 300 arranged in this order. To form a region where the separator 400 overlaps in three layers between the edge portion 200E of the positive electrode 200 and the negative electrode 300, the positive electrode 200 is inserted into the winding core 10W so that it is positioned between the first separator 410 and the second separator 420, and the negative electrode 300 is positioned below the second separator 420. This arrangement may correspond to the arrangement when the winding core 10W is wound clockwise.

[0078] More specifically, when manufacturing the electrode assembly 100b in a form in which the first separator 410, the positive electrode 200, the second separator 420, and the negative electrode 300 are arranged in this order and wound, the first folding portion 410F and the second folding portion 420F may be formed by folding the first separator 410 and the second separator 420, which are inserted first, in the winding direction, as shown in Fig. 6. In this case, the winding direction may be the direction in which the winding core 10W rotates, for example, clockwise as shown in Fig. 6.

[0079] The first separator 410 may be folded clockwise around the first boundary 410B to form the first folding portion 410F. The first boundary 410B corresponds to the boundary where the first separator 410 bends after passing between the winding cores 10W, and the first folding portion 410F corresponds to the region between the first boundary 410B and one end 410E of the first separator 410. That is, the first separator 410 may include the first folding portion 410F folded in the winding direction, and the first folding portion 410F overlaps with the other portion of the first separator 410 when wound together.

[0080] Similarly, the second separator 420 may be folded clockwise around the second boundary 420B to form the second folding portion 420F. The second boundary 420B corresponds to the boundary where the second separator 420 bends after passing between the winding cores 10W, and the second folding portion 420F corresponds to the region between the second boundary 420B and one end 420E of the second separator 420. In other words, the second separator 420 may include the second folding portion 420F folded in the winding direction, and the second folding portion 420F overlaps with the other portion of the second separator 420 when wound together.

[0081] 7, two layers of first separator 410 and one layer of second separator 420 may be positioned between edge portion 200E of positive electrode 200 and negative electrode 300 in the radial direction of the jelly roll structure. That is, a total of three layers of separator 400 may be positioned in this configuration. More specifically, of the three layers of separator 400 overlapping between edge portion 200E of positive electrode 200 and negative electrode 300, two layers may be first folding portion 410F and second folding portion 420F, respectively. The remaining layer may be a region of first separator 410 rather than first folding portion 410F.

[0082] Meanwhile, in the electrode assembly 100b manufactured in the above manner, a region where the separator 400 is overlapped in two or more layers, particularly three layers, may be located inside the edge portion 200E of the positive electrode 200 in the radial direction of the jelly roll structure. The point indicated by L3 is located inside the edge portion 200E of the positive electrode 200 in the radial direction of the jelly roll structure. That is, the region where the separator 400 is overlapped in three layers may be located between the edge portion 200E of the positive electrode 200 and the negative electrode 300, and may be located closer to the center 100C of the jelly roll structure than the edge portion 200E of the positive electrode 200.

[0083] As described above, a positive electrode active material layer is formed on both sides of the positive electrode 200. The side of the positive electrode 200 facing the center 100C of the jelly roll structure corresponds to the back surface, and the opposite side corresponds to the top surface. The electrode assembly 100b according to this embodiment corresponds to a positive electrode 200 back surface reinforcement design in which the overlapping region of the three layers of separator 400 is located on the back surface of the positive electrode 200.

[0084] In summary, the edge portion 200E of the positive electrode 200 is covered with three layers of the separator 400, and the other portions of the separator 400 and the negative electrode 300 are protected in common. However, the electrode assemblies 100a of the embodiment shown in Figures 2 to 4 differ in that the area where the separator 400 overlaps in two or more layers is provided on the outside of the edge portion 200E of the positive electrode 200, whereas the electrode assemblies 100b of the embodiment shown in Figures 5 and 6 differ in that the area where the separator 400 overlaps in two or more layers is provided on the inside of the edge portion 200E of the positive electrode 200.

[0085] Meanwhile, the first tape 510 may be attached to a region spaced apart from one end 410E of the first separator 410, and the second tape 520 may be attached to a region spaced apart from one end 420E of the second separator 420. More specifically, as shown in FIG. 7 , the first tape 510 and the second tape 520 may be attached to regions spaced apart by a predetermined distance from one end 410E of the first separator 410 and one end 420E of the second separator 420, respectively, so that the first tape 510 and the second tape 520 do not attach to a portion (denoted as L3) of the separator 400 that covers the edge portion 200E of the positive electrode 200. In other words, it is preferable that only the separator 400 be located between the edge portion 200E of the positive electrode 200 and the inner negative electrode 300, without the first tape 510 and the second tape 520.

[0086] If the first tape 510 or the second tape 520 were attached to cover the edge portion 200E of the positive electrode 200, the portion of the positive electrode 200 where the first tape 510 or the second tape 520 is attached would be an unreacted region, resulting in a decrease in battery capacity. In contrast, the electrode assembly 100b according to this embodiment prevents the first tape 510 or the second tape 520 from being attached to the two or more layers of separator 400 that cover the edge portion 200E of the positive electrode 200, thereby forming the back surface of the positive electrode 200 as a reaction region and increasing capacity.

[0087] Meanwhile, the electrode assemblies 100a and 100b according to this embodiment can be housed in a cylindrical can, a square can, or a pouch case to form a secondary battery.

[0088] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are used for convenience of explanation and may differ depending on the position of the object of interest, the position of the observer, etc.

[0089] A number of secondary batteries according to this embodiment can be assembled to form a battery module, and the battery module can be mounted with various control and protection systems, such as a Battery Management System (BMS) and a cooling system, to form a battery pack.

[0090] The secondary battery, the battery module, or the battery pack can be applied to various devices. Specifically, the secondary battery, the battery module, or the battery pack can be applied to transportation means such as electric bicycles, electric cars, and hybrid vehicles, but is not limited thereto. The secondary battery, the battery module, or the battery pack can be applied to various devices that can use secondary batteries.

[0091] Although the preferred embodiments of the present invention have been described in detail above, 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 claims below also fall within the scope of the present invention. [Explanation of symbols]

[0092] 100a, 100b Electrode assembly 200 positive electrode 300 negative electrode 410 1st separation membrane 420 Second separation membrane 510 Tape 1 520 Second Tape

Claims

1. Positive electrode; a negative electrode; and a separator disposed between the positive electrode and the negative electrode; The separator includes a first separator disposed on one surface of the positive electrode and a second separator disposed on one surface of the negative electrode; the positive electrode, the first separator, the negative electrode, and the second separator are wound together to form a jelly roll structure; a region in which two or more layers of the separator overlap each other exists between an edge portion of the positive electrode and the negative electrode in a radial direction of the jelly roll structure; a first tape and a second tape are attached to one surface of the first separation membrane and one surface of the second separation membrane, respectively; The first tape is attached to a region between one end of the first separator and a point where the positive electrode is inserted, The second tape is attached to an area between one end of the second separator and a point where the negative electrode is inserted. Electrode assembly.

2. The electrode assembly according to claim 1 , wherein a region where the separator overlaps in three layers exists between the edge portion of the positive electrode and the negative electrode in a radial direction of the jelly roll structure.

3. 2. The electrode assembly of claim 1, wherein the first tape is attached to a region spaced apart from one end of the first separator, and the second tape is attached to a region spaced apart from one end of the second separator.

4. The electrode assembly of claim 1 , wherein the first tape is attached to one surface of the first separator opposite to a surface on which the second separator is located.

5. The electrode assembly of claim 1 , wherein the second tape is attached to one surface of the second separator opposite to a surface on which the first separator is located.

6. The electrode assembly of claim 1 , wherein the first tape and the second tape comprise an electrically insulating material.

7. 2. The electrode assembly according to claim 1, wherein two layers of the first separator and one layer of the second separator are located between an edge portion of the positive electrode and the negative electrode in a radial direction of the jelly roll structure.

8. the first separator includes a first folding portion folded in a winding direction, and the first folding portion overlaps with another portion of the first separator and is wound together; The electrode assembly of claim 1 , wherein the second separator includes a second folding portion folded in a winding direction, the second folding portion overlapping another portion of the second separator when wound together.

9. The separator is overlapped in three layers between the edge portion of the positive electrode and the negative electrode in a radial direction of the jelly roll structure, The electrode assembly according to claim 8 , wherein two of the three layers of the separator overlapped between the edge portion of the positive electrode and the negative electrode are the first folding portion and the second folding portion, respectively.

10. 2. The electrode assembly of claim 1, wherein the edge of the negative electrode is located closer to the center of the jelly roll structure than the edge of the positive electrode.

11. The electrode assembly of claim 1 , wherein the jelly roll structure is wound up with the negative electrode, the second separator, the positive electrode, and the first separator arranged in this order.

12. The electrode assembly according to claim 11 , wherein a region where the separator is overlapped in two or more layers is located outside an edge portion of the positive electrode in a radial direction of the jelly roll structure.

13. The electrode assembly of claim 1 , wherein the jelly roll structure is wound up with the first separator, the positive electrode, the second separator, and the negative electrode arranged in this order.

14. The electrode assembly according to claim 13 , wherein a region where the separator is overlapped in two or more layers is located inside an edge portion of the positive electrode in a radial direction of the jelly roll structure.

15. A secondary battery comprising the electrode assembly according to any one of claims 1 to 14.

Images