Jelly roll type electrode assembly and secondary battery including the same

Abstract

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

Description

Technical Field

[0001] The present invention relates to a jelly roll type electrode assembly and a secondary battery including the same, and more specifically, to a jelly roll type electrode assembly having an outer peripheral tab structure and a cylindrical secondary battery including the same. This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0088851, filed with the Korean Intellectual Property Office on July 19, 2022, and all of its contents are incorporated herein by reference.

Background Art

[0002] In the case of a cylindrical battery, a long electrode with a determined width is wound in a roll form to manufacture a jelly roll type electrode assembly.

[0003] Today, cylindrical batteries are designed to have a structure that increases the number of tabs, which are paths through which electrons can move in the positive electrode, in order to achieve low resistance and obtain high output characteristics.

[0004] However, the lead portion of the jelly roll type electrode assembly uses a tab attached to an uncoated plain portion as a current path. In particular, when there is an outer negative tab, there is a step due to the thickness of the negative tab, and local stress is generated in the jelly roll during the charge and discharge process, thereby inducing disconnection and deformation.

[0005] Therefore, there is a need to develop a technology that can solve the above problems while achieving low resistance and having high output characteristics.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a jelly roll type electrode assembly with a modified design of the jelly roll type electrode assembly and a secondary battery including the same.

[0007] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned should be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0008] One embodiment of the present invention is a jelly roll type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially laminated and wound, wherein among the first electrode, the first separator, the second electrode, and the second separator, when the outermost layer and the layer in contact with the inner peripheral surface of the outermost layer are defined as the first layer and the second layer, respectively, the first layer and the second layer each include a first end portion where winding starts along the length direction and a second end portion where winding ends, and the second layer is bent so as to surround one side edge portion parallel to the length direction of the first layer, and the second end portion of the second layer is exposed on the outer peripheral surface of the first layer, thereby providing a jelly roll type electrode assembly.

[0009] Another embodiment of the present invention provides a secondary battery including the jelly roll type electrode assembly and a battery case for accommodating the electrode assembly.

Advantages of the Invention

[0010] The jelly roll type electrode assembly according to one embodiment of the present invention and the secondary battery including the same do not include a separate tab on the outermost periphery, so that disconnection and deformation due to the thickness of the tab can be prevented.

[0011] Further, the jelly roll type electrode assembly according to one embodiment of the present invention and the secondary battery including the same can change the design of the jelly roll type electrode assembly to solve local problems such as side reactions and lithium precipitation caused by the thickness of the tape for finishing treatment.

[0012] The advantages of the present invention are not limited to the advantages described above, and advantages not mentioned should be clearly understood by those skilled in the art from the specification of the present application and the attached drawings.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Explanation of Reference Numerals

[0014] 100, 100' ··· Jelly roll type electrode assembly 10 ··· First layer 11 ··· First end portion of the first layer 12 ··· Second end portion of the first layer 20 ··· Second layer 21 ··· First end portion of the second layer 22 ··· Second end portion of the second layer 50, 50' ··· Seal tape 60 ··· Battery case W1 ··· Width of the second end portion of the first layer W2 ··· Width of the second end portion of the second layer L2 ··· Length of the second layer exposed on the outer peripheral surface of the first layer

Mode for Carrying Out the Invention

[0015] Throughout this specification, when a part includes a certain component, this means that, unless otherwise stated to the contrary, it can further include other components rather than excluding other components.

[0016] Throughout this specification, when a member is located "above" another member, this includes not only the case where a member is in contact with another member, but also the case where there is another member between the two members.

[0017] Hereinafter, the present invention will be described in detail with reference to the drawings. However, the drawings are for illustrative purposes only, and the scope of the present invention is not limited by the drawings.

[0018] FIG. 1 shows a jelly roll type electrode assembly according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view obtained by cutting the jelly roll type electrode assembly according to an embodiment of the present invention in FIG. 1 in the A-A' direction after being housed in a battery case.

[0019] Referring to FIGS. 1 and 6, a jelly roll type electrode assembly 100 according to an embodiment of the present invention includes a first layer 10 which is the outermost layer, and a second layer 20 which is a layer in contact with the inner peripheral surface of the outermost layer. The first layer and the second layer each include a first end portion (the first end portion 11 of the first layer, the second end portion 21 of the second layer) where winding starts along the length direction, and a second end portion (the second end portion 12 of the first layer, the second end portion 22 of the second layer) where winding ends. The second layer 20 may be bent so as to surround one side edge parallel to the length direction of the first layer 10, and the second end portion 22 of the second layer may be exposed on the outer peripheral surface of the first layer 10.

[0020] Here, the outer peripheral surface may mean a surface facing the winding axis in each layer included in the jelly roll type electrode assembly, and the inner peripheral surface may mean a surface opposite to the outer peripheral surface in each layer.

[0021] According to an embodiment of the present invention, the width of the second end portion of the second layer exposed on the outer peripheral surface of the first layer may be 90% or more and 140% or less based on the outer peripheral surface of the first layer. Specifically, the width W2 of the second end portion 22 of the second layer 20 exposed on the outer peripheral surface of the first layer 10 may be 90% or more and 120% or less or 120% or more and 140% or less based on the outer peripheral surface of the first layer. When the width of the second end portion of the second layer exposed on the outer peripheral surface of the first layer is less than 90%, the ratio of a part of the first layer exposed at the lower end portion of the electrode assembly increases, so that in the insertion process of being housed in the battery case, the protection effect of the lower end portion of the jelly roll type electrode assembly may be inferior. When it is 140% or more, finishing defects may occur due to the second layer that is excessively additionally wound, and problems such as side reactions due to insufficient electrolyte and lithium precipitation may occur depending on the thickness of the second layer in the region where the second layer is superimposed.

[0022] According to an embodiment of the present invention, the area of the second layer 20 exposed on the outer peripheral surface of the first layer 10 may be 2% or more and 40% or less based on the total area of the outer peripheral surface of the first layer. Specifically, the area of the second layer exposed on the outer peripheral surface of the first layer may be 2% or more, 4% or more, 6% or more, 8% or more, or 10% or more based on the total area of the outer peripheral surface of the first layer, and may be 40% or less, 38% or less, 36% or less, 34% or less, 32% or less, or 30% or less. When the area of the second layer exposed on the outer peripheral surface of the first layer satisfies the above range, the bending process of the second layer and the finishing of the second end portion can be facilitated, and an excellent protection effect of the lower end portion of the jelly roll type electrode assembly by the second layer can be achieved.

[0023] According to an embodiment of the present invention, the thickness of the second layer 20 exposed on the outer peripheral surface of the first layer 10 may be 1 μm or more and 20 μm or less. Specifically, the thickness of the second layer may be 1 μm or more, 3 μm or more, or 5 μm or more, and the thickness of the second layer may be 18 μm or less, 16 μm or less, 14 μm or less, or 12 μm or less. When the thickness of the second layer satisfies the above conditions, since the second layer is generally thinner than the seal tape used for finishing the upper and lower ends of the electrode assembly, after being housed in the battery case, when the volume of the electrode assembly changes due to the charge and discharge cycles of the secondary battery, local problems such as damage to the electrode assembly due to increased pressure can be reduced. Also, even when using a second layer having a thickness similar to that of the seal tape, i.e., a separator, the separator surrounds one edge portion located at the upper or lower end of the electrode assembly, and the seal tape has a structure that adheres and finishes in a direction perpendicular to the length direction, so that compared with a structure in which a seal tape having a predetermined thickness is adhered and finished in parallel with the length direction at the upper and lower end edge portions of the electrode assembly, the step formation region can be significantly reduced, thereby reducing the local problems occurring in the step formation region described above.

[0024] According to an embodiment of the present invention, the second layer 20 may be bent so as to surround one edge portion parallel to the length direction of the first layer 10, and the second end portion 22 of the second layer 20 may be exposed on the outer peripheral surface of the first layer parallel to the length direction of the first layer. By bending the second end portion 22 of the second layer 20 so as to surround one edge portion parallel to the length direction of the first layer 10, in the insertion process of housing the jelly roll type electrode assembly 100 in the battery case, the second layer 20 can serve as a protective layer or a seal tape for preventing defects due to damage to the lower end portion of the electrode assembly, and the finishing of the second end portion can be facilitated.

[0025] According to an embodiment of the present invention, when the second end portion 22 of the second layer 20 is exposed on the outer peripheral surface of the first layer 10 so as to be parallel to the longitudinal direction of the first layer, the length L2 of the second layer exposed on the outer peripheral surface of the first layer 10 may be 2% or more and 40% or less based on the width W1 of the first layer. Specifically, the length of the second layer exposed on the outer peripheral surface of the first layer may be 2% or more, 4% or more, 6% or more, 8% or more, or 10% or more based on the width of the first layer, and may be 40% or less, 38% or less, 36% or less, 34% or less, 32% or less, or 30% or less. When the length of the second end portion of the second layer exposed on the outer peripheral surface of the first layer satisfies the above range, the finishing of the second end portion of the second layer can be facilitated, and the second layer can have an excellent effect of protecting the lower end portion of the jelly roll type electrode assembly.

[0026] According to an embodiment of the present invention, the jelly roll type electrode assembly further includes a seal tape 50 attached to finish the second end portion of the first layer, and the seal tape may be attached in a direction parallel to the winding axis across the second end portion 12 of the first layer 10. In other words, the seal tape may be attached in a direction perpendicular to the longitudinal direction of the first layer across the second end portion of the first layer.

[0027] Specifically, in a jelly roll type electrode assembly 100 according to an embodiment of the present invention, when the jelly roll type electrode assembly 100 is inserted into a battery case for accommodating the electrode assembly, the second end portion 22 of the second layer 20 is bent so as to surround one side edge portion parallel to the length direction of the first layer 10, thereby preventing the lower end portion of the electrode assembly from being damaged. This substitutes for the role of a sealing tape. As a result, the sealing tape does not necessarily have to adhere to the upper and lower end portions of the jelly roll type electrode assembly in order to finish the second end portions of the first layer and the second layer and to function as a protective layer, and may be adhered in a direction parallel to the winding axis of the first layer, that is, in a direction perpendicular to the length direction of the first layer, across the second end portion of the first layer. Thus, as can be seen in FIGS. 2 and 4, problems occurring in a stepped region formed by the sealing tape adhered to the upper and lower end portions of the first layer, which is the outermost layer, can be solved.

[0028] In one embodiment of the present invention, the sealing tape may be selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polyester, polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), polyether ether ketone (PEEK), polyarylate (PAR), polycyclic olefin (PCO), polynorbornene, polyether sulfone (PES), and cycloolefin polymer (COP).

[0029] The sealing tape can be used without limitation as long as it has such rigidity that it can finish the second ends of the first layer and the second layer located at the outermost contour of the wound jelly roll type electrode assembly, prevent the second ends of the first layer and the second layer from folding during winding, and prevent defects such as dents on the jelly roll type electrode assembly during the insertion process into the battery case. Specifically, PET may be used.

[0030] In one embodiment of the present invention, the thickness of the sealing tape may be 10 μm or more and 100 μm or less. Specifically, the thickness of the sealing tape may be 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more, and the thickness of the sealing tape may be 100 μm or less, 90 μm or less, or 70 μm or less. When the thickness of the above sealing tape is satisfied, defects such as folding of the second ends of the first layer and the second layer can be easily prevented during winding and the insertion process into the battery case. Further, by surrounding one edge portion located at the upper end or the lower end of the electrode assembly with a separator and having a structure in which the sealing tape is attached and finished in a direction perpendicular to the length direction, compared with a structure in which a sealing tape having a predetermined thickness is attached and finished in parallel with the length direction to the upper and lower edge portions of the electrode assembly, the step formation region can be significantly reduced, and thereby, local problems occurring in the above-described step formation region can be reduced.

[0031] According to an embodiment of the present invention, the sealing tape may be attached so as to cover all or a part of the second end portion of the first layer in a direction parallel to the winding shaft across the second end portion of the first layer. Specifically, when the sealing tape is attached so as to cover a part of the second end portion of the first layer in a direction parallel to the winding shaft across the second end portion of the first layer, the sealing tape 50 may be attached so as to cover 50% or more and 90% or less based on the width W1 of the second end portion of the first layer. More specifically, the sealing tape may be attached so as to cover 50% or more and 70% or less or 60% or more and 90% or less based on the width of the second end portion of the first layer in a direction parallel to the winding shaft across the second end portion of the first layer. When the sealing tape is attached so as to cover the above region of the second end portion of the first layer, while the problem of poor finish of the second end portion of the first layer does not occur, the stepped formation region due to the thickness of the outermost layer of the electrode assembly and the sealing tape can be minimized, and the problems of lifting and wrinkling defects of the first layer that may occur during attachment of the sealing tape can be minimized.

[0032] Referring to FIG. 2, in the jelly roll type electrode assembly 100 according to an embodiment of the present invention, since the sealing tape 50 is attached to the outermost surface of the electrode assembly in a direction parallel to the winding shaft on the outer peripheral surface of the first layer, when the electrode assembly is accommodated in the battery case, steps due to the thickness of the sealing tape are not formed at the upper and lower end portions of the first layer, which is the outermost layer of the electrode assembly. In other words, a part around the inner peripheral surface of the battery case comes into contact with the inner wall of the battery case via the sealing tape, and the remaining part can form a region where the outermost layer of the electrode assembly directly contacts the inner wall of the battery case.

[0033] Thereby, when the first layer, which is the outermost layer, is the first electrode, the first electrode can be directly electrically connected to the inner wall of the battery case, and since a separate tab does not need to be included in the outermost part, disconnection and deformation due to the thickness of the tab can be prevented.

[0034] In addition, since steps due to the thickness of the seal tape are not formed at the upper and lower ends of the outermost layer of the electrode assembly, damage to the electrode assembly that occurs when the volume of the electrode assembly changes due to the charge and discharge cycles of the secondary battery can be prevented, and side reactions due to insufficient electrolyte and local problems such as lithium precipitation that may occur in the seal tape portions attached to the upper and lower ends of the electrode assembly can be reduced.

[0035] FIG. 3 shows a jelly roll type electrode assembly as a reference drawing, and FIG. 4 is a cross-sectional view obtained by cutting the jelly roll type electrode assembly of FIG. 3 in the A-A' direction after being housed in a battery case.

[0036] Referring to FIG. 3, in the insertion process of housing the jelly roll type electrode assembly 100' in a battery case for housing the electrode assembly, in order to prevent defects such as the lower end of the outermost layer of the electrode assembly being indented or bent by the upper end corner of the battery case, seal tape 50' may be attached to the upper and lower ends of the outermost layer, the first layer, in a direction perpendicular to the winding shaft.

[0037] Referring to FIG. 4, since the seal tape 50' has a predetermined thickness, a step due to the thickness of the seal tape is formed on the outer peripheral surface of the outermost layer of the electrode assembly, and when the electrode assembly is housed in the battery case 60, a region where the electrode assembly and the inner wall of the battery case do not come into contact can be formed.

[0038] The step formation regions located at the upper and lower ends of the region where the electrode assembly and the inner wall of the battery case do not come into contact cause damage to the electrode assembly when the volume of the electrode assembly changes due to the charge and discharge cycles of the secondary battery, and relatively high pressure is applied to the seal tape portions attached to the upper and lower ends of the electrode assembly, and problems such as side reactions due to insufficient electrolyte and lithium precipitation may occur in this portion.

[0039] FIG. 5 is an image showing the lifting and wrinkling defects of the outermost layer appearing in the jelly roll type electrode assembly of FIG. 3.

[0040] Referring to FIG. 5, the seal tape 50' may be attached to finish the upper and lower edge portions of the jelly roll type electrode assembly 100' in a direction perpendicular to the winding axis. However, in this case, there is a problem that the lifting and wrinkling defects of the first layer, which is the outermost layer, may occur due to the external force applied during the process of attaching the seal tape 50'.

[0041] However, the jelly roll type electrode assembly according to an embodiment of the present invention can solve the above-mentioned problems by changing the design of the jelly roll electrode assembly. Specifically, in the insertion process in which the jelly roll type electrode assembly is accommodated in the battery case, the second layer bent so as to surround one edge portion parallel to the length direction of the first layer can serve to protect the lower end portion of the electrode assembly. As a result, the seal tape attached to finish the second end portion of the first layer may be attached in a direction parallel to the winding axis over the second end portion of the first layer. In this case, even after the jelly roll type assembly is accommodated in the battery case, no step is formed due to the thickness of the seal tape at the upper and lower end portions of the first layer, which is the outermost layer of the electrode assembly. Therefore, it is possible to prevent damage to the electrode assembly that occurs when the volume of the electrode assembly changes due to the charge and discharge cycles of the secondary battery, and to reduce local problems such as side reactions and lithium precipitation due to the lack of electrolyte that may occur in the seal tape portions attached to the upper and lower end portions of the electrode assembly. Also, since the seal tape may be attached in a direction parallel to the winding axis over the second end portion of the first layer, as can be seen in FIG. 5, when the seal tape is attached in a direction perpendicular to the winding axis, the lifting and wrinkling defect problems that may occur in the first layer, which is the outermost layer, can be minimized.

[0042] FIG. 6 shows the laminated structure of the jelly roll type electrode assembly according to an embodiment of the present invention, and FIG. 7 shows a form in which the second layer included in the jelly roll type electrode assembly according to an embodiment of the present invention is bent and the second end portion is exposed on the outer peripheral surface of the first layer.

[0043] Referring to FIGS. 6 and 7, a jelly roll type electrode assembly 100 according to an embodiment of the present invention includes a first layer 10 which is the outermost layer, and a second layer 20 which is a layer in contact with the inner peripheral surface of the outermost layer. The first layer and the second layer each include a first end portion (the first end portion 11 of the first layer, the first end portion 21 of the second layer) where winding starts along the length direction, and a second end portion (the second end portion 12 of the first layer, the second end portion 22 of the second layer) where winding ends. The first layer and the second layer may be extended in the length direction with respect to the remaining layers and additionally wound. The first layer may be a first electrode, and the second layer may be a first separator.

[0044] Specifically, the electrode assembly may have a structure in which a first electrode / a first separator / a second electrode / a second separator are sequentially laminated and wound. Since the first layer and the second layer are extended in the length direction with respect to the remaining layers and additionally wound, the outer peripheral surface of the second layer may be in contact with the inner peripheral surface of the first layer located on the outermost periphery of the wound jelly roll type electrode assembly, or the outer peripheral surface of the first layer may be in contact with the inner peripheral surface of the second layer. In other words, a structure in which a first electrode and a first separator are additionally wound on the outermost periphery of a structure in which a first electrode / a first separator / a second electrode / a second separator are sequentially laminated and wound may be used. In this case, the jelly roll type electrode assembly may have a structure in which a first electrode / a first separator / a first electrode / a first separator / a second electrode / a second separator are sequentially positioned from the outermost layer. Since the inner peripheral surface of the second electrode does not contact the first electrode which is the outermost layer, an insulation problem with the second electrode does not occur. Further, since the first layer which is the outermost layer is a first electrode, when it is inserted into a battery case after winding, it can be directly electrically connected to the inner wall of the battery case, and it may not include a separate tab on the outermost periphery. Therefore, disconnection and deformation due to the thickness of the outermost tab can be prevented.

[0045] According to an embodiment of the present invention, the first layer and the second layer may be extended in the length direction with respect to the remaining layers and additionally wound. When the first layer is a first electrode and the second layer is a first separator, a portion of the current collector of the first electrode that is additionally wound may include a plain portion on which an active material is not applied on at least one surface. Specifically, a portion of the current collector of the first electrode that is additionally wound may include a plain portion on which an active material is not applied on one surface, which is the outer peripheral surface, and may serve as an outer peripheral tab. A portion of the current collector of the first electrode that is additionally wound may include a plain portion on which an active material is not applied on one surface, which is the inner peripheral surface, and economic problems caused by unnecessary application of the active material can be solved. In this case, a portion of the current collector of the first electrode that is additionally wound is arranged such that a first separator other than the second electrode contacts the inner peripheral surface, and an insulation problem with the second electrode does not occur.

[0046] According to an embodiment of the present invention, the lengths of the first layer and the second layer that are extended in the length direction with respect to the remaining layers and additionally wound may be 90% or more and 140% or less based on the circumference of the outer peripheral surface of the first layer. Specifically, the lengths of the first layer and the second layer that are extended in the length direction with respect to the remaining layers and additionally wound may be 100% or more and 120% or less or 120% or more and 140% or less based on the circumference of the outer peripheral surface of the first layer. When the lengths of the first layer and the second layer that are extended in the length direction with respect to the remaining layers and additionally wound are less than 90% based on the circumference of the outer peripheral surface of the first layer, the process of bending the second layer of the electrode assembly so as to surround one edge portion of the first layer may not be easy. Further, when the lengths of the first layer and the second layer that are extended in the length direction with respect to the remaining layers and additionally wound are 140% or more based on the circumference of the outer peripheral surface of the first layer, problems such as an increase in manufacturing cost and an increase in the volume of the electrode assembly may occur due to the excessively additionally wound first layer and second layer.

[0047] According to an embodiment of the present invention, the first electrode may be a negative electrode, and the second electrode may be a positive electrode. Specifically, the first layer, which is the outermost layer of the electrode assembly, may be a negative electrode as the first electrode, and the electrode assembly may have a negative electrode outermost structure in which a negative electrode / separator / positive electrode / separator is wound. In other words, it may have an outer peripheral tab structure that exposes the negative electrode on the outermost periphery of the jelly roll type electrode assembly.

[0048] In this case, different from the conventional separator outer structure, the negative electrode is positioned on the outermost periphery in the electrode assembly, so that the two separators surround the positive electrode which is the second electrode and are present inside the electrode assembly. When winding the electrode assembly, a tab is attached to the plain part of the first end where winding starts along the length direction of the positive electrode, and winding starts from this tab towards the second end where winding ends, thereby forming a jelly roll type electrode assembly.

[0049] As a result, when the electrode assembly is inserted into the battery case, the negative electrode exposed on the outermost periphery can be directly electrically connected to the inner wall of the battery case, so that low resistance characteristics and an increase in capacity can be achieved simultaneously.

[0050] According to an embodiment of the present invention, the first electrode may be a negative electrode, and may include a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. Specifically, the negative electrode as the first electrode may include a negative electrode current collector and a negative electrode active material layer formed on one or both surfaces of the negative electrode current collector and containing a negative electrode active material. In other words, the negative electrode active material layer may be formed on the negative electrode active material part of the negative electrode current collector, and the surface without the negative electrode active material layer may be represented as a negative electrode plain part.

[0051] According to an embodiment of the present invention, when the first electrode is a negative electrode, the negative electrode current collector, which is the current collector of the first electrode, may include a negative electrode active material part where a negative electrode active material is applied and a negative electrode plain part where no negative electrode active material is applied, and may include a tab on the negative electrode plain part. However, in the case of the negative electrode outermost structure, since the outermost layer can directly contact the battery case and serve as a tab, it may not include a separate negative electrode tab.

[0052] According to one embodiment of the present invention, the negative electrode active material layer may contain a negative electrode active material including one or more selected from the group consisting of silicon-based materials and carbon-based materials. Further, the negative electrode active material layer may further contain a negative electrode conductive material and a negative electrode binder, and the negative electrode active material, the negative electrode conductive material, and the negative electrode binder can be used without limitation substances used in the art.

[0053] According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and has high conductivity. For example, as the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used. Specifically, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the negative electrode current collector. For example, the current collector of the negative electrode, which is the first electrode, may be provided in the form of a copper foil (Cu Foil), and may have an outer peripheral tab structure in which a copper (Cu) film, which is a negative electrode foil, is exposed on the outermost periphery of the jelly roll type electrode assembly. In this case, the copper foil is electrically connected to the battery case, and the copper foil itself can serve as a tab, so that an excellent resistance reduction effect can be obtained.

[0054] The thickness of the negative electrode current collector may be 6 μm or more and 20 μm or less, but the thickness of the negative electrode current collector is not limited thereto.

[0055] According to one embodiment of the present invention, the negative electrode binder may include at least any one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, poly acrylic acid, and substances in which hydrogen thereof is substituted with Li, Na, Ca, etc., and may also include these various copolymers.

[0056] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, nickel powder; conductive whiskers such as zinc oxide, potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0057] According to an embodiment of the present invention, the second electrode may be a positive electrode, and may include a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. Specifically, the positive electrode as the second electrode may include a positive electrode current collector and a positive electrode active material layer formed on one or both surfaces of the positive electrode current collector and containing a positive electrode active material. In other words, the positive electrode active material layer may be formed on the positive electrode active material portion of the positive electrode current collector, and the surface without the positive electrode active material layer may be represented as a positive electrode plain portion.

[0058] According to an embodiment of the present invention, when the second electrode is a positive electrode, the positive electrode current collector, which is the current collector of the second electrode, may include a positive electrode active material portion where the positive electrode active material is applied and a positive electrode plain portion where the positive electrode active material is not applied, and may include a tab on the positive electrode plain portion. Specifically, the positive electrode current collector may include a positive electrode plain portion and a positive electrode tab formed on the positive electrode plain portion. Thereby, the manufactured jelly roll type electrode assembly may include one positive electrode tab, and the positive electrode plain portion may be formed at the center of the positive electrode.

[0059] According to an embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity. Specifically, examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel. That is, the current collector of the positive electrode as the second electrode may be provided in the form of surface-treated stainless steel, aluminum foil, etc.

[0060] Further, the positive electrode current collector may usually have a thickness of 3 μm to 50 μm, and fine unevenness may be formed on the surface of the current collector to enhance the adhesive force of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0061] According to an embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; chemical formula Li 1+x Mn 2-x O4 (0 ≤ x ≤ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M y O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≤ y ≤ 0.3) represented by Ni-site type lithium nickel oxide; chemical formula LiMn 2-z M z O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01 ≤ z ≤ 0.1), or lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); examples include, but are not limited to, LiMn2O4 in which part of Li in the chemical formula is substituted with alkaline earth metal ions. The positive electrode may be Li-metal.

[0062] According to one embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without particular limitation as long as it does not induce chemical changes and has electronic conductivity. Specifically, the positive electrode conductive material includes graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more thereof may be used.

[0063] Also, the positive electrode binder serves to improve the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene polymer (EPDM), sulfonated - EPDM, styrene - butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these alone or a mixture of two or more thereof may be used.

[0064] According to one embodiment of the present invention, the first separator and the second separator separate the negative electrode and the positive electrode and provide a migration path for lithium ions. Usually, any separator that can be used in a secondary battery can be used without particular limitation. In particular, a separator having a low resistance to ion migration of the electrolyte and excellent electrolyte moisture retention ability is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. Further, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance may be used, and optionally, it may be used in a single layer or a multilayer structure.

[0065] FIG. 7 shows a form in which the second layer included in the jelly roll type electrode assembly according to one embodiment of the present invention is bent and the second end portion is exposed on the outer peripheral surface of the first layer. Specifically, FIG. 7(a) shows the form before the second layer is bent, FIG. 7(b) shows the form after the second layer is bent in the diagonal direction, and FIG. 7(c) shows the jelly roll type electrode assembly in which the second layer is bent and the second end portion is exposed on the outer peripheral surface of the first layer.

[0066] Referring to FIGS. 6 and 7, a jelly roll type electrode assembly 100 according to an embodiment of the present invention includes a first layer 10 which is the outermost layer, and a second layer 20 which is a layer in contact with the inner peripheral surface of the outermost layer. The first layer and the second layer each include a first end part (the first end part 11 of the first layer, the first end part 21 of the second layer) where winding starts along the length direction, and a second end part (the second end part 12 of the first layer, the second end part 22 of the second layer) where winding ends. The first layer and the second layer may each be extended in the length direction and additionally wound. The second layer of the part extended and additionally wound in the length direction may be bent so as to surround one edge part of the first layer 10, and the second end part 22 of the second layer 20 may be exposed on the outer peripheral surface of the first layer 10.

[0067] According to an embodiment of the present invention, the bending form of the second layer is not particularly limited as long as it is bent so as to surround one edge part of the first layer and serves to prevent the end part of the electrode assembly from being damaged in the insertion process of accommodating the jelly roll type assembly in a battery case for accommodating the electrode assembly. For example, the second layer may be bent so as to surround one edge part parallel to the length direction of the first layer, and the second end part of the second layer may be exposed on the outer peripheral surface of the first layer parallel to the length direction of the first layer. The second layer may be bent in a diagonal direction with respect to the length direction of the first layer, bent so as to surround one edge part parallel to the length direction of the first layer, and the second end part of the second layer may be exposed on the outer peripheral surface of the first layer parallel to the length direction of the first layer.

[0068] That is, one edge part of the first layer which is the outermost layer included in the wound jelly roll type electrode assembly may be the lower edge part of the jelly roll type electrode assembly, and the second layer in contact with the inner peripheral surface of the first layer is bent so as to be folded back in a diagonal direction, and while surrounding the lower edge part of the first layer, it may be exposed on the outer peripheral surface of the first layer which is the outermost surface parallel to the length direction of the first layer. In this case, the second end part where the winding of the second layer ends may be exposed on the outer peripheral surface of the first layer parallel to the lower end part which is one edge part of the first layer.

[0069] One embodiment of the present invention provides a secondary battery including the jelly - roll type electrode assembly; and a battery case for accommodating the electrode assembly, and the content included in the jelly - roll type electrode assembly is the same as described above.

[0070] According to one embodiment of the present invention, the secondary battery may include a cap assembly coupled to an opening of the battery case, and the cap assembly may include a top cap, a safety vent, a current interrupting device, and the like.

[0071] According to one embodiment of the present invention, the first electrode may be in direct contact with the inner surface of the battery case, and the battery case may serve as the first electrode terminal. Specifically, when the electrode assembly is accommodated in the battery case, a part around the inner peripheral surface of the battery case may be in contact with the seal tape and the inner wall of the battery case, and the remaining part may form a region where the outermost layer of the electrode assembly is in direct contact with the inner wall of the battery case. Thus, when the first layer, which is the outermost layer, is the first electrode, the first electrode can be directly electrically connected to the inner wall of the battery case, and it is not necessary to include a separate tab on the outermost periphery of the electrode assembly, so disconnection and deformation due to the thickness of the tab can be prevented.

[0072] According to one embodiment of the present invention, the inside of the battery case may contain an electrolyte. Specifically, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel - type polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may include a non - aqueous organic solvent and a metal salt.

[0073] According to one embodiment of the present invention, as the non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate may be used.

[0074] According to one embodiment of the present invention, the metal salt may be a lithium salt, and the lithium salt is a substance that is easily soluble in the non-aqueous electrolyte. For example, as the anion of the lithium salt, F - , Cl - , I - , NO3 - , N(CN) 2- , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN -and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0075] According to one embodiment of the present invention, in addition to the constituent components of the electrolyte, the electrolyte may further contain, for example, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, etc. as additives for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, improving the discharge capacity of the battery, etc.

[0076] According to one embodiment of the present invention, the battery case may be cylindrical. That is, the jelly roll type electrode assembly according to the present invention can be housed in a cylindrical battery case, and since the assembly including the positive electrode, negative electrode, and separator; the cap assembly; and the battery case containing the electrolyte has a cylindrical shape, the form of the manufactured secondary battery itself may be cylindrical.

[0077] As mentioned above, preferred embodiments have been presented to assist in the understanding of the present invention. However, it is obvious to those skilled in the art that the above embodiments are only illustrative of the description, and various changes and modifications are possible within the scope of the description and the scope of the technical idea. Naturally, such deformations and modifications belong to the scope of the claims.

Claims

1. A jelly roll type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially laminated and wound, When the outermost layer and the layer in contact with the inner peripheral surface of the outermost layer among the first electrode, the first separator, the second electrode, and the second separator are defined as a first layer and a second layer, respectively, The first layer and the second layer each include a first end portion where winding starts along the length direction and a second end portion where winding ends, The second layer is bent so as to surround one side edge parallel to the length direction of the first layer, and a second end portion of the second layer is exposed on the outer peripheral surface of the first layer. A jelly roll type electrode assembly.

2. The jelly roll type electrode assembly according to claim 1, wherein a second end portion of the second layer is exposed on the outer peripheral surface of the first layer parallel to the length direction of the first layer.

3. The second layer is bent in a diagonal direction with respect to the length direction of the first layer, bent so as to surround one side edge parallel to the length direction of the first layer, and a second end portion of the second layer is exposed on the outer peripheral surface of the first layer parallel to the length direction of the first layer. The jelly roll type electrode assembly according to claim 2.

4. Further comprising a seal tape (Seal tape) attached so as to finish the second end portion of the first layer, The jelly roll type electrode assembly according to claim 1, wherein the seal tape is attached in a direction parallel to the winding axis across the second end portion of the first layer.

5. The jelly roll type electrode assembly according to claim 4, wherein the seal tape is attached so as to cover 50% or more and 90% or less based on the width of the second end portion of the first layer.

6. The jelly roll type electrode assembly according to claim 1, wherein the first layer and the second layer are each extended in the length direction with respect to the remaining layers and additionally wound.

7. The jelly roll type electrode assembly according to claim 1, wherein the first layer is a first electrode and the second layer is a first separator.

8. The jelly roll type electrode assembly according to claim 7, wherein the first electrode is a negative electrode and the second electrode is a positive electrode.

9. The first electrode includes a current collector and an active material layer provided on the current collector. The jelly roll type electrode assembly according to any one of claims 1 to 8.

10. The jelly roll type electrode assembly according to claim 9, wherein the current collector of the first electrode is a copper foil (Cu Foil).

11. The jelly roll type electrode assembly according to any one of claims 1 to 8; and A battery case for housing the jelly roll type electrode assembly; A secondary battery comprising the above.

12. The secondary battery according to claim 11, wherein the first electrode is in direct contact with the inner surface of the battery case, and the battery case serves as a first electrode terminal.

13. The secondary battery according to claim 12, wherein the battery case is cylindrical.

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