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, and more particularly to a jelly-roll type electrode assembly having a peripheral tab structure and a cylindrical 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 particularly to a jelly roll-type electrode assembly having a 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. 10-2022-0156478 filed on November 21, 2022 in the Korean Intellectual Property Office, and all contents disclosed in the documents of the Korean patent application are incorporated herein by reference. [Background technology]

[0002] In the case of cylindrical batteries, a jelly roll-shaped electrode assembly is manufactured by winding a long electrode with a fixed width into a roll. When such a jelly roll-shaped electrode assembly is inserted into a battery case, the electrodes repeatedly contract and expand during charging and discharging, and stress is generated due to steps in the jelly roll structure.

[0003] In particular, in the case of a jelly-roll-type electrode assembly having a negative outer shell structure, the negative outer shell covers the end of the positive electrode, and the space next to the free edge of the positive electrode is left empty due to the thickness of the positive electrode. In this case, the step due to the thickness of the positive electrode creates stress in the negative electrode, and this stress is concentrated on the surface opposite to the surface facing the positive electrode during charging and discharging, causing the outer shell of the negative electrode to crack.

[0004] In order to prevent such a crack from occurring in the outer periphery of the negative electrode, it is necessary to develop a technology that can improve the negative electrode stress concentration in the corresponding region. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a jelly-roll type electrode assembly having a modified design of the jelly-roll type electrode assembly, and a secondary battery including the same.

[0006] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0007] One embodiment of the present invention provides a jelly roll type electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound up, wherein an outermost shell portion of the first electrode includes a first electrode double-sided holding portion in which a first electrode active material layer is provided on one side and an opposite side of a first electrode collector, and the first electrode double-sided holding portion includes an area corresponding to a longitudinal end of the second electrode.

[0008] Another embodiment of the present invention provides a secondary battery comprising: the jelly-roll type electrode assembly; and a battery case for housing the jelly-roll type electrode assembly. Effect of the Invention

[0009] A jelly-roll type electrode assembly and a secondary battery including the same according to an embodiment of the present invention include a first electrode double-sided support portion, thereby making it possible to prevent cracks and deformation of the electrode assembly due to stress concentration in the first electrode of the outermost shell.

[0010] In addition, in the jelly roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention, the double-sided support part can be formed using the same material and the same equipment as those for the first electrode active material layer, which is advantageous in terms of process, and a separate breakage prevention tape can be omitted, which allows for low-cost production, and the possibility of defects can be reduced by simplifying the process.

[0011] In addition, the jelly-roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention can adjust the position and thickness of the double-sided support part to prevent local problems such as lithium deposition due to reduction in roundness and formation of additional steps, and minimize the occurrence of further cracks and deformations of the electrode assembly.

[0012] The effects of the present invention are not limited to the effects described above, and effects not mentioned herein will be clearly understood by those skilled in the art from the present specification and the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 illustrates a jelly roll type electrode assembly including a double-sided holder according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a jelly roll type electrode assembly including an end surface holder according to one embodiment of the present invention. [Diagram 3] FIG. 1 shows a jelly roll type electrode assembly for reference. [Figure 4] FIG. 1 illustrates a jelly roll type electrode assembly according to one embodiment of the present invention. [Diagram 5] FIG. 2 is a schematic diagram showing a step portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 6] FIG. 1 is a diagram showing a secondary battery according to an embodiment of the present invention. [Figure 7] 11 is an image showing the results of an evaluation of crack occurrence in a core portion of an electrode assembly according to Example 1 and Comparative Example 1. [Explanation of symbols]

[0014] 100, 100'...1st electrode 10: First electrode double-sided holding portion 10': A region of the first electrode double-sided holding portion corresponding to an end portion of the second electrode in the longitudinal direction 12, 13...1st electrode end holding part 101: First electrode collector 102,103...First electrode active material layer 110 Longitudinal end portion of first electrode L1, L1': Distance between the longitudinal ends of the first electrode double-sided holding portion and the longitudinal ends of the second electrode L2, L3: Length of the first electrode end surface holding portion in the longitudinal direction 20, 20'...Separation membrane 300...2nd electrode 301 Second electrode current collector 302, 303...Second electrode active material layer 310 Longitudinal end portion of second electrode 60 Step 70 ···Disconnection prevention tape 80 Battery case 1000...Secondary battery DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Throughout this specification, when a part is said to "comprise" certain elements, this means that it may further include other elements, rather than excluding other elements, unless specifically stated to the contrary.

[0016] Throughout this specification, when a member is said to be located "on" another member, this includes not only when the member is in contact with the other member, but also when there is another member between the two members.

[0017] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrating the present invention and the scope of the present invention is not limited by the drawings.

[0018] One embodiment of the present invention provides a jelly roll type electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound up, wherein an outermost shell portion of the first electrode includes a first electrode double-sided holding portion in which a first electrode active material layer is provided on one side and an opposite side of a first electrode collector, and the first electrode double-sided holding portion includes an area corresponding to a longitudinal end of the second electrode.

[0019] The jelly-roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention include a first electrode double-sided support part, thereby preventing cracks and deformation of the electrode assembly due to stress concentration of the first electrode of the outermost shell. In addition, the jelly-roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention have a process advantage since the double-sided support part can be formed using the same material and the same equipment as the first electrode active material layer, and a separate disconnection prevention tape can be omitted, allowing low-cost production and reducing the possibility of defects due to simplified processes. In addition, the jelly-roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention can adjust the position and thickness of the double-sided support part to prevent local problems such as lithium deposition due to reduction in roundness and formation of additional steps, and minimize further cracks and deformation of the electrode assembly.

[0020] Fig. 1 is a diagram showing a jelly-roll type electrode assembly including a double-sided holder according to an embodiment of the present invention, specifically, Fig. 1 is a diagram showing an embodiment including a first electrode double-sided holder in an area of ​​a first electrode current collector corresponding to an end of a second electrode in the longitudinal direction.

[0021] 1, a jelly roll type electrode assembly according to an embodiment of the present invention is a jelly roll type electrode assembly in which a first electrode 100, 100', a separator 20, 20', and a second electrode 300 are stacked and wound up, the second electrode 300 may include a second electrode collector 301 and second electrode active material layers 302, 303 provided on at least one surface of the second electrode collector 301, and the first electrode 100 may include a first electrode collector 101 and first electrode active material layers 102, 103 provided on at least one surface of the first electrode collector 101. In addition, the outermost shell of the first electrode 100 includes a first electrode double-sided support part 10 in which the first electrode active material layers 102, 103 are provided on one surface and the opposite surface of the first electrode collector 101, and the first electrode double-sided support part 10 includes a region 10' corresponding to a longitudinal end 310 of the second electrode. Here, the "longitudinal direction" may refer to the longitudinal direction of the electrode assembly including the first electrode, the separator, the second electrode, and the electrode assembly in a stacked form before winding, i.e., the direction perpendicular to the winding axis direction of the electrode assembly after winding, and the "corresponding region" may refer to a region including a line perpendicular to the longitudinal direction of the electrode assembly and parallel to the winding axis direction. Specifically, the "region corresponding to the longitudinal end of the second electrode" may refer to a region from a line parallel to the longitudinal end of the second electrode on the first electrode double-sided holding part to the longitudinal end of the first electrode double-sided holding part, based on the longitudinal direction of the first electrode, i.e., a region having a distance L1 between the longitudinal end of the first electrode double-sided holding part and the longitudinal end of the second electrode, and a region having a distance L1' the same as L1 in the direction opposite to the longitudinal direction of the first electrode. In other words, it means an area on the first electrode double-sided holding portion having distances L1 and L1' on both sides of the longitudinal direction of the first electrode from a line parallel to the longitudinal end of the second electrode, and the area 10' corresponding to the longitudinal end 310 of the second electrode can have a length of "L1+L1'=L1+L1=2×L1".

[0022] The first electrode double-sided support portion includes an area corresponding to the longitudinal end of the second electrode, thereby preventing cracks and deformation of the electrode assembly due to stress concentration on the first electrode of the outermost shell. In other words, the outermost shell portion of the first electrode has a first electrode active material layer 102 provided on the opposite surface of the first electrode current collector 101 located in an area corresponding to the longitudinal end 310 of the second electrode, thereby increasing the thickness of the surface facing the longitudinal end of the second electrode. This prevents damage to the first electrode located in the outermost shell portion due to step formation caused by the thickness of the longitudinal end of the second electrode and cracks and deformation of the electrode assembly due to stress concentration in that area during charging and discharging, thereby improving the life characteristics of the battery.

[0023] According to one embodiment of the present invention, the longitudinal end of the first electrode active material layer may not coincide with the longitudinal end of the second electrode. Specifically, the longitudinal end of the first electrode active material layer may be formed at a position different from the longitudinal end of the second electrode, and the longitudinal end of the first electrode active material layer may be formed at a predetermined distance from the longitudinal end of the second electrode. As a result, an additional step may not be formed in relation to the thickness of the first electrode active material layer formed on the surface of the first electrode collector facing the longitudinal end of the second electrode or on the opposite surface of the facing surface, and the first electrode double-sided holding portion may be adjusted to include a region corresponding to the longitudinal end of the second electrode.

[0024] That is, referring to FIG. 1, by adjusting the distances L1, L1' between the longitudinal ends of the first electrode double-sided holding portion and the longitudinal ends of the second electrode to a specific range, the region 10' of the first electrode double-sided holding portion 10 corresponding to the longitudinal end 310 of the second electrode can be adjusted to a specific range.

[0025] According to one embodiment of the present invention, the longitudinal length of the region of the first electrode double-sided holding part corresponding to the longitudinal end of the second electrode may be 9 mm or more and 20 mm or less. Specifically, the longitudinal length of the region 10' of the first electrode double-sided holding part corresponding to the longitudinal end of the second electrode may be 11 mm or more, 13 mm or more, or 15 mm or more, and the longitudinal length of the region 10' of the first electrode double-sided holding part corresponding to the longitudinal end of the second electrode may be 18 mm or less, 16 mm or less, or 15 mm or less. When the longitudinal length of the region of the first electrode double-sided holding part corresponding to the longitudinal end of the second electrode satisfies the above-mentioned range, the opposite surface of the surface of the first electrode collector facing the longitudinal end of the second electrode can be effectively complemented, and cracks and deformation due to stress concentration of the first electrode of the outermost shell can be prevented.

[0026] According to another embodiment of the present invention, the first electrode may further include a first electrode end surface support in which a first electrode active material layer is provided on one surface of a first electrode current collector.

[0027] Fig. 2 is a diagram showing a jelly-roll type electrode assembly including an edge surface holding part according to one embodiment of the present invention. Specifically, Fig. 2(a) is a diagram showing one embodiment including a first electrode double-sided holding part 10 and further including a first electrode edge surface holding part 12 at a longitudinal end of the first electrode double-sided holding part 10, and Fig. 2(b) is a diagram showing one embodiment including a first electrode double-sided holding part 10 and further including a first electrode edge surface holding part 13 at a longitudinal end of the first electrode double-sided holding part 10.

[0028] Referring to FIG. 2, the first electrode 100 may further include a first electrode end surface holding portion 12 having a first electrode active material layer 102 provided on one surface of a first electrode collector 101, or a first electrode end surface holding portion 13 having a first electrode active material layer 103 provided on one surface. Specifically, the first electrode end surface holding portions 12 and 13 may be included at the longitudinal ends of the first electrode two-surface holding portion with a predetermined length. That is, the first electrode active material layer 102 formed on one surface of the first electrode collector 101 and the first electrode active material layer 103 formed on the opposite surface may have longitudinal ends at different positions. Thus, the length of the first electrode active material layer is adjusted so that the first electrode two-surface holding portion includes a region 10' corresponding to the longitudinal end of the second electrode, and a problem of additional step formation that may occur when the first electrode active material layers formed on one surface and the opposite surface of the first electrode collector 101 form ends at the same position can be prevented.

[0029] According to one embodiment of the present invention, the longitudinal length of the end face holding portion may be 3 mm or less. Specifically, the longitudinal lengths L2, L3 of the end face holding portion may be more than 0 mm, 1 mm or more, or 2 mm or more, and the longitudinal lengths L2, L3 of the end face holding portion may be 3 mm or less, 2 mm or less, or 1 mm or less. When the longitudinal length L2 of the end face holding portion satisfies the above-mentioned range, the opposite surface of the surface of the first electrode collector facing the longitudinal end of the second electrode can be effectively complemented. Also, when the longitudinal length L3 of the end face holding portion satisfies the above-mentioned range, the surface of the first electrode collector facing the longitudinal end of the second electrode can be effectively complemented, and the formation of a further step can be minimized in relation to the thickness of the longitudinal end of the second electrode.

[0030] According to one embodiment of the present invention, the first electrode may further include a first electrode uncoated portion where the first electrode active material layer is not provided. Specifically, according to one embodiment of the present invention, the first electrode may include a first electrode double-sided holding portion in an area corresponding to a longitudinal end of the second electrode of the first electrode collector, and may further include a first electrode uncoated portion where the first electrode active material layer is not provided at a longitudinal end of the first electrode double-sided holding portion. Also, according to one embodiment of the present invention, the first electrode may include a first electrode end face holding portion, and may further include a first electrode uncoated portion where the first electrode active material layer is not provided at a longitudinal end of the first electrode end face holding portion. By further including the first electrode uncoated portion, it is possible to prevent unnecessary application of the first electrode active material slurry in an area not facing the second electrode, thereby improving productivity, and it is possible to realize an electrode assembly having a peripheral tab structure by exposing a surface of the first electrode collector and directly facing the battery case.

[0031] According to one embodiment of the present invention, the first electrode uncoated portion may further include a first electrode tab provided on one surface of the first electrode collector. Specifically, the surface of the first electrode collector may be exposed and directly faced to the battery case to serve as a tab, but depending on the structure of the inside of the battery case and the electrode assembly, the first electrode tab may be included on the exposed surface of the first electrode collector to further form a conductive path, thereby implementing a low resistance design.

[0032] According to one embodiment of the present invention, in the first electrode double-sided holding part, the thicknesses of the first electrode active material layers provided on one side and the opposite side of the first electrode collector may be different from each other. Specifically, referring to Fig. 1, the thicknesses of the first electrode active material layers 102, 103 provided on one side and the opposite side of the first electrode collector 101 in a region 10' corresponding to the longitudinal end of the second electrode of the first electrode double-sided holding part 10 may be thinner than the thicknesses of the first electrode active material layers 102, 103 provided on one side and the opposite side of the first electrode collector 101 in a region 10' at least a part of which corresponds to the longitudinal end of the remaining second electrode. In addition, the thickness of the first electrode active material layers 102, 103 provided on one side and the opposite side of the first electrode current collector 101 in a region 10' corresponding to the longitudinal end of the second electrode of the first electrode double-sided holding part 10 may be at least partially thinner than the thickness of the first electrode active material layers 102, 103 in the remaining first electrode double-sided holding part 10. More specifically, the first electrode active material layer may be adjusted to have a thinner thickness in a specific region than in other regions by changing the degree of rolling in a part or adjusting the amount of the applied first electrode active material slurry, thereby minimizing the formation of further steps in relation to the longitudinal end of the second electrode or the first electrode tab.

[0033] According to one embodiment of the present invention, the thickness of the first electrode active material layer provided on one side and the opposite side of the first electrode collector at the first electrode two-side holding part and the thickness of the first electrode active material layer provided on one side or the opposite side of the first electrode collector at the first electrode end surface holding part may be different from each other. Specifically, referring to Fig. 2, the thickness of the first electrode active material layers 102, 103 provided on one side or the opposite side of the first electrode collector at the first electrode end surface holding parts 12, 13 may be at least partially thinner than the thickness of the first electrode active material layers 102, 103 provided on one side and the opposite side of the first electrode collector 101 at the first electrode two-side holding part 10. More specifically, the first electrode active material layer may be adjusted to have a thinner thickness in some places by changing the degree of rolling in some places or adjusting the amount of the applied first electrode active material slurry, thereby minimizing the formation of additional steps in relation to the longitudinal ends of the second electrode or the first electrode tabs, etc.

[0034] FIG. 3 shows a jelly roll type electrode assembly as a reference diagram, and FIG. 4 shows a jelly roll type electrode assembly according to an embodiment of the present invention.

[0035] Specifically, FIG. 3(a) shows a jelly roll type electrode assembly in which the first electrode double-sided holding portion does not include an area corresponding to the longitudinal end of the second electrode, and the first electrode end face holding portion includes an area corresponding to the longitudinal end of the second electrode, and FIG. 3(b) shows the jelly roll type electrode assembly shown in FIG. 3(a) further including a first electrode tab.

[0036] Meanwhile, FIG. 4(a) shows a jelly roll type electrode assembly in which the first electrode double-sided holding portion includes an area corresponding to the longitudinal end of the second electrode, and the first electrode end surface holding portion does not include an area corresponding to the longitudinal end of the second electrode, and FIG. 4(b) shows the jelly roll type electrode assembly shown in FIG. 4(a) further including a first electrode tab.

[0037] 3 and 4, if the first electrode double-sided holding portion 10 does not include a region corresponding to the longitudinal end 310 of the second electrode, i.e., if the first electrode end face holding portion or the first electrode uncoated portion includes a region corresponding to the longitudinal end 310 of the second electrode, the space next to the longitudinal end 310 of the second electrode forms a step due to the thickness of the second electrode and becomes an empty space, and stress is concentrated in the region during charging and discharging of the battery, causing cracks in the first electrode present in the outermost shell. To prevent this, a separate breakage prevention tape 70 can be attached to the region, but this requires separate installation processes and equipment, reduces the productivity of the electrode assembly, and if defects occur due to adjustment of the installation position, the life characteristics of the corresponding battery may be deteriorated. Meanwhile, in the jelly roll type electrode assembly according to an embodiment of the present invention, the thickness of the first electrode collector 101 at the corresponding position can be reinforced by adjusting the lengths of the first electrode active material layers 102, 103 provided on one side and the opposite side of the first electrode collector 101 so that the first electrode double-sided holding part 10 corresponds to the longitudinal end 310 of the second electrode, instead of using a separate breakage prevention tape, and the width, length and thickness of the first electrode double-sided holding part 10 can be adjusted to a specific range. As a result, the jelly roll type electrode assembly according to an embodiment of the present invention and the secondary battery including the same have a process advantage in that the double-sided holding part can be formed using the same material and the same equipment as the first electrode active material layer, and a separate breakage prevention tape can be omitted, allowing low-cost production and reducing the possibility of defects due to the simplified process. Furthermore, even if the electrode assembly further includes a first electrode tab according to design, by adjusting the width, length and thickness of the region 10' corresponding to the longitudinal end of the second electrode of the first electrode double-sided holding portion 10 to a specific range, it is easy to minimize the formation of additional steps in relation to the longitudinal end of the second electrode or the first electrode tab, etc.

[0038] According to an embodiment of the present invention, a longitudinal end portion of the first electrode may extend longer than a longitudinal end portion of the second electrode and may be further wound around an outer periphery of the electrode assembly.

[0039] 1 and 4, in an electrode assembly according to an embodiment of the present invention, the first electrode 100 located at the outermost shell may extend longer than the longitudinal end 310 of the second electrode 300 and may be further wound around the outer periphery of the electrode assembly, and a step portion 60, which is a region where a step is formed due to the thickness of the second electrode, may be formed next to the longitudinal end 310 of the second electrode 300. In this case, the outermost shell portion of the first electrode 100 may include a first electrode double-sided support portion 10 in which first electrode active material layers 102, 103 are provided on one side and the opposite side of a first electrode collector 101, and the first electrode double-sided support portion 10 may include a region corresponding to the longitudinal end 310 of the second electrode and the step portion 60.

[0040] According to one embodiment of the present invention, the second electrode includes a second electrode collector and a second electrode active material layer provided on at least one surface of the second electrode collector, and the second electrode active material layer may have a longitudinal end at the same position as the second electrode collector. That is, the longitudinal ends of the second electrode collector and the second electrode active material layer may coincide with each other.

[0041] In other words, the end of the second electrode in the longitudinal direction may be a free edge. Here, the free edge shape may refer to a shape in which the end of the electrode active material layer and the end of the electrode current collector coincide with each other, and may include not only a case in which the end of the longitudinal direction coincides completely with a plane perpendicular to the longitudinal direction, but also a case in which there are process and measurement errors. That is, the jelly roll type electrode assembly according to an embodiment of the present invention may have a structure in which the end of the second electrode in the longitudinal direction in the free edge shape is covered by the first electrode, which is the outermost shell, and may include a step portion, which is an empty space, formed in a region where the first electrode covers the second end of the second electrode.

[0042] 4 and 5, the first electrode 100 is present at the outermost shell of the electrode assembly, and the first electrode 100 includes first electrode active material layers 102, 103 on both sides of a first electrode collector 101, and may include a non-coating area. Meanwhile, the second electrode 300 is present at the outermost shell of the electrode assembly, and the second electrode 300 includes second electrode active material layers 302, 303 on both sides of a second electrode collector 301, but may not include a non-coating area. In other words, the second electrode may have a free edge shape in which ends of the second electrode collector and the second electrode active material layer coincide with each other. That is, the longitudinal end 310 of the second electrode 300 may include the ends of the second electrode active material layers 302 and 303 and the end of the second electrode collector 301, which have the same length in the longitudinal direction, or the longitudinal end 310 of the second electrode 300 may coincide with the ends of the second electrode active material layers 302 and 303 and the end of the second electrode collector 301. Meanwhile, according to one embodiment of the present invention, a non-coated portion on a surface of the first electrode 100 opposite to the end of the longitudinal end 310 of the second electrode 300 may further include a first electrode tab 50.

[0043] According to one 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 electrode, which is an outermost shell layer of the electrode assembly, may be a negative electrode, and the electrode assembly may have a negative outermost shell structure in which a negative electrode / separator / positive electrode / separator are wound up. In other words, the outermost shell of the jelly roll type electrode assembly may have a peripheral tab structure that exposes the negative electrode.

[0044] According to one embodiment of the present invention, the first electrode may include a first electrode collector and a first electrode active material layer provided on the first electrode collector. Specifically, the first electrode may include a first electrode active material layer formed on one or both surfaces of the first electrode collector and including a first electrode active material. In other words, the first electrode active material layer is formed on a first electrode holding portion of the first electrode collector, and the surface on which the first electrode active material layer is not provided can be represented as a first electrode uncoated portion.

[0045] According to one embodiment of the present invention, the first electrode current collector may include a first electrode holding portion on which a first electrode active material layer is formed and a first electrode uncoated portion on which the first electrode active material layer is not formed, and may include a first electrode tab on the first electrode uncoated portion. Specifically, the first electrode current collector may include a first electrode uncoated portion, and may include a first electrode tab formed in the first electrode uncoated portion. Thus, the manufactured electrode assembly may include one or more first electrode tabs.

[0046] According to one embodiment of the present invention, the first electrode active material layer may include a first electrode active material including at least one selected from the group consisting of a silicon-based material and a carbon-based material. The first electrode active material layer may further include a first electrode conductive material and a first electrode binder, and the first electrode active material, the first electrode conductive material, and the first electrode binder may be any material used in the art as a negative electrode active material, a negative electrode conductive material, and a negative electrode binder, without any limitation.

[0047] According to one embodiment of the present invention, the first electrode collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, the first electrode collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the first electrode collector.

[0048] The thickness of the first electrode current collector may be 16 μm or more and 180 μm or less, but the thickness of the first electrode current collector is not limited thereto.

[0049] According to one embodiment of the present invention, the first electrode binder may include at least 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, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0050] According to one embodiment of the present invention, the first electrode conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0051] According to one embodiment of the present invention, the second electrode may include a second electrode collector and a second electrode active material layer provided on the second electrode collector. Specifically, the second electrode may include a second electrode active material layer formed on one or both surfaces of the second electrode collector and including a second electrode active material. In other words, the second electrode active material layer is formed on a second electrode holding portion of the second electrode collector, and the surface on which the second electrode active material layer is not provided can be represented as a second electrode uncoated portion.

[0052] According to one embodiment of the present invention, the second electrode current collector may include a second electrode holding portion on which a second electrode active material layer is formed and a second electrode uncoated portion on which a second electrode active material layer is not formed, and may include a second electrode tab on the second electrode uncoated portion. Specifically, the second electrode current collector may include a second electrode uncoated portion, and may include a second electrode tab formed in the second electrode uncoated portion. Thus, the manufactured electrode assembly may include one or more second electrode tabs.

[0053] According to one embodiment of the present invention, the second electrode current collector is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. Specifically, the second electrode current collector can be made of stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like.

[0054] In addition, the second electrode collector may have a thickness of 80 μm to 190 μm, and may have fine irregularities on the surface of the second electrode collector to enhance the adhesive strength of the second electrode active material. For example, the second electrode collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0055] According to one embodiment of the present invention, the second electrode active material may be a commonly used positive electrode active material. Specifically, the second electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 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 Lithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and 0.01≦y≦0.3 is satisfied); 2-z M z Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (wherein 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 Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The second electrode may be Li-metal.

[0056] According to one embodiment of the present invention, the second electrode active material layer may further include a second electrode conductive material and a second electrode binder. The second electrode conductive material is used to impart electrical conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without causing a chemical change in the battery that is constructed. Specifically, the second electrode conductive material can be graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; 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, and the like, and one or a mixture of two or more of these may be used.

[0057] The second electrode binder plays a role of improving the adhesion between the second electrode active material particles and the adhesive strength between the second electrode active material and the second 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, and various copolymers thereof, and one or more of these may be used alone or in combination.

[0058] According to an embodiment of the present invention, the jelly roll type electrode assembly may further include a plurality of separators. For example, the jelly roll type electrode assembly may have a structure in which a first electrode / separator / second electrode / separator are laminated in this order. The separator separates the first electrode from the second electrode to provide a passage for lithium ions to move, and may be any separator that is generally used in secondary batteries, and is preferably one that has low resistance to the movement of electrolyte ions and excellent electrolyte moisture absorption ability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene 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. In addition, a typical porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, polyethylene terephthalate fiber, or the like, may be used. In addition, the separator may generally have a thickness of 10 μm or more and 20 μm or less. In order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material may be used, and the separator may be selectively used in a single-layer or multi-layer structure.

[0059] 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, wherein the contents included in the jelly-roll type electrode assembly are as described above.

[0060] The secondary battery according to an embodiment of the present invention includes a first electrode double-sided support part, which can prevent cracks and deformation of the electrode assembly due to stress concentration of the first electrode of the outermost shell. In addition, the secondary battery according to an embodiment of the present invention has a process advantage in that the double-sided support part can be formed using the same material and the same equipment as the first electrode active material layer, and a separate disconnection prevention tape can be omitted, making it possible to produce at low cost and reducing the possibility of defects due to the simplified process. In addition, the secondary battery according to an embodiment of the present invention can prevent local problems such as lithium deposition due to reduction in roundness and formation of additional steps by adjusting the position and thickness of the double-sided support part, and can minimize the occurrence of further cracks and deformation of the electrode assembly.

[0061] According to one embodiment of the present invention, the secondary battery includes a cap assembly coupled to an opening of the battery case, and the cap assembly may include a top cap, a safety vent, and a current interrupting device. According to one embodiment of the present invention, the first electrode may be in direct contact with an inner surface of a battery case, with the battery case serving as a first electrode terminal.

[0062] According to one embodiment of the present invention, the inside of the battery case may contain an electrolyte. Specifically, the electrolyte may be, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used in manufacturing a lithium secondary battery. Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0063] According to one embodiment of the present invention, the non-aqueous organic solvent may be, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, or ethyl propionate.

[0064] 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 dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt is 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.

[0065] According to one embodiment of the present invention, the electrolyte may further contain, in addition to the constituent components of the electrolyte, one or more additives such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid 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 for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, improving the discharge capacity of the battery, and the like.

[0066] According to one embodiment of the present invention, the battery case may be cylindrical. That is, referring to Fig. 6, the jelly roll type electrode assembly according to the present invention may be housed in a cylindrical battery case 80, and since the battery case containing the assembly including the first electrode, the separator, and the second electrode, the cap assembly, and the electrolyte has a cylindrical shape, the shape of the manufactured secondary battery 1000 itself may be cylindrical.

[0067] According to an embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high battery stability, and improved life characteristics, and therefore can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0068] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the present invention. However, the examples of the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the examples described below. The examples in the present specification are provided to more completely explain the present invention to those having average knowledge in the art.

[0069] Working Example Example 1 Manufacturing of electrode assemblies Li(Ni) as the second electrode active material 0.89 Co 0.07 Mn 0.04 A second electrode active material slurry was prepared by adding 02, CNT as a second electrode conductive material, and polyvinylidenefluoride (PVdF) as a binder to N-methyl-2-pyrrolidone (NMP) in a weight ratio of 97.8:0.6:1.6. The second electrode active material slurry was coated on an aluminum current collector having a thickness of 15 μm and a width direction length of 62 mm, and then dried and rolled to form a second electrode active material layer, thereby preparing a second electrode having a total thickness of 129 μm.

[0070] Next, 50 parts by weight of natural graphite and artificial graphite were prepared as the first electrode active material, and the first electrode active material, carbon black as a conductive material, and a mixture of styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as a binder were mixed in a weight ratio of 97.12:0.4:2.48 to prepare a first electrode active material slurry. The first electrode active material slurry was coated on a copper (Cu) current collector having a thickness of 8 μm and a width length of 64.9 mm, and then dried and rolled to form a first electrode active material layer, thereby forming a first electrode having a total thickness of 162 μm. At this time, the first electrode double-sided holding portion and the first electrode end surface holding portion were formed so that the longitudinal length L1+L1' of the first electrode double-sided holding portion corresponding to the longitudinal end of the second electrode was 20 mm, and the longitudinal length L3 of the first electrode end surface holding portion was 2 mm, thereby forming a structure as shown in FIG. 2(b).

[0071] Thereafter, two separators were sequentially arranged and wound around a winding core, and the first electrode was inserted between the two separators and further wound.

[0072] After the separator and the first electrode were wound for about one turn, the second electrode was inserted and wound, and a PET seal tape was attached to the end where the winding was completed so as to wrap the outer periphery of the upper and lower ends of the jelly roll, thereby completing the process and preparing a jelly roll type electrode assembly.

[0073] Secondary battery manufacturing The jelly-roll type electrode assembly was inserted into a cylindrical battery case, and an electrolyte prepared by mixing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl methyl carbonate (DMC) in a volume ratio of 20:5:75 and dissolving LiPF6 to a concentration of 0.7 M was poured into the case, and the cylindrical battery case was sealed with a cap assembly to manufacture a secondary battery.

[0074] Comparative Example 1 A jelly-roll type electrode assembly and secondary battery were fabricated in the same manner as in Example 1, except that no first electrode double-sided holding portion was provided at a position corresponding to the longitudinal end of the second electrode, and a breakage prevention tape with a longitudinal length of 17 mm was attached so that the longitudinal end of the second electrode coincided with the center of the breakage prevention tape to have a structure similar to that shown in Fig. 3(a). At this time, the longitudinal length of the end face holding portion of the first electrode was adjusted to 54 mm in the winding direction of the electrode assembly and 9 mm in the opposite direction to winding, based on the longitudinal end of the second electrode.

[0075] Experimental example: Evaluation of core crack occurrence The electrode assemblies of Example 1 and Comparative Example 1 were evaluated for the occurrence of core cracks by the following method, and the results are shown in FIG.

[0076] Specifically, the secondary batteries manufactured in Example 1 and Comparative Example 1 were activated by three cycles of 4.2V-2.5V, 0.2C charge, and 0.2C discharge, to prepare secondary batteries. Then, the activated secondary batteries were each activated for 30 cycles under conditions of 4.35V (1C)-2.0V (1C) and 25°C, and then disassembled to visually check whether cracks or wrinkles occurred in the core part. If cracks or wrinkles were present in the core part, it was evaluated that core part cracks occurred.

[0077] FIG. 7 is an image showing the evaluation results of the occurrence of cracks in the core portions of the electrode assemblies according to Example 1 and Comparative Example 1.

[0078] Referring to FIG. 7, it was confirmed that the electrode assembly according to Comparative Example 1 does not have a first electrode double-sided holding portion formed at a position corresponding to the longitudinal end of the second electrode in the core portion of the electrode assembly, so that stress generated by a step formed by the thickness of the longitudinal end of the second electrode is concentrated on the first electrode corresponding to the longitudinal end of the second electrode, resulting in wrinkles or cracks in the core portion.

[0079] Meanwhile, it was confirmed that the electrode assembly according to Example 1 can prevent cracks and deformation of the first electrode corresponding to the longitudinal end of the second electrode by forming a first electrode double-sided holding portion at a position corresponding to the longitudinal end of the second electrode in the core of the electrode assembly. Also, it was confirmed that the electrode assembly according to Example 1 can disperse stress concentrated on the first electrode of the outermost shell by preventing a decrease in roundness and the formation of an additional step by providing an additional first electrode end face holding portion.

[0080] As a result, the jelly roll type electrode assembly according to an embodiment of the present invention prevents cracks and deformations of the electrode assembly due to stress concentration in the first electrode of the outermost shell, and has excellent stability and life characteristics of the secondary battery. In addition, the jelly roll type electrode assembly according to an embodiment of the present invention has a process advantage since the double-sided support part can be formed using the same material and the same equipment as the first electrode active material layer, and can be produced at low cost since a separate break prevention tape can be omitted, and the possibility of defects can be reduced by simplifying the process.

[0081] The above describes preferred embodiments to aid in understanding the present invention. However, the above embodiments are merely illustrative of the present description. It will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description. Naturally, such changes and modifications fall within the scope of the appended claims.

Claims

1. A jelly roll type electrode assembly in which a first electrode, a separator and a second electrode are stacked and wound, the outermost shell portion of the first electrode includes a first electrode double-sided support portion in which a first electrode active material layer is provided on one side and an opposite side of a first electrode current collector; a first electrode double-sided holding portion including an area corresponding to a longitudinal end of the second electrode;

2. 2. The jelly roll type electrode assembly of claim 1, wherein a longitudinal end of the first electrode active material layer does not coincide with a longitudinal end of the second electrode.

3. The jelly-roll type electrode assembly of claim 1 , wherein the first electrode further comprises a first electrode end surface holder on one surface of the first electrode collector, the first electrode active material layer being provided thereon.

4. The jelly roll type electrode assembly according to claim 3 , wherein the first electrode end surface holding portion does not include an area corresponding to an end portion in the longitudinal direction of the second electrode.

5. 4. The jelly-roll type electrode assembly according to claim 3, wherein the length of the first electrode end surface holding portion in the longitudinal direction is 3 mm or less.

6. The jelly roll type electrode assembly of claim 1 , wherein the first electrode further comprises a first electrode uncoated portion where the first electrode active material layer is not provided.

7. The jelly roll type electrode assembly of claim 6 , wherein the first electrode uncoated portion further comprises a first electrode tab provided on one surface of the first electrode current collector.

8. 2 . The jelly roll type electrode assembly of claim 1 , wherein the first electrode active material layers provided on one surface and the opposite surface of the first electrode current collector in the first electrode double-sided support portion have different thicknesses.

9. 2. The jelly roll type electrode assembly of claim 1, wherein a longitudinal end of the first electrode extends longer than a longitudinal end of the second electrode and is further wound around an outer periphery of the jelly roll type electrode assembly.

10. the second electrode includes a second electrode current collector; and a second electrode active material layer provided on at least one surface of the second electrode current collector, 2. The jelly roll type electrode assembly of claim 1, wherein the second electrode active material layer forms a longitudinal end at the same position as the second electrode current collector.

11. 2. The jelly roll type electrode assembly of claim 1, wherein the first electrode is a negative electrode and the second electrode is a positive electrode.

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

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

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