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, more particularly to a jelly-roll-type electrode assembly including a separator overlapping portion and a cylindrical secondary battery including the same. This application claims the benefit of Korean Patent Application No. 10-2022-0165774 filed with the Korean Intellectual Property Office on December 1, 2022, and Korean Patent Application No. 10-2022-0165783 filed with the Korean Intellectual Property Office on December 1, 2022, and all contents disclosed in the documents of the relevant Korean patent applications 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 predetermined width into a roll. A cylindrical battery manufactured by inserting such a jelly roll-shaped electrode assembly into a battery case undergoes repeated contraction and expansion of the electrodes during charging and discharging. In particular, if a tab is located in the core of the jelly roll-shaped electrode assembly or if a silicon-based active material is added to the negative electrode, which increases the degree of contraction and expansion of the electrode assembly, the pressure acting on the core of the electrode assembly increases significantly.

[0003] In recent years, as low resistance / high capacity designs have become more common, jelly roll-type electrode assemblies have increasingly included multiple tabs or silicon-based active materials, and separators have become thinner and thinner to accommodate high capacity designs.

[0004] As the thickness decreases, the physical strength of the separator weakens, increasing the possibility of deformation of the electrode assembly located in the core portion due to contraction / expansion of the electrode assembly. In particular, if the separator located between the anode and cathode is damaged, the anode and cathode may come into direct contact with each other, resulting in an internal short circuit, which may cause heat generation and fire.

[0005] In order to solve the problems of separator breakage and internal short circuiting caused by deformation of the electrode assembly, it is necessary to develop a technology that can protect the electrodes and separators in the corresponding areas and prevent internal short circuiting. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a jelly-roll type electrode assembly with a modified design, and a secondary battery including the same.

[0007] 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]

[0008] Provided is a jelly roll-type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound up, wherein the second electrode has a first surface in the winding axis direction of the jelly roll-type electrode assembly and a second surface opposite the first surface, and a core portion of the electrode assembly includes a first separator overlapping portion provided on the first surface of the second electrode; and a second separator overlapping portion provided on the second surface of the second electrode, and the first separator overlapping portion and the second separator overlapping portion are provided in regions corresponding to longitudinal ends of the second electrode.

[0009] Another embodiment of the present invention provides a secondary battery comprising the jelly-roll type electrode assembly; and a battery case for accommodating the electrode assembly. [Effects of the Invention]

[0010] A jelly roll-type electrode assembly according to one embodiment of the present invention includes a separator overlapping portion in which the folding and overlapping structure of the core separator is adjusted. This prevents damage to the first electrode and separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes during charging / discharging of the battery. Even if the separator is damaged, the separator overlapping portion prevents internal short circuits between the first and second electrodes, thereby improving battery stability and lifespan characteristics.

[0011] In addition, the secondary battery according to the present invention can improve battery stability and lifespan characteristics by preventing internal short circuits between the first and second electrodes due to the separator overlapping portion even when the electrode assembly is deformed due to electrode contraction / expansion during battery charge / discharge.

[0012] The effects of the present invention are not limited to those 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 explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Figure 3] 1 is a schematic diagram illustrating a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram illustrating a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Figure 5] 1 is a schematic diagram illustrating a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Figure 6] 1 is a schematic diagram illustrating a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Figure 7] 1 shows a secondary battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] Throughout this specification, when an element is said to be located "on" another element, this includes not only when the element is in contact with the other element, but also when there is another element between the two elements.

[0016] One embodiment of the present invention provides a jelly roll-type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound up, wherein the second electrode has a first surface in the winding axis direction of the jelly roll-type electrode assembly and a second surface opposite the first surface, and a core portion of the electrode assembly includes a first separator overlapping portion provided on the first surface of the second electrode and a second separator overlapping portion provided on the second surface of the second electrode, and the first separator overlapping portion and the second separator overlapping portion are provided in regions corresponding to longitudinal ends of the second electrode.

[0017] A jelly roll-type electrode assembly according to one embodiment of the present invention includes a separator overlapping portion in which the folding and overlapping structure of the core separator is adjusted, thereby preventing damage to the first electrode and separator due to deformation of the electrode assembly caused by electrode contraction / expansion during battery charge / discharge, and even if the separator is damaged, the separator overlapping portion prevents internal short circuits between the first electrode and the second electrode, thereby improving battery stability and lifespan characteristics. Here, the "core portion" may refer to a hollow located on the winding shaft of the electrode assembly and a region including a portion of the wound first electrode / first separator / second electrode / second separator laminate structure, and may refer to a region within two turns of the second electrode from one end of the second electrode in the longitudinal direction located at the innermost corner of the electrode assembly.

[0018] According to one embodiment of the present invention, the first separation membrane overlapping portion and the second separation membrane overlapping portion may be provided in regions corresponding to longitudinal ends of the second electrode. Specifically, the first separation membrane overlapping portion and the second separation membrane overlapping portion may be provided in regions corresponding to longitudinal ends where winding of the second electrode begins. In other words, an extension line perpendicular to the longitudinal direction of the longitudinal ends of the second electrode may be located between both longitudinal ends of the first separation membrane overlapping portion and the second separation membrane overlapping portion. When the first separation membrane overlapping portion and the second separation membrane overlapping portion are provided in regions corresponding to the longitudinal ends of the second electrode, damage to the first electrode and the separator due to sharp longitudinal ends of the second electrode can be effectively prevented during battery charge and discharge.

[0019] Figure 1 shows a jelly-roll type electrode assembly including a separator overlap portion according to one embodiment of the present invention. Specifically, Figure 1(a) shows a jelly-roll type electrode assembly including a first separator overlap portion and a second separator overlap portion formed by bending a first separator and a second separator toward a second electrode, respectively, and Figure 1(b) shows a jelly-roll type electrode assembly including a first separator overlap portion and a second separator overlap portion formed by bending a first separator and a second separator toward an opposite side of the second electrode.

[0020] According to one embodiment of the present invention, the first separation membrane overlapping portion and the second separation membrane overlapping portion may be formed by folding the first separation membrane and the second separation membrane, respectively. Specifically, the first separation membrane may be folded to form the first separation membrane overlapping portion provided on the first surface of the second electrode, and the second separation membrane may be folded to form the second separation membrane overlapping portion provided on the second surface of the second electrode. By forming the first separation membrane overlapping portion and the second separation membrane overlapping portion on the first surface and the second surface of the second electrode, respectively, damage to the first electrode and the separation membrane due to the longitudinal end of the second electrode can be effectively prevented. Furthermore, by adjusting the folding direction of the separation membrane forming the first separation membrane overlapping portion and the second separation membrane overlapping portion, further effects can be obtained from each folding structure.

[0021] 1 and 2, the first separator 20 may be bent to form a first separator overlapping portion S1 provided on a first surface of the second electrode 300 facing the first electrode 100, and the second separator 40 may be bent to form a second separator overlapping portion S2 provided on a second surface of the second electrode 300 facing the first electrode 100′.

[0022] According to one embodiment of the present invention, the first separator overlapping portion and the second separator overlapping portion may be formed by bending the first separator and the second separator toward the second electrode, respectively. Specifically, referring to FIG. 1(a), the first separator overlapping portion S1 may be formed on a first surface of the second electrode 300 by bending the first separator 20 toward the second electrode 300. In addition, the second separator overlapping portion S2 may be formed on a second surface of the second electrode 300 by bending the second separator 40 toward the second electrode 300. In this case, the empty space between the first electrode and the separator can be minimized, thereby minimizing local problems that may occur due to additional steps, such as lithium deposition in the space between the first electrode and the separator, even during high-speed charging.

[0023] According to one embodiment of the present invention, the first separator overlapping portion and the second separator overlapping portion may be formed by bending the first separator and the second separator, respectively, toward the opposite side of the second electrode. Specifically, referring to FIG. 1(b), the first separator overlapping portion S1 may be formed on the first surface of the second electrode 300 by bending the first separator 20 toward the opposite side of the second electrode 300. Furthermore, the second separator overlapping portion S2 may be formed on the second surface of the second electrode 300 by bending the second separator 40 toward the opposite side of the second electrode 300. In this case, even if the diameter of the winding core is small or the loading amount of the second electrode active material layer is increased, the second electrode does not directly face a step caused by the separator overlapping portion located on the first surface or the second surface, thereby reducing the occurrence of cracks in the second electrode. In addition, even when sliding due to contraction / expansion of the first electrode is repeated during long-term cycling, deformation of the separator overlapping portion can be minimized, thereby improving the crack prevention effect of the first electrode and battery life characteristics.

[0024] According to one embodiment of the present invention, the first separator overlapping portion may be formed by bending the first separator toward the second electrode, and the second separator overlapping portion may be formed by bending the second separator toward the opposite side of the second electrode. Specifically, referring to FIG. 2(a), the first separator overlapping portion S1 may be formed on the first side of the second electrode 300 by bending the first separator 20 toward the second electrode. Furthermore, the second separator overlapping portion S2 may be formed on the second side of the second electrode 300 by bending the second separator 40 away from the second electrode 300. In this case, even if the longitudinal end of the second electrode faces the second side during winding of the electrode assembly, the second separator overlapping portion may provide a more effective protection for the first electrode and the separator, minimizing damage to the first separator overlapping portion and further improving the battery life characteristics.

[0025] According to one embodiment of the present invention, the first separator overlapping portion may be formed by bending the first separator 20 away from the second electrode, and the second separator overlapping portion may be formed by bending the second separator toward the second electrode. Specifically, referring to FIG. 2(b), the first separator overlapping portion S1 may be formed on a first surface of the second electrode 300 by bending the first separator 20 away from the second electrode. The second separator overlapping portion S2 may be formed on a second surface of the second electrode 300 by bending the second separator 40 toward the second electrode 300. In this case, even if the separator overlapping portion is interposed between the first electrode and the second electrode when the electrode assembly is wound up, a step can be formed depending on the thickness of the second separator overlapping portion S2 and the thickness of the first separator overlapping portion S1, thereby improving the roundness of the electrode assembly.

[0026] According to one embodiment of the present invention, the first separator overlapping portion and the second separator overlapping portion may be formed by folding the first separator and the second separator, respectively, two or more times. Specifically, the first separator overlapping portion and the second separator overlapping portion may be formed by folding the first separator and the second separator, respectively, two to four times. More specifically, the first separator overlapping portion and the second separator overlapping portion may be formed by folding the first separator and the second separator, respectively, two or four times. If the number of folding times is less than two, the effect of preventing damage to the first electrode and the separator may be poor. If the number of folding times is more than four, additional steps may be formed, which may cause stress concentration in the corresponding area, resulting in additional separator damage, and local problems such as lithium precipitation due to insufficient electrolyte may occur.

[0027] According to one embodiment of the present invention, the first separator overlapping portion and the second separator overlapping portion may be formed by overlapping three or more layers of the first separator and the second separator, respectively. Specifically, the first separator overlapping portion and the second separator overlapping portion may be formed by overlapping three to five layers of the first separator and the second separator, respectively. More specifically, the first separator overlapping portion and the second separator overlapping portion may be formed by overlapping three or five layers of the first separator and the second separator, respectively. If the separator overlapping portion is less than three layers, the effect of preventing damage to the first electrode and the separator may be poor. If the separator overlapping portion is more than five layers, additional steps may be formed, which may cause stress concentration in the corresponding region, resulting in additional separator damage and local problems such as lithium precipitation due to insufficient electrolyte.

[0028] According to one embodiment of the present invention, the widthwise lengths of the first separator overlapping portion and the second separator overlapping portion may be 100% to 110% of the 100% width of the second electrode. Specifically, the widthwise lengths of the first separator overlapping portion and the second separator overlapping portion may be 100% to 105% or 105% to 110% of the 100% width of the second electrode. The widths of the first electrode and the separator may be greater than the width of the second electrode to improve charge / discharge efficiency and battery stability. This may ensure that damage to the first electrode and the separator caused by sharp longitudinal edges of the second electrode occurs evenly across the entire longitudinal edge of the second electrode. Therefore, by adjusting the widthwise lengths of the first separator overlapping portion and the second separator overlapping portion to cover the entire width of the second electrode, more effective damage prevention for the first electrode and the separator may be achieved. Meanwhile, when the widthwise lengths of the first and second separation membrane overlapping portions satisfy the above-mentioned ranges, the difference between the widthwise lengths of the first and second separation membranes can be minimized, thereby improving processability.

[0029] According to one embodiment of the present invention, the longitudinal lengths of the first and second separator membrane overlapping portions may be 0.1 mm to 30 mm. Specifically, the longitudinal lengths of the first and second separator membrane overlapping portions may be 1 mm or more, 2 mm or more, 3 mm or more, 4 mm or more, or 5 mm or more, and may be 29 mm or less, 28 mm or less, 27 mm or less, 26 mm or less, or 25 mm or less. When the widthwise lengths of the first and second separator membrane overlapping portions satisfy the above-described ranges, even if sliding of the second electrode occurs during charging / discharging of the battery, the separator membrane overlapping portions can be positioned in a region corresponding to the longitudinal end of the second electrode. Furthermore, even if a certain process error exists, the separator membrane overlapping portions can more effectively prevent damage to the first electrode and the separator. Here, the longitudinal length of the first separator overlapping portion may refer to the sum of distances L1 and L1' from the longitudinal end 320 of the second electrode to both longitudinal ends of the first separator overlapping portion S1. Also, the longitudinal length of the second separator overlapping portion may refer to the sum of distances L2 and L2' from the longitudinal end 320 of the second electrode to both longitudinal ends of the second separator overlapping portion S2.

[0030] According to one embodiment of the present invention, the centers of the first and second separator overlapping portions may be located in regions corresponding to the longitudinal ends of the second electrode. For example, a line extending from a point 1 / 2 of the longitudinal length of the first and second separator overlapping portions may coincide with the longitudinal end where winding of the second electrode begins. Here, the "center" refers to the region between a line connecting a point 1 / 3L away from one longitudinal end and a line connecting a point 2 / 3L away from the longitudinal end, where L is the longitudinal length. "Coinciding" may also include cases where the ends are formed at substantially the same position due to process errors that may occur during a separator folding process, etc. When the centers of the first and second separator overlapping portions are located in regions corresponding to the longitudinal ends of the second electrode, damage to the first electrode and the separator caused by sharp longitudinal ends of the second electrode during battery charge and discharge may be more effectively prevented.

[0031] Figure 3 illustrates a jelly-roll-type electrode assembly including a separator overlap portion according to one embodiment of the present invention. Specifically, Figure 3(a) illustrates a jelly-roll-type electrode assembly including a first separator overlap portion and a second separator overlap portion formed by bending a first separator and a second separator toward a second electrode, respectively, and Figure 3(b) illustrates a jelly-roll-type electrode assembly including a first separator overlap portion and a second separator overlap portion formed by bending the first separator and the second separator toward the opposite side of the second electrode.

[0032] According to one embodiment of the present invention, the distance between the longitudinal end of the second electrode and the longitudinal end of the first separator overlapping portion may be 0.5 mm to 15 mm. Specifically, referring to FIG. 3, the distances L1 and L1' between the longitudinal end of the second electrode and the longitudinal end of the first separator overlapping portion may be the same or different and may be 1 mm or more, 1.5 mm or more, 2 mm or more, 2.5 mm or more, or 3 mm or more, respectively, and may be 14.5 mm or less, 14 mm or less, 13.5 mm or less, or 13 mm or less. When the distances L1 and L1' between the longitudinal end of the second electrode and the longitudinal end of the first separator overlapping portion satisfy the above-mentioned ranges, the first separator overlapping portion can effectively surround the first surface of the second electrode and the longitudinal end of the second electrode, thereby more effectively preventing damage to the first electrode and the separator on the first surface of the second electrode and minimizing the formation of additional steps.

[0033] According to one embodiment of the present invention, the distance between the longitudinal end of the second electrode and the longitudinal end of the second separator overlapping portion may be 0.5 mm to 15 mm. Specifically, referring to FIG. 3, the distances L2 and L2' between the longitudinal end of the second electrode and the longitudinal end of the second separator overlapping portion may be the same or different and may be 1 mm or more, 1.5 mm or more, 2 mm or more, 2.5 mm or more, or 3 mm or more, respectively, and may be 14.5 mm or less, 14 mm or less, 13.5 mm or less, or 13 mm or less. When the distances L2 and L2' between the longitudinal end of the second electrode and the longitudinal end of the second separator overlapping portion satisfy the above-mentioned ranges, the second separator overlapping portion can effectively surround the second surface of the second electrode and the longitudinal end of the second electrode, thereby providing excellent protection against damage to the first electrode and the separator on the second surface of the second electrode and minimizing the formation of additional steps.

[0034] According to one embodiment of the present invention, the first separator, the first electrode, and the second separator may extend beyond the longitudinal end of the second electrode and be further wound in the core of the electrode assembly. Specifically, the first separator, the first electrode, and the second separator may be wound together with the second electrode after being wound. For example, the first separator, the first electrode, and the second separator may be wound together around a winding core for one or more turns and then wound together with the second electrode. That is, in the core of the jelly roll-type electrode assembly, the longitudinal ends of the first separator, the first electrode, and the second separator may be located inside the longitudinal end of the second electrode. In other words, the length and width of the first electrode may be greater than those of the second electrode, and the length and width of the first separator and the second separator located on one side and the opposite side of the first electrode may also be greater than those of the second electrode. When the first separator, first electrode, and second separator extend beyond the longitudinal end of the second electrode and are further wound up, lithium ions from the second electrode can be more easily transferred to the first electrode during the chemical reaction of the lithium ion battery. When the first electrode is formed to be longer or wider, the area of ​​the first electrode that receives lithium ions increases, preventing a decrease in charge / discharge efficiency and improving battery stability and lifespan characteristics.

[0035] According to one embodiment of the present invention, in the core portion of the electrode assembly, the first separation membrane and the second separation membrane extending from the longitudinal end of the first electrode may be folded together in opposite directions in the winding axis direction of the electrode assembly, and the second separation membrane overlapping portion may have two or more overlapping separation membranes.

[0036] By including a separator overlapping part with a modified folding structure of the core separator, it is possible to prevent damage to the first electrode and separator due to deformation of the electrode assembly caused by electrode contraction / expansion during battery charge / discharge. Even if the separator is damaged, the separator overlapping part prevents internal short circuits between the first and second electrodes, thereby improving battery stability and lifespan characteristics.

[0037] 4 and 5 show jelly-roll type electrode assemblies including a separator overlap part according to an embodiment of the present invention. Specifically, Fig. 4 shows a jelly-roll type electrode assembly including a second separator overlap part according to an embodiment of the present invention, and Fig. 5 shows a jelly-roll type electrode assembly further including a first separator overlap part according to an embodiment of the present invention.

[0038] According to one embodiment of the present invention, in the core portion of the electrode assembly, the first separator and the second separator extending from the longitudinal end of the first electrode may be folded together in opposite directions in the winding axis direction of the electrode assembly.

[0039] Specifically, the first separation membrane and the second separation membrane may extend from a longitudinal end of the first electrode in the core portion of the electrode assembly, be bent together in a direction opposite to the direction facing the winding shaft of the first electrode, and be arranged overlapping between the second electrode and the first electrode facing the first surface or second surface of the second electrode, respectively.

[0040] Specifically, referring to (a) and (b) of FIG. 4, the first separator 20′ and the second separator 40′ extending from the longitudinal end 120 of the first electrode may be folded together in the opposite direction to the direction facing the winding axis of the first electrode, i.e., toward the longitudinal end 320 of the second electrode, and the extended first separator 20′ and the second separator 40′ may be overlapped and disposed between the second electrode 300 and the first electrode 100′ facing the second surface of the second electrode to form a second separator overlap portion S2.

[0041] In other words, the first separator 20′ and the second separator 40′ extending from the longitudinal end 120 of the first electrode may be folded back in the direction opposite to the direction facing the winding shaft of the first electrode, i.e., toward the outer periphery of the electrode assembly, and the extended first separator 20′ and second separator 40′ may be overlapped and disposed between the second electrode 300 and the first electrode 100′ facing the second surface of the second electrode to form a second separator overlap portion S2.

[0042] This allows the separation membrane constituting the second separation membrane overlapping portion to be doubled or more with a simpler folding structure. Also, by providing the second separation membrane overlapping portion, it is possible to more effectively prevent damage to the first electrode and separation membrane that face the second surface, which is the surface opposite to the winding axis direction of the second electrode.

[0043] FIG. 6 is a schematic diagram illustrating a separator overlapping portion of a jelly-roll type electrode assembly according to an embodiment of the present invention.

[0044] According to one embodiment of the present invention, the jelly-roll type electrode assembly may include a second separation membrane overlapping portion between the second electrode and the first electrode facing a second surface of the second electrode, and the separation membrane overlapping portion may include two or more overlapping separation membranes.

[0045] Specifically, the second separation membrane overlapping portion may have two or more or three or more overlapping separation membranes, and the second separation membrane overlapping portion may have five or less, four or less, or three or less overlapping separation membranes.

[0046] Referring to Figures 4 and 5, the core portion of the electrode assembly includes a second separator overlap portion S2 between the second electrode 300 and the first electrode 100' facing the second surface of the second electrode, and the second separator overlap portion S2 may refer to a portion of an area where two or more separators are overlapped around the longitudinal end portion 320 of the second electrode.

[0047] Here, the second separator overlapping portion S2 may refer to the end of a region in which two or more separators are overlapped, centered on the longitudinal end portion 320 of the second electrode, i.e., a region having the same length in the core portion direction of the electrode assembly as the region up to the longitudinal end portion of the second separator overlapping portion.

[0048] Specifically, referring to FIG. 4(a), the second separation membrane overlapping portion S2 may refer to a region from the longitudinal end of the second separation membrane overlapping portion S2 to a length L2' in the direction toward the core portion of the electrode assembly, the length being the same as the distance L2 between the longitudinal end of the second separation membrane overlapping portion and the longitudinal end of the second electrode, centered on the longitudinal end 320 of the second electrode, or may refer to a region having a length of L2 + L2' = L2 + L2 = 2L2 from the longitudinal end of the second separation membrane overlapping portion S2.

[0049] According to one embodiment of the present invention, the first and second separators may extend beyond the longitudinal end portions of the first electrode and then be wound up. That is, the first and second separators 20 and 40 may include regions extending from the longitudinal end portions 120 of the first electrode. In other words, the first and second separators 20 and 40 may be wound up to a predetermined length and then wound up together with the first electrode 100.

[0050] Therefore, the first separation membrane 20' and the second separation membrane 40' extending from the longitudinal end 120 of the first electrode may be a part of the first separation membrane 20 and the second separation membrane 40 that were wound up before the first electrode 100, or may be folded and overlapped to form the first separation membrane overlapping portion S1 or the second separation membrane overlapping portion S2.

[0051] That is, the first separation membrane overlapping portion or the second separation membrane overlapping portion can be formed by a folded structure extending integrally from the first separation membrane and the second separation membrane without providing a separate auxiliary separation membrane, etc. This allows the number of separation membranes constituting the first separation membrane overlapping portion or the second separation membrane overlapping portion to be adjusted to two or more layers with a simpler structure.

[0052] According to one embodiment of the present invention, the second separation membrane overlapping portion may be such that the extended second separation membrane is disposed between the second electrode and a second separation membrane facing a second surface of the second electrode.

[0053] 4 and 5, the second separator overlapping portion S2 may be formed by the second separator 40' extending from the longitudinal end portion 120 of the first electrode in the core portion of the electrode assembly and overlapping with the second separator 40. When the extended second separator is disposed between the second electrode and a second separator facing the second surface of the second electrode, the second separator overlapping portion may be formed by a folded structure extending integrally from the second separator without providing a separate auxiliary separator. This allows the number of separators constituting the second separator overlapping portion to be adjusted to two or more layers with a simpler structure.

[0054] According to one embodiment of the present invention, the second separation membrane overlapping portion may be such that the extended first separation membrane and the extended second separation membrane are overlapped between the second electrode and the second separation membrane facing the second surface of the second electrode.

[0055] Specifically, referring to FIG. 4, the second separator overlapping portion S2 may be arranged such that the first separator 20′ and the second separator 40′ extend from the longitudinal end 120 of the first electrode in the core portion of the electrode assembly and overlap with the second separator 40.

[0056] When the extended first separator and the extended second separator are overlapped between the second electrode and the second separator facing the second surface of the second electrode, a second separator overlap portion can be formed by a folded structure extending integrally from the first separator and the second separator without providing a separate auxiliary separator, etc. This makes it possible to adjust the number of separators constituting the second separator overlap portion to three or more layers with a simpler structure.

[0057] When the first separator and the second separator extending from the longitudinal end of the first electrode are overlapped two or more times to form a second separator overlap portion, damage to the first electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes can be prevented, and even if the separator is damaged, the second separator overlap portion can prevent an internal short circuit between the first electrode and the second electrode, thereby improving battery stability and lifespan characteristics. Furthermore, when the second separator overlap portion is included, damage prevention effect on the first electrode and the separator facing the second surface opposite to the winding axis direction of the second electrode can be more excellent.

[0058] According to one embodiment of the present invention, a first separator overlap portion may be further included between the second electrode and the first electrode facing the first surface of the second electrode. Specifically, referring to Figures 5(a) and 5(b), the first separator 20' and the second separator 40' extending from the longitudinal end 120 of the first electrode may be folded together in the opposite direction to the direction facing the winding shaft of the first electrode, i.e., toward the longitudinal end 320 of the second electrode, and the extended second separator 40' may be overlapped between the second electrode 300 and the first electrode 100' facing the second surface of the second electrode to form the second separator overlap portion S2, and the extended first separator 20' may be overlapped between the second electrode 300 and the first electrode 100' facing the first surface of the second electrode to form the first separator overlap portion S1.

[0059] This allows the separators constituting the first and second separator overlapping portions to be double or more layers each with a simpler folding structure. Also, by further including the first separator overlapping portion, damage to the first electrode and separator facing the first surface, which is the winding axis direction of the second electrode, can be more effectively prevented.

[0060] According to one embodiment of the present invention, a first separation membrane overlapping portion may be included between the second electrode and the first electrode facing a first surface of the second electrode, and the first separation membrane overlapping portion may have two or more overlapping separation membranes. Specifically, the first separation membrane overlapping portion may have two or more overlapping separation membranes or three or more overlapping separation membranes, and the first separation membrane overlapping portion may have five or less, four or less, or three or less overlapping separation membranes.

[0061] Referring to FIG. 5, the core portion of the electrode assembly includes a first separator overlap portion S1 between the second electrode 300 and the first electrode 100 facing the first surface of the second electrode, and the first separator overlap portion S1 may refer to a portion of an area where two or more separators are overlapped around the longitudinal end portion 320 of the second electrode.

[0062] Here, the first separator overlapping portion S1 may refer to the end of a region in which two or more separators are overlapped, centered on the longitudinal end portion 320 of the second electrode, i.e., a region having the same length in the core portion direction of the electrode assembly as the region up to the longitudinal end portion of the first separator overlapping portion.

[0063] Specifically, referring to FIG. 5(b), the first separator overlapping portion S1 may refer to a region from the longitudinal end of the first separator overlapping portion S1 to a length L1' that is the same as the distance L1 between the longitudinal end of the first separator overlapping portion and the longitudinal end of the second electrode, centered on the longitudinal end 320 of the second electrode, and in the direction of the core portion of the electrode assembly, or may refer to a region having a length of L1 + L1' = L1 + L1 = 2L1 from the longitudinal end of the first separator overlapping portion S1.

[0064] According to one embodiment of the present invention, the first separator overlapping portion S1 may be disposed between the second electrode and the first separator facing the first surface of the second electrode. Specifically, referring to Fig. 5, the first separator overlapping portion S1 may be disposed such that the first separator 20' extending from the longitudinal end 120 of the first electrode overlaps with the first separator 20 in the core portion of the electrode assembly.

[0065] When the extended first separator is disposed between the second electrode and the first separator facing the first surface of the second electrode, a first separator overlap portion can be formed by a folded structure extending integrally from the first separator without providing a separate auxiliary separator, etc. This makes it possible to adjust the number of separators constituting the first separator overlap portion to be two or more with a simpler structure.

[0066] According to one embodiment of the present invention, the first separation membrane overlapping portion may be such that the extended first separation membrane is disposed between the second electrode and the first separation membrane facing the first surface of the second electrode, and the second separation membrane overlapping portion may be such that the extended second separation membrane is disposed between the second electrode and the second separation membrane facing the second surface of the second electrode.

[0067] Specifically, referring to FIG. 5, the first separator overlapping portion S1 may be a portion in which the first separator 20′ extending from the longitudinal end 120 of the first electrode overlaps with the first separator 20 in the core portion of the electrode assembly, and the second separator overlapping portion S2 may be a portion in which the second separator 40′ extending from the longitudinal end 120 of the first electrode overlaps with the second separator 40 in the core portion of the electrode assembly.

[0068] When the extended first separator is disposed between the second electrode and the first separator facing the first surface of the second electrode, and the extended second separator is disposed between the second electrode and the second separator facing the second surface of the second electrode, the first separator overlap portion and the second separator overlap portion can be formed by a folded structure extending integrally from the first separator and the second separator without providing a separate auxiliary separator, etc. This makes it possible to adjust the number of separators constituting the first separator overlap portion and the second separator overlap portion to be two or more with a simpler structure.

[0069] When the first and second separators extending from the longitudinal ends of the first electrode are overlapped two or more times to form a first separator overlapping portion and a second separator overlapping portion, damage to the first electrode and separator due to deformation of the electrode assembly caused by electrode contraction / expansion can be prevented, and even if separator damage occurs, the first separator overlapping portion and the second separator overlapping portion can prevent internal short circuits between the first and second electrodes, thereby improving battery stability and lifespan characteristics. Furthermore, when both the first separator overlapping portion and the second separator overlapping portion are included, damage prevention effect on the first electrode and separator facing the first surface in the winding axis direction of the second electrode and the second surface opposite the first surface can be more excellent.

[0070] According to one embodiment of the present invention, the jelly roll electrode assembly may include multiple separators. For example, the jelly roll electrode assembly may have a structure in which the second electrode / first separator / first electrode / second separator are stacked in this order, or a structure in which the first separator / first electrode / second separator / second electrode are stacked in this order. The separator separates the second electrode from the first electrode and provides a path for lithium ions to move. Any separator typically used as a separator in a secondary battery may be used. It is particularly preferable for the separator to have low resistance to electrolyte ion movement and excellent electrolyte humidification capability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. The separation membrane may generally have a thickness of 10 μm to 20 μm. The separation membrane may be formed by coating a substrate layer of the above-described separation membrane material with a slurry containing a ceramic component or a polymeric material to ensure heat resistance or mechanical strength. The separation membrane may be used in a single-layer or multi-layer structure.

[0071] According to one embodiment of the present invention, the longitudinal length of the second separator overlapping portion may be 10% to 50% of the circumference of the inner circumferential surface of the electrode assembly. Specifically, the longitudinal length of the second separator overlapping portion may be 15% to 15%, 20% to 25%, or 30% or more, or 45%, 40%, 35%, or 30% or less, based on 100% of the circumference of the inner circumferential surface of the electrode assembly.

[0072] That is, the longitudinal length of the second separator overlapping portion may be 1 / 10 to 1 / 2 turn, or 1 / 5 to 1 / 3 turn, around the inner circumferential surface of the core portion of the electrode assembly. Here, the "around the inner circumferential surface" may refer to a virtual circle whose radius is the longest distance from the winding shaft of the electrode assembly to the innermost stratum corneum, which is adjacent to the hollow of the electrode assembly. Referring to Figure 6, the longitudinal length of the second separator overlapping portion may refer to the length L2 + L2' = L2 + L2 = 2L2.

[0073] When the longitudinal length range of the second separator overlapping portion is satisfied, damage to the first electrode and separator facing the second surface, which is opposite the winding axis direction of the second electrode, due to deformation of the electrode assembly caused by contraction / expansion of the electrode during battery charge / discharge can be prevented, and a decrease in charge / discharge efficiency due to an excessive decrease in the area of ​​the negative electrode that receives lithium ions can be prevented, resulting in excellent battery stability and life characteristics.

[0074] According to one embodiment of the present invention, the distance between the longitudinal end of the second separator overlapping portion and the longitudinal end of the second electrode may be 2 mm to 10 mm. Specifically, referring to FIG. 6, the distance L2, L2' between the longitudinal end of the second separator overlapping portion and the longitudinal end of the second electrode may be 3 mm to 4 mm, or 5 mm, and may be 9 mm to 8 mm, or 7 mm. That is, in the core portion of the electrode assembly, the first separator 20' or the second separator 40' extending from the longitudinal end 120 of the first electrode may be disposed between the second electrode 300 and the first electrode 100' facing the second surface of the second electrode, 2 mm to 10 mm from the longitudinal end 320 of the second electrode.

[0075] When the longitudinal length range of the second separator overlapping part is satisfied, even if a process error occurs when the first separator and the second separator are introduced, the second separator overlapping part can be disposed between the second electrode and the first electrode facing the second surface of the second electrode, which is sufficient to prevent damage to the first electrode facing the second surface of the second electrode and the separator. This also prevents an excessive reduction in the area of ​​the first electrode that receives lithium ions, thereby preventing a decrease in charge / discharge efficiency and resulting in excellent battery stability and life characteristics.

[0076] According to one embodiment of the present invention, the longitudinal length of the first separator overlapping portion may be the same as or different from the longitudinal length of the second separator overlapping portion. Specifically, the longitudinal length of the first separator overlapping portion may be the same as or smaller than the longitudinal length of the second separator overlapping portion. When the longitudinal length of the first separator overlapping portion is smaller than the longitudinal length of the second separator overlapping portion, the formation of additional steps due to the thicknesses of the first separator overlapping portion and the second separator overlapping portion can be minimized, and damage to the first electrode and separator facing the first surface in the winding axis direction of the second electrode and the second surface in the opposite direction to the winding axis can be prevented.

[0077] According to one embodiment of the present invention, the longitudinal length of the first separator overlapping portion may be 10% to 50% of the circumference of the inner circumferential surface of the electrode assembly. Specifically, the longitudinal length of the first separator overlapping portion may be 15% to 15%, 20% to 25%, or 30% of the circumference of the inner circumferential surface of the electrode assembly, and may be 45%, 40%, 35%, or 30% or less.

[0078] That is, the longitudinal length of the first separator overlapping portion may be 1 / 10 to 1 / 2 turn, or 1 / 5 to 1 / 3 turn, around the inner circumferential surface of the core portion of the electrode assembly. Referring to Figure 6, the longitudinal length of the first separator overlapping portion may be L1 + L1' = L1 + L1 = 2L1.

[0079] When the longitudinal length range of the first separator overlapping portion is satisfied, damage to the first electrode and separator facing the first surface of the second electrode, which is in the winding axis direction, due to deformation of the electrode assembly caused by contraction / expansion of the electrode during battery charge / discharge can be prevented, and a decrease in charge / discharge efficiency due to an excessive decrease in the area of ​​the first electrode that receives lithium ions can be prevented, resulting in excellent battery stability and life characteristics.

[0080] According to one embodiment of the present invention, a distance between a longitudinal end of the first separation membrane overlapping part and a longitudinal end of the second electrode may be 2 mm or more and 10 mm or less.

[0081] 6, the distance L1, L1' between the longitudinal end of the first separator overlapping portion and the longitudinal end of the second electrode may be 3 mm or more, 4 mm or more, or 5 mm or more, and may be 9 mm or less, 8 mm or less, or 7 mm or less. That is, the first separator 20' extending from the longitudinal end 120 of the first electrode in the core portion of the electrode assembly may be disposed between the second electrode 300 and the first electrode 100 facing the first surface of the second electrode, at a distance of 2 mm to 10 mm from the longitudinal end 320 of the second electrode.

[0082] When the longitudinal length range of the first separator overlapping part is satisfied, even if a process error occurs when the first separator is inserted, the first separator overlapping part can be disposed between the second electrode and the first electrode facing the first surface of the second electrode, which is sufficient to prevent damage to the first electrode facing the first surface of the second electrode and the separator. This also prevents an excessive reduction in the area of ​​the first electrode that receives lithium ions, thereby preventing a decrease in charge / discharge efficiency and resulting in excellent battery stability and life characteristics.

[0083] According to one embodiment of the present invention, the first electrode may include a first electrode current collector and a first electrode active material layer formed on at least one surface of the first electrode current collector. Specifically, the first electrode may include a first electrode current collector and a first electrode active material layer formed on one or both surfaces of the first electrode current collector and including a first electrode active material. In other words, the first electrode active material layer is formed on a first electrode support portion of the first electrode current collector, and the surface on which the first electrode active material layer is not formed may be referred to as a first electrode uncoated portion.

[0084] 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 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. As a result, the manufactured electrode assembly may include one or more first electrode tabs.

[0085] According to one embodiment of the present invention, the second electrode may include a second electrode current collector and a second electrode active material layer formed on at least one surface of the second electrode current collector. Specifically, the second electrode may include a second electrode current collector and a second electrode active material layer formed on one or both surfaces of the second electrode current 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 current collector, and the surface on which the second electrode active material layer is not formed may be referred to as a second electrode uncoated portion.

[0086] According to one embodiment of the present invention, the second electrode current collector may include a second electrode holding portion to which a second electrode active material is applied and a second electrode uncoated portion to which the second electrode active material is not applied, and may include a 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.

[0087] According to one embodiment of the present invention, the second electrode current collector of the second electrode and the second electrode active material layer formed on the second electrode current collector may have longitudinal ends at the same position. In other words, one longitudinal end of the second electrode may be free-edge shaped. This can reduce the area of ​​the unnecessary uncoated portion of the second electrode current collector, ensuring economic efficiency. The slitting process can be performed after the active material layer is formed on the electrode, thereby more efficiently performing a roll-to-roll process including the slitting process and the winding process. Here, "the same position" means that the longitudinal ends are identical, and may also include cases where the ends are formed at substantially the same position due to process errors that may occur in the slitting process, etc.

[0088] 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, first electrode current collector, and first electrode active material layer may be a negative electrode, a negative electrode current collector, and a negative electrode active material layer, respectively, and the second electrode, second electrode current collector, and second electrode active material layer may be a positive electrode, a positive electrode current collector, and a positive electrode active material layer, respectively.

[0089] According to one embodiment of the present invention, the negative electrode active material layer may include a negative electrode active material including at least one selected from the group consisting of a silicon-based material and a carbon-based material. The negative electrode active material layer may further include a negative electrode conductive material and a negative electrode binder, and the negative electrode active material, negative electrode conductive material, and negative electrode binder may be materials commonly used in the art without limitation.

[0090] According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that effectively adsorbs carbon, such as copper or nickel, may be used as the negative electrode current collector. The thickness of the negative electrode current collector may be 6 μm or more and 80 μm or less, but is not limited thereto.

[0091] According to one embodiment of the present invention, the negative 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.

[0092] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it is conductive 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.

[0093] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity, and specifically, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface is surface-treated with carbon, nickel, titanium, silver, etc. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, etc.

[0094] The positive electrode current collector may have a thickness of typically 3 to 50 μm, and may have fine irregularities on its surface to enhance the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

[0095] According to one 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 may be a layered compound such as lithium cobalt oxide (LiCoO2) or 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-xO4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-y M y Ni-site type lithium nickel oxide 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 oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and 0.01≦z≦0.1) or Li2Mn3MO8 (where 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 substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0096] 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 can be any material that exhibits electronic conductivity without undergoing chemical changes in the resulting battery. Specifically, the positive electrode conductive material may 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 fiber; metal powder or metal fiber, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in combination.

[0097] The positive electrode binder serves to improve adhesion between particles of the positive electrode active material and 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, and various copolymers thereof. These may be used alone or in combination.

[0098] Another embodiment of the present invention provides a secondary battery including the jelly-roll-type electrode assembly and a battery case for housing the electrode assembly. Specifically, the secondary battery may include the electrode assembly according to the above-described embodiment and a battery case for housing the electrode assembly.

[0099] The secondary battery according to the present invention includes a separator overlapping part in which the folding and overlapping structure of the core separator is adjusted, thereby preventing internal short circuits between the second electrode and the first electrode even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery, thereby improving battery stability and lifespan characteristics.

[0100] According to one embodiment of the present invention, the battery case may be cylindrical. Specifically, the battery case may be cylindrical, prismatic, or pouch-shaped depending on the application. A cylindrical battery case is more suitable for accommodating a jelly-roll electrode assembly. When the battery case is cylindrical, the shape of a secondary battery including the jelly-roll electrode assembly and a battery case for accommodating the electrode assembly may also be cylindrical. That is, referring to FIG. 7 , the jelly-roll electrode assembly according to the present invention may be accommodated in a cylindrical battery case 50. Since the battery case containing the electrode assembly, cap assembly, and electrolyte has a cylindrical shape, the shape of the manufactured secondary battery 1000 itself may also be cylindrical.

[0101] According to one embodiment of the present invention, the interior 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 include a non-aqueous organic solvent and a metal salt.

[0102] 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, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, or ethyl propionate.

[0103] 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 may be 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:

[0104] According to one embodiment of the present invention, in addition to the electrolyte constituent components, the electrolyte may further contain 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 derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0105] According to one 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 may be used as a power source for a medium- to large-sized device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.

[0106] The above detailed description is illustrative and explanatory of the present invention. Furthermore, the foregoing merely represents and describes preferred embodiments of the present invention. As noted above, the present invention can be used in various other combinations, modifications, and environments, and changes or modifications are possible within the scope of the inventive concept disclosed herein, the scope of equivalents to the foregoing disclosure, and / or the skill or knowledge of the art. Therefore, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Furthermore, the appended claims are intended to be construed to include other embodiments. [Explanation of symbols]

[0107] 100, 100' 1st electrode 101 First electrode current collector 102, 103 First electrode active material layer 120 Longitudinal end of first electrode 20, 20' 1st separation membrane 300 2nd electrode 301 Second electrode current collector 302, 303 Second electrode active material layer 320 Longitudinal end of second electrode 40, 40' 2nd separation membrane S1 First separation membrane overlapping section S2 2nd separation membrane overlapping section L1, L1': Distance between the longitudinal end of the second electrode and the longitudinal end of the overlapping portion of the first separation membrane L2, L2': Distance between the longitudinal end of the second electrode and the longitudinal end of the overlapping portion of the second separation membrane 50 Battery Case 1000 secondary battery

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 stacked and wound up, the second electrode includes a first surface in a winding axis direction of the jelly roll-type electrode assembly and a second surface opposite to the first surface, a second electrode current collector, and a second electrode active material layer provided on at least one surface of the second electrode current collector and having a longitudinal end portion at the same position as the second electrode current collector; a core portion of the jelly-roll type electrode assembly including a first separator overlapping portion provided on a first surface of the second electrode and a second separator overlapping portion provided on a second surface of the second electrode; a jelly-roll type electrode assembly, wherein the first separation membrane overlapping portion and the second separation membrane overlapping portion are provided in regions corresponding to longitudinal ends of the second electrode;

2. 2. The jelly-roll type electrode assembly according to claim 1, wherein the first separator overlapping portion and the second separator overlapping portion are formed by bending the first separator and the second separator toward the second electrode, respectively.

3. The jelly-roll type electrode assembly of claim 1 , wherein the first separator overlapping portion and the second separator overlapping portion are formed by folding the first separator and the second separator at least two times, respectively.

4. The jelly-roll type electrode assembly according to claim 1 , wherein the first separator overlapping portion and the second separator overlapping portion each include three or more overlapping layers of the first separator and the second separator.

5. 2. The jelly-roll type electrode assembly of claim 1, wherein the width of the first separator overlapping portion and the width of the second separator overlapping portion are each 100% to 110% of the width of the second electrode.

6. The jelly-roll type electrode assembly according to claim 1 , wherein the first separator overlapping portion and the second separator overlapping portion have a longitudinal length of 0.1 mm to 30 mm.

7. In the core portion of the jelly-roll type electrode assembly, the first separator and the second separator extending from longitudinal ends of the first electrode are folded together in opposite directions along a winding axis of the jelly-roll type electrode assembly, The jelly-roll type electrode assembly of claim 1 , wherein the second separator overlapping portion has two or more overlapping separators.

8. 8. The jelly-roll type electrode assembly of claim 7, wherein the first separator, the first electrode, and the second separator extend beyond a longitudinal end of the second electrode and are further wound up in the core portion of the jelly-roll type electrode assembly.

9. 8. The jelly-roll type electrode assembly according to claim 7, wherein in the second separation membrane overlapping portion, the second separation membrane extending from the longitudinal end of the first electrode is disposed between the second electrode and a second separation membrane facing the second surface of the second electrode.

10. 8. The jelly-roll type electrode assembly according to claim 7, wherein in the second separation membrane overlapping portion, the first separation membrane and the second separation membrane extending from longitudinal ends of the first electrode are overlapped between the second electrode and the second separation membrane facing the second surface of the second electrode.

11. a first separator overlapping portion between the second electrode and the first electrode facing the first surface of the second electrode; The jelly-roll type electrode assembly of claim 7 , wherein the first separator overlapping portion has two or more overlapping separators.

12. a first separator overlapping portion between the second electrode and the first electrode facing the first surface of the second electrode; 8. The jelly-roll type electrode assembly according to claim 7, wherein in the first separation membrane overlapping portion, the first separation membrane extending from the longitudinal end of the first electrode is disposed between the second electrode and the first separation membrane facing the first surface of the second electrode.

13. a first separator overlapping portion between the second electrode and the first electrode facing the first surface of the second electrode; In the first separation membrane overlapping portion, the first separation membrane extending from the longitudinal end of the first electrode is disposed between the second electrode and the first separation membrane facing the first surface of the second electrode, 8. The jelly-roll type electrode assembly according to claim 7, wherein in the second separation membrane overlapping portion, the second separation membrane extending from the longitudinal end of the first electrode is disposed between the second electrode and the second separation membrane facing the second surface of the second electrode.

14. 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.

15. The jelly roll type electrode assembly according to claim 1; a battery case for accommodating the jelly-roll type electrode assembly.

16. The secondary battery according to claim 15 , wherein the battery case is cylindrical.

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