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 specifically, to a jelly roll type electrode assembly including a separator overlapping part and a cylindrical secondary battery including the same. This application claims the benefit of the filing dates of Korean Patent Application No. 10-2022-0165774 filed on December 1, 2022 with the Korean Intellectual Property Office and Korean Patent Application No. 10-2022-0165783 filed on December 1, 2022 with the Korean Intellectual Property Office, 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 fixed width into a roll. A cylindrical battery manufactured by inserting such a jelly roll-shaped electrode assembly into a battery case undergoes repeated electrode contraction / expansion during charging / discharging. In particular, if an in-tab is located in the core of the jelly roll-shaped electrode assembly or a silicon-based active material is added to the negative electrode, which increases the degree of contraction / 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 increased, jelly roll type electrode assemblies have increasingly included multiple tabs or silicon-based active materials, and the thickness of the separator has become thinner and thinner for high capacity designs.

[0004] As the thickness becomes thinner, the physical strength of the separator becomes weaker, and the possibility of deformation of the electrode assembly located in the core part due to contraction / expansion of the electrode assembly increases. In particular, if the separator located between the negative and positive electrodes is damaged, the negative and positive electrodes 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 circuit caused by deformation of the electrode assembly, it is necessary to develop a technology that can protect the electrodes and separator in the corresponding regions and suppress the occurrence of internal short circuit. Summary of the Invention [Problem to be solved by the invention]

[0006] 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.

[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] 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, the second electrode having a first surface in a winding axial direction of the jelly roll type electrode assembly and a second surface opposite to the first surface, a core portion of the electrode assembly including 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, the first separator overlapping portion and the second separator overlapping portion being 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 housing the electrode assembly. Effect of the Invention

[0010] A jelly roll type electrode assembly according to an embodiment of the present invention includes a separator overlapping part in which a folding and overlapping structure of a core separator is adjusted, thereby preventing damage to the first electrode and the 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 part prevents an internal short circuit between the first electrode and the second electrode, thereby improving battery stability and life characteristics.

[0011] In addition, the secondary battery according to the present invention can improve battery stability and life characteristics by preventing internal short circuit between the first electrode and the second electrode by the separator overlapping part even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery.

[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] 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. [Diagram 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. [Diagram 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. [Diagram 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 PREFERRED EMBODIMENTS

[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, the second electrode including a first surface in a winding axial direction of the jelly roll type electrode assembly and a second surface opposite to the first surface, a core portion of the electrode assembly including 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, the first separator overlapping portion and the second separator overlapping portion being provided in regions corresponding to longitudinal ends of the second electrode.

[0017] According to an embodiment of the present invention, a jelly roll type electrode assembly includes a separator overlapping part in which the folding and overlapping structure of the core separator is adjusted, thereby preventing damage to the first electrode and the separator from deformation of the electrode assembly due to electrode contraction / expansion during charging / discharging of the battery, and even if the separator is damaged, the separator overlapping part prevents an internal short circuit between the first electrode and the second electrode, thereby improving battery stability and life characteristics. Here, the "core part" may refer to a hollow located on the winding shaft of the electrode assembly and a region including a part of the wound first electrode / first separator / second electrode / second separator laminated 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 a region corresponding to the longitudinal end of the second electrode. Specifically, the first separation membrane overlapping portion and the second separation membrane overlapping portion may be provided in a region corresponding to the longitudinal end where the winding of the second electrode is started. In other words, an extension line perpendicular to the longitudinal direction of the longitudinal end 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 a region corresponding to the longitudinal end of the second electrode, damage to the first electrode and the separation membrane caused by the sharp longitudinal end of the second electrode during charging and discharging of the battery can be effectively prevented.

[0019] Fig. 1 illustrates a jelly-roll type electrode assembly including a separator overlap part according to an embodiment of the present invention. Specifically, Fig. 1(a) illustrates a jelly-roll type electrode assembly including a first separator overlap part and a second separator overlap part formed by folding a first separator and a second separator respectively toward a second electrode, and Fig. 1(b) illustrates a jelly-roll type electrode assembly including a first separator overlap part and a second separator overlap part formed by folding a first separator and a second separator respectively 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. In addition, 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 due to each folding structure can be obtained.

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

[0022] According to an 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 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 folding the first separator 20 toward the second electrode 300. Also, the second separator overlapping portion S2 may be formed on a second surface of the second electrode 300 by folding the second separator 40 toward the second electrode 300. In this case, the vacant space between the first electrode and the separator can be minimized, and thus the occurrence of local problems that may occur due to additional steps, such as lithium deposition in the space between the first electrode and the separator, can be minimized even during high-speed charging.

[0023] According to an 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 to the opposite side of the second electrode, respectively. 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 folding the first separator 20 to the opposite side of the second electrode 300. Also, the second separator overlapping portion S2 may be formed on the second surface of the second electrode 300 by folding the second separator 40 to 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 the step due to the separator overlapping portion located on the first surface or the second surface, so that the occurrence of cracks in the second electrode can be reduced. In addition, even if sliding due to contraction / expansion of the first electrode is repeated during long-term cycles, deformation of the separator overlapping portion can be minimized, thereby providing better crack prevention effect for the first electrode and battery life characteristics.

[0024] According to an embodiment of the present invention, the first separator overlapping portion may be formed by folding the first separator toward the second electrode, and the second separator overlapping portion may be formed by folding 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 surface of the second electrode 300 by folding the first separator 20 toward the second electrode. Also, the second separator overlapping portion S2 may be formed on the second surface of the second electrode 300 by folding the second separator 40 toward the opposite side of the second electrode 300. In this case, even if the longitudinal end of the second electrode faces the second surface when the electrode assembly is wound, the second separator overlapping portion can provide a better protection effect for the first electrode and the separator, thereby minimizing damage to the first separator overlapping portion and further improving the life characteristics of the battery.

[0025] According to an embodiment of the present invention, the first separation membrane overlapping portion may be formed by folding the first separation membrane to the opposite side of the second electrode, and the second separation membrane overlapping portion may be formed by folding the second separation membrane to the second electrode side. Specifically, referring to FIG. 2(b), the first separation membrane overlapping portion S1 may be formed on the first surface of the second electrode 300 by folding the first separation membrane 20 to the opposite side of the second electrode. Also, the second separation membrane overlapping portion S2 may be formed on the second surface of the second electrode 300 by folding the second separation membrane 40 to the second electrode 300 side. In this case, even if the separation membrane overlapping portion is interposed between the first electrode and the second electrode when the electrode assembly is wound up, a stepwise step can be formed due to the thickness of the second separation membrane overlapping portion S2 and the thickness of the first separation membrane overlapping portion S1, and the roundness of the electrode assembly can be improved.

[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 or more times and four or less 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 times of folding is less than two, the effect of preventing damage to the first electrode and the separator may be poor, and if the number of times is more than four, additional steps may be formed, stress may be concentrated in the corresponding area, causing additional separator damage, and local problems such as lithium precipitation due to lack of electrolyte may occur.

[0027] 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 overlapping the first separation membrane and the second separation membrane three or more times. Specifically, the first separation membrane overlapping portion and the second separation membrane overlapping portion may be formed by overlapping the first separation membrane and the second separation membrane three or more times and five or less times. More specifically, the first separation membrane overlapping portion and the second separation membrane overlapping portion may be formed by overlapping the first separation membrane and the second separation membrane three or five times. If the separation membrane overlapping portion is less than three times, the effect of preventing damage to the first electrode and the separation membrane may be poor, and if it is more than five times, additional steps may be formed, stress may be concentrated in the corresponding area, and additional separation membrane damage may occur, and local problems such as lithium precipitation due to lack of electrolyte may occur.

[0028] According to one embodiment of the present invention, the widthwise length of the first separator overlapping part and the second separator overlapping part may be 100% or more and 110% or less based on the 100% width of the second electrode. Specifically, the widthwise length of the first separator overlapping part and the second separator overlapping part may be 100% or more and 105% or more and 105% or less based on the 100% width of the second electrode. The width of the first electrode and the separator may be larger than the width of the second electrode to improve charge / discharge efficiency and battery stability, so that damage to the first electrode and the separator caused by the sharp longitudinal end of the second electrode may occur equally over the entire longitudinal end of the second electrode. Therefore, by adjusting the widthwise length of the first separator overlapping part and the second separator overlapping part to cover the entire width of the second electrode, the effect of preventing damage to the first electrode and the separator may be more excellent. Meanwhile, when the widthwise lengths of the first and second separation membrane overlapping parts 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 length of the first and second separator overlapping parts in the longitudinal direction may be 0.1 mm or more and 30 mm or less. Specifically, the length of the first and second separator overlapping parts in the longitudinal direction 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 length of the first and second separator overlapping parts satisfies the above-mentioned range, even if the second electrode slides during charging / discharging of the battery, the separator overlapping parts can be located in a region corresponding to the end of the second electrode in the longitudinal direction. In addition, even if a certain process error exists, the separator overlapping parts can have a better effect of preventing 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, 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, L2' from the longitudinal end 320 of the second electrode to both longitudinal ends of the second separator overlapping portion S2.

[0030] According to an embodiment of the present invention, the center of the first separator overlapping part and the second separator overlapping part may be provided in a region corresponding to the longitudinal end of the second electrode. For example, a line extending from a 1 / 2 point of the longitudinal length of the first separator overlapping part and the second separator overlapping part may coincide with the longitudinal end where the winding of the second electrode is started. Here, the "center" refers to a 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 other end, where the longitudinal length is L, and "coincidence" may include a case where the ends are formed at substantially the same position due to process errors that may occur in a process such as a bending process of the separator. When the center of the first separator overlapping part and the second separator overlapping part are provided in a region corresponding to the longitudinal end of the second electrode, the effect of preventing damage to the first electrode and the separator caused by the sharp longitudinal end of the second electrode during charging and discharging of the battery may be more excellent.

[0031] Fig. 3 illustrates a jelly-roll type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. Specifically, Fig. 3(a) illustrates a jelly-roll type electrode assembly including a first separator overlapping portion and a second separator overlapping portion formed by folding a first separator overlapping portion and a second separator overlapping portion, respectively, toward a second electrode, and Fig. 3(b) illustrates a jelly-roll type electrode assembly including a first separator overlapping portion and a second separator overlapping portion formed by folding a first separator overlapping portion and a second separator overlapping portion toward an 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 part may be 0.5 mm or more and 15 mm or less. 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 part 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, 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 part satisfy the above-mentioned range, the first separator overlapping part can effectively surround the first surface of the second electrode and the longitudinal end of the second electrode, so that the effect of preventing damage to the first electrode and the separator on the first surface of the second electrode is more excellent, and the formation of further steps can be minimized.

[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 separation membrane overlapping part may be 0.5 mm or more and 15 mm or less. Specifically, referring to FIG. 3, the distances L2, L2' between the longitudinal end of the second electrode and the longitudinal end of the second separation membrane overlapping part 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, 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, L2' between the longitudinal end of the second electrode and the longitudinal end of the second separation membrane overlapping part satisfy the above-mentioned range, the second separation membrane overlapping part can effectively surround the second surface of the second electrode and the longitudinal end of the second electrode, so that the effect of preventing damage to the first electrode and the separation membrane on the second surface of the second electrode can be more excellent, and the formation of further steps can be minimized.

[0034] According to one embodiment of the present invention, in the core of the electrode assembly, the first separator, the first electrode, and the second separator may extend beyond the longitudinal end of the second electrode and be further wound up. Specifically, the first separator, the first electrode, and the second separator may be wound up together with the second electrode after being wound up. For example, the first separator, the first electrode, and the second separator may be wound up together around a winding core for one or more turns and then wound up 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 larger than 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 larger than the second electrode. When the first separator, the first electrode, and the second separator extend beyond the longitudinal end of the second electrode and are wound up, the lithium ions of 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 the lithium ions increases, preventing a decrease in charge / discharge efficiency and providing excellent battery stability and life 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 are 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, damage to the first electrode and separator due to deformation of the electrode assembly caused by electrode contraction / expansion during battery charge / discharge can be prevented. Even if the separator is damaged, the separator overlapping part can prevent internal shorts between the first and second electrodes, thereby improving battery stability and life characteristics.

[0037] Figures 4 and 5 show a jelly-roll type electrode assembly including a separator overlap part according to an embodiment of the present invention. Specifically, Figure 4 shows a jelly-roll type electrode assembly including a second separator overlap part according to an embodiment of the present invention, and Figure 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 a core portion of the electrode assembly, the first separator and the second separator extending from longitudinal ends of the first electrode may be folded together in opposite directions in a 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 folded together in a direction opposite to a direction facing a winding shaft of the first electrode, and be arranged overlapping between the second electrode and the first electrode facing a first surface or a 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 opposite direction 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 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.

[0042] As a result, the separation membrane constituting the second separation membrane overlapping portion can be made to be two or more layers 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 includes 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 have 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 separation membrane overlap portion S2 between the second electrode 300 and the first electrode 100' facing the second surface of the second electrode, and the second separation membrane overlap portion S2 may refer to a portion of an area in which two or more separation membranes are overlapped and arranged around the longitudinal end 320 of the second electrode.

[0047] Here, the second separator overlap portion S2 may refer to an 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 as the region up to the longitudinal end portion of the second separator overlap portion in the core portion direction of the electrode assembly.

[0048] Specifically, referring to FIG. 4(a), the second isolation membrane overlapping portion S2 may refer to a region from the longitudinal end of the second isolation membrane overlapping portion S2 to a length L2' in the core portion direction of the electrode assembly, which is the same as the separation distance L2 between the longitudinal end of the second isolation 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 isolation membrane overlapping portion S2.

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

[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 portion 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 overlap portion S1 or the second separation membrane overlap 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 makes it possible to adjust the number of separation membranes constituting the first separation membrane overlapping portion or the second separation membrane overlapping portion to be two or more 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 disposed such that the second separator 40' extending from the longitudinal end portion 120 of the first electrode overlaps with the second separator 40 in the core portion of the electrode assembly. When the extended second separator is disposed between the second electrode and the 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 be two or more with a simpler structure.

[0054] According to one embodiment of the present invention, the second separation membrane overlap 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 overlap portion S2 may be arranged such that the first separator 20' and the second separator 40' extending from the longitudinal end 120 of the first electrode in the core portion of the electrode assembly overlap with the second separator 40.

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

[0057] When the first separator and the second separator extending from the longitudinal end of the first electrode are overlapped at least twice to form a second separator overlapping portion, damage to the first electrode and the separator caused by deformation of the electrode assembly due to contraction / expansion of the electrodes can be prevented, and even if the separator is damaged, the second separator overlapping portion can prevent an internal short circuit between the first electrode and the second electrode, thereby improving battery stability and life characteristics. In addition, when the second separator overlapping portion is included, the effect of preventing damage to 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 an embodiment of the present invention, a first separator overlapping portion may be further included between the second electrode and the first electrode facing the first surface of the second electrode. Specifically, referring to Fig. 5 (a) and (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 a direction opposite 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 a second separator overlapping 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 a first separator overlapping portion S1.

[0059] As a result, the separation membranes constituting the first separation membrane overlapping portion and the second separation membrane overlapping portion can each be made to be two or more layers with a simpler folding structure. In addition, by further including the first separation membrane overlapping portion, the effect of preventing damage to the first electrode and separation membrane facing the first surface, which is the winding axis direction of the second electrode, can be more excellent.

[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 the 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 separation membrane overlap portion S1 between the second electrode 300 and the first electrode 100 facing the first surface of the second electrode, and the first separation membrane overlap portion S1 may refer to a portion of an area in which two or more separation membranes are overlapped and arranged around the longitudinal end portion 320 of the second electrode.

[0062] Here, the first separator overlap portion S1 may refer to an 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 as the region up to the longitudinal end portion of the first separator overlap portion in the core portion direction of the electrode assembly.

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

[0064] According to an 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, and the extended first separator 20' may be disposed in the core portion of the electrode assembly such that the first separator 20' extends from the end 120 of the first electrode in the longitudinal direction and overlaps the first separator 20.

[0065] When the extended first separator is disposed between the second electrode and the first separator facing the first surface of the second electrode, the first separator overlap portion may be formed by a folded structure integrally extending from the first separator without providing a separate auxiliary separator, etc. This allows the number of separators constituting the first separator overlap portion to be adjusted 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 a 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 a second surface of the second electrode.

[0067] Specifically, referring to FIG. 5, the first separation membrane overlapping portion S1 may be disposed such that the first separation membrane 20' extending from the longitudinal end 120 of the first electrode overlaps with the first separation membrane 20 in the core portion of the electrode assembly, and the second separation membrane overlapping portion S2 may be disposed such that the second separation membrane 40' extending from the longitudinal end 120 of the first electrode overlaps with the second separation membrane 40 in the core portion of the electrode assembly.

[0068] When 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 extended second separation membrane is disposed between the second electrode and the second separation membrane facing the second surface of the second electrode, the first separation membrane overlapping portion and 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 makes it possible to adjust the number of separation membranes constituting the first separation membrane overlapping portion and the second separation membrane overlapping 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 at least twice to form a first separator overlapping portion and a second separator overlapping portion, damage to the first electrode and the separator caused by deformation of the electrode assembly due to contraction / expansion of the electrodes can be prevented, and even if the separator is damaged, the first and second separator overlapping portions can prevent an internal short circuit between the first and second electrodes, thereby improving battery stability and life characteristics. In addition, when both the first and second separator overlapping portions are included, the effect of preventing damage to the first electrode and the separator facing the first surface in the winding axis direction of the second electrode and the second surface opposite to the first surface can be more excellent.

[0070] According to an embodiment of the present invention, the jelly roll type electrode assembly may include a plurality of separators. For example, the jelly roll type electrode assembly may have a structure in which the second electrode / first separator / first electrode / second separator are laminated in order, or may have a structure in which the first separator / first electrode / second separator / second electrode are laminated in order. The separator separates the second electrode from the first electrode to provide a path for lithium ions to move, and may be any separator that is generally used in secondary batteries without any particular limitations. In particular, it is preferable that the separator has low resistance to ion movement of the electrolyte 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 conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, or the like, may be used. In addition, 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-mentioned separation membrane material with a slurry containing a ceramic component or a polymeric material in order to ensure heat resistance or mechanical strength, and may be used in a single-layer or multi-layer structure.

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

[0072] That is, the length of the second separator overlapping part in the longitudinal direction may be 1 / 10 to 1 / 2 turn, or 1 / 5 to 1 / 3 turn of the inner circumferential surface of the core part of the electrode assembly. Here, the "around the inner circumferential surface" may refer to a virtual circle having a radius of the largest value among the distances from the winding axis of the electrode assembly to the innermost stratum in contact with the hollow of the electrode assembly. Referring to FIG. 6, the length of the second separator overlapping part in the longitudinal direction may refer to the length of L2+L2'=L2+L2=2L2.

[0073] When the longitudinal length range of the second separator overlapping part is satisfied, damage to the first electrode and separator facing the second surface, which is in the opposite direction to the winding axis direction of the second electrode, due to deformation of the electrode assembly caused by contraction / expansion of the electrode during charging / discharging of the battery can be prevented, and a decrease in charge / discharge efficiency due to an excessive reduction 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 an embodiment of the present invention, the separation distance between the longitudinal end of the second separator overlapping portion and the longitudinal end of the second electrode may be 2 mm or more and 10 mm or less. Specifically, referring to FIG. 6, the separation 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 or more, 4 mm or more, or 5 mm or more, and 9 mm or less, 8 mm or less, or 7 mm or less. 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, and may be disposed 2 mm or more and 10 mm or less 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 exists 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 prevents an excessive reduction in the area of ​​the first electrode that receives lithium ions, thereby preventing a decrease in charge / discharge efficiency, and thus provides excellent battery stability and life characteristics.

[0076] According to one embodiment of the present invention, the longitudinal length of the first separation membrane overlapping part may be the same as or different from the longitudinal length of the second separation membrane overlapping part. Specifically, the longitudinal length of the first separation membrane overlapping part may be the same as or smaller than the longitudinal length of the second separation membrane overlapping part. When the longitudinal length of the first separation membrane overlapping part is smaller than the longitudinal length of the second separation membrane overlapping part, the formation of an additional step due to the thickness of the first separation membrane overlapping part and the second separation membrane overlapping part can be minimized, and damage to the first electrode and the separation membrane 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 direction can be prevented.

[0077] According to one embodiment of the present invention, the longitudinal length of the first separator overlapping portion may be 10% or more and 50% or less based on 100% 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% or more, 20% or more, 25% or more, or 30% or more based on 100% of the circumference of the inner circumferential surface of the electrode assembly, and may be 45% or less, 40% or less, 35% or less, or 30% or less.

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

[0079] When the longitudinal length range of the first separator overlapping part is satisfied, damage to the first electrode and separator facing the first surface, which is the winding axis direction of the second electrode, due to deformation of the electrode assembly caused by contraction / expansion of the electrode during charging / discharging of the battery 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 separation 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 exists when the first separator is introduced, 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, and prevents a decrease in charge / discharge efficiency due to an excessive reduction in the area of ​​the first electrode that receives lithium ions, thereby achieving excellent battery stability and life characteristics.

[0083] 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 at least one surface of 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 may be referred to as a first electrode non-coating 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. Thus, 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 collector; and a second electrode active material layer provided on at least one surface of 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 may be represented 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 provided 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 part of the second electrode collector to ensure economy, and the slitting process can be performed after the active material layer is formed on the electrode, so that the roll-to-roll process including the slitting process and the winding process can be performed more efficiently. Here, "the same position" means that the longitudinal ends are the same, and may include the case 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, the first electrode current collector, and the 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, the second electrode current collector, and the 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 an 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, the negative electrode conductive material, and the negative electrode binder may be materials used in the art without any restrictions.

[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, baked carbon, or aluminum or stainless steel surface-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 negative electrode current collector. The thickness of the negative electrode current collector may be 6 μm or more and 80 μm or less, but the thickness of the negative electrode current collector 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 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.

[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 a chemical change in the battery and has conductivity, and specifically, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, baked 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, nonwoven fabric, etc.

[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 is lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ) and compounds substituted with one or more transition metals; LiFe 3 O 4 Lithium iron oxide, etc.; chemical formula Li 1+x Mn 2-x O 4(0≦x≦0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 Lithium manganese oxides such as lithium copper oxide (Li 2 CuO 2 );LiV 3 O 8 , V 2 O 5 , Cu 2 V 2 O 7 Vanadium oxides such as LiNi 1-y M y O 2 (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 O 2 (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 Li 2 Mn 3 MO 8 Lithium manganese composite oxide represented by the formula LiMn (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn) 2 O 4 The positive electrode may be Li metal, but is not limited to these.

[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 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 positive 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.

[0097] The positive electrode binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these may be used alone or in combination.

[0098] An 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 embodiment described above 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 an internal short circuit 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 life characteristics.

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

[0101] According to an embodiment of the present invention, the inside of the battery case may contain an electrolyte. Specifically, the electrolyte may be 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, but is not limited thereto. Specifically, the electrolyte may contain 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, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 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 is F - , Cl - , I - , NO 3 - , N(CN) 2- , B.F. 4 - , ClO 4 - , P.F. 6 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , C.F. 3 SO 3 - , C.F. 3CF 2 SO 3 - , (CF 3 SO 2 ) 2 N - , (FSO 2 ) 2 N - , C.F. 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - ,(SCIENCE FICTION 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , C.F. 3 (CF 2 ) 7 SO 3 - , C.F. 3 CO 2 - , C.H. 3 CO 2 - , SCN - and (CF 3 CF 2 SO 2 ) 2 N - One or more selected from the group consisting of may be used.

[0104] According to one embodiment of the present invention, in addition to the electrolyte 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 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, and improving the discharge capacity of the battery.

[0105] 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 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. Moreover, the above content merely represents and describes preferred embodiments of the present invention, and as stated above, the present invention can be used in various other combinations, modifications, and environments, and changes or modifications can be made within the scope of the inventive concept disclosed herein, the scope of the above 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. Moreover, the appended claims are intended to be construed to include other embodiments. [Explanation of symbols]

[0107] 100, 100' 1st electrode 101 First electrode 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 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 first separation membrane overlapping portion 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 core portion of the jelly-roll type electrode assembly including a first separator overlap portion provided on a first surface of the second electrode and a second separator overlap portion provided on a second surface of the second electrode; 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 of 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. 2. 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. 2 . The jelly-roll type electrode assembly of 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 three or more overlapping layers of 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. 2 . The jelly-roll type electrode assembly of claim 1 , wherein the first separator overlapping portion and the second separator overlapping portion have a length in a longitudinal direction 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 the longitudinal end portions of the first electrode are folded together in opposite directions in a winding axis direction of the jelly roll type electrode assembly, The jelly-roll type electrode assembly of claim 1 , wherein the second separator overlapping portion has a separator overlapped in two or more layers.

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

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 the 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. The second electrode further includes 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 a separator overlapped in two or more layers.

12. The second electrode further includes 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 a 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. The second electrode further includes 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 a longitudinal end portion of the first electrode is disposed between the second electrode and the first separation membrane facing a 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 a 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. The second electrode is A second electrode current collector; a second electrode active material layer provided on at least one surface of the second electrode current collector and having a longitudinal end at the same position as the second electrode current collector.

15. 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.

16. The jelly roll type electrode assembly according to claim 1 ; and a battery case for housing the jelly-roll type electrode assembly.

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

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