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] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0173898 filed with the Korean Intellectual Property Office on December 7, 2021, and all of the contents disclosed in the documents of the Korean patent application are incorporated herein by reference. The present invention relates to a jelly roll type electrode assembly and a secondary battery including the same, specifically to a jelly roll type electrode assembly including a separator overlapping portion and a cylindrical secondary battery including the same, and more specifically to a jelly roll type electrode assembly including a first separator overlapping portion and a second separator overlapping portion and a cylindrical secondary battery including the same. [Background technology]

[0002] In the case of cylindrical batteries, a jelly roll type 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 type electrode assembly into a battery case undergoes repeated electrode contraction / expansion during charging and discharging. In particular, when an in tab is located in the core of the jelly roll type electrode assembly or a silicon-based active material is added to the negative electrode, the degree of contraction / expansion of the electrode assembly increases, and the pressure acting on the core of the electrode assembly increases significantly.

[0003] Recently, as low resistance / high capacity designs have become more common, jelly roll type electrode assemblies have come to include multiple tabs or have silicon-based active materials added thereto. This increases the possibility of deformation of the electrode assembly located in the core portion due to contraction / expansion of the electrode assembly. In particular, if a 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.

[0004] In order to solve the problem of separator damage and internal short circuit occurrence due to deformation of the electrode assembly, it is necessary to develop a technology that can protect the negative electrode and separator in the corresponding area and suppress the occurrence of internal short circuit. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a jelly-roll type electrode assembly having a modified design of a jelly-roll type electrode assembly, and a secondary battery including the same.

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

[0007] Provided is a jelly roll type electrode assembly in which a negative electrode, a first separator, a positive electrode, and a second separator are sequentially stacked and wound up, wherein the positive electrode has a first surface which is a winding axis direction of the jelly roll type electrode assembly and a second surface which is the opposite surface to the first surface, and a first separator overlapping portion and a second separator overlapping portion are provided on the first surface and the second surface of the positive electrode, respectively, at one end of the positive electrode in the longitudinal direction located in a core part of the electrode assembly, and the first separator overlapping portion and the second separator overlapping portion have three or more overlapping separators.

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

[0009] A jelly roll type electrode assembly according to an embodiment of the present invention includes a separator overlapping part having a modified folding structure of a core separator, thereby preventing damage to the negative 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 part prevents an internal short circuit between the positive and negative electrodes, thereby improving battery stability and life characteristics.

[0010] In addition, the secondary battery according to the present invention can prevent an internal short circuit between the positive and negative electrodes by the separator overlapping portion 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.

[0011] The effects of the present invention are not limited to the effects described above, and effects not mentioned herein should be clearly understood by those skilled in the art from the present specification and the accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 illustrates a jelly roll-type electrode assembly according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing a cross section and a core portion of a jelly roll-type electrode assembly according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly-roll type electrode assembly according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Diagram 5] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 6] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly-roll type electrode assembly according to an embodiment of the present invention. [Figure 7] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 8] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly-roll type electrode assembly according to an embodiment of the present invention. [Figure 9] FIG. 2 is a schematic diagram illustrating a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 10] FIG. 2 is a schematic diagram illustrating a core portion including a separator overlap portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Explanation of symbols]

[0013] 1000 ···Jelly roll type electrode assembly C: Core section 100, 100'...Negative electrode 101...Negative electrode current collector 102, 103...Negative electrode active material layer 110: End portion in the longitudinal direction of the negative electrode 130 Negative electrode tab 20 First separator 300...Positive electrode 301...Positive electrode current collector 302, 303...Cathode active material layer 310 One end in the longitudinal direction of the positive electrode 330 Positive electrode tab 40 Second separator 50 ···Step 60...empty space S1: First separator overlap S2: Second separator overlapping section L, L': The separation distance between the end of the step in the longitudinal direction and one end of the positive electrode in the longitudinal direction. T: Thickness of positive electrode L11, L12: Separation distance between the longitudinal end of the overlapping portion of the first separator and one longitudinal end of the positive electrode L21, L22: Separation distance between the longitudinal end of the overlapping portion of the second separator and one longitudinal end of the positive electrode P... Cutting separator L13, L14: Separation distance between the longitudinal end of the separator included in the first separator overlapping portion and one longitudinal end of the positive electrode L23, L24: Distance between the longitudinal end of the separator included in the overlapping portion of the second separator and one longitudinal end of the positive electrode DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Throughout this specification, when a part is said to "comprise" a certain element, this means that it can further include other elements, not excluding other elements, unless specifically stated to the contrary.

[0015] Throughout this specification, when an element is said to be "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 negative electrode, a first separator, a positive electrode, and a second separator are sequentially stacked and wound up, in which the positive electrode includes a first surface which is a winding axis direction of the jelly roll type electrode assembly and a second surface which is the opposite surface to the first surface, and a first separator overlapping portion and a second separator overlapping portion which are provided on the first surface and the second surface of the positive electrode, respectively, at one end of the length of the positive electrode located in a core part of the electrode assembly, and the first separator overlapping portion and the second separator overlapping portion have three or more overlapping separators.

[0017] A jelly roll type electrode assembly according to an embodiment of the present invention includes a separator overlapping part having a modified folding structure of a core separator, thereby preventing damage to the negative 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 part prevents an internal short circuit between the positive and negative electrodes, thereby improving battery stability and life characteristics.

[0018] Fig. 1 is a diagram showing a jelly-roll type electrode assembly according to an embodiment of the present invention, and Fig. 2 is a diagram showing a cross section and a core part of the jelly-roll type electrode assembly according to an embodiment of the present invention. Specifically, Fig. 2(a) is a cross section of the jelly-roll type electrode assembly according to an embodiment of the present invention in Fig. 1 cut in the A-A' direction, and Fig. 2(b) is a diagram showing a core part of the electrode assembly.

[0019] According to an embodiment of the present invention, in the core of the electrode assembly (jelly roll type electrode assembly 1000), the negative electrode may be extended longer than one end of the positive electrode in the length direction and then further wound. Specifically, referring to FIG. 1 and FIG. 2, the negative electrode 100' may be extended longer than one end 310 of the positive electrode in the length direction and then further wound. That is, the negative electrode 100' may be wound together with the positive electrode 300 after being wound to a predetermined length. For example, the negative electrode 100' may be wound around a winding core one or more times and then wound together with the positive electrode 300. That is, in the core of the jelly roll type electrode assembly, the end of the negative electrode in the length direction may be located inside the one end of the positive electrode in the length direction. In other words, the length and width of the negative electrode may be larger than those of the positive electrode. When the negative electrode is extended longer than one end of the positive electrode in the length direction and then further wound, lithium ions from the positive electrode can be more easily transferred to the negative electrode in the chemical reaction of the battery. When the negative electrode is formed to be wider in length or width, the area of ​​the negative electrode that receives lithium ions increases, preventing a decrease in charge / discharge efficiency and improving battery stability and life characteristics. Here, the core part may refer to a region including a hollow located on the winding shaft of the electrode assembly and a part of the wound laminated structure of negative electrode / first separator / positive electrode / second separator, and may refer to a region within two turns of the positive electrode from one end of the positive electrode in the length direction located at the innermost position of the electrode assembly.

[0020] According to one embodiment of the present invention, the core part of the electrode assembly may include a step part, which is a region where the negative electrode covers one end of the positive electrode in the length direction. Specifically, the step part may refer to a region where the negative electrode of the core part covers the end of the positive electrode in the length direction where winding starts, i.e., a region where a step is formed due to the thickness of one end of the positive electrode in the length direction. The step part may be a region where the negative electrode covers one end of the positive electrode in the length direction, and a space beside the end of the positive electrode in the length direction is left open due to the thickness of the positive electrode. In this case, the step due to the thickness of the positive electrode may cause stress to be generated in the facing negative electrode, and the stress may be concentrated on the surface of the negative electrode opposite to the surface facing the positive electrode during charging and discharging, which may cause anode cracks. In addition, the step part may be a region where damage (core impingement) of the separator and the negative electrode on the first and second surfaces of the positive electrode is concentrated due to the sharp end of the positive electrode in the length direction when the electrode shrinks / expands during charging and discharging of the battery.

[0021] 2(b), the core part C of the electrode assembly may have a length of the positive electrode 300 shorter than the remaining layers, and may have an empty space 60 surrounded by the negative electrode 100, one end part 310 of the positive electrode in the longitudinal direction, and the negative electrode 100'. That is, the core part C of the jelly roll type electrode assembly according to an embodiment of the present invention may include a step part 50 including a region forming a stacked structure of the negative electrode 100' / separator (not shown) / positive electrode 300 / separator (not shown) / negative electrode 100 when wound around one end part 310 of the positive electrode in the longitudinal direction, and a region forming a stacked structure of the negative electrode 100' / separator (not shown) / empty space 60 / separator (not shown) / negative electrode 100.

[0022] According to one embodiment of the present invention, the stepped portion 50 may include a first region having a predetermined length L according to the thickness T of the positive electrode, that is, a region from one end 310 of the positive electrode in the length direction to a point where the negative electrodes 100, 100' are in direct contact with each other, and the first region may include a space 60 between the negative electrodes 100, 100'. The stepped portion 50 may include a second region having the same length L' as the first region on the other side of the positive electrode in the length direction, and the second region may refer to a region including the positive electrode 300 between the negative electrodes 100, 100'. That is, the stepped portion 50 may refer to a region having a total length of L+L'=L+L=2L, centered on one end 310 of the positive electrode in the length direction.

[0023] 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 a negative electrode / a first separator / a positive electrode / a second separator are sequentially laminated. The separators (first separator 20, second separator 40) separate the negative electrode 100 and the positive electrode 300 to provide a path for lithium ion movement, and may be any separator that is generally used as a separator in a secondary battery without any particular limitation. In particular, a separator that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption ability may be used. 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. Also, a typical porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc., may be used. Also, the separator may have a thickness of 10 um to 20 um, and may be a separator in which the above separator material is used as a substrate layer and a slurry containing a ceramic component or a polymeric substance is coated on the substrate layer to ensure heat resistance or mechanical strength, or may be selectively used in a single layer or multilayer structure.

[0024] According to one embodiment of the present invention, the positive electrode may include a first separator overlapping portion and a second separator overlapping portion provided on a first surface of the positive electrode and a second surface of the positive electrode, respectively, at one end in the longitudinal direction of the positive electrode located in the core portion of the electrode assembly. When the positive electrode includes a first separator overlapping portion and a second separator overlapping portion provided on the first surface of the positive electrode and the second surface of the positive electrode, respectively, damage to the negative electrode and the separator that may be caused by one end in the longitudinal direction of the positive electrode is prevented, and even if the separator is damaged, an internal short circuit between the positive electrode and the negative electrode is prevented by the separator overlapping portion, thereby improving battery stability and life characteristics.

[0025] According to one embodiment of the present invention, the first separator overlapping portion and the second separator overlapping portion may have three or more separators overlapping each other. Specifically, the first separator overlapping portion and the second separator overlapping portion may have three or more and five or less separators overlapping each other. More specifically, the first separator overlapping portion and the second separator overlapping portion may have three, four, or five separators overlapping each other. If the separators overlapping each other are less than three times, the effect of preventing damage to the negative electrode and the separator may be deteriorated, and if the separators overlap each other are more than five times, a step is formed due to the thickness of the separator overlapping portion, and stress is concentrated in the area, which may cause further damage to the separator or cause local problems such as lithium precipitation due to lack of electrolyte.

[0026] According to one embodiment of the present invention, the first separator overlapping portion and the second separator overlapping portion may be formed by overlapping the first separator and the second separator extended from one end of the positive electrode in the length direction. Specifically, the jelly roll type electrode assembly according to one embodiment of the present invention may be formed by sequentially stacking and winding a negative electrode, a first separator, a positive electrode, and a second separator, and the positive electrode may include a first surface in the winding axis direction of the jelly roll type electrode assembly and a second surface opposite to the first surface. In this case, the first separator facing the first surface of the positive electrode may be extended from one end of the positive electrode in the length direction and folded to overlap the second separator on the second surface of the positive electrode, thereby forming the second separator overlapping portion. In addition, the second separator facing the second surface of the positive electrode may be extended from one end of the positive electrode in the longitudinal direction and folded to overlap with the first separator on the first surface of the positive electrode to form the first separator overlapping portion. This allows the separators constituting the first separator overlapping portion and the second separator overlapping portion to be three or more times folded by a simple folding structure of the separators included in the electrode assembly. That is, the first separator overlapping portion and the second separator overlapping portion can be formed by a folding structure integrally extended from the first separator and the second separator without providing a separate additional separator.

[0027] 3 to 5 are diagrams illustrating a separator overlapping portion of a jelly-roll type electrode assembly according to one embodiment of the present invention.

[0028] According to one embodiment of the present invention, the end in the length direction of the first separator may be folded so as to surround one end in the length direction of the positive electrode and be located on the second surface side of the positive electrode, and the end in the length direction of the second separator may be folded so as to surround the folded first separator and be located on the first surface side of the positive electrode. Specifically, referring to Fig. 3(a), Fig. 4(a) and Fig. 5(a), the end in the length direction of the first separator 20 may be folded so as to surround one end in the length direction of the positive electrode 310 and be located on the second surface side of the positive electrode 300, and the end in the length direction of the second separator 40 may be folded so as to surround the folded first separator 20 and be located on the first surface side of the positive electrode 300. As a result, the first separator 20 can be overlapped with the second separator 40 on the second surface of the positive electrode 300 to form the second separator overlapping portion S2, and the second separator 40 can be overlapped with the first separator 20 on the first surface of the positive electrode 300 to form the first separator overlapping portion S1.

[0029] According to one embodiment of the present invention, the end in the length direction of the second separator may be folded to surround one end in the length direction of the positive electrode and located on the first surface side of the positive electrode, and the end in the length direction of the first separator may be folded to surround the folded second separator and located on the second surface side of the positive electrode. Specifically, referring to Fig. 3(b), Fig. 4(b) and Fig. 5(b), the end in the length direction of the second separator 40 may be folded to surround one end in the length direction of the positive electrode 310 and located on the first surface side of the positive electrode 300, and the end in the length direction of the first separator 20 may be folded to surround the folded second separator 40 and located on the second surface side of the positive electrode 300. As a result, the second separator 40 can be overlapped with the first separator 20 on the first surface of the positive electrode 300 to form the first separator overlap portion S1, and the first separator 20 can be overlapped with the second separator 40 on the second surface of the positive electrode 300 to form the second separator overlap portion S2.

[0030] Here, the meaning of "folding to surround A" includes the case where the separator facing A is folded and turned back at a position spaced a predetermined distance from A during the manufacturing process, so that the separator before folding and the separator after folding are superimposed in contact with each other with A in between. In other words, it may include a region where the separator before folding and the separator after folding are superimposed in direct contact with each other without A in between, and a region where they are superimposed with A in between. In this case, it is self-evident that the case where the folded portion of the separator facing A is adjacent to A and the folded portion of the separator is in direct contact with A is also included.

[0031] According to one embodiment of the present invention, the first separator overlapping portion may be formed by folding the first separator and one end of the positive electrode in the longitudinal direction so as to surround the first end of the positive electrode, and overlapping the second separator located on the first surface of the positive electrode. In other words, the second separator facing the second surface of the positive electrode may be extended from one end of the positive electrode in the longitudinal direction and folded to surround the one end of the positive electrode in the longitudinal direction, thereby overlapping the first separator on the first surface of the positive electrode to form the first separator overlapping portion. This allows the first separator overlapping portion to be formed with three or more layers of separators by a simpler folding structure.

[0032] According to one embodiment of the present invention, the end portion in the length direction of the first separator and the end portion in the length direction of the second separator may be folded on the first or second surface of the positive electrode in a direction facing the positive electrode or in a direction opposite to the direction facing the positive electrode, and then further overlapped. In this case, the folding directions of the end portion in the length direction of the first separator and the end portion in the length direction of the second separator may be different or the same. Thus, the facing direction of the overlapped separators can be adjusted by simply changing the folding structure. In addition, the separator may have a coating layer formed on one or both surfaces, and the roughness of the one surface and the other surface may be the same or different, so that the facing direction of the separators may be adjusted to adjust the friction coefficient between the separators or between the separator and the electrode included in the separator overlapping portion.

[0033] In particular, when a separator having a coating layer formed on one side is used, the coefficient of friction between the separators or between the separator and the electrode facing each other can be easily adjusted by changing the folding structure of the separator overlapping portion. In addition, in some cases, when a separator having a coating layer formed on one or both sides is used, as described below, the coefficient of friction between the separators or between the separator and the electrode can be easily adjusted. This may prevent damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes during charging and discharging of the battery.

[0034] According to one embodiment of the present invention, the end portion in the length direction of the second separator may be folded in a direction facing the positive electrode on the first surface of the positive electrode, and then further overlapped. Specifically, referring to FIG. 4(b), the first separator overlapping portion S1 may be folded to surround the first separator 20 and one end portion 310 in the length direction of the positive electrode, and the second separator 40 located on the first surface of the positive electrode 300 may be overlapped, and the end portion in the length direction of the second separator 40 may be folded in a direction facing the positive electrode 300 on the first surface of the positive electrode 300, i.e., in the opposite direction to the winding axis direction of the jelly roll type electrode assembly, and then further overlapped.

[0035] According to one embodiment of the present invention, the end portion in the length direction of the second separator may be folded in a direction opposite to the direction facing the positive electrode on the first surface of the positive electrode, and then further overlapped. Specifically, referring to FIG. 3(b), the first separator overlapping portion S1 may be folded to surround the first separator 20 and one end portion 310 in the length direction of the positive electrode, and the second separator 40 located on the first surface of the positive electrode 300 may be overlapped, and the end portion in the length direction of the second separator 40 may be folded in a direction opposite to the direction facing the positive electrode 300 on the first surface of the positive electrode 300, i.e., in the direction of the winding axis of the jelly roll type electrode assembly, and then further overlapped.

[0036] According to one embodiment of the present invention, the second separator overlapping portion may be formed by folding the second separator and one end of the positive electrode in the longitudinal direction so as to surround the first separator located on the second surface of the positive electrode. In other words, the first separator facing the first surface of the positive electrode may be extended from one end of the positive electrode in the longitudinal direction and folded to surround one end of the positive electrode in the longitudinal direction so as to overlap the second separator on the second surface of the positive electrode to form the second separator overlapping portion. This allows the separator to be formed in three or more layers by a simpler folding structure.

[0037] According to one embodiment of the present invention, the end portion in the length direction of the first separator may be folded in a direction facing the positive electrode on the second surface of the positive electrode, and then further overlapped. Specifically, referring to (a) of FIG. 4, the second separator overlapping portion S2 may be folded to surround the second separator 40 and one end portion 310 in the length direction of the positive electrode, and the first separator 20 located on the second surface of the positive electrode 300 may be overlapped, and the end portion in the length direction of the first separator 20 may be folded in a direction facing the positive electrode 300 on the second surface of the positive electrode 300, i.e., in the direction of the winding axis of the jelly roll type electrode assembly, and then further overlapped.

[0038] According to one embodiment of the present invention, the end portion in the length direction of the first separator may be folded in a direction opposite to the direction facing the positive electrode on the second surface of the positive electrode, and then further overlapped. Specifically, referring to (a) of FIG. 3, the second separator overlapping portion S2 may be folded to surround the second separator 40 and one end portion 310 in the length direction of the positive electrode, and the first separator 20 located on the second surface of the positive electrode 300 may be overlapped, and the end portion in the length direction of the first separator 20 may be folded in a direction opposite to the direction facing the positive electrode 300 on the second surface of the positive electrode 300, i.e., in a direction opposite to the winding axis direction of the jelly roll type electrode assembly, and then further overlapped.

[0039] According to one embodiment of the present invention, the end portion in the length direction of the first separator may be folded on the second surface of the positive electrode in a direction opposite to the direction facing the positive electrode and then further overlapped, and the end portion in the length direction of the second separator may be folded on the first surface of the positive electrode in a direction opposite to the direction facing the positive electrode and then further overlapped. Specifically, referring to (a) of FIG. 5, the end portion in the length direction of the first separator 20 may be folded on the second surface of the positive electrode 300 in a direction opposite to the direction facing the positive electrode 300 and then further overlapped to form the second separator overlapping portion S2, and the end portion in the length direction of the second separator 40 may be folded on the first surface of the positive electrode 300 in a direction opposite to the direction facing the positive electrode 300 and then further overlapped to form the first separator overlapping portion S1.

[0040] According to one embodiment of the present invention, the end portion in the length direction of the first separator may be folded on the second surface of the positive electrode in a direction opposite to the direction facing the positive electrode and then further overlapped, and the end portion in the length direction of the second separator may be folded on the first surface of the positive electrode in a direction opposite to the direction facing the positive electrode and then further overlapped. Specifically, referring to (b) of FIG. 5, the end portion in the length direction of the first separator 20 may be folded on the second surface of the positive electrode 300 in a direction opposite to the direction facing the positive electrode 300 and then further overlapped to form the first separator overlapping portion S2, and the end portion in the length direction of the second separator 40 may be folded on the first surface of the positive electrode 300 in a direction facing the positive electrode 300 and then further overlapped to form the first separator overlapping portion S1.

[0041] According to one embodiment of the present invention, the first separator overlapping portion S1 and the second separator overlapping portion S2 may each include a region from one longitudinal end portion 310 of the positive electrode to a position where the second separator 40 or the first separator 20 is further folded, i.e., a region on the first or second surface of the positive electrode, and the length of the region on the first or second surface may be expressed as L11 or L21.

[0042] Furthermore, the first separator overlapping portion S1 and the second separator overlapping portion S2 may each include a region from one longitudinal end portion 310 of the positive electrode to the longitudinal end portion of the second separator 40 or the first separator 20, i.e., a region where the first separator overlapping portion and the second separator overlapping portion do not directly contact the positive electrode 300, and the longitudinal lengths of the regions where the first separator overlapping portion and the second separator overlapping portion do not directly contact the positive electrode 300 may be expressed as L12 or L22, respectively.

[0043] In this case, the longitudinal length of the first separator overlapping portion S1 may be L11+L12, and the longitudinal length of the second separator overlapping portion S2 may be L21+L22, and the longitudinal lengths of the first separator overlapping portion S1 and the second separator overlapping portion S2 may be the same or different from each other.

[0044] According to one embodiment of the present invention, the length of the region of the separator overlapping portion up to the position where the second separator or the first separator is further folded and the length of the region up to the longitudinal end of the second separator or the first separator may be the same or different from each other. That is, the length L11 of the first separator overlapping portion on the first surface of the positive electrode and the length L21 of the second separator overlapping portion on the second surface may be the same or different from the lengths L12, L22 of the regions where the first separator overlapping portion and the second separator overlapping portion do not directly contact the positive electrode 300.

[0045] According to one embodiment of the present invention, the length direction length L11 of the first separator overlapping portion on the first surface of the positive electrode may be 10% or more and 100% or less based on 100% of the circumference of the inner circumferential surface of the electrode assembly. Specifically, the length direction length L11 of the first separator overlapping portion on the first surface of the positive electrode may be 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more based on 100% of the circumference of the inner circumferential surface of the electrode assembly, or may be 100% or less, 90% or less, 80% or less, 70% or less, or 60% or less.

[0046] The length of the first separator overlapping portion on the first surface of the positive electrode in the longitudinal direction may be 1 / 10 turn or more and 1 turn or less of the inner circumferential surface of the core part of the electrode assembly. Specifically, the length L21 of the first separator overlapping portion on the first surface of the positive electrode may be 1 / 10 turn or more, 1 / 5 turn or more, 1 / 3 turn or more, or 1 / 2 turn or more of the inner circumferential surface of the core part of the electrode assembly, or may be 1 turn or less, 4 / 5 turn or less, 2 / 3 turn or less, or 1 / 2 turn or less.

[0047] When the above-described length range in the longitudinal direction of the first separator overlapping portion on the first surface of the positive electrode is satisfied, damage to the negative electrode and separator facing the first surface in the winding axis direction of the positive electrode due to deformation of the electrode assembly caused by contraction / expansion of the electrode during charging / discharging of the battery can be prevented, while 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.

[0048] According to one embodiment of the present invention, the length of the first separator overlapping portion on the first surface of the positive electrode may be 1 mm or more and 10 mm or less. Specifically, the length L21 of the first separator overlapping portion on the first surface of the positive electrode 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 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, or 6 mm or less. In other words, the first separator overlapping portion may be disposed between the positive electrode 300 and the negative electrode 100' facing the first surface of the positive electrode, from one end 310 in the length direction of the positive electrode, 1 mm or more and 10 mm or less, for example, 3 mm or more and 5 mm or less. When the above-mentioned longitudinal length range of the first separator overlapping portion on the first surface of the positive electrode is satisfied, even if a process error exists when the second separator is inserted, the first separator overlapping portion can be disposed between the positive electrode and the negative electrode facing the first surface of the positive electrode, which may be sufficient to prevent damage to the negative electrode and separator facing the first surface of the positive electrode.

[0049] According to one embodiment of the present invention, the length direction length L21 of the second separator overlapping portion on the second surface of the positive electrode may be 10% or more and 100% or less based on 100% of the inner circumferential surface of the electrode assembly. Specifically, the length direction length L21 of the second separator overlapping portion on the second surface of the positive electrode may be 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more based on 100% of the inner circumferential surface of the electrode assembly, or may be 100% or less, 90% or less, 80% or less, 70% or less, or 60% or less.

[0050] The length of the second separator overlapping portion on the second surface of the positive electrode in the longitudinal direction may be 1 / 10 turn or more and 1 turn or less of the inner circumferential surface of the core part of the electrode assembly. Specifically, the length L21 of the second separator overlapping portion on the second surface of the positive electrode may be 1 / 10 turn or more, 1 / 5 turn or more, 1 / 3 turn or more, or 1 / 2 turn or more of the inner circumferential surface of the core part of the electrode assembly, or may be 1 turn or less, 4 / 5 turn or less, 2 / 3 turn or less, or 1 / 2 turn or less.

[0051] When the above-mentioned length range in the longitudinal direction of the second separator overlapping portion on the second surface of the positive electrode is satisfied, damage to the negative electrode and separator facing the second surface, which is in the opposite direction to the winding axis direction of the positive 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.

[0052] According to one embodiment of the present invention, the length of the second separator overlapping portion on the second surface of the positive electrode may be 1 mm or more and 10 mm or less. Specifically, the second separator overlapping portion may be disposed between the positive electrode 300 and the negative electrode 100 facing the second surface of the positive electrode, from one end 310 in the length direction of the positive electrode, 1 mm or more and 10 mm or less, for example, 3 mm or more and 5 mm or less. When the length range of the second separator overlapping portion on the second surface of the positive electrode is satisfied, even if there is a process error when the first separator is inserted, the second separator overlapping portion can be disposed between the positive electrode and the negative electrode facing the second surface of the positive electrode, so that it may be sufficient to prevent damage to the negative electrode and the separator facing the second surface of the positive electrode.

[0053] According to one embodiment of the present invention, the length of the region where the first separator overlapping portion does not directly contact the positive electrode and the length of the region where the second separator overlapping portion does not directly contact the positive electrode may be the same or different from each other, and may be 50% or more and 500% or less based on 100% of the inner circumferential surface of the electrode assembly. Specifically, the length L12 of the region where the first separator overlapping portion does not directly contact the positive electrode and the length L22 of the region where the second separator overlapping portion does not directly contact the positive electrode may be the same or different from each other, and may be 50% or more, 100% or more, 150% or more, 200% or more, or 250% or more, or 500% or less, 450% or less, 400% or less, 350% or less, or 300% or less based on 100% of the inner circumferential surface of the electrode assembly.

[0054] The length of the region where the first separator overlapping portion does not directly contact the positive electrode and the length of the region where the second separator overlapping portion does not directly contact the positive electrode may be 1 / 2 turn or more and 5 turns or less of the inner circumferential surface of the core part of the electrode assembly. Specifically, the length L12 of the region where the first separator overlapping portion does not directly contact the positive electrode and the length L22 of the region where the second separator overlapping portion does not directly contact the positive electrode may be 1 / 2 turn or more, 1 turn or more, 3 / 2 turn or more, or 2 turns or more, or may be 5 turns or less, 9 / 2 turns or less, 4 turns or less, or 7 / 2 turns or less of the inner circumferential surface of the core part of the electrode assembly.

[0055] When the above-mentioned length of the region where the first separator overlapping portion does not directly contact the positive electrode and the length of the region where the second separator overlapping portion does not directly contact the positive electrode are satisfied, the first separator overlapping portion and the second separator overlapping portion can be disposed between the positive electrode and the negative electrode facing the positive electrode without a separate fixing member, and the first separator overlapping portion and the second separator overlapping portion can be formed using existing equipment without the need for separate equipment, thereby improving productivity.

[0056] 3 to 5 and 7 to 9 are schematic diagrams showing a separator overlapping part of a jelly-roll type electrode assembly according to one embodiment of the present invention. Specifically, Figs. 3 to 5 are schematic diagrams showing an embodiment of a separator overlapping part in which the first separator and the second separator are folded in different patterns. Also, Fig. 7 corresponds to (a) in Fig. 3, and Fig. 8 corresponds to (a) in Fig. 4, except for the length of the region where the first separator overlapping part does not directly contact the positive electrode, the length of the region where the second separator overlapping part does not directly contact the positive electrode, and the pattern of one end of the positive electrode in the longitudinal direction.

[0057] Fig. 10 is a schematic diagram showing a core part including a separator overlapping part of a jelly-roll type electrode assembly according to an embodiment of the present invention. Specifically, Fig. 10 is a schematic diagram showing a core part including a separator overlapping part of Fig. 7.

[0058] According to one embodiment of the present invention, the length of the region where the first separator overlapping portion does not directly contact the positive electrode and the length of the region where the second separator overlapping portion does not directly contact the positive electrode may be the same as or different from each other, and may be 50% or less based on 100% of the inner circumferential surface of the electrode assembly. Specifically, the length L12 of the region where the first separator overlapping portion does not directly contact the positive electrode and the length L22 of the region where the second separator overlapping portion does not directly contact the positive electrode may be the same as or different from each other, and may be 50% or less, 45% or less, 40% or less, 35% or less, or 30% or less based on 100% of the inner circumferential surface of the electrode assembly.

[0059] Furthermore, the length of the region where the first separator overlapping portion does not directly contact the positive electrode and the length of the region where the second separator overlapping portion does not directly contact the positive electrode may be 1 / 2 turn or less of the inner circumferential surface of the core part of the electrode assembly. Specifically, the length L12 of the region where the first separator overlapping portion does not directly contact the positive electrode and the length L22 of the region where the second separator overlapping portion does not directly contact the positive electrode may be 1 / 2 turn or less, 1 / 3 turn or less, 1 / 4 turn or less, or 1 / 5 turn or less of the inner circumferential surface of the core part of the electrode assembly.

[0060] When the above-mentioned length range of the region where the first separator overlapping portion does not directly contact the positive electrode and the length range of the region where the second separator overlapping portion does not directly contact the positive electrode are satisfied, an additional fixing member may be further included so that the first separator overlapping portion and the second separator overlapping portion can be disposed between the positive electrode and the negative electrode facing the positive electrode, as described below, and one side of the first separator overlapping portion and the second separator overlapping portion can be directly fixed onto the first surface or the second surface of the positive electrode, thereby making it possible to more effectively prevent damage to the negative electrode and separator facing the first surface or the second surface of the positive electrode.

[0061] Figures 6 and 9 are schematic diagrams showing a separator overlapping part of a jelly-roll type electrode assembly according to one embodiment of the present invention. Specifically, Figure 6 is a schematic diagram showing one embodiment of a separator overlapping part including a cut separator, and Figure 9 is a schematic diagram showing a separator overlapping part corresponding to (a) of Figure 6, except for the length of the region where the first separator overlapping part does not directly contact the positive electrode, the length of the region where the second separator overlapping part does not directly contact the positive electrode, and the shape of one end of the positive electrode in the longitudinal direction.

[0062] According to one embodiment of the present invention, at least one of the first separator overlapping portion and the second separator overlapping portion may include a cut separator. Specifically, referring to Figs. 6(a) and 6(b) and Fig. 9, the first separator overlapping portion S1 provided on the first surface of the positive electrode 300 may include the first separator 20; the second separator 40 extended from one end of the positive electrode in the longitudinal direction; and a cut separator P. Also, the second separator overlapping portion S2 provided on the second surface of the positive electrode 300 may include the second separator 40; the first separator 20 extended from one end of the positive electrode in the longitudinal direction; and a cut separator P. When at least one of the first separator overlap portion and the second separator overlap portion includes a split separator, the separators constituting the separator overlap portion can be more easily adjusted to three or more layers, and by forming a coating layer on one or both sides of the split separator, the friction coefficient between the separators or between the separator and the positive electrode included in the separator overlap portion can be more easily adjusted.

[0063] According to one embodiment of the present invention, the first separator overlapping portion S1 and the second separator overlapping portion S2 may each include a region from one longitudinal end 310 of the positive electrode to one longitudinal end of the cut separator P, and the longitudinal lengths of the region may be expressed as L13 and L23, respectively. Also, the first separator overlapping portion S1 and the second separator overlapping portion S2 may each include a region from one longitudinal end 310 of the positive electrode to the other longitudinal end of the cut separator P, and the longitudinal lengths of the region may be expressed as L14 and L24, respectively. The L13 and L14, and the L23 and L24 may be the same or different from each other, and the longitudinal length of the cut separator included in the first separator overlapping portion S1 may be L13+L14, and the longitudinal length of the cut separator included in the second separator overlapping portion S2 may be L23+L24.

[0064] Furthermore, L13 and L23 may be the same as or different from L11 and L21, respectively, L14 and L24 may be the same as or different from L12 and L22, respectively, the longitudinal length of the first separator overlapping portion S1 and the longitudinal length L13+L14 of the cut separator P included in the first separator overlapping portion S1 may be the same as or different from each other, and the longitudinal length of the second separator overlapping portion S2 and the longitudinal length L23+L24 of the cut separator P included in the second separator overlapping portion S2 may be the same as or different from each other.

[0065] According to one embodiment of the present invention, the length of the cut separator included in the first separator overlapping portion S1 in the longitudinal direction may be 5 mm or more and 50 mm or less. When the length of the cut separator P in the longitudinal direction satisfies the above-mentioned L13+L14 range, damage to the negative electrode and separator facing the first surface in the winding axis direction of the positive 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 negative electrode that receives lithium ions can be prevented, resulting in excellent battery stability and life characteristics.

[0066] According to one embodiment of the present invention, the length of the cut separator included in the second separator overlapping portion S2 in the longitudinal direction may be 5 mm or more and 50 mm or less. When the length of the cut separator P in the longitudinal direction satisfies the range of L23+L24 described above, damage to the negative electrode and separator facing the second surface, which is in the opposite direction to the winding axis direction of the positive 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.

[0067] According to one embodiment of the present invention, at least one of the first separator overlapping portion and the second separator overlapping portion may further include a fixing member provided on one side. The fixing member is not limited as long as it can fix the first separator overlapping portion or the second separator overlapping portion to the first surface or the second surface of the positive electrode, respectively. The fixing member may be, for example, a tape having an adhesive layer on at least one surface of a base layer or an adhesive layer. When a tape having an adhesive layer on one surface of a base layer is used, it is more suitable for a roll-to-roll process and processability can be improved.

[0068] According to one embodiment of the present invention, the width direction length of the fixing member may be 15% or more and 100% or less based on 100% of the width direction length of the positive electrode. Specifically, the width direction length of the fixing member may be 30% or more or 50% or more, 80% or less or 60% or less based on 100% of the width direction length of the positive electrode, for example, 10 mm or more and 65 mm or less. In addition, the length direction length of the fixing member may be 5 mm or more and 30 mm or less, for example, 5 mm or more and 15 mm or less, 10 mm or more and 20 mm or less, or 15 mm or more and 30 mm or less. When the above-mentioned length range of the fixing member is satisfied, the first separator overlapping portion and the second separator overlapping portion can be easily disposed between the positive electrode and the negative electrode facing the positive electrode.

[0069] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. Specifically, referring to Fig. 3, the positive electrode 300 may include a positive electrode current collector 301 and positive electrode active material layers 302, 303 formed on one or both sides of the positive electrode current collector 301 and including a positive electrode active material. In other words, the positive electrode active material layer may be formed on a positive electrode active material-coated portion of the positive electrode current collector, and a surface not including the positive electrode active material layer may be represented as a positive electrode uncoated portion.

[0070] According to an embodiment of the present invention, the positive electrode current collector may include a positive electrode active material coated portion on which a positive electrode active material is coated and a positive electrode uncoated portion on which a positive electrode active material is not coated, or may include a tab on the positive electrode uncoated portion. Specifically, the positive electrode current collector may include a positive electrode uncoated portion, or may include a positive electrode tab 330 formed on the positive electrode uncoated portion.

[0071] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and having a longitudinal end at the same position as the positive electrode current collector. Specifically, referring to FIG. 3 to FIG. 6, the positive electrode 300 may include a positive electrode current collector 301; and a positive electrode active material layer 302, 303 provided on at least one surface of the positive electrode current collector 301 and having a longitudinal end (one longitudinal end 310 of the positive electrode) at the same position as the positive electrode current collector 301. In other words, one longitudinal end 310 of the positive electrode may be in the form of a free edge. This can reduce the area of ​​the unnecessary positive electrode current collector uncoated portion to ensure economic efficiency. In addition, a slitting process may be performed after forming an active material layer on an electrode, so that a roll-to-roll process including a slitting process and a winding process can be performed more efficiently. Here, "the same position" means that the longitudinal ends are the same, and may include cases where the ends are formed at substantially the same position due to process errors that may occur in a slitting process, etc.

[0072] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and having no end in the longitudinal direction at the same position as the positive electrode current collector. Specifically, referring to Fig. 7 to Fig. 9, the positive electrode 300 may include a positive electrode current collector 301; and positive electrode active material layers 302, 303 provided on at least one surface of the positive electrode current collector 301 and having no end in the longitudinal direction (one end 310 in the longitudinal direction of the positive electrode) at the same position as the positive electrode current collector 301.

[0073] 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 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.

[0074] The positive electrode current collector may have a thickness of 3 to 50 um, and may have fine irregularities on the surface of the current collector 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, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, etc.

[0075] 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), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+x Mn 2-x O4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M yLithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦y≦0.3 is satisfied); 2-z M z Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese oxide represented by Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦z≦0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The positive electrode may be Li-metal.

[0076] 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 used without any particular limitation as long as it does not induce chemical changes in the battery that is constructed and has electronic conductivity. 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 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. One or a mixture of two or more of these may be used.

[0077] In addition, 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, and various copolymers thereof, and one or more of these may be used alone or in combination.

[0078] According to one embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. Specifically, referring to Fig. 3, the negative electrode 100 may include a negative electrode current collector 101 (including a longitudinal end 110 of the negative electrode) and a negative electrode active material layer 102, 103 formed on one or both sides of the negative electrode current collector 101 and including a negative electrode active material. In other words, the negative electrode active material layer may be formed on a negative electrode active material coated portion of the negative electrode current collector, and a surface not provided with the negative electrode active material layer may be represented as a negative electrode uncoated portion.

[0079] According to an embodiment of the present invention, the negative electrode current collector may include a negative electrode active material coated portion where a negative electrode active material layer is formed, and a negative electrode uncoated portion where a negative electrode active material layer is not formed, and may include a tab on the negative electrode uncoated portion. Specifically, the negative electrode current collector may include a negative electrode uncoated portion, and may include a negative electrode tab 130 formed on the negative electrode uncoated portion. Thus, the manufactured electrode assembly may include one or more negative electrode tabs.

[0080] 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 silicon-based materials and carbon-based materials. 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.

[0081] According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and has high conductivity. For example, 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 easily 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 um or more and 80 um or less, but the thickness of the negative electrode current collector is not limited thereto.

[0082] 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.

[0083] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity, and examples of the negative electrode conductive material that may be used 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.

[0084] 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.

[0085] According to one 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, and when the battery case is cylindrical, it may be 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 the battery case for accommodating the electrode assembly may be cylindrical.

[0086] The secondary battery according to the present invention can prevent an internal short circuit between the positive and negative electrodes by the separator overlapping portion 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.

[0087] According to one embodiment of the present invention, the inside of the battery case may contain an electrolyte. Specifically, the electrolyte may be, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used in manufacturing a lithium secondary battery. Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0088] 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, γ-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.

[0089] 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. For example, the anion of the lithium salt is F - , Cl - , I - , NO3 - , N(CN) 2- , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 -, (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0090] According to one embodiment of the present invention, in addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, 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, and 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.

[0091] The above detailed description is illustrative and explanatory of the present invention. Moreover, the above content merely shows 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 can be changed or modified 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 claims should be construed to include other embodiments.

Claims

1. A jelly-roll type electrode assembly in which a negative electrode, a first separator, a positive electrode, and a second separator are sequentially stacked and wound, The positive 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 first separator overlapping portion and a second separator overlapping portion provided on a first surface of the positive electrode and a second surface of the positive electrode, respectively, at one end of the positive electrode in a longitudinal direction located at a core portion of the jelly-roll type electrode assembly; The first separator overlapping portion and the second separator overlapping portion each include three or more overlapping separators.

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 overlapping the first separator and the second separator extending from one end of the positive electrode in a longitudinal direction.

3. a longitudinal end portion of the first separator is folded so as to surround one longitudinal end portion of the positive electrode and is positioned on a second surface side of the positive electrode; 3. The jelly roll type electrode assembly according to claim 2, wherein a longitudinal end of the second separator is folded so as to surround the folded first separator and is positioned on a first surface side of the positive electrode.

4. a longitudinal end portion of the second separator is folded so as to surround one longitudinal end portion of the positive electrode and is positioned on a first surface side of the positive electrode; 3. The jelly roll type electrode assembly according to claim 2, wherein a longitudinal end of the first separator is folded to surround the folded second separator and is positioned on a second surface side of the positive electrode.

5. In the first separator overlapping portion, 2. The jelly roll type electrode assembly according to claim 1, wherein the first separator and the second separator are folded to surround one longitudinal end of the positive electrode and positioned on the first surface of the positive electrode, and are overlapped.

6. 6. The jelly roll type electrode assembly of claim 5, wherein the second separator is folded and overlapped at a longitudinal end of the second separator in a direction facing the positive electrode on the first surface of the positive electrode.

7. 6. The jelly roll type electrode assembly of claim 5, wherein the second separator is folded and overlapped at a longitudinal end of the second separator in a direction opposite to a direction facing the positive electrode on the first surface of the positive electrode.

8. In the second separator overlapping portion, 2. The jelly roll type electrode assembly according to claim 1, wherein the second separator and the first separator, which is folded to surround one longitudinal end of the positive electrode and positioned on the second surface of the positive electrode, are overlapped.

9. 9. The jelly roll type electrode assembly of claim 8, wherein the first separator is folded and overlapped at a longitudinal end of the first separator in a direction facing the positive electrode on the second surface of the positive electrode.

10. 9. The jelly roll type electrode assembly of claim 8, wherein the first separator is folded and overlapped at a longitudinal end of the first separator in a direction opposite to a direction facing the positive electrode on the second surface of the positive electrode.

11. The jelly-roll type electrode assembly of claim 1 , wherein at least one of the first separator overlapping portion and the second separator overlapping portion includes a cut separator.

12. The jelly-roll type electrode assembly of claim 1 , wherein at least one of the first separator overlapping portion and the second separator overlapping portion further comprises a fixing member provided on one side thereof.

13. 2. The jelly roll type electrode assembly of claim 1, wherein the positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and having a longitudinal end at the same position as the positive electrode current collector.

14. A jelly roll type electrode assembly according to any one of claims 1 to 13, and a battery case for housing the jelly-roll type electrode assembly; A secondary battery comprising:

15. The secondary battery according to claim 14 , wherein the battery case is cylindrical.

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