Electrode assembly and electrochemical element including the same

Abstract

A negative electrode structure and an electrode assembly including a plurality of positive electrodes are provided. The negative electrode structure includes a first and a second separator, and a lithium metal layer interposed between the first and the second separators. The negative electrode structure is divided into a plurality of stack portions, a plurality of folding portions, and first and second wrapping portions according to its position in the electrode assembly. Between the first and the second wrapping portions respectively located at the ends of the negative electrode structure, the stack portions and the folding portions are alternately positioned, and the first and the second wrapping portions are each in contact with a stack portion. Due to the folding portions, in the electrode assembly, the plurality of stack portions are sequentially arranged side by side in the thickness direction, and at least one positive electrode is positioned between adjacent stack portions in the thickness direction. The second wrapping portion in the electrode assembly is positioned to be in contact with the first wrapping portion, and has a structure in which the outer surfaces in the thickness direction and the length direction are surrounded by the second wrapping portion, or the second wrapping portion and one or more of the first wrapping portion and the outermost stack portion.

Description

Technical Field

[0001] The present invention relates to an electrode assembly and an electrochemical device including the same. Specifically, the present invention relates to an electrode assembly including a lithium metal in a negative electrode and an electrochemical device including the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0136198 filed on October 21, 2022, Korean Patent Application No. 10-2023-0070481 filed on May 31, 2023, and Korean Patent Application No. 10-2023-0139505 filed on October 18, 2023, and includes all the contents disclosed in the documents of the Korean patent applications as part of this specification.

Background Art

[0003] Recently, interest in energy storage technology has been increasing. The application fields have expanded to include mobile phones, video cameras, notebook PCs, and even the energy of electric vehicles, and efforts in battery research and development have become more concrete. Electrochemical devices are the most notable fields in this regard, and in particular, with the recent trend of miniaturization and weight reduction of electronic devices, the development of secondary batteries as small, lightweight, and high-capacity rechargeable batteries has become the focus of interest.

[0004] In addition, secondary batteries may be classified according to the structure of the electrode assembly having a positive electrode / separator / negative electrode structure. As a representative example, the electrode assembly is a jelly-roll (wound type) electrode assembly having a structure in which a long sheet-shaped positive electrode and a negative electrode are wound with a separator interposed therebetween, and a stack type (laminated type) electrode assembly in which a large number of positive electrodes and negative electrodes cut out in a predetermined size unit are sequentially laminated with a separator interposed therebetween.

[0005] However, such conventional electrode assemblies have several problems.

[0006] First, the jelly-roll electrode assembly winds a long sheet-like positive electrode and negative electrode in a densely packed state to form a cylindrical or elliptical structure in cross-section. In such a structure, stress induced by the expansion and contraction of the electrodes during charge and discharge is accumulated inside the electrode assembly. When the accumulation of such stress exceeds a certain limit, deformation of the electrode assembly occurs. Furthermore, the deformation of the electrode assembly may cause problems such as making the distance between the electrodes non-uniform, rapidly degrading the performance of the battery, and threatening the safety of the battery due to internal short circuit. Also, since the jelly-roll electrode assembly needs to wind a long sheet-like positive electrode and negative electrode, it is difficult to quickly wind while keeping the distance between the positive electrode and the negative electrode constant, and there is also a problem of reduced productivity.

[0007] Second, the stacked electrode assembly must sequentially stack a large number of positive and negative electrode units. At this time, a separate process for transferring the electrode plates for manufacturing the units is required, and a large amount of time and effort are required for the sequential stacking process. Therefore, the stacked electrode assembly has a problem of low productivity.

[0008] To solve such problems, a stack-folded type electrode assembly with an evolved structure, which is a hybrid form of the jelly-roll type and the stacked type, has been developed. The stack-folded type electrode assembly has a structure in which a bi-cell or full cell stacked with a separator interposed between a positive electrode and a negative electrode of a predetermined unit is wound using a long continuous separator sheet (folded separator).

[0009] The stack-foldable electrode assembly generally extends a separator that is easier to fold than the electrodes to connect the electrodes of each layer. At this time, the electrodes of each layer are supplied for forming the electrode assembly in a cut state, similar to the stack-type electrode assembly. Among the various electrode materials constituting the secondary battery in the art, when the secondary battery is constituted only of materials that are easy to cut or not easy to fold, such a general stack-foldable electrode assembly is more suitable. On the other hand, lithium metal, which is well-known as a negative electrode material of a secondary battery in the art, has physical properties of high ductility and viscosity, so processing such as cutting is not easy, and relatively easy to fold, so it may not be suitable for a conventional stack-foldable electrode assembly.

[0010] As a result of continuous research on the structure of the electrode assembly, the inventor designed a structure suitable for an electrode assembly containing lithium metal particularly as a negative electrode, and completed the present invention.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention provides an electrode assembly having a new structure suitable for an electrode assembly containing lithium metal as a negative electrode, and an electrochemical element including the same.

Means for Solving the Problems

[0013] According to a first aspect of the present invention, The present invention provides an electrode assembly including a negative electrode structure and a plurality of positive electrodes.

[0014] In one embodiment of the present invention, the negative electrode structure includes a first and a second separator, and a lithium metal layer interposed between the first and second separators.

[0015] In one embodiment of the present invention, the negative electrode structure is divided into a plurality of stack portions, a plurality of folding portions, and first and second wrapping portions according to its position in the electrode assembly.

[0016] In one embodiment of the present invention, between the first and second wrapping portions respectively located at the ends of the negative electrode structure, the stack portions and the folding portions are alternately positioned, and the first and second wrapping portions are each in contact with a stack portion.

[0017] In one embodiment of the present invention, in the electrode assembly, due to the folding portions, a plurality of stack portions are sequentially arranged side by side in the thickness direction, and at least one positive electrode is positioned between adjacent stack portions in the thickness direction.

[0018] In one embodiment of the present invention, the second wrapping portion in the electrode assembly is positioned in contact with the first wrapping portion, and the outer surfaces in the thickness direction and the length direction have a structure surrounded by the second wrapping portion, or the second wrapping portion and one or more of the first wrapping portion and the outermost stack portion.

[0019] In one embodiment of the present invention, the plurality of stack portions and the plurality of positive electrodes in the electrode assembly are in close contact in the thickness direction by the first and second wrapping portions.

[0020] In one embodiment of the present invention, the second wrapping portion of the negative electrode structure surrounds both the first wrapping portion surrounding one side surface of the electrode laminate and the opposite side surface of the electrode laminate.

[0021] In one embodiment of the present invention, the ends of the first and second wrapping portions of the negative electrode structure are located on the same line.

[0022] In one embodiment of the present invention, at least one positive electrode is located between a stack portion positioned in contact with a first wrapping portion of the negative electrode structure and a second wrapping portion positioned parallel to the stack portion.

[0023] In one embodiment of the present invention, one positive electrode is located between stack portions adjacent in the thickness direction, and the total number of positive electrodes located between stack portions in the electrode assembly is 2n (where n is a natural number).

[0024] In one embodiment of the present invention, the positive electrode in the electrode assembly includes a positive electrode active material layer and a current collector that supports the positive electrode active material layer, and the negative electrode does not include a current collector that supports a lithium metal layer.

[0025] In one embodiment of the present invention, the lengths of the lithium metal layer and the first and second separator membranes in the negative electrode structure are the same.

[0026] In one embodiment of the present invention, the end of the first wrapping portion in the negative electrode structure is located on the stack portion in contact with the second wrapping portion by turning around one side surface of the electrode assembly adjacent to the first wrapping portion so as to wrap the side surface, and the end of the second wrapping portion is located on the first wrapping portion.

[0027] In one embodiment of the present invention, the electrode assembly further includes a fixing member for fixing the ends of the first and second wrapping portions on the outermost stack portion.

[0028] In one embodiment of the present invention, the length of the folding portion in the negative electrode structure is 2 to 10 times based on the total thickness of the positive electrode and the negative electrode structure.

[0029] In one embodiment of the present invention, the length of the folding portion in the negative electrode structure is 2 to 10 times based on the vertical distance between the end of the positive electrode and the side wrapping portion that wraps it.

[0030] In one embodiment of the present invention, the folding portion has an asymmetric shape with respect to a plane along the length direction.

[0031] In one embodiment of the present invention, the thickness of the lithium metal layer in the negative electrode structure occupies 50% to 90% based on the total thickness of the negative electrode structure.

[0032] In one embodiment of the present invention, the thickness of the positive electrode is greater than the thickness of the negative electrode structure.

[0033] In one embodiment of the present invention, the fixing member is an insulating tape.

[0034] In one embodiment of the present invention, the center point of the length of the folding portion is not aligned with the center point of the thickness of the positive electrode wrapped by the folding portion.

[0035] In one embodiment of the present invention, the positive electrode located between the stack portion in contact with the first wrapping portion and the second wrapping portion adjacent in the thickness direction is longer than other positive electrodes.

[0036] In one embodiment of the present invention, the end of the second wrapping portion is located on the first wrapping portion.

[0037] In one embodiment of the present invention, the end of the second wrapping portion is located on the outermost stack portion.

[0038] In one embodiment of the present invention, the electrode assembly includes a first fixing member for fixing the first wrapping portion and a second fixing member for fixing the second wrapping portion.

[0039] According to a second aspect of the present invention, The present invention provides an electrochemical element including the aforementioned electrode assembly.

[0040] In one embodiment of the present invention, the electrochemical element is a lithium secondary battery.

[0041] In one embodiment of the present invention, the electrochemical element is a lithium-sulfur battery.

Advantages of the Invention

[0042] By manufacturing an electrode assembly by utilizing a single negative electrode structure in a continuous form in which a negative electrode containing lithium metal is interposed between two separator membranes, cutting of the lithium metal can be minimized, and the process efficiency in manufacturing the electrode assembly can be improved.

[0043] Further, by adjusting the methods and conditions in stacking, folding, and wrapping according to the material characteristics of the negative electrode structure, the manufactured electrode assembly not only has a stable structure but also the performance of the battery can be improved.

Brief Description of the Drawings

[0044]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0045] Hereinafter, embodiments will be described in detail through exemplary drawings. It should be noted that when adding reference numerals to the components of each drawing, the same components are given the same reference numerals as much as possible even if they are shown on different drawings. Further, in describing the embodiments, if a specific description of a related known configuration or function is determined to impede the understanding of the embodiments, the detailed description thereof will be omitted.

[0046] Also, when describing the components of the embodiments, terms such as first, second, A, B, (a), (b), etc. can be used. These terms are for distinguishing the components from other components, and the essence, order, or sequence of the components are not limited by these terms. When a component is described as being "connected", "coupled", or "joined" to another component, it may be directly connected or joined to the other component, but it should be understood that other components may also be "connected", "coupled", or "joined" between the components.

[0047] Components included in any one embodiment and components having a common function will be described using the same name in other embodiments. Unless otherwise stated, the description given in any one embodiment can be applied to other embodiments, and specific descriptions within the overlapping scope will be omitted.

[0048] The present invention relates to an electrode assembly, which improves problems that may occur when applying lithium metal as a negative electrode to a conventional stack-foldable electrode assembly structure, and provides a novel-structured electrode assembly suitable for using lithium metal as a negative electrode. The electrode assembly according to the present invention can not only improve the processability during the assembly process by minimizing the processing of lithium metal, but also enhance the reliability of the manufactured product. In addition, the electrode assembly has a structure that can maximize the utilization of the positive electrode included in the electrode assembly, and can contribute to improving the performance of the battery.

[0049] In this specification, the terms "length direction", "width direction" and "thickness direction" (or "height direction") are used. In this specification, drawings such as FIGS. 1 to 6 are front views. Based on the front view, the "length direction" means the left-right direction in the drawing, the "width direction" means the front-back direction in the drawing, and the "thickness direction" (or "height direction") means the up-down direction in the drawing.

[0050] In this specification, the term "adjacent" means the object that is located closest to the reference among a plurality of objects referred to. The adjacent object is not necessarily in contact with the reference.

[0051] According to an embodiment of the present invention, an electrode assembly includes a positive electrode, a negative electrode, and a separator. In the electrode assembly, the positive electrode and the separator are not particularly limited as long as they are materials generally used in the art, but the negative electrode contains lithium metal. In this specification, lithium metal may have some components added to lithium or be in the form of an alloy with some metals, as long as there is no significant difference in physical properties from lithium metal and the same problems may occur when applied to a conventional electrode assembly as with lithium metal, it can be broadly interpreted. In this specification, since the negative electrode contains lithium metal, it can be named a lithium metal layer, and since the negative electrode and the separator are supplied in an integrated configuration, it can be named a negative electrode structure.

[0052] According to an embodiment of the present invention, the negative electrode is interposed between two separators to form a negative electrode structure. In this specification, the two separators constituting the negative electrode structure can be named the first and second separators. The negative electrode structure has a structure extending in the length direction, and the electrode assembly includes only one negative electrode structure. A basic electrode assembly structure is formed by folding the negative electrode structure having a structure extending in the length direction and fixing the positive electrode inside.

[0053] According to an embodiment of this specification, the negative electrode structure includes a plurality of stack portions, a plurality of folding portions, and two wrapping portions according to its position in the electrode assembly. In this specification, the two wrapping portions included in the negative electrode structure can be named the first and second wrapping portions. To assist in understanding the structure of the negative electrode structure, FIG. 1 provides an exemplary structure of a negative electrode structure including a stack portion, a folding portion, and a wrapping portion. In the negative electrode structure (10), the stack portions (10A, 10A’, 10A’’), the folding portion (10B), and the wrapping portions (10C, 10C’) are units that divide positions having different functions according to the length direction of the negative electrode structure (10). The stack portions (10A, 10A’, 10A’’), the folding portion (10B), and the wrapping portions (10C, 10C’) are not divided by materials other than positions.

[0054] The stack portions (10A, 10A', 10A'') mean the negative electrode structures (10) at the positions where the positive electrodes are stacked, and mainly have a linear shape based on FIG. 2 and the like. The folding portion (10B) means the negative electrode structure (10) at the position connecting between the stack portions, and mainly has a curved shape based on FIG. 2 and the like. The folding portion (10B) can also be named as a bending portion. The first wrapping portion (10C) means the negative electrode structure at the position wrapping the stacked structure of the positive electrode and the negative electrode structure from the time point of contacting the lowermost outermost stack portion (10A'). Also, the second wrapping portion (10C') means the negative electrode structure at the position wrapping the stacked structure of the positive electrode and the negative electrode structure and the first wrapping portion (10C) from the time point of contacting the uppermost outermost stack portion (10A''). Based on FIG. 2 and the like, a linear shape and a curved shape are mixed.

[0055] As shown in FIG. 1, at both ends of the negative electrode structure (10) with respect to the length direction, the first and second wrapping portions (10C, 10C') are located. That is, the two wrapping portions (10C, 10C') are respectively located at the ends in the length direction of the negative electrode structure (10). Here, the first wrapping portion (10C) contacts the first outermost stack portion (10A'), and the second wrapping portion (10C') contacts the second outermost stack portion (10A''). Between the first outermost stack portion (10A') and the second outermost stack portion (10A''), the folding portion (10B) and the stack portion (10A) are alternately located. Since the stack portions (10A, 10A', 10A'') are substantially the same as the length of the positive electrode, the lengths of the respective stack portions (10A, 10A', 10A'') are substantially the same.

[0056] The two wrapping portions (10C) located at both ends of the negative electrode structure (10) can have different lengths. In this specification, in order to distinguish the two wrapping portions (10C), if the wrapping portion (10C) located at the starting point of the lamination is named the first wrapping portion, the wrapping portion (10C') located at the ending point of the lamination is named the second wrapping portion. The first and second wrapping portions can also be named the other way around. According to an embodiment of the present invention, the second wrapping portion (10C') of the negative electrode structure surrounds both the first wrapping portion (10C) surrounding one side surface of the electrode laminate and the side surface opposite to the electrode laminate. Therefore, the second wrapping portion (10C') is located outside the electrode assembly (1) compared to the first wrapping portion (10C). Considering the convenience of the process, the first wrapping portion (10C) located at the starting point of the lamination may be shorter than the second wrapping portion (10C') located at the ending point of the lamination. The second wrapping portion (10C') can have a length that is even longer so as to wrap, in addition to the first wrapping portion (10C), the side surface opposite to the electrode laminate and the stack portion (10A') in contact with the first wrapping portion (10C) or an additional positive electrode.

[0057] According to one embodiment of the present invention, the ends of the first and second wrapping portions (10C, 10C') of the negative electrode structure are located on the same line. The electrode assembly (1) according to one embodiment of the present invention basically has a structure in which the second wrapping portion (10C') wraps the first wrapping portion (10C). The fact that the second wrapping portion (10C') wraps the first wrapping portion (10C) does not, in a strict sense, allow the inner wrapping portion (10C, 10C') to be exposed to the outside, but in this specification, it is not interpreted in a strict sense. Therefore, in the electrode assembly according to one embodiment of the present invention, the ends of the first wrapping portion (10C) and the second wrapping portion (10C') may be located on the same line, but they are not located on the same line, the second wrapping portion (10C') is slightly shorter, and the end of the first wrapping portion (10C) is exposed, or the second wrapping portion (10C') is slightly longer and can completely cover the end of the first wrapping portion (10C). According to one embodiment of the present invention, the end of the second wrapping portion is located on the first wrapping portion, or the end of the second wrapping portion is located on the outermost stack portion. When the ends of the first wrapping portion (10C) and the second wrapping portion (10C') are located on the same line, the structure can be arranged more simply. When the second wrapping portion (10C') is slightly shorter and the end of the first wrapping portion (10C) is exposed, the second wrapping portion (10C') and the first wrapping portion (10C) can be fixed simultaneously by taping. Also, when the second wrapping portion (10C') is slightly longer and completely wraps the end of the first wrapping portion (10C), the negative electrode at the end of the first wrapping portion may not be exposed to the outside either.

[0058] The negative electrode structure (10) forms an electrode assembly together with a plurality of positive electrodes. To assist in understanding the structure of the electrode assembly, FIG. 2 provides an exemplary structure of an electrode assembly including a negative electrode structure and a positive electrode. Since the negative electrode structure (10) includes a negative electrode (11) and a separator (12), the electrode assembly (1) includes a positive electrode (20), a negative electrode (11), and a separator (12).

[0059] According to an embodiment of the present invention, in the electrode assembly (1), a plurality of stack portions (10A, 10A', 10A'') are sequentially arranged side by side in the thickness direction by a folding portion (10B), and at least one positive electrode is located between the stack portions (10A, 10A', 10A'') adjacent to each other in the thickness direction. According to an embodiment of the present invention, in the electrode assembly (1), the second wrapping portion (10C') is located so as to be in contact with the first wrapping portion (10C), and has a structure in which the outer surfaces in the thickness direction and the length direction are surrounded by the second wrapping portion (10C'), or one or more of the second wrapping portion (10C') and the first wrapping portion (10C) and the outermost stack portion (10A''). Here, the reason for expressing "one or more of the first wrapping portion (10C) and the outermost stack portion (10A'')" is that the ends of the second wrapping portion and the first wrapping portion may not coincide. With reference to FIG. 2, in other words, one side surface of the electrode laminate in which the stack portions (10A, 10A', 10A'') of the negative electrode structure and the positive electrode are alternately laminated in sequence is surrounded by the first wrapping portion (10C). At this time, only one positive electrode (20) is located between the stack portions (10A, 10A', 10A'') of the negative electrode structure. Further, the outside of the electrode assembly (1) has a structure surrounded by the stack portion (10A'') of the negative electrode structure and the second wrapping portion (10C'). Here, the inside and the outside of the electrode assembly (1) are divisions of the region of the electrode assembly (1) for helping the understanding of the structure of the electrode assembly (1) according to the present invention. With reference to FIG. 2, in the electrode assembly, in the thickness direction and the length direction, the layer exposed to the outside means the outside of the electrode assembly (1), and the inner portion of the outside of the electrode assembly (1) means the inside of the electrode assembly (1).In the negative electrode structure (10), the stack portions (10A, 10A', 10A'') mean the negative electrode structure (10) at the position where the positive electrodes are stacked. Since the second wrapping portion (10C') starts when the uppermost second outermost stack portion (10A'') ends, as shown in FIG. 2, when the end of the second wrapping portion (10C') is located above the uppermost second outermost stack portion (10A''), a part of the uppermost second outermost stack portion (10A'') can be located outside the electrode assembly (1), and the remaining part of the uppermost second outermost stack portion (10A'') can be located inside the electrode assembly (1). Therefore, in this specification, the stack portion located inside or outside may mean the whole or a part of one stack portion. Different from FIG. 2, when the second wrapping portion (10C') covers the whole of the uppermost second outermost stack portion (10A''), the outside of the electrode assembly (1) can be formed only by the second wrapping portion. When the first wrapping (10C) covers the whole of the uppermost second outermost stack portion (10A'') and the end of the second wrapping portion cannot reach the end of the first wrapping portion, the outside of the electrode assembly (1) can be formed only by the first and second wrapping portions. Also, when the first wrapping portion (10C) covers only a part of the uppermost second outermost stack portion (10A'') and the end of the second wrapping portion cannot reach the end of the first wrapping portion, the outside of the electrode assembly (1) can be formed by the first and second wrapping portions (10C, 10C') and the second outermost stack portion (10A''). In any case, the plurality of folding portions (10B) are wrapped by the first and second wrapping portions (10C, 10C') and are not exposed to the outside in the thickness direction and the length direction.

[0060] According to one embodiment of the present invention, in the electrode assembly (1), since the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are alternately and sequentially stacked inside, the negative electrode structure (10) including the folding portion (10B) has a zigzag shape. That is, the folding portions (10B) sequentially positioned from the stack portion (10A') in contact with the first or second wrapping portion (10C, 10C') of the negative electrode structure (10) are alternately positioned on the left or right side in the electrode assembly (1). If the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are not alternately stacked and two or more of the stack portions or the positive electrodes are continuously stacked, no potential difference will occur between the continuously stacked layers, and the efficiency of the battery may decrease.

[0061] According to one embodiment of the present invention, in the electrode assembly (1), the plurality of stack portions (10A, 10A', 10A'') and the plurality of positive electrodes (20) are adhered in the thickness direction by the first and second wrapping portions (10C, 10C'). The first and second wrapping portions (10C, 10C') can wrap the inside of the electrode assembly (1) with a higher tension compared to the stack portions (10A, 10A', 10A'') or the folding portion (10B), whereby the internal components of the electrode assembly (1) are adhered in the thickness direction. In such a manner, when the internal components of the electrode assembly (1) are adhered in the thickness direction, inevitably, the internal components of the electrode assembly (1) will be adhered in the length direction. However, even if the internal components of the electrode assembly (1) are adhered in the thickness direction and the length direction, due to the structure of the electrode assembly (1), there may be voids above a certain level around the folding portion (10B).

[0062] According to an embodiment of the present invention, at least one positive electrode is located between a stack portion (10A') positioned in contact with a first wrapping portion (10C) of the negative electrode structure (10) and a second wrapping portion (10C') positioned parallel to the stack portion (10A'). When no positive electrode is added, the stack portion (10A') of the negative electrode structure (10) and the second wrapping portion (10C') adjacent in the thickness direction are in face-to-face contact. Here, the added positive electrode (20) means the lowermost positive electrode among the positive electrodes in FIG. 2. By adding the positive electrode (20) to this portion, the second wrapping portion (10C') positioned adjacent to the stack portion (10A') also has the functionality as a negative electrode, contributing to the improvement of the overall battery performance. According to an embodiment of the present invention, the positive electrode located between the stack portion (10A') positioned in contact with the first wrapping portion (10C) and the second wrapping portion (10C') adjacent in the thickness direction is longer than other positive electrodes. This is because there is a longer gap in the length direction at this position, and making the positive electrode located between the stack portion (10A') of the negative electrode structure (10) and the second wrapping portion (10C') adjacent in the thickness direction longer is useful for the performance of the battery.

[0063] According to an embodiment of the present invention, one positive electrode is located between the stack portions (10A, 10A', 10A'') adjacent in the thickness direction and the stack portions (10A, 10A', 10A''), and the total number of positive electrodes (20) located between the stack portions (10A, 10A', 10A'') and the stack portions (10A, 10A', 10A'') is 2n (where n is a natural number). In the electrode assembly (1), since one positive electrode (20) exists between the stack portions (10A, 10A', 10A'') and the stack portions, the total number of positive electrodes referred to here means the total number of positive electrodes placed in the same situation, and does not mean that 2n positive electrodes are stacked between the stack portions and the stack portions. For example, in FIG. 2, the total number of positive electrodes located between the stack portions and the stack portions is 4. Here, the positive electrode located between the stack portion (10A') and the wrapping portion (10C) is excluded. The upper limit of the number of the total positive electrodes (20) is not particularly limited and can be adjusted within the range generally used in the art. When the total number of positive electrodes (20) located between the stack portions and the stack portions is 2n, the starting position of the first wrapping portion (10C) is on the opposite side of the starting position of the second wrapping portion (10C'). For example, in FIG. 2, the starting position of the first wrapping portion (10C) is on the left side, but the starting position of the second wrapping portion (10C') is on the right side. In this case, when wrapping, the second wrapping portion (10C') covers one side surface of the electrode laminate, and the length until the ends of the first wrapping portion and the second wrapping portion of the negative electrode structure are located on the same line can be shortened.

[0064] According to an embodiment of the present invention, in the electrode assembly (1), the number of stack portions (10A, 10A', 10A'') is the same as the number of positive electrodes. According to the above description, the number of all positive electrodes (20) located between the stack portions is 2n (where n is a natural number), and since the number of stack portions (10A, 10A', 10A'') is one more than this, it is 2n + 1 (where n is a natural number). Since the number of positive electrodes included in the electrode assembly (1) must also consider the positive electrodes located between the stack portion (10A') and the wrapping portion (10C), the number of stack portions and positive electrodes in the electrode assembly (1) is the same.

[0065] According to an embodiment of the present invention, the positive electrode (20) includes a positive electrode active material layer (not shown) and a current collector (not shown) that supports the positive electrode active material layer. The positive electrode (20) has a structure in which positive electrode active material layers are formed on at least one surface, specifically, both surfaces of the current collector. The positive electrode active material layer contains a positive electrode active material and may further contain a conductive material, a binder, an additive, etc. The current collector, positive electrode active material, conductive material, binder, additive, etc. are not particularly limited as long as they are generally used in the art.

[0066] The positive electrode current collector is not particularly limited as long as it supports the positive electrode active material layer, does not cause a chemical change in the battery, and has high conductivity. According to an embodiment of the present invention, the positive electrode current collector can be copper, stainless steel, aluminum, nickel, titanium, palladium, fired carbon, a surface-treated product of copper or stainless steel with carbon, nickel, silver, etc. on its surface, an aluminum-cadmium alloy, etc.

[0067] The positive electrode current collector can form fine irregularities on its surface to strengthen the bonding force with the positive electrode active material, and various forms such as a film, a sheet, a foil, a mesh, a net, a porous body, a foam, a non-woven fabric body, etc. can be used.

[0068] The positive electrode active material can use a lithium-containing transition metal oxide. According to one embodiment of the present invention, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(Ni a Co b Mn c )O2(0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), LiNi 1-y Co y O2(0 < y < 1), LiCo 1-y Mn y O2(0 < y < 1), LiNi 1-y Mn y O2(0 < y < 1), Li(Ni a Co b Mn c )O4(0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-z Ni z O4(0 < z < 2), LiMn 2-z Co z O4(0 < z < 2), LiCoPO4, and LiFePO4, or a mixture of two or more of these may be used. In addition to these oxides, sulfides, selenides, halides, etc. can also be used.

[0069] The positive electrode active material can contain a sulfur compound. According to one embodiment of the present invention, the sulfur compound is one or more selected from the group consisting of elemental sulfur (S8), organic sulfur compounds Li2S n (n ≧ 1), and carbon-sulfur polymers ((C2S x ) n :x = 2.5 to 50, n ≧ 1). Preferably, inorganic sulfur (S8) may be used.

[0070] When the positive electrode active material contains a sulfur compound, the electrode assembly (1) according to an embodiment of the present invention can be applied to a lithium-sulfur battery. In the case of sulfur contained in the positive electrode active material, since it has no electrical conductivity alone, it can be used in combination with a conductive material such as a carbon material. Thereby, the sulfur is contained in the form of a sulfur-carbon composite, and preferably, the positive electrode active material can be a sulfur-carbon composite.

[0071] When considering the above-mentioned content, the positive electrode (20) is relatively difficult to fold and easy to cut compared to the negative electrode. Therefore, the positive electrode (20) is cut into an appropriate size so that a plurality of positive electrodes are applied inside the electrode assembly (1).

[0072] According to an embodiment of the present invention, the negative electrode (11) does not include a current collector that supports a lithium metal layer. Since the negative electrode (11) does not include a current collector, it is possible to improve the loading amount of the negative electrode active material in the electrode assembly and contribute to the improvement of the battery performance. When the negative electrode (11) is mainly composed of lithium metal, although lithium metal has high ductility and viscosity and processing such as cutting may not be easy, in the electrode assembly (1) according to an embodiment of the present invention, the negative electrode can be applied in the form of the negative electrode structure (10) while minimizing cutting to improve the processability. The lithium metal layer according to an embodiment of the present invention can be a free standing lithium metal layer that can maintain a certain shape by itself.

[0073] In the negative electrode structure (10), the separator (12) that covers both surfaces of the negative electrode (11) is not particularly limited as long as it does not contain a binder on its surface. Specifically, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. or a polyolefin-based porous substrate can be used as the separator (12), but it is not limited thereto.

[0074] The material of the porous base material is not particularly limited in the present invention. Generally, any porous base material that is usually used in electrochemical elements can be used. According to one embodiment of the present invention, the porous base material includes one or more materials selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, cellulose, nylon, poly(p-phenylene benzobisoxazole), and polyarylate.

[0075] According to one embodiment of the present invention, in the negative electrode structure (10), the lengths of the negative electrode (11) and the first and second separator membranes (12) are the same. Based on the end of the negative electrode structure where the second wrapping portion is located, the separator membrane located outside the electrode assembly (1) is named the first separator membrane, and the separator membrane located inside the electrode assembly (1) can be named the second separator membrane. The negative electrode (11) and the separator membrane in the electrode assembly are supplied in the form of a negative electrode structure (10) with the negative electrode (11) interposed between the first and second separator membranes (12). At this time, the negative electrode and the separator membrane are cut at once. As shown in FIG. 1, in the negative electrode structure (10), the lengths of the negative electrode (11) and the first and second separator membranes (12) are substantially the same. However, depending on the method of cutting the negative electrode structure (10), there may be a slight difference in the lengths of the negative electrode (11) and the first and second separator membranes (12). In some cases, the ends of the first and second separator membranes (12) may curve toward the center of the negative electrode structure (10). According to one embodiment of the present invention, at the end of the negative electrode structure (10), the first and second separator membranes are in contact. Even if the lengths of the negative electrode (11) and the first and second separator membranes (12) are substantially the same during the supply process of the negative electrode structure (10), when applied to the electrode assembly (1), due to the ductility of the lithium metal during the folding process, the length of the lithium metal may be extended. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the side of the wrapping portion (10C), the lithium metal protrudes in the length direction from the first and second separator membranes. Also, depending on the number of folding times, the separator membranes located outside the inside of the folding portion (10B) may become shorter. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the side of the first or second wrapping portion (10C, 10C'), the first separator membrane protrudes in the length direction from the second separator membrane. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the side of the first or second wrapping portion (10C, 10C'), the second separator membrane protrudes in the length direction from the first separator membrane.

[0076] According to one embodiment of the present invention, in the negative electrode structure (10), the end of the first wrapping portion (10C) wraps around one side surface of the electrode assembly adjacent to the first wrapping portion (10C) and is located on the stack portion (10A'') in contact with the second wrapping portion (10C'), and the end of the second wrapping portion (10C') is located on one wrapping portion (10C). The ends of the first and second wrapping portions (10C, 10C') can adhere on the stack portion (10A'') in a broad sense. In some cases, the end of the second wrapping portion (10C') can adhere on the first wrapping portion (10C), which is also included in the above-mentioned broad sense because it is also on the stack portion (10A''). If the ends of the first wrapping portion (10C) or the second wrapping portion (10C') can be effectively adhered on the stack portion (10A''), the adhesion means and method are not particularly limited. According to one embodiment of the present invention, the electrode assembly (1) further includes a fixing member for fixing the ends of the first and second wrapping portions (10C, 10C') on the outermost stack portion. By wrapping the first wrapping portion (10C) once again through the second wrapping portion (10C'), the electrode assembly (1) has a more stable structure. In the negative electrode structure (10), in order to help understand the positions where the ends of the first and second wrapping portions (10C, 10C') are adhered, FIG. 3 provides an exemplary structure of the electrode assembly in which the ends of the wrapping portions are adhered as fixing members in the negative electrode structure. In the negative electrode structure (10), since the negative electrode (11) and the separator (12) are not adhered, as shown in FIG. 3, it may be preferable that the tape (T) as a fixing member adheres to wrap the outer surface of the electrode assembly (1). When manufacturing the electrode assembly (1), considering situations such as the length of the lithium metal being extended and protruding due to the ductility of the lithium metal during the process of folding the negative electrode structure (10), according to one embodiment of the present invention, the tape (T) has insulation and entirely covers the ends of the first and second wrapping portions (10C, 10C') in the width direction. By such a taping method, the electrode assembly is covered by the separator or the tape on the top, bottom, left, and right. The first wrapping portion (10C) and the second wrapping portion (10C') can be adhered individually.According to an embodiment of the present invention, the electrode assembly includes a first fixing member for fixing the first wrapping portion (10C) and a second fixing member for fixing the second wrapping portion (10C').

[0077] When manufacturing the electrode assembly (1), when alternately laminating the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20), since the negative electrode structure (10) is folded according to the same standard, the folding portions (10B) also have substantially the same length. The negative electrode structure (10) utilizes a specific form of mandrel in order to apply the same standard during folding. When the length of the folding portion (10B) is short, there may be defects such as an unnecessary load being applied to the lithium metal located at the center of the negative electrode structure (10) and the lithium metal being disconnected. Therefore, by ensuring that the length of the folding portion (10B) is sufficiently above a certain level, the lithium metal can be flexibly arranged in the gap between the portion where the electrodes are laminated and the wrapping portion.

[0078] In the negative electrode structure (10), in order to facilitate understanding of the length of the folding portion (10B), FIG. 4 provides a drawing showing an enlarged view of the folding portion (10B) in the electrode assembly (1). According to an embodiment of the present invention, in the negative electrode structure (10), the length of the folding portion (10B) is 2 to 10 times based on the total thickness of the positive electrode (20) and the negative electrode structure (10). The length of the folding portion (10B) means the length of the curve of the folding portion. In the case of a curve, since the inner and outer lengths may be different, the length of the central portion is measured. For example, after cutting the portion indicated by the dotted line in FIG. 4 and spreading it, the length can be measured. Specifically, the length of the folding portion (10B) is 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more based on the total thickness of the positive electrode (20) and the negative electrode structure (10), and 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, and may be 2 to 10 times, 3 to 9 times, 4 to 8 times. When the length of the folding portion (10B) is adjusted within the above range, defects in the folding portion in the electrode assembly can be reduced, and the electrode assembly can be stably wrapped.

[0079] The length of the aforementioned folding portion (10B) means that it is formed to be even longer as shown in FIG. 4 than being folded into a semi-circular shape as shown in FIG. 2. Specifically, when the folding portion (10B) has a perfect semi-circular shape with an eccentricity of 0, the length of the folding portion is the value obtained by multiplying the total thickness of the positive electrode (20) and the negative electrode structure (10), which is the diameter, by π and dividing by 2. This is approximately 1.57 times the value based on the total thickness of the positive electrode (20) and the negative electrode structure (10). Judging based on this, it can be said that the length of the folding portion (10B) according to an embodiment of the present invention is longer at a significant level.

[0080] When manufacturing the electrode assembly (1), after alternately laminating the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20), when wrapping the electrode assembly (1) with the wrapping portions (10C, 10C'), the folding portion (10B) receives a pressure of a certain level or more in the inner direction of the electrode assembly (1). As a result, the folding portion (10B) can be appropriately arranged in the gap between the portion where the electrodes are laminated and the wrapping portion. The folding portion (10B) appropriately arranged between the gaps contains a lithium metal layer (11) inside, and thus can contribute to further improvement of battery performance through an electrochemical reaction in relation to the positive electrode (20) on the side surface. By appropriately filling the gap between the folding portions (10B), two or more lithium metal layers can be located on the side surface of the positive electrode not wrapped by the folding portion (10B). Further, when wrapping the electrode assembly (1) with the wrapping portions (10C, 10C'), when wrapping is performed such that the wrapping portion (10C) has a tension of a certain level or more, it helps to maintain the shape of the electrode laminate located inside the electrode assembly (1) without distortion of the structure.

[0081] According to an embodiment of the present invention, the folding portion (10B) has an asymmetric shape with respect to the surface along the length direction. Such an asymmetric shape is a shape formed by the folding portion (10B) being pressurized in the length direction by the wrapping portions (10C, 10C') and the folding portion (10B) being appropriately arranged in the gap. According to an embodiment of the present invention, the center point of the length of the folding portion (10B) does not align with the center point of the thickness of the positive electrode wrapped by the folding portion (10B). The center point of the length of the folding portion (10B) can be inclined in the direction in which wrapping progresses with respect to the center point of the thickness of the positive electrode. For example, referring to FIG. 2, the folding portion located on the right side of the electrode laminate, since wrapping is performed from top to bottom, the center point of the length of the folding portion can be located below the center point of the thickness of the positive electrode. On the other hand, the folding portion located on the left side of the electrode laminate, since wrapping is performed from bottom to top, the center point of the length of the folding portion can be located above the center point of the thickness of the positive electrode.

[0082] In order to facilitate the understanding of the vertical distance between the end of the reference positive electrode (20) and the side wrapping portions (10C, 10C') when comparing the lengths of the folding portions (10B) below, FIG. 5 provides a drawing showing an enlarged view of the portion of the electrode assembly (1) where the end of the positive electrode (20) and the side wrapping portions (10C, 10C') are located. Here, the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portions (10C, 10C') is the distance between the end of the positive electrode (20) and the side wrapping portions (10C, 10C') adjacent to the folding portion (10B). When one wrapping portion (10C) overlaps with the other wrapping portion (10C'), the wrapping portion serving as the reference for the distance is the one wrapping portion (10C) located inside. As shown in FIG. 5, the folding portion (10B) may be deformed in shape by the pressure applied from the side wrapping portions (10C, 10C') located on the side during the process of wrapping the electrode assembly. However, FIG. 5 is only one exemplary structure, and the folding portion (10B) does not necessarily deform in such a form. Due to the pressure, the distance (d) between the end of the positive electrode (20) and the side wrapping portions (10C, 10C') can be shortened, and the folding portion (10B) can be naturally arranged in a reduced space as the distance (d) becomes shorter. According to an embodiment of the present invention, in the electrode assembly (1), the length of the folding portion (10B) is 2 to 10 times based on the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portions (10C, 10C'). The side wrapping portions (10C, 10C') mean a linear one wrapping portion (10C) located on the left side of the electrode assembly or a linear other wrapping portion (10C') located on the right side with reference to FIG. 2 or FIG. 3. In an actual electrode assembly, when this portion is not straight, the vertical distance (d) is measured based on the end of the positive electrode at the central portion in the thickness direction of the electrode laminate and the vertical distance from the side wrapping portion. Also, as another method, in one aspect, the vertical distance (d) can be measured as the average value of the vertical distances between the end of the positive electrode (20) at the portion where the wrapping portions (10C, 10C') are in contact with the folding portion (10B).Specifically, the length of the folding portion (10B) is 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more, based on the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portion (10C), and is 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, and may be 2 to 10 times, 3 to 9 times, 4 to 8 times. As described above, this means that the length of the folding portion (10B) is longer at a significant level, but the vertical distance (d) is also short, meaning that the folding portion is compactly packed in the space on the side of the electrode laminate. When adjusting the length of the folding portion (10B) within the above range, the folding portion can be compactly packed at an appropriate level in the void in the electrode assembly without applying excessive pressure to the folding portion by the wrapping of the electrode assembly, contributing to the improvement of the battery performance.

[0083] In terms of folding one negative electrode structure (10) to form the basic structure of the electrode assembly (1) according to an embodiment of the present invention, the thickness of the negative electrode structure (10) should not be excessively thick so that it can be flexibly folded, and considering the battery performance, a certain level or more of lithium metal, which is a negative electrode active material, must be ensured in the negative electrode structure (10). According to an embodiment of the present invention, in the negative electrode structure (10), the thickness of the lithium metal occupies 50% to 90% based on the total thickness of the negative electrode structure (10). Specifically, the range of the thickness of the lithium metal may be 50% to 90%, specifically 55% to 85%, and more specifically 60% to 80%. When the lithium metal satisfies the above thickness range, it can help improve the processability and functionality of the electrode assembly. According to an embodiment of the present invention, since the negative electrode structure (10) does not include a separate current collector, the thickness of the remaining portion excluding the thickness of the lithium metal can mean the thickness of two separator films.

[0084] According to one embodiment of the present invention, the thickness of the lithium metal can be 10 μm to 90 μm. Specifically, the thickness of the lithium metal may be 10 μm or more, 20 μm or more, or 30 μm or more, and may also be 70 μm or less, 80 μm or less, or 90 μm or less. The thickness of the lithium metal is not necessarily limited to this and can be appropriately adjusted according to the actual size of the battery.

[0085] The electrode assembly (1) according to one embodiment of the present invention, unlike the negative electrode structure (10), the positive electrode is cut in consideration of characteristics such as materials and is applied between the stack portions (10A, 10A', 10A'') of the negative electrode structure (10). The positive electrode includes a current collector in addition to the positive electrode active material and has independence distinct from the negative electrode. However, considering the performance of the electrode, etc., its thickness can be adjusted in relation to the negative electrode or the negative electrode structure. According to one embodiment of the present invention, the thickness of the positive electrode (20) is greater than the thickness of the negative electrode structure (10). According to one embodiment of the present invention, the thickness of the positive electrode (20) has a thickness exceeding 100% and not exceeding 400% based on the thickness of the negative electrode structure (10). Specifically, the range of the thickness of the positive electrode (20) may be exceeding 100% and not exceeding 400%, specifically 150% to 350%, more specifically 200% to 300%. When the positive electrode satisfies the above-mentioned thickness range, it can achieve an appropriate harmony with the negative electrode structure.

[0086] Hereinafter, the process of manufacturing the above-mentioned electrode assembly will be specifically described. To assist in understanding the manufacturing process of the electrode assembly, FIG. 6 schematically shows the process and state in the manufacturing process of the electrode assembly.

[0087] The manufacturing process of the electrode assembly according to one embodiment of the present invention includes: (1) folding the negative electrode structure to produce an electrode laminate in which the positive electrode and the negative electrode structure are alternately laminated; (2) after manufacturing the electrode laminate, surrounding the electrode laminate with an extra negative electrode structure; (3) positioning the end of the first wrapping portion of the negative electrode structure above the electrode laminate and positioning and fixing the end of the second wrapping portion on the first wrapping portion.

[0088] The step (1) is manufactured through a process exemplified as in FIG. 6a. As shown in FIG. 6a, with the positive electrode placed at the bottommost layer, the positive electrode and the negative electrode structure can be sequentially laminated while placing the negative electrode structure thereon. Although not shown in FIG. 6a, when folding the negative electrode structure, a device such as a mandrel can be utilized to manufacture the folding at each position based on the same criterion. When starting the lamination, instead of starting from the end of the negative electrode structure, a first wrapping portion that can later wrap one side surface of the electrode laminate is left, and the lamination starts from the stack portion in contact with such a wrapping portion. The step (2) is manufactured through processes exemplified as in FIGS. 6b and 6c. The extra negative electrode structures all exist at both ends as the first and second wrapping portions, and the first and second wrapping portions wrap the side surfaces of the adjacent electrode laminates respectively. Further, the second wrapping portion wraps the upper or lower stage of the electrode laminate and is positioned to be in contact with the first wrapping portion. When wrapping with the extra negative electrode structure such that the negative electrode structure has a tension above a specific level, the folding portions are compactly packed in the voids, which helps maintain the shape of the electrode laminate without distorting its structure. After the step (3), the completed electrode assembly becomes in a state as shown in FIG. 6d or FIG. 6e. It has the effect of preventing the positive electrode between the stack portions from flowing down due to wrapping. Considering such functionality, the end of the negative electrode structure may preferably be positioned at the upper stage of the electrode laminate. By fixing the negative electrode structure, the tension applied to the negative electrode structure during the wrapping process can be maintained as it is. Wrapping with a tape (T) as shown in FIG. 6e can be an exemplary method.

[0089] In the manufacturing process, the specific characteristics of the positive electrode and the negative electrode structure not specifically described follow the foregoing content. The electrode assembly according to an embodiment of the present invention can weld a plurality of layers of tabs and leads like a conventional large-capacity cell and can maintain performance such as cell resistance and output.

[0090] An electrode assembly according to an embodiment of the present invention is applied to an electrochemical element. The electrochemical element can include all elements that undergo an electrochemical reaction. For example, the electrochemical element can be any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor. When the electrochemical element is a secondary battery, the electrochemical element can be a lithium secondary battery, and the lithium secondary battery can include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, etc.

[0091] As described above, even if the embodiments are described by way of limited embodiments and drawings, those having ordinary knowledge in the art can make various modifications and variations from the above description. For example, whether the described technology is performed in a different order from the described method, and / or whether the components of the described system, structure, device, circuit, etc. are combined or assembled in a different form from the described method, or replaced or substituted by other components or equivalents, appropriate results can be achieved.

[0092] Hereinafter, preferred examples are shown to assist in understanding the present invention. However, the following examples are provided to more easily understand the present invention, and the present invention is not limited thereto.

[0093] Example Example 1: Manufacture of an electrode assembly wrapped with a negative electrode structure A negative electrode structure was manufactured with 60 μm of lithium metal interposed between two polyethylene (PE) separator films (11 μm). Also, after manufacturing a positive electrode slurry by adding a positive electrode mixture composed of 85% by weight of a positive electrode active material manufactured by mixing sulfur and carbon nanotubes (CNT) at a weight ratio of 7:3, 5% by weight of carbon nanofiber as a conductive material, and 10% by weight of a binder to deionized water, it was coated on an aluminum current collector to manufacture a 200 μm positive electrode.

[0094] The manufactured negative electrode structure was folded, and after manufacturing the electrode laminate in the manner shown in Fig. 6a, the electrode laminate was wrapped with the extra negative electrode structure in the manners shown in Figs. 6b and 6c to manufacture the electrode assembly shown in Fig. 6d. The end of the negative electrode structure exposed from the electrode assembly was adhered with an insulating tape as shown in Fig. 6e. At this time, in the electrode assembly, the length of the folding portion was measured to be 1,453 μm, and the vertical distance between the end of the positive electrode and the side wrapping portion was measured to be 268 μm.

[0095] Comparative Example 1: Manufacture of an electrode assembly by cutting and laminating a negative electrode structure After cutting the negative electrode structure according to each layer of the positive electrode, the positive electrode and the negative electrode structure were laminated to manufacture an electrode laminate, and then the electrode assembly was completed with the negative electrode structure without separate wrapping. In the said electrode assembly, the material and thickness of the positive electrode and the negative electrode structure were manufactured in the same manner as in Example 1.

[0096] Experimental Example Each electrode assembly manufactured according to Example 1 and Comparative Example 1 was placed in the same pouch, filled with an electrolyte in which 0.4 M of LiFSI salt and 4 wt% of LiNO3 were added to an ether-based electrolyte, and a lithium secondary battery was manufactured. The manufactured lithium secondary battery was charged and discharged at 0.3C to measure the Coulomb efficiency for each cycle, and the results are shown in Fig. 7.

[0097] It can be confirmed that the electrode assembly according to the present invention not only has advantages in terms of process compared to the conventional electrode assembly, but also can improve the long-term performance of the battery such as Coulomb efficiency according to Fig. 7.

[0098] All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

Explanation of Reference Numerals

[0099] 1, 1', 1'': Electrode assembly 10: Negative electrode structure 10A, 10A', 10A'': Stack portions (10A', 10A'': outermost stack portions) 10B: Folding portion 10C, 10C': Wrapping portions (first and second wrapping portions) 11: Negative electrode (lithium metal layer) 12: Separation membrane (first and second separation membranes) 20: Positive electrode T: Fixing member (tape) d: Vertical distance between the end of the positive electrode and the side wrapping portion

Claims

1. An electrode assembly including a negative electrode structure and a plurality of positive electrodes, wherein the negative electrode structure includes a first separator, a second separator, and a lithium metal layer interposed between the first separator and the second separator, the negative electrode structure is divided into a plurality of stack portions, a plurality of folding portions, and a first wrapping portion and a second wrapping portion according to its position in the electrode assembly, and between the first wrapping portion and the second wrapping portion respectively located at the ends of the negative electrode structure, the stack portions and the folding portions are alternately located, and the first wrapping portion and the second wrapping portion are each in contact with a stack portion, in the electrode assembly, due to the folding portions, a plurality of stack portions are sequentially arranged side by side in the thickness direction, and at least one positive electrode is located between adjacent stack portions in the thickness direction, in the electrode assembly, the second wrapping portion is positioned to be in contact with the first wrapping portion, and the outer surfaces in the thickness direction and the length direction are surrounded by the second wrapping portion, or by the second wrapping portion and one or more of the first wrapping portion and the outermost stack portion, having a structure.

2. In the electrode assembly, the plurality of stack portions and the plurality of positive electrodes are adhered in the thickness direction by the first wrapping portion and the second wrapping portion, characterized in that the electrode assembly according to claim 1.

3. The second wrapping portion of the negative electrode structure surrounds both the first wrapping portion surrounding one side surface of the electrode laminate and the side surface opposite to the electrode laminate, characterized in that the electrode assembly according to claim 1.

4. The ends of the first wrapping portion and the second wrapping portion of the negative electrode structure are located on the same straight line, characterized in that the electrode assembly according to claim 1.

5. In the electrode assembly, at least one positive electrode is located between the stack portion in contact with the first wrapping portion of the negative electrode structure and the second wrapping portion located parallel to the stack portion, characterized in that the electrode assembly according to claim 1.

6. In the electrode assembly, one positive electrode is located between adjacent stack portions in the thickness direction, the total number of positive electrodes located between stack portions in the electrode assembly is 2n (where n is a natural number), characterized in that the electrode assembly according to claim 1.

7. In the electrode assembly, the positive electrode includes a positive electrode active material and a current collector that supports the positive electrode active material, and the negative electrode does not include a current collector that supports lithium metal. The electrode assembly according to claim 1.

8. In the negative electrode structure, the lengths of the lithium metal layer, the first separator, and the second separator are the same. The electrode assembly according to claim 1.

9. In the negative electrode structure, the end of the first wrapping portion is located on a stack portion that contacts the second wrapping portion after turning around to wrap one side surface of the electrode assembly adjacent to the first wrapping portion, and the end of the second wrapping portion is located on the first wrapping portion. The electrode assembly according to claim 1.

10. The electrode assembly further includes a fixing member that fixes the ends of the first wrapping portion and the second wrapping portion on the outermost stack portion. The electrode assembly according to claim 1.

11. In the negative electrode structure, the length of the folding portion is 2 to 10 times based on the total thickness of the positive electrode and the negative electrode structure. The electrode assembly according to claim 1.

12. In the negative electrode structure, the length of the folding portion is 2 to 10 times based on the vertical distance between the end of the positive electrode and the side wrapping portion that wraps it. The electrode assembly according to claim 1.

13. The folding portion has an asymmetric shape based on the plane along the length direction. The electrode assembly according to claim 1.

14. In the negative electrode structure, the thickness of the lithium metal layer occupies 50% to 90% based on the total thickness of the negative electrode structure. The electrode assembly according to claim 1.

15. The thickness of the positive electrode is greater than the thickness of the negative electrode structure. The electrode assembly according to claim 1.

16. The fixing member is an insulating tape. The electrode assembly according to claim 10.

17. The center point of the length of the folding portion is not aligned with the center point of the thickness of the positive electrode wrapped by the folding portion. The electrode assembly according to claim 1.

18. The positive electrode located between the stack portion in contact with the first wrapping portion and the second wrapping portion adjacent in the thickness direction is longer than other positive electrodes. The electrode assembly according to claim 5.

19. The electrode assembly according to claim 1, wherein the end of the second wrapping portion is located on the first wrapping portion.

20. The electrode assembly according to claim 1, wherein the end of the second wrapping portion is located on the outermost stack portion.

21. The electrode assembly according to claim 10, wherein the electrode assembly includes a first fixing member for fixing the first wrapping portion and a second fixing member for fixing the second wrapping portion.

22. An electrochemical element including the electrode assembly according to any one of claims 1 to 21.

23. The electrochemical element according to claim 22, wherein the electrochemical element is a lithium secondary battery.

24. The electrochemical element according to claim 23, wherein the electrochemical element is a lithium-sulfur battery.

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