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 separation membrane and a second separation membrane, and a lithium metal layer interposed between the first separation membrane and the second separation membrane. 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. 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, the 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. The electrode assembly has a structure in which the outer surface is surrounded by the first wrapping portion and the second wrapping portion, or the first wrapping portion and the second wrapping portion and at least one outermost stack portion in the thickness direction and the length direction.

Description

Technical Field

[0001] The present invention relates to an electrode assembly and an electrochemical element including the same. Specifically, the present invention relates to an electrode assembly including a lithium metal in a negative electrode and an electrochemical element 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. 10-2023-0070472 filed on May 31, 2023, and Korean Patent Application No. 10-2023-0139636 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 technologies 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 elements 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] Also, 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, or 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-shaped 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 circuits. Also, since the jelly-roll electrode assembly needs to wind a long sheet-shaped 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 electrode 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 by 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 especially 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 separator, a second separator, and a lithium metal layer interposed between the first separator and the second separator.

[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 a first wrapping portion and a second wrapping portion according to its position in the electrode assembly.

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

[0017] In one embodiment of the present invention, in the electrode assembly, a plurality of stack portions are sequentially arranged side by side in the thickness direction by folding portions, 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 electrode assembly has a structure in which the outer surfaces in the thickness direction and the length direction are surrounded by the first wrapping portion and the second wrapping portion, or the first wrapping portion, the second wrapping portion, and at least one 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 wrapping portion and the second wrapping portion.

[0020] In one embodiment of the present invention, the first wrapping portion and the second wrapping portion do not overlap each other.

[0021] In one embodiment of the present invention, the first wrapping portion and the second wrapping portion have the same length as each other.

[0022] In one embodiment of the present invention, the first wrapping portion and the second wrapping portion are fixed on different outermost stack portions.

[0023] In one embodiment of the present invention, one positive electrode is located between stack portions adjacent in the thickness direction in the electrode assembly, and the total number of positive electrodes located between stack portions 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 structure 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, the first separator, and the second separator 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 a stack portion where the first wrapping portion turns around to contact the second wrapping portion so as to wrap one side surface of an adjacent electrode assembly, and the end of the second wrapping portion is located on a stack portion where the second wrapping portion turns around to contact the first wrapping portion so as to wrap one side surface of an adjacent electrode assembly.

[0027] In one embodiment of the present invention, the electrode assembly further includes fixing members that fix the ends of the first wrapping portion and the second wrapping portion on the outermost stack portions, respectively.

[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 the 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 accounts for 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 first wrapping portion and the second wrapping portion respectively located on the stacking portion do not overlap each other in the thickness direction.

[0036] In one embodiment of the present invention, the first wrapping portion and the second wrapping portion respectively located on the stacking portion overlap each other in the thickness direction.

[0037] In one embodiment of the present invention, the ends of the first wrapping portion and the ends of the second wrapping portion are located on the same line in the thickness direction.

[0038] According to a second aspect of the present invention, The present invention provides an electrochemical element including the aforementioned electrode assembly.

[0039] In one embodiment of the present invention, the electrochemical element is a lithium secondary battery.

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

Advantages of the Invention

[0041] According to one embodiment of the present invention, an electrode assembly is manufactured by utilizing a single negative electrode structure in a continuous form with a negative electrode containing lithium metal interposed between two separator membranes, thereby minimizing the cutting of lithium metal and improving the process efficiency in the manufacture of the electrode assembly.

[0042] In addition, by adjusting the methods and conditions in stacking, folding, and wrapping according to the material properties of the negative electrode structure, the manufactured electrode assembly not only has a stable structure but also can improve the performance of the battery.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6a

Figure 6b

Figure 6c

Figure 6d

Figure 7

Mode for Carrying Out the Invention

[0044] Hereinafter, embodiments will be described in detail through exemplary drawings. When adding reference numerals to the components of each drawing, it should be noted that for the same components, as much as possible, they have the same reference numerals even if they are shown on different drawings. Further, when explaining the embodiments, if a specific explanation of a related known configuration or function is determined to hinder the understanding of the embodiments, the detailed explanation thereof will be omitted.

[0045] Also, when explaining 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 is 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 also be understood that other components may be "connected", "coupled", or "joined" between the components.

[0046] Components included in any one of the embodiments 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 of the embodiments can be applied to other embodiments, and specific descriptions in the overlapping range will be omitted.

[0047] 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 workability in 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.

[0048] In this specification, the terms "length direction", "width direction", and "thickness direction" (or "height direction") are used. In this specification, the 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.

[0049] In this specification, the term "adjacent" means the object that is located closest to the reference among a plurality of referred objects. The adjacent object does not necessarily contact the reference.

[0050] The electrode assembly according to an embodiment of the present invention 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 technical field, 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 applying it to a conventional electrode assembly as with lithium metal, it can be widely and expansively interpreted. In this specification, in terms of the negative electrode containing lithium metal, it can be named a lithium metal layer, and in terms of the negative electrode and the separator being supplied in an integrated configuration, it can be named a negative electrode structure.

[0051] According to an embodiment of the present invention, the negative electrode is interposed between two separator membranes to form a negative electrode structure. In this specification, the two separator membranes constituting the negative electrode structure can be named as the first separator membrane and the second separator membrane. 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.

[0052] 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 as the first wrapping portion and the second wrapping portion. To assist in understanding the structure of the negative electrode structure, FIG. 1 provides an exemplary structure of the 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'), the folding portion (10B), and the wrapping portion (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'), the folding portion (10B), and the wrapping portion (10C) are not divided by materials but by positions.

[0053] The stack portions (10A, 10A') mean the negative electrode structure at the position where the positive electrode is laminated, and mainly have a linear shape based on FIG. 2 etc. The folding portion (10B) means the negative electrode structure at the position connecting between the stack portions, and mainly has a curved shape based on FIG. 2 etc. The folding portion (10B) can also be named as a bending portion. The wrapping portion (10C) means the negative electrode structure at the position wrapping the laminated structure of the positive electrode and the negative electrode structure from the end point of the outermost stack portion (10A') at the uppermost or lowermost stage, and a linear shape and a curved shape are mixed based on FIG. 2 etc.

[0054] As shown in Fig. 1, at both ends of the negative electrode structure (10) in the length direction, there are wrapping portions (10C). That is, the two wrapping portions (10C) are respectively located at the ends of the negative electrode structure (10) in the length direction. Further, each of the wrapping portions (10C) is in contact with the outermost stack portion (10A'), and between the outermost stack portions (10A'), there are folding portions (10B) and stack portions (10A) alternately located. Since the stack portions (10A, 10A') are substantially the same as the length of the positive electrode, the lengths of the respective stack portions (10A, 10A') are substantially the same.

[0055] The two wrapping portions (10C) located at both ends of the negative electrode structure (10) can have different lengths from each other. In this specification, in order to distinguish the two wrapping portions (10C), if the wrapping portion (10C) located at the starting point of lamination is named the first wrapping portion, then the wrapping portion (10C) located at the ending point of lamination is named the second wrapping portion. For example, if stacking starts from the left side portion in Fig. 1, the wrapping portion (10C) located at the left end becomes the first wrapping portion, and the wrapping portion (10C) located at the right end becomes the second wrapping portion. The first wrapping portion and the second wrapping portion do not necessarily have the same length as long as they can wrap one side surface inside the electrode assembly. However, by adjusting the process conditions in the repeated process to make the lengths of the first wrapping portion and the second wrapping portion the same, when the electrode assembly has a symmetric structure, the structural stability of the electrode assembly can be enhanced. According to an embodiment of the present invention, the first wrapping portion and the second wrapping portion have the same length as each other.

[0056] 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).

[0057] According to an embodiment of the present invention, in the electrode assembly (1), due to the folding portion (10B), a plurality of stack portions (10A, 10A') are sequentially arranged side by side in the thickness direction, and at least one positive electrode is located between the stack portions (10A, 10A') adjacent in the thickness direction and the stack portions (10A, 10A'). According to an embodiment of the present invention, the electrode assembly (1) has a structure in which the outer surfaces in the thickness direction and the length direction are surrounded by the first wrapping portion and the second wrapping portion (10C), or the first wrapping portion and the second wrapping portion (10C) and at least one outermost stack portion (10A'). In other words, the inside of the electrode assembly (1) has a structure in which the stack portions (10A, 10A') of the negative electrode structure and the positive electrode (20) are alternately stacked in sequence. At this time, only one positive electrode (20) is located between the stack portions (10A, 10A') of the negative electrode structure. Further, the outside of the electrode assembly (1) has a structure surrounded by at least one stack portion (10A') of the negative electrode structure and two wrapping portions. Here, the inside and the outside of the electrode assembly (1) are divisions of the region of the electrode assembly (1) for helping to understand the structure of the electrode assembly (1) according to the present invention. Based on 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 part 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') mean the negative electrode structure (10) at the position where the positive electrode is stacked, and the wrapping portion (10C) starts from the end of the outermost stack portion (10A') at the uppermost or lowermost stage. Therefore, as shown in FIG. 2, when the end of the first wrapping portion is located above the uppermost outermost stack portion (10A'), a part of the uppermost outermost stack portion (10A') can be located outside the electrode assembly (1), and the remaining part of the uppermost outermost stack portion (10A') can be located inside the electrode assembly (1).Also, when the end of the second wrapping portion is located above the lowermost outermost stack portion (10A'), a part of the lowermost outermost stack portion (10A') may be located outside the electrode assembly (1), and the remaining part of the lowermost outermost stack portion (10A') may be located inside the electrode assembly (1). Therefore, in this specification, the outermost stack portion located inside or outside may mean the whole or a part of one stack portion. Different from FIG. 2, when one of the first wrapping portion and the second wrapping portion covers the whole of the outermost stack portion (10A'), the outside of the electrode assembly (1) can be formed by the first wrapping portion, the second wrapping portion, and one outermost stack portion. Also, when both the first wrapping portion and the second wrapping portion cover the whole of the outermost stack portion (10A'), the outside of the electrode assembly (1) can be formed only by the first wrapping portion and the second wrapping portion. In any case, the plurality of folding portions (10B) are wrapped by the wrapping portion (10C) and are not exposed to the outside in the thickness direction and the length direction.

[0058] In the electrode assembly (1) according to an embodiment of the present invention, since the stack portions (10A, 10A') of the negative electrode structure (10) and the positive electrode (20) are alternately stacked in sequence inside, the negative electrode structure (10) including the folding portions (10B) has a zigzag shape. That is, the folding portions (10B) sequentially positioned from the stack portion (10A') in contact with the first wrapping portion or the second wrapping portion of the negative electrode structure (10) are alternately positioned on the left side or the right side in the electrode assembly (1). If the stack portions (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 and the positive electrode are continuously stacked, no potential difference is generated between the continuously stacked layers, and the efficiency of the battery may decrease.

[0059] According to an embodiment of the present invention, in the electrode assembly (1), a plurality of stack portions (10A, 10A') and a plurality of positive electrodes (20) are adhered in the thickness direction by a first wrapping portion and a second wrapping portion (10C). The first wrapping portion and the second wrapping portion (10C) can wrap the inside of the electrode assembly (1) with a higher tension than the stack portions (10A, 10A') or the folding portion (10B), whereby the internal structure of the electrode assembly (1) is adhered in the thickness direction. In such a manner, when the internal structure of the electrode assembly (1) is adhered in the thickness direction, inevitably the internal structure of the electrode assembly (1) comes to be adhered in the length direction. However, even when the internal structure of the electrode assembly (1) is 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).

[0060] According to an embodiment of the present invention, the first wrapping portion and the second wrapping portion do not contact each other and are fixed on different outermost stack portions (10A') of the negative electrode structure. That is, when forming the exterior in the final electrode assembly, the first wrapping portion and the second wrapping portion do not overlap. When the first wrapping portion and the second wrapping portion overlap, more unnecessary negative electrode structure is used in the overlapping portion, which is not preferable in terms of material optimization. As described above, the end of the first wrapping portion and the end of the second wrapping portion can be located on the upper part of the stack portion. However, in order to produce an efficient structure of the electrode assembly, the stack portion where the end of the first wrapping portion is located and the stack portion where the end of the second wrapping portion is located may be different from each other.

[0061] According to one embodiment of the present invention, in the electrode assembly (1), one positive electrode is located between the stack portions (10A, 10A') adjacent in the thickness direction, and the number of the entire positive electrodes (20) located between the stack portions (10A, 10A') in the electrode assembly (1) is 2n (where n is a natural number). In the electrode assembly (1), since there is one positive electrode (20) between the stack portions (10A, 10A'), the number of the entire 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. For example, in FIG. 2, the number of the entire positive electrodes located between the stack portions is 4. In the electrode assembly according to one embodiment of the present invention, all the positive electrodes (20) are located between the stack portions. The upper limit of the number of the entire positive electrodes (20) is not particularly limited and can be adjusted within the range generally used in the art. When the number of the entire positive electrodes (20) located between the stack portions is 2n, the direction in which the end of the first wrapping portion faces is opposite to the direction in which the end of the second wrapping portion faces. For example, in FIG. 2, the end of the first wrapping portion is located on the left side, while the end of the second wrapping portion is located on the right side. In this case, even if the left and right side surfaces inside the electrode assembly are wrapped by the first wrapping portion and the second wrapping portion respectively, the first wrapping portion and the second wrapping portion may not overlap each other, and an electrode assembly with an efficient structure can be manufactured.

[0062] According to one embodiment of the present invention, in the electrode assembly (1), the number of the stack portions (10A, 10A') may be one more than the number of the positive electrodes (20). According to the above description, in order for 2n (where n is a natural number) entire positive electrodes (20) to be located between the stack portions, the number of the stack portions (10A, 10A') becomes 2n + 1 (where n is a natural number).

[0063] According to one 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. The positive electrode (20) has a structure in which the positive electrode active material layer is 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, and the like. The current collector, the positive electrode active material, the conductive material, the binder, the additive, and the like are not particularly limited as long as they are generally used in the art.

[0064] 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 one embodiment of the present invention, the positive electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, palladium, fired carbon, or a material obtained by surface-treating the surface of copper or stainless steel with carbon, nickel, silver, etc., or an aluminum-cadmium alloy.

[0065] 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, and a non-woven fabric can be used.

[0066] As the positive electrode active material, a lithium-containing transition metal oxide can be used. 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 Niz O4(0 < z < 2), LiMn 2-z Co z Any one selected from the group consisting of 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.

[0067] The positive electrode active material may contain a sulfur compound. According to one embodiment of the present invention, the sulfur compound is elemental sulfur (S8), an organic sulfur compound Li2S n (n ≧ 1) and a carbon-sulfur polymer ((C2S x ) n :x = 2.5 to 50, n ≧ 1) and may be one or more selected from the group consisting of. Preferably, inorganic sulfur (S8) may be used.

[0068] When the positive electrode active material contains a sulfur compound, the electrode assembly (1) according to one 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.

[0069] 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 and a plurality of positive electrodes are applied inside the electrode assembly (1).

[0070] 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 workability can be improved by minimizing cutting while applying the negative electrode in the form of the negative electrode structure (10). 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.

[0071] 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, or the like, or a polyolefin-based porous substrate can be used as the separator (12), but it is not limited thereto.

[0072] 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.

[0073] According to an 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 first 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 (12) in the electrode assembly are supplied in the form of the negative electrode structure (10) with the negative electrode (11) interposed between the first and second separator membranes (12). At this time, in that the negative electrode and the separator membrane are cut at once, as shown in FIG. 1, the lengths of the negative electrode (11) and the first and second separator membranes (12) in the negative electrode structure (10) 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), and 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 an embodiment of the present invention, at the end of the negative electrode structure (10), the first and second separator membranes are in contact. Even though 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 an 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 foldings, the separator membranes located more outside than the inside of the folding portion (10B) may become shorter. According to an 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), the first separator membrane protrudes in the length direction from the second separator membrane. According to an 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), the second separator membrane protrudes in the length direction from the first separator membrane.

[0074] According to one embodiment of the present invention, the end of the first wrapping portion is located on a stack portion (10A') that contacts the second wrapping portion by turning around one side surface of an adjacent electrode assembly so that the first wrapping portion wraps around it. The end of the second wrapping portion is located on a stack portion where the second wrapping portion contacts the first wrapping portion by turning around one side surface of an adjacent electrode assembly. The stack portion means the outermost stack portion (10A'). The ends of the first wrapping portion and the second wrapping portion can be located in various ways on the outermost stack portion (10A'). According to one embodiment of the present invention, the first wrapping portion and the second wrapping portion respectively located on the stack portion do not overlap each other in the thickness direction. The greater the distance between the first wrapping portion and the second wrapping portion in the thickness direction, the more the amount of the negative electrode structure can be reduced and it can be efficient. According to one embodiment of the present invention, the first wrapping portion and the second wrapping portion respectively located on the stack portion overlap each other in the thickness direction. The greater the overlap between the first wrapping portion and the second wrapping portion in the thickness direction, the more the electrode assembly can have a stable structure. According to one embodiment of the present invention, the ends of the first wrapping portion and the second wrapping portion are located on the same line in the thickness direction. The above-described positional relationship in the thickness direction indicates whether the first wrapping portion or the second wrapping portion overlaps or does not overlap, or the ends contact each other when the first wrapping portion or the second wrapping portion is moved in the thickness direction.

[0075] According to one embodiment of the present invention, the ends of the first wrapping portion and the second wrapping portion (10C) located on the outermost stack portion can adhere to the outermost stack portion (10A'). If the ends of the first wrapping portion and the second wrapping portion (10C) can be effectively adhered to the outermost 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 wrapping portion and the second wrapping portion (10C) onto the outermost stack portion (10A'). In the negative electrode structure (10), in order to assist in understanding the position where the end of the wrapping portion (10C) is adhered, FIG. 3 provides an exemplary structure of an electrode assembly in which the ends of the respective wrapping portions are adhered with a fixing member in the negative electrode structure. In the negative electrode structure (10), the negative electrode (11) and the separator (12) are not adhered, but according to the electrode assembly as shown in FIG. 3, both ends of the negative electrode structure (10) can be fixed, and a stable structure can be formed. As shown in FIG. 3, it may be preferable that the tape (T), which is a fixing member, adheres so as to cover the outer surface of the electrode assembly (1). In the process of folding the negative electrode structure (10) 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, according to one embodiment of the present invention, the tape (T) has insulation and entirely covers the ends of the wrapping portion (10C) in the width direction. By such a taping method, the electrode assembly is covered with the separator or the tape on the top, bottom, left, and right.

[0076] When manufacturing the electrode assembly (1), when alternately laminating the stack portions (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. In order to apply the same standard when folding the negative electrode structure (10), a mandrel of a specific form is utilized. When the length of the folding portion (10B) is short, an unnecessary load may be applied to the lithium metal located at the center of the negative electrode structure (10), and defects such as the lithium metal being severed may occur. 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.

[0077] In the negative electrode structure (10), in order to assist in understanding 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 adjusting the length of the folding portion (10B) within the above range, defects in the folding portion in the electrode assembly can be reduced, and the electrode assembly can be stably wrapped.

[0078] The length of the aforementioned folding portion (10B) means that it is formed to be even longer as shown in FIG. 4 rather than being folded into a semi-circular shape as shown in FIG. 2. Specifically, when the folding portion (10B) has a perfect semi-circular form with an eccentricity of 0, the length of the folding portion is a value obtained by multiplying the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10), which is the diameter, by π and then dividing by 2. Based on the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10), this is approximately 1.57 times the value. 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.

[0079] In manufacturing the electrode assembly (1), when the stacking portions (10A, 10A') of the negative electrode structure (10) and the positive electrode (20) are alternately stacked and then the electrode assembly (1) is wrapped by the wrapping portion (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 stacked and the wrapping portion. Since the folding portion (10B) includes the lithium metal layer (11) inside, in relation to the positive electrode (20) on the side surface, it can contribute to further improvement of battery performance through an electrochemical reaction. By appropriately filling the gap with the folding portion (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). When wrapping the electrode assembly (1) with the wrapping portion (10C), if the 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 distorting its structure.

[0080] According to an embodiment of the present invention, the folding portion (10B) has an asymmetric shape with respect to a plane along the length direction. Such an asymmetric shape is a shape formed by the folding portion (10B) being pressed in the length direction by the wrapping portion (10C) and the folding portion (10B) being appropriately arranged in the void. 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 proceeds 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 has wrapping performed from top to bottom, so 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 has wrapping performed from bottom to top, so the center point of the length of the folding portion can be located above the center point of the thickness of the positive electrode.

[0081] In order to assist in understanding the vertical distance between the end of the reference positive electrode (20) and the side wrapping portion (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 portion (10C) are located. As shown in FIG. 5, in the process of wrapping the electrode assembly, the shape of the folding portion (10B) may be deformed by the pressure applied from the wrapping portion (10C) located on the side. However, FIG. 5 is only an 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 portion (10C) can be shortened, and the folding portion (10B) can be naturally arranged in a reduced space as the distance (d) shortens. 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 portion (10C). The side wrapping portion (10C) means a linear wrapping portion (10C) located on the left or right side of the electrode assembly 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 with respect to 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 distance from the end of the positive electrode (20) at the portion where the wrapping portion (10C) contacts 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 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. This means that, as described above, the length of the folding portion (10B) is longer at a significant level, but the vertical distance (d) is also short, indicating that the folding portion is compactly packed in the space on the side of the electrode laminate.When adjusting the length of the folding part (10B) within the above range, the folding part can be compactly packed at an appropriate level in the void in the electrode assembly without applying excessive pressure to the folding part by wrapping the electrode assembly, which can contribute to improving the performance of the battery.

[0082] According to an embodiment of the present invention, the electrode assembly (1) folds one negative electrode structure (10) to form the basic structure of the electrode assembly (1). In this regard, the negative electrode structure (10) should not be overly thick so that it can be flexibly folded. Considering the performance of the battery, a certain level or more of lithium metal, which is the negative electrode active material, must be ensured within 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% - 90% based on the overall thickness of the negative electrode structure (10). Specifically, the range of the thickness of the lithium metal may be 50% - 90%, specifically 55% - 85%, and more specifically 60% - 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 part excluding the thickness of the lithium metal can mean the thickness of two separator films.

[0083] According to an embodiment of the present invention, the thickness of the lithium metal can be 10 μm - 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.

[0084] According to an embodiment of the present invention, unlike the negative electrode structure (10), the positive electrode is cut considering characteristics such as materials, and is applied between the stack portions (10A, 10A') of the negative electrode structure (10). The positive electrode includes a current collector in addition to the positive electrode active material, etc., and is distinguished from the negative electrode and has independence. 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 an 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 an 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.

[0085] 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.

[0086] The manufacturing process of the electrode assembly according to an 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 excess negative electrode structure; (3) positioning and fixing the end of the negative electrode structure above the electrode laminate.

[0087] The (1) stage is manufactured through a process exemplified as in FIG. 6a. As shown in FIG. 6a, the negative electrode structure is placed at the bottommost layer, and while placing the positive electrode thereon, the negative electrode structure and the positive electrode can be sequentially laminated. 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 standard. When starting the lamination, instead of starting from the end of the negative electrode structure, a first wrapping portion capable of later wrapping 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 (2) stage is manufactured through a process exemplified as in FIG. 6b. The extra negative electrode structures all exist at both ends as the first wrapping portion and the second wrapping portion, and the first wrapping portion and the second wrapping portion each wrap the side surface of the adjacent electrode laminate. When wrapping with the extra negative electrode structure such that the negative electrode structure has a tension above a specific level, the folding portion is compactly packed in the void, which helps to maintain the shape of the electrode laminate without distorting its structure. After the (3) stage, the completed electrode assembly becomes in a state as shown in FIG. 6c or FIG. 6d. 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. 6d can be one exemplary method.

[0088] 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.

[0089] 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, and the like.

[0090] As described above, even if the embodiments are described by way of limited embodiments and drawings, those with ordinary knowledge in the relevant technical field 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.

[0091] 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.

[0092] Example Example 1: Manufacture of an electrode assembly wrapped with a negative electrode structure A negative electrode structure was manufactured by interposing 60 μm of lithium metal between two polyethylene (PE) separator membranes (11 μm). Further, a positive electrode mixture having a composition 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 was added to deionized water to manufacture a positive electrode slurry, and then coated on an aluminum current collector to manufacture a 200 μm positive electrode.

[0093] 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 excess negative electrode structure in the manner shown in Fig. 6b to manufacture an electrode assembly as shown in Fig. 6c. The end of the negative electrode structure exposed from the electrode assembly was adhered with insulating tape as shown in Fig. 6d. 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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

[0098] 1, 1', 1'': Electrode assembly 10: Negative electrode structure 10A, 10A’: Stack portion (10A’: Outermost stack portion) 10B: Folding portion 10C: Wrapping portion (First wrapping portion and second wrapping portion) 11: Negative electrode (Lithium metal layer) 12: Separation membrane (First separation membrane and second separation membrane) 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 and 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 positioned, 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, 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 electrode assembly has a structure in which the outer surface is surrounded by the first wrapping portion and the second wrapping portion, or the first wrapping portion and the second wrapping portion and at least one outermost stack portion in the thickness direction and the length direction.

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, and the electrode assembly according to claim 1 is characterized in that.

3. The first wrapping portion and the second wrapping portion do not contact each other, and the electrode assembly according to claim 1 is characterized in that.

4. The first wrapping portion and the second wrapping portion have the same length as each other, and the electrode assembly according to claim 1 is characterized in that.

5. The first wrapping portion and the second wrapping portion are fixed on different outermost stack portions, and the electrode assembly according to claim 1 is characterized in that.

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

7. In the electrode assembly, the positive electrode includes a positive electrode active material layer and a current collector supporting the positive electrode active material layer, and the negative electrode structure does not include a current collector supporting the lithium metal layer, and the electrode assembly according to claim 1 is characterized in that.

8. The electrode assembly according to claim 1, wherein in the negative electrode structure, the lengths of the lithium metal layer, the first separation membrane, and the second separation membrane are the same.

9. The electrode assembly according to claim 1, wherein in the negative electrode structure, the end of the first wrapping portion is located on the stack portion where the first wrapping portion turns around to contact the second wrapping portion so as to wrap one side surface of an adjacent electrode assembly, and the end of the second wrapping portion is located on the stack portion where the second wrapping portion turns around to contact the first wrapping portion so as to wrap one side surface of an adjacent electrode assembly.

10. The electrode assembly according to claim 1, further comprising a fixing member for fixing the ends of the first wrapping portion and the second wrapping portion on the outermost stack portion respectively.

11. The electrode assembly according to claim 1, wherein 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.

12. The electrode assembly according to claim 1, wherein 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.

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

14. The electrode assembly according to claim 1, wherein 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.

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

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

17. The electrode assembly according to claim 1, wherein 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.

18. The electrode assembly according to claim 9, wherein the first wrapping portion and the second wrapping portion respectively located on the stack portion do not overlap each other in the thickness direction.

19. The first wrapping part and the second wrapping part, which are respectively positioned on the stack part, are characterized in that they overlap each other in the thickness direction. The electrode assembly according to claim 9.

20. The electrode assembly according to claim 9, wherein the ends of the first wrapping part and the ends of the second wrapping part are positioned on the same line in the thickness direction.

21. An electrochemical element including the electrode assembly according to any one of claims 1 to 20.

22. The electrochemical element according to claim 21, wherein the electrochemical element is a lithium secondary battery.

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

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