Electrode assembly and electrochemical device including the same

Abstract

Provided is an electrode assembly including a negative electrode structure and a plurality of positive electrodes. The negative electrode structure includes first and second separation membranes and a lithium metal layer interposed between the first and second separation membranes. The negative electrode structure is divided into a plurality of stacked portions, a plurality of folded portions, and first and second wrapping portions according to positions in the electrode assembly. In the negative electrode structure, a stacked portion and a folded portion are alternately located between first and second wrapping portions respectively located at end portions, and the first and second wrapping portions abut the stacked portion. In the electrode assembly, a plurality of stacked portions are sequentially positioned side by side in a thickness direction by a folded portion, and at least one positive electrode is positioned between stacked portions adjacent to each other in the thickness direction. The electrode assembly has a structure in which an outer surface in the thickness direction and the longitudinal direction is surrounded by the first and second wrapping portions or is surrounded by the first and second wrapping portions and at least one outermost stacked portion.

Description

Technical Field

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

[0002] This application claims the benefit of priority to 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 the entire contents of these applications are incorporated as part of this specification. Background Art

[0003] In recent years, there has been a growing interest in energy storage technology. As the application areas continue to expand, from mobile phones, portable cameras and notebook PCs to energy sources for electric vehicles, efforts on research and development are being reflected. In this regard, electrochemical devices are one of the most promising fields, and in particular, in view of the recent trend of miniaturization and lightweight electronic devices, the development of secondary batteries is attracting attention as batteries that are miniaturized and lightweight and can be charged and discharged at a high capacity.

[0004] Secondary batteries are also classified according to the structure of the electrode assembly consisting of positive electrode / separator / negative electrode. For example, the electrode assembly is classified into: a jelly roll (wound) electrode assembly, which is a wound long sheet of positive and negative electrodes with a separator; and a stacked electrode assembly, in which a plurality of positive and negative electrodes cut into predetermined size units with a separator are sequentially stacked.

[0005] However, these conventional electrode assemblies suffer from several problems.

[0006] First, the jelly roll electrode assembly is made by winding long sheets of positive and negative electrodes in a dense state, thereby having a cylindrical or elliptical cross-section. In this structure, stress caused by the expansion and contraction of the electrodes during charging and discharging accumulates in the electrode assembly, and when this stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs. Furthermore, the deformation of the electrode assembly can cause non-uniform spacing between the electrodes, resulting in a sharp decrease in battery performance, and internal short circuits may occur, thereby threatening the safety of the battery. Furthermore, because the jelly roll electrode assembly requires winding long sheets of positive and negative electrodes, it is difficult to quickly wind the positive and negative electrodes while maintaining a constant spacing between the positive and negative electrodes, resulting in reduced productivity.

[0007] Second, the stackable electrode assembly requires sequential stacking of multiple positive and negative electrode units. In this process, because a separate plate transfer process is required to manufacture the units, and the sequential stacking process requires a lot of time and effort, the stackable electrode assembly has a problem of low productivity.

[0008] In order to solve these problems, a stackable-foldable electrode assembly with an advanced structure, which is a hybrid of a jelly roll type and a stackable type, has been developed. The stackable-foldable electrode assembly has a structure in which a double cell or a full cell with a separator is stacked between the positive and negative electrodes of a predetermined unit using a long continuous separator film sheet (foldable separator film) wound around it.

[0009] The stackable-foldable electrode assembly typically connects the electrodes of each layer by extending a separator that is easier to fold rather than extending the electrode. In this process, as in the stacked electrode assembly, the electrodes of each layer are supplied in a cut state to form an electrode assembly. In the related art, if among the various traditional electrode materials used for secondary batteries in the technical field, the secondary battery is composed of a material that is not easy to cut or fold, then a conventional stackable-foldable electrode assembly is more suitable. On the other hand, lithium metal (as a negative electrode material for secondary batteries, which is well known in the technical field) may not be suitable for conventional stackable-foldable electrode assemblies because it is not easy to handle by processes such as cutting due to its physical properties such as high ductility and viscosity, and it is relatively easy to be folded.

[0010] After continuously conducting research on the structure of an electrode assembly, the inventors of the present invention have designed a structure suitable for an electrode assembly particularly containing lithium metal as a negative electrode, and have completed the present invention.

[0011] Patent References

[0012] (Patent Reference 1) Korean Patent No. 10-2023530 Summary of the invention

[0013] Technical issues

[0014] The present invention seeks to provide an electrode assembly having a novel structure suitable for an electrode assembly containing lithium metal as a negative electrode and an electrochemical device including the electrode assembly.

[0015] Technical Solution

[0016] According to a first aspect of the present invention, the present invention provides an electrode assembly, which includes a negative electrode structure and a plurality of positive electrodes.

[0017] 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.

[0018] In one embodiment of the present invention, the negative electrode structure is divided into: a plurality of stacked parts, a plurality of folded parts, and a first wrapping part and a second wrapping part according to positions of the following in the electrode assembly.

[0019] In one embodiment of the present invention, the stacked portion and the folded portion are alternately located between first and second wrapping portions respectively located at ends of the negative electrode structure, wherein the first and second wrapping portions respectively adjoin the stacked portion.

[0020] In one embodiment of the present invention, the electrode assembly has a plurality of stacking parts sequentially positioned side by side in a thickness direction by folding parts, and at least one positive electrode is positioned between the stacking parts adjacent to each other in the thickness direction.

[0021] In one embodiment of the present invention, the electrode assembly has a structure in which the outer surface in the thickness direction and the longitudinal direction is surrounded by the first wrapping part and the second wrapping part or by the first wrapping part and the second wrapping part and at least one outermost stacking part.

[0022] In one embodiment of the present invention, in the electrode assembly, the plurality of stacking portions and the plurality of positive electrodes become closer to each other in a thickness direction by the wrapping portion.

[0023] In one embodiment of the invention, the first wrapping portion and the second wrapping portion do not overlap each other.

[0024] In one embodiment of the present invention, the first wrapping portion and the second wrapping portion have the same length as each other.

[0025] In one embodiment of the invention, the first wrapping portion and the second wrapping portion are secured to different outermost stacking portions.

[0026] In one embodiment of the present invention, in the electrode assembly, one positive electrode is located between stacked portions adjacent to each other in the thickness direction, and the total number of positive electrodes located between the stacked portions is 2n (where n is a natural number).

[0027] In one embodiment of the present invention, in the electrode assembly, the positive electrode includes a positive electrode active material and a current collector supporting the positive electrode active material, and the negative electrode structure does not include a current collector supporting the lithium metal layer.

[0028] In one embodiment of the present invention, in the negative electrode structure, the lithium metal layer has the same length as the first separator and the second separator.

[0029] In one embodiment of the present invention, in the negative electrode structure, the end of the first wrapping portion is located on the stacking portion adjacent to the second wrapping portion so that the first wrapping portion turns to wrap around one side of the adjacent electrode assembly, and the end of the second wrapping portion is located on the stacking portion adjacent to the first wrapping portion so that the second wrapping portion turns to wrap around one side of the adjacent electrode assembly.

[0030] In one embodiment of the present invention, the electrode assembly further includes a fixing member for fixing an end portion of each of the first wrapping portion and the second wrapping portion to the outermost stack portion.

[0031] In one embodiment of the present invention, the length of the folded portion in the negative electrode structure is 2 to 10 times the sum of the thicknesses of the positive and negative electrode structures.

[0032] In one embodiment of the present invention, the length of the folded portion in the negative electrode structure is 2 to 10 times the vertical distance between the end of the positive electrode and the lateral wrapping portion surrounding it.

[0033] In one embodiment of the present invention, the folded portion has an asymmetrical shape with respect to a plane along the longitudinal direction.

[0034] In one embodiment of the present invention, the thickness of the lithium metal layer in the negative electrode structure is 50% to 90% based on the overall thickness of the negative electrode structure.

[0035] In one embodiment of the present invention, the thickness of the positive electrode is greater than the thickness of the negative electrode structure.

[0036] In one embodiment of the present invention, the fixing member is an insulating tape.

[0037] In one embodiment of the present invention, the center point of the length of the folded portion is not aligned with the center point of the thickness of the positive electrode surrounded by the folded portion.

[0038] In one embodiment of the present invention, each of the first wrapping portion and the second wrapping portion located on the stacking portion does not overlap each other in the thickness direction.

[0039] In one embodiment of the present invention, each of the first wrapping portion and the second wrapping portion located on the stacking portion overlaps each other in the thickness direction.

[0040] In one embodiment of the present invention, an end portion of the first wrapping portion and an end portion of the second wrapping portion are located on the same line in the thickness direction.

[0041] According to a second aspect of the present invention, the present invention provides an electrochemical device comprising the electrode assembly described above.

[0042] In one embodiment of the present invention, the electrochemical device is a lithium secondary battery.

[0043] In one embodiment of the present invention, the electrochemical device is a lithium sulfur battery.

[0044] Effects of the Invention

[0045] An electrode assembly according to an embodiment of the present invention is manufactured by using a negative electrode structure in a continuous form of a negative electrode containing lithium metal interposed between two separators, thereby minimizing the cutting of lithium metal and correspondingly improving process efficiency when manufacturing the electrode assembly.

[0046] Furthermore, by adjusting the methods and conditions of stacking, folding, and wrapping according to the material properties of the negative electrode structure, not only can the manufactured electrode assembly have a stable structure, but also the performance of the battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of the structure of a negative electrode structure including a stacking portion, a folding portion and a wrapping portion according to an embodiment of the present invention.

[0048] Figure 2 FIG. 1 is a schematic diagram of the structure of an electrode assembly including a negative electrode structure and a positive electrode according to an embodiment of the present invention.

[0049] Figure 3 FIG. 1 is a schematic diagram of a structure of an electrode assembly in which an end of a wrapping portion is fixed to a negative electrode structure by a fixing member according to an embodiment of the present invention.

[0050] Figure 4 FIG. 1 is an enlarged schematic diagram of a folded portion of an electrode assembly according to an embodiment of the present invention.

[0051] Figure 5 It is an enlarged schematic diagram of a portion of an electrode assembly according to one embodiment of the present invention, where the end and lateral wrapping portion of the positive electrode are located.

[0052] FIG. 6 is a diagram schematically illustrating the process and state of the manufacturing process of the electrode assembly according to one embodiment of the present invention. Here, Figure 6a schematically illustrates a process of folding a negative electrode structure to form an electrode laminate in which positive and negative electrode structures are alternately stacked, and Figure 6b The process of wrapping one side of the electrode laminate with the first and second wrapping parts after the electrode laminate is formed is schematically illustrated. Figure 6c A state in which the electrode assembly is completed after wrapping is schematically illustrated, in which the ends of the first and second wrapped parts are located on the stacked part, and Figure 6dThe state where the ends of the first and second wrapping parts are fixed is schematically shown.

[0053] Figure 7 is a graph depicting results of measuring the cycle-by-cycle coulombic efficiency of a lithium secondary battery including each of the electrode assemblies manufactured according to Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0054] Details of embodiments of the present invention are provided in the following description. It should be noted that when assigning reference numerals to components in each of the drawings, the same components are given the same reference numerals as much as possible even in different drawings. In addition, when describing an embodiment, if it is considered that a detailed description of a related known structure or feature hinders the understanding of the embodiment, the detailed description is omitted.

[0055] In addition, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of the embodiments. Such terms are intended only to distinguish one component from another, and the nature, sequence or order of such components is not limited by such terms. When a component is described as being "connected," "coupled," or "adjacent" to another component, it should be understood that the component may be directly connected or in contact with the other component, but another component may be "connected," "coupled," or "adjacent" between these components.

[0056] The same terms are used in other embodiments to describe components included in one embodiment and components having common functions. Unless otherwise indicated, the description in one embodiment can be applied to other embodiments, and redundant detailed descriptions are omitted.

[0057] The present invention relates to an electrode assembly that improves problems that may occur when lithium metal is applied to a conventional stackable-foldable electrode assembly structure as a negative electrode to provide an electrode assembly having a novel structure suitable for using lithium metal as a negative electrode. By minimizing the handling of lithium metal, the electrode assembly according to the present invention can not only improve the processability of the assembly process, but also increase the reliability of the manufactured product. Furthermore, the electrode assembly has a structure that can maximize the utilization of the positive electrode included in the electrode assembly, which can contribute to improving the performance of the battery.

[0058] The terms “longitudinal direction”, “width direction”, and “thickness direction” (or “height direction”) are used in this specification. Figure 1 6 are front views, and based on these front views, a “longitudinal direction” indicates a left-right direction, a “width direction” indicates a front-rear direction, and a “thickness direction” (or a “height direction”) indicates an up-down direction.

[0059] As used herein, the term "adjacent" means an object that is closest to a reference among a plurality of objects referred to thereby. An adjacent object does not necessarily touch the reference.

[0060] An electrode assembly according to one 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 commonly used in the technical field, but the negative electrode includes lithium metal. As used herein, lithium metal can be generally understood, even if lithium is added with specific components or is an alloy with a specific metal, as long as it is not significantly different from lithium metal in nature and can be applied to traditional electrode assemblies, which causes the same problems as lithium metal. As used herein, the negative electrode can be referred to as a lithium metal layer because it includes lithium metal, and the negative electrode and the separator can be referred to as a negative electrode structure because they are provided as a single integrated structure.

[0061] According to one embodiment of the present invention, the negative electrode is placed between two separators to form a negative electrode structure. The two separators constituting the negative electrode structure may be referred to herein as a first separator and a second separator. The negative electrode structure has a longitudinally extending structure, and the electrode assembly includes only one negative electrode structure. The basic electrode assembly structure is formed by folding the negative electrode structure having a longitudinally extending structure and fixing the positive electrode therein.

[0062] According to one embodiment of the present invention, the negative electrode structure includes a plurality of stacked portions, a plurality of folded portions, and two wrapped portions according to their positions in the electrode assembly. In this specification, the two wrapped portions included in the negative electrode structure may be referred to as a first wrapped portion and a second wrapped portion. In order to facilitate understanding of the structure of the negative electrode structure, Figure 1 An exemplary structure of a negative electrode structure including a stacking portion, a folding portion, and a wrapping portion is provided. In the negative electrode structure (10), the stacking portion (10A, 10A'), the folding portion (10B), and the wrapping portion (10C) are units that are distinguished at positions having different functions depending on the longitudinal direction of the negative electrode structure (10). The stacking portion (10A, 10A'), the folding portion (10B), and the wrapping portion (10C) are not distinguished by material except for the position.

[0063] The stacking portion (10A, 10A') refers to the negative electrode structure (10) at a position where the positive electrode is stacked, and Figure 2 The folded portion (10B) refers to the negative electrode structure (10) in a position where the stacked portions are connected to each other, and Figure 2The folded portion (10B) may also be referred to as a curved portion. The wrapped portion (10C) refers to the negative electrode structure in the position of the stacked structure wrapping the positive and negative electrode structures at the point where the outermost stacked portion (10A') from the top or bottom ends, and Figure 2 There are straight and curved shapes.

[0064] As in Figure 1 As shown in , the negative electrode structure (10) has a wrapping portion (10C) at both ends relative to the longitudinal direction. That is, two wrapping portions (10C) are located at each of the longitudinal ends of the negative electrode structure (10). Furthermore, each of the wrapping portions (10C) contacts the outermost stacking portion (10A'), and between the outermost stacking portions (10A'), the folding portion (10B) and the stacking portion (10A) are alternately positioned. Because the length of the stacking portions (10A, 10A') is substantially equal to the length of the positive electrode, the length of each stacking portion (10A, 10A') is substantially the same.

[0065] The two wrapping parts (10C) located at both ends of the negative electrode structure (10) may have different lengths. In order to distinguish the two wrapping parts (10C), the wrapping part (10C) located at the point where the stacking starts here is called the first wrapping part, and the wrapping part (10C) located at the point where the stacking ends here is called the second wrapping part. For example, Figure 1 , if stacking starts from the left, the wrapping portion (10C) located at the left end is the first wrapping portion, and the wrapping portion (10C) located at the right end is 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 around one side of the interior of the electrode assembly. However, by adjusting the process conditions in a repeated process to balance the lengths of the first wrapping portion and the second wrapping portion so that the electrode assembly has a symmetrical structure, the structural stability of the electrode assembly can be increased. According to one embodiment of the present invention, the first wrapping portion and the second wrapping portion have the same length as each other.

[0066] The negative electrode structure (10) forms an electrode assembly together with a plurality of positive electrodes. To better understand the structure of the electrode assembly, Figure 2 An exemplary structure of an electrode assembly including a negative electrode structure and a positive electrode is provided. Since the negative electrode structure (10) includes a negative electrode (11) and a separator (12), the electrode assembly (1) includes a positive electrode (10), a negative electrode (11) and a separator (12).

[0067] According to one embodiment of the present invention, an electrode assembly (1) has a plurality of stacking portions (10A, 10A') sequentially positioned side by side in a thickness direction by a folding portion (10B), and at least one positive electrode is located between the stacking portions (10A, 10A') adjacent to each other in the thickness direction. According to one embodiment of the present invention, the electrode assembly (1) has a structure in which the outside in the thickness direction and the longitudinal direction is surrounded by the first and second wrapping portions (10C) or the first and second wrapping portions and at least one outermost stacking portion (10A'). In other words, the inside of the electrode assembly (1) has a structure in which the stacking portions (10A, 10A') of the negative electrode structure and the positive electrodes (20) are sequentially stacked in an alternating manner. In this case, only one positive electrode (20) is respectively located between the stacking portions (10A, 10A', 10A'') of the negative electrode structure. Furthermore, the outside of the electrode assembly (1) is surrounded by at least one stacking portion (10A') of the negative electrode structure and two wrapping portions (10C) of the negative electrode structure. The interior and exterior of the electrode assembly (1) are distinguished for the purpose of understanding the structure of the electrode assembly (1) according to the present invention, and are Figure 2 In the negative electrode structure (10), the layer exposed to the outside of the electrode assembly (1) in the thickness direction and the longitudinal direction indicates the outside of the electrode assembly (1), and the inner part of the outside of the electrode assembly (1) indicates the inside of the electrode assembly (1). In the negative electrode structure (10), because the stacking part (10A, 10A') is the negative electrode structure (10) at the position where the positive electrode is stacked, and the wrapping part (10C) starts from the point where the top or bottom outermost stacking part (10A') ends, when the end of the first wrapping part (10C) is located on the top of the outermost stacking part (10A'), as in Figure 2 As shown in , a portion of the outermost stacking portion (10A') may be located on the outside of the electrode assembly (1), and the remaining portion of the outermost stacking portion (10A') may be located on the inside of the electrode assembly (1). Moreover, when the end of the second wrapping portion (10C) is located on the bottom outermost stacking portion (10A'), a portion of the bottom outermost stacking portion (10A') may be located on the outside of the electrode assembly (1), and the remaining portion of the bottom outermost stacking portion (10A') may be located on the inside of the electrode assembly (1). Therefore, as used herein, the outermost stacking portion located on the inside or outside may refer to all or part of a stacking portion. Figure 2 Differently, if one of the first and second wrapping parts (10C) covers the entire outermost stacking part (10A'), the outside of the electrode assembly (1) may be formed with only the first or second wrapping part (10C). The plurality of folded parts (10B) are wrapped by the wrapping part (10C) so that they are not exposed to the outside in the thickness direction and the longitudinal direction.

[0068] Because the electrode assembly (1) according to one embodiment of the present invention has the stacking parts (10A, 10A') of the negative electrode structure (10) and the positive electrode (20) stacked alternately and sequentially therein, the negative electrode structure (10) including the folding part (10B) has a zigzag shape. In other words, the folding parts (10B) sequentially positioned from the stacking part (10A') in contact with the first or second wrapping part of the negative electrode structure (10) are alternately located on the left or right side of the electrode assembly (1). If the stacking parts (10A, 10A') of the negative electrode structure (10) and the positive electrode (20) are not alternately stacked, and two or more of the stacking parts or the positive electrodes are stacked sequentially, a potential difference may not occur between the sequentially stacked layers, and the efficiency of the battery may be reduced.

[0069] According to one embodiment of the present invention, in an electrode assembly (1), the plurality of stacking portions (10A, 10A') and the plurality of positive electrodes (20) become closer to each other in the thickness direction through the first and second wrapping portions (10C). The first and second wrapping portions (10C) are capable of wrapping the interior of the electrode assembly (1) with a higher tension than the stacking portions (10A, 10A') or the folding portion (10B), which causes the internal structure of the electrode assembly (1) to be closer to each other in the thickness direction. When the internal structure of the electrode assembly (1) becomes closer to each other in the thickness direction by this method, the internal structure of the electrode assembly (1) inevitably becomes closer to each other in the longitudinal direction. However, even if the internal structure of the electrode assembly (1) becomes closer to each other in the thickness direction and the longitudinal direction, a certain level of gap may exist around the folding portion (10B) due to the structure of the electrode assembly (1).

[0070] According to one embodiment of the present invention, the first wrapping portion and the second wrapping portion are not in contact with each other, but are fixed to different outermost stacking portions (10A') of the negative electrode structure. In other words, the first wrapping portion and the second wrapping portion do not overlap when forming the outside of the final electrode assembly. If the first wrapping portion and the second wrapping portion overlap, unnecessary negative electrode structure is used as much as the overlapping portion, which is not ideal 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 top of the stacking portion, and the stacking portion on which the end of the first wrapping portion is located and the stacking portion on which the end of the second wrapping portion is located can be different, thereby forming an effective electrode assembly structure.

[0071] According to one embodiment of the present invention, in the electrode assembly (1), one positive electrode is located between stacking parts (10A, 10A') adjacent to each other in the thickness direction, and the total number of positive electrodes (20) located between the stacking parts (10A, 10A') is 2n (where n is a natural number). Because there is only one positive electrode (20) between the stacking parts (10A, 10A') in the electrode assembly (1), the number of total positive electrodes here refers to the total number of positive electrodes under the same circumstances, and does not mean that 2n positive electrodes are stacked between the stacking parts. For example, in Figure 2 , the total number of positive electrodes located between the stacked parts is 4. In an electrode assembly according to one embodiment of the present invention, all positive electrodes (20) are located between the stacked parts. The upper limit of the number of total positive electrodes (20) is not particularly limited and can be adjusted within the conventional range in the technical field. When the total number of positive electrodes (20) located between the stacked parts (10A, 10A') is 2n, the end of the first wrapped part is opposite to the end of the second wrapped part. For example, in Figure 2 In the embodiment of the present invention, the end of the first wrapping part is on the left side, and the end of the second wrapping part is on the right side. In this case, even if the left and right sides of the inner side of the electrode assembly are respectively wrapped by the first wrapping part and the second wrapping part, the first wrapping part and the second wrapping part may not overlap each other, and an electrode assembly with an effective structure can be manufactured.

[0072] According to one embodiment of the present invention, the number of stacking parts (10A, 10A') in the electrode assembly (1) may be one more than the number of positive electrodes (20). As described above, if 2n (where n is a natural number) total positive electrodes (20) are to be located between the stacking parts, the number of stacking parts (10A, 10A') is 2n+1 (where n is a natural number).

[0073] According to one embodiment of the present invention, a positive electrode (20) includes a positive electrode active material layer (not shown in the drawings) and a current collector (not shown in the drawings) supporting 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 side, more specifically both sides, of the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a conductive material, a binder, and an additive. The current collector, the positive electrode active material, the conductive material, the binder, or the additive is not particularly limited as long as it is commonly used in the technical field.

[0074] The positive electrode current collector supports the positive electrode active material and is not particularly limited to having high conductivity without causing any chemical changes in the battery. According to one embodiment of the present invention, the positive electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel whose surface is treated with carbon, nickel or silver, or aluminum-cadmium alloy.

[0075] The positive electrode current collector can form microscopic irregularities on its surface to strengthen the bonding with the positive electrode active material, and can be in various forms, such as films, sheets, foils, meshes, nets, porous materials, foams, non-woven materials, etc.

[0076] As the positive electrode active material, a lithium-containing transition metal oxide can be used. According to an embodiment of the present invention, it is selected from the group consisting of LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li(Ni a Co b Mn c )O 2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, and a + b + c = 1), LiNi 1-y Co y O 2 (where 0 < y < 1), LiCo 1-y Mn y O 2 (where 0 < y < 1), LiNi 1-y Mn y O 2 (where 0 < y < 1), Li(Ni a Co b Mn c )O 4 (where 0 < a < 2, 0 < b < 2, 0 < c < 2, and a + b + c = 2), LiMn 2-z Ni z O 4 (where 0 < z < 2), LiMn 2- z Co z O 4 (where 0 < z < 2), LiCoPO 4 and LiFePO 4 and any one or a mixture of two or more of the group consisting of. In addition to these oxides, sulfides, selenides or halides can be used.

[0077] The positive electrode active material can include a sulfur compound. According to an embodiment of the present invention, the sulfur compound can be selected from the group consisting of elemental sulfur (S 8 ), organic sulfur compound Li 2 S n (where n ≥ 1) and carbon-sulfur polymer ((C 2 S x ) n, wherein x is 2.5 to 50, and n ≥ 1). Preferably, inorganic sulfur (S 8 ).

[0078] When the positive electrode active material includes a sulfur compound, the electrode assembly (1) according to one embodiment of the present invention can be applied to a lithium-sulfur battery. Since the sulfur contained in the positive electrode active material itself is not conductive, it can be used in combination with a conductive material such as a carbon material. Accordingly, the sulfur is included in the form of a sulfur-carbon composite, and preferably, the positive electrode active material can be a sulfur-carbon composite.

[0079] In view of the foregoing, the positive electrode (20) is relatively less likely to be folded and more easily cut than the negative electrode. Therefore, the positive electrode (20) can be cut into appropriate sizes so that a plurality of positive electrodes can be applied to the interior of the electrode assembly (1).

[0080] According to one embodiment of the present invention, the negative electrode (11) does not include a current collector supporting the lithium metal layer. Because the negative electrode (11) does not include a current collector, the loading amount of the negative electrode active material within the electrode assembly can be improved, which can contribute to improving the performance of the battery. When the negative electrode (11) is mainly composed of lithium metal, because the lithium metal is highly ductile and viscous, it may not be easy to handle, such as cutting, but in the electrode assembly (1) according to one embodiment of the present invention, the handleability 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 one embodiment of the present invention may be a free-standing lithium metal layer that can maintain a shape to a certain level on its own.

[0081] The separator (12) covering both sides of the negative electrode (11) in the negative electrode structure (10) is not particularly limited in type as long as it does not include a binder on its surface. The separator (12) may be a nonwoven or polyolefin-based porous material made of, for example, glass fiber or polyethylene terephthalate fiber having a high melting point, but is not limited thereto.

[0082] The material of the porous material is not particularly limited in the present invention, but any porous material conventionally used in electrochemical devices can be used. According to one embodiment of the present invention, the porous material may include at least one selected from the group consisting of polyolefins such as polyethylene or polypropylene, polyesters such as polyethylene terephthalate or polybutylene terephthalate, polyamides, polyacetals, polycarbonates, polyimides, polyetheretherketones, polyethersulfones, polyphenylene oxides, polyphenylene sulfides, polyethylene phthalates, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, cellulose, nylon, poly(p-phenylene benzobisoxazole) and polyarylates.

[0083] According to one embodiment of the present invention, the negative electrode (11) in the negative electrode structure (10) has the same length as the first and second separators (12). With reference to the end of the negative electrode structure (10) where the wrapping portion (10C) is located, the separator located on the outside of the electrode assembly (1) can be referred to as the first separator, and the separator located on the inside of the electrode assembly (1) can be referred to as the second separator. The negative electrode (11) and the separator (12) are provided to the electrode assembly (1) in the form of a negative electrode structure (10) having the negative electrode (11) interposed between the first and second separators (12), wherein the negative electrode and the separator are cut at one time so as to be as shown in Figure 1 As shown in FIG. 1 , the lengths of the negative electrode (11) and the first and second separators (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 separators (12), and in some cases, the ends of the first and second separators (12) may be bent toward the center of the negative electrode structure (10). According to one embodiment of the present invention, the first and second separators are folded at the ends of the negative electrode structure (10). Although the negative electrode structure (10) has substantially the same lengths of the negative electrode (11) and the first and second separators (12) during the supply process, when applied to the electrode assembly (1), the length of the lithium metal may be extended due to the ductility of the lithium metal during the folding process. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the wrapping portion (10C) side, the lithium metal protrudes longer than the first or second separator. Moreover, depending on the number of folds, the separator located more on the outside than on the inside of the folded portion (10B) may be shorter. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the first or second wrapping part (10C) side, the first separator protrudes longer than the second separator. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the first or second wrapping part (10C) side, the second separator protrudes longer than the first separator.

[0084] According to one embodiment of the present invention, the end of the first wrapping portion is located on the stacking portion (10A') adjacent to the second wrapping portion, where the first wrapping portion turns to wrap around one side of the adjacent electrode assembly, and the end of the second wrapping portion is located on the stacking portion adjacent to the first wrapping portion, where the second wrapping portion turns to wrap around one side of the adjacent electrode assembly. The stacking portion refers to the outermost stacking portion (10A'). The ends of the first and second wrapping portions can be positioned on the outermost stacking portion (10A') in various ways. According to one embodiment of the present invention, the first and second wrapping portions respectively located on the stacking portion do not overlap each other in the thickness direction. The farther the first and second wrapping portions are spaced apart in the thickness direction, the less the amount of negative electrode structure required, which can be effective. According to one embodiment of the present invention, each of the first wrapping portion and the second wrapping portion located on the stacking portion overlap each other in the thickness direction. The longer the first wrapping portion and the second wrapping portion overlap in the thickness direction, the more stable the electrode structure can be. According to one embodiment of the present invention, the end of the first wrapping portion and the end of the second wrapping portion are located on the same line in the thickness direction. The positional relationship in the thickness direction described above shows whether the first or second wrapping portion overlaps, does not overlap, or has its ends contacted with each other when the first or second wrapping portion moves in the thickness direction.

[0085] According to one embodiment of the present invention, the ends of the first and second wrapping parts (10C) located on the outermost stacking part can be attached to the outermost stacking part (10A'). As long as the end of the first or second wrapping part (10C) can be effectively attached to the outermost stacking part (10A'), the device and method for attachment are not particularly limited. According to one embodiment of the present invention, the electrode assembly (1) further includes a fixing component for fixing the end of the first or second wrapping part (10C) to the outermost stacking part (10A'). In order to provide a better understanding of where the end of the wrapping part (10C) is attached in the negative electrode structure (10), Figure 3 An exemplary structure of an electrode assembly is provided, in which an end of a wrapping portion is attached to a negative electrode structure by a fixing member. Although the negative electrode (11) and the separator (12) in the negative electrode structure (10) are not bonded, according to Figure 3 In the electrode structure, both ends of the negative electrode structure (10) can be fixed to form a stable structure. Figure 3As shown in , it may be desirable to attach a tape (T) as a fixing member to wrap around the outer surface of the electrode assembly (1). According to one embodiment of the present invention, while taking into account a case where lithium metal extends and protrudes due to the ductility of lithium metal in a process of folding the negative electrode structure (10) when manufacturing the electrode assembly (1), the tape (T) has an insulating property and covers the entire end of the wrapping portion (10C) in the width direction. By this tape connection method, the electrode assembly (1) is covered with a separator or tape from top to bottom and from left to right.

[0086] In manufacturing an electrode assembly (1), when stacked portions (10A, 10A') of a negative electrode structure (10) and a positive electrode (20) are alternately stacked, the negative electrode structure (10) is folded according to the same criteria, so that the folded portions (10B) also have substantially the same length. When folding, the negative electrode structure (10) applies the same criteria using a mandrel of a specific form. If the folded portion (10B) has a shorter length, an unnecessary load is applied to the lithium metal located at the center of the negative electrode structure (10), resulting in defects such as lithium metal fracture. Therefore, ensuring a sufficient length of the folded portion (10B) above a specific level enables the lithium metal to be flexibly placed in the gap between the portion in which the electrode is stacked and the wrapped portion.

[0087] To better understand the length of the folded portion (10B) in the negative electrode structure (10), Figure 4 An enlarged illustration of a portion of a folded portion (10B) in an electrode assembly (1) is provided. According to one embodiment of the present invention, the length of the folded portion (10B) in the negative electrode structure (10) is 2 to 10 times the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10). The length of the folded portion (10B) means the length of the curve of the folded portion. In the curve, because the lengths of the inner and outer sides may be different from each other, the length of the center portion is measured. For example, it is possible to cut the folded portion by Figure 4 The length is measured by folding the portion indicated by the dotted line in the figure and then unfolding it. Specifically, the length of the folded portion (10B) may be 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more, 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, 2 to 10 times, 3 to 9 times, or 4 to 8 times the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10). When the length of the folded portion (10B) is adjusted within this range, defects of the folded portion in the electrode assembly can be reduced, and the electrode assembly can be stably wrapped.

[0088] The length of the folded portion (10B) described above indicates that it is Figure 4 is formed longer than it is as shown in Figure 2 Specifically, when the folded portion (10B) has the form of a complete semicircle with an eccentricity of 0, the length of the folded portion becomes the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10), which is the diameter multiplied by π and divided by 2. This is approximately 1.57 times the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10). Based on this, it can be seen that the length of the folded portion (10B) according to one embodiment of the present invention is quite long.

[0089] When manufacturing an electrode assembly (1), after stacking portions (10A, 10A') of a negative electrode structure (10) and a positive electrode (20) in an alternating manner and wrapping the electrode laminate (1) with a wrapping portion (10C), the folded portion (10B) is subjected to a certain level of pressure in the inner direction of the electrode assembly (1). Accordingly, the folded portion (10B) can be appropriately placed in a gap between a portion on which the electrode is stacked and the wrapping portion. Because the folded portion (10B) appropriately placed in the gap includes a lithium metal layer (11) therein, this can contribute to further improving battery performance through an electrochemical reaction with the positive electrode (20) on its side. When the folded portion (10B) appropriately fills the gap, two or more lithium metal layers can also be located on the side of the positive electrode that is not wrapped by the folded portion (10B). When the electrode laminate (1) is wrapped with the wrapping portion (10C) so that the wrapping portion (10C) has tension higher than a certain level, this helps maintain the structure of the electrode laminate in the electrode assembly (1) without distortion.

[0090] According to one embodiment of the present invention, the folded portion (10B) has an asymmetric shape relative to a plane along the longitudinal direction. This asymmetric shape is formed when the folded portion (10B) is pressed in the longitudinal direction by the wrapping portion (10C) so that the folded portion (10B) is properly positioned in the gap. According to one embodiment of the present invention, the center point of the length of the folded portion (10B) is not aligned with the center point of the thickness of the positive electrode around which the folded portion (10B) is wrapped. The center point of the length of the folded portion (10B) can be oriented in the wrapping direction relative to the center point of the thickness of the positive electrode. For example, referring to Figure 2 , because wrapping is performed from top to bottom, the folded portion located on the right side of the electrode laminate may have the center point of the length of the folded portion below the center point of the thickness of the positive electrode. Conversely, because wrapping is performed from bottom to top, the folded portion on the left side of the electrode laminate may have the center point of the length of the folded portion above the center point of the thickness of the positive electrode.

[0091] In order to provide a better understanding of the vertical distance between the end of the positive electrode (20) and the lateral wrapping portion (10C) (which is the basis for comparing the length of the folded portion (10B) below), Figure 5 An enlarged view of a portion of an electrode assembly (1) where the end of a positive electrode (20) and a lateral wrapping portion (10C) are located is provided. Figure 5 As shown in , the folded portion (10B) can be deformed by pressure applied from the laterally positioned wrapping portion (10C) during the process of wrapping the electrode assembly. However, Figure 5 This is merely an exemplary structure and the folded portion (10B) is not necessarily deformed to this shape. Due to the pressure, the distance (d) between the end of the positive electrode (20) and the lateral wrapping portion (10C) can be shortened, and, as the distance (d) is shortened, the folded portion (10B) can be naturally placed in the shortened space. According to one embodiment of the present invention, the length of the folded portion (10B) in the electrode assembly (1) is 2 to 10 times the vertical distance (d) between the end of the positive electrode (20) and the lateral wrapping portion (10C). The lateral wrapping portion (10C) refers to the distance (d) between the positive electrode (20) and the lateral wrapping portion (10C). Figure 2 or Figure 3 A straight wrapping portion (10C) located on the left or right side of the electrode assembly. If the corresponding portion in the actual electrode assembly is not straight, the vertical distance (d) is measured as the vertical distance from the lateral wrapping portion to the end of the positive electrode at the center portion of the electrode laminate in the thickness direction. Alternatively, the vertical distance (d) can be measured as the average of the vertical distances from the end of the positive electrode (20) to the portion of the wrapping portion (10C) adjacent to the folding portion (10B) on one side. Specifically, the length of the folding portion (10B) can be 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more, 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, 2 times to 10 times, 3 times to 9 times, or 4 times to 8 times the vertical distance (d) between the end of the positive electrode (20) and the lateral wrapping portion (10C). This means that the length of the folded portion (10B) is significantly longer as described above, but the vertical distance (d) is also shorter, so that the folded portion is compactly packed in the lateral space of the electrode laminate. When the length of the folded portion (10B) is adjusted within this range, the folded portion can be compactly packed into the gap in the electrode assembly to an appropriate extent without applying excessive pressure on the folded portion due to the wrapping of the electrode assembly, thereby helping to improve the performance of the battery.

[0092] Since the electrode assembly (1) according to one embodiment of the present invention forms the basic structure of the electrode assembly (1) by folding a negative electrode structure (10), the negative electrode structure (10) should not be too thick so that it can be folded flexibly, and considering the performance of the battery, a certain level of lithium metal (negative electrode active material) should be ensured in the negative electrode structure (10). According to one embodiment of the present invention, based on the overall thickness of the negative electrode structure (10), the thickness of the lithium metal in the negative electrode structure (10) accounts for 50% to 90%. Specifically, the thickness of the lithium metal can range from 50% to 90%, specifically from 55% to 85%, and more specifically from 60% to 80%. When the lithium metal satisfies the above-mentioned thickness range, it can help improve the processability and functionality of the electrode assembly. According to one 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 lithium metal can refer to the thickness of two separators.

[0093] According to one embodiment of the present invention, the thickness of the lithium metal may be from 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 be 70 μm or less, 80 μm or less, or 90 μm or less. The thickness of the lithium metal is not necessarily limited thereto, and may be appropriately adjusted according to the actual size of the battery.

[0094] In an electrode assembly (1) according to an 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 stacked parts (10A, 10A') of the negative electrode structure (10). Although the positive electrode is different from and independent of the negative electrode, the thickness can be adjusted with respect to the negative electrode or the negative electrode structure in consideration of the performance of the electrode, such as including a current collector in addition to the positive electrode active material. 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 greater than 100% and less than 400% relative to the thickness of the negative electrode structure (10). Specifically, the thickness of the positive electrode (20) can range from greater than 100% or less than 400%, specifically from 150% to 350%, and more specifically from 200% to 300%. When the positive electrode satisfies the thickness range described above, it can be appropriately matched with the negative electrode structure.

[0095] Hereinafter, a detailed description is provided on a process for manufacturing an electrode assembly. In order to facilitate understanding of the manufacturing process of the electrode assembly, FIG. 6 schematically illustrates processes and states in the manufacturing process of the electrode assembly.

[0096] A manufacturing process for an electrode assembly according to one embodiment of the present invention includes the following steps: (1) folding a negative electrode structure to form an electrode laminate in which positive and negative electrode structures are alternately stacked; (2) surrounding the electrode laminate with an excess of the negative electrode structure after manufacturing the electrode laminate; and (3) positioning and fixing an end of the negative electrode structure to the top of the electrode laminate.

[0097] Step (1) is performed by Figure 6a The process shown in is exemplarily fabricated. Figure 6a As shown in , the negative electrode structure and the positive electrode can be stacked sequentially so that the negative electrode structure is at the bottom and the positive electrode is on top. Figure 6a , but the negative electrode structure may be folded using a device such as a mandrel so that the folding at each position is performed according to the same criteria. Stacking does not start at the end of the negative electrode structure, but at the stacking portion that is in contact with the first wrapping portion, so that the first wrapping portion is retained enough to cover one side of the electrode laminate later. Step (2) is performed by Figure 6b The additional negative electrode structure is present as first and second wrapping portions at both ends, and each of the first and second wrapping portions wraps the side of the adjacent electrode laminate. During the wrapping process with the additional negative electrode structure, wrapping the negative electrode structure so that the negative electrode structure is under a certain level of tension helps to pack the folded portion compactly within the gap and helps the structure of the electrode laminate maintain its shape without distortion. After step (3), the completed electrode assembly is in a state as in Figure 6c or Figure 6d Wrapping has the effect of preventing the positive electrode from flowing downward between the stacked parts, and considering this function, it may be desirable to position the end of the negative electrode structure at the top 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, and as in Figure 6d Wrapping with tape (T) as shown in FIG. 1 may be an exemplary method.

[0098] The specific characteristics of the positive and negative electrode structures not specifically described in the manufacturing process are consistent with the foregoing. An electrode assembly according to an embodiment of the present invention can weld multiple layers of tabs and leads, such as in a conventional large-capacity cell, to maintain performance such as cell resistance and output.

[0099] An electrode assembly according to one embodiment of the present invention is applied to an electrochemical device. The electrochemical device may include any device that performs an electrochemical reaction. For example, the electrochemical device may be any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor. If the electrochemical device is a secondary battery, the electrochemical device may be a lithium secondary battery, which may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0100] As shown above, although the embodiments have been described by limited examples and drawings, a person of ordinary skill in the art can make various modifications and changes in view of the above description. For example, even if the provided techniques can be performed in a different order than the method described above, and / or the provided components such as systems, structures, devices, circuits, etc. can be combined in a different form than the method described above, or replaced or substituted by other components or equivalents, the desired results can be achieved.

[0101] Hereinafter, examples are given to facilitate understanding of the present invention. The following examples are provided to illustrate the present invention, but the present invention is not limited thereto.

[0102] Example

[0103] Example 1: Fabrication of an electrode assembly wrapped with a negative electrode structure

[0104] The negative electrode structure was prepared by inserting 60 μm of lithium metal between two polyethylene (PE) separators (11 μm). In addition, a positive electrode compound was added to deionized water to prepare a positive electrode slurry consisting of 85 wt% of a positive electrode active material prepared by mixing sulfur and carbon nanotubes (CNT) at a weight ratio of 7:3, 5 wt% of carbon nanofibers as a conductive material, and 10 wt% of a binder, and then an aluminum current collector was coated with the positive electrode slurry to produce a 200 μm positive electrode.

[0105] The fabricated negative electrode structure is Figure 6a The electrode laminate is folded in the manner shown and then Figure 6b The electrode laminate is wrapped with excess negative electrode structure to form a Figure 6c As shown in the electrode assembly. Figure 6d The exposed end of the negative electrode structure in the electrode assembly is fixed with an insulating tape as shown in FIG. In the electrode assembly, the length of the folded portion is measured to be 1453 μm, and the vertical distance between the end of the positive electrode and the lateral wrapping portion is measured to be 268 μm.

[0106] Comparative Example 1: Fabrication of an electrode assembly in which a negative electrode structure is cut and laminated

[0107] The negative electrode structure is cut to fit the positive electrode of each layer, and then the positive and negative electrode structures are laminated to form an electrode laminate, and the electrode assembly is completed without any separate wrapping with the negative electrode structure. In the electrode assembly, the materials and thicknesses of the positive and negative electrode structures are the same as in Example 1.

[0108] Experimental Example

[0109] Each electrode assembly prepared according to Example 1 and Comparative Example 1 was placed in the same bag and heated with 0.4 M LiFSI salt and 4 wt % LiNO 3 The ether-based electrolyte was filled to prepare a lithium secondary battery. The coulombic efficiency of the prepared lithium secondary battery was measured by charging and discharging it at 0.3C, and the results were Figure 7 Shown in.

[0110] The electrode assembly according to the present invention is not only superior to the conventional electrode assembly in terms of process, but also Figure 7 , it can be seen that the long-term performance of the battery, such as Coulombic efficiency, can also be improved.

[0111] All simple variations or modifications of the invention are within the scope of the invention, and the specific scope of protection sought will be clear from the appended claims.

[0112] Reference numerals

[0113] 1, 1', 1'': Electrode assembly

[0114] 10: Negative electrode structure

[0115] 10A, 10A': stacking part (10A': outermost stacking part)

[0116] 10B: Folding part

[0117] 10C: Wrapping part (first and second wrapping parts)

[0118] 11: Negative electrode (lithium metal layer)

[0119] 12: Separation film (first and second separation films)

[0120] 20: Positive electrode

[0121] T: Fixed part (belt)

[0122] d: vertical distance between the end of the positive electrode and the lateral wrapping part

Claims

1. An electrode assembly, comprising a negative electrode structure and a plurality of positive electrodes, in, The negative electrode structure includes a first separator film, a second separator film, and a lithium metal layer interposed between the first separator film and the second separator film. wherein the negative electrode structure is divided into a plurality of stacked portions, a plurality of folded portions, and a first wrapped portion and a second wrapped portion according to the position in the electrode assembly as follows, wherein the stacked portions and the folded portions are alternately located between the first wrapped portion and the second wrapped portion respectively located at the ends of the negative electrode structure, and the first wrapped portion and the second wrapped portion are adjacent to the stacked portions, wherein the plurality of stacked portions are sequentially positioned side by side in the thickness direction by the folded portion, and at least one positive electrode is positioned between the stacked portions adjacent to each other in the thickness direction, Wherein the outside in the thickness direction and the longitudinal direction is surrounded by the first wrapping part and the second wrapping part, or is surrounded by the first wrapping part and the second wrapping part and at least one outermost stacking part.

2. The electrode assembly according to claim 1, wherein: The plurality of stacked portions and the plurality of positive electrodes become closer to each other in the thickness direction by the first wrapping portion and the second wrapping portion.

3. The electrode assembly according to claim 1, wherein: The first wrapping portion and the second wrapping portion do not contact each other.

4. The electrode assembly according to claim 1, wherein: The first wrapping portion and the second wrapping portion have the same length as each other.

5. The electrode assembly according to claim 1, wherein: The first wrapping portion and the second wrapping portion are secured to different outermost stacking portions.

6. The electrode assembly according to claim 1, wherein: In the electrode assembly, one positive electrode is positioned between the stacked portions adjacent to each other in the thickness direction, and The total number of the positive electrodes located between the stacked portions is 2n (where n is a natural number).

7. The electrode assembly according to claim 1, wherein: 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.

8. The electrode assembly according to claim 1, wherein: The lithium metal layer in the negative electrode structure has the same length as the first separator and the second separator.

9. The electrode assembly according to claim 1, wherein: In the negative electrode structure, an end of the first wrapping portion is located on a stacking portion adjacent to the second wrapping portion, wherein the first wrapping portion turns to wrap around one side of an adjacent electrode assembly, and an end of the second wrapping portion is located on a stacking portion adjacent to the first wrapping portion, wherein the second wrapping portion turns to wrap around one side of an adjacent electrode assembly.

10. The electrode assembly according to claim 1, wherein: The electrode assembly further includes fixing members for fixing an end portion of the first wrapping portion and an end portion of the second wrapping portion to the outermost stack portion, respectively.

11. The electrode assembly according to claim 1, wherein: The length of the folded portion in the negative electrode structure is 2 to 10 times the sum of the thicknesses 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 folded portion is 2 to 10 times the vertical distance between the end of the positive electrode and the lateral wrapping portion surrounding it.

13. The electrode assembly according to claim 1, wherein: The folded portion has an asymmetrical shape with respect to a plane along the longitudinal direction.

14. The electrode assembly according to claim 1, wherein: The thickness of the lithium metal layer in the negative electrode structure is 50% to 90% based on the overall 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: A center point of the length of the folded portion is not aligned with a center point of the thickness of the positive electrode surrounded by the folded portion.

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

19. The electrode assembly according to claim 9, wherein: The first wrapping portion and the second wrapping portion, each of which is located on the stack portion, overlap each other in the thickness direction.

20. The electrode assembly according to claim 9, wherein: An end portion of the first wrapping portion and an end portion of the second wrapping portion are located on the same line in the thickness direction.

21. An electrochemical device comprising the electrode assembly according to any one of claims 1 to 20.

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

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

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