Electrode assemblies and electrochemical elements containing the same

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to an electrode assembly and an electrochemical element including the same. Specifically, the present invention relates to an electrode assembly containing lithium metal as the negative electrode and an electrochemical element including the same.

[0002] This application claims priority rights under Korean Patent Application No. 10-2022-0136198 dated October 21, 2022, Korean Patent Application No. 10-2023-0070481 dated May 31, 2023, and Korean Patent Application No. 10-2023-0139505 dated October 18, 2023, and incorporates all the contents disclosed in the documents of said Korean Patent Applications as part of this Specification. [Background technology]

[0003] Recently, interest in energy storage technologies has been growing. With applications expanding to mobile phones, video cameras and laptops, and even electric vehicles, efforts in battery research and development are becoming increasingly concrete. Electrochemical devices are one of the most noteworthy fields in this regard, and especially with the recent trend towards miniaturization and weight reduction of electronic devices, the development of rechargeable batteries—small, lightweight, and high-capacity batteries that can be charged and discharged—has become a focal point of interest.

[0004] Furthermore, secondary batteries can sometimes be classified according to the structure of their electrode assembly, which consists of a positive electrode, a separator membrane, and a negative electrode. Typical examples of electrode assemblies include jelly-roll (wind-up type) electrode assemblies, which are constructed by winding long, sheet-like positive and negative electrodes with a separator membrane in between, and stack-type (stacked type) electrode assemblies, which are constructed by sequentially stacking numerous positive and negative electrodes cut into predetermined size units with a separator membrane in between.

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

[0006] Firstly, the jelly-roll electrode assembly is manufactured by winding long, sheet-like positive and negative electrodes in a densely packed state, creating a cylindrical or elliptical structure in cross-section. In such a structure, stress induced by the expansion and contraction of the electrodes during charging and discharging accumulates inside the electrode assembly, and if such stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs. Furthermore, this deformation of the electrode assembly can cause uneven spacing between electrodes, leading to a rapid decrease in battery performance and potentially jeopardizing battery safety due to internal short circuits. In addition, because the jelly-roll electrode assembly requires winding long, sheet-like positive and negative electrodes, it is difficult to wind them quickly while maintaining a constant spacing between the positive and negative electrodes, resulting in reduced productivity.

[0007] Secondly, the stacked electrode assembly requires sequentially stacking numerous positive and negative electrode units. This process necessitates a separate plate transfer process for manufacturing the units, and the sequential stacking process requires considerable time and effort. As a result, the stacked electrode assembly suffers from low productivity.

[0008] To solve these problems, an advanced stack-fold type electrode assembly, which is a hybrid form of the jelly-roll type and the stack type, has been developed. The stack-fold type electrode assembly has a structure in which bi-cells or full cells, which are stacked with a separation membrane interposed between predetermined units of positive and negative electrodes, are wound using a long, continuous separation membrane sheet (folded separation membrane).

[0009] The aforementioned stack-fold type electrode assembly connects the electrodes of each layer by extending a separator membrane, which is generally easier to fold than the electrodes themselves. In this case, the electrodes of each layer are supplied for electrode assembly formation in a cut state, similar to that of a stack-type electrode assembly. Among the various electrode materials that make up secondary batteries in the art, if a secondary battery is to be constructed using only materials that are either easy to cut or not easy to fold, then such a general stack-fold type electrode assembly is more suitable. On the other hand, lithium metal, which is well known as a negative electrode material for secondary batteries in the art, has high ductility and viscosity, making it difficult to process such as cutting, and is relatively easy to fold, so it may not be suitable for conventional stack-fold type electrode assemblies.

[0010] After continuous research into the structure of electrode assemblies, the inventors designed a structure suitable for electrode assemblies, particularly those containing lithium metal as the negative electrode, and thus completed the present invention. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Korean Registered Patent No. 10-2023530 [Overview of the project] [Problems that the invention aims to solve]

[0012] The present invention provides a novel electrode assembly suitable for electrode assemblies containing lithium metal as the negative electrode, and an electrochemical element containing the same. [Means for solving the problem]

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

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

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

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

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

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

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

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

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

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

[0023] In one embodiment of the present invention, the electrode assembly has one positive electrode located between adjacent stack portions in the thickness direction, 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 supporting the positive electrode active material layer, while the negative electrode does not include a current collector supporting a lithium metal layer.

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

[0026] In one embodiment of the present invention, the end of the first wrapping portion in the negative electrode structure is located on a stack portion that wraps around one side of an adjacent electrode assembly and comes into contact with the second wrapping portion, and the end of the second wrapping portion is located on the first wrapping portion.

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

[0028] 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 electrode and the negative electrode structure.

[0029] 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 side wrapping portion that surrounds it.

[0030] In one embodiment of the present invention, the folding portion has an asymmetrical shape with respect to a plane along the longitudinal 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% of 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 folded portion is not located at the same time as the center point of the thickness of the positive electrode enclosed by the folded portion.

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

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

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

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

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

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

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

[0042] An electrode assembly according to one embodiment of the present invention can minimize the cutting of lithium metal and improve process efficiency in electrode assembly manufacturing by utilizing a single continuous negative electrode structure in which a lithium metal negative electrode is interposed between two separation membranes.

[0043] Furthermore, by adjusting the methods and conditions for stacking, folding, and wrapping in accordance with the material properties of the negative electrode structure, the manufactured electrode assembly can not only have a stable structure, but the performance of the battery can also be improved. [Brief explanation of the drawing]

[0044] [Figure 1] This figure schematically shows the structure of a negative electrode structure including a stacking section, a folding section, and a wrapping section according to one embodiment of the present invention. [Figure 2] This figure schematically shows the structure of an electrode assembly including a negative electrode structure and a positive electrode according to one embodiment of the present invention. [Figure 3] This figure schematically shows the structure of an electrode assembly in which the end of the wrapping portion is attached with a fixing member in a negative electrode structure according to one embodiment of the present invention. [Figure 4] This figure shows a schematic, enlarged view of the folding portion of an electrode assembly according to one embodiment of the present invention. [Figure 5] This figure shows a schematic, enlarged view of the portion where the end of the positive electrode and the side wrapping portion are located in an electrode assembly according to one embodiment of the present invention. [Figure 6]This figure schematically shows the process and state in the manufacturing process of an electrode assembly according to one embodiment of the present invention. Here, Figure 6a schematically shows the process of folding the negative electrode structure to produce an electrode laminate in which positive and negative electrode structures are alternately stacked; Figure 6b schematically shows the process of wrapping both sides of the electrode laminate with first and second wrapping sections after the electrode laminate has been produced; Figure 6c schematically shows the process of further wrapping with a second wrapping section. Furthermore, Figure 6d schematically shows the state in which the electrode assembly has been completed after wrapping, with the ends of the first and second wrapping sections aligned on the same line; and Figure 6e schematically shows the state in which the ends of the first and second wrapping sections are fixed. [Figure 7] This graph shows the results of measuring the cycle-by-cycle Coulomb efficiency of lithium secondary batteries, including the respective electrode assemblies manufactured according to Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0045] The embodiments will be described in detail below with reference to illustrative drawings. It should be noted that, when assigning reference numerals to the components in each drawing, the same component will, to the greatest extent possible, have the same reference numeral even if shown in different drawings. Furthermore, when describing the embodiments, if a specific description of a related known configuration or function is deemed to hinder understanding of the embodiments, such detailed description will be omitted.

[0046] Furthermore, when describing the components of an embodiment, terms such as First, Second, A, B, (a), (b), etc., may be used. These terms are used to distinguish a component from other components, and do not limit the nature, order, or sequence of the component. When it is stated that a component is “linked,” “joined,” or “connected” to another component, it should be understood that the component may be directly linked or connected to other components, but that other components may also be “linked,” “joined,” or “connected” between each component.

[0047] Components included in any one embodiment and components with common functions will be described using the same names in the other embodiments. Unless otherwise stated, descriptions in any one embodiment can be applied to the other embodiments, and specific descriptions will be omitted to the extent that they overlap.

[0048] The present invention relates to an electrode assembly and improves upon the problems that may arise when applying lithium metal as the negative electrode to conventional stack-fold type electrode assembly structures, providing a novel electrode assembly structure suitable for using lithium metal as the negative electrode. The electrode assembly according to the present invention can improve processability during the assembly process by minimizing the processing of lithium metal, and can also enhance the reliability of the manufactured product. Furthermore, the electrode assembly has a structure that can make maximum use of the positive electrode included in the electrode assembly, and can contribute to improving the performance of the battery.

[0049] In this specification, the terms “length direction,” “width direction,” and “thickness direction” (or “height direction”) are used. In this specification, drawings such as Figures 1 to 6 are front views, and with respect to these front views, the “length direction” means the left-right direction in the drawing, the “width direction” means the front-back direction in the drawing, and the “thickness direction” (or “height direction”) means the up-down direction in the drawing.

[0050] In this specification, the term "adjacent" means the object among the multiple objects referred to that is closest to the criterion. Adjacent objects are not necessarily touching the criterion.

[0051] An electrode assembly according to one embodiment of the present invention includes a positive electrode, a negative electrode, and a separator membrane. In the electrode assembly, the positive electrode and the separator membrane are not particularly limited as long as they are made of materials commonly used in the art, but the negative electrode contains lithium metal. In this specification, lithium metal can be broadly interpreted as long as it does not differ significantly in physical properties from lithium metal, even if it is lithium with some components added or in the form of an alloy with some metals, and the same problems as lithium metal may occur when applied to conventional electrode assemblies. In this specification, the negative electrode can be named a lithium metal layer because it contains lithium metal, and the negative electrode and the separator membrane can be named a negative electrode structure because they are supplied as a single integrated structure.

[0052] According to one 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 may be named the first and second separator membranes. The negative electrode structure has a structure that extends in the longitudinal direction, and the electrode assembly includes only one negative electrode structure. The negative electrode structure having a structure that extends in the longitudinal direction is folded to form a basic electrode assembly structure, such as fixing the positive electrode inside.

[0053] According to one embodiment of this specification, the negative electrode structure includes a plurality of stacks, a plurality of folds, and two wrappings, depending on their position in the electrode assembly. In this specification, the two wrappings included in the negative electrode structure may be named the first and second wrappings. To aid in understanding the structure of the negative electrode structure, Figure 1 provides an exemplary structure of a negative electrode structure including stacks, folds, and wrappings. In the negative electrode structure (10), the stacks (10A, 10A', 10A''), folds (10B), and wrappings (10C, 10C') are units that divide positions having different functionalities along the length of the negative electrode structure (10). The stacks (10A, 10A', 10A''), folds (10B), and wrappings (10C, 10C') are not distinguished by material, not by position.

[0054] The stacked sections (10A, 10A', 10A'') refer to the negative electrode structure (10) at the position where the positive electrode is stacked, and mainly have a linear shape based on Figure 2, etc. The folded section (10B) refers to the negative electrode structure (10) at the position connecting the stacked sections, and mainly has a curved shape based on Figure 2, etc. The folded section (10B) can also be named the bending section. The first wrapping section (10C) refers to the negative electrode structure at the position that encloses the stacked structure of the positive electrode and negative electrode structure from the point where it contacts the outermost stacked section (10A') of the lowest stage. The second wrapping section (10C') refers to the negative electrode structure at the position that encloses the stacked structure of the positive electrode and negative electrode structure, and the first wrapping section (10C), from the point where it contacts the outermost stacked section (10A'') of the uppermost stage. Based on Figure 2, etc., linear and curved shapes are mixed.

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

[0056] The two wrapping portions (10C) located at both ends of the negative electrode structure (10) may have different lengths. In this specification, to distinguish the two wrapping portions (10C), the wrapping portion (10C) located at the point where lamination begins is named the first wrapping portion, and the wrapping portion (10C') located at the point where lamination ends is named the second wrapping portion. The first and second wrapping portions may also be named in reverse. According to one embodiment of the present invention, the second wrapping portion (10C') of the negative electrode structure surrounds both the first wrapping portion (10C) that surrounds one side of the electrode stack and the opposite side of the electrode stack. Therefore, the second wrapping portion (10C') is located outside the electrode assembly (1) than the first wrapping portion (10C). For ease of process, the first wrapping portion (10C) located at the point where lamination begins may be shorter than the second wrapping portion (10C') located at the point where lamination ends. The second wrapping portion (10C') may have a length longer than the first wrapping portion (10C) so as to be able to wrap the opposite side of the electrode stack and the stack portion (10A') that is in contact with the first wrapping portion (10C), or an additional positive electrode.

[0057] According to one embodiment of the present invention, the ends of the first and second wrapping portions (10C, 10C') of the negative electrode structure are located on the same line. The electrode assembly (1) according to one embodiment of the present invention basically has a structure in which the second wrapping portion (10C') wraps around the first wrapping portion (10C). Strictly speaking, the fact that the second wrapping portion (10C') wraps around the first wrapping portion (10C) means that the wrapping portion (10C, 10C') located inside cannot be exposed to the outside, but this is not interpreted strictly in this specification. Therefore, in the electrode assembly according to one embodiment of the present invention, the ends of the first wrapping portion (10C) and the second wrapping portion (10C') can be located on the same line, or they can not be located on the same line, with the second wrapping portion (10C') being slightly shorter and the end of the first wrapping portion (10C) being exposed, or the second wrapping portion (10C') being slightly longer and completely covering the end of the first wrapping portion (10C). According to one embodiment of the present invention, the end of the second wrapping portion is located on the first wrapping portion, or the end of the second wrapping portion is located on the outermost stack portion. When the ends of the first wrapping portion (10C) and the second wrapping portion (10C') are located on the same line, the structure can be made simpler. If the second wrapping portion (10C') is slightly shorter and the end of the first wrapping portion (10C) is exposed, the second wrapping portion (10C') and the first wrapping portion (10C) can be fixed together with tape. Also, if the second wrapping portion (10C') is slightly longer and completely encloses the end of the first wrapping portion (10C), the negative electrode at the end of the first wrapping portion may not be exposed to the outside.

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

[0059] According to one embodiment of the present invention, the electrode assembly (1) has a folding portion (10B) that positions a plurality of stack portions (10A, 10A', 10A'') sequentially in the thickness direction, and at least one positive electrode is positioned between adjacent stack portions (10A, 10A', 10A'') in the thickness direction and between stack portions (10A, 10A', 10A''). According to one embodiment of the present invention, in the electrode assembly (1), the second wrapping portion (10C') is positioned in contact with the first wrapping portion (10C), and has a structure in which the outer surface in the thickness direction and the length direction is surrounded by the second wrapping portion (10C'), or by the second wrapping portion (10C'), the first wrapping portion (10C), and the outermost stack portion (10A''). The reason for phrasing it as "one or more of the first wrapping portion (10C) and the outermost stack portion (10A'')" is that the end of the second wrapping portion and the end of the first wrapping portion may not coincide. Referring to Figure 2, in other words, the inside of the electrode assembly (1) has a structure in which one side of an electrode stack, in which stack portions (10A, 10A', 10A'') of the negative electrode structure and positive electrodes are stacked alternately in sequence, is surrounded by the first wrapping portion (10C). At this time, only one positive electrode (20) is located between each stack portion (10A, 10A', 10A'') of the negative electrode structure. Furthermore, the outside of the electrode assembly (1) has a structure surrounded by the stack portion (10A'') of the negative electrode structure and the second wrapping portion (10C'). Here, the internal and external regions of the electrode assembly (1) are defined to aid in understanding the structure of the electrode assembly (1) according to the present invention. Using Figure 2 as a reference, in the thickness and length directions of the electrode assembly, the layers exposed to the outside represent the external region of the electrode assembly (1), and the inner portion of the external region of the electrode assembly (1) represents the internal region of the electrode assembly (1).In the negative electrode structure (10), the stack portions (10A, 10A', 10A'') refer to the negative electrode structure (10) at the position where the positive electrodes are stacked, and the second wrapping portion (10C') begins at the end of the uppermost second outermost stack portion (10A''). Therefore, as shown in Figure 2, if the end of the second wrapping portion (10C') is located above the uppermost second outermost stack portion (10A''), a portion of the uppermost second outermost stack portion (10A'') may be located outside the electrode assembly (1), and the remaining portion of the uppermost second outermost stack portion (10A'') may be located inside the electrode assembly (1). Accordingly, in this specification, a stack portion located inside or outside may refer to the entirety of a single stack portion or a portion thereof. Unlike in Figure 2, if the second wrapping portion (10C') covers the entirety of the uppermost second outermost stack portion (10A''), the exterior of the electrode assembly (1) may be formed solely by the second wrapping portion. If the first wrapping (10C) covers the entire uppermost second outermost stack portion (10A'') and the end of the second wrapping portion cannot reach the end of the first wrapping portion, the exterior of the electrode assembly (1) can be formed by the first and second wrapping portions alone. Alternatively, if the first wrapping portion (10C) covers only a portion of the uppermost second outermost stack portion (10A'') and the end of the second wrapping portion cannot reach the end of the first wrapping portion, the exterior of the electrode assembly (1) can be formed by the first and second wrapping portions (10C, 10C') and the second outermost stack portion (10A''). In any case, the plurality of folded portions (10B) are wrapped by the first and second wrapping portions (10C, 10C') and are not exposed to the outside in the thickness direction and length direction.

[0060] In one embodiment of the present invention, the electrode assembly (1) has a zigzag shape because the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are stacked alternately and sequentially inside. This includes the folded portion (10B). Specifically, the folded portions (10B), which are sequentially positioned from the stack portion (10A') that is in contact with the first or second wrapping portion (10C, 10C') of the negative electrode structure (10), are alternately located on the left or right side of the electrode assembly (1). If the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are not stacked alternately, and two or more stack portions or positive electrodes are stacked continuously, no potential difference will be generated between the continuously stacked layers, which may reduce the efficiency of the battery.

[0061] According to one embodiment of the present invention, in the electrode assembly (1), a plurality of stack portions (10A, 10A', 10A'') and a plurality of positive electrodes (20) are tightly bound in the thickness direction by first and second wrapping portions (10C, 10C'). The first and second wrapping portions (10C, 10C') can wrap the inside of the electrode assembly (1) with higher tension than the stack portions (10A, 10A', 10A'') or the folding portion (10B), thereby tightly binding the internal structure of the electrode assembly (1) in the thickness direction. When the internal structure of the electrode assembly (1) is tightly bound in the thickness direction in this manner, it inevitably becomes tightly bound in the length direction. However, even if the internal structure of the electrode assembly (1) is tightly bound in the thickness direction and the length direction, due to the structure of the electrode assembly (1), a certain level of void may exist around the folding portion (10B).

[0062] According to one embodiment of the present invention, the electrode assembly (1) has at least one positive electrode located between a stack portion (10A') adjacent to a first wrapping portion (10C) of the negative electrode structure (10) and a second wrapping portion (10C') parallel to the stack portion (10A'). If no additional positive electrode is provided, the stack portion (10A') of the negative electrode structure (10) and the second wrapping portion (10C') adjacent in the thickness direction are in face-to-face contact. Here, the added positive electrode (20) refers to the bottommost positive electrode in Figure 2. By adding the positive electrode (20) to this portion, the second wrapping portion (10C') adjacent to the stack portion (10A') also functions as a negative electrode, contributing to an overall improvement in battery performance. According to one embodiment of the present invention, the positive electrode located between the stack portion (10A') adjacent to the first wrapping portion (10C) and the second wrapping portion (10C') adjacent in the thickness direction is longer than the other positive electrodes. This is because a longer gap exists in the length direction at that location, and making the positive electrode located between the stack portion (10A') of the negative electrode structure (10) and the second wrapping portion (10C') adjacent in the thickness direction longer is beneficial to the performance of the battery.

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

[0064] According to one embodiment of the present invention, in the electrode assembly (1), the number of stack portions (10A, 10A', 10A'') and the number of positive electrodes are the same. As described above, the total number of positive electrodes (20) located between the stack portions is 2n (where n is a natural number), and the number of stack portions (10A, 10A', 10A'') is 2n+1 (where n is a natural number), since there is one more than this. The number of positive electrodes included in the electrode assembly (1) must also take into account the positive electrode located between the stack portion (10A') and the wrapping portion (10C), so the number of stack portions and positive electrodes in the electrode assembly (1) are the same.

[0065] 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) supporting the positive electrode active material layer. 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 includes a positive electrode active material and may further include a conductive material, a binder, and additives. The current collector, positive electrode active material, conductive material, binder, and additives are not particularly limited as long as they are commonly used in the art.

[0066] The positive electrode current collector is not particularly limited as long as it supports the positive electrode active material layer, does not cause chemical changes 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, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., or aluminum-cadmium alloy.

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

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

[0069] The positive electrode active material can contain a sulfur compound. According to one embodiment of the present invention, the sulfur compound is 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 these. Preferably, inorganic sulfur (S8) may be used.

[0070] 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. Since the sulfur contained in the positive electrode active material does not have electrical conductivity on its own, it can be used in combination with a conductive material such as carbon material. Thus, the sulfur is contained in the form of a sulfur-carbon composite, and preferably, the positive electrode active material can be a sulfur-carbon composite.

[0071] Considering the above, the positive electrode (20) is relatively less easy to fold and easier to cut compared to the negative electrode. Therefore, the positive electrode (20) is cut to an appropriate size, and multiple positive electrodes are applied inside the electrode assembly (1).

[0072] According to one embodiment of the present invention, the negative electrode (11) does not include a current collector that supports the lithium metal layer. Since the negative electrode (11) does not include a current collector, the amount of negative electrode active material loaded into the electrode assembly can be improved, contributing to improved battery performance. When the negative electrode (11) is mainly composed of lithium metal, lithium metal has high ductility and viscosity, making it difficult to process such as cutting. However, in the electrode assembly (1) according to one embodiment of the present invention, the negative electrode can be applied in the form of a negative electrode structure (10) while minimizing cutting and improving processability. The lithium metal layer according to one embodiment of the present invention may be a free-standing lithium metal layer that can maintain its shape to a certain extent on its own.

[0073] In the negative electrode structure (10), the separation membrane (12) covering both sides of the negative electrode (11) is not particularly limited in type, as long as it does not contain a binder on its surface. Specifically, the separation membrane (12) can be, for example, a nonwoven fabric or a polyolefin-based porous substrate made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc., but is not limited thereto.

[0074] The material of the porous substrate is not particularly limited in this invention, and any porous substrate commonly used in electrochemical elements can be used. According to one embodiment of the present invention, the porous substrate is a polyolefin such as polyethylene and polypropylene, a polyester such as polyethylene terephthalate and polybutylene terephthalate, a polyamide, a polyacetal, a polycarbonate, a polyimide, a polyetheretherketone, a polyethersulfone, a polyphenylene oxide, a polyphenylene sulfide, a polyethylene naphthalate, a polytetrafluoroethylene, a polyvinylidene fluoride, or a polyvinyl chloride. It may also contain one or more materials selected from the group consisting of chloride, polyacrylonitrile, cellulose, nylon, poly(p-phenylene benzobisoxazole), and polyarylate.

[0075] According to one embodiment of the present invention, in the negative electrode structure (10), the negative electrode (11) and the first and second separation membranes (12) are of the same length. Using the end of the negative electrode structure where the second wrapping portion is located as a reference, the separation membrane located outside the electrode assembly (1) can be named the first separation membrane, and the separation membrane located inside the electrode assembly (1) can be named the second separation membrane. The negative electrode (11) and the separation membranes (12) are supplied to the electrode assembly in the form of a negative electrode structure (10) in which the negative electrode (11) is interposed between the first and second separation membranes (12). In this case, the negative electrode and the separation membranes are cut at the same time, and as shown in Figure 1, the lengths of the negative electrode (11) and the first and second separation membranes (12) in the negative electrode structure (10) are substantially the same. However, depending on the method of cutting the negative electrode structure (10), slight differences may occur 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 one embodiment of the present invention, the first and second separator membranes are in contact at the ends of the negative electrode structure (10). Even if the lengths of the negative electrode (11) and the first and second separator membranes (12) are substantially the same during the supply process, when applied to the electrode assembly (1), the length of the lithium metal may be extended during the folding process due to the ductility of the lithium metal. According to one embodiment of the present invention, at the ends of the negative electrode structure (10) on the wrapping portion (10C) side, the lithium metal protrudes longitudinally beyond the first and second separator membranes. Also, depending on the number of folds, the separator membranes located more on the outside than on the inside of the folded portion (10B) may become shorter. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the first or second wrapping portion (10C, 10C') side, the first separation membrane protrudes longitudinally from the second separation membrane. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the first or second wrapping portion (10C, 10C') side, the second separation membrane protrudes longitudinally from the first separation membrane.

[0076] According to one embodiment of the present invention, in the negative electrode structure (10), the end of the first wrapping portion (10C) is located on a stack portion (10A'') that wraps around one side of an adjacent electrode assembly and is in contact with the second wrapping portion (10C'), and the end of the second wrapping portion (10C') is located on the first wrapping portion (10C). The ends of the first and second wrapping portions (10C, 10C') can be attached to the stack portion (10A'') in a broad sense. In some cases, the end of the second wrapping portion (10C') can be attached to the first wrapping portion (10C), but the broad sense mentioned above includes this as well because it is also on the stack portion (10A''). The adhesive means and methods are not particularly limited as long as the end of the first wrapping portion (10C) or the second wrapping portion (10C') can be effectively attached to the stack portion (10A''). According to one embodiment of the present invention, the electrode assembly (1) further includes a fixing member for fixing the ends of the first and second wrapping portions (10C, 10C') onto the outermost stack portion. By wrapping the first wrapping portion (10C) again through the second wrapping portion (10C'), the electrode assembly (1) has a more stable structure. To help understand the position to which the ends of the first and second wrapping portions (10C, 10C') are attached in the negative electrode structure (10), Figure 3 provides an exemplary structure of the electrode assembly in which the ends of the wrapping portions are attached as a fixing member in the negative electrode structure. In the negative electrode structure (10), since the negative electrode (11) and the separator membrane (12) are not bonded, it may be preferable that the fixing member, tape (T), is attached so as to wrap around the outer surface of the electrode assembly (1), as shown in Figure 3. When manufacturing the electrode assembly (1), considering situations such as the extension and protrusion of the lithium metal due to the ductility of the lithium metal during the folding process of the negative electrode structure (10), according to one embodiment of the present invention, the tape (T) is insulating and covers the ends of the first and second wrapping portions (10C, 10C') in the width direction. With this taping method, the electrode assembly is covered on all sides (top, bottom, left, and right) with a separator film or tape. The first wrapping portion (10C) and the second wrapping portion (10C') can be attached individually.According to one embodiment of the present invention, the electrode assembly includes a first fixing member for fixing a first wrapping portion (10C) and a second fixing member for fixing a second wrapping portion (10C').

[0077] When manufacturing the electrode assembly (1), the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are stacked alternately. Since the negative electrode structure (10) is folded according to the same standard, the folded portion (10B) also has substantially the same length. The negative electrode structure (10) utilizes a specific form of mandrel to apply the same standard during folding. If the length of the folded portion (10B) is short, unnecessary stress may be placed on the lithium metal located in the center of the negative electrode structure (10), potentially causing defects such as the lithium metal being disconnected. Therefore, by ensuring that the length of the folded portion (10B) is sufficiently above a certain level, the lithium metal can be flexibly arranged in the gap between the stacked electrode portion and the wrapping portion.

[0078] To aid in understanding the length of the folded portion (10B) in the negative electrode structure (10), Figure 4 provides an enlarged view of the folded portion (10B) in the electrode assembly (1). According to one embodiment of the present invention, in the negative electrode structure (10), the length of the folded portion (10B) 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) refers to the length of the curve of the folded portion. In the case of a curve, the lengths of the inner and outer parts may differ, so the length of the central part is measured. For example, the portion shown by the dotted line in Figure 4 can be cut, and then it can be unfolded to measure its length. Specifically, the length of the folded 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, 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, based on 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 the above range, defects in the folded portion of the electrode assembly can be reduced, and the electrode assembly can be stably wrapped.

[0079] The aforementioned folding portion (10B) is formed to be longer than when it is folded into a semicircle as shown in Figure 2, as shown in Figure 4. Specifically, when the folding portion (10B) has a perfect semicircular shape with an eccentricity of 0, the length of the folding portion is the sum of the diameter, which is the thickness of the positive electrode (20) and the negative electrode structure (10), 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). Judging from this, the length of the folding portion (10B) in one embodiment of the present invention can be said to be significantly longer.

[0080] When manufacturing the electrode assembly (1), after alternately stacking the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20), the electrode assembly (1) is wrapped with the wrapping portions (10C, 10C'), at which point the folded portion (10B) is subjected to a certain level of pressure in the inward direction of the electrode assembly (1). As a result, the folded portion (10B) can be properly positioned in the gap between the portion where the electrodes are stacked and the wrapping portion. The folded portion (10B), properly positioned in the gap, contains a lithium metal layer (11) inside, and in relation to the positive electrode (20) on its side, can contribute to further improvement of battery performance through electrochemical reactions. By properly filling the gap with the folded portion (10B), two or more lithium metal layers can be positioned on the side of the positive electrode that is not wrapped by the folded portion (10B). Furthermore, when wrapping the electrode assembly (1) with the wrapping portion (10C, 10C'), if the wrapping is performed such that the wrapping portion (10C) has a tension of a certain level or higher, it helps to maintain the shape of the electrode stack located inside the electrode assembly (1) without distortion.

[0081] According to one embodiment of the present invention, the folded portion (10B) has an asymmetric shape with respect to a plane along its length. Such an asymmetric shape is formed when the folded portion (10B) is pressed in the length direction by the wrapping portions (10C, 10C') and the folded portion (10B) is appropriately 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 located adjacent to the center point of the thickness of the positive electrode wrapped by the folded portion (10B). The center point of the length of the folded portion (10B) can be located at an angle in the direction in which the wrapping progresses with respect to the center point of the thickness of the positive electrode. For example, with respect to Figure 2, the folded portion located on the right side of the electrode stack can have its center point below the center point of the thickness of the positive electrode because the wrapping is performed from top to bottom. On the other hand, the folded portion located on the left side of the electrode stack can have its center point above the center point of the thickness of the positive electrode because the wrapping is performed from bottom to top.

[0082] To help understand the vertical distance between the end of the reference positive electrode (20) and the side wrapping portions (10C, 10C') when comparing the lengths of the folded portions (10B) below, Figure 5 provides an enlarged view of the portion of the electrode assembly (1) where the end of the positive electrode (20) and the side wrapping portions (10C, 10C') are located. Here, the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portions (10C, 10C') is the distance between the end of the positive electrode (20) and the side wrapping portions (10C, 10C') adjacent to the folded portion (10B). When one wrapping portion (10C) and the other wrapping portion (10C') overlap, the wrapping portion that serves as the reference for the distance is the wrapping portion (10C) located inside. As shown in Figure 5, the folded portion (10B) may deform in shape due to pressure applied from the side wrapping portions (10C, 10C') during the process of wrapping the electrode assembly. However, Figure 5 is only an exemplary structure, and the folded portion (10B) does not necessarily deform in this manner. Due to the pressure, the distance (d) between the end of the positive electrode (20) and the side wrapping portions (10C, 10C') may be shortened, and the folded portion (10B) can be naturally positioned within the reduced space as the distance (d) decreases. According to one embodiment of the present invention, in the electrode assembly (1), the length of the folded portion (10B) is 2 to 10 times the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portions (10C, 10C'). The aforementioned side wrapping portions (10C, 10C') refer to a linear wrapping portion (10C) located on the left side of the electrode assembly or a linear wrapping portion (10C') located on the right side, with reference to Figure 2 or Figure 3. In an actual electrode assembly, if the portion is not linear, the vertical distance (d) is measured by taking the end of the positive electrode at the center of the electrode stack in the thickness direction as the reference point to the vertical distance from the side wrapping portion. Alternatively, in one embodiment, 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, 10C') contacts the folded portion (10B).Specifically, the length of the folded 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, 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, and 2 to 10 times, 3 to 9 times, and 4 to 8 times, based on the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portion (10C). This means that, as mentioned above, the length of the folded portion (10B) is significantly longer, but the vertical distance (d) is also shorter, and the folded portion is compactly packed in the space on the side of the electrode stack. When the length of the folded portion (10B) is adjusted within the above range, the folded portion is compactly packed in the gap within the electrode assembly at an appropriate level without applying excessive pressure to the folded portion due to the wrapping of the electrode assembly, which can contribute to improving the performance of the battery.

[0083] In one embodiment of the present invention, the electrode assembly (1) folds a single negative electrode structure (10) to form the basic structure of the electrode assembly (1). In this respect, the negative electrode structure (10) must not be excessively thick so that it can be flexibly folded, and a certain level or more of lithium metal, which is the negative electrode active material, must be ensured within the negative electrode structure (10) considering the performance of the battery. According to one embodiment of the present invention, in the negative electrode structure (10), the thickness of the lithium metal accounts for 50% to 90% of the total thickness of the negative electrode structure (10). Specifically, the range of the lithium metal thickness may be 50% to 90%, more specifically 55% to 85%, or more specifically 60% to 80%. When the lithium metal satisfies the aforementioned 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 thickness of the lithium metal can represent the thickness of the two separator membranes.

[0084] According to one embodiment of the present invention, the thickness of the lithium metal can be 10 μm to 90 μm. Specifically, the thickness of the lithium metal may be 10 μm or more, 20 μm or more, or 30 μm or more, and may 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 can be appropriately adjusted according to the actual size of the battery.

[0085] In one embodiment of the present invention, the electrode assembly (1) differs from the negative electrode structure (10) in that the positive electrode is cut considering the properties of the material, etc., and applied between the stack portions (10A, 10A', 10A'') of the negative electrode structure (10). The positive electrode is distinct from the negative electrode and has independence, for example, by including a current collector in addition to the positive electrode active material, but its thickness can be adjusted in relation to the negative electrode or negative electrode structure, considering the performance of the electrode, etc. According to one embodiment of the present invention, the thickness of the positive electrode (20) is greater than the thickness of the negative electrode structure (10). According to one embodiment of the present invention, the thickness of the positive electrode (20) is greater than 100% and less than or equal to 400% of the thickness of the negative electrode structure (10). Specifically, the thickness range of the positive electrode (20) may be greater than 100% and less than or equal to 400%, specifically 150% to 350%, and more specifically 200% to 300%. When the positive electrode satisfies the aforementioned thickness range, it can be properly harmonized with the negative electrode structure.

[0086] The process for manufacturing the aforementioned electrode assembly will be described in detail below. To aid in understanding the manufacturing process of the electrode assembly, Figure 6 schematically shows the processes and states in the manufacturing process of the electrode assembly.

[0087] A manufacturing step for an electrode assembly according to one embodiment of the present invention includes: (1) folding a negative electrode structure to produce an electrode stack in which positive electrode and negative electrode structures are alternately stacked; (2) surrounding the electrode stack with an extra negative electrode structure after the electrode stack has been manufactured; and (3) positioning the end of the first wrapping portion of the negative electrode structure on the upper layer of the electrode stack and positioning the end of the second wrapping portion on the first wrapping portion and fixing it in place.

[0088] The (1) stage is manufactured through a process as shown in Figure 6a as an example. As shown in Figure 6a, the positive electrode and negative electrode structures can be stacked sequentially, with the positive electrode placed at the bottom and the negative electrode structure placed on top of it. Although not shown in Figure 6a, a device such as a mandrel can be used when folding the negative electrode structure, and the folding at each position can be manufactured according to the same standard. When starting the stacking process, stacking does not begin from the end of the negative electrode structure, but rather from the stack portion in contact with the first wrapping portion, leaving a first wrapping portion that can later wrap one side of the electrode stack. The (2) stage is manufactured through a process as shown in Figures 6b and 6c as an example. The excess negative electrode structure is entirely present at both ends as first and second wrapping portions, and the first and second wrapping portions each wrap the side of the adjacent electrode stack. Furthermore, the second wrapping portion wraps the upper or lower layer of the electrode stack and is positioned in contact with the first wrapping portion. During the wrapping process with the extra negative electrode structure, wrapping the negative electrode structure so that it has a tension above a certain level allows the folded portion to be compactly packed within the gap, helping to maintain the shape of the electrode stack without distortion. After step (3), the completed electrode assembly will be in the state shown in Figure 6d or Figure 6e. Wrapping has the effect of preventing the positive electrode from flowing out between the stack portions, and considering this functionality, it may be preferable to position the end of the negative electrode structure on the upper layer of the electrode stack. Fixing the negative electrode structure allows the tension applied to the negative electrode structure during the wrapping process to be maintained, and wrapping with tape (T), as shown in Figure 6e, is one exemplary method.

[0089] In the manufacturing process, the specific characteristics of the positive and negative electrode structures not specifically described shall be as stated above. An electrode assembly according to one embodiment of the present invention can weld multiple layers of tabs and leads together, as in conventional high-capacity cells, while maintaining performance such as cell resistance and output.

[0090] An electrode assembly according to one embodiment of the present invention is applied to an electrochemical element. The electrochemical element can include any element that performs an electrochemical reaction. For example, the electrochemical element can be any kind of primary battery, secondary battery, fuel cell, solar cell, or capacitor. If the electrochemical element is a secondary battery, it 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, or a lithium ion polymer secondary battery, etc.

[0091] As described above, even if embodiments are described by limited embodiments and drawings, a person with ordinary skill in the art can make various modifications and variations from the above description. For example, the described technique may be performed in a different order than described, and / or the components of the described system, structure, apparatus, circuit, etc. may be combined or assembled in a different manner than described, or replaced by other components or equivalents, and the appropriate results may still be achieved.

[0092] The following are preferred embodiments to aid in understanding the present invention, but these embodiments are provided to make the present invention easier to understand and are not limited thereto.

[0093] Examples Example 1: Manufacturing of an electrode assembly wrapped with a negative electrode structure A negative electrode structure was fabricated by interposing a 60 μm lithium metal between two polyethylene (PE) separation membranes (11 μm). Furthermore, a positive electrode slurry was prepared by adding a positive electrode mixture consisting of 85% by weight of a positive electrode active material (made by mixing sulfur and carbon nanotubes (CNTs) in a 7:3 weight ratio), 5% by weight of a conductive material (carbon nanofiber), and 10% by weight of a binder) to deionized water. This slurry was then coated onto an aluminum current collector to produce a 200 μm positive electrode.

[0094] The manufactured negative electrode structure was folded to produce an electrode stack in the manner shown in Figure 6a. Then, the electrode stack was wrapped with the excess negative electrode structure in the manner shown in Figures 6b and 6c to produce an electrode assembly as shown in Figure 6d. The ends of the negative electrode structure exposed from the electrode assembly were bonded with insulating tape as shown in Figure 6e. At this time, the length of the folded portion of the electrode assembly was measured to be 1,453 μm, and the vertical distance between the end of the positive electrode and the side wrapping portion was measured to be 268 μm.

[0095] Comparative Example 1: Manufacturing of an electrode assembly by cutting and stacking negative electrode structures After cutting the negative electrode structure to match the positive electrode of each layer, the positive electrode and negative electrode structures were stacked to manufacture an electrode laminate, and then the electrode assembly was completed with the negative electrode structure without any further wrapping. In the electrode assembly, the material and thickness of the positive electrode and negative electrode structures were manufactured in the same manner as in Example 1.

[0096] Experimental example Each electrode assembly manufactured according to Example 1 and Comparative Example 1 was placed in the same pouch, and an electrolyte solution containing 0.4 M LiFSI salt and 4% by weight of LiNO3 was added to an ether-based electrolyte to manufacture a lithium secondary battery. The manufactured lithium secondary battery was charged and discharged at 0.3C, and the cycle-by-cycle Coulomb efficiency was measured, and the results are shown in Figure 7.

[0097] The electrode assembly according to the present invention not only offers process advantages compared to conventional electrode assemblies, but as can be seen in Figure 7, it can also be confirmed that it can improve the long-term performance of the battery, such as Coulomb efficiency.

[0098] Any simple modifications or changes to the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will become clear from the appended claims. [Explanation of symbols]

[0099] 1, 1', 1'': Electrode Assembly 10:Negative electrode structure 10A, 10A', 10A'': Stack section (10A', 10A'': outermost stack section) 10B: Folding section 10C, 10C': Wrapping section (1st and 2nd wrapping sections) 11: Negative electrode (lithium metal layer) 12: Separation membranes (first and second separation membranes) 20: Positive electrode T: Fixing material (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 multiple positive electrodes, The negative electrode structure includes a first separation membrane, a second separation membrane, and a lithium metal layer interposed between the first and second separation membranes. The negative electrode structure is divided into a plurality of stacking sections, a plurality of folding sections, and a first wrapping section and a second wrapping section, depending on its position in the electrode assembly, with the stacking sections and folding sections alternately positioned between the first wrapping section and the second wrapping section, which are located at the ends of the negative electrode structure, and the first wrapping section and the second wrapping section are in contact with the stacking section, The electrode assembly has a folding portion which causes multiple stack portions to be arranged sequentially in the thickness direction, and at least one positive electrode is located between adjacent stack portions in the thickness direction. The electrode assembly wherein the second wrapping portion is positioned in contact with the first wrapping portion, and the outer surface in the thickness direction and length direction is surrounded by the second wrapping portion, or by one or more of the second wrapping portion, the first wrapping portion, and the outermost stack portion.

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

3. The electrode assembly according to claim 1, characterized in that a first wrapping portion surrounds one side of the electrode stack and a second wrapping portion surrounds the opposite side of the electrode stack.

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

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

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

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

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

9. The electrode assembly according to claim 1, characterized in that, in the negative electrode structure, the end of the first wrapping portion is located on a stack portion that wraps around one side of an adjacent electrode assembly and comes into contact with the second wrapping portion, and the end of the second wrapping portion is located on the first wrapping portion.

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 onto the outermost stack portion.

11. The electrode assembly according to claim 1, characterized in that the length of the folded portion of 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, characterized in that 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 side wrapping portion that encloses it.

13. The electrode assembly according to claim 1, characterized in that the folding portion has an asymmetrical shape with respect to a plane along the longitudinal direction.

14. The electrode assembly according to claim 1, characterized in that the thickness of the lithium metal layer in the negative electrode structure accounts for 50% to 90% of the total thickness of the negative electrode structure.

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

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

17. The electrode assembly according to claim 1, characterized in that the center point of the length of the folded portion is not located adjacent to the center point of the thickness of the positive electrode enclosed by the folded portion.

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

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

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

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

22. The electrode assembly according to claim 1, wherein the plurality of stacking portions, the plurality of folding portions, the first wrapping portion, and the second wrapping portion are integrally formed.

23. An electrochemical element comprising an electrode assembly according to any one of claims 1 to 22.

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

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

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