Electrode assembly and electrochemical element including the same

Abstract

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

Description

Technical Field

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

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0136198 filed on October 21, 2022, Korean Patent Application No. 10-2023-0070466 filed on May 31, 2023, and Korean Patent Application No. 10-2023-0138672 filed on October 17, 2023, and includes all the contents disclosed in the documents of the Korean patent applications as part of this specification.

Background Art

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

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

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

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

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

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

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

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

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

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

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

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

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

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

[0018] In one embodiment of the present invention, the electrode assembly has a structure in which the outer surface is surrounded by the wrapping portion or the wrapping portion and the outermost stack portion in the thickness direction and the length direction.

[0019] In one embodiment of the present invention, the stack start portion, 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 wrapping portion.

[0020] In one embodiment of the present invention, the length of the stack start portion is longer than the length of the stack portion.

[0021] In one embodiment of the present invention, at least one positive electrode is positioned between the stack start portion and the wrapping portion adjacent in the thickness direction in the electrode assembly.

[0022] In one embodiment of the present invention, one positive electrode is located between the stack start portion and the stack portion adjacent in the thickness direction, and between the stack portion and the stack portion, and the total number of positive electrodes located between the stack start portion and the stack portion and between the stack portion and the stack portion is 2n (where n is a natural number).

[0023] In one embodiment of the present invention, the positive electrode in the electrode assembly includes a positive electrode active material layer and a current collector that supports the positive electrode active material layer, and the negative electrode structure does not include a current collector that supports a lithium metal layer.

[0024] In one embodiment of the present invention, the lengths of the lithium metal layer, the first separator, and the second separator in the negative electrode structure are the same.

[0025] In one embodiment of the present invention, a part of the wrapping portion in the negative electrode structure is in contact with the outermost stack portion, and the end of the wrapping portion is located on the outermost stack portion.

[0026] In one embodiment of the present invention, the electrode assembly further includes a fixing member that fixes the end of the wrapping portion on the outermost stack portion.

[0027] In one embodiment of the present invention, the length of the folding portion in the negative electrode structure is 2 to 10 times based on the total thickness of the positive electrode and the negative electrode structure.

[0028] In one embodiment of the present invention, the length of the folding portion in the negative electrode structure is 2 to 10 times based on the vertical distance between the end of the positive electrode and the side wrapping portion that encloses it.

[0029] In one embodiment of the present invention, the folding portion has an asymmetric shape based on the plane along the length direction.

[0030] 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 total thickness of the negative electrode structure.

[0031] In one embodiment of the present invention, the thickness of the positive electrode is greater than the thickness of the negative electrode structure.

[0032] In one embodiment of the present invention, the length of the stack start portion is equal to or greater than the thickness of the positive electrode and longer than the length of the stack portion.

[0033] In one embodiment of the present invention, the positive electrode located between the stack start portion and the wrapping portion adjacent in the thickness direction is longer than the other positive electrodes.

[0034] In one embodiment of the present invention, the fixing member is an insulating tape.

[0035] In one embodiment of the present invention, the end of the stack start portion does not contact the wrapping portion.

[0036] In one embodiment of the present invention, the center point of the length of the folding portion is not aligned with the center point of the thickness of the positive electrode wrapped by the folding portion.

[0037] In one embodiment of the present invention, the stack start portion protruding in the length direction from the other stack portions in the electrode assembly contacts the adjacent folding portion.

[0038] In one embodiment of the present invention, at least a part of the end of the stack start portion is covered with an insulating layer.

[0039] In one embodiment of the present invention, at least a part of the end of the positive electrode adjacent to the end of the stack start portion is covered with an insulating layer.

[0040] According to a second aspect of the present invention, The present invention provides an electrochemical element including the aforementioned electrode assembly.

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

[0042] In one embodiment of the present invention, the electrochemical element is a lithium-sulfur battery.

Advantages of the Invention

[0043] By manufacturing an electrode assembly using a continuous form of a negative electrode structure in which a negative electrode containing lithium metal is interposed between two separator membranes, cutting of the lithium metal can be minimized, and the process efficiency in manufacturing the electrode assembly can be improved.

[0044] Further, by adjusting the methods and conditions in stacking, folding, and wrapping according to the material characteristics of the negative electrode structure, the manufactured electrode assembly not only has a stable structure but also the performance of the battery can be improved.

Brief Description of the Drawings

[0045]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6a

Figure 6b

Figure 6c

Figure 6d

Figure 7

Embodiments for Carrying Out the Invention

[0046] Hereinafter, embodiments will be described in detail through exemplary drawings. It should be noted that when adding reference numerals to the components of each drawing, for the same components, as much as possible, the same numerals are used even if they are shown on different drawings. Further, when explaining the embodiments, if it is determined that a specific explanation of related known configurations or functions hinders the understanding of the embodiments, the detailed explanation thereof will be omitted.

[0047] Also, when explaining the components of the embodiments, terms such as first, second, A, B, (a), (b), etc. can be used. These terms are for distinguishing the components from other components, and the essence, order, or sequence of the components are not limited by these terms. When a component is described as being "connected", "coupled", or "connected" to another component, it should be understood that the component may be directly connected or connected to the other component, but there may also be other components "connected", "coupled", or "connected" between each component.

[0048] Components included in any one of the embodiments and components having a common function are described using the same names in other embodiments. Unless otherwise stated, the descriptions given in any one of the embodiments can be applied to other embodiments, and specific descriptions within the overlapping scope are omitted.

[0049] The present invention relates to an electrode assembly, which improves problems that may occur when applying lithium metal as a negative electrode to a conventional stack-foldable electrode assembly structure, and provides a novel-structured electrode assembly suitable for using lithium metal as a negative electrode. The electrode assembly according to the present invention can not only improve the processability in the assembly process by minimizing the processing of lithium metal, but also enhance the reliability of the manufactured product. In addition, the electrode assembly has a structure that can maximize the utilization of the positive electrode included in the electrode assembly, and can contribute to improving the performance of the battery.

[0050] In this specification, the terms "length direction", "width direction", and "thickness direction" (or "height direction") are used. In this specification, drawings such as FIGS. 1 to 6 are front views. Based on the front view, the "length direction" means the left-right direction in the drawing, the "width direction" means the front-back direction in the drawing, and the "thickness direction" (or "height direction") means the up-down direction in the drawing.

[0051] In this specification, the term "adjacent" means the object that is closest to the reference among a plurality of objects being referred to. The adjacent object does not necessarily contact the reference.

[0052] An electrode assembly according to an embodiment of the present invention includes a positive electrode, a negative electrode, and a separator. In the electrode assembly, the positive electrode and the separator are not particularly limited as long as they are materials generally used in the art, but the negative electrode contains lithium metal. In this specification, lithium metal can be broadly interpreted as long as some components are added to lithium or it is in the form of an alloy with some metals, and there is no significant difference in physical properties from lithium metal, and the same problems may occur when applied to a conventional electrode assembly as with lithium metal. In this specification, the negative electrode can be named a lithium metal layer in that it contains lithium metal, and the negative electrode and the separator can be named a negative electrode structure in that they are supplied in an integrated configuration.

[0053] According to an embodiment of the present invention, the negative electrode is interposed between two separators to form a negative electrode structure. In this specification, the two separators constituting the negative electrode structure can be named a first separator and a second separator. The negative electrode structure has a structure extending in the length direction, and the electrode assembly includes only one negative electrode structure. A basic electrode assembly structure is formed by folding the negative electrode structure having a structure extending in the length direction and fixing the positive electrode inside.

[0054] According to one embodiment of the present specification, the negative electrode structure includes one stack start portion, a plurality of stack portions, a plurality of folding portions, and one wrapping portion according to the position in the electrode assembly. The stack start portion has no special functional difference from the stack portion and may be included in the stack portion. When the stack start portion is explicitly stated, the stack portion means other stack portions excluding the stack start portion. To assist in understanding the structure of the negative electrode structure, FIG. 1 provides an exemplary structure of a negative electrode structure including a stack portion (including the stack start portion), a folding portion, and a wrapping portion. In the negative electrode structure (10), the stack portion (10A, 10A', 10A''), the folding portion (10B), and the wrapping portion (10C) are units that divide positions having different functionalities according to the longitudinal direction of the negative electrode structure (10). Here, the stack portion located at one end of the negative electrode structure is the stack start portion (10A'). The stack portion (10A, 10A', 10A''), the folding portion (10B), and the wrapping portion (10C) are not divided by materials but by positions.

[0055] The stack portion (10A, 10A', 10A'') means the negative electrode structure (10) at the position where the positive electrode is laminated, and mainly has a linear shape based on FIG. 2 and the like. The folding portion (10B) means the negative electrode structure (10) at the position connecting between the stack portions, and mainly has a curved shape based on FIG. 2 and the like. The folding portion (10B) can also be named as a bending portion. The wrapping portion (10C) means the negative electrode structure at the position wrapping the laminated structure of the positive electrode and the negative electrode structure when the uppermost stack portion (10A'') ends, and a linear shape and a curved shape are mixed based on FIG. 2 and the like.

[0056] As shown in FIG. 1, in the negative electrode structure (10), a stack start portion (10A') is located at one end with respect to the length direction, and a wrapping portion (10C) is located at the other end. Further, between the stack start portion (10A') and the wrapping portion (10C), folding portions (10B) and stack portions (10A, 10A'') are alternately located. The stack start portion (10A') is in contact with the folding portion (10B), and the wrapping portion (10C) is in contact with the stack portion (10A''). Since the stack portions (10A, 10A'') are substantially the same as the length of the positive electrode, the lengths of the respective stack portions (10A, 10A'') are substantially the same. However, the stack start portion (10A') located at the start point of the laminated structure may be different from the length of the positive electrode depending on the position of the start point.

[0057] According to an embodiment of the present invention, the stack start portion (10A') located at one end of the negative electrode structure (10) is longer than the other stack portions (10A, 10A''). The stack start portion (10A') may be further longer than the thickness of the positive electrode by the thickness of the positive electrode or more compared to the other stack portions (10A, 10A''). By making the stack start portion (10A') located at one end of the negative electrode structure (10) further longer than the thickness of the positive electrode or more compared to the other stack portions (10A, 10A''), even if the shape is deformed by wrapping or the like, it is possible to prevent the phenomenon that the negative electrode and the positive electrode come into contact and a short circuit occurs. In the stack start portion (10A'), the portion protruding from the positive electrode can be in a curved shape. According to an embodiment of the present invention, the stack start portion (10A') located at one end of the negative electrode structure (10) is 1 to 5 times, specifically 1 to 4 times, more specifically 1 to 3 times longer than the other stack portions (10A, 10A'') based on the thickness of the positive electrode. The stack start portion (10A') protruding from the positive electrode within the above range can be stably positioned by the space between the wrapping portion (10C).

[0058] When the stack start portion (10A’) located at one end of the negative electrode structure (10) is longer than the other stack portions (10A, 10A’’), the end of the stack start portion (10A’) can be positioned to protrude in the length direction from the ends of the other stack portions (10A, 10A’’) in the same direction. According to an embodiment of the present invention, in the electrode assembly, the stack start portion (10A’) protruding in the length direction from the other stack portions (10A, 10A’’) is in contact with the adjacent folding portion. By the stack start portion (10A’) being in contact with the adjacent folding portion, the possibility that the negative electrode structure is folded and contacts the positive electrode can be reduced, and a more stable structure can be formed.

[0059] According to an embodiment of the present invention, at least a part of the end of the stack start portion (10A’) is covered with an insulating layer (not shown). By covering at least a part of the end of the stack start portion (10A’) with an insulating layer, the possibility that the negative electrode structure is folded and contacts the positive electrode can be reduced, and a more stable structure can be formed. According to an embodiment of the present invention, at least a part of the end of the positive electrode (20) adjacent to the end of the stack start portion (10A’) is covered with an insulating layer. By also covering the end of the positive electrode (20) adjacent to the end of the stack start portion (10A’) with an insulating layer, the possibility that the negative electrode structure is folded and contacts the positive electrode can be further reduced.

[0060] The negative electrode structure (10) forms an electrode assembly together with a plurality of positive electrodes. To assist in understanding the structure of the electrode assembly, FIG. 2 provides an exemplary structure of an electrode assembly including a negative electrode structure and a positive electrode. Since the negative electrode structure (10) includes a negative electrode (11) and a separator (12), the electrode assembly (1) includes a positive electrode (20), a negative electrode (11), and a separator (12).

[0061] According to an embodiment of the present invention, in the electrode assembly (1), due to the folding portion (10B), the stack start portion (10A') and the plurality of stack portions (10A, 10A'') are sequentially arranged side by side in the thickness direction, and at least one positive electrode is located between the stack start portion (10A') and the stack portions (10A, 10A'') adjacent in the thickness direction and between the stack portions (10A, 10A'') and the stack portions (10A, 10A''). According to an embodiment of the present invention, the electrode assembly (1) has a structure in which the outer surface is surrounded by the wrapping portion (10C) or the wrapping portion and the outermost stack portion (10A'') in the thickness direction and the length direction. In other words, the inside of the electrode assembly (1) has a structure in which the stack portions (10A, 10A', 10A'') of the negative electrode structure and the positive electrode (20) are alternately laminated in sequence. At this time, only one positive electrode (20) is located between the stack portions (10A, 10A', 10A'') of the negative electrode structure. Also, the outside of the electrode assembly (1) has a structure surrounded by the wrapping portion (10C) of the negative electrode structure or the stack portion (10A'') and the wrapping portion (10C). Here, the inside and the outside of the electrode assembly (1) are for helping to understand the structure of the electrode assembly (1) according to the present invention, and are a division of the region of the electrode assembly (1). Based on FIG. 2, in the thickness direction and the length direction of the electrode assembly, the layer exposed to the outside means the outside of the electrode assembly (1), and the inner part of the outside of the electrode assembly (1) means the inside of the electrode assembly (1). In the negative electrode structure (10), the stack portions (10A, 10A', 10A'') mean the negative electrode structure (10) at the position where the positive electrode is laminated, and the wrapping portion (10C) starts from the end of the outermost stack portion (10A''). Therefore, when the end of the wrapping portion (10C) is located above the outermost stack portion (10A'') as shown in FIG. 2, a part of the outermost stack portion (10A'') can be located outside the electrode assembly (1), and the remaining part of the outermost stack portion (10A'') can be located inside the electrode assembly (1). Therefore, in this specification, the stack portion located inside or outside may mean the whole or a part of one stack portion.Unlike FIG. 2, when the wrapping portion (10C) covers the entire outermost stack portion (10A''), the outside of the electrode assembly (1) can be formed only by the wrapping portion (10C). The plurality of folding portions (10B) are wrapped by the wrapping portion (10C) and are not exposed to the outside in the thickness direction and the length direction.

[0062] In the electrode assembly (1) according to an embodiment of the present invention, since the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are alternately and sequentially stacked inside, the negative electrode structure (10) including the folding portion (10B) has a zigzag shape. That is, the folding portions (10B) sequentially positioned from the stack portion (10A') located at one end of the negative electrode structure (10) are alternately positioned on the left or right side in the electrode assembly (1). If the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are not alternately stacked and two or more of the stack portions or the positive electrodes are continuously stacked, no potential difference will occur between the continuously stacked layers, and the efficiency of the battery may decrease.

[0063] According to an embodiment of the present invention, in the electrode assembly (1), the stack start portion (10A'), the plurality of stack portions (10A, 10A'') and the plurality of positive electrodes (20) are closely adhered in the thickness direction by the wrapping portion (10C). The wrapping portion (10C) can wrap the inside of the electrode assembly (1) with a higher tension than the stack portions (10A, 10A', 10A'') or the folding portions (10B), whereby the internal components of the electrode assembly (1) are closely adhered in the thickness direction. In such a way, when the internal components of the electrode assembly (1) are closely adhered in the thickness direction, inevitably the internal components of the electrode assembly (1) will be closely adhered in the length direction. However, even if the internal components of the electrode assembly (1) are closely adhered in the thickness direction and the length direction, due to the structure of the electrode assembly (1), there may be a void of a certain level or more around the folding portion (10B).

[0064] According to an embodiment of the present invention, at least one positive electrode (20) is further located between the stack starting portion (10A') of the negative electrode structure (10) and the wrapping portion (10C) adjacent in the thickness direction. When the positive electrode is not added, the stack starting portion (10A') of the negative electrode structure (10) and the wrapping portion (10C) adjacent in the thickness direction are in face-to-face contact. Here, the added positive electrode (20) means the lowermost positive electrode among the positive electrodes in FIG. 2. By adding the positive electrode (20) to this portion, the wrapping portion (10C) located adjacent to the stack starting portion (10A') also has the functionality as a negative electrode, contributing to the improvement of the overall battery performance. According to an embodiment of the present invention, the positive electrode located between the stack starting portion (10A') of the negative electrode structure (10) and the wrapping portion (10C) adjacent in the thickness direction is longer than other positive electrodes. This is because there is a longer gap in the length direction at this position. Making the positive electrode located between the stack starting portion (10A') of the negative electrode structure (10) and the wrapping portion (10C) adjacent in the thickness direction longer not only helps the battery performance but also can alleviate the phenomenon that the end of the stack starting portion (10A') is folded. According to an embodiment of the present invention, the end of the stack starting portion (10A') does not contact the wrapping portion (10C). Even if it is tightly wrapped by the wrapping portion (10C), the end of the stack starting portion (10A') may not contact the wrapping portion (10C) due to the added positive electrode or the folding portion (10B).

[0065] According to one embodiment of the present invention, in the electrode assembly (1), a single positive electrode is positioned between the stack starting part (10A') and the stack parts (10A, 10A'') adjacent in the thickness direction, and between the stack parts (10A, 10A'') and the stack parts (10A, 10A''), and the total number of positive electrodes positioned between the stack starting part (10A') and the stack parts (10A, 10A'') and between the stack parts (10A, 10A'') and the stack parts (10A, 10A'') is 2n (where n is a natural number). In other words, in the electrode assembly (1), the total number of positive electrodes (20) positioned between the stack parts (10A, 10A', 10A'') and the stack parts is 2n (where n is a natural number). In the electrode assembly (1), since there is one positive electrode (20) between the stack parts (10A, 10A', 10A'') and the stack parts, the total number of positive electrodes mentioned here means the total number of positive electrodes placed in the same situation, and does not mean that 2n positive electrodes are stacked between the stack parts and the stack parts. For example, in FIG. 2, the total number of positive electrodes positioned between the stack parts and the stack parts is 4. Here, the positive electrode positioned between the stack starting part (10A') and the wrapping part (10C) is excluded. The upper limit of the total number of the positive electrodes (20) is not particularly limited and can be adjusted within the range generally used in the technical field. When the total number of positive electrodes (20) positioned between the stack parts (10A, 10A', 10A'') and the stack parts is 2n, the wrapping part (10C) is on the side opposite to one end of the negative electrode structure (10) where the outermost stack part (10A') is located. For example, in FIG. 2, one end of the negative electrode structure (10) where the stack starting part (10A') is located is on the left side, but the position where the wrapping part (10C) starts is on the right side. In this case, when wrapping, the part protruding from the positive electrode at the stack starting part (10A') naturally locates inside the electrode assembly, etc., and the processability in the manufacture of the electrode assembly can be improved.

[0066] According to one embodiment of the present invention, in the electrode assembly (1), the number of stack portions (10A, 10A', 10A'') is the same as the number of positive electrodes. According to the above description, the number of all positive electrodes (20) located between the stack portions is 2n (where n is a natural number), and since the number of stack portions (10A, 10A', 10A'') is one more than this, it is 2n + 1 (where n is a natural number). Since it is necessary to consider the positive electrodes located between the stack start portion (10A') and the wrapping portion (10C) as well, the number of stack portions and positive electrodes in the electrode assembly (1) is the same.

[0067] According to one embodiment of the present invention, the positive electrode (20) includes a positive electrode active material layer (not shown) and a current collector (not shown) that supports the positive electrode active material 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 contains a positive electrode active material and may further contain a conductive material, a binder, an additive, and the like. The current collector, positive electrode active material, conductive material, binder, additive, etc. are not particularly limited as long as they are generally used in the art.

[0068] The positive electrode current collector is not particularly limited as long as it supports the positive electrode active material, does not cause a chemical change in the battery, and has high conductivity. According to one embodiment of the present invention, the positive electrode current collector can be copper, stainless steel, aluminum, nickel, titanium, palladium, fired carbon, a material obtained by surface treatment with carbon, nickel, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, or the like.

[0069] The positive electrode current collector can form fine irregularities on its surface to strengthen the bonding force with the positive electrode active material, and various forms such as a film, sheet, foil, mesh, net, porous body, foam, non-woven fabric body, etc. can be used.

[0070] 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.

[0071] The positive electrode active material can contain a sulfur compound. According to one embodiment of the present invention, the sulfur compound is one or more selected from the group consisting of elemental sulfur (S8), organic sulfur compounds Li2S n (n ≧ 1), and carbon-sulfur polymers ((C2S x ) n : x = 2.5 to 50, n ≧ 1). Preferably, inorganic sulfur (S8) may be used.

[0072] When the positive electrode active material contains a sulfur compound, the electrode assembly (1) according to an embodiment of the present invention can be applied to a lithium-sulfur battery. In the case of sulfur contained in the positive electrode active material, since it has no electrical conductivity alone, it can be used in combination with a conductive material such as a carbon material. Thereby, the sulfur is contained in the form of a sulfur-carbon composite, and preferably, the positive electrode active material can be a sulfur-carbon composite.

[0073] When considering the above-mentioned content, the positive electrode (20) is relatively difficult to fold and easy to cut compared to the negative electrode. Therefore, the positive electrode (20) is cut into an appropriate size so that a plurality of positive electrodes are applied inside the electrode assembly (1).

[0074] According to an embodiment of the present invention, the negative electrode (11) does not include a current collector that supports a lithium metal layer. Since the negative electrode (11) does not include a current collector, it is possible to improve the loading amount of the negative electrode active material in the electrode assembly and contribute to the improvement of the battery performance. When the negative electrode (11) is mainly composed of lithium metal, although lithium metal has high ductility and viscosity and processing such as cutting may not be easy, in the electrode assembly (1) according to an embodiment of the present invention, the negative electrode can be applied in the form of a negative electrode structure (10) while minimizing cutting to improve processability. The lithium metal layer according to an embodiment of the present invention can be a free standing lithium metal layer that can maintain a certain shape by itself.

[0075] In the negative electrode structure (10), the separator (12) that covers both surfaces of the negative electrode (11) is not particularly limited as long as it does not contain a binder on its surface. Specifically, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. or a polyolefin-based porous substrate can be used as the separator (12), but it is not limited thereto.

[0076] The material of the porous base material is not particularly limited in the present invention, and any porous base material that is usually used in an electrochemical element can be used. According to one embodiment of the present invention, the porous base material includes one or more materials selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, cellulose, nylon, poly(p-phenylene benzobisoxazole), and polyarylate.

[0077] According to one embodiment of the present invention, in the negative electrode structure (10), the lengths of the negative electrode (11) and the first and second separator membranes (12) are the same. Based on the end of the negative electrode structure where the wrapping portion (10C) is located, the separator membrane located outside the electrode assembly (1) can be named the first separator membrane, and the separator membrane located inside the electrode assembly (1) can be named the second separator membrane. The negative electrode (11) and the separator membrane in the electrode assembly (1) are supplied in the form of the negative electrode structure (10) with the negative electrode (11) interposed between the first and second separator membranes (12). At this time, the negative electrode and the separator membrane are cut at once. As shown in FIG. 1, the lengths of the negative electrode (11) and the first and second separator membranes (12) in the negative electrode structure (10) are substantially the same. However, depending on the method of cutting the negative electrode structure (10), there may be a slight difference in the lengths of the negative electrode (11) and the first and second separator membranes (12). In some cases, the ends of the first and second separator membranes (12) may curve towards the center of the negative electrode structure (10). According to one embodiment of the present invention, at the end of the negative electrode structure (10), the first and second separator membranes are in contact. Even if the lengths of the negative electrode (11) and the first and second separator membranes (12) are substantially the same during the supply process of the negative electrode structure (10), when applied to the electrode assembly (1), 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 in the length direction beyond the first or second separator membrane. Also, depending on the number of folding times, the separator membranes located more outside than inside the folding portion (10B) may become shorter. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the wrapping portion (10C) side, the first separator membrane protrudes in the length direction beyond the second separator membrane. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the wrapping portion (10C) side, the second separator membrane protrudes in the length direction beyond the first separator membrane.

[0078] According to an embodiment of the present invention, in the negative electrode structure, a part of the wrapping portion (10C) is in contact with the outermost stack portion (10A''), and the end of the wrapping portion (10C) is located on the outermost stack portion (10A''). In the negative electrode structure (10), the end of the wrapping portion (10C) can be attached to the outermost stack portion (10A'') by turning around so that the wrapping portion (10C) wraps the inside of the electrode assembly (1). If the end of the wrapping portion (10C) can be effectively attached to the outermost stack portion (10A''), the adhesion means and method are not particularly limited. According to an embodiment of the present invention, the electrode assembly (1) further includes a fixing member for fixing the end of the wrapping portion (10C) on the outermost stack portion (10A''). In the negative electrode structure (10), in order to help understand the position where the end of the wrapping portion is attached, FIG. 3 provides an exemplary structure of an electrode assembly in which the end of the wrapping portion is attached with a fixing member in the negative electrode structure. In the negative electrode structure (10), since the negative electrode (11) and the separator (12) are not adhered, as shown in FIG. 3, it may be preferable that a tape (T) as a fixing member is attached so as to wrap the outer surface of the electrode assembly (1). In the process of folding the negative electrode structure (10) when manufacturing the electrode assembly (1), considering situations such as the length of the lithium metal being extended and protruding due to the ductility of the lithium metal, according to an embodiment of the present invention, the tape (T) has insulation properties and entirely covers the end of the wrapping portion (10C) in the width direction. By such a taping method, the electrode assembly (1) is covered with a separator or a tape on the top, bottom, left, and right.

[0079] When manufacturing the electrode assembly (1), when alternately laminating the stack portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20), since the negative electrode structure (10) is folded according to the same standard, the folding portions (10B) also have substantially the same length. The negative electrode structure (10) utilizes a specific form of mandrel in order to apply the same standard during folding. If the length of the folding portion (10B) is short, an unnecessary load may be applied to the lithium metal located at the center of the negative electrode structure (10), and defects such as the lithium metal being severed may occur. Therefore, by ensuring that the length of the folding portion (10B) is sufficiently above a certain level, the lithium metal can be flexibly arranged in the gap between the portion where the electrodes are laminated and the wrapping portion.

[0080] In the negative electrode structure (10), in order to assist in understanding the length of the folding portion (10B), FIG. 4 provides a drawing showing an enlarged view of the folding portion (10B) in the electrode assembly (1). According to an embodiment of the present invention, in the negative electrode structure (10), the length of the folding portion (10B) is 2 to 10 times based on the total thickness of the positive electrode (20) and the negative electrode structure (10). The length of the folding portion (10B) means the length of the curve of the folding portion. In the case of a curve, since the inner and outer lengths may be different, the length of the central portion is measured. For example, after cutting the portion indicated by the dotted line in FIG. 4 and spreading it, the length can be measured. Specifically, the length of the folding portion (10B) is 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more based on the total thickness of the positive electrode (20) and the negative electrode structure (10), and 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, and may be 2 to 10 times, 3 to 9 times, 4 to 8 times. When adjusting the length of the folding portion (10B) within the above range, defects in the folding portion in the electrode assembly can be reduced, and the electrode assembly can be stably wrapped.

[0081] The length of the aforementioned folding portion (10B) means that it is formed to be even longer as shown in FIG. 4 rather than being folded into a semi-circular shape as shown in FIG. 2. Specifically, when the folding portion (10B) has a perfect semi-circular form with an eccentricity of 0, the length of the folding portion is a value obtained by multiplying the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10), which is the diameter, by π and then dividing by 2. Based on the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10), this is a value about 1.57 times that. Judging based on this, it can be said that the length of the folding portion (10B) according to an embodiment of the present invention is longer at a significant level.

[0082] In manufacturing the electrode assembly (1), when the stacking portions (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are alternately stacked and then the electrode assembly (1) is wrapped by the wrapping portion (10C), the folding portion (10B) receives a pressure of a certain level or more in the inner direction of the electrode assembly (1). Thereby, the folding portion (10B) can be appropriately arranged in the gap between the portion where the electrodes are stacked and the wrapping portion. Since the folding portion (10B) disposed appropriately between the gaps contains the lithium metal layer (11) inside, in relation to the positive electrode (20) on the side surface, it can contribute to further improvement of battery performance through an electrochemical reaction. By the folding portion (10B) appropriately filling the gaps between, two or more lithium metal layers can also be positioned on the side surface of the positive electrode not wrapped by the folding portion (10B). When wrapping the electrode assembly (1) by the wrapping portion (10C), if the wrapping is performed such that the wrapping portion (10C) has a tension of a certain level or more, it helps to maintain the shape of the electrode laminate located inside the electrode assembly (1) without distortion of the structure.

[0083] According to one embodiment of the present invention, the folding portion (10B) has an asymmetric shape with respect to the surface along the length direction. Such an asymmetric shape is a shape formed by the folding portion (10B) being pressed in the length direction by the wrapping portion (10C) and the folding portion (10B) being appropriately arranged in the gap. According to one embodiment of the present invention, the center point of the length of the folding portion (10B) does not align with the center point of the thickness of the positive electrode wrapped by the folding portion (10B). The center point of the length of the folding portion (10B) can be inclined in the direction in which wrapping progresses with respect to the center point of the thickness of the positive electrode. For example, referring to FIG. 2, the folding portion located on the right side of the electrode laminate has wrapping performed from top to bottom, so the center point of the length of the folding portion can be located below the center point of the thickness of the positive electrode. On the other hand, the folding portion located on the left side of the electrode laminate has wrapping performed from bottom to top, so the center point of the length of the folding portion can be located above the center point of the thickness of the positive electrode.

[0084] In comparing the length of the folding portion (10B) below, to assist in understanding the vertical distance between the end of the reference positive electrode (20) and the side wrapping portion (10C), FIG. 5 provides a drawing showing an enlarged view of the portion of the electrode assembly (1) where the end of the positive electrode (20) and the side wrapping portion (10C) are located. As shown in FIG. 5, in the process of wrapping the electrode assembly, the shape of the folding portion (10B) may be deformed by the pressure applied from the wrapping portion (10C) located on the side. However, FIG. 5 is only one exemplary structure, and it is not necessarily the case that the folding portion (10B) is deformed in such a form. Due to the pressure, the distance (d) between the end of the positive electrode (20) and the side wrapping portion (10C) can be shortened, and the folding portion (10B) can be naturally arranged in a reduced space as the distance (d) shortens. According to an embodiment of the present invention, in the electrode assembly (1), the length of the folding portion (10B) is 2 to 10 times based on the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portion (10C). The side wrapping portion (10C) means a linear wrapping portion (10C) located on the left or right side of the electrode assembly with reference to FIG. 2 or FIG. 3. In an actual electrode assembly, when this portion is not straight, the vertical distance (d) is measured based on the end of the positive electrode at the central portion in the thickness direction of the electrode laminate with respect to the vertical distance from the side wrapping portion. Also, as another method, in one aspect, the vertical distance (d) can be measured as the average value of the vertical distance from the end of the positive electrode (20) at the portion where the wrapping portion (10C) is in contact with the folding portion (10B). Specifically, the length of the folding portion (10B) is 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more based on the vertical distance (d) between the end of the positive electrode (20) and the side wrapping portion (10C), and 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, and may be 2 to 10 times, 3 to 9 times, 4 to 8 times. This means that, as described above, the length of the folding portion (10B) is longer at a significant level, but the vertical distance (d) is also short, indicating that the folding portion is compactly packed in the space on the side of the electrode laminate.When adjusting the length of the folding part (10B) within the above range, the folding part can be compactly packed at an appropriate level in the void in the electrode assembly without applying excessive pressure to the folding part by wrapping the electrode assembly, which can contribute to improving the performance of the battery.

[0085] According to one embodiment of the present invention, the electrode assembly (1) folds one negative electrode structure body (10) to form the basic structure of the electrode assembly (1). In this regard, the thickness of the negative electrode structure body (10) should not be excessively thick so that it can be flexibly folded. Considering the performance of the battery, a certain level or more of lithium metal, which is the negative electrode active material, must be ensured in the negative electrode structure body (10). According to one embodiment of the present invention, in the negative electrode structure body (10), the thickness of the lithium metal accounts for 50% - 90% based on the overall thickness of the negative electrode structure body (10). Specifically, the range of the thickness of the lithium metal may be 50% - 90%, specifically 55% - 85%, and more specifically 60% - 80%. When the lithium metal satisfies the above thickness range, it can help improve the processability and functionality of the electrode assembly. According to one embodiment of the present invention, since the negative electrode structure body (10) does not include a separate current collector, the thickness of the remaining part excluding the thickness of the lithium metal can mean the thickness of two separator films.

[0086] According to one embodiment of the present invention, the thickness of the lithium metal can be 10μm - 90μm. Specifically, the thickness of the lithium metal may be 10μm or more, 20μm or more, or 30μm or more, and may also be 70μm or less, 80μm or less, or 90μm or less. The thickness of the lithium metal is not necessarily limited to this and can be appropriately adjusted according to the actual size of the battery.

[0087] According to an embodiment of the present invention, unlike the negative electrode structure (10), the positive electrode is cut considering characteristics such as the material, and is applied between the stack portions (10A, 10A', 10A'') of the negative electrode structure (10). The positive electrode includes a current collector in addition to the positive electrode active material and is distinguished from the negative electrode and has independence. However, considering the performance of the electrode, etc., its thickness can be adjusted in relation to the negative electrode or the negative electrode structure. According to an embodiment of the present invention, the thickness of the positive electrode (20) is greater than the thickness of the negative electrode structure (10). According to an embodiment of the present invention, the thickness of the positive electrode (20) has a thickness exceeding 100% and not exceeding 400% based on the thickness of the negative electrode structure (10). Specifically, the range of the thickness of the positive electrode (20) may be exceeding 100% and not exceeding 400%, specifically 150% to 350%, more specifically 200% to 300%. When the positive electrode satisfies the above-mentioned thickness range, it can achieve an appropriate harmony with the negative electrode structure.

[0088] Hereinafter, the process of manufacturing the above-mentioned electrode assembly will be specifically described. To assist in understanding the manufacturing process of the electrode assembly, FIG. 6 schematically shows the process and state in the manufacturing process of the electrode assembly.

[0089] The manufacturing process of the electrode assembly according to an embodiment of the present invention includes: (1) folding the negative electrode structure to produce an electrode laminate in which the positive electrode and the negative electrode structure are alternately laminated; (2) after manufacturing the electrode laminate, surrounding the electrode laminate with an excess negative electrode structure; (3) positioning and fixing the end of the negative electrode structure above the electrode laminate.

[0090] The (1) stage is manufactured through a process exemplified as in FIG. 6a. As shown in FIG. 6a, with the positive electrode placed at the lowermost layer, while placing the negative electrode structure thereon, the positive electrode and the negative electrode structure can be sequentially laminated. Although not shown in FIG. 6a, when folding the negative electrode structure, a device such as a mandrel can be utilized to manufacture the folding at each position based on the same criterion. The (2) stage is manufactured through a process exemplified as in FIG. 6b. In the process of wrapping with the excess negative electrode structure, when wrapping such that the negative electrode structure has a tension above a specific level, the folded portion is compactly packed in the void, which helps to maintain the shape of the electrode laminate without distorting its structure. After the (3) stage, the completed electrode assembly becomes in a state as shown in FIG. 6c or FIG. 6d. It has the effect of preventing the positive electrode between the stack portions from flowing down due to wrapping. Considering such functionality, the end of the negative electrode structure may preferably be positioned at the upper stage of the electrode laminate. By fixing the negative electrode structure, the tension applied to the negative electrode structure during the wrapping process can be maintained as it is. Wrapping with a tape (T) as shown in FIG. 6d can be an exemplary method.

[0091] In the manufacturing process, the specific characteristics of the positive electrode and the negative electrode structure not specifically described follow the foregoing content. The electrode assembly according to an embodiment of the present invention can weld a plurality of layers of tabs and leads like a conventional large-capacity cell and can maintain performance such as cell resistance and output.

[0092] The electrode assembly according to an embodiment of the present invention is applied to an electrochemical element. The electrochemical element can include all elements that undergo an electrochemical reaction. For example, the electrochemical element can be any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor. When the electrochemical element is a secondary battery, the electrochemical element can be a lithium secondary battery, and the lithium secondary battery can include a lithium metal secondary battery, a lithium-ion secondary battery, a lithium polymer secondary battery, or a lithium-ion polymer secondary battery, etc.

[0093] As described above, even if the embodiments are described by way of example with limited embodiments and drawings, those having ordinary knowledge in the relevant technical field can make various modifications and variations from the above description. For example, whether the described technology is performed in a different order from the described method, and / or whether the components of the described system, structure, device, circuit, etc. are combined or assembled in a different form from the described method, or replaced or substituted by other components or equivalents, appropriate results can be achieved.

[0094] Hereinafter, preferred examples are shown to assist in understanding the present invention. However, the following examples are provided to more easily understand the present invention, and the present invention is not limited thereto.

[0095] Example Example 1: Manufacture of an electrode assembly wrapped with a negative electrode structure A negative electrode structure was manufactured with 60 μm of lithium metal interposed between two polyethylene (PE) separator films (11 μm). Also, a positive electrode slurry was manufactured by adding a positive electrode mixture composed of 85% by weight of a positive electrode active material manufactured by mixing sulfur and carbon nanotubes (CNT) at a weight ratio of 7:3, 5% by weight of carbon nanofiber as a conductive material, and 10% by weight of a binder to deionized water, and then coating it on an aluminum current collector to manufacture a 200 μm positive electrode.

[0096] The manufactured negative electrode structure was folded to manufacture an electrode laminate in the manner shown in Fig. 6a, and then the electrode laminate was wrapped with an extra negative electrode structure in the manner shown in Fig. 6b to manufacture an electrode assembly as shown in Fig. 6c. The end of the negative electrode structure exposed from the electrode assembly was adhered with insulating tape as shown in Fig. 6d. At this time, in the electrode assembly, the length of the folded portion was measured to be 1,453 μm, and the vertical distance between the end of the positive electrode and the side wrapping portion was measured to be 268 μm.

[0097] Comparative Example 1: Manufacture of an electrode assembly with a cut and laminated negative electrode structure After cutting the negative electrode structure to match the positive electrode of each layer, the positive electrode and the negative electrode structure were laminated to produce an electrode laminate, and then the electrode assembly was completed with the negative electrode structure without separate wrapping. In the said electrode assembly, the materials and thicknesses of the positive electrode and the negative electrode structure were manufactured in the same manner as in Example 1.

[0098] Experimental Example Each electrode assembly manufactured according to Example 1 and Comparative Example 1 was placed in the same pouch, filled with an electrolyte in which 0.4 M of LiFSI salt and 4 wt% of LiNO3 were added to an ether-based electrolyte, and a lithium secondary battery was manufactured. The manufactured lithium secondary battery was charged and discharged at 0.3C to measure the Coulomb efficiency for each cycle, and the results are shown in FIG. 7.

[0099] It can be confirmed that the electrode assembly according to the present invention not only has advantages in terms of process compared to the conventional electrode assembly, but also can improve the long-term performance of the battery such as Coulomb efficiency according to FIG. 7.

[0100] All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

Explanation of Reference Numerals

[0101] 1, 1’, 1’’: Electrode assembly 10: Negative electrode structure 10A, 10A’’: Stacked portion 10A’: Stack start portion 10B: Folding portion 10C: Wrapping portion 11: Negative electrode (lithium metal layer) 12: Separator (first separator and second separator) 20: Positive electrode T: Fixing member (tape) d: Vertical distance between the end of the positive electrode and the side wrapping portion

Claims

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

2. The electrode assembly according to claim 1, wherein in the electrode assembly, the stack start portion, the plurality of stack portions, and the plurality of positive electrodes are adhered in the thickness direction by the wrapping portion.

3. The electrode assembly according to claim 1, wherein the length of the stack start portion is longer than the length of the stack portion.

4. The electrode assembly according to claim 1, wherein at least one positive electrode is positioned between the stack start portion and the wrapping portion adjacent in the thickness direction.

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

6. The electrode assembly according to claim 1, wherein in the electrode assembly, the positive electrode includes a positive electrode active material layer and a current collector supporting the positive electrode active material layer, and the negative electrode structure does not include a current collector supporting the lithium metal layer.

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

8. In the negative electrode structure, a part of the wrapping portion is in contact with the outermost stack portion, and the end of the wrapping portion is located on the outermost stack portion. The electrode assembly according to claim 1, characterized in that.

9. The electrode assembly according to claim 1, further comprising a fixing member for fixing the end of the wrapping portion on the outermost stack portion.

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

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

12. The folding portion has an asymmetric shape with respect to the plane along the length direction. The electrode assembly according to claim 1, characterized in that.

13. In the negative electrode structure, the thickness of the lithium metal layer is 50% to 90% based on the total thickness of the negative electrode structure. The electrode assembly according to claim 1, characterized in that.

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

15. The length of the stack start portion is equal to or greater than the thickness of the positive electrode and longer than the length of the stack portion. The electrode assembly according to claim 3, characterized in that.

16. The positive electrode located between the stack start portion and the wrapping portion adjacent in the thickness direction is longer than other positive electrodes. The electrode assembly according to claim 4, characterized in that.

17. The fixing member is an insulating tape. The electrode assembly according to claim 9, characterized in that.

18. The end of the stack start portion is not in contact with the wrapping portion. The electrode assembly according to claim 1, characterized in that.

19. The center point of the length of the folding portion is not aligned with the center point of the thickness of the positive electrode wrapped by the folding portion. The electrode assembly according to claim 1, characterized in that.

20. In the electrode assembly, the stack start portion protruding in the length direction more than other stack portions is in contact with the adjacent folding portion. The electrode assembly according to claim 3, characterized in that.

21. The electrode assembly according to claim 3, wherein at least a part of the end of the stack starting portion is covered with an insulating layer.

22. The electrode assembly according to claim 21, wherein at least a part of the end of the positive electrode adjacent to the end of the stack starting portion is covered with an insulating layer.

23. An electrochemical element including the 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.

Images