Electrode assembly and electrochemical device including the same

Abstract

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

Description

Technical Field

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

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2022-0136198 filed on October 21, 2022, Korean Patent Application No. 10-2023-0070481 filed on May 31, 2023, and Korean Patent Application No. 10-2023-0139505 filed on October 18, 2023, the entire contents of which are incorporated as part of this specification. Background Art

[0003] In recent years, there has been an increasing interest in energy storage technology. As the application areas expand to range from mobile phones, camcorders and laptop PCs to electric vehicle energy, efforts in research and development are being implemented. In this regard, electrochemical devices are one of the most promising areas, especially as batteries are miniaturized and lightweight and can be charged and discharged at high capacity in accordance with the recent trend of miniaturization and lightweighting of electronic devices, the development of secondary batteries has received attention.

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

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

[0006] First, a jelly roll electrode assembly is manufactured by winding long sheets of positive and negative electrodes in a dense state, so as to have a cylindrical or elliptical cross-section. In this structure, the stress caused by the expansion and contraction of the electrodes during charging and discharging accumulates in the electrode assembly, and when this stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs. In addition, the deformation of the electrode assembly may cause uneven spacing between the electrodes, resulting in a sharp drop in the performance of the battery, and an internal short circuit may occur, threatening the safety of the battery. In addition, since the jelly roll electrode assembly requires winding long sheets of positive and negative electrodes, it is difficult to quickly wind the positive and negative electrodes while maintaining a constant spacing between the positive and negative electrodes, resulting in reduced productivity.

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

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

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

[0010] After continuously studying the structure of an electrode assembly, the inventors of the present invention designed a structure suitable for an electrode assembly, especially a battery assembly containing lithium metal as a negative electrode, and completed the present invention.

[0011] [Patent References]

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

[0013] [Technical issues]

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

[0015] [Technical solution]

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

[0017] In one embodiment of the present invention, the negative electrode structure includes first and second separators, and a lithium metal layer between the first and second separators.

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

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

[0020] In one embodiment of the present invention, the electrode assembly has a plurality of stacked portions sequentially positioned side by side in a thickness direction through a folded portion, and at least one positive electrode is positioned between the stacked portions, which are adjacent to each other in the thickness direction.

[0021] In one embodiment of the present invention, in the electrode assembly, the second wrapping portion is positioned adjacent to the first wrapping portion, and the outer surface in the thickness direction and the longitudinal direction is surrounded by the second wrapping portion, or by the second wrapping portion and at least one of the first wrapping portion and the outermost stacking portion.

[0022] In one embodiment of the present invention, in the electrode assembly, the plurality of stacking parts and the plurality of positive electrodes are closer to each other in a thickness direction through the wrapping part.

[0023] In one embodiment of the present invention, the second wrapping portion of the negative electrode structure surrounds the first wrapping portion surrounding one side of the electrode laminate together with the opposite side of the electrode laminate.

[0024] In one embodiment of the present invention, ends of the first and second wrapping parts of the negative electrode structure are located on the same line.

[0025] In one embodiment of the present invention, the electrode assembly has at least one positive electrode between a stack portion adjacent to a first wrap portion of the negative electrode structure and a second wrap portion positioned parallel to the stack portion.

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

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

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

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

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

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

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

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

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

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

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

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

[0038] In one embodiment of the present invention, the positive electrode between the stacked portion adjacent to the first package portion and the second package portion adjacent thereto in the thickness direction is longer than the other positive electrodes.

[0039] In one embodiment of the present invention, one end of the second wrapping portion is located on the first wrapping portion.

[0040] In one embodiment of the present invention, one end of the second wrapping portion is located on the outermost stacking portion.

[0041] In one embodiment of the present invention, the electrode assembly includes a first fixing member fixing the first wrapping portion and a second fixing member fixing the second wrapping portion.

[0042] According to a second aspect of the present invention, the present invention provides an electrochemical device comprising the above-mentioned electrode assembly.

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

[0044] In one embodiment of the present invention, the electrochemical device is a lithium sulfur battery.

[0045] [Effects of the Invention]

[0046] An electrode assembly according to an embodiment of the present invention is manufactured by using a negative electrode structure in a continuous form in which a negative electrode including lithium metal is interposed between two separators, thereby minimizing cutting of lithium metal and thus improving process efficiency of manufacturing the electrode assembly.

[0047] In addition, by adjusting the stacking, folding and wrapping methods and conditions according to the material properties of the negative electrode structure, not only can the manufactured electrode assembly have a stable structure but also the performance of the battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of a negative electrode structure including a stacking portion, a folding portion, and a wrapping portion according to an embodiment of the present invention.

[0049] Figure 2 FIG. 4 is a schematic diagram of a structure of an electrode assembly including a negative electrode structure and a positive electrode according to an embodiment of the present invention.

[0050] Figure 3 is a schematic diagram of a structure of an electrode assembly according to an embodiment of the present invention, in which an end portion of a wrapping portion is fixed to a negative electrode structure using a fixing member.

[0051] Figure 4 is an enlarged schematic diagram of a folded portion of an electrode assembly according to an embodiment of the present invention.

[0052] Figure 5 is an enlarged schematic diagram of a portion of an electrode assembly according to one embodiment of the present invention, wherein an end portion of a positive electrode and a transverse wrapping portion are located in the portion.

[0053] FIG. 6 is a diagram schematically showing a process and a state in a manufacturing process of an electrode assembly according to an embodiment of the present invention. Here, Figure 6a Schematic diagram of the process of folding the negative electrode structure to form an electrode laminate, in which positive and negative electrode structures are alternately stacked. Figure 6b schematically shows a process of wrapping one side of the electrode laminate with the first and second wrapping parts after forming the electrode laminate, and Figure 6c The wrapping process using the second wrapping unit is schematically shown. Figure 6dThe electrode assembly after wrapping is schematically shown, wherein the ends of the first and second wrapping parts are on the same line, and Figure 6e The state in which the ends of the first and second wrapping parts are fixed is schematically shown.

[0054] Figure 7 is a graph depicting results of measuring cycle-by-cycle coulombic efficiency of a lithium secondary battery including each of the electrode assemblies manufactured according to Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0055] The following describes the details of an embodiment of the present invention. It should be noted that when assigning reference numerals to components in each figure, the same components are given the same reference numerals as much as possible even in different figures. In addition, when describing an embodiment, if a detailed description of a related known configuration or feature is considered to interfere with the understanding of the embodiment, the detailed description is omitted.

[0056] In addition, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of the embodiments. These terms are intended only to distinguish one component from another, and the nature, order, or sequence of these components is not limited by these terms. When a component is described as being "connected," "coupled," or "adjacent" to another component, it should be understood that the component may be directly connected or in contact with the other component, but the other component may be "connected," "coupled," or "adjacent" between these components.

[0057] Components included in one embodiment and components having common functions are described in other embodiments using the same terms. Unless otherwise specified, the description in one embodiment can be applied to other embodiments, and redundant detailed descriptions are omitted.

[0058] The present invention relates to an electrode assembly that improves problems that may occur when lithium metal is applied as a negative electrode to a conventional stackable-foldable electrode assembly structure to provide an electrode assembly having a novel structure suitable for using lithium metal as a negative electrode. By minimizing the processing of lithium metal, the electrode assembly according to the present invention can not only improve the feasibility of the assembly process, but also improve 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, which can help improve the performance of the battery.

[0059] The terms “longitudinal direction”, “width direction”, and “thickness direction” (or “height direction”) are used in this specification. Figure 1 6 to 6 are front views, and based on these front views, a “longitudinal direction” indicates a left-right direction, a “width direction” indicates a front-rear direction, and a “thickness direction” (or “height direction”) indicates an up-down direction.

[0060] As used herein, the term "adjacent" refers to an object that is closest to a reference object among a plurality of objects referred to thereby. An adjacent object is not necessarily in contact with the reference object.

[0061] An electrode assembly according to one embodiment of the present invention includes a positive electrode, a negative electrode and a separator. In the electrode assembly, the positive electrode and the separator are not particularly limited as long as they are materials commonly used in the art, but the negative electrode includes lithium metal. As used herein, lithium metal can be broadly understood as even if lithium is added with a specific component or is an alloy with a specific metal, as long as it is not significantly different in nature from lithium metal and can be applied to conventional electrode assemblies, which leads to the same problems as lithium metal. As used herein, the negative electrode can be referred to as a lithium metal layer because it includes lithium metal, and the negative electrode and the separator can be referred to as a negative electrode structure because they are provided as a single integral structure.

[0062] According to one embodiment of the present invention, the negative electrode is interposed between two separators to form a negative electrode structure. The two separators constituting the negative electrode structure may be referred to herein as first and second separators. The negative electrode structure has a longitudinally extending structure, and the electrode assembly includes only one negative electrode structure. The negative electrode structure having a longitudinally elongated structure is folded to form a basic electrode assembly structure, such as fixing the positive electrode therein.

[0063] According to one embodiment of the present invention, the negative electrode structure includes: a plurality of stacking parts, a plurality of folding parts, and two wrapping parts according to the positions of the following items in the electrode assembly. In this specification, the two wrapping parts included in the negative electrode structure may be named as a first wrapping part and a second wrapping part. In order to facilitate understanding of the structure of the negative electrode structure, Figure 1 An exemplary structure of a negative electrode structure including a stacking portion, a folding portion, and a wrapping portion is provided. In the negative electrode structure (10), the stacking portion (10A, 10A', 10A''), the folding portion (10B), and the wrapping portion (10C, 10C') are units that are distinguished in positions having different functions according to the longitudinal direction of the negative electrode structure 10. The stacking portion (10A, 10A', 10A''), the folding portion (10B), and the wrapping portion (10C, 10C') are not distinguished in material except for the position.

[0064] The stacking part (10A, 10A', 10A'') refers to the negative electrode structure (10) at the position where the positive electrode is stacked, and Figure 2 The folded portion (10B) refers to the negative electrode structure (10) in a position connecting the stacked portions to each other, and Figure 2The folded portion (10B) may also be referred to as a bent portion. The first wrapping portion (10C) refers to the negative electrode structure at a position where the stacked structure of the positive and negative electrode structures is wrapped at a point where the stacked structure of the positive and negative electrode structures is in contact with the bottom outermost stacking portion (10A'). In addition, the second wrapping portion (10C') refers to the negative electrode structure at a position where the stacked structure of the positive and negative electrode structures and the first wrapping portion (10C) are wrapped at a point where the stacked structure of the positive and negative electrode structures and the first wrapping portion (10C) are in contact with the top outermost stacking portion (10A''). They are Figure 2 There are straight and curved shapes.

[0065] like Figure 1 As shown, the negative electrode structure 10 has first and second wrapping portions (10C, 10C') at both ends relative to the longitudinal direction. That is, the two wrapping portions (10C, 10C') are located at each of the longitudinal ends of the negative electrode structure (10). In addition, the first wrapping portion (10C) contacts the first outermost stacking portion (10A'), and the second wrapping portion (10C') contacts the second outermost stacking portion (10A''). Between the first outermost stacking portion (10A') and the second outermost stacking portion (10A''), the folding portion (10B) and the stacking portion (10A) are alternately positioned. Since the length of the stacking portions (10A, 10A', 10A'') is substantially equal to the length of the positive electrode, the length of each stacking portion (10A, 10A', 10A'') is substantially the same.

[0066] The two wrapping portions (10C) located at both ends of the negative electrode structure (10) may have different lengths. In order to distinguish the two wrapping portions (10C), the wrapping portion (10C) located at the point where stacking starts is named as the first wrapping portion, and the wrapping portion (10C) located at the point where stacking ends is named as 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 the first wrapping portion (10C) on one side of the electrode laminate and the opposite side of the electrode laminate together. Therefore, compared with the first wrapping portion (10C), the second wrapping portion (10C') is located outside the electrode assembly (1). Considering the convenience of the process, the first wrapping portion (10C) located at the point where lamination starts may be shorter than the second wrapping portion (10C') located at the point where lamination ends. In addition to wrapping the first wrapping portion ( 10C), the second wrapping portion ( 10C′) may have a longer length to wrap the opposite side of the electrode laminate, and the stacking portion ( 10A′) or an additional positive electrode adjacent to the first wrapping portion ( 10C).

[0067] According to one embodiment of the present invention, the ends of the first and second wrapping parts (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 has a structure in which the second wrapping part (10C') is substantially wrapped on the first wrapping part (10C). In a strict sense, wrapping the first wrapping part (10C) with the second wrapping part (10C') indicates that the wrapping parts (10C, 10C') located inside cannot be exposed to the outside, but this is not strictly interpreted in this specification. Therefore, the electrode assembly according to one embodiment of the present invention may have the ends of the first wrapping part (10C) and the second wrapping part (10C') on the same line, but may not be on the same line, and the second wrapping part (10C') may be slightly shorter so that the end of the first wrapping part (10C) is exposed, or the second wrapping part (10C') may be slightly longer so that the end of the first wrapping part (10C) is completely covered. According to one embodiment of the present invention, the end of the second wrapping part is located on the first wrapping part, or the end of the second wrapping part is located on the outermost stacking part. If the ends of the first wrapping portion (10C) and the second wrapping portion (10C') are located on the same line, the structure can be further simplified. If the second wrapping portion (10C') is slightly shorter, exposing the end of the first wrapping portion (10C), the second wrapping portion (10C') and the first wrapping portion (10C) can be fixed simultaneously by taping. Moreover, if the second wrapping portion (10C') is slightly longer and completely wrapped around 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.

[0068] The negative electrode structure (10) forms an electrode assembly together with a plurality of positive electrodes. To better understand the structure of the electrode assembly, Figure 2 An exemplary structure of an electrode assembly including a negative electrode structure and a positive electrode is provided. Since the negative electrode structure (10) includes a negative electrode (11) and a separator (12), the electrode assembly (1) includes a positive electrode (10), a negative electrode (11) and a separator (12).

[0069] According to one embodiment of the present invention, an electrode assembly (1) has a plurality of stacking portions (10A, 10A', 10A''), which are positioned side by side in sequence in the thickness direction by a folding portion (10B), and at least one positive electrode is positioned between stacking portions (10A, 10A', 10A'') adjacent to each other in the thickness direction. According to one embodiment of the present invention, in the electrode assembly (1), a second wrapping portion (10C') is positioned adjacent to a first wrapping portion (10C), and has a structure such that its outer surface in the thickness direction and the longitudinal direction is surrounded by the second wrapping portion (10C'), or by the second wrapping portion (10C') and at least one of the first wrapping portion (10C) and the outermost stacking portion (10A''). Here, the expression "at least one of the first wrapping portion (10C) and the outermost stacking portion (10A'')" is used because the end of the second wrapping portion and the end of the first wrapping portion may not overlap. Reference Figure 2 , the interior of the electrode assembly (1) has a structure in which one side of an electrode laminate in which stacked portions (10A, 10A', 10A'') of negative electrode structures and positive electrodes are stacked in an alternating sequence is surrounded by a first wrapping portion (10C). In this case, only one positive electrode (20) is located between the stacked portions (10A, 10A', 10A'') of negative electrode structures. In addition, the outer surface of the electrode assembly (1) has a structure surrounded by the stacked portions (10A'') of negative electrode structures and the second wrapping portion (10C'). Here, the interior and exterior of the electrode assembly (1) are different regions of the electrode assembly (1) to facilitate understanding of the structure of the electrode assembly (1) according to the present invention, and Figure 2 In the present invention, the layer exposed to the outside in the thickness direction and the longitudinal direction of the electrode assembly (1) refers to the outside of the electrode assembly (1), and the inner part of the outside of the electrode assembly (1) refers to the inside of the electrode assembly (1). In the negative electrode structure (10), the stacking part (10A, 10A', 10A'') refers to the negative electrode structure (10) at the position where the positive electrode is stacked, and the second wrapping part (10C') starts from the point where the uppermost second outermost stacking part (10A'') ends, when the end of the second wrapping part (10C') is located above the uppermost second outermost stacking part (10A''), as shown in FIG. Figure 2 As shown, a portion of the uppermost second outermost stacking portion (10A'') may be located on the outer side of the electrode assembly (1), and the remaining portion of the uppermost second outermost stacking portion (10A'') may be located on the inner side of the electrode assembly (1). Therefore, as used herein, a stacking portion located inside or outside may refer to all or part of a stacking portion. Figure 2Differently, when the second wrapping portion (10C') covers the entirety of the uppermost second outermost stacking portion (10A''), the exterior of the electrode assembly (1) may consist only of the second wrapping portion. If the first wrapping portion (10C) covers the entirety of the uppermost second outermost stacking portion (10A'') and the end of the second wrapping portion does not reach the end of the first wrapping portion, the exterior of the electrode assembly (1) may consist only of the first and second wrapping portions. In addition, if the first wrapping portion (10C) covers only a portion of the uppermost second outermost stacking portion (10A'') and the end of the second wrapping portion does not reach the end of the first wrapping portion, the exterior of the electrode assembly (1) may be formed by the first and second wrapping portions (10C, 10C') and the second outermost stacking 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 the longitudinal direction.

[0070] Since the electrode assembly (1) according to one embodiment of the present invention has the stacking parts (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) alternately and sequentially stacked therein, the negative electrode structure (10) including the folding part (10B) has a zigzag shape. In other words, the folding part 10B sequentially positioned from the stacking part 10A' contacting the first or second wrapping part 10C, 10C' of the negative electrode structure 10 is alternately located on the left or right side of the electrode assembly 1. If the stacking parts (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are not alternately stacked, and two or more of the stacking parts or the positive electrodes are continuously stacked, a potential difference may not occur between the continuously stacked layers, and the efficiency of the battery may be reduced.

[0071] According to one embodiment of the present invention, in an electrode assembly (1), a plurality of stacking portions (10A, 10A', 10A'') and a plurality of positive electrodes (20) are brought closer to each other in the thickness direction through first and second wrapping portions (10C, 10C'). The first and second wrapping portions (10C, 10C') can wrap the interior of the electrode assembly (1) with a higher tension than the stacking portions (10A, 10A', 10A'') or the folding portion (10B), which causes the internal structure of the electrode assembly (1) to be brought closer to each other in the thickness direction. When the internal structure of the electrode assembly (1) is brought closer to each other in the thickness direction by this method, the internal structure of the electrode assembly (1) inevitably becomes closer to each other in the longitudinal direction. However, even if the internal structure of the electrode assembly (1) becomes closer to each other in the thickness direction and the longitudinal direction, a certain level of voids may exist around the folding portion (10B) due to the structure of the electrode assembly (1).

[0072] According to one embodiment of the present invention, the electrode assembly (1) has at least one positive electrode located between a stacking portion (10A') adjacent to a first wrapping portion (10C) of a negative electrode structure (10) and a second wrapping portion (10C') located parallel to the stacking portion (10A'). If no positive electrode is added, the stacking portion (10A') of the negative electrode structure (10) and the second wrapping portion (10C') adjacent thereto in the thickness direction are in face-to-face contact. Here, the added positive electrode (20) refers to the one located Figure 2 The positive electrode at the lowest point of the positive electrode in the battery. By adding the positive electrode (20) to this part, the second wrapping part (10C') adjacent to the stacking part (10A') also has the function of a negative electrode, thereby helping to improve the overall performance of the battery. According to one embodiment of the present invention, the positive electrode located between the stacking part (10A') adjacent to the first wrapping part (10C) and the second wrapping part (10C') adjacent thereto in the thickness direction is longer than other positive electrodes. This is because there is a more longitudinally extended gap at this position, and therefore, making the positive electrode located between the stacking part (10A') of the negative electrode structure (10) and the second wrapping part (10C') adjacent thereto in the thickness direction longer is beneficial to the performance of the battery.

[0073] According to one embodiment of the present invention, in an electrode assembly (1), one positive electrode is located between stacking parts (10A, 10A', 10A'') adjacent to each other in the thickness direction, and the total number of positive electrodes (20) located between the stacking parts (10A, 10A', 10A'') is 2n (where n is a natural number). Since there is only one positive electrode (20) between the stacking parts (10A, 10A', 10A'') in the electrode assembly (1), the number of total positive electrodes herein refers to the total number of positive electrodes under the same circumstances, and does not mean that 2n positive electrodes are stacked between the stacking parts. For example, in Figure 2 , the total number of positive electrodes located between the stacked portions is 4. The positive electrodes located between the stacked portion (10A') and the wrapped portion (10C) are excluded therefrom. The upper limit of the number of total positive electrodes (20) is not particularly limited and can be adjusted within the conventional range in the art. When the number of total positive electrodes (20) located between the stacked portions is 2n, the point at which the first wrapped portion (10C) starts is opposite to the point at which the second wrapped portion (10C') starts. For example, in Figure 2 In the embodiment, the point where the first wrapping portion (10C) starts is on the left, and the point where the second wrapping portion (10C') starts is on the right. In this case, when wrapping, the second wrapping portion (10C') covers one side of the electrode laminate, and the ends of the first and second wrapping portions of the negative electrode structure can be shortened to be located on the same line.

[0074] According to an embodiment of the present invention, the number of stacking portions (10A, 10A', 10A'') in the electrode assembly (1) is the same as the number of positive electrodes. As described above, the total number of positive electrodes (20) located between the stacking portions is 2n (where n is a natural number), and the number of stacking portions (10A, 10A', 10A'') is one more than that, so it is 2n + 1 (where n is a natural number). Since the number of positive electrodes included in the electrode assembly (1) should consider the positive electrode located between the stacking portion (10A') and the wrapping portion (10C), the number of stacking portions and positive electrodes in the electrode assembly (1) becomes the same.

[0075] According to an embodiment of the present invention, the positive electrode (20) includes a positive electrode active material layer (not shown in the figure) and a current collector that supports the positive electrode active material (not shown in the figure). The positive electrode (20) has a structure in which the positive electrode active material layer is formed on at least one side (more specifically, on both sides) of the current collector. The positive electrode active material layer includes a positive electrode active material, and may also include a conductive material, a binder, and an additive. There is no particular limitation on the current collector, the positive electrode active material, the conductive material, the binder, or the additive, as long as it is commonly used in the art.

[0076] The positive electrode current collector supports the positive electrode active material and is not particularly limited to having high conductivity without causing any chemical changes in the battery. According to an embodiment of the present invention, the positive electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel whose surface is treated with carbon, nickel or silver, or an aluminum-cadmium alloy.

[0077] The positive electrode current collector can form micro-irregularities on its surface to strengthen the adhesion with the positive electrode active material, and can be used in various forms, such as films, sheets, foils, grids, meshes, porous materials, foams, non-woven materials, etc.

[0078] As the positive electrode active material, a lithium-containing transition metal oxide can be used. According to an embodiment of the present invention, selected from LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1 and a + b + c = 1), LiNi 1-y Co y O2 (where 0 < y < 1), LiCo 1-y Mn y O2 (where 0 < y < 1), LiNi 1-y Mn y O2 (where 0 < y < 1), Li(Ni a Co b Mn c)O4 (where 0 < a < 2, 0 < b < 2, 0 < c < 2 and a + b + c = 2), LiMn 2-z Ni z O4 (where 0 < z < 2), LiMn 2- z Co z O4 (where 0 < z < 2), any one or a mixture of two or more selected from the group consisting of LiCoPO4 and LiFePO4. In addition to these oxides, sulfides, selenides or halides can be used.

[0079] The positive electrode active material may include a sulfur compound. According to an embodiment of the present invention, the sulfur compound may be selected from elemental sulfur (S8), an organic sulfur compound Li2S n (where n ≥ 1) and a carbon-sulfur polymer ((C2S x ) n , where x is from 2.5 to 50, and n ≥ 1). Preferably, inorganic sulfur (S8) can be used.

[0080] When the positive electrode active material includes a sulfur compound, the electrode assembly (1) according to an embodiment of the present invention can be applied to a lithium-sulfur battery. Since sulfur itself contained in the positive electrode active material is not conductive, it can be used in combination with a conductive material such as a carbon material. Therefore, sulfur is included in the form of a sulfur-carbon composite material, and preferably, the positive electrode active material may be a sulfur-carbon composite material.

[0081] In view of the foregoing, compared with the negative electrode, the positive electrode (20) is relatively less likely to be folded and more likely to be cut. Therefore, the positive electrode (20) can be cut into a suitable size so that a plurality of positive electrodes are applied inside the electrode assembly (1).

[0082] According to an embodiment of the present invention, the negative electrode (11) does not include a current collector supporting a lithium metal layer. Since the negative electrode (11) does not include a current collector, the loading amount of the negative electrode active material in the electrode assembly can be improved, which can contribute to improving the performance of the battery. When the negative electrode (11) is mainly composed of lithium metal, since lithium metal is highly malleable and viscous, it is not easy to process, such as cutting, but in the electrode assembly (1) according to an embodiment of the present invention, the processability can be improved by minimizing cutting while applying the negative electrode in the form of the negative electrode structure (10). The lithium metal layer according to an embodiment of the present invention may be a self-supporting lithium metal layer, which can maintain its shape at a certain level by itself.

[0083] The separator (12) covering both sides of the negative electrode (11) in the negative electrode structure (10) is not particularly limited in type as long as no binder is included on its surface. The separator (12) may be a non-woven or polyolefin-based porous material made of, for example, glass fiber or polyethylene terephthalate fiber having a high melting point, but is not limited thereto.

[0084] The material of the porous material is not particularly limited in the present invention, but any porous material conventionally used in electrochemical devices can be used. According to one embodiment of the present invention, the porous material may include at least one selected from the group consisting of polyolefins such as polyethylene or polypropylene, polyesters such as polyethylene terephthalate or polybutylene terephthalate, polyamides, polyacetals, polycarbonates, polyimides, polyetheretherketones, polyethersulfones, polyphenylene oxides, polyphenylene sulfides, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, cellulose, nylon, poly(p-phenylene benzobisoxazole) and polyarylates.

[0085] According to one embodiment of the present invention, the negative electrode (11) and the first and second separators (12) in the negative electrode structure (10) are of the same length. With reference to the end of the negative electrode structure (10) where the second wrapping portion is located, the separator located outside the electrode assembly (1) can be named as the first separator, and the separator located inside the electrode assembly (1) can be named as the second separator. The negative electrode (11) and the separator (12) are provided to the electrode assembly (1) in the form of a negative electrode structure (10), the negative electrode structure (10) having the negative electrode (11) between the first and second separators (12), wherein the negative electrode and the separator are cut at one time so that the negative electrode (11) and the first and second separators (12) in the negative electrode structure (10) are substantially the same length, as Figure 1As shown. However, depending on the method of cutting the negative electrode structure (10), there may be a slight difference in the length of the negative electrode (11) and the first and second separator films (12), and in some cases, the ends of the first and second separator films (12) may be bent toward the center of the negative electrode structure (10). According to one embodiment of the present invention, the first and second separator films are folded at the ends of the negative electrode structure (10). Although the negative electrode structure (10) has substantially the same length of the negative electrode (11) and the first and second separator films (12) during the supply process, when applied to the electrode assembly (1), the length of the lithium metal may be extended due to the ductility of the lithium metal during the folding process. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the winding portion (10C) side, the lithium metal protrudes longer than the first or second separator film. In addition, depending on the number of folds, the separator film located on the more outer side of the folded portion (10B) than the inner side may be shorter. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the first or second wrapping portion (10C, 10C') side, the first separator protrudes more than the second separator. According to one embodiment of the present invention, at the end of the negative electrode structure (10) on the first or second wrapping portion (10C, 10C') side, the second separator protrudes more than the first separator.

[0086] 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 the stacking portion (10A"), at which the first wrapping portion (10C) turns to wrap on one side of the adjacent electrode assembly and abuts against the second wrapping portion (10C'), and the end of the second wrapping portion (10C') is located on the wrapping portion (10C). The ends of the first and second wrapping portions (10C, 10C') can be attached to the stacking 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) in the above-mentioned broad sense because it is also on the stacking portion (10A") . The attachment device and method 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 stacking portion (10A"). According to one embodiment of the present invention, the electrode assembly (1) further includes a fixing member for fixing an end of the first or second wrapping portion (10C, 10C') to the outermost stacking portion. By wrapping the first wrapping portion (10C) again with the second wrapping portion (10C'), the electrode assembly (1) has a more stable structure. In order to better understand where to attach the end of the first or second wrapping portion (10C, 10C') in the negative electrode structure (10), Figure 3An exemplary structure of an electrode assembly is provided, in which the end of the wrapping portion is attached by a fixing member in the negative electrode structure. Since the negative electrode (11) and the separator (12) in the negative electrode structure (10) are not in contact, as Figure 3 As shown, it is desirable to attach a tape (T) as a fixing member to wrap around the outer surface of the electrode structure (1). According to one embodiment of the present invention, the tape (T) has insulating properties and covers the entire end of the first or second wrapping portion (10C, 10C') in the width direction, while taking into account the situation in which the lithium metal extends and protrudes due to the ductility of the lithium metal during the process of folding the negative electrode structure (10) when manufacturing the electrode assembly (1). Through this tape connection method, the electrode assembly (1) is covered with a separator or tape from top to bottom and from left to right. The first wrapping portion (10C) and the second wrapping portion (10C') can be attached separately. According to one embodiment of the present invention, the electrode assembly includes a first fixing member fixing the first wrapping portion (10C) and a second fixing member fixing the second wrapping portion (10C').

[0087] When manufacturing an electrode assembly (1), when the stacking parts (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are alternately stacked, the negative electrode structure (10) is folded according to the same standard, and therefore, the folded parts (10B) also have substantially the same length. The negative electrode structure (10) utilizes a mandrel of a specific form to apply the same standard when folding. If the folded part (10B) has a shorter length, an unnecessary load is applied to the lithium metal located at the center of the negative electrode structure (10), resulting in defects such as fracture of the lithium metal. Therefore, ensuring a sufficient length of the folded part (10B) greater than a certain level enables the lithium metal to be flexibly placed in the gap between the stacked portion of the electrode and the wrapping part.

[0088] To better understand the length of the folded portion 10B in the negative electrode structure 10, Figure 4 An enlarged view of a portion of a folded portion 10B in an electrode assembly 1 is provided. According to one embodiment of the present invention, the length of the folded portion (10B) in the negative electrode structure (10) is 2-10 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 curve, since the lengths of the inner and outer sides may be different from each other, the length of the center portion is measured. For example, the length of the folded portion (10B) may be obtained by cutting the inner and outer sides of the folded portion. Figure 4The portion indicated by the dotted line in the figure is then unfolded to measure the length. Specifically, the length of the folded portion (10B) may be 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more, 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, 2 to 10 times, 3 to 9 times, or 4 to 8 times the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10). When the length of the folded portion (10B) is adjusted within this range, defects of the folded portion in the electrode assembly can be reduced, and the electrode assembly can be stably wrapped.

[0089] The length of the folded portion (10B) indicates how well it is formed. Figure 4 Longer than shown Figure 2 The folded portion (10B) is folded into a semicircle as shown. Specifically, when the folded portion (10B) has the form of a complete semicircle with an eccentricity of 0, the length of the folded portion becomes the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10) (which is the diameter) multiplied by π and divided by 2. This is approximately 1.57 times the sum of the thicknesses of the positive electrode (20) and the negative electrode structure (10). Based on this, it can be seen that the length of the folded portion (10B) according to one embodiment of the present invention is significantly longer.

[0090] When manufacturing an electrode assembly (1), after the stacking parts (10A, 10A', 10A'') of the negative electrode structure (10) and the positive electrode (20) are stacked in an alternating manner and the electrode laminate (1) is wrapped by the wrapping parts (10C, 10C'), the folding part (10B) is subjected to a certain level of pressure in the inner direction of the electrode assembly (1). Therefore, the folding part (10B) can be appropriately placed in the gap between the stacked part of the electrode and the wrapping part. Since the folding part (10B) appropriately placed in the gap includes a lithium metal layer (11) therein, it can contribute to further battery performance improvement by electrochemical reaction with the positive electrode (20) on its side. When the folding part (10B) appropriately fills the gap, two or more lithium metal layers can also be located on the side of the positive electrode not wrapped by the folding part (10B). When the electrode laminate (1) is wrapped by the wrapping portion (10C, 10C') so that the wrapping portion (10C) has tension above a certain level, it helps to maintain the structure of the electrode laminate in the electrode assembly (1) without distortion.

[0091] According to one embodiment of the present invention, the folded portion (10B) has an asymmetric shape relative to a plane along the longitudinal direction. When the folded portion (10B) is squeezed by the wrapping portion (10C, 10C') in the longitudinal direction, such an asymmetric shape is formed so that the folded portion (10B) is properly positioned in the gap. According to one embodiment of the present invention, the center point of the length of the folded portion (10B) is not aligned with the center point of the thickness of the positive electrode wrapped by the folded portion (10B). The center point of the length of the folded portion (10B) can be oriented in the wrapping direction relative to the center point of the thickness of the positive electrode. For example, referring to Figure 2 , a fold located on the right side of the electrode laminate may have a center point of the length of the fold below a center point of the thickness of the positive electrode because wrapping proceeds from top to bottom. In contrast, a fold on the left side of the electrode laminate may have a center point of the length of the fold above a center point of the thickness of the positive electrode because wrapping proceeds from bottom to top.

[0092] In order to better understand the vertical distance between the end of the positive electrode (20) and the transverse wrapping portion (10C, 10C') (which is the basis for comparing the length of the folded portion (10B) below), Figure 5 An enlarged view of a portion of an electrode assembly (1) is provided, in which an end of a positive electrode (20) and a transverse wrapping portion (10C, 10C') are located. A vertical distance (d) between the end of the positive electrode (20) and the transverse wrapping portion (10C, 10C') is the distance between the end of the positive electrode (20) and the transverse wrapping portion (10C, 10C') adjacent to the folding portion (10B). When one wrapping portion (10C) overlaps another wrapping portion (10C'), the wrapping portion on which the distance is based is the wrapping portion (10C) located inside. As Figure 5 As shown, during the process of wrapping the electrode assembly, the folded portion (10B) may be deformed by pressure applied from the wrapping portion (10C, 10C') positioned laterally. However, Figure 5 This is only an exemplary structure, and the folded portion (10B) does not necessarily have to be deformed to this shape. Due to pressure, the distance (d) between the end of the positive electrode (20) and the lateral wrapping portion (10C, 10C') can be shortened, and as the distance (d) is shortened, the folded portion (10B) can be naturally placed in the shortened space. According to one embodiment of the present invention, the length of the folded portion (10B) in the electrode assembly (1) is 2 to 10 times the vertical distance (d) between the end of the positive electrode (20) and the lateral wrapping portion (10C, 10C'). The lateral wrapping portion (10C, 10C') refers to Figure 2 or Figure 3A straight wrapping portion (10C) located on the left side of the electrode assembly, or another straight wrapping portion (10C') located on the right side of the electrode assembly. If the corresponding portion in the actual electrode assembly is not straight, the vertical distance (d) is measured as the vertical distance from the transverse wrapping portion to the end of the positive electrode at the center of the positive electrode in the thickness direction. Alternatively, the vertical distance (d) can be measured as the average of the vertical distances from the end of the positive electrode (20) to the portion of the wrapping portion (10C, 10C') adjacent to the folding portion (10B) on one side. Specifically, the length of the folding portion (10B) can be 2 times or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more, 10 times or less, 9.5 times or less, 9 times or less, 8.5 times or less, 8 times or less, 2 times to 10 times, 3 times to 9 times, or 4 times to 8 times the vertical distance (d) between the end of the positive electrode (20) and the transverse wrapping portion (10C). This means that the length of the folded portion (10B) is significantly longer as described above, but the vertical distance (d) is also shorter, so that the folded portion is compactly packed in the lateral space of the electrode laminate. When the length of the folded portion (10B) is adjusted within this range, the folded portion can be compactly filled into the gap in the electrode assembly to an appropriate extent without applying excessive pressure on the folded portion due to winding the electrode assembly, thereby helping to improve the performance of the battery.

[0093] Since the electrode assembly (1) according to one embodiment of the present invention forms the basic structure of the electrode assembly (1) by folding one negative electrode structure (10), the negative electrode structure (10) should not be too thick so that it can be folded flexibly, and considering the performance of the battery, a certain level of lithium metal (negative electrode active material) should be ensured in the negative electrode structure (10). According to one embodiment of the present invention, based on the total thickness of the negative electrode structure (10), the thickness of the lithium metal in the negative electrode structure (10) accounts for 50% to 90%. Specifically, the thickness of the lithium metal may be 50% to 90%, specifically 55% to 85%, and more specifically 60% to 80%. When the lithium metal meets 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 (10) does not include a separate current collector, the thickness of the remaining portion excluding the lithium metal may refer to the thickness of two separators.

[0094] According to one embodiment of the present invention, the thickness of the lithium metal may 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 may be appropriately adjusted according to the actual size of the battery.

[0095] In an electrode assembly (1) according to an embodiment of the present invention, unlike the negative electrode structure (10), the positive electrode is cut in consideration of characteristics such as materials and applied between stacked portions (10A, 10A', 10A'') of the negative electrode structure (10). Although the positive electrode is different from and independent of the negative electrode, the thickness may be adjusted relative to the negative electrode or the negative electrode structure in consideration of the performance of the electrode, for example, in terms of including a current collector in addition to the positive electrode active material. According to an embodiment of the present invention, the thickness of the positive electrode (20) is greater than the thickness of the negative electrode structure (10). According to an embodiment of the present invention, the thickness of the positive electrode (20) has a thickness greater than 100% and less than 400% relative to the thickness of the negative electrode structure (10). Specifically, the thickness of the positive electrode (20) may range from greater than 100% to less than 400%, specifically from 150% to 350%, and more specifically from 200% to 300%. When the positive electrode satisfies the above thickness range, it may be appropriately matched with the negative electrode structure.

[0096] Hereinafter, a detailed description of a process for manufacturing an electrode assembly is provided. To facilitate understanding of the manufacturing process of the electrode assembly, FIG. 6 schematically illustrates processes and states in the manufacturing process of the electrode assembly.

[0097] A manufacturing process for an electrode assembly according to one embodiment of the present invention includes the following steps: (1) folding a negative electrode structure to form an electrode laminate in which positive and negative electrode structures are alternately stacked; (2) surrounding the electrode laminate with an excess of the negative electrode structure after manufacturing the electrode laminate; and (3) positioning an end of a first wrapping portion of the negative electrode structure to the top of the electrode laminate, and positioning and fixing an end of a second wrapping portion on the first wrapping portion.

[0098] pass Figure 6a The process shown is an exemplary manufacturing step (1). Figure 6a As shown, the positive and negative electrode structures can be stacked sequentially, with the positive electrode at the bottom and the negative electrode structure on top. Figure 6a It is not shown in the figure, but a device such as a mandrel can be used to fold the negative electrode structure so that the fold at each location is made according to the same standard. The stacking does not start from the end of the negative electrode structure, but from the stacking portion that is in contact with the first wrapping portion, where the first wrapping portion remains enough to cover one side of the electrode laminate. Figure 6b or Figure 6cThe process shown exemplarily manufactures step (2). In addition, the second wrapping portion is positioned to be wrapped on the top or bottom of the electrode laminate and adjacent to the first wrapping portion. The additional negative electrode structure exists as the first and second wrapping portions at both ends, and the first and second wrapping portions each wrap the sides of the adjacent electrode laminate. During the process of wrapping with the additional negative electrode structure, wrapping the negative electrode structure so that the negative electrode structure is under a certain level of tension helps to pack the folded portion compactly within the gap and helps the structure of the electrode laminate maintain its shape without distortion. After step (3), the completed electrode assembly is in a state as shown in FIG. Figure 6d or Figure 6e The wrapping has the effect of preventing the positive electrode from flowing downward between the stacked parts, and considering this function, it is desirable to position the end of the negative electrode structure at the top of the electrode laminate. By fixing the negative electrode structure, the tension applied to the negative electrode structure during the wrapping process can be maintained, and as Figure 6e Wrapping with tape (T) as shown may be an exemplary method.

[0099] The specific characteristics of the positive and negative electrode structures not specifically described in the manufacturing process are consistent with the foregoing. The electrode assembly according to one embodiment of the present invention can weld multiple layers of tabs and leads, such as in a conventional large-capacity cell, to maintain performance such as cell resistance and output.

[0100] The electrode assembly according to one embodiment of the present invention is applied to an electrochemical device. The electrochemical device may include any device that performs an electrochemical reaction. For example, the electrochemical device may be any kind of primary battery, secondary battery, fuel cell, solar cell or capacitor. If the electrochemical device is a secondary battery, the electrochemical device may be a lithium secondary battery, which may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

[0101] As described above, although the embodiments have been described through limited examples and drawings, a person of ordinary skill in the art may make various modifications and changes in view of the above description. For example, even if the provided techniques can be performed in a different order than the above method, and / or the provided components (such as systems, structures, devices, circuits, etc.) can be combined in a different form than the above method, or replaced or substituted by other components or equivalents, the desired results can be achieved.

[0102] Hereinafter, examples are presented to facilitate understanding of the present invention. The following examples are used to illustrate the present invention, but the present invention is not limited thereto.

[0103] Example

[0104] Example 1: Fabrication of an electrode assembly wrapped with a negative electrode structure

[0105] The negative electrode structure was prepared by inserting 60μm lithium metal between two polyethylene (PE) separators (11μm). In addition, a positive electrode compound consisting of 85wt% of a positive electrode active material prepared by mixing sulfur and carbon nanotubes (CNTs) in a weight ratio of 7:3, 5wt% of carbon nanofibers as a conductive material, and 10wt% of a binder was added to deionized water to prepare a positive electrode slurry, and then an aluminum current collector was coated with the positive electrode slurry to produce a 200μm positive electrode.

[0106] by Figure 6a The negative electrode structure is folded in the manner shown to produce an electrode laminate, and then Figure 6b or Figure 6c The electrode laminate is wrapped with an excess negative electrode structure in the manner shown to form a Figure 6d The exposed end of the negative electrode structure in the electrode assembly is fixed with insulating tape, such as Figure 6e In the electrode assembly, the length of the folded portion was measured to be 1453 μm, and the vertical distance between the end of the positive electrode and the transverse wrapping portion was measured to be 268 μm.

[0107] Comparative Example 1: Fabrication of an electrode assembly in which the negative electrode structure is cut and laminated

[0108] The negative electrode structure is cut to fit the positive electrode of each layer, and then the positive and negative electrode structures are laminated to form an electrode laminate, and the electrode assembly is completed without any separate wrapping of the negative electrode structure. In the electrode assembly, the materials and thicknesses of the positive and negative electrode structures are the same as those of Example 1.

[0109] Experimental Example

[0110] Each electrode assembly prepared according to Example 1 and Comparative Example 1 was placed in the same bag, and the ether-based electrolyte was charged with 0.4 M LiFSI salt and 4 wt % LiNO3 to prepare a lithium secondary battery. The coulombic efficiency of the prepared lithium secondary battery was measured by charging and discharging it at 0.3°C, and the results are shown in Figure 7 middle.

[0111] The electrode assembly according to the present invention has advantages over conventional electrode assemblies not only in terms of process, but also in terms of Figure 7 , it can be seen that the long-term performance of the battery, such as Coulombic efficiency, can also be improved.

[0112] All simple variations or modifications of the invention are within the scope of the invention, and the specific scope of protection sought will be apparent from the appended claims.

[0113] [reference numerals]

[0114] 1, 1', 1'': electrode assembly

[0115] 10: Negative electrode structure

[0116] 10A, 10A', 10A'': stacking part (10A', 10A'': outermost stacking part)

[0117] 10B: Folding part

[0118] 10C, 10C': Wrapping portion (first and second wrapping portions)

[0119] 11: Negative electrode (lithium metal layer)

[0120] 12: Separation film (first and second separation films)

[0121] 20: Positive electrode

[0122] T: Fixing member (tape)

[0123] d: The vertical distance between the end of the positive electrode and the lateral wrapping part

Claims

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

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

3. The electrode assembly according to claim 1, wherein: The second wrapping portion of the negative electrode structure surrounds the first wrapping portion surrounding one side of the electrode laminate together with the opposite side of the electrode laminate.

4. The electrode assembly according to claim 1, wherein: 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, wherein: At least one positive electrode is located between a stack portion adjacent to the first wrap portion of the negative electrode structure and the second wrap portion located parallel to the stack portion.

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

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

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

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

10. The electrode assembly according to claim 1, wherein: The electrode assembly further includes a fixing member for fixing ends of the first wrapping portion and the second wrapping portion to the outermost stacking portion, respectively.

11. The electrode assembly according to claim 1, wherein: The length of the folded portion in the negative electrode structure is 2 to 10 times the sum of the thicknesses of the positive electrode and the negative electrode structure.

12. The electrode assembly according to claim 1, wherein: In the negative electrode structure, the length of the folded portion is 2 to 10 times the vertical distance between the end of the positive electrode and a lateral wrapping portion surrounding the positive electrode.

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

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

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

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

17. The electrode assembly according to claim 1, wherein: A center point of the length of the folded portion is not aligned with a center point of the thickness of the positive electrode surrounded by the folded portion.

18. The electrode assembly according to claim 5, wherein: The positive electrode positioned between the stacked portion abutting against the first package portion and the second package portion adjacent to the stacked portion in the thickness direction is longer than the other positive electrodes.

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

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

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

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

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

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

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