Electrode assembly and electrochemical device including the same

Abstract

An electrode assembly is provided that includes a positive electrode, a negative electrode, and a separator. In the electrode assembly, the negative electrode includes lithium metal and is sandwiched between two notched separators to form a negative electrode structure. The negative electrode structure has a structure in which negative electrode structures and positive electrodes are alternately stacked. In the negative electrode structure, the negative electrode is exposed to the outside through a notched region of the separator. The electrode assembly according to one embodiment of the present invention not only improves processability but also has a stable structure, thereby improving battery performance, because the tab can be formed without cutting or welding the negative electrode.

Description

[Technical Field]

[0001] The present invention relates to an electrode assembly and an electrochemical device including the same, more particularly to an electrode assembly including a negative electrode sandwiched between two notched separators, and an electrochemical device including the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0068571, filed May 26, 2023, and incorporates all of the contents disclosed in the documents of that Korean patent application as part of this specification. [Background technology]

[0003] Recently, interest in energy storage technology has been growing. As its application fields expand to include mobile phones, video cameras, laptops, and even electric vehicles, efforts in battery research and development are becoming more and more concrete. Electrochemical devices are the field that has attracted the most attention in this regard. In particular, with the recent trend toward smaller and lighter electronic devices, the development of rechargeable batteries, which are small, lightweight, and have high capacity, is gaining attention.

[0004] Secondary batteries can also be classified according to the structure of their electrode assembly, which has a positive electrode / separator / negative electrode structure. Typical examples include jelly-roll (wound) electrode assemblies, in which long sheet-shaped positive and negative electrodes are wound with a separator between them, and stacked (layered) electrode assemblies, in which multiple positive and negative electrodes cut to a specified size are stacked in order with a separator between them.

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

[0006] First, the jelly-roll electrode assembly is fabricated by closely winding long, sheet-like positive and negative electrodes to form a cylindrical or elliptical cross-section. In this structure, stress induced by the expansion and contraction of the electrodes during charge and discharge accumulates within the electrode assembly. When this stress accumulation exceeds a certain limit, the electrode assembly deforms. Furthermore, the electrode assembly deformation can lead to uneven spacing between the electrodes, rapidly degrading battery performance and threatening battery safety due to internal short circuits. Furthermore, because the jelly-roll electrode assembly requires winding long, sheet-like positive and negative electrodes, it is difficult to quickly wind the electrode assembly while maintaining a consistent spacing between the positive and negative electrodes, resulting in reduced productivity.

[0007] Second, the stacked electrode assembly requires sequential stacking of a number of positive and negative electrode units, which requires a separate electrode plate transfer process for manufacturing the units and requires a lot of time and effort for the sequential stacking process, resulting in low productivity.

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

[0009] In the stack-folded electrode assembly, the electrodes of each layer are connected by extending a separator, which is generally easier to fold than the electrodes. In this case, the electrodes of each layer are supplied in a cut state, similar to the stack-type electrode assembly, to form the electrode assembly. This general stack-folded electrode assembly is more suitable when a secondary battery is constructed using only materials that are easy to cut or difficult to fold, among the various electrode materials constituting secondary batteries in the art. Meanwhile, lithium metal, which is well known in the art as a negative electrode material for secondary batteries, has physical properties such as high ductility and viscosity, making it difficult to process, such as cutting, but relatively easy to fold, and therefore may not be suitable for a conventional stack-folded electrode assembly.

[0010] After continuous research into the structure of electrode assemblies, the inventors have designed a structure suitable for forming a negative electrode tab in a new stack-folded electrode assembly that utilizes a negative electrode structure in which a negative electrode containing lithium metal is sandwiched between two separators, thereby completing the present invention. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent No. 2023530 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention aims to provide an electrode assembly having a structure suitable for forming a negative electrode tab in a stack-folded electrode assembly having a new structure utilizing a negative electrode structure in which a negative electrode containing lithium metal is sandwiched between two separators, and an electrochemical device including the electrode assembly. [Means for solving the problem]

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

[0014] In one embodiment of the present invention, the negative electrode comprises lithium metal and is sandwiched between two notched separators to form a negative electrode structure.

[0015] In one embodiment of the present invention, the electrode assembly comprises a structure in which negative electrode structures and positive electrodes are alternately stacked.

[0016] In one embodiment of the present invention, the negative electrode in the negative electrode structure is exposed to the outside through a notched region of the separator.

[0017] In one embodiment of the present invention, the notched region is present in each layer of the negative electrode structure in a structure in which negative electrode structures and positive electrodes are alternately stacked, and the notched regions of each layer are positioned side by side in the height direction of the electrode assembly.

[0018] In one embodiment of the present invention, the positive electrode includes a positive electrode tab that protrudes beyond the negative electrode structure.

[0019] In one embodiment of the invention, the notched area has a rectangular shape.

[0020] In one embodiment of the present invention, the length of the notched region is 1.5 times or more based on the length of the positive electrode tab.

[0021] In one embodiment of the present invention, the notched region is located at only one of both ends in the width direction of the negative electrode structure.

[0022] In one embodiment of the present invention, the positive electrode tab is located in the same direction as the notching area in the width direction of the electrode assembly, and the positive electrode tab does not overlap with the notching area in the height direction of the electrode assembly.

[0023] In one embodiment of the present invention, the positive electrode tab is located opposite to the notching area in the width direction of the electrode assembly, and the positive electrode tab is located next to the notching area in the width direction of the electrode assembly.

[0024] In one embodiment of the present invention, the electrode assembly includes one negative electrode structure and multiple positive electrodes.

[0025] In one embodiment of the present invention, the negative electrode structure includes a plurality of stack portions and a plurality of folded portions.

[0026] In one embodiment of the present invention, the stacked portions and folded portions are arranged alternately in the negative electrode structure.

[0027] In one embodiment of the present invention, the electrode assembly includes a structure in which stack portions of negative electrode structures and positive electrodes are alternately stacked in order.

[0028] In one embodiment of the invention, the notched region extends in the length direction of the negative electrode structure, continuing from one stack section to the adjacent other stack section.

[0029] In one embodiment of the present invention, the length of the notched region in the stack portion of the negative electrode structure is 70% or less of the length of the stack portion.

[0030] According to a second aspect of the present invention, The present invention provides an electrochemical device comprising the electrode assembly described above.

[0031] In one embodiment of the present invention, the electrochemical device is a lithium secondary battery. [Effects of the Invention]

[0032] According to one embodiment of the present invention, an electrode assembly is manufactured using a negative electrode structure in which a negative electrode containing lithium metal is interposed between two notched separators, thereby minimizing breakage of the lithium metal and improving process efficiency in manufacturing the electrode assembly.

[0033] Furthermore, this structure not only ensures that the manufactured electrode assembly has a stable structure, but also improves the performance of the battery by forming the negative electrode tab without additional cutting or welding of the lithium metal. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a plan view schematically illustrating a notched separator according to an embodiment of the present invention. [Figure 2] 2A is a perspective view schematically illustrating a negative electrode structure according to an embodiment of the present invention, in which each layer of the negative electrode structure according to the embodiment of the present invention is separated. [Figure 2b] 2A and 2B are schematic diagrams illustrating an anode structure according to an embodiment of the present invention, and Fig. 2A is a plan view schematically illustrating an anode structure according to an embodiment of the present invention. [Figure 2c] 2A and 2B are schematic diagrams illustrating an anode structure according to an embodiment of the present invention;FIG. 2C is a schematic front view of an anode structure according to an embodiment of the present invention;FIG. [Figure 3a] 3a to 6a are plan views showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention, with the folded portion of the negative electrode structure unfolded, and the position of a positive electrode on the negative electrode structure in an electrode assembly according to an embodiment of the present invention. 3b to 6b are front views showing the same arrangement as in FIGS. 3a to 6a. [Figure 3b] 3b to 6b are schematic front views of an electrode assembly having the same arrangement as in FIGS. 3a to 6a, each of which is a schematic diagram showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention. [Figure 4a] 3a to 6a are plan views showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention, in which the folded portion of the negative electrode structure is unfolded, and the position of a positive electrode on the negative electrode structure. [Figure 4b] 3b to 6b are schematic front views of an electrode assembly having the same arrangement as in FIGS. 3a to 6a, each of which is a schematic diagram showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention. [Figure 5a] 3a to 6a are plan views showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention, in which the folded portion of the negative electrode structure is unfolded, and the position of a positive electrode on the negative electrode structure. [Figure 5b] 3b to 6b are schematic front views of an electrode assembly having the same arrangement as in FIGS. 3a to 6a, each of which is a schematic diagram showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention. [Figure 6a] 3a to 6a are plan views showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention, in which the folded portion of the negative electrode structure is unfolded, and the position of a positive electrode on the negative electrode structure. [Figure 6b] 3b to 6b are schematic front views of an electrode assembly having the same arrangement as in FIGS. 3a to 6a, each of which is a schematic diagram showing the positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, embodiments will be described in detail with reference to exemplary drawings. When assigning reference numerals to components in each drawing, it should be noted that identical components are assigned the same numerals as much as possible even if they are shown in different drawings. Furthermore, when describing embodiments, if a detailed description of related known structures or functions is deemed to hinder understanding of the embodiments, the detailed description will be omitted.

[0036] Furthermore, when describing components of an embodiment, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are merely used to distinguish the component from other components, and do not limit the nature, order, or sequence of the components. When a component is described as being "coupled," "coupled," or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but that other components may also be "coupled," "coupled," or "connected" between each component.

[0037] Components included in one embodiment and components having common functions will be described using the same names in other embodiments. Unless otherwise specified, the description of one embodiment may also be applied to other embodiments, and detailed descriptions will be omitted to the extent that they overlap.

[0038] As used herein, the term "length direction" refers to the left-right direction in plan views such as Figures 1, 2b, 3a, 4a, 5a, and 6a and in front views such as Figures 2c, 3b, 4b, 5b, and 6b. As used herein, the term "width direction" refers to the up-down direction in plan views such as Figures 1, 2b, 3a, 4a, 5a, and 6a, and refers to the undifferentiated front-to-back direction in front views such as Figures 2c, 3b, 4b, 5b, and 6b. As used herein, the term "height direction" refers to the undifferentiated front-to-back direction in plan views such as Figures 1, 2b, 3a, 4a, 5a, and 6a, and refers to the undifferentiated front-to-back direction in front views such as Figures 2c, 3b, 4b, 5b, and 6b.

[0039] The present invention relates to an electrode assembly, and provides an electrode assembly having a structure suitable for forming a negative electrode tab in a stack-folded electrode assembly having a novel structure that utilizes a negative electrode structure in which a negative electrode containing lithium metal is sandwiched between two separators. The electrode assembly according to one embodiment of the present invention can minimize cutting of the lithium metal during the manufacturing process, improving process efficiency. Furthermore, when the electrode assembly is actually applied, the negative electrode tab is formed without additional cutting or welding of the lithium metal, reducing defects that may occur due to processing of the lithium metal. This results in a highly reliable and stable structure of the manufactured product, which can improve battery performance.

[0040] An electrode assembly according to one embodiment of the present invention includes a positive electrode, a negative electrode, and a separator. The positive electrode and the separator may be made of any material commonly used in the art, but the negative electrode may include lithium metal. In this specification, the term "lithium metal" may be broadly interpreted as meaning that the physical properties of the material are not significantly different from those of lithium metal, even if some components are added to lithium or the material is in the form of an alloy with some other metal, and the same problems may occur when the material is applied to a conventional electrode assembly, as with lithium metal.

[0041] According to one embodiment of the present invention, the negative electrode is sandwiched between two notched separators to form a negative electrode structure. Here, separator notching refers to a process of cutting out a portion of the separator to expose the negative electrode located inside the separator in the negative electrode structure and fabricate a negative electrode tab. The two notched separators have a substantially symmetrical structure. Therefore, the position and number of notches, the shape of the notched region, etc. will be described herein based on one separator. To facilitate understanding of the structure of the notched separator, FIG. 1 is a schematic plan view of a notched separator according to one embodiment of the present invention. The plan view shows the separator as viewed from above, and the separator according to one embodiment of the present invention has a longitudinally elongated structure.

[0042] In the drawings of this specification, such as Figure 1, the "notched portion" is indicated by "A," and the notched portion (A) refers to the three-dimensional shape removed by notching. Therefore, the position of the notched portion (A) can be confirmed in a front view, such as Figure 2c. On the other hand, in this specification, the "notched region" refers to the cross-sectional shape removed by notching, and has a length direction and a width direction, but not a height direction. Therefore, the shape of the notched region can be confirmed in a plan view, such as Figure 1, but not in a front view, such as Figure 2c.

[0043] In the manufactured electrode assembly, the position of the notch (A) on the separator (11) is not particularly limited as long as it can expose the negative electrode to the outside and function solely as a negative electrode tab. However, in an electrode assembly in which a positive electrode and a negative electrode structure are stacked, the negative electrode structure basically needs to protrude from the positive electrode to expose the negative electrode to the outside, and it may be preferable to form the notch (A) on such a protruding negative electrode structure. According to one embodiment of the present invention, the notch (A) is located at the end of the negative electrode structure in the width direction. Furthermore, the number of notches (A) on the separator (11) is also not particularly limited. However, in a stacked structure of a negative electrode structure and a positive electrode, it may be preferable to form one or more notches (A) on one layer of the negative electrode structure. FIG. 1 etc. shows an exemplary structure of a notched separator. The separator may be shortened in the length direction to form one or two notches (A) on one separator, or the separator may be extended in the length direction to form four or more notches (A) on one separator.

[0044] To facilitate understanding of the structure of a negative electrode structure having a negative electrode sandwiched between two notched separators, FIG. 2 provides a schematic diagram of a negative electrode structure according to one embodiment of the present invention. Specifically, FIG. 2a shows the shape of the negative electrode structure with each layer separated, while FIGS. 2b and 2c show the shape of the negative electrode structure at different positions. As shown in FIGS. 2a and 2c, the upper and lower separators 11 and 12 are substantially symmetrical with respect to the negative electrode 12, so that the negative electrode is exposed at both the top and bottom. In an electrode assembly according to one embodiment of the present invention, the positive electrode 20, negative electrode 12, and separator 11 are all exposed when viewed from the front, as shown in FIG. 3b, etc. Therefore, notching the separators to expose the negative electrode at both the top and bottom is technically significant in the present invention. The separator 11 completely separates the positive electrode 20 and the negative electrode 12 to prevent electrical shorts during battery operation. The width of the separator 11 may be the same as or longer than the width of the negative electrode. Therefore, as shown in Figure 2b, the negative electrode 12 is not exposed unless the separator 11 is notched. In this specification, the exposed portions of the negative electrode at the top and bottom are referred to as negative electrode tabs.

[0045] According to one embodiment of the present invention, the electrode assembly 1 has a structure in which anode structures 10 and cathodes 20 are alternately stacked. In this structure, the cathodes 20 located above and below the anode structures 10 also prevent the anode 12 from being exposed to the outside. Therefore, in order for the anode 12 in the electrode assembly 1 to be exposed to the outside, the anode structure 10 must protrude in the width or length direction beyond the cathode 20 in the stacked structure. Unless a notch A is formed in the protruding portion, the anode 12 cannot be exposed to the outside. According to one embodiment of the present invention, the anode 12 in the anode structure 10 is exposed to the outside through the notched region of the separator 11. The negative electrode (12) is exposed to the outside through the notched portion (A), but the thickness of the notched portion of the separator (11) is not particularly related to the exposure of the negative electrode (12), so it can be said that the negative electrode (12) is exposed to the outside through the notched region.

[0046] According to one embodiment of the present invention, the notch region is present in each layer of the negative electrode structure 10 in a structure in which the negative electrode structures 10 and the positive electrodes 20 are alternately stacked, and the notch regions of each layer are aligned in the height direction of the electrode assembly 1. As described above, in the negative electrode structure 10, the upper and lower separators have a substantially symmetrical structure, so the negative electrode 12 is exposed at the top and bottom by the notch regions of each layer. In addition, as shown in Figure 3b, etc., aligning the notch regions of each layer in the height direction of the electrode assembly 1 makes it easy to connect the negative electrode tabs of each layer together by welding, etc.

[0047] According to one embodiment of the present invention, the positive electrode 20 includes a positive electrode tab that protrudes beyond the negative electrode structure 10 in the lengthwise or widthwise direction. The positive electrode tab protrudes beyond the negative electrode structure 10 in the lengthwise or widthwise direction, and the positive electrode 20 of the electrode assembly 1 can be electrically connected through the protruding positive electrode tab. Because the positive electrode 20 uses a different material, the tab need not be formed in the same manner as the negative electrode tab according to one embodiment of the present invention, and any method commonly used in the art may be used. In this specification, the positive electrode tab is considered to be a component included in the positive electrode 20, and refers to the portion that protrudes beyond the separator 11 of the negative electrode structure 10 in the widthwise direction, as shown in FIG. 3a.

[0048] According to one embodiment of the present invention, the notching region has a rectangular shape. The notching region can be manufactured in various shapes, but a rectangular shape such as that shown in FIG. 3a is common. According to one embodiment of the present invention, the length of the notching region is 1.5 times or more the length of the positive electrode tab. If the notching region is rectangular, the lengths of the notching region and the positive electrode tab may be the same at all positions. If not, the length is determined by the average value of the lengths at all positions. Specifically, the length of the notching region may be 1.5 times or more, 1.6 times or more, 1.7 times or more, 1.8 times or more, 1.9 times or more, or 2.0 times or more the length of the positive electrode tab. In one embodiment of the present invention, the negative electrode tab is manufactured by notching a separator, and therefore does not have a typical protruding shape like the positive electrode tab. The negative electrode tab can be joined to a negative electrode tab formed on another layer by welding, etc. In this case, if the notch region is long enough to secure the negative electrode tab, it may be easy to join the negative electrode tab without bonding, utilizing the ductility of lithium metal that is not fixed by a separator. Since the notch region is formed in a portion that does not overlap with the positive electrode tab, the length of the notch region may be limited. Unlike the length of the notch region, the width of the notch region is directly related to the area in which the positive electrode can be applied in the electrode assembly, so it is appropriately adjusted in consideration of battery performance. It may be preferable to minimize the width of the notch region so long as it can only function as a negative electrode tab.

[0049] According to one embodiment of the present invention, the notch region is located at only one of the widthwise ends of the negative electrode structure 10. Because the negative electrode structure 10 can be extended in the lengthwise direction, it may be advantageous in terms of processing to locate the notch region at one of the widthwise ends. There is no significant difference in functionality between having the notch region located at one of the widthwise ends and having it located at both ends. In fact, locating the notch region at one of the widthwise ends may be preferable in terms of simplifying processing. For the same reason, the positive electrode tab may also be located at one of the widthwise ends. In this case, the notch region and the positive electrode tab may be located in the same direction or in different directions.

[0050] 3 to 6 illustrate an exemplary electrode assembly in which a negative electrode structure (10) and a positive electrode (20) are arranged according to one embodiment of the present invention. In FIGS. 3 and 4, the notching area and the positive electrode tab are positioned in opposite directions. When the notching area and the positive electrode tab are positioned in opposite directions, the notching area and the positive electrode tab do not overlap each other, which is advantageous in that they can be positioned freely, and both the notching area and the positive electrode tab can be positioned at the center in the longitudinal direction. In FIGS. 5 and 6, the notching area and the positive electrode tab are positioned in the same direction. When the notching area and the positive electrode tab are positioned in the same direction, there is a structural advantage in that the negative electrode tab and the positive electrode tab can be positioned to one side.

[0051] According to one embodiment of the present invention, the electrode assembly 1 includes one negative electrode structure 10 and multiple positive electrodes 20. The negative electrode structures 10 can be cut into the same number as the positive electrodes 20 and applied to the electrode assembly 1, but this increases the number of times the negative electrode containing lithium metal needs to be cut, potentially reducing the effectiveness of the present invention. Therefore, in one embodiment of the present invention, the negative electrode structure 10 is extended lengthwise, and only one negative electrode structure 10 is applied to the electrode assembly 1. In order to create a stacked structure having multiple layers with one negative electrode structure 10, it may be important to properly fold the negative electrode structure 10.

[0052] According to one embodiment of the present invention, the negative electrode structure (10) includes a plurality of stack sections and a plurality of folded sections. In the negative electrode structure (10), the stack sections and folded sections are units that separate positions having different functions along the length of the negative electrode structure (10). The stack sections and folded sections are not distinguished by their positions but by their materials. To facilitate understanding of the positions of the stack sections and folded sections, FIG. 3b shows the positions of the stack section (10S) and folded section (10F) as an example. The stack section (10S) refers to the position of the negative electrode structure (10) where the positive electrode (20) is stacked, and has a primarily linear shape as shown in FIG. 3b. The length of the stack section (10S) is substantially the same as the length of the positive electrode. The folded section (10F) refers to the position of the negative electrode structure (10) that connects the stack sections (10S) and (10S), and has a primarily curved shape as shown in FIG. 3b. According to one embodiment of the present invention, the stack portions (10S) and the folded portions (10F) are alternately positioned in the negative electrode structure (10). In other words, the stack portions can be separated by the folded portions, and the folded portions can be separated by the stack portions.

[0053] According to one embodiment of the present invention, the electrode assembly (1) has a structure in which the stack portion (10S) of the anode structure (10) and the cathode (20) are alternately stacked. Because the electrode assembly (1) has a structure in which the stack portion (10S) of the anode structure (10) and the cathode (20) are alternately stacked, the anode structure (10) including the stack portion (10S) and the folded portion (10F) in this structure has a zigzag shape, as shown in FIG. 3a. In other words, the folded portions (10F) located sequentially from the stack portion (10S) of the anode structure (10), where stacking begins, are alternately located on the left or right side of the electrode assembly (1). If the stack portion (10S) of the anode structure (10) and the cathode (20) are not alternately stacked, and two or more of the stack portions or cathodes are stacked consecutively, no potential difference is generated between the consecutively stacked layers, which may result in reduced battery efficiency.

[0054] An electrode assembly according to one embodiment of the present invention may have an arrangement as shown in Figures 3a and 3b. In this arrangement, the positive electrode tab is disposed in the opposite direction from the notching area based on the width direction of the electrode assembly (1). As shown in Figure 3a, the positive electrode tab in this arrangement may be positioned side by side with the notching area in the width direction of the electrode assembly, and its position may be the center of the length direction of the stack unit (10S). The positive electrode (20) is positioned at a position spaced apart from the notching area in the width direction to some extent, so that the positive electrode (20) and the negative electrode (12) do not overlap. In this case, as shown in Figure 3b, the notching area (A) is positioned side by side with the center position of the stack unit in the height direction of the electrode assembly (1).

[0055] An electrode assembly according to one embodiment of the present invention may have an arrangement as shown in Figures 5a and 5b. In this arrangement, the positive electrode tabs are positioned in the same direction as the notching area in the width direction of the electrode assembly (1). As shown in Figure 3a, the positive electrode tabs in this arrangement are stacked at different positions in the length direction from the notching area. In an electrode assembly such as Figure 3b, the positive electrode tabs (not shown) may not overlap with the notching area (or notching portion (A)) in the height direction of the electrode assembly, but may overlap with each other, and notching areas may overlap with each other. In this case, if the notching area or positive electrode tab is positioned at the center of the stack portion, it may be difficult to efficiently utilize space.

[0056] According to one embodiment of the present invention, the notch region extends in the length direction of the negative electrode structure, continuing from one stack section to the adjacent stack section. For the notch region to extend from one stack section to the adjacent stack section, the stack sections are connected by a fold, and the notch region passes through the entire fold. In this regard, if the positive electrode tab is positioned opposite the notch region in the width direction of the electrode assembly 1, the exemplary electrode assembly 1 may have a structure as shown in FIGS. 4a and 4b. Since there is no positive electrode tab in the length direction of the negative electrode structure relative to the notch region, the extension direction of the notch region is not particularly limited and may extend to the left or right. If the positive electrode tab is positioned in the same direction as the notch region in the width direction of the electrode assembly 1, the exemplary electrode assembly 1 may have a structure as shown in FIGS. 6a and 6b. In this case, since the positive electrode tab exists in the longitudinal direction of the negative electrode structure based on the notching region, the extending direction of the notching region may be opposite to the direction in which the positive electrode tab exists.

[0057] According to one embodiment of the present invention, even if the notch regions extend from one stack section to the adjacent stack section, the multiple notch regions are aligned in the height direction of the electrode assembly 1. In the electrode assembly according to one embodiment of the present invention, the notch regions are aligned and the negative electrode tabs of each layer are joined together by welding or the like. In this case, if the notch extends to the folded section, the flexibility of the negative electrode tab to be joined increases, making it easier to join the negative electrode tab.

[0058] In terms of the flexibility of the negative electrode tab, it may be preferable to make the notched area as long as possible. However, a highly flexible negative electrode tab may cause defects during the manufacture of an electrode assembly. Therefore, it is preferable to appropriately adjust the notched area within a certain range. According to one embodiment of the present invention, the length of the notched area in the negative electrode structure is 70% or less of the length of the stack portion. This may mean 70% or less of the length of a single negative electrode structure when multiple cut negative electrode structures are used. Specifically, the length of the notched area may be 70% or less, 69% or less, 68% or less, 67% or less, 66% or less, 65% or less, 64% or less, 63% or less, 62% or less, 61% or less, or 60% or less of the length of the stack portion. By ensuring that the separator is not notched to a certain level, the electrode assembly may have a more stable structure.

[0059] According to one embodiment of the present invention, the negative electrode structure further includes a wrapping section (not shown) in addition to the stack section (10S) and the folding section (10F). By wrapping the stack section of the positive electrode and negative electrode structures once through the wrapping section, the electrode assembly can have a more stable structure. The wrapping section can have a mixed linear and curved shape.

[0060] According to one embodiment of the present invention, the positive electrode 20 includes a positive electrode active material layer and a current collector. The positive electrode 20 has a structure in which a positive electrode active material layer is formed on at least one surface, specifically both surfaces, of a current collector. The positive electrode active material layer includes a positive electrode active material and may further include a conductive material, a binder, an additive, and the like. The current collector, positive electrode active material, conductive material, binder, additive, and the like are not particularly limited as long as they are commonly used in the relevant technical field.

[0061] The positive electrode current collector is not particularly limited as long as it supports the positive electrode active material, does not cause chemical changes in the battery, and has high conductivity. According to one embodiment of the present invention, the positive electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, palladium, fired carbon, or a material obtained by surface treatment of copper or stainless steel with carbon, nickel, silver, etc., or an aluminum-cadmium alloy, etc.

[0062] 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 films, sheets, foils, meshes, nets, porous bodies, foams, non-woven bodies, etc. can be used.

[0063] As the positive electrode active material, a lithium-containing transition metal oxide can be used. According to one embodiment of the present invention, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(Ni[[ID=⑨]] z , , z , ,

[0064] , 2-z 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 s 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, or 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.

[0064] The positive electrode active material may include a sulfur compound. According to one embodiment of the present invention, the sulfur compound may be elemental sulfur (S8), an organic sulfur compound Li2S, or the like. n (n≧1) and carbon-sulfur polymers (C2S x ) n : x=2.5 to 50, n≧1). Preferably, inorganic sulfur (S8) may be used.

[0065] When the positive electrode active material includes a sulfur compound, the electrode assembly (1) according to an embodiment of the present invention can be used in a lithium-sulfur battery. Sulfur contained in the positive electrode active material does not have electrical conductivity by itself, so it can be used in a composite with a conductive material such as a carbon material. Therefore, the sulfur can be contained in the form of a sulfur-carbon composite, and preferably, the positive electrode active material can be a sulfur-carbon composite.

[0066] Considering the above, the positive electrode 20 is relatively difficult to fold and easy to cut compared to the negative electrode, so the positive electrode 20 is cut to an appropriate size and multiple positive electrodes are applied inside the electrode assembly 1.

[0067] According to one embodiment of the present invention, the anode 12 does not include a current collector. Because the anode 12 does not include a current collector, the loading amount of the anode active material within the electrode assembly can be increased, contributing to improved battery performance. When the anode 12 is primarily composed of lithium metal, the lithium metal can be difficult to process, such as by cutting, due to its high ductility and viscosity. However, in the electrode assembly 1 according to one embodiment of the present invention, the anode is applied in the form of anode structure 10, minimizing cutting and improving processability.

[0068] In the negative electrode structure 10, the separator 11 covering both sides of the negative electrode 12 is not particularly limited in type as long as it does not contain a binder on its surface. The separator 11 may be, for example, a nonwoven fabric or a polyolefin-based porous substrate made of high-melting-point glass fiber, polyethylene terephthalate fiber, or the like, but is not limited thereto. Because the separator 11 is much easier to process than the lithium metal negative electrode 12, the separator 11 is notched in the present invention to manufacture the negative electrode tab.

[0069] The material of the porous substrate is not particularly limited in the present invention, and any porous substrate generally used in electrochemical devices can be used. According to one embodiment of the present invention, the porous substrate is made of a material selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides, polyacetals, polycarbonates, polyimides, polyetheretherketones, polyethersulfones, polyphenylene oxides, polyphenylene sulfides, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, and the like. The material may include one or more materials selected from the group consisting of poly(p-phenylene benzobisoxazole), polyacrylonitrile, cellulose, nylon, poly(p-phenylene benzobisoxazole), and polyarylate.

[0070] According to one embodiment of the present invention, the separator 11 and the anode 12 in the anode structure 10 have the same length. The separator 11 and the anode 12 are supplied to the electrode assembly in the form of an anode structure 10 in which the anode 12 is sandwiched between two notched separators 11. Since the anode and the separator are cut together, the lengths of the separator 11 and the anode 12 in the anode structure 10 are substantially the same. However, depending on the method for cutting the anode structure 10, slight differences in the lengths of the separator 11 and the anode 12 may occur. In some cases, the end of the separator 12 may bend toward the center of the anode structure 10. Even if the lengths of the separator 11 and the anode 12 are substantially the same during the supply process, the length of the lithium metal may be extended during the folding process when the anode structure 10 is applied to the electrode assembly 1 due to the ductility of lithium metal.

[0071] In one embodiment of the present invention, the electrode assembly 1 is formed by folding a single anode structure 10 to form the basic structure of the electrode assembly 1. Therefore, the anode structure 10 must not be excessively thick to allow for flexible folding. Furthermore, a certain level of lithium metal, the anode active material, must be secured within the anode structure 10 in consideration of battery performance. According to one embodiment of the present invention, the thickness of the lithium metal in the anode structure 10 accounts for 50% to 90% of the total thickness of the anode structure 10. Specifically, the thickness of the lithium metal may range from 50% to 90%, more specifically, 55% to 85%, or more specifically, 60% to 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, the anode structure 10 does not include a separate current collector, and therefore the remaining thickness excluding the lithium metal thickness may refer to the thickness of two separators.

[0072] 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, or 70 μm or less, 80 μm or less, or 90 μm or less. The thickness of the lithium metal is not necessarily limited to these values ​​and can be appropriately adjusted depending on the actual battery size.

[0073] In an electrode assembly (1) according to one embodiment of the present invention, the positive electrode is cut according to the characteristics of the material and is applied between the stack portions (10S) of the negative electrode structure (10). The positive electrode is independent from the negative electrode, for example, it includes a current collector in addition to a positive electrode active material. However, considering the electrode performance, its thickness can be adjusted in relation to the negative electrode or the negative electrode structure. According to one embodiment of the present invention, the thickness of the positive electrode (20) is 100% to 400% of the thickness of the negative electrode structure (10). Specifically, the thickness of the positive electrode (20) may range from 100% to 400%, more specifically 150% to 350%, and more specifically 200% to 300%. When the positive electrode satisfies the above thickness range, it can be properly matched with the negative electrode structure.

[0074] An electrode assembly according to an embodiment of the present invention is applied to an electrochemical device. The electrochemical device may include any device that performs an electrochemical reaction. For example, the electrochemical device may be any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor. When the electrochemical device is a secondary battery, the electrochemical device may be a lithium secondary battery, and the lithium secondary battery may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. [Explanation of symbols]

[0075] 1: Electrode assembly 10: Negative electrode structure 10S: Stack section 10F: Folding section 11: Separation membrane 12: Negative electrode (including lithium metal) 20: Positive electrode A: Notching part

Claims

1. An electrode assembly including a positive electrode, a negative electrode, and a separator; the negative electrode includes lithium metal and is sandwiched between two notched separators to form a negative electrode structure; The electrode assembly includes a structure in which negative electrode structures and positive electrodes are alternately stacked, The negative electrode in the negative electrode structure is exposed to the outside through a notched region of the separator.

2. 2. The electrode assembly according to claim 1, wherein the notched region is present in each layer of the negative electrode structure in a structure in which the negative electrode structures and the positive electrode are alternately stacked, and the notched regions of each layer are positioned side by side in a height direction of the electrode assembly.

3. The electrode assembly of claim 1 , wherein the positive electrode includes a positive electrode tab that protrudes beyond the negative electrode structure.

4. the notched area has a rectangular shape; The electrode assembly according to claim 3 , wherein the length of the notched area is 1.5 times or more the length of the positive electrode tab.

5. The electrode assembly according to claim 3 , wherein the notched region is located at only one of both ends in the width direction of the negative electrode structure.

6. the positive electrode tab is located in the same direction as the notching area based on the width direction of the electrode assembly, The electrode assembly according to claim 5 , wherein the positive electrode tab does not overlap with the notched area in the height direction of the electrode assembly.

7. the positive electrode tab is located opposite to the notching region in the width direction of the electrode assembly, The electrode assembly according to claim 5 , wherein the positive electrode tab is positioned next to the notched area in the width direction of the electrode assembly.

8. The electrode assembly includes a negative electrode structure and a plurality of positive electrodes; the negative electrode structure includes a plurality of stack portions and a plurality of folded portions; In the negative electrode structure, the stack portions and the folded portions are alternately arranged, The electrode assembly according to claim 1 , wherein the electrode assembly has a structure in which stack portions of negative electrode structures and positive electrodes are alternately stacked in order.

9. 9. The electrode assembly of claim 8, wherein the notched area extends along the length of the negative electrode structure from one stack section to the adjacent other stack section.

10. 2. The electrode assembly according to claim 1, wherein the length of the notched region in the stack portion of the negative electrode structure is 70% or less of the length of the stack portion.

11. An electrochemical device comprising the electrode assembly according to any one of claims 1 to 10.

12. The electrochemical device according to claim 11, wherein the electrochemical device is a lithium secondary battery.

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