Electrode assembly and electrochemical device including the same

Abstract

An electrode assembly includes a positive electrode, a negative electrode, and a separator. In the electrode assembly, a negative electrode contains lithium metal and is interposed between two cutout separators to form a negative electrode structure. The electrode assembly includes a negative electrode structure and a positive electrode that are alternately stacked. In the negative electrode structure, the negative electrode is exposed to the outside through the cutout region of the separator. The electrode assembly according to one embodiment of the present invention can form a tab without cutting or welding a negative electrode, which not only improves processability, but also has a stable structure, thereby having an effect of improving battery performance.

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 and an electrochemical device including the same, the electrode assembly including a negative electrode between two separators having cutouts.

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0068571, filed on May 26, 2023, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] In recent years, there has been an increasing interest in energy storage technology. As the application of batteries expands to include energy sources for mobile phones, cameras, laptops, and even electric vehicles, efforts in research and development of batteries are being materialized. Electrochemical devices are one of the most prominent areas, and especially with the recent trend towards miniaturization and lightweighting of electronic products, the development of secondary batteries as small, lightweight, and high-capacity rechargeable batteries has become a focus of interest.

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

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

[0006] First, the rolled electrode assembly is made by winding the positive and negative electrodes of the long sheets in a dense state to form a structure with 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 inside 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, which may cause a sharp drop in the performance of the battery and may cause an internal short circuit, which may endanger the safety of the battery. In addition, because the above-mentioned rolled electrode assembly requires winding long sheets of the positive and negative electrodes, it is difficult to quickly wind the positive and negative electrodes while keeping the spacing between the electrodes constant, resulting in a decrease in productivity.

[0007] Second, the stackable electrode assembly requires multiple positive and negative electrode units to be stacked in sequence. At this time, the stackable electrode assembly has a problem of low productivity because the manufacturing unit requires a separate electrode plate transfer process and the sequential stacking process requires a lot of time and effort.

[0008] In order to solve these problems, a stack-folding type electrode assembly having an advanced structure of a mixture of a roll type and a stack type has been developed. The stack-folding type electrode assembly has a structure in which a bi-cell or a full cell stacked with a separator interposed between the positive and negative electrodes of a predetermined unit is wound using a long continuous separator sheet (folded separator).

[0009] The stacking-folding type electrode assembly connects the electrodes of each layer by extending the diaphragm, which is generally easier to fold than the electrode. In this case, the electrodes of each layer are supplied to form an electrode assembly in a cut state, as in the case of a stackable electrode assembly. If, among the various electrode materials constituting a secondary battery in the art, the secondary battery is composed only of electrode materials that are not easy to cut or fold, this general stacking-folding type electrode assembly is more suitable. On the other hand, lithium metal, which is well known in the art as a negative electrode material for secondary batteries, may not be suitable for conventional stacking-folding type electrode assemblies because it includes physical properties of high ductility and viscosity that make it difficult to perform processing such as cutting and relatively easy to fold.

[0010] After continuous research on the structure of electrode assemblies, the inventors of the present invention have designed a structure suitable for forming negative electrode tabs in a stacked-folded electrode assembly of a novel structure using a negative electrode structure containing lithium metal between two separators, thereby completing the present invention.

[0011] Prior art literature

[0012] [Patent Document]

[0013] (Patent Document 1) Korean Patent No. 2023530 Summary of the invention

[0014] Technical issues

[0015] The present invention aims to provide a stack-folding type electrode assembly using a novel structure of a negative electrode structure including a negative electrode including lithium metal interposed between two separators, and an electrochemical device including the same, the electrode assembly having a structure suitable for forming a negative electrode tab.

[0016] Technical Solution

[0017] According to a first aspect of the present invention, the present invention provides an electrode assembly, the electrode assembly comprising a positive electrode, a negative electrode and a separator.

[0018] In one embodiment of the present invention, the negative electrode comprises lithium metal and is interposed between two notched separators to form a negative electrode structure.

[0019] In one embodiment of the present invention, the electrode assembly includes negative electrode structures and positive electrodes stacked alternately.

[0020] In one embodiment of the present invention, in the negative electrode structure, the negative electrode is exposed to the outside through the cutout region of the separator.

[0021] In one embodiment of the present invention, the cutout regions exist in the negative electrode structures of each layer in the structure in which the negative electrode structures and the positive electrodes are alternately stacked, and the cutout regions of each layer are positioned side by side in the height direction of the electrode assembly.

[0022] In one embodiment of the present invention, the positive electrode comprises a positive electrode tab protruding above the negative electrode structure.

[0023] In one embodiment of the invention, the cutout area has a rectangular shape.

[0024] In one embodiment of the present invention, the length of the cutout region is at least 1.5 times the length of the positive electrode tab.

[0025] In one embodiment of the present invention, the cutout region is located only at one of the two ends in the width direction of the negative electrode structure.

[0026] In one embodiment of the present invention, the positive electrode tab is located in the same direction as the cutout region relative to the width direction of the electrode assembly, and the positive electrode tab does not overlap the cutout region relative to the height direction of the electrode assembly.

[0027] In one embodiment of the present invention, the positive electrode tab is located in a direction opposite to the cutout region with respect to the width direction of the electrode assembly, and the positive electrode tab is positioned parallel to the cutout region in the width direction of the electrode assembly.

[0028] In one embodiment of the present invention, the electrode assembly comprises a single negative electrode structure and a plurality of positive electrodes.

[0029] In one embodiment of the present invention, the negative electrode structure includes a plurality of stacked portions and a plurality of folded portions.

[0030] In one embodiment of the present invention, the stacked portions and the folded portions of the negative electrode structure are alternately positioned.

[0031] In one embodiment of the present invention, an electrode assembly includes stacking parts of negative electrode structures and positive electrodes that are alternately and sequentially stacked.

[0032] In one embodiment of the present invention, the cutout region extends along the length direction of the negative electrode structure and extends from one stacking portion to another adjacent stacking portion.

[0033] In one embodiment of the present invention, the length of the cutout region in the stacked portion of the negative electrode structure is 70% or less of the length of the stacked portion.

[0034] According to a second aspect of the present invention, the present invention provides an electrochemical device, wherein the electrochemical device comprises the electrode assembly as described above.

[0035] In one embodiment of the present invention, the electrochemical device is a lithium secondary battery.

[0036] Beneficial Effects

[0037] The electrode assembly according to one embodiment of the present invention may be manufactured using a negative electrode structure in which a negative electrode including lithium metal is interposed between two notched separators, thereby minimizing the cutting of lithium metal, thereby improving process efficiency in manufacturing the electrode assembly.

[0038] In addition, this structure can form the negative electrode tab without additionally cutting or welding the lithium metal, so that the manufactured electrode assembly not only has a stable structure but also improves the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic plan view of a slit diaphragm according to one embodiment of the present invention.

[0040] FIG. 2 is a schematic diagram of a negative electrode structure according to one embodiment of the present invention.

[0041] Figure 2a 1 is a perspective view schematically showing a separated form of each layer of a negative electrode structure according to one embodiment of the present invention.

[0042] Figure 2b FIG. 1 is a plan view schematically showing a negative electrode structure according to one embodiment of the present invention.

[0043] Figure 2c FIG. 1 is a front view schematically showing a negative electrode structure according to one embodiment of the present invention.

[0044] 3 to 6 are views schematically showing positions of a negative electrode structure and a positive electrode in an electrode assembly according to an embodiment of the present invention.

[0045] Figures 3a to 6a is a plan view schematically showing the position of a positive electrode on a negative electrode structure by unfolding a folded portion of the negative electrode structure in an electrode assembly according to one embodiment of the present invention.

[0046] Figures 3b to 6b is a schematic diagram showing Figures 3a to 6a Front view of an electrode assembly with the same configuration as in FIG. DETAILED DESCRIPTION

[0047] The embodiments will be described in detail below using exemplary drawings. It should be noted that when assigning reference numerals to the constituent elements in the drawings, even if the same constituent elements appear in different drawings, they are given the same reference numerals as much as possible. In addition, when describing the embodiments, if it is determined that the detailed description of the relevant known components or features will hinder the understanding of the embodiments, such detailed description will be omitted.

[0048] In addition, terms such as first, second, A, B, (a), (b) and the like may be used to describe the constituent elements of the embodiments. These terms are intended only to distinguish one constituent element from another constituent element, and the nature, order or sequence of the constituent elements are not limited by the terms. When a constituent element is described as "connected", "combined" or "connected to" another constituent element, it should be understood that the constituent element may be directly connected or connected to other constituent elements, but another constituent element may be "connected", "combined" or "connected to" between various constituent elements.

[0049] The constituent elements included in one embodiment and the constituent elements having common features are described in other embodiments using the same names. Unless otherwise specified, the description of one embodiment is applicable to other embodiments, and repeated description is omitted.

[0050] As used herein, "length direction" refers to the length of the Figure 1 , 2b , 3a, 4a, 5a and 6a and the front view as shown Figure 2c , 3b , 4b, 5b and 6b. As used herein, "width direction" refers to the left-right direction of the plan view. Figure 1 , 2b , 3a, 4a, 5a and 6a in the up-down direction and the front view as shown Figure 2c , 3b , 4b, 5b and 6b. In this specification, the "height direction" refers to the front-to-back direction of the plan view. Figure 1 , 2b , 3a, 4a, 5a and 6a, the undifferentiated front and rear directions and the front view are shown in Figure 2c , 3b , the up and down directions in 4b, 5b and 6b.

[0051] The present invention relates to an electrode assembly and provides a stacked-folding type electrode assembly of a novel structure, which utilizes a negative electrode structure including a negative electrode including lithium metal between two separators, and has a structure suitable for forming a negative electrode tab. An electrode assembly according to an embodiment of the present invention can minimize the cutting of lithium metal during manufacturing, thereby improving process efficiency. In addition, in the practical application of the electrode assembly, since the negative electrode tab can be formed without additionally cutting or welding the lithium metal, defects that may be generated due to the processing of the lithium metal are reduced, and the manufactured product has a reliable and stable structure, thereby being able to improve the performance of the battery.

[0052] The electrode assembly according to one embodiment of the present invention comprises a positive electrode, a negative electrode and a separator. In the electrode assembly, there is no particular limitation on the positive electrode and the separator, as long as they are materials commonly used in the art, but the negative electrode comprises lithium metal. The lithium metal used herein can be broadly understood to refer to any lithium metal, even if it is in the form of lithium with certain components added or an alloy with certain metals, as long as its properties are not too different from lithium metal, so that when applied to conventional electrode assemblies, the same problems as lithium metal will be encountered.

[0053] According to one embodiment of the present invention, the negative electrode is interposed between two notched separators to form a negative electrode structure. Here, notching the separator refers to the process of cutting off a portion of the separator in the negative electrode structure to expose the negative electrode located on the inside of the separator to the outside to manufacture the negative electrode tab. The two notched separators have a substantially symmetrical structure, and therefore, the position and number of the notched portions, the shape of the notched area, etc. will be described herein with reference to one separator. In order to provide a better understanding of the structure of the notched separator, Figure 1 A top view schematically showing a slit diaphragm according to one embodiment of the present invention is provided. The plan view shows the diaphragm from above, and the diaphragm according to one embodiment of the present invention has a lengthwise elongated structure.

[0054] In the drawings of this specification, for example Figure 1 In the figure, the "cutout portion" is referred to as A, and the cutout portion (A) refers to the three-dimensional shape removed by the cutout, so in the front view, for example Figure 2c On the other hand, as used herein, "cutout area" refers to a cross-sectional shape removed by a cutout, which has a length direction and a width direction but no height direction. Therefore, in a plan view such as Figure 1 The incision area is confirmed in the front view, but Figure 2c The incision area was not identified.

[0055] There is no particular restriction on the position of the cutout portion (A) in the separator (11), as long as it can serve as a negative electrode tab by exposing the negative electrode to the outside of the manufactured electrode assembly. However, in an electrode assembly having stacked positive and negative electrode structures, it may be desirable that the negative electrode structure protrudes further than the positive electrode so as to expose the negative electrode to the outside, and the cutout portion (A) is formed on the protruding negative electrode structure. According to one embodiment of the present invention, the cutout portion (A) is located at the end of the negative electrode structure in the width direction. In addition, there is no particular restriction on the number of cutout portions (A) in the separator (11). However, in a stacked structure of a negative electrode structure and a positive electrode, it may be desirable to form more than one cutout portion (A) in one layer of the negative electrode structure. Figure 1 As an exemplary structure of a diaphragm having a cutout, the diaphragm may be shortened in the length direction so that one or two cutout portions (A) are formed in one diaphragm, or the diaphragm may be extended in the length direction so that four or more cutout portions (A) are formed in one diaphragm.

[0056] In order to provide a better understanding of the structure of a negative electrode structure having a negative electrode between two notched separators, FIG2 provides a schematic diagram of a negative electrode structure according to one embodiment of the present invention. Specifically, Figure 2a Provides a view of the layers of the negative electrode structure, Figure 2b and 2c Provides views of the negative electrode structure viewed from different positions. Figure 2a and Figure 2c As shown in , the upper separator (11) and the lower separator (11) have a substantially symmetrical structure with respect to the negative electrode (12), so that the negative electrode is exposed at the upper and lower parts at the same time. In an electrode assembly according to one embodiment of the present invention, the positive electrode (20), the negative electrode (12) and the separator (11) have a structure in which the positive electrode, the negative electrode and the separator are all exposed when viewed from the front, as shown in Figure 3b As shown in , the negative electrode is exposed upward and downward by cutting the separator, which has technical significance in the present invention. Because the separator (11) completely separates the positive electrode (20) and the negative electrode (12) to prevent electrical short circuit when the battery is driven, the width of the separator (11) can be the same as or longer than the width of the negative electrode. Therefore, as Figure 2b As shown in FIG. 1 , unless the separator ( 11 ) is cut, the negative electrode ( 12 ) will not be exposed. The exposed upper and lower portions of the negative electrode are referred to herein as negative electrode tabs.

[0057] According to one embodiment of the present invention, an electrode assembly (1) includes a structure in which negative electrode structures (10) and positive electrodes (20) are alternately stacked. In this structure, the positive electrodes (20) located at the upper and lower parts of the negative electrode structures (10) may also prevent the negative electrode (12) from being exposed to the outside. Therefore, in order to expose the negative electrode (12) in the electrode assembly (1) to the outside, the negative electrode structure (10) in the stacked structure must protrude more than the positive electrode (20) in the width or length direction, and a cutout portion (A) must be formed in the protruding portion so that the negative electrode (12) is exposed to the outside. According to one embodiment of the present invention, in the negative electrode structure (10), the negative electrode (12) is exposed to the outside through the cutout area of ​​the separator (11). Because the negative electrode (12) is exposed to the outside through the cutout portion (A), it can be expressed as the negative electrode (12) is exposed to the outside through the cutout area, but the thickness of the separator (11) cutout has no particular relationship with the exposure of the negative electrode (12).

[0058] According to one embodiment of the present invention, in a structure in which negative electrode structures (10) and positive electrodes (20) are alternately stacked, cutout regions exist in each layer of the negative electrode structure (10), and the cutout regions in each layer are positioned side by side in the height direction of the electrode assembly (1). As described above, in the negative electrode structure (10), the upper separator and the lower separator have a substantially symmetrical structure, so that the negative electrode (12) is exposed to the upper side and the lower side through the cutout regions in each layer. In addition, as Figure 3b As shown in , when the cutout regions of the layers are positioned side by side in the height direction of the electrode assembly (1), it is easy to connect the negative electrode tabs of the layers together by welding or the like.

[0059] According to one embodiment of the present invention, the positive electrode (20) includes a positive electrode tab that protrudes more than the negative electrode structure (10). The positive electrode tab protrudes more than the negative electrode structure (10) in the length direction or the width direction, and the positive electrode (20) of the electrode assembly (1) can be electrically connected via the protruding positive electrode tab. Because the positive electrode (20) is made of a different material, it is not formed in the same manner as the negative electrode tab according to one embodiment of the present invention, and there is no particular limitation as long as it is commonly used in the art. In this specification, the positive electrode tab is regarded as a structure included in the positive electrode (20), and refers to a portion protruding from the width direction of the separator (11) of the negative electrode structure (10), such as Figure 3a as shown in .

[0060] According to one embodiment of the present invention, the cutout area has a rectangular shape. The cutout area can be made into various shapes, but typically is as follows Figure 3aThe rectangular shape shown in . According to one embodiment of the present invention, the length of the cutout area is at least 1.5 times the length of the positive electrode ear. If the cutout area is rectangular, the length of the cutout area and the positive electrode ear can be the same at all positions, otherwise the length is based on the average value of the length of all positions. Specifically, based on the length of the positive electrode ear, the length of the cutout area can be more than 1.5 times, more than 1.6 times, more than 1.7 times, more than 1.8 times, more than 1.9 times, more than 2.0 times. In one embodiment of the present invention, the negative electrode ear is manufactured by cutting the diaphragm so that they do not have a typical protruding shape like the positive electrode ear. The negative electrode ear can be joined to the negative electrode ear formed on another layer by welding, etc. In this case, if the length of the cutout area is sufficient to ensure the fixing of the negative electrode ear, the negative electrode ear can be easily joined without bonding by utilizing the ductility of the lithium metal that is not fixed by the diaphragm. Because the cutout area is formed in a portion that does not overlap with the positive electrode ear, the length of the cutout area may be limited. Unlike the length of the cutout area, the width of the cutout area is directly related to the area in the electrode assembly where the positive electrode can be applied, so it is appropriately adjusted for battery performance, and if it can only be used as a negative electrode tab, it may be desirable to minimize the width of the cutout area.

[0061] According to one embodiment of the present invention, the cutout region is located only at one of the two ends in the width direction of the negative electrode structure (10). Because the negative electrode structure (10) can extend in the length direction, it may be advantageous for the cutout region to be located at the end in the width direction in terms of the process. Even if the cutout region is located at one of the two ends, there is no significant difference in functionality between being located at one end and being located at both ends; on the contrary, being located at one of the two ends may be preferred in terms of simplifying the process. For the same reason, the positive electrode tab may also be located at one of the two ends, in which case the cutout region and the positive electrode tab may be oriented in the same direction or in different directions.

[0062] Figures 3 to 6 show an electrode assembly having an exemplary negative electrode structure (10) and a positive electrode (20) arranged according to one embodiment of the present invention. In Figures 3 and 4, the cutout area and the positive electrode tab are located in opposite directions. When the cutout area and the positive electrode tab are located in opposite directions, they do not overlap each other, with the advantage that their positions can be freely configured and they can both be located in the center in the length direction. In Figures 5 and 6, the cutout area and the positive electrode tab are located in the same direction. When the cutout area and the positive electrode tab are located in the same direction, there is a structural advantage that the negative electrode tab and the positive electrode tab can be located on one side.

[0063] According to one embodiment of the present invention, an electrode assembly (1) includes one negative electrode structure (10) and a plurality of positive electrodes (20). The negative electrode structure (10) may be cut into the same number as the number of positive electrodes (20) and applied to the electrode assembly (1), but this may increase the number of cutting times of the negative electrode containing lithium metal, thereby reducing the effect of the present invention. Therefore, in one embodiment of the present invention, only one negative electrode structure (10) is applied to the electrode assembly (1) by extending the negative electrode structure (10) in the length direction. In order to produce a stacked structure having multiple layers as a single negative electrode structure (10), appropriate folding of the negative electrode structure (10) may be important.

[0064] According to one embodiment of the present invention, the negative electrode structure (10) includes a plurality of stacked portions and a plurality of folded portions. In the negative electrode structure (10), the stacked portions and the folded portions are units that are divided into positions with different functions along the length direction of the negative electrode structure (10). The stacked portions and the folded portions are not distinguished by material except for their positions. In order to facilitate understanding of the positions of the stacked portions and the folded portions, Figure 3b An example of the positions of the stacking portion (10S) and the folding portion (10F) is shown. The stacking portion (10S) refers to the negative electrode structure (10) at the position where the positive electrode (20) is stacked, and has Figure 3b The shape shown in the figure is mainly a straight line. The length of the stacking part (10S) is substantially the same as the length of the positive electrode. The folding part (10F) refers to the negative electrode structure (10) at the position connecting the stacking part (10S) and the stacking part (10S), and has the following Figure 3b The shape shown in the figure is mainly curved. According to one embodiment of the present invention, in the negative electrode structure (10), the stacked portion (10S) and the folded portion (10F) are alternately positioned. In other words, the stacked portion can be separated by the folded portion, and the folded portion can be separated by the stacked portion.

[0065] According to one embodiment of the present invention, an electrode assembly (1) includes a structure in which a stacking portion (10S) of a negative electrode structure (10) and a positive electrode (20) are alternately and sequentially stacked. Since the electrode assembly (1) includes a structure in which a stacking portion (10S) of a negative electrode structure (10) and a positive electrode (20) are alternately and sequentially stacked, the negative electrode structure (10) including the stacking portion (10S) and the folding portion (10F) in this structure has the following characteristics: Figure 3a In other words, the folded portions (10F) sequentially positioned from the stacked portion (10S) of the negative electrode structure (10) stacked initially are alternately located on the left or right side of the electrode assembly (1). If the stacked portion (10S) of the negative electrode structure (10) and the positive electrode (20) are not alternately stacked, and if more than two stacked portions or positive electrodes are stacked continuously, a potential difference may not be generated between the continuously stacked layers, and the efficiency of the battery may be reduced.

[0066] The electrode assembly according to one embodiment of the present invention may have Figure 3a and 3b According to this configuration, the positive electrode tab is located in the opposite direction of the cutout region relative to the width direction of the electrode assembly (1). Figure 3a As shown in , in this configuration, the positive electrode tab can be positioned side by side with the cutout region in the width direction of the electrode assembly, and the position can be at the center of the stack (10S) in the length direction. By positioning the positive electrode (20) at a certain distance from the cutout region in the width direction, the positive electrode (20) and the negative electrode (12) do not overlap. In this case, as Figure 3b As shown in , the cutout portions (A) are positioned side by side at the center of the stacked portion in the height direction of the electrode assembly (1).

[0067] The electrode assembly according to one embodiment of the present invention may have Figure 5a and Figure 5b According to this configuration, the positive electrode tab is located in the same direction as the cutout region relative to the width direction of the electrode assembly (1). In the above configuration, Figure 3a As shown in , the positive electrode tabs are stacked at different positions in the length direction from the cutout area. Figure 3b In the electrode assembly in the embodiment, the positive electrode tab (not shown in the figure) does not overlap with the cutout region (or cutout portion (A)) relative to the height direction of the electrode assembly, the positive electrode tab may overlap with another positive electrode tab, and the cutout region may overlap with another cutout region. In this case, if the cutout region or the positive electrode tab is located at the center of the stacking portion, it may be difficult to effectively use the space.

[0068] According to one embodiment of the present invention, the cutout region extends along the length direction of the negative electrode structure and extends from one stacking portion to another adjacent stacking portion. In order to extend the cutout region from one stacking portion to another adjacent stacking portion, one stacking portion and another stacking portion are connected by a folding portion, and the cutout region passes through the entire folding portion. In this regard, if the positive electrode tab is located in the opposite direction to the cutout region relative to the width direction of the electrode assembly (1), the exemplary electrode assembly (1) may have a shape such as Figure 4a and Figure 4b In this case, since there is no positive electrode tab relative to the cutout region in the length direction of the negative electrode structure, there is no particular limitation on the direction in which the cutout region extends, and it may extend in the left or right direction. If the positive electrode tab is located in the same direction as the cutout region relative to the width direction of the electrode assembly (1), the exemplary electrode assembly (1) may have the following structure: Figure 6a and 6bIn this case, since the positive electrode tab exists in the length direction of the negative electrode structure relative to the cutout region, the direction in which the cutout region extends may be opposite to the direction in which the positive electrode tab exists.

[0069] According to one embodiment of the present invention, even if the cutout area extends from one stacking portion to another adjacent stacking portion, a plurality of cutout areas are positioned side by side in the height direction of the electrode assembly (1). In an electrode assembly according to one embodiment of the present invention, the cutout areas are positioned side by side to join the negative electrode tabs of each layer together by welding or the like. In this case, even if the folded portion is cutout, the flexibility of the negative electrode tab to be joined is increased, and the negative electrode tab can be joined more easily.

[0070] In terms of the flexibility of the negative electrode tab, it may be desirable to make the cutout area as long as possible, but a highly flexible negative electrode tab may cause defects in the manufacture of the electrode assembly. Therefore, the cutout area is preferably controlled within a suitable range. According to one embodiment of the present invention, the length of the cutout area in the negative electrode structure is less than 70% of the length of the stacked portion. This may mean that when a plurality of cut negative electrode structures are applied, the length of the negative electrode structure in one layer is less than 70%. Specifically, the length of the cutout area may be less than 70%, less than 69%, less than 68%, less than 67%, less than 66%, less than 65%, less than 64%, less than 63%, less than 62%, less than 61%, less than 60% of the length of the stacked portion. By making the uncut diaphragm exceed a certain level, the electrode assembly can have a more stable structure.

[0071] According to one embodiment of the present invention, in addition to the stacking part (10S) and the folding part (10F), the negative electrode structure further includes a winding part (not shown in the figure). By winding the stacking part of the negative electrode structure and the positive electrode through the winding part at one time, the electrode assembly can have a more stable structure. The winding part can have a mixture of a straight line shape and a curved shape.

[0072] 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 the positive electrode active material layer is formed on at least one face of the current collector, more specifically on both faces. The positive electrode active material layer includes a positive electrode active material, and may further 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, and the additive, as long as they are commonly used in the art.

[0073] The positive electrode current collector supports the positive electrode active material, and there is no particular limitation on it as long as it has high electrical conductivity and does not cause any chemical changes in the battery. According to an embodiment of the present invention, the positive electrode current collector can be made of the following materials: copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon; copper or stainless steel surface-treated with carbon, nickel, silver, etc.; aluminum-cadmium alloy, etc.

[0074] The positive electrode current collector can form fine concavities and convexities on its surface to enhance the bonding force with the positive electrode active material, and can be used in various forms, such as films, sheets, foils, sieves, meshes, porous bodies, foams, non-woven fabric bodies, etc.

[0075] As the positive electrode active material, a lithium-containing transition metal oxide can be used. According to an embodiment of the present invention, any one or a mixture of two or more selected from the following can be used: 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), LiCoPO4 and LiFePO4. In addition to these oxides, sulfides, selenides and halides can also be used.

[0076] The positive electrode active material can contain a sulfur compound. According to an embodiment of the present invention, the sulfur compound can be one or more selected from the following: elemental sulfur (S8), organic sulfur compound Li2S n (where n ≥ 1) and carbon-sulfur polymer ((C2S x ) n , where x = 2.5 to 50, n ≥ 1). Preferably, inorganic sulfur (S8) can be used.

[0077] If the positive electrode active material contains a sulfur compound, the electrode assembly (1) according to one embodiment of the present invention can be applied to a lithium-sulfur battery. Since sulfur contained in the positive electrode active material alone has no conductivity, it can be used in a composite with a conductive material such as a carbon material. Therefore, sulfur is contained in the form of a sulfur-carbon composite, and preferably, the positive electrode active material can be a sulfur-carbon composite.

[0078] In view of the above, the positive electrode (20) is relatively difficult to fold and easier to cut than the negative electrode. Therefore, the positive electrode (20) can be cut into a suitable size, so that a plurality of positive electrodes can be applied to the inside of the electrode assembly (1).

[0079] According to one embodiment of the present invention, the negative electrode (12) does not include a current collector. Because the negative electrode (12) does not include a current collector, the amount of negative electrode active material loaded in the electrode assembly can be improved, which can help improve the performance of the battery. In the electrode assembly (1) according to one embodiment of the present invention, while the negative electrode is applied in the form of a negative electrode structure (10), the processability can be improved by minimizing cutting, because the negative electrode (12) is mainly composed of lithium metal, which may not be easy to process such as cutting due to its high ductility and viscosity.

[0080] There is no particular limitation on the type of the separator (11) covering both surfaces of the negative electrode (12) in the negative electrode structure (10), as long as no binder is contained on its surface. The separator (11) may be, but is not limited to, for example: a non-woven fabric material made of high melting point glass fiber or polyethylene terephthalate fiber; or a polyolefin porous material. Since the separator (11) is easier to process than the negative electrode (12) of lithium metal, in the present invention, the negative electrode tab is manufactured by cutting the separator (11).

[0081] The present invention has no particular restrictions on the material of the porous substrate, but any porous substrate commonly used in electrochemical devices can be used. According to one embodiment of the present invention, the porous substrate may include at least one material selected from the following: 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.

[0082] According to one embodiment of the present invention, in the negative electrode structure (10), the separator (11) and the negative electrode (12) have the same length. The separator (11) and the negative electrode (12) are supplied to the electrode assembly in the form of a negative electrode structure (10) having a negative electrode (12) between two notched separators (11), wherein the negative electrode and the separator are cut once at the same time, so that the lengths of the separator (11) and the negative electrode (12) in the negative electrode structure (10) are substantially the same. However, depending on the method of cutting the negative electrode structure (10), there may be a slight difference in the lengths of the separator (11) and the negative electrode (12), and in some cases, the end of the separator (11) may be bent toward the center of the negative electrode structure (10). Even if the negative electrode structure (10) has a separator (11) and a negative electrode (12) having substantially the same length during the supply process, when applied to the electrode assembly (1), the length of the lithium metal can be extended due to the ductility of the lithium metal during the folding process.

[0083] Since the electrode assembly (1) according to one embodiment of the present invention is formed by folding a negative electrode structure (10) to form the basic structure of the electrode assembly (1), the thickness of 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 as a 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%. More specifically, the thickness of the lithium metal can be 50% to 90%, more specifically 55% to 85%, and more specifically 60% to 80%. If the lithium metal satisfies the above thickness range, it may help to 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 part other than the thickness of the lithium metal can refer to the thickness of two separators.

[0084] 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.

[0085] 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 the stacked portions (10S) of the negative electrode structure (10). The positive electrode is different from and independent of the negative electrode by including a current collector in addition to the positive electrode active material, but the thickness of the positive electrode can be adjusted relative to the negative electrode or the negative electrode structure in consideration of the performance of the electrode, etc. According to an embodiment of the present invention, the thickness of the positive electrode (20) is 100% to 400% of the thickness based on the thickness of the negative electrode structure (10). More specifically, the thickness of the positive electrode (20) can be 100% to 400%, more specifically 150% to 350%, and more specifically 200% to 300%. When the positive electrode meets the above thickness range, it can be appropriately matched with the negative electrode structure.

[0086] 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 type of primary battery, secondary battery, fuel cell, solar cell or capacitor. If the electrochemical device is a secondary battery, the electrochemical device may be a lithium secondary battery, 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.

[0087] [reference numerals]

[0088] 1: Electrode assembly

[0089] 10: Negative electrode structure

[0090] 10S: Stacking

[0091] 10F: Folding part

[0092] 11: Diaphragm

[0093] 12: Negative electrode (including lithium metal)

[0094] 20: Positive electrode

[0095] A: Incision

Claims

1. An electrode assembly, comprising a positive electrode, a negative electrode and a separator, The negative electrode comprises lithium metal and is sandwiched between two separators with cutouts to form a negative electrode structure. The electrode assembly comprises a negative electrode structure and a positive electrode stacked alternately, in, In the negative electrode structure, the negative electrode is exposed to the outside through the cutout region of the separator.

2. The electrode assembly according to claim 1, wherein the cutout region exists in the negative electrode structure of each layer, the negative electrode structure having a structural form in which the negative electrode structure and the positive electrode are alternately stacked, and The cutout regions of the layers are positioned side by side in the height direction of the electrode assembly. 3 . The electrode assembly according to claim 1 , wherein the positive electrode comprises a positive electrode tab protruding above the negative electrode structure. 4 . The electrode assembly according to claim 3 , wherein the cutout region has a rectangular shape, and a length of the cutout region is at least 1.5 times a length of the positive electrode tab. 5 . The electrode assembly according to claim 3 , wherein the cutout region is located only at one of both ends in the width direction of the negative electrode structure.

6. The electrode assembly according to claim 5, wherein the positive electrode tab is located in the same direction as the cutout region with respect to the width direction of the electrode assembly, and The positive electrode tab does not overlap with the cutout region in a height direction relative to the electrode assembly.

7. The electrode assembly according to claim 5, wherein the positive electrode tab is located in a direction opposite to the cutout region with respect to a width direction of the electrode assembly, and The positive electrode tab is positioned side by side with the cutout region in a width direction of the electrode assembly.

8. The electrode assembly according to claim 1, wherein the electrode assembly comprises a single negative electrode structure and a plurality of positive electrodes, The negative electrode structure comprises a plurality of stacked portions and a plurality of folded portions. in, In the negative electrode structure, the stacked portions and the folded portions are alternately positioned, The electrode assembly includes a structure in which a stacking portion of the negative electrode structure and a positive electrode are alternately and sequentially stacked. 9 . The electrode assembly according to claim 8 , wherein the cutout region extends along a length direction of the negative electrode structure and extends from one stacking portion to another adjacent stacking portion. 10 . The electrode assembly according to claim 1 , wherein in the stacked portion of the negative electrode structure, a length of the cutout region is 70% or less of a length of the stacked portion. 11 . An electrochemical device comprising the electrode assembly according to claim 1 .

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

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