Pole piece, electrochemical device, and electronic device

Abstract

The utility model discloses an electrode sheet, electrochemical device and electronic equipment, the electrode sheet is used to be mutually laminated with diaphragm and is wound and forms electrode assembly, including current collector and active material layer, and active material layer is located the surface of current collector, and active material layer forms multiple corner areas after the winding of electrode sheet, and at least partial corner area is equipped with at least one first wire slot, at least one second wire slot and at least one third wire slot, and the first wire slot is arranged along the width direction of electrode sheet, and one end of the second wire slot communicates with the first wire slot, and the first wire slot and the second wire slot form the first included angle, and one end of the third wire slot communicates with the second wire slot, and the second wire slot and the third wire slot form the second included angle. The electrode sheet of the application aims at improving the infiltration speed and infiltration effect of electrolyte at the corner in the electrochemical device, and improving the crack resistance of the electrode sheet.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage, and in particular to an electrode, an electrochemical device, and an electronic device. Background Technology

[0002] Lithium-ion batteries are widely used in energy storage, 3C products, new energy vehicles and other fields due to their advantages such as high energy density, long cycle life, high plateau voltage and good safety performance.

[0003] In lithium-ion battery manufacturing, to solve the problem of lithium plating at the electrode interface in high-silicon systems, it is necessary to improve the electrolyte wetting effect. Generally, laser etching is used to construct grooves to store electrolyte. However, the coverage of grooves formed by vertical etching at corners is not wide, and there are still wetting dead zones at corners, which reduces the electrolyte storage effect and weakens the effect of improving lithium plating. Furthermore, during winding, the corners are subjected to stress compression, and the large-angle opening of the straight groove etching area can lead to powder shedding or even cracking. Utility Model Content

[0004] The main objective of this application is to provide an electrode that improves the wetting rate and effect of the electrolyte at the corners of an electrochemical device, and enhances the crack resistance of the electrode.

[0005] To achieve the above objectives, this application proposes an electrode sheet for being stacked and wound with a diaphragm to form an electrode assembly, the electrode sheet comprising: current collector; An active material layer is disposed on one surface of the current collector. After the electrode is wound, the active material layer forms multiple corner areas. At least a portion of the corner areas are provided with at least one first groove, at least one second groove, and at least one third groove. The first groove is disposed along the width direction of the electrode. One end of the second groove is connected to the first groove, and a first angle is formed between the second groove and the first groove. One end of the third groove is connected to the second groove, and a second angle is formed between the third groove and the second groove.

[0006] In some embodiments, a plurality of second grooves connected to the same first groove are arranged symmetrically about the first groove.

[0007] In some embodiments, a plurality of third grooves connected to the same second groove are arranged symmetrically about the second groove as an axis.

[0008] In some embodiments, the ratio between the depth of the first groove and the thickness of the active material layer is A, wherein A satisfies: 0.3 ≤ A ≤ 0.7; and / or, The width of the first groove is W, and W satisfies: 40μm≤W≤90μm.

[0009] In some embodiments, the first included angle between the second groove and the first groove is α, wherein α satisfies: 30°≤α≤60°; and / or, The ratio B between the depth of the second groove and the depth of the first groove satisfies: 0.3 ≤ B ≤ 0.7; and / or, The ratio of the width of the second groove to the width of the first groove is C, where C satisfies: 0.3≤C≤0.7.

[0010] In some embodiments, the second included angle between the third groove and the second groove is β, wherein β satisfies: 30°≤β≤60°; and / or, The ratio of the depth of the third groove to the depth of the second groove is D, where D satisfies: 0.3 ≤ D ≤ 0.7; and / or, The ratio of the width of the third groove to the width of the second groove is E, and E satisfies: 0.3≤E≤0.7.

[0011] In some embodiments, the corner area includes a central area and two edge areas located on opposite sides of the central area, wherein the distance between the two first grooves in the central area is greater than the distance between the two first grooves in the edge areas.

[0012] In some embodiments, the first included angle between the second groove and the first groove in the central region is greater than the first included angle between the second groove and the first groove in the edge region.

[0013] This application further proposes an electrochemical device, including an electrode assembly, the electrode assembly including a first electrode, a diaphragm and a second electrode arranged in a stacked and wound manner, the second electrode having the opposite polarity to the first electrode; Wherein, at least one of the first electrode and the second electrode is an electrode as described above.

[0014] This application further proposes an electronic device, including the electrochemical device described above.

[0015] The electrode in this application includes a current collector and an active material layer disposed on one surface of the current collector. The active material layer includes multiple spaced corner regions. During the electrode winding process to form an electrode assembly, the corner regions on the active material layer are bent to form curved sections of the electrode assembly. At least a portion of the corner regions are provided with at least one first groove, at least one second groove, and at least one third groove. The first groove allows the electrolyte to flow along the width direction of the current collector. One end of each second groove is connected to a first groove, allowing the electrolyte to flow into the second groove through the first groove and along the second groove. The electrolyte flows along the extension direction of the first groove, and the second groove forms a first angle with the first groove. Compared with the traditional vertical straight structure, the second groove, which forms an angle with the first groove, allows the electrode to have a longer extension length in the plane. The electrolyte can wet the coating along a longer oblique path, significantly increasing the penetration coverage area. One end of each third groove is connected to a second groove, allowing the electrolyte to flow into the third groove through the second groove and flow along the extension direction of the third groove, thereby deeply constructing lithium-ion transport channels and improving the wetting effect. By setting the first, second, and third grooves in the corner area, multi-level diffusion paths can be provided, shortening the lateral diffusion distance of lithium ions, improving the wetting speed and effect of the electrolyte in the corner area of ​​the electrode, and the self-similarity of the fractal structure can disperse the charging and discharging stress, suppress crack propagation, and improve the crack resistance compared with the straight groove, thus improving the problems of powder shedding or cracking of the electrode during the winding process. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an embodiment of the electrode sheet of this application; Figure 2 for Figure 1 A magnified view of a section at point A in the middle; Figure 3 This is a schematic diagram of another embodiment of the electrode sheet of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0018] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0019] As used in this article, the terms “roughly,” “generally,” “substantially,” and “about” are used to describe and explain minor variations.

[0020] When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two numerical values ​​is less than or equal to ±10% of the average of the values ​​(e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), then the two numerical values ​​can be considered "substantially" the same.

[0021] Furthermore, for ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0022] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0023] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0024] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0025] In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction with them. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within that range are specifically disclosed: R = RL + k (RU-RL), where k is a variable with an increment of 1% from 1% to 100%, that is, k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any numerical range defined by the two R values ​​as defined above is also specifically disclosed.

[0026] Throughout this specification, references to “implementation,” “partial implementation,” “one implementation,” “another implementation,” “specific method,” or “partial method” mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0027] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0028] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

[0029] Lithium-ion batteries are widely used in energy storage, 3C products, new energy vehicles and other fields due to their advantages such as high energy density, long cycle life, high plateau voltage and good safety performance.

[0030] In lithium-ion battery manufacturing, to solve the problem of lithium plating at the electrode interface in high-silicon systems, it is necessary to improve the electrolyte wetting effect. Generally, laser etching is used to construct grooves to store electrolyte. However, the coverage of grooves formed by vertical etching at corners is not wide, and there are still wetting dead zones at corners, which reduces the electrolyte storage effect and weakens the effect of improving lithium plating. Furthermore, during winding, the corners are subjected to stress compression, and the large-angle opening of the straight groove etching area can lead to powder shedding or even cracking.

[0031] This application proposes an electrode 100, with reference to... Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of the electrode 100 in one embodiment of this application. Figure 2 for Figure 1 A partial enlarged view at point A. In some embodiments, the electrode 100 includes a current collector 110 and an active material layer 120. The active material layer 120 is disposed on a surface of the current collector 110. After the electrode 100 is wound, the active material layer 120 forms a plurality of corner regions 121. At least some of the corner regions 121 are provided with at least one first groove 122, at least one second groove 123 and at least one third groove 124. The first groove 122 is disposed along the width direction of the electrode 100. One end of the second groove 123 is connected to the first groove 122, and a first included angle α is formed between the second groove 123 and the first groove 122. One end of the third groove 124 is connected to the second groove 123, and a second included angle β is formed between the third groove 124 and the second groove 123.

[0032] In this embodiment, the current collector 110 can be a metal foil or a composite current collector 110. Depending on the polarity, the metal foil can be an aluminum foil or a copper foil. The composite current collector 110 can include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate. Depending on the polarity, the metal foil substrate can be an aluminum foil substrate or a copper foil substrate. The conductive layer can be carbon, carbon black, graphite, expanded graphite, or other carbon materials. The active material layer can include an active material, a binder, and a conductive agent. The active material can be lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, NMC, NCA, or other materials that can be used as active materials. The binder can be polyvinylidene fluoride (PVDF), poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), or other materials that can be used as battery binders. The conductive agent can be carbon, carbon black, graphite, expanded graphite, graphene, or other materials that can be used as battery conductive agents. During the process of winding the electrode sheet 100 to form an electrode assembly, the corner area 121 on the active material layer 120 bends to form the bent section of the electrode assembly. The bend of the corner area 121 makes it easier for dead zones of electrolyte to appear, and the wetting rate and effect are not ideal.

[0033] The first groove 122 is a main flow guiding structure arranged along the width direction of the current collector 110, serving to store electrolyte and conduct ion flow along the width direction of the current collector 110. The first groove 122 can be formed by laser drilling, specifically it can be a straight groove structure, or a structure of multiple circular holes arranged in a straight line and connected, or a structure of multiple polygonal holes arranged in a straight line and connected, etc., without further limitation. The length of the first groove 122 can be the same as the width of the current collector 110, or there can be gaps between the two ends of the first groove 122 and the two sides of the current collector 110.

[0034] Multiple first grooves 122 within the same corner area 121 are spaced apart along the length of the current collector 110. These grooves can store more electrolyte and also divert the electrolyte, ensuring the stored electrolyte is also spaced along the length of the current collector 110, thus improving the wetting speed and effect. In a preferred embodiment, the multiple first grooves 122 are evenly distributed along the length of the current collector 110, and the electrolyte is also evenly distributed along the length of the current collector 110, thereby making the lithium ions more evenly distributed on the surface of the electrode 100, reducing the polarization concentration difference on the electrode 100 surface, and making the current distribution more uniform. The orientation of the first grooves 122 can be parallel to one edge of the width direction of the current collector 110, or it can be at an angle to one edge of the width direction of the current collector 110.

[0035] The second groove 123 is a primary branching current-guiding structure forming a first angle α with the first groove 122. It serves to divert the electrolyte and distribute the ion flow to smaller regional units, covering the middle region of the two first grooves 122 with lithium-ion transport channels. The other ends of adjacent second grooves 123 maintain a certain distance. The second groove 123 can be formed by laser drilling. Specifically, it can be a straight groove structure, or a structure of multiple interconnected circular holes arranged in a straight line, or a structure of multiple interconnected polygonal holes arranged in a straight line, etc., without further limitation.

[0036] One end of each second groove 123 is connected to the first groove 122, and the other end of the second groove 123 extends outwards. The direction of extension of the second groove 123 can be from top to bottom, gradually moving away from the first groove 122, or from top to bottom, gradually moving closer to the first groove 122. Multiple second grooves 123 connected to both sides of the same first groove 122 can be arranged symmetrically about the first groove 122, or they can be staggered on opposite sides of the first groove 122. Multiple second grooves 123 connected to the same side of the same first groove 122 are evenly spaced. Multiple second grooves 123 connected to different first grooves 122 can be connected at the same position of the corresponding first grooves 122. Each first groove 122 and the multiple second grooves 123 on it form a flow guiding structure of the same shape, making the distribution and wetting of the electrolyte more uniform and improving its wetting and liquid retention effect. The included angle between the second groove 123 and the first groove 122 can be an acute angle, a right angle, or an obtuse angle, and is not further limited here.

[0037] The active material layer 120 also has multiple third grooves 124. Each third groove 124 is a secondary branching flow-guiding structure forming a second angle β with the second groove 123. Its function is to divert the electrolyte and allow it to penetrate between the active particles of the active material layer 120, thereby improving the wetting effect of the electrolyte within the battery. The third grooves 124 can be formed by laser drilling. Specifically, they can be straight groove structures, multiple circular holes arranged in a straight line, or multiple polygonal holes arranged in a straight line, etc., without further limitation.

[0038] One end of each third groove 124 is connected to the second groove 123, and the other end of the third groove 124 extends outwards. The direction of extension of the third groove 124 can be from top to bottom, gradually moving away from the second groove 123, or from top to bottom, gradually moving closer to the second groove 123. Multiple third grooves 124 connected to both sides of the same second groove 123 can be arranged symmetrically about the second groove 123, or they can be staggered on opposite sides of the second groove 123. Multiple third grooves 124 connected to the same side of the same second groove 123 are evenly spaced. Multiple third grooves 124 connected to different second grooves 123 can be connected at the same position of the corresponding second grooves 123. Each second groove 123 and the multiple third grooves 124 on it form a flow guiding structure with the same shape, making the distribution and wetting of the electrolyte more uniform and improving its wetting and liquid retention effect. The included angle between the third groove 124 and the second groove 123 can be an acute angle, a right angle, or an obtuse angle, without further limitation.

[0039] The electrode 100 in this application includes a current collector 110 and an active material layer 120 disposed on one surface of the current collector 110. The active material layer 120 includes a plurality of spaced corner regions 121. During the winding process of the electrode 100 to form an electrode assembly, the corner regions 121 on the active material layer 120 are bent to form a bent section of the electrode assembly. At least a portion of the corner regions 121 are provided with at least one first groove 122, at least one second groove 123, and at least one third groove 124. The first groove 122 allows the electrolyte to flow along the width direction of the current collector 110. One end of each second groove 123 is connected to a first groove 122, allowing the electrolyte to flow into the second groove 124 through the first groove 122. The second groove 123 flows along the extension direction of the first groove 122, and the second groove 123 forms a first angle α with the first groove 122. Compared with the traditional vertical straight structure, the second groove 123, which forms an angle with the first groove 122, allows the electrode 100 to have a longer extension length in the plane. The electrolyte can wet the coating along a longer oblique path, significantly increasing the coverage area of ​​the penetration. One end of each third groove 124 is connected to a second groove 123. The electrolyte can flow into the third groove 124 through the second groove 123 and flow along the extension direction of the third groove 124 to deeply construct lithium-ion transport channels and improve the wetting effect. By setting the first groove 122, the second groove 123 and the third groove 124 in the corner area 121, a multi-level diffusion path can be provided, shortening the lateral diffusion distance of lithium ions, improving the wetting speed and wetting effect of the electrolyte in the corner area 121 of the electrode 100, and the self-similarity of the fractal structure can disperse the charging and discharging stress and suppress crack propagation. Compared with the crack resistance of straight grooves, the crack resistance is improved, which can improve the powder shedding or cracking of the electrode 100 during the winding process.

[0040] like Figure 1 As shown, in a preferred embodiment, a plurality of second grooves 123 connected to the same first groove 122 are arranged symmetrically about the first groove 122.

[0041] In this embodiment, second grooves 123 are connected to both sides of the first groove 122 to increase the coverage area of ​​the multiple second grooves 123, thereby improving the wetting speed and effect of the electrolyte. The multiple second grooves 123 connected to the opposite sides of the same first groove 122 are symmetrically arranged with the first groove 122 as the axis, which facilitates processing and makes the wetting of the electrolyte more symmetrical and uniform, thereby improving the wetting speed and effect of the electrolyte in the corner area 121 of the electrode 100.

[0042] like Figure 1 As shown, in a preferred embodiment, a plurality of third grooves 124 connected to the same second groove 123 are arranged symmetrically about the second groove 123.

[0043] In this embodiment, third grooves 124 are connected to both sides of the second groove 123 to increase the coverage area of ​​the multiple third grooves 124, thereby improving the wetting speed and effect of the electrolyte. Furthermore, the multiple third grooves 124 connected to the opposite sides of the same second groove 123 are symmetrically arranged with the second groove 123 as the axis, which facilitates processing and makes the wetting of the electrolyte more symmetrical and uniform, further improving the wetting speed and effect of the electrolyte in the corner area 121 of the electrode 100.

[0044] In this application embodiment, the depth of the first groove 122 can be selected in various ways. In a preferred embodiment, the ratio between the depth of the first groove 122 and the thickness of the active material layer 120 is defined as A, where A satisfies: 0.3≤A≤0.7.

[0045] For example, the ratio A between the depth of the first groove 122 and the thickness of the active material layer 120 is 0.3, 0.4, 0.5, 0.6, or 0.7, or falls within the range of any two of the above values. When the ratio A between the depth of the first groove 122 and the thickness of the active material layer 120 is less than 0.3, the volume of the first groove 122 is small, and the amount of electrolyte that can be contained in the first groove 122 is also small, which affects the wetting rate and wetting effect of the electrolyte in the battery. When the ratio between the depth of the first groove 122 and the thickness of the active material layer 120 is greater than 0.7, the volume of the first groove 122 is large, which leads to a lower content of active material in the active material layer 120, affecting the performance of the battery.

[0046] In this application embodiment, the width of the first groove 122 can also be selected in various ways. In a preferred embodiment, the width of the first groove 122 is defined as W, where W satisfies: 40μm≤W≤90μm.

[0047] For example, the width W of the first groove 122 is 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm, or falls within any two of the above values. When the width of the first groove 122 is less than 30 μm, the volume of the first groove 122 is small, and the amount of electrolyte that can be contained in the first groove 122 is also small, which affects the wetting rate and wetting effect of the electrolyte in the battery. When the width of the first groove 122 is greater than 90 μm, the volume of the first groove 122 is large, which leads to a low content of active material in the active material layer 120, thus affecting the performance of the battery.

[0048] In this application embodiment, the first included angle α between the second groove 123 and the first groove 122 can be selected in multiple ways. In a preferred embodiment, the first included angle α between the second groove 123 and the first groove 122 is defined as α, and α satisfies: 30°≤α≤60°.

[0049] For example, the first included angle α is 30°, 45°, or 60°, or falls within the range of any two of the above values. When the first included angle α is less than 30°, the streamline radius of curvature at the connection between the first groove 122 and the second groove 123 becomes too small, causing boundary layer separation and forming a low-pressure dead zone. This, in turn, hinders the flow of the electrolyte, reduces the wetting rate of the electrolyte, and affects the wetting effect. When the first included angle α is greater than 60°, with the horizontal distance between the far end of the second groove 123 and the first groove 122 remaining constant, the larger the first included angle α, the shorter the length of the second groove 123, resulting in a smaller wetting area covered by the second groove 123 and affecting the wetting effect of the electrolyte.

[0050] In this application embodiment, the depth of the second groove 123 can be selected in various ways. In a preferred embodiment, the ratio between the depth of the second groove 123 and the depth of the first groove 122 is defined as B, where B satisfies: 0.3≤B≤0.7.

[0051] For example, the depth ratio B of the second groove 123 to the first groove 122 is 0.3, 0.4, 0.5, 0.6, or 0.7, or falls within the range of any two of the above values. When the depth ratio B of the second groove 123 to the first groove 122 is less than 0.3, the volume of electrolyte that the second groove 123 can accommodate is small, reducing the wetting rate and wetting effect of the electrolyte. When the depth ratio B of the second groove 123 to the first groove 122 is greater than 0.7, the volume of the first groove 122 is large, which leads to a low content of active material in the active material layer 120, thereby affecting the performance of the battery.

[0052] In this embodiment, the width of the second groove 123 can be selected in various ways. In a preferred embodiment, the ratio between the width of the second groove 123 and the width of the first groove 122 is defined as C, where C satisfies: 0.3≤C≤0.7.

[0053] For example, the width ratio C of the second groove 123 to the first groove 122 is 0.3, 0.4, 0.5, 0.6, or 0.7, or falls within the range of any two of the above values. When the width ratio C of the second groove 123 to the first groove 122 is less than 0.3, according to the Hagen-Poiseuille formula, the flow resistance is inversely proportional to the fourth power of the radius. When the width ratio decreases, the flow resistance increases sharply, reducing the actual flow rate of the electrolyte and making it prone to clogging. When the width ratio C is greater than 0.7, it weakens the capillary drive gradient, causing the electrolyte to wet the end of the second groove 123 with delay, affecting the wetting rate and wetting effect of the electrolyte.

[0054] In this application embodiment, the second included angle β between the third groove 124 and the second groove 123 can be selected in multiple ways. In a preferred embodiment, the second included angle β between the third groove 124 and the second groove 123 is defined as β, and β satisfies: 30°≤β≤60°.

[0055] For example, the second included angle β is 30°, 45°, or 60°, or falls within the range of any two of the above values. When the second included angle β is less than 30°, the streamline radius of curvature at the connection between the second groove 123 and the third groove 124 becomes too small, resulting in boundary layer separation and the formation of a low-pressure dead zone. This, in turn, hinders the flow of the electrolyte, reduces the wetting rate of the electrolyte, and affects the wetting effect. When the second included angle β is greater than 60°, with the horizontal distance between the distal end of the third groove 124 and the second groove 123 remaining constant, the larger the second included angle β, the shorter the length of the third groove 124, reducing the wetting area covered by the third groove 124 and affecting the wetting effect of the electrolyte.

[0056] In this application embodiment, the depth of the third groove 124 can be selected in various ways. In a preferred embodiment, the ratio between the depth of the third groove 124 and the depth of the second groove 123 is defined as D, where D satisfies: 0.3≤D≤0.7.

[0057] For example, the depth ratio D of the third groove 124 to the second groove 123 is 0.3, 0.4, 0.5, 0.6, or 0.7, or falls within any two of the above values. When the depth ratio D of the third groove 124 to the second groove 123 is less than 0.3, the volume of electrolyte that the third groove 124 can accommodate is small, reducing the wetting rate and wetting effect of the electrolyte. When the depth ratio D of the third groove 124 to the second groove 123 is greater than 0.7, the volume of the second groove 123 is large, which leads to a low content of active material in the active material layer 120, thereby affecting the performance of the battery.

[0058] In this embodiment, the width of the third groove 124 can be selected in various ways. In a preferred embodiment, the ratio between the width of the third groove 124 and the width of the second groove 123 is defined as E, where E satisfies: 0.3≤E≤0.7.

[0059] For example, the width ratio E of the third groove 124 to the second groove 123 is 0.3, 0.4, 0.5, 0.6, or 0.7, or falls within the range of any two of the above values. When the width ratio E of the third groove 124 to the second groove 123 is less than 0.3, according to the Hagen-Poiseuille formula, the flow resistance is inversely proportional to the fourth power of the radius. When the width ratio decreases, the flow resistance increases sharply, reducing the actual flow rate of the electrolyte and making it prone to clogging. When the width ratio E is greater than 0.7, it weakens the capillary drive gradient, causing a delay in the wetting of the electrolyte at the end of the third groove 124, affecting the wetting rate and wetting effect of the electrolyte.

[0060] Reference Figure 3 , Figure 3 This is a schematic diagram of the structure of the electrode 100 in another embodiment of the present application. In a preferred embodiment, the corner area 121 includes a central area 1211 and two edge areas 1212 located on opposite sides of the central area 1211. The distance between the two first grooves 122 in the central area 1211 is greater than the distance between the two first grooves 122 in the edge areas 1212.

[0061] In this embodiment, the corner area 121 includes a central area 1211 and two edge areas 1212 distributed along the length of the electrode 100. The two edge areas 1212 are located on opposite sides of the central area 1211. During the winding process of the electrode 100 to form a core, the central area 1211 is located at the center of the bend, and the edge areas 1212 are located at the edge of the bend. Correspondingly, the stress on the central area 1211 is greater than the stress on the edge areas 1212. The distance between the two first grooves 122 in the central area 1211 is greater than the distance between the two first grooves 122 in the edge areas 1212. That is, the distribution of the first grooves 122 in the central area 1211 is relatively sparse, so as to reduce the powder shedding and cracking of the central area 1211 during the winding process and improve the product quality of the battery cell assembly.

[0062] Furthermore, please refer to again Figure 3 In a preferred embodiment, the first included angle α between the second groove 123 and the first groove 122 in the central region 1211 is greater than the first included angle α between the second groove 123 and the first groove 122 in the edge region 1212.

[0063] In this embodiment, based on the fact that the distance between the two first grooves 122 in the central region 1211 is greater than the distance between the two first grooves 122 in the edge region 1212, in order to increase the length of the second groove 123 in the central region 1211, the first included angle α between the second groove 123 in the central region 1211 and the first groove 122 should be greater than the first included angle α between the second groove 123 in the edge region 1212 and the first groove 122, thereby increasing the coverage area of ​​the second groove 123 in the central region 1211, improving the wetting effect of the electrolyte, and reducing powder shedding and cracking in the central region 1211 during the winding process.

[0064] This application also provides an electrochemical device, including any device in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy, including, but not limited to, all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0065] This application further proposes an electrochemical device, including an electrode assembly, the electrode assembly including a first electrode, a diaphragm and a second electrode arranged in a stacked and wound manner, the second electrode having the opposite polarity to the first electrode; Wherein, at least one of the first electrode and the second electrode is an electrode 100 as described above.

[0066] This application further proposes an electronic device, including the electrochemical device described above.

[0067] According to some embodiments of this application, electronic devices include, but are not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, and android robots.

[0068] The above description is only a part or preferred embodiment of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. An electrode sheet for being stacked and wound with a diaphragm to form an electrode assembly, characterized in that, The electrode includes: current collector; An active material layer is disposed on one surface of the current collector. After the electrode is wound, the active material layer forms multiple corner areas. At least a portion of the corner areas are provided with at least one first groove, at least one second groove, and at least one third groove. The first groove is disposed along the width direction of the electrode. One end of the second groove is connected to the first groove, and a first angle is formed between the second groove and the first groove. One end of the third groove is connected to the second groove, and a second angle is formed between the third groove and the second groove.

2. The electrode sheet according to claim 1, characterized in that, Multiple second grooves connected to the same first groove are arranged symmetrically about the first groove as an axis.

3. The electrode sheet according to claim 1, characterized in that, The plurality of third grooves connected to the same second groove are arranged symmetrically about the second groove as an axis.

4. The electrode sheet according to claim 1, characterized in that, The ratio A between the depth of the first groove and the thickness of the active material layer satisfies: 0.3 ≤ A ≤ 0.7; and / or, The width of the first groove is W, and W satisfies: 40μm≤W≤90μm.

5. The electrode sheet according to claim 1, characterized in that, The first included angle between the second groove and the first groove is α, where α satisfies: 30°≤α≤60°; and / or, The ratio B between the depth of the second groove and the depth of the first groove satisfies: 0.3 ≤ B ≤ 0.7; and / or, The ratio of the width of the second groove to the width of the first groove is C, where C satisfies: 0.3≤C≤0.

7.

6. The electrode sheet according to claim 1, characterized in that, The second included angle between the third groove and the second groove is β, where β satisfies: 30°≤β≤60°; and / or, The ratio of the depth of the third groove to the depth of the second groove is D, where D satisfies: 0.3 ≤ D ≤ 0.7; and / or, The ratio of the width of the third groove to the width of the second groove is E, and E satisfies: 0.3≤E≤0.

7.

7. The electrode sheet according to any one of claims 1 to 6, characterized in that, The corner area includes a central area and two edge areas located on opposite sides of the central area. The distance between the two first grooves in the central area is greater than the distance between the two first grooves in the edge areas.

8. The electrode sheet according to claim 7, characterized in that, The first included angle between the second groove and the first groove in the central area is greater than the first included angle between the second groove and the first groove in the edge area.

9. An electrochemical device, characterized in that, The device includes an electrode assembly comprising a first electrode, a diaphragm, and a second electrode arranged in a stacked and wound manner, wherein the polarity of the second electrode is opposite to that of the first electrode. Wherein, at least one of the first electrode and the second electrode is an electrode as described in any one of claims 1 to 8.

10. An electronic device, characterized in that, Includes the electrochemical device as described in claim 9.

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