Pole piece, electrode assembly, battery monomer, battery and electric device

Abstract

The utility model discloses a pole piece, an electrode assembly, a battery monomer, a battery and an electric device. The pole piece comprises: a current collector (10) having a plurality of first surfaces (11); the active material layer (20) is arranged on at least one of the plurality of first surfaces (11) and is provided with a second surface (21) far away from one side of the current collector (10); wherein the second surface (21) is provided with at least one concave part (30) which is concave relative to the second surface (21), the sum of the volumes of cavities formed by the at least one concave part (30) is a first volume V1, the material volume of the active substance layer (20) is a second volume V2, and the first volume V1 and the second volume V2 meet the condition that V1: (V1 + V2) = 0.1%-30%.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims priority to the Chinese patent application with application number 202210324931.1 and application date March 30, 2022. The disclosed content of the Chinese patent application is hereby introduced as a whole into this application. Technical Field

[0003] The present disclosure relates to the field of battery technology, and in particular to a pole piece, an electrode assembly, a battery cell, a battery, and an electrical device. Background Art

[0004] Rechargeable battery cells, also known as secondary battery cells, are cells that can be recharged after discharge to activate the active material and continue to be used. Rechargeable battery cells are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric vehicles, electric aircraft, electric boats, electric toy cars, electric toy boats, electric toy planes, and power tools.

[0005] As a key component of a battery cell, the electrode assembly can be formed by winding the positive and negative electrode sheets. However, wound electrode assemblies have issues such as lithium deposition and poor electrolyte wettability, which can affect safety and cycle performance. Summary of the Invention

[0006] In one aspect of the present disclosure, a pole piece is provided, comprising: a current collector having a plurality of first surfaces; and an active material layer, arranged on at least one of the plurality of first surfaces and having a second surface away from the current collector; wherein, at least one recessed portion is provided on the second surface and is recessed relative to the second surface, the sum of the volumes of the cavities formed by the at least one recess is a first volume V1, the material volume of the active material layer is a second volume V2, and the first volume V1 and the second volume V2 satisfy: V1: (V1+V2)=0.1%~30%.

[0007] In this embodiment, at least one recess is provided on the second surface of the active material layer. The recess can store a certain amount of electrolyte. During the cycle, it is not easy for the battery pole piece to squeeze out too much electrolyte and cause lithium deposition. In addition, the recess also reserves expansion buffer space for the expansion of the active material layer itself, so that the expansion force of the area corresponding to the recess is not too large. During the battery charging and discharging process, the recess can also serve as a liquid guide channel to guide the electrolyte backflow. On this basis, by making the sum of the volumes of the cavities formed by the recesses and the volume of the active material layer material meet a specific numerical relationship, the energy loss caused by the recesses on the active material layer can be improved to a certain extent while improving the cycle performance of the battery.

[0008] In some embodiments, the first volume V1 and the second volume V2 satisfy: V1: (V1+V2)=0.5%-5%.

[0009] By making the first volume V1 and the second volume V2 satisfy the preferred range of V1: (V1+V2)=0.5% to 5%, the cycle performance of the battery can be effectively improved while the energy loss caused by the recessed portion on the active material layer can be improved.

[0010] In some embodiments, the first volume V1 and the second volume V2 satisfy: V1: (V1+V2)=0.5%-3%.

[0011] By having the first volume V1 and the second volume V2 satisfy the further preferred range of V1: (V1+V2)=0.5% to 3%, the energy loss caused by the recessed portion on the active material layer can be effectively improved while the cycle performance of the battery is more effectively improved.

[0012] By making the first volume V1 and the second volume V2 satisfy V1: (V1+V2)=0.5% to 5%, the cycle performance of the battery can be effectively improved while the energy loss caused by the concave portion on the active material layer can be improved.

[0013] In some embodiments, an included angle θ between a sidewall of the at least one recess and the second surface is 5° to 175°.

[0014] By setting the side wall of the recess to form an angle of 5° to 175° with the second surface, the processing difficulty and cost of the recess can be reduced while meeting the needs of electrolyte circulation and forming an expansion space.

[0015] In some embodiments, an included angle θ between a sidewall of the at least one recess and the second surface is 30° to 85°.

[0016] By setting the side wall of the recess to form an angle of 30° to 85° with the second surface, the electrolyte circulation needs and the expansion space function can be effectively met, the processing difficulty of the recess can be reduced to a greater extent, the processing cost can be reduced, and the stress concentration on the side wall can be reduced or avoided, thereby reducing the risk of active material falling off during cold pressing of the electrode.

[0017] In some embodiments, the sidewall of the at least one recess comprises a plane, an outer convex arc surface, or an inner concave arc surface.

[0018] By configuring the inclined sidewalls of the recess to include a flat surface or an arc surface, stress concentration on the sidewalls can be more effectively reduced or avoided, thereby reducing the risk of active material falling off during cold pressing of the electrode.

[0019] In some embodiments, a micro-concave-convex structure is provided on a sidewall of the at least one recess or at a junction between the sidewall and the second surface.

[0020] The micro concave-convex structure located on the side wall of the concave portion or at the junction of the side wall and the second surface can help retain the electrolyte, enhance the electrolyte infiltration effect, and improve the electrolyte circulation performance.

[0021] In some embodiments, the sum of the widths of the bottom surface of the at least one recess in the first direction is a first width W1, the width of the active material layer in the first direction is a second width W2, the first direction is a direction perpendicular to the length direction of the current collector and parallel to the first surface, and the first width W1 and the second width W2 satisfy: W1 = 3 μm ~ (2 / 3) * W2.

[0022] By setting the sum of the widths of the recess in the first direction perpendicular to the length direction of the current collector and parallel to the first surface to be no less than 3 μm and no more than 2 / 3 times the width of the active material layer in the first direction, it is possible to ensure that the recess can maintain a certain amount of electrolyte while reducing the impact of the recess on the energy loss of the active material layer.

[0023] In some embodiments, the distance from the bottom surface of the at least one recess to the second surface is a first height H1, the distance from the first surface to the second surface is a second height H2, and the first height H1 and the second height H2 satisfy: H1 = 3 μm ~ H2.

[0024] By ensuring that the distance from the bottom surface of the recess to the second surface is no less than 3 μm, it is ensured that the recess can store a certain amount of electrolyte and achieve a certain expansion buffer space. The maximum distance can reach the distance between the first surface and the second surface, which is equivalent to the bottom surface of the recess exposing or basically exposing the current collector, thereby greatly increasing the electrolyte storage space and expansion buffer space, and improving the battery cycle performance.

[0025] In some embodiments, the at least one recess extends along a second direction, which is a direction parallel to a length direction of the current collector.

[0026] By extending the recess in a second direction parallel to the length direction of the current collector, the layers of the wound structure can circulate the electrolyte between the layers through the channels formed by the recess, thereby improving the cycle performance of the battery.

[0027] In some embodiments, the at least one recess includes two groups of first recesses, and the two groups of first recesses are respectively located at positions of the second surface adjacent to two sides extending along the second direction.

[0028] For some electrode winding structures, such as a square winding structure in which the pole ear is parallel to the winding direction, two groups of first recesses are respectively provided on the two side edges of the second surface, which can improve the electrolyte wetting effect of the winding structure in the upper corner area, provide an electrolyte flow channel in the area, and enable the electrolyte to climb and replenish through the first recess in the area, thereby improving the problems of local lithium deposition and insufficient electrolyte wetting and improving the cycle performance of the battery.

[0029] In some embodiments, the width of the active material layer in the first direction is a second width W2, the first direction is a direction perpendicular to the length direction of the current collector and parallel to the first surface, the minimum distance between the two groups of first recesses and the adjacent sides extending along the second direction is a distance D, and the second width W2 and the distance D satisfy: W2 = 140mm~2000mm, D = 0~50mm.

[0030] For the aforementioned pole piece with two groups of first recesses respectively arranged on the two side edges of the second surface, the width of the active material layer in the first direction is further limited, and the minimum distance between the first recess and the adjacent side edge is limited, so that the first recess can be set according to the actual lithium deposition position, thereby improving the problems of local lithium deposition and insufficient electrolyte infiltration in the battery to a greater extent.

[0031] In some embodiments, the at least one recess includes a group of second recesses, and the group of second recesses is located at a middle position of the second surface in the second direction.

[0032] For some winding structures of electrode sheets, such as cylindrical structures, a group of second recesses are provided in the middle position of the second surface, which can improve the problem of lithium deposition in the middle of the winding structure. The expansion buffer space realized by the second recesses improves the concentration of expansion force in the middle position, and the second recesses reduce the amount of electrolyte squeezed out due to the expansion of the electrode sheet, maintain a certain amount of electrolyte, and serve as a channel to realize the backflow of the electrolyte, thereby improving the cycle performance of the battery.

[0033] In some embodiments, the at least one recess further includes two groups of third recesses, the two groups of third recesses are respectively located on the second surface adjacent to two side edges extending along the second direction, and the group of second recesses is located between the two groups of third recesses.

[0034] In the aforementioned winding structure, for example, a cylindrical structure, if the cylindrical battery formed is tall, there will also be a problem of insufficient electrolyte infiltration at both ends. Therefore, setting two groups of third recesses on the two sides respectively can effectively improve the problems of concentrated expansion force in the middle and at both ends and insufficient electrolyte infiltration, thereby improving the battery cycle performance.

[0035] In some embodiments, the sum of the widths of the bottom surfaces of the group of second recesses and the bottom surfaces of the two groups of third recesses in the first direction is a first width W1, and the width of the active material layer in the first direction is a second width W2. The first direction is a direction perpendicular to the length direction of the current collector and parallel to the first surface, and the first width W1 and the second width W2 satisfy: W2 = 55 mm ~ 2000 mm, W1 = 3 μm ~ (2 / 3) * W2.

[0036] By setting the sum of the widths of the second recess and the third recess to no less than 3 μm and no more than 2 / 3 times the width of the active material layer in the first direction, it is possible to ensure that the recess can maintain a certain amount of electrolyte while reducing the impact of the recess on the energy loss of the active material layer.

[0037] In some embodiments, the second surface includes at least three surface regions divided along the second direction, and the group of second recesses is located in a surface region between two surface regions adjacent to both side ends along the second direction of the at least three surface regions.

[0038] For some winding structures, such as the winding structures of some cylindrical batteries, the expansion force of the middle layer of the electrode after winding is greater than the expansion force of the inner and outer layers. Therefore, the second recess can be set in the surface area other than the two ends of at least three surface areas divided by the second surface along the second direction. By reducing the number of recesses in the surface areas at both ends, the influence of the recesses on the energy loss of the active material layer can be reduced.

[0039] In some embodiments, the at least one recess includes a plurality of recesses arranged at intervals along the first direction.

[0040] For some electrode winding structures, such as a square winding structure in which the electrode tabs are perpendicular to the winding direction, by arranging a plurality of recesses at intervals in the first direction, the winding structure can be improved so that the electrolyte can circulate back between the layers through the channels formed by the plurality of recesses after winding, thereby improving the cycle performance of the battery.

[0041] In some embodiments, the at least one recess includes a plurality of recesses spaced apart along a second direction, the second direction being a direction parallel to the length direction of the current collector, and each recess extends along a first direction, the first direction being a direction perpendicular to the length direction of the current collector and parallel to the first surface.

[0042] For the winding structure of some electrode sheets, such as the square winding structure in which the electrode ears are perpendicular to the winding direction, by arranging multiple recesses at intervals in the second direction, recesses can be set at some positions where the expansion force is more concentrated after winding (such as bending parts, etc.), thereby effectively obtaining expansion buffer space at these positions to eliminate lithium deposition in these parts.

[0043] In some embodiments, the plurality of recesses are located in at least one of a horizontal region and a corner region of a square structure formed by winding the pole piece.

[0044] When the electrode is wound into a square structure, the concentration of expansion force in the horizontal area and the corner area is different. By setting multiple recesses arranged along the second square interval in at least one of the horizontal area and the corner area of ​​the square structure, the liquid storage channel and expansion buffer space realized by the recesses can be used to improve the electrolyte wetting performance of different areas, so that the electrolyte infiltration of various parts of the battery is more balanced, thereby improving the battery performance as a whole.

[0045] In some embodiments, the active material layer is disposed on two opposite first surfaces among the plurality of first surfaces and has two second surfaces respectively located away from the two first surfaces, and the at least one recess is disposed on at least one of the two surfaces.

[0046] For pole pieces with active material layers on opposite sides of the current collector, the recess can be provided in the active material layer on only one side or in the active material layers on both sides. This improves the adaptability of the recess setting, meets the needs of use, and minimizes the impact of the recess on energy loss.

[0047] In some embodiments, the at least one recess includes recesses respectively disposed on the two surfaces, and the recesses respectively disposed on the two second surfaces are symmetrical or asymmetrical with respect to the current collector.

[0048] Active material layers are disposed on opposite first surfaces of the current collector. The recesses can be symmetrically arranged on the active material layers on the two first surfaces, thereby reducing processing difficulty or achieving more balanced expansion forces. Alternatively, the recesses can be asymmetrically arranged on the active material layers on the two first surfaces to better accommodate different winding structures and improve battery performance.

[0049] In some embodiments, the active material layer includes at least two layers, and the at least one recess is formed by an opening of at least a portion of a layer of the at least two layers that is located away from the current collector.

[0050] The recesses can be formed by removing the active material layer or by not coating a specific portion of the active material. Accordingly, the openings can be formed by coating multiple layers of active material, thereby obtaining recesses in a more flexible manner.

[0051] In one aspect of the present disclosure, an electrode assembly is provided, comprising: a negative electrode sheet, a positive electrode sheet, and a separator disposed between the negative electrode sheet and the positive electrode sheet, wherein the negative electrode sheet, the separator, and the positive electrode sheet are wound along a winding direction to form a wound structure, and at least one of the negative electrode sheet and the positive electrode sheet is the aforementioned electrode sheet. An electrode assembly employing the aforementioned electrode sheet has superior performance.

[0052] In some embodiments, the winding structure is a cylindrical structure, a first square structure in which the tabs are parallel to the winding direction, or a second square structure in which the tabs are perpendicular to the winding direction.

[0053] In combination with the aforementioned arrangement of the recesses in different surface areas, a cylindrical structure or a square structure is adaptively adopted to improve battery performance.

[0054] In one aspect of the present disclosure, a battery cell is provided, comprising the aforementioned electrode assembly. The battery cell using the aforementioned electrode assembly has better performance.

[0055] In one aspect of the present disclosure, a battery is provided, comprising the aforementioned battery cell. The battery using the aforementioned battery cell has better performance.

[0056] In one aspect of the present disclosure, an electrical device is provided, comprising the aforementioned battery. The electrical device using the aforementioned battery has better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on the drawings without any creative work.

[0058] The present disclosure can be more clearly understood from the following detailed description with reference to the accompanying drawings, in which:

[0059] Figure 1 is a schematic structural diagram of some embodiments of the electric device according to the present disclosure;

[0060] Figure 2 is a schematic diagram of the exploded structure of some embodiments of the battery according to the present disclosure;

[0061] Figure 3is a schematic structural diagram of a wound structure formed according to some embodiments of the electrode assembly of the present disclosure;

[0062] Figure 4 is a schematic diagram of the exploded structure of other embodiments of the battery according to the present disclosure;

[0063] Figure 5 is a schematic structural diagram of a winding structure formed according to other embodiments of the electrode assembly disclosed herein;

[0064] Figure 6 is a schematic diagram of the three-dimensional structure of some embodiments of the pole piece disclosed herein;

[0065] Figure 7 is a schematic diagram of the cross-sectional structure of some embodiments of the pole piece disclosed herein;

[0066] Figure 8 is a schematic diagram of the volume relationship between the concave portion and the active material layer in some embodiments of the electrode disclosed herein;

[0067] Figures 9A-12 They are schematic cross-sectional views of other embodiments of the pole piece disclosed herein;

[0068] Figure 13A 、 Figure 14A 、 Figure 15A 、 Figure 16A 、 Figure 17A 、 Figure 18A and Figure 19A They are respectively schematic diagrams of the distribution of the concave portions on the second surface of the active material layer in some embodiments of the electrode of the present disclosure;

[0069] Figure 13B 、 Figure 14B 、 Figure 15B 、 Figure 16B 、 Figure 17B 、 Figure 18B and Figure 19B They are Figure 13A 、 Figure 14A 、 Figure 15A 、 Figure 16A 、 Figure 17A 、 Figure 18A and Figure 19A Schematic diagram of the structure of the winding structure formed by the pole pieces shown.

[0070] It should be understood that the size of each part shown in the drawings is not drawn according to the actual proportional relationship.In addition, the same or similar reference numerals represent the same or similar components.

[0071] Description of reference numerals:

[0072] 10: current collector; 100, 100': battery cell; 11: first surface;

[0073] 20: active material layer; 21: second surface; 22: side; 23: end; 24: opening; 20a: first layer; 20b: second layer;

[0074] 30: concave portion; 31: side wall; 32: bottom surface; 33: first concave portion; 34: second concave portion; 35: third concave portion; 36: micro concave-convex structure;

[0075] 41: first square structure; 42: cylindrical structure; 43: second square structure; 44: tab; 4A: negative electrode; 4B: positive electrode; 4C: separator; 40A: horizontal area; 40B: corner area;

[0076] 50: battery; 51: box; 52: end cap; 521: electrode terminal;

[0077] 60: Vehicle. DETAILED DESCRIPTION

[0078] The following detailed description of the embodiments of the present disclosure is provided in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of the present disclosure, but are not intended to limit the scope of the present disclosure, that is, the present disclosure is not limited to the described embodiments.

[0079] In the description of the present disclosure, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present disclosure. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly perpendicular, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0080] The directional words appearing in the following description are all directions shown in the figures and do not limit the specific structure of the present disclosure. In the description of the present disclosure, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances.

[0081] The following describes some embodiments of the present invention in detail with reference to the accompanying drawings. In the absence of conflict, the features of the following embodiments can be combined with each other.

[0082] In some related technologies, the electrode assembly is formed by winding the positive and negative electrode sheets. The inventors have found that the wound electrode assembly expands during the battery charging process, and the expansion force is concentrated in some parts of the winding structure, resulting in a lack of gaps in these parts, which causes the electrolyte to be squeezed out and reduces the wetting performance. These parts are also difficult to achieve electrolyte reflux when the battery is discharged. Some related technologies overcome the problem of concentrated expansion force by injecting different compression densities into different areas of the square winding structure, but this method cannot provide expansion space and a channel to guide the electrolyte reflux, so the effect on lithium plating is limited and affects the cycle performance of the battery.

[0083] In view of this, embodiments of the present disclosure provide a pole piece, an electrode assembly, a battery cell, a battery, and an electrical device, which can improve battery performance.

[0084] The electrode sheet of the embodiment of the present disclosure can be applied to anode electrode sheets, cathode electrode sheets, etc. in various electrode assemblies. The electrode assembly can be a wound structure or a laminated structure, which is not limited in the embodiment of the present application.

[0085] The electrode assembly of the embodiments of the present disclosure can be applied to various types of battery cells. Battery cells can include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., which are not limited in the embodiments of the present disclosure. Battery cells can be cylindrical, flat, rectangular, or other shapes, etc., which are not limited in the embodiments of the present application. Battery cells are generally divided into cylindrical battery cells, square battery cells, and soft-pack battery cells according to the packaging method, which are not limited in the embodiments of the present application.

[0086] The battery cells of the embodiments of the present disclosure are applicable to various types of batteries. The battery can be used to power electrical equipment such as vehicles, for example, to provide power for vehicle operation or driving. The battery may include a housing and a battery module. The housing is used to provide a storage space for the battery module, and the battery module is installed in the housing. The housing can be made of metal. The battery module may include multiple battery cells connected in series, parallel, or mixed. A battery cell is the smallest unit that makes up a battery. A battery cell includes an electrode assembly that can undergo an electrochemical reaction.

[0087] The battery of the embodiment of the present disclosure can be applied to various types of battery-using electrical devices. Electrical devices can be mobile phones, portable devices, laptop computers, battery cars, electric cars, ships, spacecraft, electric toys and electric tools, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecrafts, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc. Electric tools include metal cutting power tools, grinding power tools, assembly power tools and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers. The embodiment of the present invention does not impose any special restrictions on the above-mentioned electrical devices.

[0088] Figure 1 This is a schematic diagram of the structure of some embodiments of the electric device disclosed in the present invention. For convenience, the electric device is described as a vehicle. Figure 1 Vehicle 60 is equipped with a battery 50, located at the bottom, front, or rear of the vehicle. Battery 50 provides power to the vehicle, for example, serving as its operating power source. Battery 50 can be used as a power source for devices such as new energy vehicles, ships, and smart electrical cabinets. Battery 50 can also serve as a power supply, providing the required electrical energy to various electrical components of the device.

[0089] Figure 2 Schematic diagram of the exploded structure of some embodiments of the battery according to the present disclosure. Figure 3 Schematic diagram of a wound structure formed according to some embodiments of the electrode assembly of the present disclosure. Figure 4 Schematic diagrams of the exploded structures of other embodiments of the battery according to the present disclosure. Figure 5 Schematic diagram of a winding structure formed according to other embodiments of the electrode assembly disclosed herein.

[0090] refer to Figure 2 and Figure 4 In some embodiments, the battery 50 includes a housing 51, a cover 52, and one or more battery cells 100 or 100' disposed within the housing 51. The battery cells are electrically connected, such as in series, parallel, or hybrid, to achieve the desired electrical performance parameters of the battery 50. Multiple battery cells are arranged in rows, and one or more rows of battery cells can be arranged within the housing as needed. Electrode terminals 521 can be disposed on the cover 52 to electrically connect to the anode and cathode of the battery cells, respectively.

[0091] In some embodiments, the battery cells of the battery 50 may be arranged along at least one of the length and width of the housing. Depending on actual needs, at least one row or column of battery cells may be provided. Alternatively, one or more layers of battery cells may be provided along the height of the battery 50 as needed.

[0092] In some embodiments, multiple battery cells may be connected in series, parallel, or hybrid to form a battery module, and then the multiple battery modules may be connected in series, parallel, or hybrid to form a whole, and then housed in the box 51. In other embodiments, all battery cells may be directly connected in series, parallel, or hybrid, and then the whole formed by all battery cells may be housed in the box.

[0093] refer to Figure 2-Figure 5 In some embodiments, a battery cell 100 or 100' may include a housing, an end cap, and an electrode assembly. The housing has a cavity for accommodating the electrode assembly, and the ends of the housing may be open for receiving the end cap assembly. The electrode assembly is mounted in the cavity of the housing. In addition to the electrode assembly, end cap, and housing, the battery cell 100 or 100' also includes an electrolyte.

[0094] refer to Figure 3 and Figure 5 In some embodiments, the electrode assembly includes: a first electrode sheet 4A, a second electrode sheet 4B, and a separator 4C disposed between the first electrode sheet 4A and the second electrode sheet 4B. The first electrode sheet 4A, the separator 4C, and the second electrode sheet 4B are wound along a winding direction r to form a wound structure. Figure 3 The winding structure 41 or 43 is pressed into a square structure after winding, which has a central horizontal region 40A and corner regions 40B located on the left and right sides of the horizontal region 40A. Accordingly, the housing used by the battery cell including the electrode assembly is a square shell structure. Figure 5 The winding structure 42 shown forms a cylindrical structure (eg, a hollow cylindrical structure) after winding. Accordingly, the housing used by the battery cell including the electrode assembly is a cylindrical housing structure.

[0095] The battery cell 100 or 100' mainly relies on the movement of metal ions between the positive electrode and the negative electrode to work. The material of the separator 4C can be PP (polypropylene) or PE (polyethylene).

[0096] The positive electrode sheet consists of a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector. The uncoated positive current collector protrudes from the coated positive current collector, and the uncoated positive current collector serves as the positive electrode tab. For lithium-ion batteries, for example, the positive current collector can be made of aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide.

[0097] The negative electrode sheet consists of a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative current collector. The negative current collector uncoated with the negative active material layer protrudes from the negative current collector coated with the negative active material layer. The negative current collector uncoated with the negative active material layer serves as the negative electrode tab. The negative current collector can be made of copper, and the negative active material can be carbon, silicon, or other materials. To ensure that high currents can pass without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together.

[0098] Figure 6 It is a schematic diagram of the three-dimensional structure of some embodiments of the pole piece disclosed in the present invention. Figure 7 Schematic diagram of the cross-sectional structure of some embodiments of the pole piece disclosed herein. Figure 8 Schematic diagram of the volume relationship between the concave portion and the active material layer in some embodiments of the electrode disclosed herein. Figure 6-Figure 8 The present disclosure provides a pole piece, comprising: a current collector 10 and an active material layer 20. The current collector 10 has a plurality of first surfaces 11. The active material layer 20 is disposed on at least one of the plurality of first surfaces 11 and has a second surface 21 away from the current collector 10. At least one recess 30 is provided on the second surface 21, which is recessed relative to the second surface 21.

[0099] At least one recess is provided on the second surface of the active material layer. This recess can store a certain amount of electrolyte, preventing lithium deposition caused by excessive electrolyte extrusion due to expansion of the battery electrode during cycling. Furthermore, the recess provides a buffer for the active material layer itself to expand, minimizing the expansion force in the area corresponding to the recess. Furthermore, during the battery's charge and discharge processes, the recess acts as a channel for electrolyte backflow, thereby improving the battery's cycling performance.

[0100] refer to Figure 8 The sum of the volumes of the cavities formed by the at least one recess 30 is a first volume V1, the material volume of the active material layer 20 is a second volume V2, and the first volume V1 and the second volume V2 satisfy: V1: (V1+V2)=0.1%~30%.

[0101] For example, in Figure 8In the figure, the three areas with oblique cross-section lines correspond to the three recesses. Here, v1, v2, and v3 illustrate the volume of the cavity formed by each of these three recesses. Therefore, the first volume V1 = v1 + v2 + v3. Two of the three recesses are located on the second surface of the active material layer on the upper side of the current collector in the figure, and one recess is located on the second surface of the active material layer on the lower side of the current collector in the figure. The material volume of the upper active material layer is v4, and the material volume of the lower active material layer is v5. Therefore, the second volume V2 = v4 + v5. V1: (V1 + V2) is equivalent to the proportion of the volume of all recesses in the total volume of the active material layer without recesses.

[0102] Because the recesses reduce the amount of material in the active material layer, the higher the volume of the recesses, the higher the energy loss in the active material layer. In this embodiment, the first volume V1 and the second volume V2 are set to satisfy the following: V1: (V1 + V2) = 0.1% to 30%. This improves the battery's cycle performance while also somewhat mitigating the energy loss caused by the recesses in the active material layer.

[0103] In some embodiments, the first volume V1 and the second volume V2 satisfy the following relationship: V1:(V1+V2)=0.5%-5%. Compared to the previous embodiment, this embodiment further limits the maximum value of V1:(V1+V2) to no more than 5%, thereby minimizing energy loss caused by the reduction of the active material layer due to the recess and effectively improving the cycle performance of the battery.

[0104] Furthermore, the first volume V1 and the second volume V2 can preferably satisfy the following ratio: V1: (V1 + V2) = 0.5% to 3%. This preferred range can effectively improve the cycle performance of the battery while effectively reducing the energy loss caused by the concave portion on the active material layer.

[0105] refer to Figure 7 In some embodiments, the angle θ between the sidewall 31 of the at least one recess 30 and the second surface 21 is between 5° and 175°. The sidewalls and bottom of the recess together form a cavity structure that can accommodate electrolyte. An angle between the sidewalls of the recess and the second surface that is too large or too small can affect the function of the recess and its processing difficulty to a certain extent. By setting this angle between 5° and 175°, the processing difficulty and cost of the recess can be reduced while meeting the requirements of electrolyte circulation and forming expansion space.

[0106] In some embodiments, the angle θ between the sidewall 31 of the at least one recess 30 and the second surface 21 is 30° to 85°. By setting the sidewall of the recess at an angle of 30° to 85° with the second surface, the electrolyte circulation requirements and the expansion space can be effectively met, which greatly reduces the processing difficulty and cost of the recess, and reduces or avoids stress concentration on the sidewall, thereby reducing the risk of active material falling off during cold pressing of the electrode.

[0107] refer to Figure 6 and Figure 7 In some embodiments, the sum of the widths of the bottom surface 32 of the at least one recess 30 in a first direction x is a first width W1, and the width of the active material layer 20 in the first direction x is a second width W2. The first direction x is perpendicular to the length direction of the current collector 10 and parallel to the first surface 11, and the first width W1 and the second width W2 satisfy: W1 = 3 μm to (2 / 3) * W2.

[0108] By setting the sum of the widths of the recess in the first direction perpendicular to the length direction of the current collector and parallel to the first surface to be no less than 3 μm and no more than 2 / 3 times the width of the active material layer in the first direction, it is possible to ensure that the recess can maintain a certain amount of electrolyte while reducing the impact of the recess on the energy loss of the active material layer.

[0109] Also refer to Figure 6 and Figure 7 In some embodiments, the distance from the bottom surface 32 of the at least one recess 30 to the second surface 21 is a first height H1, and the distance from the first surface 11 to the second surface 21 is a second height H2. The first height H1 and the second height H2 satisfy: H1 = 3 μm ~ H2.

[0110] By ensuring that the distance from the bottom surface of the recess to the second surface is no less than 3 μm, it is ensured that the recess can store a certain amount of electrolyte and achieve a certain expansion buffer space. The maximum distance can reach the distance between the first surface and the second surface, which is equivalent to the bottom surface of the recess exposing or basically exposing the current collector, thereby greatly increasing the electrolyte storage space and expansion buffer space, and improving the battery cycle performance.

[0111] Figures 9A-12 They are schematic cross-sectional views of other embodiments of the pole piece disclosed herein. Figure 7 and Figures 9A-9C In some embodiments, the sidewall 31 of the at least one recess 30 comprises a flat surface. Figure 10 In some embodiments, the sidewall 31 of the at least one recess 30 comprises an inner concave arc surface. Figure 11In some embodiments, the sidewall 31 of the at least one recess 30 includes an outwardly convex curved surface. In other embodiments, the sidewall of the at least one recess 30 may be a combination of any two or three of a flat surface, an inwardly concave curved surface, and an outwardly convex curved surface, or a combination of flat surfaces at different angles or inwardly concave curved surfaces or outwardly convex curved surfaces of different curvatures. By configuring the inclined sidewalls of the recess to include flat surfaces or curved surfaces, stress concentration on the sidewalls can be more effectively reduced or avoided, thereby reducing the risk of active material falling from the electrode during cold pressing.

[0112] refer to Figure 7-9C The active material layer 20 is provided on two opposite first surfaces 11 among the plurality of first surfaces 11 and has two second surfaces 21 respectively located away from the two first surfaces 11. At least one recess 30 is provided on at least one of the two surfaces 21. For example Figure 9A The concave portion 30 may be provided only on the second surface of the active material layer on one side of the current collector. Figure 7 and Figure 8 , at least one recess 30 includes recesses 30 respectively provided on the two surfaces 21. Figure 7 The recesses 30 respectively provided on the two second surfaces 21 may be symmetrical with respect to the current collector 10 , which helps to reduce the processing difficulty or make the expansion force more balanced.

[0113] refer to Figure 8 In other embodiments, the recesses 30 respectively provided on the two second surfaces 21 may be asymmetric with respect to the current collector, so as to adapt to different winding structures and improve battery performance.

[0114] The recessed portion on the second surface of the active material layer can be formed by laser or chemical etching after the active material layer is formed, or can be formed by other methods. In some embodiments, the active material layer 20 includes at least two layers, and the at least one recessed portion 30 is formed by an opening in at least a portion of the at least two layers on a side away from the current collector 10.

[0115] For example, reference Figure 9B , the active material layer comprises at least two layers, e.g. Figure 9B The first layer 20a and the second layer 20b are formed on the first surface of the current collector 10, and the second layer 20b formed on the surface of the first layer 20a away from the current collector 10 may have an opening 24. The opening 24 and the surface of the first layer 20a exposed from the opening 24 form a recess 30.

[0116] refer to Figure 9CIn some embodiments, the active material layer can be applied without coating the area corresponding to the recess, thereby exposing the current collector at the bottom of the recess. This can greatly increase the electrolyte storage space and expansion buffer space, improving battery cycle performance.

[0117] refer to Figure 12 In some embodiments, a micro-concave-convex structure 36 is provided on the sidewall 31 of the at least one recess 30 or at the intersection of the sidewall 31 and the second surface 21. The depth of the micro-concave-convex structure (e.g., 0.01-0.3 μm) is generally much smaller than the depth of the recess. The micro-concave-convex structure located on the sidewall of the recess or at the intersection of the sidewall and the second surface can help retain the electrolyte, enhance electrolyte wetting, and improve electrolyte circulation performance.

[0118] Figure 13A 、 Figure 14A 、 Figure 15A 、 Figure 16A 、 Figure 17A 、 Figure 18A and Figure 19A They are schematic diagrams of the distribution of the recesses on the second surface of the active material layer in some embodiments of the electrode disclosed herein. Figure 13B 、 Figure 14B 、 Figure 15B 、 Figure 16B 、 Figure 17B 、 Figure 18B and Figure 19B They are Figure 13A 、 Figure 14A 、 Figure 15A 、 Figure 16A 、 Figure 17A 、 Figure 18A and Figure 19A Schematic diagram of the structure of the winding structure formed by the pole pieces shown.

[0119] refer to Figure 13A 、 Figure 14A 、 Figure 15A 、 Figure 16A 、 Figure 17A and Figure 18A In some embodiments, the at least one recess 30 extends along a second direction y, which is parallel to the length of the current collector 10. By extending the recess along the second direction parallel to the length of the current collector, the electrolyte can be circulated and refluxed between the layers of the wound structure through the channels formed by the recess, thereby improving the cycle performance of the battery.

[0120] Different electrode winding structures have different locations where the expansion force is concentrated during charging, and the degree of electrolyte penetration in each location is also different. Therefore, for different electrode winding structures, the present disclosure provides different embodiments to improve the cycle performance of the battery.

[0121] refer to Figure 13A and Figure 13B In some embodiments, the at least one recess 30 includes two groups of first recesses 33, and the two groups of first recesses 33 are respectively located on the second surface 21 adjacent to the two side edges 22 extending along the second direction y. Each group of first recesses here can include one or more elongated first recesses extending along the second direction y.

[0122] Figure 13B yes Figure 13A The pole piece shown is a winding structure formed by winding along the second direction y as at least one of the cathode pole piece and the anode pole piece. This winding structure is a first square structure 41 in which the pole ear 44 is parallel to the winding direction y. The pole ear 44 extends out from the left and right ends of the winding structure respectively. The square battery cell formed by the first square structure 41 is placed vertically along the z-axis, and its left and right sides are bent parts, and the electrolyte infiltration effect is usually poor. By arranging two groups of first recesses on the two side edges respectively, the electrolyte infiltration effect of this winding structure in the upper corner area can be improved, and an electrolyte flow channel in this area is provided, so that the electrolyte can be climbed and replenished through the first recess in this area, thereby improving the problems of local lithium precipitation and insufficient electrolyte infiltration and improving the cycle performance of the battery.

[0123] refer to Figure 7 and Figure 13A In some embodiments, the width of the active material layer 20 in the first direction x is a second width W2, the first direction x is a direction perpendicular to the length direction of the current collector 10 and parallel to the first surface 11, the minimum distance between the two groups of first recesses 33 and the adjacent side edges 22 extending along the second direction y is a distance D, and the second width W2 and the distance D satisfy: W2 = 140 mm ~ 2000 mm, D = 0 ~ 50 mm.

[0124] For the aforementioned pole piece with two groups of first recesses respectively arranged on the two side edges of the second surface, the width range of the active material layer in the first direction is further limited, and the minimum distance between the first recess and the adjacent side edge is limited to 0 to 50 mm, so that the first recess can be set according to the actual lithium deposition position, thereby improving the problems of local lithium deposition and insufficient electrolyte infiltration in the battery to a greater extent.

[0125] refer to Figure 14A and Figure 14B In some embodiments, the at least one recess 30 includes a group of second recesses 34, and the group of second recesses 34 is located in the middle of the second surface 21 in the second direction y. Each group of second recesses here can include one or more elongated second recesses extending along the second direction y.

[0126] Figure 14B yes Figure 14A The pole piece shown is a winding structure formed by winding along the second direction y as at least one of the cathode pole piece and the anode pole piece. This winding structure is a cylindrical structure 42 (for example, a hollow cylindrical structure). The pole lugs 44 extend out from the upper and lower ends of the winding structure respectively. The cylindrical battery cell formed by the cylindrical structure 42 is placed vertically along the z-axis, and the expansion force is relatively concentrated in the middle part of the z-axis direction. When the battery is charged, the electrolyte is easily squeezed out due to expansion, thereby reducing the degree of electrolyte infiltration in this part. By providing a group of second recesses in the middle position of the second surface, the problem of intermediate lithium deposition in this winding structure can be improved, and the expansion buffer space realized by the second recess improves the concentration of expansion force in the middle position, and the electrolyte squeezed out due to the expansion of the pole piece is reduced by the second recess, a certain amount of electrolyte is maintained, and the electrolyte is realized as a channel for reflux, thereby improving the cycle performance of the battery.

[0127] refer to Figure 15A and Figure 15B , compared to Figure 14A and Figure 14B In some embodiments, the at least one recess 30 further includes two groups of third recesses 35, the two groups of third recesses 35 being respectively located on the second surface 21 adjacent to the two side edges 22 extending along the second direction y, and the group of second recesses 34 being located between the two groups of third recesses 35. Each group of third recesses may include one or more elongated third recesses extending along the second direction y.

[0128] Figure 15B yes Figure 15A The electrode sheet shown is a wound structure formed by winding at least one of the cathode electrode sheet and the anode electrode sheet along the second direction y. This wound structure is a cylindrical structure 42 (e.g., a hollow cylindrical structure). The cylindrical battery cell formed by the cylindrical structure 42 is placed vertically along the z-axis. The expansion force is relatively concentrated in the middle of the z-axis. When the cylindrical battery cell is tall, there will also be the problem of insufficient electrolyte infiltration at both ends. Therefore, the two sets of third recesses are respectively arranged on the two sides, which can effectively improve the problems of concentrated expansion force in the middle and at both ends and insufficient electrolyte infiltration, thereby improving the battery's cycle performance.

[0129] refer to Figure 7 and Figure 15AThe sum of the widths of the bottom surfaces 32 of the group of second recesses 34 and the bottom surfaces of the two groups of third recesses 35 in the first direction x is a first width W1, and the width of the active material layer 20 in the first direction x is a second width W2. The first direction x is a direction perpendicular to the length direction of the current collector 10 and parallel to the first surface 11. The first width W1 and the second width W2 satisfy: W2 = 55 mm ~ 2000 mm, W1 = 3 μm ~ (2 / 3) * W2.

[0130] By setting the sum of the widths of the second recess and the third recess to not less than 0.8 mm and not more than 2 / 3 times the width of the active material layer in the first direction, it is possible to ensure that the recess can maintain a certain amount of electrolyte while reducing the impact of the recess on the energy loss of the active material layer.

[0131] refer to Figure 16A and Figure 16B In some embodiments, the second surface 21 includes at least three surface areas divided along the second direction y, and the group of second recesses 34 is located in the surface area between two surface areas adjacent to the two side ends 23 along the second direction y among the at least three surface areas.

[0132] Figure 16B yes Figure 16A The electrode shown is a winding structure formed by winding along the second direction y as at least one of the cathode electrode and the anode electrode. This winding structure is a cylindrical structure 42 (for example, a hollow cylindrical structure). The cylindrical battery cell formed by the cylindrical structure 42 is placed vertically along the z-axis. For the internal hollow cylindrical structure, the internal expansion force is relatively small, and the expansion force of the outer electrode winding layer is also small, so the expansion force is mainly concentrated in the middle electrode winding layer. By setting the second recess in the surface area other than the two ends where the expansion force is relatively concentrated, the recess can be omitted in the surface area at both ends. This not only balances the expansion forces of the inner and outer layers of the winding structure, but also reduces the adverse effects of the energy loss of the active material layer due to the provision of more recesses.

[0133] In other embodiments, the two groups of third recesses 35 may also be located in a surface region between two surface regions adjacent to the two side ends 23 along the second direction y among the at least three surface regions.

[0134] refer to Figure 18A and Figure 18B In some embodiments, the at least one recess 30 includes a plurality of recesses 30 spaced apart along the first direction x. Figure 17A and Figure 17B In other embodiments, the at least one recess may include only one recess 30 provided in the first direction.

[0135] Figure 17B and Figure 18B They are Figure 17A and Figure 18A The electrode sheet shown is a wound structure formed by winding at least one of the cathode electrode sheet and the anode electrode sheet along the second direction y. This wound structure is a second square structure 43 in which the electrode tabs 44 are perpendicular to the winding direction y. The electrode tabs 44 extend from the upper side of the wound structure. The square battery cell formed by the second square structure 43 is placed vertically along the z-axis. By arranging multiple recesses at intervals in the first direction, the winding structure can be improved so that the electrolyte can circulate back between the layers through the channels formed by the multiple recesses after winding, thereby improving the cycle performance of the battery.

[0136] Considering that the expansion force of the second square structure is relatively concentrated at the bent parts on the left and right sides, it is easy to squeeze out the electrolyte due to expansion when the battery is charged, thereby reducing the electrolyte infiltration degree of this part, so reference Figure 19A and Figure 19B In some embodiments, the at least one recess 30 includes a plurality of recesses 30 spaced apart along a second direction y, wherein the second direction y is a direction parallel to the length direction of the current collector 10 , and each recess 30 extends along a first direction x, wherein the first direction x is a direction perpendicular to the length direction of the current collector 10 and parallel to the first surface 11 .

[0137] Figure 19B for Figure 19A The electrode sheet shown is a wound structure formed by winding at least one of the cathode and anode electrodes along a second direction y. This wound structure comprises a second square structure 43, with electrode tabs 44 perpendicular to the winding direction y. The electrode tabs 44 extend from the upper side of the wound structure. Expansion forces are concentrated at the bent ends of this second square structure. By providing recesses in the layers corresponding to these locations, these locations are effectively buffered for expansion, thereby eliminating lithium deposition in these areas.

[0138] refer to Figure 19B and Figure 3 In some embodiments, the plurality of recesses may be located in at least one of the horizontal region 40A and the corner region 40B of the square structure formed by winding the pole piece. Figure 19B In the embodiment, some recesses are located in horizontal region 40A adjacent to corner region 40B. For another example, the recesses can be located entirely in corner region 40B to effectively enhance electrolyte wetting in these corner regions. Alternatively, recesses can be located partially in corner region 40B and partially in horizontal region 40A. This approach can achieve more uniform expansion force across the entire wound structure and reduce processing and winding difficulties.

[0139] The widths of the recesses in different layers of the wound structure can be the same or different. For example, the width of the recesses in each layer of the pole piece corresponding to the corner region 40B increases from the inside to the outside to match the trend of the corner region size gradually increasing from the inside to the outside. The recess can also be appropriately set in the horizontal region 40A near the corner region 40B (for example, at a position 1 to 12 mm away from the dividing line between the corner region and the horizontal region). The inner layers of the pole piece may not be provided with recesses.

[0140] For example, the width of the recesses in each layer of the pole piece corresponding to the corner area 40B is equal, and the recesses located in the outermost layer of the pole piece can basically overlap with the corner area 40. Correspondingly, the recesses in the inner layers of the pole piece will not only cover the corner area 40B but also part of the horizontal area 40A.

[0141] The various embodiments of the above-mentioned electrode sheets can be applied to various types of electrode assemblies. Figure 3 and Figure 5 The present disclosure provides an electrode assembly, including: a negative electrode sheet 4A, a positive electrode sheet 4B and a separator 4C arranged between the negative electrode sheet 4A and the positive electrode sheet 4B. The negative electrode sheet 4A, the separator 4C and the positive electrode sheet 4B are wound along a winding direction to form a winding structure. At least one of the negative electrode sheet 4A and the positive electrode sheet 4B is an embodiment of any of the aforementioned electrode sheets.

[0142] In the above embodiments, the winding structure can be a cylindrical structure 42 (e.g., a hollow cylindrical structure), a first square structure 41 with the tabs parallel to the winding direction, or a second square structure 43 with the tabs perpendicular to the winding direction. Combined with the aforementioned arrangement of recesses in different surface areas, the adaptive use of a cylindrical structure or a square structure can effectively improve battery performance.

[0143] In one aspect of the present disclosure, a battery cell is provided, comprising the aforementioned electrode assembly. The battery cell using the aforementioned electrode assembly has better performance, such as improved battery cycle performance and reduced energy loss.

[0144] In one aspect of the present disclosure, a battery is provided, comprising the aforementioned battery cell. The battery using the aforementioned battery cell has better performance, can improve battery cycle performance, and reduce energy loss.

[0145] In one aspect of the present disclosure, an electrical device is provided, comprising the aforementioned battery. The electrical device using the aforementioned battery has better performance, is more energy-efficient, and has greater reliability.

[0146] While the present disclosure has been described with reference to preferred embodiments, various modifications may be made thereto and equivalent components may be substituted without departing from the scope of the present disclosure. In particular, the various technical features described in the various embodiments may be combined in any manner, provided no structural conflicts exist. The present disclosure is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A pole piece, characterized in that: include: A current collector (10) having a plurality of first surfaces (11); and an active material layer (20) disposed on at least one of the plurality of first surfaces (11) and having a second surface (21) on a side away from the current collector (10); Wherein, at least one recess (30) is provided on the second surface (21), which is recessed relative to the second surface (21) and capable of storing electrolyte, the sum of the volumes of the cavities formed by the at least one recess (30) is a first volume V1, the material volume of the active material layer (20) is a second volume V2, and the first volume V1 and the second volume V2 satisfy: V1: (V1+V2) = 0.1% to 30%.

2. The pole piece according to claim 1, characterized in that: The first volume V1 and the second volume V2 satisfy: V1:(V1+V2)=0.5%-5%.

3. The pole piece according to claim 2, characterized in that: The first volume V1 and the second volume V2 satisfy: V1:(V1+V2)=0.5%-3%.

4. The pole piece according to claim 1, characterized in that: An included angle θ between the side wall (31) of the at least one recess (30) and the second surface (21) is 5° to 175°.

5. The pole piece according to claim 4, characterized in that: An included angle θ between the side wall (31) of the at least one recess (30) and the second surface (21) is 30° to 85°.

6. The pole piece according to claim 5, characterized in that: The side wall (31) of the at least one recess (30) comprises a plane, an outer convex arc surface or an inner concave arc surface.

7. The pole piece according to claim 1, characterized in that: A micro-concave-convex structure (36) is provided on the side wall (31) of the at least one recess (30) or at the junction of the side wall (31) and the second surface (21).

8. The pole piece according to claim 1, characterized in that: The sum of the widths of the bottom surface (32) of the at least one recess (30) in the first direction (x) is a first width W1, and the width of the active material layer (20) in the first direction (x) is a second width W2, the first direction (x) is a direction perpendicular to the length direction of the current collector (10) and parallel to the first surface (11), and the first width W1 and the second width W2 satisfy: W1 = 3 μm ~ (2 / 3) * W2.

9. The pole piece according to claim 1, characterized in that: The distance from the bottom surface (32) of the at least one recess (30) to the second surface (21) is a first height H1, the distance from the first surface (11) to the second surface (21) is a second height H2, and the first height H1 and the second height H2 satisfy: H1 = 3 μm ~ H2.

10. The pole piece according to claim 1, characterized in that: The at least one recess (30) extends along a second direction (y), and the second direction (y) is a direction parallel to the length direction of the current collector (10).

11. The pole piece according to claim 10, characterized in that: The at least one recess (30) includes two groups of first recesses (33), and the two groups of first recesses (33) are respectively located at positions of the second surface (21) adjacent to two side edges (22) extending along the second direction (y).

12. The pole piece according to claim 11, characterized in that: The width of the active material layer (20) in the first direction (x) is a second width W2, the first direction (x) is a direction perpendicular to the length direction of the current collector (10) and parallel to the first surface (11), the minimum distance between the two groups of first recesses (33) and the adjacent side edges (22) extending along the second direction (y) is a distance D, and the second width W2 and the distance D satisfy: W2 = 140 mm to 2000 mm, D = 0 to 50 mm.

13. The pole piece according to claim 10, characterized in that: The at least one recess (30) includes a group of second recesses (34), and the group of second recesses (34) is located at a middle position of the second surface (21) in the second direction (y).

14. The pole piece according to claim 13, characterized in that: The at least one recess (30) further includes two groups of third recesses (35), wherein the two groups of third recesses (35) are respectively located at positions of the second surface (21) adjacent to two side edges (22) extending along the second direction (y), and the group of second recesses (34) is located between the two groups of third recesses (35).

15. The pole piece according to claim 14, characterized in that: The sum of the widths of the bottom surfaces (32) of the group of second recesses (34) and the bottom surfaces of the two groups of third recesses (35) in the first direction (x) is a first width W1, and the width of the active material layer (20) in the first direction (x) is a second width W2, the first direction (x) is a direction perpendicular to the length direction of the current collector (10) and parallel to the first surface (11), and the first width W1 and the second width W2 satisfy: W2 = 55 mm to 2000 mm, W1 = 3 μm to (2 / 3) * W2.

16. The pole piece according to claim 13, characterized in that: The second surface (21) includes at least three surface areas divided along the second direction (y), and the group of second recesses (34) is located in a surface area between two surface areas adjacent to the two side ends (23) along the second direction (y) among the at least three surface areas.

17. The pole piece according to claim 10, characterized in that: The at least one recess (30) includes a plurality of recesses (30) arranged at intervals along a first direction (x).

18. The pole piece according to claim 1, characterized in that: The at least one recess (30) includes a plurality of recesses (30) spaced apart along a second direction (y), wherein the second direction (y) is a direction parallel to the length direction of the current collector (10), and each recess (30) extends along a first direction (x), wherein the first direction (x) is a direction perpendicular to the length direction of the current collector (10) and parallel to the first surface (11).

19. The pole piece according to claim 18, characterized in that: The plurality of recesses are located in at least one of a horizontal region (40A) and a corner region (40B) of the square structure formed by winding the pole piece.

20. The pole piece according to claim 1, characterized in that: The active material layer (20) is provided on two opposite first surfaces (11) among the plurality of first surfaces (11), and has two second surfaces (21) respectively located away from the two first surfaces (11), and the at least one recess (30) is provided on at least one of the two surfaces (21).

21. The pole piece according to claim 20, characterized in that: The at least one recess (30) includes recesses (30) respectively arranged on the two surfaces (21), and the recesses (30) respectively arranged on the two second surfaces (21) are symmetrical or asymmetrical relative to the current collector (10).

22. The pole piece according to claim 1, characterized in that: The active material layer (20) includes at least two layers, and the at least one recess (30) is formed by an opening of at least a portion of the layer on a side away from the current collector (10) among the at least two layers.

23. An electrode assembly, characterized in that include: A negative electrode sheet (4A), a positive electrode sheet (4B) and a separator (4C) arranged between the negative electrode sheet (4A) and the positive electrode sheet (4B), wherein the negative electrode sheet (4A), the separator (4C) and the positive electrode sheet (4B) are wound along a winding direction to form a winding structure, and at least one of the negative electrode sheet (4A) and the positive electrode sheet (4B) is a sheet according to any one of claims 1 to 22.

24. The electrode assembly according to claim 23, wherein The winding structure is a cylindrical structure (42), a first square structure (41) in which the tabs are parallel to the winding direction, or a second square structure (43) in which the tabs are perpendicular to the winding direction.

25. A battery cell, characterized in that: include: The electrode assembly according to claim 23 or 24.

26. A battery, characterized in that: Comprising the battery cell according to claim 25.

27. An electrical device, characterized in that: Including the battery of claim 26.

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