Battery cell and electric equipment

Abstract

The invention provides a battery cell and electric equipment, the battery cell comprises an electrode assembly, the electrode assembly comprises a first pole piece, the first pole piece comprises a first current collector and a first active material layer, and the first active material layer is arranged on at least one side of the first current collector along the thickness direction of the first current collector; wherein a plurality of grooves are formed in the surface, deviating from the first current collector, of at least one first active material layer at intervals, and distances are formed between the grooves and the two ends of the first active material layer in the width direction of the first current collector, so that the risk that the edge area of the first pole piece in the width direction is wrinkled and curled is reduced; therefore, risks of problems of lithium separation, short circuit and the like of the battery cell caused by wrinkling of the first pole piece are reduced, and the safety performance of the battery cell is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and an electrical device. Background Art

[0002] With the rapid development of new energy technologies, battery cells have been widely used in electronic equipment, electric vehicles, electric two-wheeled vehicles, power tools, etc. As the application of battery cells becomes more and more extensive, higher requirements are placed on the safety performance of battery cells. Summary of the invention

[0003] The embodiments of the present application provide a battery cell extraction and power-consuming equipment to improve the safety performance of the battery cell.

[0004] In a first aspect, an embodiment of the present application provides a battery cell, comprising an electrode assembly, the electrode assembly comprising a first electrode sheet, the first electrode sheet comprising a first current collector and a first active material layer, wherein the first active material layer is provided on at least one side of the first current collector along a thickness direction of the first current collector; wherein a plurality of grooves are provided on a surface of at least one first active material layer facing away from the first current collector, and along a width direction of the first current collector, the grooves are spaced from both ends of the first active material layer.

[0005] In one or more of the above optional embodiments, a plurality of grooves are provided at intervals between at least one first active material layer of the first pole piece, which can increase the contact area between the first active material layer and the electrolyte, and is beneficial for the first pole piece to be fully infiltrated by the electrolyte, thereby facilitating the improvement of the cycle performance of the battery cell. Along the width direction of the first current collector, there is a distance between the groove and both ends of the first active material layer, that is, the groove does not extend to both ends of the first active material layer along the width direction of the first current collector. Then, along the width direction of the first current collector, the strength of the edge area of ​​the first pole piece is better, reducing the risk of wrinkling and curling of the edge area of ​​the first pole piece in the width direction, thereby reducing the risk of problems such as lithium deposition and short circuit of the battery cell caused by wrinkling of the first pole piece, and improving the safety performance of the battery cell. Since there is a distance between the groove and both ends of the first active material layer along the width direction of the first current collector, when it is necessary to connect the first pole piece and the isolation membrane, the area between the groove and the end face of the first active material layer in the width direction of the first current collector can provide a connection space for the isolation membrane to be connected to the first pole piece, and can provide a larger connection area for the first active material layer and the isolation membrane, which is convenient for the connection between the first pole piece and the isolation membrane and is beneficial to improving the connection stability between the first pole piece and the isolation membrane, reducing the risk of curling and wrinkling at the edge area of ​​the first pole piece and the edge area of ​​the isolation membrane, thereby reducing the risk of lithium deposition, short circuit and other problems in the battery cell caused by wrinkling and curling of the first pole piece and the isolation membrane, and improving the safety performance of the battery cell.

[0006] In some embodiments of the first aspect of the present application, along the width direction of the first current collector, the minimum distance between any end of the first active material layer and the groove is L1, and 0.05 mm≤L1≤3 mm.

[0007] In one or more optional embodiments above, the minimum distance between any end of the first active material layer in the width direction of the first current collector and the groove is greater than or equal to 0.05 mm, so that the size of the area with better strength in the width direction of the first current collector is larger, reducing the risk of wrinkling in the edge area of ​​the first pole piece in the width direction, thereby reducing the risk of problems such as lithium deposition and short circuit in the battery cell caused by wrinkling of the first pole piece, and improving the safety performance of the battery cell. The minimum distance between any end of the first active material layer in the width direction of the first current collector and the groove is greater than or equal to 0.05 mm. When it is necessary to connect the first pole piece and the isolation membrane, a larger connection area can be provided for the connection between the first active material layer and the isolation membrane, which is convenient for connecting the first pole piece and the isolation membrane and is conducive to improving the connection stability of the first pole piece and the isolation membrane, reducing the risk of curling and wrinkling in the edge area of ​​the first pole piece and the edge area of ​​the isolation membrane, thereby reducing the risk of problems such as lithium deposition and short circuit in the battery cell caused by wrinkling and curling of the first pole piece and the isolation membrane, and improving the safety performance of the battery cell. By making the minimum distance between any end of the first active material layer in the width direction of the first current collector and the groove less than or equal to 3mm, the size of the groove in the width direction of the first current collector is larger, which increases the contact area between the first active material layer and the electrolyte, and is conducive to the first electrode being fully infiltrated by the electrolyte, thereby improving the cycle performance of the battery cell, and also helping the battery cell to have a good capacity retention rate, slowing down the attenuation rate during the use of the battery cell, and extending the service life of the battery cell. Therefore, 0.05mm≤L1≤3mm can not only reduce the risk of wrinkling in the edge area of ​​the first electrode sheet in the width direction, improve the safety performance of the battery cell, but also improve the cycle performance of the battery cell and extend the service life of the battery cell.

[0008] In some embodiments of the first aspect of the present application, 0.1 mm≤L1≤2 mm.

[0009] In one or more optional embodiments above, the minimum distance between any end of the first active material layer in the width direction of the first current collector and the groove is greater than or equal to 0.1 mm, so that the size of the area with better strength of the first pole piece in the width direction of the first current collector is larger, further reducing the risk of wrinkling of the edge area of ​​the first pole piece in the width direction, thereby further reducing the risk of problems such as lithium deposition and short circuit of the battery cell caused by wrinkling of the first pole piece, and improving the safety performance of the battery cell. The minimum distance between any end of the first active material layer in the width direction of the first current collector and the groove is greater than or equal to 0.1 mm. When it is necessary to connect the first pole piece and the isolation membrane, a larger connection area can be provided for the connection of the first active material layer and the isolation membrane, which is convenient for the connection of the first pole piece and the isolation membrane and is conducive to further improving the connection stability of the first pole piece and the isolation membrane, further reducing the risk of curling and wrinkling of the edge area of ​​the first pole piece and the edge area of ​​the isolation membrane, thereby reducing the risk of problems such as lithium deposition and short circuit of the battery cell caused by wrinkling of the first pole piece and the isolation membrane, and improving the safety performance of the battery cell. By making the minimum distance between any end of the first active material layer in the width direction of the first current collector and the groove less than or equal to 2mm, the size of the groove in the width direction of the first current collector is made larger, further increasing the contact area between the first active material layer and the electrolyte, which is conducive to the first pole piece being fully infiltrated by the electrolyte, thereby improving the cycle performance of the battery cell. Therefore, 0.1mm≤L1≤2mm can further reduce the risk of wrinkling the edge area of ​​the first pole piece in the width direction, improve the safety performance of the battery cell, and further improve the cycle performance of the battery cell.

[0010] In some embodiments of the first aspect of the present application, the depth of the groove is less than the thickness of the first active material layer.

[0011] In one or more of the above optional embodiments, the depth of the groove is less than the thickness of the first active material layer, so that the first current collector at the corresponding position of the groove is not exposed, reducing the risk of short circuit of the battery cell and improving the safety performance of the battery cell. The depth of the groove is less than the thickness of the first active material layer, so that the first active material layer is less lost during the groove forming process, less active material waste and cost saving.

[0012] In some embodiments of the first aspect of the present application, the depth of the groove is H, 10 μm≤H≤50 μm.

[0013] In one or more of the above optional embodiments, by the depth of the groove being greater than or equal to 10μm, the depth of the groove is larger, so that the area of ​​the groove wall of the groove is larger, so that the first active material layer and the electrolyte have a larger contact area, which is conducive to the first pole piece being fully infiltrated and improving the cycle performance of the battery cell. By the depth of the groove being less than or equal to 50μm, the loss of active materials during the groove forming process is reduced. If the first pole piece is a positive pole piece, less loss of positive active materials is conducive to improving energy density. If the first pole piece is a negative pole piece, less loss of negative active materials is conducive to reducing the risk of lithium precipitation and improving the safety performance of the battery cell. Therefore, 10μm≤H≤50μm is beneficial to improving the cycle performance of the battery cell and reducing the loss of active materials.

[0014] In some embodiments of the first aspect of the present application, 13 μm≤H≤30 μm.

[0015] In one or more of the above optional embodiments, by the depth of the groove being greater than or equal to 13μm, the depth of the groove is greater, so that the area of ​​the groove wall of the groove is larger, so that the first active material layer and the electrolyte have a larger contact area, which is conducive to the first pole piece being fully infiltrated, and the cycle performance of the battery cell is further improved. By the depth of the groove being less than or equal to 30μm, the loss of active materials during the groove forming process is further reduced. If the first pole piece is a positive pole piece, less loss of positive active materials is conducive to further improving the energy density. If the first pole piece is a negative pole piece, less loss of negative active materials is conducive to further reducing the risk of lithium precipitation and improving the safety performance of the battery cell. Therefore, 13μm≤H≤30μm is not only conducive to further improving the cycle performance of the battery cell, but also can further reduce the loss of active materials.

[0016] In some embodiments of the first aspect of the present application, a width of the groove on a surface of the first active material layer facing away from the first current collector is W, and 50 μm≤W≤100 μm.

[0017] In one or more of the above optional embodiments, the width of the groove on the surface of the first active material layer away from the first current collector is greater than or equal to 50μm, and the groove has a larger width, so that the area of ​​the groove wall of the groove is larger, so that the first active material layer and the electrolyte have a larger contact area, which is conducive to the first pole piece being fully infiltrated, improving the cycle performance of the battery cell, and also making the notch width of the groove larger, which is convenient for the electrolyte to enter the groove. By making the width of the groove on the surface of the first active material layer away from the first current collector less than or equal to 100μm, the loss of active material during the groove forming process is reduced. If the first pole piece is a positive pole piece, less loss of positive active material is conducive to improving energy density. If the first pole piece is a negative pole piece, less loss of negative active material is conducive to reducing the risk of lithium precipitation and improving the safety performance of the battery cell. Therefore, 50μm≤W≤100μm is beneficial to improving the cycle performance of the battery cell and reducing the loss of active material.

[0018] In some embodiments of the first aspect of the present application, 60 μm≤W≤80 μm.

[0019] In one or more optional embodiments above, the width of the groove on the surface of the first active material layer away from the first current collector is greater than or equal to 60μm, and the groove has a larger width, so that the area of ​​the groove wall surface is larger, so that the first active material layer and the electrolyte have a larger contact area, which is conducive to the first pole piece being fully infiltrated and improving the cycle performance of the battery cell. By making the width of the groove on the surface of the first active material layer away from the first current collector less than or equal to 80μm, the loss of active material during the groove forming process is further reduced. If the first pole piece is a positive pole piece, less loss of positive active material is conducive to further improving the energy density. If the first pole piece is a negative pole piece, less loss of negative active material is conducive to further reducing the risk of lithium precipitation and improving the safety performance of the battery cell. Therefore, 60μm≤W≤80μm is conducive to further improving the cycle performance of the battery cell and further reducing the loss of active material.

[0020] In some embodiments of the first aspect of the present application, a distance between adjacent grooves on a surface of the first active material layer facing away from the first current collector is L2, and 1.8 μm≤L2≤4 μm.

[0021] In one or more of the above optional embodiments, the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector is greater than or equal to 1.8μm, so that the distribution of the grooves is not too dense, the number of grooves is reasonable, and the loss of active materials during the groove forming process is reduced. By making the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector less than or equal to 4μm, it is convenient to set a sufficient number of grooves on the first active material layer, so that the contact area between the first active material layer and the electrolyte is large, which is beneficial to the full infiltration of the first pole piece and the battery cell having better cycle performance. Therefore, 1.8μm≤L2≤4μm can not only reduce the loss of active materials during the groove forming process, but also improve the cycle performance of the battery cell.

[0022] In some embodiments of the first aspect of the present application, 2 μm≤L2≤2.5 μm.

[0023] In one or more of the above optional embodiments, the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector is greater than or equal to 2μm, so that the distribution of the grooves is not too dense, the number of grooves is reasonable, and the loss of active materials during the groove forming process is further reduced. By making the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector less than or equal to 2.5μm, it is convenient to set more grooves on the first active material layer, so that the contact area between the first active material layer and the electrolyte is larger, which is beneficial to the full infiltration of the first pole piece and the battery cell having better cycle performance. Therefore, 2μm≤L2≤2.5μm can not only further reduce the loss of active materials during the groove forming process, but also further improve the cycle performance of the battery cell.

[0024] In some embodiments of the first aspect of the present application, the plurality of grooves are arranged at intervals along the length direction of the first current collector.

[0025] In one or more of the above optional embodiments, multiple grooves are spaced apart along the length direction of the first current collector to facilitate uniform distribution of the grooves on the first active material layer, thereby improving the wetting uniformity of the first pole piece and improving the cycle performance of the battery cell.

[0026] In some embodiments of the first aspect of the present application, the plurality of grooves include a first groove and a second groove, and along the width direction of the first current collector, the length of the first groove is greater than the length of the second groove.

[0027] In one or more of the above optional embodiments, along the width direction of the first current collector, the length of the first groove among the multiple grooves is greater than the length of the second groove among the multiple grooves. Compared with the solution in which the lengths of all the grooves are larger, this solution can improve the problem of weakened strength of the first pole piece and large loss of active materials due to the large lengths of all the grooves. Compared with the solution in which the lengths of all the grooves are smaller, this solution can improve the problem of insufficient wetting of the first pole piece due to the smaller lengths of all the grooves, which is beneficial to improving the cycle performance of the battery cell.

[0028] In some embodiments of the first aspect of the present application, the plurality of grooves include a plurality of first grooves and a plurality of second grooves, and the first grooves and the second grooves are alternately arranged along the length direction of the first current collector.

[0029] In one or more of the above optional embodiments, the first grooves and the second grooves are alternately arranged along the length direction of the first current collector, which is beneficial to uniform wetting of the first pole piece, so that the battery cell has higher cycle performance.

[0030] In some embodiments of the first aspect of the present application, the battery cell also includes an isolation membrane and a second pole piece, the first pole piece and the second pole piece have opposite polarities, and the isolation membrane insulates and separates the first pole piece and the second pole piece; along the width direction of the first current collector, the first active material layer includes a middle area and two edge areas, the groove is arranged in the middle area, and along the width direction of the first current collector, the middle area is located between the two edge areas, one edge area is located between one end of the groove and one end surface of the first active material layer, and part of the other edge area is located between the other end of the groove and the other end surface of the first active material layer, and the isolation membrane is bonded to the edge area.

[0031] In one or more of the above optional embodiments, the groove is located in the middle area, and the isolation film is bonded to the edge area, which is conducive to increasing the bonding area between the isolation film and the first pole piece, improving the bonding stability, reducing the risk of wrinkling and curling of the edge area of ​​the isolation film, reducing the risk of the battery cell short circuit due to wrinkling and curling of the isolation film, and improving the safety performance of the battery cell. The isolation film is bonded to the edge area, making bonding more convenient, and can also reduce the risk of the adhesive material covering or filling the groove and reducing the wetting effect.

[0032] In some embodiments of the first aspect of the present application, the first pole piece is a negative pole piece, and along the width direction of the first pole piece, the first pole piece exceeds the edge of the second pole piece.

[0033] In one or more of the above optional embodiments, the first electrode sheet is a negative electrode sheet, and the second electrode sheet is a positive electrode sheet. Along the width direction, the negative electrode sheet exceeds the edge of the positive electrode sheet, which can make the negative electrode sheet have more active substances and prevent lithium precipitation. However, the edge of the negative electrode sheet is longer, and the exceeding part has no corresponding support from the positive electrode sheet on the opposite side, so it is more prone to wrinkling. The solution of the present application can effectively prevent this phenomenon.

[0034] In some embodiments of the first aspect of the present application, when observed along the thickness direction of the first current collector, the groove does not exceed the edge of the second pole piece in the width direction.

[0035] In one or more of the above optional embodiments, by limiting the groove to not exceed the edge of the second pole piece, the risk of wrinkling of the portion of the first pole piece that exceeds the second pole piece is further reduced.

[0036] In some embodiments of the first aspect of the present application, the bonding force between the isolation film and the edge area is F, 4N / m≤F≤8N / m.

[0037] In one or more of the above optional embodiments, the bonding force between the isolation membrane and the edge area is greater than or equal to 4N / m, which is conducive to improving the bonding stability between the isolation membrane and the edge area, reducing the risk of wrinkling and curling of the edge area of ​​the isolation membrane, reducing the risk of short circuit of the battery cell due to wrinkling and curling of the isolation membrane, and improving the safety performance of the battery cell. The bonding force between the isolation membrane and the edge area is less than or equal to 8N / m, which reduces the influence of the bonding between the isolation membrane and the edge area on the wetting of the first pole piece, avoids the problem of poor wetting effect caused by excessive bonding between the isolation membrane and the edge area, and is conducive to the first pole piece being fully wetted, so that the battery cell has better cycle performance. Therefore, 4N / m≤F≤8N / m can improve the bonding stability between the isolation membrane and the first pole piece, reduce the risk of wrinkling and curling of the isolation membrane, reduce the risk of short circuit of the battery cell due to wrinkling and curling of the isolation membrane, improve the safety performance of the battery cell, and be conducive to the first pole piece being fully wetted, so that the battery cell has better cycle performance.

[0038] In some embodiments of the first aspect of the present application, F≥5N / m.

[0039] In one or more of the above optional embodiments, the bonding force between the isolation membrane and the edge area is greater than or equal to 5N / m, thereby further improving the bonding stability between the isolation membrane and the edge area, further reducing the risk of wrinkling and curling in the edge area of ​​the isolation membrane, and further reducing the risk of short circuit of the battery cell due to wrinkling and curling of the isolation membrane, thereby improving the safety performance of the battery cell.

[0040] In some embodiments of the first aspect of the present application, the groove extends along the width direction of the first current collector.

[0041] In one or more of the above optional embodiments, the groove extends along the width direction of the first current collector, and the size of the groove along the width direction of the first current collector is relatively large, which facilitates the manufacturing and molding of the groove.

[0042] In some embodiments of the first aspect of the present application, along the thickness direction of the first current collector, a first active material layer is provided on both sides of the first current collector, and the first active material layer on both sides of the first current collector is provided with a plurality of grooves.

[0043] In one or more of the above optional embodiments, multiple grooves are provided in the first active material layer on both sides of the first current collector, which further increases the contact area between the first pole piece and the electrolyte, so that the first pole piece can be fully wetted, further improving the cycle performance of the battery cell.

[0044] In some embodiments of the first aspect of the present application, the bottom wall and any side wall of the groove are the first active material layer.

[0045] In some embodiments of the first aspect of the present application, the first electrode plate is a negative electrode plate.

[0046] In one or more of the above optional embodiments, the first electrode sheet is a negative electrode sheet, and by providing a plurality of grooves in the active material layer of the negative electrode sheet, and each groove is spaced apart from both ends of the active material layer along the width direction of the first current collector, it is not only beneficial for the negative electrode sheet to be fully infiltrated by the electrolyte, but also can reduce costs. The negative electrode sheet is fully infiltrated by the electrolyte, which is also beneficial for reducing the risk of lithium plating in the battery cell and improving the safety performance of the battery cell.

[0047] In a second aspect, an embodiment of the present application provides an electrical device, and the electrical device includes a battery cell provided by any embodiment of the first aspect.

[0048] In one or more of the above optional embodiments, the battery cell provided in the first aspect embodiment has good safety performance and cycle performance, which is beneficial to improving the power safety and power reliability of electrical equipment powered by the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope.

[0050] Figure 1 A cross-sectional view of a battery cell provided in some embodiments of the present application;

[0051] Figure 2 A schematic structural diagram of a first pole piece in an unfolded state provided in some embodiments of the present application;

[0052] Figure 3 for Figure 2 A1-A1 sectional view;

[0053] Figure 4 A schematic structural diagram of a first pole piece in an unfolded state provided in some other embodiments of the present application;

[0054] Figure 5 for Figure 4 A2-A2 sectional view;

[0055] Figure 6 A schematic structural diagram of a first pole piece in an unfolded state provided in some further embodiments of the present application;

[0056] Figure 7 A schematic diagram of bonding and unfolding a first pole piece and an isolation film provided in some embodiments of the present application;

[0057] Figure 8 for Figure 7 A3-A3 sectional view;

[0058] Fig. 9 A schematic diagram of the structure of a second pole piece in an unfolded state provided in some embodiments of the present application;

[0059] Fig.10 for Fig. 9 A4-A4 cross-sectional view.

[0060] Icon: 100-battery cell; 10-housing; 20-electrode assembly; 21-first pole piece; 211-first current collector; 212-first active material layer; 2121-groove; 2121a-first groove; 2121b-second groove; 21211-first end; 21212-second end; 2122-first end face; 2123-second end face; 213-first pole ear; 22-second pole piece; 221-second current collector; 222-second active material layer; 23-isolation membrane; X-thickness direction of the first current collector; Y-width direction of the first current collector; Z-length direction of the first current collector; X'-thickness direction of the second current collector; Y'-width direction of the second current collector; Z'-length direction of the second current collector; Q1-edge area; Q2-middle area. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0062] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed for protection, but merely represents selected embodiments of the present application. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0063] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0064] In the description of the embodiments of the present application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0065] At present, judging from the development of the market situation, the application of battery cells is becoming more and more extensive. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, as well as electric tools, drones, energy storage equipment and other fields. With the continuous expansion of the application field of battery cells, the market demand is also constantly expanding, and the requirements for battery cell safety are becoming higher and higher.

[0066] In the related art, in order to improve the wetting effect of the pole piece, grooves are usually set in the active material layer of the pole piece. By setting the grooves, the contact area between the active material layer and the electrolyte can be increased, thereby improving the wetting effect of the pole piece. Generally, the grooves run through both ends of the active material layer along the width direction of the pole piece, which reduces the strength of the edge area of ​​the pole piece in the width direction, and the pole piece is prone to wrinkling and curling. In the case where the isolation membrane and the first pole piece need to be connected, the presence of the groove reduces the connection area between the isolation membrane and the pole piece, thereby reducing the connection stability, making the pole piece and the isolation membrane more likely to wrinkle and curl, thereby reducing the safety performance of the battery cell.

[0067] Based on the above considerations, in order to improve the safety performance of the battery cell, an embodiment of the present application provides a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a first electrode sheet, the first electrode sheet includes a first current collector and a first active material layer, and along the thickness direction of the first current collector, the first active material layer is provided on at least one side of the first current collector; wherein, at least one first active material layer is provided with a plurality of grooves on the surface facing away from the first current collector, and along the width direction of the first current collector, the grooves are spaced from both ends of the first active material layer.

[0068] By providing multiple grooves at intervals between at least one first active material layer of the first pole piece, the contact area between the first active material layer and the electrolyte can be increased, which is beneficial for the first pole piece to be fully infiltrated by the electrolyte, thereby facilitating the improvement of the cycle performance of the battery cell. Along the width direction of the first current collector, there is a distance between the groove and both ends of the first active material layer, that is, the groove does not extend to both ends of the first active material layer along the width direction of the first current collector. Then, along the width direction of the first current collector, the strength of the edge area of ​​the first pole piece is better, reducing the risk of wrinkling and curling of the edge area of ​​the first pole piece in the width direction, thereby reducing the risk of problems such as lithium deposition and short circuit of the battery cell caused by wrinkling of the first pole piece, and improving the safety performance of the battery cell.

[0069] The bottom wall and any side wall of the groove are both the first active material layer.

[0070] Since there is a distance between the groove and both ends of the first active material layer along the width direction of the first current collector, when it is necessary to connect the first pole piece and the isolation membrane, the area between the groove and the end face of the first active material layer in the width direction of the first current collector can provide a connection space for the isolation membrane to be connected to the first pole piece, and can provide a larger connection area for the first active material layer and the isolation membrane, which is convenient for the connection between the first pole piece and the isolation membrane and is beneficial to improving the connection stability between the first pole piece and the isolation membrane, reducing the risk of curling and wrinkling at the edge area of ​​the first pole piece and the edge area of ​​the isolation membrane, thereby reducing the risk of lithium deposition, short circuit and other problems in the battery cell caused by wrinkling and curling of the first pole piece and the isolation membrane, and improving the safety performance of the battery cell.

[0071] The battery cell disclosed in the embodiment of the present application can be used in, but not limited to, electric two-wheeled vehicles, electric tools, drones, energy storage devices and other electrical equipment. The battery cell with the working condition of the present application can also be used as a power supply system for electrical equipment, which is conducive to improving the safety performance of the battery cell.

[0072] The embodiment of the present application provides an electric device using a battery cell 100 as a power source, and the electric device may be, but is not limited to, an electronic device, an electric tool, an electric vehicle, an unmanned aerial vehicle, and an energy storage device. Among them, the electronic device may include a mobile phone, a tablet, a laptop computer, etc., the electric tool may include an electric drill, an electric saw, etc., and the electric vehicle may include an electric car, an electric motorcycle, an electric bicycle, etc.

[0073] like Figure 1 As shown, an embodiment of the present application provides a battery cell 100 , which includes a housing 10 and an electrode assembly 20 , wherein the electrode assembly 20 is accommodated in the housing 10 .

[0074] The housing 10 forms a storage space. The storage space can be used to store the electrode assembly 20, electrolyte, etc. The housing 10 can be a hard shell, such as a steel shell or an aluminum shell to form a steel shell battery 100 or an aluminum shell battery. The housing 10 can also be formed of a softer material, such as an aluminum-plastic film or a steel-plastic film to form a soft-pack battery. Figure 1 Schematic diagram showing a case where the battery cell 100 is a soft-pack battery cell.

[0075] The electrode assembly 20 includes a first electrode sheet 21, a second electrode sheet 22 and a separator 23. The first electrode sheet 21 and the second electrode sheet 22 have opposite polarities, that is, one of the first electrode sheet 21 and the second electrode sheet 22 is a positive electrode sheet and the other is a negative electrode sheet. The separator 23 insulates and separates the first electrode sheet 21 and the second electrode sheet 22 to reduce the risk of short circuit of the battery cell 100. The material of the separator 23 may include PP (polypropylene) or PE (polyethylene). In this embodiment, the first electrode sheet 21 is a negative electrode sheet.

[0076] The electrode assembly 20 may be a wound structure, wherein the first pole piece 21, the separator 23, the second pole piece 22 and the other separator 23 are stacked in a certain order and then wound to form the electrode assembly 20 of the wound structure; or, the separator 23, the first pole piece 21, the other separator 23 and the second pole piece 22 are stacked in a certain order and then wound to form the electrode assembly 20 of the wound structure. The wound electrode assembly 20 may be a flat wound electrode assembly 20.

[0077] The electrode assembly 20 may also be a laminated structure, where the first electrode sheet 21 , the isolation membrane 23 , and the second electrode sheet 22 are stacked in a certain order to form a laminated electrode assembly 20 .

[0078] like Figure 2 , Figure 3As shown, the first electrode sheet 21 includes a first current collector 211 and a first active material layer 212 . Along the thickness direction X of the first current collector, the first active material layer 212 is disposed on at least one side of the first current collector 211 .

[0079] The thickness direction X of the first current collector is the thickness direction of the first pole piece 21 , and the thickness direction of the first pole piece 21 is the stacking direction of the first current collector 211 and the first active material layer 212 .

[0080] Along the thickness direction X of the first current collector, the first current collector 211 may be provided with a first active material layer 212 on one side, or the first current collector 211 may be provided with a first active material layer 212 on both sides. In the embodiment where the first pole sheet 21 is a positive pole sheet, the first current collector 211 is a positive current collector, and the first active material layer 212 is a positive active material layer. For lithium-ion batteries, the material of the positive current collector may be aluminum. The positive active material layer may be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The positive current collector may be a composite current collector or a non-composite current collector.

[0081] In the embodiment where the first electrode sheet 21 is a negative electrode sheet, the first current collector 211 is a negative electrode current collector, and the first active material layer 212 is a negative electrode active material layer. For lithium-ion batteries, the negative electrode current collector may be made of copper. The negative electrode active material layer may be made of carbon material or silicon material. The negative electrode current collector may be a composite current collector or a non-composite current collector.

[0082] The first pole piece 21 further includes a first pole ear 213, and along the width direction Y of the first current collector, the first pole ear 213 protrudes from one end of the first current collector 211. The first pole ear 213 and the first current collector 211 can be separately provided and connected, and there can be multiple ways to connect the first pole ear 213 and the first current collector 211, such as welding, conductive adhesive, riveting, etc.

[0083] The first pole tab 213 and the first current collector 211 may be integrally formed, and along the width direction Y of the first current collector, the first pole tab 213 is connected to one end of the first current collector 211. The first pole tab 213 and the first current collector 211 may be formed by die-cutting a substrate. The first pole tab 213 may be a split-type pole tab, or the first pole tab 213 may be a full-pole tab structure. In an embodiment where the first pole tab 213 is a split-type pole tab, the first pole sheet 21 may include a plurality of first pole tabs 213, and the plurality of first pole tabs 213 are spaced apart along the length direction Z of the first current collector. Figure 2 FIG. 2 shows a case where the first electrode tab 213 is a split electrode tab.

[0084] A plurality of grooves 2121 are arranged on a surface of at least one first active material layer 212 away from the first current collector 211 . Along the width direction Y of the first current collector, the grooves 2121 are spaced apart from both ends of the first active material layer 212 .

[0085] The width direction Y of the first current collector is the width direction of the first pole piece 21. In the embodiment in which the electrode assembly 20 is a wound structure, the width direction Y of the first current collector is parallel to the extension direction of the winding axis of the electrode assembly 20. When the first pole piece 21 is in the unfolded state, the thickness direction X of the first current collector, the width direction Y of the first current collector, and the length direction Z of the first current collector are perpendicular to each other.

[0086] In the embodiment where the first active material layer 212 is disposed on both sides of the first current collector 211 , one of the first active material layers 212 may be provided with the groove 2121 , or both of the first active material layers 212 may be provided with the groove 2121 .

[0087] A plurality of grooves 2121 are disposed in the first active material layer 212 at intervals.

[0088] The groove 2121 is recessed from the surface of the first active material layer 212 away from the first current collector 211 toward the direction close to the first current collector 211. The cross-sectional shape of the groove 2121 can be various, for example, the cross-sectional shape of the groove 2121 can be rectangular, trapezoidal, arc-shaped, etc. Figure 3 FIG. 2 shows a case where the cross-section of the groove 2121 is rectangular. Figure 5 The case where the shape of the cross section of the groove 2121 is a trapezoid is shown in FIG. The width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is not less than the width of the groove 2121 at other positions along the thickness direction X of the first current collector. In the embodiment where the shape of the cross section of the groove 2121 is a trapezoid, the long bottom side of the trapezoid is located on the surface of the first active material layer 212 away from the first current collector 211, that is, the width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is greater than the width of the groove 2121 at other positions along the thickness direction X of the first current collector, so that the groove 2121 forms a larger opening on the first active material layer 212, which facilitates the electrolyte to enter the groove 2121.

[0089] Along the width direction Y of the first current collector, each groove 2121 has a distance from both ends of the first active material layer 212. Along the width direction Y of the first current collector, the minimum distances between both ends of the groove 2121 and the end of the first active material layer 212 can be the same or different. Specifically, Figure 2 , Figure 4As shown, along the width direction Y of the first current collector, the groove 2121 has a first end 21211 and a second end 21212 relative to each other, the first active material layer 212 has a first end face 2122 and a second end face 2123 relative to each other, the first end 21211 is closer to the first end face 2122 than the second end face 2123, the second end 21212 is closer to the second end face 2123 than the first end 21211, there is a distance between the first end 21211 and the first end face 2122, there is a distance between the second end 21212 and the second end face 2123, the distance between the first end 21211 and the first end face 2122 and the distance between the second end 21212 and the second end face 2123 may be the same or different.

[0090] The distances between the first end 21211 of each groove 2121 and the first end surface 2122 may be the same or different. The distances between the second end 21212 of each groove 2121 and the second end surface 2123 may be the same or different.

[0091] A plurality of grooves 2121 are arranged at intervals between at least one first active material layer 212 of the first electrode sheet 21, so that the contact area between the first active material layer 212 and the electrolyte can be increased, which is beneficial for the first electrode sheet 21 to be fully infiltrated by the electrolyte, thereby facilitating the improvement of the cycle performance of the battery cell 100. Along the width direction Y of the first current collector, the grooves 2121 are spaced apart from both ends of the first active material layer 212, that is, the grooves 2121 do not extend to both ends of the first active material layer 212 along the width direction Y of the first current collector. Then, along the width direction Y of the first current collector, the strength of the edge region of the first electrode sheet 21 is better, reducing the risk of wrinkling and curling of the edge region of the first electrode sheet 21 in the width direction, thereby reducing the risk of lithium deposition, short circuit and other problems of the battery cell 100 caused by wrinkling of the first electrode sheet 21, and improving the safety performance of the battery cell 100.

[0092] Since there is a distance between the groove 2121 and both ends of the first active material layer 212 along the width direction Y of the first current collector, when it is necessary to connect the first pole piece 21 and the isolation membrane 23, the area between the groove 2121 and the end surface of the first active material layer 212 in the width direction Y of the first current collector can provide a connection space for the isolation membrane 23 to be connected to the first pole piece 21, and can provide a larger connection area for the connection between the first active material layer 212 and the isolation membrane 23, which is convenient for the connection between the first pole piece 21 and the isolation membrane 23 and is beneficial to improving the connection stability between the first pole piece 21 and the isolation membrane 23, reducing the risk of curling and wrinkling of the edge area of ​​the first pole piece 21 and the edge area of ​​the isolation membrane 23, thereby reducing the risk of lithium deposition, short circuit and other problems of the battery cell 100 caused by wrinkling and curling of the first pole piece 21 and the isolation membrane 23, and improving the safety performance of the battery cell 100.

[0093] like Figure 3 , Figure 5 As shown, along the thickness direction X of the first current collector, the first active material layer 212 is disposed on both sides of the first current collector 211 , and the first active material layer 212 on both sides of the first current collector 211 is disposed with a plurality of grooves 2121 .

[0094] The first active material layer 212 on both sides of the first current collector 211 is provided with a plurality of grooves 2121 , which further increases the contact area between the first pole piece 21 and the electrolyte, so that the first pole piece 21 can be fully wetted, further improving the cycle performance of the battery cell 100 .

[0095] like Figure 2 , Figure 4 As shown, in some embodiments, along the width direction Y of the first current collector, the minimum distance between any end of the first active material layer 212 and the groove 2121 is L1, and 0.05 mm≤L1≤3 mm.

[0096] It should be noted that L1 is only a symbol for the minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121, and does not mean that the minimum distance between any end of the first active material layer 212 and any groove 2121 along the width direction Y of the first current collector is the same. It can be understood that along the width direction Y of the first current collector, the minimum distance between any end of the first active material layer 212 and any groove 2121 satisfies 0.05 mm to 3 mm, for example, the minimum distance between the first end 21211 and the first end face 2122 of any groove 2121 satisfies 0.05 mm to 3 mm.

[0097] Illustratively, along the width direction Y of the first current collector, the minimum distance L1 between any end of the first active material layer 212 and the groove 2121 can be 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm, 2.2 mm, 2.5 mm, 2.7 mm, 3 mm, etc.

[0098] By ensuring that the minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121 is greater than or equal to 0.05 mm, the area of ​​the first pole sheet 21 with better strength in the width direction Y of the first current collector is larger, thereby reducing the risk of wrinkling in the edge area of ​​the first pole sheet 21 in the width direction, thereby reducing the risk of lithium deposition, short circuit and other problems in the battery cell 100 caused by wrinkling of the first pole sheet 21, and improving the safety performance of the battery cell 100. The minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121 is greater than or equal to 0.05 mm. When it is necessary to connect the first pole piece 21 and the isolation membrane 23, a larger connection area can be provided for the connection between the first active material layer 212 and the isolation membrane 23, which is convenient for the connection between the first pole piece 21 and the isolation membrane 23 and is beneficial to improving the connection stability between the first pole piece 21 and the isolation membrane 23, reducing the risk of curling and wrinkling of the edge area of ​​the first pole piece 21 and the edge area of ​​the isolation membrane 23, thereby reducing the risk of lithium deposition, short circuit and other problems in the battery cell 100 caused by wrinkling and curling of the first pole piece 21 and the isolation membrane 23, and improving the safety performance of the battery cell 100. The minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121 is less than or equal to 3 mm, so that the size of the groove 2121 in the width direction Y of the first current collector is larger, which increases the contact area between the first active material layer 212 and the electrolyte, which is conducive to the first electrode 21 being fully infiltrated by the electrolyte, thereby improving the cycle performance of the battery cell 100, and also helps the battery cell 100 to have a good capacity retention rate, slow down the attenuation rate of the battery cell 100 during use, and extend the service life of the battery cell 100. Therefore, 0.05mm≤L1≤3mm can reduce the risk of wrinkling in the edge area of ​​the first electrode 21 in the width direction, improve the safety performance of the battery cell 100, and improve the cycle performance of the battery cell 100.

[0099] Furthermore, 0.1mm≤L1≤2mm.

[0100] Illustratively, along the width direction Y of the first current collector, the minimum distance L1 between any end of the first active material layer 212 and the groove 2121 can be 0.1 mm, 0.15 mm, 0.25 mm, 0.35 mm, 0.45 mm, 0.55 mm, 0.65 mm, 0.75 mm, 0.85 mm, 0.95 mm, 1.05 mm, 1.15 mm, 1.25 mm, 1.35 mm, 1.45 mm, 1.55 mm, 1.65 mm, 1.75 mm, 1.85 mm, 1.95 mm, etc.

[0101] By ensuring that the minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121 is greater than or equal to 0.1 mm, the area of ​​the first pole sheet 21 with better strength in the width direction Y of the first current collector is larger, thereby further reducing the risk of wrinkling in the edge area of ​​the first pole sheet 21 in the width direction, thereby further reducing the risk of lithium deposition, short circuit and other problems in the battery cell 100 caused by wrinkling of the first pole sheet 21, and improving the safety performance of the battery cell 100. The minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121 is greater than or equal to 0.1 mm. When it is necessary to connect the first pole piece 21 and the isolation membrane 23, a larger connection area can be provided for the connection between the first active material layer 212 and the isolation membrane 23, which is convenient for the connection between the first pole piece 21 and the isolation membrane 23 and is beneficial to further improve the connection stability between the first pole piece 21 and the isolation membrane 23, further reduce the risk of curling and wrinkling of the edge area of ​​the first pole piece 21 and the edge area of ​​the isolation membrane 23, thereby reducing the risk of lithium deposition, short circuit and other problems in the battery cell 100 caused by wrinkling of the first pole piece 21 and the isolation membrane 23, and improving the safety performance of the battery cell 100. The minimum distance between any end of the first active material layer 212 in the width direction Y of the first current collector and the groove 2121 is less than or equal to 2 mm, so that the size of the groove 2121 in the width direction Y of the first current collector is larger, further increasing the contact area between the first active material layer 212 and the electrolyte, which is conducive to the first electrode sheet 21 being fully infiltrated by the electrolyte, thereby facilitating the improvement of the cycle performance of the battery cell 100. Therefore, 0.1mm≤L1≤2mm can further reduce the risk of wrinkling the edge area of ​​the first electrode sheet 21 in the width direction, improve the safety performance of the battery cell 100, and further improve the cycle performance of the battery cell 100.

[0102] In some embodiments, the depth of the groove 2121 is less than the thickness of the first active material layer 212 .

[0103] The depth of the groove 2121 is the depth of the groove 2121 sunken from the surface of the first active material layer 212 away from the first current collector 211 toward the first current collector 211 , and the bottom wall of the groove 2121 and any side wall of the groove 2121 are the first active material layer 212 .

[0104] The depths of the grooves 2121 may be the same or different.

[0105] Since the depth of the groove 2121 is less than the thickness of the first active material layer 212, the first current collector 211 at the position corresponding to the groove 2121 is not exposed, thereby reducing the risk of short circuit of the battery cell 100 and improving the safety performance of the battery cell 100. Since the depth of the groove 2121 is less than the thickness of the first active material layer 212, the first active material layer 212 is less lost during the molding process of the groove 2121, thereby reducing the waste of active materials and saving costs.

[0106] like Figure 3 , Figure 5 As shown, in some embodiments, the depth of the groove 2121 is H, 10 μm≤H≤50 μm.

[0107] By way of example, the depth H of the groove 2121 may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0108] When the depth of the groove 2121 is greater than or equal to 10 μm, the depth of the groove 2121 is greater, so that the area of ​​the groove wall of the groove 2121 is larger, so that the first active material layer 212 and the electrolyte have a larger contact area, which is conducive to the first pole piece 21 being fully infiltrated and improving the cycle performance of the battery 100. When the depth of the groove 2121 is less than or equal to 50 μm, the loss of active material during the molding process of the groove 2121 is reduced. If the first pole piece 21 is a positive pole piece, less loss of positive active material is conducive to improving energy density. If the first pole piece 21 is a negative pole piece, less loss of negative active material is conducive to reducing the risk of lithium precipitation and improving the safety performance of the battery 100. Therefore, 10 μm ≤ H ≤ 50 μm is conducive to improving the cycle performance of the battery 100 and reducing the loss of active material.

[0109] Further, 13 μm ≤ H ≤ 30 μm.

[0110] For example, H may be 13 μm, 14 μm, 16 μm, 17 μm, 18 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, etc.

[0111] When the depth of the groove 2121 is greater than or equal to 13 μm, the depth of the groove 2121 is greater, so that the area of ​​the groove wall of the groove 2121 is larger, so that the first active material layer 212 and the electrolyte have a larger contact area, which is conducive to the first pole piece 21 being fully infiltrated, and the cycle performance of the battery 100 is further improved. When the depth of the groove 2121 is less than or equal to 30 μm, the loss of active material during the molding process of the groove 2121 is further reduced. If the first pole piece 21 is a positive pole piece, less loss of positive active material is conducive to further improving the energy density. If the first pole piece 21 is a negative pole piece, less loss of negative active material is conducive to further reducing the risk of lithium precipitation and improving the safety performance of the battery 100. Therefore, 13 μm ≤ H ≤ 30 μm is conducive to further improving the cycle performance of the battery 100 and further reducing the loss of active material.

[0112] Villain 2- Figure 5 As shown, in some embodiments, the width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is W, and 50 μm≤W≤100 μm.

[0113] For example, W can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0114] The width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is greater than or equal to 50 μm, and the groove 2121 has a larger width, so that the area of ​​the groove wall of the groove 2121 is larger, so that the first active material layer 212 and the electrolyte have a larger contact area, which is conducive to the first pole piece 21 being fully infiltrated, improving the cycle performance of the battery cell 100, and also making the notch width of the groove 2121 larger, which facilitates the electrolyte to enter the groove 2121. The width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is less than or equal to 100 μm, which reduces the loss of active materials during the formation of the groove 2121. If the first pole piece 21 is a positive pole piece, less loss of positive active materials is conducive to improving energy density. If the first pole piece 21 is a negative pole piece, less loss of negative active materials is conducive to reducing the risk of lithium precipitation and improving the safety performance of the battery cell 100. Therefore, 50 μm ≤ W ≤ 100 μm is beneficial to improving the cycle performance of the battery cell 100 and reducing the loss of active materials.

[0115] Further, 60μm≤W≤80μm.

[0116] For example, W can be 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm, etc.

[0117] When the width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is greater than or equal to 60 μm, the groove 2121 has a larger width, so that the area of ​​the groove wall of the groove 2121 is larger, so that the first active material layer 212 and the electrolyte have a larger contact area, which is conducive to the first pole piece 21 being fully infiltrated and improving the cycle performance of the battery cell 100. When the width of the groove 2121 on the surface of the first active material layer 212 away from the first current collector 211 is less than or equal to 80 μm, the loss of active material during the formation of the groove 2121 is further reduced. If the first pole piece 21 is a positive pole piece, less loss of positive active material is conducive to further improving the energy density. If the first pole piece 21 is a negative pole piece, less loss of negative active material is conducive to further reducing the risk of lithium precipitation and improving the safety performance of the battery cell 100. Therefore, 60 μm≤W≤80 μm is conducive to further improving the cycle performance of the battery cell 100 and further reducing the loss of active material.

[0118] In some embodiments, the distance between adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is L2, and 1.8 μm≤L2≤4 μm.

[0119] L2 may be a minimum distance between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 .

[0120] It should be noted that L2 is only a symbol for the minimum spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211, and does not mean that the minimum spacing between any two adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 is the same. It can be understood that the minimum spacing between any two adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 meets 1.8 μm to 4 μm.

[0121] L2 can be 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, etc.

[0122] By making the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 greater than or equal to 1.8 μm, the distribution of the grooves 2121 is not too dense, the number of grooves 2121 is reasonable, and the loss of active material during the molding process of the grooves 2121 is reduced. By making the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 less than or equal to 4 μm, it is convenient to set a sufficient number of grooves 2121 on the first active material layer 212, so that the contact area between the first active material layer 212 and the electrolyte is large, which is conducive to the full infiltration of the first pole piece 21 and the battery cell 100 having good cycle performance. Therefore, 1.8 μm ≤ L2 ≤ 4 μm can not only reduce the loss of active material during the molding process of the grooves 2121, but also improve the cycle performance of the battery cell 100.

[0123] Furthermore, 2μm≤L2≤2.5μm.

[0124] L2 can be 2μm, 2.1μm, 2.15μm, 2.25μm, 2.3μm, 2.35μm, 2.4μm, 2.45μm, 2.5μm, etc.

[0125] By making the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 greater than or equal to 2μm, the distribution of the grooves 2121 is not too dense, so that the number of grooves 2121 is reasonable, and the loss of active materials in the molding process of the grooves 2121 is further reduced. By making the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 less than or equal to 2.5μm, it is convenient to set more grooves 2121 on the first active material layer 212, so that the contact area between the first active material layer 212 and the electrolyte is larger, which is conducive to the full infiltration of the first pole piece 21 and the battery cell 100 having better cycle performance. Therefore, 2μm≤L2≤2.5μm can not only further reduce the loss of active materials in the molding process of the grooves 2121, but also further improve the cycle performance of the battery cell 100.

[0126] In some embodiments, the plurality of grooves 2121 are spaced apart along the length direction Z of the first current collector.

[0127] L2 is the minimum distance between two adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 .

[0128] By arranging the plurality of grooves 2121 at intervals along the length direction Z of the first current collector, the grooves 2121 are evenly distributed on the first active material layer 212 , thereby improving the wetting uniformity of the first pole piece 21 and improving the cycle performance of the battery cell 100 .

[0129] In other embodiments, some of the plurality of grooves 2121 may be arranged at intervals along the length direction Z of the first current collector, and another portion of the plurality of grooves 2121 may be arranged at intervals along the width direction Y of the first current collector.

[0130] In some embodiments, the groove 2121 extends along the width direction Y of the first current collector.

[0131] The extending direction of the groove 2121 is the direction in which the size of the groove 2121 is the largest, that is, the size of the groove 2121 in the width direction Y of the first current collector is the largest.

[0132] The groove 2121 extends along the width direction Y of the first current collector, so the size of the groove 2121 along the width direction Y of the first current collector is relatively large, which facilitates the manufacturing and molding of the groove 2121.

[0133] Along the width direction Y of the first current collector, the lengths of all the grooves 2121 may be the same, or at least two of the plurality of grooves 2121 may have different lengths, or the lengths of any two of the plurality of grooves 2121 may be different. In some embodiments, Figure 6 As shown, the plurality of grooves 2121 include a first groove 2121 a and a second groove 2121 b , and along the width direction Y of the first current collector, the length of the first groove 2121 a is greater than the length of the second groove 2121 b .

[0134] Each groove 2121 extends along the width direction Y of the first current collector. The length of the first groove 2121a along the width direction Y of the first current collector is greater than the length of the second groove 2121b along the width direction Y of the first current collector, and at least two grooves 2121 among the plurality of grooves 2121 have different lengths.

[0135] Along the width direction Y of the first current collector, the length of the first groove 2121a among the multiple grooves 2121 is greater than the length of the second groove 2121b among the multiple grooves 2121. Compared with the solution in which the lengths of all the grooves 2121 are larger, this solution can improve the problem of weakened strength of the first pole piece 21 and large loss of active materials due to the large lengths of all the grooves 2121. Compared with the solution in which the lengths of all the grooves 2121 are smaller, this solution can improve the problem of insufficient wetting of the first pole piece 21 due to the smaller lengths of all the grooves 2121, which is beneficial to improving the cycle performance of the battery cell 100.

[0136] like Figure 6 As shown, in some embodiments, the plurality of grooves 2121 include a plurality of first grooves 2121 a and a plurality of second grooves 2121 b , and along the length direction Z of the first current collector, the first grooves 2121 a and the second grooves 2121 b are alternately arranged.

[0137] Along the length direction Z of the first current collector, the first grooves 2121a and the second grooves 2121b are alternately arranged, which means that along the length direction Z of the first current collector, a second groove 2121b is arranged between two adjacent first grooves 2121a, and a first groove 2121a is arranged between two adjacent second grooves 2121b.

[0138] Along the length direction Z of the first current collector, the first grooves 2121a and the second grooves 2121b are alternately arranged, which is beneficial for uniform wetting of the first pole piece 21, so that the battery cell 100 has higher cycle performance.

[0139] like Figure 7 , Figure 8 As shown, in some embodiments, the first active material layer 212 includes a middle region Q2 and two edge regions Q1, the groove 2121 is arranged in the middle region Q2, along the width direction Y of the first current collector, the middle region Q2 is located between the two edge regions Q1, one edge region Q1 is located between one end of the groove 2121 and one end surface of the first active material layer 212, and part of the other edge region Q1 is located between the other end of the groove and the other end surface of the first active material layer, and the isolation film 23 is bonded to the edge region Q1.

[0140] Specifically, a portion of one edge region Q1 is located between the first end 21211 of the groove 2121 and the first end face 2122 of the first active material layer 212, and the first end face 2122 and the first end 21211 are respectively two edges of the edge region Q1 in the width direction Y of the first current collector. A portion of another edge region Q1 is located between the second end 21212 of the groove 2121 and the second end face 2123 of the first active material layer 212, and the second end face 2123 and the second end 21212 are respectively two edges of the edge region Q1 in the width direction Y of the first current collector. In this embodiment, the aforementioned L1 may be the size of a portion of the edge region Q1 in the width direction Y of the first current collector.

[0141] The edge region Q1 may be a region of equal width or a region of unequal width.

[0142] In an embodiment where all grooves 2121 have the same size along the width direction Y of the first current collector, the first ends 21211 of all grooves 2121 are flush, and the second ends 21212 of all grooves 2121 are flush, along the length direction Z of the first current collector, the size of the edge region Q1 in the width direction Y of the first current collector is the same at any position along the length direction Z of the first current collector, that is, the edge region Q1 is an equal width region.

[0143] In an embodiment in which the first ends 21211 of at least two grooves 2121 among the multiple grooves 2121 are not flush and the second ends 21212 of at least two second grooves are not flush, along the length direction Z of the first current collector, the size of any edge region Q1 in the width direction Y of the first current collector is different in the length direction Z of the first current collector, that is, the edge region Q1 is a non-uniform width region.

[0144] In other embodiments, the two edge regions Q1 may be regions respectively extending a distance from the two end faces of the first active material layer 212 to the middle region Q2 along the width direction Y of the first current collector, that is, one edge region Q1 is a region extending a distance from the first end face 2122 of the first active material layer 212 along the width direction Y of the first current collector toward the second end face 2123, and the other edge region Q1 is a region extending a distance from the second end face 2123 of the first active material layer 212 along the width direction Y of the first current collector toward the first end face 2122. The size of the edge region Q1 in the width direction Y of the first current collector may be 1% of the size of the first active material layer 212 along the width direction Y of the first current collector.

[0145] The sizes of the two edge regions Q1 along the width direction Y of the first current collector may be the same or different.

[0146] The groove 2121 is located in the middle area Q2, and the isolation film 23 is bonded to the edge area Q1, which is conducive to increasing the bonding area between the isolation film 23 and the first pole piece 21, improving the bonding stability, reducing the risk of wrinkling and curling of the edge area of ​​the isolation film 23, reducing the risk of the battery cell 100 short-circuiting due to wrinkling and curling of the isolation film 23, and improving the safety performance of the battery cell 100. The isolation film 23 is bonded to the edge area Q1, making bonding more convenient, and can also reduce the risk of the adhesive material covering or filling the groove 2121 and reducing the wetting effect.

[0147] In some embodiments, the bonding force between the isolation film 23 and the edge region Q1 is F, 4N / m≤F≤8N / m.

[0148] The bonding force between the isolation film 23 and the edge region Q1 can be tested by the following method:

[0149] Take the finished battery cell 100 after formation, discharge it at a low rate of 0.5C to 3.0V, and then use a sampler to remove the composite of the first electrode piece 21 and the isolation film 23 corresponding to the edge area Q1 after bonding. The composite of the edge area Q1 and the isolation film 23 after bonding is made into a spline with a length and width of 100mm*15mm. Clamp one end of the isolation film 23 to the upper clamp of the high-speed rail tensile machine, and clamp one end of the edge area Q1 of the first electrode piece 21 to the lower clamp of the high-speed rail tensile machine. The stretching speed is 50mm / min. Test 5 times and take the average value. The average value is recorded as the bonding force F, which is the bonding force of the isolation film 23 of a group of edge areas Q1.

[0150] Exemplarily, F may be 4 N / m, 4.5 N / m, 5 N / m, 5.5 N / m, 6 N / m, 6.5 N / m, 7 N / m, 7.5 N / m, 8 N / m, etc.

[0151] The bonding force between the isolating film 23 and the edge region Q1 is greater than or equal to 4 N / m, which is conducive to improving the bonding stability between the isolating film 23 and the edge region Q1, reducing the risk of wrinkling and curling of the edge region Q1 of the isolating film 23, reducing the risk of short circuit of the battery cell 100 due to wrinkling and curling of the isolating film 23, and improving the safety performance of the battery cell 100. The bonding force between the isolating film 23 and the edge region Q1 is less than or equal to 8 N / m, reducing the influence of the bonding between the isolating film 23 and the edge region Q1 on the wetting of the first pole piece 21, avoiding the problem of poor wetting effect caused by excessive bonding between the isolating film 23 and the edge region Q1, which is conducive to the first pole piece 21 being fully wetted, so that the battery cell 100 has better cycle performance. Therefore, 4N / m≤F≤8N / m can improve the bonding stability between the isolation membrane 23 and the first pole piece 21, reduce the risk of wrinkling and curling of the isolation membrane 23, reduce the risk of short circuit of the battery cell 100 due to wrinkling and curling of the isolation membrane 23, and improve the safety performance of the battery cell 100, and can be beneficial to the full wetting of the first pole piece 21, so that the battery cell 100 has better cycle performance.

[0152] Furthermore, F can be 5N / m, 5.2N / m, 5.3N / m, 5.4N / m, 5.8N / m, 6.2N / m, 6.3N / m, 6.6N / m, 6.8N / m, 7N / m, 7.2N / m, 7.6N / m, 7.8N / m, etc.

[0153] By making the bonding force between the isolation film 23 and the edge region Q1 greater than or equal to 5 N / m, the bonding stability between the isolation film 23 and the edge region Q1 is further improved, the risk of wrinkling and curling of the edge region Q1 of the isolation film 23 is further reduced, and the risk of short circuit of the battery cell 100 due to wrinkling and curling of the isolation film 23 is further reduced, thereby improving the safety performance of the battery cell 100. In some embodiments, the first pole piece 21 is a negative pole piece, and along the width direction of the first pole piece 21, the first pole piece 21 exceeds the edge of the second pole piece 22.

[0154] In one or more of the above optional embodiments, the first electrode sheet 21 is a negative electrode sheet, and the second electrode sheet 22 is a positive electrode sheet. Along the width direction, the negative electrode sheet exceeds the edge of the positive electrode sheet, which can make the negative electrode sheet have more active substances and prevent lithium precipitation. However, the edge of the negative electrode sheet is longer, and the exceeding part has no corresponding support from the positive electrode sheet on the opposite side, so it is more prone to wrinkling. The solution of the present application can effectively prevent this phenomenon.

[0155] In some embodiments of the first aspect of the present application, when observed along the thickness direction of the first current collector, the groove 2121 does not exceed the edge of the second pole piece 22 .

[0156] In one or more of the above optional embodiments, by limiting the groove 2121 to not exceed the edge of the second pole piece 22 , the risk of wrinkling of the portion of the first pole piece 21 that exceeds the second pole piece 22 is further reduced.

[0157] The first electrode sheet 21 is a negative electrode sheet. By providing a plurality of grooves 2121 in the active material layer of the negative electrode sheet, and each groove 2121 is spaced from both ends of the active material layer along the width direction Y of the first current collector, it is not only beneficial for the negative electrode sheet to be fully infiltrated by the electrolyte, but also can reduce costs. The negative electrode sheet is fully infiltrated by the electrolyte, which is also beneficial for reducing the risk of lithium deposition in the battery cell 100 and improving the safety performance of the battery cell 100.

[0158] In the electrode assembly 20 , only the first active material layer 212 of the first electrode sheet 21 may be provided with the groove 2121 , or both the first electrode sheet 21 and the second electrode sheet 22 may be provided with the groove 2121 .

[0159] like Fig. 9 , Fig.10 As shown, in some embodiments, the second pole piece 22 includes a second current collector 221 and a second active material layer 222, and the second active material layer 222 is arranged on at least one side of the second current collector 221 along the thickness direction X' of the second current collector; wherein, at least one second active material layer 222 is provided with a plurality of grooves 2121 on the surface away from the second current collector 221, and along the width direction Y' of the second current collector, the grooves 2121 are spaced from both ends of the second active material layer 222.

[0160] The relevant structure of the groove 2121 arranged on the second active material layer 222 can refer to the structure of the groove 2121 arranged on the first active material layer 212, for example, the groove 2121 on the second active material layer 222 can extend along the width direction Y' of the second current collector, and multiple grooves 2121 can be arranged at intervals along the length direction Z' of the second current collector.

[0161] When the second pole piece 22 is in the unfolded state, the thickness direction X′ of the second current collector, the width direction Y′ of the second current collector, and the length direction Z′ of the second current collector are perpendicular to each other.

[0162] A plurality of grooves 2121 are arranged at intervals between at least one second active material layer 222 of the second pole piece 22, which can increase the contact area between the second active material layer 222 and the electrolyte, and is conducive to the second pole piece 22 being fully infiltrated by the electrolyte, thereby facilitating the improvement of the cycle performance of the battery cell 100. Along the width direction Y' of the second current collector, there is a distance between the groove 2121 and both ends of the second active material layer 222, that is, the groove 2121 does not extend to both ends of the second active material layer 222 along the width direction of the second current collector 221, and the strength of the edge region Q1 of the second pole piece 22 along the width direction Y' of the second current collector is good, reducing the risk of wrinkling and curling of the edge region of the second pole piece 22 in the width direction, thereby reducing the risk of lithium deposition, short circuit and other problems of the battery cell 100 caused by the wrinkling of the second pole piece 22, and improving the safety performance of the battery cell 100. Since there is a distance between the groove 2121 and both ends of the second active material layer 222 along the width direction of the second current collector 221, when it is necessary to connect the second pole piece 22 and the isolation membrane 23, the area between the groove 2121 and the end surface of the second active material layer 222 in the width direction of the second current collector 221 can provide a connection space for the isolation membrane 23 to be connected to the second pole piece 22, and can provide a larger connection area for the second active material layer 222 and the isolation membrane 23, which is convenient for the connection between the second pole piece 22 and the isolation membrane 23 and is beneficial to improving the connection stability between the second pole piece 22 and the isolation membrane 23, reducing the risk of curling and wrinkling of the edge area of ​​the second pole piece 22 and the edge area of ​​the isolation membrane 23, thereby reducing the risk of lithium deposition, short circuit and other problems of the battery cell 100 caused by wrinkling and curling of the second pole piece 22 and the isolation membrane 23, and improving the safety performance of the battery cell 100.

[0163] In order to verify the influence of setting a plurality of grooves 2121 in the first active material layer 212 of the first electrode sheet 21 on the cycle performance of the battery cell 100, taking the first electrode sheet 21 as a negative electrode sheet as an example, a cycle interface test is performed on the lithium ion battery cell, and the data in Table 1 are obtained:

[0164] After 500 cycles, the lithium-ion battery cell is charged at 0.7C constant current at 25°C to a voltage of 4.5V, and then charged at 4.5V constant voltage to a current of 0.05C. The battery is then disassembled and the operator observes the cycle interface of the negative electrode plate with the naked eye. If intermittent purple spots, lithium deposition, or lithium deposition on purple spots appear on the surface of the negative electrode plate, it is determined that the negative electrode plate has a slight interface problem; if large-area continuous purple spots, lithium deposition, or lithium deposition on purple spots appear on the main body of the negative electrode plate, it is determined that the negative electrode plate has a serious interface problem. The following table shows the proportion of the interface area.

[0165] The capacity retention rate of the lithium-ion battery after 500 cycles = the discharge capacity after the 500th cycle / the discharge capacity after the first cycle × 100%.

[0166] Table 1

[0167] Example <![CDATA[L1]]> Cycle interface (lithium deposition effect) Capacity retention rate (influence of wetting) Comparative Example 1 0mm 15％ 93％ Example 1 0.03mm 14％ 90％ Example 2 0.05mm 10％ 87％ Example 3 0.1mm 7％ 85％ Example 4 1mm 5％ 84％ Example 5 1.5mm 4％ 83％ Example 6 2mm 4％ 82％ Example 7 3mm 3％ 80％ Example 8 3.1mm 3％ 77％

[0168] As shown in Table 1:

[0169] (I) It can be seen from Comparative Example 1 and Examples 1 to 8 that when L1>0, the area ratio of the purple spots on the negative electrode plate is reduced compared to when L1 is 0. Therefore, along the width direction Y of the first current collector, there is a distance between the groove 2121 and both ends of the first active material layer 212, which can improve the problem of lithium deposition in the battery cell 100.

[0170] (II) It can be seen from Examples 1 to 8 that when L1 is 0.05mm, 0.1mm, 1mm, 1.5mm, 2mm, 3mm, and 3.1mm, the area of ​​the negative electrode sheet with purple spots is significantly reduced compared to when L1 is 0.03mm. Therefore, L1≥0.05mm can effectively improve the problem of lithium deposition in the battery cell 100. When L1 is 3.1mm, the capacity retention rate is significantly reduced compared to when L1 is 0.03mm, 0.05mm, 0.1mm, 1mm, 1.5mm, 2mm, and 3mm. Therefore, L1≤3mm is conducive to slowing down the attenuation rate of the battery cell 100 during use, and is conducive to extending the service life of the battery cell 100. Therefore, 0.05mm≤L1≤3mm can improve the lithium deposition problem of the battery cell 100, improve the safety performance of the battery cell 100, and extend the service life of the battery cell 100.

[0171] (ii) It can be seen from Examples 2 to 7 that when L1 is 0.1mm, 1mm, 1.5mm, 2mm, 3mm, and 3.1mm, the area ratio of the purple spots on the negative electrode plate is further reduced compared to when L1 is 0.05mm. Therefore, L1≥0.1mm can further improve the problem of lithium deposition of the battery cell 100. When L1 is 3mm, there is no obvious change in the capacity retention rate compared to when L1 is 2mm. Therefore, L1≤2mm can slow down the attenuation rate of the battery cell 100 during use, making the battery cell 100 have a longer service life, and reduce the loss of active substances. Therefore, 0.1mm≤L1≤2mm can further improve the problem of lithium deposition of the battery cell 100, improve the safety performance of the battery cell 100, and also prolong the service life of the battery cell 100.

[0172] An embodiment of the present application further provides an electrical device, and the electrical device includes the battery cell 100 provided in any of the above embodiments.

[0173] The battery cell 100 provides electric energy for the operation of the electric device. The battery cell 100 provided in any of the above embodiments has good safety performance and cycle performance, which is beneficial to improving the power safety and power reliability of the electric device powered by the battery cell 100.

[0174] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes.

Claims

1. A battery cell, characterized in that: include: An electrode assembly, comprising a first pole piece, wherein the first pole piece comprises a first current collector and a first active material layer, and along a thickness direction of the first current collector, at least one side of the first current collector is provided with the first active material layer; A plurality of grooves are arranged on a surface of at least one of the first active material layers facing away from the first current collector, and along the width direction of the first current collector, the grooves are spaced apart from both ends of the first active material layer.

2. The battery cell according to claim 1, characterized in that: Along the width direction of the first current collector, a minimum distance between any end of the first active material layer and the groove is L1, and 0.05 mm≤L1≤3 mm.

3. The battery cell according to claim 2, characterized in that: 0.1mm≤L1≤2mm.

4. The battery cell according to claim 1, characterized in that: The depth of the groove is smaller than the thickness of the first active material layer.

5. The battery cell according to claim 4, characterized in that: The depth of the groove is H, 10 μm≤H≤50 μm.

6. The battery cell according to claim 5, characterized in that: 13μm≤H≤30μm.

7. The battery cell according to claim 1, characterized in that: The width of the groove on the surface of the first active material layer facing away from the first current collector is W, and 50 μm≤W≤100 μm.

8. The battery cell according to claim 7, characterized in that: 60μm≤W≤80μm.

9. The battery cell according to any one of claims 1 to 8, characterized in that: The distance between adjacent grooves on the surface of the first active material layer facing away from the first current collector is L2, and 1.8 μm≤L2≤4 μm.

10. The battery cell according to claim 9, characterized in that: 2μm≤L2≤2.5μm.

11. The battery cell according to any one of claims 1 to 8, characterized in that: The plurality of grooves are arranged at intervals along the length direction of the first current collector.

12. The battery cell according to claim 11, characterized in that: The plurality of grooves include a first groove and a second groove, and along a width direction of the first current collector, a length of the first groove is greater than a length of the second groove.

13. The battery cell according to claim 12, characterized in that: The plurality of grooves include a plurality of first grooves and a plurality of second grooves, and along a length direction of the first current collector, the first grooves and the second grooves are alternately arranged.

14. The battery cell according to any one of claims 1 to 8, characterized in that: The battery cell further includes an isolation film and a second pole piece, the first pole piece and the second pole piece have opposite polarities, and the isolation film insulates and separates the first pole piece and the second pole piece; The first active material layer includes a middle area and two edge areas, the groove is arranged in the middle area, the isolation film is bonded to the edge area, and along the width direction of the first current collector, the middle area is located between the two edge areas, a part of one edge area is located between one end of the groove and one end surface of the first active material layer, and a part of the other edge area is located between the other end of the groove and the other end surface of the first active material layer.

15. The battery cell according to claim 14, characterized in that: The first pole piece is a negative pole piece, and along the width direction of the first pole piece, the first pole piece exceeds the edge of the second pole piece.

16. The battery cell according to claim 15, characterized in that: When observed along the thickness direction of the first current collector, the groove does not exceed the edge of the second pole piece in the width direction.

17. The battery cell according to claim 14, characterized in that: The bonding force between the isolation film and the edge area is F, 4N / m≤F≤8N / m.

18. The battery cell according to claim 17, characterized in that: 5N / m≤F.

19. The battery cell according to any one of claims 1 to 8, characterized in that: The groove extends along a width direction of the first current collector.

20. The battery cell according to any one of claims 1 to 8, characterized in that: The first active material layer is disposed on both sides of the first current collector along the thickness direction of the first current collector, and the first active material layer on both sides of the first current collector is disposed with the groove.

21. The battery cell according to any one of claims 1 to 8, characterized in that: The bottom wall and any side wall of the groove are both the first active material layer.

22. An electrical equipment, characterized in that: Comprising a battery cell according to any one of claims 1-21.

Images