Battery cell and electric device

Abstract

A battery cell and an electric device. The battery cell comprises an electrode assembly; the electrode assembly comprises a first electrode sheet; the first electrode sheet comprises a first current collector and a first active material layer; in the 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 provided at intervals on the surface of at least one first active material layer facing away from the first current collector; and in the width direction of the first current collector, each groove is spaced from both ends of the first active material layer, so as to reduce the risk of wrinkling and edge curling in edge regions of the first electrode sheet in the width direction, thereby reducing the risk of the occurrence of problems such as lithium plating and short circuits in the battery cell caused by wrinkling of the first electrode sheet, and improving the safety performance of the battery cell.

Description

Battery cells and electrical equipment

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 2025101207040, filed on January 24, 2025, entitled “Battery Cell and Electrical Equipment”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and more specifically, to a battery cell and an electrical device. Background Technology

[0004] With the rapid development of new energy technologies, battery cells have been widely used in electronic devices, electric vehicles, electric two-wheelers, power tools, and other fields. As the application of battery cells becomes more widespread, higher requirements are being placed on their safety performance. Summary of the Invention

[0005] This application provides a battery cell extraction and power consumption device to improve the safety performance of the battery cell.

[0006] In a first aspect, embodiments of this application provide a battery cell, the battery cell including an electrode assembly, the electrode assembly including a first electrode sheet, the first electrode sheet including a first current collector and a first active material layer, the first active material layer being disposed on at least one side of the first current collector along the thickness direction of the first current collector; wherein, at least one first active material layer is provided with a plurality of grooves spaced apart from the surface of the first current collector, and the grooves are spaced apart from both ends of the first active material layer along the width direction of the first current collector.

[0007] In one or more of the above optional embodiments, multiple grooves are spaced apart on at least one first active material layer of the first electrode, which increases the contact area between the first active material layer and the electrolyte, facilitating the full wetting of the first electrode by the electrolyte and thus improving the cycle performance of the battery cell. Along the width direction of the first current collector, the grooves are spaced apart from both ends of the first active material layer, meaning the grooves do not extend to both ends of the first active material layer along the width direction of the first current collector. This results in better strength at the edge region of the first electrode along the width direction, reducing the risk of wrinkling or curling at the edge region of the first electrode in the width direction. This reduces the risk of lithium plating or short circuits caused by wrinkling of the first electrode, thereby 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 electrode and the separator, the area between the end faces of the groove and the first active material layer in the width direction of the first current collector can provide a connection space for the separator to be connected to the first electrode. This provides a larger connection area for the connection of the first active material layer and the separator, which facilitates the connection of the first electrode and the separator and helps to improve the connection stability of the first electrode and the separator. It also reduces the risk of curling and wrinkling at the edges of the first electrode and the separator, thereby reducing the risk of lithium plating and short circuits in the cell caused by wrinkling and curling of the first electrode and the separator, and improving the safety performance of the cell.

[0008] In some embodiments of the first aspect of this 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, where 0.05mm≤L1≤3mm.

[0009] In one or more of the above optional embodiments, by ensuring that 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, the area of ​​the first electrode sheet with good strength in the width direction of the first current collector is larger, reducing the risk of wrinkling at the edge of the first electrode sheet in the width direction. This reduces the risk of lithium plating, short circuits, and other problems caused by wrinkling of the first electrode sheet, thereby improving the safety performance of the battery cell. Furthermore, a minimum distance of 0.05 mm between any end of the first active material layer in the width direction of the first current collector and the groove provides a larger connection area for connecting the first active material layer and the separator when connection between the first electrode sheet and the separator is required. This facilitates the connection between the first electrode sheet and the separator and improves the connection stability, reducing the risk of curling and wrinkling at the edges of the first electrode sheet and the separator. This further reduces the risk of lithium plating, short circuits, and other problems caused by wrinkling and curling of the first electrode sheet and the separator, thereby improving the safety performance of the battery cell. By ensuring that the minimum distance between the first active material layer and the groove at any end of the first current collector in the width direction is less than or equal to 3 mm, the groove has a larger dimension in the width direction of the first current collector. This increases the contact area between the first active material layer and the electrolyte, facilitating the full wetting of the first electrode by the electrolyte. This, in turn, improves the cell's cycle performance, enhances capacity retention, slows down the rate of cell degradation during use, and extends the cell's lifespan. Therefore, a distance of 0.05 mm ≤ L1 ≤ 3 mm reduces the risk of wrinkling at the edge of the first electrode in the width direction, improving the cell's safety performance, cycle performance, and lifespan.

[0010] In some embodiments of the first aspect of this application, 0.1mm ≤ L1 ≤ 2mm.

[0011] In one or more of the above optional embodiments, by ensuring that 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, the size of the area with better strength of the first electrode in the width direction of the first current collector is larger, further reducing the risk of wrinkling of the edge area of ​​the first electrode in the width direction. This further reduces the risk of lithium plating, short circuits, and other problems caused by wrinkling of the first electrode, thus 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 electrode and the separator, this also provides a larger connection area for the connection of the first active material layer and the separator, facilitating the connection between the first electrode and the separator and further improving the connection stability between the first electrode and the separator. This further reduces the risk of curling and wrinkling in the edge areas of the first electrode and the separator, thereby reducing the risk of lithium plating, short circuits, and other problems caused by wrinkling of the first electrode and the separator, and improving the safety performance of the battery cell. By ensuring that the minimum distance between the first active material layer and the groove at any end of the first current collector in the width direction is less than or equal to 2 mm, the groove is made larger in the width direction of the first current collector. This further increases the contact area between the first active material layer and the electrolyte, which is beneficial for the first electrode to be fully wetted by the electrolyte, thereby improving the cycle performance of the battery cell. Therefore, 0.1 mm ≤ L1 ≤ 2 mm can further reduce the risk of wrinkling of the first electrode in the edge area in the width direction, improving the safety performance of the battery cell, and further improving the cycle performance of the battery cell.

[0012] In some embodiments of the first aspect of this application, the depth of the groove is less than the thickness of the first active material layer.

[0013] In one or more of the above optional embodiments, by making the depth of the groove less than the thickness of the first active material layer, the first current collector at the corresponding position of the groove is not exposed, reducing the risk of short circuit in the battery cell and improving the safety performance of the battery cell. By making the depth of the groove less than the thickness of the first active material layer, less loss of the first active material layer is achieved during the groove forming process, resulting in less waste of active material and cost savings.

[0014] In some embodiments of the first aspect of this application, the depth of the groove is H, where 10 μm ≤ H ≤ 50 μm.

[0015] In one or more of the above optional embodiments, a groove depth greater than or equal to 10 μm results in a larger groove wall area, providing a larger contact area between the first active material layer and the electrolyte. This facilitates thorough wetting of the first electrode and improves the cycle performance of the battery cell. A groove depth less than or equal to 50 μm reduces active material loss during groove formation. If the first electrode is a positive electrode, less loss of positive active material is beneficial for increasing energy density; if the first electrode is a negative electrode, less loss of negative active material is beneficial for reducing the risk of lithium plating and improving the safety performance of the battery cell. Therefore, 10 μm ≤ H ≤ 50 μm is beneficial for both improving the cycle performance of the battery cell and reducing active material loss.

[0016] In some embodiments of the first aspect of this application, 13μm≤H≤30μm.

[0017] In one or more of the above optional embodiments, a groove depth greater than or equal to 13 μm results in a larger groove wall area, providing a greater contact area between the first active material layer and the electrolyte. This facilitates thorough wetting of the first electrode and further improves the cycle performance of the battery cell. A groove depth less than or equal to 30 μm further reduces active material loss during groove formation. If the first electrode is a positive electrode, less loss of positive active material is beneficial for further increasing energy density; if the first electrode is a negative electrode, less loss of negative active material is beneficial for further reducing the risk of lithium plating and improving the safety performance of the battery cell. Therefore, 13 μm ≤ H ≤ 30 μm is beneficial for both further improving the cycle performance of the battery cell and further reducing active material loss.

[0018] In some embodiments of the first aspect of this application, the width of the groove on the surface of the first active material layer away from the first current collector is W, 50 μm ≤ W ≤ 100 μm.

[0019] In one or more of the above optional embodiments, if 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 50 μm, the groove has a larger width, resulting in a larger area of ​​the groove wall surface. This provides a larger contact area between the first active material layer and the electrolyte, which is beneficial for the first electrode to be fully wetted, improving the cycle performance of the cell. It also makes the groove opening wider, facilitating the entry of the electrolyte. If the width of the groove on the surface of the first active material layer away from the first current collector is less than or equal to 100 μm, the loss of active material during groove formation is reduced. If the first electrode is a positive electrode, less loss of positive active material is beneficial for improving energy density; if the first electrode is a negative electrode, less loss of negative active material is beneficial for reducing the risk of lithium plating and improving the safety performance of the cell. Therefore, 50 μm ≤ W ≤ 100 μm is beneficial for both improving the cycle performance of the cell and reducing active material loss.

[0020] In some embodiments of the first aspect of this application, 60μm≤W≤80μm.

[0021] In one or more of the above optional embodiments, if 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 60 μm, the groove has a larger width, resulting in a larger area of ​​the groove wall surface and a larger contact area between the first active material layer and the electrolyte. This facilitates the full wetting of the first electrode and improves the cycle performance of the battery cell. If the width of the groove on the surface of the first active material layer away from the first current collector is less than or equal to 80 μm, the loss of active material during the groove forming process is further reduced. If the first electrode is a positive electrode, less loss of positive active material is beneficial for further improving energy density; if the first electrode is a negative electrode, less loss of negative active material is beneficial for further reducing the risk of lithium plating and improving the safety performance of the battery cell. Therefore, 60 μm ≤ W ≤ 80 μm is beneficial for both further improving the cycle performance of the battery cell and further reducing the loss of active material.

[0022] In some embodiments of the first aspect of this application, the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector is L2, where 1.8 μm ≤ L2 ≤ 4 μm.

[0023] In one or more of the above optional embodiments, by ensuring that 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 1.8 μm, the distribution of grooves is not too dense, ensuring a reasonable number of grooves and reducing active material loss during the groove forming process. By ensuring that the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector is less than or equal to 4 μm, it is easier to set a sufficient number of grooves on the first active material layer, resulting in a larger contact area between the first active material layer and the electrolyte. This is beneficial for the first electrode to be fully wetted, which in turn benefits the cell to have better cycle performance. Therefore, 1.8 μm ≤ L2 ≤ 4 μm can both reduce active material loss during the groove forming process and improve the cycle performance of the cell.

[0024] In some embodiments of the first aspect of this application, 2μm≤L2≤2.5μm.

[0025] In one or more of the above optional embodiments, by ensuring that 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 2 μm, the distribution of grooves is not too dense, ensuring a reasonable number of grooves and further reducing active material loss during the groove forming process. By ensuring that the spacing between adjacent grooves on the surface of the first active material layer away from the first current collector is less than or equal to 2.5 μm, it is easier to set more grooves on the first active material layer, resulting in a larger contact area between the first active material layer and the electrolyte, which is beneficial for the first electrode to be fully wetted and for the cell to have better cycle performance. Therefore, 2 μm ≤ L2 ≤ 2.5 μm can further reduce active material loss during the groove forming process and further improve the cycle performance of the cell.

[0026] In some embodiments of the first aspect of this application, a plurality of grooves are spaced apart along the length direction of the first current collector.

[0027] In one or more of the above optional embodiments, multiple grooves are spaced apart along the length direction of the first current collector, which facilitates the uniform distribution of the grooves on the first active material layer, improves the wetting uniformity of the first electrode, and thus improves the cycle performance of the battery cell.

[0028] In some embodiments of the first aspect of this application, the plurality of grooves includes a first groove and a second groove, wherein the length of the first groove is greater than the length of the second groove along the width direction of the first current collector.

[0029] 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 plurality of grooves is greater than the length of the second groove among the plurality of grooves. Compared with the scheme in which the length of all grooves is large, this scheme can improve the problem of weakened strength of the first electrode and greater loss of active material caused by the large length of all grooves. Compared with the scheme in which the length of all grooves is small, this scheme can improve the problem of insufficient wetting of the first electrode caused by the small length of all grooves, which is beneficial to improving the cycle performance of the battery cell.

[0030] In some embodiments of the first aspect of this application, the plurality of grooves includes a plurality of first grooves and a plurality of second grooves, and the first grooves and second grooves are alternately arranged along the length direction of the first current collector.

[0031] In one or more of the above optional embodiments, the first groove and the second groove are alternately arranged along the length direction of the first current collector, which is conducive to uniform wetting of the first electrode sheet, so that the cell has high cycle performance.

[0032] In some embodiments of the first aspect of this application, the battery cell further includes a separator and a second electrode, the first electrode and the second electrode having opposite polarities, and the separator insulatingly separating the first electrode and the second electrode; along the width direction of the first current collector, the first active material layer includes a central region and two edge regions, a groove is disposed in the central region, and along the width direction of the first current collector, the central region is located between the two edge regions, one edge region is located between one end of the groove and one end face of the first active material layer, and a portion of the other edge region is located between the other end of the groove and the other end face of the first active material layer, and the separator is bonded to the edge regions.

[0033] In one or more of the above optional embodiments, by positioning the groove in the middle region and bonding the separator to the edge region, it is beneficial to increase the bonding area between the separator and the first electrode, improve bonding stability, reduce the risk of wrinkling or curling at the edge region of the separator, reduce the risk of short circuit in the battery cell due to wrinkling or curling of the separator, and improve the safety performance of the battery cell. Bonding the separator to the edge region makes bonding more convenient and also reduces the risk of the adhesive material covering or filling the groove, thus reducing the wetting effect.

[0034] In some embodiments of the first aspect of this application, the first electrode is a negative electrode, and the first electrode extends beyond the edge of the second electrode along the width direction of the first electrode.

[0035] In one or more of the above optional embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode. Along the width direction, the negative electrode extends beyond the edge of the positive electrode, which can make the active material of the negative electrode more abundant and prevent lithium plating. However, the edge of the negative electrode is longer, and the part that extends outward does not have a corresponding support from the positive electrode, so it is more prone to wrinkling. The solution of this application can effectively prevent this phenomenon.

[0036] In some embodiments of the first aspect of this application, when viewed along the thickness direction of the first current collector, the groove does not extend beyond the edge of the second electrode in the width direction.

[0037] In one or more of the above alternative embodiments, by limiting the groove to not extend beyond the edge of the second electrode, the risk of wrinkling of the portion of the first electrode extending beyond the second electrode is further reduced.

[0038] In some embodiments of the first aspect of this application, the adhesion force between the release membrane and the edge region is F, where 4 N / m ≤ F ≤ 8 N / m.

[0039] In one or more of the above optional embodiments, having an adhesion force between the separator and the edge region greater than or equal to 4 N / m helps improve the bonding stability between the separator and the edge region, reduces the risk of wrinkling or curling of the separator edge region, reduces the risk of short circuits in the battery cell due to wrinkling or curling of the separator, and improves the safety performance of the battery cell. Having an adhesion force between the separator and the edge region less than or equal to 8 N / m reduces the impact of the adhesion between the separator and the edge region on the wetting of the first electrode, avoids the problem of poor wetting effect due to excessive adhesion between the separator and the edge region, and promotes full wetting of the first electrode, resulting in better cycle performance of the battery cell. Therefore, 4 N / m ≤ F ≤ 8 N / m can improve the bonding stability between the separator and the first electrode, reduce the risk of wrinkling or curling of the separator, reduce the risk of short circuits in the battery cell due to wrinkling or curling of the separator, improve the safety performance of the battery cell, and promote full wetting of the first electrode, resulting in better cycle performance of the battery cell.

[0040] In some embodiments of the first aspect of this application, F ≥ 5 N / m.

[0041] In one or more of the above optional embodiments, by having an adhesion force between the separator and the edge area greater than or equal to 5 N / m, the bonding stability between the separator and the edge area is further improved, the risk of wrinkling and curling of the separator edge area is further reduced, the risk of short circuit of the battery cell due to wrinkling and curling of the separator is further reduced, and the safety performance of the battery cell is improved.

[0042] In some embodiments of the first aspect of this application, the groove extends along the width direction of the first current collector.

[0043] In one or more of the above optional embodiments, if the groove extends along the width direction of the first current collector, the size of the groove along the width direction of the first current collector is larger, which facilitates the manufacturing and forming of the groove.

[0044] In some embodiments of the first aspect of this application, a first active material layer is provided on both sides of the first current collector along the thickness direction of the first current collector, and a plurality of grooves are provided on both sides of the first active material layer.

[0045] In one or more of the above optional embodiments, multiple grooves are provided on both sides of the first active material layer of the first current collector, which further increases the contact area between the first electrode and the electrolyte, so that the first electrode can be fully wetted and further improve the cycle performance of the battery cell.

[0046] In some embodiments of the first aspect of this application, the bottom wall and any sidewall of the groove are both layers of a first active material.

[0047] In some embodiments of the first aspect of this application, the first electrode is a negative electrode.

[0048] In one or more of the above optional embodiments, if the first electrode is a negative electrode, then by providing multiple grooves in the active material layer of the negative electrode, and each groove having a distance 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 to be fully wetted by the electrolyte, but also for reducing costs. Fully wetted by the electrolyte, the negative electrode also helps reduce the risk of lithium plating in the battery cell, improving the safety performance of the battery cell.

[0049] Secondly, embodiments of this application provide an electrical device, which includes the battery cell provided in any embodiment of the first aspect.

[0050] In one or more of the above optional embodiments, the battery cell provided in the first aspect embodiment has better safety performance and cycle performance, which is beneficial to improving the power safety and power reliability of electrical equipment powered by the battery cell. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0052] Figure 1 is a cross-sectional view of a battery cell provided in some embodiments of this application;

[0053] Figure 2 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0054] Figure 3 is a cross-sectional view along line A1-A1 in Figure 2;

[0055] Figure 4 is a schematic diagram of the first electrode sheet in an unfolded state according to some other embodiments of this application;

[0056] Figure 5 is a cross-sectional view along line A2-A2 in Figure 4;

[0057] Figure 6 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0058] Figure 7 is a schematic diagram of the bonding and unfolding of the first electrode and the separator provided in some embodiments of this application;

[0059] Figure 8 is a sectional view along line A3-A3 in Figure 7;

[0060] Figure 9 is a schematic diagram of the second pole piece in an unfolded state according to some embodiments of this application;

[0061] Figure 10 is a sectional view along line A4-A4 in Figure 9.

[0062] Icons: 100 - Cell; 10 - Casing; 20 - Electrode assembly; 21 - First electrode; 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 tab; 22 - Second electrode; 221 - Second current collector; 222 - Second active material layer; 23 - Separator; 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 region; Q2 - Middle region. Embodiments of the present invention

[0063] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0064] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0065] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0066] In the description of the embodiments of this 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 commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0067] Currently, judging from market trends, the application of battery cells is becoming increasingly widespread. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in power tools, drones, energy storage devices, and many other fields. As the application areas of battery cells continue to expand, the market demand is also constantly increasing, and the requirements for battery cell safety are becoming increasingly stringent.

[0068] In related technologies, to improve the wetting effect of the electrode, grooves are typically created in the active material layer of the electrode. These grooves increase the contact area between the active material layer and the electrolyte, thereby improving the wetting effect. Generally, the grooves penetrate the active material layer at both ends along the width of the electrode. This reduces the strength of the electrode's edge region in the width direction, making it prone to wrinkling and curling. When a separator and the first electrode need to be connected, the presence of the grooves reduces the connection area between the separator and the electrode, resulting in weakened connection stability and a greater risk of wrinkling and curling of the electrode and separator, ultimately reducing the safety performance of the battery cell.

[0069] Based on the above considerations, in order to improve the safety performance of the battery cell, this application provides a battery cell including an electrode assembly, the electrode assembly including a first electrode sheet, the first electrode sheet including a first current collector and a first active material layer, the first active material layer being disposed on at least one side of the first current collector along the thickness direction of the first current collector; wherein, at least one first active material layer is provided with a plurality of grooves spaced apart from the surface of the first current collector, and the grooves are spaced apart from both ends of the first active material layer along the width direction of the first current collector.

[0070] Multiple grooves are spaced apart on at least one first active material layer of the first electrode, which increases the contact area between the first active material layer and the electrolyte, facilitating full wetting of the first electrode by the electrolyte and thus improving the cycle performance of the battery cell. Along the width direction of the first current collector, the grooves are spaced apart from both ends of the first active material layer; that is, the grooves do not extend to both ends of the first active material layer along the width direction of the first current collector. This results in better edge strength of the first electrode along the width direction, reducing the risk of wrinkling or curling of the first electrode edge in the width direction. This reduces the risk of lithium plating, short circuits, and other problems caused by wrinkling of the first electrode, thus improving the safety performance of the battery cell.

[0071] The bottom wall and any side wall of the groove are all the first active material layer.

[0072] 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 electrode and the separator, the area between the end faces of the groove and the first active material layer in the width direction of the first current collector can provide a connection space for the separator to be connected to the first electrode. This provides a larger connection area for the connection of the first active material layer and the separator, which facilitates the connection of the first electrode and the separator and helps to improve the connection stability of the first electrode and the separator. It also reduces the risk of curling and wrinkling at the edges of the first electrode and the separator, thereby reducing the risk of lithium plating and short circuits in the cell caused by wrinkling and curling of the first electrode and the separator, and improving the safety performance of the cell.

[0073] The battery cells disclosed in the embodiments of this application can be used, but are not limited to, in electrical equipment such as electric two-wheelers, power tools, drones, and energy storage devices. The battery cells conforming to the operating conditions of this application can also be used as the power supply system for electrical equipment, which helps improve the safety performance of the battery cells.

[0074] This application provides an embodiment of an electrical device that uses a battery cell 100 as a power source. The electrical device can be, but is not limited to, electronic devices, power tools, electric vehicles, drones, and energy storage devices. Electronic devices can include mobile phones, tablets, laptops, etc.; power tools can include electric drills, chainsaws, etc.; and electric vehicles can include electric cars, electric motorcycles, electric bicycles, etc.

[0075] As shown in Figure 1, this application provides a battery cell 100, which includes a housing 10 and an electrode assembly 20, with the electrode assembly 20 housed within the housing 10.

[0076] The outer casing 10 forms a receiving space. This receiving space can be used to house the electrode assembly 20, electrolyte, etc. The outer casing 10 can be a rigid shell, such as a steel or aluminum shell, to form a steel-cased battery cell 100 or an aluminum-cased battery cell. The outer casing 10 can also be formed of a softer material, such as an aluminum-plastic film or a steel-plastic film, to form a pouch cell. Figure 1 shows the case where the battery cell 100 is a pouch cell.

[0077] The electrode assembly 20 includes a first electrode 21, a second electrode 22, and a separator 23. The first electrode 21 and the second electrode 22 have opposite polarities; that is, one of the first electrode 21 and the second electrode 22 is the positive electrode, and the other is the negative electrode. The separator 23 provides insulation between the first electrode 21 and the second electrode 22 to reduce the risk of short circuit in the cell 100. The material of the separator 23 may include PP (polypropylene) or PE (polyethylene), etc. In this embodiment, the first electrode 21 is the negative electrode.

[0078] The electrode assembly 20 can be a wound structure, in which the first electrode 21, the separator 23, the second electrode 22, and another separator 23 are stacked in a certain order and then wound to form the wound electrode assembly 20; or, the separator 23, the first electrode 21, the other separator 23, and the second electrode 22 are stacked in a certain order and then wound to form the wound electrode assembly 20. The wound electrode assembly 20 can also be a flat wound electrode assembly 20.

[0079] The electrode assembly 20 can also be a stacked structure, with the first electrode 21, the separator 23, and the second electrode 22 stacked in a certain order to form a stacked electrode assembly 20.

[0080] As shown in Figures 2 and 3, the first electrode 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.

[0081] The thickness direction X of the first current collector is the thickness direction of the first electrode 21, and the thickness direction of the first electrode 21 is the stacking direction of the first current collector 211 and the first active material layer 212.

[0082] Along the thickness direction X of the first current collector, the first current collector 211 may have a first active material layer 212 disposed on one side, or the first current collector 211 may have a first active material layer 212 disposed on both sides. In an embodiment where the first electrode 21 is a positive electrode, 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 cells, the material of the positive current collector can be aluminum. The positive active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The positive current collector can be a composite current collector or a non-composite current collector.

[0083] In an embodiment where the first electrode 21 is the negative electrode, the first current collector 211 is the negative current collector, and the first active material layer 212 is the negative active material layer. For lithium-ion cells, the negative current collector can be made of copper. The negative active material layer can be made of carbon or silicon, etc. The negative current collector can be a composite current collector or a non-composite current collector.

[0084] The first electrode 21 also includes a first electrode tab 213, which protrudes from one end of the first current collector 211 along the width direction Y of the first current collector. The first electrode tab 213 and the first current collector 211 can be separately configured and connected. There are various ways to connect the first electrode tab 213 and the first current collector 211, such as welding, conductive adhesive, riveting, etc.

[0085] The first tab 213 and the first current collector 211 can be integrally formed, with the first tab 213 connected to one end of the first current collector 211 along the width direction Y of the first current collector. The first tab 213 and the first current collector 211 can be formed by die-cutting a substrate. The first tab 213 can be a split tab or a full tab structure. In an embodiment where the first tab 213 is a split tab, the first electrode 21 can include multiple first tabs 213, which are spaced apart along the length direction Z of the first current collector. Figure 2 shows the case where the first tab 213 is a split tab.

[0086] At least one first active material layer 212 has a plurality of grooves 2121 spaced apart from the surface of the first current collector 211, and the grooves 2121 are spaced apart from both ends of the first active material layer 212 along the width direction Y of the first current collector.

[0087] The width direction Y of the first current collector is the same as the width direction of the first electrode 21. In embodiments where the electrode assembly 20 has 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 electrode 21 is in the unfolded state, the thickness direction X, the width direction Y, and the length direction Z of the first current collector are perpendicular to each other.

[0088] In an embodiment where a first active material layer 212 is provided on both sides of the first current collector 211, one of the first active material layers 212 may be provided with a groove 2121, or both of the first active material layers 212 may be provided with a groove 2121.

[0089] Multiple refers to two or more. Multiple grooves 2121 are spaced apart on the first active material layer 212.

[0090] The groove 2121 is recessed from the surface of the first active material layer 212 away from the first current collector 211 towards the first current collector 211. The cross-sectional shape of the groove 2121 can be various, such as rectangular, trapezoidal, or arc-shaped. Figure 3 shows the case where the cross-sectional shape of the groove 2121 is rectangular, and Figure 5 shows the case where the cross-sectional shape of the groove 2121 is trapezoidal. 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 locations along the thickness direction X of the first current collector. In an embodiment where the cross-sectional shape of the groove 2121 is trapezoidal, the long base 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 locations 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 entry of electrolyte into the groove 2121.

[0091] 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 distance between the two ends of the groove 2121 and the ends of the first active material layer 212 can be the same or different. Specifically, as shown in Figures 2 and 4, along the width direction Y of the first current collector, the groove 2121 has a first end 21211 and a second end 21212, and the first active material layer 212 has a first end face 2122 and a second end face 2123, with the first end 21211 being closer to the first end face 2122 than the second end face 2123, and the second end 21212 being 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, and 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 can be the same or different.

[0092] The distance between the first end 21211 and the first end face 2122 of each groove 2121 can be the same or different. The distance between the second end 21212 and the second end face 2123 of each groove 2121 can be the same or different.

[0093] Multiple grooves 2121 are spaced apart on at least one first active material layer 212 of the first electrode 21, which increases the contact area between the first active material layer 212 and the electrolyte, facilitating the full wetting of the first electrode 21 by the electrolyte and thus improving the cycle performance of the 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, meaning 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. This results in better edge strength of the first electrode 21 along the width direction Y, reducing the risk of wrinkling or curling of the first electrode 21 in the width direction, thereby reducing the risk of lithium plating or short circuits in the cell 100 due to wrinkling of the first electrode 21 and improving the safety performance of the cell 100.

[0094] 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 electrode 21 and the separator 23, the area between the end faces of the groove 2121 and the first active material layer 212 in the width direction Y of the first current collector can provide a connection space for the separator 23 to be connected to the first electrode 21. This provides a larger connection area for the connection of the first active material layer 212 and the separator 23, which facilitates the connection of the first electrode 21 and the separator 23 and helps to improve the connection stability of the first electrode 21 and the separator 23. It also reduces the risk of edge curling and wrinkling in the edge areas of the first electrode 21 and the separator 23, thereby reducing the risk of lithium plating, short circuits and other problems caused by wrinkling and curling of the first electrode 21 and the separator 23, and improving the safety performance of the battery cell 100.

[0095] As shown in Figures 3 and 5, along the thickness direction X of the first current collector, a first active material layer 212 is provided on both sides of the first current collector 211, and a plurality of grooves 2121 are provided on both sides of the first active material layer 212.

[0096] Multiple grooves 2121 are provided on both sides of the first active material layer 212 of the first current collector 211, which further increases the contact area between the first electrode 21 and the electrolyte, so that the first electrode 21 can be fully wetted and further improve the cycle performance of the cell 100.

[0097] As shown in Figures 2 and 4, 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, where 0.05mm≤L1≤3mm.

[0098] It should be noted that L1 is merely a symbol representing 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. It does not mean that the minimum distance between any end of the first active material layer 212 and any groove 2121 is the same along the width direction Y of the first current collector. It can be understood 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 satisfies 0.05mm~3mm. For example, the minimum distance between the first end 21211 and the first end face 2122 of any groove 2121 satisfies 0.05mm~3mm.

[0099] For example, 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 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.5mm, 0.7mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm, 2.2mm, 2.5mm, 2.7mm, 3mm, etc.

[0100] 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 size of the area with good strength of the first electrode 21 in the width direction Y of the first current collector is larger, reducing the risk of wrinkling of the first electrode 21 in the edge area in the width direction, thereby reducing the risk of problems such as lithium plating and short circuit of the cell 100 caused by wrinkling of the first electrode 21, and improving the safety performance of the 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 electrode 21 and the separator 23, it can also provide a larger connection area for the connection of the first active material layer 212 and the separator 23, which facilitates the connection of the first electrode 21 and the separator 23 and helps to improve the connection stability of the first electrode 21 and the separator 23. It also reduces the risk of edge curling and wrinkling in the edge areas of the first electrode 21 and the separator 23, thereby reducing the risk of lithium plating, short circuit and other problems caused by wrinkling and curling of the first electrode 21 and the separator 23, and improving the safety performance of the battery cell 100. 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 less than or equal to 3 mm, the size of the groove 2121 in the width direction Y of the first current collector is relatively large. This increases the contact area between the first active material layer 212 and the electrolyte, which is beneficial for the first electrode 21 to be fully wetted by the electrolyte. This, in turn, improves the cycle performance of the battery cell 100, and also helps the battery cell 100 to have a better capacity retention rate, slows down the decay rate of the battery cell 100 during use, and extends the service life of the battery cell 100. Therefore, 0.05 mm ≤ L1 ≤ 3 mm can reduce the risk of wrinkling of the first electrode 21 in the width direction edge area, improve the safety performance of the battery cell 100, and also improve the cycle performance of the battery cell 100.

[0101] Furthermore, 0.1mm≤L1≤2mm.

[0102] For example, 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 0.1mm, 0.15mm, 0.25mm, 0.35mm, 0.45mm, 0.55mm, 0.65mm, 0.75mm, 0.85mm, 0.95mm, 1.05mm, 1.15mm, 1.25mm, 1.35mm, 1.45mm, 1.55mm, 1.65mm, 1.75mm, 1.85mm, 1.95mm, etc.

[0103] 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 size of the area with better strength of the first electrode 21 in the width direction Y of the first current collector is larger, which further reduces the risk of wrinkling of the first electrode 21 in the edge area in the width direction, thereby further reducing the risk of lithium plating, short circuit and other problems caused by wrinkling of the first electrode 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 electrode 21 and the separator 23, it can also provide a larger connection area for the connection of the first active material layer 212 and the separator 23, which facilitates the connection of the first electrode 21 and the separator 23 and helps to further improve the connection stability of the first electrode 21 and the separator 23. It further reduces the risk of curling and wrinkling in the edge areas of the first electrode 21 and the separator 23, thereby reducing the risk of lithium plating, short circuit and other problems caused by wrinkling of the first electrode 21 and the separator 23 in the cell 100, and improving the safety performance of the cell 100. 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 less than or equal to 2 mm, 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. This facilitates the full wetting of the first electrode 21 by the electrolyte, thereby improving the cycle performance of the cell 100. Therefore, 0.1 mm ≤ L1 ≤ 2 mm can further reduce the risk of wrinkling of the first electrode 21 in the edge area in the width direction, improving the safety performance of the cell 100, and further improving the cycle performance of the cell 100.

[0104] In some embodiments, the depth of the groove 2121 is less than the thickness of the first active material layer 212.

[0105] The depth of the groove 2121 is the depth by which the groove 2121 is recessed from the surface of the first active material layer 212 away from the first current collector 211 into the first current collector 211. Therefore, the bottom wall of the groove 2121 and any side wall of the groove 2121 are both the first active material layer 212.

[0106] The depths of the various grooves 2121 can be the same or different.

[0107] 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 corresponding position of the groove 2121 is not exposed, reducing the risk of short circuit in 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, resulting in less waste of active material and cost savings.

[0108] As shown in Figures 3 and 5, in some embodiments, the depth of the groove 2121 is H, where 10μm≤H≤50μm.

[0109] For example, the depth H of the groove 2121 can be 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, etc.

[0110] If the depth of the groove 2121 is greater than or equal to 10 μm, the greater depth results in a larger groove wall area, providing a larger contact area between the first active material layer 212 and the electrolyte. This facilitates thorough wetting of the first electrode 21, improving the cycle performance of the cell 100. If the depth of the groove 2121 is less than or equal to 50 μm, the loss of active material during the groove 2121 formation process is reduced. If the first electrode 21 is a positive electrode, less loss of positive active material is beneficial for increasing energy density; if the first electrode 21 is a negative electrode, less loss of negative active material is beneficial for reducing the risk of lithium plating, improving the safety performance of the cell 100. Therefore, 10 μm ≤ H ≤ 50 μm is beneficial for both improving the cycle performance of the cell 100 and reducing active material loss.

[0111] Furthermore, 13μm≤H≤30μm.

[0112] For example, H can be 13μm, 14μm, 16μm, 17μm, 18μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, etc.

[0113] When the depth of groove 2121 is greater than or equal to 13 μm, the greater depth of groove 2121 results in a larger surface area of ​​groove wall, providing a larger contact area between the first active material layer 212 and the electrolyte. This facilitates the full wetting of the first electrode 21, further improving the cycle performance of the cell 100. When the depth of groove 2121 is less than or equal to 30 μm, the loss of active material during the formation of groove 2121 is further reduced. If the first electrode 21 is a positive electrode, less loss of positive active material is beneficial for further improving energy density; if the first electrode 21 is a negative electrode, less loss of negative active material is beneficial for further reducing the risk of lithium plating and improving the safety performance of the cell 100. Therefore, 13 μm ≤ H ≤ 30 μm is beneficial for both further improving the cycle performance of the cell 100 and further reducing the loss of active material.

[0114] As shown in Figures 2-5, 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, 50μm≤W≤100μm.

[0115] 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.

[0116] If 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, then the groove 2121 has a large width, resulting in a larger area of ​​the groove wall and a larger contact area between the first active material layer 212 and the electrolyte. This facilitates the full wetting of the first electrode 21, improves the cycle performance of the cell 100, and also makes the groove opening of the groove 2121 wider, which is convenient for the electrolyte to enter the groove 2121. If 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, the loss of active material during the molding of the groove 2121 is reduced. If the first electrode 21 is a positive electrode, less loss of positive active material is beneficial to improving energy density; if the first electrode 21 is a negative electrode, less loss of negative active material is beneficial to reducing the risk of lithium plating and improving the safety performance of the cell 100. Therefore, 50μm≤W≤100μm is beneficial for improving the cycle performance of cell 100 and reducing the loss of active material.

[0117] Furthermore, 60μm≤W≤80μm.

[0118] 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.

[0119] If the width of the groove 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is greater than or equal to 60 μm, then the groove 2121 has a larger width, resulting in a larger area of ​​the groove wall and a larger contact area between the first active material layer 212 and the electrolyte. This facilitates the full wetting of the first electrode 21 and improves the cycle performance of the cell 100. If the width of the groove 2121 on the surface of the first active material layer 212 facing 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 electrode 21 is a positive electrode, less loss of positive active material is beneficial for further improving energy density; if the first electrode 21 is a negative electrode, less loss of negative active material is beneficial for further reducing the risk of lithium plating and improving the safety performance of the cell 100. Therefore, 60 μm ≤ W ≤ 80 μm is beneficial for both improving the cycle performance of the cell 100 and further reducing the loss of active material.

[0120] In some embodiments, the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211 is L2, where 1.8μm≤L2≤4μm.

[0121] L2 can be the minimum spacing between adjacent grooves 2121 on the surface of the first active material layer 212 away from the first current collector 211.

[0122] It should be noted that L2 is merely a symbol representing the minimum distance between adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211, and does not mean that the minimum distance between any two adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is the same. It can be understood that the minimum distance between any two adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 satisfies 1.8μm~4μm.

[0123] 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.

[0124] By ensuring that the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is greater than or equal to 1.8 μm, the distribution of grooves 2121 is not too dense, ensuring a reasonable number of grooves and reducing active material loss during the groove forming process. Conversely, by ensuring that the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is less than or equal to 4 μm, a sufficient number of grooves 2121 can be formed on the first active material layer 212, resulting in a larger contact area between the first active material layer 212 and the electrolyte. This facilitates thorough wetting of the first electrode 21 and improves the cycle performance of the battery cell 100. Therefore, 1.8 μm ≤ L2 ≤ 4 μm not only reduces active material loss during groove forming but also improves the cycle performance of the battery cell 100.

[0125] Furthermore, 2μm≤L2≤2.5μm.

[0126] L2 can be 2μm, 2.1μm, 2.15μm, 2.25μm, 2.3μm, 2.35μm, 2.4μm, 2.45μm, 2.5μm, etc.

[0127] By ensuring that the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is greater than or equal to 2 μm, the distribution of grooves 2121 is not too dense, ensuring a reasonable number of grooves and further reducing active material loss during the groove 2121 forming process. By ensuring that the spacing between adjacent grooves 2121 on the surface of the first active material layer 212 facing away from the first current collector 211 is less than or equal to 2.5 μm, more grooves 2121 can be formed on the first active material layer 212, resulting in a larger contact area between the first active material layer 212 and the electrolyte. This facilitates sufficient wetting of the first electrode 21 and improves the cycle performance of the battery cell 100. Therefore, 2 μm ≤ L2 ≤ 2.5 μm not only further reduces active material loss during the groove 2121 forming process but also further improves the cycle performance of the battery cell 100.

[0128] In some embodiments, a plurality of grooves 2121 are spaced apart along the length direction Z of the first current collector.

[0129] 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.

[0130] By arranging multiple grooves 2121 at intervals along the length direction Z of the first current collector, it is easy to make the grooves 2121 evenly distributed on the first active material layer 212, thereby improving the wetting uniformity of the first electrode 21 and thus improving the cycle performance of the cell 100.

[0131] In other embodiments, some of the plurality of grooves 2121 may be spaced apart along the length direction Z of the first collector, and other portions of the plurality of grooves 2121 may be spaced apart along the width direction Y of the first collector.

[0132] In some embodiments, the groove 2121 extends along the width direction Y of the first current collector.

[0133] The extension 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 is the largest in the width direction Y of the first current collector.

[0134] If the groove 2121 extends along the width direction Y of the first current collector, then the size of the groove 2121 along the width direction Y of the first current collector is relatively large, which facilitates the manufacturing and forming of the groove 2121.

[0135] Along the width direction Y of the first current collector, all grooves 2121 may have the same length, or at least two grooves 2121 may have different lengths, or any two grooves 2121 may have different lengths. In some embodiments, as shown in FIG6, the plurality of grooves 2121 includes a first groove 2121a and a second groove 2121b, and along the width direction Y of the first current collector, the length of the first groove 2121a is greater than the length of the second groove 2121b.

[0136] 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, so at least two of the multiple grooves 2121 have different lengths.

[0137] 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 scheme where the length of all grooves 2121 is large, this scheme can improve the problem of weakened strength of the first electrode 21 and large loss of active material caused by the large length of all grooves 2121. Compared with the scheme where the length of all grooves 2121 is small, this scheme can improve the problem of insufficient wetting of the first electrode 21 caused by the small length of all grooves 2121, which is beneficial to improving the cycle performance of the cell 100.

[0138] As shown in Figure 6, in some embodiments, the plurality of grooves 2121 include a plurality of first grooves 2121a and a plurality of second grooves 2121b, and the first grooves 2121a and second grooves 2121b are alternately arranged along the length direction Z of the first current collector.

[0139] Along the length direction Z of the first collector, the first groove 2121a and the second groove 2121b are alternately arranged, which means that along the length direction Z of the first 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.

[0140] Along the length direction Z of the first current collector, the first groove 2121a and the second groove 2121b are alternately arranged, which is conducive to the uniform wetting of the first electrode 21, so that the cell 100 has high cycle performance.

[0141] As shown in Figures 7 and 8, in some embodiments, the first active material layer 212 includes a central region Q2 and two edge regions Q1. A groove 2121 is disposed in the central region Q2 along the width direction Y of the first current collector. The central 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 face of the first active material layer 212, and a portion of the other edge region Q1 is located between the other end of the groove and the other end face of the first active material layer. The isolation membrane 23 is bonded to the edge region Q1.

[0142] Specifically, a portion of an 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, where the first end face 2122 and the first end 21211 are respectively the two edges of the edge region Q1 in the width direction Y of the first current collector. Another portion of an 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, where the second end face 2123 and the second end 21212 are respectively the two edges of the edge region Q1 in the width direction Y of the first current collector. In this embodiment, the aforementioned L1 can be the dimension of a portion of the edge region Q1 in the width direction Y of the first current collector.

[0143] The edge region Q1 can be a region of equal width or a region of non-equal width.

[0144] In an embodiment where all grooves 2121 have the same size along the width direction Y of the first collector and the first ends 21211 of all grooves 2121 are flush and the second ends 21212 of all grooves 2121 are flush, the edge region Q1 has the same size along the length direction Z of the first collector at any position in the width direction Y of the first collector, that is, the edge region Q1 is a region of equal width.

[0145] In an embodiment where at least two of the grooves 2121 have non-aligned first ends 21211 and at least two of the second grooves have non-aligned second ends 21212, along the length direction Z of the first collector, the size of any edge region Q1 is different along the width direction Y of the first collector, i.e., the edge region Q1 is a non-uniform width region.

[0146] In other embodiments, the two edge regions Q1 can be regions formed by extending a certain distance from the two end faces of the first active material layer 212 toward the middle region Q2 along the width direction Y of the first current collector. That is, one edge region Q1 is a region formed by extending a certain distance from the first end face 2122 of the first active material layer 212 toward the second end face 2123 along the width direction Y of the first current collector, and the other edge region Q1 is a region formed by extending a certain distance from the second end face 2123 of the first active material layer 212 toward the first end face 2122 along the width direction Y of the first current collector. The size of the edge region Q1 in the width direction Y of the first current collector can be 1% of the size of the first active material layer 212 in the width direction Y of the first current collector.

[0147] The dimensions of the two edge regions Q1 along the width direction Y of the first current collector can be the same or different.

[0148] With the groove 2121 located in the middle region Q2, the separator 23 is bonded to the edge region Q1. This increases the bonding area between the separator 23 and the first electrode 21, improves bonding stability, reduces the risk of wrinkling or curling at the edge of the separator 23, and lowers the risk of short circuit in the battery cell 100 due to wrinkling or curling of the separator 23, thus improving the safety performance of the battery cell 100. Bonding the separator 23 to the edge region Q1 also makes bonding easier and reduces the risk of adhesive material covering or filling the groove 2121, thus reducing the wetting effect.

[0149] In some embodiments, the adhesion force between the isolation membrane 23 and the edge region Q1 is F, where 4 N / m ≤ F ≤ 8 N / m.

[0150] The adhesion between the release membrane 23 and the edge region Q1 can be tested using the following method:

[0151] Take the finished battery cell 100 after formation and discharge it to 3.0V at a low rate of 0.5C. Then, use a sampler to remove the composite of the first electrode 21 and the separator 23 corresponding to the bonded edge region Q1. The composite of the bonded edge region Q1 and the separator 23 is made into a strip with a length and width of 100mm*15mm. Clamp one end of the separator 23 to the upper fixture of the high-speed rail tensile testing machine and clamp one end of the edge region Q1 of the first electrode 21 to the lower fixture of the high-speed rail tensile testing machine. The tensile speed is 50mm / min. The test is performed 5 times and the average value is taken. The average value is recorded as the adhesive force F. This is the adhesive force of the separator 23 of a set of edge regions Q1.

[0152] For example, F can be 4N / m, 4.5N / m, 5N / m, 5.5N / m, 6N / m, 6.5N / m, 7N / m, 7.5N / m, 8N / m, etc.

[0153] A bonding force of 4 N / m or greater between the separator 23 and the edge region Q1 improves the bonding stability between them, reduces the risk of wrinkling or curling of the separator 23 at the edge region Q1, and lowers the risk of short circuits in the cell 100 due to wrinkling or curling of the separator 23, thus improving the safety performance of the cell 100. A bonding force of 8 N / m or less between the separator 23 and the edge region Q1 reduces the impact of the bonding between the separator 23 and the edge region Q1 on the wetting of the first electrode 21, avoiding poor wetting due to excessive bonding force. This ensures that the first electrode 21 is fully wetted, resulting in better cycle performance of the cell 100. Therefore, 4N / m≤F≤8N / m can improve the bonding stability between the separator 23 and the first electrode 21, reduce the risk of wrinkling and curling of the separator 23, reduce the risk of short circuit in the cell 100 due to wrinkling and curling of the separator 23, improve the safety performance of the cell 100, and facilitate the full wetting of the first electrode 21, so that the cell 100 has better cycle performance.

[0154] Furthermore, F can be 5 N / m, 5.2 N / m, 5.3 N / m, 5.4 N / m, 5.8 N / m, 6.2 N / m, 6.3 N / m, 6.6 N / m, 6.8 N / m, 7 N / m, 7.2 N / m, 7.6 N / m, 7.8 N / m, etc.

[0155] By ensuring that the adhesion force between the separator 23 and the edge region Q1 is greater than or equal to 5 N / m, the bonding stability between the separator 23 and the edge region Q1 is further improved, the risk of wrinkling or curling of the separator 23 at the edge region Q1 is further reduced, and the risk of short circuit in the cell 100 due to wrinkling or curling of the separator 23 is further reduced, thereby improving the safety performance of the cell 100. In some embodiments, the first electrode 21 is a negative electrode, and along the width direction of the first electrode 21, the first electrode 21 extends beyond the edge of the second electrode 22.

[0156] In one or more of the above optional embodiments, the first electrode 21 is a negative electrode and the second electrode 22 is a positive electrode. Along the width direction, the negative electrode extends beyond the edge of the positive electrode, which can make the active material of the negative electrode more abundant and prevent lithium plating. However, the edge of the negative electrode is longer, and the part that extends beyond it does not have a corresponding support from the positive electrode, so it is more prone to wrinkling. The solution of this application can effectively prevent this phenomenon.

[0157] In some embodiments of the first aspect of this application, when viewed along the thickness direction of the first current collector, the groove 2121 does not extend beyond the edge of the second electrode 22.

[0158] In one or more of the above alternative embodiments, by limiting the groove 2121 to not extend beyond the edge of the second electrode 22, the risk of wrinkling of the portion of the first electrode 21 extending beyond the second electrode 22 is further reduced.

[0159] The first electrode 21 is a negative electrode. By setting multiple grooves 2121 in the active material layer of the negative electrode, and each groove 2121 having a distance 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 to be fully wetted by the electrolyte, but also reduces costs. The full wettability of the negative electrode by the electrolyte also helps reduce the risk of lithium plating in the cell 100, improving the safety performance of the cell 100.

[0160] The electrode assembly 20 may have grooves 2121 provided only in the first active material layer 212 of the first electrode 21, or both the first electrode 21 and the second electrode 22 may have grooves 2121 provided.

[0161] As shown in Figures 9 and 10, in some embodiments, the second electrode 22 includes a second current collector 221 and a second active material layer 222. Along the thickness direction X' of the second current collector, the second active material layer 222 is disposed on at least one side of the second current collector 221. At least one second active material layer 222 has a plurality of grooves 2121 spaced apart from the surface of the second current collector 221. Along the width direction Y' of the second current collector, the grooves 2121 are spaced apart from both ends of the second active material layer 222.

[0162] The structure of the groove 2121 provided on the second active material layer 222 can refer to the structure of the groove 2121 provided 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 spaced apart along the length direction Z' of the second current collector.

[0163] When the second electrode 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.

[0164] Multiple grooves 2121 are spaced apart on at least one second active material layer 222 of the second electrode 22, which increases the contact area between the second active material layer 222 and the electrolyte, facilitating the full wetting of the second electrode 22 by the electrolyte and thus improving the cycle performance of the cell 100. Along the width direction Y' of the second current collector, the grooves 2121 are spaced apart from both ends of the second active material layer 222, meaning the grooves 2121 do not extend to both ends of the second active material layer 222 along the width direction of the second current collector 221. Therefore, along the width direction Y' of the second current collector, the edge region Q1 of the second electrode 22 has better strength, reducing the risk of wrinkling or curling of the second electrode 22 in the width direction. This reduces the risk of lithium plating or short circuits in the cell 100 due to wrinkling of the second electrode 22, improving the safety performance of the 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 electrode 22 and the separator 23, the area between the groove 2121 and the end face of the second active material layer 222 in the width direction of the second current collector 221 can provide a connection space for the separator 23 to be connected to the second electrode 22. This provides a larger connection area for the connection of the second active material layer 222 and the separator 23, which facilitates the connection of the second electrode 22 and the separator 23 and helps to improve the connection stability of the second electrode 22 and the separator 23. It also reduces the risk of edge curling and wrinkling in the edge areas of the second electrode 22 and the separator 23, thereby reducing the risk of lithium plating, short circuits and other problems caused by wrinkling and curling of the second electrode 22 and the separator 23, and improving the safety performance of the battery cell 100.

[0165] To verify the effect of setting multiple grooves 2121 in the first active material layer 212 of the first electrode 21 on the cycle performance of the battery cell 100, taking the first electrode 21 as the negative electrode as an example, a cycle interface test was performed on the lithium-ion battery cell, and the data in Table 1 were obtained:

[0166] After 500 cycles, the lithium-ion battery cell was charged at 25°C with a constant current rate of 0.7C to a voltage of 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.05C. The battery was then disassembled, and the negative electrode interface was visually inspected by the operator. If intermittent dotted purple spots, lithium plating, or lithium plating on purple spots appeared on the surface of the negative electrode, it was determined that the negative electrode had a minor interface problem. If the main body of the negative electrode showed large areas of continuous purple spots, lithium plating, or lithium plating on purple spots, it was determined that the negative electrode had a serious interface problem. The table below shows the percentage of interface areas present.

[0167] The capacity retention rate of a lithium-ion cell after 500 cycles = discharge capacity after the 500th cycle / discharge capacity after the first cycle × 100%.

[0168] Table 1

[0169]

[0170] As shown in Table 1:

[0171] (a) As can be seen from Comparative Example 1 and Examples 1-8, when L1>0, the area of ​​purple spots on the negative electrode sheet decreases compared to when L1 is 0. Therefore, along the width direction Y of the first current collector, there is a distance between the two ends of the groove 2121 and the first active material layer 212, which can improve the problem of lithium plating in the cell 100.

[0172] (II) As shown in Examples 1-8, when L1 is 0.05mm, 0.1mm, 1mm, 1.5mm, 2mm, 3mm, and 3.1mm, the area of ​​purple spots on the negative electrode sheet decreases significantly compared to when L1 is 0.03mm. Therefore, L1 ≥ 0.05mm can effectively improve the lithium plating problem of cell 100. When L1 is 3.1mm, the capacity retention rate decreases significantly compared to when L1 is 0.03mm, 0.05mm, 0.1mm, 1mm, 1.5mm, 2mm, and 3mm. Therefore, L1 ≤ 3mm is beneficial to slowing down the degradation rate of cell 100 during use and extending the service life of cell 100. Therefore, 0.05mm ≤ L1 ≤ 3mm can improve the lithium plating problem of cell 100, enhance the safety performance of cell 100, and extend the service life of cell 100.

[0173] (II) As shown in Examples 2-7, when L1 is 0.1mm, 1mm, 1.5mm, 2mm, 3mm, and 3.1mm, the area ratio of purple spots on the negative electrode further decreases compared to when L1 is 0.05mm. Therefore, L1 ≥ 0.1mm can further improve the lithium plating problem of cell 100. When L1 is 3mm, there is no significant change in capacity retention compared to when L1 is 2mm. Therefore, L1 ≤ 2mm not only makes the decay rate of cell 100 during use slower, resulting in a longer service life, but also reduces the loss of active material. Therefore, 0.1mm ≤ L1 ≤ 2mm can further improve the lithium plating problem of cell 100, improve the safety performance of cell 100, and also make cell 100 have a longer service life.

[0174] This application also provides an electrical device, which includes the battery cell 100 provided in any of the above embodiments.

[0175] The battery cell 100 provides electrical energy for the operation of electrical equipment. The battery cell 100 provided in any of the above embodiments has good safety performance and cycle performance, which is beneficial to improving the electrical safety and reliability of electrical equipment powered by the battery cell 100.

[0176] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art.

Claims

1. A battery cell, comprising: An electrode assembly includes a first electrode, the first electrode including a first current collector and a first active material layer, and the first active material layer is disposed on at least one side of the first current collector along the thickness direction of the first current collector. In this embodiment, at least one of the first active material layers has multiple grooves spaced apart from the surface of the first current collector, and the grooves are spaced apart from both ends of the first active material layer along the width direction of the first current collector.

2. The battery cell according to claim 1, wherein, 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, where 0.05mm≤L1≤3mm.

3. The battery cell according to claim 2, wherein, 0.1mm≤L1≤2mm.

4. The battery cell according to any one of claims 1-3, wherein, The depth of the groove is less than the thickness of the first active material layer.

5. The battery cell according to claim 4, wherein, The depth of the groove is H, where 10μm≤H≤50μm.

6. The battery cell according to claim 5, wherein, 13μm≤H≤30μm.

7. The battery cell according to any one of claims 1-6, wherein, The width of the groove on the surface of the first active material layer away from the first current collector is W, 50μm≤W≤100μm.

8. The battery cell according to claim 7, wherein, 60μm≤W≤80μm.

9. The battery cell according to any one of claims 1-8, wherein, The spacing between adjacent grooves on the surface of the first active material layer away from the first current collector is L2, where 1.8μm≤L2≤4μm.

10. The battery cell according to claim 9, wherein, 2μm≤L2≤2.5μm.

11. The battery cell according to any one of claims 1-10, wherein, The plurality of grooves are spaced apart along the length direction of the first current collector.

12. The battery cell according to claim 11, wherein, The plurality of grooves includes 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.

13. The battery cell according to claim 12, wherein, The plurality of grooves includes a plurality of first grooves and a plurality of second grooves, and the first grooves and second grooves are alternately arranged along the length direction of the first current collector.

14. The battery cell according to any one of claims 1-10, wherein, The battery cell also includes a separator and a second electrode, the first electrode and the second electrode having opposite polarities, and the separator insulatingly separating the first electrode and the second electrode; The first active material layer includes a central region and two edge regions. The groove is disposed in the central region, and the isolation membrane is bonded to the edge regions. Along the width direction of the first current collector, the central region is located between the two edge regions. A portion of one edge region is located between one end of the groove and one end face of the first active material layer, and a portion of the other edge region is located between the other end of the groove and the other end face of the first active material layer.

15. The battery cell according to claim 14, wherein, The first electrode is a negative electrode, and along the width direction of the first electrode, the first electrode extends beyond the edge of the second electrode.

16. The battery cell according to claim 15, wherein, Viewed along the thickness direction of the first current collector, the groove does not extend beyond the width edge of the second electrode.

17. The battery cell according to any one of claims 14-16, wherein, The adhesion force between the isolation membrane and the edge region is F, where 4N / m≤F≤8N / m.

18. The battery cell according to claim 17, wherein, 5N / m≤F.

19. The battery cell according to any one of claims 1-18, wherein, The groove extends along the width direction of the first current collector.

20. The battery cell according to any one of claims 1-19, wherein, Along the thickness direction of the first current collector, the first active material layer is provided on both sides of the first current collector, and the groove is provided on both sides of the first active material layer.

21. The battery cell according to any one of claims 1-20, wherein, The bottom wall and any side wall of the groove are both the first active material layer.

22. An electrical device comprising a battery cell according to any one of claims 1-21.

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