Battery cell and electric device

Abstract

Provided in the present application are a battery cell and an electric device. The battery cell comprises an electrode assembly, wherein a first portion of a positive electrode sheet of the electrode assembly comprises a first bent section, a first straight section and a second straight section, the first straight section and the second straight section being respectively connected to two ends of the first bent section, and the end of the first straight section facing away from the first bent section being a positive electrode winding starting end of the positive electrode sheet; a negative electrode sheet of the electrode assembly comprises a third straight section located between the first straight section and the second straight section, the end of the third straight section facing the first bent section being a negative electrode winding starting end of the negative electrode sheet; and the first portion comprises a first current collector and a first active material layer, a first surface of the first current collector facing the third straight section is provided with a first active material layer, the first surface has a first uncoated foil region located in the first bent section, the first insulation layer covers the first uncoated foil region, and the first insulation layer is configured to insulate and isolate the third straight section from the first uncoated foil region. In this way, the safety performance of a battery is improved.

Description

Battery cells and electrical devices

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 2025103195989 entitled “Battery Cell and Electrical Equipment”, filed on March 18, 2025, 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] Currently, 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 and an electrical device to improve the safety 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 having a wound structure, the electrode assembly including a flat region and a first bending region, the first bending region being connected to one end of the flat region; the electrode assembly including a positive electrode sheet and a negative electrode sheet, the positive electrode sheet having a first portion, the first portion including a first bending segment located in the first bending region and a first flat segment and a second flat segment located in the flat region, the first flat segment and the second flat segment being respectively connected to the two ends of the first bending segment, the end of the first flat segment facing away from the first bending segment being the positive electrode winding start end of the positive electrode sheet, the negative electrode sheet including a position In the third straight section of the straight region, along the first direction, the third straight section is located between the first straight section and the second straight section, and the end of the third straight section facing the first bending section is the negative electrode winding start end of the negative electrode sheet; wherein, the first part includes a first current collector and a first active material layer, the first current collector has a first surface facing the third straight section, the first surface is provided with the first active material layer, the first surface has a first empty foil area located in the first bending region, the electrode assembly also includes a first insulating layer, the first insulating layer covers the first empty foil area, the first insulating layer is configured to insulate and isolate the third straight section and the first empty foil area.

[0007] In the interlocking structure, the positive current collector may develop tiny cracks at the innermost corner due to winding. Since there is no corresponding negative electrode for lithium intercalation on the side of the positive current collector facing the inside of the cell, lithium ions can move away from the inside of the cell through the cracks in the current collector, causing a risk of lithium plating. In one or more of the above optional embodiments, a first empty foil area is formed on the inner side of the first bending region of the first portion of the positive electrode sheet. This removes the active material on the inner side of the first bending region, which helps to reduce the risk of lithium plating on the negative electrode sheet at the third straight section. It also prevents ions on the first surface in the first bending region from moving to the negative electrode sheet outside the first bending section through the cracks in the first current collector in the first bending section, thereby reducing the risk of lithium plating on the negative electrode sheet outside the first bending section and improving the safety performance of the cell. By covering the first empty foil area with the first insulating layer, the risk of ions on the side of the first bent section of the positive electrode sheet away from the first surface moving through the cracks in the first empty foil area to the third straight section of the negative electrode sheet can be reduced, further reducing the risk of lithium deposition in the third straight section of the negative electrode sheet. Covering the first empty foil area with the first insulating layer can also reduce the risk of short circuit caused by burrs in the first empty foil area puncturing the insulation, thus improving the safety performance of the battery.

[0008] In some embodiments of the first aspect of this application, the first active material layer includes a first segment and a second segment spaced apart along the winding direction of the positive electrode sheet, at least a portion of the first segment is located in a first straight segment, at least a portion of the second segment is located in a second straight segment, and a first empty foil area is located between the first segment and the second segment along the winding direction.

[0009] In one or more of the above optional embodiments, since at least a portion of the first segment of the first active material layer is located in the first straight segment, and at least a portion of the second segment of the first active material layer is located in the second straight segment, and the first empty foil area is located between the first segment and the second segment along the winding direction, the first empty foil area is closer to the negative electrode winding start end, so that the active material mass in the region corresponding to the positive electrode sheet and the negative electrode winding start end is less, which helps to reduce the risk of lithium plating on the negative electrode sheet at the negative electrode winding start end and improve the safety performance of the battery cell.

[0010] In some embodiments of the first aspect of this application, a portion of the first insulating layer overlaps with a portion of the first segment to form a first overlapping area, and a portion of the first insulating layer overlaps with a portion of the second segment to form a second overlapping area. Along the winding direction, the second overlapping area and the first overlapping area are located on both sides of the first empty foil area.

[0011] In one or more of the above optional embodiments, by having a portion of the first insulating layer overlap with the first segment to form a first overlapping area, and a portion of the first insulating layer overlap with the second segment to form a second overlapping area, the connection area between the first insulating layer and the positive electrode sheet can be increased, thereby improving the connection stability of the first insulating layer.

[0012] In some embodiments of the first aspect of this application, along the thickness direction of the positive electrode sheet, in the first overlapping region, the first insulating layer is closer to the first surface than the first segment; in the second overlapping region, the first insulating layer is closer to the first surface than the second segment.

[0013] In one or more of the above optional embodiments, in the first overlap region, the first insulating layer is closer to the first surface than the first segment, so the first segment of the first active material layer covers the surface of the first insulating layer away from the first surface; in the second overlap region, the first insulating layer is closer to the first surface than the second segment, so the second segment of the first active material layer covers the surface of the first insulating layer away from the first surface. The first active material layer enables the first insulating layer to be stably connected to the first surface.

[0014] In some embodiments of the first aspect of this application, the projections of the first overlapping area and the second overlapping area do not overlap in a projection plane perpendicular to the first direction.

[0015] In one or more of the above optional embodiments, by ensuring that the projections of the first overlapping area and the second overlapping area do not overlap in the projection plane perpendicular to the first direction, the overlap of the first overlapping area and the second overlapping area in the first direction is avoided, which would cause the local thickness of the electrode assembly to be too large. This can reduce the thickness difference of each part of the electrode assembly, reduce the risk of local stress concentration in the positive electrode and / or negative electrode, and reduce the risk of breakage due to excessive local stress in the positive electrode and / or negative electrode, thereby improving the safety of the battery cell.

[0016] In some embodiments of the first aspect of this application, along the winding direction, the size of the first overlapping area is W1, the size of the second overlapping area is W2, 0mm < W1 ≤ 5mm, and 0mm < W2 ≤ 5mm.

[0017] In one or more of the above optional embodiments, if the dimension of the first overlapping region along the winding direction is greater than 0 mm, then the dimension of the portion of the first insulating layer located in the first overlapping region along the winding direction is greater than 0 mm; if the dimension of the second overlapping region along the winding direction is greater than 0 mm, then the dimension of the portion of the first insulating layer located in the second overlapping region along the winding direction is greater than 0 mm. This is beneficial to increasing the connection area between the first insulating layer and the positive electrode sheet, thereby improving the connection stability of the first insulating layer. If the dimension of the first overlapping region along the winding direction is less than or equal to 5 mm, then the dimension of the portion of the first insulating layer located in the first overlapping region along the winding direction is less than or equal to 5 mm; if the dimension of the second overlapping region along the winding direction is less than 5 mm, then the dimension of the portion of the first insulating layer located in the second overlapping region along the winding direction is less than or equal to 5 mm. This is beneficial to reducing the space occupied by the first insulating layer, thereby improving the energy density of the battery cell. Therefore, 0 mm < W1 ≤ 5 mm and 0 mm < W2 ≤ 5 mm are beneficial to improving both the connection stability of the first insulating layer and the energy density of the battery cell.

[0018] In some embodiments of the first aspect of this application, both the first segment and the second segment are located in a flat area.

[0019] In one or more of the above optional embodiments, by placing both the first segment and the second segment in the flat region, the first surface at least in the region of the first bending segment forms the first empty foil region, making the area of ​​the first empty foil region larger, further reducing the risk of lithium plating on the negative electrode sheet in the third flat segment, and improving the safety performance of the battery cell.

[0020] In some embodiments of the first aspect of this application, the thickness of the first insulating layer is less than the maximum thickness of the first segment, and / or the thickness of the first insulating layer is less than the maximum thickness of the second segment.

[0021] In one or more of the above optional embodiments, by making the thickness of the first insulating layer smaller than the maximum thickness of the first segment or the second segment, the first insulating layer can be made not to protrude from the active material, thereby preventing an increase in the thickness of the battery cell.

[0022] In some embodiments of the first aspect of this application, the electrode assembly further includes a second insulating layer. Along the thickness direction of the positive electrode sheet, the first insulating layer is located between the second insulating layer and the first empty foil area, and along the winding direction, the second insulating layer is located between the first segment and the second segment.

[0023] In one or more of the above optional embodiments, by providing a second insulating layer, with the first insulating layer located between the second insulating layer and the first empty foil area, and the second insulating layer located between the first and second sections along the winding direction, the overall thickness of the insulating structure covering the first empty foil area can be increased, reducing the risk of the insulating structure covering the first empty foil area being punctured by burrs in the first empty foil area. This reduces the risk of burrs in the first empty foil area puncturing the insulating structure and the separator, lowers the risk of cell short circuits, and improves the safety performance of the cell. The second insulating layer being located between the first and second sections reduces the thickness stacking of the second insulating layer and the first active material layer, which is beneficial for improving the energy density of the cell. Furthermore, the second insulating layer can prevent the negative electrode winding start end from puncturing the first bending section.

[0024] In some embodiments of the first aspect of this application, the sum of the thicknesses of the first insulating layer and the second insulating layer is less than the maximum thickness of the first segment, and / or the sum of the thicknesses of the first insulating layer and the second insulating layer is less than the maximum thickness of the second segment.

[0025] In one or more of the above optional embodiments, if the sum of the thicknesses of the first insulating layer and the second insulating layer is less than the maximum thickness of the first segment and / or the maximum thickness of the second segment, the overall structural thickness formed by the first insulating layer and the second insulating layer is smaller. This prevents the structure from protruding beyond the maximum thickness position of the first active material layer and moving away from the surface of the first current collector. This alleviates the problem of increased electrode assembly thickness caused by the installation of the first insulating layer and the second insulating layer. It helps to reduce the thickness difference between different parts of the electrode assembly, reduce the risk of local stress concentration in the positive electrode and / or negative electrode, and reduce the risk of breakage due to excessive local stress in the positive electrode and / or negative electrode, thereby improving the safety of the battery cell.

[0026] In some embodiments of the first aspect of this application, the second insulating layer is adhesive paper.

[0027] In one or more of the above optional embodiments, the second insulating layer is adhesive paper, which facilitates the second insulating layer to be disposed on the surface of the first insulating layer, and the adhesive paper has good flexibility, is easy to bend, and is not prone to curling.

[0028] In some embodiments of the first aspect of this application, the first bending region is connected to one end of the straight region along the second direction. Along the winding direction, the second insulating layer has a first end and a second end opposite to each other. The first end is closer to the positive electrode winding start end than the second end. Along the second direction, the distance between the first end and the positive electrode winding start end is a first distance, the distance between the second end and the positive electrode winding start end is a second distance, and the distance between the negative electrode winding start end and the positive electrode winding start end is a third distance. The first distance is less than the third distance, and the second distance is less than the third distance.

[0029] In one or more of the above optional embodiments, by making the first distance smaller than the third distance and the second distance smaller than the third distance, the overlapping area of ​​the second insulating layer and the third straight section is larger when viewed along the first direction, thereby increasing the coverage area of ​​the second insulating layer and increasing the area with a larger insulation structure thickness corresponding to the first empty foil area. This helps to reduce the risk of burrs in the first empty foil area puncturing the insulation structure and the separator, reduce the risk of cell short circuit, and improve the safety performance of the cell.

[0030] In some embodiments of the first aspect of this application, the first distance and the second distance are equal.

[0031] In one or more of the above optional embodiments, by making the first distance and the second distance equal, the dimensions of the portion of the second insulating layer located on one side of the third straight section along the winding direction and the dimensions of the portion of the second insulating layer located on the other side of the third straight section along the winding direction are the same along the first direction. Under the condition that the dimensions of the portion of the second insulating layer located on one side of the third straight section along the winding direction and the dimensions of the portion of the second insulating layer located on the other side of the third straight section along the winding direction both meet the minimum size requirements, by making the first distance and the second distance equal, the total length of the second insulating layer in the winding direction can be reduced, thereby reducing the space occupied by the second insulating layer, which is beneficial to improving the energy density of the battery cell.

[0032] In some embodiments of the first aspect of this application, the first distance is L1, the second distance is L2, the third distance is L, 0.5mm≤L-L1≤8mm, and 0.5mm≤L-L2≤8mm.

[0033] In one or more of the above optional embodiments, by setting L-L1≥0.5mm and L-L2≥0.5mm, a portion of the second insulating layer is located on one side of the third straight section along the first direction, and another portion of the second insulating layer is located on the other side of the third straight section. This allows the second insulating layer to overlap with the third straight section on both sides of the third straight section, resulting in a larger coverage area for the second insulating layer. With L-L1≤8mm and L-L2≤8mm, this helps to reduce the size of the portion of the second insulating layer distributed on both sides of the third straight section along the first direction, thereby reducing the area of ​​overlap between the second insulating layer and the third straight section on both sides of the third straight section, thus reducing the space occupied by the second insulating layer and improving the energy density of the battery cell.

[0034] In some embodiments of the first aspect of this application, along the winding direction, there is a first gap between the second insulating layer and the first segment, and a second gap between the second insulating layer and the second segment.

[0035] In one or more of the above optional embodiments, by having a first gap between the second insulating layer and the first segment and a second gap between the second insulating layer and the second segment along the winding direction, it is convenient to place the second insulating layer between the first segment and the second segment, reducing the process difficulty. Moreover, the first gap and the second gap reserve expansion space for the first active material layer and the second insulating layer, reducing the risk of the second insulating layer being squeezed against the first segment and the second segment after the second insulating layer and the second active material layer expand, thereby reducing the risk of powder shedding and the second insulating layer falling off or curling.

[0036] In some embodiments of the first aspect of this application, the first gap is L3, the second gap is L4, 0mm < L3 ≤ 2mm, and 0mm < L4 ≤ 2mm.

[0037] In one or more of the above optional embodiments, by having a first gap greater than 0 mm and a second gap greater than 0 mm, it is easier to place the second insulating layer between the first and second segments, reducing the difficulty of the process. Furthermore, the first and second gaps provide expansion space for the first active material layer and the second insulating layer, reducing the risk of compression between the second insulating layer and the first segment, and between the second insulating layer and the second segment after expansion. This reduces the risk of powder shedding and the second insulating layer detaching or warping. If the first gap is less than or equal to 2 mm and the second gap is less than or equal to 2 mm, it helps to reduce the area of ​​the first insulating layer not covered by the second insulating layer, and the area of ​​the first empty foil area covered by a thinner insulating layer. This reduces the risk of the insulating layer being punctured by burrs in the first empty foil area, thereby reducing the risk of burrs puncturing the insulating layer and the separator, reducing the risk of short circuits in the battery cell, and improving the safety performance of the battery cell. Therefore, 0 mm < L3 ≤ 2 mm and 0 mm < L4 ≤ 2 mm reduce the difficulty of setting the second insulating layer and reduce the risk of powder shedding and the second insulating layer detaching or warping.

[0038] In some embodiments of the first aspect of this application, the first bending region is connected to one end of the straight region along the second direction, and a third gap is formed between the second insulating layer and the negative electrode winding start end along the second direction.

[0039] In one or more of the above optional embodiments, by having a third gap between the second insulating layer and the negative electrode winding start end along the second direction, the risk of contact between the negative electrode winding start end and the second insulating layer is reduced, thereby improving the safety performance of the battery cell.

[0040] In some embodiments of the first aspect of this application, the sum of the thicknesses of the first insulating layer and the second insulating layer is greater than or equal to 40 μm.

[0041] In one or more of the above optional embodiments, by having the sum of the thicknesses of the first insulating layer and the second insulating layer greater than or equal to 40 μm, the overall insulating structure covering the first empty foil area is thicker, which helps to reduce the risk of the insulating structure being punctured by burrs in the first empty foil area, thereby reducing the risk of the insulating structure and the separator being punctured by burrs in the first empty foil area, reducing the risk of cell short circuit, and improving the safety performance of the cell.

[0042] In some embodiments of the first aspect of this application, the first insulating layer is an insulating coating.

[0043] In one or more of the above optional embodiments, by using the first insulating layer as an insulating coating, the connection stability between the first insulating layer and the first empty foil area is improved.

[0044] In some embodiments of the first aspect of this application, the first bending region is connected to one end of the straight region along the second direction. Along the winding direction of the positive electrode sheet, the first insulating layer has a third end and a fourth end opposite to each other. Along the second direction, the distance between the third end and the positive electrode winding start end is a fourth distance, the distance between the fourth end and the positive electrode winding start end is a fifth distance, and the distance between the negative electrode winding start end and the positive electrode winding start end is a third distance. The fourth distance is smaller than the third distance, and the fifth distance is smaller than the third distance.

[0045] In one or more of the above optional embodiments, by making the fourth distance smaller than the third distance and the fifth distance smaller than the third distance, the overlapping area of ​​the first insulating layer and the third straight segment is larger when viewed along the first direction, thereby increasing the connection area between the first insulating layer and the first active material layer and improving the connection stability of the first insulating layer.

[0046] In some embodiments of the first aspect of this application, the fourth distance and the fifth distance are equal.

[0047] In one or more of the above optional embodiments, by making the fourth distance and the fifth distance equal, the dimensions of the portion of the first insulating layer located on one side of the third straight section along the winding direction are the same as the dimensions of the portion of the first insulating layer located on the other side of the third straight section along the winding direction. While ensuring that the dimensions of the portion of the first insulating layer located on one side of the third straight section along the winding direction and the dimensions of the portion of the first insulating layer located on the other side of the third straight section along the winding direction both meet the minimum size requirements, by making the fourth distance and the fifth distance equal, the total length of the first insulating layer in the winding direction can be reduced, thereby reducing the space occupied by the first insulating layer and improving the energy density of the battery cell.

[0048] In some embodiments of the first aspect of this application, the fourth distance and the fifth distance are not equal.

[0049] In one or more of the above optional embodiments, since the fourth distance and the fifth distance are not equal, when setting the first insulating layer, it is not necessary to precisely position the first insulating layer to ensure that the fourth distance and the fifth distance are equal, which helps to reduce the manufacturing difficulty of the battery cell.

[0050] Secondly, embodiments of this application also provide an electrical device, which includes the battery cell provided in any embodiment of the first aspect.

[0051] In one or more of the above optional embodiments, the battery cell provided in any embodiment of the first aspect has good safety and can improve the power safety and power reliability of electrical equipment powered by the battery cell. Attached Figure Description

[0052] 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.

[0053] Figure 1 is a cross-sectional view of a battery cell provided in some embodiments of this application;

[0054] Figure 2 is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0055] Figure 3 is a partial schematic diagram of the battery assembly in Figure 2;

[0056] Figure 4 is a schematic diagram of the structure of an electrode assembly provided in some other embodiments of this application;

[0057] Figure 5 is a partial schematic diagram of the battery assembly in Figure 4;

[0058] Figure 6 is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0059] Figure 7 is a partial schematic diagram of the electrode assembly in Figure 6;

[0060] Figure 8 is a partial schematic diagram of an electrode assembly provided in some embodiments of this application;

[0061] Figure 9 is a partial structural schematic diagram of an electrode assembly provided in some further embodiments of this application;

[0062] Figure 10 is a partial structural schematic diagram of an electrode assembly provided in some further embodiments of this application.

[0063] Icons: 100 - Cell; 10 - Packaging; 20 - Electrode assembly; 21 - Positive electrode; 21' - Positive electrode winding start; 211 - First section; 2111 - First bent section; 2112 - First straight section; 2113 - Second straight section; 2114 - First current collector; 21141 - First surface; 21142 - First empty foil area; 2115 - First active material layer; 21151 - First segment; 21152 - Second segment; 22 - Negative electrode; 22' - Negative electrode winding start; 221 - Second section; 221 1-Second bending section; 2212-Third straight section; 2213-Fourth straight section; 23-Separating membrane; 24-First insulating layer; 241-Third end; 242-Fourth end; 25-Second insulating layer; 251-First end; 252-Second end; Q1-Straight area; Q2-First bending area; Q3-Second bending area; X-First direction; M1-First overlapping area; M2-Second overlapping area; M3-First gap; M4-Second gap; M5-Third gap; Y-Second direction; Z-Extension direction of winding axis; K-Wound direction. Embodiments of the present invention

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] A battery cell includes an electrode assembly, which comprises a separator, a positive electrode, and a negative electrode. The electrode assembly operates by the movement of metal ions between the positive and negative electrode. The battery cell's cycling process is the process of metal ions moving from the positive electrode to the negative electrode and then from the negative electrode to the positive electrode.

[0070] In related technologies, during the winding process of electrode assemblies, the positive and negative electrode sheets of the electrode assembly are wound in the same direction. This means the starting ends of the positive and negative windings of the positive and negative electrode sheets face the same direction. The innermost electrode sheet of the electrode assembly is the negative electrode sheet. Since the innermost negative electrode sheet only has a positive electrode sheet opposite it on the side facing away from the winding axis, the innermost negative electrode sheet only has a negative active material layer on the side facing away from the winding axis. This creates an empty foil area on the side of the innermost negative electrode sheet facing the winding axis, preventing the full utilization of the negative current collector. Therefore, it is necessary to coat only one side of the innermost negative electrode sheet. However, when manufacturing the negative electrode sheet, since the starting section of winding for each negative electrode sheet requires single-sided coating of the negative active material layer, the coating method needs to be changed, severely affecting coating efficiency and thus production efficiency. When winding to form an electrode assembly, the positive and negative electrode sheets are usually wound in the same direction, with the separator being wound first. The length of the separator winding is longer than that of the negative electrode sheet, and the starting end of the separator winding extends beyond the starting end of the negative electrode winding of the negative electrode sheet. The length of the negative electrode winding is longer than that of the positive electrode sheet, and the starting end of the negative electrode winding of the negative electrode sheet extends beyond the starting end of the positive electrode winding of the positive electrode sheet. This winding method leads to a reduction in the production efficiency of the battery cell.

[0071] To alleviate the aforementioned problems, related technologies employ a method that alters the winding direction of the positive and negative electrode sheets. The positive electrode's winding direction is reversed compared to the negative electrode's. The corner segment of the innermost winding of the negative electrode sheet, facing the positive electrode, is positioned at the starting point of the negative winding, while the corner segment of the innermost winding of the positive electrode sheet, facing the negative electrode, forms a plug-in electrode assembly. This allows for double-sided coating of the innermost ring of the negative electrode sheet, eliminating the need to change the coating process during negative electrode sheet manufacturing. Furthermore, both sides of the innermost ring of the negative electrode sheet have corresponding positive electrode sheets, maximizing the utilization of the negative electrode sheet's active layer. However, the corner segment of the innermost winding of the negative electrode sheet, where the starting point of the negative winding faces the positive electrode, results in less active material at the corresponding positions, making lithium deposition more likely near the starting point of the negative winding. To mitigate the issue of lithium plating near the negative electrode winding start point in plug-in electrode assemblies, related technologies remove a portion of the active material from the innermost corner section of the positive electrode winding facing the negative electrode winding start point. This reduces the thickness of the active layer on the side of the innermost corner section facing the negative electrode winding start point, thereby lowering the risk of lithium plating. However, due to the winding bend, cracks easily appear in the current collector of the positive electrode at the innermost corner section. This allows ions from the current collector inside the innermost corner section to easily migrate through the cracks to the negative electrode outside the innermost corner section of the positive electrode, leading to lithium plating at the negative electrode outside the innermost corner section of the positive electrode, thus reducing cell safety.

[0072] 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 has a wound structure and includes a flat region and a first bending region, with the first bending region connected to one end of the flat region. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a first insulating layer. The positive electrode sheet has a first portion, which includes a first bending segment located in the first bending region and a first flat segment and a second flat segment located in the flat region. The first flat segment and the second flat segment are respectively connected to the two ends of the first bending segment, and the end of the first flat segment facing away from the first bending segment is the positive electrode sheet. The positive electrode winding start end and the negative electrode sheet include a third straight section located in the straight region. Along the first direction, the third straight section is located between the first straight section and the second straight section. The end of the third straight section facing the first bending section is the negative electrode winding start end of the negative electrode sheet. The first part includes a first current collector and a first active material layer. The first current collector has a first surface facing the third straight section. The first surface is provided with the first active material layer. The first surface has a first empty foil area located at least partially in the first bending region. A first insulating layer covers the first empty foil area. The first insulating layer is configured to insulate and isolate the third straight section and the first empty foil area.

[0073] A first empty foil area is formed inside the first bending region of the first portion of the positive electrode sheet. This removes the active material inside the first bending region, which helps reduce the risk of lithium plating on the negative electrode sheet at the third straight section. It also prevents ions on the first surface from moving through the crack in the first bending section via the first current collector to the negative electrode sheet outside the first bending section, thus reducing the risk of lithium plating on the negative electrode sheet outside the first bending section and improving the cell's safety performance. If only a first insulating layer is provided, active material remains inside the first bending region. Because one direction of lithium ion movement in this remaining active material is blocked by the first insulating layer, lithium ions will move towards the crack from the negative electrode sheet outside the first bending section, leading to lithium plating on the outer negative electrode sheet. By covering the first empty foil area with the first insulating layer, the risk of ions on the side of the first bent section of the positive electrode sheet away from the first surface moving through the cracks in the first empty foil area to the third straight section of the negative electrode sheet can be reduced, further reducing the risk of lithium deposition in the third straight section of the negative electrode sheet. Covering the first empty foil area with the first insulating layer can also reduce the risk of short circuit caused by burrs in the first empty foil area puncturing the insulation, thus improving the safety performance of the battery.

[0074] In this application, the empty foil area refers to the area where the active material has been removed to expose the current collector foil.

[0075] The battery cells disclosed in this application can be used, but are not limited to, in electrical devices such as electric two-wheelers, power tools, drones, and energy storage devices. Battery cells with the operating conditions described in this application can also be used as the power supply system for electrical devices, which helps improve the safety performance of the power supply system.

[0076] This application provides an electrical device that uses battery cells 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.

[0077] As shown in Figures 1 and 2, this application provides a battery cell 100, which includes a package 10 and an electrode assembly 20, with the electrode assembly 20 housed within the package 10.

[0078] The packaging component 10 can be a rigid shell, such as a stainless steel shell or an aluminum hard shell, forming a steel-shell battery or an aluminum-shell battery.

[0079] The packaging component 10 can also be made of a softer material, such as aluminum-plastic film or steel-plastic film, to form a soft-pack battery cell.

[0080] The electrode assembly 20 has a wound structure. The electrode assembly 20 includes a straight region Q1, a first bending region Q2, and a second bending region Q3, with the second direction Y. The first bending region Q2 and the second bending region Q3 are respectively connected to the two ends of the straight region Q1.

[0081] The electrode assembly 20 includes a positive electrode 21, a negative electrode 22, and a separator 23. The separator 23 is disposed between the positive electrode 21 and the negative electrode 22, and the separator 23 provides insulation between the positive electrode 21 and the negative electrode 22 to reduce the risk of short circuit in the cell 100 caused by contact between the positive electrode 21 and the negative electrode 22.

[0082] The electrode assembly 20 includes two separators 23, a positive electrode 21, a negative electrode 22, and the two separators 23 are stacked in a certain order and wound around a winding axis.

[0083] The positive electrode 21 includes a positive current collector and a positive active material layer, wherein the positive current collector has a positive active material layer disposed on at least one side in its thickness direction.

[0084] The negative electrode 22 includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode current collector has a negative electrode active material layer disposed on at least one side in its thickness direction.

[0085] Taking cell 100 as an example of a lithium-ion battery, the positive electrode current collector can be made of aluminum, and the positive electrode active material layer can be made of lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode current collector can be made of copper, and the negative electrode active material layer can be made of carbon or silicon, etc.

[0086] As shown in Figures 2 and 3, the positive electrode 21 has a first portion 211, which includes a first bent segment 2111 located in the first bent region Q2 and a first straight segment 2112 and a second straight segment 2113 located in the straight region Q1. The first straight segment 2112 and the second straight segment 2113 are respectively connected to the two ends of the first bent segment 2111. The end of the first straight segment 2112 facing away from the first bent segment 2111 is the positive electrode winding start end of the positive electrode 21. The positive electrode winding start end can be located at the connection position of the second bent region Q3 and the straight region Q1. There can be a distance between the positive electrode winding start end and the connection position of the second bent region Q3 and the straight region Q1.

[0087] The negative electrode 22 includes a third straight segment 2212 located in the straight region Q1. Along the first direction X, the third straight segment 2212 is located between the first straight segment 2112 and the second straight segment 2113. The end of the third straight segment 2212 facing the first bending segment 2111 is the negative electrode winding start end of the negative electrode 22. The negative electrode winding start end can be located at the connection point between the first bending region Q2 and the straight region Q1. There can be a distance between the negative electrode winding start end and the connection point between the first bending region Q2 and the straight region Q1.

[0088] The first part 211 includes a first current collector 2114 and a first active material layer 2115. The first current collector 2114 has a first surface 21141 facing the third straight section 2212. The first surface 21141 is provided with the first active material layer 2115. The first surface 21141 has a first empty foil located at least partially in the first bending region Q2.

[0089] The first part 211 can be the innermost ring of the positive electrode 21. The first bending segment 2111 is the corner segment of the innermost ring of the positive electrode 21. The first current collector 2114 of the first part 211 is part of the positive current collector, and the first active material layer 2115 is part of the positive active material layer. The first surface 21141 of the first current collector 2114 has a first empty foil region 21142, which is the area of ​​the first surface 21141 where the first active material layer 2115 is not provided. The first empty foil region 21142 is at least partially located in the first bending region Q2. It can be understood that the first current collector 2114 located in the first bending segment 2111 has the positive active material layer only on the side opposite to the third straight segment 2212. As shown in Figure 2, the first active material layer 2115 includes a first segment 21151 and a second segment 21152 spaced apart along the winding direction K of the positive electrode sheet, and the first empty foil area 21142 is located between the first segment 21151 and the second segment 21152.

[0090] A first empty foil region 21142 is formed inside the first bending region Q2 of the first portion 211 of the positive electrode 21, which reduces the mass of active material inside the first portion 211. This helps to reduce the risk of lithium deposition on the negative electrode 22 at the third straight section 2212. It also prevents ions from moving from the first surface 21141 in the first bending region Q2 through the cracks in the first current collector 2114 in the first bending section 2111 to the negative electrode 22 outside the first bending section 2111, thereby reducing the risk of lithium deposition on the negative electrode 22 outside the first bending section 2111 and improving the safety performance of the cell 100.

[0091] The negative electrode 22 includes a second part 221, which includes a second bent section 2211, a third straight section 2212, and a fourth straight section 2213. The second bent section 2211 is located at the second bent section 2211. The third straight section 2212 and the fourth straight section 2213 are respectively connected to the two ends of the second bent section 2211. Along the first direction X, the third straight section 2212 and the fourth straight section 2213 are located on both sides of the first straight section 2112, and the first straight section 2112 is located between the third straight section 2212 and the fourth straight section 2213. The second part 221 can be the innermost ring of the negative electrode 22, and the second bent section 2211 is the corner segment of the innermost ring of the negative electrode 22.

[0092] The positive electrode winding start end faces the second bending section 2211, therefore, the negative electrode winding start end and the positive electrode winding start end face opposite directions. Negative electrode active material layers are provided on both sides of the portion of the negative electrode current collector located in the third straight section 2212.

[0093] As shown in Figures 2 and 3, the electrode assembly 20 also includes a first insulating layer 24, which covers the first empty foil area 21142. The first insulating layer 24 is configured to insulate and isolate the third straight section 2212 and the first empty foil area 21142.

[0094] Along the extension direction Z of the winding axis of the electrode assembly 20, the first empty foil region 21142 extends to both edges of the first active material layer. The first insulating layer 24 covering the first empty foil region 21142 means that the first insulating layer 24 completely covers the first empty foil region 21142. Specifically, the first insulating layer 24 covers the first empty foil region 21142 along the extension direction Z of the winding axis of the electrode assembly 20, and the first insulating layer 24 also covers the first empty foil region 21142 along the winding direction K.

[0095] By covering the first empty foil area 21142 with the first insulating layer 24, the risk of ions on the side of the first bent section 2111 of the positive electrode 21 away from the first surface 21141 moving through the cracks in the first empty foil area 21142 to the third straight section 2212 of the negative electrode 22 can be reduced, further reducing the risk of lithium deposition in the third straight section 2212 of the negative electrode 22. Covering the first empty foil area 21142 with the first insulating layer 24 can also reduce the risk of short circuit caused by burrs in the first empty foil area 21142 puncturing the insulation, thus improving the safety performance of the battery.

[0096] The thickness of the portion of the first insulating layer 24 covering the first empty foil area 21142 can be less than the thickness of the first segment 21151 and the second segment 21152. This prevents the first insulating layer 24 from protruding from the first active material layer 2115 and away from the surface of the first surface 21141 in the portion of the first empty foil area 21142. It also prevents the increase in the thickness of the electrode assembly 20 due to the increase of the first insulating layer 24, which is beneficial to improving the energy density of the battery cell 100.

[0097] The first insulating layer 24 can be adhesive tape, an insulating coating, etc. In some embodiments, the first insulating layer 24 is an insulating coating.

[0098] Insulating coatings can be made of materials such as ceramic layers, adhesive layers, or PP (Polypropylene) layers.

[0099] By using the first insulating layer 24 as an insulating coating, the connection stability between the first insulating layer 24 and the first empty foil area 21142 is improved.

[0100] The first empty foil area 21142 can be completely located in the first bending area Q2, or the first empty foil area 21142 can be partially located in the first bending area Q2, with the other part of the first empty foil area 21142 located in the flat area Q1. Figure 2 shows the case where the first empty foil area 21142 is partially located in the first bending area Q2 and the other part is located in the flat area Q1.

[0101] In embodiments where the first empty foil region 21142 can be completely located within the first bending region Q2, both the first segment 21151 and the second segment 21152 are located within the flat region Q1; or, the first segment 21151 can be located within the flat region Q1, a portion of the second segment 21152 is located within the flat region Q1, and the other portion of the second segment 21152 is located within the first bending region Q2; or, the second segment 21152 can be located within the flat region Q1, a portion of the first segment 21151 is located within the flat region Q1, and the other portion of the first segment 21151 is located within the first bending region Q2; or, a portion of the first segment 21151 is located within the flat region Q1, and the other portion of the first segment 21151 is located within the first bending region Q2, a portion of the second segment 21152 is located within the flat region Q1, and the other portion of the second segment 21152 is located within the first bending region Q2.

[0102] As shown in Figures 2 and 3, the first segment 21151 and the second segment 21152 are both located in the flat region Q1, and the portion of the first surface 21141 located in the first bending region Q2 completely forms the first empty foil region 21142. By having both the first segment 21151 and the second segment 21152 located in the flat region Q1, the first surface 21141 at least in the region of the first bending segment 2111 forms the first empty foil region 21142, making the area of ​​the first empty foil region 21142 larger, further reducing the risk of lithium plating on the negative electrode sheet 22 in the third flat segment 2212, and improving the safety performance of the cell 100.

[0103] In an embodiment where a portion of the first empty foil area 21142 is located in the first bending area Q2 and another portion of the first empty foil area 21142 is located in the straight area Q1, and in an embodiment where both the first segment 21151 and the second segment 21152 are located in the straight area Q1, in the winding direction K, both ends of the first empty foil area 21142 may be located in the straight area Q1; or, one end of the first empty foil area 21142 may be located in the first bending area Q2 and the other end of the first empty foil area 21142 may be located in the straight area Q1.

[0104] For example, as shown in FIG2, in some embodiments, at least a portion of the first segment 21151 is located in the first straight segment 2112, at least a portion of the second segment 21152 is located in the second straight segment 2113, and along the winding direction K, the first empty foil area 21142 is located between the first segment 21151 and the second segment 21152.

[0105] The first segment 21151 can be entirely located in the first straight segment 2112 (as shown in Figure 2). Alternatively, the first segment 21151 can be partially located in the first straight segment 2112, with the other part of the first segment 21151 located in the first bent segment 2111.

[0106] The second segment 21152 can be entirely located in the second straight segment 2113 (as shown in Figure 2). Alternatively, the second segment 21152 can be partially located in the second straight segment 2113, with the other part of the second segment 21152 located in the first bent segment 2111.

[0107] Along the winding direction K, the first empty foil area 21142 can be entirely located in the first bent section 2111; or, the first empty foil area 21142 can be partially located in the first bent section 2111 and partially located in the first straight section 2112; or, the first empty foil area 21142 can be partially located in the first bent section 2111 and partially located in the second straight section 2113; or, the first empty foil area 21142 can be partially located in the first bent section 2111, partially located in the first straight section 2112, and partially located in the second straight section 2113. Figure 2 shows the case where the first empty foil area 21142 is partially located in the first bent section 2111, partially located in the first straight section 2112, and partially located in the second straight section 2113.

[0108] With at least a portion of the first segment 21151 of the first active material layer 2115 located in the first straight segment 2112, and at least a portion of the second segment 21152 of the first active material layer 2115 located in the second straight segment 2113, along the winding direction K, the first empty foil area 21142 is located between the first segment 21151 and the second segment 21152. Thus, the first empty foil area 21142 is closer to the negative electrode winding start end, resulting in less active material mass in the region corresponding to the positive electrode 21 and the negative electrode winding start end. This helps to reduce the risk of lithium plating on the negative electrode 22 at the negative electrode winding start end and improves the safety performance of the cell 100.

[0109] Along the winding direction K, the first insulating layer 24 can be completely located between the first segment 21151 and the second segment 21152 to reduce the space occupied by the first insulating layer 24, which is beneficial to improving energy density.

[0110] Along the winding direction K, the first insulating layer 24 can also extend beyond the space beyond the first segment 21151 and the second segment 21152, which facilitates the setting of the first insulating layer 24, increases the coverage area of ​​the first insulating layer 24, and thus increases the connection area between the first insulating layer 24 and the first portion 211, improving connection stability. The first insulating layer 24 can extend beyond the space beyond the first segment 21151 and the second segment 21152 at one end, or it can extend beyond the space beyond the first segment 21151 and the second segment 21152 at both ends.

[0111] As shown in Figures 2 and 3, in some embodiments, a portion of the first insulating layer 24 overlaps with a portion of the first segment 21151 to form a first overlapping area M1, and a portion of the first insulating layer 24 overlaps with a portion of the second segment 21152 to form a second overlapping area M2. Along the winding direction K, the second overlapping area M2 and the first overlapping area M1 are located on both sides of the first empty foil area 21142.

[0112] If a portion of the first insulating layer 24 overlaps with a portion of the first segment 21151, and a portion of the first insulating layer 24 overlaps with a portion of the second segment 21152, then both ends of the first insulating layer 24 extend beyond the space beyond the first segment 21151 and the second segment 21152.

[0113] By having a portion of the first insulating layer 24 overlap with the first segment 21151 to form a first overlapping area M1, and a portion of the first insulating layer 24 overlap with the second segment 21152 to form a second overlapping area M2, the connection area between the first insulating layer 24 and the positive electrode plate 21 can be increased, the connection stability of the first insulating layer 24 can be improved, and the first insulating layer 24 does not need to be precisely positioned between the first segment 21151 and the second segment 21152, thus reducing the difficulty of the process.

[0114] As shown in Figures 2 and 3, in some embodiments, along the thickness direction of the positive electrode 21, in the first overlap region M1, the first insulating layer 24 is closer to the first surface 21141 than the first segment 21151; in the second overlap region M2, the first insulating layer 24 is closer to the first surface 21141 than the second segment 21152.

[0115] Specifically, in the first overlapping region M1, the two surfaces of the first insulating layer 24 are respectively connected to the first surface 21141 and the first segment 21151, and in the second overlapping region M2, the two surfaces of the first insulating layer 24 are respectively connected to the first surface 21141 and the second segment 21152.

[0116] Specifically, in the first overlap region M1, the thickness of the first segment 21151 can be less than the thickness of the first segment 21151 outside the first overlap region M1, so that the surface of the first segment 21151 in the first overlap region M1 facing away from the first surface 21141 can be flush with the surface of the first segment 21151 outside the first overlap region M1 facing away from the first surface 21141, thereby alleviating the problem of increased thickness of the electrode assembly 20 due to the provision of the first insulating layer 24. In particular, in the first overlap region M1, the sum of the thickness of the first segment 21151 and the thickness of the first insulating layer 24 is the same as the thickness of the portion of the first segment 21151 outside the first overlap region M1.

[0117] In the second overlap region M2, the thickness of the second segment 21152 can be less than the thickness of the second segment 21152 outside the second overlap region M2, so that the surface of the second segment 21152 in the second overlap region M2 facing away from the first surface 21141 can be flush with the surface of the second segment 21152 outside the second overlap region M2 facing away from the first surface 21141, thereby alleviating the problem of increased thickness of the electrode assembly 20 due to the provision of the first insulating layer 24. Specifically, in the second overlap region M2, the sum of the thickness of the second segment 21152 and the thickness of the first insulating layer 24 is the same as the thickness of the portion of the second segment 21152 outside the second overlap region M2.

[0118] In other embodiments, in the first overlapping region M1, the thickness of the first segment 21151 may be equal to the thickness of the first segment 21151 in the region outside the first overlapping region M1, and in the second overlapping region M2, the thickness of the second segment 21152 may be equal to the thickness of the second segment 21152 in the region outside the second overlapping region M2.

[0119] In the first overlap region M1, the first insulating layer 24 is closer to the first surface 21141 than the first segment 21151. Therefore, the first segment 21151 of the first active material layer 2115 covers the surface of the first insulating layer 24 away from the first surface 21141. In the second overlap region M2, the first insulating layer 24 is closer to the first surface 21141 than the second segment 21152. Therefore, the second segment 21152 of the first active material layer 2115 covers the surface of the first insulating layer 24 away from the first surface 21141. The first active material layer 2115 enables the first insulating layer 24 to be stably connected to the first surface 21141.

[0120] In other embodiments, in the first overlap region M1, the first segment 21151 is closer to the first surface 21141 than the first insulating layer 24; in the second overlap region M2, the second segment 21152 is closer to the first surface 21141 than the first insulating layer 24.

[0121] As shown in Figures 2 and 3, in some embodiments, at least a portion of the projection of the first overlapping region M1 overlaps with at least a portion of the projection of the second overlapping region M2 in a projection plane perpendicular to the first direction X.

[0122] Understandably, when viewed along the first direction X, at least a portion of the projection of the first overlapping region M1 overlaps with at least a portion of the projection of the second overlapping region M2. Specifically, when viewed along the first direction X, the projection of the first overlapping region M1 may partially overlap with a portion of the projection of the second overlapping region M2. Alternatively, when viewed along the first direction X, the projection of the first overlapping region M1 may completely overlap with the projection of the second overlapping region M2.

[0123] While ensuring that the dimensions of the first overlapping region M1 and the second overlapping region M2 in the winding direction K both meet the minimum size requirements, by having at least a portion of the projection of the first overlapping region M1 overlap with at least a portion of the projection of the second overlapping region M2 in a projection plane perpendicular to the first direction X, the total length of the first insulating layer 24 in the winding direction K can be reduced, thereby reducing the space occupied by the first insulating layer 24, which is beneficial to improving the energy density of the cell 100. In the first overlapping region M1, the first insulating layer 24 is closer to the first surface 21141 than the first segment 21151; in the second overlapping region M2, the first insulating layer 24 is closer to the first surface 21141 than the second segment 21152. The reduction in the total length of the first insulating layer 24 in the winding direction K is also beneficial to reducing the loss of the first active material layer 2115, further improving the energy density of the cell 100.

[0124] As shown in Figures 4 and 5, in some embodiments, the projections of the first overlapping region M1 and the second overlapping region M2 do not overlap in the projection plane perpendicular to the first direction X.

[0125] Understandably, when viewed along the first direction X, the projections of the first overlapping region M1 and the second overlapping region M2 are arranged side-by-side along the second direction Y. In some embodiments, along the second direction Y, the distance between the first overlapping region M1 and the positive electrode winding start end is greater than the distance between the second overlapping region M2 and the positive electrode winding start end. Alternatively, in other embodiments, along the second direction Y, the distance between the first overlapping region M1 and the positive electrode winding start end is less than the distance between the second overlapping region M2 and the positive electrode winding start end (as shown in Figures 4 and 5).

[0126] By ensuring that the projections of the first overlapping area M1 and the second overlapping area M2 do not overlap in the projection plane perpendicular to the first direction X, the overlap of the first overlapping area M1 and the second overlapping area M2 in the first direction X is avoided, which would cause excessive thickness in a local area of ​​the electrode assembly 20. This reduces the thickness difference between different parts of the electrode assembly 20, lowers the risk of local stress concentration in the positive electrode 21 and / or the negative electrode 22, and lowers the risk of breakage due to excessive local stress in the positive electrode 21 and / or the negative electrode 22, thereby improving the safety of the battery cell 100.

[0127] In some embodiments, the size of the first overlapping region M1 is not equal to the size of the second overlapping region M2 along the winding direction K.

[0128] The size of the first overlapping region M1 is W1, and the size of the second overlapping region M2 is W2. W1 and W2 may not be equal.

[0129] Along the winding direction K, the size of the first overlapping area M1 can be smaller than the size of the second overlapping area M2, and the size of the first overlapping area M1 can also be larger than the size of the second overlapping area M2.

[0130] Since the dimensions of the first overlapping region M1 along the winding direction are not equal to those of the second overlapping region M2 along the winding direction, when the first insulating layer 24 is set on the positive electrode 21, precise positioning is not required, which helps to reduce the manufacturing difficulty of the cell 100.

[0131] In some embodiments, along the winding direction K, the size of the first overlapping region M1 is the same as the size of the second overlapping region M2.

[0132] The size of the first overlapping region M1 is W1, and the size of the second overlapping region M2 is W2. W1 and W2 can be equal.

[0133] Along the second direction Y, the distance between the end of the first overlapping region M1 near the positive electrode winding start end and the distance between the end of the second overlapping region M2 near the positive electrode winding start end and the positive electrode winding start end can be equal. The distance between the end of the first overlapping region M1 away from the positive electrode winding start end and the distance between the end of the second overlapping region M2 away from the positive electrode winding start end and the positive electrode winding start end can be equal. Therefore, the first overlapping region M1 and the second overlapping region M2 can be symmetrically arranged about the symmetrical plane passing through the center of the first bending segment 2111.

[0134] While ensuring that the dimensions of the first overlapping region M1 and the second overlapping region M2 in the winding direction K both meet the minimum size requirements, by making the dimensions of the first overlapping region M1 in the winding direction K equal to those of the second overlapping region M2 in the winding direction K, the total length of the first insulating layer 24 in the winding direction K can be reduced, thereby reducing the space occupied by the first insulating layer 24 and improving the energy density of the cell 100. In the first overlapping region M1, the first insulating layer 24 is closer to the first surface 21141 than the first segment 21151; in the second overlapping region M2, the first insulating layer 24 is closer to the first surface 21141 than the second segment 21152. The reduction in the total length of the first insulating layer 24 in the winding direction K also helps to reduce the loss of the first active material layer 2115 and further improve the energy density of the cell 100.

[0135] In an embodiment where the dimensions of the first overlapping region M1 and the second overlapping region M2 are the same along the winding direction K, the distance between the end of the first overlapping region M1 near the positive electrode winding start end and the positive electrode winding start end along the second direction Y may not be equal to the distance between the end of the second overlapping region M2 near the positive electrode winding start end and the positive electrode winding start end.

[0136] As shown in Figures 2-5, in some embodiments, along the winding direction K, the size of the first overlapping area M1 is W1, the size of the second overlapping area M2 is W2, 0mm < W1 ≤ 5mm, and 0mm < W2 ≤ 5mm.

[0137] W1 is the distance between the two ends of the first overlapping region M1 along the winding direction K. W2 is the distance between the two ends of the first overlapping region M1 along the winding direction K. W1 and W2 may be equal or unequal.

[0138] For example, W1 can be 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc.

[0139] W2 can be 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc.

[0140] If the dimension of the first overlapping region M1 along the winding direction K is greater than 0 mm, then the portion of the first insulating layer 24 located in the first overlapping region M1 along the winding direction K is greater than 0 mm. Similarly, if the dimension of the second overlapping region M2 along the winding direction is greater than 0 mm, then the portion of the first insulating layer 24 located in the second overlapping region M2 along the winding direction K is greater than 0 mm. This increases the connection area between the first insulating layer 24 and the positive electrode 21, thereby improving the connection stability of the first insulating layer 24. If the dimension of the first overlapping region M1 along the winding direction K is less than or equal to 5 mm, then the portion of the first insulating layer 24 located in the first overlapping region M1 along the winding direction K is less than or equal to 5 mm. Similarly, if the dimension of the second overlapping region M2 along the winding direction K is less than 5 mm, then the portion of the first insulating layer 24 located in the second overlapping region M2 along the winding direction K is less than or equal to 5 mm. This reduces the space occupied by the first insulating layer 24, thereby improving the energy density of the cell 100. Therefore, 0mm < W1 ≤ 5mm and 0mm < W2 ≤ 5mm are beneficial to improving the connection stability of the first insulation layer 24 and the energy density of the cell 100.

[0141] In embodiments where both W1 and W2 are 0, the first insulating layer 24 is completely located between the first segment 21151 and the second segment 21152.

[0142] Furthermore, 0.5mm≤W1≤1mm, 0.5mm≤W2≤1mm.

[0143] For example, W1 can be 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, etc.

[0144] W2 can be 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, etc.

[0145] If the dimension of the first overlapping region M1 along the winding direction K is greater than or equal to 0.5 mm, then the portion of the first insulating layer 24 located in the first overlapping region M1 along the winding direction K has a dimension greater than or equal to 0.5 mm. Similarly, if the dimension of the second overlapping region M2 along the winding direction K is greater than or equal to 0.5 mm, then the portion of the first insulating layer 24 located in the second overlapping region M2 along the winding direction K has a dimension greater than or equal to 0.5 mm. This results in a larger connection area between the first insulating layer 24 and the positive electrode 21, further improving the connection stability of the first insulating layer 24. Conversely, if the dimension of the first overlapping region M1 along the winding direction is less than or equal to 1 mm, then the portion of the first insulating layer 24 located in the first overlapping region M1 along the winding direction K has a dimension less than or equal to 1 mm. Similarly, if the dimension of the second overlapping region M2 along the winding direction K is less than 1 mm, then the portion of the first insulating layer 24 located in the second overlapping region M2 along the winding direction K has a dimension less than or equal to 1 mm. This further reduces the space occupied by the first insulating layer 24, thereby improving the energy density of the battery cell 100. Therefore, 0.5mm≤W1≤1mm and 0.5mm≤W2≤1mm are beneficial to improving the connection stability of the first insulation layer 24 and the energy density of the cell 100.

[0146] As shown in Figures 2-5, in some embodiments, along the winding direction K of the positive electrode sheet, the first insulating layer 24 has a third end 241 and a fourth end 242 opposite to each other. Along the second direction Y, the distance between the third end 241 and the positive electrode winding start end is the fourth distance, the distance between the fourth end 242 and the positive electrode winding start end is the fifth distance, and the distance between the negative electrode winding start end and the positive electrode winding start end is the third distance. The fourth distance is smaller than the third distance, and the fifth distance is smaller than the third distance.

[0147] The third distance is L, the fourth distance is L5, the fifth distance is L6, L5≤L, L6≤L.

[0148] If the fourth distance is less than the third distance, and the fifth distance is less than the third distance, then both ends of the second insulating layer 25 extend to both sides of the third straight segment 2212 in the first direction X.

[0149] By making the fourth distance smaller than the third distance and the fifth distance smaller than the third distance, the area of ​​overlap between the first insulating layer 24 and the third straight segment 2212 is larger when viewed along the first direction X. This increases the connection area between the first insulating layer 24 and the first active material layer 2115, which is beneficial to improving the connection stability of the first insulating layer 24.

[0150] In some embodiments, the fourth distance and the fifth distance are equal.

[0151] It can be understood that the first insulating layer 24 is a symmetrical structure about the center of the first bending segment 2111.

[0152] It should be noted that the fourth and fifth distances are equal, but not necessarily absolutely equal. The allowable error range for the dimensions of the fourth and fifth distances is ±0.5mm.

[0153] By making the fourth and fifth distances equal, the dimensions of the portion of the first insulating layer 24 located on one side of the third straight section 2212 along the winding direction K are the same as the dimensions of the portion of the first insulating layer 24 located on the other side of the third straight section 2212 along the winding direction K. While ensuring that the dimensions of the portion of the first insulating layer 24 located on one side of the third straight section 2212 along the winding direction K and the portion of the first insulating layer 24 located on the other side of the third straight section 2212 along the winding direction K both meet the minimum size requirements, making the fourth and fifth distances equal can reduce the total length of the first insulating layer 24 in the winding direction K, thereby reducing the space occupied by the first insulating layer 24 and improving the energy density of the battery cell 100.

[0154] In another embodiment, the fourth distance and the fifth distance are not equal.

[0155] Since the fourth distance and the fifth distance are not equal, when setting the first insulation layer 24, it is not necessary to precisely position the first insulation layer 24 to ensure that the fourth distance and the fifth distance are equal, which helps to reduce the manufacturing difficulty of the battery cell 100.

[0156] In some embodiments, the thickness of the first insulating layer 24 is less than the maximum thickness of the first segment 21151, and / or the thickness of the first insulating layer 24 is less than the maximum thickness of the second segment 21152.

[0157] By making the thickness of the first insulating layer 24 smaller than the maximum thickness of the first segment 21151 and / or the second segment 21152, the first insulating layer 24 can be made not to protrude from the active material, thereby preventing an increase in the thickness of the cell 100.

[0158] As shown in Figures 6 and 7, in some embodiments, the electrode assembly 20 further includes a second insulating layer 25. Along the thickness direction of the positive electrode sheet 21, the first insulating layer 24 is located between the second insulating layer 25 and the first empty foil area 21142. Along the winding direction K, the second insulating layer 25 is located between the first segment 21151 and the second segment 21152.

[0159] The second insulating layer 25 is completely located between the first segment 21151 and the second segment 21152. Along the thickness direction of the second insulating layer 25, the two surfaces of the first insulating layer 24 are respectively connected to the first surface 21141 and the second insulating layer 25.

[0160] By setting a second insulating layer 25, with the first insulating layer 24 located between the second insulating layer 25 and the first empty foil area 21142, and the second insulating layer 25 located between the first segment 21151 and the second segment 21152 along the winding direction K, the overall thickness of the insulating structure covering the first empty foil area 21142 can be increased, reducing the risk of the insulating structure covering the first empty foil area 21142 being punctured by the burrs of the first empty foil area 21142. This reduces the risk of the burrs of the first empty foil area 21142 puncturing the insulating structure and the separator 23, reducing the risk of short circuit in the cell 100 and improving the safety performance of the cell 100. The second insulating layer 25 being located between the first segment 21151 and the second segment 21152 reduces the thickness stacking of the second insulating layer 25 and the first active material layer 2115, which is beneficial for improving the energy density of the cell 100.

[0161] The second insulating layer 25 can be adhesive tape, an insulating coating, etc. In some embodiments, the second insulating layer 25 is adhesive tape, which facilitates the second insulating layer 25 being disposed on the surface of the first insulating layer 24, and the adhesive tape has good flexibility, is easy to bend, and is not prone to curling at the edges.

[0162] In some embodiments, the sum of the thicknesses of the first insulating layer 24 and the second insulating layer 25 is less than the maximum thickness of the first segment 21151, and / or the sum of the thicknesses of the first insulating layer 24 and the second insulating layer 25 is less than the maximum thickness of the second segment 21152.

[0163] In the embodiment where the first insulating layer 24 and the first segment 21151 overlap to form the first overlapping area M1, the maximum thickness of the first segment 21151 may be the thickness of the portion of the first segment 21151 outside the first overlapping area M1.

[0164] In the embodiment where the first insulating layer 24 and the second segment 21152 overlap to form the second overlapping area M2, the maximum thickness of the first segment 21151 can be the thickness of the portion of the second segment 21152 outside the second overlapping area M2.

[0165] Since the sum of the thicknesses of the first insulating layer 24 and the second insulating layer 25 is less than the maximum thickness of the first segment 21151 and / or the maximum thickness of the second segment 21152, the overall structural thickness formed by the first insulating layer 24 and the second insulating layer 25 is smaller. This prevents the structure from protruding beyond the maximum thickness position of the first active material layer 2115 and moving away from the surface of the first current collector 2114. This alleviates the problem of increased thickness of the electrode assembly 20 caused by the installation of the first insulating layer 24 and the second insulating layer 25. It also helps to reduce the thickness difference between different parts of the electrode assembly 20, reduce the risk of local stress concentration in the positive electrode 21 and / or the negative electrode 22, and reduce the risk of breakage due to excessive local stress in the positive electrode 21 and / or the negative electrode 22, thereby improving the safety of the battery cell 100.

[0166] As shown in Figures 6 and 7, in some embodiments, the sum of the thicknesses of the first insulating layer 24 and the second insulating layer 25 is greater than or equal to 40 μm.

[0167] The thickness of the first insulating layer 24 is H1, and the thickness of the second insulating layer 25 is H2, where H1 + H2 ≥ 40 μm. For example, H1 + H2 can be 40 μm, 40.5 μm, 50 μm, 50.5 μm, 51 μm, 51.5 μm, 52 μm, 52.5 μm, 53 μm, 53.5 μm, 54 μm, 55 μm, etc.

[0168] With the sum of the thicknesses of the first insulating layer 24 and the second insulating layer 25 being greater than or equal to 40 μm, the overall insulating structure covering the first empty foil area 21142 is relatively thick. This helps to reduce the risk of the insulating structure being punctured by the burrs in the first empty foil area 21142, thereby reducing the risk of the burrs in the first empty foil area 21142 puncturing the insulating structure and the separator 23, reducing the risk of short circuit in the cell 100, and improving the safety performance of the cell 100.

[0169] As shown in Figures 7 and 8, in some embodiments, along the winding direction K, the second insulating layer 25 has a first end 251 and a second end 252 opposite to each other, the first end 251 being closer to the positive electrode winding start end than the second end 252; along the second direction Y, the distance between the first end 251 and the positive electrode winding start end is a first distance, the distance between the second end 252 and the positive electrode winding start end is a second distance, and the distance between the negative electrode winding start end and the positive electrode winding start end is a third distance, the first distance being less than the third distance, and the second distance being less than the third distance.

[0170] If the first distance is less than the third distance and the second distance is less than the third distance, then both ends of the second insulating layer 25 extend to both sides of the third straight segment 2212 in the first direction X.

[0171] In embodiments where the first distance is less than the third distance and the second distance is less than the third distance, the fourth distance and the fifth distance can be equal (shown in Figure 7), or the fourth distance and the fifth distance can be unequal (shown in Figure 8).

[0172] By making the first distance smaller than the third distance and the second distance smaller than the third distance, the area of ​​overlap between the second insulating layer 25 and the third straight section 2212 when viewed along the first direction X is larger, thereby increasing the coverage area of ​​the second insulating layer 25 and increasing the area with a larger insulation structure thickness corresponding to the first empty foil area 21142. This helps to reduce the risk of burrs in the first empty foil area 21142 puncturing the insulation structure and the separator 23, reduce the risk of short circuit in the cell 100, and improve the safety performance of the cell 100.

[0173] As shown in Figures 7 and 8, in some embodiments, the first distance is L1, the second distance is L2, the third distance is L, 0.5mm≤L-L1≤8mm, and 0.5mm≤L-L2≤8mm.

[0174] For example, L-L1 can be 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, etc.

[0175] L-L2 can be 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, etc.

[0176] By setting L-L1≥0.5mm and L-L2≥0.5mm, along the first direction X, a portion of the second insulating layer 25 is located on one side of the third straight section 2212, and the other portion is located on the other side of the third straight section 2212. This results in the second insulating layer 25 overlapping with the third straight section 2212 on both sides of the third straight region Q1, giving the second insulating layer 25 a larger coverage area. With L-L1≤8mm and L-L2≤8mm, this helps to reduce the size of the portion of the second insulating layer 25 distributed on both sides of the third straight section 2212 along the first direction X, thereby reducing the area of ​​overlap between the second insulating layer 25 and the third straight section 2212 on both sides of the third straight region Q1, thus reducing the space occupied by the second insulating layer 25 and improving the energy density of the battery cell 100.

[0177] As shown in Figures 7 and 8, in some embodiments, the first distance and the second distance are equal.

[0178] In embodiments where the first and second distances are equal, the fourth and fifth distances may be equal (as shown in Figure 7), and the fourth and fifth distances may not be equal (as shown in Figure 8).

[0179] It can be understood that the second insulating layer 25 has a symmetrical structure about the center of the first bending segment 2111. By making the first distance and the second distance equal, the size of the portion of the second insulating layer 25 on one side of the third straight segment 2212 along the winding direction K is the same as the size of the portion of the second insulating layer 25 on the other side of the third straight segment 2212 along the winding direction K. While ensuring that the size of the portion of the second insulating layer 25 on one side of the third straight segment 2212 along the winding direction and the size of the portion of the second insulating layer 25 on the other side of the third straight segment 2212 along the winding direction both meet the minimum size requirements, by making the first distance and the second distance equal, the total length of the second insulating layer 25 in the winding direction K can be reduced, thereby reducing the space occupied by the second insulating layer 25 and improving the energy density of the battery cell 100.

[0180] It should be noted that the first distance and the second distance are equal, but not necessarily absolutely equal. The allowable error range for the dimensions of the first distance and the second distance is ±0.5mm.

[0181] As shown in Figures 9 and 10, in some other embodiments, the first distance and the second distance are not equal.

[0182] That is, L1 and L2 are not equal.

[0183] In embodiments where the first and second distances are not equal, the fourth and fifth distances may be equal (as shown in Figure 9), or the fourth and fifth distances may be unequal (as shown in Figure 10).

[0184] Since the first distance and the second distance are not equal, when the second insulating layer 25 is set on the first insulating layer 24, it is not necessary to precisely position the second insulating layer 25 to ensure that the first distance and the second distance are equal, which helps to reduce the manufacturing difficulty of the battery cell 100.

[0185] As shown in Figures 7 and 8, in some embodiments, along the winding direction K, there is a first gap M3 between the second insulating layer 25 and the first segment 21151, and a second gap M4 between the second insulating layer 25 and the second segment 21152.

[0186] Understandably, along the winding direction K, the second insulating layer 25 does not contact the first segment 21151, and the second insulating layer 25 does not contact the second segment 21152.

[0187] By having a first gap M3 between the second insulating layer 25 and the first segment 21151 and a second gap M4 between the second insulating layer 25 and the second segment 21152 along the winding direction K, it is convenient for the second insulating layer 25 to be placed between the first segment 21151 and the second segment 21152, reducing the difficulty of the process. Moreover, the first gap M3 and the second gap M4 reserve expansion space for the first active material layer 2115 and the second insulating layer 25, reducing the risk of the second insulating layer 25 being squeezed with the first segment 21151 and the second segment 21152 after the second insulating layer 25 and the second active material layer expand, thereby reducing the risk of powder shedding and the second insulating layer 25 falling off or curling.

[0188] As shown in Figure 7, in one embodiment, the first gap M3 and the second gap M4 are equal.

[0189] The first gap M3 and the second gap M4 are equal, which means that along the winding direction K, the distance between the first segment 21151 and the second insulating layer 25 is equal to the distance between the second segment 21152 and the second insulating layer 25.

[0190] By making the first gap M3 and the second gap M4 equal, the problem of the first empty foil area 21142 being covered by a thinner insulating structure due to the first gap M3 and the second gap M4 being too large can be reduced. This reduces the risk of the first empty foil area 21142 puncturing the insulating structure and the separator 23, reduces the risk of the cell 100 short circuit, and improves the safety performance of the cell 100.

[0191] As shown in Figure 8, in some embodiments, the first gap M3 and the second gap M4 are not equal.

[0192] The first gap M3 and the second gap M4 are not equal, which means that along the winding direction K, the distance between the first segment 21151 and the second insulating layer 25 is not equal to the distance between the second segment 21152 and the second insulating layer 25.

[0193] Since the first gap M3 and the second gap M4 are not equal, when the second insulating layer 25 is set on the first insulating layer 24, it is not necessary to precisely position the second insulating layer 25 to ensure that the first gap M3 and the second gap M4 are equal, which helps to reduce the manufacturing difficulty of the battery cell 100.

[0194] As shown in Figures 7 and 8, in some embodiments, the first gap M3 is L3, the second gap M4 is L4, 0mm < L3 ≤ 2mm, and 0mm < L4 ≤ 2mm.

[0195] L3 is the dimension of the first gap M3 along the winding direction K, and it is also the dimension of the first segment 21151 and the second insulating layer 25 along the winding direction. For example, L3 can be 0.1mm, 0.2mm, 0.5mm, 0.7mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm, etc.

[0196] L4 is the dimension of the second gap M4 along the winding direction K, and it is also the dimension of the second segment 21152 and the second insulating layer 25 along the winding direction K. For example, L4 can be 0.1mm, 0.2mm, 0.5mm, 0.7mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm, etc.

[0197] With the first gap M3 greater than 0 mm and the second gap M4 greater than 0 mm, it is convenient to set the second insulating layer 25 between the first segment 21151 and the second segment 21152, reducing the difficulty of the process. Furthermore, the first gap M3 and the second gap M4 reserve expansion space for the first active material layer 2115 and the second insulating layer 25, reducing the risk of the second insulating layer 25 being squeezed with the first segment 21151 and the second segment 21152 after the second insulating layer 25 expands. This reduces the risk of powder shedding and the second insulating layer 25 falling off or curling. When the first gap M3 is less than or equal to 2mm and the second gap M4 is less than or equal to 2mm, it helps to reduce the area of ​​the first insulating layer 24 not covered by the second insulating layer 25, and the area of ​​the first empty foil area 21142 covered by the thinner insulating layer. This reduces the risk of the insulating layer being punctured by burrs in the first empty foil area 21142, thereby reducing the risk of burrs in the first empty foil area 21142 puncturing the insulating layer and the separator 23, reducing the risk of short circuit in the battery cell 100, and improving the safety performance of the battery cell 100. Therefore, 0mm < L3 ≤ 2mm and 0mm < L4 ≤ 2mm reduce the process difficulty of setting the second insulating layer 25 and reduce the risk of powder shedding and the second insulating layer 25 falling off or curling.

[0198] When L3 and L4 are 0, that is, along the winding direction K, the first segment 21151 and the second insulating layer 25 are in contact, and the second segment 21152 and the second insulating layer 25 are in contact.

[0199] As shown in Figures 3, 5, and 7-10, in some embodiments, the first bending region Q2 is connected to one end of the straight region Q1 along the second direction Y, and a third gap M5 is formed between the second insulating layer 25 and the negative electrode winding start end along the second direction Y.

[0200] Understandably, along the second direction Y, the second insulating layer 25 and the negative electrode winding start end do not contact each other.

[0201] By having a third gap M5 between the second insulating layer 25 and the negative electrode winding start end along the second direction Y, the risk of contact between the negative electrode winding start end and the second insulating layer 25 is reduced, thereby improving the safety performance of the cell 100.

[0202] This application also provides an electrical device, which includes the battery cell 100 provided in any of the above embodiments.

[0203] The battery cell 100 provides electrical energy for the electrical device to perform its functions. The electrical device may include one battery cell 100 or multiple battery cells 100. In embodiments where the electrical device includes multiple battery cells 100, the multiple battery cells 100 may be connected in series, in parallel, or in a mixed manner, wherein a mixed manner means that the multiple battery cells 100 are connected in both series and parallel.

[0204] The battery cell 100 provided in any of the above embodiments has good safety and can improve the power safety and reliability of electrical equipment powered by the battery cell 100.

[0205] 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: The electrode assembly has a wound structure, and the electrode assembly includes a straight region and a first bending region, wherein the first bending region is connected to one end of the straight region; The electrode assembly includes a positive electrode and a negative electrode. The positive electrode has a first portion, which includes a first bent segment located in the first bent region and a first straight segment and a second straight segment located in the straight region. The first straight segment and the second straight segment are respectively connected to the two ends of the first bent segment. The end of the first straight segment facing away from the first bent segment is the positive electrode winding start end of the positive electrode. The negative electrode includes a third straight segment located in the straight region. Along a first direction, the third straight segment is located between the first straight segment and the second straight segment. The end of the third straight segment facing the first bent segment is the negative electrode winding start end of the negative electrode. The first part includes a first current collector and a first active material layer. The first current collector has a first surface facing the third straight section. The first surface is provided with the first active material layer. The first surface has a first empty foil area located in the first bending area. The electrode assembly also includes a first insulating layer. The first insulating layer covers the first empty foil area. The first insulating layer is configured to insulate and isolate the third straight section and the first empty foil area.

2. The battery cell according to claim 1, wherein, The first active material layer includes a first segment and a second segment spaced apart along the winding direction of the positive electrode sheet. At least a portion of the first segment is located in the first straight segment, and at least a portion of the second segment is located in the second straight segment. Along the winding direction, the first empty foil area is located between the first segment and the second segment.

3. The battery cell according to claim 2, wherein, A portion of the first insulating layer overlaps with a portion of the first segment to form a first overlapping area, and a portion of the first insulating layer overlaps with a portion of the second segment to form a second overlapping area. Along the winding direction, the second overlapping area and the first overlapping area are located on opposite sides of the first empty foil area.

4. The battery cell according to claim 3, wherein, Along the thickness direction of the positive electrode sheet, in the first overlapping region, the first insulating layer is closer to the first surface than the first segment, and in the second overlapping region, the first insulating layer is closer to the first surface than the second segment.

5. The battery cell according to claim 3 or 4, wherein, In a projection plane perpendicular to the first direction, the projections of the first overlapping area and the second overlapping area do not overlap.

6. The battery cell according to any one of claims 3-5, wherein, Along the winding direction, the size of the first overlapping area is W1, the size of the second overlapping area is W2, 0mm < W1 ≤ 5mm, and 0mm < W2 ≤ 5mm.

7. The battery cell according to any one of claims 2-6, wherein, Both the first segment and the second segment are located in the flat area.

8. The battery cell according to any one of claims 2-7, wherein, The thickness of the first insulating layer is less than the maximum thickness of the first segment. And / or, The thickness of the first insulating layer is less than the maximum thickness of the second segment.

9. The battery cell according to any one of claims 2-8, wherein, The electrode assembly further includes a second insulating layer. Along the thickness direction of the positive electrode sheet, the first insulating layer is located between the second insulating layer and the first empty foil area. Along the winding direction, the second insulating layer is located between the first segment and the second segment.

10. The battery cell according to claim 9, wherein, The sum of the thicknesses of the first insulating layer and the second insulating layer is less than the maximum thickness of the first segment. And / or, The sum of the thicknesses of the first insulating layer and the second insulating layer is less than the maximum thickness of the second segment.

11. The battery cell according to claim 10, wherein, The second insulating layer is adhesive paper.

12. The battery cell according to any one of claims 9-11, wherein, The first bending region is connected to one end of the straight region along the second direction. Along the winding direction, the second insulating layer has a first end and a second end opposite to each other. The first end is closer to the positive electrode winding start end than the second end. Along the second direction, the distance between the first end and the positive electrode winding start end is a first distance, the distance between the second end and the positive electrode winding start end is a second distance, and the distance between the negative electrode winding start end and the positive electrode winding start end is a third distance. The first distance is smaller than the third distance, and the second distance is smaller than the third distance.

13. The battery cell according to claim 12, wherein, The first distance and the second distance are equal.

14. The battery cell according to claim 13, wherein, The first distance is L1, the second distance is L2, and the third distance is L, where 0.5mm ≤ L - L1 ≤ 8mm and 0.5mm ≤ L - L2 ≤ 8mm.

15. The battery cell according to any one of claims 9-14, wherein, Along the winding direction, there is a first gap between the second insulating layer and the first segment, and a second gap between the second insulating layer and the second segment.

16. The battery cell according to claim 15, wherein, The first gap is L3, the second gap is L4, 0mm < L3 ≤ 2mm, and 0mm < L4 ≤ 2mm.

17. The battery cell according to any one of claims 9-16, wherein, The first bending region is connected to one end of the straight region along the second direction, and along the second direction, there is a third gap between the second insulating layer and the negative electrode winding start end.

18. The battery cell according to any one of claims 9-17, wherein, The sum of the thicknesses of the first insulating layer and the second insulating layer is greater than or equal to 40 μm.

19. The battery cell according to any one of claims 1-18, wherein, The first insulating layer is an insulating coating.

20. The battery cell according to any one of claims 1-19, wherein, The first bending region is connected to one end of the straight region along the second direction. Along the winding direction of the positive electrode sheet, the first insulating layer has a third end and a fourth end opposite to each other. Along the second direction, the distance between the third end and the starting end of the positive electrode winding is a fourth distance, the distance between the fourth end and the starting end of the positive electrode winding is a fifth distance, and the distance between the starting end of the negative electrode winding and the starting end of the positive electrode winding is a third distance. The fourth distance is smaller than the third distance, and the fifth distance is smaller than the third distance.

21. The battery cell according to claim 20, wherein, The fourth distance and the fifth distance are equal.

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

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