Battery cell, electric device and method for preparing electrode sheet

Abstract

Provided in the present application are a battery cell, an electric device and a method for preparing an electrode sheet. An electrode assembly of the battery cell comprises a first electrode sheet and a second electrode sheet, which have opposite polarities, wherein the first electrode sheet comprises a first current collector and a first active material layer; in a winding direction, the first current collector comprises a start section, a middle section and a termination section, which are sequentially connected; the surface of the start section that faces a winding axis is provided with the first active material layer, the surface of the start section that faces away from the winding axis forms a first bare foil region, the surface of the termination section that faces the winding axis is provided with the first active material layer, and the surface of the termination section that faces away from the winding axis forms a second bare foil region; a first termination end of the first current collector is located on an outer side of the outermost turn of the second electrode sheet; a first insulating layer covers at least part of the first bare foil region, and one end face of the first insulating layer is coplanar with an end face of a first start end; and a second insulating layer covers at least part of the second bare foil region, and one end face of the second insulating layer is coplanar with an end face of the first termination end, which is beneficial to improving production efficiency and safety performance.

Description

Preparation methods of battery cells, electrical devices and electrodes Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a method for preparing a battery cell, an electrical device, and an electrode sheet. Background Technology

[0002] 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 and their production volume increases, higher demands are being placed on their production efficiency.

[0003] Summary of the Invention

[0004] This application provides a method for preparing a battery cell, an electrical device, and an electrode sheet to improve the production efficiency of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, the battery cell comprising a wound electrode assembly, a first insulating layer, and a second insulating layer. The electrode assembly includes a first electrode and a second electrode with opposite polarities. The first electrode includes a first current collector and a first active material layer. Along the winding direction of the electrode assembly, the first current collector includes a starting section, an intermediate section, and a ending section connected in sequence. The end of the starting section away from the intermediate section is a first starting end, and the end of the ending section away from the intermediate section is a first ending end. The surface of the starting section facing the winding axis of the electrode assembly is provided with the first active material layer. The active material layer has a first empty foil area formed on the surface of the starting section away from the winding axis, and a second empty foil area formed on the surface of the ending section facing the winding axis. The first ending end is located outside the outermost ring of the second electrode. The first insulating layer covers at least a portion of the first empty foil area, and one end face of the first insulating layer is coplanar with the end face of the first starting end. The second insulating layer covers at least a portion of the second empty foil area, and one end face of the second insulating layer is coplanar with the end face of the first ending end.

[0006] In one or more of the above optional embodiments, a first active material layer is provided on the surface of the first current collector of the first electrode facing the winding axis of the electrode assembly. A first empty foil area is formed on the surface of the first current collector facing the winding axis of the electrode assembly. A first active material layer is provided on the surface of the first current collector facing the winding axis of the electrode assembly. A second empty foil area is formed on the surface of the first current collector facing the winding axis of the electrode assembly. That is, both the winding start section and the winding end section of the first electrode are single-sided coated structures. The first end is located outside the outermost ring of the second electrode. Therefore, the outermost end electrode of the electrode assembly is a single-sided coated structure. There is no active material that does not exert its capacity on the side of the outermost end electrode of the electrode assembly facing away from the winding axis, which is beneficial to improving energy density and reducing the waste of active material. In the process of producing battery cells, when cutting to form the first electrode sheet, in order to ensure that the winding tail section of the first electrode sheet has a single-sided coating structure, the cutting position should be in the single-sided coating area of ​​the substrate. On both sides of the cutting position, a winding start section and a winding tail section of the first electrode sheet are formed respectively. Since both the winding start section and the winding tail section of the first electrode sheet have single-sided coating structures, on the one hand, compared to an electrode sheet with a double-sided coating structure for the winding start section and a single-sided coating structure for the winding tail section, in this embodiment, both the winding start section and the winding tail section of the first electrode sheet have single-sided coating structures. Therefore, when cutting to form the first electrode sheet, the cutting can be performed at any position in the single-sided coating area of ​​the substrate. During cutting, it is not necessary to precisely locate the boundary between the double-sided and single-sided coating areas of the substrate, which is beneficial to improving cutting efficiency and thus improving the production efficiency of the battery cell. On the other hand, to form a double-sided coating structure for the winding start section and the winding tail section, the winding tail section... For electrode sheets with a single-sided coating structure at the end, it is difficult to accurately locate the boundary between the single-sided and double-sided coating areas of the substrate. Therefore, during cutting, a first cut can be made in the single-sided coating area of ​​the strip to achieve a single-sided coating structure at the winding end of one electrode sheet, and a second cut can be made in the double-sided coating area of ​​the strip to achieve a double-sided coating structure at the winding start of the next electrode sheet. This not only increases the number of cuts, but also wastes substrate and active material between the first and second cut positions. In the embodiments of this application, both the winding start and winding end of the first electrode sheet are single-sided coating structures. When cutting to form the first electrode sheet, only one cut is needed in each single-sided coating area of ​​the substrate. It is not necessary to make a first cut in the single-sided coating area of ​​the substrate and then a second cut in the double-sided coating area of ​​the substrate, which improves cutting efficiency and reduces waste of substrate and active material. Furthermore, the cutting in this embodiment can be performed only once on a single-sided coated area of ​​the substrate, which can reduce powder shedding during the cutting process, reduce the risk of short circuit in the battery cell caused by powder shedding, and improve the safety of the battery cell.By covering at least a portion of the first empty foil area with a first insulating layer and a portion of the second empty foil area with a second insulating layer, the risk of short circuits caused by burrs puncturing the separator in the first and second empty foil areas can be reduced, thus improving the safety performance of the battery cell. Since the first starting end and the first ending end are the two cutting positions when cutting the substrate to form the first electrode sheet, and one end face of the first insulating layer is coplanar with the end face of the first starting end, and one end face of the second insulating layer is coplanar with the end face of the first ending end, the insulating element can be placed in the single-sided coating area of ​​the substrate before cutting. Cutting is then performed in the area where the insulating element and the single-sided coating area overlap. A portion of the insulating element forms the first insulating layer of one first electrode sheet, and the other portion forms the second insulating layer of another first electrode sheet. After cutting, one end of the first insulating layer is coplanar with the first starting end, and one end of the second insulating layer is coplanar with the first ending end, which helps improve production efficiency.

[0007] In some embodiments of the first aspect of this application, a portion of the first insulating layer is connected to the first empty foil region, and another portion of the first insulating layer is connected to the first active material layer of the intermediate segment.

[0008] In one or more of the above optional embodiments, by connecting a portion of the first insulating layer to the first empty foil area and another portion of the first insulating layer to the first active material layer in the middle section, the difficulty of setting the first insulating layer is reduced, the connection between the first insulating layer and the first electrode is facilitated, and the connection stability between the first insulating layer and the first electrode is improved.

[0009] In some embodiments of the first aspect of this application, the first insulating layer includes a first portion connected to the first active material layer of the intermediate segment, the first portion overlapping a portion of the first active material layer of the intermediate segment, and the length of the first portion along the winding direction is L1, 0.5mm≤L1≤10mm.

[0010] In one or more of the above optional embodiments, L1 ≥ 0.5 mm results in a larger connection area between the first insulating layer and the first active material layer in the intermediate section, which is beneficial to improving the connection stability between the first insulating layer and the first active material layer in the intermediate section. L1 ≤ 10 mm reduces the space occupied by the first insulating layer inside the cell and reduces the impact of the first insulating layer on the energy density of the cell. Therefore, 0.5 mm ≤ L1 ≤ 10 mm not only ensures good connection stability between the first insulating layer and the first active material layer in the intermediate section, but also enables the cell to have a high energy density even with the first insulating layer.

[0011] In some embodiments of the first aspect of this application, the thickness of the first insulating layer is less than the thickness of the first active material layer.

[0012] In one or more of the above optional embodiments, the thickness of the first insulating layer is less than the thickness of the first active material layer, thereby reducing the space occupied by the first insulating layer inside the cell and thus reducing the impact of the first insulating layer on the energy density of the cell.

[0013] In some embodiments of the first aspect of this application, the thickness of the first insulating layer is H1, where 5μm≤H1≤40μm.

[0014] In one or more of the above optional embodiments, H1≥5μm reduces the risk of the first insulating layer being punctured by burrs in the first empty foil area, which is beneficial to improving the safety performance of the battery cell. H1≤40μm reduces the space occupied by the first insulating layer in the battery cell, thereby reducing the impact of the first insulating layer on the energy density of the battery cell. Therefore, 5μm≤H1≤40μm can improve the safety performance of the battery cell and enable the battery cell to have a high energy density when the first insulating layer is provided.

[0015] In some embodiments of the first aspect of this application, the intermediate segment has a first end connected to the terminal segment; the portion of the terminal segment located outside the first end includes a first segment extending beyond the first end along the winding direction, and the second insulating layer is connected within the first segment.

[0016] In one or more of the above optional embodiments, the portion of the tail section located outside the first end includes a first segment extending beyond the first end along the winding direction. The second insulating layer is connected to the first segment, thus the second insulating layer is located in the region where the electrode assembly size is smaller, reducing the impact of the second insulating layer on the electrode assembly size, thereby contributing to a higher energy density in the battery cell. The second insulating layer's connection to the first segment also results in smaller dimensional differences between different parts of the electrode assembly, which helps improve the uniformity of stress on the electrode sheets during the expansion of the electrode assembly.

[0017] In some embodiments of the first aspect of this application, the orthographic projection of the first end does not overlap with the orthographic projection of the second insulating layer in a plane perpendicular to a first radial direction of the electrode assembly, wherein the first radial direction is a direction perpendicular to the winding axis and passing through the first end.

[0018] In one or more of the above optional embodiments, if the orthographic projection of the first end and the orthographic projection of the second insulating layer do not overlap in the first radial plane of the vertical electrode assembly, then there is a distance between the orthographic projections of the first end and the second insulating layer in the first radial plane of the vertical electrode assembly. This reduces the risk of overlap between the orthographic projections of the first end and the second insulating layer in the first radial plane of the vertical electrode assembly during cell cycling. Therefore, the second insulating layer can always be located in the region where the electrode assembly size is smaller, reducing the impact of the second insulating layer on the electrode assembly size, which is beneficial for the cell to have a higher energy density. It also makes the size difference between different parts of the electrode assembly smaller, which is beneficial for improving the uniformity of the stress on the electrode sheets during the expansion of the electrode assembly.

[0019] In some embodiments of the first aspect of this application, the length of the starting segment along the winding direction is L2, where 0.5mm ≤ L2 ≤ 10mm.

[0020] In one or more of the above optional embodiments, L2 ≥ 0.5 mm facilitates cutting to form the first electrode sheet. L2 ≤ 10 mm reduces the length of the first empty foil area, resulting in a longer middle section and thus a higher energy density in the battery cell. Therefore, 0.5 mm ≤ L2 ≤ 10 mm not only facilitates cutting to form the first electrode sheet but also makes the middle section of the first electrode sheet longer, resulting in a higher energy density in the battery cell.

[0021] In some embodiments of the first aspect of this application, the second insulating layer covers a portion of the second empty foil area; the cell further includes a third insulating layer, which is connected to the first electrode and covers a portion of the second empty foil area, and the third insulating layer is arranged side by side with the second insulating layer along the winding direction.

[0022] In one or more of the above optional embodiments, connecting the third insulating layer to the first electrode and covering a portion of the second empty foil area also helps reduce the risk of short circuits caused by burrs puncturing the separator in the second empty foil area, thus improving the safety performance of the battery cell. The third insulating layer and the second insulating layer are arranged side by side along the winding direction to avoid overlapping areas between the second insulating layer and the third insulating layer in the thickness direction of the first electrode, which would increase the size of the electrode assembly.

[0023] In some embodiments of the first aspect of this application, a portion of the third insulating layer is connected to the second empty foil region, and another portion of the third insulating layer is connected to the first active material layer of the intermediate segment.

[0024] In one or more of the above optional embodiments, by connecting a portion of the third insulating layer to the second empty foil area and another portion of the third insulating layer to the first active material layer in the middle section, the difficulty of setting the third insulating layer is reduced, the connection between the third insulating layer and the first electrode is facilitated, and the connection stability between the third insulating layer and the first electrode is improved.

[0025] In some embodiments of the first aspect of this application, the third insulating layer includes a second portion connected to the first active material layer of the intermediate segment, the second portion overlapping a portion of the first active material layer of the intermediate segment, and the length of the second portion along the winding direction is L3, 0.5mm≤L3≤10mm.

[0026] In one or more of the above optional embodiments, L3 ≥ 0.5 mm results in a larger connection area between the third insulating layer and the first active material layer in the intermediate section, which is beneficial to improving the connection stability between the third insulating layer and the first active material layer in the intermediate section. L3 ≤ 10 mm can reduce the space occupied by the third insulating layer in the internal space of the cell and reduce the impact of the third insulating layer on the energy density of the cell. Therefore, 0.5 mm ≤ L3 ≤ 10 mm not only ensures good connection stability between the third insulating layer and the first active material layer in the intermediate section, but also enables the cell to have a high energy density when the third insulating layer is provided.

[0027] In some embodiments of the first aspect of this application, the thickness of the second insulating layer is less than the thickness of the first active material layer; and / or, the thickness of the third insulating layer is less than the thickness of the first active material layer.

[0028] In one or more of the above optional embodiments, by making the thickness of the second insulating layer smaller than the thickness of the first active material layer, the occupancy of the second insulating layer on the internal space of the battery cell is reduced, thereby reducing the impact of the second insulating layer on the energy density of the battery cell. Similarly, by making the thickness of the third insulating layer smaller than the thickness of the first active material layer, the occupancy of the third insulating layer on the internal space of the battery cell is reduced, thereby reducing the impact of the third insulating layer on the energy density of the battery cell.

[0029] In some embodiments of the first aspect of this application, the thickness of the second insulating layer is H2, 5μm≤H2≤40μm; and / or, the thickness of the third insulating layer is H3, 5μm≤H3≤40μm.

[0030] In one or more of the above optional embodiments, by setting H2 ≥ 5μm, the risk of the second insulating layer being punctured by burrs in the second empty foil area is reduced, which is beneficial to improving the safety performance of the battery cell; H2 ≤ 40μm reduces the space occupied by the second insulating layer inside the battery cell, thereby reducing the impact of the second insulating layer on the energy density of the battery cell. Therefore, 5μm ≤ H2 ≤ 40μm can both improve the safety performance of the battery cell and enable the battery cell to have a high energy density when the second insulating layer is provided. By setting H3 ≥ 5μm, the risk of the third insulating layer being punctured by burrs in the second empty foil area is reduced, which is beneficial to improving the safety performance of the battery cell; H3 ≤ 40μm reduces the space occupied by the third insulating layer inside the battery cell, thereby reducing the impact of the third insulating layer on the energy density of the battery cell. Therefore, 5μm ≤ H3 ≤ 40μm can both improve the safety performance of the battery cell and enable the battery cell to have a high energy density when the third insulating layer is provided.

[0031] In some embodiments of the first aspect of this application, the first electrode is a positive electrode, the second electrode has a second terminal end, and along the opposite direction of the winding direction, the portion of the third insulating layer located in the second empty foil area extends beyond the second terminal end; and / or, along the winding direction, the portion of the third insulating layer located in the second empty foil area extends beyond the second terminal end.

[0032] In one or more of the above optional embodiments, by extending the portion of the third insulating layer located in the second empty foil area beyond the second end of the positive electrode sheet in the opposite direction of the winding direction, the risk of lithium plating in the cell is reduced, as is the risk of the positive electrode sheet and the second empty foil area being directly opposite each other, thereby improving the safety performance of the cell.

[0033] In some embodiments of the first aspect of this application, in the opposite direction to the winding direction, the third insulating layer includes a third portion extending beyond the second end, the third portion being located in the second empty foil area, the length of the third portion being L4, L4≥2mm; and / or, in the winding direction, the third insulating layer includes a fourth portion extending beyond the second end, the fourth portion being located in the second empty foil area, the length of the fourth portion being L5, L5≥2mm.

[0034] In one or more of the above optional embodiments, by setting L4 ≥ 2mm, the risk of lithium plating in the cell is reduced, as is the risk of the positive electrode sheet and the second empty foil area being directly aligned, thereby improving the safety performance of the cell. Similarly, setting L5 ≥ 2mm reduces the risk of lithium plating in the cell and the risk of the positive electrode sheet and the second empty foil area being directly aligned, thus improving the safety performance of the cell.

[0035] In some embodiments of the first aspect of this application, the first electrode is a positive electrode.

[0036] In one or more of the above optional embodiments, if the first electrode is a positive electrode, then the final electrode of the electrode assembly is also a positive electrode, which is beneficial for the cell to have a higher energy density.

[0037] Secondly, embodiments of this application also provide an electrical device, including the battery cell provided in any of the above embodiments.

[0038] Thirdly, embodiments of this application also provide a method for preparing an electrode sheet, the method comprising:

[0039] A strip is provided, comprising a substrate and an active material layer. Along the thickness direction of the substrate, the substrate has opposing first and second surfaces, and along the length direction of the substrate, the substrate has opposing second and third ends. The active material layer is disposed on both the first and second surfaces, with the active material layer on the first surface being continuously disposed and the active material layers on the second surface being spaced apart. On the second surface, along the length direction of the substrate, empty foil areas are formed on both sides of each active material layer.

[0040] Provide the first insulating component;

[0041] Along the length direction of the substrate, the first insulating element is disposed on the side of each active material layer on the second surface near the second end, and the first insulating element covers at least a portion of the empty foil area;

[0042] The area where each of the first insulating elements overlaps with the empty foil area is cut to form a first sub-electrode and a second sub-electrode, and the first insulating element is cut into a first insulating layer and a second insulating layer, wherein the first insulating layer is located at the beginning of the current collector of the first sub-electrode and the second insulating layer is located at the end of the current collector of the second sub-electrode.

[0043] In one or more of the above optional embodiments, the area where the first insulating member and the empty foil area overlap is cut to divide the first insulating member into a first insulating layer and a second insulating layer. A portion of this forms the first insulating layer of the first sub-electrode. The first insulating layer is located at the beginning section of the current collector of the first sub-electrode, and the second insulating layer is located at the end section of the current collector of the second sub-electrode. The final first and second sub-electrodes are both single-sided coated structures at both the beginning and end sections of the winding, compared to a double-sided coated structure at the beginning section and a single-sided coated structure at the end section. In this method, the first and second sub-electrodes formed have single-sided coated sections at both the starting and ending points. Therefore, when cutting to form the first and second sub-electrodes, cutting can be performed at any position within the single-sided coated area of ​​the substrate. Precise positioning of the boundary between the double-sided and single-sided coated areas of the substrate is not required during cutting, which improves cutting efficiency and thus increases the production efficiency of the battery cell. On the other hand, when manufacturing electrode sheets with a double-sided coated starting section and a single-sided coated ending section, the substrate... Precisely locating the boundary between the single-sided and double-sided coating areas is challenging. Therefore, during cutting, a first cut can be made in the single-sided coating area of ​​the substrate to achieve a single-sided coating structure at the winding end of one electrode sheet. A second cut is then made in the double-sided coating area of ​​the substrate to achieve a double-sided coating structure at the winding start of the next electrode sheet. This not only increases the number of cuts but also wastes substrate and active material between the first and second cut positions. The first and second sub-electrodes formed by this method have winding start and winding end sections that are not ideal for the first and second sub-electrodes. The tail sections are all single-sided coated structures. When cutting to form the first and second sub-electrodes, only one cut is needed in each area where the first insulating element overlaps with the empty foil area. This eliminates the need for a first cut in the single-sided coated area of ​​the substrate (the area where the first insulating element and the empty foil area overlap) and a second cut in each double-sided coated area of ​​the substrate (the area where the active material layers on the first and second surfaces overlap). This improves cutting efficiency and reduces waste of substrate and active material. Furthermore, this method allows for a single cut only in the single-sided coated area of ​​the substrate during electrode fabrication, reducing powder shedding during the cutting process, lowering the risk of short circuits due to powder shedding, and improving the safety of the battery cell.

[0044] In some embodiments of the third aspect, the provision of the first insulating member on the side of each active material layer on the second surface near the second end along the length direction of the substrate, and the first insulating member covering at least a portion of the empty foil area, includes:

[0045] A portion of the first insulating member is attached to the active material layer on the second surface, and another portion of the first insulating member is attached to the empty foil area, such that the first insulating member covers at least a portion of the empty foil area.

[0046] In one or more of the above optional embodiments, by connecting a portion of the first insulating member to the active material layer of the second surface and connecting another portion of the first insulating member to the empty foil area, so that the first insulating member covers at least a portion of the empty foil area, after cutting to form the first sub-electrode and the second sub-electrode, a portion of the first insulating layer is connected to the empty foil area of ​​the winding start section of the first sub-electrode, and another portion of the first insulating layer is connected to the active material layer of the first sub-electrode, which facilitates the connection between the first insulating layer and the first sub-electrode and helps to improve the connection stability between the first insulating layer and the first sub-electrode.

[0047] In some embodiments of the third aspect, the method of preparing the electrode sheet further includes, prior to cutting the region where each of the first insulating elements overlaps with the empty foil region to form a plurality of first and second sub-electrodes:

[0048] Provide a second insulating component;

[0049] Along the length direction of the substrate, a second insulating member is disposed on the side of each active material layer on the second surface near the third end, and the second insulating member covers at least a portion of the empty foil area;

[0050] After the area where each of the first insulating elements overlaps with the empty foil area is cut to form the first sub-electrode and the second sub-electrode, the second insulating element is located at the end of the current collector of the second sub-electrode.

[0051] In one or more of the above optional embodiments, by providing a second insulating member on the side of each active material layer on the second surface near the third end, and making the second insulating member cover at least a portion of the empty foil area, after cutting the area where each first insulating member overlaps with the empty foil area to form a first sub-electrode and a second sub-electrode, the second insulating member is located at the end of the current collector of the second sub-electrode, and the second insulating member covers a portion of the empty foil area of ​​the winding end of the second sub-electrode, which can reduce the risk of burrs in the empty foil area puncturing the separator and causing a short circuit in the cell, and improve the safety performance of the cell with the second sub-electrode.

[0052] In some embodiments of the third aspect, the provision of the second insulating member on the side of each active material layer on the second surface near the third end along the length direction of the substrate, and the second insulating member covering at least a portion of the empty foil area, includes:

[0053] The adjacent second insulating element and the first insulating element are spaced apart along the length direction of the substrate.

[0054] In one or more of the above optional embodiments, if adjacent second insulating members and first insulating members are spaced apart along the length direction of the substrate, after cutting, a portion of the first insulating member and the second insulating member of the first electrode sheet and the second electrode sheet are spaced apart along their length direction, so as to avoid the second insulating member and the first insulating member having a stacked area in the thickness direction of the first electrode sheet, thereby increasing the size of the electrode assembly having the electrode sheet formed by the above method.

[0055] In some embodiments of the third aspect, the provision of the material strip includes:

[0056] Provide the substrate;

[0057] An active material is continuously coated on the first surface so that the active material layer on the first surface is continuously disposed;

[0058] An active material is intermittently coated on the second surface so that the active material layers on the second surface are spaced apart.

[0059] In one or more of the above optional embodiments, by continuously coating an active material on the first surface to make the active material layer on the first surface continuously disposed, and intermittently coating an active material on the second surface to make the active material layer on the second surface spaced apart, it is convenient to form the strip and improve the production efficiency of the electrode sheet. Attached Figure Description

[0060] 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.

[0061] Figure 1 is an exploded view of a battery cell provided in some embodiments of this application;

[0062] Figure 2 is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0063] Figure 3 is an enlarged view of point A1 in Figure 2;

[0064] Figure 4 is an enlarged view of section A2 in Figure 2;

[0065] Figure 5 is a schematic diagram of the first perspective after the first electrode sheet is unfolded according to some embodiments of this application;

[0066] Figure 6 is a schematic diagram of the second view after the first electrode sheet is unfolded according to some embodiments of this application;

[0067] Figure 7 is a flowchart of the electrode preparation method provided in some embodiments of this application;

[0068] Figure 8 is a schematic diagram of a strip provided with a first insulating element and a second insulating element according to some embodiments of this application.

[0069] Icons: 100-Cell; 10-Casing; 11-Shell; 12-Cover; 20-Electrode Assembly; 21-First Electrode; 211-First Current Collector; 2111-Starting Section; 21111-First Starting End; 2112-Intermediate Section; 21121-First End; 2113-Ending Section; 21131-First Ending End; 21132-First Section; 212-First Active Material Layer; 22-Second Electrode; 221-Second Ending End; 23-Separating Membrane; 30-First Insulating Layer; 31-First Part; 40-Second Insulating Layer; 50-Third Insulating Layer; 51-Second Part; 52-Third Part ; 53 - Fourth part; 1000 - Strip; 1100 - Substrate; 1101 - Second end; 1102 - Third end; 1103 - First surface; 1104 - Second surface; 1200 - Active material layer; 2000 - First insulating element; 3000 - Second insulating element; 21a - First sub-electrode; 21b - Second sub-electrode; X - Winding direction; X' - Length direction of the first current collector; Y - Width direction of the first current collector; Z - Thickness direction of the first current collector; Q - Empty foil area; Q1 - First empty foil area; Q2 - Second empty foil area; P1 - First reference surface; P2 - Second reference surface; P3 - First radial direction. Detailed Implementation

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] Currently, in pursuit of higher energy density, the outermost electrode of a wound cell typically has double-sided coating at the beginning of the winding process, with the starting ends of the two films aligned. The winding tail section is usually single-sided coated. However, when this structure is obtained by cutting the interstitial coated electrode, existing processes struggle to accurately cut the connection between the single-sided and double-sided coated areas of the strip during the cutting process. To alleviate the difficulty in accurately cutting at the connection between the single-sided and double-sided coated areas of the strip, a first cut can be made in the single-sided coated area of ​​the strip to achieve a single-sided coated structure at the winding tail section of one electrode. Then, a second cut can be made in the double-sided coated area of ​​the strip to achieve a double-sided coated structure at the winding start section of the next electrode. This not only increases the number of cuts and makes the process more complex and reduces production efficiency, but also wastes the substrate and active material between the first and second cut positions. Furthermore, cutting in the double-sided coated area can cause severe powder shedding, and the resulting burrs can easily lead to short circuits.

[0076] Based on the above considerations, in order to alleviate the problems of low electrode production efficiency and low cell safety, this application provides a cell comprising a wound electrode assembly, a first insulating layer, and a second insulating layer. The electrode assembly includes a first electrode and a second electrode with opposite polarities. The first electrode includes a first current collector and a first active material layer. Along the winding direction of the electrode assembly, the first current collector includes a starting section, an intermediate section, and a closing section connected in sequence. The end of the starting section away from the intermediate section is the first starting end, and the end of the closing section away from the intermediate section is the first closing end. The starting section faces... A first active material layer is disposed on the surface of the winding axis of the electrode assembly. A first empty foil area is formed on the surface of the starting section facing away from the winding axis. A first active material layer is disposed on the surface of the ending section facing the winding axis, and a second empty foil area is formed on the surface of the ending section facing away from the winding axis. The first ending end is located outside the outermost ring of the second electrode. A first insulating layer covers at least a portion of the first empty foil area, and one end face of the first insulating layer is coplanar with the end face of the first starting end. A second insulating layer covers at least a portion of the second empty foil area, and one end face of the second insulating layer is coplanar with the end face of the first ending end. It can be understood that coplanarity means that the extended plane formed by one end face coincides with or lies in the same plane as the other end face.

[0077] The first current collector of the first electrode sheet has a first active material layer on the surface of the starting section facing the winding axis of the electrode assembly. The surface of the starting section away from the winding axis forms a first empty foil area. The first current collector of the first electrode sheet has a first active material layer on the surface of the ending section facing the winding axis of the electrode assembly. The surface of the ending section away from the winding axis forms a second empty foil area. That is, both the starting and ending sections of the first electrode sheet are single-sided coated structures. The first ending end is located outside the outermost ring of the second electrode sheet. Therefore, the outermost ending electrode sheet of the electrode assembly is a single-sided coated structure. There is no active material that does not play its capacity on the side of the outermost ending electrode sheet of the electrode assembly away from the winding axis, which is beneficial to improving energy density and reducing the waste of active material.

[0078] In the process of producing battery cells, when cutting to form the first electrode sheet, in order to ensure that the winding tail section of the first electrode sheet has a single-sided coating structure, the cutting position should be in the single-sided coating area of ​​the substrate. On both sides of the cutting position, a winding start section and a winding tail section of the first electrode sheet are formed respectively. Since both the winding start section and the winding tail section of the first electrode sheet have single-sided coating structures, on the one hand, compared to an electrode sheet with a double-sided coating structure for the winding start section and a single-sided coating structure for the winding tail section, in this embodiment, both the winding start section and the winding tail section of the first electrode sheet have single-sided coating structures. Therefore, when cutting to form the first electrode sheet, the cutting can be performed at any position in the single-sided coating area of ​​the substrate. During cutting, it is not necessary to precisely locate the boundary between the double-sided and single-sided coating areas of the substrate, which is beneficial to improving cutting efficiency and thus improving the production efficiency of the battery cell. On the other hand, to form a double-sided coating structure for the winding start section and the winding tail section, the winding tail section... For electrode sheets with a single-sided coating structure at the end, it is difficult to accurately locate the boundary between the single-sided and double-sided coating areas of the substrate. Therefore, during cutting, a first cut can be made in the single-sided coating area of ​​the strip to achieve a single-sided coating structure at the winding end of one electrode sheet, and a second cut can be made in the double-sided coating area of ​​the strip to achieve a double-sided coating structure at the winding start of the next electrode sheet. This not only increases the number of cuts, but also wastes substrate and active material between the first and second cut positions. In the embodiments of this application, both the winding start and winding end of the first electrode sheet are single-sided coating structures. When cutting to form the first electrode sheet, only one cut is needed in each single-sided coating area of ​​the substrate. It is not necessary to make a first cut in the single-sided coating area of ​​the substrate and then a second cut in the double-sided coating area of ​​the substrate, which improves cutting efficiency and reduces waste of substrate and active material. Furthermore, the cutting in this embodiment can be performed only once on a single-sided coated area of ​​the substrate, which can reduce powder shedding during the cutting process, reduce the risk of short circuit in the battery cell caused by powder shedding, and improve the safety of the battery cell.

[0079] By covering at least a portion of the first empty foil area with a first insulating layer and a portion of the second empty foil area with a second insulating layer, the risk of short circuits caused by burrs puncturing the separator in the first and second empty foil areas can be reduced, thus improving the safety performance of the battery cell. Since the first starting end and the first ending end are the two cutting positions when cutting the substrate to form the first electrode sheet, and one end face of the first insulating layer is coplanar with the end face of the first starting end, and one end face of the second insulating layer is coplanar with the end face of the first ending end, the insulating element can be placed in the single-sided coating area of ​​the substrate before cutting. Cutting is then performed in the area where the insulating element and the single-sided coating area overlap. A portion of the insulating element forms the first insulating layer of one first electrode sheet, and the other portion forms the second insulating layer of another first electrode sheet. After cutting, one end of the first insulating layer is coplanar with the first starting end, and one end of the second insulating layer is coplanar with the first ending end, which helps improve production efficiency.

[0080] The battery cells disclosed in the embodiments of 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 manufactured using electrode sheets conforming to the operating conditions of this application can also be used as the power supply system for electrical devices.

[0081] This application provides an embodiment of 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.

[0082] As shown in Figures 1 and 2, this application embodiment provides a battery cell 100, which includes a housing 10 and an electrode assembly 20. The electrode assembly 20 is housed within the housing 10.

[0083] The outer casing 10 forms a receiving space. The receiving space can be used to house the electrode assembly 20, electrolyte, etc. The outer casing 10 can be a rigid shell, such as a steel shell or an aluminum shell, forming a steel-shelled battery cell or an aluminum-shelled battery cell. The outer casing 10 can also be formed of a softer material, such as an aluminum-plastic film or a steel-plastic film, forming a pouch cell.

[0084] The housing 10 may include a housing 11 and a cover 12, the housing 11 having an opening at at least one end, and the cover 12 for sealing the opening of the housing 11 so that the housing 11 and the cover 12 together define an accommodating space.

[0085] The electrode assembly 20 includes a separator 23, a first electrode 21, another separator 23, and a second electrode 22.

[0086] The first electrode 21 and the second electrode 22 have opposite polarities, that is, one of the first electrode 21 and the second electrode 22 is the positive electrode, and the other of the first electrode 21 and the second electrode 22 is the negative electrode.

[0087] The first electrode 21 includes a first current collector 211 and a first active material layer 212. At least one side of the first current collector 211 along its thickness direction is disposed with the first active material layer 212. In embodiments where the first electrode 21 is a positive electrode, the first current collector 211 is a positive current collector, and the first active material layer 212 is a positive active material layer. At least one side of the positive current collector is disposed with the positive active material layer. For the lithium-ion cell 100, the material of the positive current collector can be aluminum. The positive active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The positive current collector can be a composite current collector or a non-composite current collector.

[0088] In an embodiment where the first electrode 21 is the negative electrode, the first current collector 211 is the negative current collector, and the first active material layer 212 is the negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector. For the lithium-ion cell 100, the material of the negative current collector can be copper. The negative current collector can be a composite current collector or a non-composite current collector. The negative active material 1200 can be a carbon material or a silicon material, etc.

[0089] The separator 23 provides insulation between the positive and negative electrode plates, reducing the risk of short circuits in the cell 100. The material of the separator 23 may include polypropylene (PP) or polyethylene (PE), etc.

[0090] The electrode assembly 20 has a wound structure. Specifically, the first electrode 21, the separator 23, the second electrode 22, and another separator 23 are stacked and then wound to form the wound electrode assembly 20; or, the separator 23, the first electrode 21, the other separator 23, and the second electrode 22 are stacked and then wound to form the wound electrode assembly 20. The wound electrode assembly 20 can be a flat wound electrode assembly 20 or a cylindrical electrode assembly 20. In embodiments where the electrode assembly 20 has a cylindrical structure, the battery cell 100 can be a cylindrical battery cell 100 or a columnar battery cell 100. Figure 1 shows the case where the battery cell 100 is a cylindrical battery cell 100, and Figure 2 shows the case where the electrode assembly 20 has a cylindrical structure.

[0091] In this embodiment, as shown in FIG1, the outermost electrode of the electrode assembly 20 is a part of the first electrode 21. It can be understood that the terminal electrode of the electrode assembly 20 is the first electrode 21, and the outermost ring of the second electrode 22 is located inside the outermost ring of the first electrode 21. The inner side of the outermost ring of the first electrode 21 refers to the side of the outermost ring of the first electrode 21 facing the winding axis of the electrode assembly 20, or, along the radial direction of the electrode assembly 20, the outermost ring of the second electrode 22 is closer to the winding axis of the electrode assembly 20 than the outermost ring of the first electrode 21.

[0092] As shown in Figures 3-6, in some embodiments, along the winding direction X of the electrode assembly 20, the first current collector 211 includes a starting segment 2111, an intermediate segment 2112, and a closing segment 2113 connected in sequence. The end of the starting segment 2111 away from the intermediate segment 2112 is the first starting end 21111, and the end of the closing segment 2113 away from the intermediate segment 2112 is the first closing end 21131.

[0093] The first starting end 21111 is the end of the first current collector 211 closest to the winding axis of the electrode assembly 20 along the winding direction X, or the end face where the first current collector 211 begins to be wound. The first ending end 21131 is the end of the first current collector 211 furthest from the winding axis of the electrode assembly 20 along the winding direction X, or the end face where the first current collector 211 ends to be wound.

[0094] A first active material layer 212 is disposed on the surface of the starting segment 2111 facing the winding axis of the electrode assembly 20, and a first empty foil region Q1 is formed on the surface of the starting segment 2111 facing away from the winding axis. It is understood that the first active material layer 212 is disposed only on the surface of the starting segment 2111 facing the winding axis of the electrode assembly 20, and the first active material layer 212 is not disposed on the surface of the starting segment 2111 facing away from the winding axis of the electrode assembly 20, so that the first empty foil region Q1 is formed on the surface of the starting segment 2111 facing away from the winding axis of the electrode assembly 20. The starting segment 2111 and the first active material layer 212 disposed on the starting segment 2111 together form the winding starting segment of the first electrode 21, that is, the winding starting segment of the first electrode 21 is a single-sided coated structure.

[0095] The middle section 2112 has a first active material layer 212 on both the surface facing the winding axis and the surface away from the winding axis. That is, the middle section 2112 has a first active material layer 212 on both opposite surfaces in the thickness direction Z of the first current collector.

[0096] The surface of the termination section 2113 facing the winding axis is provided with a first active material layer 212, and the surface of the termination section 2113 facing away from the winding axis forms a second empty foil area Q2. It can be understood that the termination section 2113 only has the first active material layer 212 on the surface facing the winding axis of the electrode assembly 20, and the surface of the termination section 2113 facing away from the winding axis of the electrode assembly 20 does not have the first active material layer 212, so that the surface of the termination section 2113 facing away from the winding axis of the electrode assembly 20 forms the second empty foil area Q2. The termination section 2113 and the first active material layer 212 disposed on the termination section 2113 together form the winding termination section of the first electrode 21, that is, the termination section 2113 of the first electrode 21 has a single-sided coating structure.

[0097] The first termination point 21131 is located outside the outermost ring of the second electrode 22, meaning the electrode assembly 20 terminates with the first electrode 21. Since the termination point 2113 of the first electrode 21 has a single-sided coating structure, the electrode assembly 20 terminates with a single-sided coated electrode. Therefore, the side of the first electrode 21's winding termination point away from the winding axis does not contain an active material layer that does not contribute to its capacity. This is beneficial for improving the energy density of the cell 100 and reducing the waste of active material.

[0098] Along the winding direction X, the length of the starting segment 2111 can be designed according to actual conditions. As shown in Figures 3 and 5-6, the length of the starting segment 2111 is the distance between the connection point of the starting segment 2111 and the intermediate segment 2112 and the first starting end 21111 along the winding direction X. When the first electrode 21 is in the unfolded state, the length of the starting segment 2111 is the dimension of the starting segment 2111 along the length direction of the first current collector 211. In some embodiments, along the winding direction X, the length of the starting segment 2111 is L2, where 0.5mm ≤ L2 ≤ 10mm.

[0099] For example, 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, 8.5mm, 9mm, 9.5mm, 10mm, etc.

[0100] L2 ≥ 0.5 mm facilitates cutting to form the first electrode 21. L2 ≤ 10 mm reduces the length of the first empty foil area Q1, making the length of the middle section 2112 larger, thus enabling the cell 100 to have a higher energy density. Therefore, 0.5 mm ≤ L2 ≤ 10 mm not only facilitates cutting to form the first electrode 21, but also makes the middle section 2112 of the first electrode 21 longer, thus enabling the cell 100 to have a higher energy density.

[0101] It should be noted that when the first electrode 21 is unfolded, the length direction of the first current collector 211 corresponds to the winding direction X when the first electrode 21 is wound, and the width direction of the first electrode 21 when unfolded corresponds to the extension direction of the winding axis when the first electrode 21 is wound. The length direction, width direction Y, and thickness direction of the first current collector 211 are perpendicular to each other.

[0102] In some embodiments, the first electrode 21 is a positive electrode, and the first terminal end 21131 is located outside the outermost ring of the second electrode 22. Along the winding direction X, the second electrode 22 extends beyond the first terminal end 21131. Figure 2 shows the case where the first electrode 21 is a positive electrode and the second electrode 22 is a negative electrode.

[0103] Of course, in other embodiments, the first electrode 21 is a negative electrode, and the first end 21131 is located outside the outermost ring of the second electrode 22. Along the winding direction X, the winding end of the first electrode 21 extends beyond the second end 221 of the second electrode 22.

[0104] As shown in Figures 3 and 5-6, in some embodiments, the battery cell 100 further includes a first insulating layer 30, which covers at least a portion of the first empty foil region Q1, and one end face of the first insulating layer 30 is coplanar with the end face of the first starting end 21111.

[0105] The first insulating layer 30 is connected to the first electrode 21. The first insulating layer 30 can be completely connected to the first empty foil area Q1. The first insulating layer 30 can be partially connected to the first empty foil area Q1, and the other part of the first insulating layer 30 can be connected to other areas of the first electrode 21 outside the first empty foil area Q1.

[0106] The first insulating layer 30 can cover the entire first empty foil area Q1. Along the width direction Y of the first current collector, the two opposite end faces of the first insulating layer 30 are coplanar with the two opposite end faces of the starting segment 2111. Along the winding direction X, the end face of the first starting end 21111 is coplanar with one end face of the first insulating layer 30, so that the first insulating layer 30 completely covers the first empty foil area Q1. The width direction Y of the first current collector is parallel to the extension direction of the winding axis of the electrode assembly 20.

[0107] In other embodiments, the first insulating layer 30 may also cover a portion of the first empty foil region Q1. Exemplarily, as shown in Figures 3 and 5-6, a portion of the first insulating layer 30 is connected to the surface of the first empty foil region Q1, and another portion of the first insulating layer 30 is connected to the first active material layer 212 of the intermediate section 2112. By connecting a portion of the first insulating layer 30 to the first empty foil region Q1 and the other portion to the first active material layer 212 of the intermediate section 2112, the manufacturing process of the first insulating layer 30 is simplified, facilitating the connection between the first insulating layer 30 and the first electrode 21, and improving the connection stability between the first insulating layer 30 and the first electrode 21.

[0108] Another portion of the first insulating layer 30 may be attached to the surface of the first active material layer 212 of the intermediate section 2112 away from the winding axis.

[0109] By covering at least a portion of the first empty foil area Q1 with the first insulating layer 30, the risk of burrs in the first empty foil area Q1 puncturing the separator 23 and causing a short circuit in the cell 100 can be reduced, thereby improving the safety performance of the cell 100.

[0110] Further, as shown in Figures 3 and 5-6, the first insulating layer 30 includes a first portion 31 connected to the first active material layer 212 of the intermediate section 2112. The first portion 31 overlaps with a portion of the first active material layer 212 of the intermediate section 2112. Along the winding direction X, the length of the first portion 31 is L1, 0.5mm≤L1≤10mm.

[0111] For example, 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, 8.5mm, 9mm, 9.5mm, 10mm, etc.

[0112] A value of L1 ≥ 0.5 mm results in a larger connection area between the first insulating layer 30 and the first active material layer 212 of the intermediate section 2112, which is beneficial to improving the connection stability between the first insulating layer 30 and the first active material layer 212 of the intermediate section 2112. A value of L1 ≤ 10 mm reduces the space occupied by the first insulating layer 30 in the internal space of the cell 100 and reduces the impact of the first insulating layer 30 on the energy density of the cell 100. Therefore, a value of 0.5 mm ≤ L1 ≤ 10 mm not only ensures good connection stability between the first insulating layer 30 and the first active material layer 212 of the intermediate section 2112, but also allows the cell 100 to have a high energy density even with the first insulating layer 30 in place.

[0113] The first insulating layer 30 can be adhesive tape or an insulating coating. In embodiments where the first insulating layer 30 is adhesive tape, the adhesive tape can be made of polymers such as polypropylene, polyimide, and polyethylene terephthalate, or their derivative compounds. In embodiments where the first insulating layer 30 is an insulating coating, the first insulating layer 30 can include non-conductive inorganic particulate matter such as alumina, zeolite, or boehmite, or it can include some non-conductive polymers.

[0114] In some embodiments, the thickness of the first insulating layer 30 is less than the thickness of the first active material layer 212.

[0115] When the first electrode 21 and the first insulating layer 30 are in the unfolded state, the thickness of the first insulating layer 30 is the distance between the surface of the first insulating layer 30 facing the first current collector 211 and the surface of the first insulating layer 30 away from the first current collector 211.

[0116] When the first electrode 21 and the first insulating layer 30 are in the unfolded state, the thickness of the first active material layer 212 is the distance between the surface of the first active material layer 212 facing the first current collector 211 and the surface facing away from the first current collector 211.

[0117] The thickness of the first insulating layer 30 is less than the thickness of the first active material layer 212, which reduces the space occupied by the first insulating layer 30 in the internal space of the cell 100, thereby reducing the impact of the first insulating layer 30 on the energy density of the cell 100.

[0118] Of course, in other embodiments, the thickness of the first insulating layer 30 may be greater than or equal to the thickness of the first active material layer 212.

[0119] In some embodiments, the thickness of the first insulating layer 30 is H1, where 5μm≤H1≤40μm.

[0120] For example, H1 can be 5μm, 7μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, etc.

[0121] H1≥5μm reduces the risk of the first insulating layer 30 being punctured by the burrs in the first empty foil area Q1, which is beneficial to improving the safety performance of the cell 100. H1≤40μm reduces the occupation of the first insulating layer 30 on the internal space of the cell 100, thereby reducing the impact of the first insulating layer 30 on the energy density of the cell 100. Therefore, 5μm≤H1≤40μm can improve the safety performance of the cell 100 and enable the cell 100 to have a high energy density when the first insulating layer 30 is provided.

[0122] As shown in Figures 4-6, in some embodiments, the battery cell 100 further includes a second insulating layer 40, which covers at least a portion of the second empty foil region Q2, and one end face of the second insulating layer 40 is coplanar with the end face of the first termination end 21131.

[0123] The second insulating layer 40 is connected to the first electrode 21. The second insulating layer 40 can be completely connected to the second empty foil region Q2. The second insulating layer 40 can be partially connected to the second empty foil region Q2, and the other part of the second insulating layer 40 can be connected to other areas of the first electrode 21 outside the second empty foil region Q2.

[0124] The second insulating layer 40 can completely cover the second empty foil area Q2. Along the width direction Y of the first current collector, the two opposite end faces of the second insulating layer 40 are coplanar with the two opposite end faces of the starting section 2111. Along the winding direction X, the end face of the first ending end 21131 is coplanar with one end face of the second insulating layer 40, so that the second insulating layer 40 completely covers the second empty foil area Q2.

[0125] In other embodiments, the second insulating layer 40 may also cover a portion of the second empty foil region Q2.

[0126] By covering at least a portion of the second empty foil area Q2 with the second insulating layer 40, the risk of burrs in the second empty foil area Q2 puncturing the isolation film 23 and causing a short circuit in the cell 100 can be reduced, thereby improving the safety performance of the cell 100.

[0127] The second insulating layer 40 can be adhesive tape or an insulating coating. In embodiments where the second insulating layer 40 is adhesive tape, the adhesive tape can be made of polymers such as polypropylene, polyimide, and polyethylene terephthalate, or their derivative compounds. In embodiments where the second insulating layer 40 is an insulating coating, the second insulating layer 40 can include non-conductive inorganic particulate matter such as alumina, zeolite, or boehmite, or it can include some non-conductive polymers.

[0128] In this embodiment, a first active material layer 212 is provided on the surface of the starting section 2111 of the first current collector 211 of the first electrode 21 facing the winding axis of the electrode assembly 20. A first empty foil area Q1 is formed on the surface of the starting section 2111 away from the winding axis. A first active material layer 212 is provided on the surface of the ending section 2113 of the first current collector 211 of the first electrode 21 facing the winding axis of the electrode assembly 20. A second empty foil area Q2 is formed on the surface of the ending section 2113 away from the winding axis. That is, both the starting and ending sections of the winding of the first electrode 21 are single-sided coated structures. The first ending end 21131 is located outside the outermost ring of the second electrode 22. Therefore, the outermost ending electrode of the electrode assembly 20 is a single-sided coated structure. There is no active material 1200 that does not exert its capacity on the side of the outermost ending electrode of the electrode assembly 20 away from the winding axis, which is beneficial to improving energy density and reducing the waste of active material 1200. During the production of the battery cell 100, when cutting to form the first electrode 21, in order to ensure that the winding end section of the first electrode 21 has a single-sided coating structure, the cutting position should be in the single-sided coating area of ​​the substrate 1100. On both sides of the cutting position, a winding start section and a winding end section of the first electrode 21 are formed respectively. Since both the winding start section and the winding end section of the first electrode 21 have single-sided coating structures, compared to the double-sided coating structure of the winding start section, the single-sided coating of the winding end section provides a more balanced and efficient design. In the electrode sheet design with a double-sided coating, in this embodiment, both the starting and ending sections of the first electrode sheet 21 are single-sided coated. Therefore, when cutting to form the first electrode sheet 21, cutting can be performed at any position on the single-sided coated area of ​​the substrate 1100. Precise positioning of the boundary between the double-sided and single-sided coated areas of the substrate 1100 is not required during cutting, which improves cutting efficiency and thus increases the production efficiency of the battery cell 100. On the other hand, to form a double-sided coated structure for the starting section and a single-sided coated structure for the ending section... For electrode sheets with a single-sided coating structure, the precise positioning of the boundary between the single-sided and double-sided coating areas of the substrate 1100 is difficult. Therefore, during cutting, a first cut can be made in the single-sided coating area of ​​the strip 1000 to achieve a single-sided coating structure at the winding end of one electrode sheet. A second cut is then made in the double-sided coating area of ​​the strip 1000 to achieve a double-sided coating structure at the winding start of the next electrode sheet. This not only increases the number of cuts but also increases the difficulty of precisely positioning the boundary between the first and second cut positions of the substrate 1100. In this embodiment, the winding start section and winding end section of the first electrode 21 are both single-sided coated structures. When cutting to form the first electrode 21, it is only necessary to cut once in each single-sided coated area of ​​the substrate 1100. When cutting to form the first electrode 21, it is not necessary to cut once in the single-sided coated area of ​​the substrate 1100 and then cut a second time in the double-sided coated area of ​​the substrate 1100, which improves the cutting efficiency and reduces the waste of the substrate 1100 and the active material layer.

[0129] Furthermore, the cutting in this embodiment can be performed only once on a single-sided coated area of ​​the substrate 1100, which can reduce powder shedding during the cutting process, reduce the risk of short circuit in the cell 100 due to powder shedding, and improve the safety of the cell 100. By covering at least a portion of the first empty foil area Q1 with the first insulating layer 30 and covering a portion of the second empty foil area Q2 with the second insulating layer 40, the risk of burrs in the first empty foil area Q1 and the second empty foil area Q2 puncturing the separator 23 and causing a short circuit in the cell 100 can be reduced, thus improving the safety performance of the cell 100. Since the first starting end 21111 and the first ending end 21131 are the two cutting positions when cutting the substrate 1100 to form the first electrode 21, and one end face of the first insulating layer 30 is coplanar with the end face of the first starting end 21111, and one end face of the second insulating layer 40 is coplanar with the end face of the first ending end 21131, the insulating element can be set in the single-sided coating area of ​​the substrate 1100 before cutting. Cutting is performed in the area where the insulating element and the single-sided coating area overlap. Then, a part of the insulating element forms the first insulating layer 30 of the first electrode 21, and the other part of the insulating element forms the second insulating layer 40 of the other first electrode 21. After cutting, one end of the first insulating layer 30 is coplanar with the first starting end 21111, and one end of the second insulating layer 40 is coplanar with the first ending end 21131, which is beneficial to improving production efficiency.

[0130] As shown in Figure 4, in some embodiments, the intermediate section 2112 has a first end 21121 connected to the end section 2113; the portion of the end section 2113 located outside the first end 21121 includes a first section 21132 extending beyond the first end 21121 along the winding direction X, and the second insulating layer 40 is connected within the first section 21132.

[0131] The outer side of the first end 21121 refers to the side of the end face of the first end 21121 that faces away from the winding axis. The first segment 21132 is a segment of the portion of the tail segment 2113 located outside the first end 21121 along the winding direction X between the first tail end 21131 and the first end 21121. The electrode assembly 20 is defined as having a first reference plane P1 coplanar with the end face of the first end 21121 and a second reference plane P2 coplanar with the end face of the first tail end 21131. The first segment 21132 is defined between the position where the first reference plane intersects with the portion of the tail segment 2113 located outside the first end 21121 and the position where the second reference plane intersects with the portion of the tail segment 2113 located outside the first end 21121.

[0132] The first insulating layer 30 is connected within the first segment 21132, and it can be understood that any region of the first insulating layer 30 is connected to the first segment 21132.

[0133] The portion of the finishing section 2113 located outside the first end 21121 includes a first segment 21132 extending beyond the first end 21121 along the winding direction X. The second insulating layer 40 is connected to the first segment 21132. Since the second insulating layer 40 is located in the region where the electrode assembly 20 has a smaller size, its influence on the size of the electrode assembly 20 is reduced, thus contributing to a higher energy density in the cell 100. The connection of the second insulating layer 40 to the first segment 21132 also results in smaller dimensional differences between different parts of the electrode assembly 20, which helps improve the uniformity of stress on the electrode sheets during the expansion of the electrode assembly 20.

[0134] As shown in Figure 4, in some embodiments, the orthographic projection of the first end 21121 in the plane of the first radial direction P3 of the vertical electrode assembly 20 does not overlap with the orthographic projection of the second insulating layer 40, wherein the first radial direction P3 is the direction perpendicular to the winding axis and passing through the first end 21121.

[0135] That is, when viewed along the direction perpendicular to the winding axis and passing through the end face of the first end 21121, the orthographic projection of the first end 21121 and the orthographic projection of the second insulating layer 40 do not overlap.

[0136] In the plane of the first radial direction P3 of the vertical electrode assembly 20, the orthographic projection of the first end 21121 does not overlap with the orthographic projection of the second insulating layer 40. Therefore, there is a distance between the orthographic projections of the first end 21121 and the second insulating layer 40 in the plane of the first radial direction P3 of the vertical electrode assembly 20. This reduces the risk of overlap between the orthographic projections of the first end 21121 and the second insulating layer 40 in the plane of the first radial direction P3 of the vertical electrode assembly 20 during cell cycling. This allows the second insulating layer 40 to always be located in the smaller area of ​​the electrode assembly 20, reducing the impact of the second insulating layer 40 on the size of the electrode assembly 20, thus contributing to a higher energy density in the cell 100. It also results in smaller dimensional differences between different parts of the electrode assembly 20, which helps improve the uniformity of stress on the electrode plates during the expansion of the electrode assembly 20.

[0137] In an embodiment where the second insulating layer 40 covers a portion of the second empty foil area Q2, as shown in Figures 4-6, the cell 100 further includes a third insulating layer 50. The third insulating layer 50 is connected to the first electrode 21 and covers a portion of the second empty foil area Q2. Along the winding direction X, the third insulating layer 50 and the second insulating layer 40 are arranged side by side or spaced apart.

[0138] The third insulating layer 50 can be completely connected to the second empty foil area Q2. The third insulating layer 50 can be partially connected to the second empty foil area Q2, and the other part of the third insulating layer 50 can be connected to other areas of the first electrode 21 outside the second empty foil area Q2.

[0139] The third insulating layer 50 is connected to the first electrode 21 and covers a portion of the second empty foil area Q2. This also helps to reduce the risk of short circuit caused by burrs piercing the separator 23 in the second empty foil area Q2, thereby improving the safety performance of the cell 100.

[0140] Along the winding direction X, the third insulating layer 50 and the second insulating layer 40 are arranged side by side. Understandably, the third insulating layer 50 and the second insulating layer 40 do not overlap in the thickness direction of the first electrode 21. Therefore, by arranging the third insulating layer 50 and the second insulating layer 40 side by side along the winding direction X, the size of the electrode assembly 20 is avoided from having a stacked area between the second insulating layer 40 and the third insulating layer 50 in the thickness direction of the first electrode 21.

[0141] For example, as shown in Figures 4-6, a portion of the third insulating layer 50 is connected to the second empty foil region Q2, and another portion of the third insulating layer 50 is connected to the first active material layer 212 of the intermediate section 2112. By connecting a portion of the third insulating layer 50 to the second empty foil region Q2 and the other portion of the third insulating layer 50 to the first active material layer 212 of the intermediate section 2112, the manufacturing process of the third insulating layer 50 is simplified, facilitating the connection between the third insulating layer 50 and the first electrode 21, and improving the connection stability between the third insulating layer 50 and the first electrode 21.

[0142] The third insulating layer 50 can be connected to the first active material layer 212 on the surface of the intermediate section 2112 facing away from the winding axis. The third insulating layer 50 can be connected to the first active material layer 212 on the surface of the intermediate section 2112 facing away from the intermediate section 2112.

[0143] Furthermore, the third insulating layer 50 includes a second portion 51 connected to the first active material layer 212 of the intermediate section 2112. The second portion 51 overlaps with a portion of the first active material layer 212 of the intermediate section 2112 along the winding direction X. The length of the second portion 51 is L3, 0.5mm≤L3≤10mm.

[0144] For example, L3 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, 8.5mm, 9mm, 9.5mm, 10mm, etc.

[0145] A value of L3 ≥ 0.5 mm results in a larger connection area between the third insulating layer 50 and the first active material layer 212 of the intermediate section 2112, which is beneficial to improving the connection stability between the third insulating layer 50 and the first active material layer 212 of the intermediate section 2112. A value of L3 ≤ 10 mm reduces the space occupied by the third insulating layer 50 within the cell 100 and reduces the impact of the third insulating layer 50 on the energy density of the cell 100. Therefore, a value of 0.5 mm ≤ L3 ≤ 10 mm not only ensures good connection stability between the third insulating layer 50 and the first active material layer 212 of the intermediate section 2112, but also allows the cell 100 to have a high energy density even with the third insulating layer 50.

[0146] The third insulating layer 50 can be adhesive tape or an insulating coating. In embodiments where the third insulating layer 50 is adhesive tape, the adhesive tape can be made of polymers such as polypropylene, polyimide, and polyethylene terephthalate, or their derivative compounds. In embodiments where the third insulating layer 50 is an insulating coating, the first insulating layer 30 can be non-conductive inorganic particulate matter such as alumina, zeolite, or boehmite, or it can include some non-conductive polymers.

[0147] In some embodiments, the thickness of the second insulating layer 40 is less than the thickness of the first active material layer 212.

[0148] When the first electrode 21 and the second insulating layer 40 are in the unfolded state, the thickness of the second insulating layer 40 is the distance between the surface of the second insulating layer 40 facing the first current collector 211 and the surface of the second insulating layer 40 away from the first current collector 211.

[0149] By making the thickness of the second insulating layer 40 smaller than the thickness of the first active material layer 212, the second insulating layer 40 occupies less space inside the cell 100, thereby reducing the impact of the second insulating layer 40 on the energy density of the cell 100.

[0150] As shown in Figures 4 and 6, the thickness of the second insulating layer 40 is H2, where 5μm ≤ H2 ≤ 40μm. For example, H2 can be 5μm, 7μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, etc.

[0151] By setting H2≥5μm, the risk of the second insulating layer 40 being punctured by the burrs in the second empty foil area Q2 is reduced, which is beneficial to improving the safety performance of the cell 100. H2≤40μm reduces the occupation of the second insulating layer 40 on the internal space of the cell 100, thereby reducing the impact of the second insulating layer 40 on the energy density of the cell 100. Therefore, 5μm≤H2≤40μm can not only improve the safety performance of the cell 100, but also enable the cell 100 to have a high energy density when the second insulating layer 40 is provided.

[0152] In some embodiments, the thickness of the third insulating layer 50 is less than the thickness of the first active material layer 212.

[0153] When the first electrode 21 and the third insulating layer 50 are in the unfolded state, the thickness of the third insulating layer 50 is the distance between the surface of the third insulating layer 50 facing the first current collector 211 and the surface of the third insulating layer 50 away from the first current collector 211.

[0154] By making the thickness of the third insulating layer 50 smaller than the thickness of the first active material layer 212, the third insulating layer 50 occupies less space inside the cell 100, thereby reducing the impact of the third insulating layer 50 on the energy density of the cell 100.

[0155] As shown in Figures 4 and 6, the thickness of the third insulating layer 50 is H3, where 5μm ≤ H3 ≤ 40μm. For example, H3 can be 5μm, 7μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, etc.

[0156] By setting H3≥5μm, the risk of the third insulating layer 50 being punctured by the burrs in the second empty foil area Q2 is reduced, which is beneficial to improving the safety performance of the cell 100. H3≤40μm reduces the occupation of the third insulating layer 50 in the internal space of the cell 100, thereby reducing the impact of the third insulating layer 50 on the energy density of the cell 100. Therefore, 5μm≤H3≤40μm can not only improve the safety performance of the cell 100, but also enable the cell 100 to have a high energy density when the third insulating layer 50 is provided.

[0157] In an embodiment where the first electrode 21 is a positive electrode, the second electrode 22 has a second terminal end 221, and the portion of the third insulating layer 50 located in the second empty foil region Q2 extends beyond the second terminal end in the opposite direction of the winding direction X.

[0158] The portion of the third insulating layer 50 located in the second empty foil area Q2 includes a second segment located inside the second end. In the opposite direction of the winding direction X, a portion of the second segment extends beyond the second end. In the thickness direction of the second electrode 22, the second end faces the third insulating layer 50.

[0159] In the opposite direction of the winding direction X, by extending the portion of the third insulating layer 50 located in the second empty foil region Q2 beyond the second end of the positive electrode sheet, the risk of lithium plating in the cell 100 is reduced, as is the risk of the positive electrode sheet being directly opposite the second empty foil region Q2, thereby improving the safety performance of the cell 100.

[0160] In some embodiments, in the opposite direction to the winding direction X, the third insulating layer 50 includes a third portion 52 extending beyond the second end 221, the third portion 52 being located in the second empty foil region Q2, and the length of the third portion 52 being L4, where L4 ≥ 2 mm.

[0161] For example, L4 can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.

[0162] By setting L4≥2mm, the risk of lithium plating in cell 100 is reduced, as is the risk of the positive electrode sheet being directly opposite the second empty foil region Q2, thereby improving the safety performance of cell 100.

[0163] In some embodiments, along the winding direction X, the portion of the third insulating layer 50 located in the second empty foil region Q2 extends beyond the second end.

[0164] Along the winding direction X, a portion of the second section of the third insulating layer 50 located in the second empty foil area Q2 and inside the second terminal end 221 extends beyond the second terminal end, so in the thickness direction of the second electrode 22, the second terminal end faces the third insulating layer 50.

[0165] Along the winding direction X, by extending the portion of the third insulating layer 50 located in the second empty foil region Q2 beyond the second end of the positive electrode sheet, the risk of lithium plating in the cell 100 is reduced, as is the risk of the positive electrode sheet being directly opposite the second empty foil region Q2, thereby improving the safety performance of the cell 100.

[0166] As shown in Figure 4, in some embodiments, along the winding direction X, the third insulating layer 50 includes a fourth portion 53 extending beyond the second end 221, the fourth portion 53 being located in the second empty foil area Q2, and the length of the fourth portion 53 being L5, where L5 ≥ 2 mm.

[0167] For example, L5 can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.

[0168] By setting L5≥2mm, the risk of lithium plating in cell 100 is reduced, as is the risk of the positive electrode sheet being directly opposite the second empty foil region Q2, thereby improving the safety performance of cell 100.

[0169] This application also provides an electrical device, which includes the battery cell 100 provided in any of the above embodiments.

[0170] As shown in Figures 7 and 8, this application embodiment also provides a method for preparing an electrode sheet, the method comprising:

[0171] Step S100: Provide a strip 1000, including a substrate 1100 and an active material layer 1200. Along the thickness direction of the substrate 1100, the substrate 1100 has a first surface 1103 and a second surface 1104. Along the length direction of the substrate 1100, the substrate 1100 has a second end 1101 and a third end 1102. The first surface 1103 and the second surface 1104 are both provided with active material layers 1200. The active material layers 1200 on the first surface 1103 are continuously provided, and the active material layers 1200 on the second surface 1104 are spaced apart. On the second surface 1104, along the length direction of the substrate 1100, empty foil areas Q are formed on both sides of each active material layer 1200.

[0172] Step S200: Provide the first insulating element 2000;

[0173] In step S300, along the length direction of the substrate 1100, a first insulating member 2000 is provided on the side of each active material layer 1200 on the second surface 1104 near the second end 1101, and the first insulating member 2000 covers at least a portion of the empty foil area Q.

[0174] In step S400, the area where each first insulating element 2000 overlaps with the empty foil area Q is cut to form a first sub-electrode 21a and a second sub-electrode 21b. The first insulating element 2000 is cut into a first insulating layer 30 and a second insulating layer 40. The first insulating layer 30 is located at the starting segment 2111 of the current collector of the first sub-electrode 21a, and the second insulating layer 40 is located at the ending segment 2113 of the current collector of the second sub-electrode 21b. The dashed line in Figure 8 indicates the cutting position.

[0175] The first electrode 21 can be a first sub-electrode 21a or a second sub-electrode 21b prepared by the above-described electrode preparation method.

[0176] After the cutting process in step S400, a portion of the substrate 1100 in the strip 1000 forms the current collector of the first sub-electrode 21a, and a portion of the substrate 1100 forms the current collector of the second sub-electrode 21b.

[0177] Cutting is performed in the area where the first insulating component 2000 and the empty foil area Q overlap, cutting the first insulating component 2000 into a first insulating layer 30 and a second insulating layer 40. A portion of this forms the first insulating layer 30 of the first sub-electrode 21a. The first insulating layer 30 is located at the starting section 2111 of the current collector of the first sub-electrode 21a, and the second insulating layer 40 is located at the ending section 2113 of the current collector of the second sub-electrode 21b. The final first sub-electrode 21a and the second sub-electrode 21b both have a single-sided coating structure at both the starting and ending sections of the winding. Compared to an electrode with a double-sided coating structure at the starting section and a single-sided coating structure at the ending section, this is a significant improvement. Since both the starting and ending sections of the winding of the first sub-electrode 21a and the second sub-electrode 21b formed by this method are single-sided coated structures, the cutting of the first sub-electrode 21a and the second sub-electrode 21b can be performed at any position on the single-sided coated area of ​​the substrate 1100 during the cutting process. Precise positioning of the boundary between the double-sided and single-sided coated areas of the substrate 1100 is not required during cutting, which improves cutting efficiency and thus increases the production efficiency of the battery cell 100. On the other hand, when manufacturing electrode sheets with a double-sided coated structure at the starting section and a single-sided coated structure at the ending section, the single-sided and double-sided coated areas of the substrate 1100... Precisely locating the boundary position is difficult. Therefore, during cutting, a first cut can be made in the single-sided coating area of ​​the substrate 1100 to achieve a single-sided coating structure for the winding end section of one electrode sheet. Then, a second cut is made in the double-sided coating area of ​​the substrate 1100 to achieve a double-sided coating structure for the winding start section of the next electrode sheet. This not only increases the number of cuts, but also wastes the substrate 1100 and active material 1200 between the first and second cut positions. The winding start and winding end sections of the first sub-electrode sheet 21a and the second sub-electrode sheet 21b formed by this method are both single-sided coating structures. When preparing the first and second sub-electrodes 21a and 21b, only one cutting is needed in each area where the first insulating element 2000 overlaps with the empty foil area Q. Therefore, when forming the first and second sub-electrodes 21a and 21b, it is not necessary to perform a first cutting in the single-sided coated area of ​​the substrate 1100 (the area where the first insulating element 2000 and the empty foil area Q overlap) and a second cutting in each double-sided coated area of ​​the substrate 1100 (the area where the active material layer 1200 of the first surface 1103 overlaps with the active material layer 1200 of the second surface 1104). This improves cutting efficiency and reduces waste of the substrate 1100 and active material 1200. Furthermore, in preparing the electrode using this method, cutting can be performed only once in the single-sided coated area of ​​the substrate 1100, reducing powder shedding during the cutting process, lowering the risk of short circuits in the cell 100 due to powder shedding, and improving the safety of the cell 100.

[0178] In some embodiments, along the length direction of the substrate 1100, a first insulating member 2000 is provided on one side of each active material layer 1200 on the second surface 1104 near the second end 1101, and the first insulating member 2000 covers at least a portion of the empty foil area Q, including:

[0179] In step S310, a portion of the first insulating member 2000 is connected to the active material layer 1200 of the second surface 1104, and another portion of the first insulating member 2000 is connected to the empty foil area Q, so that the first insulating member 2000 covers at least a portion of the empty foil area Q.

[0180] Understandably, the way the first insulating member 2000 is set in step S300 is to connect a portion of each first insulating member 2000 to the surface of the active material layer 1200 of the second surface 1104 away from the substrate 1100, and to connect another portion of the first insulating member 2000 to the empty foil area Q on the side of the active material layer 1200 facing the second end 1101.

[0181] By connecting a portion of the first insulating member 2000 to the active material layer 1200 of the second surface 1104 and connecting another portion of the first insulating member 2000 to the empty foil area Q, so that the first insulating member 2000 covers at least a portion of the empty foil area Q, after cutting to form the first sub-electrode 21a and the second sub-electrode 21b, a portion of the first insulating layer 30 is connected to the empty foil area Q of the winding start section of the first sub-electrode 21a, and another portion of the first insulating layer 30 is connected to the active material layer 1200 of the first sub-electrode 21a, which facilitates the connection between the first insulating layer 30 and the first sub-electrode 21a and helps to improve the connection stability between the first insulating layer 30 and the first sub-electrode 21a.

[0182] In other embodiments, a first insulating member 2000 is provided on one side of each active material layer 1200 on the second surface 1104 near the second end 1101 along the length direction of the substrate 1100, and the first insulating member 2000 covers at least a portion of the empty foil area Q, and may also include:

[0183] Step S310: The first insulating element 2000 is fully connected to the empty foil area Q of the active material layer 1200 on the second surface 1104 near the second end 1101.

[0184] That is, the way to set the first insulating member 2000 in step S300 is to completely connect each first insulating member 2000 to the empty foil area Q on the side of the active material layer 1200 facing the second end 1101.

[0185] In some embodiments, before cutting the region where each first insulating element 2000 overlaps with the empty foil region Q to form a plurality of first sub-electrodes 21a and second sub-electrodes 21b, the electrode preparation method further includes:

[0186] Step S500: Provide the second insulating element 3000;

[0187] In step S600, along the length direction of the substrate 1100, a second insulating member 3000 is provided on the side of each active material layer 1200 on the second surface 1104 near the third end 1102, and the second insulating member 3000 covers at least a portion of the empty foil area Q.

[0188] After cutting the area where each first insulating element 2000 overlaps with the empty foil area Q to form the first sub-electrode 21a and the second sub-electrode 21b, the second insulating element 3000 is located at the end section 2113 of the current collector of the second sub-electrode 21b.

[0189] That is, before performing step S300, a second insulating member 3000 is provided on the side of each active material layer 1200 on the second surface 1104 near the third end 1102. In step S500, among adjacent first insulating members 2000 and second insulating members 3000, the second insulating member 3000 can be arranged side-by-side with the first insulating member 2000 along the length direction of the substrate 1100, meaning the first insulating member 2000 and the second insulating member 3000 do not overlap in the thickness direction of the substrate 1100. The end of the first insulating member 2000 near the second insulating member 3000 can contact the end of the second insulating member 3000 near the first insulating member 2000. If the end of the first insulating member 2000 near the second insulating member 3000 can be spaced apart from the end of the second insulating member 3000 near the first insulating member 2000, then after step S300 is completed, the second insulating layer 40 of the first sub-electrode 21a and the second insulating member 3000 are arranged side by side and spaced apart along the length direction of the first electrode 21.

[0190] By providing a second insulating member 3000 on the side of each active material layer 1200 on the second surface 1104 near the third end 1102, and making the second insulating member 3000 cover at least a portion of the empty foil area Q, after cutting the area where each first insulating member 2000 overlaps with the empty foil area Q to form the first sub-electrode 21a and the second sub-electrode 21b, the second insulating member 3000 is located at the end section 2113 of the current collector of the second sub-electrode 21b. The second insulating member 3000 covers a portion of the empty foil area Q of the winding end section of the second sub-electrode 21b, which can reduce the risk of burrs in the empty foil area Q puncturing the separator 23 and causing a short circuit in the cell 100, thereby improving the safety performance of the cell 100 equipped with the second sub-electrode 21b.

[0191] In some embodiments, along the length direction of the substrate 1100, a second insulating member 3000 is provided on one side of each active material layer 1200 on the second surface 1104 near the third end 1102, and the second insulating member 3000 covers at least a portion of the empty foil area Q, including:

[0192] In step S610, the adjacent second insulating member 3000 and the first insulating member 2000 are spaced apart along the length direction of the substrate 1100.

[0193] That is, during the execution of step S600, the adjacent first insulating member 2000 and second insulating member 3000 are arranged side by side at intervals along the length direction of the substrate 1100.

[0194] When adjacent second insulating members 3000 and first insulating members 2000 are spaced apart along the length direction of the substrate 1100, after cutting, a portion of the first insulating member 2000 and the second insulating member 3000 of the first electrode 21 and the second electrode 22 are spaced apart along their length direction, so as to avoid the second insulating member and the first insulating member 2000 having a stacked area in the thickness direction of the first electrode 21, thereby increasing the size of the electrode assembly 20 having the electrode formed by the above method.

[0195] In some embodiments, the provision of the feed strip 1000 includes:

[0196] Step S110: Provide substrate 1100;

[0197] Step S120: An active material is continuously coated on the first surface 1103 so that the active material layer 1200 on the first surface 1103 is continuously disposed.

[0198] In step S130, an active material is intermittently coated on the second surface 1104 so that the active material layers 1200 on the second surface 1104 are spaced apart.

[0199] After cutting to form the first sub-electrode 21a and the second sub-electrode 21b, the substrate 1100 is cut into current collectors for the first sub-electrode 21a and the second sub-electrode 21b.

[0200] In step S120, the active material is continuously coated on the first surface 1103 so that the active material layer 1200 on the first surface 1103 is continuously provided. This means that during the process of coating the active material on the first surface 1103, the coating equipment continuously coats the material, and no empty foil area Q is formed on the second surface 1104.

[0201] In step S130, intermittently coating the active material on the second surface 1104 means that during the process of coating the active material on the second surface 1104, the coating equipment operates intermittently, that is, the active material is coated on some areas of the second surface 1104 while the active material is not coated on some areas, so that the active material layers 1200 on the second surface 1104 are spaced apart and empty foil areas Q are formed between adjacent active material layers 1200.

[0202] By continuously coating the first surface 1103 with active material 1200 so that the active material layer 1200 on the first surface 1103 is continuously arranged, and intermittently coating the second surface 1104 with active material 1200 so that the active material layer 1200 on the second surface 1104 is spaced out, the forming of the strip 1000 is facilitated and the production efficiency of the electrode sheet is improved.

[0203] 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, characterized in that, include: A wound electrode assembly includes a first electrode and a second electrode with opposite polarities. The first electrode includes a first current collector and a first active material layer. Along the winding direction of the electrode assembly, the first current collector includes a starting section, an intermediate section, and a closing section connected in sequence. The end of the starting section away from the intermediate section is a first starting end, and the end of the closing section away from the intermediate section is a first closing end. The first active material layer is disposed on the surface of the starting section facing the winding axis of the electrode assembly, and a first empty foil area is formed on the surface of the starting section away from the winding axis. The first active material layer is disposed on the surface of the closing section facing the winding axis, and a second empty foil area is formed on the surface of the closing section away from the winding axis. The first closing end is located outside the outermost ring of the second electrode. A first insulating layer covers at least a portion of the first empty foil area, and one end face of the first insulating layer is coplanar with the end face of the first starting end; A second insulating layer covers at least a portion of the second empty foil area, and one end face of the second insulating layer is coplanar with the end face of the first termination end.

2. The battery cell according to claim 1, characterized in that, A portion of the first insulating layer is connected to the first empty foil area, and another portion of the first insulating layer is connected to the first active material layer of the intermediate segment.

3. The battery cell according to claim 2, characterized in that, The first insulating layer includes a first portion connected to the first active material layer of the intermediate segment, the first portion overlapping a portion of the first active material layer of the intermediate segment, and the length of the first portion along the winding direction is L1, 0.5mm≤L1≤10mm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The thickness of the first insulating layer is less than the thickness of the first active material layer.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The thickness of the first insulating layer is H1, where 5μm≤H1≤40μm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The intermediate segment has a first end connected to the terminal segment; The portion of the finishing section located outside the first end includes a first segment extending beyond the first end along the winding direction, and the second insulating layer is connected within the first segment.

7. The battery cell according to claim 6, characterized in that, In a plane perpendicular to the first radial direction of the electrode assembly, the orthographic projection of the first end does not overlap with the orthographic projection of the second insulating layer, wherein the first radial direction is perpendicular to the winding axis and passes through the first end.

8. The battery cell according to any one of claims 1 to 7, characterized in that, Along the winding direction, the length of the starting segment is L2, 0.5mm≤L2≤10mm.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The second insulating layer covers a portion of the second empty foil area; The battery cell also includes a third insulating layer, which is connected to the first electrode and covers a portion of the second empty foil area. Along the winding direction, the third insulating layer and the second insulating layer are arranged side by side.

10. The battery cell according to claim 9, characterized in that, A portion of the third insulating layer is connected to the second empty foil region, and another portion of the third insulating layer is connected to the first active material layer of the intermediate segment.

11. The battery cell according to claim 10, characterized in that, The third insulating layer includes a second portion connected to the first active material layer of the intermediate section, the second portion overlapping a portion of the first active material layer of the intermediate section, and the length of the second portion along the winding direction is L3, 0.5mm≤L3≤10mm.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The thickness of the second insulating layer is less than the thickness of the first active material layer; and / or, the thickness of the third insulating layer is less than the thickness of the first active material layer.

13. The battery cell according to claim 12, characterized in that, The thickness of the second insulating layer is H2, 5μm≤H2≤40μm; and / or, the thickness of the third insulating layer is H3, 5μm≤H3≤40μm.

14. The battery cell according to any one of claims 9 to 11, characterized in that, The first electrode is a positive electrode, the second electrode has a second terminal end, and along the opposite direction of the winding direction, the portion of the third insulating layer located in the second empty foil area extends beyond the second terminal end; and / or, along the winding direction, the portion of the third insulating layer located in the second empty foil area extends beyond the second terminal end.

15. The battery cell according to claim 14, characterized in that, In the opposite direction of the winding direction, the third insulating layer includes a third portion extending beyond the second end, the third portion being located in the second empty foil area, and the length of the third portion being L4, L4≥2mm; and / or, in the winding direction, the third insulating layer includes a fourth portion extending beyond the second end, the fourth portion being located in the second empty foil area, and the length of the fourth portion being L5, L5≥2mm.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The first electrode is a positive electrode.

17. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1-16.

18. A method for preparing an electrode sheet, characterized in that, The method for preparing the electrode includes: A strip is provided, comprising a substrate and an active material layer. Along the thickness direction of the substrate, the substrate has opposing first and second surfaces, and along the length direction of the substrate, the substrate has opposing second and third ends. Both the first and second surfaces are provided with... The active material layer is provided, the active material layer on the first surface is continuously disposed, and the active material layer on the second surface is disposed at intervals; on the second surface, along the length direction of the substrate, empty foil areas are formed on both sides of each active material layer. Provide the first insulating component; Along the length direction of the substrate, the first insulating element is disposed on the side of each active material layer on the second surface near the second end, and the first insulating element covers at least a portion of the empty foil area; The area where each of the first insulating elements overlaps with the empty foil area is cut to form a first sub-electrode and a second sub-electrode, and the first insulating element is cut into a first insulating layer and a second insulating layer, wherein the first insulating layer is located at the beginning of the current collector of the first sub-electrode, and the second insulating layer is located at the end of the current collector of the second sub-electrode.

19. The method for preparing the electrode according to claim 18, characterized in that, The first insulating element is disposed on the side of each active material layer on the second surface near the second end along the length direction of the substrate, and the first insulating element covers at least a portion of the empty foil area, including: A portion of the first insulating member is attached to the active material layer on the second surface, and another portion of the first insulating member is attached to the empty foil area, such that the first insulating member covers at least a portion of the empty foil area.

20. The method for preparing the electrode according to claim 18 or 19, characterized in that, Before cutting the area where each of the first insulating elements overlaps with the empty foil area to form the first and second sub-electrodes, the method for preparing the electrode further includes: Provide a second insulating component; Along the length direction of the substrate, a second insulating member is disposed on the side of each active material layer on the second surface near the third end, and the second insulating member covers at least a portion of the empty foil area; After the area where each of the first insulating elements overlaps with the empty foil area is cut to form the first sub-electrode and the second sub-electrode, the second insulating element is located at the end of the current collector of the second sub-electrode.

21. The method for preparing the electrode according to claim 20, characterized in that, The provision of a second insulating member along the length of the substrate, on the side of each active material layer on the second surface near the third end, and the second insulating member covering at least a portion of the empty foil area, includes: The adjacent second insulating element and the first insulating element are spaced apart along the length direction of the substrate.

22. The method for preparing the electrode according to any one of claims 18-21, characterized in that, The provided material strip includes: Provide the substrate; An active material is continuously coated on the first surface so that the active material layer on the first surface is continuously disposed; An active material is intermittently coated on the second surface so that the active material layers on the second surface are spaced apart.

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