Battery cell and electric equipment

Abstract

The invention provides a battery cell and electric equipment. The battery cell comprises an electrode assembly and two separators, an electrode assembly of the battery cell comprises a positive pole piece, a negative pole piece and an isolating membrane, the isolating membrane insulates and isolates the positive pole piece and the negative pole piece, the positive pole piece is provided with a positive ending end, and the negative pole piece exceeds the positive ending end in the winding direction of the electrode assembly; each separator comprises a first separation part and a second separation part which is connected with the first separation part and exceeds the positive ending end, the first separation parts of the two separators are respectively arranged on two opposite surfaces of the positive pole piece along the thickness direction of the positive pole piece, and the second separation parts of the two separators are oppositely arranged; the sum of the thicknesses of the first separation parts of the two separators is smaller than the sum of the thicknesses of the second separation parts of the two separators, so that the risk of short circuit failure caused by the fact that the two edges of the positive ending end pierce the isolating membrane when the battery cell is in a drop mechanical test or in a drop working condition is reduced; the safety of the battery cell is improved; and the qualified rate of the battery cell drop test is improved.

Description

Technical Field

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

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

[0003] The embodiments of the present application provide a battery cell and an electrical device to improve the safety performance of the battery cell.

[0004] In the first aspect, an embodiment of the present application provides a battery cell, comprising an electrode assembly and two separators. The electrode assembly is a winding structure, comprising a positive electrode sheet, a negative electrode sheet and a separator, the separator is insulated and separated from the positive electrode sheet and the negative electrode sheet, the positive electrode sheet has a positive electrode tail end, and the negative electrode sheet exceeds the positive electrode tail end along the winding direction of the electrode assembly. The separator comprises a first separator and a second separator connected to the first separator and exceeding the positive electrode tail end, along the thickness direction of the positive electrode sheet, the first separators of the two separators are respectively arranged on the two opposite surfaces of the positive electrode sheet, and the second separators of the two separators are arranged oppositely; wherein the sum of the thicknesses of the first separators of the two separators is less than the sum of the thicknesses of the second separators of the two separators.

[0005] In one or more of the above optional embodiments, the first separators of the two separators are respectively arranged on two opposite surfaces of the positive electrode sheet in the thickness direction, so as to facilitate the fixing of the separators. The second separator is connected to the first separator and extends beyond the positive electrode tail end. On the one hand, the separator can separate the two edges and the isolation membrane formed by the positive electrode sheet at the positive electrode tail end, thereby reducing the risk of the two edges of the positive electrode tail end piercing the isolation membrane and causing short circuit failure during the drop mechanical test of the battery cell or when the battery cell is in a drop condition, thereby improving the safety of the battery cell drop mechanical test and the drop condition, and improving the pass rate of the battery cell drop test. On the other hand, the separator can also separate the edges corresponding to the positive electrode tail end and the negative electrode sheet closest to the positive electrode tail end. After the electrode assembly expands to abut against the outer shell, the separator can effectively relieve or release the stress of the negative electrode sheet closest to the positive electrode tail end at the position corresponding to the positive electrode tail end, thereby making the negative electrode collector of the negative electrode sheet not easy to break. On the other hand, since the second separators of the two separators extend beyond the positive electrode tail end, the two second separators fill the space between the positive electrode tail end and the negative electrode tail end of the negative electrode plate, and fill the gap on one side of the negative electrode tail section close to the positive electrode tail end, thereby improving the uniformity of the force acting on the outer shell when the electrode assembly expands, reducing the risk of the electrode assembly being sunken due to the force of the outer shell, or alleviating the degree of the electrode assembly being sunken due to the action of the outer shell after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane due to the sunken electrode assembly during a drop mechanical test or when the battery cell is in a drop condition, further improving the yield of the battery cell and the safety performance of the battery cell. The sum of the thicknesses of the first separators of the two separators is less than the sum of the thicknesses of the second separators of the two separators, which further improves the uniformity of the force acting on the outer shell when the electrode assembly expands, further reduces the risk of the electrode assembly being sunken due to the force of the outer shell, or alleviates the degree of the electrode assembly being sunken due to the action of the outer shell after expansion, thereby further reducing the risk of short-circuit failure caused by puncturing the isolation membrane due to the sunken electrode assembly during a drop mechanical test or when the battery cell is in a drop condition, further improving the yield of the battery cell and the safety performance of the battery cell.

[0006] In some embodiments of the first aspect of the present application, the thickness of the first partition is less than the thickness of the second partition.

[0007] In one or more of the above optional embodiments, the thickness of the first separator is less than that of the second separator. The first separator has a smaller thickness, which reduces the effect of the first separator on the size of the electrode assembly, thereby reducing the loss of battery cell capacity and reducing the defective rate of electrode assembly shell entry.

[0008] In some embodiments of the first aspect of the present application, the thickness of the first partitioning parts of the two partitions is equal; and / or the thickness of the second partitioning parts of the two partitions is equal.

[0009] In one or more of the above optional embodiments, the thickness of the first partitioning parts of the two separators is equal; and / or the thickness of the second partitioning parts of the two separators is equal, which is beneficial for uniform force on the electrode assembly during expansion and facilitates the manufacturing and forming of the separators and battery cells.

[0010] In some embodiments of the first aspect of the present application, the thickness of the first separator is smaller than the dimension of the second separator along the winding direction of the electrode assembly.

[0011] In one or more of the above optional embodiments, the thickness of the first separator is smaller than the size of the second separator along the winding direction of the electrode assembly, that is, the size of the second separator along the winding direction of the electrode assembly is larger, reducing the risk of the second separator warping during the winding process. When the two second separators are connected, the size of the second separator along the winding direction of the electrode assembly is larger, which can also reduce the risk of the two second separators connected being partially separated during the falling process of the battery cell, causing the edge of the positive electrode tail end to pierce the diaphragm and cause short-circuit failure, thereby improving the safety performance of the battery cell. The thickness of the first separator is smaller than the size of the second separator along the winding direction of the electrode assembly, that is, the thickness of the first separator is smaller, reducing the influence of the first separator on the size of the electrode assembly, thereby reducing the capacity loss of the battery cell and reducing the defective rate of the electrode assembly into the shell.

[0012] In some embodiments of the first aspect of the present application, the second partitioning portions of two of the partitions are connected.

[0013] In one or more of the above optional embodiments, the second separators of the two separators are connected, which reduces the risk of the separators detaching from the positive electrode sheets and enables the two separators to form a closed space at the positive electrode tail end, so that the separators can more stably separate the edges of the positive electrode tail end and the isolation membrane, thereby reducing the risk of the edges of the positive electrode tail end piercing the isolation membrane when the battery cell is in a drop test or in a drop condition, thereby improving the safety of the battery cell and the pass rate of the drop test.

[0014] In some embodiments of the first aspect of the present application, the second separator has a first surface facing the positive electrode tail end, and the first surface is connected to the positive electrode tail end.

[0015] In one or more of the above optional embodiments, the first surface of the second separator facing the positive electrode tail end is connected to the positive electrode tail end, so that the separator can better separate the edges of the positive electrode tail end and the isolation membrane, and can also improve the stability of the connection between the separator and the positive electrode sheet, thereby further improving the safety performance of the battery cell.

[0016] In some embodiments of the first aspect of the present application, in the thickness direction of the positive electrode sheet, the surface of the second separator of each separator away from the positive electrode sheet is flush with the surface of the first separator away from the positive electrode sheet.

[0017] In one or more of the above optional embodiments, the second separator of each separator is flush with the surface of the first separator away from the positive electrode sheet, which is beneficial for uniform force on the negative electrode sheet adjacent to the positive electrode tail end when the electrode assembly expands.

[0018] In some embodiments of the first aspect of the present application, along the winding direction of the electrode assembly, a size of the first separator is greater than or equal to 1 mm and less than or equal to 5 mm.

[0019] In one or more of the above optional embodiments, the size of the first separator is greater than or equal to 1 mm, reducing the risk of the first separator warping during the manufacturing process and the risk of the first separator separating from the positive electrode sheet, so that the separator can stably separate the edge of the positive electrode tail end and the separator, and reduce the risk of the first separator of the two connected separators partially separating during the cell drop process, causing the edge of the positive electrode tail end to pierce the diaphragm and cause short circuit failure, effectively improving the safety performance of the cell and effectively improving the pass rate of the cell drop test. Along the winding direction of the electrode assembly, the size of the first separator is less than or equal to 5 mm, reducing the impact of the first separator on the size of the electrode assembly, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0020] In some embodiments of the first aspect of the present application, along the winding direction of the electrode assembly, a size of the first separator is greater than or equal to 2 mm and less than or equal to 3.5 mm.

[0021] In one or more of the above optional embodiments, the size of the first separator is greater than or equal to 2 mm, further reducing the risk of the first separator warping during the manufacturing process and the first separator separating from the positive electrode sheet, so that the separator can stably separate the edge of the positive electrode tail end and the separator, and reduce the risk of the first separator of the two connected separators partially separating during the cell drop process, causing the edge of the positive electrode tail end to pierce the diaphragm and cause short circuit failure, effectively improving the safety performance of the cell and effectively improving the pass rate of the cell drop test. Along the winding direction of the electrode assembly, the size of the first separator is less than or equal to 3.5 mm, further reducing the impact of the first separator on the size of the electrode assembly, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0022] In some embodiments of the first aspect of the present application, along the winding direction of the electrode assembly, a size of the second separator is greater than or equal to 1 mm and less than or equal to 5 mm.

[0023] In one or more of the above optional embodiments, along the winding direction of the electrode assembly, the size of the second separator is greater than or equal to 1 mm, reducing the risk of the second separator warping during the winding process. When the two second separators are connected, the size of the second separator along the winding direction of the electrode assembly is larger, which can also reduce the risk of the two second separators connected partially separating during the drop of the battery cell, causing the edge of the positive electrode tail end to pierce the diaphragm and cause short-circuit failure, effectively improving the safety performance of the battery cell and effectively improving the pass rate of the battery cell drop test. Along the winding direction of the electrode assembly, the size of the second separator is less than or equal to 5 mm, and the size of the second separator is controlled within a reasonable range, reducing the impact of the second separator on the size of the electrode assembly, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0024] In some embodiments of the first aspect of the present application, along the winding direction of the electrode assembly, a size of the second separator is greater than or equal to 2 mm and less than or equal to 3.5 mm.

[0025] In one or more of the above optional embodiments, along the winding direction of the electrode assembly, the size of the second separator is greater than or equal to 2 mm, which further reduces the risk of the second separator lifting during the winding process. When the two second separators are connected, the size of the second separator along the winding direction of the electrode assembly is larger, which can further reduce the risk of the two second separators connected partially separating during the drop of the battery cell, causing the edge of the positive electrode tail end to pierce the diaphragm and cause short-circuit failure, further effectively improving the safety performance of the battery cell and effectively improving the pass rate of the battery cell drop test. Along the winding direction of the electrode assembly, the size of the second separator is less than or equal to 3.5 mm, and the size of the second separator is controlled within a reasonable range, further reducing the impact of the second separator on the size of the electrode assembly, thereby reducing the positive electrode capacity loss and the shell failure rate, thereby further reducing the energy density loss and product failure rate, and ensuring production quality.

[0026] In some embodiments of the first aspect of the present application, a ratio of a thickness of the first partition portion to a thickness of the second partition portion of each of the partitions is greater than or equal to 0.2 and less than or equal to 1.

[0027] In one or more of the above optional embodiments, the ratio of the thickness of the first separator of each separator to the thickness of the second separator is greater than or equal to 0.2, which reduces the thickness difference of each part of the separator during the actual production and processing, and reduces the risk of the positive electrode sheet and the separator being broken due to stress concentration during winding. The ratio of the thickness of the first separator of each separator to the thickness of the second separator is less than or equal to 1, which reduces the risk of the second separator warping after the electrode assembly is wound. When the second separators of the two separators are connected, the risk of the two second separators being separated and unable to form a closed space can also be reduced, so that the separator can effectively separate the edge of the positive electrode tail end and the isolation membrane, thereby reducing the risk of the edge of the electrode tail end piercing the isolation membrane and improving the safety performance of the battery cell.

[0028] In some embodiments of the first aspect of the present application, a ratio of a thickness of the first partition portion to a thickness of the second partition portion of each of the partitions is greater than or equal to 0.5 and less than or equal to 0.8.

[0029] In one or more of the above optional embodiments, the ratio of the thickness of the first separator to the thickness of the second separator of each separator is greater than or equal to 0.5, which further reduces the thickness difference of each part of the separator during the actual production and processing, thereby further reducing the risk of the positive electrode sheet and the separator being broken due to stress concentration during winding. The ratio of the thickness of the first separator to the thickness of the second separator of each separator is less than or equal to 0.8, which further reduces the risk of the second separator warping after the electrode assembly is wound. When the second separators of the two separators are connected, the risk of the two second separators being separated and unable to form a closed space can also be reduced, so that the separator can effectively separate the edge of the positive electrode tail end and the isolation membrane, thereby reducing the risk of the edge of the pole tail end piercing the isolation membrane and improving the safety performance of the battery cell.

[0030] In some embodiments of the first aspect of the present application, the positive electrode plate includes a positive electrode collector and a positive electrode active material layer, and the positive electrode active material layer is provided on both side surfaces of the positive electrode collector along the thickness direction of the positive electrode plate; the ratio of the thickness of the second separator to the thickness of the positive electrode active material layer is greater than or equal to 1.05 and less than or equal to 1.8.

[0031] In one or more of the above optional embodiments, the ratio of the thickness of the second separator to the thickness of the positive electrode active material layer is greater than or equal to 1.05, which reduces the risk of the second separator lifting after the electrode assembly is wound. When the second separators of the two separators are connected, the risk of the two second separators lifting and failing to form a closed space can also be reduced, so that the separator can effectively separate the edges of the positive electrode tail end and the isolation membrane, thereby reducing the risk of the edges of the electrode tail end piercing the isolation membrane and improving the safety performance of the battery cell. The ratio of the thickness of the second separator to the thickness of the positive electrode active material layer is less than or equal to 1.8, which reduces the size of the second separator protruding from the surface of the positive electrode active material layer away from the positive electrode current collector during actual production and processing, avoiding serious capacity loss and difficulty in shell entry due to the over-sizing of the electrode assembly caused by the provision of the separator, so that the battery cell has a higher energy density and shell entry rate.

[0032] In some embodiments of the first aspect of the present application, a ratio of the thickness of the second separator to the thickness of the positive electrode active material layer is greater than or equal to 1.1 and less than or equal to 1.5.

[0033] In one or more of the above optional embodiments, the ratio of the thickness of the second separator to the thickness of the positive electrode active material layer is greater than or equal to 1.1, which further reduces the risk of the second separator lifting after the electrode assembly is wound. When the second separators of the two separators are connected, the risk of the two second separators lifting and failing to form a closed space can also be reduced, so that the separator can effectively separate the edges of the positive electrode tail end and the isolation membrane, thereby reducing the risk of the edges of the electrode tail end piercing the isolation membrane and improving the safety performance of the battery cell. The ratio of the thickness of the second separator to the thickness of the positive electrode active material layer is less than or equal to 1.5, which further reduces the size of the second separator protruding from the surface of the positive electrode active material layer away from the positive electrode current collector during actual production and processing, avoiding serious capacity loss and difficulty in shell entry due to the over-sizing of the electrode assembly caused by the provision of the separator, so that the battery cell has a higher energy density and shell entry rate.

[0034] In some embodiments of the first aspect of the present application, the thickness of the first partition is greater than or equal to 5 μm and less than or equal to 60 μm.

[0035] In one or more optional embodiments, the thickness of the first separator is greater than or equal to 5 μm, so that the thickness of the first separator is relatively large, reducing the risk of short circuit failure caused by the edge of the positive electrode end piercing the first separator and the separator at the same time during the fall, thereby improving the safety performance of the battery cell. The thickness of the first separator is less than or equal to 60 μm, avoiding serious capacity loss and difficulty in shell insertion due to the oversize of the electrode assembly caused by the provision of the separator, so that the battery cell has a higher energy density and excellent shell insertion rate.

[0036] In some embodiments of the first aspect of the present application, the thickness of the first partition is greater than or equal to 10 μm and less than or equal to 30 μm.

[0037] In one or more optional embodiments, the thickness of the first separator is greater than or equal to 10 μm, so that the thickness of the first separator is greater, further reducing the risk of short circuit failure caused by the edge of the positive electrode end piercing the first separator and the separator at the same time during the fall, and further improving the safety performance of the battery cell. The thickness of the first separator is less than or equal to 30 μm, avoiding serious capacity loss and difficulty in shell entry due to the oversize of the electrode assembly caused by the provision of the separator, so that the battery cell has a higher energy density and shell entry rate.

[0038] In some embodiments of the first aspect of the present application, the positive electrode sheet includes a positive electrode body and a positive electrode tab. Along the extension direction of the winding axis of the electrode assembly, the positive electrode body has a first end and a second end relative to each other, and the positive electrode tab is connected to the first end; the separator also includes a third separator, along the extension direction, the third separator is connected to the first separator and exceeds the second end, and the thickness of the third separator is greater than the thickness of the first separator.

[0039] In one or more of the above optional embodiments, the third separator is connected to the first separator and extends beyond the second end. On the one hand, the separator can separate the two edges and the isolation membrane formed by the positive electrode plate at the second end, thereby reducing the risk of the two edges at the second end of the battery cell piercing the isolation membrane and causing short circuit failure during the drop mechanical test or when the battery cell is in a drop condition, thereby improving the safety of the battery cell drop mechanical test and the drop condition, and improving the pass rate of the battery cell drop test. On the other hand, the separator can also separate the edges corresponding to the second end and the negative electrode plate closest to the positive terminal end. After the electrode assembly expands to abut against the outer shell, the separator can effectively relieve or release the stress of the negative electrode plate closest to the second end at the position corresponding to the second end, thereby making the negative current collector of the negative electrode plate less likely to break. On the other hand, since the third partitioning parts of the two partitions extend beyond the second end, the two third partitioning parts fill the space between the second end and the negative electrode tail end of the negative electrode sheet, and fill the gap on one side of the negative electrode tail section close to the second end, thereby improving the uniformity of the force acting on the outer shell when the electrode assembly expands, reducing the risk of the electrode assembly being sunken due to the force of the outer shell, or alleviating the degree of the electrode assembly being sunken due to the action of the outer shell after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane due to the sunken electrode assembly during a drop mechanical test or when the battery cell is in a drop condition, further improving the yield of the battery cell and the safety performance of the battery cell.

[0040] In some embodiments of the first aspect of the present application, along the extension direction of the winding axis of the electrode assembly, a size of the third separator is greater than or equal to 1 mm and less than or equal to 4 mm.

[0041] In one or more of the above optional embodiments, the size of the third separator along the extension direction of the winding axis of the electrode assembly is greater than or equal to 1 mm, and the size of the third separator along the extension direction of the winding axis of the electrode assembly is relatively large, which can effectively reduce the risk of short circuit failure caused by the two edges of the second end of the battery cell piercing the isolation membrane during the drop mechanical test or when the battery cell is in a drop condition, improve the safety of the battery cell drop mechanical test and the drop condition, and improve the pass rate of the battery cell drop test. Along the extension direction of the winding axis of the electrode assembly, the size of the third separator is less than or equal to 4 mm, and the size of the third separator in the extension direction of the winding axis of the electrode assembly is controlled within a reasonable range, avoiding serious capacity loss and difficulty in shell entry due to the excessive size of the electrode assembly in the extension direction of the winding axis of the electrode assembly caused by the provision of a separator, so that the battery cell has a higher energy density and excellent shell entry rate.

[0042] In some embodiments of the first aspect of the present application, along the extension direction of the winding axis of the electrode assembly, a size of the third separator is greater than or equal to 1.5 mm and less than or equal to 3.5 mm.

[0043] In one or more of the above optional embodiments, the size of the third separator along the extension direction of the winding axis of the electrode assembly is greater than or equal to 1.5 mm, and the size of the second separator along the extension direction of the winding axis of the electrode assembly is larger, which can further effectively reduce the risk of short circuit failure caused by the two edges of the second end of the battery cell piercing the isolation membrane during the drop mechanical test or when the battery cell is in a drop condition, improve the safety of the battery cell drop mechanical test and the drop condition, and improve the pass rate of the battery cell drop test. Along the extension direction of the winding axis of the electrode assembly, the size of the third separator is less than or equal to 3.5 mm, and the size of the third separator in the extension direction of the winding axis of the electrode assembly is controlled within a reasonable range, avoiding the serious capacity loss and difficulty in shell entry caused by the excessive size of the electrode assembly in the extension direction of the winding axis of the electrode assembly due to the provision of a separator, so that the battery cell has a higher energy density and shell entry rate.

[0044] In some embodiments of the first aspect of the present application, the positive electrode sheet includes a positive electrode body and a positive electrode tab. Along the extension direction of the winding axis of the electrode assembly, the positive electrode body has a first end and a second end relative to each other, and the positive electrode tab is connected to the first end; the separator also includes a fourth separator. Along the extension direction, the fourth separator is connected to the first separator and extends beyond the first end, or the fourth separator is connected to the first separator and extends beyond an end of the positive electrode tab away from the first end, and the thickness of the fourth separator is greater than the thickness of the first separator.

[0045] In one or more of the above optional embodiments, the fourth separator is connected to the first separator and extends beyond the first end or beyond the end of the positive electrode tab away from the first end. On the one hand, the separator can separate the two edges and the isolation membrane formed at the first end of the positive electrode plate or separate the two edges and the isolation membrane formed by the positive electrode tab away from the first end, thereby reducing the risk of the two edges at the first end of the battery cell or the two edges of the positive electrode tab away from the first end piercing the isolation membrane and causing short circuit failure during the drop mechanical test or when the battery cell is in a drop condition, thereby improving the safety of the battery cell drop mechanical test and the drop condition and improving the pass rate of the battery cell drop test. On the other hand, the separator can also separate the edges corresponding to the first end and the negative electrode plate closest to the positive electrode tail end. After the electrode assembly expands to abut against the outer shell, the separator can effectively relieve or release the stress of the negative electrode plate closest to the first end at the position corresponding to the first end, thereby making the negative electrode collector of the negative electrode plate less likely to break. On the other hand, since the fourth partitioning portions of the two partitions extend beyond the first end, the two fourth partitioning portions fill the space between the first end and the negative electrode tail end of the negative electrode sheet, and fill the gap on one side of the negative electrode tail section close to the first end, thereby improving the uniformity of the force acting on the outer shell when the electrode assembly expands, reducing the risk of the electrode assembly being sunken due to the force of the outer shell, or alleviating the degree of the electrode assembly being sunken due to the action of the outer shell after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane due to the sunken electrode assembly during a drop mechanical test or when the battery cell is in a drop condition, further improving the yield of the battery cell and the safety performance of the battery cell.

[0046] In some embodiments of the first aspect of the present application, the negative electrode sheet has a negative electrode tailing section extending beyond the positive electrode tailing end, and along the thickness direction of the positive electrode sheet, the negative electrode tailing section is located outside the positive electrode tailing end.

[0047] In one or more of the above optional embodiments, in the thickness direction of the positive electrode sheet, the negative electrode tail section is located outside the positive electrode tail end, which is beneficial to improving the energy density of the battery cell.

[0048] In a second aspect, an embodiment of the present application provides an electrical device, comprising a battery cell provided by any of the above embodiments.

[0049] In one or more of the above optional embodiments, the battery cells provided in the above embodiments have better safety, and the electrical equipment powered by the battery cells has better electrical safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 An exploded diagram of a battery cell provided in some embodiments of the present application;

[0052] Figure 2 A schematic diagram of the structure of an electrode assembly and a separator provided in some embodiments of the present application;

[0053] Figure 3 for Figure 2 The enlarged view of A1 in the middle;

[0054] Figure 4 A schematic diagram of the structure of a positive electrode sheet provided with a separator after unfolding according to some embodiments of the present application;

[0055] Figure 5 for Figure 4 Sectional view along P1-P1 direction;

[0056] Figure 6 A schematic diagram of the structure of a positive electrode sheet provided with a separator after unfolding provided in some other embodiments of the present application;

[0057] Figure 7 for Figure 6 A cross-sectional view taken along P2-P2 direction;

[0058] Figure 8 for Figure 6 A cross-sectional view taken along P3-P3 direction;

[0059] Fig. 9 A schematic diagram of the structure of a positive electrode sheet provided with a separator after unfolding provided in some other embodiments of the present application;

[0060] Fig.10 for Fig. 9 A cross-sectional view taken along P4-P4 direction;

[0061] Fig.11 A schematic diagram of the structure of a positive electrode sheet provided with a separator after unfolding provided in some other embodiments of the present application;

[0062] Fig.12 for Fig.11 A cross-sectional view taken along P5-P5 direction;

[0063] Fig.13 A schematic diagram of the structure of a positive electrode sheet with a separator after unfolding provided in some embodiments of the present application;

[0064] Fig.14 for Fig.13 Cross-sectional view along P6-P6.

[0065] Icon: 100-battery cell; 10-casing; 11-shell; 12-cover; 20-electrode assembly; 21-positive electrode sheet; 211-positive current collector; 212-positive active material layer; 213-positive electrode tail end; 214-positive electrode body; 2141-first end; 2142-second end; 215-positive electrode ear; 216-positive electrode starting end; 22-negative electrode sheet; 221-negative electrode tail section; 23-separation membrane; 30-separator; 31-first separator; 32-second separator; 321-first surface; 33-third separator; 34-fourth separator; X-thickness direction of positive electrode sheet; Y-length direction of positive electrode sheet; Z-width direction of positive electrode sheet; Y'-winding direction; Z'-extension direction. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0067] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0068] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0069] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0070] In the description of the embodiments of the present application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0071] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0072] At present, judging from the development of the market situation, the application of battery cells is becoming more and more extensive. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, as well as electric tools, drones, energy storage equipment and other fields. With the continuous expansion of the application field of battery cells, the market demand is also constantly expanding, and the requirements for battery cell safety are becoming higher and higher.

[0073] The electrode assembly of the battery cell includes a positive electrode sheet and a negative electrode sheet. Along the winding direction of the electrode assembly, the positive electrode tail end of the positive electrode sheet is the cutting position in the production process of the positive electrode sheet. After the electrode assembly is wound, the negative electrode sheet exceeds the positive electrode tail end along the winding direction of the electrode assembly. The size of the electrode assembly at the position corresponding to the positive electrode tail end is larger, and the position of the electrode assembly at the positive electrode tail end is closer to the inner wall of the shell than other positions. After the electrode assembly expands, the position of the electrode assembly at the positive electrode tail end first abuts against the inner wall of the shell, and the shell exerts a force on the position of the electrode assembly at the positive electrode tail end, so that the edge formed at the positive electrode tail end can easily pierce the isolation membrane, causing the battery cell to short-circuit and fail, thereby reducing the safety performance of the battery cell during drop test and use, and also reducing the pass rate of the battery cell drop test.

[0074] Based on the above considerations, in order to alleviate the problem that the edge of the positive electrode tail end pierces the isolation membrane and causes the safety performance of the battery cell to be reduced, an embodiment of the present application provides a battery cell, which includes an electrode assembly and two separators; the electrode assembly is a winding structure, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a isolation membrane, the isolation membrane insulates and isolates the positive electrode sheet and the negative electrode sheet, the positive electrode sheet has a positive electrode tail end, and the negative electrode sheet extends beyond the positive electrode tail end along the winding direction of the electrode assembly; the separator includes a first separator and a second separator connected to the first separator and extending beyond the positive electrode tail end, along the thickness direction of the positive electrode sheet, the first separators of the two separators are respectively arranged on the two opposite surfaces of the positive electrode sheet, and the second separators of the two separators are arranged opposite to each other; wherein the sum of the thicknesses of the first separators of the two separators is less than the sum of the thicknesses of the second separators of the two separators.

[0075] The first separators of the two separators are respectively arranged on two opposite surfaces of the positive electrode sheet in the thickness direction thereof, so as to facilitate the fixing of the separators.

[0076] The second separator is connected to the first separator and extends beyond the positive electrode tail end. On the one hand, the separator can separate the two edges and the isolation membrane formed by the positive electrode plate at the positive electrode tail end, reducing the risk of the two edges of the positive electrode tail end piercing the isolation membrane and causing short circuit failure during the drop mechanical test of the battery cell or when the battery cell is in a drop condition, thereby improving the safety of the battery cell drop mechanical test and the drop condition, and improving the pass rate of the battery cell drop test. On the other hand, the separator can also separate the edges corresponding to the positive electrode tail end and the negative electrode plate closest to the positive electrode tail end. After the electrode assembly expands to abut against the outer shell, the separator can effectively relieve or release the stress of the negative electrode plate closest to the positive electrode tail end at the position corresponding to the positive electrode tail end, thereby making the negative electrode collector of the negative electrode plate less likely to break. On the other hand, since the second separators of the two separators extend beyond the positive electrode tail end, the two second separators fill the space between the positive electrode tail end and the negative electrode tail end of the negative electrode plate, and fill the gap on one side of the negative electrode tail section close to the positive electrode tail end, thereby improving the uniformity of the force acting on the outer shell when the electrode assembly expands, reducing the risk of the electrode assembly being sunken due to the force of the outer shell, or alleviating the degree of the electrode assembly being sunken due to the action of the outer shell after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane due to the sunken electrode assembly during a drop mechanical test or when the battery cell is in a drop condition, further improving the yield of the battery cell and the safety performance of the battery cell.

[0077] The sum of the thicknesses of the first separators of the two separators is less than the sum of the thicknesses of the second separators of the two separators, which further improves the uniformity of the force acting on the outer shell when the electrode assembly expands, further reduces the risk of the electrode assembly being sunken due to the force of the outer shell, or alleviates the degree of the electrode assembly being sunken due to the action of the outer shell after expansion, thereby further reducing the risk of short-circuit failure caused by puncturing the isolation membrane due to the sunken electrode assembly during a drop mechanical test or when the battery cell is in a drop condition, further improving the yield of the battery cell and the safety performance of the battery cell.

[0078] The battery cell disclosed in the embodiment of the present application can be used in, but not limited to, electric two-wheeled vehicles, electric tools, drones, energy storage devices and other electrical equipment. The battery cell with the working condition of the present application can also be used as a power supply system for electrical equipment, which is conducive to improving the safety performance of the battery cell.

[0079] The present application provides an electric device using a battery cell as a power source, and the electric device may be, but is not limited to, electronic equipment, electric tools, electric vehicles, drones, and energy storage devices. Among them, electronic equipment may include mobile phones, tablets, laptops, etc., electric tools may include electric drills, electric saws, etc., and electric vehicles may include electric cars, electric motorcycles, electric bicycles, etc.

[0080] like Figure 1 , Figure 2 As shown, an embodiment of the present application provides a battery cell 100 , which includes a housing 10 and an electrode assembly 20 ; the electrode assembly 20 is accommodated in the housing 10 .

[0081] The housing 10 forms a storage space. The storage space can be used to store the electrode assembly 20, electrolyte, etc. The housing 10 can be a hard shell 11, for example, the housing 10 is a steel shell or an aluminum shell, forming a steel shell battery cell or an aluminum shell battery cell. The housing 10 can also be formed of a softer material, for example, the housing 10 is an aluminum plastic film or a steel plastic film, forming a soft package battery cell.

[0082] The housing 10 may include a shell 11 and a cover 12 . The shell 11 has an opening at at least one end. The cover 12 is used to cover the opening of the shell 11 , so that the shell 11 and the cover 12 together define a receiving space.

[0083] The electrode assembly 20 includes a positive electrode sheet 21 , a negative electrode sheet 22 and a separator 23 .

[0084] The positive electrode sheet 21 includes a positive current collector 211 and a positive active material layer 212. The positive active material layer 212 is disposed on at least one side of the positive current collector 211. For the lithium-ion battery cell 100, the material of the positive current collector 211 can be aluminum. The positive active material layer 212 can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide. The positive current collector 211 can be a composite current collector or a non-composite current collector.

[0085] The negative electrode sheet 22 includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is disposed on at least one side of the negative electrode current collector. For the lithium-ion battery cell 100, the negative electrode current collector may be made of copper, and the negative electrode active material may be carbon or silicon, etc. The negative electrode current collector may be a composite current collector or a non-composite current collector.

[0086] The separator 23 insulates and separates the positive electrode sheet 21 and the negative electrode sheet 22 to reduce the risk of short circuit of the battery cell 100. The material of the separator 23 may include PP (polypropylene) or PE (polyethylene).

[0087] The electrode assembly 20 is a wound structure. The positive electrode sheet 21, the separator 23, the negative electrode sheet 22 and another separator 23 are stacked in a certain order and then wound to form an electrode assembly with a wound structure; or, the separator 23, the positive electrode sheet 21, another separator 23 and the negative electrode sheet 22 are stacked in a certain order and then wound to form an electrode assembly with a wound structure. The wound electrode assembly 20 can be a flat wound electrode assembly 20, a cylindrical electrode assembly 20, or a columnar electrode assembly 20. In the embodiment where the electrode assembly 20 is a cylindrical structure, the battery cell 100 can be a cylindrical battery cell 100. Figure 1 FIG. 4 shows a case where the battery cell 100 is a cylindrical battery cell 100. Figure 2 , the electrode assembly 20 is shown as a cylindrical structure.

[0088] The positive electrode sheet 21 has a positive electrode tail end 213, and the positive electrode tail end 213 of the positive electrode sheet 21 is the end of the positive electrode sheet 21 that is farthest from the winding center of the electrode assembly 20 along the winding direction Y' of the electrode assembly 20. Along the winding direction Y' of the electrode assembly, one end of the positive electrode sheet 21 and the positive electrode tail end 213 is the positive electrode starting end 216. The negative electrode sheet 22 exceeds the positive electrode tail end 213 along the winding direction of the electrode assembly 20, reducing the risk of lithium deposition in the battery cell 100. Specifically, the negative electrode sheet 22 has a negative electrode tail section 221 that exceeds the positive electrode tail end 213. Among them, along the thickness direction X of the positive electrode sheet, the negative electrode tail section 221 can be located outside the positive electrode tail end 213. Along the thickness direction X of the positive electrode sheet, the negative electrode tail section 221 is located outside the positive electrode tail end 213, which is beneficial to improve the energy density of the battery cell 100. Of course, in another embodiment, along the thickness direction X of the positive electrode sheet, the negative electrode tailing section 221 is located inside the positive electrode tailing end 213 . Figure 2 2 shows the situation that the negative electrode tailing section 221 is located outside the positive electrode tailing end 213 along the thickness direction X of the positive electrode sheet.

[0089] like Figure 2 , Figure 3 As shown, the battery cell 100 also includes two separators 30, the separator 30 includes a first separator 31 and a second separator 32 connected to the first separator 31 and extending beyond the positive electrode tail end 213, along the thickness direction X of the positive electrode sheet, the first separators 31 of the two separators 30 are respectively arranged on the two opposite surfaces of the positive electrode sheet 21, and the second separators 32 of the two separators 30 are relatively arranged; wherein the sum of the thicknesses of the first separators 31 of the two separators 30 is less than the sum of the thicknesses of the second separators 32 of the two separators 30.

[0090] The first separators 31 of the two separators 30 may be bonded to the two surfaces of the positive electrode sheet 21 in the thickness direction thereof. According to the different structures of the positive electrode sheet 21 at the positive terminal end 213, the first separators 31 of the two separators 30 may be connected to different positions. For example, if the positive electrode sheet 21 has a positive active material layer 212 only on one side of the positive current collector 211 at the positive terminal end 213, the first separator 31 of one of the two separators 30 is connected to the surface of the positive active material layer 212 away from the positive current collector 211, and the first separator 31 of the other of the two separators 30 is connected to the surface of the positive current collector 211 away from the positive active material layer 212. If the positive electrode sheet 21 has a positive active material layer 212 on both sides of the positive current collector 211 at the positive terminal end 213, the first separators 31 of the two separators 30 are respectively connected to the surfaces of the two positive active material layers 212 away from the positive current collector 211.

[0091] The first separators 31 of the two separators 30 are respectively disposed on two opposite surfaces of the positive electrode sheet 21 in the thickness direction thereof, so as to facilitate the fixing of the separators 30 .

[0092] The second partition 32 is connected to the first partition 31 , and the first partition 31 and the second partition 32 may be separate structures that are then connected into one.

[0093] The first partition 31 and the second partition 32 may also be integrally formed, thereby forming a partition 30 of an integrally formed structure, which facilitates the manufacture of the partition 30 and provides the partition 30 with better structural performance.

[0094] The second separator 32 is connected to the first separator 31 and exceeds the positive electrode tail end 213. On the one hand, the separator 30 can separate the two edges formed by the positive electrode plate 21 at the positive electrode tail end 213 and the separator 23, thereby reducing the risk of the two edges of the positive electrode tail end 213 of the battery cell 100 piercing the separator 23 and causing short circuit failure during the drop mechanical test or when the battery cell 100 is in a drop condition, thereby improving the safety of the battery cell 100 in the drop mechanical test and in the drop condition and improving the pass rate of the drop test of the battery cell 100. On the other hand, the separator 30 can also separate the edges corresponding to the positive electrode tail end 213 and the negative electrode plate 22 closest to the positive electrode tail end 213. After the electrode assembly 20 expands to abut against the housing 10, the separator 30 can effectively relieve or release the stress of the negative electrode plate 22 closest to the positive electrode tail end 213 at the position corresponding to the positive electrode tail end 213, thereby making the negative electrode collector of the negative electrode plate 22 not easy to break. On the other hand, since the second separators 32 of the two separators 30 extend beyond the positive electrode tail end 213, the two second separators 32 fill the space between the positive electrode tail end 213 and the negative electrode tail end of the negative electrode plate 22, and fill the gap on one side of the negative electrode tail section 221 close to the positive electrode tail end 213, thereby improving the uniformity of the force acting on the outer shell 10 when the electrode assembly 20 expands, reducing the risk of the electrode assembly 20 being sunken due to the force of the outer shell 10, or alleviating the degree of the electrode assembly 20 being sunken due to the action of the outer shell 10 after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane 23 due to the sunken electrode assembly 20 during a drop mechanical test or when the battery cell 100 is in a drop condition, thereby further improving the yield of the battery cell 100 and the safety performance of the battery cell 100.

[0095] The thickness of the first separator 31 is the dimension of the first separator 31 in the thickness direction X of the positive electrode sheet. The thickness of the second separator 32 is the dimension of the second separator 32 in the thickness direction X of the positive electrode sheet. It should be noted that when the positive electrode sheet 21 is in a wound state, the thickness direction X of the positive electrode sheet is different at different positions of the positive electrode sheet 21, but the thickness direction at any position of the positive electrode sheet 21 is perpendicular to the extension direction of the winding axis of the electrode assembly 20. In order to conveniently obtain the thickness of the first separator 31 and the thickness of the second separator 32, the positive electrode sheet 21 can be unfolded and measured. It should be noted that after the positive electrode sheet 21 is unfolded, the length direction Y of the positive electrode sheet corresponds to the winding direction Y' of the electrode assembly 20, and the width direction Z of the positive electrode sheet corresponds to the extension direction Z' of the winding axis of the electrode assembly 20.

[0096] The sum of the thicknesses of the first partition portions 31 of the two partitions 30 is less than the sum of the thicknesses of the second partition portions 32 of the two partitions 30, which further improves the uniformity of the force acting on the outer shell 10 when the electrode assembly 20 expands, further reduces the risk of the electrode assembly 20 being sunken due to the force of the outer shell 10, or alleviates the degree of the electrode assembly 20 being sunken due to the action of the outer shell 10 after expansion, thereby further reducing the risk of short-circuit failure caused by puncturing the isolation membrane 23 due to the sunken electrode assembly 20 during a drop mechanical test or when the battery cell 100 is in a drop condition, further improving the yield of the battery cell 100 and the safety performance of the battery cell 100.

[0097] The structural dimensions of the first partitions 31 of the two partitions 30 may be the same or different, and the structural dimensions of the second partitions 32 of the two partitions 30 may be the same or different.

[0098] There are many ways to achieve that the sum of the thicknesses of the first partitions 31 of the two partitions 30 is less than the sum of the thicknesses of the second partitions 32 of the two partitions 30. For example, the thickness of the first partition 31 of one partition 30 is less than or equal to the thickness of the second partition 32, and the thickness of the first partition 31 of the other partition 30 is less than the thickness of the second partition 32; for another example, the thickness of the first partition 31 of each partition 30 is less than the thickness of the second partition 32.

[0099] Combined with reference Figure 4 , Figure 5 In some embodiments, the thickness of the first partition 31 is less than the thickness of the second partition 32 .

[0100] The thickness of the first partition 31 of one of the two partitions 30 is H1, and the thickness of the second partition 32 is H2, H1<H2; the thickness of the first partition 31 of the other of the two partitions 30 is H3, and the thickness of the second partition 32 is H4, H3<H4.

[0101] The thickness of each first partition 31 is smaller than the thickness of the second partition 32 of the partition 30 , and the sum of the thicknesses of the first partitions 31 of the two partitions 30 is smaller than the sum of the thicknesses of the two second partitions 32 .

[0102] The thickness of the first separator 31 is less than that of the second separator 32 . The first separator 31 is relatively thin, which reduces the influence of the first separator 31 on the size of the electrode assembly 20 , thereby reducing the capacity loss of the battery cell 100 and reducing the failure rate of the electrode assembly 20 into the shell.

[0103] In some embodiments, a ratio of a thickness of the first partition 31 to a thickness of the second partition 32 of each partition 30 is greater than or equal to 0.2 and less than or equal to 1.

[0104] like Figure 4 , Figure 5 As shown, the thickness of the first partition 31 of one of the two partitions 30 is H1, the thickness of the second partition 32 is H2, 0.2≤H1 / H2≤1; the thickness of the first partition 31 of the other of the two partitions 30 is H3, the thickness of the second partition 32 is H4, 0.2≤H3 / H4≤1.

[0105] For example, the ratio of the thickness of the first partition 31 to the thickness of the second partition 32 of each partition 30 may be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0106] The ratio of the thickness of the first separator 31 of each separator 30 to the thickness of the second separator 32 is greater than or equal to 0.2, which reduces the thickness difference of each part of the separator 30 during the actual production and processing process, and reduces the risk of the positive electrode sheet 21 and the separator 30 being broken due to stress concentration during winding. The ratio of the thickness of the first separator 31 of each separator 30 to the thickness of the second separator 32 is less than or equal to 1, which reduces the risk of the second separator 32 warping after the electrode assembly 20 is wound. When the second separators 32 of two separators 30 are connected, the risk of the two second separators 32 being separated and unable to form a closed space can also be reduced, so that the separator 30 can effectively separate the edge of the positive electrode tail end 213 and the separator 23, thereby reducing the risk of the edge of the positive electrode tail end piercing the separator 23, and improving the safety performance of the battery cell 100.

[0107] Further, the ratio of the thickness of the first partition portion 31 to the thickness of the second partition portion 32 of each partition 30 is greater than or equal to 0.5 and less than or equal to 0.8.

[0108] That is, 0.5≤H1 / H2≤0.8, 0.5≤H3 / H4≤0.8.

[0109] Illustratively, the ratio of the thickness of the first partition 31 to the thickness of the second partition 32 of each partition 30 may be 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65, 0.58, 0.7, 0.72, 0.75, 0.78, or 0.8.

[0110] The ratio of the thickness of the first separator 31 of each separator 30 to the thickness of the second separator 32 is greater than or equal to 0.5, which further reduces the thickness difference of each part of the separator 30 during the actual production and processing, thereby further reducing the risk of the positive electrode sheet 21 and the separator 30 being broken due to stress concentration during winding. The ratio of the thickness of the first separator 31 of each separator 30 to the thickness of the second separator 32 is less than or equal to 0.8, which further reduces the risk of the second separator 32 warping after the electrode assembly 20 is wound. When the second separators 32 of two separators 30 are connected, the risk of the two second separators 32 being separated and unable to form a closed space can also be reduced, so that the separator 30 can effectively separate the edge of the positive electrode tail end 213 and the separator 23, thereby reducing the risk of the edge of the positive electrode tail end piercing the separator 23, and improving the safety performance of the battery cell 100.

[0111] In some embodiments, the thickness of the first partition 31 is greater than or equal to 5 μm and less than or equal to 60 μm.

[0112] like Figure 5 As shown, the thickness of the first partition 31 of one of the two partitions 30 is H1, 5 μm≤H1≤60 μm; the thickness of the first partition 31 of the other of the two partitions 30 is H3, 5 μm≤H3≤60 μm.

[0113] Illustratively, the thickness of the first partition 31 may be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, or the like.

[0114] The thickness of the first separator 31 is greater than or equal to 5 μm, so that the thickness of the first separator 31 is relatively large, reducing the risk of short circuit failure after the edge of the positive electrode tail end 213 pierces the first separator 31 and the separator 23 during the drop process, thereby improving the safety performance of the battery cell 100. The thickness of the first separator 31 is less than or equal to 60 μm, avoiding the serious capacity loss and difficulty in shell insertion caused by the oversize of the electrode assembly 20 due to the provision of the separator 30, so that the battery cell 100 has a higher energy density and shell insertion rate.

[0115] Furthermore, the thickness of the first partition 31 is greater than or equal to 10 μm and less than or equal to 30 μm, that is, 10 μm≤H1≤30 μm, and 10 μm≤H3≤30 μm.

[0116] Exemplarily, the thickness of the first partition 31 may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 16 μm, 17 μm, 18 μm, 19 μm, 21 μm, 22 μm, 23 μm, 24 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, etc.

[0117] The thickness of the first separator 31 is greater than or equal to 10 μm, so that the thickness of the first separator 31 is greater, further reducing the risk of short circuit failure after the edge of the positive electrode tail end 213 pierces the first separator 31 and the separator 23 during the drop process, further improving the safety performance of the battery cell 100. The thickness of the first separator 31 is less than or equal to 30 μm, avoiding the serious capacity loss and difficulty in shell insertion caused by the oversize of the electrode assembly 20 due to the provision of the separator 30, so that the battery cell 100 has a higher energy density and shell insertion rate.

[0118] In some embodiments, the positive electrode sheet 21 includes a positive electrode current collector 211 and a positive electrode active material layer 212. Along the thickness direction X of the positive electrode sheet, the positive electrode active material layer 212 is provided on both side surfaces of the positive electrode current collector 211; the ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 is greater than or equal to 1.05 and less than or equal to 1.8.

[0119] like Figure 5 As shown, the thickness of the positive electrode active material layer 212 is H, the thickness of the second separator 32 of one of the two separators 30 is H2, 1.05≤H2 / H≤1.8; the thickness of the second separator 32 of the other of the two separators 30 is H4, 1.05≤H4 / H≤1.8.

[0120] For example, the ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 may be 1.05, 1.15, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or the like.

[0121] The ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 is greater than or equal to 1.05, which reduces the risk of the second separator 32 warping after the electrode assembly 20 is wound. When the second separators 32 of two separators 30 are connected, the risk of the two second separators 32 being separated and unable to form a closed space can also be reduced, so that the separator 30 can effectively separate the edge of the positive electrode tail end 213 and the separator 23, thereby reducing the risk of the edge of the positive electrode tail end piercing the separator 23 and improving the safety performance of the battery cell 100. The ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 is less than or equal to 1.8, which reduces the size of the second separator 32 protruding from the surface of the positive electrode active material layer 212 away from the positive electrode current collector 211 during actual production and processing, and avoids the serious capacity loss and difficulty in shell insertion caused by the excessive size of the electrode assembly 20 due to the provision of the separator 30, so that the battery cell 100 has a higher energy density and shell insertion rate.

[0122] Furthermore, the ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 is greater than or equal to 1.1 and less than or equal to 1.5.

[0123] like Figure 5 As shown, 1.1≤H2 / H≤1.5, 1.1≤H4 / H≤1.5.

[0124] For example, the ratio of the thickness of the second separator 32 to the thickness of the positive active material layer 212 may be 1.1, 1.13, 1.15, 1.18, 1.23, 1.25, 1.28, 1.32, 1.35, 1.38, 1.42, 1.45, 1.48, 1.5, etc.

[0125] The ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 is greater than or equal to 1.1, which further reduces the risk of the second separator 32 warping after the electrode assembly 20 is wound. When the second separators 32 of two separators 30 are connected, the risk of the two second separators 32 being separated and unable to form a closed space can also be reduced, so that the separator 30 can effectively separate the edge of the positive electrode tail end 213 and the separator 23, thereby reducing the risk of the edge of the positive electrode tail end piercing the separator 23 and improving the safety performance of the battery cell 100. The ratio of the thickness of the second separator 32 to the thickness of the positive electrode active material layer 212 is less than or equal to 1.5, which further reduces the size of the second separator 32 protruding from the surface of the positive electrode active material layer 212 away from the positive electrode current collector 211 during actual production and processing, avoiding the serious capacity loss and difficulty in shell insertion caused by the excessive size of the electrode assembly 20 due to the provision of the separator 30, so that the battery cell 100 has a higher energy density and shell insertion rate.

[0126] In some embodiments, the first separators 31 of the two separators 30 have the same thickness. The first separators 31 of the two separators 30 have the same thickness, which is beneficial for the electrode assembly 20 to be evenly stressed during expansion and facilitates the manufacturing of the separators 30 and the battery cell 100.

[0127] When the thicknesses of the first partitions 31 of the two partitions 30 are equal, the thicknesses of the second partitions 32 of the two partitions 30 may be the same or different.

[0128] In some embodiments, the second separators 32 of the two separators 30 have the same thickness. The second separators 32 of the two separators 30 have the same thickness, which is beneficial for the electrode assembly 20 to be evenly stressed during expansion and facilitates the manufacturing of the separators 30 and the battery cell 100.

[0129] When the thicknesses of the second partitioning parts 32 of the two partitioning members 30 are equal, the thicknesses of the first partitioning parts 31 of the two partitioning members 30 may be the same or different. Figure 5 2 shows a case where the thicknesses of the first partitions 31 of the two partitions 30 are equal, and the thicknesses of the second partitions 32 of the two partitions 30 are equal.

[0130] like Figure 3 , Figure 5 As shown, in some embodiments, the thickness of the first separator 31 is smaller than the dimension of the second separator 32 along the winding direction Y′ of the electrode assembly 20 .

[0131] The sizes of the second separators 32 of the two separators 30 along the winding direction Y′ of the electrode assembly 20 are L1 and L2 , respectively, that is, H1 < L1 , H3 < L2 .

[0132] The thickness of the first separator 31 is smaller than the size of the second separator 32 along the winding direction Y' of the electrode assembly 20, that is, the size of the second separator 32 along the winding direction Y' of the electrode assembly 20 is larger, which reduces the risk of the second separator 32 warping during the winding process. When the two second separators 32 are connected, the size of the second separator 32 along the winding direction Y' of the electrode assembly 20 is larger, which can also reduce the risk of the two connected second separators 32 partially separating during the falling process of the battery cell 100, causing the edge of the positive electrode tail end 213 to pierce the diaphragm and cause short circuit failure, thereby improving the safety performance of the battery cell 100. The thickness of the first separator 31 is smaller than the size of the second separator 32 along the winding direction Y' of the electrode assembly 20, that is, the thickness of the first separator 31 is smaller, which reduces the influence of the first separator 31 on the size of the electrode assembly 20, thereby reducing the capacity loss of the battery cell 100 and reducing the failure rate of the electrode assembly 20 into the shell.

[0133] Of course, in other embodiments, the thickness of the first separator 31 may be greater than or equal to the dimension of the second separator 32 along the winding direction Y′ of the electrode assembly 20 .

[0134] like Figure 3 , Figure 5 As shown, in some embodiments, along the winding direction Y′ of the electrode assembly 20 , the size of the first separator 31 is greater than or equal to 1 mm and less than or equal to 5 mm.

[0135] like Figure 5 As shown, the sizes of the first separators 31 of the two separators 30 along the winding direction Y' of the electrode assembly 20 are D1 and D2, respectively, 1mm≤D1≤5mm, 1mm≤D2≤5mm. The sizes of the first separators 31 of the two separators 30 along the winding direction Y' of the electrode assembly 20 can be the same, that is, D1=D2. The sizes of the first separators 31 of the two separators 30 along the winding direction Y' of the electrode assembly 20 can also be different, that is, D1≠D2.

[0136] Illustratively, along the winding direction Y′ of the electrode assembly 20 , the size of the first separator 31 may be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0137] Along the winding direction Y' of the electrode assembly 20, the size of the first separator 31 is greater than or equal to 1 mm, reducing the risk of the first separator 31 warping during the manufacturing process and the first separator 31 and the positive electrode sheet 21 being separated and falling off, so that the separator 30 can stably separate the edge of the positive electrode tail end 213 and the separator 23, reducing the risk of the first separator 31 of the two connected separators 30 partially separating during the drop of the battery cell 100, causing the edge of the positive electrode tail end 213 to pierce the diaphragm and cause short circuit failure, effectively improving the safety performance of the battery cell 100 and effectively improving the pass rate of the drop test of the battery cell 100. Along the winding direction Y' of the electrode assembly 20, the size of the first separator 31 is less than or equal to 5 mm, reducing the influence of the first separator 31 on the size of the electrode assembly 20, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0138] Further, in some embodiments, along the winding direction Y′ of the electrode assembly 20 , a size of the first separator 31 is greater than or equal to 2 mm and less than or equal to 3.5 mm.

[0139] That is, 2 mm ≤ D1 ≤ 3.5 mm, 2 mm ≤ D2 ≤ 3.5 mm. For example, along the winding direction Y' of the electrode assembly 20, the size of the first separator 31 may be 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, etc.

[0140] Along the winding direction Y' of the electrode assembly 20, the size of the first separator 31 is greater than or equal to 2 mm, further reducing the risk of the first separator 31 warping and the first separator 31 and the positive electrode sheet 21 being separated during the manufacturing process, so that the separator 30 can stably separate the edge of the positive electrode tail end 213 and the separator 23, and reduce the risk of the first separator 31 of the two connected separators 30 partially separating during the drop of the battery cell 100, resulting in the edge of the positive electrode tail end 213 piercing the diaphragm and causing short circuit failure, effectively improving the safety performance of the battery cell 100 and effectively improving the pass rate of the drop test of the battery cell 100. Along the winding direction Y' of the electrode assembly 20, the size of the first separator 31 is less than or equal to 3.5 mm, further reducing the impact of the first separator 31 on the size of the electrode assembly 20, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0141] In some embodiments, along the winding direction Y′ of the electrode assembly 20 , a size of the second separator 32 is greater than or equal to 1 mm and less than or equal to 5 mm.

[0142] like Figure 5 As shown, the sizes of the second separators 32 of the two separators 30 along the winding direction Y' of the electrode assembly 20 are L1 and L2, respectively, 1mm≤L1≤5mm, 1mm≤L2≤5mm. The sizes of the second separators 32 of the two separators 30 along the winding direction Y' of the electrode assembly 20 can be the same, that is, L1=L2. The sizes of the second separators 32 of the two separators 30 along the winding direction Y' of the electrode assembly 20 can also be different, that is, L1≠L2.

[0143] Illustratively, along the winding direction Y′ of the electrode assembly 20 , the size of the second separator 32 may be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0144] Along the winding direction Y' of the electrode assembly 20, the size of the second separator 32 is greater than or equal to 1 mm, which reduces the risk of the second separator 32 warping during the winding process. When the two second separators 32 are connected, the size of the second separator 32 along the winding direction Y' of the electrode assembly 20 is large, which can also reduce the risk of the two second separators 32 connected during the falling process of the battery cell 100 being partially separated, causing the edge of the positive electrode tail end 213 to pierce the diaphragm and cause short-circuit failure, effectively improving the safety performance of the battery cell 100 and effectively improving the pass rate of the drop test of the battery cell 100. Along the winding direction Y' of the electrode assembly 20, the size of the second separator 32 is less than or equal to 5 mm, and the size of the second separator 32 is controlled within a reasonable range, reducing the impact of the second separator 32 on the size of the electrode assembly 20, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0145] Further, along the winding direction Y′ of the electrode assembly 20 , a size of the second separator 32 is greater than or equal to 2 mm and less than or equal to 3.5 mm.

[0146] That is, 2mm≤L1≤3.5mm, 2mm≤L2≤3.5mm.

[0147] Illustratively, along the winding direction Y' of the electrode assembly 20, the size of the second separator 32 can be 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, etc.

[0148] Along the winding direction Y' of the electrode assembly 20, the size of the second separator 32 is greater than or equal to 2 mm, which further reduces the risk of the second separator 32 warping during the winding process. When the two second separators 32 are connected, the size of the second separator 32 along the winding direction Y' of the electrode assembly 20 is large, which can further reduce the risk of the two second separators 32 connected during the falling process of the battery cell 100 being partially separated, causing the edge of the positive electrode tail end 213 to pierce the diaphragm and cause short-circuit failure, further effectively improving the safety performance of the battery cell 100 and effectively improving the pass rate of the drop test of the battery cell 100. Along the winding direction Y' of the electrode assembly 20, the size of the second separator 32 is less than or equal to 3.5 mm, and the size of the second separator 32 is controlled within a reasonable range, further reducing the impact of the second separator 32 on the size of the electrode assembly 20, thereby reducing the positive electrode capacity loss and the shell defect rate, thereby further reducing the energy density loss and product defect rate, and ensuring the production quality rate.

[0149] like Figure 5As shown, in some embodiments, there may be a gap between the second separators 32 of the two separators 30 in the thickness direction X of the positive electrode sheet, which can provide a buffer space for the electrode assembly 20 to expand.

[0150] In some embodiments, the second separators 32 of the two separators 30 can contact each other in the thickness direction X of the positive electrode sheet, and the two separators 30 can form a closed space at the positive electrode tail end 213, so that the separator 30 can better separate the edges of the positive electrode tail end 213 and the isolation membrane 23, thereby reducing the risk of the edges of the positive electrode tail end 213 piercing the isolation membrane 23 when the battery cell 100 is in a drop test or in a drop condition, thereby improving the safety of the battery cell 100 and the pass rate of the drop test.

[0151] like Figure 6 , Figure 7 As shown, the second partitioning portions 32 of the two partitioning members 30 are connected.

[0152] Specifically, the second separators 32 of the two separators 30 are connected at two opposite surfaces in the thickness direction X of the positive electrode sheet. The second separators 32 of the two separators 30 may be connected by bonding, welding, or the like.

[0153] The second separators 32 of the two separators 30 are connected, which reduces the risk of the separator 30 detaching from the positive electrode plate 21, and also enables the two separators 30 to form a closed space at the positive electrode tail end 213, so that the separator 30 can more stably separate the edges of the positive electrode tail end 213 and the isolation membrane 23, thereby reducing the risk of the edges of the positive electrode tail end 213 piercing the isolation membrane 23 when the battery cell 100 is in a drop test or in a drop condition, thereby improving the safety of the battery cell 100 and the pass rate of the drop test.

[0154] The second separator 32 has a first surface 321 facing the positive electrode tail end 213 . The first surface 321 may have a gap with the positive electrode tail end 213 , or may be in contact with the first surface 321 .

[0155] like Figure 5 , Figure 7 As shown, in some embodiments, the first surface 321 is connected to the positive electrode tail end 213 .

[0156] The first surface 321 and the positive electrode tail end 213 may be connected by bonding or other methods.

[0157] The first surface 321 of the second separator 32 facing the positive electrode tail end 213 is connected to the positive electrode tail end 213, so that the separator 30 can better separate the edges of the positive electrode tail end 213 and the isolation membrane 23, and can also improve the stability of the connection between the separator 30 and the positive electrode plate 21, thereby further improving the safety performance of the battery cell 100.

[0158] like Figure 5 , Figure 7 As shown, in some embodiments, in the thickness direction X of the positive electrode sheet, the surface of the second separator 32 of each separator 30 away from the positive electrode sheet 21 is flush with the surface of the first separator 31 away from the positive electrode sheet 21 .

[0159] In an embodiment where the thickness of the first separator 31 is less than the thickness of the second separator 32, when the positive electrode sheet 21 is in the unfolded state, in the thickness direction X of the positive electrode sheet, the surface of the second separator 32 of each separator 30 away from the positive electrode sheet 21 is flush with the surface of the first separator 31 away from the positive electrode sheet 21, and the second separator 32 protrudes from the surface of the first separator 31 close to the positive electrode sheet 21.

[0160] The surface of the second separator 32 of each separator 30 away from the positive electrode sheet 21 is flush with the surface of the first separator 31 away from the positive electrode sheet 21, which is beneficial for uniform force on the negative electrode sheet 22 adjacent to the positive electrode tail end 213 when the electrode assembly 20 expands.

[0161] like Figure 7 , Figure 8 As shown, in some embodiments, the positive electrode sheet 21 includes a positive electrode body 214 and a positive electrode ear 215. Along the extension direction of the winding axis of the electrode assembly 20, the positive electrode body 214 has a first end 2141 and a second end 2142 relative to each other, and the positive electrode ear 215 is connected to the first end 2141; the separator 30 also includes a third separator 33. Along the extension direction, the third separator 33 is connected to the first separator 31 and exceeds the second end 2142, and the thickness of the third separator 33 is greater than the thickness of the first separator 31.

[0162] The extension direction of the winding axis of the electrode assembly 20 corresponds to the width direction of the unfolded positive electrode sheet 21. The positive electrode tab 215 may also be a full tab protruding from the first end 2141 and having a size in the length direction Y of the positive electrode sheet equal to the size of the positive current collector 211, such as Figure 7 , Figure 8 The positive electrode tab 215 may be a split tab protruding from the first end 2141 and having a size in the length direction Y of the positive electrode sheet smaller than the size of the positive electrode collector 211, as shown in FIG. Fig. 9 , Fig.10 shown.

[0163] The third partition 33 is connected to the first partition 31 , and the first partition 31 and the third partition 33 may be separate structures that are then connected into one.

[0164] The first partition 31 , the second partition 32 and the third partition 33 may also be integrally formed, thereby forming a partition 30 of an integrally formed structure, which facilitates the manufacture of the partition 30 and provides the partition 30 with better structural performance.

[0165] Along the thickness direction X of the positive electrode sheet, the surface of the third separator 33 away from the positive electrode sheet 21 is flush with the surface of the first separator 31 away from the positive electrode sheet 21, and the third separator 33 protrudes from the surface of the first separator 31 close to the positive electrode sheet 21, then the thickness of the third separator 33 is greater than the thickness of the first separator 31.

[0166] The third partition portions 33 of the two separators 30 are connected, which reduces the risk of the separator 30 detaching from the positive electrode plate 21, and also enables the two separators 30 to form a closed space at the second end 2142, so that the separator 30 can more stably separate the edges of the second end 2142 and the isolation membrane 23, thereby reducing the risk of the edges of the second end 2142 of the battery cell 100 piercing the isolation membrane 23 during a drop test or in a drop condition, thereby improving the safety of the battery cell 100 and the pass rate of the drop test.

[0167] Along the width direction Z of the positive electrode sheet, the surface of the third separator 33 facing the second end 2142 can be connected to the second end 2142. The surface of the third separator 33 facing the second end 2142 is connected to the second end 2142, so that the separator 30 can better separate the edge of the second end 2142 and the isolation film 23, and can also improve the stability of the connection between the separator 30 and the positive electrode sheet 21, thereby further improving the safety performance of the battery cell 100.

[0168] The third separator 33 is connected to the first separator 31 and extends beyond the second end 2142. On the one hand, the separator 30 can separate the two edges formed by the positive electrode sheet 21 at the second end 2142 and the isolation film 23, thereby reducing the risk of the two edges of the second end 2142 of the battery cell 100 piercing the isolation film 23 and causing short circuit failure during the drop mechanical test or when the battery cell 100 is in a drop condition, thereby improving the safety of the battery cell 100 in the drop mechanical test and in the drop condition, and improving the pass rate of the drop test of the battery cell 100. On the other hand, the separator 30 can also separate the edges corresponding to the second end 2142 and the negative electrode sheet 22 closest to the positive electrode tail end 213. After the electrode assembly 20 expands to abut against the housing 10, the separator 30 can effectively relieve or release the stress of the negative electrode sheet 22 closest to the second end 2142 at the position corresponding to the second end 2142, thereby making the negative electrode collector of the negative electrode sheet 22 less likely to break. On the other hand, since the third separators 33 of the two separators 30 extend beyond the second end 2142, the two third separators 33 fill the space between the second end 2142 and the negative electrode tail end of the negative electrode plate 22, and fill the gap on one side of the negative electrode tail section 221 close to the second end 2142, thereby improving the uniformity of the force acting on the outer shell 10 when the electrode assembly 20 expands, reducing the risk of the electrode assembly 20 being sunken due to the force of the outer shell 10, or alleviating the degree of the electrode assembly 20 being sunken due to the action of the outer shell 10 after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane 23 due to the sunken electrode assembly 20 during a drop mechanical test or when the battery cell 100 is in a drop condition, further improving the yield of the battery cell 100 and the safety performance of the battery cell 100.

[0169] In some embodiments, along the extension direction of the winding axis of the electrode assembly 20 , a size of the third separator 33 is greater than or equal to 1 mm and less than or equal to 4 mm.

[0170] like Figure 8 , Fig.10 As shown, the dimensions of the third separators 33 of the two separators 30 along the winding direction Y' of the electrode assembly 20 are L3 and L4, respectively, 1mm≤L3≤4mm, 1mm≤L4≤4mm. The dimensions of the third separators 33 of the two separators 30 along the winding direction of the electrode assembly 20 may be the same, that is, L3=L4. The dimensions of the third separators 33 of the two separators 30 along the winding direction Y' of the electrode assembly 20 may also be different, that is, L3≠L4. If necessary, the extension direction Z' of the winding axis of the electrode assembly 20 may correspond to the width direction Z of the positive electrode sheet.

[0171] For example, along the winding direction Y′ of the electrode assembly 20 , the size of the third separator 33 may be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, etc.

[0172] Along the extension direction Z' of the winding axis of the electrode assembly 20, the size of the third separator 33 is greater than or equal to 1 mm. The size of the third separator 33 along the extension direction Z' of the winding axis of the electrode assembly 20 is relatively large, which can effectively reduce the risk of the two edges of the second end 2142 of the battery cell 100 piercing the isolation film 23 during the drop mechanical test or when the battery cell 100 is in a drop condition, thereby improving the safety of the battery cell 100 in the drop mechanical test and in the drop condition, and improving the pass rate of the drop test of the battery cell 100. Along the extension direction Z' of the winding axis of the electrode assembly 20, the size of the third separator 33 is less than or equal to 4 mm, and the size of the third separator 33 in the extension direction Z' of the winding axis of the electrode assembly 20 is controlled within a reasonable range, so as to avoid the serious capacity loss and difficulty in shell entry caused by the excessive size of the electrode assembly 20 in the extension direction Z' of the winding axis of the electrode assembly 20 due to the provision of the separator 30, so as to make the battery cell 100 have a higher energy density and shell entry rate.

[0173] Further, along the extension direction Z′ of the winding axis of the electrode assembly 20 , the size of the third separator 33 is greater than or equal to 1.5 mm and less than or equal to 3.5 mm.

[0174] That is, 1.5 mm ≤ L3 ≤ 3.5 mm, 1.5 mm ≤ L4 ≤ 3.5 mm. For example, along the winding direction Y' of the electrode assembly 20, the size of the third separator 33 may be 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 2.1 mm, 2.4 mm, 2.6 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, etc.

[0175] Along the extension direction Z' of the winding axis of the electrode assembly 20, the size of the third separator 33 is greater than or equal to 1.5 mm, and the size of the second separator 32 along the extension direction Z' of the winding axis of the electrode assembly 20 is larger, which can further effectively reduce the risk of the two edges of the second end 2142 of the battery cell 100 piercing the isolation film 23 and causing short circuit failure during the drop mechanical test or when the battery cell 100 is in a drop condition, improve the safety of the battery cell 100 in the drop mechanical test and in the drop condition, and improve the pass rate of the drop test of the battery cell 100. Along the extension direction Z' of the winding axis of the electrode assembly 20, the size of the third separator 33 is less than or equal to 3.5 mm, and the size of the third separator 33 in the extension direction Z' of the winding axis of the electrode assembly 20 is controlled within a reasonable range, avoiding the serious capacity loss and difficulty in shell entry caused by the excessive size of the electrode assembly 20 in the extension direction Z' of the winding axis of the electrode assembly 20 due to the provision of the separator 30, so that the battery cell 100 has a higher energy density and shell entry rate.

[0176] like Fig.11 , Fig.12 As shown, the separator 30 also includes a fourth separator 34. Along the extension direction Z', the fourth separator 34 is connected to the first separator 31 and extends beyond the end of the positive electrode tab 215 away from the first end 2141. The thickness of the fourth separator 34 is greater than the thickness of the first separator 31. Fig.11 , Fig.12 2 shows a situation in which, in an embodiment where the positive electrode tab 215 is a full tab, the fourth separator 34 is connected to the first separator 31 and extends beyond the end of the positive electrode tab 215 away from the first end 2141 .

[0177] like Fig.13 , Fig.14 As shown, the partition 30 further includes a fourth partition 34 . Along the extension direction Z′, the fourth partition 34 is connected to the first partition 31 and extends beyond the first end 2141 . The thickness of the fourth partition 34 is greater than that of the first partition 31 . Fig.13 , Fig.14 FIG. 2 shows an embodiment in which the positive electrode tab 215 is a split-type tab, in which the fourth partition 34 is connected to the first partition 31 and extends beyond the first end 2141. Fig.13 and Fig.14 In the case shown in FIG. 2 , the fourth separators 34 of the two separators 30 can be connected. The fourth separators 34 of the two separators 30 are connected, which reduces the risk of the separator 30 being separated from the positive electrode sheet 21, and also enables the two separators 30 to form a closed space at the first end 2141, so that the separator 30 can more stably separate the edge of the first end 2141 and the isolation film 23, thereby reducing the risk of the edge of the first end 2141 of the battery cell 100 piercing the isolation film 23 during the drop test or in the drop condition, and improving the safety of the battery cell 100 and the pass rate of the drop test.

[0178] The fourth partition 34 is connected to the first partition 31 , and the first partition 31 and the fourth partition 34 may be separate structures that are then connected into one.

[0179] Along the width direction Z of the positive electrode sheet, the surface of the fourth separator 34 facing the first end 2141 can be connected to the first end 2141. The surface of the fourth separator 34 facing the first end 2141 is connected to the first end 2141, so that the separator 30 can better separate the edge of the first end 2141 and the isolation film 23, and can also improve the stability of the connection between the separator 30 and the positive electrode sheet 21, thereby further improving the safety performance of the battery cell 100.

[0180] The first partition 31 , the second partition 32 , the third partition 33 and the fourth partition 34 may also be integrally formed, thereby forming a partition 30 of an integrally formed structure, which facilitates the manufacture of the partition 30 and provides the partition 30 with better structural performance.

[0181] Along the thickness direction X of the positive electrode sheet, the surface of the fourth separator 34 away from the positive electrode sheet 21 is flush with the surface of the first separator 31 away from the positive electrode sheet 21, and the fourth separator 34 protrudes from the surface of the first separator 31 close to the positive electrode sheet 21, then the thickness of the fourth separator 34 is greater than the thickness of the first separator 31.

[0182] The fourth separator 34 is connected to the first separator 31 and extends beyond the first end 2141 or beyond the end of the positive electrode tab 215 away from the first end 2141. On the one hand, the separator 30 can separate the two edges formed by the positive electrode plate 21 at the first end 2141 and the isolation membrane 23, or separate the two edges formed by the positive electrode tab 215 away from the first end 2141 and the isolation membrane 23, thereby reducing the risk of the two edges of the first end 2141 of the battery cell 100 or the two edges of the positive electrode tab 215 away from the first end 2141 piercing the isolation membrane 23 and causing short circuit failure during the drop mechanical test of the battery cell 100 or when the battery cell 100 is in a drop condition, thereby improving the safety of the battery cell 100 in the drop mechanical test and in the drop condition, and improving the pass rate of the drop test of the battery cell 100. On the other hand, the separator 30 can also separate the edge corresponding to the first end 2141 and the negative electrode plate 22 closest to the positive electrode tail end 213. After the electrode assembly 20 expands to abut against the outer shell 10, the separator 30 can effectively relieve or release the stress of the negative electrode plate 22 closest to the first end 2141 at the position corresponding to the first end 2141, so that the negative electrode collector of the negative electrode plate 22 is not easy to break. On the other hand, since the fourth partition portions 34 of the two partitions 30 extend beyond the first end 2141, the two fourth partition portions 34 fill the space between the first end 2141 and the negative electrode tail end of the negative electrode plate 22, and fill the gap on one side of the negative electrode tail section 221 close to the first end 2141, thereby improving the uniformity of the force acting on the outer shell 10 when the electrode assembly 20 expands, reducing the risk of the electrode assembly 20 being sunken due to the force of the outer shell 10, or alleviating the degree of the electrode assembly 20 being sunken due to the action of the outer shell 10 after expansion, thereby reducing the risk of short-circuit failure caused by puncturing the isolation membrane 23 due to the sunken electrode assembly 20 during a drop mechanical test or when the battery cell 100 is in a drop condition, thereby further improving the yield of the battery cell 100 and the safety performance of the battery cell 100.

[0183] An embodiment of the present application further provides an electrical device, and the electrical device includes the battery cell 100 provided in any of the above embodiments.

[0184] The battery cell 100 provided in the above embodiment has good safety, and the electrical equipment powered by the battery cell 100 has good electrical safety.

[0185] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes.

Claims

1. A battery cell, characterized in that: include: An electrode assembly with a winding structure, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet and a separator, the separator is used to insulate and separate the positive electrode sheet from the negative electrode sheet, the positive electrode sheet has a positive electrode tail end, and the negative electrode sheet extends beyond the positive electrode tail end along the winding direction of the electrode assembly; Two separators, the separators comprising a first separator and a second separator connected to the first separator and extending beyond the positive electrode tail end, along the thickness direction of the positive electrode sheet, the first separators of the two separators are respectively arranged on two opposite surfaces of the positive electrode sheet, and the second separators of the two separators are arranged opposite to each other; Wherein, the sum of thicknesses of the first partitions of the two partitions is smaller than the sum of thicknesses of the second partitions of the two partitions.

2. The battery cell according to claim 1, characterized in that: The thickness of the first partition is smaller than the thickness of the second partition.

3. The battery cell according to claim 1, characterized in that: The first partitions of the two partitions have the same thickness; and / or the second partitions of the two partitions have the same thickness.

4. The battery cell according to claim 1, characterized in that: The thickness of the first separator is smaller than a dimension of the second separator along a winding direction of the electrode assembly.

5. The battery cell according to claim 1, characterized in that: The second partitions of the two partitions are connected.

6. The battery cell according to claim 1, characterized in that: The second separator has a first surface facing the positive electrode tail end, and the first surface is connected to the positive electrode tail end.

7. The battery cell according to claim 1, characterized in that: In the thickness direction of the positive electrode sheet, a surface of the second separator of each separator that is away from the positive electrode sheet is flush with a surface of the first separator that is away from the positive electrode sheet.

8. The battery cell according to any one of claims 1 to 7, characterized in that: Along the winding direction of the electrode assembly, a size of the first separator is greater than or equal to 1 mm and less than or equal to 5 mm.

9. The battery cell according to claim 8, characterized in that: Along the winding direction of the electrode assembly, a size of the first separator is greater than or equal to 2 mm and less than or equal to 3.5 mm.

10. The battery cell according to claim 1, characterized in that: Along the winding direction of the electrode assembly, a size of the second separator is greater than or equal to 1 mm and less than or equal to 5 mm.

11. The battery cell according to claim 10, characterized in that: Along the winding direction of the electrode assembly, a size of the second separator is greater than or equal to 2 mm and less than or equal to 3.5 mm.

12. The battery cell according to claim 1, characterized in that: A ratio of a thickness of the first partition portion to a thickness of the second partition portion of each of the partitions is greater than or equal to 0.2 and less than or equal to 1.

13. The battery cell according to claim 12, characterized in that: A ratio of a thickness of the first partition portion to a thickness of the second partition portion of each of the partitions is greater than or equal to 0.5 and less than or equal to 0.

8.

14. The battery cell according to claim 1, characterized in that: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, and along the thickness direction of the positive electrode sheet, the positive electrode active material layer is disposed on both sides of the positive electrode current collector; A ratio of a thickness of the second separator to a thickness of the positive electrode active material layer is greater than or equal to 1.05 and less than or equal to 1.

8.

15. The battery cell according to claim 14, characterized in that: A ratio of a thickness of the second separator to a thickness of the positive electrode active material layer is greater than or equal to 1.1 and less than or equal to 1.

5.

16. The battery cell according to claim 1, characterized in that: The thickness of the first partition is greater than or equal to 5 μm and less than or equal to 60 μm.

17. The battery cell according to claim 16, characterized in that: The thickness of the first partition is greater than or equal to 10 μm and less than or equal to 30 μm.

18. The battery cell according to claim 1, characterized in that: The positive electrode sheet comprises a positive electrode body and a positive electrode tab. Along the extension direction of the winding axis of the electrode assembly, the positive electrode body has a first end and a second end opposite to each other, and the positive electrode tab is connected to the first end. The partition also includes a third partition. Along the extending direction, the third partition is connected to the first partition and exceeds the second end. The thickness of the third partition is greater than that of the first partition.

19. The battery cell according to claim 18, characterized in that: Along the extension direction of the winding axis of the electrode assembly, a size of the third separator is greater than or equal to 1 mm and less than or equal to 4 mm.

20. The battery cell according to claim 19, characterized in that: Along the extension direction of the winding axis of the electrode assembly, a size of the third separator is greater than or equal to 1.5 mm and less than or equal to 3.5 mm.

21. The battery cell according to claim 1, characterized in that: The positive electrode sheet comprises a positive electrode body and a positive electrode tab. Along the extension direction of the winding axis of the electrode assembly, the positive electrode body has a first end and a second end opposite to each other, and the positive electrode tab is connected to the first end. The separator also includes a fourth separator, which is connected to the first separator and extends beyond the first end along the extension direction, or is connected to the first separator and extends beyond an end of the positive electrode tab away from the first end, and the thickness of the fourth separator is greater than the thickness of the first separator.

22. The battery cell according to claim 1, characterized in that: The negative electrode sheet has a negative electrode tailing section that exceeds the positive electrode tailing end, and along the thickness direction of the positive electrode sheet, the negative electrode tailing section is located outside the positive electrode tailing end.

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

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