Battery cell and electric equipment

Abstract

The invention provides a battery cell and electric equipment. The battery cell comprises an electrode assembly and a separator, the electrode assembly comprises a positive pole piece, a negative pole piece and an isolating membrane, the positive pole piece comprises a first section wound by one circle from a positive starting end in the winding direction of the electrode assembly, the separator comprises a first separating part located on the outer side of the first section, and the first separating part separates the positive starting end and the negative pole piece; one of the negative pole piece, the isolating membrane and the first section is provided with a first surface, the first separation part is provided with a second surface and a third surface which are opposite in the thickness direction of the first separation part, the second surface faces the first surface and is connected with the first surface, and the surface roughness of the third surface is smaller than that of the first surface; and the safety performance of the battery cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery cell and a power consumption device. BACKGROUND

[0002] At present, with the rapid development of new energy technology, battery cells have been widely used in the fields of electronic devices, electric vehicles, electric two-wheel vehicles, electric tools and the like. With the increasingly wide application of battery cells, higher requirements are put forward for the safety performance of battery cells. SUMMARY

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

[0004] In a first aspect, the embodiments of the present application provide a battery cell, which includes an electrode assembly and a separator. The electrode assembly is in a wound structure. The electrode assembly includes a positive electrode tab, a negative electrode tab and a separator film. The separator film insulates and separates the positive electrode tab and the negative electrode tab. The positive electrode tab has a positive electrode starting end. The positive electrode tab includes a first segment wound one turn along a winding direction of the electrode assembly from the positive electrode starting end. The separator includes a first separation part located on the outside of the first segment. The first separation part separates the positive electrode starting end and the negative electrode tab. One of the negative electrode tab, the separator film and the first segment has a first surface. The first separation part has opposite second and third surfaces along the thickness direction of the first separation part. The second surface is arranged to face the first surface and is connected to the first surface. The surface roughness of the third surface is less than the surface roughness of the first surface.

[0005] In one or more optional embodiments described above, the first separation part of the separator separates the positive electrode starting end and the negative electrode tab, reducing the risk of short circuit after the positive electrode starting segment pierces the separator film and improving the safety performance of the battery cell. By making the surface roughness of the third surface less than the surface roughness of the first surface, the friction between the surfaces in contact with the third surface in the thickness direction of the first separation part is smaller. Compared with the scheme without the separator, the present scheme can reduce the friction experienced by the positive electrode tab relative to the negative electrode tab when the positive electrode tab slides in the winding direction, so that the positive electrode tab can smoothly slide relative to the negative electrode tab in the winding direction, reducing the risk of increased internal pressure due to the one turn of the negative electrode tab outside the positive electrode starting end being raised at the position close to the positive electrode starting end to hinder the sliding of the positive electrode tab. This is conducive to improving the safety performance of the battery cell.

[0006] In some embodiments of the first aspect of the present application, the difference between the surface roughness of the first surface and the surface roughness of the third surface is Ra0.1-Ra0.7.

[0007] In one or more optional embodiments above, by the difference between the surface roughness of the first surface and the surface roughness of the third surface being greater than or equal to Ra 0.1, the surface roughness of the third surface is small enough compared to the surface roughness of the first surface, which is conducive to reducing the friction between the third surface and the surface in contact with the third surface, thereby reducing the friction experienced by the positive electrode tab when it slides in the winding direction relative to the negative electrode tab, thereby enabling the positive electrode tab to smoothly slide in the winding direction relative to the negative electrode tab, reducing the risk of increased internal pressure due to the outermost circle of negative electrode tabs near the positive electrode starting end being raised and hindering the sliding of the positive electrode tab, and improving the safety performance of the battery cell. By the difference between the surface roughness of the first surface and the surface roughness of the third surface being less than or equal to Ra 0.7, the surface roughness of the third surface is not too small compared to the surface roughness of the first surface, so that there is a certain friction between the third surface and the surface in contact with the third surface, which is conducive to maintaining the relative stability of each circle layer of the electrode assembly, reducing the risk of lithium precipitation in the battery cell, and improving the safety performance of the battery cell. Therefore, the difference between the surface roughness of the first surface and the surface roughness of the third surface is Ra 0.1-Ra 0.7, which is conducive to improving the safety performance of the battery cell.

[0008] In some embodiments of the first aspect of the application, the difference between the surface roughness of the first surface and the surface roughness of the third surface is Ra 0.2-Ra 0.7.

[0009] In one or more optional embodiments above, by the difference between the surface roughness of the first surface and the surface roughness of the third surface being greater than or equal to Ra 0.2, the surface roughness of the third surface is smaller compared to the surface roughness of the first surface, which is conducive to further reducing the friction between the third surface and the surface in contact with the third surface, thereby reducing the friction experienced by the positive electrode tab when it slides in the winding direction relative to the negative electrode tab, thereby enabling the positive electrode tab to smoothly slide in the winding direction relative to the negative electrode tab, reducing the risk of increased internal pressure due to the outermost circle of negative electrode tabs near the positive electrode starting end being raised and hindering the sliding of the positive electrode tab, and improving the safety performance of the battery cell. Therefore, the difference between the surface roughness of the first surface and the surface roughness of the third surface is Ra 0.2-Ra 0.7, which is conducive to further improving the safety performance of the battery cell.

[0010] In some embodiments of the first aspect of the application, the surface roughness of the first surface is Ra 0.25-Ra 0.8.

[0011] In one or more of the above optional embodiments, having a surface roughness greater than or equal to Ra0.25 on the first surface is beneficial for improving the connection stability between the first surface and the second surface of the first separator. Having a surface roughness less than or equal to Ra0.8 on the first surface prevents excessive friction between surfaces in contact with the first surface, thereby reducing the friction experienced by the positive electrode relative to the negative electrode in the winding direction. This allows the positive electrode to slide smoothly relative to the negative electrode in the winding direction, reducing the risk of increased indentation due to the negative electrode near the positive electrode starting end lifting up and hindering the sliding of the positive electrode, thus improving the safety performance of the battery cell. Therefore, a surface roughness of Ra0.25-Ra0.8 on the first surface can improve the safety performance of the battery cell and the connection stability between the separator and the electrode assembly.

[0012] In some embodiments of the first aspect of this application, the surface roughness of the third surface is Ra0.05-Ra0.2.

[0013] In one or more of the above optional embodiments, by having a surface roughness greater than or equal to Ra0.05, a certain amount of friction is maintained between the third surface and the surface in contact with it. This helps maintain the relative stability of each layer of the electrode assembly, reduces the risk of lithium plating in the cell, and improves the safety performance of the cell. By having a surface roughness less than or equal to Ra0.2, the friction between the third surface and the surface in contact with it is not too large, thereby reducing the friction experienced by the positive electrode relative to the negative electrode in the winding direction. This allows the positive electrode to slide smoothly relative to the negative electrode in the winding direction, reducing the risk of increased indentation due to the negative electrode near the positive electrode starting end lifting up and hindering the sliding of the positive electrode, thus improving the safety performance of the cell. Therefore, a surface roughness of Ra0.05-Ra0.2 for the third surface results in better safety performance for the cell.

[0014] In some embodiments of the first aspect of this application, the surface of the negative electrode facing the winding center of the electrode assembly includes a first surface.

[0015] In one or more of the above optional embodiments, the surface of the negative electrode sheet facing the winding center of the electrode assembly includes a first surface. The first separator is connected to the negative electrode sheet, and the third surface of the separator contacts the surface of the separator film. The surface roughness of the third surface is less than that of the first surface. Compared to a scheme where the first surface and the separator film are in direct contact, the frictional force of the third surface and the separator film is smaller. This reduces the frictional force experienced by the positive electrode sheet when sliding relative to the negative electrode sheet in the winding direction, allowing the positive electrode sheet to slide smoothly relative to the negative electrode sheet in the winding direction. This reduces the risk of increased indentation due to the outer ring of negative electrode sheets near the positive electrode starting end lifting and hindering the sliding of the positive electrode sheet, thus improving the safety performance of the battery cell. Furthermore, the first separator can enhance the strength of the negative electrode sheet and support the negative electrode sheet on the side facing the winding center, alleviating the problem of indentation in the battery cell and improving its safety performance.

[0016] In some embodiments of the first aspect of this application, the negative electrode includes a negative electrode active material layer. Along the extension direction of the winding axis of the electrode assembly, the width of the first partition is W1, the width of the negative electrode active material layer is W2, and 0.7≤W1 / W2≤0.95.

[0017] In one or more of the above optional embodiments, by having W1 / W2 greater than or equal to 0.7, the coverage area of ​​the first separator in the winding axis direction is larger, which can reduce the risk of short circuit caused by the positive electrode starting end puncturing the separator, improve the safety performance of the battery cell, and also make the connection area between the first separator and the negative electrode sheet larger, improving the connection stability between the negative electrode sheet and the separator. W1 / W2 less than or equal to 0.95 ensures that the size of the first separator in the winding axis direction is not too large, reducing the space occupied by the separator, reducing energy density loss, and enabling the battery cell to have a higher energy density. Therefore, 0.7≤W1 / W2≤0.95 makes the battery cell both safe and energy-dense, and also makes the connection stability between the first separator and the negative electrode sheet better.

[0018] In some embodiments of the first aspect of this application, the isolation membrane includes a first surface.

[0019] In one or more of the above optional embodiments, the separator includes a first surface, and the first separator is connected to the separator. The third surface of the first separator is in contact with the surface of the positive electrode or the third surface of the first separator is in contact with the surface of the negative electrode. The surface roughness of the third surface is less than that of the first surface. Compared with the scheme where the first surface and the surface of the positive electrode are in direct contact or the scheme where the first surface and the surface of the negative electrode are in contact, the frictional force between the surface of the third surface and the surface of the positive electrode or the surface of the third surface and the surface of the negative electrode is smaller. This can reduce the frictional force experienced by the positive electrode relative to the negative electrode when sliding in the winding direction, thereby enabling the positive electrode relative to the negative electrode to slide smoothly in the winding direction. This reduces the risk of increased indentation due to the negative electrode near the positive electrode starting end lifting up and hindering the sliding of the positive electrode, thus improving the safety performance of the battery cell.

[0020] In some embodiments of the first aspect of this application, the surface of the separator facing the winding center of the electrode assembly includes a first surface.

[0021] In one or more of the above optional embodiments, the surface of the separator facing the winding center of the electrode assembly includes a first surface. If the first separator is connected to the surface of the separator facing the winding center of the electrode assembly, the risk of excessive compression of each layer of the electrode assembly due to the setting of the separator can be reduced. This is beneficial to improving the wetting efficiency of the electrode assembly and ensuring that the electrode assembly is fully wetted, thereby improving the cycle performance of the battery cell.

[0022] In some embodiments of the first aspect of this application, the surface of the first segment facing away from the winding center of the electrode assembly includes a first surface.

[0023] In one or more of the above optional embodiments, the surface of the first segment away from the winding center of the electrode assembly includes a first surface. The first separator is connected to the surface of the first segment away from the winding center of the electrode assembly. The third surface of the first separator is disposed opposite to the surface of the first segment away from the winding center. The third surface is in contact with the surface of the separator facing the first segment away from the winding center. The surface roughness of the third surface is less than that of the first surface. Compared with the scheme where the separator is in contact with the surface of the first segment away from the winding center, the friction between the third surface and the surface of the separator is smaller in this scheme. This reduces the resistance encountered when the positive electrode sheet slides along the winding direction, thereby enabling the positive electrode sheet to slide smoothly relative to the negative electrode sheet in the winding direction. This reduces the risk of further increase in the degree of indentation caused by the negative electrode sheet on the outer ring of the positive electrode starting end lifting up near the positive electrode starting end and hindering the sliding of the positive electrode sheet, thus improving the safety performance of the battery cell.

[0024] In some embodiments of the first aspect of this application, the positive electrode includes a positive active material layer. Along the extension direction of the winding axis of the electrode assembly, the width of the first partition is W1, the width of the positive active material layer is W3, and 0.7≤W1 / W3≤0.95.

[0025] In one or more of the above optional embodiments, by having W1 / W3 greater than or equal to 0.7, the coverage area of ​​the first separator in the winding axis direction is larger, which can reduce the risk of short circuit caused by the positive electrode starting end puncturing the separator, improve the safety performance of the battery cell, and also make the connection area between the first separator and the positive electrode sheet larger, improving the connection stability between the positive electrode sheet and the separator. W1 / W3 less than or equal to 0.95 ensures that the size of the first separator in the winding axis direction is not too large, reducing the space occupied by the separator, reducing energy density loss, and enabling the battery cell to have a higher energy density. Therefore, 0.7≤W1 / W3≤0.95 makes the battery cell both safe and energy-dense, and also makes the connection stability between the first separator and the positive electrode sheet better.

[0026] In some embodiments of the first aspect of this application, the separator further includes a second partition portion, the second partition portion and the first partition portion being located on both sides of the first segment, and the first partition portion and the second partition portion being connected.

[0027] In one or more of the above optional embodiments, the second partition and the first partition are located on both sides of the first segment, and the first partition and the second partition are connected to each other, thereby increasing the connection area between the partition and the first segment and improving the connection stability between the first segment and the partition.

[0028] In some embodiments of the first aspect of this application, the separator further includes a third separator portion, which is disposed facing the positive electrode starting end and connects the first separator portion and the second separator portion.

[0029] In one or more of the above optional embodiments, the third separator connects the first separator and the second separator, which helps to increase the connection area between the separator and the first segment and improve the connection stability between the first segment and the separator. The third separator is disposed facing the positive electrode starting end and connects the first separator and the second separator, so that the first separator can cover the edge of the positive electrode starting end, reducing the risk of short circuit caused by the positive electrode starting end piercing the insulation and improving the safety performance of the battery cell.

[0030] In some embodiments of the first aspect of this application, the first partition, the second partition, and the third partition are integrally formed.

[0031] In one or more of the above optional embodiments, the first partition, the second partition, and the third partition are integrally formed, so that the partition has better mechanical properties.

[0032] In some embodiments of the first aspect of this application, the first partition extends beyond the positive electrode start end in the opposite direction to the winding direction of the electrode assembly.

[0033] In one or more of the above optional embodiments, the first separator extends beyond the positive electrode starting end in the opposite direction of the winding direction of the electrode assembly, so that the first separator can have a large coverage area in the winding direction, reducing the risk of short circuit, improving the safety performance of the battery cell, and eliminating the need for precise positioning when setting the separator on the first segment, thus reducing the positioning accuracy requirement and simplifying the manufacturing process.

[0034] In some embodiments of the first aspect of this application, the size of the first partition is L along the winding direction of the electrode assembly, where 3mm ≤ L ≤ 10mm.

[0035] In one or more of the above optional embodiments, by using L greater than or equal to 3mm, the size of the first separator in the winding direction is relatively large, resulting in a larger coverage area. This reduces the risk of short circuits, improves the safety performance of the battery cell, and also helps to increase the connection area between the first separator and the electrode assembly, improving the connection stability of the separator. By using L less than or equal to 10mm, the size of the first separator in the winding direction is not too large, reducing the space occupied by the separator and minimizing energy density loss caused by its installation. Therefore, 3mm ≤ L ≤ 10mm results in a battery cell with good safety performance and high energy density.

[0036] In some embodiments of the first aspect of this application, the separator is adhesive tape.

[0037] In one or more of the above optional embodiments, the adhesive tape has good flexibility, and the separator is made of adhesive tape, which makes it easy for the separator to be wound along with the positive electrode sheet, negative electrode sheet, or separator film, reducing the risk of the separator curling up or falling off after winding. In addition, the adhesive tape has its own adhesive, which can easily connect the separator to the electrode assembly.

[0038] In some embodiments of the first aspect of this application, the innermost electrode of the electrode assembly is part of the negative electrode.

[0039] In one or more of the above optional embodiments, the innermost electrode of the electrode assembly is part of the negative electrode, which helps to reduce the risk of lithium plating in the cell and improve the safety performance of the cell.

[0040] In some embodiments of the first aspect of this application, the battery cell is a cylindrical battery cell.

[0041] Secondly, embodiments of this application provide an electrical device, which includes the battery cells provided in any of the above embodiments.

[0042] In one or more of the above optional embodiments, the battery cell provided in any embodiment of the first aspect has good safety performance, which is beneficial to improving the power safety and reliability of electrical equipment powered by the battery cell. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0044] Figure 1 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application; Figure 2 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application; Figure 3 for Figure 2 Enlarged view at point A1; Figure 4 This application provides schematic diagrams of the structure of electrode assemblies for other adverse embodiments. Figure 5 for Figure 4 Enlarged view at point A2; Figure 6 A schematic diagram showing the unfolded state of the first partition portion after it is connected to the negative electrode plate, as provided in some embodiments of this application; Figure 7 for Figure 6 A schematic diagram from another perspective showing the first dividing section connected to the negative electrode plate; Figure 8 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application; Figure 9 for Figure 8 Enlarged view at point A3; Figure 10 This application provides schematic diagrams of the structure of electrode assemblies in some of its embodiments. Figure 11 for Figure 10 Enlarged view at A4 in the middle; Figure 12 This application provides schematic diagrams of the structure of electrode assemblies in some further embodiments; Figure 13 This is an enlarged view of section A5 in image 12; Figure 14 A schematic diagram showing the unfolded state of the first partition portion after it is connected to the positive electrode plate, as provided in some embodiments of this application; Figure 15 for Figure 14 A schematic diagram showing another perspective of the first dividing section after it is connected to the positive electrode plate; Figure 16 This is a schematic diagram of the structure of an electrode assembly provided in some other embodiments of this application; Figure 17 for Figure 16 Enlarged view at A6 in the image; Figure 18 This is a schematic diagram of the structure of an electrode assembly provided in some further embodiments of this application; Figure 19 for Figure 18 Enlarged view at A7 in the middle; Figure 20 This is a schematic diagram of the structure of an electrode assembly provided in some other embodiments of this application; Figure 21 for Figure 20 Enlarged view of section A8 in the middle.

[0045] Icons: 100-Cell; 10-Casing; 20-Electrode Assembly; 21-Positive Electrode; 211-Positive Current Collector; 212-Positive Active Material Layer; 213-Positive Starting End; 2131-First Edge; 2132-Second Edge; 214-First Segment; 22-Negative Electrode; 221-Negative Current Collector; 222-Negative Active Material Layer; 23-Separator; 30-Separator; 31-First End; 32-Second End; 33-First Separator Part; 331-Second surface; 332-Third surface; 333-First region; 34-Second partition; 341-Second region; 35-Third partition; Q-First surface; X-Wounding direction; X1-Length direction of negative electrode sheet; X2-Length direction of positive electrode sheet; Y-Wounding axis direction; Y1-Width direction of negative electrode sheet; Y2-Width direction of positive electrode sheet; Z1-Thickness direction of negative electrode sheet; Z2-Thickness direction of positive electrode sheet. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0049] In the description of the embodiments of this application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0050] Currently, judging from market trends, the application of battery cells is becoming increasingly widespread. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in power tools, drones, energy storage devices, and many other fields. As the application areas of battery cells continue to expand, the market demand is also constantly increasing.

[0051] After the battery cell is cycled, the negative electrode sheet expands, resulting in significant internal stress inside the cell. For wound cells, due to the presence of the winding center hole, the supporting force of the layers near the winding center hole is relatively weak. When the radial internal stress exceeds the supporting force of the inner layer, the layers of the negative electrode sheet located outside the positive electrode starting end will deform and collapse in the direction closer to the winding axis. This phenomenon is also known as indentation. When the indentation is too great, the negative electrode sheet will break, leading to a short circuit in the battery cell. In severe cases, it can cause safety problems such as thermal runaway.

[0052] Based on the above considerations, in order to improve the safety performance of the battery cell, this application provides a battery cell including an electrode assembly and a separator; the electrode assembly is a wound structure. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, with the separator insulatingly separating the positive and negative electrode sheets. The positive electrode sheet has a positive starting end and includes a first segment wound once from the positive starting end along the winding direction of the electrode assembly. The separator includes a first dividing portion located outside the first segment, which separates the positive starting end and the negative electrode sheet. One of the negative electrode sheet, the separator, and the first segment has a first surface. Along the thickness direction of the first dividing portion, the first dividing portion has opposing second and third surfaces. The second surface faces and is connected to the first surface, and the surface roughness of the third surface is less than that of the first surface.

[0053] The first separating part of the separator separates the positive electrode starting end and the negative electrode plate, reducing the risk of short circuit after the positive electrode starting section punctures the separator film and improving the safety performance of the cell.

[0054] By making the surface roughness of the third surface less than that of the first surface, the friction between the surfaces in contact with the third surface in the thickness direction of the first separator is smaller. Compared with the solution without a separator, this solution can reduce the friction force experienced by the positive electrode sheet when it slides relative to the negative electrode sheet in the winding direction. This allows the positive electrode sheet to slide smoothly relative to the negative electrode sheet in the winding direction, reducing the risk of increased indentation caused by the negative electrode sheet on the outer ring of the positive electrode starting end lifting up near the positive electrode starting end and hindering the sliding of the positive electrode sheet, thus improving the safety performance of the battery cell.

[0055] The battery cells disclosed in the embodiments of this application can be used, but are not limited to, in electrical equipment such as electric two-wheelers, power tools, drones, and energy storage devices. Battery cells conforming to the operating conditions of this application can also be used as the power supply system for electrical equipment.

[0056] This application provides an electrical device that uses battery cells as a power source. The electrical device can be, but is not limited to, electronic devices, power tools, electric vehicles, drones, and energy storage devices. Electronic devices can include mobile phones, tablets, laptops, etc.; power tools can include electric drills, chainsaws, etc.; and electric vehicles can include electric cars, electric motorcycles, electric bicycles, etc.

[0057] like Figure 1 As shown, this application provides a battery cell 100, which includes a housing 10 and an electrode assembly 20, with the electrode assembly 20 housed within the housing 10.

[0058] The outer casing 10 can be a rigid casing, such as a stainless steel casing or an aluminum hard casing, forming a steel-cased battery or an aluminum-cased battery.

[0059] The electrode assembly 20 includes a positive electrode 21, a negative electrode 22, and a separator 23.

[0060] The positive electrode 21 includes a positive current collector 211 and a positive active material layer 212. Along the thickness direction Z2 of the positive electrode, the positive current collector 211 may have the positive active material layer 212 on one surface or both opposite surfaces of the positive current collector 211 may have the positive active material layer 212.

[0061] The negative electrode sheet 22 includes a negative electrode current collector 221 and a negative electrode active material layer 222. Along the thickness direction Z1 of the negative electrode sheet, the negative electrode current collector 221 may have a negative electrode active material layer 222 on one surface or both opposite surfaces of the negative electrode current collector 221 may have a negative electrode active material layer 222.

[0062] For lithium-ion cells, the positive electrode current collector 211 can be made of aluminum. The positive electrode active material layer 212 can be lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium manganese oxide, etc. The positive electrode current collector 211 can be a composite current collector or a non-composite current collector. For lithium-ion cells 100, the negative electrode current collector 221 can be made of copper. The negative electrode current collector 221 can be a composite current collector or a non-composite current collector. The negative electrode active material can be carbon material or silicon material, etc.

[0063] The separator 23 provides insulation between the positive electrode 21 and the negative electrode 22 to reduce the risk of short circuit in the cell 100. The material of the separator 23 may include PP (polypropylene) or PE (polyethylene), etc.

[0064] The electrode assembly 20 has a wound structure. The negative electrode 22, the separator 23, the positive electrode 21, and another separator 23 are stacked in a specific order and then wound to form the wound electrode assembly 20; alternatively, the separator 23, the positive electrode 21, another separator 23, and the negative electrode 22 are stacked in a specific order and then wound to form the wound electrode assembly 20. The wound electrode assembly 20 can be cylindrical, flat, or similar. The battery cell 100 can be cylindrical, prismatic, or similar.

[0065] When the positive electrode 21 and the negative electrode 22 are in the unfolded state, the length direction X2 of the positive electrode and the length direction X1 of the negative electrode both correspond to the winding direction X when the positive electrode 21 and the negative electrode 22 are in the wound state. The width direction Y2 of the positive electrode 21 and the width direction Y1 of the negative electrode both correspond to the winding axis direction Y of the electrode assembly 20 when the positive electrode 21 and the negative electrode 22 are in the wound state. When the positive electrode 21 and the negative electrode 22 are in the unfolded state, the length direction X2, the width direction Y2, and the thickness direction Z2 of the positive electrode are perpendicular to each other, and the length direction X1, the width direction Y1, and the thickness direction Z1 of the negative electrode are perpendicular to each other.

[0066] The winding center P is the central axis of the winding during the process of forming the electrode assembly 20. The winding center P is a virtual feature of the wound electrode assembly 20. The winding center P shown in the accompanying drawings of the embodiments of this application represents the position of the winding center P in the structure of the electrode assembly 20, so as to make the orientation descriptions such as "facing the winding center P", "away from the winding center P", and "close to the winding center P" in this application clearer.

[0067] The positive electrode 21 has a positive electrode starting end 213 and includes a first segment 214 that is wound once from the positive electrode starting end 213 along the winding direction X of the electrode assembly 20.

[0068] The positive electrode starting end 213 refers to the end face where the positive electrode sheet 21 begins to be wound. The edge of the positive electrode starting end 213 closest to the winding axis P is the first edge 2131, and the edge of the positive electrode starting end 213 furthest from the winding axis P is the second edge 2132. In some embodiments, the first edge 2131 and the second edge 2132 are two opposite edges of the positive electrode starting end 213 in a direction perpendicular to the winding axis Y.

[0069] The positive electrode 21 is wound once from the positive electrode starting end 213 along the winding direction X of the electrode assembly 20. This means that it is wound 360° along the winding direction X, starting from the positive electrode starting end 213, which constitutes one turn. It can be understood that after winding, the first segment 214 is the innermost loop of the positive electrode 21. The dotted line position shown on P1 in the accompanying drawings of this application is the ending position of the first segment 214.

[0070] like Figure 2 , Figure 3 As shown, in this embodiment, the separator 30 includes a first separator 33 located outside the first segment 214, which separates the positive electrode starting end 213 and the negative electrode plate 22. By separating the positive electrode starting end 213 and the negative electrode plate 22 by the first separator 33, the risk of short circuit after the positive electrode starting end 213 punctures the separator 23 is reduced, thereby improving the safety performance of the battery cell 100.

[0071] The separator 30 is an insulating component. The separator 30 includes, but is not limited to, electrolyte-resistant acrylic pressure-sensitive adhesive, PET (polyethylene terephthalate), PI (polyimide), and PP (polypropylene). The first separator 33 can be a part of the separator 30, or the first separator 33 can be the separator 30 itself.

[0072] For example, the separator 30 can be adhesive tape. Adhesive tape has good flexibility, and using adhesive tape for the separator 30 facilitates its winding along with the positive electrode 21, negative electrode 22, or separator 23, reducing the risk of the separator 30 warping or falling off after winding. Furthermore, the adhesive tape itself provides easy bonding of the separator 30 to the electrode assembly 20. The separator 30 can also be an insulating coating formed on the first segment 214, separator 23, or negative electrode 22.

[0073] The first separator 33 is located between the outermost layers of the positive electrode starting end 213 and the negative electrode plate 22 closest to the positive electrode starting end 213, so that the first separator 33 can separate the positive electrode starting end 213 and the negative electrode plate 22, reducing the risk of short circuit after the positive electrode starting end 213 punctures the separator 23, and improving the safety performance of the cell 100. Along the winding direction X, the first separator 33 has a first end 31 and a second end 32, the first end 31 being the winding starting end of the first separator 33, and the second end 32 being the winding ending end of the first separator 33. Viewed along a direction perpendicular to the winding axis and passing through the positive electrode starting end 213, the projection of the second end 32 is located within the first segment 214. In some embodiments, such as Figure 2 , Figure 3 As shown, in the opposite direction of the winding direction X, the first dividing part 33 extends beyond the positive electrode starting end 213, so that the first dividing part 33 can separate the positive electrode starting end 213 and the outermost negative electrode sheet 22 closest to the positive electrode starting end 213.

[0074] Along the opposite direction of the winding direction X of the electrode assembly 20, the first dividing part 33 extends beyond the positive electrode starting end 213, so that the first dividing part 33 can have a large coverage area in the winding direction X, reducing the risk of short circuit, improving the safety performance of the cell 100, and when the dividing part 30 is set on the first segment 214, it does not need to be precisely positioned, the positioning accuracy requirement is low, and the process difficulty is reduced.

[0075] Or, such as Figure 4 , Figure 5 As shown, the first end 31 can be flush with the positive electrode starting end 213. In this embodiment, the inner side of the positive electrode starting end 213 refers to the side of the positive electrode starting end 213 closer to the winding center, and the outer side of the positive electrode starting end 213 refers to the side of the positive electrode starting end 213 away from the winding center.

[0076] The first separator 33 is disposed between the positive electrode starting end 213 and the negative electrode plate 22 closest to the positive electrode starting end 213. The first separator 33 is connected to the negative electrode plate 22, or the first separator 33 is connected to the first segment 214, or the first separator 33 is connected to the separator membrane 23.

[0077] In this embodiment, one of the negative electrode sheet 22, the separator 23 and the first segment 214 has a first surface Q. Along the thickness direction of the first partition 33, the first partition 33 has a second surface 331 and a third surface 332 facing each other. The second surface 331 is disposed facing the first surface Q and is connected to the first surface Q.

[0078] The surface roughness of the third surface 332 is less than that of the first surface Q. Surface roughness is characterized by the coefficient of sliding friction measured between the material surface being tested and another surface of the same material. For example, the first partition 33 can be divided into a first part and a second part, with one part of the third surface 332 located in the first part and the other part in the second part. The surface roughness of the third surface 332 can be the coefficient of sliding friction measured by the friction between the third surface 332 of the first part and the third surface 332 of the second part. Surface roughness measurement can be performed with reference to standard GB / T 3505-2009.

[0079] By making the surface roughness of the third surface 332 less than that of the first surface Q, the friction between the surfaces that contact the third surface 332 in the thickness direction of the first separator 33 is smaller. Compared with the solution without the separator 30, this solution can reduce the friction force experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of increased indentation caused by the negative electrode 22 on the outer side of the positive electrode starting end 213 lifting up near the positive electrode starting end 213 and hindering the sliding of the positive electrode 21. This improves the safety performance of the cell 100.

[0080] In some embodiments, the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is Ra0.1-Ra0.7.

[0081] For example, the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is Ra0.1, Ra0.15, Ra0.2, Ra0.25, Ra0.3, Ra0.35, Ra0.4, Ra0.45, Ra0.5, Ra0.55, Ra0.6, Ra0.65, Ra0.7, etc., and any range between any two values.

[0082] By ensuring that the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is greater than or equal to Ra0.1, the surface roughness of the third surface 332 is sufficiently smaller than that of the first surface Q. This helps to reduce the frictional force between the third surface 332 and the surface in contact with it, thereby reducing the frictional force experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the frictional force experienced by the outer ring of the negative electrode 22 near the positive electrode starting end 213. The upward tilting of the initial end 213 hinders the slippage of the positive electrode 21, thus increasing the risk of indentation and improving the safety performance of the cell 100. By ensuring that the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is less than or equal to Ra0.7, the surface roughness of the third surface 332 is not too small compared to the surface roughness of the first surface Q. This ensures a certain amount of friction between the third surface 332 and the surfaces in contact with it, which helps maintain the relative stability of the various layers of the electrode assembly 20, reduces the risk of lithium plating in the cell 100, and improves the safety performance of the cell 100. Therefore, the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is Ra0.1-Ra0.7, which is beneficial to improving the safety performance of the cell 100.

[0083] In some embodiments, the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is Ra0.2-Ra0.7.

[0084] For example, the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is Ra0.2, Ra0.22, Ra0.26, Ra0.28, Ra0.32, Ra0.34, Ra0.36, Ra0.38, Ra0.42, Ra0.44, Ra0.46, Ra0.48, Ra0.52, Ra0.54, Ra0.56, Ra0.58, Ra0.62, Ra0.64, Ra0.68, Ra0.7, etc., as well as any range between any two values.

[0085] By ensuring that the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is greater than or equal to Ra0.2, the surface roughness of the third surface 332 is smaller than that of the first surface Q. This helps to further reduce the frictional force between the third surface 332 and the surface in contact with it, thereby reducing the frictional force experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of increased indentation due to the negative electrode 22 near the positive electrode starting end 213 lifting up and hindering the sliding of the positive electrode 21, thus improving the safety performance of the cell 100. Therefore, the difference between the surface roughness of the first surface Q and the surface roughness of the third surface 332 is Ra0.2-Ra0.7, which is beneficial to further improving the safety performance of the cell 100.

[0086] In some embodiments, the surface roughness of the first surface Q is Ra0.25-Ra0.8.

[0087] For example, the surface roughness of the first surface Q can be Ra0.25, Ra0.3, Ra0.35, Ra0.4, Ra0.45, Ra0.5, Ra0.55, Ra0.6, Ra0.65, Ra0.7, Ra0.75, Ra0.8, etc., as well as any range between two values.

[0088] By ensuring that the surface roughness of the first surface Q is greater than or equal to Ra0.25, the connection stability between the first surface Q and the second surface 331 of the first separator 33 is improved. By ensuring that the surface roughness of the first surface Q is less than or equal to Ra0.8, the friction between the surfaces in contact with the first surface Q is not excessive, thereby reducing the friction experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of increased indentation due to the negative electrode 22 near the positive electrode starting end 213 lifting and hindering the sliding of the positive electrode 21, thus improving the safety performance of the cell 100. Therefore, a surface roughness of Ra0.25-Ra0.8 for the first surface Q can improve the safety performance of the cell 100 and the connection stability between the separator 30 and the electrode assembly 20.

[0089] In some embodiments, the surface roughness of the third surface 332 is Ra0.05-Ra0.2.

[0090] For example, the surface roughness of the third surface 332 can be Ra0.05, Ra0.06, Ra0.0.07, Ra0.08, Ra0.09, Ra0.1, Ra0.11, Ra0.12, Ra0.13, Ra0.14, Ra0.15, Ra0.16, Ra0.17, Ra0.18, Ra0.19, Ra0.2, etc., as well as a range between any two values.

[0091] With the surface roughness of the third surface 332 being greater than or equal to Ra0.05, there is a certain friction between the third surface 332 and the surface in contact with it. This helps to maintain the relative stability of each layer of the electrode assembly 20, reduces the risk of lithium plating in the cell 100, and improves the safety performance of the cell 100. With the surface roughness of the third surface 332 being less than or equal to Ra0.2, the friction between the third surface 332 and the surface in contact with it is not too large. This reduces the friction force experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of increased indentation caused by the negative electrode 22 outside the positive electrode starting end 213 lifting up near the positive electrode starting end 213 and hindering the sliding of the positive electrode 21. This improves the safety performance of the cell 100. Therefore, the surface roughness of the third surface 332 is Ra0.05-Ra0.2, which gives the battery cell 100 good safety performance.

[0092] like Figures 2-5 As shown, in some embodiments, the surface of the negative electrode 22 facing the winding center of the electrode assembly 20 includes a first surface Q.

[0093] The first surface Q is a portion of the surface of the negative electrode 22 facing the winding center. The first surface Q is also part or all of the surface of the negative electrode 22 closest to the positive electrode starting end 213 on the outer side of the positive electrode starting end 213 facing the winding center. The first separator 33 connects to the surface of the negative electrode 22 on the outer side of the positive electrode starting end 213 facing the winding center.

[0094] The surface of the negative electrode 22 facing the winding center of the electrode assembly 20 includes a first surface Q. The first separator 33 is connected to the negative electrode 22. The third surface 332 of the separator 30 is in contact with the surface of the separator 23. The surface roughness of the third surface 332 is less than that of the first surface Q. Compared with the scheme where the first surface Q and the separator 23 are in direct contact, the frictional force of the surface contact between the third surface 332 and the separator 23 is smaller. This can reduce the frictional force experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of increased indentation caused by the negative electrode 22 outside the positive electrode starting end 213 lifting up near the positive electrode starting end 213 and hindering the sliding of the positive electrode 21. This improves the safety performance of the cell 100. Furthermore, the first partition 33 can enhance the strength of the negative electrode 22 and support the negative electrode 22 on the side of the negative electrode 22 facing the winding center, thereby alleviating the problem of cell 100 sinking and improving the safety performance of cell 100.

[0095] like Figure 6 , Figure 7 As shown, in an embodiment where the first partition 33 is connected to the negative electrode plate 22, the first partition 33 is connected to the surface of the negative electrode active material layer 222 facing away from the negative electrode current collector 221. In some embodiments, along the extension direction of the winding axis of the electrode assembly 20, the width of the first partition 33 is W1, the width of the negative electrode active material layer 222 is W2, and 0.7≤W1 / W2≤0.95.

[0096] W1 is the dimension of the first partition 33 in the Y direction of the winding axis of the electrode assembly 20. W2 is the dimension of the negative electrode active material layer 222 in the Y direction of the winding axis of the electrode assembly 20.

[0097] For example, W1 / W2 can be 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, etc., as well as a range between any two values.

[0098] With W1 / W2 greater than or equal to 0.7, the first separator 33 has a larger coverage area in the winding axis direction Y, which reduces the risk of short circuit caused by the positive electrode starting end 213 puncturing the separator 23, improving the safety performance of the cell 100. It also makes the connection area between the first separator 33 and the negative electrode 22 larger, improving the connection stability between the negative electrode 22 and the separator 30. With W1 / W2 less than or equal to 0.95, the size of the first separator 33 in the winding axis direction Y is not too large, reducing the space occupied by the separator 30 and reducing energy density loss, so that the cell 100 has a higher energy density. Therefore, 0.7≤W1 / W2≤0.95 makes the cell 100 have both high safety and high energy density, and also makes the connection stability between the first separator 33 and the negative electrode 22 better.

[0099] like Figures 8-11 As shown, the isolation membrane 23 includes a first surface Q.

[0100] The first surface Q can be at least a portion of the surface of the separator 23 facing away from the winding center (e.g., Figure 8 , Figure 9 As shown), the first surface Q can also be at least a portion of the surface of the separator 23 facing the winding center (e.g. Figure 10 , Figure 11 (As shown). Wherein, when the first separator 33 is connected to the separator 23, in the opposite direction to the winding direction X, the first separator 33 can extend beyond the positive electrode starting end 213 (as shown). Figures 8-11 (as shown); in some other embodiments, the first end 31 of the first partition 33 may also be flush with the positive electrode starting end 213.

[0101] The separator 23 includes a first surface Q. The first separating portion 33 is connected to the separator 23. The third surface 332 of the first separating portion 33 is in contact with the surface of the positive electrode 21, or the third surface 332 of the first separating portion 33 is in contact with the surface of the negative electrode 22. The surface roughness of the third surface 332 is less than the surface roughness of the first surface Q. Compared to the scheme where the first surface Q and the surface of the positive electrode 21 are in direct contact, or compared to the scheme where the first surface Q and the surface of the negative electrode 22 are in contact, the third surface 332 and the surface of the positive electrode 21 are in contact. The frictional force of the surface contact of 1 or the frictional force of the surface contact between the third surface 332 and the negative electrode 22 is small, which can reduce the frictional force on the positive electrode 21 relative to the negative electrode 22 when it slides in the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of increased indentation caused by the negative electrode 22 on the outer side of the positive electrode starting end 213 lifting up near the positive electrode starting end 213 and hindering the sliding of the positive electrode 21, thus improving the safety performance of the cell 100.

[0102] like Figure 10 , Figure 11 As shown, the surface of the separator 23 facing the winding center of the electrode assembly 20 includes a first surface Q. That is, the first surface Q is at least a portion of the surface of the separator 23 facing the winding center of the electrode assembly 20.

[0103] The surface of the separator 23 facing the winding center of the electrode assembly 20 includes a first surface Q. The first separator 33 is connected to the surface of the separator 23 facing the winding center of the electrode assembly 20. This reduces the risk of excessive compression of each layer of the electrode assembly 20 due to the separation member 30. It is beneficial to improve the wetting efficiency of the electrode assembly 20 and to ensure that the electrode assembly 20 is fully wetted, thereby improving the cycle performance of the cell 100.

[0104] like Figure 12 , Figure 13 As shown, in some embodiments, the surface of the first segment 214 facing away from the winding center of the electrode assembly 20 includes a first surface Q.

[0105] That is, the first surface Q is at least a portion of the surface of the first segment 214 that is away from the winding center of the electrode assembly 20.

[0106] The surface of the first segment 214 away from the winding center of the electrode assembly 20 includes a first surface Q. The first separating portion 33 is connected to the surface of the first segment 214 away from the winding center of the electrode assembly 20. The third surface 332 of the first separating portion 33 is disposed opposite to the surface of the first segment 214 away from the winding center. The third surface 332 contacts the surface of the separator 23 facing the first segment 214 away from the winding center. The surface roughness of the third surface 332 is less than the surface roughness of the first surface Q. Compared to the separator 23 and the first segment 214... With the surface contact scheme away from the winding center, the friction between the third surface 332 and the surface of the separator 23 is smaller, reducing the resistance encountered by the positive electrode 21 when it slides along the winding direction X. This allows the positive electrode 21 to slide smoothly relative to the negative electrode 22 in the winding direction X, reducing the risk of further indentation caused by the negative electrode 22 on the outer ring of the positive electrode starting end 213 lifting up near the positive electrode starting end 213 and hindering the sliding of the positive electrode 21. This improves the safety performance of the cell 100.

[0107] In an embodiment where the surface of the first segment 214 away from the winding center of the electrode assembly 20 includes a first surface Q, the first surface Q is at least a portion of the surface of the positive active material layer 212 outside the positive current collector 211 located in the first segment 214 away from the winding center, and the first partition 33 is connected to the surface of the positive active material layer 212 outside the positive current collector 211 located in the first segment 214 away from the winding center.

[0108] likeFigure 14 , Figure 15 As shown, in some embodiments, along the extension direction of the winding axis of the electrode assembly 20, the width of the first partition 33 is W1, the width of the positive electrode active material layer 212 is W3, and 0.7≤W1 / W3≤0.95.

[0109] W3 is the dimension of the positive electrode active material layer 212 in the Y direction of the winding axis of the electrode assembly 20.

[0110] For example, W1 / W3 can be 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, etc., as well as a range between any two values.

[0111] With W1 / W3 greater than or equal to 0.7, the first separator 33 has a larger coverage area in the winding axis direction Y, which reduces the risk of short circuit caused by the positive electrode starting end 213 puncturing the separator 23, improving the safety performance of the cell 100. It also makes the connection area between the first separator 33 and the positive electrode 21 larger, improving the connection stability between the positive electrode 21 and the separator 30. With W1 / W3 less than or equal to 0.95, the size of the first separator 33 in the winding axis direction Y is not too large, reducing the space occupied by the separator 30 and reducing energy density loss, so that the cell 100 has a higher energy density. Therefore, 0.7≤W1 / W3≤0.95 makes the cell 100 have both high safety and high energy density, and also makes the connection stability between the first separator 33 and the positive electrode 21 better.

[0112] like Figures 16-19 As shown, in some embodiments, the separator 30 further includes a second separator 34, the second separator 34 and the first separator 33 are located on both sides of the first segment 214, and the first separator 33 and the second separator 34 are connected.

[0113] The first dividing part 33 is connected to the surface of the first segment 214 away from the winding center, and the second dividing part 34 is connected to the surface of the second segment facing the winding center.

[0114] The second partition 34 and the first segment 214 can be bonded together by adhesive or adsorption.

[0115] The second partition 34 and the first partition 33 are located on both sides of the first segment 214, respectively. The first partition 33 and the second partition 34 are connected to each other, increasing the connection area between the partition 30 and the first segment 214 and improving the connection stability between the first segment 214 and the partition 30.

[0116] like Figure 18 , Figure 19As shown, in some embodiments, the separator 30 further includes a third separator 35, which faces the positive electrode starting end 213 and connects to the first separator 33 and the second separator 34. Connecting the first separator 33 and the second separator 34 via the third separator 35 increases the connection area between the separator 30 and the first segment 214, improving the connection stability between the first segment 214 and the separator 30. The third separator 35, facing the positive electrode starting end 213 and connecting to the first separator 33 and the second separator 34, allows the first separator 33 to cover the edge of the positive electrode starting end 213, reducing the risk of short circuit caused by the positive electrode starting end 213 puncturing the insulation, and improving the safety performance of the cell 100.

[0117] The first partition 33 and the second partition 34 are connected by a third partition 35. In the opposite direction to the winding direction X, the first partition 33 has a first region 333 extending beyond the positive electrode starting end 213, and the second partition 34 has a second region 341 extending beyond the positive electrode starting end 213. The first region 333 and the second region 341 are disposed opposite each other in the thickness direction of the first partition 33. The third partition 35 connects the surface of the first region 333 facing the second region 341 and the surface of the second region 341 facing the first region 333. Figure 19 In the middle, P1 is the boundary between the first region 333 of the first dividing part 33 that extends beyond the positive electrode starting end 213 and the region that overlaps with the first segment 214, and P2 is the boundary between the second region 341 of the second dividing part 34 that extends beyond the positive electrode starting end 213 and the region that overlaps with the first segment 214.

[0118] In the winding direction X, the third separator 35 and the positive electrode starting end 213 can be spaced apart. The third separator 35 and the positive electrode starting end 213 can also be attached but not connected. Of course, the third separator 35 and the positive electrode starting end 213 can also be connected, such as by adhesive bonding or adsorption. The third connecting part connects the first separator 33 and the second separator 34, so the separator 30 can cover at least a portion of the edge of the positive electrode starting end 213 (at least a portion of the first edge 2131 and at least a portion of the second edge 2132), thus eliminating the risk of the edge of the positive electrode starting end 213 piercing the separator 23 and causing a short circuit in the cell 100.

[0119] The first partition 33, the second partition 34, and the third partition 35 can be separately installed and connected.

[0120] The first partition 33, the second partition 34, and the third partition 35 can also be integrally formed, so that the partition 30 has better mechanical properties.

[0121] like Figure 18 , Figure 19As shown, in the embodiment where the first partition 33, the second partition 34, and the third partition 35 are integrally formed, the extended surface of the surface where the first partition 33 connects to the first segment 214 can serve as the boundary between the first partition 33 and the third partition 35, i.e., the surface shown in Q1 in the figure. Similarly, the extended surface of the surface where the second partition 34 connects to the first segment 214 can serve as the boundary between the second partition 34 and the third partition 35, i.e., the surface shown in Q2 in the figure.

[0122] like Figure 6 , Figure 7 ,like Figure 14 , Figure 15 As shown, along the winding direction X of the electrode assembly 20, the size of the first partition 33 is L, 3mm≤L≤10mm.

[0123] L can be the length measured when the positive electrode 21, the negative electrode 22, and the separator 23 are in the unfolded state.

[0124] For example, L can be 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, etc.

[0125] By ensuring that L is greater than or equal to 3 mm, the first separator 33 has a larger dimension in the winding direction X, resulting in a larger coverage area. This reduces the risk of short circuits, improves the safety performance of the cell 100, and also increases the connection area between the first separator 33 and the electrode assembly 20, enhancing the connection stability of the separator 30. Conversely, by ensuring that L is less than or equal to 10 mm, the dimension of the first separator 33 in the winding direction X is not excessively large, reducing the space occupied by the separator 30 and minimizing energy density loss due to its placement. Therefore, 3 mm ≤ L ≤ 10 mm results in the cell 100 exhibiting both good safety performance and high energy density.

[0126] In some embodiments, such as Figure 19 As shown, the innermost electrode of the electrode assembly 20 can be part of the positive electrode 21.

[0127] In other embodiments, such as Figure 20 , Figure 21 As shown, the innermost electrode of the electrode assembly 20 is part of the negative electrode 22. This arrangement helps reduce the risk of lithium plating in the cell 100 and improves the safety performance of the cell 100.

[0128] This application also provides an electrical device, which includes the battery cell 100 provided in any of the above embodiments. The battery cell 100 provides electrical energy to the electrical device.

[0129] The battery cell 100 provided in any of the above embodiments has good safety performance, which is conducive to improving the power safety and reliability of electrical equipment powered by the battery cell 100.

[0130] The electrode indentation distance of electrode assembly 20 is tested as follows: The battery cell 100 was subjected to charge-discharge cycle testing at an ambient temperature of 25°C. The charge-discharge voltage range was 2.5V to 4.2V. It was charged to 4.2V with a constant current of 6A, then charged to 0.05C with a constant voltage of 4.2V and left to stand for 5 minutes. Then it was discharged to 2.5V with a constant current of 30A. The above charge-discharge process was repeated 200 times. After the battery was fully charged, industrial computed tomography (CT, Zeiss Xradia 620 Versa) was used to perform a CT scan of the wound electrode assembly 20 along the radial direction (one or more directions perpendicular to the winding axis P of the electrode assembly 20). The distance from the position where the electrode assembly 20 shows indentation to the position where the innermost electrode sheet has the maximum indentation is the indentation distance.

[0131] Through the above tests, compared with the cell 100 without the separator 30, the electrode assembly 20 of the cell 100 with the separator 30 has a significantly reduced degree of electrode indentation.

[0132] Example 1: (1) Preparation of positive electrode 21 The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.9 Co 0.5 Mn 0.5 O2), polyvinylidene fluoride (PVDF) binder, and conductive carbon black were dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 97.1:1.6:1.3 and thoroughly mixed to obtain a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector 211 (such as aluminum foil) with a thickness of 13 μm and dried at 105 °C to obtain a positive electrode sheet 21 with a first positive electrode material layer coated on one side. Then, the above steps were repeated on the other surface of the positive electrode current collector 211 to obtain a positive electrode sheet 21 with a first positive electrode material layer and a second positive electrode material layer coated.

[0133] The coating weights of the first and second cathode material layers are 196.5 mg / 1540.25 mm, respectively. 2 The compacted density is 3.57 g / cm³. 3The positive electrode 21 has a size of 64.5mm×1688mm, the first positive electrode material layer has a size of 60mm×1688mm, the second positive electrode material layer has the same size as the first positive electrode material layer, and the width of the empty foil area of ​​the positive electrode 21 is 4.5mm.

[0134] (2) Preparation of negative electrode 22 Artificial graphite (anode active material), silicon carbide (SiC) (anode active material), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 82.45:14.55:1.7:1.3. Deionized water was then added as a solvent, and the mixture was stirred until homogeneous, yielding a negative electrode slurry with a solid content of 50 wt%. This negative electrode slurry was uniformly coated onto one surface of a 6 μm thick negative electrode current collector 221 (e.g., copper foil), and dried at 105 °C to obtain a negative electrode sheet 22 with a single-sided coating of the first negative electrode material layer. The above steps were then repeated on the other surface of the same current collector 221 to obtain a negative electrode sheet 22 coated with both the first and second negative electrode material layers. After cold pressing, cutting, and slitting, negative electrode sheets 22 with dimensions of 67.45 mm × 1730 mm were obtained for later use. The coating weights of the first and second negative electrode material layers were 78 mg / 1540.25 mm, respectively. 2 The first negative electrode material layer has a size of 62mm × 1730mm, the second negative electrode material layer has the same size as the first negative electrode material layer, and the width of the empty foil area of ​​the negative electrode sheet 22 is 5.45mm.

[0135] (3) Separating membrane 23 A polyethylene (PE) film with a thickness of 12 μm was used as the separator 23.

[0136] (4) Preparation of electrolyte In a dry argon-atmospheric glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to obtain a base solvent. Lithium hexafluorophosphate (LiPF6) was then added to the base solvent and mixed thoroughly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, with the remainder being the base solvent.

[0137] (5) Preparation of cell 100 The separator 23, negative electrode 22, separator 23, and positive electrode 21 prepared above are stacked sequentially and pre-wound to ensure that the separator 23 is positioned between the negative electrode 22 and the positive electrode 21, while ensuring that the first positive electrode material layer is away from the center of the pre-wound electrode assembly 20, and that the first segment 214 in the first positive electrode material layer is located close to the center of the pre-wound electrode assembly 20. Then, a separator 30 (first separator 33) (5 mm in length and 30 μm in thickness along the winding direction) is attached to the surface of the first segment 214 of the positive electrode 21 away from the winding center P. Along the opposite direction of the winding direction X, the separator 30 (first separator 33) extends beyond the positive electrode starting end 213 by 2 mm.

[0138] The electrode assembly 20 obtained above is subjected to transfer welding, casing, inkjet printing, vacuum drying, electrolyte injection, sealing, high-temperature standing, and capacity formation to obtain a lithium-ion battery (cell 100). The upper limit of the formation voltage is 3.6V, the formation temperature is 45℃, and after formation, it is left to stand at room temperature (25℃) for 24 hours.

[0139] Examples 2 to 5 are basically the same as Example 1 above, except that the roughness of the first or third surface is changed with reference to Table 1.

[0140] Examples 6-7: Basically the same as Example 1 above, except that the position of the separator 30 (first separator 33) is different, and along the radial direction of the electrode assembly 20, the separator 30 is opposite to the winding start end 213 of the positive electrode sheet 21.

[0141] Comparative Example 1: It is basically the same as Example 1 above, except that the electrode assembly 20 does not have a separator 30.

[0142] The indentation distance of the battery cells 100 of Examples 1-7 and Comparative Example 1 were tested, and the test results are listed in Table 1.

[0143] Table 1

[0144] As can be seen from Table 1 above: (1) According to Comparative Example 1 and Examples 1 to 6, after the separator 30 is provided, the indentation distance of the battery cell 100 is significantly reduced, and the safety performance of the battery cell 100 is better. The specific reason is that the friction force experienced by the positive electrode 21 relative to the negative electrode 22 when sliding in the winding direction X is reduced, so that the positive electrode 21 can slide smoothly relative to the negative electrode 22 in the winding direction X, and the friction force caused by the negative electrode 22 on the outer side of the positive electrode starting end 213 near the positive electrode starting end 213 is reduced. The risk of increased indentation due to the obstruction of the positive electrode 21's slippage is reduced by the addition of the separator 30, which improves the safety performance of the battery cell. As can be seen from Comparative Example 1 and Example 7, the indentation distance of the battery cell 100 is reduced after the separator 30 is provided, resulting in better safety performance of the battery cell 100. The main reason is that the separator 30 can enhance the strength of the negative electrode 22 and support the negative electrode 22 on the side facing the winding center, thereby alleviating the indentation problem of the battery cell 100 and improving its safety performance.

[0145] (2) According to Examples 1-5, when the surface roughness of the first surface Q is Ra0.25-Ra0.8, the indentation distance of the cell 100 is smaller. Therefore, when the surface roughness of the first surface Q is Ra0.25-Ra0.8, the safety performance of the cell 100 is better.

[0146] (3) According to Embodiment 1 and Embodiment 6, when the separator 30 is disposed on the surface of the first segment 214 away from the winding center, the indentation of the cell 100 is smaller and the safety of the cell 100 is better.

[0147] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art.

Claims

1. A battery cell, characterized in that, include: An electrode assembly, wherein the electrode assembly is a wound structure, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the separator insulatingly separating the positive electrode sheet and the negative electrode sheet, the positive electrode sheet having a positive starting end, the positive electrode sheet including a first segment wound once from the positive starting end along the winding direction of the electrode assembly; The separator includes a first separator located outside the first segment, the first separator separating the positive electrode starting end and the negative electrode sheet, one of the negative electrode sheet, the separator and the first segment having a first surface, the first separator having opposing second and third surfaces along the thickness direction of the first separator, the second surface being disposed facing the first surface and connected to the first surface, the surface roughness of the third surface being less than the surface roughness of the first surface.

2. The battery cell according to claim 1, characterized in that, The difference between the surface roughness of the first surface and the surface roughness of the third surface is Ra0.1-Ra0.7, preferably Ra0.2-Ra0.

7.

3. The battery cell according to claim 1 or 2, characterized in that, The surface roughness of the first surface is Ra0.25-Ra0.8; and / or the surface roughness of the third surface is Ra0.05-Ra0.

2.

4. The battery cell according to any one of claims 1-3, characterized in that, The surface of the negative electrode sheet facing the winding center of the electrode assembly includes the first surface.

5. The battery cell according to claim 4, characterized in that, The negative electrode sheet includes a negative electrode active material layer. Along the extension direction of the winding axis of the electrode assembly, the width of the first partition is W1, the width of the negative electrode active material layer is W2, and 0.7≤W1 / W2≤0.

95.

6. The battery cell according to any one of claims 1-3, characterized in that, The isolation membrane includes the first surface.

7. The battery cell according to claim 6, characterized in that, The surface of the insulating membrane facing the winding center of the electrode assembly includes the first surface.

8. The battery cell according to any one of claims 1-3, characterized in that, The first surface, which is away from the winding center of the electrode assembly, includes the first surface.

9. The battery cell according to claim 8, characterized in that, The positive electrode includes a positive active material layer. Along the extension direction of the winding axis of the electrode assembly, the width of the first partition is W1, the width of the positive active material layer is W3, and 0.7≤W1 / W3≤0.

95.

10. The battery cell according to claim 8, characterized in that, The separator further includes a second separator portion, which and the first separator portion are located on opposite sides of the first segment, and the first separator portion and the second separator portion are connected.

11. The battery cell according to claim 10, characterized in that, The separator further includes a third separator, which is disposed facing the positive electrode starting end and connects the first separator and the second separator.

12. The battery cell according to claim 11, characterized in that, The first partition, the second partition, and the third partition are integrally formed.

13. The battery cell according to any one of claims 1-12, characterized in that, In the opposite direction to the winding direction of the electrode assembly, the first dividing portion extends beyond the positive electrode starting end.

14. The battery cell according to any one of claims 1-13, characterized in that, Along the winding direction of the electrode assembly, the size of the first dividing portion is L, where 3mm ≤ L ≤ 10mm.

15. The battery cell according to any one of claims 1-14, characterized in that, The separator is adhesive tape.

16. The battery cell according to any one of claims 1-15, characterized in that, The innermost electrode of the electrode assembly is part of the negative electrode.

17. The battery cell according to any one of claims 1-16, characterized in that, The battery cell is a cylindrical battery cell.

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

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