Battery cells, electrode assemblies, batteries, and electrical devices

Abstract

This application relates to a battery cell, an electrode assembly, a battery, and an electrical device. The battery cell includes a casing, an electrode assembly, and an end cap assembly. The electrode assembly includes a first electrode, a second electrode, and a separator with opposite polarities. The first electrode, the second electrode, and the separator are wound along a winding direction to form a winding structure, which includes a straight region and a bending region. The first electrode includes a first current collector and a first active material layer connected together. The first current collector includes a base portion and a thickened portion. The thickened portion is located in the bending region and extends a predetermined length into the straight region. The base portion is located in the straight region and connected to the thickened portion. The thickness of the thickened portion is greater than the thickness of the base portion and protrudes from the base portion. The first active material layer covers the base portion and the thickened portion. The electrode assembly, battery cell, battery, and electrical device provided by this application can reduce the short-circuit risk of the battery cell and ensure the overall reliability of the battery cell.

Description

Battery cell, electrode assembly, battery and electric device TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a battery cell, an electrode assembly, a battery and an electric device. BACKGROUND

[0002] Energy saving and emission reduction is the key to the sustainable development of the automobile industry. Electric vehicles have become an important part of the sustainable development of the automobile industry due to their energy saving and environmental protection advantages. For electric vehicles, battery technology is an important factor for their development.

[0003] In the related art, the electrode assembly of the battery cell, the current collector of the pole piece is easy to separate from the active material layer, causing short circuit of the battery cell, affecting the reliability of the whole battery cell.

[0004] SUMMARY

[0005] The embodiments of the present application provide a battery cell, an electrode assembly, a battery and an electric device, which can reduce the risk of short circuit of the electrode cell and ensure the reliability of the whole battery cell.

[0006] In one aspect, according to an embodiment of the present application, a battery cell is provided, comprising: a shell having a receiving cavity;

[0007] An electrode assembly is arranged in the receiving cavity, the electrode assembly comprising a first pole piece, a second pole piece and a separator with opposite polarities, the first pole piece, the second pole piece and the separator being wound to form a winding structure along a winding direction, the winding structure comprising a flat area and a bending area; an end cover assembly covering the shell and electrically connected with the electrode assembly; wherein the first pole piece comprises a first current collector and a first active material layer connected with each other, the first current collector comprising a base portion and a thickened portion, the thickened portion being located in the bending area and extending to the flat area by a predetermined length, the base portion being located in the flat area and connected with the thickened portion, the thickness of the thickened portion being greater than the thickness of the base portion and protruding from the base portion, and the first active material layer covering the base portion and the thickened portion.

[0008] The battery cell provided by one embodiment of the present application is characterized in that the first pole piece comprises a first current collector and a first active material layer, the first current collector comprises a base portion and a thickened portion, the thickened portion is located at the bending area and extends to the flat area by a predetermined length, the base portion is located at the flat area and is connected with the thickened portion, the thickness of the thickened portion is greater than that of the base portion and protrudes from the base portion, so that the thickened portion and the base portion have a thickness difference and form a step, the first active material layer covers the base portion and the thickened portion, so that the first active material layer can be embedded in the first current collector, the first active material layer and the first current collector are bound to each other, the position of the first active material layer is fixed, and the first active material layer and the first current collector are prevented from being displaced and disengaged. The first active material layer covers the thickened portion, which not only covers the surface in the stacking direction, but also covers the side wall surface located in the winding direction and protruding from the base portion. The contact surface between the first active material layer and the first current collector at the step of the thickened portion can provide a certain normal friction force, improve the connection strength of the first active material layer and the first current collector, reduce the probability of separation of the first active material layer and the first current collector, improve the comprehensive performance and stability of the first pole piece, and further reduce the risk of short circuit of the battery cell, thereby ensuring the reliability of the battery cell as a whole.

[0009] According to one aspect of the embodiment of the present application, in the stacking direction of the first pole piece, the second pole piece and the separator, the two sides of the thickened portion protrude from the base portion.

[0010] The battery cell provided by one embodiment of the present application is characterized in that the first current collector in the stacking direction is covered by the first active material layer on each side, and the two sides of the thickened portion protrude from the base portion in the stacking direction, so that the first active material layer on the two sides of the first current collector and the first current collector can be bound to each other, the connection strength of the two is improved, and the probability of separation of the first active material layer and the first current collector is reduced.

[0011] According to one aspect of the embodiment of the present application, in the stacking direction, the thickness of the thickened portion protruding from the base portion on the two sides is equal.

[0012] By making the thickness of the thickened portion protruding from the base portion on the two sides equal, the thickness size requirement of the thickened portion protruding from the base portion on the two sides can be ensured, and the requirements of limiting separation and connection strength of the first active material layer on the two sides are ensured. At the same time, the above-mentioned setting can also ensure the consistency of the thickness of the first active material layer on the two sides of the first current collector, which is beneficial to ensuring the electrical performance of the first pole piece.

[0013] According to one aspect of the embodiment of the present application, in the stacking direction, the size of the thickened portion protruding from the base portion is d, and the thickness of the base portion is D, wherein 1 / 5≤d / D≤3 / 5.

[0014] The battery cell provided by one embodiment of the present application adopts the above value range of d / D, which can ensure that the size of the thickened part protruding from the base part is moderate, thereby ensuring the binding effect on the first active material layer.

[0015] According to one aspect of the embodiments of the present application, the thickened part includes a first part and a second part distributed along the winding direction, the first part is located in the bending area, and the second part is located in the flat area, and the extension length of the second part in the winding direction is H, where 0.5mm≤H≤25mm.

[0016] The battery cell provided by one embodiment of the present application can improve the ductility range of the first current collector in the bending area while fixing the position of the first active material layer in the flat area, effectively reduce the probability of separation of the first current collector and the first active material layer, and improve the comprehensive performance of the flat area and the bending area of the first pole piece. At the same time, the extension size of the second part in the flat area is moderate, so that the base part can be coated with more first active material than the un-thickened part of the protruding part, the corresponding first active material layer at this position is thicker, and the energy density of the electrode assembly is improved.

[0017] According to one aspect of the embodiments of the present application, the first current collector further includes a plurality of concave-convex structures, the plurality of concave-convex structures are located in the flat area and are arranged at intervals, and the concave-convex structures are arranged on at least one of the base part and the thickened part.

[0018] The battery cell provided by one embodiment of the present application can increase the contact area of the first active material layer and the first current collector, improve the contact force of the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis, fix the position of the first active material layer, and prevent the occurrence of interlayer cracks due to excessive shear strength of the first active material layer accumulated during use.

[0019] According to one aspect of the embodiments of the present application, the base part is provided with concave-convex structures on both sides in the stacking direction of the first pole piece, the second pole piece, and the separator; and / or the thickened part is provided with concave-convex structures on both sides.

[0020] The battery cell provided by one embodiment of the present application is provided with a first active material layer on both sides of the first current collector in the stacking direction. By providing the base portion and / or the thickened portion with the concave-convex structure on both sides in the stacking direction, the contact area of the first active material layer and the first current collector on each side can be increased, and the contact force of the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis can be improved.

[0021] According to one aspect of the embodiments of the present application, the base portion is provided with the concave-convex structure on both sides in the stacking direction; and / or the thickened portion is provided with the concave-convex structure on both sides.

[0022] The battery cell provided by one embodiment of the present application is provided with a first active material layer on both sides of the first current collector in the stacking direction. By providing the base portion and / or the thickened portion with the concave-convex structure on both sides in the stacking direction, the contact area of the first active material layer and the first current collector on each side can be increased, and the contact force of the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis can be improved.

[0023] According to one aspect of the embodiments of the present application, each concave-convex structure comprises a convex portion, and a plurality of convex portions are arranged at intervals, and the orthogonal projection of the convex portion in the stacking direction is circular, elliptical or polygonal.

[0024] The battery cell provided by one embodiment of the present application is provided with a first active material layer on both sides of the first current collector in the stacking direction. By providing the base portion and / or the thickened portion with the concave-convex structure on both sides in the stacking direction, the contact area of the first active material layer and the first current collector on each side can be increased, and the contact force of the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis can be improved.

[0025] According to one aspect of the embodiments of the present application, a plurality of concave-convex structures are arranged in groups, each of the concave-convex structures in one group comprises a convex portion, each of the concave-convex structures in one group comprises a concave portion, and the concave portion is formed by concave on at least one of the base portion and the thickened portion.

[0026] The battery cell provided by one embodiment of the present application is provided with a first active material layer on both sides of the first current collector in the stacking direction. By providing the base portion and / or the thickened portion with the concave-convex structure on both sides in the stacking direction, the contact area of the first active material layer and the first current collector on each side can be increased, and the contact force of the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis can be improved.

[0027] According to one aspect of the embodiments of the present application, the first pole piece is wound n turns along the winding direction from inside to outside, each of the first pole pieces from the 1st turn to the mth turn has a thickened portion, n > m, and 3 ≤ m ≤ 5.

[0028] The battery cell provided by one embodiment of the present application can reduce the probability of separation and demolding of the inner first current collector and the first active material layer of the electrode assembly, and the above-mentioned setting will not make the thickened size of the bending area and the area adjacent to the bending area of the electrode assembly too large to affect the energy density of the whole electrode assembly, thereby ensuring the use requirement of the battery cell.

[0029] According to one aspect of the embodiment of the present application, the first electrode tab is wound n turns along the winding direction from inside to outside, and each turn of the first electrode tab has a thickened part from the fth turn to the nth turn, where n-5≤f≤n.

[0030] The battery cell provided by one embodiment of the present application can reduce the probability of separation and demolding of the inner first current collector and the first active material layer of the electrode assembly, and the above-mentioned setting will not make the thickened size of the bending area and the area adjacent to the bending area of the electrode assembly too large to affect the energy density of the whole electrode assembly, thereby ensuring the use requirement of the battery cell.

[0031] According to one aspect of the embodiment of the present application, the first electrode tab is a positive electrode tab, and the second electrode tab is a negative electrode tab. Since the separation and demolding risk of the current collector and the active material layer of the positive electrode tab is relatively high, the first electrode tab is a positive electrode tab, which can reduce the separation and demolding risk of the electrode tab of the electrode assembly and improve the reliability of the electrode assembly.

[0032] On the other hand, according to one embodiment of the present application, an electrode assembly is provided, which includes first and second electrode tabs with opposite polarities and a separator. The first and second electrode tabs and the separator are wound to form a winding structure along a winding direction, and the winding structure includes a flat area and a bending area. The first electrode tab includes a first current collector and a first active material layer connected to each other. The first current collector includes a base part and a thickened part. The thickened part is located in the bending area and extends to the flat area by a predetermined length. The base part is located in the flat area and connected to the thickened part. The thickness of the thickened part is greater than that of the base part and protrudes from the base part. The first active material layer covers the base part and the thickened part.

[0033] On the other hand, according to one embodiment of the present application, an electrode assembly is provided, which includes first and second electrode tabs with opposite polarities and a separator. The first and second electrode tabs and the separator are wound to form a winding structure along a winding direction, and the winding structure includes a flat area and a bending area. The first electrode tab includes a first current collector and a first active material layer connected to each other. The first current collector includes a base part and a thickened part. The thickened part is located in the bending area and extends to the flat area by a predetermined length. The base part is located in the flat area and connected to the thickened part. The thickness of the thickened part is greater than that of the base part and protrudes from the base part. The first active material layer covers the base part and the thickened part.

[0034] On the other hand, according to one embodiment of the present application, an electrode assembly is provided, which includes first and second electrode tabs with opposite polarities and a separator. The first and second electrode tabs and the separator are wound to form a winding structure along a winding direction, and the winding structure includes a flat area and a bending area. The first electrode tab includes a first current collector and a first active material layer connected to each other. The first current collector includes a base part and a thickened part. The thickened part is located in the bending area and extends to the flat area by a predetermined length. The base part is located in the flat area and connected to the thickened part. The thickness of the thickened part is greater than that of the base part and protrudes from the base part. The first active material layer covers the base part and the thickened part. BRIEF DESCRIPTION OF DRAWINGS

[0035] The features, advantages, and technical and scientific effects of the exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

[0036] Fig. 1 is a schematic view of a vehicle according to an embodiment of the present application;

[0037] Fig. 2 is a schematic view of a structure of a battery according to an embodiment of the present application;

[0038] Fig. 3 is a schematic view of a structure of a battery cell according to an embodiment of the present application;

[0039] Fig. 4 is a schematic view of a cross section of an electrode assembly according to an embodiment of the present application;

[0040] Fig. 5 is a schematic view of a partial structure of an electrode assembly according to an embodiment of the present application;

[0041] Fig. 6 is a schematic view of a partial structure of an electrode assembly according to another embodiment of the present application;

[0042] Fig. 7 is a schematic view of a partial structure of an electrode assembly according to still another embodiment of the present application;

[0043] Fig. 8 is a schematic view of a partial structure of an electrode assembly according to yet another embodiment of the present application;

[0044] Fig. 9 is a schematic view of a concave-convex structure according to an embodiment of the present application;

[0045] Fig. 10 is a schematic view of a concave-convex structure according to an embodiment of the present application.

[0046] Wherein: 1 - vehicle; 100 - battery; 200 - battery module; 300 - controller; 400 - motor; 10 - case; 11 - first case portion; 12 - second case portion; 20 - battery cell; 21 - end cap assembly; 211 - cover plate; 212 - electrode terminal; 22 - housing; 23 - electrode assembly; 23a - bent region; 23b - flat region; 231 - first tab; 2311 - first current collector; 23111 - base portion; 23112 - thickened portion; 23112a - first portion; 23112b - second portion; 23113 - protruding portion; 23114 - recessed portion; 2312 - first active material layer; 232 - second tab; 2321 - second current collector; 2322 - second active material layer; 233 - separator; X - winding direction; Y - stacking direction. In the drawings, the same components are designated by the same reference numerals. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0047] The technical scheme of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical scheme of the present application, and therefore only serve as examples, but cannot be used to limit the protection scope of the present application.

[0048] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the embodiments of the present application should be understood as the general meaning understood by the skilled in the art to which the embodiments of the present application belong.

[0049] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential” and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0050] In addition, the technical terms “first”, “second” and the like are only for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. In the description of the embodiments of the present application, the meaning of “a plurality of” is two or more, unless otherwise explicitly specified and limited.

[0051] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms “mounting”, “connection”, “connecting”, “fixing” and the like should be understood in a broad sense, for example, can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through an intermediate medium; or can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0052] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the first feature is “on” or “under” the second feature, which can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0053] At present, from the development of market situation, the application of power battery is more and more widely. Power battery is not only applied to energy storage power supply system of water power, thermal power, wind power and solar power station, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, military equipment and aerospace and other fields. With the continuous expansion of the application field of power battery, the demand of its market is also increasing.

[0054] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery monomers to provide higher voltage and capacity. For example, the battery mentioned in the present application can include a battery module or a battery pack, etc.

[0055] The battery monomer includes a shell, an end cover assembly and an electrode assembly, the electrode assembly is arranged in the shell, and the end cover assembly closes the opening of the shell.

[0056] The battery monomer in the related art has the risk of short circuit. Further research shows that during use of the battery monomer, the active material layer of the pole piece is prone to separation from the current collector due to insufficient adhesion, causing the pole piece to produce a film peeling phenomenon, not only causing the performance of the battery monomer to decrease, but also the film layer peeling off may pierce the diaphragm to cause the risk of short circuit of the battery monomer, seriously affecting the reliability of the battery monomer.

[0057] Based on the above consideration, after in-depth research, a kind of battery monomer is designed, including a shell, an electrode assembly and an end cover assembly, the shell has a receiving cavity;The electrode assembly is arranged in the receiving cavity, and the electrode assembly includes first and second pole pieces with opposite polarity and a diaphragm, the first and second pole pieces and the diaphragm are wound to form a winding structure along the winding direction, the winding structure includes a straight area and a bending area;The end cover assembly covers the shell and is electrically connected with the electrode assembly;Wherein, the first pole piece includes a first current collector and a first active material layer connected thereto, the first current collector includes a base portion and a thickened portion, the thickened portion is located in the bending area and extends to the straight area by a predetermined length, the base portion is located in the straight area and connected with the thickened portion, the thickness of the thickened portion is greater than that of the base portion and protrudes from the base portion, and the first active material layer covers the base portion and the thickened portion. The electrode monomer can reduce the probability of separation of the current collector and the active material layer, reduce the risk of short circuit, and ensure the reliability of the whole battery monomer.

[0058] The technical solutions described in the embodiments of the present application are applicable to various devices using motor monomers, for example, mobile phones, portable devices, notebook computers, electric bicycles, electric toys, electric tools, electric vehicles, ships and spacecraft, etc. For example, the spacecraft includes airplanes, rockets, space shuttles and spacecraft, etc.

[0059] It should be understood that the technical solutions described in the embodiments of the present application are not only limited to the above-described devices, but can also be applied to all devices using batteries, but for the sake of brevity, the following embodiments are described with an electric vehicle as an example.

[0060] For example, as shown in FIG. 1, which is a structural schematic diagram of a vehicle 1 according to an embodiment of the present application, the vehicle 1 can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid vehicle, or a range extended vehicle, etc. The vehicle 1 can be provided with a motor 400, a controller 300, and a battery 100 inside, and the controller 300 is used to control the power supply of the battery 100 to the motor 400. For example, the battery 100 can be arranged at the bottom, the front, or the rear of the vehicle 1. The battery 100 can be used for power supply of the vehicle 1, for example, the battery 100 can be used as an operating power source of the vehicle 1, and can be used for the circuit system of the vehicle 1, for example, for the power demand of the vehicle 1 during starting, navigation, and operation. In another embodiment of the present application, the battery 100 can not only be used as an operating power source of the vehicle 1, but also be used as a driving power source of the vehicle 1, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1.

[0061] As shown in FIG. 2 and FIG. 3, in order to meet different power requirements, the battery 100 can include a plurality of battery monomers 20, wherein the plurality of battery monomers 20 can be connected in series, in parallel, or in a mixed connection, and the mixed connection refers to a mixture of series and parallel connection. The battery 100 can also be referred to as a battery pack. Alternatively, the plurality of battery monomers 20 can be connected in series, in parallel, or in a mixed connection to form a battery module 200, and the plurality of battery modules 200 can be connected in series, in parallel, or in a mixed connection to form the battery 100. That is, the plurality of battery monomers 20 can directly form the battery 100, or can first form the battery module 200, and then the battery module 200 forms the battery 100.

[0062] For example, as shown in FIG. 2, which is a structural schematic diagram of a battery 100 according to an embodiment of the present application, the battery 100 can include a plurality of battery monomers 20. The battery 100 can also include a box body 10 (or a cover body), which is a hollow structure, and the plurality of battery monomers 20 are accommodated in the box body 10.

[0063] The box body 10 can be a simple solid structure such as a cuboid, a cylinder, or a sphere, or can be a complex solid structure composed of a cuboid, a cylinder, or a sphere, and the embodiments of the present application are not limited thereto. The material of the box body 10 can be an alloy material such as aluminum alloy or iron alloy, a high polymer material such as polycarbonate or polyisocyanurate foam plastic, or a composite material such as glass fiber and epoxy resin, and the embodiments of the present application are not limited thereto.

[0064] The box 10 is used to accommodate the battery cell 20, and the box 10 can be of various structures. In some embodiments, the box 10 can include a first box part 11 and a second box part 12, the first box part 11 and the second box part 12 are mutually covered, and the first box part 11 and the second box part 12 jointly define an accommodation space for accommodating the battery cell 20. The second box part 12 can be a hollow structure with one end open, and the first box part 11 is a plate-shaped structure, which is covered on the open side of the second box part 12 to form the box 10 with the accommodation space; both the first box part 11 and the second box part 12 can also be a hollow structure with one side open, and the open side of the first box part 11 is covered on the open side of the second box part 12 to form the box 10 with the accommodation space. Of course, the first box part 11 and the second box part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0065] In order to improve the sealing performance of the first box part 11 and the second box part 12 after being connected, a sealing member such as sealing glue, a sealing ring, etc. can be arranged between the first box part 11 and the second box part 12.

[0066] Suppose that the first box part 11 is covered on the top of the second box part 12, the first box part 11 can also be called an upper box cover, and the second box part 12 can also be called a lower box 10.

[0067] In the battery 100, the battery cell 20 can be one or multiple. If the battery cell 20 is multiple, the multiple battery cells 20 can be connected in series, in parallel or in a mixed manner, and the mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel or in a mixed manner, and then the whole of the multiple battery cells 20 is accommodated in the box 10; of course, the multiple battery cells 20 can be first connected in series, in parallel or in a mixed manner to form a battery module 200, and then the multiple battery modules 200 are connected in series, in parallel or in a mixed manner to form a whole, which is accommodated in the box 10.

[0068] In some embodiments, as shown in FIG. 2, the battery cell 20 is multiple, and the multiple battery cells 20 are first connected in series, in parallel or in a mixed manner to form a battery module 200. Then the multiple battery modules 200 are connected in series, in parallel or in a mixed manner to form a whole, which is accommodated in the box 10.

[0069] The multiple battery cells 20 in the battery module 200 can be electrically connected through a busbar component to realize the parallel connection, series connection or mixed connection of the multiple battery cells 20 in the battery module 200.

[0070] In the present application, the battery cell 20 can include a lithium ion battery cell 20, a sodium ion battery cell, or a magnesium ion battery cell, etc., and the embodiments of the present application are not limited thereto. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc., and the embodiments of the present application are not limited thereto. The battery cell 20 is generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells, and soft package battery cells, and the embodiments of the present application are not limited thereto. However, for the sake of simplicity, the following embodiments will be described by taking the cylindrical battery cell 20 as an example.

[0071] As shown in FIG. 3, the battery cell 20 can include a shell 22, an electrode assembly 23, and an end cover assembly 21, the end cover assembly 21 covers the shell 22 and is electrically connected with the electrode assembly 23, and the shell 22 is an assembly for cooperating with the end cover assembly 21 to form an internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, electrolyte (not shown in the figure), and other components. The shell 22 and the end cover assembly 21 can be independent components, and an opening can be provided on the shell 22, and the end cover assembly 21 covers the opening to form the internal environment of the battery cell 20. Without limitation, the end cover assembly 21 and the shell 22 can also be integrated, specifically, the end cover assembly 21 and the shell 22 can form a common connecting surface before other components enter the shell, and when it is necessary to seal the internal environment of the shell 22, the end cover assembly 21 covers the shell 22.

[0072] The shell 22 can be in various shapes and sizes, such as a cuboid, a cylinder, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations thereto.

[0073] The end cover assembly 21 refers to a component that covers the opening of the shell 22 and forms an accommodation cavity with the shell 22, the accommodation cavity is used to accommodate the electrode assembly 23, and the end cover assembly 21 isolates the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cover assembly 21 can be adapted to the shape of the shell 22 to cooperate with the shell 22. Alternatively, the end cover assembly 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that the end cover assembly 21 is not easy to deform when subjected to extrusion and collision, so that the battery cell 20 can have higher structural strength, and the safety performance can also be improved. The end cover assembly 21 can include a cover plate 211 and an electrode terminal 212, the cover plate 211 is mechanically connected with the shell 22, and the electrode terminal 212 is electrically connected with the electrode assembly 23.

[0074] In some embodiments, the battery cell 20 can include a pressure relief mechanism for releasing pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.

[0075] For example, the pressure relief mechanism can be located between the positive electrode terminal and the negative electrode terminal, and can be a component such as a rupture disc, a burst disc, a gas valve, a pressure relief valve, or a safety valve.

[0076] The positive electrode terminal and the negative electrode terminal can be mounted on the same end cap or on different end caps. The pressure relief mechanism can be mounted on one end cap or on both end caps.

[0077] The electrode assembly 23 is a component in which an electrochemical reaction occurs in the battery cell 20. One or more electrode assemblies 23 can be included in the housing 22.

[0078] As shown in FIGS. 4 and 5, in some alternative embodiments, the battery cell 20 according to an embodiment of the present application can include an electrode assembly 23 having first and second polar plates 231 and 232 having opposite polarities and a separator 23. The electrode assembly 23 can be wound in a winding direction X to form a wound structure including flat regions 23b and bent regions 23a. The first polar plate 231 can include a first current collector 2311 and a first active material layer 2312 connected to each other. The first current collector 2311 can include a base portion 23111 and a thickened portion 23112. The thickened portion 23112 can be located at the bent region 23a and extend toward the flat region 23b by a predetermined length. The base portion 23111 can be located at the flat region 23b and connected to the thickened portion 23112. The thickened portion 23112 can have a thickness greater than that of the base portion 23111 and can protrude from the base portion 23111. The first active material layer 2312 can cover the base portion 23111 and the thickened portion 23112.

[0079] One of the first and second polar plates 231 and 232 can be a positive polar plate, and the other can be a negative polar plate. The first and second polar plates 231 and 232 can have the same structure, and the second polar plate 232 can also have a conventional structure including a current collector and an active material layer.

[0080] The separator 23 can be made of PP (polypropylene) or PE (polyethylene), or the like. The separator 23 can be interposed between the first and second polar plates 231 and 232 to insulate the first and second polar plates 231 and 232 from each other.

[0081] The first pole piece 231 and the second pole piece 232 can be wound in multiple turns in the winding direction X, and the first pole piece 231 can include a thickened portion 23112 in at least part of the turns, for example, the first pole piece 231 can include the thickened portion 23112 in each of the turns from the innermost first turn to the innermost third turn in the winding direction X, and of course, the first pole piece 231 can include the thickened portion 23112 in each of the turns from the outermost first turn to the outermost third turn. Of course, the above is only an example, and the first pole piece 231 can include the thickened portion 23112 in more or fewer turns on the innermost side in the winding direction X, or the first pole piece 231 can include the thickened portion 23112 in more or fewer turns on the outermost side in the winding direction X. The first pole piece 231 can include the thickened portion 23112 in each of the turns.

[0082] The flat area 23b of the winding structure is connected with the bending area 23a, and the flat area 23b can be provided with the bending area 23a at both ends. The flat area 23b is an area where the winding structure has a flat structure, and the part of the first pole piece 231 and the part of the second pole piece 232 in the flat area 23b are arranged substantially flat. The bending area 23a is an area where the winding structure has a bending structure, and the part of the first pole piece 231 and the part of the second pole piece 232 in the bending area 23a are arranged in a bending manner. For example, the part of the first pole piece 231 and the part of the second pole piece 232 in the bending area 23a can be in a circular arc shape.

[0083] The thickened portion 23112 is located in the bending area 23a and extends to the flat area 23b by a predetermined length, and the predetermined length can be greater than zero, and the specific length can be set according to the connection strength requirement of the first current collector 2311 and the first active material layer 2312 and the capacity density requirement of the electrode assembly.

[0084] The thickness of the thickened portion 23112 is greater than the thickness of the base portion 23111, and the thickened portion 23112 protrudes from the base portion 23111 in the stacking direction Y of the first pole piece 231, the second pole piece 232 and the separator 23. Or in the radial direction of the winding structure, the thickened portion 23112 protrudes from the base portion 23111. The stacking direction Y can also be understood as the thickness direction of the film layers such as the first pole piece 231, the second pole piece 232 and the separator 23.

[0085] The thickened portion 23112 can protrude from the base portion 23111 on one side of the stacking direction Y, or can protrude from the base portion 23111 on both sides of the stacking direction Y.

[0086] The first active material layer 2312 can be arranged on both sides of the base portion 23111 in the arrangement direction Y and on both sides of the thickened portion 23112 in the arrangement direction Y.

[0087] In one embodiment, the battery cell 20 includes a first pole piece 231 including a first current collector 2311 and a first active material layer 2312. The first current collector 2311 includes a base portion 23111 and a thickened portion 23112. The thickened portion 23112 is located in the bending area 23a and extends to the flat area 23b by a predetermined length. The base portion 23111 is located in the flat area 23b and is connected to the thickened portion 23112. The thickened portion 23112 has a thickness greater than that of the base portion 23111 and protrudes from the base portion 23111. The thickened portion 23112 and the base portion 23111 have a thickness difference and form a step. The first active material layer 2312 is arranged on the base portion 23111 and the thickened portion 23112. The first active material layer 2312 can be embedded in the first current collector 2311. The first active material layer 2312 and the first current collector 2311 are bound to each other. The position of the first active material layer 2312 is fixed, and displacement of the first active material layer 2312 from the first current collector 2311 is avoided. The first active material layer 2312 is arranged on the thickened portion 23112. The first active material layer 2312 covers not only the surface in the stacking direction Y but also the side wall surface protruding from the base portion 23111 in the winding direction X. The contact surface between the first active material layer 2312 and the first current collector 2311 at the step can provide a certain normal friction force, improve the connection strength between the first active material layer 2312 and the first current collector 2311, reduce the probability of separation of the first active material layer 2312 from the first current collector 2311, improve the comprehensive performance and stability of the first pole piece 231, and further reduce the risk of short circuit of the battery cell 20, thereby ensuring the reliability of the battery cell 20.

[0088] In some optional embodiments, the battery cell 20 includes a first pole piece 231, a second pole piece 232, and a separator 23. The thickened portion 23112 protrudes from the base portion 23111 on both sides in the stacking direction Y.

[0089] The size of the thickened portion 23112 protruding from the base portion 23111 on both sides in the stacking direction Y can be equal, or the size of the thickened portion 23112 protruding from the base portion 23111 on one side can be greater than the size of the thickened portion 23112 protruding from the base portion 23111 on the other side.

[0090] The battery cell 20 provided by one of the embodiments of the present application is covered with the first active material layer 2312 on each side of the first current collector 2311 in the stacking direction. The two sides of the thickened portion 23112 are arranged to protrude from the base portion 23111 in the stacking direction, so that the first active material layers 2312 on the two sides of the first current collector 2311 can be bound to the first current collector 2311, the connection strength is improved, and the probability of separation of the first current collector 2311 and the first active material layer 2312 is reduced.

[0091] In some optional embodiments, the battery cell 20 provided by one of the embodiments of the present application is arranged such that the thickness of the two sides of the thickened portion 23112 protruding from the base portion 23111 is equal in the stacking direction Y.

[0092] Since the thicknesses of the first current collector 2311 and the first active material layer 2312 are relatively small, the thicknesses of the two sides of the thickened portion 23112 protruding from the base portion 23111 are arranged to be equal, so that the thickened portion 23112 can meet the thickness requirement of the two sides of the base portion 23111, thereby meeting the requirements of the connection strength and the limited separation of the first active material layers 2312 on the two sides. Meanwhile, the above arrangement can also ensure the consistency of the thicknesses of the first active material layers 2312 on the two sides of the first current collector 2311, which is beneficial to ensuring the electrical performance of the first electrode sheet 231.

[0093] As shown in FIG. 6, in some optional embodiments, the battery cell 20 provided by one of the embodiments of the present application is arranged such that the size of the thickened portion 23112 protruding from the base portion 23111 is d, and the thickness of the base portion 23111 is D, where 1 / 5≤d / D≤3 / 5.

[0094] The value of d / D can be any value between 1 / 5 and 3 / 5, and can be 2 / 5.

[0095] The battery cell 20 provided by one of the embodiments of the present application adopts the above value range of d / D, which can ensure that the size of the thickened portion 23112 protruding from the base portion 23111 is moderate, thereby ensuring the binding effect on the first active material layer 2312.

[0096] Continuing to refer to FIG. 6, in some optional embodiments, the battery cell 20 provided by one of the embodiments of the present application includes the first portion 23112a and the second portion 23112b distributed along the winding direction X, the first portion 23112a is located in the bending area 23a, and the second portion 23112b is located in the flat area 23b. The extension length of the second portion 23112b in the winding direction X is H, where 0.5mm≤H≤25mm.

[0097] The first portion 23112a is located at the bending area 23a, which can be arranged in a bending manner.

[0098] The first portion 23112a can be provided with the second portion 23112b on one side in the winding direction X, and of course, the second portion 23112b can be provided on both sides of the second portion 23112b.

[0099] The second portion 23112b can have an extension length of 0.5 mm to 25 mm in the winding direction X, optionally 1 mm to 20 mm, optionally 2 mm, 5 mm, 10 mm, 14 mm, 16 mm, 18 mm, etc.

[0100] The battery monomer 20 provided by one embodiment of the present application can prevent the first current collector 2311 from separating from the first active material layer 2312 due to insufficient connection strength between the first current collector 2311 and the first active material layer 2312 at the large area and the corner position. By arranging the thickened portion 23112 to include the first portion 23112a and the second portion 23112b distributed along the winding direction X, and arranging the first portion 23112a at the bending area 23a and the second portion 23112b at the flat area 23b, while limiting the extension length of the second portion 23112b in the flat area 23b along the winding direction X, the extension range of the first current collector 2311 in the bending area 23a can be improved, and the first active material layer 2312 in the flat area 23b can be fixed. This can effectively reduce the probability of separation of the first current collector 2311 from the first active material layer 2312, and improve the comprehensive performance of the first electrode sheet 231 in the flat area 23b and the bending area 23a. At the same time, the extension size of the second portion 23112b in the flat area 23b is moderate, so that the first active material can be applied more to the part of the base portion 23111 that is not thickened relative to the protruding portion 23113, so that the corresponding first active material layer 2312 is thicker, and the energy density of the electrode assembly 23 is improved.

[0101] As shown in FIG. 7 and FIG. 8, in some optional embodiments, the battery monomer 20 provided by one embodiment of the present application, the first current collector 2311 further includes a plurality of concave-convex structures, the plurality of concave-convex structures are arranged at the flat area 23b and spaced apart from each other, the concave-convex structures are arranged on at least one of the base portion 23111 and the thickened portion 23112, and the first active material layer 2312 covers the protruding portion 23113.

[0102] The number of concave-convex structures is not limited, and the plurality of concave-convex structures can be at least partially distributed along the circumferential direction, and of course, can be at least partially distributed along the extension direction of the winding axis of the winding structure.

[0103] The concave-convex structure can include a protrusion 23113, and of course, can include a recess 23114.

[0104] The concave-convex structure can be arranged on the base portion 23111, or can be arranged on the portion where the thickened portion 23112 is located on the flat area 23b. Of course, the concave-convex structure can be arranged on both the base portion 23111 and the thickened portion 23112.

[0105] The battery monomer 20 provided by the embodiment of the present application can increase the contact area of the first active material layer 2312 and the first current collector 2311, improve the contact force of the first active material layer 2312 and the first current collector 2311 in the winding direction X and the extension direction of the winding axis, fix the position of the first active material layer 2312, and prevent the first active material layer 2312 from being too strong in shear strength and accumulating to cause interlayer cracks.

[0106] In some optional embodiments, the battery monomer 20 provided by the embodiment of the present application is arranged with the concave-convex structure on both sides of the base portion 23111 in the stacking direction Y of the first pole piece 231, the second pole piece 232 and the diaphragm 23; and / or the concave-convex structure is arranged on both sides of the thickened portion 23112.

[0107] In the stacking direction Y, the concave-convex structure can be arranged on both sides of the base portion 23111, or can be arranged on both sides of the thickened portion 23112. Of course, in some embodiments, the concave-convex structure can be arranged on both sides of the base portion 23111 and both sides of the thickened portion 23112.

[0108] Optionally, in the stacking direction Y, the concave-convex structures arranged on both sides of the base portion 23111 can be arranged one by one and face each other, or can be arranged staggered with each other in the winding direction X. Optionally, in the stacking direction Y, the concave-convex structures arranged on both sides of the thickened portion 23112 can be arranged one by one and face each other, or can be arranged staggered with each other in the winding direction X.

[0109] The battery monomer 20 provided by the embodiment of the present application is arranged with the first active material layer 2312 on both sides of the first current collector 2311 in the stacking direction Y. By arranging the concave-convex structure on both sides of the base portion 23111 and / or the thickened portion 23112 in the stacking direction Y, the contact area of the first active material layer 2312 and the first current collector 2311 on each side can be increased, and the contact force of the first active material layer 2312 and the first current collector 2311 in the winding direction X and the extension direction of the winding axis can be improved.

[0110] As shown in FIG. 7, in some optional embodiments, each concave-convex structure includes a convex portion 23113, and a plurality of convex portions 23113 are arranged at intervals from each other, and the orthographic projection of the convex portion 23113 on the stacking direction Y is a circle, an ellipse, or a polygon.

[0111] When the convex portion 23113 is arranged on the base portion 23111, the orthographic projection of the convex portion 23113 on the base portion 23111 can be a polygon as shown in FIG. 9, or can be a circle as shown in FIG. 10, and of course, can also be an ellipse or other forms.

[0112] Of course, the convex portion 23113 can also be arranged on the thickened portion 23112, and when arranged on the thickened portion 23112, the orthographic projection of the convex portion 23113 on the thickened portion 23112 can also be a circle, an ellipse, or a polygon.

[0113] The battery monomer 20 provided by one embodiment of the application can increase the contact area of the first active material layer 2312 and the first current collector 2311, fix the area of the first active material layer 2312, and ensure the connection strength between the first active material layer 2312 and the first current collector 2311, because the expansion and deformation will occur during the charging and discharging process.

[0114] It can be understood that the above embodiments are described by taking that each concave-convex structure includes a convex portion 23113 as an example, which is an optional implementation.

[0115] As shown in FIG. 8, in some embodiments, a plurality of concave-convex structures can also be arranged in groups, each of the concave-convex structures in one group includes a convex portion 23113, and each of the concave-convex structures in one group includes a concave portion 23114, and the concave portion 23114 is recessed on at least one of the base portion 23111 and the thickened portion 23112.

[0116] For example, a plurality of concave-convex structures can be arranged in two groups, one group of concave-convex structures includes a convex portion 23113, and the other group of concave-convex structures includes a concave portion 23114, and the two groups of concave-convex structures are arranged opposite to each other on the base portion 23111 and / or the thickened portion 23112 in the stacking direction Y.

[0117] The number of the convex portions 23113 and the concave portions 23114 can be equal, and of course, the number of one can be greater than the number of the other. The convex portions 23113 and the concave portions 23114 can be arranged opposite to each other, or can be staggered, and are optionally arranged opposite to each other.

[0118] The battery cell 20 provided by the embodiment of the present application, through the above arrangement, ensures the connection strength between the first current collector 2311 and the first active material layer 2312 while increasing the content of the first active material layer 2312, thereby ensuring the electrical performance requirement of the electrode assembly 23.

[0119] The projection of the concave-convex structure in the stacking direction Y is also circular, elliptical or polygonal.

[0120] In some optional embodiments, the battery cell 20 provided by the embodiment of the present application, the first pole piece 231 is wound n times along the winding direction X from inside to outside, wherein each of the first pole piece 231 from the first to the m-th has the thickened portion 23112, n > m, and 3 ≤ m ≤ 5.

[0121] The value of n can be determined according to the electrical performance of the electrode assembly 23, and the value of n is subject to the functional requirement of the battery cell 20 to which the electrode assembly 23 is applied.

[0122] The value of m can be 3, 4, 5, etc.

[0123] The battery cell 20 provided by the embodiment of the present application, since the first current collector 2311 and the first active material layer 2312 of the innermost part of the electrode assembly 23 have a high risk of separation and demolding, through the above arrangement, the probability of separation and demolding of the inner first current collector 2311 and the first active material layer 2312 of the electrode assembly 23 can be reduced, and at the same time, the above arrangement will not make the thickened size of the bending area 23a and the flat area 23b and the adjacent area of the bending area 23a of the electrode assembly 23 too large to affect the overall energy density of the electrode assembly 23, thereby ensuring the use requirement of the battery cell 20.

[0124] In some optional embodiments, the battery cell 20 provided by the embodiment of the present application, the first pole piece 231 is wound n times along the winding direction X from inside to outside, wherein each of the first pole piece 231 from the f-th to the n-th has the thickened portion 23112, n-5 ≤ f ≤ n.

[0125] The thickened portion 23112 can be provided in the first to fifth outermost turns

[0126] The battery monomer 20 provided by one embodiment of the present application can reduce the probability of separation and demolding of the inner first current collector 2311 and the first active material layer 2312 of the electrode assembly 23, while the above-mentioned setting will not make the thickened size of the bending area 23a and the area adjacent to the bending area 23a of the flat area 23b of the electrode assembly 23 too large to affect the energy density of the whole electrode assembly 23, thereby ensuring the use requirement of the battery monomer 20.

[0127] The battery monomer 20 provided by one embodiment of the present application is provided with the first electrode tab 231 as a positive electrode tab and the second electrode tab 232 as a negative electrode tab.

[0128] Since the separation and demolding risk of the current collector and the active material layer of the positive electrode tab is high, the first electrode tab 231 as a positive electrode tab can reduce the separation and demolding risk of the electrode tab of the electrode assembly 23 and improve the reliability of the electrode assembly 23.

[0129] In some optional embodiments, the second electrode tab 232 can include a second current collector 2321 and a second active material layer 2322. The second current collector 2321 and the second active material layer 2322 can have the same structure as the first current collector 2311 and the first active material layer 2312 provided by the above-mentioned embodiments, that is, the structure of the second electrode tab 232 can be the same as that of the first electrode tab 231, which will not be repeated here.

[0130] The battery monomer 20 provided by one embodiment of the present application is provided with the first electrode tab 231 and the second electrode tab 232 having the part of the active material layer constituting the main part of the electrode assembly 23, the part of the first electrode tab 231 and the second electrode tab 232 not having the active material layer constituting the tab, and the tab of the first electrode tab 231 and the tab of the second electrode tab 232 can be located at one end of the main part or at two ends of the main part respectively. In the battery monomer 20 and during the charging and discharging process of the battery monomer 20, the first active material layer 2312 of the first electrode tab 231 and the second active material layer 2322 of the second electrode tab 232 react with the electrolyte, the tab is connected to the electrode terminal 212 on the end cover assembly 21 to form a current loop, thereby realizing the charging and discharging function.

[0131] As shown in FIG. 6, the battery cell 20 provided by an embodiment of the application includes a shell 22, an electrode assembly 23, and an end cover assembly 21. The shell 22 can be a square shell. The electrode assembly 23 includes first and second polar plates 231 and 232 and a separator 23. The first and second polar plates 231 and 232 and the separator 23 are wound in a winding direction X to form a winding structure. The first polar plate 231 is a positive polar plate, and the second polar plate 232 is a negative polar plate. The winding structure includes a flat area 23b and a bending area 23a. The first polar plate 231 includes a first current collector 2311 and a first active material layer 2312 connected to each other. The second polar plate 232 includes a second current collector 2321 and a second active material layer 2322. The first current collector 2311 includes a base portion 23111, a thickened portion 23112, and a plurality of concave-convex structures. The thickened portion 23112 includes a first portion 23112a and a second portion 23112b distributed along the winding direction X. The first portion 23112a is located in the bending area 23a, and the second portion 23112b is located in the flat area 23b. The second portion 23112b has an extension length in the winding direction X of 5 mm. The base portion 23111 is located in the flat area 23b and connected to the thickened portion 23112. The thickened portion 23112 has a thickness greater than that of the base portion 23111 and protrudes from the base portion 23111 and is located on both sides of the base portion 23111 in a stacking direction Y. The protrusions have the same size. The first active material layer 2312 covers the base portion 23111 and the thickened portion 23112. The thickened portion 23112 protrudes from the base portion 23111 by 2 μm on one side of the base portion 23111 in the stacking direction Y. The base portion 23111 is provided with the concave-convex structures on both sides in the stacking direction Y and one-to-one. The concave-convex structures include a protruding portion 23113. The protruding portions 23113 of the concave-convex structures located on both sides of the thickened portion 23112 have opposite protruding directions. The protruding portion 23113 has a circular shape in the projection in the stacking direction Y. The first polar plate 231 is wound n times in the winding direction X from inside to outside. From the first to the third turns, each turn of the first polar plate 231 has the thickened portion 23112. From the n-3th to the nth turns, each turn of the first polar plate 231 has the thickened portion 23112. The first current collector of the second polar plate 232 has the same thickness in the flat area 23b and the bending area 23a. The end cover assembly 21 covers and is connected to the shell 22. The end cover assembly 21 includes a cover plate 211 and electrode terminals 212. The number of the electrode terminals 212 can be two and have opposite polarities. The electrode terminals 212 and the tabs of the electrode assembly are electrically connected through adapter pieces.

[0132] In another aspect, the application provides a battery cell 20 including the above-described electrode assembly 23.

[0133] In another aspect, a battery 100 according to an embodiment of the present application includes the battery cell 20 described above, and the battery cell 20 is housed in a case 10.

[0134] In still another aspect, an electric device according to an embodiment of the present application includes the battery 100 described above.

[0135] Although the present application has been described with reference to preferred embodiments, various modifications can be made to it without departing from the scope of the application. In particular, the technical features mentioned in each of the embodiments can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized by, The application relates to a battery, comprising: a shell having a receiving cavity; an electrode assembly arranged in the receiving cavity, the electrode assembly comprising a first polar tab, a second polar tab and a separator, the first polar tab, the second polar tab and the separator being wound to form a winding structure along a winding direction, the winding structure comprising a flat area and a bending area; an end cover assembly covering the shell and being electrically connected with the electrode assembly; wherein the first polar tab comprises a first current collector and a first active material layer connected with each other, the first current collector comprises a base part and a thickened part, the thickened part is located in the bending area and extends to the flat area by a predetermined length, the base part is located in the flat area and is connected with the thickened part, the thickness of the thickened part is greater than that of the base part and the thickened part protrudes from the base part, and the first active material layer covers the base part and the thickened part.

2. The battery cell of claim 1, wherein, In a stacking direction of the first polar tab, the second polar tab and the separator, the thickened part protrudes from the base part on both sides.

3. The battery cell of claim 2, wherein, In the stacking direction, the thickness of the thickened part protruding from the base part on both sides is equal.

4. The battery cell of claim 2, wherein, In the stacking direction, the size of the thickened part protruding from the base part is d and the thickness of the base part is D, wherein 1 / 5<=d / D<=3 / 5.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The thickened part comprises a first part and a second part distributed along the winding direction, the first part is located in the bending area, and the second part is located in the flat area, and the extension length of the second part in the winding direction is H, wherein 0.5mm<=H<=25mm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The first current collector further comprises a plurality of concave-convex structures, the plurality of concave-convex structures are arranged at intervals in the flat area, the concave-convex structures are arranged on at least one of the base part and the thickened part, and the first active material layer covers the concave-convex structures.

7. The battery cell of claim 6, wherein, In the stacking direction of the first polar tab, the second polar tab and the separator, the base part is provided with the concave-convex structures on both sides; and / or the thickened part is provided with the concave-convex structures on both sides.

8. The battery cell of claim 7, wherein, In the stacking direction, the base part is provided with the concave-convex structures on both sides in a relative manner; and / or the thickened part is provided with the concave-convex structures on both sides in a relative manner.

9. The battery cell of claim 7, wherein, Each of the concave-convex structures comprises a convex part, a plurality of convex parts are arranged at intervals, and the orthographic projection of the convex part in the stacking direction is circular, elliptical or polygonal.

10. The battery cell of claim 6, wherein, The plurality of concave-convex structures are arranged in groups, each of the concave-convex structures in one group comprises a convex part, each of the concave-convex structures in one group comprises a concave part, and the concave part is formed by concave arrangement on at least one of the base part and the thickened part.

11. The battery cell according to any one of claims 1 to 10, characterized in that The first polar tab is wound n times along the winding direction from inside to outside, each of the first polar tabs from the first circle to the mth circle has the thickened part, n>m, and 3<=m<=5.

12. The battery cell according to any one of claims 1 to 11, characterized in that The first polar tab is wound n times along the winding direction from inside to outside, each of the first polar tabs from the fth circle to the nth circle has the thickened part, n-5<=f<=n.

13. The battery cell of claim 1, wherein, The first polar tab is a positive polar tab, and the second polar tab is a negative polar tab.

14. An electrode assembly, characterized by The battery includes first and second polar pieces and a separator having opposite polarities, the first and second polar pieces and the separator being wound in a winding direction to form a winding structure, the winding structure including a flat region and a bent region. The first polar piece includes a first current collector and a first active material layer connected to each other, the first current collector including a base portion and a thickened portion, the thickened portion being located at the bent region and extending to the flat region by a predetermined length, the base portion being located at the flat region and connected to the thickened portion, the thickened portion having a thickness greater than that of the base portion and being convexly disposed with respect to the base portion, the first active material layer covering the base portion and the thickened portion.

15. A battery, characterized by A battery pack including the battery cell as claimed in any one of claims 1 to 13 and a case in which the battery cell is accommodated.

16. An electrical device, comprising: A battery including the battery as claimed in claim 15.

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