Battery cell, electrode assembly, battery, and electric device

Abstract

The utility model relates to a battery monomer, an electrode assembly, a battery and a power utilization device, the battery monomer comprises a shell, the electrode assembly and an end cover assembly, the electrode assembly comprises a first pole piece, a second pole piece and a diaphragm which are opposite in polarity, and the first pole piece, the second pole piece and the diaphragm are wound along a winding direction to form a winding structure; the winding structure comprises a straight area and a bent area; the first pole piece comprises a first current collector and a first active material layer which are connected, the first current collector comprises a base part and a thickening part, the thickening part is located in the bending area and extends towards the straight area by a preset length, the base part is located in the straight area and is connected with the thickening part, and the thickness of the thickening part is larger than that of the base part and protrudes out of the base part; the first active material layer covers the base portion and the thickened portion. According to the electrode assembly, the battery monomer, the battery and the power utilization device provided by the invention, the electrode assembly can reduce the short-circuit risk of the battery monomer and ensure the overall reliability of the battery monomer.

Description

Technical Field

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

[0002] Energy conservation and emission reduction are 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 advantages in energy conservation and environmental protection. For electric vehicles, battery technology is an important factor in their development.

[0003] In the related art, in the electrode assembly of a battery cell, the current collector and the active material layer of the electrode sheet are easily separated, causing a short circuit in the battery cell, thus affecting the overall reliability of the battery cell. Utility Model Content

[0004] The embodiments of the present application provide a battery cell, an electrode assembly, a battery, and an electrical device. The electrode cell can reduce the risk of short circuit itself and ensure the reliability of the battery cell as a whole.

[0005] On the one hand, according to one embodiment of the present application, there is provided a battery cell, comprising: a housing having a receiving cavity;

[0006] An electrode assembly is arranged in the accommodating cavity, the electrode assembly includes a first electrode sheet, a second electrode sheet and a diaphragm with opposite polarities, the first electrode sheet, the second electrode sheet and the diaphragm are wound along a winding direction to form a winding structure, the winding structure includes a straight area and a bending area; an end cover assembly is covered on the shell and is electrically connected to the electrode assembly; wherein the first electrode sheet includes a first current collector and a first active material layer connected to each other, the first current collector includes a base portion and a thickened portion, the thickened portion is located in the bending area and extends a predetermined length to the straight area, the base portion is located in the straight area 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, and the first active material layer covers the base portion and the thickened portion.

[0007] A battery cell provided by an embodiment of the present application is provided with a first pole piece including a first current collector and a first active material layer, the first current collector including a base portion and a thickened portion, the thickened portion being located in a bending area and extending to a predetermined length toward a straight area, the base portion being located in the straight area and connected to the thickened portion, the thickness of the thickened portion being greater than the thickness of the base portion and being protruded from the base portion, so that there is a thickness difference between the thickened portion and the base portion and a step is formed, so that there is a thickness difference between the thickened portion and the base portion, 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, so as to achieve an effect of mutual restraint between the first active material layer and the first current collector, fix the position of the first active material layer, and avoid displacement and dislocation of the first active material layer and the first current collector to cause separation. 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 in the winding direction and protruding from the base portion. The newly added contact surface between the first current collector and the first active material layer at the step can provide a certain normal friction force, thereby improving the connection strength between the two, reducing the probability of separation and demolding of the first current collector and the first active material layer, improving the comprehensive performance and stability of the first pole piece, and thereby reducing the risk of short circuit of the battery cell, thereby ensuring the overall reliability of the battery cell.

[0008] 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 diaphragm, both sides of the thickened portion are protruding from the base portion.

[0009] In a battery cell provided by an embodiment of the present application, since the first current collector is covered with a first active material layer on each side in the stacking direction, the thickened portion is arranged so that both sides thereof protrude from the base portion along the stacking direction, so that the first active material layer located on both sides of the first current collector and the first current collector can be bound to each other, thereby improving the connection strength between the two and reducing the probability of separation of the first current collector and the first active material layer.

[0010] According to one aspect of the embodiment of the present application, in the stacking direction, the thickness of the protruding base portion on both sides of the thickened portion is equal.

[0011] By making the thickness of the protruding base part on both sides of the thickened part equal, the thickness dimension requirements of the protruding base part on both sides of the thickened part can be guaranteed, thereby ensuring the restricted separation and connection strength requirements of the first active material layer on both sides. At the same time, the above arrangement can also ensure the consistency of the thickness of the first active material layer on both sides of the first current collector, which is conducive to ensuring the electrical performance of the first pole piece.

[0012] According to one aspect of the embodiment of the present application, in the stacking direction, the dimension 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.

[0013] In a battery cell provided by an embodiment of the present application, d / D adopts the above value range, which can ensure that the size of the thickened portion protruding from the base portion is moderate, and further ensure the binding effect on the first active material layer.

[0014] According to one aspect of an embodiment of the present application, the thickened portion includes a first part and a second part distributed along the winding direction, the first part is located in the bending area, the second part is located in the straight area, and the extension length of the second part in the winding direction is H, wherein 0.5mm≤H≤25mm.

[0015] The battery cell provided in one embodiment of the present application, by making the thickened portion include a first portion and a second portion distributed along the winding direction, and making the first portion located in the bending area and the second portion located in the straight area, and limiting the extension length of the second portion in the straight area along the winding direction, 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 straight area, which can effectively reduce the probability of separation of the first current collector and the first active material layer, and improve the comprehensive performance of the straight area and the bending area of ​​the first pole piece. At the same time, it can also make the extension size of the second portion in the straight area moderate, so that the part of the base portion that is not thickened relative to the protruding portion can be coated with more of the first active material, so that the corresponding first active material layer at this location is thicker, and the energy density of the electrode assembly is improved.

[0016] According to one aspect of an embodiment of the present application, the first current collector also includes a plurality of concave-convex structures, the plurality of concave-convex structures are located in the straight area and are spaced apart from each other, a concave-convex structure is arranged on at least one of the base portion and the thickened portion, and the first active material layer covers the concave-convex structure.

[0017] A battery cell provided in an embodiment of the present application increases the contact area between the first active material layer and the first current collector, improves the contact force between the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis, fixes the position of the first active material layer, and prevents the shear strength of the first active material layer from being too large and accumulated during use to cause interlayer cracks.

[0018] According to one aspect of an embodiment of the present application, in the stacking direction of the first pole piece, the second pole piece and the diaphragm, concave-convex structures are provided on both sides of the base portion; and / or concave-convex structures are provided on both sides of the thickened portion.

[0019] In a battery cell provided by an embodiment of the present application, since the first current collector is covered with the first active material layer on both sides in the stacking direction, the contact area between the first active material layer and the first current collector on each side can be increased by providing the base portion and / or both sides in the stacking direction with a concave-convex structure, thereby improving the contact force between the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis.

[0020] According to one aspect of the embodiment of the present application, in the stacking direction, concave-convex structures are relatively arranged on both sides of the base portion; and / or, concave-convex structures are relatively arranged on both sides of the thickened portion.

[0021] A battery cell provided in one embodiment of the present application can increase the contact area between the first active material layer and the first current collector on each side and improve the contact force between the first active material layer and the first current collector in the winding direction and the extension direction of the winding axis by providing a concave-convex structure on both sides of the base part and / or the thickened part in the stacking direction.

[0022] According to one aspect of the embodiments of the present application, each concave-convex structure includes a protruding portion, and a plurality of protruding portions are arranged at intervals from each other, and an orthographic projection of the protruding portion in the stacking direction is circular, elliptical or polygonal.

[0023] The battery cell provided in one embodiment of the present application will expand and deform during the charging and discharging process. Through the above-mentioned configuration, the contact area between the first active material layer and the first current collector can be increased, the position of the first active material layer can be fixed, and the connection strength between the first active material layer and the first current collector can be ensured.

[0024] According to one aspect of an embodiment of the present application, a plurality of concave-convex structures are arranged in groups, wherein each of a group of concave-convex structures includes a protruding portion, wherein each of a group of concave-convex structures includes a concave portion, and a concave portion is formed on at least one of the base portion and the thickened portion.

[0025] The battery cell provided in one embodiment of the present application, through the above configuration, increases the content of the first active material layer while ensuring the connection strength between the first current collector and the first active material layer, thereby ensuring the electrical performance requirements of the electrode assembly.

[0026] According to one aspect of an embodiment of the present application, the first pole piece is wound n times along the winding direction from inside to outside, wherein from the 1st turn to the mth turn, each turn of the first pole piece has a thickened portion, n>m, 3≤m≤5.

[0027] The battery cell provided by an embodiment of the present application has a high risk of separation and demolding of the first current collector and the first active material layer in the innermost part of the electrode assembly. Through the above-mentioned configuration, the probability of separation and demolding of the inner first current collector and the first active material layer of the electrode assembly can be reduced. At the same time, the above-mentioned configuration will not make the thickening dimensions of the electrode assembly in the bending zone and the straight zone and the area adjacent to the bending zone too large to affect the overall energy density of the electrode assembly, thereby ensuring the use requirements of the battery cell.

[0028] According to one aspect of an embodiment of the present application, the first pole piece is wound n times along a winding direction from inside to outside, wherein from the fth turn to the nth turn, each turn of the first pole piece has a thickened portion, n-5≤f≤n.

[0029] The battery cell provided by an embodiment of the present application has a high risk of separation and demolding of the first current collector and the first active material layer at the outermost part of the electrode assembly. Through the above-mentioned configuration, the probability of separation and demolding of the inner first current collector and the first active material layer of the electrode assembly can be reduced. At the same time, the above-mentioned configuration also does not make the thickening dimensions of the electrode assembly in the bending zone and the straight zone and the area adjacent to the bending zone too large to affect the overall energy density of the electrode assembly, thereby ensuring the use requirements of the battery cell.

[0030] According to one aspect of the embodiment of the present application, the first pole piece is a positive pole piece, and the second pole piece is a negative pole piece. Since the current collector and the active material layer of the positive pole piece have a high risk of separation and demolding, by making the first pole piece a positive pole piece, the risk of separation and demolding of the pole pieces of the electrode assembly can be reduced, thereby improving the reliability of the electrode assembly.

[0031] On the other hand, according to an embodiment of the present application, an electrode assembly is provided, including a first pole piece, a second pole piece and a diaphragm with opposite polarities, the first pole piece, the second pole piece and the diaphragm are wound along a winding direction to form a winding structure, the winding structure includes a straight area and a bending area; the first pole piece includes a first current collector and a first active material layer connected to each other, the first current collector includes a base portion and a thickened portion, the thickened portion is located in the bending area and extends a predetermined length to the straight area, the base portion is located in the straight area and is 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, and the first active material layer covers the base portion and the thickened portion.

[0032] On the other hand, according to an embodiment of the present application, a battery is provided, including a box body and the above-mentioned battery cell, wherein the battery cell is accommodated in the box body.

[0033] On the other hand, according to an embodiment of the present application, an electrical device includes the above-mentioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

[0035] Figure 1 is a schematic diagram of a vehicle according to an embodiment of the present application;

[0036] Figure 2 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0037] Figure 3 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0038] Figure 4 is a schematic cross-sectional view of an electrode assembly provided by an embodiment of the present application along the extension direction of the winding axis;

[0039] Figure 5 is a partial structural schematic diagram of an electrode assembly according to an embodiment of the present application;

[0040] Figure 6 is a partial structural schematic diagram of an electrode assembly of another embodiment of the present application;

[0041] Figure 7 is a partial structural schematic diagram of an electrode assembly of another embodiment of the present application;

[0042] Figure 8 is a partial structural schematic diagram of an electrode assembly of yet another embodiment of the present application;

[0043] Fig. 9 is a schematic top view of a concave-convex structure of an embodiment of the present application;

[0044] Fig.10 It is a schematic top view of a concave-convex structure of an embodiment of the present application.

[0045] in:

[0046] 1- Vehicle;

[0047] 100-battery; 200-battery module; 300-controller; 400-motor;

[0048] 10-box; 11-first box portion; 12-second box portion;

[0049] 20-battery cell;

[0050] 21-end cover assembly;

[0051] 211-cover plate; 212-electrode terminal;

[0052] 22-housing;

[0053] 23-electrode assembly; 23a-bending area; 23b-straight area;

[0054] 231-first pole piece; 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

[0055] 232 - second pole piece; 2321 - second current collector; 2322 - second active material layer;

[0056] 233-diaphragm;

[0057] X-winding direction; Y-stacking direction;.

[0058] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0059] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0060] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the embodiments of the present application should have the common meanings understood by technicians in the field to which the embodiments of the present application belong.

[0061] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0062] In addition, the technical terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0063] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0064] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0065] At present, from the perspective of market development, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.

[0066] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery module or a battery pack.

[0067] The battery cell comprises a shell, an end cover assembly and an electrode assembly. The electrode assembly is arranged in the shell, and the end cover assembly is arranged to close the opening of the shell.

[0068] The battery cells in the related technology have the risk of short circuit. Further research has found that during the use of the battery cells, the active material layer of the electrode and the current collector are easily separated due to insufficient adhesion, resulting in the film peeling phenomenon of the electrode. This not only causes the performance of the battery cells to decline, but also the shedding of the film layer may puncture the diaphragm and cause the risk of short circuit in the battery cells, seriously affecting the reliability of the battery cells.

[0069] Based on the above considerations, after in-depth research, a battery cell is designed, including a shell, an electrode assembly and an end cap assembly, the shell has a receiving cavity; the electrode assembly is arranged in the receiving cavity, the electrode assembly includes a first pole piece, a second pole piece and a diaphragm with opposite polarities, the first pole piece, the second pole piece and the diaphragm are wound along the winding direction to form a winding structure, and the winding structure includes a straight area and a bending area; the end cap assembly covers the shell and is electrically connected to the electrode assembly; wherein the first pole piece 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 straight area by a predetermined length, the base part is located in the straight area and connected to the thickened part, the thickness of the thickened part is greater than the thickness of the base part and protrudes from the base part, and the first active material layer covers the base part and the thickened part. The electrode cell can reduce the probability of separation between the current collector and the active material layer, reduce the risk of short circuit, and ensure the overall reliability of the battery cell.

[0070] The technical solutions described in the embodiments of the present application are applicable to various devices that use motor monomers, such as mobile phones, portable devices, laptop computers, electric vehicles, electric toys, electric tools, electric vehicles, ships and spacecraft, for example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.

[0071] It should be understood that the technical solutions described in the embodiments of the present application are not limited to the devices described above, but can also be applied to all devices using batteries. However, for the sake of simplicity, the following embodiments are described using electric vehicles as examples.

[0072] For example, Figure 1 As shown, it is a structural schematic diagram of a vehicle 1 according to an embodiment of the present application. The vehicle 1 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 400, a controller 300 and a battery 100 may be arranged inside the vehicle 1. The controller 300 is used to control the battery 100 to supply power to the motor 400. For example, a battery 100 may be arranged at the bottom, front or rear of the vehicle 1. The battery 100 may be used to supply power to the vehicle 1. For example, the battery 100 may be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery 100 may not only be used as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0073] like Figure 2 as well as Figure 3As shown, in order to meet different power requirements, the battery 100 may include a plurality of battery cells 20, wherein the plurality of battery cells 20 may be connected in series, in parallel, or in a hybrid connection, wherein the hybrid connection refers to a mixture of series and parallel connections. The battery 100 may also be referred to as a battery pack. Optionally, a plurality of battery cells 20 may first be connected in series, in parallel, or in a hybrid connection to form a battery module 200, and a plurality of battery modules 200 may then be connected in series, in parallel, or in a hybrid connection to form a battery 100. In other words, a plurality of battery cells 20 may directly form a battery 100, or may first form a battery module 200, and then the battery module 200 may form a battery 100.

[0074] For example, Figure 2 , which is a schematic diagram of the structure of a battery 100 according to an embodiment of the present application, the battery 100 may include a plurality of battery cells 20. The battery 100 may also include a housing 10 (or housing), the interior of the housing 10 is a hollow structure, and the plurality of battery cells 20 are accommodated in the housing 10.

[0075] The box 10 can be a simple three-dimensional structure such as a single cuboid, a cylinder, or a sphere, or a complex three-dimensional structure composed of simple three-dimensional structures such as cuboids, cylinders, or spheres, which is not limited in the present embodiment. The box 10 can be made of alloy materials such as aluminum alloy, iron alloy, etc., or a polymer material such as polycarbonate, polyisocyanurate foam plastic, or a composite material such as glass fiber plus epoxy resin, which is not limited in the present embodiment.

[0076] The box 10 is used to accommodate the battery cell 20, and the box 10 can be a variety of structures. In some embodiments, the box 10 may include a first box portion 11 and a second box portion 12, the first box portion 11 and the second box portion 12 cover each other, and the first box portion 11 and the second box portion 12 jointly define a storage space for accommodating the battery cell 20. The second box portion 12 may be a hollow structure with one end open, the first box portion 11 is a plate-like structure, and the first box portion 11 covers the open side of the second box portion 12 to form a box 10 with a storage space; the first box portion 11 and the second box portion 12 may also be a hollow structure with one side open, and the open side of the first box portion 11 covers the open side of the second box portion 12 to form a box 10 with a storage space. Of course, the first box portion 11 and the second box portion 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0077] In order to improve the sealing performance after the first box body 11 and the second box body 12 are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 11 and the second box body 12 .

[0078] Assuming that the first box body portion 11 covers the top of the second box body portion 12 , the first box body portion 11 can also be referred to as an upper box cover, and the second box body portion 12 can also be referred to as a lower box body 10 .

[0079] In the battery 100, there can be one or more battery cells 20. If there are more than one battery cell 20, the battery cells 20 can be connected in series, in parallel, or in a mixed connection. A mixed connection means that the battery cells 20 are both connected in series and in parallel. The battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the battery cells 20 can be accommodated in the box 10; of course, the battery modules 200 can also be formed by connecting the battery cells 20 in series, in parallel, or in a mixed connection, and then the battery modules 200 can be formed into a whole by connecting the battery cells 20 in series, in parallel, or in a mixed connection, and then accommodated in the box 10.

[0080] In some embodiments, as shown in FIG. 2 , there are multiple battery cells 20, and multiple battery cells 20 are first connected in series, parallel or mixed to form a battery module 200. Multiple battery modules 200 are then connected in series, parallel or mixed to form a whole, and are accommodated in the box 10.

[0081] The multiple battery cells 20 in the battery module 200 can be electrically connected through a busbar component to achieve parallel connection, series connection, or mixed connection of the multiple battery cells 20 in the battery module 200 .

[0082] In the present application, the battery cell 20 may 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 do not limit this. The battery cell 20 may be cylindrical, flat, rectangular or other shapes, etc., and the embodiments of the present application do not limit this. The battery cell 20 is generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells, and the embodiments of the present application do not limit this. However, for the sake of simplicity, the following embodiments are all described by taking the cylindrical battery cell 20 as an example.

[0083] like Figure 3As shown, the battery cell 20 may include a shell 22, an electrode assembly 23 and an end cap assembly 21. The end cap assembly 21 covers the shell 22 and is electrically connected to the electrode assembly 23. The shell 22 is a component used to cooperate with the end cap 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, the electrolyte (not shown in the figure) and other components. The shell 22 and the end cap assembly 21 can be independent components, and an opening can be set on the shell 22. The end cap assembly 21 covers the opening at the opening to form the internal environment of the battery cell 20. Without limitation, the end cap assembly 21 and the shell 22 can also be integrated. Specifically, the end cap assembly 21 and the shell 22 can form a common connection surface before other components are put into the shell. When it is necessary to encapsulate the interior of the shell 22, the end cap assembly 21 covers the shell 22.

[0084] The shell 22 can be in various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism shape, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The shell 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0085] The end cap assembly 21 refers to a component that covers the opening of the shell 22 and is enclosed with the shell 22 to form a receiving cavity, and the receiving cavity is used to accommodate the electrode assembly 23. The end cap assembly 21 isolates the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap assembly 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap assembly 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap assembly 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. The end cap assembly 21 may include a cover plate 211 and an electrode terminal 212. The cover plate 21 is mechanically connected to the shell 22, and the electrode terminal 212 is electrically connected to the electrode assembly 23.

[0086] In some embodiments, the battery cell 20 may include a pressure relief mechanism for releasing the pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.

[0087] Exemplarily, the pressure relief mechanism is located between the positive electrode terminal and the negative electrode terminal, and the pressure relief mechanism may be a component such as an explosion-proof valve, an explosion-proof disk, an air valve, a pressure relief valve or a safety valve.

[0088] The positive electrode terminal and the negative electrode terminal may be installed on the same end cover or on different end covers; the pressure relief mechanism may be installed on one end cover or on both end covers.

[0089] The electrode assembly 23 is a component where an electrochemical reaction occurs in the battery cell 20. One or more electrode assemblies 23 may be contained in the housing 22.

[0090] like Figure 4 as well as Figure 5 As shown, in some optional embodiments, a battery cell 20 provided in one embodiment of the present application, its electrode assembly 23 may include a first pole piece 231, a second pole piece 232 and a diaphragm 23 with opposite polarities, the first pole piece 231, the second pole piece 232 and the diaphragm 23 are wound along a winding direction X to form a winding structure, and the winding structure includes a straight area 23b and a bending area 23a. The first pole piece 231 includes a first current collector 2311 and a first active material layer 2312 connected to each other. 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 straight area 23b by a predetermined length. The base portion 23111 is located in the straight area 23b and is connected to the thickened portion 23112. The thickness of the thickened portion 23112 is greater than the thickness of the base portion 23111 and protrudes from the base portion 23111. The first active material layer 2312 covers the base portion 23111 and the thickened portion 23112.

[0091] One of the first pole piece 231 and the second pole piece 232 may be a positive pole piece, and the other may be a negative pole piece. The first pole piece 231 and the second pole piece 232 may have the same structure. Of course, the second pole piece 232 may also be a conventional pole piece including a current collector and an active material layer.

[0092] The material of the isolation film may be PP (polypropylene) or PE (polyethylene), etc. The diaphragm 23 may be clamped between the first pole piece 231 and the second pole piece 232 to insulate the first pole piece 231 and the second pole piece 232 from each other.

[0093] The first pole piece 231 and the second pole piece 232 can be wound multiple times in the winding direction X, so that the first pole piece 231 can include a thickened portion 23112 on at least a portion of the wound layers. For example, along the winding direction X, from the innermost 1st circle to the innermost 3rd circle, the first pole piece 231 corresponding to each circle includes a thickened portion 23112. Of course, it is also possible to make the first pole piece 231 corresponding to each circle from the outermost 1st circle to the outermost 3rd circle include a thickened portion 23112. Of course, the above is only an example, and the first pole piece 231 can also include a thickened portion 23112 on more or less innermost circles of the winding direction X, and can also include a thickened portion 23112 on more or less outermost circles of the first pole piece 231 on the winding direction X. It is also possible to make the first pole piece 231 include a thickened portion 23112 on each circle.

[0094] The straight area 23b of the winding structure is connected to the bending area 23a, and the bending areas 23a may be provided at both opposite ends of the straight area 23b. The straight area 23b is the area where the winding structure has a straight structure, and the portion of the first pole piece 231 located in the straight area 23b and the portion of the second pole piece 232 located in the straight area 23b are both basically arranged straight. The bending area 23a is the area where the winding structure has a bending structure, and the portion of the first pole piece 231 located in the bending area 23a and the portion of the second pole piece 232 located in the bending area 23a are both bent. Exemplarily, the portions of the first pole piece 231 and the second pole piece 232 located in the bending area 23a may be arc-shaped.

[0095] The thickened portion 23112 is located in the bending area 23a and extends to the straight area 23b by a predetermined length, which may be greater than zero. The specific length may be set according to the connection strength requirements of the first current collector 2311 and the first active material layer 2312 and the capacity density requirements of the electrode assembly.

[0096] The thickness of the thickened portion 23112 is greater than the thickness of the base portion 23111 and the protrusion of the base portion 23111 can be understood as: the thickened portion 23112 is protruding from the base portion 23111 in the stacking direction Y of the first pole piece 231, the second pole piece 232 and the diaphragm 23. In other words, in the radial direction of the winding structure, the thickened portion 23112 is protruding 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 diaphragm 23.

[0097] The thickened portion 23112 may be arranged on one side of the stacking direction Y protruding from the base portion 23111 , or may be arranged on both sides of the stacking direction Y protruding from the base portion 23111 .

[0098] The first active material layer 2312 may cover both sides of the base portion 23111 in the arrangement direction Y and the thickened portion 23112 in the arrangement direction Y.

[0099] The battery cell 20 provided in one embodiment of the present application is configured such that the first pole piece 231 includes 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 straight area 23b by a predetermined length, the base portion 23111 is located in the straight area 23b and connected to the thickened portion 23112, the thickness of the thickened portion 23112 is greater than the thickness of the base portion 23111 and is protruding from the base portion 23111, so that the thickened portion 23112 There is a thickness difference between the thickened portion 23112 and the base portion 23111 and a step is formed, so that there is a thickness difference between the thickened portion 23112 and the base portion 23111. The first active material layer 2312 covers the base portion 23111 and the thickened portion 23112, so that the first active material layer 2312 can be embedded in the first current collector 2311, so as to achieve the effect of mutual restraint between the first active material layer 2312 and the first current collector 2311, fix the position of the first active material layer 2312, and avoid displacement and dislocation of the first active material layer 2312 and the first current collector 2311 to cause separation. The first active material layer 2312 covers the thickened portion 23112, not only covering the surface in the stacking direction Y, but also covering the side wall surface located in the winding direction X and protruding from the base portion 23111. The newly added contact surface between the first current collector 2311 and the first active material layer 2312 at the step can provide a certain normal friction force, thereby improving the connection strength between the two, reducing the probability of separation and demolding of the first current collector 2311 and the first active material layer 2312, improving the comprehensive performance and stability of the first pole piece 231, and thereby reducing the risk of short circuit of the battery cell 20, thereby ensuring the overall reliability of the battery cell 20.

[0100] In some optional embodiments, in a battery cell 20 provided in an embodiment of the present application, in a stacking direction Y of the first pole piece 231 , the second pole piece 232 , and the diaphragm 23 , both sides of the thickened portion 23112 are protruding from the base portion 23111 .

[0101] The dimensions of the thickened portion 23112 protruding from the base portion 23111 on both sides of the stacking direction Y may be equal. Of course, the dimension of the thickened portion 23112 protruding from the base portion 23111 on one side may be larger than the dimension of the other side protruding from the base portion 23111 .

[0102] In a battery cell 20 provided by an embodiment of the present application, since each side of the first current collector 2311 in the stacking direction is covered with the first active material layer 2312, by making the two sides of the thickened portion 23112 protrude from the base portion 23111 along the stacking direction, the first active material layer 2312 located on both sides of the first current collector 2311 can be bound to the first current collector 2311, thereby improving the connection strength between the two and reducing the probability of separation of the first current collector 2311 and the first active material layer 2312.

[0103] In some optional embodiments, in a battery cell 20 provided in an embodiment of the present application, in the stacking direction Y, the thickness of the protruding base portion 23111 on both sides of the thickened portion 23112 is equal.

[0104] Since the thickness of the first current collector 2311 and the first active material layer 2312 is relatively thin, by making the thickness of the protruding base part 23111 on both sides of the thickened part 23112 equal, the thickness dimension requirement of the protruding base part 23111 on both sides of the thickened part 23112 can be guaranteed, and then the restriction separation and connection strength requirements of the first active material layer 2312 on both sides can be guaranteed. At the same time, the above arrangement can also ensure the consistency of the thickness of the first active material layer 2312 on both sides of the first current collector 2311, which is conducive to ensuring the electrical performance of the first electrode 231.

[0105] like Figure 6 As shown, in some optional embodiments, in a battery cell 20 provided by an embodiment of the present application, in the stacking direction Y, the dimension of the thickened portion 23112 protruding from the base portion 23111 is d, and the thickness of the base portion 23111 is D, wherein 1 / 5≤d / D≤3 / 5.

[0106] The value of d / D can be any value between 1 / 5≤d / D≤3 / 5, and can be 2 / 5.

[0107] In a battery cell 20 provided in an embodiment of the present application, d / D adopts the above value range, which can ensure that the protrusion of the thickened portion 23112 from the base portion 23111 is moderate, thereby ensuring the binding effect on the first active material layer 2312 .

[0108] Continue reading Figure 6 As shown, in some optional embodiments, a battery cell 20 provided by an embodiment of the present application, 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, the second portion 23112b is located in the straight area 23b, and the extension length of the second portion 23112b in the winding direction X is H, wherein 0.5mm≤H≤25mm.

[0109] The first portion 23112a is located in the bending area 23a and can be bent.

[0110] The first portion 23112a may have a second portion 23112b disposed on one side of the winding direction X. Of course, the second portion 23112b may optionally be disposed on both sides of the second portion 23112b.

[0111] The extension length of the second portion 23112b in the winding direction X can be any value between 0.5 mm and 25 mm, or any value between 1 mm and 20 mm, or 2 mm, 5 mm, 10 mm, 14 mm, 16 mm, 18 mm, etc.

[0112] In a battery cell 20 provided in an embodiment of the present application, the first current collector 2311 and the first active material layer 2312 are separated due to insufficient connection strength at the large surface and corners. By making the thickened portion 23112 include a first portion 23112a and a second portion 23112b distributed along the winding direction X, and making the first portion 23112a located in the bending area 23a and the second portion 23112b located in the straight area 23b, and limiting the extension length of the second portion 23112b in the straight area 23b along the winding direction X, the ductility range of the first current collector 2311 in the bending area 23a can be increased while fixing the position of the first active material layer 2312 in the straight area 23b, which can effectively reduce the probability of separation between the first current collector 2311 and the first active material layer 2312, and improve the comprehensive performance of the straight area 23b and the bending area 23a of the first pole piece 231. At the same time, the extension size of the second part 23112b in the straight area 23b can be moderate, so that the part of the base part 23111 that is not thickened relative to the protruding part 23113 can be coated with more first active material, making the corresponding first active material layer 2312 thicker, thereby improving the energy density of the electrode assembly 23.

[0113] like Figure 7 as well as Figure 8 As shown, in some optional embodiments, a battery cell 20 provided by an embodiment of the present application, the first current collector 2311 also includes a plurality of concave-convex structures, the plurality of concave-convex structures are located in the straight region 23b and are spaced apart from each other, the concave-convex structure is provided 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.

[0114] The number of the concave-convex structures is not limited, and the multiple concave-convex structures may be at least partially distributed along the winding direction, and of course, may also be at least partially distributed along the extension direction of the winding axis of the winding structure.

[0115] The concave-convex structure may include a protrusion 23113 , and of course may also include a concave portion 23114 .

[0116] A concave-convex structure may be provided on the base portion 23111 , or on the portion of the thickened portion 23112 located in the straight region 23 b . Of course, a concave-convex structure may be provided on both the base portion 23111 and the thickened portion 23112 .

[0117] A battery cell 20 provided in an embodiment of the present application increases the contact area between the first active material layer 2312 and the first current collector 2311, improves the contact force between 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, fixes the position of the first active material layer 2312, and prevents the shear strength of the first active material layer 2312 from being too large and accumulated during use, thereby preventing the formation of interlayer cracks.

[0118] In some optional embodiments, a battery cell 20 provided in an embodiment of the present application has a 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 a concave-convex structure on both sides of the thickened portion 23112.

[0119] In the stacking direction Y, the concave-convex structure may be provided on both sides of the base portion 23111, and the concave-convex structure may be provided on both sides of the thickened portion 23112. Of course, in some embodiments, the concave-convex structure may be provided on both sides of the base portion 23111 and both sides of the thickened portion 23112 at the same time.

[0120] Optionally, in the stacking direction Y, the concave-convex structures disposed on both sides of the base portion 23111 may be disposed one-to-one oppositely, and of course, they may also be disposed offset from each other in the winding direction X. Optionally, in the stacking direction Y, the concave-convex structures disposed on both sides of the thickened portion 23112 may be disposed one-to-one oppositely, and of course, they may also be disposed offset from each other in the winding direction X.

[0121] In a battery cell 20 provided in one embodiment of the present application, the first current collector 2311 is covered with the first active material layer 2312 on both sides of the stacking direction Y. By providing the base portion 23111 and / or the thickened portion 23112 with a concave-convex structure on both sides of the stacking direction Y, the contact area between the first active material layer 2312 and the first current collector 2311 on each side can be increased, and the contact force between 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.

[0122] like Figure 7 As shown, in some optional embodiments, each concave-convex structure includes a protrusion 23113, and a plurality of protrusions 23113 are arranged at intervals from each other, and the orthographic projection of the protrusion 23113 in the stacking direction Y is circular, elliptical or polygonal.

[0123] When the protrusion 23113 is disposed on the base 23111, the orthographic projection of the protrusion 23113 on the base 23111 may be Fig. 9 The polygon shown can also be Fig.10 The circle shown may, of course, also be in other forms such as an ellipse.

[0124] Of course, the protrusion 23113 may also be disposed on the thickened portion 23112. When disposed on the thickened portion 23112, the orthographic projection of the protrusion 23113 on the thickened portion 23112 may also be a circular, elliptical or polygonal orthographic projection.

[0125] The battery cell 20 provided in an embodiment of the present application will expand and deform during the charging and discharging process. Through the above-mentioned configuration, the contact area between the first active material layer 2312 and the first current collector 2311 can be increased, the area of ​​the first active material layer 2312 can be fixed, and the connection strength between the first active material layer 2312 and the first current collector 2311 can be ensured.

[0126] It can be understood that the above embodiments are described by taking the example that the concave-convex structure includes the protruding portion 23113, which is an optional implementation.

[0127] like Figure 8 As shown, in some embodiments, a plurality of concave-convex structures can be arranged in groups, wherein each of a group of concave-convex structures includes a protrusion 23113, wherein each of a group of concave-convex structures includes a concave portion 23114, and the concave portion 23114 is formed on at least one of the base portion 23111 and the thickened portion 23112.

[0128] For example, multiple concave-convex structures can be divided into two groups, one group of concave-convex structures includes a protruding portion 23113, and the other group of concave-convex structures includes a concave portion 23114. The two groups of concave-convex structures are relatively arranged in the base portion 23111 and / or the thickened portion 23112 in the stacking direction Y.

[0129] The number of the protrusions 23113 and the recesses 23114 can be equal, and of course, the number of one can be greater than the other. The protrusions 23113 and the recesses 23114 can be arranged opposite to each other in the stacking direction Y, or can be arranged in a staggered manner, or can be arranged opposite to each other.

[0130] The battery cell 20 provided in one embodiment of the present application, through the above configuration, increases the content of the first active material layer 2312 while ensuring the connection strength between the first current collector 2311 and the first active material layer 2312 , thereby ensuring the electrical performance requirements of the electrode assembly 23 .

[0131] The orthographic projection of the concave portion 23114 in the stacking direction Y is also circular, elliptical or polygonal. In other words, the orthographic projection of the concavo-convex structure in the stacking direction Y is also circular, elliptical or polygonal.

[0132] In some optional embodiments, in a battery cell 20 provided by an embodiment of the present application, the first pole piece 231 is wound n times along a winding direction X from inside to outside, wherein, from the 1st turn to the mth turn, each turn of the first pole piece 231 has a thickened portion 23112, n>m, 3≤m≤5.

[0133] The value of n can be determined according to the electrical performance of the electrode assembly 23 to meet the functional requirements of the battery cell 20 to which it is applied.

[0134] The value of m can be 3, 4, 5, etc.

[0135] The battery cell 20 provided in one embodiment of the present application has a high risk of separation and demolding of the first current collector 2311 and the first active material layer 2312 at the innermost part of the electrode assembly 23. Through the above-mentioned configuration, 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. At the same time, the above-mentioned configuration will not make the thickening dimensions of the electrode assembly 23 in the bending zone 23a and the straight zone 23b and the area adjacent to the bending zone 23a too large to affect the overall energy density of the electrode assembly 23, thereby ensuring the use requirements of the battery cell 20.

[0136] In some optional embodiments, in a battery cell 20 provided by an embodiment of the present application, the first pole piece 231 is wound n times along a winding direction X from inside to outside, wherein from the fth turn to the nth turn, each turn of the first pole piece 231 has a thickened portion 23112, n-5≤f≤n.

[0137] It is possible to make the outermost 1st to 5th circles have thickened parts 23112

[0138] In a battery cell 20 provided in an embodiment of the present application, since the risk of separation and demolding of the first current collector 2311 and the first active material layer 2312 at the outermost part of the electrode assembly 23 is relatively high, the above-mentioned arrangement 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. At the same time, the above-mentioned arrangement also will not cause the thickening dimensions of the electrode assembly 23 in the bending zone 23a and the straight zone 23b and the area adjacent to the bending zone 23a to be too large, thereby affecting the overall energy density of the electrode assembly 23, thereby ensuring the use requirements of the battery cell 20.

[0139] In a battery cell 20 provided in one embodiment of the present application, the first pole piece 231 is a positive pole piece, and the second pole piece 232 is a negative pole piece.

[0140] Since the current collector and active material layer of the positive electrode plate have a high risk of separation and demolding, by making the first electrode plate 231 a positive electrode plate, the risk of separation and demolding of the electrode plate of the electrode assembly 23 can be reduced, thereby improving the reliability of the electrode assembly 23.

[0141] In some optional embodiments, the second pole piece 232 may 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 may have the same structure as the first current collector 2311 and the first active material layer 2312 provided in the above embodiments, that is, the second pole piece 232 may also have the same structural form as the first pole piece 231, which will not be repeated here.

[0142] In a battery cell 20 provided by an embodiment of the present application, the first pole piece 231 and the second pole piece 232 have active material layers, which constitute the main body of the electrode assembly 23, and the first pole piece 231 and the second pole piece 232 do not have active material layers, which constitute the pole ears. The pole ears of the first pole piece 231 and the pole ears of the second pole piece 232 can be located at one end of the main body or at two ends of the main body respectively. When used in the battery cell 20 and during the charging and discharging process of the battery cell 20, the first active material layer 2312 of the first pole piece 231 and the second active material layer 2322 of the second pole piece 232 react with the electrolyte, and the pole ears are connected to the electrode terminal 212 on the end cap assembly 21 to form a current loop to achieve the charging and discharging function.

[0143] like Figure 6As shown, a battery cell 20 provided by an embodiment of the present application includes a shell 22, an electrode assembly 23 and an end cap assembly 21. The shell 22 can be a square shell. The electrode assembly 23 includes a first pole piece 231, a second pole piece 232 and a diaphragm 23 with opposite polarities. The first pole piece 231, the second pole piece 232 and the diaphragm 23 are wound along a winding direction X to form a winding structure. The first pole piece 231 is a positive pole piece, and the second pole piece 232 is a negative pole piece. The winding structure includes a straight area 23b and a bending area 23a. The first pole piece 231 includes a first current collector 2311 and a first active material layer 2312 connected to each other. The second pole piece 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, the second portion 23112b is located in the straight area 23b, the extension length of the second portion 23112b in the winding direction X can be selected to be 5 mm, the base portion 23111 is located in the straight area 23b and is connected to the thickened portion 23112, the thickness of the thickened portion 23112 is greater than the thickness of the base portion 23111 and the protruding base portion 23111 is arranged and the base portion 23111 is protruded on both sides in the stacking direction Y, and the protruding sizes are equal, the first active material layer 2312 covers the base portion 23111 and the thickened portion 23112, and the thickness of the thickened portion 23112 protruding from the base portion 23111 on one side in the stacking direction Y can be selected to be 2 μm. The base part 23111 is provided with a concave-convex structure on both sides of the stacking direction Y and is arranged one to one. The concave-convex structure includes a protrusion 23113. The protrusions 23113 of the concave-convex structures on both sides of the thickened cloth have opposite protrusion directions. The positive projection of the protrusion 23113 on the stacking direction Y can be a circle. The first pole piece 231 is wound n times from the inside to the outside along the winding direction X, wherein from the first turn to the third turn, each turn of the first pole piece 231 has a thickened portion 23112, and from the n-3rd turn to the nth turn, each turn of the first pole piece 231 has a thickened portion 23112. The first excitation fluid of the second pole piece 232 can be set with equal thickness in the straight area 23b and the bending area 23a. The end cover assembly 23 covers the shell 22 and is connected to the shell 22. The end cover assembly 23 includes a cover plate 211 and an electrode terminal 212. The number of the electrode terminals 212 can be two with opposite polarities. The electrode terminal 212 and the pole ear of the electrode assembly can be electrically connected through a adapter.

[0144] On the other hand, according to one embodiment of the present application, a battery cell 20 is provided, comprising the above-mentioned electrode assembly 23 .

[0145] On the other hand, according to an embodiment of the present application, a battery 100 is provided, including the above-mentioned battery cell 20 , and the battery cell 20 is accommodated in a box body 10 .

[0146] On the other hand, according to the present application, an electrical device includes the battery 100 described above.

[0147] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. 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 in that: include: A housing having a receiving cavity; An electrode assembly is disposed in the accommodating cavity, the electrode assembly comprising a first electrode sheet, a second electrode sheet and a diaphragm with opposite polarities, the first electrode sheet, the second electrode sheet and the diaphragm are wound along a winding direction to form a winding structure, and the winding structure comprises a straight area and a bending area; An end cap assembly, covering the housing and electrically connected to the electrode assembly; Among them, the first pole piece includes a first current collector and a first active material layer connected to each other, the first current collector includes a base portion and a thickened portion, the thickened portion is located in the bending area and extends a predetermined length to the straight area, the base portion is located in the straight area 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, and the first active material layer covers the base portion and the thickened portion.

2. The battery cell according to claim 1, characterized in that: In the stacking direction of the first pole piece, the second pole piece and the diaphragm, both sides of the thickened portion are protruding from the base portion.

3. The battery cell according to claim 2, characterized in that: In the stacking direction, the thickness of the two sides of the thickened portion protruding from the base portion is equal.

4. The battery cell according to claim 2, characterized in that: In the stacking direction, the thickness 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.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The thickened portion includes a first portion and a second portion distributed along the winding direction, the first portion is located in the bending area, the second portion is located in the straight area, and the extension length of the second portion 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 includes a plurality of concave-convex structures, which are located in the straight region and spaced apart from each other. The concave-convex structures are disposed on at least one of the base portion and the thickened portion, and the first active material layer covers the concave-convex structures.

7. The battery cell according to claim 6, characterized in that: In the stacking direction of the first pole piece, the second pole piece and the diaphragm, the concave-convex structure is provided on both sides of the base portion; and / or the concave-convex structure is provided on both sides of the thickened portion.

8. The battery cell according to claim 7, characterized in that: In the stacking direction, the concave-convex structures are disposed on both sides of the base portion in a relative manner; and / or the concave-convex structures are disposed on both sides of the thickened portion in a relative manner.

9. The battery cell according to claim 7, characterized in that: Each of the concave-convex structures comprises a protruding portion, a plurality of the protruding portions are arranged at intervals from each other, and an orthographic projection of the protruding portion in the stacking direction is circular, elliptical or polygonal.

10. The battery cell according to claim 6, characterized in that: A plurality of the concave-convex structures are arranged in groups, wherein each of a group of the concave-convex structures includes a protruding portion, wherein each of a group of the concave-convex structures includes a concave portion, and the concave portion is formed by being recessed on at least one of the base portion and the thickened portion.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The first pole piece is wound n times along the winding direction from inside to outside, wherein from the 1st turn to the mth turn, each turn of the first pole piece has the thickened portion, n>m, 3≤m≤5.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The first pole piece is wound n times along the winding direction from inside to outside, wherein from the fth turn to the nth turn, each turn of the first pole piece has the thickened portion, and n-5≤f≤n.

13. The battery cell according to claim 1, characterized in that: The first pole piece is a positive pole piece, and the second pole piece is a negative pole piece.

14. An electrode assembly, characterized in that: It includes a first pole piece, a second pole piece and a diaphragm with opposite polarities, wherein the first pole piece, the second pole piece and the diaphragm are wound along a winding direction to form a winding structure, and the winding structure includes a straight area and a bending area; The first pole piece includes a first current collector and a first active material layer connected to each other, the first current collector includes a base portion and a thickened portion, the thickened portion is located in the bending area and extends a predetermined length to the straight area, the base portion is located in the straight area 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, and the first active material layer covers the base portion and the thickened portion.

15. A battery, characterized in that: The invention comprises a box body and a battery cell according to any one of claims 1 to 13, wherein the battery cell is accommodated in the box body.

16. An electrical device, characterized in that: Comprising the battery of claim 15.

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