Electrode assembly, battery monomer, battery device and electric equipment

Abstract

The invention relates to the technical field of batteries, and particularly discloses an electrode assembly, a battery monomer, a battery device and electric equipment, and the battery monomer comprises a shell and the electrode assembly arranged in the shell; the electrode assembly comprises a diaphragm, a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece are opposite in polarity, and the diaphragm, the first pole piece and the second pole piece are stacked according to a preset sequence and are formed by winding; each first pole piece and each second pole piece comprise a plurality of straight parts and a plurality of bent parts which are alternately arranged; the joint between one straight part and one bent part is a connecting part; the first pole piece is partially located on the outermost ring of the electrode assembly, the first pole piece is provided with a thickened area and a normal thickness area, the thickness of a current collector in the thickened area is larger than that of a current collector in the normal thickness area, and at least a connecting part located on the outermost ring of the first pole piece is the thickened area. According to the battery device, the cracking risk of the electrode assembly at the corner can be reduced, and the cost is reduced.

Description

Technical Field

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

[0002] During the aging process of lithium-ion batteries, the electrode assemblies inside the battery usually have complex stress conditions at the corners, such as traction caused by their own expansion, aluminum shell pressure and / or friction between aluminum shells, which makes the electrode assemblies prone to cracking risks at the corners.

[0003] In the related technology, a composite current collector design is usually used, but the composite current collector structure is relatively complex and the process flow is relatively cumbersome, which is not conducive to reducing the cost and increasing the efficiency of the battery cell. Summary of the invention

[0004] The main purpose of the present invention is to provide a battery cell, aiming to solve the problem that the electrode assembly in the battery cell is prone to cracking at the corners.

[0005] To achieve the above object, the battery cell proposed in the present invention comprises a shell and an electrode assembly arranged in the shell; the electrode assembly comprises a diaphragm, a first pole piece and a second pole piece with opposite polarities, and the diaphragm, the first pole piece and the second pole piece are stacked and wound in a preset order; Each of the first pole pieces and each of the second pole pieces comprises a plurality of straight portions and a plurality of curved portions arranged alternately; a connection portion between a straight portion and a curved portion is a connection portion; The first pole piece is partially located at the outermost circle of the electrode assembly. The first pole piece has a thickened area and a normal thickness area. The thickness of the current collector in the thickened area is greater than the thickness of the current collector in the normal thickness area. At least the connecting part located at the outermost circle of the first pole piece is the thickened area.

[0006] In the battery cell of this embodiment, the diaphragm, the first pole piece of two opposite polarities and the second pole piece are wound in sequence to form a runway-type electrode assembly, the connection portion is the corner, the normal thickness area of ​​the first pole piece refers to the pole piece structure of normal thickness, the thickened area refers to the pole piece structure with a thickness greater than the normal thickness, the thickened area refers to the thickness of the current collector in the thickened pole piece, and the thickness of the current collector can be changed by controlling the strength and speed of rolling, so that the thickness of the current collector in the thickened area is greater than the thickness of the current collector in the normal thickness area, so that the first pole piece has a thickened area and a normal thickness area. At least setting the outermost connection of the first pole piece as a thickened area can enhance the structural strength of the connection and reduce the risk of cracking at the connection. In this structure, only the thickness of the current collector in the first pole piece is increased, and no other materials need to be added, which effectively simplifies the process and reduces costs.

[0007] In one embodiment of the present invention, the connecting portion of N circles from the outside to the inside of the first pole piece is the thickened area, wherein N is an integer greater than 1 and less than or equal to 3.

[0008] By thickening each connection portion of the first pole piece from the outside to the inside of the N circles, the risk of cracking at the corners of the electrode assembly can be further reduced.

[0009] In one embodiment of the present invention, at least part of the bent portion located at the outermost circle of the first pole piece is the thickened area; And / or, at least part of the straight portion located at the outermost circle of the first pole piece is the thickened area.

[0010] The electrode assembly of this structure can reduce the risk of cracking of the outermost circle of the first pole piece.

[0011] In one embodiment of the present invention, the connecting parts, the curved parts and the straight parts of N circles from the outside to the inside of the first pole piece are all the thickened areas, wherein N is an integer greater than 1 and less than or equal to 3.

[0012] The risk of cracking of the first pole piece in the N-turn area close to the outside is further reduced, and processing is facilitated.

[0013] In one embodiment of the present invention, the second pole piece has the thickened area and the normal thickness area, and at least the connecting portion located at the outermost circle of the second pole piece is the thickened area.

[0014] At least the outermost connection portion of the second pole piece is set as a thickened area, which can enhance the structural strength of the connection and reduce the risk of cracking at the connection.

[0015] In one embodiment of the present invention, the connecting portion of the M circles from the outside to the inside of the second pole piece is the thickened area, where M is an integer greater than 1 and less than or equal to 2.

[0016] By thickening each connection portion of the second pole piece from the outside to the inside of the N circles, the risk of cracking at the corners of the electrode assembly can be further reduced.

[0017] In one embodiment of the present invention, at least part of the bent portion located at the outermost circle of the second pole piece is the thickened area; And / or, at least part of the straight portion located at the outermost circle of the second pole piece is the thickened area.

[0018] In this structure, the risk of cracking of the outermost second pole piece can be reduced.

[0019] In one embodiment of the present invention, the connecting portion, the curved portion, and the straight portion of the M circles from the outside to the inside of the second pole piece are all the thickened areas, where M is an integer greater than 1 and less than or equal to 2.

[0020] The second pole pieces wound in the last few turns are all set as thickened areas to facilitate the processing of the pole pieces.

[0021] In one embodiment of the present invention, the first pole piece is an anode pole piece.

[0022] The battery cells with this structure can reduce the interface resistance and improve the performance.

[0023] In one embodiment of the present invention, the electrode assembly further comprises a transition zone, wherein the transition zone is located at the connection between the thickened zone and the normal thickness zone; The thickness of one end of the transition zone is the same as that of the normal thickness zone, and the thickness of the other end is the same as that of the thickened zone. The thickness of the transition zone gradually increases from one end to the other end.

[0024] The electrode assembly of this structure can reduce the stress concentration caused by the thickness difference between the normal thickness area and the thickened area, and enhance the overall structural strength.

[0025] In one embodiment of the present invention, the thickness of the normal thickness area is X, and X is greater than or equal to 3 μm and less than or equal to 15 μm; The difference between the thickness of the thickened area and the thickness of the normal thickness area is Y, and Y is greater than 0 and less than or equal to 5 μm.

[0026] The thickened area within this thickness range can improve the structural strength without increasing the thickness of the pole piece too much, thereby increasing the energy density of the battery device.

[0027] In one embodiment of the present invention, the extension length of the transition zone is Z, and Z is greater than or equal to 5 cm and less than or equal to 10 cm.

[0028] The transition zone in this length range can achieve the effect of relieving stress and increase the area of ​​the pole piece with high structural strength, further reducing the risk of cracking.

[0029] In one embodiment of the present invention, a surface of the current collector in the thickened area is provided with a reinforcement texture, and the reinforcement texture is extended along a line connecting the normal thickness area to the thickened area.

[0030] The setting of reinforcing texture can improve the yield strength and fatigue performance of the thickened area.

[0031] In one embodiment of the present invention, the reinforcement texture is a strip-shaped roll-pressed groove, the depth of the roll-pressed groove is D, and D is greater than 0 and less than or equal to 4 μm.

[0032] This depth range guarantees a strength-enhancing effect.

[0033] In one embodiment of the present invention, there are a plurality of roll-embossed grooves, and the plurality of roll-embossed grooves are arranged at intervals in a direction perpendicular to a line connecting the normal thickness area to the thickened area.

[0034] Further improve the yield strength and fatigue performance of the thickened area.

[0035] In one embodiment of the present invention, the width of the roller groove in a direction perpendicular to the line connecting the normal thickness area to the thickened area is W, and W is greater than 1 cm and less than or equal to 3 cm; And / or, the distance between two adjacent roller-pressed grooves is S, and S is greater than 0 and less than or equal to 2 cm; And / or, the distance between the opening edge of the rolling groove closest to the edge of the thickened area and the edge of the thickened area is T, and T is greater than 1 cm and less than or equal to 2 cm.

[0036] The setting of the above parameters can improve the uniformity of the yield strength and fatigue performance of the thickened area at various positions.

[0037] In one embodiment of the present invention, along the winding direction, a positioning hole is provided at one end of the thickened area away from the normal thickness area, and the positioning hole is used for identification by the winding machine.

[0038] The provision of the positioning holes can ensure that the thickened area is located at the outermost turns of the electrode assembly, thereby increasing the risk of cracking at the connection of the outer ring of the electrode assembly.

[0039] The present invention further provides an electrode assembly, the electrode assembly comprising a diaphragm, a first pole piece and a second pole piece with opposite polarities, wherein the diaphragm, the first pole piece and the second pole piece are stacked and wound in a preset order; Each of the first pole piece and each of the second pole piece comprises a plurality of straight portions and a plurality of curved portions arranged alternately; the connection between a straight portion and a curved portion is a connection portion; The first pole piece has a thickened area and a normal thickness area. The thickness of the current collector in the thickened area is greater than the thickness of the current collector in the normal thickness area. At least the connecting portion located at the outermost circle of the first pole piece is the thickened area.

[0040] In this solution, the diaphragm, the first pole piece and the second pole piece of two opposite polarities are wound in sequence to form a racetrack-shaped electrode assembly, the connection portion is the corner, the normal thickness area of ​​the first pole piece refers to the pole piece structure of normal thickness, the thickened area refers to the pole piece structure with a thickness greater than the normal thickness, the thickened area refers to the thickness of the current collector in the thickened pole piece, and the thickness of the current collector can be changed by controlling the strength and speed of rolling, so that the thickness of the current collector in the thickened area is greater than the thickness of the current collector in the normal thickness area, so that the first pole piece has a thickened area and a normal thickness area. At least setting the outermost connection of the first pole piece as a thickened area can enhance the structural strength of the connection and reduce the risk of cracking at the connection. In this structure, only the thickness of the current collector in the first pole piece is increased, and no other materials need to be added, which effectively simplifies the process and reduces costs.

[0041] The present invention further provides a battery device, comprising any battery cell as described above.

[0042] The present invention also provides an electrical device, comprising the battery device as described above.

[0043] Theme app for battery device protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0045] Figure 1 It is a structural schematic diagram of the electrical equipment of the present invention; Figure 2 A partial exploded view of the battery device of the present invention; Figure 3 It is a structural schematic diagram of an embodiment of an electrode assembly of the present invention; Figure 4 for Figure 3 a partially enlarged view of a cross section of the electrode assembly shown; Figure 5 for Figure 3 Schematic diagram of part of the structure of the electrode assembly shown.

[0046] Description of Figure Numbers: 100. Battery device; 10. Housing; 11. First part; 12. Second part; 20. Battery cell; 21. Electrode assembly; 211. Diaphragm; 212. Pole piece; 2121. Straight portion; 2122. Curved portion; 2123. Connecting portion; 2123a. First connecting portion; 2123b. Second connecting portion; 2124. Normal thickness area; 2125. Thickened area; 2125a. Rolled groove; 2126. Transition area; 2127. Positioning hole; 200. Controller; 300. Motor.

[0047] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0050] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" 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, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel solutions. Taking "A and / or B as an example", it includes solution A, or solution B, or a solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0052] The battery devices mentioned in this field can be divided into disposable batteries and rechargeable batteries according to whether they are rechargeable. The common types of rechargeable batteries are: lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries. Lithium-ion batteries are currently widely used in pure electric vehicles and hybrid vehicles. The capacity of lithium-ion batteries used for this purpose is relatively low, but they have larger output and charging current, and also have a longer service life, but the cost is higher.

[0053] The battery device described in the embodiments of the present invention refers to a rechargeable battery. The embodiments disclosed in the present invention will be described below mainly by taking a lithium-ion battery as an example. It should be understood that the embodiments disclosed in the present invention are applicable to any other appropriate type of rechargeable battery. The battery device mentioned in the embodiments disclosed in the present invention can be directly or indirectly applied to an appropriate device to power the device.

[0054] The battery device mentioned in the embodiments disclosed in the present invention refers to a single physical module including one or more battery cells to provide a predetermined voltage and capacity, which can be a battery module or a battery pack. The battery cell is the basic unit in the battery device, which can be used to make a battery module or a battery pack. The battery module is formed by connecting a certain number of battery cells in series and / or in parallel and placing them in a frame in order to protect the battery cells from external impact, heat, vibration, etc. The battery pack generally includes a battery module, a battery management system, and a box that accommodates the battery module and the battery management system. The battery management system is used to monitor and manage the charging and discharging process of the battery module.

[0055] The electrode assembly is an important component of the battery device. According to the preparation method of the electrode assembly, it can be divided into a wound electrode assembly and a laminated electrode assembly. Among them, the wound electrode assembly is widely used because it is relatively simple to operate and the quality is easy to control. The wound electrode assembly generally includes a negative electrode sheet, a positive electrode sheet and a separator arranged in a preset order. The positive electrode sheet and the negative electrode sheet are generally composed of a current collector and an active material layer coated on the current collector, respectively. The wound electrode assembly can be a square structure or a cylindrical structure. Among them, the square wound electrode assembly is widely used due to its advantages such as good heat dissipation.

[0056] The temperature of the battery cell will increase during use. When the temperature rises, the active material layer on each pole piece in the wound electrode assembly will expand due to the temperature rise, and then exert an outward expansion force on the corresponding part wound outside it, such as the pole piece located in the outer ring. In addition, as the electrode assembly expands, the outer wall of the electrode assembly will contact and squeeze the inner wall of the outer shell of the battery device (for ease of description, this phenomenon is referred to as the top shell below), so that the electrode assembly will receive the pressure applied by the outer shell to the electrode assembly, and at the same time, the pole piece located in the outer ring of the electrode assembly will also come into frictional contact with the outer shell during the expansion process, thereby receiving the friction force from the outer shell.

[0057] At this time, due to the characteristics of the square wound electrode assembly's own winding structure, the pole pieces located on the outer ring will be subject to the outward pressure exerted by the inner ring pole pieces due to the expansion of the active material layer. After the electrode assembly is topped, the pole pieces located on the outer ring will also be subject to the pressure and friction exerted by the outer shell, which will cause stress concentration in the connection area between the straight part and the curved part of the pole piece located on the outer ring. As the wound electrode assembly ages, the pole pieces are prone to cracking in the above-mentioned connection area (i.e., the corners).

[0058] Based on the above background, the present invention proposes a battery cell, which improves the electrode assembly in the battery cell and sets the connection part of the first pole piece located at the outer ring of the winding as a thickened area, thereby improving the structural strength at this position, thereby reducing the occurrence of cracking. In this structure, only the thickness of the current collector in the first pole piece is increased, and no other materials need to be added, which effectively simplifies the process and reduces costs.

[0059] The battery device disclosed in the embodiment of the present application can be used in various energy storage systems that use batteries as power sources or use batteries as energy storage elements. The electrical equipment can be, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0060] For the convenience of explanation, the following examples are referred to Figure 1 , an electrical device in one embodiment of the present application is taken as an example of a vehicle.

[0061] Figure 1 The electrical equipment provided for some embodiments of the present application is a schematic diagram of the structure of a vehicle. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery device 100 is provided inside the vehicle, and the battery device 100 may be provided at the bottom, head or tail of the vehicle. The battery device 100 may be used to power the vehicle, for example, the battery device 100 may be used as an operating power source for the vehicle. The vehicle may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery device 100 to power the motor 300, for example, for starting, navigating and driving the vehicle.

[0062] In some embodiments of the present application, the battery device 100 can be used not only as an operating power source for the vehicle, but also as a driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0063] refer to Figure 2 , Figure 2 An exploded view of a battery device 100 provided in some embodiments of the present application. The battery device 100 includes a box 10 and at least two battery cells 20, wherein the box 10 is used to provide a storage space for the battery cells 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space. The second part 12 may be a hollow structure with one end open, the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0064] In the battery device 100, there may be a plurality of battery cells 20, which may be connected in series, in parallel, or in mixed series to form a whole and accommodated in the box 10. Mixed series means that the plurality of battery cells 20 are both connected in series and in parallel. The battery device 100 may also include other structures, for example, a busbar component for realizing electrical connection between the plurality of battery cells 20.

[0065] The battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, etc. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0066] In some cases, the battery cells can also be directly installed in the vehicle without a box or shell, that is, there is no need to form a battery pack, and the structure of the vehicle body itself serves as a fixing structure for the battery cells.

[0067] The battery cell of the present application is introduced below with specific embodiments: Please refer to Figures 3 to 5 In one embodiment of the present invention, the battery cell 20 includes a shell and an electrode assembly 21 disposed in the shell; the electrode assembly 21 includes a diaphragm 211, a first electrode sheet and a second electrode sheet, and the diaphragm 211, the first electrode sheet and the second electrode sheet are stacked and wound in a preset order; Each of the first pole piece and the second pole piece includes a plurality of straight portions 2121 and a plurality of curved portions 2122 arranged alternately; the connection between a straight portion 2121 and a curved portion 2122 is a connection portion 2123; The first pole piece has a thickened area 2125 and a normal thickness area 2124 . The thickness of the current collector in the thickened area 2125 is greater than the thickness of the current collector in the normal thickness area 2124 . At least the connecting portion 2123 located at the outermost circle of the first pole piece is the thickened area 2125 .

[0068] In this embodiment, the battery cell 20 includes a shell and an electrode assembly 21. The shell is a closed structure, forming the internal space required by the electrode assembly 21. The shell generally includes an end cap and a shell body. The shell body forms a receiving cavity with an opening. The electrode assembly 21 is installed in the receiving cavity, and the end cap covers the opening to seal the receiving cavity. The specific structure of the end cap and other functional components arranged thereon can refer to the existing end cap structure, which will not be described in detail here. Of course, electrolyte and other components are also arranged in the shell, which will not be described in detail here.

[0069] One, two or more electrode assemblies 21 may be provided in one battery cell 20. The electrode assembly 21 includes a diaphragm 211, a first electrode sheet and a second electrode sheet with opposite polarities, the first electrode sheet and the second electrode sheet refer to a cathode electrode sheet and an anode electrode sheet, which are generally stacked in the order of anode electrode sheet, diaphragm 211, cathode electrode sheet, diaphragm 211, or cathode electrode sheet, diaphragm 211, anode electrode sheet, diaphragm 211. When the electrode assembly 21 includes multiple anode electrode sheets and multiple cathode electrode sheets, the stacking principle is equivalent to the above, and will not be repeated here.

[0070] In one example, after the anode electrode sheet, cathode electrode sheet and diaphragm 211 are stacked and wound in a preset order, a flat multi-turn winding body is formed. The electrode sheet of the innermost circle is composed of two sheets bonded together, which is defined as the first sheet. Except for the electrode sheet portion located in the innermost circle, the electrode sheet portion of each other circle includes two oppositely arranged straight portions 2121 and two curved portions 2122 connecting the two straight portions 2121. It should be noted that, if Figure 3 In the embodiment, a curved portion 2122 in the pole piece portion of the outermost circle connects two straight portions 2121 in the circle, and another curved portion 2122 connects a straight portion 2121 in the circle and a straight portion 2121 in another adjacent circle.

[0071] The portion corresponding to the position of the first sheet of the innermost circle and having the same length is defined as a straight portion 2121, and the portion between two adjacent straight portions 2121 is defined as a curved portion 2122. Figure 3 The portion between the upper line bodies L1 and L2 of the outermost circle is the straight portion 2121, and the curved portion 2122 is the arc portion on the right side of L2 and the arc portion on the left side of L1. Any connected straight portion 2121 and curved portion 2122 have a connecting end face, such as Figure 4 At the line L3 in the middle, the plane where the line L3 is located extends a distance toward the straight portion 2121 to form a first connection portion 2123a, and the plane where the line L3 is located extends a distance toward the curved portion 2122 to form a second connection portion 2123b. In one example, because the position of the second connection portion 2123b is subject to both internal expansion force and easy friction with the shell, and there is no pressing and restraining force of the shell, this place is the most prone to cracking, so the connection portion 2123 may only include the second connection portion 2123b. In another example, the connection portion 2123 includes a first connection portion 2123a and a second connection portion 2123b that are connected to each other, and the lengths of the first connection portion 2123a and the second connection portion 2123b are not limited.

[0072] Since the pole pieces are all sheets and are wound, each pole piece has a thickness dimension, a length dimension and a width dimension, and the thickness dimension is much smaller than the dimensions in the length direction and the width direction. The first pole piece has a thickened area 2125 and a normal thickness area 2124, which means that the first pole piece has a normal thickness area 2124 in its extension direction, that is, the thickness of the wound pole piece is set according to the performance of the battery device 100. The thickness can be set according to actual needs and is not limited here. The thickened area 2125 is set with an increased thickness based on the thickness of the normal thickness area 2124, that is, the thickness of the thickened area 2125 is greater than the thickness of the normal thickness area 2124. The thickness of the thickened area 2125 is not limited here and can be set according to actual needs. Because the pole piece is composed of a current collector and an active material layer coated on the current collector, the thickness of the thickened area 2125 here is greater than the thickness of the normal thickness area 2124, which means that the thickness of the current collector is increased, that is, the thickness of the current collector in the thickened area 2125 is greater than the thickness of the current collector in the normal thickness area 2124, and the thickness of the coated active material layer is constant, which is reflected in the different thicknesses at different positions on the first pole piece. Optionally, the thickness of the current collector is controlled by controlling the speed and pressure of the roller when rolling the substrate, thereby forming current collectors of different thicknesses, so that the current collector has different structural strengths at different thicknesses. In one example, the thickness value of the current collector in the normal thickness area 2124 is X, X is greater than or equal to 3μm, less than or equal to 15μm, and can have a higher energy density and a suitable winding volume. Here and in the subsequent thickening treatment of the pole piece thickness refers to thickening the thickness of the current collector at the connection portion, by rolling the current collector, and controlling the thickness of the current collector by the rolling intensity and rate. The thickened area 2125 refers to the thickness of the current collector in the thickened pole piece.

[0073] The outermost circle refers to the outermost circle of the electrode structure after the electrode assembly 21 is wound, that is, the part of the electrode that is not wrapped inside and exposed. The first electrode is located at the outermost circle of the electrode assembly 21, and at least the connection part 2123 located at the outermost circle of the first electrode refers to at least one connection part 2123 of the connection parts 2123 of the outermost circle of the first electrode, and setting the connection part 2123 as the thickened area 2125 means that the thickness of the electrode where the connection part 2123 is located is thickened to form the thickened area 2125. Of course, in other examples, it can also be two connection parts 2123 of the outermost circle, or three connection parts 2123 of the outermost circle, or a connection part 2123 located on the inner side of the outermost circle, etc.

[0074] In the battery device 100 of this embodiment, at least the connection portion 2123 of the outermost circle of the first pole piece is set as a thickened area 2125, which can enhance the structural strength of the connection portion 2123, thereby improving the ability to resist the expansion force and friction force, reducing the risk of cracking at the connection portion 2123, and thus reducing the failure risk of the battery device 100. In addition, in this structure, only the thickness of the current collector needs to be increased, and no other additional materials need to be added, and no composite pole piece needs to be used, so that the process is simple and the cost is effectively reduced.

[0075] Optionally, each connection portion 2123 located in the outermost circle is a thickened area 2125. In this example, the first pole piece structure of the outermost circle includes four connection portions 2123, and each connection portion 2123 located in the outermost circle is a thickened area 2125, which means that the four connection portions 2123 are all set as thickened areas 2125, that is, the pole piece structures of the four connection portions 2123 are all thickened, which can reduce the cracking risk of the most easily cracked part of the first pole piece of the outermost circle of the electrode assembly 21, and further reduce the failure risk of the battery device 100.

[0076] Please combine Figure 4 and Figure 5 In one embodiment of the present invention, the connecting portion 2123 of the N-circle connecting portion from the outside to the inside of the first pole piece is a thickened area 2125, wherein N is an integer, N is greater than 1, and is less than or equal to 3.

[0077] In this example, the wound electrode assembly 21 is a multi-turn winding body. Counting from the outside to the center of the electrode assembly 21, the outermost circle is the first circle, that is, the outermost circle, followed by the second circle, the third circle... Here, the N circles of the first pole piece arranged in sequence from the outermost circle to the inside refer to the N circles of the first pole piece counted from the outside to the inside, where N can be 2 or 3. The connecting parts 2123 of these N circles are all set to thickened areas 2125, which can reduce the overall volume of the electrode assembly 21 and improve the energy density and charging and discharging efficiency while ensuring that the risk of cracking of the electrode assembly 21 is low.

[0078] Since the connection parts of the pole piece parts close to the outer several circles are all subject to a large expansion force, the setting of this structure can further reduce the risk of cracking of the connection part 2123 of the first pole piece in the N circles close to the outer side, and further reduce the failure risk of the battery cell 20.

[0079] In one embodiment of the present invention, at least part of the bent portion 2122 located at the outermost circle of the first pole piece is a thickened area 2125; And / or, at least a portion of the straight portion 2121 located at the outermost circle of the first pole piece is a thickened area 2125 .

[0080] In this embodiment, at least part of the curved portion 2122 of the outermost circle of the first pole piece refers to a partial structure of one of the curved portions 2122, or the entire structure of one of the curved portions 2122, or the entire structure of two curved portions 2122. The electrode assembly 21 of this structure can further reduce the risk of cracking of the curved portion 2122 of the outermost circle of the first pole piece.

[0081] On the basis of limiting or not limiting the thickening of the curved portion 2122, setting at least part of the straight portion 2121 of the outermost circle of the first pole piece as a thickened area refers to a partial structure of one of the straight portions 2121 of the outermost circle of the first pole piece, or the entire structure of one of the straight portions 2121, or the entire structure of two straight portions 2121. The electrode assembly 21 of this structure can further reduce the risk of cracking of the straight portion 2121 of the outermost circle of the first pole piece.

[0082] The first pole piece located at the outermost circle includes two straight portions 2121, two curved portions 2122 and four connecting portions 2123. The four connecting portions 2123, the two curved portions 2122 and the two straight portions 2121 are all set as thickened areas 2125, so that the first pole piece after the penultimate circle of winding can be thickened. When processing the pole piece, the rolling conditions of the rear section of the current collector can be directly set and remain unchanged until the very end, without repeatedly adjusting the rolling conditions.

[0083] The electrode assembly 21 of this structure can reduce the adjustment of rolling conditions, facilitate the processing of the current collector of the first electrode sheet, and improve the processing efficiency.

[0084] In one embodiment of the present invention, the connecting portion 2123 , the curved portion 2122 and the straight portion 2121 located in N circles from the outside to the inside of the first pole piece are all thickened areas 2125 , wherein N is an integer greater than 1 and less than or equal to 3.

[0085] In this embodiment, N is 2 or 3, and the pole piece structures of N circles from the outside to the inside of the first pole piece are all set to the thickened area 2125, further reducing the risk of cracking of the first pole piece in the N circles close to the outside, and facilitating the unified thickening of the structures of the last few circles of the collector in the first pole piece, which can reduce the adjustment of the rolling conditions, facilitate the processing of the first pole piece, and improve the processing efficiency.

[0086] In one embodiment of the present invention, the second pole piece has a thickened area 2125 and a normal thickness area 2124 , and at least the connecting portion 2123 located at the outermost circle of the second pole piece is the thickened area 2125 .

[0087] At least the connection portion 2123 of the outermost circle of the second pole piece is set as a thickened area 2125. The thickened area 2125 here is the same as the setting of the thickened area mentioned above, both of which thicken the thickness of the current collector in the second pole piece, which can enhance the structural strength of the connection and reduce the risk of cracking at the connection portion 2123. Combined with the connection portion 2123 of the outermost circle of the first pole piece being the thickened area 2125, the connection portions 2123 of the two outermost circles of the electrode assembly 21 can be thickened, further reducing the risk of cracking of the electrode assembly 21. Combined with the connection portion 2123, the straight portion 2121 and the curved portion 2122 of the outermost circle of the first pole piece being the thickened area 2125, the risk of cracking of the electrode assembly 21 can be further reduced.

[0088] Please refer to Figure 4 In one embodiment of the present invention, the connecting portion 2123 of the M-circle from the outside to the inside of the second pole piece is a thickened area 2125, where M is an integer, M is greater than 1, and less than or equal to 2.

[0089] In this embodiment, M can be 2, and each connection portion 2123 of the second pole piece from the outside to the inside M circles is thickened, which can further reduce the risk of cracking at the corners of the electrode assembly 21. This example is combined with the thickening treatment of the connection portion 2123 of the first pole piece from the outside to the inside N circles, which can improve the strength of the pole piece of the electrode assembly 21 from the inside to the outside M+N circles at the corners and reduce the risk of cracking at the corners.

[0090] In one embodiment of the present invention, at least part of the bent portion 2122 located at the outermost circle of the second pole piece is a thickened area 2125; And / or, at least a portion of the straight portion 2121 located at the outermost circle of the second pole piece is a thickened area 2125 .

[0091] In this structure, at least part of the curved portion 2122 of the outermost circle of the second pole piece refers to a partial structure of one of the curved portions 2122, or the entire structure of one of the curved portions 2122, or the entire structure of two curved portions 2122. The electrode assembly 21 of this structure can further reduce the risk of cracking of the curved portion 2122 of the outermost circle of the second pole piece.

[0092] On the basis of whether or not the curved portion 2122 is thickened, at least part of the straight portion 2121 of the outermost circle of the second pole piece is set as a thickened area, which refers to a partial structure of one of the straight portions 2121 of the outermost circle of the second pole piece, or the entire structure of one of the straight portions 2121, or the entire structure of two straight portions 2121. The electrode assembly 21 of this structure can further reduce the risk of cracking of the straight portion 2121 of the outermost circle of the second pole piece. Combined with the solution that both the curved portion 2122 and the straight portion 2121 of the outermost circle of the first pole piece are thickened, the pole piece structures of the two outermost circles of the electrode assembly 21 can be thickened, effectively reducing the risk of cracking of the overall structure, while facilitating pole piece processing.

[0093] The second pole piece located at the outermost circle includes two straight portions 2121, two curved portions 2122 and four connecting portions 2123. The four connecting portions 2123, the two curved portions 2122 and the two straight portions 2121 are all set as thickened areas 2125, so that the current collector of the second pole piece after the penultimate circle of winding can be thickened. When processing the current collector, the rolling conditions of the rear section can be directly set and remain unchanged until the very end, without repeatedly adjusting the rolling conditions.

[0094] The electrode assembly 21 of this structure can reduce the adjustment of rolling conditions, facilitate the processing of the first electrode sheet, and improve the processing efficiency.

[0095] Please refer to Figure 4 In one embodiment of the present invention, the connecting portion 2123, the curved portion 2122, and the straight portion 2121 of the M circles located from the outside to the inside of the second pole piece are all thickened areas 2125, where M is an integer, M is greater than 1, and less than or equal to 2.

[0096] Wherein, M is 2, and the overall structure of the last few turns of the second pole piece is set as a thickened area 2125, which further reduces the risk of cracking of the outermost M turns and facilitates the processing of the pole piece. Combined with the solution that the curved portion 2122 and the straight portion 2121 of the outermost N turns of the first pole piece are thickened, the pole piece structure of the outermost N+M turns of the electrode assembly 21 can be thickened, further reducing the risk of cracking of the overall structure. At the same time, on the basis that each connection portion 2123 in the pole piece structure of M turns counted from the outside to the inside is a thickened area 2125, the multiple curved portions 2122 and the multiple straight portions 2121 between the multiple connection portions 2123 are all set as thickened areas 2125, that is, the pole piece portion of the outer M turns is continuously thickened, which can simplify the process conditions for processing the current collector in the pole piece, facilitate the processing of the current collector, and improve the processing efficiency.

[0097] In one embodiment of the present invention, the first pole piece is an anode pole piece.

[0098] In this example, the structure of the battery cell 20 is a structure in which an anode electrode sheet covers a cathode electrode sheet. The battery cell 20 with this structure can reduce interface resistance and improve performance.

[0099] In the following examples, the pole piece can be either the first pole piece or the second pole piece.

[0100] Please refer to Figure 5 In one embodiment of the present invention, the electrode assembly 21 further has a transition zone 2126, and the transition zone 2126 is located at the connection between the thickened zone 2125 and the normal thickness zone 2124; The thickness of one end of the transition zone 2126 is the same as that of the normal thickness zone 2124 , and the thickness of the other end is the same as that of the thickened zone 2125 . The thickness of the transition zone 2126 gradually increases from one end to the other end.

[0101] In this example, the transition zone 2126 refers to the gradual transition of the thickness of the normal thickness zone 2124 of the pole piece to the thickness of the thickened zone 2125. Therefore, the thickness of the transition zone 2126 changes gradually, and in the direction from the normal thickness zone 2124 to the thickened zone 2125, the thickness of the transition zone 2126 increases gradually. The increase rule here is not limited. For example, it can increase linearly or curvilinearly, such as J-type increase or S-type increase. Optionally, the connection between the transition zone 2126 and the normal thickness zone 2124 is an arc transition connection, and the connection between the transition zone 2126 and the thickened zone 2125 is also an arc transition connection, which further reduces the sharp structure. It can be understood that the thickness of the transition zone 2126 changes gradually, which means that the thickness of the current collector in the pole piece changes gradually, and it is adjusted by setting the spacing and speed of the rollers for rolling the current collector.

[0102] The setting of the transition zone 2126 can reduce the step difference stress concentration caused by the thickness difference between the normal thickness zone 2124 and the thickened zone 2125, and enhance the overall structural strength.

[0103] It can be understood that when only the connection portion 2123 is set as the thickened area 2125, the transition area 2126 can be set on both sides of the thickened area 2125 in the length direction, so as to perform thickness transition on both sides of the thickened area 2125 to improve the structural strength.

[0104] In one embodiment of the present invention, the thickness of the current collector in the normal thickness region 2124 is X, where X is greater than or equal to 3 μm and less than or equal to 15 μm; The difference between the thickness of the thickened area 2125 and the thickness of the normal thickness area 2124 is Y, and Y is greater than 0 and less than or equal to 5 μm.

[0105] In this example, the current collector thickness X of the normal thickness zone 2124 can be 3μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, etc., which has good winding performance and ensures the energy density of the battery. The thickness increase value Y of the thickened zone 2125 compared to the normal thickness zone 2124 can be 1μm, 2μm, 3μm, 4μm, etc. The thickened zone 2125 in this thickness range can improve the structural strength and reduce the risk of cracking without increasing the thickness of the pole piece too much, thereby improving the energy density of the battery device 100.

[0106] Please continue to refer to Figure 5 In one embodiment of the present invention, the extension length of the transition zone 2126 is Z, and Z is greater than or equal to 5 cm and less than or equal to 10 cm.

[0107] In this example, the extension length of the transition zone 2126 can be set according to the winding specifications of the electrode assembly 21. Here, Z is set to be greater than or equal to 5 cm and less than or equal to 10 cm, for example, 6 cm, 7 cm, 8 cm or 9 cm, etc. The transition zone 2126 in this length range can achieve the effect of relieving stress, and does not occupy too much length of the thickened area 2125, thereby increasing the area of ​​the pole piece with high structural strength and further reducing the risk of cracking.

[0108] Please refer to Figure 5 In one embodiment of the present invention, a reinforcement texture is provided on the surface of the current collector in the thickened area 2125 , and the reinforcement texture is extended along the line direction from the normal thickness area 2124 to the thickened area 2125 .

[0109] In this example, the reinforcing texture refers to the pattern or lines on the surface of the current collector in the thickened area 2125, which can strengthen the structural strength of the thickened area 2125 itself. It can be understood that the reinforcing texture is formed when processing the current collector, and the reinforcing texture can still be seen after coating the active material layer. The specific shape of the reinforcing texture is not limited, but because the cracking of the pole piece is usually along the height direction of the electrode assembly 21, that is, perpendicular to the extension direction of the first pole piece or the second pole piece, the reinforcing texture needs to be extended along the line direction from the normal thickness area 2124 to the thickened area 2125, that is, the extension direction of the first pole piece or the second pole piece, so it has a certain extension length and extension direction, and the extension direction is consistent with the extension direction of the first pole piece or the second pole piece, so that the strength of the thickened area 2125 in the direction perpendicular to the extension can be improved, effectively reducing the risk of cracking.

[0110] The setting of the reinforced texture can improve the yield strength and fatigue performance of the thickened area 2125 and further reduce the risk of cracking.

[0111] In one embodiment of the present invention, the reinforcing texture is a strip-shaped rolling groove 2125 a , and the depth of the rolling groove 2125 a is D, where D is greater than 0 and less than or equal to 4 μm.

[0112] In this example, the reinforcing texture is set as a strip-shaped rolling groove 2125a, that is, the reinforcing texture is a groove structure formed by rolling by a specially set roller or a roller with a width smaller than the width of the current collector. The rolling groove 2125a has a straight extension direction, and the extension direction of the rolling groove 2125a is parallel to the extension direction of the first pole piece or the second pole piece. In other examples, the reinforcing texture can also be wavy or other shapes; or, the reinforcing texture can also be a convex structure. Or the reinforcing texture can also be a groove body or a convex structure formed by stamping or die cutting.

[0113] The depth D of the rolled groove 2125a can be 1 μm, 2 μm, 3 μm or 4 μm, which can be specifically set according to the overall thickness of the current collector in the thickened area 2125. On the basis of significantly improving the yield strength and fatigue performance of the thickened area 2125, the thickness of the current collector in the thickened area 2125 will not be excessively reduced, thereby ensuring the effect of improving strength.

[0114] Please refer to Figure 5 In one embodiment of the present invention, there are multiple rolling grooves 2125a, and the multiple rolling grooves 2125a are arranged at intervals in a direction perpendicular to the direction of the line connecting the normal thickness area 2124 to the thickened area 2125.

[0115] In this example, a plurality of roll-pressed grooves 2125a are provided, and the plurality of roll-pressed grooves 2125a are arranged at intervals in the extending direction perpendicular to the first pole piece or the second pole piece. Optionally, the extending length of the roll-pressed grooves 2125a is the same as the length of the current collector of the thickened area 2125, and can be formed by one-time processing with a roller, further improving the yield strength and fatigue performance of the pole piece thickened area 2125. In other examples, the extending length of the roll-pressed grooves 2125a may also be different from the length of the thickened area 2125.

[0116] Please continue to refer to Figure 5 In one embodiment of the present invention, the width of the rolling groove 2125a in the direction perpendicular to the line connecting the normal thickness area 2124 and the thickened area 2125 is W, and W is greater than 1 cm and less than or equal to 3 cm; And / or, the distance between two adjacent roller pressing grooves 2125a is S, and S is greater than 0 and less than or equal to 2 cm; And / or, the distance between the opening edge of the rolling groove 2125a closest to the edge of the thickened area 2125 and the edge of the thickened area 2125 is T, and T is greater than 1 cm and less than or equal to 2 cm.

[0117] In this example, the opening width W of the roll-pressed groove 2125a can be 2 cm, 2.5 cm or 3 cm, etc., and can be appropriately adjusted according to the width of the current collector. The roll-pressed groove 2125a of this width range combined with the depth range can further improve the yield strength and fatigue performance and reduce the risk of cracking.

[0118] On the basis of limiting or not limiting the opening width of the roll-pressed groove 2125a, the spacing S between two adjacent roll-pressed grooves 2125a can be 1 cm, 1.5 cm or 2 cm, etc., which can further improve the yield strength and fatigue performance and reduce the risk of cracking.

[0119] On the basis of limiting or not limiting the opening width of the roll-rolled groove 2125a and / or the distance between the two roll-rolled grooves 2125a, the distance T between the opening edge of the roll-rolled groove 2125a closest to the edge of the thickened area 2125 and the edge of the pole piece can be set to 1.2 cm, 1.5 cm or 2 cm, etc., so that the roll-rolled groove 2125a is not too close to the edge in the width direction of the current collector, thereby improving the yield strength and fatigue performance, and ensuring the strength uniformity at various positions of the pole piece.

[0120] The combination of the above parameters can improve the uniformity of the yield strength and fatigue performance of the thickened area 2125 pole piece at various positions.

[0121] Please combine again Figure 5 In one embodiment of the present invention, along the winding direction, a positioning hole 2127 is provided at one end of the thickened area 2125 away from the normal thickness area 2124, and the positioning hole 2127 is used for identification by the winding machine.

[0122] In this example, the positioning hole 2127 is located at one end of the thickened area 2125 away from the normal thickness area 2124, and can be located on one side of the end in the width direction, or in the middle in the width direction, which is not limited here. The opening shape of the positioning hole 2127 is not limited, for example, it can be circular, square, or other regular or irregular shapes. The number of positioning holes 2127 is also not limited, and can be one or more. The distance from the end edge of the thickened area 2125 in the extension direction of the pole piece is not limited, as long as it does not affect the structural strength of the pole piece.

[0123] It is understandable that a detection device, such as a camera or a distance detection device, is provided on the winding machine, so that the positioning hole 2127 can be detected when the thickened area 2125 is wound to the end away from the normal thickness area 2124, so that the electrode piece can be cut off for finishing. The provision of the positioning hole 2127 can ensure that the thickened area 2125 is located in the outermost circle or several circles of the electrode assembly 21, thereby increasing the risk of cracking of the connection portion 2123 of the outermost circle or several outer circles of the electrode assembly 21.

[0124] The present invention further provides an electrode assembly 21, the electrode assembly 21 comprising a diaphragm 211, a first pole piece and a second pole piece with opposite polarities, the diaphragm 211, the first pole piece and the second pole piece are stacked and wound in a preset order; Each first pole piece and each second pole piece includes a plurality of straight portions 2121 and a plurality of curved portions 2122 arranged alternately; the connection between a straight portion 2121 and a curved portion 2122 is a connection portion 2123; The first pole piece has a thickened area 2125 and a normal thickness area 2124, the thickness of the current collector in the thickened area 2125 is greater than the thickness of the current collector in the normal thickness area 2124, and at least the connecting portion 2123 located at the outermost circle of the first pole piece is the thickened area 2125. The battery management system adopts all the technical solutions of all the above embodiments, and therefore has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here one by one.

[0125] In this solution, the separator 211, the first pole piece, and the second pole piece of the electrode assembly 21 are wound in sequence, and at least the outermost connection portion 2123 of the first pole piece is set as a thickened area 2125, which can enhance the structural strength of the connection portion 2123, thereby improving the ability to resist the expansion force and friction force, reducing the risk of cracking at the connection portion 2123, and thus reducing the failure risk of the battery device 100. In this structure, only the thickness of the current collector in the first pole piece is increased, and no other materials need to be added, which effectively simplifies the process and reduces costs.

[0126] The present invention also provides a battery device, including any of the above-mentioned battery cells 20. The battery cell 20 of the battery device 100 adopts all the technical solutions of all the above-mentioned embodiments, and thus has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0127] The battery device 100 may be a battery module or a battery pack, which is not limited here. At this time, the battery device 100 may also include a box body 10, and the battery cell 20 is installed in the box body 10. The box body 10 and the battery cell 20 can refer to the structure discussed above, and will not be repeated here.

[0128] The present invention further provides an electric device, comprising the battery device 100 as described above. The battery device 100 of the electric device adopts all the technical solutions of all the above embodiments, and thus has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0129] The power-consuming device may be a mobile phone, a laptop computer, a battery car, an electric car, an energy storage station, etc. The present application does not limit the specific type of the power-consuming device. When the power-consuming device includes the battery device 100, the battery device 100 may provide power.

[0130] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A battery cell, characterized in that: The battery cell comprises a shell and an electrode assembly arranged in the shell; the electrode assembly comprises a diaphragm, a first pole piece and a second pole piece with opposite polarities, and the diaphragm, the first pole piece and the second pole piece are stacked and wound in a preset order; Each of the first pole piece and each of the second pole piece comprises a plurality of straight portions and a plurality of curved portions arranged alternately; the connection between a straight portion and a curved portion is a connection portion; The first pole piece is partially located at the outermost circle of the electrode assembly. The first pole piece has a thickened area and a normal thickness area. The thickness of the current collector in the thickened area is greater than the thickness of the current collector in the normal thickness area. At least the connecting part located at the outermost circle of the first pole piece is the thickened area.

2. The battery cell according to claim 1, characterized in that: The connecting portion of N circles from the outside to the inside of the first pole piece is the thickened area, where N is an integer greater than 1 and less than or equal to 3.

3. The battery cell according to claim 2, characterized in that: At least part of the bent portion located at the outermost circle of the first pole piece is the thickened area; And / or, at least part of the straight portion located at the outermost circle of the first pole piece is the thickened area.

4. The battery cell according to claim 3, characterized in that: The connecting parts, the curved parts and the straight parts of the N circles from the outside to the inside of the first pole piece are all the thickened areas, where N is an integer greater than 1 and less than or equal to 3.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The second pole piece has the thickened area and the normal thickness area, and at least the connecting portion located at the outermost circle of the second pole piece is the thickened area.

6. The battery cell according to claim 5, characterized in that: The connecting portion of the M circles from the outside to the inside of the second pole piece is the thickened area, where M is an integer greater than 1 and less than or equal to 2.

7. The battery cell according to claim 5, characterized in that: At least part of the bent portion located at the outermost circle of the second pole piece is the thickened area; And / or, at least part of the straight portion located at the outermost circle of the second pole piece is the thickened area.

8. The battery cell according to claim 5, characterized in that: The connecting portion, the curved portion, and the straight portion of the M circles from the outside to the inside of the second pole piece are all the thickened areas, where M is an integer greater than 1 and less than or equal to 2.

9. The battery cell according to claim 1, characterized in that: The first pole piece is an anode pole piece.

10. The battery cell according to any one of claims 1 to 4, characterized in that: The electrode assembly also has a transition zone, which is located at the connection between the thickened zone and the normal thickness zone; The thickness of one end of the transition zone is the same as that of the normal thickness zone, and the thickness of the other end is the same as that of the thickened zone. The thickness of the transition zone gradually increases from one end to the other end.

11. The battery cell according to claim 10, characterized in that: The thickness of the current collector in the normal thickness region is X, where X is greater than or equal to 3 μm and less than or equal to 15 μm; The difference between the thickness of the thickened area and the thickness of the normal thickness area is Y, and Y is greater than 0 and less than or equal to 5 μm.

12. The battery cell according to claim 11, characterized in that: The extension length of the transition zone is Z, and Z is greater than or equal to 5 cm and less than or equal to 10 cm.

13. The battery cell according to any one of claims 1 to 4, characterized in that: A surface of the current collector in the thickened area is provided with a reinforcement texture, and the reinforcement texture is extended along a line connecting the normal thickness area to the thickened area.

14. The battery cell according to claim 13, characterized in that: The reinforcing texture is a strip-shaped roll-pressed groove, the depth of the roll-pressed groove is D, and D is greater than 0 and less than or equal to 4 μm.

15. The battery cell according to claim 14, characterized in that: There are a plurality of roll-pressed grooves, and the plurality of roll-pressed grooves are arranged at intervals in a direction perpendicular to a direction of a line connecting the normal thickness area to the thickened area.

16. The battery cell according to claim 15, characterized in that: The width of the roll-pressed groove in the direction perpendicular to the line connecting the normal thickness area to the thickened area is W, and W is greater than 1 cm and less than or equal to 3 cm; And / or, the distance between two adjacent roller-pressed grooves is S, and S is greater than 0 and less than or equal to 2 cm; And / or, the distance between the opening edge of the rolling groove closest to the edge of the thickened area and the edge of the thickened area is T, and T is greater than 1 cm and less than or equal to 2 cm.

17. The battery cell according to any one of claims 1 to 4, characterized in that: Along the winding direction, a positioning hole is provided at one end of the thickened area away from the normal thickness area, and the positioning hole is used for identification by the winding machine.

18. An electrode assembly, characterized in that: The electrode assembly comprises a diaphragm, a first pole piece and a second pole piece with opposite polarities, wherein the diaphragm, the first pole piece and the second pole piece are stacked and wound in a preset order; Each of the first pole piece and each of the second pole piece comprises a plurality of straight portions and a plurality of curved portions arranged alternately; the connection between a straight portion and a curved portion is a connection portion; The first pole piece has a thickened area and a normal thickness area. The thickness of the current collector in the thickened area is greater than the thickness of the current collector in the normal thickness area. At least the connecting portion located at the outermost circle of the first pole piece is the thickened area.

19. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 17.

20. An electrical equipment, characterized in that: Comprising a battery device as claimed in claim 19.

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