Preparation method of battery cell, battery device, power-consuming device and electrode assembly

Abstract

The present application discloses a method for preparing a battery cell, a battery device, an electric device and an electrode assembly, wherein the battery cell comprises a shell, an electrode assembly and an end cap: the shell has a first accommodation space and an opening connected to the first accommodation space; the first accommodation space is used to accommodate the electrode assembly; the end cap is connected to the shell and closes the second opening; wherein the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet arranged in a winding manner, and the number of turns of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; wherein the interlayer spacing of at least a part of the area of ​​the electrode assembly extending along its circumferential direction gradually increases from the (x+1)th turn to the ith turn, and the ratio between the difference between i and x and i is greater than or equal to 1 / 4. The present application can reduce the risk of cracking of the electrode sheet and improve the reliability of the battery cell and the battery device.

Description

Technical Field

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

[0002] With the development of battery device technology, in order to improve the energy capacity and charging speed of the battery device, wound batteries came into being.

[0003] As the number of cycles of the battery device increases, the outward expansion force of the electrode assembly's pole pieces will also increase, especially the increase in the expansion force of the outer ring is particularly obvious, causing the pole pieces located on the outer ring of the electrode assembly to be prone to cracking. There is a risk of puncturing the diaphragm and causing a short circuit at the cracked pole pieces, resulting in lower reliability of the battery cells and battery devices. Summary of the invention

[0004] In view of the above problems, the present application provides methods for preparing battery cells, battery devices, electrical devices and electrode assemblies to reduce or eliminate the risk of cracking of the pole pieces on the outer ring of the electrode assembly, thereby improving the reliability of the battery cells and battery devices.

[0005] In a first aspect, the present application provides a battery cell, which includes: a shell having a first accommodating space and an opening connected to the first accommodating space; an electrode assembly, which is arranged in the shell, and the first accommodating space is used to accommodate the electrode assembly; and an end cover, which is connected to the shell and closes the opening; the electrode assembly includes a positive electrode sheet, a diaphragm and a negative electrode sheet that are wound, and the number of turns of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; wherein the interlayer spacing of at least a portion of the area of ​​the electrode assembly extending along its circumferential direction gradually increases from the (x+1)th turn to the i-th turn, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4. By gradually increasing the interlayer spacing of at least part of the area of ​​the electrode assembly extending along its circumferential direction from the (x+1)th circle to the i-th circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4, the distance between two adjacent pole pieces in the (x+1)th circle to the i-th circle is increased, providing sufficient buffer space for the expansion of the pole pieces, reducing the stress caused by the expansion and contraction of the pole pieces, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole pieces, reducing the risk of lithium plating, and improving the reliability of the battery cell and the battery device.

[0006] In some embodiments, the tail end of the positive electrode sheet and / or the tail end of the negative electrode sheet are located in at least a part of the area. By making the tail end of the positive electrode sheet and / or the tail end of the negative electrode sheet located in at least a part of the area, the shear stress of the tail end of the negative electrode sheet toward the inner adjacent electrode sheet can be reduced or eliminated, and / or the shear stress of the tail end of the positive electrode sheet toward the inner adjacent electrode sheet can be reduced or eliminated, thereby reducing or eliminating the cracking of the inner adjacent electrode sheet of the tail end of the positive electrode sheet and / or the tail end of the negative electrode sheet, and scratching the diaphragm to cause the positive electrode sheet and the negative electrode sheet to overlap, causing the risk of short circuit, etc., and further improving the reliability of the battery cell and the battery device.

[0007] In some embodiments, the interlayer spacings of at least some regions from the 1st circle to the xth circle are the same and smaller than the interlayer spacings of the (x+1)th circle. By making the interlayer spacings of at least some regions of the electrode assembly extending along its circumferential direction the same from the 1st circle to the xth circle and smaller than the interlayer spacings of the (x+1)th circle, the interlayer spacings of the 1st circle to the xth circle of the electrode assembly are adapted to the magnitude of the expansion force of the region, so that the stress distribution of the electrode assembly is uniform, and the problems such as the inability to effectively release the pressure between the pole piece and the diaphragm due to the excessively large interlayer spacing and the excessively small expansion force of the region can be reduced or overcome, so as to reduce or eliminate the risk of cracking of the pole piece of the electrode assembly from the 1st circle to the xth circle, thereby further improving the reliability of the battery cell and the battery device.

[0008] In some embodiments, the ratio is less than or equal to 1 / 2. By making the ratio between the difference between i and x and i less than or equal to 1 / 2, the lower limit of the xth circle is limited so that the value of the xth circle is not too small, thereby making the interlayer spacing from the 1st circle to the xth circle compatible with the size of the expansion force in the area.

[0009] In some embodiments, the interlayer spacing of at least a part of the region increases linearly, exponentially, or stepwise from the (x+1)th turn to the i-th turn. According to the need, the winding parameters are adjusted for each turn or the winding parameters are adjusted once for multiple turns, so that the interlayer spacing of at least a part of the region increases linearly, exponentially, or stepwise from the (x+1)th turn to the i-th turn, so that the expansion force on the pole piece is adapted to the size of the interlayer spacing, which can better improve the problems of wrinkling, deformation, cracking, etc. of the pole piece.

[0010] In some embodiments, at least a portion of the surface of the diaphragm is provided with a coating, and the weight of the coating gradually increases from the (x+1)th circle to the i-th circle; the interlayer spacing is the distance between two adjacent negative electrode sheets, or the distance between two adjacent positive electrode sheets. By gradually increasing the weight of the coating of at least a portion of the diaphragm from the (x+1)th circle to the i-th circle, the radial dimension of the diaphragm in at least a portion of the area along the electrode assembly gradually increases from the (x+1)th circle to the i-th circle, thereby better relieving the stress accumulation and stress concentration between the positive electrode sheet and the negative electrode sheet, and improving the reliability of the battery cell and the battery device.

[0011] In some embodiments, a coating is provided on the first inner surface and / or the first outer surface of the diaphragm, and the size of the coating provided on the first inner surface along the radial direction of the electrode assembly gradually increases from the (x+1)th circle to the i-th circle, and / or the size of the coating provided on the first outer surface along the radial direction gradually increases from the (x+1)th circle to the i-th circle. By gradually increasing the size of the coating provided on the first inner surface along the radial direction of the electrode assembly from the (x+1)th circle to the i-th circle, and / or gradually increasing the size of the coating provided on the first outer surface along the radial direction from the (x+1)th circle to the i-th circle, the size of the diaphragm along the radial direction of the electrode assembly gradually increases from the (x+1)th circle to the i-th circle, thereby better dispersing the stress between the positive electrode sheet and the negative electrode sheet, relieving the stress concentration between the positive electrode sheet and the negative electrode sheet, and improving the reliability of the battery cell and the battery device.

[0012] In some embodiments, at least a portion of the area has protrusions formed on the positive electrode sheets and / or negative electrode sheets from the (x+1)th to the ith circles, and the size of the protrusions along the radial direction of the electrode assembly gradually increases, and the interlayer spacing is the distance between two diaphragms located on the second inner surface or the second outer surface of the adjacent positive electrode sheets, or the distance between two diaphragms located on the second inner surface or the second outer surface of the adjacent negative electrode sheets. Such a configuration, on the one hand, makes the internal structure of the electrode assembly more stable, and the current distribution more uniform, which helps to improve the overall performance of the battery cell; on the other hand, it can reduce the stress generated by the expansion and contraction of the electrode sheet, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the risk of wrinkling, deformation, cracking, etc. of the electrode sheet, reducing the risk of lithium plating, and further improving the reliability of the battery cell and the battery device.

[0013] In some embodiments, the second inner surface and / or the second outer surface of at least one of the positive electrode sheet and the negative electrode sheet are provided with convex points, and the radial size of the convex points provided on the second inner surface gradually increases from the (x+1)th circle to the i-th circle, and / or the radial size of the convex points provided on the second outer surface gradually increases from the (x+1)th circle to the i-th circle. By gradually increasing the radial size of the convex points provided on the second inner surface from the (x+1)th circle to the i-th circle, and / or gradually increasing the radial size of the convex points provided on the second outer surface from the (x+1)th circle to the i-th circle, not only the internal structure of the electrode assembly is stabilized, the current distribution is more uniform, and it is helpful to improve the overall performance of the battery cell; it can also reduce the stress caused by the expansion and contraction of the pole piece, reduce the risk of cracking of the pole piece, and further improve the reliability of the battery cell and the battery device.

[0014] In some embodiments, at least part of the region includes a fan-shaped region extending in the circumferential direction, and the tail end of the positive electrode sheet is located in the fan-shaped region, and / or the tail end of the negative electrode sheet is located in the fan-shaped region. By gradually increasing the interlayer spacing of the fan-shaped region from the (x+1)th circle to the i-th circle, and the tail end of the positive electrode sheet is located in the fan-shaped region, and / or the tail end of the negative electrode sheet is located in the fan-shaped region, the shear stress of the tail end of the negative electrode sheet toward the inner adjacent electrode sheet can be reduced or eliminated, and / or the shear stress of the tail end of the positive electrode sheet toward the inner adjacent electrode sheet can be reduced or eliminated, thereby reducing or eliminating the cracking of the inner adjacent electrode sheet of the tail end of the positive electrode sheet and / or the tail end of the negative electrode sheet, and scratching the diaphragm to cause the positive electrode sheet and the negative electrode sheet to overlap, causing the risk of short circuit, etc., and further improving the reliability of the battery cell and the battery device.

[0015] In the second aspect, the present application provides a battery device, the battery device comprising: a battery box, formed with a second accommodation space; and the above-mentioned battery cell; the battery cell is arranged in the second accommodation space. By gradually increasing the interlayer spacing of at least a part of the area where the electrode assembly is extended along its circumferential direction from the (x+1)th circle to the i-th circle, and the ratio between the difference between i and x and i is greater than or equal to 1 / 4, thereby increasing the distance between two adjacent pole pieces arranged in the (x+1)th circle to the i-th circle, providing sufficient buffer space for the expansion of the pole piece, being able to reduce the stress generated by the expansion and contraction of the pole piece, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole piece, reducing the risk of lithium deposition, and improving the reliability of the battery cell and the battery device.

[0016] In a third aspect, the present application provides an electrical device, which includes: the above-mentioned battery device. By gradually increasing the interlayer spacing of at least part of the area where the electrode assembly is extended along its circumferential direction from the (x+1)th circle to the i-th circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4, the distance between two adjacent pole pieces in the (x+1)th circle to the i-th circle is increased, providing sufficient buffer space for the expansion of the pole piece, reducing the stress caused by the expansion and contraction of the pole piece, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole piece, reducing the risk of lithium plating, and improving the reliability of the battery cell and the battery device.

[0017] In a fourth aspect, the present application provides a method for preparing an electrode assembly, wherein the number of turns of the positive electrode sheet, the negative electrode sheet and the separator of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; the preparation method comprises: providing positive electrode sheets, negative electrode sheets and separators; winding the positive electrode sheets, the negative electrode sheets and the separators to obtain an electrode assembly; wherein the interlayer spacing from the (x+1)th turn to the i-th turn of at least a portion of the area extending circumferentially thereof gradually increases, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4. Through the above steps, the distance between two adjacent pole pieces in the (x+1)th circle to the i-th circle can be increased, providing sufficient buffer space for the expansion of the pole pieces, reducing the stress caused by the expansion and contraction of the pole pieces, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole pieces, reducing the risk of lithium plating, and improving the reliability of the battery cell and the battery device.

[0018] In some embodiments, the operation of providing a diaphragm includes: providing a diaphragm; determining a weight parameter, a start and end position parameter of each diaphragm circle from the (x+1)th circle to the i-th circle in at least a partial region, and forming a coating with a gradually increasing thickness on the surface of the diaphragm from the (x+1)th circle to the i-th circle in at least a partial region based on the weight parameter and the start and end position parameter; wherein the first inner surface and / or the first outer surface of the diaphragm is provided with a coating. By forming a coating with a gradually increasing thickness on the surface of the diaphragm from the (x+1)th circle to the i-th circle in at least a partial region through the above steps, the radial dimension of the diaphragm in at least a partial region along the electrode assembly can be gradually increased from the (x+1)th circle to the i-th circle, thereby better dispersing the stress between the positive electrode sheet and the negative electrode sheet, relieving the stress concentration between the positive electrode sheet and the negative electrode sheet, and improving the reliability of the battery cell and the battery device.

[0019] In some embodiments, the operation of providing a positive electrode sheet or a negative electrode sheet includes: providing a positive electrode sheet and / or a negative electrode sheet; determining pressure parameters and start and end position parameters of each circle of the positive electrode sheet and / or the negative electrode sheet from the (x+1)th circle to the i-th circle in at least a partial area, and rolling the positive electrode sheet and / or the negative electrode sheet using a convex point roller based on the pressure parameters and the start and end position parameters to form convex points with gradually increasing heights on the surface of the positive electrode sheet and / or the negative electrode sheet from the (x+1)th circle to the i-th circle in at least a partial area; wherein the second inner surface and / or the second outer surface of at least one of the positive electrode sheet and the negative electrode sheet is provided with convex points. Through the above steps, from the (x+1)th circle to the i-th circle, the surface of the positive electrode sheet and / or the negative electrode sheet forms convex points with gradually increasing heights, which, on the one hand, makes the internal structure of the battery more stable and the current distribution more uniform, which helps to improve the overall performance of the battery; on the other hand, it can reduce the stress caused by the expansion and contraction of the electrode sheet, and the generated stress can be evenly distributed, which helps to alleviate stress accumulation and stress concentration, thereby reducing the risks of wrinkling, deformation, cracking, etc. of the electrode sheet, reducing the risk of lithium plating, and further improving the reliability of battery cells and battery devices.

[0020] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator are wound, including: determining tension parameters, start and end position parameters of each circle of the positive electrode sheet, the negative electrode sheet and the separator in the (x+1)th circle to the i-th circle of at least a partial area, and controlling the winding tension of the positive electrode sheet, the negative electrode sheet and the separator in the (x+1)th circle to the i-th circle of at least a partial area based on the tension parameters and the start and end position parameters; wherein the winding tension decreases circle by circle from the (x+1)th circle to the i-th circle of at least a partial area. Through the above steps, the distance between the positive electrode sheet and the separator and the distance between the negative electrode sheet and the separator gradually increase from the (x+1)th circle to the i-th circle, which can provide sufficient buffer space for the expansion of the electrode sheet, reduce the stress generated by the expansion and contraction of the electrode sheet, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the risk of wrinkling, deformation, cracking, etc. of the electrode sheet, reducing the risk of lithium plating, and improving the reliability of the battery cell and the battery device.

[0021] In some embodiments, the winding operation of the positive electrode sheet, the negative electrode sheet and the separator further includes: winding the electrode assembly from the 1st to the xth circle based on a constant tension; wherein the constant tension is greater than the winding tension of the (x+1)th circle. The electrode assembly from the 1st to the xth circle is wound with a constant tension so that the interlayer spacing from the 1st to the xth circle is the same, so that the change of the interlayer spacing from the 1st to the xth circle of the electrode assembly is adapted to the magnitude of the expansion force of the region, so that the stress distribution of the electrode assembly is uniform, and the problem of the pressure between the electrode sheet and the separator being unable to be effectively released due to the excessive interlayer spacing and the excessively small expansion force of the region is overcome, so as to reduce or eliminate the risk of cracking of the electrode sheet from the 1st to the xth circle of the electrode assembly, thereby further improving the reliability of the battery cell and the battery device.

[0022] The battery cell provided in the present application includes a shell, an electrode assembly and an end cover, wherein the shell has a first accommodating space and an opening connected to the first accommodating space; the electrode assembly is arranged in the shell, and the first accommodating space is used to accommodate the electrode assembly; the end cover is connected to the shell and closes the opening; the electrode assembly includes a positive electrode plate, a diaphragm and a negative electrode plate that are wound, and the number of turns of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; wherein the interlayer spacing of at least a part of the area where the electrode assembly is extended along its circumferential direction gradually increases from the (x+1)th turn to the i-th turn, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4. By gradually increasing the interlayer spacing of at least part of the area of ​​the electrode assembly extending along its circumferential direction from the (x+1)th circle to the i-th circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4, the distance between two adjacent pole pieces in the (x+1)th circle to the i-th circle is increased, providing sufficient buffer space for the expansion of the pole pieces, reducing the stress caused by the expansion and contraction of the pole pieces, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole pieces, reducing the risk of lithium plating, and improving the reliability of the battery cell and the battery device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0024] Figure 1 It is a structural schematic diagram of an embodiment of an electric device provided by the present application;

[0025] Figure 2 is a schematic diagram of the exploded structure of an embodiment of a battery device provided in the present application;

[0026] Figure 3 is a schematic cross-sectional structure diagram of a first embodiment of a battery cell provided in the present application;

[0027] Figure 4 is a schematic diagram of a variation curve of the interlayer spacing of the electrode assembly of the battery cell provided in the present application;

[0028] Figure 5 is another schematic diagram of a variation curve of the interlayer spacing of the electrode assembly of the battery cell provided in the present application;

[0029] Figure 6 is a schematic cross-sectional structure diagram of a second embodiment of a battery cell provided in the present application;

[0030] Figure 7 is a schematic cross-sectional structure diagram of a third embodiment of a battery cell provided in the present application;

[0031] Figure 8 It is a schematic flow chart of a first embodiment of a method for preparing an electrode assembly of a battery cell provided in the present application;

[0032] Fig. 9 It is a schematic flow chart of a second embodiment of a method for preparing an electrode assembly of a battery cell provided in the present application;

[0033] Fig.10 It is a schematic flow chart of a third embodiment of a method for preparing an electrode assembly of a battery cell provided in the present application;

[0034] Fig.11 It is a schematic flow chart of a fourth embodiment of a method for preparing an electrode assembly of a battery cell provided in the present application.

[0035] The reference numerals in the specific implementation manner are as follows:

[0036] Vehicle 1000a, battery device 100a, controller 200a, motor 300a, battery case 500a, second accommodating space 501, first part 502, second part 503, third part 504, battery cell 400a, shell 20, electrode assembly 10, pole piece 11, negative pole piece 111, positive pole piece 112, second inner surface 11a, second outer surface 11b, tail end 11c, diaphragm 12, first diaphragm 121, second diaphragm 122, first inner surface 12a, first outer surface 12b, interlayer spacing 13, fan-shaped area 14. DETAILED DESCRIPTION

[0037] The following embodiments of the technical solution of the present application will be 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.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0039] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0041] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which 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.

[0042] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0043] 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 one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate heat exchange 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.

[0044] With the development of battery device technology, in order to improve the energy capacity and charging speed of battery devices, wound batteries came into being. Different from traditional dry batteries, alkaline batteries, etc., the positive electrode sheet, negative electrode sheet and separator in the wound battery are wound together in the form of thin sheets to form an electrode assembly, so that the chemical reaction inside the battery device is more sufficient, and the conductivity between the positive electrode sheet and the negative electrode sheet is improved, thereby improving the energy capacity and charging speed of the battery device.

[0045] As the number of cycles of the battery device increases, the expansion force of the electrode assembly's pole piece will also increase, especially the increase in the expansion force of the outer ring is particularly obvious. The pole piece of the outer ring of the electrode assembly cannot expand outward due to the characteristics of the electrode assembly structure and the restraint of the termination tape provided on the outer surface of the electrode assembly, resulting in the gradual accumulation of stress in the outer ring of the electrode assembly. When the stress of the outer ring of the electrode assembly accumulates to a certain extent, the pole piece will crack, and burrs and / or metal chips will be generated at the cracks of the pole piece. These burrs and metal chips will pierce the diaphragm, etc., causing the positive pole piece and the negative pole piece to overlap, causing risks such as short circuits, thereby resulting in low reliability of the battery cell and the battery device. Among them, the number of cycles of a battery device refers to the number of times the battery device completes a complete charge and discharge process.

[0046] Based on the above considerations, the present application provides a method for preparing a battery cell, a battery device, an electrical device and an electrode assembly. The battery cell includes a shell, an electrode assembly and an end cover, the shell having a first accommodation space and an opening connected to the first accommodation space; the electrode assembly is arranged in the shell, and the first accommodation space is used to accommodate the electrode assembly; the end cover is connected to the shell and closes the opening; the electrode assembly includes a positive electrode sheet, a diaphragm and a negative electrode sheet arranged in a winding manner, and the number of turns of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; wherein the interlayer spacing of at least a part of the area of ​​the electrode assembly extending along its circumferential direction gradually increases from the (x+1)th turn to the ith turn, and the ratio between the difference between i and x and i is greater than or equal to 1 / 4. By gradually increasing the interlayer spacing of at least part of the area of ​​the electrode assembly extending along its circumferential direction from the (x+1)th circle to the i-th circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4, the distance between two adjacent pole pieces in the (x+1)th circle to the i-th circle is increased, providing sufficient buffer space for the expansion of the pole pieces, reducing the stress caused by the expansion and contraction of the pole pieces, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly during the cycle of the battery cell, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole pieces, reducing the risk of lithium plating, and improving the reliability of the battery cell and the battery device.

[0047] The preparation methods of the battery cells, battery devices, power devices and electrode assemblies disclosed in the embodiments of the present application can be used for power devices that use battery devices as power sources or various energy storage systems that use battery devices as energy storage elements. The power devices may be, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0048] For the convenience of description, the following embodiments are described by taking a vehicle 1000a as an example of an electrical device in an embodiment of the present application.

[0049] Please refer to Figure 1The vehicle 1000a 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 battery device 100a is provided inside the vehicle 1000a. The battery device 100a may be provided at the bottom, head or tail of the vehicle 1000a. The battery device 100a may be used to power the vehicle 1000a. For example, the battery device 100a may be used as an operating power source for the vehicle 1000a. The vehicle 1000a may also include a controller 200a and a motor 300a. The controller 200a is used to control the battery device 100a to power the motor 300a, for example, to meet the power requirements for starting, navigating and driving the vehicle 1000a.

[0050] In some embodiments of the present application, the battery device 100a can not only serve as an operating power source for the vehicle 1000a, but also serve as a driving power source for the vehicle 1000a, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000a.

[0051] In some embodiments, the battery device 100a may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0052] The battery device 100 a mentioned in the embodiment of the present application refers to a single physical module including one or more battery cells 400 a to provide higher voltage and capacity.

[0053] In the embodiment of the present application, the battery device 100a may be a secondary battery, which refers to a battery that can be recharged to activate the active material after discharge and continue to be used. The battery device 100a may also be a primary battery.

[0054] The battery device 100a is a wound battery. For example, the battery device 100a can be a wound lithium-ion battery, a wound sodium-ion battery, a wound sodium-lithium-ion battery, a wound lithium-sulfur battery, a wound magnesium-ion battery, a wound nickel-hydrogen battery, a wound nickel-cadmium battery, or a wound lead-acid battery, but is not limited thereto.

[0055] In some embodiments, the battery device 100 a may be a battery module. When there are multiple battery cells 400 a , the multiple battery cells 400 a are arranged and fixed to form a battery module.

[0056] Please refer to Figure 2 The battery device 100a may be a battery pack, which includes a battery case 500a and a battery cell 400a, wherein the battery cell 400a or a battery module is accommodated in the battery case 500a.

[0057] In some embodiments, the battery box 500a can be used as part of the chassis structure of the vehicle 1000a. For example, a portion of the battery box 500a can become at least a portion of the floor of the vehicle 1000a, or a portion of the battery box 500a can become at least a portion of the cross beam and longitudinal beam of the vehicle 1000a.

[0058] The battery device 100a includes a battery case 500a and a battery cell 400a. The battery cell 400a is contained in the battery case 500a. The battery case 500a is formed with a second accommodating space 501, and the battery cell 400a is disposed in the second accommodating space 501. The battery case 500a may adopt a variety of structures. In some embodiments, the battery case 500a may include a first part 502, a second part 503 and a third part 504, wherein the first part 502 may be a hollow structure with openings formed at both ends, the second part 503 may be a hollow structure with an opening at one end, and the third part 504 may also be a hollow structure with an opening at one end, and the first part 502, the second part 503 and the third part 504 cover each other and jointly define a second accommodating space 501 for accommodating the battery cell 400a. In some embodiments, the first part 502 forms a second accommodation space 501, the first part 502 may be a hollow structure with openings formed at both ends, the second part 503 and the third part 504 are both plate-like structures, the second part 503 covers one opening of the first part 502, and the third part 504 covers the other opening of the first part 502 to close the second accommodation space 501. In some embodiments, the battery case 500a includes only the first part 502 and the second part 503, the first part 502 may be a hollow structure with an opening at one end, the second part 503 may be a plate-like structure, and the second part 503 covers the opening side of the first part 502, so that the first part 502 and the second part 503 jointly define the second accommodation space 501; the first part 502 and the second part 503 may also be hollow structures with one side opening, and the opening side of the first part 502 covers the opening side of the second part 503. The battery case 500a may be in various shapes, such as a cylinder, a cuboid, etc.

[0059] In the battery device 100a, there may be multiple battery cells 400a, and the multiple battery cells 400a may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 400a are both connected in series and in parallel. The multiple battery cells 400a may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 400a is accommodated in the battery box 500a; of course, the battery device 100a may also be a battery module formed by connecting multiple battery cells 400a in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the battery box 500a. The battery device 100a may also include other structures. For example, the battery device 100a may also include a busbar component for realizing electrical connection between the multiple battery cells 400a.

[0060] In some embodiments, Figure 3 As shown, the battery cell 400a includes: a shell 20, an electrode assembly 10 and an end cover; the shell 20 has a first accommodating space and an opening connected to the first accommodating space; the electrode assembly 10 is arranged in the shell 20, and the first accommodating space is used to accommodate the electrode assembly 10; the end cover is connected to the shell 20 and closes the opening; wherein, the electrode assembly 10 includes a positive electrode plate 112, a diaphragm 12 and a negative electrode plate 111 arranged in a wound manner, and the number of turns of the electrode assembly 10 is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly 10 is greater than or equal to 4; wherein, the interlayer spacing 13 of at least a portion of the area of ​​the electrode assembly 10 extending along its circumferential direction gradually increases from the (x+1)th turn to the i-th turn, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4.

[0061] The battery cell 400a includes one or more electrode assemblies 10, a housing 20 and an end cap. The housing 20 has a first accommodation space and an opening communicating with the first accommodation space, and the first accommodation space is used to accommodate the electrode assembly 10. The end cap is connected to the housing 20 and closes the opening.

[0062] The shell 20 is a component for accommodating the electrode assembly 10. The shell 20 can be a hollow structure with an opening at one end, or a hollow structure with openings at two opposite ends. The shell 20 can be in various shapes, such as a cylindrical shape, a rectangular parallelepiped shape, etc. The shell 20 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc.

[0063] Among them, the end cap is a component that closes the opening of the shell 20 to isolate the internal environment of the battery cell 400a from the external environment. The end cap and the shell 20 together define a receiving space for accommodating the electrode assembly 10, the electrolyte and other components. The end cap can be connected to the shell 20 by welding or crimping to close the opening of the shell 20. The shape of the end cap can be adapted to the shape of the shell 20. For example, the shell 20 is a rectangular parallelepiped structure, and the end cap is a rectangular plate structure adapted to the shell 20. For another example, the shell 20 is a cylindrical structure, and the end cap is a circular plate structure adapted to the shell 20. The material of the end cap can also be a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, plastic, etc. The material of the end cap and the shell 20 can be the same or different.

[0064] The negative electrode sheet 111 and the positive electrode sheet 112 constitute the electrode sheet 11 of the electrode assembly 10, and the first separator 121 and the second separator 122 constitute the separator 12 of the electrode assembly 10. During the charge and discharge process of the battery cell 400a, the negative electrode active material on the negative electrode sheet 111 and the positive electrode active material on the positive electrode sheet 112 can react with the electrolyte to achieve charge and discharge.

[0065] In some embodiments, the first separator 121, the negative electrode sheet 111, the second separator 122 and the positive electrode sheet 112 are sequentially stacked and wound to form the electrode assembly 10; or the second separator 122, the positive electrode sheet 112, the first separator 121 and the negative electrode sheet 111 are sequentially stacked and wound to form the electrode assembly 10, wherein the first separator 121 and the second separator 122 may be the same, or may be different. The embodiment of the present application takes the first separator 121, the negative electrode sheet 111, the second separator 122 and the positive electrode sheet 112 as an example of sequentially stacking and winding to form the electrode assembly 10.

[0066] In some embodiments, part of the first separator 121 is located in the innermost layer of the electrode assembly 10, forming the inner side wall of the electrode assembly 10, and part of the second separator 122 is exposed on the outer surface of the electrode assembly 10, forming the outer side wall of the electrode assembly 10. The electrode sheet 11 located partially on the outer ring of the electrode assembly 10 is the negative electrode sheet 111. The first separator 121, the negative electrode sheet 111, the second separator 122 and the positive electrode sheet 112 are stacked on each other in their respective thickness directions. The electrode sheet 11 and the separator 12 can be wound to form a cylindrical electrode assembly 10, or they can be wound to form a square electrode assembly 10. The first separator 121 and the second separator 122 together isolate the negative electrode sheet 111 and the positive electrode sheet 112, so that the negative electrode sheet 111 and the positive electrode sheet 112 will not contact each other, thereby reducing the risk of short circuit between the negative electrode sheet 111 and the positive electrode sheet 112.

[0067] The number of turns of the electrode assembly 10 is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly 10 is greater than or equal to 4. The turn closest to the winding center of the electrode assembly 10 is the first turn, and the turn farthest from the winding center of the electrode assembly 10 is the i-th turn, that is, the first turn is the innermost turn of the electrode assembly 10, and the i-th turn is the outermost turn of the electrode assembly 10.

[0068] The number of turns of the electrode assembly 10 is equal to the number of interlayer spacings 13 of the electrode assembly 10, and each turn layer of the electrode assembly 10 has a corresponding interlayer spacing 13. For example, when the number of turns of the electrode assembly 10 is 12, i=12, and the number of turns of the electrode assembly 10 is defined as N=1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12; at this time, the number of interlayer spacings 13 is also 12.

[0069] The interlayer spacing 13 of at least a portion of the electrode assembly 10 extending along its circumferential direction gradually increases from the (x+1)th circle to the ith circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4. For example, when the number of circles of the electrode assembly 10 is 12, the xth circle can be the 6th circle, and the interlayer spacing 13 can gradually increase from the 7th circle to the 12th circle; of course, the xth circle can also be the 9th circle, and the interlayer spacing 13 can gradually increase from the 10th circle to the 12th circle. The increase method of the interlayer spacing 13 is not limited to the above method, and it only needs that the ratio of the difference between i and x to i is greater than or equal to 1 / 4.

[0070] In some embodiments, the interlayer spacing 13 of the electrode assembly 10 may be the distance between two adjacent negative electrode sheets 111 ; or the distance between two adjacent positive electrode sheets 112 .

[0071] In some embodiments, both the positive electrode sheet 112 and the negative electrode sheet 111 have a second inner surface 11a and a second outer surface 11b, wherein the second inner surface 11a of the positive electrode sheet 112 is the surface of the positive electrode sheet 112 facing the winding center of the electrode assembly 10, and the second outer surface 11b of the positive electrode sheet 112 is the surface of the positive electrode sheet 112 facing away from the winding center of the electrode assembly 10; the second inner surface 11a of the negative electrode sheet 111 is the surface of the negative electrode sheet 111 facing the winding center of the electrode assembly 10, and the second outer surface 11b of the negative electrode sheet 111 is the surface of the negative electrode sheet 111 facing away from the winding center of the electrode assembly 10. The second inner surface 11a is a concave arc surface, and the second outer surface 11b is a convex arc surface. The interlayer spacing 13 of the electrode assembly 10 may also be the distance between two separators 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent positive electrode sheet 112, or the distance between two separators 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent negative electrode sheet 111. That is, the interlayer spacing 13 of the electrode assembly 10 may be the distance between two adjacent first separators 121, or the distance between two adjacent second separators 122.

[0072] In some embodiments, at least a portion of the area of ​​the electrode assembly 10 extending along its circumferential direction may include all coils of the electrode assembly 10, and the cross-sectional structure of all coils perpendicular to the winding axis of the electrode assembly 10 may be annular, and the center of the ring is the winding center of the electrode assembly 10. Of course, the cross-sectional structure of all coils perpendicular to the winding axis of the electrode assembly 10 may also be a continuously arranged triangle, fan, circle, polygon, etc., but is not limited thereto.

[0073] The embodiment of the present application is first described by taking as an example that the cross-sectional structure of all coil layers perpendicular to the winding axis of the electrode assembly 10 is annular, and the ring is described with the winding center of the electrode assembly 10 as the center.

[0074] In some embodiments, the inner ring of the electrode assembly 10 is defined as the ring layer from the 1st ring to the xth ring; the outer ring of the electrode assembly 10 is defined as the ring layer from the (x+1)th ring to the i-th ring. The pole piece 11 located in the inner ring of the electrode assembly 10 is less affected by the expansion force, and the pole piece 11 is not easy to break under the action of the expansion force. The pole piece 11 located in the outer ring of the electrode assembly 10 is more affected by the expansion force than the pole piece 11 in the inner ring, and is easy to break under the action of the expansion force. By gradually increasing the interlayer spacing 13 of at least a part of the area of ​​the electrode assembly 10 extending along its circumferential direction from the (x+1)th ring to the i-th ring, and the ratio between the difference between i and x and i is greater than or equal to 1 / 4, sufficient expansion space can be provided for the (x+1)th ring to the i-th ring, so that the stress of the (x+1)th ring to the i-th ring can be released, reducing the risk of cracking of the pole piece 11.

[0075] By gradually increasing the interlayer spacing 13 of at least part of the area of ​​the electrode assembly 10 extending along its circumferential direction from the (x+1)th circle to the i-th circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4, the distance between two adjacent pole pieces 11 in the (x+1)th circle to the i-th circle is increased, providing sufficient buffer space for the expansion of the pole piece 11, reducing the stress caused by the expansion and contraction of the pole piece 11, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly 10 during the cycle of the battery cell 400a, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole piece 11, reducing the risk of lithium plating, and improving the reliability of the battery cell 400a and the battery device 100a.

[0076] In some embodiments, the tail end 11 c of the positive electrode sheet 112 and / or the tail end 11 c of the negative electrode sheet 111 are located at least in a partial area.

[0077] The negative electrode sheet 111 and the positive electrode sheet 112 both have a tail end 11c. The tail end 11c of the negative electrode sheet 111 is located at the end of the negative electrode sheet 111 away from the winding center of the electrode assembly 10, and the tail end 11c of the positive electrode sheet 112 is located at the end of the positive electrode sheet 112 away from the winding center of the electrode assembly 10.

[0078] In some embodiments, part of the negative electrode sheet 111 is located outside the tail end 11c of the positive electrode sheet 112, and the tail end 11c of the negative electrode sheet 111 exceeds the tail end 11c of the positive electrode sheet 112 along the winding direction of the electrode assembly 10. The electrode sheet 11 adjacent to the inner side of the tail end 11c of the negative electrode sheet 111 refers to a portion of the negative electrode sheet 111 close to the tail end 11c of the negative electrode sheet 111. The electrode sheet 11 adjacent to the inner side of the tail end 11c of the positive electrode sheet 112 refers to a portion of the negative electrode sheet 111 on the side of the tail end 11c of the positive electrode sheet 112 close to the winding center of the electrode assembly 10.

[0079] The tail end 11c of the positive electrode sheet 112 and the tail end 11c of the negative electrode sheet 111 are both located on the outer circle of the electrode assembly 10, and are equivalent to forming a step. As the expansion force of the electrode assembly 10 increases, the steps formed by the tail end 11c of the negative electrode sheet 111 and the tail end 11c of the positive electrode sheet 112 will respectively block the inner adjacent electrode sheet 11 from expanding outward, and apply shear stress to the inner adjacent electrode sheet 11. When the shear stress increases to a certain extent, the inner adjacent electrode sheet 11 will crack.

[0080] By locating the tail end 11c of the positive electrode sheet 112 and / or the tail end 11c of the negative electrode sheet 111 in at least part of the above-mentioned area, the shear stress of the tail end 11c of the negative electrode sheet 111 toward the inner adjacent electrode sheet 11 can be reduced or eliminated, and / or the shear stress of the tail end 11c of the positive electrode sheet 112 toward the inner adjacent electrode sheet 11 can be reduced or eliminated, thereby reducing or eliminating the risk of cracking of the inner adjacent electrode sheet 11 of the tail end 11c of the positive electrode sheet 112 and / or the tail end 11c of the negative electrode sheet 111, and scratching the diaphragm 12, resulting in the overlap of the positive electrode sheet 112 and the negative electrode sheet 111, causing the risk of short circuit, etc., and further improving the reliability of the battery cell 400a and the battery device 100a.

[0081] In some embodiments, at least in a partial area, the interlayer spacing 13 of the 1st to xth circles is the same and smaller than the interlayer spacing 13 of the (x+1)th circle.

[0082] If the interlayer spacing 13 of the electrode assembly 10 is too large but the expansion force in the area is too small, the reliability of the battery device 100a will be reduced. This is because if the interlayer spacing 13 of the electrode assembly 10 is too large, the pressure in the area will increase, while if the expansion force is too small, the pressure in the area cannot be effectively released, which will increase the stress in the area. When the stress increases to a certain extent, the pole piece 11 will crack.

[0083] Since the pole piece 11 located in the inner circle of the electrode assembly 10 is less affected by the expansion force, the pole piece 11 is not easy to break under the action of the expansion force. By making the interlayer spacing 13 of the first circle to the xth circle of at least part of the region of the electrode assembly 10 extending along its circumferential direction the same and smaller than the interlayer spacing 13 of the (x+1)th circle, so that the interlayer spacing 13 of the first circle to the xth circle of the electrode assembly 10 is adapted to the magnitude of the expansion force of the region, the stress distribution of the electrode assembly 10 is uniform, and the problem that the pressure between the pole piece 11 and the diaphragm 12 cannot be effectively released due to the excessive interlayer spacing 13 and the excessive expansion force of the region can be reduced or overcome, so as to reduce or eliminate the risk of cracking of the pole piece 11 of the electrode assembly 10 from the first circle to the xth circle, thereby further improving the reliability of the battery cell 400a and the battery device 100a.

[0084] In some embodiments, the ratio is less than or equal to 1 / 2.

[0085] The ratio is the ratio of the difference between i and x to i. If the ratio of the difference between i and x to i is greater than 1 / 2, the value of the xth circle may be too small, which may cause the xth circle and some circles located in the xth circle far away from the first circle to increase the interlayer spacing 13, resulting in the interlayer spacing 13 being too large and the expansion force in the area being too small, causing the pressure between the pole piece 11 and the diaphragm 12 to be unable to be effectively released.

[0086] By making the ratio of the difference between i and x and i less than or equal to 1 / 2, the lower limit of the xth circle is limited so that the value of the xth circle will not be too small, thereby making the interlayer spacing 13 from the 1st circle to the xth circle adapt to the size of the expansion force in the area.

[0087] In some embodiments, the ratio of the difference between i and x to i is greater than or equal to 1 / 4 and less than or equal to 1 / 2. When the number of turns of the electrode assembly 10 is 12, the xth turn may be the 6th turn, the 7th turn, the 8th turn or the 9th turn.

[0088] If the ratio of the difference between i and x to i is less than 1 / 4, the value of the xth circle may be too large, which may cause the pole piece 11 to crack due to the excessive expansion force, while the interlayer spacing 13 of the xth circle and the part of the circle located near the first circle remains unchanged. By making the ratio of the difference between i and x to i greater than or equal to 1 / 4, the upper limit of the xth circle is limited so that the value of the xth circle will not be too large, so that the interlayer spacing 13 from the first circle to the xth circle is adapted to the expansion force of the region.

[0089] The ratio of the difference between i and x to i is 1 / 4 to 1 / 2. For example, the ratio of the difference between i and x to i can be 1 / 4 or 1 / 2. Of course, other ratios are also possible, such as 0.26, 0.28, 0.3, 0.32, 0.344, 0.365, 0.378, 0.39, 0.395, 0.4, 0.415, 0.44, 0.455, 0.478, 0.491, 0.499, etc., but not limited thereto. The ratio can be selected according to actual needs, as long as the ratio of the difference between i and x to i is within the range of 1 / 4 to 1 / 2.

[0090] By making the difference between i and x and the ratio between i in the range of 1 / 4 to 1 / 2, on the one hand, the lower limit and the upper limit of the xth circle are limited, and there will be no problem that the xth circle and the part of the circle located in the xth circle far from the first circle will increase the interlayer spacing 13 due to the xth circle value being too small, and the interlayer spacing 13 will be too large, and the expansion force in the area will be too small, causing the pressure between the pole piece 11 and the diaphragm 12 to be unable to be effectively released. There will also be no problem that the xth circle and the part of the circle located in the xth circle close to the first circle will not have the interlayer spacing 13 unchanged but the expansion force will be too small due to the xth circle value being too large. The problem of cracking of the pole piece 11 due to excessive force can be solved, which can improve the reliability of the battery cell 400a and extend the service life of the battery cell 400a; on the other hand, it is only necessary to keep the interlayer spacing 13 the same from the 1st circle to the xth circle, and the interlayer spacing 13 from the 1st circle to the xth circle is smaller than the interlayer spacing 13 of the (x+1)th circle, so as to reduce or eliminate the risk of cracking of the pole piece 11 from the 1st circle to the xth circle of the electrode assembly 10, so that there is no need to control the change of the interlayer spacing 13 from the 1st circle to the xth circle during the preparation process of the electrode assembly 10, thereby improving the preparation efficiency of the electrode assembly 10.

[0091] In some embodiments, please refer to Figures 4 to 5 , the interlayer spacing 13 of at least part of the area increases linearly, exponentially or stepwise from the (x+1)th circle to the i-th circle.

[0092] During the use of the battery cell 400a, high-temperature charging and discharging of the electrode assembly 10 will cause the electrode piece 11 to expand and generate stress. The expansion force exerted on the electrode piece 11 of the electrode assembly 10 from the (x+1)th circle to the i-th circle is different, wherein the expansion force exerted on the electrode piece 11 of the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle. By gradually increasing the interlayer spacing 13 from the (x+1)th circle to the i-th circle, the stress distribution from the (x+1)th circle to the i-th circle of the electrode assembly 10 is uniform. By changing the interlayer spacing 13 according to the stress exerted on the electrode piece 11, a reasonable expansion space is reserved, thereby better improving the problems of wrinkling, deformation, cracking, etc. of the electrode piece 11.

[0093] In some embodiments, Figure 4 As shown, the winding parameters can be adjusted for each turn so that the interlayer spacing 13 increases uniformly from the (x+1)th turn to the i-th turn, so that the interlayer spacing 13 in at least part of the area increases linearly or exponentially from the (x+1)th turn to the i-th turn, so that the interlayer spacing 13 is more adapted to the size of the expansion force, thereby making the stress distribution from the (x+1)th turn to the i-th turn of the electrode assembly 10 uniform, which can better improve the problems of wrinkling, deformation, cracking, etc. of the electrode sheet 11.

[0094] In some embodiments, Figure 5As shown, the winding parameters can be adjusted for multiple turns at a time so that the interlayer spacing 13 of at least part of the area increases in a step-by-step manner from the (x+1)th turn to the i-th turn. On the one hand, the stress distribution from the (x+1)th turn to the i-th turn of the electrode assembly 10 is uniform, which can better improve the problems of wrinkling, deformation, cracking, etc. of the electrode sheet 11; on the other hand, the number of times the winding parameters are adjusted can be reduced, thereby improving the preparation efficiency of the electrode assembly 10.

[0095] According to the needs, the winding parameters are adjusted for each turn or for multiple turns, so that the interlayer spacing 13 of at least part of the area increases linearly, exponentially or stepwise from the (x+1)th turn to the i-th turn, so that the expansion force on the pole piece 11 is adapted to the size of the interlayer spacing 13, which can better improve the problems of wrinkling, deformation, cracking, etc. of the pole piece 11.

[0096] In some embodiments, the difference between the maximum and minimum values ​​of the interlayer spacing 13 is greater than or equal to 10um, that is, the difference between the i-th circle and any circle from the 1st circle to the x-th circle is greater than or equal to 10um. For example, the difference between the maximum and minimum values ​​of the interlayer spacing 13 can be 10um, 12um, 15um, 16.55um, 16.8um, 17um, 17.5um, 18um, 18.452um, 18.88um, 19um, 19.88um, 20um, 20.5um, 24um, 25um, 28um, 30um, 35um, 40um, 44um, 48um, 50um, 60um, 80um, 100um, etc., but is not limited thereto.

[0097] In some embodiments, please refer to Figure 3 , at least part of the area of ​​the diaphragm 12 has a coating on its surface, and the weight of the coating gradually increases from the (x+1)th circle to the i-th circle; the interlayer spacing 13 is the distance between two adjacent negative electrode sheets 111, or the distance between two adjacent positive electrode sheets 112.

[0098] In some embodiments, the coating may be at least one of a polymer coating separator (PCS) and a polymer & ceramic coating separator (PCCS). The PCS coating and the PCCS coating can enhance the adhesion between the positive electrode sheet 112 and the negative electrode sheet 111 and alleviate the deformation of the electrode assembly 10.

[0099] In some embodiments, the coating may be at least one of a polypropylene (PP) coating, a polyimide (PI) coating, a polymethyl methacrylate (PMMA) coating, and an aluminum oxide coating.

[0100] In some embodiments, the initial weight of the coating is 0.3 mg / 1540.25 mm 2 ~0.75mg / 1540.25mm 2 First, the coating is applied to the surface of the (x+1)th circle of the diaphragm 12 with an initial weight; then, the initial weight value is 0.3 mg / 1540.25 mm 2 ~0.75mg / 1540.25mm 2 On the basis of the coating from the (x+2)th circle to the ith circle, each circle is 0.1mg / 1540.25mm 2 ~1mg / 1540.25mm 2 The weight gradually increases, so that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0101] Since the weight of the coating on the diaphragm 12 gradually increases from the (x+1)th circle to the i-th circle, the radial dimension of the diaphragm 12 along the electrode assembly 10 is changed. Therefore, in this embodiment, the interlayer spacing 13 is the distance between two adjacent negative electrode sheets 111, or the distance between two adjacent positive electrode sheets 112, so that the control of the interlayer spacing 13 is more accurate, the measurement error is reduced, and the degree of adaptation between the interlayer spacing 13 and the expansion force is improved, so that the stress distribution of the electrode assembly 10 is uniform, which can better improve the problems of wrinkling, deformation, cracking, etc. of the electrode sheet 11.

[0102] The coating on the surface of the diaphragm 12 can disperse the stress between the positive electrode sheet 112 and the negative electrode sheet 111, and relieve the stress concentration between the positive electrode sheet 112 and the negative electrode sheet 111. The thicker the coating on the surface of the diaphragm 12, the better the effect of relieving stress concentration. By gradually increasing the weight of the coating of the diaphragm 12 in at least a part of the area from the (x+1)th circle to the i-th circle, so that the radial size of the diaphragm 12 in at least a part of the area along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, the stress accumulation and stress concentration between the positive electrode sheet 112 and the negative electrode sheet 111 can be better relieved, and the reliability of the battery cell 400a and the battery device 100a can be improved.

[0103] In some embodiments, the first inner surface 12a and / or the first outer surface 12b of the diaphragm 12 are provided with a coating, and the radial size of the coating provided on the first inner surface 12a gradually increases from the (x+1)th circle to the i-th circle along the radial direction of the electrode assembly 10, and / or the radial size of the coating provided on the first outer surface 12b gradually increases from the (x+1)th circle to the i-th circle.

[0104] The diaphragm 12 has a first inner surface 12a and a first outer surface 12b. The first inner surface 12a is located on the side of the diaphragm 12 facing the winding center of the electrode assembly 10, and the first outer surface 12b is located on the side of the diaphragm 12 away from the winding center of the electrode assembly 10. The first inner surface 12a is a concave arc surface, and the first outer surface 12b is a convex arc surface. The diaphragm 12 includes a first diaphragm 121 and a second diaphragm 122, and the first inner surface 12a and / or the first outer surface 12b of at least one of the first diaphragm 121 and the second diaphragm 122 are provided with a coating.

[0105] In some embodiments, the first inner surface 12a of the diaphragm 12 is provided with a coating, and the radial dimension of the coating along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, that is, the thickness of the coating gradually increases from the (x+1)th circle to the i-th circle, wherein the diaphragm 12 includes a first diaphragm 121 and a second diaphragm 122.

[0106] In some embodiments, the first outer surface 12b of the diaphragm 12 is provided with a coating, and the radial dimension of the coating along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, that is, the thickness of the coating gradually increases from the (x+1)th circle to the i-th circle, wherein the diaphragm 12 includes a first diaphragm 121 and a second diaphragm 122.

[0107] In some embodiments, the first inner surface 12a and the first outer surface 12b of the diaphragm 12 are both provided with a coating, and the radial size of the coating provided on the first inner surface 12a along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, and the radial size of the coating provided on the first outer surface 12b along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, wherein the diaphragm 12 includes a first diaphragm 121 and a second diaphragm 122.

[0108] By gradually increasing the radial size of the coating provided on the first inner surface 12a along the electrode assembly 10 from the (x+1)th circle to the i-th circle, and / or gradually increasing the radial size of the coating provided on the first outer surface 12b along the electrode assembly 10 from the (x+1)th circle to the i-th circle, the radial size of the diaphragm 12 along the electrode assembly 10 is gradually increased from the (x+1)th circle to the i-th circle, thereby better dispersing the stress between the positive electrode sheet 112 and the negative electrode sheet 111, relieving the stress concentration between the positive electrode sheet 112 and the negative electrode sheet 111, and improving the reliability of the battery cell 400a and the battery device 100a.

[0109] In some embodiments, please refer to Figure 6 , at least in a partial area, protrusions are formed on the positive electrode sheets 112 and / or the negative electrode sheets 111 from the (x+1)th circle to the i-th circle, and the radial size of the protrusions gradually increases along the radial direction of the electrode assembly 10, and the interlayer spacing 13 is the distance between two diaphragms 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent positive electrode sheets 112, or the distance between two diaphragms 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent negative electrode sheets 111.

[0110] In some embodiments, the positive electrode sheet 112 and / or the negative electrode sheet 111 are rolled by a convex roller of a rolling device, so that convex points are formed on the positive electrode sheet 112 and / or the negative electrode sheet 111. The initial pressure value of the convex roller is 0.1MPa~2MPa. First, the convex roller is used to roll the (x+1)th circle of the positive electrode sheet 112 and / or the negative electrode sheet 111 with the initial pressure value; then, based on the initial pressure value, the convex roller increases the pressure of 0.01MPa~0.5Mpa per circle from the (x+2)th circle to the i-th circle to roll the positive electrode sheet 112 and / or the negative electrode sheet 111, so that the radial size of the convex points of the positive electrode sheet 112 and / or the negative electrode sheet 111 gradually increases from the (x+1)th circle to the i-th circle, thereby realizing that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0111] Since the pressure value set on the convex point roller gradually increases from the (x+1)th circle to the i-th circle, the radial size of the positive electrode sheet 112 and / or the negative electrode sheet 111 along the electrode assembly 10 is changed. Therefore, in this embodiment, the interlayer spacing 13 is the distance between the two diaphragms 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent positive electrode sheet 112, or the distance between the two diaphragms 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent negative electrode sheet 111, that is, the interlayer spacing 13 of the electrode assembly 10 can be the distance between two adjacent first diaphragms 121, or the distance between two adjacent second diaphragms 122, so that the control of the interlayer spacing 13 is more accurate, the measurement error is reduced, and the adaptability of the interlayer spacing 13 to the expansion force is improved, so that the stress distribution of the electrode assembly 10 is uniform, thereby better improving the problems of wrinkling, deformation, cracking, etc. of the electrode sheet 11.

[0112] By forming convex points on the positive electrode sheet 112 and / or the negative electrode sheet 111 of at least a partial area from the (x+1)th circle to the i-th circle, and the radial size of the convex points gradually increases along the radial direction of the electrode assembly 10, a gap is formed between the positive electrode sheet 112 and the diaphragm 12 and between the negative electrode sheet 111 and the diaphragm 12, and the radial size of the gap gradually increases from the (x+1)th circle to the i-th circle, and the gap can absorb the stress generated by the electrode sheet 11. From the (x+1)th circle to the i-th circle, as the radial size of the gap gradually increases along the radial direction of the electrode assembly 10, the ability of the gap to absorb stress gradually increases. Gradual strengthening can alleviate stress accumulation and stress concentration. On the one hand, it makes the internal structure of the electrode assembly 10 more stable and the current distribution more uniform, which helps to improve the overall performance of the battery cell 400a; on the other hand, it can reduce the stress caused by the expansion and contraction of the pole piece 11, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly 10 during the cycle of the battery cell 400a, thereby reducing the risks of wrinkling, deformation, cracking, etc. of the pole piece 11, reducing the risk of lithium plating, and further improving the reliability of the battery cell 400a and the battery device 100a.

[0113] In some embodiments, the second inner surface 11a and / or the second outer surface 11b of at least one of the positive electrode plate 112 and the negative electrode plate 111 are provided with protrusions, and the radial size of the protrusions provided on the second inner surface 11a gradually increases from the (x+1)th circle to the i-th circle, and / or the radial size of the protrusions provided on the second outer surface 11b gradually increases from the (x+1)th circle to the i-th circle.

[0114] The positive electrode sheet 112 and the negative electrode sheet 111 both have a second inner surface 11a and a second outer surface 11b. The surfaces of the positive electrode sheet 112 and the negative electrode sheet 111 facing the winding center of the electrode assembly 10 are both the second inner surface 11a, and the surfaces of the positive electrode sheet 112 and the negative electrode sheet 111 facing away from the winding center of the electrode assembly 10 are both the second outer surface 11b. The second inner surface 11a is a concave arc surface, and the second outer surface 11b is a convex arc surface.

[0115] In some embodiments, the second inner surface 11a of the positive electrode sheet 112 is provided with protrusions; or the second outer surface 11b of the positive electrode sheet 112 is provided with protrusions; or both the second inner surface 11a and the second outer surface 11b of the positive electrode sheet 112 are provided with protrusions.

[0116] In some embodiments, the second inner surface 11a of the negative electrode plate 111 is provided with protrusions; or the second outer surface 11b of the negative electrode plate 111 is provided with protrusions; or both the second inner surface 11a and the second outer surface 11b of the negative electrode plate 111 are provided with protrusions.

[0117] In some embodiments, the second inner surface 11a of the positive electrode sheet 112 is provided with a protrusion, and the second inner surface 11a of the negative electrode sheet 111 is provided with a protrusion; or the second outer surface 11b of the positive electrode sheet 112 is provided with a protrusion, and the second inner surface 11a of the negative electrode sheet 111 is provided with a protrusion; or the second outer surface 11b of the positive electrode sheet 112 is provided with a protrusion, and the second inner surface 11a of the negative electrode sheet 111 is provided with a protrusion; or the second inner surface 11a and the second outer surface 11b of the positive electrode sheet 112 and the negative electrode sheet 111 are both provided with protrusions.

[0118] By gradually increasing the radial size of the protrusions provided on the second inner surface 11a from the (x+1)th circle to the i-th circle, and / or gradually increasing the radial size of the protrusions provided on the second outer surface 11b from the (x+1)th circle to the i-th circle, not only the internal structure of the electrode assembly 10 is stabilized and the current distribution is more uniform, which helps to improve the overall performance of the battery cell 400a; it can also reduce the stress caused by the expansion and contraction of the pole piece 11, reduce the risk of cracking of the pole piece 11, and further improve the reliability of the battery cell 400a and the battery device 100a.

[0119] In some embodiments, by regulating the winding tension of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 of different layers during the winding process so that the winding tension decreases from the (x+1)th circle to the i-th circle, the interlayer spacing 13 can be gradually increased from the (x+1)th circle to the i-th circle.

[0120] In some embodiments, the initial winding tension value of the winding device is 0.05MPa~0.5MPa, and the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 of the (x+1)th circle are wound with the initial winding tension value. On the basis of the initial winding tension value of 0.05MPa~0.5MPa, the winding device reduces the winding tension by 0.01MPa~0.5Mpa per circle from the (x+2)th circle to the i-th circle, and performs winding operations on the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12, so that the distance between the positive electrode sheet 112 and the separator 12 and the distance between the negative electrode sheet 111 and the separator gradually increase from the (x+1)th circle to the i-th circle, thereby achieving an increase of 1um~20um in the interlayer spacing 13 from the (x+1)th circle to the i-th circle.

[0121] In some embodiments, the winding device performs winding operation on the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 from the 1st to the xth circle at a constant tension, so that the distance between the positive electrode sheet 112 and the separator 12 and the distance between the negative electrode sheet 111 and the separator 12 are the same on the 1st to the xth circle. The tension value corresponding to the constant tension is greater than the initial winding tension value.

[0122] In some embodiments, please refer to Figure 7 At least part of the area includes a fan-shaped area 14 extending along the circumferential direction, the tail end 11 c of the positive electrode sheet 112 is located in the fan-shaped area 14, and / or the tail end 11 c of the negative electrode sheet 111 is located in the fan-shaped area 14.

[0123] Among them, at least part of the area of ​​the electrode assembly 10 extending along its circumferential direction may be a fan-shaped area 14 formed by taking the line connecting the end of the tail end 11c of the negative electrode sheet 111 or the end of the tail end 11c of the positive electrode sheet 112 and the winding center of the electrode assembly 10 as the symmetry axis, and extending along the circumference of the electrode assembly 10 toward both sides of the end of the tail end 11c of the negative electrode sheet 111 or the end of the tail end 11c of the positive electrode sheet 112. The interlayer spacing 13 of the fan-shaped area 14 gradually increases from the (x+1)th circle to the i-th circle.

[0124] In some embodiments, the tail end 11 c of the positive electrode sheet 112 is located in the fan-shaped area 14 .

[0125] In some embodiments, the tail end 11 c of the negative electrode sheet 111 is located in the fan-shaped area 14 .

[0126] In some embodiments, the tail end 11 c of the positive electrode sheet 112 and the tail end 11 c of the negative electrode sheet 111 are both located in the fan-shaped area 14 .

[0127] In some embodiments, the ratio of the cross-sectional area of ​​the electrode assembly 10 perpendicular to the winding axis to the area of ​​the fan-shaped region 14 is greater than or equal to 1 / 4. For example, the ratio of the cross-sectional area of ​​the electrode assembly 10 perpendicular to the winding axis to the area of ​​the fan-shaped region 14 may be 1 / 4, 1 / 3, 1 / 2, 2 / 3, 3 / 4, 3 / 5, 4 / 5, 5 / 6, 2 / 7, 4 / 7, 3 / 8, 5 / 8, 7 / 8, 8 / 9, etc., but is not limited thereto and may be selected according to actual needs.

[0128] By gradually increasing the interlayer spacing 13 of the fan-shaped area 14 from the (x+1)th circle to the i-th circle, and the tail end 11c of the positive pole sheet 112 is located in the fan-shaped area 14, and / or the tail end 11c of the negative pole sheet 111 is located in the fan-shaped area 14, the shear stress of the tail end 11c of the negative pole sheet 111 toward the inner adjacent pole sheet 11 can be reduced or eliminated, and / or the shear stress of the tail end 11c of the positive pole sheet 112 toward the inner adjacent pole sheet 11 can be reduced or eliminated, thereby reducing or eliminating the cracking of the inner adjacent pole sheet 11 of the tail end 11c of the positive pole sheet 112 and / or the tail end 11c of the negative pole sheet 111, and scratching the diaphragm to cause the positive pole sheet 112 and the negative pole sheet 111 to overlap, causing the risk of short circuit, etc., and further improving the reliability of the battery cell 400a and the battery device 100a.

[0129] In some embodiments, Figures 1 to 6 As shown, the electrode assembly 10 includes a positive electrode sheet 112, a separator 12 and a negative electrode sheet 111 which are wound, and the number of turns of the electrode assembly 10 is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly 10 is greater than or equal to 4; the positive electrode sheet 112 and / or the negative electrode sheet 111 of the (x+1)th turn to the ith turn are rolled by a convex point roller of a rolling device, so that convex points are formed on the positive electrode sheet 112 and / or the negative electrode sheet 111 of the (x+1)th turn to the ith turn, wherein the positive electrode sheet 112 and / or the negative electrode sheet 111 of the (x+1)th turn to the ith turn. The convex points on the 1st to the ith circle of 11 gradually increase in radial dimension along the electrode assembly 10; or a coating is applied on the surface of the diaphragm 12, wherein the weight of the coating gradually increases from the (x+1)th circle to the ith circle, so that the radial dimension of the diaphragm 12 gradually increases from the (x+1)th circle to the ith circle; or the winding tension of the positive electrode sheet 112, the negative electrode sheet 111 and the diaphragm 12 of different layers is regulated during the winding process, so that the winding tension decreases from the (x+1)th circle to the ith circle in at least part of the area, thereby realizing that the interlayer spacing 13 gradually increases from the (x+1)th circle to the ith circle.

[0130] The interlayer spacing 13 increases linearly, exponentially, or stepwise from the (x+1)th circle to the i-th circle.

[0131] The difference between the maximum value and the minimum value of the interlayer spacing 13 is greater than or equal to 10 um.

[0132] Among them, the initial weight of the coating is 0.3mg / 1540.25mm 2 ~0.75mg / 1540.25mm 2 First, the coating is placed on the surface of the (x+1)th circle of the diaphragm 12 with an initial weight; then the initial weight value is 0.3mg / 1540.25mm 2 ~0.75mg / 1540.25mm 2 On the basis of the coating from the (x+2)th circle to the ith circle, each circle is 0.1mg / 1540.25mm 2 ~1mg / 1540.25mm 2 The weight gradually increases, so that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0133] The positive electrode sheet 112 and / or the negative electrode sheet 111 are rolled by the convex roller of the rolling equipment, so that convex points are formed on the positive electrode sheet 112 and / or the negative electrode sheet 111. The initial pressure value of the convex roller is 0.1MPa~2MPa. First, the (x+1)th circle of the positive electrode sheet 112 and / or the negative electrode sheet 111 is rolled with the initial pressure value; then, on the basis of the initial pressure value, the pressure of the convex roller is increased by 0.01MPa~0.5Mpa per circle from the (x+2)th circle to the i-th circle to roll the positive electrode sheet 112 and / or the negative electrode sheet 111, so that the radial size of the convex points of the positive electrode sheet 112 and / or the negative electrode sheet 111 along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, thereby realizing that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0134] The initial winding tension value of the winding device is 0.05MPa~0.5MPa, and the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 of the (x+1)th circle are wound with the initial winding tension value. On the basis of the initial winding tension value of 0.05MPa~0.5MPa, the winding tension of the winding device is reduced by 0.01MPa~0.5Mpa per circle from the (x+2)th circle to the i-th circle, and the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 are wound, so that the positive electrode sheet The distance between the positive electrode sheet 112 and the separator 12 and the distance between the negative electrode sheet 111 and the separator 12 gradually increase from the (x+1)th circle to the i-th circle, so that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle; the winding device winds the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 from the 1st circle to the xth circle with a constant tension, so that the distance between the positive electrode sheet 112 and the separator 12 and the distance between the negative electrode sheet 111 and the separator are the same on the 1st circle to the xth circle. The tension value corresponding to the constant tension is greater than the initial winding tension value.

[0135] In some embodiments, Figure 7 As shown, at least part of the area includes a fan-shaped area 14 extending along the circumferential direction, the tail end 11c of the positive electrode sheet 112 is located in the fan-shaped area 14, and / or the tail end 11c of the negative electrode sheet 111 is located in the fan-shaped area 14, and the interlayer spacing 13 of the fan-shaped area 14 gradually increases from the (x+1)th circle to the i-th circle; the ratio of the cross-sectional area of ​​the electrode assembly 10 perpendicular to its winding axis to the area of ​​the fan-shaped area 14 is greater than or equal to 1 / 4.

[0136] The present application further provides a battery device 100 a . The battery device 100 a includes a battery case 500 a and a battery cell 400 a in any of the above embodiments. The battery case 500 a is formed with a second accommodation space 501 . The battery cell 400 a is disposed in the second accommodation space 501 .

[0137] The present application further provides an electrical device, which includes the battery device 100a.

[0138] According to some embodiments of the present application, the battery device 100a can be used in an electrical device. In this way, the interlayer spacing 13 of at least a portion of the electrode assembly 10 extending along its circumferential direction gradually increases from the (x+1)th circle to the ith circle, and the ratio between the difference between i and x and i is greater than or equal to 1 / 4, thereby increasing the distance between two adjacent pole pieces 11 in the (x+1)th circle to the ith circle, providing sufficient buffer space for the expansion of the pole piece 11, reducing the stress generated by the expansion and contraction of the pole piece 11, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly 10, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole piece 11, reducing the risk of lithium deposition, and improving the reliability of the battery cell 400a and the battery device 100a.

[0139] The present application further proposes a method for preparing an electrode assembly, which is the method for preparing the electrode assembly 10 in the above embodiment.

[0140] In some embodiments, please refer to Figure 8 , the number of turns of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 of the electrode assembly 10 is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly 10 is greater than or equal to 4; the preparation method of the electrode assembly 10 includes: providing a positive electrode sheet 112, a negative electrode sheet 111 and a separator 12; winding the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 to obtain the electrode assembly 10; wherein, the interlayer spacing 13 of the electrode assembly 10 from the (x+1)th turn to the i-th turn of at least a part of the area extending along its circumferential direction gradually increases, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4.

[0141] The number of turns of the electrode assembly 10 is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly 10 is greater than or equal to 4. The turn closest to the winding center of the electrode assembly 10 is the first turn, and the turn farthest from the winding center of the electrode assembly 10 is the i-th turn, that is, the first turn is the innermost turn of the electrode assembly 10, and the i-th turn is the outermost turn of the electrode assembly 10.

[0142] The method for preparing the electrode assembly 10 comprises the following steps:

[0143] S11: providing a positive electrode sheet 112 , a negative electrode sheet 111 and a separator 12 .

[0144] In some embodiments, the positive electrode plate 112 includes a positive current collector and a positive active material disposed on at least one surface of the positive current collector. The positive current collector may be a metal foil or a composite current collector. For example, as a metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material on a polymer material substrate, wherein the metal material may be aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc., but is not limited thereto; the polymer material substrate may be a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc., but is not limited thereto. The positive active material may be selected from lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds, etc., but is not limited thereto.

[0145] In some embodiments, the negative electrode plate 111 includes a negative current collector and a negative active material disposed on at least one surface of the negative current collector. The negative current collector may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, aluminum or stainless steel treated with silver, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, titanium, etc. may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material on a polymer material substrate, wherein the metal material includes copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc., but is not limited thereto; the polymer material substrate includes a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc., but is not limited thereto. The negative active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate.

[0146] In some embodiments, the material of the diaphragm 12 may be polypropylene, polyethylene (PE), polyvinylidene fluoride (PVDE), etc., but is not limited thereto.

[0147] S12: Winding the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 to obtain an electrode assembly 10; wherein, the interlayer spacing 13 of at least a portion of the electrode assembly 10 extending along its circumferential direction gradually increases from the (x+1)th circle to the i-th circle, and the ratio of the difference between i and x to i is greater than or equal to 1 / 4.

[0148] In some embodiments, the separator 12 includes a first separator 121 and a second separator 122. The first separator 121, the negative electrode sheet 111, the second separator 122 and the positive electrode sheet 112 are stacked and wound in sequence to form the electrode assembly 10, so that the interlayer spacing 13 of the electrode assembly 10 from the (x+1)th circle to the i-th circle in at least a partial area extending along its circumferential direction gradually increases, and the ratio between the difference between i and x and i is greater than or equal to 1 / 4, and the tail end 11c of the positive electrode sheet 112 and / or the tail end 11c of the negative electrode sheet 111 are located in at least a partial area.

[0149] Through step S11 and step S12, the distance between the two adjacent pole pieces 11 in the (x+1)th circle to the i-th circle is increased, providing sufficient buffer space for the expansion of the pole piece 11, which can reduce the stress caused by the expansion and contraction of the pole piece 11, and the generated stress can be evenly distributed, which helps to alleviate the stress accumulation and stress concentration of the electrode assembly 10 during the cycle of the battery cell 400a, thereby reducing the problems of wrinkling, deformation, cracking, etc. of the pole piece 11, reducing the risk of lithium plating, and improving the reliability of the battery cell 400a and the battery device 100a.

[0150] In some embodiments, please refer to Fig. 9 , providing an operation of the diaphragm 12, including: providing the diaphragm 12; determining a weight parameter, a start and end position parameter of each circle of the diaphragm 12 from the (x+1)th circle to the i-th circle in at least a partial area, and forming a coating with gradually increasing thickness on the surface of the diaphragm 12 from the (x+1)th circle to the i-th circle in at least a partial area based on the weight parameter and the start and end position parameter; wherein the first inner surface 12a and / or the first outer surface 12b of the diaphragm 12 is provided with a coating.

[0151] The step S11 of providing the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 includes the following steps:

[0152] S21: Provide a diaphragm 12.

[0153] The separator 12 has a first inner surface 12 a and a first outer surface 12 b . The first inner surface 12 a of the separator 12 is used to face the winding center of the electrode assembly 10 , and the first outer surface 12 b of the separator 12 is used to face away from the winding center of the electrode assembly 10 .

[0154] S22: Determine the weight parameter and the start and end position parameters of each circle of the diaphragm 12 from the (x+1)th circle to the i-th circle in at least a partial area.

[0155] The weight parameter is the weight parameter of the coating. In some embodiments, the weight parameter of the coating can be determined based on factors such as the diameter of the electrode assembly 10, the total number of turns of the electrode assembly 10, and the preset expansion force of each turn of the electrode assembly 10. The preset expansion force of each turn of the electrode assembly 10 can be obtained by performing a charge-discharge cycle test on an electrode assembly with the same specifications as the electrode assembly 10 of the present application and without changing the interlayer spacing 13.

[0156] The initial weight of the coating can be 0.3mg / 1540.25mm 2 ~0.75mg / 1540.25mm 2 , the coating is placed on the surface of the (x+1)th circle of the diaphragm 12 with an initial weight; when the initial weight value is 0.3mg / 1540.25mm 2 ~0.75mg / 1540.25mm 2 Based on the coating from the (x+2)th circle to the ith circle, each circle is 0.1mg / 1540.25mm 2 ~1mg / 1540.25mm 2 The weight gradually increases.

[0157] The start and end position parameters in step S22 are the start and end position parameters of the (x+1)th to i-th turns of the diaphragm 12 , and the start and end position parameters include an initial position parameter and an end position parameter.

[0158] In some embodiments, the initial position of the diaphragm 12 of the layer is located at the connection between the diaphragm 12 of the layer and the diaphragm 12 of the previous layer, and the initial position parameter can be the size from the initial position of the diaphragm 12 of the layer to the end of the diaphragm 12 close to the winding center of the electrode assembly 10; the terminal position of the diaphragm 12 of the layer is located at the connection between the diaphragm 12 of the layer and the diaphragm 12 of the next layer, and the terminal position parameter can be the size from the terminal position of the diaphragm 12 of the layer to the end of the diaphragm 12 close to the winding center of the electrode assembly 10. For example, the initial position of the (x+1)th circle diaphragm 12 is located at the connection between the (x+1)th circle diaphragm 12 and the xth circle diaphragm 12, and the initial position parameter is the size from the initial position of the (x+1)th circle diaphragm 12 to the end of the diaphragm 12 close to the winding center of the electrode assembly 10. The terminal position of the (x+1)th circle diaphragm 12 is located at the connection between the (x+1)th circle diaphragm 12 and the (x+2)th circle diaphragm 12, and the terminal position parameter is the size from the terminal position of the (x+1)th circle diaphragm 12 to the end of the diaphragm 12 close to the winding center of the electrode assembly 10.

[0159] S23: Based on the weight parameters and the start and end position parameters, a coating with gradually increasing thickness is formed on the surface of the diaphragm 12 in at least a partial area from the (x+1)th circle to the i-th circle; wherein the first inner surface 12a and / or the first outer surface 12b of the diaphragm 12 is provided with a coating.

[0160] In some embodiments, the coating may be at least one of a polymer coating separator (PCS) and / or a polymer and ceramic particle coating (PCCS). The PCS coating and the PCCS coating can enhance the adhesion between the positive electrode sheet 112 and the negative electrode sheet 111 and alleviate the deformation of the electrode assembly 10.

[0161] In some embodiments, the coating may be at least one of a polypropylene (PP) coating, a polyimide (PI) coating, a polymethyl methacrylate (PMMA) coating, and an aluminum oxide coating.

[0162] In some embodiments, the initial weight of the coating is 0.3 mg / 1540.25 mm 2 ~0.75mg / 1540.25mm 2 First, the coating is applied to the surface of the (x+1)th circle of the diaphragm 12 with an initial weight; then, the initial weight value is 0.3 mg / 1540.25 mm 2~0.75mg / 1540.25mm 2 On this basis, the coating from the (x+2)th circle to the ith circle is 0.1mg / 1540.25mm 2 ~1mg / 1540.25mm 2 The weight gradually increases, so that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0163] According to the above steps S21 to S23 , the coating is disposed on the first inner surface 12 a and / or the first outer surface 12 b of the diaphragm 12 .

[0164] In some embodiments, the weight parameters obtained in the above step S22 and the start and end position parameters of the (x+1)th to i-th circles of the diaphragm 12 are uploaded to the coating device. Based on the weight parameters and the start and end position parameters of the (x+1)th to i-th circles of the diaphragm 12, the coating device forms a coating with gradually increasing thickness on the first inner surface 12a and / or the first outer surface 12b of the diaphragm 12 in at least a partial area from the (x+1)th to i-th circles.

[0165] In some embodiments, based on the weight parameter and the start and end position parameters, the coating is manually applied to the first inner surface 12a and / or the first outer surface 12b of the diaphragm 12 .

[0166] Through the above steps, a coating with gradually increasing thickness is formed on the surface of the diaphragm 12 from the (x+1)th circle to the i-th circle in at least a partial area, so that the radial size of the diaphragm 12 in at least a partial area along the electrode assembly 10 can be gradually increased from the (x+1)th circle to the i-th circle, thereby better dispersing the stress between the positive electrode sheet 112 and the negative electrode sheet 111, alleviating the stress concentration between the positive electrode sheet 112 and the negative electrode sheet 111, and improving the reliability of the battery cell 400a and the battery device 100a.

[0167] In some embodiments, please refer to Fig.10 , providing an operation of a positive electrode sheet 112 or a negative electrode sheet 111, including: providing a positive electrode sheet 112 and / or a negative electrode sheet 111; determining a pressure parameter, a start and end position parameter of each circle of the positive electrode sheet 112 and / or the negative electrode sheet 111 from the (x+1)th circle to the i-th circle in at least a partial area, and rolling the positive electrode sheet 112 and / or the negative electrode sheet 111 using a convex point roller based on the pressure parameter and the start and end position parameter, so as to form convex points with gradually increasing height on the surface of the positive electrode sheet 112 and / or the negative electrode sheet 111 from the (x+1)th circle to the i-th circle in at least a partial area; wherein, a second inner surface 11a and / or a second outer surface 11b of at least one of the positive electrode sheet 112 and the negative electrode sheet 111 is provided with convex points.

[0168] The step S11 of providing the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 further includes the following steps:

[0169] S31: providing a positive electrode sheet 112 and / or a negative electrode sheet 111 .

[0170] The positive electrode sheet 112 and the negative electrode sheet 111 both have a second inner surface 11 a and a second outer surface 11 b . The second inner surface 11 a faces the winding center of the electrode assembly 10 , and the second outer surface 11 b faces away from the winding center of the electrode assembly 10 .

[0171] S32: Determine the pressure parameters and the starting and ending position parameters of each circle of the positive electrode sheet 112 and / or the negative electrode sheet 111 in at least a partial area from the (x+1)th circle to the i-th circle.

[0172] In some embodiments, a convex roller is used to roll the positive electrode sheet 112 and / or the negative electrode sheet 111, so that convex points are formed on the positive electrode sheet 112 and / or the negative electrode sheet 111. When the convex roller rolls the second inner surface 11a, convex points are formed on the second outer surface 11b; when the convex roller rolls the second outer surface 11b, convex points are formed on the second inner surface 11a; when the convex roller rolls the second inner surface 11a and the second outer surface 11b, convex points are formed on both the second inner surface 11a and the second outer surface 11b.

[0173] The pressure parameter is the pressure parameter when the convex roller rolls at least one of the positive electrode sheet 112 and the negative electrode sheet 111. In some embodiments, the pressure parameter of the convex roller can be determined according to factors such as the diameter of the electrode assembly 10, the total number of turns of the electrode assembly 10, and the preset expansion force of each turn of the electrode assembly 10. The preset expansion force of each turn of the electrode assembly 10 can be obtained by performing a charge and discharge cycle test on an electrode assembly with the same specification as the electrode assembly 10 of the present application and without changing the interlayer spacing 13.

[0174] The initial pressure value of the embossing roller is 0.1MPa~2MPa, and the (x+1)th circle of the positive electrode sheet 112 and / or the negative electrode sheet 111 is rolled at the initial pressure value; on the basis of the initial pressure value of the embossing roller being 0.1MPa~2MPa, the pressure of the embossing roller is increased by 0.01MPa~0.5Mpa per circle from the (x+2)th circle to the i-th circle to roll the positive electrode sheet 112 and / or the negative electrode sheet 111.

[0175] Among them, the starting and ending position parameters in step S32 are the starting and ending position parameters of the (x+1)th circle to the ith circle of the positive electrode sheet 112 and / or the negative electrode sheet 111, and the starting and ending position parameters include the initial position parameter and the ending position parameter. In some embodiments, the initial position of the positive electrode sheet 112 of the circle layer is located at the connection between the positive electrode sheet 112 of the circle layer and the positive electrode sheet 112 of the previous circle layer, and the initial position parameter can be the size from the initial position of the positive electrode sheet 112 of the circle layer to the end of the positive electrode sheet 112 close to the winding center of the electrode assembly 10; the ending position of the positive electrode sheet 112 of the circle layer is located at the connection between the positive electrode sheet 112 of the circle layer and the positive electrode sheet 112 of the next circle layer, and the ending position parameter can be the size from the ending position of the positive electrode sheet 112 of the circle layer to the end of the positive electrode sheet 112 close to the winding center of the electrode assembly 10. For example, the initial position of the positive electrode sheet 112 of the (x+1)th circle is located at the connection between the positive electrode sheet 112 of the (x+1)th circle and the positive electrode sheet 112 of the xth circle, and the initial position parameter is the dimension from the initial position of the positive electrode sheet 112 of the (x+1)th circle to the end of the positive electrode sheet 112 close to the winding center of the electrode assembly 10. The terminal position of the positive electrode sheet 112 of the (x+1)th circle is located at the connection between the positive electrode sheet 112 of the (x+1)th circle and the positive electrode sheet 112 of the (x+2)th circle, and the terminal position parameter is the dimension from the terminal position of the positive electrode sheet 112 of the (x+1)th circle to the end of the positive electrode sheet 112 close to the winding center of the electrode assembly 10.

[0176] For the definitions of the initial position parameters and the final position parameters of the (x+1)th to i-th turns of the negative electrode sheet 111 , please refer to the description of the initial position parameters and the final position parameters of the positive electrode sheet 112 .

[0177] S33: Roll the positive electrode sheet 112 and / or the negative electrode sheet 111 using a convex roller based on the pressure parameters and the start and end position parameters to form convex points with gradually increasing heights on the surface of the positive electrode sheet 112 and / or the negative electrode sheet 111 in at least a partial area from the (x+1)th circle to the i-th circle; wherein the second inner surface 11a and / or the second outer surface 11b of at least one of the positive electrode sheet 112 and the negative electrode sheet 111 is provided with convex points.

[0178] In some embodiments, the initial pressure value of the convex roller is 0.1MPa~2MPa. First, the convex roller is used to roll the (x+1)th circle of the positive electrode sheet 112 and / or the negative electrode sheet 111 with the initial pressure value; then, based on the initial pressure value, the convex roller increases the pressure of 0.01MPa~0.5Mpa per circle from the (x+2)th circle to the i-th circle to roll the positive electrode sheet 112 and / or the negative electrode sheet 111, so that the radial size of the convex points of the positive electrode sheet 112 and / or the negative electrode sheet 111 along the electrode assembly 10 gradually increases from the (x+1)th circle to the i-th circle, thereby realizing that the interlayer spacing 13 increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0179] Through the above steps S31 to S33 , convex points are formed on the second inner surface 11 a and / or the second outer surface 11 b of at least one of the positive electrode sheet 112 and the negative electrode sheet 111 .

[0180] In some embodiments, the weight parameters obtained in the above step S32 and the starting and ending position parameters of the positive electrode sheet 112 and / or the negative electrode sheet 111 from the (x+1)th circle to the i-th circle are uploaded to a rolling device with a convex point roller. The rolling device can drive the convex point roller to roll the positive electrode sheet 112 and / or the negative electrode sheet 111 based on the weight parameters and the starting and ending position parameters of the positive electrode sheet 112 and / or the negative electrode sheet 111 from the (x+1)th circle to the i-th circle, so as to form convex points with gradually increasing height on the surface of the positive electrode sheet 112 or the negative electrode sheet 111 from the (x+1)th circle to the i-th circle in at least a partial area.

[0181] Through the above steps, from the (x+1)th circle to the i-th circle, the surface of the positive electrode plate 112 and / or the negative electrode plate 111 forms convex points with gradually increasing heights. On the one hand, this makes the internal structure of the electrode assembly 10 more stable and the current distribution more uniform, which helps to improve the overall performance of the battery cell 400a; on the other hand, it can reduce the stress caused by the expansion and contraction of the electrode plate 11, and the generated stress can be evenly distributed, which helps to alleviate stress accumulation and stress concentration, thereby reducing the risks of wrinkling, deformation, cracking, etc. of the electrode plate 11, reducing the risk of lithium plating, and further improving the reliability of the battery cell 400a and the battery device 100a.

[0182] In some embodiments, please refer to Fig.11, the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 are wound, including: determining the tension parameter, the start and end position parameters of each circle of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 in the (x+1)th circle to the i-th circle in at least a part of the area, and controlling the winding tension of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 in the (x+1)th circle to the i-th circle in at least a part of the area based on the tension parameter and the start and end position parameters. Wherein, the winding tension decreases circle by circle from the (x+1)th circle to the i-th circle in at least a part of the area.

[0183] The winding operation of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 includes the following steps:

[0184] S41: Determine the tension parameters and the starting and ending position parameters of each circle of the positive electrode sheet 112, the negative electrode sheet 111 and the diaphragm 12 in at least a partial area from the (x+1)th circle to the i-th circle.

[0185] In some embodiments, a winding device is used to wind the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12. The tension parameter is the tension value acting on the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 when the winding device winds the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12.

[0186] In some embodiments, the tension parameter of the winding device can be determined based on factors such as the diameter of the electrode assembly 10, the total number of turns of the electrode assembly 10, and the preset expansion force of each turn of the electrode assembly 10. The preset expansion force of each turn of the electrode assembly 10 can be obtained by performing a charge-discharge cycle test on an electrode assembly with the same specification as the electrode assembly 10 of the present application and without changing the interlayer spacing 13.

[0187] The initial winding tension value of the winding device is 0.05MPa~0.5MPa, and the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 of the (x+1)th circle are wound with the initial winding tension value. On the basis of the tension value of the winding device being 0.05MPa~0.5MPa, the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 are wound with the tension of the winding device being reduced by 0.01MPa~0.5MPa per circle from the (x+2)th circle to the i-th circle.

[0188] Regarding the definition of the starting and ending position parameters of the (x+1)th to i-th circles of the positive electrode sheet 112 , the negative electrode sheet 111 , and the separator 12 , please refer to the above embodiment and will not be repeated here.

[0189] S42: Control the winding tension of the positive electrode plate 112, the negative electrode plate 111 and the diaphragm 12 from the (x+1)th circle to the i-th circle in at least a partial area based on the tension parameters and the start and end position parameters; wherein the winding tension decreases circle by circle from the (x+1)th circle to the i-th circle in at least a partial area.

[0190] In some embodiments, the initial winding tension value of the winding device is 0.05MPa~0.5MPa, and the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 of the (x+1)th circle are wound with the initial winding tension value. From the (x+2)th circle to the i-th circle, the winding device reduces the winding tension by 0.01MPa~0.5Mpa per circle to wind the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12, so that the distance between the positive electrode sheet 112 and the separator 12 and the distance between the negative electrode sheet 111 and the separator gradually increase from the (x+1)th circle to the i-th circle, thereby achieving an interlayer spacing 13 that increases by 1um~20um from the (x+1)th circle to the i-th circle.

[0191] Among them, the interlayer spacing 13 is the distance between two adjacent negative electrode sheets 111, or the distance between two adjacent positive electrode sheets 112, or the distance between two diaphragms 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent positive electrode sheets 112, or the distance between two diaphragms 12 respectively located on the second inner surface 11a or the second outer surface 11b of the adjacent negative electrode sheets 111.

[0192] Through the above steps S41 to S42, the distance between the positive electrode plate 112 and the diaphragm 12 and the distance between the negative electrode plate 111 and the diaphragm are gradually increased from the (x+1)th circle to the i-th circle.

[0193] In some embodiments, the weight parameters obtained in the above step S42 and the start and end position parameters of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 from the (x+1)th circle to the i-th circle are uploaded to the winding equipment used to wind the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12, so that the winding equipment performs a winding operation on the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 based on the tension parameters and the start and end position parameters of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 from the (x+1)th circle to the i-th circle, so that the interlayer spacing 13 of at least part of the area gradually increases from the (x+1)th circle to the i-th circle.

[0194] Through the above steps, it can be achieved that from the (x+1)th circle to the i-th circle, the distance between the positive electrode plate 112 and the diaphragm 12, as well as the distance between the negative electrode plate 111 and the diaphragm 12 gradually increase, which can provide sufficient buffer space for the expansion of the electrode plate 11, reduce the stress caused by the expansion and contraction of the electrode plate 11, and the generated stress can be evenly distributed, which helps to alleviate stress accumulation and stress concentration, thereby reducing the risks of wrinkling, deformation, cracking, etc. of the electrode plate 11, reducing the risk of lithium plating, and improving the reliability of the battery cell 400a and the battery device 100a.

[0195] In some embodiments, please refer to Fig.11 , winding the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12, also includes: winding the 1st to xth turns of the electrode assembly 10 based on a constant tension; wherein the constant tension is greater than the winding tension of the (x+1)th turn.

[0196] The winding operation of the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 further includes the following steps:

[0197] S43: Winding the electrode assembly 10 from the 1st to the xth turns based on a constant tension; wherein the constant tension is greater than the winding tension of the (x+1)th turn.

[0198] In some embodiments, the winding device performs winding operation on the positive electrode sheet 112, the negative electrode sheet 111 and the separator 12 from the 1st to the xth circle at a constant tension, so that the distance between the positive electrode sheet 112 and the separator 12 and the distance between the negative electrode sheet 111 and the separator are the same on the 1st to the ith circle. The tension value corresponding to the constant tension is greater than the initial winding tension value.

[0199] In some embodiments, the tension value corresponding to the constant tension is 0.05MPa~0.5MPa. For example, the tension value corresponding to the constant tension can be 0.05MPa, 0.08MPa, 0.1MPa, 0.12MPa, 0.135MPa, 0.15MPa, 0.18MPa, 0.2MPa, 0.225MPa, 0.25MPa, 0.28MPa, 0.295MPa, 0.3MPa, 0.315MPa, 0.33MPa, 0.35MPa, 0.388MPa, 0.4MPa, 0.42MPa, 0.44MPa, 0.455MPa, 0.48MPa, 0.5MPa, etc., but not limited thereto. The specific value of the tension value corresponding to the constant tension can be selected according to the actual situation, as long as the tension value corresponding to the constant tension is within the range of 0.05MPa~0.5MPa.

[0200] The electrode assembly 10 is wound from the 1st circle to the xth circle with a constant tension so that the interlayer spacing 13 from the 1st circle to the xth circle is the same, so that the change of the interlayer spacing 13 from the 1st circle to the xth circle of the electrode assembly 10 is adapted to the size of the expansion force of the area, thereby making the stress distribution of the electrode assembly 10 uniform, overcoming the problem that the pressure between the pole piece 11 and the diaphragm 12 cannot be effectively released due to the excessively large interlayer spacing 13 and the excessively small expansion force of the area, so as to reduce or eliminate the risk of cracking of the pole piece 11 of the electrode assembly 10 from the 1st circle to the xth circle, thereby further improving the reliability of the battery cell 400a and the battery device 100a.

[0201] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: The battery cell comprises: A housing having a first accommodating space and an opening communicating with the first accommodating space; an electrode assembly, wherein the electrode assembly is disposed in the housing, and the first accommodation space is used to accommodate the electrode assembly; and an end cover connected to the housing and closing the opening; The electrode assembly includes a positive electrode sheet, a separator and a negative electrode sheet that are wound, and the number of turns of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; Among them, the interlayer spacing of the electrode assembly gradually increases from the (x+1)th circle to the i-th circle, the ratio of the difference between i and x to i is greater than or equal to 1 / 4 and less than or equal to 1 / 2, and the interlayer spacing from the 1st circle to the xth circle is the same and less than the interlayer spacing of the (x+1)th circle.

2. The battery cell according to claim 1, characterized in that: The interlayer spacing increases linearly, exponentially, or stepwise from the (x+1)th circle to the i-th circle.

3. The battery cell according to claim 1, characterized in that: The surface of the diaphragm is provided with a coating, and the weight of the coating gradually increases from the (x+1)th circle to the i-th circle; the interlayer spacing is the distance between two adjacent negative electrode plates, or the distance between two adjacent positive electrode plates.

4. The battery cell according to claim 3, characterized in that: The coating is provided on the first inner surface and / or the first outer surface of the diaphragm, and the radial size of the coating provided on the first inner surface gradually increases from the (x+1)th circle to the i-th circle along the radial direction of the electrode assembly, and / or the radial size of the coating provided on the first outer surface gradually increases from the (x+1)th circle to the i-th circle.

5. The battery cell according to claim 1, characterized in that: Bumps are formed on the positive electrode sheets and / or the negative electrode sheets from the (x+1)th circle to the i-th circle, and the radial size of the bumps gradually increases along the radial direction of the electrode assembly. The interlayer spacing is the distance between the two diaphragms respectively located on the second inner surface or the second outer surface of the adjacent positive electrode sheets, or the distance between the two diaphragms respectively located on the second inner surface or the second outer surface of the adjacent negative electrode sheets.

6. The battery cell according to claim 5, characterized in that: The second inner surface and / or the second outer surface of at least one of the positive electrode sheet and the negative electrode sheet is provided with the protrusion, and the size of the protrusion provided on the second inner surface along the radial direction gradually increases from the (x+1)th circle to the i-th circle, and / or the size of the protrusion provided on the second outer surface along the radial direction gradually increases from the (x+1)th circle to the i-th circle.

7. A battery device, characterized in that: The battery device comprises: A battery box is formed with a second accommodation space; and A battery cell as claimed in any one of claims 1 to 6; wherein the battery cell is arranged in the second accommodation space.

8. An electrical device, characterized in that: The electrical device comprises: A battery device as claimed in claim 7.

9. A method for preparing an electrode assembly, characterized in that: The number of turns of the positive electrode sheet, the negative electrode sheet and the separator of the electrode assembly is defined as N=1, 2, 3...(i-4), (i-3), (i-2), (i-1), i; wherein i is a positive integer, and the total number of turns of the electrode assembly is greater than or equal to 4; the preparation method comprises: Providing the positive electrode sheet, the negative electrode sheet and the separator; Winding the positive electrode sheet, the negative electrode sheet and the separator to obtain the electrode assembly; Among them, the interlayer spacing from the (x+1)th circle to the i-th circle of the electrode assembly gradually increases, the ratio of the difference between i and x to i is greater than or equal to 1 / 4 and less than or equal to 1 / 2, and the interlayer spacing from the 1st circle to the xth circle is the same and less than the interlayer spacing of the (x+1)th circle.

10. The preparation method according to claim 9, characterized in that: An operation of providing the diaphragm comprises: Providing a diaphragm; Determine a weight parameter and a start and end position parameter of each circle of the diaphragm from the (x+1)th circle to the i-th circle, and form a coating with gradually increasing thickness on the surface of the diaphragm from the (x+1)th circle to the i-th circle based on the weight parameter and the start and end position parameters; Wherein, the first inner surface and / or the first outer surface of the diaphragm is provided with the coating.

11. The preparation method according to claim 9, characterized in that: The operation of providing the positive electrode sheet or the negative electrode sheet includes: Providing positive electrode sheets and / or negative electrode sheets; Determine the pressure parameter, the starting and ending position parameters of the positive electrode sheet and / or the negative electrode sheet in each circle from the (x+1)th circle to the i-th circle, and roll the positive electrode sheet and / or the negative electrode sheet using a convex point roller based on the pressure parameter and the starting and ending position parameters, so as to form convex points with gradually increasing heights on the surface of the positive electrode sheet and / or the negative electrode sheet in the (x+1)th circle to the i-th circle; Wherein, the protrusions are provided on the second inner surface and / or the second outer surface of at least one of the positive electrode sheet and the negative electrode sheet.

12. The preparation method according to claim 9, characterized in that: The winding operation of the positive electrode sheet, the negative electrode sheet and the separator includes: Determine the tension parameter, the start and end position parameters of the positive electrode sheet, the negative electrode sheet and the separator in each circle from the (x+1)th circle to the i-th circle, and control the winding tension of the positive electrode sheet, the negative electrode sheet and the separator in the (x+1)th circle to the i-th circle based on the tension parameter and the start and end position parameters; The winding tension decreases gradually from the (x+1)th turn to the i-th turn.

13. The preparation method according to claim 12, characterized in that: The winding operation of the positive electrode sheet, the negative electrode sheet and the separator also includes: Winding the first to xth turns of the electrode assembly based on a constant tension; Wherein, the constant tension is greater than the winding tension of the (x+1)th turn.

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