Electrode assembly winding method, electrode assembly winding equipment, and battery cell

Abstract

This application relates to the field of batteries, providing a method for winding an electrode assembly, an apparatus for winding an electrode assembly, and a single battery cell. The method for winding an electrode assembly includes the following steps: providing a separator and an electrode sheet; providing a rolling mechanism, which rolls at least a portion of the separator under a preset rolling pressure to form a rolling region in at least a portion of the separator, and pre-compresses the coating in the rolling region. The preset rolling pressure is determined based on the interlayer pressure distribution law of different layers of the electrode assembly. The interlayer pressure distribution law of different layers of the electrode assembly is obtained through simulation analysis or experimental testing. The preset rolling pressure applied to the rolling region has an inverse adaptation relationship with the interlayer pressure of the corresponding electrode assembly layer in the rolling region; conveying the electrode sheet and separator to a winding needle; and winding the electrode sheet and separator through the winding needle to obtain an electrode assembly, where the interlayer gap of each turn of the electrode assembly tends to be consistent. This improves the consistency of the interlayer gap of each turn of the electrode assembly.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a method for winding an electrode assembly, a winding device for an electrode assembly, and a battery cell. Background Technology

[0002] Electrode assemblies are essential components for electrochemical reactions to occur in a single battery cell. An electrode assembly includes wound electrodes and a separator. The separator includes a base layer and a coating applied to at least one surface of the base layer.

[0003] However, the winding process of the electrode assembly exhibits complex mechanical behavior, resulting in a large change in interlayer pressure from the inner ring to the outer ring of the electrode assembly. This leads to differential elastoplastic deformation of the diaphragm from the inner ring to the outer ring, resulting in a large difference in the coating compression of the inner and outer ring diaphragms and poor consistency in the interlayer gap between the inner and outer rings. Summary of the Invention

[0004] This application provides a method for winding an electrode assembly, which aims to solve the problem of poor consistency in the gap between the inner and outer layers of the electrode assembly.

[0005] To achieve the above objectives, the technical solution adopted in the embodiments of this application is as follows:

[0006] In a first aspect, a method for winding an electrode assembly is provided, comprising the following steps:

[0007] A diaphragm and an electrode are provided, wherein the diaphragm includes a base layer and a coating applied to at least one surface of the base layer;

[0008] A rolling mechanism is provided, which rolls at least a portion of the diaphragm under a preset rolling pressure to form a rolling region in at least a portion of the diaphragm, and causes the coating in the rolling region to generate a pre-compression amount corresponding to the preset rolling pressure. The preset rolling pressure is determined according to the interlayer pressure distribution law of different layers of the electrode assembly. The interlayer pressure distribution law of different layers of the electrode assembly is obtained through simulation analysis or experimental testing. The preset rolling pressure applied to the rolling region has an inverse adaptation relationship with the interlayer pressure of the corresponding electrode assembly layer in the rolling region.

[0009] The electrode and diaphragm are fed to the winding needle;

[0010] Electrode assemblies are obtained by winding electrode sheets and diaphragms with a needle, wherein the interlayer spacing of each turn of the electrode assembly tends to be uniform.

[0011] By adopting the above scheme, at least a portion of the diaphragm can be rolled during the diaphragm conveying process by a rolling mechanism. A preset rolling pressure is applied according to the interlayer pressure distribution law of different layers of the electrode assembly to form a rolling region in at least a portion of the diaphragm. This causes the coating in the rolling region to generate a pre-compression amount corresponding to the preset rolling pressure, thereby making the pre-compression amount of the diaphragm coating corresponding to the layer with higher interlayer pressure smaller, and the pre-compression amount of the diaphragm coating corresponding to the layer with lower interlayer pressure larger. Building upon this foundation, the electrode assembly is obtained by winding the electrode sheets and separator using a needle winding method. This allows the separator coating, which has a smaller pre-compression and a larger reserved thickness, to undergo further compression due to greater interlayer pressure, and vice versa. This reduces the impact of significant interlayer pressure variations from the inner to the outer ring of the electrode assembly, minimizes the difference in compression between the inner and outer separator coatings, and effectively addresses the issue of inconsistent interlayer gaps. This improves the uniformity of electrolyte wetting within the electrode assembly, optimizes stress distribution during electrode assembly expansion in battery cells, and enhances the electrochemical performance, reliability, and lifespan of the battery cells. Furthermore, since rolling thins the separator, it facilitates the compression and control of the electrode assembly's dimensions, making it suitable for electrode assemblies with diameters exceeding specifications.

[0012] In some embodiments, the rolling mechanism rolls the entire area of ​​the diaphragm under a preset rolling pressure.

[0013] By adopting the above scheme, the separator can be subjected to differentiated rolling treatment that is inversely adapted to the interlayer pressure of each layer of the corresponding electrode assembly through the rolling mechanism. This allows the coating in different areas of the separator to form a pre-compression amount that matches the subsequent winding pressure, which can effectively offset the difference in coating compression caused by interlayer pressure during the winding process. This can significantly improve the consistency of the gap between the inner and outer layers of the electrode assembly, and improve the electrochemical performance, reliability and service life of the battery cell.

[0014] In some embodiments, the rolling mechanism rolls a portion of the diaphragm under a preset rolling pressure.

[0015] By adopting the above solution, the rolling mechanism can be used to perform reverse rolling treatment on key areas with significant differences in interlayer pressure of the corresponding electrode components (such as the middle ring with interlayer pressure close to the peak and the outer ring with lower pressure). This allows for precise control of the pre-compression of the coating in the rolling area, effectively compensating for the coating compression imbalance caused by interlayer pressure during winding without rolling the entire separator. This simplifies the rolling process, reduces processing costs, improves the consistency of the gaps between the layers of the electrode components, and enhances the overall performance and reliability of the battery cells.

[0016] In some embodiments, the diaphragm region corresponding to the 1st to 5th turns of the diaphragm winding from the inside out is not rolled.

[0017] By adopting the above scheme, when the rolling mechanism rolls a portion of the separator under a preset rolling pressure, based on the characteristics that the inner 1-5 turns have higher interlayer pressure and the coating is easily compressed, the separator area from the innermost to the outermost 1-5 turns can be excluded from the rolling process. This allows the original coating thickness and compression allowance to be retained, enabling the area to naturally generate a suitable compression amount during winding and compression. This helps to improve the problem of excessively small interlayer gaps caused by excessive pre-rolling of the inner turns. Furthermore, by combining this with the design of "reverse adaptive rolling of the separator areas of the remaining turns according to the interlayer pressure distribution pattern," the total compression amount of the separator coating in each turn can be precisely balanced. This effectively improves the overall interlayer gap consistency of the electrode assembly, and simultaneously enhances process feasibility, the electrochemical performance of the battery cells, and the reliability of the battery cells.

[0018] In some embodiments, the preset roller pressure increases continuously with the increase of the first parameter, so that the coating thickness decreases continuously with the increase of the first parameter, wherein the first parameter is the winding length of the diaphragm, the number of winding turns of the diaphragm, or the winding radius.

[0019] By adopting the above scheme, the preset roller pressure and the interlayer pressure exhibiting a gradient attenuation trend can be accurately and continuously matched. As the first parameter increases (corresponding to the increase of the winding radius and the decrease of the interlayer pressure), the preset roller pressure can be continuously increased to increase the pre-compression of the coating, so that the coating thickness continuously decreases. This can accurately compensate for the compression deviation caused by the difference in interlayer pressure in different layers, improve the consistency and uniformity of the interlayer gap of each layer of the electrode assembly, reduce the abrupt change in interlayer gap caused by segmented control, and optimize the overall performance of the battery cell.

[0020] In some embodiments, the preset roller pressure is linearly related to the first parameter.

[0021] By adopting the above scheme, a simple and easily controllable linear regulation relationship can be established based on the law that the interlayer pressure decreases with the increase of the first parameter. This allows the preset rolling pressure to increase steadily with the first parameter, and the pre-compression of the coating to change synchronously and linearly. Based on this, the interlayer pressure differences of each ring can be accurately matched, and the total compression of each ring of coating in the electrode assembly can be made uniform. This improves the consistency and uniformity of the gaps between each ring of the electrode assembly. Furthermore, it eliminates the need for complex segmented parameter settings, reduces process errors caused by complex regulation, lowers the control difficulty of the rolling process, simplifies the process control flow, and improves production efficiency.

[0022] In some embodiments, the preset roller pressure is non-linearly related to the first parameter.

[0023] By adopting the above scheme, the law of nonlinear gradient change of interlayer pressure with the first parameter can be adapted. For critical intervals where the interlayer pressure changes drastically (such as the 3rd to 6th turns near the peak), the increase of the preset roller pressure can be precisely controlled. For areas where the interlayer pressure changes slowly, the rate of change of the preset roller pressure can be appropriately adjusted. This can achieve fine compensation of the pre-compression of the coating. Compared with linear control, it can better fit the actual winding mechanical behavior, reduce the difference in the total compression of the coating in each turn of the electrode assembly, and improve the consistency of the interlayer gap in each turn of the electrode assembly.

[0024] In some embodiments, the preset roller pressure is P, the first parameter is x, and the relationship between P and x is:

[0025] P=K / (1+EXP(-r·(x-x0)))

[0026] Where K is the saturation value of the preset roller pressure, r is the rate of change of the preset roller pressure, and x0 is the first parameter value corresponding to the inflection point where the preset roller pressure changes the fastest.

[0027] By adopting the above scheme, under the condition that "the preset rolling pressure increases continuously with the increase of the first parameter", and under the condition that "the preset rolling pressure is linearly or non-linearly related to the first parameter", the interlayer pressure gradient attenuation characteristics of different rings of the electrode assembly can be accurately matched based on the relationship between P and x. By adjusting the preset rolling pressure, the winding stress distribution can be dynamically matched. Thus, the preset rolling pressure can be continuously changed by adjusting the parameters, the thickness change of the coating and the diaphragm can be accurately controlled, the rolling process requirements can be met, the control accuracy of the rolling process can be improved, and the interlayer gap difference between the inner and outer rings of the electrode assembly can be effectively eliminated.

[0028] In some embodiments, the preset roller pressure increases gradually with the increase of a first parameter, so that the coating thickness decreases gradually with the increase of the first parameter, wherein the first parameter is the winding length of the diaphragm, the number of winding turns of the diaphragm, or the winding radius.

[0029] By adopting the above scheme, the characteristic of interlayer pressure decreasing gradually with the increase of the first parameter can be matched. Through staged preset roller pressure control, a step-like decrease in coating thickness can be achieved. This precisely compensates for compression deviations caused by differences in interlayer pressure among different layers, improving the consistency and uniformity of the gaps between each layer of the electrode assembly and optimizing the overall performance of the battery cell. Furthermore, it eliminates the need for complex continuous control formulas, significantly simplifying process parameter setting and control, and effectively improving production efficiency and process stability.

[0030] In some embodiments, the interlayer gap difference between each turn of the electrode assembly is less than 10 μm (micrometers).

[0031] By adopting the above scheme, the interlayer gap difference of each ring of the electrode assembly can be controlled within a very small range, with the quantitative index clearly defined and controlled within 10μm. This can optimize and improve the consistency and uniformity of the interlayer gap of each ring of the electrode assembly, and optimize the electrochemical performance, reliability and service life of the battery cell.

[0032] Secondly, a winding apparatus for an electrode assembly is provided, for performing the winding method for the electrode assembly provided in the embodiments of this application. The winding apparatus for the electrode assembly includes:

[0033] curling needles;

[0034] The first unwinding mechanism is used to unwind the electrode sheet to transport it to the winding needle;

[0035] The second unwinding mechanism is used to unwind the diaphragm to convey it to the winding needle;

[0036] A rolling mechanism is provided on the conveying path of the diaphragm from the second unwinding mechanism to the winding needle. The rolling mechanism is configured to roll at least a portion of the diaphragm under a preset rolling pressure to form a rolling region in at least a portion of the diaphragm and to generate a pre-compression amount in the coating of the rolling region corresponding to the preset rolling pressure. The preset rolling pressure applied to the rolling region is inversely compatible with the interlayer pressure of the corresponding electrode assembly layer in the rolling region.

[0037] By adopting the above solution, a rolling mechanism can be integrated into the winding equipment of the electrode assembly. Before the diaphragm is wound into the winding needle, the rolling mechanism performs online rolling on the diaphragm conveying path as the diaphragm passes through the rolling area, forming a rolling area. This causes the coating in the rolling area to generate a pre-compression amount corresponding to a preset rolling pressure. Furthermore, the preset rolling pressure, the starting position of the rolling, and the ending position of the rolling can be dynamically adjusted, thereby achieving closed-loop control of the interlayer gap and diameter of the wound electrode assembly. Based on this, the winding equipment for the electrode assembly provided in this embodiment can provide reliable support for the above-mentioned winding method and standardized mass production of electrode assemblies. It can achieve compatibility and seamless connection between the rolling process and the winding process. Moreover, the online rolling design eliminates the need for transfer and secondary positioning processes in offline rolling, shortening the production cycle and improving production yield and efficiency.

[0038] In some embodiments, the length of the conveying path of the diaphragm from the rolling mechanism to the needle is less than the length of the conveying path of the diaphragm from the second unwinding mechanism to the rolling mechanism.

[0039] By adopting the above scheme, the roller pressing mechanism can be positioned relatively close to the winding needle and relatively far from the second unwinding mechanism along the conveying path of the diaphragm. Based on this, the conveying distance of the diaphragm after being processed by the roller pressing mechanism to before being wound can be shortened. This can reduce the impact of roller pressing lag on the control of parameters such as coating thickness, diaphragm thickness, and electrode assembly diameter. It can also improve the control accuracy of the layer gap of the electrode assembly, which is conducive to accurately controlling the layer gap difference of each turn of the electrode assembly within the target range. This is beneficial for standardized mass production and for improving process stability and production consistency.

[0040] In some embodiments, the rolling mechanism includes two first rollers and at least one dust removal assembly. The two first rollers are disposed on opposite sides of the diaphragm, and the dust removal assembly is disposed on the periphery of the first rollers to remove powder adhering to the surface of the first rollers.

[0041] By adopting the above scheme, the rolling mechanism can achieve rolling of the diaphragm's rolling area using two first rollers located on both sides of the diaphragm. The rolling mechanism can also promptly remove powder adhering to the surface of the first rollers due to slight coating damage and peeling using dust removal components located around the first rollers. This effectively improves problems such as uneven rolling, over-rolling contamination, and diaphragm wrinkling caused by powder residue. It optimizes the structure of the rolling mechanism, improves its performance, operational stability, reliability, and service life, reduces product defect rates caused by rolling defects, and enhances the structural consistency, production consistency, and production yield of the electrode assembly.

[0042] Thirdly, a battery cell is provided, including an electrode assembly formed by winding the electrode assembly using the winding method provided in the embodiments of this application, wherein the electrode assembly is cylindrical.

[0043] By adopting the above solution, the winding method of the electrode assembly provided in the embodiments of this application can be used to specifically solve the prominent problem of inconsistent interlayer gaps in cylindrical electrode assemblies, and to prepare cylindrical electrode assemblies with consistent and uniform interlayer gaps. These assemblies can then be used to construct battery cells, thereby improving the electrochemical performance, reliability, and service life of the battery cells. Attached Figure Description

[0044] To clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0046] Figure 2 Cross-sectional views of a battery cell provided in some embodiments of this application;

[0047] Figure 3 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0048] Figure 4 This is a schematic flowchart illustrating a method for winding an electrode assembly according to some embodiments of this application.

[0049] Figure 5 Schematic diagrams of the winding equipment, electrode sheet, and diaphragm of the electrode assembly provided in some embodiments of this application;

[0050] Figure 6 The diagram shows the structure of a diaphragm provided in some embodiments of this application, wherein the thickness of the coating continuously decreases along a first direction;

[0051] Figure 7 A pressure curve showing a linear relationship between preset roller pressure and number of winding turns, provided for some embodiments of this application;

[0052] Figure 8 A pressure curve showing a non-linear relationship between preset roller pressure and number of winding turns, provided for some embodiments of this application;

[0053] Figure 9 Pressure curves showing a non-linear relationship between preset roller pressure and number of winding turns are provided for other embodiments of this application;

[0054] Figure 10 The diagram below is a structural schematic of a diaphragm provided in some other embodiments of this application, wherein the thickness of the coating decreases gradually along a first direction.

[0055] The following are the labeling elements in the figure:

[0056] 10-Battery cell, 11-Casing, 111-Side wall, 112-First end wall, 113-Second end wall, 12-Electrode assembly, 121-Main body, 122-Taper, 122a-Positive electrode tab, 122b-Negative electrode tab, 123-Electrode sheet, 123a-Positive electrode sheet, 123b-Negative electrode sheet, 124-Separator, 1241-Base layer, 1242-Coating, 124a-Rolling area, 13-Electrode terminal, 14-Insulation structure, 15-Adapter, 15a-Positive adapter, 15b-Negative adapter, 16-Pressure relief mechanism, 20-Rolling needle, 30-First unwinding mechanism, 40-Second unwinding mechanism, 50-Rolling mechanism, 51-First roller, 52-Dust removal assembly, 60-Second roller, x-Thickness direction, y-First direction. Detailed Implementation

[0057] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clear, the application will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application. Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0058] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0061] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0062] A battery cell is the smallest unit for storing and outputting electrical energy. Inside a battery cell, there is typically an electrode assembly, which is essential for the electrochemical reactions that occur within the cell. The electrode assembly includes wound electrodes and a separator. The electrodes include positive and negative electrodes with opposite polarities, and the separator separates the positive and negative electrodes. The separator includes a base layer and a coating applied to at least one surface of the base layer. The coating is more compressible than the base layer; that is, the base layer is less susceptible to compression by interlaminar pressure, while the coating is more easily compressed by interlaminar pressure.

[0063] In some cases, cylindrical electrode assemblies can be formed by winding with a smaller diameter needle. In this case, the curvature of the electrode assembly changes significantly from the inner to the outer ring, resulting in large variations in interlayer pressure. This means the winding process of the electrode assembly exhibits complex mechanical behavior. Simulation results show that the interlayer pressure is relatively high in the inner 5 rings (rings 1-5 from the inside out), and high again, approaching the peak pressure, in rings approximately 3-6 from the inside out. The interlayer pressure is relatively low in the outer 5 rings (rings 1-5 from the outside in). Therefore, as the winding radius increases, the interlayer pressure exhibits a gradient decrease trend, leading to differentiated elasto-plastic deformation of the diaphragm from the inner to the outer ring. This results in significant differences in coating compression between the inner and outer rings, leading to poor consistency in the interlayer gap between the inner and outer rings. Specifically, the diaphragm coating compression is greater where the interlayer pressure is higher, resulting in a smaller interlayer gap for the corresponding ring; conversely, the coating compression is smaller where the interlayer pressure is lower, resulting in a larger interlayer gap for the corresponding ring. The interlayer gap refers to the remaining space between two adjacent electrode layers (i.e., adjacent positive and negative electrode layers) excluding the space occupied by the membrane base layer. In other words, the interlayer gap is the difference between "the gap between two adjacent electrode layers" and "the thickness of the membrane base layer located between two adjacent electrode layers".

[0064] If the electrode assembly exhibits significant interlayer inconsistency, it will negatively impact the electrochemical performance, reliability, and lifespan of the battery cell containing that electrode assembly. For example, during the electrolyte wetting process, the wetting rate is slower in areas with smaller interlayer gaps and faster in areas with larger interlayer gaps, resulting in inconsistent wetting. Furthermore, during battery cell use, areas with larger interlayer gaps provide expansion space for the electrode sheet, while areas with smaller interlayer gaps have less expansion space, hindering electrode sheet expansion and leading to inconsistent stress distribution during expansion. Therefore, improving the consistency of the interlayer gaps between the inner and outer rings of the electrode assembly is a pressing issue that needs to be addressed.

[0065] Therefore, some embodiments of this application provide a method for winding an electrode assembly. This method can perform roller pressing on at least a portion of the diaphragm during the conveying process of the diaphragm, and apply a preset roller pressing pressure according to the interlayer pressure distribution law of different layers of the electrode assembly to form a roller pressing area in at least a portion of the diaphragm. This causes the coating in the roller pressing area to generate a pre-compression amount corresponding to the preset roller pressing pressure, thereby making the pre-compression amount of the diaphragm coating corresponding to the layer with higher interlayer pressure smaller, and the pre-compression amount of the diaphragm coating corresponding to the layer with lower interlayer pressure larger. Based on this, the electrode assembly is obtained by winding the electrode sheet and separator with a needle. This allows the separator coating, which has a small pre-compression and a large reserved thickness, to generate a large compression due to the large interlayer pressure, and vice versa. This reduces the impact of large interlayer pressure changes from the inner to the outer ring of the electrode assembly, reduces the difference in compression between the inner and outer ring separator coatings, and can complementaryly solve the problem of inconsistent gaps between the inner and outer rings. It can effectively improve the consistency of the gaps between each ring, thereby improving the uniformity of electrolyte wetting in the electrode assembly, optimizing the stress distribution of the electrode assembly during the expansion of the battery cell, and optimizing the electrochemical performance, reliability, and service life of the battery cell.

[0066] The electrode assembly winding method disclosed in this application can be used for winding and forming electrode assemblies of battery cells. The electrode assembly winding equipment disclosed in this application can be used to perform the electrode assembly winding method disclosed in this application. Battery cells prepared from electrode assemblies produced by the electrode assembly winding method disclosed in this application can be used independently or combined with other battery cells to form modular battery devices (e.g., battery modules, battery packs) that can provide higher voltage and capacity. The battery cells disclosed in this application, and battery devices having the battery cells disclosed in this application, can be used in electrical devices that use the battery cells and battery devices as power sources, or in various energy storage systems that use the battery cells and battery devices as energy storage elements. Electrical devices can be, but are not limited to, vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline vehicles, natural gas vehicles, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0067] To illustrate the technical solutions provided in this application, the following detailed description is provided in conjunction with specific drawings and embodiments.

[0068] Please see Figure 1 , Figure 2 , Figure 3 The battery cell 10 is the smallest unit for storing and outputting electrical energy. The battery cell 10 includes components such as a casing 11, electrode assembly 12, electrode terminals 13, insulation structure 14, adapter 15, and electrolyte.

[0069] The outer casing 11 is a component that isolates the internal environment of the battery cell 10 from the external environment. The internal environment enclosed by the outer casing 11 can be used to house components such as the electrode assembly 12 and the electrolyte. The outer casing 11 may include a side wall 111, a first end wall 112, and a second end wall 113. The side wall 111 may be cylindrical, such as a cylindrical, rectangular, or polygonal cylinder. The first end wall 112 and the second end wall 113 respectively cover the opposite ends of the side wall 111, thereby isolating the internal space enclosed by the side wall 111, the first end wall 112, and the second end wall 113 from the external environment. In some embodiments, the first end wall 112 and the side wall 111 can be integrated. For example, the first end wall 112 and the side wall 111 can form a common connecting surface before other components are inserted into the housing. When the housing 11 needs to be encapsulated, the first end wall 112 can cover the side wall 111. In other embodiments, the first end wall 112 and the side wall 111 can be independent components. The first end wall 112 can cover one end opening of the side wall 111 and the first end wall 112 and the side wall 111 can be connected and fixed. Similarly, in some embodiments, the second end wall 113 and the side wall 111 can be independent components. The second end wall 113 can be fitted over one end opening of the side wall 111, and the second end wall 113 and the side wall 111 can be connected and fixed. In other embodiments, the second end wall 113 and the side wall 111 can be integrated. For example, the second end wall 113 and the side wall 111 can form a common connecting surface before other components are inserted into the shell. When the shell 11 needs to be encapsulated, the second end wall 113 can then be fitted over the side wall 111. In some embodiments, the shape of the first end wall 112 and the shape of the second end wall 113 can be adapted to the shape of the side wall 111. In some embodiments, the first end wall 112, the second end wall 113, and the side wall 111 can be made of a material with a certain hardness and strength. In this way, the shell 11 is not easily deformed when subjected to compression and impact, so that the battery cell 10 can have high structural strength and structural reliability. The materials of the first end wall 112, the second end wall 113, and the side wall 111 can be the same or different. The materials of the first end wall 112, the second end wall 113, and the side wall 111 can be set as needed. For example, the side wall 111, the first end wall 112, and the second end wall 113 can each be made of copper, iron, aluminum, stainless steel, aluminum alloy, nickel-plated copper, iron-plated copper, copper-nickel composite material, copper-iron composite material, etc., as needed.

[0070] Electrode assembly 12 is the component in the battery cell 10 where the electrochemical reaction occurs. In some cases, electrode assembly 12 may also be referred to as a bare cell, a wound assembly, etc. Electrode assembly 12 is disposed within the housing 11. Electrode assembly 12 includes a separator 124 and two electrodes 123 with opposite polarities, the separator 124 separating the two electrodes 123 with opposite polarities. "Two electrodes 123 with opposite polarities" means that one of the two electrodes 123 is a positive electrode 123a and the other is a negative electrode 123b. The two electrodes 123 and the separator 124 are wound together to form a rolled electrode assembly 12. In electrode assembly 12, the portions of the two electrodes 123 with active material and the separator 124 together constitute the main body 121 of electrode assembly 12, and the portions of the two electrodes 123 without active material each constitute a tab 122, which is the current transmission terminal of electrode assembly 12 for transmitting current. The tab 122 of the positive electrode 123a is the positive electrode tab 122a, and the tab 122 of the negative electrode 123b is the negative electrode tab 122b. The positive electrode tab 122a and the negative electrode tab 122b can be located together at one end of the main body 121 or at both ends of the main body 121 respectively.

[0071] The electrolyte is a liquid that wets the electrode assembly 12. The battery cell 10 primarily functions by the movement of active ions between the positive electrode 123a and the negative electrode 123b. When the battery cell 10 is charging, active ions are generated on the positive electrode 123a. These active ions can penetrate the pores of the separator 124, move through the electrolyte to the negative electrode 123b, and embed themselves in the negative electrode active material. Conversely, when the battery cell 10 discharges, the active ions embedded in the negative electrode active material of the negative electrode 123b are released. These released active ions can penetrate the pores of the separator 124, move through the electrolyte to the positive electrode 123a, and embed themselves in the positive electrode active material. The active ions can be lithium ions, sodium ions, etc.

[0072] Electrode terminal 13 is a component electrically connected to electrode assembly 12 and used for outputting or inputting electrical energy. One or two electrode terminals 13 may be provided as needed. Electrode terminal 13 can be a positive electrode terminal electrically connected to the positive electrode tab 122a of electrode assembly 12, or a negative electrode terminal electrically connected to the negative electrode tab 122b of electrode assembly 12. Electrode terminal 13 can be mounted on housing 11 and stably mounted in position and state relative to housing 11. In some embodiments, electrode terminal 13 can be mounted on housing 11 by means of flange riveting.

[0073] In some embodiments, an insulating structure 14 is provided at the area where the electrode terminal 13 and the housing 11 mate. The insulating structure 14 has insulating properties, which can insulate the electrode terminal 13 and the housing 11 from each other, thereby reducing the risk of short circuit. Optionally, the insulating structure 14 may include plastic, rubber, etc.

[0074] The adapter 15 is a current collector electrically connected between the tab 122 of the electrode assembly 12 and the corresponding electrode terminal 13. The adapter 15 may also be called an adapter connector, current collector plate, current collector, or adapter piece, etc. The adapter 15 has conductive properties and is made of a conductive material. The material of the adapter 15 may include aluminum, aluminum alloy, copper, copper alloy, copper-aluminum alloy, etc. The adapter 15 includes a positive electrode adapter 15a and a negative electrode adapter 15b. The positive electrode tab 122a of the electrode assembly 12 can be electrically connected to the positive electrode terminal 13 through the positive electrode adapter 15a, and the negative electrode tab 122b of the electrode assembly 12 can be electrically connected to the negative electrode terminal 13 through the negative electrode adapter 15b to form a current loop. In some embodiments, the adapter 15 can be connected to the tab 122 of the electrode assembly 12 by welding, abutment, or other methods. The adapter 15 can be connected to the electrode terminal 13 by welding, abutment, or other methods. The shape of the adapter 15 can be varied, such as square, round, irregular shape, etc.

[0075] In some embodiments, the housing 11 may also be provided with a pressure relief mechanism 16 for releasing internal pressure when the internal pressure or temperature of the battery cell 10 reaches a threshold. In some cases, the pressure relief mechanism 16 may also be referred to as an explosion-proof valve. In some embodiments, the pressure relief mechanism 16 may be integrally formed with the wall portion (e.g., end cap) of the housing 11 for which the pressure relief mechanism 16 is provided (i.e., an integral structure), for example, the pressure relief mechanism 16 may be a groove provided on the corresponding wall portion of the housing 11. In other embodiments, the pressure relief mechanism 16 may be separately formed and separately connected with the corresponding wall portion (e.g., end cap) of the housing 11 (i.e., a separate structure).

[0076] Please see Figure 3 , Figure 4 , Figure 5 , Figure 6 Some embodiments of this application provide a method for winding an electrode assembly, including the following steps:

[0077] S1. A separator 124 and an electrode 123 are provided. The separator 124 includes a base layer 1241 and a coating 1242 applied to at least one surface of the base layer 1241. The electrode 123 may include a positive electrode 123a and a negative electrode 123b with opposite polarities. Two separators 124 may be provided, with the two separators 124 located on opposite sides of the negative electrode 123b, and one separator 124 located between the positive electrode 123a and the negative electrode 123b. The separator 124 is used to isolate the positive electrode 123a and the negative electrode 123b. The separator 124 includes a base layer 1241 and a coating 1242. In some embodiments, one coating 1242 is provided and applied to one side of the base layer 1241; in other embodiments, two coatings 1242 are provided, with the two coatings 1242 applied to opposite sides of the base layer 1241. The compressibility of the coating 1242 is greater than that of the base layer 1241. That is, the base layer 1241 of the diaphragm 124 is more difficult to compress, while the coating 1242 of the diaphragm 124 is more easily compressed.

[0078] S2. A rolling mechanism 50 is provided. The rolling mechanism 50 rolls at least a portion of the diaphragm 124 under a preset rolling pressure to form a rolling region 124a in at least a portion of the diaphragm 124. The coating 1242 of the rolling region 124a generates a pre-compression amount corresponding to the preset rolling pressure. The preset rolling pressure is determined according to the interlayer pressure distribution law of different layers of the electrode assembly 12. The interlayer pressure distribution law of different layers of the electrode assembly 12 is obtained through simulation analysis or experimental testing. The preset rolling pressure applied to the rolling region 124a is inversely compatible with the interlayer pressure of the corresponding layer of the electrode assembly 12 in the rolling region 124a. The roller pressing mechanism 50 is disposed on the conveying path of the diaphragm 124. The roller pressing mechanism 50 may include two first rollers 51, which are respectively disposed on opposite sides of the diaphragm 124. The two first rollers 51 can move close to each other to press the roller pressing area 124a, and the two first rollers 51 can move away from each other to release the roller pressing on the diaphragm 124 and allow the diaphragm 124 to pass smoothly. At least one of the first rollers 51 is an active pressure adjusting roller, which can adjust the preset roller pressing pressure in real time according to a preset pressure distribution curve. The interlayer pressure distribution pattern of different turns of the electrode assembly 12 can be obtained through, but is not limited to, simulation analysis or experimental testing. For example, in one simulation result, the interlayer pressure distribution pattern of different turns of the electrode assembly 12 shows that the interlayer pressure of the inner 5 turns (i.e., turns 1-5 from the inside out) is relatively high, the interlayer pressure of turns approximately 3-6 from the inside out is relatively high and close to the peak value, and the interlayer pressure of the outer 5 turns (i.e., turns 1-5 from the outside in) is relatively low. With the increase of the winding radius, the interlayer pressure roughly shows a gradient decay trend. In this step, based on the interlayer pressure distribution pattern of different turns of the electrode assembly 12, a differentiated preset rolling pressure can be applied to the rolling region 124a, so that the coating 1242 of the rolling region 124a can generate different pre-compression amounts under different preset rolling pressures, thus enabling the coating 1242 of the rolling region 124a to generate differentiated pre-compression amounts. Specifically, based on the interlayer pressure distribution pattern of different turns of the electrode assembly 12, at least a portion of the diaphragm 124 (i.e., all or part of the diaphragm 124 along its length) can be selected as the roll-pressing area. This roll-pressing area can correspond to all turns of the electrode assembly 12, or only to key turns with significant interlayer pressure differences (e.g., the inner 5 turns and the outer 5 turns), etc. Before the roll-pressing area is wound onto the winding needle 20 (i.e., before it is wound around the outer circumference of the winding needle 20), as the roll-pressing area passes through the roll-pressing mechanism 50, it can be roll-pressed to form a roll-pressing area 124a, and the coating 1242 of the roll-pressing area 124a will generate a pre-compression amount. The pre-compression amount generated by the coating 1242 corresponds to a preset roll-pressing pressure.The preset rolling pressure applied to the rolling area 124a is inversely matched with the interlayer pressure of the corresponding 12 layers of the electrode assembly in the rolling area 124a. This ensures that the pre-compression of the coating 1242 is also matched with the interlayer pressure of the corresponding 12 layers of the electrode assembly. That is, for the rolling area 124a with a higher interlayer pressure of the electrode assembly 12, the applied preset rolling pressure is smaller, and the pre-compression of the corresponding coating 1242 is smaller. In other words, the thicker coating 1242 is matched to the layers with higher interlayer pressure of the electrode assembly 12 (e.g., the inner 5 layers). Thus, the interlayer pressure is higher. The coating 1242 corresponding to the ring can generate a small pre-compression amount before winding, so as to reserve a larger thickness to cope with the high pressure compression after winding. Conversely, for the rolling area 124a with smaller interlayer pressure of electrode assembly 12, the applied preset rolling pressure is greater, and the pre-compression amount of the corresponding coating 1242 is greater. That is, the ring with smaller interlayer pressure (e.g., the outer 5 rings) is matched with a thinner coating 1242. In this way, the coating 1242 corresponding to the ring with smaller interlayer pressure can generate a larger pre-compression amount before winding, so as to reserve a smaller thickness to cope with the low pressure compression after winding. Here, the thickness of coating 1242 refers to the dimension of coating 1242 along the thickness direction x, which is perpendicular to the length direction (i.e., the extension direction) of diaphragm 124. The length direction of diaphragm 124 is parallel to the first direction y. Since the base layer 1241 of diaphragm 124 is difficult to compress, the thinning effect of rolling on the base layer 1241 is weak. It can be assumed that the thickness of the base layer 1241 along the thickness direction x remains unchanged before and after rolling. The winding radius refers to the real-time radius of the core (i.e., the wound body) formed by the electrode 123 and the diaphragm 124 during or after the winding process.

[0079] S3. The electrode 123 and the diaphragm 124 are conveyed to the winding needle 20. In some embodiments, the electrode 123 or the diaphragm 124 can be unwound by an unwinding mechanism, and the electrode 123 or the diaphragm 124 can be guided along a preset path and a preset direction to the outer periphery of the winding needle 20 by one or more second rollers 60 on the conveying path, wherein the second rollers 60 can be active rollers or passive rollers.

[0080] S4. The electrode assembly 12 is obtained by winding the electrode sheet 123 and the separator 124 using a winding needle 20, wherein the interlayer gap of each turn of the electrode assembly 12 tends to be consistent. The winding needle 20 can wind the electrode sheet 123 and the rolled separator 124 in a preset direction to form the electrode assembly 12. The interlayer gap refers to the remaining space between two adjacent electrode sheets 123 (i.e., adjacent positive electrode sheet 123a and negative electrode sheet 123b) excluding the space occupied by the separator 124 base layer 1241. That is, the interlayer gap is the difference between "the gap between two adjacent electrode sheets 123" and "the thickness of the separator 124 base layer 1241 located between two adjacent electrode sheets 123". This means that the greater the thickness of the coating 1242, the larger the interlayer gap; the smaller the thickness of the coating 1242, the smaller the interlayer gap. Based on this, in the wound electrode assembly 12, the coating 1242 corresponding to the loop with higher interlayer pressure first has a larger thickness due to step S2, and then experiences greater compression due to the greater interlayer pressure. Conversely, the coating 1242 corresponding to the loop with lower interlayer pressure first has a smaller thickness due to step S2, and then experiences less compression due to the lesser interlayer pressure. This allows the actual compression of the coating 1242 in each loop of the wound electrode assembly 12 to tend to be consistent, the actual thickness of the coating 1242 in each loop to tend to be consistent, and the interlayer gap in each loop to tend to be consistent. Here, "tends to be consistent" means that the difference is controlled within a preset threshold range. This preset threshold can be set as needed, for example, based on the battery cell 10 (e.g., ...). Figure 2 The requirements for electrochemical performance, reliability, and service life (as shown) are set.

[0081] By adopting the above scheme, during the conveying process of the diaphragm 124, at least a portion of the diaphragm 124 can be rolled by the rolling mechanism 50, and a preset rolling pressure is applied according to the interlayer pressure distribution law of different layers of the electrode assembly 12, so as to form a rolling region 124a in at least a portion of the diaphragm 124, and the coating 1242 of the rolling region 124a generates a pre-compression amount corresponding to the preset rolling pressure, so that the pre-compression amount of the coating 1242 corresponding to the layer with larger interlayer pressure is smaller, and the pre-compression amount of the coating 1242 corresponding to the layer with smaller interlayer pressure is larger. Based on this, the electrode assembly 12 is obtained by winding the electrode sheet 123 and the separator 124 using the winding needle 20. This allows the coating 1242, which has a small pre-compression and a large reserved thickness, to generate a large compression due to the large interlayer pressure, and vice versa. This reduces the impact of the large interlayer pressure variation from the inner to the outer ring of the electrode assembly 12, reduces the difference in compression between the coating 1242 of the inner and outer separators, and complementarily solves the problem of inconsistent interlayer gaps between the inner and outer rings. It effectively improves the consistency of the gaps between each ring, thereby improving the uniformity of electrolyte wetting within the electrode assembly 12. This also helps optimize the stress distribution of the electrode assembly 12 during the expansion of the battery cell 10, and optimizes the electrochemical performance, reliability, and service life of the battery cell 10. Furthermore, since the rolling process has a thinning effect on the separator 124, it is beneficial for compressing and controlling the size of the electrode assembly 12, making it suitable for situations where the diameter of the electrode assembly 12 exceeds the specifications.

[0082] Please see Figure 2 , Figure 4 , Figure 5 , Figure 6 In some embodiments of this application, the rolling mechanism 50 rolls the entire area of ​​the diaphragm 124 under a preset rolling pressure.

[0083] The entire area of ​​the diaphragm 124 refers to the entire area of ​​the diaphragm 124 along its length, corresponding to all loops of the electrode assembly 12.

[0084] By adopting the above scheme, the diaphragm 124 can be subjected to differentiated rolling treatment by the rolling mechanism 50, which is adapted to the interlayer pressure of each layer of the corresponding electrode assembly 12. This allows the coating 1242 in different areas of the diaphragm 124 to form a pre-compression amount that matches the subsequent winding pressure. This can effectively offset the difference in the compression amount of the coating 1242 caused by the interlayer pressure during the winding process, thereby significantly improving the consistency of the gap between the inner and outer layers of the electrode assembly 12, and improving the electrochemical performance, reliability and service life of the battery cell 10.

[0085] Please see Figure 2 , Figure 4 , Figure 5 , Figure 6 In some embodiments of this application, the rolling mechanism 50 rolls a portion of the diaphragm 124 under a preset rolling pressure.

[0086] As an example, a portion of the diaphragm 124 corresponding to the interval between the first parameter 1 / a and 1 / b can be selected as the rolling area to be rolled, so that the rolling mechanism 50 can roll the area to be rolled under a preset rolling pressure, thereby forming the rolling area 124a. That is, the partial rolling starts at 1 / a of the first parameter and ends at 1 / b of the first parameter. Wherein, a > b ≥ 1, and the first parameter is the winding length of the diaphragm 124, the number of winding turns of the diaphragm 124, or the winding radius.

[0087] By adopting the above scheme, the rolling mechanism 50 can specifically perform reverse rolling treatment on key areas of the separator 124 corresponding to the electrode assembly 12 with significant differences in interlayer pressure (such as the middle ring with interlayer pressure close to the peak and the outer ring with lower pressure). This can precisely control the pre-compression amount of the coating 1242 in the rolling area 124a. It can effectively compensate for the imbalance of coating 1242 compression caused by interlayer pressure during winding without rolling the entire separator 124. Thus, it can improve the consistency of the gap between each ring of the electrode assembly 12 while simplifying the rolling process and reducing processing costs, thereby improving the overall performance and reliability of the battery cell 10.

[0088] Please see Figure 2 , Figure 3 , Figure 5 , Figure 6 In some embodiments of this application, the diaphragm 124 region corresponding to the 1st to 5th turns of the diaphragm 124 winding from the inside out is not rolled.

[0089] That is, when the roller pressing mechanism 50 performs roller pressing on a portion of the diaphragm 124 under a preset roller pressing pressure, the diaphragm 124 area corresponding to the 1st to 5th turns of the diaphragm 124 winding from the inside out is not considered as the roller pressing area and is not subjected to roller pressing.

[0090] By adopting the above scheme, when the rolling mechanism 50 rolls a portion of the separator 124 under a preset rolling pressure, based on the characteristics that the interlayer pressure of the inner 1-5 turns is relatively large and the coating 1242 is easily fully compressed, the area of ​​the separator 124 corresponding to the 1st to 5th turns from the inside out can be excluded from the rolling area and not rolled. This allows the original thickness and original compression allowance of the coating 1242 to be retained in this area, enabling it to naturally generate an appropriate compression amount when wound and compressed. This helps to improve the problem of excessively small interlayer gaps caused by excessive pre-rolling of the inner turns. On this basis, combined with the design of "implementing reverse adaptive rolling for the remaining layers of the separator 124 according to the interlayer pressure distribution law", the total compression amount of the coating 1242 of each layer can be accurately balanced. This can effectively improve the overall interlayer gap consistency of the electrode assembly 12, and simultaneously improve process feasibility, electrochemical performance of the battery cell 10, and reliability of the battery cell 10.

[0091] Please see Figure 2 , Figure 3 , Figure 6 In some embodiments of this application, the preset roller pressure increases continuously with the increase of the first parameter, so that the thickness of the coating 1242 decreases continuously with the increase of the first parameter, wherein the first parameter is the winding length of the diaphragm 124, the number of winding turns of the diaphragm 124, or the winding radius.

[0092] The thickness of the coating 1242 in the roll forming region 124a decreases continuously with the increase of the first parameter. That is, the thickness of the coating 1242 in the roll forming region 124a gradually thins from the inner ring to the outer ring like a smooth line. The thickness difference between any two adjacent positions is very small, and the boundary is almost invisible to the naked eye. Based on this, after the roll forming region 124a is rolled and before winding, the roll forming region 124a can form a gradient diaphragm. After the electrode assembly 12 is wound, the gap between the inner and outer rings tends to be consistent, so that the thickness of the diaphragm 124 tends to be consistent and the gradient diaphragm is not visible.

[0093] Since the interlayer pressure exhibits a gradient decrease trend as the winding radius increases, by adopting the above scheme, the preset roller pressure and the interlayer pressure exhibiting a gradient decrease trend can be accurately and continuously matched. As the first parameter increases (corresponding to the increase of the winding radius and the decrease of the interlayer pressure), the preset roller pressure can be continuously increased to increase the pre-compression of the coating 1242, so that the thickness of the coating 1242 continuously decreases. This can accurately compensate for the compression deviation caused by the difference in interlayer pressure in different layers, improve the consistency and uniformity of the interlayer gap of each layer of the electrode assembly 12, reduce the abrupt change in interlayer gap caused by segmented control, and optimize the overall performance of the battery cell 10.

[0094] Please see Figure 3 , Figure 6 , Figure 7 In some embodiments of this application, the preset roller pressure is linearly related to the first parameter.

[0095] The preset rolling pressure applied to the rolling area 124a is linearly related to the first parameter, that is, the relationship between the preset rolling pressure and the first parameter is a straight line, where the first parameter is the number of turns of the diaphragm 124 (e.g., ...). Figure 7 (As shown), the winding length or winding radius of the diaphragm 124. That is, the preset roller pressure increases linearly with the increase of the first parameter at a fixed ratio, and the corresponding pre-compression of the coating 1242 also increases linearly at a fixed ratio.

[0096] By adopting the above scheme, a simple and easily controllable linear regulation relationship can be established based on the law that the interlayer pressure decreases with the increase of the first parameter. This allows the preset rolling pressure to increase steadily with the first parameter, and the pre-compression of the coating 1242 to change synchronously and linearly. Based on this, the interlayer pressure differences of each ring can be accurately matched, and the total compression of each ring of coating 1242 in the electrode assembly 12 can be made uniform. This improves the consistency and uniformity of the gaps between each ring of the electrode assembly 12. Furthermore, it eliminates the need for complex segmented parameter settings, reduces process errors caused by complex regulation, lowers the control difficulty of the rolling process, simplifies the process control flow, and improves production efficiency.

[0097] Please see Figure 3 , Figure 6 , Figure 8 , Figure 9 In some embodiments of this application, the preset roller pressure is non-linearly related to the first parameter.

[0098] The preset rolling pressure applied to the rolling area 124a is non-linearly related to the first parameter, that is, the relationship between the preset rolling pressure and the first parameter is a non-linear curve, where the first parameter is the number of turns of the diaphragm 124 (e.g., ...). Figure 8 , Figure 9 (as shown), the winding length or winding radius of the diaphragm 124. For example, when the first parameter is within a certain range, the increase in the preset roller pressure accelerates as the first parameter increases, while after the first parameter exceeds this range, the increase in the preset roller pressure slows down, so as to accurately match the nonlinear distribution law of the actual interlayer pressure of different layers of the electrode assembly 12.

[0099] By adopting the above scheme, the law of nonlinear gradient change of interlayer pressure with the first parameter can be adapted. For critical intervals where the interlayer pressure changes drastically (such as the 3rd to 6th turns near the peak), the increase of the preset roller pressure can be precisely controlled. For areas where the interlayer pressure changes slowly, the rate of change of the preset roller pressure can be appropriately adjusted. This can achieve fine compensation of the pre-compression of coating 1242. Compared with linear control, it can better fit the actual winding mechanical behavior, reduce the difference in the total compression of coating 1242 in each turn of electrode assembly 12, and improve the consistency of interlayer gap in each turn of electrode assembly 12.

[0100] Please see Figure 6 , Figure 7 , Figure 8 , Figure 9 In some embodiments of this application, the preset roller pressure is P, the first parameter is x, and the relationship between P and x is:

[0101] P=K / (1+EXP(-r·(x-x0)))

[0102] EXP (Exponential Function) is an abbreviation for exponential function in mathematics, which represents the power operation with the natural constant "e" (approximately equal to 2.71828) as the base. EXP(-r·(x-x0)) is e^(-r·(x-x0)).

[0103] Where K is the preset saturation value (i.e. maximum value) of the roller pressure. When x is large enough, P will approach K infinitely (because EXP(-r·(x-x0)) approaches 0, the denominator ≈ 1, P ≈ K).

[0104] Where r is the rate of change of the preset roller pressure. r > 0. The larger r is, the steeper the change of the preset roller pressure near x0; the smaller r is, the gentler the change of the preset roller pressure near x0.

[0105] Where x0 is the first parameter value corresponding to the inflection point where the preset roller pressure changes the fastest. The inflection point can be set near the starting point, the midpoint, or the ending point. When x=x0, EXP(-r·(x-x0))=1, the denominator=2, and at this time P=K / 2, that is, the preset roller pressure reaches half of the saturation value.

[0106] This relationship applies to the case where "the preset roller pressure is linearly related to the first parameter". For example, such as... Figure 7 In the pressure curve diagram shown, the vertical axis represents the preset roller pressure, and the first parameter in both directions is the number of turns of the diaphragm 124. K=2, x0=35, r=0.01. The preset roller pressure is linearly related to the number of turns of the diaphragm 124. Figure 7 The parameter values ​​corresponding to the pressure curves shown are shown in Table 1.

[0107]

[0108] This relationship also applies to the case where "the preset roller pressure is non-linearly related to the first parameter." For example, as shown... Figure 8 In the pressure curve diagram shown, the vertical axis represents the preset roller pressure, and the first parameter in both directions is the number of turns of the diaphragm 124. K=2, x0=10, r=0.1. The preset roller pressure and the number of turns of the diaphragm 124 are non-linearly related. Figure 8 The parameter values ​​corresponding to the pressure curves shown are shown in Table 2.

[0109]

[0110] This relationship applies to the case where "the preset roller pressure is non-linearly related to the first parameter," as an example, such as... Figure 9 In the pressure curve diagram shown, the vertical axis represents the preset roller pressure, and the first parameter in both directions is the number of turns of the diaphragm 124. K=2, x0=35, r=0.1. The preset roller pressure and the number of turns of the diaphragm 124 are non-linearly related. Figure 9 The parameter values ​​corresponding to the pressure curves shown are shown in Table 3.

[0111]

[0112] By adopting the above scheme, it is possible to accurately match the electrode assembly 12 (e.g., ...) based on the relationship between P and x, in cases where "the preset roller pressure increases continuously with the increase of the first parameter" and in cases where "the preset roller pressure and the first parameter are linearly or non-linearly related". Figure 3 As shown, the interlayer pressure gradient attenuation characteristics of different rings are dynamically matched with the winding stress distribution by adjusting the preset rolling pressure. Thus, the preset rolling pressure can be continuously changed by adjusting the parameters, which can accurately control the thickness change of the coating 1242 and the diaphragm 124, meet the requirements of the rolling process, improve the control accuracy of the rolling process, and effectively eliminate the layer gap difference between the inner and outer rings of the electrode assembly 12.

[0113] Please see Figure 2 , Figure 3 , Figure 10 In some embodiments of this application, the preset roller pressure increases gradually with the increase of the first parameter, so that the thickness of the coating 1242 decreases gradually with the increase of the first parameter, wherein the first parameter is the winding length of the diaphragm 124, the number of winding turns of the diaphragm 124, or the winding radius.

[0114] In this process, the thickness of the coating 1242 in the roll forming region 124a decreases gradually with the increase of the first parameter. That is, the thickness of the coating 1242 in the roll forming region 124a thins in stages from the inner ring to the outer ring, with each stage having a relatively consistent thickness, thinning slightly at the next stage, forming a clear thickness step with distinct boundaries. Based on this, in the roll forming process, the length of the roll forming region 124a can be directly set as the same stage, and a preset roll forming pressure can be applied to the same stage; no formula is required. After roll forming in the roll forming region 124a and before winding, the roll forming region 124a can form a gradient diaphragm. However, after winding to form the electrode assembly 12, the gap between the inner and outer rings tends to be consistent, making the thickness of the diaphragm 124 consistent and obscuring the gradient diaphragm.

[0115] By adopting the above scheme, the characteristic of interlayer pressure decreasing gradually with the increase of the first parameter can be matched. Through staged preset roller pressure control, the thickness of coating 1242 can be reduced in a stepwise manner. This accurately compensates for the compression deviation caused by the difference in interlayer pressure between different layers, improving the consistency and uniformity of the gaps between the layers of the electrode assembly 12, and optimizing the overall performance of the battery cell 10. Furthermore, it eliminates the need for complex continuous control formulas, significantly simplifying the setting and control of process parameters, and effectively improving production efficiency and process stability.

[0116] Please see Figure 2 , Figure 3 In some embodiments of this application, the interlayer gap difference of each turn of the electrode assembly 12 is less than 10 μm.

[0117] Among them, the interlayer gap of each ring of the electrode assembly 12 tends to be consistent, and the difference in interlayer gap of each ring of the electrode assembly 12 can be controlled within 10μm (i.e., less than 10μm).

[0118] By adopting the above scheme, the interlayer gap difference of each ring of the electrode assembly 12 can be controlled within a very small range, and the quantitative index can be clearly controlled within 10μm. This can optimize and improve the consistency and uniformity of the interlayer gap of each ring of the electrode assembly 12, and optimize the electrochemical performance, reliability and service life of the battery cell 10.

[0119] Please see Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 Based on the above embodiments, this application provides a specific example of a method for winding an electrode assembly, which includes the following steps:

[0120] S1. A separator 124 and an electrode 123 are provided. The electrode 123 may include a positive electrode 123a and a negative electrode 123b with opposite polarities. Two separators 124 may be provided, with one separator 124 located on each side of the negative electrode 123b, and the other separator 124 located between the positive electrode 123a and the negative electrode 123b. The separator 124 is used to isolate the positive electrode 123a and the negative electrode 123b. The separator 124 includes a base layer 1241 and two coatings 1242 coated on opposite sides of the base layer 1241. The compressibility of the coatings 1242 is greater than that of the base layer 1241; that is, the base layer 1241 of the separator 124 is more difficult to compress, while the coatings 1242 of the separator 124 are more easily compressed.

[0121] S2. A rolling mechanism 50 is provided on the conveying path of the diaphragm 124. The rolling mechanism 50 rolls a portion of the diaphragm 124 under a preset rolling pressure to form a rolling region 124a in that portion of the diaphragm 124, and to generate a pre-compression amount in the coating 1242 of the rolling region 124a corresponding to the preset rolling pressure. The diaphragm 124 regions corresponding to the 1st to 5th turns from the inside out are not rolled. The preset rolling pressure is determined according to the interlayer pressure distribution law of different layers of the electrode assembly 12. The preset rolling pressure increases continuously with the increase of a first parameter, causing the thickness of the coating 1242 to decrease continuously with the increase of the first parameter. The first parameter is the winding length of the diaphragm 124, the number of winding turns of the diaphragm 124, or the winding radius. The preset rolling pressure is linearly or non-linearly related to the first parameter. Wherein, the preset roller pressure is P, the first parameter is x, and the relationship between P and x is: P=K / (1+EXP(-r·(x-x0))), where K is the saturation value of the preset roller pressure, r is the rate of change of the preset roller pressure, and x0 is the first parameter value corresponding to the inflection point of the fastest rate of change of the preset roller pressure.

[0122] S3. The electrode 123 and the diaphragm 124 are conveyed to the winding needle 20. Specifically, the electrode 123 is unwound by the first unwinding mechanism 30 to convey the electrode 123 to the winding needle 20. The diaphragm 124 is unwound by the second unwinding mechanism 40 to convey the diaphragm 124 to the winding needle 20.

[0123] S4. Electrode assembly 12 is obtained by winding electrode sheet 123 and diaphragm 124 using winding needle 20. The interlayer gap of each turn of electrode assembly 12 tends to be consistent, and the difference in interlayer gap of each turn of electrode assembly 12 is less than 10 μm.

[0124] By adopting the above scheme, during the conveying process of the diaphragm 124, a portion of the diaphragm 124 can be rolled by the rolling mechanism 50, and a preset rolling pressure is applied according to the interlayer pressure distribution law of different layers of the electrode assembly 12, so as to form a rolling region 124a in a portion of the diaphragm 124. This causes the coating 1242 in the rolling region 124a to generate a pre-compression amount corresponding to the preset rolling pressure, thereby making the pre-compression amount of the coating 1242 corresponding to the layer with larger interlayer pressure smaller, and the pre-compression amount of the coating 1242 corresponding to the layer with smaller interlayer pressure larger. Based on this, the electrode assembly 12 is obtained by winding the electrode sheet 123 and the separator 124 using the winding needle 20. This allows the coating 1242, which has a small pre-compression and a large reserved thickness, to generate a large compression due to the large interlayer pressure, and vice versa. This reduces the impact of the large interlayer pressure variation from the inner to the outer ring of the electrode assembly 12, reduces the difference in compression between the coating 1242 of the inner and outer separators, and complementarily solves the problem of inconsistent interlayer gaps between the inner and outer rings. It effectively improves the consistency of the gaps between each ring, thereby improving the uniformity of electrolyte wetting within the electrode assembly 12. This also helps optimize the stress distribution of the electrode assembly 12 during the expansion of the battery cell 10, and optimizes the electrochemical performance, reliability, and service life of the battery cell 10. Furthermore, since the rolling process has a thinning effect on the separator 124, it is beneficial for compressing and controlling the size of the electrode assembly 12, making it suitable for situations where the diameter of the electrode assembly 12 exceeds the specifications.

[0125] Please see Figure 3 , Figure 4 , Figure 5 , Figure 6 Some embodiments of this application provide a winding apparatus for an electrode assembly, used to perform the winding method for the electrode assembly provided in the embodiments of this application. The winding apparatus for the electrode assembly includes a winding needle 20, a first unwinding mechanism 30, a second unwinding mechanism 40, and a rolling mechanism 50. The first unwinding mechanism 30 is used to unwind the electrode sheet 123 to convey the electrode sheet 123 to the winding needle 20. The second unwinding mechanism 40 is used to unwind the diaphragm 124 to convey the diaphragm 124 to the winding needle 20. The rolling mechanism 50 is disposed on the conveying path of the diaphragm 124 from the second unwinding mechanism 40 to the winding needle 20. The rolling mechanism 50 is configured to roll at least a portion of the diaphragm 124 under a preset rolling pressure to form a rolling region 124a in at least a portion of the diaphragm 124, and to generate a pre-compression amount of the coating 1242 of the rolling region 124a corresponding to the preset rolling pressure. The preset rolling pressure applied to the rolling region 124a is inversely compatible with the interlayer pressure of the corresponding electrode assembly 12 layers in the rolling region 124a.

[0126] In some embodiments, the winding needle 20 may include two semi-circular winding needles with semi-circular cross-sections. During the winding process of the electrode assembly 12, the two semi-circular winding needles clamp the diaphragm 124 to form a quasi-cylindrical structure. Subsequently, the winding needle 20 rotates, and the negative electrode 123b and the positive electrode 123a are sequentially inserted into the rotating diaphragm 124 for winding until the electrode assembly 12 is formed. In other embodiments, the winding needle 20 may also be an integral structure. During the winding process of the electrode assembly 12, the winding needle 20 and the auxiliary needle may clamp the diaphragm 124 to form a quasi-cylindrical structure. Subsequently, the winding needle 20 rotates, and the negative electrode 123b and the positive electrode 123a are sequentially inserted into the rotating diaphragm 124 for winding until the electrode assembly 12 is formed.

[0127] The first unwinding mechanism 30 is arranged at a staggered interval from the winding needle 20 for unwinding the electrode sheet 123. Since the electrode sheet 123 includes a positive electrode sheet 123a and a negative electrode sheet 123b with opposite polarities, correspondingly, two first unwinding mechanisms 30 can be provided, arranged at a staggered interval. One first unwinding mechanism 30 is used to unwind the positive electrode sheet 123a, and the other first unwinding mechanism 30 is used to unwind the negative electrode sheet 123b. In some embodiments, one or more second rollers 60 can be provided as needed between the first unwinding mechanism 30 and the winding needle 20, along the conveying path of the electrode sheet 123. The second rollers 60 can be active rollers or passive rollers, and the second rollers 60 can guide the electrode sheet 123 to be conveyed from the first unwinding mechanism 30 to the outer periphery of the winding needle 20 along a preset path and a preset direction.

[0128] The second unwinding mechanism 40 is arranged at a staggered interval from the winding needle 20 for unwinding the diaphragm 124. Since there are two diaphragms 124, located on opposite sides of the negative electrode 123b, with one diaphragm 124 positioned between the positive electrode 123a and the negative electrode 123b, the diaphragm 124 serves to isolate the positive and negative electrode 123a. Correspondingly, two second unwinding mechanisms 40 can be provided, arranged at a staggered interval, each used to unwind the two diaphragms 124. In some embodiments, one or more second rollers 60 can be provided as needed along the conveying path of the diaphragm 124 between the second unwinding mechanism 40 and the winding needle 20. The second rollers 60 can be either active or passive rollers, guiding the diaphragm 124 along a preset path and direction from the second unwinding mechanism 40 to the outer periphery of the winding needle 20.

[0129] Between the second unwinding mechanism 40 and the winding needle 20, on the conveying path of the diaphragm 124, a rolling mechanism 50 can be provided. Before the area of ​​the diaphragm 124 to be rolled is wound onto the winding needle 20, as the area to be rolled passes through the rolling mechanism 50, the rolling mechanism 50 can perform rolling processing on the area to be rolled, so that the area to be rolled forms a rolling area 124a, and the coating 1242 of the rolling area 124a generates a pre-compression amount corresponding to a preset rolling pressure. The rolling mechanism 50 includes two first rollers 51, which are respectively disposed on opposite sides of the diaphragm 124. The two first rollers 51 can approach each other to roll the rolling area 124a, and the two first rollers 51 can move away from each other to release the rolling pressure on the diaphragm 124, allowing the diaphragm 124 to pass smoothly.

[0130] Because the winding equipment for the electrode assembly first conveys the diaphragm 124 from the second unwinding mechanism 40 to the winding needle 20 via the rolling mechanism 50 during the winding operation of the first electrode assembly 12, and then rolls at least a portion of the diaphragm 124 via the rolling mechanism 50, if the rolling mechanism 50 needs to roll the entire area of ​​the diaphragm 124, then during the winding process of the first electrode assembly 12, the portion of the diaphragm 124 located between the rolling mechanism 50 and the winding needle 20 before the start of winding cannot be rolled by the rolling mechanism 50, while the portion of the diaphragm 124 located between the rolling mechanism 50 and the second unwinding mechanism 40 before the start of winding can be rolled by the rolling mechanism 50. In this case, the first electrode assembly 12 can be considered a defective product, and the entire area of ​​the diaphragm 124 can be rolled normally via the rolling mechanism 50 starting from the second electrode assembly 12; that is, assuming the diaphragm 124 of an electrode assembly 12... The winding length is S, the conveying path length of the diaphragm 124 from the rolling mechanism 50 to the winding needle 20 is P1, and the belt length (i.e. unwinding length) of the diaphragm 124 belonging to the same electrode assembly 12 after the winding starts is P2 (P2 of the next electrode assembly 12 will be reset to zero and recalculated, P2≤S). If the rolling mechanism 50 needs to roll the entire area of ​​the diaphragm 124, the rolling logic can be configured as follows: when P2>0, start and continue rolling, but the head of the diaphragm 124 in the first electrode assembly 12 has a length of P1 that is not rolled, while from the second electrode assembly 12 onwards, the diaphragm 124 of length S can be rolled normally by the rolling mechanism 50.

[0131] When the roller pressing mechanism 50 performs roller pressing on a portion of the diaphragm 124, if the starting position of the roller pressing is set to "the portion of the diaphragm 124 located between the roller pressing mechanism 50 and the winding needle 20 before the start of winding", then the portion of the diaphragm 124 located between the roller pressing mechanism 50 and the starting position of the roller pressing before the start of winding cannot be roller pressed by the roller pressing mechanism 50, while the portion of the diaphragm 124 located between the roller pressing mechanism 50 and the second unwinding mechanism 40 before the start of winding can be roller pressed by the roller pressing mechanism 50. In this case, the first electrode assembly 12 formed by winding can be regarded as a defective product, and the roller pressing mechanism 50 can normally perform roller pressing on a portion of the diaphragm 124 starting from the second electrode assembly 12. That is, assuming the winding length of the diaphragm 124 of an electrode assembly 12 is S, the conveying path length of the diaphragm 124 from the rolling mechanism 50 to the winding needle 20 is P1, and the belt travel length (i.e., unwinding length) of the diaphragm 124 belonging to the same electrode assembly 12 after the winding starts is P2 (P2 of the next electrode assembly 12 will be reset to zero and recalculated, P2≤S), partial rolling starts at 1 / a of S and ends at 1 / b of S, if the rolling mechanism 50 needs to roll a portion of the diaphragm 124 and P1≥1 / a of S, then the rolling logic of the first electrode assembly 12 can be configured as follows: when P2>0, rolling starts, when P1+ When P2 = 1 / b of S, the rolling process ends, but the head of the diaphragm 124 in the first electrode assembly 12 has a length of (P1 - 1 / a of S) that is not rolled. Starting from the second electrode assembly 12, the rolling logic can be configured as follows: when P2 = 1 / a of S, the rolling process begins, and when P2 = 1 / b of S, the rolling process ends. That is, starting from the second electrode assembly 12, the rolling mechanism 50 can normally perform partial rolling, which begins at 1 / a of S and ends at 1 / b of S.

[0132] When the rolling mechanism 50 rolls a portion of the diaphragm 124, during the winding and forming process of the first electrode assembly 12, if the starting position of the rolling is set to "the portion of the diaphragm 124 located between the rolling mechanism 50 and the second unwinding mechanism 40 before the winding begins", then the rolling mechanism 50 can normally roll the diaphragm 124 partially. That is, starting from the first electrode assembly 12, the rolling mechanism 50 can normally roll a portion of the diaphragm 124. That is, assuming the winding length of the diaphragm 124 of an electrode assembly 12 is S, the conveying path length of the diaphragm 124 from the rolling mechanism 50 to the winding needle 20 is P1, and the belt travel length (i.e., unwinding length) of the diaphragm 124 belonging to the same electrode assembly 12 after the winding starts is P2 (P2 of the next electrode assembly 12 will be reset to zero and recalculated, P2≤S), the partial rolling starts at 1 / a of S and ends at 1 / b of S. If the rolling mechanism 50 needs to roll a part of the diaphragm 124 and P1<1 / a of S, then the rolling logic of the first electrode assembly 12 can be configured as follows: when P1+P2=1 / a of S, the rolling starts, and when P1+P2=1 / b of S, the rolling ends. Starting from the second electrode assembly 12, the rolling logic can be configured as follows: when P2=1 / a of S, the rolling starts, and when P2=1 / b of S, the rolling ends.

[0133] By adopting the above scheme, a rolling mechanism 50 can be integrated into the winding equipment of the electrode assembly. Before the diaphragm 124 is wound into the winding needle 20, the rolling mechanism 50 performs online rolling on the diaphragm 124 conveying path as the diaphragm 124 passes through the area to be rolled, forming a rolling area 124a. This causes the coating 1242 of the rolling area 124a to generate a pre-compression amount corresponding to the preset rolling pressure. Furthermore, the preset rolling pressure, the starting position of the rolling, and the ending position can be dynamically adjusted, thereby achieving closed-loop control of the interlayer gap and diameter of the wound electrode assembly 12. Based on this, the winding equipment of the electrode assembly provided in this embodiment can provide reliable support for the above-mentioned winding method of the electrode assembly and the standardized mass production of the electrode assembly 12. It can achieve compatibility and seamless connection between the rolling process and the winding process. Moreover, the online rolling design can eliminate the transfer and secondary positioning processes of offline rolling, shortening the production cycle and improving production yield and efficiency.

[0134] Please see Figure 3 , Figure 5 , Figure 6 In some embodiments of this application, the length of the conveying path of the diaphragm 124 from the rolling mechanism 50 to the winding needle 20 is less than the length of the conveying path of the diaphragm 124 from the second unwinding mechanism 40 to the rolling mechanism 50. That is, on the conveying path of the diaphragm 124, the rolling mechanism 50 is arranged relatively close to the winding needle 20 and relatively far away from the second unwinding mechanism 40.

[0135] By adopting the above scheme, the roller pressing mechanism 50 can be arranged relatively close to the winding needle 20 and relatively far away from the second unwinding mechanism 40 along the conveying path of the diaphragm 124. Based on this, the conveying distance of the diaphragm 124 after being processed by the roller pressing mechanism 50 to before being wound can be shortened. The influence of roller pressing lag on the control of parameters such as the thickness of the coating 1242, the thickness of the diaphragm 124, and the diameter of the electrode assembly 12 can be reduced. The control accuracy of the layer gap of the electrode assembly 12 can be improved. It is beneficial to accurately control the layer gap difference of each turn of the electrode assembly 12 within the target range. It is beneficial to standardized mass production and to improve process stability and production consistency.

[0136] Please see Figure 3 , Figure 5 , Figure 6 In some embodiments of this application, the rolling mechanism 50 includes two first rollers 51 and at least one dust removal component 52. The two first rollers 51 are disposed on opposite sides of the diaphragm 124, and the dust removal component 52 is disposed on the periphery of the first rollers 51 for removing powder adhering to the surface of the first rollers 51.

[0137] The two first rollers 51 are respectively located on opposite sides of the diaphragm 124. The two first rollers 51 can approach each other to roll the diaphragm 124a, and the two first rollers 51 can move away from each other to release the rolling pressure on the diaphragm 124 and allow the diaphragm 124 to pass smoothly.

[0138] After the first roller 51 rolls the coating 1242 onto the diaphragm 124, the coating 1242 may be slightly damaged and peel off, adhering to the outer periphery of the first roller 51. If not controlled, this may cause uneven rolling, contamination of the roller, and wrinkling of the diaphragm 124. To solve this problem, the rolling mechanism 50 is provided with one or more dust removal components 52. In the case of multiple dust removal components 52, the multiple dust removal components 52 can be distributed around the periphery of the two first rollers 51. Based on this, the dust removal components 52 can remove dust from the first roller 51 to remove powder (such as coating 1242 powder) adhering to the surface of the first roller 51. The dust removal components 52 can use, but are not limited to, negative pressure suction, brush dust removal, etc., to achieve the dust removal effect on the first roller 51.

[0139] By adopting the above scheme, the rolling mechanism 50 can roll the rolling area 124a of the diaphragm 124 through two first rollers 51 respectively disposed on both sides of the diaphragm 124. The rolling mechanism 50 can also use the dust removal component 52 disposed around the first roller 51 to promptly remove the powder adhering to the surface of the first roller 51 due to slight damage and peeling of the coating 1242. This can effectively improve problems such as uneven local rolling, over-rolling contamination, and wrinkling of the diaphragm 124 caused by powder residue. It can optimize the structure of the rolling mechanism 50, improve the performance, operational stability, reliability, and service life of the rolling mechanism 50, reduce the product defect rate caused by rolling defects, and improve the structural consistency, production consistency, and production yield of the electrode assembly 12.

[0140] Please see Figure 2 , Figure 3 , Figure 4 , Figure 5 Some embodiments of this application provide a battery cell 10, including an electrode assembly 12 formed by winding the electrode assembly using the winding method provided in the embodiments of this application. The electrode assembly 12 is cylindrical.

[0141] Among them, the battery cell 10 can be a secondary battery, which refers to a battery cell 10 that can be recharged after being discharged to activate the active materials and continue to be used. The battery cell 10 can be a lithium-ion battery cell, a sodium-ion battery cell, a sodium-lithium-ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a magnesium-ion battery cell, a nickel-metal hydride battery cell, a nickel-cadmium battery cell, a lead-acid battery cell, etc.

[0142] The electrode assembly 12 is cylindrical. In some embodiments, the battery cell 10 is a cylindrical battery cell.

[0143] Because the electrode assembly 12 of the prismatic battery cell is a flat electrode assembly, a large-diameter winding needle 20 is often used during the winding process of the electrode assembly 12. This results in a small change in curvature from the inner to the outer ring of the electrode assembly 12, making the problem of inconsistent interlayer spacing between the inner and outer rings of the electrode assembly 12 less prominent. In contrast, the electrode assembly 12 of the cylindrical battery cell is a cylindrical electrode assembly. During the winding process of the electrode assembly 12, a smaller-diameter winding needle 20 is often used, resulting in a larger change in curvature and interlayer pressure from the inner to the outer ring of the electrode assembly 12. This leads to a more prominent problem of inconsistent interlayer spacing between the inner and outer rings of the electrode assembly 12. Therefore, the electrode assembly winding method provided in this application embodiment is particularly suitable for specifically solving the prominent problem of inconsistent interlayer spacing of the electrode assembly 12 of the cylindrical battery cell.

[0144] Therefore, by adopting the above-described solution, the winding method of the electrode assembly provided in this application embodiment can be used to specifically solve the prominent problem of inconsistent interlayer spacing in the cylindrical electrode assembly 12, thereby preparing a cylindrical electrode assembly with consistent and uniform interlayer spacing, and constructing the battery cell 10 accordingly. This is beneficial for optimizing the electrochemical performance, reliability, and service life of the battery cell 10. In other words, this application has strong adaptability to cylindrical battery cells and significant optimization effects, which can significantly improve the structural consistency of the electrode assembly 12 of the cylindrical battery cell, and effectively improve the cycle life, charge-discharge performance, and reliability of the cylindrical battery cell.

[0145] The above are merely optional embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for winding an electrode assembly, characterized in that, Includes the following steps: A diaphragm and an electrode are provided, wherein the diaphragm includes a base layer and a coating applied to at least one surface of the base layer; A rolling mechanism is provided, which is disposed on the conveying path of the diaphragm. The rolling mechanism rolls at least a portion of the diaphragm under a preset rolling pressure to form a rolling region in the at least a portion of the diaphragm, and causes the coating in the rolling region to generate a pre-compression amount corresponding to the preset rolling pressure. The preset rolling pressure is determined according to the interlayer pressure distribution law of different layers of the electrode assembly. The interlayer pressure distribution law of different layers of the electrode assembly is obtained through simulation analysis or experimental testing. The preset rolling pressure applied to the rolling region has an inverse adaptation relationship with the interlayer pressure of the corresponding layer of the electrode assembly in the rolling region. The preset rolling pressure increases continuously with the increase of a first parameter, causing the thickness of the coating to decrease continuously with the increase of the first parameter, or the preset rolling pressure increases gradually with the increase of the first parameter, causing the thickness of the coating to decrease gradually with the increase of the first parameter. The first parameter is the winding length of the diaphragm, the number of winding turns of the diaphragm, or the winding radius. The electrode and the diaphragm are conveyed to the winding needle; An electrode assembly is obtained by winding the electrode sheet and the diaphragm using the winding needle, wherein the interlayer spacing of each turn of the electrode assembly tends to be uniform.

2. The method for winding the electrode assembly as described in claim 1, characterized in that, The roller pressing mechanism performs roller pressing on the entire area of ​​the diaphragm under the preset roller pressing pressure.

3. The method for winding the electrode assembly as described in claim 1, characterized in that, The roller pressing mechanism performs roller pressing on a portion of the diaphragm under the preset roller pressing pressure.

4. The method for winding the electrode assembly as described in claim 3, characterized in that, The diaphragm region corresponding to the 1st to 5th turns of the diaphragm winding from the inside out is not subjected to rolling.

5. The method for winding the electrode assembly as described in claim 1, characterized in that, The preset roller pressure is linearly related to the first parameter.

6. The method for winding the electrode assembly as described in claim 1, characterized in that, The preset roller pressure is non-linearly related to the first parameter.

7. The method for winding the electrode assembly as described in claim 1, characterized in that, The preset roller pressure is P, the first parameter is x, and the relationship between P and x is: P=K / (1+EXP(-r·(x-x0))) Where K is the saturation value of the preset roller pressure, r is the rate of change of the preset roller pressure, and x0 is the first parameter value corresponding to the inflection point where the rate of change of the preset roller pressure is the fastest.

8. The method for winding the electrode assembly as described in any one of claims 1-7, characterized in that, The interlayer gap difference between each ring of the electrode assembly is less than 10 μm.

9. A winding device for an electrode assembly, characterized in that, A method for performing a winding of an electrode assembly as described in any one of claims 1-8, wherein the winding apparatus for the electrode assembly comprises: curling needles; A first unwinding mechanism is used to unwind the electrode sheet to convey the electrode sheet to the winding needle; A second unwinding mechanism is used to unwind the diaphragm to convey the diaphragm to the winding needle; A rolling mechanism is provided on the conveying path of the diaphragm from the second unwinding mechanism to the winding needle. The rolling mechanism is configured to roll at least a portion of the diaphragm under a preset rolling pressure to form a rolling region in the at least a portion of the diaphragm and to generate a pre-compression amount in the coating of the rolling region corresponding to the preset rolling pressure. The preset rolling pressure applied to the rolling region is inversely compatible with the interlayer pressure of the electrode assembly coil corresponding to the rolling region.

10. The winding apparatus for the electrode assembly as described in claim 9, characterized in that, The length of the conveying path of the diaphragm from the rolling mechanism to the winding needle is less than the length of the conveying path of the diaphragm from the second unwinding mechanism to the rolling mechanism.

11. The winding apparatus for the electrode assembly as described in claim 9, characterized in that, The rolling mechanism includes two first rollers and at least one dust removal component. The two first rollers are disposed on opposite sides of the diaphragm, and the dust removal component is disposed on the periphery of the first rollers to remove powder adhering to the surface of the first rollers.

12. A single battery cell, characterized in that, The electrode assembly includes an electrode assembly formed by winding an electrode assembly using the winding method described in any one of claims 1-8, wherein the electrode assembly is cylindrical.

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