Method for manufacturing square winding battery pole piece and square winding battery

Abstract

The application relates to a square winding battery pole piece preparation method and a square winding battery. The method comprises the following steps: determining a surface density standard area and a surface density change area of an active coating on a designed pole piece after winding, wherein the surface density of the surface density standard area is a target surface density, the surface density of the surface density change area is different from the target surface density, the surface density change area comprises a large surface density area, and the surface density of the large surface density area is greater than the target surface density; comparing the surface density standard area and the surface density change area to determine a to-be-cleaned area of the active coating on the designed pole piece, wherein the to-be-cleaned area is located in the large surface density area; and performing laser cleaning on the designed pole piece according to the to-be-cleaned area of the designed pole piece to obtain a target pole piece of the square winding battery. The scheme provided in the application can reduce the manufacturing cost of the square winding battery, and improve the electrical performance and cycle life of the square winding battery.

Description

Technical Field

[0001] This application relates to the field of wound battery technology, and in particular to a method for preparing square wound battery electrodes and a square wound battery. Background Technology

[0002] In the manufacturing process of square wound batteries, the winding shape of the electrode sheets causes the accumulation or thinning of active material in local areas (such as curved areas) of the wound electrode sheets, resulting in variations in the local N / P value (the ratio of the negative electrode capacity to the positive electrode capacity) of the battery, affecting the battery's electrical performance and lifespan. Related coating processes have limitations in controlling the uniformity of coating surface density, making it difficult to achieve high-precision and high-efficiency adjustment of coating surface density, and thus unable to avoid the accumulation or thinning of active material in local areas of the electrode sheets caused by electrode winding.

[0003] Related technologies adjust the coating surface density through mechanical scraping or chemical etching to avoid the accumulation or sparse distribution of active material in localized areas of the electrode caused by electrode winding. However, these technologies for adjusting coating surface density have the following problems:

[0004] (1) It is difficult to achieve high-precision control of coating surface density, especially when dealing with small local differences caused by bending, which can easily lead to over-processing or under-processing, affecting battery performance.

[0005] (2) More human intervention and longer processing cycles are required, which not only reduces production efficiency but also increases manufacturing costs, including material waste and environmental costs of handling chemicals.

[0006] (3) It is difficult to ensure the consistency of the treatment effect, and there are challenges in the reuse between batches. It is difficult to apply it to the large-scale industrial production of high-quality batteries.

[0007] (4) It will affect the surface quality of the electrode, such as causing scratches or changing the material properties, which in turn affects the wettability of the electrolyte and the electrochemical performance of the battery.

[0008] (5) In the rapid iteration of battery product development, there is a lack of sufficient adaptability and flexibility in the face of electrode sheets with different materials, thicknesses and designs, and it is difficult to optimize the surface density of the coating.

[0009] In summary, the relevant technologies cannot effectively address the surface density of the coating, especially the accumulation or sparseness of active material in localized areas of the electrode caused by electrode winding. This increases the manufacturing cost of square wound batteries and reduces their electrical performance and cycle life. Summary of the Invention

[0010] To address or partially address the problems existing in related technologies, this application provides a method for preparing square wound battery electrodes and a square wound battery, which can reduce the manufacturing cost of square wound batteries and improve their electrical performance and cycle life.

[0011] The first aspect of this application provides a method for preparing a square wound battery electrode sheet, the method comprising:

[0012] Obtain designed electrodes with current collectors and active coatings;

[0013] The designed electrode and diaphragm are wound to form a reference square core;

[0014] Measure each turn of the reference square core to determine the standard area and the area density variation area of ​​the active coating on the designed electrode after winding. The area density of the standard area is the target area density. The area density variation area is different from the target area density. The area density variation area includes a large area density area, and the area density of the large area density area is greater than the target area density.

[0015] By comparing the areal density standard region and the areal density variation region, the area to be cleaned of the active coating on the designed electrode is determined, wherein the area to be cleaned is located in the high areal density region;

[0016] Based on the area to be cleaned of the designed electrode sheet, laser cleaning is performed on the designed electrode sheet to obtain the target electrode sheet for the square wound battery.

[0017] Preferably, the step of winding the designed electrode and diaphragm into a reference square core includes:

[0018] The designed electrode and diaphragm are physically or simulatedly wound to form a reference square core.

[0019] Preferably, measurements are taken on each turn of the reference square core to determine the standard area and the area of ​​varying areal density of the active coating on the wound electrode sheet, including:

[0020] The design electrode sheet of each turn of the reference square core is measured to determine the standard area and the area density variation area of ​​the active coating that are alternately distributed along the winding direction on the wound design electrode sheet. The standard area corresponds to the straight area of ​​the design electrode sheet in the winding direction, and the area density variation area corresponds to the curved area of ​​the design electrode sheet after winding. The inner side of the curved area of ​​each turn of the design electrode sheet is the large area density area.

[0021] Preferably, the designed electrode includes a designed negative electrode and a designed positive electrode;

[0022] The step of comparing the areal density standard region and the areal density variation region to determine the area to be cleaned of the active coating on the designed electrode includes:

[0023] By comparing the areal density standard region and the areal density variation region of the designed negative electrode sheet, comparing the areal density standard region and the areal density variation region of the designed positive electrode sheet, and comparing the areal density variation regions of the two opposing layers of the designed negative electrode sheet and the areal density variation region of the designed positive electrode sheet, the areas to be cleaned on the active coating on the designed negative electrode sheet and the active coating on the designed positive electrode sheet are determined respectively.

[0024] Preferably, the active coating is present on both the front and back sides of the designed electrode sheet;

[0025] The determination of the areal density variation region of the active coating on the wound electrode sheet further includes: determining that the outer side of the curved region of each turn of the electrode sheet is a region with low areal density.

[0026] The step of comparing the areal density standard region and the areal density variation region of the designed negative electrode sheet, comparing the areal density standard region and the areal density variation region of the designed positive electrode sheet, and comparing the areal density variation region of the designed negative electrode sheet and the areal density variation region of the designed positive electrode sheet, respectively, to determine the areas to be cleaned of the active coating on the designed negative electrode sheet and the active coating on the designed positive electrode sheet, includes:

[0027] Compare the areal density standard region of the designed negative electrode sheet with the areal density variation region of the designed negative electrode sheet.

[0028] Compare the areal density standard region of the designed positive electrode sheet with the areal density variation region of the designed positive electrode sheet.

[0029] By comparing the large area density region of the designed negative electrode sheet with the small area density region of the designed positive electrode sheet, the area to be cleaned of the active coating on the designed negative electrode sheet is determined, such that the area density ratio of the large area density region of the designed negative electrode sheet to the small area density region of the designed positive electrode sheet is equal to the area density ratio of the area density standard region of the designed negative electrode sheet to the area density standard region of the designed positive electrode sheet.

[0030] By comparing the small areal density region of the designed negative electrode sheet with the large areal density region of the designed positive electrode sheet, the area to be cleaned of the active coating on the designed positive electrode sheet is determined, such that the areal density ratio of the small areal density region of the designed negative electrode sheet to the large areal density region of the designed positive electrode sheet is equal to the areal density ratio of the standard areal density region of the designed negative electrode sheet to the standard areal density region of the designed positive electrode sheet.

[0031] Preferably, the step of determining the areas to be cleaned for the active coating on the designed positive electrode and the active coating on the designed negative electrode further includes:

[0032] The region parameters of the area to be cleaned in the active coating on the designed negative electrode sheet and the region parameters of the area to be cleaned in the active coating on the designed positive electrode sheet are determined respectively. The region parameters include one or a combination of the following: the region location of the area to be cleaned, the coating area, the coating thickness, the coating surface density, the coating three-dimensional morphology, and the coating material properties.

[0033] Preferably, before performing laser cleaning on the designed electrode sheet according to the area to be cleaned to obtain the target electrode sheet for the square wound battery, the following steps are included:

[0034] Based on the area parameters of the area to be cleaned in the designed negative electrode sheet, the cleaning path of the designed negative electrode sheet is determined;

[0035] The cleaning path of the designed positive electrode is determined based on the area parameters of the area to be cleaned in the designed positive electrode.

[0036] Preferably, determining the cleaning path of the designed negative electrode sheet based on the area parameters of the area to be cleaned of the designed negative electrode sheet further includes:

[0037] Based on the correspondence between the coating thickness and coating surface density of the standard area of ​​the designed negative electrode sheet, the coating thickness and coating surface density of the area to be cleaned of the designed negative electrode sheet are used to determine the cleaning thickness of the area to be cleaned of the designed negative electrode sheet.

[0038] The step of determining the cleaning path of the designed positive electrode sheet based on the region parameters of the area to be cleaned of the designed positive electrode sheet further includes:

[0039] Based on the correspondence between the coating thickness and coating surface density of the standard area of ​​the designed positive electrode sheet, the coating thickness and coating surface density of the area to be cleaned of the designed positive electrode sheet are used to determine the cleaning thickness of the area to be cleaned of the designed positive electrode sheet.

[0040] Preferably, the step of performing laser cleaning on the designed electrode sheet according to the cleaning area of ​​the designed electrode sheet to obtain the target electrode sheet for the square wound battery includes:

[0041] Based on the area parameters and cleaning thickness of the area to be cleaned in the designed negative electrode sheet, the cleaning parameters of the area to be cleaned in the designed negative electrode sheet are determined.

[0042] Laser cleaning is performed on the designed negative electrode sheet according to the cleaning path and cleaning parameters of the area to be cleaned in the designed negative electrode sheet to obtain the target negative electrode sheet of the square wound battery.

[0043] Based on the area parameters and cleaning thickness of the area to be cleaned in the designed positive electrode sheet, the cleaning parameters of the area to be cleaned in the designed positive electrode sheet are determined.

[0044] Laser cleaning is performed on the designed positive electrode sheet according to the cleaning path and cleaning parameters of the area to be cleaned in the designed positive electrode sheet to obtain the target positive electrode sheet of the square wound battery.

[0045] Preferably, the cleaning parameters include the laser power of the laser cleaning equipment; the coating material properties include the specific heat capacity of the active coating in the area to be cleaned.

[0046] The step of determining the cleaning parameters of the area to be cleaned of the designed negative electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed negative electrode sheet further includes:

[0047] Based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating in the area to be cleaned of the designed negative electrode sheet, the laser power P of the laser cleaning equipment for laser cleaning the active coating in the area to be cleaned of the designed negative electrode sheet is determined. 负 ,in,

[0048] P 负 =(△d) 负 ×A 负 ×ρ 负 ×C 负 )÷(η 负 ×t 负 ), Vl 负 =L 负 ÷t 负 ;

[0049] In the formula, △d 负 It is the cleaning thickness of the area to be cleaned in the negative electrode sheet of the design;

[0050] A 负 It is the area of ​​the laser spot when the laser cleaning equipment laser cleans the area to be cleaned of the designed negative electrode sheet;

[0051] ρ 负 It is the surface density of the coating in the area to be cleaned of the negative electrode sheet in the design;

[0052] C 负 It is the specific heat capacity of the active coating in the area to be cleaned of the negative electrode sheet in the design;

[0053] η 负 It is the efficiency of converting laser energy into laser cleaning of the active coating in the area to be cleaned of the designed negative electrode sheet;

[0054] t 负 It is the total time during which the laser from the laser cleaning device acts on the active coating in the area to be cleaned of the designed negative electrode sheet;

[0055] Vl 负 The laser scanning speed is the laser speed at which the laser cleaning equipment cleans the area to be cleaned of the designed negative electrode sheet.

[0056] L 负 It is the total length of the laser moving in the area to be cleaned when the laser cleaning equipment cleans the area to be cleaned of the designed negative electrode sheet;

[0057] The step of determining the cleaning parameters of the area to be cleaned of the designed positive electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed positive electrode sheet further includes:

[0058] Based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating in the area to be cleaned of the designed positive electrode sheet, the laser power P of the laser cleaning equipment for laser cleaning the active coating in the area to be cleaned of the designed positive electrode sheet is determined. 正 ,in,

[0059] P 正 =(△d) 正 ×A 正 ×ρ 正 ×C 正 )÷(η 正 ×t 正 ), Vl 正 =L 正 ÷t 正 ;

[0060] In the formula, △d 正 It is the cleaning thickness of the area to be cleaned in the positive electrode sheet of the design;

[0061] A 正 It is the area of ​​the laser spot when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode sheet;

[0062] ρ 正 It is the coating surface density of the area to be cleaned in the positive electrode sheet of the design;

[0063] C 正 It is the specific heat capacity of the active coating in the area to be cleaned of the designed positive electrode sheet;

[0064] η 正 It is the efficiency of converting laser energy into laser cleaning of the active coating in the area to be cleaned of the designed positive electrode sheet;

[0065] t 正 It is the total time during which the laser from the laser cleaning device acts on the active coating in the area to be cleaned of the designed positive electrode sheet;

[0066] Vl 正 It is the scanning speed of the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode sheet;

[0067] L 正 It is the total length that the laser moves in the area to be cleaned when the laser cleaning equipment lasers the area to be cleaned of the designed positive electrode sheet.

[0068] Preferably, the cleaning parameters also include the laser pulse frequency of the laser cleaning equipment;

[0069] The step of determining the cleaning parameters of the area to be cleaned of the designed negative electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed negative electrode sheet further includes:

[0070] Based on the cleaning thickness of the area to be cleaned in the designed negative electrode sheet, the laser pulse frequency f for the laser cleaning equipment to perform laser cleaning on the active coating of the area to be cleaned in the designed negative electrode sheet is determined. 负 ,in,

[0071] f 负 =Vm 负 / (S 负 ×τ 负 ),

[0072] In the formula, Vm 负 τ is the conveyor belt speed at which the laser cleaning equipment performs laser cleaning on the designed negative electrode sheet; 负 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed negative electrode sheet; S 负 The negative electrode sheet of the design is at a belt travel speed Vm 负 During the duration τ 负 The distance traveled;

[0073] The step of determining the cleaning parameters of the area to be cleaned of the designed positive electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed positive electrode sheet further includes:

[0074] Based on the cleaning thickness of the area to be cleaned in the designed positive electrode sheet, the laser pulse frequency f for the laser cleaning equipment to perform laser cleaning on the active coating of the area to be cleaned in the designed positive electrode sheet is determined. 正 ,in,

[0075] f 正 =Vm 正 / (S 正 ×τ 正 ),

[0076] In the formula, Vm 正 τ is the conveyor belt speed at which the laser cleaning equipment performs laser cleaning on the designed positive electrode sheet; 正 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed positive electrode sheet; S 正 The designed positive electrode sheet is at a belt travel speed Vm 正 During the duration τ 正 The distance traveled.

[0077] Preferably, the moving distance S 正 Less than or equal to one-tenth of the laser spot diameter of the laser cleaning equipment;

[0078] The moving distance S 负 It is less than or equal to one-tenth of the laser spot diameter of the laser cleaning equipment.

[0079] A second aspect of this application provides a square wound battery, the square wound battery comprising a negative electrode sheet prepared according to the method described above, and a positive electrode sheet prepared according to the method described above.

[0080] The technical solution provided in this application may include the following beneficial effects:

[0081] The technical solution of this application first determines the standard area and the area of ​​varying areal density of the active coating on the designed electrode sheet after winding by measuring each turn of the reference square core. Then, it determines the area to be cleaned of the active coating on the designed electrode sheet. Next, based on the area to be cleaned, the designed electrode sheet is laser-cleaned to obtain the target electrode sheet for the square wound battery. Furthermore, the active coating in the curved areal density variation areas of the positive and negative electrode sheets of the square wound battery is pre-cleaned with laser to adjust the areal density of the coating in these areas, improving the areal density distribution of the positive and negative electrode sheets after winding. This reduces the difference between the areal density ratio of the curved areal density variation areas and the areal density ratio of the straight areal density standard areas, and reduces the N / P value of the curved areal density variation areas compared to the non-curved areal density standard areas. The difference in N / P value in the curved region (the flat area of ​​standard areal density) can significantly reduce the difference in local coating areal density of the positive and negative electrodes caused by the bending of the square winding. This makes the local performance of each electrode more consistent after square winding, making the overall performance of the square-wound battery more reliable and improving its electrical performance. It also ensures a uniform distribution of N / P value in the square-wound positive and negative electrodes, avoiding localized increases in internal resistance and overheating caused by uneven N / P values. This solves the problem of uneven current distribution caused by variations in local N / P value in the bending region of the positive and negative electrodes. For square-wound lithium-ion batteries, it reduces the possibility of localized lithium plating in the bending region, improving the safety performance and cycle life of square-wound batteries, and opening up new avenues for improving the safety and performance of square-wound batteries.

[0082] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0083] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0084] Figure 1 This is a schematic flowchart illustrating the method for preparing square wound battery electrode sheets according to an embodiment of this application;

[0085] Figure 2 This is another schematic diagram of the process for preparing square wound battery electrode sheets shown in the embodiments of this application;

[0086] Figure 3 This is a schematic diagram comparing the capacity retention rates of a square wound lithium-ion battery according to an embodiment of this application with those of a comparative square wound lithium-ion battery. Detailed Implementation

[0087] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0088] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0089] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. 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.

[0090] This application provides a method for preparing square wound battery electrodes, which can reduce the manufacturing cost of square wound batteries and improve their electrical performance and cycle life.

[0091] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0092] Figure 1 This is a schematic flowchart illustrating the method for preparing square wound battery electrodes according to an embodiment of this application.

[0093] See Figure 1 A method for preparing a square wound battery electrode includes:

[0094] Step 101: Obtain the designed electrode with current collector and active coating.

[0095] In one embodiment, the electrodes of the square wound battery include a negative electrode and a positive electrode. Based on the design parameters of the square wound battery, the negative current collector and negative active material of the negative electrode, and the positive current collector and positive active material of the positive electrode can be selected. A negative electrode slurry and a positive electrode slurry are prepared based on the negative and positive active materials, respectively. The negative electrode slurry is coated onto the negative current collector to obtain a designed negative electrode with a negative current collector and a negative active coating for the square wound battery. The positive electrode slurry is coated onto the positive current collector to obtain a designed positive electrode with a positive current collector and a positive active coating for the square wound battery.

[0096] Step 102: The designed electrode and diaphragm are wound to form a reference square core.

[0097] In one embodiment, the designed negative electrode, designed positive electrode, and separator of the square wound battery can be squarely wound to obtain a reference square core of the square wound battery.

[0098] Step 103: Measure each turn of the reference square core to determine the standard area and the area of ​​variation of the areal density of the active coating on the designed electrode sheet after winding.

[0099] In one embodiment, referring to the design negative electrode sheet and design positive electrode sheet in the square core, which respectively have straight regions and curved regions, the areal density and / or thickness of the design negative electrode sheet and design positive electrode sheet in each loop of the square core are measured to obtain the areal density and / or thickness of the design negative electrode sheet and design positive electrode sheet in each loop. Based on the areal density and / or thickness of the design negative electrode sheet and design positive electrode sheet in each loop, the straight areal density standard region and the curved areal density variation region of the active coating on the square wound design negative electrode sheet can be determined, and the straight areal density standard region and the curved areal density variation region of the active coating on the square wound design positive electrode sheet can be determined. The areal density of the areal density standard region of the design negative electrode sheet is the target areal density of the design negative electrode sheet, and the areal density of the areal density standard region of the design positive electrode sheet is the target areal density of the design positive electrode sheet. The areal density of the areal density variation region is different from the target areal density. The areal density variation region includes a large areal density region, and the areal density of the large areal density region is greater than the target areal density.

[0100] Step 104: Compare the areal density standard area and the areal density variation area to determine the area to be cleaned of the active coating on the designed electrode.

[0101] In one embodiment, the areal density and / or thickness of the areal density standard region and the areal density variation region of the designed negative electrode sheet and the designed positive electrode sheet can be compared, as well as the areal density and / or thickness of the areal density standard region and the large areal density region of the designed negative electrode sheet, the areal density and / or thickness of the areal density standard region and the large areal density region of the designed positive electrode sheet, and the areal density and / or thickness of the large areal density region of the designed negative electrode sheet and the designed positive electrode sheet. This process determines the areas to be cleaned in the large areal density region of the designed negative electrode sheet, the areas to be cleaned in the large areal density region of the designed positive electrode sheet, and the areas to be cleaned in the active coating on the designed negative electrode sheet and the active coating on the designed positive electrode sheet.

[0102] Step 105: Based on the area to be cleaned of the designed electrode sheet, perform laser cleaning on the designed electrode sheet to obtain the target electrode sheet for the square wound battery.

[0103] In one embodiment, a laser cleaning device can be used to perform laser cleaning on the active coating of the area to be cleaned of the designed positive electrode sheet according to the design of the positive electrode sheet, thereby removing the area to be cleaned and obtaining the target positive electrode sheet of the square wound battery; similarly, a laser cleaning device can be used to perform laser cleaning on the active coating of the area to be cleaned of the designed negative electrode sheet according to the design of the negative electrode sheet, thereby removing the area to be cleaned and obtaining the target negative electrode sheet of the square wound battery; this ensures that after the target positive and negative electrodes are squarely wound according to the design parameters of the square wound battery, the areal density ratio of the target positive and negative electrodes in the curved areal density variation area is consistent with the areal density ratio of the target positive and negative electrodes in the straight areal density standard area, and the N / P value of the target positive and negative electrodes in the curved areal density variation area is consistent with the N / P value of the target positive and negative electrodes in the non-curved area (straight areal density standard area).

[0104] The method for preparing square wound battery electrodes in this application first determines the standard area and the area density variation area of ​​the active coating on the designed electrode after winding by measuring each turn of a reference square core. Then, it determines the area to be cleaned of the active coating on the designed electrode. Next, based on the area to be cleaned, the designed electrode is laser-cleaned to obtain the target electrode for the square wound battery. The active coating in the curved area of ​​the positive and negative electrodes of the square wound battery is pre-cleaned with a laser to adjust the coating area of ​​the curved area, improving the area density distribution of the positive and negative electrodes after winding, reducing the difference between the area density ratio of the curved area and the flat standard area, and reducing the N / P value of the curved area of ​​the positive and negative electrodes. The difference in N / P values ​​in the non-bending regions (flat, standard areal density regions) of the positive and negative electrodes can significantly reduce the local coating areal density differences caused by the bending of the square-wound positive and negative electrodes. This makes the local performance of each electrode more consistent after square winding, resulting in more reliable overall performance of the square-wound battery and improved electrical performance. Furthermore, the uniform distribution of N / P values ​​in the square-wound positive and negative electrodes avoids increased local internal resistance and overheating caused by uneven N / P values. This solves the problem of uneven current distribution caused by variations in local N / P values ​​in the bending regions of the positive and negative electrodes. For square-wound lithium-ion batteries, this reduces the possibility of local lithium plating in the bending regions, improving the safety performance and cycle life of square-wound batteries, and opening up new avenues for improving the safety and performance of square-wound batteries.

[0105] Figure 2 This is another schematic diagram of the process for preparing square wound battery electrode sheets as shown in the embodiments of this application.

[0106] See Figure 2 A method for preparing a square wound battery electrode includes:

[0107] Step 201: Obtain a designed negative electrode sheet with a negative current collector and a negative active coating, and a designed positive electrode sheet with a positive current collector and a positive active coating.

[0108] In one embodiment, the electrodes of the square wound battery include a negative electrode and a positive electrode. The negative electrode and positive electrode of the square wound battery can be designed according to the design parameters of the square wound battery.

[0109] In one embodiment, a negative current collector and a negative active material can be selected according to the design of the negative electrode sheet; a negative electrode slurry can be prepared according to the negative active material; the negative electrode slurry can be coated onto the negative current collector, and after drying, rolling, and cutting, a designed negative electrode sheet with a negative current collector and a negative active coating that conforms to the design parameters of a square wound battery can be obtained; a positive current collector and a positive active material can be selected according to the design of the positive electrode sheet; a positive electrode slurry can be prepared according to the positive active material; the positive electrode slurry can be coated onto the positive current collector, and after drying, rolling, and cutting, a designed positive electrode sheet with a positive current collector and a positive active coating that conforms to the design parameters of a square wound battery can be obtained.

[0110] Step 202: The negative electrode sheet, positive electrode sheet, and separator are physically or simulatedly wound to form a reference square core.

[0111] In one embodiment, the designed electrodes and separator of a square wound battery can be physically or simulatedly wound to form a reference square core. Based on the design parameters of the square wound battery, the designed negative electrode, designed positive electrode, and separator can be physically wound to obtain a reference square core. Alternatively, the length, width, and thickness of the designed negative electrode, designed positive electrode, and separator can be obtained through laser thickness measurement or X-ray thickness measurement. Based on the areal density of the designed negative electrode and designed positive electrode, the design parameters of the square wound battery, and the length, width, and thickness of the designed negative electrode, designed positive electrode, and separator, combined with high-precision image recognition and analysis technology, the designed negative electrode, designed positive electrode, and separator can be simulated and wound to form a reference square core using software simulation, thus obtaining a three-dimensional model of the reference square core.

[0112] Step 203: Measure the design negative electrode sheet and design positive electrode sheet of each turn of the reference square core to determine the standard area and the area of ​​variation of the surface density of the design negative electrode sheet and design positive electrode sheet after winding.

[0113] In one embodiment, the design electrode sheet of each loop of the reference square core can be measured to determine the areal density standard area and areal density variation area of ​​the active coating that is alternately distributed along its winding direction on the wound design electrode sheet. The areal density standard area corresponds to the straight area of ​​the design electrode sheet in the winding direction, and the areal density variation area corresponds to the curved area of ​​the design electrode sheet in the winding direction. The inner side of the curved area of ​​each loop of the design electrode sheet is the high areal density area. The areal density of the areal density standard area is the target areal density. The areal density of the areal density variation area is different from the target areal density. The areal density variation area includes the high areal density area, and the areal density of the high areal density area is greater than the target areal density.

[0114] In one embodiment, referring to the design negative electrode sheet and design positive electrode sheet in the square core, which are alternately distributed in straight and curved regions along their winding direction, the areal density and / or thickness of the design negative electrode sheet and design positive electrode sheet in each turn of the square core are measured to obtain the areal density and / or thickness of the design negative electrode sheet and design positive electrode sheet in each turn. Based on the areal density and / or thickness of the design negative electrode sheet and design positive electrode sheet in each turn, the position, area, three-dimensional shape, areal density, and thickness of the straight areal density standard region of the square wound design negative electrode sheet can be determined, and the curved areal density variation region of the square wound design negative electrode sheet can be determined. The location, area, three-dimensional shape, surface density, and thickness of the domain; the location, area, three-dimensional shape, surface density, and thickness of the large surface density region on the inner side of the bend in the surface density variation area of ​​the square-wound negative electrode sheet; the location, area, three-dimensional shape, surface density, and thickness of the straight surface density standard region of the square-wound positive electrode sheet; the location, area, three-dimensional shape, surface density, and thickness of the bend in the surface density variation area of ​​the square-wound positive electrode sheet; and the location, area, three-dimensional shape, surface density, and thickness of the inner side of the bend in the large surface density region of the square-wound positive electrode sheet.

[0115] Step 204: Determine the area to be cleaned in the high-density region of the negative electrode sheet and the high-density region of the positive electrode sheet.

[0116] In one embodiment, the areal density standard region of the designed negative electrode sheet and the areal density variation region of the designed negative electrode sheet can be compared, the areal density standard region of the designed positive electrode sheet and the areal density variation region of the designed positive electrode sheet can be compared, and the areal density variation regions of the two opposing designed negative electrode sheets and the areal density variation regions of the designed positive electrode sheet can be compared to determine the areas to be cleaned of the active coating on the designed negative electrode sheet and the active coating on the designed positive electrode sheet, respectively.

[0117] In one embodiment, the electrode sheet has an active coating on both sides; determining the areal density variation region of the active coating on the wound electrode sheet further includes: determining that the outer side of the curved region of each loop of the electrode sheet is a low areal density region.

[0118] In one embodiment, the areal density standard region of the designed negative electrode sheet and the areal density variation region of the designed negative electrode sheet can be compared; the areal density standard region of the designed positive electrode sheet and the areal density variation region of the designed positive electrode sheet can be compared; the large areal density region of the designed negative electrode sheet and the small areal density region of the designed positive electrode sheet opposite to it can be compared; the area to be cleaned of the active coating on the designed negative electrode sheet can be determined such that the areal density ratio of the large areal density region of the designed negative electrode sheet to the small areal density region of the designed positive electrode sheet opposite to it is equal to the areal density ratio of the areal density standard region of the designed negative electrode sheet and the areal density standard region of the designed positive electrode sheet; the area to be cleaned of the active coating on the designed positive electrode sheet can be determined such that the areal density ratio of the small areal density region of the designed negative electrode sheet to the large areal density region of the designed positive electrode sheet opposite to it is equal to the areal density ratio of the areal density standard region of the designed negative electrode sheet and the areal density standard region of the designed positive electrode sheet.

[0119] In one embodiment, the areal density of the standard region of the designed negative electrode sheet can be compared with the areal density of the variation region of the designed negative electrode sheet. The inner curved region corresponding to the areal density of the variation region of the designed negative electrode sheet being greater than that of the standard region of the designed negative electrode sheet is determined as the high areal density region of the designed negative electrode sheet, and the outer curved region corresponding to the areal density of the variation region of the designed negative electrode sheet being less than that of the standard region of the designed negative electrode sheet is determined as the low areal density region of the designed negative electrode sheet.

[0120] In one embodiment, the areal density of the standard region of the designed positive electrode sheet can be compared with the areal density of the variation region of the designed positive electrode sheet. The inner curved region corresponding to the areal density of the variation region of the designed positive electrode sheet being greater than the areal density of the standard region of the designed positive electrode sheet is determined as the high areal density region of the designed positive electrode sheet, and the outer curved region corresponding to the areal density of the variation region of the designed positive electrode sheet being less than the areal density of the standard region of the designed positive electrode sheet is determined as the low areal density region of the designed positive electrode sheet.

[0121] In one embodiment, the areal density of the large areal density region of the negative electrode sheet can be compared with the areal density of the small areal density region of the opposite positive electrode sheet. Based on the areal density ratio of the areal density of the standard areal density region of the negative electrode sheet to the areal density of the standard areal density region of the opposite positive electrode sheet, the areal density of the small areal density region of the opposite positive electrode sheet is used as a reference to determine the area to be cleaned in the large areal density region of the negative electrode sheet. After the large areal density region of the negative electrode sheet is laser cleaned according to the area to be cleaned, the areal density ratio of the large areal density region of the negative electrode sheet to the small areal density region of the opposite positive electrode sheet is equal to the areal density ratio of the standard areal density regions of the negative electrode sheet and the standard areal density regions of the positive electrode sheet.

[0122] In one embodiment, the areal density of a small areal density region of the negative electrode sheet can be compared with the areal density of a large areal density region of the opposite positive electrode sheet. Based on the areal density ratio of the areal density of the standard areal density region of the negative electrode sheet to the areal density of the standard areal density region of the opposite positive electrode sheet, the areal density of the small areal density region of the negative electrode sheet is used as a reference to determine the area to be cleaned in the large areal density region of the opposite positive electrode sheet. After the large areal density region of the opposite positive electrode sheet is laser cleaned according to the area to be cleaned, the areal density ratio of the small areal density region of the negative electrode sheet to the large areal density region of the opposite positive electrode sheet is equal to the areal density ratio of the standard areal density regions of the negative electrode sheet and the standard areal density regions of the positive electrode sheet.

[0123] In one embodiment, the area to be cleaned in the high-area-density region of the designed electrode sheet is the area formed by bending the designed electrode sheet after it is bent into a square shape, and the area has an area-density greater than that of the flat area (area-density standard area) of the designed electrode sheet. This area is where the active coating of the designed electrode sheet accumulates under bending after it is bent into a square shape, and the thickness of the active coating changes, resulting in a coating area-density greater than that of the coating area-density standard area.

[0124] In one specific embodiment, after the square-wound positive electrode, negative electrode, and separator of the battery are squarely wound, the areal density of the active coating in the bending areal density variation regions of the positive electrode and negative electrode changes under bending. The areal density of the concave inner region of the bending areal density variation region of the positive electrode coating is greater than the areal density of the flat standard region. The concave inner region of the bending areal density variation region of the positive electrode coating is defined as the high areal density region of the positive electrode. The areal density of the convex outer region of the bending areal density variation region of the positive electrode coating is less than the areal density of the flat standard region. The areal density of the convex outer region of the bending areal density variation region of the positive electrode coating is less than the areal density of the flat standard region. The curved outer convex surface region corresponding to the surface density of the standard area of ​​the positive electrode sheet is determined as the small surface density region of the designed positive electrode sheet; the surface density of the curved inner concave surface region of the area of ​​the surface density variation region of the designed negative electrode coating is greater than the surface density of the flat surface density standard area, and the curved inner concave surface region corresponding to the surface density of the area of ​​the surface density variation region of the designed negative electrode sheet is determined as the large surface density region of the designed negative electrode sheet; the surface density of the curved outer convex surface region of the area of ​​the surface density variation region of the designed negative electrode coating is less than the surface density of the flat surface density standard area, and the curved outer convex surface region corresponding to the surface density of the area of ​​the surface density variation region of the designed negative electrode sheet is determined as the small surface density region of the designed negative electrode sheet.

[0125] For example, the areal density of the coating on the positive electrode of a square wound battery is set to 220 g / m². 2 The surface density of the coating on the negative electrode is set to 120 g / m². 2 After the square-wound battery is set with positive and negative electrode sheets, the coating surface density of the concave area inside the bend of the positive electrode sheet, where the surface density changes during bending, is greater than 220 g / m². 2 The concave area inside the bend of the positive electrode sheet, where the surface density changes during bending, is defined as the area with the high surface density of the positive electrode sheet. The surface density of the coating on the convex area outside the bend of the positive electrode sheet, where the surface density changes during bending, is less than 220 g / m³. 2 The outer convex region of the bend in the area of ​​surface density variation of the positive electrode sheet is defined as the low surface density region of the positive electrode sheet; the coating surface density of the inner concave region of the bend in the area of ​​surface density variation of the negative electrode sheet is greater than 120 g / m². 2 The concave area inside the bend of the negative electrode sheet, where the surface density changes during bending, is defined as the area with the highest surface density of the negative electrode sheet. The surface density of the coating on the convex area outside the bend of the negative electrode sheet, where the surface density changes during bending, is less than 120 g / m². 2The outer convex surface region of the bending area of ​​the negative electrode sheet is defined as the low surface density region of the negative electrode sheet.

[0126] In one embodiment, based on the designed positive electrode, negative electrode, and separator after the square winding of the battery, the coating thickness of the designed positive electrode, the coating thickness of the designed negative electrode, and the thickness of the separator can be obtained by laser thickness measurement or X-ray thickness measurement, respectively. Based on the images of the designed positive electrode, negative electrode, and separator, as well as the coating thicknesses of the designed positive electrode, negative electrode, and separator, and combined with high-precision image recognition and analysis technology, a three-dimensional model of the designed positive electrode, negative electrode, and separator can be established through software simulation. Based on the three-dimensional model of the designed positive electrode, negative electrode, and separator, the areas to be cleaned for the designed positive electrode and negative electrode can be determined, respectively.

[0127] In one embodiment, the areal density of the standard area of ​​the negative electrode sheet can be compared with the areal density of the standard area of ​​the positive electrode sheet. The areal density of the large areal density area of ​​the negative electrode sheet and the areal density of the small areal density area of ​​the positive electrode sheet can be compared. The area parameters of the area to be cleaned in the large areal density area of ​​the negative electrode sheet can be determined. The area parameters include one or a combination of the area location of the area to be cleaned, coating area, coating thickness, coating areal density, coating three-dimensional morphology, and coating material properties.

[0128] In one embodiment, the areal density of the standard area of ​​the negative electrode sheet can be compared with the areal density of the standard area of ​​the positive electrode sheet. The areal density of the small areal density area of ​​the negative electrode sheet can be compared with the areal density of the large areal density area of ​​the positive electrode sheet. The area parameters of the area to be cleaned in the large areal density area of ​​the positive electrode sheet can be determined. The area parameters include one or a combination of the following: the area location of the area to be cleaned, the coating area, the coating thickness, the coating areal density, the three-dimensional morphology of the coating, and the coating material properties.

[0129] In one embodiment, based on the three-dimensional models of the square-wound positive and negative electrode designs, software simulation can be used to determine the areas to be cleaned in the large area density regions of the square-wound positive and negative electrode designs. Based on the three-dimensional models of the square-wound positive and negative electrode designs, software simulation can be used to determine the areas to be cleaned in the large area density regions of the negative electrode design, the large area density regions of the negative electrode design, and the area density of the small area density regions of the opposite positive electrode design, as well as the area density of the standard area of ​​the positive electrode design, the small area density regions of the negative electrode design, and the large area density regions of the opposite positive electrode design.

[0130] In one embodiment, based on the three-dimensional models of the square wound positive and negative electrode sheets, software can be used to locate the areas to be cleaned in the high-density areas of the positive and negative electrode sheets. This allows for the identification of specific areas in the positive and negative electrode sheets where the coating density increases due to the bending of the electrode sheets, as well as the determination of the location of these inner concave areas. This process identifies localized areas of uneven coating density in the positive and negative electrode sheets, and ultimately determines the location of the areas to be cleaned in each high-density area of ​​the square wound battery's positive and negative electrode sheets.

[0131] In one embodiment, based on the three-dimensional model of the square-wound positive electrode sheet and the negative electrode sheet, the specific area of ​​the concave inner curved surface region and / or local region of each coating surface density variation of the positive electrode sheet and the negative electrode sheet can be calculated using software, thereby determining the coating area of ​​the active coating of the area to be cleaned in each high surface density region of the positive electrode sheet and the negative electrode sheet.

[0132] In one embodiment, based on the three-dimensional models of the square-wound positive and negative electrode sheets, software can be used to calculate the coating thickness and coating areal density of each area to be cleaned for the positive and negative electrode sheets. This calculation is based on the coating thickness and areal density of the standard areas of the positive and negative electrode sheets, and the corresponding relationships between these areas. Furthermore, for each area to be cleaned, the actual coating thickness (coating thickness of the inner curved area) of each area can be calculated based on the actual coating thickness of the positive and negative electrode sheets. The correspondence between the coating thickness and coating areal density in the areal density standard area, the coating thickness and coating areal density in the areal density standard area of ​​the designed positive electrode sheet, and the coating thickness and coating areal density in the areal density standard area of ​​the designed negative electrode sheet are calculated. The areal density and coating thickness of the coating after cleaning are calculated for each area to be cleaned in the designed positive and negative electrode sheets. The deviation between the actual coating areal density of each area to be cleaned in the designed positive and negative electrode sheets and the coating areal density standard area is calculated. The areal density deviation of each area to be cleaned in the designed positive and negative electrode sheets is calculated. The deviation between the actual coating thickness of each area to be cleaned in the designed positive and negative electrode sheets and the coating thickness of the areal density standard area is calculated. The thickness deviation of each area to be cleaned in the designed positive and negative electrode sheets is calculated.

[0133] In one embodiment, based on the three-dimensional models of the positive and negative electrode sheets designed after the square is wound, the three-dimensional morphology of each area to be cleaned in the positive and negative electrode sheets can be obtained by software simulation, including but not limited to the arc size and curvature change of each area to be cleaned.

[0134] In one embodiment, determining the region parameters of the area to be cleaned for the designed negative electrode sheet may further include determining the coating material properties of the area to be cleaned for the designed negative electrode sheet of the square wound battery. The coating material properties include, but are not limited to, the constituent substances of the active coating in the area to be cleaned, as well as the physical and chemical properties of each constituent substance. Similarly, determining the region parameters of the area to be cleaned for the designed positive electrode sheet may also include determining the coating material properties of the area to be cleaned for the designed positive electrode sheet of the square wound battery. The coating material properties include, but are not limited to, the constituent substances of the active coating in the area to be cleaned, as well as the physical and chemical properties of each constituent substance.

[0135] In one embodiment, before stacking and winding the designed positive electrode sheet and the designed negative electrode sheet that conform to the design parameters of the square wound battery, the correspondence between the coating surface density and the coating thickness of the standard area of ​​the surface density of the designed positive electrode sheet and the coating surface density of the designed negative electrode sheet can be obtained based on the coating thickness and coating surface density of the designed positive electrode sheet and the coating surface density of the designed negative electrode sheet.

[0136] In one embodiment, the designed positive electrode, separator, and designed negative electrode of a square wound battery can be stacked and then wound in a square shape to obtain a reference square cell for the square wound battery. The coating thickness of the designed positive and negative electrode sheets of the reference square cell is obtained by laser thickness measurement or X-ray thickness measurement. Based on the coating thickness of the designed positive and negative electrode sheets of the reference square cell, the regions where the coating thickness of the designed positive and negative electrode sheets of the reference square cell changes are determined. Based on the regions where the coating thickness of the designed positive and negative electrode sheets of the reference square cell changes, and the coating thickness of the standard area of ​​the areal density of the designed positive electrode sheet, the coating thickness of the designed positive electrode sheet is determined. The correspondence between layer density and coating thickness, and the correspondence between coating surface density and coating thickness in the standard area of ​​the negative electrode sheet, are used to obtain the area of ​​surface density variation where the coating surface density of the positive and negative electrodes changes. This identifies the small and large surface density areas of the area of ​​surface density variation in the positive and negative electrodes of the square wound battery. Based on the coating surface density of the standard area of ​​the positive and negative electrodes, the small and large surface density areas of the coating surface density variation in the positive and negative electrodes of the square wound battery are determined.

[0137] In one embodiment, the areas to be cleaned for the positive and negative electrode sheets of the square wound battery can be determined based on the coating surface density of the small and large surface density areas of the surface density variation region of the positive and negative electrode sheets of the square wound battery, as well as the area parameters of the areas to be cleaned for the positive and negative electrode sheets of the square wound battery.

[0138] Step 205: Determine the cleaning path for the negative electrode and the cleaning path for the positive electrode.

[0139] In one embodiment, the cleaning path for the negative electrode can be determined based on the area parameters of the area to be cleaned in the negative electrode; and the cleaning path for the positive electrode can be determined based on the area parameters of the area to be cleaned in the positive electrode.

[0140] In one embodiment, a high-precision laser cleaning device can be used to laser clean the active coating of each area to be cleaned on the designed negative electrode sheet according to the cleaning path of the negative electrode sheet. The cleaning path for laser cleaning of each area to be cleaned on the square wound battery negative electrode sheet can be precisely determined based on the area location, coating area, coating thickness, coating areal density, coating three-dimensional morphology, and coating material properties of each area to be cleaned. This includes, but is not limited to, determining the laser cleaning location, and determining the cleaning area of ​​each area to be cleaned on the designed negative electrode sheet. This allows the laser cleaning device to perform laser cleaning of the active coating of each area to be cleaned on the designed negative electrode sheet according to the cleaning thickness and the cleaning path of the designed negative electrode sheet, thereby obtaining the target negative electrode sheet of the square wound battery.

[0141] In one embodiment, the cleaning area of ​​each area to be cleaned in the negative electrode sheet can be the coating area of ​​the active coating in the large area density region of the negative electrode sheet.

[0142] In one embodiment, the cleaning path for laser cleaning of each area to be cleaned in the square wound battery positive electrode sheet can be precisely determined based on the area location, coating area, coating thickness, coating areal density, coating three-dimensional morphology, and coating material properties of each area to be cleaned in the square wound battery positive electrode sheet. This includes, but is not limited to, determining the laser cleaning of each area to be cleaned in the design positive electrode sheet, determining the cleaning position of each area to be cleaned in the design positive electrode sheet, and determining the cleaning area of ​​each area to be cleaned in the design positive electrode sheet. This allows the laser cleaning equipment to perform laser cleaning of the active coating of each area to be cleaned in the design positive electrode sheet based on the cleaning thickness and the cleaning path of the design positive electrode sheet, thereby obtaining the target positive electrode sheet of the square wound battery.

[0143] In one embodiment, the cleaning area of ​​each area to be cleaned in the positive electrode sheet can be the coating area of ​​the active coating in the large area density region of the positive electrode sheet.

[0144] Step 206: Determine the cleaning thickness of the area to be cleaned for the negative electrode sheet and the cleaning thickness of the area to be cleaned for the positive electrode sheet.

[0145] In one embodiment, the coating thickness and coating areal density of the area to be cleaned of the negative electrode sheet can be designed based on the correspondence between the coating thickness and coating areal density of the standard area of ​​the negative electrode sheet, and the cleaning thickness of the area to be cleaned of the negative electrode sheet can be determined. Similarly, the coating thickness and coating areal density of the area to be cleaned of the positive electrode sheet can be designed based on the correspondence between the coating thickness and coating areal density of the standard area of ​​the positive electrode sheet, and the cleaning thickness of the area to be cleaned of the positive electrode sheet can be determined.

[0146] In one embodiment, the areal density of the coating in the large areal density region (the concave region on the inner side of the bend) of each bend after the square winding of the negative and positive electrode sheets can be adjusted to make the areal density ratio of each bend of the square winding of the negative and positive electrode sheets consistent with the areal density ratio of the standard area of ​​the coating areal density of the negative and positive electrode sheets. This ensures that the N / P value of each bend of the square winding of the negative and positive electrode sheets is consistent with the N / P value of the standard area of ​​the coating areal density of the negative and positive electrode sheets.

[0147] In one embodiment, the surface density of the coating in the large surface density region of each bend of the square-wound negative electrode sheet and positive electrode sheet after the design is rolled can be adjusted by adjusting the coating thickness of the large surface density region of each bend of the square-wound negative electrode sheet and positive electrode sheet after the design is rolled. This makes the surface density ratio of the surface density change region of each bend of the square-wound negative electrode sheet and positive electrode sheet consistent with the surface density ratio of the standard area of ​​the surface density of the coating of the negative electrode sheet and positive electrode sheet.

[0148] In one embodiment, a laser cleaning device can be used to perform laser cleaning on the active coating in the large area of ​​the areal density variation region of each bend of the designed negative electrode and the designed positive electrode, based on the cleaning thickness of the active coating in that area. This removes an active coating of the corresponding cleaning thickness from the large area of ​​the areal density variation region of each bend of the designed negative electrode and the designed positive electrode. By adjusting the coating thickness in the large area of ​​the areal density variation region of each bend of the designed negative electrode and the designed positive electrode after square winding, the areal density ratio of each bend of the designed negative electrode and the designed positive electrode after square winding is made consistent with the areal density ratio of the straight areal density standard region of the designed negative electrode and the designed positive electrode. This ensures that the N / P value of each bend of the designed negative electrode and the designed positive electrode after square winding is consistent with the N / P value of the straight areal density standard region.

[0149] In one embodiment, the coating thickness and coating surface density of each area to be cleaned before cleaning of the positive electrode and the negative electrode can be obtained based on the correspondence between the coating thickness and coating surface density of the standard area (flat area) of the positive electrode and the standard area (flat area) of the negative electrode, as well as the coating thickness (coating thickness before cleaning) of each area to be cleaned (curved inner concave surface area) of the positive electrode and the negative electrode. Based on the coating surface density of each area to be cleaned before cleaning of the positive electrode and the negative electrode, and the coating surface density of the standard area of ​​the positive electrode and the negative electrode, the coating surface density of each area to be cleaned after cleaning of the positive electrode and the negative electrode can be obtained.

[0150] In one embodiment, the coating thickness of each area to be cleaned after cleaning of the designed positive electrode sheet and the designed negative electrode sheet can be obtained based on the coating surface density of each area to be cleaned after cleaning, as well as the correspondence between the coating thickness and coating surface density of the standard area of ​​the designed positive electrode sheet and the corresponding correspondence between the coating thickness and coating surface density of the standard area of ​​the designed negative electrode sheet. The cleaning thickness of each area to be cleaned of the designed positive electrode sheet and the cleaning thickness of each area to be cleaned before cleaning can be obtained based on the coating thickness of each area to be cleaned after cleaning and the coating thickness before cleaning. The laser cleaning equipment adjusts the cleaning thickness of the active coating in each area of ​​the designed positive electrode and negative electrode according to the designed cleaning thickness of each area to be cleaned. This adjusts the coating thickness of each area of ​​the designed positive and negative electrode from the pre-cleaning thickness to the post-cleaning thickness, thus obtaining the target positive and negative electrode of the square wound battery. This ensures that the areal density ratio of each curved areal density variation area after the square winding of the target positive and negative electrode is consistent with the areal density ratio of the flat areal density standard area, and that the N / P value of each curved areal density variation area after the square winding of the target positive and negative electrode is consistent with the N / P value of the flat areal density standard area.

[0151] In another embodiment, the N / P value of the flat areal density standard region of the square wound positive and negative electrode sheets can be used to determine the N / P value of the areal density variation region of each bend after the square winding of the positive and negative electrode sheets. Based on the N / P value of the areal density variation region of each bend after the square winding of the positive and negative electrode sheets, the coating areal density after cleaning of the large areal density region of the areal density variation region of each bend after the square winding of the positive and negative electrode sheets can be determined. Based on the coating areal density after cleaning of the large areal density region of the areal density variation region of each bend after the square winding of the positive and negative electrode sheets, and the flatness of the positive electrode sheet... The correspondence between the coating thickness and coating areal density of the straight areal density standard area and the correspondence between the coating thickness and coating areal density of the straight areal density standard area of ​​the designed negative electrode sheet are used to determine the coating thickness after cleaning of the large areal density area of ​​each curved areal density change region after the square winding of the designed positive and negative electrode sheets. Based on the coating thickness after cleaning of the large areal density area of ​​each curved areal density change region after the square winding of the designed positive and negative electrode sheets, and the coating thickness before cleaning of the large areal density area of ​​each curved areal density change region after the square winding of the designed positive and negative electrode sheets, the cleaning thickness of the active coating of each area to be cleaned of the designed positive and negative electrode sheets is determined.

[0152] In one embodiment, the cleaning thickness of the area to be cleaned can be a set of continuous, gradually changing values. This allows the laser cleaning equipment to adjust the coating thickness of each area to be cleaned according to the cleaning thickness of the designed electrode. After the laser cleaning equipment adjusts the coating thickness of each area to be cleaned from the pre-cleaning coating thickness to the post-cleaning coating thickness, the areal density ratio of each curved areal density variation area of ​​the square-wound target positive electrode and target negative electrode is consistent with the areal density ratio of the flat areal density standard area. This also ensures that the N / P value of each curved areal density variation area of ​​the square-wound target positive electrode and target negative electrode is consistent with the N / P value of the flat areal density standard area. Furthermore, the laser cleaning equipment can laser clean the large areal density areas of each curved areal density variation area of ​​the target positive electrode and target negative electrode to create arc-shaped grooves that are symmetrical along the electrode length direction and / or electrode width direction and match the three-dimensional shape of each curved areal density variation area (the concave area on the inner side of the curve and / or the convex area on the outer side of the curve).

[0153] Step 207: Determine the cleaning parameters for the laser cleaning equipment to perform laser cleaning on the area to be cleaned of the designed negative electrode sheet, and determine the cleaning parameters for the laser cleaning equipment to perform laser cleaning on the area to be cleaned of the designed positive electrode sheet.

[0154] In one embodiment, when using a high-precision laser cleaning device to perform laser cleaning on the area to be cleaned of the designed electrode sheet according to the cleaning path, the cleaning parameters for laser cleaning of the area to be cleaned by the laser cleaning device can be precisely determined based on one or a combination of the following: the area location of the area to be cleaned of the square wound battery designed electrode sheet, coating area, coating thickness, coating areal density, coating three-dimensional morphology, coating material properties, and the cleaning thickness of the area to be cleaned. The cleaning parameters include, but are not limited to, one or a combination of the following: laser power, laser pulse frequency, laser pulse width, unwinding tension, winding tension, belt speed, scanning speed, and spot diameter. This ensures that the laser cleaning of each area to be cleaned of the designed electrode sheet can be precisely controlled to achieve the set cleaning thickness and the set laser cleaning effect. This ensures that the areal density ratio of each curved areal density variation area of ​​the square wound positive and negative electrode sheet is consistent with the areal density ratio of the straight areal density standard area, and that the N / P value of each curved areal density variation area of ​​the square wound positive and negative electrode sheet is consistent with the N / P value of the straight areal density standard area of ​​the positive and negative electrode sheet.

[0155] In one embodiment, the cleaning parameters of the area to be cleaned for the negative electrode sheet can be determined based on the area parameters and cleaning thickness of the area to be cleaned for the negative electrode sheet; the cleaning parameters of the area to be cleaned for the positive electrode sheet can be determined based on the area parameters and cleaning thickness of the area to be cleaned for the positive electrode sheet.

[0156] In one embodiment, the cleaning parameters of the laser cleaning equipment can be optimized through a process of initial setting, experimental testing, data analysis, and gradual adjustment, based on the location of the areas to be cleaned for the negative and positive electrode sheets of the square wound battery, the coating area, coating areal density, coating thickness, coating three-dimensional morphology, and one or a combination of coating material properties, as well as the cleaning thickness of the areas to be cleaned for the negative and positive electrode sheets. Finally, the cleaning parameters for laser cleaning of the active coatings in the areas to be cleaned for the negative and positive electrode sheets are determined. The laser cleaning equipment then performs laser cleaning based on the cleaning path and cleaning parameters. Laser cleaning is performed on the active coating of the area to be cleaned to achieve the cleaning thickness set by the laser cleaning. The areal density of the coating of the designed negative electrode and the designed positive electrode of the square wound battery is precisely adjusted to obtain the target negative electrode and the target positive electrode of the square wound battery. The areal density ratio of each curved areal density variation area of ​​the square wound target negative electrode and the target positive electrode is consistent with the areal density ratio of the flat areal density standard area. The N / P value of each curved areal density variation area of ​​the square wound target negative electrode and the target positive electrode is consistent with the N / P value of the flat areal density standard area of ​​the target negative electrode and the target positive electrode.

[0157] In one embodiment, the higher the laser power of the laser cleaning equipment, the stronger its ability to remove the active coating per unit time. With other cleaning parameters of the laser cleaning equipment remaining constant, if it is necessary to clean more active coatings in a shorter time, i.e., to clean thicker active coatings, a higher laser power can be selected. However, excessively high laser power may damage the electrode substrate or cause uncontrollable thermal effects, leading to irreversible changes in the electrode coating.

[0158] In one embodiment, the coating material properties may further include the specific heat capacity of the active coating in the area to be cleaned. In some embodiments, the laser power for laser cleaning of the active coating in the area to be cleaned by the laser cleaning equipment can be determined based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating in the area to be cleaned.

[0159] In one embodiment, the laser power P for laser cleaning of the active coating in the area to be cleaned of the negative electrode sheet can be determined based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating in the area to be cleaned. 负 ,in,

[0160] P 负 =(△d) 负 ×A 负 ×ρ 负 ×C 负 )÷(η 负 ×t 负 ), Vl 负 =L 负 ÷t 负 ;

[0161] In the formula, △d 负 It refers to the cleaning thickness of the area to be cleaned in the negative electrode plate; A 负 ρ is the laser spot area when the laser cleaning equipment is used to clean the area to be cleaned on the negative electrode sheet; 负 It is the coating surface density of the area to be cleaned in the negative electrode plate; C 负 It is the specific heat capacity of the active coating in the area to be cleaned of the negative electrode sheet; η 负 It refers to the efficiency of converting laser energy into laser cleaning of the active coating in the area to be cleaned on the negative electrode sheet; t 负 It is the total time that the laser in the laser cleaning equipment acts on the active coating in the area to be cleaned on the negative electrode sheet; Vl 负 L is the scanning speed of the laser when the laser cleaning equipment is used to clean the area of ​​the negative electrode sheet to be cleaned; 负 It is the total length that the laser moves in the area to be cleaned when the laser is used to clean the negative electrode sheet of the laser cleaning equipment.

[0162] In one embodiment, the laser spot diameter is D (m); then the laser spot area is...

[0163]

[0164] In one embodiment, the laser power P for laser cleaning of the active coating in the area to be cleaned of the designed positive electrode sheet can be determined based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating. 正 ,in,

[0165] P 正 =(△d) 正 ×A 正 ×ρ 正 ×C 正 )÷(η 正 ×t 正 ), Vl 正 =L 正 ÷t 正 ;

[0166] In the formula, △d 正 It refers to the cleaning thickness of the area to be cleaned in the design of the positive electrode sheet; A 正 ρ is the laser spot area when the laser cleaning equipment is used to clean the area to be cleaned on the positive electrode sheet; 正 It is the areal density of the active coating in the area to be cleaned in the design of the positive electrode sheet; C 正 It is the specific heat capacity of the active coating in the area to be cleaned of the positive electrode; η 正 It refers to the efficiency of converting laser energy into laser cleaning of the active coating in the area to be cleaned on the positive electrode sheet; t 正 It is the total time that the laser in the laser cleaning equipment acts on the active coating in the area to be cleaned on the positive electrode sheet; Vl 正 L is the scanning speed of the laser when the laser cleaning equipment is used to clean the area to be cleaned on the positive electrode sheet; 正 It is the total length that the laser moves in the area to be cleaned when the positive electrode sheet of the laser cleaning equipment is being cleaned.

[0167] In one embodiment, the laser spot diameter is D (m); then the laser spot area is...

[0168]

[0169] In one embodiment, the laser pulse frequency refers to the number of pulses emitted by the laser in the laser cleaning equipment per unit time. The higher the laser pulse frequency of the laser cleaning equipment, the stronger its ability to remove the active coating per unit time. With other cleaning parameters of the laser cleaning equipment remaining constant, if it is necessary to clean more active coatings in a shorter time (i.e., to clean thicker active coatings), a higher laser pulse frequency can be selected to improve laser cleaning efficiency. However, excessively high laser pulse frequencies may cause localized overheating of the electrode due to the superposition of energy from each pulse on the surface of the active coating, potentially leading to uncontrollable thermal effects and irreversible changes to the coating, thus affecting the quality of laser cleaning.

[0170] In one embodiment, the laser pulse frequency f for laser cleaning the active coating of the area to be cleaned on the negative electrode sheet can be determined based on the cleaning thickness of the area to be cleaned. 负 Laser pulse frequency f 负 The unit is Hz (Hertz), where,

[0171] f 负 =Vm 负 / (S 负 ×τ 负 ),

[0172] In the formula, Vm 负 This refers to the conveyor belt speed used by the laser cleaning equipment to perform laser cleaning on the designed negative electrode sheet, measured in m / s (meters per second); τ 负 This refers to the duration of each laser pulse during laser cleaning of the designed negative electrode sheet by the laser cleaning equipment, measured in seconds (s). 负 The design of the negative electrode plate at the belt travel speed Vm 负 During the duration τ 负 The distance traveled.

[0173] In one embodiment, the laser pulse frequency f for laser cleaning the active coating of the area to be cleaned on the positive electrode sheet can be determined based on the cleaning thickness of the area to be cleaned. 正 ,in,

[0174] f 正 =Vm 正 / (S 正 ×τ 正 ),

[0175] In the formula, Vm 正 τ is the conveyor belt speed used by the laser cleaning equipment to perform laser cleaning on the designed positive electrode sheet; 正 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed positive electrode sheet; S 正The design of the positive electrode plate at the belt travel speed Vm 正 During the duration τ 正 The distance traveled.

[0176] In one embodiment, to ensure that each laser pulse leaves a complete spot in each cleaning area of ​​both the negative and positive electrode sheets, and that there is sufficient overlap between the spots, thus guaranteeing uniform distribution and coverage of laser energy in each cleaning area of ​​both the negative and positive electrode sheets, and achieving effective and uniform laser cleaning of the active coating in each cleaning area of ​​both the negative and positive electrode sheets, the negative electrode sheet is positioned at a conveyor belt speed Vm. 负 Duration τ of each pulse 负 Internally, the negative electrode plate is designed at a belt travel speed Vm. 负 During the duration τ 负 The distance S traveled 负 It should be a small fraction of the laser spot diameter D. The negative electrode is designed with a conveyor belt speed Vm. 负 During the duration τ 负 The distance S traveled 负 The laser spot diameter D of the laser used in the laser cleaning equipment is less than or equal to one-tenth of the laser spot diameter D, and the unit is meters. In a specific embodiment, the negative electrode is designed to operate at a belt conveyor speed Vm. 负 During the duration τ 负 The distance S traveled 负 It is equal to one-tenth of the laser spot diameter D of the laser cleaning equipment; the design of the positive electrode plate at the belt conveyor speed Vm 正 Duration τ of each pulse 正 Internally, the design of the positive electrode plate at the belt travel speed Vm 正 During the duration τ 正 The distance S traveled 正 It should be a small portion of the laser spot diameter D. The design of the positive electrode plate at the belt travel speed Vm... 正 During the duration τ 正 The distance S traveled 正 The diameter of the laser spot, D, is less than or equal to one-tenth of the diameter of the laser beam in the laser cleaning equipment. In a specific embodiment, the positive electrode is designed to operate at a belt travel speed Vm. 正 During the duration τ 正 The distance S traveled 正 It is equal to one-tenth of the laser spot diameter D of the laser cleaning equipment.

[0177] In one embodiment, when the laser cleaning equipment performs laser cleaning on the active coating of the areas to be cleaned of the designed negative and positive electrode sheets, the designed negative and positive electrode sheets can be fixed to the laser cleaning equipment. The conveyor speed of the laser cleaning equipment refers to the moving speed of the designed negative or positive electrode sheet relative to the laser source during the laser cleaning process. The laser scanning speed of the laser cleaning equipment is the moving speed of the laser beam on the surface of the active coating of the designed negative or positive electrode sheet. Both the laser scanning speed and the conveyor speed of the laser cleaning equipment affect the residence time of the laser on the surface of the active coating of the designed negative and positive electrode sheets, thus affecting the cleaning thickness. The faster the laser scanning speed, the shorter the irradiation time of the active coating surface and the smaller the cleaning thickness; the slower the laser scanning speed, the longer the irradiation time of the active coating surface and the larger the cleaning thickness. A faster conveyor belt speed results in a shorter irradiation time on the active coating surface and a thinner cleaning thickness; conversely, a slower conveyor belt speed results in a longer irradiation time and a thicker cleaning thickness. In laser cleaning, the conveyor belt speed and laser scanning speed of the laser cleaning equipment must be matched. This matching includes the conveyor belt speed and scanning speed being equal, or the conveyor belt speed and scanning speed meeting a set multiple relationship, to ensure that the laser can uniformly clean the active coating areas of the designed negative and positive electrode sheets. If the conveyor belt speed is too fast while the laser scanning speed remains constant, the energy deposition per unit area will decrease, potentially leading to incomplete laser cleaning and failure to achieve the set cleaning thickness. Conversely, if the conveyor belt speed is too slow while the laser scanning speed remains constant, excessive energy deposition per unit area will result in over-cleaning, exceeding the set cleaning thickness and damaging the designed negative and positive electrode sheets, or causing irreversible changes or damage to the active coating due to overheating.

[0178] In one embodiment, to ensure that each laser pulse acts on the cleaning area of ​​the designed negative electrode and the designed positive electrode within the specified time, the designed negative electrode is at a belt speed Vm. 负 During the duration τ 负 The distance S traveled 负 The diameter of the laser spot in the laser cleaning equipment is less than or equal to one-tenth of the laser spot diameter D. The design of the positive electrode plate at the belt conveyor speed Vm is as follows. 正 During the duration τ 正 The distance S traveled 正 The laser spot diameter D of the laser used in the laser cleaning equipment must be less than or equal to one-tenth of the laser spot diameter D. This ensures uniform distribution and coverage of laser energy across each area to be cleaned on both the designed negative and positive electrodes. For effective laser cleaning of each area on both the designed negative and positive electrodes, the required laser scanning speed Vl is... 负The belt travel speed Vm of the designed negative electrode sheet 负 Matching, scan speed Vl 负 With belt speed Vm 负 Matching includes scan speed Vl 负 With belt speed Vm 负 Equal, or scan speed Vl 负 With belt speed Vm 负 To meet the set multiplier relationship and the required laser scanning speed Vl 正 The belt travel speed Vm of the designed positive electrode sheet 正 Matching, scan speed Vl 正 With belt speed Vm 正 Matching includes scan speed Vl 正 With belt speed Vm 正 Equal, or scan speed Vl 正 With belt speed Vm 正 The set multiplier relationship must be met. If the laser scanning speed is too fast or too slow, it may cause uneven distribution of laser energy in each area to be cleaned of the negative and positive electrodes, affecting the laser cleaning effect on each area of ​​the negative and positive electrodes. This can result in cleaning excessively thick or thin active coatings in each area of ​​the negative and positive electrodes, and may prevent the coating surface density of each area from being adjusted from the pre-cleaning coating surface density to the post-cleaning coating surface density.

[0179] In one embodiment, during the laser cleaning process of each area to be cleaned on the designed negative and positive electrode sheets, the laser pulse frequency, laser scanning speed, and the conveyor belt speed of the designed negative and positive electrode sheets jointly determine the distribution of laser energy on the coating surface of each area to be cleaned. A higher laser pulse frequency allows more pulses to act on the active coating within the same time period, which can improve laser cleaning efficiency. However, if the laser pulse frequency is set too high, and the laser scanning speed and the conveyor belt speed of the designed negative and positive electrode sheets do not increase accordingly, the superposition of the energy of each pulse on the active coating surface of the designed negative and positive electrode sheets may lead to local overheating, potentially causing uncontrollable thermal effects and irreversible changes to the active coating of the designed negative and positive electrode sheets, thus affecting the quality of laser cleaning.

[0180] In one embodiment, to achieve high-quality laser cleaning of the areas to be cleaned for the negative and positive electrode sheets of a square wound battery, the laser pulse frequency, laser scanning speed, and the conveyor belt speed of the negative and positive electrode sheets in the laser cleaning equipment can be adjusted based on the material properties of the negative and positive electrode sheets, the precision and efficiency of laser cleaning. This determines the optimal parameter combination to ensure uniform laser energy distribution. Excessive energy will not result in cleaning an overly thick active coating or overheating and damaging the electrode sheets, while insufficient energy will result in cleaning an underlying coating density, failing to adjust the coating surface density of the areas to be cleaned from its pre-cleaning state to its post-cleaning state. For example, for areas requiring fine laser cleaning, a lower laser scanning speed and conveyor belt speed, along with a moderate laser pulse frequency, may be needed to ensure sufficient energy deposition and precise adjustment of the coating surface density in the area to be cleaned. For large-area scenarios requiring rapid laser cleaning, it may be necessary to increase the laser scanning speed and conveyor belt speed, and appropriately increase the laser pulse frequency to improve efficiency while ensuring cleaning effectiveness. In short, the coordination between laser pulse frequency, laser scanning speed, and conveyor belt speed is a key technical parameter for laser cleaning. Correctly setting these parameters is crucial for achieving efficient and high-quality laser cleaning.

[0181] In one embodiment, the laser pulse width refers to the duration of a single laser pulse. Pulse width is a key parameter in applications requiring precise control of thermal effects and cleaning depth. The laser pulse width for laser cleaning the active coatings of the areas to be cleaned on the square wound battery's negative and positive electrode plates, as well as the coating material properties of these areas, can be determined by the laser cleaning equipment. A wider laser pulse width results in greater cleaning intensity of the active coating. With other cleaning parameters of the laser cleaning equipment remaining constant, for heat-sensitive active coatings, a smaller laser pulse width reduces the thermal impact, preventing substrate deformation or damage. Furthermore, a smaller laser pulse width allows for precise control, making it easier to achieve the required precision in laser cleaning and enabling refined laser cleaning. However, for thicker cleaning layers or harder active coatings, a larger laser pulse width is needed to provide sufficient energy to achieve the desired laser cleaning effect. For example, with other cleaning parameters of the laser cleaning equipment being the same, the laser pulse width used for cleaning a thickness of 30µm (micrometer) needs to be higher than that used for cleaning a thickness of 10µm; similarly, for laser cleaning silicon-carbon anodes and graphite anodes, the laser pulse width used for laser cleaning graphite anodes needs to be higher than that used for laser cleaning silicon-carbon anodes.

[0182] In a specific embodiment, the laser spot diameter of the laser cleaning equipment used for laser cleaning the areas to be cleaned, which are designed as negative and positive electrode sheets, can be 4-5.5 mm, the laser power can be 4 kW-5 kW, the laser scanning speed can be 11000 mm / s-15000 mm / s, the laser pulse frequency can be 100 kHz-200 kHz, the laser pulse width can be 300 ns-500 ns, the unwinding tension of the laser cleaning equipment can be 30 N-90 N, the winding tension of the laser cleaning equipment can be 60 N-120 N, and the conveyor belt speed of the laser cleaning equipment can be 400 mm / s-900 mm / s.

[0183] Step 208: Perform laser cleaning on the designed negative electrode sheet according to the cleaning path and cleaning parameters of the designed negative electrode sheet to obtain the target negative electrode sheet of the square wound battery; perform laser cleaning on the designed positive electrode sheet according to the cleaning path and cleaning parameters of the designed positive electrode sheet to obtain the target positive electrode sheet of the square wound battery.

[0184] In one embodiment, a laser cleaning device can be used to perform laser cleaning on the designed negative electrode sheet according to the cleaning path and cleaning parameters of the area to be cleaned of the designed negative electrode sheet, to obtain the target negative electrode sheet of the square wound battery; the same method can be used to perform laser cleaning on the designed positive electrode sheet according to the cleaning path and cleaning parameters of the area to be cleaned of the designed positive electrode sheet, to obtain the target positive electrode sheet of the square wound battery; the coating surface density of each area to be cleaned of the designed negative electrode sheet can be adjusted from the coating surface density before cleaning to the coating surface density after cleaning, to obtain the target negative electrode sheet of the square wound battery; the coating surface density of each area to be cleaned of the designed positive electrode sheet can be adjusted from the coating surface density before cleaning to the coating surface density after cleaning, to obtain the target positive electrode sheet of the square wound battery; the surface density ratio of each curved surface density change area after the square winding of the target negative electrode sheet and the target positive electrode sheet is made consistent with the surface density ratio of the flat surface density standard area, and the N / P value of each curved surface density change area after the square winding of the target negative electrode sheet and the target positive electrode sheet is made consistent with the N / P value of the flat surface density standard area.

[0185] In one embodiment, a laser cleaning device can be used to perform laser cleaning on the active coating of each area to be cleaned of the designed positive electrode sheet according to the cleaning path and cleaning parameters. This adjusts the coating surface density of each area to be cleaned from the pre-cleaning density to the post-cleaning density. The laser cleaning removes the active coating from the surface of the designed positive electrode sheet, thus obtaining the target positive electrode sheet for the square wound battery. Similarly, the same laser cleaning device can be used to perform laser cleaning on the active coating of each area to be cleaned of the designed negative electrode sheet according to the cleaning path and cleaning parameters. The process involves washing the surface of the negative electrode sheet, adjusting the coating density of each area to be cleaned from the pre-cleaning density to the post-cleaning density, and cleaning the active coating removed by laser cleaning on the surface of the negative electrode sheet to obtain the target negative electrode sheet for the square-wound battery. The surface density ratio of each curved surface density variation area after the square winding of the target negative and positive electrode sheets is made consistent with the surface density ratio of the flat surface density standard area, ensuring that the N / P value of each curved surface density variation area after the square winding of the target negative and positive electrode sheets is consistent with the N / P value of the flat surface density standard area.

[0186] The method for preparing square wound battery electrodes according to embodiments of this application involves winding a designed electrode and a separator to form a reference square core. First, by measuring each turn of the reference square core, the standard area and the area of ​​varying areal density of the active coating on the wound electrode are determined. Then, the areas of the active coating on the designed electrode to be cleaned are determined. Next, based on the areas to be cleaned, the designed electrode is laser-cleaned to obtain the target electrode for the square wound battery. By pre-cleaning the active coating in the areas of varying areal density where the positive and negative electrode sheets of the square wound battery are bent using a laser cleaning device, the areal density of the coating in these areas is adjusted, which improves the production efficiency of the square wound battery, reduces waste in the production process, and lowers the manufacturing cost. Pre-cleaning the active coating in the areas of varying areal density where the positive and negative electrode sheets of the square wound battery are bent, and adjusting the areal density of the coating in these areas, improves the areal density distribution of the positive and negative electrode sheets after the square winding, resulting in a more efficient and effective square wound battery. The areal density ratio of the bend region of the electrode sheet is consistent with that of the flat standard region. This ensures that the N / P value of the bend region of the positive and negative electrodes after square winding is consistent with the N / P value of the non-bend region (flat standard region). This significantly reduces the difference in local coating areal density of the positive and negative electrodes caused by the bend of the square winding, resulting in more consistent local performance of each electrode after square winding. This makes the overall performance of the square-wound battery more reliable and improves its electrical performance. Furthermore, the uniform distribution of the N / P value of the square-wound positive and negative electrodes avoids the increase in local internal resistance and local overheating caused by uneven N / P values. It solves the problem of uneven current distribution caused by local N / P value variations in the bend region of the positive and negative electrodes. For square-wound lithium-ion batteries, this reduces the possibility of local lithium plating in the bend region, improving the safety performance and cycle life of square-wound batteries. This opens up new avenues for improving the safety and performance of square-wound batteries.

[0187] Furthermore, the method for preparing square wound battery electrodes in this application embodiment determines the cleaning path for laser cleaning of the active coating of the area to be cleaned by the laser cleaning equipment based on the area parameters of the area to be cleaned of the designed electrode; determines the cleaning parameters for laser cleaning of the active coating of the area to be cleaned by the laser cleaning equipment based on the area parameters and cleaning thickness of the area to be cleaned of the designed electrode; and performs laser cleaning of the active coating of the area to be cleaned by the laser cleaning equipment according to the cleaning path and cleaning parameters. This allows for dynamic adjustment of the cleaning path and cleaning parameters of the designed electrode based on the area parameters of each area to be cleaned, achieving differentiated treatment for each area to be cleaned and ensuring a smooth transition in the surface density of the coating in each area to be cleaned of the designed electrode.

[0188] Furthermore, the method for preparing square wound battery electrodes in this application involves using a laser cleaning device to perform laser cleaning on the active coating of each area to be cleaned in the designed electrode according to the cleaning path and cleaning parameters. Laser cleaning technology is used to precisely adjust and optimize the coating thickness of the designed electrode, thereby achieving precise adjustment and optimization of the coating areal density of each area to be cleaned in the designed electrode. This ensures that the areal density ratio of each curved areal density variation area of ​​the positive and negative electrodes after square winding is consistent with the areal density ratio of the straight areal density standard area. This results in the N / P value of the square wound electrode being evenly distributed in each curved areal density variation area and the straight areal density standard area. This method can be applied to the large-scale preparation of electrodes and can guarantee the consistency of large-scale electrode preparation.

[0189] Furthermore, the method for preparing square wound battery electrodes in this application embodiment uses a laser cleaning device to perform laser cleaning on the active coating of each area to be cleaned of the designed electrode according to the cleaning path and cleaning parameters. Utilizing the thermal and physical effects of the laser, not only can the active coating of each area to be cleaned be removed through laser cleaning, and the areal density of the coating in each area to be cleaned be adjusted and optimized, but the surface microstructure of the active coating in each area to be cleaned can also be reshaped, fine-tuning the microstructure of the active coating surface, improving the wettability of the active coating to the electrolyte, and further optimizing the electrochemical performance of the square wound battery. Laser cleaning of the active coating in each area of ​​the designed electrode utilizes laser energy to rapidly heat minute areas on the surface of the active coating. This instantaneous high temperature melts and re-solidifies the active coating in these minute areas. The binders and additives in these minute areas soften or melt at the high temperature and then re-solidify during rapid cooling, forming new crystalline structures or tighter molecular arrangements. This enhances the adhesion between the active coating in each area of ​​the designed electrode and the electrode substrate (e.g., current collector), while optimizing the electrolyte penetration path. The thermal effect generated by the active coating causes the active coating in each area of ​​the designed electrode to undergo laser heating and cooling cycles, inducing a phase transition and reconstruction (e.g., from amorphous to crystalline state) in the active coating. This alters the physical and chemical properties of the active coating, forming a microstructure more conducive to ion transport. Laser cleaning of the active coating in each area of ​​the designed electrode, through the physical action of the laser, can "carve" micron or nanometer-level uneven structures in the active coating of each area of ​​the designed electrode, increasing the specific surface area of ​​the designed electrode. This promotes electrolyte penetration and ion transport at the interface, improving the charge-discharge efficiency and cycle stability of the square wound battery.

[0190] In addition, this application embodiment also provides a square wound battery, which includes a negative electrode sheet prepared according to the above method and a positive electrode sheet prepared according to the above method.

[0191] In the square wound battery of this application embodiment, the other components besides the positive electrode and negative electrode, such as the battery casing, separator, electrolyte, etc., can all adopt existing conventional structures and materials.

[0192] In one embodiment, a negative electrode and a positive electrode of a 14500-600mAh ternary + graphite system square wound lithium-ion battery are prepared according to the above method; the negative electrode, positive electrode and separator prepared according to the above method are square wound to prepare a cell; and a 14500-600mAh ternary + graphite system square wound lithium-ion battery A is prepared based on the cell.

[0193] In the comparative example, negative and positive electrode sheets of a 14500-600mAh ternary + graphite system square wound lithium-ion battery were prepared according to conventional methods. The negative and positive electrode sheets prepared by conventional methods did not undergo laser cleaning of the active coating in the bending area with varying areal density. The prepared negative and positive electrode sheets and separator were then squarely wound to prepare a battery cell. Based on this battery cell, a 14500-600mAh ternary + graphite system square wound lithium-ion battery B of the comparative example was prepared.

[0194] Cyclic tests were performed on the square wound lithium-ion battery A of the embodiment and the square wound lithium-ion battery B of the comparative example. The battery was charged at 3C constant current and constant voltage to 4.2V, then stopped at 0.05C; rested for 15 minutes; discharged at 5C constant current to 3.0V; rested for 20 minutes; and cycled 500 times to obtain the desired result. Figure 3 This diagram illustrates a comparison of the capacity retention rates of a square wound lithium-ion battery according to an embodiment of this application with a comparative square wound lithium-ion battery.

[0195] like Figure 3As shown, curve 301 illustrates the capacity retention rate (%) of a square-wound lithium-ion battery, including the positive and negative electrode sheets prepared according to the square-wound battery electrode preparation method of this application. Curve 302 illustrates the capacity retention rate (%) of a comparative square-wound lithium-ion battery. Comparing curves 301 and 302, the capacity retention rate (%) of the square-wound lithium-ion battery, including the positive and negative electrode sheets prepared according to the square-wound battery electrode preparation method of this application, is significantly higher than that of the comparative square-wound lithium-ion battery. This demonstrates that by pre-treating the active coating in the area to be cleaned of the designed electrode sheet with laser cleaning, the coating surface density in the bending surface density variation area of ​​the square-wound negative and positive electrode sheets is adjusted, thereby improving the square-wound negative and positive electrode sheets. The coating's areal density distribution ensures that the areal density ratio of each curved areal density variation region of the square-wound positive and negative electrode sheets is consistent with the areal density ratio of the straight standard areal density region. This makes the N / P value of each curved areal density variation region of the square-wound negative and positive electrode sheets consistent with the N / P value of the straight standard areal density region, resulting in a uniform distribution of the N / P value of the square-wound negative and positive electrode sheets. This avoids the increased local internal resistance and local overheating caused by uneven N / P values ​​in the square-wound negative and positive electrode sheets, and solves the problem of uneven current distribution caused by local N / P value variations in the curved regions of the negative and positive electrode sheets. For square-wound lithium-ion batteries, this reduces the possibility of local lithium plating in the curved regions, thereby improving the cycle performance and cycle life of square-wound lithium-ion batteries.

[0196] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a square wound battery electrode, characterized in that, include: Obtain a designed electrode sheet with a current collector and an active coating, wherein the designed electrode sheet includes a designed negative electrode sheet and a designed positive electrode sheet, and the active coating is present on both the front and back sides of the designed electrode sheet; The designed electrode and diaphragm are wound to form a reference square core; The method involves measuring each turn of the reference square core to determine the standard area and the area density variation area of ​​the active coating on the wound electrode sheet. This includes measuring each turn of the design electrode sheet of the reference square core to determine the standard area and the area density variation area of ​​the active coating that is alternately distributed along the winding direction on the wound electrode sheet. The method further determines that the outer side of the curved area of ​​each turn of the design electrode sheet is a low area density region. The standard area corresponds to the straight area of ​​the design electrode sheet in the winding direction. The area density variation area corresponds to the curved area of ​​the wound electrode sheet. The inner side of the curved area of ​​each turn of the design electrode sheet is a high area density region. The area density of the standard area is the target area density. The area density of the area density variation area is different from the target area density. The area density variation area includes a high area density region, and the area density of the high area density region is greater than the target area density. By comparing the areal density standard region and the areal density variation region, the area to be cleaned of the active coating on the designed electrode sheet is determined. This includes: comparing the areal density standard region and the areal density variation region of the designed negative electrode sheet; comparing the areal density standard region and the areal density variation region of the designed positive electrode sheet; comparing the large areal density region of the designed negative electrode sheet and the small areal density region of the designed positive electrode sheet opposite to it, to determine the area to be cleaned of the active coating on the designed negative electrode sheet, such that the large areal density region of the designed negative electrode sheet and the small areal density region of the designed positive electrode sheet opposite to it are determined. The areal density ratio of the area is equal to the areal density ratio of the standard areal density area of ​​the designed negative electrode sheet and the standard areal density area of ​​the designed positive electrode sheet; by comparing the small areal density area of ​​the designed negative electrode sheet and the large areal density area of ​​the designed positive electrode sheet opposite to it, the area to be cleaned of the active coating on the designed positive electrode sheet is determined, such that the areal density ratio of the small areal density area of ​​the designed negative electrode sheet and the large areal density area of ​​the designed positive electrode sheet opposite to it is equal to the areal density ratio of the standard areal density area of ​​the designed negative electrode sheet and the standard areal density area of ​​the designed positive electrode sheet; the area to be cleaned is located in the large areal density area; Based on the area to be cleaned of the designed electrode sheet, laser cleaning is performed on the designed electrode sheet to obtain the target electrode sheet for the square wound battery.

2. The method according to claim 1, characterized in that, The step of winding the designed electrode and diaphragm into a reference square core includes: physically winding or simulatedly winding the designed electrode and diaphragm into a reference square core.

3. The method according to claim 1, characterized in that, The step of determining the area to be cleaned of the active coating on the designed electrode sheet further includes: The region parameters of the area to be cleaned in the active coating on the designed negative electrode sheet and the region parameters of the area to be cleaned in the active coating on the designed positive electrode sheet are determined respectively. The region parameters include one or a combination of the following: the region location of the area to be cleaned, the coating area, the coating thickness, the coating surface density, the coating three-dimensional morphology, and the coating material properties.

4. The method according to claim 3, characterized in that, Before performing laser cleaning on the designed electrode sheet according to the area to be cleaned to obtain the target electrode sheet for the square wound battery, the process includes: Based on the area parameters of the area to be cleaned in the designed negative electrode sheet, the cleaning path of the designed negative electrode sheet is determined; The cleaning path of the designed positive electrode is determined based on the area parameters of the area to be cleaned in the designed positive electrode.

5. The method according to claim 4, characterized in that, The step of determining the cleaning path of the designed negative electrode sheet based on the area parameters of the area to be cleaned of the designed negative electrode sheet further includes: determining the cleaning thickness of the area to be cleaned of the designed negative electrode sheet based on the correspondence between the coating thickness and the coating surface density of the standard area of ​​the surface density of the designed negative electrode sheet, the coating thickness and the coating surface density of the area to be cleaned of the designed negative electrode sheet. The step of determining the cleaning path of the designed positive electrode sheet based on the area parameters of the area to be cleaned of the designed positive electrode sheet further includes: determining the cleaning thickness of the area to be cleaned of the designed positive electrode sheet based on the correspondence between the coating thickness and the coating surface density of the standard area of ​​the surface density of the designed positive electrode sheet, the coating thickness and the coating surface density of the area to be cleaned of the designed positive electrode sheet.

6. The method according to claim 5, characterized in that, The step of performing laser cleaning on the designed electrode sheet according to the area to be cleaned to obtain the target electrode sheet for the square wound battery includes: Based on the area parameters and cleaning thickness of the area to be cleaned in the designed negative electrode sheet, the cleaning parameters of the area to be cleaned in the designed negative electrode sheet are determined. Laser cleaning is performed on the designed negative electrode sheet according to the cleaning path and cleaning parameters of the area to be cleaned in the designed negative electrode sheet to obtain the target negative electrode sheet of the square wound battery. Based on the area parameters and cleaning thickness of the area to be cleaned in the designed positive electrode sheet, the cleaning parameters of the area to be cleaned in the designed positive electrode sheet are determined. Laser cleaning is performed on the designed positive electrode sheet according to the cleaning path and cleaning parameters of the area to be cleaned in the designed positive electrode sheet to obtain the target positive electrode sheet of the square wound battery.

7. The method according to claim 6, characterized in that, The cleaning parameters include the laser power of the laser cleaning equipment; the coating material properties include the specific heat capacity of the active coating in the area to be cleaned. The step of determining the cleaning parameters of the area to be cleaned of the designed negative electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed negative electrode sheet further includes: Based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating in the area to be cleaned of the designed negative electrode sheet, the laser power P of the laser cleaning equipment for laser cleaning the active coating in the area to be cleaned of the designed negative electrode sheet is determined. 负 ,in, P 负 =(△d 负 ×A 负 ×ρ 负 ×C 负 (÷(η 负 ×t 负 ),Vl 负 =L 负 ÷t 负 4 In the formula, △d 负 It is the cleaning thickness of the area to be cleaned in the negative electrode sheet of the design; A 负 It is the area of ​​the laser spot when the laser cleaning equipment laser cleans the area to be cleaned of the designed negative electrode sheet; ρ 负 It is the surface density of the coating in the area to be cleaned of the negative electrode sheet in the design; C 负 It is the specific heat capacity of the active coating in the area to be cleaned of the negative electrode sheet in the design; η 负 It is the efficiency of converting laser energy into laser cleaning of the active coating in the area to be cleaned of the designed negative electrode sheet; t 负 It is the total time during which the laser from the laser cleaning device acts on the active coating in the area to be cleaned of the designed negative electrode sheet; Vl 负 The laser scanning speed is the laser speed at which the laser cleaning equipment cleans the area to be cleaned of the designed negative electrode sheet. L 负 It is the total length of the laser moving in the area to be cleaned when the laser cleaning equipment cleans the area to be cleaned of the designed negative electrode sheet; The step of determining the cleaning parameters of the area to be cleaned of the designed positive electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed positive electrode sheet further includes: Based on the specific heat capacity, coating areal density, and cleaning thickness of the active coating in the area to be cleaned of the designed positive electrode sheet, the laser power P of the laser cleaning equipment for laser cleaning the active coating in the area to be cleaned of the designed positive electrode sheet is determined. 正 ,in, P 正 =(△d 正 ×A 正 ×ρ 正 ×C 正 (÷(η 正 ×t 正 ),Vl 正 =L 正 ÷t 正 4 In the formula, △d 正 It is the cleaning thickness of the area to be cleaned in the positive electrode sheet of the design; A 正 It is the area of ​​the laser spot when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode sheet; ρ 正 It is the coating surface density of the area to be cleaned in the positive electrode sheet of the design; C 正 It is the specific heat capacity of the active coating in the area to be cleaned of the designed positive electrode sheet; η 正 It is the efficiency of converting laser energy into laser cleaning of the active coating in the area to be cleaned of the designed positive electrode sheet; t 正 It is the total time during which the laser from the laser cleaning device acts on the active coating in the area to be cleaned of the designed positive electrode sheet; Vl 正 It is the scanning speed of the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode sheet; L 正 It is the total length that the laser moves in the area to be cleaned when the laser cleaning equipment lasers the area to be cleaned of the designed positive electrode sheet.

8. The method according to claim 7, characterized in that: The cleaning parameters also include the laser pulse frequency of the laser cleaning equipment; The step of determining the cleaning parameters of the area to be cleaned of the designed negative electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed negative electrode sheet further includes: Based on the cleaning thickness of the area to be cleaned in the designed negative electrode sheet, the laser pulse frequency f for the laser cleaning equipment to perform laser cleaning on the active coating of the area to be cleaned in the designed negative electrode sheet is determined. 负 ,in, f 负 = Vm 负 / (S 负 ×τ 负 ), In the formula, Vm 负 τ is the conveyor belt speed at which the laser cleaning equipment performs laser cleaning on the designed negative electrode sheet; 负 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed negative electrode sheet; S 负 The negative electrode sheet of the design is at a belt travel speed Vm 负 During the duration τ 负 The distance traveled; The step of determining the cleaning parameters of the area to be cleaned of the designed positive electrode sheet based on the area parameters and cleaning thickness of the area to be cleaned of the designed positive electrode sheet further includes: Based on the cleaning thickness of the area to be cleaned in the designed positive electrode sheet, the laser pulse frequency f for the laser cleaning equipment to perform laser cleaning on the active coating of the area to be cleaned in the designed positive electrode sheet is determined. 正 ,in, f 正 = Vm 正 / (S 正 ×τ 正 ), In the formula, Vm 正 τ is the conveyor belt speed at which the laser cleaning equipment performs laser cleaning on the designed positive electrode sheet; 正 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed positive electrode sheet; S 正 The designed positive electrode sheet is at a belt speed Vm 正 During the duration τ 正 The distance traveled.

9. The method according to claim 8, characterized in that: Distance S 正 Less than or equal to one-tenth of the laser spot diameter of the laser cleaning equipment; moving distance S 负 It is less than or equal to one-tenth of the laser spot diameter of the laser cleaning equipment.

10. A square wound battery, characterized in that: It includes a negative electrode sheet prepared by the method according to any one of claims 1-9, and a positive electrode sheet prepared by the method according to any one of claims 1-9.

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