Preparation method of square winding battery pole piece and square winding battery

Abstract

The invention relates to a square winding battery pole piece preparation method and a square winding battery. The method comprises the steps that the surface density standard area and the surface density change area of an active coating on a wound designed pole piece are determined, the surface density of the surface density standard area is the 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 larger than the target surface density. The surface density of the large-surface-density region is greater than the target surface density; the surface density standard area and the surface density change area are compared, a to-be-cleaned area of the active coating on the designed pole piece is determined, and the to-be-cleaned area is located in a 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. According to the scheme provided by the invention, the manufacturing cost of the square winding battery can be reduced, and the electrical performance and the cycle life of the square winding battery are improved.

Description

Technical Field

[0001] The present application relates to the technical field of wound batteries, and in particular to a method for preparing a square wound battery electrode sheet and a square wound battery. Background Art

[0002] In the manufacturing process of square wound batteries, the winding shape of the pole piece causes the accumulation or sparseness of active materials in local areas of the pole piece (such as the bending area) after winding, 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 electrical performance and service life of the battery. The coating process of the related technology has limitations in controlling the uniformity of the coating surface density, making it difficult to achieve high-precision and high-efficiency coating surface density adjustment, and unable to avoid the accumulation or sparseness of active materials in local areas of the pole piece caused by the winding of the pole piece.

[0003] Related technologies adjust the coating surface density by mechanical scraping or chemical etching to avoid accumulation or sparseness of active materials in local areas of the pole piece caused by pole piece winding. However, the related technologies for adjusting the coating surface density have the following problems:

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

[0005] (2) more manual 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 reusing between batches, making it difficult to apply it to 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, thereby affecting the wettability of the electrolyte and the electrochemical performance of the battery;

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

[0009] In short, the relevant technology cannot handle the coating surface density, especially the accumulation or sparseness of active materials in the local area of ​​the electrode caused by the winding of the electrode well, which increases the manufacturing cost of the square wound battery and reduces the electrical performance and cycle life of the square wound battery. Summary of the invention

[0010] In order to solve or partially solve the problems existing in the related art, the present application provides a method for preparing a square wound battery electrode sheet and a square wound battery, which can reduce the manufacturing cost of the square wound battery and improve the electrical performance and cycle life of the square wound battery.

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

[0012] Obtaining a designed pole piece with a current collector and an active coating;

[0013] Winding the designed pole piece and diaphragm to form a reference square winding core;

[0014] Measuring each turn of the reference square winding core to determine a standard area of ​​surface density and a surface density variation area of ​​the active coating on the designed pole piece after winding, wherein the surface density of the standard area of ​​surface density is a target surface density, the surface density of the surface density variation area is different from the target surface density, the surface density variation area includes a large surface density area, and the surface density of the large surface density area is greater than the target surface density;

[0015] Comparing the standard surface density area with the surface density variation area, determining the area to be cleaned of the active coating on the designed pole piece, wherein the area to be cleaned is located in the high surface density area;

[0016] According to the to-be-cleaned area of ​​the designed pole piece, the designed pole piece is laser cleaned to obtain the target pole piece of the square wound battery.

[0017] Preferably, the step of winding the designed pole piece and the diaphragm to form a reference square winding core comprises:

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

[0019] Preferably, measuring each turn of the reference square winding core to determine the standard area of ​​surface density and the area of ​​surface density variation of the active coating on the designed pole piece after winding includes:

[0020] The designed pole piece of each turn of the reference square winding core is measured to determine the standard surface density area and the surface density variation area of ​​the active coating alternately distributed along the winding direction of the designed pole piece after winding, wherein the standard surface density area corresponds to the straight area of ​​the designed pole piece in the winding direction, and the surface density variation area corresponds to the curved area of ​​the designed pole piece after winding, and the inner side of the curved area of ​​each turn of the designed pole piece is the high surface density area.

[0021] Preferably, the electrode sheet design includes designing a negative electrode sheet and designing a positive electrode sheet;

[0022] The comparing the standard surface density area with the surface density variation area to determine the area to be cleaned of the active coating on the designed pole piece includes:

[0023] Compare the surface density standard area of ​​the designed negative electrode sheet and the surface density variation area of ​​the designed negative electrode sheet, compare the surface density standard area of ​​the designed positive electrode sheet and the surface density variation area of ​​the designed positive electrode sheet, compare the surface density variation area of ​​the two relative layers of the designed negative electrode sheet and the surface density variation area of ​​the designed positive electrode sheet, and respectively 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.

[0024] Preferably, both the front and back sides of the designed pole piece have the active coating;

[0025] The determining of the surface density variation region of the active coating on the designed pole piece after winding also includes: determining the outer side of the bending region of each turn of the designed pole piece as a small surface density region;

[0026] The step of comparing the standard area of ​​the surface density of the designed negative electrode sheet with the area of ​​the surface density variation of the designed negative electrode sheet, comparing the standard area of ​​the surface density of the designed positive electrode sheet with the area of ​​the surface density variation of the designed positive electrode sheet, and comparing the area of ​​the surface density variation of the designed negative electrode sheet with the area of ​​the surface density variation of the designed positive electrode sheet, and respectively determining the area to be cleaned of the active coating on the designed negative electrode sheet and the active coating on the designed positive electrode sheet, comprises:

[0027] comparing the surface density standard area of ​​the designed negative electrode sheet with the surface density variation area of ​​the designed negative electrode sheet,

[0028] comparing the surface density standard area of ​​the designed positive electrode sheet with the surface density variation area of ​​the designed positive electrode sheet,

[0029] Comparing the large surface density area of ​​the designed negative electrode plate with the small surface density area of ​​the designed positive electrode plate opposite thereto, determining the area to be cleaned of the active coating on the designed negative electrode plate, so that the surface density ratio of the large surface density area of ​​the designed negative electrode plate to the small surface density area of ​​the designed positive electrode plate opposite thereto is equal to the surface density ratio of the surface density standard area of ​​the designed negative electrode plate to the surface density standard area of ​​the designed positive electrode plate;

[0030] Compare the small surface density area of ​​the designed negative electrode plate and the large surface density area of ​​the designed positive electrode plate opposite thereto, and determine the area to be cleaned of the active coating on the designed positive electrode plate, so that the surface density ratio of the small surface density area of ​​the designed negative electrode plate and the large surface density area of ​​the designed positive electrode plate opposite thereto is equal to the surface density ratio of the standard surface density area of ​​the designed negative electrode plate and the standard surface density area of ​​the designed positive electrode plate.

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

[0032] The regional parameters of the area to be cleaned of the active coating on the designed negative electrode plate and the regional parameters of the area to be cleaned of the active coating on the designed positive electrode plate are determined respectively, and the regional parameters include one or a combination of the regional position 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, the step of laser cleaning the designed pole piece according to the area to be cleaned of the designed pole piece to obtain the target pole piece of the square wound battery includes:

[0034] Determining a cleaning path of the designed negative electrode sheet according to the area parameters of the to-be-cleaned area of ​​the designed negative electrode sheet;

[0035] The cleaning path of the designed positive electrode sheet is determined according to the area parameters of the area to be cleaned of the designed positive electrode sheet.

[0036] Preferably, the step of determining the cleaning path of the designed negative electrode sheet according to the area parameter of the area to be cleaned of the designed negative electrode sheet further comprises:

[0037] Determine the cleaning thickness of the area to be cleaned of the designed negative electrode plate according to the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area of ​​the designed negative electrode plate, the coating thickness and the coating surface density of the area to be cleaned of the designed negative electrode plate;

[0038] The step of determining a cleaning path of the designed positive electrode sheet according to the area parameter of the area to be cleaned of the designed positive electrode sheet further includes:

[0039] According to the corresponding relationship between the coating thickness and the coating surface density in the surface density standard area of ​​the designed positive electrode plate, the coating thickness and coating surface density of the area to be cleaned of the designed positive electrode plate are determined, and the cleaning thickness of the area to be cleaned of the designed positive electrode plate is determined.

[0040] Preferably, the step of laser cleaning the designed pole piece according to the area to be cleaned of the designed pole piece to obtain the target pole piece of the square wound battery includes:

[0041] Determining cleaning parameters of the area to be cleaned of the designed negative electrode sheet according to the area parameters and cleaning thickness of the area to be cleaned of the designed negative electrode sheet;

[0042] Laser cleaning the designed negative electrode sheet according to the cleaning path and cleaning parameters of the to-be-cleaned area of ​​the designed negative electrode sheet to obtain the target negative electrode sheet of the square wound battery;

[0043] Determining cleaning parameters of the area to be cleaned of the designed positive electrode sheet according to the area parameters and cleaning thickness of the area to be cleaned of the designed positive electrode sheet;

[0044] The designed positive electrode sheet is laser cleaned 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.

[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 plate according to the area parameters and the cleaning thickness of the area to be cleaned of the designed negative electrode plate further includes:

[0047] According to the specific heat capacity, coating surface density and cleaning thickness of the active coating in the to-be-cleaned area of ​​the designed negative electrode plate, the laser power P of the laser cleaning equipment for laser cleaning the active coating in the to-be-cleaned area of ​​the designed negative electrode plate 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 is the cleaning thickness of the to-be-cleaned area of ​​the designed negative electrode plate;

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

[0051] ρ 负 is the coating surface density of the area to be cleaned of the designed negative electrode plate;

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

[0053] η 负 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 plate;

[0054] t 负 is the total time that the laser of the laser cleaning equipment acts on the active coating of the area to be cleaned of the designed negative electrode plate;

[0055] V 负 is the scanning speed of the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed negative electrode plate;

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

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

[0058] According to the specific heat capacity, coating surface density and cleaning thickness of the active coating in the area to be cleaned of the designed positive electrode plate, 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 plate 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 is the cleaning thickness of the area to be cleaned of the designed positive electrode plate;

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

[0062] ρ 正 is the coating surface density of the area to be cleaned of the designed positive electrode plate;

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

[0064] η 正 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 plate;

[0065] t 正 is the total time that the laser of the laser cleaning equipment acts on the active coating of the area to be cleaned of the designed positive electrode plate;

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

[0067] L 正 It is the total length of the laser moving in the area to be cleaned when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode plate.

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

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

[0070] According to the cleaning thickness of the to-be-cleaned area of ​​the designed negative electrode plate, the laser pulse frequency f of the laser cleaning equipment for laser cleaning the active coating of the to-be-cleaned area of ​​the designed negative electrode plate is determined. 负 ,in,

[0071] f 负 =Vm 负 / (S 负 ×τ 负 ),

[0072] Where Vm 负 is the tape speed at which the laser cleaning equipment performs laser cleaning on the designed negative electrode plate; τ 负 is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed negative electrode plate; S 负 The designed negative electrode plate is at the tape running speed Vm 负 During the duration τ 负 The moving distance;

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

[0074] According to the cleaning thickness of the to-be-cleaned area of ​​the designed positive electrode plate, the laser pulse frequency f of the laser cleaning equipment for laser cleaning the active coating of the to-be-cleaned area of ​​the designed positive electrode plate is determined. 正 ,in,

[0075] f 正 =Vm 正 / (S 正 ×τ 正 ),

[0076] Where, Vm 正 is the tape speed at which the laser cleaning equipment performs laser cleaning on the designed positive electrode plate; τ 正 is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed positive electrode plate; S 正 The designed positive electrode plate is at the tape running speed Vm 正 During the duration τ 正 moving distance.

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

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

[0079] A second aspect of the present application 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.

[0080] The technical solution provided by this application may have the following beneficial effects:

[0081] The technical solution of the present application first determines the surface density standard area and surface density variation area of ​​the active coating on the designed electrode after winding by measuring each circle of the reference square winding core, and then determines the area to be cleaned of the active coating on the designed electrode, and then laser cleans the designed electrode according to the area to be cleaned of the designed electrode to obtain the target electrode for the square wound battery; laser cleans the active coating in the curved surface density variation area of ​​the positive and negative electrodes of the square wound battery in advance, adjusts the coating surface density in the curved surface density variation area of ​​the positive and negative electrodes, improves the surface density distribution of the positive and negative electrodes after square winding, reduces the difference between the surface density ratio of the curved surface density variation area of ​​the positive and negative electrodes after square winding and the surface density ratio of the straight surface density standard area, reduces the difference between the N / P value of the curved surface density variation area of ​​the positive and negative electrodes after square winding and the difference between the N / P value of the curved surface density variation area of ​​the positive and negative electrodes after square winding and the difference between the N / P value of the curved surface density variation area of ​​the positive and negative electrodes and the non-curved area of ​​the positive and negative electrodes The difference in N / P values ​​in the curved area (straight surface density standard area) can significantly reduce the difference in local coating surface density of the positive and negative electrode sheets caused by the bending of the square winding of the positive and negative electrode sheets, so that the local performance of each positive and negative electrode sheet after square winding is more consistent, making the overall performance of the square wound battery more reliable, and can improve the electrical performance of the square wound battery; the N / P values ​​of the positive and negative electrode sheets after square winding are evenly distributed, which can avoid the increase in local internal resistance and local overheating caused by the uneven N / P value of the electrode sheet after square winding, and solve the problem of uneven current distribution caused by the variation of local N / P values ​​in the curved area of ​​the positive and negative electrode sheets. For square wound lithium-ion batteries, the possibility of local lithium precipitation in the curved area is reduced, which can improve the safety performance and cycle life of square wound batteries, and open up a new way to improve the safety performance and battery performance of square wound batteries.

[0082] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The above and other objects, features and advantages of the present application will become more apparent by describing in more detail exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0084] Figure 1 It is a schematic diagram of the process of preparing a square wound battery electrode sheet shown in an embodiment of the present application;

[0085] Figure 2 It is another schematic diagram of the process of preparing a square wound battery electrode sheet shown in an embodiment of the present application;

[0086] Figure 3 3 is a schematic diagram comparing the capacity retention rates of the square wound lithium-ion battery of the embodiment of the present application and the square wound lithium-ion battery of the comparative example. DETAILED DESCRIPTION

[0087] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0088] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more 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 the same type of information from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0090] The embodiment of the present application provides a method for preparing a square wound battery electrode sheet, which can reduce the manufacturing cost of the square wound battery and improve the electrical performance and cycle life of the square wound battery.

[0091] The technical solution of the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0092] Figure 1 It is a schematic diagram of the process of preparing a square wound battery electrode sheet shown in an embodiment of the present application.

[0093] See also Figure 1 , a method for preparing a square wound battery electrode sheet, comprising:

[0094] Step 101, obtaining a designed pole piece with a current collector and an active coating.

[0095] In one embodiment, the electrode sheets of the square wound battery include a negative electrode sheet and a positive electrode sheet. According to the design parameters of the square wound battery, the negative electrode collector and the negative electrode active material of the negative electrode sheet, the positive electrode collector and the positive electrode active material of the positive electrode sheet can be selected; the negative electrode slurry and the positive electrode slurry are prepared according to the negative electrode active material and the positive electrode active material respectively; the negative electrode slurry is applied to the negative electrode collector to obtain the designed negative electrode sheet with the negative electrode collector and the negative electrode active coating of the square wound battery; the positive electrode slurry is applied to the positive electrode collector to obtain the designed positive electrode sheet with the positive electrode collector and the positive electrode active coating of the square wound battery.

[0096] Step 102, winding the designed pole piece and the diaphragm to form a reference square winding core.

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

[0098] Step 103, measuring each turn of the reference square winding core to determine the standard area of ​​surface density and the area of ​​surface density variation of the active coating on the designed pole piece after winding.

[0099] In one embodiment, the designed negative electrode sheet and the designed positive electrode sheet in the reference square winding core have a straight area and a curved area, respectively, and the surface density and / or thickness of the designed negative electrode sheet and the designed positive electrode sheet of each circle of the reference square winding core are measured to obtain the surface density and / or thickness of the designed negative electrode sheet and the designed positive electrode sheet of each circle; according to the surface density and / or thickness of the designed negative electrode sheet and the designed positive electrode sheet of each circle, the straight surface density standard area and the curved surface density variation area of ​​the active coating on the designed negative electrode sheet after square winding can be determined, and the straight surface density standard area and the curved surface density variation area of ​​the active coating on the designed positive electrode sheet after square winding are determined, the surface density of the surface density standard area of ​​the designed negative electrode sheet is the target surface density of the designed negative electrode sheet, the surface density of the surface density standard area of ​​the designed positive electrode sheet is the target surface density of the designed positive electrode sheet, the surface density of the surface density variation area is different from the target surface density, and the surface density variation area includes a large surface density area, and the surface density of the large surface density area is greater than the target surface density.

[0100] Step 104 , comparing the standard area of ​​surface density and the area of ​​surface density variation to determine the area to be cleaned of the active coating on the designed pole piece.

[0101] In one embodiment, the surface density and / or thickness of the surface density standard area and surface density variation area of ​​the designed negative electrode plate and the designed positive electrode plate can be compared, the surface density and / or thickness of the surface density standard area and large surface density area of ​​the designed negative electrode plate, the surface density and / or thickness of the surface density standard area and large surface density area of ​​the designed positive electrode plate, and the surface density and / or thickness of the large surface density area of ​​the designed negative electrode plate and the designed positive electrode plate can be compared, the area to be cleaned of the large surface density area of ​​the designed negative electrode plate is determined, the area to be cleaned of the large surface density area of ​​the designed positive electrode plate is determined, and the area to be cleaned of the active coating on the designed negative electrode plate and the active coating on the designed positive electrode plate is determined.

[0102] Step 105 , laser cleaning the designed pole piece according to the area to be cleaned of the designed pole piece, to obtain the target pole piece of the square wound battery.

[0103] In one embodiment, laser cleaning equipment can be used to perform laser cleaning on the active coating in the designed positive electrode area to be cleaned according to the designed positive electrode area to be cleaned, and the designed positive electrode area to be cleaned is removed to obtain the target positive electrode of the square wound battery; laser cleaning equipment can be used to perform laser cleaning on the active coating in the designed negative electrode area to be cleaned according to the designed negative electrode area to be cleaned, and the designed negative electrode area to be cleaned is removed to obtain the target negative electrode of the square wound battery; so that after the target positive electrode and the target negative electrode are squarely wound according to the design parameters of the square wound battery, the surface density ratio of the target positive electrode and the target negative electrode in the curved surface density change area is consistent with the surface density ratio of the target positive electrode and the target negative electrode in the straight surface density standard area, and the N / P value of the target positive electrode and the target negative electrode in the curved surface density change area is consistent with the N / P value of the target positive electrode and the target negative electrode in the non-curved area (straight surface density standard area).

[0104] The square wound battery electrode sheet preparation method of the embodiment of the present application first determines the surface density standard area and surface density variation area of ​​the active coating on the designed electrode sheet after winding by measuring each circle of the reference square winding core, and then determines the area to be cleaned of the active coating on the designed electrode sheet, and then laser cleans the designed electrode sheet according to the area to be cleaned of the designed electrode sheet to obtain the target electrode sheet for the square wound battery; laser cleans the active coating in the curved surface density variation area of ​​the positive and negative electrode sheets of the square wound battery in advance, adjusts the coating surface density in the curved surface density variation area of ​​the positive and negative electrode sheets, improves the surface density distribution of the positive and negative electrode sheets after square winding, reduces the difference in surface density ratio between the curved surface density variation area of ​​the positive and negative electrode sheets after square winding and the straight surface density standard area, and reduces the N / P value and the difference in the curved surface density variation area of ​​the positive and negative electrode sheets after square winding. The difference in N / P values ​​in the non-bending areas (flat surface density standard areas) of the positive and negative electrode sheets can significantly reduce the difference in local coating surface density of the positive and negative electrode sheets caused by the bending of the square winding of the positive and negative electrode sheets, so that the local performance of each electrode sheet of the positive and negative electrode sheets after square winding is more consistent, making the overall performance of the square wound battery more reliable, and can improve the electrical performance of the square wound battery; the N / P values ​​of the positive and negative electrode sheets after square winding are evenly distributed, which can avoid the increase in local internal resistance and local overheating caused by uneven N / P values ​​of the electrode sheets after square winding, and solve the problem of uneven current distribution caused by local N / P value variation in the bending area of ​​the positive and negative electrode sheets. For square wound lithium-ion batteries, the possibility of local lithium precipitation in the bending area is reduced, which can improve the safety performance and cycle life of square wound batteries, and open up a new way to improve the safety performance and battery performance of square wound batteries.

[0105] Figure 2 It is another schematic diagram of the process of preparing a square wound battery electrode sheet shown in an embodiment of the present application.

[0106] See also Figure 2 , a method for preparing a square wound battery electrode sheet, comprising:

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

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

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

[0110] Step 202 , physically or simulatedly wind the designed negative electrode sheet, the designed positive electrode sheet and the separator to form a reference square winding core.

[0111] In one embodiment, the designed electrode sheet and separator of the square wound battery can be physically wound or simulated to form a reference square core. According to the design parameters of the square wound battery, the designed negative electrode sheet, the designed positive electrode sheet and the separator of the square wound battery can be physically wound to obtain the reference square core of the square wound battery; or, the length, width and thickness of the designed negative electrode sheet, the designed positive electrode sheet and the separator can be obtained by laser thickness measurement or X-ray thickness measurement, and according to the surface density of the designed negative electrode sheet, the designed positive electrode sheet, the design parameters of the square wound battery, and the length, width and thickness of the designed negative electrode sheet, the designed positive electrode sheet and the separator, combined with high-precision image recognition and analysis technology, the designed negative electrode sheet, the designed positive electrode sheet and the separator are simulated and wound to form a reference square core through software simulation to obtain a three-dimensional model of the reference square core.

[0112] Step 203, measuring the designed negative electrode sheet and the designed positive electrode sheet of each circle of the reference square winding core, and determining the surface density standard area and surface density variation area of ​​the designed negative electrode sheet and the designed positive electrode sheet after winding.

[0113] In one embodiment, the designed pole piece of each circle of the reference square winding core can be measured to determine the standard surface density area and the surface density variation area of ​​the active coating alternately distributed along the winding direction of the designed pole piece after winding, wherein the standard surface density area corresponds to the straight area of ​​the designed pole piece in the winding direction, the surface density variation area corresponds to the curved area of ​​the designed pole piece in the winding direction, the curved inner side of the curved area of ​​each circle of the designed pole piece is the large surface density area, the surface density of the standard surface density area is the target surface density, the surface density of the surface density variation area is different from the target surface density, the surface density variation area includes a large surface density area, and the surface density of the large surface density area is greater than the target surface density.

[0114] In one embodiment, the designed negative electrode sheet and the designed positive electrode sheet in the reference square winding core are respectively alternately distributed with straight areas and curved areas in their winding directions, and the surface density and / or thickness of the designed negative electrode sheet and the designed positive electrode sheet of each circle of the reference square winding core are measured to obtain the surface density and / or thickness of the designed negative electrode sheet and the designed positive electrode sheet of each circle; according to the surface density and / or thickness of the designed negative electrode sheet and the designed positive electrode sheet of each circle, the position, area, three-dimensional shape, surface density, and thickness of the straight surface density standard area of ​​the designed negative electrode sheet after square winding can be determined, and the curved surface density change area of ​​the designed negative electrode sheet after square winding can be determined. The position, area, three-dimensional shape, surface density, thickness of the domain, as well as the position, area, three-dimensional shape, surface density, and thickness of the large surface density area on the inner side of the bend of the surface density change area of ​​the negative electrode sheet designed after square winding; determine the position, area, three-dimensional shape, surface density, and thickness of the straight surface density standard area of ​​the positive electrode sheet designed after square winding, determine the position, area, three-dimensional shape, surface density, and thickness of the curved surface density change area of ​​the positive electrode sheet designed after square winding, as well as the position, area, three-dimensional shape, surface density, and thickness of the inner side of the bend of the large surface density area of ​​the surface density change area of ​​the positive electrode sheet designed after square winding.

[0115] Step 204, determine the area to be cleaned of the high surface density area of ​​the designed negative electrode plate, and determine the area to be cleaned of the high surface density area of ​​the designed positive electrode plate.

[0116] In one embodiment, the surface density standard area of ​​the designed negative electrode plate and the surface density variation area of ​​the designed negative electrode plate can be compared, the surface density standard area of ​​the designed positive electrode plate and the surface density variation area of ​​the designed positive electrode plate can be compared, and the surface density variation area of ​​two relatively layers of the designed negative electrode plate and the surface density variation area of ​​the designed positive electrode plate can be compared to determine the areas to be cleaned of the active coating on the designed negative electrode plate and the active coating on the designed positive electrode plate, respectively.

[0117] In one embodiment, the front and back surfaces of the designed pole piece are both provided with active coatings; determining the surface density change area of ​​the active coating on the designed pole piece after winding also includes: determining the curved outer side of the curved area of ​​each circle of the designed pole piece as a small surface density area.

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

[0119] In one embodiment, the surface density of the standard surface density area of ​​the designed negative electrode pole sheet can be compared with the surface density of the change surface density area of ​​the designed negative electrode pole sheet, and the inner curved area corresponding to the surface density of the change surface density area of ​​the designed negative electrode pole sheet is greater than the surface density of the standard surface density area of ​​the designed negative electrode pole sheet, and the outer curved area corresponding to the surface density of the change surface density area of ​​the designed negative electrode pole sheet is less than the surface density of the standard surface density area of ​​the designed negative electrode pole sheet as the small surface density area of ​​the designed negative electrode pole sheet.

[0120] In one embodiment, the surface density of the standard surface density area of ​​the designed positive electrode pole piece can be compared with the surface density of the change surface density area of ​​the designed positive electrode pole piece, and the inner curved area corresponding to the surface density of the change surface density area of ​​the designed positive electrode pole piece is greater than the surface density of the standard surface density area of ​​the designed positive electrode pole piece, and the outer curved area corresponding to the surface density of the change surface density area of ​​the designed positive electrode pole piece is less than the surface density of the standard surface density area of ​​the designed positive electrode pole piece as the small surface density area of ​​the designed positive electrode pole piece.

[0121] In one embodiment, the surface density of the large surface density area of ​​the designed negative electrode pole piece can be compared with the surface density of the small surface density area of ​​the designed positive electrode pole piece opposite thereto, and based on the surface density ratio of the surface density of the standard surface density area of ​​the designed negative electrode pole piece to the surface density of the standard surface density area of ​​the designed positive electrode pole piece opposite thereto, the surface density of the small surface density area of ​​the designed positive electrode pole piece opposite thereto is used as a reference to determine the area to be cleaned of the large surface density area of ​​the designed negative electrode pole piece, so that after the large surface density area of ​​the designed negative electrode pole piece is laser cleaned according to the area to be cleaned, the surface density ratio of the large surface density area of ​​the designed negative electrode pole piece to the small surface density area of ​​the designed positive electrode pole piece opposite thereto is equal to the surface density ratio of the standard surface density area of ​​the designed negative electrode pole piece to the standard surface density area of ​​the designed positive electrode pole piece.

[0122] In one embodiment, the surface density of the small surface density area of ​​the designed negative electrode pole piece can be compared with the surface density of the large surface density area of ​​the designed positive electrode pole piece opposite thereto, and based on the surface density ratio of the surface density of the standard surface density area of ​​the designed negative electrode pole piece to the surface density of the standard surface density area of ​​the designed positive electrode pole piece opposite thereto, the surface density of the small surface density area of ​​the designed negative electrode pole piece is used as a reference to determine the area to be cleaned of the large surface density area of ​​the designed positive electrode pole piece opposite thereto, so that after the large surface density area of ​​the designed positive electrode pole piece opposite thereto is laser cleaned according to the area to be cleaned, the surface density ratio of the small surface density area of ​​the designed negative electrode pole piece to the large surface density area of ​​the designed positive electrode pole piece opposite thereto is equal to the surface density ratio of the standard surface density area of ​​the designed negative electrode pole piece to the surface density standard area of ​​the designed positive electrode pole piece.

[0123] In one embodiment, the area to be cleaned of the large surface density area of ​​the designed electrode is an area formed by bending the designed electrode after square winding of the designed electrode of a square wound battery, and the surface density is greater than the surface density of the straight area (surface density standard area) of the designed electrode. It is an area where the designed electrode of the square wound battery is bent after square winding, causing the active coating of the designed electrode to accumulate under the action of bending, and the thickness of the active coating changes, resulting in the coating surface density being greater than the coating surface density of the standard surface density area.

[0124] In a specific embodiment, after the designed positive electrode sheet, the designed negative electrode sheet and the separator of the square wound battery are squarely wound, the surface density of the active coating in the surface density change area of ​​the designed positive electrode sheet and the surface density change area of ​​the designed negative electrode sheet changes under the action of bending, and the surface density of the curved inner concave area of ​​the designed positive electrode coating surface density change area is greater than the surface density of the straight surface density standard area, and the curved inner concave area corresponding to the surface density of the surface density change area of ​​the designed positive electrode sheet is greater than the surface density of the surface density standard area of ​​the designed positive electrode sheet is determined as the large surface density area of ​​the designed positive electrode sheet; the surface density of the curved outer convex area of ​​the designed positive electrode coating surface density change area is less than the surface density of the straight surface density standard area, and the surface density of the surface density change area of ​​the designed positive electrode sheet is less than the surface density of the straight surface density standard area. The curved outer convex area corresponding to the surface density of the standard surface density area of ​​the designed positive electrode pole piece is determined as the small surface density area of ​​the designed positive electrode pole piece; the surface density of the curved inner concave area of ​​the surface density change area of ​​the designed negative electrode coating is greater than the surface density of the straight surface density standard area, and the curved inner concave area corresponding to the surface density of the surface density change area of ​​the designed negative electrode pole piece is greater than the surface density of the surface density standard area of ​​the designed negative electrode pole piece is determined as the large surface density area of ​​the designed negative electrode pole piece; the surface density of the curved outer convex area of ​​the surface density change area of ​​the designed negative electrode coating is less than the surface density of the straight surface density standard area, and the curved outer convex area corresponding to the surface density of the surface density change area of ​​the designed negative electrode pole piece is less than the surface density of the surface density standard area of ​​the designed negative electrode pole piece is determined as the small surface density area of ​​the designed negative electrode pole piece.

[0125] For example, the coating surface density of the positive electrode sheet of the square wound battery is set to 220g / m 2 , set the coating surface density of the negative electrode sheet to 120g / m 2 After the square wound battery is set with the positive electrode sheet and the negative electrode sheet being wound in a square shape, the coating surface density of the curved inner concave area of ​​the curved surface density change area of ​​the positive electrode sheet is set to be greater than 220g / m 2 The inner concave area of ​​the curved surface density change area of ​​the positive electrode sheet is determined as the high surface density area of ​​the positive electrode sheet, and the coating surface density of the outer convex area of ​​the curved surface density change area of ​​the positive electrode sheet is set to be less than 220g / m 2 The outer convex area of ​​the curved surface density change area of ​​the positive electrode sheet is determined as the small surface density area of ​​the positive electrode sheet; the coating surface density of the inner concave area of ​​the curved surface density change area of ​​the negative electrode sheet is set to be greater than 120g / m 2 The inner concave area of ​​the curved surface density change area of ​​the negative electrode plate is determined as the high surface density area of ​​the negative electrode plate, and the coating surface density of the outer convex area of ​​the curved surface density change area of ​​the negative electrode plate is set to be less than 120g / m 2The convex area outside the curved surface density change area of ​​the negative electrode pole piece is determined as the small surface density area of ​​the negative electrode pole piece.

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

[0127] In one embodiment, the surface density of the standard surface density area of ​​the designed negative electrode pole piece can also be compared with the surface density of the standard surface density area of ​​the designed positive electrode pole piece, and the surface density of the large surface density area of ​​the designed negative electrode pole piece and the surface density of the small surface density area of ​​the designed positive electrode pole piece can be compared to determine the regional parameters of the area to be cleaned in the large surface density area of ​​the designed negative electrode pole piece. The regional parameters include one or a combination of the regional position 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.

[0128] In one embodiment, the surface density of the standard surface density area of ​​the designed negative electrode plate can also be compared with the surface density of the standard surface density area of ​​the designed positive electrode plate, and the surface density of the small surface density area of ​​the designed negative electrode plate and the surface density of the large surface density area of ​​the designed positive electrode plate can be compared to determine the regional parameters of the area to be cleaned in the large surface density area of ​​the designed positive electrode plate. The regional parameters include one or a combination of the regional position 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.

[0129] In one embodiment, the area to be cleaned of the large surface density area of ​​the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery can be determined by software simulation based on the three-dimensional model of the designed positive electrode sheet and the designed negative electrode sheet after square winding. The area to be cleaned of the large surface density area of ​​the designed negative electrode sheet and the large surface density area of ​​the designed positive electrode sheet can be determined by software simulation based on the surface density of the standard surface density area of ​​the designed negative electrode sheet, the surface density of the large surface density area of ​​the designed negative electrode sheet, and the surface density of the small surface density area of ​​the designed positive electrode sheet opposite thereto, as well as the surface density of the standard surface density area of ​​the designed positive electrode sheet, the surface density of the small surface density area of ​​the designed negative electrode sheet, and the surface density of the large surface density area of ​​the designed positive electrode sheet opposite thereto.

[0130] In one embodiment, the areas to be cleaned of the large surface density areas of the designed positive electrode sheet and the designed negative electrode sheet can be regionally located based on the three-dimensional models of the designed positive electrode sheet and the designed negative electrode sheet after square winding through software, and the specific areas of the designed positive electrode sheet and the designed negative electrode sheet where the coating surface density increases due to the bending of the electrode sheet can be determined respectively, and the positions of the inner concave areas of the bending can be determined, so as to find out the local areas where the coating surface density of the designed positive electrode sheet and the designed negative electrode sheet is uneven, and determine the regional positions of the areas to be cleaned of each large surface density area of ​​the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery.

[0131] In one embodiment, based on the three-dimensional model of the designed positive electrode plate and the designed negative electrode plate after square winding, the specific area of ​​the curved inner concave area and / or the local area where the coating surface density of each designed positive electrode plate and the designed negative electrode plate changes can be calculated through software to determine the coating area of ​​the active coating in the area to be cleaned in each large surface density area of ​​the designed positive electrode plate and the designed negative electrode plate.

[0132] In one embodiment, the three-dimensional model of the designed positive electrode sheet and the designed negative electrode sheet after square winding can be used to calculate the coating thickness and coating surface density of each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet through software according to the coating thickness and coating surface density of the surface density standard area of ​​the designed positive electrode sheet and the designed negative electrode sheet, as well as the corresponding relationship between the coating thickness and coating surface density of the surface density standard area of ​​the designed positive electrode sheet and the corresponding relationship between the coating thickness and coating surface density of the surface density standard area of ​​the designed negative electrode sheet; for each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet, the actual coating thickness of each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet (the coating thickness of the inner side of the bend), and the corresponding relationship between the coating thickness and coating surface density of the surface density standard area of ​​the designed positive electrode sheet and the designed negative electrode sheet can be calculated. The coating thickness and coating surface density of the surface density standard area, the corresponding relationship between the coating thickness and coating surface density of the surface density standard area of ​​the designed positive electrode plate, and the corresponding relationship between the coating thickness and coating surface density of the surface density standard area of ​​the designed negative electrode plate, calculate the coating surface density and coating thickness after cleaning of each area to be cleaned of the designed positive electrode plate and the designed negative electrode plate, and calculate the deviation between the actual coating surface density of each area to be cleaned of the designed positive electrode plate and the designed negative electrode plate and the coating surface density of the surface density standard area, calculate the surface density deviation of each area to be cleaned of the designed positive electrode plate and the designed negative electrode plate, and calculate the deviation between the actual coating thickness of each area to be cleaned of the designed positive electrode plate and the designed negative electrode plate and the coating thickness of the surface density standard area, and calculate the thickness deviation of each area to be cleaned of the designed positive electrode plate and the designed negative electrode plate.

[0133] In one embodiment, the three-dimensional model of the designed positive electrode sheet and the designed negative electrode sheet after square winding can be used to obtain the three-dimensional shape of each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet through 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 regional parameters of the area to be cleaned of the designed negative electrode plate may also include determining the coating material properties of the area to be cleaned of the designed negative electrode plate of the square wound battery, the coating material properties including but not limited to the components of the active coating of the area to be cleaned, and the physical and chemical properties of the components. Determining the regional parameters of the area to be cleaned of the designed positive electrode plate may also include determining the coating material properties of the area to be cleaned of the designed positive electrode plate of the square wound battery, the coating material properties including but not limited to the components of the active coating of the area to be cleaned, and the physical and chemical properties of the components.

[0135] In one embodiment, before stacking the designed positive electrode sheets and the designed negative electrode sheets that meet the design parameters of the square wound battery in a square shape and winding them, the corresponding relationship between the coating surface density and the coating thickness in the surface density standard area of ​​the designed positive electrode sheets and the corresponding relationship between the coating surface density and the coating thickness in the surface density standard area of ​​the designed negative electrode sheets can be obtained based on the coating thickness and the coating surface density of the designed positive electrode sheets and the coating thickness and the coating surface density of the designed negative electrode sheets that meet the design parameters.

[0136] In one embodiment, the designed positive electrode sheet, separator, and designed negative electrode sheet of a square wound battery can be stacked and then wound in a square shape to obtain a reference square battery cell of the square wound battery; the coating thickness of the designed positive electrode sheet and the designed negative electrode sheet of the reference square battery cell can be respectively obtained by laser thickness measurement or X-ray thickness measurement; according to the coating thickness of the designed positive electrode sheet and the designed negative electrode sheet of the reference square battery cell, the area where the coating thickness of the designed positive electrode sheet and the designed negative electrode sheet of the reference square battery cell changes is determined; according to the area where the coating thickness of the designed positive electrode sheet and the designed negative electrode sheet of the reference square battery cell changes, and the coating thickness of the surface density standard area of ​​the designed positive electrode sheet is determined; The correspondence between the layer density and the coating thickness and the correspondence between the coating surface density and the coating thickness in the surface density standard area of ​​the designed negative electrode sheet are used to obtain the surface density change area where the coating surface density of the designed positive electrode sheet and the designed negative electrode sheet changes, and determine the small surface density area and the large surface density area of ​​the surface density change area of ​​the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery; according to the coating surface density in the surface density standard area of ​​the designed positive electrode sheet and the coating surface density in the surface density standard area of ​​the designed negative electrode sheet, determine the coating surface density of the small surface density area and the large surface density area of ​​the surface density change area of ​​the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery.

[0137] In one embodiment, the area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery can be determined based on the small surface density area and the coating surface density of the large surface density area of ​​the surface density change area of ​​the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery, and the regional parameters of the area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet of the square wound battery can be determined.

[0138] Step 205, determine and design a cleaning path for the negative electrode sheet, and determine and design a cleaning path for the positive electrode sheet.

[0139] In one embodiment, the cleaning path of the designed negative electrode sheet can be determined according to the regional parameters of the area to be cleaned of the designed negative electrode sheet; the cleaning path of the designed positive electrode sheet can be determined according to the regional parameters of the area to be cleaned of the designed positive electrode sheet.

[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 of the designed negative electrode sheet according to the cleaning path of the designed negative electrode sheet. The cleaning path of the laser cleaning device for laser cleaning each area to be cleaned of the designed negative electrode sheet of the square wound battery can be accurately determined according to the area position, coating area, coating thickness, coating surface density, coating three-dimensional morphology, and coating material properties of each area to be cleaned of the designed negative electrode sheet of the square wound battery, including but not limited to determining to laser clean each area to be cleaned of the designed negative electrode sheet, determining the cleaning position of each area to be cleaned of the designed negative electrode sheet by laser cleaning, and determining the cleaning area of ​​each area to be cleaned of the designed negative electrode sheet by laser cleaning, so that the laser cleaning device can laser clean the active coating of each area to be cleaned of the designed negative electrode sheet according to the cleaning thickness of each area to be cleaned of the designed negative electrode sheet and the cleaning path of the designed negative electrode sheet, and obtain the target negative electrode sheet of the square wound battery.

[0141] In one embodiment, the cleaning area of ​​each to-be-cleaned region of the negative electrode plate may be designed to be the coating area of ​​the active coating in the high-area density region of the negative electrode plate.

[0142] In one embodiment, the cleaning path of the laser cleaning equipment for laser cleaning each area to be cleaned of the designed positive electrode sheet of the square wound battery can be accurately determined based on the area position, coating area, coating thickness, coating surface density, coating three-dimensional morphology, and coating material properties of each area to be cleaned of the designed positive electrode sheet, including but not limited to determining to laser clean each area to be cleaned of the designed positive electrode sheet, determining the cleaning position of laser cleaning each area to be cleaned of the designed positive electrode sheet, and determining the cleaning area of ​​laser cleaning each area to be cleaned of the designed positive electrode sheet, so that the laser cleaning equipment can laser clean the active coating of each area to be cleaned of the designed positive electrode sheet according to the cleaning thickness of each area to be cleaned of the designed positive electrode sheet and the cleaning path of the designed positive electrode sheet, and obtain the target positive electrode sheet of the square wound battery.

[0143] In one embodiment, the cleaning area of ​​each to-be-cleaned region of the positive electrode plate may be designed to be the coating area of ​​the active coating in the high-area density region of the positive electrode plate.

[0144] Step 206, determining the cleaning thickness of the area to be cleaned of the designed negative electrode plate, and determining the cleaning thickness of the area to be cleaned of the designed positive electrode plate.

[0145] In one embodiment, the coating thickness and coating surface density of the area to be cleaned of the negative electrode plate can be designed based on the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area of ​​the designed negative electrode plate, and the cleaning thickness of the area to be cleaned of the designed negative electrode plate can be determined; the coating thickness and coating surface density of the area to be cleaned of the positive electrode plate can be designed based on the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area of ​​the designed positive electrode plate, and the cleaning thickness of the area to be cleaned of the designed positive electrode plate can be determined.

[0146] In one embodiment, by adjusting the coating surface density of the large surface density area (concave area inside the bend) of each curved surface density change area after square winding of the designed negative electrode plate and the designed positive electrode plate, the surface density ratio of each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate after square winding can be made consistent with the surface density ratio of the designed negative electrode plate and the designed positive electrode coating surface density standard area, so that the N / P value of each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate after square winding is consistent with the N / P value of the designed negative electrode plate and the designed positive electrode coating surface density standard area.

[0147] In one embodiment, by adjusting the coating thickness of the large surface density area of ​​each curved surface density change area of ​​the designed negative electrode sheet and the designed positive electrode sheet after square winding, and adjusting the coating surface density of each curved surface density change area of ​​the designed negative electrode sheet and the designed positive electrode sheet after square winding, the surface density ratio of each curved surface density change area of ​​the designed negative electrode sheet and the designed positive electrode sheet after square winding can be achieved to be consistent with the surface density ratio of the standard area of ​​the designed negative electrode sheet and the designed positive electrode coating surface density.

[0148] In one embodiment, laser cleaning equipment can be used to perform laser cleaning on the active coating in the large surface density area of ​​each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate according to the cleaning thickness of the active coating in the large surface density area of ​​each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate, remove the active coating in the large surface density area of ​​each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate by the corresponding cleaning thickness, adjust the coating thickness of the large surface density area of ​​each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate after square winding, achieve the surface density ratio of each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate after square winding to be consistent with the surface density ratio of the straight surface density standard area of ​​the designed negative electrode plate and the designed positive electrode plate, and achieve the N / P value of each curved surface density change area of ​​the designed negative electrode plate and the designed positive electrode plate after square winding to be consistent with the N / P value of the straight surface density standard area.

[0149] In one embodiment, the coating surface density of each area to be cleaned of the designed positive electrode plate and the coating surface density of each area to be cleaned of the designed negative electrode plate can be obtained according to the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area (straight area) of the designed positive electrode plate of the square wound battery, the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area (straight area) of the designed negative electrode plate, and the coating thickness (coating thickness before cleaning) of each area to be cleaned (inner concave area of ​​the curve) of the designed positive electrode plate and the coating thickness (coating thickness before cleaning) of each area to be cleaned (inner concave area of ​​the curve) of the designed negative electrode plate; the coating surface density of each area to be cleaned of the designed positive electrode plate and the coating surface density of each area to be cleaned of the designed negative electrode plate can be obtained according to the coating surface density of each area to be cleaned of the designed positive electrode plate and the coating surface density of each area to be cleaned of the designed negative electrode plate, the coating surface density of the surface density standard area of ​​the designed positive electrode plate and the coating surface density of the surface density standard area of ​​the designed negative electrode plate.

[0150] In one embodiment, the coating thickness of each area to be cleaned of the designed positive electrode plate after cleaning and the coating thickness of each area to be cleaned of the designed negative electrode plate after cleaning can be obtained based on the coating surface density of each area to be cleaned of the designed positive electrode plate after cleaning and the coating surface density of each area to be cleaned of the designed negative electrode plate, as well as the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area of ​​the designed positive electrode plate and the coating surface density of the designed negative electrode plate; the cleaning thickness of each area to be cleaned of the designed positive electrode plate can be obtained based on the coating thickness of each area to be cleaned of the designed positive electrode plate after cleaning and the coating thickness before cleaning; the cleaning thickness of each area to be cleaned of the designed negative electrode plate can be obtained based on the coating thickness of each area to be cleaned of the designed negative electrode plate after cleaning and the coating thickness before cleaning; The laser cleaning equipment performs laser cleaning of the active coating of each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet according to the cleaning thickness of each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet, and adjusts the coating thickness of each area to be cleaned of the designed positive electrode sheet and the designed negative electrode sheet from the coating thickness before cleaning to the coating thickness after cleaning, respectively, to obtain the target positive electrode sheet and the target negative electrode sheet of the square wound battery; the surface density ratio of each curved surface density change area after the target positive electrode sheet and the target negative electrode sheet are squarely wound is made consistent with the surface density ratio of the straight surface density standard area, and the N / P value of each curved surface density change area after the target positive electrode sheet and the target negative electrode sheet are squarely wound is made consistent with the N / P value of the straight surface density standard area.

[0151] In another embodiment, the N / P value of each curved surface density change area of ​​the square wound positive electrode sheet and the designed negative electrode sheet after square winding can be determined according to the N / P value of the straight surface density standard area of ​​the square wound positive electrode sheet and the designed negative electrode sheet; the coating surface density of each curved surface density change area after square winding of the designed positive electrode sheet and the designed negative electrode sheet can be determined according to the N / P value of each curved surface density change area after square winding of the designed positive electrode sheet and the designed negative electrode sheet; the coating surface density of each curved surface density change area after square winding of the designed positive electrode sheet and the designed negative electrode sheet can be determined according to the N / P value of each curved surface density change area after square winding of the designed positive electrode sheet and the designed negative electrode sheet; The corresponding relationship between the coating thickness and the coating surface density of the straight surface density standard area and the corresponding relationship between the coating thickness and the coating surface density of the straight surface density standard area of ​​the designed negative electrode plate are used to determine the coating thickness after cleaning of the large surface density area of ​​each curved surface density change area after square winding of the designed positive electrode plate and the designed negative electrode plate; according to the coating thickness after cleaning of the large surface density area of ​​each curved surface density change area after square winding of the designed positive electrode plate and the designed negative electrode plate, and the coating thickness before cleaning of the large surface density area of ​​each curved surface density change area after square winding of the designed positive electrode plate and the designed negative electrode plate, the cleaning thickness of the active coating in each area to be cleaned of the designed positive electrode plate and the designed negative electrode plate is determined.

[0152] In one embodiment, the cleaning thickness of the area to be cleaned can be a set of continuous and gradually changing values, so that after the laser cleaning equipment laser cleans the active coating of each area to be cleaned of the designed pole piece according to the cleaning thickness of each area to be cleaned of the designed pole piece, not only the coating thickness of each area to be cleaned of the designed pole piece is adjusted accordingly from the coating thickness before cleaning to the coating thickness after cleaning, so that the surface density ratio of each curved surface density change area of ​​the target positive pole piece and the target negative pole piece after square winding is consistent with the surface density ratio of the flat surface density standard area, so that the N / P value of each curved surface density change area of ​​the target positive pole piece and the target negative pole piece after square winding is consistent with the N / P value of the flat surface density standard area, and the laser cleaning equipment laser cleans the large surface density area of ​​each curved surface density change area of ​​the target positive pole piece and the target negative pole piece to form an arc groove that is symmetrical along the length direction and / or the width direction of the pole piece and matches the three-dimensional shape of each curved surface density change 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, determining cleaning parameters for laser cleaning equipment to perform laser cleaning on the area to be cleaned of the designed negative electrode plate, and determining cleaning parameters for laser cleaning equipment to perform laser cleaning on the area to be cleaned of the designed positive electrode plate.

[0154] In one embodiment, when using high-precision laser cleaning equipment to laser clean the area to be cleaned of the designed pole piece according to the cleaning path, the cleaning parameters of the laser cleaning equipment for laser cleaning the area to be cleaned of the designed pole piece can be accurately determined according to the area position of the area to be cleaned of the designed pole piece of the square wound battery, the coating area, the coating thickness, the coating surface density, the coating three-dimensional morphology, one or a combination of the 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 laser power, laser pulse frequency, laser pulse width, unwinding tension, winding tension, tape speed, scanning speed, and spot diameter, to ensure that the laser cleaning of each area to be cleaned of the designed pole piece can be accurately controlled to achieve the set cleaning thickness for laser cleaning of each area to be cleaned of the designed pole piece, and to achieve the set laser cleaning effect, so that the surface density ratio of each curved surface density change area of ​​the positive and negative pole pieces after square winding is consistent with the surface density ratio of the straight surface density standard area, so that the N / P value of each curved surface density change area of ​​the positive and negative pole pieces after square winding is consistent with the N / P value of the straight surface density standard area of ​​the positive and negative pole pieces.

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

[0156] In one embodiment, the cleaning parameters of the laser cleaning device can be optimized through the processes of preliminary setting, experimental testing, data analysis and gradual adjustment according to the regional position of the to-be-cleaned area of ​​the designed negative electrode sheet and the designed positive electrode sheet of the square wound battery, the coating area, the coating surface density, the coating thickness, the coating three-dimensional morphology, and one or a combination of the coating material properties, and the cleaning thickness of the to-be-cleaned area of ​​the designed negative electrode sheet and the designed positive electrode sheet, and finally the cleaning parameters of the laser cleaning device for laser cleaning the active coating of the to-be-cleaned area of ​​the designed negative electrode sheet and the designed positive electrode sheet are determined respectively, and the laser cleaning device optimizes the cleaning parameters according to the cleaning path, the cleaning parameters ... The active coating in the area to be cleaned is laser cleaned to achieve the cleaning thickness set by laser cleaning, and the coating surface density of the designed negative electrode sheet and the designed positive electrode sheet of the square wound battery is accurately adjusted to obtain the target negative electrode sheet and the target positive electrode sheet of the square wound battery, so that the surface density ratio of each curved surface density change area of ​​the target negative electrode sheet and the target positive electrode sheet after square winding is 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 of ​​the target negative electrode sheet and the target positive electrode sheet after square winding is consistent with the N / P value of the flat surface density standard area of ​​the target negative electrode sheet and the target positive electrode sheet.

[0157] In one embodiment, the higher the laser power of the laser cleaning device, the stronger the ability to remove the active coating per unit time. If more active coatings need to be cleaned in a shorter time, that is, thicker active coatings need to be cleaned, a higher laser power can be selected, but too high a laser power may cause damage to the pole piece substrate, or may cause uncontrollable thermal effects, causing irreversible changes in the pole piece coating.

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

[0159] In one embodiment, the laser power P of the laser cleaning device for laser cleaning the active coating in the designed negative electrode plate to be cleaned can be determined according to the specific heat capacity, coating surface density and cleaning thickness of the active coating in the designed negative electrode plate 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 A is the cleaning thickness of the area to be cleaned of the negative electrode plate; 负 is the spot area of ​​the laser when the laser cleaning equipment cleans the area to be cleaned of the negative electrode; ρ 负 C is the coating surface density of the area to be cleaned of the designed negative electrode plate; 负 is the specific heat capacity of the active coating of the area to be cleaned of the negative electrode; η 负 is the efficiency of converting laser energy into the active coating of the area to be cleaned in the negative electrode plate designed for laser cleaning; 负 Vl is the total time that the laser cleaning equipment laser acts on the active coating in the area to be cleaned of the designed negative electrode plate; 负 It is the scanning speed of the laser when the laser cleaning equipment cleans the area to be cleaned of the negative electrode; L 负 It is the total length that the laser moves in the area to be cleaned when the laser cleaning equipment is used to clean the area to be cleaned of the negative electrode piece.

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

[0163]

[0164] In one embodiment, the laser power P of the laser cleaning device for laser cleaning the active coating in the area to be cleaned of the designed positive electrode plate can be determined according to the specific heat capacity, coating surface density and cleaning thickness of the active coating in the area to be cleaned of the designed positive electrode plate. 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 A is the cleaning thickness of the area to be cleaned of the positive electrode plate; 正 is the spot area of ​​the laser when the laser cleaning equipment is used to clean the area to be cleaned of the positive electrode; ρ 正 C is the surface density of the active coating in the area to be cleaned of the designed positive electrode; 正 is the specific heat capacity of the active coating of the area to be cleaned of the positive electrode; η 正 is the efficiency of converting laser energy into the active coating of the area to be cleaned in the positive electrode plate designed for laser cleaning; 正 Vl is the total time that the laser cleaning equipment laser acts on the active coating in the area to be cleaned of the positive electrode plate; 正 It is the scanning speed of the laser when the laser cleaning equipment cleans the area to be cleaned of the positive electrode piece; L 正 It is the total length that the laser moves in the area to be cleaned when the laser cleaning equipment is used to clean the area to be cleaned of the positive electrode piece.

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

[0168]

[0169] In one embodiment, the laser pulse frequency refers to the number of pulses emitted by the laser of the laser cleaning equipment per unit time. The higher the laser pulse frequency of the laser cleaning equipment, the stronger the ability to remove the active coating per unit time. If it is necessary to clean more active coatings in a shorter time, that is, to clean thicker active coatings, a higher laser pulse frequency can be selected to improve the laser cleaning efficiency. However, if the laser pulse frequency is too high, the superposition of the energy of each pulse on the surface of the active coating may cause local overheating of the pole piece, which may lead to uncontrollable thermal effects, causing irreversible changes in the coating of the pole piece, and affecting the quality of laser cleaning.

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

[0171] f 负 =Vm 负 / (S 负 ×τ 负 ),

[0172] Where Vm 负 It is the tape speed of the laser cleaning equipment for laser cleaning of the designed negative electrode, in m / s (meters per second); τ 负 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed negative electrode, in seconds; S 负 The negative electrode is designed to be at the tape speed Vm 负 In duration τ 负 moving distance.

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

[0174] f 正 =Vm 正 / (S 正 ×τ 正 ),

[0175] Where Vm 正 is the tape speed of the laser cleaning equipment for laser cleaning of the designed positive electrode; τ 正 It is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed positive electrode; S 正The positive electrode is designed to be at the tape speed Vm 正 In duration τ 正 moving distance.

[0176] In one embodiment, in order to ensure that each laser pulse can leave a complete light spot in each area to be cleaned of the designed negative electrode piece and the designed positive electrode piece, and that there is sufficient overlap between the light spots, and to ensure that the laser energy is evenly distributed and evenly covered in each area to be cleaned of the designed negative electrode piece and the designed positive electrode piece, so as to achieve effective and uniform laser cleaning of the active coating in each area to be cleaned of the designed negative electrode piece and the designed positive electrode piece, the designed negative electrode piece is at a tape speed Vm. 负 , each pulse duration τ 负 The negative electrode is designed to be at the tape speed Vm 负 In duration τ 负 The moving distance S 负 It should be a small part of the laser spot diameter D. Design the negative electrode to be at the tape speed Vm 负 In duration τ 负 The moving distance S 负 Less than or equal to one tenth of the spot diameter D of the laser cleaning equipment, in meters. In a specific embodiment, the negative electrode is designed to be at a tape speed Vm 负 In duration τ 负 The moving distance S 负 Equal to one tenth of the spot diameter D of the laser cleaning equipment; Design the positive electrode to be at the tape speed Vm 正 , each pulse duration τ 正 Design the positive electrode to be at the tape speed Vm 正 In duration τ 正 The moving distance S 正 It should be a small part of the laser spot diameter D. Design the positive electrode to be at the tape speed Vm 正 In duration τ 正 The moving distance S 正 Less than or equal to one tenth of the spot diameter D of the laser cleaning equipment. In a specific embodiment, the positive electrode is designed to be at a tape speed Vm 正 In duration τ 正 The moving distance S 正 It is equal to one tenth of the spot diameter D of the laser cleaning equipment.

[0177] In one embodiment, when the laser cleaning device performs laser cleaning on the active coating of the designed negative electrode plate and the designed positive electrode plate in the area to be cleaned, the designed negative electrode plate and the designed positive electrode plate can be fixed to the laser cleaning device, and the tape speed of the laser cleaning device refers to the moving speed of the designed negative electrode plate or the designed positive electrode plate relative to the laser source during the laser cleaning process of the designed negative electrode plate or the designed positive electrode plate. The laser scanning speed of the laser cleaning device is the moving speed of the laser beam of the laser cleaning device on the surface of the active coating of the area to be cleaned of the designed negative electrode plate or the designed positive electrode plate. The laser scanning speed and tape speed of the laser cleaning device both affect the residence time of the laser on the surface of the active coating of the designed negative electrode plate and the designed positive electrode plate, and thus affect the cleaning thickness. The faster the laser scanning speed, the shorter the laser irradiation time on the surface of the active coating, and the smaller the cleaning thickness; the slower the laser scanning speed, the longer the laser irradiation time on the surface of the active coating, and the greater the cleaning thickness. The faster the tape speed, the shorter the laser irradiation time on the active coating surface, and the smaller the cleaning thickness; the slower the tape speed, the longer the laser irradiation time on the active coating surface, and the greater the cleaning thickness. In laser cleaning, the tape speed of the laser cleaning equipment is required to match the laser scanning speed. The tape speed and the scanning speed match, including the tape speed and the scanning speed are equal, or the tape speed and the scanning speed meet the set multiple relationship, to ensure that the laser can evenly laser clean the active coating in the cleaning area of ​​the designed negative electrode and the designed positive electrode. If the tape speed is too fast and the laser scanning speed remains unchanged, the energy deposition of the laser per unit area will be reduced, which may lead to incomplete laser cleaning and fail to achieve the set cleaning thickness; if the tape speed is too slow and the laser scanning speed remains unchanged, the energy deposition of the laser per unit area will be too much, which may cause excessive laser cleaning, and the laser cleaning exceeds the set cleaning thickness, causing damage to the designed negative electrode and the designed positive electrode, 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 designed negative electrode plate and the designed positive electrode plate within the time of the cleaning area to be cleaned, the designed negative electrode plate is at the tape speed Vm. 负 In duration τ 负 The moving distance S 负 Less than or equal to one tenth of the spot diameter D of the laser cleaning equipment, design the positive electrode to be at the tape speed Vm 正 In duration τ 正 The moving distance S 正 Less than or equal to one tenth of the spot diameter D of the laser cleaning equipment, to ensure uniform distribution and uniform coverage of the laser energy in each area to be cleaned of the designed negative electrode piece and the designed positive electrode piece, and to effectively laser clean each area to be cleaned of the designed negative electrode piece and the designed positive electrode piece, the laser scanning speed Vl is required. 负The designed negative electrode tape speed Vm 负 Matching, scanning speed Vl 负 With tape speed Vm 负 Matching includes scanning speed Vl 负 With tape speed Vm 负 Equal, or scanning speed Vl 负 With tape speed Vm 负 Satisfy the set multiple relationship and require the laser scanning speed Vl 正 The designed positive electrode tape speed Vm 正 Matching, scanning speed Vl 正 With tape speed Vm 正 Matching includes scanning speed Vl 正 With tape speed Vm 正 Equal, or scanning speed Vl 正 With tape speed Vm 正 Satisfy the set multiple relationship. If the laser scanning speed is too fast or too slow, the laser energy may be unevenly distributed in each area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet, affecting the laser cleaning effect of each area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet, cleaning the active coating that is too thick or too thin in each area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet, and failing to adjust the coating surface density of each area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet from the coating surface density before cleaning to the coating surface density after cleaning.

[0179] In one embodiment, during the laser cleaning process of each area to be cleaned of the designed negative electrode plate and the designed positive electrode plate, the laser pulse frequency, the laser scanning speed and the tape running speed of the designed negative electrode plate and the designed positive electrode plate jointly determine the distribution of the laser energy on the coating surface of each area to be cleaned of the designed negative electrode plate and the designed positive electrode plate. A higher laser pulse frequency has more pulses acting on the active coating in the same time, which can improve the laser cleaning efficiency. However, if the laser pulse frequency is set too high, and the laser scanning speed and the tape running speed of the designed negative electrode plate and the designed positive electrode plate are not increased accordingly, then the superposition of the energy of each pulse on the active coating surface of the designed negative electrode plate and the designed positive electrode plate may cause local overheating, which may cause uncontrollable thermal effects, causing irreversible changes in the active coating of the designed negative electrode plate and the designed positive electrode plate, affecting the quality of laser cleaning.

[0180] In one embodiment, in order to achieve high-quality laser cleaning of the area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet of the square wound battery, the laser pulse frequency, the laser scanning speed and the belt speed of the designed negative electrode sheet and the designed positive electrode sheet in the laser cleaning equipment can be adjusted according to the material properties of the designed negative electrode sheet and the designed positive electrode sheet of the square wound battery, the accuracy and efficiency of laser cleaning, and the optimal parameter combination of the laser pulse frequency, the laser scanning speed and the belt speed of the designed negative electrode sheet and the designed positive electrode sheet in the laser cleaning equipment is determined to ensure uniform distribution of laser energy, so that the active coating in the area to be cleaned will not be too thick due to excessive energy cleaning and the electrode sheet will not be damaged by overheating, nor will the coating surface density of the area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet be adjusted from the coating surface density before cleaning to the coating surface density after cleaning due to insufficient energy. For example, for the area to be cleaned that requires fine laser cleaning, a lower laser scanning speed and belt speed, as well as a moderate laser pulse frequency, may be required to ensure sufficient energy deposition and accurately adjust the coating surface density of the area to be cleaned. For large areas that require rapid laser cleaning, it may be necessary to increase the laser scanning speed and tape speed, and appropriately increase the laser pulse frequency, so as to ensure the cleaning effect of laser cleaning while improving the efficiency of laser cleaning. In short, the coordination between laser pulse frequency, laser scanning speed, and tape speed is the key technical parameter of laser cleaning. Correctly setting the laser pulse frequency, laser scanning speed, and tape speed is crucial to achieve efficient and high-quality laser cleaning.

[0181] In one embodiment, the laser pulse width refers to the duration of a single laser pulse. In applications where thermal effects and cleaning depths need to be precisely controlled, pulse width is one of the key parameters. The laser pulse width of the laser cleaning equipment for laser cleaning the active coating in the area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet can be determined based on the area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet of the square wound battery, and the coating material properties of the area to be cleaned of the designed negative electrode sheet and the designed positive electrode sheet. The larger the laser pulse width, the greater the cleaning intensity of the active coating. When other cleaning parameters of the laser cleaning equipment remain unchanged, for heat-sensitive active coatings, a smaller laser pulse width can reduce thermal effects and avoid deformation or damage to the substrate, and a smaller laser pulse width can achieve precise control, making it easier to achieve the accuracy requirements of laser cleaning and achieve refined laser cleaning; but for thicker cleaning thicknesses or harder active coatings, a larger laser pulse width is required to provide sufficient energy to achieve the purpose of laser cleaning. For example, when other cleaning parameters of the laser cleaning equipment are the same, when the cleaning thickness is 10um (micrometer) and 30um, the laser pulse width used for cleaning the thickness of 30um needs to be higher than the laser pulse width used for cleaning the thickness of 10um; when laser cleaning the silicon-carbon negative electrode and the graphite negative electrode, the laser pulse width for laser cleaning the graphite negative electrode needs to be higher than the laser pulse width for laser cleaning the silicon-carbon negative electrode.

[0182] In a specific embodiment, the laser spot diameter of the laser cleaning equipment for laser cleaning the area to be cleaned of the designed negative electrode plate and the designed positive electrode plate can be 4 to 5.5 mm (millimeter), the laser power can be 4 kW (kilowatts) to 5 kW, the laser scanning speed can be 11000 mm / s (millimeter per second) to 15000 mm / s, the laser pulse frequency can be 100 kHz (kilohertz) to 200 kHz, the laser pulse width can be 300 ns (nanosecond) to 500 ns, the unwinding tension of the laser cleaning equipment can be 30N (Newton) to 90N, the winding tension of the laser cleaning equipment can be 60N to 120N, and the tape travel speed of the laser cleaning equipment can be 400 mm / s (millimeter per second) to 900 mm / s.

[0183] Step 208, laser cleaning 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; laser cleaning 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, the designed negative electrode sheet can be laser cleaned by a laser cleaning device according to the cleaning path and cleaning parameters of the designed area to be cleaned of the negative electrode sheet, so as to obtain the target negative electrode sheet of the square wound battery; the designed positive electrode sheet can be laser cleaned according to the cleaning path and cleaning parameters of the designed area to be cleaned of the positive electrode sheet, so as 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 is adjusted from the coating surface density before cleaning to the coating surface density after cleaning, so as 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 is adjusted from the coating surface density before cleaning to the coating surface density after cleaning, so as 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 straight surface density standard area, so that 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 consistent with the N / P value of the straight surface density standard area.

[0185] In one embodiment, the active coating of each to-be-cleaned area of ​​the designed positive electrode sheet can be laser cleaned by a laser cleaning device according to the cleaning path and cleaning parameters of the designed positive electrode sheet, the coating surface density of each to-be-cleaned area of ​​the designed positive electrode sheet can be adjusted from the coating surface density before cleaning to the coating surface density after cleaning, and the active coating removed by laser cleaning on the surface of the designed positive electrode sheet can be cleaned to obtain the target positive electrode sheet of the square wound battery; the active coating of each to-be-cleaned area of ​​the designed negative electrode sheet can be laser cleaned by a laser cleaning device according to the cleaning path and cleaning parameters of the designed negative electrode sheet. Wash, adjust the coating surface density of each to-be-cleaned area of ​​the designed negative electrode plate from the coating surface density before cleaning to the coating surface density after cleaning, clean the active coating removed by laser cleaning on the surface of the designed negative electrode plate, and obtain the target negative electrode plate of the square wound battery; make the surface density ratio of each curved surface density change area after the target negative electrode plate and the target positive electrode plate are square wound consistent with the surface density ratio of the straight surface density standard area, and make the N / P value of each curved surface density change area after the target negative electrode plate and the target positive electrode plate are square wound consistent with the N / P value of the straight surface density standard area.

[0186] The square wound battery electrode sheet preparation method of the embodiment of the present application is to wind the designed electrode sheet and the diaphragm to form a reference square winding core; firstly, by measuring each circle of the reference square winding core, the surface density standard area and the surface density change area of ​​the active coating on the designed electrode sheet after winding are determined, and then the area to be cleaned of the active coating on the designed electrode sheet is determined, and then the designed electrode sheet is laser cleaned according to the area to be cleaned of the designed electrode sheet to obtain the target electrode sheet for the square wound battery; the active coating in the surface density change area of ​​the curved positive and negative electrode sheets of the square wound battery is laser cleaned in advance by laser cleaning equipment, and the coating surface density in the curved surface density change area of ​​the positive and negative electrode sheets is adjusted, which can improve the production efficiency of the square wound battery, reduce the waste in the production process of the square wound battery, and reduce the manufacturing cost of the square wound battery; the active coating in the surface density change area of ​​the curved positive and negative electrode sheets of the square wound battery is laser cleaned in advance, and the coating surface density in the curved surface density change area of ​​the positive and negative electrode sheets is adjusted, so as to improve the surface density distribution of the positive and negative electrode sheets after the square winding, so that the positive and negative electrode sheets after the square winding have good surface density distribution. The surface density ratio of the surface density change area of ​​the bent electrode sheet is consistent with the surface density ratio of the straight surface density standard area, so that the N / P value of the surface density change area of ​​the bent positive and negative electrode sheets after square winding is consistent with the N / P value of the non-bending area (straight surface density standard area) of the positive and negative electrode sheets, which can significantly reduce the difference in local coating surface density of the positive and negative electrode sheets caused by the square winding bending of the positive and negative electrode sheets, so that the performance of each local electrode sheet of the positive and negative electrode sheets after square winding is more consistent, so that the overall performance of the square wound battery is more reliable, and the electrical performance of the square wound battery can be improved; the N / P values ​​of the positive and negative electrode sheets after square winding are uniformly distributed, which can avoid the increase of local internal resistance and local overheating caused by the uneven N / P values ​​of the positive and negative electrode sheets after square winding, and solve the problem of uneven current distribution caused by the variation of local N / P values ​​in the bending area of ​​the positive and negative electrode sheets. For square wound lithium-ion batteries, the possibility of local lithium precipitation in the bending area is reduced, which can improve the safety performance and cycle life of square wound batteries, and open up a new way to improve the safety performance and battery performance of square wound batteries.

[0187] Furthermore, the method for preparing a square wound battery pole piece in an embodiment of the present application determines a cleaning path for a laser cleaning device to perform laser cleaning on an active coating in an area to be cleaned of the designed pole piece according to area parameters of the area to be cleaned of the designed pole piece; determines cleaning parameters for a laser cleaning device to perform laser cleaning on an active coating in an area to be cleaned of the designed pole piece according to area parameters and a cleaning thickness of the area to be cleaned of the designed pole piece; performs laser cleaning on the active coating in an area to be cleaned of the designed pole piece according to the cleaning path and cleaning parameters by the laser cleaning device; and can dynamically adjust the cleaning path and cleaning parameters of the designed pole piece according to the area parameters of each area to be cleaned of the designed pole piece, thereby achieving differentiated treatment of each area to be cleaned of the designed pole piece, and ensuring a smooth transition of the coating surface density of each area to be cleaned of the designed pole piece.

[0188] Furthermore, the square wound battery pole piece preparation method of the embodiment of the present application uses a laser cleaning device to laser clean the active coating of each area to be cleaned of the designed pole piece according to the cleaning path and cleaning parameters; the laser cleaning technology is used to accurately adjust and optimize the coating thickness of the designed pole piece, so as to achieve accurate adjustment and optimization of the coating surface density of each area to be cleaned of the designed pole piece, so that the surface density ratio of each curved surface density change area of ​​the positive and negative pole pieces after square winding is consistent with the surface density ratio of the flat surface density standard area, so that the N / P value of the designed pole piece after square winding is evenly distributed in each curved surface density change area and the flat surface density standard area, which can be applied to the large-scale preparation of pole pieces and can ensure the consistency of large-scale preparation of pole pieces.

[0189] Furthermore, the square wound battery pole piece preparation method of the embodiment of the present application uses a laser cleaning device to laser clean the active coating of each area to be cleaned of the designed pole piece according to the cleaning path and cleaning parameters; it can utilize the thermal effect and physical action of the laser, not only to remove the active coating of each area to be cleaned of the designed pole piece by laser cleaning, but also to adjust and optimize the coating surface density of each area to be cleaned of the designed pole piece; it can also reshape the surface microstructure of the active coating of each area to be cleaned of the designed pole piece, fine-tune the microstructure of the surface of the active coating, improve the wettability of the active coating to the electrolyte, and further optimize the electrochemical performance of the square wound battery. By laser cleaning the active coating in each area to be cleaned of the designed pole piece, the thermal effect generated by the laser energy in the active coating in each area to be cleaned of the designed pole piece can quickly heat a tiny area on the surface of the active coating, generate instantaneous high temperature, melt and re-solidify the active coating in the tiny area, the binder and additives in the tiny area soften or melt at high temperature, and then re-solidify during rapid cooling to form a new crystalline structure or a tighter molecular arrangement, which can enhance the adhesion between the active coating in each area to be cleaned of the designed pole piece and the pole piece substrate (for example, the current collector), while optimizing the penetration path of the electrolyte; by laser energy in each area to be cleaned of the designed pole piece The thermal effect of the active coating causes the active coating in each area to be cleaned of the designed pole piece to undergo a laser heating and cooling cycle, inducing a phase change reconstruction of the active coating (for example, from an amorphous state to a crystalline state), changing the physical and chemical properties of the active coating, and forming a microstructure that is more conducive to ion transmission; by laser cleaning the active coating in each area to be cleaned of the designed pole piece, through the physical action of the laser, a micron or nanometer-level concave and convex structure can be "carved" in the active coating in each area to be cleaned of the designed pole piece, thereby increasing the specific surface area of ​​the designed pole piece, promoting the penetration of the electrolyte and the transmission of ions at the interface, and improving the charge and discharge efficiency and cycle stability of the square wound battery.

[0190] In addition, an embodiment of the present application further 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] The square wound battery in the embodiment of the present application, other components except the positive electrode sheet and the negative electrode sheet, such as the battery housing, the separator, the electrolyte, etc., can adopt existing conventional structures and materials.

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

[0193] In the comparative example, the negative electrode sheet and the positive electrode sheet of the ternary + graphite system square wound lithium-ion battery of the comparative example with a capacity of 14500-600mAh were prepared according to the conventional method, and the negative electrode sheet and the positive electrode sheet prepared by the conventional method did not undergo laser cleaning of the active coating in the curved surface density change area; the prepared negative electrode sheet, the positive electrode sheet and the diaphragm were square wound to prepare a battery cell; based on the battery cell, a ternary + graphite system square wound lithium-ion battery B of the comparative example with a capacity of 14500-600mAh was prepared.

[0194] The square wound lithium ion battery A of the embodiment and the square wound lithium ion battery B of the comparative example were subjected to a cycle test, and the battery was charged to 4.2V at 3C constant current and constant voltage, and then cut off at 0.05C; left for 15 minutes; discharged to 3.0V at 5C constant current; left for 20 minutes; and cycled 500 times; and the battery was obtained as shown in the following figure: Figure 3 The schematic diagram shown is a comparison of the capacity retention rate of the square wound lithium ion battery of the embodiment of the present application and the square wound lithium ion battery of the comparative example.

[0195] like Figure 3As shown, the capacity retention rate (%) of the square wound lithium-ion battery including the positive electrode sheet and the negative electrode sheet prepared by the method for preparing the square wound battery electrode sheet according to the embodiment of the present application is shown as curve 301, and the capacity retention rate (%) of the square wound lithium-ion battery of the comparative example is shown as curve 302. By comparing curve 301 and curve 302, the capacity retention rate (%) of the square wound lithium-ion battery including the positive electrode sheet and the negative electrode sheet prepared by the method for preparing the square wound battery electrode sheet according to the embodiment of the present application is significantly higher than the capacity retention rate (%) of the square wound lithium-ion battery of the comparative example, indicating that by pre-laser cleaning the active coating of the to-be-cleaned area of ​​the designed electrode sheet, adjusting the coating surface density of the negative electrode sheet and the positive electrode sheet of the square wound battery in the curved surface density change area, the negative electrode sheet and the positive electrode sheet after square winding are improved. The coating surface density distribution makes the surface density ratio of each curved surface density change area of ​​the positive and negative electrodes after square winding consistent with the surface density ratio of the straight surface density standard area, makes the N / P value of each curved surface density change area of ​​the negative electrode sheet and the positive electrode sheet after square winding consistent with the N / P value of the straight surface density standard area, makes the N / P values ​​of the negative electrode sheet and the positive electrode sheet after square winding evenly distributed, can avoid the local internal resistance increase and local overheating caused by the uneven N / P value of the negative electrode sheet and the positive electrode sheet after square winding, solves the problem of uneven current distribution caused by the variation of the local N / P value in the curved area of ​​the negative electrode sheet and the positive electrode sheet, and reduces the possibility of local lithium precipitation in the curved area for the square wound lithium-ion battery, which can improve the cycle performance and cycle life of the square wound lithium-ion battery.

[0196] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a square wound battery electrode sheet, characterized in that: include: Obtaining a designed pole piece with a current collector and an active coating; Winding the designed pole piece and diaphragm to form a reference square winding core; Measuring each turn of the reference square winding core to determine a standard area of ​​surface density and a surface density variation area of ​​the active coating on the designed pole piece after winding, wherein the surface density of the standard area of ​​surface density is a target surface density, the surface density of the surface density variation area is different from the target surface density, the surface density variation area includes a large surface density area, and the surface density of the large surface density area is greater than the target surface density; Comparing the standard surface density area with the surface density variation area, determining the area to be cleaned of the active coating on the designed pole piece, wherein the area to be cleaned is located in the high surface density area; According to the to-be-cleaned area of ​​the designed pole piece, the designed pole piece is laser cleaned to obtain the target pole piece of the square wound battery.

2. The method according to claim 1, characterized in that The step of winding the designed pole piece and the diaphragm to form a reference square winding core comprises: The designed pole piece and diaphragm are physically wound or simulatedly wound to form a reference square winding core.

3. The method according to claim 1, characterized in that Each turn of the reference square winding core is measured to determine the standard area of ​​surface density and the area of ​​surface density variation of the active coating on the designed pole piece after winding, including: The designed pole piece of each turn of the reference square winding core is measured to determine the standard surface density area and the surface density variation area of ​​the active coating alternately distributed along the winding direction of the designed pole piece after winding, wherein the standard surface density area corresponds to the straight area of ​​the designed pole piece in the winding direction, and the surface density variation area corresponds to the curved area of ​​the designed pole piece after winding, and the inner side of the curved area of ​​each turn of the designed pole piece is the high surface density area.

4. The method according to claim 3, characterized in that The design of the electrode sheet includes designing a negative electrode sheet and designing a positive electrode sheet; The comparing the standard surface density area with the surface density variation area to determine the area to be cleaned of the active coating on the designed pole piece includes: Compare the surface density standard area of ​​the designed negative electrode sheet and the surface density variation area of ​​the designed negative electrode sheet, compare the surface density standard area of ​​the designed positive electrode sheet and the surface density variation area of ​​the designed positive electrode sheet, compare the surface density variation area of ​​the two relative layers of the designed negative electrode sheet and the surface density variation area of ​​the designed positive electrode sheet, and respectively 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.

5. The method according to claim 4, characterized in that The front and back sides of the designed pole piece both have the active coating; The determining of the surface density variation region of the active coating on the designed pole piece after winding also includes: determining the outer side of the bending region of each turn of the designed pole piece as a small surface density region; The step of comparing the standard area of ​​the surface density of the designed negative electrode sheet with the area of ​​the surface density variation of the designed negative electrode sheet, comparing the standard area of ​​the surface density of the designed positive electrode sheet with the area of ​​the surface density variation of the designed positive electrode sheet, and comparing the area of ​​the surface density variation of the designed negative electrode sheet with the area of ​​the surface density variation of the designed positive electrode sheet, and respectively determining the area to be cleaned of the active coating on the designed negative electrode sheet and the active coating on the designed positive electrode sheet, comprises: comparing the surface density standard area of ​​the designed negative electrode sheet with the surface density variation area of ​​the designed negative electrode sheet, comparing the surface density standard area of ​​the designed positive electrode sheet with the surface density variation area of ​​the designed positive electrode sheet, Comparing the large surface density area of ​​the designed negative electrode plate with the small surface density area of ​​the designed positive electrode plate opposite thereto, determining the area to be cleaned of the active coating on the designed negative electrode plate, so that the surface density ratio of the large surface density area of ​​the designed negative electrode plate to the small surface density area of ​​the designed positive electrode plate opposite thereto is equal to the surface density ratio of the surface density standard area of ​​the designed negative electrode plate to the surface density standard area of ​​the designed positive electrode plate; Compare the small surface density area of ​​the designed negative electrode plate and the large surface density area of ​​the designed positive electrode plate opposite thereto, and determine the area to be cleaned of the active coating on the designed positive electrode plate, so that the surface density ratio of the small surface density area of ​​the designed negative electrode plate and the large surface density area of ​​the designed positive electrode plate opposite thereto is equal to the surface density ratio of the standard surface density area of ​​the designed negative electrode plate and the standard surface density area of ​​the designed positive electrode plate.

6. The method according to claim 5, characterized in that The step of respectively determining the areas to be cleaned of the active coating on the designed positive electrode sheet and the active coating on the designed negative electrode sheet further includes: The regional parameters of the area to be cleaned of the active coating on the designed negative electrode plate and the regional parameters of the area to be cleaned of the active coating on the designed positive electrode plate are determined respectively, and the regional parameters include one or a combination of the regional position 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.

7. The method according to claim 6, characterized in that According to the to-be-cleaned area of ​​the designed pole piece, before laser cleaning the designed pole piece to obtain the target pole piece of the square wound battery, the method includes: Determining a cleaning path of the designed negative electrode sheet according to the area parameters of the to-be-cleaned area of ​​the designed negative electrode sheet; The cleaning path of the designed positive electrode sheet is determined according to the area parameters of the area to be cleaned of the designed positive electrode sheet.

8. The method according to claim 7, characterized in that The step of determining the cleaning path of the designed negative electrode sheet according to 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 according to the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area 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 method of determining the cleaning path of the designed positive electrode plate according to the area parameters of the area to be cleaned of the designed positive electrode plate also includes: determining the cleaning thickness of the area to be cleaned of the designed positive electrode plate according to the corresponding relationship between the coating thickness and the coating surface density of the surface density standard area of ​​the designed positive electrode plate, the coating thickness and the coating surface density of the area to be cleaned of the designed positive electrode plate.

9. The method according to claim 8, characterized in that The method of laser cleaning the designed pole piece according to the area to be cleaned of the designed pole piece to obtain the target pole piece of the square wound battery includes: Determining cleaning parameters of the area to be cleaned of the designed negative electrode sheet according to the area parameters and cleaning thickness of the area to be cleaned of the designed negative electrode sheet; Laser cleaning the designed negative electrode sheet according to the cleaning path and cleaning parameters of the to-be-cleaned area of ​​the designed negative electrode sheet to obtain the target negative electrode sheet of the square wound battery; Determining cleaning parameters of the area to be cleaned of the designed positive electrode sheet according to the area parameters and cleaning thickness of the area to be cleaned of the designed positive electrode sheet; The designed positive electrode sheet is laser cleaned 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.

10. The method according to claim 9, 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 plate according to the area parameters and the cleaning thickness of the area to be cleaned of the designed negative electrode plate further includes: According to the specific heat capacity, coating surface density and cleaning thickness of the active coating in the to-be-cleaned area of ​​the designed negative electrode plate, the laser power P of the laser cleaning equipment for laser cleaning the active coating in the to-be-cleaned area of ​​the designed negative electrode plate 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 is the cleaning thickness of the to-be-cleaned area of ​​the designed negative electrode plate; A 负 is the spot area of ​​the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed negative electrode plate; ρ 负 is the coating surface density of the area to be cleaned of the designed negative electrode plate; C 负 is the specific heat capacity of the active coating of the designed negative electrode plate in the area to be cleaned; η 负 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 plate; t 负 is the total time that the laser of the laser cleaning equipment acts on the active coating of the area to be cleaned of the designed negative electrode plate; V 负 is the scanning speed of the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed negative electrode plate; L 负 is the total length of the laser moving in the area to be cleaned when the laser cleaning equipment laser cleans the area to be cleaned of the designed negative electrode plate; The step of determining the cleaning parameters of the area to be cleaned of the designed positive electrode plate according to the area parameters and the cleaning thickness of the area to be cleaned of the designed positive electrode plate further includes: According to the specific heat capacity, coating surface density and cleaning thickness of the active coating in the area to be cleaned of the designed positive electrode plate, 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 plate 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 is the cleaning thickness of the area to be cleaned of the designed positive electrode plate; A 正 is the spot area of ​​the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode plate; ρ 正 is the coating surface density of the area to be cleaned of the designed positive electrode plate; C 正 is the specific heat capacity of the active coating of the area to be cleaned of the designed positive electrode plate; η 正 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 plate; t 正 is the total time that the laser of the laser cleaning equipment acts on the active coating of the area to be cleaned of the designed positive electrode plate; V 正 is the scanning speed of the laser when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode plate; L 正 It is the total length of the laser moving in the area to be cleaned when the laser cleaning equipment laser cleans the area to be cleaned of the designed positive electrode plate.

11. The method according to claim 10, characterized in that: The cleaning parameters also include the laser pulse frequency of the laser cleaning device; The step of determining the cleaning parameters of the area to be cleaned of the designed negative electrode plate according to the area parameters and the cleaning thickness of the area to be cleaned of the designed negative electrode plate further includes: According to the cleaning thickness of the to-be-cleaned area of ​​the designed negative electrode plate, the laser pulse frequency f of the laser cleaning equipment for laser cleaning the active coating of the to-be-cleaned area of ​​the designed negative electrode plate is determined. 负 ,in, f 负 =Vm 负 / (S 负 ×τ 负 ), Where, Vm 负 is the tape speed at which the laser cleaning equipment performs laser cleaning on the designed negative electrode plate; τ 负 is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed negative electrode plate; S 负 The designed negative electrode plate is at the tape running speed Vm 负 During the duration τ 负 The moving distance; The step of determining the cleaning parameters of the area to be cleaned of the designed positive electrode plate according to the area parameters and the cleaning thickness of the area to be cleaned of the designed positive electrode plate further includes: According to the cleaning thickness of the to-be-cleaned area of ​​the designed positive electrode plate, the laser pulse frequency f of the laser cleaning equipment for laser cleaning the active coating of the to-be-cleaned area of ​​the designed positive electrode plate is determined. 正 ,in, f 正 =Vm 正 / (S 正 ×τ 正 ), Where, Vm 正 is the tape speed at which the laser cleaning equipment performs laser cleaning on the designed positive electrode plate; τ 正 is the duration of each laser pulse when the laser cleaning equipment performs laser cleaning on the designed positive electrode plate; S 正 The designed positive electrode plate is at the tape running speed Vm 正 During the duration τ 正 moving distance.

12. The method according to claim 11, characterized in that: The moving distance S 正 Less than or equal to one tenth of the spot diameter of the laser cleaning equipment laser; the moving distance S 负 Less than or equal to one tenth of the spot diameter of the laser of the laser cleaning equipment.

13. A square wound battery, characterized in that: It comprises a negative electrode sheet prepared by the method according to any one of claims 1-12, and a positive electrode sheet prepared by the method according to any one of claims 1-12.

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