A method for improving the inner circle fold of a lithium ion battery and a lithium ion battery

Abstract

The present application relates to the technical field of lithium ion batteries, in particular to a method for improving the inner circle wrinkle of a lithium ion battery and the lithium ion battery; the method comprises the following steps: after controlling the positive and negative electrode materials, adjusting the unloading pull rod and the winding needle leveling angle position, adjusting the positive electrode cutting rubber size and the positive and negative electrode entering sheet position, and winding the battery cell; by increasing the first circle tension of the electrode sheet and the first circle tension of the diaphragm, and decreasing the electrode sheet tension and the diaphragm tension with the increase of the number of circles, the electrode sheet tension and the diaphragm tension are matched, and the inner circle wrinkle of the lithium ion battery is improved. Compared with the prior art, the method for improving the inner circle wrinkle of the lithium ion battery provided by the present application is realized by the combined action of multiple factors: on the basis of controlling the positive and negative electrode materials, the tension between the diaphragm and the electrode sheet is adjusted to achieve matching, thereby significantly reducing the inner circle wrinkle rate and improving the safety of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a method for improving the inner ring wrinkles of a lithium-ion battery and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, as core components of new energy storage, are widely used in consumer electronics, electric vehicles, and large-scale energy storage systems. Currently, most lithium-ion battery cell processing employs fully automated winding processes. Compared to stacking processes, winding offers higher production efficiency, lower risk of burrs, more precise control over cell dimensions, and higher battery safety. However, during the winding process, the instability of the inner ring electrode and separator during the winding needle winding process leads to collapse. After cold pressing, a through-type wrinkle forms at the second fold corner of the innermost negative electrode, near the edge, at the single-sided lithium intercalation area. After full charging, powder falls from the negative electrode wrinkles when the separator is torn open, adversely affecting the safety of lithium-ion batteries. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for improving the inner ring wrinkles of a lithium-ion battery and a lithium-ion battery. The method provided by the present invention, based on controlling the negative electrode peeling force and the positive electrode wavy edge, adjusts the size of the positive electrode cutting adhesive and the position of the positive and negative electrodes inserting into the sheet, so that the tension between the separator and the electrode sheet is matched, thereby significantly reducing the inner ring wrinkle rate and improving the safety of the lithium-ion battery.

[0004] This invention provides a method for improving the inner ring wrinkles of a lithium-ion battery, comprising the following steps:

[0005] After controlling the incoming positive and negative electrode materials, adjust the angle and position of the feeding rod and the winding needle, and at the same time adjust the size of the positive electrode cutting glue and the position of the positive and negative electrode inserting sheet to wind the battery cell.

[0006] By increasing the tension of the first coil of the electrode and the tension of the first coil of the separator, and decreasing the tension of the electrode and the tension of the separator as the number of coils increases, the tension of the electrode and the tension of the separator are matched, thus improving the inner coil wrinkles of the lithium-ion battery.

[0007] Preferably, the control of incoming positive and negative electrode materials includes:

[0008] Control the negative electrode stripping force; and / or, control the positive electrode wavy edge.

[0009] Preferably, the controlled negative electrode stripping force is ≥7N / m;

[0010] And / or, the controlled positive electrode wavy edge is <1mm.

[0011] Preferably, the process of adjusting the angle between the feed rod and the winding needle includes:

[0012] Adjust the material feeding height to 6mm~7mm, and the torque at the pull-out position to 28N~32N, so that the material feeding pull rod is in the center position when the core is flattened by 180°.

[0013] Preferably, the process of adjusting the size of the positive electrode cutting adhesive and the position of the positive and negative electrodes includes:

[0014] Adjust the width of the positive electrode cutting adhesive to 35mm-45mm, with the adhesive tape extending beyond the radius (R). The negative electrode insertion position should be 0-3mm away from the radius (R), and the inserted negative electrode should extend more than 5mm beyond the positive electrode.

[0015] Preferably, the cell winding process includes:

[0016] The core is formed by winding the diaphragm-negative electrode-diaphragm-positive electrode in a clockwise or counterclockwise manner.

[0017] Preferably, the electrode tension is increased to 600 gf in the first cycle; the diaphragm tension is increased to 300 gf in the first cycle; the electrode tension decreases by 6 gf every 5 cycles; and the diaphragm tension decreases by 2 gf every 5 cycles.

[0018] Preferably, the electrode tension satisfies the tension function Y. a =600-6 / 5×M; the diaphragm tension satisfies the tension function Y b =300-2 / 5×N; where M is the number of turns of the electrode and N is the number of turns of the diaphragm.

[0019] Preferably, the process of adapting the electrode tension to the diaphragm tension further includes:

[0020] Adjust the electrode flipping tension to 360gf~400gf; and / or, adjust the diaphragm flipping tension to 260gf~300gf.

[0021] The present invention also provides a lithium-ion battery, wherein the method for preparing the lithium-ion battery includes the method for improving the inner ring wrinkles of the lithium-ion battery as described in the above technical solution.

[0022] This invention provides a method for improving inner ring wrinkles in lithium-ion batteries and a lithium-ion battery itself. The method for improving inner ring wrinkles in lithium-ion batteries includes the following steps: after controlling the incoming positive and negative electrode materials, adjusting the angle and position of the feeding rod and the winding needle, and simultaneously adjusting the size of the positive electrode cutting adhesive and the insertion position of the positive and negative electrodes, and then winding the battery cell; by increasing the tension of the first turn of the electrode sheet and simultaneously increasing the tension of the first turn of the separator, and decreasing the tension of the electrode sheet and the separator with the increase of the number of turns, the tension of the electrode sheet and the tension of the separator are matched, thereby improving the inner ring wrinkles of the lithium-ion battery. Compared with the prior art, the method for improving inner ring wrinkles in lithium-ion batteries provided by this invention works through the combined effect of multiple factors: based on controlling the negative electrode peeling force and the positive electrode wavy edge, adjusting the angle of the feeding rod and different winding positions, simultaneously adjusting the size of the positive electrode cutting adhesive and the insertion position of the positive and negative electrodes, and adjusting the tension to match the tension between the separator and the electrode sheet, thereby significantly reducing the inner ring wrinkle rate and improving the safety of the lithium-ion battery. Attached Figure Description

[0023] Figure 1 This is an analysis and schematic diagram of the causes of inner ring wrinkles in an embodiment of the present invention.

[0024] Figure 2 This is a disassembly diagram of a battery cell showing wrinkles in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the extended positive electrode cutting adhesive in an embodiment of the present invention.

[0026] Figure 4 This is a trend diagram showing the improvement in the peeling force of the negative electrode sheet in an embodiment of the present invention.

[0027] Figure 5 This is a histogram showing the negative electrode stripping force data before and after improvement in an embodiment of the present invention.

[0028] Figure 6 This is a trend diagram showing the improvement of the wavy edge of the positive electrode die-cutting blade surface (non-tab side) in an embodiment of the present invention.

[0029] Figure 7 This is a histogram showing the improvement of the wavy edge of the positive electrode die-cutting blade surface (non-tab side) in an embodiment of the present invention.

[0030] Figure 8 This is a trend diagram showing the improvement of the wavy edge of the positive electrode die-cutting blade surface (electrode side) in an embodiment of the present invention.

[0031] Figure 9 This is a histogram showing the improvement of the wavy edge of the positive electrode die-cutting blade surface (tab side) in an embodiment of the present invention before and after.

[0032] Figure 10 This is a photograph of a physical object used in an embodiment of the present invention to control the wrinkling state of the core after hot pressing before the electrode sheet arrives.

[0033] Figure 11 This is a photograph of an actual object used in an embodiment of the present invention to control the wrinkling state of the core after hot pressing of the incoming electrode sheet.

[0034] Figure 12 This is a trend chart of the 100% wrinkle ratio after hot pressing in an embodiment of the present invention.

[0035] Figure 13 This is a photograph of the disassembled hot-pressed core and finished battery cell in an embodiment of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present application, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0038] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0039] Unless otherwise stated, all technical terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. All patents and publications referenced in this application are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this application but do not exclude other contents.

[0040] Terminology Explanation:

[0041] Peel strength: refers to the maximum force required to peel bonded materials from the contact surface per unit width; the peel angle can be 90° or 180°, and the unit is N / m. It reflects the bond strength of the materials.

[0042] Currently, the existing lithium-ion battery cell winding process has the problem of inner ring wrinkles. Technicians generally use the following methods to improve it: (1) The tension functions of the negative electrode sheet and the positive electrode sheet are both reduced according to the logarithmic function. The tension function of the negative electrode sheet is Y c=a1+b1·ln(M), the tension function of the positive electrode is Y. a =a2+b2·ln(N); where M is the number of turns of the negative electrode, a1 and b1 are constants; N is the number of turns of the positive electrode, a2 and b2 are constants; and / or, (2) reduce process deformation: reduce tension fluctuation, use hot pressing process to reduce the rebound of the electrode in the later stage, reduce baking time (reduce the thermal shrinkage of the diaphragm), liquid injection method (three liquid injections to reduce impact, etc.); reduce diaphragm deformation: attach Teflon tape to the winding needle, use machine cutter to improve the inner ring diaphragm wrinkles, apply glued diaphragm, etc.; however, the above improvement methods still cannot guarantee the tension between the diaphragm and the electrode in actual application, and the effect of improving the inner ring wrinkles is not good.

[0043] Based on this, the present invention conducts a large number of experiments and combines experimental data to comprehensively analyze the causes of inner ring wrinkles, and proposes a method to improve the inner ring wrinkles of lithium-ion batteries. By controlling the negative electrode peeling force and the positive electrode wavy edge, adjusting the size of the positive electrode cutting adhesive and the position of the positive and negative electrodes, and at the same time making the tension between the separator and the electrode sheet match, the inner ring wrinkle rate is significantly reduced and the safety of lithium-ion batteries is improved.

[0044] This invention provides a method for improving the inner ring wrinkles of a lithium-ion battery, comprising the following steps:

[0045] After controlling the incoming positive and negative electrode materials, adjust the angle and position of the feeding rod and the winding needle, and at the same time adjust the size of the positive electrode cutting glue and the position of the positive and negative electrode inserting sheet to wind the battery cell.

[0046] By increasing the tension of the first coil of the electrode and the tension of the first coil of the separator, and decreasing the tension of the electrode and the tension of the separator as the number of coils increases, the tension of the electrode and the tension of the separator are matched, thus improving the inner coil wrinkles of the lithium-ion battery.

[0047] In this invention, the control of incoming positive and negative electrode materials is a process of controlling incoming materials in the upstream section, and preferably includes:

[0048] Control the negative electrode stripping force; and / or, control the positive electrode wavy edge;

[0049] More preferably:

[0050] Control the negative electrode stripping force and control the positive electrode wave edge.

[0051] In this invention, the controlled negative electrode peeling force is preferably ≥7N / m, more preferably 7N / m~9N / m. By appropriately increasing the negative electrode peeling force, the powder shedding of the negative electrode sheet can be improved. The process of controlling the negative electrode peeling force is preferably as follows:

[0052] A dual planetary mixing device was used to mix the negative electrode material, and the PAA of the negative electrode design formula was increased to 1.6% to 1.8%. At the same time, the temperature and air frequency of the coating oven were adjusted, which increased the peel force of the negative electrode from an average of 4.9 N / m before the improvement to 7 N / m to 9 N / m, which is a significant improvement.

[0053] In this invention, the controlled positive electrode wavy edge is preferably <1mm; by tightening the size of the positive electrode wavy edge, inward curling wrinkles can be reduced; the process of controlling the positive electrode wavy edge is preferably as follows:

[0054] The roller pressing uses a bending cylinder function to control the roller pressing tension, ensuring the uniformity of electrode thickness, and monitors the wavy edge on the die-cutting blade side and laser side of each roll of electrode to ensure that the wavy edge size is controlled to <1mm (the original control size is <3mm), thereby reducing the wrinkle rate to a certain extent.

[0055] Subsequently, the present invention adjusts the angle and position of the feeding rod and the winding needle, and at the same time adjusts the size of the positive electrode cutting glue and the position of the positive and negative electrode inserts to wind the battery cell.

[0056] In this invention, the process of adjusting the angle between the feed rod and the winding needle preferably includes:

[0057] Adjust the material feeding height to 6mm~7mm, and the pull-out torque to 28N~32N, so that the material feeding rod is in the center position when the core is flattened by 180°.

[0058] More preferably:

[0059] Adjust the material feeding height to 6mm and the pull-out torque to 30N, so that the material feeding rod is horizontally centered at the 180° flattening position of the core.

[0060] In this invention, the process of adjusting the size of the positive electrode cutting adhesive and the positions of the positive and negative electrodes preferably includes:

[0061] Adjust the width of the positive electrode cutting adhesive to 35mm~45mm, with the adhesive tape extending beyond the R-angle. The negative electrode insertion position should be 0~3mm away from the R-angle, and the inserted negative electrode should extend more than 5mm beyond the positive electrode.

[0062] More preferably:

[0063] The positive electrode cutting adhesive width is adjusted to 40mm, with the adhesive tape extending beyond the radius (R-angle). The negative electrode insertion position is 0-3mm away from the R-angle, and the inserted negative electrode extends more than 5mm beyond the positive electrode. In this invention, the positive electrode cutting adhesive width is adjusted to 40mm, with the adhesive tape extending beyond the radius (R-angle), but the positive electrode insertion position does not exceed the R-angle. Simultaneously, the negative electrode insertion position is 0-3mm away from the R-angle, and the inserted negative electrode extends more than 5mm beyond the positive electrode (including the adhesive tape). Furthermore, during insertion, neither the positive nor negative electrode extends beyond the R-angle, and the inserted negative electrode effectively covers the positive electrode.

[0064] In this invention, the cell winding process preferably includes:

[0065] The core is formed by winding the separator-negative electrode-separator-positive electrode in a clockwise or counterclockwise cycle. This invention does not change the overall manufacturing method of lithium-ion batteries; instead, it adapts the conditions and parameters for the cell winding process while maintaining the overall process flow. This improves the inner ring wrinkles of lithium-ion batteries and reduces potential safety risks while ensuring production efficiency. Furthermore, the improvements also address the issues of electrode shedding and positive electrode wavy edges.

[0066] In this invention, during the cell winding process, the tension of the first turn of the electrode is increased while the tension of the first turn of the separator is also increased. The tension of the electrode and the tension of the separator are decreased as the number of turns increases, so that the tension of the electrode and the tension of the separator are matched, thereby improving the inner ring wrinkles of the lithium-ion battery.

[0067] This invention reduces the impact of the separator on the electrode during winding by increasing the tension of the first turn of the electrode sheet and the tension of the first turn of the separator, while gradually decreasing the tension at each turn. This effectively improves the problem of wrinkles at the electrode sheet entry point. The tension of the first turn of the electrode sheet is preferably increased to 600 gf (400 gf in conventional processes); the tension of the first turn of the separator is preferably increased to 300 gf (200 gf in conventional processes); the tension of the electrode sheet is preferably decreased by 6 gf every 5 turns; and the tension of the separator is preferably decreased by 2 gf every 5 turns.

[0068] Based on this, the electrode tension preferably satisfies the tension function Y. a =600-6 / 5×M; the diaphragm tension preferably satisfies the tension function Y. b =300-2 / 5×N; where M is the number of turns of the electrode and N is the number of turns of the diaphragm.

[0069] In this invention, the electrode includes a positive electrode and / or a negative electrode, and there are no special limitations on this.

[0070] Through the above improvements, the present invention can achieve a suitable tension between the diaphragm and the electrode, thereby significantly reducing the inner wrinkle rate.

[0071] In this invention, the step of matching the electrode tension with the diaphragm tension preferably further includes:

[0072] The electrode flipping tension is preferably adjusted to 360gf to 400gf, more preferably 380gf; and / or the diaphragm flipping tension is preferably adjusted to 260gf to 300gf, more preferably 280gf.

[0073] The method for improving inner ring wrinkles in lithium-ion batteries provided by this invention works through the combined effect of multiple factors: on the basis of controlling the negative electrode peeling force and the positive electrode wavy edge, adjusting the angle of the feeding rod and different flattening positions, adjusting the size of the positive electrode cutting adhesive and the positive and negative electrode insertion positions, and adjusting the tension to make the tension between the separator and the electrode sheet match, thereby significantly reducing the inner ring wrinkle rate and improving the safety of lithium-ion batteries.

[0074] The present invention also provides a lithium-ion battery, wherein the method for preparing the lithium-ion battery includes the method for improving the inner ring wrinkles of the lithium-ion battery as described in the above technical solution.

[0075] In this invention, the lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, all of which can be conventional functional units from commercially available sources well known to those skilled in the art. Furthermore, this invention allows for the production of a lithium-ion battery using methods well known to those skilled in the art, and there are no particular limitations in this regard. Specifically, the lithium-ion battery cell is manufactured by a winding process using a positive electrode, a negative electrode, and a separator, followed by the injection of an electrolyte, thus obtaining the lithium-ion battery using conventional techniques. The lithium-ion battery may include an outer packaging that can be used for encapsulation.

[0076] In this invention, the method for preparing the lithium-ion battery includes the method for improving the inner ring wrinkles of the lithium-ion battery as described in the above-described technical solution. Therefore, this lithium-ion battery possesses all the features and advantages of the method for improving the inner ring wrinkles of the lithium-ion battery as described in the above-described technical solution, which will not be repeated here.

[0077] This invention provides a method for improving inner ring wrinkles in lithium-ion batteries and a lithium-ion battery itself. The method for improving inner ring wrinkles in lithium-ion batteries includes the following steps: after controlling the incoming positive and negative electrode materials, adjusting the angle and position of the feeding rod and the winding needle, and simultaneously adjusting the size of the positive electrode cutting adhesive and the insertion position of the positive and negative electrodes, and then winding the battery cell; by increasing the tension of the first turn of the electrode sheet and simultaneously increasing the tension of the first turn of the separator, and decreasing the tension of the electrode sheet and the separator with the increase of the number of turns, the tension of the electrode sheet and the tension of the separator are matched, thereby improving the inner ring wrinkles of the lithium-ion battery. Compared with the prior art, the method for improving inner ring wrinkles in lithium-ion batteries provided by this invention works through the combined effect of multiple factors: based on controlling the negative electrode peeling force and the positive electrode wavy edge, adjusting the angle of the feeding rod and different winding positions, simultaneously adjusting the size of the positive electrode cutting adhesive and the insertion position of the positive and negative electrodes, and adjusting the tension to match the tension between the separator and the electrode sheet, thereby significantly reducing the inner ring wrinkle rate and improving the safety of the lithium-ion battery.

[0078] To further illustrate the present invention, the following embodiments are provided for detailed description. The raw materials used in the following embodiments of the present invention are shown in Table 1 below.

[0079] Table 1

[0080]

[0081]

[0082] Example

[0083] (1) Wrinkle problem: After disassembling 100 pieces of hot-pressed core, 50 pieces of finished battery cells were obtained (see disassembly photos). Figure 13 Based on the comprehensive disassembly results, it was determined that both the core and the finished product had wrinkles, with 100% wrinkles on the inner ring.

[0084] First, let's analyze the reasons for the inner circle wrinkles:

[0085] ① Deviation in material levelness; ② Diaphragm wrinkles; ③ Tension mismatch between positive and negative electrodes and diaphragm; see also Figure 1 As shown.

[0086] The following steps verified the following parameters before verification: positive / negative electrode tension: 450±100gf; diaphragm tension: 250±100gf; average negative electrode peel force before improvement: 4.9N / m; standard positive electrode wavy edge before improvement: <3mm; see disassembly diagram before verification. Figure 2 As shown.

[0087] (2) First step verification: Verify approximately 300 pieces, the inner circle wrinkle rate is 12.5%:

[0088] ① Adjust the horizontality of the pull rod and calibrate the concentricity of the winding needle: Set a benchmark, find the fold position, adjust the angle of the pull rod, check the accuracy of each feeding mechanism, fine-tune the relative position of the pull rod lifting / pre-pressing / pulling, and ensure that all mechanisms are accurately debugged;

[0089] ② Move the positive electrode sheet 20mm forward before winding (the negative electrode effectively covers the positive electrode), the positive electrode approaches the R angle, and the terminating adhesive passes the R angle, so that the positive electrode cutting adhesive has a supporting effect on the negative electrode sheet and prevents the negative electrode sheet from being deformed laterally.

[0090] ③ Increase the number of diaphragm rings by 2 to reduce the interaction force between the innermost positive electrode and the negative electrode, thus reducing indentation after hot pressing.

[0091] (3) Second step verification: Verify 8100pcs cores, disassemble 1562pcs, inner ring wrinkle rate 6.47%:

[0092] ① Batch use of negative electrode sheets with peel strength increased from 4.9 N / m to >7 N / m (using slurry from Shangrao double planetary slurry);

[0093] ② The wavy edge of the electrode sheet was adjusted and improved from <3mm to <1mm: the wavy edge size was controlled in batches; at the same time, after die cutting, a full inspection was carried out to control the wavy edge of each roll of electrode sheet.

[0094] The results are shown in Table 2 below.

[0095] Table 2

[0096]

[0097]

[0098] (4) The final solution is as follows:

[0099] ① Adjustment of machine equipment parameters:

[0100] a. Adjust the angle of the pull rod (by adjusting the feeding position) and different flattening positions: Adjust the feeding height to 6mm, and the torque at the pulling position to 30N, so that the pulling rod is in the center position when the core is flattened by 180°.

[0101] b. Adjust the size of the positive electrode cutting adhesive and the position of the positive and negative electrodes during winding: adjust the width of the positive electrode cutting adhesive from 20mm to 40mm, the adhesive tape should extend beyond the R-angle (the position of the positive electrode insertion should not extend beyond the R-angle), the negative electrode insertion position should be 0-3mm away from the R-angle, and the inserted negative electrode should extend beyond the positive electrode (including the adhesive tape) by more than 5mm to prevent the negative electrode sheet from undergoing lateral deformation; after verification on 140pcs, the wrinkle ratio was reduced to about 12.8%.

[0102] Extend the positive electrode cutting adhesive; increase the positive electrode winding length. See [link / reference]. Figure 3 As shown.

[0103] c. Tension adjustment:

[0104] The core is wound in a diaphragm-negative-diaphragm-positive winding pattern, either clockwise or counterclockwise. The tension of the first turn of the diaphragm is adjusted from 200gf to 300gf, decreasing by 2gf taper every 5 turns. The tension of the first turn of the positive and negative electrode sheets is adjusted from 400gf to 600gf, decreasing by 6gf taper every 5 turns. The tension function of the positive / negative electrode sheets is Y. a =600-6 / 5×M, the tension function of the diaphragm is Y b =300-2 / 5×N; where M is the number of turns of the negative electrode and N is the number of turns of the diaphragm.

[0105] Before verification, the positive / negative electrode tension parameters were 450±100gf, and the diaphragm tension parameters were 250±100gf.

[0106] The final tension parameters after verification are shown in Table 3 below.

[0107] Table 3

[0108]

[0109]

[0110] ② Control of incoming electrode materials in the preceding process: negative electrode peeling force and positive electrode wavy edge.

[0111] a. Improved negative electrode peel strength: By adjusting the use of a dual planetary mixer for negative electrode material mixing, the PAA (paleaceous area and alkali) in the negative electrode design formulation was increased to 1.6%. Simultaneously, the coating oven temperature and airflow frequency were adjusted, resulting in a significant improvement in peel strength after coating (from an average of 4.9 N / m before improvement to 7–9 N / m). Verification was conducted on 5000 cores; see the comparison of negative electrode peel strength data before and after the improvement for details. Figures 4-5 .

[0112] b. Improvement of Positive Electrode Wavy Edge: The rolling process utilizes a bending cylinder function to control rolling tension, maintaining the positive electrode rolling thickness at 154±3μm. Wavy edges on both the die-cutting blade side and the laser side are monitored for each coil of electrode sheet, ensuring the wavy edge size is controlled below 1mm. Verification was performed on 292 coil cores, controlling the wavy edge size to <1mm and maintaining the wrinkle ratio below 10%. See [link / reference]. Figures 6-9 And as shown in Table 4 below (Controlling the wrinkle rate after wavy edge).

[0113] Table 4

[0114] Verification batch Average wavy edge / mm Number of pleats / pcs Number of pieces invested Wrinkle rate / % 1 0.75 14 146 9.59 2 0.82 13 146 8.90

[0115] c. Control the occurrence of negative electrode wrinkling and powder loss after hot pressing of the core before and after the electrode sheet is received. See [link / reference] Figures 10-11 ,in, Figure 10 To control the wrinkling state of the core after hot pressing before the electrode sheet arrives, it can be seen that the phenomenon of powder falling off and copper exposure after wrinkling is serious. Figure 11 To control the wrinkling state of the core after hot pressing of the incoming electrode sheet, it can be seen that the powder loss of the negative electrode at the wrinkled area is significantly improved.

[0116] See the trend chart of the 100% wrinkle ratio after hot pressing assembly. Figure 12 As shown.

[0117] (5) The verified tension parameters are shown in Table 5 below.

[0118] Table 5

[0119]

[0120] Experimental results show that by increasing electrode tension and reducing separator tension, the present invention optimizes the tension of the electrode and separator to a suitable level, effectively improving the problem of wrinkles at the negative electrode insertion point. It can reduce the inner ring wrinkle rate from 100% to about 5%, reducing safety risks. In addition, the present invention controls the manufacturing cost of the battery without requiring other additional cost consumption, while also promoting the improvement of the problems of negative electrode shedding and positive electrode wavy edges.

[0121] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0122] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving wrinkles in the inner ring of a lithium-ion battery, characterized in that, Includes the following steps: After controlling the incoming positive and negative electrode materials, adjust the angle and position of the feeding rod and the winding needle, and at the same time adjust the size of the positive electrode cutting glue and the position of the positive and negative electrode inserting sheet to wind the battery cell. By increasing the tension of the first coil of the electrode and the tension of the first coil of the separator, and decreasing the tension of the electrode and the tension of the separator as the number of coils increases, the tension of the electrode and the tension of the separator are matched, thus improving the inner coil wrinkles of the lithium-ion battery. The control of incoming positive and negative electrode materials includes: Control the negative electrode peeling force to be ≥7N / m, and control the positive electrode wavy edge to be <1mm; The process of adjusting the angle between the material feeding lever and the needle winding flattening position includes: Adjust the material feeding height to 6mm~7mm, and the torque at the pull-out position to 28N~32N, so that the material feeding pull rod is in the center position when the core is flattened by 180°. The process of adjusting the size of the positive electrode cutting adhesive and the position of the positive and negative electrodes includes: Adjust the width of the positive electrode cutting adhesive to 35mm~45mm, with the adhesive tape extending beyond the R-angle. The negative electrode insertion position should be 0~3mm away from the R-angle, and the inserted negative electrode should extend more than 5mm beyond the positive electrode. The electrode tension is increased to 600 gf in the first cycle; the diaphragm tension is increased to 300 gf in the first cycle; the electrode tension is decreased by 6 gf every 5 cycles; the diaphragm tension is decreased by 2 gf every 5 cycles.

2. The method for improving inner ring wrinkles in a lithium-ion battery according to claim 1, characterized in that, The cell winding process includes: The core is formed by winding the diaphragm-negative electrode-diaphragm-positive electrode in a clockwise or counterclockwise manner.

3. The method for improving inner ring wrinkles in a lithium-ion battery according to claim 1, characterized in that, The electrode tension satisfies the tension function Y. a =600-6 / 5×M; the diaphragm tension satisfies the tension function Y. b =300-2 / 5×N; where M is the number of turns of the electrode and N is the number of turns of the diaphragm.

4. The method for improving inner ring wrinkles in a lithium-ion battery according to claim 1, characterized in that, The process of matching the electrode tension with the diaphragm tension also includes: Adjust the electrode flipping tension to 360gf~400gf; and / or, adjust the diaphragm flipping tension to 260gf~300gf.

5. A lithium-ion battery, characterized in that, The method for preparing the lithium-ion battery includes the method for improving the inner ring wrinkles of the lithium-ion battery as described in any one of claims 1 to 4.

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