A omni-tab battery cell for use in large cylindrical batteries, its preparation method and application

Abstract

This invention relates to the field of lithium-ion battery manufacturing technology, specifically providing a full-tab battery cell for large cylindrical batteries, its preparation method, and applications. This invention innovatively employs a "winding-fixing-laser axial cutting-graded flattening" process flow, changing the traditional "cut-then-winding" process long used in the industry, achieving a breakthrough in the precision of tab forming. Specifically, after the bare cell is wound, the blank areas of each current collector layer have formed a stable stacked structure, which is precisely fixed using a special fixture and simultaneously cut along the axial direction by laser, completing the high-precision forming of multiple tabs in one step. This method fundamentally eliminates the problem of accumulated deviations caused by step-by-step operations in traditional winding processes, stably controlling the tab alignment accuracy within 0.1mm, effectively solving the long-standing problem of alignment consistency in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, and in particular to a full-tab cell for use in large cylindrical batteries, its preparation method, and its application. Background Technology

[0002] With the increasing demand for high-performance batteries from new energy vehicles and energy storage systems, large cylindrical tabless batteries such as the 4680 have become an important development direction due to their structural advantages. Tables technology uses the entire edge of the current collector as a current path, significantly shortening the current conduction distance. Theoretically, this can reduce internal resistance by several times, which is key to achieving fast charging and high power.

[0003] However, the large-scale manufacturing of this technology faces significant challenges, with mass production yields generally ranging from 85% to 95%, hindering its large-scale application. The current mainstream "laser die-cutting tabs—winding—flattening" process suffers from the following core bottlenecks: First, the dispersed tabs formed during pre-winding can accumulate misalignment during the winding process due to factors such as tension fluctuations, electrode transport deviations, and uneven material thickness. For example, a 1μm thickness deviation during 50 turns can lead to over 7mm of tab misalignment, directly affecting the consistency of subsequent processing. Second, the subsequent tab flattening process requires extremely high precision, and improper force control can easily damage the current collector and generate metal debris. Third, the full tab structure leads to a surge in the number of welding points, requiring the welding process to find an extremely narrow process window between incomplete welds and burn-through, becoming a key factor affecting yield. Furthermore, the compact internal structure of the battery also makes electrolyte wetting difficult, affecting the consistency of electrical performance.

[0004] To address these challenges, the industry has developed optimization solutions such as laser flying cutting and planetary rolling, but these are all improvements to specific aspects of the existing "cut first, then wind" process and have failed to fundamentally solve systemic problems such as cumulative winding errors.

[0005] Therefore, existing processes still face systemic bottlenecks in areas such as tab alignment, non-destructive forming, reliable welding, and electrolyte wetting, making it difficult to meet the stringent requirements for consistency and high yield in the large-scale production of large cylindrical batteries. A new approach to tab processing and manufacturing methods is urgently needed to improve cell manufacturing capabilities from the root of the process. Summary of the Invention

[0006] This invention provides a omni-tab cell for use in large cylindrical batteries, its preparation method, and its application, with the aim of solving the aforementioned problems existing in the background art.

[0007] To achieve the above objectives, embodiments of the present invention provide a method for preparing a tabbed battery cell for use in large cylindrical batteries, comprising the following steps: S1: The positive electrode, separator, and negative electrode are stacked in sequence and then wound into a bare cell; both ends of the bare cell are respectively provided with uncoated current collector blank areas; the width of the current collector blank areas is 12-15mm; S2: The bare battery cell is fixed in a special fixture by mechanical clamping and / or vacuum adsorption; wherein the positioning accuracy of the special fixture is not less than ±0.05mm; S3: Under inert gas protection, the blank area of ​​the current collector is axially cut by laser to obtain multiple parallel micro tabs that are uniformly distributed along the axis of the bare cell. S4: Perform graded flattening treatment on the micro tabs, so that the micro tabs are flattened from a radial outward state to a state parallel to the end face of the bare cell; the flatness error of the ends of all micro tabs does not exceed 0.1mm; S5: Assemble the bare battery cell after the flattening process in step S4 into the casing, and then prepare the omnipolar battery cell by welding, liquid injection, and encapsulation.

[0008] Preferably, in step S1, the winding tension is 0.5-3N and the winding speed is 50-200r / min to ensure that the winding density of the bare cell is uniform and that there are no wrinkles or offsets in the blank area; the positive electrode sheet and the negative electrode sheet are obtained by coating, drying, rolling and cutting aluminum foil as the positive electrode current collector and copper foil as the negative electrode current collector, respectively.

[0009] Preferably, in step S2, the vacuum adsorption pressure is -0.06 to -0.09 MPa.

[0010] Preferably, in step S2, the special fixing fixture includes: a base, a side positioning plate, an end limiting block, and a vacuum adsorption groove; the base is provided with the side positioning plate, the end limiting block, and the vacuum adsorption groove; the side positioning plate is symmetrically arranged on both sides of the bare battery cell and has an arc-shaped surface that fits against the shell of the bare battery cell to limit the radial displacement of the bare battery cell; the end limiting block is tightly fitted to the non-cut end face of the bare battery cell to limit the axial displacement of the bare battery cell; the vacuum adsorption groove is located directly below the bare battery cell and is connected to an external vacuum source through a vacuum pipeline to adsorb and fix the bare battery cell.

[0011] Preferably, in step S3, the laser wavelength is 1060-1080nm, the laser power is 50-300W, and the cutting speed is 100-500mm / s to avoid excessive cutting that could damage the diaphragm or electrode active material; the inert gas is nitrogen or argon, and the gas flow rate is 5-20L / min to prevent metal debris generated during the cutting process from adhering to the surface of the bare battery cell.

[0012] Preferably, in step S3, the number of microtabs is 8-32, the width of a single microtab is 2-8mm, and the cutting gap between adjacent microtabs is 0.5-2mm.

[0013] Preferably, in step S4, the graded kneading process includes pre-kneading and fine kneading.

[0014] More preferably, the pre-kneading pressure is 0.1-0.2 MPa, and the number of reciprocations is 2-3 times, which is used to initially smooth the warping of the micro-electrode; the fine kneading pressure is 0.3-0.5 MPa, and the number of reciprocations is 1-2 times, which is used to ensure the flatness and surface smoothness of the micro-electrode.

[0015] An embodiment of the present invention provides a omnipolar battery cell prepared by the above-described preparation method.

[0016] The embodiments of the present invention also provide an application of the omni-tab cell prepared by the above-described preparation method in a large cylindrical battery.

[0017] The above-described solution of the present invention has the following beneficial effects: (1) This invention changes the traditional "cut-then-wind" process mode that has been used in the industry for a long time. By innovatively adopting the process flow of "winding-fixing-laser axial cutting-graded flattening", it achieves a breakthrough in the precision of tab forming. Specifically, after the bare cell is wound, the blank areas of each current collector have formed a stable stacked structure. It is precisely fixed by a special fixture and simultaneously cut along the axial direction by laser to complete the high-precision forming of multi-layer tabs in one go. This method eliminates the problem of deviation accumulation caused by step-by-step operation in the traditional winding process from the root, and stably controls the tab alignment accuracy within 0.1mm, effectively solving the long-standing problem of alignment consistency in the prior art.

[0018] (2) The significantly improved alignment accuracy of the tabs ensures that the subsequent micro-tabs are smooth and wrinkle-free after grading and flattening, with neat ends. This greatly increases the welding contact area with the top cover and current collector, and improves the uniformity of welding stress distribution. This not only helps reduce welding defects such as incomplete welding and missing welding, but also significantly improves the overall yield of the cells, from the current general level of 85%-95% to over 96%. While reducing production costs, it better meets the consistency and reliability requirements of large-scale mass production of cylindrical batteries.

[0019] (3) The alignment accuracy of the micro-tabs reaches within 0.1 mm, which is beneficial to reduce the internal resistance of the cell, promote the uniform conduction of current in the tab area, and thus improve the overall electrochemical performance of the battery. Test results show that the internal resistance of the full-tab cell prepared based on the present invention is reduced by 15%-25% compared with the cell prepared by the traditional process. After 500 cycles under 1C charge and discharge conditions, the capacity retention rate is improved by 8%-12%, and the rate performance and cycle life of the battery are optimized.

[0020] (4) In terms of implementation, the present invention does not require large-scale modification of existing winding equipment, but only requires the addition of special fixing fixtures and laser axial cutting system, resulting in relatively low equipment investment costs. The overall process is simple and easy to integrate into existing production lines, with good feasibility for industrialization and promotion, providing efficient and stable technical support for large-scale battery production. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a top view schematic diagram of the structure of the special fixture according to an embodiment of the present invention; Figure 2 This is a side view schematic diagram of the structure of the special fixture according to an embodiment of the present invention.

[0023] [Explanation of Labels in the Attached Image] Base-11, side positioning plate-12, end limiting block-13, vacuum adsorption tank-14, bare battery cell-20. Detailed Implementation

[0024] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0025] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0027] This invention addresses existing problems by providing a omni-tab battery cell for use in large cylindrical batteries, its preparation method, and its application.

[0028] The following description is provided through specific embodiments and comparative examples. Example 1 This embodiment provides a method for preparing a tabbed battery cell for use in large cylindrical batteries, comprising the following steps: S1: Using 12μm thick aluminum foil as the positive current collector and 8μm thick copper foil as the negative current collector, positive and negative electrode sheets are obtained after coating, drying, rolling, and slitting. The positive electrode sheet, separator, and negative electrode sheet are then stacked in sequence and wound using a winding machine. The winding tension is controlled at 1.5N and the winding speed is 120r / min to obtain bare cell 20. The bare cell 20 has a 15mm wide blank area for the positive current collector and a blank area for the negative current collector at both ends. S2: Place the wound bare battery cell 20 in a special fixing fixture. The radial displacement is restricted by the side positioning plate 12 adhering to the side of the bare battery cell 20, and the axial displacement is restricted by the end limiting block 13 adhering to the non-cut end face of the bare battery cell 20. At the same time, the vacuum adsorption function of the base 11 is turned on and the adsorption pressure is set to -0.07MPa to further fix the bare battery cell. S3: A CNC machine tool equipped with a fiber laser is used to perform axial cutting on the positive current collector blank area at the end of the bare cell 20. The CNC machine tool is set and controlled as follows: laser wavelength is 1070nm, laser power is 150W, cutting speed is 300mm / s, the distance between the laser cutting head and the end face of the bare cell is precisely controlled to 12mm, and the cutting depth matches the thickness of 12μm aluminum foil. During the cutting process, the CNC machine tool coordinates with the inert gas protection device to introduce nitrogen gas at a flow rate of 12L / min. Under the precise control of the CNC machine tool, a one-time continuous cutting is completed, forming 16 parallel microtaper in the positive current collector blank area. Each microtaper is 4mm wide, and the cutting gap between adjacent microtaper is 1mm. The above operation is repeated to complete the microtaper cutting of the negative current collector blank area at the other end of the bare cell 20.

[0029] S4: Using Cr 12 The MoV alloy steel flattening head performs graded flattening treatment on the microtaper formed by cutting. First, pre-flattening is performed with a flattening pressure of 0.15MPa, and the flattening head is rolled back and forth 3 times along the extension direction of the microtaper. Then, fine flattening is performed with a flattening pressure of 0.4MPa and rolled back and forth 2 times. After flattening, the flatness error of the microtaper end is measured to be 0.08mm.

[0030] S5: The flattened bare cell 20 is then assembled into a casing, current collector welding, top cover welding, electrolyte injection, and encapsulation processes to produce the finished all-tab cell.

[0031] Example 2 This embodiment provides a method for preparing a tabbed battery cell for use in large cylindrical batteries, comprising the following steps: S1: Using a 10μm thick aluminum foil as the positive current collector and a 6μm thick copper foil as the negative current collector, positive and negative electrode sheets are obtained after coating, drying, rolling, and slitting. The positive electrode sheet, separator, and negative electrode sheet are then stacked in sequence and wound using a winding machine. The winding tension is controlled at 0.8N and the winding speed is 80r / min to obtain a bare cell 20. The bare cell 20 has a 12mm wide blank area for the positive current collector and a blank area for the negative current collector at both ends. S2: Place the wound bare battery cell in a special fixing fixture. The side positioning plate 12 is attached to the side of the bare battery cell 20 to limit radial displacement, and the end limiting block 13 is attached to the non-cut end face of the bare battery cell 20 to limit axial displacement, ensuring that the bare battery cell 20 has no displacement. S3: A CNC machine tool equipped with a fiber laser is used to perform axial cutting on the positive current collector blank area at the end of the bare cell 20. The CNC machine tool is set and controlled as follows: laser wavelength is 1060nm, laser power is 80W, cutting speed is 150mm / s, the distance between the laser cutting head and the end face of the bare cell is precisely controlled to 8mm, and the cutting depth matches 10μm aluminum foil. During the cutting process, the CNC machine tool coordinates with the inert gas protection device to introduce argon gas at a flow rate of 8L / min. Under the precise control of the CNC machine tool, a one-time continuous cutting is completed, forming 24 parallel microtabs in the positive current collector blank area. Each microtab is 2.5mm wide, and the cutting gap between adjacent microtabs is 0.8mm. The above operation is repeated to complete the microtab cutting of the negative current collector blank area at the other end of the bare cell 20.

[0032] S4: Using Cr 12 The MoV alloy steel flattening head is used to flatten the microtaper formed by cutting: first, pre-flattening is performed with a flattening pressure of 0.1MPa, and the flattening head is rolled back and forth twice along the extension direction of the microtaper; then fine flattening is performed with a flattening pressure of 0.3MPa, and the head is rolled back and forth once; after flattening, the flatness error of the end of the microtaper is measured to be 0.06mm.

[0033] S5: The flattened bare cell 20 is then assembled into a casing, current collector welding, top cover welding, electrolyte injection, and encapsulation processes to produce the finished all-tab cell.

[0034] Comparative Example 1 This comparative example provides a method for fabricating a large cylindrical omnipolar battery cell, including the following steps: S1: Using 12μm thick aluminum foil as the positive electrode current collector and 8μm thick copper foil as the negative electrode current collector, positive electrode sheet and negative electrode sheet are obtained after coating, drying, rolling and cutting. S2: The positive electrode and negative electrode are laser-cut (cutting accuracy is ±0.1mm) to form 16 micro tabs in the blank area of ​​the current collector. Each micro tab is 4mm wide and the cutting gap between adjacent micro tabs is 1mm. S3: Stack and wind the positive electrode, separator, and negative electrode in sequence, with the winding tension controlled at 1.5N and the winding speed at 120r / min. S4: Using Cr 12 The MoV alloy steel flattening head is used to flatten the micro-ears at a flattening pressure of 0.3 MPa, and the flattening is repeated twice. S5: The flattened bare cells are then assembled into a casing, current collector welding, top cover welding, electrolyte injection, and encapsulation processes to produce the finished all-tab battery cell.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that the special fixture in step S2 is replaced by a common cylinder fixture (positioning accuracy ±0.3mm) to fix the bare battery cell, and the laser axial cutting in step S3 is replaced by laser radial dispersion cutting. During the cutting process, the laser is perpendicular to the winding axis and cuts the tabs one turn at a time. Other steps and parameters are the same as in Example 1.

[0036] Comparative Example 3 The difference between this comparative example and Example 1 is that the special fixture in step S2 is replaced by a conventional elastic fixture (positioning accuracy ±0.2mm, and without vacuum adsorption function) to fix the bare battery cell. All other steps and parameters are the same as in Example 1.

[0037] Comparative Example 4 The difference between this comparative example and Example 1 is that the laser axial cutting in step S3 is replaced by laser flying cutting. During the cutting process, the tab points are cut first, and then the parts are separated radially. All other steps and parameters are the same as in Example 1.

[0038] Comparative Example 5 The difference between this comparative example and Comparative Example 1 is that the die-cutting accuracy in step S2 is ±0.05mm, while the other steps and parameters are the same as those in Comparative Example 1.

[0039] Comparative Example 6 The difference between this comparative example and Comparative Example 1 is that step S4 is a graded kneading process: first, pre-kneading is performed with a kneading pressure of 0.1 MPa, and the kneading head is rolled back and forth twice along the extension direction of the micro-taper; then, fine kneading is performed with a kneading pressure of 0.3 MPa, and the head is rolled back and forth once. All other steps and parameters are the same as those in Comparative Example 1.

[0040] Alignment accuracy and production yield were tested on the omni-tab cells of the above embodiments and comparative examples, and they were assembled into large cylindrical batteries. The internal resistance and 1C charge-discharge rate cycle performance at 25°C were tested. The test results are shown in Table 1 below.

[0041] Table 1

[0042] As shown in Table 1, a comparison of Examples 1 and 2 with Comparative Examples 1 to 6 reveals that the all-tab battery cell prepared by the present invention through winding, fixing, laser axial cutting, and graded flattening significantly outperforms existing products in terms of yield, internal resistance, and cycle performance. A comparison of Comparative Example 2 with Example 1 shows that if only the process steps are changed to use a fixture that does not match the special fixing jig of the present invention (positioning accuracy ±0.05mm, while limiting radial / axial displacement), the wound flexible bare battery cell will shift during cutting, leading to misalignment of the multi-layer tabs. The yield of the resulting tabs (82.2%) is worse than that of existing processes, and the tab alignment accuracy and internal resistance are also significantly deteriorated. If the laser axial synchronous cutting method of the present invention (cutting direction parallel to the winding center axis, power / speed matching the current collector thickness) is not used, incomplete cutting or damage to the separator will occur, resulting in a significant reduction in battery cell yield. Furthermore, if the cutting direction is radial rather than axial, complete alignment of all micro-tabs cannot be achieved. The graded flattening process (pre-flattening + fine flattening) solves the problem that the radial outward flatness of the micro-tabs after winding cannot reach ≤0.1mm under the conventional single flattening process. A comparison of Comparative Examples 3 and 4 with Example 1 shows that, without using either the dedicated fixture or laser axial synchronous cutting technique of this invention, even following the winding, laser die-cutting, and graded flattening process flow of this invention, the yield, internal resistance, and cycle performance of the obtained tabs are far inferior to those of this invention. This indicates that the dedicated fixture (positioning accuracy ±0.05mm, while limiting radial / axial displacement) or laser axial synchronous cutting (cutting direction parallel to the winding center axis, power / speed matching the current collector thickness) of this invention has a synergistic effect. A comparison of Comparative Examples 5 and 6 with Comparative Example 1 shows that optimizing only a single step such as die-cutting accuracy or flattening process in the existing process only improves the tab yield by 1.3%-1.7%, and the tab alignment accuracy is still ≥0.4mm, failing to fundamentally solve the problem of deviation accumulation during the winding process.

[0043] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a tabbed battery cell for use in large cylindrical batteries, characterized in that, Includes the following steps: S1: The positive electrode, separator, and negative electrode are stacked in sequence and then wound into a bare cell; both ends of the bare cell are respectively provided with uncoated current collector blank areas; the width of the current collector blank areas is 12-15mm; S2: The bare battery cell is fixed in a special fixture by mechanical clamping and / or vacuum adsorption; wherein the positioning accuracy of the special fixture is not less than ±0.05mm; S3: Under inert gas protection, the blank area of ​​the current collector is axially cut by laser to obtain multiple parallel micro tabs that are uniformly distributed along the axis of the bare cell. S4: Perform graded flattening treatment on the micro tabs, so that the micro tabs are flattened from the radial outward state to the state parallel to the end face of the bare cell. After flattening, the end flatness error of all micro tabs does not exceed 0.1mm. S5: Assemble the bare battery cell after the flattening process in step S4 into the casing, and then prepare the omnipolar battery cell by welding, liquid injection, and encapsulation.

2. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 1, characterized in that, In step S1, the winding tension is 0.5-3N and the winding speed is 50-200r / min; the positive electrode sheet and the negative electrode sheet are obtained by coating, drying, rolling and cutting aluminum foil as the positive current collector and copper foil as the negative current collector, respectively.

3. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 1, characterized in that, In step S2, the vacuum adsorption pressure is -0.06 to -0.09 MPa.

4. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 1, characterized in that, In step S2, the special fixing fixture includes: a base, a side positioning plate, an end limiting block, and a vacuum adsorption groove; the base is provided with the side positioning plate, the end limiting block, and the vacuum adsorption groove; the side positioning plate is symmetrically arranged on both sides of the bare cell and has an arc-shaped surface that fits against the shell of the bare cell to limit the radial displacement of the bare cell; the end limiting block is tightly fitted at the non-cut end face of the bare cell to limit the axial displacement of the bare cell; the vacuum adsorption groove is located directly below the bare cell and is connected to an external vacuum source through a vacuum pipeline to adsorb and fix the bare cell.

5. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 1, characterized in that, In step S3, the laser wavelength is 1060-1080nm, the laser power is 50-300W, and the cutting speed is 100-500mm / s; the cutting process is carried out under the protection of an inert gas; the inert gas is nitrogen or argon, and the gas flow rate is 5-20L / min.

6. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 1, characterized in that, In step S3, the number of microtaper is 8-32, the width of a single microtaper is 2-8mm, and the cutting gap between adjacent microtaper is 0.5-2mm.

7. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 6, characterized in that, In step S4, the graded kneading process includes pre-kneading and fine kneading.

8. The method for preparing a tabbed battery cell for use in large cylindrical batteries according to claim 7, characterized in that, The pre-kneading pressure is 0.1-0.2 MPa, and the number of reciprocating strokes is 2-3; the fine kneading pressure is 0.3-0.5 MPa, and the number of reciprocating strokes is 1-2.

9. A omnipolar battery cell prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a omni-tab cell prepared by the preparation method according to any one of claims 1 to 8 in a large cylindrical battery.

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