A device for eliminating wrinkles in the rolling of lithium-ion battery electrode sheets and its application

Abstract

This invention relates to a device for eliminating wrinkles in the rolling process of lithium-ion battery electrodes. The device is positioned after the electrode (4) is rolled and before a tensioning mechanism or a winding mechanism. The electrode (4) includes a coated area and an uncoated area. The device includes at least two sets of rolling assemblies, each set symmetrically arranged on the upper and lower surfaces of the electrode (4). A conductive ring device (3) is mounted on each rolling assembly, directly contacting the uncoated foil (5) of the electrode (4). A magnet is positioned between adjacent rolling assemblies, generating a magnetic field perpendicular to the surface of the electrode (4). The uncoated foil (5) is subjected to Ampere force in the magnetic field, generating a non-contact tensioning force to both sides, thus eliminating rolling wrinkles. Compared with the prior art, this invention utilizes the non-contact method of Ampere force to improve the uneven stress field within the lithium-ion battery electrode after rolling, effectively solving the wrinkles and buckling problems that occur during the rolling process.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and in particular relates to a device for eliminating wrinkles in lithium-ion battery electrode rolling and its application. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density and long cycle life, and are widely used in new energy, new energy vehicles and other industries. The electrode rolling process is a key step in the manufacturing process of lithium-ion batteries. It involves compacting the dried electrode sheets through a rolling mill to obtain the required thickness and has a significant impact on the electrode energy density, rate performance and cycle stability.

[0003] Because of the significant difference in thickness between the active material coating area and the tab area on the electrode sheet, the different elongations of these two areas during the rolling process create an uneven residual stress field within the electrode sheet after rolling. The compressive stress in the pressed area leads to defects such as buckling instability and wrinkles (wavy, herringbone) on the electrode sheet. The traditional solution is to use a tensioning mechanism to apply tension to the electrode sheet along the rolling direction, changing the internal stress state of the electrode sheet, which can suppress the formation of wrinkles to some extent. However, once the tension is released, the uneven stress field easily leads to defects, and increasing the tension can easily cause sheet breakage, which is detrimental to improving production efficiency.

[0004] A review of existing literature revealed two patents: Chinese Patent Publication No. CN 109037589 A, titled "A Roller Pressing Anti-Wrinkle Device and Method for Lithium-ion Battery Electrodes," which uses a curved roller to smooth and unfold the electrode. The first, Chinese Patent Publication No. CN 109742317 A, titled "A Roller Pressing and Slitting Anti-Wrinkle Device for Lithium-ion Battery Electrodes," uses a curved roller to smooth and unfold the electrode. The second, Chinese Patent Publication No. CN 109742317 A, titled "A Roller Pressing and Slitting Anti-Wrinkle Device for Lithium-ion Battery Electrodes," uses a curved roller to smooth and unfold the electrode. The third, Chinese Patent Publication No. CN 109742317 A, titled "A Roller Pressing and Slitting Anti-Wrinkle Device for Lithium-ion Battery Electrodes," uses a curved roller to smooth and unfold the electrode. The fourth, Chinese Patent Publication No. CN 109037589 A, titled "A Utilization of Friction Between the Curved Roller and the Electrode for Flattening," finds that the flattening force is difficult to control, potentially causing electrode breakage. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a lithium-ion battery electrode roll forming wrinkle elimination device and its application. A magnetic field perpendicular to the electrode surface is applied, and the foil material in the uncoated area is energized. The energized conductor is subjected to a transverse Ampere force in the magnetic field. This non-contact tension force can improve the internal stress state of the electrode, prevent buckling instability in the compressive stress area of ​​the electrode, effectively reduce the occurrence of electrode wrinkle defects, and improve production efficiency.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A device for eliminating wrinkles in the rolling of lithium-ion battery electrode sheets is disclosed. This device is positioned after the electrode rolling process and before a tensioning mechanism or a winding mechanism. The electrode sheet includes a coated area and an uncoated area. The device comprises at least two sets of rolling assemblies, each set symmetrically arranged on the upper and lower surfaces of the electrode sheet. Each rolling assembly is equipped with a conductive ring device that directly contacts the uncoated foil area of ​​the electrode sheet. Magnets are positioned between adjacent rolling assemblies, generating a magnetic field perpendicular to the electrode surface. This device utilizes the Ampere force experienced by the uncoated foil area in the magnetic field to apply a non-contact tension force to both sides of the electrode sheet, thereby improving the stress distribution within the electrode sheet.

[0008] Furthermore, the roller pressing assembly has an external lead wire connected to a power source to apply high and low voltages. The roller pressing assembly is a roller, and in a preferred embodiment, it includes a first roller and a second roller. Each roller pressing assembly includes a pressure roller and a support roller, which are symmetrically arranged on the upper and lower surfaces of the electrode sheet.

[0009] Furthermore, the conductive ring device is made of conductive materials such as graphite, gold, silver or copper, and at least two conductive ring devices are installed at intervals on each rolling assembly.

[0010] Furthermore, the magnet is a permanent magnet or an electromagnet, including an N pole and a S pole, which are respectively disposed on the surface and below the pole piece. The magnet has at least two sets, symmetrically disposed on both sides of the center line of the pole piece, and the S poles and N poles of adjacent magnets are opposite, so that the generated magnetic field is symmetrically distributed on both sides of the center line of the pole piece, with equal magnitude and opposite direction.

[0011] The present invention also provides an application of a lithium-ion battery electrode roll forming wrinkle elimination device. The device applies a current along the rolling direction to the uncoated foil area. The uncoated foil area is subjected to Ampere force in the magnetic field, generating a non-contact tension force to both sides, thereby eliminating roll forming wrinkles.

[0012] Furthermore, the application includes the following operational steps:

[0013] S1. Adjust the gap between the rollers of the roller pressing assembly to ensure good contact between the conductive ring device and the foil material in the uncoated area;

[0014] S2. Adjust and fix the positions of the N and S poles of the magnet;

[0015] S3. The rolling assembly is connected to the power supply through an external conductor, which generates a current in the uncoated foil area along the rolling direction. The current intensity is adjusted according to the actual production conditions.

[0016] Furthermore, the roller pressing assembly in step S1 is either actively driven by a motor or passively rotated by friction with the electrode sheet.

[0017] Furthermore, the contact force between the conductive ring device and the uncoated foil in step S1 can be freely adjusted according to the actual operating conditions to ensure stable and reliable contact without disconnection or power loss. The contact force adjustment range is 1-10N.

[0018] Furthermore, the magnetic field generated by the magnet in step S2 is a uniform magnetic field or a magnetic field with a gradient variation law, and the magnetic field strength is 0.1-3T.

[0019] Furthermore, the current in step S3 is either DC or AC. The magnitude of the current can be adjusted manually or automatically in real time according to the actual production situation of wrinkles, thereby changing the magnitude of the Ampere force and thus the magnitude of the lateral tension force, so that the wrinkle elimination effect can be optimized. The current adjustment range is 1-50A.

[0020] After steps S1-S3, the internal stress distribution of the electrode is affected by non-contact lateral tension force, which improves the stress state of the compressive stress area and avoids the occurrence of planar defects such as buckling instability and wrinkles.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The present invention uses Ampere force to apply transverse tension force to the electrode sheet, thereby changing the internal uneven stress state caused by the different elongation rates of the electrode sheet coating area and the tab area, avoiding compressive stress that causes wrinkles in the electrode sheet, and improving the yield and production efficiency of the electrode sheet rolling process.

[0023] (2) Ampere force tensions the electrode laterally in a non-contact manner, avoiding the risk of the electrode being cracked or torn, and the magnitude of the tension force can be easily controlled in real time by controlling the magnitude of the current.

[0024] (3) The lateral tension is not affected by the size of the electrode itself. For different electrode thicknesses, different coating thicknesses, different tab widths, etc., it can be applied to the rolling process of different types of lithium-ion battery electrodes without changing any equipment. Attached Figure Description

[0025] Figure 1 This is a front view schematic diagram of the lithium-ion battery electrode roll forming wrinkle elimination device of the present invention;

[0026] Figure 2 This is a left-side schematic diagram of the lithium-ion battery electrode roll forming wrinkle elimination device of the present invention;

[0027] Figure 3 This is a top view schematic diagram of the lithium-ion battery electrode roll forming wrinkle elimination device of the present invention.

[0028] Markings in the image:

[0029] 1—First roll; 2—Second roll; 3—Conductive ring device; 4—Electrode sheet; 5—Uncoated foil; 6—N electrode; 7—S electrode. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] Example

[0032] like Figures 1 to 3 As shown, a lithium-ion battery electrode rolling wrinkle elimination device is provided. This device is positioned after electrode rolling and before the tensioning mechanism or winding mechanism. The device includes at least two sets of rolling assemblies; in this embodiment, two sets are provided: a first roller 1 and a second roller 2. High and low voltages are applied respectively using external wires. Each rolling assembly includes a pressure roller and a support roller, symmetrically arranged on the upper and lower surfaces of the electrode 4. At least two conductive ring devices 3 are installed at intervals on each roller; in this embodiment, three conductive ring devices 3 are provided, with a diameter slightly larger than the diameter of the roller itself. Each conductive ring device 3 is in direct contact with the uncoated foil 5. At least two sets of magnets are provided between the first roll 1 and the second roll 2. In this embodiment, two sets of magnets are provided. Each magnet includes an N pole 6 and an S pole 7. The two sets of magnets are symmetrically arranged on both sides of the center line of the pole piece 4, and the N poles 6 and S poles 7 of the two sets of magnets are arranged oppositely on the surface and below the surface of the pole piece 4. A magnetic field perpendicular to the surface of the pole piece 4 is generated between the N poles 6 and S poles 7 of each magnet. The N poles 6 and S poles 7 on both sides of the center line of the pole piece 4 are arranged oppositely, that is, the intensity of the magnetic field lines is the same and the direction is opposite.

[0033] The conductive ring device 3 is made of conductive materials such as graphite, gold, silver, or copper. In this embodiment, graphite is preferred as the conductive material because it has good conductivity and wear resistance. By adjusting the gap between the first roller 1 and the second roller 2, the contact pressure between the rollers and the electrode 4 is adjusted to ensure good contact between the conductive ring device 3 and the uncoated foil 5.

[0034] The magnet is a permanent magnet or an electromagnet, preferably an electromagnet in this embodiment. A conductive coil is wound around the outside of the iron core, resulting in a lightweight structure with high magnetic field strength that is easily adjustable. The magnetic field is a uniform magnetic field or a magnetic field with a gradient variation, preferably a uniform magnetic field in this embodiment, with its direction perpendicular to the plane of the pole pieces.

[0035] The power supply output current is DC or AC. In this embodiment, the power supply is preferably a current source. The second roller 2 is connected to the positive terminal of the current source through a wire, and the first roller 1 is connected to the negative terminal of the current source through a wire. The current magnitude is adjusted in real time according to the actual production situation, and the adjustment range is 1-50A.

[0036] The contact pressure between the first roll 1 and the second roll 2 and the electrode sheet is preferably adjusted using a hydraulic cylinder. This method is simple in structure, reliable in operation, and ensures good contact between the conductive ring device 3 and the uncoated foil 5 without detachment.

[0037] The application of the above-mentioned lithium-ion battery electrode roll forming wrinkle elimination device has the following operating steps:

[0038] S1. Pass the electrode 4 through the rolling mechanism and connect it to the winding mechanism. Adjust the pressure of the first roller 1 and the second roller 2 to ensure good contact between the conductive ring device 3 and the uncoated foil 5. Adjust the hydraulic cylinder to keep the contact pressure constant to avoid fluctuations in the electrode 4 during the rolling process, which could cause the electrode 4 to detach from the conductive ring device 3 and result in power failure.

[0039] S2. Adjust and fix the positions of the N pole 6 and S pole 7 of the magnet, and set the current through the electromagnetic coil to generate a magnetic field strength of 0.1-3T, preferably 2T in this embodiment;

[0040] S3, the first roll 1 and the second roll 2 are connected to the negative and positive terminals of the current source respectively through external wires, so that a current is generated in the uncoated foil 5 along the rolling direction. The current generates Ampere force under the action of the magnetic field. The current intensity is adjusted according to the actual production conditions to control the magnitude of the Ampere force and minimize the occurrence of wrinkles.

[0041] In the actual design, the first roll 1 and the second roll 2 can be actively driven by a motor, with their speeds matching the forward speed of the electrode sheet 4, thus avoiding relative friction that could cause the electrode sheet 4 to break. Auxiliary measures such as blowers are used to enhance heat dissipation of the electrode sheet 4, preventing it from overheating and melting due to the thermal effect of the current and the heat generated by friction, thereby improving the continuous production efficiency of the electrode sheet 4.

[0042] The above-described lithium-ion battery electrode roll forming wrinkle elimination device and its application can apply non-contact tension to both sides of the electrode 4, avoiding the risk of buckling and wrinkling of the electrode 4 due to residual compressive stress caused by the difference in elongation after roll forming. For different coating thicknesses, different current collector thicknesses, different tab widths, etc., only the gap between the rollers and the contact pressure need to be adjusted. No changes or replacements to any device are required to meet the needs of eliminating roll forming wrinkles of various types of lithium-ion battery electrodes.

[0043] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An application of a lithium-ion battery electrode rolling wrinkle elimination device, wherein the device is disposed after the electrode (4) is rolled and before the tensioning mechanism or the winding mechanism, the electrode (4) comprising a coated area and an uncoated area, characterized in that, The device includes at least two sets of roller pressing components. Each set of roller pressing components is symmetrically arranged on the upper and lower surfaces of the electrode (4). A conductive ring device (3) is installed on the roller pressing component. The conductive ring device (3) is in direct contact with the uncoated foil material (5) of the electrode (4). A magnet is provided between adjacent roller pressing components. The magnet generates a magnetic field perpendicular to the surface of the electrode (4). Using the device, an electric current is applied to the uncoated foil (5) along the rolling direction. The uncoated foil (5) is subjected to Ampere force in the magnetic field, generating non-contact tension force to both sides, thus eliminating rolling wrinkles.

2. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 1, characterized in that, The roller pressing assembly has an external wire leading out and connected to a power source. The roller pressing assembly is a rolling mill.

3. The application of the lithium-ion battery electrode rolling wrinkle elimination device according to claim 1, characterized in that, The conductive ring device (3) is made of conductive materials such as graphite, gold, silver or copper, and at least two conductive ring devices (3) are installed at intervals on each roller pressing assembly.

4. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 1, characterized in that, The magnet is a permanent magnet or an electromagnet, and the magnetic field is symmetrically distributed on both sides of the center line of the pole piece (4), with equal magnitude and opposite direction.

5. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 1, characterized in that, The application includes the following steps: S1. Adjust the gap between the rollers of the roller pressing assembly to ensure good contact between the conductive ring device (3) and the uncoated foil (5); S2. Adjust and fix the position of the magnet; S3. The rolling assembly is connected to the power supply through the external wire, so that the current in the uncoated foil (5) is generated along the rolling direction, and the current intensity is adjusted according to the actual production conditions.

6. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 5, characterized in that, The roller pressing assembly in step S1 is either actively driven or passively rotated.

7. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 5, characterized in that, The contact force between the conductive ring device (3) and the uncoated foil (5) in step S1 is 1-10 N.

8. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 5, characterized in that, The magnetic field generated by the magnet in step S2 is a uniform magnetic field or a non-uniform magnetic field, with a magnetic field strength of 0.1-3 T.

9. The application of the lithium-ion battery electrode roll forming wrinkle elimination device according to claim 5, characterized in that, The current in step S3 is either direct current or alternating current, and the current magnitude is 1-50 A.

Images