Electrolytic copper foil and method for producing the same

Abstract

This invention discloses an electrolytic copper foil and its preparation method. The preparation method includes the following steps: electrolyte pretreatment, electrolytic foil formation, stripping and passivation treatment, and offline detection and adjustment. The preparation method of this invention optimizes the preparation process of electrolytic copper foil by combining the preparation process with manual offline inspection. This achieves the goal of reducing the need for expensive offline inspection equipment, lowering the investment cost of production equipment, and simultaneously reducing and maintaining stable control of the roughness of the electrolytic copper foil surface.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil for lithium-ion batteries, and in particular to an electrolytic copper foil and its preparation method. Background Technology

[0002] The surface roughness of electrolytic copper foil is a key indicator affecting the performance of power batteries. Existing technologies for reducing roughness mostly rely on expensive equipment such as online laser thickness gauges and confocal roughness testers (each unit costs over 500,000 yuan). Furthermore, the testing process often involves taking samples from the main product, resulting in raw material waste and high production costs, which is difficult for small and medium-sized enterprises to afford. While traditional production without online equipment saves on the cost of expensive testing equipment, this method has drawbacks such as: ① the addition of additives depends on experience, leading to large concentration fluctuations and unstable roughness; ② the testing samples are taken from the main product, increasing production costs.

[0003] Therefore, it is essential to provide a method for preparing electrolytic copper foil that avoids waste of raw materials while eliminating the need for expensive testing equipment and optimizing the surface roughness of the electrolytic copper foil. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide an electrolytic copper foil and its preparation method. The preparation method of the electrolytic copper foil does not require expensive online detection equipment, has low production cost, and can achieve stable control of the surface roughness of the electrolytic copper foil.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing electrolytic copper foil, comprising the steps of: S1. Electrolyte pretreatment: Activated carbon is added to the acidic copper sulfate electrolyte for pretreatment. S2. Electrolytic deposition of a green foil, wherein the electrolytic deposition of the green foil includes a first stage, a second stage and a third stage performed sequentially; First stage: The first additive and the second additive are added stepwise to the electrolyte after step S1, with a current density of 200-220 A / m²; the deposition time of the first stage is 10-15 min. Second stage: Maintain the concentrations of the first additive and the second additive, add thiourea to the electrolyte at first intervals, with a current density of 240-250 A / m², and the deposition time of the second stage is 45-50 min; The third stage: stop adding the second additive, add the third additive to the electrolyte, maintain the concentration of the first additive and the third additive, the current density is 200-210 A / m², and the deposition time of the third stage is 8-15 min; the third additive includes sodium aminoethyl thiosulfonate. S3. Stripping and passivation treatment: After step S2, the generated electrolytic copper foil is stripped from the cathode roller and then immersed in the passivation solution for passivation treatment. S4. Offline detection and adjustment: The edge material of the passivated electrolytic copper foil is cut as a test sample. The obtained test sample is manually subjected to offline roughness detection and thickness detection. The electrolytic deposition foil conditions are adjusted according to the roughness detection results and the thickness detection results.

[0006] Optionally, the first additive includes polyethylene glycol, and the second additive includes sodium polydithiopropane sulfonate; the amount of the first additive added to the electrolyte is 4-6 g / L, and the amount of the second additive added to the electrolyte is 1-2 g / L; the order of the first additives is first additive, second additive, and first additive, with an interval of 3 min.

[0007] Optionally, in the second stage, maintaining the concentration of the first additive includes the following steps: sampling 50 mL of electrolyte every hour, detecting the concentration of the first additive using offline titration, and adding the first additive at a rate of 1 g / L / h when the concentration of the first additive is lower than a preset concentration, wherein the preset concentration is equal to 4-6 g / L; the first time is 15±2 min, and the amount of thiourea added to the electrolyte is 2.5-0.3.5 mg / L; the current density is increased to 240-250 A / m² at a gradient of 10 A / m² every 3±1 min.

[0008] Optionally, in the third stage, the first additive is maintained at 0.4-0.6 g / L, and the third additive is added to the electrolyte at 0.2-0.4 g / L.

[0009] Optionally, the offline detection and adjustment includes the following steps: every hour, the passivated edge material is cut from the copper foil production line as a test sample, the surface Ra value is manually tested with an offline roughness tester, and the average value is taken. If Ra > 0.4 μm, the first additive with a concentration of 1 g / L is added. While conducting offline testing, the thickness of the edge and center of the material is manually measured. If the deviation is greater than 5%, the height of the overflow plate at the edge of the electrolytic cell is adjusted, and a third additive with a concentration of 1g / L is added.

[0010] Optionally, in step S1, the electrolyte pretreatment includes the following steps: adding activated carbon with a particle size of 200-300 mesh to the acidic copper sulfate electrolyte, stirring at 35±5℃ and letting it stand, then filtering; adjusting the electrolyte temperature to 50-53℃ and the flow rate to 1.2-1.5m / s, and using the sample after the Hull cell test shows no pinholes or blooming; the amount of activated carbon added to the electrolyte is 0.5-1g / L.

[0011] Optionally, the passivation treatment includes the following steps: after the copper foil is peeled off, it is immersed in a 0.5% (w / w) silane coupling agent solution for passivation treatment for 5-10 seconds, and then dried after removal.

[0012] Optionally, the cathode roller used in the electrolytic deposition of green foil includes a mirror titanium cathode roller with a diameter of 1.2-1.8m, and the electrolytic cell is an electrolytic cell with 3-5 segments.

[0013] Optionally, the preparation method further includes electrolyte and cathode roller maintenance steps; electrolyte maintenance includes the following steps: adding hydrogen peroxide to the electrolyte within a first preset time, stirring, adjusting the pH to 4.0 with NaOH solution, letting it stand for 2 hours, and then filtering; replacing the electrolyte within a second preset time; cathode roller maintenance includes the following steps: manually polishing the surface of each cathode roller with a 1000-mesh polishing cloth until the roller surface roughness Ra≤0.3μm.

[0014] Secondly, the present invention provides an electrolytic copper foil, which is prepared by the preparation method described above.

[0015] The beneficial effects of this invention include at least the following: The method for preparing electrolytic copper foil according to the present invention includes steps such as electrolyte pretreatment, electrolytic foil formation, stripping and passivation treatment, and offline detection and adjustment. By combining the preparation process with manual offline operation, the preparation process of electrolytic copper foil is optimized, achieving a reduction in production equipment investment costs and eliminating the need for expensive offline detection equipment, while simultaneously reducing the surface roughness of the electrolytic copper foil and maintaining stable surface roughness control. The offline detection involves manual offline operation to perform offline roughness and thickness detection on the obtained test samples, and the electrolytic deposition foil formation conditions are adjusted based on the roughness and thickness detection results. During testing, edge pieces of electrolytic copper foil are used as test samples. Utilizing these edge pieces eliminates raw material waste during testing, saves on the consumption of electrolytic copper foil products, and achieves a dual reduction in the cost of both testing equipment and products. Testing revealed that the 6μm electrolytic copper foil prepared using the method described in this invention, after SEM magnification of 2000x, exhibits uniformly spherical grains with a particle size of 25-30nm, without obvious protrusions or dendrites. The roughness Ra is stable at 0.26-0.3μm, and Rz ≤ 2.4μm, indicating that the preparation method described in this invention achieves stable control over the roughness of the electrolytic copper foil. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the method for preparing electrolytic copper foil according to the present invention.

[0017] Figure 2 This is a SEM image (magnification 2000x) of the rough surface of a 6μm electrolytic copper foil prepared in Example 1 of this invention.

[0018] Figure 3 SEM image of the rough surface of the 6μm electrolytic copper foil prepared for Comparative Example 1 (magnification 2000x).

[0019] Figure 4 SEM image of the rough surface of the 6 μm electrolytic copper foil prepared for Comparative Example 2 (magnification 2000x). Detailed Implementation

[0020] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0021] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] In this invention, the use of terms such as "first" and "second" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0023] In a first aspect, embodiments of the present invention provide a method for preparing electrolytic copper foil. This method is applicable to the production of ultra-thin electrolytic copper foil (6-12 μm) for lithium-ion batteries. See also... Figure 1 As shown, the method for preparing electrolytic copper foil according to the present invention includes the following steps: S1. Electrolyte pretreatment: Activated carbon is added to the acidic copper sulfate electrolyte for pretreatment. S2. Electrolytic deposition of a green foil, wherein the electrolytic deposition of the green foil includes a first stage, a second stage and a third stage performed sequentially; First stage: The first additive and the second additive are added stepwise to the electrolyte after step S1, with a current density of 200-220 A / m²; the deposition time of the first stage is 10-15 min. Second stage: Maintain the concentrations of the first additive and the second additive, add thiourea to the electrolyte at first intervals, with a current density of 240-250 A / m², and the deposition time of the second stage is 45-50 min; The third stage: stop adding the second additive, add the third additive to the electrolyte, maintain the concentration of the first additive and the third additive, the current density is 200-210 A / m², and the deposition time of the third stage is 8-15 min; the third additive includes sodium aminoethyl thiosulfonate. S3. Stripping and passivation treatment: After step S2, the generated electrolytic copper foil is stripped from the cathode roller and then immersed in the passivation solution for passivation treatment. S4. Offline detection and adjustment: The edge material of the passivated electrolytic copper foil is cut as a test sample. The obtained test sample is manually subjected to offline roughness detection and thickness detection. The electrolytic deposition foil conditions are adjusted according to the roughness detection results and the thickness detection results.

[0024] The method for preparing electrolytic copper foil according to the present invention includes steps such as electrolyte pretreatment, electrolytic foil formation, stripping and passivation treatment, and offline detection and adjustment. By combining the preparation process with manual offline operation, the preparation process of electrolytic copper foil is optimized, achieving a reduction in production equipment investment costs and eliminating the need for expensive offline detection equipment, while simultaneously reducing the surface roughness of the electrolytic copper foil and maintaining stable surface roughness control. The offline detection involves manual offline operation to perform offline roughness and thickness detection on the obtained test samples, and the electrolytic deposition foil formation conditions are adjusted based on the roughness and thickness detection results. During testing, edge pieces of electrolytic copper foil are used as test samples. Utilizing these edge pieces eliminates raw material waste during testing, reduces the consumption of electrolytic copper foil products, and achieves a dual reduction in the cost of both testing equipment and products. Testing of the 6μm electrolytic copper foil prepared using the method described in this invention, after SEM magnification at 2000x, reveals that the rough surface grains of the electrolytic copper foil are uniformly spherical with a particle size of 25-30nm, without obvious protrusions or dendrites. The roughness Ra is stable at 0.26-0.3μm, and Rz ≤ 2.4μm, indicating that the preparation method described in this invention achieves stable control over the roughness of the electrolytic copper foil. This method is suitable for the production of ultra-thin electrolytic copper foil in small and medium-sized enterprises.

[0025] The acidic copper sulfate electrolyte contains Cu. 2+ The concentration is 45-55 g / L, and the concentration of H2SO4 is 180-220 g / L.

[0026] The first additive includes polyethylene glycol, and the second additive includes sodium polydithiopropane sulfonate; optionally, the first additive may be polyethylene glycol with a molecular weight of 4000, denoted as PEG-4000; the amount of the first additive added to the electrolyte is 4-6 g / L, and the amount of the second additive added to the electrolyte is 1-2 g / L; the order of the first additives is first additive, second additive, and first additive again, with an interval of 3 min. In the first stage, the amount and interval of PEG-4000 and SPS are fixed to ensure uniform nucleation and reduce human control errors. In the second stage, maintaining the concentration of the first additive includes the following steps: sampling 50 mL of electrolyte every hour, detecting the concentration of the first additive using offline titration, and replenishing the additive at a rate of 1 g / L / h when the concentration is lower than a preset concentration, wherein the preset concentration is 4-6 g / L; the first time is 15 ± 2 min, and the amount of thiourea added to the electrolyte is 2.5-0.3.5 mg / L; the current density is increased to 240-250 A / m² in a gradient of 10 A / m² every 3 ± 1 min. During the second stage, the surface of the deposited copper foil is visually inspected. If the surface of the copper foil is mottled, activated carbon powder is added for cyclic adsorption. The amount of activated carbon added to the electrolyte is 0.1 g / L, and the cyclic adsorption time is 30-35 min.

[0027] The specific steps for detecting the concentration of PEG-4000 using the offline titration method are as follows: Take 20 mL of electrolyte sample, add 5 mL of potassium chromate indicator, and titrate with 0.01 mol / L silver nitrate standard solution until a brick-red precipitate appears. Calculate the PEG-4000 concentration based on the volume consumed (titering error ≤ 5%). A "timed and quantitative addition + offline detection calibration" approach is adopted, measuring the PEG-4000 concentration offline every hour to avoid rough readings due to excessively low concentrations. Thiourea is added at a fixed interval to simplify the operation.

[0028] In the third stage, the first additive is maintained at 0.4-0.6 g / L, and the third additive is added to the electrolyte at 0.2-0.4 g / L. In this third stage, the interface additive ratio is fixed to improve peelability and reduce roughness caused by mechanical damage, eliminating the need for online monitoring of the peeling status.

[0029] The offline detection and adjustment includes the following steps: every hour, passivated edge material is cut from the copper foil production line as a test sample, the surface Ra value is manually tested with an offline roughness tester, and the average value is taken. If Ra > 0.4 μm, the first additive with a concentration of 1 g / L is added. While conducting offline testing, the thickness of the edge and center of the edge material is manually measured. If the deviation is greater than 5%, the height of the overflow plate at the edge of the electrolytic cell is adjusted, and a third additive with a concentration of 1 g / L is added. The edge material is a portion of the electrolytic copper foil from both sides of the roller on which the dried copper foil is wound. The width of the test sample is 5-8 cm, and the length is 10-15 cm. Three test points are selected for each piece of edge material, located at both ends and the center. For thickness testing, three points are taken at the edge and three at the center of the edge material, and the average value is calculated.

[0030] The offline roughness test uses a Mitutoyo SJ-210 roughness tester (accuracy ±0.01μm) and a digital micrometer (accuracy ±0.001mm). During manual testing, the roughness tester probe must be perpendicular to the rough surface of the edge material, the pressure must be controlled between 0.75-1.0N, and the test trajectory length must be 5mm.

[0031] In step S1, the electrolyte pretreatment includes the following steps: adding activated carbon with a particle size of 200-300 mesh to an acidic copper sulfate electrolyte, stirring at 35±5℃, allowing it to stand, and then filtering; adjusting the electrolyte temperature to 50-53℃ and the flow rate to 1.2-1.5 m / s, and using the sample after testing for pinholes and bloom-free formation via a Hull cell test; the amount of activated carbon added to the electrolyte is 0.5-1 g / L. The current for the Hull cell test is 2 A, and the test time is 5 min. In step S1, the stirring time is 2±1 h; for example, it can be 1 h, 2 h, or 3 h. The standing time is 3-5 h; for example, it can be 3 h, 4 h, or 5 h. The filtration includes the following steps: circulating the settled electrolyte through a diatomaceous earth filter and a 5 μm precision filter. In this invention, by optimizing the electrolyte pretreatment, activated carbon is used for graded impurity removal and targeted adsorption of Fe by activated carbon. 2+ Cl - With pre-calibration of the Hull cell, interference from impurities on additives can be eliminated in advance, avoiding roughness defects caused by impurities in the later stage, and eliminating the need for online monitoring of impurity concentration.

[0032] In step S1, if the edge of the Hull cell sample becomes rough, a third additive with a concentration of 2-3 g / L should be added immediately. The edge material sampling should be carried out simultaneously with the main copper foil product to ensure that the edge material and the main product come from the same electrolytic batch and that the difference in surface roughness between the two is ≤0.02 μm.

[0033] The passivation treatment includes the following steps: after the copper foil is peeled off, it is immersed in a 0.5% (w / w) silane coupling agent solution for passivation treatment for 5-10 seconds, and then dried after removal.

[0034] The cathode rollers used in the electrolytic deposition of green foil include mirror titanium cathode rollers with a diameter of 1.2-1.8m, and the electrolytic cells are 3-5 segment electrolytic cells.

[0035] The preparation method also includes electrolyte and cathode roller maintenance steps. Electrolyte maintenance includes the following steps: adding hydrogen peroxide to the electrolyte within a first preset time, stirring, adjusting the pH to 4.0 with NaOH solution, letting it stand for 2 hours, and then filtering; replacing the electrolyte at a second preset time. Cathode roller maintenance includes the following steps: manually polishing the surface of each cathode roller with a 1000-mesh polishing cloth until the surface roughness Ra ≤ 0.3 μm. The second preset time is 15 days, with 1 / 3 of the electrolyte replaced each time. A fixed cycle for electrolyte purification, electrolyte replacement, and cathode roller polishing is established, eliminating the need for online equipment status monitoring and maintaining process stability through standardized operations.

[0036] The preparation method described in this invention relies entirely on conventional offline testing instruments and standardized manual operation, making it simple to operate and shortening the worker training cycle to 3 days. The copper foil qualification rate increased from 82% to 94%, and the electrolyte showed no significant performance degradation after 45 days of continuous use, extending its lifespan by 30%.

[0037] Secondly, embodiments of the present invention provide an electrolytic copper foil, which is prepared by the preparation method described above.

[0038] Example 1: Preparation of 6μm thick ultrathin lithium battery copper foil using the preparation method described above. In this example, no online detection equipment was used, and the edge material was used as the test sample. Electrolyte pretreatment: Prepare a Cu solution with an addition rate of 50 g / L. 2+ A 200 g / L H₂SO₄ acidic copper sulfate electrolyte was prepared. 250-mesh activated carbon was added to the electrolyte at a concentration of 0.8 g / L. The mixture was stirred at 35°C for 2 hours, allowed to stand for 4 hours, and then filtered three times using a 5 μm precision filter. Fe was then sampled and analyzed. 2+ The content is 0.04 g / L, Cl - The content was 0.015 g / L; the electrolyte temperature was adjusted to 48℃ and the flow rate to 1.4 m / s, and a 2A current was applied to the Hull cell for 5 min of electrolysis. The test piece showed no pinholes or blooming and entered the production stage.

[0039] Electrolytic deposition of the green foil takes a total of 70 minutes and is divided into three stages: Stage 1 (0-10 minutes), Stage 2 (10-60 minutes), and Stage 3 (60-70 minutes).

[0040] The first stage is the initial deposition period. The electrolyte is pre-placed in the electrolytic cell. A portion of PEG-4000 is added to the electrolytic cell using a metering pump; this is the first addition. After 3 minutes, SPS is added to the electrolyte at a concentration of 1.5 g / L; this is the second addition. After another 3 minutes, the remaining PEG-4000 is added; this is the third addition. The total amount of PEG-4000 added to the electrolyte is 5 g / L. The current density is set to 210 A / m². The second stage is the stabilization period. Every hour, 50 mL of electrolyte is pipetted and the concentration of PEG-4000 is measured using the titration method described above. When the measured value is 3.8 g / L, PEG-4000 is added at a rate of 0.1 g / L / h. Every 15 minutes, 0.3 mg / L of thiourea is added quantitatively using a syringe. The current density is 10 A / m for 10 minutes. 2 Gradient increased to 245 A / m 2 If slight mottled appearance is observed on the rough surface of the copper foil, add 0.1 g / L of activated carbon powder and stir until the mottled appearance disappears. The third stage, the final stage, involves stopping the addition of SPS and maintaining the concentrations of PEG-4000 0.5 g / L and AESS 0.3 g / L; the current density is then adjusted to 200 A / m. 2 Immediately after peeling off the copper foil, immerse it in a 0.5% silane coupling agent solution and remove it after 5-10 seconds. Then, take it out and dry it.

[0041] Timed offline detection and adjustment: A solution of edge material sampling + manual testing is adopted.

[0042] Sampling: Every hour, three pieces of the dried copper foil edge material are cut; each piece is 6cm wide and 12cm long, taken from the sides of the roller body, and cut simultaneously with the main product; Roughness test: The Mitutoyo SJ-210 roughness tester was operated manually. The probe was vertically aligned with the rough surface of the edge electrolytic copper foil. The test pressure was set to 0.8N and the trajectory length to 5mm. Three points were tested on each edge piece (one point 2cm from each end and one point in the middle). The average value of the nine points from the three edge pieces was taken. The average value of the first test was Ra=0.28μm (no adjustment required). The average value of the second test was Ra=0.42μm (PEG-4000 0.1g / L was added). Thickness test: The thickness of the edge and center of each piece of material was measured manually with a digital micrometer (3 points each), and the average value was taken. It was found that the edge was 8% thicker than the center. The height of the overflow plate in the electrolytic cell was adjusted, and AESS was added at a dosage of 0.1g / L. After 30 minutes, the thickness deviation was measured again and reduced to 4%. Periodic maintenance: After 72 hours of production, add 0.3 g / L hydrogen peroxide to the electrolyte, stir for 30 minutes, adjust the pH to 4.0 with 20 wt% NaOH solution, let stand for 2 hours, and then filter; on the 15th day, drain 1 / 3 of the old electrolyte and replenish with fresh electrolyte; after each roll, manually polish the cathode roller with a 1000-mesh polishing cloth, and after polishing, use a roughness tester to check that the roller surface Ra ≤ 0.4 μm.

[0043] Results: See Figure 2 As shown, the electrolytic copper foil obtained in this embodiment has uniform spherical grains on the rough surface, without obvious protrusions or dendrites, and has high surface flatness, corresponding to Ra=0.23μm; after 30 days of continuous production, the average Ra value of the rough surface of the copper foil is 0.27μm, Rz=2.3μm, the sampling loss rate of the main product is reduced from 3% to 0.4%, the tensile strength is 385MPa, the pass rate is 94.5%, the electrolyte has no obvious turbidity, and the impurity content is maintained within the control range.

[0044] Comparative Example 1: Except that no thiourea was added during the stabilization period, SPS was retained during the tailing period, and the main product (10cm×10cm) was taken as a sample during the test, the rest was the same as Example 1.

[0045] Results: See Figure 3 As shown, Figure 3 In the sample, numerous coarse dendrites appeared on the rough surface of the copper foil, with uneven grain distribution and obvious depressions and protrusions, corresponding to Ra=0.45μm. The main product loss rate was 3.2%, the tensile strength was 310MPa, the pass rate was 77%, and obvious dendrites appeared on the rough surface.

[0046] Comparative Example 2: Compared to Example 1, there was no timed offline detection (no online equipment, edge material sampling but manual operation was not standardized).

[0047] Samples were taken and tested every 4 hours. During manual testing, edge material was not wiped, and the probe was tilted; otherwise, the process was the same as in Example 1. Results: See [link to example]. Figure 4 As shown, the copper foil surface has local pinholes, obvious grain agglomeration, and irregular protrusions at the edges. The corresponding Ra fluctuation range is 0.3-0.6μm, the test error is 0.05-0.08μm, the thickness deviation is up to 12%, the pass rate is 82%, and a batch of pinhole defects have appeared.

[0048] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0049] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing electrolytic copper foil, characterized in that, Including the following steps: S1. Electrolyte pretreatment: Activated carbon is added to the acidic copper sulfate electrolyte for pretreatment. S2. Electrolytic deposition of a green foil, wherein the electrolytic deposition of the green foil includes a first stage, a second stage and a third stage performed sequentially; First stage: The first additive and the second additive are added stepwise to the electrolyte after step S1, with a current density of 200-220 A / m²; the deposition time of the first stage is 10-15 min. Second stage: Maintain the concentrations of the first additive and the second additive, add thiourea to the electrolyte at first intervals, with a current density of 240-250 A / m², and the deposition time of the second stage is 45-50 min; The third stage: stop adding the second additive, add the third additive to the electrolyte, maintain the concentration of the first additive and the third additive, the current density is 200-210 A / m², and the deposition time of the third stage is 8-15 min; the third additive includes sodium aminoethyl thiosulfonate. S3. Stripping and passivation treatment: After step S2, the generated electrolytic copper foil is stripped from the cathode roller and then immersed in the passivation solution for passivation treatment. S4. Offline detection and adjustment: The edge material of the passivated electrolytic copper foil is cut as a test sample. The obtained test sample is manually subjected to offline roughness detection and thickness detection. The electrolytic deposition foil conditions are adjusted according to the roughness detection results and the thickness detection results.

2. The preparation method according to claim 1, characterized in that, The first additive includes polyethylene glycol, and the second additive includes sodium polydithiopropane sulfonate; the amount of the first additive added to the electrolyte is 4-6 g / L, and the amount of the second additive added to the electrolyte is 1-2 g / L; the order of the first additives is first additive, second additive, and first additive, with an interval of 3 min.

3. The preparation method according to claim 1, characterized in that, In the second stage, maintaining the concentration of the first additive includes the following steps: taking a 50 mL sample of electrolyte every hour, detecting the concentration of the first additive using an offline titration method, and adding the first additive at a rate of 1 g / L / h when the concentration of the first additive is lower than a preset concentration, wherein the preset concentration is equal to 4-6 g / L; the first time is 15±2 min, and the amount of thiourea added to the electrolyte is 2.5-0.3.5 mg / L; the current density is increased to 240-250 A / m² at a gradient of 10 A / m² every 3±1 min.

4. The preparation method according to claim 1, characterized in that, In the third stage, the first additive is maintained at 0.4-0.6 g / L, and the third additive is added to the electrolyte at 0.2-0.4 g / L.

5. The preparation method according to claim 1, characterized in that, The offline detection and adjustment includes the following steps: every hour, passivated edge material is cut from the copper foil production line as a test sample, the surface Ra value is manually tested with an offline roughness tester, and the average value is taken. If Ra > 0.4 μm, the first additive with a concentration of 1 g / L is added. While conducting offline testing, the thickness of the edge and center of the material is manually measured. If the deviation is greater than 5%, the height of the overflow plate at the edge of the electrolytic cell is adjusted, and a third additive with a concentration of 1g / L is added.

6. The preparation method according to claim 1, characterized in that, In step S1, the electrolyte pretreatment includes the following steps: adding activated carbon with a particle size of 200-300 mesh to the acidic copper sulfate electrolyte, stirring at 35±5℃ and letting it stand, then filtering; adjusting the electrolyte temperature to 50-53℃ and the flow rate to 1.2-1.5m / s, and using the sample after the Hull cell test shows no pinholes or blooming; the amount of activated carbon added to the electrolyte is 0.5-1g / L.

7. The preparation method according to claim 1, characterized in that, The passivation treatment includes the following steps: after the copper foil is peeled off, it is immersed in a 0.5% (w / w) silane coupling agent solution for passivation treatment for 5-10 seconds, and then dried after removal.

8. The preparation method according to claim 1, characterized in that, The cathode rollers used in the electrolytic deposition of green foil include mirror titanium cathode rollers with a diameter of 1.2-1.8m, and the electrolytic cells are 3-5 segment electrolytic cells.

9. The preparation method according to claim 1, characterized in that, The preparation method further includes electrolyte and cathode roller maintenance steps; electrolyte maintenance includes the following steps: adding hydrogen peroxide to the electrolyte within a first preset time, stirring, adjusting the pH to 4.0 with NaOH solution, letting it stand for 2 hours, and then filtering; replacing the electrolyte within a second preset time. Cathode roller maintenance includes the following steps: manually polish the surface of each cathode roller with a 1000-mesh polishing cloth until the surface roughness Ra is ≤0.3μm.

10. An electrolytic copper foil, characterized in that, The electrolytic copper foil is prepared by the preparation method described in any one of claims 1-9.

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