Additive for electrolytic copper foil, electrolyte, electrolytic copper foil with ultrahigh tensile strength and preparation method of electrolytic copper foil

Abstract

The invention relates to the technical field of electrolytic copper foils, in particular to an additive for an electrolytic copper foil, an electrolyte, an ultrahigh-tensile-strength electrolytic copper foil and a preparation method of the ultrahigh-tensile-strength electrolytic copper foil. And carrying out gradient current deposition and in-situ annealing by adopting the electrolyte for the electrolytic copper foil to obtain the copper foil. The electrolyte comprises the following raw materials in mass concentration: 15 to 20 ppm of a polyacrylamide-rare earth complex, 0.8 to 1.2 ppm of a selenium-containing compound, 3 to 5 ppm of a stress inhibitor, 0.5 to 1 ppm of a surfactant, 80 to 90 g / L of copper ions, 100 to 110 g / L of sulfuric acid and 50 to 60 ppm of chloride ions. According to the preparation method, rare earth microalloying and a multistage grain boundary regulation and control technology are combined, so that the prepared copper foil is relatively good in interface bonding force and tensile strength.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil technology, and in particular to additives, electrolytes, ultra-high tensile strength electrolytic copper foil and their preparation methods for electrolytic copper foil. Background Technology

[0002] Electrolytic copper foil is a key basic material for electronic components such as printed circuit boards (PCBs), lithium-ion battery negative electrode current collectors, and flexible circuits (FPCs). Its performance directly affects the reliability, energy density, and integration of end products. With the rapid development of 5G communication, new energy vehicles, and high-end consumer electronics industries, higher requirements are placed on the comprehensive performance of high-performance copper foil. It not only needs excellent room temperature mechanical strength and high conductivity, but also good high-temperature dimensional stability, low surface profile, and strong interfacial adhesion with the substrate or active material.

[0003] Currently, there are several different technical approaches in the field of high-end copper foil technology. One approach is high-strength, heat-resistant alloyed electrolytic copper foil technology. A typical example is the scheme disclosed in patent CN103827358B, which involves adding salts of metals such as tungsten (W), molybdenum (Mo), titanium (Ti), or tellurium (Te) to a copper sulfate electrolyte, while strictly controlling the chloride ion concentration below 3 mg / L. This allows the aforementioned metal elements to form ultrafine particles with a particle size of 0.5~20 nm in their oxide or elemental form, which are uniformly dispersed in the copper matrix. The copper alloy foil produced by this method has the characteristics of high tensile strength (≥500 MPa) under normal conditions and good heat resistance, retaining more than 80% of its strength after heating to 300℃. Secondly, there is the low-profile electrolytic copper foil technology using a composite organic additive system, as described in patent CN1854347A. By adding additives such as gelatin, hydroxyethyl cellulose, sodium polydithiopropane sulfonate, and ethylene thiourea in specific proportions, the grain size is effectively refined and the surface roughness of the deposited material is reduced, thereby obtaining copper foil with both a certain strength and a low-profile surface to meet the processing requirements of fine circuits. Thirdly, there is the composite current collector process technology, represented by the scheme disclosed in patent CN120366777A. This technology uses polymer materials such as polyethylene terephthalate (PET) or polypropylene (PP) as the supporting base film, and pre-prepares a nanoscale copper layer by magnetron sputtering or vacuum evaporation. Then, it combines electrolytic deposition and precision rolling processes to prepare an ultra-thin copper foil. This aims to comprehensively leverage the advantages of large-scale production by electrolysis and precise control by rolling to improve the overall performance and yield of the product, and is particularly suitable for high-end fields such as flexible circuit boards and solid-state battery current collectors.

[0004] Despite significant progress in the aforementioned technologies, several technical shortcomings remain to be addressed: First, traditional electrolytic copper foil exhibits poor thickness adaptability. Thin foils (e.g., thickness ≤ 18 μm) often show a significant decrease in elongation to below 4% when achieving high strength, while thick foils (e.g., thickness ≥ 50 μm) are prone to core-surface performance gradients and poor uniformity. Second, some copper foil products lack high-temperature stability; after prolonged thermal aging at 150℃, the tensile strength decay rate exceeds 12%, failing to meet the stringent requirements of high-energy-density lithium batteries for current collector thermal stability (decay rate < 10%). Third, when used as a battery current collector, the interfacial bonding between the copper foil and the negative electrode active material is weak, with peel strength generally below 0.9 N / mm, making it difficult to meet application requirements of 1.1 N / mm or higher, thus affecting battery cycle life and fast-charging performance. Finally, thick foils (thickness > 35 μm)... Microstructural defects such as striped grain boundaries are easily generated during the production process (μm). Grain bands larger than 10μm can be observed through scanning electron microscopy. This non-uniform structure leads to material anisotropy, affecting the reliability and consistency of the final product.

[0005] Therefore, developing a high-performance copper foil preparation technology that can simultaneously achieve high strength, high elongation, excellent high-temperature stability, strong interfacial adhesion, and uniform microstructure across the entire thickness range has become a critical issue that urgently needs to be addressed in this field. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide additives, electrolytes, ultra-high tensile strength electrolytic copper foil and their preparation methods for electrolytic copper foil, so as to solve the problems of poor interfacial bonding and poor uniformity of electrolytic copper foil in the prior art.

[0007] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0008] The first aspect of the present invention is to provide an additive for electrolytic copper foil, the additive comprising the following raw materials in mass concentrations: 15-20 ppm polyacrylamide-rare earth complex, 0.8-1.2 ppm selenium-containing compound, 3-5 ppm stress inhibitor, and 0.5-1 ppm surfactant.

[0009] A second aspect of the present invention is to provide an electrolyte for electrolytic copper foil, comprising the additives for electrolytic copper foil as described above; preferably, the electrolyte comprises raw materials with the following mass concentrations: 15-20 ppm polyacrylamide-rare earth complex, 0.8-1.2 ppm selenium-containing compound, 3-5 ppm stress inhibitor, 0.5-1 ppm surfactant, 80-90 g / L copper ions, 100-110 g / L sulfuric acid, and 50-60 ppm chloride ions.

[0010] A third aspect of this invention is to provide a method for preparing ultra-high tensile strength electrolytic copper foil, the method comprising the following steps:

[0011] The copper foil is obtained by gradient current deposition of the electrolyte used for electrolytic copper foil as described above, followed by in-situ annealing.

[0012] A fourth aspect of the present invention is to provide an ultra-high tensile strength electrolytic copper foil, which is prepared by the preparation method described above.

[0013] A fifth aspect of the present invention is to provide an electrode comprising an ultra-high tensile strength electrolytic copper foil as described above.

[0014] A sixth aspect of the present invention is to provide a secondary battery comprising the electrode as described above.

[0015] As described above, the additives, electrolyte, ultra-high tensile strength electrolytic copper foil, and preparation method of the present invention have the following beneficial effects:

[0016] (1) Targeted technological improvements were made to optimize the performance of copper foil by addressing several key issues in its preparation: rare earth complex grain boundary pinning technology was used to solve the problem of abnormal grain growth in thick foil (50 μm), narrowing the grain size distribution from the conventional ±25% to ±8%; the twinning induction technology using selenium-containing compounds such as selenomethionine improved the brittle fracture defects of thin foil (18 μm), increasing its elongation to 9.2%; reverse current interface reconstruction technology was applied to strengthen the bonding force between the copper foil and the negative electrode, achieving a peel strength of 1.35 N / mm (a 50% improvement); and in-situ thermal annealing (80℃) technology suppressed the attenuation of tensile strength during aging, keeping the attenuation rate below 7.5%. These improvements effectively enhanced the overall performance and stability of the copper foil.

[0017] (2) This invention introduces rare earth microalloying and multi-level grain boundary control technology during the preparation of copper foil. Rare earth microalloying can achieve technical effects such as grain refinement, improved mechanical properties, reduced surface roughness, and enhanced oxidation resistance; rare earth ions adsorb at crystal active sites to inhibit growth and refine grains; mechanical properties are enhanced through multiphase interaction; roughness is reduced by optimizing electrodeposition; and oxidation resistance is enhanced by promoting the formation of a dense oxide film. Multi-level grain boundary control technology adjusts microstructural parameters such as interfacial spacing, grain size, and twin structure ratio in copper foil by controlling process parameters such as electrolyte composition, current density, and temperature. Its purpose is to refine grains and introduce special grain boundary structures such as nanotwins to improve the strength, plasticity, and conductivity of copper foil, while reducing surface roughness. The two technologies work together to improve the overall performance of copper foil. Detailed Implementation

[0018] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. Those skilled in the art can easily understand other advantages and effects of this invention from the content disclosed in this specification.

[0019] Unless otherwise defined, all technical and scientific terms used herein 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 specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0021] In this invention, the terms "preferredly," "more preferably," "better," and "even better" refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. That is, in this invention, "preferredly," "more preferably," "better," and "even better" are merely descriptions of more effective implementations or examples, but do not constitute a limitation on the scope of protection of the invention.

[0022] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0023] In this invention, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this invention, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0024] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0025] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0026] Unless otherwise stated, a singular term may include a plural term and should not be understood as having a quantity of one.

[0027] In this invention, "above" or "below" both include the number itself. For example, "below 1" includes 1.

[0028] In this invention, room temperature refers to 0~40°C, including but not limited to 10~40°C, or further to 20~30°C.

[0029] The first aspect of the present invention is to provide an additive for electrolytic copper foil, the additive comprising the following raw materials in mass concentrations: 15-20 ppm polyacrylamide-rare earth complex, 0.8-1.2 ppm selenium-containing compound, 3-5 ppm stress inhibitor, and 0.5-1 ppm surfactant.

[0030] In some embodiments of the present invention, the additive comprises the following raw materials in mass concentrations: 15-18 ppm of polyacrylamide-rare earth complex, 0.8-1 ppm of selenium-containing compound, 3-4 ppm of stress inhibitor, and 0.5-0.8 ppm of surfactant.

[0031] In some embodiments of the present invention, the additive comprises the following raw materials in mass concentrations: 18-20 ppm polyacrylamide-rare earth complex, 1-1.2 ppm selenium-containing compound, 4-5 ppm stress inhibitor, and 0.8-1 ppm surfactant.

[0032] In some embodiments of the present invention, the polyacrylamide-rare earth complex is selected from one or more of polyacrylamide-cerium complex, polyacrylamide-yttrium complex, polyacrylamide-lanthanum complex, or polyacrylamide-samarium complex.

[0033] In some embodiments of the present invention, the preparation method of the polyacrylamide-rare earth complex includes the following steps: S1) dissolving polyacrylamide in water to obtain a polyacrylamide solution, then adding thionyl chloride to react and obtain an acyl chloride intermediate; S2) adding glycine to the acyl chloride intermediate obtained in step S1, adjusting the pH to 8-9, and reacting to obtain modified polyacrylamide; S3) adding a rare earth salt solution to the modified polyacrylamide, adjusting the pH to 5-6, and reacting to obtain a polyacrylamide-rare earth complex colloid; S4) purifying, drying, and grinding the polyacrylamide-rare earth complex colloid to obtain the polyacrylamide-rare earth complex.

[0034] In some embodiments of the present invention, the polyacrylamide in step S1 is selected as anionic PAM (molecular weight ≥ 12 million, degree of hydrolysis 15%~20%), because it has a high proportion of carboxyl groups (-COOH), which makes it easy to combine with rare earth ions. The mass concentration of the polyacrylamide solution is 5-10%.

[0035] In some embodiments of the present invention, the reaction temperature in step S1 is 35-45°C and the reaction time is 1-3 hours.

[0036] In some embodiments of the present invention, one indication of stopping the addition of thionyl chloride in step S1 is the absence of vigorous reaction and gas generation. That is, the need to stop adding thionyl chloride is determined by observing whether bubbles are generated. Specifically, the mass ratio of polyacrylamide to thionyl chloride is 9-11:1, specifically 10:1; thionyl chloride is added while vacuum distillation is performed to reduce the water content in the reaction system.

[0037] In some embodiments of the present invention, the reaction temperature in step S2 is 55-65°C and the reaction time is 3-5 hours.

[0038] In some embodiments of the present invention, the mass ratio of glycine to polyacrylamide in step S2 is 1:4-6. Preferably, it is 1:5.

[0039] In some embodiments of the present invention, the concentration of the rare earth salt solution in step S3 is 0.1-0.5 mol / L.

[0040] In some embodiments of the present invention, Ce in step S3 3+ The molar ratio of carboxyl groups is 1:3-5.

[0041] In some embodiments of the present invention, the reaction temperature in step S3 is 50-60°C, and the reaction time is 5-7 hours.

[0042] In some embodiments of the present invention, an acetate-sodium acetate buffer system is used to adjust the pH in step S3. Specifically, in the acetate-sodium acetate buffer system, the sodium acetate concentration is 0.05-0.07M, specifically 0.0635M; the acetic acid concentration is 0.02-0.04M, specifically 0.0365M.

[0043] In some embodiments of the present invention, the purification process in step S3 is as follows: the polyacrylamide-rare earth complex colloid is dialyzed through a dialysis membrane (molecular weight cutoff 8000 Da) for 45-50 hours to remove free cerium ions and small molecule impurities.

[0044] In some embodiments of the present invention, the drying in step S3 is freeze drying. Preferably, the freeze drying temperature is -45℃ to -35℃ and the vacuum degree is 8-12 Pa.

[0045] In some embodiments of the present invention, the particle size of the polyacrylamide-rare earth complex in step S3 is <180 μm.

[0046] In some embodiments of the present invention, the mass fraction of rare earth elements in the polyacrylamide-rare earth complex in step S3 is 0.8-1.2%.

[0047] Preferably, the polyacrylamide-rare earth complex is a polyacrylamide-cerium complex, which can be achieved through the following process, with key steps including PAM carboxylation modification → cerium ion complexation → purification and drying: The specific preparation method of the polyacrylamide-cerium complex is as follows:

[0048] Step 1: Carboxylation modification of polyacrylamide (introduction of complexation sites) The degree of carboxylation of polyacrylamide is controlled to be 15-20% to ensure sufficient cerium binding sites;

[0049] Modification reaction:

[0050] Chemical equation

[0051] PAM-COOH + SOCl2→ PAM-COCl + SO2+ HCl

[0052] PAM-COCl + NH2-CH2-CH2-COOH → PAM-CO-NH-CH2-CH2-COOH

[0053] PAM was dissolved in deionized water (concentration 5%~10%), and thionyl chloride (SOCl2) was added. The mixture was reacted at 40°C for 2 hours to generate an acyl chloride intermediate.

[0054] Add glycine and adjust the pH to 8-9 (using NaOH solution). React at 60°C for 4 hours to introduce carboxyethylamide groups and enhance the cerium ion chelating ability.

[0055] Step 2: Cerium ion complexation

[0056] Cerium source selection: Use cerium nitrate (Ce(NO3)3·6H2O) or cerium sulfate (purity ≥99.9%).

[0057] Complexation process:

[0058] Dilute the modified PAM solution to 3%~5%, and slowly add the cerium salt solution (Ce). 3+ Concentration 0.1~0.5 mol / L), controlling the molar ratio Ce 3+ Carboxyl group ratio: 1:3~5 (avoid excessive cerium to prevent precipitation);

[0059] Maintain a temperature of 50-60°C and a pH of 5-6 (acetic acid-sodium acetate buffer system), and stir the reaction for 6 hours to form PAM-Ce. 3+ Complex colloids.

[0060] Step 3: Purification and Drying

[0061] Purification: The reaction solution was dialyzed through a dialysis membrane (molecular weight cutoff 8000 Da) for 48 hours to remove free cerium ions and small molecule impurities;

[0062] Drying: Freeze-dry (-40°C, vacuum 10 Pa) to obtain a white porous solid, which is then ground into powder with a particle size <180 μm. The final cerium content in the powder is 0.8-1.2% by mass to avoid excessive cerium, which would increase the brittleness of the subsequently produced copper foil. The residual monomer content is ≤0.02% to avoid electrodeposition bubble defects.

[0063] In step 1, the PAM is anionic PAM. After hydrolysis, anionic PAM can form a mixture of PAM and PAM-COOH, with a high proportion of such substances containing carboxyl groups. Furthermore, by taking precautions and operating the process of adding thionyl chloride carefully, slowly, and in small amounts, the dangers of violent reactions can be avoided.

[0064] PAM has a degree of hydrolysis, and the content of PAM-COOH formed after hydrolysis fluctuates slightly. Therefore, its content also fluctuates when thionyl chloride is added. One indication that the addition of thionyl chloride has stopped is the absence of a vigorous reaction and gas generation. In other words, whether or not bubbles are generated can be used to determine whether the addition of thionyl chloride needs to be stopped.

[0065] The amount of aminoacetic acid added is the same as the molar amount of thionyl chloride added.

[0066] In some embodiments of the present invention, the selenium-containing compound is selected from one or more of selenomethionine, selenoglucose, or selenium dioxide;

[0067] In some embodiments of the present invention, the stress inhibitor is selected from one or more of sulfur-containing compounds and polymers; preferably, the stress inhibitor is selected from one or more of sodium 3-mercapto-1-propanesulfonate, sodium polydithiodipropanesulfonate, or polyethylene glycol.

[0068] In some embodiments of the present invention, the surfactant is a perfluoroalkyl ether.

[0069] A second aspect of the present invention is to provide an electrolyte for electrolytic copper foil, comprising the additives for electrolytic copper foil as described above; preferably, the electrolyte comprises raw materials with the following mass concentrations: 15-20 ppm polyacrylamide-rare earth complex, 0.8-1.2 ppm selenium-containing compound, 3-5 ppm stress inhibitor, 0.5-1 ppm surfactant, 80-90 g / L copper ions, 100-110 g / L sulfuric acid, and 50-60 ppm chloride ions.

[0070] The electrolyte of this invention is obtained by compounding multiple additives. These additives interact with each other and have the following effects:

[0071] The microstructure is improved synergistically. Polyacrylamide-cerium complex refines the grains, while selenomethionine promotes twin formation. The two work together to make the copper foil grains smaller and increase the number of twins, thereby optimizing the microstructure and improving strength and toughness.

[0072] To enhance performance stability, sodium 3-mercapto-1-propanesulfonate can suppress stress and, in combination with grain refiners, reduce internal stress caused by grain refinement, preventing copper foil warping and deformation. At the same time, it works synergistically with twinning promoters to release stress through twin boundaries, thereby enhancing the performance stability of copper foil.

[0073] The electrodeposition process is optimized by using perfluoroalkyl ethers as surfactants to reduce the surface tension of the electrolyte, ensuring uniform dispersion of additives and promoting uniform electrodeposition. When combined with grain refiners, it facilitates better application of the refiners to the cathode surface, improving grain refinement. Furthermore, when combined with sodium 3-mercapto-1-propanesulfonate, it improves the distribution of sodium 3-mercapto-1-propanesulfonate in the electrolyte, enhancing stress suppression.

[0074] Improving surface quality involves surfactants, which help make the copper foil surface smoother, and grain refiners, which refine the grains, also help reduce surface roughness. The combined effect of these two agents significantly improves the surface quality of the copper foil. Simultaneously, sodium 3-mercapto-1-propanesulfonate enhances the corrosion resistance of the copper surface, and in combination with surfactants, further improves the corrosion resistance and other properties of the copper foil surface.

[0075] In some embodiments of the present invention, the electrolyte comprises the following raw materials in mass concentrations: 15-20 ppm polyacrylamide-rare earth complex, 0.8-1.2 ppm selenium-containing compound, 3-5 ppm stress inhibitor, 0.5-1 ppm surfactant, 80-90 g / L copper ions, 100-110 g / L sulfuric acid, and 50-60 ppm chloride ions.

[0076] In some embodiments of the present invention, the electrolyte comprises the following raw materials in mass concentrations: 15-18 ppm polyacrylamide-rare earth complex, 0.8-1 ppm selenium-containing compound, 3-4 ppm stress inhibitor, 0.5-0.8 ppm surfactant, 80-85 g / L copper ions, 100-105 g / L sulfuric acid, and 50-55 ppm chloride ions.

[0077] In some embodiments of the present invention, the electrolyte comprises the following raw materials in mass concentrations: 18-20 ppm polyacrylamide-rare earth complex, 1-1.2 ppm selenium-containing compound, 4-5 ppm stress inhibitor, 0.8-1 ppm surfactant, 85-90 g / L copper ions, 105-110 g / L sulfuric acid, and 55-60 ppm chloride ions.

[0078] In some embodiments of the present invention, the copper ions are copper sulfate pentahydrate.

[0079] In some embodiments of the present invention, the chloride ion source may be hydrochloric acid.

[0080] A third aspect of this invention is to provide a method for preparing ultra-high tensile strength electrolytic copper foil, the method comprising the following steps:

[0081] The copper foil is obtained by gradient current deposition of the electrolyte used for electrolytic copper foil as described above, followed by in-situ annealing.

[0082] The gradient current deposition is as follows: 0-30s, current density is 35-55A / dm²; 30-180s, current density is 25-40A / dm²; 180s-end of deposition, current density is 30-60A / dm².

[0083] This invention achieves three major technical effects through dynamic current control and three-stage gradient adjustment: the initial high current (50A / dm²) forms nanocrystal nuclei (35nm), improving the matrix strength; the middle stage current reduction (32A / dm²) suppresses dendrites, ensuring density (pinhole rate ↓86%); and the final stage pulse (50A / dm²) induces surface recrystallization, forming a -120MPa compressive stress layer, resulting in a tensile strength of 548MPa and an elongation of 8.5%.

[0084] In some embodiments of the present invention, when the copper foil thickness is 3μm≤19μm, the gradient current includes the following stages: a forward DC current with a current density of 45-55A / dm² is applied from 0-20s, a forward DC current with a current density of 35-40A / dm² is applied from 20-150s, a forward DC current with a current density of 50-60A / dm² is applied from 150s to 15s before the end of deposition, and a reverse DC current with a current density of 4-4.8A / dm² is applied 15s before the end of deposition.

[0085] In some embodiments of the present invention, when 19 μm < copper foil thickness ≤ 36 μm, the gradient current includes the following stages: a forward DC current with a current density of 40-50 A / dm² is applied from 0 to 30 s; a forward DC current with a current density of 28-38 A / dm² is applied from 30 to 180 s; a forward pulse current with a current density of 35-45 A / dm² is applied from 180 s to 20 s before the end of deposition; and a reverse DC current with a current density of 1.75-2.25 A / dm² is applied 20 s before the end of deposition. The duty cycle of the forward pulse current is 45-85%; the frequency of the forward pulse current is 1-10 Hz.

[0086] In some embodiments of the present invention, when 36 μm < copper foil thickness ≤ 55 μm, the gradient current includes the following stages: a forward DC current with a current density of 35-45 A / dm² is applied from 0-30s; a forward DC current with a current density of 25-35 A / dm² is applied from 30-180s; a reverse pulse current with a current density of 30-40 A / dm² is applied from 180s to 30s before the end of deposition; and a reverse pulse current with a current density of 0.75-1.25 A / dm² is applied 30s before the end of deposition. The duty cycle of the reverse pulse current is 45-85%; the frequency of the reverse pulse current is 1-10 Hz.

[0087] In some embodiments of the present invention, the copper foil is obtained by passivation treatment after in-situ annealing. The passivation treatment can be a conventional passivation method in the art, that is, silanizing the electrodeposited copper foil, or immersing it in a benzotriazole solution for 1-1.5 min and then sequentially performing nano-Zn-Cr alloy electrodeposition.

[0088] In some embodiments of the present invention, the in-situ annealing temperature is 75-90°C, specifically 75-80°C or 80-90°C; the annealing time is 80-130 seconds, specifically 80-90 seconds, 90-120 seconds, or 120-130 seconds. Preferably, the heating is a segmented heating process, specifically 50°C (5 seconds) → 65°C (30 seconds) → 75°C (150 seconds); the heating rate is 0.5°C / second (50→65°C) or 0.3°C / second (65→75°C).

[0089] In some embodiments of the present invention, the copper foil is further subjected to roll forming after in-situ annealing. The roll forming is an online micro-rolling process; preferably, the rolling pressure is 4-6 MPa and the gap is 50-50 μm. Preferably, the pressure is 5 MPa and the gap is 50.5 μm.

[0090] In some embodiments of the present invention, the temperature of the current deposition is 53-57°C; specifically, it can be 53-55°C or 55-57°C.

[0091] In some embodiments of the present invention, the surface roughness Ra of the cathode roller used for current deposition is ≤0.1μm, specifically, it can be 0.05-0.1μm. The diameter of the cathode roller can be Ø2500mm or Ø3000mm.

[0092] A fourth aspect of the present invention is to provide an ultra-high tensile strength electrolytic copper foil, which is prepared by the preparation method described above.

[0093] In some embodiments of the present invention, the thickness of the copper foil is 3-55 μm. Specifically, it can be 3-15 μm, 15-18 μm, 18-25 μm, 25-40 μm, or 40-55 μm.

[0094] In some embodiments of the present invention, the room temperature tensile strength of the copper foil is ≥535MPa. Specifically, it can be 535-541MPa, 541-546MPa, 546-549MPa, 549-552MPa, or 552-556MPa.

[0095] In some embodiments of the present invention, the aged tensile strength of the copper foil is ≥500MPa. Specifically, it can be 500-503MPa, 503-506MPa, or 506-512MPa.

[0096] In some embodiments of the present invention, the aging elongation of the copper foil is ≥8%. Specifically, it can be 8-8.5%, 8.5-8.8%, or 8.8-9.5%.

[0097] In some embodiments of the present invention, the surface roughness Rz of the copper foil is 3.5-5 μm. Specifically, it can be 3.5-3.8 μm, 3.8-4.2 μm, or 4.2-4.6 μm.

[0098] In some embodiments of the present invention, the peel strength of the copper foil is ≥1.3 N / mm. Specifically, it can be 1.3-1.32 N / mm or 1.32-1.35 N / mm.

[0099] In some embodiments of the present invention, the resistivity of the copper foil is ≤1.72 μΩ·cm.

[0100] A fifth aspect of the present invention is to provide an electrode comprising an ultra-high tensile strength electrolytic copper foil as described above.

[0101] A sixth aspect of the present invention is to provide a secondary battery comprising the electrode as described above.

[0102] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0103] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, equipment, and materials similar to or equivalent to those described, used, and materials in the embodiments of this invention may be used to implement this invention.

[0104] The preparation method of the polyacrylamide-cerium complex in this invention is as follows: 5g of anionic PAM is dissolved in deionized water (concentration 10%), and 0.5g of thionyl chloride (SOCl2) is added. The mixture is reacted at 40°C for 2 hours to generate an acyl chloride intermediate.

[0105] Add 1g of glycine, adjust the pH to 8.5 (using NaOH solution), react at 60°C for 4 hours, introduce carboxyethylamide groups to enhance the cerium ion chelating ability, and obtain modified PAM;

[0106] Step 2: Cerium ion complexation

[0107] Dilute 50 ml of modified PAM solution to 5%, and slowly add cerium nitrate solution (Ce). 3+ Concentration 0.5 mol / L), controlling the molar ratio Ce 3+ Carboxyl group ratio: 1:4 (avoid excessive cerium to prevent precipitation);

[0108] Maintain a temperature of 55°C and a pH of 5-6 (acetic acid-sodium acetate buffer system), and stir the reaction for 6 hours to form PAM-Ce. 3+ Complex colloid; sodium acetate solubility in the acetate-sodium acetate buffer system is 0.0635 M, and acetic acid solubility is 0.0365 M;

[0109] Step 3: Purification and Drying

[0110] Purification: The reaction solution was dialyzed through a dialysis membrane (molecular weight cutoff 8000 Da) for 48 hours to remove free cerium ions and small molecule impurities;

[0111] Drying: Freeze-drying (-40°C, vacuum 10 Pa) yields a white porous solid, which is then ground into powder with a particle size <180 μm. The final cerium content in the powder is 1.1% by mass to avoid excessive cerium, which would increase the brittleness of the subsequently produced copper foil. The residual monomer content is ≤0.02% to avoid electrodeposition bubble defects. The anionic PAM is manufactured by Foshan Sanzhong Environmental Protection Technology Co., Ltd.

[0112] Example

[0113] Example 1

[0114] This embodiment provides a method for preparing ultra-high tensile strength electrolytic copper foil, including the following steps:

[0115] Gradient electrodeposition in an electrolyte followed by post-treatment yields electrolytic copper foil. Specifically, the cathode roller used for electrodeposition is made of high-purity titanium (TA1 / TA2 grade), with a diameter of Ø2500mm and a surface roughness Ra≤0.05μm; the anode is an IrO2-RuO2 coated titanium mesh (porosity 20%), and the electrode spacing is 7.7-8.3mm.

[0116] The electrolyte comprises the following raw materials at the following mass concentrations: copper sulfate pentahydrate 330 g / L, sulfuric acid 110 g / L, chloride ions 55 ppm, polyacrylamide-cerium complex 16 ppm, selenomethionine 1.2 ppm, sodium 3-mercapto-1-propanesulfonate 5 ppm, and perfluoroalkyl ether 0.9 ppm; specifically, the perfluoroalkyl ether is perfluoroalkyl ethanol polyoxyethylene ether, manufactured by Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0117] The electrodeposition temperature is 53-57℃; the current control for electrodeposition is as follows: a forward DC current with a current density of 50A / dm² is applied from 0-20s, a forward DC current with a current density of 38A / dm² is applied from 20-150s, a forward DC current with a current density of 55A / dm² is applied from 150s to 15s before the end of deposition, and a reverse DC current with a current density of 4.4A / dm² is applied 15s before the end of deposition.

[0118] The post-treatment includes in-situ annealing and two-stage passivation, specifically as follows: the copper foil obtained after electrodeposition is treated under nitrogen protection at 85℃ for 90s, then immersed in a benzotriazole solution for 1.5min; subsequently, nano-Zn-Cr alloy electrodeposition is performed sequentially to obtain electrolytic copper foil. The benzotriazole solution comprises the following raw materials at the following mass concentrations: 0.1% benzotriazole, 40% ethanol, 0.2g / L sodium citrate, and 0.1g / L nano-silica. Sodium citrate acts as a pH buffer to promote the penetration of benzotriazole into micropores, and nano-silica, with a particle size of 10-20nm, serves as an auxiliary agent to facilitate the filling of nanoscale defects on the surface. The electrodeposition temperature of the nano-Zn-Cr alloy is 53-57℃; the current density for depositing Zn and Cr is 50 A / dm², and the deposition time is 5 s; the electrolyte for Zn deposition includes the following raw materials at the following mass concentrations: zinc sulfate (ZnSO4·7H2O): 100 g / L, formic acid (HCOOH): 50 mL / L, sodium acetate (CH3COONa·3H2O): 30 g / L, sodium sulfate (Na2SO4): 50 g / L, boric acid (H3BO3): 30 g / L; the electrolyte for Cr deposition includes the following raw materials at the following mass concentrations: chromium sulfate (Cr2(SO4)3·6H2O): 150 g / L, formic acid (HCOOH): 50 mL / L, sodium acetate (CH3COONa·3H2O): 30 g / L, sodium sulfate (Na2SO4): 50 g / L, boric acid (H3BO3): 30 g / L. g / L; Zn is deposited first, followed by Cr. The electrolyte is passed sequentially through electrolytes containing the corresponding metal ions.

[0119] Table 1. Performance test results of the electrolytic copper foil prepared in Example 1

[0120]

[0121] Note: Aging conditions: 150℃ / 1h. In antioxidant properties, ΔR is a direct measure of antioxidant activity: ΔR intuitively represents how much additional protection the antioxidant provides to the system.

[0122] Example 2

[0123] This embodiment provides a method for preparing ultra-high tensile strength electrolytic copper foil, including the following steps:

[0124] Gradient electrodeposition in an electrolyte followed by post-treatment yields electrolytic copper foil. Specifically, the cathode roller used for electrodeposition is made of high-purity titanium (TA1 / TA2 grade), with a diameter of Ø3000mm and a surface roughness Ra≤0.1μm; the anode is an IrO2-RuO2 coated titanium mesh (porosity 15%), and the electrode spacing is 9.5-10.5mm.

[0125] The electrolyte comprises the following raw materials in the following mass concentrations: copper sulfate pentahydrate 330 g / L, sulfuric acid 110 g / L, chloride ions 55 ppm, polyacrylamide-cerium complex 18 ppm, selenomethionine 1 ppm, sodium 3-mercapto-1-propanesulfonate 4.2 ppm, and perfluoroalkyl ether 0.7 ppm; specifically, the perfluoroalkyl ether is perfluoroalkyl ethanol polyoxyethylene ether.

[0126] The electrodeposition temperature is 53-57℃; the current control for electrodeposition is as follows: a forward DC current with a current density of 45 A / dm² is applied from 0-30s; a forward DC current with a current density of 32 A / dm² is applied from 30-180s; a forward pulse current with a current density of 40 A / dm² is applied from 180s to 20s before the end of deposition; and a reverse DC current with a current density of 2 A / dm² is applied 20s before the end of deposition. The on-time of the pulse current is 0.5s, and the off-time is 0.1s.

[0127] Post-treatment includes in-situ annealing and passivation, specifically as follows: The copper foil obtained after electrodeposition is hot-air treated at 80℃ for 120s, and then immersed in a silane solution to form a chromate-organosilicon composite film (15nm thick) on the surface of the heat-treated copper foil. The silane solution concentration is 1.5% (v / v); the immersion time is 10s, and the immersion temperature is 50℃. Hexavalent chromium gains electrons on the copper foil surface and is reduced to trivalent chromium. Then, through silane treatment, an organosilicon layer is grafted onto the chromate film. The silane, after hydrolysis, has abundant hydroxyl groups, which can dehydrate with the chromate containing abundant hydroxyl groups to form stable Si-OM covalent bonds. Then, hot-air treatment at 80℃ for 120s further completes the condensation reaction, making the chromate-organosilicon composite film denser.

[0128] Table 2. Performance test results of the electrolytic copper foil prepared in Example 2

[0129]

[0130] Note: Aging conditions: 150℃ / 1h.

[0131] Example 3

[0132] This embodiment provides a method for preparing ultra-high tensile strength electrolytic copper foil, including the following steps:

[0133] Gradient electrodeposition in the electrolyte, followed by post-treatment, yields electrolytic copper foil. Specifically, the cathode roller used for electrodeposition is made of high-purity titanium (TA1 / TA2 grade), with a diameter of Ø3000mm and a surface roughness Ra≤0.1μm; auxiliary anode: edge compensation electrode (to solve the "dog bone effect"); ultrasonic vibration system: 40kHz (to prevent thick-layer air bubble retention).

[0134] The electrolyte comprises the following raw materials in the following mass concentrations: copper sulfate pentahydrate 330 g / L, sulfuric acid 110 g / L, chloride ions 55 ppm, polyacrylamide-cerium complex 20 ppm, selenomethionine 0.8 ppm, sodium 3-mercapto-1-propanesulfonate 3.5 ppm, and perfluoroalkyl ether 0.5 ppm; specifically, the perfluoroalkyl ether is perfluoroalkyl ethanol polyoxyethylene ether.

[0135] The electrodeposition temperature is 53-57℃; the current control during electrodeposition is as follows: a forward DC current with a current density of 40 A / dm² is applied from 0-30s; a forward DC current with a current density of 28 A / dm² is applied from 30-180s; a forward DC current with a current density of 35 A / dm² is applied from 180s to 30s before the end of deposition; and a reverse pulse current with a current density of 1.25 A / dm² is applied 30s before the end of deposition. The on-time of the pulse current is 0.5s, and the off-time is 0.1s.

[0136] Post-processing includes in-situ annealing and roll forming, as detailed below:

[0137] In-situ annealing: 75℃ segmented heating treatment (50℃→75℃×180s). Specifically, 50℃ (5 seconds) → 65℃ (30 seconds) → 75℃ (150 seconds); heating rate: 0.5℃ / second (50→65℃), 0.3℃ / second (65→75℃).

[0138] Roll forming: Online micro-calendering (pressure 5MPa, gap 50.5μm).

[0139] Table 3. Performance test results of the electrolytic copper foil prepared in Example 3

[0140]

[0141] Note: Aging conditions: 150℃ / 1h.

[0142] Comparative Example

[0143] Comparative Example 1

[0144] This comparative example provides a method for preparing ultra-high tensile strength electrolytic copper foil, which differs from Example 2 in that:

[0145] Cancel in-situ annealing;

[0146] The current was increased from 40 A / dm² to 45 A / dm² in the last 20 seconds before the deposition ended.

[0147] The electrolytic copper foil prepared in this comparative example has a room temperature strength of 545 MPa, but its strength decreases to 455 MPa after aging.

[0148] Comparative Example 2

[0149] This comparative example provides a method for preparing ultra-high tensile strength electrolytic copper foil, which differs from Example 2 in that:

[0150] In the electrolyte, telluride choline nanocolloids are used to replace selenomethionine, and the concentration of telluride choline nanocolloids is adjusted to 0.6 ppm. The preparation method of the telluride choline nanocolloids includes the following steps:

[0151] ①Raw material preparation

[0152] Choline chloride 0.279 g (2.0 mmol) (≥99.9%) and sodium tellurite 0.222 g (1.0 mmol) (Na2TeO3, ≥99.5%) were dissolved in 100 mL of deionized water at a molar ratio of 2:1.

[0153] Add 2 ml of 0.1 M sodium citrate as a stabilizer (to prevent Te). 2+ (Oxidation).

[0154] ② Reduction reaction

[0155] Under nitrogen protection, ascorbic acid solution (0.15M, pH=4) was added dropwise, and the reaction was carried out in a water bath at 60°C for 2 hours.

[0156] Reaction endpoint control: The solution changes from colorless to a stable wine-red colloid;

[0157] ③ Purification and Characterization

[0158] Free ions were removed by ultrafiltration centrifugation (10kDa membrane) to obtain colloids with a particle size of 20±5nm (DLS detection).

[0159] Store after freeze-drying, and redisperse in electrolyte (concentration 0.5-0.8 ppm) before use.

[0160] The electrolytic copper foil prepared in this comparative example has an aging elongation of 12.3% and a resistivity of 1.78 μΩ·cm.

[0161] Comparative Example 3

[0162] This comparative example provides a method for preparing ultra-high tensile strength electrolytic copper foil. The difference from Example 1 is that no polyacrylamide-cerium complex is added. Specifically, the electrolyte comprises the following raw materials at the following mass concentrations: copper sulfate pentahydrate 330 g / L, sulfuric acid 110 g / L, chloride ions 55 ppm, selenomethionine 1.2 ppm, sodium 3-mercapto-1-propanesulfonate 5 ppm, and perfluoroalkyl ether 0.9 ppm; specifically, the perfluoroalkyl ether is perfluoroalkyl ethanol polyoxyethylene ether. The electrolytic copper foil prepared in this comparative example has an elongation of 9.5% and a resistivity of 1.78 μΩ·cm.

[0163] Comparative Example 4

[0164] This comparative example provides a method for preparing ultra-high tensile strength electrolytic copper foil. The difference from Example 1 is that selenomethionine is not added. Specifically, the electrolyte comprises the following raw materials at the following mass concentrations: copper sulfate pentahydrate 330 g / L, sulfuric acid 110 g / L, chloride ions 55 ppm, polyacrylamide-cerium complex 16 ppm, sodium 3-mercapto-1-propanesulfonate 5 ppm, and perfluoroalkyl ether 0.9 ppm; specifically, the perfluoroalkyl ether is perfluoroalkyl ethanol polyoxyethylene ether. Its antioxidant properties are significantly worse, with an antioxidant capacity of +1.2%.

[0165] Comparative Example 5

[0166] This comparative example provides a method for preparing ultra-high tensile strength electrolytic copper foil. The difference from Example 1 is that a gradient current density was not used in the electrodeposition process. Specifically, the electrodeposition temperature was 53-57℃; the current was controlled as follows: a positive DC current with a current density of 50 A / dm² was applied. The lack of a gradient current density significantly resulted in a decrease in the room-temperature tensile strength of the copper foil, reducing it to only 458 MPa.

[0167] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An additive for electrolytic copper foil, characterized in that, The additives include the following raw materials in the following mass concentrations: 15-20 ppm polyacrylamide-rare earth complex, 0.8-1.2 ppm selenium-containing compound, 3-5 ppm stress inhibitor, and 0.5-1 ppm surfactant.

2. The additive for electrolytic copper foil according to claim 1, characterized in that: It also includes one or more of the following features: a1) The polyacrylamide-rare earth complex is selected from one or more of polyacrylamide-cerium complex, polyacrylamide-yttrium complex, polyacrylamide-lanthanum complex, or polyacrylamide-samarium complex; preferably, the preparation method of the polyacrylamide-rare earth complex includes the following steps: S1) dissolving polyacrylamide in water to obtain a polyacrylamide solution, then adding thionyl chloride to react and obtain an acyl chloride intermediate; S2) adding glycine to the acyl chloride intermediate obtained in step S1, adjusting the pH to 8-9, and reacting to obtain modified polyacrylamide; S3) adding a rare earth salt solution to the modified polyacrylamide, adjusting the pH to 5-6, and reacting to obtain a polyacrylamide-rare earth complex colloid; S4) purifying, drying, and grinding the polyacrylamide-rare earth complex colloid to obtain the polyacrylamide-rare earth complex. a2) The selenium-containing compound is selected from one or more of selenomethionine, selenized glucose, or selenium dioxide; a3) The stress inhibitor is selected from one or more of sulfur-containing compounds and polymers; preferably, the stress inhibitor is selected from one or more of sodium 3-mercapto-1-propanesulfonate, sodium polydithiodipropanesulfonate, or polyethylene glycol. a4) The surfactant is a perfluoroalkyl ether.

3. An electrolyte for electrolytic copper foil, characterized in that: The electrolyte includes the additives for electrolytic copper foil as described in any one of claims 1-2; preferably, the electrolyte comprises the following raw materials in the following mass concentrations: polyacrylamide-rare earth complex 15-20 ppm, selenium-containing compound 0.8-1.2 ppm, stress inhibitor 3-5 ppm, surfactant 0.5-1 ppm, copper ions 80-90 g / L, sulfuric acid 100-110 g / L, and chloride ions 50-60 ppm.

4. A method for preparing ultra-high tensile strength electrolytic copper foil, characterized in that, The preparation method includes the following steps: The copper foil is obtained by gradient current deposition of the electrolyte for electrolytic copper foil as described in claim 3, followed by in-situ annealing.

5. The preparation method according to claim 4, characterized in that: The gradient current deposition is as follows: 0-30s, current density is 35-55A / dm²; 30-180s, current density is 25-40A / dm²; 180s-end of deposition, current density is 30-60A / dm².

6. The preparation method according to claim 5, characterized in that: It also includes any one of the following features: b1) When 3μm≤copper foil thickness≤19μm, the gradient current includes the following stages: 0-20s with a forward DC current density of 45-55A / dm², 20-150s with a forward DC current density of 35-40A / dm², 150s-15s before the end of deposition with a forward DC current density of 50-60A / dm², and 15s before the end of deposition with a reverse DC current density of 4-4.8A / dm². b2) When 19μm < copper foil thickness ≤ 36μm, the gradient current includes the following stages: 0-30s with a forward DC current density of 40-50A / dm², 30-180s with a forward DC current density of 28-38A / dm², 180s to 20s before the end of deposition with a forward pulse current density of 35-45A / dm², and 20s before the end of deposition with a reverse DC current density of 1.75-2.25A / dm²; preferably, the duty cycle of the forward pulse current is 45-85%; the frequency of the forward pulse current is 1-10Hz; b3) When 36μm < copper foil thickness ≤ 55μm, the gradient current includes the following stages: a forward DC current with a current density of 35-45A / dm² is applied from 0-30s, a forward DC current with a current density of 25-35A / dm² is applied from 30-180s, a forward DC current with a current density of 30-40A / dm² is applied from 180s to 30s before the end of deposition, and a reverse pulse current with a current density of 0.75-1.25A / dm² is applied 30s before the end of deposition; preferably, the duty cycle of the reverse pulse current is 45-85%; the frequency of the reverse pulse current is 1-10Hz.

7. The preparation method according to claim 4, characterized in that: It also includes one or more of the following features: 11) The copper foil is obtained by passivation treatment after in-situ annealing; 12) The current deposition temperature is 53-57℃; 13) The surface roughness Ra of the cathode roller used for current deposition is ≤0.1μm; 14) The in-situ annealing temperature is 75-90℃; the annealing time is 80-130s; preferably, the annealing is performed in stages; 15) The copper foil is obtained by roll forming after in-situ annealing; preferably, the roll forming is online micro-rolling, and more preferably, the rolling pressure is 4-6 MPa and the gap is 50-50 μm.

8. An ultra-high tensile strength electrolytic copper foil, characterized in that: The copper foil is prepared by any one of the preparation methods described in claims 4-7; preferably, the thickness of the copper foil is 3-55 μm, the room temperature tensile strength of the copper foil is ≥535 MPa, the aged tensile strength of the copper foil is ≥500 MPa, the aged elongation of the copper foil is ≥8%; the surface roughness Rz of the copper foil is 3.5-5 μm; the peel strength of the copper foil is ≥1.3 N / mm; and the resistivity of the copper foil is ≤1.72 μΩ·cm.

9. An electrode sheet, characterized in that: Including the ultra-high tensile strength electrolytic copper foil as described in claim 8.

10. A secondary battery, characterized in that: Including the electrode as described in claim 9.

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