Application of cyclic thiourea derivatives as high-resistance agents in the preparation of electrolytic copper foil

Abstract

This invention discloses the application of cyclic thiourea derivatives as high-resistance agents in the preparation of ultra-high tensile electrolytic copper foil. Four types of cyclic thiourea derivatives—ethylene thiourea, thiobarbituric acid, 2-thiourea pyrimidine, and methimazole—are selected as high-resistance agents specifically for the electrolyte of electrolytic copper foil. Based on the different molecular π-conjugated structural characteristics, the application scenarios of the materials are divided, and differentiated concentration ranges are matched. Simultaneously, the basic components of the electrolyte, the types and concentrations of auxiliary additives, and the complete set of electrodeposition process parameters are limited, constructing a complete system for the preparation of ultra-high tensile electrolytic copper foil. This invention establishes for the first time the structure-activity relationship between the degree of π-conjugation of cyclic thiourea derivative molecules and the high-temperature tensile properties of electrolytic copper foil and the amount of additives used. It achieves graded and controllable high-temperature tensile strength of 6μm ultrathin electrolytic copper foil. Derivatives with large and moderate π-conjugation systems can increase the high-temperature tensile strength of copper foil to over 600MPa, meeting the requirements for high-end lithium-ion battery negative electrode current collectors.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil preparation technology, specifically to the application of cyclic thiourea derivatives as high-resistance agents in the preparation of ultra-high tensile electrolytic copper foil. Background Technology

[0002] Sulfur-containing organic compounds are the most widely used high-resistance agent systems in the field of electrolytic copper foil because sulfur atoms readily form coordination adsorption bonds with copper atoms. Thiourea and its derivatives have become mainstream high-resistance agent raw materials due to their advantages such as strong adsorption capacity, significant grain refinement effect, moderate cost, and good industrial adaptability. Although thiourea derivatives have achieved industrial application, existing technologies still have four core defects that seriously restrict the large-scale and customized production of ultra-high tensile strength ultra-thin electrolytic copper foil: (1) Lack of structure-activity relationship and blind molecular design. Existing studies only use thiourea derivatives as general additives without systematically exploring the intrinsic relationship between molecular structure (especially cyclic structure and π-conjugated system) and high tensile strength. Technicians cannot screen and design thiourea derivative molecules specifically according to the target tensile strength requirements. Additive screening relies entirely on a large number of repeated experiments, resulting in low R&D efficiency and high cost.

[0003] (2) The dosage of additives is inconsistent. The effective concentration and limit concentration of thiourea derivatives with different structures vary greatly. The existing technology does not divide the concentration range according to molecular characteristics. In actual production, it is easy to cause problems such as insufficient dosage leading to substandard tensile strength, and excessive dosage causing powdering of copper foil surface and a sharp drop in elongation. The product qualification rate is difficult to guarantee.

[0004] (3) The performance upper limit is not clearly defined. There are significant differences in the upper limit of tensile strength of different cyclic thiourea derivatives. The existing technology does not classify the application of materials, which cannot meet the differentiated requirements of different grades of lithium battery products for the tensile strength of copper foil. It is difficult to obtain ultra-high temperature tensile copper foil with a strength of more than 600MPa for high-end batteries, while low-end products will waste raw materials.

[0005] (4) The mechanism of action is poorly studied. Existing technologies only describe the tensile strength enhancement effect of thiourea derivatives macroscopically, without clarifying the influence of π-conjugated structure on cathodic polarization, copper deposition behavior and grain boundary stability, which cannot provide theoretical support for the development of a new generation of high-resistance agents.

[0006] In summary, this systematic study of the structure-property relationship between the molecular structure, π-conjugation degree, concentration, and high-temperature tensile properties of cyclic thiourea derivatives and electrolytic copper foil, the establishment of standardized electrolyte formulations and electrodeposition processes, and the development of graded and controllable ultra-high tensile electrolytic copper foil preparation technology have significant engineering value and theoretical significance for promoting the upgrading of the lithium-ion battery copper foil industry and meeting the high-end needs of new energy batteries.

[0007] Conventional electrolytic copper foil electrolytes typically use a copper sulfate-sulfuric acid system with chloride ions as an auxiliary coordinating agent. This system boasts excellent conductivity and copper ion solubility, making it a standard system in the industry. However, when this conventional system is combined with traditional thiourea-based high-resistance agents, the following problems arise: First, the compatibility range of traditional high-resistance agents with accelerators and inhibitors is narrow, and some mainstream additives cannot be mixed, limiting the scope for process adjustment. Second, there is a lack of specific process parameters for 6μm ultrathin copper foil; under general electrodeposition parameters, the grain distribution of ultrathin copper foil is uneven, resulting in large fluctuations in mechanical properties. Third, auxiliary processes such as cathode pretreatment and stirring methods are not optimized based on the molecular characteristics of the high-resistance agents, further exacerbating product performance instability. Summary of the Invention

[0008] To address the shortcomings of existing technologies, such as unclear structure-activity relationships, blind selection of additives, chaotic dosage matching, low upper limit of high-temperature tensile strength, poor compatibility of additives, and unstable mechanical properties of ultra-thin copper foil, this invention solves the following technical problems in sequence: (1) To clarify the structure-activity relationship between the degree of π conjugation of cyclic thiourea derivative molecules and the high-temperature tensile strength of electrolytic copper foil, the effective dosage of additives, and the upper limit of performance, to fill the theoretical gap in the existing technology and realize the targeted screening of high resistance agents.

[0009] (2) For the four types of cyclic thiourea derivatives (ethylene thiourea, thiobarbituric acid, 2-thiourea pyrimidine, and methimazole), a precise range of application concentrations is defined to avoid problems such as copper foil pulverization and insufficient strength caused by improper dosage, thus balancing product performance and production costs.

[0010] (3) Construct a complete electrolyte composition that is compatible with four types of cyclic thiourea derivatives, optimize the types and concentrations of basic components, promoters and inhibitors, improve the compatibility between different additives, and be compatible with the mainstream raw materials of existing production lines.

[0011] (4) Optimize the complete electrodeposition process of 6μm ultrathin electrolytic copper foil, including electrode configuration, temperature, current density, deposition time, cathode pretreatment, stirring method, etc., to ensure uniform grain size and stable mechanical properties of ultrathin copper foil.

[0012] (5) Achieve graded and controllable high-temperature tensile strength of electrolytic copper foil, and prepare products with high-temperature tensile strength of ≤500MPa and ≥600MPa respectively to meet the differentiated needs of different grades of lithium-ion batteries, while ensuring that the copper foil elongation meets the industrial use standards.

[0013] To achieve the above objectives, the present invention provides the following technical solution: the application of cyclic thiourea derivatives as high-resistance agents in the preparation of electrolytic copper foil, wherein the cyclic thiourea derivatives are selected from at least one of ethylene thiourea, thiobarbituric acid, 2-thiourea pyrimidine, and methimazole, and the cyclic thiourea derivatives are used in electrolyte compositions for electrolytic copper foil.

[0014] Furthermore, thiobarbituric acid, 2-thiouracil, and methimazole are used to prepare electrolytic copper foil with a high-temperature tensile strength of not less than 600 MPa, while ethylene thiourea is used to prepare electrolytic copper foil with a high-temperature tensile strength of not more than 500 MPa.

[0015] Furthermore, the electrolyte composition consists of a copper ion source, sulfuric acid, chloride ions, a high-resistance agent, an accelerator, an inhibitor, and deionized water; with Cu... 2+ The concentration of the copper ion source is 80–100 g / L, the concentration of the sulfuric acid is 80–150 g / L, and the concentration of the chloride ion is 10–50 mg / L; the concentration of the high-resistance agent is 1–40 mg / L; the accelerator is selected from at least one of sodium dithiodipropane sulfonate, sodium 3-mercaptopropane sulfonate, and sodium dithiodipropane sulfonate, and the concentration is 1–20 mg / L; the inhibitor is selected from at least one of polyethylene glycol, hydroxyethyl cellulose, gelatin, and collagen, and the concentration is 5–50 mg / L.

[0016] Furthermore, when the high-resistance agent is thiobarbituric acid or 2-thiouracil, the concentration is 20–40 mg / L; when the high-resistance agent is methimazole, the concentration is 5–14 mg / L; and when the high-resistance agent is ethylene thiourea, the concentration is 1–8 mg / L.

[0017] Furthermore, the concentration of the promoter is 3–10 mg / L, and the concentration of the inhibitor is 10–30 mg / L.

[0018] Furthermore, the polyethylene glycol has a molecular weight of 600–20000 Da, the hydroxyethyl cellulose has a molecular weight of 10000–30000 Da, the gelatin has a molecular weight of 20000–30000 Da, and the collagen has a molecular weight of 2000–5000 Da.

[0019] Furthermore, the preparation method of electrolytic copper foil includes the following steps: (1) Add copper ion source, sulfuric acid, chloride ion, high resistance agent, accelerator and inhibitor to deionized water in sequence, stir until completely dissolved, and prepare electrolyte; (2) Using a pure titanium plate as the cathode and an iridium-plated titanium plate as the anode, the two electrodes are placed in the electrolyte, the electrode spacing is fixed at 2 cm, and electrodeposition is performed for 30 to 50 s under the conditions of current density of 25 to 35 A / dm² and electrolyte temperature of 40 to 60 °C. (3) After the electrodeposited copper foil is washed and dried, it is peeled off from the cathode to obtain the finished electrolytic copper foil.

[0020] Furthermore, the electrolyte is stirred by bubbling during the electrodeposition process.

[0021] Furthermore, in step (2), the cathode plate pretreatment method is as follows: the pure titanium cathode plate is mechanically polished to a roughness Rz < 0.3 μm, and then ultrasonically cleaned in acetone, ethanol, and deionized water for 5 min each, and then set aside.

[0022] Furthermore, the copper foil is 6μm thick, and after heat treatment at 140℃ for 15min, its high-temperature tensile strength is not less than 500MPa and its elongation is not less than 6.5%.

[0023] Compared with the prior art, the present invention has the following advantages: (1) This invention systematically elucidates for the first time the structure-property relationship between the π-conjugated structure of cyclic thiourea derivatives and the high resistance properties of electrolytic copper foil, clarifying the conduction mechanism between molecular structure, reduction characteristics, cathodic polarization, grain boundary stability, and macroscopic mechanical properties. This theory can not only guide the screening and application of existing thiourea derivatives, but also provide theoretical support for the molecular design, modification, and synthesis of a new generation of high resistance agents, promoting the transformation of the field of electrolytic copper foil additives from "experience-driven" to "theory-driven", which has profound significance for the long-term technological development of the industry.

[0024] (2) This invention defines the optimal concentration range for each cyclic thiourea derivative and distinguishes the limit failure concentration. During the production process, the corresponding high-resistance agent and concentration can be directly selected according to the strength requirements of the target product without repeated formula adjustments. This effectively avoids the problems of copper foil pulverization and scrapping caused by excessive additive dosage, and performance failure caused by insufficient dosage, improving product yield by more than 10%. At the same time, the dosage is matched according to the characteristics of the raw materials. High-end products use high-upper-level raw materials, and mid-to-low-end products use low-cost raw materials, maximizing the value of raw materials and reducing the overall production cost by 5% to 8%.

[0025] (3) The high-resistance agent of this invention has good compatibility with mainstream accelerators and inhibitors on the market. Manufacturers can use the existing auxiliary agent system without purchasing raw materials again. The entire set of electrodeposition process parameters, cathode pretreatment methods and electrode configurations are all compatible with existing mature production lines. No new equipment or production line layout modifications are required. The technology transfer is simple and the production speed is fast. At the same time, the special process parameters are optimized for 6μm ultrathin copper foil, resulting in uniform product thickness, fewer surface defects and significantly improved batch stability.

[0026] (4) The method proposed in this invention, "predicting high resistance effect by evaluating the degree of π-conjugation of cyclic thiourea derivatives," can serve as a general screening criterion for high-performance additives for electrolytic copper foil. It is not limited to the four types of compounds of this invention, but can also be extended to the screening of other similar cyclic thiourea derivatives and sulfur-containing heterocyclic compounds, offering broad technological expansion potential. Besides lithium-ion battery copper foil, with slight adjustments, this invention can also be applied to high-strength electrolytic copper foil for PCBs, electronic shielding copper foil, and other fields. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 Schematic diagram of the electrodeposition experimental apparatus of this invention; Figure 2 This is a graph showing the relationship between the concentration and high-temperature tensile strength of four types of cyclic thiourea derivatives in this invention. Detailed Implementation

[0029] The technical solution of the present invention will be described in detail below with reference to specific embodiments, comparative examples, compatibility experiments, and concentration gradient experiments. All embodiments and comparative examples are based on Figure 1 The electrodeposition apparatus shown was used, with all raw materials being industrial-grade conventional chemical raw materials and deionized water as the solvent. Copper foil performance testing was performed according to industry standards: the prepared 6μm copper foil was heat-treated at 140℃ for 15 minutes, followed by testing of high-temperature tensile strength and elongation. It should be noted that the following examples are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Simple adjustments to the formula and process made by those skilled in the art without departing from the core technical concept of this invention fall within the scope of protection of this invention.

[0030] General pretreatment and experimental conditions: Cathode pretreatment: The pure titanium plate is mechanically polished to a roughness Rz < 0.3 μm, and then ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 5 min in sequence. It is then removed and drained for later use. Electrode configuration: The anode is an iridium-plated titanium plate, and the cathode is a pretreated pure titanium plate. The electrode spacing is fixed at 2cm. Electrolyte basic system (general): based on Cu²⁺ + The concentrations are: 80 g / L (copper sulfate pentahydrate), 100 g / L sulfuric acid, and 30 mg / L chloride ions. General electrodeposition conditions: electrolyte temperature 55℃, current density 25A / dm², electrodeposition time 45s, with bubbling and stirring throughout the process; Post-processing: After electrodeposition, the copper foil is rinsed with deionized water, dried with hot air, and peeled off to obtain a standard thickness copper foil of 6μm. Performance testing: Heat treatment at 140℃ for 15 minutes, and test the high-temperature tensile strength (MPa) and elongation (%).

[0031] Comparative Example 1 Single-concentration experiment of ethylene thiourea (without π-conjugated system) This comparative example uses ethylene thiourea as a high-resistance agent to verify the upper limit of the performance of cyclic thiourea derivatives in a π-conjugated system.

[0032] Electrolyte formulation: basic system + ethylene thiourea 8mg / L + accelerator (SPS) 10mg / L + inhibitor (PEG, molecular weight 10000Da) 5mg / L; Experimental procedure: Electrolyte preparation, electrodeposition, and post-treatment were completed according to general conditions; Performance test results: High-temperature tensile strength 523 MPa, elongation 8.63%; Experimental conclusion: At the optimal concentration of ethylene thiourea, the highest high-temperature tensile strength of copper foil is 523 MPa, which cannot reach 600 MPa, making it suitable for the preparation of low- to mid-range electrolytic copper foil.

[0033] Comparative Example 2 Ethylene thiourea concentration gradient experiment To define the complete concentration range and the ineffective concentration of ethylene thiourea, five concentration gradients were set up, with the remaining raw materials and processes being completely consistent with Comparative Example 1.

[0034] Concentration settings: 2 mg / L, 4 mg / L, 6 mg / L, 8 mg / L, 10 mg / L; The performance test data for each group is summarized in Table 1:

[0035] Table 1 Experimental Analysis: (1) Within the concentration range of 1~8 mg / L, as the concentration of ethylene thiourea increases, the high-temperature tensile strength of copper foil continues to rise, the elongation remains stable (>8.3%), and the surface condition of copper foil is good; (2) When the concentration reaches 10 mg / L (exceeding the limit concentration of 8 mg / L), the copper foil surface becomes powdery, the tensile strength drops sharply to 249 MPa, the elongation is only 3.65%, and the product is completely ineffective. (3) Determine the optimal usage range of ethylene thiourea as 1~8 mg / L, the limit failure concentration as 8 mg / L, and the high temperature tensile strength range of the product as 417~523 MPa.

[0036] Example 1 Single-concentration experiment of thiobarbituric acid (large π conjugated system) In this embodiment, thiobarbituric acid (large π-conjugated six-membered ring structure) was used as a high-resistance agent to verify the ultra-high tensile properties of the derivatives of the large π-conjugated system.

[0037] Electrolyte formulation: basic system + thiobarbituric acid 40mg / L + promoter (SPS) 10mg / L + inhibitor (PEG, molecular weight 10000Da) 5mg / L; Experimental procedure: General process conditions were followed; Performance test results: High-temperature tensile strength 623 MPa, elongation 6.27%; Experimental conclusion: At a concentration of 40 mg / L, thiobarbituric acid can enhance the high-temperature tensile strength of copper foil to over 600 MPa, classifying it as an ultra-high tensile electrolytic copper foil suitable for high-end lithium battery applications.

[0038] Example 2 Thiobarbituric acid concentration gradient experiment Five concentration gradients were set up to define the optimal range and inactivation concentration of thiobarbituric acid, with the remaining conditions the same as in Example 1.

[0039] Concentration settings: 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L; The performance test data for each group is summarized in Table 2:

[0040] Table 2 Experimental Analysis: (1) In the concentration range of 20~40mg / L, the tensile strength increases from 497MPa to 623MPa, and is close to 600MPa at 30mg / L and above, and reaches the performance peak at 40mg / L; (2) When the concentration exceeds 40 mg / L, the copper foil will pulverize and fail, and its strength and elongation will decrease significantly. (3) The optimal usage range of thiobarbituric acid is determined to be 20~40 mg / L, the limit failure concentration is 40 mg / L, and 30~40 mg / L can stably prepare ultra-high tensile copper foil with a strength of over 600 MPa.

[0041] Example 3 Single-concentration experiment of 2-thiouracil (large π-conjugated system) In this embodiment, 2-thiouracil (large π conjugated six-membered ring structure) is used as a high resistance agent.

[0042] Electrolyte formulation: basic system + 2-thiouracil 25mg / L + promoter (SPS) 10mg / L + inhibitor (PEG, molecular weight 10000Da) 5mg / L; Experimental procedure: General process conditions were followed; Performance test results: High-temperature tensile strength 642 MPa, elongation 7.05%; Experimental conclusion: The upper limit of tensile strength of 2-thiouracil is higher than that of thiobarbituric acid, with a strength of 642 MPa at a concentration of 25 mg / L and better elongation.

[0043] Example 4 2-Thiouracil Concentration Gradient Experiment Five concentration gradients were set up, and concentration ranges were defined. The remaining conditions were the same as in Example 3.

[0044] Concentration settings: 5 mg / L, 10 mg / L, 20 mg / L, 25 mg / L, 30 mg / L; The performance test data for each group is summarized in Table 3:

[0045] Table 3 Experimental Analysis: (1) In the range of 20~25mg / L, the tensile strength increases rapidly, reaching a peak of 642MPa at 25mg / L; (2) The product becomes ineffective when the concentration exceeds 25 mg / L; (3) The optimal usage range of 2-thiouracil was determined to be 20~25 mg / L, and the limit failure concentration was 25 mg / L. It is the variety with a higher upper limit of tensile strength among the three types of ultra-high tensile strength agents.

[0046] Example 5 Single-concentration experiment of methimazole (moderate π-conjugated system) In this embodiment, methimazole (with a moderate π-conjugated five-membered ring structure) is used as a high-resistance agent.

[0047] Electrolyte formulation: basic system + methimazole 14mg / L + promoter (SPS) 15mg / L + inhibitor (PEG, molecular weight 10000Da) 5mg / L; Experimental procedure: General process conditions were followed; Performance test results: High-temperature tensile strength 657 MPa, elongation 7.98%; Experimental conclusion: When the dosage of methimazole is lower than that of compounds in the large π-conjugated system, the tensile strength reaches the highest value of 657 MPa among all samples, the elongation is excellent, and the overall cost performance is the best.

[0048] Example 6 Methimazole Concentration Gradient Experiment Five concentration gradients were set up, and concentration ranges were defined. The remaining conditions were the same as in Example 5.

[0049] Concentration settings: 5 mg / L, 8 mg / L, 11 mg / L, 14 mg / L, 17 mg / L; The performance test data for each group is summarized in Table 4:

[0050] Table 4 Experimental Analysis: (1) The intensity continued to rise in the range of 5~14 mg / L, and it could break through 600 MPa at 11 mg / L and reach the peak at 14 mg / L; (2) The limit failure concentration is 14 mg / L. If this concentration is exceeded, the product must be scrapped. (3) The optimal usage range of methimazole is determined to be 5~14 mg / L. The dosage is much lower than that of large π conjugated derivatives, making it the preferred raw material for high-end mass production.

[0051] Example 7 Compatibility experiments with different accelerators (to verify the universality of the additives) To verify the compatibility of the high-resistance agent of this invention with different accelerators, two representative high-resistance agents, thiobarbituric acid and methimazole, were selected, and the original SPS accelerator was replaced by MPS and DPS, respectively, while other conditions remained unchanged.

[0052] Experimental group setup: Group A: Thiobarbituric acid 30 mg / L, combined with MPS and DPS (both 10 mg / L). Group B: Methimazole 14 mg / L, combined with MPS and DPS (both 10 mg / L). The test results are summarized in Table 5:

[0053] Table 5 Experimental conclusion: After replacing different types of accelerators, the high-temperature tensile strength of the copper foils corresponding to the two groups of high-resistance agents remained above 600 MPa, with minimal performance degradation. This proves that the cyclic thiourea derivative of this invention has excellent compatibility with the three mainstream accelerators, SPS, MPS, and DPS, and offers a large range of process adjustment options.

[0054] Example 8 Compatibility experiments with different inhibitors (to verify the universality of adjuvants) Thiobarbituric acid and methimazole were selected, and HEC, gelatin, and collagen were used to replace the original PEG inhibitors to verify the compatibility of the inhibitors.

[0055] Experimental group setup: Group A: Thiobarbituric acid 30mg / L, combined with HEC, gelatin, and collagen (all at a concentration of 10mg / L). Group B: Methimazole 15mg / L, combined with HEC, gelatin, and collagen (all at a concentration of 10mg / L). The test results are summarized in Table 6:

[0056] Table 6 Experimental conclusion: After replacing the four mainstream inhibitors, the high-temperature tensile strength of all samples was ≥614MPa and remained stable above 600MPa, proving that the high-resistance agent of this invention has no compatibility conflict with the mainstream inhibitors in the industry, and the existing production line can directly use the original inhibitor system.

[0057] Example 9 Full-parameter optimization industrial simulation experiment Based on all the above experimental conclusions and in accordance with all the parameters defined in the claims, industrial-scale simulated production experiments were carried out to prepare batches of 6μm electrolytic copper foil.

[0058] Electrolyte formulation (high-end ultra-high tensile strength system): Cu² + 90 g / L, sulfuric acid 120 g / L, chloride ion 30 mg / L, methimazole 10 mg / L (optimal range), SPS 5 mg / L (preferred promoter concentration), collagen 20 mg / L (preferred inhibitor concentration, molecular weight 3000 Da). Process parameters: Electrolyte temperature 50℃, current density 30A / dm², electrodeposition time 40s, electrode spacing 2cm, bubbling and stirring, cathode standard pretreatment; Batch sampling test (randomly select 10 samples): High-temperature tensile strength range: 632~651MPa, elongation range: 7.6%~8.2%, copper foil thickness: 5.95~6.05μm, and no surface defects; Experimental conclusion: The complete set of parameters is adapted for industrial mass production, the product has stable performance and uniform thickness, and fully meets the standards for use as a negative electrode current collector in high-end lithium-ion batteries.

[0059] Example 10 Industrialization simulation experiment of low-to-mid-range products Ethylene thiourea was used to prepare low-to-medium-end electrolytic copper foil, which was matched with general industrial parameters.

[0060] Electrolyte formulation: Cu² + 85 g / L, sulfuric acid 90 g / L, chloride ion 20 mg / L, ethylene thiourea 5 mg / L, SPS 4 mg / L, PEG 15 mg / L (molecular weight 8000 Da). Process parameters: temperature 45℃, current density 28A / dm², deposition time 35s; Test results: High-temperature tensile strength 465MPa, elongation 8.42%, the product is qualified, low cost, and suitable for common electronic device batteries.

[0061] Combining all comparative examples, implementation examples, gradient experiments, compatibility experiment data, and... Figure 2 The data shown comprehensively summarizes the core structure-activity relationship, formulation range, and process effects of this invention, further demonstrating the scientific nature and inventiveness of the technical solution: 1. The correspondence between the degree of π conjugation and performance and dosage π-free conjugation (ethylene thiourea): The molecules are easily reduced, have strong cathodic polarization, and have a significant effect on inhibiting copper deposition. Therefore, the dosage is the lowest (1~8 mg / L) and the effect is the fastest. However, the molecular adsorption stability is weak, the grain boundary pinning effect is poor at high temperature, and the upper limit of tensile strength is the lowest (≤523 MPa). Moderate π-conjugation (methimazole): The molecular reduction difficulty is moderate, the cathodic polarization and adsorption stability are balanced, the dosage is moderate (5~14mg / L), and the onset of action is moderate; the grain boundary strengthening effect is excellent, the upper limit of tensile strength is the highest (657MPa), and the overall performance is the best. Large π conjugation (thiobarbituric acid, 2-thiouracil): The molecular conjugation system is large, the reduction is difficult, and the cathodic polarization is relatively weak. Therefore, the dosage is the largest (20~40mg / L) and the onset of action is the slowest. However, the molecules have extremely strong adsorption stability on the copper surface, and the high-temperature grain boundary pinning effect is outstanding. The upper limit of tensile strength is second only to methimazole (623~642MPa).

[0062] All concentration gradient experiments demonstrate that each cyclic thiourea derivative has an optimal concentration range and a critical failure concentration. When the concentration is below the optimal range, the number of high-resistance molecules is insufficient, resulting in weak grain refinement and grain boundary strengthening effects, and lower tensile strength. When the concentration is within the optimal range, additive molecules are uniformly adsorbed on the cathode and grain boundaries, achieving peak performance. When the concentration exceeds the critical concentration, excessive additives lead to excessive inhibition of copper ion reduction, abnormal grain growth, and internal stress in the copper foil, ultimately resulting in surface pulverization and a sharp drop in strength. The concentration range defined in this invention is entirely based on experimental data, possessing strong scientific validity and industrial applicability.

[0063] Compatibility experiments with accelerators and inhibitors confirmed that the four types of cyclic thiourea derivatives of this invention are compatible with all mainstream organic additives currently used in the electrolytic copper foil industry, exhibiting no precipitation, no antagonism, and no significant performance degradation. The electrodeposition process parameters, cathode pretreatment, and stirring methods are all based on existing production line designs, requiring no equipment modifications and making industrialization extremely easy.

[0064] Existing conventional thiourea derivative-based 6μm electrolytic copper foils typically exhibit high-temperature tensile strengths of 450-550 MPa, and suffer from narrow additive compatibility and low product yield. This invention: Mid-to-low-end products (ethylene thiourea): strength 417~523MPa, covering the range of existing conventional products, with less raw material usage; High-end products (methimazole, thiobarbituric acid, 2-thiouracil): with a stable strength of 600~657MPa, significantly exceeding the upper limit of existing technical performance, while maintaining an elongation of over 6.5%, solving the industry problem of "high strength but low elongation" in ultra-thin copper foil.

[0065] The technology of this invention can be directly applied to the industrial production line of 6μm ultrathin lithium battery electrolytic copper foil. The application process is as follows: Production line modification: No need to modify existing core equipment such as electrolytic cells, electrodes, power supplies, and temperature control systems; only the types and amounts of electrolyte additives need to be adjusted. Formula switching: Based on the customer's product grade requirements, we can flexibly switch the types of high-resistance agents: ethylene thiourea is used for low- and mid-range batteries, methimazole is used for high-end power batteries, and 2-thiourea pyrimidine or thiobarbituric acid is used for top-end energy storage batteries. Process control: Production is carried out strictly in accordance with the electrolyte component concentration, electrodeposition temperature, current density and deposition time specified in this invention, and the cathode maintains standard polishing and ultrasonic cleaning processes; Quality inspection: Finished copper foil is tested according to national standards for thickness, surface morphology, high-temperature tensile strength, and elongation. The batch performance is stable and the pass rate is ≥98%.

[0066] The technology of this invention is backward compatible with the production of conventional 8~12μm electrolytic copper foil. With just appropriate adjustment of the electrodeposition time, it can be extended to the fields of PCB copper foil and general electronic copper foil, with a wide range of application scenarios and broad market prospects.

[0067] The above detailed embodiments, combined with experimental data, illustrate the technical solution, principle, and beneficial effects of the present invention. The embodiments are merely preferred examples and are not intended to limit the invention. Those skilled in the art, within the scope of the present invention's technical concept, can make simple modifications, equivalent substitutions, or combinations of the formulation components, concentrations, and process parameters to form technical solutions that fall within the protection scope defined by the claims of this invention. Raw materials, equipment, testing methods, and operating procedures not described in detail in this invention are all conventional technical means in the prior art.

Claims

1. The application of cyclic thiourea derivatives as high-resistance agents in the preparation of electrolytic copper foil, characterized in that, The cyclic thiourea derivative is selected from at least one of ethylene thiourea, thiobarbituric acid, 2-thiourea pyrimidine, and methimazole, and is used in electrolyte compositions for electrolytic copper foil.

2. The application of the cyclic thiourea derivative according to claim 1 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, Thiobarbituric acid, 2-thiouracil, and methimazole are used to prepare electrolytic copper foil with a high-temperature tensile strength of not less than 600 MPa, while ethylene thiourea is used to prepare electrolytic copper foil with a high-temperature tensile strength of not more than 500 MPa.

3. The application of the cyclic thiourea derivative according to claim 1 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, The electrolyte composition comprises a copper ion source, sulfuric acid, chloride ions, a high-resistance agent, an accelerator, an inhibitor, and deionized water; with Cu... 2+ The concentration of the copper ion source is 80–100 g / L, the concentration of the sulfuric acid is 80–150 g / L, and the concentration of the chloride ion is 10–50 mg / L; the concentration of the high-resistance agent is 1–40 mg / L; the accelerator is selected from at least one of sodium dithiodipropane sulfonate, sodium 3-mercaptopropane sulfonate, and sodium dithiodipropane sulfonate, and the concentration is 1–20 mg / L; the inhibitor is selected from at least one of polyethylene glycol, hydroxyethyl cellulose, gelatin, and collagen, and the concentration is 5–50 mg / L.

4. The application of the cyclic thiourea derivative according to claim 3 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, When the high-resistance agent is thiobarbituric acid or 2-thiouracil, the concentration is 20-40 mg / L; when the high-resistance agent is methimazole, the concentration is 5-14 mg / L; when the high-resistance agent is ethylene thiourea, the concentration is 1-8 mg / L.

5. The application of the cyclic thiourea derivative according to claim 3 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, The concentration of the promoter is 3–10 mg / L, and the concentration of the inhibitor is 10–30 mg / L.

6. The application of the cyclic thiourea derivative according to claim 3 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, The polyethylene glycol has a molecular weight of 600–20000 Da, the hydroxyethyl cellulose has a molecular weight of 10000–30000 Da, the gelatin has a molecular weight of 20000–30000 Da, and the collagen has a molecular weight of 2000–5000 Da.

7. The application of the cyclic thiourea derivative according to claim 1 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, The method for preparing the electrolytic copper foil includes the following steps: (1) Add copper ion source, sulfuric acid, chloride ion, high resistance agent, accelerator and inhibitor to deionized water in sequence, stir until completely dissolved, and prepare electrolyte; (2) Using a pure titanium plate as the cathode and an iridium-plated titanium plate as the anode, the two electrodes are placed in the electrolyte, the electrode spacing is fixed at 2 cm, and electrodeposition is performed for 30 to 50 s under the conditions of current density of 25 to 35 A / dm² and electrolyte temperature of 40 to 60 °C. (3) After the electrodeposited copper foil is washed and dried, it is peeled off from the cathode to obtain the finished electrolytic copper foil.

8. The application of the cyclic thiourea derivative according to claim 7 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, The electrolyte is stirred by bubbling during the electrodeposition process.

9. The application of the cyclic thiourea derivative according to claim 7 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, In step (2), the cathode plate pretreatment method is as follows: the pure titanium cathode plate is mechanically polished to a roughness Rz < 0.3 μm, and then ultrasonically cleaned in acetone, ethanol, and deionized water for 5 min each, and then set aside.

10. The application of the cyclic thiourea derivative according to claim 7 as a high-resistance agent in the preparation of electrolytic copper foil, characterized in that, The copper foil is 6μm thick. After heat treatment at 140℃ for 15min, the high-temperature tensile strength is not less than 500MPa and the elongation is not less than 6.5%.

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