Electrolyte, electrolytic copper foil and preparation method of electrolytic copper foil

Abstract

The invention discloses an electrolyte, an electrolytic copper foil and a preparation method of the electrolytic copper foil. The electrolyte comprises a basic electrolyte and a composite additive, the basic electrolyte comprises copper sulfate and sulfuric acid, and the composite additive comprises a polarization agent, an auxiliary additive and a grain refiner. The electrolyte is prepared from the following raw material components in mass concentration: 180 to 220 g / L of copper sulfate, 80 to 120 g / L of sulfuric acid, 0.5 to 2 g / L of polarization agent, 0.05 to 0.2 g / L of auxiliary additive and 0.1 to 0.5 g / L of grain refiner. The electrolyte provided by the invention can effectively improve the elongation of the electrolytic copper foil, and also considers the process stability, the cost controllability and other comprehensive properties such as the tensile strength, the surface roughness and the corrosion resistance of the electrolytic copper foil.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil technology, and in particular to an electrolyte, electrolytic copper foil, and a method for preparing the same. Background Technology

[0002] As electrolytic copper foil serves as a crucial material in the electronics and information industry, its performance directly impacts the quality and reliability of downstream products such as lithium-ion batteries and printed circuit boards. Elongation is a key indicator of copper foil's ability to undergo plastic deformation under stress. Higher elongation allows the copper foil to better withstand tensile and bending forces during processing, assembly, and use, reducing defects such as breakage and cracking. Optimal elongation enables electrolytic copper foil to meet the production demands of high-energy-density, long-cycle-life lithium-ion batteries and high-energy, lightweight printed circuit boards. Electrolytic copper foil is typically formed on the surface of a cathode substrate such as a titanium or stainless steel roller using an electrolytic deposition process, employing a copper sulfate solution as the electrolyte. However, electrolytic copper foil prepared by this process often suffers from coarse grains and uneven grain boundary distribution, resulting in low elongation and generally failing to meet the requirements of high-end applications. To improve the elongation of electrolytic copper foil, existing technologies employ the following methods: First, adjusting the concentration of copper ions and sulfuric acid in the electrolyte. However, this method has limited effect on improving elongation and can easily affect the stability of the electrolysis process. Second, adding a single type of additive, such as chloride ions or gelatin, can refine the grains to some extent, but it is difficult to achieve a significant increase in elongation and may introduce other performance defects, such as increased surface roughness and decreased corrosion resistance. Third, optimizing subsequent heat treatment processes, such as high-temperature annealing. However, high-temperature treatment can easily lead to oxidation and deformation of the copper foil, increasing production costs and process complexity.

[0003] Therefore, providing an electrolyte that can effectively improve the elongation of electrolytic copper foil while taking into account process stability, cost controllability, and other comprehensive properties of electrolytic copper foil, as well as electrolytic copper foil and its preparation method, has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide an electrolyte, an electrolytic copper foil, and a method for preparing the same. The use of the electrolyte can effectively improve the elongation of the electrolytic copper foil, while also taking into account the process stability, cost controllability, and other comprehensive properties of the electrolytic copper foil preparation method.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an electrolyte for preparing electrolytic copper foil; the electrolyte components include a base electrolyte and a composite additive, the base electrolyte including copper sulfate and sulfuric acid, and the composite additive including a polarizing agent, an auxiliary additive, and a grain refiner; the raw material components of the electrolyte, by mass concentration, include: 180-220 g / L of the copper sulfate, 80-120 g / L of the sulfuric acid, 0.5-2 g / L of the polarizing agent, 0.05-0.2 g / L of the auxiliary additive, and 0.1-0.5 g / L of the grain refiner.

[0006] Optionally, the polarizing agent includes polyvinyl alcohol, the auxiliary additive includes 2-mercaptobenzimidazole, and the grain refiner includes nano-silica treated with a silane coupling agent; the nano-silica has a particle size of 50-100 nm.

[0007] Secondly, the present invention provides a method for preparing electrolytic copper foil, wherein the method uses the electrolyte described above to prepare the electrolytic copper foil; The method for preparing the electrolytic copper foil includes the following steps: S1. Preparation of the electrolyte: Copper sulfate and sulfuric acid are added to a solvent to obtain a basic electrolyte, and a composite additive is added to the basic electrolyte to obtain the electrolyte; the composite additive includes a polarizing agent, an auxiliary additive, and a grain refiner; S2, Electrolytic deposition: The electrolyte obtained in step S1 is injected into an electrolytic cell, and an electrolytic deposition is performed using a cathode roller as the cathode and a DSA insoluble anode to form an initial electrolytic copper foil layer on the titanium roller. S3. Post-processing: The initial electrolytic copper foil layer obtained in step S2 is peeled off from the titanium roller to obtain the initial electrolytic copper foil. The initial electrolytic copper foil is then subjected to passivation treatment, low-temperature annealing treatment and drying treatment in sequence to obtain the electrolytic copper foil.

[0008] Optionally, the raw material components of the electrolyte obtained in step S1, based on mass concentration, include: 180-220 g / L of copper sulfate, 80-120 g / L of sulfuric acid, 0.5-2 g / L of polarizing agent, 0.05-0.2 g / L of auxiliary additives, and 0.1-0.5 g / L of grain refiner.

[0009] Optionally, the low-temperature annealing process includes the following steps: placing the initial electrolytic copper foil that has undergone the passivation treatment into an inert gas protected annealing furnace for low-temperature annealing; the annealing temperature of the low-temperature annealing is 150-200℃, the holding time is 30-60min, the heating rate is 5-10℃ / min, and the cooling rate is controlled at 3-5℃ / min.

[0010] Optionally, in step S2, the surface roughness Ra of the cathode roller is ≤0.1μm.

[0011] Optionally, in step S2, the electrolytic deposition is carried out under the conditions of an electrolysis temperature of 40-50℃, a current density of 20-30A / dm², and an electrolyte pH of 1.5-2.5; during the electrolytic deposition process, the circulation rate of the electrolyte is 5-8m / s.

[0012] Optionally, in step S3, the passivation treatment includes the following steps: immersing the obtained initial electrolytic copper foil in a passivation solution for passivation treatment; the mass concentration of the passivation solution is 0.5-1.5 g / L, and the passivation temperature is 25-35℃.

[0013] Optionally, the drying process is carried out in an environment with a vacuum degree of -0.08 to -0.09 MPa and a drying temperature of 60-80℃.

[0014] Thirdly, the present invention provides an electrolytic copper foil, which is prepared using the electrolyte as described above.

[0015] The beneficial effects of this invention include at least the following: The electrolyte of this invention includes the composite additive. During the production of electrolytic copper foil, the polarizing agent can form a uniform adsorption film on the cathode surface, slowing down the deposition rate of copper ions and providing more favorable conditions for the formation of crystal nuclei, thereby inhibiting the excessively rapid growth of a few grains and promoting uniform grain growth and refinement. The auxiliary additive is used to form a complex with copper ions to adsorb active growth points on the cathode surface, further regulating the reduction process of copper ions, further refining the grains, and reducing grain boundary defects. The grain refining agent has a high surface area and surface activity, and can act as a heterogeneous nucleation site, significantly refining the grain size of the copper foil. The electrolyte of this invention is based on an extrusion electrolyte composed of copper sulfate and sulfuric acid, with the addition of the composite additive. The composite additive synergistically plays a role in regulating the deposition process, reducing grain boundary defects, and refining grains. The raw materials used for the composite additive are readily available and inexpensive, and the amount added is small, so it will not significantly increase the production cost. Attached Figure Description

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

[0017] To facilitate understanding of the present invention, preferred embodiments are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] In this invention, the use of terms such as "first" and "second" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0020] In a first aspect, embodiments of the present invention provide an electrolyte for preparing electrolytic copper foil; the electrolyte components include a basic electrolyte and a composite additive, the basic electrolyte includes copper sulfate and sulfuric acid, and the composite additive includes a polarizing agent, an auxiliary additive, and a grain refiner; based on mass concentration, the raw material components of the electrolyte include: 180-220 g / L of the copper sulfate, 80-120 g / L of the sulfuric acid, 0.5-2 g / L of the polarizing agent, 0.05-0.2 g / L of the auxiliary additive, and 0.1-0.5 g / L of the grain refiner.

[0021] The electrolyte of this invention includes the composite additive. During the production of electrolytic copper foil, the polarizing agent can form a uniform adsorption film on the cathode surface, slowing down the deposition rate of copper ions and providing more favorable conditions for the formation of crystal nuclei, thereby inhibiting the excessively rapid growth of a few grains and promoting uniform grain growth and refinement. The auxiliary additive is used to form a complex with copper ions to adsorb active growth points on the cathode surface, further regulating the reduction process of copper ions, further refining the grains, and reducing grain boundary defects. The grain refining agent has a high surface area and surface activity, and can act as a heterogeneous nucleation site, significantly refining the grain size of the copper foil. The electrolyte of this invention is based on an extrusion electrolyte composed of copper sulfate and sulfuric acid, with the addition of the composite additive. The composite additive synergistically plays a role in regulating the deposition process, reducing grain boundary defects, and refining grains. The raw materials used for the composite additive are readily available and inexpensive, and the amount added is small, so it will not significantly increase the production cost.

[0022] Optionally, the polarizing agent includes polyvinyl alcohol, the auxiliary additive includes 2-mercaptobenzimidazole, and the grain refiner includes nano-silica.

[0023] Optionally, the nano-silica is nano-silica treated with a silane coupling agent; the particle size of the nano-silica is 50-100 nm. The modified nano-silica can be better dispersed in the electrolyte, avoiding agglomeration, thereby more effectively exerting the grain refinement effect.

[0024] Secondly, embodiments of the present invention provide a method for preparing electrolytic copper foil, which is prepared using the electrolyte described above; see [link to previous section]. Figure 1 As shown, the steps include: S1. Preparation of the electrolyte: Copper sulfate and sulfuric acid are added to a solvent to obtain a basic electrolyte, and a composite additive is added to the basic electrolyte to obtain the electrolyte; the composite additive includes a polarizing agent, an auxiliary additive, and a grain refiner; S2, Electrolytic deposition: The electrolyte obtained in step S1 is injected into an electrolytic cell, and an electrolytic deposition is performed using a cathode roller as the cathode and a DSA insoluble anode to form an initial electrolytic copper foil layer on the titanium roller. S3. Post-processing: The initial electrolytic copper foil layer obtained in step S2 is peeled off from the titanium roller to obtain the initial electrolytic copper foil. The initial electrolytic copper foil is then subjected to passivation treatment, low-temperature annealing treatment, and drying treatment in sequence to obtain the final electrolytic copper foil. Passivation treatment can form a dense oxide film on the surface of the copper foil, improving its corrosion resistance. Low-temperature annealing can eliminate the internal stress of the copper foil, further optimize the grain structure, and avoid oxidation and deformation problems caused by high temperature.

[0025] Optionally, the raw material components of the electrolyte obtained in step S1, based on mass concentration, include: 180-220 g / L of copper sulfate, 80-120 g / L of sulfuric acid, 0.5-2 g / L of polarizing agent, 0.05-0.2 g / L of auxiliary additives, and 0.1-0.5 g / L of grain refiner.

[0026] The low-temperature annealing process includes the following steps: placing the passivated initial electrolytic copper foil into an inert gas-protected annealing furnace for low-temperature annealing; the annealing temperature is 150-200℃, the holding time is 30-60 min, the heating rate is 5-10℃ / min, and the cooling rate is controlled at 3-5℃ / min. Optionally, the inert protective gas is nitrogen with a purity of not less than 99.99%.

[0027] Optionally, in step S1, after adding the composite additive to the basic electrolyte, a filtration step is further included: filtering the mixture of the composite additive and the basic electrolyte using a microfiltration membrane to remove impurity particles from the mixture and obtain a refined electrolyte. The microfiltration membrane has a pore size of 0.22 μm.

[0028] Optionally, in step S2, the surface roughness Ra of the cathode roller is ≤0.1μm. In some embodiments, the cathode roller is a titanium roller. Further, the cathode roller undergoes polishing treatment before use. The polishing treatment is used to improve the flatness and consistency of the cathode roller surface, providing a good deposition base for the initial copper foil layer deposition and reducing defects in subsequent copper foil deposition. The polishing treatment includes chemical polishing and / or mechanical polishing. The chemical polishing treatment includes: cleaning and degreasing the surface of the titanium roller with an alkaline solution; providing a polishing liquid; immersing the alkaline-cleaned cathode roller in the polishing liquid for exposure treatment, and removing the oxide layer on the surface of the cathode roller through a chemical reaction. The mechanical polishing is performed on its surface using a resin grinding wheel containing silicon carbide abrasive.

[0029] Optionally, in step S2, the electrolytic deposition is carried out at an electrolysis temperature of 40-50℃, a current density of 20-30 A / dm², and an electrolyte pH of 1.5-2.5; the circulation rate of the electrolyte during the electrolytic deposition process is 5-8 m / s. The electrolysis temperature ensures a suitable ion migration rate in the electrolyte while preventing excessive temperature from causing decomposition of the composite additive; the current density setting ensures uniform deposition of copper ions on the cathode roller surface, avoiding coarse grains due to excessive current density; the pH value of the electrolyte is adjusted by adding a pH adjuster to the electrolytic cell, which is beneficial for the composite additive to function and reduces anode corrosion; the pH adjuster includes sulfuric acid or copper hydroxide solution.

[0030] Optionally, in step S2, during the electrolytic deposition process, the component content and temperature of the electrolyte are monitored; when the mass concentration of copper sulfate decreases by more than 10 g / L, copper sulfate crystals are added to the electrolytic cell to maintain the component content of the electrolyte. It is understood that the electrolytic deposition time can be adjusted according to the desired thickness of the copper foil product; optionally, the electrolytic deposition time is 10-30 min.

[0031] Optionally, in step S3, the passivation treatment includes the following steps: immersing the obtained initial electrolytic copper foil in a passivation solution for passivation treatment; the mass concentration of the passivation solution is 0.5-1.5 g / L, and the passivation temperature is 25-35℃. The passivation solution includes a potassium chromate solution.

[0032] Optionally, the drying process is carried out under a vacuum of -0.08 to -0.09 MPa at a drying temperature of 60-80°C. The drying time is 10-20 minutes.

[0033] Optionally, prior to the passivation treatment, a first cleaning treatment is further included, comprising the steps of: spraying the obtained initial electrolytic copper foil with a cleaning solution to remove residual electrolyte and impurities on the surface of the initial electrolytic copper foil. The cleaning time for the first cleaning is 2-5 minutes, and the cleaning solution is at a temperature of 30-40°C. Optionally, in some embodiments, the cleaning solution is deionized water.

[0034] Optionally, after the passivation treatment and before the low-temperature annealing treatment, a second cleaning treatment is further included, comprising the steps of: using a cleaning solution to perform a second cleaning treatment on the initial electrolytic copper foil after passivation treatment, in order to remove the passivation solution remaining on the surface of the initial electrolytic copper foil, so as to avoid the impurities in the passivation solution from having an adverse effect on the final copper foil.

[0035] Thirdly, embodiments of the present invention provide an electrolytic copper foil, which is prepared using the electrolyte as described above.

[0036] The electrolytic copper foil provided by this invention has a thickness of 6-12 μm, a tensile strength at room temperature greater than or equal to 300 MPa, an elongation greater than or equal to 15%, a surface roughness Ra less than or equal to 0.3 μm, and a salt spray corrosion resistance time greater than or equal to 48 h. This indicates that the electrolyte, electrolytic copper foil, and preparation method provided by this invention are suitable for producing ultra-thin electrolytic copper foils with high elongation, and can be widely used in the manufacture of high-end electronic devices such as lithium-ion batteries and printed circuit boards.

[0037] Example 1: A method for preparing electrolytic copper foil, comprising the following steps: S1. Electrolyte preparation: Prepare a basic electrolyte with a copper sulfate concentration of 200 g / L and a sulfuric acid concentration of 100 g / L by mass. Add composite additives to the obtained basic electrolyte with a polyvinyl alcohol concentration of 1 g / L, a 2-mercaptobenzimidazole concentration of 0.1 g / L, and a nano-silica concentration (80 nm particle size, modified with a silane coupling agent) of 0.3 g / L by mass. After mixing, filter the mixture through a 0.22 μm microfiltration membrane to obtain a refined electrolyte.

[0038] S2. Electrolytic deposition: The refined electrolyte is injected into the electrolytic cell. The cathode is a polished titanium roller with a surface roughness of Ra=0.08μm, and the anode is a DSA insoluble anode. The electrolysis temperature is controlled at 45℃, the current density at 25A / dm², the electrolyte pH at 2.0, and the electrolyte circulation rate at 6m / s. Electrolytic deposition is carried out for 20min to obtain the initial electrolytic copper foil.

[0039] S3. Post-treatment: After peeling off the initial electrolytic copper foil, spray it with 35℃ deionized water for 3 min; immerse it in 1.0 g / L potassium chromate solution and passivate it at 30℃ for 2 min; after passivation, rinse it again with deionized water for 2 min; place it in a nitrogen-protected annealing furnace (nitrogen purity 99.99%), heat it to 180℃ at 8℃ / min, hold it for 45 min, and then cool it down at 4℃ / min; finally, dry it at 70℃ and -0.085MPa vacuum for 15 min to obtain an electrolytic copper foil with a thickness of 10 μm.

[0040] The performance of the obtained electrolytic copper foil was tested, and the results are as follows: tensile strength 320MPa, elongation 16.5%, surface roughness Ra=0.25μm, and salt spray corrosion resistance time 52h.

[0041] Example 2: A method for preparing electrolytic copper foil, comprising the following steps: S1. Electrolyte preparation: Prepare a basic electrolyte with a copper sulfate concentration of 180 g / L and a sulfuric acid concentration of 80 g / L; add composite additives to the basic electrolyte, with polyvinyl alcohol concentration of 0.5 g / L, 2-mercaptobenzimidazole concentration of 0.05 g / L, and nano-silica (particle size 50 nm, modified with silane coupling agent) concentration of 0.1 g / L; after mixing, filter through a 0.22 μm microfiltration membrane to obtain a refined electrolyte.

[0042] S2. Electrolytic deposition: The refined electrolyte is injected into the electrolytic cell. The cathode is a polished titanium roller with a surface roughness of Ra=0.09μm, and the anode is a DSA insoluble anode. The electrolysis temperature is controlled at 40℃, the current density at 20A / dm², the electrolyte pH at 1.5, and the electrolyte circulation rate at 5m / s. Electrolytic deposition is carried out for 30min to obtain the initial electrolytic copper foil.

[0043] S3. Post-treatment: After peeling off the initial electrolytic copper foil, spray it with 30℃ deionized water for 2 min; immerse it in 0.5 g / L potassium chromate solution and passivate it at 25℃ for 1 min; after passivation, rinse it again with deionized water for 1 min; place it in a nitrogen-protected annealing furnace (nitrogen purity 99.99%), heat it to 150℃ at 5℃ / min, hold it for 60 min, and then cool it down at 3℃ / min; finally, dry it at 60℃ and -0.08MPa vacuum for 20 min to obtain an electrolytic copper foil with a thickness of 12 μm.

[0044] Performance test results: tensile strength 305MPa, elongation 15.2%, surface roughness Ra=0.28μm, salt spray corrosion resistance time 49h.

[0045] Example 3: A method for preparing electrolytic copper foil, comprising the following steps: S1. Electrolyte preparation: Prepare a basic electrolyte with a copper sulfate concentration of 220 g / L and a sulfuric acid concentration of 120 g / L; add composite additives to the basic electrolyte, with polyvinyl alcohol concentration of 2 g / L, 2-mercaptobenzimidazole concentration of 0.2 g / L, and nano-silica (particle size 100 nm, modified with silane coupling agent) concentration of 0.5 g / L; after mixing, filter through a 0.22 μm microfiltration membrane to obtain a refined electrolyte.

[0046] S2. Electrolytic deposition: The refined electrolyte is injected into the electrolytic cell. The cathode is a polished titanium roller with a surface roughness of Ra=0.07μm, and the anode is a DSA insoluble anode. The electrolysis temperature is controlled at 50℃, the current density at 30A / dm², the electrolyte pH at 2.5, and the electrolyte circulation rate at 8m / s. Electrolytic deposition is carried out for 10min to obtain the initial electrolytic copper foil.

[0047] S3. Post-treatment: After peeling off the initial electrolytic copper foil, spray it with 40℃ deionized water for 5 min; immerse it in 1.5 g / L potassium chromate solution and passivate it at 35℃ for 3 min; after passivation, rinse it again with deionized water for 3 min; place it in a nitrogen-protected annealing furnace (nitrogen purity 99.99%), heat it to 200℃ at 10℃ / min, hold it for 30 min, and then cool it down at 5℃ / min; finally, dry it at 80℃ and -0.09MPa vacuum for 10 min to obtain an electrolytic copper foil with a thickness of 6μm.

[0048] Performance test results: tensile strength 315MPa, elongation 15.8%, surface roughness Ra=0.22μm, salt spray corrosion resistance time 55h.

[0049] Comparative Example 1: The specific steps for preparing electrolytic copper foil using traditional methods are as follows: 1. Prepare the basic electrolyte: copper sulfate concentration 200g / L, sulfuric acid concentration 100g / L, without adding any additives; 2. Electrolytic deposition: The cathode uses a common titanium roller (Ra=0.2μm), the electrolysis temperature is 45℃, the current density is 25A / dm², the pH value is 2.0, and the electrolysis time is 20min; 3. Post-treatment: Only cleaning (35℃ deionized water cleaning for 3 min) and drying (70℃ vacuum drying for 15 min) are performed; passivation and low-temperature annealing are not performed.

[0050] Performance test results: tensile strength 280 MPa, elongation 9.5%, surface roughness Ra=0.5 μm, salt spray corrosion resistance time 24 h. It is understood that, unless otherwise stated, the raw materials used in Examples 1 to 3 and Comparative Example 1 of this invention are from the same source, and the performance test results were obtained under the same test conditions.

[0051] By comparing the performance test results of Examples 1 to 3 with those of Comparative Example 1, it can be seen that: This invention adds the composite additive to the electrolyte, and through the synergistic effect of the components in the composite additive, it regulates the deposition process, reduces grain boundary defects, and refines grains. At the same time, combined with optimized electrolytic process parameters and low-temperature annealing, it effectively eliminates internal stress in copper foil, optimizes grain structure, and increases the elongation of the prepared electrolytic copper foil to more than 15%, which is much higher than that of the electrolytic copper foil prepared by the traditional process in Comparative Example 1.

[0052] Therefore, compared to the conventional technique in Comparative Example 1: The electrolytic copper foil prepared using the method of this invention exhibits significantly improved elongation, and its comprehensive properties, including tensile strength, surface roughness, and corrosion resistance, are significantly superior to those of electrolytic copper foil prepared using traditional methods. This demonstrates that the electrolytic copper foil products obtained using the electrolyte, electrolytic copper foil, and preparation method provided by this invention can meet the production requirements of high-energy-density, long-cycle-life lithium-ion batteries and high-energy, lightweight printed circuit boards.

[0053] While improving elongation, this invention ensures that the electrolytic copper foil has high tensile strength (≥300MPa), low surface roughness (Ra≤0.3μm) and excellent corrosion resistance (salt spray corrosion resistance time ≥48h) by strictly controlling the purity of the electrolyte, electrolysis temperature, pH value and subsequent cleaning and passivation treatment, which can meet the requirements of high-end electronic fields such as lithium-ion batteries and printed circuit boards.

[0054] The non-electrolyte and electrolyte preparation method provided by this invention have high process stability and controllable cost: the composite additive raw materials used in this invention are readily available and inexpensive, and the amount added is small, which will not significantly increase the production cost; the electrolysis and subsequent processing parameters are easy to control, suitable for large-scale industrial production, while avoiding the oxidation and deformation risks caused by complex processes such as high-temperature annealing, thus improving the stability of the production process and the product qualification rate.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. An electrolyte, characterized in that: Used for preparing electrolytic copper foil; the electrolyte components include a basic electrolyte and composite additives, the basic electrolyte includes copper sulfate and sulfuric acid, and the composite additives include polarizing agents, auxiliary additives and grain refiners; The electrolyte comprises, by mass concentration: 180-220 g / L of copper sulfate, 80-120 g / L of sulfuric acid, 0.5-2 g / L of polarizing agent, 0.05-0.2 g / L of auxiliary additives, and 0.1-0.5 g / L of grain refiner.

2. The electrolyte according to claim 1, characterized in that: The polarizing agent includes polyvinyl alcohol, the auxiliary additive includes 2-mercaptobenzimidazole, and the grain refiner includes nano-silica treated with a silane coupling agent; the particle size of the nano-silica is 50-100 nm.

3. A method for preparing electrolytic copper foil, characterized in that, The method uses the electrolyte as described in any one of claims 1-2 to prepare electrolytic copper foil; The method for preparing the electrolytic copper foil includes the following steps: S1. Preparation of the electrolyte: Copper sulfate and sulfuric acid are added to a solvent to obtain a basic electrolyte, and a composite additive is added to the basic electrolyte to obtain the electrolyte; the composite additive includes a polarizing agent, an auxiliary additive, and a grain refiner; S2, Electrolytic deposition: The electrolyte obtained in step S1 is injected into an electrolytic cell, and an electrolytic deposition is performed using a cathode roller as the cathode and a DSA insoluble anode to form an initial electrolytic copper foil layer on the titanium roller. S3. Post-processing: The initial electrolytic copper foil layer obtained in step S2 is peeled off from the titanium roller to obtain the initial electrolytic copper foil. The initial electrolytic copper foil is then subjected to passivation treatment, low-temperature annealing treatment and drying treatment in sequence to obtain the electrolytic copper foil.

4. The method for preparing electrolytic copper foil according to claim 3, characterized in that: The raw material components of the electrolyte obtained in step S1, based on mass concentration, include: 180-220 g / L of copper sulfate, 80-120 g / L of sulfuric acid, 0.5-2 g / L of polarizing agent, 0.05-0.2 g / L of auxiliary additives, and 0.1-0.5 g / L of grain refiner.

5. The method for preparing electrolytic copper foil according to claim 3, characterized in that: The low-temperature annealing process includes the following steps: placing the initial electrolytic copper foil that has undergone the passivation treatment into an inert gas protected annealing furnace for low-temperature annealing; the annealing temperature of the low-temperature annealing is 150-200℃, the holding time is 30-60min, the heating rate is 5-10℃ / min, and the cooling rate is controlled at 3-5℃ / min.

6. The method for preparing electrolytic copper foil according to claim 3, characterized in that: In step S2, the surface roughness Ra of the cathode roller is ≤0.1μm.

7. The method for preparing electrolytic copper foil according to claim 3, characterized in that: In step S2, the electrolytic deposition is carried out under the conditions of an electrolysis temperature of 40-50℃, a current density of 20-30A / dm², and an electrolyte pH of 1.5-2.5; during the electrolytic deposition process, the circulation rate of the electrolyte is 5-8m / s.

8. The method for preparing electrolytic copper foil according to claim 3, characterized in that: In step S3, the passivation treatment includes the following steps: immersing the obtained initial electrolytic copper foil in a passivation solution for passivation treatment; the mass concentration of the passivation solution is 0.5-1.5 g / L, and the passivation temperature is 25-35℃.

9. The method for preparing electrolytic copper foil according to claim 3, characterized in that: The drying process is carried out in an environment with a vacuum degree of -0.08 to -0.09 MPa and a drying temperature of 60-80℃.

10. An electrolytic copper foil, characterized in that: The electrolytic copper foil is prepared using the electrolyte as described in any one of claims 1-2.

Images