Highly oxidation-resistant copper thin film and method for preparing the same

Abstract

This invention discloses a high-oxidation-resistant copper thin film and its preparation method, relating to the field of current collector technology. The method includes the following steps: Step 1: Prepare a magnetron sputtering device and use a copper circuit assembly for power transmission and grounding; Step 2: Use a single-crystal copper target to perform magnetron sputtering on both sides of the base film to deposit a copper seed layer; thus obtaining a high-oxidation-resistant copper thin film; the single-crystal copper target has a Cu(111) crystal plane, a purity of 99.99%, and a thickness of 9.8~10.2 mm; the copper circuit assembly includes a wire and a grounding platform, both made of single-crystal copper, with the single-crystal copper having a Cu(111) crystal plane or a close-packed crystal plane with an atomic density difference of ≤5% from the Cu(111) crystal plane. The high-oxidation-resistant copper thin film prepared by this invention exhibits excellent oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of current collector technology, specifically to a high-oxidation-resistant copper thin film and its preparation method. Background Technology

[0002] In recent years, the rapid development of new energy and electronic technologies has placed higher demands on the cycle life, energy density, and safety performance of batteries. As a core component of the battery, the current collector is mainly used to collect the current generated by the battery's active materials and form a large current output. Therefore, the performance of the current collector directly affects the overall performance of the battery.

[0003] Currently, the key components of batteries, the positive and negative electrodes, typically use pure copper / aluminum foil as current collectors. These current collectors have high cost and weight, which is detrimental to battery cost control and energy density improvement. In contrast, composite foil current collectors offer better advantages over traditional foil materials. They are typically a "sandwich" structure with an inner polymer layer and conductive metal layers on both sides. This allows for a thinner metal layer and a lighter inner polymer layer, effectively reducing the weight of the current collector and increasing battery energy density. Furthermore, the thinner metal layer effectively reduces the risk of thermal runaway.

[0004] In existing technologies, metal films of composite foils are usually prepared using traditional magnetron sputtering. However, the resulting metal films have limitations in terms of oxidation resistance: First, traditional metal films are often prepared using polycrystalline copper targets for deposition. However, the irregular atomic arrangement and numerous defects at the grain boundaries of polycrystalline copper become channels for rapid diffusion of oxygen atoms, accelerating the oxidation reaction and resulting in poor oxidation resistance. Second, due to the large difference in thermal expansion coefficients between the inner polymer layer and the metal film, the stress dispersion effect is poor, resulting in poor adhesion between the magnetron sputtered metal film and the polymer layer, making it easy to detach and leading to a decrease in oxidation resistance.

[0005] Therefore, in order to solve the above problems, it is of great significance to provide a high-oxidation-resistant copper thin film and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a high-oxidation-resistant copper thin film and its preparation method, so as to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-oxidation-resistant copper thin film includes the following steps: Step 1: Prepare the magnetron sputtering equipment and use copper circuit components for power transmission and grounding; Step 2: Use a single-crystal copper target to perform magnetron sputtering on both sides of the base film to deposit a copper seed layer; thus obtaining a copper thin film with high oxidation resistance.

[0008] In a more optimized manner, the crystal plane of the single crystal copper target is (111), the purity of the single crystal copper target is 99.99%, and the thickness is 9.8~10.2mm.

[0009] In a more optimized manner, the copper circuit assembly includes a conductor and a grounding platform, both of which are made of single-crystal copper. The crystal plane of the single-crystal copper is Cu(111) or a close-packed crystal plane with an atomic arrangement density difference of ≤5% from the Cu(111) crystal plane.

[0010] The wires are used to connect the RF power generator to the AC power supply, and to connect the RF power generator to the magnetron sputtering cavity for power transmission; the grounding platform is used to provide a grounding loop.

[0011] The optimized process parameters for magnetron sputtering are: sputtering power 5.8~6.2kW, and base vacuum degree 3×10⁻⁶. -3 ~5×10 -3 Pa, argon flow rate 120~140sccm, sputtering main roller cooling temperature -35~0℃, copper target power 8~12kW, winding speed 5~8m / min.

[0012] Ideally, the base film includes a PET base film.

[0013] More preferably, the base film is a modified PET base film; the preparation method of the modified PET base film is as follows: Step 1: (1) Under a nitrogen atmosphere, [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, trithiocarbonate, and tetrabutylammonium chloride were added to DMF in sequence and mixed. The mixture was stirred for 10-15 hours. Then, mercaptoacetic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine were added and stirred for 5-7 hours. The mixture was filtered and rotary evaporated to obtain a mercapto-containing polysulfide polymer. (2) Under a nitrogen atmosphere, the mercapto-containing polysulfide polymer, vinylpyridine, and azobisisobutyronitrile were added to DMF in sequence. The temperature was set at 60-70°C and the mixture was stirred for 6-8 hours. The mixture was then added to methanol to precipitate and dried to obtain a pyridine-polysulfide polymer. Step 2: Under a nitrogen atmosphere, terephthalic acid and ethylene glycol are mixed and stirred at 240~260℃ for 2~3 hours. Then, the temperature is lowered to 220~240℃, and pyridine-polysulfide polymer and tetrabutyl titanate are added in sequence. The mixture is stirred for 2~3 hours to obtain modified PET masterbatch. Step 3: Extrude the modified PET masterbatch, cast it into sheets, biaxially stretch it, and perform post-treatment to obtain the modified PET base film.

[0014] More preferably, the raw materials of the mercapto-containing polysulfide polymer, by weight, are: 8-12 parts [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, 0.08-0.12 parts trithiocarbonate, 0.08-0.12 parts tetrabutylammonium chloride, 4.5-5.5 parts mercaptoacetic acid, 10-12 parts N,N'-dicyclohexylcarbodiimide, and 0.3-0.5 parts 4-dimethylaminopyridine; The raw materials for the pyridine-polysulfide polymer, by weight, are: 15-20 parts of thiol-containing polysulfide polymer, 5-10 parts of vinylpyridine, and 0.05-0.1 parts of azobisisobutyronitrile; The modified PET masterbatch contains, by weight, 90-100 parts terephthalic acid, 50-55 parts ethylene glycol, 8-15 parts pyridine-polysulfide polymer, and 0.07-0.1 parts tetrabutyl titanate.

[0015] A more optimized method for preparing [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane is as follows: p-hydroxybenzyl alcohol, potassium carbonate, and potassium iodide are added sequentially to acetonitrile, the temperature is raised to 85-95°C, and the mixture is stirred for 2-3 hours. Then, cyclothiochloropropane is added, and the mixture is stirred for another 20-24 hours. The mixture is then cooled, filtered, washed with water, and dried to obtain [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane.

[0016] In a more optimized manner, the raw material of [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane comprises, by weight: 5-7 parts p-hydroxybenzyl alcohol, 16-20 parts potassium carbonate, 2-3 parts potassium iodide, and 8-10 parts cyclothiochloropropane.

[0017] A method for preparing a high-oxidation-resistant copper thin film yields a high-oxidation-resistant copper thin film, which is used as a current collector.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. In the preparation of functional current collectors, magnetron sputtering improves the oxidation resistance of copper films by controlling the crystal orientation and growth conditions of the copper films. The copper atoms in the single-crystal copper target have a continuous and consistent crystal structure with no grain boundaries and very few defects. Among them, the Cu(111) crystal plane is the closest packing plane of copper, with the most compact atomic packing and the lowest surface energy. Therefore, its crystal plane is the most stable. When ions bombard the single-crystal target with a consistent crystal orientation, the sputtered copper atoms have highly consistent kinetic energy and ejection direction, thus laying the foundation for epitaxial growth. At this time, the crystal structure of the deposited thin film will grow under the guidance of the substrate crystal structure, rather than being randomly stacked. As a result, an ordered structure without multi-atom steps or defects will be formed on its surface, resulting in a flat surface containing only single-atom steps. This effectively eliminates the fastest diffusion channels for oxygen and water vapor. The corrosive medium can only diffuse through bulk diffusion (through the complete lattice), and its diffusion rate is significantly reduced. In addition, the crystal structure has very few defects such as dislocations and vacancies. The crystal structure is in a lower energy state, which is more thermodynamically stable and less likely to react with oxygen in the environment, thus improving its antioxidant capacity. To further ensure the stability of the sputtering process, monocrystalline copper components and connecting components are used instead of traditional polycrystalline copper components. This eliminates current noise caused by electron-grain boundary scattering in traditional wires, ensuring plasma stability during sputtering. A stable plasma provides a moderately energetic and uniform particle flow. On one hand, this ensures that deposited atoms have sufficient kinetic energy and mobility, aligning regularly on the substrate surface to form a dense, non-porous thin film structure that effectively blocks the penetration of corrosive media such as oxygen and water vapor. On the other hand, a stable deposition environment reduces defects caused by sudden energy changes, thereby reducing reaction initiation points. Simultaneously, a stable energy supply promotes the formation of more crystalline films, further reducing the number of grain boundaries and synergistically improving the oxidation resistance of the copper thin film.

[0019] 2. The high-oxidation-resistant copper film in this invention uses PET as the base film. However, due to insufficient interfacial bonding between the PET base film and metallic copper, the PET base film is functionally modified: First, a hydroxymethyl-containing polysulfide is obtained through ring-opening polymerization of cyclic sulfur monomers. Then, thiol groups are introduced by reacting hydroxymethyl with mercaptoacetic acid. Subsequently, 4-vinylpyridine is grafted to form a pyridine-polysulfide polymer. Then, nitrogen-containing groups (pyridine groups) and flexible polysulfide segments are introduced into the PET molecular backbone through esterification. Since the pyridine group contains nitrogen atoms, when magnetron sputtering copper plating is performed subsequently, the highly active copper atoms sputtered interact with the nitrogen atoms in the PET base film. The bonding strength of this chemical bond is much higher than that of traditional physical adsorption, effectively improving the interlayer bonding force. Meanwhile, the polysulfide segments possess a low glass transition temperature, enabling a transition between the rigid PET backbone and the copper metal layer. The flexible polysulfide segments disperse stress through conformational adjustments of the molecular chains, preventing stress concentration and detachment at the interface caused by differences in thermal expansion coefficients. It should be noted that an excessively high proportion of flexible polysulfide segments can lead to decreased matrix strength and increased susceptibility to phase separation; conversely, an excessively low proportion results in insufficient stress buffering, and the interface remains prone to cracking due to differences in thermal expansion. Therefore, the proportion of flexible polysulfide segments must be controlled to be lower than that of the PET matrix segments to ensure performance, guarantee a strong interfacial bond between the copper film and the PET substrate, achieve a seamless interface, eliminate interfacial infiltration channels, and effectively improve oxidation resistance. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following embodiments, the parts are by weight; it should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention, which include, for example: trithiocarbonate (CAS: 2314-48-9), tetrabutylammonium chloride (CAS: 1112-67-0), DMF (CAS: 68-12-2), mercaptoacetic acid (CAS: 367-51-1), N,N'-dicyclohexylcarbodiimide (CAS: 538-75-0), 4-dimethylaminopyridine (CAS: 1122-58-3), vinylpyridine (CAS: 536-75-4), Azobisisobutyronitrile (CAS: 78-67-1), Terephthalic acid (CAS: 100-21-0), Ethylene glycol (CAS: 107-21-1), Tetrabutyl titanate (CAS: 5593-70-4), p-hydroxybenzyl alcohol (CAS: 623-05-2), Potassium carbonate (CAS: 584-08-7), Potassium iodide (CAS: 7681-11-0), Acetonitrile (CAS: 75-05-8), Cyclothiochloropropane (CAS: 3221-15-6).

[0022] Pre-preparation: Preparation of [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane: 6 parts of p-hydroxybenzyl alcohol, 18 parts of potassium carbonate, and 2.5 parts of potassium iodide were added sequentially to 50 parts of acetonitrile. The mixture was heated to 90°C and stirred for 2.5 hours. Then, 9 parts of cyclothiochloropropane were added, and stirring was continued for 22 hours. The mixture was cooled, filtered, washed with water, and dried to obtain [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane.

[0023] Example 1: A method for preparing a high-oxidation-resistant copper thin film, the specific steps of which are as follows: Step 1: Prepare a high-vacuum winding magnetron sputtering device. The device includes a single-crystal copper (111) wire and a single-crystal copper (111) grounding platform. The single-crystal copper wire connects the RF power generator to the AC power supply and connects the RF power generator to the magnetron sputtering cavity for power transmission. The output RF power range is 13.77W. The single-crystal copper grounding platform is used to provide a grounding loop. Step 2: Perform surface treatment on a single crystal copper (111) target material with a purity of 99.99% and a thickness of 10mm to ensure that the target material surface is flat and free of impurities, and set it aside for later use; Step 3: Perform magnetron sputtering on both sides of the PET base film. The target material is the single-crystal copper (111) target from Step 2. The magnetron sputtering parameters are: sputtering power of 6KW and background vacuum of 4×10⁻⁶. -3 With an argon flow rate of 130 sccm, a sputtering main roller cooling temperature of -10℃, a copper target power of 10KW, and a winding speed of 6.5m / min, a copper seed layer, i.e. a high-oxidation-resistant copper film, is obtained on both sides of a PET base film.

[0024] Example 2: A method for preparing a high-oxidation-resistant copper thin film, the specific steps of which are as follows: Step 1: Prepare a high-vacuum winding magnetron sputtering device. The device includes a single-crystal copper (111) wire and a single-crystal copper (111) grounding platform. The single-crystal copper wire connects the RF power generator to the AC power supply and connects the RF power generator to the magnetron sputtering cavity for power transmission. The output RF power range is 13.77W. The single-crystal copper grounding platform is used to provide a grounding loop. Step 2: Perform surface treatment on a single crystal copper (111) target material with a purity of 99.99% and a thickness of 10mm to ensure that the target material surface is flat and free of impurities, and set it aside for later use; Step 3: Perform magnetron sputtering on both sides of the PET base film. The target material is the single-crystal copper (111) target from Step 2. The magnetron sputtering parameters are: sputtering power of 6KW and background vacuum of 5×10⁻⁶. -3 With an argon flow rate of 130 sccm, a sputtering main roller cooling temperature of -20℃, a copper target power of 11KW, and a winding speed of 8m / min, a copper seed layer, i.e., a high-oxidation-resistant copper film, is obtained on both sides of the PET base film.

[0025] Example 3: A method for preparing a high-oxidation-resistant copper thin film, the specific steps of which are as follows: I. Preparation of modified PET base film: Step 1: (1) Under a nitrogen atmosphere, 10 parts of [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, 0.1 parts of trithiocarbonate, and 0.1 parts of tetrabutylammonium chloride were added to 30 parts of DMF and mixed. The temperature was raised to 75°C and the mixture was stirred for 13 hours. Then, 5 parts of mercaptoacetic acid, 11 parts of N,N'-dicyclohexylcarbodiimide, and 0.4 parts of 4-dimethylaminopyridine were added. The temperature was set at 40°C and the mixture was stirred for 6 hours. The mixture was filtered and rotary evaporated to obtain a mercapto-containing polysulfide polymer. (2) Under a nitrogen atmosphere, 17 parts of the mercapto-containing polysulfide polymer, 7.5 parts of vinylpyridine, and 0.08 parts of azobisisobutyronitrile were added to 50 parts of DMF and the temperature was set at 65°C. The mixture was stirred for 7 hours. The mixture was added to methanol to precipitate and dried to obtain a pyridine-polysulfide polymer. Step 2: Under a nitrogen atmosphere, 95 parts of terephthalic acid and 52 parts of ethylene glycol were stirred at 250°C for 2.5 hours, then cooled to 230°C. 12 parts of pyridine-polysulfide polymer and 0.08 parts of tetrabutyl titanate were added sequentially, and the mixture was stirred for 2.5 hours to obtain modified PET masterbatch. Step 3: Extrude the modified PET masterbatch, cast it into sheets, biaxially stretch it, and perform post-treatment to obtain the modified PET base film.

[0026] II. Preparation of high-oxidation-resistant copper thin films: Step 1: Prepare a high-vacuum winding magnetron sputtering device. The device includes a single-crystal copper (111) wire and a single-crystal copper (111) grounding platform. The single-crystal copper wire connects the RF power generator to the AC power supply and connects the RF power generator to the magnetron sputtering cavity for power transmission. The output RF power range is 13.77W. The single-crystal copper grounding platform is used to provide a grounding loop. Step 2: Perform surface treatment on a single crystal copper (111) target material with a purity of 99.99% and a thickness of 10mm to ensure that the target material surface is flat and free of impurities, and set it aside for later use; Step 3: Magnetron sputtering was performed on both sides of the modified PET base film. The target material was the single-crystal copper (111) target from Step 2. The magnetron sputtering parameters were: sputtering power of 6KW and background vacuum of 4×10⁻⁶. -3 With an argon flow rate of 130 sccm, a sputtering main roller cooling temperature of -10℃, a copper target power of 10KW, and a winding speed of 6.5m / min, a copper seed layer, i.e., a high-oxidation-resistant copper film, is obtained on both sides of the base film.

[0027] Example 4: A method for preparing a high-oxidation-resistant copper thin film, the specific steps of which are as follows: I. Preparation of modified PET base film: Step 1: (1) Under a nitrogen atmosphere, 8 parts of [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, 0.08 parts of trithiocarbonate, and 0.08 parts of tetrabutylammonium chloride were added to 30 parts of DMF and mixed. The mixture was heated to 70°C and stirred for 10 hours. Then, 4.5 parts of mercaptoacetic acid, 10 parts of N,N'-dicyclohexylcarbodiimide, and 0.3 parts of 4-dimethylaminopyridine were added. The mixture was set to 35°C and stirred for 5 hours. The mixture was filtered and rotary evaporated to obtain a mercapto-containing polysulfide polymer. (2) Under a nitrogen atmosphere, 15 parts of the mercapto-containing polysulfide polymer, 5 parts of vinylpyridine, and 0.05 parts of azobisisobutyronitrile were added to 50 parts of DMF. The mixture was set to 60°C and stirred for 6 hours. The mixture was added to methanol to precipitate and dried to obtain a pyridine-polysulfide polymer. Step 2: Under a nitrogen atmosphere, 90 parts of terephthalic acid and 50 parts of ethylene glycol are stirred at 250°C for 2 hours, then cooled to 230°C. 8 parts of pyridine-polysulfide polymer and 0.07 parts of tetrabutyl titanate are added sequentially, and the mixture is stirred for 2 hours to obtain modified PET masterbatch. Step 3: Extrude the modified PET masterbatch, cast it into sheets, biaxially stretch it, and perform post-treatment to obtain the modified PET base film.

[0028] II. Preparation of high-oxidation-resistant copper thin films: Step 1: Prepare a high-vacuum winding magnetron sputtering device. The device includes a single-crystal copper (111) wire and a single-crystal copper (111) grounding platform. The single-crystal copper wire connects the RF power generator to the AC power supply and connects the RF power generator to the magnetron sputtering cavity for power transmission. The output RF power range is 13.77W. The single-crystal copper grounding platform is used to provide a grounding loop. Step 2: Perform surface treatment on a single crystal copper (111) target material with a purity of 99.99% and a thickness of 10mm to ensure that the target material surface is flat and free of impurities, and set it aside for later use; Step 3: Magnetron sputtering was performed on both sides of the modified PET base film. The target material was the single-crystal copper (111) target from Step 2. The magnetron sputtering parameters were: sputtering power of 6KW and background vacuum of 4×10⁻⁶. -3 With an argon flow rate of 130 sccm, a sputtering main roller cooling temperature of -10℃, a copper target power of 10KW, and a winding speed of 6.5m / min, a copper seed layer, i.e., a high-oxidation-resistant copper film, is obtained on both sides of the base film.

[0029] Example 5: A method for preparing a high-oxidation-resistant copper thin film, the specific steps of which are as follows: I. Preparation of modified PET base film: Step 1: (1) Under a nitrogen atmosphere, 12 parts of [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, 0.12 parts of trithiocarbonate, and 0.12 parts of tetrabutylammonium chloride were added to 30 parts of DMF and mixed. The mixture was heated to 80°C and stirred for 15 hours. Then, 5.5 parts of mercaptoacetic acid, 12 parts of N,N'-dicyclohexylcarbodiimide, and 0.5 parts of 4-dimethylaminopyridine were added. The mixture was set to 45°C and stirred for 7 hours. The mixture was filtered and rotary evaporated to obtain a mercapto-containing polysulfide polymer. (2) Under a nitrogen atmosphere, 20 parts of the mercapto-containing polysulfide polymer, 10 parts of vinylpyridine, and 0.1 parts of azobisisobutyronitrile were added to 50 parts of DMF. The mixture was set to 70°C and stirred for 8 hours. The mixture was then added to methanol to precipitate and dried to obtain a pyridine-polysulfide polymer. Step 2: Under a nitrogen atmosphere, 100 parts of terephthalic acid and 55 parts of ethylene glycol are stirred at 250°C for 3 hours, then cooled to 230°C. 15 parts of pyridine-polysulfide polymer and 0.1 parts of tetrabutyl titanate are added sequentially, and the mixture is stirred for 3 hours to obtain modified PET masterbatch. Step 3: Extrude the modified PET masterbatch, cast it into sheets, biaxially stretch it, and perform post-treatment to obtain the modified PET base film.

[0030] II. Preparation of high-oxidation-resistant copper thin films: Step 1: Prepare a high-vacuum winding magnetron sputtering device. The device includes a single-crystal copper (111) wire and a single-crystal copper (111) grounding platform. The single-crystal copper wire connects the RF power generator to the AC power supply and connects the RF power generator to the magnetron sputtering cavity for power transmission. The output RF power range is 13.77W. The single-crystal copper grounding platform is used to provide a grounding loop. Step 2: Perform surface treatment on a single crystal copper (111) target material with a purity of 99.99% and a thickness of 10mm to ensure that the target material surface is flat and free of impurities, and set it aside for later use; Step 3: Magnetron sputtering was performed on both sides of the modified PET base film. The target material was the single-crystal copper (111) target from Step 2. The magnetron sputtering parameters were: sputtering power of 6KW and background vacuum of 4×10⁻⁶. -3 With an argon flow rate of 130 sccm, a sputtering main roller cooling temperature of -10℃, a copper target power of 10KW, and a winding speed of 6.5m / min, a copper seed layer, i.e., a high-oxidation-resistant copper film, is obtained on both sides of the base film.

[0031] Comparative Example 1: Based on Example 1, the difference between this comparative example and Example 1 is that a high-oxidation-resistant copper thin film is prepared using a polycrystalline copper target and conventional wires; the rest is the same as Example 1.

[0032] Comparative Example 2: Based on Example 1, the difference between this comparative example and Example 1 is that a high-oxidation-resistant copper thin film is prepared using a polycrystalline copper target + a single-crystal copper (111) wire; the rest is the same as Example 1.

[0033] Comparative Example 3: Based on Example 1, the difference between this comparative example and Example 1 is that a high-oxidation-resistant copper thin film was prepared using a single-crystal copper (111) target material and conventional wires; the rest is the same as Example 1.

[0034] Comparative Example 4: Based on Example 3, the difference between this comparative example and Example 3 is that a thiol-containing polysulfide polymer is used instead of a pyridine-polysulfide polymer to prepare the modified PET base film, while the rest is the same as in Example 3.

[0035] Comparative Example 5: Based on Example 3, the difference between this comparative example and Example 3 is that 72 parts of terephthalic acid, 52 parts of ethylene glycol, and 35 parts of pyridine-polysulfide polymer were added to prepare a modified PET base film; the rest remained the same as in Example 3.

[0036] Performance testing: The high-oxidation-resistant copper films prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to the following performance tests: (1) Surface oxygen content: The surface oxygen content of the high oxidation-resistant copper film was analyzed using EDS (energy dispersive X-ray spectroscopy); (2) Noise current density detection: The high antioxidant copper film sample was placed in an electrochemical workstation and a three-electrode system was used to monitor the change of its current over time at open circuit potential, and the noise current density was calculated.

[0037] (3) Peel force test: The high oxidation-resistant copper film sample is fixed in the upper clamp of the tensile testing machine, and the rest is fixed in the lower clamp. Then, the peel force is tested by setting the angle to 180° and the peeling speed to 100 mm / min to characterize the degree of bonding between the base film and the copper thin layer.

[0038]

[0039] Conclusion: The test data from Examples 1-5 show that the copper thin film formed by magnetron sputtering using a single-crystal copper (111) target with a magnetron sputtering device employing a single-crystal copper conductor and grounding platform exhibits excellent oxidation resistance. In Example 3, the composite copper foil prepared using a modified PET base film significantly reduced the surface oxygen content of the copper thin film, noticeably decreased the noise current density, and substantially improved the peel force between the base film and the copper thin film. This indicates that the nitrogen-containing functional groups in the modified PET base film form a stronger interfacial bond with copper atoms, improving the density and conductivity stability of the copper thin film, thereby significantly enhancing the overall performance of the composite copper foil.

[0040] Comparing Example 1 with Comparative Examples 1-3, it can be seen that when polycrystalline copper targets are used instead of monocrystalline copper (111) targets, or conventional wires are used instead of monocrystalline copper wires, the crystal integrity of the copper film decreases, providing more diffusion channels for oxygen atoms and leading to intensified oxidation. Simultaneously, stress concentration and increased defects at grain boundaries weaken the interfacial interaction, resulting in decreased peel strength. Similarly, comparing the test data of Example 3 with Comparative Examples 4-5, it can be seen that in Comparative Example 4, the modified PET base film uses only a thiol-containing polysulfide polymer without introducing a vinylpyridine nitrogen-containing component, thus lacking effective copper-nitrogen coordination bonding ability. In Comparative Example 5, the pyridine-polysulfide polymer to PET ratio is unbalanced, leading to decreased matrix strength and an inability to effectively construct a stable interfacial structure, resulting in decreased oxidation resistance and bonding strength. In conclusion, the synergistic effect of using a monocrystalline copper source and a modified PET base film can effectively improve the oxidation resistance of composite copper foil.

[0041] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-oxidation-resistant copper thin film, characterized in that: Includes the following steps: Step 1: Prepare the magnetron sputtering equipment and use copper circuit components for power transmission and grounding; Step 2: Use a single-crystal copper target to perform magnetron sputtering on both sides of the base film to deposit a copper seed layer; thus obtaining a copper thin film with high oxidation resistance.

2. The method for preparing a high-oxidation-resistant copper thin film according to claim 1, characterized in that: The single-crystal copper target has a crystal plane of (111), a purity of 99.99%, and a thickness of 9.8~10.2 mm.

3. The method for preparing a high-oxidation-resistant copper thin film according to claim 1, characterized in that: The copper circuit assembly includes wires and a grounding platform. The wires and the grounding platform are both made of single-crystal copper. The crystal plane of the single-crystal copper is Cu(111) or a close-packed crystal plane with an atomic arrangement density difference of ≤5% from the Cu(111) crystal plane.

4. The method for preparing a high-oxidation-resistant copper thin film according to claim 1, characterized in that: The magnetron sputtering process parameters are: sputtering power 5.8~6.2kW, background vacuum degree 3×10 -3 ~5×10 -3 Pa, argon flow rate 120~140sccm, sputtering main roller cooling temperature -35~0℃, copper target power 8~12kW, winding speed 5~8m / min.

5. The method for preparing a high-oxidation-resistant copper thin film according to claim 1, characterized in that: The base film includes a PET base film.

6. The method for preparing a high-oxidation-resistant copper thin film according to claim 5, characterized in that: The base film is a modified PET base film, and the preparation method is as follows: Step 1: (1) Under a nitrogen atmosphere, [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, trithiocarbonate, and tetrabutylammonium chloride were added to DMF in sequence and mixed. The mixture was stirred for 10-15 hours. Then, mercaptoacetic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine were added and stirred for 5-7 hours. The mixture was filtered and rotary evaporated to obtain a mercapto-containing polysulfide polymer. (2) Under a nitrogen atmosphere, the mercapto-containing polysulfide polymer, vinylpyridine, and azobisisobutyronitrile were added to DMF in sequence. The temperature was set at 60-70°C and the mixture was stirred for 6-8 hours. The mixture was then added to methanol to precipitate and dried to obtain a pyridine-polysulfide polymer. Step 2: Under a nitrogen atmosphere, terephthalic acid and ethylene glycol are mixed and stirred at 240~260℃ for 2~3 hours. Then, the temperature is lowered to 220~240℃, and pyridine-polysulfide polymer and tetrabutyl titanate are added in sequence. The mixture is stirred for 2~3 hours to obtain modified PET masterbatch. Step 3: Extrude the modified PET masterbatch, cast it into sheets, biaxially stretch it, and perform post-treatment to obtain the modified PET base film.

7. The method for preparing a high-oxidation-resistant copper thin film according to claim 6, characterized in that: The raw materials of the thiol-containing polysulfide polymer, by weight, are: 8-12 parts [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, 0.08-0.12 parts trithiocarbonate, 0.08-0.12 parts tetrabutylammonium chloride, 4.5-5.5 parts mercaptoacetic acid, 10-12 parts N,N'-dicyclohexylcarbodiimide, and 0.3-0.5 parts 4-dimethylaminopyridine; The raw materials for the pyridine-polysulfide polymer, by weight, are: 15-20 parts of thiol-containing polysulfide polymer, 5-10 parts of vinylpyridine, and 0.05-0.1 parts of azobisisobutyronitrile; The modified PET masterbatch contains, by weight, 90-100 parts terephthalic acid, 50-55 parts ethylene glycol, 8-15 parts pyridine-polysulfide polymer, and 0.07-0.1 parts tetrabutyl titanate.

8. The method for preparing a high-oxidation-resistant copper thin film according to claim 7, characterized in that: The preparation method of [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane is as follows: p-hydroxybenzyl alcohol, potassium carbonate, and potassium iodide are added to acetonitrile in sequence, the temperature is raised to 85~95℃, and the mixture is stirred for 2~3 hours. Then, cyclothiochloropropane is added, and the mixture is stirred for another 20~24 hours. The mixture is then cooled, filtered, washed with water, and dried to obtain [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane.

9. The method for preparing a high-oxidation-resistant copper thin film according to claim 8, characterized in that: The raw materials for [2-(4-hydroxymethyl)phenoxymethyl]cyclothioethane, by weight, are: 5-7 parts p-hydroxybenzyl alcohol, 16-20 parts potassium carbonate, 2-3 parts potassium iodide, and 8-10 parts cyclothiochloropropane.

10. The high-oxidation-resistant copper thin film prepared by the method according to any one of claims 1 to 9, characterized in that: The high-oxidation-resistant copper film is used as a current collector.

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