Highly conductive graphene / copper composite wire and method for manufacturing the same

Abstract

The application discloses a kind of high-conductivity graphene / copper composite wires and preparation method thereof.The preparation method uses the circulating process of "chemical vapor deposition-low-power oxygen plasma activation-non-aqueous solution electroplating", and multiple layers of "graphene-copper" alternating composite structure units can be autonomously controlled on the surface of copper core.Through the synergistic design of interface chemical bonding, non-aqueous solution system pulse electroplating and parallel graphene channel, the problems of high interface resistance, insufficient high-frequency performance and heat dissipation capacity of traditional materials are solved.The prepared graphene / copper composite wire has high conductivity, high strength interface and excellent current-carrying heat dissipation capacity, and is suitable for medium and high voltage power transmission.

Description

Technical Field

[0001] This invention belongs to the technical field of composite material applications, specifically relating to a highly conductive graphene / copper composite wire and its preparation method. Background Technology

[0002] Copper, as a typical transition metal element, possesses excellent electrical properties and is a fundamental conductive material widely used in modern industry. Copper is extensively used in wire manufacturing. With technological advancements, higher performance requirements are being placed on copper wires, especially high-conductivity copper wires, in numerous application fields such as aerospace, transportation, military, emerging electronics industries, and high-power equipment.

[0003] Existing technologies for improving the conductivity of copper conductors mainly include microstructure control, alloying design, surface / interface engineering, and advanced fabrication processes. While these methods have achieved some performance optimization in areas such as integrated circuit leadframes and electronic connectors, they still have the following limitations: alloying design typically requires the addition of precious metals such as silver, which not only significantly increases material costs but also introduces additional scattering sources, causing the conductivity to drop to 95%–97% of the International Annealed Copper Standard (IACS); advanced fabrication processes mostly rely on specialized equipment, resulting in high costs and low production efficiency, making large-scale applications difficult. Overall, existing technologies cannot break through the theoretical limit of copper's intrinsic conductivity (approximately 106% IACS), and limitations remain in performance stability under high-temperature and high-frequency operating conditions, synergistic optimization of mechanical and electrical properties, and process cost control.

[0004] Graphene is a nanomaterial with a two-dimensional planar structure and unique electrical properties, with an intrinsic conductivity of up to 10⁻⁶. 8 The electron mobility is on the order of S / m, exceeding 200,000 cm² / V·s at room temperature. In conductive composite materials, graphene and the copper matrix can form a synergistic reinforcement effect: graphene not only helps to improve the overall conductivity of the composite material, but its high strength properties can also compensate for the lack of mechanical strength of pure copper, thereby achieving synergistic optimization of electrical and mechanical properties.

[0005] The current preparation of graphene / copper composites faces a core contradiction: easily scalable processes cannot guarantee the structural integrity and ordered arrangement of graphene, while high-performance processes are often difficult to scale up due to their complexity and long production cycles. This contradiction constitutes the main factor restricting the potential of the material's electrical and mechanical properties, and also limits its large-scale application in fields such as electronics, electrical engineering, and high-end equipment manufacturing. Therefore, developing a method for preparing graphene / copper composite wires that can balance preparation efficiency, structural quality, and comprehensive performance is of significant practical importance for promoting the practical application of this material. Summary of the Invention

[0006] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a highly conductive graphene / copper composite wire and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a graphene / copper composite wire, the method comprising the following steps:

[0009] S1. Prepare the bare copper core;

[0010] S2. A continuous graphene layer is grown in situ on the surface of the copper core by chemical vapor deposition.

[0011] S3. The graphene layer is activated by low-power oxygen plasma.

[0012] S4. On the surface of the activated graphene layer, an outer copper layer is directly deposited by a non-aqueous solution electroplating method to form a "graphene-copper" composite structural unit.

[0013] S5. Repeat steps S2 to S4, repeating the process 1 to 3 times, to construct multi-layered alternating composite structural units.

[0014] S6. Anneal the composite structural unit obtained in step S5 to obtain a graphene / copper composite wire.

[0015] Further, step S2 is as follows: The copper core is annealed at 900-1050℃ for 10-60 minutes in a reducing atmosphere; subsequently, a carbon source gas is introduced at 950-1050℃ for growth for 5-60 minutes. High-temperature annealing in a reducing atmosphere cleans and reconstructs the copper core surface, obtaining a clean, grain-coarsened, and flat substrate; then, a carbon source is introduced at a suitable temperature, causing it to decompose and complete the diffusion and ordered nucleation growth of carbon atoms on the copper surface.

[0016] Furthermore, in step S3, the process parameters for the low-power oxygen plasma treatment include: power 50-250W, treatment time 30-120 seconds, process gas is oxygen, and gas flow rate is 20-80 sccm. By bombarding the graphene surface with low-power oxygen plasma, oxygen-containing functional groups such as carboxyl and hydroxyl groups are introduced as active sites for subsequent copper layer deposition, while simultaneously avoiding graphene structural damage caused by over-treatment.

[0017] Furthermore, the electroplating solution used in the non-aqueous electroplating method in step S4 is a deep eutectic solvent system, wherein the deep eutectic solvent system is composed of choline chloride (hydrogen bond acceptor) and ethylene glycol (hydrogen bond donor) mixed in a molar ratio of 1:1.5-2.5. Choline chloride and ethylene glycol form a eutectic mixture through hydrogen bonding, possessing low vapor pressure, low toxicity, excellent chemical and thermal stability, and a wide electrochemical window. A specific molar ratio (1:1.5-2.5) can optimize its viscosity, ionic conductivity, and electrochemical performance, thereby ensuring uniform transport and dense deposition of copper ions.

[0018] Furthermore, the deep eutectic solvent system contains dissolved copper salts at a concentration of 0.15-0.4 mol / L; the copper salt is at least one of copper chloride, copper sulfate, and copper acetate. Copper chloride, copper sulfate, and copper acetate can all provide Cu²⁺ and have good compatibility with the deep eutectic system described in step S4. This concentration range ensures sufficient deposition current density and a reasonable deposition rate, while maintaining good conductivity and stability of the solution.

[0019] Furthermore, the non-aqueous electroplating method described in step S4 is pulse electroplating, and the pulse electroplating parameters include: an average current density of 0.5-2 A / dm², a pulse frequency of 50-300 Hz, a duty cycle of 25%-45%, and an electroplating temperature of 60-90℃.

[0020] By periodically switching current on and off, nucleation is promoted under high instantaneous current to refine the grains, and ions are replenished during the intermittent period to alleviate concentration polarization. Combined with appropriate temperature to optimize the mass transfer process, a copper coating with fine grains, dense structure, low internal stress and strong bonding with graphene is obtained, which significantly improves the mechanical integrity of the interface and the reliability of electrical contact.

[0021] Furthermore, the process parameters for the annealing treatment in step S6 include: an annealing temperature of 200-400℃ and an annealing time of 60-180 minutes under a protective atmosphere; the protective atmosphere is argon or an argon-hydrogen mixture.

[0022] Low-temperature annealing under a protective atmosphere drives interfacial atomic diffusion and the formation of chemical bonds (such as Cu-OC bonds), strengthening the interfacial bonding from physical to chemical bonding while eliminating internal stress. This process enhances interfacial strength and stability, reduces contact resistance, and thus improves the overall performance of the composite wire. Furthermore, the annealing process maintains a clean copper surface under a protective atmosphere, providing a favorable surface condition for subsequent chemical vapor deposition cycles.

[0023] Secondly, the present invention provides a graphene / copper composite wire, which is prepared by the above-mentioned method for preparing a graphene / copper composite wire. The highly conductive graphene / copper composite wire includes a copper wire and a multilayer composite structural unit of alternating graphene and copper wrapped around the surface of the copper wire.

[0024] Furthermore, the diameter of the copper wire is 10-50 mm, and the thickness of the single-layer "graphene-copper" composite structural unit is 5-50 μm.

[0025] Furthermore, the highly conductive graphene / copper composite conductor has two or more layers of alternating graphene-copper composite structural units, and the highly conductive graphene / copper composite conductor is suitable for medium and high voltage power transmission scenarios of 10kV and above.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] (1) Traditional graphene / copper composite materials rely on physical adsorption, resulting in contact gaps and a high Schottky barrier at the interface, leading to high contact resistance. This invention introduces a combination of low-power oxygen plasma activation treatment and subsequent annealing processes to introduce Cu-OC chemical bonds at the graphene-copper interface. These chemical bonds effectively strengthen the connection between the two phases, eliminate physical gaps, and reduce contact resistance, thus laying a crucial microscopic interfacial foundation for improving the overall conductivity of copper / graphene composite wires.

[0028] (2) To address the skin effect of high-frequency current, this invention, for the first time, utilizes a cyclic process of "chemical vapor deposition - low-power oxygen plasma activation - non-aqueous solution electroplating" to autonomously and controllably fabricate multilayer "graphene-copper" composite structural units. This structure allows the high-electron-mobility graphene layer to be parallel to the current direction and coated on the copper surface, providing an additional low-resistance channel for high-frequency current; simultaneously, the graphene network also constitutes an efficient axial heat conduction path. This synergistic design from the micro-interface to the macro-structure achieves, in principle, simultaneous optimization of AC resistance and current-carrying temperature rise.

[0029] (3) This invention uses a choline chloride-ethylene glycol-based deep eutectic solvent system to replace traditional aqueous solution electroplating, fundamentally avoiding the damage to the interface caused by the hydrogen evolution reaction. Combined with pulse electroplating technology, it is possible to achieve precise control over the nucleation and growth of the copper layer, resulting in a dense and uniform coating. The parameters of this environmentally friendly process system are precisely controllable, ensuring the reproducible preparation of high-performance graphene / copper interfaces, and providing a guarantee for the uniformity of product performance and large-scale reliability. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of a method for preparing a highly conductive graphene / copper composite wire disclosed in this invention.

[0032] Figure 2 This is a schematic diagram of the physical process of a method for preparing a highly conductive graphene / copper composite wire disclosed in this invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0034] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0035] Example 1

[0036] like Figure 1 The flowchart of a method for preparing a highly conductive graphene / copper composite wire disclosed herein is shown. This embodiment specifically discloses a method for preparing a graphene / copper composite wire having two layers of "graphene-copper" composite structural units. The steps of this preparation method are as follows:

[0037] S1. Prepare the bare copper core;

[0038] S2. A continuous graphene layer is grown in situ on the surface of the copper core by chemical vapor deposition.

[0039] S3. The graphene layer is activated by low-power oxygen plasma: The copper core with graphene grown on it is placed in a plasma treatment device, oxygen is introduced (flow rate of 50 sccm), and the treatment is carried out for 60 seconds at a power of 100 W.

[0040] S4. Non-aqueous electroplating deposition of the outer copper layer: On the surface of the activated graphene layer, an outer copper layer is directly deposited using a non-aqueous electroplating method to form a "graphene-copper" composite structural unit. The electroplating solution used in this non-aqueous electroplating method is a deep eutectic solvent system, composed of choline chloride (hydrogen bond acceptor) and ethylene glycol (hydrogen bond donor) mixed in a molar ratio of 1:2, containing dissolved copper chloride at a concentration of 0.25 mol / L as a copper salt. The electroplating adopts a pulse process with the following parameters: average current density 1.0 A / dm², pulse frequency 100 Hz, duty cycle 30%, and electroplating solution temperature 70℃.

[0041] S5. In this embodiment, steps S2 to S4 are repeated once.

[0042] S6. Annealing the composite structural unit obtained in step S5: Place the electroplated wire in a tube furnace and purge it with argon gas. Anneal at 300°C for 120 minutes, then cool it to room temperature in the furnace to obtain the graphene / copper composite wire.

[0043] Figure 2 This is a schematic diagram of the physical process for implementing the above-mentioned method for preparing a highly conductive graphene / copper composite wire. This schematic diagram can help to understand steps S1 to S6 of the preparation method.

[0044] Example 2

[0045] This embodiment specifically discloses a method for preparing a graphene / copper composite wire with two layers of graphene-copper composite structural units. The oxygen plasma activation parameters are different from those in Example 1. The steps of this preparation method are as follows:

[0046] S1. Prepare the bare copper core;

[0047] S2. A continuous graphene layer is grown in situ on the surface of the copper core by chemical vapor deposition.

[0048] S3. Perform oxygen plasma activation treatment on the graphene layer: Place the copper core with graphene grown on it in a plasma treatment device, introduce oxygen (flow rate of 80 sccm), and treat for 180 seconds under a power of 300W.

[0049] S4. Non-aqueous electroplating deposition of the outer copper layer: On the surface of the activated graphene layer, an outer copper layer is directly deposited using a non-aqueous electroplating method to form a "graphene-copper" composite structural unit. The electroplating solution used in this non-aqueous electroplating method is a deep eutectic solvent system, composed of choline chloride (hydrogen bond acceptor) and ethylene glycol (hydrogen bond donor) mixed in a molar ratio of 1:2, containing dissolved copper chloride at a concentration of 0.25 mol / L as a copper salt. The electroplating adopts a pulse process with the following parameters: average current density 1.0 A / dm², pulse frequency 100 Hz, duty cycle 30%, and electroplating solution temperature 70℃.

[0050] S5. In this embodiment, steps S2 to S4 are repeated once.

[0051] S6. Annealing the composite structural unit obtained in step S5: Place the electroplated wire in a tube furnace and purge it with argon gas. Anneal at 300°C for 120 minutes, then cool it to room temperature in the furnace to obtain the graphene / copper composite wire.

[0052] Example 3

[0053] This embodiment specifically discloses a method for preparing a graphene / copper composite wire with a three-layer graphene-copper composite structural unit. The steps of the preparation method are as follows:

[0054] S1. Prepare the bare copper core;

[0055] S2. A continuous graphene layer is grown in situ on the surface of the copper core by chemical vapor deposition.

[0056] S3. The graphene layer is activated by low-power oxygen plasma: The copper core with graphene grown on it is placed in a plasma treatment device, oxygen is introduced (flow rate of 50 sccm), and the treatment is carried out for 60 seconds at a power of 100 W.

[0057] S4. Non-aqueous electroplating deposition of the outer copper layer: On the surface of the activated graphene layer, an outer copper layer is directly deposited using a non-aqueous electroplating method to form a "graphene-copper" composite structural unit. The electroplating solution used in this non-aqueous electroplating method is a deep eutectic solvent system, composed of choline chloride (hydrogen bond acceptor) and ethylene glycol (hydrogen bond donor) mixed in a molar ratio of 1:2, containing dissolved copper chloride at a concentration of 0.25 mol / L as a copper salt. The electroplating adopts a pulse process with the following parameters: average current density 1.0 A / dm², pulse frequency 100 Hz, duty cycle 30%, and electroplating solution temperature 70℃.

[0058] S5. In this embodiment, steps S2 to S4 are repeated twice.

[0059] S6. Annealing the composite structural unit obtained in step S5: Place the electroplated wire in a tube furnace and purge it with argon gas. Anneal at 300°C for 120 minutes, then cool it to room temperature in the furnace to obtain the graphene / copper composite wire.

[0060] Example 4

[0061] This embodiment specifically discloses a method for preparing a graphene / copper composite wire with two layers of graphene-copper composite structural units, wherein the type of copper salt is changed. The steps of the preparation method are as follows:

[0062] S1. Prepare the bare copper core;

[0063] S2. A continuous graphene layer is grown in situ on the surface of the copper core by chemical vapor deposition.

[0064] S3. The graphene layer is activated by low-power oxygen plasma: The copper core with graphene grown on it is placed in a plasma treatment device, oxygen is introduced (flow rate of 50 sccm), and the treatment is carried out for 60 seconds at a power of 100 W.

[0065] S4. Non-aqueous electroplating deposition of the outer copper layer: On the surface of the activated graphene layer, an outer copper layer is directly deposited using a non-aqueous electroplating method to form a "graphene-copper" composite structural unit. The electroplating solution used in this non-aqueous electroplating method is a deep eutectic solvent system, composed of choline chloride (hydrogen bond acceptor) and ethylene glycol (hydrogen bond donor) mixed in a molar ratio of 1:2, containing dissolved copper sulfate at a concentration of 0.25 mol / L as a copper salt. The electroplating adopts a pulse process with the following parameters: average current density 1.0 A / dm², pulse frequency 100 Hz, duty cycle 30%, and electroplating solution temperature 70℃.

[0066] S5. In this embodiment, steps S2 to S4 are repeated once.

[0067] S6. Annealing the composite structural unit obtained in step S5: Place the electroplated wire in a tube furnace and purge it with argon gas. Anneal at 300°C for 120 minutes, then cool it to room temperature in the furnace to obtain the graphene / copper composite wire.

[0068] Example 5

[0069] This embodiment specifically discloses a method for preparing a graphene / copper composite wire with two layers of graphene-copper composite structural units. Traditional aqueous solution electroplating is used instead of deep eutectic solvent non-aqueous solution electroplating. The steps of this preparation method are as follows:

[0070] S1. Prepare the bare copper core;

[0071] S2. A continuous graphene layer is grown in situ on the surface of the copper core by chemical vapor deposition.

[0072] S3. The graphene layer is activated by low-power oxygen plasma: The copper core with graphene grown on it is placed in a plasma treatment device, oxygen is introduced (flow rate of 50 sccm), and the treatment is carried out for 60 seconds at a power of 100 W.

[0073] S4. On the surface of the activated graphene layer, an outer layer of copper is directly deposited using a traditional aqueous solution electroplating method to form a "graphene-copper" composite structural unit. The electroplating solution used in the traditional aqueous solution electroplating method is a sulfate system, composed of 200 g / L copper sulfate, 50 g / L sulfuric acid, and 50 mg / L chloride ions, with 0.5 g / L polyethylene glycol added as a leveling agent and 0.1 g / L sodium dodecyl sulfate added as a wetting agent. The electroplating adopts a pulse process with the following parameters: average current density 1.0 A / dm², pulse frequency 100 Hz, duty cycle 30%, and electroplating solution temperature 70℃.

[0074] S5. In this embodiment, steps S2 to S4 are repeated once.

[0075] S6. Annealing the composite structural unit obtained in step S5: Place the electroplated wire in a tube furnace and purge it with argon gas. Anneal at 300°C for 120 minutes, then cool it to room temperature in the furnace to obtain the graphene / copper composite wire.

[0076] The performance testing methods described in the above embodiments are consistent: conductivity testing is conducted according to national standard GB / T 3048.2-2007, using the double-arm bridge method (Kelvin four-terminal method) under constant temperature conditions of 20±0.5℃ to measure the DC resistance of the wire sample. Volume resistivity is calculated based on the precisely measured sample geometry (length and cross-sectional area) and converted to a percentage (%IACS) relative to the International Standard for Annealed Copper (IACS) for characterization. Interfacial shear strength is tested according to standard ASTM C1624-05. A nano-scratch method is used, employing a scratch instrument equipped with acoustic emission and friction sensors and a diamond indenter to scratch the interface region of the wire cross-section. The critical load (Lc) leading to interface failure is determined by monitoring signal abrupt changes and characterized by this value. AC resistance is tested according to standard IEC 60287-1-1. The four-terminal method was used to apply AC current at the power frequency and a typical 100 kHz harmonic frequency to the linear sample under constant temperature conditions. The voltage drop was measured, and the AC resistance per unit length was calculated. The resistance was characterized by the ratio of AC resistance to DC resistance (Rac / Rdc). The current-carrying temperature rise was tested according to the test framework of IEC 60287 and GB / T 11017.1. The wire sample was placed in a simulated heat dissipation environment and a constant current of 5 A / mm² was applied until thermal equilibrium was reached. The steady-state temperature rise (ΔT) was monitored and recorded using thermocouples or an infrared thermal imager for characterization.

[0077] Table 1. Conductivity, interfacial shear strength, AC / DC resistivity ratio, and steady-state temperature rise of the embodiments.

[0078]

[0079] Effect of Oxygen Plasma Activation Parameters: Example 2 used excessive oxygen plasma activation parameters (oxygen flow rate 80 sccm, activation power 300 W, processing time 180 s), with other process parameters identical to Example 1. Compared to Example 1 (oxygen flow rate 50 sccm, activation power 100 W, processing time 60 s), the interfacial shear strength of Example 2 decreased from 295 mN to 90 mN (a decrease of approximately 70%), the conductivity decreased from 105.8% IACS to 97.5% IACS (a decrease of 8.3% IACS), and the steady-state temperature rise increased from 37.0 K to 47.5 K (an increase of 10.5 K). This is because moderate oxygen plasma activation can achieve controllable and mild oxidation on the graphene surface, introducing an appropriate amount of oxygen-containing functional groups as active sites for subsequent Cu-OC chemical bonding, while excessive activation destroys the graphene lattice and forms a defect layer, leading to a comprehensive deterioration of interfacial properties. This indicates that there is an optimized process window for the oxygen plasma activation parameters of this invention, and the parameters selected in Example 1 are key to achieving a highly conductive and high-strength interface.

[0080] Influence of the number of composite structural unit layers: Example 3 uses a three-layer "graphene-copper" composite structural unit, with other process parameters identical to Example 1. Compared to Example 1 (two-layer structure), Example 3 maintains high conductivity (105.0% IACS vs 105.8% IACS) and high-strength interface (280 mN vs 295 mN), while optimizing the AC / DC resistivity ratio (Rac / Rdc) from 1.07 to 1.04 and reducing the steady-state temperature rise (ΔT) from 37.0 K to 35.2 K. This is because increasing the number of graphene layers parallel to the axial direction is equivalent to constructing more low-resistance electron channels and efficient heat conduction paths within the conductor, thereby directionally enhancing the suppression of high-frequency skin effects and overall heat dissipation performance, demonstrating the synergistic enhancement effect of multilayer structure design.

[0081] Influence of Copper Salt in Non-Aqueous Plating Solution: Example 4 used copper sulfate as the copper salt, and other process parameters were exactly the same as in Example 1. Compared with Example 1 (copper chloride), Example 4 showed no significant differences in conductivity (105.5% IACS vs 105.8% IACS), interfacial shear strength (290 mN vs 295 mN), AC / DC resistivity ratio (1.06 vs 1.07), and steady-state temperature rise (37.5 K vs 37.0 K). This is because the choline chloride-ethylene glycol-based non-aqueous solution system has a special ionic coordination environment, which allows the cathode reaction to be completely dominated by the controlled reduction of copper ions. Regardless of whether the anion is Cl⁻ or SO₄²⁻, copper ions exist in a similar coordination form and achieve dense, epitaxial electrocrystallization growth on the oxygen plasma-activated graphene substrate. This indicates that the non-aqueous solution system has good universality for copper salt types, and the interface and coating quality can maintain a high degree of consistency under different copper salt conditions.

[0082] Effects of the electroplating system: Example 5 used a traditional sulfate aqueous solution electroplating system, with other process parameters identical to Example 1. Compared to Example 1 (choline chloride-ethylene glycol-based non-aqueous solution system), the conductivity of Example 5 decreased from 105.8% IACS to 98.2% IACS, the interfacial shear strength decreased from 295 mN to 165 mN, the AC / DC resistivity ratio increased from 1.07 to 1.18, and the steady-state temperature rise increased from 37.0 K to 43.5 K. This is because the hydrogen evolution side reaction (2H⁺ + 2e⁻ → H₂↑) inevitably occurs during aqueous solution electroplating. The generated hydrogen bubbles interfere with the normal deposition of copper ions, destroying the initial interfacial bonding between graphene and copper, resulting in decreased coating density and weakened interfacial bonding. The choline chloride-ethylene glycol-based non-aqueous solution system used in this invention fundamentally eliminates the proton source (H⁺), allowing the cathode reaction to be completely dominated by the controlled reduction of copper ions, achieving dense and uniform electrocrystallization growth on the activated graphene surface, and ensuring a high degree of consistency between the interface and the coating quality.

[0083] In summary, through the comparison of the above embodiments, it can be seen that by adopting the "chemical vapor deposition-low-power oxygen plasma activation-non-aqueous solution electroplating" cyclic preparation process provided by the present invention, the interfacial bonding strength, DC / AC conductivity and current-carrying heat dissipation capacity of the composite wire can be optimized individually or synergistically by precisely selecting and controlling the oxygen plasma activation parameters, the number of composite structural unit layers and the type of electroplated copper salt. This successfully achieves the preparation of high-performance graphene / copper composite wires with high-strength interface, high conductivity (especially at high frequencies) and excellent thermal management performance.

[0084] 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.

[0085] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a highly conductive graphene / copper composite wire, characterized in that, The preparation method includes the following steps: S1. Prepare the bare copper core; S2. On the surface of the copper core, a continuous graphene layer is grown in situ by chemical vapor deposition. The process is as follows: under a reducing atmosphere, the copper core is annealed at 900-1050°C for 10-60 minutes; then, carbon source gas is introduced at 950-1050°C for 5-60 minutes for growth. S3. The graphene layer is subjected to low-power oxygen plasma activation treatment. The process parameters of oxygen plasma activation treatment include: power 50-250W, treatment time 30-120 seconds, process gas is oxygen, and gas flow rate is 20-80 sccm. S4. On the surface of the activated graphene layer, an outer copper layer is directly deposited by a non-aqueous electroplating method to form a "graphene-copper" composite structural unit. The electroplating solution used in the non-aqueous electroplating method is a deep eutectic solvent system, wherein the deep eutectic solvent system is composed of hydrogen bond acceptor choline chloride and hydrogen bond donor ethylene glycol mixed in a molar ratio of 1:1.5-2.

5. The deep eutectic solvent system contains dissolved copper salts with a concentration of 0.15-0.4 mol / L. The copper salts are one or more of copper chloride, copper sulfate, and copper acetate. S5. Repeat steps S2 to S4 for 1-3 times to construct a multi-layered alternating composite structure unit. This multi-layered alternating composite structure unit is parallel to the direction of the conductor current and is wrapped around the copper surface. S6. Anneal the composite structural unit obtained in step S5 to obtain a graphene / copper composite wire.

2. The preparation method according to claim 1, characterized in that, The non-aqueous solution electroplating method described in step S4 is pulse electroplating. The pulse electroplating parameters include: an average current density of 0.5-2 A / dm², a pulse frequency of 50-300 Hz, a duty cycle of 25%-45%, and an electroplating temperature of 60-90℃.

3. The preparation method according to claim 1, characterized in that, The process parameters for the annealing treatment in step S6 include: an annealing temperature of 200-400℃ and an annealing time of 60-180 minutes under a protective atmosphere; the protective atmosphere is argon or an argon-hydrogen mixture.

4. A highly conductive graphene / copper composite wire, characterized in that, The highly conductive graphene / copper composite wire is prepared by any one of the preparation methods described in claims 1 to 3, and includes a copper wire and a multilayer composite structural unit of alternating graphene and copper wrapped around the surface of the copper wire.

5. The highly conductive graphene / copper composite wire according to claim 4, characterized in that, The diameter of the copper wire is 10-50 mm, and the thickness of the single-layer "graphene-copper" composite structure unit is 5-50 μm.

6. The highly conductive graphene / copper composite wire according to claim 4, characterized in that, The highly conductive graphene / copper composite conductor has two or more layers of alternating graphene-copper composite structural units, and is suitable for medium and high voltage power transmission scenarios of 10kV and above.

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