Preparation method of carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity

Abstract

The present invention relates to the field of preparation of high-performance carbon nanotube composite fibers, and specifically to a method for preparing carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity. Using a carbon nanotube fiber containing abundant oxygen-containing functional groups prepared by wet spinning as the core, a copper shell layer is uniformly coated on the surface of the carbon nanotube fiber by a method combining magnetron sputtering and electroplating to obtain a core-shell structure carbon nanotube / copper composite fiber. The present invention utilizes the characteristic that copper particles have high kinetic energy under the action of an electromagnetic field, so that they are combined with the abundant oxygen-containing functional groups on the surface of the carbon nanotube fiber prepared by wet spinning, thereby greatly improving the interfacial combination of copper and carbon nanotubes; in addition, the copper particles sputtered by magnetron can be deposited in the gaps between the bundles on the surface of the carbon nanotube fiber and serve as the nucleation sites for the subsequent electroplated copper layer, making the electroplated copper shell layer uniform and complete; finally, carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity are obtained.

Description

Technical Field

[0001] The present invention relates to the field of preparation of high-performance carbon nanotube composite fibers, and specifically to a preparation method of carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity. Background Art

[0002] Copper has good electrical conductivity, thermal conductivity and excellent ductility, and copper wires are widely used in fields such as electrical, electronics, light industry, aerospace, and national defense industries. However, copper has a large density and a low current-carrying capacity, making it difficult to meet the development trend of continuous lightweight and miniaturization of electronic devices. Therefore, it is urgent to develop and design new lightweight conductor materials. Carbon nanotubes have excellent mechanical, electrical and thermal properties, and also have the advantages of low density, high current-carrying capacity and corrosion resistance, and are considered to be ideal next-generation wires. However, the carbon nanotube fibers prepared at present still have lower conductivity and specific conductivity than copper due to the large inter-tube contact resistance, which limits the practical application of carbon nanotube fibers. The carbon nanotube / copper composite fiber is expected to organically combine the light weight and high current-carrying capacity of carbon nanotubes with the high conductivity of metallic copper (Literature 1: Li, Q. et al. Adv. Mater. 2007, 19(20), 3358-3363.), and become the next-generation lightweight, high-strength and high-conductivity material.

[0003] The methods for preparing carbon nanotube / copper composite fibers mainly include chemical deposition (Literature 2: Daneshvar, F. et al. Carbon. 2020, 157, 583-593), electrochemical deposition (Literature 3: Randeniya, L. K. et al. Small. 2010, 6(16), 1806-1811.) and physical vapor deposition (Literature 4: Han, B. et al. Carbon. 2017, 123, 593-604.), etc. However, due to the chemical inertness of the sp 2 hybrid carbon that constitutes carbon nanotubes, its wettability with metallic copper is very poor, resulting in a weak interfacial bonding force of the carbon nanotube / copper composite fiber (Literature 5: Lim, S. C. et al. Appl. Phys. Lett. 2009, 95(26), 264103). For the core-shell structure composite fiber, the strength of the interfacial bonding directly affects the microstructure and mechanical and electrical transport properties of the composite fiber. When the interfacial bonding is poor, holes and cracks will appear at the interface of the composite fiber, and at the same time, it will affect the transport of electrons between the carbon nanotubes and the copper layer, introducing a large contact resistance.

[0004] Therefore, a major problem in the current preparation of high-performance carbon nanotube / copper composite fibers is: how to improve the interfacial bonding between carbon nanotube fibers and copper, reduce the interfacial resistance, so as to obtain carbon nanotube / copper composite fibers with high specific conductivity and high current-carrying capacity, and promote their large-scale application. Summary of the Invention

[0005] Aiming at the problem of poor wettability and weak interfacial bonding force between carbon nanotube fibers and copper shell in carbon nanotube / copper core-shell structure composite fibers, the purpose of the present invention is to provide a preparation method of carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity, and the key technology to improve the interfacial bonding of core-shell structure fibers.

[0006] The technical solution of the present invention is:

[0007] A preparation method of carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity, fix the carbon nanotube fibers containing rich oxygen-containing functional groups prepared by wet spinning on a loop frame, and perform magnetron sputtering on the carbon nanotube fibers with a copper target. Utilize the characteristic that copper particles have high kinetic energy under the action of electromagnetic field, so that the copper particles combine with the oxygen-containing functional groups on the surface of the carbon nanotube fibers; on the one hand, it improves the interfacial bonding between Cu and carbon nanotubes, and on the other hand, it makes the Cu particles deposit at the inter-tube gaps on the fiber surface; during the subsequent constant-current electroplating of copper, these copper particles serve as nucleation sites, so that the copper shell uniformly coats the surface of the carbon nanotube fibers; finally, carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity are obtained.

[0008] For the preparation method of the carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity, the diameter of the inner core carbon nanotube fibers is 15 - 50 μm, and the oxygen-containing functional groups on the surface of the carbon nanotube fibers are hydroxyl groups, carboxyl groups or carbonyl groups.

[0009] For the preparation method of the carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity, in the magnetron sputtering, the purity of the pure copper target is 99.999 wt%, and the working distance is 10 - 30 cm.

[0010] For the preparation method of the carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and ultra-high current-carrying capacity, in the magnetron sputtering, the rotation rate of the sample stage fixing the loop frame is 10 - 20 rpm, the working power is 50 - 200 W, the working temperature is 30 - 500 °C, and the sputtering time is 1 - 30 s.

[0011] The preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity involves placing the carbon nanotube fiber after magnetron sputtering in an electroplating solution for electroplating treatment during the constant-current electroplating of copper. The composition of the electroplating solution is as follows: copper sulfate 160 - 220 g / L, sulfuric acid 25 - 35 mL / L, hydrochloric acid 30 - 35 μL / L; among them, the concentration of sulfuric acid is 95 - 98 wt%, and the concentration of hydrochloric acid is 36 - 38 wt%.

[0012] The preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity involves placing the carbon nanotube fiber after magnetron sputtering in an electroplating solution for electroplating treatment during the constant-current electroplating of copper. The process conditions of the electroplating treatment include: using a DC power supply, with a temperature of 20 - 60 °C and a current density of 1 - 2 A / dm 2 。

[0013] In the preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity, the thickness of the copper layer coated in the carbon nanotube / copper core-shell structure fiber is 1 - 20 μm, and the overall density of the carbon nanotube / copper core-shell structure fiber is 2.5 - 6.5 g / cm 3 。

[0014] In the preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity, there are no pores and cracks at the interface of the prepared carbon nanotube / copper core-shell structure fiber, and the interface bonding is good.

[0015] In the preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity, the conductivity of the carbon nanotube / copper core-shell structure fiber is 2×10 7 ~5×10 7 S / m, and the specific conductivity is 6.0×10 3 ~10.1×10 3 Sm 2 kg -1 。

[0016] In the preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity, the current-carrying capacity of the carbon nanotube / copper core-shell structure fiber is 2.0×10 5 ~3.1×10 5 A cm -2 。

[0017] The design concept of the present invention is:

[0018] The present invention uses carbon nanotube fibers containing rich oxygen-containing functional groups prepared by wet spinning as the core material, and adopts a method combining magnetron sputtering and electroplating to uniformly coat a copper shell layer on the surface of the carbon nanotube fibers, thereby obtaining carbon nanotube / copper core-shell structure composite fibers. By utilizing the characteristic that copper particles obtain high kinetic energy under the action of an electromagnetic field during magnetron sputtering, the copper particles are combined with the rich oxygen-containing functional groups on the surface of the carbon nanotube fibers prepared by wet spinning, thus greatly improving the interfacial structure between copper and the carbon nanotube core-shell structure fibers.

[0019] In addition, the copper particles sputtered by magnetron can be deposited in the gaps between the carbon nanotube fiber bundles on the surface of the carbon nanotube fibers. The carbon nanotube fibers with copper sputtered by magnetron are electroplated with a constant current. The copper particles on the surface of the carbon nanotube fibers serve as the nucleation sites for the electroplated copper layer. On the one hand, the electroplating process is accelerated, and on the other hand, the Cu at the gaps grows uniformly during electroplating and then tightly and completely coats the surface of the carbon nanotube fibers; this technology solves the problem of weak interfacial bonding between Cu and carbon nanotube fibers, realizes seamless and uniform coating of the carbon nanotube fibers and the copper shell, and finally prepares carbon nanotube / copper core-shell structure fibers with ultra-high specific conductivity and large current-carrying capacity.

[0020] The advantages and beneficial effects of the present invention are as follows:

[0021] 1. The present invention utilizes the characteristics of carbon nanotube fibers rich in oxygen-containing functional groups prepared by wet spinning technology, combines with the characteristic that magnetron sputtering technology endows Cu particles with high kinetic energy, and enables the Cu particles to form strong bonds with the surface of the carbon nanotube fibers through Cu-O-C bonds; thus, it solves the problem that the performance of the composite fibers is not ideal due to poor wettability and weak interfacial bonding force between the carbon nanotube fibers and copper in the core-shell structure fibers.

[0022] 2. The present invention solves the problem of uneven copper plating on the surface of carbon nanotube fibers, and prepares carbon nanotube / copper core-shell structure fibers with good interfacial bonding, no holes and cracks.

[0023] 3. The method of the present invention is simple, does not introduce other medium buffer layers, reduces the manufacturing cost, and is conducive to industrial production.

[0024] 4. The diameter of the core-shell structure fibers prepared by the present invention can be adjusted in the range of 17 - 90 μm, and the highest specific conductivity reaches 10.1×10 3 S m 2 kg -1 , which is 56% higher than that of metallic copper; the highest current-carrying capacity reaches (3.1×10 5 A cm -2 ), which is three times that of copper wires.

[0025] 4. The carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity prepared by the present invention is expected to find important applications in high-performance cables, flexible sensors, aerospace, military and national defense and other fields. Description of the Drawings

[0026] Figure 1 . Schematic diagram of the preparation process of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity. In the figure, 1. Stainless steel wire loop, 2. Carbon nanotube fiber, 3. Pure copper target, 4. Electroplating device, 5. Carbon nanotube / copper core-shell structure fiber.

[0027] Figure 2 . Structure characterization diagram of the carbon nanotube / copper core-shell structure fiber. Among them, (a) and (b) are low-magnification and high-magnification SEM photos of the carbon nanotube fiber; (c) and (d) are low-magnification and high-magnification SEM photos of the carbon nanotube / copper core-shell structure fiber.

[0028] Figure 3 . Cross-section characterization diagram of the carbon nanotube / copper core-shell structure fiber. Among them, (a) and (b) are low-magnification and high-magnification focused ion beam cutting cross-section diagrams of the carbon nanotube / copper core-shell structure fiber prepared by the present invention; (c) and (d) are low-magnification and high-magnification focused ion beam cutting cross-section diagrams of the carbon nanotube / copper core-shell structure fiber prepared by direct electroplating. In figure (b), CNT fiber represents the carbon nanotube fiber, and Copper layer represents the copper shell layer; in figure (c), Voids represents voids; in figure (d), Gap represents cracks.

[0029] Figure 4 . Conductivity performance comparison diagram of the carbon nanotube / copper core-shell structure fiber. Among them, the abscissa SpecificElectrical Conductivity represents the specific conductivity (×10 3 S m 2 kg -1 ), and the ordinate Conductivity represents the conductivity (×10 7 S / m). In the figure, the pentagram This represents this work, the square Metal represents the metal wire, the equilateral triangle CNT / CuFiber represents the carbon nanotube / copper core-shell fiber reported in the literature, and the inverted triangle CNT Fiber represents the carbon nanotube fiber.

[0030] Figure 5 . Ampacity comparison diagram of the carbon nanotube / copper core-shell structure fiber. Among them, the abscissa SpecificElectrical Conductivity represents the specific conductivity (×10 3 S m 2 kg -1 ), and the ordinate Ampacity represents the ampacity (Acm-2 )。In the figure, the five-pointed star This work represents this work, the equilateral triangle Metal represents the metal wire, the square CNT / Cucore-shell fiber represents the carbon nanotube / copper core-shell fiber reported in the literature, the circle CNT fiber represents the carbon nanotube fiber, and the rhombus CNT / Cu Composite fiber represents the carbon nanotube / copper core-shell structure fiber.

[0031] Figure 6 . SEM image of the carbon nanotube / copper core-shell structure fiber after 30 s of electroplating following magnetron sputtering on the carbon nanotube fiber.

[0032] Figure 7 . Low-magnification (a) and high-magnification (b) SEM images of the carbon nanotube fiber after magnetron sputtering. Detailed implementation mode

[0033] In the specific implementation process, as Figure 1 shown, the present invention proposes a preparation device for carbon nanotube / copper core-shell structure fibers, mainly including a stainless steel wire frame 1, a carbon nanotube fiber 2, a pure copper target 3, an electroplating device 4, and a carbon nanotube / copper core-shell structure fiber 5. The specific structure and preparation process are as follows: First, the carbon nanotube fiber 2 prepared by wet spinning is wound and fixed on the stainless steel wire frame 1; subsequently, in the magnetron sputtering device, the front and back surfaces of the carbon nanotube fiber 2 are surface-modified by magnetron sputtering using the pure copper target 3, and the thickness of the copper modification layer can be controlled by changing the power, working distance, and temperature during operation; finally, in the electroplating device 4, the modified carbon nanotube fiber is electroplated to obtain the carbon nanotube / copper core-shell structure fiber 5; among them, the electroplating device 4 is composed of a power meter, two pure copper anodes, and a cathode composed of a carbon nanotube fiber and a stainless steel wire frame. By changing the current density and electroplating time during the electroplating process, the structure and thickness of the copper shell can be regulated.

[0034] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail below through examples and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0035] Example 1

[0036] In this example, the preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity includes the following steps:

[0037] (1) As Figure 2 (a) and Figure 2As shown in Fig. (b), carbon nanotube fibers with a diameter of 25 μm were wound around a stainless-steel loop and fixed on the sample stage of the magnetron sputtering device. A pure copper target was installed in the target position of the magnetron sputtering device. The rotation speed of the sample stage was set to 10 rpm, the working power was adjusted to 100 W, and the sputtering time was 10 s.

[0038] (2) The modified carbon nanotube fibers and the stainless-steel loop prepared in step (1) were used as the cathode, and two pieces of pure copper were used as the anode to form a sandwich electrode structure. A mixed solution of copper sulfate (180 g / L), sulfuric acid (30 mL / L), and hydrochloric acid (33 μL / L) was used as the electroplating solution. The electroplating temperature was 25 °C, and the current density was 1 A / dm 2 , and the electroplating time was 10 min. Among them, the concentration of sulfuric acid was 95 - 98 wt%, and the concentration of hydrochloric acid was 36 - 38 wt%.

[0039] The carbon nanotube / copper core-shell structure fibers prepared in step (2) were characterized for their structure. As shown in Fig. (c) and Figure 2 (d), the low-magnification and high-magnification SEM photos of the carbon nanotube / copper core-shell structure fibers show that the fiber diameter is uniform, the surface copper particles are uniform and complete, and the fiber diameter is 45 μm. As shown in Fig. (a) and Figure 2 (b), the cross-sectional view of the core-shell structure fiber obtained by focused ion beam cutting shows that there are no holes and cracks at the interface of the core-shell structure fiber, and the interface between the carbon nanotube core structure and the copper shell is well combined. Figure 3 (a) and Figure 3 (b), the cross-sectional view of the core-shell structure fiber obtained by focused ion beam cutting shows that there are no holes and cracks at the interface of the core-shell structure fiber, and the interface between the carbon nanotube core structure and the copper shell is well combined.

[0040] The carbon nanotube / copper core-shell structure fibers prepared in step (2) were characterized for their electrical properties. As shown in Figure 4 , the conductivity of the carbon nanotube / copper core-shell structure fibers measured by the four-wire method was 5×10 7 S / m, and the specific conductivity was 10.1×10 3 S m 2 kg -1 ( Figure 4 ), and the current-carrying capacity of the fiber was 3.1×10 5 A cm -2 ( Figure 5 ).

[0041] Example 2

[0042] In this example, step (1) was the same as step (1) of Example 1, except that carbon nanotube fibers with a diameter of 35 μm were selected, the working power of the magnetron sputtering was adjusted to 200 W, and the sputtering time was 5 s.

[0043] Step (2) was the same as step (2) of Example 1, except that the current density was 1.5 A / dm 2, the electroplating time is 5 min.

[0044] Perform structural characterization on the carbon nanotube / copper core-shell structure fiber prepared in step (2). The SEM photos show that the carbon nanotube / copper core-shell structure fiber has a uniform diameter, and the copper particles on the surface are uniform and complete. The diameter of the fiber is 50 μm. From the cross-sectional view of the core-shell structure fiber obtained by focused ion beam cutting, it can be seen that there are no pores and cracks at the interface of the core-shell structure fiber, and the interface between the carbon nanotube core structure and the copper shell is well combined. Perform electrical property characterization on the carbon nanotube / copper core-shell structure fiber prepared in step (2). Use the four-probe method to measure the conductivity of the carbon nanotube / copper core-shell structure fiber to be 4×10 7 S / m, and the specific conductivity is 1.0×10 4 S m 2 kg -1 , and the current-carrying capacity is 2.8×10 5 A cm -2 .

[0045] Example 3

[0046] In this example, step (1) is the same as step (1) of Example 1, except that the working power of magnetron sputtering is adjusted to 150 W and the sputtering time is 10 s.

[0047] Step (2) is the same as step (2) of Example 1, except that the electroplating solution is a mixed solution of copper sulfate (200 g / L), sulfuric acid (35 mL / L), and hydrochloric acid (35 μL / L), the electroplating temperature is 55 °C, and the electroplating time is 30 s. Among them, the concentration of sulfuric acid is 95-98 wt%, and the concentration of hydrochloric acid is 36-38 wt%.

[0048] Perform structural characterization on the carbon nanotube / copper core-shell structure fiber prepared in step (2). As Figure 6 shown, from the SEM photos of the carbon nanotube / copper core-shell structure fiber, it can be seen that even within a very short electroplating time, the copper particles on the fiber surface are connected to each other to form a copper film, and a carbon nanotube / copper core-shell structure fiber with a complete copper shell coating can be obtained. The diameter of the fiber is 27 μm. From the cross-sectional view of the core-shell structure fiber obtained by focused ion beam cutting, it can be seen that there are no voids and cracks at the interface of the core-shell structure fiber, and the interface between the carbon nanotube core structure and the copper shell is well combined. Perform property characterization on the carbon nanotube / copper core-shell structure fiber prepared in step (2). Use the four-probe method to measure the conductivity of the carbon nanotube / copper core-shell structure fiber to be 2.5×10 7 S / m, and the specific conductivity is 8.0×10 3 S m 2 kg -1 , and the current-carrying capacity is 2.3×10 5 A cm -2 .

[0049] Comparative Example 1

[0050] In this comparative example, step (1) is the same as that in Example 1, except that the magnetron sputtering of Cu is omitted.

[0051] Step (2) is the same as that in Example 1, that is, the carbon nanotube fiber is directly electroplated for 10 min.

[0052] The structure and properties of the prepared carbon nanotube / copper core-shell structure fiber were characterized. The SEM photographs show that the diameter of the carbon nanotube / copper core-shell structure fiber is uniform, the copper particles on the surface are relatively uniform, and the diameter of the fiber is 45 μm. Figure 3 (c) and Figure 3 (d) are cross-sectional views of the core-shell structure fiber obtained by focused ion beam cutting. It can be seen that there are large voids and cracks at the interface of the core-shell structure fiber, and the interfacial bonding between the carbon nanotube core structure and the copper shell is poor. The conductivity of the fiber was measured by the four-wire method to be 1.0×10 7 S / m, and the specific conductivity is 3.0×10 3 S m 2 kg -1 , and the current-carrying capacity is 8.0×10 4 A cm -2 .

[0053] Comparative Example 2

[0054] In this comparative example, step (1) is the same as that in Example 1.

[0055] The electroplating process in step (2) of Example 1 is omitted, that is, only the carbon nanotube fiber is magnetron sputtered for 10 s.

[0056] The structure and properties of the prepared fiber were characterized. As Figure 7 (a) and Figure 7 (b) show, the low-magnification and high-magnification SEM photographs of the fiber after magnetron sputtering show that there are a large number of nanoscale copper particles on the surface of the carbon nanotube fiber after magnetron sputtering, but they are not connected into a complete copper film. The conductivity of the fiber was measured by the four-wire method to be 5.0×10 6 S / m, and the specific conductivity is 2.5×10 3 S m 2 kg -1 , and the current-carrying capacity is 6.0×10 4 A cm -2 .

[0057] Comparative Example 3

[0058] In this comparative example, step (1) is the same as step (1) of Example 1, except that a dry-spun fiber without oxygen-containing functional groups on its surface is selected as the core structure.

[0059] Step (2) is the same as step (2) of Example 1.

[0060] The structure and properties of the prepared carbon nanotube / copper core-shell structure fiber were characterized. The SEM photograph shows that the diameter of the carbon nanotube / copper core-shell structure fiber is uniform, and the copper particles on the surface are relatively uniform. The diameter of the fiber is 40 μm. The cross-sectional view of the core-shell structure fiber obtained by focused ion beam cutting shows that there are large voids and cracks at the interface of the core-shell structure fiber, and the interfacial bonding between the carbon nanotube core structure and the copper shell is poor. The conductivity of the fiber was measured by the four-wire method to be 8.0×10 6 S / m, and the specific conductivity is 1.6×10 3 S m 2 kg -1 , and the current-carrying capacity is 5.0×10 4 A cm -2 .

[0061] The results of the examples and comparative examples show that the carbon nanotube fiber containing rich oxygen-containing functional groups prepared by wet spinning in the present invention is used as the inner core, and the combination of magnetron sputtering and electroplating is adopted to improve the problem of poor interfacial bonding of the composite fiber; a carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity with good interfacial contact between the carbon nanotube core structure and the copper shell structure, without voids and cracks, is obtained. The carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity prepared by the present invention is expected to be applied in the fields of aerospace, wearable electronic devices, solar cells, supercapacitors, artificial muscles, etc.

[0062] Although the present invention has been described in detail above with general descriptions and specific embodiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of the present invention claimed.

Claims

1. A preparation method of a carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity, characterized in that, Fix the carbon nanotube fiber prepared by wet spinning and containing rich oxygen-containing functional groups on a loop frame, and perform magnetron sputtering on the carbon nanotube fiber using a copper target. Utilize the characteristic that copper particles have high kinetic energy under the action of an electromagnetic field, so that the copper particles combine with the oxygen-containing functional groups on the surface of the carbon nanotube fiber; on the one hand, it improves the interfacial bonding between Cu and carbon nanotubes, and on the other hand, it makes the Cu particles deposit at the intertubular gaps on the fiber surface; during the subsequent constant-current electroplating of copper, these copper particles serve as nucleation sites, enabling the copper shell to uniformly coat the surface of the carbon nanotube fiber; finally, a carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity is obtained. Utilize the characteristic that the carbon nanotube fiber prepared by wet spinning technology is rich in oxygen-containing functional groups, and combine the magnetron sputtering technology to endow the Cu particles with high kinetic energy characteristics, so that the Cu particles form strong bonds with the surface of the carbon nanotube fiber through Cu-O-C bonds; The diameter of the inner core carbon nanotube fiber is 15 - 50 μm, and the oxygen-containing functional groups on the surface of the carbon nanotube fiber are hydroxyl groups, carboxyl groups or carbonyl groups; During magnetron sputtering, the purity of the pure copper target is 99.999 wt%, and the working distance is 10 - 30 cm; the rotation rate of the sample stage fixing the loop frame is 10 - 20 rpm, the working power is 50 - 200 W, the working temperature is 30 - 500 °C, and the sputtering time is 1 - 30 s; The conductivity of the carbon nanotube / copper core-shell structure fiber is 2×10 7 ~5×10 7 S / m, and the specific conductivity is 6.0×10 3 ~10.1×10 3 Sm 2 kg -1 ; the current-carrying capacity of the carbon nanotube / copper core-shell structure fiber is 2.0×10 5 ~3.1×10 5 Acm -2 .

2. The preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity according to claim 1, characterized in that, During the constant-current electroplating of copper, place the carbon nanotube fiber after magnetron sputtering in the electroplating solution for electroplating treatment. The composition of the electroplating solution is: copper sulfate 160 - 220 g / L, sulfuric acid 25 - 35 mL / L, hydrochloric acid 30 - 35 μL / L; among them, the concentration of sulfuric acid is 95 - 98 wt%, and the concentration of hydrochloric acid is 36 - 38 wt%.

3. The preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity according to claim 1, characterized in that, During the process of electroplating copper under a constant current, the carbon nanotube fibers after magnetron sputtering are placed in an electroplating solution for electroplating treatment. The process conditions for the electroplating treatment include: using a DC power supply, the temperature is 20 - 60 °C, and the current density is 1 - 2 A / dm 2 .

4. The preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity according to claim 1, characterized in that, The thickness of the copper layer coated in the carbon nanotube / copper core-shell structure fiber is 1 to 20 μm, and the overall density of the carbon nanotube / copper core-shell structure fiber is 2.5 to 6.5 g / cm 3 .

5. The preparation method of the carbon nanotube / copper core-shell structure fiber with ultra-high specific conductivity and ultra-high current-carrying capacity according to claim 1, characterized in that, There are no pores and cracks at the interface of the prepared carbon nanotube / copper core-shell structure fiber, and the interface bonding is good.

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