Highly conductive motor winding material and method of making same

Abstract

The application relates to a high-conductivity motor winding material and a preparation method thereof, and belongs to the technical field of motor design of new energy vehicles; the method is characterized in that copper powder is added into a graphene oxide dispersion solution, deionized water is added to dilute the solution uniformly to obtain a suspension; the suspension is heated to 50-80 DEG C with nitrogen bubbling, and nitrogen bubbling is continuously carried out at constant temperature for not less than 30 min; solid-liquid separation is carried out, the obtained solid is vacuum dried to obtain a mixed powder; the mixed powder is subjected to hot-pressing sintering treatment, and the process parameters of the hot-pressing sintering treatment are as follows: hot-pressing sintering is carried out at 600-950 DEG C and 30-50 MPa for not less than 40 min, and the high-conductivity motor winding material is obtained; the method is simple in process steps, convenient for large-scale production, and the prepared graphene / copper composite material is excellent and stable in conductive performance and mechanical performance, and can meet the high-standard requirements of winding copper wire materials in the motor winding field.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-conductivity motor winding material and a preparation method thereof, and belongs to the technical field of motor design of new energy vehicles. BACKGROUND

[0002] New energy vehicles have become an indispensable means of transportation in recent years, and the performance of the key core component driving motor will have a high impact on the vehicle performance. With the development of technology, it is difficult to improve the power efficiency by optimizing the structure of electrical and electronic equipment, so designing high-conductivity materials has become the main research direction of energy saving. Copper, as an excellent conductor material, has become an indispensable material in electronic equipment such as motors and cables due to its abundant reserves and low price, and plays an important role in the field of new energy vehicles, rail transportation, power electronics and military industry.

[0003] When current flows through the motor winding, heat is generated due to the existence of winding resistance, resulting in loss. Most windings are made of copper material, so it is called "copper loss", which is a kind of active loss. High-efficiency motor is the direction of motor development today, and the best way to improve motor efficiency is to increase slot fill factor, that is, to reduce the resistance of the winding to reduce the heating loss of the motor winding (i.e. copper loss).

[0004] Using flat wire winding instead of round wire winding is one of the ways to improve the slot fill factor of the motor winding. The method uses rectangular wire to improve space utilization and increase the cross-sectional area of copper, thereby reducing the resistance of the winding. However, the space of the core slot is limited, and after it is completely filled with copper (equivalent to a slot fill factor of 100%, that is, the core slot is completely filled with copper wire), the resistance cannot be further reduced. Although there are many technologies that further reduce the copper loss of flat wire winding in different ways, for example, patent application CN201910866734.0 discloses a motor winding with reduced copper loss, which reduces the resistance of part of the winding copper wire at the end by increasing the cross-sectional area of the end wire; patent application CN202222431005.2 discloses a motor winding and a motor, the motor winding improves the slot fill factor of the core by designing winding units with equal angle distance, but the effect is very limited, so there is an urgent need to develop a new type of motor winding material that can significantly reduce the resistance of the motor winding copper wire.

[0005] Graphene is a two-dimensional carbon material with a π-bond structure similar to carbon nanotubes and metal-like properties with zero band gap, exhibiting very high charge carrier mobility. Copper and graphene possess complementary electrical properties; graphene's charge carrier mobility is four orders of magnitude higher than copper's, but its charge carrier density is lower, while copper's charge carrier density is fourteen orders of magnitude higher than graphene's. Therefore, under a synergistic effect, the composite interface of these two components will have extremely high electrical conductivity. Studies have shown that when graphene comes into contact with metal surfaces such as copper, it retains its zero band gap characteristic while inducing Fermi energy transfer, causing an electron doping effect, increasing the concentration of free electrons in graphene, and achieving even higher conductivity. Therefore, graphene / copper composites have enormous development potential in the field of high-conductivity copper materials and can become a reliable material for reducing the resistance of motor windings.

[0006] However, although graphene / copper composites have great application prospects as a new way to improve the resistance of copper wires in motor windings, the graphene / copper composites prepared by existing synthesis methods are not stable enough and are difficult to apply on a large scale to copper wires in motor windings, thus failing to meet the high standards required for copper wire materials in the field of motor windings. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the present invention aims to provide a high-conductivity motor winding material and its preparation method. The method has simple process steps, is easy to scale up production, and the prepared graphene / copper composite material has excellent and stable electrical and mechanical properties, which can meet the high standard requirements for winding copper wire materials in the field of motor winding.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing a high conductivity motor winding material, the method comprising the following steps:

[0010] (1) Add copper powder to graphene oxide dispersion, then add deionized water to dilute evenly to obtain a suspension; heat the suspension to 50℃~80℃, accompanied by nitrogen bubbling during the heating process, and continue to bubbling with nitrogen at a constant temperature for no less than 30 minutes after heating to 50℃~80℃, and separate the solid and liquid. Vacuum dry the obtained solid to obtain mixed powder.

[0011] The copper powder has a purity greater than 99% and a particle size less than 45 μm.

[0012] The graphene oxide dispersion contains a graphene oxide mass concentration of 1.0 g / L. -1 ~1.5g L -1 The solvent is deionized water;

[0013] The mass ratio of the graphene oxide to the copper powder is (0.25-1.5):100;

[0014] (2) performing hot-press sintering treatment on the mixed powder obtained in step (1) to obtain a graphene / copper composite material, which is the high-conductivity motor winding material;

[0015] The process parameters of the hot-press sintering treatment are: hot-press sintering at 600-950℃ and 30-50MPa for not less than 40min.

[0016] Preferably, in step (1), the mass concentration of the copper powder in the suspension is 1.67-1.94g / L; the copper powder is electrolytic copper powder; and the solid-liquid separation is performed by centrifugal separation.

[0017] Preferably, in step (1), the mass ratio of the graphene oxide to the copper powder is 0.75:100; the suspension is heated to 50-75℃, nitrogen bubbling is performed during the heating process, and nitrogen bubbling is continuously performed at a constant temperature of 50-75℃ for 30-120min; and the temperature of the vacuum drying is 80℃, and the vacuum drying time is more than 24h.

[0018] Preferably, before the hot-press sintering treatment in step (2), the mixed powder obtained in step (1) is preheated to improve the density of the graphene / copper composite material obtained in the subsequent hot-press sintering; the process conditions of the preheating are: the mixed powder obtained in step (1) is placed in a graphite mold, and is kept at a temperature of 300-500℃ under normal pressure for not less than 10min.

[0019] Further preferably, before the preheating treatment, the hot-press cavity of a hot-press sintering furnace used in the hot-press sintering treatment is vacuumed, argon is introduced for washing after the air pressure in the hot-press cavity is reduced to below 10Pa, and then the air pressure is vacuumed again to below 10Pa, and the above process is repeated for 3-5 times to remove oxygen in the hot-press cavity, and then the preheating treatment is started.

[0020] Preferably, during the hot-press sintering treatment, the air pressure in the hot-press cavity of the hot-press sintering furnace is kept at 10 -3 Pa-10 - 1 Pa, which can prevent the copper powder from being oxidized during the high-temperature and high-pressure forming process, and is beneficial to improving the conductivity of the graphene / copper composite material.

[0021] More preferably, in step (2), the process parameters of the hot-press sintering treatment are: hot-press sintering at 600-950 DEG C, 30-50 MPa for 40-120 min; the preheating process parameters are: preheating at 300-500 DEG C, normal pressure for 10-60 min; during the hot-press sintering treatment, the gas pressure in the hot-press sintering furnace is kept at 1.0*10 -3 ~7.5*10 - 2 Pa.

[0022] A high-conductivity motor winding material is prepared by the method.

[0023] Advantages

[0024] (1) The application provides a preparation method of a high-conductivity motor winding material, which uniformly mixes graphene oxide dispersion liquid and copper powder, and then obtains a graphene / copper composite material through hot-press sintering treatment. The electrostatic adsorption of graphene oxide and copper powder is beneficial to the uniform dispersion of graphene oxide, and the effect of graphene oxide and copper powder surface residual copper ions can also reduce graphene oxide to graphene, realizing the uniform blending of copper powder and graphene, avoiding the damage of the structure of graphene oxide caused by the severe impact of grinding balls on graphene oxide in the conventional mechanical grinding and blending process, and further ensuring the size and integrity of graphene in the finally prepared motor winding material, and improving the stability of the performance of the prepared graphene / copper composite material.

[0025] (2) The application provides a preparation method of a high-conductivity motor winding material, which is simple in process steps, short in blending time, does not need to use toxic and harmful reducing agents such as hydrazine or other chemical drugs to reduce graphene oxide, is environmentally friendly and low in cost, and is suitable for large-scale production.

[0026] (3) The application provides a preparation method of a high-conductivity motor winding material, which adopts a vacuum hot-press sintering treatment process, can exclude the oxidation of copper in the forming process of the graphene / copper composite material, and can further exclude the influence of oxidation on copper through gas washing, so as to improve the conductivity of the graphene / copper composite material.

[0027] (4) The application provides a high-conductivity motor winding material, which is prepared by using graphene oxide dispersion liquid and copper powder as raw materials and adopting the method (mixing under constant temperature and nitrogen protection, vacuum hot-press sintering) of the application; the high-conductivity motor winding material prepared by the method has excellent and stable conductivity and mechanical properties, and can meet the high-standard requirements for winding copper wire materials in the field of motor winding. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a transmission electron microscope (TEM) image of the interface of the graphene / copper composite material prepared in Example 1;

[0029] Figure 2 is a high-resolution transmission electron microscope (HRTEM) image of the interface of the graphene / copper composite material in Example 1; Figure 1

[0030] Figure 3 is a scanning electron microscope (SEM) image of the graphene / copper composite material prepared in Example 1;

[0031] Figure 4 is a schematic diagram of the electrical conductivity of the high-conductivity graphene / copper composite material of the present application as a function of the mass ratio of graphene oxide and copper powder;

[0032] Figure 5 is a schematic diagram of the microhardness of the high-conductivity graphene / copper composite material of the present application as a function of the mass ratio of graphene oxide and copper powder. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings and specific embodiments, and the methods are all conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

[0034] Example 1

[0035] A preparation method of a high-conductivity motor winding material, the specific steps of the method are as follows:

[0036] (1) 2 g of copper powder is added to 3.3 mL of graphene oxide dispersion solution, and then 100 mL of deionized water is added to dilute uniformly to obtain a suspension; the suspension is heated to 75°C, nitrogen bubbling is accompanied during the heating process, and nitrogen bubbling is continued for 30 min after heating to 75°C, centrifugal separation is performed, the obtained solid is dried at 80°C for 24 h to obtain a mixed powder;

[0037] The copper powder is electrolytic copper powder with a purity of greater than 99% and a particle size of less than 45 μm;

[0038] The mass concentration of graphene oxide in the graphene oxide dispersion solution is 1.5 g / L -1 , and the solvent is deionized water;

[0039] The mass ratio of graphene oxide to copper powder is 0.25:100;

[0040] The mass concentration of copper powder in the suspension is 1.94 g / L;

[0041] ​(2) The mixed powder obtained in step (1) is subjected to hot-pressing sintering treatment. Before the hot-pressing sintering treatment, the hot-pressing cavity of the hot-pressing sintering furnace used in the hot-pressing sintering process is vacuumed, and after the air pressure in the hot-pressing cavity is reduced to 10 Pa, argon gas is introduced for washing, and then the air pressure is vacuumed again to 10 Pa, and the process is repeated 3 times to remove oxygen in the hot-pressing cavity, and then the preheating treatment is started. The process conditions of the preheating treatment are as follows: the mixed powder obtained in step (1) is placed in a graphite mold, and is kept at 300℃ under normal pressure for 10 min. Then the mixed powder after preheating is subjected to hot-pressing sintering treatment, and the process parameters of the hot-pressing sintering treatment are as follows: hot-pressing sintering at 600℃ under 50 MPa for 40 min, and during the hot-pressing sintering process, the air pressure in the hot-pressing cavity of the hot-pressing sintering furnace is kept at 1x10 -3 Pa, to obtain the high-conductivity motor winding material.

[0042] Example 2

[0043] A method for preparing a high-conductivity motor winding material, and the specific steps of the method are as follows:

[0044] (1) 2g of copper powder is added to 8.3mL of graphene oxide dispersion liquid, and then 100mL of deionized water is added for dilution to obtain a suspension. The suspension is heated to 70℃, and nitrogen bubbling is accompanied during the heating process. After heating to 70℃, nitrogen bubbling is continued for 40 min at constant temperature. Centrifugal separation is performed, and the obtained solid is dried at 80℃ for 24h to obtain a mixed powder;

[0045] The copper powder is electrolytic copper powder with a purity of more than 99% and a particle size of less than 45μm.

[0046] In the graphene oxide dispersion liquid, the mass concentration of graphene oxide is 1.2g / L -1 , and the solvent is deionized water.

[0047] The mass ratio of graphene oxide to copper powder is 0.50:100.

[0048] In the suspension, the mass concentration of copper powder is 1.85g / L.

[0049] (2) The mixed powder obtained in step (1) is subjected to hot-pressing sintering treatment. Before the hot-pressing sintering treatment, the hot-pressing cavity of the hot-pressing sintering furnace used in the hot-pressing sintering process is vacuumed, and after the air pressure in the hot-pressing cavity is reduced to 10 Pa, argon gas is introduced for washing, and then the air pressure is vacuumed again to 10 Pa. The above process is repeated 5 times to remove oxygen in the hot-pressing cavity, and then the preheating treatment is started. The process conditions of the preheating treatment are as follows: the mixed powder obtained in step (1) is placed in a graphite mold, and is preheated at 500°C under normal pressure for 10 min. Then, the preheated mixed powder is subjected to hot-pressing sintering treatment. The process parameters of the hot-pressing sintering treatment are as follows: hot-pressing sintering at 950°C and 30 MPa for 40 min, and during the hot-pressing sintering process, the air pressure in the hot-pressing cavity of the hot-pressing sintering furnace is kept at 1x10 -2 Pa, thereby obtaining the high-conductivity motor winding material.

[0050] Example 3

[0051] A method for preparing a high-conductivity motor winding material, and the specific steps of the method are as follows:

[0052] (1) 2 g of copper powder is added to 15 mL of graphene oxide dispersion liquid, and then 100 mL of deionized water is added for dilution to obtain a suspension. The suspension is heated to 60°C, and nitrogen bubbling is accompanied during the heating process. After heating to 60°C, nitrogen bubbling is continued at a constant temperature for 90 min. Centrifugal separation is performed, and the obtained solid is dried at 80°C for 24 h to obtain a mixed powder;

[0053] The copper powder is electrolytic copper powder with a purity greater than 99% and a particle size less than 45 μm.

[0054] In the graphene oxide dispersion liquid, the mass concentration of graphene oxide is 1.0 g / L -1 , and the solvent is deionized water.

[0055] The mass ratio of graphene oxide to copper powder is 0.75:100.

[0056] In the suspension, the mass concentration of copper powder is 1.74 g / L.

[0057] (2) The mixed powder obtained in step (1) is subjected to hot-pressing sintering treatment. Before the hot-pressing sintering treatment, the hot-pressing cavity of the hot-pressing sintering furnace used in the hot-pressing sintering process is vacuumed, and after the air pressure in the hot-pressing cavity is reduced to 10 Pa, argon gas is introduced for washing, and then the air pressure is vacuumed again to 10 Pa. The above process is repeated 6 times to remove oxygen in the hot-pressing cavity, and then the preheating treatment is started. The process conditions of the preheating treatment are as follows: the mixed powder obtained in step (1) is placed in a graphite mold, and is preheated at 450℃ under normal pressure for 20 min. Then, the preheated mixed powder is subjected to hot-pressing sintering treatment. The process parameters of the hot-pressing sintering treatment are as follows: hot-pressing sintering is carried out at 925℃ and 45 MPa for 50 min, and during the hot-pressing sintering process, the air pressure in the hot-pressing cavity of the hot-pressing sintering furnace is kept at 2x10 -2 Pa, thereby obtaining the high-conductivity motor winding material.

[0058] Example 4

[0059] A method for preparing a high-conductivity motor winding material, and the specific steps of the method are as follows:

[0060] (1) 2g of copper powder is added to 13.33mL of graphene oxide dispersion liquid, and then 100mL of deionized water is added for dilution to obtain a suspension. The suspension is heated to 50℃, and nitrogen bubbling is carried out during the heating process. After heating to 50℃, nitrogen bubbling is continued at constant temperature for 120 min. Centrifugal separation is carried out, and the obtained solid is dried at 80℃ for 24h to obtain a mixed powder;

[0061] The copper powder is electrolytic copper powder with a purity of more than 99% and a particle size of less than 45μm.

[0062] In the graphene oxide dispersion liquid, the mass concentration of graphene oxide is 1.5g / L -1 , and the solvent is deionized water.

[0063] The mass ratio of graphene oxide to copper powder is 1.0:100.

[0064] In the suspension, the mass concentration of copper powder is 1.76g / L.

[0065] (2) The mixed powder obtained in step (1) is subjected to hot-pressing sintering treatment. Before the hot-pressing sintering treatment, the hot-pressing cavity of the hot-pressing sintering furnace used in the hot-pressing sintering process is vacuumed, and after the air pressure in the hot-pressing cavity is reduced to 1 Pa, argon gas is introduced for washing, and then the air pressure is vacuumed again to 1 Pa, and the process is repeated 3 times to remove oxygen in the hot-pressing cavity, and then the preheating treatment is started. The process conditions of the preheating treatment are as follows: the mixed powder obtained in step (1) is placed in a graphite mold, and is preheated at 400°C under normal pressure for 60 min. Then the mixed powder after preheating is subjected to hot-pressing sintering treatment, and the process parameters of the hot-pressing sintering treatment are as follows: hot-pressing sintering at 900°C under a pressure of 40 MPa for 60 min, and during the hot-pressing sintering process, the air pressure in the hot-pressing cavity of the hot-pressing sintering furnace is kept at 5x10 -2 Pa, to obtain the high-conductivity motor winding material.

[0066] Example 5

[0067] A method for preparing a high-conductivity motor winding material, and the specific steps of the method are as follows:

[0068] (1) 2g of copper powder is added to 20mL of graphene oxide dispersion liquid, and then 100mL of deionized water is added for dilution to obtain a suspension. The suspension is heated to 50°C, and nitrogen bubbling is accompanied during the heating process. After heating to 50°C, nitrogen bubbling is continued at a constant temperature for 120 min. Centrifugal separation is performed, and the obtained solid is dried at 80°C for 24h to obtain a mixed powder;

[0069] The copper powder is electrolytic copper powder with a purity of more than 99% and a particle size of less than 45μm.

[0070] In the graphene oxide dispersion liquid, the mass concentration of graphene oxide is 1.5g / L -1 , and the solvent is deionized water.

[0071] The mass ratio of graphene oxide to copper powder is 1.5:100.

[0072] In the suspension, the mass concentration of copper powder is 1.67g / L.

[0073] (2) The mixed powder obtained in step (1) is subjected to hot pressing sintering. Before hot pressing sintering, the hot pressing chamber of the hot pressing furnace used in the hot pressing sintering process is evacuated until the gas pressure in the hot pressing chamber drops to 1 Pa. Then, argon gas is introduced for cleaning. After that, the gas pressure is evacuated to 1 Pa again. This process is repeated 3 times to remove oxygen from the hot pressing chamber before preheating. The preheating process conditions are as follows: the mixed powder obtained in step (1) is placed in a graphite mold and kept at 400°C and normal pressure for 60 min. Then, the preheated mixed powder is subjected to hot pressing sintering. The process parameters of the hot pressing sintering process are: hot pressing sintering at 850°C and 50 MPa for 120 min. During the hot pressing sintering process, the gas pressure in the hot pressing chamber of the hot pressing sintering furnace is maintained at 7.5 × 10⁻⁶. -2 Pa, to obtain the high conductivity motor winding material.

[0074] Comparative Example 1

[0075] Comparative Example 1 was based solely on Example 1, without the addition of graphene oxide dispersion, and all other conditions remained unchanged, resulting in copper material for motor windings.

[0076] The morphology of the high-conductivity motor winding material prepared in Example 1 was characterized using transmission electron microscopy (TEM), high-power transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM). The results are as follows: Figures 1 to 3 As shown, there is a clear two-phase interface inside the material, indicating that the prepared high conductivity motor winding material is a graphene / copper composite material; the test results of the morphology of the high conductivity motor winding materials prepared in Examples 2 to 5 are similar to those in Example 1.

[0077] The composition of the high conductivity motor winding material prepared in Example 1 was tested using Fourier transform infrared spectroscopy (FTIR). The test results showed that Cu-O characteristic peaks and C=O characteristic peaks appeared in the FTIR spectrum. The Cu-O peak was significantly lower than that of pure copper powder, and the C=O peak was significantly lower than that of graphene oxide. This indicates that the interaction between graphene oxide and residual copper ions on the surface of copper powder can reduce graphene oxide to graphene. The high conductivity motor winding material prepared by the method of the present invention is a graphene / copper composite material. The Fourier transform infrared spectra of Examples 2 to 5 are similar to those of Example 1.

[0078] Under testing conditions of 25℃, the microhardness, conductivity, elongation, and tensile strength of the high conductivity motor winding materials prepared in Examples 1-5 and the copper motor winding material prepared in Comparative Example 1 were tested using a microhardness tester, the van der Burg method testing system, and the tensile test method. The results are shown in Table 1.

[0079] Table 1. Test results of performance parameters of the motor winding materials described in Examples 1-5 and Comparative Example 1.

[0080]

[0081]

[0082] As can be seen from Table 1, the elongation of the motor winding material prepared in Examples 1-5 can reach 59.8%, the tensile strength can reach 270.7 MPa, the microhardness can reach 142.2 VHM, and the electrical conductivity can reach 62.1 Ms / m -1 , which shows good mechanical properties and electrical conductivity, and the graphene / copper composite material can meet the use requirements of the motor winding material;

[0083] In the motor winding materials of Comparative Example 1 and Examples 1-5, the mass ratio of graphene oxide and copper powder gradually increases from 0, and the microhardness and electrical conductivity also change accordingly. In Comparative Example 1 and Examples 1-5, the mass ratio of graphene oxide and copper powder is taken as the abscissa, and the corresponding microhardness is taken as the ordinate, to draw a schematic diagram of the change of the electrical conductivity of the high-conductive graphene / copper composite material of the application with the mass ratio of graphene oxide and copper powder ( Figure 4 );from Figure 4 It can be seen from the figure that as the mass ratio of graphene oxide and copper increases, the graphene content in the prepared high-conductive graphene / copper composite material increases accordingly, and the microhardness of the high-conductive graphene / copper composite material first increases significantly and then gradually stabilizes.

[0084] In Comparative Example 1 and Examples 1-5, the mass ratio of graphene oxide and copper powder is taken as the abscissa, and the corresponding electrical conductivity is taken as the ordinate, to draw a schematic diagram of the change of the electrical conductivity of the high-conductive graphene / copper composite material of the application with the mass ratio of graphene oxide and copper powder ( Figure 5 );from Figure 5 It can be seen from the figure that as the mass ratio of graphene oxide and copper increases, the graphene content in the prepared high-conductive graphene / copper composite material increases accordingly, and the electrical conductivity of the high-conductive graphene / copper composite material first increases significantly and then decreases; when the mass ratio of graphene oxide and copper powder is 0.75:100, the electrical conductivity is the highest.

[0085] The above only describes specific embodiments of the application and is not used to limit the protection scope of the application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method of making a high conductive motor winding material, characterized by: The method comprises the following steps: (1) adding copper powder into a graphene oxide dispersion solution, then adding deionized water to dilute uniformly to obtain a suspension; heating the suspension to 50-80 DEG C, bubbling nitrogen during the heating process, and continuing to bubble nitrogen at a constant temperature for not less than 30 min after heating to 50-80 DEG C, solid-liquid separation, vacuum drying the obtained solid to obtain a mixed powder; The purity of the copper powder is greater than 99%, and the particle size is less than 45 μm; The mass concentration of the graphene oxide in the graphene oxide dispersion liquid is 1.0 g / L -1 ~1.5 g / L -1 , and the solvent is deionized water; The mass ratio of the graphene oxide to the copper powder is (0.25-1.5):100; (2) performing hot-pressing sintering treatment on the mixed powder to obtain a graphene / copper composite material, which is the high-conductivity motor winding material; The process parameters of the hot-pressing sintering treatment are: hot-pressing sintering at 600-950 DEG C, 30-50 MPa for not less than 40 min; Before the hot-pressing sintering treatment, the mixed powder is preheated, and the process conditions of the preheating are: placing the mixed powder in a graphite mold, and heat preservation at 300-500 DEG C, normal pressure for not less than 10 min.

2. The method for preparing a high conductivity motor winding material according to claim 1, characterized in that: The mass concentration of the copper powder in the suspension is 1.67-1.94 g / L; the copper powder is electrolytic copper powder; and the solid-liquid separation is centrifugal separation.

3. The method for preparing a high conductivity motor winding material according to claim 1 or 2, characterized in that: The mass ratio of the graphene oxide to the copper powder is 0.75:100; the suspension is heated to 50-75 DEG C, nitrogen is bubbled during the heating process, and the nitrogen bubbling is continued for 30-120 min at a constant temperature after heating to 50-75 DEG C; the temperature of the vacuum drying is 80 DEG C, and the vacuum drying time is more than 24 h.

4. The method for preparing a high conductivity motor winding material according to claim 1, characterized in that: Before the preheating treatment starts, the hot-pressing cavity of the hot-pressing sintering furnace used for the hot-pressing sintering treatment is vacuumed, argon is introduced for washing after the air pressure of the hot-pressing cavity is reduced to below 10 Pa, then the air pressure is vacuumed again to below 10 Pa, and the above steps are repeated for 3-5 times to remove oxygen in the hot-pressing cavity, and then the preheating treatment is started.

5. The method for preparing a high conductivity motor winding material according to claim 1 or 2, characterized in that: During the hot-press sintering process, the hot-pressing cavity pressure of the hot-press sintering furnace is kept at 10 -3 Pa~10 -1 Pa.

6. The method of making a high-conductivity motor winding material of claim 3, wherein: The process parameters of the hot-press sintering treatment are: hot-press sintering at 600-950℃, 30-50MPa for 40-120min; the process conditions of preheating are: heat preservation at 300-500℃, normal pressure for 10-60min; during the hot-press sintering treatment, the air pressure in the hot-press cavity of the hot-press sintering furnace is kept at 1.0x10 -3 -7.5x10 -2 Pa.

7. A high conductive motor winding material characterized by: The high-conductivity motor winding material is prepared by the method for preparing the high-conductivity motor winding material according to any one of claims 1-6.

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