Composite conductor, preparation method therefor, and use thereof

Abstract

Disclosed in the present application are a composite conductor, a preparation method therefor, and a use thereof. The preparation method for a composite conductor comprises: (A) providing an initial metal matrix and performing oxidation treatment on the initial metal matrix to obtain a pre-oxidized metal matrix; (B) performing annealing treatment on the pre-oxidized metal matrix in a reducing atmosphere, then placing the pre-oxidized metal matrix in a deposition chamber, and introducing a carbon source into the deposition chamber at a first temperature for a period of time to perform graphene deposition; (C) stopping the introduction of the carbon source and introducing an oxygen-containing gas for a period of time, then stopping the introduction of the oxygen-containing gas and changing to introduce the carbon source to perform graphene deposition; and repeating step (C) n times, where n is an integer greater than or equal to 0, to obtain a composite conductor. The composite conductor has relatively high electrical conductivity.

Description

Composite conductor, preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410886593.X, filed on July 03, 2024 in the China Patent Office, and entitled "Composite conductor, preparation method and application thereof", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of conductor materials, in particular to a composite conductor, a preparation method and application thereof. BACKGROUND

[0003] Graphene has very high specific surface area, electron mobility, Young's modulus and thermal conductivity, and has broad application prospects in many fields such as lithium ion batteries, transparent conductive films, supercapacitors, fuel cells, solar cells, hydrogen storage materials, etc.

[0004] Metal conductors are widely used in the fields of electric power, transportation, industrial equipment and electronic information due to their good electrical conductivity, thermal conductivity, ductility and other properties. However, in recent years, higher requirements have been put forward for the electrical conductivity, thermal conductivity and stability of metal conductors.

[0005] In the prior art, graphene is usually combined with metal conductors, such as mixing copper powder with graphene powder, vapor deposition of a graphene layer on the surface of a copper metal matrix, etc., in order to obtain a composite conductor that takes into account the excellent properties of both metal and graphene.

[0006] However, the electrical conductivity of the existing composite conductor is poor and needs to be further improved. SUMMARY

[0007] Therefore, the present application provides a composite conductor, aiming to improve the problem of poor electrical conductivity of the existing composite conductor.

[0008] In a first aspect, the present application provides a preparation method of a composite conductor, comprising the following steps:

[0009] A. providing an initial metal matrix, and performing oxidation treatment on the initial metal matrix to obtain a pre-oxidized metal matrix;

[0010] B. performing annealing treatment on the pre-oxidized metal matrix in a reducing atmosphere, and then placing the pre-oxidized metal matrix in a deposition chamber, and introducing a carbon source into the deposition chamber at a first temperature for a period of time;

[0011] C. stopping the introduction of the carbon source and instead introducing an oxygen-containing gas for a period of time, and then stopping the introduction of the oxygen-containing gas and instead introducing the carbon source;

[0012] D, repeating the step C for n times, wherein n is an integer greater than or equal to 0, to obtain the composite conductor.

[0013] In a second aspect, the embodiments of the present application provide a composite conductor, comprising a metal matrix, a transition layer located on at least one surface of the metal matrix, and a graphene layer located on a surface of the transition layer away from the metal matrix, wherein the metal matrix comprises a first metal, the transition layer comprises a second metal and a first graphene, and the graphene layer comprises a second graphene, and the average flake diameter of the first graphene is smaller than that of the second graphene.

[0014] In a third aspect, the embodiments of the present application also provide an application of the composite conductor as an electric wire or cable or an electric contact. Advantages

[0015] The composite conductor prepared by the preparation method has high electrical conductivity, thermal conductivity and mechanical strength. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] FIG. 1 is a structural schematic diagram of a composite conductor provided by an embodiment of the present application;

[0018] FIG. 2 is a structural schematic diagram of another composite conductor provided by an embodiment of the present application;

[0019] FIG. 3 is a flow chart of a preparation method of a composite conductor provided by an embodiment of the present application;

[0020] FIG. 4 is a structural schematic diagram of a pre-oxidized metal matrix provided by an embodiment of the present application;

[0021] FIG. 5 is a structural schematic diagram of another pre-oxidized metal matrix provided by an embodiment of the present application;

[0022] FIG. 6 is a structural schematic diagram of an initial metal matrix provided by an embodiment of the present application;

[0023] FIG. 7 is a structural schematic diagram of another initial metal matrix provided by an embodiment of the present application;

[0024] FIG. 8 is a structural schematic diagram of another initial metal matrix provided by an embodiment of the present application;

[0025] FIG. 9 is a structural schematic diagram of another initial metal matrix provided by an embodiment of the present application. Embodiments of the present application

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0027] In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, specifically the drawing surface direction in the drawings, and "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish an order.

[0028] In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0029] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0030] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it means that any cited number (fraction or integer) within the indicated range is included.

[0031] Currently, the main preparation methods of graphene include mechanical exfoliation, oxidation-reduction method, chemical vapor deposition (CVD), epitaxial growth, etc.

[0032] Among them, the chemical vapor deposition method is a method of growing graphene on the substrate surface by the interaction of carbon atoms generated by the pyrolysis of carbon source and the substrate. The production process of graphene prepared by chemical vapor deposition method using metal (such as copper) as substrate is relatively perfect, and the number of layers of the grown graphene is uniform and the quality is high. It is the most promising method for large-scale production at present.

[0033] Although the quality of graphene synthesized by CVD method has been improved after years of development, it still has many structural defects, so there is still a big gap in its physical or chemical properties compared with natural graphene (mechanical exfoliation graphene), which limits its application in the direction of electrical conductivity and thermal conductivity. In addition, the preparation process is quite expensive, so synthetic graphene has not been widely used so far. Therefore, the breakthrough of the preparation process is one of the most important key factors for the application of graphene.

[0034] In the preparation of graphene by CVD method, controlling the nucleation density and expanding the size of single-crystal graphene domains is a common strategy. The active sites on the copper foil can be reduced by focusing on two methods: (i) reducing the number of active sites on the copper by electro-polishing and re-solidification; (ii) passivating the active sites with oxygen. In recent years, research has shown that the introduction of oxygen into the growth environment plays a crucial role in the study of graphene CVD growth. In the presence of oxygen, micron-sized graphene sheets can be obtained on commercial copper foils. The addition of oxygen is a widely used pretreatment method for polycrystalline copper foils, which can reduce the roughness of the copper foil surface and remove impurities on the copper foil surface. In addition, the introduction of oxygen not only passivates the nucleation sites on the copper foil surface, but also helps to reduce the dehydrogenation barrier of the carbon source and increase the edge attachment of carbon species, thereby significantly reducing the nucleation density and achieving ultrafast growth of large graphene single crystals.

[0035] In recent years, researchers have done a lot of work on the introduction of oxygen into the graphene growth environment. Different works have adopted different methods to introduce oxygen. In 2020, Li Na et al. published a paper in Nanotechnology, which mentioned that oxygen can be introduced by pre-oxidizing the copper foil before growth, which is one of the most common methods. However, the oxygen content will be consumed by the reducing gas (hydrogen) as the growth time is prolonged, resulting in insufficient oxygen supply. In response to this, Xu Xiaozhi et al. chose to place a compound that can stably release oxygen (such as copper oxide) under the copper foil during the growth process to achieve continuous oxygen supply. However, this method inevitably reduces production efficiency and increases production costs, and is not suitable for mass production.

[0036] The technical solution of the present application is as follows:

[0037] In a first aspect, with reference to FIGS. 1-9, the present application further provides a preparation method of a composite conductor, comprising the following steps:

[0038] A. providing an initial metal substrate 1, and performing an oxidation treatment on the initial metal substrate 1 to obtain a pre-oxidized metal substrate 200;

[0039] B. performing an annealing treatment on the pre-oxidized metal substrate 200 in a reducing atmosphere, and then placing the pre-oxidized metal substrate 200 in a deposition chamber, introducing a carbon source into the deposition chamber at a first temperature for a period of time to perform graphene deposition;

[0040] C. stopping the introduction of the carbon source and instead introducing an oxygen-containing gas for a period of time, then stopping the introduction of the oxygen-containing gas and instead introducing the carbon source to perform graphene deposition;

[0041] D. repeating the step C for n times, wherein n is an integer greater than or equal to 0, to obtain a composite conductor 100.

[0042] It can be understood that when n is 0, the step C is not repeated.

[0043] Referring to FIGS. 4-5, the pre-oxidized metal substrate 200 in the step A comprises a metal substrate 10 and a metal oxide layer 201 located on at least one surface of the metal substrate 10. The metal oxide layer 201 comprises a first metal oxide layer 2011 combined with the metal substrate 10 and a second metal oxide layer 2012 combined with the first metal oxide layer 2011 and away from the surface of the metal substrate 10. The metal substrate 10 comprises a first metal, the first metal oxide layer 2011 comprises a metal oxide and a metal suboxide, and the second metal oxide layer 2012 comprises a metal oxide.

[0044] The preparation method of the composite conductor is to introduce a gas phase deposition gas into the deposition chamber at a first temperature, and under the action of the first temperature, oxygen elements in the metal oxide and metal sub-oxide in the metal oxide layer 201 in the pre-oxidized metal base 200 are released, and the metal oxide and metal sub-oxide are reduced. Taking copper as an example, copper oxide and cuprous oxide undergo the following reactions at high temperatures: CuO→CuO2, CuO2→Cu, and oxygen is released. The presence of oxygen can effectively reduce the carbon precursor cracking reaction energy barrier and improve the cracking efficiency, thereby obtaining fully cracked carbon species (CH4+O→CH3·; CH3+O→CH2·; CH2+O→CH·; CH2+O→C·), and improving the deposition rate of graphene. After the pre-oxidation treatment, the metal is oxidized to a metal oxide, which can increase the surface roughness and increase the theoretical nucleation site number. However, at the first temperature, the released oxygen elements can passivate the copper on the surface of the pre-oxidized metal base 200, preventing the carbon species from nucleating at some of the theoretical nucleation sites, thereby reducing the activity of copper in the oxygen-containing region of the base and reducing the actual number of nucleation sites, thereby promoting the formation of large-grain-size graphene. In this way, the pre-oxidation treatment can not only improve the deposition rate, but also facilitate the formation of large-grain-size graphene.

[0045] In addition, the metal oxide and metal sub-oxide in the pre-oxidized metal base 200 are reduced to a second metal at the first temperature, and water or carbon dioxide is generated at the same time. The water or carbon dioxide can be discharged with the gas phase deposition gas and will not introduce new impurities into the composite conductor 100.

[0046] In addition, the change from metal oxide to metal sub-oxide and then to metal, such as the change from copper oxide to cuprous oxide and then to copper, occurs during the reaction process at the first temperature. The change from metal to metal oxide increases the surface roughness of the base, while the conversion of metal oxide to metal sub-oxide and metal can further reduce the surface roughness of the base, further improving the flatness of the surface compared to the untreated base, thereby further reducing the number of nucleation sites. During the deposition of graphene, some high-temperature cracked carbon atoms will directly deposit on the surface of the metal oxide layer 201 of the pre-oxidized metal base 200 to form large-grain second graphene, thereby obtaining a graphene layer 30. In addition, due to the release of oxygen from the metal oxide and metal sub-oxide at high temperatures, a metal with defects is formed. Some high-temperature cracked carbon atoms will deposit at the defects of these metals to form small-grain first graphene, thereby converting the metal oxide layer 201 into a transition layer 20 containing a second metal and small-grain first graphene.

[0047] The preparation method described in the present application can effectively promote the formation of the first graphene with large crystal grains and promote the cracking of the carbon source by pre-oxidizing the initial metal substrate 1. However, during the graphene deposition process, the oxygen content in the pre-oxidized metal substrate will be consumed (for example, consumed by reacting with a reducing gas) as the graphene is deposited, causing insufficient oxygen supply. The present application stops the introduction of the carbon source after a period of time and instead introduces oxygen. In this way, the metal can be re-oxidized to form metal oxides and / or metal suboxides, thereby replenishing the oxygen and reducing the number of active sites on the substrate surface. Therefore, after the oxygen is replenished, the carbon source is introduced again for graphene deposition, which is conducive to the continuous formation of graphene with large crystal grain size. Thus, the average crystal grain size of the second graphene in the graphene layer 30 in the composite conductor 100 prepared is large, and the uniformity of the crystal grain size of the second graphene is high, thereby making the composite conductor 100 prepared have high electrical conductivity, thermal conductivity and mechanical strength.

[0048] Further, the pre-oxidized metal substrate obtained by the pre-oxidation treatment has a high oxygen content on the surface, which increases the surface roughness. The annealing treatment of the pre-oxidized metal substrate 200 in a reducing atmosphere can reduce the oxygen content in the pre-oxidized metal substrate 200 to some extent. The process of oxidizing first and then reducing annealing seems contradictory, but it is actually used to more accurately control the oxygen content in the growth precursor. This is conducive to the subsequent deposition of graphene. On the one hand, the annealing treatment of the pre-oxidized metal substrate 200 in a reducing atmosphere can reduce some metal oxides in the second metal oxide layer 2012 of the pre-oxidized metal substrate 200 to generate elemental metal and metal sub-oxides. When graphene is deposited on the surface of the pre-oxidized metal substrate 200, the metal sub-oxides can promote the cracking of the carbon source, and the elemental metal can release oxygen, which can effectively promote the cracking of the carbon source and is conducive to the formation of large-grained graphene. On the other hand, the material of the second metal oxide layer 2012 of the pre-oxidized metal substrate 200 is mainly metal oxide, which can cause the surface roughness of the pre-oxidized metal substrate 200 to be high. High surface roughness can cause a sharp increase in the number of theoretical nucleation sites. The annealing treatment of the pre-oxidized metal substrate 200 in a reducing atmosphere can convert at least some of the metal oxides in the second metal oxide layer 2012 to metal sub-oxides. In this way, the surface roughness of the pre-oxidized metal substrate 200 can be reduced, thereby effectively avoiding a sharp increase in the number of theoretical nucleation sites and more effectively reducing the number of actual nucleation sites on the surface of the pre-oxidized metal substrate 200. In addition, the oxygen content in the metal oxide is higher than that in the metal sub-oxide. Under the action of the first temperature, more oxygen is released. The more oxygen will react with free carbon to form carbon dioxide and / or carbon monoxide. The released oxygen will also react with the graphene deposited around it to cause etching. To some extent, this will hinder the formation of graphene, resulting in poor film uniformity and density of the graphene layer 30, which will affect the conductivity and hardness of the prepared composite conductor. Reducing the metal oxide to the metal sub-oxide can reduce the oxygen content to some extent, thereby effectively improving the conductivity and hardness of the prepared composite conductor.

[0049] In addition, the first metal oxide layer 2011 of the pre-oxidized metal substrate 200 includes metal oxides and metal sub-oxides. In this way, compared with a first metal oxide layer that is entirely composed of metal oxides, the number of active sites on the surface of the pre-oxidized metal substrate 200 can be effectively reduced, which promotes the formation of large-grained graphene and promotes the cracking of the carbon source.

[0050] In the step A, the pre-oxidized metal substrate 200 is obtained by the following steps:

[0051] The material of the initial metal substrate 1 includes one or more of a metal element and an alloy, the metal element includes one or more of Cu and Al, and the alloy includes one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy.

[0052] The initial metal substrate 1 can be a metal particle, a metal foil, or a metal wire.

[0053] Referring to FIGS. 6-7, in some embodiments, the initial metal substrate 1 includes a first initial metal substrate 11, and the material of the first initial metal substrate 11 includes one or more of a metal element and an alloy, the metal element includes one or more of Cu and Al, and the alloy includes one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy. At this time, the pre-oxidation treatment oxidizes the surface of the first initial metal substrate 11 to obtain the metal oxide layer 201, and the unoxidized part is the metal substrate 10, thereby obtaining the pre-oxidized metal substrate 200. At this time, the metal in the metal oxide layer 201 is the same as the metal in the metal substrate 10. Correspondingly, in the graphene deposition process, the second metal in the transition layer 20 is the same as the first metal in the metal substrate 10.

[0054] Referring to FIGS. 8-9, in other embodiments, the initial metal substrate 1 includes a first initial metal substrate 11 and a second initial metal substrate 12 on the surface of the first initial metal substrate 11. The material of the first initial metal substrate 11 and the second initial metal substrate 12 each independently includes one or more of a metal element and an alloy, the metal element includes one or more of Cu and Al, and the alloy includes one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy. It can be understood that the material of the first initial metal substrate 11 and the second initial metal substrate 12 can be the same or different. In the pre-oxidation treatment, the second initial metal substrate 12 is oxidized to obtain the metal oxide layer 201, and the first initial metal substrate 11 is the metal substrate 10, thereby obtaining the pre-oxidized metal substrate 200. At this time, the metal in the metal oxide layer 201 can be the same as or different from the metal in the metal substrate 10. Correspondingly, in the graphene deposition process, the second metal in the transition layer 20 can be the same as or different from the first metal in the metal substrate 10.

[0055] In some embodiments, the thickness of the second initial metal substrate 12 is 0.1-1 μm.

[0056] In some embodiments, the oxidation treatment of the initial metal substrate 1 includes placing the initial metal substrate 1 in an oxygen-containing atmosphere and heat treating at a second temperature for a period of time t1.

[0057] In some embodiments, the oxygen-containing atmosphere includes, but is not limited to, air, oxygen, a first inert gas containing oxygen, and the like.

[0058] In some embodiments, the first inert gas includes, but is not limited to, one or more of nitrogen, helium, argon, xenon.

[0059] In some embodiments, the second temperature ranges from 60 to 150°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, and the like; and the time t1 ranges from 1 to 5 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, and the like. Within the temperature and time ranges, the prepared pre-oxidized metal substrate 200 can have a metal oxide layer 201 with a specific thickness ratio, so that the pre-oxidized metal substrate can not only ensure that its strength and overall density are not changed due to oxidation, but also effectively inhibit the number of active sites in the initial stage of vapor deposition, especially in the early stage of graphene lattice formation, and ensure that sufficient oxygen is precipitated to promote the formation of carbon atoms from methane cracking.

[0060] In addition, the second temperature is low and the oxidation time is long, so that low-temperature oxidation can be realized for a long time. On the one hand, low-temperature oxidation is conducive to the formation of cuprous oxide as the main product, and long-time oxidation can increase the oxidation degree of the initial metal substrate 1. On the other hand, low-temperature oxidation can make the copper foil have a greater depth of oxygen action under the same oxidation degree, and the internal oxygen elements in the metal oxide and / or metal sub-oxide with a greater depth are difficult to be completely removed unless the reduction time is long enough. Therefore, it is conducive to the long-term and continuous release of oxygen and the continuous generation of large-grained second graphene.

[0061] In some embodiments, the metal oxide layer 201 in the pre-oxidized metal substrate 200 can cover 99.6% to 100% of the surface of the metal substrate 10, so that the number of active sites on the surface of the pre-oxidized metal substrate 200 can be small, which is conducive to making the average grain size of the second graphene in the graphene layer 30 in the prepared composite conductor 100 larger, and further making the prepared composite conductor 100 have higher electrical conductivity, thermal conductivity, and mechanical strength.

[0062] In some embodiments, the mass ratio of metal oxide to metal suboxide in the first metal oxide layer 2011 ranges from (0.001-0.05): 1, such as 0.001: 1, 0.005: 1, 0.01: 1, 0.015: 1, 0.02: 1, 0.025: 1, 0.03: 1, 0.035: 1, 0.04: 1, 0.045: 1, 0.05: 1, etc. Within the ratio range, it is beneficial to make the average grain size of graphene in the graphene layer 30 in the prepared composite conductor 100 larger, and thus make the prepared composite conductor 100 have higher electrical conductivity, thermal conductivity and mechanical strength.

[0063] In some embodiments, the metal oxide includes, but is not limited to, one or more of copper oxide, aluminum oxide, nickel oxide, triniickel tetroxide, nickel suboxide, silver oxide, zinc oxide.

[0064] In some embodiments, the metal suboxide includes, but is not limited to, cuprous oxide (Cu2O).

[0065] In some embodiments, the ratio of the thickness of the first metal oxide layer 2011 to the thickness of the second metal oxide layer 2012 ranges from (0.1-9): 1, such as 0.1: 1, 0.5: 1, 1: 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, 3.5: 1, 4: 1, 4.5: 1, 5: 1, 5.5: 1, 6: 1, 6.5: 1, 7: 1, 7.5: 1, 8: 1, 8.5: 1, 9: 1, etc.

[0066] In some embodiments, when the metal substrate is a metal foil, the thickness of the metal substrate 10 ranges from 25-50 μm, such as 25 μm, 28 μm, 30 μm, 32 μm, 33 μm, 35 μm, 36 μm, 38 μm, 40 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 48 μm, 50 μm, etc.

[0067] In some embodiments, the thickness of the first metal oxide layer 2011 is 0.06-0.45 μm, such as 0.06 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, etc.

[0068] In some embodiments, the thickness of the second metal oxide layer 2012 is 0.05-0.6 μm, such as 0.05 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, etc.

[0069] In some embodiments, the thickness of the metal oxide layer 201 is 0.1-1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0070] In the thickness range of the first metal oxide layer 2011, the second metal oxide layer 2012, and the metal oxide layer 201, the oxygen element in the metal oxide layer 201 can be preserved at a sufficient concentration to promote the growth of graphene even after annealing with a reducing gas during the subsequent deposition of graphene.

[0071] In some embodiments, after obtaining the pre-oxidized metal substrate 200, further comprising: performing a deoxygenation and dehydration treatment on the pre-oxidized metal substrate 200.

[0072] Due to the presence of oxygen and water vapor physically adsorbed on the surface of the pre-oxidized metal substrate 200, these oxygen and water vapor can form chemical corrosion on the surface of the pre-oxidized metal substrate 200, which is not conducive to the control of the oxidation degree of the pre-oxidized metal substrate 200, resulting in affecting the repeatability of the composite conductor preparation under the same parameters. The deoxygenation and dehydration treatment can effectively remove the oxygen and water vapor physically adsorbed on the surface of the pre-oxidized metal substrate 200, especially the water vapor, thereby improving the repeatability of the preparation of the composite conductor 100.

[0073] In some embodiments, the deoxygenation and dehydration treatment comprises: performing a vacuum treatment on the pre-oxidized metal substrate 200.

[0074] In some embodiments, the vacuum treatment on the pre-oxidized metal substrate 200 comprises: placing the pre-oxidized metal substrate 200 in a sealed environment, vacuumizing to a vacuum degree below 0.1 Pa, and then maintaining for a period of time t3.

[0075] In some embodiments, the time t3 is 2-10 min, for example, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc. Within the range, it is conducive to quickly and effectively removing the oxygen and water vapor physically adsorbed on the surface of the pre-oxidized metal substrate 200.

[0076] In some embodiments, the reducing gas in the reducing atmosphere includes but is not limited to hydrogen.

[0077] In some embodiments, the reducing atmosphere further comprises a second inert gas, and the second inert gas includes but is not limited to one or more of nitrogen, helium, argon, and xenon.

[0078] In some embodiments, the volume ratio of the second inert gas to the reducing gas ranges from (0.5 to 2):1, for example, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.3:1, 1.5:1, 1.6:1, 1.8:1, 2:1, etc. Within this range, the pre-oxidized metal substrate 200 can be appropriately reduced, which is beneficial for preparing a second graphene with a large grain size, for preparing a graphene layer 30 with good crystallinity and film-forming properties, and further beneficial for preparing a composite conductor 100 with good electrical conductivity, thermal conductivity, and mechanical strength.

[0079] In some embodiments, the annealing temperature of the pre-oxidized metal substrate 200 is 1000~1055℃, for example, 1000℃, 1005℃, 1010℃, 1015℃, 1020℃, 1025℃, 1030℃, 1035℃, 1040℃, 1045℃, 1050℃, 1055℃, etc.; the annealing time is 30~40min, for example, 30min, 35min, 40min, etc. Within the temperature and time range, the pre-oxidized metal substrate 200 can be appropriately reduced, which is beneficial to preparing a second graphene with a large grain size, and beneficial to preparing a graphene layer 30 with good crystallinity and film-forming properties, and further beneficial to preparing a composite conductor 100 with good electrical conductivity, thermal conductivity and mechanical strength.

[0080] In some embodiments, the oxygen content in the pre-oxidized metal matrix 200 before annealing in a reducing atmosphere is 150~300ppm, for example, 150ppm, 180ppm, 200ppm, 230ppm, 250ppm, 280ppm, 300ppm, etc.

[0081] In some embodiments, the oxygen content in the pre-oxidized metal matrix 200 after annealing in a reducing atmosphere is 20 to 100 ppm, for example, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, etc.

[0082] In step B:

[0083] The first temperature range is 1000~1055℃, for example, 1000℃, 1005℃, 1010℃, 1015℃, 1020℃, 1025℃, 1030℃, 1035℃, 1040℃, 1045℃, 1050℃, 1055℃, etc. Within this temperature range, it is beneficial to deposit graphene with good crystallinity and large grain size.

[0084] The carbon source includes, but is not limited to, one or more of methane, natural gas, acetylene, propane, and other carbon source gases known for use in vapor deposition to produce graphene.

[0085] The carbon source gas flow rate is 3-40 seem, for example, 3 seem, 5 seem, 8 seem, 10 seem, 15 seem, 20 seem, 25 seem, 30 seem, 35 seem, 40 seem, and the like.

[0086] The protective gas includes, but is not limited to, one or more of nitrogen, helium, argon, xenon.

[0087] In some embodiments, the protective gas flow rate is 0-1000 seem, for example, 10 seem, 50 seem, 100 seem, 150 seem, 200 seem, 250 seem, 300 seem, 500 seem, 600 seem, 800 seem, 900 seem, 1000 seem, and the like. It is understood that when the protective gas flow rate is 0, no protective gas is introduced.

[0088] It is understood that the introduction of the protective gas is also stopped when the introduction of the carbon source is stopped.

[0089] In some embodiments, a reducing gas is also introduced while the carbon source is introduced. The reducing gas can be a reducing gas known for use in producing graphene by vapor deposition, for example, can include, but is not limited to, hydrogen.

[0090] In some embodiments, the reducing gas flow rate is 5-500 seem, for example, 5 seem, 10 seem, 50 seem, 100 seem, 150 seem, 200 seem, 250 seem, 300 seem, 350 seem, 400 seem, 450 seem, 500 seem, and the like.

[0091] It is understood that the introduction of the reducing gas is also stopped when the introduction of the carbon source is stopped.

[0092] In step C:

[0093] The oxygen-containing gas includes, but is not limited to, air, oxygen, a first inert gas containing oxygen, and the like. The first inert gas is described above.

[0094] In some embodiments, the flow rate of the oxygen-containing gas is 3-40 seem, for example, 3 seem, 5 seem, 8 seem, 10 seem, 15 seem, 20 seem, 25 seem, 30 seem, 35 seem, 40 seem, etc. Within the flow rate range, it is beneficial to have an appropriate oxygen content in the pre-oxidized metal substrate.

[0095] It can be understood that in the steps B-D, the type of the oxygen-containing gas introduced each time can be the same or different, the type of the carbon source introduced each time can be the same or different, the type of the reducing gas introduced each time can be the same or different, and the type of the protective gas introduced each time can be the same or different.

[0096] It can be understood that in the steps B-D, the flow rate of the oxygen-containing gas introduced each time can be the same or different, the flow rate of the carbon source introduced each time can be the same or different, the flow rate of the reducing gas introduced each time can be the same or different, and the flow rate of the protective gas introduced each time can be the same or different.

[0097] In the preparation method, the total time for introducing the carbon source is 60-90 min, for example, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, etc.

[0098] In the steps B-D, the time for introducing the carbon source each time can be the same or different.

[0099] In some embodiments, the time for introducing the carbon source each time is the same, and is 15-30 min, for example, 15 min, 20 min, 25 min, 30 min, etc.

[0100] In other embodiments, the time for introducing the carbon source each time is different, and the time for introducing the carbon source the previous time is (1 / 3-1 / 2) times the time for introducing the carbon source the next time. For example, the time for introducing the carbon source the first time is h1, the time for introducing the carbon source the second time h2=(1 / 3-1 / 2) x h1, the time for introducing the carbon source the third time h3=(1 / 3-1 / 2) x h2, and so on. In some embodiments, the time for introducing the carbon source the first time is 30-40 min.

[0101] In some embodiments, after introducing the oxygen-containing gas each time, the oxygen content in the pre-oxidized metal substrate can reach 20-100 ppm, for example, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, etc.

[0102] In some embodiments, before the carbon source is introduced into the deposition chamber, the carbon source is subjected to a pre-cracking treatment to release hydrogen atoms from the carbon source, forming free carbon.

[0103] The pre-cracking treatment is beneficial to effectively reducing the content of carbon impurities (i.e., insufficiently cracked substances) in the graphene layer during subsequent deposition of graphene, so that the graphene prepared has larger crystal domains and fewer grain boundaries, which is beneficial to preparing the composite conductor 100 with better electrical conductivity and thermal conductivity.

[0104] In some embodiments, the pre-cracking is performed in a cracking chamber.

[0105] In some embodiments, the pre-cracking is performed at a temperature of 850-1050℃, such as 850℃, 860℃, 880℃, 900℃, 920℃, 930℃, 950℃, 960℃, 980℃, 1000℃, 1020℃, 1030℃, 1050℃, etc.

[0106] In some embodiments, the medium for the pre-cracking is a metal oxide, which includes but is not limited to copper oxide.

[0107] In some embodiments, the medium for the pre-cracking can be a film layer, a plate layer, or a granular form.

[0108] The preparation method of the present application can supplement oxygen in time when the initial metal substrate 1 has a low oxygen content and thus has an increased number of active sites and cannot continue to generate graphene with a large grain size. In this way, on the one hand, it can ensure that the graphene has a large flake size during the entire deposition process, thereby improving the electrical conductivity, thermal conductivity, and mechanical properties of the composite conductor prepared; on the other hand, it can also promote the cracking of the carbon source, thereby promoting the rapid growth of graphene. In addition, the present application has low production cost and is suitable for large-scale mass production.

[0109] In a second aspect, referring to FIGS. 1-2, the present application provides a composite conductor 100, which includes a metal substrate 10, a transition layer 20 located on at least one surface of the metal substrate 10, and a graphene layer 30 located on a surface of the transition layer 20 away from the metal substrate 10, wherein the metal substrate 10 includes a first metal, the transition layer 20 includes a second metal and a first graphene, and the graphene layer 30 includes a second graphene.

[0110] The first metal includes but is not limited to one or more of a metal element and an alloy. The metal element includes but is not limited to one or more of Cu and Al, and the alloy includes but is not limited to one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy.

[0111] The second metal includes, but is not limited to, one or more of a metal element and an alloy. The metal element includes, but is not limited to, one or more of Cu and Al, and the alloy includes, but is not limited to, one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy.

[0112] It can be understood that the first metal and the second metal are the same or different. In at least one embodiment, the first metal and the second metal are the same. Further, in at least some embodiments, the first metal and the second metal are both Cu.

[0113] The average flake diameter of the first graphene is smaller than the average flake diameter of the second graphene.

[0114] In some embodiments, the average flake diameter of the first graphene ranges from 0.01 to 0.1 μm, such as 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, etc.

[0115] In some embodiments, the average flake diameter of the second graphene ranges from 2 to 6 μm, such as 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.2 μm, 3.5 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.6 μm, 4.8 μm, 5 μm, 5.3 μm, 5.5 μm, 5.8 μm, 6 μm, etc.

[0116] The flake diameter, i.e., the grain size, of the second graphene in the graphene layer 30 of the composite conductor 100 described herein is large, which can make the composite conductor 100 have high electrical conductivity, thermal conductivity, and mechanical strength.

[0117] Referring to FIG. 1, in some embodiments, the metal matrix 10 is a metal foil. Referring to FIG. 2, in other embodiments, the metal matrix 10 is a metal particle. In other embodiments, the metal matrix 10 can also be a metal wire, and a cross-sectional view of the metal wire can refer to FIG. 2.

[0118] In some embodiments, the mass ratio of the second metal to the first graphene in the transition layer 20 ranges from (0.5 to 50): 1, such as 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc. Within the range, it is beneficial to make the composite conductor 100 have high electrical conductivity, thermal conductivity, and mechanical strength.

[0119] In some embodiments, the thickness of the transition layer 20 ranges from 0.1 to 1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0120] In some embodiments, when the metal substrate 10 is a metal foil, the thickness of the metal foil ranges from 25 to 50 μm, for example, 25 μm, 28 μm, 30 μm, 32 μm, 33 μm, 35 μm, 36 μm, 38 μm, 40 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 48 μm, 50 μm, etc.

[0121] In some embodiments, the thickness of the graphene layer 30 ranges from 0.335 to 3 nm, for example, 0.335 nm, 0.4 nm, 0.5 nm, 0.8 nm, 1 nm, 1.2 nm, 1.3 nm, 1.5 nm, 1.6 nm, 1.8 nm, 2 nm, 2.1 nm, 2.3 nm, 2.5 nm, 2.6 nm, 2.8 nm, 3 nm, etc.

[0122] Within the thickness ranges of the transition layer 20 and the graphene layer 30, the composite conductor 100 can have high electrical conductivity, thermal conductivity and mechanical strength.

[0123] In some embodiments, the electrical conductivity of the composite conductor 100 ranges from 87 to 121% (IACS, International Annealed Copper Standard), for example, 87%, 90%, 92%, 93%, 95%, 96%, 98%, 100%, 102%, 103%, 105%, 106%, 107%, etc. It can be seen that the composite conductor 100 has high electrical conductivity, and the highest electrical conductivity can reach 121%.

[0124] The composite conductor 100 includes the metal substrate 10, the transition layer 20 and the graphene layer 30. The transition layer 20 includes metal and graphene, so that the bonding force between the metal substrate 10 and the graphene layer 30 can be effectively enhanced, and the electrical conductivity, thermal conductivity and mechanical strength of the composite conductor 100 can be effectively enhanced. In addition, the graphene in the graphene layer 30 has a large grain size and high uniformity, so that the composite conductor 100 has high electrical conductivity, thermal conductivity and mechanical strength.

[0125] In a third aspect, the embodiments of the present application also provide an application of the composite conductor 100, which can be used in any device requiring electrical conductivity and / or thermal conductivity, such as a conductor of an electric wire, a cable, an electric contact, etc.

[0126] The application will be described in detail below through specific examples. The following examples are only part of the examples of the application and are not a limitation of the application. The raw materials used in the following examples are commercially available unless otherwise specified.

[0127] Example 1

[0128] Step A, expose the copper foil to air, and treat it at 105°C for 3h using an electric hot plate to obtain a pre-oxidized copper foil; place the pre-oxidized copper foil in a quartz boat, push it into a CVD tube furnace, and vacuumize it to 0.1 Pa and stabilize it for 2 min, then reduce anneal it at 1025°C for 35 min in an Ar2 and H2 (volume ratio 2:1) mixed gas atmosphere;

[0129] Pre-oxidized copper foil includes a metal substrate and a metal oxide layer on one surface of the metal substrate, the metal oxide layer includes a first metal oxide layer combined with the metal substrate and a second metal oxide layer combined with the first metal oxide layer away from the surface of the metal substrate, the metal substrate includes copper, the first metal oxide layer includes copper oxide and cuprous oxide, and the second metal oxide layer includes copper oxide, the thickness of the metal substrate is 30 µm, the thickness of the first metal oxide layer is 0.25 µm, the thickness of the second metal oxide layer is 0.32 µm, and the mass ratio of copper oxide to cuprous oxide in the first metal oxide layer is 0.03:1;

[0130] The content of oxygen element in the pre-oxidized copper foil obtained after treating the electric hot plate at 105°C for 3h is about 225 ppm, and the content of oxygen element in the pre-oxidized copper foil after reduction annealing is about 60 ppm;

[0131] Step B, then introduce CH4 gas (flow rate 20 sccm) into the system for 40 min;

[0132] Step C, stop introducing CH4 gas, and immediately introduce oxygen gas (flow rate 20 sccm) into the tube furnace for 2 min to replenish the oxygen element in the pre-oxidized metal substrate to about 60 ppm again, realizing secondary oxygen replenishment; then, stop introducing oxygen gas and change to introducing CH4 gas (flow rate 22 sccm) into the tube furnace for 20 min, then stop introducing CH4 gas, open the furnace cover, and naturally cool to room temperature to obtain a composite conductor.

[0133] The composite conductor of the present embodiment includes a copper layer, a transition layer on one surface of the copper layer, and a graphene layer on a surface of the transition layer away from the copper layer, the transition layer includes copper and first graphene, and the graphene layer includes second graphene.

[0134] Example 2

[0135] This example is basically the same as Example 1, except that:

[0136] In Step A of this example, the copper foil was treated at 60°C for 1 h using an electric hot plate, at which time the oxygen content in the copper foil was about 150 ppm, the thickness of the first metal oxide layer was 0.06 µm, the thickness of the second metal oxide layer was 0.05 µm, and the mass ratio of cupric oxide to cuprous oxide in the first metal oxide layer was 0.001:1. After the reduction anneal, the oxygen content in the pre-oxidized copper foil was about 20 ppm;

[0137] In Step C of this example, oxygen was introduced into the tube furnace (flow rate of 3 seem) for 2 min, so that the oxygen content in the pre-oxidized metal substrate was replenished to about 20 ppm.

[0138] Example 3

[0139] This example is basically the same as Example 1, except that:

[0140] In Step A of this example, the copper foil was treated at 150°C for 3 h using an electric hot plate, at which time the oxygen content in the copper foil was about 300 ppm, the thickness of the first metal oxide layer was 0.45 µm, the thickness of the second metal oxide layer was 0.6 µm, and the mass ratio of cupric oxide to cuprous oxide in the first metal oxide layer was 0.05:1. After the reduction anneal, the oxygen content in the pre-oxidized copper foil was about 100 ppm;

[0141] In Step C of this example, oxygen was introduced into the tube furnace (flow rate of 40 seem) for 2 min, so that the oxygen content in the pre-oxidized metal substrate was replenished to about 100 ppm.

[0142] Example 4

[0143] This example is basically the same as Example 1, except that:

[0144] In Step B of this example, the anneal was performed at 1000°C for 60 min, after which the oxygen content in the pre-oxidized copper foil was about 70 ppm;

[0145] In Step C of this example, oxygen was introduced into the tube furnace (flow rate of 15 seem) for 2 min, so that the oxygen content in the pre-oxidized metal substrate was replenished to about 70 ppm.

[0146] Example 5

[0147] This example is basically the same as Example 1, except that:

[0148] In Step B of this example, the anneal was performed at 1055°C for 60 min, after which the oxygen content in the pre-oxidized copper foil was about 40 ppm;

[0149] In step C of this example, oxygen was introduced into the tube furnace (flow rate 25 sccm) for 2 min to replenish the oxygen element in the pre-oxidized metal matrix to about 40 ppm.

[0150] Example 6

[0151] This example is basically the same as Example 1, except that the flow rate of CH4 gas in steps B and C of this example is 3 sccm.

[0152] Example 7

[0153] This example is basically the same as Example 1, except that the flow rate of CH4 gas in steps B and C of this example is 40 sccm.

[0154] Example 8

[0155] This example is basically the same as Example 1, except that after step C, it further includes:

[0156] Step D: Repeat step C a total of 1 time. When repeating step C, the CH4 gas is introduced into the tube furnace for 10 min.

[0157] Example 9

[0158] This example is basically the same as Example 1, except that after step C, it further includes:

[0159] Step D: Repeat step C a total of 3 times. When repeating step C, the CH4 gas is introduced into the tube furnace for 10 min, 5 min, and 2.5 min, respectively.

[0160] Example 10

[0161] This example is basically the same as Example 1, except that in steps B and C of this example, the CH4 gas is introduced into the tube furnace for 30 min.

[0162] Example 11

[0163] This example is basically the same as Example 1, except that in step A of this example, "then annealed at 1025°C for 35 min under Ar2 atmosphere" is used to replace "then reduced annealed at 1025°C for 35 min under Ar2 and H2 (volume ratio 2:1) mixed gas atmosphere" in Example 1.

[0164] Comparative Example 1

[0165] This comparative example is basically the same as Example 1, except that the composite conductor prepared in this comparative example does not undergo secondary oxygen replenishment. Specifically, it includes:

[0166] Step A, expose the copper foil to air, treat at 105℃ for 3h using an electric hot plate to obtain a pre-oxidized copper foil; put the pre-oxidized copper foil into a quartz boat, push into a CVD tube furnace and vacuumize to 0.1Pa and stabilize for 2min, then reduce anneal at 1025℃ for 35min under Ar2 and H2 (volume ratio 2:1) mixed gas atmosphere;

[0167] The pre-oxidized copper foil comprises a metal substrate and a metal oxide layer located on one surface of the metal substrate, the metal oxide layer comprises a first metal oxide layer combined with the metal substrate and a second metal oxide layer combined with the first metal oxide layer and away from the surface of the metal substrate, the metal substrate comprises copper, the first metal oxide layer comprises cupric oxide and cuprous oxide, and the second metal oxide layer comprises cupric oxide, the thickness of the first metal oxide layer is 0.25µm, the thickness of the second metal oxide layer is 0.325µm, and the mass ratio of cupric oxide to cuprous oxide in the first metal oxide layer is 0.03:1;

[0168] The content of oxygen element in the pre-oxidized copper foil obtained after the electric hot plate is treated at 105℃ for 3h is about 225ppm, and the content of oxygen element in the pre-oxidized copper foil after reduction anneal is about 60ppm;

[0169] Step B, then introduce CH4 gas (flow rate 20sccm) into the system for 60min, then stop introducing CH4 gas, open the furnace cover and naturally cool to room temperature to obtain a composite conductor.

[0170] The electrical conductivity IACS and mechanical properties of the composite conductor 100 of Examples 1~11 and Comparative Example 1 were tested, and the test results are shown in Table 1.

[0171] Table 1:

[0172]

[0173] From Table 1, it can be seen that:

[0174] The electrical conductivity of the composite conductor 100 of Examples 1~11 is above 119%, and the highest can reach 121%, which is obviously improved compared with the electrical conductivity of copper 100% and the composite conductor of Comparative Example 1, so the composite conductor 100 of the present application has better electrical conductivity.

[0175] The Vickers hardness of the composite conductor 100 of Examples 1~11 is above 56.0, so the composite conductor 100 of the present application has strong hardness.

[0176] The technical solutions provided by the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method of making a composite conductor, wherein, The method comprises the following steps: A. providing an initial metal substrate, subjecting the initial metal substrate to an oxidation treatment to obtain a pre-oxidized metal substrate, the pre-oxidized metal substrate comprising a metal substrate and a metal oxide layer located on at least one surface of the metal substrate, the metal oxide layer comprising a first metal oxide layer combined with the metal substrate and a second metal oxide layer combined with the first metal oxide layer and away from the surface of the metal substrate, the metal substrate comprising a first metal, the first metal oxide layer comprising a metal oxide and a metal suboxide, and the second metal oxide layer comprising a metal oxide, the mass ratio of the metal oxide to the metal suboxide in the first metal oxide layer being in the range of (0.001-0.05):1; B. subjecting the pre-oxidized metal substrate to an annealing treatment in a reducing atmosphere, the oxygen content of the pre-oxidized metal substrate before the annealing treatment in the reducing atmosphere being 150-300 ppm, the oxygen content of the pre-oxidized metal substrate after the annealing treatment in the reducing atmosphere being 20-100 ppm, then placing the pre-oxidized metal substrate in a deposition chamber, and introducing a carbon source into the deposition chamber at a first temperature for a period of time; C. stopping the introduction of the carbon source and instead introducing an oxygen-containing gas for a period of time, then stopping the introduction of the oxygen-containing gas and instead introducing the carbon source; D. repeating the step C. for n times, wherein n is an integer greater than or equal to 0, to obtain a composite conductor.

2. The production method according to claim 1, wherein The material of the initial metal substrate comprises one or more of a metal element and an alloy, the metal element comprises one or more of Cu and Al, and the alloy comprises one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy.

3. The preparation method of claim 2, wherein the initial metal substrate comprises a first initial metal substrate, the material of the first initial metal substrate comprises one or more of a metal element and an alloy, the metal element comprises one or more of Cu and Al, and the alloy comprises one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy; or the initial metal substrate comprises a first initial metal substrate and a second initial metal substrate located on the surface of the first initial metal substrate, the material of the first initial metal substrate and the second initial metal substrate each independently comprises one or more of a metal element and an alloy, the metal element comprises one or more of Cu and Al, and the alloy comprises one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy; and the material of the first initial metal substrate and the second initial metal substrate is the same or different.

4. The preparation method of claim 1, wherein the first metal comprises one or more of a metal element and an alloy, the metal element comprises one or more of Cu and Al, and the alloy comprises one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy; and / or the metal oxide comprises one or more of copper oxide, aluminum oxide, nickel oxide, triniickel tetroxide, di-nickel trioxide, silver oxide, and zinc oxide; and / or the metal suboxide comprises cuprous oxide.

5. The preparation method of claim 1, wherein, the carbon source comprises one or more of methane, natural gas, acetylene, propane; and / or the oxygen-containing gas comprises air, oxygen, oxygen-containing inert gas.

6. The preparation method of claim 1, wherein, the initial metal substrate is a metal particle, a metal foil or a metal wire; and / or the metal substrate is a metal particle, a metal foil or a metal wire.

7. The preparation method of claim 1, wherein, in the pre-oxidized metal substrate, the metal oxide layer covers 99.6% to 100% of the surface of the metal substrate; and / or the thickness of the first metal oxide layer is 0.06 to 0.45 μm; and / or the thickness of the second metal oxide layer is 0.05 to 0.6 μm; and / or the ratio of the thickness of the first metal oxide layer to the thickness of the second metal oxide layer is in the range of (0.1-9): 1; and / or the thickness of the metal oxide layer is 0.1 to 1 μm.

8. The preparation method of claim 1, wherein, the first temperature is in the range of 1000 to 1055 °C; and / or the gas flow rate of the carbon source is 3 to 40 sccm; and / or the flow rate of the oxygen-containing gas is 3 to 40 sccm; and / or the total time for introducing the carbon source is 60 to 90 min; and / or the temperature of the annealing treatment is 1000 to 1055 °C and the time is 30 to 40 min.

9. The preparation method of claim 1, wherein, the time for introducing the carbon source each time is the same and is 15 to 30 min; and / or the time for introducing the carbon source each time is different, and the time for introducing the carbon source in the previous time is (1 / 3-1 / 2) times the time for introducing the carbon source in the later time, and the time for introducing the carbon source in the first time is 30 to 40 min.

10. The production method according to claim 1, wherein The oxidation treatment of the initial metal substrate comprises: placing the initial metal substrate in an oxygen-containing atmosphere, and heat treating at a second temperature for a time t1.

11. The preparation method of claim 10, wherein, the oxygen-containing atmosphere comprises air, oxygen, oxygen-containing inert gas; and / or the second temperature is in the range of 60 to 150 °C, and the time t1 is in the range of 1 to 5 h.

12. The production method as claimed in claim 1, wherein, After obtaining the pre-oxidized metal substrate, further comprising: placing the pre-oxidized metal substrate in a closed environment, vacuumizing to a vacuum degree of 0.1 Pa or less, and then maintaining for a time t3, wherein the time t3 is 2 to 10 min.

13. The preparation method of claim 1, wherein, the reducing gas in the reducing atmosphere comprises hydrogen; and / or the reducing atmosphere further comprises a second inert gas, the second inert gas comprises one or more of nitrogen, helium, argon, xenon, and the volume ratio of the second inert gas to the reducing gas in the reducing atmosphere is in the range of (0.5-2):

1.

14. The production method according to claim 1, wherein The protective gas is introduced at the same time as the carbon source.

15. The preparation method of claim 14, wherein, the protective gas comprises one or more of nitrogen, helium, argon, xenon; and / or The gas flow of the protective gas is 0-1000 sccm.

16. The production method as claimed in claim 1, wherein, The reducing gas is supplied while the carbon source is supplied.

17. The preparation method of claim 16, wherein, the reducing gas comprises hydrogen; and / or The flow of the reducing gas is 5-500 sccm.

18. A composite conductor, wherein, The composite conductor is prepared by the preparation method of any one of claims 1-17, and comprises a metal matrix, a transition layer on at least one surface of the metal matrix, and a graphene layer on a surface of the transition layer away from the metal matrix, wherein the metal matrix comprises a first metal, the transition layer comprises a second metal and a first graphene, and the graphene layer comprises a second graphene, the average flake diameter of the first graphene is smaller than that of the second graphene.

19. The composite conductor of claim 18, wherein, the first metal comprises one or more of a metal element and an alloy, the metal element comprises one or more of Cu and Al, and the alloy comprises one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy; and / or the second metal comprises one or more of a metal element and an alloy, the metal element comprises one or more of Cu and Al, and the alloy comprises one or more of copper-nickel alloy, copper-silver alloy, and copper-zinc alloy; and / or the average flake diameter of the first graphene ranges from 0.01 to 0.1 μm; and / or the average flake diameter of the second graphene ranges from 2 to 6 μm; and / or the mass ratio of the metal to the first graphene in the transition layer ranges from (0.5-50):1; and / or the metal matrix is a metal particle, a metal wire, or a metal foil; and / or the thickness of the transition layer ranges from 0.1 to 1 μm; and / or the thickness of the graphene layer ranges from 0.335 to 3 nm; and / or the electrical conductivity of the composite conductor ranges from 87 to 121%.

20. Use of the composite conductor of any one of claims 18-19 as an electric wire or cable or an electric contact head.

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