A graphene-copper composite material and its preparation method

Abstract

This invention belongs to the field of composite materials, and particularly relates to a graphene-copper composite material and its preparation method. The preparation method provided by this invention includes the following steps: a) preparing graphene copper foil, wherein the graphene copper foil comprises a copper substrate and graphene layers deposited on both sides of the copper substrate; b) ablating both sides of the graphene copper foil using a femtosecond laser to form exposed areas of the copper substrate without graphene layer coverage; c) stacking two or more layers of graphene copper foil treated in step b), with the exposed areas of the copper substrate of adjacent layers of graphene copper foil in contact, to obtain a material to be pressed; d) hot-pressing the material to be pressed to achieve metallurgical bonding of the exposed areas of the copper substrate of adjacent layers of graphene copper foil, thereby obtaining the graphene-copper composite material. The preparation method provided by this invention can reduce the damage to the graphene film during the hot-pressing composite process of multilayer graphene copper foil, and the resulting graphene-copper composite material has excellent electrical conductivity.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, and particularly relates to a graphene-copper composite material and its preparation method. Background Technology

[0002] Copper, due to its relatively high electrical conductivity, chemical stability, mature manufacturing processes, abundant natural reserves, and recyclability, has been widely used in various fields such as electronics, electrical engineering, aerospace, machinery, metallurgy, transportation, and power generation. However, the inherent resistance heating phenomenon in copper-based materials not only wastes a significant amount of electricity but also limits the output power and reliability of motors. To date, considerable efforts have been made to improve the conductivity of copper. Methods for purifying and preparing high-purity copper have gradually approached their physical limits, but the conductivity has only increased by about 3%. While the addition of other metallic materials (such as silver and tin) and non-metallic elements (such as carbon or its allotropes) to form novel alloys or copper-based composite materials has significantly improved mechanical strength, most studies have shown a decrease in electrical conductivity.

[0003] Graphene, a novel carbon material consisting of a single layer of tightly packed carbon atoms forming a two-dimensional honeycomb structure, has attracted widespread attention due to its unique structure and extremely high carrier mobility. The effective combination of graphene and copper to prepare graphene-copper composites with excellent electrical conductivity is considered by the industry to be one of the most promising areas for development. Currently, graphene-copper composites prepared by in-situ growth of graphene layers on copper foil have achieved high electrical conductivity. This method first uses chemical vapor deposition to catalytically decompose the carbon source under high temperature conditions, forming a graphene film on a copper foil substrate. This reduces the introduction of impurity atoms and the generation of defects, avoiding structural damage to the graphene film. Then, the multilayer graphene copper foil is hot-pressed and sintered to obtain a copper-based composite material with uniform and oriented graphene distribution and high electrical conductivity. However, this method uses graphene copper foil with graphene grown on both sides. Applying high pressure during the hot-pressing process disrupts the integrity and continuity of the graphene film, hindering further improvement in the conductivity of the graphene-copper composite material. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a graphene-copper composite material and its preparation method. The preparation method provided by the present invention can reduce the damage to the graphene film layer during the hot pressing composite process of multilayer graphene copper foil, and the obtained graphene-copper composite material has excellent electrical conductivity.

[0005] This invention provides a method for preparing a graphene-copper composite material, comprising the following steps:

[0006] a) Prepare a graphene copper foil, wherein the graphene copper foil comprises a copper substrate and graphene layers deposited on both sides of the copper substrate.

[0007] b) Use a femtosecond laser to ablate both sides of the graphene copper foil to form an exposed copper substrate area without graphene layer coverage.

[0008] c) Stack two or more layers of graphene copper foil that have been treated in step b), with the exposed copper substrate areas of two adjacent layers of graphene copper foil in contact, to obtain the material to be pressed.

[0009] d) The material to be pressed is hot-pressed to achieve metallurgical bonding of the exposed copper substrate areas of two adjacent layers of graphene copper foil in the material, thereby obtaining a graphene-copper composite material.

[0010] In step d), the pressure of the hot pressing is 5-20 MPa, and the temperature of the hot pressing is 650-950 °C.

[0011] Preferably, in step a), the thickness of the copper substrate is 15–40 μm; and the number of graphene layers deposited on one side of the copper substrate is 1–5.

[0012] Preferably, in step b), the femtosecond laser has a laser power of 5-15W, a pulse width of 100-300fs, a frequency of 500-2000kHz, and a scanning speed of 500-2000mm / s.

[0013] Preferably, in step b), the ablation is carried out in a vacuum or inert gas atmosphere.

[0014] Preferably, in step b), the width of the exposed area of ​​the copper substrate is 20–100 μm.

[0015] Preferably, in step c), the copper substrate exposed areas of the two adjacent graphene copper foil layers completely overlap.

[0016] Preferably, in step c), the number of layers is 10 to 500.

[0017] Preferably, in step c), the lamination is carried out in an inert gas atmosphere.

[0018] Preferably, in step d), the vacuum degree of the hot pressing is 4 × 10⁻⁶. -3 ~7×10 -3 Pa; the hot pressing time is 10 to 60 minutes.

[0019] This invention provides a graphene-copper composite material, which is prepared according to the preparation method described in the above technical solution.

[0020] Compared with existing technologies, this invention provides a graphene-copper composite material and its preparation method. The preparation method provided by this invention includes the following steps: a) preparing graphene copper foil, wherein the graphene copper foil includes a copper substrate and graphene layers deposited on both sides of the copper substrate; b) using a femtosecond laser to ablate both sides of the graphene copper foil to form exposed areas of the copper substrate without graphene layer coverage; c) stacking two or more layers of graphene copper foil treated in step b), with the exposed areas of the copper substrate of adjacent layers of graphene copper foil in contact, to obtain a material to be pressed; d) hot-pressing the material to be pressed to achieve metallurgical bonding of the exposed areas of the copper substrate of adjacent layers of graphene copper foil, to obtain a graphene-copper composite material; in step d), the pressure of the hot pressing is 5-20 MPa, and the temperature of the hot pressing is 650-950℃. The preparation method provided by this invention first utilizes a femtosecond laser to form copper substrate exposure areas with predetermined trajectories on both sides of a graphene-copper foil; then, the graphene-copper foils are stacked, and the copper substrate exposure areas of adjacent layers of graphene-copper foil are brought into contact; finally, under a temperature below the melting point of the copper substrate and a pressure that does not cause significant deformation, atomic diffusion occurs in the copper substrate exposure areas of adjacent layers of graphene-copper foil to achieve metallurgical bonding, reducing the damage to the integrity and continuity of graphene under high pressure. The technical solution provided by this invention can improve the continuity and integrity of graphene in graphene-copper composite materials, and the prepared material has high conductivity, making it more conducive to promotion and application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 This is a microstructure diagram of the graphene-copper composite material provided in Example 1 of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for preparing a graphene-copper composite material, comprising the following steps:

[0025] a) Prepare a graphene copper foil, wherein the graphene copper foil comprises a copper substrate and graphene layers deposited on both sides of the copper substrate.

[0026] b) Use a femtosecond laser to ablate both sides of the graphene copper foil to form an exposed copper substrate area without graphene layer coverage.

[0027] c) Stack two or more layers of graphene copper foil that have been treated in step b), with the exposed copper substrate areas of two adjacent layers of graphene copper foil in contact, to obtain the material to be pressed.

[0028] d) The material to be pressed is hot-pressed to achieve metallurgical bonding of the exposed copper substrate areas of two adjacent layers of graphene copper foil, thereby obtaining a graphene-copper composite material.

[0029] In the preparation method provided by the present invention, in step a), the purity of the copper substrate is preferably ≥99.9%. A high-purity copper substrate has less impurity content, which can reduce scattering during electron transport and improve the conductivity of the material. The thickness of the copper substrate is preferably 15-40 μm, specifically 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm or 40 μm. The number of graphene layers deposited on one side of the copper substrate is preferably 1-5 layers, specifically 1 layer, 2 layers, 3 layers, 4 layers or 5 layers.

[0030] In the preparation method provided by the present invention, in step b), a pre-drawn laser scanning trajectory is first imported into a femtosecond laser system, and then a femtosecond laser scan is performed on the graphene copper foil. The graphene layer in the area swept by the laser spot is rapidly ablated and vaporized. The copper substrate is exposed after the graphene layer is ablated and removed, forming a copper substrate exposed area without graphene layer coverage.

[0031] In the preparation method provided by this invention, in step b), the laser power of the femtosecond laser is preferably 5-15W, specifically 5W, 6W, 7W, 8W, 9W, 10W, 11W, 12W, 13W, 14W, or 15W; the pulse width of the femtosecond laser is preferably 100-300fs, specifically 100fs, 120fs, 150fs, 170fs, 200fs, 230fs, 250fs, 270fs, or 300fs; the frequency of the femtosecond laser is preferably 500-2000kHz, specifically 500kHz, 700kHz, 100kHz, or 2000kHz. The scanning speed of the femtosecond laser is preferably 500–2000 mm / s, specifically 500 mm / s, 600 mm / s, 700 mm / s, 800 mm / s, 900 mm / s, 1000 mm / s, 1100 mm / s, 1200 mm / s, 1300 mm / s, 1400 mm / s, 1500 mm / s, 1600 mm / s, 1700 mm / s, 1800 mm / s, 1900 mm / s, or 2000 mm / s.

[0032] In the preparation method provided by the present invention, in step b), in order to avoid oxidation of the copper substrate exposed after graphene ablation, the ablation process is preferably carried out in a vacuum or inert gas atmosphere, wherein the inert gas includes, but is not limited to, nitrogen and / or argon.

[0033] In the preparation method provided by the present invention, in step b), the specific process of ablation preferably includes: first ablation of one side of the graphene copper foil, then flipping the graphene copper foil and ablation of the other side of the graphene copper foil.

[0034] In the preparation method provided by the present invention, in step b), the range of the copper substrate exposure area on both sides of the graphene copper foil is preferably the same, that is, the laser scanning trajectory is the same when performing femtosecond laser ablation.

[0035] In the preparation method provided by this invention, in step b), the width of the exposed copper substrate area of ​​the graphene copper foil is preferably 20–100 μm, specifically 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm. In this invention, the width of the exposed copper substrate area refers to the width of the ablation trajectory left by the ablation removal of graphene during the process of a femtosecond laser scanning the surface of the graphene copper foil according to a preset trajectory.

[0036] In the preparation method provided by the present invention, in step b), the area ratio of the copper substrate exposed area on the surface of the graphene copper foil is preferably 2% to 10%, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0037] In the preparation method provided by this invention, in step c), the lamination is preferably carried out in a pre-prepared mold, and the mold material is preferably a high-temperature resistant material. In this invention, considering that graphite molds have a low coefficient of thermal expansion, can withstand high temperatures without cracking, and possess high strength under high-temperature conditions, enabling them to be used under high pressure, graphite molds are preferably used. In this invention, the inner diameter of the mold is preferably slightly larger than that of the graphene copper foil to avoid contact between the graphene-copper composite material and the mold during subsequent hot pressing, which could lead to uneven product thickness.

[0038] In the preparation method provided by the present invention, in step c), in order to avoid the introduction of impurity atoms and oxidation of the copper foil substrate, the lamination is preferably carried out in an inert gas atmosphere, the inert gas including but not limited to nitrogen and / or argon.

[0039] In the preparation method provided by the present invention, in step c), the number of layers is preferably 10 to 500, specifically 10, 20, 30, 40, 50, 70, 100, 120, 150, 200, 250, 300, 350, 400, 450 or 500 layers.

[0040] In the preparation method provided by the present invention, in step c), the copper substrate exposed areas of two adjacent graphene copper foil layers are preferably completely overlapping in the stacked material to be pressed.

[0041] In the preparation method provided by this invention, in step d), the pressure of the hot pressing is preferably 5-20 MPa, specifically 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, or 20 MPa; the temperature of the hot pressing is preferably 650-950℃, specifically 650℃, 670℃, 700℃, 720℃, 750℃, 780℃, 800℃, 820℃, 850℃, 870℃, 900℃, 920℃, or 950℃; the vacuum degree of the hot pressing is preferably 4×10⁻⁶. -3 ~7×10 -3 Pa, specifically 4 × 10 -3 Pa, 4.2 × 10 -3 Pa, 4.5 × 10 -3 Pa, 4.7 × 10-3 Pa, 5×10 -3 Pa, 5.2 × 10 -3 Pa, 5.5 × 10 -3 Pa, 5.7 × 10 -3 Pa, 6×10 -3 Pa, 6.2 × 10 -3 Pa, 6.5 × 10 -3 Pa, 6.7 × 10 -3 Pa or 7×10 -3 Pa; the hot pressing time is preferably 10 to 60 minutes, specifically 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes.

[0042] The present invention also provides a graphene-copper composite material, which is prepared according to the preparation method described in the above technical solution.

[0043] The technical solution provided by this invention can reduce the damage to the graphene film during the hot-pressing composite process of multilayer graphene and copper foil, and the resulting graphene-copper composite material exhibits superior electrical conductivity. More specifically, the technical solution provided by this invention has at least the following advantages:

[0044] (1) Femtosecond lasers have high energy density (which can exceed the graphene ablation threshold) and can ablate and remove graphene in the area swept by the laser spot.

[0045] (2) The short pulse width of the femtosecond laser suppresses the formation of the heat-affected zone, and the thermal damage to the copper substrate can be ignored.

[0046] (3) According to the preset femtosecond laser scanning path, the copper substrate exposed areas without graphene layer are regularly distributed on the surface of the copper foil, which is conducive to the copper substrate exposed areas of adjacent graphene copper foils overlapping each other during the subsequent hot pressing process.

[0047] (4) At a temperature below the melting point of copper foil and under pressure without significant deformation, the copper interfaces in the exposed area of ​​the copper substrate of the stacked graphene copper foil come into contact with each other, and atomic diffusion occurs to achieve metallurgical bonding, which reduces the damage to the integrity and continuity of graphene under high pressure.

[0048] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0049] Example 1

[0050] (1) Prepare a graphene copper foil, wherein the graphene copper foil includes a copper substrate and graphene layers deposited on both sides of the copper substrate; wherein the copper substrate has a thickness of 25 μm, a purity of 99.9%, and one graphene layer is deposited on each side of the copper substrate.

[0051] (2) Place the graphene copper foil on the worktable of the femtosecond laser chamber and fix it in place. Turn on the femtosecond laser system and adjust the laser to face the scanning starting point. Import the laser scanning trajectory drawn according to the size of the graphene copper foil into the femtosecond laser system, adjust the laser parameters, and scan the graphene copper foil. The graphene in the range swept by the laser spot is rapidly ablated and vaporized, and the copper substrate is exposed after the graphene is ablated and removed. The specific laser parameters are: laser power of 5W, pulse width of 100fs, frequency of 2000kHz, and scanning speed of 500mm / s. In order to avoid oxidation of the copper substrate exposed after the graphene is ablated, the laser scanning should be carried out in a nitrogen atmosphere. After the femtosecond laser treatment is completed, a copper substrate exposure area without graphene layer coverage is formed on the surface of the graphene copper foil. The width of the exposure area is 20μm, and the area ratio of the exposure area on the surface of the graphene copper foil is 2%.

[0052] (3) Flip the graphene copper foil sample after femtosecond laser treatment in step (2) and fix it on the laser processing stage. Scan the graphene copper foil under the same laser parameters so that the copper substrate exposure areas on both sides of the graphene copper foil overlap.

[0053] (4) After the femtosecond laser scanning is completed, the processed graphene copper foil sample is transferred to a pre-prepared graphite mold. The graphite mold is also placed in a nitrogen atmosphere to avoid the introduction of impurity atoms and oxidation of the copper foil substrate. The inner diameter of the graphite mold is slightly larger than that of the graphene copper foil to avoid the graphene-copper composite material from contacting the mold during the subsequent hot pressing process, which could lead to uneven thickness of the product.

[0054] (5) Repeat steps (2) to (4) to stack multiple layers of femtosecond laser-scanned graphene copper foil inside the graphite mold. The number of sample layers can be 20, and the copper substrate exposure areas of adjacent graphene copper foil layers completely overlap. Transfer the mold containing the stacked graphene copper foil to the vacuum hot pressing chamber for vacuum hot pressing. The vacuum hot pressing degree reaches 5.5 × 10⁻⁶. -3 The hot-pressing temperature was 950℃, the pressure was 10MPa, and the holding time was 30min; after vacuum hot pressing, a graphene-copper composite material was obtained (microstructure as shown in the figure). Figure 1 (As shown).

[0055] The electrical conductivity of the graphene-copper composite material prepared in this embodiment was tested, and its conductivity was 109.2% IACS.

[0056] Example 2

[0057] (1) Prepare a graphene copper foil, wherein the graphene copper foil includes a copper substrate and graphene layers deposited on both sides of the copper substrate; wherein the copper substrate has a thickness of 25 μm, a purity of 99.9%, and 3 graphene layers are deposited on each side of the copper substrate.

[0058] (2) Place the graphene copper foil on the worktable of the femtosecond laser chamber and fix it in place. Turn on the femtosecond laser system and adjust the laser to face the scanning starting point. Import the laser scanning trajectory drawn according to the size of the graphene copper foil into the femtosecond laser system, adjust the laser parameters, and scan the graphene copper foil. The graphene in the range swept by the laser spot is rapidly ablated and vaporized, and the copper substrate is exposed after the graphene is ablated and removed. The specific laser parameters are: laser power of 10W, pulse width of 200fs, frequency of 1000kHz, and scanning speed of 1000mm / s. In order to avoid oxidation of the copper substrate exposed after the graphene is ablated, the laser scanning should be carried out in a nitrogen atmosphere. After the femtosecond laser treatment is completed, a copper substrate exposure area without graphene layer coverage is formed on the surface of the graphene copper foil. The width of the exposure area is 50μm, and the area of ​​the exposure area on the surface of the graphene copper foil accounts for 5%.

[0059] (3) Flip the graphene copper foil sample after femtosecond laser treatment in step (2) and fix it on the laser processing stage. Scan the graphene copper foil under the same laser parameters so that the copper substrate exposure areas on both sides of the graphene copper foil overlap.

[0060] (4) After the femtosecond laser scanning is completed, the processed graphene copper foil sample is transferred to a pre-prepared graphite mold. The graphite mold is also placed in a nitrogen atmosphere to avoid the introduction of impurity atoms and oxidation of the copper foil substrate. The inner diameter of the graphite mold is slightly larger than that of the graphene copper foil to avoid the graphene-copper composite material from contacting the mold during the subsequent hot pressing process, which could lead to uneven thickness of the product.

[0061] (5) Repeat steps (2) to (4) to stack multiple layers of femtosecond laser-scanned graphene copper foil inside the graphite mold. The number of sample layers can be 100, and the copper substrate exposure areas of adjacent graphene copper foil layers completely overlap. Transfer the mold containing the stacked graphene copper foil to the vacuum hot pressing chamber for vacuum hot pressing. The vacuum hot pressing degree reaches 5.5 × 10⁻⁶. -3 The hot pressing temperature was 850℃, the pressure was 15MPa, and the holding time was 60min; after vacuum hot pressing, graphene-copper composite material was obtained.

[0062] The electrical conductivity of the graphene-copper composite material prepared in this embodiment was tested, and its conductivity was 106.5% IACS.

[0063] Example 3

[0064] (1) Prepare a graphene copper foil, wherein the graphene copper foil includes a copper substrate and graphene layers deposited on both sides of the copper substrate; wherein the copper substrate has a thickness of 25 μm, a purity of 99.9%, and 5 graphene layers are deposited on each side of the copper substrate.

[0065] (2) Place the graphene copper foil on the worktable of the femtosecond laser chamber and fix it in place. Turn on the femtosecond laser system and adjust the laser to face the scanning starting point. Import the laser scanning trajectory drawn according to the size of the graphene copper foil into the femtosecond laser system, adjust the laser parameters, and scan the graphene copper foil. The graphene in the range swept by the laser spot is rapidly ablated and vaporized, and the copper substrate is exposed after the graphene is ablated and removed. The specific laser parameters are: laser power of 15W, pulse width of 300fs, frequency of 500kHz, and scanning speed of 2000mm / s. In order to avoid oxidation of the copper substrate exposed after the graphene is ablated, the laser scanning should be carried out in a nitrogen atmosphere. After the femtosecond laser treatment is completed, a copper substrate exposure area without graphene layer coverage is formed on the surface of the graphene copper foil. The width of the exposure area is 100μm, and the area ratio of the exposure area on the surface of the graphene copper foil is 10%.

[0066] (3) Flip the graphene copper foil sample after femtosecond laser treatment in step (2) and fix it on the laser processing stage. Scan the graphene copper foil under the same laser parameters so that the copper substrate exposure areas on both sides of the graphene copper foil overlap.

[0067] (4) After the femtosecond laser scanning is completed, the processed graphene copper foil sample is transferred to a pre-prepared graphite mold. The graphite mold is also placed in a nitrogen atmosphere to avoid the introduction of impurity atoms and oxidation of the copper foil substrate. The inner diameter of the graphite mold is slightly larger than that of the graphene copper foil to avoid the graphene-copper composite material from contacting the mold during the subsequent hot pressing process, which could lead to uneven thickness of the product.

[0068] (5) Repeat steps (2) to (4) to stack multiple layers of femtosecond laser-scanned graphene copper foil inside the graphite mold. The number of sample layers can be 500, and the copper substrate exposure areas of adjacent graphene copper foil layers completely overlap. Transfer the mold containing the stacked graphene copper foil to the vacuum hot pressing chamber for vacuum hot pressing. The vacuum hot pressing degree reaches 5.5 × 10⁻⁶. -3 The hot pressing temperature was 750℃, the pressure was 20MPa, and the holding time was 60min; after vacuum hot pressing, graphene-copper composite material was obtained.

[0069] The electrical conductivity of the graphene-copper composite material prepared in this embodiment was tested, and its conductivity was 104.9% IACS.

[0070] Comparative Example 1

[0071] The preparation process is the same as in Example 1, except that: the graphene copper foil is not scanned by a femtosecond laser; instead, the graphene copper foil sample is directly stacked in a pre-prepared graphite mold and then transferred to a vacuum hot-pressing chamber for vacuum hot pressing; wherein, the vacuum hot-pressing degree reaches 5.5 × 10⁻⁶. -3 The hot pressing temperature was 950℃, the pressure was 20MPa, and the holding time was 60min; after vacuum hot pressing, graphene-copper composite material was obtained.

[0072] The electrical conductivity of the graphene-copper composite material prepared in this comparative example was tested, and its conductivity was 101.5% IACS.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a graphene-copper composite material, characterized in that, Includes the following steps: a) Prepare a graphene copper foil, wherein the graphene copper foil comprises a copper substrate and graphene layers deposited on both sides of the copper substrate; b) Use a femtosecond laser to ablate both sides of the graphene copper foil to form an exposed copper substrate area without graphene layer coverage. In step b), the width of the exposed area of ​​the copper substrate is 20~100μm; c) Stack two or more layers of graphene copper foil that have been treated in step b), with the exposed copper substrate areas of two adjacent layers of graphene copper foil in contact, to obtain the material to be pressed. d) The material to be pressed is hot-pressed to achieve metallurgical bonding of the exposed copper substrate areas of two adjacent layers of graphene copper foil in the material, thereby obtaining a graphene-copper composite material. In step d), the pressure of the hot pressing is 5~20MPa, and the temperature of the hot pressing is 650~950℃.

2. The preparation method according to claim 1, characterized in that, In step a), the thickness of the copper substrate is 15~40μm; the number of graphene layers deposited on one side of the copper substrate is 1~5.

3. The preparation method according to claim 1, characterized in that, In step b), the femtosecond laser has a laser power of 5~15W, a pulse width of 100~300fs, a frequency of 500~2000kHz, and a scanning speed of 500~2000mm / s.

4. The preparation method according to claim 1, characterized in that, In step b), the ablation is performed in a vacuum or inert gas atmosphere.

5. The preparation method according to claim 1, characterized in that, In step c), the copper substrate exposed areas of the two adjacent graphene copper foil layers completely overlap.

6. The preparation method according to claim 1, characterized in that, In step c), the number of layers is 10 to 500.

7. The preparation method according to claim 1, characterized in that, In step c), the lamination is performed in an inert gas atmosphere.

8. The preparation method according to claim 1, characterized in that, In step d), the vacuum degree of the hot pressing is 4 × 10⁻⁶. -3 ~7×10 -3 Pa; the hot pressing time is 10~60 min.

9. A graphene-copper composite material, characterized in that, It is prepared according to the preparation method according to any one of claims 1 to 8.

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