Method for preparing multi-layer graphene film in double-sided rolling manner and multi-layer graphene film

Abstract

The invention relates to a preparation method of a graphene film, in particular to a method for preparing a multi-layer graphene film in a double-sided rolling mode. The invention discloses a method for preparing a multi-layer graphene film in a double-sided rolling manner. The method comprises the following steps: (1) alternately winding a metal substrate and a flexible porous isolation material around a rolling center; (2) carrying out high-temperature annealing on the metal substrate / flexible porous isolation material coiled material by using reducing gas; (3) after annealing is finished, carbon source gas / reducing gas mixed gas is introduced, and first-layer graphene film growth is synchronously carried out on the two sides of the metal substrate under the low-pressure condition; (4) after the growth of the first layer of graphene film is finished, introducing oxidizing gas to etch the graphene films on the two sides of the metal substrate; (5) after etching is finished, carbon source gas / reducing gas mixed gas is introduced, and growth of a graphene film is carried out; and (6) repeating the step (4) and the step (5) for N times to obtain an N + 2-layer graphene film.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a graphene film, in particular to a method for preparing a multilayer graphene film by a double-sided roll-to-roll method. BACKGROUND Since graphene was discovered, it has attracted much attention from the industry due to its excellent mechanical, electrical and optical properties. At present, the mainstream technology for mass production of graphene in the industry includes chemical vapor deposition (CVD method), oxidation-reduction method, liquid phase exfoliation method, epitaxial growth method and physical exfoliation method. Compared with other technologies, the CVD method can prepare high-quality and large-size graphene films on metal substrates, and has the advantage of large-scale production. At the same time, with the self-limiting growth mechanism of copper substrate, the current large-size, high-quality and single-layer graphene film is mainly prepared by copper foil as the substrate, and the preparation technology can be divided into sheet stacking CVD graphene film preparation technology and roll-to-roll preparation technology. However, when these two preparation technologies are applied to the mass production of large-size, high-quality and double-sided multilayer long roll graphene film, there are still many defects.

[0002] When graphene films are produced by sheet stacking CVD graphene film preparation technology with copper foil as the substrate, rigid isolation materials such as graphite paper and copper foil substrates are alternately stacked, which is mainly to avoid the problem of adhesion of copper foil substrate at high temperature. In order to improve the yield of graphene film, the industry often increases the number of stacked layers, but when the number of stacked layers increases, there is a significant difference in the growth quality of graphene film between different layers. At the same time, due to the size restriction of the CVD furnace chamber, the maximum length of a single copper foil substrate is only 1.5-2m, and if the size of the chamber is blindly expanded, it will not be able to guarantee the uniformity of the temperature in the furnace, thereby destroying the stability of graphene growth, so it is difficult to further improve the production capacity by expanding the size of the copper foil. In addition, due to the self-limiting growth mechanism of the copper foil substrate, when the surface of the copper foil substrate is covered with graphene film, its ability to catalyze the cracking of carbon-containing gas will decrease significantly, making it difficult to continue to grow multilayer graphene. At present, the mainstream technology provides an additional metal substrate to improve the cracking efficiency of carbon-containing gas to break through the self-limiting growth mechanism, thereby preparing multilayer graphene film, such as Chinese patent application CN108706574A, which discloses the following steps: (1) the copper foil substrate is pretreated and placed in a support; (2) a layer of metal foil is wrapped outside the support; (3) the support wrapped with the metal foil is placed in a vacuum system for annealing treatment; (4) carbon-containing gas is introduced for 30 60min, and multilayer graphene is formed on the surface of the copper foil after cooling. However, this method is complex and difficult to ensure that the multilayer graphene film with uniform growth quality can be grown on both sides of the substrate. In summary, at present, only small-size, single-layer graphene film can be prepared in small batches by sheet stacking technology, which is difficult to meet the market demand for large-size, high-quality, double-sided multilayer long roll graphene film.

[0003] There are also many problems in the production of graphene film by roll-to-roll technology with copper foil as the substrate: the copper foil substrate is prone to recrystallization and softening due to heat during CVD deposition (usually 800-1000℃), and the dynamic transmission process in the roll-to-roll method is easy to cause the copper foil substrate to deform and break, which will cause the entire roll to be scrapped and greatly reduce the production efficiency. In order to avoid the above problems, a graphite support or quartz support needs to be placed under the substrate in the roll-to-roll production process as a supporting structure, which will directly block the lower surface of the copper foil, making it difficult for process gases (carbon source gas, reducing gas) to penetrate into the lower surface of the copper foil substrate. The lower surface is prone to growth vacancies, multiple impurities or lattice defects due to insufficient gas mass transfer. At the same time, due to the displacement in the dynamic transmission process, the supporting structure will also scratch the graphene film, thereby making it difficult for the roll-to-roll method to meet the preparation of double-sided high-quality graphene film. The roll-to-roll method is also difficult to meet the market demand for large-size, high-quality, double-sided and multi-layer long roll graphene film. In summary, the existing CVD graphene film preparation technology is not sufficient to support the mass production of large-size, high-quality, double-sided and multi-layer long roll graphene film, which seriously restricts the industrialization process.

[0004] The contents of the background art section merely represent the technology known to the inventors, and do not necessarily represent the state of the art. SUMMARY

[0005] In view of the above problems, the present application discloses a method for preparing multi-layer graphene film by double-sided roll, which comprises the following steps: (1) The metal substrate and the flexible porous isolation material are alternately wound around the roll core to form a layered metal substrate / flexible porous isolation material roll; and the metal substrate / flexible porous isolation material roll is placed on a carrier in the vacuum chamber of a CVD furnace; (2) The CVD furnace is evacuated, and a reducing gas is used to anneal the metal substrate / flexible porous isolation material roll at high temperature; (3) After annealing, carbon source gas / reducing gas mixed gas is introduced to grow the first layer of graphene film on both sides of the metal substrate simultaneously, and the pressure is controlled within 500 Pa during the growth stage; (4) After the growth of the first layer of graphene film, an oxidizing gas is introduced to etch the graphene film on both sides of the metal substrate; (5) After etching, carbon source gas / reducing gas mixed gas is introduced to grow the graphene film; (6) Steps (4) and (5) are repeated N times to obtain N+2 layers of graphene film.

[0006] Further, in step (1): The metal substrate is a copper foil, and the thickness of the copper foil is 4-100 μm; and / or, The flexible porous isolation material is a porous carbon fiber material with a thickness of 0.2-0.8 mm; and / or, The winding is performed using a constant tension device: when the metal substrate has a width of 65 mm and a thickness of 25 μm, the tension control is 10-15 N.

[0007] Further, the copper foil has a thickness of 25 μm; and / or, The porous carbon fiber material has a thickness of 0.2 mm; and / or, The tension control is 12-14 N.

[0008] Further, in the step (2): The reducing gas is hydrogen with a flow rate of 20-200 sccm; and / or, The annealing temperature is 900-1050 °C; and / or, The annealing time is ≥1 h.

[0009] Further, the reducing gas flow rate is 50-200 sccm; and / or, The annealing temperature is 950-1000 °C; and / or, The annealing time is 1-2 h.

[0010] Further, in the step (3): The carbon source gas is one or more of methane, acetylene, ethylene, methanol, and ethanol; and / or, The reducing gas is hydrogen; and / or, The flow rate ratio of the carbon source gas to the reducing gas is 1:20-1:40, the carbon source gas flow rate is 20-40 sccm, and the reducing gas flow rate is 400-1600 sccm; and / or, The graphene film growth temperature is 900-1050 °C, and the growth time is ≥1 h.

[0011] Further, the carbon source gas is methane; and / or, The flow rate ratio of the carbon source gas to the reducing gas is 1:25-1:35, the carbon source gas flow rate is 25-35 sccm, and the reducing gas flow rate is 625-1300 sccm; and / or, The graphene film growth temperature is 950-1000 °C, and the growth time is 1-2 h.

[0012] Further, in the step (4), the oxidizing gas is any one of argon-oxygen mixed gas, nitrogen-oxygen mixed gas, and pure oxygen, and is preferably argon-oxygen mixed gas, and the etching time is 30-45 min; and / or, In the step (5), the carbon source gas is one or more of methane, acetylene, ethylene, methanol and ethanol; the reducing gas is hydrogen; the flow ratio of the carbon source gas to the reducing gas is 1:30-1:40, the flow of the carbon source gas is 20-40 sccm, and the flow of the reducing gas is 600-1600 sccm; the graphene film growth temperature is 900-1050℃, and the growth time is ≥1h; and / or, In the step (6), N is 0-10.

[0013] Further, in the step (4), the etching time is 35-40min; and / or, In the step (5), the carbon source gas is methane; the reducing gas is hydrogen; the flow ratio of the carbon source gas to the reducing gas is 1:35-1:40, the flow of the carbon source gas is 20-40 sccm, and the flow of the reducing gas is 700-1600 sccm; the graphene film growth temperature is 900-1050℃, and the growth time is ≥1h; and / or, In the step (6), N is 0-5.

[0014] The application also discloses a multilayer graphene film prepared by any one of the above-mentioned methods for preparing a double-sided roll-type multilayer graphene film.

[0015] In view of the defects of the two mainstream CVD graphene film preparation technologies of the sheet stacking method and the roll-to-roll method in preparing large-size, high-quality, double-sided multilayer long roll-type graphene films, the application discloses a double-sided roll-type multilayer graphene film preparation technology: the double-sided roll-type graphene film is prepared in a CVD furnace through the design of metal substrate / soft porous isolation material alternately winding + vertical loading, and then the first layer of graphene film is subjected to the oxidative etching action of argon-oxygen mixed gas to expose the metal substrate again, so that the catalytic carbon source gas cracking ability is restored in the subsequent growth, and the active carbon atoms formed after cracking are provided with a migration channel to the first layer of graphene film, thereby breaking through the self-limiting growth mechanism and successfully preparing a large-size, high-quality, double-sided multilayer long roll-type graphene film without introducing a copper substrate. Compared with the two existing technologies, the improvements of the application are as follows: Compared with the traditional sheet stacking technology: firstly, the first layer of graphene film is etched by argon-oxygen mixed gas to expose the metal substrate again, so that the catalytic carbon source gas cracking ability is restored in the subsequent growth, thereby breaking through the limitation of the self-limiting growth of the metal substrate on the preparation of the multilayer graphene film in the traditional sheet stacking technology; secondly, the winding structure breaks through the limitation of the size of the CVD furnace cavity, and the winding structure can be used for the preparation of a super-large-size graphene film with a length of 1-1000 meters.

[0016] Without dynamic transmission, no additional support structure such as quartz support / graphite support is needed, which ensures that the process gas uniformly contacts both sides of the substrate and avoids the scratch of the lower graphene film during displacement.

[0017] Due to the self-limiting growth mechanism, the copper substrate covered by the graphene film loses the ability to catalyze methane cracking, and the graphene film produced at this time is mainly single-layer. The present application destroys the first layer of graphene film by the penetration of oxidizing gas to the surface of the copper substrate, so that the copper substrate is exposed. Since the penetration opportunity of the gas to both sides of the copper substrate is equal, the etching is relatively uniform. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application together with the embodiments thereof, and explain the present application, but do not limit the present application. In the drawings: Figure 1 a is a top view of a roll formed by alternately winding the copper foil substrate and the flexible porous isolation material around the roll core; b is a top view of the roll vertically loaded on the graphite fixture; Figure 2 In-situ SEM photos of the multilayer graphene film grown on the copper foil substrate in Example 1: a is the front side; b is the back side; Figure 3 In-situ SEM photos of the multilayer graphene film grown on the copper foil substrate in Example 2: a is the front side; b is the back side; Figure 4 In-situ SEM photos of the multilayer graphene film grown on the copper foil substrate in Example 3: a is the front side; b is the back side; Figure 5 In-situ SEM photos of the multilayer graphene film grown on the copper foil substrate after repeating steps (4) and (5) 3 times in Example 4: a is the front side; b is the back side; Figure 6 In-situ SEM photos of the single-layer-based graphene film grown on the copper foil substrate in Comparative Example 1: a is the front side; b is the back side; Figure 7 In-situ SEM photos of the few-layer graphene film grown on the copper foil substrate when the etching time of argon-oxygen mixed gas is insufficient in Comparative Example 2: a is the front side; b is the back side; Figure 8 In-situ SEM photos of the graphene film grown on the copper foil substrate when the tension is too small in Comparative Example 3: a is the front side; b is the back side; Figure 9 In-situ SEM photos of the graphene film grown on the copper foil substrate when the tension is too large in Comparative Example 4: a is the front side; b is the back side. DETAILED DESCRIPTION

[0019] In the following description, certain example embodiments are simply described. As those skilled in the art will realize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the application. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0020] Unless otherwise defined herein, scientific and technical terms used in connection with the present application shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. More specifically, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. In this application, the use of "or" means "and / or" unless stated otherwise. Furthermore, the use of the term "including" as well as other forms such as "include", "includes," and "included" is not limiting. Also, ranges are used herein to include endpoints and all values between the endpoints. The preferred embodiments of the present application are described herein, it being understood that the preferred embodiments described herein are merely illustrative and are not intended to limit the scope of the present application.

[0021] The specific technical solutions of the above-mentioned double-sided multi-layer roll-type graphene film preparation technology are as follows: 1. Using a constant tension device to alternately wind the metal substrate and the flexible porous isolation material around the roll core to form a laminated structure roll. Then vertically place the metal substrate / flexible porous isolation material roll on the carrier in the vacuum chamber of the CVD furnace; 2. Using a reducing gas to anneal the metal substrate / flexible porous isolation material roll at high temperature, removing organic impurities and metal oxides on the surface of the metal substrate during the annealing process, and at the same time, recrystallizing the metal substrate at high temperature to eliminate stress, process stripes, etc., optimizing the copper foil grain orientation, and realizing surface flattening; 3. After the reducing gas annealing is completed, carbon source gas / reducing gas mixed gas is introduced to grow the first layer of CVD graphene film on both sides of the metal substrate under low pressure conditions; 4. After the growth is completed, an oxidizing gas is introduced to etch the graphene film on both sides of the metal substrate, and the etching temperature is consistent with the graphene film growth temperature, so that the metal substrate is exposed and the ability to catalyze carbon source gas cracking is restored; 5. After etching is completed, carbon source gas / reducing gas mixed gas is introduced, and under the action of the newly exposed metal substrate on both sides of the metal substrate catalyzing carbon source gas cracking, multi-layer graphene film growth is carried out; 6. Repeat steps (4) and (5) N times to obtain N+2 layers of graphene film.

[0022] According to the above step 1, the metal substrate used is a copper foil, which can be selected from a rolled copper foil or an electrolytic copper foil, preferably a rolled copper foil; the thickness of the copper foil can be between 4-100 μm, such as 4 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, preferably 25 μm; the flexible porous isolation material used is a porous carbon fiber material, preferably a flexible carbon fiber cloth, and the thickness of the material is 0.2-0.8 mm, such as 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, preferably 0.2 mm.

[0023] According to the above step 1, when the metal substrate / flexible porous isolation material roll is alternately wound around the roll core, a constant tension device is used for winding: when the width of the metal substrate / flexible porous isolation material roll is 65 mm and the thickness is 25 μm, the tension control is 10-15 N, such as 10 N, 11 N, 12 N, 13 N, 14 N, 15 N, preferably 12 N-14 N. If <10 N, the layers of the roll material are loose and the structure is unstable, the surface of the metal substrate is prone to wrinkles / indentations, which affects the growth quality of the graphene film; if >15 N, the metal substrate and the flexible porous isolation material are too tightly bonded, making it difficult for the gas to penetrate during the deposition process, which affects the growth quality of the graphene film. The winding length of the flexible porous isolation material-metal substrate roll can be between 10 meters and 1000 meters. According to the above step 2, the reducing gas is preferably hydrogen; the hydrogen flow rate is between 20-200 sccm, such as 50 sccm, 80 sccm, 100 sccm, 120 sccm, 140 sccm, 160 sccm, 180 sccm, 200 sccm, preferably 50 sccm-200 sccm; the annealing temperature can be between 900-1050℃, such as 900℃, 920℃, 940℃, 960℃, 980℃, 1000℃, 1020℃, 1050℃, preferably 950℃-1000℃. If the annealing temperature <900℃, the recrystallization effect on the surface of the copper foil substrate is weak, which cannot optimize the grain orientation of the copper foil and flatten the surface of the copper foil; if the annealing temperature ≥1050℃, it is close to the melting point of the copper foil (1083℃), and the copper foil is in a molten state when the carbon source gas is subsequently introduced, which is not conducive to the growth of the graphene film on the substrate surface; due to the influence of the winding structure on the penetration of the reducing gas, if the annealing time <1 h, the reducing gas cannot completely remove the impurities (such as oxidation defects) on both sides of the copper foil substrate, which is not conducive to the growth quality of the graphene film, preferably 1-2 h.

[0024] According to the above step 3, the carbon source gas can be selected from one or more of methane, acetylene, ethylene, methanol, ethanol, etc., and is preferably methane gas. The reducing gas is preferably hydrogen. The flow ratio of the carbon source gas to the reducing gas is between 1:20 and 1:40, for example 1:20, 1:25, 1:30, 1:35, 1:40, and is preferably between 1:25 and 1:35. If the ratio of the carbon source gas to the reducing gas is >1:20, for example 1:10, the proportion of the carbon source gas is too high, and the graphene film grows too fast under the catalytic action of the copper foil, which adversely affects the growth quality. If the ratio is <1:40, for example 1:50, the proportion of the carbon source gas is too low, and there is a risk that the graphene film cannot completely cover the two sides of the copper foil after the growth stage is over. The carbon source gas flow is between 20 and 40 seem, for example 20 seem, 25 seem, 30 seem, 35 seem, and 40 seem. The reducing gas flow is between 400 and 1600 seem, for example 400 seem, 500 seem, 600 seem, 700 seem, 800 seem, 900 seem, 1000 seem, 1100 seem, 1200 seem, 1300 seem, 1400 seem, 1500 seem, and 1600 seem. The graphene film growth temperature can be between 900 and 1050°C, for example 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, 1020°C, and 1050°C, and is preferably between 950°C and 1000°C. If the growth temperature is lower than 900°C, the ability of the copper foil substrate to catalyze the cracking of the carbon source gas decreases, which is not conducive to the growth of the graphene film. If the growth temperature is >1050°C, it is close to the melting point of the copper foil (1083°C), and the molten copper foil is not conducive to the growth of the graphene film on the surface. The winding structure has a certain influence on the penetration of the carbon source gas to both sides of the copper foil substrate. If the growth time is <1h, the graphene film cannot completely cover both sides of the copper foil, and the growth time is preferably between 1 and 2h.

[0025] According to the above step 4, the oxidizing gas is any one of argon-oxygen mixed gas, nitrogen-oxygen mixed gas, and pure oxygen, and is preferably argon-oxygen mixed gas. The etching time is between 30 and 45 min, for example 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, and 45 min, and is preferably between 35 and 40 min. If the etching time is ≤30 min, the first layer of graphene film on both sides of the copper foil is weakly etched by the argon-oxygen mixed gas, and the exposed copper foil substrate cannot effectively catalyze the cracking of the carbon source gas to form a dense multi-layer graphene film. If the etching time is ≥45 min, the graphene film on both sides of the copper foil is excessively etched by the argon-oxygen mixed gas, and the exposed copper substrate is oxidized and loses the ability to catalyze the cracking of methane.

[0026] According to the above step 5, the carbon source gas is one or more of methane, acetylene, ethylene, methanol, ethanol, preferably methane gas, and the reducing gas is preferably hydrogen gas. The ratio of carbon source gas / reducing gas is between 1:30-1:40, for example 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, preferably 1:35-1:40. The carbon source gas flow is between 20-40 sccm, for example 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm; the reducing gas flow is between 400-1600 sccm, for example 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm. Since the argon-oxygen mixed gas etches the first layer of graphene film, the bare exposed copper substrate is oxidized, and the oxidized copper substrate does not have the ability to catalyze the cracking of the carbon source gas. If the ratio of carbon source gas / reducing gas is >1:30, for example 1:25, the reducing gas cannot completely reduce the copper substrate, which will cause the density of the multilayer to decrease, and the graphene film cannot completely cover both sides of the copper foil substrate. If the ratio is <1:40, for example 1:45, the proportion of carbon source gas is too low, which is not conducive to the formation of multilayer graphene film, resulting in a decrease in the density of the multilayer. The growth time is ≥1 h, preferably 1-2 h. If the growth time is <1 h, the density of the multilayer on both sides of the copper foil substrate decreases significantly.

[0027] According to the above step 6, N can be 0, 1, 2, 3, 4, 5, etc., and N+2 layers of graphene film are prepared accordingly. When N is 0, 1, 2, 3, 4, 5, the graphene film has 2, 3, 4, 5, 6, 7 layers.

[0028] Example The application generally described herein will be more readily understood by reference to the following examples, which are provided by way of illustration and are not intended to limit the application. In addition, the experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials, reagents and materials used in the following examples are commercially available unless otherwise specified.

[0029] Example 1 (1) Using a constant tension winding device, a size of 65 mm x 50 m x 25 μm of a rolled copper foil and a size of 80 mm x 50 m x 200 μm of a porous flexible carbon fiber cloth are alternately wound around the winding core to form a laminated structure, as shown in Figure 1 After winding is completed, the copper foil / porous carbon fiber cloth roll is placed in the CVD furnace chamber, as shown inFigure 1 As shown, the copper foil substrate loading direction is parallel to the flow field, and the process gas has equal penetration opportunity to both sides of the metal substrate; (2) After the CVD furnace background vacuum is pumped to 5 Pa, the CVD furnace chamber temperature is raised to 950°C, and hydrogen gas with a flow rate of 50 sccm is introduced to start the reducing gas annealing, and the processing time is 1.5 h; (3) After the reducing gas annealing is completed, the CVD furnace chamber temperature is maintained at 950°C, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 400 sccm are introduced, and the growth of the first layer of graphene film on both sides of the copper foil substrate is started simultaneously, at this time the methane:hydrogen = 1:20, and the growth time is 1 h; (4) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 100 sccm is introduced to etch the graphene film on both sides, and the etching time is 30 min; (5) After etching is completed, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 600 sccm are introduced, the methane flow rate:hydrogen flow rate = 1:30, and the growth of the multilayer graphene film is started, and the growth time is 1 h; The SEM image of the grown graphene film is shown in Figure 2 .

[0030] Example 2 (1) Using a constant tension winding device, a size of 65 mm x 100 m x 25 μm of a calendered copper foil and a size of 80 mm x 100 m x 200 μm of a porous flexible carbon fiber cloth are alternately wound around the winding core to form a laminated structure under the condition of a tension of 13 N. After winding is completed, the copper foil / porous carbon fiber cloth roll is placed in the CVD furnace chamber, the copper foil substrate loading direction is parallel to the flow field, and the process gas has equal penetration opportunity to both sides of the metal substrate; (2) After the CVD furnace background vacuum is pumped to 5 Pa, the CVD furnace chamber temperature is raised to 1000°C, and hydrogen gas with a flow rate of 100 sccm is introduced to start the reducing gas annealing, and the processing time is 2 h; (3) After the reducing gas annealing is completed, the CVD furnace chamber temperature is maintained at 1000°C, methane gas with a flow rate of 30 sccm and hydrogen gas with a flow rate of 900 sccm are introduced, and the growth of the first layer of graphene film on both sides of the copper foil substrate is started simultaneously, at this time the methane:hydrogen = 1:30, and the growth time is 1.5 h; (4) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 150 sccm is introduced to etch the graphene film on both sides, and the etching time is 40 min; (5) After etching, methane gas with a flow rate of 30 sccm and hydrogen gas with a flow rate of 900 sccm are introduced, the flow rate of methane:hydrogen = 1:30, and the growth of the multilayer graphene film is performed, with a growth time of 1.5 h; SEM image of the grown graphene film is shown in Figure 3 .

[0031] Example 3 (1) The constant tension winding equipment is used to alternately wind the size of 65 mm x 200 m x 25 μm of the rolled copper foil and the size of 80 mm x 200 m x 200 μm of the porous flexible carbon fiber cloth around the winding core to form a laminated structure. After winding, the copper foil / porous carbon fiber cloth roll is placed in the CVD furnace chamber, the loading direction of the copper foil substrate is parallel to the flow field, and the process gas penetrates the opportunity of the two sides of the metal substrate equally; (2) After the CVD furnace background vacuum is pumped to 5 Pa, the CVD furnace chamber temperature is increased to 1020℃, hydrogen gas with a flow rate of 200 sccm is introduced to start the reduction gas annealing, and the processing time is 2 h; (3) After the reduction gas annealing is completed, the CVD furnace chamber temperature is maintained at 1020℃, methane gas with a flow rate of 40 sccm and hydrogen gas with a flow rate of 1600 sccm are introduced, and the growth of the first layer of graphene film on both sides of the copper foil substrate is started simultaneously, at this time the methane:hydrogen = 1:40, and the growth time is 2 h; (4) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 200 sccm is introduced to etch the graphene film on both sides, and the etching time is 40 min; (5) After etching, methane gas with a flow rate of 40 sccm and hydrogen gas with a flow rate of 1600 sccm are introduced, the flow rate of methane:hydrogen = 1:40, and the growth of the multilayer graphene film is performed, with a growth time of 2 h; SEM image of the grown graphene film is shown in Figure 4 .

[0032] Example 4 (1) The constant tension winding equipment is used to alternately wind the size of 65 mm x 200 m x 25 μm of the rolled copper foil and the size of 80 mm x 200 m x 200 μm of the porous flexible carbon fiber cloth around the winding core to form a laminated structure. After winding, the copper foil / porous carbon fiber cloth roll is placed in the CVD furnace chamber, the loading direction of the copper foil substrate is parallel to the flow field, and the process gas penetrates the opportunity of the two sides of the metal substrate equally; (2) After the CVD furnace background vacuum is extracted to 5 Pa, the CVD furnace chamber temperature is increased to 1020℃, and hydrogen gas with a flow rate of 200 sccm is introduced to start the reduction gas annealing, and the processing time is 2 h; (3) After the reduction gas annealing is completed, the CVD furnace chamber temperature is maintained at 1020℃, methane gas with a flow rate of 40 sccm is introduced, and hydrogen gas with a flow rate of 1600 sccm is introduced to start the growth of the first layer of graphene film on both sides of the copper foil substrate at the same time, at this time, the methane:hydrogen = 1:40, and the growth time is 2 h; (4) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 200 sccm is introduced to etch the graphene film on both sides, and the etching time is 40 min; (5) After the etching is completed, methane gas with a flow rate of 40 sccm and hydrogen gas with a flow rate of 1600 sccm are introduced, the methane flow rate:hydrogen flow rate = 1:40, and the growth of the multilayer graphene film is carried out, and the growth time is 2 h; (6) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 200 sccm is introduced to etch the graphene film on both sides, and the etching time is 40 min; (7) After the etching is completed, methane gas with a flow rate of 40 sccm and hydrogen gas with a flow rate of 1600 sccm are introduced, the methane flow rate:hydrogen flow rate = 1:40, and the growth of the multilayer graphene film is carried out, and the growth time is 2 h; (8) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 200 sccm is introduced to etch the graphene film on both sides, and the etching time is 40 min; (9) After the etching is completed, methane gas with a flow rate of 40 sccm and hydrogen gas with a flow rate of 1600 sccm are introduced, the methane flow rate:hydrogen flow rate = 1:40, and the growth of the multilayer graphene film is carried out, and the growth time is 2 h; The SEM image of the grown graphene film is shown in Figure 5 .

[0033] Comparative Example 1 (1) A constant tension winding device is used to alternately wind the length of 65 mm x 20 m x 25 μm of the rolled copper foil and the size of 80 mm x 20 m x 200 μm of the porous flexible carbon fiber cloth around the winding core to form a laminated structure. After winding is completed, the copper foil / porous carbon fiber cloth roll is vertically placed in the CVD furnace chamber, the copper foil substrate loading direction is parallel to the flow field, and the process gas penetrates the opportunity of the metal metal substrate on both sides equally; (2) After the CVD furnace background vacuum is pumped to 5 Pa, the temperature of the CVD furnace chamber is raised to 960°C, and hydrogen gas with a flow rate of 50 sccm is introduced to start the reduction gas annealing, and the processing time is 1 h; (3) After the reduction gas annealing is completed, the temperature of the CVD furnace chamber is maintained at 960°C, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 400 sccm are introduced, and the growth of the first layer of graphene film on both sides of the copper foil substrate is started simultaneously, at this time the methane:hydrogen = 1:20, and the growth time is 1 h; The static winding overhead view of the copper foil substrate / flexible porous isolation material is shown in Figure 1 a, and the wound material after winding is placed in the jig and loaded into the CVD furnace chamber, as shown in Figure 1 b. Figure 6 The front and back of the double-sided single-layer-based CVD graphene film prepared for Comparative Example 1.

[0034] Comparative Example 2 (1) The calendered copper foil with a size of 65 mm x 50 m x 25 μm and the porous flexible carbon fiber cloth with a size of 80 mm x 50 m x 200 μm are alternately wound around the winding core to form a laminated structure under the condition that the tension is 12 N, as shown in Figure 1 a. After winding is completed, the copper foil / porous carbon fiber cloth roll is placed in the CVD furnace chamber, as shown in Figure 1 b, the loading direction of the copper foil substrate is parallel to the flow field, and the process gas has equal penetration opportunity to both sides of the metal substrate; (2) After the CVD furnace background vacuum is pumped to 5 Pa, the temperature of the CVD furnace chamber is raised to 950°C, and hydrogen gas with a flow rate of 50 sccm is introduced to start the reduction gas annealing, and the processing time is 1.5 h; (3) After the reduction gas annealing is completed, the temperature of the CVD furnace chamber is maintained at 950°C, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 400 sccm are introduced, and the growth of the first layer of graphene film on both sides of the copper foil substrate is started simultaneously, at this time the methane:hydrogen = 1:20, and the growth time is 1 h; (4) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas (oxygen content is 5%) with a flow rate of 100 sccm is introduced to etch the graphene film on both sides, and the etching time is 25 min; (5) After etching is completed, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 600 sccm are introduced, and the methane flow rate:hydrogen flow rate = 1:30, and the growth of the multilayer graphene film is started, and the growth time is 1 h; The SEM image of the grown graphene film is shown in Figure 7 .

[0035] Comparative Example 3 (1) The constant tension winding equipment was used to alternately wind the size of 65 mm x 50 m x 25 μm of the rolled copper foil and the size of 80 mm x 50 m x 200 μm of the porous flexible carbon fiber cloth around the winding core to form a laminated structure, as shown in FIG. 1. After the winding was completed, the copper foil / porous carbon fiber cloth roll was placed in the CVD furnace chamber, as shown in FIG. 2, the loading direction of the copper foil substrate was parallel to the flow field, and the process gas had equal penetration opportunity to both sides of the metal substrate. Figure 1 Figure 1 (2) After the CVD furnace background vacuum was pumped to 5 Pa, the CVD furnace chamber temperature was increased to 950℃, and the reduction gas annealing was started by inputting hydrogen gas with a flow rate of 50 sccm, and the processing time was 1.5 h. (3) After the reduction gas annealing was completed, the CVD furnace chamber temperature was maintained at 950℃, and the first layer of graphene film was grown on both sides of the copper foil substrate by inputting methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 400 sccm, at this time, the methane:hydrogen = 1:20, and the growth time was 1 h. (4) After the first layer of graphene film was grown on both sides of the copper foil substrate, the etching of the graphene film on both sides was started by inputting argon-oxygen mixed gas (oxygen content was 5%) with a flow rate of 100 sccm, and the etching time was 30 min. (5) After the etching was completed, the growth of the multilayer graphene film was started by inputting methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 600 sccm, the methane flow rate:hydrogen flow rate = 1:30, and the growth time was 1 h. The SEM image of the grown graphene film is shown in FIG. 3. Figure 8 .

[0036] Comparative Example 4 (1) The constant tension winding equipment was used to alternately wind the size of 65 mm x 50 m x 25 μm of the rolled copper foil and the size of 80 mm x 50 m x 200 μm of the porous flexible carbon fiber cloth around the winding core to form a laminated structure, as shown in FIG. 1. After the winding was completed, the copper foil / porous carbon fiber cloth roll was placed in the CVD furnace chamber, as shown in FIG. 2, the loading direction of the copper foil substrate was parallel to the flow field, and the process gas had equal penetration opportunity to both sides of the metal substrate. Figure 1 Figure 1 (2) After the CVD furnace background vacuum was pumped to 5 Pa, the CVD furnace chamber temperature was increased to 950℃, and the reduction gas annealing was started by inputting hydrogen gas with a flow rate of 50 sccm, and the processing time was 1.5 h. ​​​​(3) After the reducing gas annealing is completed, the temperature of the CVD furnace chamber is maintained at 950°C, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 400 sccm are introduced, and the growth of the first layer of graphene film on both sides of the copper foil substrate is started simultaneously, at this time, the ratio of methane to hydrogen is 1:20, and the growth time is 1 h; (4) After the growth of the first layer of graphene film on both sides of the copper foil substrate is completed, argon-oxygen mixed gas with a flow rate of 100 sccm (oxygen content is 5%) is introduced to etch the graphene film on both sides, and the etching time is 30 min; (5) After the etching is completed, methane gas with a flow rate of 20 sccm and hydrogen gas with a flow rate of 600 sccm are introduced, the ratio of methane flow rate to hydrogen flow rate is 1:30, and the growth of the multilayer graphene film is started, and the growth time is 1 h; The SEM image of the grown graphene film is shown in Figure 9 .

[0037] When the scanning electron microscope (SEM) uses an electron beam to irradiate a sample, the information of the secondary electrons generated by the sample is collected and processed to reflect the microstructure of the sample. Different regions of different materials are shown with different contrasts. When using SEM to characterize the graphene film, the single-layer graphene, multilayer graphene and additional layer grown on the surface of the copper foil substrate have differences in scattering and absorption of electrons. In the SEM image, different types of graphene films on the copper foil substrate have different contrasts, so that the number of layers of the graphene film grown on the copper foil substrate and whether there is an additional layer can be determined by directly observing the contrast of the SEM image, which means that the time for transferring the graphene is saved, and the size, number of layers, nucleation density and coverage of the graphene on the copper foil surface can be more efficiently obtained to determine the number of layers of the graphene film grown on the copper foil substrate and whether there is an additional layer.

[0038] Compared with the single-layer graphene film on both sides of the copper foil substrate in Comparative Example 1 in Figure 6 , the single-layer graphene film on both sides of the copper foil substrate in Example 1, Example 2 and Example 3, shown in Figures 2-4 , is successfully prepared by introducing argon-oxygen mixed gas to etch the single-layer graphene film on both sides of the copper foil substrate and then regrowing.

[0039] In Example 4, by repeating the argon-oxygen mixed gas etching and regrowth steps in steps (4) and (5), a double-sided multilayer graphene film with higher coverage and larger additional layer size in the multilayer region is successfully prepared.

[0040] In Comparative Example 2, due to the insufficient etching time of the argon-oxygen mixed gas on the first layer of graphene film, only a few-layer graphene film with low multilayer density is prepared.

[0041] In Comparative Example 3, the tension of the constant tension winding is only 7 N, at this time, the copper foil substrate / flexible porous isolation material is alternately wound around the winding core to form a loose winding structure, and the metal substrate cannot be fully flattened when winding, and problems such as relaxation, wrinkles, and wave-shaped deformation occur. As can be seen from the in-situ SEM of the graphene film on both sides of the grown copper foil substrate, the copper foil has wrinkles, and the graphene film is obviously damaged at the wrinkle protrusions. Details are shown in Figure 8 .

[0042] In Comparative Example 4, the set tension of the constant tension winding is 20 N, and after the copper foil substrate and the flexible porous isolation material are alternately wound around the winding core, the winding material is excessively compacted due to excessive tension, which seriously hinders the uniform penetration of process gas to both sides of the copper foil substrate. Since the growth of CVD graphene depends on the penetration of process gas through the flexible porous isolation material, the uniform diffusion of process gas to both sides of the copper foil substrate and the provision of carbon source, the excessively compacted winding material leads to a serious shortage of carbon source supply, and carbon atoms cannot meet the needs of continuous nucleation and ordered growth, resulting in a large number of blank areas, holes and fragmentation of the grown graphene film. The graphene film cannot form a complete and continuous film layer. Details are shown in Figure 9 .

[0043] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application. In addition, although the elements of the present application can be described or claimed in individual form, it is also possible to have multiple elements, unless explicitly limited to a single element.

Claims

1. A method of producing a multilayer graphene film by a double-sided roll-to-roll process, characterized by, The method comprises the following steps: (1) alternately winding the metal substrate and the flexible porous isolation material around the roll core to form a metal substrate / flexible porous isolation material roll material with a laminated structure; (2) vacuumizing the CVD furnace and using a reducing gas to perform high-temperature annealing on the metal substrate / flexible porous isolation material roll material; (3) after the annealing is completed, a carbon source gas / reducing gas mixed gas is introduced to synchronously perform first-layer graphene film growth on both sides of the metal substrate; (4) after the first-layer graphene film growth is completed, an oxidizing gas is introduced to etch the graphene film on both sides of the metal substrate; (5) after the etching is completed, a carbon source gas / reducing gas mixed gas is introduced to perform graphene film growth; (6) repeating steps (4) and (5) N times to obtain N+2 layers of graphene film.

2. The method of claim 1, wherein the method is characterized by, In the step (1): the metal substrate is a copper foil with a thickness of 4-100 μm; and / or, the flexible porous isolation material is a porous carbon fiber material with a thickness of 0.2-0.8 mm; and / or, the alternately winding is performed using a constant tension device: when the metal substrate has a width of 65 mm and a thickness of 25 μm, the tension control is 10-15 N.

3. The method of claim 2, wherein the method is characterized by, the copper foil has a thickness of 25 μm; and / or, the porous carbon fiber material has a thickness of 0.2 mm; and / or, the tension control is 12-14 N.

4. The method of claim 1, wherein the method is characterized by, In the step (2): the reducing gas is hydrogen with a flow rate of 20-200 sccm; and / or, the annealing temperature is 900-1050 °C; and / or, the annealing time is ≥1 h.

5. The method for preparing a multi-layer graphene film by double-sided rolling according to claim 4, characterized in that: the flow rate of the reducing gas is 50-200 sccm; and / or, the annealing temperature is 950-1000 °C; and / or, the annealing time is 1-2 h.

6. The method of claim 1, wherein the method is characterized by: In the step (3): the carbon source gas is one or more of methane, acetylene, ethylene, methanol and ethanol; and / or, the reducing gas is hydrogen; and / or, the pressure control during the growth stage is within 500 Pa; and / or, the flow rate ratio of the carbon source gas to the reducing gas is 1:20-1:40, the flow rate of the carbon source gas is 20-40 sccm, and the flow rate of the reducing gas is 400-1600 sccm; and / or, the graphene film growth temperature is 900-1050 °C, and the growth time is ≥1 h.

7. The method of claim 6, wherein the method further comprises: the carbon source gas is methane; and / or, the flow rate ratio of the carbon source gas to the reducing gas is 1:25-1:35, the flow rate of the carbon source gas is 25-35 sccm, and the flow rate of the reducing gas is 625-1300 sccm; and / or, the graphene film growth temperature is 950-1000 °C, and the growth time is 1-2 h.

8. The method of claim 1, wherein the method is characterized by, In the step (4), the oxidizing gas is any one of argon-oxygen mixed gas, nitrogen-oxygen mixed gas and pure oxygen, and the etching time is 30-45 min; and / or, In the step (5), the carbon source gas is one or more of methane, acetylene, ethylene, methanol, and ethanol; the reducing gas is hydrogen; the flow ratio of the carbon source gas to the reducing gas is 1:30-1:40, the flow rate of the carbon source gas is 20-40 sccm, and the flow rate of the reducing gas is 600-1600 sccm; the graphene film growth temperature is 900-1050°C, and the growth time is ≥1 h; and / or, In the step (6), N is 0-10.

9. The method of claim 8, wherein the method further comprises, In the step (4), the oxidizing gas is preferably argon-oxygen mixed gas, and the etching time is 35-40 min; and / or, In the step (5), the carbon source gas is methane; the reducing gas is hydrogen; the flow ratio of the carbon source gas to the reducing gas is 1:35-1:40, the flow rate of the carbon source gas is 20-40 sccm, and the flow rate of the reducing gas is 700-1600 sccm; the graphene film growth temperature is 900-1050°C, and the growth time is ≥1 h; and / or, In the step (6), N is 0-5.

10. A multilayer graphene film prepared by the method of any one of claims 1-9 for preparing a multilayer graphene film from a double-sided roll.

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