Graphene material and preparation method and device thereof

Abstract

The application relates to the technical field of graphene, in particular to a graphene material and a preparation method and a preparation device thereof, the preparation method comprises the following steps: preparing an electrolysis system, including an anode, a cathode and an electrolyte, a first extension direction of the anode intersects with a second extension direction of the cathode; graphite is used as the anode to perform an electrolysis reaction, and the graphite is driven to move along the first extension direction to adjust the distance between the anode and the cathode; as the distance between the anode and the cathode decreases, the current density on the surface of the graphite gradually increases; the graphite is first subjected to electrochemical intercalation and then subjected to electrolytic exfoliation to obtain a graphene dispersion liquid; the graphene dispersion liquid is subjected to purification treatment to obtain graphene. In the preparation method, the electrochemical intercalation and the electrolytic exfoliation reaction on the graphite are performed in sequence, the prepared graphene material has a high few-layer (carbon layer number is less than or equal to 5) rate, and the types and contents of oxygen-containing functional groups can be controlled.

Description

Technical Field

[0001] This application relates to the field of graphene technology, and in particular to graphene materials and their preparation methods and apparatus. Background Technology

[0002] Graphene materials have been extensively studied due to their excellent properties. Currently, the mainstream preparation methods for graphene materials are divided into "top-down" and "bottom-up" methods, specifically including oxidation-reduction method, CVD method, physical exfoliation method, and electrochemical exfoliation method. Compared with other preparation methods, electrochemical exfoliation method has the potential for large-scale commercial preparation because it introduces fewer defects into the graphene layer during the preparation process, and the equipment is simple and the cost is low.

[0003] In the process of preparing graphene materials using the electrochemical exfoliation method, oxide intercalations are inserted into the interlayers of graphite to introduce a certain degree of oxygen-containing functional groups, and the graphite layers are exfoliated through a vaporization reaction. In the conventional electrochemical exfoliation method, the insertion of oxide intercalations and the vaporization exfoliation process occur simultaneously. It is difficult for the oxide intercalations to be uniformly inserted into the carbon interlayers, making it impossible to uniformly exfoliate the carbon layers of the graphite material. Ultimately, this results in a low few-layer (carbon layer number ≤ 5) ratio in the prepared graphene material, which is mostly graphite microcrystals. Summary of the Invention

[0004] This application provides a graphene material and its preparation method and apparatus, which is beneficial to improving the low few-layer (carbon layer number ≤ 5) ratio of the graphene material.

[0005] In a first aspect, embodiments of this application provide a method for preparing graphene material, comprising the following steps:

[0006] An electrolysis system is prepared, the electrolysis system comprising an anode, a cathode and an electrolyte, wherein a first extending direction of the anode intersects a second extending direction of the cathode;

[0007] Electrolytic reaction is carried out by passing electricity through graphite as the anode, and the graphite is moved along the first extension direction to adjust the distance between the anode and the cathode. As the distance between the anode and the cathode decreases, the current density on the graphite surface gradually increases. The graphite is first electrochemically intercalated and then electrolytically exfoliated to obtain a graphene dispersion.

[0008] The graphene dispersion was purified to obtain graphene.

[0009] In some embodiments, the voltage between the anode and the cathode is 5V to 40V.

[0010] In some embodiments, the angle between the first extending direction and the second extending direction is α, where 20°≤α≤60°;

[0011] In some embodiments, the upper end of the cathode is located at a first liquid level height, and the lower end of the cathode is located at a second liquid level height. At the first liquid level height, the distance between the cathode and the anode is d1, where 8cm ≤ d1 ≤ 30cm.

[0012] In some embodiments, at the second liquid level height, the distance between the cathode and the anode is d2, where 0.2cm ≤ d2 ≤ 3cm.

[0013] In some embodiments, the extension length of the anode in the first extension direction is l1, where 10cm ≤ l1 ≤ 40cm.

[0014] In some embodiments, the cathode extends for a length of l2 in the second extension direction, where 10cm ≤ l2 ≤ 80cm.

[0015] In some embodiments, the graphite is provided by rotating and unfolding a graphite roll, which moves along the first extension direction into the electrolyte to achieve electrical connection with the cathode.

[0016] In some embodiments, the graphite roll is rotated and unfolded, and the graphite moves along the first extension direction so that the distance between the end of the graphite and the cathode remains constant.

[0017] In some embodiments, the graphite moves at a speed of 0.2 cm / min to 3 cm / min along the first extension direction.

[0018] In some embodiments, the graphite includes at least one of natural graphite aggregates, synthetic graphite aggregates, expanded graphite aggregates, highly oriented pyrolytic graphite, graphite fibers, and graphite films.

[0019] In some embodiments, the cathode is a metallic material or a graphite material.

[0020] In some embodiments, the metallic material includes at least one selected from platinum, gold, silver, copper, copper alloys, titanium, titanium alloys, and nickel.

[0021] In some embodiments, the concentration of the solute in the electrolyte is 0.1 mol / L to 5 mol / L.

[0022] In some embodiments, the electrolyte comprises a solute and a solvent, wherein the solute comprises one or more of an acid, a base, and a sulfate.

[0023] In some embodiments, the electrolyte comprises a solute and an organic solvent, wherein the organic solvent comprises one or more of malonic acid, terephthalic acid, and ethylene carbonate.

[0024] In some embodiments, the purification process includes centrifuging the graphene dispersion to obtain a graphene slurry and an electrolyte recovery solution.

[0025] In some embodiments, the centrifugation speed is not less than 3000 r / min.

[0026] In some embodiments, the electrolyte recovery solution is pretreated and then reused as electrolyte.

[0027] In some embodiments, the method further includes filtering, washing, and drying the graphene slurry.

[0028] Secondly, this application also proposes a graphene material prepared by the method described above.

[0029] In some embodiments, the graphene material contains ≥95% by mass of graphene with 5 or fewer graphene layers.

[0030] In some embodiments, the oxygen content in the graphene material is 3wt%-15wt%.

[0031] In some embodiments, the oxygen and carbon elements in the graphene material are bonded together through carbon-oxygen single bonds and / or carbon-oxygen double bonds.

[0032] In some embodiments, the mass ratio of carbon-oxygen single bonds to carbon-oxygen double bonds in the graphene material is 0.25 to 2.

[0033] In some embodiments, the defect density of the graphene material is measured to be I by Raman spectroscopy. D / I G Value, I D / I G ≤0.5.

[0034] Thirdly, this application also proposes an electrochemical preparation device for graphene materials, comprising:

[0035] An electrolytic cell is provided with a feed inlet and contains electrolyte.

[0036] A cathode is disposed in the electrolyte and extends along a second extending direction;

[0037] A feeder is used to continuously insert graphite into the electrolyte through the feed port along a first extending direction. The graphite serves as the anode and is connected to the cathode via a power source. The first extending direction intersects with the second extending direction, and the deeper the graphite is inserted into the electrolyte, the smaller the distance between the graphite and the cathode.

[0038] In some implementations, the voltage of the power supply is 5V-40V.

[0039] In some embodiments, the angle between the first extending direction and the second extending direction is α, where 20°≤α≤60°.

[0040] In some embodiments, the upper end of the cathode is located at a first liquid level height, and the lower end of the cathode is located at a second liquid level height. At the first liquid level height, the distance between the cathode and the anode is d1, where 8cm ≤ d1 ≤ 30cm.

[0041] In some embodiments, at the second liquid level height, the distance between the cathode and the anode is d2, where 0.2cm ≤ d2 ≤ 3cm.

[0042] In some embodiments, the extension length of the anode in the first extension direction is l1, where 10cm ≤ l1 ≤ 40cm.

[0043] In some embodiments, the cathode extends for a length of l2 in the second extension direction, where 10cm ≤ l2 ≤ 80cm.

[0044] In some embodiments, the graphite is provided by rotating and unfolding a graphite roll stored in the feeder, which drives the graphite roll to rotate and unfold in order to continuously supply the graphite as an anode to the electrolytic cell.

[0045] In some embodiments, the feeder is used to drive the graphite roll to rotate and unfold, so as to continuously supply the graphite as an anode to the electrolytic cell, and to maintain the length of the graphite immersed in the electrolyte within a preset length range.

[0046] In some embodiments, the lower wall of the electrolytic cell is provided with a discharge port for collecting the graphene dispersion in the electrolytic cell, and the upper wall of the electrolytic cell is provided with an injection port for adding electrolyte into the electrolytic cell.

[0047] In some embodiments, the preparation apparatus further includes a centrifuge device for centrifuging the graphene dispersion collected from the electrolytic cell.

[0048] Compared with the prior art, this technical solution has at least the following technical advantages:

[0049] In the preparation method of this application, by extending the graphite (anode) along a first extension direction and the cathode along a second extension direction intersecting the first extension direction, and by moving the graphite along the first extension direction during the electrolytic reaction to adjust the distance between the graphite and the cathode, the electrochemical intercalation and electrolytic exfoliation reactions on the graphite can proceed sequentially. This results in a graphene material with a high few-layer ratio (carbon layer number ≤ 5), and the types and contents of its oxygen-containing functional groups are controllable. During the preparation process, as the graphite moves along the first extension direction, the depth of the graphite (anode) inserted into the electrolyte increases, the distance between the graphite (anode) and the cathode decreases, the electric field strength between the graphite and the cathode increases, and the current density generated on the graphite surface also increases accordingly. Figure 1 and Figure 2 As shown, when the current density is low, graphite mainly undergoes an oxidation intercalation (electrochemical intercalation) reaction; for example... Figure 3 As shown, as the current density increases, graphite electrolyzes to produce gas, which pushes apart the carbon layer on the graphite surface, causing the carbon layer to peel off from the graphite.

[0050] In the preparation apparatus of this application, the feeder serves two purposes: firstly, it continuously replenishes graphite into the electrolyte, enabling the continuous preparation of graphene materials; secondly, it drives the graphite to move along the first extension direction, gradually increasing the depth of graphite insertion into the electrolyte. In this application, because the extension directions of the graphite and the cathode intersect, the electric field strength between the graphite and the cathode increases with the depth of graphite insertion into the electrolyte, thus increasing the current density on the graphite surface. During operation, as the feeder continuously feeds, the depth of graphite (anode) insertion into the electrolyte increases, the distance between the graphite (anode) and the cathode decreases, the electric field strength between them increases, and the current density generated on the graphite surface also increases. When the current density is low, the graphite mainly undergoes an oxidation intercalation (electrochemical intercalation) reaction; as the current density increases, the graphite electrolyzes to produce gas, which expands the carbon layer, causing the carbon layer to peel off from the graphite. In the preparation process of graphene materials, the preparation device of this application enables the electrochemical intercalation and electrolytic exfoliation reactions on graphite to proceed sequentially. The resulting graphene material has a high few-layer (carbon layer number ≤ 5) ratio, and the types and contents of its oxygen-containing functional groups can be controlled. Attached Figure Description

[0051] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0052] Figure 1 and Figure 2 This is a diagram illustrating the electrochemical intercalation reaction mechanism in the preparation method of this application;

[0053] Figure 3 This is a diagram illustrating the electrolytic stripping reaction mechanism in the preparation method of this application;

[0054] Figure 4 This is a process flow diagram of the preparation method of this application;

[0055] Figure 5 This is a schematic diagram of the electrochemical preparation apparatus of this application.

[0056] Figure label:

[0057]

[0058] Detailed Implementation

[0059] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0060] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0061] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0062] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0063] Firstly, this application proposes a method for preparing graphene materials.

[0064] Please see Figure 4 In an embodiment of this application, the preparation method includes the following steps:

[0065] S10. Prepare an electrolytic system, which includes an anode, a cathode, and an electrolyte, wherein the first extension direction of the anode intersects the second extension direction of the cathode;

[0066] S20. Electrolysis reaction is carried out by passing electricity through graphite as the anode, and the graphite is moved along the first extension direction to adjust the distance between the anode and the cathode. As the distance between the anode and the cathode decreases, the current density on the graphite surface gradually increases. The graphite is first electrochemically intercalated and then electrolytically exfoliated to obtain a graphene dispersion.

[0067] S30. The graphene dispersion is purified to obtain graphene.

[0068] In the preparation method of this application, by extending the graphite (anode) along a first extension direction and the cathode along a second extension direction intersecting the first extension direction, and by moving the graphite along the first extension direction during the electrolytic reaction to adjust the distance between the graphite and the cathode, the electrochemical intercalation and electrolytic exfoliation reactions on the graphite can proceed sequentially. This results in a graphene material with a high few-layer ratio (carbon layer number ≤ 5), and the types and contents of its oxygen-containing functional groups are controllable. During the preparation process, as the graphite moves along the first extension direction, the depth of the graphite (anode) inserted into the electrolyte increases, the distance between the graphite (anode) and the cathode decreases, the electric field strength between the graphite and the cathode increases, and the current density generated on the graphite surface also increases accordingly. Figure 1 and Figure 2 As shown, when the current density is low, graphite mainly undergoes an oxidation intercalation (electrochemical intercalation) reaction; for example... Figure 3 As shown, as the current density increases, graphite electrolyzes to produce gas, which pushes the carbon layer apart, causing the carbon layer to peel off from the graphite.

[0069] In some implementations, the graphene material contains ≥95% by mass of graphene with 5 or fewer graphene layers.

[0070] In some embodiments, the oxygen content in the graphene material is 3 wt% to 15 wt%, specifically 3 wt%, 6 wt%, 9 wt%, 12 wt%, 15 wt%, or any value between them. In graphene materials, an appropriate amount of oxygen-containing functional groups is beneficial for improving the dispersibility of the graphene material and can provide loading sites; excessive oxygen-containing functional groups in the graphene material will weaken the inherent properties of the graphene material; insufficient oxygen-containing functional groups in the graphene material are detrimental to improving the dispersibility of the graphene material and to increasing the number of loading sites.

[0071] In some embodiments, the mass ratio of carbon-oxygen single bonds to carbon-oxygen double bonds in the graphene material is 0.25 to 2, specifically 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, or 2.0, etc., and of course, other values ​​within the above range are also possible and are not limited here. In this application, by controlling the mass ratio of carbon-oxygen single bonds to carbon-oxygen double bonds within the above range, it is beneficial to introduce specific polymers, small molecule compounds, or copolymers into the functional group positions of the graphene material through the covalent bond positions of carbon-oxygen single bonds and carbon-oxygen double bonds to achieve the functionalization of the graphene material.

[0072] In some implementations, the defect density of the graphene material is measured to be I using Raman spectroscopy. D / I G Value, I D / I G ≤0.5.

[0073] In some embodiments, the voltage between the anode and cathode is 5V to 40V, specifically 5V, 10V, 15V, 20V, 25V, 30V, 35V, 40V, or any value between them. If the voltage is too high, a large current density may be generated on the surface of the graphite immediately after it is inserted into the electrolyte, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic stripping reaction on the graphite. If the voltage is too low, the current density on the graphite may still be too low when the graphite moves to the corresponding position at the lower end of the cathode, failing to reach the current density required for the electrolytic stripping reaction. By controlling the voltage between the anode and cathode within the above range, it is beneficial for the portion of the graphite near the liquid surface to achieve intercalation, and for the portion near the bottom to achieve stripping, thereby increasing the few-layer (carbon layer number ≤ 5) ratio of the graphene material.

[0074] In some embodiments, the angle between the first extension direction and the second extension direction is α, where 20° ≤ α ≤ 60°, specifically 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, or any value between them. When the value of α is within the above range, it is beneficial to control the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite during the electrolysis process to proceed separately. This can effectively improve the few-layer (carbon layer number ≤ 5) ratio of the graphene material and better control the type and content of oxygen-containing functional groups in the graphene material.

[0075] In some embodiments, the upper end of the cathode is located at a first liquid level height, and the lower end of the cathode is located at a second liquid level height. At the first liquid level height, the distance between the cathode and the anode is d1, where 8cm ≤ d1 ≤ 30cm, specifically 8cm, 10cm, 15cm, 20cm, 25cm, 30cm, or any value between them. When the voltage is constant, if d1 is too small, a large current density may be generated on the surface of the graphite as soon as it is inserted into the electrolyte, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite. If d1 is too large, it may be difficult to control the reaction time of the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite within an appropriate range, thereby reducing the preparation efficiency of graphene materials and making it difficult to control the type and content of oxygen-containing functional groups in graphene materials. By controlling d1 within the above range, it is beneficial for the part of the graphite near the liquid surface to be intercalated and the part of the graphite near the bottom to be exfoliated, thereby improving the preparation efficiency of graphene materials and the few-layer (carbon layer number ≤ 5) ratio of graphene materials, and facilitating the control of the type and content of oxygen-containing functional groups in graphene materials.

[0076] In some embodiments, at the second liquid level height, the distance between the cathode and the anode is d2, 0.2cm≤d2≤3cm, specifically 0.2cm, 0.4cm, 0.8cm, 1.2cm, 1.6cm, 2cm, 2.4cm, 2.8cm, 3cm, or any value between them. When the voltage is constant and the extension length of the cathode in the first extension direction is constant, if d2 is too large, the current density on the graphite may still be too small when the graphite moves to the corresponding position at the lower end of the cathode, failing to reach the current density required for the electrolytic stripping reaction. If d2 is too small, the current gradient on the graphite surface may be large in the first extension direction during the electrolytic reaction, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic stripping reaction on the graphite. By controlling d2 within the above range, it is beneficial for the portion of the graphite near the liquid surface immersed in the electrolyte to achieve intercalation, and for the portion of the graphite near the bottom to achieve stripping, thereby increasing the few-layer (carbon layer number ≤ 5) ratio of the graphene material.

[0077] In some embodiments, the extension length of the anode in the first extension direction is l1. Specifically, it can be 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm or any value between them.

[0078] In some embodiments, the cathode extends for a length of l2 in the second extension direction. Specifically, it can be 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm or any value between them.

[0079] In some embodiments, graphite is provided by the rotation and unfolding of a graphite roll. The rotation and unfolding of the graphite roll causes the graphite to move along the first extension direction into the electrolyte and achieve electrical connection with the cathode. The graphite roll can continuously provide graphite (i.e., anode material) for the electrolytic reaction, thereby enabling the electrolytic reaction to proceed continuously without interruption due to the consumption of graphite feed. This enables the continuous preparation of graphene materials and improves the preparation efficiency of graphene materials.

[0080] In some embodiments, during the carbon layer peeling process on graphite, the graphite roll rotates and unfolds, keeping the distance between the graphite end and the cathode constant. Specifically, during electrolysis, the current density on the graphite surface increases sequentially from top to bottom. The carbon layer at the lower end of the graphite is peeled off before the carbon layer at the upper end. As the carbon layer is peeled off, the lower end of the graphite is transformed into graphene particles dispersed in the electrolyte. During this process, by controlling the unfolding rate of the graphite roll, the length of the graphite along the first extension direction remains constant. This ensures that the electrochemical intercalation and electrolytic peeling on the graphite are carried out separately while maximizing the efficiency of graphene material preparation.

[0081] In some embodiments, the graphite moving speed along the first extension direction is 0.2 cm / min to 3 cm / min, specifically 0.2 cm / min, 0.8 cm / min, 1.2 cm / min, 1.7 cm / min, 2.2 cm / min, 2.7 cm / min, 3 cm / min or any value between them; by controlling the graphite moving speed along the first extension direction within the above range, it is beneficial to improve the preparation efficiency of graphene materials while ensuring that the electrochemical intercalation and electrolytic exfoliation reactions on the graphite are carried out separately.

[0082] In some embodiments, the preparation efficiency of graphene material is not less than 12 g / h, that is, using the preparation method of this application, at least 12 g of graphene material can be prepared per hour.

[0083] In some embodiments, the graphite (i.e., the anode) includes at least one of natural graphite aggregates, synthetic graphite aggregates, expanded graphite aggregates, highly oriented pyrolytic graphite, graphite fibers, and graphite films; of course, the anode can also be other types of graphite, which is not particularly limited in this application, as long as it is convenient to use as an anode for carbon layer stripping.

[0084] In some embodiments, the cathode is a metallic material or a graphite material.

[0085] In some embodiments, the metallic material includes at least one selected from platinum, gold, silver, copper, copper alloys, titanium, titanium alloys, and nickel.

[0086] In some embodiments, the graphite material used as the cathode includes at least one of natural graphite aggregates, synthetic graphite aggregates, expanded graphite aggregates, highly oriented pyrolytic graphite, graphite fibers, and graphite films.

[0087] In some embodiments, the concentration of the solute in the electrolyte is 0.1 mol / L to 5 mol / L, specifically 0.1 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or any value between them. If the concentration of the solute in the electrolyte is too high, the amount of oxide intercalations between the graphite carbon layers will be excessive, potentially leading to an excessive content of oxygen-containing functional groups in the final graphene material. Excessive oxygen-containing functional groups weaken the inherent properties of the graphene material. Conversely, if the concentration of the solute in the electrolyte is too low, the amount of oxide intercalations between the graphite carbon layers may be insufficient, which is detrimental to improving the dispersibility of the obtained graphene material and to increasing the number of loading sites. By controlling the concentration of the solute in the electrolyte within the above-mentioned range, it is beneficial to regulate the content of oxygen-containing functional groups in the graphene material within an appropriate range.

[0088] In some embodiments, the electrolyte includes a solute and a solvent, the solute including one or more of an acid, a base, and a sulfate.

[0089] In some embodiments, the acid includes one or more of sulfuric acid, phosphoric acid, and perchloric acid.

[0090] In some embodiments, the base includes one or more of sodium hydroxide and potassium hydroxide.

[0091] In some embodiments, the solvent includes water and / or organic solvents.

[0092] In some embodiments, the organic solvent includes one or more of malonic acid, terephthalic acid, and ethylene carbonate;

[0093] In some embodiments, the purification process includes centrifuging the graphene dispersion to obtain graphene slurry and electrolyte recovery liquid, that is, the upper clear liquid after centrifugation is the electrolyte recovery liquid, and the lower material is the graphene slurry.

[0094] In some embodiments, the centrifugation speed is not less than 3000 r / min, which is advantageous for separating the graphene slurry and the electrolyte recovery liquid.

[0095] In some embodiments, the preparation method of this application further includes pretreating the electrolyte recovery solution for reuse as an electrolyte. The specific pretreatment steps include adjusting the pH value of the electrolyte recovery solution to a preset pH range. This embodiment improves raw material utilization and saves raw material costs by reusing the pretreated electrolyte recovery solution as an electrolyte.

[0096] In some embodiments, the purification process includes centrifuging the graphene dispersion to obtain a graphene slurry and an electrolyte recovery solution. The preparation method of this application also includes filtering, washing and drying the graphene slurry.

[0097] Secondly, this application also proposes a graphene material prepared by the above-described preparation method.

[0098] In some implementations, the graphene material contains ≥95% by mass of graphene with 5 or fewer graphene layers.

[0099] In some embodiments, the oxygen content in the graphene material is 3wt%-15wt%, specifically 3wt%, 6wt%, 9wt%, 12wt%, 15wt%, or any value between them.

[0100] In some implementations, the oxygen and carbon elements in the graphene material are bonded together through carbon-oxygen single bonds and / or carbon-oxygen double bonds.

[0101] In some implementations, the defect density of the graphene material is measured to be I using Raman spectroscopy. D / I G Value, I D / I G ≤0.5.

[0102] Please see Figure 5 Thirdly, this application also proposes an electrochemical preparation apparatus 100 for graphene materials, comprising:

[0103] The electrolytic cell 110 has a feed inlet 113 and contains an electrolyte 160.

[0104] Cathode 120 is inserted into electrolyte 160, and cathode 120 extends along the second extending direction S2;

[0105] The feeder 140 is used to continuously insert graphite 130 into the electrolyte 160 through the feed port 113 along the first extension direction S1. The graphite serves as the anode 130 and is connected to the cathode 120 via the power supply 150. The first extension direction S1 intersects with the second extension direction S2, and the deeper the graphite 130 is inserted into the electrolyte 160, the smaller the distance between the graphite 130 and the cathode 120.

[0106] In the preparation apparatus 100 of this application, the feeder 140 is configured to continuously replenish graphite 130 into the electrolyte 160, thereby achieving continuous preparation of graphene material. Furthermore, it drives the graphite 130 to move along the first extension direction S1, gradually increasing the depth of insertion of the graphite 130 into the electrolyte 160. In this application, since the extension directions of the graphite 130 and the cathode 120 intersect, the electric field strength between the graphite 130 and the cathode 120 increases with the increase of the insertion depth of the graphite 130 into the electrolyte 160, which also results in an increase in the current density on the surface of the graphite 130 with the increase of the insertion depth into the electrolyte 160. During the operation, as the feeder 140 continuously feeds, the depth of the graphite (anode) 130 inserted into the electrolyte 160 increases, the distance between the graphite (anode) 130 and the cathode 120 decreases, the electric field strength between the graphite 130 and the cathode 120 increases, and the current density generated on the surface of the graphite 130 also increases accordingly. When the current density is low, the graphite 130 mainly undergoes an oxidative intercalation (electrochemical intercalation) reaction. As the current density increases, the graphite 130 electrolyzes to generate gas, which expands the carbon layers, causing the carbon layers to peel off from the graphite 130. In the preparation process of graphene materials, the preparation apparatus 100 of this application enables the electrochemical intercalation and electrolytic peeling reactions on the graphite 130 to proceed sequentially. The graphene material obtained thereby has a high few-layer ratio (carbon layer number ≤ 5), and the types and contents of its oxygen-containing functional groups are controllable.

[0107] In some embodiments, the voltage between the anode 130 and the cathode 120 is 5V-40V, specifically 5V, 10V, 15V, 20V, 25V, 30V, 35V, 40V, or any value between them. If the voltage is too high, a large current density may be generated on the surface of the graphite immediately after it is inserted into the electrolyte, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic stripping reaction on the graphite. If the voltage is too low, the current density on the graphite may still be too low when the graphite moves to the corresponding position at the lower end of the cathode, failing to reach the current density required for the electrolytic stripping reaction. By controlling the voltage between the anode and cathode within the above range, it is beneficial for the portion of the graphite near the liquid surface to achieve intercalation, and for the portion near the bottom to achieve stripping, thereby increasing the few-layer (carbon layer number ≤ 5) ratio of the graphene material.

[0108] In some embodiments, the angle between the first extension direction S1 and the second extension direction S2 is α, where 20° ≤ α ≤ 60°, specifically 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, or any value between them. When the value of α is within the above range, it is beneficial to control the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite during the electrolysis process to proceed separately. This can effectively improve the few-layer (carbon layer number ≤ 5) ratio of the graphene material and better control the type and content of oxygen-containing functional groups in the graphene material.

[0109] In some embodiments, the upper end of the cathode is located at a first liquid level height, and the lower end of the cathode is located at a second liquid level height. At the first liquid level height, the distance between the cathode and the anode is d1, where 8cm ≤ d1 ≤ 30cm, specifically 8cm, 10cm, 15cm, 20cm, 25cm, 30cm, or any value between them. When the voltage is constant, if d1 is too small, a large current density may be generated on the surface of the graphite as soon as it is inserted into the electrolyte, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite. If d1 is too large, it may be difficult to control the reaction time of the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite within an appropriate range, thereby reducing the preparation efficiency of graphene materials and making it difficult to control the type and content of oxygen-containing functional groups in graphene materials. By controlling d1 within the above range, during the preparation of graphene materials, it is beneficial for the part of the graphite near the liquid surface to be intercalated and the part of the graphite near the bottom to be exfoliated, thereby improving the preparation efficiency of graphene materials and the few-layer (carbon layer number ≤ 5) rate of graphene materials, and facilitating the control of the type and content of oxygen-containing functional groups in graphene materials.

[0110] In some embodiments, at the second liquid level height, the distance between the cathode and the anode is d2, 0.2cm≤d2≤3cm, specifically 0.2cm, 0.4cm, 0.8cm, 1.2cm, 1.6cm, 2cm, 2.4cm, 2.8cm, 3cm, or any value between them. When the voltage is constant and the extension length of the cathode in the first extension direction is constant, if d2 is too large, the current density on the graphite may still be too small when the graphite moves to the corresponding position at the lower end of the cathode, failing to reach the current density required for the electrolytic stripping reaction. If d2 is too small, the current gradient on the graphite surface may be large in the first extension direction during the electrolytic reaction, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic stripping reaction on the graphite. By controlling d2 within the above range, it is beneficial for the portion of the graphite near the liquid surface immersed in the electrolyte to achieve intercalation, and for the portion of the graphite near the bottom to achieve stripping, thereby increasing the few-layer (carbon layer number ≤ 5) ratio of the graphene material.

[0111] In some embodiments, the extension length of the anode in the first extension direction S1 is l1. Specifically, it can be 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm or any value between them.

[0112] In some embodiments, the cathode extends for a length of l2 in the second extension direction S2. Specifically, it can be 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm or any value between them.

[0113] In some embodiments, graphite 130 is provided by rotating and unfolding graphite roll 170, which is stored in feeder 140. Feeder 140 is used to drive graphite roll 170 to rotate and unfold, so as to continuously provide graphite 130 as anode 130 to the electrolytic cell 110.

[0114] In some embodiments, graphite roll 170 is graphite roll paper or graphite roll strip.

[0115] In some embodiments, the feeder 140 drives the graphite roll 170 to rotate and unfold, providing graphite 130 as an anode 130 to the electrolytic cell 110, and maintaining the length of the graphite 130 immersed in the electrolyte within a preset length range. Specifically, during electrolysis, the current density on the surface of the graphite 130 increases sequentially from top to bottom. The carbon layer at the lower end of the graphite 130 is peeled off from the graphite before the carbon layer at the upper end. As the carbon layer is peeled off, the lower end of the graphite 130 is transformed into graphene particles dispersed in the electrolyte 160. During this process, by controlling the unfolding rate of the graphite roll 170, the length of the graphite 130 along the first extension direction S1 remains unchanged, thereby maximizing the efficiency of graphene material preparation while ensuring that the electrochemical intercalation and electrolytic peeling on the graphite 130 are carried out separately.

[0116] In some embodiments, the preparation apparatus 100 further includes a centrifuge 180 for centrifuging the graphene dispersion collected from the electrolytic cell 110. By centrifuging the collected graphene dispersion, the supernatant can be recovered and used as electrolyte 160 after pretreatment. The lower graphene slurry can be further purified, specifically by filtration, washing and drying.

[0117] In some embodiments, the lower end wall of the electrolytic cell 110 is provided with a discharge port 112, through which the graphene dispersion in the electrolytic cell 110 is collected. The upper end wall of the electrolytic cell 110 is provided with a liquid injection port 111, through which electrolyte 160 is added to the electrolytic cell 110. The added electrolyte 160 can be reconfigured or obtained by pretreatment of recycled electrolyte 160.

[0118] The embodiments of this application will be further described below with reference to several examples. However, the embodiments of this application are not limited to the specific embodiments described below. Appropriate modifications can be made within the scope of the main claims.

[0119] Test method:

[0120] 1. Graphene preparation efficiency:

[0121] Preparation efficiency = Graphene mass / Preparation time;

[0122] 2. Graphene layer distribution:

[0123] Using an atomic force microscope (Dimension icon / Dimension icon XR; Bruker (Germany)), 100 graphene sheets were randomly selected, and their thicknesses and the number of graphene layers were calculated (single-layer graphene thickness: 0.7-1.2 nm).

[0124] 3. Test method for defect density in graphene:

[0125] Raman spectroscopy was used to measure the activity of graphene at 1350 cm⁻¹. -1 Peak intensity I at the location D With at 1580cm -1 Peak intensity I at the location G The ratio I D / I G I D / I G The smaller the value, the fewer defects the graphite material has.

[0126] 4. Characterization method for the content of oxygen-containing functional groups on the graphene surface:

[0127] The relative elemental content of C and O and functional groups of graphene materials were analyzed using a Thermo Scientific K-Alpha+ X-ray photoelectron spectrometer manufactured by Thermo Scientific, USA. A monochromatic Al target Kα line with a full-spectrum pass energy of 100 eV and a fine-spectrum pass energy of 30 eV was used to perform peak separation analysis on the C1s peaks of the material's XPS fine spectrum. The analyzed peaks included C=C bonds (284.0 eV), CCC bonds (284.8 eV), CO bonds (286.6 eV), C=O bonds (287.8 eV), and a stacked satellite peak of π*-π* (289.8 eV). The ratio of the CO bond C=O bond peak area was calculated, which is the content ratio of CO functional groups / C=O functional groups.

[0128] Example 1

[0129] Carbon layer stripping: Prepare a 1.0 mol / L H₂SO₄ solution (i.e., electrolyte) and inject it into the electrolytic cell. Graphite paper, as the anode, is vertically inserted into the electrolyte and connected to the positive terminal of the power supply. A platinum sheet, as the cathode, is obliquely inserted into the electrolyte and connected to the negative terminal of the power supply. Slowly move the graphite paper downwards, ensuring that the lower end of the graphite paper remains flush with the lower end of the platinum sheet. The power supply is 30V; near the electrolyte interface, the distance between the anode and cathode (d1) is 10 cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (d2) is 2 cm; the angle between the extensions of the anode and cathode is 30°.

[0130] Purification process: After collecting the graphene dispersion, centrifuge it and add concentrated H2SO4 to the supernatant obtained by centrifugation to make the H2SO4 concentration of the supernatant reach 1.0 mol / L, and then re-inject it into the electrolytic cell; filter the lower graphene slurry obtained by centrifugation and wash it with pure water until neutral, then freeze-dry it to obtain graphene powder.

[0131] Example 2

[0132] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 20cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 45°.

[0133] Example 3

[0134] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 30cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 60°.

[0135] Example 4

[0136] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 20cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 0.2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 45°.

[0137] Example 5

[0138] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 8 cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 0.2 cm; and the angle between the extensions of the anode and cathode (i.e., α) is 30°.

[0139] Example 6

[0140] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 15cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 3cm; and the angle between the extensions of the anode and cathode (i.e., α) is 30°.

[0141] Example 7

[0142] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 15cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 20°.

[0143] Example 8

[0144] The difference from Example 1 is that the power supply voltage is 5V.

[0145] Example 9

[0146] The difference from Example 1 is that the power supply voltage is 40V.

[0147] Example 10

[0148] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 7 cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 0.3 cm; and the angle between the extensions of the anode and cathode (i.e., α) is 30°.

[0149] Example 11

[0150] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 10cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 0.1cm; and the angle between the extensions of the anode and cathode (i.e., α) is 30°.

[0151] Example 12

[0152] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 10cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 15°.

[0153] Example 13

[0154] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 20cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 65°.

[0155] Example 14

[0156] The difference from Example 1 is that: near the electrolyte interface, the distance between the anode and cathode (i.e., d1) is 40cm; near the bottom of the electrolytic cell, the distance between the anode and cathode (i.e., d2) is 2cm; and the angle between the extensions of the anode and cathode (i.e., α) is 60°.

[0157] Comparative Example 1

[0158] The difference from Example 1 is that the graphite paper and platinum sheet are inserted into the electrolyte in parallel (i.e., α = 0°), and the distance between them is 10 cm (i.e., d1 = d2 = 10 cm).

[0159] Comparative Example 2

[0160] The difference from Example 1 is that the graphite paper and the platinum sheet are inserted into the electrolyte in parallel (i.e., α = 0°) and the distance between them is 10 cm (i.e., d1 = d2 = 10 cm); the graphite paper is covered with a platinum mesh to achieve confined stripping of the carbon layer.

[0161] The key preparation parameters for Examples 1-14 and Comparative Examples 1-2 are shown in Table 1 below:

[0162] sample <![CDATA[d1 / cm]]> <![CDATA[d2 / cm]]> α / ° <![CDATA[l1 / cm]]> Voltage / V Example 1 10 2 30 13.9 30 Example 2 20 2 45 18.0 30 Example 3 30 2 60 16.2 30 Example 4 20 0.2 45 19.8 30 Example 5 8 0.2 30 13.5 30 Example 6 15 3 30 20.7 30 Example 7 15 2 20 35.7 30 Example 8 10 2 30 13.9 5 Example 9 10 2 30 13.9 40 Example 10 7 0.2 30 11.6 30 Example 11 10 0.1 30 17.1 30 Example 12 10 2 15 29.9 30 Example 13 20 2 65 8.39 30 Example 14 40 2 60 21.9 30 Comparative Example 1 10 10 0 15 30 Comparative Example 2 10 10 0 15 30

[0163] The performance tests of the graphene materials prepared in Examples 1-14 and Comparative Examples 1-2 are shown in Table 2 below:

[0164]

[0165] Analyzing Tables 1 and 2 above, and comparing Examples 1-14 with Comparative Examples 1-2, it can be concluded that, compared to inserting the graphite anode and cathode parallel to each other into the electrolyte, this application can significantly improve the few-layer (carbon layer number ≤ 5) ratio of the obtained graphene material by inserting the graphite anode at an angle relative to the cathode into the electrolyte.

[0166] Comparing Example 10 with Example 5, it can be concluded that when d2, α, and voltage are constant, if d1 is too small, excessive current density may occur on the surface of the graphite immediately after insertion into the electrolyte. This is detrimental to separating the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite, resulting in reduced graphene material preparation efficiency, reduced few-layer (carbon layer number ≤ 5) rate, and difficulty in controlling the oxygen content in the graphene material within a suitable range. Comparing Example 11 with Example 1, it can be concluded that when d1, α, and voltage are constant, if d2 is too small, excessive current density may occur during electrolysis. During the reaction process, it is not conducive to controlling the reaction time of both the electrochemical intercalation reaction and the electrolytic exfoliation reaction on graphite within an appropriate range, which will reduce the preparation efficiency of graphene materials and make it difficult to control the oxygen content in the graphene materials within a suitable range. By comparing Example 12 with Example 1, it can be concluded that when d1, d2, and voltage are constant, if α is too small, it may lead to a small current increase gradient on the graphite surface in the first extension direction during the electrolytic reaction, which is not conducive to separating the electrochemical intercalation reaction and the electrolytic exfoliation reaction on graphite, and will reduce the I of the graphene materials. D / I G Increased α leads to a decrease in the few-layer (carbon layer number ≤ 5) ratio and makes it difficult to control the CO / C=O content in graphene materials within a suitable range. A comparison of Example 13 and Example 2 shows that when d1, d2, and voltage are constant, an excessively large α may result in an excessively large current gradient on the graphite surface in the first extension direction during the electrolytic reaction. This is detrimental to separating the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite, leading to a decrease in the preparation efficiency of graphene materials, a decrease in the few-layer (carbon layer number ≤ 5) ratio, and difficulty in controlling the oxygen content in the graphene materials within a suitable range. A comparison of Example 14 and Example 3 shows that when d2, α, and voltage are constant, an excessively large d1 may be detrimental to controlling the reaction time of both the electrochemical intercalation reaction and the electrolytic exfoliation reaction on the graphite within an appropriate range, thus reducing the preparation efficiency of graphene materials and the I... D / I G This increases the risk of oxygen content in graphene materials and makes it difficult to control the oxygen content within a suitable range.

[0167] In summary, by comparing Examples 10-14 with Examples 1-9, it can be concluded that when the power supply voltage is 5V-40V, 20°≤α≤60°, 8cm≤d1≤30cm, and 0.2cm≤d2≤3cm, it is beneficial to separate the electrochemical intercalation reaction and the electrolytic exfoliation reaction on graphite. While taking into account the preparation efficiency, the resulting graphene material not only has a high few-layer (carbon layer number ≤5) ratio, but also small graphite defects, and suitable oxygen content and CO to C=O content ratio.

[0168] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing graphene material, characterized in that, Includes the following steps: An electrolytic system is prepared, the electrolytic system including an anode, a cathode and an electrolyte, wherein a first extending direction of the anode intersects a second extending direction of the cathode, and the angle between the first extending direction and the second extending direction is α, where 20°≤α≤60°; Electrolytic reaction is carried out by passing electricity through graphite as the anode, and the graphite is moved along the first extension direction to adjust the distance between the anode and the cathode. As the distance between the anode and the cathode decreases, the current density on the graphite surface gradually increases. The graphite is first electrochemically intercalated and then electrolytically exfoliated to obtain a graphene dispersion. The graphene dispersion was purified to obtain graphene. The graphite is provided by rotating and unfolding a graphite roll to continuously supply the anode to the electrolytic cell, and to maintain the length of the graphite immersed in the electrolyte within a preset length range.

2. The preparation method according to claim 1, characterized in that, It also includes at least one of the following features (1)-(5): (1) The voltage between the anode and the cathode is 5V to 40V; (2) The upper end of the cathode is located at the first liquid level height, and the lower end of the cathode is located at the second liquid level height. At the first liquid level height, the distance between the cathode and the anode is d1, where 8cm≤d1≤30cm. (3) The upper end of the cathode is located at the first liquid level height, and the lower end of the cathode is located at the second liquid level height. At the second liquid level height, the distance between the cathode and the anode is d2, 0.2cm≤d2≤3cm; (4) The anode extends along the first extension direction in the electrolyte for a length of l1, where 10cm≤l1≤40cm; (5) The cathode extends in the electrolyte along the second extension direction for a length of l2, where 10cm≤l2≤80cm.

3. The preparation method according to claim 1, characterized in that, It also includes at least one of the following features (1)-(13): (1) The graphite moves along the first extension direction into the electrolyte and is electrically connected to the cathode; (2) The graphite roll is rotated and unfolded, and the graphite moves along the first extension direction so that the distance between the end of the graphite and the cathode remains unchanged; (3) The graphite moves at a speed of 0.2 cm / min to 3 cm / min along the first extension direction; (4) The graphite includes at least one of natural graphite aggregates, synthetic graphite aggregates, expanded graphite aggregates, highly oriented pyrolytic graphite, graphite fibers, and graphite films. (5) The cathode is a metallic material or a graphite material; (6) The cathode is a metallic material or a graphite material, wherein the metallic material includes at least one of platinum, gold, silver, copper, copper alloy, titanium, titanium alloy and nickel; (7) The concentration of the solute in the electrolyte is 0.1 mol / L-5 mol / L; (8) The electrolyte comprises a solute and a solvent, wherein the solute comprises one or more of an acid, a base and a sulfate; (9) The electrolyte includes a solute and an organic solvent, wherein the organic solvent includes one or more of malonic acid, terephthalic acid, and ethylene carbonate; (10) The purification process includes centrifuging the graphene dispersion to obtain graphene slurry and electrolyte recovery solution; (11) The purification process includes centrifuging the graphene dispersion to obtain graphene slurry and electrolyte recovery liquid; wherein the centrifugation speed is not less than 3000 r / min; (12) The purification process includes centrifuging the graphene dispersion to obtain graphene slurry and electrolyte recovery liquid, and pre-treating the electrolyte recovery liquid for reuse as electrolyte. (13) The purification process includes centrifuging the graphene dispersion to obtain graphene slurry and electrolyte recovery liquid. The method also includes filtration, washing and drying of the graphene slurry.

4. A graphene material, characterized in that, It is prepared by the preparation method according to any one of claims 1-3.

5. The graphene material as described in claim 4, characterized in that, It has at least one of the following features (1)-(5): (1) In the graphene material, the mass percentage of graphene with 5 or less graphene layers is ≥95%. (2) The oxygen content in the graphene material is 3wt%-15wt%; (3) The oxygen and carbon elements in the graphene material are bonded together through carbon-oxygen single bonds and / or carbon-oxygen double bonds. (4) The oxygen and carbon elements in the graphene material are combined through carbon-oxygen single bonds and carbon-oxygen double bonds, and the ratio between the mass content of carbon-oxygen single bonds and the mass content of carbon-oxygen double bonds in the graphene material is 0.25 to 2. (5) The defect density of the graphene material was determined by Raman spectroscopy to be the ID / IG value, where ID / IG ≤ 0.

5.

6. An electrochemical preparation apparatus for graphene material, characterized in that, include: An electrolytic cell is provided with a feed inlet and contains electrolyte. A cathode is disposed in the electrolyte and extends along a second extending direction; A feeder is used to continuously insert graphite into the electrolyte through the feed port along a first extending direction. The graphite serves as the anode and is connected to the cathode via a power source. The first extending direction intersects with the second extending direction, and the angle between the first extending direction and the second extending direction is α, where 20°≤α≤60°. Furthermore, the deeper the graphite is inserted into the electrolyte, the smaller the distance between the graphite and the cathode. The graphite is provided by rotating and unfolding a graphite roll, which is stored in the feeder. The feeder is used to drive the graphite roll to rotate and unfold in order to continuously supply the anode to the electrolytic cell, and to maintain the length of the graphite immersed in the electrolyte within a preset length range.

7. The preparation apparatus according to claim 6, characterized in that, It also includes at least one of the following features (1)-(5): (1) The voltage of the power supply is 5V to 40V; (2) The upper end of the cathode is located at the first liquid level height, and the lower end of the cathode is located at the second liquid level height. At the first liquid level height, the distance between the cathode and the anode is d1, where 8cm≤d1≤30cm. (3) The upper end of the cathode is located at the first liquid level height, and the lower end of the cathode is located at the second liquid level height. At the second liquid level height, the distance between the cathode and the anode is d2, 0.2cm≤d2≤3cm; (4) The extension length of the anode in the first extension direction is l1, 10cm≤l1≤40cm; (5) The extension length of the cathode in the second extension direction is l2, 10cm≤l2≤80cm.

8. The preparation apparatus as described in claim 6, characterized in that, The lower wall of the electrolytic cell is provided with a discharge port for collecting graphene dispersion in the electrolytic cell, and the upper wall of the electrolytic cell is provided with an injection port for adding electrolyte into the electrolytic cell.

9. The preparation apparatus according to claim 6, characterized in that, The preparation apparatus further includes a centrifuge device for centrifuging the graphene dispersion collected from the electrolytic cell.

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