Self-supporting dopamine hydrochloride coated carbon material as well as preparation method and application thereof

Abstract

The invention discloses a self-supporting dopamine hydrochloride coated carbon material as well as a preparation method and application thereof.Through coating of dopamine hydrochloride, hard carbon surface defects can be reduced, the first effect of the material is improved, a self-supporting membrane structure is constructed through vacuum filtration of graphene oxide dispersion liquid, the sodium storage performance of the carbon material is improved, and the self-supporting dopamine hydrochloride coated carbon material is prepared. The volume expansion of the carbon nanoflowers is inhibited, so that the material has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and in particular to a self-supporting carbon material coated with dopamine hydrochloride, a preparation method thereof, and an application thereof. Background Art

[0002] Hard carbon materials are widely used as anodes in sodium-ion batteries due to their relatively high sodium storage capacity. However, due to the relatively large number of surface defects in hard carbon materials, this will lead to a reduction in the first efficiency; at present, coating technology is usually used to reduce the surface defects of materials.

[0003] Chinese Patent Application No. CN202011323238.X discloses a method for preparing a novel silicon-carbon anode material using dopamine hydrochloride, which is carried out according to the following steps: dissolving a certain mass of tris(hydroxymethyl)aminomethane hydrochloride in a certain amount of deionized water, denoted as solution A; adding a certain mass of hydrochloric acid to a certain amount of deionized water, denoted as solution B; adding solution B dropwise to solution A while stirring to make the pH of the mixture = 8.5, denoted as solution C; dissolving a certain mass of dopamine hydrochloride in a certain amount of solution C, and dispersing it by electromagnetic stirring to form solution D, adding a certain amount of SiO2 to solution D, denoted as solution B; continuing to stir solution B for 24 h; after the stirring is completed, carrying out suction filtration and washing with water, and drying the obtained material at 60 °C for 4 h, denoted as material C; placing material C in a tube furnace filled with a protective atmosphere, heating to 800 °C and holding for 3 h for carbonization to obtain SiO2 / C; mixing SiO2 / C with a certain mass of reducing agent, placing it in a tube furnace filled with a protective atmosphere, heating to 950 °C, holding for 5 h for a reduction reaction, after the reaction is completed, pickling with dilute HCl of a certain concentration, washing with a large amount of deionized water, and carrying out vacuum drying after detecting that the pH = 7, finally obtaining the novel anode material Si / C; although this technology can reduce the synthesis cost of the silicon-carbon anode material, it still cannot solve the problem of poor cycling performance of the silicon-carbon anode.

[0004] Chinese Patent Application No. CN202310035331.8 discloses a multi-layer nitrogen-doped carbon-coated bismuth material, its preparation method and application, which include the following steps: (1) Prepare an alginate solution: Add sodium alginate and urea to water, stir well to obtain an alginate solution; (2) Prepare a bismuth salt solution: Dissolve bismuth nitrate pentahydrate in a nitric acid solution, add water to obtain a bismuth salt solution; (3) Drop the alginate solution into the bismuth salt solution, let it stand and then filter to obtain bismuth alginate gel balls, and freeze-dry the bismuth alginate gel balls; (4) First-step calcination and coating: After freeze-drying the bismuth alginate gel balls, calcine them in an inert atmosphere, grind them into powder after calcination, take the ground powder and add it to Tris-HCl buffer solution, disperse it ultrasonically, add dopamine hydrochloride for coating, keep stirring, filter and then dry; (5) Second-step calcination and coating: The material after the first-step coating is calcined in an inert atmosphere, ground into powder after calcination, take the ground powder and add it to Tris-HCl buffer solution, disperse it ultrasonically, add dopamine hydrochloride for coating, keep stirring, filter and then dry; (6) Grind the material after the second-step coating to obtain the multi-layer nitrogen-doped carbon-coated bismuth material. Although this technology can improve the discharge specific capacity and cycling performance of the battery, multiple coatings increase the specific surface area of the material and reduce the first efficiency of the initial material.

[0005] In view of the above situation, there is an urgent need to develop a technology for coating carbon materials with dopamine hydrochloride, which can reduce the surface defects of hard carbon materials, improve the first efficiency of the materials, improve the sodium storage performance of the materials, and improve the electrochemical performance of the materials. Summary of the Invention

[0006] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a self-supporting dopamine hydrochloride-coated carbon material, its preparation method and application. By coating with dopamine hydrochloride, the surface defects of hard carbon can be reduced and the first efficiency of the material can be improved. By vacuum filtration of the rGO dispersion, a self-supporting membrane structure is constructed to improve the sodium storage performance of the carbon material and inhibit the volume expansion of carbon nanoflowers, so that the material has excellent electrochemical performance.

[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a preparation method of a self-supporting dopamine hydrochloride-coated carbon material, which includes the following steps:

[0009] S1, Disperse acrylonitrile in acetone, add azobisisobutyronitrile for free radical polymerization, wash and dry to obtain polyacrylonitrile nanoflowers, and perform low-temperature carbonization on the polyacrylonitrile nanoflowers to obtain polyacrylonitrile carbon nanoflowers;

[0010] S2. Dissolve tris(hydroxymethyl)aminomethane in deionized water to obtain an alkaline buffer solution. Disperse polyacrylonitrile carbon nanoflowers in the alkaline buffer solution, add dopamine hydrochloride to the alkaline buffer solution, stir well, wash until neutral, and dry to obtain a dopamine hydrochloride-coated material;

[0011] S3. Subject the dopamine hydrochloride-coated material to high-temperature carbonization to obtain dopamine hydrochloride-coated carbon nanoflowers;

[0012] S4. Add the dopamine hydrochloride-coated carbon nanoflowers to a graphene oxide dispersion, and obtain a dopamine hydrochloride-coated carbon-rGO membrane by vacuum filtration;

[0013] S5. Subject the dopamine hydrochloride-coated carbon-rGO membrane to thermal reduction treatment to obtain a self-supporting dopamine hydrochloride-coated carbon material.

[0014] Preferably, in step S1:

[0015] The volume ratio of acrylonitrile to acetone and azobisisobutyronitrile is 1:0.8 - 1.2:0.5 - 1; and / or

[0016] During the free radical polymerization process, the polymerization temperature is 70 - 85°C, and the polymerization time is 2 - 3 h; and / or

[0017] During the low-temperature carbonization process, the carbonization temperature is 200 - 250°C, and the carbonization time is 2 - 4 h.

[0018] Preferably, in step S2:

[0019] The pH of the alkaline buffer solution is 8.0 - 8.5, and the concentration of tris(hydroxymethyl)aminomethane is 1.10 - 1.18 mg / ml; and / or

[0020] The addition amount of dopamine hydrochloride is 1 - 10 wt% of the polyacrylonitrile carbon nanoflowers; and / or

[0021] The stirring is carried out at room temperature, and the stirring time is 18 - 24 h.

[0022] Preferably, in step S3, during the high-temperature carbonization process, the carbonization temperature is 800 - 1200°C, and the carbonization time is 2 - 4 h.

[0023] Preferably, in step S4, the graphene oxide dispersion is prepared in the following manner:

[0024] Mix graphite powder with concentrated sulfuric acid under stirring conditions to obtain a first dispersion;

[0025] Potassium permanganate was added to the first dispersion and mixed evenly. After stirring and reacting under a water bath condition, deionized water was added and the temperature was controlled below 85 °C. Then it was heated to 98 ± 2 °C and maintained for 5 - 10 min to obtain the second dispersion.

[0026] The second dispersion was centrifuged to obtain a centrifuged precipitate, which was washed with hydrochloric acid. Then it was washed with deionized water until the supernatant was neutral to obtain a graphene oxide dispersion.

[0027] Preferably, when preparing the first dispersion, the stirring temperature is 0 ± 2 °C, the stirring time is 30 ± 5 min, and the stirring rate is 60 - 90 r / min; and / or

[0028] The mass ratio of the graphene powder to the potassium permanganate is 3:7 - 1:3; and / or

[0029] When preparing the second dispersion, the water bath temperature is 35 ± 2 °C and the reaction time is 6 - 8 h; and / or

[0030] The centrifugation time is 10 - 30 min.

[0031] Preferably, in the step S4, the mass ratio of the hydrochloric acid dopamine-coated carbon nanoflowers to the graphene oxide dispersion is 7:3 - 9:1.

[0032] Preferably, in the step S5, the thermal reduction temperature is 300 - 350 °C and the reduction time is 2 - 4 h.

[0033] Preferably, in the steps S1, S3, and S5, the atmosphere is selected from one or a mixture of several of nitrogen, argon, helium, and neon.

[0034] The second aspect of the present invention provides a self-supporting hydrochloric acid dopamine-coated carbon material prepared by the preparation method of the self-supporting hydrochloric acid dopamine-coated carbon material as described in the first aspect of the present invention.

[0035] The third aspect of the present invention provides an application of the self-supporting hydrochloric acid dopamine-coated carbon material as described in the second aspect of the present invention in a sodium ion battery.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1. In the present invention, polyacrylonitrile carbon nanoflowers are obtained by free radical polymerization of acrylonitrile and low-temperature carbonization. Then, the coating with hydrochloric acid dopamine can reduce the surface defects of hard carbon and improve the initial efficiency of the material. The rGO dispersion is used for vacuum filtration to construct a self-supporting membrane structure, which improves the sodium storage performance of the material and inhibits the volume expansion of the carbon nanoflowers, so that the material has excellent electrochemical performance;

[0038] 2. The raw material of this application is polyacrylonitrile-based carbon, which can solve the problem of poor cycling performance. After carbonization with a single coating, it can solve the problem of low initial efficiency of the material, and constructing the electrode structure can eliminate the use of current collectors. Description of the Drawings

[0039] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0040] Figure 1 It is a flowchart of the preparation method of the self-supporting dopamine hydrochloride-coated carbon material of the present invention;

[0041] Figure 2 It is the charge-discharge curve of the self-supporting dopamine hydrochloride-coated carbon material prepared in Example 1 of the present invention at a rate of 0.1C;

[0042] Figure 3 It is the cycle curve of the self-supporting dopamine hydrochloride-coated carbon material prepared in Example 1 of the present invention at a rate of 0.1C;

[0043] Figure 4 It is the rate curve of the self-supporting dopamine hydrochloride-coated carbon material prepared in Example 1 of the present invention. Detailed Embodiments

[0044] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0045] The present invention aims to provide a self-supporting dopamine hydrochloride-coated carbon material and a preparation method. After acrylonitrile is subjected to free radical polymerization with azobisisobutyronitrile, polyacrylonitrile nanoflowers are obtained. After low-temperature carbonization and shaping, polyacrylonitrile carbon nanoflowers are obtained. Then, they are dispersed in an alkaline buffer solution and a certain amount of dopamine hydrochloride is added for coating. After carbonization, dopamine hydrochloride-coated carbon nanoflowers are obtained. After vacuum filtration with a graphene oxide dispersion, a dopamine hydrochloride-coated carbon-rGO membrane is obtained. After thermal reduction of the self-supporting membrane, a self-supporting dopamine hydrochloride-coated carbon material with excellent electrochemical performance can be obtained.

[0046] Combined with Figure 1 As shown, a preparation method of a self-supporting dopamine hydrochloride-coated carbon material provided by the present invention includes the following steps:

[0047] S1. Disperse acrylonitrile in acetone, add azobisisobutyronitrile for free radical polymerization, wash and dry to obtain polyacrylonitrile nanoflowers, and subject the polyacrylonitrile nanoflowers to low-temperature carbonization to obtain polyacrylonitrile carbon nanoflowers;

[0048] Specifically, acrylonitrile is used as raw material, dispersed in acetone, and azobisisobutyronitrile is added as an initiator for free radical polymerization (polymerization temperature is 70-85°C, polymerization time is 2-3h). After the reaction is completed, polyacrylonitrile nanoflowers are obtained after washing and drying; wherein the volume ratio of acrylonitrile to acetone and azobisisobutyronitrile is 1:0.8-1.2:0.5-1.

[0049] Then, the polyacrylonitrile nanoflowers are carbonized at a carbonization temperature of 200-250° C. for 2-4 hours to finally obtain polyacrylonitrile carbon nanoflowers; wherein, the low-temperature carbonization atmosphere is selected from one or a mixture of nitrogen, argon, helium, and neon.

[0050] S2, dissolving tris(hydroxymethyl)aminomethane in deionized water to obtain an alkaline buffer solution, dispersing polyacrylonitrile carbon nanoflowers in the alkaline buffer solution, adding dopamine hydrochloride to the alkaline buffer solution, stirring thoroughly, washing to neutrality, and drying to obtain a dopamine hydrochloride coated material;

[0051] Specifically, tris(hydroxymethyl)aminomethane is dissolved in deionized water to obtain an alkaline buffer solution with a pH of 8.0 to 8.5, wherein the concentration of tris(hydroxymethyl)aminomethane is 1.10 to 1.18 mg / ml, and its main function is to adjust the pH value of the solution; then the polyacrylonitrile carbon nanoflower prepared in step S1 is dispersed in its alkaline buffer solution, and dopamine hydrochloride is added to the alkaline buffer solution, and stirred at room temperature for 18 to 24 hours, and then washed until the pH is neutral and dried to obtain a dopamine hydrochloride coated material. The amount of dopamine hydrochloride added is 1 to 10 wt% of the polyacrylonitrile carbon nanoflower.

[0052] S3, carbonizing the dopamine hydrochloride coated material at high temperature to obtain dopamine hydrochloride coated carbon nanoflowers;

[0053] Specifically, the dopamine hydrochloride coated material is subjected to high-temperature carbonization at a carbonization temperature of 800 to 1200°C for 2 to 4 hours to finally obtain dopamine hydrochloride coated carbon nanoflowers; wherein the high-temperature carbonization atmosphere is selected from one or a mixture of nitrogen, argon, helium, and neon.

[0054] S4, adding dopamine hydrochloride-coated carbon nanoflowers into graphene oxide dispersion, and obtaining dopamine hydrochloride-coated carbon-rGO membrane by vacuum filtration;

[0055] First, prepare a graphene oxide dispersion, and the preparation process is as follows:

[0056] Graphite powder and concentrated sulfuric acid are mixed under stirring conditions to obtain a first dispersion; wherein the stirring temperature is 0±2°C, the stirring time is 30±5min, and the stirring rate is 60-90r / min. Potassium permanganate is added to the first dispersion and mixed evenly. After stirring and reacting under water bath conditions, deionized water is added and the temperature is controlled below 85°C, and then heated to 98±2°C for 5-10min to obtain a second dispersion; wherein the water bath temperature is 35±2°C and the reaction time is 6-8h. The second dispersion is centrifuged to obtain a centrifugal precipitate, wherein the centrifugation time is 10-30min. The centrifugal precipitate is then washed with hydrochloric acid, and the washing can be repeated 2-3 times with hydrochloric acid, and then the centrifugal precipitate is washed with deionized water, and the centrifugation is repeated for 3-5 times until the pH of the supernatant is neutral to obtain a graphene oxide dispersion (rGO dispersion). In the process of preparing the above graphene oxide dispersion, the mass ratio of graphene powder to potassium permanganate is 1:2 to 1:3, preferably 3:7 to 1:3.

[0057] Then, the dopamine hydrochloride coated carbon nanoflowers prepared in step S3 are added to the graphene oxide dispersion, and after sufficient stirring, the dopamine hydrochloride coated carbon-rGO membrane is obtained by vacuum filtration; wherein the mass ratio of the dopamine hydrochloride coated carbon nanoflowers to the graphene oxide dispersion is 7:3 to 9:1.

[0058] S5, subjecting the dopamine hydrochloride coated carbon-rGO membrane to thermal reduction treatment to obtain a self-supporting dopamine hydrochloride coated carbon material; wherein the thermal reduction temperature is 300-350° C., and the reduction time is 2-4 hours. The atmosphere during the thermal reduction treatment is selected from one or a mixture of nitrogen, argon, helium, and neon.

[0059] When the self-supporting dopamine hydrochloride coated carbon material prepared above is applied to sodium ion batteries, the reversible specific capacity is ≥280 mAh g at 0.1C. -1 , first coulombic efficiency ≥ 85%, capacity ≥ 260Ah g after 100 cycles -1 .

[0060] The self-supporting dopamine hydrochloride coated carbon material and the preparation method thereof of the present invention are further introduced below with reference to specific examples.

[0061] Example 1

[0062] The preparation method of the self-supporting dopamine hydrochloride coated carbon material of this embodiment is as follows:

[0063] (1) Disperse 4 mL of acrylonitrile in 4 mL of acetone, and then add 4 mL of AIBN as an initiator. React the mixture at 70 °C for 2 hours, and after drying, polyacrylonitrile nanoflowers are obtained. Then place the sample in a tube furnace and heat-treat it in an Ar atmosphere at 250 °C for 2 hours to obtain polyacrylonitrile carbon nanoflowers.

[0064] (2) Dissolve 2.5 g of tris(hydroxymethyl)aminomethane in 200 ml of deionized water to prepare an alkaline buffer solution with a pH of 8.5. Take 1 g of the polyacrylonitrile carbon nanoflowers obtained in step (1), add it to the alkaline buffer solution and disperse it evenly, then add 0.05 g of dopamine hydrochloride and continuously stir at room temperature for 20 h. Wash it to neutrality and dry it to obtain a dopamine hydrochloride-coated material.

[0065] (3) Place the dopamine hydrochloride-coated material obtained in step (2) in a corundum boat and heat it in a tube furnace at 1000 °C for 3 h in an Ar atmosphere to obtain dopamine hydrochloride-coated carbon nanoflowers.

[0066] (4) Combine 3.5 g of graphite powder with an average particle size of 75 μm with 60 ml of concentrated sulfuric acid with a mass concentration of 98%, and then stir at a speed of 60 r / min at 0 °C for 30 min to obtain a first dispersion liquid. At 0 °C and a rotation speed of 60 r / min, mix the first dispersion liquid with 7.5 g of potassium permanganate for 60 min; place the obtained mixed dispersion liquid in a constant-temperature water bath at 35 °C and stir the reaction at a speed of 60 r / min for 6 hours; add 60 mL of deionized water, control the temperature of the dispersant below 85 °C, and then heat the dispersant to 98 °C and keep it for 5 min to obtain a secondary dispersant. Under the condition of a relative centrifugal force of 7000, centrifuge the second dispersion liquid for 10 min, and then add 3 mol / L -1 hydrochloric acid to the centrifuged precipitate for washing. After washing three times, add deionized water to the centrifuged precipitate for washing, repeat centrifugation and washing 5 times, and measure the pH value of the supernatant to be 7 to obtain an rGO dispersion liquid.

[0067] (5) Mix the dopamine hydrochloride-coated carbon nanoflowers with the rGO dispersion liquid obtained in step (4) at a ratio of dopamine hydrochloride-coated carbon nanoflowers:rGO of 9:1, stir well and perform vacuum filtration to obtain a dopamine hydrochloride-coated carbon-rGO membrane.

[0068] (6) Heat the dopamine-coated carbon-rGO membrane obtained in step (5) in a tube furnace at 300 °C for 2 h in an Ar atmosphere to obtain a self-supporting dopamine hydrochloride-coated carbon material.

[0069] The self-supported dopamine hydrochloride-coated carbon material prepared in this example was made into a battery, and the process is as follows: The self-supported dopamine hydrochloride-coated carbon was cut into a (8×8) mm2 electrode. The electrode was dried at 120 °C for 10 hours under vacuum conditions and then immediately transferred to a glove box for standby. The battery was assembled in a glove box under an Ar atmosphere, with metallic sodium as the counter electrode and 1 mole of NaClO4 dissolved in a 1:1 volume ratio solution of ethylene carbonate and diethyl carbonate as the electrolyte to assemble a CR2025 button cell.

[0070] The assembled battery was tested for charge-discharge performance under the following conditions: The charge-discharge mode was rate charge-discharge; the current density was 0.1C; the discharge cut-off voltage was 0.01V, and the charge cut-off voltage was 3V; the constant current charge-discharge curve of the battery assembled in this example is as shown in Figure 2 ; It can be seen from Figure 2 that the reversible specific capacity of the battery assembled in this example is 283.6 mAh g -1 , and the initial Coulombic efficiency is 86.9%.

[0071] The assembled battery was tested for cycling performance under the following conditions: The charge-discharge mode was rate charge-discharge, the rate was 0.1C, the discharge cut-off voltage was 0.01V, and the charge cut-off voltage was 3V. The cycling curve of the battery prepared in this example is as shown in Figure 3 ; It can be seen from Figure 3 that after 100 cycles, the capacity of the battery prepared in this example is 267.6 mAh g -1 , and the capacity retention rate is 92.9%, indicating that the cycling stability of this material is good.

[0072] The battery prepared in this example was tested for rate performance under the following conditions: The charge-discharge mode was rate charge-discharge, and it was cycled 10 times at rates of 0.1C, 0.2C, 0.5C, 1C, and 2C respectively. The discharge cut-off voltage was 0.01, and the charge cut-off voltage was 3V. The rate performance of the battery prepared in Application Example 1 is as shown in Figure 4 ; It can be seen from Figure 4 that the specific capacities of the battery made in this example at 0.1C, 0.2C, 0.5C, 1C, and 2C are 287.0 mAh g -1 , 264.3 mAh g -1 , 238.6 mAh g -1 , 213.8 mAh g -1 , 148.3 mAh g -1 respectively. When the rate returns to 0.1C again, the capacity returns to 234.8 mAh g -1 , showing good rate performance.

[0073] It can be seen that the dopamine hydrochloride coated carbon material prepared in this example has excellent electrochemical performance when used as the negative electrode of a sodium ion battery.

[0074] Example 2

[0075] The preparation method of the self-supporting dopamine hydrochloride coated carbon material of this embodiment is as follows:

[0076] (1) Disperse 4 mL of acrylonitrile in 4 mL of acetone, and then add 4 mL of AIBN as an initiator. The reaction is allowed to react at 80 °C for 2 hours, and after drying, polyacrylonitrile nanoflowers are obtained. The sample is then placed in a tubular furnace and heat treated in an Ar atmosphere at 200 °C for 4 hours to obtain polyacrylonitrile carbon nanoflowers.

[0077] (2) Take 2.5g of tris(hydroxymethyl)aminomethane and dissolve it in 200ml of deionized water to prepare an alkaline buffer solution with a pH of 8.5. Take 1g of polyacrylonitrile carbon nanoflowers in step (1), add it into the alkaline buffer solution and evenly disperse it, then add 0.05g of dopamine hydrochloride and stir it continuously at room temperature for 20h, wash it until it is neutral and dry it to obtain a dopamine hydrochloride coated material.

[0078] (3) The dopamine hydrochloride coated material in step (2) is placed in a corundum boat, and heated at 1200° C. for 2.5 h in a tube furnace under an Ar atmosphere to obtain dopamine hydrochloride coated carbon nanoflowers.

[0079] (4) Combine 3.5 g of graphite powder with an average particle size of 75 um with 60 ml of concentrated sulfuric acid with a mass concentration of 98%, and then stir at 0°C at a speed of 60 r / min for 30 minutes to obtain a first dispersed liquid. At 0°C, at a rotation speed of 60 r / min, mix the first dispersed liquid with 8.0 g of potassium permanganate for 60 minutes; put the resulting mixed dispersion into 35°C constant temperature water, and stir the reaction at a speed of 60 r / min for 8 hours; add 60 mL of deionized water, control the temperature of the dispersant below 85°C, and then heat the dispersant to 98°C and maintain for 5 minutes to obtain a secondary dispersant. Centrifuge the second dispersion for 10 minutes under a relative centrifugal force of 7000, and then add 3 mol L -1 The mixture was washed with hydrochloric acid for three times, and deionized water was added to the centrifugal precipitate for washing. The centrifugation was repeated. After washing for 5 times, the pH value of the supernatant was measured to be 7, and an rGO dispersion was obtained.

[0080] (5) The dopamine hydrochloride coated carbon nanoflowers and the rGO dispersion in step (4) are mixed in a ratio of 7:3 of dopamine hydrochloride coated carbon nanoflowers: rGO, and the mixture is fully stirred and vacuum filtered to obtain a dopamine hydrochloride coated carbon-rGO membrane.

[0081] (6) Heat the dopamine-coated carbon-rGO film obtained in step (5) in a tubular furnace at 300 °C for 3 h in an N2 atmosphere to obtain a self-supporting hydrochloric acid dopamine-coated carbon material.

[0082] Example 3

[0083] The preparation method of the self-supporting hydrochloric acid dopamine-coated carbon material in this example is as follows: (1) Disperse 4 mL of acrylonitrile into 4 mL of acetone, and then add 3.5 mL of AIBN as an initiator. React at 85 °C for 3 hours, and obtain polyacrylonitrile nanoflowers after drying. Then put the sample into a tubular furnace and heat-treat it in an Ar atmosphere at 200 °C for 4 hours to obtain polyacrylonitrile carbon nanoflowers.

[0084] (2) Dissolve 2.5 g of tris(hydroxymethyl)aminomethane in 200 ml of deionized water to make an alkaline buffer solution with a pH of 8.5. Take 1 g of the polyacrylonitrile carbon nanoflowers in step (1), add it to the alkaline buffer solution and disperse it evenly, then add 0.05 g of hydrochloric acid dopamine and continuously stir at room temperature for 20 h. Wash it to neutral and dry it to obtain a hydrochloric acid dopamine-coated material.

[0085] (3) Put the hydrochloric acid dopamine-coated material in step (2) into a corundum boat and heat it in a tubular furnace at 1200 °C for 2.5 h in an Ar atmosphere to obtain hydrochloric acid dopamine-coated carbon nanoflowers.

[0086] (4) Combine 3.5 g of graphite powder with an average particle size of 75 μm with 60 ml of concentrated sulfuric acid with a mass concentration of 98%, and then stir at a speed of 75 r / min at 0 °C for 30 min to obtain a first dispersion liquid. At 0 °C, mix the first dispersion liquid with 9.0 g of potassium permanganate at a rotation speed of 75 r / min for 60 min; put the obtained mixed dispersion liquid into a constant temperature water at 35 °C and stir the reaction at a speed of 75 r / min for 7.5 h; add 60 mL of deionized water, control the temperature of the dispersant below 85 °C, and then heat the dispersant to 98 °C and keep it for 5 min to obtain a secondary dispersant. Under the condition of a relative centrifugal force of 7000, centrifuge the second dispersion liquid for 30 min, and then add 3 mol L -1 of hydrochloric acid to the centrifuged precipitate for cleaning. After cleaning three times, add deionized water to the centrifuged precipitate for cleaning, and repeat centrifugation and cleaning 5 times. After measuring that the pH value of the supernatant is 7, obtain an rGO dispersion liquid.

[0087] (5) The dopamine hydrochloride-coated carbon nanoflowers and the rGO dispersion liquid in step (4) are mixed at a ratio of dopamine hydrochloride-coated carbon nanoflowers: rGO of 8:2, and after sufficient stirring and vacuum filtration, a dopamine hydrochloride-coated carbon-rGO membrane is obtained.

[0088] (6) The dopamine-coated carbon-rGO membrane obtained in step (5) is heated in a tube furnace at 300 °C for 3 h in an N2 atmosphere to obtain a self-supporting dopamine hydrochloride-coated carbon material.

[0089] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a self-supporting carbon material coated with dopamine hydrochloride, characterized in that, It includes the following steps: S1. Disperse acrylonitrile in acetone, add azobisisobutyronitrile for free radical polymerization, and obtain polyacrylonitrile nanoflowers after washing and drying. Then, subject the polyacrylonitrile nanoflowers to low-temperature carbonization to obtain polyacrylonitrile carbon nanoflowers; S2. Dissolve tris(hydroxymethyl)aminomethane in deionized water to obtain an alkaline buffer solution. Disperse the polyacrylonitrile carbon nanoflowers in the alkaline buffer solution, add dopamine hydrochloride to the alkaline buffer solution, stir well, wash until neutral, and dry to obtain a dopamine hydrochloride-coated material; S3. Subject the dopamine hydrochloride-coated material to high-temperature carbonization to obtain dopamine hydrochloride-coated carbon nanoflowers; S4. Add the dopamine hydrochloride-coated carbon nanoflowers to a graphene oxide dispersion, and obtain a dopamine hydrochloride-coated carbon-rGO membrane through vacuum filtration; S5. Subject the dopamine hydrochloride-coated carbon-rGO membrane to thermal reduction treatment to obtain a self-supporting dopamine hydrochloride-coated carbon material.

2. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 1, wherein, In the step S1: The volume ratio of the acrylonitrile to the acetone and the azobisisobutyronitrile is 1:0.8 - 1.2:0.5 - 1; and / or During the free radical polymerization process, the polymerization temperature is 70 - 85°C, and the polymerization time is 2 - 3 h; and / or During the low-temperature carbonization process, the carbonization temperature is 200 - 250°C, and the carbonization time is 2 - 4 h.

3. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 1, characterized in that, In the step S2: The pH of the alkaline buffer solution is 8.0 - 8.5, and the concentration of the tris(hydroxymethyl)aminomethane is 1.10 - 1.18 mg / ml; and / or The addition amount of the dopamine hydrochloride is 1 - 10 wt% of the polyacrylonitrile carbon nanoflowers; and / or The stirring is carried out at room temperature, and the stirring time is 18 - 24 h.

4. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 1, wherein, In the step S3, during the high-temperature carbonization process, the carbonization temperature is 800 - 1200°C, and the carbonization time is 2 - 4 h.

5. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 1, characterized in that In the step S4, the graphene oxide dispersion is prepared in the following manner: Mix graphite powder and concentrated sulfuric acid under stirring conditions to obtain a first dispersion; Add potassium permanganate to the first dispersion and mix evenly. After stirring and reacting under a water bath condition, add deionized water and control the temperature below 85°C, and then heat to 98 ± 2°C and keep for 5 - 10 min to obtain a second dispersion; Centrifuge the second dispersion to obtain a centrifugal precipitate, wash the centrifugal precipitate with hydrochloric acid, and then wash the centrifugal precipitate with deionized water until the supernatant is neutral to obtain a graphene oxide dispersion.

6. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material as described in claim 5, wherein: When preparing the first dispersion, the stirring temperature is 0 ± 2°C, the stirring time is 30 ± 5 min, and the stirring rate is 60 - r / min; and / or The mass ratio of the graphene powder to the potassium permanganate is 1:2 - 1:3; and / or When preparing the second dispersion, the water bath temperature is 35 ± 2°C, and the reaction time is 6 - 8 h; and / or The centrifugation time is 10 - 30 min.

7. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 1, characterized in that, In the step S4, the mass ratio of the dopamine hydrochloride-coated carbon nanoflowers to the graphene oxide dispersion is 7:3 - 9:

1.

8. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 7, characterized in that, In the step S5, the thermal reduction temperature is 300 to 350 °C, and the reduction time is 2 to 4 h.

9. The preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to claim 1, characterized in that, In the steps S1, S3, and S5, the atmosphere is selected from one or a mixture of several of nitrogen, argon, helium, and neon.

10. A self-supporting dopamine hydrochloride-coated carbon material prepared by the preparation method of the self-supporting dopamine hydrochloride-coated carbon material according to any one of claims 1-9.

11. An application of the self-supporting dopamine hydrochloride-coated carbon material according to claim 10 in a sodium ion battery.

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