Super-ordered carbon nanotube, and preparation method and application thereof

Abstract

The application belongs to the field of carbon materials, and particularly relates to a super-ordered structure carbon nanotube and a preparation method and application thereof. The preparation method comprises the following steps: immersing a carrier in a catalyst precursor solution to obtain a carrier loaded with the catalyst precursor; and growing the super-ordered structure carbon nanotube on the surface of the carrier loaded with the catalyst precursor through a chemical deposition method. The carrier is subjected to special treatment, including heat treatment, inorganic acid pretreatment and carboxylic acid modification treatment. The carrier subjected to the special treatment can promote the catalyst precursor to be better adsorbed and loaded on the surface of the carrier, and can interfere with and limit the growth of the carbon nanotube, so that the obtained carbon nanotube has high orientation, long and straight morphology and special resin bifurcation structure, and excellent conductive performance, and can be applied to the preparation of a conductive agent for lithium ion batteries.

Description

Technical Field

[0001] The present invention belongs to the field of carbon materials, and in particular relates to a super-ordered carbon nanotube and a preparation method and application thereof. Background Art

[0002] Carbon nanotubes (CNTs) are one-dimensional carbon nanomaterials with excellent properties such as high electrical conductivity, high thermal conductivity, large specific surface area, and high strength. They are widely used as conductive additives in lithium-ion batteries, catalyst carriers, drug carriers, reinforced composite materials, and electronic devices. Currently, the most mature application of CNTs is as a conductive additive in lithium-ion batteries. Adding CNTs to the cathode material of lithium-ion batteries effectively forms a conductive network, enhancing the electrode's conductivity. This results in higher battery capacity and longer cycle life, making them suitable for high-end digital devices and new energy vehicle batteries.

[0003] It's well known that the process determines the material's structure, and the structure, in turn, determines the material's properties. Currently, carbon nanotube production methods primarily involve placing a pre-prepared catalyst in a fluidized, moving, or fixed bed to catalytically decompose a carbon source gas to grow carbon nanotubes. These carbon nanotubes typically exhibit a curved, entangled, and disordered structure and are relatively short. This structure significantly limits the full potential of the carbon nanotubes' conductive properties.

[0004] Therefore, improving the structure of carbon nanotubes and reducing the resistivity of carbon nanotubes are the key to meeting the current lithium-ion battery's demand for higher conductivity of carbon nanotube conductive agents. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for preparing super-ordered carbon nanotubes. The preparation method is simple and low-cost. The obtained carbon nanotubes are long, straight, highly oriented, and have good conductivity.

[0006] The present invention also provides a super-ordered carbon nanotube and its application.

[0007] In a first aspect of the present invention, a method for preparing super-ordered carbon nanotubes is provided, comprising the following steps:

[0008] Immersing the support in a catalyst precursor solution to obtain a support loaded with the catalyst precursor;

[0009] Super-ordered carbon nanotubes are grown on the surface of the support carrying the catalyst precursor by chemical deposition;

[0010] The carrier is specially treated, including heat treatment, inorganic acid pretreatment, and carboxylic acid modification treatment.

[0011] According to the first aspect of the present invention, there are at least the following beneficial effects:

[0012] The present invention performs heat treatment on the carrier to remove grease and other impurities adsorbed on the carrier surface; performs inorganic acid pretreatment to oxidize the carrier surface, and then utilizes the carboxyl group in the carboxylic acid to modify the functional groups of the carrier; the carrier after the above treatment can promote the catalyst precursor to be better adsorbed and loaded on the carrier surface, interfere with and confine the growth of carbon nanotubes, and the carbon nanotubes obtained by chemical vapor deposition are highly oriented, have a long and straight morphology, have a special resin bifurcation structure, and have excellent conductive properties.

[0013] Preferably, the temperature of the heat treatment is 300-400° C., more preferably 330-370° C.; the time of the heat treatment is 1-2 h, more preferably about 1.5 h.

[0014] Preferably, the inorganic acid pretreatment time is 5 to 30 minutes, more preferably 10 to 27 minutes.

[0015] Preferably, the inorganic acid includes at least one of nitric acid, concentrated sulfuric acid, concentrated hydrochloric acid, and perchloric acid.

[0016] Preferably, the mass concentration of the inorganic acid is 30-50%, more preferably 40-50%; and the solvent is at least one of water and ethanol.

[0017] Preferably, the carboxylic acid modification treatment lasts for 10 to 20 minutes, more preferably about 15 minutes. Specifically, the carboxylic acid modification treatment comprises placing the support pretreated with inorganic acid in carboxylic acid and subjecting it to ultrasonic treatment.

[0018] Preferably, the carboxylic acid comprises at least one of citric acid and ethylenediaminetetraacetic acid (EDTA). In the present invention, the fiber surface is functionalized using the abundant carboxyl groups in citric acid and EDTA, which can promote the uniform distribution of the catalyst precursor on the carrier surface.

[0019] Preferably, the mass concentration of the carboxylic acid is 5-20%, more preferably 5-15%; and the solvent is at least one of water, ethanol, and isopropanol.

[0020] Preferably, the catalyst precursor includes at least one of an iron salt, a cobalt salt, and a nickel salt; more preferably, the catalyst precursor includes at least one of an iron nitrate, a cobalt nitrate, and a nickel nitrate.

[0021] Preferably, the carrier is a fiber material, including at least one of glass fiber, alumina fiber, carbon fiber, high silica fiber, carbonized fiber, and mullite fiber.

[0022] Preferably, the concentration of the catalyst precursor solution is 5 to 100 g / L, more preferably 20 to 80 g / L.

[0023] Preferably, the catalyst precursor solution is prepared by dissolving the catalyst precursor in a solvent and stirring or ultrasonicating for 12 to 25 minutes; the solvent includes at least one of ethanol, isopropanol, n-propanol, and water.

[0024] Preferably, the carrier is immersed in the catalyst precursor solution, specifically, the carrier is immersed in the catalyst precursor solution, ultrasonically treated, impregnated, and dried to obtain a carrier loaded with a catalyst precursor; the ultrasonic treatment time is 2 to 30 minutes, more preferably 10 to 15 minutes; the impregnation time is 0.5 to 10 hours, more preferably about 1 hour; the drying temperature is 100 to 120°C, more preferably 105 to 110°C; the drying time is 1 to 10 hours, more preferably about 3 hours.

[0025] Preferably, the super-ordered carbon nanotubes are grown on the surface of the support carrying the catalyst precursor by chemical deposition. Specifically, under the protection of carrier gas and auxiliary gas, the support carrying the catalyst precursor catalytically decomposes the carbon source to obtain the super-ordered carbon nanotubes.

[0026] Preferably, the temperature of the catalytic cracking reaction is 600-1000° C., more preferably 650-800° C.; the time of the catalytic cracking reaction is 10-60 min, more preferably 40-60 min.

[0027] Preferably, the carbon source includes at least one of ethylene, propylene and propane.

[0028] Preferably, the volume concentration of the carbon source is 10-50 vol%, more preferably 15-45 vol%; the carbon source is a gas, and the flow rate of the carbon source is 70-120 mL / min, more preferably 80-120 mL / min.

[0029] Preferably, the carrier gas includes at least one of nitrogen and argon.

[0030] Preferably, the auxiliary gas comprises hydrogen.

[0031] Preferably, the volume ratio of the carrier gas to the auxiliary gas is 1.5 to 6.5:1, more preferably 1.8 to 4.2:1.

[0032] In a second aspect of the present invention, a super-ordered carbon nanotube prepared by the above preparation method is provided.

[0033] Preferably, the aspect ratio of the super-ordered carbon nanotubes is 3000-5500, more preferably 3000-5000, further preferably 3300-4800.

[0034] Preferably, the specific surface area of ​​the super-ordered carbon nanotubes is 250 to 350 m 2 / g, more preferably 280 to 310 m 2 / g, more preferably 283 to 306m 2 / g.

[0035] Preferably, the resistivity of the super-ordered carbon nanotubes is 10 to 30 mΩ·cm, more preferably 15 to 25 mΩ·cm, and further preferably 16 to 23 mΩ·cm.

[0036] The third aspect of the present invention proposes the use of the super-ordered carbon nanotubes in preparing a conductive agent for lithium-ion batteries.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] 1. The preparation method of the present invention is safe and simple, does not require special equipment, can be put into production quickly, has a simple process, and is easy to control and operate.

[0039] 2. The carrier material used in the present invention is cheap, readily available, safe and non-toxic, and can greatly reduce the production cost of carbon nanotubes.

[0040] 3. The super-ordered carbon nanotubes prepared by the present invention have long and straight morphology, high orientation and special dendritic bifurcation structure, powder resistivity reaches 15-25 mΩ·cm, and specific surface area reaches 280-310 m 2 / g, the aspect ratio reaches 3000-5000, the conductivity is better than similar products, and it can be used to prepare conductive agents for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0042] Figure 1 This is a SEM image of the carbon nanotubes prepared in Example 1 of the present invention;

[0043] Figure 2 This is a SEM image of the carbon nanotubes prepared in Example 3 of the present invention;

[0044] Figure 3 This is the SEM image of the carbon nanotubes prepared in Comparative Example 1;

[0045] Figure 4 This is the SEM image of the carbon nanotubes prepared in Comparative Example 2;

[0046] Figure 5 This is the SEM image of the carbon nanotubes prepared in Comparative Example 3. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0048] Unless otherwise specified, the raw materials used in the specific embodiments of the present invention are conventional raw materials in the art; and the test / test methods are commonly used methods in the art.

[0049] Example 1

[0050] This embodiment prepares a super-ordered carbon nanotube, and the specific process is as follows:

[0051] Step 1: Dissolve ferric nitrate nonahydrate in anhydrous ethanol, stir or ultrasonically disperse for 17 minutes to prepare a ferric nitrate ethanol solution with a concentration of 20 g / L.

[0052] Step 2: The glass fiber is subjected to special treatment: first, it is heat-treated at 330° C. for 1.5 hours, then treated with a 40% nitric acid aqueous solution for 10 minutes, and then cleaned and ultrasonically treated with a 5% citric acid aqueous solution for 15 minutes.

[0053] Step 3: Fully immerse the specially treated glass fiber in the ferric nitrate ethanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain a glass fiber-supported catalyst precursor.

[0054] Step 4: In nitrogen and hydrogen (V 氮气 :V 氢气 =3.6:1), the glass fiber-supported catalyst precursor was used to catalytically crack ethylene at 660° C. (flow rate of 100 mL / min) for 40 min to obtain carbon nanotubes with a super-ordered structure.

[0055] The powder resistivity of the super-ordered carbon nanotubes prepared in this example is 17 mΩ·cm, and the specific surface area is 301 m 2 / g, and the aspect ratio reaches 4500.

[0056] Example 2

[0057] This embodiment prepares a super-ordered carbon nanotube, and the specific process is as follows:

[0058] Step 1: Dissolve cobalt nitrate hexahydrate in isopropanol and stir or ultrasonically disperse for 17 minutes to prepare a cobalt nitrate isopropanol solution with a concentration of 20 g / L.

[0059] Step 2: The glass fiber is subjected to special treatment: first, it is heat-treated at 330° C. for 1.5 hours, then treated with a 40% nitric acid aqueous solution for 10 minutes, and then cleaned and ultrasonically treated with a 5% citric acid aqueous solution for 15 minutes.

[0060] Step 3: Fully immerse the specially treated glass fiber in the cobalt nitrate isopropanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, and then take out and dry at 105° C. for 3 hours to obtain a glass fiber-supported catalyst precursor.

[0061] Step 4: In nitrogen and hydrogen (V 氮气 :V 氢气 =2.5:1), the glass fiber-supported catalyst precursor was used to catalytically crack ethylene at 650° C. (flow rate of 90 mL / min) for 40 min to obtain carbon nanotubes with a super-ordered structure.

[0062] The powder resistivity of the super-ordered carbon nanotubes prepared in this example is 21 mΩ·cm, and the specific surface area is 289 m 2 / g, and the aspect ratio reaches 3900.

[0063] Example 3

[0064] This embodiment prepares a super-ordered carbon nanotube, and the specific process is as follows:

[0065] Step 1: Dissolve ferric nitrate nonahydrate in anhydrous ethanol, stir or ultrasonically disperse for 17 minutes to prepare a ferric nitrate ethanol solution with a concentration of 60 g / L.

[0066] Step 2: The carbon fiber is specially treated: first heat treated at 350°C for 1.5 hours, then treated with a 47% nitric acid aqueous solution for 10 minutes, and then cleaned and ultrasonically treated with a 10% ethylenediaminetetraacetic acid (EDTA) aqueous solution for 15 minutes.

[0067] Step 3: Fully immerse the specially treated carbon fiber in the ferric nitrate ethanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain a carbon fiber-supported catalyst precursor.

[0068] Step 4: In nitrogen and hydrogen (V 氮气 :V 氢气 =4.2:1), the carbon fiber-supported catalyst precursor was used to catalytically crack ethylene at 690° C. (flow rate of 80 mL / min) for 60 min to obtain carbon nanotubes with a super-ordered structure.

[0069] The powder resistivity of the super-ordered carbon nanotubes prepared in this example is 16 mΩ·cm, and the specific surface area is 306 m 2 / g, and the aspect ratio reaches 4800.

[0070] Example 4

[0071] This embodiment prepares a super-ordered carbon nanotube, and the specific process is as follows:

[0072] Step 1: Dissolve nickel nitrate hexahydrate in deionized water, stir or ultrasonically disperse for 12 minutes to prepare a nickel nitrate aqueous solution with a concentration of 45 g / L.

[0073] Step 2: The alumina fiber is specially treated: first heat treated at 370°C for 2 hours, then treated with a 40% nitric acid aqueous solution for 10 minutes, cleaned and then ultrasonically treated with a 15% ethylenediaminetetraacetic acid (EDTA) aqueous solution for 15 minutes.

[0074] Step 3: Fully immerse the specially treated alumina fibers in the nickel nitrate aqueous solution, perform ultrasonic treatment for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain an alumina fiber-supported catalyst precursor.

[0075] Step 4: In nitrogen and hydrogen (V 氮气 :V 氢气 =1.8:1), the alumina fiber-supported catalyst precursor was used to catalytically crack ethylene at 800° C. (flow rate of 110 mL / min) for 50 min to obtain carbon nanotubes with a super-ordered structure.

[0076] The powder resistivity of the super-ordered carbon nanotubes prepared in this example is 19 mΩ·cm, and the specific surface area is 295 m 2 / g, and the aspect ratio reaches 4200.

[0077] Example 5

[0078] This embodiment prepares a super-ordered carbon nanotube, and the specific process is as follows:

[0079] Step 1: Dissolve ferric nitrate nonahydrate in isopropanol and stir or ultrasonically disperse for 25 minutes to prepare an 80 g / L ferric nitrate isopropanol solution.

[0080] Step 2: The high-silica fiber is specially treated: first, it is heat-treated at 370°C for 1.5 hours, then treated with an aqueous solution of 50% nitric acid for 27 minutes, and then cleaned and ultrasonically treated with an aqueous solution of 12% citric acid for 15 minutes.

[0081] Step 3: Fully immerse the specially treated high-silica fiber in the ferric nitrate isopropanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain a high-silica fiber-loaded catalyst precursor.

[0082] Step 4: In nitrogen and hydrogen (V 氮气 :V 氢气 =5.5:1), the high silica fiber-supported catalyst precursor was catalytically cracked with ethylene at 750° C. (flow rate of 120 mL / min) for 30 min to obtain super-ordered carbon nanotubes.

[0083] The powder resistivity of the super-ordered carbon nanotubes prepared in this example is 23 mΩ·cm, and the specific surface area is 283 m 2 / g, and the aspect ratio reaches 3300.

[0084] Comparative Example 1

[0085] This comparative example prepares a carbon nanotube. The main difference from Example 1 is that the glass fiber is not subjected to special treatment (heat treatment, inorganic acid pretreatment, and carboxylic acid modification treatment). The specific process is as follows:

[0086] Step 1: Dissolve ferric nitrate nonahydrate in anhydrous ethanol, stir or ultrasonically disperse for 17 minutes to prepare a ferric nitrate ethanol solution with a concentration of 20 g / L.

[0087] Step 2: Fully immerse the untreated glass fiber in the ferric nitrate ethanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain a glass fiber-supported catalyst precursor.

[0088] Step 3: In nitrogen and hydrogen (V 氮气 :V 氢气 =3.6:1), the glass fiber-supported catalyst precursor was used to catalytically crack ethylene at 660° C. (flow rate of 100 mL / min) for 40 min to obtain carbon nanotubes.

[0089] The carbon nanotubes prepared in this comparative example have poor structural order, a powder resistivity of 67 mΩ·cm, and a specific surface area of ​​198 m 2 / g, and the aspect ratio is only 1700.

[0090] Comparative Example 2

[0091] This comparative example prepared a carbon nanotube, which differed from Example 1 mainly in that the carboxylic acid modification treatment was omitted. The specific process was as follows:

[0092] Step 1: Dissolve ferric nitrate nonahydrate in anhydrous ethanol, stir or ultrasonically disperse for 17 minutes to prepare a ferric nitrate ethanol solution with a concentration of 20 g / L.

[0093] Step 2: The glass fiber is subjected to special treatment: firstly, it is heat treated at 330° C. for 1.5 hours, and then treated with a 40% nitric acid aqueous solution for 10 minutes.

[0094] Step 3: Fully immerse the specially treated glass fiber in the ferric nitrate ethanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain a glass fiber-supported catalyst precursor.

[0095] Step 4: In nitrogen and hydrogen (V 氮气 :V 氢气 =1:1), the glass fiber-supported catalyst precursor was used to catalytically crack ethylene at 660° C. (flow rate of 100 mL / min) for 40 min to obtain carbon nanotubes.

[0096] The powder resistivity of the carbon nanotubes prepared in this comparative example is 59 mΩ·cm and the specific surface area is 206 m 2 / g, and the aspect ratio reaches 1900.

[0097] Comparative Example 3

[0098] This comparative example prepares a carbon nanotube. The main difference from Example 1 is that the inorganic acid pretreatment is omitted. The specific process is as follows:

[0099] Step 1: Dissolve ferric nitrate nonahydrate in anhydrous ethanol, stir or ultrasonically disperse for 17 minutes to prepare a ferric nitrate ethanol solution with a depth of 20 g / L.

[0100] Step 2: The glass fiber is subjected to special treatment: firstly, it is heat-treated at 330° C. for 1.5 h, and then directly ultrasonically treated with a 5% mass concentration citric acid aqueous solution for 15 min.

[0101] Step 3: Fully immerse the specially treated glass fiber in the ferric nitrate ethanol solution, ultrasonically treat for 10 minutes, immerse for 1 hour, then take out and dry at 105° C. for 3 hours to obtain a glass fiber-supported catalyst precursor.

[0102] Step 4: Under the protection of nitrogen and hydrogen, the glass fiber supported catalyst precursor is catalytically cracked at 660 ° C for ethylene (V 氮气 :V 氢气 =3.6:1), reaction time 40min, to obtain carbon nanotubes.

[0103] The powder resistivity of the carbon nanotubes prepared in this comparative example is 54 mΩ·cm and the specific surface area is 213 m 2 / g, and the aspect ratio reaches 2100.

[0104] Test example

[0105] This test example tests the properties of carbon nanotubes prepared in the examples and comparative examples.

[0106] The test method / test basis for resistivity is GB-T 37152-2018 Sheet Resistance of Carbon Nanotube Materials;

[0107] The test method / test basis for specific surface area is GB / T 10722-2014 Carbon black - Determination of total surface area and external surface area - Nitrogen adsorption method.

[0108] Table 1 Properties of carbon nanotubes prepared in Examples and Comparative Examples

[0109]

[0110] From Table 1 and Figures 1 to 5 It can be seen that the present invention performs special treatment on the carrier surface, including heat treatment, inorganic acid pretreatment and carboxylic acid modification treatment, and the resulting carbon nanotube powder has a resistivity of 16 to 23 mΩ·cm and a specific surface area of ​​283 to 306 m 2 / g, and an aspect ratio of 3300-4800, with superior conductivity compared to other similar products, making it suitable for the preparation of conductive agents. Furthermore, the carbon nanotubes are highly oriented, with long, straight morphologies and a unique tree-like bifurcated structure. Comparative Examples 1-3, which did not undergo special carrier treatment, or omitted carboxylic acid modification or inorganic acid pretreatment, produced carbon nanotubes with significantly poorer conductivity, decreased orientation, and some exhibited clumping and agglomeration.

[0111] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing super-ordered carbon nanotubes, characterized in that: The steps include: Immersing the support in a catalyst precursor solution to obtain a support loaded with the catalyst precursor; Super-ordered carbon nanotubes are grown on the surface of the support carrying the catalyst precursor by chemical deposition; The support is specially treated, including heat treatment, inorganic acid pretreatment and carboxylic acid modification treatment; The heat treatment temperature is 300-400°C; The inorganic acid pretreatment time is 10 to 27 minutes; the mass concentration of the inorganic acid is 30 to 50%; the carboxylic acid modification treatment time is 10 to 20 minutes; the carboxylic acid includes at least one of citric acid and ethylenediaminetetraacetic acid.

2. The preparation method according to claim 1, characterized in that The inorganic acid includes at least one of nitric acid, concentrated sulfuric acid, concentrated hydrochloric acid, and perchloric acid.

3. The preparation method according to claim 1, characterized in that The catalyst precursor includes at least one of iron salt, cobalt salt and nickel salt.

4. The preparation method according to claim 1, characterized in that The super-ordered carbon nanotubes are grown on the surface of the carrier carrying the catalyst precursor by chemical deposition. Specifically, under the protection of carrier gas and auxiliary gas, the carrier carrying the catalyst precursor catalytically decomposes the carbon source to obtain the super-ordered carbon nanotubes.

5. The preparation method according to claim 4, characterized in that The temperature of the catalytic cracking reaction is 600-1000° C., and the time of the catalytic cracking reaction is 10-60 minutes.

6. A super-ordered carbon nanotube, characterized in that: The super-ordered carbon nanotubes are prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the super-ordered carbon nanotubes according to claim 6 in preparing a conductive agent for lithium-ion batteries.

Images