Carbon nanotube, method for modifying the same, and slurry containing modified carbon nanotube

Abstract

The present application relates to a kind of carbon nanotube and its modification method and slurry comprising modified carbon nanotube, belong to the technical field of modified carbon nanotube.The present application is by using low concentration nitric acid and hydrochloric acid mixture liquid oxidation treatment carbon nanotube, then using silane coupling agent again treatment carbon nanotube, in the case where not destroying the side wall structure of carbon nanotube, only to the end cap of carbon nanotube is modified, to improve its dispersibility and stability in slurry, and improve its conductivity and application performance.

Description

Technical Field

[0001] This invention belongs to the technical field of modified carbon nanotubes, specifically relating to a carbon nanotube, a method for modifying the same, and a slurry containing modified carbon nanotubes. Background Technology

[0002] Carbon nanotubes possess exceptional physical and chemical properties, including excellent mechanical properties, thermal stability, unique electrical properties, thermal conductivity, hydrogen storage, adsorption, and catalytic activity. Therefore, they have attracted considerable attention from researchers both domestically and internationally since their discovery. Carbon nanotubes show broad application prospects in numerous fields, including nanoelectronic devices, catalyst supports, electrochemical materials, and composite materials.

[0003] Carbon nanotubes are tubular structures formed by rolling up one or more layers of graphene structures composed of six-membered carbon rings. Both ends of the carbon nanotubes are closed, with diameters ranging from a few nanometers to hundreds of nanometers and lengths reaching several centimeters. However, due to the strong van der Waals forces between carbon nanotubes, they exist in an aggregated state, making dispersion difficult and severely limiting their applications. Currently, the main methods for dispersing carbon nanotubes are physical dispersion and chemical dispersion. Chemical dispersion, because it avoids secondary aggregation, is more stable than physical dispersion and has therefore attracted increasing attention.

[0004] Chinese patent CN103665389A discloses a modified carbon nanotube and its preparation method, which grafts polyvinyl alcohol onto carbon nanotubes to introduce hydroxyl groups onto the surface of the carbon nanotubes, thereby improving the dispersibility of the carbon nanotubes in aqueous solutions. However, this method introduces a large number of hydroxyl groups onto the surface of the carbon nanotubes, resulting in numerous surface defects. These surface defects, especially those on the sidewalls, can affect the conductivity of the carbon nanotubes to some extent, thus impacting their application in the battery field. Summary of the Invention

[0005] To address the problem that existing methods for modifying carbon nanotubes often result in excessive grafting of hydroxyl and carboxyl groups onto the sidewalls, affecting their conductivity, this invention provides a carbon nanotube, its modification method, and a slurry containing the modified carbon nanotubes to solve the aforementioned problems. The cap of a carbon nanotube is typically composed of five-membered or seven-membered rings, while the sidewalls are generally composed of six-membered rings. Since the five-membered or seven-membered rings C and C are connected by sp... 3 Hybridization, relative to the sp of a six-membered ring 2Hybridized orbitals, particularly those on five- or seven-membered rings, result in higher carbon reactivity and facilitate reactions with other alcohols and carboxylic acids. By selecting specific reaction conditions and modifiers, the end caps of carbon nanotubes can be modified without damaging the sidewall structure. This invention modifies only the end caps of carbon nanotubes by choosing specific reaction conditions and modifiers, without altering the sidewall structure. This improves their dispersibility and stability in slurries, as well as their conductivity and application performance.

[0006] In a first aspect, the present invention provides a method for modifying carbon nanotubes, as detailed below: (1) Take multi-walled carbon nanotubes and treat them in a mixed acid solution of nitric acid and hydrochloric acid; (2) The carbon nanotubes treated in step (1) are added to a toluene solution containing silane coupling agent KH-570 and dispersed into a first suspension; then the first suspension is heated and reacted under inert gas protection; after the reaction is completed, the carbon nanotubes are washed and dried to obtain surface-modified carbon nanotubes. (3) The surface-modified carbon nanotubes prepared in step (2) are added to an N,N-dimethylformamide solution containing hydrogenated nitrile rubber and ultrasonically dispersed to form a second suspension; then, under inert gas protection, the second suspension is heated to 120~130°C for reaction; after the reaction is completed, the carbon nanotubes with only modified end caps are obtained.

[0007] Furthermore, in step (1), the multi-walled carbon nanotubes have a purity of ≥95%, a diameter of 20~50nm, and a length of 1~5μm.

[0008] Furthermore, in step (1), the mass ratio of carbon nanotubes, nitric acid and hydrochloric acid is 1:(1~2):(4~6).

[0009] Furthermore, in step (2), the mass fraction of silane coupling agent KH-570 in the toluene solution containing silane coupling agent KH-570 is 5%.

[0010] Furthermore, in step (4), the mass fraction of hydrogenated nitrile rubber in the N,N-dimethylformamide solution containing hydrogenated nitrile rubber is 10%.

[0011] Secondly, the present invention provides a modified carbon nanotube prepared using the above-described modification method.

[0012] Thirdly, the present invention provides a slurry comprising the above-mentioned modified carbon nanotubes, comprising the following components by mass percentage: 0.5% to 2% polyvinylpyrrolidone, 0.4% to 2% piperazine, 3% to 6% modified carbon nanotubes, and the balance being N-methylpyrrolidone.

[0013] Fourthly, the present invention provides a method for preparing the above-mentioned slurry, comprising the following steps: (1) Preparation of dispersant solution: Dissolve polyvinylpyrrolidone in N-methylpyrrolidone, heat and filter to remove insoluble polyvinylpyrrolidone, and obtain N-methylpyrrolidone solution of polyvinylpyrrolidone for later use; (2) Preparation of viscosity reducing agent solution: Dissolve piperazine in N-methylpyrrolidone, heat and filter to obtain piperazine N-methylpyrrolidone solution for later use; (3) Under stirring, the prepared modified carbon nanotubes are mixed with the dispersant solution prepared in step (1) and the viscosity reducer solution prepared in step (2) and stirred evenly; (4) Grind using grinding beads with a diameter of 1.0~1.2mm; (5) Add N-methylpyrrolidone to the mixture, and repeat steps (3) and (4) until N-methylpyrrolidone is completely added to the reaction system; (6) Grind with zirconium beads with a diameter of 0.6~0.8mm, take out the ground slurry, and obtain a slurry containing modified carbon nanotubes.

[0014] Furthermore, the viscosity of the slurry after grinding in step (5) is 5000~8000 mPa·s.

[0015] Furthermore, the fineness of the slurry containing modified carbon nanotubes is ≤10μm.

[0016] The beneficial effects of this invention are as follows: (1) This invention provides a novel method for modifying carbon nanotubes, which can modify the end caps of carbon nanotubes without damaging the sidewall structure, thereby improving the dispersibility and conductivity of carbon nanotubes. This is of great significance for improving the application performance of carbon nanotubes in fields such as batteries. Secondly, the preparation method of this invention is simple, the reaction conditions are mild, and the modifier is inexpensive, which will greatly reduce the preparation cost of carbon nanotubes and promote their industrial application. Finally, due to the excellent physicochemical properties of carbon nanotubes, the carbon nanotubes of this invention have broad application prospects in fields such as catalysis, composite materials, energy storage materials, and microelectronic devices.

[0017] (2) The dispersant polyvinylpyrrolidone disperses the modified carbon nanotubes. The prepared slurry can still maintain uniformity after standing at room temperature for 180 days. The particle size D99 of the slurry remains below 10 μm and there is no secondary agglomeration.

[0018] (3) Compared with the slurry prepared by using sidewall modified carbon nanotubes, the slurry prepared by the present invention has better conductivity and the performance is improved by 30%~50%. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a graph showing the viscosity change of the slurry prepared in Example 5 of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0022] Example 1 A modified carbon nanotube, the specific preparation method of which is as follows: (1) Preparation of mixed acid: Mix 300g of concentrated HNO3 with a mass concentration of 68%, 1000g of hydrochloric acid with a mass fraction of 30% and 5000g of deionized water to obtain a mixed acid solution.

[0023] (2) Take 200g of multi-walled carbon nanotubes GT-210 (produced by Shandong Dazhan Nanomaterials Co., Ltd.), with a carbon nanotube purity ≥95%, diameter = 7~15nm, and length ≤50μm; add it to the mixed acid solution prepared in step (1); stir and acidify at 80℃ for 2 hours to pretreat the carbon nanotubes.

[0024] (3) Take out the carbon nanotubes after step (2), rinse them repeatedly with deionized water until the filtrate is neutral, and then vacuum dry them at 60°C for 12 hours.

[0025] (4) The dried carbon nanotubes were added to 5000 ml of a toluene solution of 5% KH-570 silane coupling agent and ultrasonically dispersed for 30 minutes to form a uniform suspension. Then, under nitrogen protection, the suspension was heated to 80°C and reacted for 24 hours. After the reaction was completed, the product was washed with toluene and ethanol in sequence and then vacuum dried at 60°C for 12 hours to obtain end-cap modified carbon nanotubes. (5) The surface-modified carbon nanotubes were added to 5000 ml of N,N-dimethylformamide solution containing 10% hydrogenated nitrile rubber and ultrasonically dispersed for 30 minutes to form a uniform suspension. Then, under nitrogen protection, the suspension was heated to 120 °C and reacted for 48 hours. After the reaction was completed, the product was washed sequentially with N,N-dimethylformamide and ethanol, and then vacuum dried at 60 °C for 12 hours to obtain 164 g of modified carbon nanotubes with only modified end caps.

[0026] Example 2 A modified carbon nanotube, the specific preparation method of which is as follows: (1) Preparation of mixed acid: Mix 500g of concentrated nitric acid with a mass concentration of 68%, 2500g of hydrochloric acid with a mass fraction of 27% and 11250g of deionized water to obtain a mixed acid solution.

[0027] (2) Take 450g of multi-walled carbon nanotubes GT-210 (produced by Shandong Dazhan Nanomaterials Co., Ltd.), with a carbon nanotube purity ≥95%, diameter = 7~15nm, and length ≤50μm; add the mixed acid solution prepared in step (1) to it; stir and acidify at 70℃ for 2 hours to pretreat the carbon nanotubes.

[0028] (3) Take out the carbon nanotubes after step (2), rinse them repeatedly with deionized water until the filtrate is neutral, and then vacuum dry them at 65°C for 10 hours.

[0029] (4) The dried carbon nanotubes were added to 12000 ml of a toluene solution of 5% KH-570 silane coupling agent and ultrasonically dispersed for 30 minutes to form a uniform suspension. Then, under nitrogen protection, the suspension was heated to 90°C and reacted for 20 hours. After the reaction was completed, the product was washed with toluene and ethanol in sequence and then vacuum dried at 60°C for 12 hours to obtain end-cap modified carbon nanotubes. (5) The surface-modified carbon nanotubes were added to 10,000 ml of N,N-dimethylformamide solution containing 10% hydrogenated nitrile rubber and ultrasonically dispersed for 30 minutes to form a uniform suspension. Then, under nitrogen protection, the suspension was heated to 110 °C and reacted for 40 hours. After the reaction was completed, the product was washed sequentially with N,N-dimethylformamide and ethanol, and then vacuum dried at 60 °C for 12 hours to obtain 368 g of modified carbon nanotubes with only modified end caps.

[0030] Example 3 A modified carbon nanotube, the specific preparation method of which is as follows: (1) Prepare mixed acid: Mix 600g of concentrated nitric acid with a mass concentration of 68%, 1500g of hydrochloric acid with a mass fraction of 30% and 7500g of deionized water to obtain a mixed acid solution.

[0031] (2) Take 300g of multi-walled carbon nanotubes GT-210 (produced by Shandong Dazhan Nanomaterials Co., Ltd.), with a carbon nanotube purity ≥95%, diameter = 7~15nm, and length ≤50μm; add the mixed acid solution prepared in step (1) to it; stir and acidify at 70℃ for 2 hours to pretreat the carbon nanotubes.

[0032] (3) Take out the carbon nanotubes after step (2), rinse them repeatedly with deionized water until the filtrate is neutral, and then vacuum dry them at 65°C for 10 hours.

[0033] (4) The dried carbon nanotubes were added to 9000 ml of a toluene solution of 5% KH-570 silane coupling agent and ultrasonically dispersed for 30 minutes to form a uniform suspension. Then, under nitrogen protection, the suspension was heated to 70°C and reacted for 30 hours. After the reaction was completed, the product was washed with toluene and ethanol in sequence and then vacuum dried at 60°C for 12 hours to obtain end-cap modified carbon nanotubes. (5) The surface-modified carbon nanotubes were added to 7000 ml of N,N-dimethylformamide solution containing 10% hydrogenated nitrile rubber and ultrasonically dispersed for 30 minutes to form a uniform suspension. Then, under nitrogen protection, the suspension was heated to 110 °C and reacted for 40 hours. After the reaction was completed, the product was washed sequentially with N,N-dimethylformamide and ethanol, and then vacuum dried at 60 °C for 12 hours to obtain 243 g of modified carbon nanotubes with only modified end caps.

[0034] Example 4 A slurry containing modified carbon nanotubes includes 50g of polyvinylpyrrolidone (PVP, molecular weight distribution 40000~58000), 40g of anhydrous piperazine, 190g of the modified carbon nanotubes prepared in Example 1, and 4500g of N-methylpyrrolidone.

[0035] The preparation method is as follows: (1) Preparation of dispersant solution: Dissolve polyvinylpyrrolidone in 300g N-methylpyrrolidone, heat at 55℃ for 6h, and then filter through 200 mesh to remove insoluble macromolecular polyvinylpyrrolidone to obtain N-methylpyrrolidone solution of polyvinylpyrrolidone for later use; (2) Preparation of viscosity reducing agent solution: Dissolve anhydrous piperazine in 200g N-methylpyrrolidone, heat at 50℃ for 3h and filter through 200 mesh to obtain anhydrous piperazine N-methylpyrrolidone solution for later use; (3) Reduce the stirring speed to 600 rpm, mix the modified carbon nanotubes prepared in Example 1 with the solutions prepared in steps (1) and (2) under stirring and stir for 30 min; (4) Grind using grinding beads with a diameter of 1.0~1.2mm, and adjust the speed to high speed of 3000rpm for 120~250min; (5) Add 300g of N-methylpyrrolidone to the mixture, repeat steps (3) and (4) until N-methylpyrrolidone is completely added to the reaction system, and grind until the viscosity of the liquid is 5000~8000mPa·s; (6) Grind with zirconium beads with a diameter of 0.6~0.8 mm until the fineness is ≤10μm. Take out the ground slurry to obtain a slurry containing modified carbon nanotubes.

[0036] Example 5 A slurry containing modified carbon nanotubes includes 47g of polyvinylpyrrolidone (PVP, molecular weight distribution 40000~58000), 50g of anhydrous piperazine, 180g of the modified carbon nanotubes prepared in Example 1, and 3000g of N-methylpyrrolidone.

[0037] The preparation method is as follows: (1) Preparation of dispersant solution: Dissolve polyvinylpyrrolidone in 200g N-methylpyrrolidone, heat at 50℃ for 8h, and then filter through 200 mesh to remove undissolved macromolecular polyvinylpyrrolidone to obtain N-methylpyrrolidone solution of polyvinylpyrrolidone for later use; (2) Preparation of viscosity reducing agent solution: Dissolve anhydrous piperazine in 150g N-methylpyrrolidone, heat at 50℃ for 3h and filter through 200 mesh to obtain anhydrous piperazine N-methylpyrrolidone solution for later use; (3) Reduce the stirring speed to 600 rpm, mix the modified carbon nanotubes prepared in Example 1 with the solution prepared in steps (1) and (2) under stirring and stir for 50 min; (4) Grind using grinding beads with a diameter of 1.2 mm, and adjust the speed to high speed of 3000 rpm for 120~250 min; (5) Add 250g of N-methylpyrrolidone to the mixture, repeat steps (3) and (4) until N-methylpyrrolidone is completely added to the reaction system, and grind until the viscosity of the liquid is 5000~8000mPa·s; (6) Grind with zirconium beads with a diameter of 0.6~0.8 mm until the fineness is ≤10μm. Take out the ground slurry to obtain a slurry containing modified carbon nanotubes.

[0038] Example 6 A slurry containing modified carbon nanotubes includes 50g of polyvinylpyrrolidone (PVP, molecular weight distribution 40000~58000), 30g of anhydrous piperazine, 380g of the modified carbon nanotubes prepared in Example 1, and 6800g of N-methylpyrrolidone.

[0039] The preparation method is as follows: (1) Preparation of dispersant solution: Dissolve polyvinylpyrrolidone in 300g N-methylpyrrolidone, heat at 55℃ for 6h, and then filter through 200 mesh to remove insoluble macromolecular polyvinylpyrrolidone to obtain N-methylpyrrolidone solution of polyvinylpyrrolidone for later use; (2) Preparation of viscosity reducing agent solution: Dissolve anhydrous piperazine in 200g N-methylpyrrolidone, heat at 50℃ for 3h and filter through 200 mesh to obtain anhydrous piperazine N-methylpyrrolidone solution for later use; (3) Reduce the stirring speed to 600 rpm, mix the modified carbon nanotubes prepared in Example 1 with the solution prepared in steps (1) and (2) under stirring and stir for 60 min; (4) Grind using grinding beads with a diameter of 1.2 mm, and adjust the speed to high speed of 3000 rpm for 120~250 min; (5) Add 300g of N-methylpyrrolidone to the mixture, repeat steps (3) and (4) until N-methylpyrrolidone is completely added to the reaction system, and grind until the viscosity of the liquid is 5000~8000mPa·s; (6) Grind with zirconium beads with a diameter of 0.6~0.8 mm until the fineness is ≤10μm. Take out the ground slurry to obtain a slurry containing modified carbon nanotubes.

[0040] Comparative Example 1 A modified carbon nanotube, the specific preparation method of which is as follows: (1) Take 1000g of multi-walled carbon nanotubes GT-210 produced by the applicant (produced by Shandong Dazhan Nanomaterials Co., Ltd.), with a carbon nanotube purity ≥95%, diameter = 7~15nm, and length ≤50μm; place them in sulfuric acid with a mass concentration of 98%; and treat them at 80℃ for 2 hours.

[0041] (2) Take out the carbon nanotubes after step (1), rinse them repeatedly with deionized water until the filtrate is neutral, and then vacuum dry them at 60°C for 12 hours to obtain surface-modified carbon nanotubes.

[0042] Comparative Example 2 A slurry containing modified carbon nanotubes includes 50g of polyvinylpyrrolidone (PVP, molecular weight distribution 40,000-58,000), 40g of anhydrous piperazine, 190g of the modified carbon nanotubes prepared in Example 1, and 4500g of N-methylpyrrolidone (NMP).

[0043] The preparation method is as follows: (1) Mix 4500g of polyvinylpyrrolidone, anhydrous piperazine, modified carbon nanotubes and N-methylpyrrolidone, and stir for 60~100min; (2) Use grinding beads with a diameter of 1.0~1.2mm to grind, adjust the speed to high speed of 3000rpm and grind for 400~600min, and take out the ground slurry for later use; (3) Filter to remove filter residue and obtain a slurry containing modified carbon nanotubes.

[0044] Comparative Example 3 A slurry containing modified carbon nanotubes includes 50g of polyvinylpyrrolidone (PVP, molecular weight distribution 40000~58000), 40g of anhydrous piperazine, 190g of the modified carbon nanotubes prepared in Example 1, and 4500g of N-methylpyrrolidone.

[0045] The preparation method is as follows: (1) Mix 4500g of polyvinylpyrrolidone, anhydrous piperazine, modified carbon nanotubes and N-methylpyrrolidone, and stir for 60~100min; (2) Use grinding beads with a diameter of 0.6~0.8mm to grind, adjust the speed to high speed of 3000rpm and grind for 400~600min, and take out the ground slurry for later use; (3) Filter to remove filter residue and obtain slurry containing modified carbon nanotubes.

[0046] Comparative Example 4 A slurry containing modified carbon nanotubes includes 50g of polyvinylpyrrolidone (PVP, molecular weight distribution 40000~58000), 40g of anhydrous piperazine, 190g of the modified carbon nanotubes prepared in Example 1, and 4500g of N-methylpyrrolidone.

[0047] The preparation method is as follows: (1) Mix 4500g of polyvinylpyrrolidone, anhydrous piperazine, modified carbon nanotubes and N-methylpyrrolidone, and stir for 60~100min; (2) Grind using grinding beads with a diameter of 1.0~1.2mm, and adjust the speed to high speed of 3000rpm for 200~400min; (3) Grind with grinding beads with a diameter of 0.6~0.8mm, adjust the speed to high speed of 3000rpm and grind for 200~300min; take out the ground slurry for later use; (4) Filter to remove filter residue and obtain slurry containing modified carbon nanotubes.

[0048] Test case 1. Solid content detection The carbon nanotube conductive pastes prepared in Examples 4-6 were placed in three 100ml graduated cylinders and left to stand at room temperature for 90 days and 180 days respectively. Then, samples were taken from the top (90-100mL mark) and bottom (0-10mL mark) of each beaker to determine the solid content of each sample. The results are shown in Table 1.

[0049] Table 1 - Solid content test results for each sample

[0050] As can be seen, the solid content at various locations of the carbon nanotube conductive slurries prepared in Examples 4-6 was similar after standing for 90 and 180 days, proving that the carbon nanotube conductive slurry prepared by this invention has better dispersibility. After standing for 180 days, no obvious repolymerization or sedimentation was observed. In contrast, the slurry prepared using comparatively modified carbon nanotubes showed more significant carbon nanotube sedimentation after standing for 90 and 180 days.

[0051] Comparative examples and comparative examples show that the conductive paste obtained using the preparation process provided by this invention has better stability. According to Comparative Examples 2-4, the conductive paste obtained by simply grinding with 0.6-0.8 mm zirconium beads has the worst stability, while the conductive paste obtained by first grinding with 1.0-1.2 mm zirconium beads and then grinding with 0.6-0.8 mm zirconium beads has better stability. The applicant, through real-time monitoring of the viscosity of the conductive paste, knows that the viscosity curve of the liquid during the grinding process is as follows... Figure 1 As shown, the viscosity of the liquid exhibits two peaks before decreasing and gradually stabilizing. Analysis suggests this may be because, immediately after the carbon nanotubes are added, the liquid wets the nanotubes, leading to significant adsorption and causing the viscosity to reach peak A. As the carbon nanotubes disperse, some adsorbed nanotubes are released, and the viscosity gradually decreases to valley B. Then, as the carbon nanotubes continue to be ground and dispersed, the frequency of interactions between them increases, causing the viscosity to gradually increase to peak C. After peak C, the dispersant's effect on the carbon nanotubes becomes prominent, isolating them and increasing system stability. The viscosity of the liquid gradually decreases and stabilizes.

[0052] Through multiple experiments conducted by the applicant, it was found that in the early stages of the slurry grinding, using zirconium beads with a diameter of 1.0~1.2mm for grinding, and then switching to zirconium beads with a diameter of 0.6~0.8mm after the viscosity value exceeds the C peak and reaches 5000~8000mPa·s, results in a more stable conductive slurry. This is because the viscosity of the slurry changes significantly before reaching the C peak, where the viscosity reaches as high as 20000~50000mPa·s. Using larger diameter zirconium beads for grinding allows for rapid grinding of carbon nanotubes and prevents the movement of the zirconium beads from being restricted by the high viscosity of the slurry, thus ensuring smooth grinding of the slurry.

[0053] 2. Conductivity testing The carbon nanotube slurries prepared in Examples 4-5 and the comparative example were stirred to prepare a conductive slurry with a carbon nanotube mass content of 0.3%. After being combined with lithium iron phosphate, polyvinylidene fluoride and other components and stirred evenly, the evenly stirred slurry was coated onto a PI film using a 200 μm coating blade and dried at 150 °C for 1.5 h to prepare a 1% lithium iron phosphate coated film. The resistivity of the electrode after the conductive slurry was combined was tested using a four-probe tester. The results are shown in Table 2.

[0054] Table 2 - Electrode Resistivity Test

[0055] As shown in Table 2, the average resistivity of the oily conductive slurry prepared by the present invention is increased by about 18.5% after being coated with the positive electrode material. Compared with the carbon nanotubes prepared by Comparative Example 1, the conductivity is significantly improved.

[0056] 3. Particle size detection The particle size of the conductive slurry was detected using a laser particle size analyzer, and the results are shown in Table 3.

[0057] Table 3 - Test Results

[0058] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for modifying carbon nanotubes, characterized in that, Specifically as follows: (1) Take multi-walled carbon nanotubes and treat them in a mixed acid solution of nitric acid and hydrochloric acid; (2) The carbon nanotubes treated in step (1) are added to a toluene solution containing silane coupling agent KH-570 and dispersed into a first suspension; then the first suspension is heated and reacted under inert gas protection; after the reaction is completed, the carbon nanotubes are washed and dried to obtain surface-modified carbon nanotubes. (3) The surface-modified carbon nanotubes prepared in step (2) are added to an N,N-dimethylformamide solution containing hydrogenated nitrile rubber and ultrasonically dispersed to form a second suspension; then, under inert gas protection, the second suspension is heated to 120~130°C for reaction; after the reaction is completed, the carbon nanotubes with only modified end caps are obtained.

2. The method for modifying carbon nanotubes as described in claim 1, characterized in that, In step (1), the multi-walled carbon nanotubes have a purity of ≥95%, a diameter of 20~50nm, and a length of 1~5μm.

3. The method for modifying carbon nanotubes as described in claim 1, characterized in that, In step (1), the mass ratio of carbon nanotubes, nitric acid and hydrochloric acid is 1:(1~2):(4~6).

4. The method for modifying carbon nanotubes as described in claim 1, characterized in that, In step (2), the mass fraction of silane coupling agent KH-570 in the toluene solution containing silane coupling agent KH-570 is 5%.

5. The method for modifying carbon nanotubes as described in claim 1, characterized in that, In step (4), the mass fraction of hydrogenated nitrile rubber in the N,N-dimethylformamide solution containing hydrogenated nitrile rubber is 10%.

6. A modified carbon nanotube prepared using the modification method as described in claim 1.

7. A slurry comprising the modified carbon nanotubes as described in claim 6, characterized in that, The following components are included by weight percentage: 0.5% to 2% polyvinylpyrrolidone, 0.4% to 2% piperazine, 3% to 6% modified carbon nanotubes, and the balance being N-methylpyrrolidone.

8. A method for preparing the slurry as described in claim 7, characterized in that, Includes the following steps: (1) Preparation of dispersant solution: Dissolve polyvinylpyrrolidone in N-methylpyrrolidone, heat and filter to remove insoluble polyvinylpyrrolidone, and obtain N-methylpyrrolidone solution of polyvinylpyrrolidone for later use; (2) Preparation of viscosity reducing agent solution: Dissolve piperazine in N-methylpyrrolidone, heat and filter to obtain piperazine N-methylpyrrolidone solution for later use; (3) Under stirring, the prepared modified carbon nanotubes are mixed with the dispersant solution prepared in step (1) and the viscosity reducer solution prepared in step (2) and stirred evenly; (4) Grind using grinding beads with a diameter of 1.0~1.2mm; (5) Add N-methylpyrrolidone to the mixture, and repeat steps (3) and (4) until N-methylpyrrolidone is completely added to the reaction system; (6) Grind with zirconium beads with a diameter of 0.6~0.8mm, take out the ground slurry, and obtain a slurry containing modified carbon nanotubes.

9. The method as described in claim 7, characterized in that, The viscosity of the slurry after grinding in step (5) is 5000~8000 mPa·s.

10. The method as described in claim 7, characterized in that, The fineness of the slurry containing modified carbon nanotubes is ≤10μm.

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