Multi-walled carbon nanotube as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nano material processing, and discloses a multi-walled carbon nanotube as well as a preparation method and application thereof. The method comprises the steps that under the hydrothermal condition, a carbon nano tube and a polymer dispersing agent are subjected to a contact reaction, and the polymer dispersing agent is selected from at least one of polyvinylpyrrolidone, a vinyl pyrrolidone / styrene copolymer, a vinyl pyrrolidone / acrylic acid copolymer and a vinyl pyrrolidone / imidazole copolymer. The multi-walled carbon nanotube comprises a carbon nanotube and a polymer dispersant loaded on the carbon nanotube, and the viscosity of an N-methyl pyrrolidone dispersion liquid of the multi-walled carbon nanotube is reduced by 34-60% compared with the viscosity of an N-methyl pyrrolidone dispersion liquid containing the same content of the carbon nanotube and the same content of the polymer dispersant. The preparation method is simple and convenient, and the prepared multi-walled carbon nanotube has a better dispersion effect on the basis of ensuring that the original properties are not changed, and does not introduce impurities.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterial processing, in particular to a multi-walled carbon nanotube and a preparation method and application thereof. BACKGROUND

[0002] Carbon nanotubes are formed by rolling graphite layers along a certain helical vector, and the unique one-dimensional tubular structure endows them with excellent physical and chemical properties. Carbon nanotubes have the characteristics of light weight, high strength, high electrical conductivity, etc., and are known as "future materials", and are widely used in electronic industry, aerospace industry, biological and pharmaceutical industry, composite materials, energy storage batteries and other fields. In recent years, the production of carbon nanotubes by chemical vapor deposition method has realized industrialized production, and the production cost has been greatly reduced, which has laid a good foundation for the application of carbon nanotubes.

[0003] Carbon nanotubes have a large tube length to diameter ratio, and present line and point contact in lithium ion battery materials, which can form a better conductive network structure compared with traditional particle type conductive agents. When achieving the same or better conductive effect, the addition amount of carbon nanotubes is greatly reduced. Carbon nanotubes have the same sheet structure as graphite and have good electrical conductivity. The resistance of carbon nanotubes is independent of its length and diameter, and electrons passing through carbon nanotubes will not heat the carbon nanotubes. The transmission of electrons in carbon nanotubes is like the transmission of optical signals in optical fiber cables, with little energy loss, which is an excellent battery conductive agent. The hollow tube cavity of carbon nanotubes, the gap between tubes, the gap between layers in the tube wall, and various defects in the tube structure provide abundant storage space and transportation channels for lithium ions. In the field of power and energy storage batteries, carbon nanotubes are applied to electrode materials, which can maintain electrical conductivity in repeated cycles, exhibit good rate and cycle performance, and have high capacity and stable coulombic efficiency in repeated charge and discharge processes.

[0004] However, the agglomeration of carbon nanotubes has always been one of the key factors restricting its application. Carbon nanotube agglomeration refers to the re-aggregation of originally dispersed carbon nanotubes due to van der Waals forces, electrostatic interactions and other interactions during the dispersion process. This phenomenon can seriously affect the performance and application effect of carbon nanotubes. The main reasons for the occurrence of carbon nanotube agglomeration are as follows: ① van der Waals force: there is a van der Waals force between carbon nanotubes, which is a weak attractive force, but it plays a key role in the process of carbon nanotube agglomeration. When the distance between carbon nanotubes is less than a certain value, van der Waals force will cause mutual attraction between carbon nanotubes, thus promoting carbon nanotube agglomeration. ② Electrostatic effect: the surface of carbon nanotubes has a certain charge distribution, which will cause electrostatic effect between carbon nanotubes. When the electrostatic force is greater than the van der Waals force, the agglomeration phenomenon between carbon nanotubes will be more serious. ③ Solvent effect: in the process of dispersing carbon nanotubes, a certain solvent is usually needed. The nature and concentration of the solvent have a great influence on the agglomeration phenomenon of carbon nanotubes. For example, polar solvents can effectively disperse carbon nanotubes and reduce the occurrence of agglomeration phenomenon; while some non-polar solvents may cause more serious carbon nanotube agglomeration.

[0005] At present, the dispersion methods of carbon nanotubes mainly include physical dispersion method and chemical dispersion method. The physical dispersion method mainly uses sanding, ball milling and other means to make carbon nanotubes form a uniform suspension in the medium. This method is simple and easy to operate, but it cannot be denied that it will damage the structure of carbon nanotubes and introduce other impurities. The chemical dispersion method changes the surface properties of carbon nanotubes so that they can form stable chemical bonds with other substances in the medium, thereby realizing dispersion. This method has good dispersion effect, but it may change the original properties of carbon nanotubes and affect their application in batteries, functional polymer materials, coatings and other fields. SUMMARY

[0006] The purpose of the present application is to overcome the problems of poor dispersion effect of carbon nanotubes in the prior art, and the existing preparation method of carbon nanotubes can improve the dispersion effect to a certain extent, but it will change the original properties of carbon nanotubes or introduce impurities. A multi-walled carbon nanotube and its preparation method and application are provided. The preparation method is simple and convenient, and the multi-walled carbon nanotube prepared has good dispersion effect without changing the original properties and introducing impurities.

[0007] In order to achieve the above purpose, one aspect of the present application provides a preparation method of multi-walled carbon nanotubes, which comprises: under hydrothermal conditions, carbon nanotubes and a polymer dispersant are contacted and reacted, and the polymer dispersant is selected from at least one of polyvinylpyrrolidone, vinylpyrrolidone / styrene copolymer, vinylpyrrolidone / acrylic acid copolymer and vinylpyrrolidone / imidazole copolymer.

[0008] Preferably, the mass ratio of the carbon nanotubes and the polymer dispersant is 1:0.25-0.5.

[0009] Further preferably, the weight average molecular weight of the polymer dispersant is 45000-58000.

[0010] Preferably, the polymer dispersant is a vinyl pyrrolidone / acrylic acid copolymer and / or a vinyl pyrrolidone / imidazole copolymer.

[0011] Preferably, in the copolymer, the content of the vinyl pyrrolidone structural unit is 10-30wt%.

[0012] Preferably, the conditions of the hydrothermal reaction at least satisfy: temperature is 140-180℃, and time is 6-10h.

[0013] Preferably, in the hydrothermal reaction system, the concentration of the carbon nanotubes is 0.5-1g / mL.

[0014] The second aspect of the present application provides a multi-walled carbon nanotube, which comprises carbon nanotubes and a polymer dispersant loaded on the carbon nanotubes, and the viscosity reduction rate of an N-methyl pyrrolidone dispersion liquid of the multi-walled carbon nanotube is 34-60% compared with the viscosity of an N-methyl pyrrolidone dispersion liquid containing the same content of carbon nanotubes and the same content of polymer dispersant.

[0015] Preferably, the polymer dispersant is at least one selected from polyvinyl pyrrolidone modification, a vinyl pyrrolidone / styrene copolymer, a vinyl pyrrolidone / acrylic acid copolymer and a vinyl pyrrolidone / imidazole copolymer.

[0016] Further preferably, the polymer dispersant is a vinyl pyrrolidone / acrylic acid copolymer and / or a vinyl pyrrolidone / imidazole copolymer.

[0017] Further preferably, in the copolymer, the content of the vinyl pyrrolidone structural unit is 10-30wt%.

[0018] Further preferably, in the multi-walled carbon nanotube, the loading amount of the polymer dispersant is 20-35wt%.

[0019] The third aspect of the present application provides the application of the multi-walled carbon nanotube prepared by the preparation method provided in the first aspect or the multi-walled carbon nanotube provided in the second aspect in a battery, a functional polymer material or a coating.

[0020] By the technical scheme, the preparation method of the multi-walled carbon nanotube provided by the application can make the prepared multi-walled carbon nanotube have good dispersion effect, and still have good dispersion effect and good storage stability after long-term storage. Moreover, the method is simple, has high repeatability, ensures the purity of the multi-walled carbon nanotube in use, and does not affect the performance of the carbon nanotube itself. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is an SEM image of the carbon nanotube raw material used in Example 4;

[0022] Figure 2 is an SEM image of the multi-walled carbon nanotube prepared in Example 4;

[0023] Figure 3 is a battery rate performance graph of the carbon nanotube slurries obtained in Example 4 and Comparative Example 4 as conductive agents, respectively. DETAILED DESCRIPTION

[0024] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as implicitly disclosed by the above description. Ranges can be expressed as from one endpoint to the other, and endpoints are included. Unless otherwise stated, the endpoints do not include the recited values themselves. Any numerical range recited is intended to include all sub-ranges subsumed therein. Specify for numerical values the accuracy of the rounded off, for example, "40 %" is intended to mean, accurate to the nearest 1 %. It is specifically intended that examples values described and disclosed in this patent are for purposes of illustration and are not intended to be limiting.

[0025] In the production of carbon nanotube conductive slurry, it is common in industry to use polyvinylpyrrolidone as a dispersant to obtain a stable dispersion of carbon nanotube slurry by sanding. However, this method easily damages the structure of the carbon nanotube, introduces other impurities, and seriously affects the performance in batteries.

[0026] As described above, the first method of the application provides a preparation method of multi-walled carbon nanotube, which comprises: under hydrothermal conditions, contacting and reacting carbon nanotube and a polymer dispersant, the polymer dispersant being at least one selected from polyvinylpyrrolidone, vinylpyrrolidone / styrene copolymer, vinylpyrrolidone / acrylic acid copolymer and vinylpyrrolidone / imidazole copolymer.

[0027] The method provided above is simple and convenient, has high repeatability, and can make the prepared multi-walled carbon nanotubes have good dispersion effect and good dispersion effect after long-term storage, and has good storage stability. Moreover, it will not affect the performance of the carbon nanotubes, ensure the purity of the multi-walled carbon nanotubes during use, and will not introduce new impurities.

[0028] Preferably, the mass ratio of the carbon nanotubes to the polymer dispersant is 1:0.25-0.5, and can be 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, or any value between these values. By limiting the mass ratio of the carbon nanotubes to the polymer dispersant to the above range, the reaction between the polymer dispersant and the carbon nanotubes can be better, thereby further improving the dispersion effect of the multi-walled carbon nanotubes in the solvent, and reducing the amount of residual raw materials after the reaction as much as possible, and reducing the cost.

[0029] Preferably, the weight average molecular weight of the polymer dispersant is 45000-58000. Research has found that by controlling the weight average molecular weight of the polyvinylpyrrolidone within the above range, the dispersion effect of the prepared multi-walled carbon nanotubes in the solvent can be further improved.

[0030] Preferably, the polymer dispersant is a vinylpyrrolidone / acrylic acid copolymer and / or a vinylpyrrolidone / imidazole copolymer. The inventors have found that the multi-walled carbon nanotubes prepared using the above polymer dispersants have better dispersion effect.

[0031] Preferably, in the copolymer, the content of the vinylpyrrolidone structural unit is 10-30wt%, and can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, or any value between these values. Research has found that by controlling the content of the vinylpyrrolidone structural unit in the polymer within the above range, the dispersion effect of the prepared multi-walled carbon nanotubes in the solvent can be further improved. The vinylpyrrolidone structural unit refers to the existence structure of the vinylpyrrolidone monomer in the polymer.

[0032] Preferably, the hydrothermal reaction is carried out under conditions of a temperature of 140-180°C, specifically 140°C, 150°C, 160°C, 170°C, 180°C, or any value between these values; and a time of 6-10h, specifically 6h, 7h, 8h, 9h, 10h, or any value between these values. Under the above conditions, the carbon nanotubes and the polymer dispersant have a better reaction effect, and thus the dispersion effect of the prepared multi-walled carbon nanotubes in the solvent can be further improved. To further improve the dispersion effect of the prepared multi-walled carbon nanotubes in the solvent, the hydrothermal reaction is preferably carried out under conditions of a temperature of 150-170°C and a time of 7-9h.

[0033] Preferably, in the hydrothermal reaction system, the concentration of the carbon nanotubes is 0.5-1g / mL, specifically 0.5g / mL, 0.6g / mL, 0.7g / mL, 0.8g / mL, 0.9g / mL, 1g / mL, or any value between these values. It has been found that, when the concentration of the carbon nanotubes is controlled within the above range, the carbon nanotubes and the polymer dispersant have a better reaction effect, and thus the prepared multi-walled carbon nanotubes have a better dispersion effect in the solvent.

[0034] Preferably, the method further comprises separating and drying the product obtained from the contact reaction. The separation and drying can be carried out in any feasible manner. As a specific embodiment of the present application, the separation is carried out by evaporation, and the drying is carried out by baking.

[0035] In a second aspect, the present application provides a multi-walled carbon nanotube, which comprises carbon nanotubes and a polymer dispersant loaded on the carbon nanotubes, and the viscosity reduction rate of an N-methylpyrrolidone dispersion of the multi-walled carbon nanotube compared to that of an N-methylpyrrolidone dispersion containing the same amount of carbon nanotubes and the same amount of polymer dispersant is 34-60%.

[0036] The inventors have found that, when a multi-walled carbon nanotube is prepared by loading a polymer dispersant on carbon nanotubes, the viscosity reduction rate of a dispersion obtained by mixing the multi-walled carbon nanotube with N-methylpyrrolidone compared to that of an N-methylpyrrolidone dispersion containing the same amount of carbon nanotubes and the same amount of polymer dispersant is 34-60%, and thus the multi-walled carbon nanotube has a better dispersion effect in the solvent.

[0037] Preferably, the polymer dispersant is at least one of polyvinylpyrrolidone modified, vinylpyrrolidone / styrene copolymer, vinylpyrrolidone / acrylic acid copolymer and vinylpyrrolidone / imidazole copolymer. The use of the above polymer dispersant can effectively reduce the viscosity of the N-methylpyrrolidone dispersion of the multi-walled carbon nanotube, so that it has a better dispersion effect in the solution.

[0038] Preferably, the polymer dispersant is vinylpyrrolidone / acrylic acid copolymer and / or vinylpyrrolidone / imidazole copolymer. The inventors have found that the use of the above polymer dispersant can produce multi-walled carbon nanotubes with better dispersion effect.

[0039] Preferably, in the copolymer, the content of vinylpyrrolidone structural unit is 10-30wt%, and can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, or any value between these values. The inventors have found that controlling the content of vinylpyrrolidone structural unit in the polymer within the above range can further improve the dispersion effect of the prepared multi-walled carbon nanotube in the solvent.

[0040] Preferably, in the multi-walled carbon nanotube, the loading amount of the polymer dispersant is 12-50wt%. Further preferably, in the multi-walled carbon nanotube, the loading amount of the polymer dispersant is 25-35wt%, and can be 25wt%, 27wt%, 29wt%, 31wt%, 33wt%, 35wt%, or any value between these values. The inventors have found that controlling the loading amount within the above range can further reduce the viscosity of the N-methylpyrrolidone dispersion of the multi-walled carbon nanotube, so that it has a better dispersion effect in the solution.

[0041] The third aspect of the present application provides a multi-walled carbon nanotube prepared by the preparation method of the first aspect or the multi-walled carbon nanotube prepared by the second method, and the application of the multi-walled carbon nanotube in a battery, a functional polymer material or a coating.

[0042] The high dispersion effect of the multi-walled carbon nanotube can make it have a better application in a battery, a functional polymer material or a coating. Preferably, the battery is a lithium ion battery.

[0043] According to a particularly preferred embodiment of the present application, a preparation method of a multi-walled carbon nanotube is provided, and the method comprises: reacting carbon nanotubes, a dispersant and water at a temperature of 140-180℃ for 6-10h, evaporating water after cooling, and then drying to obtain the multi-walled carbon nanotube.

[0044] The concentration of the carbon nanotubes in the hydrothermal reaction system is 0.5-1 g / mL, the mass ratio of the carbon nanotubes to the dispersant is 1:0.25-0.5, and the dispersant is selected from polyvinylpyrrolidone and vinylpyrrolidone / styrene copolymer, vinylpyrrolidone / acrylic acid copolymer, and vinylpyrrolidone / imidazole copolymer, and the weight average molecular weight of the polymeric dispersant is 45,000-58,000.

[0045] The above method can effectively improve the dispersing effect of the carbon nanotubes by sufficiently and firmly adsorbing the dispersant on the surface of the carbon nanotubes. Moreover, the obtained multi-walled carbon nanotubes are relatively stable and have good dispersing effect after being stored in a dispersion liquid state for a long time. The method is simple in process and high in repeatability, and the multi-walled carbon nanotubes prepared by the method have good dispersing effect.

[0046] The application will be described in detail below through examples. In the following examples, the carbon nanotubes were purchased from Guanyu New Material Technology Co., Ltd., and the model numbers were TC115 and AC135; polyvinylpyrrolidone (PVP) was purchased from Guanyu New Material Technology Co., Ltd., and the weight average molecular weight was 50,000; vinylpyrrolidone / styrene copolymer, vinylpyrrolidone / acrylic acid copolymer, and vinylpyrrolidone / imidazole copolymer were all purchased from YUANG Technology Co., Ltd., wherein the weight average molecular weight of the vinylpyrrolidone / styrene copolymer was 46,000, and the content of the vinylpyrrolidone structural unit was 30%; the weight average molecular weight of the vinylpyrrolidone / acrylic acid copolymer was 53,000, and the content of the vinylpyrrolidone structural unit was 15%; and the weight average molecular weight of the vinylpyrrolidone / imidazole copolymer was 58,000, and the content of the vinylpyrrolidone structural unit was 30%.

[0047] Example 1

[0048] 1.5 g of PVP dispersant was dissolved in 60 mL of water, 3 g of carbon nanotubes (TC115) was added, and after being uniformly stirred, the mixture was transferred into a hydrothermal kettle, the temperature was set to 180°C, and the hydrothermal time was 6 h. After natural cooling, the water was evaporated, and the mixture was placed in a vacuum oven for drying for more than 12 h to obtain multi-walled carbon nanotubes.

[0049] The above multi-walled carbon nanotubes were added to 55.5 g of NMP solvent to obtain dispersion liquid-1.

[0050] Comparative Example 1

[0051] 1.5 g of PVP and 3 g of carbon nanotubes (TC115) were added to 55.5 g of NMP solvent to obtain comparative dispersion liquid-1.

[0052] Example 2

[0053] 1.5 g PVP dispersant was dissolved in 60 mL of water, 6 g carbon nanotubes (TC115) were added, and after stirring uniformly, it was moved into an autoclave, the temperature was set to 160°C, and the hydrothermal time was 8 h. After natural cooling, the water was evaporated, and it was placed in a vacuum oven for drying for more than 12 h to obtain multi-walled carbon nanotubes.

[0054] The above multi-walled carbon nanotubes were added to 84 g of NMP solvent to obtain dispersion liquid-3.

[0055] Comparative Example 2

[0056] 1.5 g PVP and 6 g carbon nanotubes (TC115) were added to 112.5 g of NMP solvent to obtain comparative dispersion liquid-2.

[0057] Example 3

[0058] 1.5 g PVP dispersant was dissolved in 60 mL of water, 4.5 g carbon nanotubes (TC115) were added, and after stirring uniformly, it was moved into an autoclave, the temperature was set to 140°C, and the hydrothermal time was 10 h. After natural cooling, the water was evaporated, and it was placed in a vacuum oven for drying for more than 12 h to obtain multi-walled carbon nanotubes.

[0059] The above multi-walled carbon nanotubes were added to 84 g of NMP solvent to obtain dispersion liquid-3.

[0060] Comparative Example 3

[0061] 1.5 g PVP and 4.5 g carbon nanotubes were added to 84 g of NMP solvent to obtain comparative dispersion liquid-3.

[0062] Example 4

[0063] 0.75 g PVP dispersant was dissolved in 60 mL of water, 3 g carbon nanotubes (TC115) were added, and after stirring uniformly, it was moved into an autoclave, the temperature was set to 160°C, and the hydrothermal time was 8 h. After natural cooling, the water was evaporated, and it was placed in a vacuum oven for drying for more than 12 h to obtain multi-walled carbon nanotubes.

[0064] The above multi-walled carbon nanotubes were added to 56.3 g of NMP solvent to obtain dispersion liquid-4.

[0065] Comparative Example 4

[0066] 0.75 g PVP and 3 g carbon nanotubes (TC115) were added to 56.3 g of NMP solvent to obtain comparative dispersion liquid-4.

[0067] Example 5

[0068] The multi-walled carbon nanotubes were prepared according to the method of Example 4, except that the type of carbon nanotubes used was AC135, and the PVP was replaced with a vinylpyrrolidone / styrene copolymer.

[0069] The above multi-walled carbon nanotubes were added to 496.25 g of water to obtain dispersion-5.

[0070] Comparative Example 5

[0071] The above multi-walled carbon nanotubes were added to 496.25 g of water to obtain dispersion-5.

[0072] Example 6

[0073] The multi-walled carbon nanotubes were prepared according to the method of Example 4, except that the type of carbon nanotubes used was AC135, and the PVP was replaced with a vinylpyrrolidone / styrene copolymer.

[0074] The above multi-walled carbon nanotubes were added to 746.25 g of water to obtain dispersion-6.

[0075] Comparative Example 6

[0076] The above multi-walled carbon nanotubes were added to 746.25 g of water to obtain dispersion-6.

[0077] Example 7

[0078] The multi-walled carbon nanotubes were prepared according to the method of Example 4, except that the type of carbon nanotubes used was AC135, and the 0.75 g of PVP was replaced with 0.75 g of a vinylpyrrolidone / imidazole copolymer.

[0079] The above multi-walled carbon nanotubes were added to 746.25 g of water to obtain dispersion-7.

[0080] Comparative Example 7

[0081] The above multi-walled carbon nanotubes were added to 746.25 g of water to obtain dispersion-7.

[0082] Example 8

[0083] The multi-walled carbon nanotubes (TC115) were prepared according to the method of Example 1, except that the amount of PVP added was 3 g.

[0084] The above multi-walled carbon nanotubes were added to 54 g of NMP solvent to obtain dispersion-8.

[0085] Comparative Example 8

[0086] 3 g of PVP and 3 g of carbon nanotubes (TC115) were added to 54 g of NMP solvent to obtain comparative dispersion-8.

[0087] Example 9

[0088] The multi-walled carbon nanotubes (TC115) were prepared according to the method of Example 2, except that the amount of PVP added was 1 g.

[0089] The above multi-walled carbon nanotubes were added to 113 g of NMP solvent to obtain dispersion-9.

[0090] Comparative Example 9

[0091] 1 g of PVP and 6 g of carbon nanotubes (TC115) were added to 113 g of NMP solvent to obtain comparative dispersion-9.

[0092] Test Example 1

[0093] The multi-walled carbon nanotubes prepared in Example 4 and the raw carbon nanotubes were characterized by scanning electron microscopy (JSM-7500F field emission scanning electron microscope). The picture of the raw carbon nanotubes is shown in Figure 1 , and the multi-walled carbon nanotubes prepared in Example 4 are shown in Figure 2 From the figures, it can be seen that the degree of agglomeration and entanglement of the multi-walled carbon nanotubes prepared in Example 4 is reduced.

[0094] Test Example 2

[0095] The carbon nanotube dispersion prepared in Example 1 was subjected to viscosity testing, and a Shanghai Niran NDJ-5S digital viscometer was used to test at room temperature.

[0096] The viscosity data of Example 1 and Comparative Example 1 are shown in Table 1.

[0097] The viscosity data of all examples and comparative examples are shown in Table 2.

[0098] Test Example 3

[0099] The loading amount of the polymer dispersant was calculated according to the mass of the product after the reaction and the amount of carbon nanotubes added, and is recorded in Table 2.

[0100] Table 1

[0101] Viscosity of Example 1 / mPa s Viscosity of Comparative Example 1 / mPa s Reduction rate / % Day 1 45 100 55 Day 3 42 102 59 Day 5 57 113 50 Day 7 45 111 60 Day 15 69 127 46 Day 30 80 213 62

[0102] Table 2

[0103]

[0104]

[0105] Test Example 4

[0106] The hydrothermally treated carbon nanotubes in Example 4 and the untreated carbon nanotubes were respectively used as conductive agents to test the battery performance. The active material was lithium iron phosphate, the binder was PVDF, and the lithium iron phosphate:CNT:PVP:PVDF was 90:4:1:5. The rate test was performed by using a LAND battery tester, and the test results are shown in Table 3. Figure 3

[0107] As shown in Table 1, Table 2 and Figure 3 It can be seen that the viscosity of the dispersion prepared in the examples is significantly reduced compared with the comparative examples, and the battery rate performance of the dispersion prepared in the examples as a conductive agent is better than that of the dispersion of the comparative examples, which indicates that the multi-walled carbon nanotubes have better dispersion effect and conductivity in the solvent.

[0108] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.​

Claims

1. A method for producing multi-walled carbon nanotubes, characterized by, The method comprises: contacting carbon nanotubes and a polymer dispersant under hydrothermal conditions, the polymer dispersant being at least one selected from polyvinylpyrrolidone, a vinylpyrrolidone / styrene copolymer, a vinylpyrrolidone / acrylic acid copolymer and a vinylpyrrolidone / imidazole copolymer.

2. The production method according to claim 1, characterized by, The mass ratio of the carbon nanotubes to the polymer dispersant is 1:0.25-0.

5.

3. The production method according to claim 1 or 2, characterized by, The weight average molecular weight of the polymer dispersant is 45000-58000.

4. The production method according to claim 1 or 2, characterized by, The polymer dispersant is a vinylpyrrolidone / acrylic acid copolymer and / or a vinylpyrrolidone / imidazole copolymer. Preferably, the content of vinylpyrrolidone structural units in the copolymer is 10-30wt%.

5. The production method according to claim 1 or 2, characterized by, The hydrothermal reaction is performed under conditions of at least a temperature of 140-180℃ and a time of 6-10h.

6. The production method according to claim 1 or 2, characterized by, In the hydrothermal reaction system, the concentration of the carbon nanotubes is 0.5-1g / mL.

7. A multi-walled carbon nanotube, characterized by, The multi-walled carbon nanotubes comprise carbon nanotubes and a polymer dispersant loaded on the carbon nanotubes, and the viscosity of an N-methylpyrrolidone dispersion of the multi-walled carbon nanotubes is reduced by 34-60% compared to the viscosity of an N-methylpyrrolidone dispersion containing the same amount of carbon nanotubes and the same amount of polymer dispersant.

8. The multi-walled carbon nanotube of claim 7, wherein, The polymer dispersant is at least one selected from polyvinylpyrrolidone, a vinylpyrrolidone / styrene copolymer, a vinylpyrrolidone / acrylic acid copolymer and a vinylpyrrolidone / imidazole copolymer, preferably a vinylpyrrolidone / acrylic acid copolymer and / or a vinylpyrrolidone / imidazole copolymer. Preferably, the content of vinylpyrrolidone structural units in the copolymer is 10-30wt%.

9. The multi-walled carbon nanotube of claim 8, wherein, In the multi-walled carbon nanotubes, the loading amount of the polymer dispersant is 25-35wt%.

10. Use of the multi-walled carbon nanotubes prepared by the method of any one of claims 1 to 6 or the multi-walled carbon nanotubes of any one of claims 7 to 9 in a battery, a functional polymer material or a coating.

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