Carbon nanotube dispersion and method for producing same

Abstract

The present invention relates to a carbon nanotube dispersion liquid using an auxiliary dispersant containing polyethylene glycol, polystyrene, and a cellulose-based component, and a method for producing the same, and the carbon nanotube dispersion liquid of the present invention has excellent viscosity stability when stored at room temperature and at high temperatures.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0007983, filed January 19, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a carbon nanotube dispersion liquid that exhibits little change in viscosity over time when stored at room temperature or at high temperatures, has excellent storage stability, and is excellent in conductivity, and can therefore be suitably used as a conductive material, and a method for producing the same. [Background technology]

[0003] Carbon nanotubes are giant molecules consisting of hexagonal honeycomb-shaped graphite sheets, in which one carbon atom is bonded to three other carbon atoms, rolled up into a nanometer-sized diameter. Carbon nanotubes are lightweight due to their hollow structure, and have electrical conductivity as good as copper, thermal conductivity as good as diamond, and tensile strength comparable to that of steel. Depending on their rolled shape, they can be classified as single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and rope carbon nanotubes.

[0004] In recent years, carbon nanotubes have been widely used as conductive materials in secondary batteries due to their excellent electrical conductivity. However, carbon-based conductive materials, including carbon nanotubes, have the problem of being unevenly dispersed in electrode slurry compositions and prone to agglomeration. If the conductive material aggregates in the electrode slurry composition, the conductive material cannot be uniformly distributed in the active material layer during the electrode formation process, which can lead to reduced performance of the secondary battery. Therefore, various techniques for uniformly dispersing the conductive material in the electrode slurry composition have been studied.

[0005] The most common approach is to improve dispersibility by incorporating a dispersant along with the conductive material. Specifically, a method for improving dispersibility in a dispersion state by incorporating a polymer component such as polyvinylpyrrolidone (PVP) or hydrogenated nitrile butadiene rubber (HNBR) as a dispersant is known. However, when such components are used as dispersants, the viscosity of the dispersion itself increases rapidly as the content of the conductive material increases, resulting in a further problem of poor processability of the dispersion itself. Therefore, when such components are used alone as dispersants, the content of the conductive material cannot be significantly increased, resulting in a disadvantage that the range in which electrical conductivity can be improved is limited. Furthermore, when such components are used alone as dispersants, even if the initial viscosity of the dispersion is low, the viscosity of the dispersion changes significantly over time, resulting in a problem of deterioration in the quality of the dispersion during distribution.

[0006] Therefore, there is a need to develop a novel carbon nanotube dispersion that can maintain the content of conductive material at a specific level or above while also maintaining excellent viscosity and viscosity stability. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Registration No. 10-2125963 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to provide a carbon nanotube dispersion that has excellent initial viscosity, a low rate of change in viscosity over time, and excellent storage stability while maintaining a carbon nanotube content in the dispersion at a certain level or above. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a carbon nanotube dispersion and a method for producing the same.

[0010] Specifically, (1) the present invention provides a carbon nanotube dispersion comprising carbon nanotubes, a solvent, a primary dispersant, and an auxiliary dispersant, wherein the auxiliary dispersant comprises polyethylene glycol, polystyrene, and a cellulose-based component.

[0011] (2) The present invention provides the carbon nanotube dispersion liquid according to (1) above, wherein the cellulose-based component is one or more selected from the group consisting of methyl cellulose, (hydroxypropyl)methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose.

[0012] (3) The present invention provides the carbon nanotube dispersion liquid according to (1) or (2) above, wherein the polyethylene glycol is contained in an amount of 10 to 30 parts by weight per 100 parts by weight of the total amount of auxiliary dispersants.

[0013] (4) The present invention provides a carbon nanotube dispersion liquid according to any one of (1) to (3), wherein the polystyrene is contained in an amount of 10 to 30 parts by weight per 100 parts by weight of the total of the auxiliary dispersants.

[0014] (5) The present invention provides a carbon nanotube dispersion liquid according to any one of (1) to (4), wherein the cellulose-based component is contained in an amount of 20 to 60 parts by weight per 100 parts by weight of the total of the auxiliary dispersant.

[0015] (6) The present invention provides a carbon nanotube dispersion liquid according to any one of (1) to (5), wherein the content of the auxiliary dispersant in the dispersion liquid is 5% by weight to 100% by weight relative to the content of the primary dispersant in the dispersion liquid.

[0016] (7) The present invention provides the carbon nanotube dispersion liquid according to any one of (1) to (6), wherein the primary dispersant is one or more selected from the group consisting of nitrile butadiene rubber (HNBR), styrene butylene rubber, carboxymethyl cellulose, polyvinylpyrrolidone, and polyvinyl butyral.

[0017] (8) The present invention provides a carbon nanotube dispersion liquid according to any one of (1) to (7), wherein the content of the primary dispersant in the dispersion liquid is 0.1% by weight to 10.0% by weight based on the weight of the total dispersion liquid.

[0018] (9) The present invention provides a carbon nanotube dispersion liquid according to any one of (1) to (8), wherein the solvent is one or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), acetone, and methyl butyl ketone (MBK).

[0019] (10) The present invention provides the carbon nanotube dispersion liquid according to any one of (1) to (9) above, wherein the carbon nanotube content in the dispersion liquid is 3% by weight to 10% by weight.

[0020] (11) The present invention provides the carbon nanotube dispersion liquid according to any one of (1) to (10) above, wherein the viscosity change rate over one week is 3% or less.

[0021] (12) The present invention provides a method for producing a carbon nanotube dispersion liquid described in any one of (1) to (11), comprising a step (S1) of mixing carbon nanotubes, a solvent, a primary dispersant, and an auxiliary dispersant, and a step (S2) of dispersing the mixture.

[0022] (13) The present invention provides the method for producing a carbon nanotube dispersion according to (12) above, wherein the step S1 is carried out in a homomixer for 0.5 to 2 hours.

[0023] (14) The present invention provides a method for producing a carbon nanotube dispersion liquid according to (12) or (13), wherein the step S2 is carried out by a dispersion method selected from the group consisting of a bead mill, a ball mill, and high-pressure homogenization. [Effects of the Invention]

[0024] The carbon nanotube dispersion of the present invention has a high carbon nanotube content in the dispersion above a certain level, thereby realizing excellent electrical conductivity, and also has an appropriate initial viscosity of the dispersion itself, resulting in excellent processability.

[0025] Furthermore, the carbon nanotube dispersion exhibits a low rate of change in viscosity over time when stored at high and low temperatures, and has excellent storage stability. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will now be described in more detail.

[0027] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0028] Carbon nanotube dispersion The present invention provides a carbon nanotube dispersion comprising carbon nanotubes, a solvent, a primary dispersant, and a secondary dispersant, wherein the secondary dispersant comprises polyethylene glycol, polystyrene, and a cellulose-based component.

[0029] As described above, when a polymeric dispersant, such as hydrogenated nitrile butadiene rubber (HNBR), which is a conventional dispersant for carbon nanotube dispersions, is used as the sole dispersant, it has the effect of reducing the initial viscosity, but there is a problem that the viscosity increases significantly over time after the dispersion is produced. Therefore, the inventors of the present invention attempted to reduce the rate of change in viscosity over time by using a co-dispersant together with the polymeric dispersant.

[0030] In particular, in the present invention, it has been confirmed that by applying an auxiliary dispersant containing at least three components, namely polyethylene glycol, polystyrene, and a cellulose-based component, together with a primary dispersant, the rate of change in viscosity over time can be reduced, the increase in initial viscosity can be suppressed, and the carbon nanotube content of the dispersion can be maintained at a certain level or above.

[0031] Dispersant Auxiliary The co-dispersing agent used in the present invention is characterized by including polyethylene glycol, polystyrene, and a cellulosic component.

[0032] 1) Polyethylene glycol Polyethylene glycol is a polymer formed by dehydration condensation of multiple ethylene glycol molecules, and is hydrophilic, so when applied to the carbon nanotube dispersion of the present invention, it can play a role in maintaining a uniform phase with the solvent.

[0033] The polyethylene glycol used in the present invention may have a weight-average molecular weight (Mw) of 100 g / mol to 5,000 g / mol, preferably 300 g / mol to 2,000 g / mol. When the weight-average molecular weight of the polyethylene glycol is within the above range, there is a technical advantage in that the phase separation phenomenon between the carbon nanotubes and the solvent can be suppressed and the viscosity of the dispersion can be reduced.

[0034] The polyethylene glycol may be contained in an amount of 10 to 30 parts by weight, preferably 15 to 25 parts by weight, based on a total of 100 parts by weight of the auxiliary dispersant. If the content of polyethylene glycol in the auxiliary dispersant is less than the above range, the effect achieved by polyethylene glycol may be insufficient, and if the content of polyethylene glycol is more than the above range, the content of other components may be relatively reduced, and the effect of improving the viscosity stability of the dispersion may not be fully achieved.

[0035] 2) Polystyrene Polystyrene is a polymer formed by polymerizing a plurality of styrene monomolecules, and when applied to the carbon nanotube dispersion of the present invention, it can play a role in reducing the viscosity of the dispersion.

[0036] The polystyrene used in the present invention may have a weight average molecular weight (Mw) of 800 g / mol to 50,000 g / mol, preferably 1,000 g / mol to 10,000 g / mol. When the weight average molecular weight of the polystyrene is within the above range, the effect of reducing the viscosity of the polystyrene dispersion can be particularly enhanced.

[0037] The polystyrene may be included in an amount of 10 to 30 parts by weight, preferably 15 to 25 parts by weight, based on a total of 100 parts by weight of the auxiliary dispersant. If the content of polystyrene in the auxiliary dispersant is less than the above range, the effect achieved by polystyrene may be insufficient, and if the content of polystyrene is more than the above range, the content of other components may be relatively reduced, and the effect of improving the viscosity stability of the dispersion may not be fully achieved.

[0038] 3) Cellulose-based components In the present invention, in addition to the above two components, a cellulose-based component is also used as an auxiliary dispersant. The cellulose-based component may be one or more selected from the group consisting of methyl cellulose, (hydroxypropyl) methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose. The cellulose-based component significantly contributes to suppressing the increase in viscosity of the dispersion over time, and can improve viscosity stability without losing the initial viscosity.

[0039] The cellulose-based component may be included in an amount of 40 to 80 parts by weight, preferably 50 to 70 parts by weight, based on a total of 100 parts by weight of the auxiliary dispersant. If the content of the cellulose-based component in the auxiliary dispersant is less than the above range, the effect achieved by the cellulose-based component may be insufficient, and if the content of the cellulose-based component is more than the above range, the contents of other components may be relatively reduced, resulting in an excessively high initial viscosity.

[0040] The content of the auxiliary dispersant containing the above three components in the dispersion may be 10% by weight to 100% by weight, preferably 20% by weight to 50% by weight, relative to the content of the primary dispersant in the dispersion. If the content of the auxiliary dispersant is too low, the effect of the auxiliary dispersant in improving viscosity stability may be minimal, while if the content of the auxiliary dispersant is too high, the presence of the auxiliary dispersant may instead cause a problem of excessively high initial viscosity.

[0041] Primary dispersant The above-mentioned auxiliary dispersant is intended to solve the problem of increased viscosity of the primary dispersant, which will be explained below. In the present invention, the following primary dispersant is used together with the above-mentioned auxiliary dispersant in order to achieve sufficient dispersibility of the dispersion.

[0042] Specifically, the primary dispersant may be one or more selected from the group consisting of hydrogenated nitrile butadiene rubber (HNBR), styrene butylene rubber, carboxymethyl cellulose, polyvinylpyrrolidone, and polyvinyl butyral.

[0043] In the carbon nanotube dispersion of the present invention, the content of the primary dispersant in the dispersion may be 5% by weight to 100% by weight, preferably 10% by weight to 50% by weight, based on the carbon nanotube content. The content of the primary dispersant may be 0.1% by weight to 10.0% by weight, preferably 0.5% by weight to 5% by weight, and particularly preferably 0.5% by weight to 3.0% by weight, based on the total weight of the dispersion. If the content of the primary dispersant is too low, the carbon nanotubes may not be sufficiently dispersed. If the content of the primary dispersant is too high, the initial viscosity increases excessively, making it impossible to increase the carbon nanotube content in the dispersion beyond a certain level.

[0044] solvent The solvent is a medium for dispersing carbon nanotubes and may be an aqueous or oil-based solvent, more specifically, one or more selected from the group consisting of water, methanol, ethanol, propanol, acetone, dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP).

[0045] carbon nanotubes The carbon nanotubes function as a conductive material in the dispersion of the present invention, and may be single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0046] The carbon nanotubes used in the present invention are not particularly limited, but the bulk density of the carbon nanotubes is preferably 20 kg / m 3 ~40kg / m 3 and the specific surface area is 100m 2 / g~400m 2 / g is preferred. When carbon nanotubes satisfy the above conditions, they are particularly excellent in terms of electrical conductivity. Meanwhile, the bulk density can be calculated by filling a container having a specific volume with carbon nanotubes and then dividing the measured mass by the volume of the container. The specific surface area is measured by the BET method, and more specifically, can be calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77K) using a specific surface area analyzer (BEL Japan, BELSORP-mini II).

[0047] In the carbon nanotube dispersion of the present invention, the carbon nanotube content may be 3% by weight to 10% by weight, and preferably 3% by weight to 6% by weight. The present invention is characterized in that by using both a primary dispersant and an auxiliary dispersant, the carbon nanotube content in the dispersant is at least 3% by weight or more. On the other hand, if the carbon nanotube content is too low, sufficient conductivity cannot be achieved when used in applications such as conductive materials, and if the carbon nanotube content is too high, the viscosity of the dispersion may become excessively high, resulting in poor processability.

[0048] In the carbon nanotube dispersion of the present invention, the viscosity change rate of the dispersion over one week may be 3% or less, preferably 2% or less. The viscosity change rate over one week is calculated by calculating the increase in viscosity over one week when the dispersion is stored at 25°C, and can be calculated using the following formula 1.

[0049] [Formula 1] Viscosity change rate (%) = (viscosity after storage for 1 week at 25°C - viscosity at the time of manufacturing the dispersion) / (viscosity at the time of manufacturing the dispersion) * 100%

[0050] Meanwhile, the viscosity can be measured using a viscometer (Toki Sangyo Co., Ltd., TV-25) by starting measurement at 1 rpm with rotor No. 1 and recording the value after 10 minutes.

[0051] The carbon nanotube dispersion of the present invention can reduce the viscosity change rate as described above by using an auxiliary dispersant, thereby achieving excellent viscosity stability. On the other hand, if an auxiliary dispersant is not used, the viscosity change rate may be as high as 10% or more.

[0052] Method for producing carbon nanotube dispersion The present invention provides a method for producing the above-mentioned carbon nanotube dispersion liquid, specifically, a method for producing a carbon nanotube dispersion liquid, which includes a step (S1) of mixing carbon nanotubes, a solvent, a primary dispersant, and an auxiliary dispersant, and a step (S2) of dispersing the mixture.

[0053] In the method for producing a carbon nanotube dispersion of the present invention, the carbon nanotubes, the solvent, the primary dispersant, and the auxiliary dispersant are as described above.

[0054] Meanwhile, step S1 of mixing all the above components may be carried out in a homomixer for 0.5 to 2 hours, preferably 0.5 to 1.5 hours. When a homomixer is used in the mixing process, the components can be mixed more uniformly, and particularly when mixed for the above time, a mixture can be formed without deterioration in the quality of the carbon nanotubes.

[0055] In step S2, the resulting mixture may be dispersed to produce a final dispersion. This dispersion step may result in uniform physical properties of the carbon nanotubes in the dispersion. The dispersion method may be selected from the group consisting of a bead mill, a ball mill, and high-pressure homogenization, and preferably a bead mill. When using the above dispersion method, more uniform dispersion is possible, and the viscosity of the resulting carbon nanotube dispersion can be maintained at a lower level.

[0056] The carbon nanotube dispersion produced by the production method of the present invention may have an initial viscosity of 15,000 cps or less, preferably 14,000 cps or less.

[0057] Hereinafter, the present invention will be described in more detail with reference to examples and experimental examples in order to specifically explain the present invention, but the present invention is not limited to these examples and experimental examples. The examples of the present invention can be modified into various different forms, and the scope of the present invention should not be interpreted as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0058] material Bulk density 36kg / m 3 The specific surface area is 186m 2 Carbon nanotubes with a mass of 1000 s / g were prepared. Hydrogenated nitrile butadiene rubber (HNBR) was used as the primary dispersant, and N-methyl-2-pyrrolidone (NMP) was used as the solvent.

[0059] The auxiliary dispersants used in the examples were auxiliary dispersant A, which was a mixture of polyethylene glycol (weight average molecular weight: 750 g / mol), polystyrene (weight average molecular weight: 2,500 g / mol), and methylcellulose in a weight ratio of 1:1:3, and auxiliary dispersant B, which was a mixture of polyethylene glycol (weight average molecular weight: 750 g / mol), polystyrene (weight average molecular weight: 2,500 g / mol), and (hydroxypropyl)methylcellulose in a weight ratio of 1:1:3.

[0060] The auxiliary dispersants used in the comparative examples were auxiliary dispersant C, which did not contain any cellulose-based components and was a mixture of polyethylene glycol (weight average molecular weight: 750 g / mol), polystyrene (weight average molecular weight: 2,500 g / mol), and ethylene glycol in a weight ratio of 1:1:1; auxiliary dispersant D, which was a mixture of polystyrene (weight average molecular weight: 2,500 g / mol) and ethylene glycol in a weight ratio of 1:1; auxiliary dispersant E, which was a mixture of the polyethylene glycol and methylcellulose in a weight ratio of 1:3; and auxiliary dispersant F, which was a mixture of the polystyrene and methylcellulose in a weight ratio of 1:3.

[0061] On the other hand, the auxiliary dispersants were prepared by dissolving the components to be used in each auxiliary dispersant in NMP solvent in advance, and then mixing them in a paste mixer at 1300 rpm for 10 minutes.

[0062] Examples and Comparative Examples The carbon nanotubes, solvent, primary dispersant, and auxiliary dispersant were mixed in a homomixer for 1 hour. The mixture was then milled at 3000 rpm for 30 minutes using a bead mill to produce a dispersion. The carbon nanotube concentrations and the types and amounts (based on the total weight of the dispersion) of the primary dispersant and auxiliary dispersant used in each example and comparative example are summarized in Table 1 below.

[0063] [Table 1]

[0064] Experimental example 1: Confirmation of viscosity stability of dispersion liquid when stored at room temperature The initial viscosity of the carbon nanotube dispersions prepared in the examples and comparative examples was measured, and the viscosity was measured again after storing them at 25° C. The viscosity change rate was calculated from the measured viscosity and summarized in Table 2 below.

[0065] [Table 2]

[0066] As can be seen from Table 2, comparing Examples 1 and 3, which use the same primary dispersant and carbon nanotube content, with Comparative Examples 1, 3, and 4, it can be seen that Examples 1 and 3, which also use the auxiliary dispersant component of the present invention, exhibit a lower viscosity change rate. In particular, Comparative Example 1, which used auxiliary dispersant C, which does not contain a cellulose-based component, exhibited a slightly lower initial viscosity than the Examples of the present invention, but in terms of viscosity stability, the viscosity change rate was over 16%, indicating a significant decrease in viscosity stability during storage at room temperature. Furthermore, Comparative Example 3, which used auxiliary dispersant D, which does not contain either a cellulose-based component or polyethylene glycol as the auxiliary dispersant, exhibited a lower initial viscosity and a lower viscosity change rate than the other Comparative Examples. When the appearance of the dispersion was observed after one week of storage, while the other Examples and Comparative Examples all showed good results, Comparative Example 3 exhibited phase separation with the solvent. This means that the structure in which the carbon nanotubes were dispersed in the dispersion collapsed, meaning that the dispersion of Comparative Example 3 lost its dispersion function even after short-term storage at room temperature after production. Comparative Example 4, which did not use an auxiliary dispersant, also showed a high viscosity change rate and poor viscosity stability. Furthermore, Comparative Examples 5 and 6, which used only a portion of the auxiliary dispersant components of the present invention, either exhibited excessively high initial viscosity (Comparative Example 5) or, despite a low initial viscosity and low viscosity change rate, exhibited problems such as phase separation from the solvent (Comparative Example 6).

[0067] Similar findings were also confirmed from the results of comparing Example 2, which used a high molecular weight primary dispersant, with Comparative Example 2. Comparative Example 2 showed a significantly higher viscosity change rate than Example 2, confirming that viscosity stability can vary depending on the components of the auxiliary dispersant used, regardless of the type of primary dispersant and the carbon nanotube content.

[0068] Experimental Example 2: Confirmation of viscosity stability of dispersion liquid during high-temperature storage The viscosity stability during high-temperature storage of the dispersions of Example 1 and Comparative Example 1 was further confirmed. Considering that the viscosity increases more rapidly at high temperatures when stored at 60°C, the viscosity was measured after storage for 3 days instead of 7 days. The measured initial viscosity and viscosity after storage for 3 days, as well as the viscosity change rate, were calculated and are shown in Table 3 below.

[0069] [Table 3]

[0070] As can be seen from the results in Table 3, the viscosity of both Example 1 and Comparative Example 1 increased rapidly during high-temperature storage, but the viscosity change rate of Comparative Example 1 was higher.

[0071] This confirms that the auxiliary dispersant of the present invention has the effect of suppressing viscosity changes not only during storage at room temperature but also during storage at high temperatures.

Claims

1. Carbon nanotubes and a solvent; A primary dispersant; a co-dispersant, The carbon nanotube dispersion, wherein the auxiliary dispersant comprises polyethylene glycol, polystyrene, and a cellulose-based component.

2. 2. The carbon nanotube dispersion according to claim 1, wherein the cellulose-based component is one or more selected from the group consisting of methyl cellulose, (hydroxypropyl) methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose.

3. 2. The carbon nanotube dispersion according to claim 1, wherein the polyethylene glycol is contained in an amount of 10 to 30 parts by weight based on a total of 100 parts by weight of the auxiliary dispersant.

4. 2. The carbon nanotube dispersion according to claim 1, wherein the polystyrene is contained in an amount of 10 to 30 parts by weight based on a total of 100 parts by weight of the auxiliary dispersant.

5. 2. The carbon nanotube dispersion according to claim 1, wherein the cellulose-based component is contained in an amount of 40 to 80 parts by weight per 100 parts by weight of the auxiliary dispersant.

6. 2. The carbon nanotube dispersion according to claim 1, wherein the content of the auxiliary dispersant in the dispersion is 5% by weight to 100% by weight based on the content of the primary dispersant in the dispersion.

7. 2. The carbon nanotube dispersion according to claim 1, wherein the primary dispersant is one or more selected from the group consisting of nitrile butadiene rubber (HNBR), styrene butylene rubber, carboxymethyl cellulose, polyvinylpyrrolidone, and polyvinyl butyral.

8. 2. The carbon nanotube dispersion according to claim 1, wherein the content of the primary dispersant in the dispersion is 0.1% by weight to 10.0% by weight based on the weight of the entire dispersion.

9. 2. The carbon nanotube dispersion according to claim 1, wherein the solvent is one or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), acetone, and methyl butyl ketone (MBK).

10. 2. The carbon nanotube dispersion according to claim 1, wherein the content of the carbon nanotubes in the dispersion is 3% by weight to 10% by weight.

11. The carbon nanotube dispersion according to any one of claims 1 to 10, wherein the viscosity change rate over one week is 3% or less.

12. A step (S1) of mixing carbon nanotubes, a solvent, a primary dispersant, and an auxiliary dispersant; The method for producing a carbon nanotube dispersion liquid according to claim 1 , further comprising: a step (S2) of dispersing the mixture.

13. The method for producing a carbon nanotube dispersion liquid according to claim 12, wherein the step S1 is carried out in a homomixer for 0.5 to 2 hours.

14. The method for producing a carbon nanotube dispersion liquid according to claim 12 , wherein the step S2 is performed by a dispersion method selected from the group consisting of a bead mill, a ball mill, and high-pressure homogenization.

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