Surface-modified carbon nanotube, and dispersion and secondary battery, which comprise same

Abstract

The present invention relates to a surface-modified carbon nanotube having both excellent conductivity and improved dispersibility, and a dispersion and a secondary battery, which comprise same.

Description

Surface-modified carbon nanotubes, dispersions containing the same, and secondary batteries

[0001] The present invention relates to surface-modified carbon nanotubes, a dispersion containing the same, and a secondary battery.

[0002]

[0003] Since their emergence in the 1990s, secondary batteries have undergone steady research and development. Research and development is ongoing not only on the key components of secondary batteries—the cathode / anode active materials, electrolytes, and separators—but also on auxiliary components that complement and enhance their properties. To develop high-capacity secondary batteries, increased electrode thickness is essential, along with the formation of effective conductive paths to receive electrons from the current collector.

[0004] Conductive agents are used to improve the conductivity of electrode active materials. Conventionally, dot-shaped conductive agents, such as carbon black, were primarily used. However, dot-shaped conductive agents do not significantly improve electrical conductivity, requiring excessive use to achieve sufficient effects. This, in turn, reduces the electrode active material content and lowers battery capacity.

[0005] To address these issues, active efforts are being made to apply highly conductive carbon nanotubes (CNTs) as conductive materials. Because CNTs can achieve high conductivity even in small quantities, their use allows for a significant reduction in conductive material content compared to carbon black, resulting in increased electrical capacity.

[0006] Meanwhile, in order to disperse CNTs with a high aspect ratio into single tubes due to strong van der Waals interactions and tube entanglement between tubes, it was necessary to improve the dispersion force through chemical surface modification or perform a process of applying high-energy shear force.

[0007] In addition, in the past, high-concentration CNT dispersions were manufactured by inducing cutting of tubes through excessive acid treatment, ultrasonic treatment, or dry grinding. However, these methods have problems in that the CNTs are cut during processing, shortening their length, or defects occur due to oxidation, resulting in deterioration of electrical and mechanical properties.

[0008]

[0009] The present invention provides surface-modified carbon nanotubes having excellent conductivity and improved dispersibility, a dispersion solution containing the same, and a secondary battery.

[0010] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0011]

[0012] One embodiment of the present invention provides a surface-modified carbon nanotube comprising a carbon nanotube; and a surfactant adsorbed on the surface of the carbon nanotube; and satisfying the following mathematical formula 1 when subjected to thermogravimetric analysis at a temperature of 30°C or more and 900°C or less:

[0013] [Mathematical Formula 1]

[0014] 14.0% ≤ A ≤ 40.0%

[0015] In the above mathematical expression 1, A is a value expressed as a percentage of the sum of the areas of peaks included in the range of 400°C to 600°C among the total areas of peaks corresponding to carbon nanotubes included in the range of 400°C to 800°C, obtained by separating the overlapping peaks of the thermal decomposition differential curve of the surface-modified carbon nanotubes.

[0016] According to one embodiment of the present invention, the surfactant may include at least one of an anionic surfactant and a cationic surfactant.

[0017] According to one embodiment of the present invention, the molecular weight of the surfactant may be 200 g / mol or more and 500 g / mol or less.

[0018] According to one embodiment of the present invention, the surface-modified carbon nanotube may have a G / D ratio of 20 or more and 60 or less in the Raman spectrum, and the G may be 1560 to 1600 cm in the Raman spectrum. -1 is the maximum peak intensity within the range of , and D is 1310 to 1360 cm -1 is the maximum peak intensity within the range.

[0019] According to one embodiment of the present invention, the surface-modified carbon nanotube may include an oxidizing agent.

[0020] According to one embodiment of the present invention, the oxidizing agent may include a potassium-based oxidizing agent having an ionization constant of -9 or more and 4 or less.

[0021] According to one embodiment of the present invention, the surface-modified carbon nanotube containing the oxidizing agent is a reaction product of a mixture containing the carbon nanotube, a surfactant, and an oxidizing agent, and the mixture may have a molar ratio of the surfactant and the oxidizing agent of 1:5 to 1:200.

[0022] According to one embodiment of the present invention, the surface-modified carbon nanotube may include an organic acid containing one or more carboxyl groups.

[0023] According to one embodiment of the present invention, the carbon number of the organic acid may be 1 or more and 7 or less.

[0024] According to one embodiment of the present invention, the content of the organic acid may be 0.3 wt% or more and 1.3 wt% or less.

[0025] According to one embodiment of the present invention, the surface-modified carbon nanotube containing the organic acid is a reaction product of a mixture containing the carbon nanotube, a surfactant, and an organic acid, and the mixture may have a molar ratio of the surfactant and the organic acid of 1:100 to 1:600.

[0026] One embodiment of the present invention provides a surface-modified carbon nanotube comprising: a carbon nanotube; and a surfactant bonded to the surface of the carbon nanotube; wherein the content of the surfactant is 0.5 wt% or more and 4.0 wt% or less.

[0027] One embodiment of the present invention provides a dispersion containing the surface-modified carbon nanotube.

[0028] According to one embodiment of the present invention, the dispersion containing the surface-modified carbon nanotubes may have a surface resistance value of 0.5 Ω / □ or more and less than 1 Ω / □ when coated to a thickness of 10 μm.

[0029] According to one embodiment of the present invention, the dispersion containing the surface-modified carbon nanotubes may have an absorbance of 0.4 or more for light having a wavelength of 550 nm.

[0030] One embodiment of the present invention provides a secondary battery including an electrode including the surface-modified carbon nanotube.

[0031]

[0032] A surface-modified carbon nanotube according to one embodiment of the present invention may have excellent conductivity and dispersibility.

[0033] In addition, the surface-modified carbon nanotube according to one embodiment of the present invention has the advantage of being able to realize excellent dispersibility and conductivity without damage to the carbon nanotube by adsorbing a surfactant on the surface of the carbon nanotube.

[0034] In addition, the dispersion according to one embodiment of the present invention can exhibit excellent conductivity and dispersibility by including the surface-modified carbon nanotubes.

[0035] In addition, the secondary battery according to one embodiment of the present invention has the advantage of excellent electrochemical performance by including the surface-modified carbon nanotube.

[0036] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and the attached drawings.

[0037]

[0038] Figure 1 is a drawing showing the results of thermogravimetric analysis of surface-modified carbon nanotubes manufactured in Example 6 of the present invention.

[0039]

[0040] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0041] Throughout this specification, when it is said that an element is "on" another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0042] Throughout this specification, the unit “parts by weight” may mean the weight ratio between each component.

[0043] Throughout this specification, terms containing ordinal numbers, such as "first" and "second," are used to distinguish one component from another and are not limited by the ordinal numbers. For example, within the scope of the invention, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

[0044] Throughout the present specification, the "weight average molecular weight", "molecular weight", etc. of a compound can be calculated using the molecular weight and molecular weight distribution of the compound. Specifically, a sample having a concentration of 1 wt% of the compound is prepared by adding tetrahydrofuran (THF) and the compound to a 1 ml glass bottle, and a standard sample (polystyrene) and the sample sample are filtered through a filter (pore size: 0.45 μm), and then injected into a GPC injector. The elution time of the sample sample is compared with the calibration curve of the standard sample, thereby obtaining the molecular weight and molecular weight distribution of the compound. At this time, Infinity II 1260 (Agilient) can be used as the measuring device, and the flow rate can be set to 1.00 mL / min and the column temperature to 40.0 °C.

[0045] Throughout this specification, the viscosity of the compound or composition is 50 s at a temperature of 23 ℃ using a rotational rheometer DHR-2 (Plate Φ40 mm). -1 It may be a value measured in .

[0046]

[0047] Hereinafter, the present specification will be described in more detail.

[0048] One embodiment of the present invention provides a surface-modified carbon nanotube comprising a carbon nanotube; and a surfactant adsorbed on the surface of the carbon nanotube; and satisfying the following mathematical formula 1 when subjected to thermogravimetric analysis at a temperature of 30°C or more and 900°C or less:

[0049] [Mathematical Formula 1]

[0050] 14.0% ≤ A ≤ 40.0%

[0051] In the above mathematical expression 1, A is a value expressed as a percentage of the sum of the areas of peaks included in the range of 400°C to 600°C among the total areas of peaks corresponding to carbon nanotubes included in the range of 400°C to 800°C, obtained by separating the overlapping peaks of the thermal decomposition differential curve of the surface-modified carbon nanotubes.

[0052] Surface-modified carbon nanotubes according to one embodiment of the present invention can exhibit excellent conductivity and dispersibility. Furthermore, the surface-modified carbon nanotubes have the advantage of achieving excellent dispersibility and conductivity without damage to the carbon nanotubes, as a surfactant is adsorbed onto the surface of the carbon nanotubes.

[0053] According to one embodiment of the present invention, the above mathematical formula 1 may be established based on data analyzed using a thermogravimetric analyzer (TGA) of the surface-modified carbon nanotube under the conditions of an air atmosphere (flow rate 100 ml / min), a heating rate of 5 ℃ / min, and a temperature range of 30 ℃ to 900 ℃. When the surface-modified carbon nanotube is subjected to a thermogravimetric analysis, the peaks constituting the curve can be separated, displayed, and confirmed by deconvoluting the differential curve.

[0054] According to one embodiment of the present invention, the surface-modified carbon nanotube satisfies the above mathematical formula 1. Specifically, the value of A calculated by the following mathematical formula 2 of the surface-modified carbon nanotube may be 14.0% or more and 40.0% or less.

[0055] [Equation 2]

[0056] A = B / CX 100

[0057] In the above mathematical expression 2, C is the sum of the areas of peaks corresponding to carbon nanotubes in the range of 400°C to 800°C. B is the sum of the areas of peaks corresponding to carbon nanotubes in the range of 400°C to 600°C.

[0058] For example, as a result of thermogravimetric analysis of surface-modified carbon nanotubes, peaks corresponding to carbon nanotubes, CNT1, CNT2, CNT3, CNT4, CNT5, and CNT6, may appear in the range of 400°C to 800°C. At this time, the sum of the peak areas of CNT1, CNT2, CNT3, CNT4, CNT5, and CNT6 corresponding to the range of 400°C to 800°C may correspond to C. In addition, the sum of the peak areas of CNT1, CNT2, and CNT3 corresponding to the range of 400°C to 600°C may correspond to B.

[0059] Specifically, the value of A calculated by the above mathematical formula 2 of the surface-modified carbon nanotube may be 16.0% or more and 38.0% or less, 18.0% or more and 36.0% or less, 20.0% or more and 34.0% or less, 22.0% or more and 32.0% or less, 24.0% or more and 30.0% or less, 26.0% or more and 28.0% or less, 14.0% or more and 30.0% or less, 16.0% or more and 28.0% or less, 18.0% or more and 26.0% or less, 20.0% or more and 24.0% or less, 26.0% or more and 40.0% or less, 28.0% or more and 38.0% or less, 30.0% or more and 36.0% or less, or 32.0% or more and 34.0% or less. The surface-modified carbon nanotube satisfying the above mathematical expression 1 can have improved conductivity and also effectively improved dispersibility.

[0060] According to one embodiment of the present invention, the surfactant may include at least one of anionic surfactant and cationic surfactant. By using at least one of anionic surfactant and cationic surfactant as the surfactant adsorbed on the surface of the carbon nanotube, the dispersibility of the surface-modified carbon nanotube can be improved, and at the same time, the conductivity can be improved. When an amphoteric surfactant or a nonionic surfactant is used as the surfactant, it may be difficult to effectively improve both dispersibility and conductivity.

[0061] According to one embodiment of the present invention, the molecular weight of the surfactant may be 200 g / mol or more and 500 g / mol or less. Specifically, the molecular weight of the surfactant may be 230 g / mol or more and 450 g / mol or less, 250 g / mol or more and 400 g / mol or less, 275 g / mol or more and 380 g / mol or less, 200 g / mol or more and 400 g / mol or less, 250 g / mol or more and 350 g / mol or less, 300 g / mol or more and 500 g / mol or less, 300 g / mol or more and 450 g / mol or less, or 300 g / mol or more and 400 g / mol or less. The surfactant having a molecular weight satisfying the above-mentioned range may be easily adsorbed onto the surface of the carbon nanotube, and may effectively improve the dispersibility and conductivity of the carbon nanotube.

[0062] According to one embodiment of the present invention, the number of carbon atoms in the surfactant may be 10 or more and 20 or less. Specifically, the number of carbon atoms contained in the surfactant may be 12 or more and 19 or less, 15 or more and 19 or less, 18 or more and 19 or less, 10 or more and 15 or less, or 16 or more and 20 or less. When the number of carbon atoms contained in the surfactant satisfies the above-mentioned range, the surfactant may be easily adsorbed onto the surface of the carbon nanotube, and may effectively improve the dispersibility and conductivity of the carbon nanotube.

[0063] According to one embodiment of the present invention, the surfactant may be any surfactant used in the art without limitation as long as it satisfies the above-described properties. For example, the surfactant may include at least one of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate as an anionic surfactant satisfying the above-described molecular weight and carbon number ranges. In addition, the surfactant may include at least cetyl trimethyl ammonium bromide as a cationic surfactant satisfying the above-described molecular weight and carbon number ranges.

[0064] According to one embodiment of the present invention, the surface-modified carbon nanotube may have a G / D ratio of 20 or more and 60 or less in the Raman spectrum, and the G is 1560 to 1600 cm in the Raman spectrum. -1 is the maximum peak intensity within the range of , and D is 1310 to 1360 cm -1 is the maximum peak intensity within the range. Specifically, the G / D ratio in the Raman spectrum of the surface-modified carbon nanotube may be 30 or more and 60 or less, 35 or more and 55 or less, 40 or more and 50 or less, 20 or more and 50 or less, 30 or more and 45 or less, 40 or more and 60 or less, or 45 or more and 55 or less. When the G / D ratio of the surface-modified carbon nanotube satisfies the above-mentioned range, the conductivity and dispersibility of the surface-modified carbon nanotube may be improved. Specifically, the dispersibility of the surface-modified carbon nanotube satisfying the G / D ratio of the above-mentioned range in a solvent may be excellent, and thereby the conductivity of the dispersion may be improved.

[0065] According to one embodiment of the present invention, the surface-modified carbon nanotubes may include an oxidizing agent. That is, the surface-modified carbon nanotubes may be treated with an oxidizing agent. The carbon nanotubes whose surfaces have been modified with the surfactant may be oxidized by being treated with the oxidizing agent. By treating the surface-modified carbon nanotubes with the oxidizing agent, the dispersibility of the surface-modified carbon nanotubes may be further improved. Meanwhile, the surface-modified carbon nanotubes treated with the oxidizing agent still contain the surfactant, thereby suppressing the aggregation of the carbon nanotubes and effectively preventing the reduction in conductivity.

[0066] According to one embodiment of the present invention, the oxidizing agent may include a potassium-based oxidizing agent having an ionization constant of -9 or more and 4 or less. Specifically, the ionization constant of the potassium-based oxidizing agent may be -9 or more and 3 or less, -8 or more and 4 or less, -8 or more and 3 or less, or -7 or more and 2 or less. When the oxidizing agent having an ionization constant satisfying the above-mentioned range is used, the surface-modified carbon nanotubes can be oxidized more stably. The potassium-based oxidizing agent may include at least one of potassium peroxymono sulfate and potassium permanganate (KMnO4). Meanwhile, an acid or potassium peroxymonosulfate may be used together to control pH when treating the surface-modified carbon nanotubes with the oxidizing agent.

[0067] According to one embodiment of the present invention, the surface-modified carbon nanotube containing the oxidizing agent is a reaction product of a mixture containing the carbon nanotube, a surfactant, and an oxidizing agent, and the mixture may have a molar ratio of the surfactant and the oxidizing agent of 1:5 to 1:200. Specifically, the molar ratio of the surfactant and the oxidizing agent included in the mixture may be 1:5 to 1:180, 1:5 to 1:160, 1:5 to 1:140, 1:5 to 1:120, 1:5 to 1:100, 1:5 to 1:80, 1:5 to 1:60, 1:5 to 1:40, 1:5 to 1:20, 1:100 to 1:200, 1:120 to 1:200, 1:140 to 1:200, or 1:160 to 1:200. When the molar ratio of the surfactant and the oxidizing agent is within the above-mentioned range, the carbon nanotube surface-modified with the surfactant can be stably oxidized.

[0068] According to one embodiment of the present invention, the content of the surfactant in the mixed solution may be 1 mmol or more and 10 mmol or less, 1 mmol or more and 8 mmol or less, 1 mmol or more and 6 mmol or less, 1 mmol or more and 4 mmol or less, 1 mmol or more and 5 mmol or less, or 5 mmol or more and 10 mmol or less. In addition, the content of the oxidizing agent in the mixed solution may be 3 mmol or more and 350 mmol or less, 3 mmol or more and 330 mmol or less, 3 mmol or more and 300 mmol or less, 3 mmol or more and 250 mmol or less, 3 mmol or more and 200 mmol or less, 3 mmol or more and 150 mmol or less, 3 mmol or more and 100 mmol or less, 3 mmol or more and 80 mmol or less, 3 mmol or more and 60 mmol or less, or 3 mmol or more and 30 mmol or less. When the content of the surfactant and the oxidizing agent included in the above mixture is within the above-mentioned range, the carbon nanotubes can be effectively oxidized, and the surfactant adsorbed on the surface of the carbon nanotubes can be stably retained.

[0069] Based on 100 parts by weight of the above mixture, the content of the carbon nanotubes may be 0.1 parts by weight or more and 5 parts by weight or less.

[0070] According to one embodiment of the present invention, the surface-modified carbon nanotube treated with the oxidizing agent may contain 0.5 wt% or more and 4.0 wt% or less of the surfactant. That is, based on 100 wt% of the surface-modified carbon nanotube subjected to oxidation treatment, the content of the surfactant adsorbed on the surface of the carbon nanotube may be 0.5 wt% or more and 4.0 wt% or less, 1 wt% or more and 3.5 wt% or less, 1.5 wt% or more and 3.0 wt% or less, 2.0 wt% or more and 2.5 wt% or less, 0.5 wt% or more and 2.5 wt% or less, 1.5 wt% or more and 2.0 wt% or less, 1.5 wt% or more and 2.0 wt% or less, 2.0 wt% or more and 4.0 wt% or less, 2.5 wt% or more and 3.5 wt% or less, or 3.0 wt% or more and 4.0 wt% or less. When the content of the surfactant included in the oxidized surface-modified carbon nanotube is within the above-mentioned range, the dispersibility and conductivity of the carbon nanotube can be effectively improved.

[0071] The content of the surfactant contained in the oxidized surface-modified carbon nanotubes can be measured using thermogravimetric analysis (TGA). Specifically, in the thermal decomposition curve obtained through TGA, the content of the surfactant present in the oxidized surface-modified carbon nanotubes can be calculated using the area of ​​the alkyl chain decomposition peak in the temperature range where the surfactant decomposes. For example, when sodium dodecyl sulfate (SDS) is used as the surfactant, the content of the SDS surfactant can be calculated using the area of ​​the alkyl chain peak that decomposes at 200 to 270°C.

[0072] According to one embodiment of the present invention, the surface-modified carbon nanotube may include an organic acid containing one or more carboxyl groups. That is, the surface-modified carbon nanotube may be treated with an organic acid containing one or more carboxyl groups. By treating the surface-modified carbon nanotube with the organic acid, aggregation of the carbon nanotube can be suppressed, and the dispersibility and conductivity of the carbon nanotube can be effectively improved. In particular, when the carbon nanotube is surface-modified with an anionic surfactant, the dispersibility can be further improved due to anionic repulsion with the organic acid.

[0073] The organic acid may contain one or more and five or less carboxyl groups. Specifically, the number of carboxyl groups contained in the organic acid may be one or more and three or less, one or more and two or less, or three or more and five or less. When the content of carboxyl groups contained in the organic acid is within the above-described range, the dispersibility and conductivity of the carbon nanotube can be effectively improved.

[0074] According to one embodiment of the present invention, the carbon number of the organic acid may be 1 or more and 7 or less. Specifically, the carbon number of the organic acid may be 1 or more and 6 or less, the carbon number may be 1 or more and 5 or less, the carbon number may be 1 or more and 3 or less, or the carbon number may be 3 or more and 7 or less. The organic acid may be a straight-chain or branched-chain organic acid having the above-mentioned carbon number. By using the organic acid having the carbon number satisfying the above-mentioned range, the dispersibility and conductivity of the carbon nanotube can be effectively improved.

[0075] The organic acid may have 1 to 3 carbon atoms and contain 1 to 2 carboxyl groups. In addition, the organic acid may have 4 to 7 carbon atoms and contain 3 to 5 carboxyl groups. In particular, when a branched-chain organic acid having 4 to 7 carbon atoms and containing 3 to 5 carboxyl groups is used, the conductivity of the carbon nanotube can be effectively improved.

[0076] According to one embodiment of the present invention, the surface-modified carbon nanotubes including the organic acid are a reaction product of a mixture including the carbon nanotubes, a surfactant, and an organic acid, and the mixture may have a molar ratio of the surfactant and the organic acid of 1:100 to 1:600. Specifically, the molar ratio of the surfactant and the organic acid included in the mixture may be 1:150 to 1:500, 1:150 to 1:400, or 1:150 to 1:300. When the molar ratio of the surfactant and the organic acid is within the above-mentioned range, the organic acid can be stably reacted with the carbon nanotubes surface-modified with the surfactant.

[0077] According to one embodiment of the present invention, the content of the surfactant in the mixture may be 1 mmol or more and 10 mmol or less, 1 mmol or more and 8 mmol or less, 1 mmol or more and 6 mmol or less, 1 mmol or more and 4 mmol or less, 1 mmol or more and 5 mmol or less, or 5 mmol or more and 10 mmol or less. In addition, the content of the organic acid in the mixture may be 100 mmol or more and 1,000 mmol or less, 100 mmol or more and 800 mmol or less, 100 mmol or more and 600 mmol or less, 100 mmol or more and 400 mmol or less, 100 mmol or more and 500 mmol or less, or 600 mmol or more and 1,000 mmol or less. When the content of the surfactant and the organic acid included in the mixture is within the above-mentioned range, the organic acid can be stably reacted with the carbon nanotube surface-modified with the surfactant.

[0078] Based on 100 parts by weight of the above mixture, the content of the carbon nanotubes may be 0.1 parts by weight or more and 5 parts by weight or less.

[0079] According to one embodiment of the present invention, the content of the organic acid may be 0.3 wt% or more and 1.3 wt% or less. Specifically, based on 100 wt% of the surface-modified carbon nanotubes treated with organic acid, the content of the organic acid may be 0.5 wt% or more and 1.1 wt% or less, 0.7 wt% or more and 0.9 wt% or less, 0.3 wt% or more and 1.0 wt% or less, 0.5 wt% or more and 0.7 wt% or less, 0.7 wt% or more and 1.3 wt% or less, 0.9 wt% or more and 1.3 wt% or less, or 1.1 wt% or more and 1.3 wt% or less. When the content of the organic acid is within the above-mentioned range, the dispersibility and conductivity of the surface-modified carbon nanotubes can be further improved.

[0080] The content of the organic acid contained in the surface-modified carbon nanotubes treated with the organic acid can be measured using thermogravimetric analysis (TGA). Specifically, the content of the organic acid present in the surface-modified carbon nanotubes treated with the organic acid can be calculated using the area of ​​the organic acid decomposition peak of the thermal decomposition curve obtained through TGA.

[0081] According to one embodiment of the present invention, the surface-modified carbon nanotube treated with the organic acid may contain 0.5 wt% or more and 4.0 wt% or less of the surfactant. That is, based on 100 wt% of the organic acid-treated surface-modified carbon nanotube, the content of the surfactant adsorbed on the surface of the carbon nanotube may be 0.5 wt% or more and 4.0 wt% or less, 1 wt% or more and 3.5 wt% or less, 1.5 wt% or more and 3.0 wt% or less, 2.0 wt% or more and 2.5 wt% or less, 0.5 wt% or more and 2.5 wt% or less, 1.5 wt% or more and 2.0 wt% or less, 1.5 wt% or more and 2.0 wt% or less, 2.0 wt% or more and 4.0 wt% or less, 2.5 wt% or more and 3.5 wt% or less, or 3.0 wt% or more and 4.0 wt% or less. When the content of the surfactant contained in the organic acid-treated surface-modified carbon nanotube is within the aforementioned range, the dispersibility and conductivity of the carbon nanotube can be effectively improved. The content of the surfactant contained in the organic acid-treated surface-modified carbon nanotube can be calculated through the aforementioned method using thermogravimetric analysis.

[0082]

[0083] One embodiment of the present invention provides a surface-modified carbon nanotube comprising: a carbon nanotube; and a surfactant bonded to the surface of the carbon nanotube; wherein the content of the surfactant is 0.5 wt% or more and 4.0 wt% or less.

[0084] Surface-modified carbon nanotubes according to one embodiment of the present invention can exhibit excellent conductivity and dispersibility. Furthermore, the surface-modified carbon nanotubes have the advantage of being able to achieve excellent dispersibility and conductivity without damage to the carbon nanotubes, as a surfactant is adsorbed onto the surface of the carbon nanotubes.

[0085] Specifically, based on 100 wt% of the surface-modified carbon nanotubes, the content of the surfactant adsorbed on the surface of the carbon nanotubes may be 0.5 wt% or more and 4.0 wt% or less, 1 wt% or more and 3.5 wt% or less, 1.5 wt% or more and 3.0 wt% or less, 2.0 wt% or more and 2.5 wt% or less, 0.5 wt% or more and 2.5 wt% or less, 1.5 wt% or more and 2.0 wt% or less, 1.5 wt% or more and 2.0 wt% or less, 2.0 wt% or more and 4.0 wt% or less, 2.5 wt% or more and 3.5 wt% or less, or 3.0 wt% or more and 4.0 wt% or less. When the content of the surfactant included in the organic acid-treated surface-modified carbon nanotubes is within the above-mentioned range, the dispersibility and conductivity of the carbon nanotubes can be effectively improved. The content of the surfactant contained in the surface-modified carbon nanotube can be calculated using the above-described method using thermogravimetric analysis.

[0086] The surface-modified carbon nanotube according to the present embodiment may be the same as the surface-modified carbon nanotube according to the above-described embodiment. That is, the surface-modified carbon nanotube having a surfactant content of 0.5 wt% or more and 4.0 wt% or less may satisfy the above-described mathematical formula 1.

[0087] In addition, the surface-modified carbon nanotube according to the present embodiment may use the same surfactant, oxidizing agent, and organic acid as those described in the surface-modified carbon nanotube according to the above-described embodiment. In addition, the surface-modified carbon nanotube according to the present embodiment may contain the same components as those described in the surface-modified carbon nanotube according to the above-described embodiment, and the contents thereof may be the same.

[0088]

[0089] One embodiment of the present invention provides a dispersion comprising the surface-modified carbon nanotubes. By including the surface-modified carbon nanotubes, the dispersion can exhibit excellent conductivity and dispersibility.

[0090] According to one embodiment of the present invention, the content of the surface-modified carbon nanotubes may be 0.1 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the dispersion.

[0091] According to one embodiment of the present invention, the dispersion containing the surface-modified carbon nanotubes may have a sheet resistance value of 0.5 Ω / □ or more and less than 1 Ω / □, 0.5 Ω / □ or more and 0.99 Ω / □ or less, 0.55 Ω / □ or more and 0.99 Ω / □ or less, 0.6 Ω / □ or more and 0.99 Ω / □ or less, 0.65 Ω / □ or more and 0.99 Ω / □ or less, or 0.7 Ω / □ or more and 0.99 Ω / □ or less when coated with a thickness of 10 ㎛. As described above, the surface-modified carbon nanotubes have excellent conductivity and can exhibit the sheet resistance value described above when coated.

[0092] According to one embodiment of the present invention, the dispersion containing the surface-modified carbon nanotubes may have an absorbance of 0.4 or more for light having a wavelength of 550 nm. Specifically, the absorbance of the dispersion for light having a wavelength of 550 nm may be 0.4 or more and 0.6 or less, or 0.45 or more and 0.6 or less. As described above, the surface-modified carbon nanotubes have excellent dispersibility and may be homogeneously present in the dispersion.

[0093]

[0094] One embodiment of the present invention provides a method for producing surface-modified carbon nanotubes. Specifically, the method may include the steps of: mixing carbon nanotubes and a surfactant to produce a mixture and reacting the mixture; filtering the carbon nanotubes that have completed the reaction from the mixture; and washing and drying the filtered carbon nanotubes to obtain surface-modified carbon nanotubes.

[0095] Through a method according to an embodiment of the present invention, a surface-modified carbon nanotube according to the above-described embodiment can be manufactured. That is, through the above-described manufacturing method, a surface-modified carbon nanotube satisfying the above-described mathematical formula 1 can be manufactured. In addition, through the above-described manufacturing method, a surface-modified carbon nanotube having a surfactant content of 0.5 wt% or more and 4.0 wt% or less can be manufactured. In addition, through the above-described manufacturing method, a surface-modified carbon nanotube satisfying the above-described mathematical formula 1 and having a surfactant content of 0.5 wt% or more and 4.0 wt% or less can be manufactured.

[0096] According to one embodiment of the present invention, the content of the surfactant in the mixture may be 5 parts by weight or more and 35 parts by weight or less, 10 parts by weight or more and 30 parts by weight or less, 15 parts by weight or more and 25 parts by weight or less, 5 parts by weight or more and 20 parts by weight or less, or 15 parts by weight or more and 35 parts by weight or less, based on 100 parts by weight of the carbon nanotubes. By adjusting the content of the carbon nanotubes and the surfactant included in the mixture within the above-mentioned range, a surface-modified carbon nanotube having a surfactant content of 0.5 wt% or more and 4.0 wt% or less can be effectively manufactured. In addition, a surface-modified carbon nanotube satisfying the above-mentioned mathematical expression 1 can be easily manufactured.

[0097] According to one embodiment of the present invention, the molar number of the surfactant included in the mixture may be 0.5 mmol or more and 7.5 mmol or less, or 0.5 mmol or more and 7.0 mmol or less. By adjusting the molar number of the surfactant included in the mixture within the above-mentioned range, surface-modified carbon nanotubes having a surfactant content of 0.5 wt% or more and 4.0 wt% or less can be effectively produced. In addition, surface-modified carbon nanotubes satisfying the above-mentioned mathematical expression 1 can be easily produced.

[0098] The step of reacting the above mixture may be performed at a temperature of 20°C or higher and 40°C or lower, for a time of 10 minutes or higher and 60 minutes or lower. When the temperature and time for reacting the above mixture are within the above-mentioned range, the surfactant may be stably adsorbed onto the surface of the carbon nanotube.

[0099] According to one embodiment of the present invention, the method further comprises a step of adding an oxidizing agent to the mixture, wherein the molar ratio of the surfactant to the oxidizing agent may be 1:5 to 1:200, 1:5 to 1:180, 1:5 to 1:160, 1:5 to 1:140, 1:5 to 1:120, 1:5 to 1:100, 1:5 to 1:80, 1:5 to 1:60, 1:5 to 1:40, 1:5 to 1:20, 1:100 to 1:200, 1:120 to 1:200, 1:140 to 1:200, or 1:160 to 1:200. When the molar ratio of the surfactant and the oxidizing agent is within the above-mentioned range, the carbon nanotube surface-modified with the surfactant can be stably oxidized.

[0100] According to one embodiment of the present invention, the content of the surfactant in the mixed solution may be 1 mmol or more and 10 mmol or less, 1 mmol or more and 8 mmol or less, 1 mmol or more and 6 mmol or less, 1 mmol or more and 4 mmol or less, 1 mmol or more and 5 mmol or less, or 5 mmol or more and 10 mmol or less. In addition, the content of the oxidizing agent in the mixed solution may be 3 mmol or more and 350 mmol or less, 3 mmol or more and 330 mmol or less, 3 mmol or more and 300 mmol or less, 3 mmol or more and 250 mmol or less, 3 mmol or more and 200 mmol or less, 3 mmol or more and 150 mmol or less, 3 mmol or more and 100 mmol or less, 3 mmol or more and 80 mmol or less, 3 mmol or more and 60 mmol or less, or 3 mmol or more and 30 mmol or less. When the content of the surfactant and the oxidizing agent included in the above mixture is within the above-mentioned range, the carbon nanotubes can be effectively oxidized, and the surfactant adsorbed on the surface of the carbon nanotubes can be stably retained.

[0101] Based on 100 parts by weight of the above mixture, the content of the carbon nanotubes may be 0.1 parts by weight or more and 5 parts by weight or less.

[0102] The step of reacting the above mixture may be performed at a temperature of 20°C or higher and 40°C or lower, for a time of 1 hour or higher and 5 hours or lower. When the temperature and time for reacting the above mixture are within the above-mentioned range, the surface-modified carbon nanotubes can be effectively oxidized.

[0103] According to one embodiment of the present invention, the method further comprises a step of adding an organic acid to the mixture, and the molar ratio of the surfactant and the organic acid may be 1:100 to 1:600, 1:150 to 1:500, 1:150 to 1:400, or 1:150 to 1:300. When the molar ratio of the surfactant and the organic acid is within the above-mentioned range, the organic acid can be stably reacted with the carbon nanotube surface-modified with the surfactant.

[0104] According to one embodiment of the present invention, the content of the surfactant in the mixture may be 1 mmol or more and 10 mmol or less, 1 mmol or more and 8 mmol or less, 1 mmol or more and 6 mmol or less, 1 mmol or more and 4 mmol or less, 1 mmol or more and 5 mmol or less, or 5 mmol or more and 10 mmol or less. In addition, the content of the organic acid in the mixture may be 100 mmol or more and 1,000 mmol or less, 100 mmol or more and 800 mmol or less, 100 mmol or more and 600 mmol or less, 100 mmol or more and 400 mmol or less, 100 mmol or more and 500 mmol or less, or 600 mmol or more and 1,000 mmol or less. When the content of the surfactant and the organic acid included in the mixture is within the above-mentioned range, the organic acid can be stably reacted with the carbon nanotube surface-modified with the surfactant.

[0105] Based on 100 parts by weight of the above mixture, the content of the carbon nanotubes may be 0.1 parts by weight or more and 5 parts by weight or less.

[0106] The step of reacting the above mixture may be performed at a temperature of 30°C or higher and 60°C or lower, for a time of 5 hours or higher and 10 hours or lower. When the temperature and time for reacting the above mixture are within the above-mentioned ranges, the organic acid can be effectively reacted with the surface-modified carbon nanotubes.

[0107] According to one embodiment of the present invention, the step of filtering the carbon nanotubes in the mixture solution after the reaction is completed can be performed using any method and device used in the art without limitation. For example, the mixture solution after the reaction is completed can be subjected to reduced pressure filtration to filter out unreacted compounds and impurities, thereby obtaining surface-modified carbon nanotubes.

[0108] According to one embodiment of the present invention, the filtered carbon nanotubes can be washed and dried to obtain surface-modified carbon nanotubes. The surface-modified carbon nanotubes can be washed with water, and the washing process can be performed until the pH becomes neutral.

[0109]

[0110] One embodiment of the present invention provides a secondary battery including an electrode including the surface-modified carbon nanotube.

[0111] A secondary battery according to one embodiment of the present invention has the advantage of excellent electrochemical performance by including the surface-modified carbon nanotubes. Specifically, the secondary battery can effectively improve electrochemical performance by including the surface-modified carbon nanotubes as a conductive material.

[0112] According to one embodiment of the present invention, the secondary battery may include a positive electrode including the surface-modified carbon nanotube, a negative electrode including the surface-modified carbon nanotube, or a positive electrode and a negative electrode including the surface-modified carbon nanotube. The secondary battery may include secondary batteries used in the art without limitation.

[0113] According to one embodiment of the present invention, the secondary battery may include a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0114] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a conductive material, and a positive electrode binder.

[0115] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the positive electrode current collector may be made of copper, stainless steel, aluminum, titanium, calcined carbon, stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. The positive electrode current collector may typically have a thickness of 6 to 20 μm.

[0116] According to one embodiment of the present invention, the cathode active material may include a lithium transition metal oxide. The lithium transition metal oxide may be, for example, Li x1 CoO2(0.5 <x1<1.3), Li x2 NiO2(0.5 <x2<1.3), Li x3 MnO2(0.5 <x3<1.3), Li x4 Mn2O4(0.5 <x4<1.3), Li x5 (Ni a1 Co b1 Mn c1)O2(0.5 <x5<1.3, 0<a1<1, 0<b1<1, 0<c1<1, a1+b1+c1=1), Li x6 Ni 1-y1 Co y1 O2(0.5 <x6<1.3, 0<y1<1), Li x7 Co 1-y2 Mn y2 O2(0.5 <x7<1.3, 0≤y2<1), Li x8 Ni 1-y3 Mn y3 O2(0.5 <x8<1.3, O≤y3<1), Li x9 (Ni a2 Co b2 Mn c2 )O4(0.5 <x9<1.3, 0<a2<2, 0<b2<2, 0<c2<2, a2+b2+c2=2), Li x10 Mn 2-z1 Ni z1 O4(0.5 <x10<1.3, 0<z1<2), Li x11 Mn 2-z2 Co z2 O4(0.5 <x11<1.3, 0<z2<2), Li x12 CoPO4(0.5 <x12<1.3) 및 Li x13 FePO4(0.5 <x13<1.3)로 이루어진 군에서 선택되는 하나 이상일 수 있다.

[0117] According to one embodiment of the present invention, the surface-modified carbon nanotubes can be used as a conductive material for the positive electrode. In addition, the positive electrode binder may be the same as or different from the negative electrode binder.

[0118] According to one embodiment of the present invention, a method for manufacturing a negative electrode may include the steps of preparing a negative electrode slurry including a negative electrode active material, a conductive material, and a negative electrode binder; coating and drying the negative electrode slurry on at least one surface of a negative electrode current collector to form a negative electrode active material layer; and rolling the current collector on which the negative electrode active material layer is formed.

[0119] The above-described negative electrode current collector can serve as a passage to transfer electrons from the outside to cause an electrochemical reaction in the negative electrode active material or to receive electrons from the negative electrode active material and send them to the outside. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. Specifically, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the current collector. For example, the thickness of the negative electrode current collector may be 6 ㎛ to 55 ㎛, but the thickness of the negative electrode current collector is not limited thereto.

[0120] According to one embodiment of the present invention, the negative electrode slurry may further include at least one of a silicon-based negative electrode active material and a graphite-based active material. For example, the silicon-based negative electrode active material may be Si, SiO. x (0 <x≤2), Si-C 복합체 및 Si-Y 합금(Y는 알칼리금속, 알칼리토금속, 전이금속, 13 족 원소, 14 족 원소 및 희토류 원소로 이루어진 군에서 선택된 어느 하나의 원소이다)으로 이루어진 군에서 선택되는 1종 이상을 포함할 수 있다. 예를 들어, 상기 흑연계 활물질은 인조흑연, 천연흑연, 흑연화탄소 섬유 및 흑연화 메조카본마이크로비드로 이루어진 군에서 선택되는 1종 이상을 포함할 수 있다.

[0121] According to one embodiment of the present invention, the surface-modified carbon nanotubes can be used as a conductive material for the negative electrode. The negative electrode binder can suppress separation between negative electrode active material (silicon negative electrode active material) particles, or between the negative electrode and the current collector. A polymer commonly used in electrodes in the relevant technical field can be used as the negative electrode binder. This negative electrode binder may be, without limitation, the same as or different from the positive electrode binder.

[0122] According to one embodiment of the present invention, the separator may be composed of a porous substrate, or may include a porous substrate and a coating layer. The porous substrate may be a porous structure having high electrolyte resistance and fine pore diameters, capable of electrically insulating the negative and positive electrodes to prevent short circuits while providing a path for lithium ions to move.

[0123] Any organic or inorganic material having electrical insulation properties may be used as a constituent material of the porous substrate without particular limitation. The porous substrate may include, for example, at least one selected from the group consisting of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyvinyl variether ether ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, and may specifically include polyolefin. Polyolefin not only has excellent coatability, but also can increase the ratio of the electrode active material layer in the battery by making the separator thinner, thereby increasing the capacity per volume.

[0124] Specifically, the weight average molecular weight (Mw) of the polyolefin may be 100,000 to 500,000 g / mol. If the weight average molecular weight of the polyolefin is less than the above numerical range, it may be difficult to secure sufficient mechanical properties, and if it exceeds the above numerical range, the shutdown function may not be implemented or molding may become difficult. The shutdown function refers to the function of blocking the movement of ions and preventing thermal runaway of the battery by melting the thermoplastic resin and closing the pores of the porous substrate when the temperature of the secondary battery increases.

[0125] The thickness of the porous substrate may be, for example, 3 to 50 μm or 4 to 30 μm. If the thickness of the porous substrate is less than the numerical range, the function of the conductive barrier may not be sufficient, and if it exceeds the numerical range, the resistance of the separator may excessively increase.

[0126] The average diameter of the pores included in the porous substrate may be, for example, 10 to 100 nm. The pores included in the porous substrate have a structure that is interconnected with each other, so that gas or liquid can pass from one side of the porous substrate to the other side.

[0127] According to one embodiment of the present invention, the separator can improve the mechanical strength and heat resistance of the separator for a secondary battery, and can include a coating layer disposed on at least one surface of a porous substrate of a water-soluble polymer that increases ion conductivity within the secondary battery.

[0128] According to one embodiment of the present invention, the coating layer may include a binder polymer and inorganic particles. The polymer can connect the inorganic particles and stably fix them. The binder polymer may be, for example, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, poly(ethylene-co-vinyl acetate), polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, One or more selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber may be used in combination.

[0129] According to one embodiment of the present invention, the weight ratio of the inorganic particles and the binder polymer (inorganic particles: binder polymer) may be 50:50 to 99:1, specifically 70:30 to 95:5. If the content ratio of the inorganic particles to the binder polymer is less than the above numerical range, the content of the binder polymer may increase, thereby lowering the thermal safety improvement performance of the separator, and the pore size and porosity may decrease due to a decrease in the empty space formed between the inorganic particles, thereby causing a deterioration in the performance of the final battery, and if the content exceeds the above numerical range, the content of the binder polymer may be too small, thereby weakening the peeling resistance of the coating layer.

[0130] According to one embodiment of the present invention, inorganic particles can contribute to improving the mechanical strength and heat resistance of a separator for a secondary battery. Specifically, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the secondary battery to which they are applied (e.g., 0 to 5 V based on Li / Li+). For example, when inorganic particles having a high dielectric constant are used, they can contribute to increasing the degree of dissociation of an electrolyte salt, such as a lithium salt, in a liquid electrolyte, thereby improving the ionic conductivity of the electrolyte.

[0131] For the reasons described above, the inorganic particles may be inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transport capability, or a mixture thereof.

[0132] The inorganic particles having the dielectric constant of 5 or more are Al2O3, SiO2, ZrO2, AlO(OH), Al(OH)3, Mg(OH)2, BaSO4, TiO2, BaTiO3, Pb(Zr x Ti 1-x )O3(PZT, where 0 <x<1), Pb 1-x La x Zr 1-y Tiy O3(PLZT, where 0 < x < 1, 0 < y < 1), (1-x)Pb(Mg 1 / 3 Nb 2 / 3 )O 3-x It may be a mixture of one or more selected from the group consisting of PbTiO3 (PMN-PT, where 0 < x < 1), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, and SiC.

[0133] The inorganic particles having the above lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0< x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y Series glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x <4, 0 < y < 2), SiS2 series glass(Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5 series glass(Li x P y S z, 0 < x < 3, 0 < y < 3, 0 < z < 7) may be a mixture of one or more selected from the group consisting of:

[0134] For example, the average particle diameter (D) of the above inorganic particles 50 ) may be 1 nm to 10 μm, specifically 10 nm to 2 μm, and more specifically 50 nm to 1 μm, for forming a coating layer of uniform thickness and having an appropriate porosity. The "average particle diameter (D 50 )" means the particle diameter at the 50% point of the cumulative distribution of the number of particles according to particle diameter. The above average particle diameter can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, thereby calculating the particle size distribution.

[0135] Specifically, the thickness of the coating layer may be 0.1 to 10 μm, specifically 1 to 3 μm, and more specifically 1.4 to 1.6 μm. When the thickness of the coating layer satisfies the above numerical range, the insulation and thermal stability of the separator can be increased, and the energy density of the battery can be improved.

[0136] According to one embodiment of the present invention, the electrolyte may include a solvent and a lithium salt. The solvent may be, for example, one or a mixture of two or more selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (GBL), fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, ethyl propionate, and butyl propionate. The lithium salt may be, for example, NO3. - , F - , Cl - , Br - , I - , PF6 - It may contain anions such as:

[0137] According to one embodiment of the present invention, the secondary battery may be a cylindrical, square, or pouch-shaped secondary battery, but is not particularly limited as long as it corresponds to a charging / discharging device.

[0138] According to one embodiment of the present invention, a battery module including the secondary battery as a unit cell and a battery pack including the same can be provided. The battery pack can be used as a power source for one or more medium- to large-sized devices selected from the group consisting of, for example, power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0139]

[0140] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0141]

[0142] Surfactant selection

[0143] Carbon nanotube powder having a G / D ratio of 50 or more was prepared, and sodium carboxymethyl cellulose (CMC) was prepared as a binder.

[0144] In addition, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) were prepared as anionic surfactants. In addition, cetyl trimethyl ammonium bromide (CTAB) was prepared as a cationic surfactant. In addition, dodecylamine, Triton X-100, Polysorbate 20, high molecular weight BYK-191, high molecular weight BYK-194N, high molecular weight BYK-2091, and polyvinylpyrrolidone with different molecular weights were prepared as surfactants.

[0145]

[0146] Reference Example 1

[0147] Afterwards, carbon nanotube powder, binder, and water were mixed and passed through a high-pressure homogenizer 5 times at a pressure of 700 bar to prepare a carbon nanotube slurry (dispersion). At this time, based on 100 parts by weight of carbon nanotube slurry, the content of carbon nanotubes was 0.5 parts by weight and the content of binder was 0.3 parts by weight.

[0148] Thereafter, the prepared surfactant, SDS, was mixed into the carbon nanotube slurry manufactured above, and a mechanical homogenizer was used for secondary dispersion to manufacture a slurry mixed with the surfactant. At this time, the content of the surfactant was 0.1 part by weight based on 100 parts by weight of the manufactured slurry.

[0149]

[0150] Experimental example

[0151] The slurry prepared above was coated on a PET film using a bar coater and then dried in a 90°C oven for 3 hours to form a coating layer with a thickness of 10 μm. Thereafter, the sheet resistance of the coating layer was measured using a 4-point probe using MCP-T610 (Mitsubishi Chemical Co.), and the results are shown in Table 1 below.

[0152] In addition, for the slurry manufactured above, a dispersion was prepared by diluting the content of carbon nanotubes to 0.05%. Thereafter, the dispersion was centrifuged (6,000 g, 10 minutes) to obtain a supernatant, and the absorbance for 550 nm light of the dispersion (supernatant) diluted 1 / 10 was measured using UV-Vis spectroscopy (Cary4000), and the results are shown in Table 1 below.

[0153]

[0154] Reference examples 2 and 3

[0155] Regarding the above Reference Example 1, a carbon nanotube slurry was prepared and the surface resistance and absorbance were measured in the same manner as in the above Reference Example 1, except that a different type of surfactant was used as shown in Table 1 below.

[0156]

[0157] Reference Comparison Example 1

[0158] For the above Reference Example 1, a slurry without adding a surfactant was prepared, and the surface resistance and absorbance were measured in the same manner as in the above Reference Example 1.

[0159]

[0160] Reference Comparison Examples 2 to 8

[0161] Regarding the above Reference Example 1, a carbon nanotube slurry was prepared and the surface resistance and absorbance were measured in the same manner as in the above Reference Example 1, except that a different type of surfactant was used as shown in Table 1 below.

[0162]

[0163] Surfactant Surface resistance (Ω / □) Absorbance (@550 nm) Type Molecular weight (g / mol) Carbon number Reference Example 1 SDS 2 88.4 1 20.73 0.35 Reference Example 2 SDBS 3 48.5 1 80.75 0.362 Reference Example 3 CTAB 3 64.5 1 90.89 0.372 Reference Comparative Example 1-10.17 Reference Comparative Example 2 Dodecylamine 1 85.4 1 21.08 0.168 Reference Comparative Example 3 Triton X-100 6 25.03 22.46 0.163 Reference Comparative Example 4 Polysorbate 201227.5582.190.188Reference Comparative Example 5 BYK-191 Polymer-3.2 10.738Reference Comparative Example 6 BYK-194 N-1.5 0.275Reference Comparative Example 7 BYK-2091-1.7 10.172Reference Comparative Example 8 Polyvinylpyrrolidone 2,500-1.86 1.155Reference Comparative Example 9 Polyvinylpyrrolidone 10,000-21.765Reference Comparative Example 10 Polyvinylpyrrolidone 40,000-3.4 4 1.211

[0164]

[0165] Referring to Table 1 above, when the surfactants of Reference Examples 1 to 3 were used, it was confirmed that the sheet resistance value was effectively reduced and the absorbance increased, thereby improving the dispersibility, compared to Reference Comparative Examples 1 to 10. On the other hand, in the case of Reference Comparative Examples 8 to 10, although the absorbance increased, the sheet resistance value increased, resulting in inferior conductivity.

[0166] Accordingly, in the following examples, the excellent effect of carbon nanotubes surface-modified with surfactants was confirmed by using anionic surfactants and cationic surfactants satisfying the aforementioned carbon number range and molecular weight range.

[0167]

[0168] Fabrication of surface-modified carbon nanotubes

[0169] Example 1

[0170] Carbon nanotubes and the surfactant SDS were mixed and homogenized for 20 minutes using a homogenizer. The carbon nanotube solution was then filtered using a vacuum filtration device, and water was added once to remove any excess surfactant. The carbon nanotubes, surface-modified with SDS, were then filtered and dried. At this time, 3 parts by weight (0.51 mmol) of surfactant was added per 100 parts by weight of carbon nanotubes.

[0171] Afterwards, the surface-modified carbon nanotube powder, the binder CMC, and water were mixed and passed through a high-pressure homogenizer 5 times at a pressure of 700 bar to prepare a carbon nanotube slurry. At this time, based on 100 parts by weight of the carbon nanotube slurry, the content of the surface-modified carbon nanotube was 0.5 parts by weight and the content of the binder was 0.3 parts by weight.

[0172]

[0173] Experimental example

[0174] For the manufactured surface-modified carbon nanotubes, the content of surfactant present in the surface-modified carbon nanotubes was measured using the thermogravimetric analysis (TGA) method described above, and the results are shown in Table 2 below.

[0175] In addition, for the manufactured surface-modified carbon nanotubes, under the conditions of an air atmosphere (flow rate 100 ml / min), a heating rate of 5 ℃ / min, and a temperature range of 30 ℃ to 900 ℃, the A value was calculated according to the above mathematical formula 2 through thermogravimetric analysis (TGA) using the method described above, and is shown in Table 3 below.

[0176] The carbon nanotube slurry prepared above was coated on a PET film using a bar coater and then dried in a 90°C oven for 3 hours to form a coating layer with a thickness of 10 μm. Thereafter, the sheet resistance of the coating layer was measured using a 4-point probe using MCP-T610 (Mitsubishi Chemical Co.), and the results are shown in Table 3 below.

[0177] In addition, the viscosity of the carbon nanotube slurry manufactured above was measured and shown in Table 3 below. Specifically, the viscosity was measured at a temperature of 23°C using a rotational rheometer DHR-2 (Plate Φ40mm) at 50 s. -1 was measured in .

[0178] In addition, Raman spectrum analysis was performed on the manufactured surface-modified carbon nanotubes. In the analyzed Raman spectrum, 1560 to 1600 cm -1 The maximum peak intensity within the range of G, 1310 to 1360 cm -1 The maximum peak intensity D within the range was derived, and the G / D ratio was calculated, and the results are shown in Table 3 below.

[0179] In addition, a dispersion was prepared by diluting the CNT slurry manufactured above to have a surface-modified carbon nanotube content of 0.05%. Thereafter, the dispersion was centrifuged (6,000 g, 10 minutes) to obtain a supernatant, and the absorbance for 550 nm light of the dispersion (supernatant) diluted 1 / 10 was measured using UV-Vis spectroscopy (Cary4000), and the results are shown in Table 3 below.

[0180]

[0181] Examples 2 to 5

[0182] Regarding the above Example 1, surface-modified carbon nanotubes and CNT slurry were manufactured in the same manner as in Example 1, except that the content of the surfactant added during the manufacture of the surface-modified carbon nanotubes was adjusted as shown in Table 2 below.

[0183] In addition, the content of the surfactant for the surface-modified carbon nanotubes manufactured using the same method as Example 1 was calculated and shown in Table 2 below.

[0184] In addition, using the same method as in Example 1, the surface resistance, viscosity, G / D ratio, absorbance, and A value were measured and shown in Table 3 below.

[0185]

[0186] Comparative Examples 1 to 6

[0187] Regarding the above Example 1, surface-modified carbon nanotubes and CNT slurry were manufactured in the same manner as in Example 1, except that the type and content of the surfactant used in the manufacture of the surface-modified carbon nanotubes were adjusted as shown in Table 2 below.

[0188] In addition, the content of the surfactant for the surface-modified carbon nanotubes manufactured using the same method as Example 1 was calculated and shown in Table 2 below.

[0189] In addition, using the same method as in Example 1, the surface resistance, viscosity, G / D ratio, absorbance, and A value were measured and shown in Table 3 below.

[0190]

[0191] Surfactant type, input amount, content (wt%), weight part, mmol, Example 1, SDS 30.5, 10.52, Example 2, SDS 50.8, 50.66, Example 3, SDS 101.7, 1.39, Example 4, SDS 203.4, 2.53, Example 5, SDS 305.13, 9, Comparative Example 1, SDS 406.8, 4.59, Comparative Example 2, SDS 508.5, 5.86, Comparative Example 3, SDS 6010.2, 7.21, Comparative Example 4, SDS 10.17, 0.36, Comparative Example 5, Dodecylamine 102.6, 4.03, Comparative Example 6, Triton X-100, 10-5

[0192]

[0193] In Table 2 above, the amount of surfactant added is the content (parts by weight) relative to 100 parts by weight of carbon nanotubes, and the content (wt%) of surfactant is relative to 100% by weight of surface-modified carbon nanotubes.

[0194]

[0195] Surfactant Sheet Resistance (Ω / □) Viscosity (cp) G / D Ratio Absorbance @ 550 nm A Example 1 SDS 0.98 1, 76 5 6 1.8 0.40 5 16.25 Example 2 SDS 0.97 1, 47 6 5 7.3 0.43 2 25.62 Example 3 SDS 0.87 1, 26 0 5 6.8 0.44 0 28.34 Example 4 SDS 0.81 0.1 1 5 8.0 0.44 6 3 0.66 Example 5 SDS 0.93 8 6 3 5 5.6 0.45 5 3 8 .84Comparative Example 1 SDS 1.0667257.20.46840.65Comparative Example 2 SDS 1.45230 (Poor coating) 55.90.48041.02Comparative Example 3 SDS 1.98108 (Poor coating) 56.00.49342.86Comparative Example 4 SDS 1.021,89063.20.37413.58Comparative Example 5 Dodecylamine 1.092,00861.60.36412.89Comparative Example 6 Triton X-1003.6498053.30.45240.08

[0196]

[0197] Referring to Tables 2 and 3 above, in the case of Examples 1 to 5 in which the content of the surfactant present in the surface-modified carbon nanotubes satisfies the above-mentioned range, it was confirmed that the sheet resistance value was low and thus the conductivity was excellent compared to Comparative Examples 1 to 6 in which the content of the surfactant present in the surface-modified carbon nanotubes was outside the above-mentioned range. In addition, in the case of Examples 1 to 5 in which mathematical expression 1 is satisfied, it was confirmed that the sheet resistance value was low and thus the conductivity was excellent compared to Comparative Examples 1 to 6 in which mathematical expression 1 is not satisfied.

[0198]

[0199] Surface-modified carbon nanotubes treated with an oxidizing agent

[0200] Potassium peroxymono sulfate (PMS), potassium permanganate (KMnO4), HClO4, formic acid, H2SO4, and NaOCl were prepared as oxidizing agents.

[0201]

[0202] Example 6

[0203] 5 g of carbon nanotubes were mixed with SDS, a surfactant, and homogenized for 20 minutes using a homogenizer. Thereafter, an oxidizing agent was added to the homogenized solution without removing the surfactant, and the mixture was stirred at room temperature for 3 hours to oxidize the carbon nanotubes surface-modified with the surfactant. At this time, 1.7 mmol of surfactant and 16.3 mmol of oxidizing agent were added. The content of carbon nanotubes was 5 parts by weight based on 100 parts by weight of the mixture (homogenized solution).

[0204] Afterwards, the carbon nanotube solution, after the reaction, was filtered using a vacuum filtration device while washing with water. The washing process was continued until the pH of the filtrate became neutral. After washing, the oxidized, surface-modified carbon nanotubes were filtered and dried.

[0205] Afterwards, the surface-modified carbon nanotube powder, the binder CMC, and water were mixed and passed through a high-pressure homogenizer 5 times at a pressure of 700 bar to prepare a carbon nanotube slurry. At this time, based on 100 parts by weight of the carbon nanotube slurry, the content of the surface-modified carbon nanotube was 0.5 parts by weight and the content of the binder was 0.3 parts by weight.

[0206]

[0207] Experimental example

[0208] The content of the surfactant for the oxidized surface-modified carbon nanotubes manufactured in the same manner as in Example 1 was calculated and shown in Table 4 below.

[0209] In addition, using the same method as Example 1, the surface resistance, G / D ratio, absorbance, and A value were measured and shown in Table 5 below.

[0210] FIG. 1 is a diagram showing the results of thermogravimetric analysis of surface-modified carbon nanotubes manufactured in Example 6 of the present invention. Referring to FIG. 1, the results of thermogravimetric analysis of the surface-modified carbon nanotubes manufactured in Example 6 showed that peaks of CNT1, CNT2, CNT3, CNT4, CNT5, and CNT6 corresponding to carbon nanotubes appeared in the range of 400°C to 800°C. Thereafter, the sum of the peak areas of CNT1, CNT2, CNT3, CNT4, CNT5, and CNT6 corresponding to the range of 400°C to 800°C was set as C. In addition, the sum of the peak areas of CNT1, CNT2, and CNT3 corresponding to the range of 400°C to 600°C was set as B. Afterwards, it was confirmed that the A value of the surface-modified carbon nanotube manufactured in Example 5 corresponds to 14.51 through the following mathematical formula 2.

[0211] [Equation 2]

[0212] A = B / CX 100

[0213]

[0214] Examples 7 to 20

[0215] Regarding the above Example 6, surface-modified carbon nanotubes and CNT slurry subjected to oxidation treatment were manufactured in the same manner as in the above Example 6, except that the type of oxidizing agent, the content of surfactant, and the content of oxidizing agent were adjusted as shown in Table 4 below.

[0216] In addition, the content of the surfactant for the oxidized surface-modified carbon nanotubes manufactured in the same manner as in Example 6 was calculated and shown in Table 4 below.

[0217] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 6 and are shown in Table 5 below.

[0218]

[0219] Oxidizing agent surfactant (mmol) Oxidizing agent (mmol) Surfactant: Oxidizing agent surfactant content (wt%) Example 6 PMS 1.7 16.31 : 91.76 Example 7 PMS 1.7 48.81 : 281.94 Example 8 PMS 1.7 81.31 : 471.72 Example 9 PMS 1.7 100.91 : 581.64 Example 10 PMS 1.7 162.71 : 941.30 Example 11 PMS 1.7 325.31 : 1911.20 Example 12 PMS 3.5 48.81 : 142.48 Example 13 PMS 3.5 81.31 : 242.06 Example 14 PMS 6.9 48.81 : 73.26 Example 15 PMS 6.9 8 1.31 : 122.68 Example 16 KMnO 4 1.7 10 0.41 : 58 1.75 Example 17 HClO 4 1.7 10 0.31:58 0.72 Example 18 Formic acid 1.7 10 0.91:58 1.66 Example 19 PMS 1.7 4.91:32.15 Example 20 PMS 1.7 3 5 7.91:21 10.98

[0220]

[0221] In Table 4 above, the content (wt%) of the surfactant is based on 100 wt% of the oxidized surface-modified carbon nanotubes. At this time, the pKa of HClO4 used as the oxidizing agent is -9, and the pKa of formic acid is 3.75.

[0222]

[0223] Surfactant G / D Ratio Sheet Resistance (Ω / □) Absorbance (@550 nm) A Example 6 SDS 5 1.2 0.8 2 0.4 7 6 14.5 1 Example 7 SDS 5 0.5 0.7 6 0.4 8 17.2 3 Example 8 SDS 4 0.1 0.8 8 0.4 6 3 19.3 5 Example 9 SDS 3 2.1 0.8 4 0.5 2 5 25.6 6 Example 10 SDS 2 3.8 0.9 6 0.5 4 8 3 8.9 6 Example 11 SDS 2 2.2 0.9 9 0.5 6 8 3 9.8 2 Example 12 SDS 5 2.8 0.8 3 0.4 8 15.0 9Example 13SDS46.70.740.51516.84Example 14SDS55.90.880.49416.16Example 15SDS50.10.80.52417.11Example 16SDS30.90.860.53232.16Example 17SDS59.20.960.41014.22Example 18SDS58.60.920.42615.2Example 19SDS59.80.900.46614.05Example 20SDS21.90.990.57239.84

[0224] Referring to Tables 4 and 5 above, it was confirmed that Examples 6 to 20 of the present invention had excellent conductivity due to low sheet resistance values. In addition, it was confirmed that Examples 6 to 20 had excellent dispersibility considering the absorbance value for 550 nm.

[0225]

[0226] Example 21 (using surfactant CTAB)

[0227] 5 g of carbon nanotubes were mixed with CTAB, a surfactant, and homogenized for 20 minutes using a homogenizer. Thereafter, an oxidizing agent was added to the homogenized solution without removing the surfactant, and the mixture was stirred at room temperature for 3 hours to oxidize the carbon nanotubes surface-modified with the surfactant. At this time, 1.7 mmol of surfactant and 48.8 mmol of oxidizing agent were added. The content of carbon nanotubes was 5 parts by weight based on 100 parts by weight of the mixture (homogenized solution).

[0228] Afterwards, the carbon nanotube solution, after the reaction, was filtered using a vacuum filtration device while washing with water. The washing process was continued until the pH of the filtrate became neutral. After washing, the oxidized, surface-modified carbon nanotubes were filtered and dried.

[0229] Afterwards, the surface-modified carbon nanotube powder, the binder CMC, and water were mixed and passed through a high-pressure homogenizer 5 times at a pressure of 700 bar to prepare a carbon nanotube slurry. At this time, based on 100 parts by weight of the carbon nanotube slurry, the content of the surface-modified carbon nanotube was 0.5 parts by weight and the content of the binder was 0.3 parts by weight.

[0230]

[0231] Experimental example

[0232] The content of the surfactant for the oxidized surface-modified carbon nanotubes manufactured using the same method as in Example 1 was calculated and shown in Table 6 below.

[0233] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 1 and are shown in Table 7 below.

[0234]

[0235] Examples 22 to 23 (using surfactant CTAB)

[0236] Regarding the above Example 21, surface-modified carbon nanotubes and CNT slurry subjected to oxidation treatment were manufactured in the same manner as in the above Example 21, except that the content of the surfactant and the content of the oxidizing agent were adjusted as shown in Table 6 below.

[0237] In addition, the content of the surfactant for the oxidized surface-modified carbon nanotubes manufactured using the same method as Example 1 was calculated and shown in Table 6 below.

[0238] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 1 and are shown in Table 7 below.

[0239]

[0240] Oxidizing agent surfactant (mmol) Oxidizing agent (mmol) Surfactant: Oxidizing agent surfactant content (wt%) Example 21 PMS 1.7 48.81 : 281.58 Example 22 PMS 3.5 48.81 : 141.96 Example 23 PMS 6.9 48.81 : 72.38

[0241]

[0242] In Table 6 above, the content (wt%) of the surfactant is based on 100 wt% of the oxidized surface-modified carbon nanotubes.

[0243]

[0244] Surfactant G / D ratio Sheet resistance (Ω / □) Absorbance (@550 nm) A Example 21 CTAB 4 6.8 0.7 9 0.4 6 16.0 5 Example 22 CTAB 5 2.2 0.8 2 0.4 7 1 14.5 8 Example 23 CTAB 5 3.1 0.8 6 0.4 8 1 4.2 3

[0245]

[0246] Referring to Tables 6 and 7 above, it was confirmed that Examples 21 to 23 of the present invention had excellent conductivity due to low sheet resistance values. In addition, it was confirmed that Examples 21 to 23 had excellent dispersibility considering the absorbance value for 550 nm.

[0247]

[0248] Comparative Examples 7 to 11

[0249] As shown in Table 8 below, Comparative Example 7 used carbon nanotubes without using a surfactant or oxidizing agent, and prepared a CNT slurry using the same method as Example 6.

[0250] Comparative Examples 8 and 9 produced CNTs and CNT slurries treated with an oxidizing agent in the same manner as Example 6, except that only an oxidizing agent was used and the content of the oxidizing agent was adjusted as shown in Table 8 below.

[0251] Comparative Examples 10 and 11 were prepared by oxidizing surface-modified carbon nanotubes and CNT slurries in the same manner as in Example 6, except that the content of surfactant (SDS), the type of oxidizing agent, and the content of oxidizing agent were adjusted as shown in Table 8 below.

[0252]

[0253] Experimental example

[0254] The content of surfactant for the carbon nanotubes manufactured using the same method as in Example 1 was calculated and shown in Table 8 below.

[0255] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 1 and are shown in Table 9 below.

[0256]

[0257] Oxidizing agent surfactant (mmol) Oxidizing agent (mmol) Surfactant: Oxidizing agent surfactant content (wt%) Comparative Example 7-----Comparative Example 8 PMS-48.8--Comparative Example 9 PMS-81.3--Comparative Example 10 H2SO4 1.7 100.21 : 580.36 Comparative Example 11 NaOCl 1.7 100.81 : 580

[0258]

[0259] In Table 9 above, the content (wt%) of the surfactant is based on 100 wt% of the oxidized surface-modified carbon nanotubes.

[0260]

[0261] Surfactant G / D ratio Sheet resistance (Ω / □) Absorbance (@550 nm) A Comparative Example 7 - 68.6 10.36 3 11.41 Comparative Example 8 - 64.5 1.0 6 0.4 1 7 12.15 Comparative Example 9 - 61.6 1.2 2 0.4 2 13.18 Comparative Example 10 SDS 5 1.2 1.10 4 4 12.98 Comparative Example 11 SDS 4 5.5 1.2 1 0.4 3 4 0.08

[0262]

[0263] Referring to Table 8 and Table 9 above, it was confirmed that in Comparative Examples 7 to 11, the surface resistance value was higher and the conductivity was inferior compared to Examples 1 to 23 of the present invention described above.

[0264]

[0265] Surface-modified carbon nanotubes treated with organic acids

[0266] Acetic acid, citric acid, caproic acid, and suberic acid were prepared as organic acids.

[0267]

[0268] Example 24

[0269] 5 g of carbon nanotubes were mixed with SDS, a surfactant, and citric acid, an organic acid, and homogenized for 20 minutes using a homogenizer. The homogenized solution was then stirred at 40°C for 8 hours, and the carbon nanotubes surface-modified with the surfactant were treated with the organic acid. At this time, 1.7 mmol of the surfactant and 10 mmol of the organic acid were added. The content of carbon nanotubes was 5 parts by weight based on 100 parts by weight of the mixed solution (homogenized solution).

[0270] Afterwards, the carbon nanotube solution, after the reaction, was filtered using a vacuum filtration device while washing with water. The washing process was continued until the pH of the filtrate became neutral. After washing, the oxidized, surface-modified carbon nanotubes were filtered and dried.

[0271] Afterwards, the surface-modified carbon nanotube powder, the binder CMC, and water were mixed and passed through a high-pressure homogenizer 5 times at a pressure of 700 bar to prepare a carbon nanotube slurry. At this time, based on 100 parts by weight of the carbon nanotube slurry, the content of the surface-modified carbon nanotube was 0.5 parts by weight and the content of the binder was 0.3 parts by weight.

[0272]

[0273] Experimental example

[0274] In the same manner as in Example 1, the content of surfactant and organic acid for surface-modified carbon nanotubes treated with organic acid were calculated and shown in Table 10 below.

[0275] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 1 and are shown in Table 11 below.

[0276]

[0277] Examples 25 to 40

[0278] For the above Example 24, surface-modified carbon nanotubes and CNT slurries treated with organic acids were manufactured in the same manner as in Example 24, except that the type and content of the surfactant, the type and content of the organic acid were adjusted as shown in Table 10 below. At this time, CTAB was used as the surfactant in Examples 31 to 33.

[0279] In addition, the content of surfactant and organic acid for surface-modified carbon nanotubes treated with organic acid were calculated using the same method as in Example 1 and are shown in Table 10 below.

[0280] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 1 and are shown in Table 11 below.

[0281]

[0282] Organic acid surfactant (mmol) Organic acid (mmol) Surfactant: Organic acid Organic acid content (wt%) Surfactant content (wt%) Example 24 Citric acid SDS 1.7 10 1 : 6 < 0.2 2.66 Example 25 Citric acid SDS 1.7 5 0 1 : 29 < 0.2 2.73 Example 26 Citric acid SDS 1.7 10 0 1 : 59 < 0.2 2.68 Example 27 Acetic acid SDS 1.7 3 0 0 1 : 176 0.3 1 2.72 Example 28 Citric acid SDS 1.7 3 0 0 1 : 176 0.3 4 2.63 Example 29 Citric acid SDS 1.7 6 0 0 1 : 35 20.7 7 2.20 Example 30 Citric acid SDS 1.7 1,00 0 1 : 5880.941.89 Example 31 Citric acid CTAB 1.73001: 1761.271.74 Example 32 Citric Acid CTAB 1.76001: 3521.520.89 Example 33 Citric Acid CTAB 1.71,0001: 5881.880.72 Example 34 Citric acid SDS 1.71,2001: 7061.181.65 Example 35 Citric acid SDS 1.71,5001: 8821.321.34 Example 36 Suberic acid SDS 1.71,2001: 7060.42.10 Example 37 Caproic acid SDS 3.51,0001: 2861.322.45 Example 38 Suberic acid SDS 1.7 10 1:06<0.2 1.66 Example 39 Caproic acid SDS 1.7 30 0 1 : 176<0.2 2.42 Example 40 Suberic acid SDS 1.7 30 0 1 : 176<0.2 2.34

[0283]

[0284] In Table 10 above, the content (wt%) of organic acid and the content (wt%) of surfactant are based on 100 wt% of the surface-modified carbon nanotube treated with organic acid.

[0285]

[0286] Surfactant G / D Ratio Sheet Resistance (Ω / □) Absorbance (@550 nm) A Example 24 SDS 57.10.8 9 0.43 3 25.49 Example 25 SDS 56.50.8 4 0.43 6 25.88 Example 26 SDS 56.20.8 5 0.43 5 25.62 Example 27 SDS 56.80.9 2 0.42 5 24.22 Example 28 SDS 57.50.8 2 0.43 6 23.89 Example 29 SDS 56.50.8 9 0.42 0 25.08 Example 30 SDS 57.10.8 8 0.41 5 23.46 Example 31 CTAB 56.20.8 5 0.43 3 19. 55 Example 32 CTAB 56.90.980.41 114.20 Example 33 CTAB 57.80.990.406 14.01 Example 34 SDS 57.50.900.402 20.92 Example 35 SDS 58.60.93 0.400 19.86 Example 36 SDS 56.40.94 0.400 16.21 Example 37 SDS 55.80.84 0.45 129.34 Example 38 SDS 57.00.980.408 19.66 Example 39 SDS 55.40.96 0.41 223.25 Example 40 SDS 56.90.94 0.41 8 24.61

[0287]

[0288] Referring to Tables 10 and 11 above, it was confirmed that Examples 24 to 40 of the present invention had low sheet resistance values ​​and thus excellent conductivity. In addition, it was confirmed that Examples 24 to 40 had excellent dispersibility when considering the absorbance value for 550 nm.

[0289]

[0290] Comparative Examples 12 and 13

[0291] As shown in Table 12 below, Comparative Examples 12 and 13 used only organic acids and adjusted the type and content of organic acids as shown in Table 12 below, and CNTs and CNT slurries treated with organic acids were prepared in the same manner as in Example 24.

[0292]

[0293] Experimental example

[0294] Using the same method as Example 1, the contents of surfactant and organic acid for the manufactured carbon nanotubes were calculated and shown in Table 12 below.

[0295] In addition, the G / D ratio, surface resistance, absorbance, and A value were measured using the same method as in Example 1 and are shown in Table 13 below.

[0296]

[0297] Organic acid surfactant (mmol) Organic acid (mmol) Surfactant: Organic acid Organic acid content Surfactant content (wt%) Comparative example 12 Caproic acid-10-<0.2- Comparative example 13 Suberic acid-10-<0.2-

[0298]

[0299] In Table 12 above, the content (wt%) of organic acid and the content (wt%) of surfactant are based on 100 wt% of the surface-modified carbon nanotube treated with organic acid.

[0300]

[0301] G / D ratio surface resistance (Ω / □) absorbance (@550 nm) A Comparative example 1255.8 1.10.39 211.39 Comparative example 1356.31.08 0.38 011.58

[0302]

[0303] Referring to Tables 12 and 13 above, it was confirmed that in Comparative Examples 12 and 13, the surface resistance value was higher and the conductivity was inferior compared to Examples 1 to 40 of the present invention described above.

[0304]

[0305] Referring to the experimental data described above, it can be seen that the surface-modified carbon nanotube according to one embodiment of the present invention implements excellent conductivity and improved dispersibility.

Claims

1. Carbon nanotubes; and A surfactant adsorbed on the surface of the carbon nanotube; Surface-modified carbon nanotubes satisfying the following mathematical formula 1 when subjected to thermogravimetric analysis under temperature conditions of 30°C or higher and 900°C or lower: [Mathematical formula 1] 14.0 % ≤ A ≤ 40.0 % In the above mathematical expression 1, A is a value expressed as a percentage of the sum of the areas of peaks included in the range of 400°C to 600°C among the total areas of peaks corresponding to carbon nanotubes included in the range of 400°C to 800°C, obtained by separating the overlapping peaks of the thermal decomposition differential curve of the surface-modified carbon nanotubes.

2. In paragraph 1, A surface-modified carbon nanotube, wherein the surfactant comprises at least one of anionic surfactant and cationic surfactant.

3. In paragraph 1, A surface-modified carbon nanotube, wherein the molecular weight of the surfactant is 200 g / mol or more and 500 g / mol or less.

4. In paragraph 1, The above surface-modified carbon nanotube has a G / D ratio in the Raman spectrum of 20 or more and 60 or less, The above G is 1560 to 1600 cm in the Raman spectrum. -1 is the maximum peak intensity within the range of , and D is 1310 to 1360 cm -1 Surface-modified carbon nanotube having a maximum peak intensity within a range of .

5. In paragraph 1, The surface-modified carbon nanotube is a surface-modified carbon nanotube containing an oxidizing agent.

6. In paragraph 5, A surface-modified carbon nanotube, wherein the oxidizing agent comprises a potassium-based oxidizing agent having an ionization constant of -9 or more and 4 or less.

7. In paragraph 5, The surface-modified carbon nanotube containing the above oxidizing agent is a reaction product of a mixture containing the carbon nanotube, a surfactant and an oxidizing agent, The above mixture is a surface-modified carbon nanotube having a molar ratio of the surfactant and the oxidizer of 1:5 to 1:

200.

8. In paragraph 1, The surface-modified carbon nanotube above is a surface-modified carbon nanotube comprising an organic acid containing at least one carboxyl group.

9. In paragraph 8, A surface-modified carbon nanotube, wherein the carbon number of the organic acid is 1 to 7.

10. In paragraph 8, A surface-modified carbon nanotube having an organic acid content of 0.3 wt% or more and 1.3 wt% or less.

11. In paragraph 8, The surface-modified carbon nanotube containing the organic acid is a reaction product of a mixture containing the carbon nanotube, a surfactant, and an organic acid, The above mixture is a surface-modified carbon nanotube having a molar ratio of the surfactant and the organic acid of 1:100 to 1:

600.

12. Carbon nanotubes; and A surfactant bonded to the surface of the carbon nanotube; Surface-modified carbon nanotubes having a content of the surfactant of 0.5 wt% or more and 4.0 wt% or less.

13. A dispersion containing surface-modified carbon nanotubes according to claim 1 or 12.

14. In paragraph 13, A dispersion having a surface resistance value of 0.5 Ω / □ or more and less than 1 Ω / □ when coated with a thickness of 10 ㎛.

15. In paragraph 13, A dispersion having an absorbance of 0.4 or more for light having a wavelength of 550 nm.

16. A secondary battery comprising an electrode including a surface-modified carbon nanotube according to claim 1 or 12.

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