Single-walled carbon nanotube, single-walled carbon nanotube dispersion, and electrode and secondary battery comprising same

Abstract

The present invention provides: a single-walled carbon nanotube having a weight change of 5% or less at 40 ℃ to 550 ℃ when the temperature is increased at 10 ℃ / min using a thermogravimetric analyzer, wherein the content of the sulfur element is less than 0.1 wt% on the basis of the total weight of elements measured by using an elemental analyzer; a single-walled carbon nanotube dispersion; and an electrode and a secondary battery comprising same.

Description

Single-walled carbon nanotubes, and single-walled carbon nanotube dispersions, and electrodes and secondary batteries containing the same

[0001] The present invention relates to single-walled carbon nanotubes, single-walled carbon nanotube dispersions, electrodes and secondary batteries comprising the same.

[0002]

[0003] Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy sources is increasing. A representative example of an electrochemical device that utilizes this electrochemical energy is the secondary battery, and its application areas are expanding. A secondary battery is a battery that can be used repeatedly through a discharge process, in which chemical energy is converted into electrical energy, and a charge process, in the reverse direction. A secondary battery may include a positive electrode, a negative electrode, an electrolyte, and a separator. The positive and negative electrodes may generally include an electrode current collector and an electrode active material layer formed on the electrode current collector. The electrode active material layer can be manufactured by applying an electrode slurry composition containing an electrode active material, a conductive material, a binder, etc., to the electrode current collector, drying the composition, and then rolling the electrode slurry.

[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 are not very effective in improving electrical conductivity. Therefore, they must be used in excessive amounts to achieve sufficient effects. This reduces the electrode active material content and, consequently, battery capacity.

[0005] To improve these problems, active efforts are being made to apply highly conductive carbon nanotubes (CNTs) as a challenge material.

[0006] However, due to the nature of carbon nanotubes, their dispersibility within the slurry was poor, which lowered the manufacturing process of the secondary battery, and as the cycle of the secondary battery progressed, the conductivity decreased, which resulted in a problem of lowering the performance of the secondary battery.

[0007]

[0008] The present invention provides a single-walled carbon nanotube having improved electrical conductivity, structural stability, dispersibility, and storage stability, and provides an electrode and a secondary battery containing the single-walled carbon nanotube having improved battery performance.

[0009]

[0010] A single-walled carbon nanotube according to the present invention may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0011] In one embodiment of the present invention, the weight change at 40°C to 550°C may be 2% or less.

[0012] In one embodiment of the present invention, the single-walled carbon nanotube may have a thermal decomposition start temperature of 550°C or higher as measured by the thermogravimetric analyzer.

[0013] In one embodiment of the present invention, the single-walled carbon nanotube may have a content of residue after completion of thermal decomposition measured by the thermogravimetric analyzer of 1% or less.

[0014] In one embodiment of the present invention, the sum of the contents of oxygen elements and nitrogen elements relative to the total weight of elements measured by the elemental analyzer may be 0.3 wt% to 2.0 wt%.

[0015] In one embodiment of the present invention, the average diameter (D) of the single-walled carbon nanotube 50) may be greater than 1 nm and less than or equal to 5 nm.

[0016] A single-walled carbon nanotube dispersion according to the present invention comprises a solvent, a dispersant, and a single-walled carbon nanotube, wherein the single-walled carbon nanotube has a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element is less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0017] In one embodiment of the present invention, the content of the single-walled carbon nanotubes relative to the total weight of the single-walled carbon nanotube dispersion may be 0.01 wt% to 15.00 wt%.

[0018] In one embodiment of the present invention, the initial viscosity of the single-walled carbon nanotube dispersion at room temperature may be 1,000 cP to 10,000 cP, and the viscosity change rate according to the following calculation formula 1 may be 30% or less.

[0019] [Calculation Formula 1]

[0020] Viscosity change rate (%) = [(viscosity after one month - initial viscosity) / initial viscosity] × 100

[0021] In one embodiment of the present invention, the BET surface area of ​​the single-walled carbon nanotube is 1,000 m 2 / g to 2,000 m 2 / g may be.

[0022] In one embodiment of the present invention, the length of the single-walled carbon nanotube may be from 10 nm to 3,000 nm.

[0023] In one embodiment of the present invention, the average diameter (D) of the single-walled carbon nanotube 50 ) can be 0.5 nm to 25 nm.

[0024] In one embodiment of the present invention, the pore volume of the single-walled carbon nanotube may be 0.1 cc / g to 1.5 cc / g.

[0025] In one embodiment of the present invention, when the single-walled carbon nanotube is measured by XRD (X-ray diffraction) and the section of 2θ = 14° to 30° is used as the base line, the peak area around 2θ = 26° may be 70% or more of the total peak area at 2θ = 14° to 30°.

[0026] The negative electrode according to the present invention comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0027] A secondary battery according to the present invention comprises an electrode, a separator, and an electrolyte, wherein the electrode comprises an electrode active material, a binder, and a conductive material, and the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0028] The single-walled carbon nanotube according to the present invention includes an oxygen element and a carbon element, and the weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0029] In one embodiment of the present invention, the content of the oxygen element relative to the total weight of elements measured by the elemental analyzer may be 1 wt% to 2 wt%.

[0030] In one embodiment of the present invention, the content of the carbon element relative to the total weight of elements measured by the elemental analyzer may be 90 wt% to 94 wt%.

[0031] A single-walled carbon nanotube dispersion according to the present invention comprises a solvent, a dispersant, and a single-walled carbon nanotube, wherein the single-walled carbon nanotube comprises an oxygen element and a carbon element, and the weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0032] In one embodiment of the present invention, the content of the single-walled carbon nanotubes relative to the total weight of the single-walled carbon nanotube dispersion may be 0.01 wt% to 15.00 wt%.

[0033] In one embodiment of the present invention, the initial viscosity of the single-walled carbon nanotube dispersion at room temperature may be 1,000 cP to 10,000 cP.

[0034] An electrode according to the present invention comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube comprises an oxygen element and a carbon element, and a weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0035] A secondary battery according to the present invention comprises an electrode, a separator, and an electrolyte, wherein the electrode comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube comprises an oxygen element and a carbon element, and a weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0036] The single-walled carbon nanotube according to the present invention has a BET surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the following equation 1.

[0037] [Formula 1]

[0038] 12 ≤ X / (100-Y) ≤ 20

[0039] In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

[0040] In one embodiment of the present invention, the value of the above formula 1 may be 14.5 to 17.5.

[0041] In one embodiment of the present invention, the content of the nickel element may be less than 7 mg / kg.

[0042] In one embodiment of the present invention, the content of iron element measured by the inductively coupled plasma optical emission spectrometry may be less than 200 mg / kg.

[0043] In one embodiment of the present invention, the single-walled carbon nanotube has a bulk density of 5 kg / m 3 10 kg / m 3 , and can satisfy the following equation 2.

[0044] [Formula 2]

[0045] 1.0 ≤ TD / BD < 1.3

[0046] In the above equation 2, the BD is the bulk density of the single-walled carbon nanotube (unit: kg / m 3 ) is a number representing the tap density of the single-walled carbon nanotube (unit: kg / m). 3 ) is a number representing .

[0047] In one embodiment of the present invention, the single-walled carbon nanotube may have a powder resistance of 0.001 ohm·cm or less at a rolling density of 1 g / cc or more.

[0048] In one embodiment of the present invention, the single-walled carbon nanotube has an I measured by Raman spectrum. G / I D It can be 35 to 150 days.

[0049] A single-walled carbon nanotube dispersion according to the present invention comprises a solvent, a dispersant, and a single-walled carbon nanotube, wherein the single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the following equation 1.

[0050] [Formula 1]

[0051] 12 ≤ X / (100-Y) ≤ 20

[0052] In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

[0053] In one embodiment of the present invention, the content of the single-walled carbon nanotubes relative to the total weight of the single-walled carbon nanotube dispersion may be 0.01 wt% to 15.00 wt%.

[0054] In one embodiment of the present invention, the initial viscosity of the single-walled carbon nanotube dispersion at room temperature may be 1,000 cP to 10,000 cP.

[0055] The negative electrode according to the present invention comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the following equation 1.

[0056] [Formula 1]

[0057] 12 ≤ X / (100-Y) ≤ 20

[0058] In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

[0059] A secondary battery according to the present invention comprises an electrode, a separator, and an electrolyte, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the following equation 1.

[0060] [Formula 1]

[0061] 12 ≤ X / (100-Y) ≤ 20

[0062] In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

[0063]

[0064] The single-walled carbon nanotubes according to the present invention can improve electrical conductivity by reducing carbon impurities and suppressing viscosity increase effects due to sulfur element by satisfying specific ranges of thermogravimetric change values ​​and sulfur element content, and can improve storage stability by minimizing viscosity increase over time when manufactured as a dispersion. In addition, when the single-walled carbon nanotubes are used as a conductive material, structural stability and electron transfer paths are improved, thereby improving electrical conductivity, thereby improving the performance of secondary batteries.

[0065] The single-walled carbon nanotubes, by satisfying the above formula 1, have excellent powder resistance due to their high specific surface area and improved electrical conductivity while reducing the content of nickel as an impurity, thereby improving the performance of secondary batteries. In addition, the dispersibility and dispersion stability can be improved when manufactured into a dispersion. In addition, the single-walled carbon nanotubes have a high thermal decomposition initiation temperature and can have improved crystallinity. In addition, the dispersion containing the single-walled carbon nanotubes can have improved storage stability by minimizing the increase in viscosity over time.

[0066] The single-walled carbon nanotubes described above can have increased structural stability and improved dispersibility within a dispersion by satisfying a specific weight ratio of oxygen and carbon elements. Furthermore, the electron transfer path is improved, thereby enhancing electrical conductivity, thereby improving the performance of a secondary battery. Furthermore, the single-walled carbon nanotubes have a high thermal decomposition initiation temperature and can have improved crystallinity. Furthermore, impurities can be significantly reduced through a purification process under room temperature conditions, thereby enabling economical production. Furthermore, a dispersion containing the single-walled carbon nanotubes can have improved storage stability by minimizing viscosity increases over time.

[0067]

[0068] The structural or functional descriptions of the embodiments disclosed in this specification or application are merely illustrative for the purpose of explaining embodiments according to the technical idea of ​​the present invention, and the embodiments according to the technical idea of ​​the present invention can be implemented in various forms other than the embodiments disclosed in this specification or application, and the technical idea of ​​the present invention is not construed as being limited to the embodiments described in this specification or application.

[0069] In addition, when a component is referred to as "including" in this specification or application, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated. In addition, all numerical ranges indicating physical property values, dimensions, etc. of the components described in this specification or application should be understood to be modified by the term "about" in all cases unless otherwise specified. In addition, "ppm" in this specification or application means based on weight. In addition, the description of "A and / or B" in this specification or application means "A, B, or, A and B."

[0070]

[0071] Hereinafter, single-walled carbon nanotubes and single-walled carbon nanotube dispersions according to the present invention, and electrodes and secondary batteries including the same will be described.

[0072]

[0073] The single-walled carbon nanotubes described above can be used as a conductive material. The single-walled carbon nanotubes can be manufactured using a catalyst. To manufacture high-purity single-walled carbon nanotubes and control the diameter of the single-walled carbon nanotubes by adjusting the size of the catalyst, a large amount of elemental sulfur can be used as a promoter. However, it is difficult to sufficiently remove elemental sulfur during the purification process of the single-walled carbon nanotubes. If a large amount of elemental sulfur remains in the single-walled carbon nanotubes, the viscosity of the dispersion containing the single-walled carbon nanotubes may increase significantly over time, resulting in a problem of significantly reduced storage stability. If a small amount of elemental sulfur is used as a promoter during the manufacture of single-walled carbon nanotubes to reduce the content of residual elemental sulfur, the size of the catalyst may increase significantly, making it difficult to control the diameter of the single-walled carbon nanotubes. In addition, carbonaceous impurities may increase, making it difficult to manufacture high-purity single-walled carbon nanotubes. In this way, the factors of high-purity single-walled carbon nanotubes with reduced carbon impurities and improved storage stability of single-walled carbon nanotubes can be achieved by satisfying a specific range of thermogravimetric change values ​​and a range of sulfur element content.

[0074] The single-walled carbon nanotube may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% based on the total weight of elements measured by an elemental analyzer. The single-walled carbon nanotube may have a weight change according to temperature change measured by a thermogravimetric analyzer. The temperature change may be measured while heating at 10°C / min intervals in a temperature range of 40°C to 1,000°C under a nitrogen atmosphere.

[0075] The temperature at which thermal decomposition of the single-walled carbon nanotube begins can be measured by the thermogravimetric analyzer. By measuring the weight change of the single-walled carbon nanotube according to the temperature change, the purity of the single-walled carbon nanotube can be evaluated.

[0076] The single-walled carbon nanotube may have a weight change of 2% or less, 1.9% or less, 1.8% or less, 1.7% or less, or 1.5% or less when measured by the thermogravimetric analyzer at a temperature of 40° C. to 300° C. The single-walled carbon nanotube may have a weight change of 2% or less, 1.5% or less, 1.3% or less, 1.2% or less, or 1% or less when measured by the thermogravimetric analyzer at a temperature of 300° C. to 550° C. The single-walled carbon nanotube may have a weight change of 2% or less, 1.98% or less, 1.97% or less, 1.96% or less, or 1.95% or less when measured by the thermogravimetric analyzer at a temperature of 40° C. to 550° C. The single-walled carbon nanotube may have a thermal decomposition start temperature measured by the thermogravimetric analyzer of 550°C or higher, 570°C or higher, 590°C or higher, 500°C to 700°C, 520°C to 700°C, 530°C to 650°C, or 550°C to 600°C. The thermal decomposition start temperature may be derived from a peak point obtained by differentiating a temperature-weight graph measured by the thermogravimetric analyzer.

[0077] The above single-walled carbon nanotube may have a content of residue after completion of thermal decomposition measured by the thermogravimetric analyzer of 1% or less, 0.6% or less, 0.4% or less, 0.2% or less, 0.1% or less, 0.05% or less, 0.03% or less, 0.02% or less, or 0.01% or less.

[0078] In the above range, when the single-walled carbon nanotube is used as a conductive material, the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved due to the improved electrical conductivity.

[0079] The above single-walled carbon nanotubes may have a sulfur element content of less than 0.1 wt%, less than 0.08 wt%, less than 0.07 wt%, or less than 0.05 wt% relative to the total weight of elements measured by the elemental analyzer. Preferably, the single-walled carbon nanotubes may not contain the sulfur element. When the above range is satisfied, the viscosity increase over time of the dispersion including the single-walled carbon nanotubes may be minimized, thereby improving the storage stability.

[0080] The above single-walled carbon nanotube may have an oxygen element content of 1.5 wt% or less, 1.2 wt% or less, 1.0 wt% or less, 0.5 wt% or less, 0.45 wt% or less, 0.4 wt% or less, 0.35 wt% or less, or 0.4 wt% or less relative to the total weight of elements measured by the above elemental analyzer.

[0081] The above single-walled carbon nanotube may have a nitrogen element content of 0.01 wt% to 1 wt%, 0.01 wt% to 0.5 wt%, 0.01 wt% to 0.3 wt%, or 0.01 wt% to 0.25 wt% relative to the total weight of elements measured by the above elemental analyzer.

[0082] The above single-walled carbon nanotube may have a sum of the oxygen element and the nitrogen element content relative to the total weight of elements measured by the elemental analyzer of 0.3 wt% to 2.0 wt%, 0.5 wt% to 2.0 wt%, 0.7 wt% to 2.0 wt%, or 1.0 wt% to 2.0 wt%. The oxygen element and the nitrogen element may participate in hydrogen bonding, and when the above range is satisfied, the dispersibility of the single-walled carbon nanotube in the dispersion may be improved.

[0083] The single-walled carbon nanotube may have a carbon element content of 90 wt% to 99 wt%, 91 wt% to 99 wt%, 92 wt% to 99 wt%, 93 wt% to 99 wt%, 94 wt% to 99 wt%, 95 wt% to 99 wt%, 95.5 wt% to 99 wt%, 96 wt% to 99 wt%, 96.5 wt% to 99 wt%, or 97 wt% to 99 wt% relative to the total weight of elements measured by the elemental analyzer.

[0084] The above single-walled carbon nanotube may have a hydrogen element content of 1 wt% or less, 0.8 wt% or less, 0.6 wt% or less, 0.5 wt% or less, or 0 wt% (excluding) to 0.5 wt% relative to the total weight of elements measured by the above elemental analyzer.

[0085] The single-walled carbon nanotube may contain nickel element. The nickel element may be an impurity generated during the process of manufacturing and / or purifying the single-walled carbon nanotube. The nickel element may be measured using inductively coupled plasma optical emission spectrometry (ICP-OES) under the following measurement conditions when the single-walled carbon nanotube is dissolved in a solution containing an acid.

[0086] [Measurement conditions]

[0087] - Device: Agilent 5110 SVDV

[0088] - RF power: 1.2 kW

[0089] - Nebulizer flow: 0.7 L / min

[0090] - Plasma flow: 12 L / min

[0091] - Aux flow: 1 L / min

[0092] - Read time: 5 sec

[0093] The content of the above nickel element may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg.

[0094] The BET surface area of ​​the above single-walled carbon nanotube is 1,200 m 2 / g to 1,800 m 2 / g, 1,200 m 2 / g to 1,700 m 2 / g, 1,300 m 2 / g to 1,700 m 2 / g, 1,400 m 2 / g to 1,700 m 2 / g, or 1,500 m 2 / g to 1,700 m 2 / g. The above BET specific surface area can be measured from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.

[0095] In the past, multi-walled carbon nanotubes (MWCNTs) with a large number of bonds forming the walls were used to improve electrical conductivity. However, when the multi-walled carbon nanotubes were used in secondary batteries, their relatively short length did not ensure sufficient electrical conductivity between active materials, and there was a problem that the electrical conductivity decreased as the cycle progressed. To solve the above problem, single-walled carbon nanotubes that were relatively longer than the length of the multi-walled carbon nanotubes were used. However, due to the relatively long length, the dispersibility was reduced, which lowered the coatability and processability, and there was a problem that the carbon nanotubes were not evenly distributed within the electrode active material layer. Furthermore, when the oxygen content in the single-walled carbon nanotubes was increased to improve the dispersibility, there was a problem that the electrical conductivity was reduced, which deteriorated the performance of the secondary battery.

[0096] The single-walled carbon nanotubes above include oxygen elements and carbon elements, and the weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95. The single-walled carbon nanotubes having the weight ratio of the oxygen element and the carbon element according to the measurement method means a weight ratio at which the single-walled carbon nanotubes can sufficiently secure electrical conductivity between active materials, and at the same time, it can have meaning as an indicator that the dispersibility of the single-walled carbon nanotubes can be improved, thereby securing coatability and processability.

[0097] The weight ratio of the oxygen element:carbon element may be 1:50 to 1:90, 1:50 to 1:85, 1:53 to 1:85, 1:55 to 1:85, or 1:55 to 1:83. When the above range is satisfied, structural stability may be increased, dispersibility within a dispersion may be improved, and electrical conductivity may be improved when used as a conductive material.

[0098] The content of the oxygen element relative to the total weight of the elements measured by the elemental analyzer may be 1 wt% to 2 wt%, 1 wt% to 1.9 wt%, 1 wt% to 1.85 wt%, 1 wt% to 1.83 wt%, or 1 wt% to 1.81 wt%. The content of the carbon element relative to the total weight of the elements measured by the elemental analyzer may be 90 wt% to 94 wt%, 90 wt% to 93.8 wt%, 90 wt% to 93.6 wt%, 90 wt% to 93.4 wt%, 90 wt% to 93.2 wt%, or 90.2 wt% to 93.2 wt%.

[0099] The single-walled carbon nanotube may contain a nitrogen element. The nitrogen element may be measured by the elemental analyzer. The content of the nitrogen element relative to the total weight of the elements measured by the elemental analyzer may be 0.01 wt% to 1 wt%, 0.01 wt% to 0.5 wt%, 0.01 wt% to 0.3 wt%, or 0.01 wt% to 0.25 wt%.

[0100] The single-walled carbon nanotube may contain a hydrogen element. The single-walled carbon nanotube may not contain the hydrogen element. The hydrogen element may be measured by the elemental analyzer. The content of the hydrogen element relative to the total weight of the elements measured by the elemental analyzer may be 1 wt% or less, 0.8 wt% or less, 0.6 wt% or less, 0.5 wt% or less, or 0 wt% (excluding) to 0.5 wt%.

[0101] The above single-walled carbon nanotube has a BET surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the following equation 1.

[0102] [Formula 1]

[0103] 12 ≤ X / (100-Y) ≤ 20

[0104] In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

[0105] Nickel element, which is an impurity of the single-walled carbon nanotube, is difficult to sufficiently remove during the purification process. If the content of nickel element, which is an impurity, in the single-walled carbon nanotube increases, the purity of the single-walled carbon nanotube may decrease, and even if the BET specific surface area increases, the electrical conductivity may not improve. In addition, even if the content of nickel element decreases and the purity of the single-walled carbon nanotube improves, the BET specific surface area may decrease, and thus the electrical conductivity may not improve. The relationship of the above Equation 1 was derived by combining the factors of the content of nickel element and the BET specific surface area in this relationship, and by adjusting the content of nickel element and the BET specific surface area based on the above Equation 1, the electrical conductivity of the single-walled carbon nanotube can be improved more efficiently.

[0106] The value of the above formula 1 may be 14.5 to 17.5, 15.0 to 17.5, 15.5 to 17.5, 15.7 to 16.7, 15.8 to 16.7, 15.8 to 16.6, or 15.8 to 16.5. In the above range, when the single-walled carbon nanotube is used as a conductive material, the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery may be improved due to the improved electrical conductivity.

[0107] The BET surface area of ​​the above single-walled carbon nanotube is 1,200 m 2 / g to 1,800 m 2 / g, 1,200 m 2 / g to 1,700 m 2 / g, 1,300 m 2 / g to 1,700 m 2 / g, 1,400 m 2 / g to 1,700 m 2 / g, or 1,500 m 2 / g to 1,700 m 2 / g. The above BET specific surface area can be measured from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.

[0108] The nickel element may be an impurity generated during the process of manufacturing and / or refining the single-walled carbon nanotube. The nickel element may be measured using inductively coupled plasma optical emission spectrometry (ICP-OES) under the following measurement conditions when the single-walled carbon nanotube is dissolved in a solution containing an acid.

[0109] [Measurement conditions]

[0110] - Device: Agilent 5110 SVDV

[0111] - RF power: 1.2 kW

[0112] - Nebulizer flow: 0.7 L / min

[0113] - Plasma flow: 12 L / min

[0114] - Aux flow: 1 L / min

[0115] - Read time: 5 sec

[0116] The content of the nickel element may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg. The content of the iron element included in the single-walled carbon nanotube may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg. The content of the cobalt element included in the single-walled carbon nanotube may be less than 10 mg / kg, less than 8 mg / kg, less than 6 mg / kg, less than 4 mg / kg, or less than 2 mg / kg. The content of the chromium element included in the single-walled carbon nanotube may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg. The content of the copper element contained in the single-walled carbon nanotube may be less than 10 mg / kg, less than 8 mg / kg, less than 6 mg / kg, less than 5 mg / kg, or less than 2 mg / kg. The content of the manganese element contained in the single-walled carbon nanotube may be less than 10 mg / kg, less than 5 mg / kg, less than 3 mg / kg, less than 2 mg / kg, or less than 1 mg / kg. The content of the zinc element contained in the single-walled carbon nanotube may be less than 50 mg / kg, less than 40 mg / kg, less than 30 mg / kg, less than 25 mg / kg, or less than 18 mg / kg. The single-walled carbon nanotube may have a bulk density of 10 kg / m. 3 Below 8 kg / m 3 Below 7 kg / m 3 or less, or 5 kg / m 3 More than 10 kg / m 3 It could be as follows:

[0117] The above single-walled carbon nanotube has a bulk density of 5 kg / m. 310 kg / m 3 , and can satisfy the following equation 2.

[0118] [Formula 2]

[0119] 1.0 ≤ TD / BD < 1.3

[0120] In the above equation 2, the BD is the bulk density of the single-walled carbon nanotube (unit: kg / m 3 ) is a number representing the tap density of the single-walled carbon nanotube (unit: kg / m). 3 ) is a number representing .

[0121] The above equation 2 may be an indicator representing the dispersibility and dispersion stability of the single-walled carbon nanotube.

[0122] The above formula 2 may be 1.0 to 1.25, 1.0 to 1.2, 1.0 to 1.15, 1.0 to 1.1, or 1.0 to 1.05. When the above range is satisfied, the dispersibility and dispersion stability of the single-walled carbon nanotube in the dispersion containing the single-walled carbon nanotube may be improved.

[0123] The above bulk density can be calculated by filling the single-walled carbon nanotube into a glass cylinder of known weight, measuring the weight, and using the following equation 3.

[0124] [Formula 3]

[0125] Bulk density (kg / m) 3 ) = Single-walled carbon nanotube weight (kg) / Single-walled carbon nanotube volume (m 3 )

[0126] The tap density is determined by placing a glass cylinder on a scale, zeroing it, tilting the cylinder, and placing the single-walled carbon nanotubes therein. The volume is measured by aligning the height of the single-walled carbon nanotubes with the eye level, reading the scale, and then placing the cylinder on the scale to measure the weight. Afterwards, the cylinder is gently tapped approximately 100 times on the floor, reading the scale, and measuring the volume again. This can be calculated according to Equation 4 below.

[0127] [Formula 4]

[0128] Tap density (kg / m) 3 ) = Single-wall carbon nanotube weight (kg) / Single-wall carbon nanotube volume (m) after 100 taps 3 )

[0129] The above single-walled carbon nanotube has a tap density of 10 kg / m 3 Below 8 kg / m 3 Below 7 kg / m 3 or less, or 5 kg / m 3 More than 10 kg / m 3 It could be as follows:

[0130] The single-walled carbon nanotube may have a powder resistance of 0.001 ohm·cm or less, 0.0009 ohm·cm or less, 0.0008 ohm·cm or less, or 0.0007 ohm·cm or less at a rolling density of 1 g / cc or more. The lower the powder resistance value, the more the electrical conductivity of the single-walled carbon nanotube may be improved. When the above range is satisfied, the performance of a secondary battery using the single-walled carbon nanotube as a conductive material may be improved.

[0131] The above powder resistance can be measured as a powder resistance value when the rolling density is 1 g / cc using a powder resistance meter (MCP-PD51) equipped with a 4-pin probe.

[0132] The above single-walled carbon nanotube may have an oxygen element content of 0.5 wt% or less, 0.45 wt% or less, 0.4 wt% or less, 0.35 wt% or less, or 0.4 wt% or less relative to the total weight of elements measured by an elemental analyzer.

[0133] The single-walled carbon nanotube may have a carbon element content of 94 wt% to 99 wt%, 95 wt% to 99 wt%, 95.5 wt% to 99 wt%, 96 wt% to 99 wt%, 96.5 wt% to 99 wt%, or 97 wt% to 99 wt% relative to the total weight of elements measured by the elemental analyzer.

[0134] The above single-walled carbon nanotube may have a nitrogen element content of 0.01 wt% to 1 wt%, 0.01 wt% to 0.5 wt%, 0.01 wt% to 0.3 wt%, or 0.01 wt% to 0.25 wt% relative to the total weight of elements measured by the above elemental analyzer.

[0135] The above single-walled carbon nanotube may have a hydrogen element content of 1 wt% or less, 0.8 wt% or less, 0.6 wt% or less, 0.5 wt% or less, or 0 wt% (excluding) to 0.5 wt% relative to the total weight of elements measured by the above elemental analyzer.

[0136] The above single-walled carbon nanotube may not contain the sulfur element. The sulfur element can be measured by the elemental analyzer.

[0137] The length of the single-walled carbon nanotube may be 10 nm to 3,000 nm, 100 nm to 3,000 nm, 300 nm to 3,000 nm, 500 nm to 3,000 nm, or 800 nm to 3,000 nm.

[0138] The average diameter (D) of the above single-walled carbon nanotubes 50) may be 0.5 nm to 25 nm, 0.5 nm to 20 nm, 0.5 nm to 15 nm, 0.5 nm to 10 nm, 0.8 nm to 10 nm, 1 nm to 10 nm, or 1 nm to 5 nm.

[0139] The above length and diameter can be measured using an atomic force microscope (AFM). The above length can correspond to the average value of the top 100 single-walled carbon nanotubes with a large average length and the bottom 100 single-walled carbon nanotubes, and the above diameter can correspond to the average value of the top 100 single-walled carbon nanotubes with a large average diameter and the bottom 100 single-walled carbon nanotubes.

[0140] The pore volume of the single-walled carbon nanotube may be 0.1 cc / g to 1.5 cc / g, 0.5 cc / g to 1.5 cc / g, 0.8 cc / g to 1.5 cc / g, or 1.0 cc / g to 1.5 cc / g.

[0141] The above pore volume can be measured from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using BELSORP-mini II of BEL Japan.

[0142] The crystallinity of the single-walled carbon nanotube can be measured by Raman spectrum analysis. The single-walled carbon nanotube has a vibration frequency of 1560 cm by Raman spectrum analysis. -1 1600 cm inland -1 It can have peaks in the range, I G may mean the maximum peak intensity in the above range. The single-walled carbon nanotube has a vibration frequency of 1310 cm by the Raman spectrum analysis. -1 1350 cm inland -1 It can have peaks in the range, I Dmay mean the maximum peak intensity in the above range. The above I G has a vibration frequency of 1591 cm -1 It may mean a nearby peak, and the above I D has a vibration frequency of 1343 cm -1 It may mean a nearby peak. The above I D Peak intensity can indicate the degree of defects in the carbon structure, and the above I G Peak intensity can indicate the crystalline characteristics of the carbon structure.

[0143] The above single-walled carbon nanotubes have I measured by Raman spectrum G / I D It can be 35 to 150, 35 to 120, 35 to 100, 35 to 80, 35 to 75, 35 to 55, 40 to 55, 45 to 55, 47 to 55, or 50 to 55.

[0144] The above single-walled carbon nanotube has an I of the above range. G / I D When this is satisfied, impurities are minimized and the material has high crystallinity, so when used as a conductive material, the electrical conductivity is improved, which can improve the performance of the secondary battery.

[0145] The above single-walled carbon nanotubes can be measured for carbon crystallinity and impurities by XRD (X-ray diffraction). The XRD can be performed using Rigaku's Ultima IV X-ray diffraction equipment. The XRD can be measured from the intensity at the diffraction angle (2theta, degree) of the diffracted X-ray by irradiating X-rays. The vertical axis of the XRD graph can represent the intensity of the diffracted X-ray, and the horizontal axis can represent the diffraction angle (2theta, degree). In the XRD graph, carbon crystallinity in the section of 2θ = 14° to 30° can be confirmed by a peak value around 2θ = 26°, and matters related to impurities can be confirmed by a peak value other than around 2θ = 26° in the section of 2θ = 14° to 30°. In the XRD graph above, the metallic element, which is an impurity in the range of 2θ = 14° to 30°, can be identified as a peak value around 2θ = 15°.

[0146] The above 2θ = 26° vicinity may mean 2θ = 26°± 1°, and the above 2θ = 15° vicinity may mean 2θ = 15°± 1°.

[0147] The single-walled carbon nanotube may have a peak area around 2θ = 26° of 70% or more, 75% or more, 77% or more, or 80% or more of the total peak area at 2θ = 14° to 30°, when the range of 2θ = 14° to 30° in the XRD graph is used as a baseline. The peak area may be calculated as a Gaussian type using MDI's JADE 9 software. When the above range is satisfied, impurities are minimized and the nanotube has high crystallinity, so that when used as a conductive material, the electrical conductivity is improved, thereby improving the performance of a secondary battery.

[0148] The single-walled carbon nanotube may have a secondary shape formed by agglomeration or arrangement of multiple single-walled carbon nanotubes. The single-walled carbon nanotube may exhibit a bundle type in which multiple single-walled carbon nanotubes are arranged in a bundle or rope shape in a certain direction, or an entangled type in which multiple single-walled carbon nanotubes are entangled in a sphere or potato shape without a certain direction.

[0149] The above single-walled carbon nanotube can be manufactured by a step of synthesizing a single-walled carbon nanotube and a step of purifying the synthesized single-walled carbon nanotube.

[0150] The single-walled carbon nanotubes can be synthesized by laser ablation. The laser ablation may refer to a process of irradiating a laser beam to a mixture of a raw material containing carbon and a catalyst under an inert gas atmosphere, and a single-walled carbon nanotube can be synthesized by the process. The inert gas may be argon or nitrogen. The raw material containing carbon may be graphite. The catalyst may be a metal catalyst. The intensity of the laser beam is 100 mJ / cm. 2 300 mJ / cm 2 , 110 mJ / cm 2 300 mJ / cm 2 , 110 mJ / cm 2 290 mJ / cm 2 , or 120 mJ / cm 2 280 mJ / cm 2 It could be.

[0151] The single-walled carbon nanotubes can be synthesized by an arc discharge method. The arc discharge method may refer to a process of causing an arc discharge between a pair of electrodes to deposit vaporized material generated at an anode, and a single-walled carbon nanotube can be synthesized by the process. The anode may include a raw material including carbon. The raw material including carbon may be graphite. The anode may include a transition metal. The transition metal may include at least one of iron, cobalt, yttrium, and nickel. The graphite may be in the form of a rod having pores. The transition metal may be mixed into the pores of the graphite. The arc discharge method may be performed under an atmosphere of an inert gas, or an atmosphere of an inert gas and hydrogen gas. The arc discharge method may be performed under an atmosphere of a small amount of hydrocarbon gas. The hydrocarbon gas may include at least one of methane, ethylene, and acetylene. The pair of electrodes may be spaced apart by a predetermined distance. The pair of electrodes may be spaced apart by 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less. The arc discharge method may be a direct current arc discharge method. The direct current power source in the direct current arc discharge method may have a voltage range of 20 V to 70 V, 22 V to 70 V, 22 V to 65 V, or 25 V to 65 V. The direct current power source in the direct current arc discharge method may have a current range of 40 A to 120 A, 40 V to 115 V, 40 V to 100 V, or 45 V to 100 V.

[0152] Preferably, the single-walled carbon nanotube can be synthesized by chemical vapor deposition. The chemical vapor discharge method may refer to a process of thermally decomposing hydrocarbons such as methane, ethylene, and acetylene, or toluene, in the gas phase in the presence of a catalyst, and single-walled carbon nanotubes can be synthesized by the process. The catalyst may be alumina or silica supported with iron, cobalt, nickel, molybdenum, or the like. The chemical vapor deposition method has the advantage of being able to easily control the diameter, length, density, structure, crystallinity, etc. of the single-walled carbon nanotube, and mass-producing high-purity single-walled carbon nanotubes.

[0153] The synthesized single-walled carbon nanotube may contain impurities. The impurities may include at least one of a metal oxide, a metal, and a non-metal. The metal oxide may include a ceramic metal. The ceramic metal may be derived from a catalyst support in the synthesis process of the single-walled carbon nanotube. The metal may include at least one of iron, cobalt, nickel, chromium, copper, manganese, nickel, and zinc. The non-metal may include sulfur. The metal and non-metal may be derived from a catalyst in the synthesis process of the single-walled carbon nanotube.

[0154] Among the impurities, the nickel element may cause the single-walled carbon nanotube to be cut, shortened in length, or oxidized on the surface, thereby deteriorating electrical and mechanical properties. The nickel element may damage the unique characteristics of the single-walled carbon nanotube. Therefore, it is more preferable to perform a process of purifying the synthesized single-walled carbon nanotube to remove the nickel element. The BET specific surface area and the nickel element content of the single-walled carbon nanotube may be controlled not only according to the synthesis process of the single-walled carbon nanotube but also according to the process conditions for removing the impurities.

[0155] The content of elemental sulfur contained in the single-walled carbon nanotube before the above purification can be measured by the above-described elemental analyzer. The content of elemental sulfur relative to the total weight of elements measured by the elemental analyzer may be 0.01 wt% or more, 0.02 wt% or more, 0.03 wt% or more, 0.04 wt% or more, or 0.05 wt% or more.

[0156] Nickel element contained in the single-walled carbon nanotube before purification can be measured using inductively coupled plasma optical emission spectrometry (ICP-OES) under the measurement conditions described above.

[0157] The content of iron element contained in the single-walled carbon nanotube before purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more. The content of cobalt element contained in the single-walled carbon nanotube before purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more. The content of chromium element contained in the single-walled carbon nanotube before purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more. The content of copper element contained in the single-walled carbon nanotube before purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more. The content of manganese element contained in the single-walled carbon nanotube before purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more. The content of nickel element contained in the single-walled carbon nanotube before purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more. The content of zinc element contained in the single-walled carbon nanotube before the above purification may be 10 mg / kg or more, 50 mg / kg or more, 100 mg / kg or more, 200 mg / kg or more, or 300 mg / kg or more.

[0158] The synthesized single-walled carbon nanotubes can be purified by physical or chemical methods. The physical methods include centrifugation, carbon nanotube solubilization, and high-temperature annealing. The centrifugation is a process of applying centrifugal force to a mixture of different masses to separate substances based on differences in sedimentation rates. By the centrifugation, amorphous carbon, carbon nanoparticles, and single-walled carbon nanotubes contained in the synthesized single-walled carbon nanotubes can be separated. The carbon nanotube solubilization can be performed by introducing a functional group to the surface of the single-walled carbon nanotubes, dissolving them in a solvent, and then separating high-purity carbon nanotubes from the impurities using filtration or chromatography. The above high-temperature annealing is performed at a temperature higher than about 1,500°C, where carbon does not undergo a phase change under inert gas or vacuum conditions. Therefore, by treating the single-walled carbon nanotube at a high temperature higher than the vaporization temperature of the impurity under inert gas or vacuum conditions, the impurity formed in the carbon nanotube can be removed.

[0159] The chemical methods include electrochemical oxidation, gas phase oxidation, and liquid phase oxidation. The electrochemical oxidation may be performed by electrically oxidizing the synthesized single-walled carbon nanotubes in a potassium hydroxide solution or a sulfuric acid solution, thereby removing the amorphous carbon and impurities contained in the single-walled carbon nanotubes. The liquid phase oxidation may be performed by reacting the synthesized single-walled carbon nanotubes with an oxidizing liquid, thereby removing the amorphous carbon and impurities contained in the single-walled carbon nanotubes. The oxidizing liquid may be hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or the like. The liquid phase oxidation may be performed by removing metal oxides and metals among the impurities contained in the single-walled carbon nanotubes. The liquid phase oxidation may be performed at a temperature of about 20°C to 25°C. In the past, the liquid phase oxidation was performed at a high temperature range of about 50°C to 70°C, but during the purification process, the structure of the single-walled carbon nanotube, such as cutting or opening of the end, may be destroyed, and there was a problem that the oxidizing liquid reactant existed as a secondary impurity on the single-walled carbon nanotube. Therefore, when the liquid phase oxidation satisfies the temperature range, the problem of secondary impurities being generated on the purified single-walled carbon nanotube can be suppressed, and the structural stability of the single-walled carbon nanotube after purification can be improved. The gas phase oxidation can remove the amorphous carbon and impurities contained in the single-walled carbon nanotube by heat-treating the synthesized single-walled carbon nanotube in a temperature range of about 700°C to 1,000°C in an oxidizing gas atmosphere. The oxidizing gas can be air, chlorine, a mixture of water vapor and hydrogen chloride, hydrogen sulfide, argon, or the like.

[0160] The above purification step can be performed for 30 to 200 minutes, 30 to 150 minutes, 40 to 120 minutes, 40 to 110 minutes, or 40 to 100 minutes. The purification step can be performed at a temperature of 900°C or higher, 920°C or higher, 950°C or higher, or 1,000°C or higher. After the purification step, a step of cooling to room temperature in a vacuum can be performed. By the purification step, metal impurities contained in the single-walled carbon nanotubes can be removed more efficiently.

[0161] The content of elemental sulfur contained in the single-walled carbon nanotube after the purification can be measured by the above-described elemental analyzer. The content of elemental sulfur relative to the total weight of elements measured by the elemental analyzer may be less than 0.01 wt%, less than 0.005 wt%, less than 0.003 wt%, less than 0.002 wt%, or less than 0.001 wt%. Preferably, the single-walled carbon nanotube after the purification may not contain elemental sulfur.

[0162] The removal rate of the above sulfur element can be expressed by the following calculation formula. In the calculation formula below, the removal rate of the sulfur element can be 98% or more, 98.5% or more, 98.5% or more, 99% or more, 99.5% or more, or 100%.

[0163] [Calculation formula]

[0164] Sulfur element removal rate (%) = (content of sulfur element contained in single-walled carbon nanotubes before purification - content of sulfur element contained in single-walled carbon nanotubes after purification) / (content of sulfur element contained in single-walled carbon nanotubes before purification) × 100

[0165] The content of nickel element contained in the single-walled carbon nanotube after the purification may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg. The content of cobalt element contained in the single-walled carbon nanotube after the purification may be less than 10 mg / kg, less than 8 mg / kg, less than 6 mg / kg, less than 4 mg / kg, or less than 2 mg / kg. The content of chromium element contained in the single-walled carbon nanotube after the purification may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg. The content of copper element contained in the single-walled carbon nanotube after the purification may be less than 10 mg / kg, less than 8 mg / kg, less than 6 mg / kg, less than 5 mg / kg, or less than 2 mg / kg. The content of iron element contained in the single-walled carbon nanotube after the purification may be less than 50 mg / kg, less than 40 mg / kg, less than 20 mg / kg, less than 10 mg / kg, or less than 3 mg / kg. The content of manganese element contained in the single-walled carbon nanotube after the purification may be less than 10 mg / kg, less than 5 mg / kg, less than 3 mg / kg, less than 2 mg / kg, or less than 1 mg / kg. The content of zinc element contained in the single-walled carbon nanotube after the purification may be less than 50 mg / kg, less than 40 mg / kg, less than 30 mg / kg, less than 25 mg / kg, or less than 18 mg / kg. The single-walled carbon nanotube may be manufactured using a catalyst. To manufacture high-purity single-walled carbon nanotubes and control the diameter of the single-walled carbon nanotubes by adjusting the size of the catalyst, a large amount of elemental sulfur can be used as a promoter. However, it is difficult to sufficiently remove elemental sulfur during the purification process of the single-walled carbon nanotubes.When a large amount of sulfur element remains in single-walled carbon nanotubes, the viscosity change of the dispersion containing the single-walled carbon nanotubes may increase significantly over time, which may cause a problem in that the storage stability may be significantly reduced. If a small amount of sulfur element is used as a promoter during the production of single-walled carbon nanotubes in order to reduce the content of residual sulfur element, the size of the catalyst may increase significantly, making it difficult to control the diameter of the single-walled carbon nanotubes, and the carbonaceous impurities may increase, making it difficult to produce high-purity single-walled carbon nanotubes. In this way, the factors of high-purity single-walled carbon nanotubes with reduced carbonaceous impurities and single-walled carbon nanotubes with improved storage stability can be achieved by satisfying a specific range of thermogravimetric change values ​​and a range of sulfur element content.

[0166] A single-walled carbon nanotube dispersion according to the present invention comprises a solvent, a dispersant, and a single-walled carbon nanotube, wherein the single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the following equation 1.

[0167] [Formula 1]

[0168] 12 ≤ X / (100-Y) ≤ 20

[0169] In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

[0170] A single-walled carbon nanotube dispersion according to the present invention comprises a solvent, a dispersant, and a single-walled carbon nanotube, wherein the single-walled carbon nanotube may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0171] A single-walled carbon nanotube dispersion according to the present invention comprises a solvent, a dispersant, and a single-walled carbon nanotube, wherein the single-walled carbon nanotube comprises an oxygen element and a carbon element, and the weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0172] The above single-walled carbon nanotube dispersion may mean that the single-walled carbon nanotubes are dispersed in the dispersion in a non-agglomerated state.

[0173] The above single-walled carbon nanotube dispersion contains a solvent. When the single-walled carbon nanotubes are mixed with an electrode active material or the like to form an electrode slurry composition, the solvent can suppress aggregation between the single-walled carbon nanotubes or aggregation with the electrode active material by dispersing the single-walled carbon nanotubes in advance.

[0174] The solvent may be an aqueous solvent. The aqueous solvent may be water. The solvent may be an aqueous solvent, an organic solvent, or a mixture thereof. The organic solvent may be an amide polar organic solvent such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), N-methyl pyrrolidone (NMP); an alcohol such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; Examples thereof include ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone; and any one or a mixture of two or more of these may be used.

[0175] The single-walled carbon nanotube dispersion may include a dispersant. The dispersant may improve the dispersibility of the single-walled carbon nanotube. When the solvent is an aqueous solvent, the dispersant may be any one or a mixture of two or more of carboxymethyl cellulose, polyvinylpyrrolidone (PVP), an acrylic resin emulsion, a water-soluble acrylic polymer, a styrene emulsion, a silicone emulsion, an acrylic silicone emulsion, a fluororesin emulsion, an EVA emulsion, a vinyl acetate emulsion, a vinyl chloride emulsion, and a urethane resin emulsion. When the solvent is an organic solvent, the dispersant may be any one or a mixture of two or more of polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), an acrylic resin, an alkyd resin, and a urethane resin.

[0176] The dispersant may be included in the single-walled carbon nanotube dispersion in an amount of 1 part by weight to 100 parts by weight, 1 part by weight to 90 parts by weight, 5 parts by weight to 90 parts by weight, or 10 parts by weight to 90 parts by weight, relative to 100 parts by weight of the single-walled carbon nanotube. When the above range is satisfied, the dispersibility of the single-walled carbon nanotube may be further improved.

[0177] The above single-walled carbon nanotube dispersion comprises the above single-walled carbon nanotube. The single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the above-mentioned equation 1. In the above range, when the single-walled carbon nanotube dispersion is used as a conductive material, the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery can be improved due to the improved electrical conductivity.

[0178] The single-walled carbon nanotube dispersion may include the single-walled carbon nanotubes described above. The single-walled carbon nanotubes may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% based on the total weight of elements measured by an elemental analyzer. In the above range, the storage stability of the single-walled carbon nanotube dispersion may be improved, and when the single-walled carbon nanotube dispersion is used as a conductive material, the initial efficiency, life characteristics, and high-rate discharge characteristics of a secondary battery may be improved due to the improved electrical conductivity.

[0179] The single-walled carbon nanotube dispersion comprises the single-walled carbon nanotubes described above. The single-walled carbon nanotubes comprise oxygen and carbon, and the weight ratio of the oxygen element to the carbon element as measured by an elemental analyzer may be 1:50 to 1:95. When the above range is satisfied, the phenomenon of agglomeration within the dispersion may be minimized while dispersibility may be improved, and the increase in viscosity over time may be minimized, thereby improving storage stability. In addition, when used as a conductive material in a secondary battery, the electrical conductivity may be improved, thereby improving the performance of the secondary battery.

[0180] The content of the single-walled carbon nanotubes relative to the total weight of the single-walled carbon nanotube dispersion may be 0.01 wt% to 15.00 wt%, 0.01 wt% to 10.00 wt%, 0.01 wt% to 8.00 wt%, 0.05 wt% to 8.00 wt%, 0.1 wt% to 8.00 wt%, or 0.1 wt% to 5.00 wt%. When the above range is satisfied, an increase in the viscosity of the single-walled carbon nanotube dispersion can be suppressed, and when used as a conductive material for a secondary battery, it can have appropriate adhesiveness with a binder during electrode manufacturing, and can have an appropriate loading amount, so that process efficiency can be improved.

[0181] The initial viscosity of the single-walled carbon nanotube dispersion at room temperature may be 1,000 cP to 10,000 cP, 1,000 cP to 9,000 cP, 1,000 cP to 8,000 cP, 1,000 cP to 7,000 cP, or 1,000 cP to 5,000 cP. When the above range is satisfied, the aggregation of the single-walled carbon nanotubes can be suppressed, and the process of repeating the reintroduction and dispersion treatment of the single-walled carbon nanotubes can be minimized, thereby improving process efficiency. The viscosity can be measured using a B-type viscometer, a rotating cylinder viscometer, etc., and specifically, can be measured using a DV2T LV viscometer (Brookfield).

[0182] The above single-walled carbon nanotube dispersion may have a viscosity change rate of 30% or less, 28% or less, 26% or less, 24% or less, 22% or less, or 20% or less according to the following formula. When the above range is satisfied, the dispersion containing the single-walled carbon nanotube may have improved storage stability by minimizing viscosity increase over time.

[0183] [ceremony]

[0184] Viscosity change rate (%) = (Viscosity after one month - Initial viscosity) / Initial viscosity × 100

[0185] The pH of the single-walled carbon nanotube dispersion at room temperature may be 3 to 10, 4 to 10, 4 to 9, 5 to 9, 5 to 8, or 6 to 8. When the above range is satisfied, the aggregation phenomenon due to hydrogen bonding can be suppressed.

[0186] The above single-walled carbon nanotube dispersion can measure absorbance. The absorbance may be an indicator indicating the degree to which light is absorbed. The absorbance is proportional to the concentration of a substance, and thus, a high absorbance of the single-walled carbon nanotube dispersion may indicate that single-walled carbon nanotubes capable of absorbing light are evenly dispersed at a high concentration. In other words, the absorbance may be an indicator of the dispersibility of the single-walled carbon nanotubes included in the single-walled carbon nanotube dispersion.

[0187] The absorbance of the single-walled carbon nanotube dispersion may be 0.1 to 10, 0.15 to 10, 0.15 to 5, or 0.2 to 5. When the above range is satisfied, the aggregates included in the single-walled carbon nanotube dispersion are minimized, and the single-walled carbon nanotubes included in the single-walled carbon nanotube dispersion may be included in a high purity and have excellent dispersibility. The absorbance may be measured in a wavelength range of 550 nm using a spectrophotometer.

[0188] An electrode according to the present invention comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the above-mentioned formula 1.

[0189] An electrode according to the present invention comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0190] An electrode according to the present invention comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube comprises an oxygen element and a carbon element, and a weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0191] The electrode may be a cathode. The cathode may include a cathode active material, a binder, and a conductive material. The cathode may be manufactured by applying a cathode slurry composition containing a cathode active material onto a cathode current collector, followed by drying to form a cathode active material layer. The cathode active material layer may be formed by applying the cathode slurry composition onto the cathode current collector, followed by drying, or by applying the cathode slurry composition onto a separate support, peeling it off from the support, and laminating the resulting film onto a cathode current collector. After the cathode active material layer is formed, a rolling process may be performed. The drying and rolling may be performed under appropriate conditions in consideration of the physical properties of the electrode to be ultimately manufactured.

[0192] The positive electrode current collector is made of a highly conductive metal to which the slurry of the positive electrode active material can easily adhere. There are no particular limitations on the material as long as it has high conductivity and does not cause chemical changes in the secondary battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric, and may have a thickness of 3 ㎛ to 500 ㎛.

[0193] The positive electrode slurry composition may include the positive electrode active material, a binder, and a conductive material. In addition, the positive electrode slurry composition may further include a solvent.

[0194] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0195] The above lithium composite metal oxides include lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-z Ni z O4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 MnY2 O2 (here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), and any one or two or more compounds thereof may be included. Among these, the lithium composite metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05)O2, etc.), and considering the remarkable improvement effect according to the control of the type and content ratio of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one of these or a mixture of two or more of them may be used.

[0196] The above binder can improve the adhesion between the positive electrode active materials or between the positive electrode active material and the positive electrode current collector. The above binder may be a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and various types of binder polymers such as polymers in which hydrogens of these are substituted with Li, Na, Ca, etc., or various copolymers.

[0197] The conductive material can improve electrical conductivity. The conductive material can include the single-walled carbon nanotubes described above. The conductive material can further include a conductive material such as graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black; metal powder such as fluorocarbon, aluminum, nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives.

[0198] The solvent can mix each component in the positive electrode slurry composition and control the viscosity. The solvent may be an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide, or water, and these solvents may be used alone or in combination of two or more. The amount of the solvent used may be used to an extent that can dissolve and disperse the positive electrode active material, the binder, and the conductive material, taking into account the coating thickness and manufacturing yield of the positive electrode slurry composition.

[0199] The above electrode may be an anode. The anode may include a negative electrode active material, a binder, and a conductive material. The anode may be manufactured by applying a negative electrode slurry composition containing a negative electrode active material onto a negative electrode current collector, and then drying the composition to form a negative electrode active material layer.

[0200] The above negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the secondary battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0201] The above-described negative electrode slurry composition may include the above-described single-walled carbon nanotube dispersion, the negative electrode active material, and the binder. In addition, the above-described negative electrode slurry composition may further include a solvent.

[0202] The single-walled carbon nanotubes included in the single-walled carbon nanotube dispersion may be a conductive material. The single-walled carbon nanotubes may have a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the above-mentioned Equation 1. When the above range is satisfied, the phenomenon of agglomeration with other materials in the negative electrode slurry composition can be suppressed, and the electrical conductivity between the negative electrode active materials can be improved, so that the performance of the secondary battery can be improved.

[0203] The above negative active material may be included in an amount of 90 wt% to 99 wt%, 91 wt% to 99 wt%, 92 wt% to 99 wt%, 94 wt% to 99 wt%, or 95 wt% to 95 wt% relative to the total weight of the slurry for manufacturing the negative active material layer. When the above range is satisfied, the charge / discharge capacity of the secondary battery may be increased.

[0204] The above negative active material may include a carbon-based material. The carbon-based material may include natural graphite particles or artificial graphite particles. The above negative active material may include a silicon-based material. The above negative active material may include a silicon-graphite composite. The weight ratio of the silicon in the silicon-graphite composite may be 1 wt% to 70 wt%, 5 wt% to 70 wt%, 5 wt% to 50 wt%, 5 wt% to 40 wt%, or 10 wt% to 40 wt%. When the above range is satisfied, the deterioration of the life characteristics of the secondary battery is minimized, and the charge / discharge capacity can be significantly increased.

[0205] The above silicon-based material is metal silicon (Si), silicon oxide (SiOx, 0 <x<2), 실리콘카바이드(SiC) 및 Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님)으로 이루어진 군으로부터 선택된 1종 이상을 포함할 수 있다. 상기 원소 Y로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0206] The silicon-based material can exhibit higher capacity characteristics than the carbon-based material. When the silicon-based material is included in the negative electrode active material, the capacity characteristics can be improved. However, the silicon-based material has a problem in that the volume change during charge and discharge is large compared to the carbon-based material, resulting in lower cycle characteristics. Therefore, when the single-walled carbon nanotube according to the present invention is used as a conductive material, the high electron movement path can be improved compared to the conventional conductive material, thereby improving the electrical conductivity, and the dispersibility is improved, thereby increasing the structural stability. Therefore, when the negative electrode active material includes the silicon-based material, not only the capacity characteristics can be improved, but also the cycle characteristics can be improved.

[0207] The above binder may be used to bind particles included in the negative active material to maintain the molded body. The binder may be a non-aqueous binder or an aqueous binder. For example, the non-aqueous binder may be polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethylene, or polypropylene, and further, the aqueous binder may be any one selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber, and acrylic rubber, or a mixture of two or more thereof. The above aqueous binder is more economical and environmentally friendly than a non-aqueous binder, is harmless to the health of workers, and has a superior binding effect compared to a non-aqueous binder, so that the ratio of active material per volume can be increased, enabling high capacity. Specifically, styrene-butadiene rubber can be used as the aqueous binder.

[0208] The above binder may be included in an amount of 0.1 wt% to 10 wt%, 0.1 wt% to 8 wt%, 0.1 wt% to 7 wt%, 0.1 wt% to 6 wt%, or 0.1 wt% to 5 wt% relative to the total weight of the slurry for manufacturing the negative electrode active material layer. When the above range is satisfied, the binder may be excellent in effect without a decrease in volumetric capacity due to a decrease in the relative content of the negative electrode active material.

[0209] The above solvent can mix each component in the cathode slurry composition and control the viscosity. The same solvent as the above-described solvent can be used.

[0210] A secondary battery according to the present invention comprises an electrode, a separator, and an electrolyte, wherein the electrode comprises an electrode active material, a binder, and a conductive material, and the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube has a BET specific surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and the content of nickel element measured by inductively coupled plasma optical emission spectrometry (ICP-OES) is less than 100 mg / kg, and can satisfy the above-mentioned formula 1.

[0211] A secondary battery according to the present invention comprises an electrode, a separator, and an electrolyte, wherein the electrode comprises an electrode active material, a binder, and a conductive material, and the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube may have a weight change of 5% or less between 40°C and 550°C when heated at 10°C / min using a thermogravimetric analyzer, and the content of sulfur element may be less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

[0212] A secondary battery according to the present invention comprises an electrode, a separator, and an electrolyte, wherein the electrode comprises an electrode active material, a binder, and a conductive material, wherein the conductive material comprises a single-walled carbon nanotube, and the single-walled carbon nanotube comprises an oxygen element and a carbon element, and a weight ratio of the oxygen element:carbon element measured by an elemental analyzer may be 1:50 to 1:95.

[0213] The above electrode may refer to a cathode and an anode. The anode and the cathode may be the same as the anode and the cathode described above. The electrode active material may refer to a cathode active material and a cathode active material. The cathode active material and the cathode active material may be the same as the anode active material and the cathode active material described above. The conductive material including the binder and the single-walled carbon nanotube may be the same as the binder and the single-walled carbon nanotube described above.

[0214] The above secondary battery includes the single-walled carbon nanotube described above as a conductive material, thereby improving electrical conductivity and thus improving the initial efficiency, life characteristics, and high-rate discharge characteristics of the secondary battery.

[0215] The separator may be interposed between the cathode and the anode. The separator may be configured to prevent electrical short-circuiting between the cathode and the anode and to allow ion flow. The separator may include a porous polymer film or a porous non-woven fabric. The porous polymer film may be composed of a single layer or multiple layers including a polyolefin polymer such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer. The porous non-woven fabric may include high-melting-point glass fibers or polyethylene terephthalate fibers. However, the present invention is not limited thereto, and according to an embodiment, the separator may be a high-heat-resistant separator (CCS; Ceramic Coated Separator) including ceramic.

[0216] The electrolyte may be a non-aqueous electrolyte. The electrolyte may include a lithium salt and an organic solvent. The organic solvent may include at least one of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), dipropyl carbonate (DPC), vinylene carbonate (VC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, propylene sulfide, and tetrahydrofuran.

[0217] The positive electrode, negative electrode, and separator may be manufactured into an electrode assembly by a winding, lamination, folding, or zigzag stacking process. The electrode assembly may be provided together with the electrolyte to be manufactured into a secondary battery. The secondary battery may be any one of a cylindrical shape using a can, a square shape, a pouch shape, and a coin shape, but is not limited thereto.

[0218] The secondary battery can be used in a high-power and large-capacity secondary battery that requires a long lifespan and excellent durability, or in a module or pack including a plurality of the secondary batteries as unit batteries. The plurality of secondary batteries can be manufactured into a module. The plurality of modules can be manufactured into a pack. The pack can be used as a power source for medium- to large-sized devices that require high-temperature stability, long cycle characteristics, and high-rate characteristics. Examples of the medium- to large-sized devices include a power tool that is powered by a battery motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; an electric truck; an electric commercial vehicle, or a power storage system.

[0219]

[0220] Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the following examples and comparative examples are merely illustrative examples for further explaining the present invention, and the present invention is not limited to the following examples and comparative examples.

[0221]

[0222] Manufacturing Example 1

[0223] Manufacturing Example 1-1

[0224] 200 mg of single-walled carbon nanotubes were prepared by chemical vapor deposition (CVD) using a catalyst. The single-walled carbon nanotubes were then charged into a reactor.

[0225] Afterwards, the reactor was purified at about 1,000°C for 60 minutes under an argon atmosphere and vacuum conditions, and then cooled to room temperature to produce purified single-walled carbon nanotubes.

[0226] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0227]

[0228] Manufacturing Example 1-2

[0229] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 1-1, except that the purification treatment was performed at about 950°C for 80 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 1-1.

[0230]

[0231] Manufacturing Example 1-3

[0232] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 1-1, except that the purification treatment was performed at about 950°C for 85 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 1-1.

[0233]

[0234] Manufacturing Example 1-4

[0235] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 1-1, except that the purification treatment was performed at about 900°C for 85 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 1-1.

[0236]

[0237] Manufacturing Example 1-5

[0238] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 1-1, except that the purification treatment was performed at about 900°C for 75 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 1-1.

[0239]

[0240] Manufacturing Example 1-6

[0241] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 1-1, except that the purification treatment was performed at about 900°C for 80 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 1-1.

[0242]

[0243] Manufacturing Example 1-7

[0244] 200 mg of single-walled carbon nanotubes were prepared by chemical vapor deposition (CVD) using a catalyst. The single-walled carbon nanotubes were then charged into a reactor. Subsequently, the single-walled carbon nanotubes were added to 60 L of a 36% hydrochloric acid solution and stirred at approximately 25°C for approximately 3 hours, thereby producing purified single-walled carbon nanotubes.

[0245] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0246]

[0247] Comparative Manufacturing Example 1-1

[0248] 200 mg of single-walled carbon nanotubes (TUBALL, OCSiAl) were prepared. Then, the single-walled carbon nanotubes were added to 100 ml of a 40% nitric acid aqueous solution and stirred at approximately 55°C for approximately 8 hours to produce purified single-walled carbon nanotubes.

[0249] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0250]

[0251] Comparative Manufacturing Example 1-2

[0252] A single-wall carbon nanotube dispersion was prepared by the same process as in Comparative Manufacturing Example 1-1, except that stirring was performed at about 50°C for about 6 hours instead of stirring at about 55°C for about 8 hours in Comparative Manufacturing Example 1-1.

[0253]

[0254] Comparative Manufacturing Example 1-3

[0255] 200 mg of single-walled carbon nanotubes were prepared by chemical vapor deposition (CVD) using a catalyst.

[0256] Thereafter, 1 kg of a mixture was prepared by mixing carboxymethyl cellulose (Sigma Aldrich 419273, Mw 85,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent into the single-walled carbon nanotubes. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0257]

[0258] Example 1

[0259] Example 1-1

[0260] <Cathode Manufacturing>

[0261] Silicon graphite composite: A negative electrode active material slurry containing the single-walled carbon nanotube dispersion of the above Manufacturing Example 1-1: carboxymethyl cellulose (CMC) thickener: starene butadiene rubber (SBR) binder in a weight ratio of 96.5:0.1:1.2:2.2 was coated on a Cu foil current collector having a thickness of about 10 μm to a thickness of about 30 μm, and then dried at 100°C for about 12 hours to manufacture a negative electrode.

[0262] <Secondary Battery (Coin Half-Cell) Manufacturing>

[0263] A metal lithium foil of about 0.3 mm was used as the positive electrode, and a polyethylene separator was interposed between the positive electrode and the negative electrode. Then, EC:EMC was mixed in a ratio of 3:7 and a non-aqueous electrolyte of LiPF61M was injected to manufacture a coin half-cell.

[0264]

[0265] Example 1-2

[0266] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 1-2 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0267]

[0268] Example 1-3

[0269] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 1-3 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0270]

[0271] Example 1-4

[0272] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 1-4 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0273]

[0274] Example 1-5

[0275] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 1-5 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0276]

[0277] Example 1-6

[0278] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 1-6 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0279]

[0280] Example 1-7

[0281] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 1-7 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0282]

[0283] Comparative Example 1-1

[0284] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 1-1 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0285]

[0286] Comparative Example 1-2

[0287] A coin half-cell was manufactured by the same process as in Example 1-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 1-2 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0288]

[0289] Comparative Example 1-3

[0290] A coin half-cell was manufactured by the same process as Example 1-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 1-3 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 1-1 in the above Example 1-1.

[0291]

[0292] Experimental Example 1

[0293] Experimental Example 1-1 - Surface Area Measurement

[0294] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3, the specific surface area was measured using the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using BELSORP-mini II of BEL Japan, and the results are shown in Table 1 below.

[0295]

[0296] Experimental Example 1-2 - Measurement of nickel and iron content

[0297] After dissolving each of the purified single-walled carbon nanotubes of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3 in 65 wt% nitric acid, the nickel and iron contents were measured using inductively coupled plasma optical emission spectrometry (ICP-OES) under the following measurement conditions, and the results are shown in Table 1 below.

[0298] [Measurement conditions]

[0299] - Device: Agilent 5110 SVDV

[0300] - RF power: 1.2 kW

[0301] - Nebulizer flow: 0.7 L / min

[0302] - Plasma flow: 12 L / min

[0303] - Aux flow: 1 L / min

[0304] - Read time: 5 sec

[0305]

[0306] Experimental Example 1-3 - Bulk Density Measurement

[0307] Each of the purified single-walled carbon nanotubes of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3 was filled into a 20 ml glass cylinder (Ronyes Co.) of known weight, and the weight was measured, and the bulk density was calculated according to Equation 3 below. The results are shown in Table 1-1 below.

[0308] [Formula 3]

[0309] Bulk density (kg / m) 3 ) = Single-walled carbon nanotube weight (kg) / Single-walled carbon nanotube volume (m 3 )

[0310]

[0311] Experimental Example 1-4 - Tap Density Measurement

[0312] A 10 ml glass cylinder (Ronyes) was placed on a scale and zeroed. Thereafter, the glass cylinder was tilted, and 10 ml of each of the purified single-walled carbon nanotubes of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3 was slowly added. The volume was measured by reading the graduation by aligning the height of the single-walled carbon nanotube with the eye level, and then the cylinder was placed on the scale and the weight was measured. Thereafter, the cylinder was lightly tapped on the floor about 100 times, and the volume was measured again by reading the graduation of the cylinder, and the tap density was calculated according to Equation 4 below. The results are shown in Table 1 below.

[0313] [Formula 4]

[0314] Tap density (kg / m) 3 ) = Single-wall carbon nanotube weight (kg) / Single-wall carbon nanotube volume (m) after 100 taps 3 )

[0315]

[0316] Experimental Example 1-5 - Powder Resistance Measurement

[0317] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3, the powder resistance was measured using a powder resistance meter (MCP-PD51) equipped with a 4-pin probe, and the powder resistance values ​​when the rolling density was 1 g / cc are shown in Table 1 below.

[0318]

[0319] Experimental Example 1-6 - Raman Measurement

[0320] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3, the Raman spectrum was measured using Renishaw's invia. In the Raman spectrum analysis, the G band (approximately 1,591 cm -1 ) peak intensity (I G) and D band (approximately 1,343 cm -1 ) peak intensity (I D ) measured and expressed as a peak intensity ratio (I G / I D ) are shown in Table 1 below.

[0321]

[0322] Experimental Example 1-7 - Thermogravimetric Analysis

[0323] For each of the purified single-walled carbon nanotubes of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3, the weight change by temperature range, the start temperature of thermal decomposition, and the content of residue after completion of thermal decomposition were measured using a thermogravimetric analyzer, and the results are shown in Table 1 below.

[0324]

[0325] Experimental Example 1-8 - Storage Stability

[0326] For each of the single-walled carbon nanotube dispersions of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3, the initial viscosity and the viscosity after one month were measured at room temperature using a DV2T LV viscometer (Brookfield), and the viscosity change rate was calculated according to Equation 5 below. The results are shown in Table 1 below.

[0327] [Formula 5]

[0328] Viscosity change rate (%) = (Viscosity after one month - Initial viscosity) / Initial viscosity × 100

[0329]

[0330] Experimental Example 1-9 - Dispersibility

[0331] Zeta potential was measured for each of the single-walled carbon nanotube dispersions of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3. The evaluation was performed according to the following criteria, and the results are shown in Table 1 below.

[0332] - ○: Absolute value exceeds 25 mV

[0333] - △: Absolute value is 10 mV to 25 mV or less

[0334] - ×: Absolute value is less than 10mV

[0335]

[0336] Experimental Example 1-10 - Dispersion Stability

[0337] Each of the single-walled carbon nanotube dispersions of Manufacturing Examples 1-1 to 1-7 and Comparative Manufacturing Examples 1-1 to 1-3 was placed in a glass bottle, and the presence or absence of aggregation was measured for 50 days. The evaluation was performed according to the following criteria, and the results are shown in Table 1 below.

[0338] - ○: Coagulation occurs after 2 weeks

[0339] - △: Coagulation occurs within 1 to 2 weeks

[0340] - ×: Coagulation occurs within 1 week

[0341]

[0342] Experimental Example 1-11 - Initial Efficiency of Coin Half-Cell

[0343] For each coin half-cell of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3, formation was performed by performing one charge / discharge cycle at 0.1 C, and then the initial charge / discharge characteristics were confirmed by one charge / discharge cycle at 0.2 C. The initial efficiency was calculated according to Equation 6 below, and the results are shown in Table 1 below.

[0344] The above charging and discharging process was set to start in CC (constant current) mode at a current of 0.1 C up to 0.01 V under room temperature conditions, then switch to CV (constant voltage) and cut off at 0.01 C, and proceed in CC (constant current) mode at a current of 0.1 C up to 1.5 V during discharging.

[0345] [Formula 6]

[0346] Initial efficiency (%) = (discharge capacity in 1 cycle) / (charge capacity in 1 cycle) Х 100

[0347]

[0348] Experimental Example 1-11 - Coin Half-Cell Lifetime Characteristics

[0349] For each coin half-cell of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3, charge / discharge was repeated 70 times under the same conditions as in Experimental Example 1-10, and then the discharge capacity was measured, and the capacity retention rate compared to the discharge capacity in one cycle of Experimental Example 1-10 was measured. The results are shown in Table 1 below.

[0350]

[0351] Experimental Example 1-12 - High-Rate Discharge Characteristics of a Coin Half-Cell

[0352] For each of the coin half-cells of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3, they were charged under constant current (0.1 C) and constant voltage (0.01 V, 0.01 C cut-off) conditions, rested for 10 minutes, and discharged under constant current (0.2 C, 0.5 C, 1 C, 2 C, or 3 C) conditions until the voltage reached 1.5 V.

[0353] The rate capability of each coin half cell was evaluated according to Equation 7 below by periodically changing the discharge rate to 0.2 C, 0.5 C, 1 C, 2 C, and 3 C, respectively, as the number of charge / discharge cycles increased. The half cell was discharged at a rate of 0.1 C during the 1st to 3rd charge / discharge cycles.

[0354] [Formula 7]

[0355] High-rate discharge characteristics (%) = (discharge capacity when discharging a half cell at a rate of 3 C) / (discharge capacity when discharging a half cell at a rate of 0.2 C) Х 100

[0356]

[0357] Unit of classification Example 1-1 Example 1-2 Example 1-3 Example 1-4 Example 1-5 Example 1-6 Example 1-7 Comparative Example 1-1 Comparative Example 1-2 Comparative Example 1-3 Single-walled carbon nanotube - Manufacturing Example 1-1 Manufacturing Example 1-2 Manufacturing Example 1-3 Manufacturing Example 1-4 Manufacturing Example 1-5 Manufacturing Example 1-6 Manufacturing Example 1-7 Comparative Manufacturing Example 1-1 Comparative Manufacturing Example 1-2 Comparative Manufacturing Example 1-3 Specific surface area m 2 / g1,5571,5501,6501,4201,5531,3021,5101,1501,7801,830Nickel contentmg / kg544433431425Formula 1 1) 16.3916.1517.1914.7916.0113.4215.7311.8620.7024.40Iron contentmg / kg1311371731771301751322.0302,0493,905Bulk densitykg / m 3 7.57.57.47.47.67.27.37.57.14.8Tap Density7.57.67.47.67.87.27.48.29.37.1Formula 2 2) 1.001.011.001.031.031.001.011.091.311.48 Powder resistivity value ohm·cm< 0.001< 0.001< 0.001< 0.001< 0.001< 0.0010.01400.01350.0130 Raman measurement peak intensity ratio (I G / I D)-51.352.152.053.651.352.551.952.741.131.2Thermogravity Analysis 40℃~300℃% 0.85 0.92 0.97 1.03 1.16 1.01 0.98 1.86 1.68 1.84 300℃~550℃ 0.39 0.51 0.67 0.33 0.62 0.34 0.55 2.95 3.82 59.31 40℃~550℃ 1.24 1.43 1.64 1.36 1.78 1.35 1.70 4.8 15.50 61.15 Thermal decomposition start temperature ℃ 630 60 55 80 610 57 56 10 59 55 20 5 10 35 0 Residue content % None None None None None None None 0.56 0.64 2.13 Storage stability Initial Viscosity cP1,4201,3501,3321,4501,1241,3251,3201,1501,8231,125 Viscosity after one month1,8391,6751,5201,7501,2901,7531,5101,7803,2641,620 Viscosity change rate%29.519.412.717.112.924.414.435.417930.6 Dispersibility-○○○○○○○○×△Dispersion stability○○○○○○○△×△Initial efficiencyCharge in 1 cycle Capacity mAh / g543.1545.2541.5542.5541.8542.7541.3522.2528.8528.11 Discharge in 1 cycle Capacity474.7475.4476.0475.2475.2472.1474.3415.7455.8443.6Initial Efficiency%87.487.287.987.687.787.087.679.686.284.0Life CharacteristicsCapacity Retention Rate74757276737274486965High Rate Discharge Characteristic discharge capacity (@0.2C) mAh / g 530.5535.3531.2530.3531531.2531.3490.2518.6510.3 Discharge capacity (@0.5C) 510.2511.3512.8510.5509.5510.3509.5411.6500.5480.6 Discharge capacity (@1C) 502.6503.1504.55 01.6501.5502.6500.3352.6482.5420.9Discharge capacity (@2C)491.1492.5491.6490.2489.9491.8490.6308.6469.7380.4Discharge capacity (@3C)476.9478478.1478.9478.4481.8480.3229.9459.5306.7High-rate discharge characteristics%89.989.39090.390.190.790.446.988.660.11) Equation 1: X / (100-Y), where X is the BET surface area of ​​a single-walled carbon nanotube (unit: m. 2 / g), and the Y is a number representing the content of nickel element (unit: mg / kg). 2) Equation 2: TD / BD, where BD is the bulk density of the single-walled carbon nanotube (unit: kg / m 3 ) is a number representing the tap density of the single-walled carbon nanotube (unit: kg / m). 3 ) is a number representing .

[0358]

[0359] As can be confirmed in Table 1 above, the single-walled carbon nanotubes of Manufacturing Examples 1-1 to 1-7 that satisfy Equation 1 have improved electrical conductivity compared to the single-walled carbon nanotubes of Comparative Manufacturing Examples 1-1 to 1-3 that do not satisfy Equation 1.

[0360] In addition, it was confirmed that the single-walled carbon nanotube dispersions of Manufacturing Examples 1-1 to 1-7 satisfying the above formulas 1 and 2 had improved dispersibility and storage stability.

[0361] In addition, it was confirmed that the secondary batteries of Examples 1-1 to 1-7, which applied the single-walled carbon nanotubes of Manufacturing Examples 1-1 to 1-7 that satisfy Equation 1 as a conductive material, had improved initial efficiency, life characteristics, and high-rate discharge characteristics compared to the secondary batteries of Comparative Examples 1-1 to 1-3, which applied the single-walled carbon nanotubes of Comparative Manufacturing Examples 1-1 to 1-3 that do not satisfy Equation 1 as a conductive material.

[0362]

[0363] Manufacturing example 2

[0364] Manufacturing Example 2-1

[0365] A mixture containing iron sulfide (FeS) was prepared by first heating methane, a catalyst containing iron element, and a promoter containing sulfur element at approximately 420°C. Subsequently, 200 mg of single-walled carbon nanotubes were prepared from particles containing iron sulfide (FeS) and carbon atoms by second heating at approximately 800°C.

[0366] Afterwards, the reactor was purified at about 1,000°C for 60 minutes under an argon atmosphere and vacuum conditions, and then cooled to room temperature to produce purified single-walled carbon nanotubes.

[0367] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0368]

[0369] Manufacturing Example 2-2

[0370] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 2-1, except that the purification treatment was performed at about 950°C for 80 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 2-1.

[0371]

[0372] Manufacturing Example 2-3

[0373] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 2-1, except that instead of preparing a mixture containing iron sulfide (FeS) by first heating at about 420°C in Manufacturing Example 2-1, a mixture containing iron sulfide (FeS) was prepared by first heating at about 450°C.

[0374]

[0375] Manufacturing Example 2-4

[0376] A single-walled carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 2-1, except that single-walled carbon nanotubes were prepared from particles containing iron sulfide (FeS) and carbon atoms by secondary heating at about 820°C instead of preparing single-walled carbon nanotubes from particles containing iron sulfide (FeS) and carbon atoms by secondary heating at about 800°C in Manufacturing Example 2-1.

[0377]

[0378] Manufacturing Example 2-5

[0379] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 2-1, except that the purification treatment was performed at about 900°C for 80 minutes instead of at about 1,000°C for 60 minutes in Manufacturing Example 2-1.

[0380]

[0381] Manufacturing Example 2-6

[0382] A mixture containing iron sulfide (FeS) was prepared by first heating methane, a catalyst containing iron element, and a promoter containing sulfur element at approximately 420°C. Subsequently, 200 mg of single-walled carbon nanotubes were prepared from particles containing iron sulfide (FeS) and carbon atoms by second heating at approximately 800°C. Subsequently, the single-walled carbon nanotubes were added to 60 L of a 36% hydrochloric acid aqueous solution and stirred at approximately 25°C for approximately 10 hours, thereby preparing purified single-walled carbon nanotubes.

[0383] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0384]

[0385] Comparative Manufacturing Example 2-1

[0386] 200 mg of single-walled carbon nanotubes (TUBALL, OCSiAl) were prepared. Then, the single-walled carbon nanotubes were added to 100 ml of a 40% nitric acid aqueous solution and stirred at approximately 55°C for approximately 8 hours to produce purified single-walled carbon nanotubes.

[0387] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0388]

[0389] Comparative Manufacturing Example 2-2

[0390] A single-wall carbon nanotube dispersion was prepared by the same process as in Comparative Manufacturing Example 2-1, except that stirring was performed at about 50°C for about 6 hours instead of stirring at about 55°C for about 8 hours in Comparative Manufacturing Example 2-1.

[0391]

[0392] Comparative Manufacturing Example 2-3

[0393] A mixture containing iron sulfide (FeS) was prepared by first heating methane, a catalyst containing iron element, and a promoter containing sulfur element at approximately 350°C. Subsequently, 200 mg of single-walled carbon nanotubes were prepared from particles containing iron sulfide (FeS) and carbon atoms by second heating at approximately 650°C.

[0394] Thereafter, 1 kg of a mixture was prepared by mixing carboxymethyl cellulose (Sigma Aldrich 419273, Mw 85,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent into the single-walled carbon nanotubes. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0395]

[0396] Second Example

[0397] Example 2-1

[0398] <Cathode Manufacturing>

[0399] Silicon graphite composite: A negative electrode active material slurry containing the single-walled carbon nanotube dispersion of the above Preparation Example 1: carboxymethyl cellulose (CMC) thickener: starene butadiene rubber (SBR) binder in a weight ratio of 96.52:0.08:1.2:2.2 was coated on a Cu foil current collector having a thickness of about 10 μm to a thickness of about 30 μm, and then dried at 100°C for about 12 hours to manufacture a negative electrode.

[0400] <Secondary Battery (Coin Half-Cell) Manufacturing>

[0401] A metal lithium foil of about 0.3 mm was used as the positive electrode, and a polyethylene separator was interposed between the positive electrode and the negative electrode. Then, EC:EMC was mixed in a ratio of 3:7 and a non-aqueous electrolyte of LiPF61M was injected to manufacture a coin half-cell.

[0402]

[0403] Example 2-2

[0404] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 2-2 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0405]

[0406] Example 2-3

[0407] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 2-3 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0408]

[0409] Example 2-4

[0410] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 2-4 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0411]

[0412] Example 2-5

[0413] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 2-5 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0414]

[0415] Example 2-6

[0416] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 2-6 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0417]

[0418] Comparative Example 2-1

[0419] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 2-1 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0420]

[0421] Comparative Example 2-2

[0422] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 2-2 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0423]

[0424] Comparative Example 2-3

[0425] A coin half-cell was manufactured by the same process as Example 2-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 2-3 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 2-1 in the above Example 2-1.

[0426]

[0427] Experimental Example 2

[0428] Experimental Example 2-1 - Thermogravimetric Analysis

[0429] For each of the purified single-walled carbon nanotubes of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3, the weight change by temperature range, the start temperature of thermal decomposition, and the content of residue after completion of thermal decomposition were measured using a thermogravimetric analyzer, and the results are shown in Table 2 below.

[0430]

[0431] Experimental Example 2-2 - Elemental Content Measurement

[0432] 1 mg of each of the purified single-walled carbon nanotubes of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3 was combusted at high temperature in an elemental analyzer. Thereafter, the tube was reduced and passed through a GC column, whereby the contents of sulfur, oxygen, and nitrogen were measured based on the migration speed. The results are shown in Table 2 below.

[0433]

[0434] Experimental Example 2-3 - Average Diameter

[0435] The diameter of each purified single-walled carbon nanotube of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3 was measured.

[0436] The above average diameter was obtained using an atomic force microscope (AFM). The above diameter corresponds to the average value of the top 100 single-walled carbon nanotubes with the largest average diameter and the bottom 100 single-walled carbon nanotubes.

[0437]

[0438] Experimental Example 2-4 - Powder Resistance Measurement

[0439] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3, the powder resistance was measured using a powder resistance meter (MCP-PD51) equipped with a 4-pin probe, and the powder resistance values ​​when the rolling density was 1 g / cc are shown in Table 2 below.

[0440]

[0441] Experimental Example 2-5 - Bulk Density Measurement

[0442] Each of the purified single-walled carbon nanotubes of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3 was filled into a 20 ml glass cylinder (Ronyes Co.) of known weight, and the weight was measured, and the bulk density was calculated according to the following equation. The results are shown in Table 2 below.

[0443] [ceremony]

[0444] Bulk density (kg / m) 3 ) = Single-walled carbon nanotube weight (kg) / Single-walled carbon nanotube volume (m 3 )

[0445]

[0446] Experimental Example 2-6 - Tap Density Measurement

[0447] A 10 ml glass cylinder (Ronyes) was placed on a scale and zeroed. Thereafter, the glass cylinder was tilted, and 10 ml of each of the purified single-walled carbon nanotubes of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3 was slowly added. The volume was measured by reading the graduation by aligning the height of the single-walled carbon nanotube with the eye level, and then the cylinder was placed on the scale and the weight was measured. Thereafter, the cylinder was lightly tapped on the floor about 100 times, and the volume was measured again by reading the graduation of the cylinder, and the tap density was calculated according to the following equation. The results are shown in Table 2 below.

[0448] [ceremony]

[0449] Tap density (kg / m) 3 ) = Single-wall carbon nanotube weight (kg) / Single-wall carbon nanotube volume (m) after 100 taps 3 )

[0450]

[0451] Experimental Example 2-7 - Raman Measurement

[0452] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3, the Raman spectrum was measured using Renishaw's invia. In the Raman spectrum analysis, the G band (approximately 1,591 cm -1 ) peak intensity (I G ) and D band (approximately 1,343 cm -1 ) peak intensity (I D ) measured and expressed as a peak intensity ratio (I G / I D ) are shown in Table 2 below.

[0453]

[0454] Experimental Example 2-8 - Storage Stability

[0455] For each of the single-walled carbon nanotube dispersions of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3, the initial viscosity and the viscosity after one month were measured at room temperature using a DV2T LV viscometer (Brookfield), and the viscosity change rate was calculated according to the following calculation formula. The results are shown in Table 2 below.

[0456] [Calculation formula]

[0457] Viscosity change rate (%) = [(viscosity after one month - initial viscosity) / initial viscosity] × 100

[0458]

[0459] Experimental Example 2-9 - Dispersibility

[0460] Zeta potential was measured for each of the single-walled carbon nanotube dispersions of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3. The evaluation was performed according to the following criteria, and the results are shown in Table 2 below.

[0461] - ○: Absolute value exceeds 25 mV

[0462] - △: Absolute value is 10 mV to 25 mV or less

[0463] - ×: Absolute value is less than 10mV

[0464]

[0465] Experimental Example 2-10 - Dispersion Stability

[0466] The single-walled carbon nanotube dispersions of each of Manufacturing Examples 2-1 to 2-6 and Comparative Manufacturing Examples 2-1 to 2-3 were placed in glass bottles and the presence or absence of aggregation was measured for 50 days. The evaluation was performed according to the following criteria, and the results are shown in Table 2 below.

[0467] - ○: Coagulation occurs after 2 weeks

[0468] - △: Coagulation occurs within 1 to 2 weeks

[0469] - ×: Coagulation occurs within 1 week

[0470]

[0471] Experimental Example 2-11 - Initial Efficiency of Coin Half-Cell

[0472] For each coin half-cell of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, formation was performed by performing one charge / discharge cycle at 0.1 C, and then the initial charge / discharge characteristics were confirmed by one charge / discharge cycle at 0.2 C. The initial efficiency was calculated according to the following equation, and the results are shown in Table 2 below.

[0473] The above charging and discharging process was set to start in CC (constant current) mode at a current of 0.1 C up to 0.01 V under room temperature conditions, then switch to CV (constant voltage) and cut off at 0.01 C, and proceed in CC (constant current) mode at a current of 0.1 C up to 1.5 V during discharging.

[0474] [ceremony]

[0475] Initial efficiency (%) = (discharge capacity in 1 cycle) / (charge capacity in 1 cycle) Х 100

[0476]

[0477] Experimental Example 2-12 - Coin Half-Cell Lifetime Characteristics

[0478] For each coin half-cell of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, charge / discharge was repeated 70 times under the same conditions as in Experimental Example 2-11, and then the discharge capacity was measured, and the capacity retention rate compared to the discharge capacity in one cycle of Experimental Example 2-11 was measured. The results are shown in Table 2 below.

[0479]

[0480] Experimental Example 2-13 - High-Rate Discharge Characteristics of a Coin Half-Cell

[0481] For each of the coin half-cells of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, they were charged under constant current (0.1 C) and constant voltage (0.01 V, 0.01 C cut-off) conditions, rested for 10 minutes, and discharged to 1.5 V under constant current (0.2 C, 0.5 C, 1 C, 2 C, or 3 C) conditions.

[0482] The rate capability of each coin half cell was evaluated according to the following equation by periodically changing the discharge rate to 0.2C, 0.5C, 1C, 2C, and 3C, respectively, as the number of charge / discharge cycles increased. The half cell was discharged at a rate of 0.1 C during the 1st to 3rd charge / discharge cycles.

[0483] [ceremony]

[0484] High-rate discharge characteristics (%) = (discharge capacity when discharging a half cell at a rate of 3 C) / (discharge capacity when discharging a half cell at a rate of 0.2 C) Х 100

[0485]

[0486] Unit of classification Example 2-1 Example 2-2 Example 2-3 Example 2-4 Example 2-5 Example 2-6 Comparative Example 2-1 Comparative Example 2-2 Comparative Example 2-3 Single-walled carbon nanotube - Manufacturing Example 2-1 Manufacturing Example 2-2 Manufacturing Example 2-3 Manufacturing Example 2-4 Manufacturing Example 2-5 Manufacturing Example 2-6 Comparative Manufacturing Example 2-1 Comparative Manufacturing Example 2-2 Comparative Manufacturing Example 2-3 Thermal weight Analysis 40℃~300℃% 0.85 0.92 0.97 1.03 1.16 1.01 1.86 1.68 1.84 300℃~550℃ 0.39 0.51 0.67 0.33 0.62 0.34 2.95 3.82 59.31 40℃~550℃ 1.24 1.43 1.64 1.36 1.78 1.35 4.8 15.50 61.15 Thermal decomposition start temperature ℃ 630 60 55 80 610 57 56 10 52 0 5 10 35 0 Residue content % Not detected Not detected Not detected Not detected Not detected Not detected Not detected 0.56 0.64 2.13 Sulfur element content Weight % Not detected Not detected Not detected Not detected Not detected Not detected Not detected 0.23 50.63 10.42 1 Oxygen element Content 0.1930.2860.4120.1280.0751.3551.5212.8691.325Nitrogen Element Content 0.2660.1090.101Not Detected 0.0880.1270.1240.5310.846Oxygen + Nitrogen Element Content 0.4590.3950.5130.1280.1631.4821.6453.4002.171Average Diameter nm 2.02.12.22.02.02.01.01.81.8Powder Resistivity Value ohm cm< 0.001< 0.001< 0.001< 0.001< 0.0010.01450.01350.0132Bulk Density kg / m 3 7.57.57.47.47.67.29.233.210.1Tap density7.57.67.47.67.87.210.252.512.3Raman measurement peak intensity ratio (I G / I D)-51.351.253.251.550.850.134.449.150.1Storage stabilityInitial viscositycP1,4201,3501,3321,4501,1241,3251,1501,8231,125Viscosity after one month1,8391,6751,5201,7501,2901,7531,7803,2641,620Viscosity change rate%29.519.412.717.112.924.435.417930.6Dispersibility-○○○○○○○×△Dispersion stability○○○○○○△×△Initial efficiencyCharge in 1 cycle Capacity mAh / g 543.35 41.45 42.55 45.25 40.25 41.85 20.25 40.35 34.5 Discharge capacity in 1 cycle 474.84 72.14 76.9 477.64 73.84 71.44 1246 6.34 49 Initial efficiency % 87.48 7.28 7.9 87.68 7.78 7.0 79.28 6.38 4.0 Life characteristics Capacity retention 7376 7375 727 248 69 65 High rate discharge Characteristic discharge capacity (@0.2C) mAh / g 531.5530.6 531.9532.1530.9531.1490.5528.5510.3 Discharge capacity (@0.5C) 510510.3509.5510.3511.3510.2429.5502.3480.6 Discharge capacity (@1C) 500.2501.2500 .3501.4499.5500.3350.2492.2420.3Discharge capacity (@2C)490.2491.3490.6490.2490.3490.8300.6481.6365.3Discharge capacity (@3C)477.8473.8478.7480.5478.3481.7230468.3306.7High-rate discharge characteristics%89.989.39090.390.190.746.988.660.1

[0487]

[0488] As can be confirmed in Table 2 above, the single-walled carbon nanotubes of Manufacturing Examples 2-1 to 2-6, which had a weight change of 5% or less in the range of 40°C to 550°C and a content of residual sulfur element of less than 0.1 wt%, had improved electrical conductivity compared to the single-walled carbon nanotubes of Comparative Manufacturing Examples 2-1 to 2-3, and the increase in viscosity over time was minimized, thereby improving storage stability.

[0489] In addition, it was confirmed that the secondary batteries of Examples 2-1 to 2-6, which include the single-walled carbon nanotubes of Manufacturing Examples 2-1 to 2-6 as a conductive material, have improved initial efficiency, life characteristics, and high-rate discharge characteristics compared to the secondary batteries of Comparative Examples 2-1 to 2-3.

[0490]

[0491] Manufacturing example 3

[0492] Manufacturing Example 3-1

[0493] 200 mg of single-walled carbon nanotubes were prepared by chemical vapor deposition (CVD) using a catalyst. Then, the single-walled carbon nanotubes were added to 60 L of a 36% hydrochloric acid aqueous solution and stirred at approximately 25°C for approximately 3 hours, thereby preparing purified single-walled carbon nanotubes.

[0494] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0495]

[0496] Manufacturing Example 3-2

[0497] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 3-1, except that stirring was performed at about 25°C for about 2 hours and 30 minutes instead of stirring at about 25°C for about 3 hours in Manufacturing Example 3-1.

[0498]

[0499] Manufacturing Example 3-3

[0500] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 3-1, except that stirring was performed at about 25°C for about 5 hours instead of stirring at about 25°C for about 3 hours in Manufacturing Example 3-1.

[0501]

[0502] Manufacturing Example 3-4

[0503] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 3-1, except that a 38% hydrochloric acid aqueous solution was used instead of the 36% hydrochloric acid aqueous solution in Manufacturing Example 3-1.

[0504]

[0505] Manufacturing Example 3-5

[0506] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 3-1, except that a 65% nitric acid aqueous solution was used instead of the 36% hydrochloric acid aqueous solution in Manufacturing Example 3-1.

[0507]

[0508] Manufacturing Example 3-6

[0509] A single-wall carbon nanotube dispersion was prepared by the same process as in Manufacturing Example 3-1, except that a 98% concentrated sulfuric acid aqueous solution was used instead of the 36% hydrochloric acid aqueous solution in Manufacturing Example 3-1.

[0510]

[0511] Comparative Manufacturing Example 3-1

[0512] 200 mg of single-walled carbon nanotubes were prepared by chemical vapor deposition (CVD) using a catalyst.

[0513] Thereafter, 1 kg of a mixture was prepared by mixing carboxymethyl cellulose (Sigma Aldrich 419273, Mw 85,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent into the single-walled carbon nanotubes. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0514]

[0515] Comparative Manufacturing Example 3-2

[0516] 200 mg of single-walled carbon nanotubes were prepared by chemical vapor deposition (CVD) using a catalyst. Then, the single-walled carbon nanotubes were added to 100 ml of a 40% nitric acid aqueous solution and stirred at approximately 55°C for approximately 8 hours to prepare purified single-walled carbon nanotubes.

[0517] Thereafter, 1 kg of a mixture was prepared by mixing the purified single-walled carbon nanotubes with carboxymethyl cellulose (Sigma Aldrich 419273, Mw 90,000 g / mol, degree of substitution 0.87) as a dispersant and water as a solvent. Thereafter, the mixture was mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to prepare a single-walled carbon nanotube dispersion.

[0518]

[0519] Comparative Manufacturing Example 3-3

[0520] Single-walled carbon nanotubes (TUBALL, OCSiAl) were prepared. Then, polyvinylpyrrolidone (a dispersant) and water (a solvent) were mixed with the single-walled carbon nanotubes to produce a 1 kg mixture. The mixture was then mixed using a mixer and subjected to high-pressure treatment using a high-pressure homogenizer to produce a single-walled carbon nanotube dispersion.

[0521]

[0522] Third Example

[0523] Example 3-1

[0524] <Cathode Manufacturing>

[0525] Silicon graphite composite: A negative electrode active material slurry containing the single-walled carbon nanotube dispersion of the above Manufacturing Example 3-1: carboxymethyl cellulose (CMC) thickener: starene butadiene rubber (SBR) binder in a weight ratio of 96.5:0.1:1.1:2.3 was coated on a Cu foil current collector having a thickness of about 10 μm to a thickness of about 30 μm, and then dried at 100°C for about 12 hours to manufacture a negative electrode.

[0526] <Secondary Battery (Coin Half-Cell) Manufacturing>

[0527] A metal lithium foil of about 0.3 mm was used as the positive electrode, and a polyethylene separator was interposed between the positive electrode and the negative electrode. Then, EC:EMC was mixed in a ratio of 3:7 and a non-aqueous electrolyte of LiPF61M was injected to manufacture a coin half-cell.

[0528]

[0529] Example 3-2

[0530] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 3-2 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1.

[0531]

[0532] Example 3-3

[0533] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 3-3 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0534]

[0535] Example 3-4

[0536] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 3-4 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0537]

[0538] Example 3-5

[0539] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 3-5 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0540]

[0541] Example 3-6

[0542] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Manufacturing Example 3-6 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0543]

[0544] Comparative Example 3-1

[0545] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 3-1 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0546]

[0547] Comparative Example 3-2

[0548] A coin half-cell was manufactured by the same process as Example 3-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 3-2 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0549]

[0550] Comparative Example 3-3

[0551] A coin half-cell was manufactured by the same process as in Example 3-1, except that the single-walled carbon nanotube dispersion of Comparative Manufacturing Example 3-3 was used instead of the single-walled carbon nanotube dispersion of Manufacturing Example 3-1 in the above Example 3-1.

[0552]

[0553] Experimental Example 3

[0554] Experimental Example 3-1 - Elemental Content Measurement

[0555] 1 mg of each of the purified single-walled carbon nanotubes of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3 was combusted at high temperature in an elemental analyzer. Thereafter, the contents of carbon and oxygen elements were measured by reducing them in a reaction tube and passing them through a GC column and separating them according to their migration speeds. The results are shown in Table 3 below.

[0556]

[0557] Experimental Example 3-2 - Measurement of Impurity Content

[0558] After dissolving each of the purified single-walled carbon nanotubes of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3 in 65 wt% nitric acid, the element content was measured using inductively coupled plasma optical emission spectrometry (ICP-OES) under the following measurement conditions, and the results are shown in Table 3 below.

[0559] [Measurement conditions]

[0560] - Device: Agilent 5110 SVDV

[0561] - RF power: 1.2 kW

[0562] - Nebulizer flow: 0.7 L / min

[0563] - Plasma flow: 12 L / min

[0564] - Aux flow: 1 L / min

[0565] - Read time: 5 sec

[0566]

[0567] Experimental Example 3-3 - XRD Measurement

[0568] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3, X-rays were irradiated using Rigaku's X-ray diffraction equipment Ultima IV, and the diffraction angle (2θ) of the diffracted X-rays was measured.

[0569] For the measured XRD graph results, the section of 2θ = 14° to 30° was designated as the baseline, and the area of ​​the peak of 2θ = 14° to 30° and the area of ​​the peak around 2θ = 26° were calculated in Gaussian type using MDI's JADE 9 software, and the results are shown in Table 3 below.

[0570]

[0571] Experimental Example 3-4 - Raman Measurement

[0572] For each of the purified single-walled carbon nanotubes of the above Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3, the Raman spectrum was measured using Renishaw's invia. In the Raman spectrum analysis, the G band (approximately 1,591 cm -1 ) peak intensity (I G ) and D band (approximately 1,343 cm -1 ) peak intensity (I D ) measured and expressed as a peak intensity ratio (I G / I D ) are shown in Table 3 below.

[0573]

[0574] Experimental Example 3-5 - Thermogravimetric Analysis

[0575] For each of the purified single-walled carbon nanotubes of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3, the weight change by temperature range, the start temperature of thermal decomposition, and the content of residue after completion of thermal decomposition were measured using a thermogravimetric analyzer, and the results are shown in Table 3 below.

[0576]

[0577] Experimental Example 3-6 - Specific surface area, length, average diameter, and pore volume

[0578] For each of the purified single-walled carbon nanotubes of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3, the length, diameter, specific surface area, and pore volume were measured.

[0579] The above length and average diameter were obtained using an atomic force microscope (AFM). The above length corresponds to the average value of the top 100 single-walled carbon nanotubes with the largest average length and the bottom 100 single-walled carbon nanotubes, and the above diameter corresponds to the average value of the top 100 single-walled carbon nanotubes with the largest average diameter and the bottom 100 single-walled carbon nanotubes.

[0580] The above specific surface area and pore volume were measured from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using BELSORP-mini II of BEL Japan, and the results are shown in Table 3 below.

[0581]

[0582] Experimental Example 3-7 - Storage Stability

[0583] For each of the single-walled carbon nanotube dispersions of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3, the initial viscosity and the viscosity after one month were measured at room temperature using a DV2T LV viscometer (Brookfield), and the viscosity change rate was calculated according to the following calculation formula. The results are shown in Table 3 below.

[0584] [Calculation formula]

[0585] Viscosity change rate (%) = [(viscosity after one month - initial viscosity) / initial viscosity] × 100

[0586]

[0587] Experimental Example 3-8 - Dispersibility

[0588] Zeta potential was measured for each of the single-walled carbon nanotube dispersions of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3. The evaluation was performed according to the following criteria, and the results are shown in Table 3 below.

[0589] - ○: Absolute value exceeds 25 mV

[0590] - △: Absolute value is 10 mV to 25 mV or less

[0591] - ×: Absolute value is less than 10mV

[0592]

[0593] Experimental Example 3-9 - Dispersion Stability

[0594] The single-walled carbon nanotube dispersions of each of Manufacturing Examples 3-1 to 3-6 and Comparative Manufacturing Examples 3-1 to 3-3 were placed in glass bottles and the presence or absence of aggregation was measured for 50 days. The evaluation was performed according to the following criteria, and the results are shown in Table 3 below.

[0595] - ○: Coagulation occurs after 2 weeks

[0596] - △: Coagulation occurs within 1 to 2 weeks

[0597] - ×: Coagulation occurs within 1 week

[0598]

[0599] Experimental Example 3-10 - Initial Efficiency of Coin Half-Cell

[0600] For each coin half-cell of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-3, formation was performed by performing one charge / discharge cycle at 0.1 C, and then the initial charge / discharge characteristics were confirmed by one charge / discharge cycle at 0.2 C. The initial efficiency was calculated according to the following calculation formula, and the results are shown in Table 1 below.

[0601] The above charging and discharging process was set to start in CC (constant current) mode at a current of 0.1 C up to 0.01 V under room temperature conditions, then switch to CV (constant voltage) and cut off at 0.01 C, and proceed in CC (constant current) mode at a current of 0.1 C up to 1.5 V during discharging.

[0602] [Calculation formula]

[0603] Initial efficiency (%) = (discharge capacity in 1 cycle) / (charge capacity in 1 cycle) Х 100

[0604]

[0605] Experimental Example 3-11 - Coin Half-Cell Lifetime Characteristics

[0606] For each coin half-cell of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-3, charge / discharge was repeated 70 times under the same conditions as in Experimental Example 3-10, and then the discharge capacity was measured, and the capacity retention rate compared to the discharge capacity in one cycle of Experimental Example 3-10 was measured. The results are shown in Table 3 below.

[0607]

[0608] Experimental Example 3-12 - High-Rate Discharge Characteristics of a Coin Half-Cell

[0609] For each of the coin half-cells of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-3, they were charged under constant current (0.1 C) and constant voltage (0.01 V, 0.01 C cut-off) conditions, rested for 10 minutes, and discharged to 1.5 V under constant current (0.2 C, 0.5 C, 1 C, 2 C, or 3 C) conditions.

[0610] The rate capability of each coin half cell was evaluated according to the following calculation formula by periodically changing the discharge rate to 0.2C, 0.5C, 1C, 2C, and 3C, respectively, as the number of charge / discharge cycles increased. The half cell was discharged at a rate of 0.1 C during the 1st to 3rd charge / discharge cycles.

[0611] [Calculation formula]

[0612] High-rate discharge characteristics (%) = (discharge capacity when discharging a half cell at a rate of 3 C) / (discharge capacity when discharging a half cell at a rate of 0.2 C) Х 100

[0613]

[0614] Unit of classification Example 3-1 Example 3-2 Example 3-3 Example 3-4 Example 3-5 Example 3-6 Comparative Example 3-1 Comparative Example 3-2 Comparative Example 3-3 Single-walled carbon nanotube - Manufacturing Example 3-1 Manufacturing Example 3-2 Manufacturing Example 3-3 Manufacturing Example 3-4 Manufacturing Example 3-5 Manufacturing Example 3-6 Comparative Manufacturing Example 3-1 Comparative Manufacturing Example 3-2 Comparative Manufacturing Example 3-3 Element ContentO Weight % 1.3551.2551.0471.8051.5101.4252.8240.9821.855C92.97293.12692.40290.79490.23191.64987.18295.10491.2400:C1:68.611:74.201:88.251:50.301:59.761:64.321:30.871:96.851:49.19 Impurity Content Comg / kg< 2< 2< 2< 2< 2< 250< 2< 2Cr17173242321035202430Cu< 2< 2< 2< 2< 2150< 2< 2Fe1,1691,0941,4701,3311,3561,7788,4502,1741,954Mn< 1< 1< 1< 1< 115< 1< 1Ni< 7< 7< 7< 7< 759.520.730.1Zn< 18< 18< 18< 18< 1845< 18< 18XRD measurement Peak area around 2θ = 26° 1) %807780757573507365Raman measurement peak intensity ratio (I G / I D )-51.351.752.251.550.950.534.450.150.4Thermogravity Analysis 40℃~300℃% 1.561.891.561.731.431.751.861.681.84300℃~550℃1.651.691.651.622.012.3162.123.8259.3140℃~550℃3.213.583.213.353.444.0663.985.5061.15 Thermal decomposition start temperature℃580550570560555520390500450 Residue content%0.170.220.490.460.550.572.560.881.13 Specific surface area m 2 / g1,5571,4501,4101,3901,1201,1501351,180850Lengthnm1,5001,6501,6001,5201,1001,050501,310895Average diameter2.02.12.22.02.02.01.01.81.8Pore volumecc / g1.0621.0501.0261.0530.9860.9890.0860.9560.936Storage stabilityInitial viscositycP1,4201,3501,3321,4501,1241,3251,1501,8231,125After one month Viscosity 1,839 1,675 1,520 1,750 1,290 1,753 1,780 3,264 1,620 Viscosity change rate % 29.5 19.4 12.7 17.1 12.9 24.4 35.4 179 30.6 Dispersibility - ○○○○○○○○ × △ Dispersion stability ○○○○○○○ △ × △ Initial efficiency Charge capacity in 1 cycle mAh / g 5 31.25 32.15 30.6 5 31.25 29.25 31.5 49 1.25 28.5 5 11.5 Discharge capacity in 1 cycle 464.3 464 464.8 465.3 464.1 462.439 1455.6 4 29.7 Initial Efficiency %87.487.287.687.687.787.079.686.284.0Life CharacteristicsCapacity Retention Rate747572767372486965High Rate Discharge CharacteristicsDischarge Capacity (@0.2C)mAh / g530.5531.5530.8530.9531.1530.4491.5520.5511.3Discharge Capacity (@0.5C)510.5511.3510.2512.1510.9509.8410.5502.3480.2Discharge Capacity (@1C)502.6499.8501 .6498.3502.3500.1352.2485.3458.2Discharge capacity (@2C)490.2490.5490.6489.3490.5489.6300.2470.6382.6Discharge capacity (@3C)476.9474.6477.7479.4478.5481.1230.5461.2307.3High rate Discharge characteristics %89.989.39090.390.190.746.988.660.11) Peak area around 2θ = 26°: When the section of 2θ = 14° to 30° is used as the baseline, the peak area around 2θ = 26° compared to the total peak area at 2θ = 14° to 30°

[0615]

[0616] As can be confirmed in Table 3 above, the single-walled carbon nanotubes of Manufacturing Examples 3-1 to 3-6 were found to have improved dispersibility and storage stability compared to the single-walled carbon nanotubes of Comparative Manufacturing Examples 3-1 to 3-3, as the oxygen element and the carbon element satisfied a specific weight ratio.

[0617] In addition, it was confirmed that the secondary batteries of Examples 3-1 to 3-6, which applied the single-walled carbon nanotubes of Manufacturing Examples 3-1 to 3-6 as a conductive material, had improved initial efficiency, life characteristics, and high-rate discharge characteristics compared to the secondary batteries of Comparative Examples 3-1 to 3-3, which applied the single-walled carbon nanotubes of Comparative Manufacturing Examples 3-1 to 3-3 as a conductive material.

[0618]

[0619] The embodiments can be applied to single-walled carbon nanotubes, single-walled carbon nanotube dispersions, electrodes and secondary batteries including the same.

Claims

1. When the temperature is increased at 10 ℃ / min using a thermogravimetric analyzer, the weight change between 40 ℃ and 550 ℃ is 5% or less, A single-walled carbon nanotube having a sulfur element content of less than 0.1 wt% relative to the total weight of elements measured by an elemental analyzer.

2. In paragraph 1, A single-walled carbon nanotube having a weight change of 2% or less at a temperature of 40°C to 550°C.

3. In paragraph 1, The above single-walled carbon nanotube is a single-walled carbon nanotube having a thermal decomposition start temperature of 550°C or higher as measured by the thermogravimetric analyzer.

4. In paragraph 1, The above single-walled carbon nanotube is a single-walled carbon nanotube having a content of residue after completion of thermal decomposition measured by the thermogravimetric analyzer of 1% or less.

5. In paragraph 1, The above single-walled carbon nanotubes have I measured by Raman spectrum G / I D Single-walled carbon nanotubes having a diameter of 35 to 150 nm.

6. In paragraph 1, A single-walled carbon nanotube having a length of 10 nm to 3,000 nm.

7. In paragraph 1, The average diameter (D) of the above single-walled carbon nanotubes 50 ) is a single-walled carbon nanotube having a diameter of 0.5 nm to 25 nm.

8. In paragraph 1, A single-walled carbon nanotube having a pore volume of 0.1 cc / g to 1.5 cc / g.

9. In paragraph 1, The above single-walled carbon nanotube is a single-walled carbon nanotube in which, when the base line is set at 2θ = 14° to 30° in a graph measured by XRD (X-ray diffraction), the peak area around 2θ = 26° is 70% or more of the total peak area at 2θ = 14° to 30°.

10. In paragraph 1, The single-walled carbon nanotube comprises an oxygen element and a carbon element, and the weight ratio of the oxygen element:carbon element measured by the elemental analyzer is 1:50 to 1:

95.

11. In paragraph 10, A single-walled carbon nanotube, wherein the content of the oxygen element is 1 wt% to 2 wt% relative to the total weight of elements measured by the elemental analyzer.

12. In paragraph 10, A single-walled carbon nanotube having a content of the carbon element of 90 to 94 wt% relative to the total weight of elements measured by the elemental analyzer.

13. In paragraph 1, The above single-walled carbon nanotube has a BET surface area of ​​1,200 m 2 / g to 1,800 m 2 / g, and a single-walled carbon nanotube having a nickel element content of less than 100 mg / kg as measured by inductively coupled plasma optical emission spectrometry (ICP-OES) and satisfying the following equation 1: [Formula 1] 12 ≤ X / (100-Y) ≤ 20 In the above equation 1, X is the BET surface area (unit: m) of the single-walled carbon nanotube. 2 / g), and the Y is a number representing the content of the nickel element (unit: mg / kg).

14. In paragraph 13, A single-walled carbon nanotube having a value of the above formula 1 of 14.5 to 17.

5.

15. In paragraph 13, A single-walled carbon nanotube having a content of the nickel element of less than 7 mg / kg.

16. In paragraph 13, A single-walled carbon nanotube having an iron element content of less than 200 mg / kg as measured by the above-mentioned inductively coupled plasma optical emission spectrometry.

17. In paragraph 13, The above single-walled carbon nanotube has a bulk density of 5 kg / m 3 10 kg / m 3 , and a single-walled carbon nanotube satisfying the following equation 2: [Formula 2] 1.0 ≤ TD / BD < 1.3 In the above equation 2, the BD is the bulk density of the single-walled carbon nanotube (unit: kg / m 3 ) is a number representing the tap density of the single-walled carbon nanotube (unit: kg / m). 3 ) is a number representing .

18. In paragraph 13, The above single-walled carbon nanotube is a single-walled carbon nanotube having a powder resistance of 0.001 ohm·cm or less at a rolling density of 1 g / cc or more.