Carbon nanotube dispersion, slurry for electrode production, and secondary battery

Abstract

The present invention relates to a carbon nanotube dispersion, a slurry for producing an electrode containing carbon nanotubes, and a secondary battery, and by controlling the particle size and amount of carbon nanotubes, the performance of the secondary battery containing carbon nanotubes can be improved.

Description

[Technical Field]

[0001] The present invention relates to a carbon nanotube dispersion, a slurry containing carbon nanotubes for producing an electrode, and a secondary battery. [Background technology]

[0002] Rapid development of the electronics, communications, and computer industries has led to remarkable development of electric vehicles, mobile phones, laptops, etc., and batteries with high energy density and stable output are required as power sources for driving portable electronic devices. In particular, lithium secondary batteries are the high-performance batteries with the highest energy density among currently commercially available secondary batteries, and are the most actively developed.

[0003] Conductive materials are substances used to facilitate the transfer of electrons between electrode active materials or between electrode active materials and current collectors, and are primarily developed as carbon-based materials. Conductive material slurry is a solution in which such conductive materials are dispersed in a solvent, and later becomes a material that makes up electrode slurry together with electrode active materials and binders. These materials have recently become increasingly important as secondary batteries expand into the medium- to large-sized battery market, such as electric vehicles and energy storage systems (ESS), and research into increasing their theoretical capacity is ongoing.

[0004] Carbon nanotubes (CNTs) are a conductive material that can increase energy density and improve battery life compared to existing powdered carbon, while also reducing battery size. These advantages are particularly significant in electric vehicle batteries, which require high capacity and rapid charging and discharging. However, despite their excellent properties, carbon nanotubes have strong hydrophobic properties and an intertwined structure between the tubes. To fully utilize these advantages, the development of new dispersion and processing methods for carbon nanotubes is essential. Furthermore, various battery manufacturers are demanding low-viscosity, high-content conductive dispersions for secondary batteries. However, as the carbon nanotube content increases, the dispersion's dispersibility decreases, which can lead to coating non-uniformity and high viscosity, potentially resulting in poor electrode coating.

[0005] Therefore, there is a need for a method to achieve high carbon nanotube content dispersions with low viscosity. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a carbon nanotube dispersion that can provide an electrode with excellent electrical performance such as high conductivity despite low viscosity by controlling the amount of fine powder during processing of carbon nanotubes, a slurry for manufacturing an electrode containing the carbon nanotubes, and an electrode and a secondary battery manufactured therefrom. [Means for solving the problem]

[0007] In the present invention, we confirmed that the size of carbon nanotube fine powder in a dispersion containing carbon nanotubes becomes smaller, and that the greater the amount of fine powder, the lower the battery performance during electrode production. As a result of extensive research to solve this problem, we found that the size and amount of fine powder corresponding to D5 in the total particle size distribution of carbon nanotubes are directly correlated with battery performance. Therefore, in the present invention, we controlled the particle size distribution D5 to be 7 μm or more, which resulted in improved battery performance during electrode production.

[0008] Therefore, according to one aspect of the present invention, there is provided a carbon nanotube dispersion in which the particle size distribution D5 of the carbon nanotubes is 7 μm or more.

[0009] According to one embodiment, the particle size distribution D5 may be, for example, 7 μm to 14 μm, 7 μm to 9 μm, 7.5 μm to 14 μm, or 7.5 μm to 9 μm. The D5 can be measured using a particle size analyzer and refers to the particle size value when the cumulative volume density reaches 5% volume density, starting from the smallest particle size sample. According to the present invention, controlling the particle size in the particle size distribution D5 of carbon nanotubes to be 7 μm or more can contribute to improving not only electrical properties such as powder conductivity of carbon nanotubes but also battery performance during electrode production.

[0010] According to another embodiment of the present invention, the carbon nanotubes may have a particle size distribution D50 of 15 to 50 μm, 20 to 45 μm, 20 to 40 μm, or 25 to 35 μm. According to another embodiment of the present invention, the carbon nanotubes may have a particle size distribution D90 of 45 to 200 μm, specifically 45 to 100 μm, 45 to 95 μm, 45 to 90 μm, 45 to 85 μm, or 50 to 80 μm. Within the adjusted ranges, the average particle size (D50) and the macro particle size (D90) alone have not been observed to have a direct correlation with battery performance. However, by controlling both the average particle size and the macro particle size while satisfying the aforementioned particle size D5, the quality of the carbon nanotube powder can be improved.

[0011]

[0012] According to one embodiment of the present invention, the carbon nanotubes may have a content of carbon nanotubes having a particle size of 17.4 μm or less of 30% by volume or less, based on the total volume of the carbon nanotubes. According to the present invention, controlling the content of carbon nanotubes having a particle size of 17.4 μm or less to 30% or less can contribute to improving not only electrical properties such as powder conductivity of the carbon nanotubes but also battery performance during electrode production. The content of carbon nanotubes having a particle size of 17.4 μm or less may be, for example, 6 to 30% by volume, 7 to 30% by volume, or 7 to 27% by volume. When these ranges are satisfied, a carbon nanotube dispersion that satisfies both low viscosity and high conductivity can be provided.

[0013]

[0014] The carbon nanotubes may be at least one selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, triple-walled carbon nanotubes, and multi-walled carbon nanotubes. The type of carbon nanotube can be appropriately selected as needed. Because carbon nanotubes can be used as conductive materials in secondary batteries, single-walled carbon nanotubes are advantageous in terms of conductivity. However, single-walled carbon nanotubes have disadvantages, such as difficulty in controlling the synthesis process due to the need for higher temperatures than multi-walled carbon nanotubes, and significant increases in costs due to the need to remove metal impurities. Therefore, according to one embodiment of the present invention, the carbon nanotubes may be a mixture of single-walled carbon nanotubes with double-walled carbon nanotubes, triple-walled carbon nanotubes, or multi-walled carbon nanotubes, or may be double-walled carbon nanotubes, triple-walled carbon nanotubes, or multi-walled carbon nanotubes.

[0015] According to one embodiment, the multi-walled carbon nanotube may be a carbon nanotube with 30 or less walls, 20 or less walls, 10 or less walls, or 4 to 30 walls. The walls can be confirmed from a TEM image, and the number of walls can be determined by directly counting them from the TEM image. Carbon nanotubes with a small number of walls, walls that are not broken, and walls that are not connected to other walls to form complex paths are preferred in terms of electrical conductivity.

[0016] According to one embodiment of the present invention, the carbon nanotubes may have a central diameter of 4 to 50 nm, specifically 4 to 30 nm. For example, the carbon nanotubes may be triple-walled or multi-walled carbon nanotubes with a central diameter of 4 to 20 nm. When such carbon nanotubes are used, electrodes with excellent electrical performance can be provided. The central diameter is the sum of the core diameter and the number of walls of the carbon nanotube. Here, since the number of walls is not uniform throughout the carbon nanotube, it is the diameter that accounts for the majority of the core diameter. The central diameter can be measured directly from a TEM image. However, since there may be deviations depending on the measurement position within the sample, this value is obtained by statistically analyzing values ​​measured at various measurement positions within the sample. The central diameter can also be estimated by measuring the core diameter, counting the number of walls, and measuring the spacing between the walls. For example, for a carbon nanotube whose central diameter is 30.5 nm actually measured from a TEM image, the central diameter of 30.5 nm can be calculated from a measured core diameter of 10 nm, 30 walls, and a spacing between the walls of 3.4 Å.

[0017]

[0018] According to one embodiment of the present invention, the carbon nanotubes may be in an entangled state or a bundled state. In a bundled state, carbon nanotube units are aligned and bundled, which is advantageous for dispersion in strands. Therefore, according to one embodiment, the carbon nanotubes may be in a bundled state. In the dispersion of the present invention, the bundled carbon nanotubes may exist in a state in which at least a portion of the long carbon nanotube threads of the bundle are unraveled during the dispersion process.

[0019] According to one embodiment of the present invention, the carbon nanotubes may be mixed with a metal catalyst for carbon nanotube synthesis, such as iron (Fe), cobalt (Co), aluminum (Al), or nickel (Ni), and the amount of the metal catalyst in the carbon nanotubes may be as small as possible, for example, 2.5 wt% or less, specifically 2.1 wt% or less. The metal content can be measured by dispersing the carbon nanotubes in an acid solution, dissolving the metal using a high-temperature microwave, or the like, and then measuring it with ICP.

[0020]

[0021] The carbon nanotube dispersion liquid may further contain a dispersion medium, which may be one or more selected from the group consisting of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutanol, acetone, tetrahydrofuran (THF), water, etc., but is not limited thereto.

[0022]

[0023] According to one embodiment of the present invention, the carbon nanotube dispersion of the present invention may have a solid content of 5% or more. According to another embodiment, the carbon nanotube dispersion of the present invention may have a viscosity of 2,000 cp or less, or 1,000 cp or less, based on a shear rate of 50 / s. According to yet another embodiment, the carbon nanotubes have a powder conductivity of 50 S / cm or more. According to the present invention, by controlling the particle size distribution D5, a high-solids dispersion having a solid content of 5% or more can have low viscosity and high powder conductivity. Therefore, an electrode manufactured using the carbon nanotubes, or a dispersion or slurry thereof, and a secondary battery including the same can exhibit excellent electrical performance.

[0024]

[0025] Carbon nanotubes satisfying the particle size distribution D5 requirement according to the present invention can be produced by controlling the processing equipment and processing conditions for pulverizing carbon nanotubes. The type of processing equipment usable for pulverizing carbon nanotubes is not particularly limited as long as the carbon nanotubes of the present invention can be produced by controlling the processing conditions, etc.; for example, various processing equipment such as those shown in FIG. 1 can be used. According to one embodiment, the carbon nanotubes of the present invention can be produced using a low-speed bead mill, specifically, a rotary bead mill that rotates at a low speed, for example, 20 to 200 rpm, 20 to 100 rpm, or 20 to 50 rpm. According to one embodiment of the present invention, the carbon nanotubes of the present invention can be produced using a rotary bead mill without an internal mixer, preferably a rotary bead mill that rotates at a low speed and without an internal mixer. The low-speed bead mill may be used in place of an improved rotor-type bead mill (which is further classified as a pin or disk type depending on the type of rotor) and a vibration ball mill. However, the rotor-type bead mill has a disadvantage in that it is difficult to control the generation of fine powder because the rotor inside the cylinder rotates and the beads move quickly between the rotors.

[0026] According to one embodiment of the present invention, the carbon nanotubes can be pulverized by a dry method.

[0027] Meanwhile, the processing conditions for pulverizing the carbon nanotubes, specifically, the bead filling rate, pulverization strength, pulverization time, bead size, etc., can be appropriately adjusted by those skilled in the art as needed.

[0028] Specifically, when a bead mill is used, the processing of the carbon nanotubes can be carried out at a filling rate of 30 to 90% or 60 to 90%, although this varies depending on the size of the beads, the volume of the container, etc. Within this filling rate range, the amount of beads is sufficient, the movement of the beads is not restricted, and excellent processing effects can be achieved.

[0029] The processing of the carbon nanotubes can be carried out at a speed of 10 to 100 rpm or 20 to 50 rpm, and excellent processing effects can be achieved within the above rpm range.

[0030] Furthermore, the carbon nanotubes may be processed using a single type of beads or a mixture of two or more types of beads. When a single type of beads is used, the diameter of the beads may be greater than 2 mm or between 2 and 5 mm. According to one embodiment, processing can be performed using a bead mill using beads with a diameter of 5 mm. When the diameter of the single type of beads is between 2 and 5 mm, excellent grinding effects are achieved, and when two or more types of mixed beads are used, the grinding effect can be further improved. An example of a mixture of two or more types of mixed beads is a mixture of beads with a diameter of 5 mm and beads with a diameter of 2 mm. The ratio of beads with different diameters in the mixed beads can be appropriately adjusted by those skilled in the art, taking into account factors such as grinding intensity. For example, when performing weak grinding using a low-speed bead mill, more 5 mm diameter beads can be used than 2 mm diameter beads.

[0031] The pulverization time may be 20 hours or less, for example, 14 hours or less, but is not limited to this, and can be adjusted appropriately depending on the type of beads used, the state of the carbon nanotube raw material, and the like.

[0032]

[0033] According to another aspect of the present invention, there is provided a slurry for manufacturing an electrode, comprising carbon nanotubes having a particle size distribution D5 of 7 μm or more. For details regarding the carbon nanotubes, including the D5, please refer to the above description.

[0034] The slurry for preparing an electrode may further include at least one selected from a conductive material, an electrode active material, and a binder, in addition to the carbon nanotubes.

[0035] The conductive material refers to a conductive material added to carbon nanotubes. The conductive material may be one or more selected from nonlinear carbon conductive materials, such as dotted carbon black, low-structure dotted carbon black (LSCB), medium-structure dotted carbon black (MSCB), metal powder, metal fiber, denka black, polyaniline, polythiophene, polypyrrole, acetylene, etc., but is not limited thereto, and may be any conductive material known in the art that can be used together with carbon nanotubes to manufacture an electrode.

[0036] The binder may be one or more selected from polyvinylpyrrolidone, polyvinylidene fluoride (PVdF), polyvinylidene fluoride copolymer, chlorotrifluoroethylene (CTFE), polyvinyl alcohol, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, starch, styrene-butadiene rubber, nitrile rubber, etc., but is not limited thereto. Any binder known in the art may be used. Polyvinylidene fluoride (PVdF) is a commonly used binder in electrode manufacturing because it can be solubilized in a wide range of solvents, has high electrochemical durability, and exhibits low swelling. The binder may have a molecular weight ranging from 500,000 to 1,200,000 g / mol.

[0037] The electrode active material may be a positive electrode active material. The positive electrode active material may be, but is not limited to, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, LiMnO3, LiMn2O3), lithium vanadium oxide (LiV3O4, LiV3O8, V2O5, etc.), lithium copper oxide (Li2CuO2), lithium manganese composite oxide, lithium sulfide, etc. Any active material known in the art may be used. For example, the electrode active material may be Li x1 NiO2(0.5 <x1<1.3)、Li x2 (Nia1 Co b1 Mn c1 )O2(0.5 < x2 < 1.3, 0 < a1 < 1, 0 < b1 < 1, 0 < c1 < 1, a1 + b1 + c1 = 1), Li x3 Ni 1-y1 Co y1 O2(0.5 < x3 < 1.3, 0 < y1 < 1), Li x4 Ni 1-y2 Mn y2 O2(0.5 < x4 < 1.3, 0 ≤ y2 < 1), Li x5 (Ni a2 Co b2 Mn c2 )O4(0.5 < x5 < 1.3, 0 < a2 < 2, 0 < b2 < 2, 0 < c2 < 2, a2 + b2 + c2 = 2), and Li x6 Mn 2-z1 Ni z1 O4(0.5 < x6 < 1.3, 0 < z1 < 2) may be a positive electrode active material selected from the group consisting of.

[0038]

[0039] According to another aspect of the present invention, a secondary battery including the above-described slurry for electrode production is provided. Here, when it is said that the secondary battery includes the slurry for electrode production, it means that it is manufactured using the slurry for electrode production and thus contains the components included in the slurry.

[0040] The secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode is manufactured by the slurry for electrode production including the carbon nanotubes. The secondary battery may be a lithium secondary battery. Further, the secondary battery may be a cylindrical, rectangular, or pouch-type secondary battery, but is not particularly limited as long as it corresponds to a charge / discharge device.

[0041] The secondary battery may have a DCIR value (internal resistance value) of 10 Ω or less. Here, the DCIR value is a value measured with an electrode manufactured by mixing a lithium manganese composite oxide active material as used in the examples described later of the present invention with the carbon nanotubes and a binder according to the present invention.

[0042]

[0043] According to yet another aspect of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the battery module. The battery pack can be used as a power source for one or more medium- to large-sized devices selected from the group consisting of power tools, electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), and power storage systems. [Effects of the Invention]

[0044] According to the present invention, by controlling the amount of fine powder during processing of carbon nanotubes, it is possible to provide a carbon nanotube dispersion liquid that can be used for electrodes with excellent electrical performance such as high conductivity despite having low viscosity.

[0045] According to the present invention, control of the size and amount of fine powder of the carbon nanotubes can be achieved by a low-speed dry powder processing method as a carbon nanotube powder processing technology, and the low-speed dry powder processing method not only makes it possible to control the size and amount of fine powder as described above, but also provides a high-content, low-viscosity slurry while reducing damage to carbon nanotubes that occurs during processing. [Brief explanation of the drawings]

[0046] [Figure 1] Schematic diagrams or photographs of various processing devices that can be used to process carbon nanotubes are shown.

[0047] [Figure 2]From Experimental Example 3, the change in powder conductivity or surface resistance of the slurry depending on the fine powder particle size D5 and the amount of fine powder (17.4 μm or less) is shown in a graph, and the change in the internal resistance DCIR value depending on the surface resistance of the obtained slurry is also shown in the graph.

[0048] [Figure 3] Experimental Example 4 shows the change in powder conductivity depending on the fine powder particle size D50 and D90. DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention will be described in more detail below with reference to preferred examples for better understanding of the present invention. The following examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention.

[0050]

[0051] [Examples and Comparative Examples]

[0052] 1. Processing of carbon nanotubes

[0053] Multi-walled carbon nanotubes (10-wall, bundled, 10-nm central diameter) were dry-processed under different conditions depending on the processing equipment. The types of processing equipment (low-speed bead mill, cutting mill, rotor bead mill) and processing conditions (time, rpm, bead size, etc.) used in each comparative example and example are listed in Table 1 below. Also, schematic diagrams and photographs of the low-speed bead mill used in the examples of the present invention and various processing equipment that can be used as comparative examples are shown in Figure 1.

[0054]

[0055] 2. Preparation of carbon nanotube dispersion

[0056] The finely powdered carbon nanotubes were mixed in accordance with the content into a solution of polyvinylpyrrolidone (PVP, molecular weight 40,000-80,000 g / mol) dissolved in N-methylpyrrolidone, and a dispersion composition was prepared using a homomixer.

[0057]

[0058] 3. Fabrication of the positive electrode

[0059] Cathode active material NCM811 [composition formula Li1(Ni 0.8 Co 0.1 Mn 0.1 The layered compound represented by )O2]:conductive material [prepared carbon nanotubes]:binder [PVDF, molecular weight 60,000 Da] were mixed in a ratio of 98:1:1 to prepare a slurry, which was then applied to an aluminum foil current collector using a coater and dried to prepare a positive electrode.

[0060]

[0061] 4. Secondary battery manufacturing

[0062] A coin cell was manufactured using an electrolyte solution of LiPF6 with a concentration of about 1.2M in a 3:7 ratio of ethylene carbonate and dimethyl carbonate, the positive electrode prepared above, and a lithium electrode as a counter electrode.

[0063]

[0064] [Analysis conditions]

[0065] The following analyses were carried out on the processed carbon nanotubes, the dispersion containing the carbon nanotubes, and the secondary battery.

[0066]

[0067] 1. Viscosity

[0068] The viscosity of the prepared dispersion was measured at 23° C. and 50 s −1 using a Haake Viscometer (Plate Φ35 mm).

[0069]

[0070] 2.Powder conductivity

[0071] The powder conductivity of carbon nanotubes dry-processed using a processing device such as a low-speed bead mill was measured. The powder conductivity was measured using a Han Tech (HPRM model) at an applied pressure range of 200 to 2,000 kgf / cm2, and calculated by comparing the resistance value with a density of 0.8 g / cc.

[0072]

[0073] 3.Particle size distribution

[0074] The dispersion of the dry-processed carbon nanotubes was diluted and then the particle size distribution was measured using a particle size analyzer (Malvern's Mastersizer 2000).

[0075]

[0076] 4. Surface resistance

[0077] The dispersion containing the carbon nanotubes was coated on a PET film using a bar coater, dried at 120° C., and then measured with a 4-point probe using Mitsubishi Chemical's MCP-T610.

[0078]

[0079] 5. DCIR

[0080] The secondary battery was charged and discharged under constant C-rate conditions under coin cell conditions, and the DCIR value was measured.

[0081]

[0082] [Experimental Example 1] Comparison of carbon nanotube processing methods

[0083] As described above, the properties of the multi-walled carbon nanotubes and their dispersions after dry processing using a processing device under different conditions were measured, and the results are shown in Table 1 below.

[0084]

[0085] [Table 1]

[0086] From Table 1, it can be seen that Comparative Examples 1 to 7, in which the particle size distribution D5 is less than 7 μm, have lower powder conductivity than Example 1, in which the particle size distribution D5 is 7 μm or more, which means that the electrical properties are deteriorated. In particular, Example 1, in which the particle size distribution D5 is 7 μm or more and 14 μm or less, exhibits not only high powder conductivity but also low viscosity, thereby realizing uniform coating properties during electrode manufacturing.

[0087]

[0088] [Experimental Example 2] Comparison of bead mill conditions

[0089] Using the conditions of Example 1 as a reference, the powder conductivity of the powders processed under different bead mill conditions (time, filling rate, RPM, bead mixing) and the particle size and viscosity of the dispersions prepared using the processed powders were compared, and the results are shown in Table 2 below.

[0090]

[0091] [Table 2]

[0092] Table 2 shows that the particle size distribution D5 conditions according to the present invention can be controlled by changing the milling time. In Comparative Examples 11 and 12, the conditions were changed to milder conditions than in Comparative Example 8, and the amount of fine powder was reduced. However, D5 still did not satisfy the requirement of 7 μm or more, confirming low powder conductivity and uneven powder processing. In Example 5, two types of beads were mixed, and it was confirmed that the particle size distribution D5 conditions can be achieved by changing conditions other than milling time (bead conditions). Furthermore, as can be seen from Example 6, a reproduction experiment of Example 1 showed reproducibility.

[0093]

[0094] [Experimental Example 3] Confirmation of the relationship between the size and amount of fine powder and battery performance

[0095] To confirm the battery performance depending on the fine powder particle size D5 and the amount of fine powder, a cathode was fabricated using carbon nanotubes and a cathode active material as described above, and a secondary battery was fabricated using the cathode. The powder conductivity, the surface resistance of the dispersion, and DCIR were measured, and the results are shown in Table 3 and Figure 2 below.

[0096]

[0097] [Table 3]

[0098] 2, it was confirmed that the particle size distribution D5 and the amount of fine powder (content of particle size 17.4 μm or less) affect the powder conductivity, and the powder conductivity affects the surface resistance of the dispersion, resulting in differences in the performance of the final battery. In other words, it was found that the particle size distribution D5 and the amount of fine powder (content of particle size 17.4 μm or less) are directly related to battery performance, and in particular, it was confirmed that when the particle size distribution D5 is 7 μm or more and the content of carbon nanotubes with a particle size of 17.4 μm or less is 30 vol% or less, the dispersion can exhibit low surface resistance and low DCIR.

[0099]

[0100] [Experimental Example 4] Confirmation of the relationship between the size and amount of fine powder and battery performance

[0101] The relationship between the average particle size (D50) and the large particle size (D90) in the particle size distribution and the powder conductivity was confirmed in the same manner as in Experimental Example 3, and the results are shown in Tables 4 and 5 and FIG.

[0102]

[0103] [Table 4]

[0104] [Table 5]

[0105] It was confirmed from Tables 4, 5, and Figure 3 that the average particle size (D50) and the particle size (D90) do not affect the powder conductivity. In addition, it was confirmed that high conductivity cannot be achieved when D5 does not satisfy 7 μm or more, even when the grinding conditions are different, as in Comparative Examples 2-1 and 1-1.

[0106]

[0107] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that the present invention can be modified and changed in various ways without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. A carbon nanotube dispersion in which the particle size distribution D5 of the carbon nanotubes is 7 μm or more.

2. The carbon nanotubes have a particle size of 17.4 μm or less, and the content of the carbon nanotubes is 30% by volume or less based on the total volume of the carbon nanotubes. The carbon nanotube dispersion liquid according to claim 1 .

3. 2. The carbon nanotube dispersion according to claim 1, having a solid content of 5% or more.

4. 2. The carbon nanotube dispersion according to claim 1, having a viscosity of 2,000 cp or less at a shear rate of 50 / s.

5. 2. The carbon nanotube dispersion liquid according to claim 1, wherein the particle size distribution D5 is 7 μm or more and 14 μm or less.

6. The carbon nanotube dispersion liquid according to claim 5 , wherein the particle size distribution D5 is 7 μm or more and 9 μm or less.

7. 2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes have a particle size distribution D50 of 15 to 50 μm.

8. 2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes have a particle size distribution D90 of 45 to 200 μm.

9. 2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes have a powder conductivity of 50 S / cm or more.

10. 2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes are at least one selected from the group consisting of single-wall carbon nanotubes, double-wall carbon nanotubes, triple-wall carbon nanotubes, and multi-wall carbon nanotubes.

11. 2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes have a central diameter of 4 to 50 nm.

12. A slurry for producing an electrode, comprising carbon nanotubes having a particle size distribution D5 of 7 μm or more.

13. The slurry for producing an electrode according to claim 12 , further comprising at least one selected from the group consisting of a conductive material other than carbon nanotubes, an electrode active material, and a binder.

14. A secondary battery comprising the electrode manufacturing slurry according to claim 13.

Images