Purification method of single-walled carbon nanotube, high-purity single-walled carbon nanotube and application of high-purity single-walled carbon nanotube

Abstract

The invention relates to the technical field of carbon nanotube impurity removal, in particular to a purification method of a single-walled carbon nanotube, the high-purity single-walled carbon nanotube and application of the high-purity single-walled carbon nanotube. The invention provides a high-purity single-walled carbon nanotube. The high-purity single-walled carbon nanotube is characterized in that in mixed acid prepared from perchloric acid, concentrated sulfuric acid and concentrated nitric acid according to the volume ratio of 1: 3: 3, the mass content of metal measured in a test that the mass ratio of the high-purity single-walled carbon nanotube to the mixed acid is 1: 100 and the temperature is 200 DEG C for 30 min is smaller than or equal to 0.5%; the rapid oxidation weight loss temperature in a thermogravimetric differential curve obtained by testing the high-purity single-walled carbon nanotube in an air atmosphere under the condition that the heating rate is 10 DEG C / min is 740-800 DEG C. The high-purity single-walled carbon nanotube has relatively low metal impurities and carbon impurities, high conductivity and good conductivity, and is beneficial to improving the electrochemical performance of a battery prepared from the high-purity single-walled carbon nanotube.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube purification technology, and more specifically, to a purification method for single-walled carbon nanotubes, high-purity single-walled carbon nanotubes, and their applications. Background Technology

[0002] Single-walled carbon nanotubes (SWCNTs) are one-dimensional nanomaterials composed of rolled-up layers of graphite sheets, with diameters ranging from 0.8 to 2 nm. They possess exceptional electrical properties, toughness, and strength. Since their discovery in the late 20th century, they have shown broad application prospects in new energy storage, catalysts, and nanodevices. In particular, the current-carrying capacity of SWCNTs is 1000 times higher than that of copper, which has good conductivity. Compared to traditional battery conductive agents such as conductive carbon black, their conductivity and stability are superior, making them considered one of the most promising conductive agents for lithium-ion batteries.

[0003] It is generally believed that the growth mechanism of single-walled carbon nanotubes (SWCNTs) involves carbon atoms forming a solid carbon cap on the surface of a metal catalyst, leading to the growth of a tubular structure. Based on this growth mechanism, the prepared SWCNTs inevitably contain metal particles (primarily nano-sized iron). The presence of metal impurities not only reduces the purity of the SWCNTs but also affects their physicochemical properties such as electrical conductivity, thermal conductivity, and oxidation resistance, negatively impacting the full potential of SWCNTs. For example, when SWCNTs are used as conductive agents in lithium-ion batteries, residual metal catalysts such as iron and nickel can easily cause micro-short circuits inside the battery, posing a safety hazard. Therefore, purifying and removing impurities from the prepared SWCNTs is essential.

[0004] The impurities in unpurified single-walled carbon nanotubes are mainly metal particles, with a small amount of carbon impurities such as amorphous carbon, graphite, and graphene. Metal impurities can be categorized into three types based on particle size and morphology: First, metal particles with a size >20 nm. These particles are encapsulated by graphite layers, forming a core-shell structure. Due to the strong van der Waals forces between the walls of single-walled carbon nanotubes, individual nanotubes easily form bundles, and impurity particles are trapped within these bundles, becoming further encapsulated and difficult to remove. Second, small to medium-sized impurities with a size between 2 and 20 nm. These metal particles are also encapsulated by a few layers of graphite and adsorbed onto the tube walls or trapped within the bundles due to π-π bonds. Third, tiny particles with a size <2 nm exist inside the tubes or at the end caps, and are also difficult to remove.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One objective of this invention is to provide a high-purity single-walled carbon nanotube with low levels of metal and carbon impurities, high purity, high electrical conductivity, and good electrical conductivity.

[0007] Another objective of this invention is to provide a purification method for single-walled carbon nanotubes. This method, through the coordination of various steps, can effectively remove metal and carbon impurities of different forms, thereby improving its purity, high conductivity, and good electrical conductivity.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] A high-purity single-walled carbon nanotube, wherein the mass content of metal in a test conducted at 200°C for 30 min in a mixed acid prepared by perchloric acid, concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3:3, with a mass ratio of high-purity single-walled carbon nanotube to mixed acid of 1:100, is less than or equal to 0.5%; and the rapid oxidation weight loss temperature in the thermogravimetric differential curve obtained by testing the high-purity single-walled carbon nanotube in air at a heating rate of 10°C / min is 740–800°C.

[0010] In some embodiments, the metal content in the high-purity single-walled carbon nanotubes is 0.1% to 0.5% by mass.

[0011] In some embodiments, the thermogravimetric differential curve of the high-purity single-walled carbon nanotube is a single-peak curve with the peak located at 740–800°C.

[0012] In some embodiments, the mass content of carbon impurities in the high-purity single-walled carbon nanotubes is less than 2%; the mass content of carbon impurities is the longitudinal axis attenuation value in the 300-600℃ range of the thermogravimetric curve obtained by testing the high-purity single-walled carbon nanotubes in air at a heating rate of 10℃ / min.

[0013] In some embodiments, the Raman shift of the high-purity single-walled carbon nanotubes is between 100 and 200 cm⁻¹. -1 The peak at the position is denoted as the characteristic RBM peak of the high-purity single-walled carbon nanotube, with a Raman shift of 1300–1350 cm⁻¹. -1 The peak at the location is denoted as the defect peak D, and the peak intensity I of the characteristic peak RBM peak is... RBM The peak intensity I of the defect peak D D The ratio is greater than 2.5.

[0014] In some embodiments, the Raman shift of the high-purity single-walled carbon nanotubes is between 1500 and 1600 cm⁻¹. -1 The strongest peak at that location is designated as the G peak, with a Raman shift between 1300 and 1350 cm. -1 The peak at the location is denoted as the defect peak D, and the peak intensity I of the G peak is... G and the peak intensity I of the defect peak DD The ratio is greater than 70.

[0015] In some embodiments, the peak intensity I of the characteristic peak RBM peak RBM The peak intensity I of the defect peak D D The ratio is 2.51 to 3.5.

[0016] In some implementations, the peak intensity I of the G peak G and the peak intensity I of the defect peak D D The ratio is 70 to 160.

[0017] In some embodiments, the conductive film prepared by the high-purity single-walled carbon nanotubes has a conductivity of 150–600 s / mm; the conductive film includes a PET substrate and a conductive coating, the conductive coating including the high-purity single-walled carbon nanotubes and sodium carboxymethyl cellulose in a mass ratio of 4:6, and the thickness of the conductive film is 2–3 μm.

[0018] In some embodiments, the voltage of the coin cell obtained by combining the high-purity single-walled carbon nanotubes with silicon-carbon anode active material, conductive agent and binder in a mass ratio of 1:80:9:10 is 2.8 to 3.1 V.

[0019] In some embodiments, the specific surface area of ​​the high-purity single-walled carbon nanotubes is 450–1200 m². 2 / g.

[0020] A method for purifying single-walled carbon nanotubes includes the following steps:

[0021] The single-walled carbon nanotube material is dispersed to obtain a first single-walled carbon nanotube material; the first single-walled carbon nanotube material is subjected to medium-temperature oxidation and acid washing to obtain a second single-walled carbon nanotube material; the second carbon nanotube material is subjected to high-temperature evaporation to obtain high-purity single-walled carbon nanotubes.

[0022] In some embodiments, the dispersion treatment method includes ultrasonic dispersion and / or high-pressure homogenization; the ultrasonic dispersion method includes ultrasonically dispersing the single-walled carbon nanotube material to be treated in a liquid, allowing it to stand, then removing the bottom precipitate, filtering and drying the remaining material.

[0023] In some embodiments, the temperature of the intermediate-temperature oxidation treatment is 400–700°C, and the intermediate-temperature oxidation treatment is carried out in an oxygen-containing atmosphere.

[0024] In some embodiments, the acid solution used for pickling is a strong acid that can react with the metal and its oxides.

[0025] In some embodiments, the high-temperature evaporation treatment is carried out at a temperature of 1500–2000°C under an inert atmosphere or vacuum.

[0026] In some embodiments, the frequency of the ultrasonic dispersion is 19 kHz-25 kHz, and the ultrasonic treatment time is 0.5 to 2 hours; the liquid includes water and / or alcohol.

[0027] In some embodiments, the time for the intermediate-temperature oxidation treatment is 0.2 to 6 hours; and / or, the oxygen-containing atmosphere is air; and / or, the flow rate of the oxygen-containing gas in the intermediate-temperature oxidation is 0.1 to 10 L / min.

[0028] In some embodiments, the acid solution for pickling includes hydrochloric acid, and / or sulfuric acid, and / or nitric acid; and / or, the concentration of the acid solution is 3 to 16 mol / L; and / or, the liquid-to-solid ratio of the pickling treatment is 50 to 500; and / or, the pickling time is 1 to 24 hours; and / or, ultrasonic vibration is performed during the pickling process.

[0029] In some embodiments, the high-temperature evaporation process is performed under vacuum; and / or, the vacuum level is 1 × 10⁻⁶. -1 ~9×10 -1 Pa; and / or, the high-temperature evaporation treatment time is 1 to 6 hours.

[0030] In some embodiments, the single-walled carbon nanotube material to be treated contains 40% to 80% by mass of single-walled carbon nanotubes, 10% to 30% by mass of metal impurities, and 2% to 10% by mass of carbon impurities.

[0031] In some embodiments, the single-walled carbon nanotubes to be processed include single-walled carbon nanotubes prepared by a floating catalytic method and / or single-walled carbon nanotubes prepared by an arc discharge method.

[0032] The applications of high-purity single-walled carbon nanotubes as described above in lithium-ion batteries, sodium-ion batteries, and (semi)solid-state batteries.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) In the high-purity single-walled carbon nanotubes of the present invention, the mass content of metal is less than or equal to 0.5%, and the rapid oxidation weight loss temperature of the single-walled carbon nanotubes in the thermogravimetric differential curve is 740-800℃, that is, high purity, high conductivity, and good electrical conductivity, which is beneficial to improving the electrochemical performance of the battery prepared by it.

[0035] (2) The purification method for single-walled carbon nanotubes of the present invention, through the combination of dispersion treatment, medium-temperature oxidation treatment, acid washing treatment, and high-temperature evaporation treatment, can effectively remove metal impurity particles and carbon impurities of different forms from single-walled carbon nanotubes. First, the dispersion treatment can open the bundle of carbon nanotubes, and the large-particle metal impurities wrapped inside the bundle can be removed from the carbon nanotubes under ultrasonic vibration conditions. At the same time, some carbon impurities are also removed. The medium-temperature oxidation treatment further removes amorphous carbon and other carbon impurities, and can also enhance the oxidation of medium-particle metal impurities. The generated metal oxides will break through the few-layer graphite coating due to volume expansion, thereby exposing the metal and its metal oxides in the impurity particles. The metal and its oxides are further consumed by acid washing treatment. Finally, the fine metal particles existing in the single carbon nanotubes are vaporized and removed from the carbon nanotubes by high-temperature evaporation treatment, thereby removing extremely fine metal impurities. Through the combination of these steps, high-purity single-walled carbon nanotubes can be obtained, improving their conductivity and giving them excellent electrical conductivity, thereby further improving the electrochemical performance of the batteries prepared from them. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 The image shows a transmission electron microscope image of high-purity single-walled carbon nanotubes in Example 1 of the present invention, where (a1) and (a2) correspond to different magnifications.

[0038] Figure 2 The images are transmission electron microscope images of impurity particles of different morphologies in the single-walled carbon nanotube material to be treated. Among them, (a2) is a large metal impurity particle wrapped in the tube bundle, (b2) is a medium-sized metal impurity particle, and (c2) is a fine metal particle inside a single carbon nanotube.

[0039] Figure 3 The thermogravimetric analysis (TGA) curves of the single-walled carbon nanotube material to be treated in Example 1 of the present invention before and after ultrasonic treatment are shown.

[0040] Figure 4 The thermogravimetric curves (TGA curves) and thermogravimetric differential curves (DTG curves) of single-walled carbon nanotubes after oxidative acid washing treatment in Example 1 of the present invention (i.e., Comparative Example 2) are shown.

[0041] Figure 5The images are transmission electron microscope images of single-walled carbon nanotubes before and after the oxidation and acid washing treatment in Example 1 of the present invention. (a3) ​​represents the single-walled carbon nanotubes before the oxidation and acid washing treatment, and (b3) represents the single-walled carbon nanotubes after the oxidation and acid washing treatment.

[0042] Figure 6 The thermogravimetric curves (TGA curves) and thermogravimetric differential curves (DTG curves) of the high-purity single-walled carbon nanotubes in Example 1 of the present invention are shown.

[0043] Figure 7 This is the Raman spectrum of the high-purity single-walled carbon nanotubes in Example 1 of the present invention. Detailed Implementation

[0044] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0045] According to one aspect of the present invention, the present invention relates to a high-purity single-walled carbon nanotube, wherein the mass content of metal in a test conducted by digesting the high-purity single-walled carbon nanotube in a mixed acid prepared by mixing 70% perchloric acid, 98% concentrated sulfuric acid and 65% concentrated nitric acid in a volume ratio of 1:3:3, with a mass ratio of high-purity single-walled carbon nanotube to mixed acid of 1:100, at 200°C for 30 min, is less than or equal to 0.5%; and the rapid oxidation weight loss temperature of the high-purity single-walled carbon nanotube in the thermogravimetric differential (DTG) curve is 740–800°C.

[0046] The high-purity single-walled carbon nanotubes of this invention have low levels of metal and carbon impurities and high purity. A mixed acid, prepared by mixing perchloric acid, concentrated sulfuric acid, and concentrated nitric acid in a volume ratio of 1:3:3, is designated as the carbon nanotube digestion acid. The high-purity single-walled carbon nanotubes and the carbon nanotube digestion acid are digested at a mass ratio of 1:100 in a digestion vessel at 200°C for 30 minutes. The resulting digestion solution is subjected to ICP trace element analysis, and the metal content is less than or equal to 0.5%, including but not limited to 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value within a range of two. Preferably, the metal content in the high-purity single-walled carbon nanotubes is less than 0.35%.

[0047] The point where the vertical axis of the DTG curve of single-walled carbon nanotubes (SWC) contains the minimum value is denoted as the rapid oxidation weight loss point. The horizontal axis of this rapid oxidation weight loss point represents the rapid oxidation weight loss temperature of SWC. Without theoretical constraints, the oxidation temperature of amorphous carbon impurities in air is 300–500℃, graphitic carbon impurities are 500–600℃, multi-walled and oligo-walled carbon nanotubes are 600–700℃, while the oxidation temperature of single-walled carbon nanotubes is above 700℃. Furthermore, the nano-sized metal particles within SWC can catalyze the oxidation of SWC, causing the rapid oxidation weight loss temperature to shift to a lower temperature range. The rapid oxidation temperature decreases, and the rapid oxidation weight loss temperature of unpurified or poorly purified SWC is typically less than 740℃ (e.g., [missing information]). Figure 4 The rapid oxidation weight loss temperature of the DTG curve in the figure is 720℃. The rapid oxidation weight loss temperature of the high-purity single-walled carbon nanotubes of the present invention is between 740℃ and 800℃.

[0048] In some embodiments, the thermogravimetric differential curve (DTG curve) of the high-purity single-walled carbon nanotubes is a single-peak curve with the peak located between 740 and 800 °C. A single-peak DTG curve (usually with a narrow half-peak width) indicates that the material is relatively pure, meaning that the oxidation temperature of a certain substance is constant. If other carbon impurities are present, multiple carbon impurity peaks will appear instead of a single peak.

[0049] In some embodiments, the mass content of carbon impurities in the high-purity single-walled carbon nanotubes is less than 2%, including but not limited to 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.5%, or 2%, or any value in the range between two. The mass content of carbon impurities is the longitudinal axis decay value in the range of 300–600°C of the thermogravimetric curve obtained by testing the high-purity single-walled carbon nanotubes in air at a heating rate of 10°C / min.

[0050] In some implementations, the Raman shift in the Raman spectrum of high-purity single-walled carbon nanotubes is between 100 and 200 cm⁻¹. -1 The peak at the position is denoted as the characteristic RBM peak of high-purity single-walled carbon nanotubes. The higher the peak intensity, the higher the content (i.e., purity) of single-walled carbon nanotubes in the material; the Raman shift is between 1300 and 1350 cm⁻¹. -1 The peak at the location is denoted as the defect peak (D peak), and the peak intensity (I) of the characteristic peak (RBM peak) is... RBM Peak intensity I of defect peak D D The ratio is greater than 2.5, including but not limited to 2.6, 2.7, 2.8, 2.9, 3, 3.2, 3.5, 4, 5, 10, or any value between two values. In some embodiments, the peak intensity I of the characteristic peak RBM peak is... RBMThe peak intensity I of the defect peak D D The ratio is 2.51 to 3.5. RBM and I D The lower the ratio, the lower the content of single-walled carbon nanotubes in the sample and the more structural defects there are. This results in lower electrical conductivity of the carbon nanotubes, leading to poorer rate performance and cycle performance when the carbon nanotubes are used as conductive agents in the battery. RBM and I D The ratio is greater than 2.5 to ensure that the single-walled carbon nanotubes have excellent electrical conductivity.

[0051] In some implementations, the Raman shift in the Raman spectrum of high-purity single-walled carbon nanotubes is between 1500 and 1600 cm⁻¹. -1 The strongest peak at that location is designated as the G peak, with a Raman shift between 1300 and 1350 cm. -1 The peak at the location is denoted as the defect peak D, and the peak intensity of peak G is I. G And the peak intensity I of the defect peak D D The ratio is greater than 70. In some implementations, the peak intensity I of peak G is... G And the peak intensity I of the defect peak D D The ratio is 71, 72, 75, 80, 82, 85, 90, 100, 120, 130, 140, 150, 160, 180, 200, etc., or any range between two. In some embodiments, the peak intensity I of the G peak is... G and the peak intensity I of the defect peak D D The ratio is 70 to 160.

[0052] In some embodiments, the conductive film prepared from the high-purity single-walled carbon nanotubes has a conductivity of 150–600 S / mm, including but not limited to 150 S / mm, 200 S / mm, 300 S / mm, 400 S / mm, 500 S / mm, 550 S / mm, 600 S / mm, or any value within a range of both. The conductive film comprises a PET substrate and a conductive coating, wherein the conductive coating comprises the high-purity single-walled carbon nanotubes and sodium carboxymethyl cellulose (CMC) in a mass ratio of 4:6, and the thickness of the conductive film is 2–3 μm. The high-purity single-walled carbon nanotubes of the present invention exhibit excellent conductivity. Specifically, the method for preparing conductive thin films from high-purity single-walled carbon nanotubes includes the following steps: High-purity single-walled carbon nanotube powder and sodium carboxymethyl cellulose are mixed at a mass ratio of 4:6 to prepare a conductive slurry with a solid content of 1%. The slurry is then uniformly coated onto a PET substrate using a coating machine, resulting in a coating thickness of 200 μm. After drying, the carbon nanotube film thickness is 2–3 μm. The conductivity measured using a four-probe resistivity meter (Ningbo Ruikewei FT-340 four-probe sheet resistance meter) is recorded as the conductivity of the high-purity single-walled carbon nanotube film.

[0053] In some embodiments, the specific surface area of ​​high-purity single-walled carbon nanotubes is 450–1200 m². 2 / g. In some embodiments, the specific surface area of ​​high-purity single-walled carbon nanotubes includes, but is not limited to, 450 m². 2 / g、500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g, or any value within a range of both. Specific surface area was determined using the BET method with a Guoyi Precision Measurement F-Sorb X400 specific surface area analyzer.

[0054] In some embodiments, the voltage of a coin cell obtained by mixing high-purity single-walled carbon nanotubes with silicon-carbon anode active material, conductive agent, and binder in a mass ratio of 1:80:9:10 is 2.8–3.1V. Specifically, the high-purity single-walled carbon nanotube powder is dispersed to obtain a single-walled carbon nanotube conductive slurry. After preparing the slurry in a mass ratio of high-purity single-walled carbon nanotubes: silicon-carbon anode active material: conductive agent: binder = 1:80:9:10, it is coated and made into a coin cell. The voltage is tested using a battery internal resistance tester. The voltage of the coin cell made by using high-purity single-walled carbon nanotubes as a conductive agent is 2.8–3.1V.

[0055] According to another aspect of the present invention, the present invention also relates to a method for purifying single-walled carbon nanotubes, comprising the following steps:

[0056] The single-walled carbon nanotube material to be processed is dispersed to obtain a first single-walled carbon nanotube material. The first single-walled carbon nanotube material is then subjected to medium-temperature oxidation and acid washing to obtain a second single-walled carbon nanotube material. The second carbon nanotube material is then subjected to high-temperature evaporation to obtain high-purity single-walled carbon nanotubes.

[0057] This invention utilizes a combined physicochemical method, employing dispersion, medium-temperature oxidation, acid washing, and high-temperature evaporation to remove metal and carbon impurities of various forms from single-walled carbon nanotubes. First, dispersion opens the carbon nanotube bundles, allowing large-particle metal impurities encapsulated within to detach and be removed under ultrasonic vibration. Simultaneously, some carbon impurities are also removed. Medium-temperature oxidation further removes amorphous carbon and other carbon impurities, while also enhancing the oxidation of medium-particle metal impurities. The resulting metal oxides, due to volume expansion, rupture the few-layer graphite encapsulation, exposing the metals and their oxides within the impurity particles. Acid washing then further reacts and consumes the metals and oxides. Finally, high-temperature evaporation vaporizes and removes the fine metal particles within the individual carbon nanotubes, thus eliminating extremely fine metal impurities. Through the combined use of these steps, high-purity single-walled carbon nanotubes are obtained.

[0058] In some embodiments, the single-walled carbon nanotube (SUV) material to be treated includes SUVs prepared by a floating catalytic method and / or SUVs prepared by an arc discharge method. The mass content of the SUVs is 40%–80%, including but not limited to 40%, 50%, 60%, 65%, 70%, 75%, 80%, or any value between these two ranges. The SUV material to be treated contains a large amount of metal impurities and carbon impurities in different states. The mass content of the metal impurities is 10%–30%, including but not limited to 10%, 15%, 20%, 25%, 30%, or any value between these two ranges. The mass content of the carbon impurities is 2%–10%, including but not limited to 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value between these two ranges.

[0059] In some embodiments, the dispersion treatment method includes ultrasonic dispersion and / or high-pressure homogenization. The ultrasonic dispersion method involves ultrasonically dispersing the single-walled carbon nanotube material in a liquid, allowing it to stand, removing the bottom precipitate, filtering the remaining material, and drying it. The frequency of the ultrasonic dispersion is 19 kHz-25 kHz, including but not limited to 19 kHz, 20 kHz, 21 kHz, 22 kHz, 25 kHz, or any value between these two ranges. The ultrasonic treatment time is 0.5 to 2 hours, including but not limited to 0.5 hours, 1 hour, 1.5 hours, 2 hours, or any value between these two ranges. The liquid includes water and / or alcohol. This invention employs suitable ultrasonic dispersion frequency and time to better ensure the dispersion effect of the single-walled carbon nanotube material. In this invention, the single-walled carbon nanotube material to be treated is ultrasonically dispersed in an ultrasonic disperser. After ultrasonication, the slurry is allowed to stand. Large metal particles will detach from the carbon nanotube bundles and settle to the bottom of the container, while the less dense carbon nanotubes will float in the upper part of the container. After being poured out, filtered and dried, it is ready for use.

[0060] In some embodiments, the temperature of the intermediate-temperature oxidation treatment is 400–700°C, including but not limited to 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, or any range between two values. The duration of the intermediate-temperature oxidation treatment is 0.2–6 hours, including but not limited to 0.2 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any range between two values. The flow rate of compressed air used in the intermediate-temperature oxidation treatment is 0.1–10 L / min, including but not limited to 0.1 L / min, 0.5 L / min, 1 L / min, 2 L / min, 5 L / min, 10 L / min, or any range between two values. This invention employs suitable medium-temperature oxidation conditions to enhance the oxidation of medium-sized metal impurities. The generated metal oxides, due to volume expansion, will break through the few-layer graphite coating, thereby exposing the metal and its metal oxides in the impurity particles. At the same time, carbon impurities such as amorphous carbon can be removed.

[0061] In some embodiments, the acid solution used for pickling is a strong acid capable of reacting with the metal and its oxides, including at least one of hydrochloric acid, sulfuric acid, and nitric acid. The concentration of the strong acid is 3–16 mol / L, including but not limited to 3 mol / L, 5 mol / L, 10 mol / L, 15 mol / L, or 16 mol / L, or any value between two of these. The liquid-to-solid ratio is 50–500, including but not limited to 50, 100, 150, 200, 300, 400, or 500, or any value between two of these. The pickling time is 1–24 hours, including but not limited to 1 hour, 2 hours, 3 hours, 5 hours, 6 hours, 8 hours, 10 hours, 15 hours, 20 hours, or 24 hours, or any value between two of these. In some embodiments, the pickling process is carried out in a sealed environment. After the pickling process, solid-liquid separation is performed, and the collected solids are washed and dried. The present invention employs suitable pickling conditions, in which the acid solution can further react with the metal and its metal oxides formed by oxidation treatment, thereby removing them and further reducing the metal content.

[0062] In some embodiments, the temperature for high-temperature evaporation is 1500–2000°C, including but not limited to 1500°C, 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, or any range between these two. The duration of high-temperature evaporation is 1–6 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any range between these two. The vacuum degree for high-temperature evaporation is 1 × 10⁻⁶. -1 Pa~9×10 -1 Pa, including but not limited to 1×10 -1 Pa, 2×10 -1 Pa, 3×10 - 1 Pa, 5×10 -1 Pa, 7×10 -1 Pa, 9×10 -1 Pa, or any value within a range of both. Finally, the extremely small metallic particles remaining inside and at the end caps of the single-walled carbon nanotubes are difficult to remove by the aforementioned liquid-phase acid washing due to the hydrophobicity of the carbon nanotube walls. However, by employing the aforementioned suitable high-temperature evaporation conditions, the nano-metal particles are vaporized from the solid phase to the gas phase under conditions reaching their saturated vapor pressure, thereby detaching from the carbon nanotubes and further improving the purity and electrical properties of the final single-walled carbon nanotubes.

[0063] According to another aspect of the present invention, the single-walled carbon nanotubes described above are used in lithium-ion batteries, sodium-ion batteries, and (semi)solid-state batteries.

[0064] In some embodiments, the high-purity single-walled carbon nanotubes are used as conductive agents in lithium-ion batteries, sodium-ion batteries, and (semi-)solid-state batteries. Typically, but not limitingly, they are used as negative electrode conductive agents and positive electrode conductive agents, for example. In other embodiments, the high-purity single-walled carbon nanotubes can also be used for other applications in the aforementioned batteries.

[0065] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0066] Example 1

[0067] A method for purifying single-walled carbon nanotubes includes the following steps:

[0068] (1) Place the single-walled carbon nanotube material to be treated in an ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency is 25 kHz and the ultrasonic time is 0.5 h. After ultrasonication, the slurry is allowed to stand. The carbon nanotubes with lower density float in the upper part of the container. After pouring it out, filter and dry it for later use.

[0069] (2) After the dried powder is broken up, it is placed in a corundum crucible and compressed air is introduced into a tube furnace for medium-temperature oxidation treatment. The compressed air flow rate is 0.5 L / min, the oxidation temperature is 450℃, and the oxidation time is 2 h. After the oxidized powder is cooled, it is placed in a clean glass beaker.

[0070] (3) Pour 6 mol / L hydrochloric acid into a beaker containing the oxidized material, with a liquid-to-solid ratio of 100. Seal the beaker with plastic wrap and place it in an ultrasonic vibrator for ultrasonic vibration for 6 hours. After the reaction is complete, filter, wash, and dry the mixture for later use.

[0071] (4) Place the low-purity carbon nanotubes dried in step (3) above into a vacuum sintering furnace, keep them at a high temperature of 1600℃ and a vacuum degree of 0.1Pa for 4 hours, and then cool them down to obtain high-purity single-walled carbon nanotubes with a metal content of less than 0.5%.

[0072] Transmission electron microscopy images of impurity particles of different morphologies in the single-walled carbon nanotube material to be treated are shown below. Figure 2 As shown, Figure 2 In the diagram, (a2) shows large metal impurities enclosed in the tube bundle, (b2) shows medium-sized metal impurities, and (c2) shows fine metal particles inside a single carbon nanotube.

[0073] Thermogravimetric curves of the single-walled carbon nanotube material before and after ultrasonic treatment are shown below. Figure 3As shown. The TG detection conditions were: heating to 1000℃ at a rate of 10℃ / min in air. The thermogravimetric analysis (TGA) curve shows that the metal oxide content in the unpurified sample before ultrasonic dispersion was 40.5%. Assuming complete oxidation of metal impurities to ferric oxide, the metal impurity content in the unpurified carbon nanotubes was 28.4%. Similarly, the metal content in the sample after ultrasonic dispersion to remove large metal particles was 11.7%. The shift in the TGA curve after ultrasonic dispersion also indicates that some carbonaceous impurities had been removed.

[0074] In steps (2) and (3), medium-temperature oxidation and acid washing (oxidation and acid washing) can remove small-to-medium-sized metal particles, thereby further reducing the metal impurity content to 1.8%. The thermogravimetric curves and thermogravimetric differential curves of the single-walled carbon nanotubes after oxidation and acid washing are shown below. Figure 4 As shown (i.e., the thermogravimetric curves and thermogravimetric differential curves of single-walled carbon nanotubes in Comparative Example 2). The oxidation temperature of amorphous carbon in carbon nanotubes is between 300℃ and 500℃. In the TGA curves, within the range of 300℃ to 500℃, the sample loses 1% of its weight, meaning that through air oxidation, amorphous carbon and a small amount of incompletely crystallized short-range ordered graphite impurities in the single-walled carbon nanotubes are removed to below 2%. Transmission electron microscope images of single-walled carbon nanotubes before and after oxidation and acid washing treatment are shown below. Figure 5 As shown, the walls of the single-walled carbon nanotubes are smooth, indicating that most of the carbon impurities attached to the nanotube walls have been removed. The obtained single-walled carbon nanotubes have high electrical conductivity. The resistance and conductivity test results of the single-walled carbon nanotubes before and after the oxidation and acid washing treatment are shown in Table 1. It can be seen that the conductivity of the single-walled carbon nanotubes is further improved after the oxidation and acid washing treatment.

[0075] Table 1. Test results of resistance and conductivity of single-walled carbon nanotubes before and after oxidative acid washing treatment in Example 1.

[0076]

[0077] The above-mentioned vacuum heat treatment (high-temperature evaporation treatment) can further remove impurities from single-walled carbon nanotubes and improve their purity. The metal content of high-purity single-walled carbon nanotubes is shown in Table 2.

[0078] Table 2 Metal content in high-purity single-walled carbon nanotubes (ICP method)

[0079] element S Co Ni Si Mn Fe Cr Mg Cu Content / ppm 28.8 0.06 70.4 0 2.6 2049 13.8 1.1 1.8

[0080] The transmission electron microscope image of the high-purity single-walled carbon nanotubes obtained in this embodiment is shown below. Figure 1 As shown, where, Figure 1 (a1) and (a2) in the image correspond to transmission electron microscope images at different magnifications.

[0081] Thermogravimetric analysis, thermogravimetric curves, and thermogravimetric differential curves of high-purity single-walled carbon nanotubes are as follows: Figure 6 As shown, the metal impurity content in the purified high-purity single-walled carbon nanotubes has been reduced to 0.23%. ICP analysis also confirmed that the Fe element content in these high-purity single-walled carbon nanotubes is 0.2% (measured by a PE company ICP-OES inductively coupled plasma atomic emission spectrometer). The results are mutually verifiable. Amorphous carbon impurities oxidize at 300–500℃ in air, graphitic carbon impurities at 500–600℃, multi-walled and oligo-walled carbon nanotubes at 600–700℃, while single-walled carbon nanotubes oxidize above 700℃. Figure 6 It is known that the rapid oxidation weight loss temperature of high-purity carbon nanotubes is approximately 740℃, and there are no weight loss peaks associated with other impurities. Nanoscale metal particles can catalyze the oxidation of carbon nanotubes; the presence of nanoscale metal particles will lead to a decrease in the rapid oxidation weight loss temperature of single-walled carbon nanotubes. Figure 4 As shown, the rapid oxidation weight loss temperature of the sample is approximately 720℃.

[0082] Raman spectra of high-purity single-walled carbon nanotubes are shown below. Figure 7 As shown. The characteristic RBM peak (100–200 cm⁻¹) of purified single-walled carbon nanotubes is observed at the same wavelength. -1 The peak intensity at (location) increased from 730 to 1189, and remained at 1300–1350 cm⁻¹. -1 The D peak at this location weakens significantly, occurring between 1500 and 1600 cm⁻¹. -1 The G peak at the location was significantly enhanced, and the I peak was significantly enhanced. G / I D Increased from 28 to 76, I RBM / I D The purity was increased from 1.64 to 2.62. Therefore, it can be shown that the purity and quality of the high-purity single-walled carbon nanotubes obtained in this embodiment were both improved.

[0083] Example 2

[0084] A method for purifying single-walled carbon nanotubes includes the following steps:

[0085] (1) Place the single-walled carbon nanotube material to be treated in an ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency is 20 kHz and the ultrasonic time is 1 h. After ultrasonic treatment, the slurry is allowed to stand. Large metal particles will be released from the carbon nanotube bundles and sink to the bottom of the container, while the carbon nanotubes with lower density will float in the upper part of the container. After pouring it out, filter and dry it for later use.

[0086] (2) After the powder dried in step (1) is broken up, it is placed in a corundum crucible and compressed air is introduced into a tube furnace for medium-temperature oxidation treatment. The compressed air flow rate is 1L / min, the oxidation temperature is 500℃, and the oxidation time is 3h. After the oxidized powder is cooled, it is placed in a clean glass beaker.

[0087] (3) Pour 6 mol / L hydrochloric acid into the beaker containing the oxidized powder from step (2), with a liquid-to-solid ratio of 200. Seal the beaker with plastic wrap and place it in an ultrasonic vibrator for ultrasonic vibration. Ultrasonic vibration time: 8 h. After the reaction is complete, filter, wash, and dry for later use.

[0088] (4) Place the low-purity carbon nanotubes obtained in step (3) in a vacuum sintering furnace, and sinter them at a vacuum degree of 5×10⁻⁶. -1 High-purity single-walled carbon nanotubes with a metal content of less than 0.5% can be obtained by holding the nanotubes at a high temperature of 1800℃ for 6 hours and then cooling them down.

[0089] Example 3

[0090] A method for purifying single-walled carbon nanotubes includes the following steps:

[0091] (1) Place the single-walled carbon nanotube material to be treated in an ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency is 25 kHz and the ultrasonic time is 0.5 h. After ultrasonication, the slurry is allowed to stand. The carbon nanotubes with lower density float in the upper part of the container. After pouring it out, filter and dry it for later use.

[0092] (2) After the powder dried in step (1) is broken up, it is placed in a corundum crucible and compressed air is introduced into a tube furnace for medium-temperature oxidation treatment. The compressed air flow rate is 0.5 L / min, the oxidation temperature is 400℃, and the oxidation time is 1.5 h. After the oxidized powder tube is cooled, it is placed in a clean glass beaker.

[0093] (3) Pour 4 mol / L hydrochloric acid into the beaker containing the oxidized powder from step (2), with a liquid-to-solid ratio of 150. Seal the beaker with plastic wrap and place it in an ultrasonic vibrator for ultrasonic vibration for 12 hours. After the reaction is complete, filter, wash, and dry the product for later use.

[0094] (4) Place the dried low-purity carbon nanotubes from step (3) above into a vacuum sintering furnace, and sinter them at a vacuum degree of 7×10⁻⁶. - 1 By holding the material at a high temperature of 1900℃ for 6 hours and then cooling it down, high-purity single-walled carbon nanotubes with a metal content of less than 0.5% can be obtained.

[0095] Example 4

[0096] A method for purifying single-walled carbon nanotubes includes the following steps:

[0097] (1) Place the unpurified single-walled carbon nanotube powder in an ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency is 25 kHz and the ultrasonic time is 1.5 h. After ultrasonication, the slurry is allowed to stand. The carbon nanotubes with lower density float in the upper part of the container. Pour it out, filter it, dry it, and set it aside for later use.

[0098] (2) After the powder dried in step (1) is broken up, it is placed in a corundum crucible and compressed air is introduced into a tube furnace for medium-temperature oxidation treatment. The compressed air flow rate is 0.5 L / min, the oxidation temperature is 600℃, and the oxidation time is 0.5 h. After the oxidized powder is cooled, it is placed in a clean glass beaker.

[0099] (3) Pour 8 mol / L hydrochloric acid into the beaker containing the oxidized powder from step (2), with a liquid-to-solid ratio of 100. Seal the beaker with plastic wrap and place it in an ultrasonic vibrator for ultrasonic vibration. Ultrasonic vibration time: 4 hours. After the reaction is complete, filter, wash, and dry for later use.

[0100] (4) Place the dried low-purity carbon nanotubes obtained in step (3) above into a vacuum sintering furnace, and sinter them at a vacuum degree of 5×10⁻⁶. -1 High-purity single-walled carbon nanotubes with a metal content of less than 0.5% can be obtained by holding the nanotubes at a high temperature of 1700℃ for 4 hours and then cooling them down.

[0101] Example 5

[0102] A method for purifying single-walled carbon nanotubes includes the following steps:

[0103] (1) Place the single-walled carbon nanotube material to be treated in an ultrasonic disperser and ultrasonically disperse it at a frequency of 25 kHz for 2 hours. After ultrasonic treatment, let the slurry stand. The carbon nanotubes with lower density float in the upper part of the container. Pour it out, filter it, dry it, and set it aside.

[0104] (2) After the powder dried in step (1) is broken up, it is placed in a corundum crucible and compressed air is introduced into a tube furnace for medium-temperature oxidation treatment. The compressed air flow rate is 0.2 L / min, the oxidation temperature is 650℃, and the oxidation time is 0.2 h. After the oxidized powder is cooled, it is placed in a clean glass beaker.

[0105] (3) Pour 12 mol / L hydrochloric acid into the beaker containing the oxidized powder from step (2) above, with a liquid-to-solid ratio of 50. Seal the beaker with plastic wrap and place it in an ultrasonic vibrator for ultrasonic vibration. The ultrasonic vibration time is 20 h. After the reaction is complete, filter, wash, and dry for later use.

[0106] (4) Place the dried low-purity carbon nanotubes from step (3) into a vacuum sintering furnace and heat them under a vacuum of 9×10⁻⁶. - 1 By holding the material at a high temperature of 2000℃ for 2 hours and then cooling it down, high-purity single-walled carbon nanotubes with a metal content of less than 0.5% can be obtained.

[0107] Comparative Example 1

[0108] A purification method for single-walled carbon nanotubes differs from that in Example 1 in that step (1) is omitted, i.e. the single-walled carbon nanotube powder to be treated is directly subjected to steps (2) to (4).

[0109] Comparative Example 2

[0110] A purification method for single-walled carbon nanotubes differs from Example 1 in that step (4) is not performed.

[0111] Comparative Example 3

[0112] Single-walled carbon nanotubes to be processed.

[0113] Experimental Example

[0114] The single-walled carbon nanotubes of each embodiment and comparative example were tested, including:

[0115] (1) Metal content test

[0116] Test method: 70% perchloric acid, 98% concentrated sulfuric acid, and 65% concentrated nitric acid were mixed at a volume ratio of 1:3:3 to obtain a special acid for carbon nanotube digestion. Single-walled carbon nanotubes and the special acid for carbon nanotube digestion were mixed at a mass ratio of 1:100 and digested in a digestion vessel at 200℃ for 30 minutes to obtain a digestion solution. The digestion solution was subjected to ICP trace element detection to obtain the metal content in the single-walled carbon nanotubes.

[0117] (2) Raman spectroscopy test

[0118] The Raman shift in the Raman spectrum of single-walled carbon nanotubes is between 100 and 200 cm⁻¹. -1 The peak at the location is denoted as the characteristic RBM peak, with a Raman shift between 1300 and 1350 cm⁻¹. -1 The peak at the location is denoted as the defect peak D, with a Raman displacement of 1500–1600 cm. -1 The strongest peak at a given location is denoted as peak G; calculate the peak intensity I of the characteristic peak RBM. RBM Peak intensity I of defect peak D D The ratio, i.e., calculating I G / I D Peak intensity of G peak I G And the peak intensity I of the defect peak D DThe ratio, i.e., I RBM / I D .

[0119] (3) Thermogravimetric analysis test

[0120] The thermogravimetric differential curve was obtained, and the rapid weight loss temperature was further obtained.

[0121] (4) Conductivity

[0122] A conductive paste with a solid content of 1% was prepared by mixing single-walled carbon nanotubes (SUVs) and CMC at a mass ratio of 4:6. The conductive paste was then uniformly coated onto a PET substrate using a coating machine to a thickness of 200 μm. The thickness of the dried carbon nanotube film was 2–3 μm. The conductivity was measured using a four-probe resistivity meter.

[0123] (5) Yield

[0124] The ratio of the mass of high-purity single-walled carbon nanotubes obtained after the above purification process to the mass of untreated crude single-walled carbon nanotubes is the purification yield.

[0125] (6) Voltage

[0126] Single-walled carbon nanotubes were mixed with silicon-carbon anode active material, Super P conductive agent and PAA binder in a mass ratio of 1:80:9:10 to obtain a conductive slurry. The slurry was then coated and dried to prepare an anode sheet. The anode sheet, separator, positive electrode (lithium sheet), electrolyte (lithium hexafluorophosphate) and other components were assembled into a coin cell, and its voltage was tested using a battery internal resistance tester.

[0127] The aforementioned silicon-carbon anode active material is a porous carbon-silicon anode active material with a silicon content of 49 wt% (relative to silicon-carbon anode active materials).

[0128] The test results of the single-walled carbon nanotubes in each embodiment and comparative example are shown in Table 3.

[0129] Table 3 Test Results

[0130]

[0131]

[0132] As can be seen from the above, the purification method for single-walled carbon nanotubes of the present invention, through the combination of the above steps, can effectively reduce the content of metal impurities and carbon impurities, with the metal content being less than 0.5%. G / I D Greater than 70, I RBM / I DThe molecular weight is greater than 2.5, the rapid weight loss temperature is 740–800°C, the electrical conductivity is greater than 150 S / m, and the yield is greater than 50%. When used in batteries, the ultrapure single-walled carbon nanotubes of this invention produce higher battery voltages compared to unpurified (or poorly purified) single-walled carbon nanotubes.

[0133] The method in Comparative Example 1, which does not involve ultrasonic dispersion, still results in single-walled carbon nanotubes containing a large number of impurities. G / I D and I RBM / I D The value is low, the rapid weight loss temperature is low, the conductivity is low, the electrical conductivity is poor, and the voltage of the resulting battery is low.

[0134] The method in Comparative Example 2 does not perform the oxidative thermal evaporation treatment in step (4). The single-walled carbon nanotubes obtained in the end still have a lot of unremoved impurities, that is, the rapid weight loss temperature is low, the electrical conductivity is poor, the electrical conductivity is poor, and the voltage of the resulting battery is low.

[0135] Comparative Example 3 is a single-walled carbon nanotube material that has not been purified. It has extremely high metal and carbon impurity content and low electrical conductivity. The resulting battery has a low voltage because the presence of conductive metal impurities causes point contacts inside the battery, forming micro-short circuits.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-purity single-walled carbon nanotube, characterized in that, Includes the following features: The metal content measured in the test of digesting the high-purity single-walled carbon nanotubes in a mixed acid prepared by perchloric acid, concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3:3, with a mass ratio of high-purity single-walled carbon nanotubes to mixed acid of 1:100, at 200°C for 30 min is less than or equal to 0.5%. The rapid oxidation weight loss temperature in the thermogravimetric differential curve of the high-purity single-walled carbon nanotubes, obtained by testing in air at a heating rate of 10℃ / min, is 740–800℃.

2. The high-purity single-walled carbon nanotube according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The mass content of the metal in the high-purity single-walled carbon nanotubes is 0.1% to 0.5%; (2) The thermogravimetric differential curve of the high-purity single-walled carbon nanotube is a single-peak curve with the peak located at 740-800℃; (3) The mass content of carbon impurities in the high-purity single-walled carbon nanotube is less than 2%; the mass content of carbon impurities is the longitudinal axis attenuation value in the thermogravimetric curve of the high-purity single-walled carbon nanotube in the range of 300 to 600℃ obtained by testing in air atmosphere under the condition of heating rate of 10℃ / min.

3. The high-purity single-walled carbon nanotubes according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) In the Raman spectrum of the high-purity single-walled carbon nanotubes, the Raman shift is in the range of 100–200 cm⁻¹. -1 The peak at the position is denoted as the characteristic RBM peak of the high-purity single-walled carbon nanotube, with a Raman shift of 1300–1350 cm⁻¹. -1 The peak at the location is denoted as the defect peak D, and the peak intensity I of the characteristic peak RBM peak is... RBM The peak intensity I of the defect peak D D The ratio is greater than 2.5; (2) In the Raman spectrum of the high-purity single-walled carbon nanotubes, the Raman shift is between 1500 and 1600 cm⁻¹. -1 The strongest peak at that location is designated as the G peak, with a Raman shift between 1300 and 1350 cm. -1 The peak at the location is denoted as the defect peak D, and the peak intensity I of the G peak is... G and the peak intensity I of the defect peak D D The ratio is greater than 70.

4. The high-purity single-walled carbon nanotubes according to claim 3, characterized in that, It includes at least one of the following features (1) to (2): (1) The peak intensity I of the characteristic peak RBM peak RBM The peak intensity I of the defect peak D D The ratio is 2.51 to 3.5; (2) The peak intensity I of the G peak G and the peak intensity I of the defect peak D D The ratio is 70 to 160.

5. The high-purity single-walled carbon nanotube according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The conductivity of the conductive film prepared by the high-purity single-walled carbon nanotubes is 150-600 s / mm; the conductive film includes a PET substrate and a conductive coating, the conductive coating includes the high-purity single-walled carbon nanotubes and sodium carboxymethyl cellulose in a mass ratio of 4:6, and the thickness of the conductive film is 2-3 μm. (2) The voltage of the coin cell obtained by the high-purity single-walled carbon nanotubes, silicon-carbon anode active material, conductive agent and binder in a mass ratio of 1:80:9:10 is 2.8 to 3.1V.

6. The high-purity single-walled carbon nanotube according to claim 1, characterized in that, The specific surface area of ​​the high-purity single-walled carbon nanotubes is 450–1200 m². 2 / g.

7. A method for purifying single-walled carbon nanotubes, characterized in that, Includes the following steps: The single-walled carbon nanotube material to be processed is dispersed to obtain the first single-walled carbon nanotube material. The first single-walled carbon nanotube material was subjected to medium-temperature oxidation and acid washing to obtain the second single-walled carbon nanotube material. The second carbon nanotube material was subjected to high-temperature evaporation to obtain high-purity single-walled carbon nanotubes.

8. The purification method for single-walled carbon nanotubes according to claim 7, characterized in that, It includes at least one of the following features (1) to (4): (1) The dispersion treatment method includes ultrasonic dispersion and / or high pressure homogenization; the ultrasonic dispersion method includes ultrasonically dispersing the single-walled carbon nanotube material to be treated in a liquid, letting it stand, then removing the bottom precipitate, filtering and drying the remaining material; (2) The temperature of the intermediate-temperature oxidation treatment is 400-700℃, and the intermediate-temperature oxidation treatment is carried out in an oxygen-containing atmosphere; (3) The acid solution used in the pickling treatment is a strong acid that can react with the metal and its oxides; (4) The temperature of the high-temperature evaporation treatment is 1500-2000℃, and the high-temperature evaporation treatment is carried out under an inert atmosphere or vacuum.

9. The purification method for single-walled carbon nanotubes according to claim 8, characterized in that, It includes at least one of the following features (1) to (4): (1) The frequency of the ultrasonic dispersion is 19kHz-25kHz, and the ultrasonic treatment time is 0.5-2h; the liquid includes water and / or alcohol; (2) The time for the intermediate temperature oxidation treatment is 0.2 to 6 hours; and / or, the oxygen-containing atmosphere is air; and / or, the flow rate of the oxygen-containing gas in the intermediate temperature oxidation is 0.1 to 10 L / min; (3) The acid solution for the pickling treatment includes hydrochloric acid, and / or sulfuric acid, and / or nitric acid; and / or the concentration of the acid solution is 3 to 16 mol / L; and / or the liquid-to-solid ratio of the pickling treatment is 50 to 500; and / or the pickling treatment time is 1 to 24 hours; and / or ultrasonic vibration is performed during the pickling treatment. (4) The high-temperature evaporation process is carried out under vacuum; and / or, the vacuum degree is 1×10⁻⁶. -1 ~9×10 -1 Pa; and / or, the high-temperature evaporation treatment time is 1 to 6 hours.

10. The purification method for single-walled carbon nanotubes according to any one of claims 7-9, characterized in that, It includes at least one of the following features (1) to (2): (1) In the single-walled carbon nanotube material to be treated, the mass content of single-walled carbon nanotubes is 40% to 80%, the mass content of metal impurities is 10% to 30%, and the mass content of carbon impurities is 2% to 10%. (2) The single-walled carbon nanotubes to be processed include single-walled carbon nanotubes prepared by floating catalysis and / or single-walled carbon nanotubes prepared by arc discharge.

11. The application of high-purity single-walled carbon nanotubes as described in any one of claims 1-6 in lithium-ion batteries, sodium-ion batteries, and (semi)solid-state batteries.

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