Single-walled carbon nanotube material, single-walled carbon nanotube purification method, and applications

Abstract

This invention provides single-walled carbon nanotube materials, methods for purifying single-walled carbon nanotubes, and their applications, relating to the field of carbon nanotube technology. Specifically, it involves multiple single-walled carbon nanotubes, performing Raman spectral scanning on the single-walled carbon nanotube material at a scanning point of 30°, and obtaining the I-wavelength of the Raman spectrum. G / I D All single-point values ​​are ≥70, I G / I D The percentage of scan points with a single-point value greater than 80 is >80%; (Plotting frequency as the ordinate and I...) G / I D The values ​​are grouped into intervals on the x-axis, and a frequency distribution histogram is plotted with intervals of 10 starting from 0. The lower limit of the interval corresponding to the peak value is ≥100. The single-walled carbon nanotubes of this invention have high purity, good Raman spectral performance, few structural defects, extremely high conductivity and mechanical properties, and the purification method can efficiently remove impurities of multiple components and types, showing good application prospects.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube technology, and more specifically, to single-walled carbon nanotube materials, methods for purifying single-walled carbon nanotubes, and their applications. Background Technology

[0002] Single-walled carbon nanotubes (SWCNTs) are one-dimensional seamless tubular nanomaterials formed by rolling up single-layer graphene sheets, with a diameter of approximately 0.8–2 nm. They possess extremely excellent electrical properties, toughness, and strength; their current-carrying capacity is 1000 times higher than that of copper, which has good conductivity, making them one of the most promising conductive agents for lithium-ion batteries. Currently, methods for preparing SWCNTs include, but are not limited to, the graphite arc method, laser evaporation method, chemical vapor deposition method, flame method, and solar energy method. A purification step is usually included after preparation, as conventionally prepared SWCNTs contain a large number of impurities, and the ability to effectively purify them is a crucial issue affecting their application.

[0003] Specifically, the impurities in unpurified single-walled carbon nanotubes are mainly metal catalysts, with a small amount of carbon impurities. These impurities not only reduce the purity of the single-walled carbon nanotubes but also affect their physicochemical properties such as electrical conductivity, thermal conductivity, and antioxidant capacity. For example, residual metal catalysts, such as iron, can form iron dendrites during charging, piercing the separator and causing micro-short circuits inside the battery, posing a safety hazard. Therefore, the purification step after preparation is crucial.

[0004] Furthermore, the aforementioned impurities mainly exist in the following forms: metal catalysts encapsulated by amorphous carbon to form a core-shell structure; metal catalysts encapsulated by a few layers of graphite to form embedded metal-carbon nanotubes; and a small amount of tiny-particle metal catalysts located at the end caps of single-walled carbon nanotubes. Carbon impurities also exist individually in the form of fullerenes, graphene, and multi-walled carbon nanotubes. These impurities differ in morphology, form of existence, and chemical properties, posing difficulties for the purification of single-walled carbon nanotubes.

[0005] Furthermore, current purification methods for single-walled carbon nanotubes mainly include liquid-phase acid washing, gas-phase oxidation-liquid-phase acid washing, high-temperature evaporation, and differential centrifugation. However, none of these methods can completely remove all types of impurities from single-walled carbon nanotubes. For example, liquid-phase acid washing can only remove exposed metals or metals encapsulated by amorphous carbon, and the reaction is slow and inefficient; centrifugation or ultrasonic dispersion is only effective for removing large-particle-size metal impurities; oxidative acid washing first oxidizes the single-walled carbon nanotubes in air to oxidize the metal into metal oxides, and then performs liquid-phase acid washing to remove the metal and its oxides. This method is not only inefficient, but the oxidation also damages the structure of the single-walled carbon nanotubes and introduces defects.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a single-walled carbon nanotube that addresses the shortcomings of conventionally prepared and purified single-walled carbon nanotube products, which suffer from impurities and low purity.

[0008] The second objective of this invention is to provide a method for purifying single-walled carbon nanotubes, which addresses the shortcomings of conventional purification methods in that they are difficult to effectively remove impurities with different morphologies, forms of existence, and chemical properties in a single step, as well as the shortcomings of conventional purification methods in that they easily damage single-walled carbon nanotubes or are inefficient.

[0009] A third objective of this invention is to provide a carbon nanotube dispersion.

[0010] A fourth objective of this invention is to provide an electrode.

[0011] The fifth objective of this invention is to provide a battery.

[0012] The sixth objective of this invention is to provide an apparatus.

[0013] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A single-walled carbon nanotube material, comprising multiple single-walled carbon nanotubes, is subjected to Raman spectral scanning of the single-walled carbon nanotube material, with 300 Raman spectral scanning points. The Raman spectrum of the single-walled carbon nanotube material has an Ig value. G / I D All single-point values ​​are ≥70, where I G / I D The percentage of scan points with a single-point value greater than 80 is >80%; Plot the frequency on the y-axis and the I-axis on the y-axis. G / I D The x-axis is the grouping interval of the values, starting from 0 and with a grouping interval of 10. A frequency distribution histogram is plotted, and the lower limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≥100.

[0014] Preferably, I G / I D The number of scan points with a single point value greater than 80 accounted for 90% to 98%.

[0015] Preferably, the upper limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≤130.

[0016] Preferably, the Raman spectrum of the single-walled carbon nanotube material has an I... G / I D The range of single-point values ​​is 70~180.

[0017] Preferably, the defect content of the single-walled carbon nanotube material is ≤10%; The method for measuring the defect content is as follows: using a Regulus 8100 field emission scanning electron microscope, the microstructure of the single-walled carbon nanotube material is detected by SEM at a magnification of 10W (i.e., 100,000 magnification), and 20 SEM images at the magnification are randomly selected. The SEM images containing single-walled carbon nanotubes with a length <1μm are considered defective images. The defect content is the ratio of the number of defective images to the total number of SEM images. More preferably, the defect content of the single-walled carbon nanotube material is ≤5%.

[0018] Preferably, the length of the single-walled carbon nanotubes in the single-walled carbon nanotube material is >5 μm.

[0019] Preferably, the content of metal impurities in the single-walled carbon nanotube material obtained by ICP testing is ≤0.5 wt%; More preferably, the metallic impurities include elemental iron, and / or oxides of iron, and / or salts of iron.

[0020] A method for purifying single-walled carbon nanotubes includes the following steps: S1: A mixture of hydrogen chloride gas and a first oxidizing gas is introduced into the crude single-walled carbon nanotubes to be purified to carry out the first heating reaction; S2: After the reaction, a second oxidizing gas is introduced to carry out a second heating reaction, thereby obtaining the single-walled carbon nanotube material.

[0021] Preferably, the oxidizing power of the second oxidizing gas is weaker than that of the first oxidizing gas.

[0022] Preferably, the temperature of the first heating reaction is higher than the boiling point of the metal chloride generated by the reaction of the metal impurities contained in the crude single-walled carbon nanotubes to be purified.

[0023] Preferably, the temperature of the first heating reaction is 600°C or below.

[0024] Preferably, the first heating reaction takes 1 to 5 hours.

[0025] Preferably, the temperature of the second heating reaction is higher than the temperature of the first heating reaction.

[0026] Preferably, the temperature of the second heating reaction is 600℃~900℃.

[0027] Preferably, the second heating reaction time is 0.5h to 4h.

[0028] Preferably, the first oxidizing gas includes an oxygen-containing gas.

[0029] Preferably, the second oxidizing gas includes at least one of water vapor or carbon dioxide; More preferably, the second oxidizing gas also includes an inert gas.

[0030] Preferably, the flow rate ratio of the hydrogen chloride gas to the first oxidizing gas is (1~5):1.

[0031] Preferably, the flow rate of the first oxidizing gas is 1 L / min to 5 L / min.

[0032] Preferably, the flow rate of the second oxidizing gas is 1 L / min to 5 L / min.

[0033] Preferably, the crude single-walled carbon nanotubes to be purified include single-walled carbon nanotubes prepared by floating catalysis, and / or single-walled carbon nanotubes prepared by arc discharge, and / or single-walled carbon nanotubes prepared by plasma.

[0034] A carbon nanotube dispersion comprising the single-walled carbon nanotube material described above or the single-walled carbon nanotube material obtained by the method described above.

[0035] An electrode comprising the single-walled carbon nanotube material described above or the single-walled carbon nanotube material obtained by the method described above.

[0036] A battery comprising the single-walled carbon nanotube material described above, or the single-walled carbon nanotube material obtained by the method described above, or the electrode described above.

[0037] An apparatus for preparing the single-walled carbon nanotube material or for implementing the method thereof; comprising an inlet unit and a thermal reaction unit connected in sequence; wherein the inlet unit is used to introduce a reaction gas into the thermal reaction unit, and the thermal reaction unit is used to hold the crude single-walled carbon nanotube to be purified and to provide a reaction space between the crude single-walled carbon nanotube to be purified and the reaction gas.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides a single-walled carbon nanotube material with high purity, low content of metallic or carbonaceous impurities, few structural defects, and extremely high electrical conductivity and mechanical properties. Further, the single-walled carbon nanotube material I in this invention... G / I DThe proportion of scan points with a single-point value greater than 80 is greater than 80%. At the same time, the lower limit of the frequency distribution histogram and the grouping interval corresponding to its peak value is limited to 100. The high proportion indicates that the structural defect content of single-walled carbon nanotubes is low, which is conducive to the mechanical performance of the three-dimensional conductive network when used as a conductive agent.

[0039] (2) This invention provides a method for purifying single-walled carbon nanotubes by replacing the traditional acid washing method with gas phase acidification. The reaction speed is fast and the purification efficiency is high. It can effectively remove various types of impurities. It not only causes little damage to the structure of single-walled carbon nanotubes, but also enables the recycling of reagents and reduces the pressure of waste liquid treatment.

[0040] (3) In the purification method of the present invention, an oxidizing gas and an acidic hydrogen chloride gas are introduced simultaneously. At high temperature, the metal oxidation reaction and the reaction between the metal and the acid washing gas are carried out simultaneously. On the one hand, this can improve the efficiency of removing metal particles. On the other hand, the metal particles are immediately consumed by the hydrogen chloride gas after being oxidized, thus being removed in time. This can prevent the metal catalyst from oxidizing the single-walled carbon nanotubes and avoid the destruction of the structure of the single-walled carbon nanotubes. Then, a weak oxidizing gas is passed through at high temperature, which can etch carbon impurities with low crystallinity without destroying the single-walled carbon nanotubes with high crystallinity. Thus, single-walled carbon nanotubes with extremely high overall purity can be obtained. Attached Figure Description

[0041] 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.

[0042] Figure 1 A comparison curve of TG values ​​between crude single-walled carbon nanotubes and intermediates is provided. Figure 2 Crude single-walled carbon nanotubes I were provided G / I D Distribution map; Figure 3 I provides a single-walled carbon nanotube intermediate G / I D Distribution map; Figure 4 SEM images of purified carbon nanotubes from Example 1 are provided; Figure 5 SEM images of purified carbon nanotubes from Example 1 are provided; Figure 6 TEM images of purified carbon nanotubes from Example 1 are provided; Figure 7 SEM images of the purified carbon nanotubes in Comparative Example 1 are provided. Figure 8 A comparison of the Raman spectra of crude single-walled carbon nanotubes and purified carbon nanotubes from Example 1 is provided. Figure 9 I of purified carbon nanotubes as described in Example 1 is provided. G / I D Distribution map; Figure 10 A cross-sectional view of the electrode before cyclic charging and discharging is provided; Figure 11 Cross-sectional views of the electrode plates after cyclic charging and discharging are provided; Figure 12 A schematic diagram of a feasible purification apparatus according to the present invention is provided. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] The first aspect of this invention is to provide a single-walled carbon nanotube material, specifically, the single-walled carbon nanotube material comprising a plurality of single-walled carbon nanotubes; Raman spectroscopy surface scanning is performed on the single-walled carbon nanotube material, with 300 Raman spectral scanning points, and the Raman spectrum of the single-walled carbon nanotube material has an Ig G / I D All single-point values ​​are ≥70, where I G / I D The percentage of scan points with a single-point value greater than 80 is >80%; (Plotting frequency as the ordinate and I...) G / I D The x-axis is the grouping interval of the values, starting from 0 and with a grouping interval of 10. A frequency distribution histogram is plotted, and the lower limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≥100.

[0045] In this invention, without being constrained by theory, the provided single-walled carbon nanotube material has low defect content, strong conductivity, and a high aspect ratio after dispersion. When used as a conductive agent, it is conducive to wrapping and encapsulating active materials, and the electrical and mechanical properties of its three-dimensional conductive network can be fully utilized.

[0046] In some embodiments of the present invention, I G / I D The percentage of scan points with a single point value greater than 80 is 90% to 98%, including but not limited to any one or any two of the following: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%.

[0047] In this invention, without being bound by theory, if I G / I D If the percentage of scan points with a single-point value greater than 80 is too low, it indicates that the single-walled carbon nanotube contains defects. The presence of defects restricts electron transport, hindering its excellent conductivity and limiting the fast-charging performance of lithium batteries when single-walled carbon nanotubes are used. If I G / I D If the proportion of scanning points with a single-point value greater than 80 is too high, the crystallinity of the material is too high, making it difficult to be wetted by the dispersant during dispersion. Because the single-walled carbon nanotubes are encapsulated by the macromolecular dispersant, steric hindrance is formed between the tubes, allowing the single-walled carbon nanotubes to be dispersed stably. Therefore, the slurry after the single-walled carbon nanotubes are dispersed without being wetted by the dispersant has poor stability and is prone to re-aggregating to form larger tube bundles, which is not conducive to the performance of its low addition amount and high conductivity characteristics.

[0048] In some embodiments of the present invention, the upper limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≤150. In some preferred embodiments of the present invention, the upper limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≤140. In some more preferred embodiments of the present invention, the upper limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≤130; that is, the grouping interval corresponding to the peak value of the frequency distribution histogram is 100~130.

[0049] In this invention, without being bound by theory, if the upper limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is too high, it indicates that the overall I of the material is... G / I DThe concentration in the higher range means that the material contains a small proportion of defective single-walled carbon nanotubes, resulting in stronger overall crystallinity and stronger surface chemical inertness. During dispersion processes (such as high-pressure homogenization and ultrasonic dispersion), the material is difficult to be effectively wetted by chain-like polymeric dispersants. The dispersed single-walled carbon nanotubes are prone to re-aggregation, resulting in a low aspect ratio of the dispersed single-walled carbon nanotube bundles, which is not conducive to exerting its unique characteristics of low addition amount and high conductivity.

[0050] In some embodiments of the present invention, the Raman spectrum of the single-walled carbon nanotube material is I G / I D The range of single-point values ​​is 70 to 180, including but not limited to any one or any two of the following values: 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 155, 160, 165, 170, 175, and 180.

[0051] In this invention, without being bound by theory, if I G / I D If the lower limit of the single-point value is <70, it indicates that the single-walled carbon nanotube contains many defects. The presence of defects restricts electron transport, hindering its excellent conductivity and limiting the fast-charging performance of lithium batteries when single-walled carbon nanotubes are used. If I G / I D If the upper limit of the single-point value is greater than 180, the crystallinity of the material is too high, the bonding force between tubes is stronger, it is difficult to be wetted by the dispersant during dispersion, and it is difficult to form steric hindrance between tubes under the action of the dispersant. The stability of the material after dispersion is poor, and it is easy to re-aggregate to form a large tube bundle, which is not conducive to exerting its characteristics of low addition amount and high conductivity.

[0052] In some embodiments of the present invention, the defect content of the single-walled carbon nanotube material is ≤10%; specifically, the method for measuring the defect content is as follows: using a Regulus 8100 field emission scanning electron microscope, the microstructure of the single-walled carbon nanotube material is detected by SEM at a magnification of 10W, and more than 20 SEM images at the magnification are randomly selected. The SEM images containing single-walled carbon nanotubes with a length <1μm are considered defective images, and the ratio of the number of defective images to the total number of SEM images is the defect content.

[0053] In this invention, if the defect content of single-walled carbon nanotubes is high, the presence of defects restricts electron transport. On the one hand, this is detrimental to their excellent conductivity, limiting the fast-charging performance of lithium batteries when single-walled carbon nanotubes are used. On the other hand, carbon nanotubes with defects are broken under stress during dispersion, resulting in a significant reduction in length, which is not conducive to wrapping and encapsulating active materials, thus hindering the improvement of lithium battery cycle performance. Therefore, single-walled carbon nanotubes with low defect content are beneficial for both the fast-charging performance of active materials and the enhancement of cycle performance when used as conductive agents in lithium batteries.

[0054] In some preferred embodiments of the present invention, the defect content of the single-walled carbon nanotube material is ≤5%.

[0055] In some embodiments of the present invention, the length of the single-walled carbon nanotubes is greater than 5 μm. In some preferred embodiments of the present invention, the length of the single-walled carbon nanotubes is between 5 and 15 μm. Since the particle size of the active material is usually between 5 and 10 μm, the length of the carbon nanotubes is slightly larger than the particle size of the active material, which is beneficial for the single-walled carbon nanotubes to entangle, adhere to, and encapsulate the active material, forming a three-dimensional conductive network.

[0056] In some embodiments of the present invention, the diameter of the single-walled carbon nanotubes is 1 nm to 3 nm. If the diameter of a single single-walled carbon nanotube is < 1 nm, the bonding force between the tubes is stronger, making it more difficult to disperse. Materials with poor dispersion are less likely to exhibit their excellent conductivity and mechanical properties. If the diameter is > 3 nm, the support force of the tube wall is weaker, and during the lithium insertion / extraction process of the active material, the single-walled carbon nanotubes are prone to collapse and breakage under stress, losing their function. In some preferred embodiments of the present invention, the diameter of the single-walled carbon nanotubes is 1 nm to 2 nm.

[0057] In some embodiments of the present invention, the content of metal impurities in the single-walled carbon nanotube material obtained by ICP testing is ≤0.5wt%. This includes, but is not limited to, any one or any two of the following values: 0.5wt%, 0.4wt%, 0.4wt%, 0.3wt%, 0.2wt%, 0.1wt%, 0.05wt%, and 0.01wt%.

[0058] In this invention, the content of metal impurities is ≤0.5%. The presence of metal impurities (such as iron) can easily lead to the formation of dendrites on the surface of the active material during charging, which can pierce the separator and cause micro-short circuits inside the battery. Therefore, the low metal content in single-walled carbon nanotubes can avoid the safety hazards caused by short circuits in lithium batteries.

[0059] In some embodiments of the present invention, the metallic impurities include elemental iron, and / or oxides of iron, and / or salts of iron.

[0060] The second aspect of the present invention is to provide a method for purifying single-walled carbon nanotubes, which mainly includes the following steps: S1: introducing a mixture of hydrogen chloride gas and a first oxidizing gas into the crude single-walled carbon nanotubes to be purified, and carrying out a first heating reaction; S2: after the reaction, introducing a second oxidizing gas, and carrying out a second heating reaction to obtain the single-walled carbon nanotube material.

[0061] The purification method of this invention has two reaction stages. In the pre-reaction stage, amorphous carbon impurities are reacted with a first oxidizing gas, and metallic impurities are reacted with hydrogen chloride gas. Simultaneously, as the reaction proceeds, the first oxidizing gas reacts with the metallic impurities, causing the structure of the complex impurities to be destroyed. The metal oxide, as an intermediate product, further reacts with hydrogen chloride gas and vaporizes, thus separating from the gas phase. In the post-reaction stage, carbon impurities are removed by a second oxidizing gas, thereby achieving the complete removal of complex impurities with multiple components and structures, and realizing the purification of carbon nanotubes.

[0062] Specifically, firstly, by introducing a mixture of an oxidizing gas and hydrogen chloride into the crude product, the following reactions occur: (1) the amorphous carbon in the unpurified single-walled carbon nanotubes (crude single-walled carbon nanotubes) is first oxidized and removed; (2) the hydrogen chloride (HCl) gas reacts rapidly with the exposed metal catalyst particles at high temperature to obtain low-valence metal chlorides, and on this basis, under the action of the first oxidizing gas, the low-valence metal chlorides are further oxidized into high-valence, low-boiling-point metal chlorides (such as ferric chloride with a boiling point of 0.05%). (3) The metal particles are first oxidized into metal oxides, and then react with hydrogen chloride gas to produce high-valence metal chlorides, which are vaporized at high temperature and separated from the single-walled carbon nanotubes; (4) The metal catalyst wrapped by the embedded metal carbon nanotubes is oxidized by the first oxidizing gas, and the generated metal oxides expand in volume, breaking the outer shell of the carbon nanotubes. Thus, the metal catalyst inside the structure is exposed and reacts rapidly with hydrogen chloride gas. The generated metal chlorides are vaporized and evaporated, separating from the single-walled carbon nanotubes. In summary, the above four processes enable the purification method of the present invention to obtain single-walled carbon nanotubes with metal catalyst removed but containing crystalline carbon impurities. Next, a second oxidizing gas is introduced to oxidize and remove the remaining multi-walled carbon nanotubes, carbon fibers, carbon nanotubes and other crystalline carbon impurities, thereby obtaining purified carbon nanotubes.

[0063] In traditional oxidation-acid washing processes, unpurified single-walled carbon nanotubes are first oxidized, followed by liquid-phase acid washing. During oxidation, the presence of a metal catalyst readily catalyzes the oxidation of single-walled carbon nanotubes, damaging their structure. In this invention, oxidizing gas and HCl gas are simultaneously introduced into a tube furnace. Once the metal catalyst is oxidized to oxide by the oxidant, it is immediately consumed by the HCl reaction, thus avoiding defects in the single-walled carbon nanotubes caused by purification. Then, a second oxidizing gas reacts at high temperature to remove carbon impurities. This yields high-purity single-walled carbon nanotubes.

[0064] In some embodiments, for the crude single-walled carbon nanotubes: the content of single-walled carbon nanotubes is ≤70%, and the content of metal impurities is ≥10%; in some more preferred embodiments, the content of single-walled carbon nanotubes is 40%~70%, and the content of metal impurities is 10%~30%.

[0065] In some embodiments, the oxidizing power of the second oxidizing gas is weaker than that of the first oxidizing gas.

[0066] In this invention, the second oxidizing gas has a weak oxidizing power. Since carbon impurities such as carbon nanotubes (onions, graphene, fullerenes, etc.) have lower crystallinity and conductivity than single-walled carbon nanotubes, their lower crystallinity results in higher chemical reactivity; that is, their oxidation weight loss temperatures are lower than those of single-walled carbon nanotubes. Using a weak oxidizing agent allows for the etching and consumption of carbon impurities without etching the single-walled carbon nanotubes. Therefore, high Ig content is obtained after etching with the weak oxidizing agent. G / I D High-purity, highly conductive single-walled carbon nanotubes.

[0067] In some embodiments, the first oxidizing gas includes an oxygen-containing gas. In other embodiments, the first oxidizing gas includes, but is not limited to, oxygen or air, or a mixture of at least one of water vapor or carbon dioxide with oxygen.

[0068] In some embodiments, the second oxidizing gas includes water vapor and / or carbon dioxide; in some embodiments, the second oxidizing gas also includes at least one inert gas, such as nitrogen, helium, neon, argon, etc.

[0069] In a preferred embodiment, the temperature of the first heating reaction is higher than the boiling point of the metal chlorides generated by the reaction of the metal impurities contained in the crude single-walled carbon nanotubes to be purified.

[0070] In some embodiments, the temperature of the first heating reaction is 600°C or below. Since the oxidizing gas introduced at the first reaction temperature is a strong oxidant, the first reaction temperature is low in order to remove amorphous carbon and metallic impurities (such as iron particles) without etching the single-walled carbon nanotubes. Above 600°C, under a strong oxidant atmosphere, the structure of the single-walled carbon nanotubes is easily damaged, forming defects.

[0071] In some embodiments, the first heating reaction takes 1 to 5 hours.

[0072] In some embodiments, the temperature of the first heating reaction includes, but is not limited to, any one or any two of the following numerical ranges: 350, 400, 450, 500, 550, and 600 (°C), and the time of the first heating reaction includes, but is not limited to, any one or any two of the following numerical ranges: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 (h).

[0073] In some embodiments, the temperature of the second heating reaction is higher than the temperature of the first heating reaction. Without being theoretically constrained, the second reaction temperature is used to etch carbon impurities under a weak oxidizing atmosphere. Since carbon nanoparticles such as onions, graphene, and fullerenes have a certain degree of crystallinity and lower chemical activity than amorphous carbon, a higher reaction temperature is required to etch carbon impurities such as carbon nanoparticles (especially in some preferred embodiments where a second oxidizing gas with weaker oxidizing power than the first oxidizing gas is used). Otherwise, under weak oxidizing atmosphere and low reaction temperature conditions, the reaction rate is extremely slow, and it may even be impossible to remove carbon impurities.

[0074] In some embodiments, the temperature of the second heating reaction is 600°C to 900°C. In some optional embodiments, the temperature of the second heating reaction includes, but is not limited to, any one or any two of 600, 650, 700, 750, 800, 850, and 900 (°C). Excessively high temperatures in the second heating reaction can easily lead to the etching of single-walled carbon nanotubes.

[0075] In some embodiments, the second heating reaction time is 0.5 h to 4 h. In some optional embodiments, the second heating reaction time includes, but is not limited to, any one or any two of the following: 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 (h).

[0076] In some embodiments, during the introduction of the hydrogen chloride gas and the first oxidizing gas, the exhaust gas is introduced to an indicator, and the color of the indicator serves as a marker for the end of the first heating reaction. Typically, the indicator includes, but is not limited to, litmus, phenol red, thymol blue, etc. It is understood that when hydrogen chloride gas appears in the exhaust gas, that is, when the exhaust gas is acidic, it can be considered that the reaction in the pre-stage has ended. In some optional embodiments, the indicator is wetted to enhance its color change sensitivity.

[0077] In some embodiments, before the second oxidizing gas is introduced, the single-walled carbon nanotube intermediate obtained from the reaction is detected by Raman spectroscopy, and it exhibits one or more of the following characteristics: (a) The I of the single-walled carbon nanotube G / I D The values ​​range from 45 to 111; (b) The I of the single-walled carbon nanotube G / I D The mode of the value distribution is 70-80; (c) In the single-walled carbon nanotubes, I G / I D The percentage of those with a value greater than 50 is 85% to 95%.

[0078] In some embodiments, the flow rate ratio of the hydrogen chloride gas to the first oxidizing gas is (1~5):1, including but not limited to any one or any two of 1:1, 2:1, 3:1, 4:1, 5:1, and more preferably (1~3):1.

[0079] In some embodiments, the flow rate of the first oxidizing gas is 1 L / min to 5 L / min, including but not limited to any one or any two of the following values: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.2, 4.5, 4.8, and 5 (L / min).

[0080] In some embodiments, the flow rate of the second oxidizing gas is 1 L / min to 5 L / min, including but not limited to any one or any two of the following values: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.2, 4.5, 4.8, and 5 (L / min).

[0081] In some embodiments, the crude single-walled carbon nanotubes to be purified include single-walled carbon nanotubes prepared by floating catalysis, and / or single-walled carbon nanotubes prepared by arc discharge, and / or single-walled carbon nanotubes prepared by plasma.

[0082] In this invention, without being bound by theory, the purification method for single-walled carbon nanotubes is not limited to single-walled carbon nanotubes prepared by the methods described above, but can also be applied to single-walled carbon nanotubes prepared by other methods. The crude single-walled carbon nanotubes to be processed in this invention can be directly prepared crude single-walled carbon nanotubes; or it can be single-walled carbon nanotube products obtained by preliminary processing of directly prepared crude single-walled carbon nanotubes.

[0083] In some embodiments, the purification method further includes tail gas recovery; in some optional embodiments, the first tail gas is recovered by passing deionized water or sodium hydroxide solution during the introduction of the hydrogen chloride gas and the first oxidizing gas. At this time, hydrochloric acid aqueous solution or sodium chloride solution is mainly recovered, and hydrogen chloride gas can be obtained by evaporation or electrolysis for recycling.

[0084] A third aspect of the present invention is to provide a carbon nanotube dispersion comprising the single-walled carbon nanotube material described above or the single-walled carbon nanotube material obtained by the method described above.

[0085] A fourth aspect of the present invention is to provide an electrode comprising the single-walled carbon nanotube material described above or the single-walled carbon nanotube material obtained by the method described above.

[0086] A fifth aspect of the present invention is to provide a battery comprising the single-walled carbon nanotube material described herein, or the single-walled carbon nanotube material obtained by the method described herein, or the electrode described herein.

[0087] A sixth aspect of the present invention is to provide an apparatus for preparing the single-walled carbon nanotube material or for carrying out the method thereof; comprising an inlet unit and a thermal reaction unit connected in sequence; wherein the inlet unit is used to introduce a reaction gas into the thermal reaction unit, and the thermal reaction unit is used to carry the crude single-walled carbon nanotube to be purified and to provide a reaction space between the crude single-walled carbon nanotube to be purified and the reaction gas.

[0088] In some embodiments, the device includes an air intake unit, a thermal reaction unit, and an exhaust gas treatment unit connected in sequence, wherein the exhaust gas treatment unit is used to treat the exhaust gas generated by the reaction; in a preferred embodiment, the exhaust gas treatment unit includes an exhaust pipe and at least two gas scrubbing components disposed on the exhaust pipe.

[0089] In some embodiments, the air intake unit includes an air intake pipe, and at least one carrier gas source and at least one gas scrubbing assembly disposed on the air intake pipe; the carrier gas source is used to provide carrier gas; wherein the gas scrubbing assembly disposed on the air intake pipe is used to contain volatile substances and provide volatile gases under the action of the carrier gas. In some specific embodiments, the gas scrubbing assembly includes a gas scrubbing bottle.

[0090] In some embodiments, the thermal reaction unit includes a reaction vessel and a heating assembly; the reaction vessel is provided with an inlet and an outlet, and the inlet is connected to the inlet unit, and the outlet is connected to the exhaust gas treatment unit; wherein, the thermal reaction unit is used to provide space for the crude single-walled carbon nanotubes to be purified to react with the carrier gas and / or volatile gas.

[0091] In some preferred embodiments, the reaction vessel is a tubular structure, and the gas inlet and the gas outlet are respectively located at both ends of the tubular structure. In some specific embodiments, the reaction vessel is a tubular furnace.

[0092] In some preferred embodiments, a first block and a second block are provided in the reaction vessel along the length of the tubular structure; the heating assembly is disposed in the first block, which is close to the air inlet, and the second block is close to the air outlet. As an example, the length ratio of the first block to the second block in the horizontal direction is (50%~80%):(50%~20%).

[0093] In some preferred embodiments, a solid-phase purging assembly is provided in the second block, and the solid-phase purging assembly is close to the gas outlet of the reaction vessel; a solid-phase collection assembly is correspondingly provided outside the reaction vessel, and the solid-phase purging assembly is connected to the solid-phase collection assembly; wherein, after the thermal reaction unit has been operated, it is cleaned by the solid-phase purging assembly, and metal chloride is recovered in the solid-phase collection assembly, which can be used as a wastewater flocculant.

[0094] In some optional embodiments, the solid phase purging assembly can be gas phase type or mechanical type; the gas phase type solid phase purging assembly includes high-pressure gas, a pulse valve and several nozzles for purging metal chlorides in the form of high-pressure gas flow; the mechanical phase purging assembly includes a vibration motor and a shock-absorbing spring for purging metal chlorides in the form of mechanical vibration; the solid phase collection assembly includes a movable guide plate, a collection pipe and a collection container.

[0095] In some optional embodiments, heating components such as electric heating sleeves and heating wires can be wrapped around the outside of the reaction vessel. In other optional embodiments, the heating components wrapped around the outside of the reaction vessel can also be covered with insulation material. In some optional embodiments, heating components such as heating rods can be disposed inside the reaction vessel. In some optional embodiments, the reaction vessel can also be covered with insulation material. In some optional embodiments, the heating component further includes a thermal control system for digitally preset or adjust the temperature of the heating component. The thermal control system includes a temperature sensor, a thermal adjustment module, and a safety protection module. The thermal control system can be a product of the prior art, such as a commercially available product, which will not be described in detail in this invention.

[0096] In some embodiments, the air intake unit includes an air intake pipe and two air scrubbing components connected to the air intake pipe, each of the two air scrubbing components being connected to a carrier gas source; or, in other embodiments, the air intake unit includes an air intake pipe and an air scrubbing component disposed on the air intake pipe, the air scrubbing component being detachably connected to the air intake pipe, and a switching switch being provided between the two carrier gas sources and the air scrubbing component.

[0097] In some embodiments, the exhaust gas treatment unit includes an exhaust pipe and a first gas washing assembly, a second gas washing assembly, and a third gas washing assembly connected in series on the exhaust pipe. In some preferred embodiments, the second gas washing assembly is provided with a color recognition device, which includes a spectrophotometer or a color sensor. In some specific embodiments, the gas washing assembly includes a gas washing bottle.

[0098] In some preferred embodiments, the first gas scrubbing assembly is connected to the gas scrubbing assembly in the intake unit; it is understood that in the exhaust gas treatment unit, the saturated solution obtained by the first gas scrubbing assembly can be directly used as a source of acidic gas generation in the intake unit.

[0099] In some preferred embodiments, the exhaust gas treatment unit further includes at least one exhaust gas collection tank, the inlet of which is connected to the side of the third gas scrubbing assembly away from the thermal reaction unit. In the exhaust gas treatment unit, the exhaust gas collection tank is used to collect unreacted inert gases or unreacted oxidizing gases, achieving economical recycling.

[0100] In the following Examples 1-6 and Comparative Examples 1-3, crude single-walled carbon nanotubes prepared by conventional arc discharge method were used as starting materials. The metal impurity content measured by ICP method was 22 wt.%, and the metal element in the metal impurities was iron.

[0101] The apparatus used in Examples 1-6 below for purifying single-walled carbon nanotubes mainly includes: a carrier gas source, a first washing bottle, a tubular furnace, a second washing bottle, a third washing bottle, and a fourth washing bottle connected in sequence. The carrier gas source and the first washing bottle are located on the inlet pipe, and the second, third, and fourth washing bottles are located on the outlet pipe. Figure 12 A schematic diagram of the device is shown. Wherein: In step (1), the carrier gas source is an oxidizing gas, and in step (3), the carrier gas source is switched to a protective gas.

[0102] The first gas washing bottle in step (1) is a gas washing bottle containing a room temperature saturated hydrogen chloride solution, and the gas washing bottle in step (3) is switched to a gas washing bottle containing deionized water at a constant temperature of 90°C.

[0103] The carrier gas source and the first washing gas bottle in steps (1) and (3) are switched manually. Of course, it is understandable that in practice, the carrier gas source and the first washing gas bottle in steps (1) and (3) can also be connected in parallel to the air inlet pipeline and switched by a valve.

[0104] The constant temperature zone of the tube furnace is used to hold the crude single-walled carbon nanotubes to be purified.

[0105] The second gas washing bottle contains deionized water, the third gas washing bottle contains acid-base indicators, and the fourth gas washing bottle contains sodium hydroxide solution. Understandably, in practice, the reagents in the respective gas washing bottles can be adjusted as needed.

[0106] During the reaction, the tubular furnace is first heated to the reaction temperature. Concentrated hydrochloric acid in the first gas washing bottle evaporates into HCl gas, which is then carried into the tubular furnace by the oxidizing gas to react with metallic impurities in the crude single-walled carbon nanotubes. The resulting low-boiling-point metal chlorides are evaporated into a gaseous state in the constant-temperature zone of the tubular furnace and moved to the low-temperature zone at the furnace inlet by the carrier gas flow to condense. After the reaction is complete, the metal chlorides can be cleaned and recovered for use as a wastewater flocculant. Unreacted HCl gas is highly soluble in the deionized water in the second gas washing bottle. Once the HCl reaches its maximum solubility, the HCl gas overflows with the carrier gas into the third gas washing bottle containing an acid-base indicator, and then enters the fourth gas washing bottle into a sodium hydroxide solution for neutralization and absorption. When the acid-base indicator changes color, it indicates that the deionized water in the second gas washing bottle is about to reach the maximum solubility of HCl. At this point, the HCl carrier gas flow can be stopped, and the saturated HCl solution in the second gas washing bottle can be placed in the first gas washing bottle as a source of HCl for the reaction gas. This device can not only achieve efficient purification of single-walled carbon nanotubes, but also avoid damage to the structure of single-walled carbon nanotubes compared with traditional liquid phase acid washing. At the same time, it can realize the recycling of HCl solution and reduce waste acid pollution.

[0107] The following comparative examples 1 to 3 are adapted to the apparatus of the embodiments based on their reaction processes.

[0108] Example 1 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace, prepare a room temperature saturated hydrogen chloride solution, use compressed air as carrier gas, pass the carrier gas into the heated saturated solution and then into the tube furnace, the total flow rate of the carrier gas is 2L / min, and the flow rate of hydrogen chloride gas entering the tube furnace is 5L / min.

[0109] (2) Heat the tubular furnace to the first oxidation temperature of 500°C and react for a total of 3 hours. After the reaction is completed, remove the hydrogen chloride solution, stop the loading of hydrogen chloride gas, and continuously introduce argon protective gas.

[0110] (3) Prepare deionized water at a constant temperature of 90°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 1L / min and the water vapor flow rate entering the tube furnace is 1L / min.

[0111] (4) Heat the tubular furnace to the second oxidation temperature of 850°C and react for a total of 3 hours. After the reaction is completed, cool down and collect the material in the tubular furnace to obtain the high-purity single-walled carbon nanotubes of this embodiment.

[0112] Example 2 The process is basically the same as in Example 1, except that: Step (2): The tube furnace is heated to the first oxidation temperature of 350°C and the reaction time is 5 hours; a moist blue litmus paper is placed at the gas outlet of the tube furnace, and when the litmus paper changes color to red, the gas introduced into the tube furnace is changed to argon protective gas; the temperature is raised to 850°C and kept for 3 hours, and the material is collected after cooling.

[0113] Example 3 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace, prepare a room temperature saturated hydrogen chloride solution, use compressed air as carrier gas, pass the carrier gas into the heated saturated solution and then into the tube furnace, the total flow rate of the carrier gas is 4 L / min, and the flow rate of hydrogen chloride gas entering the tube furnace is 10 L / min.

[0114] (2) Heat the tubular furnace to the first oxidation temperature of 500°C and react for a total of 4 hours. After the reaction is completed, remove the hydrogen chloride solution, stop the loading of hydrogen chloride gas, and continuously introduce argon protective gas.

[0115] (3) Prepare deionized water at a constant temperature of 90°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 3L / min and the water vapor flow rate entering the tube furnace is 3L / min.

[0116] (4) Heat the tubular furnace to the second oxidation temperature of 900°C and react for a total of 3 hours. After the reaction is completed, cool down and collect the material in the tubular furnace to obtain the high-purity single-walled carbon nanotubes of this embodiment.

[0117] Example 4 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace, prepare a room temperature saturated hydrogen chloride solution, use oxidizing gas such as compressed air as carrier gas, pass the carrier gas into the heated saturated solution and then into the tube furnace, the total flow rate of the carrier gas is 2L / min, and the flow rate of hydrogen chloride gas entering the tube furnace is 6L / min.

[0118] (2) Heat the tubular furnace to the first oxidation temperature of 400°C and react for a total of 2 hours. After the reaction is completed, remove the hydrogen chloride solution, stop the loading of hydrogen chloride gas, and continuously introduce argon protective gas.

[0119] (3) Prepare deionized water at a constant temperature of 90°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 2L / min and the water vapor flow rate entering the tube furnace is 2L / min.

[0120] (4) Heat the tubular furnace to the second oxidation temperature of 700°C and react for a total of 2 hours. After the reaction is completed, cool down and collect the material in the tubular furnace to obtain the high-purity single-walled carbon nanotubes of this embodiment.

[0121] Example 5 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace, prepare a room temperature saturated hydrogen chloride solution, use oxidizing gas such as compressed air as carrier gas, pass the carrier gas into the heated saturated solution and then into the tube furnace, the total flow rate of the carrier gas is 1 L / min, and the flow rate of hydrogen chloride gas entering the tube furnace is 2.5 L / min.

[0122] (2) Heat the tubular furnace to the first oxidation temperature of 400°C and react for a total of 1 hour. After the reaction is completed, remove the hydrogen chloride solution, stop the loading of hydrogen chloride gas, and continuously introduce argon protective gas.

[0123] (3) Prepare deionized water at a constant temperature of 90°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 1L / min and the water vapor flow rate entering the tube furnace is 1L / min.

[0124] (4) Heat the tubular furnace to the second oxidation temperature of 600°C and react for a total of 1 hour. After the reaction is completed, cool down and collect the material in the tubular furnace to obtain the high-purity single-walled carbon nanotubes of this embodiment.

[0125] Example 6 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace, prepare a room temperature saturated hydrogen chloride solution, use oxidizing gas such as compressed air as carrier gas, pass the carrier gas into the heated saturated solution and then into the tube furnace, the total flow rate of the carrier gas is 3L / min, and the flow rate of hydrogen chloride gas entering the tube furnace is 4L / min.

[0126] (2) Heat the tubular furnace to the first oxidation temperature of 600°C and react for a total of 2.5 hours. After the reaction is completed, remove the hydrogen chloride solution, stop the loading of hydrogen chloride gas, and continuously introduce argon protective gas.

[0127] (3) Prepare deionized water at a constant temperature of 90°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 4L / min and the water vapor flow rate entering the tube furnace is 4L / min.

[0128] (4) Heat the tubular furnace to the second oxidation temperature of 900°C and react for a total of 4 hours. After the reaction is completed, cool down and collect the material in the tubular furnace to obtain the high-purity single-walled carbon nanotubes of this embodiment.

[0129] Comparative Example 1 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace and introduce compressed air at a flow rate of 2 L / min.

[0130] (2) Heat the tubular furnace to the first oxidation temperature of 500°C and react for a total of 3 hours.

[0131] (3) After the reaction is complete, the material in the tube furnace is collected by cooling and placed in a room temperature saturated hydrogen chloride solution for liquid phase acid washing, and then the solid phase is obtained by solid-liquid separation for further processing.

[0132] (3) Prepare deionized water at a constant temperature of 70°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 1L / min and the water vapor flow rate entering the tube furnace is 1L / min.

[0133] (4) The tubular furnace was heated to the second oxidation temperature of 850°C and reacted for a total of 3 hours; the high-purity single-walled carbon nanotubes of this comparative example were collected after cooling.

[0134] Comparative Example 2 It is basically the same as Example 1, except that steps (3) to (4) are not performed.

[0135] Comparative Example 3 (1) Place 5 grams of crude single-walled carbon nanotubes in the constant temperature zone of a tube furnace, and heat the tube furnace to the first oxidation temperature of 500°C for a total of 3 hours.

[0136] (2) Prepare a saturated hydrogen chloride solution at room temperature. After step (1) is completed, use argon as the carrier gas and pass it into the saturated solution and then into a tube furnace (that is, pass the first oxidizing gas and the hydrogen chloride gas into the tube furnace in sequence). The total flow rate of the carrier gas is 2 L / min, and the flow rate of the hydrogen chloride gas entering the tube furnace is 5 L / min. After reacting for 3 hours, stop passing the hydrogen chloride gas and allow it to cool naturally under argon.

[0137] (3) Prepare deionized water at a constant temperature of 70°C. Use argon as the carrier gas and pass the carrier gas into the deionized water to carry water vapor into the tube furnace. The carrier gas flow rate is 1L / min and the water vapor flow rate entering the tube furnace is 1L / min.

[0138] (4) Heat the tubular furnace to the second oxidation temperature of 850°C and react for a total of 3 hours. After the reaction is completed, cool down and collect the material in the tubular furnace to obtain the high-purity single-walled carbon nanotubes of this embodiment.

[0139] Test case (1) The crude single-walled carbon nanotubes and the single-walled carbon nanotube intermediates obtained in the tube furnace after step (2) of Example 1, after the metal has been removed (but containing crystalline carbon impurities) were tested.

[0140] (1.1) The steps for the ICP method to detect metal content in the sample are as follows: Place 0.075±0.025 g of sample, 3 mL of 65% nitric acid, 3 mL of 98% sulfuric acid, and 1 mL of 70% perchloric acid in a microwave digester and microwave digest at 220℃ for 30 minutes. Filter the digest and dilute to volume. Use a PE Avio 200 spectrometer for spectral detection.

[0141] According to ICP analysis, the iron content decreased from 22% to 0.3% from the crude product to the intermediate.

[0142] (1.2) The procedure for determining the iron oxide content in the sample using the TG method is as follows: Take 0.075±0.025 g of sample and place it in a special crucible. Under the above atmosphere with an air flow rate of 50 mL / min and a protective gas flow rate of 20 mL / min, heat the sample from room temperature to 1000℃ at a heating rate of 10℃ / min. The instrument used is a NETZSCH STA449F3 integrated thermal analyzer.

[0143] Based on the TG method, from the crude product to the intermediate, and assuming all elemental iron is oxidized to ferric oxide, the iron content decreases from 25% to 0.4%; For example... Figure 1 The image shows a comparison of the thermogravimetric curves of the two.

[0144] (1.3) The Raman spectroscopy detection procedure in the sample is as follows: Using a RENISHAW in Via type Raman spectrometer, take 0.075±0.025 grams of sample and place it on a glass slide. Equipped with a 532nm laser, the spectral acquisition range is 100~4000cm. -1 Between, scan 300 points in a 50um*50um region.

[0145] The crude product and intermediate were detected by Raman spectroscopy, and the results were as follows: Figure 2 , Figure 3 Raman spectral imaging data I shown G / I D Distribution map.

[0146] The Raman shift in the Raman spectrum is between 1300 and 1350 cm⁻¹. -1 The D peak at this location originates from defects caused by incomplete carbon atom crystallization in single-walled carbon nanotubes and from amorphous carbon with a non-crystalline disorder. The Raman shift is between 1500 and 1600 cm⁻¹. -1 The location of the G peak represents sp 2 The lattice vibrations of carbon atoms; in this field, a lower D peak intensity and a higher G peak intensity indicate fewer defects in single-walled carbon nanotubes. Therefore, through... Figure 2 , 3 As can be seen, after the gas-phase oxidation and gas-phase acid washing in steps (1) to (2) of the embodiment, the peak intensity of G is significantly enhanced, and the peak intensity of D is significantly reduced. The ratio of the peak intensity of G to that of D is denoted as I. G / I D I obtained from a 300-point Raman spectral surface scan G / I D The range increased from 31-80 before purification to 45-111, including single-point I. G / I D The proportion of >50 increased from 20%~30% before purification to 85%~95%. Furthermore, the Raman spectroscopy imaging data I... G / I D The highest point I in the distribution map G / I D The value is recorded as the peak value, showing an increase from 40 before purification to 75. In summary, the gas-phase oxidation and gas-phase acid washing methods used in this invention significantly reduce defects in single-walled carbon nanotubes, resulting in a marked improvement in purity.

[0147] (2) The purified single-walled carbon nanotubes obtained by the post-processing in step (4) of Example 1 were observed by SEM and TEM, and the results were as follows: Figure 4 , Figure 5 The SEM image shown and Figure 6 The TEM image shown Figure 6The scale bar is 500 nm. Correspondingly, the purified single-walled carbon nanotubes obtained in Comparative Example 1 were observed using SEM, and the results are as follows: Figure 7 The SEM image shown is an example of this process. (In this invention, SEM observations were performed using a Regulus 8100 field emission scanning electron microscope.) The comparison of SEM images clearly shows that, at a magnification of 100,000, the single-walled carbon nanotubes obtained in Comparative Example 1 contain obvious defects, including fracture defects and edge defect complexes, with a length of <1 μm, while the high-purity single-walled carbon nanotubes obtained in Example 1 all have a length of >5 μm.

[0148] Furthermore, taking 20 microscopic images at this magnification level will produce the following results: Figure 7 The number of images of defective carbon nanotubes shown is denoted as Q. The defect content of high-purity single-walled carbon nanotubes is Q / 20*100%. Therefore, the defect content of Example 1 is ≤5%. The defect content of other examples or comparative examples was also tested and recorded in Table 1.

[0149] (3) The metal content of the single-walled carbon nanotubes obtained after step (4) of the example was detected by ICP method. The detection method was the same as the steps in test example (1.1). The detection results are recorded in Table 1.

[0150] (4) Raman spectroscopy was used to analyze the crude product and the purified single-walled carbon nanotubes of Example 1, respectively, and the results were as follows: Figure 8 The Raman spectrum comparison diagram is shown below; simultaneously, the purified single-walled carbon nanotubes of Example 1 were detected by Raman spectroscopy analysis, and the results are as follows. Figure 9 Raman spectral imaging data I shown G / I D Distribution map.

[0151] pass Figure 9 It can be seen that I obtained from 300 points of Raman spectroscopy surface scanning G / I D The range is all above 70, single point I G / I D >80% accounted for >90%, peak I G / I D It is 110~120.

[0152] The same tests were performed on purified single-walled carbon nanotubes from other examples or comparative examples, and their Raman spectral data are recorded in Table 1.

[0153] (5) Prepare single-walled carbon nanotube slurry as follows: Mix high-purity single-walled carbon nanotube powder, CMC and pure water in a mass ratio of 4:6:990 to form a 1 kg mixture, pour it into an emulsification pump, shear for 30 minutes, and then pour it into a high-pressure homogenizer. Homogenize it 10 times under a pressure of 1000 bar to obtain the dispersed single-walled carbon nanotube slurry. Perform the following two tests and record the test results in Table 1.

[0154] (5.1) The resistivity of the single-walled carbon nanotube slurry was tested as follows: The slurry dispersed by a high-pressure homogenizer was coated onto a clean PET film using a doctor blade coater. The coating thickness was 200 μm. After drying, it was cut into 15 mm round pieces. The thickness of the coating was measured with a micrometer and the resistivity was measured with a four-probe resistance meter.

[0155] (5.2) The method for detecting the volume expansion rate of the electrode is as follows: Single-walled carbon nanotubes, silicon-carbon negative electrode active material (chemical vapor deposition silicon-carbon composite material with a silicon content of 48 wt.%), Super P conductive agent, and PAA binder are mixed in a mass ratio of 1:80:9:10, coated, and dried to prepare a negative electrode sheet; the negative electrode sheet, separator, positive electrode (lithium sheet), and electrolyte (lithium hexafluorophosphate) are assembled into a coin cell, and after 100 cycles of 3C charge-discharge, the battery is disassembled, and the cross-section of the electrode sheet is obtained using an argon-ion cross-section polisher. The electrode sheet thickness before and after the cycle charge-discharge is measured under SEM. Figure 10 , Figure 11 The figures shown correspond to the electrode cross-sections before and after cyclic charging and discharging, respectively. The thickness before cyclic charging and discharging is denoted as H1, and the electrode thickness after cyclic charging and discharging is denoted as H2. The electrode volume expansion rate is calculated as (H2-H1) / H1.

[0156] Table 1

[0157] Combined with Table 1, Figure 2 , Figure 9 It is evident that the purification method of this invention can rapidly reduce the metal content in crude single-walled carbon nanotubes, with the iron content reduced to below 0.5%. Carbon impurities can also be efficiently removed, resulting in high-purity Raman I single-walled carbon nanotubes. G / I D The value can be increased to over 70, of which single point I G / I D The high proportion of >80, high peak value, and low defect content result in a slurry with low resistivity and good conductivity of the single-walled carbon nanotube powder dispersion. The button battery made with this single-walled carbon nanotube as a conductive agent has a low electrode volume expansion rate after cyclic charging and discharging at high current density, indicating that the single-walled carbon nanotube has excellent mechanical properties and suppresses the volume expansion of the silicon anode.

[0158] Compared to Example 1, in Example 2, the reaction temperature in step (1) was lower, and although the reaction time was longer, the reaction temperature had a greater impact on the reaction rate. Therefore, the iron removal was incomplete, and the iron content of the obtained sample was higher. Consequently, in the high-temperature reaction stage of step (4), the presence of residual iron catalyzed the etching of single-walled carbon nanotubes by a weak oxidant, resulting in defects. Although the treatment process in steps (3) and (4) of Example 2 was the same as that in Example 1, the Raman I of the obtained sample was significantly lower. G / I D Slightly lower than the sample obtained in Example 1, the presence of defects reduced the mechanical and electrical properties, and thus the resistivity of the slurry was also lower than that in Example 1. The resulting electrode also had a larger volume expansion rate after cyclic charging and discharging.

[0159] In Example 3, the reaction temperature and time in step (1) were sufficient, resulting in more thorough removal of iron particles compared to Comparative Example 1, thus yielding a sample with extremely low iron content. In steps (3) and (4), the reaction temperature and the amount of the second oxidizing gas were also higher, leading to more thorough removal of carbon impurities such as carbon nanoparticles and onions, resulting in a sample with Raman spectroscopy. G / I D The sample with fewer defects than the sample obtained in Example 1 has better mechanical and electrical properties, and its slurry resistivity, electrode volume expansion rate and other indicators are also better.

[0160] In Examples 4 and 5, the reaction temperatures and times in each stage (1), (3), and (4) were lower than in Example 1, resulting in poorer effects in removing iron and carbon impurities. Consequently, the iron content and I content of the samples obtained were lower than in Example 1. G / I D The resistivity of the slurry and the volume expansion rate of the electrode are worse than those in Example 1.

[0161] Example 6: Due to the high reaction temperature and suitable reaction time of the weak oxidant etching carbon impurities during step (3), most of the carbon impurities were etched away, thus the resulting sample had a high I content. G / I D Extremely high crystallinity. Compared to Example 1, it is more difficult to be wetted by the dispersant during dispersion, making it difficult for steric hindrance to form between tubes. The stability of the dispersed material is poor, and it is easy to re-aggregate to form larger tube bundles. Therefore, the aspect ratio of the dispersed single-walled carbon nanotubes is less than 2000, the measured film resistivity is >6 mΩ·mm, and the volume expansion rate of the electrode after cyclic charge and discharge is >20% when used as a conductive agent for silicon anodes.

[0162] Compared to the examples, Comparative Example 1 did not undergo gas-phase pickling, but instead underwent high-temperature oxidation followed by liquid-phase pickling. This resulted in low efficiency in removing metal impurities, leading to a final iron content reduction to only 0.89%. Furthermore, the metal impurities were not removed promptly within the tube furnace, causing the metal to catalyze the oxidation of single-walled carbon nanotubes, thus damaging the single-walled carbon nanotube structure and creating defects. Combined with... Figure 7 As shown, in Comparative Example 1, defects such as fractures, edge defects, aggregation, and vacancies appeared at the tube wall and end, leading to poor purification of I. G / I D Increasing the value to 55 will reduce both the electrical conductivity and mechanical properties of single-walled carbon nanotubes.

[0163] Comparative Example 2, without high-temperature weak oxidant treatment, contained carbon impurities with poor crystallinity, such as multi-walled carbon nanotubes, carbon fibers, carbon nanotubes, and defective single-walled carbon nanotubes. These impurities were chemically highly reactive and easily etched away by the weak oxidant at high temperatures, while the highly crystalline single-walled carbon nanotubes were retained. This is because the Ig of the single-walled carbon nanotubes obtained in Comparative Example 2... G / I D Increasing the value to 45 alone will also affect the electrical conductivity and mechanical properties of single-walled carbon nanotubes.

[0164] The difference between Comparative Example 3 and Comparative Example 1 is that the first oxidizing gas is introduced into the tube furnace first, and then hydrogen chloride gas is introduced after the oxidation reaction is completed. Because the iron, after initial oxidation, is not removed by hydrogen chloride in time, the iron particles exist in the form of iron oxide on the outside and iron on the inside. The iron oxide shell is not conducive to the rapid contact and reaction between the internal iron and the first oxidizing gas, thus hindering the reaction between iron and hydrogen chloride. Therefore, the residual iron is slightly higher than in Example 1. Furthermore, the iron is not removed in time, and the iron and iron oxide catalyze the oxidation of single-walled carbon nanotubes at the first oxidation temperature, generating a large number of defects. The resulting sample has a lower I... G / I D The resistivity of the slurry and the volume expansion rate of the electrode are significantly worse than those in Example 1.

[0165] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can 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, without departing from the spirit and scope of the present invention; and these 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; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A single-walled carbon nanotube material, characterized in that, The material comprises multiple single-walled carbon nanotubes. Raman spectroscopy of the single-walled carbon nanotube material is performed using 300 scanning points. The I-value of the Raman spectrum of the single-walled carbon nanotube material is... G / I D All single-point values ​​are ≥70, where I G / I D The percentage of scan points with a single-point value greater than 80 is >80%; Plot the frequency on the y-axis and the I-axis on the y-axis. G / I D The x-axis is the grouping interval of the values, starting from 0 and with a grouping interval of 10. A frequency distribution histogram is plotted, and the lower limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≥100. The defect content of the single-walled carbon nanotube material is ≤10%; The method for measuring the defect content is as follows: using a Regulus 8100 field emission scanning electron microscope, the microstructure of the single-walled carbon nanotube material is detected by SEM at a magnification of 10W, and 20 SEM images at the magnification are randomly selected. The SEM images containing single-walled carbon nanotubes with a length of <1μm are considered defective images. The ratio of the number of defective images to the total number of SEM images is the defect content. The length of the single-walled carbon nanotubes in the single-walled carbon nanotube material is >5 μm; The content of metallic impurities in the single-walled carbon nanotube material obtained by ICP testing is ≤0.5wt%; the metallic impurities include elemental iron, and / or oxides of iron, and / or salts of iron.

2. The single-walled carbon nanotube material according to claim 1, characterized in that, I G / I D The percentage of scan points with a single-point value greater than 80 was 90% to 98%. And / or, the upper limit of the grouping interval corresponding to the peak value of the frequency distribution histogram is ≤130.

3. The single-walled carbon nanotube material according to claim 1, characterized in that, The Raman spectrum of the single-walled carbon nanotube material I G / I D The range of single-point values ​​is 70~180.

4. The single-walled carbon nanotube material according to claim 1, characterized in that, The defect content of the single-walled carbon nanotube material is ≤5%.

5. A method for purifying single-walled carbon nanotube materials as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: A mixture of hydrogen chloride gas and a first oxidizing gas is introduced into the crude single-walled carbon nanotubes to be purified to carry out the first heating reaction; S2: After the reaction, a second oxidizing gas is introduced to carry out a second heating reaction, and single-walled carbon nanotube materials are obtained.

6. The purification method for single-walled carbon nanotube materials according to claim 5, characterized in that, The oxidizing power of the second oxidizing gas is weaker than that of the first oxidizing gas; And / or, the temperature of the first heating reaction is higher than the boiling point of the metal chloride generated by the reaction of the metal impurities contained in the crude single-walled carbon nanotubes to be purified; And / or, the temperature of the first heating reaction is 600°C or below; And / or, the duration of the first heating reaction is 1 h to 5 h; And / or, the temperature of the second heating reaction is higher than the temperature of the first heating reaction; And / or, the temperature of the second heating reaction is 600℃~900℃; And / or, the second heating reaction time is 0.5h to 4h.

7. The purification method for single-walled carbon nanotube materials according to claim 5 or 6, characterized in that, The first oxidizing gas includes a gas containing oxygen; And / or, the second oxidizing gas includes at least one of water vapor or carbon dioxide.

8. The purification method for single-walled carbon nanotube materials according to claim 7, characterized in that, The second oxidizing gas also includes an inert gas.

9. The purification method for single-walled carbon nanotube materials according to claim 5, characterized in that, The flow rate ratio of the hydrogen chloride gas to the first oxidizing gas is (1~5):1; And / or, the flow rate of the first oxidizing gas is 1 L / min to 5 L / min; And / or, the flow rate of the second oxidizing gas is 1 L / min to 5 L / min.

10. The purification method for single-walled carbon nanotube materials according to claim 5, characterized in that, The crude single-walled carbon nanotubes to be purified include single-walled carbon nanotubes prepared by floating catalysis, and / or single-walled carbon nanotubes prepared by arc discharge, and / or single-walled carbon nanotubes prepared by plasma.

11. A carbon nanotube dispersion, characterized in that, It includes the single-walled carbon nanotube material as described in any one of claims 1 to 4, or the single-walled carbon nanotube material obtained by the method as described in any one of claims 5 to 10.

12. An electrode, characterized in that, It includes the single-walled carbon nanotube material as described in any one of claims 1 to 4, or the single-walled carbon nanotube material obtained by the method as described in any one of claims 5 to 10.

13. A battery, characterized in that, It includes the single-walled carbon nanotube material as described in any one of claims 1 to 4, or the single-walled carbon nanotube material obtained by the method as described in any one of claims 5 to 10, or the electrode as described in claim 12.

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