Single-walled carbon nanotube film and preparation method and application thereof

Abstract

The application discloses a single-walled carbon nanotube film and a preparation method and application thereof, and the preparation method comprises the following steps: coating a single-walled carbon nanotube dispersion liquid on a substrate to obtain a single-walled carbon nanotube film original film, and performing drying on the original film after cleaning treatment to obtain the single-walled carbon nanotube film; wherein the mass fraction of the single-walled carbon nanotube is 1%-8% according to the mass of the single-walled carbon nanotube dispersion liquid. By controlling the mass fraction of the single-walled carbon nanotube to be 1%-8%, a stable liquid crystal phase can be obtained from a high-concentration single-walled carbon nanotube dispersion liquid, the single-walled carbon nanotube dispersion liquid can be used as an ideal starting point for preparing a high-strength and directional conductive film after the liquid crystal phase is generated, and excellent axial performance of the single-walled carbon nanotube can be maximally exerted, the conductivity of the obtained single-walled carbon nanotube film is greater than 3000 S / cm, the tensile stress is greater than 80 MPa, and the film has better mechanical performance and high conductivity.

Description

Technical Field

[0001] This application belongs to the field of nanomaterials technology, specifically relating to a single-walled carbon nanotube thin film, its preparation method, and its application. Background Technology

[0002] Single-walled carbon nanotubes (SUVs) are one-dimensional tubular nanomaterials formed by seamlessly rolling up a single layer of graphene sheets. Their diameter is at the nanoscale, while their length reaches the macroscopic level, exhibiting an extremely high aspect ratio. Based on the properties of SUVs, thin films prepared from SUVs show broad application prospects in fields such as electrodes for advanced energy storage devices and multifunctional structural composite materials.

[0003] Currently, single-walled carbon nanotubes often need to be prepared into uniform dispersions for practical applications to fully utilize their properties. Existing technologies mostly rely on surfactant-assisted dispersion or strong acid treatment.

[0004] Although the above methods can achieve the initial dispersion of single-walled carbon nanotubes, the actual content of single-walled carbon nanotubes in the dispersion is generally low, which is difficult to meet the requirements of high-concentration processing and application such as the preparation of high-performance thin films. Summary of the Invention

[0005] This application aims to provide a single-walled carbon nanotube thin film, its preparation method, and its application, in order to solve the problem that the actual content of single-walled carbon nanotubes in the dispersion is low, making it difficult to meet the processing and application requirements for preparing high-performance thin films.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, embodiments of this application propose a method for preparing a single-walled carbon nanotube thin film. The preparation method includes: coating a single-walled carbon nanotube dispersion onto a substrate to obtain a single-walled carbon nanotube thin film precursor; cleaning the precursor film and then drying it to obtain a single-walled carbon nanotube thin film. The mass fraction of the single-walled carbon nanotubes is 1% to 8%, based on the mass of the single-walled carbon nanotube dispersion.

[0007] Optionally, the preparation process of the single-walled carbon nanotube dispersion includes: After pretreatment, single-walled carbon nanotubes are mixed with a superacid to form a mixed system. The mixed system is stirred, and the superacid is used to protonate the single-walled carbon nanotubes to form a nematic liquid crystal, thereby obtaining a single-walled carbon nanotube dispersion. The superacid includes one or more of fuming sulfuric acid, chlorosulfonic acid, 3-fluorobenzenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and perchloric acid.

[0008] Optionally, nitrates are added to the mixture and stirred at 60-80°C to obtain a single-walled carbon nanotube dispersion. The mass fraction of the single-walled carbon nanotubes is 1% to 3%, based on the mass of the single-walled carbon nanotube dispersion.

[0009] Optionally, the nitrate includes at least one of NaNO3, KNO3, and NH4NO3; and / or, The amount of nitrate added is 10% to 30%.

[0010] Optionally, the preprocessing includes: The single-walled carbon nanotubes are dried at a temperature of 100-150°C for 10-24 hours.

[0011] Optionally, the stirring rate is 50-100 rpm, and the stirring time is 12-36 h.

[0012] Optionally, the thickness of the single-walled carbon nanotube film is 1-10 micrometers; and / or, The coating includes one of spraying, scraping, and roller coating.

[0013] Secondly, embodiments of this application provide a single-walled carbon nanotube film, which is obtained according to the preparation method described above.

[0014] Optionally, the electrical conductivity of the single-walled carbon nanotube film is greater than 3000 S / cm, and the tensile stress is greater than 80 MPa.

[0015] Thirdly, this application proposes an application of a single-walled carbon nanotube thin film, which is used in one of supercapacitors, batteries, fuel cells, and sensor electrodes.

[0016] Compared with the prior art, this application has at least the following advantages: In the embodiments of this application, a single-walled carbon nanotube dispersion is coated onto a substrate to obtain a single-walled carbon nanotube film. The film is then cleaned and dried to obtain a single-walled carbon nanotube film. The mass fraction of the single-walled carbon nanotubes is 1% to 8% based on the mass of the single-walled carbon nanotube dispersion.

[0017] By controlling the mass fraction of single-walled carbon nanotubes to 1%~8%, a stable liquid crystal phase can be obtained from a high-concentration single-walled carbon nanotube dispersion. Once the liquid crystal phase appears in the single-walled carbon nanotube dispersion, it can serve as an ideal starting point for preparing high-strength, oriented conductive films. This maximizes the excellent axial properties of single-walled carbon nanotubes, resulting in single-walled carbon nanotube films with electrical conductivity greater than 3000 S / cm and tensile stress greater than 80 MPa. The films exhibit better mechanical properties and higher electrical conductivity.

[0018] Meanwhile, the film can exist independently without being attached to a substrate, which facilitates subsequent processing and utilization.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The diagram shows the state of the single-walled carbon nanotube dispersion provided in Example 1 of this application under different light sources; Figure 1 A is a diagram showing the state under a polarizing microscope. Figure 1 B represents the state diagram under normal light source conditions; Figure 2 This illustrates a single-walled carbon nanotube thin film provided in Embodiment 1 of this application; Figure 3 This shows a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Embodiment 1 of this application; Figure 3 A is a scanning electron microscope image. Figure 3 B is a cross-sectional electron microscope scan image; Figure 4 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 1 of this application is shown; Figure 5 This application shows a single-walled carbon nanotube film provided in Embodiment 2 of this application; Figure 6 This shows a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Embodiment 2 of this application; Figure 6 A is a scanning electron microscope image. Figure 6 B is a cross-sectional electron microscope scan image; Figure 7 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 2 of this application is shown; Figure 8 This application shows a single-walled carbon nanotube thin film provided in Embodiment 3 of this application; Figure 9This shows a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Embodiment 3 of this application; Figure 9 A is a scanning electron microscope image. Figure 9 B is a cross-sectional electron microscope scan image; Figure 10 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 3 of this application is shown; Figure 11 This application shows a single-walled carbon nanotube film provided in Embodiment 4 of this application; Figure 12 This shows a scanning electron microscope image of the single-walled carbon nanotube film provided in Embodiment 4 of this application; Figure 12 A is a scanning electron microscope image. Figure 12 B is a cross-sectional electron microscope scan image; Figure 13 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 4 of this application is shown; Figure 14 This application shows a single-walled carbon nanotube thin film provided in Comparative Example 1. Figure 15 The image shown is a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Comparative Example 1 of this application; Figure 15 A is a scanning electron microscope image. Figure 15 B is a cross-sectional electron microscope scan image; Figure 16 The tensile strength test diagram of the single-walled carbon nanotube film provided in Comparative Example 1 of this application is shown; Figure 17 A schematic diagram of the preparation process of the single-walled carbon nanotube thin film provided in the embodiments of this application is shown. Detailed Implementation

[0021] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] Single-walled carbon nanotubes (SUVs) possess extremely high aspect ratios and unique chiral atomic arrangements. This chiral structure directly determines their electrical properties, allowing them to exhibit metallic or semiconducting characteristics. This characteristic underpins their core application potential in nanoelectronics. Simultaneously, SUVs combine exceptional mechanical strength with excellent electrical and thermal conductivity, making thin films fabricated from SUVs promising for applications in advanced energy storage device electrodes. In advanced energy storage devices, they can serve as self-supporting metal-free current collectors or electrode substrates for devices such as supercapacitors and thick-electrode batteries. Their high conductivity and large specific surface area allow for the construction of efficient ion / electron transport channels, enhancing the power density and cycle stability of the devices. In composite materials, their electrical, thermal, and high mechanical strength properties can be utilized to fabricate multifunctional integrated products for applications in aerospace, wearable devices, and other fields, integrating mechanical, electrical, and thermal properties.

[0023] Currently, single-walled carbon nanotubes (SUVs) often need to be prepared into uniform dispersions in practical applications to fully utilize their properties. Existing technologies mostly rely on surfactant-assisted dispersion or strong acid treatment. For example, Chinese invention patent CN202010111678.2 discloses a dispersion system using a compound of anionic and nonionic surfactants combined with polysiloxane wetting agents. After nano-grinding or high-pressure homogenization and filtration, an aqueous dispersion of SUVs is obtained, but the carbon nanotube content is generally low (approximately 0.05%-0.4%). Another patent CN201110180590.7 uses fuming sulfuric acid as the dispersion medium, stirring SUVs at high temperature for a long time, and further treating with nitric acid. The resulting dispersion has a carbon nanotube mass concentration of only 0.083%. Although these methods can achieve dispersion of SUVs to a certain extent, their processes are complex, time-consuming, and the solid content of carbon nanotubes in the dispersion system is relatively low.

[0024] While the aforementioned methods can achieve preliminary dispersion of single-walled carbon nanotubes (SUVs), significant limitations remain: First, the actual SUV content in the dispersion is generally low (typically below 0.5%), making it difficult to meet the demands of high-concentration processing and applications. This is especially true in the preparation of high-performance films, fibers, or high-load electrodes, where low solids content increases process complexity and cost. Second, while strong acid systems can promote dispersion, they involve high temperatures, long reaction times, and highly corrosive media, placing high demands on equipment, posing safety risks, and easily causing structural damage or over-functionalization of the carbon nanotubes, affecting their intrinsic properties. Third, low-concentration dispersions struggle to form stable liquid crystal phases, limiting their application in ordered assembly and the preparation of high-performance macroscopic materials. Therefore, developing a high-concentration, high-stability, and simple SUV dispersion system to meet the demands of high-concentration processing and applications such as high-performance films has become a key technological challenge driving its large-scale application.

[0025] Based on the above problems, in a first aspect, this application provides a method for preparing a single-walled carbon nanotube thin film. The preparation method includes: coating a single-walled carbon nanotube dispersion onto a substrate to obtain a single-walled carbon nanotube film base film; cleaning the base film and then drying it to obtain a single-walled carbon nanotube thin film. The mass fraction of the single-walled carbon nanotubes is 1% to 8%, based on the mass of the single-walled carbon nanotube dispersion.

[0026] It should be noted that the substrate can be a rigid substrate or a flexible substrate. For example, the rigid substrate can be a glass plate, silicon wafer, metal foil, or ceramic substrate; the flexible substrate can be polyethylene terephthalate (PET) film, polyimide (PI) film, paper substrate, fiber fabric, etc. In this application, a glass plate is preferred for preparing single-walled carbon nanotube films.

[0027] It should be noted that the cleaning process involves immersing the original single-walled carbon nanotube film in water and repeating this process multiple times to completely remove the acid from the original film. When the pH of the original single-walled carbon nanotube film is measured to be 7, the original film is separated from the substrate in water.

[0028] It should be noted that the drying process includes attaching the separated original membrane to a carrier, placing the carrier with the attached original membrane in an oven for drying, and after complete drying, naturally separating the original membrane from the carrier to obtain a complete single-walled carbon nanotube film. The carrier includes nylon mesh, polytetrafluoroethylene (PTFE) mesh, hydrophilic fiberglass mesh, pure cotton mesh, non-woven fabric, etc., and the drying temperature is 50~60℃, with a drying time of 30min~120min. For example, the drying temperature can be one or any combination of 50℃, 52℃, 55℃, 58℃, and 60℃.

[0029] It should be noted that the mass fraction of single-walled carbon nanotubes is 1% to 8%. For example, the mass fraction of single-walled carbon nanotubes is one or any two of the following values: 1.0%, 1.2%, 1.5%, 1.6%, 1.8%, 2.0%, 2.1%, 2.3%, 2.5%, 2.7%, 3.0%, 3.2%, 3.5%, 3.8%, 4.0%, 4.3%, 4.5%, 4.7%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, and 8.0%.

[0030] When the mass fraction of single-walled carbon nanotubes (SWCNTs) is controlled within the range of 1% to 3%, the steric hindrance effect between SWCNTs gradually becomes apparent, and some regions begin to form ordered liquid crystal microregions. The system exhibits a coexistence of liquid crystal phase and isotropic phase. When the mass fraction of SWCNTs is increased to 3% to 8%, the steric hindrance effect becomes dominant, and SWCNTs form a continuous, long-range, and uniform nematic phase ordered structure within the system, thus presenting a stable liquid crystal phase. Controlling the mass fraction of SWCNTs within the range of 3% to 8% ensures the stability of the liquid crystal phase while giving the system suitable viscosity and orientation, facilitating subsequent coating and film formation to obtain SWCNT films with uniform structure and high orientation.

[0031] For example, in specific implementation, such as Figure 17 As shown, a single-walled carbon nanotube dispersion was coated onto a glass plate to obtain a single-walled carbon nanotube film. The film was then immersed in water and the process was repeated several times to completely remove the acid from the film. When the pH of the film was measured to be 7, the film was separated from the substrate in water. The separated film was then attached to a nylon mesh and placed in an oven to dry. After complete drying, the film was naturally separated from the nylon mesh to obtain a complete single-walled carbon nanotube film.

[0032] In this embodiment, by controlling the mass fraction of single-walled carbon nanotubes to be 1%~8%, a stable liquid crystal phase can be obtained from the high-concentration single-walled carbon nanotube dispersion. When the liquid crystal phase appears in the single-walled carbon nanotube dispersion, it can serve as an ideal starting point for preparing high-strength, oriented conductive films. This can maximize the excellent axial properties of single-walled carbon nanotubes, and the obtained single-walled carbon nanotube films have a conductivity greater than 3000 S / cm and a tensile stress greater than 80 MPa. The films have better mechanical properties and higher electrical conductivity.

[0033] Optionally, in some embodiments, the preparation process of the single-walled carbon nanotube dispersion includes: After pretreatment, single-walled carbon nanotubes are mixed with a superacid to form a mixed system. The mixed system is stirred, and the superacid is used to protonate the single-walled carbon nanotubes to form a nematic liquid crystal, thereby obtaining a single-walled carbon nanotube dispersion. The superacid includes one or more of fuming sulfuric acid, chlorosulfonic acid, 3-fluorobenzenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and perchloric acid.

[0034] It should be noted that the aspect ratio of single-walled carbon nanotubes is greater than 1000.

[0035] It should be noted that fuming sulfuric acid is a viscous liquid mixture composed of sulfuric acid (H2SO4) and excess sulfur trioxide (SO3), and its chemical formula is often represented as H2SO4·SO3 (where x is the mass fraction of free SO3, 0%). <x<65%)。

[0036] It should be noted that the solid-liquid ratio of single-walled carbon nanotubes to superacid ranges from 1:78.5 to 1:6.3, for example, 1g of single-walled carbon nanotubes mixed with 78.5mL of superacid. Specifically, the solid-liquid ratio ranges from one or both of the following: 1:78.5, 1:75, 1:70, 1:65, 1:60, 1:55, 1:52:1:50, 1:40, 1:30, 1:20, 1:10, and 1:6.3.

[0037] It should be noted that the method for determining whether a nematic liquid crystal has formed is as follows: Take an appropriate amount of the dispersion onto a glass slide and observe it under a polarizing microscope. If you can see characteristic schlieren texture or birefringent bands, it indicates that a nematic liquid crystal has been formed. If there is no obvious schlieren texture or birefringent bands, it indicates that the mixed system is still in an aggregated state and the stirring time needs to be extended to achieve uniform dispersion, and finally obtain a single-walled carbon nanotube dispersion.

[0038] It should also be noted that carbon nanotubes possess one-dimensional linear characteristics and, due to their liquid crystal geometry, can exhibit solute liquid crystal properties under the influence of superacids. Once liquid crystal regions appear in the carbon nanotube dispersion, orienting them to prepare thin films can result in films with improved mechanical and electrical properties. Under the influence of certain superacids, such as 100% sulfuric acid, 120% sulfuric acid, trifluoro-terminated benzenesulfonic acid, methanesulfonic acid, and chlorosulfonic acid, single-walled carbon nanotubes are protonated.

[0039] The principle of protonation is as follows: Superacids, such as fuming sulfuric acid, contain excess SO3 and possess extremely strong protonic acid and oxidizing properties. They can convert protons (H+) into protons. + It can be reversibly added to the carbon framework of SWCNT to form -CH + The structure, physically equivalent to p-type doping of SWCNTs, makes them positively charged. Fuming sulfuric acid itself has an extremely high dielectric constant (~120), which can effectively shield the electrostatic attraction (van der Waals forces) between charged carbon nanotubes, preventing them from re-aggregating. When the dispersed SWCNTs with extremely high aspect ratios reach a critical concentration, the system will spontaneously transform from a disordered isotropic liquid to a nematic liquid crystal in order to obtain a higher orientation entropy. At this time, the dispersion will exhibit a typical schlieren texture under a polarizing microscope, and rainbow-like colored stripes or opalescence may also be observed with the naked eye, all of which are characteristics of long-range ordered liquid crystal phases.

[0040] In this embodiment, a nematic liquid crystal dispersion is obtained by protonation using a superacid. The advantages are reflected in the following aspects: 1. The formation of a stable liquid crystal phase signifies that carbon nanotubes have achieved a very high concentration and highly ordered arrangement. This spontaneous long-range order is an ideal starting point for manufacturing anisotropic macroscopic materials and can be used to prepare high-strength, oriented conductive thin films, maximizing the excellent axial properties of carbon nanotubes; 2. Carbon nanotubes form a true thermodynamic solution in superacids, rather than an unstable suspension, which makes the system more stable and conducive to the formation of a stable liquid crystal phase; 3. Because it does not rely on a large amount of insulating dispersant, the material prepared from the stable liquid crystal phase has higher purity. The absence of surfactants can increase the conductivity of carbon nanotube films several times over. Simultaneously, the protonated dispersion method better preserves the complete spline structure of the carbon nanotubes. 2 The structure allows the electrical and mechanical properties of the thin film to be fully utilized.

[0041] Optionally, in some embodiments, nitrates are added to the mixture and stirred at 60°C to 80°C to obtain a single-walled carbon nanotube dispersion. The mass fraction of the single-walled carbon nanotubes is 1% to 3%, based on the mass of the single-walled carbon nanotube dispersion.

[0042] It should be noted that the mass fraction of single-walled carbon nanotubes is 1% to 3%. For example, the mass fraction of single-walled carbon nanotubes is one or any two of the following values: 1%, 1.1%, 1.3%, 1.5%, 1.6%, 1.8%, 1.9%, 2.0%, 2.2%, 2.4%, 2.5%, 2.7%, 2.9%, and 3.0%.

[0043] In this embodiment, when nitrates are present, the concentration of the carbon nanotube dispersion that forms a stable liquid crystal phase can be reduced to 1-3%, which helps to reduce preparation costs. In the prior art, low concentrations (<1%) cannot form a stable liquid crystal phase, resulting in disordered dispersion of single-walled carbon nanotubes and an inability to form dense films. The 1-3% concentration in this application produces films with more stable performance and lower cost, making them more suitable for the electrode requirements of energy storage devices such as supercapacitors and lithium batteries.

[0044] The specific principle is as follows: In fuming sulfuric acid, nitrates are converted in situ into nitrate cations NO3. + Mild and selective oxidation of defect sites and endpoints of single-walled carbon nanotubes enhances the surface polarity and solvation of single-walled carbon nanotubes, thereby reducing the minimum concentration required for them to form a stable liquid crystal phase.

[0045] Optionally, in some embodiments, the nitrate includes at least one of NaNO3, KNO3, and NH4NO3; and / or, The amount of nitrate added is 10% to 30%.

[0046] For example, the amount of nitrate added is a range of 10%, 15%, 20%, 25%, 30%, or any two of these values.

[0047] Optionally, in some embodiments, the preprocessing includes: The single-walled carbon nanotubes are dried at a temperature of 100-150°C for 10-24 hours.

[0048] It should be noted that the drying temperature is 100~150℃. For example, the drying temperature is one or any two of the following: 100℃, 110℃, 120℃, 130℃, 140℃, and 150℃.

[0049] It should be noted that the drying time is 10 to 24 hours. For example, the drying time is one or any two of the following: 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, and 24 hours.

[0050] If water is present in the single-walled carbon nanotubes (SWCNTs), water molecules will form a hydrogen bond layer on the SWCNT surface, leading to enhanced van der Waals forces between the tubes and irreversible aggregation. Drying can gradually remove interfacial water, locking the nematic schlieren texture formed by the self-assembly of the liquid crystal phase and preventing the orientation structure from loosening in subsequent processes. For the original film coated with a high concentration (1%~8%) liquid crystal phase dispersion, drying can transform the SWCNT network from a wet and loose state to a dry and dense continuous state, significantly improving the film's conductivity and mechanical strength.

[0051] In this embodiment, the single-walled carbon nanotubes are dried at 100~150℃ for 10~24h, which is not only used to remove moisture, but also to fix the liquid crystal phase orientation structure of the single-walled carbon nanotubes, improve electrical conductivity and mechanical strength, and remove residual dispersant on the surface.

[0052] Optionally, in some embodiments, the stirring rate is 50-100 rpm and the stirring time is 12-36 h.

[0053] It should be noted that the stirring rate is 50~100 rpm. For example, the stirring rate is one or any two of the following: 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, and 100 rpm.

[0054] It should be noted that the stirring treatment time is 12 to 36 hours. For example, the stirring treatment time is one or any two of the following: 12 hours, 15 hours, 18 hours, 20 hours, 24 hours, 25 hours, 28 hours, 30 hours, 32 hours, 34 hours, and 36 hours.

[0055] In practice, the stirring equipment is installed on the reaction vessel and the joint is completely sealed. The complete sealing is due to the fact that the superacid is volatile and absorbs water, which reduces the effective concentration of single-walled carbon nanotubes in the mixed system, worsens the dispersion effect, and ultimately prevents the formation of a stable liquid crystal phase.

[0056] The presence of strong proton donors in the superacid system disrupts the diffusion boundary layer on the SWCNT surface, allowing protons to be rapidly and uniformly adsorbed onto the graphitized surface of the SWCNTs, forming a stable positively charged layer. This avoids excessively high local proton concentrations leading to surface oxidation, or insufficient local protons causing uneven modification. Furthermore, uniform protonation is a prerequisite for subsequent stable dispersion and liquid crystal phase formation. The electrostatic repulsion generated by the positively charged surface layer inhibits SWCNT re-aggregation, while continuous stirring accelerates SWCNT self-assembly, forming a nematic liquid crystal with schlieren texture. Finally, the protonation process is exothermic; stirring rapidly transfers the heat of reaction from localized areas to the entire system, preventing excessively high local temperatures that could lead to SO3 volatilization, SWCNT surface oxidation, or superacid decomposition.

[0057] In this embodiment, stirring is the core process step for achieving efficient protonation, monodispersion and preparation of liquid crystal phase precursors. This is not a simple physical mixing, but a full-chain transformation induced by surface modification, deagglomeration, uniform dispersion and stable liquid crystal phase through shearing and mass transfer.

[0058] Optionally, in some embodiments, the thickness of the single-walled carbon nanotube film is 1 to 10 micrometers.

[0059] It should be noted that the thickness of the single-walled carbon nanotube film is 1 to 10 micrometers. For example, the thickness of the single-walled carbon nanotube film is one or any two of the following values: 1 micrometer, 1.2 micrometer, 1.5 micrometer, 1.7 micrometer, 1.8 micrometer, 2 micrometer, 2.1 micrometer, 2.2 micrometer, 2.4 micrometer, 2.5 micrometer, 2.6 micrometer, 2.8 micrometer, 3 micrometer, 3.2 micrometer, 3.4 micrometer, 3.5 micrometer, 3.6 micrometer, 3.8 micrometer, 4 micrometer, 4.1 micrometer, 4.3 micrometer, 4.5 micrometer, 4.7 micrometer, 4.9 micrometer, 5 micrometer, 6 micrometer, 7 micrometer, 8 micrometer, 9 micrometer, and 10 micrometer.

[0060] It should be noted that the thickness of the single-walled carbon nanotube film is the thickness of the dried film after drying.

[0061] In this embodiment, the thickness of the single-walled carbon nanotube film is 1-10 micrometers. Within this thickness range, SWCNTs can form a continuous and dense oriented network, ensuring high-speed electron conduction along the axis while preventing light scattering due to excessive stacking. The final result is a pure black film that is opaque. Furthermore, the dispersion can be coated in a single step, eliminating the need for multiple coatings and saving on processing costs.

[0062] In addition, the aforementioned thickness is adapted to the rate performance requirements of energy storage electrodes, while retaining the excellent mechanical properties of SWCNT, with a tensile strength of over 80 MPa.

[0063] Optionally, in some embodiments, the coating includes one of spraying, scraping, and roller coating.

[0064] For example, in a specific implementation, an appropriate amount of single-walled carbon nanotube dispersion is placed on a glass plate and coated using a doctor blade of varying thickness, ranging from 50 to 1000 micrometers. By using a doctor blade of fixed thickness, a uniform liquid film is formed on the substrate surface. The external shear force further stretches and aligns the nematic schlieren texture of the liquid crystal phase SWCNTs, allowing for a highly oriented thin film to be obtained in a single deposition process. This solves the problem of low-concentration dispersions failing to form oriented structures and is suitable for the precise preparation of 1-10 micrometer ultrathin oriented thin films in the laboratory.

[0065] Roller coating achieves continuous coating of SWCNT liquid crystal phase dispersions through the extrusion and transport of rollers. External shear force can also induce orientation, making it suitable for industrial preparation of large-area flexible transparent conductive films and energy storage electrode films.

[0066] Spraying is suitable for coating SWCNT dispersions onto three-dimensional carriers such as porous carbon paper and nickel foam to form a porous electrode coating with high porosity and good electrolyte wettability, making it suitable for energy storage devices such as supercapacitors and fuel cells.

[0067] In this embodiment, the coating includes one of spraying, scraping, and roller coating. The coating process precisely controls the thickness uniformity, orientation, areal density, and production efficiency of the single-walled carbon nanotube film, while adapting to different scale requirements, ultimately achieving stable preparation of high-performance films.

[0068] Secondly, embodiments of this application provide a single-walled carbon nanotube film, which is obtained according to the preparation method described above.

[0069] Optionally, in some embodiments, the electrical conductivity of the single-walled carbon nanotube film is greater than 3000 S / cm; the tensile stress is greater than 80 MPa.

[0070] In this embodiment, the conductivity is greater than 3000 S / cm, which breaks through the continuity threshold of the conductive network and ensures that electrons are conducted at high speed in the SWCNT orientation network, avoiding high internal resistance of the device due to excessive contact resistance. This threshold is much higher than that of low-orientation / low-concentration SWCNT films, and at the same time, it is suitable for the basic conductivity requirements of scenarios such as opaque films, conductivity, electrodes, and electromagnetic shielding.

[0071] Tensile stress greater than 80MPa breaks through the mechanical stability threshold, ensuring that the single-walled carbon nanotube film has sufficient mechanical strength to withstand bending, stretching, assembly and other processes, and avoids cracking and falling off during use; this threshold is suitable for the mechanical requirements of flexible electronics (stable performance after 1000 bends) and self-supporting energy storage electrodes.

[0072] Thirdly, this application proposes an application of a single-walled carbon nanotube thin film, which is used in one of supercapacitors, batteries, fuel cells, and sensor electrodes.

[0073] For example, single-walled carbon nanotube films can be used in supercapacitors for self-supporting double-layer electrodes, composite pseudocapacitive electrodes, etc.; and are suitable for electric vehicle start-stop power supplies, rail transit supercapacitor energy storage, portable electronic device fast charging power supplies, and other scenarios.

[0074] For example, single-walled carbon nanotube films can be used as thick electrode carriers for lithium batteries (lithium batteries, sodium-ion batteries, etc.) and negative electrode frameworks for sodium-ion batteries; they are suitable for electric vehicle power batteries, sodium-ion batteries for energy storage power stations, lithium batteries for portable electronic devices, and other scenarios.

[0075] For example, single-walled carbon nanotube films can be used as cathode catalyst supports and proton exchange membrane interface reinforcement layers in fuel cells; they are suitable for hydrogen fuel cell vehicles, distributed power generation fuel cells, portable fuel cell power supplies, and other scenarios.

[0076] For example, single-walled carbon nanotube films can be used as gas sensor electrodes, humidity sensor electrodes, and biosensor electrodes in sensors (gas / humidity / biosensors, etc.); adaptable to scenarios such as environmental monitoring, medical diagnosis, food safety testing, and smart homes.

[0077] Test method: (1) Tensile strength test: Cut the sample into rectangles 2cm wide and 5cm long and fix them on a tensile testing machine to perform a tensile strength test, generating a stress-strain curve. The stress value corresponding to the highest point in the curve is the tensile strength.

[0078] (2) Conductivity test In an environment with a temperature of 25℃ and a humidity of 10%, a four-probe device was used to select five different locations (e.g., the four corners and the center) of the sample for conductivity testing, and the average value was taken.

[0079] Example 1 (1) Preparation of single-walled carbon nanotube dispersion 0.95 g of single-walled carbon nanotubes were dried at 120 °C for 12 h to obtain pretreated single-walled carbon nanotubes. The pretreated single-walled carbon nanotubes were then mixed with fuming sulfuric acid (SO3 mass fraction 20%) as a superacid to form a mixture system. 50 mL of fuming sulfuric acid was added, along with 0.19 g of nitrate (sodium nitrate). The mixture was stirred at 80 °C, ensuring complete sealing at the joints. The stirring rate was 50 rpm for 36 h. The fuming sulfuric acid was used to protonate the single-walled carbon nanotubes. A suitable amount of the dispersion was placed on a glass slide and observed under a polarizing microscope. If characteristic schlieren texture or birefringent bands were visible, it indicated the formation of a nematic liquid crystal. At this point, a single-walled carbon nanotube dispersion was obtained, in which the mass fraction of single-walled carbon nanotubes was 1%.

[0080] (2) Preparation of single-walled carbon nanotube thin films 1 mL of single-walled carbon nanotube dispersion was coated onto a glass plate using a doctor blade with a thickness of 50 micrometers to obtain a primary single-walled carbon nanotube film. The glass plate was then immersed in water and this process was repeated several times to completely remove the sulfuric acid from the primary film. When the pH of the primary film was measured to be 7, the primary film was separated from the glass plate in water and attached to a nylon mesh. The nylon mesh with the primary film attached was then placed in an oven and dried at 50℃~60℃ for 1 hour. After complete drying, the primary film was naturally separated from the nylon mesh to obtain a single-walled carbon nanotube film with a thickness of 2.243 micrometers.

[0081] Example 2 The difference between Example 2 and Example 1 is as follows: In Example 2, the preparation of the single-walled carbon nanotube dispersion in step (1) was adjusted to 0.95g of single-walled carbon nanotubes and 0.095g of sodium nitrate, and stirred at 60°C for 24h.

[0082] The remaining steps are the same as in Example 1 to obtain a single-walled carbon nanotube film with a thickness of 1.57 micrometers.

[0083] Example 3 The difference between Example 3 and Example 1 is that: In Example 3, in the preparation of the single-walled carbon nanotube dispersion in step (1), the amounts of single-walled carbon nanotubes, fuming sulfuric acid, and sodium nitrate were adjusted to 1.9g, 50mL, and 0.38g, respectively; and the thickness of the scraper was 250 micrometers, so that the mass fraction of single-walled carbon nanotubes was adjusted to 2%.

[0084] The remaining steps and dosages are the same as in Example 1, to obtain a single-walled carbon nanotube film with a thickness of 6.444 micrometers.

[0085] Example 4 The difference between Example 4 and Example 1 is that: Example 4 replaces the nitrate in step (1) with potassium nitrate.

[0086] The remaining steps and dosages are the same as in Example 1, to obtain a single-walled carbon nanotube film with a thickness of 3.107 micrometers.

[0087] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is as follows: Comparative Example 1: The temperature of the stirring process in step (1) was adjusted to room temperature of 25°C.

[0088] The remaining steps and dosages are the same as in Example 1, to obtain a single-walled carbon nanotube film with a thickness of 1.265 micrometers.

[0089] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is as follows: In Comparative Example 1, in the preparation of the single-walled carbon nanotube dispersion in step (1), the amount of single-walled carbon nanotubes and fuming sulfuric acid was adjusted to 0.475 g and 50 mL, respectively, so that the mass fraction of single-walled carbon nanotubes was adjusted to 0.5%.

[0090] The remaining steps and dosages are the same as in Example 1. Comparative Example 2 cannot form a dense single-walled carbon nanotube film, nor does it have mechanical strength and electrical conductivity.

[0091] Figure 1 The diagram shows the state of the single-walled carbon nanotube dispersion provided in Example 1 of this application under different light sources; Figure 1 A is a diagram showing the state under a polarizing microscope. Figure 1 B represents the state diagram under normal light source conditions; for example... Figure 1 As shown in Figure A, under a polarizing microscope, schlieren texture or birefringent bands can be clearly observed, indicating that the single-walled carbon nanotube dispersion obtained in Example 1 has formed a nematic liquid crystal; Figure 1 As shown in Figure B, the dispersion effect of single-walled carbon nanotubes in a strong acid system can be displayed. The state diagrams of the remaining embodiments are similar. Figure 1Similarly, it will not be shown again here.

[0092] Figure 2 The single-walled carbon nanotube film provided in Embodiment 1 of this application is shown; as follows: Figure 2 As shown, Figure 2 This is a real photograph of Example 1.

[0093] Figure 3 This shows a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Embodiment 1 of this application; Figure 3 A is a scanning electron microscope image. Figure 3 B is a cross-sectional electron microscope scan image; as shown Figure 3 Figure A shows a scanning electron microscope (SEM) image of the thin film surface in Example 1, which reveals the orientation degree of the single-walled carbon nanotubes, i.e., whether they are all facing the same direction; as shown... Figure 3 As shown in Figure B, the average thickness of the thin film cross-section is 2.243 micrometers.

[0094] Figure 4 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 1 of this application is shown; as follows: Figure 4 As shown, the maximum tensile stress reaches 1154.68 MPa, and the tensile strain at the maximum tensile stress is 2.31%.

[0095] Figure 5 This application illustrates a single-walled carbon nanotube thin film provided in Embodiment 2; as shown Figure 5 As shown, Figure 5 This is a real photograph of Example 2.

[0096] Figure 6 This shows a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Embodiment 2 of this application; Figure 6 A is a scanning electron microscope image. Figure 6 B is a cross-sectional electron microscope scan image; as shown Figure 6 As shown in Figure A, this is a scanning electron microscope (SEM) image of the thin film surface in Example 2, which shows the degree of orientation of the single-walled carbon nanotubes, i.e., whether they are all facing the same direction; as Figure 6 As shown in Figure B, the average thickness of the thin film cross-section is 1.57 micrometers.

[0097] Figure 7 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 2 of this application is shown; as follows: Figure 7 As shown, the maximum tensile stress reaches 85.57 MPa, and the tensile strain at the maximum tensile stress is 0.78%.

[0098] Figure 8 This application illustrates a single-walled carbon nanotube thin film provided in Embodiment 3; as shown Figure 8 As shown, this is a real-life photograph of Example 3.

[0099] Figure 9This shows a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Embodiment 3 of this application; Figure 9 A is a scanning electron microscope image. Figure 9 B is a cross-sectional electron microscope scan image; as shown Figure 9 As shown in Figure A, this is a scanning electron microscope (SEM) image of the thin film surface in Example 3, which shows the degree of orientation of the single-walled carbon nanotubes, i.e., whether they are all facing the same direction; Figure 9 As shown in Figure B, the average thickness of the thin film cross-section is 6.444 micrometers.

[0100] Figure 10 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 3 of this application is shown; as follows: Figure 10 As shown, the maximum tensile stress reaches 100.24 MPa, and the tensile strain at the maximum tensile stress is 0.61%.

[0101] Figure 11 This application illustrates a single-walled carbon nanotube thin film provided in Embodiment 4; as shown Figure 11 As shown, this is a real-life photograph of Example 4.

[0102] Figure 12 This shows a scanning electron microscope image of the single-walled carbon nanotube film provided in Embodiment 4 of this application; Figure 12 A is a scanning electron microscope image. Figure 12 B is a cross-sectional electron microscope scan image; as shown Figure 12 As shown in Figure A, this is a scanning electron microscope (SEM) image of the thin film surface in Example 4, which shows the degree of orientation of the single-walled carbon nanotubes, i.e., whether they are all facing the same direction; Figure 12 As shown in B, the average thickness of the thin film cross-section is 3.107 micrometers.

[0103] Figure 13 The tensile strength test diagram of the single-walled carbon nanotube film provided in Embodiment 4 of this application is shown; as follows: Figure 13 As shown, the maximum tensile stress reaches 95.79 MPa, and the tensile strain at the maximum tensile stress is 1.19%.

[0104] Figure 14 This application illustrates a single-walled carbon nanotube thin film provided in Comparative Example 1; as shown Figure 14 As shown, this is a real-life photo of Comparative Example 1.

[0105] Figure 15 The image shown is a scanning electron microscope image of the single-walled carbon nanotube thin film provided in Comparative Example 1 of this application; Figure 15 A is a scanning electron microscope image. Figure 15 B is a cross-sectional electron microscope scan image; as shown Figure 15 As shown in Figure A, this is a scanning electron microscope (SEM) image of the thin film surface in Comparative Example 1, which reveals the degree of orientation of the single-walled carbon nanotubes, i.e., whether they are all facing the same direction; Figure 15 As shown in Figure B, the average thickness of the thin film cross-section is 1.265 micrometers.

[0106] Figure 16 The tensile strength test diagram of the single-walled carbon nanotube film provided in Comparative Example 1 of this application is shown; as follows: Figure 16 As shown, the maximum tensile stress reaches 15.71 MPa, and the tensile strain at the maximum tensile stress is 1.5%.

[0107] Depend on Figure 3 , Figure 6 , Figure 9 , Figure 12 , Figure 15 It can be seen that the orientation degree of the single-walled carbon nanotubes in Examples 1-4 is better than that in Comparative Example 1.

[0108] The single-walled carbon nanotube films obtained in each embodiment and comparative example were subjected to tensile strength and electrical conductivity tests, respectively. The electrical conductivity test results are shown in Table 1.

[0109] Table 1

[0110] According to the tensile strength diagram and Table 1, the single-walled carbon nanotube film obtained in this application has an electrical conductivity greater than 3000 S / cm and a tensile stress greater than 80 MPa, exhibiting excellent electrical conductivity and mechanical properties.

[0111] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0112] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a single-walled carbon nanotube thin film, characterized in that, The preparation method includes: A single-walled carbon nanotube dispersion is coated onto a substrate to obtain a single-walled carbon nanotube film. The film is then cleaned and dried to obtain a single-walled carbon nanotube film. The mass fraction of the single-walled carbon nanotubes is 1% to 8%, based on the mass of the single-walled carbon nanotube dispersion.

2. The preparation method according to claim 1, characterized in that, The preparation process of the single-walled carbon nanotube dispersion includes: After pretreatment, single-walled carbon nanotubes are mixed with a superacid to form a mixed system. The mixed system is stirred, and the superacid is used to protonate the single-walled carbon nanotubes to form a nematic liquid crystal, thereby obtaining a single-walled carbon nanotube dispersion. The superacid includes one or more of fuming sulfuric acid, chlorosulfonic acid, 3-fluorobenzenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and perchloric acid.

3. The preparation method according to claim 2, characterized in that, Nitrate was added to the mixture, and the mixture was stirred at 60-80°C to obtain a single-walled carbon nanotube dispersion. The mass fraction of the single-walled carbon nanotubes is 1% to 3%, based on the mass of the single-walled carbon nanotube dispersion.

4. The preparation method according to claim 3, characterized in that, The nitrate includes at least one of NaNO3, KNO3, and NH4NO3; and / or, The amount of nitrate added is 10% to 30%.

5. The preparation method according to claim 2, characterized in that, The preprocessing includes: The single-walled carbon nanotubes are dried at a temperature of 100-150°C for 10-24 hours.

6. The preparation method according to claim 2, characterized in that, The stirring rate is 50-100 rpm, and the stirring time is 12-36 h.

7. The preparation method according to any one of claims 1-6, characterized in that, The thickness of the single-walled carbon nanotube film is 1-10 micrometers; and / or, The coating includes one of spraying, scraping, and roller coating.

8. A single-walled carbon nanotube thin film, characterized in that, The single-walled carbon nanotube film is obtained by the preparation method according to any one of claims 1-7.

9. The single-walled carbon nanotube thin film according to claim 8, characterized in that, The electrical conductivity of the single-walled carbon nanotube film is greater than 3000 S / cm; the tensile stress is greater than 80 MPa.

10. An application of a single-walled carbon nanotube thin film, characterized in that, The single-walled carbon nanotube thin film according to any one of claims 8-9 is used in one of supercapacitors, batteries, fuel cells, and sensor electrodes.

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