Single-walled carbon nanotube conductive paste and method for preparing the same

Abstract

This invention discloses a single-walled carbon nanotube (SUV) conductive slurry and its preparation method. The preparation method includes: mixing and pre-dispersing SUVs, a dispersion medium, and a removable dispersing agent; mechanically grinding the pre-dispersed slurry to reduce the size of SUV agglomerates; subjecting the resulting system to alternating cycles of pulsed ultrasonic treatment and high-pressure homogenization; applying an alternating electric field to the alternatingly treated system to promote the reconstruction of the SUV network structure in the slurry; and subsequently performing post-treatment including membrane dialysis and coarse particle removal to obtain the SUV conductive slurry. This method, through a combination of multi-stage dispersion, alternating electric field-assisted treatment, and control of dispersing agent residue, is beneficial for improving the dispersion uniformity of SUVs, the storage stability of the slurry, and its conductivity.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial dispersion and conductive slurry preparation technology, and particularly to a single-walled carbon nanotube conductive slurry and its preparation method. Background Technology

[0002] Single-walled carbon nanotubes (SWCNTs) are considered a next-generation high-performance conductive additive due to their excellent one-dimensional conductivity and extremely high aspect ratio, showing significant application potential in lithium-ion batteries, electromagnetic shielding, transparent conductive films, printed electronics, and flexible devices. However, the high specific surface area and strong intertube van der Waals forces of SWCNTs make them prone to forming bundles or larger-scale aggregates, making it difficult to obtain long-term uniform and stable dispersions in solvent media. This directly limits their conductivity and process adaptability.

[0003] In existing technologies, methods for preparing conductive single-walled carbon nanotube slurries mainly include mechanical grinding, ultrasonic dispersion, and high-pressure homogenization. However, each method has its limitations: traditional mechanical shearing has limited efficiency in breaking down stubborn micro-agglomerates and is time-consuming; continuous or prolonged high-intensity ultrasound can effectively break down agglomerates but easily leads to carbon nanotube breakage, significantly reducing tube length and aspect ratio, thereby weakening conductivity; high-pressure homogenization can generate strong shear and impact, but it requires sophisticated equipment, and a single treatment is unlikely to completely break down native agglomerates. To improve dispersion efficiency, multiple physical methods are usually combined in practical processes to achieve a balance between disintegration efficiency and maintaining structural integrity.

[0004] Chemical additives such as surfactants, polymeric dispersants, or functionalized polymers can significantly improve the dispersion of single-walled carbon nanotubes, facilitating subsequent processing (such as coating and printing). However, the adsorption of these additives inevitably forms a thin layer on the surface or between the carbon nanotubes. The residual insulating material severely hinders electron transport, resulting in the final product's conductivity being far lower than theoretically expected.

[0005] Therefore, a systematic process solution needs to be developed in this field. This solution should include multi-scale, multi-stage physical dispersion strategies and corresponding additive selection and recycling pathways, which can achieve efficient dispersion while maintaining the structural integrity of single-walled carbon nanotubes, thereby preparing a conductive paste with low residue and high stability. Summary of the Invention

[0006] The purpose of this invention is to provide a single-walled carbon nanotube conductive slurry and its preparation method, in order to improve the problems existing in the single-walled carbon nanotube slurry, such as the difficulty in fully depolymerizing agglomerates, the easy damage to the carbon nanotube structure caused by long-term high-energy dispersion, the impact of residual dispersing aids on conductivity, and the insufficient long-term stability of the slurry.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a single-walled carbon nanotube conductive paste, characterized by comprising the following steps: S1. Mix single-walled carbon nanotubes with a dispersion medium and a removable dispersing agent for pre-dispersion treatment; S2. Mechanically disperse the pre-dispersed system to reduce the size of carbon nanotube aggregates; S3. The system obtained in step S2 is subjected to alternating cyclic treatment. Each cycle of the alternating cyclic treatment includes pulsed ultrasonic treatment and high-pressure homogenization treatment in sequence, so as to further achieve the depolymerization and uniform dispersion of single-walled carbon nanotubes. S4. Apply an alternating electric field to the system obtained in step S3 to promote the reconstruction of the network structure of single-walled carbon nanotubes in the slurry. S5. The treated system is post-processed to obtain the single-walled carbon nanotube conductive slurry, wherein the post-processing includes at least partial or complete removal of the dispersing agent.

[0008] Furthermore, the dispersion medium is water, and the dispersion aid is selected from one or more of polyethylene glycol, polyvinylpyrrolidone, sodium carboxymethyl cellulose, polyvinyl alcohol, or polycarboxylic acid water-reducing agents.

[0009] Further, the dispersing agent is polyethylene glycol. Further, the weight-average molecular weight of the polyethylene glycol is 200-1000. Even further, the weight-average molecular weight of the polyethylene glycol is 400.

[0010] Furthermore, the content of the single-walled carbon nanotubes in the final conductive slurry is 0.5–5.0 wt%.

[0011] Furthermore, the mass ratio of the single-walled carbon nanotubes to the dispersion medium is 1:(20-200).

[0012] Furthermore, the pre-dispersion treatment includes: first mixing the dispersing agent with the dispersing medium, and then adding single-walled carbon nanotubes for stirring and dispersion.

[0013] Furthermore, the premixing time of the dispersing agent and the dispersion medium is 10 to 40 minutes, and the stirring speed is 100 to 5000 rpm.

[0014] Furthermore, the pre-dispersion time after adding single-walled carbon nanotubes is 30–70 min, and the stirring speed is 100–5000 rpm.

[0015] Furthermore, the mechanical grinding process is performed using a sand mill, and the grinding media is zirconia beads. Furthermore, the diameter of the zirconia beads is 0.1–1.0 mm, preferably 0.2–0.5 mm. Furthermore, the rotational speed of the sand mill is 600–2000 rpm, and the grinding time is 1–5 h.

[0016] Furthermore, after mechanical grinding, the particle size D50 of the single-walled carbon nanotube aggregates in the first intermediate slurry is ≤3 μm, preferably ≤2 μm.

[0017] Furthermore, the pulsed ultrasound processing adopts an intermittent pulse working mode, with a single pulse start time of 0.5 to 2 seconds and a single pulse stop time of 0.5 to 2 seconds.

[0018] Furthermore, the power density of the pulsed ultrasound treatment is 50–200 W·L. -1 The effective ultrasound time in a single cycle is 5–20 min.

[0019] Furthermore, the high-pressure homogenization process is carried out in a high-pressure homogenizer, with a high-pressure homogenization pressure of 50-150 MPa and a homogenization frequency of 1-3 times in a single cycle.

[0020] Furthermore, the alternating cyclic processing is performed 2 to 5 times, preferably 3 times.

[0021] Furthermore, during the alternating cycle process, the slurry temperature is controlled to not exceed 40°C by the heat exchange system built into the homogenizer or by an external cooling device.

[0022] Furthermore, no interval is set between two adjacent cycles, or a cooling interval of 1 to 5 minutes is set.

[0023] Furthermore, the alternating electric field treatment is performed using parallel electrode plates, ring electrodes, or an electric field treatment cavity, with parallel electrode plates being the preferred method.

[0024] Furthermore, the electric field strength of the alternating electric field is 100–1500 V / cm, preferably 300–1000 V / cm.

[0025] Furthermore, the frequency of the alternating electric field is 50–500 Hz, preferably 100–300 Hz.

[0026] Furthermore, the alternating electric field treatment time is 10 to 60 minutes, preferably 20 to 40 minutes.

[0027] Furthermore, the slurry temperature is controlled not to exceed 40°C during the alternating electric field treatment process.

[0028] Furthermore, the membrane dialysis treatment uses a dialysis membrane with a molecular weight cutoff of 100–1000 Da, and the dialysis time is 12–36 h.

[0029] Furthermore, the coarse particle removal process employs membrane filtration or low-speed centrifugation. Furthermore, the membrane used for membrane filtration has a pore size of 0.45–2.0 μm. Furthermore, the low-speed centrifugation is performed at a speed of 1000–3000 rpm for a time of 5–20 min.

[0030] Another object of the present invention is to provide a single-walled carbon nanotube conductive slurry prepared by any of the above preparation methods, wherein the residual amount of dispersant in the conductive slurry is not higher than 200 ppm and there is no sedimentation after standing for 60 days.

[0031] Furthermore, the content of single-walled carbon nanotubes in the single-walled carbon nanotube conductive slurry is 0.5-5.0 wt%.

[0032] Furthermore, the mass ratio of the single-walled carbon nanotubes to the solvent is 1:(20-200).

[0033] Furthermore, the solvent is water.

[0034] Furthermore, the dispersing agent is selected from organic compounds that are miscible with solvents, have an affinity for single-walled carbon nanotubes, and can be effectively removed through post-treatment.

[0035] Furthermore, the dispersing agent is selected from one or more of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), sodium carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), or polycarboxylic acid-based water-reducing agents, preferably polyethylene glycol (PEG).

[0036] Compared with the prior art, the present invention has the following beneficial effects: (1) Good dispersion effect and minimal damage to carbon nanotube structure: This invention adopts a multi-level, progressive dispersion strategy of "pre-dispersion + mechanical grinding + ultrasonic-homogeneous alternating cycle + electric field assistance". From macroscopic agglomerates to microscopic single tubes, each step adopts the energy input method most suitable for the dispersion at that scale, avoiding excessive damage to carbon nanotubes caused by single high-intensity treatment. In the final slurry, the carbon nanotubes maintain a high aspect ratio, are uniformly dispersed, and have no visible agglomerates.

[0037] (2) The slurry has extremely high stability and long storage life: Through the final electric field-assisted treatment, single-walled carbon nanotubes form a uniform and stable three-dimensional network structure in the slurry, which greatly inhibits sedimentation and meets the requirements of industrial long-term storage and transportation.

[0038] (3) Excellent conductivity: Through the design and post-processing removal of recyclable dispersants, the residual amount of additives in the final slurry is low (≤200 ppm), and "naked contact" is formed between single-walled carbon nanotubes, resulting in low electron transport resistance and excellent conductivity.

[0039] (4) The process is highly controllable and easy to scale up industrially: Each step of the present invention uses mature unit operation equipment (emulsifier, sand mill, ultrasonic equipment, high pressure homogenizer, electric field treatment device, membrane separation equipment, etc.), the process parameters are easy to control, and it is easy to realize continuous and automated production, which has good prospects for industrial application. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the following drawings are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the process for preparing single-walled carbon nanotube conductive paste as described in this application.

[0042] Figure 2 This is a transmission electron microscope (TEM) image of single-walled carbon nanotubes used to prepare conductive paste in Example 1 of this application. Detailed Implementation

[0043] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments 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.

[0044] In this specification, "dispersing aid" refers to a substance that can improve the dispersion state of carbon nanotubes in a dispersion medium; "removable dispersing aid" refers to a substance that plays a role in aiding dispersion during the dispersion process and whose residual amount in the final slurry can be reduced by membrane dialysis, membrane separation, adsorption or other post-treatment methods.

[0045] In this specification, "the level of not significantly reducing conductivity" means that the effect of residual dispersant on the volume resistivity of the slurry or its downstream film conductivity is within an acceptable range. When slurries prepared with the same formulation and dispersion process are subjected to post-treatment (removal of dispersant) and no post-treatment (retention of all dispersant) to produce identical test electrodes, and the volume resistivity of the post-treated sample is measured to be more than 50% lower than that of the untreated sample, and the volume resistivity of the post-treated sample is ≤10 Ω·cm, it is considered to have reached the level of "not significantly reducing conductivity". In some embodiments of the present invention, the above condition can be met when the residual amount of dispersant is ≤200 ppm.

[0046] In this instruction manual, "no visible sedimentation" means that after being sealed and left to stand for a specified time at 25±2℃ according to the static stability test method described in this instruction manual, there is no obvious clear liquid layer precipitating on the surface of the slurry, no visible hard sediment at the bottom of the bottle, and no obvious obstruction to the overall flow of the slurry when inverted.

[0047] In this specification, the residual amount of dispersant is calculated based on the total mass of the final slurry, determined and converted by total organic carbon analysis.

[0048] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0049] The following will describe the preparation examples of single-walled carbon nanotube conductive paste in conjunction with the above process, in order to further illustrate the present invention and make the experimental schemes involved in the present invention clearer. Example 1

[0050] The raw material formulation of this embodiment (by mass fraction) is as follows: 1 part by weight of single-walled carbon nanotubes; 0.5 parts by weight of dispersant (polyethylene glycol, PEG, weight average molecular weight Mw=400); and 98.5 parts by weight of solvent (deionized water).

[0051] A method for preparing a highly stable single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: PEG and water are stirred at 5000 rpm for 15 min in an emulsifier. After mixing evenly, single-walled carbon nanotubes are added and the speed is adjusted to 1200 rpm for preliminary pre-dispersion. After 45 min of treatment, a pre-dispersion slurry is obtained.

[0052] (2) Mechanical grinding: The obtained pre-dispersed slurry was transferred to a sand mill, and zirconia beads with a diameter of 0.3 mm were used as the grinding medium. The rotation speed was set to 1500 rpm and the grinding time was 3 h to obtain the first intermediate slurry.

[0053] (3) Ultrasonic and high-pressure homogenization: The obtained first intermediate slurry was subjected to alternating cyclic treatment, with a total of 3 cycles. In each cycle, pulsed ultrasonic treatment was performed first, with an ultrasonic power density of 100 W·L. -1 The pulse mode was activated for 1 second on and 1 second off, with a single cycle of ultrasonic treatment lasting 10 minutes. High-pressure homogenization was then performed at a pressure of 100 MPa, with two homogenization cycles per cycle. Throughout the alternating cycle process, the slurry temperature was controlled to ≤40℃ using a cooling system to obtain the second intermediate slurry.

[0054] (4) Electric Field Assistance: The second intermediate slurry was placed in a parallel electrode plate treatment tank. The electrode plates were made of stainless steel, with an electrode spacing of 1.5 cm. The tank dimensions were 20 cm × 15 cm × 2 cm, and the slurry filling height was approximately 1 cm. A sinusoidal alternating electric field with a field strength of 500 V / cm and a frequency of 100 Hz was applied. During the treatment, the slurry temperature was controlled to not exceed 40℃ using a circulating cooling system. The total treatment time was 30 min, yielding the third intermediate slurry. No bubble generation or electrode corrosion was observed in the slurry.

[0055] (5) Post-processing: The obtained third intermediate slurry was subjected to membrane dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h. Subsequently, coarse particles were removed by membrane filtration with a pore size of 1.0 μm to obtain the final single-walled carbon nanotube conductive slurry. Example 2

[0056] The raw material formulation of this embodiment (by mass fraction) is as follows: 1 part by weight of single-walled carbon nanotubes; 0.8 parts by weight of dispersant (polyethylene glycol, PEG, weight average molecular weight Mw=400); and 98.2 parts by weight of solvent (deionized water).

[0057] A method for preparing a highly stable single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: PEG and water are stirred at 5000 rpm for 15 min in an emulsifier. After mixing evenly, single-walled carbon nanotubes are added and the speed is adjusted to 1200 rpm for preliminary pre-dispersion. After 45 min of treatment, a pre-dispersion slurry is obtained.

[0058] (2) Mechanical grinding: The obtained pre-dispersed slurry was transferred to a sand mill, and zirconia beads with a diameter of 0.3 mm were used as the grinding medium. The rotation speed was set to 1500 rpm and the grinding time was 3 h to obtain the first intermediate slurry.

[0059] (3) Ultrasonic and high-pressure homogenization: The obtained first intermediate slurry was subjected to alternating cyclic treatment, with a total of 5 cycles. In each cycle, pulsed ultrasonic treatment was performed first, with an ultrasonic power density of 100 W·L. -1 The pulse mode was activated for 1 second on and 1 second off, with a single cycle of ultrasonic treatment lasting 10 minutes. High-pressure homogenization was then performed at a pressure of 100 MPa, with two homogenization cycles per cycle. Throughout the alternating cycle process, the slurry temperature was controlled to ≤40℃ using a cooling system to obtain the second intermediate slurry.

[0060] (4) Electric Field Assistance: The second intermediate slurry was placed in a parallel electrode plate treatment tank. The electrode plates were made of stainless steel, with an electrode spacing of 1.5 cm. The tank dimensions were 20 cm × 15 cm × 2 cm, and the slurry filling height was approximately 1 cm. A sinusoidal alternating electric field with a field strength of 500 V / cm and a frequency of 100 Hz was applied. During the treatment, the slurry temperature was controlled to not exceed 40℃ using a circulating cooling system. The total treatment time was 30 min, yielding the third intermediate slurry. No bubble generation or electrode corrosion was observed in the slurry.

[0061] (5) Post-processing: The obtained third intermediate slurry was subjected to membrane dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h. Subsequently, coarse particles were removed by membrane filtration with a pore size of 1.0 μm to obtain the final single-walled carbon nanotube conductive slurry. Example 3

[0062] The raw material formulation of this embodiment (by mass fraction) is as follows: 1 part by weight of single-walled carbon nanotubes; 0.8 parts by weight of dispersant (polyethylene glycol, PEG, weight average molecular weight Mw=400); and 98.2 parts by weight of solvent (deionized water).

[0063] A method for preparing a highly stable single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: PEG and water are stirred at 5000 rpm for 15 min in an emulsifier. After mixing evenly, single-walled carbon nanotubes are added and the speed is adjusted to 1200 rpm for preliminary pre-dispersion. After 45 min of treatment, a pre-dispersion slurry is obtained.

[0064] (2) Mechanical grinding: The obtained pre-dispersed slurry was transferred to a sand mill, and zirconia beads with a diameter of 0.3 mm were used as the grinding medium. The rotation speed was set to 1500 rpm and the grinding time was 3 h to obtain the first intermediate slurry.

[0065] (3) Ultrasonic and high-pressure homogenization: The obtained first intermediate slurry was subjected to alternating cyclic treatment, with a total of 3 cycles. In each cycle, pulsed ultrasonic treatment was performed first, with an ultrasonic power density of 100 W·L. -1 The pulse mode was activated for 1 second on and 1 second off, with a single cycle of ultrasonic treatment lasting 10 minutes. High-pressure homogenization was then performed at a pressure of 100 MPa, with two homogenization cycles per cycle. Throughout the alternating cycle process, the slurry temperature was controlled to ≤40℃ using a cooling system to obtain the second intermediate slurry.

[0066] (4) Electric Field Assistance: The second intermediate slurry was placed in a parallel electrode plate treatment tank. The electrode plates were made of stainless steel, with an electrode spacing of 1.5 cm. The tank dimensions were 20 cm × 15 cm × 2 cm, and the slurry filling height was approximately 1 cm. A sinusoidal alternating electric field with a field strength of 1000 V / cm and a frequency of 100 Hz was applied. During the treatment, the slurry temperature was controlled to not exceed 40℃ using a circulating cooling system. The total treatment time was 30 min, yielding the third intermediate slurry. No bubble generation or electrode corrosion was observed in the slurry.

[0067] (5) Post-processing: The obtained third intermediate slurry was subjected to membrane dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h. Subsequently, coarse particles were removed by membrane filtration with a pore size of 1.0 μm to obtain the final single-walled carbon nanotube conductive slurry.

[0068] Comparative Example 1 The raw material formulation (by mass fraction) for this comparative example is the same as that for Example 1.

[0069] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: PEG and water are stirred at 5000 rpm for 15 min in an emulsifier. After mixing evenly, single-walled carbon nanotubes are added and the speed is adjusted to 1200 rpm for preliminary pre-dispersion. After 45 min of treatment, a pre-dispersion slurry is obtained.

[0070] (2) Mechanical grinding: The obtained pre-dispersed slurry was transferred to a sand mill, and zirconia beads with a diameter of 0.3 mm were used as the grinding medium. The rotation speed was set to 1500 rpm and the grinding time was 3 h to obtain the first intermediate slurry.

[0071] (3) Electric field assistance: The first intermediate slurry was placed in a parallel electrode plate treatment tank. The electrode plates were made of stainless steel, with an electrode spacing of 1.5 cm. The treatment tank dimensions were 20 cm × 15 cm × 2 cm, and the slurry filling height was approximately 1 cm. A sinusoidal alternating electric field with an electric field strength of 500 V / cm and a frequency of 100 Hz was applied. During the treatment, the slurry temperature was controlled to not exceed 40℃ through a circulating cooling system. The total treatment time was 30 min, yielding the third intermediate slurry. No bubble generation or electrode corrosion was observed in the slurry.

[0072] (4) Post-processing: The obtained third intermediate slurry was subjected to membrane dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h. Subsequently, coarse particles were removed by membrane filtration with a pore size of 1.0 μm to obtain the final single-walled carbon nanotube conductive slurry.

[0073] Comparative Example 2 The raw material formulation (by mass fraction) for this comparative example is the same as that for Example 1.

[0074] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: PEG and water are stirred at 5000 rpm for 15 min in an emulsifier. After mixing evenly, single-walled carbon nanotubes are added and the speed is adjusted to 1200 rpm for preliminary pre-dispersion. After 45 min of treatment, a pre-dispersion slurry is obtained.

[0075] (2) Mechanical grinding: The obtained pre-dispersed slurry was transferred to a sand mill, and zirconia beads with a diameter of 0.3 mm were used as the grinding medium. The rotation speed was set to 1500 rpm and the grinding time was 3 h to obtain the first intermediate slurry.

[0076] (3) Ultrasonic and high-pressure homogenization: The obtained first intermediate slurry was subjected to alternating cyclic treatment, with a total of 3 cycles. In each cycle, pulsed ultrasonic treatment was performed first, with an ultrasonic power density of 100 W·L. -1 The pulse mode was activated for 1 second on and 1 second off, with a single cycle of ultrasonic treatment lasting 10 minutes. High-pressure homogenization was then performed at a pressure of 100 MPa, with two homogenization cycles per cycle. Throughout the alternating cycle process, the slurry temperature was controlled to ≤40℃ using a cooling system to obtain the second intermediate slurry.

[0077] (4) Post-processing: The obtained second intermediate slurry was subjected to membrane dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h. Subsequently, coarse particles were removed by membrane filtration with a pore size of 1.0 μm to obtain the final single-walled carbon nanotube conductive slurry.

[0078] Comparative Example 3 The raw material formulation (by mass fraction) for this comparative example is the same as that for Example 1.

[0079] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: PEG and water are stirred at 5000 rpm for 15 min in an emulsifier. After mixing evenly, single-walled carbon nanotubes are added and the speed is adjusted to 1200 rpm for preliminary pre-dispersion. After 45 min of treatment, a pre-dispersion slurry is obtained.

[0080] (2) Mechanical grinding: The obtained pre-dispersed slurry was transferred to a sand mill, and zirconia beads with a diameter of 0.3 mm were used as the grinding medium. The rotation speed was set to 1500 rpm and the grinding time was 3 h to obtain the first intermediate slurry.

[0081] (3) Ultrasonic and high-pressure homogenization: The obtained first intermediate slurry was subjected to alternating cyclic treatment, with a total of 3 cycles. In each cycle, pulsed ultrasonic treatment was performed first, with an ultrasonic power density of 100 W·L. -1 The pulse mode was activated for 1 second on and 1 second off, with a single cycle of ultrasonic treatment lasting 10 minutes. High-pressure homogenization was then performed at a pressure of 100 MPa, with two homogenization cycles per cycle. Throughout the alternating cycle process, the slurry temperature was controlled to ≤40℃ using a cooling system to obtain the second intermediate slurry.

[0082] (4) Electric Field Assistance: The second intermediate slurry was placed in a parallel electrode plate treatment tank. The electrode plates were made of stainless steel, with an electrode spacing of 1.5 cm. The tank dimensions were 20 cm × 15 cm × 2 cm, and the slurry filling height was approximately 1 cm. A sinusoidal alternating electric field with a field strength of 1000 V / cm and a frequency of 100 Hz was applied. During the treatment, the slurry temperature was controlled to not exceed 40℃ using a circulating cooling system. The total treatment time was 30 min, yielding the third intermediate slurry. No bubble generation or electrode corrosion was observed in the slurry.

[0083] Comparative Example 4 The raw material formulation for this comparative example is the same as that for Example 1.

[0084] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: Same as in Example 1; (2) Mechanical grinding: Same as in Example 1; (3) Ultrasonic and high-pressure homogenization: The first intermediate slurry was first subjected to continuous pulse ultrasonic treatment for a total effective ultrasonic time of 30 min; then it was subjected to continuous high-pressure homogenization for a total of 6 times; during the treatment, the slurry temperature was controlled to be ≤40℃ by the cooling system to obtain the second intermediate slurry; (4) Electric field assistance: Same as in Example 1; (5) Post-processing: Same as in Example 1.

[0085] Comparative Example 5 The raw material formulation for this comparative example is the same as that for Example 1.

[0086] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps: (1) Pre-dispersion: Same as in Example 1; (2) Mechanical grinding: Same as in Example 1; (3) Ultrasonic and high-pressure homogenization: The obtained first intermediate slurry was subjected to alternating cyclic treatment, with a total of 3 cycles. In each cycle, high-pressure homogenization was performed first, with a homogenization pressure of 100 MPa and 2 homogenization cycles per cycle; then pulsed ultrasonic treatment was performed, with an ultrasonic power density of 100 W·L. -1 The pulse mode is on for 1 second and off for 1 second, with a single cycle of ultrasonic treatment lasting 10 minutes. Throughout the alternating cycle process, the slurry temperature is controlled to ≤40℃ using a cooling system to obtain the second intermediate slurry.

[0087] (4) Electric field assistance: Same as in Example 1; (5) Post-processing: Same as in Example 1.

[0088] Performance testing methods The performance of the sample materials in each embodiment and comparative example was tested using the following methods: (1) Morphological test: Figure 2 The TEM used was a JEM-F200 with an accelerating voltage of 200 kV. Sample preparation method: A small amount of the sample to be tested was placed in a centrifuge tube, an appropriate amount of anhydrous ethanol was added, and the sample was ultrasonically dispersed for 5 minutes. The dispersion was then dropped onto a copper grid with a carbon support film and dried before testing.

[0089] (2) Viscosity test: The apparent viscosity of the slurry was measured using a Brookfield rotational viscometer at a room temperature of 25±0.5℃ and a rotation speed of 12 rpm (62# rotor). Each sample was measured 3 times and the average value was taken.

[0090] (3) Determination of residual additives: The residual amount of dispersing additives in the slurry was determined by total organic carbon (TOC) analysis. The slurry to be tested was diluted with deionized water to a suitable concentration, and the total organic carbon content was determined using a total organic carbon analyzer (model: Shimadzu TOC-L CPH). Deionized water was used as a blank control, and a calibration curve was established using standard solutions. The measured TOC values ​​were converted into the mass concentration (ppm) of organic additives. The determination was repeated 3 times and the average value was taken.

[0091] (4) Determination of stability under static conditions: The slurry sample is sealed in a transparent glass bottle, left to stand at room temperature and observed periodically.

[0092] "No sedimentation": After standing for 60 days, no clear liquid layer precipitates on the surface of the slurry, no visible sediment is found at the bottom of the bottle, and the slurry flows smoothly when inverted. "Slight sedimentation": After standing for 30-60 days, a small amount of clear liquid layer appears on the surface of the slurry (height < 5% of the total height), or a soft sediment that can be easily shaken appears at the bottom of the bottle. “Sedimentation”: A clear liquid layer (height ≥ 5% of the total height) appears within 30 days of standing, or a hard precipitate that is difficult to disperse appears at the bottom of the bottle.

[0093] (5) Volume resistivity test: The single-walled carbon nanotube conductive paste, silicon-carbon anode (SiC), and binder (polyacrylic acid, PAA) to be tested are mixed with deionized water at a mass ratio of 0.5:96.0:3.5 (the single-walled carbon nanotubes are added in the form of paste and converted to the mass of pure carbon nanotubes). The uniformly mixed paste is coated on copper foil with a wet film thickness of 200 μm. After drying at 100℃ for 1 h, it is tested using a four-probe resistivity tester (model: RTS-8). Five points are measured for each sample and the average value is taken.

[0094] The carbon nanotube conductive pastes provided in Examples 1-3 and Comparative Examples 1-5 were tested according to the above test methods. The test results are shown in Table 1. Table 1 Performance test results of each embodiment and comparative example The comparison of the above embodiments and comparative examples shows that Examples 1-3 exhibit excellent performance in all aspects, verifying the universality and stability of the technical solution of the present invention. Examples 1-3, using different combinations of process parameters (3 or 5 alternating cycles, electric field strength 500-1000 V / cm), all achieved excellent comprehensive performance: additive residue ≤200ppm, viscosity within a suitable range of 927-1189 cp, no sedimentation after 60 days of standing, and volume resistivity as low as 7.2-8.6 Ω·cm. This indicates that the method of the present invention has good parameter adaptability and can stably obtain high-quality products under different operating conditions.

[0095] Compared to Example 1, Comparative Example 1 omitted step S3. Its viscosity and volume resistivity were significantly higher than Example 1, and sedimentation occurred after 30 days of standing. This indicates that mechanical grinding alone cannot effectively dismantle the nanoscale aggregates of carbon nanotubes. The alternating action of ultrasound and high-pressure homogenization provided the necessary energy input, which is key to achieving uniform dispersion and low resistivity. Comparative Example 2 omitted step S4 (electric field-assisted treatment). Its volume resistivity was approximately 2.2 times that of Example 1, and slight sedimentation occurred after 40 days of standing. This demonstrates that electric field-assisted treatment plays an irreplaceable role in improving long-term stability and conductivity by inducing the orientation and alignment of carbon nanotubes and inhibiting re-agglomeration. Comparative Example 3 omitted step S5 (post-treatment). Its additive residue was extremely high, and its viscosity and volume resistivity were also significantly higher than Example 1. Sedimentation occurred after 30 days of standing. This indicates that excessive additive residue can also lead to decreased slurry stability and significant deterioration of conductivity. Comparative Example 4, which employed continuous sonication followed by continuous homogenization (non-alternating, with all sonication completed first, then all homogenization), exhibited a viscosity of 1780 cp and a volume resistivity of 19.3 Ω·cm. Sedimentation occurred after 30 days of standing, and all properties were significantly lower than in Example 1. This indicates that simple sequential stacking cannot achieve the dispersion effect of alternating cyclic treatment. Continuous sonication easily leads to carbon nanotube breakage, while continuous homogenization makes it difficult to further optimize dispersion at the nanoscale after ultrasonic disintegration. Although Comparative Example 5 used alternating treatment, the initial disruption of large-scale aggregates was insufficient due to the "homogenization first, then sonication" sequence, resulting in decreased efficiency of subsequent sonication and ultimately, the dispersion uniformity was still inferior to that of Example 1.

[0096] The mechanisms of action of each core step of the present invention can be revealed by comparing the comparative examples and embodiments. Mechanical grinding mainly acts on macroscopic agglomerates, while for nanoscale van der Waals force binding points, the cavitation effect of ultrasound and the shear force field of high-pressure homogenization are required for effective disintegration. The design of alternating pulsed ultrasound and high-pressure homogenization allows the two energy fields to work alternately, ensuring dispersion while avoiding carbon nanotube damage caused by a single high-intensity treatment. Electric field-assisted treatment plays a key role in constructing a stable and ordered network. Under the action of an alternating electric field, single-walled carbon nanotubes polarize and generate induced dipole moments, oriented along the direction of the electric field to form an ordered conductive network framework. This provides efficient electron transport channels on the one hand, and suppresses the Brownian motion and re-agglomeration tendency of carbon nanotubes on the other hand, thereby simultaneously improving conductivity and stability. In addition, the design and post-treatment removal of recyclable dispersing aids are also key to achieving high conductivity. Excessive residual aids will lead to increased slurry viscosity, decreased stability, and especially significant deterioration of conductivity. Post-processing steps such as membrane dialysis can control the residue of additives, which can maintain the "naked contact" between carbon nanotubes and avoid re-agglomeration that may be caused by the complete removal of additives.

[0097] This invention is not limited to the above-described embodiments. Any changes in shape or structure are within the scope of protection of this invention. The scope of protection of this invention is defined by the appended claims. Those skilled in the art can make various changes, modifications, substitutions, combinations, and simplifications to these embodiments without departing from the principles and essence of this invention. All such changes and simplifications should be considered equivalent substitutions and fall within the scope of protection of this invention.

Claims

1. A method for preparing a single-walled carbon nanotube conductive paste, characterized in that, Includes the following steps: S1. Mix single-walled carbon nanotubes with a dispersion medium and a removable dispersing agent for pre-dispersion treatment; S2. Mechanically disperse the pre-dispersed system to reduce the size of carbon nanotube aggregates; S3. The system obtained in step S2 is subjected to alternating cyclic treatment. Each cycle of the alternating cyclic treatment includes pulsed ultrasonic treatment and high-pressure homogenization treatment in sequence, so as to further achieve the depolymerization and uniform dispersion of single-walled carbon nanotubes. S4. Apply an alternating electric field to the system obtained in step S3 to promote the reconstruction of the network structure of single-walled carbon nanotubes in the slurry. S5. The treated system is post-processed to obtain the single-walled carbon nanotube conductive slurry, wherein the post-processing includes at least partial or complete removal of the dispersing agent.

2. The preparation method according to claim 1, characterized in that, The dispersion medium is water, and the dispersion aid is selected from one or more of polyethylene glycol, polyvinylpyrrolidone, sodium carboxymethyl cellulose, polyvinyl alcohol, or polycarboxylic acid water-reducing agents.

3. The preparation method according to claim 2, characterized in that, When the dispersing agent includes polyethylene glycol, the weight-average molecular weight of the polyethylene glycol is 200 to 1000.

4. The preparation method according to claim 1, characterized in that, The content of the single-walled carbon nanotubes in the single-walled carbon nanotube conductive paste is 0.5 to 5.0 wt%.

5. The preparation method according to claim 1, characterized in that, The mechanical dispersion treatment is carried out using a sand mill, with zirconia beads as the grinding media. The diameter of the zirconia beads is 0.1 to 1.0 mm. The rotation speed of the sand mill is 600 to 2000 rpm, and the grinding time is 1 to 5 hours.

6. The preparation method according to claim 5, characterized in that, After the grinding process, the particle size D50 of the single-walled carbon nanotube aggregates in the system obtained in step S2 is ≤3μm.

7. The preparation method according to claim 1, characterized in that, The power density of the pulse ultrasonic treatment is 50-200 W·L -1 The single pulse opening time is 0.5-2 s, and the single pulse closing time is 0.5-2 s; the pressure of the high-pressure homogenization treatment is 50-150 MPa; the cycle number of the alternating cycle treatment is 2-5 times, and the slurry temperature during the treatment process is not higher than 40℃.

8. The preparation method according to claim 1, characterized in that, The electric field strength of the alternating electric field treatment is 100–1500 V / cm, the frequency is 50–500 Hz, and the treatment time is 10–60 min.

9. The preparation method according to claim 1, characterized in that, The post-processing includes membrane dialysis and coarse particle removal, wherein the coarse particle removal is performed by membrane filtration or low-speed centrifugation; when the dispersing agent is polyethylene glycol, the membrane dialysis uses a dialysis membrane with a molecular weight cutoff of 100 to 1000 Da, and the residual amount of dispersing agent in the resulting single-walled carbon nanotube conductive slurry is not higher than 200 ppm.

10. A single-walled carbon nanotube conductive paste, characterized in that, The conductive slurry is prepared by any one of claims 1 to 9, wherein the residual amount of dispersant in the slurry is not higher than 200 ppm, and no visible sedimentation is observed after being sealed and left to stand for 60 days at 25±2℃.

Images