CN114538419B - Preparation method and equipment of dispersible carbon nano tube powder - Google Patents

Preparation method and equipment of dispersible carbon nano tube powder Download PDF

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CN114538419B
CN114538419B CN202011344868.5A CN202011344868A CN114538419B CN 114538419 B CN114538419 B CN 114538419B CN 202011344868 A CN202011344868 A CN 202011344868A CN 114538419 B CN114538419 B CN 114538419B
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supercritical fluid
pressure
supercritical
carbon nanotube
nano tube
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CN114538419A (en
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谢宝东
朱玉莲
韩少秋
张美杰
郑涛
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Jiangsu Cnano Technology Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/159—Carbon nanotubes single-walled
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/02—Single-walled nanotubes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/04—Nanotubes with a specific amount of walls
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/06—Multi-walled nanotubes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/22—Electronic properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

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Abstract

The application relates to the field of carbon nanotubes, and particularly discloses a preparation method and equipment of dispersible carbon nanotube powder. The preparation method comprises the following steps: A. uniformly mixing the carbon nano tube and the dispersing agent to obtain a pre-dispersed material; B. adding an additive into the pre-dispersed material in the step A, and uniformly mixing to obtain a mixture; then introducing supercritical fluid into the mixture, and performing supercritical fluid dispersion treatment to obtain supercritical suspension; C. and (3) carrying out supercritical fluid stripping treatment on the supercritical suspension to obtain the dispersible carbon nanotube powder. According to the application, the carbon nano tube, the dispersing agent and the additive are mixed and dispersed through the supercritical fluid, and then the supercritical fluid stripping treatment is carried out, so that the carbon nano tube powder with good dispersibility is prepared, the solvent is not added in the preparation process, the cost is low, the efficiency is high, the environment is protected, the large-scale production can be realized, and the prepared product can be directly applied to ternary positive electrode materials of lithium batteries and ferric phosphate positive electrode materials.

Description

Preparation method and equipment of dispersible carbon nano tube powder
Technical Field
The application relates to the field of carbon nanotubes, in particular to a preparation method and equipment of dispersible carbon nanotube powder.
Background
Carbon nanotubes are one-dimensional nano materials, are light in weight, have better mechanical, electrical and chemical properties, and have been the focus of attention and research by scientists since being discovered in 1991. The carbon nanotubes are widely used in the field of batteries because of their good conductivity; but at the same time, the problem of dispersing the carbon nano tube is also a key problem for limiting the application of the carbon nano tube.
Carbon nanotubes (especially single-walled carbon nanotubes, double-walled carbon nanotubes) are arranged in parallel, so that the acting force between the tubes is strong, and the carbon nanotube bundles or aggregates formed by aggregation are difficult to break. The current industrialized method for dispersing the carbon nano tube mainly comprises the steps of adding the carbon nano tube and a dispersing agent into a solvent (such as water, NMP, ethanol, isopropanol and the like), preparing conductive slurry by a series of process means such as stirring, ball milling, sanding and the like, and finally using the conductive slurry into positive and negative electrode materials of a lithium battery. In general, the weight percentage of the solvent in the conductive paste is more than 90%, which occupies a great part of cost; the conductive paste prepared by the processes such as sanding and the like also occupies a part of cost; in addition, NMP and other volatile organic solvents are very harmful to operators, equipment, the environment and the like.
Aiming at the related technology, the applicant believes that the related method for dispersing the carbon nano tube has the problems of high preparation process cost of stirring, ball milling, sanding and the like, high solvent cost, solvent hazard and the like.
Disclosure of Invention
In order to solve the problems of preparation cost and solvent hazard in the carbon nanotube dispersing method, the application provides a preparation method and equipment of dispersible carbon nanotube powder.
In a first aspect, the present application provides a method for preparing dispersible carbon nanotube powder, which adopts the following technical scheme:
a preparation method of dispersible carbon nano tube powder comprises the following steps:
step A: uniformly mixing the carbon nano tube and the dispersing agent to obtain a pre-dispersed material;
and (B) step (B): adding an additive into the pre-dispersed material in the step A, and uniformly mixing to obtain a mixture; then introducing supercritical fluid into the mixture, and performing supercritical fluid dispersion treatment to obtain supercritical suspension;
step C: and C, carrying out supercritical fluid stripping treatment on the supercritical suspension prepared in the step B to obtain the dispersible carbon nanotube powder.
The dispersibility of carbon nanotubes directly or indirectly affects the conductivity of a battery material, and for solving the problem of the dispersibility of carbon nanotubes, there are related arts that firstly, carbon nanotubes are mixed with a solvent capable of dispersing carbon nanotubes to form a carbon nanotube solution, then, the carbon nanotube solution is treated by methods such as bead grinding, jet milling, grinding, stirring and ball milling, so that the carbon nanotubes are physically crushed, and then, critical or supercritical fluid is flowed into the carbon nanotube solution, so that the carbon nanotubes are crushed in the subcritical or supercritical fluid atmosphere to form an active matrix. However, in the related art, the dispersion treatment of the carbon nanotubes is performed in a carbon nanotube solution system in which a solution participates, the problem of using a solvent in the dispersion treatment still cannot be solved, and even if a subcritical or supercritical fluid is used to replace the treatment procedures such as stirring, ball milling, sand milling and the like in industrial production, the problem of using a solvent still cannot be solved, and it cannot be verified or informed that the dispersion can be performed by subcritical or supercritical without adding a solvent, and the effect of performing the dispersion without adding a solvent cannot be expected. In addition, the carbon nanotubes prepared by the related technology can be applied to a lithium battery only by preparing conductive paste and then performing positive electrode paste mixing, and cannot be directly applied to a positive electrode material of the lithium battery.
In addition, there is also a related art which discloses a method for preparing a carbon nanotube composite material having good compatibility by treating a mixture containing carbon nanotubes, at least one carbon compound other than carbon nanotubes and a dispersion medium (carbon dioxide, water, fatty alcohol), and an oxidizing agent under subcritical or supercritical conditions such that further improved mutual binding force and compatibility are provided by the oxidizing agent under subcritical or supercritical conditions. Although there is no solvent added in the related art, the related art needs to improve the compatibility and binding force between the carbon nanotubes and carbon compounds other than the carbon nanotubes by means of the action of the oxidizing agent, and the composite material of the carbon nanotubes and other carbon compounds is produced, and the carbon nanotube powder is not produced, and it cannot be verified or informed that the supercritical fluid can be used to perform dispersion treatment on the carbon nanotubes without solvent participation under the condition of deleting the oxidizing agent and other carbon compounds. The carbon nano tube composite material can be applied to a lithium battery only by preparing conductive paste and then mixing the paste with the positive electrode, and cannot be directly applied to the positive electrode material of the lithium battery.
According to the technical scheme, after the carbon nano tube, the dispersing agent and the additive are mixed, the supercritical fluid is used for mixing and dispersing, and the supercritical fluid stripping treatment is carried out, so that the carbon nano tube powder with good dispersibility is prepared, and the product can be directly applied to ternary oily positive electrode materials of lithium batteries and lithium iron phosphate water-based positive electrode materials, and is wide in application; the preparation process has the advantages of no addition of solvent, low cost, environmental protection, high preparation efficiency and suitability for large-scale production. Wherein the average particle diameter D50 of the prepared dispersible carbon nano tube powder is smaller than 10 mu m.
Preferably, in the step a, the carbon nanotubes are one or a mixture of a plurality of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.
The supercritical fluid mixing dispersion and supercritical fluid stripping treatment of the application can be suitable for the dispersion treatment of single-wall carbon nanotubes, double-wall carbon nanotubes and multi-wall carbon nanotubes to prepare carbon nanotube powder, so that the dispersion treatment of the application has wide application range.
Preferably, in the step A, the mixing weight ratio of the carbon nano tube to the dispersing agent is 0.5-5:1; the dispersing agent is one or a mixture of more of polyvinylpyrrolidone, polyvinylidene fluoride and carboxymethyl cellulose.
By adopting the dispersing agent and controlling the dosage of the dispersing agent, the dispersing agent can improve the dispersibility of the carbon nano tube in the supercritical fluid mixing and dispersing treatment after being mixed with the carbon nano tube, and further the carbon nano tube is peeled and crushed uniformly in the supercritical peeling and dispersing process, so as to prepare the carbon nano tube powder with high dispersibility. If the amount of the dispersant is too small, the dispersibility to the carbon nanotubes is lowered.
Preferably, in the step B, the mixing weight ratio of the additive to the pre-dispersed material is 0.02-0.08:1; the additive is one or a mixture of more of hydroxyethyl ethylenediamine, diethylenetriamine, N-dimethylethanolamine, diethanol monoisopropanolamine and 2-amino-2-methyl-1-propanol.
By adopting the additive as the auxiliary dispersing agent, the dispersibility of the carbon nano tube is further improved, the dosage of the additive is controlled, the fluidity of the supercritical suspension after the supercritical fluid dispersing treatment is good, if the dosage of the additive is too small, or the additive is not adopted, but only the dispersing agent is adopted to disperse the carbon nano tube, the viscosity of the supercritical suspension is higher, the fluidity is poor, the subsequent supercritical stripping dispersing process is difficult to carry out, and the dispersibility of the carbon nano tube is further reduced.
Preferably, in the step B, the supercritical fluid dispersing treatment is performed by using a ball milling dispersing device, and the specific operations are as follows: adding the pre-dispersed material in the step A into a ball milling dispersing device, adding an additive, uniformly mixing, sealing the ball milling dispersing device, pressing supercritical fluid into the ball milling dispersing device, and sealing and stirring for 2-24 hours under the conditions of the temperature of 35-65 ℃, the pressure of 8-15MPa and the rotating speed of 200-500rpm to obtain the supercritical suspension.
For the mixed dispersion of the carbon nano tube and the dispersing agent, a ball milling dispersion treatment mode can be adopted, the carbon nano tube and the dispersing agent are mixed and then added into a ball milling dispersion device, then an additive is added, after the additive is added and mixed uniformly, the ball milling dispersion device is sealed, then supercritical fluid is introduced, ball milling dispersion is carried out under specific temperature, pressure and rotating speed conditions, and the dispersibility of the carbon nano tube is improved by utilizing the temperature and pressure of ball milling, the dispersing agent, the additive and the supercritical environment. The ball milling dispersing device comprises a ball milling dispersing device, a ball milling dispersing device and a ball milling dispersing device, wherein the diameter of the grinding ball is 1-7.5mm, the mass ratio of a mixture to the grinding ball is controlled to be 1:50-200, and the diameter of the grinding ball and the mixing weight ratio of the grinding ball to a pre-dispersing material are controlled, so that the grinding ball can fully disperse carbon nano tubes in the ball milling process, and the dispersibility treatment of the carbon nano tubes is ensured.
For supercritical fluid dispersion treatment, another preferred treatment scheme of the present application is: in the step B, the supercritical fluid dispersion treatment is carried out by adopting an ultrasonic dispersion device, and the specific operation is as follows: adding the pre-dispersed material in the step A into an ultrasonic dispersing device, adding an additive, uniformly mixing, sealing the ultrasonic dispersing device, pressing supercritical fluid into the ultrasonic dispersing device, and sealing the ultrasonic dispersing device for 2-6 hours under the conditions of the temperature of 35-65 ℃, the pressure of 8-10MPa and the ultrasonic power of 250-750W to prepare the supercritical suspension.
For the mixed dispersion of the carbon nano tube and the dispersing agent, the application can also adopt an ultrasonic dispersion treatment mode, the carbon nano tube and the dispersing agent are mixed and then added into an ultrasonic dispersion device, then the additive is added, after the additive is added and mixed uniformly, the ultrasonic dispersion device is sealed, the supercritical fluid is introduced, the ultrasonic dispersion can be carried out under the specific conditions of temperature, pressure and ultrasonic power, and the dispersibility of the carbon nano tube is improved by utilizing the ultrasonic conditions, the dispersing agent, the additive and the supercritical environment.
Preferably, in the step B, the supercritical fluid is one or a mixture of several of carbon dioxide, ethanol, acetone and water.
The supercritical fluid has better fluidity, can be introduced into the mixture to fully disperse the mixture, can adjust and regulate the solubility of the mixture in the supercritical fluid by controlling the operating pressure and the temperature of the supercritical fluid, and can rapidly reduce the pressure of the carbon nano tube dissolved in the supercritical fluid through a nozzle of a ball milling dispersing device or an ultrasonic dispersing device, so that the carbon nano tube can be crystallized and separated out in a fine powder mode, and further, the supercritical fluid dispersion is realized on the carbon nano tube, thereby facilitating the generation of carbon nano tube powder. Among them, carbon dioxide is preferably used as the supercritical fluid.
Preferably, in the step C, the supercritical fluid stripping treatment is performed by using a supercritical fluid stripping apparatus.
The supercritical fluid stripping device is adopted to carry out supercritical stripping and dispersion on the carbon nano tube particles subjected to supercritical fluid dispersion treatment, and the carbon nano tube particles are easy to enter the carbon nano tube powder by utilizing the high dispersibility and high permeability of the supercritical fluid to form an intercalation structure; when the pressure is released rapidly, the supercritical fluid expands to release a large amount of energy to overcome the acting force in the carbon nanotube powder, so as to prepare the carbon nanotube powder with smaller particle size.
Preferably, in the step C, the supercritical fluid stripping treatment further includes a classification treatment, and the classification treatment is performed by using a classification device.
The carbon nano tube powder after stripping and dispersing treatment is graded for a plurality of times by adopting a grading device, small-particle-diameter carbon nano tube powder is screened out after the grading for a plurality of times, and the carbon nano tube powder which does not reach the specific small particle diameter is screened out in the grading treatment, and then the carbon nano tube powder is circulated to a supercritical fluid stripping device to repeatedly carry out supercritical fluid stripping treatment until the carbon nano tube powder meeting the particle diameter requirement is achieved.
The application firstly uses supercritical fluid to uniformly disperse carbon nano tube, dispersant and additive under specific temperature and pressure, and uses the nozzle of ball milling dispersing device or ultrasonic dispersing device to quickly reduce pressure, so as to promote the generation of carbon nano tube powder; and then, the supercritical fluid is embedded into the carbon nano tube powder by using a supercritical fluid stripping device, and rapidly depressurizes again, and the supercritical fluid releases energy from the inside of the carbon nano tube powder to strip the carbon nano tube powder into carbon nano tube powder with smaller particle size. And finally, screening carbon nano tube powder products meeting the requirements through grading treatment, and circularly preparing carbon nano tube powder from carbon nano tube powder with particle size not meeting the requirements until the carbon nano tube powder meets the requirements. The carbon nano tube powder can be repeatedly dispersed by a circulating treatment means, so that the dispersibility of the carbon nano tube is improved, the carbon nano tube powder can be directly applied to a battery anode material, the resource utilization rate is high, and the carbon nano tube powder which does not reach the dispersibility requirement is not discarded.
When the ball milling dispersing device is used for dispersing, the ball milling dispersing device, the supercritical fluid stripping device and the grading device can be used for carrying out phased treatment or phased circulation treatment, and the circulation flow of the phased circulation treatment is that the supercritical fluid stripping device for preparing the supercritical fluid in a circulating way for screening the carbon nano tube powder which does not meet the requirements in the grading treatment repeatedly carries out the supercritical fluid stripping treatment.
When the ultrasonic dispersing device is used for dispersing treatment, the ultrasonic dispersing device, the supercritical fluid stripping device and the grading device can be used for carrying out staged treatment, or staged circulating treatment, or three stages of simultaneous treatment combined with a circulating flow; the circulation flow of the staged circulation treatment and the circulation flow of the simultaneous treatment of the three stages combined with the circulation flow are the supercritical fluid stripping treatment repeated by the supercritical fluid stripping device for screening the carbon nano tube powder which does not meet the requirements in the classification treatment. By adopting the means of simultaneous treatment in three stages, the dispersion efficiency and the production efficiency of the carbon nano tube powder can be improved.
In a second aspect, the present application provides an apparatus for preparing dispersible carbon nanotube powder, which adopts the following technical scheme:
The equipment for preparing the dispersible carbon nano tube powder sequentially comprises a dispersing device, a supercritical fluid stripping device and a product collecting container according to the use sequence, wherein the dispersing device is connected with a first supercritical fluid reaction device; the supercritical fluid stripping device comprises a high-pressure resistant intermediate tank and a decompression tank which are sequentially connected, a nozzle is arranged at the discharge end of the dispersing device, the nozzle is communicated with the feed end of the high-pressure resistant intermediate tank through a connecting pipeline, and the discharge end of the decompression tank is communicated with a product collecting container; the high-pressure-resistant intermediate tank is connected with a medium conveying device; the dispersing device is a ball milling dispersing device or an ultrasonic dispersing device.
By adopting the technical scheme, the supercritical fluid dispersing treatment and the supercritical fluid stripping treatment can be sequentially carried out on the carbon nanotubes, and the carbon nanotubes can be dispersed into powder with small particle size. The preparation method comprises the steps of uniformly mixing carbon nanotubes, a dispersing agent and an additive in a dispersing device (ball milling dispersing device or ultrasonic dispersing device), introducing supercritical fluid into the dispersing device, controlling the temperature of the dispersing device to be 35-65 ℃ and the pressure to be 8-15MPa, enabling the carbon nanotubes to be dissolved and dispersed in the supercritical fluid, reducing the pressure of the dispersing device, pressing to be 0.1-1MPa, opening a valve of a nozzle, enabling the supercritical suspension to flow to a connecting pipeline through the nozzle under the effect of rapid pressure reduction, further spraying the supercritical suspension into a high-pressure resistant intermediate tank, enabling the carbon nanotubes to be crystallized and separated out in a fine powder mode through the rapid pressure reduction spraying, further realizing supercritical fluid dispersion on the carbon nanotubes, and enabling the carbon nanotube powder to be generated. In the process that the carbon nano tube is sprayed into the high-pressure resistant intermediate tank through the nozzle and the connecting pipeline, the temperature of the nozzle, the connecting pipeline and the high-pressure resistant intermediate tank is kept at 40 ℃ (the temperature of the carbon dioxide is kept at 40 ℃ for the fluid medium, and the temperature of the carbon dioxide is kept at the temperature of the boiling point of the fluid medium or above for other fluid mediums), so that the carbon nano tube powder is prevented from being separated out on the nozzle and the connecting pipeline. Preferably, the diameter of the nozzle is 0.8mm, so that the flow speed of the supercritical suspension sprayed out of the connecting pipeline under the pressure release effect can be ensured, and the rapid pressure release and the precipitation of powder crystals of the carbon nano tube under the spraying condition can be ensured.
The medium conveying device inputs supercritical fluid medium into the high-pressure resistant intermediate tank, the temperature of the fluid is controlled to be 35-65 ℃, the pressure of the high-pressure resistant intermediate tank is controlled to be 8-15MPa, and the supercritical fluid is easy to enter the carbon nano tube powder by utilizing the high dispersibility and the high permeability of the supercritical fluid to form an embedded structure; and then opening a pressure release valve of the high-pressure resistant intermediate tank, and rapidly introducing the carbon nanotube powder in the high-pressure resistant intermediate tank into the pressure release tank, wherein when the pressure is rapidly released, the supercritical fluid expands, a large amount of energy is released to overcome the acting force in the carbon nanotube powder, and the carbon nanotube powder is stripped from the carbon nanotube powder to prepare the carbon nanotube powder with smaller particle size. Before a pressure release valve of the high-pressure resistant intermediate tank is opened, the pressure in the pressure release tank is regulated to be 0.01-0.1MPa, so that the pressure difference before and after pressure release is large, the carbon nano tube powder is promoted to be stripped from the inside, and after the pressure release is finished, the pressure of the pressure release tank is regulated to be normal pressure.
The supercritical fluid introduced into the dispersing device and the supercritical fluid stripping device can be the same fluid, and carbon dioxide is preferably adopted.
Preferably, the device further comprises a classifying device, wherein the classifying device comprises a plurality of cyclone separators which are communicated in sequence, the feeding end of each cyclone separator is communicated with the discharging end of the decompression tank, and the discharging end of the last cyclone separator is communicated with the product collecting container.
By adopting the technical scheme, the cyclone separator is utilized to separate the carbon nanotube powder from the supercritical fluid, the carbon nanotube powder obtained by separation is collected into the product collection container, and the supercritical fluid obtained by separation can be recycled. Meanwhile, the plurality of cyclone separators carry out multiple classification treatment on the carbon nanotube powder, so that the carbon nanotube powder with different particle sizes can be obtained, and the carbon nanotube powder with different particle sizes can be applied to different fields; or, the carbon nano tube powder which is screened out after the grading treatment and does not reach the particle size requirement is circulated to a dispersing device and a high-pressure resistant intermediate tank for repeated dispersing operation. Preferably, the number of the cyclone separators is 3-5, forming 3-5 grade grading treatment, preferably circulating the substandard carbon nanotube powder separated by the first cyclone separator to a dispersing device for supercritical fluid dispersing treatment, circulating the substandard carbon nanotube powder separated by the second cyclone separator to a high-pressure resistant intermediate tank for supercritical fluid stripping dispersing treatment, and collecting the carbon nanotube powder collected by the last cyclone separator in a product collecting container.
In summary, the application has the following beneficial effects:
1. according to the application, by utilizing the characteristic that the solvent property of the supercritical fluid can be regulated through pressure, the carbon nano tube and the dispersing agent are uniformly mixed, the material is subjected to primary dispersion by combining a ball milling or ultrasonic dispersion method, the carbon nano tube is subjected to secondary dispersion by combining a supercritical fluid stripping dispersion mode, and is stripped from the inside of the carbon nano tube to the outside to prepare the carbon nano tube powder with dispersion property, the process step of preparing the carbon nano tube powder into slurry by utilizing the solvent is omitted, the cost is low, the efficiency is high, the environment is friendly, the prepared dispersive carbon nano tube has good conductivity, and can be directly applied to ternary oily positive electrode materials of lithium batteries and lithium iron phosphate aqueous positive electrode materials without preparing conductive slurry and combining the conductive slurry with the positive electrode materials, and the application range is wide.
2. The application carries out grading treatment on the carbon nano tube powder subjected to supercritical fluid stripping treatment, can apply the graded carbon nano tube powder with different particle sizes to different fields, and can also circulate the carbon nano tube powder which does not reach the required particle size after grading to a dispersing device and a supercritical fluid stripping device for repeated dispersion treatment so as to ensure that the particle size of the carbon nano tube powder product is always stable and the quality is stable.
3. The equipment for preparing the dispersible carbon nano tube powder can sequentially perform supercritical fluid dispersion treatment and supercritical fluid stripping treatment on the carbon nano tube, and disperse the carbon nano tube into powder with small particle size, so that the carbon nano tube powder has dispersibility.
4. The grading device added in the application can grade the carbon nano tube powder subjected to supercritical fluid stripping treatment for multiple times, and the carbon nano tube powder with different particle sizes obtained after grading can be used in different fields, and the carbon nano tube powder which does not reach the particle size requirement can also be circulated to the dispersing device and the supercritical fluid stripping device through the powder circulating device for repeated dispersion treatment.
5. The fluid storage device can store the supercritical fluid separated by the cyclone separator, can be circularly used in the supercritical fluid stripping device, improves the resource utilization rate of the fluid, and reduces the energy consumption of the supercritical fluid reactor.
Drawings
FIG. 1 is a schematic view of an apparatus for preparing dispersible carbon nanotube powder according to example 1;
FIG. 2 is a schematic view of an apparatus for preparing dispersible carbon nanotube powder according to example 2;
FIG. 3 is a SEM image of a simple double walled carbon nanotube;
FIG. 4 is an SEM image of the dispersible carbon nanotube powder prepared in example 2;
FIG. 5 is an SEM image of the dispersible carbon nanotube powder of example 2 used in a lithium iron phosphate M121 system;
FIG. 6 is an SEM image of the dispersible carbon nanotube powder prepared in example 4;
FIG. 7 is an SEM image of the dispersible carbon nanotube powder of example 4 used in a lithium iron phosphate M121 system;
FIG. 8 is an SEM image of the dispersible carbon nanotube powder of example 6 used in a lithium iron phosphate M121 system;
fig. 9 is an SEM image of the dispersible carbon nanotube powder prepared in example 8 for use in a single crystal ternary system.
Description of the drawings: 1-first supercritical fluid reactor, 11-first flow valve, 2-dispersing device, 21-nozzle, 31-high pressure resistant intermediate tank, 32-decompression tank, 4-product collection container, 51-second supercritical fluid reactor, 52-compression pump, 53-heat exchanger, 54-second flow valve, 55-fluid storage container, 56-condenser, 6-classifying device, 61-cyclone, 7-powder circulation device, 71-first powder conveying pump, 72-second powder conveying pump.
Detailed Description
The application is described in further detail below with reference to figures 1-9 and examples.
The carbon nanotubes are arranged in parallel, so that the acting force between the carbon nanotubes is strong, and the formed carbon nanotube bundles or aggregates are difficult to disperse. At present, the conductive paste is prepared by mixing a solvent and a dispersing agent and stirring the mixture, but the addition of the solvent makes the preparation cost high and the solvent affects personnel, equipment and environment.
Based on the findings, the applicant researches on the dispersibility of the carbon nanotubes, and based on the absence of solvent, the dispersing agent is adopted to disperse the carbon nanotubes under the condition of supercritical fluid, and then the supercritical fluid is adopted to strip the dispersed carbon nanotubes, so that the carbon nanotubes are stripped and dispersed by reacting the reaction force from the inside of the carbon nanotubes, and the problem of realizing the dispersibility of the carbon nanotubes under the condition of no solvent is solved.
Examples
Example 1
Referring to fig. 1, this embodiment discloses an apparatus for preparing dispersible carbon nanotube powder, comprising a dispersing device 2, a supercritical fluid stripping device and a product collecting container 4 in order of use, wherein carbon nanotubes, a dispersing agent and additives are added into the dispersing device 2, and the pressure of the dispersing device 2 in the dispersing process is controlled to be 8-15MPa, so that the mixture is uniformly dispersed; the dispersing device 2 is connected with a first supercritical fluid reaction device, the first supercritical fluid reaction device generates supercritical fluid and is introduced into the dispersing device 2, the supercritical fluid is utilized to fully and uniformly disperse the carbon nano tube, the dispersing agent and the additive, and the temperature of the dispersing device 2 is controlled to be higher than the boiling point of the fluid, so that the fluid is always in a supercritical state, and a supercritical suspension is obtained; and a first flow valve 11 is preferably provided between the first supercritical fluid reaction apparatus and the dispersing apparatus 2 to control the flow rate and the flow velocity of the supercritical fluid. The first supercritical fluid reaction apparatus is preferably the first supercritical fluid reactor 1.
Wherein, the dispersing device 2 can be a ball milling dispersing device or an ultrasonic dispersing device, when the ball milling dispersing device is adopted, the carbon nano tube is milled and dispersed by a milling ball, the mass ratio of the mixture to the milling ball is 1:50-200, the pressure during the ball milling is 8-15MPa, the ball milling rotating speed is 200-500rpm, and the ball milling dispersing device preferably adopts a high-pressure ball milling tank; when an ultrasonic dispersing device is adopted, the carbon nano tubes are dispersed by ultrasonic waves, the pressure during ultrasonic dispersion is 8-10MPa, and the ultrasonic dispersing device is preferably an ultrasonic tank. In the embodiment, a ball milling dispersing device is adopted, the pressure in a high-pressure ball milling tank is controlled to be 15MPa in the preparation step, and the ball milling rotating speed is 500rpm.
The supercritical fluid stripping device comprises a high-pressure-resistant intermediate tank 31 and a decompression tank 32 which are sequentially connected, a discharge end of the dispersing device 2 is provided with a nozzle 21, the diameter of the nozzle 21 is preferably 0.8mm, and the nozzle 21 is communicated with a feed end of the high-pressure-resistant intermediate tank 31 through a connecting pipeline; in the dispersing device 2, after the supercritical fluid disperses the carbon nanotubes, the dispersing agent and the additive uniformly, a supercritical suspension is prepared, and then the nozzle 21 is opened, so that the supercritical suspension is sprayed into the high-pressure resistant intermediate tank 31 through the nozzle 21 when the internal pressure is released, and the subsequent supercritical fluid stripping treatment is performed. The temperature of the nozzle 21, the connecting pipe and the high pressure resistant intermediate tank 31 is controlled to be kept above the boiling point of the fluid, for example, when the fluid medium is carbon dioxide, the temperature of the nozzle 21, the connecting pipe and the high pressure resistant intermediate tank 31 is controlled to be maintained at 40 ℃, so that carbon nanotube powder is prevented from being precipitated on the nozzle 21 and the connecting pipe, and the jet circulation is prevented from being blocked.
The high pressure resistant intermediate tank 31 is connected with a medium conveying device, a pressure release valve (not labeled in fig. 1) is arranged at the discharge end of the high pressure resistant intermediate tank 31, the medium conveying device inputs supercritical fluid medium into the high pressure resistant intermediate tank 31, the temperature of the fluid is controlled to be 35-65 ℃ (40 ℃ in the preparation step of the embodiment), meanwhile, the pressure of the high pressure resistant intermediate tank 31 is controlled to be 8-15MPa (10 MPa in the preparation step of the embodiment), so that the supercritical fluid enters into the carbon nano tube powder under certain pressure by utilizing the dispersibility and the permeability of the supercritical fluid, the pressure release valve is opened, the carbon nano tube flows from the high pressure resistant intermediate tank 31 to the pressure release tank 32, the supercritical fluid expands in the process of rapid pressure release, the carbon nano tube is further stripped from the inside to the outside, and further the carbon nano tube is refined by the high pressure resistant intermediate tank 31 and the pressure release tank 32.
Further, a temperature detecting device and a pressure detecting device are disposed in the high pressure resistant intermediate tank 31, the temperature detecting device is used for detecting the temperature inside the high pressure resistant intermediate tank 31, and the pressure detecting device is used for detecting the pressure inside the high pressure resistant intermediate tank 31 so as to monitor the temperature and the pressure of the high pressure resistant intermediate tank 31 in real time. (whereas the temperature and pressure sensing means described above are not indicated in fig. 1).
Further, the medium delivery device comprises a second supercritical fluid reactor 51, a compression pump 52, a heat exchanger 53 and a second flow valve 54 which are sequentially connected, wherein the second supercritical fluid reactor 51 is used for generating supercritical fluid, then the supercritical fluid delivered from the second supercritical fluid reactor 51 is compressed and pressurized through the compression pump 52, the heat exchanger 53 heats the supercritical fluid, the compressed and heated supercritical fluid enters the high-pressure resistant intermediate tank 31, and the second flow valve 54 controls the flow rate of the fluid. The heated and pressurized supercritical fluid is embedded into the carbon nanotube powder by utilizing the high fluidity and high permeability of the supercritical fluid in the high-pressure-resistant intermediate tank 31, and the carbon nanotube powder is stripped from the inside by subsequent rapid depressurization, so that the dispersible carbon nanotube with smaller particle size is obtained. The pressure reducing tank 32 is used for pressure relief of the high pressure resistant intermediate tank 31.
The discharge end of the decompression tank 32 is communicated with the product collecting container 4, the carbon nanotube powder enters the decompression tank 32 under the expansion of the supercritical fluid and the high pressure of the high pressure resistant intermediate tank 31 in the decompression process of the high pressure resistant intermediate tank 31, the supercritical fluid stripping treatment is completed, and the stripped carbon nanotubes (average particle diameter D50 is smaller than 10 μm) enter the product collecting container 4 for product collection.
The preparation method of the dispersible carbon nano tube powder is realized by the preparation equipment, and comprises the following steps of:
step A: weighing 10.00g of double-wall carbon nano tube and 15.02g of carboxymethyl cellulose in a beaker, fully and uniformly mixing, and then adding the mixture into a high-pressure ball milling tank;
and (B) step (B): weighing 1000g of zirconium beads (with the diameter of 1-1.2 mm) as grinding balls, pouring the grinding balls into a high-pressure ball milling tank, adding 0.75g of 2-amino-2-methyl-1-propanol, uniformly mixing, and sealing the high-pressure ball milling tank; then the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into a high-pressure ball milling tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 15MPa, the temperature in the tank is 35 ℃, the ball milling rotating speed is 500r/min, and the supercritical suspension is obtained by stirring for 12 hours;
step C: stopping stirring, reducing the pressure in the high-pressure ball milling tank to 1MPa, opening a valve of a nozzle 21, and rapidly spraying the supercritical suspension into the high-pressure resistant intermediate tank 31, wherein the heat preservation temperature is 40 ℃;
step D: the second supercritical fluid reactor 51 generates supercritical carbon dioxide, and is pressed into the high-pressure-resistant intermediate tank 31 sequentially through the compression pump 52, the heat exchanger 53 and the second flow valve 54, the pressure of the high-pressure-resistant intermediate tank 31 is controlled to be 10MPa, the temperature is controlled to be 40 ℃, and the heat preservation and stirring are carried out for 4 hours; then controlling the pressure of the decompression tank 32 to be 0.1MPa, opening a decompression valve, expanding the supercritical fluid in the process of rapid decompression, stripping the supercritical fluid from the inside of the carbon nano tube powder, rapidly feeding the material into the decompression tank 32 in the process of decompression, and adjusting the pressure of the decompression tank 32 to be normal pressure after decompression is completed; the carbon nanotube powder in the depressurization tank 32 is collected in the product collection container 4 to obtain dispersible carbon nanotube powder.
Example 2
This embodiment differs from embodiment 1 described above in that: adding a dispersing device and a dispersing step;
referring to fig. 2, the apparatus further comprises a classifying device 6, wherein the classifying device 6 comprises a plurality of cyclone separators 61 which are sequentially communicated, the cyclone separators 61 are utilized to separate carbon nanotube powder from supercritical fluid, the separated carbon nanotube powder is collected into a product collecting container 4, and the supercritical fluid obtained by separation can be recycled; meanwhile, the plurality of cyclone separators 61 are used for classifying the carbon nanotube powder for a plurality of times, the feeding end of the first cyclone separator 61 is communicated with the discharging end of the decompression tank 32, the discharging end of the last cyclone separator 61 is communicated with the product collecting container 4, each cyclone separator 61 is used for separating carbon nanotube powder with different particle sizes, and the carbon nanotube powder with different particle sizes can be used in different fields, or each cyclone separator 61 is used for separating the carbon nanotube powder which does not reach the standard, the carbon nanotube powder is circulated to the dispersing device 2 or the high-pressure resistant intermediate tank 31 for repeatedly carrying out supercritical fluid dispersing or stripping treatment so as to ensure that the particle sizes of the collected products are uniform. The number of cyclone separators 61 is preferably 3-5, in this embodiment, 3 cyclone separators 61 are used, and the first cyclone separator 61 is more than the second cyclone separator 61 for separating the substandard carbon nanotube powder, the substandard carbon nanotube powder separated by the first cyclone separator 61 is circulated to the dispersing device 2 for repeated supercritical fluid dispersing treatment, the substandard carbon nanotube powder separated by the second cyclone separator 61 is circulated to the high-pressure resistant intermediate tank 31 for supercritical fluid stripping dispersing treatment, and the last cyclone separator 61 separates the supercritical fluid and the collected substandard carbon nanotube powder, and the product (average particle diameter D50 is smaller than 10 μm) enters the product collecting container 4 for collecting.
Further, the device also comprises a powder circulation device 7, wherein the powder circulation device 7 comprises a first powder conveying pump 71 and a second powder conveying pump 71, the first powder conveying pump 71 is arranged between the first cyclone separator 61 and the dispersing device 2 and is used for circulating the carbon nano tube powder collected by the first cyclone separator 61 into the dispersing device 2, so as to realize the circulation of the powder and the repeated supercritical fluid dispersing treatment, and prepare the carbon nano tube powder reaching the particle size requirement; and the second powder delivery pump 71 is disposed between the second cyclone separator 61 and the high pressure resistant intermediate tank 31, and is used for circulating the carbon nanotube powder collected by the second cyclone separator 61 to the high pressure resistant intermediate tank 31, so as to realize the circulation of the powder and repeated supercritical fluid stripping and dispersing treatment, and prepare the carbon nanotube powder (average particle diameter D50 is smaller than 10 μm) reaching the particle diameter requirement.
Based on the scheme, the device can be further improved: the medium transfer device may further include a fluid storage container 55, wherein the fluid storage container 55 is disposed between the second supercritical fluid reactor 51 and the compression pump 52, and the supercritical fluid generated in the second supercritical fluid reactor 51 is stored in the fluid storage container 55. The supercritical fluid separated by the cyclone 61 can be recycled to the fluid storage vessel 55, and then enters the high-pressure resistant intermediate tank 31 again through the compression pump 52, the heat exchanger 53 and the second flow valve 54 to be subjected to supercritical fluid stripping treatment. The supercritical fluid obtained by separation of the cyclone separator 61 not only comprises the supercritical fluid generated by the first supercritical fluid reactor 1, but also comprises the supercritical fluid generated by the second supercritical fluid reactor 51, so that the supercritical fluid in the whole equipment forms closed reflux, is circularly used in the high-pressure resistant intermediate tank 31, improves the resource utilization rate of the fluid, and reduces the energy consumption of the supercritical fluid reactor. When the apparatus is operated at first, the first supercritical fluid reactor 1 and the second supercritical fluid reactor 51 both generate supercritical fluid, and after at least three treatment steps are performed (supercritical fluid dispersion treatment, supercritical fluid stripping treatment, classification treatment), the supercritical fluid separated by the last cyclone 61 is circulated and returned to the fluid storage container 55, and then the second supercritical fluid reactor 51 can reduce the generation or non-generation of supercritical fluid, and the next carbon nanotube dispersion treatment is continued by using the circulated supercritical fluid.
Further, a condenser 56 may be further disposed between the supercritical fluid output end of the last cyclone 61 and the input end of the fluid storage container 55, and the cooled fluid is stored in the fluid storage container 55 for being recycled to the supercritical fluid stripping device for use, pumped by the compression pump 52, heated by the heat exchanger 53, and then enters the high pressure resistant intermediate tank 31 through the second flow valve 54.
Further, a heating jacket (not shown in fig. 2) may be disposed on the outer layer of each cyclone 61, so that the temperature of the cyclone 61 can be maintained above the boiling point of the fluid medium, so that the fluid is in a supercritical state, and the fluid is ensured to be in a supercritical state when circulated and returned to the fluid storage container 55 for recycling, so that the next carbon nanotube dispersing process is facilitated. Preferably, the fluid storage vessel 55 and the tubing used to communicate the various device components are maintained at a controlled temperature above the boiling point of the fluid medium to ensure that the fluid medium is in a supercritical state.
The preparation method of the dispersible carbon nanotube powder is implemented by the preparation apparatus of the present embodiment, specifically, in the step D, the carbon nanotube powder in the decompression tank 32 is classified by the classification device 6, and then collected in the product collection container 4, so as to obtain the dispersible carbon nanotube powder, and the other steps and condition parameters are the same as those of the embodiment 1.
Example 3
This embodiment differs from embodiment 2 described above in that: material dispersed by supercritical fluid ball milling and process condition change;
and (B) step (B): weighing 1500g of zirconium beads (with the diameter of 1-1.2 mm) as grinding balls, pouring the grinding balls into a high-pressure ball milling tank, adding 0.75g of hydroxyethyl ethylenediamine, uniformly mixing, and sealing the high-pressure ball milling tank; then the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into a high-pressure ball milling tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 15MPa, the temperature in the tank is 35 ℃, the ball milling rotating speed is 400r/min, and the supercritical suspension is obtained after stirring for 15 hours.
Example 4
This embodiment differs from embodiment 2 described above in that: the dispersing device adopts an ultrasonic dispersing device, in particular to dispersing by adopting an ultrasonic tank;
the present embodiment relates to a method for preparing dispersible carbon nanotube powder, comprising the steps of:
step A: weighing 10.25g of double-wall carbon nano tube and 3.1g of polyvinylpyrrolidone in a beaker, fully and uniformly mixing, adding into an ultrasonic tank, adding 3g of diethylenetriamine, uniformly mixing, and sealing the ultrasonic tank;
and (B) step (B): the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into an ultrasonic tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 10MPa, the temperature in the tank is 40 ℃, the ultrasonic power is 750W, and the ultrasonic power is carried out for 2 hours, so that supercritical suspension is obtained;
Step C: stopping ultrasonic treatment, reducing the pressure in the ultrasonic tank to 0.5MPa, opening a valve of a nozzle 21, and rapidly spraying the supercritical suspension into the high-pressure-resistant intermediate tank 31, wherein the heat preservation temperature is 40 ℃;
step D: the second supercritical fluid reactor 51 generates supercritical carbon dioxide, and is pressed into the high-pressure-resistant intermediate tank 31 sequentially through the compression pump 52, the heat exchanger 53 and the second flow valve 54, the pressure of the high-pressure-resistant intermediate tank 31 is controlled to be 10MPa, the temperature is controlled to be 40 ℃, and the heat preservation and stirring are carried out for 4 hours; then controlling the pressure of the decompression tank 32 to be 0.1MPa, opening a decompression valve, expanding the supercritical fluid in the process of rapid decompression, stripping the supercritical fluid from the inside of the carbon nano tube powder, rapidly feeding the material into the decompression tank 32 in the process of decompression, and adjusting the pressure of the decompression tank 32 to be normal pressure after decompression is completed; the carbon nanotube powder in the decompression tank 32 is classified by the classification device 6, and then collected in the product collection container 4 to obtain dispersible carbon nanotube powder.
Example 5
This embodiment differs from embodiment 4 described above in that: material dispersed by supercritical fluid ultrasonic and process condition change;
step A: weighing 10.25g of double-wall carbon nano tube and 3.1g of polyvinylpyrrolidone in a beaker, fully and uniformly mixing, adding into an ultrasonic tank, adding 3g of 2-amino-2-methyl-1-propanol, uniformly mixing, and sealing the ultrasonic tank;
And (B) step (B): the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into an ultrasonic tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 8MPa, the temperature in the tank is 50 ℃, the ultrasonic power is 500W, and the ultrasonic power is ultrasonic for 4 hours, so that supercritical suspension is obtained.
Example 6
This embodiment differs from embodiment 2 described above in that: dispersing the single-wall carbon nano tube;
a method for preparing dispersible carbon nanotube powder, comprising the following steps:
step A: weighing 10.78g of single-walled carbon nanotubes and 10.78g of carboxymethyl cellulose in a beaker, fully and uniformly mixing, and then adding the mixture into a high-pressure ball milling tank;
and (B) step (B): weighing 1500g of zirconium beads (with the diameter of 5-7.5 mm) as grinding balls, pouring the grinding balls into a high-pressure ball milling tank, adding 4.5g of diethylenetriamine, uniformly mixing, and sealing the high-pressure ball milling tank; then the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into a high-pressure ball milling tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 8MPa, the temperature in the tank is 35 ℃, the ball milling rotating speed is 500r/min, and the supercritical suspension is obtained by stirring for 10 hours;
Step C: stopping stirring, reducing the pressure in the high-pressure ball milling tank to 1MPa, opening a valve of a nozzle 21, and rapidly spraying the supercritical suspension into the high-pressure resistant intermediate tank 31, wherein the heat preservation temperature is 40 ℃;
step D: the second supercritical fluid reactor 51 generates supercritical carbon dioxide, and is pressed into the high-pressure-resistant intermediate tank 31 sequentially through the compression pump 52, the heat exchanger 53 and the second flow valve 54, the pressure of the high-pressure-resistant intermediate tank 31 is controlled to be 10MPa, the temperature is controlled to be 40 ℃, and the heat preservation and stirring are carried out for 4 hours; then controlling the pressure of the decompression tank 32 to be 0.1MPa, opening a decompression valve, expanding the supercritical fluid in the process of rapid decompression, stripping the supercritical fluid from the inside of the carbon nano tube powder, rapidly feeding the material into the decompression tank 32 in the process of decompression, and adjusting the pressure of the decompression tank 32 to be normal pressure after decompression is completed; the carbon nanotube powder in the decompression tank 32 is classified by the classification device 6, and then collected in the product collection container 4 to obtain dispersible carbon nanotube powder.
Example 7
This embodiment differs from embodiment 6 described above in that: the dispersing device adopts an ultrasonic dispersing device, in particular to dispersing by adopting an ultrasonic tank;
the present embodiment relates to a method for preparing dispersible carbon nanotube powder, comprising the steps of:
Step A: weighing 10.78g of single-wall carbon nanotubes and 10.78g of carboxymethyl cellulose in a beaker, fully and uniformly mixing, adding into an ultrasonic tank, adding 4.5g of diethylenetriamine, uniformly mixing, and sealing the ultrasonic tank;
and (B) step (B): the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into an ultrasonic tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 8MPa, the temperature in the tank is 50 ℃, the ultrasonic power is 700W, and the ultrasonic power is carried out for 3 hours, so that supercritical suspension is obtained;
step C: stopping ultrasonic treatment, reducing the pressure in the ultrasonic tank to 0.5MPa, opening a valve of a nozzle 21, and rapidly spraying the supercritical suspension into the high-pressure-resistant intermediate tank 31, wherein the heat preservation temperature is 40 ℃;
step D is the same as in example 6.
Example 8
This embodiment differs from embodiment 2 described above in that: dispersing the multiwall carbon nanotubes;
a method for preparing dispersible carbon nanotube powder, comprising the following steps:
step A: weighing 16.02g of multiwall carbon nanotubes and 4.00g of polyvinylpyrrolidone in a beaker, fully and uniformly mixing, and then adding the mixture into a high-pressure ball milling tank;
and (B) step (B): weighing 500g of zirconium beads (with the diameter of 0.6-0.8 mm) as grinding balls, pouring the grinding balls into a high-pressure ball milling tank, adding 0.8g of diethanol monoisopropanolamine, uniformly mixing, and sealing the high-pressure ball milling tank; then the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into a high-pressure ball milling tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 8MPa, the temperature in the tank is 35 ℃, the ball milling rotating speed is 200r/min, and the supercritical suspension is obtained by stirring for 6 hours;
Step C: stopping stirring, reducing the pressure in the high-pressure ball milling tank to 0.2MPa, opening a valve of a nozzle 21, and rapidly spraying the supercritical suspension into the high-pressure resistant intermediate tank 31, wherein the heat preservation temperature is 40 ℃;
step D: the second supercritical fluid reactor 51 generates supercritical carbon dioxide, and is pressed into the high-pressure-resistant intermediate tank 31 sequentially through the compression pump 52, the heat exchanger 53 and the second flow valve 54, the pressure of the high-pressure-resistant intermediate tank 31 is controlled to be 10MPa, the temperature is controlled to be 40 ℃, and the heat preservation and stirring are carried out for 4 hours; then controlling the pressure of the decompression tank 32 to be 0.1MPa, opening a decompression valve, expanding the supercritical fluid in the process of rapid decompression, stripping the supercritical fluid from the inside of the carbon nano tube powder, rapidly feeding the material into the decompression tank 32 in the process of decompression, and adjusting the pressure of the decompression tank 32 to be normal pressure after decompression is completed; the carbon nanotube powder in the decompression tank 32 is classified by the classification device 6, and then collected in the product collection container 4 to obtain dispersible carbon nanotube powder.
Example 9
This embodiment differs from embodiment 8 described above in that: the dispersing device adopts an ultrasonic dispersing device, in particular to dispersing by adopting an ultrasonic tank;
the present embodiment relates to a method for preparing dispersible carbon nanotube powder, comprising the steps of:
Step A: weighing 16.02g of multiwall carbon nanotubes and 4.21g of polyvinylpyrrolidone in a beaker, fully and uniformly mixing, adding the mixture into an ultrasonic tank, adding 0.8g of diethanol monoisopropanolamine, uniformly mixing, and sealing the ultrasonic tank;
and (B) step (B): the first supercritical fluid reactor 1 generates supercritical carbon dioxide, the supercritical carbon dioxide is pressed into an ultrasonic tank through a first flow valve 11, the pressure in the high-pressure ball milling tank is controlled to be 8MPa, the temperature in the tank is 40 ℃, the ultrasonic power is 500W, and the ultrasonic power is ultrasonic for 4 hours, so that supercritical suspension is obtained;
step C: stopping ultrasonic treatment, reducing the pressure in the ultrasonic tank to 0.5MPa, opening a valve of a nozzle 21, and rapidly spraying the supercritical suspension into the high-pressure-resistant intermediate tank 31, wherein the heat preservation temperature is 40 ℃;
step D is the same as in example 8.
Comparative example
Comparative example 1
1.6g of double-walled carbon nanotubes, 3.2g of carboxymethyl cellulose, 0.12g of 2-amino-2-methyl-1-propanol and 528.41g of pure water are weighed, and an aqueous slurry is prepared by a sanding process.
The prepared aqueous slurry is used for synthesizing slurry of lithium iron phosphate M121 anode material, and the formula of the slurry is as follows: 96.7% of M121+0.1% of CNT (double-wall carbon nano tube) +0.2% of dispersing agent (carboxymethyl cellulose) +3% of LA132, the solid content of the composite slurry is 56%, the composite slurry is coated on a pole piece, and the pole piece is placed in an oven for drying, so that the positive pole piece is prepared.
Wherein, the CNT and the dispersant in the paste formulation refer to the CNT and the dispersant in the aqueous paste, and 0.1% CNT and 0.2% dispersant refer to the ratio of the CNT and the dispersant in the paste formulation.
Comparative example 2
16.02g of multi-wall carbon nano tube, 4.00g of polyvinylpyrrolidone, 0.8g of diethanol monoisopropanolamine and 379.17g of NMP are weighed and prepared into oily slurry through a sand grinding process.
The prepared oily slurry is used for the positive electrode slurry combination of the monocrystal ternary material, and the slurry combination formula comprises the following components: 98.0% NCM+0.8% CNT (multi-wall carbon nano tube) +0.2% dispersant (polyvinylpyrrolidone) +1.0% PVDF, the solid content of the slurry is 74%, the slurry is coated on a pole piece, and the pole piece is dried in an oven to obtain the positive pole piece.
Wherein, the CNT and the dispersant in the paste formulation refer to the CNT and the dispersant in the oil slurry, and the 0.8% CNT and the 0.2% dispersant refer to the ratio of the CNT and the dispersant in the paste formulation.
Application example
The dispersible carbon nanotube powder prepared in the above examples 1-7 is used for the slurry mixing of the lithium iron phosphate M121 anode material, and the slurry mixing formula comprises the following components: 96.7% of M121+0.3% of dispersible CNT powder+3% of aqueous binder (LA 132), the solid content of the composite slurry is 56%, the composite slurry is coated on a pole piece, and the pole piece is placed in an oven for drying, so that the positive pole piece is prepared.
The dispersible carbon nanotube powder prepared in the above examples 8-9 is used for the positive electrode slurry mixing of the monocrystal ternary material, and the slurry mixing formula comprises the following components: 98.0% NCM+1.0% dispersible CNT powder+1.0% PVDF, wherein the solid content of the composite slurry is 74%, the composite slurry is coated on a pole piece, and the pole piece is dried in an oven to prepare the positive pole piece.
Performance test
(1) The weight of the dispersible carbon nanotube powder obtained in examples 1 to 9 was weighed, and the yield of the dispersible carbon nanotube powder was calculated from the weight of the carbon nanotube originally added in each example.
(2) The resistivity of the positive electrode sheet prepared after slurry mixing using the dispersible carbon nanotube powder of examples 1 to 9 was tested.
TABLE 1 Performance test results for examples 1-9 and comparative examples 1-2
Wherein, the resistivity before pressing refers to the resistivity of the electrode plate before pressing and compacting treatment.
Referring to Table 1, it is apparent from the above yield data that the method for preparing dispersible carbon nanotube powder according to the present application can produce a product having a high yield of more than 90% and is suitable for mass production.
Referring to table 1, the apparatus of example 2, in which the classification device 6 and the powder circulation device 7 are added, shows that the resistivity of the prepared carbon nanotube powder is not obviously different from that of example 1, and the classification device 6 and the powder circulation device 7 added have no obvious influence on the finally collected up-to-standard carbon nanotube powder, and the classification device 6 and the powder circulation device 7 can repeatedly disperse the up-to-standard carbon nanotube powder, so that the up-to-standard powder yield is higher; and the supercritical fluid separated by the classifying device 6 can be circulated to the fluid storage container 55 and then circulated to the high-pressure resistant intermediate tank 31, so that the resource utilization rate of the fluid is improved, and the energy consumption of the supercritical fluid reactor is reduced.
Referring to table 1, the double-walled carbon nanotube powder (examples 2-5) or the single-walled carbon nanotube powder (examples 6-7) was used in the lithium iron phosphate M121 cathode material, the resistivity was smaller than that of comparative example 1, the conductivity of the electrode sheet was higher, i.e., the conductivity of the lithium iron phosphate M121 cathode material using the carbon nanotube powder of examples 2-7 was better than that of comparative example 1 using the conventional conductive paste, indicating that the method for preparing the dispersible carbon nanotube powder of the present application produced a product which could not only reach the level of the current conductivity, but also was better than that of the current cathode material using the conventional conductive paste. Wherein, the dispersion treatment of the single-wall carbon nano tube can lead the prepared dispersion carbon nano tube powder product to be used for the conductive performance in the anode material, which is better than the conductive performance of the powder after the dispersion treatment of the double-wall carbon nano tube in the examples 2-5.
The resistivity of the multiwall carbon nanotubes (examples 8-9) used in the single crystal ternary cathode material is obviously lower than that of comparative example 2, that is, the conductivity of the carbon nanotube powder of examples 8-9 used in the single crystal ternary cathode material is better than that of comparative example 2 of conventional conductive paste, and the method for preparing the dispersible carbon nanotube powder also shows that the prepared product can reach the current conductivity level of the multiwall carbon nanotubes and is better than that of the conventional conductive paste used in the cathode material.
As can be seen from fig. 3 to 4, in example 2, the double-walled carbon nanotubes were dispersed by ball-milling dispersion and supercritical fluid stripping, so that the tubular double-walled carbon nanotubes could be significantly dispersed into powder, which indicates that the dispersion effect of the ball-milling dispersion and supercritical fluid stripping was remarkable, and the prepared carbon nanotube powder had good dispersibility. As can be seen from fig. 5, the carbon nanotube powder prepared in example 2 was used in the positive electrode material of lithium iron phosphate M121, and the material of the positive electrode material was uniformly dispersed without obvious agglomeration.
As can be seen from fig. 3 and 6, in example 4, the double-walled carbon nanotubes were dispersed by ultrasonic dispersion and supercritical fluid stripping, which significantly dispersed the tubular double-walled carbon nanotubes into powder, and it was shown that the ultrasonic dispersion and supercritical fluid stripping also dispersed the carbon nanotubes, but the dispersibility was slightly worse than in example 2, and the powder was finer and finer by ball milling in example 2. As can be seen from fig. 7, the carbon nanotube powder prepared in example 4 was used in the positive electrode material of lithium iron phosphate M121, and the material of the positive electrode material was uniformly dispersed without obvious agglomeration, but the dispersion in example 4 was denser than the dispersion in the positive electrode material of lithium iron phosphate M121 in example 2.
As can be seen from fig. 8, in example 6, the single-walled carbon nanotubes were subjected to dispersion treatment by ball milling dispersion and supercritical fluid stripping, and the carbon nanotube powder obtained by dispersion was used in the lithium iron phosphate M121 cathode material, and the cathode material was uniformly dispersed without significant agglomeration, which indicates that the preparation method of the present application can also be used for dispersing single-walled carbon nanotubes to prepare carbon nanotube powder with dispersibility, and can be directly used in the cathode material.
As can be seen from fig. 9, in example 8, the dispersion treatment is performed on the multiwall carbon nanotubes by using a ball milling dispersion method and a supercritical fluid stripping method, the dispersed carbon nanotube powder is used in a monocrystal ternary system, the material of the cathode material is uniformly dispersed, no obvious agglomeration phenomenon exists, and the preparation method of the application can also perform the dispersion treatment on the multiwall carbon nanotubes to prepare the carbon nanotube powder with dispersibility, and can be directly applied to the cathode material.
The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.

Claims (9)

1. A preparation method of dispersible carbon nano tube powder is characterized in that: the method comprises the following steps:
step A: uniformly mixing the carbon nano tube and the dispersing agent to obtain a pre-dispersed material;
and (B) step (B): adding an additive into the pre-dispersed material in the step A, and uniformly mixing to obtain a mixture; then introducing supercritical fluid into the mixture, and performing supercritical fluid dispersion treatment to obtain supercritical suspension;
step C: b, carrying out supercritical fluid stripping treatment on the supercritical suspension prepared in the step B to prepare dispersible carbon nanotube powder;
the supercritical fluid dispersion treatment is specifically that the supercritical fluid is dispersed under the condition that the pressure is 8-15MPa, and then the pressure is reduced to 0.1-1MPa;
the supercritical fluid stripping treatment is specifically that the supercritical fluid stripping treatment is carried out under the condition that the pressure is 8-15MPa, and then the pressure is reduced to 0.01-0.1MPa;
the mixing weight ratio of the carbon nano tube to the dispersing agent is 0.5-5:1;
the mixing weight ratio of the additive to the pre-dispersed material is 0.02-0.08:1;
the additive is one or a mixture of more of hydroxyethyl ethylenediamine, diethylenetriamine, N-dimethylethanolamine, diethanol monoisopropanolamine and 2-amino-2-methyl-1-propanol.
2. The method for preparing the dispersible carbon nanotube powder according to claim 1, wherein: in the step a, the carbon nanotubes are one or a mixture of a plurality of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.
3. The method for preparing the dispersible carbon nanotube powder according to claim 1, wherein: in the step A, the dispersing agent is one or a mixture of more of polyvinylpyrrolidone, polyvinylidene fluoride and carboxymethyl cellulose.
4. The method for preparing the dispersible carbon nanotube powder according to claim 1, wherein: in the step B, the supercritical fluid dispersion treatment is carried out by adopting a ball milling dispersion device, and the specific operation is as follows: adding the pre-dispersed material in the step A into a ball milling dispersing device, adding an additive, uniformly mixing, sealing the ball milling dispersing device, pressing supercritical fluid into the ball milling dispersing device, and sealing and stirring for 2-24 hours under the conditions of the temperature of 35-65 ℃, the pressure of 8-15MPa and the rotating speed of 200-500rpm to obtain the supercritical suspension.
5. The method for preparing the dispersible carbon nanotube powder according to claim 1, wherein: in the step B, the supercritical fluid dispersion treatment is carried out by adopting an ultrasonic dispersion device, and the specific operation is as follows: adding the pre-dispersed material in the step A into an ultrasonic dispersing device, adding an additive, uniformly mixing, sealing the ultrasonic dispersing device, pressing supercritical fluid into the ultrasonic dispersing device, and sealing the ultrasonic dispersing device for 2-6 hours under the conditions of the temperature of 35-65 ℃, the pressure of 8-10MPa and the ultrasonic power of 250-750W to prepare the supercritical suspension.
6. The method for preparing the dispersible carbon nanotube powder according to claim 1, wherein: in the step B, the supercritical fluid is one or a mixture of more of carbon dioxide, ethanol, acetone and water; in the step C, the supercritical fluid stripping treatment is performed by a supercritical fluid stripping device.
7. The method for preparing the dispersible carbon nanotube powder according to claim 1, wherein: in the step C, the supercritical fluid stripping treatment is followed by a classification treatment, wherein the classification treatment is carried out by a classification device (6).
8. An apparatus for use in the method for producing the dispersible carbon nanotube powder of any one of claims 1 to 6, characterized in that: the supercritical fluid stripping device comprises a dispersing device (2), a supercritical fluid stripping device and a product collecting container (4) in sequence of use, wherein the dispersing device (2) is connected with a first supercritical fluid reaction device; the supercritical fluid stripping device comprises a high-pressure resistant intermediate tank (31) and a decompression tank (32) which are sequentially connected, a nozzle (21) is arranged at the discharge end of the dispersing device (2), the nozzle (21) is communicated with the feed end of the high-pressure resistant intermediate tank (31) through a connecting pipeline, and the discharge end of the decompression tank (32) is communicated with a product collecting container (4); the high-pressure-resistant intermediate tank (31) is connected with a medium conveying device; the dispersing device (2) is a ball milling dispersing device or an ultrasonic dispersing device.
9. The apparatus for applying the method for preparing the dispersible carbon nanotube powder according to claim 8, wherein: the device is characterized by further comprising a grading device (6), wherein the grading device (6) comprises a plurality of cyclone separators (61) which are sequentially communicated, the feeding end of each cyclone separator (61) is communicated with the discharging end of the decompression tank (32), and the discharging end of the last cyclone separator (61) is communicated with the product collecting container (4).
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