Carbon nanoporous frameworks prepared by supercritical fluid-assisted in-situ polymerization and their preparation method

Abstract

This invention relates to the field of materials technology, and in particular to a method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization. The method comprises the following steps: carbon nanomaterials, a strong base reagent, an epoxy monomer, and a supercritical fluid solvent are introduced into a reactor for mixing. Simultaneously, the reaction pressure and temperature in the reactor are controlled to maintain the solvent in a supercritical fluid state. After the strong base reagent and the epoxy monomer have completely reacted, the pressure in the reactor is rapidly released until the reactor pressure is 1 standard atmosphere. The product is then removed from the reactor to obtain a carbon nanomaterial porous framework. The strong base reagent is soluble in an organic solvent. The carbon nanoporous framework prepared by this method can be uniformly dispersed in a solvent with simple stirring, solving the problem of difficult dispersion of carbon nanomaterials.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to carbon nanoporous frameworks and methods prepared by supercritical fluid-assisted in-situ polymerization. Background Technology

[0002] Carbon nanomaterials refer to carbon materials with at least one dimension of dispersed phase smaller than 100 nm. They mainly include three types: carbon nanotubes, carbon nanofibers, and carbon nanospheres. Among carbon nanomaterials, novel carbon nanofibers and carbon nanotubes possess many excellent physical and chemical properties and are widely used in numerous fields.

[0003] However, the carbon nanotubes grown by the current preparation method are in the form of aggregates. Aggregated carbon nanotubes seriously affect their electrical and mechanical properties and cannot be directly applied to the market. The aggregated carbon nanotubes need to be dispersed before use.

[0004] In existing technologies, the main method for dispersing carbon nanotubes is to use NMP and water as solvents and add PVP dispersant. The carbon nanotubes and PVP are mixed with the solvent in a certain proportion, and then the carbon nanotubes are cut in the solvent using a high-speed disperser or ball mill to form short carbon nanotubes. The carbon nanotubes are then bonded to the dispersant on the surface to prevent them from agglomerating.

[0005] The above-mentioned technical solutions have the following problems: 1. The physical ball milling process cuts off the carbon nanotubes, affecting their aspect ratio and physicochemical properties; 2. The dispersant used is a polymeric dispersant, which is difficult to completely penetrate the gaps between the aggregated carbon nanotubes, resulting in limited dispersion effect. Therefore, existing carbon nanotube dispersion methods are difficult, affecting the performance of carbon nanotubes. Summary of the Invention

[0006] The primary objective of this invention is to provide a porous framework for carbon nanomaterials, which, when placed in a solvent and simply stirred, can achieve uniform dispersion of the carbon nanomaterials, thus solving the problem of difficult dispersion of carbon nanomaterials.

[0007] The second objective of this invention is to provide a method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization. This method solves the problem of difficult dispersion of carbon nanomaterials.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A carbon nanotube porous framework comprises multiple carbon nanotube units, which are assembled on the surface to form a three-dimensional network framework structure. There are gaps between adjacent carbon nanotube units. Each carbon nanotube unit comprises carbon nanomaterials and a polymer uniformly coated on the surface of the carbon nanomaterials. Adjacent carbon nanotube units are interconnected by the polymer.

[0010] A method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization includes the following preparation steps:

[0011] Carbon nanomaterials, a strong base reagent, an epoxy monomer, and a supercritical fluid solvent are introduced into a reactor for mixing. The reaction pressure and temperature in the reactor are controlled to keep the solvent in a supercritical fluid state. After the strong base reagent and the epoxy monomer have completely reacted, the pressure in the reactor is quickly released until the pressure in the reactor is 1 standard atmosphere. The product in the reactor is then removed to obtain a porous framework of carbon nanomaterials. The strong base reagent is soluble in an organic solvent.

[0012] The order in which the substances are added is as follows:

[0013] First, carbon nanomaterials and supercritical fluid solvent are introduced into a reactor for mixing. Then, a strong base reagent is added to carry out the reaction, followed by the addition of epoxy monomers to carry out the reaction.

[0014] The mass ratio of the carbon nanomaterial, strong base reagent, epoxy monomer and supercritical fluid solvent is 5-15:0.05-0.2:1-3:5-15.

[0015] The strong base reagent includes at least one of sodium ethoxide, potassium ethoxide, sodium hydroxide, and potassium hydroxide.

[0016] The epoxy monomers include at least one of propylene oxide, ethylene oxide, and butane oxide.

[0017] The supercritical fluid solvent includes at least one of supercritical carbon dioxide solvent, supercritical ethanol solvent, and supercritical propanol solvent.

[0018] The carbon nanomaterials include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene.

[0019] This also includes introducing organic co-solvents into the reactor and mixing them with carbon nanomaterials, strong base reagents, epoxy monomers, and supercritical fluid solvents.

[0020] The reaction pressure in the reactor is controlled at 7-25 MPa and the reaction temperature at 80-100℃. After the substances in the reactor react for 3-5 hours, the internal pressure of the reactor is released.

[0021] The beneficial effects of this invention are:

[0022] The carbon nanoporous framework of this invention solves the problem of difficult dispersion of carbon nanomaterials. In use, simply placing it in a solvent and mechanically stirring achieves uniform dispersion of the carbon nanomaterials, resulting in excellent dispersion. No additional dispersant is needed, nor is it necessary to use high-speed dispersers or ball mills to shear or grind the carbon nanomaterials. The dispersion method is simple and maintains the original high aspect ratio of the carbon nanomaterials, preserving their good conductivity and improving the conductivity of the dispersion. This carbon nanoporous framework can be applied to lithium-ion battery electrodes, supercapacitor electrodes, and polymer composite materials.

[0023] The carbon nanoporous framework of this invention has a density of 0.01-0.3 g / cm³. 3 Specific surface area is 100-400 m² 2 / g, with a porosity of 50-98%. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 SEM image of the porous carbon nanotube framework prepared by the method of the present invention;

[0026] Figure 2 SEM image of the graphene porous framework prepared by the method of the present invention;

[0027] Figure 3 SEM image of the lithium iron phosphate cathode sheet prepared using the carbon nanoporous framework of the present invention;

[0028] Figure 4 SEM image of a conductive polymer prepared using the carbon nanoporous framework of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed; where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0030] In the description of this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In the description of this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] It should be understood that the weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0033] Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of that word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0034] This invention provides a carbon nanotube porous framework, which includes multiple carbon nanotube units. The multiple carbon nanotube units are surface-connected and assembled to form a three-dimensional network framework structure. There are gaps between adjacent carbon nanotube units. Each carbon nanotube unit includes carbon nanomaterials and a polymer uniformly coated on the surface of the carbon nanomaterials. Adjacent carbon nanotube units are interconnected by the polymer.

[0035] The carbon nanoporous framework of the present invention is a three-dimensional network framework structure formed by the interconnection and assembly of multiple carbon nanounits. The surface of the carbon nanomaterial is coated with a polymer, which separates the carbon nanomaterials from each other and prevents them from agglomerating. Furthermore, there are gaps between adjacent carbon nanounits, forming a porous and easily breakable structure. When this carbon nanoporous framework is added to a solvent, the porous structure not only facilitates the solvent to enter between the carbon nanounits and dissolve them, which is beneficial to the dispersion of the carbon nanomaterials, but also allows the carbon nanounits to be separated under simple mechanical stirring, achieving uniform dispersion of the carbon nanomaterials. Moreover, the dispersed carbon nanomaterials will not re-agglomerate.

[0036] In summary, the carbon nanoporous framework of the present invention solves the problem of difficult dispersion of carbon nanomaterials. When in use, it can be placed in a solvent and the carbon nanomaterials can be uniformly dispersed by simple mechanical stirring. The dispersion effect is good, and there is no need to add a dispersant or use a high-speed disperser or ball mill to shear or grind the carbon nanomaterials. The dispersion method is simple and can maintain the original high aspect ratio of the carbon nanomaterials, maintain the good conductivity of the carbon nanomaterials, and improve the conductivity of the dispersion.

[0037] This carbon nanoporous framework can be applied to lithium battery electrodes, supercapacitor electrodes, and polymer composite materials.

[0038] The carbon nanomaterials include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene. The polymer is an epoxy polymer. Epoxy polymers are soluble in organic solvents and have good solubility in NMP solvent. When the carbon nanoporous framework is placed in NMP solvent, simple stirring is sufficient to disperse the carbon nanomaterials without the need for additional dispersants or high-speed dispersers or ball mills to shear or grind the carbon nanomaterials. The dispersion method is simple, and the dispersed material retains its original high aspect ratio and good conductivity, thus improving the conductivity of the dispersion.

[0039] Specifically, the polymer is at least one of polypropylene oxide, ethylene oxide-propylene oxide copolyether, and polyethylene oxide.

[0040] A method for preparing the above-mentioned carbon nanoporous framework by supercritical fluid-assisted in-situ polymerization includes the following preparation steps:

[0041] Carbon nanomaterials, a strong base reagent, an epoxy monomer, and a supercritical fluid solvent are introduced into a reactor for mixing. The reaction pressure and temperature in the reactor are controlled to keep the solvent in a supercritical fluid state. After the strong base reagent and the epoxy monomer have completely reacted, the pressure in the reactor is quickly released until the pressure in the reactor is 1 standard atmosphere. The product in the reactor is then removed to obtain a porous framework of carbon nanomaterials. The strong base reagent is soluble in an organic solvent.

[0042] This invention uses supercritical fluid in-situ surface polymerization to prepare carbon nanoporous frameworks. The carbon nanoporous frameworks prepared by this invention solve the technical problem of difficult dispersion of carbon nanomaterials. When dispersing the carbon nanoporous frameworks prepared by this invention, it is only necessary to place them in a solvent, such as NMP solvent, and perform simple low-speed stirring to achieve uniform dispersion of carbon nanomaterials. Moreover, the dispersion performance can be achieved by traditional carbon nanomaterial dispersion processes.

[0043] Specifically, this invention involves mixing carbon nanomaterials, a strong base reagent, epoxy monomers, and a supercritical fluid solvent. The reaction pressure and temperature are controlled to maintain the solvent in a supercritical fluid state. Because the supercritical fluid solvent has a lower surface energy than other solvents, it can penetrate the gaps between the aggregated carbon nanomaterials. Furthermore, the supercritical fluid solvent can dissolve the strong base reagent and epoxy monomers, both of which are low molecular weight substances. When mixed with the supercritical fluid solvent, they are carried into the gaps between the aggregated carbon nanomaterials. The strong base reagent acts as a deagglomerating agent for the aggregated carbon nanomaterials, initially dispersing the entangled carbon nanomaterials and increasing the gaps between them. Reagents, epoxy monomers, and other reactants can more easily enter the gaps between carbon nanomaterials. On the other hand, the strong base reagent also acts as a catalyst, catalyzing the polymerization reaction of epoxy monomers located in the gaps between carbon nanomaterials to generate high molecular weight epoxy polymers. The generated high molecular weight epoxy polymers coat the surface of carbon nanomaterials and form steric hindrance between carbon nanomaterials, allowing the carbon nanomaterials to be completely dispersed. After the reaction is complete, the pressure in the reactor is quickly released to the standard atmospheric pressure. During the instantaneous depressurization, the supercritical fluid solvent returns to its normal phase, becoming a gas or liquid and being discharged from the interior of the carbon nanomaterials, thereby obtaining a carbon nanoporous framework product containing carbon nanomaterials, epoxy polymers, and a small amount of strong base reagent.

[0044] Specifically, when the supercritical fluid solvent undergoes a rapid phase change and is discharged from the product during rapid depressurization, a large number of pores are left in the product, causing it to expand. Due to the presence of a large number of pores, the gaps between carbon nanomaterials are larger. The numerous pores separate the epoxy polymers that coat the surfaces of adjacent carbon nanomaterials, reducing the connection area of ​​the epoxy polymers between adjacent carbon nanounits. This makes the formed carbon nanoporous framework more fragile. When added to the solvent, the carbon nanomaterials on the carbon nanoporous framework can be dispersed by simple mechanical stirring. There is no need to add dispersant again or use high-speed shearing or grinding methods to obtain a uniformly dispersed dispersion. Compared with grinding and high-speed shearing methods, low-speed mechanical stirring can maintain the original aspect ratio of the carbon nanomaterials and improve the conductivity of the dispersion.

[0045] This invention does not directly mix polymers with carbon nanomaterials and supercritical fluid solvents. Instead, it uses small-molecule strong base reagents and epoxy monomers. This is because the large molecular weight of polymers makes it difficult to completely penetrate the gaps between aggregated carbon nanomaterials for complete dispersion. This invention uses small-molecule reagents that, under the action of supercritical fluid solvents, can better penetrate these gaps and disperse among the carbon nanomaterials. Furthermore, the strong base reagents depolymerize the entangled carbon nanomaterials, initially dispersing them and increasing the gaps between them. This facilitates the entry of epoxy monomers into these gaps, allowing them to polymerize within the aggregated carbon nanomaterials under the catalysis of the strong base reagent, forming steric hindrance that disperses adjacent carbon nanomaterials. Therefore, this preparation method is more conducive to improving the dispersion performance of carbon nanomaterials. Specifically, the carbon nanomaterials are carbon nanotubes or graphene.

[0046] The order in which the substances are added is as follows:

[0047] First, carbon nanomaterials and supercritical fluid solvent are introduced into a reactor for mixing. Then, a strong base reagent is added to carry out the reaction, followed by the addition of epoxy monomers to carry out the reaction.

[0048] This invention first mixes carbon nanomaterials with a supercritical fluid solvent, which initially disperses the carbon nanomaterials, facilitating the entry of reaction reagents into the gaps between the carbon nanomaterials. Then, a strong base is added, acting as a depolymerizing agent. Under the action of the supercritical fluid solvent, the strong base is carried into the gaps between the carbon nanomaterials, depolymerizing them and increasing the gaps between them. This allows epoxy monomers to enter the gaps more quickly and uniformly. Finally, epoxy monomers are added. Under the action of the supercritical fluid, the epoxy monomers are carried into the gaps between the carbon nanomaterials, uniformly dispersing within the aggregated carbon nanomaterials. Under the catalysis of the strong base, the epoxy monomers undergo a polymerization reaction to form a high-molecular polymer, creating steric hindrance between the carbon nanomaterials and ensuring complete dispersion, thus improving the dispersion performance of the carbon nanomaterials.

[0049] The mass ratio of the carbon nanomaterial, strong base reagent, epoxy monomer and supercritical fluid solvent is 5-15:0.05-0.2:1-3:5-15.

[0050] By adopting the above mass ratio, the prepared carbon nanoporous framework has better dispersibility and higher conductivity. When the amount of strong base reagent added is too low, the strong base reagent cannot completely depolymerize the aggregated carbon nanomaterials, so that the epoxy monomers cannot be uniformly distributed in the gaps between the carbon nanomaterials, affecting the dispersion of carbon nanomaterials. It also affects the synthesis rate of epoxy polymers and the preparation efficiency of products. When the amount of strong base reagent added is too high, more strong base reagent will adhere to the prepared carbon nanoporous framework, resulting in more impurities after the carbon nanomaterials are dispersed, affecting the conductivity and subsequent applications of carbon nanomaterials. When the amount of epoxy monomers added is too small, only a small amount of epoxy polymer is generated, which cannot form steric hindrance between the carbon nanomaterials, thus affecting the dispersion performance of the carbon nanomaterials. When the amount of epoxy monomers added is too large, too much epoxy polymer is generated and coated on the surface of the carbon nanomaterials, which will affect the conductivity of the carbon nanomaterials. In addition, the excessive amount of epoxy polymer will make the carbon nanounits in the carbon nanoporous framework firmly bonded, making it difficult for the carbon nanoporous framework to break down under low-speed stirring after the carbon nanoporous framework is added to the solvent, and the carbon nanounits are difficult to separate, thus affecting the conductivity of the dispersion.

[0051] The strong base reagent includes at least one of sodium ethoxide, potassium ethoxide, sodium hydroxide, and potassium hydroxide.

[0052] The aforementioned strong base reagents can dissolve in supercritical fluid solvents, and the aforementioned metal ions can bind to the π bonds of carbon nanomaterials in supercritical fluid solvents, thereby depolymerizing aggregated carbon nanomaterials and catalyzing epoxy monomers to polymerize epoxy monomers into epoxy polymers. These epoxy polymers then form steric hindrance between carbon nanomaterials, which is beneficial for improving the dispersion effect of carbon nanomaterials.

[0053] The epoxy monomers include at least one of propylene oxide, ethylene oxide, and butane oxide.

[0054] The aforementioned epoxy monomers can enter the gaps between carbon nanomaterials under the action of supercritical fluid solvents and rapidly polymerize under the catalysis of strong base reagents. The polymerization products form steric hindrance between carbon nanomaterials, causing the carbon nanomaterials to disperse and not re-aggregate, which is beneficial to improving the dispersibility and conductivity of carbon nanomaterials.

[0055] Preferably, the epoxy monomer is a mixture of propylene oxide and ethylene oxide in a mass ratio of 1:1. The mixture of propylene oxide and ethylene oxide can form ethylene oxide-propylene oxide copolyether under the action of a catalyst, which is more conducive to improving the dispersion and conductivity of carbon nanomaterials.

[0056] The supercritical fluid solvent includes at least one of supercritical carbon dioxide solvent, supercritical ethanol solvent, and supercritical propanol solvent.

[0057] The aforementioned types of supercritical fluid solvents exhibit good solubility for strong base reagents and epoxy monomers, enabling them to be introduced into the gaps between aggregated carbon nanomaterials. This allows the strong base reagents and epoxy monomers to react within the carbon nanomaterials, resulting in steric hindrance of the polymerization products and thus dispersing the carbon nanomaterials. The product obtained after depressurization has multiple pores. Furthermore, these types of supercritical fluid solvents have relatively low supercritical temperatures and pressures, further facilitating the reaction.

[0058] Preferably, the supercritical fluid solvent is a supercritical carbon dioxide solvent. After instantaneous depressurization, the supercritical carbon dioxide solvent will turn into carbon dioxide gas and be directly discharged, resulting in higher discharge efficiency. Furthermore, the porosity of the carbon nanoporous framework product formed is higher, which is more conducive to improving the dispersion performance of carbon nanomaterials. When the prepared carbon nanoporous framework is added to the solvent, it is easier to break down and disperse, and the dispersed carbon nano dispersion has higher conductivity.

[0059] The carbon nanomaterials include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene.

[0060] This also includes introducing organic co-solvents into the reactor and mixing them with carbon nanomaterials, strong base reagents, epoxy monomers, and supercritical fluid solvents.

[0061] Organic co-solvents can improve the solubility of strong base reagents in supercritical fluid solvents, allowing the strong base reagents to enter the gaps between carbon nanomaterials more fully, combine with the π bonds on the carbon nanomaterials, improve the dispersion effect between carbon nanomaterials, and facilitate the entry of epoxy monomers into the gaps between carbon nanomaterials to undergo polymerization reactions, thereby improving the dispersion performance of carbon nanomaterials.

[0062] Preferably, the organic co-solvent is methanol, and the mass ratio of the organic co-solvent to the supercritical fluid solvent is 0.5-1:1.

[0063] The reaction pressure in the reactor is controlled at 7-25 MPa and the reaction temperature at 80-100℃. After the substances in the reactor react for 3-5 hours, the internal pressure of the reactor is released.

[0064] Preferably, when the reactor is depressurized, the internal gas pressure drops to 1 standard atmosphere within 0.1 seconds. This instantaneous and rapid depressurization transforms the supercritical fluid solvent into a gas with lower density and larger volume, increasing the gaps between carbon nanomaterials and causing the product to expand rapidly. Under pressure, the gas is quickly expelled from the product, creating more pores inside. This allows the carbon nanomaterials to disperse evenly, and the porous structure makes the product more prone to breakage in the solvent, resulting in better dispersion, stability, and conductivity of the carbon nanomaterials.

[0065] Specifically, the density of the carbon nanoporous framework is 0.01-0.3 g / cm³. 3 Specific surface area is 100-400 m² 2 / g, with a porosity of 50-98%.

[0066] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the embodiments of the present invention, the following examples illustrate the above technical solutions.

[0067] Example 1

[0068] A method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization includes the following preparation steps:

[0069] First, 5 parts by weight of multi-walled carbon nanotubes and 5 parts by weight of supercritical carbon dioxide fluid solvent were introduced into a reactor and mixed and stirred. Then, 0.05 parts by weight of sodium ethoxide were added into the reactor and mixed and stirred. Next, 5 parts by weight of methanol were added and mixed and stirred evenly. Then, 1 part by weight of propylene oxide was added into the reactor and mixed and stirred. The pressure in the reactor was 10 MPa, the reaction temperature was 80℃, and the reaction was carried out with stirring at a stirring speed of 50 r / min for 3 hours. After the reaction was completed, the gas pressure in the reactor was released within 0.1 seconds to reduce the gas pressure in the reactor to 1 standard atmosphere. The product in the reactor was taken out to obtain a carbon nanoporous framework, specifically a carbon nanotube porous framework.

[0070] Example 2

[0071] A method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization includes the following preparation steps:

[0072] First, 10 parts by weight of multi-walled carbon nanotubes and 10 parts by weight of supercritical carbon dioxide fluid solvent were introduced into a reactor and mixed and stirred. Then, 0.1 parts by weight of sodium ethoxide were added into the reactor and mixed and stirred. Next, 10 parts by weight of methanol were added and mixed and stirred evenly. Then, 2 parts by weight of propylene oxide were added into the reactor and mixed and stirred. The pressure in the reactor was 16 MPa, the reaction temperature was 90℃, and the reaction was carried out with stirring at a stirring speed of 50 r / min for 4 hours. After the reaction was completed, the gas pressure in the reactor was released within 0.1 seconds to reduce the gas pressure in the reactor to 1 standard atmosphere. The product in the reactor was taken out to obtain a carbon nanoporous framework, specifically a carbon nanotube porous framework.

[0073] Example 3

[0074] A method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization includes the following preparation steps:

[0075] First, 15 parts by weight of multi-walled carbon nanotubes and 15 parts by weight of supercritical carbon dioxide fluid solvent were introduced into a reactor and mixed and stirred. Then, 0.2 parts by weight of sodium ethoxide were added into the reactor and mixed and stirred. Next, 15 parts by weight of methanol were added and mixed and stirred evenly. Then, 3 parts by weight of propylene oxide were added into the reactor and mixed and stirred. The pressure in the reactor was 25 MPa, the reaction temperature was 100 °C, and the reaction was carried out at a stirring speed of 50 r / min for 5 h. After the reaction was completed, the gas pressure in the reactor was released within 0.1 seconds to reduce the gas pressure in the reactor to 1 standard atmosphere. The product in the reactor was taken out to obtain a carbon nanoporous framework, specifically a carbon nanotube porous framework.

[0076] Example 4

[0077] A method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization includes the following preparation steps:

[0078] Five parts by weight of multi-walled carbon nanotubes, five parts by weight of supercritical carbon dioxide fluid solvent, 0.05 parts by weight of sodium ethoxide, five parts by weight of methanol, and one part by weight of propylene oxide were added to a reactor and mixed and stirred until homogeneous. The pressure in the reactor was 10 MPa, the reaction temperature was 80 °C, and the reaction was carried out with stirring at a speed of 50 r / min for 3 h. After the reaction was completed, the pressure in the reactor was released within 0.1 seconds to reduce the pressure in the reactor to 1 standard atmosphere. The product in the reactor was then removed to obtain a carbon nanoporous framework, specifically a carbon nanotube porous framework.

[0079] Example 5

[0080] The method for preparing carbon nanoporous frameworks by supercritical fluid-assisted in-situ polymerization, the difference between the method in Example 5 and Example 1 is that the carbon nanomaterial in Example 5 is graphene. The other preparation conditions in Example 5 are the same as those in Example 1, and will not be repeated here. The carbon nanoporous framework prepared in Example 5 is a graphene porous framework.

[0081] Comparative Example 1

[0082] A method for preparing a porous carbon nanotube framework includes the following preparation steps:

[0083] Five parts by weight of multi-walled carbon nanotubes and five parts by weight of supercritical carbon dioxide fluid solvent were introduced into a reactor and mixed and stirred. Then, one part by weight of polypropylene oxide was added into the reactor and mixed and stirred. The pressure in the reactor was 10 MPa, the reaction temperature was 80 °C, and the reaction was carried out at a stirring speed of 50 r / min for 3 hours. After the reaction was completed, the gas pressure in the reactor was released within 0.1 seconds to reduce the gas pressure in the reactor to 1 standard atmosphere. The product in the reactor was then removed to obtain a porous carbon nanotube framework.

[0084] Comparative Example 2

[0085] A method for preparing a carbon nanoporous framework, the difference between Comparative Example 2 and Comparative Example 1 is that the polypropylene oxide in Comparative Example 1 is replaced with polyvinylpyrrolidone, while other conditions are the same as those in Comparative Example 1.

[0086] Comparative Example 3

[0087] A carbon nanotube dispersion is prepared by mixing 5 parts by weight of multi-walled carbon nanotubes, 1 part by weight of PVP dispersant and 100 parts by weight of NMP solvent, and then dispersing the carbon nanotube solution using a high-speed disperser at a dispersion speed of 4000 rpm for 1 hour.

[0088] Performance testing

[0089] I. Preparation of lithium iron phosphate positive electrode sheet and testing of electrode resistivity.

[0090] The preparation method of lithium iron phosphate positive electrode sheet involves mixing PVDF adhesive, conductive agent, and NMP solvent in a certain proportion in a mixing cylinder. The mixture is then stirred with a spatula to ensure uniform mixing. Next, lithium iron phosphate positive electrode material is added. The mass ratio of PVDF adhesive, conductive agent, NMP solvent, and lithium iron phosphate positive electrode material is 2.5:0.8:40:56.7. The mixture is stirred evenly with a spatula to prevent the dry powder of the positive electrode material from sticking to the wall. The mixture is dispersed at a linear velocity of 15 m / s for 1 hour. The dispersed slurry is then coated into a film, dried, and cut into 18 mm diameter discs to obtain the lithium iron phosphate positive electrode sheet. The resistivity of the sample electrode sheet is measured using a four-probe tester.

[0091] Carbon nanoporous materials prepared in Examples 1-5 and Comparative Examples 1-2, and carbon nanotube dispersion prepared in Comparative Example 3 were used as conductive agents to prepare different lithium iron phosphate positive electrode samples according to the above method. Then, the electrode resistivity of each sample was tested, and the test results are recorded in Table 1.

[0092] Table 1

[0093]

[0094] The above experimental results show that when 0.8 wt% of the carbon nanotube porous framework prepared by the method of the present invention is added to prepare lithium iron phosphate cathode plates, the resistivity of the plates can be reduced to 4.0 Ω·cm, which proves that the carbon nanotube porous framework prepared by the method of the present invention has good dispersion performance and high conductivity.

[0095] The resistivity of lithium iron phosphate cathode sheets prepared using the carbon nanotube porous frameworks of Examples 1 and 4 was compared. The cathode sheet prepared using the carbon nanotube porous framework of Example 1 had a lower resistivity, indicating that the conductivity of the carbon nanotube porous framework of Example 1 was better than that of Example 4. This is because the carbon nanotube porous framework of Example 4 was prepared by directly mixing carbon nanotubes, strong base reagents, epoxy monomers and supercritical fluid solvents, while Example 1 was prepared by sequentially mixing carbon nanotubes, supercritical fluid solvents, strong base reagents and epoxy monomers. The experimental results of Examples 1 and 4 show that adding the reaction reagents sequentially according to this method is more conducive to improving the dispersion performance and conductivity of carbon nanotubes.

[0096] The resistivity of the lithium iron phosphate cathode sheets prepared using the carbon nanotube porous frameworks of Comparative Examples 1 and 2 were 63 Ω·cm and 55.4 Ω·cm, respectively. This indicates that the conductivity and dispersibility of the carbon nanotube porous frameworks of Comparative Examples 1 and 2 are far inferior to those prepared by the method of this invention. This is because Comparative Examples 1 and 2 directly mix macromolecular polymers with carbon nanotubes, supercritical fluid solvents, and strong base reagents. During the reaction, the macromolecular polymers have difficulty entering the gaps between the aggregated carbon nanotubes; only a small portion enters the gaps, resulting in poor dispersion of the carbon nanotubes and thus poor conductivity and dispersibility of the prepared carbon nanotube porous frameworks. In contrast, since polyvinylpyrrolidone is a commonly used dispersant for carbon nanotubes, its dispersing effect on carbon nanotubes is superior to that of polypropylene oxide. Consequently, the resistivity of the cathode sheet prepared using the carbon nanotube porous framework of Comparative Example 1 is lower than that of the cathode sheet prepared using the carbon nanotube porous framework of Comparative Example 2.

[0097] As can be seen from Comparative Example 3, the method for preparing the porous carbon nanotube framework of the present invention can effectively improve the dispersion and conductivity of carbon nanotubes. Comparative Example 3 is a traditional carbon nanotube dispersion method. Because a high-speed disperser is required to disperse the carbon nanotubes during the dispersion process, the dispersed carbon nanotubes break down, the aspect ratio decreases, and it becomes difficult for the carbon nanotubes to form a continuous conductive network, resulting in reduced conductivity. However, the porous carbon nanotube framework prepared by the method of the present invention does not require the use of a high-speed disperser or grinder to disperse the carbon nanotubes during the preparation process. It maintains the high aspect ratio of the carbon nanotubes while achieving high dispersion. The method for preparing the porous carbon nanotube framework of the present invention solves the technical problem of difficult carbon nanotube dispersion.

[0098] II. Fabrication of supercapacitors and testing of capacitor performance.

[0099] Polymethyl methacrylate (AC), a conductive agent, and PVDF were mixed in a mass ratio of 92.5:3.5:4 to prepare a supercapacitor electrode, which was then used to fabricate a supercapacitor.

[0100] Using the carbon nanoporous frameworks prepared in Examples 1-5 and Comparative Examples 1-2, the carbon nanotube dispersion prepared in Comparative Example 3, and carbon black as conductive agents, different supercapacitors were prepared according to the above method. The performance of each capacitor was then tested, and the test results are recorded in Table 2.

[0101] Table 2

[0102] sample Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 carbon black Capacity (F) 0.4619 0.4613 0.4601 0.4531 0.4520 0.2350 0.4436 0.4490 0.4495 Specific capacity (F / g) 58.26 58.25 59.20 57.91 57.63 45.01 52.96 55.23 57.31 DC internal resistance (Ω) 5.26 5.24 5.23 5.38 6.0 22.31 18.36 27.52 9.00

[0103] III. Using the product of this invention, prepare conductive polymer plastics and test their relevant properties.

[0104] The carbon nanotube porous framework obtained in Example 1 was mixed with polycarbonate resin, with the carbon nanotube porous framework accounting for 5% of the total mass of the mixture. Then, it was kneaded at 20 rpm for 10 min at 250°C, and then injection molded. The performance of the molded product was tested, and the data were recorded in Table 3.

[0105] Table 3

[0106] Basic performance unit Test methods Test Results Volume resistivity Ω·cm GB / T1410 7 Surface resistivity Ω / sq GB / T1410 35 Tensile strength Mpa GB / T1040.3-2006 63 Yield strength Mpa GB / T1040.3-2006 63 Fracture tensile strain ％ GB / T1040.3-2006 20 Bending strength Mpa GB / T9341-2008 95.6 Flexural modulus Mpa GB / T9341-2008 2491 Izod Notched Impact Strength kJ / m2 ASTM D256-2010 9.6 Flame retardancy class UL94 V2

[0107] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for the preparation of carbon nanoporous frameworks by supercritical fluid assisted in-situ polymerization, characterized in that, The preparation method comprises the following steps: The carbon nanomaterial, the strong alkali reagent, the epoxy monomer and the supercritical fluid solvent are mixed in the reactor, and the reaction pressure and the reaction temperature in the reactor are controlled to keep the solvent in the supercritical fluid state; after the strong alkali reagent and the epoxy monomer are completely reacted, the pressure in the reactor is rapidly released to 1 standard atmosphere, and the product in the reactor is taken out to obtain the carbon nanomaterial porous framework; The mass ratio of the carbon nanomaterial, the strong alkali reagent, the epoxy monomer and the supercritical fluid solvent is 5-15:0.05-0.2:1-3:5-15, and the adding order of the substances is as follows: the carbon nanomaterial and the supercritical fluid solvent are mixed in the reactor first, then the strong alkali reagent is added for reaction, and then the epoxy monomer is added for reaction. The strong alkali reagent is dissolved in an organic solvent.

2. The method of claim 1, wherein the supercritical fluid assisted in-situ polymerization to produce a carbon nanoporous framework is characterized by, The strong alkali reagent comprises at least one of sodium ethoxide, potassium ethoxide, sodium hydroxide and potassium hydroxide.

3. The method of claim 1, wherein the supercritical fluid assisted in-situ polymerization to produce a carbon nanoporous framework is characterized by, The epoxy monomer comprises at least one of propylene oxide, ethylene oxide and butylene oxide.

4. The method of claim 1, wherein the supercritical fluid assisted in-situ polymerization to produce a carbon nanoporous framework is characterized by, The supercritical fluid solvent comprises at least one of supercritical carbon dioxide solvent, supercritical ethanol solvent and supercritical propanol solvent.

5. The method of claim 1, wherein the supercritical fluid assisted in-situ polymerization to produce a carbon nanoporous framework is characterized by, The carbon nanomaterial comprises at least one of single-walled carbon nanotube, multi-walled carbon nanotube and graphene.

6. The method of claim 1, wherein the supercritical fluid assisted in-situ polymerization to produce a carbon nanoporous framework is characterized by, An organic cosolvent is also introduced into the reactor to mix with the carbon nanomaterial, the strong alkali reagent, the epoxy monomer and the supercritical fluid solvent.

7. The method of claim 1, wherein the supercritical fluid assisted in-situ polymerization to produce a carbon nanoporous framework is characterized by, The reaction pressure in the reactor is controlled to be 7-25 MPa, the reaction temperature is controlled to be 80-100 DEG C, and the substances in the reactor are reacted for 3-5 h, and then the pressure in the reactor is released.

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