Self-supporting porous carbon material as well as preparation method and application thereof

Abstract

The invention discloses a self-supporting porous carbon material as well as a preparation method and application thereof. The self-supporting porous carbon material prepared by the preparation method provided by the invention comprises carbon rings, and the carbon rings form a nematic phase oriented pore structure. When the porous carbon material is used for preparing an electrode, the shape, porosity, catalytic activity, aperture size and distribution of the electrode can be accurately regulated and controlled. The method can be used for preparing ultramicro electrodes, array electrodes and the like, the preparation method is simple and efficient, the regulation and control means are diversified, and the porosity, pore size and distribution of the prepared electrodes can be accurately regulated and controlled. Compared with other electrode materials, the specific discharge capacity of the lithium-oxygen battery adopting the porous carbon material as an electrode is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium oxygen batteries, and in particular relates to a self-supporting porous carbon material for a lithium oxygen battery positive electrode, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-oxygen batteries (LiO2) are one of the most promising next-generation energy storage systems due to their high theoretical energy density (~3500Wh / kg) and environmentally friendly properties. However, a key factor currently limiting LiO2 batteries from achieving their theoretical energy density is cathode passivation induced by discharge products with poor conductivity. During discharge, the discharge products (lithium peroxide) are insoluble in the electrolyte and have poor conductivity. As discharge progresses, they continuously deposit on the electrode surface, clogging the electrode pores and severely hindering oxygen and ion transport, ultimately leading to reaction termination and premature discharge. Therefore, the porosity and pore structure of the cathode material are crucial for regulating the growth and distribution of discharge products and significantly impact the electrochemical performance of LiO2 batteries. Therefore, constructing porous electrodes with fast mass transport and high catalytic efficiency is key to improving battery performance. Porous carbon electrodes, due to their high conductivity, adjustable pore size, low cost, and relative stability, are currently the most widely studied electrode material for LiO2 batteries.

[0003] The methods for preparing porous carbon electrodes mainly include additive-mediated synthesis, template method, substrate in situ growth method, gel carbonization method, etc.

[0004] Current problems in preparing porous carbon electrodes include: 1) The pore structure in the carbon electrode is difficult to precisely adjust, and discharge products accumulate in the electrode pores, blocking the pores, hindering the transport of substances and ions, and limiting the performance of lithium-oxygen batteries; 2) The shape of the prepared electrodes is limited, and the pore size and distribution are difficult to precisely adjust; 3) The conductive polymer binders and commercial conductive substrates used in non-self-supporting carbon electrodes are expensive, and the binders will reduce catalytic activity and affect battery performance. Summary of the Invention

[0005] In view of the above problems, the present invention provides the following technical solutions:

[0006] A method for preparing a porous carbon material, wherein the porous carbon material has a nematic phase structure, that is, the pores in the porous carbon material are unidirectionally oriented pores, and the method for preparing the porous carbon material specifically comprises:

[0007] (1) preparing composite droplets of a sandwich structure, and then mixing monomers with the dispersion of the composite droplets in step (1), wherein the monomers selectively grow on the outside of the composite droplets to obtain a coating material, thereby obtaining core-shell disc-shaped colloidal particles; preferably, the composite droplets of the sandwich structure are prepared with reference to patent documents CN117186446 or CN108854871;

[0008] (2) dispersing the core-shell disc-shaped colloidal particles in a solvent, wherein the core-shell disc-shaped colloidal particles spontaneously form a nematic phase arrangement in the solvent, and after removing the solvent, obtaining a self-supporting film having a nematic phase arrangement, i.e., a carbon precursor; preferably, the self-supporting film comprises a core-shell structure, wherein the core refers to a disc-shaped core formed by the composite droplets, and the shell comprises the coating material; the core-shell structure is a nematic phase arrangement;

[0009] (3) Carbonizing the carbon precursor in step (2) at high temperature in an inert gas atmosphere to obtain the porous carbon material having a nematic phase oriented pore structure.

[0010] According to an embodiment of the present invention, in step (1), the monomer is selected from at least one or a combination of two or more of a phenolic monomer, an aldehyde monomer (such as phenol formaldehyde, resorcinol formaldehyde), polyacrylamide, a silicon source compound, a nitrogen source compound, etc., preferably resorcinol and formaldehyde. Furthermore, the molar ratio of resorcinol to formaldehyde is 1:1-1:100.

[0011] According to an embodiment of the present invention, the nitrogen source compound is at least one selected from urea, aniline, melamine and the like.

[0012] According to an embodiment of the present invention, the silicon source compound is selected from at least one selected from tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the like.

[0013] According to an embodiment of the present invention, the coating material is prepared by reacting monomers. Preferably, the monomers can be used to obtain the coating material by methods known in the art, which are not specifically limited by the present invention. Exemplarily, the coating material is, for example, silicon dioxide, or a polymer obtained by polymerizing phenolic monomers or aldehyde monomers.

[0014] According to an embodiment of the present invention, in step (2), when the coating material is an inorganic material such as silicon dioxide, the process further includes: removing the core in the self-supporting film to obtain a self-supporting film having a hollow ring structure, wherein the hollow ring structure is arranged in a nematic phase, and the material of the self-supporting film of the hollow ring structure is an inorganic material; using the self-supporting film of the hollow ring structure as a second template, and growing a carbon source on the hollow ring structure to obtain a self-supporting film of a nematic phase pore structure, i.e., the carbon precursor, and then performing high-temperature carbonization in step (3). Preferably, the carbon source can grow on the surface of the hollow ring structure of the second template, such as the outer surface.

[0015] Preferably, the inorganic material in the nematic phase pore structure self-supporting film can be carbonized at high temperature and then removed using a solvent to obtain the porous carbon material.

[0016] According to an embodiment of the present invention, the carbon source is, for example, a polymer obtained by polymerizing a phenolic monomer and an aldehyde monomer. Exemplarily, the carbon source is a polymer prepared from resorcinol and formaldehyde, wherein the molar ratio of resorcinol to formaldehyde is 1:1-1:100.

[0017] According to an embodiment of the present invention, the phenolic monomer is phenol, resorcinol, methylphenol (o-methylphenol, m-methylphenol, p-methylphenol), phenylphenol (o-phenylphenol, m-phenylphenol, p-phenylphenol), monosubstituted phenol (p-tert-butylphenol, nonylphenol, cardanol, dihydroxybiphenyl, p-dihydroxydiphenyl sulfide, bisphenol A, bisphenol F, bisphenol S), disubstituted phenol (2,6-dimethylphenol, 2,4-dimethylphenol, diethylphenol, 2-methyl-3-ethylphenol, 2-methyl-4-ethylphenol, 2-methyl- at least one of the following: 5-ethylphenol, 2-methyl-6-ethylphenol, 3-methyl-4-ethylphenol, 3-methyl-5-ethylphenol, 2-ethyl-3-methylphenol, 2-ethyl-4-methylphenol, 2-ethyl-5-methylphenol, 3-ethyl-4-methylphenol, di-n-propylphenol, diisopropylphenol, di-n-butylphenol, di-sec-butylphenol, di-tert-butylphenol, di-n-pentylphenol, diisopentylphenol, di-tert-pentylphenol, di-neobutylphenol), and trisubstituted phenols (trimethylphenol, triethylphenol, tripropylphenol).

[0018] In the present invention, the aldehyde monomer is at least one of formaldehyde, paraformaldehyde, trioxymethylene, acetaldehyde, furfural, etc.

[0019] According to an embodiment of the present invention, when the monomer is selected from a silicon source compound, the specific surface area of ​​the carbon precursor can be increased by high-temperature carbonization or solvent dissolution, thereby increasing the specific surface area of ​​the porous carbon material.

[0020] According to an embodiment of the present invention, when the monomer is selected from a nitrogen source compound, the nitrogen source compound is added during the preparation of the carbon precursor to increase the nitrogen content of the carbon precursor, thereby increasing the nitrogen content of the porous carbon material.

[0021] According to an embodiment of the present invention, in step (1), the core-shell disc-shaped colloidal particles are dispersed in a solvent containing a catalyst to further load the catalyst, thereby regulating the electrode catalytic activity.

[0022] According to an embodiment of the present invention, the catalyst is selected from transition metals or oxides, nitrides, and carbides containing transition metal elements, preferably at least one of platinum, gold, palladium, ruthenium, rhodium, iridium, cerium, cobalt, nickel, and iron.

[0023] According to an embodiment of the present invention, in step (2), the solvent is selected from at least one or a combination of two or more of water, alcohol solvents, alkane solvents, etc., preferably water, ethanol or n-hexane.

[0024] According to an embodiment of the present invention, in step (2), the method for forming the nematic phase is selected from at least one of centrifugation, sedimentation, and the addition of a poor solvent, or a combination of two or more thereof. Preferably, the poor solvent is selected from water, an alcohol solvent, or an alkane solvent, such as n-hexane, water, or ethanol.

[0025] According to an embodiment of the present invention, in step (3), the high-temperature carbonization specifically comprises: placing the self-supporting film in an inert gas atmosphere, heating it to a certain temperature, and then performing high-temperature carbonization. Preferably, the temperature of the high-temperature carbonization is 400 to 3000°C, preferably 600 to 1000°C. Preferably, the heating rate is 1 to 20°C / min, preferably 5 to 10°C / min. Preferably, the high-temperature carbonization time is 0.5 to 48 hours, preferably 1.0 to 4.0 hours.

[0026] According to an embodiment of the present invention, the porosity of the porous carbon material is adjustable, specifically by adjusting the degree of deformation of the carbon precursor, preferably by changing the thickness of the carbon precursor, or by adjusting the degree of crosslinking of the carbon precursor. Furthermore, the thickness of the carbon precursor is preferably adjusted by controlling the polymerization time and monomer concentration; the degree of crosslinking of the carbon precursor is preferably adjusted by varying the amount of crosslinking agent added during polymerization.

[0027] According to an embodiment of the present invention, in the present invention, in steps (1)-(3), the nematic phase arrangement means that the orientation of the central symmetry axis of the core-shell structure or the hollow ring structure is consistent, and the specific position of the core-shell structure or the hollow ring structure can be ordered and / or disordered, thereby preparing the nematic phase oriented pore structure of the porous carbon material of the present invention.

[0028] According to the embodiment of the present invention, in the present invention, the pore size and distribution of the porous carbon material are adjustable, and the specific implementation method is: by adjusting the diameter and distribution of the carbon precursor, or by changing the diameter, height, and size distribution of the corresponding template, the pore size and distribution of the porous carbon material are adjusted.

[0029] According to a preferred embodiment of the present invention, the method for preparing the porous carbon material comprises:

[0030] (A1) preparing core-shell disc-shaped colloidal particles: adding a silicon source compound such as tetraethyl orthosilicate to the composite droplets, adding ammonia water to grow a coating material on the outside of the composite droplets, and obtaining the core-shell disc-shaped colloidal particles, wherein the coating material is silicon dioxide;

[0031] (A2) dispersing the core-shell disc-shaped colloidal particles prepared in step (A1) in a solvent (preferably water or ethanol), and subjecting the core-shell disc-shaped colloidal particles to a nematic phase arrangement by centrifugation or sedimentation or adding a poor solvent. After the solvent is volatilized and the core is removed, a self-supporting membrane having a hollow ring structure is obtained, wherein the hollow ring structure is arranged in a nematic phase, and the material of the self-supporting membrane having the hollow ring structure is silicon dioxide; using the self-supporting membrane having the hollow ring structure as a template and loading a carbon source, a self-supporting membrane having a nematic phase pore structure is obtained, which is a carbon precursor; wherein the carbon source is phenolic aldehyde, and the carbon source is loaded on the surface of the hollow ring structure;

[0032] (A3) carbonizing the self-supporting membrane having a nematic phase pore structure obtained in step (A2) at a high temperature in an inert gas atmosphere, and removing the inorganic material with a solvent to obtain the porous carbon material.

[0033] Preferably, in step (A1), the phenolic monomer is preferably resorcinol. Preferably, in step (A1), the aldehyde monomer is preferably formaldehyde. Optionally, a silicon source compound is optionally added to the mixed dispersion to increase the specific surface area of ​​the cyclic precursor. Further, the silicon source compound is preferably 3-aminopropyltriethoxysilane. Optionally, a nitrogen source compound is optionally added to the mixed dispersion to adjust the nitrogen content in the phenolic ring and thereby adjust the catalytic activity. Further, the nitrogen source compound is preferably aniline. Optionally, a cross-linking agent is optionally added to the mixed dispersion to regulate the degree of cross-linking of the cyclic precursor and thereby regulate the degree of deformation of the cyclic precursor. Further, the cross-linking agent is preferably hexamethylenetetramine.

[0034] Preferably, the composite droplets can be prepared using methods known in the art. For example, the method for preparing the sandwich-structured composite droplets includes dispersing polystyrene spheres in a methanol / water mixed solvent containing azobisisobutyronitrile and polyvinylpyrrolidone, adding 2-ethylhexyl methacrylate, mixing thoroughly, adding decane, passing nitrogen gas through the mixture for deoxygenation, sealing the mixture, and reacting at 60°C to obtain the sandwich-structured composite droplets.

[0035] Preferably, the core-shell disc-shaped colloidal particles prepared in step (A1) are optionally mixed with the catalyst to allow the core-shell disc-shaped colloidal particles to load the catalyst.

[0036] The present invention also provides a porous carbon material, which is obtained by the above-mentioned preparation method.

[0037] According to an embodiment of the present invention, the porous carbon material includes carbon rings constituting a nematically oriented pore structure.

[0038] According to an embodiment of the present invention, the nematically oriented pore structure refers to a structure in which carbon rings in the porous carbon material are uniformly oriented overall but disordered in position.

[0039] According to an embodiment of the present invention, the carbocyclic ring is obtained by carbonizing a carbon precursor, wherein the carbon precursor has the meaning as described above. Preferably, the carbocyclic ring is obtained by carbonizing the carbon precursor, or optionally mixing the carbon precursor with a nitrogen source compound and a catalyst at a high temperature.

[0040] According to an embodiment of the present invention, the material of the carbon precursor includes at least a polymer, or optionally an inorganic material. Preferably, the inorganic material is selected from silicon dioxide. Preferably, the polymer is selected from at least one or a combination of two or more of phenol formaldehyde polymer, resorcinol formaldehyde polymer, polyacrylamide, etc., preferably resorcinol formaldehyde polymer.

[0041] According to an embodiment of the present invention, the nitrogen source compound is selected from nitrogen-containing compounds. Preferably, the nitrogen-containing compound is selected from at least one of urea, aniline, melamine, and the like.

[0042] According to an embodiment of the present invention, the catalyst is selected from transition metals or oxides, nitrides, carbides, etc. containing transition metal elements. Preferably, the noble metal is selected from at least one of platinum, gold, palladium, ruthenium, rhodium, iridium, cerium, cobalt, nickel, iron, etc.

[0043] According to an embodiment of the present invention, the catalytic activity of the porous carbon material is adjustable. Preferably, the catalytic activity of the porous carbon material is adjusted by adjusting the nitrogen content in the porous carbon material or adjusting the content of the catalyst. Preferably, the nitrogen content is 0.1%-30%.

[0044] According to an embodiment of the present invention, the diameter, height, or difference between the inner and outer diameters of the carbon precursor can be controlled. Preferably, the diameter of the carbon precursor is 0.5 microns to 10 microns. Preferably, the height of the carbon precursor is 50 nanometers to 5000 nanometers. Preferably, when the carbon precursor is a hollow ring structure, the difference between its inner and outer diameters is 5 nanometers to 3000 nanometers.

[0045] According to an embodiment of the present invention, the porosity of the porous carbon material is adjustable, and the porosity is preferably 20% to 99%, for example 97.6%.

[0046] According to an embodiment of the present invention, the specific surface area of ​​the porous carbon material is 10 m 2 / g-5000m 2 / g.

[0047] According to an embodiment of the present invention, the catalytic activity, specific surface area, porosity, pore size and distribution of the porous carbon material are adjustable.

[0048] According to an embodiment of the present invention, the porous carbon material has self-supporting properties.

[0049] The present invention also provides an electrode, which comprises the porous carbon material.

[0050] The present invention also provides the use of the porous carbon material in a lithium-oxygen battery, preferably as a positive electrode of the lithium-oxygen battery.

[0051] Compared with the existing preparation method, the advantages and positive effects of the present invention are:

[0052] 1. Annular particles are used to construct multi-level porous carbon electrodes. The micron-scale cavities of the annular particles themselves are conducive to the large-scale storage of discharge products, and the nano-scale pore structure is conducive to the material transport and ion transfer during discharge. The electrode can maintain a relatively fast material transport rate during discharge, and the electrode has a high porosity (up to 97.6%), which provides a transmission channel for the rapid diffusion of oxygen and ions. The method of directly constructing the electrode by annular carbon colloidal particles can accurately control the catalytic activity, porosity, pore size and its distribution of the electrode. During the synthesis, the present invention can accurately adjust the pore size and distribution, porosity and catalytic activity of the porous carbon material by regulating the size, cross-linking degree and catalytic activity of the single annular particle; by changing the mold shape when preparing the self-supporting film, porous carbon materials of any shape can be prepared. When the porous carbon material with an oriented pore structure of the present invention is used in a lithium-oxygen battery, the lithium-oxygen battery has excellent performance, and the discharge specific capacity is increased by more than 50% compared with the disordered pore structure.

[0053] 2. The catalytic activity, porosity, pore size, and void distribution of the porous carbon material of the present invention can be adjusted, and the control method is flexible and precise. For example, the present invention can add a nitrogen source compound during the synthesis of the carbon precursor or load the carbon precursor with precious metal nanoparticles, and then the catalytic activity of the self-supporting porous carbon electrode can be controlled after carbonization; by changing the thickness or degree of crosslinking of the carbon precursor, the degree of deformation can be controlled, and self-supporting porous carbon electrodes with different porosities can be prepared after carbonization; by preparing carbon precursors of different sizes, carbon electrodes with different pore sizes can be prepared after carbonization.

[0054] 3. Low cost, multiple active sites, no need for support on other substrates, and can be used as a standalone positive electrode material; avoiding the use of binders, reducing side reactions, and making the electrode preparation method simple and efficient. Self-supporting porous carbon electrodes do not need to be supported on other substrates and can be used as a standalone positive electrode material, eliminating the need for binders, reducing side reactions during discharge, and achieving low preparation costs.

[0055] 4. The present invention prepares self-supporting porous carbon materials of various shapes by adding a carbon precursor dispersion dropwise to molds of varying shapes, allowing the material to aggregate. Following solvent volatilization and carbonization, the materials can be used to prepare electrodes of various shapes and sizes, enabling the fabrication of ultramicroelectrodes, array electrodes, and the like. Furthermore, the preparation method is simple and efficient, and diverse control methods are available. The porosity, pore size, and distribution of the prepared electrodes can be precisely controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a scanning electron microscope image of the porous carbon material prepared in Example 1.

[0057] Figure 2 These are scanning electron microscope images and transmission electron microscope images of the porous carbon electrode prepared in Example 1.

[0058] Figure 3 These are scanning electron microscope images and transmission electron microscope images of the porous carbon electrode prepared in Example 2.

[0059] Figure 4 These are scanning electron microscope images and transmission electron microscope images of the porous carbon electrode prepared in Example 3.

[0060] Figure 5 Schematic diagram of lithium-oxygen battery assembly (a) and battery discharge curve of the porous carbon electrode prepared in Examples 1-3 as the positive electrode of the lithium-oxygen battery (b).

[0061] Figure 6 This is a transmission electron micrograph of the carbon electrode loaded with ruthenium dioxide nanoparticles prepared in Example 5.

[0062] Figure 7 These are scanning electron microscope images and transmission electron microscope images of the porous carbon electrode prepared in Comparative Example 1.

[0063] Figure 8 The battery discharge curve of the porous carbon electrode prepared in Comparative Example 2 as the positive electrode of the lithium-oxygen battery. DETAILED DESCRIPTION

[0064] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0065] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0066] Example 1

[0067] Preparation of porous carbon materials with nematically oriented pore structures:

[0068] 1) 0.30 g of azobisisobutyronitrile, 3.78 g of polyvinylpyrrolidone (K30), 180.00 g of ethanol, and 8.00 g of polystyrene spheres (1.20 μm) were ultrasonically mixed, and then 6.00 mL of styrene, 20.00 mL of ethanol, 6.00 mL of water, and 0.30 mL of methacryloyloxyethyltrimethylammonium chloride were added. After sealing, nitrogen was passed through the mixture to deoxygenate it, and the mixture was sealed. The mixture was reacted in a 70°C water bath under magnetic stirring for 1 h, and then dispersed and washed with ethanol and water to obtain modified polystyrene spheres. 0.10g of azobisisobutyronitrile, 0.40g of polyvinylpyrrolidone (K30), 32.00g of methanol, 8.00g of water, and 1.00g of modified polystyrene spheres (1.20μm) were ultrasonically mixed and then added with 1.28g of 2-ethylhexyl methacrylate and stirred at room temperature for 20min. Then, 6.84mL of n-decane was added, the mixture was sealed, deoxygenated with nitrogen, and then sealed again. The mixture was heated in a 60°C water bath with magnetic stirring for 18h to produce a sandwich-shaped composite droplet template. This was then dispersed into a mixed solution of 121.20g of methanol, 20.88g of water, 20.96mL of ammonia water, and 9.60mL of tetraethyl orthosilicate. The mixture was reacted at 30°C for 7h, and then dispersed and centrifuged with n-butanol to obtain polystyrene core-shell disc-shaped colloidal particles with silica growth on the sides. The particles were dispersed in 98% sulfuric acid, heated at 50°C for 30 min, and then dispersed in water and washed by centrifugation to obtain an aqueous dispersion of core-shell disc-shaped colloidal particles with a concentration of 10 mg / mL.

[0069] 2) 0.2 mL of the aqueous dispersion of disc-shaped colloidal particles was added to a columnar sample cell and dried naturally to obtain a self-supporting film with core-shell disc-shaped colloidal particles arranged in a nematic phase. The self-supporting film was placed in a tube furnace and heated at 400°C for 2 hours. The polystyrene discs were removed to obtain a self-supporting film with a nematic pore structure composed of silica rings. Figure 1 .Depend on Figure 1 It can be seen that in the self-supporting film with a nematic phase pore structure prepared in this embodiment, the silicon dioxide rings are all oriented along the axial direction and are disordered in position.

[0070] 3) The self-supporting film with a nematic pore structure was placed in a solution containing 0.06g of resorcinol, 0.82mL of formaldehyde solution, 0.16g of polyvinyl pyrrolidone, 4.20g of methanol, and 0.40g of water. The reaction was allowed to proceed at room temperature for 4 hours, and a layer of phenolic acid was grown on the silica ring. The film was carefully washed with water three times, dried, and transferred to a tube furnace. After heating at 800°C for 4 hours under a nitrogen atmosphere, the silica was removed with 20% HF to obtain a porous carbon material with a nematic pore structure composed of hollow carbon rings with a carbon layer thickness of 14nm. Scanning electron microscopy images are shown in Figure 2. Figure 2 In (a), such as Figure 2As shown in (a), the hollow carbon rings in the porous carbon material are all oriented along the axial direction and are disordered in position; the transmission electron microscopy image is shown in Figure 2 In (b), the carbon ring is a hollow structure, and the thickness of the carbon layer is about 14 nm.

[0071] Example 2

[0072] Preparation of porous carbon materials with nematic phase-oriented pore structures of different carbon layer thicknesses:

[0073] 1) 0.30 g of azobisisobutyronitrile, 3.78 g of polyvinylpyrrolidone (K30), 180.00 g of ethanol, and 8.00 g of polystyrene spheres (1.20 μm) were ultrasonically mixed, and then 6.00 mL of styrene, 20.00 mL of ethanol, 6.00 mL of water, and 0.30 mL of methacryloyloxyethyltrimethylammonium chloride were added. After sealing, nitrogen was passed through the mixture to deoxygenate it, and the mixture was sealed. The mixture was reacted in a 70°C water bath under magnetic stirring for 1 h, and then dispersed and washed with ethanol and water to obtain modified polystyrene spheres. 0.10g of azobisisobutyronitrile, 0.40g of polyvinylpyrrolidone (K30), 32.00g of methanol, 8.00g of water, and 1.00g of modified polystyrene spheres (1.20μm) were ultrasonically mixed and then added with 1.28g of 2-ethylhexyl methacrylate and stirred at room temperature for 20min. Then, 6.84mL of n-decane was added, the mixture was sealed, deoxygenated with nitrogen, and then sealed again. The mixture was heated in a 60°C water bath with magnetic stirring for 18h to produce a sandwich-shaped composite droplet template. This was then dispersed into a mixed solution of 121.20g of methanol, 20.88g of water, 20.96mL of ammonia water, and 9.60mL of tetraethyl orthosilicate. The mixture was reacted at 30°C for 7h, and then dispersed and centrifuged with n-butanol to obtain polystyrene core-shell disc-shaped colloidal particles with silica growth on the sides. The particles were dispersed in 98% sulfuric acid, heated at 50°C for 30 min, and then dispersed in water and washed by centrifugation to obtain an aqueous dispersion of core-shell disc-shaped colloidal particles with a concentration of 10 mg / mL.

[0074] 2) 0.2 mL of the aqueous dispersion of disc-shaped colloidal particles was added to a cylindrical sample cell and allowed to dry naturally, yielding a self-supporting film containing core-shell disc-shaped colloidal particles arranged in a nematic phase. This self-supporting film was heated in a tube furnace at 400°C for 2 hours. The polystyrene discs were removed, yielding a self-supporting film with a nematic pore structure composed of silica rings. In the self-supporting film with a nematic pore structure prepared in this example, the silica rings were axially oriented and disordered.

[0075] 3) The self-supporting film with a nematic pore structure was added to a solution containing 0.12g of resorcinol, 1.64mL of formaldehyde solution, 0.16g of polyvinyl pyrrolidone, 4.20g of methanol, and 0.40g of water. The reaction was allowed to proceed at room temperature for 4 hours, and a layer of phenolic acid was grown on the silica ring. The film was carefully washed with water three times, dried, and transferred to a tube furnace. After heating at 800°C for 4 hours under a nitrogen atmosphere, the silica was removed with 20% HF to obtain a porous carbon material with a nematic pore structure composed of hollow carbon rings with a carbon layer thickness of 20nm. Scanning electron microscopy images are shown in Figure 2. Figure 3 (a), such as Figure 3 As shown in (a), the hollow carbon rings in the porous carbon material are all oriented along the axial direction and are disordered in position; the transmission electron microscopy image is shown in Figure 3 (b), the carbon ring has a hollow structure, and the thickness of the carbon layer is about 20 nm.

[0076] Example 3

[0077] Preparation of porous carbon materials with nematic phase-oriented pore structures of different carbon layer thicknesses:

[0078] 1) 0.30 g of azobisisobutyronitrile, 3.78 g of polyvinylpyrrolidone (K30), 180.00 g of ethanol, and 8.00 g of polystyrene spheres (1.20 μm) were ultrasonically mixed, and then 6.00 mL of styrene, 20.00 mL of ethanol, 6.00 mL of water, and 0.30 mL of methacryloyloxyethyltrimethylammonium chloride were added. After sealing, nitrogen was passed through the mixture to deoxygenate it, and the mixture was sealed. The mixture was reacted in a 70°C water bath under magnetic stirring for 1 h, and then dispersed and washed with ethanol and water to obtain modified polystyrene spheres. 0.10g of azobisisobutyronitrile, 0.40g of polyvinylpyrrolidone (K30), 32.00g of methanol, 8.00g of water, and 1.00g of modified polystyrene spheres (1.20μm) were ultrasonically mixed and then added with 1.28g of 2-ethylhexyl methacrylate and stirred at room temperature for 20min. Then, 6.84mL of n-decane was added, the mixture was sealed, deoxygenated with nitrogen, and then sealed again. The mixture was heated in a 60°C water bath with magnetic stirring for 18h to produce a sandwich-shaped composite droplet template. This was then dispersed into a mixed solution of 121.20g of methanol, 20.88g of water, 20.96mL of aqueous ammonia, and 9.60mL of tetraethyl orthosilicate. The mixture was reacted at 30°C for 7h, and then dispersed and centrifuged with n-butanol to obtain polystyrene core-shell disc-shaped colloidal particles with silica growth on the sides. The particles were dispersed in 98% sulfuric acid, heated at 50°C for 30 min, and then dispersed in water and washed by centrifugation to obtain an aqueous dispersion of core-shell disc-shaped colloidal particles with a concentration of 10 mg / mL.

[0079] 2) 0.2 mL of the aqueous dispersion of disc-shaped colloidal particles was added to a cylindrical sample cell and allowed to dry naturally, yielding a self-supporting film containing core-shell disc-shaped colloidal particles arranged in a nematic phase. This self-supporting film was heated in a tube furnace at 400°C for 2 hours. The polystyrene discs were removed, yielding a self-supporting film with a nematic pore structure composed of silica rings. In the self-supporting film with a nematic pore structure prepared in this example, the silica rings were axially oriented and disordered.

[0080] 3) The self-supporting film with a nematic pore structure was added to a solution containing 0.24g of resorcinol, 3.28mL of formaldehyde solution, 0.16g of polyvinyl pyrrolidone, 4.20g of methanol, and 0.40g of water. The reaction was allowed to proceed at room temperature for 4 hours, and a layer of phenolic acid was grown on the silica ring. The film was carefully washed with water three times, dried, and transferred to a tube furnace. After heating at 800°C for 4 hours under a nitrogen atmosphere, the silica was removed with 20% HF to obtain a porous carbon material with an oriented pore structure consisting of hollow carbon rings with a carbon layer thickness of 40nm. Scanning electron microscopy images are shown in Figure 2. Figure 4 (a), such as Figure 4 As shown in (a), the hollow carbon rings in the porous carbon material are all oriented along the axial direction and are disordered in position; the transmission electron microscopy image is shown in Figure 4 (b), the carbon ring has a hollow structure, and the thickness of the carbon layer is about 20 nm.

[0081] Example 4

[0082] The porous carbon material prepared in Example 1-3 was used as the positive electrode of the lithium oxygen battery, the electrolyte was a 0.5M dimethyl sulfoxide solution of bistrifluoromethanesulfonyl imide, and the negative electrode was a metal lithium sheet. Figure 5 The cells were assembled in the order of (a) into CR2032 button cells, designated as cells 1-3, and transferred into a polytetrafluoroethylene test container.

[0083] Oxygen was passed through the polytetrafluoroethylene container for 10 minutes to remove the argon. The container was left to stand for 3 hours before the electrochemical test to allow oxygen to saturate the electrolyte. The test conditions were: current density 0.1 mA / cm 2 , cut-off voltage 2.1V, oxygen flow rate 10mL / min.

[0084] The test shows that the first cycle discharge capacity of batteries 1-3 is 26200mAh / g, 17800mAh / g, and 8570mAh / g respectively. Figure 5 In (b), it can be seen that at the same pore size, the first-cycle discharge capacity of the battery of the carbon electrode with a nematic phase-oriented pore structure increases as the thickness of the carbon layer decreases.

[0085] Example 5

[0086] The preparation of the porous carbon material with a nematic phase pore structure supporting a noble metal catalyst (ruthenium dioxide nanoparticles) is as follows:

[0087] The porous carbon material with a nematic phase pore structure prepared in Example 1 was dispersed in 0.5 mL of a 0.1 M ruthenium trichloride solution, and then 50 μL of a 1 M sodium hydroxide solution was added. After reacting at room temperature for 5 h, the mixture was washed with water three times, dried at 80° C., and heated in air at 150° C. for 2 h to obtain a porous carbon material with a nematic phase pore structure loaded with ruthenium dioxide nanoparticles. The transmission electron microscopy image is shown in FIG. Figure 6 , it can be seen that the diameter of ruthenium dioxide nanoparticles is about 2nm, and they are evenly dispersed on the carbon ring without aggregation.

[0088] Comparative Example 1

[0089] Preparation of porous carbon materials with disordered pore structures:

[0090] 1) 0.2 mL of the core-shell disc-shaped colloidal particles of Example 2 were dispersed and centrifuged in tetrahydrofuran to remove the core, and then dispersed and centrifuged in ethanol and water to wash to obtain silica rings.

[0091] 2) The water dispersion of the silica rings in step 1) was also dispersed into a circular mold and dried at 35° C. to obtain a silica self-supporting film. The self-supporting film was placed in a tube furnace and heated at 400° C. for 2 h.

[0092] 3) The heat-treated self-supporting film was added to a solution containing 0.12g of resorcinol, 1.64mL of formaldehyde solution, 0.16g of polyvinyl pyrrolidone, 4.20g of methanol, and 0.40g of water. The reaction was allowed to proceed at room temperature for 4 hours to grow phenolic aldehyde on the silica rings. The film was carefully washed with water three times, dried, and transferred to a tube furnace. After heating at 800°C for 4 hours under a nitrogen atmosphere, the silica was removed with 20% HF to obtain a porous carbon material with a disordered pore structure consisting of hollow carbon rings with a carbon layer thickness of 20nm, which served as a comparative carbon material. Scanning electron microscopy images are shown in FIG. Figure 7 (a), transmission electron microscopy image Figure 7 Middle (b).

[0093] Depend on Figure 7 It can be seen that in the comparative carbon material of this comparative example, the hollow carbon rings are disordered in orientation and arrangement.

[0094] Comparative Example 2

[0095] The lithium-oxygen battery was assembled and its electrochemical performance was tested with reference to Example 4. The difference was that the porous carbon electrode prepared in Comparative Example 1 was used as the positive electrode of the lithium-oxygen battery, which was recorded as Battery 4. The test showed that the first cycle discharge capacity of Battery 4 was 10800 mAh / g. The discharge test curve of Battery 4 is shown in FIG. Figure 8 .

[0096] It can be seen that under the same carbon layer thickness, the same number of pores, and the same pore diameter, the battery discharge capacity of the carbon electrode using the nematic phase pore structure of the present invention can reach 17800 mAh / g, which is 165% of the battery prepared with disordered pores.

[0097] The above describes exemplary embodiments of the present invention. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a porous carbon material, characterized in that: The porous carbon material has a nematic phase structure, and the method for preparing the porous carbon material specifically comprises: (1) preparing composite droplets of a sandwich structure, and then mixing monomers with the dispersion of the composite droplets in step (1), so that the monomers selectively grow on the outside of the composite droplets to obtain a coating material, thereby obtaining core-shell disc-shaped colloidal particles; (2) dispersing the core-shell disc-shaped colloidal particles in a solvent, wherein the core-shell disc-shaped colloidal particles spontaneously form a nematic phase arrangement in the solvent, and after removing the solvent, obtaining a self-supporting film having a nematic phase arrangement, namely a carbon precursor; (3) Carbonizing the carbon precursor in step (2) at high temperature in an inert gas atmosphere to obtain the porous carbon material having a nematic phase oriented pore structure.

2. The preparation method according to claim 1, characterized in that In step (1), the monomer is selected from at least one or a combination of two or more of phenolic monomers, aldehyde monomers, polyacrylamide, silicon source compounds, nitrogen source compounds, etc. Preferably, the nitrogen source compound is selected from at least one of urea, aniline, melamine and the like. Preferably, the silicon source compound is selected from at least one of tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the like. Preferably, the coating material is prepared by monomer reaction.

3. The preparation method according to claim 1 or 2, characterized in that In step (2), the self-supporting film comprises a core-shell structure, wherein the core refers to a disc-shaped core formed by the composite droplets, and the shell comprises the coating material; and the core-shell structure is arranged in a nematic phase. Preferably, in step (2), when the coating material is an inorganic material, it also includes: removing the core in the self-supporting membrane to obtain a self-supporting membrane with a hollow ring structure, the hollow ring structure is arranged in a nematic phase, and the material of the self-supporting membrane of the hollow ring structure is an inorganic material; using the self-supporting membrane of the hollow ring structure as a second template, and growing a carbon source on the hollow ring structure to obtain a self-supporting membrane with a nematic phase pore structure, which is the carbon precursor. Preferably, the inorganic material in the nematic phase pore structure self-supporting film can be carbonized at high temperature and then removed using a solvent to obtain the porous carbon material. Preferably, the carbon source is a polymer obtained by polymerizing phenolic monomers and aldehyde monomers.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (1), the core-shell disc-shaped colloidal particles are dispersed in a solvent containing a catalyst to further load the catalyst, thereby regulating the electrode catalytic activity. Preferably, the catalyst is selected from transition metals or oxides, nitrides, and carbides containing transition metal elements, preferably at least one of platinum, gold, palladium, ruthenium, rhodium, iridium, cerium, cobalt, nickel, and iron. Preferably, in step (2), the solvent is selected from at least one of water, alcohol solvents, alkane solvents, etc., or a combination of two or more thereof. Preferably, in step (2), the method for forming the nematic phase arrangement is selected from at least one or a combination of two or more of centrifugation, sedimentation, and addition of a poor solvent. Preferably, in step (3), the high-temperature carbonization specifically comprises: placing the self-supporting film in an inert gas atmosphere, heating it to a certain temperature, and then performing high-temperature carbonization.

5. The preparation method according to any one of claims 1 to 4, characterized in that The method for preparing the porous carbon material comprises: (A1) preparing core-shell disc-shaped colloidal particles: adding a silicon source compound to the composite droplets, adding ammonia water to grow a coating material on the outside of the composite droplets, and obtaining the core-shell disc-shaped colloidal particles, wherein the coating material is silicon dioxide; (A2) dispersing the core-shell disc-shaped colloidal particles prepared in step (A1) in a solvent, and forming a nematic phase arrangement by centrifugation or sedimentation or adding a poor solvent. After the solvent is volatilized and the core is removed, a self-supporting membrane having a hollow ring structure is obtained, wherein the hollow ring structure is arranged in a nematic phase, and the material of the self-supporting membrane having the hollow ring structure is silicon dioxide; using the self-supporting membrane having the hollow ring structure as a template and loading a carbon source, a self-supporting membrane having a nematic phase pore structure is obtained, which is a carbon precursor; wherein the carbon source is phenolic aldehyde, and the carbon source is loaded on the surface of the hollow ring structure; (A3) carbonizing the self-supporting membrane having a nematic phase pore structure obtained in step (A2) at a high temperature in an inert gas atmosphere, and removing the inorganic material with a solvent to obtain the porous carbon material.

6. A porous carbon material, characterized in that The porous carbon material is obtained by the preparation method according to any one of claims 1 to 5.

7. The porous carbon material according to claim 6, characterized in that The porous carbon material includes carbon rings, which form a nematically oriented pore structure. Preferably, the nematically oriented pore structure refers to a structure in which the carbon rings in the porous carbon material are uniformly oriented as a whole but disordered in position. Preferably, the carbon ring is obtained by carbonizing a carbon precursor.

8. The porous carbon material according to claim 6 or 7, characterized in that The material of the carbon precursor includes at least a polymer, or optionally an inorganic material. Preferably, the porosity of the porous carbon material is 20% to 99%. Preferably, the specific surface area of ​​the porous carbon material is 10 m 2 / g-5000m 2 / g. Preferably, the porous carbon material is self-supporting.

9. An electrode, characterized in that The electrode comprises the porous carbon material according to any one of claims 6 to 8.

10. Use of the porous carbon material according to any one of claims 6 to 8 and / or the electrode according to claim 9 in a lithium-oxygen battery.

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