CN117059828A - Integrated gradient porosity electrode material, preparation method thereof and all-vanadium redox flow battery - Google Patents
Integrated gradient porosity electrode material, preparation method thereof and all-vanadium redox flow battery Download PDFInfo
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/96—Carbon-based electrodes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
- H01M8/184—Regeneration by electrochemical means
- H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Abstract
The invention discloses an integrated gradient porosity electrode material, a preparation method thereof and an all-vanadium redox flow battery, wherein the method comprises the following steps: (1) Dipping one side of the pre-oxidized felt into a thermosetting resin solution to obtain a pre-oxidized felt material with one side dipped with resin; (2) Heating and curing the pre-oxidized felt material with one side impregnated with resin to obtain a pre-oxidized felt material with one side containing resin; (3) Immersing the other side of the pre-oxidized felt material with one side containing resin in a mixed solution of tertiary butanol and water to obtain a pre-oxidized felt material with one side containing resin and the other side immersed in the mixed solution; (4) Pre-freezing the pre-oxidized felt material with one side containing resin and the other side immersed in the mixed solution into solid, and then performing freeze drying to obtain the pre-oxidized felt material with one side containing resin and the other side having an aerogel structure; (5) And carbonizing, graphitizing and activating the pre-oxidized felt material with the resin on one side and the aerogel structure on the other side.
Description
Technical Field
The invention belongs to the field of all-vanadium redox flow batteries, and relates to an integrated gradient porosity electrode material for an all-vanadium redox flow battery, a preparation method of the electrode material and the all-vanadium redox flow battery.
Background
all-Vanadium Redox Flow Batteries (VRFB) are one of the most attractive energy storage technologies that can work in concert with renewable sources of energy such as solar and wind energy that are intermittent. VRFB has many advantages such as high battery efficiency, large energy capacity, small influence on environment, flexible design of power, and the like.
Electrode porosity is a very important parameter in influencing the performance of all vanadium redox flow batteries. Most of the existing all-vanadium redox flow battery electrodes have a porous structure with constant porosity. However, according to the structural characteristics of the all-vanadium redox flow battery, the concentration of the chemical active material is highest at the interface between the electrode and the bipolar plate, the electrochemical reaction rate is fastest, and the concentration of the chemical active material gradually decreases towards the ion exchange membrane, so that the electrochemical reaction rate at the membrane-near side is slower. Therefore, the constant porosity is disadvantageous in uniform distribution of the chemically active substance, may cause a decrease in the overall utilization of the electrode material, and may easily cause polarization phenomenon of the battery.
In the presently disclosed literature, gradient porosity is typically achieved by layering two or more layers of graphite or carbon fiber mats having different bulk densities, which treatment inevitably results in contact resistance between the different layers of mats, thereby increasing the internal resistance of the overall cell and affecting the cell performance, particularly voltage and energy efficiency.
Accordingly, there is a need to develop an integrated electrode material having gradient porosity and improved voltage and energy efficiencies.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an integrated gradient porosity electrode material for an all-vanadium redox flow battery and a preparation method thereof. The preparation method takes the pre-oxidized felt as an integrated gradient porosity electrode material precursor, forms different porosities in areas with different thicknesses by means of thermosetting resin and freeze drying technology, and obtains the integrated gradient porosity electrode material through carbonization, graphitization and activation. The gradient distribution of porosity is designed on the integrated electrode, so that contact resistance among different layers of felts is avoided, the internal resistance of the battery is reduced, and the voltage efficiency and the energy efficiency of the battery are improved. The porosity of the integrated gradient porosity electrode material is changed in a gradient manner along the thickness direction, the porosity of the near-bipolar plate side is lower than that of the near-ion exchange membrane side, so that the electrode permeability is increased from the near-bipolar plate side to the near-ion exchange membrane side, the transfer of chemical active substances on the near-ion exchange membrane side is obviously enhanced, the electrochemical reaction rate is obviously improved, and the electrochemical polarization and concentration polarization of a battery can be reduced. In the invention, the electrode material near the bipolar plate side contains resin carbon, has lower porosity and compact structure, is beneficial to reducing the contact resistance between the electrode and the bipolar plate and increases the path of electrons conducted to the bipolar plate side. The invention adopts the freeze drying technology to lead the electrode material near the ion exchange membrane to have higher porosity and more developed pore structure, thereby leading the electrode material near the membrane to have larger specific surface area. Therefore, the integrated gradient porosity electrode material for the all-vanadium redox flow battery has the advantages of enabling the flowing distribution of electrolyte to be more uniform, improving the mass transfer process of the electrode, reducing the internal resistance of the battery and improving the voltage efficiency and the energy efficiency of the battery.
Specifically, the invention provides a preparation method of an integrated gradient porosity electrode material for an all-vanadium redox flow battery, which comprises the following steps:
(1) Dipping one side of the pre-oxidized felt into a thermosetting resin solution to obtain a pre-oxidized felt material with one side dipped with resin;
(2) Heating and curing the pre-oxidized felt material with one side impregnated with the resin obtained in the step (1) to obtain a pre-oxidized felt material with one side containing the resin;
(3) Immersing the other side of the pre-oxidized felt material with one side containing the resin obtained in the step (2) in a mixed solution of tertiary butanol and water to obtain the pre-oxidized felt material with one side containing the resin and the other side immersed in the mixed solution, wherein the mass of the tertiary butanol is 3% -19% of the total mass of the tertiary butanol and the water in the mixed solution of the tertiary butanol and the water;
(4) Pre-freezing the pre-oxidized felt material with one side containing the resin and the other side immersed in the mixed solution obtained in the step (3) into solid, and then performing freeze drying to obtain the pre-oxidized felt material with one side containing the resin and the other side having an aerogel structure;
(5) And (3) carbonizing, graphitizing and activating the pre-oxidized felt material with the resin on one side and the aerogel structure on the other side obtained in the step (4) to obtain the integrated gradient porosity electrode material.
In one or more embodiments, in step (1), the pre-oxidized felt is a polyacrylonitrile-based pre-oxidized felt, a viscose-based pre-oxidized felt, or an asphalt-based pre-oxidized felt.
In one or more embodiments, in step (1), the thermosetting resin solution is formed by mixing a thermosetting resin and a solvent.
In one or more embodiments, in step (1), the time of the impregnation is 3 to 10 minutes.
In one or more embodiments, in step (1), the thickness H of the portion of the pre-oxidized mat immersed in the thermosetting resin solution 1 10% -20% of the total thickness H of the pre-oxidized felt, wherein in the step (3), the thickness H of the part of the pre-oxidized felt material with resin at one side immersed in the mixed solution of the tertiary butanol and the water 2 40% -60% of the total thickness H of the pre-oxidized fiber felt, and (H-H) 1 -H 2 ) The ratio of H is 30% -40%.
In one or more embodiments, the thermosetting resin is selected from one or more of phenolic resin, epoxy resin, urea resin, melamine formaldehyde resin, unsaturated polyester resin, and polyurethane.
In one or more embodiments, the solvent is selected from one or more of water and an alcoholic solvent.
In one or more embodiments, the mass ratio of the solvent to the thermosetting resin in the thermosetting resin solution is (65 to 85) to (10 to 25).
In one or more embodiments, in the step (2), the curing temperature is 80 to 200 ℃, and the curing time is 1 to 2 hours.
In one or more embodiments, in step (3), the mixed solution of t-butanol and water further comprises a nanocarbon material.
In one or more embodiments, in step (3), the time of the impregnation is 3 to 10 minutes.
In one or more embodiments, the ratio of the mass of the nanocarbon material to the total mass of tert-butanol and water is (0.5-2.5) to (4-10).
In one or more embodiments, in the step (4), the pre-frozen temperature is-60 to-20 ℃.
In one or more embodiments, in the step (4), the pre-freezing time is 1 to 3 hours.
In one or more embodiments, in step (4), the freeze-drying time is 24 to 72 hours.
In one or more embodiments, in the step (5), in the carbonization treatment, the carbonization temperature is 1000-1600 ℃, the heating rate is 5-50 ℃/min, the heat preservation time is 0.5-2 h, and the atmosphere is nitrogen or argon.
In one or more embodiments, in the step (5), in the graphitization treatment, the graphitization temperature is 1800-2600 ℃, the heating rate is 5-50 ℃/min, the heat preservation time is 0.5-2 h, and the atmosphere is argon.
In one or more embodiments, in step (5), the activation treatment is performed by steam activation, air activation, or CO 2 Activating, wherein the activating temperature is 300-600 ℃, the heating rate is 5-30 ℃/min, and the heat preservation time is 1-4 h.
The invention provides an integrated gradient porosity electrode material prepared by adopting the method of any embodiment of the invention.
In one or more embodiments, the porosity of the integrated gradient porosity electrode material is gradient distributed along the thickness direction, the porosity of the part impregnated with the thermosetting resin solution is 70% -80%, the porosity of the part not impregnated with the thermosetting resin solution and the mixed solution of tertiary butanol and water is 80% -90%, and the porosity of the part impregnated with the mixed solution of tertiary butanol and water is 90% -99%.
The invention provides an all-vanadium redox flow battery, which comprises the integrated gradient porosity electrode material according to any embodiment of the invention.
Drawings
FIG. 1 is a schematic diagram of an integrated gradient porosity electrode material of the present invention.
Detailed Description
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.
The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
Herein, "comprising," "including," "containing," and similar terms are intended to cover the meaning of "consisting essentially of … …" and "consisting of … …," e.g., "a consisting essentially of B and C" and "a consisting of B and C" should be considered to have been disclosed herein when "a comprises B and C" is disclosed herein.
In this document, all features such as values, amounts, and concentrations that are defined as ranges of values or percentages are for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.
Herein, unless otherwise specified, percentages refer to mass percentages, and proportions refer to mass ratios.
Herein, when embodiments or examples are described, it should be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.
The invention provides a preparation method of an integrated gradient porosity electrode material for an all-vanadium redox flow battery, which comprises the following steps:
(1) Dipping one side of the pre-oxidized felt into a thermosetting resin solution to obtain a pre-oxidized felt material with one side dipped with resin;
(2) Heating and curing the pre-oxidized felt material with one side impregnated with the resin obtained in the step (1) to obtain a pre-oxidized felt material with one side containing the resin;
(3) Immersing the other side of the pre-oxidized felt material with the resin on one side obtained in the step (2) in a mixed solution of tertiary butanol and water to obtain a pre-oxidized felt material with the resin on one side and the mixed solution on the other side;
(4) Pre-freezing the pre-oxidized felt material with one side containing resin and the other side immersed in the mixed solution obtained in the step (3) into solid, and then performing freeze drying to obtain the pre-oxidized felt material with one side containing resin and the other side having an aerogel structure;
(5) And (3) carbonizing, graphitizing and activating the pre-oxidized felt material with the resin on one side and the aerogel structure on the other side, which are obtained in the step (4), so as to obtain the integrated gradient porosity electrode material.
In the step (1), the pre-oxidized felt may be a polyacrylonitrile-based pre-oxidized felt, a viscose-based pre-oxidized felt or an asphalt-based pre-oxidized felt. The pre-oxidized felt is used as a porous material with conductive performance, can provide reaction sites for active substances, is used as a matrix of an electrode material, can be added with resin in a dipping mode, forms a pore structure in areas with different thickness by means of a freeze drying technology, and is subjected to carbonization, graphitization and activation in sequence to obtain the integrated gradient porosity electrode material.
In the step (1), the thermosetting resin solution is formed by mixing a thermosetting resin and a solvent. The thermosetting resin suitable for use in the present invention may be selected from one or more of phenolic resin, epoxy resin, urea resin, melamine formaldehyde resin, unsaturated polyester resin and polyurethane. The thermosetting resin is solid or liquid material at normal temperature, and can be prepared into solution, and is added on the pre-oxidized felt in a dipping mode, and meanwhile, the thermosetting resin forms a cross-linking bond to fix molecules in proper positions in the heating and curing process. The solvent of the thermosetting resin solution may be selected from one or more of water and an alcohol solvent. The alcoholic solvent may be a C1-C6 alcohol, including, for example, but not limited to, methanol, ethanol, n-propanol, isopropanol, and the like. In some embodiments, the solvent of the thermosetting resin solution is ethanol. The mass ratio of the solvent to the thermosetting resin in the thermosetting resin solution may be (65 to 85) to (10 to 25), for example, 65:25, 70:25, 75:25.
In the step (1), the soaking time may be 3-10 min, for example, 4min, 5min, 6min, 7min, 8min, and 9min.
Thickness H of the portion of the Pre-oxidized fiber felt immersed in the thermosetting resin solution in step (1) 1 Preferably 10% -20%, such as 11%, 13%, 15%, 17%, 19% of the total thickness H of the pre-oxidized felt. In the step (3), the thickness H of the portion of the pre-oxidized felt material having the resin at one side immersed in the mixed solution of t-butanol and water 2 Preferably 40% -60%, such as 42%, 45%, 48%, 51%, 54%, 57% of the total thickness H of the pre-oxidized felt. And (H-H) 1 -H 2 ) Preferably, H is 30% -40%, for example 31%, 33%, 35%, 37%, 39%. By scaling the thickness of each gradient (i.e. H 1 /H、H 2 /H、(H-H 1 -H 2 ) /H) is adjusted to the above range to improve the voltage efficiency and energy efficiency of the battery.
In the step (2), the curing temperature may be 80 to 200 ℃, for example, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃.
In the step (2), the curing time may be 1.0 to 2.0 hours, for example, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours.
In the present invention, the mass of t-butanol in the mixed solution of t-butanol and water may be 3% to 19%, for example, 5%, 7%, 9%, 10%, 11%, 13%, 15%, 17% of the total mass of t-butanol and water. The mixed solution of tertiary butanol and water is used for impregnating the pre-oxidized felt, so that the porosity of the material is improved in the subsequent freeze drying process, and the voltage efficiency and the energy efficiency of the battery are improved.
In step (3), preferably, the mixed solution of t-butanol and water further contains a nanocarbon material. In the present invention, the nanocarbon material is preferably added to a mixed solution of t-butanol and water. The nano carbon material is loaded on the electrode material, so that the reaction site of the near-membrane electrode can be increased, and the problem of low near-membrane reaction rate is solved, thereby improving the voltage efficiency and the energy efficiency of the battery. In the present invention, the nanocarbon material may be Graphene Oxide (GO), carboxylated carbon nanotubes (COOH-CNTs) or a mixture of graphene oxide and carboxylated carbon nanotubes. The surface functional groups of the nano carbon material can be combined with the oxygen-containing functional groups of the pre-oxidized felt, which is beneficial to improving the binding force of the nano carbon material and the felt body. In the invention, the ratio of the total mass of the nano carbon material to the tertiary butanol and the water is preferably (0.5-2.5) to (4-10), for example, 1.5:10, 2:10 and 2.5:10.
In the step (3), the soaking time may be 3-10 min, for example, 4min, 5min, 6min, 7min, 8min, and 9min.
In the present invention, the electrode obtained in the step (3) having the resin on one side and the mixed solution impregnated on the other side is pre-frozen as a solid, and then freeze-dried. The freeze drying technology can improve the porosity and connectivity of the pores, so that the membrane-near electrode material has larger specific surface area. This is advantageous in improving the mass transfer effect of the electrode and the voltage efficiency and energy efficiency of the battery.
In step (4), the prefreezing temperature may be-60 to-20 ℃, for example-55 ℃, -50 ℃, -45 ℃, -40 ℃, -35 ℃, -30 ℃, -25 ℃.
In the step (4), the pre-freezing time may be 1 to 3 hours, for example, 1.2 hours, 1.5 hours, 1.8 hours, 2.1 hours, 2.4 hours, 2.7 hours.
In the step (4), the freeze-drying time may be 24-72 h, for example, 30h, 36h, 42h, 48h, 54h, 60h, 66h.
In the invention, the pre-oxidized felt material with one side containing resin and the other side having aerogel structure obtained in the step (4) is carbonized, graphitized and activated. Carbonizing to convert organic matters into carbon to obtain a carbon felt; graphitizing causes carbon atoms to be rearranged at high temperature to form graphite carbon with a layered structure, and the conductivity of the material is obviously improved; the activation increases the content of active groups on the surface of the electrode. This is advantageous in improving the mass transfer effect of the electrode and the voltage efficiency and energy efficiency of the battery.
In step (5), the carbonization temperature may be 1000 to 1600 ℃, for example 1100 ℃, 1200 ℃, 1300 ℃, 1400 ℃, 1500 ℃ during the carbonization treatment.
In the step (5), the heating rate in the carbonization treatment process may be 5-50 ℃/min, for example, 10 ℃/min, 15 ℃/min, 20 ℃/min, 25 ℃/min, 30 ℃/min, 35 ℃/min, 40 ℃/min, 45 ℃/min.
In the step (5), the heat preservation time can be 0.5-2 h, for example 0.6h, 0.8h, 1.0h, 1.2h and 1.8h in the carbonization treatment process.
In the step (5), the atmosphere during the carbonization treatment may be a nitrogen or argon atmosphere.
In the step (5), the graphitization temperature may be 1800 to 2600 ℃, for example 1900 ℃, 2000 ℃, 2100 ℃, 2200 ℃, 2300 ℃, 2400 ℃ during the graphitization treatment.
In the step (5), the temperature rising rate in the graphitization treatment process may be 5 to 50 ℃/min, for example, 10 ℃/min, 15 ℃/min, 20 ℃/min, 25 ℃/min, 30 ℃/min, 35 ℃/min, 40 ℃/min, 45 ℃/min.
In the step (5), the heat preservation time can be 0.5-2 h, for example, 0.6h, 0.8h, 1.0h, 1.2h and 1.8h in the graphitization treatment process.
In the step (5), the atmosphere in the graphitization treatment process may be an argon atmosphere. Because nitrogen is decomposed and unstable at high temperature, an argon atmosphere is selected for graphitization.
In the step (5), in the activation treatment process, the activation mode can be steam activation, air activation or CO 2 Activating.
In the step (5), the activation temperature may be 300 to 600 ℃, for example 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃ during the activation treatment.
In the step (5), the heating rate may be 5 to 30 ℃/min, for example, 10 ℃/min, 15 ℃/min, 20 ℃/min, 25 ℃/min, during the activation treatment.
In the step (5), the heat preservation time can be 1-4 hours, for example, 1.5 hours, 2 hours, 2.5 hours, 3 hours and 3.5 hours in the activation treatment process.
The invention also provides an integrated gradient porosity electrode material prepared by the preparation method.
In the invention, the porosity of the integrated gradient porosity electrode material is distributed in a gradient manner along the thickness direction of the electrode, and the porosity of the part immersed in the thermosetting resin solution is preferably 70% -80%, such as 71%, 73%, 75%, 77% and 79%; the porosity of the portion not impregnated with the mixed solution of the thermosetting resin solution and t-butanol and water is preferably 80% to 90%, for example, 81%, 83%, 85%, 87%, 89%, and the porosity of the portion impregnated with the mixed solution of t-butanol and water is preferably 90% to 99%, for example, 92%, 94%, 96%, 98%. Controlling the porosity of each gradient portion within the aforementioned range is advantageous in improving the voltage efficiency and energy efficiency of the battery.
Fig. 1 presents a schematic view of an integrated gradient porosity electrode material of the present invention. When the all-vanadium redox flow battery is assembled, the part of the integrated gradient porosity electrode material impregnated with the thermosetting resin solution is tightly attached to the bipolar plate, and the part impregnated with the mixed solution of tertiary butanol and water is tightly attached to the ion exchange membrane.
The invention also provides an all-vanadium redox flow battery containing the integrated gradient porosity electrode material.
The invention has the following beneficial effects: the porosity of the integrated gradient porosity electrode material is gradually increased from the bipolar plate side to the ion exchange membrane side, the transfer of chemical active substances is obviously enhanced, the electrochemical reaction rate is obviously improved, the internal resistance of the battery is reduced by the integrated electrode, and the voltage efficiency and the energy efficiency of the battery are improved.
The invention will be illustrated by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. The methods, reagents and materials used in the examples are those conventional in the art unless otherwise indicated. The starting compounds in the examples are all commercially available.
The polyacrylonitrile-based pre-oxidized fiber mats in the examples and comparative examples were produced from Bidafu and had a thickness of 5.1mm.
Example 1
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 1.0mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 2.5mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:1:9.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 2
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 0.6mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 2.5mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:1:9.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 3
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 1.0mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 2.1mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:1:9.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 4
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 0.6mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 2.9mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:1:9.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 5
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 1.0mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 2.5mm, the immersion time is 3min, and the mass ratio of the tertiary butanol to the water in the mixed solution is 1:9.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 6
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 2.0 mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 1.5mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:1:9.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 7
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 1.0mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 2.5mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:0.3:9.7.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Example 8
1. One side of the polyacrylonitrile-based pre-oxidized fiber felt is immersed in a solution formed by mixing absolute ethyl alcohol and phenolic resin in a mass ratio of 70:25, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the solution is 1.0mm, and the immersing time is 3min.
2. And (3) placing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in an oven for curing treatment, and curing for 1.0h at 120 ℃ and 140 ℃ and 180 ℃ respectively by adopting a stage heating mode.
3. And (3) immersing the other side (the side which is not immersed with the resin) of the cured polyacrylonitrile-based pre-oxidized fiber felt in a mixed solution of GO, COOH-CNTs, tertiary butanol and water, wherein the thickness of the polyacrylonitrile-based pre-oxidized fiber felt immersed in the mixed solution is 2.5mm, the immersion time is 3min, and the mass ratio of GO, COOH-CNTs, tertiary butanol and water in the mixed solution is 1:1:1.9:8.1.
4. And (3) pre-freezing the impregnated polyacrylonitrile-based pre-oxidized fiber felt in a refrigerator at the temperature of 20 ℃ below zero for 2 hours, and then performing freeze drying in a freeze dryer for 48 hours to obtain the polyacrylonitrile-based pre-oxidized fiber felt with an aerogel structure on one side.
5. The freeze-dried polyacrylonitrile-based pre-oxidized fiber felt is placed in a box-type furnace, heated to 1400 ℃ at 10 ℃/min under nitrogen atmosphere and heat treated for 2 hours at the temperature.
6. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
7. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the integrated gradient porosity electrode material with gradient porosity for the vanadium redox flow battery.
Comparative example 1
1. The polyacrylonitrile-based pre-oxidized fiber felt was placed in a box furnace, heated to 1400 ℃ at 10 ℃/min under a nitrogen atmosphere, and heat-treated at this temperature for 2 hours.
2. And (3) placing the carbonized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 2000 ℃ at 20 ℃/min under the argon atmosphere, and graphitizing for 2 hours at the temperature.
3. And (3) placing the graphitized polyacrylonitrile-based fiber felt in a graphite furnace, heating to 500 ℃ at 10 ℃/min under the air atmosphere, and activating for 2 hours at the temperature to obtain the composite electrode material with constant porosity for the vanadium redox flow battery.
Test example 1
Each of the vanadium redox flow batteries of examples 1 to 8 was cut with the integrated gradient porosity electrode material, and vertical cutting was performed at the interface impregnated with the resin and the non-impregnation treatment and at the interface impregnated with the mixed solution of t-butanol and water and the non-impregnation treatment, respectively, along the total thickness direction of the electrode material, to obtain 3 portions, designated as a first gradient portion (corresponding to the resin-impregnated portion), a second gradient portion (corresponding to the non-impregnation treatment), and a third gradient portion (corresponding to the t-butanol and water-impregnated portion), respectively.
The 3 parts of the integrated gradient porosity electrode materials of examples 1 to 8 and the composite electrode material of comparative example 1 were subjected to a porosity test using a mercury porosimeter (manufactured by PMI corporation in the united states), and the results are shown in table 1.
Table 1: porosity values of the electrode materials of examples 1 to 8 and comparative example 1
As can be seen from table 1, the porosity of 3 portions of the integrated gradient porosity electrode materials of examples 1 to 8 exhibited gradient changes as compared with comparative example 1.
As is clear from table 1, the third gradient of the integrated gradient porosity electrode material (example 1) prepared by impregnating the mixed solution to which the nanocarbon material was added had a smaller porosity than the integrated gradient porosity electrode material (example 5) prepared by impregnating the mixed solution to which the nanocarbon material was not added, and the first and second gradients were substantially not different in porosity.
As can be seen from Table 1, the thicknesses of the three gradient portions satisfy the preferred requirements (H) of the present invention, as compared with the integrated gradient porosity electrode material (example 6) in which the thicknesses of the three gradient portions do not satisfy the preferred requirements of the present invention 1 /H=10%~20%，(H-H 1 -H 2 )/H=30%~40%，H 2 H=40% -60%), which means that the depth of impregnation affects the porosity of the electrode material, the porosity of the first gradient of the integrated gradient porosity electrode material is smaller, and the porosity of the first gradient decreases with the increase of the thickness of the first gradient.
Test example 2
Electrode materials for all-vanadium redox flow batteries of examples 1 to 8 and comparative example 1 were assembled as electrodes, respectively, to form all-vanadium redox flow batteries and battery characteristics were tested.
The battery preparation conditions are as follows: active substances in the positive and negative electrolyte are respectively 1.7mol/L V 4+ /V 5+ And 1.7mol/L V 2+ /V 3+ The supporting electrolyte is sulfuric acid with the concentration of 4mol/L, the volume of the positive and negative electrolyte is 70mL, the diaphragm is a perfluorosulfonic acid proton membrane (produced by Suzhou Kouzu), and the effective area of the carbon felt electrode is 48cm 2 The compression ratio was 25%.
During characteristic test, constant current test is adopted, and the density is 110, 150 and 200mA/cm in sequence 2 The upper limit of charge was 1.55V, the lower limit of discharge was 1.00V, and the cycle was 5 times at each electric density, and the results of the coulombic efficiency, voltage efficiency, and energy efficiency tests were shown in tables 2 to 4.
Table 2: coulombic efficiency of assembled batteries of the electrode materials of examples 1 to 8 and comparative example 1
Table 3: voltage efficiency of assembled electrode materials of examples 1-8 and comparative example 1 into batteries
Table 4: energy efficiency of assembled electrode materials of examples 1 to 8 and comparative example 1 into batteries
As can be seen from tables 2 to 4, the single cells assembled from the integrated gradient porosity electrode materials (examples 1 to 8) prepared according to the present invention have higher voltage efficiency and energy efficiency, higher coulombic efficiency at high electric density, and substantially flat coulombic efficiency at low electric density, compared to the composite electrode material of constant porosity (comparative example 1). The integrated gradient porosity electrode material with gradient porosity can endow the all-vanadium redox flow battery with excellent battery characteristics.
As can be seen from tables 2 to 4, the unit cell assembled from the integrated gradient porosity electrode material (example 1) prepared by impregnating the mixed solution to which the nanocarbon material was added had higher voltage efficiency and energy efficiency than the integrated gradient porosity electrode material (example 5) prepared by impregnating the mixed solution to which the nanocarbon material was not added. The nano carbon material can increase the reactive sites so as to improve the performance of the all-vanadium redox flow battery.
As can be seen from tables 2 to 4, the thickness of the three gradient portions satisfies the preferred requirements (H) of the present invention as compared with the integrated gradient porosity electrode material (example 6) in which the thickness of the three gradient portions does not satisfy the preferred requirements of the present invention 1 /H=10%~20%，(H-H 1 -H 2 )/H=30%~40%，H 2 The single cell assembled by the integrated gradient porosity electrode material (example 1) with H=40-60% has higher voltage efficiencyAnd energy efficiency.
Claims (10)
1. A method of preparing an integrated gradient porosity electrode material useful in an all-vanadium flow battery, the method comprising the steps of:
(1) Dipping one side of the pre-oxidized felt into a thermosetting resin solution to obtain a pre-oxidized felt material with one side dipped with resin;
(2) Heating and curing the pre-oxidized felt material with one side impregnated with the resin obtained in the step (1) to obtain a pre-oxidized felt material with one side containing the resin;
(3) Immersing the other side of the pre-oxidized felt material with one side containing the resin obtained in the step (2) in a mixed solution of tertiary butanol and water to obtain the pre-oxidized felt material with one side containing the resin and the other side immersed in the mixed solution, wherein the mass of the tertiary butanol is 3% -19% of the total mass of the tertiary butanol and the water in the mixed solution of the tertiary butanol and the water;
(4) Pre-freezing the pre-oxidized felt material with one side containing the resin and the other side immersed in the mixed solution obtained in the step (3) into solid, and then performing freeze drying to obtain the pre-oxidized felt material with one side containing the resin and the other side having an aerogel structure;
(5) And (3) carbonizing, graphitizing and activating the pre-oxidized felt material with the resin on one side and the aerogel structure on the other side obtained in the step (4) to obtain the integrated gradient porosity electrode material.
2. The method of claim 1, wherein the method has one or more of the following features:
in the step (1), the pre-oxidized felt is a polyacrylonitrile-based pre-oxidized felt, a viscose-based pre-oxidized felt or an asphalt-based pre-oxidized felt;
in the step (1), the thermosetting resin solution is formed by mixing thermosetting resin and a solvent;
in the step (1), the soaking time is 3-10 min;
in the step (1), the thickness of the portion of the pre-oxidized fiber felt immersed in the thermosetting resin solutionH 1 10% -20% of the total thickness H of the pre-oxidized felt, wherein in the step (3), the thickness H of the part of the pre-oxidized felt material with resin at one side immersed in the mixed solution of the tertiary butanol and the water 2 40% -60% of the total thickness H of the pre-oxidized fiber felt, and (H-H) 1 -H 2 ) The ratio of H is 30% -40%.
3. The method of claim 2, wherein the method has one or more of the following features:
the thermosetting resin is selected from one or more of phenolic resin, epoxy resin, urea resin, melamine formaldehyde resin, unsaturated polyester resin and polyurethane;
the solvent is selected from one or more of water and alcohol solvents;
in the thermosetting resin solution, the mass ratio of the solvent to the thermosetting resin is (65-85) to (10-25).
4. The method of claim 1, wherein in step (2), the curing temperature is 80 to 200 ℃ and the curing time is 1 to 2 hours.
5. The method of claim 1, wherein,
in the step (3), the mixed solution of the tertiary butanol and the water also contains a nano carbon material; and/or
In the step (3), the soaking time is 3-10 min.
6. The method of claim 5, wherein,
the nano carbon material is selected from one or two of graphene oxide and carboxylated carbon nanotubes; and/or
The ratio of the mass of the nano carbon material to the total mass of the tertiary butanol and the water is (0.5-2.5) to (4-10).
7. The method of claim 1, wherein the method has one or more of the following features:
in the step (4), the pre-freezing temperature is-60 to-20 ℃;
in the step (4), the pre-freezing time is 1-3 hours;
in the step (4), the freeze drying time is 24-72 h;
in the step (5), in the carbonization treatment, the carbonization temperature is 1000-1600 ℃, the heating rate is 5-50 ℃/min, the heat preservation time is 0.5-2 h, and the atmosphere is nitrogen or argon;
in the step (5), in the graphitization treatment, the graphitization temperature is 1800-2600 ℃, the heating rate is 5-50 ℃/min, the heat preservation time is 0.5-2 h, and the atmosphere is argon atmosphere;
in the step (5), the activation treatment is carried out by steam activation, air activation or CO 2 Activating, wherein the activating temperature is 300-600 ℃, the heating rate is 5-30 ℃/min, and the heat preservation time is 1-4 h.
8. An integrated gradient porosity electrode material prepared by the method of any one of claims 1-7.
9. The integrated gradient-porosity electrode material according to claim 8, wherein the porosity of the integrated gradient-porosity electrode material is distributed in a gradient manner in a thickness direction, and wherein the porosity of a portion impregnated with the thermosetting resin solution is 70% -80%, the porosity of a portion not impregnated with the thermosetting resin solution and the mixed solution of t-butanol and water is 80% -90%, and the porosity of a portion impregnated with the mixed solution of t-butanol and water is 90% -99%.
10. An all-vanadium flow battery, characterized in that it comprises the integrated gradient porosity electrode material of claim 8 or 9.
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| CN116031414A (en) * | 2023-02-22 | 2023-04-28 | 江苏大学 | Ordered structure gas diffusion layer with pore gradient and hydrophobic gradient and processing method thereof |
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