Preparation method of high-activity electrode material for all-vanadium redox flow battery

Abstract

The application discloses a preparation method of high-activity electrode material for a vanadium redox flow battery, and belongs to the technical field of electrode material of a liquid flow battery. The method comprises the following steps: grinding a carbon precursor of enriched core-shell nanoparticles into a powder, performing pre-oxidation and high-temperature carbonization treatment to obtain a modified porous carbon-based material; mixing supported nanometer bismuth oxide graphene and metal oxides to prepare a composite aerogel; mixing the composite aerogel and a binder to form a slurry, coating the slurry on the surface of the modified porous base material, and performing drying, roll pressing, and cutting to obtain the high-activity electrode material. Polystyrene on the surface of the core-shell nanoparticles is pyrolyzed to release nanoparticles which are filled into macropore pores of the porous carbon-based material, the macropore pores are converted into mesopore structures, and the adsorption performance on vanadium ions is improved; the porous aerogel has excellent adsorption performance, the adsorption and storage performance on vanadium ions is improved, and the service life of the electrode material is further improved.

Description

Technical Field

[0001] This invention relates to the field of flow battery electrode materials technology, specifically a method for preparing a highly active electrode material for an all-vanadium redox flow battery. Background Technology

[0002] A vanadium redox flow battery consists of two tanks containing electrolyte solutions and a set of electrochemical battery components. The electrolyte solution contains vanadium ions in different valence states. During charging and discharging, the vanadium ions in the electrolyte solution are oxidized and reduced, and electrons are exchanged between the positive and negative electrodes of the electrochemical battery to complete the charging and discharging process. As one of the key components of a vanadium redox flow battery, the performance of the electrode has a great impact on the flow battery. Porous carbon-based materials, as electrode materials for vanadium redox flow batteries, have a large surface area and excellent corrosion resistance, and are widely used in smart homes, commercial buildings, microgrids and other fields. Therefore, there is an urgent need to develop a flow battery electrode material that combines high mechanical strength and high energy storage capacity.

[0003] Porous carbon-based materials, as electrode materials for vanadium redox flow batteries, exhibit good chemical stability and a large reaction area during charge and discharge. However, their electrochemical activity is poor under high electrical density, which inhibits the operating current of the vanadium redox flow battery and leads to a decrease in charge and discharge performance. By depositing nano-bismuth powder on carbon-based materials, sufficient reactive sites for vanadium ions can be provided, improving the activity of the electrode material. However, nano-bismuth powder is a metal and is easily brittle under external forces at low temperatures, reducing the electrochemical performance and service life of the electrode material. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a highly active electrode material for vanadium redox flow batteries: Polystyrene is synthesized in situ on the surface of nanoparticles, diluted in a culture medium, and then mixed with a carbon precursor for further cultivation. This method avoids nanoparticle aggregation during cultivation, preventing uneven dispersion of nanoparticles in the plant carbon precursor, and facilitates the formation of a dense conductive network of nanoparticles in the porous carbon-based material, thereby improving the electrochemical performance of the electrode material. The enriched core-shell nanoparticle carbon precursor is ground into powder, pre-oxidized, and subjected to high-temperature carbonization. Thermal decomposition of polystyrene on the surface of the core-shell nanoparticles releases nanoparticles that fill the macropores of the porous carbon-based material, refining the pore size. As a framework for porous carbon-based materials, it improves the mechanical strength of porous carbon-based materials and avoids the brittleness caused by the presence of pores. The bismuth source is intercalated into the interlayer of graphene oxide and then reduced at high temperature to avoid the reduction in charge storage capacity caused by the stacking of graphene oxide sheets. Furthermore, the synthesis of nano-bismuth in the interlayer of graphene oxide further expands the interlayer spacing, improves the contact area with vanadium ions and the charge transfer efficiency. The nano-bismuth graphene oxide loaded with metal oxide is mixed with metal oxide, which serves as the framework of the aerogel to form a three-dimensional network structure. This gives the aerogel high mechanical properties and the prepared composite aerogel has excellent adsorption properties, improving the adsorption and storage performance of vanadium ions.

[0005] The technical problem this invention aims to solve is as follows: Porous carbon-based materials, as electrode materials for vanadium redox flow batteries, exhibit good chemical stability and a large reaction area during charge and discharge. However, porous carbon-based materials have poor electrochemical activity under high charge density, and their porous structure results in relatively low mechanical strength, making them prone to structural damage or deformation during battery operation, thus affecting battery performance and stability. Depositing nano-bismuth powder on carbon-based materials can provide sufficient reactive sites for vanadium ions, improving the activity of the electrode material. However, nano-bismuth powder is a metal and is prone to brittleness under external forces at low temperatures, reducing the electrochemical performance and lifespan of the electrode material.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a highly active electrode material for an all-vanadium redox flow battery includes the following steps:

[0008] S1. The enriched core-shell nanoparticle carbon precursor is ground into powder, and then subjected to pre-oxidation and high-temperature carbonization to obtain modified porous carbon-based materials.

[0009] Furthermore, the enriched core-shell nanoparticle carbon precursor has a particle size of 20-60 nm.

[0010] Further preferred, the enriched core-shell nanoparticle carbon precursor has a particle size of 20-50 nm.

[0011] Further preferred, the enriched core-shell nanoparticle carbon precursor has a particle size of 40 nm.

[0012] Furthermore, the pre-oxidation temperature is 250-350℃, and the time is 1-4h.

[0013] More preferably, the pre-oxidation temperature is 250-330℃ and the time is 1-3h.

[0014] Further preferred, the pre-oxidation temperature is 300℃ and the time is 2h.

[0015] Furthermore, the high-temperature carbonization temperature is 600-900℃, and the time is 2-5 hours.

[0016] Further preferred, the high-temperature carbonization temperature is 600-800℃, and the time is 2-4h.

[0017] Further preferred, the high-temperature carbonization temperature is 700℃ and the time is 3 hours.

[0018] Furthermore, the modified porous carbon-based material is prepared by the following steps:

[0019] The enriched core-shell nanoparticle carbon precursor was dried in a freeze dryer for 12 hours to better preserve the internal structure of the plant. It was then removed and ground into powder in a grinder. The powder was placed in a muffle furnace and pre-oxidized at 300°C for 2 hours to depolymerize some of the cellulose, hemicellulose and lignin into monomers. The temperature was then raised to 700°C and carbonized under a nitrogen atmosphere for 3 hours. After cooling to room temperature, the carbon precursor was placed in a potassium hydroxide solution and stirred for 2 hours to fully activate it. After filtration, the carbon precursor was washed three times with deionized water and dried in a 60°C oven for 10 minutes to obtain the modified porous carbon-based material.

[0020] Among them, under the condition of 300℃, the enriched core-shell nanoparticle carbon precursor is pre-oxidized to depolymerize the cellulose, hemicellulose and lignin in the carbon precursor water hyacinth into monomers. The monomers are dehydrated and decarboxylated to generate bio-oil and syngas, which promotes the formation of bio-carbon network.

[0021] Furthermore, high-temperature carbonization at 700℃ causes the polystyrene on the surface of the core-shell nanoparticles to decompose and release gas, which in turn forms mesoporous pores inside the biochar. The polystyrene released from the surface of the core-shell nanoparticles through thermal decomposition fills the macropores of the porous carbon-based material, refining the pore size and transforming macropores into mesoporous structures. This improves the adsorption performance of vanadium ions, provides a channel for ions to enter the carbon-based material, facilitates the diffusion and transfer of electrolyte ions during charging and discharging, and enhances electrochemical performance.

[0022] Furthermore, the ratio of the enriched core-shell nanoparticle carbon precursor to potassium hydroxide solution is (5-6) g:(20-40) mL.

[0023] Furthermore, the enriched core-shell nanoparticle carbon precursor was prepared by in-situ synthesis of polystyrene on the surface of nanoparticles, followed by dilution in a culture medium, and then the addition of the carbon precursor for mixed culture.

[0024] Furthermore, the nanoparticles are selected from any one of nano-silver, nano-copper, nano-carbon black, nano-titanium dioxide, and carbon nanotubes.

[0025] Furthermore, the nanoparticles have a particle size of 20-60 nm.

[0026] Further preferred, the nanoparticle size is 20-40 nm.

[0027] Further preferably, the nanoparticle size is 30 nm.

[0028] Furthermore, the carbon precursor is selected from either water hyacinth or water lily.

[0029] Furthermore, the culture medium is prepared by mixing Hogrange's solution, calcium nitrate, and deionized water in a volume ratio of (0.6-0.66)g:(0.4-0.5)g:(400-600)mL.

[0030] Furthermore, the enriched core-shell nanoparticle carbon precursor is prepared by the following steps:

[0031] A1. 3-(methacryloyloxy)propyltrimethoxysilane and nanoparticles were added to ethanol and stirred for 24 h. After filtration, the mixture was washed three times with deionized water and dried in an oven at 90 °C for 10 min to obtain a solid. The solid and polyvinylpyrrolidone were added to 25 mL of deionized water and 10 mL of ethanol and stirred until homogeneous. The mixture was heated to 45 °C, and styrene, potassium persulfate, and sodium styrene sulfonate were added and stirred until homogeneous. The mixture was then placed in an 80 °C water bath and stirred for 3 h. After demulsification, a 36% sodium chloride solution was added and filtered to obtain a solid. The solid was washed three times with deionized water and dried in an oven at 60 °C for 10 min to obtain core-shell nanoparticles.

[0032] In this process, 3-(methacryloyloxy)propyltrimethoxysilane reacts with the hydroxyl groups on the surface of the nanoparticles, resulting in reactive double bonds on the nanoparticle surface. Under the action of the catalyst potassium persulfate and the surfactant polyvinylpyrrolidone, styrene can polymerize on the surface of the nanoparticles to form polystyrene-coated nanoparticle microspheres, preventing the agglomeration of conductive nanoparticles. This allows the nanoparticles to be uniformly dispersed in the carbon precursor water hyacinth plant system, which is beneficial for the formation of a dense conductive network of nanoparticles in porous carbon-based materials, thereby improving the electrochemical performance of the electrode materials.

[0033] Furthermore, the ratio of solid, polyvinylpyrrolidone, styrene, potassium persulfate, and sodium styrene sulfonate is (2-3)g:(0.01-0.03)g:(0.1-0.3)g:(0.001-0.004)g:(0.3-0.7)g.

[0034] A2. Core-shell nanoparticles were added to the culture medium and ultrasonically treated to disperse the core-shell nanoparticles in the culture medium to obtain a dispersion. The carbon precursor was placed in the culture medium and cultured for 7 days. After being placed in the dispersion and cultured for 14 days, it was taken out and washed with deionized water to remove the core-shell nanoparticles adhering to the surface, thus obtaining a carbon precursor enriched with core-shell nanoparticles.

[0035] In this process, the plant carbon precursor, water hyacinth, and the core-shell nanoparticles are cultured in a culture solution. The roots of the carbon precursor water hyacinth have a porous structure. When absorbing nutrients from the culture solution, the core-shell nanoparticles enter the roots of the plant carbon precursor water hyacinth through the culture solution flow. Under the action of transpiration tension and root pressure, the nanoparticles are transported to the branches of water hyacinth, so that the core-shell nanoparticles are evenly dispersed in the carbon precursor system.

[0036] Furthermore, the ratio of core-shell nanoparticles, culture medium, and carbon precursor is (0.5-1.5)g:(8-12)mL:(8-12)g.

[0037] S2. Prepare composite aerogel by mixing supported bismuth nano-graphene oxide with metal oxide;

[0038] Furthermore, the composite aerogel has a pore size of 30-50 nm and a particle size of 8-15 μm;

[0039] More preferably, the composite aerogel has a pore size of 30-40 nm and a particle size of 8-13 μm.

[0040] Further preferably, the composite aerogel has a pore size of 35 nm and a particle size of 11 μm.

[0041] Furthermore, the metal oxide is selected from one or more of nickel oxide, zinc oxide, and manganese oxide.

[0042] Furthermore, the particle size of the metal oxide is 0.2-1.5 μm.

[0043] More preferably, the metal oxide particle size is 0.2-1 μm.

[0044] More preferably, the metal oxide particle size is 0.5 μm.

[0045] Furthermore, the nano-bismuth particles have a diameter of 50-100 nm.

[0046] Further preferred, the nano-bismuth particle size is 50-80 nm.

[0047] Further preferred, the nano-bismuth particle size is 60 nm.

[0048] Furthermore, the composite aerogel is prepared by the following steps:

[0049] Loaded nano-bismuth graphene oxide and metal oxide were added to deionized water and sonicated for 30 min. 2% glutaraldehyde was added and stirred for 40 min to crosslink the mixture. The temperature was raised to 200℃ and stirred for 30 min to remove unreacted glutaraldehyde. The mixture was cooled to room temperature and filtered to obtain a gel-like substance. The gel-like substance was placed in a freeze dryer and freeze-dried at -12℃ to obtain a composite aerogel.

[0050] Among them, the oxygen-containing functional groups on the surface and sides of the loaded bismuth oxide graphene can react with glutaraldehyde and the hydroxyl groups on the surface of the nano metal oxide to form a cross-linked gel-like substance in which the loaded bismuth oxide graphene coats the nano metal oxide. After freeze-drying to remove moisture, a composite aerogel with metal oxide as the skeleton is formed, which has high mechanical strength. Moreover, the metal oxide acts as a conductive material to form a conductive path inside the aerogel, thereby improving the electrical conductivity of the composite aerogel.

[0051] Furthermore, the ratio of the amount of supported nano-bismuth graphene oxide, metal oxide, and glutaraldehyde is (1.6-2)g:(1.4-1.8)g:(0.3-0.7)mL.

[0052] Furthermore, the loaded nano-bismuth graphene oxide is prepared by intercalating a bismuth source into the interlayer of graphene oxide and then reducing it at high temperature.

[0053] Furthermore, the bismuth source is selected from one or more of bismuth nitrate, bismuth citrate, and bismuth chloride.

[0054] Furthermore, the particle size of graphene oxide is 0.5-2.5 μm.

[0055] More preferably, the graphene oxide particle size is 0.5-2 μm.

[0056] Further preferably, the graphene oxide particle size is 1.5 μm.

[0057] Furthermore, the high-temperature reduction temperature is 600-900℃.

[0058] Further preferred, the high-temperature reduction temperature is 600-800℃.

[0059] Further preferred, the high-temperature reduction temperature is 650℃.

[0060] Furthermore, the composite aerogel is prepared by the following steps:

[0061] B1. Add graphene oxide to deionized water, stir evenly, add bismuth source, heat to 40℃, stir at 600 rpm for 40 min, add 36% sodium hydroxide solution to adjust pH to 7.5, continue stirring for 1 h, filter, wash 3 times with deionized water, and dry in an 80℃ oven for 10 min to obtain modified graphene oxide.

[0062] Under mechanical stirring, bismuth ions in the bismuth source can chemically bond with the carboxyl and hydroxyl groups between the graphene oxide layers, allowing bismuth ions to intercalate into the graphene oxide layers. This avoids the reduction in charge storage capacity caused by the accumulation of graphene oxide sheets. Furthermore, bismuth has excellent electrical conductivity, and its intercalation into the graphene oxide layers improves the charge transfer efficiency of the vanadium redox flow battery.

[0063] Furthermore, the ratio of graphene oxide, bismuth source, and sodium hydroxide solution used is (0.05-0.15)g:(0.1-0.2)g:(1-3)mL.

[0064] B2. The modified graphene oxide was placed in an atmosphere furnace, inert nitrogen gas was introduced, the temperature was raised to 650℃, and the treatment was carried out for 2 hours. After cooling to room temperature, it was washed with deionized water for 3 minutes and dried in an oven at 70℃ for 10 minutes to obtain supported nano-bismuth graphene oxide.

[0065] In this process, inert nitrogen gas is used as a reducing gas. At 650℃, bismuth ions between the modified graphene oxide layers are reduced to bismuth atoms. The reduced bismuth atoms aggregate to form nano-bismuth particles, thereby realizing the formation of nano-bismuth particles between the graphene oxide layers. This further expands the interlayer spacing, increases the contact area with vanadium ions and the charge transfer efficiency. Moreover, the layered graphene oxide can absorb external stress, improve the impact resistance of nano-bismuth, and prevent the nano-bismuth powder from becoming brittle, which would reduce the electrochemical performance and service life of the electrode material.

[0066] S3. The composite aerogel is mixed with a binder to form a slurry. The slurry is coated on the surface of the modified porous base material, and after drying, roll forming and cutting, a highly active electrode material is obtained.

[0067] Furthermore, the adhesive is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, carboxylated styrene-butadiene latex, and sodium carboxymethyl cellulose.

[0068] Furthermore, the drying temperature is 60-90℃.

[0069] Furthermore, compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) In the technical solution of the present invention, polystyrene core-shell nanoparticles are synthesized in situ on the surface of nanoparticles. After being cultured with the plant carbon precursor water hyacinth in the culture solution, the core-shell nanoparticles are transported to the branches of water hyacinth. Then, the nanoparticles fill the carbon precursor system, which is conducive to the formation of a dense conductive network in the porous carbon-based material and improves the electrochemical performance of the electrode material. After pre-oxidation treatment, the cellulose, hemicellulose and lignin in the carbon precursor water hyacinth are depolymerized into monomers. The monomers undergo dehydration and decarboxylation reactions to generate bio-oil and syngas, which promotes the formation of conductive bio-carbon network. After high-temperature carbonization treatment, the polystyrene on the surface of the core-shell nanoparticles is thermally decomposed to release gas, which forms mesoporous pores inside the biochar. The polystyrene on the surface of the core-shell nanoparticles is thermally decomposed into nanoparticles that fill the macropores of the porous carbon-based material, refine the pore size, transform the macropores into mesoporous structures, improve the adsorption performance of vanadium ions, provide a channel for ions to enter the carbon-based material, help the diffusion and transfer of electrolyte ions during the charging and discharging process, and enhance the electrochemical performance.

[0071] (2) In the technical solution of the present invention, nanoparticles serve as the framework of porous carbon-based materials, which improves the mechanical strength of porous carbon-based materials and avoids the porous carbon materials from becoming brittle due to the presence of pores. Furthermore, the nanoparticles dispersed in the porous carbon-based materials can connect the pores of the porous carbon-based materials to form a conductive network, thereby improving the charge transfer rate of the porous carbon-based materials and thus improving the electrochemical performance of the carbon-based materials.

[0072] (3) In the technical solution of this invention, the bismuth source is intercalated into the interlayer of graphene oxide, and then subjected to high-temperature reduction treatment, so that the metallic bismuth ions in the interlayer of graphene oxide are reduced to nano-bismuth particles, avoiding the reduction of charge storage capacity caused by the stacking of graphene oxide sheets, and further expanding the interlayer spacing, improving the contact area with vanadium ions and the charge transfer efficiency; the sheet-like graphene oxide can absorb external stress, improve the impact resistance of nano-bismuth, and avoid the reduction of electrochemical performance and service life of electrode materials due to the fragility of nano-bismuth powder. In addition, the synthesis of nano-bismuth powder in the interlayer of graphene oxide enables the nano-bismuth powder to... Better adhesion to graphene oxide prevents the detachment of bismuth nanoparticles; aerogels are prepared by loading bismuth nanoparticles onto graphene oxide and metal oxides. The metal oxides serve as the framework of the aerogel, forming a three-dimensional network structure, which gives the aerogel high mechanical properties. The three-dimensional network structure also has good electrical conductivity, providing channels for vanadium ions and improving electrochemical performance. In addition, the aerogel has a porous structure with good adsorption properties, improving the adsorption and storage performance of vanadium ions, and can adsorb bismuth nanoparticles to prevent them from detaching, further enhancing the fixation of bismuth nanoparticles.

[0073] (4) In the technical solution of the present invention, the composite aerogel is combined with the modified porous base material to form a composite electrode with high electrochemical activity; the porous aerogel coated on the surface of the modified porous carbon base material has excellent adsorption performance, improves the adsorption and storage performance of vanadium ions, and thus improves the service life of the electrode material. Detailed Implementation

[0074] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0075] Example 1

[0076] The modified porous carbon-based material is prepared by the following steps:

[0077] A1. 0.15g of 3-(methacryloyloxy)propyltrimethoxysilane, 0.5g of nano-silver, 0.3g of nano-copper, and 0.7g of nano-carbon black were added to 30mL of ethanol and stirred for 24h. After filtration, washing, and drying, a solid was obtained. 2.5g of the solid and 0.02g of polyvinylpyrrolidone were added to 25mL of deionized water and 10mL of ethanol and stirred evenly. The mixture was heated to 45℃, and 0.2g of styrene, 0.003g of potassium persulfate, and 0.5g of sodium styrene sulfonate were added and stirred evenly. The mixture was placed in an 80℃ water bath and stirred for 3h. Then, a 36% sodium chloride solution was added. After filtration, washing, and drying, core-shell nanoparticles were obtained.

[0078] A2. Add 1g of core-shell nanoparticles to 10mL of culture medium, sonicate to obtain a dispersion, place 7g of water hyacinth and 3g of water lily in the culture medium and culture for 7d, then place them in the dispersion and culture for 14d. Remove them, wash the roots of the carbon precursor with deionized water, and dry them at 80℃ to obtain a carbon precursor enriched with core-shell nanoparticles.

[0079] A3. 5.6 g of enriched core-shell nanoparticle carbon precursor was placed in a freeze dryer and dried for 12 h. It was then removed, ground into powder in a grinder, placed in a muffle furnace, pre-oxidized at 300 °C for 2 h, heated to 700 °C, and carbonized under a nitrogen atmosphere for 3 h. After cooling to room temperature, it was placed in 30 mL of potassium hydroxide solution and stirred for 2 h. After filtration, it was washed three times with deionized water and dried in a 60 °C oven for 10 min to obtain the modified porous carbon-based material.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is that the nanoparticles were not modified by polystyrene coating.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 1 is that core-shell nanoparticles were not added.

[0084] Example 2

[0085] The composite aerogel is prepared by the following steps:

[0086] B1. Add 0.1g of graphene oxide to 160mL of deionized water and stir until homogeneous. Add 0.06g of bismuth nitrate, 0.04g of bismuth citrate, and 0.06g of bismuth chloride. Heat to 40℃ and stir at 600rpm for 40min. Add 2mL of 36% sodium hydroxide solution to adjust the pH to 7.5 and continue stirring for 1h. After filtration, wash three times with deionized water and dry in an oven at 80℃ for 10min to obtain modified graphene oxide. Place the modified graphene oxide in an atmosphere furnace, introduce inert nitrogen gas, heat to 650℃, treat for 2h, cool to room temperature, wash three times with deionized water, and dry at 70℃ for 10min to obtain supported nano-bismuth graphene oxide.

[0087] B2. 1.8g of nano-bismuth graphene oxide, 0.7g of nickel oxide, 0.5g of zinc oxide, and 0.4g of manganese oxide were added to 70mL of deionized water and sonicated for 30min. 0.5mL of 2% glutaraldehyde was added and stirred for 40min to crosslink the mixture. The mixture was heated to 200℃ and stirred for 30min. After cooling to room temperature, a gel-like substance was obtained by filtration. The gel-like substance was placed in a freeze dryer and freeze-dried at -12℃ to obtain a composite aerogel.

[0088] Comparative Example 3

[0089] The difference between this comparative example and Example 2 is that the supported nano-bismuth graphene oxide is replaced with commercially available graphene oxide.

[0090] Comparative Example 4

[0091] The difference between this comparative example and Example 2 is that nickel oxide, zinc oxide, and manganese oxide were not added.

[0092] Example 3

[0093] A method for preparing a highly active electrode material for an all-vanadium redox flow battery includes the following steps:

[0094] 12g of composite aerogel, 2.5g of binder and 1.2g of N-methylpyrrolidone solution were mixed and stirred evenly to form a slurry. The slurry was coated on the surface of the modified porous base material and dried in an oven at 80℃. After roll forming and cutting, a highly active electrode material was obtained.

[0095] Example 4

[0096] A method for preparing a highly active electrode material for an all-vanadium redox flow battery includes the following steps:

[0097] 12g of composite aerogel, 2.5g of binder and 1.2g of N-methylpyrrolidone solution were mixed and stirred evenly to form a slurry. The slurry was coated on the surface of the modified porous base material and dried in an oven at 80℃. After roll forming and cutting, a highly active electrode material was obtained.

[0098] Example 5

[0099] A method for preparing a highly active electrode material for an all-vanadium redox flow battery includes the following steps:

[0100] 12g of composite aerogel, 2.5g of binder and 1.2g of N-methylpyrrolidone solution were mixed and stirred evenly to form a slurry. The slurry was coated on the surface of the modified porous base material and dried in an oven at 80℃. After roll forming and cutting, a highly active electrode material was obtained.

[0101] Comparative Example 5

[0102] The difference between this comparative example and Example 4 is that the modified porous matrix material is replaced with the substance prepared in Comparative Example 1.

[0103] Comparative Example 6

[0104] The difference between this comparative example and Example 4 is that the modified porous matrix material is replaced with the substance prepared in Comparative Example 2.

[0105] Comparative Example 7

[0106] The difference between this comparative example and Example 4 is that the composite aerogel is replaced with the substance prepared in Comparative Example 3.

[0107] Comparative Example 8

[0108] The difference between this comparative example and Example 4 is that the composite aerogel is replaced with the substance prepared in Comparative Example 4.

[0109] The performance of the highly active electrode materials prepared in Examples 3-5 and Comparative Examples 5-8 was then tested.

[0110] A block measuring 8cm × 6cm × 0.6cm was cut from the highly active electrode material prepared above to serve as the electrode. The positive electrode electrolyte was 60mL VO. 2+ A 1.5M solution and a 3M H2SO4 solution were used as the negative electrode electrolyte, with a volume of 60 mL. 3+ A single cell was assembled using solutions of 1.5 M H₂SO₄ and 3 M H₂SO₄, and the current density was 80 mA / cm². 2The conductivity was tested under the following conditions: charging voltage of 1.65V, discharge cutoff voltage of 0.8V, and electrolyte flow rate of 30mL / min. The test results are shown in Table 1 below.

[0111] Table 1

[0112]

[0113] As shown in Table 1, Comparative Example 5, which uses nanoparticles without polystyrene coating to prepare a modified porous carbon-based material, exhibits decreased electrochemical performance and mechanical strength when used as a high-activity electrode material for vanadium redox flow batteries. This may be because styrene can polymerize on the surface of the nanoparticles to form polystyrene-coated nanoparticle microspheres, preventing the agglomeration of conductive nanoparticles and allowing the nanoparticles to be uniformly dispersed in the carbon precursor, water hyacinth plant system. Comparative Example 6, which uses modified porous carbon-based materials without the addition of core-shell nanoparticles, also shows decreased electrochemical performance and mechanical strength when used as a high-activity electrode material for vanadium redox flow batteries. This may be because the nanoparticles act as the framework of the porous carbon-based material, improving its mechanical strength and preventing brittleness due to pores. The particles can connect the pores of porous carbon-based materials to form a conductive network, thereby improving the charge transfer rate of porous carbon-based materials. In Comparative Example 7, the loaded bismuth oxide graphene was replaced with commercially available graphene oxide. The composite aerogel prepared and coated on the surface of the porous carbon-based material showed a decrease in electrochemical performance. This may be because bismuth nanoparticles were synthesized between the graphene oxide layers, expanding the interlayer spacing, avoiding the reduction in charge storage capacity due to the accumulation of graphene oxide sheets, and preventing the shedding of bismuth nanoparticle powder. In Comparative Example 8, without the addition of metal oxide, the composite aerogel prepared and coated on the surface of the porous carbon-based material showed a decrease in strength and electrochemical performance. This may be because the aerogel prepared by loading bismuth oxide graphene with metal oxide, with the metal oxide acting as the skeleton of the aerogel, forms a three-dimensional network structure, giving the aerogel higher mechanical properties.

[0114] The data in Table 1 demonstrates that the highly active electrode materials prepared in Examples 3-5 not only possess high telephone performance and mechanical strength, but also exhibit superior service life and higher activity. Enriched core-shell nanoparticle carbon precursors were ground into powder, pre-oxidized, carbonized at high temperature, and cooled to room temperature to obtain modified porous carbon-based materials. Bismuth-supported graphene oxide nanoparticles were mixed with metal oxides to prepare a composite aerogel. The composite aerogel was then mixed with a binder to form a slurry, which was coated onto the surface of the modified porous carbon-based material. After drying, roll forming, and cutting, the prepared highly active electrode materials met the performance requirements for testing. In contrast, the highly active electrode materials prepared in Comparative Examples 5-8 did not meet the performance requirements, indicating that the highly active electrode materials prepared in this invention not only possess high telephone performance and mechanical strength, but also exhibit superior service life and higher activity.

[0115] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0116] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-activity electrode material for a vanadium redox flow battery, characterized by, The preparation method includes the following steps: S1. The enriched core-shell nanoparticle carbon precursor is ground into powder, and then subjected to pre-oxidation and high-temperature carbonization to obtain modified porous carbon-based materials. The enriched core-shell nanoparticle carbon precursor is prepared by in-situ synthesis of polystyrene on the surface of nanoparticles, followed by dilution in a culture medium, and then mixing and culturing with the carbon precursor. The nanoparticles are selected from any one of nano-silver, nano-copper, nano-carbon black, nano-titanium dioxide, and carbon nanotubes. The nanoparticles have a particle size of 20-60 nm; The carbon precursor is selected from either water hyacinth or water lily. S2. Prepare composite aerogel by mixing supported bismuth nano-graphene oxide with metal oxide; The loaded bismuth nano-graphene oxide is prepared by intercalating a bismuth source into the interlayer of graphene oxide, followed by high-temperature reduction; specifically, it includes the following steps: B1. Add graphene oxide to deionized water, stir evenly, add bismuth source, heat to 40℃, stir at 600 rpm for 40 min, add 36% sodium hydroxide solution to adjust pH to 7.5, continue stirring for 1 h, filter, wash 3 times with deionized water, dry in 80℃ oven for 10 min to obtain modified graphene oxide. B2. The modified graphene oxide was placed in an atmosphere furnace, inert nitrogen gas was introduced, the temperature was raised to 650℃, and the treatment was carried out for 2 hours. After cooling to room temperature, it was washed with deionized water for 3 hours and dried in an oven at 70℃ for 10 minutes to obtain supported nano-bismuth graphene oxide. The bismuth source is selected from one or more of bismuth nitrate, bismuth citrate, and bismuth chloride; The graphene oxide has a particle size of 0.5-2.5 μm; The ratio of graphene oxide, bismuth source, and sodium hydroxide solution used is (0.05-0.15) g:(0.1-0.2) g:(1-3) mL; S3. The composite aerogel is mixed with a binder to form a slurry. The slurry is coated on the surface of the modified porous carbon-based material, and after drying, roll forming and cutting, a highly active electrode material is obtained.

2. The method according to claim 1, characterized in that, The pre-oxidation temperature is 250-350℃, and the time is 1-4h.

3. The method for preparing a highly active electrode material for an all-vanadium redox flow battery according to claim 1, characterized in that, The high-temperature carbonization temperature is 600-900℃, and the time is 2-5 hours.

4. The method for preparing a highly active electrode material for an all-vanadium redox flow battery according to claim 1, characterized in that, The culture medium is prepared by mixing Hogrange's solution, calcium nitrate, and deionized water in a ratio of (0.6-0.66)g:(0.4-0.5)g:(400-600)mL.

5. The method for preparing a highly active electrode material for an all-vanadium redox flow battery according to claim 1, characterized in that, The metal oxide is selected from one or more of nickel oxide, zinc oxide, and manganese oxide; the particle size of the metal oxide is 0.2-0.5 μm.

6. The method for preparing a highly active electrode material for an all-vanadium redox flow battery according to claim 1, characterized in that, The composite aerogel has a pore size of 30-50 nm and a particle size of 8-15 μm.

7. The method for preparing a highly active electrode material for an all-vanadium redox flow battery according to claim 1, characterized in that, The nano-bismuth particles have a diameter of 50-100 nm.

8. The method for preparing a highly active electrode material for an all-vanadium redox flow battery according to claim 1, characterized in that, The adhesive is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, carboxylated styrene-butadiene latex, and sodium carboxymethyl cellulose.

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