CN112038654A - Graphene composite slurry, bipolar plate preparation method and bipolar plate - Google Patents
Graphene composite slurry, bipolar plate preparation method and bipolar plate Download PDFInfo
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- CN112038654A CN112038654A CN202010923780.2A CN202010923780A CN112038654A CN 112038654 A CN112038654 A CN 112038654A CN 202010923780 A CN202010923780 A CN 202010923780A CN 112038654 A CN112038654 A CN 112038654A
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- 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
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0234—Carbonaceous material
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- 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
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0241—Composites
- H01M8/0245—Composites in the form of layered or coated products
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- 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
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
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- 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
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0267—Collectors; Separators, e.g. bipolar separators; Interconnectors having heating or cooling means, e.g. heaters or coolant flow channels
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The graphene composite slurry comprises first-type graphene oxide, second-type graphene oxide, graphene, a soluble carbon source and deionized water, wherein the solid contents of the first-type graphene oxide, the second-type graphene oxide, the graphene and the soluble carbon source in the graphene composite slurry are 0.5% -30%; the mass of the soluble carbon source is 1 per mill-5% of the mass of the first type of graphene oxide, the second type of graphene oxide and the graphene; the particle diameter of the first type of graphene oxide is larger than that of the second type of graphene oxide, the first type of graphene oxide has a first type of functional group, the second type of graphene oxide has a second type of functional group, and the first type of functional group and the second type of functional group can be self-assembled into graphene sheets with intervals. The invention also provides a bipolar plate and a preparation method of the bipolar plate. The bipolar plate provided by the invention has the advantages of low manufacturing cost, simple preparation method and high heat conductivity coefficient.
Description
Technical Field
The invention relates to the technical field of graphene, in particular to graphene composite slurry, a bipolar plate preparation method and a bipolar plate.
Background
Proton Exchange Membrane (PEM) fuel cells are energy conversion devices that use hydrogen as a fuel, air or oxygen as an oxidant, and perfluorosulfonic acid polymer as an electrolyte. The theoretical energy conversion efficiency is very high, but the energy efficiency of the actual system operation is only 40-70%, and 30-60% of chemical energy is converted into heat energy. The generation of a large amount of heat easily leads to the over-high temperature of the battery, when the temperature is over-high, the water content of an electrolyte membrane of the fuel cell is reduced, when the temperature is over-high, a proton exchange membrane is dehydrated seriously, the ionic conductivity is reduced rapidly, the dynamic process of electrochemical reaction is slowed down, and the service efficiency and the service life of the battery are lost. When the temperature is too low, the negative influence on the reactor reaction is also caused, the electrochemical reaction is slow at low temperature, the polarization phenomenon is obvious, and the low energy conversion efficiency and the poor output performance of the reactor are caused. Therefore, the fuel cell stack is subjected to necessary thermal management to be kept in a certain temperature range to work, and the method has important significance for improving the reaction efficiency and the output performance stability of the fuel cell. The requirements for a thermal management system for a fuel cell are typically as follows: (1) controlling the working temperature in a range with higher efficiency; (2) the consistency of the internal temperature of the battery is ensured; (3) ensuring that the battery does not exceed a temperature limit.
In order to meet the above thermal management requirements, the cooling methods adopted by the fuel cells at present are mainly divided into the following types according to the power and volume of the electric stack: (1) the cathode reaction gas is cooled. (2) And (6) cooling the air. (3) And (5) cooling by circulating water. The first two cooling modes are respectively suitable for small fuel cells with power of 100W and below 2kW, and the large fuel cells need to be cooled by water. The cooling method of the circulating water needs to draw cooling channels on the bipolar plate of the fuel cell and needs to add an external pump to provide power for the cooling liquid, which increases the processing cost of the bipolar plate and the complexity of the whole fuel cell system.
Bipolar plates are a key component of PEM fuel cells, accounting for about 80% of the weight and 45% of the cost of the cell. Thus, in addition to supporting the cells, transporting gases, and acting as current collectors in the external circuit, the bipolar plates also play an important role in heat dissipation in PEM fuel cells. Materials for bipolar plates include graphite, metals, and graphite-polymer composites, and non-porous, electrically conductive graphite plates are desirable for bipolar plate materials due to the excellent electrical conductivity and chemical stability of graphite. And the thermal conductivity of the graphite single crystal is 2000W/(m.K), so the graphite single crystal is considered to be a novel high-thermal-conductivity material with great development potential. However, the thermal conductivity of the graphite material for the current fuel cell bipolar plate is about 100-130W/(m.K), and the thermal conductivity is not used as an advantage for the bipolar plate. The reason is that the technical difficulty of preparing the graphite plate with the thermal conductivity of more than 500W/(m.K) is high, and particularly, the technology of processing the flow channel by a graphite plate machine at the later stage is complex and the cost is high.
Disclosure of Invention
In view of this, the present invention provides a bipolar plate with low manufacturing cost, simple method and high thermal conductivity, and a graphene composite slurry for preparing the bipolar plate.
It is also necessary to provide a method for preparing the bipolar plate.
It is also necessary to provide a bipolar plate manufactured using the method of manufacturing a bipolar plate as described above.
The graphene composite slurry comprises first-type graphene oxide, second-type graphene oxide, graphene, a soluble carbon source and deionized water, wherein the solid contents of the first-type graphene oxide, the second-type graphene oxide, the graphene and the soluble carbon source in the graphene composite slurry are 0.5% -30%; the particle diameter of the first type of graphene oxide is larger than that of the second type of graphene oxide, the first type of graphene oxide has a first type of functional group, the second type of graphene oxide has a second type of functional group, and the first type of functional group and the second type of functional group can self-assemble into graphene sheets with different sizes; the mass of the soluble carbon source is 1 per mill-5% of the total mass of the graphene.
Further, the soluble carbon source is at least one of polyvinyl alcohol, polyacrylic acid, glucose and polymers thereof.
Further, the graphene composite slurry also comprises carbon nanotubes, and the mass of the carbon nanotubes is 1 per mill-5% of the total mass of the graphene material.
Further, the graphene composite slurry also comprises a cosolvent, wherein the mass of the cosolvent is 1 per thousand-5% of the total mass of the graphene material.
A method of making a bipolar plate comprising: providing a graphene composite slurry as described above; coating the graphene composite slurry on a first braided fabric; covering a second braided fabric on the first braided fabric coated with the graphene composite slurry, pressurizing and concentrating the graphene composite slurry, and extruding a solvent to reduce the moisture content in the graphene composite slurry to 30% -60%; heating and drying the concentrated graphene composite slurry until the moisture content of the graphene composite slurry is lower than 15%; stripping the first braided fabric and the second braided fabric to obtain a single graphene oxide membrane; stacking and pressing a plurality of single graphene oxide films together to enable the plurality of single graphene oxide films to be integrated to obtain a graphene oxide film block; printing the graphene composite slurry or printable carbon materials with other formulas on two opposite surfaces of the graphene oxide membrane block by using a 3D printing technology to construct bipolar plate runner rudiments on the two surfaces of the graphene oxide membrane block, and then drying and forming in a drying kiln to obtain a first bipolar plate blank structure; reducing the first type of graphene oxide and the second type of graphene oxide in the first bipolar plate blank structure into graphene; and graphitizing the reduced first bipolar plate blank structure to obtain the bipolar plate.
Further, before "stacking and pressing a plurality of single graphene oxide films together", the method further includes: and carrying out steam fumigation or water spraying treatment on the graphene oxide membrane, and coating composite graphene slurry to wet the surface of the graphene oxide membrane until a swelling effect is generated.
Further, after "graphitizing the reduced first bipolar plate blank structure", the method further comprises the steps of: dipping the graphitized first bipolar plate blank structure in a high molecular solution; and pressurizing and curing the impregnated first bipolar plate blank structure to obtain the bipolar plate.
A method of making a bipolar plate comprising: providing a graphene composite slurry as described above; coating the graphene composite slurry on a first braided fabric; covering a second braided fabric on the first braided fabric coated with the graphene composite slurry, pressurizing and concentrating the graphene composite slurry, and extruding a solvent to reduce the moisture content in the graphene composite slurry to 30% -60%; heating and drying the concentrated graphene composite slurry until the moisture content of the graphene composite slurry is lower than 15%; stripping the first braided fabric and the second braided fabric to obtain a single graphene oxide membrane; stacking and pressing a plurality of single graphene oxide films together to enable the plurality of single graphene oxide films to be integrated to obtain a graphene oxide film block; reducing the first type of graphene oxide and the second type of graphene oxide in the graphene oxide membrane block into graphene to obtain a graphite membrane block precursor; graphitizing the graphite film block precursor to obtain a graphite film block; printing the graphene composite slurry on two opposite surfaces of the graphite membrane block by using a 3D printing technology to construct a bipolar plate runner prototype on the two surfaces of the graphite membrane block, and then drying and forming in a drying kiln to obtain a second bipolar plate blank structure; reducing the first type of graphene oxide and the second type of graphene oxide in the second bipolar plate blank structure into graphene; and graphitizing the reduced second bipolar plate blank structure to obtain the bipolar plate.
Further, after "graphitizing the reduced first bipolar plate blank structure", the method further comprises the steps of: dipping the graphitized second bipolar plate blank structure in a high molecular solution; and pressurizing and curing the impregnated second bipolar plate blank structure to obtain the bipolar plate.
A bipolar plate is prepared by the preparation method of the bipolar plate.
According to the preparation method of the graphene composite slurry, the bipolar plate and the bipolar plate, the first graphene oxide and the second graphene oxide which have different particle diameters and have functional groups capable of being self-assembled into graphene sheets with different sizes and a soluble carbon source and the like are configured into the graphene composite slurry, the soluble carbon source and the second graphene oxide can fill gaps existing when the first graphene is laid flat, so that the defects of the first graphene are overcome, the second functional group of the second graphene oxide and the first functional group of the first graphene oxide can be self-assembled into graphene sheets with different sizes and intervals with the second functional group, so that the cooperation among different materials is realized, and the bipolar plate with stable structure and performance can be obtained; 2) the carbon nano tubes are added into the graphene composite slurry in a small amount, so that the overall porosity of a graphite film in the bipolar plate can be increased, a passage for gas to enter and exit is provided for the gas generated in the bipolar plate manufacturing process, the heat conduction performance of the bipolar plate can be improved, and an additional heat dissipation assembly can not be assembled in a fuel cell, so that the manufacturing cost of the bipolar plate is reduced; 3) firstly, coating the graphene composite slurry on a woven fabric, and then pressing and filtering out a solvent (filter pressing) to further concentrate the graphene composite slurry, so that the graphene oxide film cracking caused by too low concentration of the graphene composite slurry and too high drying pressure can be avoided, and the manufacturing cost of the bipolar plate is further reduced; 4) a bipolar plate runner prototype is constructed on the surface of the graphene oxide membrane block or the graphite membrane block in a 3D printing mode, the method is simple and efficient, and meanwhile, the problems of waste of raw materials and uneven local density caused by direct stamping due to machining of the bipolar plate runner prototype can be solved, so that the manufacturing cost of the bipolar plate is further reduced.
Detailed Description
In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined objects, the following detailed description will be made on the specific embodiments, structures, features and effects of the graphene composite slurry, the graphite film block, the preparation method of the graphite film block, the bipolar plate and the preparation method of the bipolar plate provided by the present invention in combination with the preferred embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that when one component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present.
Unless defined otherwise, 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. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The invention provides graphene composite slurry, which comprises first-class graphene oxide, second-class graphene oxide, graphene, a soluble carbon source and deionized water, wherein the solid contents of the first-class graphene oxide, the second-class graphene oxide, the graphene and the soluble carbon source in the graphene composite slurry are 0.5-30%; the mass of the soluble carbon source is 1 per mill-5% of the mass of the first type of graphene oxide, the second type of graphene oxide and graphene; the particle diameter of the first type of graphene oxide is larger than that of the second type of graphene oxide, the first type of graphene oxide has a first type of functional group, the second type of graphene oxide has a second type of functional group, and the first type of functional group and the second type of functional group can be self-assembled into graphene sheets with different sizes.
Wherein the first type of graphene oxide and the second type of graphene oxide may be prepared by two or more different methods.
The second graphene oxide can fill gaps existing in the first graphene oxide when the first graphene oxide is paved, so that defects of the first graphene oxide can be overcome. The first type of functional group and the second type of functional group (hydroxyl or carboxyl and the like) can be self-assembled into graphene sheets with intervals, so that the synergy among different materials is realized, and the bipolar plate with stable structure and performance is further obtained.
Wherein the soluble carbon source is at least one of polyvinyl alcohol, polyacrylic acid, glucose and polymers thereof. The soluble carbon source can provide carbon atoms in the subsequent graphitization process to fill the defects of the graphene and/or the graphene oxide, and is favorable for obtaining the graphite membrane block and the bipolar plate with stable structures and performances. If the content of the soluble carbon source exceeds 5%, non-graphite-structured carbon atoms may be generated during graphitization, which may be disadvantageous to the performance of the graphite membrane block and the bipolar plate. If the content of the soluble carbon source is less than 1 per thousand, carbon can be automatically rearranged in the graphitization process, the soluble carbon source cannot provide enough carbon atoms, and the performance of the graphite membrane block and the bipolar plate is not greatly influenced.
The graphene composite slurry further comprises carbon nanotubes, and the mass of each carbon nanotube is 1 per thousand-5% of that of the graphene material.
The small amount of carbon nano tubes can increase the overall porosity of the graphite film in the graphite film block, provide a passage for gas generated in the manufacturing process of the graphite film block to enter and exit, improve the heat conduction performance of the graphite film block and the bipolar plate, and avoid assembling extra heat dissipation assemblies in a fuel cell, thereby reducing the manufacturing cost of the graphite film block and the bipolar plate.
In addition, a small amount of the carbon nanotubes may balance the performance and manufacturing cost of the graphite film block. If the content of the carbon nanotubes exceeds 5%, the carbon nanotubes may affect the density of the graphite film block. If the content of the carbon nano tube is less than 1 per thousand, the effect of increasing the porosity is not achieved.
The graphene composite slurry further comprises a cosolvent, and the mass of the cosolvent is 1 per mill-5% of the mass of the graphene material.
Wherein the cosolvent comprises at least one of ethanol, propanol, butanol, isopropanol, acetone and the like.
The invention also provides a preparation method of the graphite membrane block, which comprises the following steps:
step S11: providing the graphene composite slurry as described above.
Step S12: coating the graphene composite slurry on a first braided fabric; covering a second braided fabric on the first braided fabric coated with the graphene composite slurry; pressurizing and concentrating the graphene composite slurry, and extruding a solvent to reduce the water content in the graphene composite slurry to 30% -60%; heating and drying the concentrated graphene composite slurry until the moisture content of the graphene composite slurry is lower than 15%; and stripping the first braided fabric and the second braided fabric to obtain a single graphene oxide membrane.
Step S13: and stacking and pressing a plurality of single graphene oxide films together to integrate the plurality of single graphene oxide films into a whole to obtain a graphene oxide film block.
Step S14: and reducing the first type of graphene oxide and the second type of graphene oxide in the graphene oxide membrane block into graphene to obtain a graphite membrane block precursor.
Step S15: and graphitizing the graphite film block precursor to obtain the graphite film block.
After the step S15, the method further includes a step S16: dipping the graphite membrane block in a high molecular solution to obtain a graphite/high molecular composite membrane block; and pressurizing and solidifying to obtain the graphite membrane block.
Wherein, after the step S6, the method further comprises a step S17 of polishing or grinding the graphite film block.
In step S12, the drying in the "graphene composite slurry after heating, drying and concentrating" is performed in a drying kiln, the temperature in the drying kiln is 60 to 95 ℃, and the relative humidity of the gas in the drying kiln is 50 to 90%. The higher humidity is kept, and the problem that the graphene oxide film is cracked due to the fact that the drying speed is too high can be avoided.
In step S12, the coating thickness of the graphene composite slurry is 0.5-20 cm. The coating of the graphene composite slurry is completed through a tape casting process, and the graphene composite slurry sequentially passes through a plurality of scrapers with different heights, so that the consistency of the coating thickness is guaranteed, and the orientation degree of graphene in the graphene composite slurry is improved.
In step S12, the first knitted fabric and the second knitted fabric are nonwoven fabrics made of nanofibers obtained by spinning or fabrics knitted with chemical fiber materials. The main components of the non-woven fabric are high polymer materials such as polyimide, polyacrylonitrile and the like. The porosity of the first braided fabric and the porosity of the second braided fabric are 30-90%, and the diameter of a gap of the first braided fabric and the second braided fabric is smaller than 1 mm.
Wherein, in step S12, the first woven fabric and the second woven fabric are washed and reused after being stripped.
Before step S13, the method further includes the steps of: and (3) carrying out steam fumigation or water spraying treatment on the graphene oxide film, and also coating a small amount of graphene slurry again to ensure that the surface of the graphene oxide film is wetted to generate a swelling effect so as to improve the binding force of the graphene oxide film during pressing.
In step S13, the phrase "stacking and laminating a plurality of single graphene oxide films" refers to a process in which 2 to 10 graphene oxide films are laminated under pressure, and may be continuously rolled or intermittently flat-pressed. Of course, the number of the graphene oxide films stacked together may also be more than 10, which may be determined as the case may be.
In step S13, the thickness of the graphene oxide film block before lamination is 5-20 mm.
In step 14, the reduction may be performed by thermal reduction, chemical reduction, electrochemical reduction, or the like. In this embodiment, the reduction is a thermal reduction method. The thermal reduction is to heat the mixture to 800 ℃ at the speed of 0.2-5 ℃ per minute under the condition of 15000Pa for 5000-. Wherein, a slow heating speed is adopted between 120 ℃ and 160 ℃, and the speed is not more than 2 ℃ per minute.
In step S15, the graphitization is performed in an inner-series graphitization furnace, and the reduced graphite film block precursor is placed around an inner-series motor and is heated by energization of electrodes, thereby achieving the purpose of graphitization. Wherein the pressure of the graphitization is 10000-300000Pa, and the graphitization temperature is more than 3000 ℃.
In step S16, the polymer solution is impregnated to reduce the gas permeability of the graphite membrane block. The polymer solution needs to satisfy the following conditions: the viscosity is relatively low, the solvent is relatively quick to dry, the solvent is cheap and safe, and after the high-molecular material in the high-molecular solution is subjected to pressure curing, the high-molecular material in the high-molecular solution must be capable of being crosslinked, so that the high-molecular material is changed from soluble to insoluble.
In step S16, pressure curing is performed in a specific mold. The pressurization is to increase the density of the graphite film block and ensure that the graphite film block is not air-permeable. The curing is to change the high molecular weight material from soluble to insoluble. The specific mold has a pattern inside that conforms to the surface of the graphite film block to avoid damaging the graphite film block.
The invention also provides a graphite membrane block prepared by the preparation method of the graphite membrane block.
The graphite film block provided by the invention can be used in the fields of soaking films, heating films, radiating blocks, bipolar plates and the like.
The present invention also provides a method of making a bipolar plate (illustrated herein as a first bipolar plate) comprising the steps of:
step S11: providing the graphene composite slurry as described above.
Step S12: coating the graphene composite slurry on a first braided fabric; covering a second braided fabric on the first braided fabric coated with the graphene composite slurry; pressurizing and concentrating the graphene composite slurry, and extruding a solvent to reduce the water content in the graphene composite slurry to 30% -60%; heating and drying the concentrated graphene composite slurry until the moisture content of the graphene composite slurry is lower than 15%; and stripping the first braided fabric and the second braided fabric to obtain a single-layer graphene oxide membrane.
Step S13: and stacking and pressing a plurality of single graphene oxide films together to integrate the plurality of single graphene oxide films into a whole to obtain a graphene oxide film block.
Step S21: and printing the graphene composite slurry obtained in the step S11 on the two opposite surfaces of the graphene oxide membrane block by using a 3D printing technology to construct a bipolar plate runner prototype on the two surfaces of the graphene oxide membrane block, and then drying and molding in a drying kiln to obtain a first bipolar plate blank structure.
Step S22: and reducing the first type of graphene oxide and the second type of graphene oxide in the first bipolar plate blank structure into graphene.
Step 23: graphitizing the reduced first bipolar plate blank structure to obtain a first bipolar plate.
In step S12, the graphene composite slurry is concentrated under pressure using a ram, and a solvent is extruded. Specifically, a container paved with the first braided fabric is provided, the graphene slurry is coated on the first braided fabric, then the second braided fabric is paved, finally the second braided fabric is extruded by using the pressure head, and moisture in the graphene composite slurry between the first braided fabric and the second braided fabric is fed and discharged, so that the concentration of the graphene composite slurry is realized.
After step 23, step S24 is further included: and soaking the graphitized first bipolar plate blank structure in a high molecular solution, and pressurizing and curing the soaked first bipolar plate blank structure to obtain the first bipolar plate.
In step 22, the reduction may be performed by thermal reduction, chemical reduction, electrochemical reduction, or the like. In this embodiment, the reduction is a thermal reduction method. The thermal reduction is to heat the mixture to 800 ℃ at the speed of 0.2-5 ℃ per minute under the condition of 5000-15000pa, preserve the temperature for 2h, and naturally cool the mixture to the normal temperature. Wherein, a slow heating speed is adopted between 120 ℃ and 160 ℃, and the speed is not more than 2 ℃ per minute.
In step S23, the graphitization is performed in an inner-string graphitization furnace, and the reduced first bipolar plate blank structure is placed around an inner-string motor and is heated by the energization of electrodes, so as to achieve the graphitization purpose. Wherein the pressure of the graphitization is 1x104-3 x105pa, the temperature of graphitization is above 3000 ℃.
In step S24, the polymer solution is impregnated to reduce the gas permeability of the first bipolar plate. The polymer solution needs to satisfy the following conditions: the viscosity is relatively low, the solvent is relatively quick to dry, the solvent is cheap and safe, and after the high-molecular material in the high-molecular solution is subjected to pressure curing, the high-molecular material in the high-molecular solution must be capable of being crosslinked, so that the high-molecular material is changed from soluble to insoluble.
In step S24, pressure curing is performed in a specific mold. The pressurization is to increase the density of the first bipolar plate and to ensure that the first bipolar plate is gas-impermeable. The curing is to change the high molecular weight material from soluble to insoluble. The specific mold has a pattern inside that conforms to the surface of the first bipolar plate to avoid damaging the first bipolar plate.
The present invention also provides another method for preparing a bipolar plate (where the first bipolar plate is distinguished by the second bipolar plate), comprising the steps of:
step S31: providing the graphite membrane block and the graphene composite slurry.
Step S32: and (4) printing the graphene composite slurry obtained in the step S31 on the two opposite surfaces of the graphite film block by using a 3D printing technology to construct a bipolar plate runner prototype on the two surfaces of the graphite film block, and then drying and molding in a drying kiln to obtain a second bipolar plate blank structure.
Step S32: and reducing the first type of graphene oxide and the second type of graphene oxide in the second bipolar plate blank structure into graphene.
Step 33: graphitizing the reduced second bipolar plate blank structure to obtain a second bipolar plate.
After step 33, step S34 is also included: and soaking the graphitized second bipolar plate blank structure in a high polymer solution, and pressurizing and curing the soaked second bipolar plate blank structure to obtain the second bipolar plate.
In step 32, the reduction may be performed by thermal reduction, chemical reduction, electrochemical reduction, or the like. In this embodiment, the reduction is a thermal reduction method. The thermal reduction is to heat the mixture to 800 ℃ at the speed of 0.2-5 ℃ per minute under the condition of 5000Pa, preserve heat for 2 hours, and naturally cool the mixture to the normal temperature. Wherein, a slow heating speed is adopted between 120 ℃ and 160 ℃, and the speed is not more than 2 ℃ per minute.
In step S33, the graphitization is performed in an inner-string graphitization furnace, and the reduced second bipolar plate blank structure is placed around an inner-string motor and is heated by the energization of electrodes, so as to achieve the graphitization purpose. The graphitization temperature is above 2700 ℃.
Wherein, in step S34, the polymer solution is impregnated to reduce the gas permeability of the second bipolar plate. The polymer solution needs to satisfy the following conditions: the viscosity is relatively low, the solvent is relatively quick to dry, the solvent is cheap and safe, and after the high-molecular material in the high-molecular solution is subjected to pressure curing, the high-molecular material in the high-molecular solution must be capable of being crosslinked, so that the high-molecular material is changed from soluble to insoluble.
In step S34, pressure curing is performed in a specific mold. The pressurization is to increase the density of the second bipolar plate and to ensure that the second bipolar plate is gas impermeable. The curing is to change the high molecular weight material from soluble to insoluble. The specific mold has a pattern inside that conforms to the surface of the second bipolar plate to avoid damaging the second bipolar plate.
The invention also provides a bipolar plate prepared by the preparation method of the bipolar plate, wherein the bipolar plate can be a first bipolar plate and/or a second bipolar plate. Wherein the bipolar plate is applied to a fuel cell. Preferably, the bipolar plate is applied to a proton exchange membrane fuel cell.
The invention also provides a fuel cell applying the bipolar plate.
The method for producing the bipolar plate of the present invention will be specifically described below by way of examples.
Example 1
Preparing graphene composite slurry: the composite slurry is prepared by mixing, fully stirring and dispersing 5% of graphene oxide (wherein 4% of graphene oxide has a sheet diameter of 20 micrometers, 0.8% of graphene oxide has a sheet diameter of 10 micrometers, and 0.2% of graphene oxide has a sheet diameter of 2 micrometers), 1% of graphene oxide, 0.03% of glucose, 2% of ethanol and the balance of deionized water.
Preparing a single-layer graphene oxide film: pouring the prepared composite slurry into a die with a braided fabric at the bottom and a metal frame at the periphery, and coating the composite slurry smoothly, wherein the thickness of the whole slurry is 10 mm; covering a layer of fabric with the same bottom on the surface, applying pressure on the upper layer of fabric by a pressure head with the size matched with that of the metal frame on the top, enabling the aqueous solvent in the sizing agent to flow out of the pores of the lower layer of fabric along with the increase of the pressure until the overall thickness is reduced by 1/2, enabling the thickness of the sizing agent to be 5mm, then removing the pressure, placing the whole in a drying kiln with the temperature of 80 ℃ and the humidity of 85%, and drying until the fabric can be naturally stripped from the graphene oxide membrane, thereby obtaining the dried graphene oxide membrane.
Preparing a graphene oxide membrane block: and (2) placing the obtained multiple single-layer graphene oxide films in a closed container for steam fumigation or water spraying treatment to wet the surfaces of the graphene oxide composite film blocks until a swelling effect is generated, then stacking the multiple film blocks, and applying a certain pressure, wherein the multiple film blocks can be pressed into a whole due to the swelling effect generated by the graphene oxide on the surfaces of the film blocks, so that the graphene oxide film blocks are obtained.
Preparing a bipolar plate: and then constructing bipolar plate runner rudiments on the upper surface and the lower surface of the whole membrane block by the prepared slurry through a 3D printing method, and then drying and forming in a drying kiln at 80 ℃ to obtain the graphene oxide-based fuel cell bipolar plate blank structure. And then placing the blank structure in a special bipolar plate graphite mold, applying 5000pa of pressure, heating to 800 ℃ at the speed of 2 ℃/min in a vacuum state, then preserving heat for 2h, and naturally cooling to normal temperature to complete the thermal reduction treatment of the graphene oxide. And increasing the pressure to 30000pa, assembling the graphite mold around the inner-series graphitization furnace, electrifying and heating by electrodes to reach the temperature of more than 2700 ℃, realizing graphitization, and naturally cooling to room temperature along with the furnace. Taking out the graphitized graphite film block, soaking the graphitized graphite film block in epoxy resin for 2 hours, taking out the graphitized graphite film block, allowing the epoxy resin with the mass fraction of about 5 percent to enter the graphite film block, and then putting the graphitized graphite film block into a specific steel bipolar plate mould for pressurization and solidification, wherein the density can reach 1.9g/cm3The thickness is about 2 mm. By measuring the in-plane thermal conductivity coefficient of the bipolar plate, the in-plane thermal conductivity coefficient can reach more than 1000W/(mK).
Example 2
Preparing graphene composite slurry: the composite slurry is prepared by mixing, fully stirring and dispersing 10% of graphene oxide (wherein 6% of graphene oxide has a sheet diameter of 20 micrometers, 3% of graphene oxide has a sheet diameter of 10 micrometers, and 1% of graphene oxide has a sheet diameter of 2 micrometers), 1% of graphene oxide has a glucose content of 0.45%, 2.5% of ethanol and 85.5% of deionized water.
Preparing a single-layer graphene oxide film: the same method as that of example 1 for preparing a single-layer graphene oxide film.
Preparing a graphene oxide membrane block: the same method as that of example 1 for preparing a graphene oxide membrane block.
Preparing a bipolar plate: the same procedure as in example 1 was used to prepare a bipolar plate. By measuring the in-plane thermal conductivity coefficient of the bipolar plate, the temperature can reach over 900W/(mK).
Example 3
Preparing graphene composite slurry: the composite slurry is prepared by mixing, fully stirring and dispersing 10% of graphene oxide (wherein 6% of graphene is 20 micrometers in sheet diameter, 3% of graphene is 10 micrometers in sheet diameter, and 1% of graphene is 2 micrometers in sheet diameter), 1% of graphene, 0.045% of glucose, 0.05% of carbon nanotube, 2.5% of ethanol and the balance of deionized water.
Preparing a single-layer graphene oxide film: the same method as that of example 1 for preparing a single-layer graphene oxide film.
Preparing a graphene oxide film structure: the same method as that of example 1 for preparing the graphene oxide film structure.
Preparing a graphite heat dissipation film: the same procedure as in example 1 was used to prepare a graphite heat-dissipating film. The heat conductivity coefficient of the graphite heat dissipation film can reach over 900W/(mK) through measurement.
From the above, it can be seen that a bulk graphite material with high thermal conductivity can be obtained by using graphene oxide + graphene + soluble carbon as raw materials and using the self-assembly effect of the nanomaterial (soluble carbon), and the thermal conductivity is more than 2 times that of the expanded graphite by compression molding.
According to the preparation method of the graphene composite slurry, the bipolar plate and the bipolar plate, the first graphene oxide and the second graphene oxide which have different particle diameters and have functional groups capable of being self-assembled into graphene sheets with different sizes and a soluble carbon source and the like are configured into the graphene composite slurry, the soluble carbon source and the second graphene oxide can fill gaps existing when the first graphene is laid flat, so that the defects of the first graphene are overcome, the second functional group of the second graphene oxide and the first functional group of the first graphene oxide can be self-assembled into graphene sheets with different sizes and intervals with the second functional group, so that the cooperation among different materials is realized, and the bipolar plate with stable structure and performance can be obtained; 2) the carbon nano tubes are added into the graphene composite slurry in a small amount, so that the overall porosity of a graphite film in the bipolar plate can be increased, a passage for gas to enter and exit is provided for the gas generated in the bipolar plate manufacturing process, the heat conduction performance of the bipolar plate can be improved, and an additional heat dissipation assembly can not be assembled in a fuel cell, so that the manufacturing cost of the bipolar plate is reduced; 3) firstly, coating the graphene composite slurry on a woven fabric, and then pressing and filtering out a solvent (filter pressing) to further concentrate the graphene composite slurry, so that cracking of a graphite film caused by too low concentration and too high drying pressure of the graphene composite slurry can be avoided, and the manufacturing cost of the bipolar plate is further reduced; 4) a bipolar plate runner prototype is constructed on the surface of the graphene oxide membrane block or the graphite membrane block in a 3D printing mode, the method is simple and efficient, and meanwhile, the problems of waste of raw materials and uneven local density caused by direct stamping due to machining of the bipolar plate runner prototype can be solved, so that the manufacturing cost of the bipolar plate is further reduced.
Although the present invention has been described with reference to the above preferred embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The graphene composite slurry is characterized by comprising a first type of graphene oxide, a second type of graphene oxide, graphene, a soluble carbon source and deionized water, wherein the solid content of the graphene composite slurry is 0.5-30%; the mass of the soluble carbon source is 1 per mill-5% of the total mass of the graphene; the particle diameter of the first type of graphene oxide is larger than that of the second type of graphene oxide, the first type of graphene oxide has a first type of functional group, the second type of graphene oxide has a second type of functional group, and the first type of functional group and the second type of functional group can be self-assembled into graphene sheets with different sizes.
2. The graphene composite paste according to claim 1, wherein the soluble carbon source is at least one of polyvinyl alcohol, polyacrylic acid, glucose, and polymers thereof.
3. The graphene composite paste according to claim 1, wherein the graphene composite paste further comprises carbon nanotubes, and the mass of the carbon nanotubes is 1% to 5% of the mass of the graphene material.
4. The graphene composite paste according to claim 1, further comprising a cosolvent, wherein the cosolvent is 1% to 5% by mass of the graphene material.
5. A method of making a bipolar plate, comprising:
providing the graphene composite paste according to any one of claims 1 to 4;
coating the graphene composite slurry on a first braided fabric; covering a second braided fabric on the first braided fabric coated with the graphene composite slurry, pressurizing and concentrating the graphene composite slurry, and extruding a solvent to reduce the moisture content in the graphene composite slurry to 30% -60%; heating and drying the concentrated graphene composite slurry until the moisture content of the graphene composite slurry is lower than 15%; stripping the first braided fabric and the second braided fabric to obtain a single-layer graphene oxide membrane;
stacking and pressing a plurality of single graphene oxide films together to enable the plurality of single graphene oxide films to be integrated to obtain a graphene oxide film block;
printing the graphene composite slurry or a printable carbon material precursor with other formula on two opposite surfaces of the graphene oxide membrane block by using a 3D printing technology to construct a bipolar plate runner prototype on the two surfaces of the graphene oxide membrane block, and then drying and molding in a drying kiln to obtain a first bipolar plate blank structure;
reducing the first type of graphene oxide and the second type of graphene oxide in the first bipolar plate blank structure into graphene; and
graphitizing the reduced first bipolar plate blank structure to obtain a bipolar plate.
6. The method of manufacturing a bipolar plate according to claim 5, further comprising, before "stacking and pressing a plurality of single graphene oxide films together:
and carrying out steam fumigation or water spraying treatment on the graphene oxide membrane to wet the surface of the graphene oxide membrane until a swelling effect is generated.
7. The method for preparing a bipolar plate according to claim 5, further comprising, after "graphitizing the reduced first bipolar plate blank structure", the steps of:
dipping the graphitized first bipolar plate blank structure in a high molecular solution; and
and pressurizing and curing the impregnated first bipolar plate blank structure to obtain the bipolar plate.
8. A method of making a bipolar plate, comprising:
providing the graphene composite paste according to any one of claims 1 to 4;
coating the graphene composite slurry on a first braided fabric; covering a second braided fabric on the first braided fabric coated with the graphene composite slurry, pressurizing and concentrating the graphene composite slurry, and extruding a solvent to reduce the moisture content in the graphene composite slurry to 30% -60%; heating and drying the concentrated graphene composite slurry until the moisture content of the graphene composite slurry is lower than 15%; stripping the first braided fabric and the second braided fabric to obtain a single-layer graphene oxide membrane;
stacking and pressing a plurality of single graphene oxide films together to enable the plurality of single graphene oxide films to be integrated to obtain a graphene oxide film block;
reducing the first type of graphene oxide and the second type of graphene oxide in the graphene oxide membrane block into graphene to obtain a graphite membrane block precursor;
graphitizing the graphite film block precursor to obtain a graphite film block;
printing the graphene composite slurry on two opposite surfaces of the graphite membrane block by using a 3D printing technology to construct a bipolar plate runner prototype on the two surfaces of the graphite membrane block, and then drying and forming in a drying kiln to obtain a second bipolar plate blank structure;
reducing the first type of graphene oxide and the second type of graphene oxide in the second bipolar plate blank structure into graphene; and
graphitizing the reduced second bipolar plate blank structure to obtain a bipolar plate.
9. The method for preparing a bipolar plate according to claim 8, further comprising, after graphitizing the reduced first bipolar plate blank structure, the steps of:
dipping the graphitized second bipolar plate blank structure in a high molecular solution; and
and pressurizing and curing the impregnated second bipolar plate blank structure to obtain the bipolar plate.
10. A bipolar plate produced by the method for producing a bipolar plate according to any one of claims 5 to 9.
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