CN117325491A - Composite bipolar plate, preparation method thereof and fuel cell - Google Patents
Composite bipolar plate, preparation method thereof and fuel cell Download PDFInfo
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- CN117325491A CN117325491A CN202311301911.3A CN202311301911A CN117325491A CN 117325491 A CN117325491 A CN 117325491A CN 202311301911 A CN202311301911 A CN 202311301911A CN 117325491 A CN117325491 A CN 117325491A
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- 239000002131 composite material Substances 0.000 title claims abstract description 82
- 239000000446 fuel Substances 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical class [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 99
- FFUAGWLWBBFQJT-UHFFFAOYSA-N hexamethyldisilazane Chemical compound C[Si](C)(C)N[Si](C)(C)C FFUAGWLWBBFQJT-UHFFFAOYSA-N 0.000 claims abstract description 95
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 70
- 239000010439 graphite Substances 0.000 claims abstract description 69
- 229920005989 resin Polymers 0.000 claims abstract description 38
- 239000011347 resin Substances 0.000 claims abstract description 38
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000002156 mixing Methods 0.000 claims abstract description 24
- 239000007770 graphite material Substances 0.000 claims abstract description 22
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 13
- 238000003825 pressing Methods 0.000 claims abstract description 4
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 15
- 229920001568 phenolic resin Polymers 0.000 claims description 15
- 239000005011 phenolic resin Substances 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 12
- 239000003960 organic solvent Substances 0.000 claims description 12
- 229920001721 polyimide Polymers 0.000 claims description 12
- 239000012779 reinforcing material Substances 0.000 claims description 11
- 239000002033 PVDF binder Substances 0.000 claims description 10
- 239000004642 Polyimide Substances 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 10
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 9
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 8
- 239000004917 carbon fiber Substances 0.000 claims description 8
- 230000035484 reaction time Effects 0.000 claims description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- 239000004734 Polyphenylene sulfide Substances 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- 229920000069 polyphenylene sulfide Polymers 0.000 claims description 6
- 238000001291 vacuum drying Methods 0.000 claims description 6
- 238000004821 distillation Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000006229 carbon black Substances 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 229910021392 nanocarbon Inorganic materials 0.000 claims description 3
- 239000000126 substance Substances 0.000 abstract description 8
- 125000002887 hydroxy group Chemical group [H]O* 0.000 abstract description 6
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 abstract description 5
- 229910052710 silicon Inorganic materials 0.000 abstract description 5
- 239000010703 silicon Substances 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 15
- 230000004048 modification Effects 0.000 description 10
- 238000012986 modification Methods 0.000 description 10
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- 239000009719 polyimide resin Substances 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- OCKGFTQIICXDQW-ZEQRLZLVSA-N 5-[(1r)-1-hydroxy-2-[4-[(2r)-2-hydroxy-2-(4-methyl-1-oxo-3h-2-benzofuran-5-yl)ethyl]piperazin-1-yl]ethyl]-4-methyl-3h-2-benzofuran-1-one Chemical compound C1=C2C(=O)OCC2=C(C)C([C@@H](O)CN2CCN(CC2)C[C@H](O)C2=CC=C3C(=O)OCC3=C2C)=C1 OCKGFTQIICXDQW-ZEQRLZLVSA-N 0.000 description 1
- 229920001342 Bakelite® Polymers 0.000 description 1
- 229910014571 C—O—Si Inorganic materials 0.000 description 1
- 229910002808 Si–O–Si Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000004637 bakelite Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
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- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
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- 239000002245 particle Substances 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D7/00—Producing flat articles, e.g. films or sheets
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/21—After-treatment
-
- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0213—Gas-impermeable carbon-containing materials
-
- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0221—Organic resins; Organic polymers
-
- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
- H01M8/0226—Composites in the form of mixtures
-
- 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
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Composite Materials (AREA)
- Mechanical Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Fuel Cell (AREA)
Abstract
The application provides a composite bipolar plate, a preparation method thereof and a fuel cell. The preparation method comprises the following steps: reacting a graphite material under the condition of introducing nitrogen and hexamethyldisilazane steam to obtain modified graphite; mixing the resin and the modified graphite by a wet method to obtain a composite material; and (3) pressing, forming and curing the composite material to obtain the composite bipolar plate. The application modifies the graphite material by HMDS to lead hydroxyl groups on the surface of the graphite to react with the HMDS to generate a silicon ether bond, and HCH in MDS 3 Also grafted to the graphite surface, a silyl ether bond and grafted CH 3 The chemical bond between the graphite and the resin is enhanced, so that the compatibility and the binding force between the graphite and the resin are enhanced, the mechanical strength and the air tightness of the composite bipolar plate are improved, and the preparation of the composite bipolar plate with thinner thickness is facilitated.
Description
Technical Field
The application relates to the technical field of fuel cells, in particular to a composite bipolar plate, a preparation method thereof and a fuel cell.
Background
A fuel cell is a device for directly converting chemical energy in fuel into electric energy, which is not limited by carnot cycle and has high energy conversion efficiency. One type of fuel cell is called a Proton Exchange Membrane (PEM) fuel cell, which has received much attention because of its advantages of high energy density, high theoretical power generation efficiency (85% -90%), long endurance, cleanliness, no pollution, etc. PEM fuel cells include the following basic components: cathode, anode, electrolyte membrane and Bipolar Plate (BP). The cathode, anode, and electrolyte membrane are typically interposed between a pair of bipolar plates that function as current collectors for the anode and cathode. And, suitable flow channels (flow passages) and openings are formed in the bipolar plates to distribute the reactant gases of the fuel cell over the surfaces of each cathode and anode.
Ultra-thin bipolar plates with high conductivity, corrosion resistance, mechanical properties and excellent gas tightness are key to reducing fuel cell quality, reducing cost, and improving fuel cell performance. At present, a composite electrode plate made of graphite materials and resin is a research hot spot due to high comprehensive performance. However, the thickness of the current composite electrode plate is relatively large (greater than 2 mm). In addition, the interface compatibility of the graphite material and the resin is poor, gaps are easy to exist at the interface between the graphite material and the resin, the air tightness of the composite bipolar plate is not up to the standard, gas permeation is easy to occur, and the operation performance of the battery is affected. In addition, stress at the gaps is easy to concentrate, and the connected gaps easily break the composite bipolar plate, so that the mechanical strength of the composite bipolar plate is affected.
Disclosure of Invention
In view of this, the present application proposes a method for preparing a composite bipolar plate, so as to improve interfacial compatibility between graphite and resin, improve mechanical strength of the composite bipolar plate, and reduce thickness thereof.
In addition, there is a need to provide a composite bipolar plate prepared by the above-described preparation method and a fuel cell including the same.
An embodiment of the present application provides a method for preparing a composite bipolar plate, including the following steps:
reacting a graphite material under the condition of introducing nitrogen and hexamethyldisilazane steam to obtain modified graphite;
mixing the resin and the modified graphite by a wet method to obtain a composite material;
and (3) pressing, forming and curing the composite material to obtain the composite bipolar plate.
In one embodiment, the mass ratio of the graphite material to the hexamethyldisilazane vapor is (5 to 10): 1.
In one embodiment, the temperature of the reaction is 120 ℃ or higher, the reaction time is 20-60 min, and the flow rate of the nitrogen in the reaction is 100-150 mL/min.
In one embodiment, the graphite material comprises one or more of expanded graphite, expanded graphite worms, microcrystalline graphite, flake graphite. The resin comprises one or more of polyphenylene sulfide, polyvinylidene fluoride, phenolic resin and polyimide.
In one embodiment, the mass ratio of the modified graphite to the resin is (70-80): 10-20.
In one embodiment, the step of wet mixing comprises: and dissolving the resin, the modified graphite and the reinforcing material in an organic solvent, stirring and mixing, and removing the organic solvent to obtain the composite material.
In one embodiment, the organic solvent comprises one or more of acetone, N-methylpyrrolidone, absolute ethyl alcohol, dimethylformamide. The stirring and mixing time is 3-6 h. The method for removing the organic solvent comprises stirring and heating, reduced pressure distillation or vacuum drying. The reinforcing material comprises one or more of nano carbon black, chopped carbon fiber and graphene.
In one embodiment, the preparation method further comprises a pretreatment step:
drying the graphite material under the conditions of introducing nitrogen and heating, wherein the flow rate of the nitrogen is 100-150 mL/min, and the drying temperature is 100-110 ℃;
heating the hexamethyldisilazane solution to vaporize the hexamethyldisilazane solution to obtain the hexamethyldisilazane vapor.
An embodiment of the present application provides a composite bipolar plate prepared by the preparation method as described above.
An embodiment of the present application provides a fuel cell comprising a composite bipolar plate as described above.
The application modifies the graphite material by HMDS so that hydroxyl groups on the surface of the graphite react with the HMDS to generate a silicon ether bond, and CH in the HMDS 3 Also grafted to the graphite surface, a silyl ether bond and grafted CH 3 The chemical bond between the graphite and the resin is enhanced, so that the compatibility and the binding force between the graphite and the resin are enhanced, the mechanical strength and the air tightness of the composite bipolar plate are improved, and the preparation of the composite bipolar plate with thinner thickness is facilitated.
Drawings
Fig. 1 is a flow chart of a method for preparing a composite bipolar plate according to an embodiment of the present application.
Fig. 2 is a cross-sectional view of a composite bipolar plate provided in an embodiment of the present application.
Fig. 3 is an infrared spectrum of the expanded graphite of example 1 of the present application before and after HMDS modification.
Description of the main reference signs
Composite bipolar plate 100
Modified graphite layer 10
Resin layer 20
The following detailed description will further illustrate embodiments of the present application in conjunction with the above-described figures.
Detailed Description
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 embodiments of the present application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the examples of the application.
Referring to fig. 1, a first aspect of the present application provides a method for preparing a composite bipolar plate, which includes steps S10 to S30.
Step S10: introducing nitrogen (N) into graphite material 2 ) And reacting with Hexamethyldisilazane (HMDS) steam to obtain the modified graphite.
Step S20: and mixing the resin and the modified graphite by a wet method to obtain a composite material.
Step S30: and (3) pressing, forming and curing the composite material to obtain the composite bipolar plate.
It will be appreciated that the reference to steps is intended to clearly describe a particular method of preparation and is not intended to limit the order of steps.
In some embodiments, in step S10, the mass ratio of the graphite material to the hexamethyldisilazane vapor is (5-10): 1. For example, the mass ratio of graphite material to hexamethyldisilazane vapor may be 5:1, 6:1, 7:1, 7.5:1, 8:1, 9:1, 10:1, etc., not explicitly recited herein.
In some embodiments, in step S10, the reaction temperature is greater than or equal to 120 ℃, the reaction time is 20min to 60min (e.g., may be 20min, 30min, 40min, 50min, 60min, etc.), the flow rate of nitrogen is 100mL/min to 150mL/min, and the reaction may be performed in an oven. The modification degree of the surface of the graphite material by HMDS is regulated and controlled by controlling the difference of the reaction time. Generally, the longer the time, the more fully the surface reaction. And (3) continuing to prolong the time, and stopping the reaction when the groups on the surface of the graphite material are reacted completely. The reaction time is controlled within 20 min-60 min, and the reaction can be ensured to be complete.
In some embodiments, the graphite material may be, but is not limited to, one or more of expanded graphite, expanded graphite worms, microcrystalline graphite, flake graphite, and the resin may be, but is not limited to, one or more of polyphenylene sulfide (PPS), polyvinylidene fluoride (PVDF), phenolic resin, polyimide (PI).
In some embodiments, in step S20, the mass ratio of the modified graphite to the resin is (70-80): 10-20. For example, the mass ratio of the modified graphite to the resin may be 70: 20. 75: 15. 77: 20. 80: 20. 80: 15. 80:10, etc., not explicitly recited herein.
In some embodiments, in step S20, the step of wet mixing includes: and dissolving the resin, the modified graphite and the reinforcing material in an organic solvent, stirring and mixing, and removing the organic solvent to obtain the composite material. The stirring and mixing may be performed in a magnetic stirrer or a planetary stirrer.
In some embodiments, the organic solvent comprises one or more of acetone, N-methylpyrrolidone (NMP), absolute ethanol, dimethylformamide. The stirring and mixing time is 3-6 h, and the method for removing the organic solvent can be, but is not limited to, stirring and heating, reduced pressure distillation, vacuum drying and the like. The reinforcing material may be, but is not limited to, one or more of nano carbon black, chopped carbon fiber, graphene. The reinforcing material may be 0% to 10% by mass (e.g., may be 1%, 5% or 10%, etc.) based on the total mass of the resin, modified graphite, and reinforcing material. In some embodiments, the reinforcing material may also be omitted.
In some embodiments, in step S30, the composite material may be pressed and formed by using a bipolar plate mold, where the molding pressure may be gradually increased from 10MPa to 90MPa, and the pressure maintaining time may be 1min. The curing process comprises the following steps: and (3) placing the pressed material into a muffle furnace, heating to 150-300 ℃, vacuumizing, and preserving heat and solidifying for 1-2 h. The curing temperature of the resin is 150-300 ℃, and the specific curing temperature of the resin can be adjusted according to different types of the resin. For example, the curing temperature of the phenolic resin is 150℃and the curing temperature of the polyimide resin is 270 ℃.
In some embodiments, prior to step S10, the preparation method further comprises a pretreatment step S00:
drying the graphite material under the conditions of introducing nitrogen and heating, wherein the flow rate of the nitrogen can be 100-150 mL/min, the drying temperature can be 100-110 ℃, and the drying can be performed in an oven;
the HMDS solution is heated (the temperature can be more than 120 ℃) and is vaporized to obtain HMDS steam. It will be appreciated that the mass of the HMDS vapor is equal to the mass of the HMDS solution.
Referring to fig. 2, a second aspect of the present application provides a composite bipolar plate 100 made by the above-described method of manufacture, comprising a laminated modified graphite layer 10 and a resin layer 20. The modified graphite layer 10 is modified with hexamethyldisilazane from graphite, which may be, but is not limited to, one or more of expanded graphite, expanded graphite worms, microcrystalline graphite, flake graphite. The resin layer 20 may be, but is not limited to, one or more of polyphenylene sulfide (PPS), polyvinylidene fluoride (PVDF), phenolic resin, polyimide (PI). The thickness of the composite bipolar plate 100 may be as low as 1.18mm to 1.20mm.
A third aspect of the present application provides a fuel cell comprising a composite bipolar plate 100 as described above. The fuel cell further includes a cathode, an anode, an electrolyte membrane, and the like, and will not be described herein. The fuel cell can be applied to the fields of automobiles and the like.
The present application will be described in detail with reference to examples and comparative examples. It will be appreciated by those skilled in the art that the following examples are for illustrative purposes only and are not to be construed as limiting the invention. The main materials and equipment used in the specific examples and comparative examples are all conventional commercial products.
Graphite: expanded graphite micropowder, particle size: 30-50 μm, very dense graphite Co.
Phenolic resin: model PR51794, sumitomo bakelite limited.
Polyimide: purity 98%, alpha chemical company.
Polyvinylidene fluoride: model: a937799, molecular weight: 64.03, alpha chemical Co., ltd.
Chopped carbon fiber: carbon content 5%, length 0.5mm, dongli carbon fiber Limited company.
Example 1
S00: placing powdered Expanded Graphite (EG) in an oven, introducing N at a flow rate of 150mL/min 2 Heating to 100deg.C, dehydrating and oven drying for 10min; the HMDS solution is heated to 120 ℃ and vaporized to obtain HMDS steam. Wherein the mass ratio of the expanded graphite to the HMDS solution is 5:1.
S10: HMDS vapor is introduced into the oven while N is introduced at a flow rate of 100mL/min 2 Reacting at 120 ℃ for 60min to obtain modified graphite (HEG).
S20: according to the weight percentage of 77:20:3, sequentially dissolving modified graphite, phenolic resin and chopped carbon fibers (reinforcing materials) in absolute ethyl alcohol, stirring and mixing for 4 hours by a magnetic stirrer, after uniform mixing, distilling at 60 ℃ under reduced pressure to remove most of absolute ethyl alcohol, and then drying at 60 ℃ in vacuum to completely remove absolute ethyl alcohol to obtain a composite material.
S30: placing the composite material into a bipolar plate mold, then pressurizing step by step from 10MPa to 90MPa, maintaining the pressure for 1min to prepare a bipolar plate with flow passage characteristics, then placing the bipolar plate into a muffle furnace, heating to 150 ℃, vacuumizing, preserving heat, and curing for 1h to prepare a graphite/phenolic resin composite bipolar plate (marked as PF) with the thickness of 1.18mm 20 EG 77 CF 3 -H)。
Example 2
This embodiment differs from embodiment 1 in that: in the step S20, according to the weight percentage of 80:20, the modified graphite and the phenolic resin are sequentially dissolved in absolute ethyl alcohol, a magnetic stirrer is adopted for stirring and mixing for 4 hours, after the uniform mixing, most absolute ethyl alcohol is removed by reduced pressure distillation at 60 ℃, and then the absolute ethyl alcohol is completely removed by vacuum drying at 60 ℃, so that a composite material is obtained.
The remaining steps are the same as those of example 1, and will not be described again.
Example 2A graphite/phenolic resin composite bipolar plate (designated PF) having a thickness of 1.20mm was prepared 20 EG 80 -H)。
Example 3
This embodiment differs from embodiment 2 in that: in step S00, the mass ratio of expanded graphite to HMDS solution (steam) is 10:1.
The remaining steps are the same as those of example 1, and will not be described again.
Example 3A graphite/phenolic resin composite bipolar plate (designated PF) having a thickness of 1.20mm was prepared 20 EG 80 -H)。
Example 4
This embodiment differs from embodiment 1 in that: the reaction time in the step S10 is 30min; in the step S20, according to the weight percentage of 80:20, the modified graphite and the phenolic resin are sequentially dissolved in absolute ethyl alcohol, a magnetic stirrer is adopted for stirring and mixing for 4 hours, after the uniform mixing, most absolute ethyl alcohol is removed by reduced pressure distillation at 60 ℃, and then the absolute ethyl alcohol is completely removed by vacuum drying at 60 ℃, so that a composite material is obtained.
The remaining steps are the same as those of example 1, and will not be described again.
Example 4A graphite/phenolic resin composite bipolar plate (designated PF) having a thickness of 1.20mm was prepared 20 EG 80 -H)。
Example 5
This embodiment differs from embodiment 1 in that: in the step S20, according to the weight percentage of 77:20:3, sequentially dissolving modified graphite, polyimide resin and chopped carbon fibers (reinforcing materials) in NMP, stirring and mixing for 4 hours by adopting a planetary stirrer, after uniform mixing, distilling at 100 ℃ under reduced pressure to remove most NMP, and then drying at 100 ℃ in vacuum to completely remove NMP to obtain a composite material; in the step S30, the composite material is placed in a bipolar plate mold, then the bipolar plate with flow channel characteristics is prepared by pressurizing and maintaining pressure step by step (the pressure maintaining time is 1 min) from 10MPa to 90MPa, then the bipolar plate is placed in a muffle furnace, the temperature is increased to 270 ℃, and the vacuum pumping, the heat preservation and the solidification are carried out for 1h, so that the composite bipolar plate is prepared.
The remaining steps are the same as those of example 1, and will not be described again.
Example 5A graphite/polyimide composite bipolar plate (designated PI) having a thickness of 1.18mm was prepared 20 EG 77 CF 3 -H)。
Example 6
This embodiment differs from embodiment 1 in that: in step S20, modified graphite, polyvinylidene fluoride and chopped carbon fiber are sequentially dissolved in a compound solution (NMP: ethanol: H) according to the weight percentage of 77:20:3 2 O=20:11:2, volume ratio), stirring and mixing for 4 hours by using a magnetic stirrer, uniformly mixing, distilling at 60 ℃ and 100 ℃ under reduced pressure to remove most of the solvent, and then vacuum drying at 110 ℃ to obtain a composite material; and step S30, placing the composite material into a bipolar plate mold, pressurizing step by step from 10MPa to 90MPa, maintaining the pressure (the pressure maintaining time is 1 min) to prepare a bipolar plate with flow passage characteristics, then placing the bipolar plate into a muffle furnace, heating to 200 ℃, vacuumizing, preserving heat, and curing for 1h to prepare the composite bipolar plate.
The remaining steps are the same as those of example 1, and will not be described again.
Example 6 preparation of graphite/polyvinylidene fluoride composite bipolar plate (noted PVDF) with a thickness of 1.18mm 20 EG 77 CF 3 -H)。
Comparative example 1
Comparative example 1 differs from example 1 in that: the procedure of example 1 was repeated except that the expanded graphite was not modified with HMDS vapor.
A graphite/phenolic resin composite bipolar plate (designated PF) having a thickness of 1.28mm was prepared in comparative example 1 20 EG 77 CF 3 )。
Comparative example 2
Comparative example 2 differs from example 2 in that: the procedure of example 2 was repeated except that the expanded graphite was not modified with HMDS vapor.
A graphite/phenolic resin composite bipolar plate (designated PF) having a thickness of 1.31mm was prepared in comparative example 2 20 EG 80 )。
Comparative example 3
Comparative example 3 differs from example 5 in that: the procedure of example 5 was repeated except that the expanded graphite was not modified with HMDS vapor.
A graphite/polyimide composite bipolar plate (designated as "1.29 mm thick") was produced in comparative example 3PI 20 EG 80 )。
Performance testing
(one) Infrared sign
The Expanded Graphite (EG) before and after HMDS modification in example 1 was subjected to infrared characterization, and the change of functional groups on the graphite surface was observed, and the infrared spectrum is shown in FIG. 3. As can be seen from FIG. 3, EG before the modification treatment and HEG after the modification treatment were both 3449cm -1 There is a stretching vibration peak of O-H, 1633cm -1 There is C=C aromatic vibration peak, 1580cm -1 There is a peak of the benzene ring skeleton, which is the peak of the expanded graphite matrix. With the difference that EG is at 1210cm -1 The vibration peak of-OH exists, the peak disappears in HEG obtained by HMDS modification, and the vibration peak exists in EG 3449cm -1 The O-H vibration peak at the position is weakened, and the reaction of hydroxyl groups on the surface of the expanded graphite in the HMDS treatment process is proved. At the same time, 1381cm of HEG infrared radiation was generated -1 、1088cm -1 And 1052cm -1 Three new peaks, respectively, -CH 3 Vibration peaks, C-O-Si and Si-O-Si telescopic vibration absorption peaks. The three new peaks show that the hydroxyl groups on the surface of the expanded graphite and the HMDS react successfully to form a silicon ether bond, and CH in the HMDS 3 Is also grafted to the surface of the expanded graphite, indicating that the expanded graphite was successfully modified by HMDS.
(II) testing of flexural Strength, conductivity and gas permeability
Reference is made to GB/T20042.6-2011 section 6 of proton exchange membrane fuel cell: method for testing properties of bipolar plate the composite bipolar plates prepared in examples 1 to 6 and comparative examples 1 to 3 were subjected to the above-described performance test.
The results of the performance test of the composite bipolar plates prepared in examples 1 to 6 and comparative examples 1 to 3 are shown in table 1.
TABLE 1
As can be seen from comparing example 1 with comparative example 1, the expanded graphite of example 1 was subjected to HMDS modification treatment to obtain a compositeThe bending strength (mechanical strength) of the composite bipolar plate is improved by 15.7 percent compared with that of the composite bipolar plate obtained by not carrying out HMDS modification treatment (50.69-43.81)/43.81). The mechanical strength is improved because hydroxyl groups on the surface of graphite react with HMDS to form a silyl ether bond, and CH in the HMDS 3 Also grafted to the graphite surface, a silyl ether bond and grafted CH 3 The chemical bond between the graphite and the resin is enhanced, so that the compatibility and the binding force between the graphite and the resin are enhanced. The improvement of mechanical strength is beneficial to preparing thinner composite bipolar plates, so that the composite bipolar plates can have both high mechanical strength and low thickness. In addition, the unmodified expanded graphite is compounded with the resin, and small molecular substance water can be adsorbed on the graphite with high specific surface energy, so that the bonding effect between the resin and the graphite is reduced, and the mechanical strength of the bipolar plate is affected; the modified graphite is favorable for forming a dry and hydrophobic surface, reduces the influence of small molecular substance water on performance, and further enhances the bonding between the graphite and the resin.
As can be seen from the comparison of examples 1 to 6 and comparative examples 1 to 3, the gas permeability of the modified composite bipolar plate is improved by about two orders of magnitude, and the gas tightness of the composite bipolar plate is improved. The improvement of the air tightness is caused by that the modification treatment leads the graphite surface to generate a silicon ether bond and graft CH 3 Thereby enhancing the interfacial bonding of the graphite and the resin and reducing voids, thereby reducing gas permeation.
Compared with examples 3 and 4, the relative content of HMDS in example 1 is higher (the mass ratio of the expanded graphite to the HMDS is 5:1), the reaction time is longer (60 min), and the performance of the prepared composite bipolar plate is more excellent (higher bending strength and conductivity and lower gas permeability). This indicates that the graphite is more fully modified and that the interface bond between the resin and the graphite is tighter.
The application modifies the graphite material by HMDS so that hydroxyl groups on the surface of the graphite react with the HMDS to generate a silicon ether bond, and CH in the HMDS 3 Also grafted to the graphite surface, a silyl ether bond and grafted CH 3 The chemical bond effect between the graphite and the resin is enhanced, so that the compatibility and the binding force between the graphite and the resin are enhanced, and the composite is promotedThe mechanical strength and air tightness of the bipolar plate are beneficial to preparing the composite bipolar plate with thinner thickness.
The foregoing description is of some embodiments of the present application, but is not limited to only those embodiments during actual application. Other variations and modifications of the present application, which are apparent to those of ordinary skill in the art, are intended to be within the scope of the present application.
Claims (10)
1. The preparation method of the composite bipolar plate is characterized by comprising the following steps of:
reacting a graphite material under the condition of introducing nitrogen and hexamethyldisilazane steam to obtain modified graphite;
mixing the resin and the modified graphite by a wet method to obtain a composite material;
and (3) pressing, forming and curing the composite material to obtain the composite bipolar plate.
2. The method of manufacturing a composite bipolar plate according to claim 1, wherein the mass ratio of the graphite material to the hexamethyldisilazane vapor is (5-10): 1.
3. The method for preparing a composite bipolar plate according to claim 1, wherein the temperature of the reaction is 120 ℃ or higher, the reaction time is 20-60 min, and the flow rate of nitrogen in the reaction is 100-150 mL/min.
4. The method of making a composite bipolar plate of claim 1, wherein the graphite material comprises one or more of expanded graphite, expanded graphite worms, microcrystalline graphite, and crystalline flake graphite, and the resin comprises one or more of polyphenylene sulfide, polyvinylidene fluoride, phenolic resin, and polyimide.
5. The method of producing a composite bipolar plate according to claim 1, wherein the mass ratio of the modified graphite to the resin is (70-80): (10-20).
6. The method of preparing a composite bipolar plate of claim 1, wherein said step of wet mixing comprises: and dissolving the resin, the modified graphite and the reinforcing material in an organic solvent, stirring and mixing, and removing the organic solvent to obtain the composite material.
7. The method of preparing a composite bipolar plate according to claim 6, wherein the organic solvent comprises one or more of acetone, N-methylpyrrolidone, absolute ethyl alcohol, dimethylformamide; the stirring and mixing time is 3-6 hours; the method for removing the organic solvent comprises stirring, heating, reduced pressure distillation or vacuum drying; the reinforcing material comprises one or more of nano carbon black, chopped carbon fiber and graphene.
8. The method of preparing a composite bipolar plate according to claim 1, further comprising the step of pretreatment:
drying the graphite material under the conditions of introducing nitrogen and heating, wherein the flow rate of the nitrogen is 100-150 mL/min, and the drying temperature is 100-110 ℃;
heating the hexamethyldisilazane solution to vaporize the hexamethyldisilazane solution to obtain the hexamethyldisilazane vapor.
9. A composite bipolar plate, characterized in that it is produced by the production method according to any one of claims 1 to 8.
10. A fuel cell comprising the composite bipolar plate of claim 9.
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