CN115763861A - Graphite composite bipolar plate with 3D metal framework and preparation method thereof - Google Patents
Graphite composite bipolar plate with 3D metal framework and preparation method thereof Download PDFInfo
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- CN115763861A CN115763861A CN202211547813.3A CN202211547813A CN115763861A CN 115763861 A CN115763861 A CN 115763861A CN 202211547813 A CN202211547813 A CN 202211547813A CN 115763861 A CN115763861 A CN 115763861A
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 197
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 194
- 239000010439 graphite Substances 0.000 title claims abstract description 194
- 239000002131 composite material Substances 0.000 title claims abstract description 121
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 108
- 239000002184 metal Substances 0.000 title claims abstract description 108
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000006260 foam Substances 0.000 claims abstract description 106
- 239000002245 particle Substances 0.000 claims abstract description 84
- 229920000642 polymer Polymers 0.000 claims abstract description 84
- 239000011148 porous material Substances 0.000 claims abstract description 32
- 238000004132 cross linking Methods 0.000 claims abstract description 12
- 239000000446 fuel Substances 0.000 claims abstract description 10
- 239000011231 conductive filler Substances 0.000 claims abstract description 9
- 239000000853 adhesive Substances 0.000 claims abstract description 7
- 230000001070 adhesive effect Effects 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 59
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 16
- 238000003825 pressing Methods 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 12
- 239000003795 chemical substances by application Substances 0.000 claims description 10
- 239000003960 organic solvent Substances 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 7
- 230000002378 acidificating effect Effects 0.000 claims description 6
- 238000007580 dry-mixing Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 238000007599 discharging Methods 0.000 claims description 5
- 238000000465 moulding Methods 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 238000004904 shortening Methods 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 4
- 238000007731 hot pressing Methods 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 4
- 238000011049 filling Methods 0.000 claims description 3
- 238000007711 solidification Methods 0.000 claims description 3
- 230000008023 solidification Effects 0.000 claims description 3
- 239000006262 metallic foam Substances 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 230000006872 improvement Effects 0.000 abstract description 3
- 239000002253 acid Substances 0.000 abstract 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 229920001169 thermoplastic Polymers 0.000 description 3
- 229920001187 thermosetting polymer Polymers 0.000 description 3
- 239000004416 thermosoftening plastic Substances 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000007770 graphite material Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000004634 thermosetting polymer Substances 0.000 description 2
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 150000004985 diamines Chemical class 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
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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
Abstract
The invention discloses a graphite composite bipolar plate with a 3D metal framework and a preparation method thereof. The invention takes foam metal as a 3D metal framework of a graphite composite bipolar plate, graphite particles as conductive filler and polymer as adhesive, and fills foam pores of the foam metal, and a stable conductive network is constructed in the graphite composite bipolar plate; by virtue of the stable conductive network provided by the foam metal, the graphite composite material bipolar plate obtains stable and high bulk conductivity, the problem that a conductive path is blocked by a polymer can be effectively reduced, and the mechanical strength of the bipolar plate is improved; the cross-linking network formed by the polymer and the 3D metal skeleton formed by the foam metal act together to enhance the mechanical strength; meanwhile, the graphite composite material fills and wraps the foam metal, so that the fuel cell works in an acid environment and is corroded; the invention realizes the simultaneous improvement of the conductivity and the mechanical strength of the graphite composite bipolar plate.
Description
Technical Field
The invention relates to a preparation technology of a bipolar plate of a proton exchange membrane fuel cell, in particular to a graphite composite material bipolar plate with a 3D metal framework and a preparation method thereof.
Background
The materials of the fuel cell bipolar plate mainly comprise graphite materials, metal materials and graphite composite materials. The graphite bipolar plate has good electric conduction, heat conduction and corrosion resistance, and in the processing process and the process of using the graphite bipolar plate, the graphite bipolar plate is brittle, so that the preparation cost of the graphite bipolar plate is high. When the metal material is used as the bipolar plate, the metal material has lower gas permeability, better mechanical strength and excellent conductivity, but the fuel cell bipolar plate needs to work in an acidic environment for a long time, and the corrosion of the metal bipolar plate can be accelerated due to the humidity and high temperature, so that the metal bipolar plate emits ions polluting a proton exchange membrane, and the service life of the fuel cell is further influenced. The graphite composite material bipolar plate is prepared by taking graphite as a main conductive filler and a polymer as a binder, uniformly mixing the conductive filler and the binder and performing injection molding or hot pressing, has high conductivity and high thermal conductivity of a graphite material and high mechanical strength of the polymer, and has excellent corrosion resistance of both the graphite and the polymer. Graphite composites have great potential as bipolar plate materials.
At present, the traditional graphite composite material bipolar plate forms a conductive path by mutual contact between graphite particles, so that a conductive network is constructed in the bipolar plate, and the bipolar plate has conductive performance. In the traditional graphite composite material bipolar plate, the contact among graphite particles has certain randomness, so that even if the bipolar plate with the same graphite content exists, the conductive network of the bipolar plate has difference. This phenomenon is particularly evident when the graphite content is low. As a result, there is instability in the conductive network established within conventional graphite composite bipolar plates.
In the traditional graphite composite material, the conductivity is increased only by continuously increasing the content of graphite, so that a denser and stable conductive network is established. However, the graphite composite material can reduce the mechanical strength of the bipolar plate due to excessive graphite proportion, and the improvement of the mechanical strength of the bipolar plate needs to be improved by increasing the content of the polymer, wherein the polymer is an insulator, and the large amount of the polymer can hinder the construction of a conductive path inside the bipolar plate, so that the conductivity of the bipolar plate is reduced. Therefore, the conductivity and the mechanical strength of the traditional graphite composite bipolar plate are mutually restricted and difficult to be simultaneously improved.
Therefore, a method for establishing a stable conductive network in a material and simultaneously improving the conductive performance and the mechanical strength of the material is urgently needed for the graphite composite material bipolar plate.
Disclosure of Invention
In order to solve the problems that graphite particles are used as conductive fillers, polymers are used as adhesives, a stable conductive network cannot be constructed, and the conductive performance and the mechanical strength of the bipolar plate are improved simultaneously, the invention provides a graphite composite bipolar plate with a 3D metal framework and a preparation method thereof.
One object of the present invention is to propose a graphite composite bipolar plate having a 3D metal skeleton.
The graphite composite bipolar plate having a 3D metal skeleton of the present invention comprises: graphite composites and metal foams; wherein the graphite composite material comprises granular graphite particles and a polymer, wherein the graphite particles account for 50-80 wt%, the particle size of the graphite particles is 100-300 meshes, and the graphite composite material is obtained by stirring and uniformly mixing; the foam metal contains foam pores, and the pore size density of the foam pores is 10-40 ppi; sequentially laying a first layer of graphite composite material, a layer of foam metal and a second layer of graphite composite material in a mold cavity, and closing the mold to form a material to be molded; vibrating the material to be molded in the mold cavity to fill the graphite composite material into foam pores of the foam metal; prepressing the material to be molded in the mold cavity, eliminating gaps among particles, discharging redundant air in the mold cavity, preheating the material to be molded in the mold cavity, improving the processability of the polymer and shortening the hot press molding period; heating the pre-pressed and preheated material to be formed, so that the polymer generates crosslinking and solidification between the graphite particles and the foam metal to form a crosslinking network; meanwhile, pressure is applied to the material to be formed, so that the foam metal, graphite particles and the polymer are crosslinked more tightly, the mechanical strength and density of the material are improved, and the graphite composite bipolar plate with the 3D metal framework is pressed; releasing pressure, cooling to room temperature, demolding, and obtaining a graphite composite bipolar plate with a 3D metal framework, wherein in the graphite composite bipolar plate, foam metal is used as the 3D metal framework of the graphite composite bipolar plate, graphite particles are used as conductive fillers and polymer is used as an adhesive, the graphite particles and the polymer are used for filling foam pores in the foam metal, the foam metal and the graphite particles are mutually contacted to construct a stable conductive network in the graphite composite bipolar plate, so that the conductive path blockage caused by polymer enrichment is reduced, and the bulk conductivity of the graphite composite bipolar plate is improved; the cross-linking network formed by the polymer and the 3D metal framework formed by the foam metal act together to enhance the mechanical strength of the graphite composite material bipolar plate, and meanwhile, the graphite composite material fills and wraps the foam metal to prevent the foam metal from being corroded when exposed to the acidic environment of the fuel cell to work.
In the graphite composite material, the graphite particles are artificial graphite particles, natural microcrystalline graphite particles or natural crystalline flake graphite particles. The polymer is thermoplastic or thermosetting polymer; the physical state of the polymer is solid and liquid. In the process of preparing the graphite composite material, the mixing method adopts dry mixing or wet mixing; when dry mixing is adopted, the solid polymer and the graphite particles are directly stirred and mixed uniformly, and the particle size of the solid polymer is 100-300 meshes; when wet mixing is adopted, selecting an organic solvent capable of dissolving the polymer, uniformly mixing the solid or liquid polymer and the graphite particles in the organic solvent to obtain a mixed material, then putting the mixed material into a vacuum drying oven, and heating in vacuum at 50-80 ℃ for 20-60 min to remove the organic solvent; and further adding a corresponding curing agent or an accelerator according to the curing conditions of the polymer, wherein the curing agent and the accelerator respectively account for 1wt% and 1-2 wt% of the mass of the polymer.
The thickness of the first layer of graphite composite material is 1-2 mm; the thickness of the foam metal is 3-5 mm; the thickness of the second layer of graphite composite material is 3-5 mm.
Another objective of the present invention is to provide a graphite composite bipolar plate having a 3D metal skeleton and a method for preparing the same.
The preparation method of the graphite composite bipolar plate with the 3D metal framework comprises the following steps:
1) Weighing granular graphite particles and a polymer, placing the graphite particles and the polymer in a container, wherein the graphite particles account for 50-80 wt%, and the particle size of the graphite particles is 100-300 meshes, and mechanically stirring to obtain a uniformly mixed graphite composite material;
2) Providing foam metal, wherein the foam metal contains foam pores, and the pore density of the foam pores is 10-40 ppi;
3) In a mould cavity, a first layer of graphite composite material with the thickness of 1-2 mm is laid, then foam metal with the thickness of 3-5 mm is placed on the graphite composite material, and finally a second layer of graphite composite material with the thickness of 3-5 mm is laid on the foam metal, and the mould is closed to form a material to be formed;
4) Vibrating the material to be molded in the mold cavity by using a vibration test bed to enable the graphite composite material to be filled into foam pores of the foam metal;
5) Placing a mold cavity on a workbench of a hot press, prepressing a material to be molded in the mold cavity, repeatedly prepressing for multiple times, prepressing to eliminate gaps among particles, discharging redundant air in the mold cavity, preheating the material to be molded in the mold cavity, preheating to improve the processability of a polymer, and shortening the hot press molding period; preheating and then prepressing, or preheating after prepressing;
6) Heating the pre-pressed and preheated material to be formed, so that the polymer generates crosslinking and solidification between the graphite particles and the foam metal to form a crosslinking network; meanwhile, pressure is applied to the material to be formed, so that the foam metal, the graphite particles and the polymer are crosslinked more tightly, the mechanical strength and the density of the material are improved, and the graphite composite material bipolar plate is pressed;
7) Releasing pressure, cooling to room temperature, demolding, and obtaining a graphite composite bipolar plate with a 3D metal framework, wherein in the graphite composite bipolar plate, foam metal is used as the 3D metal framework of the graphite composite bipolar plate, graphite particles are used as conductive fillers and polymer is used as an adhesive, the graphite particles and the polymer are used for filling foam pores in the foam metal, the foam metal and the graphite particles are mutually contacted to construct a stable conductive network in the graphite composite bipolar plate, so that the conductive path blockage caused by polymer enrichment is reduced, and the bulk conductivity of the graphite composite bipolar plate is improved; the cross-linking network formed by the polymer and the 3D metal framework formed by the foam metal act together to enhance the mechanical strength of the graphite composite material bipolar plate, and meanwhile, the graphite composite material fills and wraps the foam metal to prevent the foam metal from being corroded when exposed to the acidic environment of the fuel cell to work.
Wherein, in the step 1), the graphite particles in the graphite composite material are artificial graphite particles, natural microcrystalline graphite particles or natural crystalline flake graphite particles; the polymer is a thermoplastic or thermosetting polymer, and is a solid polymer or a liquid polymer; in the process of preparing the graphite composite material, the mixing method adopts dry mixing or wet mixing; when dry mixing is adopted, the solid polymer and the graphite particles are directly stirred and mixed uniformly, and the particle size of the solid polymer is 100-300 meshes; when wet mixing is adopted, selecting an organic solvent capable of dissolving the polymer, uniformly mixing the solid or liquid polymer and the graphite particles in the organic solvent to obtain a mixed material, then putting the mixed material into a vacuum drying oven, and heating in vacuum at 50-80 ℃ for 20-60 min to remove the organic solvent; and further adding a corresponding curing agent or an accelerator according to the curing conditions of the polymer, wherein the curing agent and the accelerator respectively account for 1wt% and 1-2 wt% of the mass of the polymer. (ii) a Mechanically stirring for 5-15 min at 100-500 r/min.
In step 2), the foam metal is foam copper, foam aluminum, foam zinc, foam nickel, foam titanium or foam iron.
In the step 4), the vibration frequency is 30-100 Hz, the amplitude is 1-2 mm, and the vibration duration is 5-20 min.
In the step 5), the prepressing pressure is 1-5 MPa, and the time is 10-15 s; after prepressing, the prepressing is repeated for 2 to 4 times at intervals of 10 to 15 s. The preheating temperature is 60-120 ℃, and the time is 3-10 min.
In the step 6), the pressure increase rate of hot pressing is 5-10 MPa/min, and the pressure is 20-80 MPa; the heating speed is 5-10 ℃/min, the heating temperature is 150-200 ℃, and the time for heat preservation and pressure maintaining is 20-60 min.
The invention has the advantages that:
the foam metal is used as a 3D metal framework of the graphite composite bipolar plate, the graphite particles are used as conductive filler and the polymer is used as adhesive, and the foam metal and the graphite particles are filled in foam pores of the foam metal and are contacted with each other, so that a stable conductive network is constructed in the graphite composite bipolar plate; by means of the stable conductive network provided by the foam metal, the graphite composite bipolar plate can obtain stable and high bulk conductivity, and can effectively reduce the problem that a polymer blocks a conductive path, improve the content of the polymer in the graphite composite bipolar plate and further improve the mechanical strength of the bipolar plate; the crosslinked network formed by the polymer and the 3D metal framework formed by the foam metal act together to enhance the mechanical strength of the graphite composite material bipolar plate; meanwhile, the graphite composite material fills and wraps the foam metal, so that the foam metal is prevented from being corroded when exposed to the acidic environment of the fuel cell to work; the graphite composite bipolar plate prepared by the invention realizes the simultaneous improvement of the conductivity and the mechanical strength of the graphite composite bipolar plate.
Drawings
Fig. 1 is a schematic view of an embodiment of a method of preparing a graphite composite bipolar plate having a 3D metal skeleton according to the present invention in a mold cavity.
Detailed Description
The invention will be further elucidated by means of specific embodiments in the following with reference to the drawing.
Example one
The preparation method of the graphite composite bipolar plate with the 3D metal skeleton of the embodiment includes the following steps:
1) Weighing 25g of granular natural crystalline flake graphite particles and 15g of epoxy resin as polymers, putting the polymers into an ethanol solvent, putting the graphite particles with the particle size of 150 meshes, 0.3g of isofeverone diamine as a curing agent and 0.15g of 2-methylimidazole as an accelerant into a beaker, mechanically stirring the materials at a rotating speed of 200r/min for 5 to 10min, putting the materials into a vacuum drying oven, and heating the materials at 60 ℃ for 20 to 30min under a vacuum environment to remove the ethanol solvent, thereby obtaining a uniformly mixed and dried graphite composite material;
2) Providing copper foam with the same horizontal size as the die cavity, wherein the size is 80mm multiplied by 80mm, the thickness is 5mm, foam pores are thick in the inner part and the surface of the foam metal, and the pore density of the foam pores is 30ppi;
3) After uniformly spraying a release agent in a mold cavity, firstly paving a layer of graphite composite material 1-1 with the thickness of 1mm, then placing foam copper 1-2 on the graphite composite material, and finally paving a layer of graphite composite material 1-1 with the thickness of 5mm on the foam metal, and closing the mold to form a material to be molded, as shown in figure 1;
4) Vibrating the material to be molded in the mold cavity for 5min at the frequency of 50Hz and the amplitude of 1.5mm by using a vibration test bed, so that the graphite composite material is filled into foam pores of the foam metal;
5) Placing a mold cavity on a workbench of a hot press, pre-pressing a material to be molded in the mold cavity, keeping the pressure at 2MPa for 15s, then removing the pressure for waiting for 10s, repeating the pre-pressing for 3 times, pre-pressing to eliminate gaps among particles, discharging redundant air in the mold cavity, preheating the material to be molded in the mold cavity at 90 ℃, improving the processability of a polymer and shortening the hot press molding period;
6) Heating the pre-pressed and preheated material to be molded to 160 ℃ at a heating rate of 10 ℃/min; meanwhile, applying pressure to the material to be molded at a pressurization speed of 10MPa/min, increasing the pressure to 50-60 MPa, and preserving heat and pressure for 30min, thereby pressing a bipolar plate structure;
7) And releasing the pressure, cooling to room temperature, and demolding to obtain the graphite composite material bipolar plate with the 3D metal framework.
Example two
The preparation method of the graphite composite bipolar plate with the 3D metal framework comprises the following steps:
1) Weighing 21g of granular natural crystalline flake graphite particles and 7g of thermosetting phenolic resin powder as polymers, putting the polymers into a beaker, mechanically stirring the polymers for 10min at a rotating speed of 250r/min, wherein the particle size of the graphite particles is 100 meshes, and the particle size of the polymers is 100 meshes to obtain a graphite composite material which is uniformly mixed;
2) Providing foamed nickel with the same horizontal size as the die cavity, wherein the size is 80mm multiplied by 80mm, the thickness is 3mm, and the pore density of foam pores is 20ppi;
3) After uniformly spraying a release agent in a mold cavity, firstly paving a layer of graphite composite material 1-1 with the thickness of 1mm, then placing foam nickel 1-2 on the graphite composite material, finally paving a layer of graphite composite material 1-1 with the thickness of 3mm on the foam metal, and closing the mold to form a material to be molded;
4) Vibrating the material to be molded in the mold cavity for 5min at the vibration frequency of 90Hz and the amplitude of 2mm by using a vibration test bed, so that the graphite composite material is filled into foam pores of the foam metal;
5) Placing a mold cavity on a workbench of a hot press, preheating a material to be molded in the mold cavity at 100 ℃, preserving heat for 5min, then pre-pressing the material to be molded in the mold cavity at 2MPa, maintaining the pressure for 15s, then removing the pressure, waiting for 10s, and repeating the pre-pressing for 3 times;
6) Heating the pre-pressed and preheated material to be formed to 180 ℃ at a heating rate of 10 ℃/min, simultaneously applying pressure to the material to be formed at a pressurizing rate of 10MPa/min, increasing the pressure to 60MPa, and keeping the temperature and the pressure for 20-30 min, thereby pressing a bipolar plate structure;
7) And releasing the pressure, cooling to room temperature, and demolding to obtain the graphite composite material bipolar plate with the 3D metal framework.
EXAMPLE III
The preparation method of the graphite composite bipolar plate with the 3D metal framework comprises the following steps:
1) Weighing 21g of granular natural crystalline flake graphite particles and 9g of thermoplastic polyvinylidene fluoride powder as polymers, putting the polymers into a beaker, mechanically stirring the polymers for 10min at a rotating speed of 300r/min, wherein the particle size of the graphite particles is 200 meshes, and the particle size of the polymers is 200 meshes, so as to obtain a graphite composite material which is uniformly mixed;
2) Providing titanium foam with the same horizontal size as the die cavity, wherein the size is 80mm multiplied by 80mm, the thickness is 3mm, and the pore density of foam pores is 40ppi;
3) After uniformly spraying a release agent in a mold cavity, firstly paving a layer of graphite composite material 1-1 with the thickness of 1mm, then placing foam titanium 1-2 on the graphite composite material, finally paving a layer of graphite composite material 1-1 with the thickness of 3mm on the foam metal, and closing the mold to form a material to be molded;
4) Vibrating the material to be molded in the mold cavity for 10min at the vibration frequency of 50Hz and the amplitude of 2mm by using a vibration test bed, so that the graphite composite material is filled into foam pores of the foam metal;
5) Placing a mold cavity on a workbench of a hot press, preheating a material to be molded in the mold cavity at the temperature of 120 ℃, preserving heat for 10min, then pre-pressing the material to be molded in the mold cavity at the pressure of 5MPa, maintaining the pressure for 15s, then removing the pressure, waiting for 10s, and repeating the pre-pressing for 3 times;
6) Heating the pre-pressed and preheated material to be formed to 180 ℃ at a heating rate of 10 ℃/min, simultaneously applying pressure to the material to be formed at a pressurizing rate of 10MPa/min, increasing the pressure to 60MPa, and preserving heat and pressure for 30min, so as to press a bipolar plate structure;
7) Releasing the pressure, cooling to room temperature, and demolding to obtain the graphite composite bipolar plate with the 3D metal framework.
Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (10)
1. A graphite composite bipolar plate having a 3D metal backbone, the graphite composite bipolar plate comprising: graphite composites and metal foams; wherein the graphite composite material comprises granular graphite particles and a polymer, wherein the graphite particles account for 50-80 wt%, the particle size of the graphite particles is 100-300 meshes, and the graphite composite material is obtained by stirring and uniformly mixing; the foam metal contains foam pores, and the pore size density of the foam pores is 10-40 ppi; sequentially laying a first layer of graphite composite material, a layer of foam metal and a second layer of graphite composite material in a mold cavity, and closing the mold to form a material to be molded; vibrating the material to be molded in the mold cavity to fill the graphite composite material into foam pores of the foam metal; prepressing the material to be molded in the mold cavity, eliminating gaps among particles, discharging redundant air in the mold cavity, preheating the material to be molded in the mold cavity, improving the processability of the polymer and shortening the hot press molding period; heating the pre-pressed and preheated material to be formed, so that the polymer generates crosslinking and solidification between the graphite particles and the foam metal to form a crosslinking network; meanwhile, pressure is applied to the material to be formed, so that the foam metal, graphite particles and the polymer are crosslinked more tightly, the mechanical strength and density of the material are improved, and the graphite composite bipolar plate with the 3D metal framework is pressed; releasing pressure, cooling to room temperature, demolding, and obtaining a graphite composite bipolar plate with a 3D metal framework, wherein in the graphite composite bipolar plate, foam metal is used as the 3D metal framework of the graphite composite bipolar plate, graphite particles are used as conductive fillers and polymer is used as an adhesive, the graphite particles and the polymer are used for filling foam pores in the foam metal, the foam metal and the graphite particles are mutually contacted to construct a stable conductive network in the graphite composite bipolar plate, so that the conductive path blockage caused by polymer enrichment is reduced, and the bulk conductivity of the graphite composite bipolar plate is improved; the cross-linking network formed by the polymer and the 3D metal framework formed by the foam metal act together to enhance the mechanical strength of the graphite composite material bipolar plate, and meanwhile, the graphite composite material fills and wraps the foam metal to prevent the foam metal from being corroded when exposed to the acidic environment of the fuel cell to work.
2. The graphite composite bipolar plate of claim 1, wherein the graphite particles in the graphite composite are artificial graphite particles, natural microcrystalline graphite particles, or natural flake graphite particles.
3. The graphite composite bipolar plate of claim 1, wherein said first layer of graphite composite has a thickness of 1 to 2mm; the thickness of the foam metal is 3-5 mm; the thickness of the second layer of graphite composite material is 3-5 mm.
4. A preparation method of a graphite composite bipolar plate with a 3D metal framework is characterized by comprising the following steps:
1) Weighing granular graphite particles and a polymer, wherein the graphite particles account for 50-80 wt%, and the particle size of the graphite particles is 100-300 meshes, and mechanically stirring to obtain a uniformly mixed graphite composite material;
2) Providing foam metal, wherein the foam metal contains foam pores, and the pore density of the foam pores is 10-40 ppi;
3) In the mould cavity, firstly, a first layer of graphite composite material is laid, then foam metal is placed on the graphite composite material,
finally, laying a second layer of graphite composite material on the foam metal, and closing the die to form a material to be molded;
4) Vibrating the material to be molded in the mold cavity by using a vibration test bed to enable the graphite composite material to be filled into foam pores of the foam metal;
5) Placing a mold cavity on a workbench of a hot press, prepressing a material to be molded in the mold cavity, repeatedly prepressing for multiple times, prepressing to eliminate gaps among particles, discharging redundant air in the mold cavity, preheating the material to be molded in the mold cavity, preheating to improve the processability of a polymer, and shortening the hot press molding period; preheating and then pre-pressing, or pre-pressing and then preheating;
6) Hot pressing the pre-pressed and pre-heated material to be formed, and heating to ensure that the polymer is in a molten state, thereby generating cross-linking and curing between the graphite particles and the foam metal to form a cross-linked network; meanwhile, pressure is applied to the material to be formed, so that the foam metal, the graphite particles and the polymer are crosslinked more tightly, the mechanical strength and the density of the material are improved, and the graphite composite material bipolar plate is pressed;
7) Releasing pressure, cooling to room temperature, demoulding to obtain the graphite composite bipolar plate with a 3D metal framework, wherein in the graphite composite bipolar plate, foam metal is used as the 3D metal framework of the graphite composite bipolar plate, graphite particles are used as conductive filler and polymer is used as adhesive, and the graphite particles and the polymer are filled in foam pores in the foam metal,
the foam metal and the graphite particles are mutually contacted to construct a stable conductive network in the graphite composite material bipolar plate, so that the conductive path blockage caused by polymer enrichment is reduced, and the bulk conductivity of the graphite composite material bipolar plate is improved; the cross-linking network formed by the polymer and the 3D metal framework formed by the foam metal act together to enhance the mechanical strength of the graphite composite material bipolar plate, and meanwhile, the graphite composite material fills and wraps the foam metal to prevent the foam metal from being corroded when exposed to the acidic environment of the fuel cell to work.
5. The method of claim 4, wherein in the step 1), the graphite particles in the graphite composite material are artificial graphite particles, natural microcrystalline graphite particles or natural flake graphite particles.
6. The method according to claim 4, wherein in step 1), the polymer is a solid polymer or a liquid polymer; in the process of preparing the graphite composite material, dry mixing or wet mixing is adopted as a mixing method; when dry mixing is adopted, the solid polymer and the graphite particles are directly stirred and mixed uniformly, and the particle size of the solid polymer is 100-300 meshes; when wet mixing is adopted, an organic solvent capable of dissolving the polymer is selected, the solid or liquid polymer and the graphite particles are uniformly mixed in the organic solvent to obtain a mixed material, then the mixed material is placed in a vacuum drying oven, and the organic solvent is removed by vacuum heating.
7. The method of claim 4, wherein in step 1), a corresponding curing agent or accelerator is added according to the curing conditions of the polymer, and the curing agent and the accelerator respectively account for 1wt% and 1-2 wt% of the mass of the polymer.
8. The method of claim 4, wherein in the step 4), the frequency of the vibration is 30 to 100Hz, the amplitude is 1 to 2mm, and the duration of the vibration is 5 to 20min.
9. The method according to claim 4, wherein in step 5), the pre-pressing pressure is 1 to 5MPa for 10 to 15s; after prepressing, the interval is 10 to 15s, and the prepressing is repeated for 2 to 4 times; the preheating temperature is 60-120 ℃, and the time is 3-10 min.
10. The production method according to claim 4, wherein in the step 6), the pressure increase rate of the hot pressing is 5 to 10MPa/min, and the pressure is 20 to 80MPa; the heating speed is 5-10 ℃/min, the heating temperature is 150-200 ℃, and the time for heat preservation and pressure maintaining is 20-60 min.
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