CN111883793A - Layered ultrathin carbon-based bipolar plate and preparation method thereof - Google Patents
Layered ultrathin carbon-based bipolar plate and preparation method thereof Download PDFInfo
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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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
- H01M8/0228—Composites in the form of layered or coated products
-
- 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
- H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Composite Materials (AREA)
- Fuel Cell (AREA)
- Laminated Bodies (AREA)
Abstract
The invention relates to the technical field of fuel cells, in particular to a layered ultrathin carbon-based bipolar plate and a preparation method thereof. Compared with the prior art, the invention solves the problems of overlarge thickness caused by the fact that the traditional carbon-based composite bipolar plate meets the strength condition and the contradiction between the technological performance and the electrical conductivity of the carbon-based composite bipolar plate; the prepreg layer can ensure good bending strength of the polar plate under the condition of effectively reducing the thickness of the bipolar plate, and simultaneously, the problem of high molding difficulty caused by low molding thickness is avoided; the thickness is within 1.4mm, the whole volume and the quality of the fuel cell can be obviously reduced, the preparation difficulty is low, the working procedures are few, and the method is suitable for batch production.
Description
Technical Field
The invention relates to the technical field of fuel cells, in particular to a layered ultrathin carbon-based bipolar plate and a preparation method thereof.
Background
The fuel cell is a power generation device that directly converts chemical energy into electric energy, as compared with an internal combustion engine, and is distinguished from a complicated energy conversion process of the internal combustion engine, and thus has a high energy conversion rate. The proton exchange membrane fuel cell respectively leads hydrogen and oxygen into the anode and the cathode, respectively generates oxidation reaction and reduction reaction under the action of a catalyst, electrons are conducted by an external circuit to generate electric energy, and hydrogen ions are transmitted to the cathode through the proton exchange membrane to generate water.
In the power generation process of the proton exchange membrane fuel cell, the bipolar plate plays an important role in the normal operation of the fuel cell. The bipolar plate needs to completely separate the reaction gases of the two electrodes to prevent the violent oxidation reaction caused by the mixing of the two gases. Meanwhile, electron conduction of an external circuit needs to pass through the bipolar plate, and thus the bipolar plate is required to have good electrical conductivity. The transmission of the reaction gas and the discharge of the generated water depend on the gas flow channels on the bipolar plate, so the bipolar plate needs to have good flow channel forming performance, and ensure smaller fluid resistance and good water and gas transmission performance. The bipolar plates occupy a considerable proportion of the mass and volume in the fuel cell system, and their thickness and mass have a great influence on the specific power of the fuel cell.
Various enterprises and research institutes have developed bipolar plates of various materials, including primarily metallic, graphite, and composite bipolar plates. Graphite has good conductivity and corrosion resistance, but has poor mechanical strength, and can keep the safe operation of the galvanic pile under the clamping force and gas pressure of the galvanic pile assembly by needing larger thickness. The metal bipolar plate has high mechanical strength and good gas isolation performance, and can be formed into an ultrathin bipolar plate by mechanical processing methods such as stamping and the like, but electrochemical corrosion is easy to occur in the working state of a fuel cell, and surface treatment is required by methods such as adding a coating and the like. The carbon-based composite bipolar plate takes the graphite polymer composite material as a substrate, has good mechanical strength and corrosion resistance, can adopt a processing method of injection molding and compression molding, is suitable for batch production, but has the performance of conductivity, gas barrier property, structural strength and the like which are difficult to balance.
Disclosure of Invention
The invention aims to provide a layered ultrathin carbon-based bipolar plate and a preparation method thereof. The functional layer of the carbon-based composite bipolar plate is respectively manufactured by adopting a conductive substrate/resin composite outer layer and an inner layer structure in which a conductive additive layer is sandwiched between prepreg. The layered ultrathin carbon-based composite bipolar plate can reduce the volume and the mass of a fuel cell stack, improve the specific power, and is low in production process difficulty and convenient for batch production.
The purpose of the invention can be realized by the following technical scheme:
the invention provides a layered ultrathin carbon-based bipolar plate which is a sandwich layered composite structure and comprises a conductive additive layer, wherein a prepreg layer and a conductive substrate/resin composite layer are sequentially arranged on two sides of the conductive additive layer from inside to outside respectively, and a flow channel structure is formed on the surface of a polar plate through hot die pressing and curing.
As a preferred technical solution of the present invention, the flow channel depth of the flow channel structure is smaller than the thickness of the conductive substrate/resin composite layer, and the prepreg layer and the conductive additive layer are planar structures. Due to different orientations, if the prepreg layer participates in the forming, the internal stress between layers is unbalanced, and the flatness of the polar plate is greatly influenced. And the prepreg layer has high strength and poor precision molding performance of the runner. Therefore, only the conductive substrate/resin composite layer participates in the molding of the runner structure.
As a preferable technical scheme of the invention, the prepreg layer is a prepreg of unidirectional carbon fibers or unidirectional carbon fiber fabrics, and the prepreg layers on the two sides of the conductive additive layer are mutually vertical in orientation. The prepreg layer has good in-plane conductivity and high mechanical strength, and is an industrial intermediate material for producing composite materials. The laminated ultrathin carbon-based composite bipolar plate prepared by the prepreg can ensure that the plate has good bending strength under the condition of effectively reducing the thickness of the bipolar plate, and the ultrathin bipolar plate is prepared by an easier production process.
The unidirectional carbon fiber prepreg or unidirectional carbon fiber fabric prepreg has good mechanical strength, is beneficial to controlling the thickness of the auxiliary composite bipolar plate and reduces the difficulty of the forming process of the ultrathin composite bipolar plate. The outer layer is made of a conductive base material/resin composite material, so that good flow channel forming performance can be guaranteed.
Unidirectional carbon fibers or unidirectional carbon fiber fabric prepreg layers are used as the intermediate layers. Compared with chopped fibers, the unidirectional carbon fibers or unidirectional carbon fiber fabrics can improve the in-plane conductivity of the bipolar plate and can also obviously enhance the mechanical properties of the carbon-based composite bipolar plate; compared with a non-unidirectional carbon fiber fabric, the electrical conductivity has single fiber orientation, and the two unidirectional carbon fibers or the prepreg layers of the unidirectional carbon fiber fabric are vertically stacked, so that the in-plane electrical conductivity of the bipolar plate in two axial directions can be improved, and the in-plane electrical conductivity of the bipolar plate in two axial directions can be uniformly distributed. Therefore, the strength of the bipolar plate is increased, the in-plane conductivity of the bipolar plate is improved, the thickness and the weight of the bipolar plate are reduced, and the specific power of the fuel cell stack is effectively improved.
In a preferred embodiment of the present invention, the thickness of the prepreg layer is 0.06mm to 0.20 mm.
As a preferred technical solution of the present invention, the prepreg layer contains single or combined semi-solid thermosetting resin, and the semi-solid thermosetting resin includes epoxy resin, phenolic resin, polyimide resin, cyanamide resin, bismaleimide resin or unsaturated polyester resin.
Conductive additive layers are prepared between the prepregs as interlayers. The prepreg is subjected to hot embossing to extrude excessive resin coated on the surface of the prepreg, so that the through resistance of the bipolar plate is increased. The conductive additive layers sandwiched between the two prepreg layers can absorb resin extruded from the prepreg layers in the compression molding process, a conductive path is constructed between the adjacent prepreg layers, and the through conductivity of the layered carbon-based composite bipolar plate is improved.
In a preferred embodiment of the present invention, the conductive additive layer contains graphite powder (mainly composed of graphite powder).
In a preferred embodiment of the present invention, the graphite powder has a diameter of 1 to 200 μm. Further preferably, the graphite powder has a diameter of 3 μm to 50 μm. More preferably, the graphite powder has a diameter of 6 to 20 μm.
In a preferred embodiment of the present invention, the amount of graphite powder contained in the conductive agent addition layer is 25g/m2～135g/m2。
As a preferable technical scheme of the invention, the graphite powder comprises natural crystalline flake graphite, and/or expanded graphite, and/or carbon fiber, and/or high-conductivity carbon black.
According to the preferable technical scheme, the conductive agent addition layer is obtained by dispersing graphite powder in a dispersing agent to form slurry, coating the slurry on the surface of a prepreg layer and drying the prepreg layer. Further preferably, the coating is performed by a coating machine.
As a preferable technical scheme of the invention, in the preparation process of the conductive agent addition layer, the dispersing agent is a volatile solvent, and comprises absolute ethyl alcohol, methanol or acetone. Further preferably, the dispersant is absolute ethanol or acetone.
As a preferred technical scheme of the invention, in the preparation process of the conductive agent addition layer, the dispersing agent is poured into the graphite powder, and the slurry with uniformly dispersed graphite is obtained through ultrasonic dispersion and centrifugation. Further preferably, the time for ultrasonic dispersion is 10min and the time for centrifugation is 30 min.
As a preferable technical scheme, in the preparation process of the conductive agent addition layer, the mass ratio of the dispersing agent to the graphite powder is 0.18: 1-0.48: 1.
As a preferable technical scheme of the invention, in the preparation process of the conductive agent addition layer, the slurry is only coated on one side of the prepreg layer, and after the coating is finished, the conductive agent addition layer positioned between the two prepreg layers is obtained by drying in a vacuum oven. The purpose is to make the conductive additive layer uniformly and stably adhered on the surface of the prepreg.
As a preferred technical scheme of the invention, in the preparation process of the conductive agent addition layer, drying refers to drying by using a vacuum oven.
As the preferable technical scheme of the invention, the drying temperature is 40-120 ℃ in the preparation process of the conductive agent addition layer.
In a preferred embodiment of the present invention, the conductive substrate/resin composite layer has a thickness of 0.01mm to 0.4 mm.
The conductive substrate/resin composite layer is used as a surface buffer layer to improve the flow channel forming performance. The prepreg has poor fine flow channel forming performance in the hot die-pressing forming process, and excessive resin components in the prepreg are easily extruded on the surface of the flow channel of the bipolar plate, so that the surface contact resistance of the bipolar plate is increased. The conductive substrate/resin composite layer is used as the buffer layer, so that the surface forming performance of the bipolar plate can be obviously improved, excessive resin extruded from the prepreg can be absorbed, and the contact resistance of the bipolar plate can be reduced.
As a preferred technical solution of the present invention, the conductive substrate/resin composite layer is made of a master batch obtained by mixing a conductive substrate and a thermosetting resin, the conductive substrate includes natural graphite, artificial graphite or expanded graphite, and the thermosetting resin is a resin material of the same type as the prepreg layer. The conductive substrate/resin composite layer master batch is made of thermosetting resin with the same prepreg resin component, so that the adhesion between layers after the mould pressing of the layered structure can be ensured.
As a preferable technical scheme of the invention, the master batch is obtained by sequentially dissolving the conductive base material and the resin in the solvent, stirring and mixing at room temperature, uniformly placing the mixture into a flat plate mold with a preset thickness, and drying and desolventizing the mixture.
As a preferable technical scheme of the invention, in the preparation process of the master batch, the diameter of the conductive base material is 4-120 μm.
As a preferable technical scheme, in the preparation process of the master batch, the mass ratio of the conductive base material to the resin is 1: 9-9: 1.
As a preferable technical scheme of the invention, in the preparation process of the master batch, the mass ratio of the solvent to the master batch is 1:9-3: 7.
As a preferred technical scheme of the invention, in the preparation process of the master batch, the solvent comprises acetone, and/or absolute ethyl alcohol, and/or n-butyl alcohol, and/or ethylene glycol, and/or isopropanol. The method for dissolving the conductive base material and the resin in the solvent in sequence includes ball-milling mixing and centrifugal stirring.
As a preferable technical scheme of the invention, in the preparation process of the master batch, the preset thickness of the flat plate die is 0.1-2.8 mm.
As a preferable technical scheme of the invention, in the preparation process of the master batch, the drying and desolventizing conditions are that the master batch is processed for 0.1 to 10 hours at the temperature of 80 ℃.
The second aspect of the invention provides a method for preparing the layered ultrathin carbon-based bipolar plate, which adopts hot die pressing molding and comprises the following steps:
(1) and the master batch, the prepreg layer coated with the conductive additive layer, the prepreg layer and the master batch are sequentially placed in the die with the runner structure from bottom to top.
(2) And (3) pressing and molding according to the set molding pressure and molding temperature, then keeping the pressure, naturally cooling to room temperature, and removing the pressure to obtain the layered ultrathin carbon-based bipolar plate.
In the preferred technical scheme of the invention, in the step (1), the conductive additive layer coated on the prepreg layer is positioned between two prepreg layers, and the orientation of two adjacent prepreg layers is perpendicular to each other.
In the preferred technical scheme of the invention, in the step (1), the inner surface of the mold is sprayed with the release agent.
In the preferred embodiment of the present invention, in the step (2), the thickness of the conductive substrate/resin composite layer after molding is 0.01mm to 0.4 mm.
As a preferable technical scheme of the invention, in the step (2), the forming pressure is 20MPa, the forming temperature is 150 ℃, and the pressurizing time is 1 h.
The thickness of the finally formed layered ultrathin carbon-based composite bipolar plate is generally less than 1.4 mm.
The hydrogen permeability coefficient of the polar plate obtained by the invention is less than 1 multiplied by 10 by using the GBT20042.6 standard test-14cm3/(s·cm2Pa) and the bending strength is between 50 and 90 MPa.
Compared with the prior art, the invention has the following beneficial effects:
through the layered structure, the requirements of the carbon-based composite bipolar plate on the aspects of thickness (volume), air tightness, structural strength, conductivity, process difficulty and the like are met respectively, and further the optimization of the overall performance of the composite graphite bipolar plate is realized. The use of the unidirectional carbon fiber prepreg cloth is beneficial to realizing the optimization of the structural strength of the ultrathin carbon-based composite bipolar plate, and has good auxiliary functions for the air tightness and the forming of ultrathin plates. The graphite/resin composite layer can realize high-precision molding of the runner structure, and the contact surface resistance of the polar plate can be kept at a lower level. Meanwhile, the invention has low process difficulty and simple and convenient steps and is suitable for mass production.
Drawings
FIG. 1 is a schematic view of a layered stack structure in a hot press molding process according to the present invention.
Fig. 2 is a schematic structural diagram of the layered ultrathin carbon-based composite bipolar plate of the present invention after hot press molding.
Fig. 3 is a partially enlarged view of fig. 2.
In the figure, 1 is a conductive substrate/resin composite layer, 2 is a prepreg layer, 3 is a conductive additive layer, and 4 is a flow channel structure.
Detailed Description
A layered ultra-thin carbon-based bipolar plate is a sandwich layered composite structure and comprises a conductive additive layer 3, wherein a prepreg layer 2 and a conductive substrate/resin composite layer 1 are sequentially arranged on two sides of the conductive additive layer 3 from inside to outside respectively, and a flow channel structure 4 is formed on the surface of a polar plate through hot-pressing and curing. As shown in fig. 2 and 3.
In a preferred embodiment, the flow channel structure 4 has a flow channel depth smaller than the thickness of the conductive substrate/resin composite layer 1, and the prepreg layer 2 and the conductive additive layer 3 are planar structures. Due to different orientations, if the prepreg layer participates in the forming, the internal stress between layers is unbalanced, and the flatness of the polar plate is greatly influenced. And the prepreg layer has high strength and poor precision molding performance of the runner. Therefore, only the conductive substrate/resin composite layer participates in forming the runner structure.
In a preferred embodiment, the prepreg layer 2 is a prepreg of unidirectional carbon fibers or unidirectional carbon fiber fabric, and the orientations of the prepreg layers 2 on both sides of the conductive additive layer 3 are perpendicular to each other. The prepreg layer 2 has good in-plane conductivity and high mechanical strength, and is an industrial intermediate material for producing composite materials. The laminated ultrathin carbon-based composite bipolar plate prepared by the prepreg can ensure that the plate has good bending strength under the condition of effectively reducing the thickness of the bipolar plate, and the ultrathin bipolar plate is prepared by an easier production process.
In a preferred embodiment, the thickness of the prepreg layer 2 is 0.06mm to 0.20 mm.
In a preferred embodiment, the prepreg layer 2 contains a single or a combination of semi-solid thermosetting resins, such as epoxy resin, phenolic resin, polyimide resin, cyanamide resin, bismaleimide resin or unsaturated polyester resin.
In a preferred embodiment, the conductive additive layer 3 contains graphite powder (mainly composed of graphite powder).
In a preferred embodiment, the graphite powder has a diameter of 1 to 200 μm. Further preferably, the graphite powder has a diameter of 3 μm to 50 μm. More preferably, the graphite powder has a diameter of 6 to 20 μm.
In a preferred embodiment, the conductive agent addition layer contains graphite powder in an amount of 25g/m2～135g/m2。
In a preferred embodiment, the graphite powder comprises natural crystalline flake graphite, expanded graphite, carbon fiber and/or highly conductive carbon black.
In a preferred embodiment, the conductive agent-added layer is obtained by dispersing graphite powder in a dispersing agent to form a slurry, coating the slurry on the surface of the prepreg layer 2, and drying the coated layer. Further preferably, the coating is performed by a coating machine.
In a preferred embodiment, during the preparation of the conductive agent addition layer, the dispersant is a volatile solvent, including absolute ethyl alcohol, methanol or acetone. Further preferably, the dispersant is absolute ethanol or acetone.
In a preferred embodiment, during the preparation of the conductive agent addition layer, a dispersing agent is poured into graphite powder, and the graphite powder is subjected to ultrasonic dispersion and centrifugation to obtain a uniform and discrete slurry of graphite. Further preferably, the time for ultrasonic dispersion is 10min and the time for centrifugation is 30 min.
In a preferred embodiment, the mass ratio of the dispersant to the graphite powder is 0.18:1 to 0.48:1 in the preparation of the conductive agent addition layer.
In a preferred embodiment, during the preparation of the conductive agent additive layer, the slurry is coated on only one side of the prepreg layer 2, and after the coating is completed, the slurry is dried in a vacuum oven to obtain the conductive additive layer 3 positioned between the two prepreg layers 2. The purpose is to make the conductive additive layer 3 adhere to the surface of the prepreg uniformly and stably.
In a preferred embodiment, in the process of preparing the conductive agent addition layer, drying refers to drying in a vacuum oven.
In a preferred embodiment, the drying temperature is 40-120 ℃ during the preparation of the conductive agent addition layer.
In a preferred embodiment of the present invention, the conductive substrate/resin composite layer 1 has a thickness of 0.01mm to 0.4 mm.
In a preferred embodiment, the conductive substrate/resin composite layer 1 is made of a master batch obtained by mixing a conductive substrate and a thermosetting resin, wherein the conductive substrate includes natural graphite, artificial graphite or expanded graphite, and the thermosetting resin is a resin material of the same type as the prepreg layer 2. The master batch of the conductive substrate/resin composite layer 1 adopts thermosetting resin with the same prepreg resin component, so that the adhesion between layers after the mould pressing of the layered structure can be ensured.
In a preferred embodiment, the masterbatch is obtained by dissolving the conductive substrate and the resin in the solvent in sequence, stirring and mixing at room temperature, uniformly placing into a flat mold with a preset thickness, and drying to remove the solvent.
In a preferred embodiment, the diameter of the conductive substrate is 4 μm to 200 μm during the preparation of the masterbatch.
In a preferred embodiment, in the preparation process of the master batch, the mass ratio of the conductive base material to the resin is 1: 9-9: 1.
In a preferred embodiment, in the preparation process of the master batch, the mass ratio of the solvent to the master batch is 1:9-3: 7.
In a preferred embodiment, the solvent comprises acetone, and/or absolute ethanol, and/or n-butanol, and/or ethylene glycol, and/or isopropanol during the preparation of the masterbatch. The method for dissolving the conductive base material and the resin in the solvent in sequence includes ball-milling mixing and centrifugal stirring.
In a preferred embodiment, during the preparation of the master batch, the preset thickness of the flat plate mold is 0.1mm to 2.8 mm.
In a preferred embodiment, the master batch is prepared by drying and desolventizing at 80 ℃ for 0.1-10 h.
The preparation method of the layered ultrathin carbon-based bipolar plate adopts hot die pressing molding, and comprises the following steps as shown in figure 1:
(1) the master batch, the prepreg layer 2 coated with the conductive additive layer 3, the prepreg layer 2 and the master batch are sequentially placed in the die with the runner structure from bottom to top.
(2) And (3) pressing and molding according to the set molding pressure and molding temperature, then keeping the pressure, naturally cooling to room temperature, and removing the pressure to obtain the layered ultrathin carbon-based bipolar plate.
In a preferred embodiment, in step (1), the conductive additive layer 3 coated on the prepreg layer 2 is between two prepreg layers 2, and the two adjacent prepreg layers 2 are oriented perpendicular to each other.
In a preferred embodiment, in step (1), the inner surface of the mold is sprayed with a release agent.
In a preferred embodiment, in the step (2), the thickness of the conductive substrate/resin composite layer 1 after molding is 0.01mm to 0.4 mm.
In a preferred embodiment, in the step (2), the molding pressure is 20MPa, the molding temperature is 150 ℃, and the pressing time is 1 h.
The thickness of the finally formed layered ultrathin carbon-based composite bipolar plate is generally less than 1.4 mm.
The invention is described in detail below with reference to the figures and specific embodiments.
Example 1
A layered ultrathin carbon-based composite bipolar plate is a sandwich layered composite structure and comprises a conductive additive layer 3, wherein two sides of the conductive additive layer 3 are respectively and sequentially provided with a prepreg layer 2 and a conductive substrate/resin composite layer 1 from inside to outside (namely, the conductive substrate/resin composite layer 1 comprises two layers of conductive substrates/resin composite layers on the surface and an inner layer formed by the two layers of prepreg layers 2 and the conductive additive layer 3), and the outer surface of the conductive substrate/resin composite layer 1 is provided with a flow channel structure.
Wherein the prepreg layer 2 is an epoxy prepreg (a unidirectional carbon fiber prepreg using epoxy resin as a matrix) with the thickness of 0.2 mm; the conductive additive layer 3 sandwiched by the prepreg layer 2 is prepared by coating natural crystalline flake graphite slurry with the particle size of 10 mu m; the conductive base material/resin composite outer layer is composed of natural crystalline flake graphite powder and epoxy resin in a mass ratio of 8:2, and the particle size of the graphite is 40 mu m.
The preparation method of the layered ultrathin carbon-based composite bipolar plate comprises the following steps:
And 2, pouring acetone serving as a dispersing agent into the natural flake graphite powder, wherein the mass ratio of the dispersing agent to graphite is 0.3:1, performing ultrasonic dispersion for 10min, and centrifuging for 30min to obtain the uniform and discrete slurry of graphite.
And 4, preparing a master batch of the surface conductive base material/resin composite layer 1 by using epoxy resin and natural crystalline flake graphite powder, wherein the diameter of the natural crystalline flake graphite is 40 mu m. Dissolving natural crystalline flake graphite powder and resin in acetone in sequence, and stirring and mixing at room temperature. Wherein the mass ratio of the natural crystalline flake graphite powder to the resin is 8: 2; the mass ratio of the acetone solvent to the master batch is 1: 9. And (3) putting the uniformly mixed master batch into a frame-shaped flat plate die, filling the master batch to the thickness of 0.8mm, and putting the master batch into a forced air drying oven to desolventize at the temperature of 80 ℃ for 1h to obtain the master batch of the surface conductive substrate/resin composite layer 1.
And 5, putting the laminated structure into a mold with a runner structure according to the sequence of the master batch of the conductive substrate/resin composite layer 1, the prepreg layer 2 coated with the conductive additive layer 3, the prepreg layer 2 and the master batch of the conductive substrate/resin composite layer 1, wherein the carbon fibers of the two prepreg layers 2 are oriented vertically, the conductive additive layer 3 is positioned between the two prepreg layers 2, and spraying methyl silicone oil on the inner surface of a mold cavity before mold assembly so as to demold.
And 6, mounting the assembled die on a flat vulcanizing machine for hot die pressing molding, setting the molding pressure to be 20MPa and the molding temperature to be 150 ℃, pressurizing for 1h, then keeping the pressure, naturally cooling to room temperature, and removing the pressure. And taking the formed bipolar plate out of the mold to obtain the layered ultrathin composite graphite bipolar plate. The maximum thickness of the formed polar plate is 1.00 +/-0.05 mm through measurement, the thickness of the composite layer is 0.2 +/-0.02 mm, and the depth of the flow channel is 0.15 +/-0.01 mm.
Example 2
A layered ultrathin carbon-based composite bipolar plate is a sandwich layered composite structure and comprises a conductive additive layer 3, wherein two sides of the conductive additive layer 3 are respectively and sequentially provided with a prepreg layer 2 and a conductive substrate/resin composite layer 1 from inside to outside (namely, the conductive substrate/resin composite layer 1 comprises two layers of conductive substrates/resin composite layers on the surface and an inner layer formed by the two layers of prepreg layers 2 and the conductive additive layer 3), and the outer surface of the conductive substrate/resin composite layer 1 is provided with a flow channel structure.
Wherein the prepreg layer 2 is an epoxy prepreg (a unidirectional carbon fiber prepreg using epoxy resin as a matrix) with the thickness of 0.1 mm; the conductive additive layer 3 sandwiched by the prepreg layer 2 is prepared by coating natural crystalline flake graphite slurry with the particle size of 20 mu m; the conductive base material/resin composite outer layer is composed of natural crystalline flake graphite powder and epoxy resin in a mass ratio of 8:2, and the particle size of the graphite is 40 mu m.
The preparation method of the layered ultrathin carbon-based composite bipolar plate comprises the following steps:
And 2, pouring absolute ethyl alcohol serving as a dispersing agent into the natural crystalline flake graphite powder, wherein the mass ratio of the dispersing agent to graphite is 0.3:1, performing ultrasonic dispersion for 10min, and centrifuging for 30min to obtain the uniform and discrete slurry of graphite.
And 4, preparing a master batch of the surface conductive base material/resin composite layer 1 by using epoxy resin and natural crystalline flake graphite powder, wherein the diameter of the natural crystalline flake graphite is 40 mu m. Dissolving natural crystalline flake graphite powder and resin in acetone in sequence, and stirring and mixing at room temperature. Wherein the mass ratio of the natural crystalline flake graphite powder to the resin is 8: 2; the mass ratio of the acetone solvent to the master batch is 1: 9. And (3) putting the uniformly mixed master batch into a frame-shaped flat plate die, and desolventizing for 1h in a forced air drying oven at the temperature of 80 ℃ to obtain the master batch of the surface conductive substrate/resin composite layer 1.
And 5, putting the laminated structure into a mold with a runner structure according to the sequence of the master batch of the conductive substrate/resin composite layer 1, the prepreg layer 2 coated with the conductive additive layer 3, the prepreg layer 2 and the master batch of the conductive substrate/resin composite layer 1, wherein the carbon fibers of the two prepreg layers 2 are oriented vertically, the conductive additive layer 3 is positioned between the two prepreg layers 2, and spraying methyl silicone oil on the inner surface of a mold cavity before mold assembly so as to demold.
And 6, mounting the assembled die on a flat vulcanizing machine for hot die pressing molding, setting the molding pressure to be 20MPa and the molding temperature to be 150 ℃, pressurizing for 1h, then keeping the pressure, naturally cooling to room temperature, and removing the pressure. And taking the molded bipolar plate out of the mold to obtain the layered ultrathin carbon-based composite bipolar plate. The maximum thickness of the formed polar plate is 0.80 +/-0.05 mm through measurement, the thickness of the composite layer is 0.2 +/-0.02 mm, and the depth of the flow channel is 0.15 +/-0.01 mm.
Example 3
A layered ultrathin carbon-based composite bipolar plate is a sandwich layered composite structure and comprises a conductive additive layer 3, wherein two sides of the conductive additive layer 3 are respectively and sequentially provided with a prepreg layer 2 and a conductive substrate/resin composite layer 1 from inside to outside (namely, the conductive substrate/resin composite layer 1 comprises two layers of conductive substrates/resin composite layers on the surface and an inner layer formed by the two layers of prepreg layers 2 and the conductive additive layer 3), and the outer surface of the conductive substrate/resin composite layer 1 is provided with a flow channel structure.
Wherein the prepreg layer 2 is an epoxy prepreg (a unidirectional carbon fiber prepreg using epoxy resin as a matrix) with the thickness of 0.06 mm; the conductive additive layer 3 sandwiched by the prepreg layer 2 is prepared by coating natural crystalline flake graphite slurry with the grain diameter of 40 mu m; the conductive base material/resin composite outer layer is composed of natural crystalline flake graphite powder and epoxy resin in a mass ratio of 8:2, and the particle size of the graphite is 40 mu m.
The preparation method of the layered ultrathin carbon-based composite bipolar plate comprises the following steps:
And 2, pouring acetone serving as a dispersing agent into the natural flake graphite powder, wherein the mass ratio of the dispersing agent to graphite is 0.3:1, performing ultrasonic dispersion for 10min, and centrifuging for 30min to obtain the uniform and discrete slurry of graphite.
And 4, preparing a master batch of the surface conductive base material/resin composite layer 1 by using epoxy resin and natural crystalline flake graphite powder, wherein the diameter of the natural crystalline flake graphite is 40 mu m. Dissolving natural crystalline flake graphite powder and resin in acetone in sequence, and stirring and mixing at room temperature. Wherein the mass ratio of the natural crystalline flake graphite powder to the resin is 8: 2; the mass ratio of the acetone solvent to the master batch is 1: 9. And (3) putting the uniformly mixed master batch into a frame-shaped flat plate die, filling the master batch to the thickness of 0.8mm, and putting the master batch into a forced air drying oven to desolventize at the temperature of 80 ℃ for 1h to obtain the master batch of the surface conductive substrate/resin composite layer 1.
And 5, putting the laminated structure into a mold with a runner structure according to the sequence of the master batch of the conductive substrate/resin composite layer 1, the prepreg layer 2 coated with the conductive additive layer 3, the prepreg layer 2 and the master batch of the conductive substrate/resin composite layer 1, wherein the carbon fibers of the two prepreg layers 2 are oriented vertically, the conductive additive layer 3 is positioned between the two prepreg layers 2, and spraying methyl silicone oil on the inner surface of a mold cavity before mold assembly so as to demold.
And 6, mounting the assembled die on a flat vulcanizing machine for hot die pressing molding, setting the molding pressure to be 20MPa, the molding temperature to be 150 ℃, pressurizing for 2 hours, then keeping the pressure, naturally cooling to room temperature, and removing the pressure. And taking the formed bipolar plate out of the mold to obtain the layered ultrathin composite graphite bipolar plate. The maximum thickness of the formed polar plate is 0.70 +/-0.05 mm through measurement, the thickness of the composite layer is 0.20 +/-0.02 mm, and the depth of the flow channel is 0.15 +/-0.01 mm.
Example 4
A layered ultrathin carbon-based composite bipolar plate is a sandwich layered composite structure and comprises a conductive additive layer 3, wherein two sides of the conductive additive layer 3 are respectively and sequentially provided with a prepreg layer 2 and a conductive substrate/resin composite layer 1 from inside to outside (namely, the conductive substrate/resin composite layer 1 comprises two layers of conductive substrates/resin composite layers on the surface and an inner layer formed by the two layers of prepreg layers 2 and the conductive additive layer 3), and the outer surface of the conductive substrate/resin composite layer 1 is provided with a flow channel structure.
Wherein the prepreg layer 2 is a phenolic prepreg (unidirectional carbon fiber prepreg taking phenolic resin as a matrix) with the thickness of 0.2 mm; the conductive additive layer 3 sandwiched by the prepreg layer 2 is prepared by coating natural crystalline flake graphite slurry with the particle size of 10 mu m; the conductive base material/resin composite outer layer is composed of natural crystalline flake graphite powder and phenolic resin in a mass ratio of 8:2, and the particle size of the graphite is 40 mu m.
The preparation method of the layered ultrathin carbon-based composite bipolar plate comprises the following steps:
And 2, pouring acetone serving as a dispersing agent into the natural flake graphite powder, wherein the mass ratio of the dispersing agent to graphite is 0.3:1, performing ultrasonic dispersion for 10min, and centrifuging for 30min to obtain the uniform and discrete slurry of graphite.
And 4, preparing a master batch of the surface conductive base material/resin composite layer 1 by using phenolic resin and natural crystalline flake graphite powder, wherein the particle size of the natural crystalline flake graphite is 40 mu m. Dissolving natural crystalline flake graphite powder and resin in acetone in sequence, and stirring and mixing at room temperature. Wherein the mass ratio of the natural crystalline flake graphite powder to the resin is 8: 2; the mass ratio of the acetone solvent to the master batch is 1: 9. And (3) filling the uniformly mixed master batch into a frame-shaped flat plate die with the filling thickness of 0.6mm, and putting the die into a forced air drying oven to remove the solvent for 1h at the temperature of 80 ℃ to obtain the master batch of the surface conductive substrate/resin composite layer 1.
And 5, putting the laminated structure into a mold with a runner structure according to the sequence of the master batch of the conductive substrate/resin composite layer 1, the prepreg layer 2 coated with the conductive additive layer 3, the prepreg layer 2 and the master batch of the conductive substrate/resin composite layer 1, wherein the carbon fibers of the two prepreg layers 2 are oriented vertically, the conductive additive layer 3 is positioned between the two prepreg layers 2, and spraying polytetrafluoroethylene on the inner surface of a mold cavity before mold assembly so as to demold.
And 6, mounting the assembled die on a flat vulcanizing machine for hot die pressing molding, setting the molding pressure to be 25MPa and the molding temperature to be 160 ℃, pressurizing for 2 hours, then keeping the pressure, naturally cooling to room temperature, and removing the pressure. And taking the formed bipolar plate out of the mold to obtain the layered ultrathin composite graphite bipolar plate. The maximum thickness of the formed polar plate is 0.6 +/-0.05 mm through measurement, the thickness of the composite layer is 0.12 +/-0.02 mm, and the depth of the flow channel is 0.09 +/-0.01 mm.
Example 5
A layered ultrathin carbon-based composite bipolar plate is a sandwich layered composite structure and comprises a conductive additive layer 3, wherein two sides of the conductive additive layer 3 are respectively and sequentially provided with a prepreg layer 2 and a conductive substrate/resin composite layer 1 from inside to outside (namely, the conductive substrate/resin composite layer 1 comprises two layers of conductive substrates/resin composite layers on the surface and an inner layer formed by the two layers of prepreg layers 2 and the conductive additive layer 3), and the outer surface of the conductive substrate/resin composite layer 1 is provided with a flow channel structure.
Wherein the prepreg layer 2 is a phenolic prepreg (unidirectional carbon fiber prepreg taking phenolic resin as a matrix) with the thickness of 0.1 mm; the conductive additive layer 3 sandwiched by the prepreg layer 2 is prepared by coating natural crystalline flake graphite slurry with the particle size of 20 mu m; the conductive base material/resin composite outer layer is composed of natural crystalline flake graphite powder and phenolic resin in a mass ratio of 8:2, and the particle size of the graphite is 40 mu m.
The preparation method of the layered ultrathin carbon-based composite bipolar plate comprises the following steps:
And 2, pouring acetone serving as a dispersing agent into the natural flake graphite powder, wherein the mass ratio of the dispersing agent to graphite is 0.4:1, performing ultrasonic dispersion for 15min, and centrifuging for 40min to obtain the uniform and discrete slurry of graphite.
And 4, preparing a master batch of the surface conductive base material/resin composite layer 1 by using phenolic resin and natural crystalline flake graphite powder, wherein the diameter of the natural crystalline flake graphite is 40 mu m. Dissolving natural crystalline flake graphite powder and resin in acetone in sequence, and stirring and mixing at room temperature. Wherein the mass ratio of the natural crystalline flake graphite powder to the resin is 8: 2; the mass ratio of the acetone solvent to the master batch is 1: 9. And (3) putting the uniformly mixed master batch into a frame-shaped flat plate die, filling the master batch to the thickness of 0.6mm, and putting the master batch into a forced air drying oven to desolventize at the temperature of 80 ℃ for 1h to obtain the master batch of the surface conductive substrate/resin composite layer 1.
And 5, putting the laminated structure into a mold with a runner structure according to the sequence of the master batch of the conductive substrate/resin composite layer 1, the prepreg layer 2 coated with the conductive additive layer 3, the prepreg layer 2 and the master batch of the conductive substrate/resin composite layer 1, wherein the carbon fibers of the two prepreg layers 2 are oriented vertically, the conductive additive layer 3 is positioned between the two prepreg layers 2, and spraying polytetrafluoroethylene on the inner surface of a mold cavity before mold assembly so as to demold.
And 6, mounting the assembled die on a flat vulcanizing machine for hot die pressing molding, setting the molding pressure to be 25MPa and the molding temperature to be 160 ℃, pressurizing for 2 hours, then keeping the pressure, naturally cooling to room temperature, and removing the pressure. And taking the formed bipolar plate out of the mold to obtain the layered ultrathin composite graphite bipolar plate. The maximum thickness of the formed polar plate is 0.45 +/-0.05 mm through measurement, the thickness of the composite layer is 0.12 +/-0.02 mm, and the depth of the flow channel is 0.09 +/-0.01 mm.
Example 6
The difference between the present example and example 1 is only that the mass ratio of the natural crystalline flake graphite powder and the phenolic resin of the conductive substrate/resin composite outer layer is 9:1, and the rest materials and the preparation method are the same as those of example 1.
Example 7
The difference between this example and example 1 is only that the curing temperature for molding is 180 ℃, and the rest of the materials and the preparation method are the same as those of example 1.
Example 8
The difference between this embodiment and embodiment 1 is only that the natural flake graphite selected for the conductive substrate/resin composite layer 1 is 80 μm, and the rest of the materials and the preparation method are the same as those in embodiment 1.
Example 9
The difference between this embodiment and embodiment 2 is only that the natural flake graphite selected for the conductive substrate/resin composite layer 1 is 80 μm, and the rest of the materials and the preparation method are the same as those in embodiment 2.
Example 10
The difference between this embodiment and embodiment 3 is only that the natural flake graphite selected for the conductive substrate/resin composite layer 1 is 80 μm, and the rest of the materials and the preparation method are the same as those in embodiment 3.
The conductivity of the bipolar plate prepared in the test examples 1-10 is as follows: GB/T20042.6-2011, the results shown in Table 1 were obtained.
TABLE 1
| Examples | 1 | 2 | 3 | 4 | 5 |
| Conductivity (S/cm) | 169 | 153 | 58 | 171 | 147 |
| Examples | 6 | 7 | 8 | 9 | 10 |
| Conductivity (S/cm) | 181 | 175 | 177 | 156 | 64 |
As can be seen from table 1, the layered ultrathin carbon-based composite bipolar plate prepared by using the prepreg interlayer to improve the bending resistance has good electrical conductivity. As can be seen from comparison of examples 1 to 3, as the particle size of the graphite selected for the conductive additive layer 3 sandwiched by the prepreg increases, the in-plane conductivity of the bipolar plate decreases significantly, and when the particle size of the graphite is 40 μm, the in-plane conductivity of the bipolar plate decreases to 58S/m, which does not achieve the ideal target of the bipolar plate of the fuel cell, i.e., when the particle size of the graphite of the conductive additive layer 3 sandwiched by the prepreg exceeds the most preferable range of the present invention, the in-plane conductivity of the bipolar plate is significantly affected. It is clear from comparison between examples 1 to 3 and examples 8 to 10 that, in the preferred range, it is advantageous to increase the particle size of the graphite in the conductive base material/resin composite layer 1 for increasing the in-plane conductivity of the bipolar plate.
The hydrogen permeability coefficient of the polar plate obtained by the invention is less than 1 multiplied by 10 by using the GBT20042.6 standard test-14cm3/(s·cm2Pa) and the bending strength is between 50 and 90 MPa.
The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. A layered ultra-thin carbon-based bipolar plate is characterized in that the layered ultra-thin carbon-based bipolar plate is of a sandwich layered composite structure and comprises a conductive additive layer, wherein a prepreg layer and a conductive substrate/resin composite layer are sequentially arranged on two sides of the conductive additive layer from inside to outside respectively, and a flow channel structure is formed on the surface of a polar plate through hot die pressing and curing.
2. A layered ultra-thin carbon-based bipolar plate according to claim 1, wherein said prepreg layer comprises any one or more of the following conditions:
(i) the prepreg layers are prepregs of unidirectional carbon fibers or unidirectional carbon fiber fabrics, and the orientations of the prepreg layers on the two sides of the conductive additive layer are mutually vertical;
(ii) the thickness of the prepreg layer is 0.06 mm-0.20 mm;
(iii) the prepreg layer contains single or combined semi-solid thermosetting resin, and the semi-solid thermosetting resin comprises epoxy resin, phenolic resin, polyimide resin, cyanamide resin, bismaleimide resin or unsaturated polyester resin.
3. A layered ultra-thin carbon-based bipolar plate as in claim 1, wherein said conductive additive layer comprises graphite powder.
4. A layered ultra-thin carbon-based bipolar plate according to claim 3, wherein said graphite powder comprises any one or more of the following conditions:
(i) the diameter of the graphite powder is 1-200 μm;
(ii) the conductive agent addition layer preferably contains graphite in an amount of 25g/m2～135g/m2。
(iii) The graphite powder comprises natural crystalline flake graphite, and/or expanded graphite, and/or carbon fiber, and/or high-conductivity carbon black.
5. A layered ultra-thin carbon-based bipolar plate as in claim 3, wherein said conductive additive layer is obtained by dispersing graphite powder in a dispersant to form a slurry, coating the slurry on the surface of the prepreg layer, and drying.
6. A layered ultra-thin carbon-based bipolar plate according to claim 5, wherein said conductive additive layer is prepared by any one or more of the following conditions:
(i) the dispersing agent is a volatile solvent, and comprises absolute ethyl alcohol, methanol or acetone;
(ii) dispersing agent is poured into graphite powder, and slurry with uniformly dispersed graphite is obtained through ultrasonic dispersion and centrifugation;
(iii) the mass ratio of the dispersing agent to the graphite powder is 0.18: 1-0.48: 1;
(iv) coating the slurry on only one side of the prepreg layer, and drying in a vacuum oven after coating to obtain a conductive additive layer positioned between the two prepreg layers;
(v) the drying refers to drying by adopting a vacuum oven;
(vi) the drying temperature is 40-120 ℃.
7. A layered ultra-thin carbon-based bipolar plate according to claim 1, wherein said conductive substrate/resin composite layer comprises any one or more of the following conditions:
(i) the thickness of the conductive substrate/resin composite layer is 0.01-0.4 mm;
(ii) the conductive substrate/resin composite layer is made of master batch formed by mixing a conductive substrate and thermosetting resin, the conductive substrate comprises natural graphite, artificial graphite or expanded graphite, and the thermosetting resin is a resin material with the same type as the prepreg layer.
8. The layered ultra-thin carbon-based bipolar plate of claim 7, wherein the master batch is prepared by sequentially dissolving the conductive substrate and the resin in a solvent, stirring and mixing at room temperature, uniformly placing the mixture in a flat mold with a predetermined thickness, and drying and desolventizing the mixture.
9. A layered ultra-thin carbon-based bipolar plate according to claim 8, wherein the masterbatch is prepared by any one or more of the following conditions:
(i) the diameter of the conductive base material is 4-200 μm;
(ii) the mass ratio of the conductive base material to the resin is 1: 9-9: 1;
(iii) the mass ratio of the solvent to the master batch is 1:9-3: 7;
(iv) the solvent comprises acetone, and/or absolute ethyl alcohol, and/or n-butyl alcohol, and/or ethylene glycol, and/or isopropanol;
(v) the preset thickness of the flat plate die is 0.1-2.8 mm;
(vi) the drying and desolventizing conditions are that the treatment is carried out for 0.1 to 10 hours at the temperature of 80 ℃.
10. The method for preparing the layered ultrathin carbon-based bipolar plate as claimed in any one of claims 1 to 9, wherein hot compression molding is adopted, and the method comprises the following steps:
(1) and the master batch, the prepreg layer coated with the conductive additive layer, the prepreg layer and the master batch are sequentially placed in the die with the runner structure from bottom to top.
(2) And (3) pressing and molding according to the set molding pressure and molding temperature, then keeping the pressure, naturally cooling to room temperature, and removing the pressure to obtain the layered ultrathin carbon-based bipolar plate.
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