CN212676306U

CN212676306U - Layered ultrathin carbon-based bipolar plate

Info

Publication number: CN212676306U
Application number: CN202021514267.XU
Authority: CN
Inventors: 郑俊生; 明平文; 张存满; 樊润林; 彭宇航
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2021-03-09
Anticipated expiration: 2030-07-27

Abstract

The utility model belongs to the technical field of the fuel cell technique and specifically relates to a ultra-thin carbon back of layer type bipolar plate is related to, and it is sandwich form layer-stepping composite construction, including the conductive additive layer, the both sides on conductive additive layer have set gradually prepreg layer and conductive substrate resin composite bed respectively from inside to outside, and the surface on conductive substrate resin composite bed has the runner structure. Compared with the prior art, the utility model solves the problem of overlarge thickness of the traditional carbon-based composite bipolar plate for meeting 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

Layered ultrathin carbon-based bipolar plate

Technical Field

The utility model belongs to the technical field of the fuel cell technique and specifically relates to an ultra-thin carbon back bipolar plate of layered is related to.

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.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing an ultra-thin carbon base bipolar plate of layered. 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 utility model can be realized through the following technical scheme:

the utility model discloses the first aspect provides an ultra-thin carbon base bipolar plate of layered type, it is with filling form layered composite construction, including conductive additive layer, the both sides on conductive additive layer have set gradually prepreg layer and electrically conductive substrate/resin composite bed respectively from inside to outside, form the runner structure at the solidification of polar plate surface through the hot embossing.

As the preferred technical scheme of the utility model, the runner depth of runner structure be less than the thickness of electrically conductive substrate/resin composite bed, prepreg layer and electrically conductive additive layer be planar structure. Due to different prepreg orientations, if prepreg layers participate in molding, internal stress imbalance among the layers can be caused, 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 of the utility model participates in the molding runner structure.

As the preferred technical scheme of the utility model, the prepreg layer be the prepreg of one-way carbon fiber or one-way carbon fiber fabric, and the orientation mutually perpendicular of the prepreg layer of conductive additive layer both sides. 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.

As the preferable technical proposal of the utility model, the thickness of the prepreg layer is 0.06 mm-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).

As a preferable technical proposal of the utility model, the diameter of the graphite powder is 1-200 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.

As the preferable technical proposal of the utility model, the amount of the graphite powder contained in the conductive agent adding layer is 25g/m²～135g/m²。

As the preferable technical proposal of the utility model, the graphite powder comprises natural crystalline flake graphite, and/or expanded graphite, and/or carbon fiber, and/or high-conductivity carbon black.

As the preferred technical scheme of the utility model, conductive agent additive layer form the thick liquids through dispersing graphite powder in the dispersant, again coat in prepreg layer surface, the stoving obtains. Further preferably, the coating is performed by a coating machine.

As the preferable technical proposal of the utility model, in the preparation process of the conductive agent addition layer, the dispersant is volatile solvent, including absolute ethyl alcohol, methanol or acetone. Further preferably, the dispersant is absolute ethanol or acetone.

As the utility model discloses preferred technical scheme, the conducting agent adds the layer and prepares the in-process, through pouring the dispersant into the graphite powder, through ultrasonic dispersion, the centrifugation obtains the even discrete thick liquids of graphite. Further preferably, the time for ultrasonic dispersion is 10min and the time for centrifugation is 30 min.

As the preferable technical scheme of the utility model, 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 the utility model discloses preferred technical scheme, the conducting agent adds the layer preparation in-process, and the thick liquids only coats in the single face of preimpregnation material layer, dries in the vacuum oven after the coating is accomplished and obtains being located the electric conduction additive layer between the two-layer preimpregnation material layer. The purpose is to make the conductive additive layer uniformly and stably adhered on the surface of the prepreg.

As the utility model discloses preferred technical scheme, the conducting agent adds the layer preparation in-process, and the stoving indicates to adopt vacuum oven to dry.

As the utility model discloses preferred technical scheme, the conducting agent adds the layer preparation in-process, and the temperature of stoving is at 40 ~ 120 ℃.

As the preferable technical proposal of the utility model, the thickness of the conductive substrate/resin composite layer is 0.01 mm-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 the utility model discloses preferred technical scheme, electrically conductive substrate/resin composite bed make with the master batch that electrically conductive substrate and thermosetting resin mixed and form, electrically conductive substrate includes natural graphite, artificial graphite or expanded graphite, thermosetting resin should choose for use with the same resin material of preimpregnation bed type. 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 the utility model discloses preferred technical scheme, the masterbatch is through dissolving electrically conductive substrate and resin in the solvent in proper order to stir the mixture under the room temperature condition, then evenly put into the flat plate mould of predetermineeing thickness, carry out the drying and desolventize and obtain.

As the preferable technical proposal of the utility model, in the preparation process of the master batch, the diameter of the conductive base material is 4-200 μm.

As the preferable technical scheme of the utility model, 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 the preferable technical proposal of the utility model, the mass ratio of the solvent to the master batch is 1:9-3:7 in the preparation process of the master batch.

As a preferred technical scheme of the utility model, 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 the utility model discloses preferred technical scheme, in the preparation process of masterbatch, dull and stereotyped mould predetermine thickness and be 0.1mm ~ 2.8 mm.

As the preferable technical proposal of the utility model, in the preparation process of the master batch, the condition of drying and desolventizing is that the master batch is processed for 0.1h to 10h at the temperature of 80 ℃.

The utility model discloses the second aspect provides a preparation method of ultra-thin carbon base bipolar plate of layer-stepping, adopt hot briquetting, including following step:

(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.

As a preferred technical scheme of the utility model, in the step (1), the conductive additive layer coated on the prepreg layers is positioned between the two prepreg layers, and the two adjacent prepreg layers are oriented mutually perpendicular.

As the preferable technical proposal of the utility model, in the step (1), the inner surface of the mould is sprayed with the release agent.

As the preferable technical proposal of the utility model, in the step (2), the thickness of the conductive substrate/resin composite layer after molding is 0.01 mm-0.4 mm.

As the preferable technical proposal of the utility model, in the step (2), the molding pressure is 20MPa, the molding temperature is 150 ℃, and the pressurizing time is 1 h.

By using the GBT20042.6 standard test, the utility model discloses the hydrogen permeability coefficient of the polar plate that obtains is less than 1 x 10^- ¹⁴cm³/(s·cm²Pa) and the bending strength is between 50 and 90 MPa.

Compared with the prior art, the utility model discloses following beneficial effect has:

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. Simultaneously the utility model discloses the technology degree of difficulty is low, and the step is simple and convenient, is applicable to mass production.

Drawings

Fig. 1 is the utility model discloses layering stack structure sketch map among the hot embossing forming process.

Fig. 2 is a schematic structural view of the layered ultra-thin 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 die pressing and curing. As shown in fig. 2 and 3.

As a preferred embodiment, the depth of the flow channel structure 4 is 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, which is beneficial to improving the precision of fine molding of the flow channel and eliminating the problem of uneven stress distribution after prepreg molding due to different orientations.

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 ℃ in the preparation process of the conductive agent addition layer.

As the preferable technical proposal of the utility model, the thickness of the conductive substrate/resin composite layer 1 is 0.01 mm-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, the ratio of the solvent to the masterbatch is 1:9 to 3:7 by mass during the preparation of the masterbatch.

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.

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 present invention will be described in detail below with reference to the accompanying drawings 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:

step 1, selecting a unidirectional carbon fiber prepreg taking epoxy resin as a matrix as an intermediate layer for enhancing mechanical property, wherein the thickness of the intermediate layer is 0.2mm (the mass per unit area of the fiber is 200 g/m)²The resin content is 20-40%).

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.

Step 3, using a film coating machine to coatThe graphite slurry in the step 2 is uniformly coated on a single surface of the prepreg, the coating thickness is not more than 50 mu m, and the content of graphite is 50g/m²～134g/m². And (3) putting the prepreg into a vacuum drying box, drying the prepreg for 24h at the temperature of 60 ℃, and cutting the dried prepreg coated with the conductive additive layer 3 into the shape and the size of the target bipolar plate by using a die cutting machine.

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) filling the uniformly mixed master batch into a frame-shaped flat plate die with the filling thickness of 0.8mm, 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 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

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.

step 1, selecting a unidirectional carbon fiber prepreg taking epoxy resin as a matrix as an intermediate layer for enhancing mechanical property, wherein the thickness of the intermediate layer is 0.1mm (the mass per unit area of the fiber is 100 g/m)²The resin content is 20-40%).

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.

Step 3, uniformly coating the graphite slurry obtained in the step 2 on a single surface of the prepreg by using a coating machine, wherein the coating thickness is not more than 50 mu m, and the content of graphite is 25g/m²～67g/m². And (3) putting the prepreg into a vacuum drying box, drying the prepreg for 24h at the temperature of 60 ℃, and cutting the dried prepreg coated with the conductive additive layer 3 into the shape and the size of the target bipolar plate by using a die cutting machine.

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 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

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.

step 1, selecting a unidirectional carbon fiber prepreg taking epoxy resin as a matrix as an intermediate layer for enhancing mechanical property, wherein the thickness of the intermediate layer is 0.06mm (the mass per unit area of the fiber is 54 g/m)²The resin content is 35 percent～40％)。

Step 3, uniformly coating the graphite slurry obtained in the step 2 on a single surface of the prepreg by using a coating machine, wherein the coating thickness is not more than 50 mu m, and the content of graphite is 29g/m²～36g/m². And (3) putting the prepreg into a vacuum drying box, drying the prepreg for 24h at the temperature of 60 ℃, and cutting the dried prepreg coated with the conductive additive layer 3 into the shape and the size of the target bipolar plate by using a die cutting machine.

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 with the thickness of 0.8mm, and putting the die into a forced air drying oven to remove the solvent for 1h at the temperature of 80 ℃, thus obtaining the master batch of the surface conductive substrate/resin composite layer 1.

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

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.

step 1, selecting a unidirectional carbon fiber prepreg taking phenolic resin as a matrix as an intermediate layer for enhancing mechanical property, wherein the thickness of the intermediate layer is 0.2mm (the mass per unit area of the fiber is 200 g/m)²The resin content is 20-40%).

Step 3, uniformly spraying the graphite slurry in the step 2 on a single surface of the prepreg by using graphite spraying equipment, wherein the coating thickness is not more than 50 mu m, and the content of graphite is 50g/m²～134g/m². And (3) putting the prepreg into a vacuum drying box, drying the prepreg for 24h at the temperature of 60 ℃, and cutting the dried prepreg coated with the conductive additive layer 3 into the shape and the size of the target bipolar plate by using a die cutting machine.

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) 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 0.6 +/-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

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.

step 1, selecting a unidirectional carbon fiber prepreg taking phenolic resin as a matrix as an intermediate layer for enhancing mechanical property, wherein the thickness of the intermediate layer is 0.1mm (the mass per unit area of the fiber is 200 g/m)²The resin content is 20-40%).

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.

Step 3, uniformly spraying the graphite slurry in the step 2 on a single surface of the prepreg by using graphite spraying equipment, wherein the coating thickness is not more than 50 mu m, and the content of graphite is 25g/m²～67g/m². And (3) putting the prepreg into a vacuum drying box, drying the prepreg for 24h at the temperature of 60 ℃, and cutting the dried prepreg coated with the conductive additive layer 3 into the shape and the size of the target bipolar plate by using a die cutting machine.

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 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 utility model discloses an use preimpregnation material intermediate level to improve the ultra-thin carbon base composite bipolar plate of layer-stepping that bending resistance prepared has good electric conductive property. It can be known from comparative example 1 ~ 3, along with the increase of the graphite particle diameter that the preimpregnation material presss from both sides conductive additive layer 3 and chooses for use, bipolar plate in-plane conductivity can obviously descend, when the graphite particle diameter is 40 mu m, bipolar plate in-plane conductivity descends to 58S/m, can not reach the ideal target of fuel cell bipolar plate, promptly when the graphite particle diameter that the preimpregnation material pressed from both sides conductive additive layer 3 surpasss the utility model discloses a most preferred scope can obviously influence the in-plane conductivity of bipolar plate. 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 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 according to the disclosure of the present invention.

Claims

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. The layered ultra-thin carbon-based bipolar plate of claim 1, wherein the runner structure has a runner depth less than the thickness of the conductive substrate/resin composite layer, and the prepreg layer and the conductive additive layer are planar structures.

3. The layered ultra-thin carbon-based bipolar plate of claim 1, wherein the prepreg layers are unidirectional carbon fibers or unidirectional carbon fiber fabric prepregs, and the orientation of the prepreg layers on both sides of the conductive additive layer are perpendicular to each other.

4. The layered ultra-thin carbon-based bipolar plate of claim 1 or 3, wherein the prepreg layer comprises single or combined semi-solid thermosetting resins, and the semi-solid thermosetting resins comprise epoxy resin, phenolic resin, polyimide resin, cyanamide resin, bismaleimide resin or unsaturated polyester resin.

5. The layered ultra-thin carbon-based bipolar plate according to claim 1 or 3, wherein the thickness of the prepreg layer is 0.06mm to 0.20 mm.

6. The layered ultra-thin carbon-based bipolar plate of claim 1, wherein the conductive additive layer comprises graphite powder having a diameter of 1 μm to 200 μm.

7. The layered ultra-thin carbon-based bipolar plate according to claim 1 or 6, wherein the conductive additive layer comprises graphite powder in an amount of 25g/m²～135g/m²。

8. The layered ultra-thin carbon-based bipolar plate of claim 1, wherein the thickness of the conductive substrate/resin composite layer is 0.01mm to 0.4 mm.

9. The layered ultrathin carbon-based bipolar plate as claimed in claim 1 or 8, wherein the conductive substrate/resin composite layer is made of a master batch formed by mixing a conductive substrate and a thermosetting resin, the diameter of the conductive substrate in the master batch is 4-200 μm, and the mass ratio of the conductive substrate to the resin is 1: 9-9: 1.

10. The layered ultra-thin carbon-based bipolar plate of claim 9, wherein said conductive substrate comprises natural graphite, artificial graphite or expanded graphite, and the thermosetting resin is a resin material of the same type as the prepreg layer.