A flexible graphite bipolar plate and a method of making the same

Abstract

The application belongs to the field of energy storage, and particularly discloses a flexible graphite bipolar plate and a preparation method thereof.The flexible graphite bipolar plate of the application is prepared from raw materials including a molded graphite plate and a resin-based mixture, wherein the molded graphite plate comprises the following components in parts by weight: main graphite 50-70 parts, and an additive 0.5-15 parts; the resin-based mixture comprises the following components in parts by weight: resin 10-30 parts, a curing agent 5-15 parts, a curing accelerator 0.1-3 parts, a release agent 1-10 parts, and a solvent 200-1500 parts; and the curing accelerator is a microcapsule pill.The flexible graphite bipolar plate prepared by the soaking-molding method has high bending strength, short forming time, low air leakage rate and low surface resistance.

Description

Technical Field

[0001] This invention belongs to the field of energy storage, specifically relating to a flexible graphite bipolar plate and its preparation method. Background Technology

[0002] Renewable energy sources such as solar, wind, and tidal power can reduce the pressure on energy demand, but due to their instability, it is difficult to guarantee a stable energy output. Therefore, they require a certain scale of energy storage devices to form a complete power supply system. Thus, developing a highly efficient energy storage system with high storage capacity and economic benefits has become one of the key focuses in the development of renewable and clean energy.

[0003] Fuel cells have garnered worldwide attention as a power source with high energy density, high specific power, environmental friendliness, long lifespan, and high reliability. They can start rapidly at room temperature without a heat engine, occupy a small space, and are not limited by the Carnot cycle, directly converting the chemical energy of hydrogen and oxygen into electrical energy. They are considered one of the best alternatives to traditional energy conversion devices. A fuel cell stack consists of a membrane electrode assembly (MEA), bipolar plates, a diffusion layer, and sealing materials. It is constructed by stacking multiple individual cells in series (with bipolar plates and MEAs alternately stacked and sealed), and then tightly fixed by front and rear end plates and compensation devices. Currently, the main problem is the low voltage of a single cell (0.6–1.0V). To increase the operating voltage, dozens to hundreds of individual cells are used in series in practical applications. The bipolar plates of a fuel cell consist of plates and a flow field. They mainly function to distribute fuel hydrogen and oxidant oxygen, conduct current, conduct heat, cool, and seal. Their cost accounts for approximately 30–60% of the total cost of the fuel cell, and their weight accounts for approximately 60–80% of the total weight. Currently, the main requirements for bipolar plates include corrosion resistance, low contact resistance, high bending strength, strong thermal conductivity, high airtightness, low density, low cost, and easy mass production. They are mainly classified into metal bipolar plates, pure graphite bipolar plates, and graphite-resin composite material bipolar plates.

[0004] Metal plates have good electrical conductivity, high mechanical strength, and strong gas barrier properties, but their surface coatings have poor corrosion resistance, high material and manufacturing costs, and are prone to hydrogen embrittlement. Pure graphite plates, while having strong corrosion resistance, low density, and high electrical conductivity, are difficult to process using existing engraving machines, have poor mechanical properties, and a high air leakage rate, requiring thicker plates to meet the requirements. Graphite / resin composite bipolar plates have been studied by many scholars due to their low cost, high conductivity, high flexibility, easy mass production, excellent corrosion resistance, and high thermal conductivity. However, currently, graphite-resin composite bipolar plates are made by blending non-conductive resin with a certain degree of fluidity with graphite. The high viscosity of the resin cannot completely fill all the pores, resulting in poor liquid resistance. At the same time, it is difficult to balance the contradiction between conductivity and mechanical strength. That is, as the carbon content increases, the conductivity will increase, but the decrease in the proportion of resin will lead to a decrease in its mechanical strength. This makes the conductivity and mechanical properties of the composite bipolar plate exhibit an inverse relationship, making it difficult to obtain a composite bipolar plate with both good mechanical and conductivity properties. In addition, current graphite-resin composite bipolar plate processes suffer from problems such as the inability to mass-produce rapidly, insufficient bending strength of the plates, low production efficiency, and complex manual operation procedures. For example, Ballard proposed a resin impregnation process for preparing polyvinylidene chloride-flexible graphite bipolar plates in patent document WO0041260. Although this process has been industrialized, its bending strength is insufficient, the plate thickness is large, and the process is complex, which is not conducive to improving the volumetric power ratio of batteries and the future rapid industrial production pace. Summary of the Invention

[0005] In view of the problems of complex preparation process and difficulty in obtaining composite bipolar plates with good mechanical properties and contact resistance properties in the above-mentioned existing technologies, the present invention will provide a flexible graphite bipolar plate and its preparation method.

[0006] To achieve the above objectives, the following technical solutions are specifically included:

[0007] A flexible graphite bipolar plate, the raw materials for which are prepared include molded graphite plates and resin-based mixtures;

[0008] The molded graphite plate comprises the following components in parts by weight: 50-70 parts of main graphite and 0.5-15 parts of additives;

[0009] The resin-based mixture comprises the following components in parts by weight: 10-30 parts resin, 5-15 parts curing agent, 0.1-3 parts curing accelerator, 1-10 parts release agent, and 200-1500 parts solvent.

[0010] The curing accelerator is a microcapsule, which consists of an outer shell and a core, with the core encapsulated by the outer shell.

[0011] The outer shell of the microcapsule is made of at least one of polyvinyl alcohol, sodium alginate, and gelatin; the core of the microcapsule is composed of at least one of propylene carbonate, dimethyl carbonate, p-toluenesulfonic acid, benzenesulfonic acid, hydroxymethyl urea, sodium bicarbonate, and lignin.

[0012] The flexible graphite bipolar plate of the present invention can be mass-produced, has high bending strength, short molding time, low air leakage rate, and low surface resistance.

[0013] In a preferred embodiment of the present invention, the main graphite includes at least one of expanded graphite, natural graphite, and artificial graphite.

[0014] In a preferred embodiment of the present invention, the additives include at least one of graphene, carbon fiber, and carbon black.

[0015] In a preferred embodiment of the present invention, the expansion ratio of the expanded graphite is 50 to 400 times, the mesh size of the expanded graphite is 5 to 100 mesh, the mesh size of the carbon fiber is 5 to 200 mesh, and the mesh size of the graphene is 20 to 100 mesh.

[0016] The main graphite, serving as the core of the molded graphite plate, possesses a certain mechanical strength, facilitating subsequent operations. It exhibits good solvent wettability with the resin mixture and has a porous structure, allowing it to penetrate the interior of the molded graphite plate and facilitate the release of internal gases during subsequent hot pressing. When the weight percentage of the main graphite is less than 50%, the resulting molded graphite plate is brittle and difficult to lift, making operation inconvenient; when the weight percentage is greater than 70%, the bending strength of the plate formed after hot pressing is insufficient.

[0017] Additives, as auxiliary materials for molded graphite plates, provide a certain bending strength for the bipolar plates after subsequent hot pressing. When the weight component is higher than 15%, it will lead to difficulties in forming the molded graphite plates and the formation of debris on the surface; when the weight component is lower than 0.5%, the bending strength of the bipolar plates prepared after hot pressing is insufficient.

[0018] In a preferred embodiment of the present invention, the resin includes at least one of phenolic resin, epoxy resin, polyamide resin, acrylic resin, and urea-formaldehyde resin.

[0019] The aforementioned resin is a high-strength resin that can penetrate the gaps in graphite to form a support network with a certain strength, providing the bipolar plate with bending strength. However, when the weight percentage of the high-strength resin is less than 10, the bipolar plate will have lower strength; when the weight percentage is greater than 30, the bipolar plate will have poor conductivity.

[0020] In a preferred embodiment of the present invention, the curing agent includes at least one of bisphenol A monomer, hexamethylenetetramine, melamine, dicyandiamide, adipic dihydrazide, and m-phenylenediamine.

[0021] The curing agent enables the formation of a cross-linked network between high-strength resin molecules, enhancing its corrosion resistance and bending strength. When the curing agent is less than 5 parts by weight, the resin cannot be fully cross-linked, causing the bipolar plate to soften at the fuel cell operating temperature (60-95°C), leading to failure. When its weight is greater than 15 parts, the bipolar plate will be more brittle and have lower bending strength.

[0022] In a preferred embodiment of the present invention, the method for preparing the microcapsule pellets includes the following steps:

[0023] (1) Mix the microcapsule core material with a solvent to obtain a core mixture;

[0024] (2) The capsule core mixture is sprayed into an aqueous solution of the microcapsule shell raw material in the form of a spray to obtain a granular product; the granular product is then sieved and vacuum dried to obtain microcapsule pellets.

[0025] The outer shell material of the microcapsule includes at least one of polyvinyl alcohol, sodium alginate, and gelatin; the core material of the microcapsule includes at least one of propylene carbonate, dimethyl carbonate, p-toluenesulfonic acid, benzenesulfonic acid, hydroxymethyl urea, sodium bicarbonate, and lignin.

[0026] In a preferred embodiment of the present invention, the solvent in step (1) includes ethanol.

[0027] In a preferred embodiment of the present invention, in step (1), the mass ratio of the solvent to the microcapsule core material is 60-80:20-40.

[0028] As a further preferred embodiment of the present invention, in step (1), the mass ratio of the solvent to the microcapsule core material is 70:30.

[0029] In a preferred embodiment of the present invention, in step (2), the mass ratio of the microcapsule shell material to water in the aqueous solution of the microcapsule shell material is 3-8:1.

[0030] As a further preferred embodiment of the present invention, in step (2), the mass ratio of the microcapsule shell material to water in the aqueous solution of the microcapsule shell material is 5:1.

[0031] In a preferred embodiment of the present invention, in step (2), the temperature of the core-capsule mixture is 40-60°C.

[0032] As a further preferred embodiment of the present invention, in step (2), the temperature of the core mixture is 50°C.

[0033] In a preferred embodiment of the present invention, the mass ratio of the outer shell to the core of the microcapsule is 1:8 to 1:16.

[0034] As a further preferred embodiment of the present invention, in step (2), the temperature of the vacuum drying is 60-80°C and the time of the vacuum drying is 10-24h.

[0035] Curing accelerators can promote the reaction between resin and curing agent. When the curing accelerator is less than 0.1 parts by weight, the curing speed is slow. When the curing accelerator is more than 3 parts by weight, the reaction speed is too fast, and bubbles appear on the surface of the product.

[0036] The function of the outer shell of the microcapsule is to encapsulate and protect the contents. In the subsequent hot pressing step, the outer shell is compressed and thermally decomposed and ruptured, releasing the core components, which are evenly distributed in every corner of the electrode plate, promoting the reaction between the resin and the curing agent. Under appropriate ratios, the resin can be completely cured within 0.5 min to 3 min.

[0037] The mechanism of action of the microcapsule curing accelerator is as follows: Due to the strong reaction-promoting effect of the curing accelerator, if it is mixed in the solvent for a long time, it will gradually cause the solvent resin to solidify, which will not only clog the impregnation tank and hinder processing, but also lose some of the curing accelerator, which is not conducive to the subsequent curing process in the molded graphite plate. In order to control the curing to occur during the hot pressing process as much as possible, the curing accelerator is stored in microcapsules. The components of the microcapsule wall are immiscible with the solvent, so the microcapsules will not rupture and release the core component when immersed in the solution. When the solvent containing the microcapsules is used to impregnate the fluffy flexible graphite plate, the microcapsules will penetrate evenly into the surface and interior of the molded graphite plate with good dispersion. Only when pressure is applied subsequently will the microcapsules be broken and cracked, releasing the core component curing agent. This curing accelerator promotes the curing reaction between the resin and the curing agent.

[0038] In a preferred embodiment of the present invention, the release agent includes at least one of stearic acid, vinyl bis-stearamide (EBS), polyethylene wax, and carnauba wax.

[0039] The release agent makes it easy to demold the bipolar plate after hot pressing. When the release agent is less than 1 part by weight, the demolding effect is poor and it cannot be easily demolded. When the release agent is more than 10 parts by weight, the release agent affects the strength of the bipolar plate, causing it to decrease.

[0040] In a preferred embodiment of the present invention, the solvent includes at least one selected from ethanol, methanol, acetone, butanone, water, isopentane, petroleum ether, isobutanol, propanol, ethylene glycol, and dimethyl sulfoxide.

[0041] The solvent can be evenly dispersed inside the molded graphite plate and can completely evaporate during the subsequent drying process. When the solvent weight is less than 200 parts, the solvent is too little and the concentration of other components is too high, which will result in too much resin residue remaining on the surface of the pre-molded plate after vacuum drying. When its weight is greater than 1500 parts, the concentration of other components is too low and the bending strength of the finished product is low.

[0042] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0043] (1) The main graphite and additives are stirred and mixed evenly, and then pressed into a molded graphite plate with a density of 0.02 to 0.70 g / cm³. 3 ;

[0044] (2) The molded graphite plate is immersed in a resin-based mixture, and then the immersed molded graphite plate is dried and molded in sequence to obtain the flexible graphite bipolar plate.

[0045] The novel immersion-molding method for preparing bipolar plates provided by this invention allows for the impregnation of multiple flexible graphite plates by a single impregnation mold due to the large impregnation tank. Subsequently, a large drying oven can be used to dry the flexible graphite plates in batches simultaneously, which can greatly save labor costs, improve production efficiency and product quality.

[0046] Because the raw materials are mixed in a solvent, the raw materials are highly uniform, and the pre-soaked graphite bipolar plates have high bending strength, making it easy to pick up and place them into the mold for hot pressing in subsequent production processes. This overcomes the shortcomings of conventional molded graphite plates, which have low strength, are fragile, and are difficult to pick up and carry out subsequent operations.

[0047] In a preferred embodiment of the present invention, in step (1), the stirring speed is 5000-10000 rpm and the stirring time is 0.5-30 min.

[0048] In a preferred embodiment of the present invention, in step (1), the pressing pressure is 5-15 MPa.

[0049] As a further preferred embodiment of the present invention, in step (1), the pressing pressure is 10 MPa.

[0050] In a preferred embodiment of the present invention, in step (2), the soaking time is 15 to 30 minutes, and the soaking is carried out at room temperature.

[0051] In a preferred embodiment of the present invention, in step (2), the drying temperature is 40-110℃, the drying time is 24-240h, and the drying vacuum degree is -0.1MPa.

[0052] The purpose of drying is to evaporate the solvent completely; then the dried, pre-soaked, molded graphite plate is molded.

[0053] In a preferred embodiment of the present invention, in step (2), the molding temperature is 160-220°C, the molding pressure is 25-500 tons, and the molding time is 0.5-3 minutes.

[0054] After being soaked and loaded, the resin in the molded graphite plate is cured at high temperature, resulting in a cross-linking reaction that gives the bipolar plate a certain bending strength.

[0055] When the molding temperature is below 160℃, the curing reaction is insufficient, the reaction speed is slow, and normal molding is impossible; when the molding temperature is above 220℃, the resin structure changes, and a brittle molecular chain structure is easily generated at high temperatures, resulting in lower strength.

[0056] Compression molding, performed under high pressure, allows the resin to flow and distribute more evenly within the bipolar plate, resulting in uniform mechanical strength across the entire plate. The high pressure also helps expel internal gases, leading to fewer defects in the bipolar plate. When the molding pressure is below 25 tons, bubbles generated during the reaction within the bipolar plate cannot be expelled in time; when the molding pressure exceeds 500 tons, the resin is subjected to excessive compression and squeezed out from the mold gaps, resulting in a poor-looking finished product.

[0057] Because the cross-linking reaction of the resin requires a certain amount of time, when the molding time is less than 0.5 minutes, the reaction is insufficient and the bipolar plate strength is low; when the molding time is greater than 3 minutes, the resin is prone to plastic flow and is squeezed out from the gaps in the mold.

[0058] Compared with the prior art, the present invention has the following advantages: The present invention provides a method for preparing high-strength composite bipolar plates more quickly. The bipolar plates produced by this method have a shorter preparation time, simpler process steps, and better mechanical strength and airtightness. Attached Figure Description

[0059] Figure 1 This is a flowchart of the preparation of the molded graphite plate in step (1) of the embodiment.

[0060] Figure 2 This is a flowchart of the bipolar plate preparation process in step (2) of the embodiment. Detailed Implementation

[0061] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below through specific embodiments.

[0062] Microcapsules can be obtained by purchasing from the market or by making them in-house. The in-house preparation method of microcapsules in this embodiment of the invention is as follows: One or more of the following substances—propylene carbonate, dimethyl carbonate, p-toluenesulfonic acid, benzenesulfonic acid, hydroxymethylurea, sodium bicarbonate, and lignin—are ground evenly. Then, 30% by mass of anhydrous ethanol is added, resulting in a viscous, wet material. This material is then added to a round pot granulator, heated to 50°C, and rotated at 180 r / min. Simultaneously, a mixture of one or more of the following substances—polyvinyl alcohol, sodium alginate, and gelatin—and water (substance:water mass ratio 5:1) is sprayed in the form of a spray. This yields a large number of particles of different sizes. The particles are then screened using a vibrating screen with a mesh size of 1000 mesh. The resulting product is then vacuum-dried at 70°C for 12 hours to obtain fine microcapsules. Preferably, the mass ratio of the microcapsule shell to the core is 1:8 to 1:16; the microcapsules are in a fine powder state, with a fracturing pressure ≥1 ton; the shell will vaporize at temperatures above 130°C, having minimal impact on the electrode plates.

[0063] In the examples and comparative examples described below, microcapsules are made of propylene carbonate as the core and polyvinyl alcohol as the shell, and the mass ratio of the shell to the core of the microcapsule is 1:10.

[0064] Examples and Comparative Examples

[0065] The preparation methods for flexible graphite bipolar plates in the examples and comparative examples include the following steps:

[0066] (1) According to the formula in Table 1, the main graphite and additives are mixed evenly in a stirrer at a speed of 5000-6000 rpm for 1-5 min; then, the resulting mixed powder is pressed into a dense mixed graphite plate with a certain area and thickness at room temperature and a pressure of 10 MPa, with a density range of 0.02-0.70 g / cm³. 3 ;

[0067] (2) According to the formula in Table 1, the raw materials are premixed to obtain a resin-based mixture;

[0068] (3) The molded graphite plate is immersed in a resin-based mixture, and then the immersed molded graphite plate is placed in an oven at 40-50°C and kept under vacuum (vacuum degree of -0.1MPa) for 12-24 hours; then the dried pre-immersed molded graphite plate is placed in a mold with a flow channel and molded at 160-220°C and 100 tons of pressure for 1 minute to obtain the flexible graphite bipolar plate.

[0069] Test methods for flexible graphite bipolar plates:

[0070] 1. Bending strength: The bending strength of three points was tested using a high-precision bending tester with a span of 600 mm, a sample thickness of 0.40-1.5 mm, and a sample width of 1.5-2.5 cm.

[0071] 2. Leakage rate: Tested using a fuel cell leak detector, with a test area of ​​120 cm² for the electrode plates. 2 The test pressure is 300–1000 psi;

[0072] 3. Surface resistance: Tested using a DC low-resistance tester, with a test area of ​​25 cm². 2 The square shape was tested under a pressure of 3–4 kN.

[0073] Bipolar plate product qualification standards: bending strength ≥ 50MPa, air leakage rate ≤ 2×10 -8 cm 3 / (cm 2 ·s), surface resistivity ≤10mΩ·cm 2 .

[0074] Table 1. Components, preparation parameters, and test performance results of the examples.

[0075]

[0076] Table 2. Components, preparation parameters, and test performance results of the comparative examples.

[0077]

[0078]

[0079] Comparative Example 9

[0080] Compared with Example 1, the only difference in this comparative example is that the curing accelerator is only a separate core and wall component in the same amount as the microcapsule core and wall in Example 1.

[0081] Some components of the curing accelerator core are added in liquid form. If they are not encapsulated by a capsule wall, the liquid form will cause the powder to clump together and cannot be mixed evenly. When pressed into a pre-pressed plate, this will result in wet spots on the pre-pressed plate (similar to adding a few drops of liquid to a bucket of powder, shaking it evenly, and finding many spherical objects). Wet spots indicate a high content of curing accelerator, which leads to uneven stress after the plate is cured.

[0082] As can be seen from Examples and Comparative Example 9, the flexible graphite bipolar plate prepared by adding the curing accelerator in the form of microcapsules has better performance.

[0083] As can be seen from the examples and comparative examples, the amount of microcapsules, resin and main graphite, as well as the molding temperature, have a significant impact on the mechanical and electrical properties of the bipolar plate.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A flexible graphite bipolar plate, characterized in that, Its raw materials include molded graphite plates and resin-based mixtures; The molded graphite plate comprises the following components in parts by weight: 50-70 parts of main graphite and 0.5-15 parts of additives; The resin-based mixture comprises the following components in parts by weight: 10-30 parts resin, 5-15 parts curing agent, 0.1-3 parts curing accelerator, 1-10 parts release agent, and 200-1500 parts solvent. The curing accelerator is a microcapsule, which consists of an outer shell and a core, with the core encapsulated by the outer shell. The outer shell of the microcapsule is made of at least one of polyvinyl alcohol, sodium alginate, and gelatin; the core of the microcapsule is composed of at least one of propylene carbonate, dimethyl carbonate, p-toluenesulfonic acid, benzenesulfonic acid, hydroxymethylurea, sodium bicarbonate, and lignin; the preparation method of the microcapsule includes the following steps: (1) Mix the microcapsule core material with a solvent to obtain a core mixture; (2) The capsule core mixture is sprayed into an aqueous solution of the microcapsule shell raw material in the form of a spray to obtain a granular product; The granular product is sequentially sieved and vacuum dried to obtain microcapsule pellets; the outer shell material of the microcapsule pellets includes at least one of polyvinyl alcohol, sodium alginate, and gelatin; the core material of the microcapsule pellets includes at least one of propylene carbonate, dimethyl carbonate, p-toluenesulfonic acid, benzenesulfonic acid, hydroxymethylurea, sodium bicarbonate, and lignin; the mass ratio of the outer shell material to the core material of the microcapsule pellets is 1:8 to 1:

16. The method for preparing the flexible graphite bipolar plate includes the following steps: (1) The main graphite and additives are stirred and mixed evenly, and then pressed into a molded graphite plate with a density of 0.02~0.70 g / cm³. 3 ; (2) The molded graphite plate is immersed in a resin-based mixture, and then the immersed molded graphite plate is dried and molded in sequence to obtain the flexible graphite bipolar plate; the molding temperature is 160~220℃, the molding pressure is 25~500 tons, and the molding time is 0.5~3min.

2. The flexible graphite bipolar plate as described in claim 1, characterized in that, The main graphite includes at least one of expanded graphite, natural graphite, and artificial graphite; the additives include at least one of graphene, carbon fiber, and carbon black.

3. The flexible graphite bipolar plate as described in claim 1 or 2, characterized in that, The resin includes at least one of phenolic resin, epoxy resin, polyamide resin, acrylic resin, and urea-formaldehyde resin.

4. The flexible graphite bipolar plate as described in claim 1, characterized in that, Includes at least one of the following (A)-(D): (A) In step (1), the solvent includes ethanol; (B) In step (1), the mass ratio of the solvent to the microcapsule core material is 60-80:20-40; (C) In step (2), the mass ratio of microcapsule shell material to water in the aqueous solution of microcapsule shell material is 3-8:1; (D) In ​​step (2), the temperature of the core mixture is 40-60℃.

5. The flexible graphite bipolar plate as described in claim 1, characterized in that, The curing agent includes at least one of bisphenol A monomer, hexamethylenetetramine, melamine, dicyandiamide, adipamide dihydrazide, and m-phenylenediamine; the solvent includes at least one of ethanol, methanol, acetone, butanone, water, isopentane, petroleum ether, isobutanol, propanol, ethylene glycol, and dimethyl sulfoxide; the release agent includes at least one of stearic acid, vinyl bis-stearamide, polyethylene wax, and palm wax.

6. A method for preparing a flexible graphite bipolar plate according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) The main graphite and additives are stirred and mixed evenly, and then pressed into a molded graphite plate with a density of 0.02~0.70 g / cm³. 3 ; (2) The molded graphite plate is immersed in a resin-based mixture, and then the immersed molded graphite plate is dried and molded in sequence to obtain the flexible graphite bipolar plate.

7. The method for preparing a flexible graphite bipolar plate as described in claim 6, characterized in that, In step (1), the pressing pressure is 5-15 MPa; in step (1), the stirring speed is 5000-10000 rpm, and the stirring time is 0.5-30 min.

8. The method for preparing a flexible graphite bipolar plate as described in claim 6, characterized in that, In step (2), the soaking time is 15-30 minutes; in step (2), the drying temperature is 40-110℃, the drying time is 24-240h, and the drying vacuum degree is -0.1MPa.

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