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

Abstract

The application discloses a flexible graphite bipolar plate for a liquid flow battery and a preparation method thereof, and the preparation method comprises the following steps: firstly, a silane coupling agent is added into a solvent to prepare a silane hydrolysis solution; then, graphene, carbon nanotubes and a MAX phase material are dispersed in the silane hydrolysis solution to perform a hydrolysis reaction; after the reaction is completed, centrifugation, washing and drying are performed to obtain modified fillers; then, the modified fillers are mixed with a thermosetting resin to obtain a functionalized resin; finally, the functionalized resin is vacuum-impregnated into an expanded graphite plate, and curing is performed to obtain the flexible graphite bipolar plate. The surface of the carbon nanotubes, the graphene and the MAX phase material is modified by the silane coupling agent, the carbon nanotubes, the graphene and the MAX phase material are uniformly dispersed in the resin matrix, and a three-dimensional network is formed in the resin. The three-dimensional network skeleton significantly enhances the mechanical strength and the electrical conductivity of the bipolar plate, the high thermal conductivity of the carbon material ensures that the temperature distribution in the bipolar plate is uniform, the deformation caused by thermal stress is reduced, and the mechanical strength of the bipolar plate is further enhanced.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, specifically relating to a flexible graphite bipolar plate for flow batteries and its preparation method. Background Technology

[0002] Flexible graphite bipolar plates are core components of fuel cells and flow batteries, and their performance directly affects battery efficiency and lifespan. In current production processes, the inherent defects of the resin matrix cause the following key problems: (1) Uneven heat distribution during resin curing leads to cracking. Thermosetting resins release a large amount of heat during curing, but the resin itself has poor thermal conductivity, resulting in a severe uneven temperature distribution inside the bipolar plate. Local areas accumulate heat to form hot spots, while the edge areas are not hot enough. This temperature difference leads to significant differences in resin shrinkage, generating high concentrated stress, and ultimately causing a microcrack network. In traditional processes, this type of curing stress cracking occurs frequently, becoming the main threat to the structural integrity of the bipolar plate. (2) The insulation of the resin restricts the conductivity. The resin matrix has natural insulating properties, and graphite particles are coated in the bipolar plate to form an electron transport barrier. Electrons are forced to travel between the graphite particles, and the path is greatly extended, resulting in a significant deterioration in the overall conductivity. More seriously, curing shrinkage will further expand the spacing between graphite particles, blocking the electron tunneling path, making it difficult for the bipolar plate to meet the conductivity requirements under high current density conditions. (3) Insufficient mechanical strength of existing formulations. Traditional resin-graphite composite systems have shortcomings in mechanical properties. The bending strength of bipolar plates is generally insufficient, making them prone to fracture under the assembly pressure of battery stacks; the low elastic modulus leads to deformation of the flow field structure under pressure, causing sealing failure; and insufficient toughness accelerates the propagation of microcracks during transportation or vibration. Therefore, existing technologies cannot simultaneously achieve conductivity, thermal management, and mechanical robustness, which seriously restricts the practical application of bipolar plates.

[0003] Existing improvement solutions mainly involve adding thermally conductive fillers, which can improve heat distribution, but the insulating properties will block the conductive path; introducing conductive polymers can improve conductivity, but at the cost of sacrificing mechanical strength and thermal stability; when increasing the resin content to enhance mechanical properties, conductivity and airtightness deteriorate sharply.

[0004] Currently, there is no effective method to simultaneously resolve the triple contradiction of resin curing cracking, conductive network defects, and insufficient mechanical strength. There is an urgent need to develop innovative technologies that can simultaneously ensure high electrical / thermal conductivity while achieving uniform control of the curing process and synergistic improvement of mechanical properties. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a flexible graphite bipolar plate for flow batteries and a method for preparing the same, wherein the flexible graphite bipolar plate can simultaneously possess good mechanical strength, electrical conductivity, and thermal conductivity.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing a flexible graphite bipolar plate, comprising the following steps:

[0007] (1) Add the silane coupling agent to the solvent to prepare a silane hydrolysate; then disperse the graphene, carbon nanotubes and MAX phase materials in the silane hydrolysate and carry out the hydrolysis reaction; after the reaction is completed, centrifuge, wash and dry to obtain the modified filler;

[0008] (2) The modified filler is mixed with a thermosetting resin to obtain a functionalized resin;

[0009] (3) The functionalized resin is vacuum impregnated with expanded graphite plate and then cured to obtain the flexible graphite bipolar plate.

[0010] Specifically, in the preparation of the flexible graphite bipolar plate of the present invention, graphene, carbon nanotubes, and MAX phase materials are first modified using a silane coupling agent to obtain modified fillers. The modified carbon nanotubes, graphene, and MAX phase materials exhibit improved wetting properties in resin solutions and are easier to disperse uniformly. After curing, a three-dimensional interpenetrating network structure composed of carbon nanotubes, graphene, and MAX phase materials is formed inside the bipolar plate, providing continuous pathways for electrons and thus improving the conductivity of the bipolar plate. Then, the modified filler is added to a thermosetting resin to obtain a functionalized resin. The modified filler can directly undergo a polymerization reaction with the resin, allowing the three-dimensional interpenetrating network structure composed of the modified filler to bond tightly with the resin, thereby greatly enhancing the mechanical strength of the cured functionalized resin. Simultaneously, the three-dimensional interpenetrating network structure composed of carbon nanotubes, graphene, and MAX phase materials also helps to improve the thermal conductivity of the functionalized resin. The improved thermal conductivity allows for more uniform temperature during resin curing, which helps reduce problems such as inconsistent reaction rates and cracking / deformation caused by uneven temperature during the curing process, thereby further enhancing the mechanical strength of the bipolar plate. Finally, functionalized resin is filled into the micropores of the expanded graphite plate through vacuum impregnation to enhance the mechanical strength and electrical conductivity of the flexible graphite bipolar plate.

[0011] Furthermore, graphene, carbon nanotubes, and MAX phase materials all possess excellent thermal conductivity, with graphene and carbon nanotubes being superior thermal conductors, exhibiting thermal conductivity coefficients of 800-3500 W / (m·K) and 2500-4000 W / (m·K), respectively. In contrast, resin has a thermal conductivity of only 0.1-0.5 W / (m·K), making it a poor conductor of heat. Therefore, this invention significantly improves the thermal conductivity of resin by adding a certain amount of graphene and carbon nanotubes.

[0012] In some embodiments of the present invention, in step (1), the silane coupling agent is selected from silane compounds containing at least one of amino, epoxy, and methacryloyloxy groups. For example, KH550 (γ-aminopropyltriethoxysilane), KH570 (γ-methacryloyloxypropyltrimethoxysilane), A-187 (γ-glycidoxypropyltrimethoxysilane), etc.

[0013] In some embodiments of the present invention, in step (1), the MAX phase material is selected from at least one of chromium aluminum carbon (Cr2AlC), tantalum aluminum carbon (Ta2AlC), or niobium aluminum carbon (Nb2AlC). The MAX phase material is a functional ceramic material that combines the electrical and thermal conductivity of metals with the high strength of ceramics, and can form a three-dimensional point-line-plane interpenetrating conductive network structure with carbon nanotubes and graphene.

[0014] In some embodiments of the present invention, in step (1), the solvent is a mixed solvent composed of water and ethanol.

[0015] In some embodiments of the present invention, in step (1), the mass ratio of silane coupling agent, water and ethanol in the silane hydrolysate is 1:(0.5-1.5):(1-5).

[0016] In some embodiments of the present invention, in step (1), the mass ratio of graphene, carbon nanotubes and MAX phase material is (0.2-1.5):(0.1-2):(0.2-1.5).

[0017] In some embodiments of the present invention, in step (1), the mass-to-volume ratio of the graphene to the silane hydrolysate is (1-5) mg: 1 mL.

[0018] In some embodiments of the present invention, in step (1), the temperature of the hydrolysis reaction is 50-60°C and the time of the hydrolysis reaction is 2-3 hours.

[0019] In some embodiments of the present invention, in step (2), the thermosetting resin is selected from at least one of epoxy resin, phenolic resin, and acrylate resin.

[0020] In some embodiments of the present invention, in step (2), the mass ratio of the modified filler to the thermosetting resin is (0.5-5):(95-99.5).

[0021] In some embodiments of the present invention, in step (3), the preparation process of the expanded graphite plate is as follows: natural graphite flakes are subjected to intercalation treatment, water washing, drying and thermal expansion treatment to obtain expanded graphite powder; then the expanded graphite powder is pressed into shape to obtain the expanded graphite plate.

[0022] In some embodiments of the present invention, the intercalation is performed by treating natural flake graphite with concentrated sulfuric acid / nitric acid at a volume ratio of (2-4):1 for 20-25 hours.

[0023] In some embodiments of the present invention, the thermal expansion treatment is a rapid thermal expansion at 1000-1100°C for 20-40 seconds.

[0024] In some embodiments of the present invention, in step (3), the mass ratio of the functionalized resin to the expanded graphite plate is (20-40):(60-80).

[0025] In some embodiments of the present invention, in step (3), the curing is carried out in a water bath at 75-85°C.

[0026] A second aspect of the present invention provides a flexible graphite bipolar plate, which is prepared by the above-described method for preparing a flexible graphite bipolar plate; the flexible graphite bipolar plate includes an expanded graphite plate, wherein the micropores of the expanded graphite plate are filled with a functionalized resin; the functionalized resin includes a modified filler and a thermosetting resin, wherein the modified filler is a filler modified with a silane coupling agent, and the filler includes graphene, carbon nanotubes and MAX phase materials.

[0027] Specifically, the flexible graphite bipolar plate of the present invention contains a three-dimensional interpenetrating network skeleton structure formed by graphene, carbon nanotubes and MAX phase, which not only enhances the mechanical and thermal properties of the bipolar plate, but also improves the mechanical strength of the bipolar plate by increasing the thermal conductivity.

[0028] A third aspect of the present invention provides a flow battery comprising the aforementioned flexible graphite bipolar plate.

[0029] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0030] (1) The flexible graphite bipolar plate of the present invention uses graphene, carbon nanotubes and MAX phase materials modified with silane coupling agent as fillers. The modified carbon nanotubes, graphene and MAX phase materials have improved wetting performance in resin solution and are easier to disperse uniformly. At the same time, the cured modified filler forms a three-dimensional interpenetrating network structure composed of carbon nanotubes, graphene and MAX phase materials inside the bipolar plate, providing a continuous pathway for electrons, thereby improving the conductivity of the bipolar plate.

[0031] (2) This invention prepares functionalized resin by mixing modified filler with thermosetting resin. The three-dimensional interpenetrating network structure of the modified filler significantly enhances the mechanical strength and thermal conductivity of the cured resin. At the same time, the improved thermal conductivity makes the temperature of the resin curing process more uniform, thereby significantly reducing problems such as inconsistent reaction rates and cracking and deformation caused by uneven temperature during the resin curing process, and further enhancing the mechanical strength of the bipolar plate.

[0032] (3) The flexible graphite bipolar plate prepared by the present invention has good mechanical strength, electrical conductivity and thermal conductivity, achieving a bending strength of 36.1-37.3MPa, a tensile strength of 26.9-28.5MPa and an electrical conductivity of 325-336S / cm. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the fabrication process of the flexible graphite bipolar plate of the present invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0035] The following is a schematic diagram of the fabrication process of the flexible graphite bipolar plate in the embodiment. Figure 1 As shown.

[0036] Example 1

[0037] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0038] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0039] (2) KH570 was added to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysis solution (the mass ratio of silane coupling agent, water and ethanol was 1:1:1); then graphene, carbon nanotubes and chromium aluminum carbon with a mass ratio of 0.2:1:0.8 were dispersed in the silane hydrolysis solution (the mass volume ratio of graphene to silane hydrolysis solution was 2 mg:1 mL), and ultrasonically dispersed to form a uniform suspension; the suspension was then heated to 50°C and continuously stirred to promote the hydrolysis reaction for 3 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the modified filler.

[0040] (3) The modified filler and acrylate resin were mixed at a mass ratio of 2:98 to obtain the functionalized resin.

[0041] (4) The functionalized resin is vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate is 3:7), and after curing and cleaning, the flexible graphite bipolar plate of this embodiment is obtained.

[0042] Example 2

[0043] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0044] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0045] (2) KH550 was added to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysate (the mass ratio of silane coupling agent, water and ethanol was 1:1:5); then graphene, carbon nanotubes and chromium aluminum carbon in a mass ratio of 0.5:0.5:1.5 were dispersed in the silane hydrolysate (the mass-volume ratio of graphene to silane hydrolysate was 1.5 mg:1 mL), and ultrasonically dispersed to form a uniform suspension; then the suspension was heated to 60°C and continuously stirred to promote the hydrolysis reaction for 2 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the modified filler.

[0046] (3) The modified filler and acrylate resin were mixed at a mass ratio of 2.5:97.5 to obtain the functionalized resin.

[0047] (4) The functionalized resin is vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate is 2:8), and after curing and cleaning, the flexible graphite bipolar plate of this embodiment is obtained.

[0048] Example 3

[0049] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0050] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0051] (2) KH550 was added to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysate (the mass ratio of silane coupling agent, water and ethanol was 1:5:1); then graphene, carbon nanotubes and chromium aluminum carbon with a mass ratio of 0.2:1:1.8 were dispersed in the silane hydrolysate (the mass-volume ratio of graphene to silane hydrolysate was 3 mg:1 mL), and ultrasonically dispersed to form a uniform suspension; the suspension was then heated to 50°C and continuously stirred to promote the hydrolysis reaction for 2 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the modified filler.

[0052] (3) The modified filler and acrylate resin were mixed at a mass ratio of 3:97 to obtain the functionalized resin.

[0053] (4) The functionalized resin is vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate is 4:6), and after curing and cleaning, the flexible graphite bipolar plate of this embodiment is obtained.

[0054] Example 4

[0055] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0056] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0057] (2) Add A-187 to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysate (the mass ratio of silane coupling agent, water and ethanol is 1:1:5); then disperse graphene, carbon nanotubes and chromium aluminum carbon in a mass ratio of 1.5:0.1:0.2 in the silane hydrolysate (the mass-volume ratio of graphene to silane hydrolysate is 1 mg:1 mL), and ultrasonically disperse to form a uniform suspension; then heat the suspension to 60°C and continuously stir to promote the hydrolysis reaction for 2 hours. After the reaction is completed, centrifuge, wash and dry to obtain the modified filler.

[0058] (3) The modified filler and acrylate resin were mixed at a mass ratio of 1.8:98.2 to obtain the functionalized resin.

[0059] (4) The functionalized resin is vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate is 7:3), and after curing and cleaning, the flexible graphite bipolar plate of this embodiment is obtained.

[0060] Example 5

[0061] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0062] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0063] (2) KH570 was added to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysate (the mass ratio of silane coupling agent, water and ethanol was 1:1:5); then graphene, carbon nanotubes and chromium aluminum carbon with a mass ratio of 0.3:0.3:1 were dispersed in the silane hydrolysate (the mass volume ratio of graphene to silane hydrolysate was 2 mg:1 mL), and ultrasonically dispersed to form a uniform suspension; the suspension was then heated to 50°C and continuously stirred to promote the hydrolysis reaction for 4 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the modified filler.

[0064] (3) The modified filler and acrylate resin were mixed at a mass ratio of 1.6:98.4 to obtain the functionalized resin.

[0065] (4) The functionalized resin is vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate is 7:3), and after curing and cleaning, the flexible graphite bipolar plate of this embodiment is obtained.

[0066] Comparative Example 1

[0067] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0068] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0069] (2) Graphene, carbon nanotubes, chromium aluminum carbon and acrylate resin were mixed in a mass ratio of 0.2:1:0.8:98 to prepare functionalized resin.

[0070] (3) The functionalized resin was vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate was 3:7), and after curing and cleaning, the flexible graphite bipolar plate of this comparative example was obtained.

[0071] The difference between Comparative Example 1 and Example 1 is that the graphene, carbon nanotubes, and chromium aluminum carbon tubes were not silanized.

[0072] Comparative Example 2

[0073] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0074] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0075] (2) KH570 was added to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysate (the mass ratio of silane coupling agent, water and ethanol was 1:1:1); then graphene and carbon nanotubes with a mass ratio of 0.2:1 were dispersed in the silane hydrolysate (the mass-volume ratio of graphene to silane hydrolysate was 2 mg:1 mL), and ultrasonically dispersed to form a uniform suspension; the suspension was then heated to 50°C and continuously stirred to promote the hydrolysis reaction for 3 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the modified filler.

[0076] (3) The modified filler and acrylate resin were mixed at a mass ratio of 2:98 to obtain the functionalized resin.

[0077] (4) The functionalized resin was vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate was 3:7), and after curing and cleaning, the flexible graphite bipolar plate of this comparative example was obtained.

[0078] The difference between Comparative Example 2 and Example 1 is that no chromium aluminum carbon was added.

[0079] Comparative Example 3

[0080] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0081] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0082] (2) KH570 was added to a mixed solvent consisting of deionized water and anhydrous ethanol to prepare a silane hydrolysate (the mass ratio of silane coupling agent, water and ethanol was 1:1:1); then graphene and chromium aluminum carbon with a mass ratio of 1.2:0.8 were dispersed in the silane hydrolysate (the mass-volume ratio of graphene to silane hydrolysate was 2 mg:1 mL), and ultrasonically dispersed to form a uniform suspension; the suspension was then heated to 50°C and continuously stirred to promote the hydrolysis reaction for 3 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the modified filler.

[0083] (3) The modified filler and acrylate resin were mixed at a mass ratio of 2:98 to obtain the functionalized resin.

[0084] (4) The functionalized resin was vacuum impregnated with expanded graphite plate (the mass ratio of functionalized resin to expanded graphite plate was 3:7), and after curing and cleaning, the flexible graphite bipolar plate of this comparative example was obtained.

[0085] The difference between Comparative Example 3 and Example 1 is that no carbon nanotubes were added.

[0086] Comparative Example 4

[0087] A method for preparing a flexible graphite bipolar plate includes the following steps:

[0088] (1) Natural flake graphite was intercalated with concentrated sulfuric acid / nitric acid at a volume ratio of 3:1 for 24 hours, and then rapidly thermally expanded at 1050℃ for 30 seconds to obtain expanded graphite powder; the expanded graphite powder was then pressed into shape to make expanded graphite plate.

[0089] (2) The flexible graphite bipolar plate of this comparative example is obtained by vacuum impregnating expanded graphite plate with acrylic resin (the mass ratio of acrylic resin to expanded graphite plate is 3:7), curing and cleaning.

[0090] The difference between Comparative Example 4 and Example 1 is that no modified filler was added to the resin.

[0091] Performance testing

[0092] The mechanical strength and electrical conductivity of the flexible graphite bipolar plate samples prepared in Examples 1-5 and Comparative Examples 1-4 were tested. Specifically, the testing methods for flexural strength and electrical conductivity followed GB / T 20042.6-2024, and the testing method for tensile strength followed GB / T 228.1-2021. The results are shown in Table 1.

[0093] Table 1:

[0094] Example 1 37.3 28.5 336 Example 2 36.5 27.2 327 Example 3 36.9 27.6 329 Example 4 36.1 26.9 325 Example 5 37.1 28.3 337 Comparative Example 1 32.5 22.5 319 Comparative Example 2 32.4 21.8 305 Comparative Example 3 31.9 23.8 313 Comparative Example 4 29.3 19.6 302

[0095] As shown in Table 1, the flexible graphite bipolar plates prepared in Examples 1-5 exhibit excellent performance in terms of flexural strength, tensile strength, and electrical conductivity. Compared with Comparative Examples 1-4, all properties have been significantly improved. This indicates that in the bipolar plate system of the present invention, the addition of graphene, carbon nanotubes, and MAX phase materials, as well as silanization modification, are crucial for the three-dimensional electrical and thermal conductivity of the resin and for the formation of the reinforcing filler network, thus affecting the performance of the flexible graphitized bipolar plate.

[0096] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method for preparing a flexible graphite bipolar plate, characterized in that, Includes the following steps: (1) Add the silane coupling agent to the solvent to prepare a silane hydrolysate; then disperse the graphene, carbon nanotubes and MAX phase materials in the silane hydrolysate and carry out the hydrolysis reaction; after the reaction is completed, centrifuge, wash and dry to obtain the modified filler; The silane coupling agent is selected from silane compounds containing at least one of amino, epoxy, and methacryloxy groups; The MAX phase material is selected from at least one of chromium aluminum carbon, tantalum aluminum carbon, and niobium aluminum carbon. The mass ratio of graphene, carbon nanotubes, and MAX phase materials is (0.2-1.5):(0.1-2):(0.2-1.5). (2) The modified filler is mixed with a thermosetting resin to obtain a functionalized resin; The thermosetting resin is selected from at least one of epoxy resin, phenolic resin, and acrylate resin; The mass ratio of the modified filler to the thermosetting resin is (0.5-5):(95-99.5). (3) The functionalized resin is vacuum impregnated with expanded graphite plate and cured to obtain the flexible graphite bipolar plate.

2. The method for preparing a flexible graphite bipolar plate according to claim 1, characterized in that, In step (1), the temperature of the hydrolysis reaction is 50-60℃ and the time of the hydrolysis reaction is 2-3 hours.

3. The method for preparing a flexible graphite bipolar plate according to claim 1, characterized in that, In step (3), the preparation process of the expanded graphite plate is as follows: natural graphite flakes are subjected to intercalation treatment, water washing, drying and thermal expansion treatment to obtain expanded graphite powder; then the expanded graphite powder is pressed into shape to obtain the expanded graphite plate.

4. The method for preparing a flexible graphite bipolar plate according to claim 1, characterized in that, In step (3), the mass ratio of the functionalized resin to the expanded graphite plate is (20-40):(60-80).

5. A flexible graphite bipolar plate, characterized in that, The flexible graphite bipolar plate is prepared by any one of claims 1-4; the flexible graphite bipolar plate includes an expanded graphite plate, and the micropores of the expanded graphite plate are filled with a functionalized resin; the functionalized resin includes a modified filler and a thermosetting resin, the modified filler is a filler modified with a silane coupling agent, and the filler includes graphene, carbon nanotubes and MAX phase materials.

6. A flow battery, characterized in that, Including the flexible graphite bipolar plate as described in claim 5.

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