Flexible graphite bipolar plate recycling process

Abstract

The invention discloses a flexible graphite bipolar plate recycling process which comprises the following steps: S1, placing a waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace for pyrolysis reaction, and cooling to room temperature to obtain a flexible graphite plate base material; and S2, carrying out cold press molding on the recycled flexible graphite plate base material by using a 400T press, pressing to 0.8 mm, and carrying out infiltration, cleaning and water bath curing to obtain the new flexible graphite bipolar plate. According to the flexible graphite bipolar plate recycling process provided by the invention, the flexible graphite base material can be effectively recycled, a new flexible graphite bipolar plate product meeting the bipolar plate use standard can be prepared, the recycling of the waste flexible graphite bipolar plate is realized, the process is simple, the cost is very low, and the flexible graphite bipolar plate recycling process has the characteristics of high repeated utilization rate, good economic benefit and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow battery bipolar plate preparation, and in particular to a flexible graphite bipolar plate recycling process. Background Art

[0002] Liquid flow batteries are high-performance batteries that utilize separate, circulating electrolytes in the positive and negative electrodes. They boast high capacity, a wide range of applications, and a long cycle life, making them a popular new energy product. Bipolar plates are important structural and functional components in liquid flow batteries. They are located between the positive and negative electrodes, separating them while also collecting electrons and guiding the flow of electrolytes. Currently, bipolar plate materials primarily include graphite, metal, and composite bipolar plates. Graphite-based bipolar plates are considered highly promising due to their high electrical and thermal conductivity and resistance to chemical corrosion.

[0003] The electrolyte system used in liquid flow batteries, such as all-vanadium liquid flow batteries and zinc-iron liquid flow batteries, is usually a liquid flow system with strong acidity, strong alkalinity, and strong redox properties, so the bipolar plates need to have high corrosion resistance. At present, the materials commonly used for bipolar plates in liquid flow energy storage batteries mainly include pure graphite plates, carbon-plastic conductive composite materials, and flexible graphite bipolar plates. However, the high cost, brittleness, and high density of pure graphite plates limit their practical application. Carbon-plastic conductive composite materials are also not widely used due to their poor electrical conductivity. Flexible graphite bipolar plates are composed of worm-like flexible graphite and resin. They have the physical and chemical properties of graphite, good electrical and thermal conductivity, high chemical stability, low cost, easy molding, and corrosion resistance. They are suitable as bipolar plate materials for liquid flow energy storage batteries and are therefore widely used in the field of liquid flow batteries.

[0004] Flexible graphite bipolar plates are typically manufactured from flake graphite through a series of processes, including high-temperature expansion, compression molding, vacuum impregnation, cleaning, curing, and drying. Over time, the bipolar plates in flow battery stacks are subject to electrochemical corrosion and resin aging, leading to performance degradation and the need for timely replacement of the plates. This leads to the generation of large quantities of waste bipolar plates, posing a significant environmental risk. Therefore, developing a novel process for recycling flexible graphite bipolar plates to repurpose these waste plates is a pressing technical challenge for those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a flexible graphite bipolar plate recycling process. While removing the aged sealing resin in the flexible graphite bipolar plate through a pyrolysis process, the residue is used to form a porous structure, which is conducive to the full contact between the subsequent impregnation liquid and the recycled flexible graphite plate substrate, thereby producing a new flexible graphite bipolar plate product that meets the usage standards, realizing the recycling and reuse of discarded flexible graphite bipolar plates, and effectively solving the environmental problems caused by a large amount of bipolar plate waste.

[0006] In order to achieve the above object, the present invention provides a flexible graphite bipolar plate recycling process, comprising the following steps: S1. Placing the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace for pyrolysis reaction, and after cooling to room temperature, obtaining a flexible graphite plate substrate; S2. The recovered flexible graphite plate substrate is cold-pressed using a 400T press and pressed to 0.8 mm. It is then impregnated, cleaned, and cured in a water bath to obtain a new flexible graphite bipolar plate.

[0007] As a preferred solution, the pyrolysis temperature is 350° C. to 500° C.; and the holding time is 1 to 2 hours.

[0008] As a preferred solution, the pyrolysis atmosphere is air.

[0009] As a preferred solution, the cold pressing is vacuum cold pressing with a vacuum degree of 50 Pa and a vacuum time of 130 s.

[0010] As a preferred embodiment, the cold pressing molding procedure is to first evacuate the vacuum for 130 seconds, set the pressure to 100T, start pressing the flexible graphite plate substrate, continue to evacuate the vacuum during the pressing process, and finally the vacuum degree is 50pa. After staying for 25 seconds, the mold is opened to obtain a molded flexible graphite plate substrate pressed to 0.8mm.

[0011] As a preferred embodiment, the impregnation is vacuum-pressure impregnation.

[0012] As a preferred solution, the impregnation procedure is to perform step-by-step pressurization, first vacuuming to -500Pa within 5 minutes, then vacuuming to -200Pa within 10 minutes, and maintaining it for 60 minutes to ensure that the gas in the pores is discharged, maintain the vacuum degree, inject the resin, and simultaneously introduce gas pressurization to make the final pressure 0.6-1.0MPa, and maintain the final pressure for 5-50 hours.

[0013] As a preferred solution, the water bath curing temperature is 90-95° C. and the curing time is 30-60 min.

[0014] Another aspect of the present invention provides a flexible graphite bipolar plate prepared by a flexible graphite bipolar plate recycling process.

[0015] The present invention also provides an application of a flexible graphite bipolar plate in a liquid flow battery.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) Conventional flexible graphite bipolar plates are usually treated as waste when they reach the end of their service life. This application proposes a flexible graphite bipolar plate recycling process, which can undergo a pyrolysis reaction under air conditions to remove the aged sealing resin in the flexible graphite bipolar plates. At the same time, the decomposition of the resin inside the plates causes the plates to become brittle, and the residues will form a porous structure. When they are cold-pressed again, the pores become interconnected, which is conducive to the infiltration of resin, thereby realizing the recycling and reuse of bipolar plate waste, which meets the current requirements of my country's circular economy development.

[0017] (2) The present invention can completely recycle the high-stability flexible graphite substrate in the flexible graphite bipolar plate, and the process is simple and the cost is very low. At the same time, the physical properties of the flexible graphite bipolar plate prepared using this substrate meet the use standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0019] Figure 1 The present invention is a flow chart of the preparation of a flexible graphite bipolar plate recycling process; Figure 2 This is a physical picture of the flexible graphite bipolar plate prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] This embodiment discloses a flexible graphite bipolar plate recycling process, comprising the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 350-500°C in an air atmosphere, keep the temperature for 1-2 hours to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. The recovered flexible graphite plate substrate is cold-pressed using a 400T press and pressed to 0.8 mm. It is then impregnated, cleaned, and cured in a water bath to obtain a new flexible graphite bipolar plate.

[0022] Pyrolysis is an important chemical process that decomposes organic matter by heating in the absence or presence of only a small amount of oxygen. It is often used to treat various organic wastes and convert them into valuable chemicals and fuels.

[0023] Cold forming is the process of adding materials into a mold at room temperature and forming them by applying high pressure. It is mainly used to process polymers that are difficult to form by conventional methods. It relies on mechanical pressure to tightly arrange the particles to form a blank with a certain shape and density.

[0024] Impregnation, also known as dipping, soaking, and penetration, is a micropore or fine crack penetration sealing process. The sealing medium, usually a low-viscosity liquid, is infiltrated into the micropores or fine cracks through natural penetration, vacuuming, and pressurization to fill the cracks. The sealing medium in the cracks is then solidified by room temperature, cooling, or heating to achieve the effect of sealing the gap.

[0025] Waterbath curing is a process that uses waterbath heating to cure materials. It is often used in situations where uniform heating and temperature control are required to ensure that the material does not suffer from local overheating or uneven curing during the curing process. It is usually applied to a variety of materials such as resins and coatings. Through the heat conduction effect of the water bath, the monomers and oligomers in the material react to form a three-dimensional polymer network, thereby achieving curing.

[0026] Among them, cold pressing is vacuum cold pressing. After vacuuming for 130 seconds, the pressure is set to 100T and the flexible graphite plate substrate is pressed. The vacuum is continuously drawn during the pressing process. The final vacuum degree is 50pa. After staying for 25 seconds, the mold is opened to obtain a molded flexible graphite plate substrate pressed to 0.8mm. The vacuum cold pressing technology combines vacuum technology and cold pressing technology. The vacuuming can effectively remove the gas inside the material and reduce the generation of bubbles, making the product more dense and the surface smoother, improving the quality and appearance of the product. The vacuum environment also helps to reduce the fluidity of the material, making the subsequent pressing process more controllable, making the molding process more efficient, and reducing the consumption of flexible graphite substrate.

[0027] The impregnation process is vacuum-pressurized, using a step-by-step pressurization process. The pressure is first evacuated to -500 Pa within 5 minutes, then to -200 Pa within 10 minutes, and maintained for 60 minutes to ensure that the gas in the pores is expelled. The vacuum is maintained, and resin is injected. Simultaneously, gas is introduced to increase the pressure to a final pressure of 0.6-1.0 MPa, and this pressure is maintained for 5-50 hours. During the impregnation process, the gas in the impregnation liquid is removed by vacuuming to prevent it from penetrating into the microporous defects of the flexible graphite substrate and affecting the sealing performance. At the same time, the impregnation liquid, under vacuum and pressure conditions, can penetrate deeply into the microporous defects of the flexible graphite substrate and solidify to form a solid film, thereby sealing the microporous defects. This significantly improves the qualified rate of flexible graphite bipolar plates and reduces the scrap rate.

[0028] Water bath curing is a staged process, starting with low-temperature preheating, then raising the water temperature to a set point of 90-95°C, where it is held for 30-60 minutes while maintaining a stable temperature. Using a water bath ensures uniform heating and a constant temperature environment, ensuring temperature stability during the curing process of the flexible graphite bipolar plate.

[0029] Example 1: A flexible graphite bipolar plate recycling process comprises the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 350°C in an air atmosphere, keep the temperature for 2 hours to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. Take out the recovered flexible graphite plate substrate, use a 400T press to evacuate and cold press for 130 seconds under the conditions of vacuum degree of 50Pa and pressure of 100T, press it to 0.8mm, then perform vacuum-pressure infiltration and cleaning, and then cure it in a water bath at 94°C for 30 minutes to obtain a new flexible graphite bipolar plate.

[0030] Example 2: A flexible graphite bipolar plate recycling process comprises the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 400°C in an air atmosphere, keep the temperature for 1 hour to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. Take out the recovered flexible graphite plate substrate, use a 400T press to evacuate and cold press for 130 seconds under the conditions of vacuum degree of 50Pa and pressure of 100T, press it to 0.8mm, then perform vacuum-pressure infiltration and cleaning, and then cure it in a water bath at 94°C for 30 minutes to obtain a new flexible graphite bipolar plate.

[0031] The difference between Example 2 and Example 1 is that the pyrolysis temperature of the waste flexible graphite bipolar plate is increased to 400° C., but the pyrolysis time is shortened to 1 h.

[0032] Example 3: A flexible graphite bipolar plate recycling process comprises the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 400°C in an air atmosphere, keep the temperature for 2 hours to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. Take out the recovered flexible graphite plate substrate, use a 400T press to evacuate and cold press for 130 seconds under the conditions of vacuum degree of 50Pa and pressure of 100T, press it to 0.8mm, then perform vacuum-pressure infiltration and cleaning, and then cure it in a water bath at 94°C for 30 minutes to obtain a new flexible graphite bipolar plate.

[0033] The difference between Example 3 and Example 2 is that the pyrolysis temperature of the waste flexible graphite bipolar plates remains unchanged, but the pyrolysis time is extended to 2 hours. The difference between Example 3 and Example 1 is that the pyrolysis temperature of the waste flexible graphite bipolar plates is increased to 400°C, but the pyrolysis time remains unchanged.

[0034] Example 4: A flexible graphite bipolar plate recycling process comprises the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 450°C in an air atmosphere, keep the temperature for 1 hour to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. Take out the recovered flexible graphite plate substrate, use a 400T press to evacuate and cold press for 130 seconds under the conditions of vacuum degree of 50Pa and pressure of 100T, press it to 0.8mm, then perform vacuum-pressure infiltration and cleaning, and then cure it in a water bath at 94°C for 30 minutes to obtain a new flexible graphite bipolar plate.

[0035] The difference between Example 4 and Examples 1-3 is that the pyrolysis temperature of the waste flexible graphite bipolar plate is increased to 450°C, but compared with Examples 1 and 3, the pyrolysis time of the waste flexible graphite bipolar plate is shortened to 1 hour, and compared with Example 2, the pyrolysis time of the waste flexible graphite bipolar plate remains unchanged.

[0036] Example 5: A flexible graphite bipolar plate recycling process comprises the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 450°C in an air atmosphere, keep the temperature for 2 hours to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. Take out the recovered flexible graphite plate substrate, use a 400T press to evacuate and cold press for 130 seconds under the conditions of vacuum degree of 50Pa and pressure of 100T, press it to 0.8mm, then perform vacuum-pressure infiltration and cleaning, and then cure it in a water bath at 94°C for 30 minutes to obtain a new flexible graphite bipolar plate.

[0037] The difference between Example 5 and Examples 1-4 is that, compared with Examples 1 and 3, the pyrolysis temperature of the waste flexible graphite bipolar plates was increased to 450°C, while the pyrolysis time remained unchanged. Compared with Example 2, the pyrolysis temperature of the waste flexible graphite bipolar plates was increased to 450°C, and the pyrolysis time was extended to 2 hours. Compared with Example 4, the pyrolysis temperature of the waste flexible graphite bipolar plates remained unchanged, while the pyrolysis time was extended to 2 hours.

[0038] Example 6: A flexible graphite bipolar plate recycling process comprises the following steps: S1. Place the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace, heat to 500°C in an air atmosphere, keep the temperature for 2 hours to perform pyrolysis reaction, and then cool to room temperature to obtain a flexible graphite plate substrate; S2. Take out the recovered flexible graphite plate substrate, use a 400T press to evacuate and cold press for 130 seconds under the conditions of vacuum degree of 50Pa and pressure of 100T, press it to 0.8mm, then perform vacuum-pressure infiltration and cleaning, and then cure it in a water bath at 94°C for 30 minutes to obtain a new flexible graphite bipolar plate.

[0039] The difference between Example 6 and Examples 1-5 is that the pyrolysis temperature of the waste flexible graphite bipolar plate is increased to 500°C, but compared with Example 1, Example 3, and Example 5, the pyrolysis time remains unchanged, and compared with Example 2 and Example 4, the pyrolysis time is extended to 2 hours.

[0040] Performance Testing The following performance tests were performed on the flexible graphite bipolar plates prepared in Examples 1-6 of the present invention.

[0041] Test Example 1 Bending Strength Test The flexural strength of the flexible graphite bipolar plate was measured using a mechanical testing machine. 60×30 mm samples were cut from the middle portion of the flexible graphite bipolar plates prepared in Examples 1-6 by wire cutting. Three samples were cut from the flexible graphite bipolar plate sample of each example, with a span of 40 mm. The flexural strength of the flexible graphite bipolar plate was tested using the three-point bending method. The test steps are as follows: (1) The flexible graphite bipolar plate sample was made into a long strip with a width of 30 mm; (2) Adjust the support span so that the indenter and support head are perpendicular to the specimen axis; (3) The indenter applies load evenly and without impact at a loading speed of 5 mm / min until the sample breaks, and the breaking load value is read.

[0042] The flexural strength is calculated according to the following formula: Among them, δ F is the flexural strength, in MPa; P is the breaking load value, in N; L is the support span, in mm; b is the width of the flexible graphite bipolar plate sample, in mm; h is the thickness of the flexible graphite bipolar plate sample, in mm.

[0043] Three valid test samples were taken as a group, and the average value was calculated as the test result. The test results are shown in Table 1.

[0044] Test Example 2 Conductivity Test Scanning electron microscopy was used to observe the distribution of graphite and resin in the flexible graphite bipolar plate. The sampling location was the middle of the flexible graphite bipolar plate sample. A four-probe resistance meter was used to test the in-plane conductivity of the flexible graphite bipolar plate. To eliminate the contact resistance between the metal probe and the flexible graphite bipolar plate sample, the DC four-probe method was used to directly test the conductivity. The test steps are as follows: (1) Sample pretreatment: First, wipe the surface of the flexible graphite bipolar plate sample three times with a dust-free cloth soaked in anhydrous ethanol to remove the oxide layer and impurities, and then dry it in an 80°C oven for 30 minutes to ensure that there is no residual solvent on the surface. Then, use a digital micrometer to measure once at each of the four corners and the center of the flexible graphite bipolar plate sample and take the average value. (2) Resistance measurement: Press the four-probe probe vertically onto the surface of the flexible graphite bipolar plate sample and read the resistance value R (unit: Ω).

[0045] Conductivity is calculated using the following formula: in, d is the thickness of the flexible graphite bipolar plate sample, in cm; A is the effective flow diversion area covered by the probe, in cm 2 .

[0046] Each bipolar plate sample was tested in five different areas, and the average value was taken as the test result after removing the outliers. The test results are shown in Table 1.

[0047] Test Example 3 Contact Resistance Test The contact resistance of the flexible graphite bipolar plate is tested using a contact resistance meter. The test steps are as follows: (1) Sample preparation: 3cm×3cm, area 9cm 2 The number of square flexible graphite bipolar plate samples is 5, and they should be free of wrinkles, scratches and damage; (2) Contact resistance test: The flexible graphite bipolar plate sample is mounted on the test device and the resistance value is measured using a low resistance meter. The measuring electrodes are gold-plated copper electrodes. During the measurement, carbon paper used for the fuel cell diffusion layer is placed on both sides of the sample as a support to further improve the contact condition. During the test, a resistance value is recorded for each 0.1 MPa increase in pressure. When the change rate between the current resistance test value and the previous resistance test value is ≤5%, it is considered that the minimum resistance value has been reached and the test is stopped. The resistance value under different pressures is R1.

[0048] In the same way, a piece of carbon paper used as a diffusion layer for a fuel cell is placed between two copper electrodes and a certain pressure is applied. The resistance value R2 under different pressures tested in the same way as above is recorded.

[0049] The contact resistance is calculated according to the following formula: Where R is the contact resistance between the flexible graphite bipolar plate and the carbon paper, in mΩ; R1 is the sum of the bulk resistance of the flexible graphite bipolar plate material, the bulk resistance of the carbon paper, the contact resistance between the two flexible graphite bipolar plates and the carbon paper, the bulk resistance of the two copper electrodes, and the contact resistance between the two carbon papers and the copper electrodes, in mΩ; R2 is the sum of the resistance of the two copper electrodes, the resistance of the carbon paper, and the contact resistance between the two carbon papers and the copper electrodes, in mΩ; R BP is the bulk resistance of the flexible graphite bipolar plate material, in mΩ; R CP is the carbon paper body resistance, in mΩ.

[0050] Three samples were taken as a group and the average value was calculated as the test result. The test results are shown in Table 1.

[0051] Test Example 4 Density Test The density of the flexible graphite bipolar plate was tested using a multifunctional electronic density meter. Three valid samples were taken as a group, and the average value was calculated as the test result. The test results are shown in Table 1.

[0052] Table 1 As shown in Table 1, the flexible graphite bipolar plates of Examples 1-6 prepared by the flexible graphite bipolar plate recycling process provided by the present invention have a bending strength of 55.43-58.94 MPa and a density of 1.511-1.707 g / cm 3 , conductivity is 400.14-499.83S / cm, contact resistance is 2.32-3.07mΩ·cm 2 , all performance indicators meet the use standards of flexible graphite bipolar plates.

[0053] Comparing the flexible graphite bipolar plates prepared in Examples 1-6, the bending strength, conductivity, density, and contact resistance of Example 5 are all superior to those of the other examples, significantly improving the bending resistance of the flexible graphite bipolar plate, having better current transmission capacity, reducing ohmic polarization loss, and improving the overall efficiency of the battery. At the same time, it reduces the resistivity of the flexible graphite bipolar plate and improves its conductivity. Figure 2 As shown, the surface of the bipolar plate maintains a high degree of flatness and smoothness, which can reduce contact resistance and ensure good contact with the membrane electrode assembly (MEA), which helps to improve the overall performance and stability of the battery.

[0054] It can be seen that the recycling process method of the present invention can completely pyrolyze the aged resin in the flexible graphite bipolar plate, construct a porous structure, and effectively recycle and utilize the flexible graphite plate substrate, which is conducive to the efficient combination of the resin and the flexible graphite plate substrate during cold pressing again, thereby realizing the recycling and reuse of bipolar plate waste. It is a method for efficiently recycling valuable resources in waste flexible graphite bipolar plates that meets the current requirements of my country's circular economy development.

[0055] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A flexible graphite bipolar plate recycling process, characterized in that: The following steps are involved: S1. Placing the waste flexible graphite bipolar plate in a pyrolysis high-temperature furnace for pyrolysis reaction, and after cooling to room temperature, obtaining a flexible graphite plate substrate; S2. The recovered flexible graphite plate substrate is cold-pressed using a 400T press to a thickness of 0.8 mm, and then impregnated, cleaned, and cured in a water bath to obtain a new flexible graphite bipolar plate; The pyrolysis temperature is 350°C to 500°C; the holding time is 1 to 2 hours; The pyrolysis atmosphere is air.

2. A flexible graphite bipolar plate recycling process according to claim 1, characterized in that: The cold pressing is vacuum cold pressing with a vacuum degree of 50 Pa and a vacuum time of 130 s.

3. The flexible graphite bipolar plate recycling process according to claim 1, characterized in that: The cold pressing procedure is to first evacuate the vacuum for 130 seconds, set the pressure to 100T, start pressing the flexible graphite plate substrate, continue to evacuate the vacuum during the pressing process, and finally the vacuum degree is 50Pa. After staying for 25 seconds, the mold is opened to obtain a shaped flexible graphite plate substrate pressed to 0.8mm.

4. The flexible graphite bipolar plate recycling process according to claim 1, characterized in that: The impregnation is vacuum-pressure impregnation.

5. The flexible graphite bipolar plate recycling process according to claim 1, characterized in that: The impregnation procedure is to increase the pressure in a step-by-step manner, first vacuuming to -500Pa within 5 minutes, then vacuuming to -200Pa within 10 minutes, and maintaining it for 60 minutes to ensure that the gas in the pores is discharged, maintain the vacuum degree, inject the resin, and at the same time introduce gas to increase the pressure to a final pressure of 0.6-1.0MPa, and maintain the final pressure for 5-50 hours.

6. The flexible graphite bipolar plate recycling process according to claim 1, characterized in that: The water bath curing temperature is 90-95° C., and the curing time is 30-60 minutes.

7. A flexible graphite bipolar plate, characterized in that: The flexible graphite bipolar plate is prepared by the recycling process of any one of claims 1 to 6.

8. Use of the flexible graphite bipolar plate according to claim 7 in a liquid flow battery.

Images