A method for preparing a flexible graphite composite bipolar plate and bipolar plate prepared therefrom and applications thereof

Abstract

The present application discloses a method for preparing a flexible graphite composite bipolar plate, a bipolar plate prepared therefrom, and applications thereof, and belongs to the field of battery materials. The method comprises the following steps: (1) preforming the expanded graphite worms by roller pressing to obtain a low-density expanded graphite preformed plate; (2) impregnating the low-density expanded graphite preformed plate obtained in (1) in a dilute resin impregnation liquid, performing surface treatment, drying, and hot pressing to obtain the flexible graphite composite bipolar plate; the dilute resin impregnation liquid contains a block copolymer and a resin. The present application proposes a method for preparing a flexible graphite composite bipolar plate, a bipolar plate prepared therefrom, and applications thereof. The preparation process is simple, the conductivity distribution of the product is uniform, and the size control is more stable.

Description

Technical Field

[0001] The present application relates to a method for preparing a flexible graphite composite bipolar plate, a bipolar plate prepared therefrom and applications thereof, and belongs to the field of battery materials. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are mainly composed of proton exchange membranes, catalyst layers, gas diffusion layers, and bipolar plates. The two sides of the bipolar plates are in contact with the membrane electrodes of the anode and cathode, respectively, and play many important roles, such as supporting the membrane electrode structure, separating hydrogen and oxygen, providing channels, collecting electrons, conducting heat, discharging water generated by the reaction, and providing coolant channels. Generally speaking, bipolar plates account for more than 70% of the total mass of the stack and about 30% of the total cost.

[0003] Bipolar plates can be divided into metal bipolar plates, graphite bipolar plates and composite bipolar plates according to different materials: metal bipolar plates have high strength, good toughness, high processing efficiency and good airtightness, but weak corrosion resistance, and require surface coating to extend service life; graphite bipolar plates have good electrical conductivity, thermal conductivity, corrosion resistance and other properties, but their toughness is poor, and a larger thickness is required to meet stacking requirements; the preparation of composite bipolar plates based on graphite and resin materials is currently a more mainstream method, which has good electrical conductivity, thermal conductivity, corrosion resistance and mechanical strength, but the preparation process of most composite bipolar plates is complicated and the processing cycle is long, which makes their cost relatively high, and because the resins used are mostly thermosetting, it is very difficult to recycle.

[0004] Therefore, developing composite bipolar plates that balance performance and cost while fully considering environmental factors can provide high economic value for the fuel cell industry. Summary of the invention

[0005] This application uses expanded graphite with excellent conductivity and chemical stability for cold preforming to obtain a low-density embryonic plate, which is then impregnated with resin and dried, and finally pressed in a hot press mold to obtain a bipolar plate with a flow field. Different from the current mainstream process of first compression molding and then impregnation with resin, the method of preparing bipolar plates in the present invention is to impregnate the resin first and then compression molding, which has the advantages of high controllability of resin content, good uniformity of molded plate density, more uniform conductivity distribution, and more stable product size control.

[0006] According to one aspect of the present application, a method for preparing a flexible graphite composite bipolar plate is provided, comprising the following steps:

[0007] (1) preforming the expanded graphite worms by roller pressing to obtain a low-density expanded graphite prefabricated plate;

[0008] (2) The low-density expanded graphite prefabricated plate obtained in (1) is immersed in a dilute resin impregnation solution, subjected to surface treatment, drying, and hot pressing to obtain the flexible graphite composite bipolar plate.

[0009] The dilute resin impregnation liquid contains block copolymer and resin.

[0010] The block copolymer is selected from at least one of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), and styrene-ethylene-ethylene-propylene block copolymer (SEEPS).

[0011] The resin is selected from at least one of C5 petroleum resin, C5-C9 copolymerized petroleum resin, terpene resin, hydrogenated C5 petroleum resin and hydrogenated terpene resin.

[0012] The dilute resin impregnation liquid also contains an antioxidant and an organic solvent.

[0013] The antioxidant is selected from at least one of antioxidant 1076, antioxidant 1010, antioxidant 168, antioxidant 412S, antioxidant HP-136, and antioxidant FS-042.

[0014] The organic solvent is selected from at least one of toluene, xylene, ethyl acetate, butanone, 120# solvent oil, 200# solvent oil, D60 solvent oil, and D80 solvent oil.

[0015] The solid content of the dilute resin impregnation liquid is 1 to 10 wt %.

[0016] Optionally, the solid content of the dilute resin impregnation liquid is any value of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or a range between any two of them.

[0017] The bulk density of the expanded graphite worms is 0.004-0.008 g / cm 3 .

[0018] The thickness of the low-density expanded graphite prefabricated plate is 3-20 mm.

[0019] The density of the low-density expanded graphite prefabricated plate is 0.075-0.125 g / cm 3 .

[0020] The impregnation is vacuum impregnation.

[0021] The vacuum degree of the immersion is -0.08 to -0.1 MPa.

[0022] The immersion time is 8 to 12 hours.

[0023] The surface treatment includes compressed air blowing, solvent washing and then compressed air blowing.

[0024] The solvent is selected from at least one of toluene, xylene, ethyl acetate, butanone, 120# solvent oil, 200# solvent oil, D60 solvent oil, and D80 solvent oil.

[0025] The drying temperature is 80-120°C.

[0026] The drying temperature is 4 to 8 hours.

[0027] The temperature of the hot pressing is 160-200°C.

[0028] The hot pressing pressure is 8-16 MPa.

[0029] The hot pressing time is 3 to 10 minutes.

[0030] According to another aspect of the present application, a flexible graphite composite bipolar plate is provided, which is prepared by the above-mentioned preparation method.

[0031] The density of the flexible graphite composite bipolar plate is 1.5-1.8 g / cm 3 .

[0032] The thickness of the flexible graphite composite bipolar plate is 0.3-1.6 mm.

[0033] The electrical conductivity of the flexible graphite composite bipolar plate is 300-400 S / cm.

[0034] According to another aspect of the present application, two applications of the above-mentioned flexible graphite composite bipolar plates are provided for use in proton exchange membrane fuel cells and energy storage liquid flow batteries.

[0035] The beneficial effects of this application include:

[0036] The present application proposes a method for preparing a flexible graphite composite bipolar plate and a bipolar plate prepared therefrom, and the preparation process is simple, the product has uniform conductivity distribution and more stable size control. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the structure of the knife die used in the embodiment of the present application.

[0038] Figure 2 This is a schematic diagram of the structure of the hot pressing mold used in the embodiments of the present application, wherein: 1. upper mold, 2. middle mold, 3. positioning pin, 4. molding effective area, 5. lower mold.

[0039] Figure 3 This is a schematic diagram of the structure of the bipolar plate obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0040] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0041] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0042] Embodiment 1:

[0043] A flexible graphite composite bipolar plate is prepared according to the following steps:

[0044] (1) The bulk density is 0.004 g / cm 3 Expanded graphite worms are preformed by roller pressing to form a density of 0.08g / cm 3 , 7mm thick plate, use Figure 1 The cutting die shown punches the plate into a predetermined shape to obtain a prefabricated plate;

[0045] (2) Add 6.0 g of SEBS resin powder and 4.0 g of C5-C9 copolymer petroleum resin particles to 190 g of xylene to prepare a 200 g solution, and stir for 6 h to obtain a dilute resin impregnation solution;

[0046] (3) Inject the dilute resin impregnation liquid obtained in step (2) into a small flat-bottomed tray with a liquid level of 15 mm (not less than 2 times the thickness of the prefabricated board). Gently place the prefabricated board obtained in step (1) on the surface of the impregnation liquid. The prefabricated board should be floating at this time. Place the tray containing the impregnation liquid and the prefabricated board in a vacuum oven and evacuate the tray. Maintain the vacuum degree at -0.08~-0.1MPa. After immersion for 6 hours, restore the pressure to normal and remove the tray. At this time, the prefabricated board sinks to the bottom layer of the impregnation liquid. Take out the prefabricated board, rinse off the residual resin on the surface with the solvent ethyl acetate, and then place it in an oven with exhaust gas treatment to dry the solvent. The drying temperature is 120°C and the drying time is 4 hours. After drying, the impregnated prefabricated board is obtained;

[0047] (4) Place the impregnated prefabricated board obtained in the previous step into Figure 2 The mold is hot-pressed and formed at 180°C and 10MPa for 3 minutes, and then the heating is stopped. When the mold is cooled to below 120°C, the pressure is released and the mold is opened to obtain a finished bipolar plate. The structure is as shown in FIG. Figure 3 According to GB / T 20042.6-2024 Proton Exchange Membrane Fuel Cell Part 6: Bipolar Plate Characteristics Test Method, the conductivity of the bipolar plate is 330S / cm and the contact resistance of the diffusion layer is 3.7mΩcm 2 .

[0048] Embodiment 2:

[0049] A flexible graphite composite bipolar plate is prepared according to the following steps:

[0050] (1) The bulk density is 0.005 g / cm 3 Expanded graphite worms are preformed by roller pressing to form a density of 0.1g / cm 3 , 7mm thick plate, use Figure 1 The cutting die shown punches the plate into a predetermined shape to obtain a prefabricated plate;

[0051] (2) Add 6.0 g of SEPS resin powder and 3.0 g of C5 hydrogenated petroleum resin particles to 191 g of D60 solvent oil to prepare a 200 g solution, stir for 4 h, and obtain a dilute resin impregnation solution;

[0052] (3) Inject the dilute resin impregnation liquid obtained in step (2) into a small flat-bottomed tray with a liquid level of 15 mm (not less than 2 times the thickness of the prefabricated board). Gently place the prefabricated board obtained in step (1) on the surface of the impregnation liquid. The prefabricated board should be floating at this time. Place the tray containing the impregnation liquid and the prefabricated board in a vacuum oven and evacuate the tray. Maintain the vacuum degree at -0.08~-0.1MPa. After immersion for 4 hours, restore the pressure to normal and take out the tray. At this time, the prefabricated board sinks to the bottom layer of the impregnation liquid. Take out the prefabricated board, rinse off the residual resin on the surface with solvent D60 solvent oil, and then place it in an oven with exhaust gas treatment to dry the solvent. The drying temperature is 120°C and the drying time is 4 hours. After drying, the impregnated prefabricated board is obtained;

[0053] (4) Place the impregnated prefabricated board obtained in the previous step into Figure 2 The mold is hot-pressed in the mold shown in the figure, and the heating is stopped after being kept at 180°C and 10MPa for 3 minutes. When the mold is cooled to below 120°C, the pressure is released and the mold is opened to obtain the finished bipolar plate. According to "GB / T 20042.6-2024 Proton Exchange Membrane Fuel Cell Part 6: Bipolar Plate Characteristics Test Method", the conductivity of the bipolar plate is 350S / cm, and the contact resistance of the diffusion layer is 3.2mΩcm 2 .

[0054] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a flexible graphite composite bipolar plate, It is characterized in that The following steps are involved: (1) preforming the expanded graphite worms by roller pressing to obtain a low-density expanded graphite prefabricated plate; (2) impregnating the low-density expanded graphite prefabricated plate obtained in (1) into a dilute resin impregnation solution, performing surface treatment, drying, and hot pressing to obtain the flexible graphite composite bipolar plate; The dilute resin impregnation solution contains block copolymer and resin; The block copolymer is selected from at least one of styrene-isoprene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, and styrene-ethylene-ethylene-propylene block copolymer; The resin is selected from at least one of C5 petroleum resin, C5-C9 copolymerized petroleum resin, terpene resin, hydrogenated C5 petroleum resin, and hydrogenated terpene resin; The solid content of the dilute resin impregnation liquid is 1-5wt%.

2. The preparation method according to claim 1, characterized in that: The dilute resin impregnation liquid also contains an antioxidant and an organic solvent; The antioxidant is selected from at least one of antioxidant 1076, antioxidant 1010, antioxidant 168, antioxidant 412S, antioxidant HP-136, and antioxidant FS-042; The organic solvent is selected from at least one of toluene, xylene, ethyl acetate, butanone, 120# solvent oil, 200# solvent oil, D60 solvent oil, and D80 solvent oil.

3. The preparation method according to claim 1, characterized in that: The bulk density of the expanded graphite worms is 0.004-0.008 g / cm 3 ; The thickness of the low-density expanded graphite prefabricated plate is 3 to 20 mm; The density of the low-density expanded graphite prefabricated plate is 0.075-0.125 g / cm 3 .

4. The preparation method according to claim 1, characterized in that: The impregnation is vacuum impregnation; The vacuum degree of the impregnation is -0.08 to -0.1 MPa; The immersion time is 8 to 12 hours.

5. The preparation method according to claim 1, characterized in that: The surface treatment includes compressed air blowing, solvent washing and then compressed air blowing; The solvent is selected from at least one of toluene, xylene, ethyl acetate, butanone, 120# solvent oil, 200# solvent oil, D60 solvent oil, and D80 solvent oil.

6. The preparation method according to claim 1, characterized in that: The drying temperature is 80-120°C; The drying temperature is 4 to 8 hours; The temperature of the hot pressing is 160-200°C; The hot pressing pressure is 8-16 MPa; The hot pressing time is 3 to 10 minutes.

7. A flexible graphite composite bipolar plate, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6; The density of the flexible graphite composite bipolar plate is 1.5-1.8 g / cm 3 ; The thickness of the flexible graphite composite bipolar plate is 0.3-1.6 mm; The electrical conductivity of the flexible graphite composite bipolar plate is 300-400 S / cm.

8. An application of the flexible graphite composite bipolar plate according to claim 7, characterized in that: For use in proton exchange membrane fuel cells.

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