A graphite bipolar plate for fuel cell and its preparation method and application

Abstract

The present application discloses a graphite bipolar plate for a fuel cell, a preparation method and an application thereof. The graphite bipolar plate includes an anode plate, a cathode plate and a high gas barrier polymer film sandwiched between the anode plate and the cathode plate. A layer of high gas barrier polymer film is adhered between the anode plate and the cathode plate to improve the air tightness of the bipolar plate. The gas barrier film itself has high conductivity and adhesion, and the adhesion process is only hot pressing, without the need to use an additional adhesive. It can be applied to various types of graphite-based bipolar plates including machined graphite bipolar plates, flexible graphite bipolar plates, graphite composite bipolar plates, and can be used as an interlayer adhesive for graphite-metal composite bipolar plates. The advantage of the present invention is that the production process of the gas barrier film is dry calendering, does not use any organic solvents, is clean and environmentally friendly, and the product has a wide range of applications.

Description

Technical Field

[0001] The present application relates to a graphite bipolar plate for a fuel cell and a preparation method and application thereof, and belongs to the field of battery materials. Background Art

[0002] The proton exchange membrane fuel cell (PEMFC) is mainly composed of a proton exchange membrane, a catalyst layer, a gas diffusion layer and a bipolar plate. The two sides of the bipolar plate are in contact with the membrane electrodes of the anode and cathode respectively, playing many important roles such as supporting the membrane electrode structure, separating hydrogen and oxygen and providing channels, collecting electrons, conducting heat, discharging water generated by the reaction, and providing coolant flow channels. Generally speaking, the bipolar plate accounts for more than 70% of the total mass of the stack and about 30% of the total cost. In my country, machined hard graphite bipolar plates and graphite resin composite bipolar plates are the most widely used types at present, with good electrical conductivity, thermal conductivity and corrosion resistance. However, due to the discontinuity of the internal structure of the graphite material, the high porosity, and the air tightness that does not meet the use requirements, it must be impregnated with resin to seal the pores before it can be used. The impregnation process is complicated and lengthy, and the use of organic solvents is not environmentally friendly.

[0003] Therefore, it is necessary to develop a clean, environmentally friendly, efficient and applicable method to improve the air tightness of a variety of graphite-based bipolar plates. Summary of the invention

[0004] The present application improves the air tightness of the bipolar plate by adhering a layer of high gas barrier polymer film between the anode plate and the cathode plate. The gas barrier film itself has high conductivity and adhesion, and the adhesion process is only hot pressing, without the need for additional adhesives. It can be applied to various types of graphite-based bipolar plates including machined graphite bipolar plates, flexible graphite bipolar plates, graphite composite bipolar plates, and can be used as an interlayer adhesive for graphite-metal composite bipolar plates. The advantage of the present invention is that the production process of the gas barrier film is dry calendering, does not use any organic solvents, is clean and environmentally friendly, and the product has a wide range of applications.

[0005] According to one aspect of the present application, a graphite bipolar plate for a fuel cell is provided, the graphite bipolar plate comprising an anode plate, a cathode plate, and a high gas barrier polymer film sandwiched between the anode plate and the cathode plate.

[0006] The thickness of the high gas barrier polymer film is 0.05-0.15 mm.

[0007] The electrical conductivity of the high gas barrier polymer film is 10-50 S / cm.

[0008] The graphite bipolar plate is a graphite-based bipolar plate of various types, including machined hard graphite bipolar plates, flexible graphite bipolar plates, graphite composite bipolar plates, etc. The air tightness of the bipolar plate is improved by adhering a layer of high gas barrier polymer film between the anode plate and the cathode plate.

[0009] According to another aspect of the present application, a method for preparing the above-mentioned graphite bipolar plate for a fuel cell is provided, comprising the following steps:

[0010] The raw materials containing polymer, conductive agent and auxiliary agent are mixed by a twin-screw extruder, pelletized underwater, dried, formed into a film by an extrusion calender, annealed to obtain the high gas barrier polymer film, and the high gas barrier polymer film is sandwiched between the anode plate and the cathode plate, hot pressed to obtain the graphite bipolar plate for the fuel cell.

[0011] The polymer is selected from at least two of ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer (EAA), ethylene-methacrylate copolymer (EMAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-vinyl alcohol copolymer (EVOH), cyclic olefin copolymer (COC), ethylene-propylene-norbornene copolymer (EPN), chlorinated polyethylene (CPE), chlorinated polypropylene (CPP), maleic anhydride grafted polyethylene (PE-g-MAH), maleic anhydride grafted polypropylene (PP-g-MAH), polyamide resin (PA), and terpene phenolic resin.

[0012] The polymer is in the form of powder or granules.

[0013] The conductive agent is selected from at least one of conductive carbon black, surface graphitized carbon black, carbon nanotubes, graphene, silver-plated copper powder and silver powder.

[0014] The auxiliary agent is selected from at least two of oxidized polyethylene wax, EVA wax, hindered phenol antioxidants, and phosphite antioxidants.

[0015] In the raw material, the content of the polymer is 50-80wt%.

[0016] Optionally, in the raw material, the content of the polymer is any value of 50 wt%, 60 wt%, 70 wt%, 80 wt%, or a range value between any two of them.

[0017] In the raw materials, the content of the conductive agent is 20-50wt%.

[0018] Optionally, in the raw material, the content of the conductive agent is any value of 20 wt%, 30 wt%, 40 wt%, 50 wt%, or a range value between any two of them.

[0019] In the raw materials, the content of the auxiliary agent is 0.2-0.4wt%.

[0020] Optionally, in the raw material, the content of the auxiliary agent is any value among 0.2 wt%, 0.3 wt%, 0.4 wt% or any range value between the two.

[0021] The screw speed of the twin-screw extruder for mixing is 150-400 rpm.

[0022] The mixing barrel temperature of the twin-screw extruder is 160-280°C.

[0023] The barrel temperature of the extrusion calender is 180-300°C.

[0024] The die temperature of the extrusion calender is 220-280°C.

[0025] The temperature of the calendering roller of the extrusion calender is 90-140°C.

[0026] The cooling roller temperature of the extrusion calender is 40-60°C.

[0027] The annealing temperature is 80-120°C.

[0028] The annealing time is 15 to 30 minutes.

[0029] The temperature of the hot pressing is 160-300°C.

[0030] The hot pressing pressure is 2-8 MPa.

[0031] The hot pressing time is 3 to 5 minutes.

[0032] According to another aspect of the present application, there is provided an application of the above-mentioned graphite bipolar plate for fuel cells, which is used in proton exchange membrane fuel cells.

[0033] The beneficial effects of this application include:

[0034] A method for improving the air tightness of fuel cell graphite bipolar plates is proposed, by adhering a layer of high gas barrier polymer film between the anode plate and the cathode plate to improve the air tightness of the bipolar plate. The film itself has high conductivity and adhesion, and the anode plate and the cathode plate can be firmly bonded by hot pressing, and the resistance of the bipolar plate is almost not increased. The application range is wide, and it can be used for various types of graphite-based bipolar plates including machined graphite bipolar plates, flexible graphite bipolar plates, and graphite composite bipolar plates. In addition, the production process of the present invention is dry calendering, does not use any organic solvents, and is clean and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of the bipolar plate obtained in Example 1, wherein: 1. anode plate, 2. anode flow field, 3. high gas barrier polymer film, 4. cathode plate, 5. cathode flow field DETAILED DESCRIPTION

[0036] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0037] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0038] Embodiment 1:

[0039] A high gas barrier conductive film is prepared according to the following steps:

[0040] (1) Weigh each component according to the following mass content

[0041] Ethylene vinyl alcohol copolymer (EVOH): 40%;

[0042] Ethylene acrylate copolymer (EAA): 20%;

[0043] Terpene phenolic resin: 7.6%;

[0044] Oxidized polyethylene wax: 0.2%;

[0045] Surface graphitized carbon black: 32%;

[0046] Antioxidant 1010: 0.1%;

[0047] Antioxidant 168: 0.1%;

[0048] (2) putting the components of step (1) into a high-speed mixer and mixing them evenly;

[0049] (3) The twin-screw extruder is started with temperature control, and the barrel temperature is set to 200°C and the die head temperature to 220°C. After the temperature stabilizes, the main machine is started and the speed is set to 280 rpm. The mixture obtained in step (2) is placed in the hopper and mixing and pelletizing is started. The pellets are placed in an oven at 80°C and dried for 4 hours to obtain calendered pellets.

[0050] (4) The calendered pellets obtained in the previous step are placed into an extrusion calendering machine for film making. The calender barrel and head temperatures are set to 220°C, the pressure roller temperature is set to 95°C, and the cooling roller temperature is set to 45°C to produce a high gas barrier polymer film with a thickness of 0.1 mm.

[0051] (5) The high gas barrier polymer film obtained in the previous step is sandwiched between the anode plate and the cathode plate processed by a hard graphite machine, heated to 180°C in a hot press, maintained at a pressure of 2 MPa for 3 minutes, cooled to room temperature, released the pressure, and opened the mold to obtain a high gas tightness bipolar plate. Its structure is as follows Figure 1According 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 483S / cm and the gas permeability is 1.5*10 -10 ml / (s*cm 2 *Pa).

[0052] Embodiment 2:

[0053] A high gas barrier conductive film is prepared according to the following steps:

[0054] (1) Weigh each component according to the following mass content

[0055] Cyclic olefin copolymer (COC): 45%;

[0056] Ethylene-propylene-norbornene copolymer (EPN): 20%;

[0057] Maleic anhydride grafted polypropylene (PP-g-MAH): 5%;

[0058] Terpene phenolic resin: 5%;

[0059] Oxidized polyethylene wax: 0.2%;

[0060] Multi-walled carbon nanotubes: 6.6%;

[0061] Surface graphitized carbon black: 18%;

[0062] Antioxidant 1790: 0.1%;

[0063] Antioxidant 9228: 0.1%;

[0064] (2) putting the components of step (1) into a high-speed mixer and mixing them evenly;

[0065] (3) The twin-screw extruder is started with temperature control, and the barrel temperature is set to 300°C and the head temperature to 320°C. After the temperature stabilizes, the main machine is started and the speed is set to 280 rpm. The mixture obtained in step (2) is placed in the hopper and mixing and pelletizing is started. The pellets are placed in an oven at 80°C and dried for 4 hours to obtain calendered pellets.

[0066] (4) The calendered pellets obtained in the previous step are placed into an extrusion calendering machine for film making. The calender barrel temperature is set to 280°C, the die head temperature is set to 300°C, the pressure roller temperature is set to 105°C, and the cooling roller temperature is set to 60°C to produce a high gas barrier polymer film with a thickness of 0.1 mm.

[0067] (5) The high gas barrier polymer film obtained in the previous step is sandwiched between the anode plate and the cathode plate processed by a hard graphite machine, heated to 300°C in a hot press, maintained at a pressure of 2.5MPa for 5 minutes, cooled to room temperature, released the pressure and opened the mold to obtain a high gas tightness 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 497S / cm, and the gas permeability is 2.1*10 -10 ml / (s*cm 2 *Pa).

[0068] 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 graphite bipolar plate for a fuel cell, characterized in that: The graphite bipolar plate comprises an anode plate, a cathode plate and a high gas barrier polymer film sandwiched between the anode plate and the cathode plate; The graphite bipolar plate for fuel cell is obtained by the following steps: The raw materials containing polymer, conductive agent and auxiliary agent are mixed by a twin-screw extruder, pelletized underwater, dried, formed into a film by an extrusion calender, and annealed to obtain the high gas barrier polymer film; the high gas barrier polymer film is sandwiched between an anode plate and a cathode plate, and hot pressed to obtain the graphite bipolar plate for fuel cells; The polymer is selected from at least two of ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-vinyl alcohol copolymer, cycloolefin copolymer, ethylene-propylene-norbornene copolymer, chlorinated polyethylene, chlorinated polypropylene, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, polyamide resin, and terpene phenolic resin; The polymer is in the form of powder or granules; The auxiliary agent is selected from at least two of oxidized polyethylene wax, EVA wax, hindered phenol antioxidants, and phosphite antioxidants.

2. The graphite bipolar plate for fuel cell according to claim 1, characterized in that: The thickness of the high gas barrier polymer film is 0.05-0.15 mm; The electrical conductivity of the high gas barrier polymer film is 10-50 S / cm.

3. The graphite bipolar plate for fuel cell according to claim 1, characterized in that: The conductive agent is selected from at least one of conductive carbon black, surface graphitized carbon black, carbon nanotubes, graphene, silver-plated copper powder and silver powder.

4. The graphite bipolar plate for fuel cell according to claim 1, characterized in that: In the raw material, the content of the polymer is 50-80wt%; In the raw materials, the content of the conductive agent is 20-50wt%; In the raw materials, the content of the auxiliary agent is 0.2-0.4wt%.

5. The graphite bipolar plate for fuel cell according to claim 1, characterized in that: The screw speed of the twin-screw extruder is 150-400 rpm; The mixing barrel temperature of the twin-screw extruder is 160-280°C; The barrel temperature of the extrusion calender is 180-300°C; The die temperature of the extrusion calender is 220-280°C; The temperature of the calendering roller of the extrusion calender is 90-140°C; The cooling roller temperature of the extrusion calender is 40-60°C.

6. The graphite bipolar plate for fuel cell according to claim 1, characterized in that: The annealing temperature is 80-120°C; The annealing time is 15 to 30 minutes.

7. The graphite bipolar plate for fuel cell according to claim 1, characterized in that: The temperature of the hot pressing is 160-200°C; The hot pressing pressure is 2-8 MPa; The hot pressing time is 3 to 5 minutes.

8. An application of the graphite bipolar plate for a fuel cell according to any one of claims 1 to 7, characterized in that: For use in proton exchange membrane fuel cells.

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