A fuel cell gas-phase deposition graphite bipolar plate and its preparation method

Abstract

The present invention provides a fuel cell gas-phase deposition graphite bipolar plate and a preparation method thereof, belonging to the field of fuel cells. The present invention utilizes the high-temperature transformation of pitch and mesophase carbon microspheres to solve the problems of high machining difficulty, poor airtightness and low strength of pure graphite plates. In the stage of plasma-enhanced chemical vapor deposition, small molecule conductive fillers are uniformly distributed in the bipolar plate through vapor deposition. Since no resin filler is added to this graphite plate, problems such as low conductivity and poor corrosion resistance caused by too high resin content are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fuel cell gas-phase deposition graphite bipolar plate and a preparation method thereof. Background Art

[0002] The most core components of a fuel cell are the membrane electrode and the bipolar plate, among which the bipolar plate has the highest cost. The bipolar plate plays an important role in separating hydrogen and air and supporting the fuel cell system. Due to the slightly acidic environment inside the fuel cell, metal bipolar plates are prone to corrosion, and graphite bipolar plates have become the focus and difficulty of research in recent years.

[0003] The prior art discloses the use of carbon microspheres to prepare bipolar plates, but the graphite bipolar plate still has the disadvantage of low conductivity. How to improve the performance of the bipolar plate by appropriate means is the focus and difficulty of current research. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a fuel cell gas-phase deposition graphite bipolar plate and a preparation method thereof. The fuel cell gas-phase deposition graphite bipolar plate prepared by the present invention has high conductivity.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a fuel cell gas-phase deposition graphite bipolar plate, including the following steps:

[0007] Mix asphalt and mesophase carbon microspheres to obtain a slurry;

[0008] Coat the slurry on the surface of carbon cloth and then perform microwave treatment to obtain a prefabricated plate;

[0009] Perform plasma-enhanced chemical vapor deposition on the prefabricated plate to deposit small molecule carbon to obtain a prefabricated bipolar plate;

[0010] Immerse the prefabricated bipolar plate in polyacrylic resin and then perform curing and forming in sequence to obtain the fuel cell gas-phase deposition graphite bipolar plate.

[0011] Preferably, the mass ratio of the asphalt to the mesophase carbon microspheres is (0.5 - 0.8):1.

[0012] Preferably, the particle size of the mesophase carbon microspheres is 20 - 60 μm.

[0013] Preferably, the time of the microwave treatment is 70 - 90 s, and the temperature is 150 - 300 °C.

[0014] Preferably, the thickness of the prefabricated plate is 1 - 3 mm.

[0015] Preferably, the parameters of the plasma-enhanced chemical vapor deposition include: a temperature of 800 to 1000 °C, a time of 20 to 50 min, and a gas carbon source amount of 0.03 to 0.3 L / min. The gas carbon source includes one or more of xylene gas, ethylene, and propyne gas.

[0016] Preferably, the curing temperature is 250 to 350 °C, and the time is 0.5 to 1 h.

[0017] Preferably, the forming is roll forming, and the roll forming adopts 3 to 5 roll forming procedures. The roll gap of the first press roll is 10 to 15 mm, and then it decreases by 1 to 4 mm step by step.

[0018] Preferably, the carbon cloth is Gore 0.4 mm carbon cloth.

[0019] The present invention also provides a fuel cell gas-phase deposition graphite bipolar plate prepared by the preparation method described in the above technical solution.

[0020] The present invention provides a preparation method of a fuel cell gas-phase deposition graphite bipolar plate, including the following steps: mixing pitch with mesophase carbon microspheres to obtain a slurry; coating the slurry on the surface of a carbon cloth and then performing microwave treatment to obtain a preform; performing plasma-enhanced chemical vapor deposition on the preform to deposit small molecule carbon to obtain a prefabricated bipolar plate; immersing the prefabricated bipolar plate in polyacrylic acid resin and then performing curing and forming in sequence to obtain the fuel cell gas-phase deposition graphite bipolar plate.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the present invention, the pitch will undergo mesophase cracking transformation in the plasma-enhanced chemical vapor deposition to generate spherical carbon materials. These spherical carbon materials have excellent properties such as self-sintering at high temperature, chemical inertness, high packing density, electrical conductivity, and thermal conductivity. They stack more closely with the added mesophase carbon microspheres. After the plasma-enhanced chemical vapor deposition, the carbon microspheres stack more closely, making the bipolar plate more dense and enhancing the strength and conductivity of the bipolar plate; and the plasma-enhanced chemical vapor deposition uses high-temperature gas transformation to uniformly attach small molecule conductive carbon molecules to the bipolar plate, avoiding the problem of uneven distribution of conductive substances and further enhancing the conductivity.

[0023] Moreover, since the graphite plate of the present invention does not add resin fillers, it avoids the problems of low conductivity and poor corrosion resistance caused by too high resin content, and avoids the dilemmas of incomplete resin curing and post-treatment of organic solvents, making the present invention have commercial prospects. Detailed Embodiments

[0024] The present invention provides a method for preparing a fuel cell gas-phase deposition graphite bipolar plate, comprising the following steps:

[0025] Mix asphalt with mesophase carbon microspheres to obtain a slurry;

[0026] Coat the surface of carbon cloth with the slurry and then perform microwave treatment to obtain a preform;

[0027] Perform plasma-enhanced chemical vapor deposition (PECVD) on the preform to deposit small molecule carbon to obtain a prefabricated bipolar plate;

[0028] Immerse the prefabricated bipolar plate in polyacrylic resin and then perform curing and forming in sequence to obtain the fuel cell gas-phase deposition graphite bipolar plate.

[0029] In the present invention, unless otherwise specified, the raw materials used are commercially available products in the art.

[0030] The present invention mixes asphalt with mesophase carbon microspheres to obtain a slurry.

[0031] In the present invention, the mass ratio of the asphalt to the mesophase carbon microspheres is preferably (0.5-0.8):1.

[0032] In the present invention, the particle size of the mesophase carbon microspheres is preferably 20-60 μm.

[0033] In the present invention, the mixing is preferably carried out by stirring with a high-speed blade mixer for 0.5-1 h, and the stirring speed is preferably 3000-5000 rpm.

[0034] After obtaining the slurry, the present invention coats the surface of the carbon cloth with the slurry and then performs microwave treatment to obtain a preform.

[0035] In the present invention, the carbon cloth is preferably Gore 0.4 mm carbon cloth.

[0036] The present invention preferably cuts carbon cloth with the same length and width as the bipolar plate, compresses and flattens it with a flat steel plate and then uses it.

[0037] The present invention uniformly coats the slurry on the carbon cloth with a scraper, then flattens it with a roller, and then performs the microwave treatment.

[0038] In the present invention, the thickness of the scraper is preferably 0.2-0.5 mm, and the scraper speed is preferably 1-2 mm / s.

[0039] In the present invention, the time of the microwave treatment is preferably 70-90 s, the temperature is preferably 150-300 °C, and the function of the microwave treatment is to stabilize the asphalt so that it will not flow and deform, enabling the bipolar plate to be placed flat in the PECVD.

[0040] In the present invention, the thickness of the prefabricated plate is preferably 1 to 3 mm. The present invention preferably repeats the steps of coating and microwave treatment until the thickness of the prefabricated plate reaches 1 to 3 mm.

[0041] After obtaining the prefabricated plate, the present invention performs plasma enhanced chemical vapor deposition (PECVD) on the prefabricated plate to deposit small molecule carbon, thereby obtaining a prefabricated bipolar plate;

[0042] In the present invention, the parameters of the plasma enhanced chemical vapor deposition preferably include: the temperature is preferably 800 to 1000 °C, the time is preferably 20 to 50 min, the gas carbon source amount is preferably 0.03 to 0.3 L / min, and the gas carbon source preferably includes one or more of xylene gas, ethylene, and propyne gas.

[0043] After obtaining the prefabricated bipolar plate, the present invention immerses the prefabricated bipolar plate in polyacrylic resin and then performs curing and forming in sequence to obtain the fuel cell gas-phase deposited graphite bipolar plate.

[0044] In the present invention, the temperature of the curing is preferably 250 to 350 °C, and the time is preferably 0.5 to 1 h.

[0045] In the present invention, the forming is preferably roll forming, and the roll forming preferably adopts 3 to 5 roll forming procedures. The roll gap of the first pressing roll is preferably 10 to 15 mm, and then preferably decreases by 1 to 4 mm step by step.

[0046] The present invention also provides a fuel cell gas-phase deposited graphite bipolar plate prepared by the preparation method described in the above technical solution.

[0047] The present invention has no special limitation on the application of the fuel cell gas-phase deposited graphite bipolar plate, and the methods well-known to those skilled in the art can be adopted.

[0048] In order to further illustrate the present invention, the fuel cell gas-phase deposited graphite bipolar plate provided by the present invention, its preparation method and application will be described in detail below with reference to examples, but they should not be construed as limiting the protection scope of the present invention.

[0049] Example 1

[0050] Cut Gore carbon cloth with the same length and width as the bipolar plate, and flatten it with a steel plate. Weigh 50 g of asphalt and 100 g of mesophase carbon microspheres and place them in a barrel. Stir for 0.5 h at a stirring rate of 4000 rpm using a high-speed blade stirrer. Spread the mixed slurry evenly on the carbon cloth with a spatula, and the spacing of the spatula is 0.5 mm. Microwave for 70 s, then flatten and dry it with a roller after microwaving, and weigh the thickness. Keep microwaving until the thickness reaches 2.5 mm. Place the prepared preform in PECVD, use acetylene as the small molecule carbon source, heat at 900 °C, the gas source reaction rate is 0.2 L / min, and the reaction time is 40 min. Take out the preform after the reaction, and flatten it again with a roller. After cooling for 30 min, immerse the bipolar plate in polyacrylic resin for 1 h, take it out and cure at 350 °C for 0.5 h. Place the cured preform in a roll press with a flow channel, and adopt 5 roll pressing processes. The first roll pressing process is set to 15 mm, and then it decreases by 3 mm step by step. Finally, the thickness of the bipolar plate obtained is 0.876 mm. Measure the conductivity and flexural strength of the bipolar plate.

[0051] Test method:

[0052] (1) Conductivity test: Use an RTS-9 double-electrode four-probe measuring instrument to measure the conductivity of the composite plate. In order to eliminate the contact resistance between the metal probe and the sample, the direct current four-probe method is directly used to test the conductivity.

[0053] (2) Flexural strength test: Use a WD-10D universal testing machine to measure the flexural performance of the composite plate, and use the three-point bending method to test the flexural strength of the composite plate. The test steps are as follows:

[0054] ① Make the sample into a long strip shape with a width of 10 mm.

[0055] ② Adjust the span of the supports so that the indenter and the support head are both perpendicular to the sample axis

[0056] ③ The indenter applies a load uniformly and without impact at a loading speed of 10 mm / s 2 until the sample breaks, and read the fracture load value.

[0057] The flexural strength is calculated according to the following formula:

[0058] δ F =3PL / 2bh 2

[0059] δ F : Flexural strength (MPa)

[0060] P: Fracture load value (N)

[0061] L: Support span (30 mm)

[0062] b: Sample width (mm)

[0063] h: Sample thickness (mm)

[0064] Example 2

[0065] Cut Gore 0.4mm carbon cloth with the same length and width as the bipolar plate, and flatten it with a steel plate. Weigh 80g of asphalt and 100g of mesophase carbon microspheres and place them in the barrel. Stir for 0.5h by means of high-speed blade stirring, and the stirring rate is 5000rpm. Use a scraper to evenly spread the mixed slurry on the carbon cloth, and the spacing of the scraper is 0.2mm. Microwave for 80s, and after microwave, flatten and dry it with a roller, and weigh the thickness. Until the thickness reaches 3mm. Place the prepared preform in PECVD, use propylene as the small molecule carbon source, the heating temperature is 1000°C, the gas source reaction rate is 0.3L / min, and the reaction time is 50min. After the reaction is completed, take out the preform and flatten it again with a roller. After cooling for 30min, immerse the bipolar plate in polyacrylic resin for 40min, take it out and cure it at 300°C for 1h. Place the cured preform in a roll press with a flow channel, and adopt four roll pressing processes. The first roll pressing process is set to 10mm, and then gradually decreases by 3mm. The finally obtained bipolar plate thickness is 0.982mm. And measure the conductivity and flexural strength of the bipolar plate.

[0066] Example 3

[0067] Cut Gore 0.4mm carbon cloth with the same length and width as the bipolar plate, and flatten it with a steel plate. Weigh 70g of asphalt and 100g of mesophase carbon microspheres and place them in the barrel. Stir for 0.5h by means of high-speed blade stirring, and the stirring rate is 3000rpm. Use a scraper to evenly spread the mixed slurry on the carbon cloth, and the spacing of the scraper is 0.3mm. Microwave for 90s, and after microwave, flatten and dry it with a roller, and weigh the thickness. Until the thickness reaches 2mm. Place the prepared preform in PECVD, use 60vol% ethylene + 40vol% propyne as the small molecule carbon source, the heating temperature is 1000°C, the gas source reaction rate is 0.2L / min, and the reaction time is 40min. After the reaction is completed, take out the preform and flatten it again with a roller. After cooling for 30min, immerse the bipolar plate in polyacrylic resin for 30min, take it out and cure it at 350°C for 1h. Place the cured preform in a roll press with a flow channel, and adopt three roll pressing processes. The first roll pressing process is set to 10mm, and then gradually decreases by 5mm. The finally obtained bipolar plate thickness is 0.762mm. And measure the conductivity and flexural strength of the bipolar plate.

[0068] Example 4

[0069] Cut Gore carbon cloth with a thickness of 0.4 mm that is the same length and width as the bipolar plate, and flatten it with a steel plate. Weigh 75 g of pitch and 100 g of mesophase carbon microspheres and place them in a barrel. Stir for 0.5 h at a stirring rate of 5000 rpm using a high-speed blade stirring method. Apply the mixed slurry evenly onto the carbon cloth with a scraper, and the spacing between the scrapers is 0.5 mm. Microwave for 80 s, and after microwaving, flatten and dry it with a roller, and weigh the thickness. Keep microwaving until the thickness reaches 3 mm. Place the prepared preform in PECVD, use 50 vol% ethylene + 50 vol% propyne as the small molecule carbon source, the heating temperature is 900 °C, the gas source reaction rate is 0.3 L / min, and the reaction time is 50 min. After the reaction is completed, take out the preform and flatten it again with a roller. After cooling for 30 min, immerse the bipolar plate in polyacrylic resin for 30 min, take it out and cure it at 300 °C for 1 h. Place the cured preform in a roll press with a flow channel, and adopt three roll pressing processes. The first roll pressing process is set to 15 mm, and then it decreases by 4 mm step by step. The finally obtained bipolar plate has a thickness of 0.853 mm. Measure the conductivity and flexural strength of the bipolar plate.

[0070] Comparative Example 1

[0071] Cut Gore carbon cloth with a thickness of 0.4 mm that is the same length and width as the bipolar plate, and flatten it with a steel plate. Weigh 100 g of mesophase carbon microspheres and place them in a barrel, and dissolve them with ethylene glycol. Stir for 0.5 h at a stirring rate of 4000 rpm using a high-speed blade stirring method. Apply the mixed slurry evenly onto the carbon cloth with a scraper, and the spacing between the scrapers is 0.5 mm. Microwave for 70 s, and after microwaving, flatten and dry it with a roller, and weigh the thickness. Keep microwaving until the thickness reaches 2.5 mm. Place the prepared preform in PECVD, use acetylene as the small molecule carbon source, the heating temperature is 900 °C, the gas source reaction rate is 0.2 L / min, and the reaction time is 40 min. After the reaction is completed, take out the preform and flatten it again with a roller. After cooling for 30 min, immerse the bipolar plate in polyacrylic resin for 1 h, take it out and cure it at 350 °C for 0.5 h. Place the cured preform in a roll press with a flow channel, and adopt 5 roll pressing processes. The first roll pressing process is set to 15 mm, and then it decreases by 3 mm step by step. The finally obtained bipolar plate has a thickness of 1.028 mm. Measure the conductivity and flexural strength of the bipolar plate.

[0072] Table 1 is a parameter test table of the bipolar plate. By comparison, it can be found that the thickness of the bipolar plates of Examples 1 to 4 is less than 1.2 mm, which greatly reduces the thickness of the bipolar plates and thus reduces the weight of the bipolar plates. The small molecule carbon source also plays a role as a conductive filler. The conductivity of the bipolar plates is ≥800 S / cm. At the same time, the strength of the mesophase carbon microspheres in the plates makes the overall bending strength of the bipolar plates higher, and the overall strength of the bipolar plates is greater. At the same time, Comparative Example 1 is compared with the bipolar plates without asphalt. The conductivity is small molecule carbon deposition, so the conductivity does not change much, but the bending strength of the bipolar plates changes greatly. The mesophase carbon microspheres produced by the cracking of the surface asphalt and the original carbon microspheres are more tightly superimposed at high temperatures, making the plates less likely to crack and improving the bending strength of the bipolar plate substrate. This makes the bipolar plates designed by the present invention extremely commercially valuable.

[0073] Table 1 Parameter test results of bipolar plates

[0074] Bipolar plate thickness / mm Conductivity S / cm Flexural strength / MPa Example 1 0.876 876 87.5 Example 2 0.982 854 92.1 Example 3 0.762 812 90 Example 4 0.853 902 88.7 Comparative example 1 1.028 876 65.2

[0075] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A preparation method of a fuel cell gas-phase deposition graphite bipolar plate, characterized in that, It includes the following steps: Mix asphalt with mesophase carbon microspheres to obtain a slurry; Coat the surface of carbon cloth with the slurry and then perform microwave treatment to obtain a preform; Perform plasma-enhanced chemical vapor deposition on the preform to deposit small molecule carbon to obtain a prefabricated bipolar plate; Immerse the prefabricated bipolar plate in polyacrylic resin and then perform curing and forming in sequence to obtain the fuel cell gas-phase deposition graphite bipolar plate; The time of the microwave treatment is 70-90 s, and the temperature is 150-300 °C; The parameters of the plasma-enhanced chemical vapor deposition include: the temperature is 800-1000 °C, the time is 20-50 min, the gas carbon source amount is 0.03-0.3 L / min, and the gas carbon source includes one or more of xylene gas, ethylene, and propyne gas.

2. The preparation method according to claim 1, characterized in that The mass ratio of the asphalt to the mesophase carbon microspheres is (0.5-0.8):

1.

3. The preparation method according to claim 1 or 2, characterized in that, The particle size of the mesophase carbon microspheres is 20-60 μm.

4. The preparation method according to claim 1, wherein The thickness of the preform is 1-3 mm.

5. The preparation method according to claim 1, wherein, The temperature of the curing is 250-350 °C, and the time is 0.5-1 h.

6. The preparation method according to claim 1, characterized in that, The forming is roll forming, and the roll forming adopts 3-5 roll forming procedures. The roll gap of the first press roll is 10-15 mm, and then it decreases by 1-4 mm step by step.

7. A fuel cell gas-phase deposition graphite bipolar plate prepared by the preparation method according to any one of claims 1-6.