Mesocarbon microbead-based bipolar plate material, and preparation method and application thereof

Abstract

The application provides a mesophase carbon microsphere-based bipolar plate material and a preparation method and application thereof, and belongs to the technical field of fuel cells. The application uses pitch as raw material, adds conductive filler and resin, and prepares resin pitch rich in mesophase carbon microspheres through polycondensation reaction, and then prepares the bipolar plate material through moulding and carbonization treatment. The prepared bipolar plate material has excellent mechanical property, conductive property, corrosion resistance and hydrophobic property, the bending strength is 29-70 MPa, the electric conductivity is 290-670 S / cm, the corrosion current density is 1.5-4.7 muA / cm 2 , and the water contact angle is 100-125 degrees, and can be used for preparing PEMFC bipolar plates. The raw material of the application is cheap and easy to obtain, the process is simple, and the prepared PEMFC bipolar plate has excellent performance.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a mesophase carbon microsphere-based bipolar plate material, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are currently the most mature type of fuel cell in the world, capable of combining hydrogen with oxygen from the air to form clean water and release electrical energy. The bipolar plate (current collector, flow field plate) is one of the key components of a PEMFC, playing a significant role in its performance, size, lifespan, cost (approximately 60%–70%), and weight (approximately 80%). A key characteristic of bipolar plates is the presence of parallel or serpentine flow channels, approximately 1 mm wide and 0.5–1.0 mm deep. Bipolar plates require certain compressive and flexural strength, good electrical and thermal conductivity, stable electrical performance under prolonged operation in the internal environment of the cell (acidic electrolyte, oxygen, hydrogen, heat, and humidity), light weight, low processing cost, and suitability for mass production. Currently, the main factor preventing fuel cells from entering the market is their high cost; reducing the cost of bipolar plates is crucial for the industrialization of proton exchange membrane fuel cells.

[0003] Currently, the main materials used to manufacture bipolar plates are graphite, metals, and resin / graphite composites. Machining graphite bipolar plates is the most common method, but this process is complex, costly, and has a low yield rate. Metal bipolar plates offer advantages due to the good machinability and mechanical properties of metals, making them suitable for mass production; however, their main problems are poor corrosion resistance and high contact resistance. Composite materials using graphite as a conductive filler and resin as a binder can be used to produce composite bipolar plates with gas flow channels in a single step through injection molding or compression molding techniques, but they suffer from poor electrical and thermal conductivity. Summary of the Invention

[0004] The purpose of this invention is to provide a mesophase carbon microsphere-based bipolar plate material, its preparation method and application. The prepared bipolar plate material has excellent mechanical properties, electrical and thermal conductivity, corrosion resistance and hydrophobic properties.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing mesophase carbon microsphere-based bipolar plate materials, comprising the following steps:

[0007] Asphalt, conductive filler and resin are mixed and subjected to thermal polycondensation to obtain resin asphalt;

[0008] The resin asphalt is molded to obtain a bipolar plate green blank;

[0009] The bipolar plate green was carbonized to obtain a mesophase carbon microsphere-based bipolar plate material.

[0010] Preferably, the asphalt is petroleum asphalt or coal tar pitch, the softening point of the asphalt is 50-150℃, the quinoline insoluble matter (QI) content is ≤0.1%, the ash content is ≤200ppm, and the sulfur content is ≤0.1%.

[0011] Preferably, the conductive filler includes conductive carbon black, flake graphite, graphene, or carbon fiber.

[0012] Preferably, the resin is a thermoplastic phenolic resin, the resin has a softening point of 70-140°C, and a free phenol content of ≤2.0%.

[0013] Preferably, the mass ratio of the asphalt, conductive filler and resin is 100:0.5-35:0.5-10.

[0014] Preferably, the thermal polycondensation is carried out under gas conditions, wherein the gas is nitrogen or air; the gas flow rate is 50-1000 mL / min; the thermal polycondensation temperature is 320-450°C, and the time is 1-8 h.

[0015] Preferably, the molding temperature is 100-200℃, the pressure is 50-300MPa, and the time is 1-10min.

[0016] Preferably, the carbonization temperature is 1000-1800℃ and the holding time is 20-200min.

[0017] This invention provides a mesophase carbon microsphere-based bipolar plate material prepared by the preparation method described in the above technical solution.

[0018] This invention provides the application of the mesophase carbon microsphere-based bipolar plate material described in the above technical solution in proton exchange membrane fuel cells.

[0019] This invention uses asphalt as raw material, first preparing resin asphalt rich in mesophase carbon microspheres through a condensation reaction, and then preparing bipolar plate materials through compression molding and carbonization. This invention generates a large number of polycyclic aromatic hydrocarbon compounds through thermal condensation, which are then oriented to form anisotropic mesophase microspheres. These mesophase microspheres precipitate from the asphalt mother liquor to form micron-sized spherical carbon materials (i.e., mesophase carbon microspheres). These mesophase carbon microspheres possess excellent physicochemical properties, chemical stability (corrosion resistance, hydrophobicity), thermal stability, and excellent electrical and thermal conductivity. Simultaneously, this invention adds conductive fillers and resin. The resin acts as a binder for the bipolar plate material, and the conductive fillers enhance the conductivity of the bipolar plate material. Therefore, the bipolar plate material prepared by this invention possesses excellent mechanical properties, electrical conductivity, corrosion resistance, and hydrophobicity, with a flexural strength of 29–70 MPa, an electrical conductivity of 290–670 S / cm, and a corrosion current density of 1.5–4.7 μA / cm. 2 With a water contact angle of 100–125°, it can be used to prepare PEMFC bipolar plates.

[0020] The raw materials used in this invention are inexpensive and readily available, the process is simple, and the prepared bipolar plates for PEMFCs have excellent performance. Attached Figure Description

[0021] Figure 1 Polarized light micrograph of the SP370℃ resin pitch prepared in Example 1;

[0022] Figure 2 The image shows a polarized light micrograph of the SP340℃ resin pitch prepared in Example 2.

[0023] Figure 3 Polarized light microscopy analysis image of the SP300℃ resin pitch prepared in Example 3;

[0024] Figure 4 The image shows a polarized light micrograph of the SP320℃ resin pitch prepared in Example 4.

[0025] Figure 5 Polarized light micrograph of the SP305℃ resin pitch prepared in Example 5;

[0026] Figure 6 Polarized light micrograph of the SP310℃ resin pitch prepared in Example 6;

[0027] Figure 7 Polarized light micrograph of SP328℃ resin pitch prepared in Example 7;

[0028] Figure 8 Polarized light micrograph of the SP335℃ resin pitch prepared in Example 8;

[0029] Figure 9Polarized light micrograph of the SP400℃ resin pitch prepared in Example 9;

[0030] Figure 10 Polarized light micrograph of SP330℃ resin pitch prepared in Example 10;

[0031] Figure 11 The image shows a polarized light micrograph of the SP300℃ resin pitch prepared in Example 11. Detailed Implementation

[0032] This invention provides a method for preparing mesophase carbon microsphere-based bipolar plate materials, comprising the following steps:

[0033] Asphalt, conductive filler and resin are mixed and subjected to thermal polycondensation to obtain resin asphalt;

[0034] The resin asphalt is molded to obtain a bipolar plate green blank;

[0035] The bipolar plate green was carbonized to obtain a mesophase carbon microsphere-based bipolar plate material.

[0036] This invention involves mixing asphalt, conductive filler, and resin, followed by thermal polycondensation to obtain resin asphalt.

[0037] In this invention, the asphalt is preferably petroleum asphalt or coal tar pitch, the softening point of the asphalt is preferably 50-150℃, the quinoline insoluble matter (QI) content is preferably ≤0.1%, the ash content is preferably ≤200ppm, and the sulfur content is preferably ≤0.1%; all contents mentioned in this invention are mass percentages.

[0038] In this invention, the conductive filler preferably includes conductive carbon black, flake graphite, graphene, or carbon fiber. This invention does not impose any special limitations on the specifications of the conductive filler; any of the aforementioned conductive fillers well-known in the art can be used.

[0039] In this invention, the resin is preferably a thermoplastic phenolic resin, the softening point of the resin is preferably 70–140°C, and the free phenol content is preferably ≤2.0% (by mass). This invention does not impose any specific limitation on the source of the thermoplastic phenolic resin; any thermoplastic phenolic resin meeting the above conditions can be obtained through methods well-known in the art.

[0040] In this invention, the mass ratio of the asphalt, conductive filler and resin is preferably 100:0.5-35:0.5-10, more preferably 100:5-30:2.5-8, and even more preferably 100:15-20:5-7.

[0041] The present invention preferably adds conductive filler and resin to the asphalt, uses a temperature controller to strictly follow the program to raise the temperature, and starts stirring after the material reaches the softening point. The stirring speed is set to 180 rpm, gas is introduced, and the temperature is raised to the temperature of thermal condensation.

[0042] In this invention, the heating rate is preferably 5°C / min; the thermal polycondensation is preferably carried out under gas conditions, the gas being preferably nitrogen or air; the gas flow rate is preferably 50-1000 mL / min, more preferably 200 mL / min.

[0043] In this invention, the thermal polycondensation is preferably carried out under normal pressure; the temperature of the thermal polycondensation is preferably 320–450°C, more preferably 350–420°C, and even more preferably 360–385°C; the time is preferably 1–8 h, more preferably 3–6 h, and even more preferably 4–4.5 h; the light components generated during the reaction are collected in the tail gas cylinder. During the thermal polycondensation process, asphalt molecules first form plate-like molecular stacking units with regular shapes, then the plate-like molecular stacking units form spherical microdomains, and then the microdomains stack together to form an intermediate phase sphere.

[0044] After the thermal polycondensation is completed, the present invention preferably processes the product under reduced pressure for 30 minutes. The pressure of the reduced pressure is preferably -0.05 to 0.09 MPa, more preferably -0.06 to 0.08 MPa, and even more preferably -0.07 MPa. The present invention removes unreacted low-molecular-weight hydrocarbons by reducing pressure, thereby increasing the softening point of the polycondensation product.

[0045] After obtaining the resin asphalt, the present invention performs molding on the resin asphalt to obtain a bipolar plate green blank.

[0046] In this invention, the resin asphalt is preferably crushed to 200 mesh using a pulverizer, placed in a steel mold, and then placed in the middle of a hot press after the mold is fitted. The required molding time, temperature and pressure are adjusted by adjusting the parameters on the hot press operation panel to perform molding and obtain a bipolar plate blank.

[0047] In this invention, the molding temperature is preferably 100-200℃, more preferably 120-180℃, and even more preferably 150℃; the pressure is preferably 50-300MPa, more preferably 100-230MPa, and even more preferably 175-200MPa; and the time is preferably 1-10min, more preferably 5min.

[0048] After obtaining the bipolar plate green body, the present invention carbonizes the bipolar plate green body to obtain mesophase carbon microsphere-based bipolar plate material.

[0049] In this invention, the carbonization is preferably carried out in a tubular furnace, preferably under nitrogen gas conditions, and the nitrogen gas flow rate is preferably 100 mL / min; the heating rate to the carbonization temperature is preferably 3 °C / min; the carbonization temperature is preferably 1000–1800 °C, more preferably 1200–1600 °C, and even more preferably 1400–1500 °C; the holding time is preferably 20–200 min, more preferably 60 min.

[0050] After the carbonization is completed, the product is preferably removed after natural cooling to obtain mesophase carbon microsphere-based bipolar plate material.

[0051] This invention provides a mesophase carbon microsphere-based bipolar plate material prepared by the preparation method described in the above technical solution.

[0052] This invention provides the application of the mesophase carbon microsphere-based bipolar plate material described in the above-mentioned technical solution in proton exchange membrane fuel cells. This invention does not specifically limit the method of application; any method well-known in the art can be used.

[0053] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] In the following examples, the softening point (SP) of the asphalt is 50–150°C, the quinoline insoluble content (QI) is ≤0.1%, the ash content is ≤200 ppm, and the sulfur content is ≤0.1%.

[0055] The softening point (SP) of phenolic resin is 70–140℃, and the free phenol content is ≤2.0%.

[0056] Example 1

[0057] Raw materials used: petroleum asphalt with a softening point SP of 150℃, QI of 0.05%, ash content of 130ppm, and sulfur content of 0.05%.

[0058] The softening point of phenolic resin is SP140℃, and the free phenol content is 2.0%.

[0059] 250g of petroleum asphalt, 12.5g of conductive carbon black, and 6.25g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous. The mass ratio of petroleum asphalt, conductive carbon black, and phenolic resin was 100:5:2.5. The temperature was increased by 5℃ / min. After reaching the softening point, the stirring was started at 180rpm, and air was introduced at a flow rate of 200mL / min. The temperature was maintained at the set temperature of 360℃ for 3 hours. Then, a depressurization operation was performed, with the system pressure at -0.05MPa for 30 minutes. After the reaction was completed, the asphalt was removed and the reactor was cleaned to obtain resin asphalt. The light components generated during the reaction were collected in the tail gas bottle.

[0060] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. The mold is then fitted and placed in the middle of a hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 200MPa and the time is 5min to obtain a bipolar plate blank.

[0061] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1000℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0062] Example 2

[0063] Raw materials used: coal tar pitch SP 120℃, QI 0.1%, ash content 200ppm, S content 0.1%;

[0064] Phenolic resin SP120℃, free phenol 0.5%.

[0065] 250g of coal tar pitch, 50g of carbon fiber, and 17.5g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of coal tar pitch, carbon fiber, and phenolic resin was 100:20:7. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 320℃ for 8 hours. Then, a depressurization operation was performed, with the system pressure at -0.09MPa for 30 minutes. After the reaction was completed, the pitch was removed and the reactor was cleaned to obtain resin pitch. The light components generated during the reaction were collected in the tail gas bottle.

[0066] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 100℃, the pressure is 100MPa and the time is 5min to obtain bipolar plate blank.

[0067] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1400℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0068] Example 3

[0069] Raw materials used: petroleum asphalt SP 50℃, QI 0.05%, ash content 150ppm, S content 0.05%;

[0070] Phenolic resin SP140℃, free phenol 2.0%.

[0071] 250g of petroleum asphalt, 75g of graphene, and 1.25g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of petroleum asphalt, graphene, and phenolic resin was 100:30:0.5. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 350℃ for 8 hours. Then, a depressurization operation was performed, with the system pressure at -0.05MPa for 30 minutes. After the reaction was completed, the asphalt was removed and the reactor was cleaned to obtain resin asphalt. The light components generated during the reaction were collected in the tail gas bottle.

[0072] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. The mold is then fitted and placed in the middle of a hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 200MPa and the time is 5min to obtain a bipolar plate blank.

[0073] The bipolar plate green was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1800℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0074] Example 4

[0075] Raw materials used: petroleum asphalt SP 120℃, QI 0.03%, ash content 180ppm, S content 0.08%;

[0076] Phenolic resin SP at 80℃, free phenol 0.5%.

[0077] 250g of petroleum asphalt, 87.5g of flake graphite, and 2.5g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of petroleum asphalt, flake graphite, and phenolic resin was 100:35:1. The temperature was increased at 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 380℃ for 4 hours. Then, a depressurization operation was performed, with the system pressure at -0.07MPa for 30 minutes. After the reaction was completed, the asphalt was removed and the reactor was cleaned to obtain resin asphalt. The light components generated during the reaction were collected in the tail gas bottle.

[0078] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted by the parameters of the hot press operation panel to perform molding. The molding temperature is 200℃, the pressure is 200MPa and the time is 5min to obtain bipolar plate blank.

[0079] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1400℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0080] Example 5

[0081] Raw materials used: coal tar pitch SP 70℃, QI 0.05%, ash content 175ppm, S content 0.07%;

[0082] Phenolic resin SP at 70℃ contains 0.6% free phenol.

[0083] 250g of coal tar pitch, 37.5g of graphene, and 12.5g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of coal tar pitch, graphene, and phenolic resin was 100:15:5. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 385℃ for 4.5h. Then, a depressurization operation was performed, with the system pressure at -0.07MPa for 30min. After the reaction was completed, the pitch was removed and the reactor was cleaned to obtain resin pitch. The light components generated during the reaction were collected in the tail gas bottle.

[0084] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted by the parameters of the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 175MPa and the time is 5min to obtain bipolar plate blank.

[0085] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1400℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0086] Example 6

[0087] Raw materials used: coal tar pitch SP 60℃, QI 0.1%, ash content 200ppm, S content 0.1%;

[0088] Phenolic resin SP at 70℃, free phenol 2.0%.

[0089] 250g of coal tar pitch, 22.5g of carbon fiber, and 17.5g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of coal tar pitch, carbon fiber, and phenolic resin was 100:9:7. The temperature was increased at 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 450℃ for 5h. Then, a depressurization operation was performed, with the system pressure at -0.05MPa for 30min. After the reaction was completed, the pitch was removed and the reactor was cleaned to obtain resin pitch. The light components generated during the reaction were collected in the tail gas bottle.

[0090] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 100℃, the pressure is 50MPa and the time is 5min to obtain bipolar plate green blank.

[0091] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1000℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0092] Example 7

[0093] Raw materials used: petroleum asphalt SP 110℃, QI 0.03%, ash content 156ppm, S content 0.03%;

[0094] Phenolic resin SP at 90℃, free phenol 0.03%.

[0095] 250g of petroleum asphalt, 1.25g of carbon fiber, and 25g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of petroleum asphalt, carbon fiber, and phenolic resin was 100:0.5:10. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min. The temperature was maintained at the set temperature of 380℃ for 6 hours. Then, a depressurization operation was performed, with the system pressure at -0.08MPa for 30 minutes. After the reaction was completed, the asphalt was removed and the reactor was cleaned to obtain resin asphalt. The light components generated during the reaction were collected in the tail gas bottle.

[0096] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. The mold is then fitted and placed in the middle of a hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 300MPa and the time is 5min to obtain a bipolar plate blank.

[0097] The bipolar plate green was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1800℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0098] Example 8

[0099] Raw materials used: coal tar pitch SP 90℃, QI 0.05%, ash content 60ppm, S content 0.1%;

[0100] Phenolic resin SP at 130℃, free phenol 0.8%.

[0101] 250g of coal tar pitch, 25g of graphene, and 20g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of coal tar pitch, graphene, and phenolic resin was 100:10:8. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 380℃ for 5 hours. Then, a depressurization operation was performed, with the system pressure at -0.07MPa for 30 minutes. After the reaction was completed, the pitch was removed and the reactor was cleaned to obtain resin pitch. The light components generated during the reaction were collected in the tail gas bottle.

[0102] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. The mold is then fitted and placed in the middle of a hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 200MPa and the time is 5min to obtain a bipolar plate blank.

[0103] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1400℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0104] Example 9

[0105] Raw materials used: coal tar pitch SP 50℃, QI 0.05%, ash content 60ppm, S content 0.01%;

[0106] Phenolic resin SP at 130℃, free phenol 0.2%.

[0107] 250g of coal tar pitch, 1.25g of conductive carbon black, and 15g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of coal tar pitch, conductive carbon black, and phenolic resin was 100:0.5:6. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min. The temperature was maintained at the set temperature of 400℃ for 2 hours. Then, a depressurization operation was performed, with the system pressure at -0.08MPa for 30 minutes. After the reaction was completed, the pitch was removed and the reactor was cleaned to obtain resin pitch. The light components generated during the reaction were collected in the tail gas bottle.

[0108] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted through the hot press operation panel to perform molding. The molding temperature is 100℃, the pressure is 50MPa and the time is 5min to obtain bipolar plate green blank.

[0109] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1200℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0110] Example 10

[0111] Raw materials used: petroleum asphalt SP 120℃, QI 0.01%, ash content 200ppm, S content 0.05%;

[0112] Phenolic resin SP at 90℃ contains 1.6% free phenol.

[0113] 250g of petroleum asphalt, 62.5g of graphene, and 17.5g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of petroleum asphalt, graphene, and phenolic resin was 100:25:2. The temperature was increased by 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 350℃ for 6 hours. Then, a depressurization operation was performed, with the system pressure at -0.07MPa for 30 minutes. After the reaction was completed, the asphalt was removed and the reactor was cleaned to obtain resin asphalt. The light components generated during the reaction were collected in the tail gas bottle.

[0114] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted by the parameters of the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 225MPa and the time is 5min to obtain bipolar plate blank.

[0115] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1500℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0116] Example 11

[0117] Raw materials used: coal tar pitch SP 100℃, QI 0.05%, ash content 70ppm, S content 0.01%;

[0118] Phenolic resin SP at 70℃ contains 0.02% free phenol.

[0119] 250g of coal tar pitch, 37.5g of flake graphite, and 12.5g of phenolic resin were placed into a 500mL reactor and stirred until homogeneous, i.e., the mass ratio of coal tar pitch, flake graphite, and phenolic resin was 100:15:5. The temperature was increased at 5℃ / min, and after reaching the softening point, the stirring was started at 180rpm. Air flow rate was introduced at 200mL / min, and the temperature was maintained at the set temperature of 410℃ for 4 hours. Then, a depressurization operation was performed, with the system pressure at -0.07MPa for 30 minutes. After the reaction was completed, the pitch was removed and the reactor was cleaned to obtain resin pitch. The light components generated during the reaction were collected in the tail gas bottle.

[0120] After the resin asphalt is crushed to 200 mesh, it is placed in a steel mold. After the mold is fitted, it is placed in the middle of the hot press. The required molding time, temperature and pressure are adjusted by the parameters of the hot press operation panel to perform molding. The molding temperature is 150℃, the pressure is 175MPa and the time is 5min to obtain bipolar plate blank.

[0121] The bipolar plate green blank was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 100 mL / min. The temperature was increased to the carbonization temperature of 1400℃ at a heating rate of 3℃ / min, and held for 1 hour to obtain the bipolar plate material.

[0122] Characterization

[0123] 1) The softening point of the resin asphalt prepared in Examples 1 to 11 was tested. The results showed that the softening point (SP) of the resin asphalt was 300-400℃. The softening points of the resin asphalt prepared in Examples 1 to 11 were 370℃, 340℃, 300℃, 320℃, 305℃, 310℃, 328℃, 335℃, 400℃, 330℃ and 300℃ respectively.

[0124] 2) The formation of mesophase microspheres in the resin asphalt prepared in Examples 1-11 was observed using a polarizing microscope. The results are shown in [Figure 1]. Figures 1-11 ;

[0125] Figure 1The image shows a polarized light micrograph of the SP370℃ resin pitch prepared in Example 1, which was found to contain 85% mesophase.

[0126] Figure 2 The image shows a polarized light micrograph of the SP340℃ resin pitch prepared in Example 2, which was found to contain 80% mesophase.

[0127] Figure 3 The image shows a polarized light micrograph of the SP300℃ resin pitch prepared in Example 3, which was found to contain 70% mesophase.

[0128] Figure 4 The image shows a polarized light micrograph of the SP320℃ resin pitch prepared in Example 4, which was found to contain 75% mesophase.

[0129] Figure 5 The image shows a polarized light micrograph of the SP305℃ resin pitch prepared in Example 5, which was found to contain 60% mesophase.

[0130] Figure 6 The polarized light micrograph of the SP310℃ resin pitch prepared in Example 6 shows that the mesophase content is 65%.

[0131] Figure 7 The image shows a polarized light micrograph of the SP328℃ resin pitch prepared in Example 7, which was found to contain 70% mesophase.

[0132] Figure 8 The polarized light micrograph of the SP335℃ resin pitch prepared in Example 8 shows that the mesophase content is 75%.

[0133] Figure 9 The polarized light micrograph of the SP400℃ resin pitch prepared in Example 9 shows that the mesophase content is 90%.

[0134] Figure 10 The image shows a polarized light micrograph of the SP330℃ resin pitch prepared in Example 10, which was found to contain 70% mesophase.

[0135] Figure 11 The image shows a polarized light micrograph of the SP300℃ resin pitch prepared in Example 11, which was found to contain 60% mesophase.

[0136] The results show that the mesophase content of the resin asphalt prepared in the embodiments of the present invention is 60-90% (mass percentage).

[0137] Performance testing

[0138] (1) Bipolar plate conductivity test

[0139] The resistivity of bipolar plate materials was tested using an ST2253 four-probe resistivity meter.

[0140] (2) Bipolar plate bending strength test

[0141] The flexural strength of bipolar plate materials was tested using a microcomputer-controlled universal testing machine, and the test method was performed in accordance with GB / T13465-2014 "Test Methods for Impermeable Graphite Materials".

[0142] (3) Bipolar plate corrosion resistance test

[0143] The corrosion resistance of the bipolar plate material was tested using an electrochemical workstation. The test method was linear potential scanning, using a 5wt% H2SO4 electrolyte solution to simulate the working environment of a PEMFC. A saturated calomel electrode was used as the reference electrode, and the bipolar plate material prepared in this invention was used as the working electrode. A platinum electrode was used as the auxiliary electrode. The potential scanning range was -0.25 to 0.25 V, and the scanning rate was 2 mV / s. Tafel curves were obtained by polarization fitting, and the ratio of corrosion current to working electrode area was calculated, which is the corrosion current density.

[0144] (4) Bipolar plate hydrophobicity test

[0145] The water contact angle of bipolar plate materials was tested using a video optical contact angle meter from Dataphysics, Germany. The testing method was the shape image analysis method, and the hydrophobic properties of the material were evaluated by the size of the contact angle presented by the water droplet on the material.

[0146] The test results are shown in Table 1.

[0147] Table 1 Performance data of bipolar plate materials prepared in Examples 1-11

[0148]

[0149] As shown in Table 1, the bipolar plate material prepared by this invention has excellent mechanical properties, electrical conductivity, corrosion resistance and hydrophobicity, and can be used as a PEMFC bipolar plate.

[0150] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a mesophase carbon microsphere-based bipolar plate material, characterized in that, Includes the following steps: Asphalt, conductive filler and resin are mixed and subjected to thermal polycondensation to obtain resin asphalt; The resin asphalt is molded to obtain a bipolar plate green blank; The bipolar plate green is carbonized to obtain a mesophase carbon microsphere-based bipolar plate material. The asphalt is petroleum asphalt or coal tar pitch, the softening point of the asphalt is 50~150℃, the quinoline insoluble matter (QI) content is ≤0.1%, the ash content is ≤200ppm, and the sulfur content is ≤0.1%. The resin is a thermoplastic phenolic resin, the softening point of the resin is 70~140℃, and the free phenol content is ≤2.0%; The mass ratio of the asphalt, conductive filler, and resin is 100:0.5~35:0.5~10; The thermal polycondensation is carried out under gas conditions, wherein the gas is nitrogen or air; the gas flow rate is 50~1000mL / min; the thermal polycondensation temperature is 320~450℃, and the time is 1~8h.

2. The preparation method according to claim 1, characterized in that, The conductive filler includes conductive carbon black, flake graphite, graphene, or carbon fiber.

3. The preparation method according to claim 1, characterized in that, The molding temperature is 100~200℃, the pressure is 50~300MPa, and the time is 1~10min.

4. The preparation method according to claim 1, characterized in that, The carbonization temperature is 1000~1800℃, and the holding time is 20~200min.

5. The mesophase carbon microsphere-based bipolar plate material prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the mesophase carbon microsphere-based bipolar plate material according to claim 5 in proton exchange membrane fuel cells.

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