A method for preparing a high-conductivity carbon fiber paper

Abstract

The application provides a preparation method of high-conductivity carbon fiber paper and belongs to the technical field of fuel cells. The method comprises the following steps: step 1, dissolving a water-soluble polymer in water to prepare a dispersion liquid with a certain concentration; step 2, dispersing short-cut carbon fibers with a certain thickness of metal plating layer in the dispersion liquid to prepare a fiber slurry; step 3, performing wet papermaking on the slurry, and performing pressing and drying to prepare a raw paper; and step 4, performing high-temperature hot pressing treatment on the raw paper under a reducing atmosphere and a certain pressure to prepare a primary carbon paper. The prepared carbon paper has an electrical resistivity less than 3 mΩ·cm, a porosity greater than 80%, and a gas permeability greater than 2200 ml·mm / [cm 2 ·h·mm·Aq]. The application improves the electrical conductivity of the carbon paper and the gas permeability of the carbon paper, and the process is simple, and the performance of the fuel cell can be obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and specifically relates to a method for preparing high-conductivity carbon fiber paper. Background Technology

[0002] Carbon paper is a core material for fuel cell membrane electrode assemblies (MEAs). It is typically composed of carbon fibers and resin-based carbon, possessing a uniform porous structure, good strength, and excellent electrical conductivity. In fuel cells, it serves as a support material for the gas diffusion layer, supporting the catalyst layer and providing electron, heat transfer, gas, and drainage channels for the electrode reactions.

[0003] Fuel cells place high demands on the conductivity of carbon paper. Traditional processes primarily rely on high-temperature graphitization to enhance the graphitization degree of carbon. This process is not only energy-intensive and time-consuming but also places high demands on equipment. Furthermore, it can induce thermal stress, leading to cracking and a decline in the mechanical properties of the carbon paper. Secondly, the porosity and pore size distribution of the carbon paper are crucial for gas permeability and drainage. Low porosity or uneven distribution can obstruct local gas diffusion and cause liquid water accumulation, thereby affecting electrochemical reaction efficiency and the power density of the fuel cell. Traditional processes use resin binders and require multiple processing steps. This limits porosity and reduces pore size uniformity, necessitating large amounts of organic solvents and placing high demands on post-processing.

[0004] In summary, traditional carbon paper preparation methods suffer from problems such as complex processes, high equipment requirements for electrical conductivity, limited porosity, and difficulty in controlling pore distribution. There is a need to develop a simple new carbon paper preparation method that can guarantee high electrical conductivity and high porosity of the base paper. Summary of the Invention

[0005] Based on this, the present invention provides a method for preparing high-conductivity carbon fiber paper. By using carbon fiber with a metal coating instead of regular carbon fiber, the conductivity is significantly improved. The high-temperature sintering of the metal coating replaces the bonding of resin and carbon, effectively simplifying the process. Carbon coating enhances structural / chemical stability and improves conductivity.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for preparing high-conductivity carbon fiber paper includes the following steps: S1, dissolving a water-soluble polymer in water to prepare a dispersion of a certain concentration; S2, dispersing short-cut carbon fibers with a certain thickness of metal coating in the dispersion to prepare a fiber slurry; S3, performing wet papermaking on the slurry, followed by pressing and drying to obtain a base paper; S4, subjecting the base paper to high-temperature hot pressing under a reducing atmosphere and a certain pressure to obtain primary carbon paper; S5, subjecting the primary carbon paper to chemical vapor deposition at a certain temperature in an organic atmosphere to obtain the final carbon paper.

[0008] In the above-mentioned method for preparing high-conductivity carbon fiber paper, in step S1, the water-soluble polymer is one or more of polyethylene oxide, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, carboxyethyl cellulose, and sodium alginate.

[0009] In the above-mentioned method for preparing high-conductivity carbon fiber paper, in step S1, the concentration of the water-soluble polymer aqueous solution is 0.02-0.2%.

[0010] In the above-mentioned method for preparing high-conductivity carbon fiber paper, in step 2, the metal-coated carbon fiber is one of nickel-plated carbon fiber, iron-plated carbon fiber, or copper-plated carbon fiber. The thickness of the metal coating is 100 nm-2 μm, and the fiber length is 3-10 mm. The concentration of the fiber slurry is 0.01-0.1%.

[0011] In the above-mentioned method for preparing high-conductivity carbon fiber paper, in step 4, the reducing atmosphere is one of hydrogen, a hydrogen / argon mixture, ammonia, a hydrogen / ammonia mixture, or an ammonia / argon mixture.

[0012] In the above-mentioned method for preparing high-conductivity carbon fiber paper, in step 4, the hot-pressing pressure is 0.1MPa-1MPa, the hot-pressing temperature is 1000-1500℃, and the hot-pressing time is 10min-2h.

[0013] In the above-mentioned method for preparing high-conductivity carbon fiber paper, in step 5, the atmosphere for vapor deposition is one of ethylene, methane, propylene, ethane, propane, toluene, benzene, and a mixture of ethanol / hydrogen or methanol / hydrogen. The deposition temperature is 600-1000℃. The deposition time is 10 min-1 h.

[0014] Furthermore, the prepared carbon paper has a resistivity of less than 3 mΩ·cm, a porosity of greater than 80%, and a gas permeability of greater than 2200 ml·mm / cm. 2 ·h·mmAq].

[0015] Compared with the prior art, the method for preparing carbon paper of the present invention has the following beneficial effects:

[0016] 1) This preparation method avoids resin impregnation, which on the one hand reduces the volume filling between fibers and effectively increases porosity; on the other hand, it avoids pore blockage caused by uneven resin carbon distribution, resulting in a more uniform pore size distribution. Ultimately, it achieves a porosity superior to traditional carbon paper, a more rational pore structure, and exhibits excellent gas permeability.

[0017] 2) This preparation method avoids the high-temperature graphitization process, which on the one hand reduces equipment investment and significantly reduces production costs, and on the other hand effectively improves production efficiency and reduces production energy consumption;

[0018] 3) The use of metal-coated carbon fibers with higher conductivity ensures that the carbon paper has excellent electrical conductivity. The use of vapor deposition to coat carbon improves the structural stability and chemical stability of the carbon paper during cycling, and further improves the conductivity of the carbon paper. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] Example 1

[0021] Polyethylene oxide was dissolved in water to prepare a dispersion with a concentration of 0.02%. Short-cut nickel-plated carbon fibers with a coating thickness of 100 nm were dispersed in the dispersion to prepare a fiber slurry with a concentration of 0.01%. The slurry was subjected to wet papermaking, followed by pressing and drying to obtain base paper. The base paper was subjected to high-temperature hot pressing treatment at 1500°C and 0.1 MPa pressure for 2 hours in a hydrogen / argon mixed atmosphere to obtain primary carbon paper. The primary carbon paper was placed in a vapor deposition furnace, ethylene was introduced, and deposition was carried out at 600°C for 10 minutes to obtain the final carbon paper. The obtained carbon paper had a resistivity of 3.0 mΩ·cm, a porosity of 83%, and a gas permeability of 2400 ml·mm / cm². 2 ·h·mmAq].

[0022] Example 2

[0023] Carboxyethyl cellulose was dissolved in water to prepare a dispersion with a concentration of 0.05%. Short-cut copper-plated carbon fibers with a coating thickness of 2 μm were dispersed in the dispersion to prepare a fiber slurry with a concentration of 0.1%. The slurry was subjected to wet papermaking, followed by pressing and drying to obtain base paper. The base paper was then subjected to high-temperature hot pressing at 1000°C and 1 MPa pressure for 10 min in an ammonia atmosphere to obtain primary carbon paper. The primary carbon paper was placed in a vapor deposition furnace, and ethanol / hydrogen gas was introduced, followed by deposition at 1000°C for 1 h to obtain the final carbon paper. The resulting carbon paper exhibited a resistivity of 2.2 mΩ·cm, a porosity of 80%, and a gas permeability of 2250 ml·mm / cm². 2 ·h·mmAq].

[0024] Example 3

[0025] Polyethylene oxide / carboxyethyl cellulose was dissolved in water in equal proportions to prepare a dispersion with a concentration of 0.2%. Short-cut iron-coated carbon fibers with a coating thickness of 500 μm were dispersed in the above dispersion to prepare a fiber slurry with a concentration of 0.03%. The slurry was subjected to wet papermaking, followed by pressing and drying to obtain base paper. The base paper was then subjected to high-temperature hot pressing at 1400 °C and 0.2 MPa pressure for 30 min in an ammonia atmosphere to obtain primary carbon paper. The primary carbon paper was placed in a vapor deposition furnace, toluene vapor was introduced, and deposition was carried out at 800 °C for 20 min to obtain the final carbon paper. The obtained carbon paper had a resistivity of 2.6 mΩ·cm, a porosity of 82%, and a gas permeability of 2300 ml·mm / cm². 2 ·h·mmAq].

[0026] Example 4

[0027] Carboxyethyl cellulose and sodium alginate were dissolved in water in equal proportions to prepare a dispersion with a concentration of 0.1%. Short-cut copper-plated carbon fibers with a coating thickness of 1 μm were dispersed in the above dispersion to prepare a fiber slurry with a concentration of 0.05%. The slurry was subjected to wet papermaking, followed by pressing and drying to obtain base paper. The base paper was then subjected to high-temperature hot pressing at 1050 °C and 0.3 MPa pressure for 10 min in an ammonia / argon atmosphere to obtain primary carbon paper. The primary carbon paper was placed in a vapor deposition furnace, and methane / hydrogen gas was introduced, with deposition at 800 °C for 20 min to obtain the final carbon paper. The obtained carbon paper exhibited a resistivity of 2.0 mΩ·cm, a porosity of 84%, and a gas permeability of 2700 ml·mm / cm². 2 ·h·mmAq].

[0028] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for preparing high-conductivity carbon fiber paper, characterized in that: Includes the following steps: Step 1: Dissolve the water-soluble polymer in water to prepare a dispersion of a certain concentration; Step 2: Disperse short carbon fibers with a certain thickness of metal coating in the above dispersion to prepare a fiber slurry; Step 3: The above pulp is subjected to wet papermaking, and after pressing and drying, the base paper is obtained; Step 4: Under a reducing atmosphere and a certain pressure, the above-mentioned base paper is subjected to high-temperature hot pressing treatment to obtain primary carbon paper. Step 5: Perform chemical vapor deposition on the primary carbon paper at a certain temperature in an organic atmosphere to obtain the final carbon paper.

2. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: In step 1, the water-soluble polymer is one or more of the following: polyethylene oxide, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, carboxyethyl cellulose, and sodium alginate.

3. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: In step 1, the concentration of the aqueous solution of the water-soluble polymer is 0.02-0.2%.

4. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: In step 2, the metal-coated carbon fiber is one of nickel-plated carbon fiber, iron-plated carbon fiber, or copper-plated carbon fiber. The thickness of the metal coating is 100 nm-2 μm, and the fiber length is 3-10 mm. The concentration of the fiber slurry is 0.01-0.1%.

5. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: In step 4, the reducing atmosphere is one of hydrogen, a hydrogen / argon mixture, ammonia, a hydrogen / ammonia mixture, or an ammonia / argon mixture.

6. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: In step 4, the hot pressing pressure is 0.1MPa-1MPa, the hot pressing temperature is 1000-1500℃, and the hot pressing time is 10min-2h.

7. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: In step 5, the atmosphere for vapor deposition is one of ethylene, methane, propylene, ethane, propane, toluene, benzene, or a mixture of ethanol / hydrogen or methanol / hydrogen. The deposition temperature is 600-1000℃. The deposition time is 10 min-1 h.

8. The method for preparing high-conductivity carbon fiber paper according to claim 1, characterized in that: The prepared carbon paper has a resistivity of less than 3 mΩ·cm, a porosity of greater than 80%, and a gas permeability of greater than 2200 ml·mm / cm. 2 ·h·mmAq].