Microporous layer slurry, microporous layer as well as preparation method and application of microporous layer

Abstract

The invention discloses microporous layer slurry, a microporous layer as well as a preparation method and application of the microporous layer. The microporous layer slurry comprises the following components in parts by mass: 1-15 parts of graphitized carbon fibers, 5-27 parts of carbon powder, 2-15 parts of an adhesive, 1-10 parts of a dispersing agent and 50-83 parts of a solvent. The microporous layer slurry can be used for preparing a microporous layer for carbon paper, the obtained microporous layer has excellent basic performance, when the microporous layer slurry is actually used for a gas diffusion layer of a fuel cell, excellent ventilation effect and water retention effect can be ensured at the same time, the performance and durability of the fuel cell are effectively improved, and the microporous layer slurry is low in cost and suitable for batch production.

Description

Technical Field

[0001] The invention relates to a microporous layer slurry, a microporous layer and a preparation method and application thereof. Background Art

[0002] A proton exchange membrane fuel cell (hereinafter referred to as a fuel cell) is a power generation device that converts chemical energy directly into electrical energy through the electrochemical reaction between a fuel (hydrogen) and an oxidant (typically air), rather than through the Carnot cycle. The membrane electrode assembly (MEA), consisting of a proton exchange membrane and a precious metal catalyst, is the core component of a fuel cell. During fuel cell operation, the membrane electrode must effectively separate the fuel and oxidant, preventing them from mixing and reacting directly. In extreme cases, this could cause an explosion, or leakage between the fuel and oxidant, leading to a decrease in cell efficiency and a shortened lifespan.

[0003] During the electrochemical process at the cathode of a fuel cell, oxygen in the air diffuses from the gas diffusion layer (GDL) to the proton exchange membrane, while hydrogen protons produced by the electrochemical reaction at the anode are transferred through the proton exchange membrane to the cathode. When the protons and oxygen meet at the active sites on the surface of the precious metal catalyst, an oxygen reduction reaction (ORR) occurs, producing water. Both reactants disappear. The reaction equation is as follows:

[0004]

[0005] Therefore, in the cathode catalyst layer, the concentrations of oxygen diffused from the GDL and protons transferred from the proton exchange membrane both exhibit a gradient—that is, the oxygen concentration is higher near the precious metal on the outside of the catalyst layer (near the GDL), while the oxygen concentration decreases as you move inward. Consequently, the uneven concentrations of reacting substances place inconsistent demands on the reaction diffusion channels. However, using traditional, uniformly distributed gas channel construction methods, such as a gas diffusion layer primarily composed of a carbon powder layer, makes it difficult to ensure improved fuel cell performance and durability.

[0006] In addition, the membrane electrode assembly used in fuel cells is relatively expensive. If the degradation of the microporous layer causes damage to the membrane electrode, it will eventually lead to greater losses.

[0007] Therefore, there is an urgent need for a low-cost, high-performance microporous layer that can effectively improve the performance and durability of fuel cells. Summary of the Invention

[0008] To address the aforementioned technical deficiencies of existing microporous layers, the present invention provides a microporous layer slurry, a microporous layer, a preparation method, and applications thereof. This microporous layer slurry can be used to prepare a microporous layer for carbon paper. The resulting microporous layer exhibits excellent basic properties. When used in a gas diffusion layer for a fuel cell, it simultaneously ensures excellent air permeability and water retention, effectively improving the performance and durability of the fuel cell. Furthermore, it is low-cost and suitable for mass production.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows.

[0010] The present invention provides a microporous layer slurry, which includes the following components in parts by mass:

[0011] 1-15 parts of graphitized carbon fiber, 5-27 parts of carbon powder, 2-15 parts of adhesive, 1-10 parts of dispersant and 50-83 parts of solvent.

[0012] In some embodiments, the amount of the graphitized carbon fiber is 5-10 parts, for example 7.5 parts.

[0013] In some embodiments, the mesh size of the graphitized carbon fiber is 500-1000 mesh, for example 800 mesh.

[0014] In some embodiments, the carbon powder is used in an amount of 5-10 parts, for example 7.5 parts.

[0015] In some embodiments, the carbon powder has a particle size of 10-100 nm, for example, 50 nm.

[0016] In some embodiments, the mass ratio of the graphitized carbon fiber to the carbon powder is (1-5):(9-5), for example, 1:1.

[0017] In some embodiments, the adhesive comprises PTFE emulsion; the solid content of PTFE in the PTFE emulsion is, for example, 60%.

[0018] In some embodiments, the amount of the binder is 5-10 parts, for example 7 parts.

[0019] In some embodiments, the dispersant comprises Triton.

[0020] In some embodiments, the amount of the dispersant is 4-6 parts, for example 5 parts.

[0021] In some embodiments, the solvent includes isopropyl alcohol and / or deionized water.

[0022] In some embodiments, the amount of the solvent used is 60-70 parts, for example 65 parts.

[0023] In some preferred embodiments, the microporous layer slurry includes the following components in parts by mass:

[0024] 5-10 parts of graphitized carbon fibers, 5-10 parts of carbon powder, 5-10 parts of adhesive, 4-6 parts of dispersant and 60-70 parts of solvent.

[0025] In some specific embodiments, the microporous layer slurry includes the following components in parts by mass:

[0026] 7.5 parts of graphitized carbon fibers, 7.5 parts of carbon powder, 7 parts of PTFE emulsion, 40 parts of isopropyl alcohol, 25 parts of deionized water and 5 parts of Triton; wherein the mesh size of the graphitized carbon fibers is 800 mesh, the particle size of the carbon powder is 50 nm, and the solid content of PTFE in the PTFE emulsion is 60%.

[0027] The present invention also provides a method for preparing the microporous layer slurry as described above. The method for preparing the microporous layer slurry comprises the following steps: mixing the components of the microporous layer slurry as described above.

[0028] The present invention also provides a microporous layer, which is prepared by using the microporous layer slurry as described above.

[0029] In some embodiments, the microporous layer has a thickness of 50-300 μm, for example 150 μm.

[0030] In some embodiments, the carbon loading of the microporous layer is 0.5-8 mg / cm 2 , for example 2mg / cm 2 .

[0031] In some embodiments, the porosity of the microporous layer is 10% to 50%, for example 30%.

[0032] In some embodiments, the transverse resistivity of the microporous layer is 0.2-0.8 Ω·cm, for example 0.6 Ω·cm.

[0033] In some preferred embodiments, the thickness of the microporous layer is 50-300 μm, and the carbon loading is 0.5-8 mg / cm 2 , porosity is 10%-50%, and lateral resistivity is 0.2-0.8Ω·cm.

[0034] In some specific embodiments, the thickness of the microporous layer is 150 μm and the carbon loading is 2 mg / cm 2 , porosity is 30%, and lateral resistivity is 0.6Ω·cm.

[0035] The present invention also provides a method for preparing the microporous layer as described above, the method for preparing the microporous layer comprising the following steps:

[0036] The microporous layer slurry as described above is coated on the carbon paper base layer and cured to obtain the product.

[0037] In some embodiments, the carbon paper base layer is made of carbon fiber paper.

[0038] In some embodiments, the carbon paper substrate has a contact angle of 110° to 150°.

[0039] In some embodiments, the carbon paper base layer is made of carbon paper subjected to hydrophobic treatment.

[0040] In some embodiments, the coating is performed by slot coating, screen printing, doctor blade coating, or spray coating.

[0041] In some embodiments, the coating speed is 15-20 mm / s, such as 10 mm / s.

[0042] In some embodiments, the curing includes primary curing and secondary curing.

[0043] The one-time curing method is preferably hot pressing curing; the temperature of the hot pressing curing is preferably 110° C.-130° C., such as 120° C., and the pressure is preferably 2-4 MPa, such as 3 MPa.

[0044] The primary curing time is preferably 4-6 minutes, for example 5 minutes.

[0045] The secondary curing method is preferably drying curing; the drying curing temperature is preferably 110°C-130°C, for example 120°C.

[0046] The secondary curing time is preferably 4-6 minutes, for example 5 minutes.

[0047] In some embodiments, the curing step further includes a drying step, and the drying method is, for example, surface drying.

[0048] In some specific embodiments, the method for preparing the microporous layer comprises the following steps:

[0049] The microporous layer slurry is coated on the surface of the carbon paper base, and after the surface is dried, it is cured at 120°C and 3MPa, and then cured at 120°C for a second time; wherein,

[0050] The formula of the microporous layer slurry is:

[0051] Graphitized carbon fiber: carbon powder: 60% PTFE emulsion: isopropyl alcohol: deionized water: Triton = 7.5:7.5:7:40:25:5;

[0052] The mesh number of the graphitized carbon fiber is 800 mesh, and the particle size of the carbon powder is 50 nm.

[0053] The present invention also provides a use of the aforementioned microporous layer slurry or the aforementioned microporous layer in a fuel cell.

[0054] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0055] The reagents and raw materials used in the present invention are commercially available.

[0056] The positive progress effect of the present invention is:

[0057] The microporous layer slurry of the present invention is prepared by combining graphitized carbon fibers with carbon powder to produce a microporous layer for carbon paper with excellent basic performance, achieving effective regulation of the thickness, hydrophobicity, loading capacity, porosity and other properties of the obtained microporous layer, and ensuring its high lateral conductivity; when actually used in the gas diffusion layer of a fuel cell, it can also simultaneously ensure excellent air permeability and water retention effects, and effectively improve the performance and durability of the fuel cell.

[0058] In addition, the preparation method of the present invention has the following advantages: 1) simple operation, only requires simple mixing of raw materials, coating and drying; 2) efficient coating and fast speed, manual operation can meet the needs of small-batch production, and it is also easy to scale up for large-scale production and realize automation on this basis; 3) customizable, microporous layers with different structures can be customized for different working scenarios of fuel cells, which can ensure both high air permeability and a certain water retention effect; 4) low cost and suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is an electron microscope image of the local surface of the microporous layer obtained in Example 1 of the present invention.

[0060] Figure 2 This is a comparison chart of the electrical conductivity data of the microporous layer obtained in Example 1 of the present invention and the microporous layer obtained in Comparative Example 1.

[0061] Figure 3 The performance diagram of the microporous layer obtained in Example 1 of the present invention and the microporous layer obtained in Comparative Example 1 after being used in a fuel cell. DETAILED DESCRIPTION

[0062] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0063] Example 1

[0064] The formula and preparation method of the microporous layer slurry used in this embodiment are as follows:

[0065] The raw materials were mixed and stirred at room temperature for 1 hour to prepare the product. The specific weight ratio was graphitized carbon fiber (800 mesh): carbon powder (particle size 50 nm): 60% PTFE emulsion: isopropyl alcohol: deionized water: Triton = 7.5:7.5:7:40:25:5.

[0066] Furthermore, the microporous layer of this embodiment was prepared on the carbon paper using the following doctor blade coating process:

[0067] 1. Cut the carbon paper base (carbon fiber paper made of carbon paper with hydrophobic treatment, with a contact angle of 130°) into a certain size, place it on the vacuum platform of the coating machine, and turn on the vacuum device.

[0068] 2. Slowly inject the microporous layer slurry. Stop injecting when the slurry overflows evenly from the die lip without bubbles to ensure that no air is mixed into the mold cavity.

[0069] 3. Set the die height to 200 μm, coating length to 300 mm, width to 150 mm, and coating speed to 10 mm / s to ensure a continuous coating process without cracks.

[0070] 4. Start the coating operation. After coating, turn off the vacuum device, remove the material, transfer the material to the hot press after it is dry, set the temperature to 120℃, the pressure to 3MPa, and hot press for 5 minutes for primary curing (hot pressing curing).

[0071] 5. Take the material obtained from the primary curing and put it into an oven for secondary curing (drying and curing). The specific temperature is 120°C and the time is 5 minutes.

[0072] Comparative Example 1

[0073] The only difference compared to Example 1 is that the microporous layer slurry is prepared with the following formula, and a conventional carbon powder microporous layer is prepared on the carbon paper base:

[0074] The weight ratio is carbon powder (particle size is 50 nm): 60% PTFE emulsion: isopropyl alcohol: deionized water: Triton = 15:7:40:25:5.

[0075] Effect embodiment

[0076] 1. Microstructure characterization

[0077] The microporous layer obtained in Example 1 was characterized by scanning electron microscopy.

[0078] The results are as follows Figure 1 The results show that the surface of the microporous layer has an obvious fiber structure.

[0079] 2. Characterization of physical and chemical parameters such as porosity, thickness, carbon loading, and resistivity

[0080] Porosity, thickness, resistivity, and other characteristics were determined according to GB / T 20042.7-2014, Proton Exchange Membrane Fuel Cells, Part 7: Carbon Paper Characterization Test Methods. Carbon loading can be measured using conventional testing methods in the art (gravimetric method).

[0081] Among them, for the microporous layer obtained in Example 1, the measurement results are as follows:

[0082] (1) The thickness is 150 μm.

[0083] (2) Carbon loading is 2 mg / cm 2 .

[0084] (3) The porosity is 30%.

[0085] (4) The lateral resistivity is 0.6Ω·cm.

[0086] Furthermore, the conductivity comparison data of the microporous layer obtained in Example 1 and the microporous layer obtained in Comparative Example 1 are as follows: Figure 2 The results show that the electrical conductivity of the microporous layer obtained in Example 1 is significantly higher than that of the microporous layer obtained in Comparative Example 1.

[0087] 3. Used for battery performance characterization after fuel cells

[0088] The microporous layer obtained in Example 1 and the microporous layer obtained in Comparative Example 1 were respectively prepared into membrane electrode assemblies (MEAs) and placed on a fuel cell platform for evaluation; specifically, conventional fuel cell single cell tests in the art were used to test the membrane electrode polarization curve (test parameters such as Figure 3 shown).

[0089] The results are as follows Figure 3 As shown in the results, when the microporous layer obtained in Example 1 was used to prepare a membrane electrode for single cell testing, when the current density was higher than 1000 mA / cm 2 Afterwards, the polarization performance is significantly improved compared with the membrane electrode obtained from the microporous layer in Comparative Example 1, indicating that the mass transfer loss is reduced and the microporous layer structure is optimized.

[0090] In summary, the present invention can achieve effective regulation of the overall thickness, hydrophobicity, loading capacity, porosity and other properties of the obtained microporous layer through a microporous layer slurry containing graphitized carbon fiber and traditional carbon powder, and ensure high lateral conductivity; when actually used in the gas diffusion layer of a fuel cell, it can also simultaneously ensure excellent air permeability and water retention effects, and effectively improve the performance and durability of the fuel cell.

Claims

1. A microporous layer slurry, characterized in that: The microporous layer slurry includes the following components in parts by mass: 1-15 parts of graphitized carbon fiber, 5-27 parts of carbon powder, 2-15 parts of adhesive, 1-10 parts of dispersant and 50-83 parts of solvent.

2. The microporous layer slurry according to claim 1, characterized in that The amount of the graphitized carbon fiber is 5-10 parts; And / or, the mesh size of the graphitized carbon fiber is 500-1000 mesh; And / or, the amount of the carbon powder is 5-10 parts; and / or, the particle size of the carbon powder is 10-100 nm; And / or, the mass ratio of the graphitized carbon fiber to the carbon powder is (1-5):(9-5).

3. The microporous layer slurry according to claim 1, characterized in that The adhesive comprises PTFE emulsion; And / or, the amount of the adhesive is 5-10 parts; and / or, the dispersant comprises Triton; and / or, the dispersant is used in an amount of 4-6 parts; and / or, the solvent comprises isopropyl alcohol and / or deionized water; And / or, the amount of the solvent is 60-70 parts.

4. The microporous layer slurry according to any one of claims 1 to 3, characterized in that The microporous layer slurry includes the following components in parts by mass: 5-10 parts of graphitized carbon fibers, 5-10 parts of carbon powder, 5-10 parts of adhesive, 4-6 parts of dispersant and 60-70 parts of solvent.

5. A method for preparing the microporous layer slurry according to any one of claims 1 to 4, characterized in that: The preparation method of the microporous layer slurry comprises the following steps: mixing the components of the microporous layer slurry.

6. A microporous layer, characterized in that The microporous layer is made of the microporous layer slurry according to any one of claims 1 to 4.

7. The microporous layer according to claim 6, wherein The thickness of the microporous layer is 50-300 μm; And / or, the carbon loading of the microporous layer is 0.5-8 mg / cm 2 ; and / or, the porosity of the microporous layer is 10%-50%; And / or, the transverse resistivity of the microporous layer is 0.2-0.8Ω·cm.

8. A method for preparing a microporous layer according to claim 6 or 7, characterized in that: The preparation method of the microporous layer comprises the following steps: The microporous layer slurry is coated on a carbon paper base layer and cured to obtain the microporous layer.

9. The method for preparing a microporous layer according to claim 8, wherein: The material of the carbon paper base layer is carbon fiber paper; And / or, the contact angle of the carbon paper substrate is 110°-150°; And / or, the curing includes primary curing and secondary curing.

10. Use of the microporous layer slurry according to any one of claims 1 to 4, or the microporous layer according to claim 6 or 7 in a fuel cell.

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