Carbon paper for fuel cell and preparation method thereof

Abstract

The invention provides carbon paper for a fuel cell and a preparation method of the carbon paper, and relates to the technical field of fuel cells, long carbon fibers of 6 mm and short carbon fibers of 3 mm are selected, mixed and added into a PVA-PVP composite water-soluble polymer solution, dried after being soaked and coated, and continuously mixed with elastic fibers and reinforced fibers to prepare slurry, and the slurry is formed, coiled and cut to prepare the carbon paper. During the period, the carbon fibers are subjected to surface treatment, and the technical means of polymer coating and multi-fiber mixing are utilized, so that the finally prepared carbon paper has higher strength, air permeability and uniformity.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to carbon paper for fuel cells and a preparation method thereof. Background Art

[0002] Fuel cells efficiently convert chemical energy into electrical energy through electrochemical reactions. In this process, hydrogen undergoes an oxidation reaction at the anode, releasing electrons, which flow to the cathode through an external circuit; at the same time, protons migrate from the anode to the cathode through the proton exchange membrane. At the cathode, oxygen undergoes a reduction reaction with protons and electrons to generate water.

[0003] The diffusion layer plays an indispensable role in the operation of fuel cells. On the one hand, it provides uniform distribution of hydrogen and oxygen to ensure efficient reaction; on the other hand, it can promptly discharge the water generated by the reaction to prevent flooding and effectively avoid gas leakage.

[0004] As the base material of the diffusion layer, carbon paper is widely used in the field of fuel cells due to its excellent conductivity, good air permeability and high mechanical strength. The preparation of carbon paper mainly includes key steps such as carbon fiber papermaking, resin impregnation and carbonization. The papermaking process achieves uniform distribution of carbon fibers, the resin impregnation enhances the bonding force between fibers, and the carbonization gives the carbon paper low resistivity and high permeability. To ensure the performance of fuel cells, carbon paper must not only have good structural strength, but also have sufficient durability.

[0005] As fuel cell technology develops towards high power and high pressure, higher requirements are placed on the mechanical strength of carbon paper. However, the air permeability of carbon paper is closely related to its pore structure. When the air permeability is enhanced, the mechanical properties are likely to decrease. Therefore, it is particularly important to achieve balance and optimization in terms of strength, air permeability and uniformity. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a carbon paper for a fuel cell and a preparation method thereof. By performing surface treatment on the carbon fiber based on the prior art and utilizing polymer coating and multi-fiber mixing techniques, the finally prepared carbon paper has higher strength, air permeability and uniformity.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing carbon paper for a fuel cell comprises the following steps: Step 1, preparing a water-soluble polymer solution: taking an appropriate amount of PVA and PVP and adding them into deionized water, stirring at 60-70°C until completely dissolved, to form a PVA-PVP composite water-soluble polymer solution; Step 2: Surface treatment and coating of carbon fiber: 6 mm long carbon fiber and 3 mm short carbon fiber are mixed, the mixed carbon fiber is placed in a PVA-PVP solution for immersion and coating, then picked up and the excess solution is removed by a low-speed centrifuge, and then placed in an oven for drying at 60°C for 2 hours to obtain a mixed carbon fiber; Step 3: Slurry preparation: Take an appropriate amount of mixed carbon fiber, elastic fiber and reinforcing fiber, add deionized water and dispersant, and continue stirring to form a uniform slurry; Step 4: Forming: The pulp is sent to the inclined web pulp forming machine to form a wet paper layer. The wet paper layer is compacted by the pre-pressing machine and then sent to the drying room for drying at 150-200℃ for 1-2 hours. Step 5: Rolling and cutting: Roll up the dried carbon paper and cut it into standard specifications as required.

[0008] Preferably, in step 1, the ratio of PVA to PVP is 5:1.

[0009] Preferably, in step 1, the method further comprises adding a surfactant Tween-80 accounting for about 0.5% of the total solution mass to the solution.

[0010] Preferably, in step 2, the mixing ratio of 6 mm long carbon fiber to 3 mm short carbon fiber is 60:40 by weight.

[0011] Preferably, in step three, the mixing ratio of the mixed carbon fiber, the elastic fiber and the reinforcing fiber is 80-110:2-5:1-3 by weight.

[0012] Preferably, in step three, the proportion of the dispersant added to the slurry is 1%-2%.

[0013] Preferably, in step 4, the drying temperature of the wet paper layer in the drying room is 180° C., and the drying time is 1.5 hours.

[0014] Preferably, in step five, the carbon paper is cut into a standard size of 1000 mm x 1000 mm or 500 mm x 500 mm.

[0015] A carbon paper for a fuel cell is prepared by any one of the above-mentioned methods for preparing the carbon paper for a fuel cell.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a carbon paper for fuel cells and a preparation method thereof, wherein 6 mm long carbon fiber and 3 mm short carbon fiber are mixed and added to a PVA-PVP composite water-soluble polymer solution, and then dried after soaking and coating, and then mixed with elastic fiber and reinforcing fiber to form a slurry, and the slurry is formed, rolled and cut to form carbon paper. During the process, the carbon fiber is surface treated, and the technical means of polymer coating and multi-fiber mixing are used to make the finally prepared carbon paper have higher strength, air permeability and uniformity. DETAILED DESCRIPTION

[0017] The present invention is described in further detail below.

[0018] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be used for other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0019] The present invention provides a method for preparing carbon paper for a fuel cell, comprising the following steps: Step 1: Prepare a water-soluble polymer solution: add appropriate amounts of PVA (polyvinyl alcohol) and PVP (polyvinyl pyrrolidone) into deionized water; Specifically, first add deionized water into the stirrer and heat it to 60-70°C, then add PVA and stir until it is completely dissolved, then add PVP and continue stirring until it is completely dissolved; the stirring time is controlled at about 1 hour, until the solution is transparent and uniform, forming a PVA-PVP composite water-soluble polymer solution; During the stirring time, in order to further optimize the fluidity and coating properties of the solution, a surfactant Tween-80 accounting for about 0.5% of the total solution mass was added to the solution; Finally, the prepared PVA-PVP composite water-soluble polymer solution is filtered through a filter to remove undissolved impurities and bubbles to ensure the uniformity of the solution.

[0020] Step 2: Surface treatment and coating of carbon fiber: Select 6 mm long carbon fiber and 3 mm short carbon fiber, mix them in a ratio of 60:40 by weight, immerse and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution, pick it up after soaking for about 30 minutes, and use a low-speed centrifuge to discard the excess solution; The polymer-coated carbon fiber is then placed in an oven and dried at 60°C for 2 hours to ensure that the polymer layer is completely cured to obtain a hybrid carbon fiber.

[0021] Step 3, slurry preparation: take appropriate amount of mixed carbon fiber and elastic fiber (such as spandex fiber) and reinforcing fiber (such as polyester fiber or glass fiber), and mix them in the following proportions: 80-110:2-5:1-3; Add an appropriate amount of deionized water into the mixing bucket and add 1-2% dispersant as needed until the carbon fiber is completely dispersed in the water. Continue stirring for 1-2 hours to ensure that the fiber and water-soluble additives are completely mixed to form a uniform slurry.

[0022] During the slurry preparation process, check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments. If the slurry viscosity is too high, add an appropriate amount of deionized water to dilute it.

[0023] Step 4: Forming: The pulp is sent to the inclined web pulp forming machine to form a wet paper layer, which is then compacted by a pre-pressing machine and sent to a drying room for drying; Specifically, a sizing pump is first used to evenly deliver the prepared slurry to the inclined web sizing machine. Through up and down vibration and pressure, the fibers are formed into a uniform wet paper layer on the web. The wet paper layer formed on the web should avoid excessive water residue to avoid affecting the subsequent drying effect. Then the wet paper layer enters the pre-pressing machine after being formed in the wet part, which performs preliminary compaction on the wet paper layer, removes excess water, and adjusts the thickness and density of the paper; Finally, the wet paper layer is initially compacted and sent to the drying room, where the temperature is controlled at 150-200°C for 1-2 hours to completely dry the paper.

[0024] Step 5: Rolling and cutting: Roll up the dried carbon paper and cut it into standard specifications as required; Among them, the dried carbon paper is rolled into a roll by a winder to ensure that the paper has no wrinkles or damage. During the winding process, the tension of the paper is kept stable to avoid unevenness; Cut the rolled carbon paper into required standard sizes, such as 1000mmx1000mm or 500mmx500mm, and then pack the cut carbon paper.

[0025] The present invention provides a carbon paper for a fuel cell, which is prepared by the above-mentioned preparation method. Different preparation ratios are used in the preparation process, and the performance thereof is analyzed. The details are as follows: Example 1

[0026] Step 1: Heat 5L of deionized water to 65°C in a blender, add 15g of PVA and stir until completely dissolved, then add 3g of PVP to the deionized water and continue stirring until completely dissolved for 1 hour; during this period, add 0.3% (15g) of the surfactant Tween-80 to the solution, accounting for 0.3% (15g) of the total solution mass, and finally filter the solution through a filter to remove undissolved impurities and bubbles to form a PVA-PVP composite water-soluble polymer solution.

[0027] Step 2: Select 6mm long carbon fiber and 3mm short carbon fiber, and mix them in a ratio of 60:40; soak and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution for about 30 minutes, remove the excess solution with a low-speed centrifuge, put them in an oven, and dry them at 60°C for 2 hours to obtain mixed carbon fiber.

[0028] Step 3: Take 80 parts of mixed carbon fiber, 2 parts of spandex fiber, and 1 part of polyester fiber, add them into a mixing bucket containing 5L of deionized water, and add 1% dispersant, stir for 1 hour to form a uniform slurry. Check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments.

[0029] Step 4: Use a slurry pump to evenly send the slurry to the inclined web slurry forming machine to form a uniform wet paper layer. The wet paper layer enters the pre-press for preliminary compaction, and after removing excess moisture, it is sent to the drying room and dried at 150°C for 2 hours.

[0030] Step 5: Roll the dried carbon paper into a roll through a winder, cut it into a standard size of 1000mmx1000mm and package it. Example 2

[0031] Step 1: Heat 4L of deionized water to 65°C in a blender, add 12g of PVA and stir until completely dissolved, then add 2.4g of PVP to the deionized water and continue stirring until completely dissolved for 1 hour; during this period, add 0.4% (16g) of the surfactant Tween-80 to the solution, accounting for 0.4% (16g) of the total solution mass, and finally filter the solution through a filter to remove undissolved impurities and bubbles to form a PVA-PVP composite water-soluble polymer solution.

[0032] Step 2: Select 6mm long carbon fiber and 3mm short carbon fiber, and mix them in a ratio of 60:40; soak and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution for about 30 minutes, remove the excess solution with a low-speed centrifuge, put them in an oven, and dry them at 60°C for 2 hours to obtain mixed carbon fiber.

[0033] Step 3: Take 90 parts of mixed carbon fiber, 3 parts of spandex fiber, and 2 parts of polyester fiber, add them into a mixing bucket containing 4L of deionized water, and add 1% dispersant, stir for 1.5 hours to form a uniform slurry. Check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments.

[0034] Step 4: Use a slurry pump to evenly send the slurry to the inclined web slurry forming machine to form a uniform wet paper layer. The wet paper layer enters the pre-press for preliminary compaction, and after removing excess moisture, it is sent to the drying room and dried at 160°C for 1.5 hours.

[0035] Step 5: Roll the dried carbon paper into a roll through a winder, cut it into a standard size of 500mmx500mm and package it. Example 3

[0036] Step 1: Heat 6L of deionized water to 65°C in a blender, add 18g of PVA and stir until completely dissolved, then add 3.6g of PVP to the deionized water and continue stirring until completely dissolved for 1 hour; during this period, add 0.6% (36g) of the surfactant Tween-80 to the solution, accounting for 0.6% (36g) of the total solution mass, and finally filter the solution through a filter to remove undissolved impurities and bubbles to form a PVA-PVP composite water-soluble polymer solution.

[0037] Step 2: Select 6mm long carbon fiber and 3mm short carbon fiber, and mix them in a ratio of 60:40; soak and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution for about 30 minutes, remove the excess solution with a low-speed centrifuge, put them in an oven, and dry them at 60°C for 2 hours to obtain mixed carbon fiber.

[0038] Step 3: Take 100 parts of mixed carbon fiber, 4 parts of spandex fiber, and 2 parts of polyester fiber, add them into a mixing bucket containing 6L of deionized water, and add 1% dispersant, stir for 2 hours to form a uniform slurry. Check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments.

[0039] Step 4: Use a slurry pump to evenly send the slurry to the inclined web slurry forming machine to form a uniform wet paper layer. The wet paper layer enters the pre-press for preliminary compaction, and after removing excess moisture, it is sent to the drying room and dried at 180°C for 1 hour.

[0040] Step 5: Roll the dried carbon paper into a roll through a winder, cut it into a standard size of 1000mmx1000mm and package it. Example 4

[0041] Step 1: Heat 3.5L of deionized water to 65°C in a blender, add 10.5g of PVA and stir until completely dissolved, then add 2.1g of PVP to the deionized water and continue stirring until completely dissolved for 1 hour; during this period, add 0.5% (17.5g) of the surfactant Tween-80 to the solution, accounting for 0.5% (17.5g) of the total solution mass, and finally filter the solution through a filter to remove undissolved impurities and bubbles to form a PVA-PVP composite water-soluble polymer solution.

[0042] Step 2: Select 6mm long carbon fiber and 3mm short carbon fiber, and mix them in a ratio of 60:40; soak and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution for about 30 minutes, remove the excess solution with a low-speed centrifuge, put them in an oven, and dry them at 60°C for 2 hours to obtain mixed carbon fiber.

[0043] Step 3: Take 110 parts of mixed carbon fiber, 5 parts of spandex fiber, and 3 parts of polyester fiber, add them into a mixing bucket containing 3.5L of deionized water, and add 1% dispersant, stir for 1.2 hours to form a uniform slurry. Check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments.

[0044] Step 4: Use a slurry pump to evenly send the slurry to the inclined web slurry forming machine to form a uniform wet paper layer. The wet paper layer enters the pre-press for preliminary compaction, and after removing excess moisture, it is sent to the drying room and dried at 170°C for 1.8 hours.

[0045] Step 5: Roll the dried carbon paper into a roll through a winder, cut it into a standard size of 500mmx500mm and package it. Example 5

[0046] Step 1: Heat 4.5L of deionized water to 65°C in a blender, add 13.5g of PVA and stir until completely dissolved, then add 2.7g of PVP to the deionized water and continue stirring until completely dissolved, stirring for 1 hour; during this period, add 0.45% (20.25g) of the surfactant Tween-80 to the solution, accounting for 0.45% (20.25g) of the total solution mass, and finally filter the solution through a filter to remove undissolved impurities and bubbles to form a PVA-PVP composite water-soluble polymer solution.

[0047] Step 2: Select 6mm long carbon fiber and 3mm short carbon fiber, and mix them in a ratio of 60:40; soak and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution for about 30 minutes, remove the excess solution with a low-speed centrifuge, put them in an oven, and dry them at 60°C for 2 hours to obtain mixed carbon fiber.

[0048] Step 3: Take 85 parts of mixed carbon fiber, 2.5 parts of spandex fiber, and 1.5 parts of polyester fiber, add them into a mixing bucket containing 4.5L of deionized water, and add 1% dispersant, stir for 1.8 hours to form a uniform slurry. Check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments.

[0049] Step 4: Use a slurry pump to evenly send the slurry to the inclined web slurry forming machine to form a uniform wet paper layer. The wet paper layer enters the pre-press for preliminary compaction, and after removing excess moisture, it is sent to the drying room and dried at 190°C for 1.2 hours.

[0050] Step 5: Roll the dried carbon paper into a roll through a winder, cut it into a standard size of 1000mmx1000mm and package it. Example 6

[0051] Step 1: Heat 5.5L of deionized water to 65°C in a blender, add 16.5g of PVA and stir until completely dissolved, then add 3.3g of PVP to the deionized water and continue stirring until completely dissolved, stirring for 1 hour; during this period, add 0.55% (30.25g) of the surfactant Tween-80 to the solution, accounting for 0.55% (30.25g) of the total solution mass, and finally filter the solution through a filter to remove undissolved impurities and bubbles to form a PVA-PVP composite water-soluble polymer solution.

[0052] Step 2: Select 6mm long carbon fiber and 3mm short carbon fiber, and mix them in a ratio of 60:40; soak and coat the mixed carbon fiber in a PVA-PVP composite water-soluble polymer solution for about 30 minutes, remove the excess solution with a low-speed centrifuge, put them in an oven, and dry them at 60°C for 2 hours to obtain mixed carbon fiber.

[0053] Step 3: Take 95 parts of mixed carbon fiber, 3.5 parts of spandex fiber, and 2.5 parts of polyester fiber, add them into a mixing bucket containing 5.5L of deionized water, and add 1% dispersant, stir for 1.6 hours to form a uniform slurry. Check the viscosity and uniformity of the slurry to ensure that there are no lumps or sediments.

[0054] Step 4: Use a slurry pump to evenly send the slurry to the inclined web slurry forming machine to form a uniform wet paper layer. The wet paper layer enters the pre-press for preliminary compaction, and after removing excess moisture, it is sent to the drying room and dried at 200°C for 1 hour.

[0055] Step 5: Roll the dried carbon paper into a roll through a winder, cut it into a standard size of 500mmx500mm and package it.

[0056] Based on the carbon paper prepared in the above embodiment, the present invention tests the strength, air permeability and uniformity, etc. and records the test parameters as shown in Table 1 below: Table 1 Test parameters Example Strength (MPa) Breathability (L / (m²・s)) Uniformity (%) 1 89 33 95 2 88 32 96 3 92 35 97 4 90 33 96.5 5 87 31 95.5 6 91 34 97.5 When the carbon paper made from the above examples was tested for strength using a universal material testing machine, Example 3 had the highest strength (92 MPa), which made its fiber distribution and material composite properties optimal and could provide higher mechanical properties. Other examples were slightly lower than Example 3, but still showed higher strength.

[0057] When the air permeability of the carbon paper made from the above examples was tested using an air permeability tester, Example 3 had the best air permeability (35L / (m²·s)), and its fiber arrangement and slurry ratio made the porosity of the carbon paper larger, thereby improving the air permeability. The air permeability of other examples was slightly lower than that of Example 4, but still at a relatively high level.

[0058] When the carbon paper made from the above embodiments was tested for uniformity, a contact thickness gauge was used to test: Embodiment 6 had the highest uniformity (97.5%), indicating that the process control in terms of slurry mixing and fiber distribution was very precise. The uniformity of other embodiments was also very close, all between 95% and 96.5%, showing relatively uniform fiber distribution and uniformity.

[0059] The method of the present invention prepares carbon paper so that it achieves balance and optimization in terms of strength, air permeability and uniformity. This is mainly because the present invention performs carbon fiber surface treatment on the basis of the existing technology, and uses polymer coating and multi-fiber mixing technical means to make the finally prepared carbon paper have higher strength, air permeability and uniformity. In addition, through reasonable slurry preparation, molding process and drying process, the performance of carbon paper is ensured to be stable, and the production efficiency and the accuracy of quality control are improved.

[0060] Those skilled in the art should understand that the embodiments of the present invention shown in the above description are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A method for preparing carbon paper for fuel cells, characterized in that: The following steps are involved: Step 1, preparing a water-soluble polymer solution: taking an appropriate amount of PVA and PVP and adding them into deionized water, stirring at 60-70°C until completely dissolved, to form a PVA-PVP composite water-soluble polymer solution; Step 2: Surface treatment and coating of carbon fiber: 6 mm long carbon fiber and 3 mm short carbon fiber are mixed, the mixed carbon fiber is placed in a PVA-PVP solution for immersion and coating, then picked up and the excess solution is removed by a low-speed centrifuge, and then placed in an oven for drying at 60°C for 2 hours to obtain a mixed carbon fiber; Step 3: Slurry preparation: Take an appropriate amount of mixed carbon fiber, elastic fiber and reinforcing fiber, add deionized water and dispersant, and continue stirring to form a uniform slurry; Step 4: Forming: The pulp is sent to the inclined web pulp forming machine to form a wet paper layer. The wet paper layer is compacted by the pre-pressing machine and then sent to the drying room for drying at 150-200℃ for 1-2 hours. Step 5: Rolling and cutting: Roll up the dried carbon paper and cut it into standard specifications as required.

2. The method for preparing carbon paper for fuel cells according to claim 1, characterized in that: In step 1, the ratio of PVA to PVP is 5:

1.

3. The method for preparing carbon paper for fuel cell according to claim 1, characterized in that: In step one, the method further includes adding a surfactant Tween-80 accounting for 0.5% of the total solution mass into the solution.

4. The method for preparing carbon paper for fuel cell according to claim 1, characterized in that: In step 2, the mixing ratio of 6 mm long carbon fiber and 3 mm short carbon fiber is 60:40 by weight.

5. The method for preparing carbon paper for fuel cell according to claim 1, characterized in that: In step 3, the mixing ratio of the mixed carbon fiber, the elastic fiber and the reinforcing fiber is 80-110:2-5:1-3 by weight.

6. The method for preparing carbon paper for fuel cell according to claim 1, characterized in that: In step three, the proportion of the dispersant added to the slurry is 1%-2%.

7. The method for preparing carbon paper for fuel cells according to claim 1, characterized in that: In step 4, the wet paper layer is dried in a drying room at a temperature of 180° C. for 1.5 hours.

8. The method for preparing carbon paper for fuel cells according to claim 1, characterized in that: In step five, the carbon paper is cut into standard sizes of 1000mmx1000mm or 500mmx500mm.

9. A carbon paper for a fuel cell, characterized in that: The carbon paper for fuel cells is prepared by the method described in any one of claims 1 to 8.