A method for fabricating a bipolar plate and a fuel cell including the bipolar plate.

Abstract

This invention discloses a method for preparing a bipolar plate and a fuel cell containing the bipolar plate, belonging to the field of fuel cells. The invention modifies the phenolic resin by adding alcohols, o-phenylenediamine, and silane coupling agents. The alcohols modify the prepared phenolic resin by grafting different chain segments, forming a network structure with multiple different chain segments and increasing the crosslinking density. Simultaneously, o-phenylenediamine modification improves local mechanical properties, and the addition of silane coupling agents further enhances the crosslinking density and improves mechanical properties by embedding alcohols and o-phenylenediamine at the ends. Graphite and nano-alumina are added to the phenolic resin. Graphite is the main conductive material in the premix, and the nano-alumina has a large specific surface area, thus filling the spaces between the graphite and phenolic resin, reducing porosity and increasing the compactness of the bipolar plate. The bipolar plate is then hot-pressed with a pretreated metal plate to form a composite structure, improving overall mechanical properties while maintaining the overall conductivity of the bipolar plate.

Description

Technical Field

[0001] This invention relates to the field of fuel cells, and more specifically, to a method for preparing a bipolar plate and a fuel cell comprising the bipolar plate. Background Technology

[0002] Fuel cells use fuel and oxygen as raw materials and have no mechanical transmission parts, resulting in advantages such as producing fewer harmful gases and having a long service life. Proton exchange membrane fuel cells, also known as solid polymer fuel cells, provide continuous electrical energy from fuel under conditions of high efficiency and power density. Bipolar plates are one of the most important components in fuel cells. Existing technologies include graphite bipolar plates, composite material bipolar plates, and metal composite bipolar plates. Composite material bipolar plates include carbon-polymer and metal-polymer bipolar plates. Although composite bipolar plates have advantages such as light weight, good chemical stability, and ease of production, carbon-polymer bipolar plates have several obvious disadvantages compared to metal-polymer bipolar plates, namely lower mechanical properties and conductivity.

[0003] In summary, based on the applicant's extensive research, it has been found that bipolar plates suffer from low mechanical properties and poor electrical conductivity. Therefore, there is a need to develop or improve a method for preparing a bipolar plate and a fuel cell containing such a bipolar plate. Summary of the Invention

[0004] Therefore, in order to solve the problems of low mechanical properties and poor conductivity of bipolar plates, the present invention provides a method for preparing a bipolar plate and a fuel cell including the bipolar plate, the specific technical solution of which is as follows:

[0005] A method for preparing a bipolar plate includes the following preparation steps:

[0006] Preparation of phenolic resin:

[0007] By weight, 45-55 parts of phenols, 78-82 parts of aldehydes and 4-6 parts of catalyst are stirred and mixed, and the temperature is raised to 80℃-90℃ for reaction, and the reaction time is 1h-1.5h.

[0008] Add 8-12 parts of alcohol and 2-4 parts of o-phenylenediamine while stirring and continue the reaction at a temperature of 100℃-110℃ for 45-50 minutes.

[0009] Add 1-2 parts of silane coupling agent while stirring, react at 80℃-90℃ for 30-40 minutes to obtain phenolic resin.

[0010] Metal sheet preparation:

[0011] Immerse the metal plate in acetone solution for 5-8 minutes.

[0012] After soaking, use sandpaper to polish the metal plate until there are no obvious scratches on the surface;

[0013] The polished metal sheet is cleaned with deionized water and then air-dried for later use to obtain a pre-treated metal sheet.

[0014] Bipolar plate fabrication:

[0015] By weight, 20-25 parts of phenolic resin, 90-100 parts of graphite, and 8-12 parts of nano-alumina are stirred and mixed, and the mixture is kept at a constant temperature to obtain a premix.

[0016] The premix is ​​coated onto a pretreated metal plate and then conveyed to a hot press for hot pressing to obtain a bipolar plate.

[0017] Further, by weight, the phenolic resin comprises the following raw materials: 50 parts of phenols, 81 parts of aldehydes, 10 parts of alcohols, 3 parts of o-phenylenediamine, 5 parts of catalyst, and 2 parts of silane coupling agent; by weight, the bipolar plate comprises the following raw materials: 20 parts of phenolic resin, 100 parts of graphite, and 10 parts of nano-alumina.

[0018] Furthermore, the phenols include one or a mixture of phenol, p-cresol, and 2-methylphenol.

[0019] Furthermore, the aldehyde is a formaldehyde solution with a mass fraction of 37%.

[0020] Furthermore, the alcohols include one or more of furfuryl alcohol, castor oil, polyvinyl alcohol, and ethanol.

[0021] Furthermore, the catalyst comprises one or a mixture of two of sodium hydroxide and potassium hydroxide.

[0022] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0023] Furthermore, the heat preservation is carried out at 120℃-130℃ for 0.5h-1h.

[0024] Furthermore, the hot pressing is carried out at 130℃-140℃ and a pressure of 10Mpa-15Mpa for 30min-40min.

[0025] This technical solution also provides a fuel cell battery, including a bipolar plate, a membrane electrode assembly, a sealing ring, and an end plate, wherein the sealing ring is disposed between the membrane electrode assembly and the bipolar plate; and the end plate is disposed on one side of the bipolar plate.

[0026] In the above technical solution, the phenolic resin is modified by adding alcohols, o-phenylenediamine, and silane coupling agents to the basic reaction system of phenols and aldehydes. The alcohols include furfuryl alcohol, castor oil, and polyvinyl alcohol. Adding multiple alcohols with different chain lengths modifies the prepared phenolic resin, grafting different chain segments to form a network structure with multiple different chain segments, increasing the crosslinking density. Simultaneously, modification with o-phenylenediamine improves local mechanical properties, and the addition of silane coupling agents further increases the crosslinking density. Embedding into the ends of alcohols and o-phenylenediamine makes the internal structure of the phenolic resin more compact, improving its mechanical properties. Graphite and nano-alumina are added to the phenolic resin. Graphite is the main conductive material in the premix. Due to the large specific surface area of ​​nano-alumina, it fills the gaps between graphite and phenolic resin, reducing porosity and improving the compactness of the bipolar plate. It is then hot-pressed with a pretreated metal plate to form a composite bipolar plate, improving the overall mechanical properties while maintaining the overall conductivity of the bipolar plate. Simultaneously, the premix is ​​coated on the pretreated metal plate and hot-pressed to obtain a bipolar plate with a metal layer and polymer composite structure. This preparation process is simple and easy to implement, solving the problems of poor mechanical and conductive properties of bipolar plates. Detailed Implementation

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] A method for preparing a bipolar plate according to one embodiment of the present invention includes the following preparation steps:

[0030] Preparation of phenolic resin:

[0031] By weight, 45-55 parts of phenols, 78-82 parts of aldehydes and 4-6 parts of catalyst are stirred and mixed, and the temperature is raised to 80℃-90℃ for reaction, and the reaction time is 1h-1.5h.

[0032] Add 8-12 parts of alcohol and 2-4 parts of o-phenylenediamine while stirring and continue the reaction at a temperature of 100℃-110℃ for 45-50 minutes.

[0033] Add 1-2 parts of silane coupling agent while stirring, react at 80℃-90℃ for 30-40 minutes to obtain phenolic resin.

[0034] Metal sheet preparation:

[0035] Immerse the metal plate in acetone solution for 5-8 minutes.

[0036] After soaking, the metal plate was polished with 400-grit, 800-grit, and 1200-grit sandpaper respectively.

[0037] Polish until the surface is free of obvious scratches;

[0038] The polished metal sheet is cleaned with deionized water and then air-dried for later use to obtain a pre-treated metal sheet.

[0039] Bipolar plate fabrication:

[0040] By weight, 20-25 parts of phenolic resin, 90-100 parts of graphite, and 8-12 parts of nano-alumina are stirred and mixed, and the mixture is kept at a constant temperature to obtain a premix.

[0041] The premix is ​​coated onto a pretreated metal plate and then conveyed to a hot press for hot pressing to obtain a bipolar plate.

[0042] In one embodiment, the metal plate includes a stainless steel plate or an aluminum alloy plate.

[0043] In one embodiment, the phenolic resin comprises, by weight, the following raw materials: 50 parts phenols, 81 parts aldehydes, 10 parts alcohols, 3 parts o-phenylenediamine, 5 parts catalyst, and 2 parts silane coupling agent; and the bipolar plate comprises, by weight, the following raw materials: 20 parts phenolic resin, 100 parts graphite, and 10 parts nano-alumina.

[0044] In one embodiment, the phenolic compounds include one or a mixture of phenol, p-cresol, and 2-methylphenol.

[0045] In one embodiment, the aldehyde is a formaldehyde solution with a mass fraction of 37%.

[0046] In one embodiment, the alcohols include one or more of furfuryl alcohol, castor oil, polyvinyl alcohol, and ethanol.

[0047] In one embodiment, the catalyst comprises one or a mixture of two of sodium hydroxide and potassium hydroxide.

[0048] In one embodiment, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0049] In one embodiment, the heat preservation is performed at 120℃-130℃ for 0.5h-1h.

[0050] In one embodiment, the hot pressing is performed at 130°C-140°C and a pressure of 10 MPa-15 MPa for 30-40 minutes.

[0051] In one embodiment, the ratio of phenol, p-cresol, and 2-methylphenol is 5:3:2 by weight.

[0052] In one embodiment, the ratio of furfuryl alcohol, castor oil, polyvinyl alcohol, and ethanol is 1:2:1:1 by weight.

[0053] In one embodiment, the nano-alumina used is 4N phase high-purity nano-alumina, model VK-L50Y, which is a white powder with a γ-phase crystal form, a particle size of 50 nm, a content of 99.99%, and a specific surface area of ​​100 m². 2 / g-150m 2 / g.

[0054] In one embodiment, a fuel cell battery includes a bipolar plate, a membrane electrode assembly, a sealing ring, and an end plate, wherein the sealing ring is disposed between the membrane electrode assembly and the bipolar plate; and the end plate is disposed on one side of the bipolar plate.

[0055] The phenolic resin is modified by adding alcohols, o-phenylenediamine, and silane coupling agents to a basic reaction system of phenols and aldehydes. Alcohols include furfuryl alcohol, castor oil, and polyvinyl alcohol. Adding multiple alcohols with different chain lengths modifies the prepared phenolic resin, grafting different chain segments to form a network structure with multiple different chain segments, increasing the crosslinking density. Simultaneously, modification with o-phenylenediamine improves local mechanical properties, and the addition of silane coupling agents further increases the crosslinking density and embeds into the ends of alcohols and o-phenylenediamine, making the internal structure of the phenolic resin more compact and improving its mechanical properties. Stone is added to the phenolic resin... In this bipolar plate, graphite is the main conductive material, and nano-alumina, due to its large specific surface area, fills the spaces between the graphite and phenolic resin, reducing porosity and increasing the compactness of the bipolar plate. It is then hot-pressed with a pretreated metal plate to form a composite bipolar plate, improving overall mechanical properties while maintaining conductivity. Simultaneously, the premix is ​​coated onto the pretreated metal plate and hot-pressed to obtain a bipolar plate with a metal layer and polymer composite structure. This preparation process is simple and easy to implement, solving the problems of poor mechanical and conductive properties in existing bipolar plates.

[0056] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0057] The difference between Examples 1-4 and Comparative Examples 1-4 is that the amount of raw materials added to prepare phenolic resin is different, but the preparation process is the same. The specific amount of raw materials added by weight is shown in Table 1.

[0058] Table 1:

[0059]

[0060]

[0061] The phenols are composed of phenol, p-cresol, and 2-methylphenol in a weight ratio of 5:3:2; the alcohols are composed of furfuryl alcohol, castor oil, polyvinyl alcohol, and ethanol in a weight ratio of 1:2:1:1; the nano-alumina is selected as 4N phase high-purity nano-alumina, model VK-L50Y, which is a white powder with a γ-phase crystal form, a particle size of 50 nm, a content of 99.99%, and a specific surface area of ​​100 m². 2 / g-150m 2 / g; the aldehyde is a 37% formaldehyde solution; the catalyst is sodium hydroxide; the silane coupling agent is γ-aminopropyltriethoxysilane;

[0062] A method for preparing a bipolar plate includes the following preparation steps:

[0063] Preparation of phenolic resin:

[0064] Phenols, aldehydes and catalysts were mixed by weight and heated to 90°C for 1 hour.

[0065] Alcohols and o-phenylenediamine were added under stirring and the reaction continued at 110°C for 50 minutes.

[0066] A silane coupling agent was added under stirring, the reaction temperature was 90℃, and the reaction time was 30 min; phenolic resin was obtained.

[0067] Metal sheet preparation:

[0068] Immerse the stainless steel plate in acetone solution for 8 minutes.

[0069] After soaking, the metal plate was polished with 400-grit, 800-grit, and 1200-grit sandpaper respectively.

[0070] Polish until the surface is free of obvious scratches;

[0071] The polished stainless steel sheet is cleaned with deionized water and then air-dried for later use to obtain a pre-treated metal sheet.

[0072] Bipolar plate fabrication:

[0073] Phenolic resin, graphite, and nano-alumina were mixed by weight and kept at 130°C for 1 hour to obtain a premix.

[0074] The premix was coated onto a pretreated metal plate and fed into a hot press, where it was hot-pressed at 130°C and 15 MPa for 30 minutes to obtain a bipolar plate.

[0075] A fuel cell includes a bipolar plate, a membrane electrode assembly, a sealing ring, and an end plate prepared in the above steps, wherein the sealing ring is disposed between the membrane electrode assembly and the bipolar plate; and the end plate is disposed on one side of the bipolar plate.

[0076] Comparative Examples 5-7:

[0077] The difference between Comparative Examples 5-7 and Example 1 lies in the different proportions of raw materials added to the alcohol components, while the preparation process is the same. The amount of alcohol added in Comparative Examples 5-7 by weight is shown in Table 2.

[0078] Table 2:

[0079]

[0080] "-" means not to add.

[0081] The bipolar plates prepared in Examples 1-4 and Comparative Examples 1-7 were subjected to relevant performance tests; the results are shown in Table 3. The resistivity and flexural strength were determined using the bipolar plate characteristic test method (GB / T20042.6-2011), as detailed in Table 3.

[0082] Table 3:

[0083]

[0084]

[0085] As shown in Table 3, the bipolar plates prepared in Examples 1-4 exhibit good resistivity and flexural strength, and their mechanical and electrical properties meet the application requirements. Specifically, the difference between Comparative Example 1 and Example 1 is that no alcohols are added to the raw materials of the phenolic resin prepared in Comparative Example 1. As shown in Table 3, compared to Example 1, the flexural strength of Comparative Example 1 is lower, while the electrical conductivity is not significantly different. This indicates that the phenolic resin prepared with added alcohols and the resulting bipolar plate possess good mechanical and electrical properties. By adding alcohols and grafting different chain segments, the phenolic resin forms a network structure with multiple different chain segments, increasing the crosslinking density and forming a composite structure with the pretreated metal plate, thus improving the overall mechanical properties.

[0086] The difference between Comparative Example 2 and Example 1 is that o-phenylenediamine was not added to the raw materials of the phenolic resin prepared in Comparative Example 2. As can be seen from the data in Table 3, compared with Example 1, the flexural strength of Comparative Example 2 is lower, while the difference in electrical conductivity is not significant. This shows that the phenolic resin prepared with o-phenylenediamine and the bipolar plate prepared thereby have good mechanical and electrical properties. Grafting different chain segments allows the phenolic resin to form a network structure with multiple different chain segments, which increases the crosslinking density, improves the local mechanical properties, and forms a composite structure with the pretreated metal plate, thus improving the overall mechanical properties.

[0087] The difference between Comparative Example 3 and Example 1 is that no silane coupling agent was added to the raw materials of the phenolic resin prepared in Comparative Example 3. As can be seen from the data in Table 3, compared with Example 1, the flexural strength of Comparative Example 3 is lower than that of Example 1, but the conductivity is not significantly different. This shows that the phenolic resin prepared with the addition of silane coupling agent and the bipolar plate prepared thereby have good mechanical and electrical properties. Adding silane coupling agent increases the crosslinking density and embeds alcohol and o-phenylenediamine terminals, making the internal structure of the phenolic resin more compact and improving its mechanical properties. The bipolar plate formed with the pretreated metal plate has a composite structure, which improves the overall mechanical properties.

[0088] The difference between Comparative Example 4 and Example 1 is that no nano-alumina was added to the bipolar plate prepared in Comparative Example 4. As can be seen from the data in Table 3, compared with Example 1, Comparative Example 4 has a higher resistivity and lower bending strength. This shows that the bipolar plate prepared without nano-alumina has lower conductivity and mechanical properties. Adding nano-alumina is beneficial to improving the mechanical properties and conductivity of the bipolar plate. Graphite and nano-alumina are added to the phenolic resin. Graphite is the main conductive material. Due to the large specific surface area of ​​nano-alumina, it fills the gap between graphite and phenolic resin, reduces porosity, and improves the compactness of the bipolar plate, thereby improving the overall mechanical properties. At the same time, the overall conductivity of the bipolar plate is maintained. The bipolar plate with the pretreated metal plate forms a composite structure, which improves the overall mechanical properties.

[0089] The difference between Comparative Example 5 and Example 1 is that the alcohol component used in the phenolic resin prepared in Comparative Example 5 did not contain polyvinyl alcohol. Compared with Example 1, the flexural strength of Comparative Example 5 is lower than that of Example 1. It can be seen that the addition of polyvinyl alcohol can effectively increase the crosslinking density of phenolic resin, thereby increasing the mechanical strength of the prepared bipolar plate, and forming a composite structure with the pretreated metal plate, thus improving the overall mechanical properties.

[0090] The difference between Comparative Example 6 and Example 1 is that castor oil was not added to the alcohol component used in the phenolic resin prepared in Comparative Example 6. Compared with Example 1, the flexural strength of Comparative Example 6 is lower than that of Example 1. Since castor oil has multiple unsaturated bonds and multiple hydroxyl groups forming alcohols, adding castor oil changes the chain segments of the phenolic resin, increases the crosslinking density of the phenolic resin, and forms a composite structure bipolar plate with the pretreated metal plate, thereby improving the overall mechanical properties and thus improving the mechanical properties of the prepared bipolar plate.

[0091] The difference between Comparative Example 7 and Example 1 is that furfuryl alcohol was not added to the alcohol component used in the phenolic resin prepared in Comparative Example 7. Compared with Example 1, the flexural strength of Comparative Example 7 is lower than that of Example 1. This shows that the addition of furfuryl alcohol can effectively increase the crosslinking density of the phenolic resin, thereby improving the mechanical strength of the prepared bipolar plate; the bipolar plate forming a composite structure with the pretreated metal plate improves the overall mechanical properties.

[0092] Alcohols composed of furfuryl alcohol, castor oil, and polyvinyl alcohol are added to modify the prepared phenolic resin. Grafting is performed on different chain segments to form a network structure of multiple different chain segments in the phenolic resin, thereby increasing the crosslinking density and forming a composite bipolar plate with a pretreated metal plate. This improves the mechanical strength of the prepared bipolar plate and maintains good electrical conductivity.

[0093] Simultaneously, modification with o-phenylenediamine improves local mechanical properties, and the addition of silane coupling agents increases crosslinking density. The insertion of alcohol and o-phenylenediamine terminals further compacts the internal structure of the phenolic resin, enhancing its mechanical properties. Graphite and nano-alumina are added to the phenolic resin. Graphite, as the main conductive material in the premix, fills the spaces between the graphite and phenolic resin due to the large specific surface area of ​​nano-alumina, reducing porosity and increasing the compactness of the bipolar plate. This is then hot-pressed with a pretreated metal plate to form a composite bipolar plate, improving overall mechanical properties while maintaining overall conductivity. The premix is ​​then coated onto the pretreated metal plate and hot-pressed to obtain a bipolar plate with a metal layer and polymer composite structure. This preparation process is simple and easy to implement, solving the problems of poor mechanical and conductive properties in existing bipolar plates, thereby improving the performance stability of fuel cells.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a bipolar plate, characterized in that, The preparation process includes the following steps: Preparation of phenolic resin: By weight, 45-55 parts of phenols, 78-82 parts of aldehydes and 4-6 parts of catalyst are stirred and mixed, and the temperature is raised to 80℃-90℃ for reaction, and the reaction time is 1h-1.5h. Add 8-12 parts of alcohol and 2-4 parts of o-phenylenediamine while stirring and continue the reaction at a temperature of 100℃-110℃ for 45-50 minutes. The alcohols include furfuryl alcohol, castor oil, and polyvinyl alcohol; Add 1-2 parts of silane coupling agent while stirring, react at 80℃-90℃ for 30-40 minutes to obtain phenolic resin. Metal sheet preparation: Immerse the metal plate in acetone solution for 5-8 minutes. After soaking, use sandpaper to polish the metal plate until there are no obvious scratches on the surface; The polished metal sheet is cleaned with deionized water and then air-dried for later use to obtain a pre-treated metal sheet. Bipolar plate fabrication: By weight, 20-25 parts of phenolic resin, 90-100 parts of graphite, and 8-12 parts of nano-alumina are stirred and mixed, and the mixture is kept at a constant temperature to obtain a premix. The premix is ​​coated onto a pretreated metal plate and then conveyed to a hot press for hot pressing to obtain a bipolar plate.

2. The method for preparing a bipolar plate according to claim 1, characterized in that, The phenolic resin comprises the following raw materials by weight: 50 parts phenols, 81 parts aldehydes, 10 parts alcohols, 3 parts o-phenylenediamine, 5 parts catalyst, and 2 parts silane coupling agent; the bipolar plate comprises the following raw materials by weight: 20 parts phenolic resin, 100 parts graphite, and 10 parts nano-alumina.

3. The method for preparing a bipolar plate according to claim 1, characterized in that, The phenols include one or a mixture of phenol, p-cresol, and 2-methylphenol.

4. The method for preparing a bipolar plate according to claim 1, characterized in that, The aldehyde is a formaldehyde solution with a mass fraction of 37%.

5. The method for preparing a bipolar plate according to claim 1, characterized in that, The catalyst includes one or a mixture of two of sodium hydroxide and potassium hydroxide.

6. The method for preparing a bipolar plate according to claim 1, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane.

7. The method for preparing a bipolar plate according to claim 1, characterized in that, The heat preservation is carried out at 120℃-130℃ for 0.5h-1h.

8. The method for preparing a bipolar plate according to claim 1, characterized in that, The hot pressing is carried out at 130℃-140℃ and a pressure of 10Mpa-15Mpa for 30min-40min.

9. A fuel cell battery, characterized in that, It includes a bipolar plate, a membrane electrode, a sealing ring, and an end plate as described in any one of claims 1-8, wherein the sealing ring is disposed between the membrane electrode and the bipolar plate; and the end plate is disposed on one side of the bipolar plate.

Images