Fuel cell stack and end plate thereof

Abstract

The application discloses a fuel cell stack and an end plate thereof, the end plate comprising a metal plate and an insulating plate; the insulating plate comprising a plate body and a protruding structure connected together, the plate body having opposite first and second surfaces, the first surface being fixedly attached to the metal plate, and the second surface being used to contact a current collecting plate of the fuel cell stack; and the protruding structure being located at the outer periphery of the plate body. Through the structural improvement, the insulating performance of the end plate is enhanced, and the insulating reliability of the fuel cell stack is improved.

Description

Technical Field

[0001] This application relates to the field of fuel cell technology, and in particular to a fuel cell stack and its endplate. Background Technology

[0002] The interior of a fuel cell stack inevitably contains exposed charged components such as cells, copper busbars, and current collectors. To ensure that the stack's insulation design meets standards, the internal insulation materials, electrical clearances, and creepage distances need to be designed. The end plates of a fuel cell stack typically integrate insulation functions, with end plates located at both ends of the cells to isolate the charged current collectors from the stack's casing.

[0003] To ensure structural strength, end plates are generally made of metal. Existing insulation designs use plastic to wrap the metal. However, in practical applications, it has been found that there are still certain insulation shortcomings in the extreme electrical environment inside the fuel cell stack. For example, exposed current collectors can still creep through the outer surface of the insulation plate, which can easily form a continuous conductive water film and lead to insulation failure. Summary of the Invention

[0004] The purpose of this application is to provide a fuel cell stack and its end plate, which improves the insulation performance of the end plate and enhances the insulation reliability of the fuel cell stack through structural improvements.

[0005] To address the aforementioned technical problems, this application provides an end plate for a fuel cell stack, comprising a metal plate and an insulating plate; the insulating plate includes a plate body and a protruding structure connected together, the plate body having a first surface and a second surface opposite to each other, the first surface being attached and fixed to the metal plate, and the second surface being used to contact the current collector of the fuel cell stack; the protruding structure is located on the outer periphery of the plate body.

[0006] By adopting the above scheme, a raised structure is added to the insulation board and placed on the outer periphery of the board body. This increases the creepage distance and, compared with the existing plastic-wrapped metal insulation design, can improve the insulation reliability of the fuel cell stack and enhance its insulation function.

[0007] As described above, the end plate of the fuel cell stack has a side peripheral wall located between the first surface and the second surface, and the side peripheral wall is provided with the protruding structure.

[0008] As described above, the end plate of the fuel cell stack includes an extension plate portion, wherein at least a wall portion of the side peripheral wall of the plate body extends outward to form the extension plate portion, and the extension plate portion is provided with the protrusion structure.

[0009] As described above, in the end plate of the fuel cell stack, the surface of the extension plate facing the metal plate is flush with the first surface, and the protrusion structure is provided on the side of the extension plate facing away from the metal plate; and / or, the extension plate has an annular structure.

[0010] As described above, the end plate of the fuel cell stack includes at least one protrusion.

[0011] As described above, in the end plate of the fuel cell stack, the protrusion has a circumferentially continuous annular structure, or the protrusion includes a plurality of discontinuous ribs arranged circumferentially.

[0012] As described above, the end plate of the fuel cell stack has two or more protrusions, with a gap between adjacent protrusions, and / or adjacent protrusions have different heights.

[0013] The end plate of the fuel cell stack as described above is integrally injection molded with the insulating plate.

[0014] As described above, the end plate of the fuel cell stack has at least a hydrophobic coating on at least a portion of the surface of the insulating plate facing the current collector.

[0015] This application also provides a fuel cell stack, including an end plate and a current collector in contact with the end plate, wherein the end plate is any of the end plates described above.

[0016] Since the endplate has the aforementioned technical effects, the fuel cell stack including the endplate also has the corresponding technical effects, which will not be discussed again here. Attached Figure Description

[0017] Figure 1 This is a partial structural schematic diagram of a fuel cell stack provided in one embodiment of this application;

[0018] Figure 2 for Figure 1 Partial sectional view of the middle plate;

[0019] Figure 3 for Figure 2 Schematic diagram of the structure of the central protrusion;

[0020] Figure 4 This is a partial structural diagram of the end plate in another embodiment provided in this application;

[0021] Figure 5 This is a schematic diagram of the cross-sectional shape of the protrusion in a specific embodiment;

[0022] Figure 6 This is a test assembly diagram for testing using the endplate provided in this application;

[0023] Figure 7 A schematic diagram comparing the results of insulation tests on stacks with end plates having raised structures and stacks with end plates without raised structures.

[0024] Figure 8 and Figure 9 The diagrams show the state of the surfaces of samples 3 and 2 after being sprayed with water.

[0025] Explanation of reference numerals in the attached figures:

[0026] End plate 10, metal plate 11, insulating plate 12, plate body 121, first surface 121a, second surface 121b, protrusion structure 122, first protrusion 1221, second protrusion 1222, extension plate 123, current collector 20, counterweight 30. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] For ease of understanding and concise description, the following text will explain the fuel cell stack and its endplates together, and the beneficial effects will not be discussed again.

[0029] Please refer to Figure 1 and Figure 2 , Figure 1 This is a partial structural schematic diagram of a fuel cell stack provided in one embodiment of this application; Figure 2 for Figure 1 Partial cross-sectional view of the middle plate.

[0030] The fuel cell stack includes structures such as end plate 10, current collector 20, bipolar plate and membrane electrode assembly. End plate 10 is in direct contact with current collector 20. This application focuses on improving the structure of end plate 10. Other structural settings of the fuel cell stack can be implemented based on existing technology and are not the core of this invention, so they are not described in detail here.

[0031] In this embodiment, the end plate 10 of the fuel cell stack integrates insulation to isolate the charged current collector 20 from the stack housing. The end plate 10 includes a metal plate 11 and an insulating plate 12, which are fixed together. The insulating plate 12 includes a plate body 121 connected together and a protrusion structure 122. The plate body 121 has a first surface 121a and a second surface 121b opposite to each other. The first surface 121a is attached and fixed to the metal plate 11, and the second surface 121b is used to contact the current collector 20. The protrusion structure 122 is located on the outer periphery of the plate body 121.

[0032] With the above settings, the raised structure 122 on the outer periphery of the main body 121 of the insulating plate 12 increases the creepage distance. The increase in creepage distance improves the insulation reliability of the insulating plate 12, thereby improving the insulation reliability of the fuel cell stack and enhancing the insulation function of the fuel cell stack. In the extreme electrical environment inside the fuel cell stack, the probability of insulation failure can be reduced, ensuring the safety of the fuel cell stack operation.

[0033] In this embodiment, as Figure 1 and Figure 2 As shown, the insulating plate 12 also includes an extension plate portion 123, which is formed by at least a wall portion of the side peripheral wall of the plate body 121 extending outward.

[0034] The outward extension length of the extension plate portion 123 and the shape of the extension plate portion 123 can be set according to requirements.

[0035] Taking the example in the figure, the main body 121 is generally rectangular, and it can extend outward from only one side wall to form an extension plate portion 123, or several side walls can extend outward to form extension plate portions 123. When each side wall of the main body 121 extends outward, the plate portions extending outward from each side wall can be on the same plane, so that the extension plate portions 123 of the main body 121 have a ring structure.

[0036] When each sidewall of the plate body 121 extends outward, the plate portion extending outward from each sidewall can also be located on different planes, that is, the distance between each extended plate portion and the first surface 121a is different.

[0037] The aforementioned protrusion structure 122 can be provided on the extension plate portion 123. In this way, with the cooperation of the extension plate portion 123 and the protrusion structure 122, the creepage distance can be further increased and the insulation performance of the fuel cell stack can be enhanced.

[0038] Figure 1 and Figure 2 As shown, each sidewall of the main plate 121 extends outward, and the resulting extended plate portion 123 is a ring structure.

[0039] In a specific configuration, the surface of the extension plate 123 facing the metal plate 11 can be flush with the first surface 121a. During assembly, the extension plate 123 is also attached and fixed to the metal plate 11, and the protruding structure 122 is specifically disposed on the side of the extension plate 123 facing away from the metal plate 11.

[0040] In this way, the surface of the metal plate 11 facing the insulating plate 12 can have a groove structure, and the bottom of the insulating plate 12 is embedded in the groove structure. The depth of the groove structure can be the same as the thickness of the extension plate portion 123. That is, after the metal plate 11 and the insulating plate 12 are fixed, the surface of the extension plate portion 123 facing away from the metal plate 11 is flush with the surface of the metal plate 11 facing the insulating plate 12. This arrangement can improve the connection strength between the metal plate 11 and the insulating plate 12, and ensure the supporting effect of the end plate 10 on the fuel cell stack body.

[0041] Please refer to this as well. Figure 3 , Figure 3 for Figure 2 A schematic diagram of the structure of the central protrusion.

[0042] In this embodiment, the protrusion structure 122 includes two protrusions, referred to here as the first protrusion 1221 and the second protrusion 1222. Both the first protrusion 1221 and the second protrusion 1222 are disposed on the extension plate portion 123, and both can extend along the outer periphery of the plate body 121 to form a closed ring-shaped protrusion. That is, the first protrusion 1221 and the second protrusion 1222 are both circumferentially continuous ring structures. This can maximize the creepage distance.

[0043] The gap between the first protrusion 1221 and the second protrusion 1222 can increase the creepage distance and prevent the formation of a continuous water film that could lead to insulation failure.

[0044] like Figure 3 As shown, the first protrusion 1221 is located inside the second protrusion 1222. The height h1 of the first protrusion 1221 is greater than the height h2 of the second protrusion 1222. For example, the height h1 of the first protrusion 1221 can be 3mm and the height h2 of the second protrusion 1222 can be 2mm. The height difference between the first protrusion 1221 and the second protrusion 1222 can more effectively block the continuous water film and improve the insulation reliability.

[0045] In other embodiments, the height of the second protrusion 1222 located on the outer side may be greater than the height of the first protrusion 1221 located on the inner side. Of course, if insulation requirements are met, the heights of the first protrusion 1221 and the second protrusion 1222 may also be set to be the same.

[0046] The insulating board 12 is generally formed by injection molding. In actual installation, the inner wall of the first protrusion 1221 can be provided with a draft angle of 5°, and the outer wall of the second protrusion 1222 can be provided with a draft angle of 6°. Here, "inner" and "outer" are based on the direction closer to or farther from the center of the board body 121. The direction closer to the center of the board body 121 is "inner", and the direction farther from the center of the board body 121 is "outer".

[0047] Figure 2 and Figure 3 In the example shown, the extension plate 123 has two annular protrusions. In other embodiments, only one annular protrusion may be provided, or three or more annular protrusions may be provided. When two or more protrusions are provided, a gap is provided between adjacent protrusions to prevent the formation of a continuous water film that would affect the insulation effect. When two or more protrusions are provided, the structural forms of each protrusion may be the same or different.

[0048] In other embodiments, the protrusions may also be a number of discontinuous ribs arranged circumferentially along the plate body 121. That is, in the circumferential direction of the plate body 121, there is a gap between adjacent ribs. The length of each rib in the circumferential direction may be the same or different. The distance between any two adjacent ribs in the circumferential direction may be the same or different.

[0049] Please refer to Figure 4 , Figure 4 This is a partial structural diagram of the end plate in another embodiment provided in this application.

[0050] In this embodiment, the end plate 10 includes a metal plate 11 and an insulating plate 12. The insulating plate 12 includes a plate body 121 and a protruding structure 122. The difference from the first embodiment is that in this embodiment, the plate body 121 does not have an extension plate portion. The protruding structure 122 is directly disposed on the side peripheral wall of the plate body 121 located between the first surface and the second surface. At this time, the height direction of the protruding structure 122 is parallel to the first surface or the second surface of the plate body 121.

[0051] Figure 4 In the example shown, the protrusion structure 122 includes a first protrusion 1221 and a second protrusion 1222, which have a gap in the thickness direction of the plate body 121. The first protrusion 1221 is relatively close to the metal plate 11, and the second protrusion 1222 is relatively far away from the metal plate 11. The height of the first protrusion 1221 is greater than the height of the second protrusion 1222.

[0052] The first protrusion 1221 and the second protrusion 1222 can be in the form of a continuous ring structure in the circumferential direction, or they can include a number of discontinuous ribs arranged in the circumferential direction.

[0053] exist Figure 4 In a modified embodiment, the protrusion structure 122 may have only one protrusion or three or more protrusions. When two or more protrusions are provided, there is a gap between adjacent protrusions. The heights of adjacent protrusions are preferably different. The structures of each protrusion may be the same or different.

[0054] refer to Figure 5 , Figure 5 The diagram shows several cross-sectional shapes of the protrusion when it is actually installed, such as rectangular, trapezoidal or triangular.

[0055] In the above embodiments, the metal plate 11 of the end plate 10 can be made of materials such as aluminum alloy, and the insulating plate 12 can be made of high-temperature resistant nylon material, such as PPA, PA9T, PPS, PA6T, etc.

[0056] In practical applications, the metal plate 11 and the insulating plate 12 can be integrally injection molded to ensure the stability and strength of the end plate 10.

[0057] Insulation performance tests were conducted under the same test conditions for the insulating plate 12 of the end plate 10 with and without the protruding structure 122.

[0058] The insulating plate 12 with raised structure 122 is sample 1. In sample 1, the metal plate 11 of the end plate 10 is made of 6061T6 aluminum alloy and is machined. The insulating plate 12 is made of PA9T material and is injection molded. The injection temperature can refer to the recommended injection molding process for PA9T material, with a mold temperature ≥140℃ and a holding pressure of 60MPa. The raised structure 122 of the insulating plate 12 consists of two annular rectangular raised parts, such as... Figure 2 and 3 As shown, the height of the protrusion on the outer side is 2mm, and the height of the protrusion on the inner side is 3mm.

[0059] The insulating plate 12 without the protrusion structure 122 is sample 2. Except for the protrusion structure 122, the material, forming method and conditions of the metal plate 11 of the end plate 10 and the insulating plate 12 in sample 2 are the same as those in sample 1.

[0060] The assembly form of the experiment is as follows Figure 6 As shown, the current collector 20 and the end plate 10 are stacked and assembled. A counterweight 30 is placed on the current collector 20 to ensure that the current collector 20 and the insulating plate 12 of the end plate 10 are tightly fitted. During testing, the assembled... Figure 6 The device shown is placed in an environmental chamber, the temperature is set to -30℃, and it is stored for 60 minutes. Then the temperature of the environmental chamber is set to 40℃ and the relative humidity is 80%RH. In this way, water vapor in the air will condense on the surface of the sample to form condensation. The insulation resistance between the current collector 20 and the metal plate 11 of the end plate 10 is recorded.

[0061] The test results are shown in Table 1 below. Initially, the insulation resistance of both Sample 1 and Sample 2 was greater than 2000 MΩ. However, as the condensation time increased, the insulation resistance of Sample 2 decreased sharply. After 35 minutes, the insulation resistance of Sample 1 remained greater than 2000 MΩ, while the insulation resistance of Sample 2 only remained at 218 MΩ. The insulation meter used in this test had a measurement range of 2000 MΩ.

[0062] Table 1

[0063]

[0064] Based on the above test results, it can be determined through testing that the addition of the protruding structure 122 significantly improves the insulation performance of the end plate 10.

[0065] It should be noted that the insulation test for end plate 10 is condensation, which is a relatively strict insulation test. Therefore, the insulation of end plate 10 can be determined more accurately by using the condensation test.

[0066] Using the same insulation test method described above, comparative tests were conducted on a stack containing sample 1 (with raised structure 122) and a stack containing sample 2 (without raised structure), respectively. The test results can be used as a reference. Figure 7 As shown, after 60 minutes of condensation, the insulation resistance of the fuel cell stack containing sample 1 (with protrusion structure 122) stabilized at 52 MΩ, which is nearly 10 times higher than that of the fuel cell stack containing sample 2 (without protrusion structure).

[0067] The raised structure 122 provided on the insulating plate 12 of the end plate 10 not only increases the creepage distance but also blocks the water film, which can significantly improve the insulation resistance.

[0068] Based on the fact that the insulating plate 12 of the end plate 10 has a raised structure 122, a hydrophobic coating can also be provided on at least a portion of the surface of the insulating plate 12 facing the current collector 20, which can further enhance the insulation of the end plate 10.

[0069] The hydrophobic coating enhances the hydrophobicity of the insulating surface of the insulating board 12, forming individual conductive bodies from the condensation. These conductive bodies have gaps between them, making it difficult to form a continuous plane, thus increasing the insulation resistance under condensation conditions. Furthermore, the hydrophobic coating also exhibits good stain resistance, protecting the surface of the end plate 10.

[0070] Hydrophobic coatings can be made of materials with certain temperature resistance. Generally speaking, the internal temperature of the fuel cell stack can reach 90°C. Hydrophobic coatings can also be made of materials that do not cause harm to the human body and do not have any additional impact on the fuel cell stack or fuel cell system. Optional hydrophobic coatings include silicone coatings or fluorine coatings.

[0071] The application of the hydrophobic coating can be determined by the type of coating selected. Generally, liquid hydrophobic coatings can be applied to at least a portion of the insulating surface of the end plate 10 by spraying or smearing, and adhesion can be accelerated by room temperature adhesion or by high temperature baking.

[0072] In specific applications, a hydrophobic coating can be applied to the entire second surface 121b of the insulating plate 12.

[0073] In other embodiments, the insulating plate 12 may not have the protrusion structure 122 as described above, but may only have a hydrophobic coating on its functional surface portion.

[0074] To visually demonstrate the effect of the hydrophobic coating on the insulation performance of the insulating plate 12, insulation performance tests were conducted on two samples of end plates 10 under the same test conditions. Neither sample had a raised structure 122 on its insulating plate 12. The comparison sample was still the aforementioned sample 2, and the sample with the hydrophobic coating was sample 3.

[0075] In Sample 3, the material selection and processing method of the metal plate 11 and the insulating plate 12 are the same as those of Sample 1. In Sample 3, a hydrophobic coating is applied to the second surface 121b of the insulating plate 12. The coating material is GN-704A hydrophobic self-cleaning nanocomposite ceramic coating.

[0076] The coating can be applied to the second surface 121b of the insulating plate 12 in the following manner:

[0077] Clean the surface of sample 3 and keep it clean after drying.

[0078] Spraying, room temperature spraying, the spraying thickness can be about 50 to 100 micrometers. Spraying can be done with a spray gun. A relatively small nozzle diameter can be selected for the spray gun to achieve a better atomization effect and ensure the spraying effect.

[0079] Drying can be done naturally, such as by leaving it for more than 12 hours; or by placing it in an oven to dry, such as by letting it air dry for 30 minutes and then baking it at 150℃ for 30 minutes.

[0080] In practical applications, the above coating process can be repeated more than twice to ensure the stability of the coating.

[0081] A surface water spray comparison was performed on sample 3 with a coating and sample 2 without a coating. (For reference...) Figure 8 and Figure 9 , Figure 8 and Figure 9The images show the state of sample 3 and sample 2 after being sprayed with water. The black arc-shaped areas in the images represent water droplets. It can be seen that the surface of sample 3 has good hydrophobicity.

[0082] Similarly, a comparative insulation test was conducted on samples 3 and 2, and the assembly method of the test was still the same. Figure 6 As shown, the test conditions can also be the same as those for the insulation tests of samples 1 and 2 mentioned above. The test results are shown in Table 2 below. At the initial stage of condensation, the insulation resistance of samples 3 and 2 is greater than 2000 MΩ. As the condensation time increases, the insulation resistance of sample 2 decreases sharply, while the insulation resistance of sample 3 remains greater than 2000 MΩ. The insulation meter used in this test has a test range of 2000 MΩ.

[0083] The test results show that the end plate 10 of sample 3 has obvious insulation advantages. The reason is that the hydrophobic coating improves the hydrophobicity and makes it difficult to form a continuous plane on the insulating surface of the end plate 10, which can improve the insulation resistance under condensation.

[0084] Table 2

[0085]

[0086] The above provides a detailed description of a fuel cell stack and its endplate provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. An end plate for a fuel cell stack, characterised in that The end plate comprises a metal plate and an insulating plate; the insulating plate comprises a plate body and a protruding structure connected together, the plate body has opposite first and second surfaces, the first surface is fixedly attached to the metal plate, and the second surface is used to contact a current collector plate of the fuel cell stack; The protruding structure is located at the outer periphery of the plate body; at least a portion of the surface of the insulating plate facing the current collector plate has a hydrophobic coating; The plate body has a side peripheral wall between the first and second surfaces, and the side peripheral wall is provided with the protruding structure.

2. The end plate of a fuel cell stack according to claim 1, characterized by The insulating plate comprises an extended plate portion, at least a wall portion of the side peripheral wall of the plate body extends outward to form the extended plate portion, and the extended plate portion is provided with the protruding structure.

3. An end plate for a fuel cell stack according to claim 2, characterised in that The surface of the extended plate portion facing the metal plate is flush with the first surface, and the protruding structure is arranged on the side of the extended plate portion away from the metal plate; and / or, the extended plate portion has a ring structure.

4. An end plate for a fuel cell stack according to any one of claims 1 to 3, characterised in that, The protruding structure comprises at least one protruding portion.

5. An end plate for a fuel cell stack according to claim 4, characterised in that The protruding portion has a circumferentially continuous ring structure, or the protruding portion comprises a plurality of discontinuous protruding ribs arranged along the circumference.

6. The end plate of a fuel cell stack according to claim 4, characterized by The protruding structure is provided with two or more protruding portions, adjacent two protruding portions have a gap therebetween, and / or the heights of adjacent two protruding portions are different.

7. An end plate for a fuel cell stack according to any one of claims 1 to 3, characterised in that, The metal plate and the insulating plate are integrally injection molded.

8. A fuel cell stack comprising an end plate and a current collector plate in contact with the end plate, characterised in that, The end plate is the end plate according to any one of claims 1-7.

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