A membrane electrode frame integrated sealing structure for a hydrogen fuel cell and a preparation method thereof

Abstract

The application discloses a membrane electrode frame integrated sealing structure for a hydrogen fuel cell and a preparation method, and relates to the technical field of hydrogen fuel cell sealing. The sealing structure is integrally injection molded with a cathode and an anode frame, and a matching stepped groove is arranged on a bipolar plate. The sealing structure comprises at least two parallel sealing protrusions protruding towards the bipolar plate, and an outer wing part and an inner wing part extending inwards and outwards. When press-fitting, the sealing protrusions abut the groove bottom surface to transmit the press-fitting force, and the wing parts are embedded in the corresponding stepped surfaces. The sealing profile matches the groove depth, and after press-fitting, the frame is flush with the bipolar plate to realize block compression. The application is prepared through a pre-vulcanization-transfer injection molding-second vulcanization process, the sealing precision reaches ±0.02 mm, the service life is more than 14000 hours, frame press-fitting deformation and membrane electrode shear damage can be avoided, and the application is suitable for 1-350 kW fuel cell stacks and sub-exchange membrane electrolytic cells.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fuel cell technology, and in particular to an integrated sealing structure and preparation method for a membrane electrode frame for a hydrogen fuel cell. Background Technology

[0002] Fuel cells are electrochemical devices that directly convert chemical energy into electrical energy. Their high efficiency, zero emissions, and rapid start-up characteristics have made them a core technology in the field of sustainable energy. In proton exchange membrane fuel cells, the membrane electrode assembly (MEA) is the core power generation unit. The sealing performance between its frame and bipolar plates directly determines the gas utilization rate, coolant isolation effect, and the safety and lifespan of the fuel cell stack.

[0003] In existing technologies, fuel cell sealing mainly employs two methods: one is an independent sealing ring structure, where O-rings, rubber sealing strips, and other independent parts are assembled in the frame groove, which has problems such as easy misalignment during assembly, a large number of parts, and easy aging and creep after long-term use; the other is silicone dispensing sealing, where liquid silicone is applied to the frame and cured, which has defects such as poor material weather resistance, easy pulverization, low processing precision, and short lifespan, and can only meet the usage requirements within 5000 hours.

[0004] Meanwhile, existing sealing structures generally suffer from two core defects: First, during press-fitting, the pressing force acts directly on the plastic frame, which has low strength and is prone to bending and permanent deformation, resulting in uneven seal compression and poor fuel cell stack assembly consistency. Second, the frame edges lack protective structures, and the hard edges can easily generate shear stress on the membrane electrode during press-fitting, causing mechanical damage to the membrane electrode and shortening the fuel cell stack life. In addition, existing single-channel seals lack redundancy design, and once a local failure occurs, it will lead to gas leakage and liquid leakage, resulting in insufficient reliability.

[0005] Therefore, how to design a membrane electrode frame sealing structure that does not require an independent sealing ring, has redundant sealing capabilities, can protect the edge of the membrane electrode, avoids deformation of the frame during press-fitting, and has high-precision machining capabilities and a long service life has become an urgent technical problem to be solved in the current hydrogen fuel cell technology field.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide an integrated sealing structure for the membrane electrode assembly frame of a hydrogen fuel cell and its preparation method, which can solve the problems of easy misalignment during assembly, short lifespan, easy deformation of the frame during press fitting, easy shear damage to the membrane electrode, and insufficient sealing reliability in the prior art.

[0008] To achieve the above objectives, the present invention provides an integrated sealing structure for membrane electrode frames of hydrogen fuel cells, including a cathode frame and an anode frame disposed opposite to each other, and two bipolar plates located on both sides of the cathode frame and the anode frame respectively;

[0009] The cathode frame and the anode frame are provided with a sealing structure on the surface facing the bipolar plate. The sealing structure and the frame are integrally injection molded. The bipolar plate is provided with a stepped groove adapted to the sealing structure.

[0010] The sealing structure includes:

[0011] At least two sealing protrusions are continuously distributed along the sealing trajectory of the frame and protrude toward the bipolar plate. The sealing protrusions are parallel to each other and abut against the bottom surface of the stepped groove of the bipolar plate during press fitting.

[0012] The outer wing is located on the side of the sealing structure near the outer periphery of the frame, extends outward along the sealing track, and is fitted into the outer step surface of the stepped groove of the bipolar plate during press fitting;

[0013] The inner wing is located on the side of the sealing structure near the inner periphery of the frame, extends inward along the sealing track, and fits into the inner step surface of the stepped groove of the bipolar plate during press-fitting.

[0014] The outer contour of the sealing structure matches the depth of the stepped groove of the bipolar plate, so that after the fuel cell stack is pressed, the surface of the frame is flush with the surface of the bipolar plate, achieving repeatable deterministic block pressing.

[0015] In one embodiment of the present invention, the stepped groove of the bipolar plate includes a first groove in the middle and second grooves on both sides of the first groove. The depth of the first groove is greater than the depth of the second groove, thereby forming a stepped structure. The depth of the first groove is less than the height of the sealing protrusion, and the depth of the second groove is less than the height of the outer wing and the inner wing.

[0016] In one embodiment of the present invention, the sealing structure is made of EPDM rubber, fluororubber or polybutene.

[0017] In one embodiment of the present invention, the inner wing and the outer wing extend toward the membrane electrode and cover the edge of the membrane electrode.

[0018] In one embodiment of the invention, a buffer groove is formed between the two sealing protrusions.

[0019] In one embodiment of the present invention, the height of the sealing protrusion is 0.53-0.63 mm, and the thickness of the outer wing and the inner wing is 0.2 mm.

[0020] In one embodiment of the present invention, the thickness tolerance of the sealing structure is ±0.02mm, the width tolerance is ±0.05mm, and the position tolerance is ±0.10-0.20mm.

[0021] The present invention also provides a hydrogen fuel cell membrane electrode assembly, including the above-mentioned integrated sealed structure of the membrane electrode frame for hydrogen fuel cells.

[0022] This invention also provides a method for preparing an integrated sealing structure for a membrane electrode frame of a hydrogen fuel cell, comprising the following steps:

[0023] S1: Add the sealant compound into the first mold cavity and pre-vulcanize it for 8 minutes at 170-175℃ and 25MPa to form a preform with sealing protrusions and inner and outer wing structures.

[0024] S2: Apply the silane coupling agent to the preset sealing track of the cathode frame and / or anode frame;

[0025] S3: Transfer the preformed component to the second mold cavity, and form the preformed component on the frame surface through a transfer injection molding process to form a sealing protrusion and inner and outer wing structure;

[0026] S4: Perform secondary vulcanization at 100-150℃ for 30 minutes to firmly bond the sealing structure with the frame, forming an integrated sealing structure.

[0027] In one embodiment of the present invention, the sealing structure obtained by the preparation method has a thickness tolerance of ±0.02mm, a width tolerance of ±0.05mm, and a position tolerance of ±0.10-0.20mm.

[0028] Compared with the prior art, the advantages of the integrated sealing structure and preparation method of the membrane electrode frame for hydrogen fuel cells according to the present invention are as follows:

[0029] (1) The seal and frame are integrally injection molded without independent sealing parts, which completely avoids the problems of misalignment and detachment during assembly and improves assembly efficiency by more than 40%.

[0030] (2) The double-seal protrusion directly abuts against the bipolar plate to transmit force. More than 90% of the pressing force is borne by the metal bipolar plate, and the plastic frame is almost unaffected by the force, which fundamentally avoids frame deformation during pressing and ensures uniform sealing.

[0031] (3) The inner and outer wings are fitted with bipolar plate grooves, which not only restricts the floating of the membrane electrode to avoid shear damage, but also achieves radial auxiliary positioning to ensure the sealing position accuracy;

[0032] (4) The double seal forms redundant protection, the sealing accuracy reaches ±0.02mm, the EPDM material life exceeds 14,000 hours, and the reliability is significantly improved;

[0033] (5) The contour matching design achieves flush fitting after pressing, with a total compression deviation of ≤5%, good assembly consistency, and can cover 1-350kW fuel cell stacks and proton exchange membrane (PEM) electrolyzers. Attached Figure Description

[0034] Figure 1 This is a top view of the cathode frame sealing structure provided in an embodiment of the present invention;

[0035] Figure 2 A top view of the anode frame sealing structure provided in an embodiment of the present invention;

[0036] Figure 3 A cross-sectional schematic diagram of the sealing structure provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the structure of the sealing protrusion and bipolar plate before compression deformation, as provided in an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the structure of the sealing protrusion and the bipolar plates on both sides after compression deformation, as provided in an embodiment of the present invention.

[0039] Figure 6 This is a schematic flowchart illustrating a method for fabricating an integrated sealing structure for a membrane electrode frame of a hydrogen fuel cell according to an embodiment of the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1-Cathode frame, 2-Anode frame, 3-Sealing structure, 31-Sealing protrusion, 32-Outer wing, 33-Inner wing, 34-Buffer groove, 4-Bipolar plate, 41-Stepped groove, 411-First groove, 412-Second groove, 5-Film electrode Detailed Implementation

[0042] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0043] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0044] In the prior art, the sealing structure has problems such as easy misalignment during assembly, deformation of the press-fit frame, easy damage to the membrane electrode, and short life. In order to address the above problems, this embodiment provides an integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell.

[0045] like Figures 1 to 5 As shown, an integrated sealing structure for a membrane electrode assembly (MEA) frame of a hydrogen fuel cell according to a preferred embodiment of the present invention includes a cathode frame 1 and an anode frame 2 arranged opposite to each other, and bipolar plates 4 on both sides. The bipolar plates 4 are provided with stepped grooves 41 corresponding to the sealing positions. The surfaces of the cathode frame 1 and the anode frame 2 facing the bipolar plates 4 are integrally injection molded with sealing structures 3, that is, the sealing structures 3 are directly formed on the surfaces of the cathode frame 1 and the anode frame 2 by injection molding.

[0046] Specifically, the sealing structure 3 includes at least two sealing protrusions 31 continuously distributed along the sealing trajectory. The sealing protrusions 31 are parallel to each other and abut against the bottom surface of the stepped groove 41 of the bipolar plate 4 during press fitting.

[0047] The sealing structure 3 extends outward to form an outer wing 32, that is, the side facing the outer periphery of the frame; the sealing structure 3 extends inward to form an inner wing 33, that is, the side facing the inner periphery of the frame.

[0048] like Figure 4 As shown, the outer contours of the sealing protrusion 31, outer wing 32 and inner wing 33 of the sealing structure 3 match the depth of the stepped groove 41 of the bipolar plate 4, so that after the stack is pressed, the surfaces of the cathode frame 1 and the anode frame 2 are flush with the surface of the bipolar plate 4, achieving repeatable deterministic block pressing. Figure 4 and Figure 5 In the diagram, the yellow part represents the proton exchange membrane, the gray part represents the gas diffusion layer (usually made of carbon paper), and the black part represents the catalyst layer (generally, a proton exchange membrane coated with a catalyst layer on both sides is called a CCM; a CCM with a frame on the top and bottom and carbon paper is called a seven-in-one membrane electrode structure).

[0049] Specifically, the stepped groove 41 includes a first groove 411 in the middle and second grooves 412 on both sides of the first groove 411. The depth of the first groove 411 is greater than the depth of the second groove 412, thus forming a stepped structure. The depth of the first groove 411 is less than the height of the sealing protrusion 31, and the depth of the second groove 412 is less than the height of the outer wing 32 and the inner wing 33. During the press-fitting of the fuel cell stack, the sealing protrusion 31 is located in the first groove 411, and the outer wing 32 and the inner wing 33 are located in the second groove 412. After the fuel cell stack press-fitting is completed, the frame surface is flush with the bipolar plate surface, achieving repeatable deterministic block pressing.

[0050] Specifically, the height of the sealing protrusion 31 is 0.53-0.63 mm or other height values ​​set according to specific sealing pressure requirements, and the thickness of the outer wing 32 and the inner wing 33 is 0.2 mm. The thickness tolerance of the sealing structure 3 is ±0.02 mm, the width tolerance is ±0.05 mm, and the positional tolerance is ±0.10-0.20 mm.

[0051] The overall sealing trajectory length of the sealing structure is 1158mm, which is suitable for 10kW-class fuel cell stacks. Furthermore, the structure and its principle can be extended to fuel cell stacks with power levels from 1kW to 350kW and above.

[0052] In this embodiment, during press-fitting, the sealing protrusion 31 first contacts the bottom surface of the stepped groove 41 of the bipolar plate 4. As press-fitting progresses, the sealing protrusion 31 is compressed, directly transferring over 90% of the press-fitting force to the metal bipolar plate 4. The plastic frame bears less than 10% of the press-fitting force, preventing bending or permanent deformation. The outer wing 32 and inner wing 33 are respectively fitted into the inner and outer stepped surfaces of the stepped groove 41, restricting the axial floating of the membrane electrode 5 and preventing the hard edge of the frame from shearing the membrane electrode 5. They also serve a radial positioning function, ensuring the accuracy of the sealing position. The total thickness of the sealing structure 3 and the thickness of the frame match the depth of the stepped groove 41. After press-fitting, the surface of the frame is flush with the surface of the bipolar plate 4, and the overall compression deviation is controlled within ±5%, achieving repeatable block compression and significantly improving assembly consistency.

[0053] Optionally, the sealing structure 3 is made of ethylene propylene diene monomer (EPDM), fluororubber (FKM), or polybutene.

[0054] Ethylene propylene diene monomer (EPDM) rubber can adapt to the acidic and humid heat environment of fuel cells and has excellent resistance to ethylene glycol coolant. Under the condition of 125℃×24h, the compression set is ≤5.5%, the low temperature stress relaxation retention rate is ≥34.6% at -40℃, and the measured sealing life is ≥14000 hours. It solves the defects of existing organosilicon materials such as easy pulverization, short life and poor low temperature elasticity, and can meet the life requirements of commercial vehicle fuel cells.

[0055] Fluororubber (FKM) has a long-term temperature resistance of up to 150℃, and its resistance to strong corrosion and chemical media is superior, making it suitable for high-power high-temperature fuel cell stacks. It also has low compression set and higher sealing reliability under extreme conditions.

[0056] Polybutene materials exhibit excellent low-temperature elasticity (maintaining good resilience even at -50℃), and have lower material costs, making them suitable for low-temperature scenarios or low-cost fuel cell stack solutions.

[0057] In this embodiment, the three materials can cover application scenarios with different power, different operating conditions and different cost requirements. Compared with traditional single organosilicon sealing materials, the weather resistance, life and media resistance can be effectively improved, and the selection flexibility is strong.

[0058] Optionally, the outer wing 32 and the inner wing 33 extend toward the membrane electrode to cover the edge of the membrane electrode, preventing the membrane electrode from being sheared during the press-fitting process.

[0059] In this embodiment, the outer wing 32 and the inner wing 33 can prevent the hard edge of the frame from directly shearing the edge of the membrane electrode, reduce the shear stress at the edge of the membrane electrode, and solve the problems of membrane electrode edge cracking, proton membrane delamination, and catalyst layer detachment during press-fitting and thermal cycling.

[0060] Optionally, a buffer groove is formed between the two sealing protrusions 31.

[0061] In this embodiment, the buffer groove provides reserved space for the compression deformation of the sealing protrusion 31, which can absorb the flatness tolerance of the bipolar plate and the thickness tolerance of the frame, reduce the requirements for the machining accuracy of the parts, and the sealing protrusion can deform evenly during press fitting, avoiding local overpressure damage or leakage caused by insufficient local compressive stress.

[0062] like Figure 6 As shown, the sealing structure preparation method provided in this embodiment of the invention includes the following steps:

[0063] S1: Add the sealant compound to the first mold cavity and pre-vulcanize it for 8 minutes at 170-175℃ and 25MPa to form a preform; the sealant is ethylene propylene diene monomer (EPDM), fluororubber (FKM) or polybutene.

[0064] S2: Apply the silane coupling agent to the preset sealing track of the cathode frame and / or anode frame.

[0065] S3: Transfer the preformed component to the second mold cavity, and form the preformed component on the frame surface through a transfer injection molding process to form a sealing protrusion and inner and outer wing structures.

[0066] S4: Perform secondary vulcanization at 100-150℃ for 30 minutes to firmly bond the sealing structure with the frame, forming an integrated sealing structure.

[0067] Specifically, the sealing structure obtained by this preparation method has a thickness tolerance of ±0.02mm, a width tolerance of ±0.05mm, and a position tolerance of ±0.10-0.20mm.

[0068] This invention employs a pre-cured preform-transfer injection molding-secondary curing method to prepare the sealing structure. Compared to traditional processes such as independent sealing ring assembly, liquid adhesive dispensing, and integral bipolar plate injection, it can stably form a fine structure with a stable sealing thickness tolerance controlled within ±0.02mm. The forming accuracy is far superior to traditional dispensing processes. Furthermore, chemical bonding between the seal and the frame is achieved through coupling agent coating and secondary curing. The high-temperature section in the process is short, and the secondary curing temperature is adapted to the heat resistance of the frame, preventing heat deformation of the plastic frame. Since the bipolar plate does not participate in the high-temperature curing step, problems such as bipolar plate coating damage and adhesive ingress into the flow channels are avoided. The process is compatible with various high-performance solid rubbers such as EPDM, FKM, and polybutene, overcoming the limitation of traditional dispensing which can only use short-life liquid silicone rubber, achieving a long-life seal of over 14,000 hours. In addition, the seal is only integrally bonded to the frame and not adhered to the bipolar plate. After press-fitting, the bipolar plate can be disassembled and repaired separately, resulting in lower total lifespan costs and a shorter overall process cycle, making it suitable for large-scale mass production of high-power fuel cell stacks.

[0069] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An integrated sealed structure for a membrane electrode assembly (MEA) frame in a hydrogen fuel cell, comprising a cathode frame and an anode frame disposed opposite to each other, and two bipolar plates respectively located on both sides of the cathode frame and the anode frame; characterized in that: The cathode frame and the anode frame are provided with a sealing structure on the surface facing the bipolar plate. The sealing structure and the frame are integrally injection molded. The bipolar plate is provided with a stepped groove adapted to the sealing structure. The sealing structure includes: At least two sealing protrusions are continuously distributed along the sealing trajectory of the frame and protrude toward the bipolar plate. The sealing protrusions are parallel to each other and abut against the bottom surface of the stepped groove of the bipolar plate during press fitting. The outer wing is located on the side of the sealing structure near the outer periphery of the frame, extends outward along the sealing track, and is fitted into the outer step surface of the stepped groove of the bipolar plate during press fitting; The inner wing is located on the side of the sealing structure near the inner periphery of the frame, extends inward along the sealing track, and fits into the inner step surface of the stepped groove of the bipolar plate during press-fitting. The outer contour of the sealing structure matches the depth of the stepped groove of the bipolar plate, so that after the fuel cell stack is pressed, the surface of the frame is flush with the surface of the bipolar plate, achieving repeatable deterministic block pressing.

2. The integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell as described in claim 1, characterized in that, The stepped groove of the bipolar plate includes a first groove in the middle and second grooves on both sides of the first groove. The depth of the first groove is greater than the depth of the second groove, thus forming a stepped structure. The depth of the first groove is less than the height of the sealing protrusion, and the depth of the second groove is less than the height of the outer wing and the inner wing.

3. The integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell as described in claim 1, characterized in that, The sealing structure is made of EPDM rubber, fluororubber, or polybutene.

4. The integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell as described in claim 1, characterized in that, The inner wing and the outer wing extend toward the membrane electrode and cover the edge of the membrane electrode.

5. The integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell as described in claim 1, characterized in that, A buffer groove is formed between the two sealing protrusions.

6. The integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell as described in claim 1, characterized in that, The height of the sealing protrusion is 0.53-0.63 mm, and the thickness of the outer wing and the inner wing is 0.2 mm.

7. The integrated sealing structure for the membrane electrode frame of a hydrogen fuel cell as described in claim 1, characterized in that, The thickness tolerance of the sealing structure is ±0.02mm, the width tolerance is ±0.05mm, and the position tolerance is ±0.10-0.20mm.

8. A membrane electrode assembly for a hydrogen fuel cell, characterized in that, Includes an integrated sealed structure for the membrane electrode frame of a hydrogen fuel cell as described in any one of claims 1 to 7.

9. A method for fabricating an integrated sealing structure for a membrane electrode frame of a hydrogen fuel cell, characterized in that, Includes the following steps: S1: Add the sealant compound into the first mold cavity and pre-vulcanize it for 8 minutes at 170-175℃ and 25MPa to form a preform with sealing protrusions and inner and outer wing structures. S2: Apply the silane coupling agent to the preset sealing track of the cathode frame and / or anode frame; S3: Transfer the preformed component to the second mold cavity, and form the preformed component on the frame surface through a transfer injection molding process to form a sealing protrusion and inner and outer wing structure; S4: Perform secondary vulcanization at 100-150℃ for 30 minutes to firmly bond the sealing structure with the frame, forming an integrated sealing structure.

10. The preparation method according to claim 9, characterized in that, The sealing structure obtained by the preparation method has a thickness tolerance of ±0.02mm, a width tolerance of ±0.05mm, and a position tolerance of ±0.10-0.20mm.

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