A wet-wet layered gluing composite sealing method for air-cooled proton exchange membrane fuel cells

Abstract

The present invention relates to the field of fuel cell sealing and screen printing technology, and in particular to a wet-wet layered gluing composite sealing method for air-cooled proton exchange membrane fuel cells; the method comprises placing a screen printing plate above the anode plate, coating a first layer of low-viscosity silicone water, and accelerating the curing by UV light curing; and applying a second layer of high-viscosity silicone water by a gluing method and curing by natural curing. The present invention applies a first layer of low-viscosity silicone water as a base layer on the anode plate, and applies the glue in conjunction with a screen printing method, which can accurately ensure the height and width of the glue after curing, and the molding size is accurate. It can also be used as a subsequent assembly component for assembly and positioning, which is beneficial to improving the consistency of the single cell; subsequently, a second layer of high-viscosity silicone water is dispensed, which can reduce glue overflow, make the glued shape regular, and at the same time improve the appearance of the battery stack caused by glue overflow after assembling the battery stack, meet the sealing and stability requirements, reduce production costs, and effectively shorten the curing time.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cell sealing and screen printing, and in particular to a wet-wet layered gluing composite sealing method for an air-cooled proton exchange membrane fuel cell. Background Art

[0002] During operation, proton exchange membrane fuel cells (PEMFCs) experience the presence of both hydrogen and oxygen at the cathode and anode on either side of the membrane electrode. Therefore, the cathode and anode working spaces must be separated and hydrogen leakage prevented. This requires sealing of the PEM fuel cell. The quality of this seal determines the airtightness, stability, and lifespan of the cell. Therefore, the precision and quality of the waterproof sealant dispensing process directly impacts product quality. For air-cooled PEMFCs, seals primarily seal around the bipolar plates and membrane electrode, preventing hydrogen leakage from the anode flow path during fuel cell operation. Materials used include EPDM, fluororubber, silicone, and polyisobutylene. A fuel cell stack can contain anywhere from a few to dozens or even hundreds of sealing rings and sealing elements. Due to the high surface roughness of graphite or metal bipolar plates, hydrogen leakage cannot be prevented through direct contact with other components. Seal selection should consider performance during operation, including temperature and humidity fluctuations, chemical corrosion, gas leakage, insulation, and shock and vibration absorption.

[0003] Currently, air-cooled proton exchange membrane fuel cells are generally used in low-power, single-stack applications to achieve a seal between the bipolar plate and the membrane electrode. Typically, the active area of ​​a single cell is small, and the flow channel dimensions are relatively small. To ensure a relatively compact cell structure, high requirements are placed on the adhesive coating, with strict requirements for both width and height. Using a sealing gasket for sealing would be difficult to meet these requirements. Therefore, a wet sealing method is commonly used, using a dispensing machine to apply a selected high-performance elastomeric organic silicone around the bipolar plate. This then achieves bonding and sealing between the bipolar plate and the membrane electrode, meeting the fuel cell sealing requirements. Silicones that meet these requirements are primarily imported and expensive. Furthermore, controlling the shape and dimensions of the sealant after molding is difficult. Due to the long curing time of this sealant, the sealant's shape easily changes after curing, making it difficult to use for positioning in subsequent processes, resulting in high sealing costs. Furthermore, this type of silicone cures by deacetic acid removal, fully curing within 24 hours at room temperature. This long curing time also makes it unsuitable for high-temperature or UV curing, impacting battery production efficiency.

[0004] Therefore, a wet-wet layered gluing composite sealing method for air-cooled proton exchange membrane fuel cells was proposed. Summary of the Invention

[0005] In order to solve the above technical problems, a wet-wet layered glue coating composite sealing method for air-cooled proton exchange membrane fuel cells is provided. This method can meet the sealing requirements of single cells and stacks of air-cooled proton exchange membrane fuel cells, as well as the performance stability and consistency of batteries under different working conditions, and greatly shorten the curing time of the stack sealant. At the same time, the glue coating has a regular shape and less glue overflow, which improves the deterioration of the stack appearance caused by glue overflow after assembling the stack, can reduce production costs and improve production efficiency.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A wet-wet layered gluing composite sealing method for an air-cooled proton exchange membrane fuel cell comprises the following steps:

[0008] Place the positioning mold on the printing table, and place several cleaned anode plates to be coated in the positioning mold, place the screen printing plate above the anode plates to be coated, introduce the first layer of low-viscosity silicone water at one end of the screen printing plate, use a scraper to apply pressure on the silicone water part on the screen printing plate, and move it to the other end of the screen printing plate. During the movement, the first layer of low-viscosity silicone water is squeezed from the screen mesh to the anode plate to be coated by the scraper. When the scraper scrapes across the entire screen printing plate, lift the screen printing plate to complete a printing process. The first layer of low-viscosity silicone water is coated, and the positioning mold and the anode plate coated with the first layer of low-viscosity silicone water are removed from the printing table. The electrode plate is assembled and UV light curing is used to accelerate the curing, with a curing time of less than 60s; the anode diffusion layer is placed with the inner ring contour surface of the cured first layer of glue as the positioning line; then a second layer of high-viscosity silicone water is applied on the first layer of coated and cured silicone by dispensing, and left at room temperature for 1-2 minutes, and then the MEA is placed on top, and pressure is applied on both sides of the anode plate and MEA. The second layer of high-viscosity silicone water is naturally cured, and the curing time is 30-60 minutes; after the curing is completed, the cathode carbon paper, rubber ring and support plate are placed in sequence, and the cathode corrugated plate is placed in the support plate positioning frame to complete the assembly process of the fuel cell single cell.

[0009] Preferably, the positioning mold includes a base plate and several cross-shaped bosses. Four positioning platforms matching the size of the anode plate to be coated with glue are arranged in a rectangular array on the positioning mold. Cross-shaped bosses are set at the four corners of each positioning platform. Each anode plate to be coated with glue is placed on the positioning platform and is positioned by the cross-shaped bosses at the four corners.

[0010] Preferably, the first layer of low-viscosity silica gel water adopts single-component silica gel with a viscosity of 1400-3000 cps.

[0011] Preferably, the second layer of high-viscosity silica gel water adopts a single-component deacetic acid curing silica gel with a viscosity of 350,000 cps.

[0012] Preferably, the MEA is a membrane electrode three-in-one assembly, comprising a proton exchange membrane, an anode catalyst layer and a cathode catalyst layer.

[0013] Specifically, the present invention relates to an air-cooled proton exchange membrane fuel cell comprising an anode plate, an anode diffusion layer, an MEA (anode catalyst layer, proton exchange membrane, cathode catalyst layer), a cathode diffusion layer, a cathode corrugated plate, and a seal. Furthermore, the present invention employs a wet-on-wet layered adhesive composite sealing method, primarily for sealing between the anode plate and the MEA. This method allows for rapid curing, and the cured profile facilitates subsequent assembly. Furthermore, to shorten curing time, the present invention utilizes two different types of silicone gels with different performance characteristics.

[0014] Specifically, a silk screen printing method is used as an auxiliary tool to achieve the coating of the first layer of low-viscosity silicone water, wherein the first layer of low-viscosity silicone water uses a single-component silicone with a low viscosity of 1400-3000cps, and then it is quickly cured, and thermal curing or UV light curing is used to accelerate the curing (wherein, thermal curing requires curing under heating or a certain temperature environment under the condition of chemical reaction, and UV light curing is through LED ultraviolet irradiation, and the photoinitiator inside the UV coating is stimulated to become a free radical or cation, thereby initiating a cross-linking polymerization reaction of an active polymer material (for example: photosensitive resin), so that the UV material is quickly cured). The curing time is less than 60s, so that the first layer of low-viscosity silicone water is quickly cured, which can ensure precise external dimensions, which will be beneficial for the inner contour of the molded part to be used as the positioning contour of the next process, and improve the consistency of the finished single battery and the aesthetic appearance.

[0015] Specifically, in order to meet the requirements of better sealing performance after the anode plate and MEA are assembled, the second layer of low-viscosity silicone water still uses high-performance (better temperature resistance: -50℃-180℃, sealing adhesion: 350000cps, insulation: 1X10 14 Ω·cm, chemical stability and tensile strength: 2Mpa), high viscosity one-component deacetic acid curing silicone is coated on the first layer of cured glue, which can combine the advantages of the two glues and reduce the use of imported glue, saving costs and ensuring its performance.

[0016] The beneficial effects of the present invention are as follows: the wet-wet layered gluing composite sealing method for the air-cooled proton exchange membrane fuel cell of the present invention adopts a single-component, low-viscosity silicone rubber that can be accelerated to cure by heat curing or UV light curing as the bottom layer on the anode plate, and is applied with the silk screen printing method, which can accurately ensure the height and width of the glue after curing, and the molding size is accurate, and can be used as a subsequent assembly component for assembly and positioning, which is beneficial to improving the consistency of the single cell; the second layer adopts a single-component, high-viscosity and high-performance deacetic acid curing silicone rubber, and is applied with the second layer of glue point coating, which can achieve a regular glue coating shape, reduce glue overflow, and at the same time improve the deterioration of the appearance of the battery stack caused by glue overflow after assembling the battery stack, which can meet the sealing performance and stability requirements, and greatly reduce production costs, effectively shorten curing time, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Flowchart of the wet-wet layered gluing composite sealing method for an air-cooled proton exchange membrane fuel cell according to an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of placing the anode plate to be coated with glue in a positioning mold according to an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of placing a screen printing plate above the anode plate in an embodiment of the present invention;

[0020] Figure 4 Schematic diagram of coating the anode plate with a first layer of low-viscosity silica gel water in an embodiment of the present invention;

[0021] Figure 5 Schematic diagram of coating the anode plate with a second layer of high-viscosity silicone gel in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of placing the anode diffusion layer using the inner contour surface of the second layer of high-viscosity silicone gel after solidification as the positioning line in an embodiment of the present invention;

[0023] Figure 7 Schematic diagram of placing MEA in an embodiment of the present invention;

[0024] Figure 8 This is a structural photo of the anode plate in an embodiment of the present invention, in which a first layer of low-viscosity silicone water is coated by screen printing, a second layer of high-viscosity silicone water is coated by dispensing and naturally cured after rapid curing, and the anode diffusion layer is placed using the cured silicone as a positioning outline. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] A wet-wet layered adhesive composite sealing method for an air-cooled proton exchange membrane fuel cell. The air-cooled proton exchange membrane fuel cell comprises an anode plate, an anode diffusion layer, an MEA, a cathode diffusion layer, a cathode corrugated plate, and a seal. The MEA is a three-in-one membrane electrode assembly comprising a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer. The wet-wet layered adhesive composite sealing method primarily seals the periphery of the anode plate and the MEA, enabling rapid curing. Furthermore, the cured profile facilitates subsequent assembly steps.

[0027] The specific steps are as follows:

[0028] S1: Prepare the anode plate to be coated, screen printing plate, scraper, first layer of low viscosity silicone water, second layer of high viscosity silicone water, high temperature curing equipment or UV curing machine.

[0029] S2: Place the positioning mold on the printing table, and place several anode plates to be coated with glue in the positioning mold after cleaning.

[0030] In this embodiment, refer to the attached Figure 2 The positioning mold consists of a base plate and several cross-shaped bosses. Four positioning platforms that match the size of the anode plate to be coated with glue are arranged in a rectangular array on the positioning mold. Cross-shaped bosses are set at the four corners of each positioning platform. Each anode plate to be coated with glue is placed on the positioning platform and is positioned by the cross-shaped bosses at the four corners, which facilitates the positioning of the anode plate to be coated with glue, and then realizes the positioning glue coating.

[0031] S3: Place the screen printing plate above the anode plate to be coated, introduce the first layer of low-viscosity silicone water at one end of the screen printing plate, use a scraper to apply pressure on the silicone water part on the screen printing plate, and move it to the other end of the screen printing plate. During the movement, the first layer of low-viscosity silicone water is squeezed from the mesh of the printing plate to the anode plate to be coated by the scraper. When the scraper scrapes across the entire screen printing plate, lift the screen printing plate to complete a printing process. The first layer of low-viscosity silicone water is applied. Remove the positioning mold together with the anode plate coated with the first layer of low-viscosity silicone water from the printing table, and use heat curing or UV light curing in high-temperature curing equipment or UV curing machine to accelerate curing. The curing time is less than 60s.

[0032] In this embodiment, the first layer of low-viscosity silicone water uses a single-component silicone with a viscosity of 1400-3000 cps to ensure that the mesh of the screen is not blocked and bonded, and uses thermal curing or UV curing to achieve short-time curing.

[0033] In this embodiment, the first layer of low-viscosity silicone water is squeezed from the mesh of the printing plate to the anode plate to be coated by the scraper during movement. Due to the viscosity of the silicone water, the screen printing plate and the anode plate are in moving line contact, and other parts of the screen printing plate are separated from the anode plate, causing the silicone water and the screen to break and move, thereby ensuring the printing size accuracy.

[0034] In this embodiment, thermal curing or UV light curing is used to accelerate curing, which is beneficial to ensuring the external dimensions and accuracy of the cured silicone water.

[0035] In this embodiment, due to the characteristics of screen printing such as strong adaptability, no restrictions on the size and shape of the printed object, soft layout, low printing pressure and strong covering power, the surface flatness of the anode plate of the air-cooled proton exchange membrane fuel cell is usually not completely flat. A method of applying a first layer of low-viscosity silicone water around the anode plate by screen printing is adopted. This method can ensure uniform coating of the first layer of low-viscosity silicone water, and since the viscosity of the first layer of low-viscosity silicone water is relatively low, it can ensure that the mesh of the screen is not blocked and bonded; then a method of accelerating curing is adopted by heat curing or UV light curing. During coating, it is noted that the required coating thickness of the glue is relatively thin, so the curing time is relatively short, generally less than 60 seconds. When applying this layer of silicone water, due to its small thickness and short curing time, it will not be affected by the gravity of the silicone water itself, which will lead to the inability to control the shape, and thus the required shape can be maintained, thereby achieving more accurate control of the height and width of the coated silicone water to meet the requirements of the cured shape size.

[0036] S4: Place the anode diffusion layer using the inner contour surface of the first layer of rubber after curing as the positioning line.

[0037] S5: Apply a second layer of high-viscosity silicone water on top of the first layer of coated and cured silicone by dispensing, leave it at room temperature for 1-2 minutes, then place the MEA on top, and apply pressure on both sides of the anode plate and MEA. The second layer of high-viscosity silicone water will cure naturally, and the curing time is 30-60 minutes.

[0038] In this embodiment, the anode plate coated with a first layer of low-viscosity silicone water and the positioning mold are placed on the dispensing machine installation platform, and then the second layer of high-viscosity silicone water is dispensed on the anode plate. When dispensing, attention is paid to the thin thickness of the dispensing, that is, the natural curing time after the silicone water is applied is short, generally 30-60 minutes, and the layer of silicone water has good fusion with the proton exchange membrane of MEA. Moreover, since the coated silicone water is thin, there will be no problems such as deformation of shape and inaccurate size due to the thicker and less easy to cure.

[0039] In this embodiment, after the first layer of low-viscosity silicone water is quickly solidified, the second layer of high-viscosity silicone water is then applied. Compared with the first layer of silicone water, it is required to have better bonding and sealing properties, higher volume resistivity, higher tensile strength, and wider high and low temperature resistance range. The reason is that the second layer of high-viscosity silicone water must not only be bonded and fused with the first layer of low-viscosity silicone water, but the outer surface of the second layer of high-viscosity silicone water also needs to be bonded to the proton exchange membrane of the MEA and withstand the extrusion force during stacking to ensure that hydrogen does not leak through the joint surface and the solidified glue to achieve sealing of the stack, while not damaging the proton exchange membrane and having sufficiently high mechanical properties. At present, the one-component deacetic acid curing silicone has a higher viscosity and is more expensive. It relies on imports. Due to the high viscosity of this silicone water, it is not suitable for gluing by screen printing. The traditional gluing process is still used. The silicone water is coated on the first layer of glue that has been cured and then naturally cured. Because there is a first layer of low-viscosity one-component silicone as the base, the thickness of the second layer of glue is very small, which is conducive to greatly reducing its curing time. The curing time is generally 30-60 minutes. Compared with the traditional process, only the second silicone water coating method is used, and the curing time usually takes more than 12-24 hours. The curing time can be greatly reduced.

[0040] In this embodiment, by adopting a wet-wet layered gluing composite sealing method, the first layer of low-viscosity silicone water can be quickly cured, and the second layer of high-viscosity silicone water can be naturally cured. This not only makes the appearance of the silicone water more precise and beautiful after curing, but also maintains the performance and requirements of the traditional sealing method, so as to achieve the key sealing steps. At the same time, it can also shorten the total curing time, and the traditional curing time can be shortened from 12-24h to less than 1h, effectively improving production efficiency.

[0041] In this embodiment, the second layer of high-viscosity silicone water adopts a single-component deacetic acid curing silicone with a viscosity of 350,000 cps.

[0042] S6: After curing is completed, the cathode carbon paper, rubber ring and support plate are placed in sequence, and the cathode corrugated plate is placed in the support plate positioning frame to complete the assembly process of the fuel cell single cell.

[0043] After curing is completed, the cathode carbon paper, rubber ring and support plate are placed in sequence, and the cathode corrugated plate is placed in the support plate positioning frame to complete the assembly process of the fuel cell single cell.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A wet-wet layered gluing composite sealing method for an air-cooled proton exchange membrane fuel cell, characterized in that: The following steps are involved: Place the positioning mold on the printing table, and place several anode plates to be coated with glue in the positioning mold after cleaning, place the screen printing plate above the anode plate to be coated with glue, introduce the first layer of low-viscosity silicone water at one end of the screen printing plate, use a scraper to apply pressure on the silicone water part on the screen printing plate, and move it to the other end of the screen printing plate. During the movement, the first layer of low-viscosity silicone water is squeezed from the printing plate mesh by the scraper to the anode plate to be coated. When the scraper scrapes across the entire screen printing plate, lift the screen printing plate to complete a printing process. The first layer of low-viscosity silicone water is coated. Remove the positioning mold together with the anode plate coated with the first layer of low-viscosity silicone water from the printing table, and use UV light curing to accelerate curing. The curing time is less than 60s. The inner ring contour surface is the positioning line, and the anode diffusion layer is placed; then, a second layer of high-viscosity silicone water is applied on top of the first layer of coated and cured silicone by the dispensing method, and placed at room temperature for 1-2 minutes, and then the MEA is placed on top, and pressure is applied on both sides of the anode plate and MEA. The second layer of high-viscosity silicone water is naturally cured, and the curing time is 30-60 minutes; after the curing is completed, the cathode carbon paper, rubber ring and support plate are placed in sequence, and the cathode corrugated plate is placed in the support plate positioning frame to complete the assembly process of the fuel cell single cell; wherein, the first layer of low-viscosity silicone water adopts a single-component silicone with a viscosity of 1400-3000cps; the second layer of high-viscosity silicone water adopts a single-component deacetic acid cured silicone with a viscosity of 350,000cps.

2. The wet-wet layered gluing composite sealing method for an air-cooled proton exchange membrane fuel cell according to claim 1, characterized in that: The positioning mold includes a base plate and several cross-shaped bosses. Four positioning platforms matching the size of the anode plate to be coated with glue are arranged in a rectangular array on the positioning mold. Cross-shaped bosses are set at the four corners of each positioning platform. Each anode plate to be coated with glue is placed on the positioning platform and is positioned by the cross-shaped bosses at the four corners.

3. The wet-wet layered gluing composite sealing method for an air-cooled proton exchange membrane fuel cell according to claim 1, characterized in that: The MEA is a membrane electrode three-in-one assembly, including a proton exchange membrane, an anode catalyst layer and a cathode catalyst layer.

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