A sealing method and sealing structure for a fuel cell frame

Abstract

The application belongs to the field of fuel cells, and particularly discloses a sealing method and a sealing structure of a fuel cell frame. The sealing method of the fuel cell frame comprises the following steps: coating a liquid treatment agent on a glue film layer in the fuel cell frame, and then bonding and sealing the glue film layer coated with the liquid treatment agent and a fuel cell assembly through hot pressing or ultraviolet light irradiation to obtain a fuel cell sealing structure. The method of the application can effectively improve the bonding performance of the frame, especially the bonding performance at high temperatures, and improve the sealing reliability of MEA under the operating conditions of the fuel cell stack.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fuel cells, and particularly relates to a sealing method and structure of a fuel cell frame. BACKGROUND

[0002] A proton exchange membrane fuel cell is composed of a plurality of single cells connected in series, and each single cell is mainly composed of a membrane electrode assembly (MEA) and a bipolar plate. The core component MEA is usually obtained by packaging a catalyst-coated proton membrane (CCM) and a GDL on a support material through an adhesive. The current mainstream packaging method and process of MEA is a double-frame structure MEA, specifically: firstly, an anode catalyst layer and a cathode catalyst layer are coated or transferred on both sides of the proton exchange membrane to prepare a CCM with a three-layer structure; then the edges of the CCM and the edges of the two frames are sealed by an adhesive to form a five-layer assembly; finally, the two gas diffusion layers are bonded to the frame by an adhesive to form a seven-layer membrane electrode. Currently, in order to match the production process and production efficiency, the frame material of commercial fuel cells is generally coated with an adhesive on the support material, and the adhesive is treated by heat treatment, pre-curing and other processes to form a solid adhesive film with a certain adhesive viscosity. The MEA assembly process is to heat press the CCM and the two frames to make the frame adhesive film adhere to the frame adhesive film and the CCM.

[0003] The support material of the membrane electrode is generally a hydrocarbon polymer such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polypropylene (PP), and polyethylene (PE); and the adhesive is generally a polyacrylate, an epoxy, a polyolefin, and a silicone. In the fuel cell, the pH of the proton exchange membrane sulfonic acid group is 1-2, the pH of the water generated by the electrochemical reaction is 3-5, and the operating temperature of the fuel cell stack is generally between 60℃ and 90℃, and the cold start temperature can reach -40℃. Therefore, the adhesive for sealing the frame of MEA needs to have good acid and moisture resistance, as well as high and low temperature adhesion. For a frame with good adhesive layer, the high temperature adhesion, i.e. the peel strength of the two frame adhesive films after adhesion at about 90℃, is small, which may cause the possibility of MEA sealing failure during the operation of the fuel cell. Therefore, if the high temperature adhesion of the frame adhesive film layer can be improved on the basis of meeting the requirements of acid and moisture resistance and low temperature, the reliability of MEA can be further improved. SUMMARY

[0004] In view of the poor high temperature adhesion of the frame adhesive film layer of the fuel cell frame involved in the prior art, the present application provides a sealing method and structure of a fuel cell frame.

[0005] To achieve the above-mentioned purpose, the following technical solutions are specifically included:

[0006] A sealing method of a fuel cell frame, comprising the following steps: coating a liquid treatment agent on a glue film layer in the fuel cell frame, and then bonding and sealing the glue film layer coated with the liquid treatment agent and a fuel cell assembly by hot pressing or ultraviolet light irradiation to obtain a fuel cell sealing structure; the liquid treatment agent is a mixed solution of an organic small molecule monomer and a free radical initiator; the fuel cell assembly comprises at least one of a fuel cell frame and a proton membrane.

[0007] Commercial fuel cell frame materials generally pre-coat an adhesive on a support material, and the adhesive is treated by heat treatment, pre-curing and the like to form a solid glue film with a certain adhesive viscosity, and the structure is shown in the accompanying Figure 1 The MEA assembly process is to assemble the CCM and the two layers of the frame, and then perform hot pressing to make the frame glue film adhere to the frame glue film and the CCM.

[0008] The inventors of the present application found that the failure interface is often glue surface / glue surface failure when testing the peel strength of the frame glue film and the frame glue film at high temperature, which indicates that the interaction between the glue surfaces is weak at high temperature. Therefore, the inventors believe that if the interaction between the glue films or the heat resistance can be enhanced, the adhesion of the frame at high temperature can be improved. Before bonding, the present application uses a liquid treatment agent to pretreat the surface of the fuel cell frame glue film. Since the organic small molecules in the liquid treatment agent can partially swell the glue films on the two layers of the frame, the organic small molecules enter the network structure formed by the two layers of the frame glue film, and under the condition of heat or light, the free radical initiator initiates the organic small molecules located in the network structure of the glue film to form a long-chain polymer network (polymer molecular chain double network) intermediate layer connecting the two layers of the glue film, and the structure is shown in the accompanying Figure 2 The intermediate layer enhances the interaction between the two layers of the glue film at the molecular level, and if the organic molecule monomer is selected appropriately, the intermediate layer can have a high glass transition temperature, so that the double-layer frame structure after the frame glue film and the frame glue film are adhered can have better adhesion strength in a high temperature environment.

[0009] The organic small molecule monomer added in the liquid treatment agent is a multi-functional cross-linking small molecule, which can further improve the glass transition temperature of the intermediate layer, enhance the double network structure of the two layers of the glue film and the intermediate layer, and further improve the adhesion strength of the double-layer frame in a high temperature environment.

[0010] As a preferred embodiment of the present application, the glue film layer of the fuel cell frame or the proton membrane in the fuel cell assembly is also treated by coating the liquid treatment agent, and the glue film layer of the fuel cell frame or the proton membrane coated with the liquid treatment agent in the fuel cell assembly is bonded and sealed with the glue film layer of the fuel cell frame coated with the liquid treatment agent.

[0011] As a preferred embodiment of the present application, the fuel cell frame comprises a support material and a film layer, the material of the support material comprises at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polypropylene (PP), polyethylene (PE); the material of the film layer comprises at least one of polyacrylate, epoxy, polyolefin, organosilicon.

[0012] As a preferred embodiment of the present application, the organic small molecule monomer comprises acrylic acid, acrylate monomer, acrylamide monomer, epoxy monomer, siloxane monomer, olefin monomer.

[0013] As a preferred embodiment of the present application, the free radical initiator comprises at least one of azo free radical initiator, peroxide free radical initiator, persulfide free radical initiator, photosensitive free radical initiator.

[0014] As a further preferred embodiment of the present application, the organic small molecule monomer is acrylic acid.

[0015] As a further preferred embodiment of the present application, the azo free radical initiator comprises at least one of azobisisobutyronitrile, benzoyl peroxide.

[0016] As a preferred embodiment of the present application, the thickness of the liquid treatment agent is 0.5-50μm.

[0017] As a further preferred embodiment of the present application, the thickness of the liquid treatment agent is 2μm.

[0018] As a preferred embodiment of the present application, the mass ratio of the organic small molecule monomer and the free radical initiator is 50-150:1.

[0019] As a further preferred embodiment of the present application, the mass ratio of the organic small molecule monomer and the free radical initiator is 100:1.

[0020] As a preferred embodiment of the present application, the temperature of the hot pressing is 100-160℃, the pressure of the hot pressing is 0.1-1Mpa, and the time of the hot pressing is 30-120s.

[0021] As a further preferred embodiment of the present application, the temperature of the hot pressing is 140℃, the pressure of the hot pressing is 0.5Mpa, and the time of the hot pressing is 60s.

[0022] As a preferred embodiment of the present application, the coating method is at least one of brushing and spraying.

[0023] The method for improving the high-temperature sealing performance of a fuel cell frame can be used to prepare a fuel cell sealing structure with good sealing performance under acidic, liquid or humid, low-temperature and high-temperature conditions, and improves the sealing reliability of the MEA under the operating conditions of the fuel cell stack.

[0024] Compared with the prior art, the present application has the following beneficial effects: the present application can effectively improve the adhesion performance of the frame, especially the adhesion performance under high temperature, by pretreating the frame adhesive film with a liquid treatment agent, and improves the sealing reliability of the MEA under the operating conditions of the fuel cell stack. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure 1 is a structural schematic diagram of a commercial fuel cell frame material.

[0026] Figure 2 Figure 2 is a schematic diagram of the sealing structure of a fuel cell according to the present application.

[0027] The above drawings include the following reference signs: 1, support material; 2, adhesive film; 3, intermediate layer; 4, organic small molecule monomer. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below through specific comparative examples and examples.

[0029] Example 1

[0030] Two pieces of fuel cell frame spare with a size of 70mmx100mm and a glue type of polyacrylate hot melt glue were cut. 10g of acrylic acid and 100mg of benzoyl peroxide were weighed into a sealed reagent bottle, and magnetically stirred at room temperature until the benzoyl peroxide was completely dissolved, to obtain a liquid treatment agent. A layer of liquid treatment agent with a thickness of about 2μm was coated on the surface of the frame adhesive film, and the two pieces of frame adhesive film were attached face to face, and hot-pressed at 140℃, 0.5Mpa for 60s to obtain a fuel cell frame sealing structure after adhesion and sealing. The fuel cell frame sealing structure was cut into a sample with a size of 20mmx100mm, and the 180° peeling strength test was carried out according to GB / T 2791-1995, and the test temperature was controlled by a high-low temperature environmental chamber.

[0031] Example 2

[0032] Two pieces of fuel cell frame with size of 70mm x 100mm and adhesive type of polyolefin hot melt adhesive were cut. 10g of acrylic acid and 100mg of azobisisobutyronitrile were weighed in a sealed reagent bottle, and the azobisisobutyronitrile was completely dissolved by magnetic stirring at room temperature to obtain a liquid treatment agent. A layer of the liquid treatment agent with a thickness of about 2μm was coated on the surface of the frame adhesive film, and the two pieces of frame adhesive film were attached face to face. The frame adhesive film was hot-pressed at 140°C and 0.5Mpa for 60s to obtain a sealed fuel cell frame structure. The fuel cell frame structure was cut into a sample with a size of 20mm x 100mm, and the 180° peeling strength was tested according to GB / T 2791-1995, and the test temperature was controlled by a high-low temperature environmental chamber.

[0033] Example 3

[0034] Two pieces of fuel cell frame with size of 70mm x 100mm and adhesive type of polyolefin hot melt adhesive were cut. 10g of acrylic acid and 100mg of azobisisobutyronitrile were weighed in a sealed reagent bottle, and the azobisisobutyronitrile was completely dissolved by magnetic stirring at room temperature to obtain a liquid treatment agent. A layer of the liquid treatment agent with a thickness of about 2μm was coated on the surface of the frame adhesive film, and the two pieces of frame adhesive film were attached face to face. The frame adhesive film was hot-pressed at 140°C and 0.5Mpa for 60s to obtain a sealed fuel cell frame structure. The fuel cell frame structure was cut into a sample with a size of 20mm x 100mm, and the 180° peeling strength was tested according to GB / T 2791-1995, and the test temperature was controlled by a high-low temperature environmental chamber.

[0035] Example 4

[0036] Two pieces of fuel cell frame with size of 70mm x 100mm and adhesive type of polyolefin hot melt adhesive were cut. 10g of acrylic acid and 100mg of azobisisobutyronitrile were weighed in a sealed reagent bottle, and the azobisisobutyronitrile was completely dissolved by magnetic stirring at room temperature to obtain a liquid treatment agent. A layer of the liquid treatment agent with a thickness of about 2μm was coated on the surface of the frame adhesive film, and the two pieces of frame adhesive film were attached face to face. The frame adhesive film was hot-pressed at 140°C and 0.5Mpa for 60s to obtain a sealed fuel cell frame structure. The fuel cell frame structure was cut into a sample with a size of 20mm x 100mm, and the 180° peeling strength was tested according to GB / T 2791-1995, and the test temperature was controlled by a high-low temperature environmental chamber.

[0037] Comparative Example 1

[0038] In comparison with Example 1, the frame of the comparative example was not coated with a liquid treatment agent.

[0039] Two pieces of fuel cell frame with size of 70mm x 100mm and adhesive type of polyolefin hot melt adhesive were cut. 10g of acrylic acid and 100mg of azobisisobutyronitrile were weighed in a sealed reagent bottle, and the azobisisobutyronitrile was completely dissolved by magnetic stirring at room temperature to obtain a liquid treatment agent. A layer of the liquid treatment agent with a thickness of about 2μm was coated on the surface of the frame adhesive film, and the two pieces of frame adhesive film were attached face to face. The frame adhesive film was hot-pressed at 140°C and 0.5Mpa for 60s to obtain a sealed fuel cell frame structure. The fuel cell frame structure was cut into a sample with a size of 20mm x 100mm, and the 180° peeling strength was tested according to GB / T 2791-1995, and the test temperature was controlled by a high-low temperature environmental chamber.

[0040] Comparative Example 2

[0041] Comparative Example 2, the frame of the present application is not coated with liquid treatment agent.

[0042] Two pieces of fuel cell frame with size of 70mmx100mm and adhesive type of polyolefin hot melt adhesive were prepared. The two pieces of frame were laminated with their adhesive films facing each other, and then hot pressed at 140℃ and 0.5Mpa for 60s to obtain the bonded sealing structure. The bonded sealing structure was cut into a sample with size of 20mmx100mm, and then tested for 180° peeling strength according to GB / T 2791-1995. The test temperature was controlled by a high-low temperature environmental chamber, and the test results are shown in Table 1.

[0043] Table 1 Peeling test results of sealing structure of examples and comparative examples

[0044]

[0045]

[0046] The peeling test results of sealing structure of examples and comparative examples are shown in Table 1. The sealing structure of the present application is formed by pretreating the frame adhesive film with liquid treatment agent before assembling the fuel cell, and the peeling force of the sealing structure at 90℃ test temperature is significantly improved compared with the comparative examples. For example 1 and 2, the peeling force is increased from about 0.7N to about 2.2N and from about 0.4N to about 1.9N, respectively. At the same time, for the frame containing polyacrylate adhesive, the peeling force of example 1 at 25℃ is also significantly improved compared with comparative example 1.

[0047] In summary, the method of pretreating the frame adhesive film with liquid treatment agent can effectively improve the bonding performance of the frame, especially the bonding performance at high temperature, and improve the sealing reliability of MEA under the operating conditions of fuel cell stack.

[0048] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application 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 application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method of sealing a fuel cell frame, characterized by, The method comprises the following steps: coating liquid treatment agent on the gasket layer of the fuel cell frame and the fuel cell assembly respectively, and then bonding and sealing the gasket layer coated with the liquid treatment agent and the fuel cell assembly by hot pressing or ultraviolet irradiation to obtain a fuel cell sealing structure; the liquid treatment agent is a mixed solution of organic small molecule monomers and a free radical initiator; the fuel cell assembly comprises at least one of a fuel cell frame and a proton membrane; the material of the gasket layer comprises at least one of polyacrylate, epoxy, polyolefin and organosilicon; the organic small molecule monomers comprise acrylic acid, acrylate monomers, acrylamide monomers, epoxy monomers, siloxane monomers and olefin monomers.

2. The method of sealing a fuel cell rim as recited in claim 1, wherein, The free radical initiator comprises at least one of azo free radical initiators, peroxide free radical initiators and persulfide free radical initiators.

3. The method of sealing a fuel cell rim as claimed in claim 2, wherein, The free radical initiator comprises at least one of azobisisobutyronitrile and benzoyl peroxide.

4. The method of sealing a fuel cell rim as recited in claim 1, wherein, The mass ratio of the organic small molecule monomers to the free radical initiator is 50-150:

1.

5. The method of sealing a fuel cell rim as recited in claim 4, wherein, The mass ratio of the organic small molecule monomers to the free radical initiator is 100:

1.

6. The method of sealing a fuel cell rim as recited in claim 1, wherein, The temperature of the hot pressing is 100-160 DEG C, the pressure of the hot pressing is 0.1-1 MPa, and the time of the hot pressing is 30-120 s.

7. The method of sealing a fuel cell rim as claimed in claim 6, wherein The temperature of the hot pressing is 140 DEG C, the pressure of the hot pressing is 0.5 MPa, and the time of the hot pressing is 60 s.

8. The method of sealing a fuel cell rim as recited in claim 1, wherein, The thickness of the liquid treatment agent is 0.5-50 microns.

9. The fuel cell sealing structure obtained by the sealing method of the fuel cell frame according to any one of claims 1-8.

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