A composite structure integrated half-cell and preparation method thereof

Abstract

The present invention belongs to the field of hydrogen fuel cells, and in particular, relates to an integrated half-cell of a novel composite structure and a preparation method thereof, the method comprising the following steps: stamping a sealing groove, a transition zone and a lowering area of ​​an active zone on a stainless steel substrate to obtain a cathode monopolar plate substrate and an anode monopolar plate substrate without a flow field, and then welding them together to obtain a bipolar plate substrate without a flow field; molding a graphite flow channel on one side of carbon paper and depositing a carbon microporous layer on the other side to obtain an anode flow field carbon paper and a cathode flow field carbon paper, and assembling to obtain an integrated half-cell. The above method reduces the processing cost of hydrogen fuel cells, and the integrated half-cell prepared by the above method can greatly reduce the complexity of stack assembly and help improve the performance of the stack.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cells, and in particular relates to a composite structure integrated half-cell and a preparation method thereof. Background Art

[0002] Hydrogen fuel cells are generally composed of two parts: a stack and an auxiliary system. The stack is generally divided into two types: a metal bipolar plate stack (hereinafter referred to as a metal stack) and a graphite bipolar plate stack (hereinafter referred to as a graphite stack). The graphite stack has the characteristics of low price and good operation in harsh environments, so it has attracted widespread attention. The advantages of the metal stack, such as ultra-thin thickness due to the scale of stainless steel production, high-speed production efficiency of stamping and sufficient mechanical strength, have also attracted a lot of research and development efforts in the industry.

[0003] The existing graphite plate stacks have the following defects that need to be solved: (1) The strength of the graphite plate is the priority, and a certain thickness is required to ensure the mechanical properties of the material, thus limiting the volume power of the graphite stack; (2) During long-term durability operation, the diffusion layer and the catalytic layer of the membrane electrode are prone to mutual penetration, which prevents Pt from fully reacting and causes insufficient exposure of the crystal surface. In metal stacks, the processing technology of metal bipolar plates has always limited its cost, mainly because: (1) The pre-coating process is easily damaged when stamping complex flow field structures; (2) Complex flow field structures are also difficult for stamping processes, and the yield rate is not high; (3) The cost of the post-coating technology development route remains high. Summary of the invention

[0004] In view of the technical problems that the existing graphite plate battery stack has a large thickness and the metal plate battery stack has a high processing cost, the present invention proposes a composite structure integrated half-cell with low processing cost and excellent battery stack performance and a preparation method thereof.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a composite structure integrated half-cell comprises the following steps:

[0007] (1) stamping a sealing groove, a transition zone, and a lowered surface area of ​​an active zone on a pre-coated stainless steel substrate to obtain a cathode monopolar plate substrate and an anode monopolar plate substrate without a flow field;

[0008] (2) pasting a water field conductive flow guide structure between the cathode monopolar plate substrate and the anode monopolar plate substrate and then welding them, and pasting a sealing gasket in the sealing groove to obtain a flow field-free bipolar plate substrate;

[0009] (3) Cut two pieces of carbon paper to serve as the base skeleton of the gas flow channel and diffusion layer;

[0010] (4) ball-milling and dry-mixing the graphite, resin and conductive filler to obtain a blended material, and using a molding machine to mold sequentially arranged strip ridges on one side of the carbon paper to obtain an anode flow field carbon paper and a cathode flow field carbon paper;

[0011] (5) sputtering a carbon microporous layer on the blank side of the cathode flow field carbon paper and the anode flow field carbon paper by a magnetron sputtering device to obtain a cathode carbon paper skeleton and an anode carbon paper skeleton;

[0012] (6) Arrange the flow field-free bipolar plate substrate, cathode carbon paper skeleton, catalyst-loaded membrane, and anode carbon paper skeleton in order and mold them by hot pressing to obtain an integrated half-cell.

[0013] Preferably, in step (4), the mass ratio of graphite, resin and conductive filler is (0.4-0.6):(0.3-0.5):(0.01-0.2).

[0014] Preferably, the conductive filler is one or more of carbon nanotubes, chopped carbon fibers with a length of 0.5 mm to 2 mm, and transition metal powder.

[0015] Preferably, the molding process in step (4) is to place the carbon paper in a molding machine, place the runner mold on the carbon paper, and then heat the blended material to a molten state and inject it into an injection mold for molding. The molding pressure is 5 to 40 MPa, nine molding sections, and the molding time is 10 to 20 minutes.

[0016] Preferably, the carbon microporous layer has a thickness of 50 μm to 100 μm.

[0017] Preferably, in step (5), the magnetron sputtering reaction gas is acetylene, the sputtering gas is argon, the gas partial pressure P (acetylene) / P (argon) is 0.2, the total pressure of the deposition gas is set to 5 Pa, the DC sputtering current is 5 A, the substrate bias is 150 V, the substrate temperature is 200 ° C, and the distance between the substrate and the target is 80 mm.

[0018] Preferably, in step (6), the hot pressing time is 90 to 120 seconds, the hot pressing pressure is 90 to 120 MPa, and the hot pressing temperature is 90 to 120°C.

[0019] Preferably, the strip ridge is trapezoidal.

[0020] The present invention also provides a composite structure integrated half-cell, which is prepared by the above-mentioned composite structure integrated half-cell preparation method.

[0021] Compared with the prior art, the advantages and positive effects of the present invention are:

[0022] (1) The composite structure integrated half-cell of the present invention uses a metal plate without complex flow channels as the substrate, and does not need to stamp complex flow channels, which reduces the difficulty of stamping the metal plate. The substrate can be a thinner metal substrate, making the hydrogen fuel cell lighter and thinner, while ensuring its mechanical strength and saving a lot of mold opening costs and improving the yield rate.

[0023] (2) Carbon paper is used as the gas mass transfer skeleton. Through the idea of ​​additive manufacturing, a flow field structure is injection molded on one side of the carbon paper, and a carbon microporous layer is grown on the other side by magnetron sputtering technology as a diffusion layer. The diffusion layer is firmly bonded to the carbon paper, which reduces the problem of mutual diffusion between the diffusion layer and the catalyst layer after long-term operation, and helps to improve the durability of the fuel cell stack.

[0024] (3) The present invention concentrates all mass transfer structures on the carbon paper, which is then hot-pressed and bonded to the metal substrate, which greatly reduces the contact resistance and helps improve the performance of the fuel cell stack.

[0025] (4) The integrated structure can significantly reduce the complexity of fuel cell stack assembly, reduce the possibility of component misalignment, and improve the gas tightness of the fuel cell stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The schematic diagram of the molding step of the preparation method of the composite structure integrated half-cell of the present invention;

[0027] Figure 2 It is a schematic diagram of the overall structure of the integrated half-cell of the present invention;

[0028] Figure 3 An exploded view of the integrated half-cell of the present invention;

[0029] Figure 4 It is a schematic diagram of the cross-sectional structure of the integrated half-cell of the present invention;

[0030] In the above figures: 1. cathode monopolar plate substrate; 2. anode monopolar plate substrate; 3. sealing gasket; 4. cathode carbon paper skeleton; 5. anode carbon paper skeleton; 6. carbon ridge; 7. flow channel; 8. catalyst loading membrane; 9. water field conductive and diverting structure; 10. carbon paper; 11. flow channel mold; 12. pressure mold; 13. blended material. DETAILED DESCRIPTION

[0031] In order to better understand the present invention, a detailed description is given below in conjunction with the accompanying drawings and embodiments.

[0032] Example: Figure 1-4As shown, a method for preparing a composite structure integrated half-cell includes the following steps: stamping a sealing groove, a transition zone, and a lowered surface area of ​​an active zone on a pre-coated stainless steel substrate to obtain a cathode monopolar plate substrate 1 and an anode monopolar plate substrate 2 without a flow field. Paste a water field conductive guide structure 9 between the cathode monopolar plate substrate and the anode monopolar plate substrate. The water field conductive guide structure is a rubber strip, a metal strip, or a composite conductive material with a conductive function, etc., arranged in a certain order to form a guide channel. Thereafter, the cathode monopolar plate substrate and the anode monopolar plate substrate are placed on a laser welding fixture for water field welding and sealing. Finally, the bipolar plate welded as one is pasted with a prefabricated sealing gasket 3 to assemble into a bipolar plate substrate without a flow field.

[0033] Cut two pieces of Toray carbon paper TGP-H-060 (300mm×100mm) as the anode and cathode gas mass transfer skeleton. Figure 1 As shown, two sheets of carbon paper 10 are placed in a molding machine with anode and cathode flow channels for standby use. 40g of expanded graphite, 30g of phenolic resin, and 2g of 50-mesh carbon fiber are weighed and blended in a ball mill for 0.5h. 30g of the blended material 13 is weighed and hot-melted and injected into the flow channel molds 11 of the two molding machines, and 5-35MPa, 9 molding sections, and a pressure mold 12 are used for molding for 15min. Trapezoidal carbon ridges arranged in sequence are molded on the upper surface of the carbon paper, and flow channels are formed between two adjacent carbon ridges, so as to obtain two carbon paper skeletons with flow channel structures on one side, namely, the cathode carbon paper skeleton 4 and the anode carbon paper skeleton 5, as the anode and cathode gas mass transfer skeletons.

[0034] The cathode carbon paper skeleton 4 and the anode carbon paper skeleton 5 are placed on the substrate of the magnetron sputtering apparatus respectively, and the smooth side of the carbon paper (i.e., the side without molded flow channel) is facing the target. The reaction gas is acetylene and the sputtering gas is argon. The gas partial pressure P (acetylene) / P (argon) is 0.2, the total pressure of the deposition gas is set to 5Pa, the DC sputtering current is 5A, the substrate bias is 150V, the substrate temperature is 200°C, and the distance between the substrate and the target is 80mm. During the magnetron sputtering process, a 50μm carbon microporous layer is sputtered and grown on the carbon paper, and finally a flow channel-diffusion layer integrated gas mass transfer skeleton is obtained. During the preparation process of the carbon microporous layer, the carbon paper pores will be partially invaded by 20 to 30μm, thereby forming a pore gradient from the surface to the inside, with better drainage capacity, and the sputtered carbon microporous layer is not easy to fall off.

[0035] The flow-free bipolar plate substrate, cathode carbon paper skeleton 4, catalyst-loaded membrane 8, and anode carbon paper skeleton 5 are bonded together using a pressure-sensitive adhesive. The carbon microporous layers of the cathode carbon paper skeleton and the anode carbon paper skeleton are bonded to the catalyst-loaded membrane, and catalysts are adhered to both sides of the catalyst-loaded membrane. The mold is pressed by hot pressing for 100 seconds, 100 MPa hot pressing pressure, and 100 ° C hot pressing temperature to obtain an integrated half-cell (specific structure as shown in FIG. Figure 2-490 integrated half-cells are positioned and assembled, and the end plates, anode insulating plates, anode current collecting plates, anode special monopolar plates, 90 integrated half-cells, cathode current collecting plates, cathode insulating plates, and end plates are assembled to obtain the final stack.

[0036] The composite structure integrated half-cell described in the present invention uses a metal plate without complex flow channels as the substrate, which reduces the difficulty of traditional metal plate stamping. A thinner metal substrate can be used to make the half-cell thinner and lighter, ensuring its mechanical strength while saving a lot of mold opening costs and improving the yield rate. Carbon paper is used as the gas mass transfer skeleton. Through the idea of ​​additive manufacturing, a flow field structure is injection molded on one side of the carbon paper and a carbon microporous layer is grown on the other side by magnetron sputtering technology as a diffusion layer. The diffusion layer is firmly combined with the carbon paper, which reduces the problem of mutual diffusion between the diffusion layer and the catalyst layer after long-term operation, which helps to improve the durability of the battery stack. At the same time, all the mass transfer structures are concentrated on the carbon paper and then hot-pressed with the metal substrate, which greatly reduces the contact resistance and helps to improve the performance of the battery stack. The integrated structure can greatly reduce the complexity of the battery stack assembly, reduce the possibility of component misalignment, and the air tightness of the battery stack will also be improved.

[0037] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite structure integrated half-cell, characterized in that: The following steps are involved: (1) stamping a sealing groove, a transition zone, and a lowered surface area of ​​an active zone on a pre-coated stainless steel substrate to obtain a cathode monopolar plate substrate and an anode monopolar plate substrate without a flow field; (2) pasting a water field conductive flow guide structure between the cathode monopolar plate substrate and the anode monopolar plate substrate and then welding them, and pasting a sealing gasket in the sealing groove to obtain a flow field-free bipolar plate substrate; (3) Cut two pieces of carbon paper to serve as the base skeleton of the gas flow channel and diffusion layer; (4) ball-milling and dry-mixing graphite, resin and conductive filler to obtain a blended material, and using a molding machine to mold sequentially arranged strip ridges on one side of the carbon paper to obtain anode flow field carbon paper and cathode flow field carbon paper; wherein the mass ratio of graphite, resin and conductive filler is (0.4-0.6): (0.3-0.5): (0.01-0.2), and the conductive filler is one or more of carbon nanotubes, short-cut carbon fibers with a length of 0.5 mm to 2 mm and transition metal powder; (5) sputtering a carbon microporous layer on the blank side of the cathode flow field carbon paper and the anode flow field carbon paper by a magnetron sputtering device to obtain a cathode carbon paper skeleton and an anode carbon paper skeleton; (6) Arrange the flow field-free bipolar plate substrate, cathode carbon paper skeleton, catalyst-loaded membrane, and anode carbon paper skeleton in order and mold them by hot pressing to obtain an integrated half-cell.

2. The method for preparing a composite structure integrated half-cell according to claim 1, characterized in that: The molding process in step (4) is to place the carbon paper in a molding machine, place the runner mold on the carbon paper, and then heat the blended material to a molten state and inject it into the injection mold for molding. The molding pressure is 5 to 40 MPa, nine molding sections, and the molding time is 10 to 20 minutes.

3. The method for preparing a composite structure integrated half-cell according to claim 1, characterized in that: The carbon microporous layer has a thickness of 50 μm to 100 μm.

4. The method for preparing a composite structure integrated half-cell according to claim 1, characterized in that: In step (5), the magnetron sputtering reaction gas is acetylene, the sputtering gas is argon, the gas partial pressure P (acetylene) / P (argon) is 0.2, the total pressure of the deposition gas is set to 5 Pa, the DC sputtering current is 5 A, the substrate bias is 150 V, the substrate temperature is 200 ° C, and the distance between the substrate and the target is 80 mm.

5. The method for preparing a composite structure integrated half-cell according to claim 1, characterized in that: In step (6), the hot pressing time is 90 to 120 seconds, the hot pressing pressure is 90 to 120 MPa, and the hot pressing temperature is 90 to 120°C.

6. The method for preparing a composite structure integrated half-cell according to claim 1, characterized in that: The strip ridge is trapezoidal.

7. A composite structure integrated half-cell, characterized in that: The composite structure integrated half-cell is prepared by the preparation method of any one of claims 1 to 6.

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