Carbon paper as a substrate for gas diffusion layer, preparation method thereof, gas diffusion layer, membrane electrode assembly and fuel cell

Abstract

The present invention discloses a carbon paper substrate for a gas diffusion layer, wherein the resin carbon distribution in the carbon paper substrate for the gas diffusion layer has a fishbone or pine leaf structure. The gas diffusion layer using the structure can significantly reduce the resistivity of the gas diffusion layer, increase water vapor transmission, and the performance of a fuel cell stack prepared using the gas diffusion layer is significantly improved. The present application also discloses a corresponding preparation method, a gas diffusion layer, a membrane electrode assembly, and a fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and more particularly to a gas diffusion layer, a preparation method, a membrane electrode assembly and a fuel cell. Background Art

[0002] As an alternative energy technology, fuel cells have attracted widespread attention and continued to be researched and developed for their easy start-up, high energy density, zero emissions, and high energy conversion efficiency. They have been widely used as power sources for automobiles, communication base stations, portable power tools, etc. As a commercial power system, its outstanding advantages are that it must have a sufficiently long operating life and high energy density, such as backup power supplies, passenger cars, material transport vehicles, submarines, etc.

[0003] Proton exchange membrane fuel cells are the most mature and commercially applicable fuel cells. The gas diffusion layer (GDL) is an important component of proton exchange membrane fuel cells and is located between the flow field and the catalyst layer in the fuel cell. The gas diffusion layer has five main functions in the membrane electrode of the proton exchange membrane fuel cell: first, to support the proton exchange membrane and the catalyst layer; second, to transfer the cathode and anode reaction gases in the flow field flow channel to the catalyst surface through molecular diffusion and Knudsen transport; third, to transfer the electrons generated by the catalyst layer to the plate. Fourth, the water produced by the catalyst layer is transferred to the flow channel in the gas diffusion layer through capillary effect and concentration diffusion and is removed in time to avoid mass transfer polarization. Fifth: Sometimes, the gas diffusion layer assumes the function of attaching the catalyst layer and directly coats the catalyst layer on the surface of the gas diffusion layer.

[0004] In proton exchange membrane fuel cells, the resistance of the gas diffusion layer is a characteristic parameter of the ability to transmit electrons. Increased resistance will cause serious ohmic polarization problems, which will not only reduce battery performance, but also cause the temperature of the catalyst layer to rise due to heat, resulting in water loss in the proton exchange membrane, thereby reducing proton conduction efficiency. At the same time, as the electrochemical reaction gradually proceeds, the reaction product water will accumulate near the cathode catalyst layer. This water will not only diffuse through the proton exchange membrane to the anode, but also diffuse more through the cathode diffusion layer to the cathode flow field. If this liquid water cannot be transferred quickly, it will cause water accumulation in the diffusion layer, that is, flooding. As a result, the reaction gas cannot be transmitted to the catalyst surface in time, resulting in serious mass transfer polarization, resulting in a decrease in battery performance.

[0005] From the above description, it can be seen that how to reduce the resistance of the gas diffusion layer and ensure the gas transmission balance in the fuel cell to ensure that the fuel cell has good performance is an urgent problem to be solved in the field of fuel cells. Summary of the invention

[0006] The purpose of the present application is to solve the above-mentioned problems and to provide a carbon paper substrate for a gas diffusion layer that can reduce the flooding phenomenon in fuel cells and improve the mass transfer capacity.

[0007] In order to solve the above problems, some embodiments of the present application provide a carbon paper substrate for a gas diffusion layer, which has a fishbone-shaped or pine-leaf-shaped resin carbon distribution structure.

[0008] In some embodiments, the resin carbon is resin carbon formed by high-temperature carbonization and graphitization of one or more thermosetting or thermoplastic resins such as phenolic resin or epoxy resin.

[0009] In some embodiments, one or more of carbon black, graphite, graphene, carbon nanotubes, modified carbon nanotubes, etc. may be added to the thermosetting or thermoplastic resin such as the phenolic resin or epoxy resin.

[0010] In some embodiments, the carbon paper substrate of the gas diffusion layer has a thickness of 50 μm to 400 μm.

[0011] Other embodiments of the present application provide a method for preparing a substrate carbon paper for a gas diffusion layer, comprising the steps of: preparing base paper by a dry papermaking process or a wet papermaking process, wherein the base paper is mainly prepared from chopped carbon fibers and an adhesive; preparing a hot melt adhesive film using one or more of thermosetting or thermoplastic resins such as phenolic resin or epoxy resin, and pressing the prepared hot melt adhesive film in a mold or a round roller having fishbone-shaped or pine-needle-shaped patterns to form fishbone-shaped or pine-needle-shaped patterns; finally, laminating the base paper and the hot melt adhesive film together, and hot-pressing and curing them to prepare a composite paper; and subjecting the composite paper to carbonization and graphitization heat treatment to prepare the substrate carbon paper.

[0012] In some embodiments, the phenolic resin or epoxy resin needs to be preheated and softened in an oven before preparing the hot melt adhesive film, the temperature is 35-65°C, the temperature for coating or rolling into a film is 70-95°C, the temperature for the hot melt adhesive film to soak the base paper should be selected at 95-140°C, the hot pressing curing temperature is 140-185°C; the graphitization temperature is 1500-2850°C.

[0013] Some embodiments of the present application provide a gas diffusion layer, which is made based on any one of the above-mentioned substrate carbon papers.

[0014] Some embodiments of the present application provide a method for preparing a gas diffusion layer, which includes performing a hydrophobic treatment on the substrate carbon paper and coating a microporous layer on one side to prepare the gas diffusion layer.

[0015] Some embodiments of the present application provide a membrane electrode assembly, which includes: a cathode side gas diffusion layer, a cathode side catalyst layer, a proton exchange membrane, an anode side catalyst layer and an anode side gas diffusion layer stacked in sequence; wherein the cathode side gas diffusion layer and / or the anode side gas diffusion layer are the above-mentioned gas diffusion layers.

[0016] Some embodiments of the present application provide a fuel cell, which includes a fuel cell stack composed of the membrane electrode assembly, electrode plates, current collecting plates, insulating plates, sealing structures, end plates, etc. as described above.

[0017] The beneficial effect of the embodiments of the present application is that the resin carbon distribution has a fishbone or pine leaf structure. This is achieved by controlling the shape of the hot melt adhesive film. The unevenness of the fishbone or pine leaf structure causes differences in the distribution of phenolic resin or epoxy resin in different areas in the plane. Then, after hot melting, it is immersed in the base paper, and different areas contain different amounts of resin, thereby achieving differentiated dispersion of resin carbon. The gas diffusion layer with a fishbone or pine leaf-shaped resin carbon distribution can obtain a gas diffusion layer with structural differences between primary and secondary branches, and such a gas diffusion layer can guide water vapor transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 A schematic diagram of a preparation method provided by an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of a substrate carbon paper having a herringbone-shaped resin carbon distribution structure provided by an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of a substrate carbon paper having a pine leaf-like resin carbon distribution structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The gas diffusion layer of the present invention has a gas diffusion layer, characterized in that the resin carbon distribution in the carbon paper of the gas diffusion layer substrate has a fishbone or pine leaf structure. The distribution of the resin carbon is achieved by controlling the shape of the hot melt adhesive film, and the unevenness of the fishbone or pine leaf structure causes the distribution amount of the phenolic resin or epoxy resin in different areas in the plane to be different, and then after hot melting, it is immersed in the base paper, and different areas contain different amounts of resin, thereby achieving differentiated dispersion of the resin carbon.

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, Figure 1 A schematic flow chart of a carbon paper preparation method provided in an embodiment of the present invention, the preparation method comprising:

[0026] Step S11: After the carbon fibers are chopped, base paper is prepared by a dry papermaking process or a wet papermaking process;

[0027] Step S12: preparing a hot melt adhesive film using one or more thermosetting or thermoplastic resins such as phenolic resin or epoxy resin, and pressing the prepared hot melt adhesive film into a herringbone or pine needle-shaped pattern in a mold or a round roller having herringbone or pine needle-shaped patterns.

[0028] Step S13: The base paper and the hot-melt adhesive film are laminated together, and the hot-melt adhesive film is melted by hot pressing, and then soaked into the base paper, and finally solidified and formed to prepare a composite paper.

[0029] Step S14: heat-treating the composite paper prepared in step S13 in a carbonization and graphitization furnace to prepare carbon paper, such as Figure 2 , Figure 3 The substrate shown is carbon paper.

[0030] In combination with specific design parameters, sample 1 will be prepared using the technical solution of this application:

[0031] Sample 1: The resin carbon distribution in the gas diffusion layer substrate carbon paper prepared by the technical solution described in the embodiment of the present invention has a fishbone or pine leaf structure:

[0032] Preparation of hot melt adhesive film: 500g of phenolic resin, Mw = 7000g / mol, Mn = 1000g / mol, produced by Deqing Tiancheng Resin Co., Ltd., was placed in a constant temperature oven at 60°C and heated for 60 minutes to prepare a phenolic resin hot melt adhesive. Then the hot melt adhesive was placed on a smooth roller coating, the thickness was controlled to be 100um, and the hot melt adhesive film was rolled out and attached with release paper;

[0033] The hot melt adhesive film is placed on a hot press plane with a size of 500mm*500mm, a mold with a herringbone or pine leaf pattern is machined, and the hot melt adhesive film with a pattern is rolled at a surface pressure of 2MPa to prepare a hot melt adhesive film;

[0034] Place the steel plate coated with release agent on the flat vulcanizer and limit it with 200um steel bars around it. Place 700um thick base paper in the middle of the steel bar, and then cover the base paper with a hot melt adhesive film with fishbone or pine leaf patterns. Finally, cover the steel plate coated with release agent;

[0035] The flat plate vulcanizer was pressed down and maintained at a surface pressure of 4.5 MPa, and the temperature was raised to 120°C and maintained for 100 minutes to melt the hot melt adhesive film and soak into the base paper substrate. The temperature of the flat plate vulcanizer was then raised to 180°C and maintained for 6 hours to prepare the composite paper;

[0036] The composite paper was placed in a carbonization furnace at 800° C. for carbonization, and then transferred to a graphitization furnace at 2600° C. for graphitization treatment to obtain a gas diffusion layer substrate carbon paper with a thickness of 200 μm.

[0037] According to different preheating temperatures; coating or rolling film forming temperatures; the temperature at which the hot melt adhesive film is immersed in the base paper, the hot pressing curing temperature, the carbonization temperature and the graphitization temperature, the resin carbon distribution can be obtained to form a fishbone or pine leaf structure, as shown in Table 1:

[0038] Hot melt adhesive film material Preheating temperature (℃) Film forming temperature (℃) Immersion temperature (℃) Thermal curing temperature (°C) Carbonization temperature (℃) Graphitization temperature (℃) The resin carbon content in the ridge corresponding area is higher than that in the groove corresponding area (%) Example 1 Phenolic resin 35 70 95 140 500 1600 5% Example 2 Phenolic resin 45 85 120 160 700 2300 15% Example 3 Phenolic resin + carbon black 65 90 135 185 980 2850 30% Example 4 Epoxy resin 35 70 95 140 500 1800 5% Example 5 Epoxy resin 50 85 120 160 700 2500 15% Example 6 Epoxy resin + carbon black 65 90 140 185 980 2850 30%

[0039] In the method for preparing the carbon paper substrate of the gas diffusion layer of the embodiment of the present application, the phenolic resin or epoxy resin needs to be preheated and softened in an oven before preparing the hot-melt adhesive film, and the temperature is 35-65°C. The temperature for coating or rolling into a film is 70-95°C. The temperature at which the hot-melt adhesive film impregnates the base paper should be selected between 95 and 140°C, the hot pressing curing temperature is between 140 and 185°C, and the graphitization temperature is between 1500 and 2850°C.

[0040] An embodiment of the present application further provides a gas diffusion layer, which is made based on any one of the above-mentioned substrate carbon papers.

[0041] The embodiment of the present application also provides a method for preparing a gas diffusion layer, which comprises performing a hydrophobic treatment on the substrate carbon paper and coating a microporous layer on one side to prepare the gas diffusion layer.

[0042] An embodiment of the present application also provides a membrane electrode assembly, which includes: a cathode side gas diffusion layer, a cathode side catalyst layer, a proton exchange membrane, an anode side catalyst layer and an anode side gas diffusion layer stacked in sequence; wherein the cathode side gas diffusion layer and / or the anode side gas diffusion layer are the above-mentioned gas diffusion layers.

[0043] An embodiment of the present application further provides a fuel cell, which includes a fuel cell stack composed of the membrane electrode assembly, electrode plates, current collecting plates, insulating plates, sealing structures, end plates, etc. as described above.

[0044] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A carbon paper substrate for a gas diffusion layer, characterized in that: The resin carbon distribution in the carbon paper substrate of the gas diffusion layer has a fishbone or pine leaf structure; Wherein, the substrate carbon paper is prepared by the following steps: The base paper is prepared from chopped carbon fibers and a binder by a dry paper-making process or a wet paper-making process; A hot melt adhesive film is prepared using one or more thermosetting or thermoplastic resins, wherein the hot melt adhesive film is pressed from a mold or a round roller having a herringbone-shaped or pine-leaf-shaped pattern to form a herringbone-shaped or pine-leaf-shaped pattern; The base paper and the hot melt adhesive film are laminated together, and the hot melt adhesive film is melted and then immersed in the base paper by heat pressing, and composite paper is prepared by curing and molding; different areas contain different amounts of resin, thereby achieving differentiated dispersion of resin carbon; The composite paper is subjected to carbonization and graphitization heat treatment to prepare carbon paper, and the resin carbon distribution in the carbon paper has a fishbone-like or pine-leaf-like structure.

2. The carbon paper substrate for the gas diffusion layer according to claim 1, characterized in that: The resin carbon is resin carbon formed by carbonizing and graphitizing one or more thermosetting or thermoplastic resins at high temperature.

3. The carbon paper substrate for the gas diffusion layer according to claim 1, characterized in that: The thermosetting or thermoplastic resin is a phenolic resin or an epoxy resin.

4. The carbon paper substrate for the gas diffusion layer according to claim 1, characterized in that: One or more of carbon black, graphite, graphene, carbon nanotubes, and modified carbon nanotubes are added to the thermosetting or thermoplastic resin.

5. The carbon paper substrate for the gas diffusion layer according to claim 1, characterized in that: The thickness of the carbon paper substrate of the gas diffusion layer is 50 μm to 400 μm.

6. The carbon paper substrate for the gas diffusion layer according to claim 3, characterized in that: The phenolic resin needs to be preheated and softened in an oven before preparing the hot-melt adhesive film, and the temperature is 35-65°C. The temperature for coating or rolling into a film is 70-95°C. The temperature for the hot-melt adhesive film to be immersed in the base paper is selected at 95-140°C, and the curing temperature is 140-185°C. The epoxy resin needs to be preheated and softened in an oven before preparing the hot-melt adhesive film, and the temperature is 35-65°C. The temperature for coating or rolling into a film is 70-95°C. The temperature for the hot-melt adhesive film to be immersed in the base paper is selected at 95-140°C, and the curing temperature is 140-185°C; the graphitization temperature is 1500-2850°C.

7. A gas diffusion layer, characterized in that: The gas diffusion layer according to any one of claims 1 to 6 is formed from a substrate carbon paper.

8. A membrane electrode assembly, characterized in that: The membrane electrode assembly comprises: A cathode side gas diffusion layer, a cathode side catalyst layer, a proton exchange membrane, an anode side catalyst layer and an anode side gas diffusion layer are sequentially stacked; Wherein, the cathode-side gas diffusion layer and / or the anode-side gas diffusion layer comprises the gas diffusion layer as claimed in claim 7.

9. A fuel cell, characterized in that: The fuel cell comprises: a fuel cell stack consisting of the membrane electrode assembly as claimed in claim 8, a polar plate, a current collecting plate, an insulating plate, a sealing structure, and an end plate.

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