Membrane electrode assembly for fuel cell and manufacturing method thereof

Abstract

The present invention relates to a membrane electrode assembly for a fuel cell and a method for manufacturing the same. More specifically, the membrane electrode assembly for a fuel cell according to the present invention comprises an electrode having a catalyst layer of high porosity and a catalyst layer of low porosity, and an adhesive layer positioned between the electrode and a polymer electrolyte membrane, so that improved durability and performance can be obtained.

Description

Technical Field

[0001] The present invention relates to a membrane electrode assembly for a fuel cell and a manufacturing method thereof. Background Art

[0002] Fuel cells are power generation systems that directly convert the chemical reaction energy of hydrogen and oxygen contained in hydrocarbons such as methanol, ethanol, and natural gas into electricity. A representative example of this type of fuel cell is the polymer electrolyte membrane fuel cell (PEMFC). These PEMFCs are attracting attention as power sources for portable devices, vehicles, and homes due to their advantages, such as an operating temperature below 100°C, fast startup and response times, and excellent durability.

[0003] In these fuel cell systems, the membrane electrode assembly (MEA), which actually generates electricity, has an electrolyte membrane sandwiched between an anode electrode (called the fuel electrode or oxidation electrode) and a cathode electrode (called the air electrode or reduction electrode). This electrolyte is an electrically insulating but ionically conductive membrane. Protons generated at the anode pass through the membrane to the cathode, where they combine with oxygen to form water.

[0004] Among membrane electrode assembly (MEA) manufacturing technologies, the transfer printing method offers advantages in mass production due to its ease of controlling the thickness and area of the catalyst layer. Furthermore, this method, which corresponds to the CCM (Catalyst Coated Membrane) method, in which the electrode layer is formed on the membrane, has the advantage of lowering the contact resistance between the membrane and the catalyst layer compared to the CCG (Catalyst Coated GDL) method, in which the catalyst layer is coated on the gas diffusion layer.

[0005] However, conventional transfer printing methods for membrane electrode assembly (MEAs) manufacturing result in uneven bonding between the electrolyte membrane and the electrodes, resulting in weak adhesion and high resistance, low output, and poor durability. Furthermore, high-pressure pressing can create insufficient porosity within the electrodes, negatively impacting oxygen diffusion and water discharge from the cathode. Summary of the Invention

[0006] Technical issues

[0007] The object of the present invention is to provide a membrane electrode assembly for a fuel cell, a fuel cell including the same, and a method for manufacturing the membrane electrode assembly, wherein the membrane electrode assembly improves the gas diffusion and moisture discharge capabilities of the electrode and has excellent bonding strength between the electrode and the electrolyte membrane.

[0008] Technical Solution

[0009] According to one aspect of the present invention, a membrane electrode assembly for a fuel cell is provided, comprising: a polymer electrolyte membrane; a first adhesive layer located on the polymer electrolyte membrane; a second adhesive layer located on the first adhesive layer; a first catalyst layer with low porosity located on the second adhesive layer; and a second catalyst layer with high porosity located on the first catalyst layer with low porosity, wherein the first adhesive layer contains a plasticizer and a cross-linking agent, and the second adhesive layer contains an ion-conductive polymer.

[0010] According to one embodiment, the plasticizer may be at least one selected from the group consisting of (poly)alkylene glycol, dihydroxybenzene, (poly)alkylene glycol dialkyl ether, benzoquinones, dialkyl phthalate, and copolymers thereof.

[0011] According to one embodiment, the plasticizer may be at least one selected from polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, tetraethylene glycol, dihydroxybenzene, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, benzoquinone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate and copolymers thereof.

[0012] According to one embodiment, the cross-linking agent may have a functional group capable of forming a hydrogen bond cross-link with the ion-conductive polymer.

[0013] According to one embodiment, the cross-linking agent may have a carbonyl group (-CO-), a hydroxyl group (-OH), a carboxyl group (-COOH), a nitro group (-NO2) and an amino group (-NR 1 R 2 )(where R 1 and R 2 Each is independently H, a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C6-C12 aryl group, or is combined with each other to form at least one functional group selected from the group consisting of a C2-C5 heterocycle.

[0014] According to one embodiment, the cross-linking agent can be substituted or unsubstituted benzoquinone, substituted or unsubstituted naphthoquinone, substituted or unsubstituted dihydroxybenzene, substituted or unsubstituted phthalic acid, substituted or unsubstituted aminophenol, substituted or unsubstituted phenylenediamine, substituted or unsubstituted bipyridinediamine, substituted or unsubstituted di(aminophenyl)amine, substituted or unsubstituted bipyrrole, or a mixture of two or more thereof.

[0015] According to one embodiment, the weight ratio of the plasticizer to the cross-linking agent may be 5:1 to 1:1.

[0016] According to one embodiment, the ion conductive polymer is a cationic conductor having a proton exchange group, and the proton exchange group may be at least one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boric acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and a combination thereof.

[0017] According to one embodiment, the ion-conductive polymer may be a fluorine-based cation conductor having a sulfonic acid group and / or a carboxyl group, a hydrocarbon-based cation conductor having a sulfonic acid group and / or a carboxyl group, or a mixture thereof.

[0018] According to one embodiment, the first catalyst layer and the second catalyst layer may each contain a first ion conductive polymer and a second ion conductive polymer, and the ion conductive polymer of the second adhesive layer may be the same as at least one of the first ion conductive polymer and the second ion conductive polymer.

[0019] According to one embodiment, the thickness of the first adhesive layer and the second adhesive layer may each independently be 0.01 μm to 5 μm.

[0020] According to one embodiment, the second catalyst layer with high porosity may have a three-dimensional network structure.

[0021] According to one embodiment, the high-porosity second catalyst layer may contain at least one fiber-forming polymer selected from the group consisting of polyether polyurethane, polyvinyl acetate (PVAc), polyvinyl acetate copolymer, polyvinyl alcohol (PVA), polyfurfuryl alcohol (PPFA), polyurethane, polyurethane copolymer including polyether polyurethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic acid copolymer, polystyrene, polystyrene copolymer, polyethylene, polyethylene glycol, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl acetal, polyvinyl chloride (PVC), polycaprolactone, polyvinyl pyrrolidone (PVP), polyvinyl fluoride, polyvinylidene fluoride copolymer and polyamide.

[0022] According to one embodiment, the porosity of the low-porosity first catalyst layer may be 1% to 50% and the pore size may be 10nm to 500nm, and the porosity of the high-porosity second catalyst layer may be 50% to 90% and the pore size may be 500nm to 5000nm.

[0023] According to one embodiment, the thickness of the first catalyst layer with low porosity may be greater than or equal to 1 μm and less than or equal to 10 μm, and the thickness of the second catalyst layer with high porosity may be greater than or equal to 1 μm and less than or equal to 20 μm.

[0024] According to another aspect of the present invention, a method for manufacturing a membrane electrode assembly for a fuel cell is provided, comprising: step (a), forming a first catalyst layer with low porosity on a substrate; step (b), forming a second adhesive layer containing an ion-conductive polymer on the first catalyst layer with low porosity; step (c), forming a first adhesive layer containing a plasticizer and a cross-linking agent on the second adhesive layer; step (d), positioning the first adhesive layer to face one or both sides of a polymer electrolyte membrane, and then bonding them; step (e), removing the substrate; and step (f), forming a second catalyst layer with high porosity on the first catalyst layer with low porosity.

[0025] According to one embodiment, in step (b), the second adhesive layer may be formed by coating a solution containing the ion conductive polymer, and the content of the ion conductive polymer in the solution may be 0.5 wt % to 60 wt % based on the total weight of the solution.

[0026] According to one embodiment, in step (c), the first adhesive layer may be formed by coating a solution containing the plasticizer and the crosslinker, and the total content of the plasticizer and the crosslinker in the solution may be 0.5 wt % to 60 wt % based on the total weight of the solution.

[0027] According to one embodiment, in the step (f), the second catalyst layer may be formed by spinning a spinning solution prepared by mixing a catalyst, an ion-conductive polymer, a fiber-forming polymer, and a solvent.

[0028] According to another aspect of the present invention, a fuel cell is provided, including a membrane electrode assembly.

[0029] Beneficial effects

[0030] The membrane electrode assembly of the present invention can be manufactured at lower temperatures and pressures than conventional high-temperature, high-pressure manufacturing methods. This low-temperature transfer method has the advantage of preventing degradation of the ionomer in the electrode and reducing deformation of the polymer electrolyte membrane and release film due to temperature and pressure, thereby improving production quality.

[0031] In addition, since the bonding is carried out at a lower temperature and pressure than the prior art, the problem of excessive pore loss due to densification under high temperature and high pressure can be solved, and since the electrode also has a high-porosity catalyst layer, the porosity of the entire membrane electrode assembly is excellent. Therefore, the membrane electrode assembly of the present invention has a lower mass transfer resistance. In addition, by combining a high-porosity catalyst layer with a low-porosity catalyst layer, the charge transfer resistance can be reduced compared to a catalyst layer consisting only of a high-porosity catalyst layer. Moreover, since the excellent gas diffusivity and moisture discharge capacity of the electrode can be maintained while increasing the bonding force between the electrode and the electrolyte membrane through the adhesive layer, the durability and performance of the membrane electrode assembly are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure is a cross-sectional view schematically showing a membrane electrode assembly according to an embodiment of the present invention.

[0033] Figure 2 FIG. 1 is a schematic diagram showing the overall structure of a fuel cell according to an embodiment of the present invention.

[0034] Figure 3 The membrane electrode assemblies prepared in comparative examples and examples of the present invention are shown. Figure 3 Parts (a) to (d) correspond to comparative examples 1 to 4, respectively, and part (e) corresponds to Example 1 and Example 2.

[0035] Figure 4 The tensile test results of Experimental Example 1 are shown. DETAILED DESCRIPTION

[0036] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various forms and is not limited to the embodiments described herein.

[0037] To clearly illustrate the various layers and regions in the drawings, the thickness is exaggerated, and the same reference numerals are used for similar parts throughout the specification. When a part (such as a layer, film, region, or plate) is referred to as being "above" or "on" another part, this includes not only the case where it is "directly above" another part, but also the case where there are other parts in between. Conversely, when a part is "directly above" another part, it means that there are no other parts in between.

[0038] As used herein, the terms "including" and "comprising" are used to list materials, compositions, devices and methods useful in the present invention, but are not limited to the listed examples.

[0039] Below, we will refer to Figure 1 A membrane electrode assembly for a fuel cell according to one aspect is described.

[0040] According to one aspect of the present invention, a membrane electrode assembly 100 for a fuel cell is provided, comprising: a polymer electrolyte membrane 50; a first adhesive layer 11, 11', located on the polymer electrolyte membrane 50; a second adhesive layer 12, 12', located on the first adhesive layer 11, 11'; a first catalyst layer 21, 21' with low porosity, located on the second adhesive layer 12, 12'; and a second catalyst layer 22, 22' with high porosity, located on the first catalyst layer 21, 21' with low porosity, wherein the first adhesive layer 11, 11' contains a plasticizer and a cross-linking agent, and the second adhesive layer 12, 12' contains an ion conductive polymer.

[0041] The first adhesive layers 11 and 11' are layers in contact with the polymer electrolyte membrane 50 and contain a plasticizer and a cross-linking agent.

[0042] The plasticizer may be a plasticizer added during the manufacture of a general solid electrolyte membrane to control the ion migration characteristics and processability of the solid electrolyte, and a compound modified to contain one or more functional groups capable of cross-linking with the polymer electrolyte or the ion conductive polymer in the second adhesive layer may also be used as the plasticizer.

[0043] The plasticizer can be one or more of an aliphatic compound and an aromatic compound selected from the group consisting of a hydroxyl end, an ether end or an ester end. Specifically, the example of the plasticizer can include at least one selected from the group consisting of (poly) alkylene glycol, dihydroxybenzene, (poly) alkylene glycol dialkyl ether, benzoquinones, dialkyl phthalate and their copolymers, wherein the alkylene group can be a C1-C10 alkylene group. For example, the plasticizer can be at least one selected from polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, tetraethylene glycol, dihydroxybenzene, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, benzoquinone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate and their copolymers.

[0044] The weight average molecular weight of the plasticizer may be 10 to 10,000 g / mol or less, for example, 100 to 9,000 g / mol. When the weight average molecular weight of the plasticizer is greater than 10,000 g / mol, hydrogen ion transfer resistance increases, which may reduce fuel cell performance.

[0045] The crosslinking agent may have a functional group capable of forming hydrogen bonds with the ion-conductive polymer. If the amount of the plasticizer is large, the physical properties may deteriorate at low temperatures or become difficult to maintain in a gel state. This can be improved by adding a crosslinking agent. Therefore, it is preferred to further include a crosslinking agent that can stabilize the first adhesive layer 11, 11′ containing the plasticizer at room temperature and form hydrogen bonds by reacting with, for example, the carboxyl or sulfonic acid groups of the ion-conductive polymer.

[0046] For example, the cross-linking agent may have a group selected from carbonyl (-CO-), hydroxyl (-OH), carboxyl (-COOH), nitro (-NO2) and amino (-NR 1 R 2 )(where R 1 and R 2 Each is independently H, a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C6-C12 aryl group, or is combined with each other to form at least one functional group selected from the group consisting of a C2-C5 heterocycle.

[0047] The cross-linking agent may be a cyclic compound. For example, the organic compound may be an aromatic compound, an alicyclic compound, a heterocyclic compound, or a homocyclic compound.

[0048] According to one embodiment of the present invention, the cross-linking agent can be substituted or unsubstituted benzoquinone, substituted or unsubstituted naphthoquinone, substituted or unsubstituted dihydroxybenzene, substituted or unsubstituted phthalic acid, substituted or unsubstituted aminophenol, substituted or unsubstituted phenylenediamine, substituted or unsubstituted bipyridinediamine, substituted or unsubstituted di(aminophenyl)amine, substituted or unsubstituted bipyrrole, or a mixture of two or more thereof.

[0049] More specifically, the cross-linking agent may include, but is not limited to, at least one member selected from the group consisting of the following compounds.

[0050]

[0051] The thickness of the first adhesive layer 11, 11' can be 0.01 μm to 5 μm, specifically 0.1 μm to 3 μm, and more specifically 0.1 μm to 1 μm. By setting the thickness within the above range, the adhesion between the polymer electrolyte membrane and the electrode can be improved while maintaining battery performance such as output and capacity and mechanical properties.

[0052] The second adhesive layer 12, 12' is a layer in contact with the catalyst layer of the electrode and contains an ion conductive polymer. The ion conductive polymer can be the catalyst layer of the electrode, specifically the ion conductive polymer contained in the first catalyst layer 21, 21' or the second catalyst layer 22, 22'.

[0053] The ion conductive polymer may be a cation conductor having a proton exchange group, wherein the cation exchange group is at least one selected from the group consisting of sulfonic acid group, carboxyl group, boric acid group, phosphoric acid group, imide group, sulfonimide group, sulfonamide group, sulfonyl fluoride group and combinations thereof.

[0054] The ion-conducting polymer may be a fluorine-based cation conductor, a hydrocarbon-based cation conductor, or a mixture thereof. Specifically, the ion-conducting polymer of one embodiment of the present invention may be a fluorine-based cation conductor having a sulfonic acid group and / or a carboxyl group, a hydrocarbon-based cation conductor having a sulfonic acid group and / or a carboxyl group, or a mixture thereof.

[0055] Examples of the fluorine-based cation conductor may include Nafion, Aciplex, Flemion, polyvinylidene fluoride, hexafluoropropylene, trifluoroethylene, polytetrafluoroethylene, or copolymers thereof.

[0056] Examples of the hydrocarbon cation conductor may include hydrocarbon polymers having the cation exchange group on the side chain, such as sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (SPAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene ether, sulfonated polyethersulfone, sulfonated polyetherketone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylether, sulfonated polyarylether nitrile, sulfonated polyarylether ether nitrile, sulfonated polyarylether sulfone ketone, and the like.

[0057] Furthermore, the second adhesive layer 12, 12' may further include an antioxidant in addition to the ion conductive polymer. The antioxidant is a particle capable of removing peroxides or free radicals and may include at least one selected from the group consisting of transition metals, noble metals, their ions, salts, oxides, nitrides, and complexes thereof. The transition metal may include, but is not limited to, one or more selected from the group consisting of cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), and neodymium (Nd). The noble metal may include, but is not limited to, one or more selected from the group consisting of silver (Au), platinum (Pt), ruthenium (Ru), palladium (Pd), and rhodium (Rh). The transition metal or noble metal salt may be a carbonate, acetate, chloride, fluoride, sulfate, phosphate, nitrate, tungstate, hydroxide, ammonium acetate, ammonium sulfate, or acetylacetonate. Specifically, taking cerium as an example, examples include cerium carbonate, cerium acetate, cerium chloride, cerium acetate, cerium sulfate, diammonium cerium acetate, tetraammonium cerium sulfate, and the like. Examples of organometallic complexes include cerium acetylacetonate, and the like. The antioxidant is present in an amount of 1 to 20 parts by weight relative to 100 parts by weight of the ion-conductive polymer. By setting the concentration within this range, the antioxidant and ion-conductive polymer can fully exhibit their functions.

[0058] The thickness of the second adhesive layer 12, 12' can be 0.01 μm to 5 μm, specifically 0.1 μm to 3 μm, and more specifically 0.1 μm to 2 μm. By setting the thickness within the above range, the adhesion between the polymer electrolyte membrane and the electrode can be improved while maintaining battery performance such as output and capacity and mechanical properties.

[0059] The second adhesive layers 12, 12' and the first adhesive layers 11, 11' can be formed in a weight ratio of 1:0.5 to 1:7, based on the weight of the solid content of each layer. Specifically, the weight ratio can be 1:0.7 to 1:7, and more specifically, the weight ratio can be 1:1 to 1:7. By setting the weight ratio of the second adhesive layer to the first adhesive layer within the above range, the effect of improving the adhesive force can be fully achieved while preventing the degradation of fuel cell performance due to an increase in hydrogen ion transfer resistance.

[0060] The low-porosity first catalyst layers 21, 21' and the high-porosity second catalyst layers 22, 22' each contain a first catalyst and a first ion-conducting polymer, and a second catalyst and a second ion-conducting polymer. The first catalyst and the second catalyst may be the same or different. Furthermore, the first ion-conducting polymer and the second ion-conducting polymer may be the same or different.

[0061] Any catalyst that can serve as the first catalyst and the second catalyst participates in the reaction of the cell and can serve as a catalyst for a conventional fuel cell. Preferably, platinum metals can be used.

[0062] Platinum metals may include platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloys (M is one or more selected from the group consisting of palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La) and rhodium (Rh)), non-platinum alloys and combinations thereof. More preferably, a combination of two or more metals selected from the platinum catalyst metal group can be used, but is not limited thereto, and any platinum catalyst metal available in the present technical field can be used without restriction.

[0063] Specifically, the platinum alloy can be used alone or in combination of two or more selected from the group consisting of Pt-Pd, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ru, Pt-Ru-W, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, Pt-Co, Pt-Co-Ni, Pt-Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe, Pt-Fe-Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni, Pt-Ni-Ir, Pt-Cr, Pt-Cr-Ir and combinations thereof.

[0064] Furthermore, non-platinum alloys may be used alone or in combination of two or more selected from the group consisting of Ir-Fe, Ir-Ru, Ir-Os, Co-Fe, Co-Ru, Co-Os, Rh-Fe, Rh-Ru, Rh-Os, Ir-Ru-Fe, Ir-Ru-0s, Rh-Ru-Fe, Rh-Ru-Os, and combinations thereof.

[0065] This catalyst can be used as a catalyst itself (black) or supported on a carrier.

[0066] The carrier can be selected from a carbon-based carrier, a porous inorganic oxide such as zirconium oxide, aluminum oxide, titanium dioxide, silicon dioxide, ceria, and zeolite, etc. The carbon-based carrier can be selected from, but not limited to, graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen Black, superconductive acetylene black (Denka black), acetylene black, carbon nanotube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanosphere, carbon nanohorn, carbon nanocage, carbon nanoring, ordered nano / meso-porous carbon, carbon aerogel, mesoporous carbon, graphene, stabilized carbon, activated carbon, and a combination thereof. Any carrier available in the art can be used without limitation.

[0067] The catalyst can be located on the surface of the carrier or can penetrate into the interior of the carrier to fill the pores inside the carrier.

[0068] When a metal supported on a carrier is used as a catalyst, a commercially available catalyst or a catalyst prepared by supporting the metal on a carrier can be used. The process of supporting the metal on a carrier is well known in the art, so a detailed description thereof is omitted in this specification, but it is easily understood by those skilled in the art.

[0069] The content of the first catalyst or the second catalyst can be 20% to 80% by weight relative to the total weight of each catalyst layer comprising the first catalyst or the second catalyst. If the content is less than 20% by weight, there may be a problem of reduced activity. If the content is greater than 80% by weight, agglomeration of catalyst particles may result in a reduction in active area, which in turn reduces catalytic activity. The catalyst weight can be the total weight of the support and the catalyst supported on the support.

[0070] The first catalyst or the second catalyst may contain 0.01 to 1 mgp in each catalyst layer. t / cm 2 The first catalyst or the second catalyst can exert sufficient catalytic activity within the above loading amount range.

[0071] The first and second ion-conductive polymers are used for hydrogen ion transfer and can also function as an adhesive. As ion-conductive polymers that can be used as the first and second ion-conductive polymers, the ion-conductive polymers described and exemplified in the aforementioned second adhesive layer can be used. Specifically, a cation conductor having at least one cation exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a boric acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and combinations thereof can be used. The cation conductor can be the same as or different from the ion-conductive polymer contained in the second adhesive layer.

[0072] The second catalyst layers 22, 22' may further include a fiber-forming polymer in addition to the second catalyst and the second ion-conductive polymer. The fiber-forming polymer is a polymer that forms a highly porous three-dimensional web structure framework in the second catalyst layer through a spinning process described below. Any material that can be formed into fibers and does not affect the activity of the catalyst and the ion-conductive polymer may be used without particular limitation.

[0073] As the fiber-forming polymer, for example, at least one of the group consisting of polyether polyurethane, polyvinyl acetate (PVAc), polyvinyl acetate copolymer, polyvinyl alcohol (PVA), polyfurfuryl alcohol (PPFA), polyurethane, polyurethane copolymer including polyether polyurethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic acid copolymer, polystyrene, polystyrene copolymer, polyethylene, polyethylene glycol, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl acetal, polyvinyl chloride (PVC), polycaprolactone, polyvinyl pyrrolidone (PVP), polyvinyl fluoride, polyvinylidene fluoride copolymer and polyamide can be used.

[0074] According to one example, when the fiber-forming polymer is spun, a hollow fiber can be formed. At this time, since a hollow is formed inside the fiber, pores can be formed without removing part or all of the polymer, and therefore it has the advantage of being heat-treated at low temperatures. Such hollow fibers can be formed by adjusting the nozzle used as a spinneret into various shapes. According to another example of the present invention, after the fiber-forming polymer forms a three-dimensional network structure framework, at least a portion of the fiber-forming polymer can be removed from the second catalyst layer as needed by methods such as heat, chemical reaction, organic solvent, etc., and pores are formed by this polymer removal method. However, since the fiber-forming polymer also acts as a binder, it is best not to remove it if possible.

[0075] The first catalyst layers 21, 21' have a low porosity. Specifically, the porosity can be 1% to 50%, more specifically, 10% to 50%, and even more specifically, 20% to 45%. The pore size can be 10nm to 500nm, specifically, 20nm to 300nm, and even more specifically, 20nm to 200nm. If the porosity is less than 1% or the pore size is less than 10nm, the movement and discharge of gas and moisture inside the electrode will be difficult. If the porosity is greater than 50% or the pore size is greater than 500nm, the reaction gas will stay in the electrode for a shorter time, which may reduce battery performance.

[0076] The thickness of the first catalyst layer 21, 21' may be 1 μm or more and 10 μm or less. If the thickness is less than 1 μm, the reaction area is small and the activity may be reduced. If the thickness is greater than 10 μm, the migration distance of ions and electrons may increase, resulting in increased resistance.

[0077] The second catalyst layers 22, 22' have a high porosity. Specifically, the porosity can be 50% to 90%, more specifically 60% to 80%, and the pore size can be 500nm to 5000nm, more specifically 600nm to 3000nm. If the porosity is less than 60% or the pore size is less than 500nm, the effect of reducing mass transfer resistance brought about by the introduction of the high-porosity catalyst layer may not be fully realized. If the porosity is greater than 90% or the pore size is greater than 5000nm, the mechanical strength of the catalyst layer may be insufficient.

[0078] The second catalyst layer 22, 22' may have a structure in which the porosity of the surface of the second catalyst layer 22, 22' (e.g., the surface in contact with the gas diffusion layer) is greater than the porosity of the surface in contact with the first catalyst layer 21, 21'. For example, the structure may be such that less than 30% of the total pores of the second catalyst layer 22, 22' exist in the region from the surface in contact with the first catalyst layer 21, 21' to half the thickness of the second catalyst layer 22, 22', and more than 70% exist in the region equivalent to the remaining half of the thickness. For example, when the three-dimensional network structure framework of the second catalyst layer is manufactured by electrospinning, the structure as described above can be formed by adjusting the spinning amount of the fiber-forming polymer from the early stage of spinning to the late stage of spinning (e.g., by the spinning speed).

[0079] The thickness of the second catalyst layer 22, 22' may be greater than 1 μm and less than 20 μm. If the thickness is less than 1 μm, the reaction area is small and the activity may be reduced. If it is greater than 20 μm, the migration distance of ions and electrons may increase, resulting in an increase in resistance, specifically an increase in charge transfer resistance. The thickness of the second catalyst layer 22, 22' may be less than, equal to, or greater than the thickness of the first catalyst layer 21, 21'. According to one embodiment of the present invention, the thickness of the second catalyst layer 22, 22' may be thicker than the thickness of the first catalyst layer 21, 21', thereby further reducing the material transfer resistance.

[0080] On the other hand, the membrane electrode assembly for a fuel cell of the present invention can be manufactured by a membrane electrode assembly manufacturing method, the method comprising: step (a), forming a first catalyst layer with low porosity on a substrate; step (b), forming a second adhesive layer containing an ion conductive polymer on the first catalyst layer with low porosity; step (c), forming a first adhesive layer containing a plasticizer and a cross-linking agent on the second adhesive layer; step (d), positioning the first adhesive layer to face one or both sides of the polymer electrolyte membrane, and then bonding them; step (e), removing the substrate; and step (f), forming a second catalyst layer with high porosity on the first catalyst layer with low porosity.

[0081] According to one embodiment of the present invention, in step (a), the low-porosity first catalyst layer can be formed by any method known in the art, such as bar coating, blade coating, roll-to-roll printing, screen printing, etc., preferably bar coating. The specific manufacturing conditions for manufacturing the first catalyst layer can be appropriately selected and implemented by those skilled in the art.

[0082] According to an example of the present invention, in the step (b), the second adhesive layer can be manufactured by coating a solution formed by mixing the ion conductive polymer with a solvent. The solvent can be selected from water, a hydrophilic solvent, and a non-aqueous polar solvent. Examples of hydrophilic solvents can include alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, butanol, etc., and non-aqueous polar solvents can be selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4,4-dimethyl-1,3-dioxolane, γ-butyrolactone, acetonitrile, etc.

[0083] The content of the ion conductive polymer in the solution may be 0.5 to 60 weight percent, specifically 1 to 40 weight percent, and more specifically 1 to 30 weight percent, based on the total weight of the ion conductive polymer solution. If the content of the ion conductive polymer is too high, it will be difficult to control the thickness of the adhesive layer to be thin, and battery performance may be reduced. Therefore, the content of the ion conductive polymer is preferably set within the above range.

[0084] The coating can be formed by any method known in the art, such as spray coating, inkjet printing, roll-to-roll printing, screen printing, etc., preferably spray coating. Specific manufacturing conditions, such as spray atomization pressure, drying temperature, drying time, etc., can be appropriately selected and implemented by those skilled in the art.

[0085] According to one embodiment of the present invention, in step (c), the first adhesive layer can be formed by coating a mixed solution of the plasticizer and cross-linking agent, which is formed by mixing the plasticizer and cross-linking agent with a solvent. The solvent can be selected from water, a hydrophilic solvent, and a non-aqueous polar solvent. Specifically, alcohols such as ethanol, isopropanol, n-propanol, butanol, and methanol, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran can be used.

[0086] The total content of the plasticizer and cross-linking agent in the solution may be 0.5% to 60% by weight, specifically 1% to 40% by weight, and more specifically 1% to 30% by weight, based on the total weight of the mixed solution. If the content of the plasticizer and cross-linking agent is too high, it will be difficult to control the thickness of the adhesive layer to be thin, and the mechanical properties may be reduced. Therefore, it is preferable to set the content of the plasticizer and cross-linking agent within the above range.

[0087] Furthermore, the weight ratio of the plasticizer to the crosslinker can be 5:1 to 1:1, specifically 4:1 to 2:1. By setting the weight ratio of the plasticizer to the crosslinker within this range, the adhesive can exhibit excellent adhesive properties while maintaining a stable adhesive layer at room temperature, without problems such as decreased physical properties or unstable layer shape caused by the plasticizer.

[0088] The coating can be formed by any method known in the art, such as spray coating, inkjet printing, roll-to-roll printing, screen printing, etc., preferably spray coating. Specific manufacturing conditions, such as spray atomization pressure, drying temperature, drying time, etc., can be appropriately selected and implemented by those skilled in the art.

[0089] According to one embodiment of the present invention, in the step (d), the bonding can be performed by roller pressing or hot pressing. When the roller pressing method is used, the polymer electrolyte membrane and the electrode must be continuously moved and high temperature and high pressure must be applied in a short time to combine the polymer electrolyte membrane and the electrode together, and a relatively higher process temperature and pressure must be applied than the flat pressing method. At this time, high temperature and high pressure will cause changes in the pore structure of the electrode, degradation of the polymer electrolyte membrane, mechanical deformation, etc. Therefore, it is very important to perform transfer bonding at low temperature and low pressure. According to the present invention, the roller pressing method and hot pressing method can be performed at lower temperatures and pressures than the conventional pressing method. For example, in the case of the roller pressing method, it can be performed under the conditions of a pressure of less than 4 MPa, a temperature of less than 140°C, and a moving speed of 0.1 to 3 m / min.

[0090] According to an example of the present invention, in the step (f), the second catalyst layer may be formed by spinning a spinning solution prepared by mixing a second catalyst, a second ion-conductive polymer, a fiber-forming polymer, and a solvent.

[0091] The spinning can be performed by any one method selected from electrospinning, melt-blown, flash spinning and electrostatic melt-blown. Preferably, the spinning can be performed by electrospinning.

[0092] Electrospinning is a spinning method in which a positive (+) or negative (-) voltage is applied directly to a spinneret to charge the solution, and then the charged solution is ejected into the air layer through the spinneret, and then the elongation of the charged filaments and the splitting of another filament in the air layer are used to produce ultrafine fibers. When electrospinning is used to form the second catalyst layer 22, 22' of high porosity, the spinning solution can be injected into the barrel of the electrospinning device, and then ejected by applying a high voltage spinneret, thereby laminating and drying on a substrate such as the first catalyst layer. Wherein, the voltage range, injection speed, viscosity of the spinning solution, the distance between the nozzle and the substrate, etc. can be appropriately adjusted by those skilled in the art. For example, a voltage of 7 to 30 kV can be applied, and the injection speed of the solution can be 10 to 50 μL / min.

[0093] A fuel cell according to an embodiment of the present invention includes a membrane electrode assembly, and may be, for example, a fuel cell using hydrogen as fuel.

[0094] Figure 2 FIG. 1 is a schematic diagram showing the overall structure of a fuel cell according to an embodiment of the present invention.

[0095] Reference Figure 2 The fuel cell 200 includes: a fuel supply unit 210 for supplying a mixed fuel composed of fuel and water; a reforming unit 220 for generating a reformed gas containing hydrogen by reforming the mixed fuel; a cell stack 230 for generating electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen supplied by the reforming unit 220 and an oxidant; and an oxidant supply unit 240 for supplying the oxidant to the reforming unit 220 and the cell stack 230.

[0096] The battery stack 230 includes a plurality of unit cells for generating electric energy by inducing an oxidation / reduction reaction between the reformed gas containing hydrogen supplied from the reformer 220 and the oxidant supplied from the oxidant supplier 240 .

[0097] Each unit cell, which generates electricity, includes a membrane electrode assembly (MEA) for oxidizing and reducing the oxygen in the hydrogen-containing reformed gas and oxidant, and a separator (also called a bipolar plate, hereinafter referred to as a "separator") for supplying the hydrogen-containing reformed gas and oxidant to the MEA. The separators are located on both sides of the MEA, with the MEA located in the center. The separators located on the outermost sides of the cell stack are also specifically referred to as end plates.

[0098] In the separator, one end plate includes: a first supply pipe 231, which is tubular and used to inject the reformed gas containing hydrogen supplied by the reforming section 220; and a second supply pipe 232, which is tubular and used to inject oxygen. The other end plate includes: a first exhaust pipe 233, which is used to finally discharge the unreacted reformed gas containing hydrogen remaining in multiple unit cells to the outside; and a second exhaust pipe 234, which is used to finally discharge the unreacted oxidant remaining in the unit cells to the outside.

[0099] Implementation Method

[0100] Specific examples of the present invention are given below. However, the following examples are only used to specifically illustrate or explain the present invention, and the present invention is not limited thereto. In addition, for the contents not described herein, since those skilled in the art can fully infer them technically, their description is omitted.

[0101] Comparative Example 1

[0102] The Pt / carbon catalyst was mixed with Nafion to prepare an electrode catalyst slurry, which was then coated on a release film using a bar coating method. Subsequently, the electrode (low-porosity catalyst layer) was formed by drying in an oven at 60°C for 4 hours (anode: 0.1 mg P t / cm 2 , cathode: 0.4mgP t / cm 2 At this time, the average pore size of the electrode is 45nm, the porosity is about 33%, the thickness of the anode is about 2μm, and the thickness of the cathode is 10μm. A hydrocarbon (sulfonated poly (arylene ether sulfone ketone) multiblock copolymer) electrolyte membrane is placed in the center, and electrodes are placed on both sides. The membrane is thermally bonded by roller pressing at 180°C, 4MPa, and a speed of 1M / min to obtain the following. Figure 3 Part (a) shows the membrane electrode assembly.

[0103] Comparative Example 2

[0104] Prepare a 5 wt% Nafion dispersion. Place the electrode (low porosity catalyst layer) prepared in Comparative Example 1 on a hot plate at 120°C, and spray 5 wt% of the Nafion dispersion onto the electrode to form an adhesive layer containing an ion-conductive polymer. As in Comparative Example 1, thermal bonding was performed using a roller pressing method at 160°C, 3 MPa, and a speed of 1 M / min to obtain the following: Figure 3 The membrane electrode assembly is shown in part (b).

[0105] Comparative Example 3

[0106] In order to form the first adhesive layer, polyethylene glycol as a plasticizer and benzoquinone as a cross-linking agent were mixed in a weight ratio of 3:1 to prepare a 10 wt% solution, which was sprayed on the low-porosity catalyst layer prepared in Comparative Example 2 and the second adhesive layer containing an ion-conductive polymer to form a first adhesive layer containing a plasticizer and a cross-linking agent. At this time, the weight ratio of the second adhesive layer to the first adhesive layer was 1:0.5. The electrode was placed in the middle of an area of 25 cm as a cathode. 2 The hydrocarbon electrolyte membrane was thermally bonded by roller pressing at 140°C, 3MPa, and a speed of 1M / min to obtain the following Figure 3 The membrane electrode assembly is shown in part (c).

[0107] Comparative Example 4

[0108] Pt catalyst, Nafion binder and PVA were mixed to prepare electrode slurry. The electrode slurry was electrospun on a hydrocarbon (sulfonated poly (arylene ethersulfone ketone) multiblock copolymer) electrolyte membrane at 5 μL / min and 13 kV to form a high-porosity web catalyst layer (0.4 mgP t / cm 2 ) as electrodes, and the Figure 3 The membrane electrode assembly shown in part (d) of FIG. At this time, the average pore size of the electrode is 1200 nm, the porosity is about 68%, and the total thickness of the cathode catalyst layer (high-porosity catalyst layer) is about 20 μm.

[0109] Comparative Example 5

[0110] In order to form the first adhesive layer, a 5 wt% solution containing a crosslinking agent benzoquinone was prepared and sprayed on the low-porosity catalyst layer prepared in Comparative Example 2 and the second adhesive layer containing an ion-conductive polymer to form a first adhesive layer containing only a crosslinking agent. At this time, the weight ratio of the second adhesive layer to the first adhesive layer was 1:0.5. In addition, in order to form the second catalyst layer, the catalyst, the adhesive Nafion and PVA were mixed to prepare an electrode slurry. The low-porosity catalyst layer of the cathode was coated and bonded to 0.3 mg PVA. t / cm 2(The porosity of the low-porosity catalyst layer is 33% and the average pore size is 45 nm). The electrode slurry was electrospun on the low-porosity catalyst layer of the prepared membrane electrode assembly at 5 μL / min and 13 kV to form a high-porosity web catalyst layer. Figure 3 The membrane electrode assembly shown in part (e) is shown in FIG. At this time, the high-porosity web catalyst layer is formed to 0.1 mgp t / cm 2 (The high-porosity catalyst layer had a porosity of 68% and an average pore size of 1200 nm.) The total thickness of the cathode catalyst layer was approximately 13 μm, with a 5 μm high-porosity catalyst layer formed on an approximately 8 μm low-porosity catalyst layer.

[0111] Comparative Example 6

[0112] To form the first adhesive layer, a 5% by weight solution containing the plasticizer polyethylene glycol was prepared and sprayed onto the low-porosity catalyst layer and the second adhesive layer containing the ion-conductive polymer prepared in Comparative Example 2, forming a first adhesive layer containing only the plasticizer. At this point, the weight ratio of the second adhesive layer to the first adhesive layer was 1:0.5. The remaining first and second catalyst layers were formed in the same manner as in Comparative Example 5.

[0113] Comparative Example 7

[0114] To form the first adhesive layer, polyethylene glycol (plasticizer) and benzoquinone (crosslinker) were mixed at a weight ratio of 10:1 and sprayed onto the second adhesive layer to form a first adhesive layer containing the plasticizer and crosslinker. The weight ratio of the second adhesive layer to the first adhesive layer was 1:0.5. The remaining catalyst layers were formed in the same manner as in Comparative Example 5.

[0115] Comparative Example 8

[0116] To form the first adhesive layer, polyethylene glycol (plasticizer) and benzoquinone (crosslinker) were mixed at a weight ratio of 1:10 and sprayed onto the second adhesive layer to form a first adhesive layer containing the plasticizer and the crosslinker. The weight ratio of the second adhesive layer to the first adhesive layer was 1:0.5. The remaining catalyst layers were formed in the same manner as in Comparative Example 5.

[0117] Example 1

[0118] To form the first adhesive layer, polyethylene glycol (plasticizer) and benzoquinone (crosslinker) were mixed in a weight ratio of 3:1 and sprayed onto the second adhesive layer to form a first adhesive layer containing the plasticizer and crosslinker. The weight ratio of the second adhesive layer to the first adhesive layer was 1:0.5. The remaining catalyst layers were formed in the same manner as in Comparative Example 5.

[0119] Example 2

[0120] The structure is the same as that of Example 1. In this case, the low-porosity catalyst layer is formed into 0.2 mg P t / cm 2 , a high porosity web catalyst layer is formed into 0.2 mg P t / cm 2 The total thickness of the cathode catalyst layer is about 15 μm, and a 10 μm high-porosity catalyst layer (the high-porosity catalyst layer has a porosity of 68% and an average pore diameter of 1200 nm) is formed on a low-porosity catalyst layer of about 5 μm (the low-porosity catalyst layer has a porosity of 33% and an average pore diameter of 45 nm).

[0121] Experimental Example 1: Bonding force between polymer electrolyte membrane and electrode

[0122] In order to test the bonding strength between the polymer electrolyte membrane and the electrode, a tensile test was carried out, and the results are shown in Figure 2. Figure 4 As shown. It was confirmed that when the bonded membrane-electrode assembly was stretched from both sides using a universal testing machine with a constant force, the polymer electrolyte membrane and electrodes easily separated if the bonding strength was poor. Although the MEA was bonded at very high temperatures, as in Comparative Example 1, it was observed that the electrodes and electrolyte membrane easily separated during the stretching test. In contrast, in Example 1, which included both a first adhesive layer and a second adhesive layer, transfer was possible at relatively low temperatures and pressures compared to conventional methods, and excellent bonding strength was achieved.

[0123] By changing the ratio of the cross-linking agent to the plasticizer in the first adhesive layer, the results confirmed that when only the plasticizer is used to form the adhesive layer, it is easy to provide ductility to the polymer and the electrolyte membrane and the electrode can be bonded at very low temperature and pressure, but the membrane electrode is easily separated during the tensile test. The cross-linking agent plays a role in increasing the bonding force between the membrane and the electrode, and the plasticizer plays a role in forming the MEA under lower process conditions (temperature, pressure). The above trend depends on the ratio of the cross-linking agent to the plasticizer. As shown in Table 1 below, when the weight ratio of the plasticizer to the cross-linking agent in the first adhesive layer is between 5:1 and 1:1, it has the advantages of simple manufacturing conditions and excellent membrane electrode bonding force.

[0124] Table 1

[0125]

[0126] Experimental Example 2: Performance Evaluation of Membrane Electrode Assembly

[0127] The membrane electrode assemblies of the comparative examples and the examples were made into unit cells and the output performance was evaluated. The cell temperature of the cell was maintained at 65°C, and hydrogen and air with a relative humidity of 100% and a stoichiometry of 1.5 / 2.0 were supplied to the anode / cathode, respectively. Table 2 shows the results of applying 2.2 A / cm 2 The voltage measured at a current density of . The higher the measured voltage, the lower the mass transfer resistance. This confirms that Example 1, which uses a high-porosity catalyst layer, has a lower mass transfer resistance than other structures.

[0128] Table 2

[0129]

[0130] Table 3 shows that the application of 1.0 A / cm 2 The voltage and charge transfer resistance are measured at a current density of .

[0131] It can be confirmed that in the case of comparative example 4 in which only a high-porosity catalyst layer is used to form an electrode, the thickness increases, which increases the transfer distance of hydrogen ions to the reaction points on the catalyst surface, thereby increasing the charge transfer resistance. On the contrary, when a portion of the low-porosity network structure is included, the charge transfer resistance will decrease in the region below the medium current.

[0132] As can be seen from Tables 2 and 3 above, the embodiments of the present invention demonstrate effectiveness in both the medium current (Table 3) and high current (Table 2) regions.

[0133] Table 3

[0134]

[0135] Although the preferred embodiments of the present invention have been described in detail above, the above embodiments are only presented as specific examples of the present invention and the present invention is not limited thereto. The scope of protection of the present invention includes various modifications and improvements made by those skilled in the art using the basic concepts of the present invention defined in the claims, which all fall within the scope of protection of the present invention.

[0136] Reference numerals

[0137] 100: Membrane Electrode Assembly

[0138] 10, 10′: Adhesive layer

[0139] 11, 11': first adhesive layer 12, 12': second adhesive layer

[0140] 20, 20′: Catalyst layer

[0141] 21, 21': first catalyst layer 22, 22': second catalyst layer

[0142] 50: Polymer electrolyte membrane

[0143] 200: Fuel Cell

[0144] 210: Fuel supply unit 220: Reformer unit

[0145] 230: Battery stack 231: First supply pipe

[0146] 232: Second supply pipe 233: First discharge pipe

[0147] 234: Second exhaust pipe 240: Oxidant supply unit

Claims

1. A membrane electrode assembly for a fuel cell, characterized in that: include: polymer electrolyte membrane; a first adhesive layer, located on the polymer electrolyte membrane; a second adhesive layer, located on the first adhesive layer; a first catalyst layer with low porosity, located on the second adhesive layer; as well as The second catalyst layer with high porosity is located on the first catalyst layer with low porosity. The first adhesive layer contains a plasticizer and a cross-linking agent, and the second adhesive layer contains an ion-conductive polymer.

2. The membrane electrode assembly for a fuel cell according to claim 1, wherein: The plasticizer is at least one selected from the group consisting of (poly)alkylene glycol, dihydroxybenzene, (poly)alkylene glycol dialkyl ether, benzoquinones, dialkyl phthalate, and copolymers thereof.

3. The membrane electrode assembly for a fuel cell according to claim 2, wherein: The plasticizer is at least one selected from polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, tetraethylene glycol, dihydroxybenzene, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, benzoquinone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate and copolymers thereof.

4. The membrane electrode assembly for a fuel cell according to claim 1, wherein: The cross-linking agent has a functional group capable of forming a hydrogen bond cross-link with the ion-conductive polymer.

5. The membrane electrode assembly for a fuel cell according to claim 4, characterized in that: The crosslinking agent has a group selected from carbonyl (-CO-), hydroxyl (-OH), carboxyl (-COOH), nitro (-NO2) and amino (-NR 1 R 2 ) is at least one functional group in the group consisting of, wherein R 1 and R 2 Each is independently H, a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C6-C12 aryl group, or they are combined to form a C2-C5 heterocycle.

6. The membrane electrode assembly for a fuel cell according to claim 5, characterized in that: The cross-linking agent is substituted or unsubstituted benzoquinone, substituted or unsubstituted naphthoquinone, substituted or unsubstituted dihydroxybenzene, substituted or unsubstituted phthalic acid, substituted or unsubstituted aminophenol, substituted or unsubstituted phenylenediamine, substituted or unsubstituted bipyridinediamine, substituted or unsubstituted di(aminophenyl)amine, substituted or unsubstituted bipyrrole, or a mixture of two or more thereof.

7. The membrane electrode assembly for a fuel cell according to claim 1, wherein: The weight ratio of the plasticizer to the cross-linking agent is 5:1 to 1:

1.

8. The membrane electrode assembly for a fuel cell according to claim 1, wherein: The ion conductive polymer is a cation conductor having a cation exchange group, wherein the cation exchange group is at least one selected from the group consisting of sulfonic acid group, carboxyl group, boric acid group, phosphoric acid group, imide group, sulfonimide group, sulfonamide group, sulfonyl fluoride group and combinations thereof.

9. The membrane electrode assembly for a fuel cell according to claim 8, characterized in that: The ion-conductive polymer is a fluorine-based cation conductor having a sulfonic acid group and / or a carboxyl group, a hydrocarbon-based cation conductor having a sulfonic acid group and / or a carboxyl group, or a mixture thereof.

10. The membrane electrode assembly for a fuel cell according to claim 1, characterized in that: The first catalyst layer and the second catalyst layer each contain a first ion-conductive polymer and a second ion-conductive polymer, and the ion-conductive polymer of the second adhesive layer is the same as at least one of the first ion-conductive polymer and the second ion-conductive polymer.

11. The membrane electrode assembly for a fuel cell according to claim 1, wherein: The thickness of the first adhesive layer and the second adhesive layer are each independently 0.01 μm to 5 μm.

12. The membrane electrode assembly for a fuel cell according to claim 1, characterized in that: The second catalyst layer with high porosity has a three-dimensional network structure.

13. The membrane electrode assembly for a fuel cell according to claim 1, characterized in that: The high-porosity second catalyst layer contains at least one fiber-forming polymer selected from the group consisting of polyether polyurethane, polyvinyl acetate, polyvinyl acetate copolymer, polyvinyl alcohol, polyfurfuryl alcohol, polyurethane, polyurethane copolymer including polyether polyurethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polymethyl methacrylate, polymethyl acrylate, polyacrylic acid copolymer, polystyrene, polystyrene copolymer, polyethylene, polyethylene glycol, polyethylene oxide, polypropylene oxide, polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate, polyvinyl acetal, polyvinyl chloride, polycaprolactone, polyvinyl pyrrolidone, polyvinyl fluoride, polyvinylidene fluoride copolymer and polyamide.

14. The membrane electrode assembly for a fuel cell according to claim 1, characterized in that: The porosity of the first catalyst layer with low porosity is 1% to 50% and the pore size is 10nm to 500nm. The porosity of the second catalyst layer with high porosity is 50% to 90% and the pore size is 500nm to 5000nm.

15. The membrane electrode assembly for a fuel cell according to claim 1, characterized in that: The thickness of the first catalyst layer with low porosity is greater than or equal to 1 μm and less than or equal to 10 μm, and the thickness of the second catalyst layer with high porosity is greater than or equal to 1 μm and less than or equal to 20 μm.

16. A method for manufacturing a membrane electrode assembly for a fuel cell, characterized in that: include: Step (a), forming a first catalyst layer with low porosity on a substrate; Step (b), forming a second adhesive layer containing an ion conductive polymer on the first catalyst layer with low porosity; Step (c), forming a first adhesive layer containing a plasticizer and a cross-linking agent on the second adhesive layer; Step (d), positioning the first adhesive layer to face one or both sides of the polymer electrolyte membrane, and then bonding; Step (e), removing the substrate; as well as Step (f) is forming a second catalyst layer with high porosity on the first catalyst layer with low porosity.

17. The method for manufacturing a membrane electrode assembly for a fuel cell according to claim 16, wherein: In the step (b), the second adhesive layer is formed by coating a solution containing the ion conductive polymer, wherein the content of the ion conductive polymer in the solution is 0.5 wt % to 60 wt % based on the total weight of the solution.

18. The method for manufacturing a membrane electrode assembly for a fuel cell according to claim 16, wherein: In the step (c), the first adhesive layer is formed by coating a solution containing the plasticizer and the crosslinking agent, wherein the total content of the plasticizer and the crosslinking agent in the solution is 0.5 wt % to 60 wt % based on the total weight of the solution.

19. The method for manufacturing a membrane electrode assembly for a fuel cell according to claim 16, wherein: In the step (f), the second catalyst layer with high porosity is formed by spinning a spinning solution prepared by mixing a catalyst, an ion-conductive polymer, a fiber-forming polymer and a solvent.

20. A fuel cell, characterized in that: The membrane electrode assembly according to claim 1 is included.

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