Reinforced composite membrane, membrane-electrode assembly and fuel cell comprising the same

Abstract

A reinforced composite membrane with improved mechanical and chemical durability is provided. The reinforced composite membrane according to the present invention is a reinforced composite membrane in which an ion conductor dispersion is impregnated into a porous support comprising a polymer compound containing a first hydrophilic functional group, wherein the ion conductor dispersion comprises a first ion conductor containing a second hydrophilic functional group as a side chain and a crown ether-based compound containing a third hydrophilic functional group as a side chain.

Description

Technology Field

[0001] The present invention relates to a reinforced composite membrane, a membrane-electrode assembly, and a fuel cell comprising the same, and more specifically, to a reinforced composite membrane, a membrane-electrode assembly, and a fuel cell comprising the same having improved chemical and mechanical durability. Background Technology

[0002] Fuel cells are batteries equipped with a power generation system that directly converts chemical reaction energy, such as the oxidation / reduction reaction of hydrogen and oxygen contained in hydrocarbon-based fuel materials like methanol, ethanol, and natural gas, into electrical energy. Due to their high energy efficiency and eco-friendly characteristics, including low pollutant emissions, they are gaining attention as a next-generation clean energy source capable of replacing fossil fuels.

[0003] These fuel cells have the advantage of being able to produce a wide range of outputs through a stack configuration formed by stacking unit cells, and are attracting attention as small and portable power sources because they exhibit an energy density 4 to 10 times that of small lithium batteries.

[0004] The stack that actually generates electricity in a fuel cell has a structure in which several to tens of unit cells, each consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate), are stacked. The membrane-electrode assembly generally has a structure in which an anode (or fuel electrode) and a cathode (or air electrode) are formed on opposite sides of an electrolyte membrane.

[0005] Fuel cells can be classified into alkaline electrolyte membrane fuel cells and polymer electrolyte membrane fuel cells (PEMFC) depending on the state and type of electrolyte. Among these, polymer electrolyte membrane fuel cells are gaining popularity as portable, automotive, and home power devices due to their advantages, such as a low operating temperature of less than 100°C, fast start-up and response characteristics, and excellent durability.

[0006] Representative examples of polymer electrolyte membrane fuel cells include proton exchange membrane fuel cells (PEMFCs) that use hydrogen gas as fuel and direct methanol fuel cells (DMFCs) that use liquid methanol as fuel.

[0007] To summarize the reactions occurring in a polymer electrolyte membrane fuel cell, first, when a fuel such as hydrogen gas is supplied to the anode, hydrogen ions (H₂) are produced at the anode through the oxidation reaction of the hydrogen gas. + ) and electrons (e - ) is generated. The generated hydrogen ions are transferred to the reduction electrode through the polymer electrolyte membrane, and the generated electrons are transferred to the reduction electrode through the external circuit. At the reduction electrode, oxygen gas is supplied, and oxygen combines with hydrogen ions and electrons to produce water through the reduction reaction of oxygen.

[0008] Meanwhile, there are still many technical barriers to overcome to realize the commercialization of polymer electrolyte membrane fuel cells, and essential improvements include achieving high performance, long lifespan, and low cost. The membrane-electrode assembly is the component that has the greatest impact on this, and among them, the polymer electrolyte membrane is one of the key factors that most significantly affects the performance and price of the MEA.

[0009] The requirements for the polymer electrolyte membrane necessary for the operation of the above-mentioned polymer electrolyte membrane fuel cell include high hydrogen ion conductivity, chemical stability, low fuel permeability, high mechanical strength, low water content, and excellent dimensional stability.

[0010] Meanwhile, metal ions used as antioxidants in polymer electrolyte membranes are prone to loss during actual fuel cell operation, leading to oxygen radicals attacking ion conductors, which in turn reduces oxidation stability and lowers ion conductivity. Furthermore, even in reinforced composite membranes introduced to overcome the limitations of the aforementioned polymer electrolyte membranes, a problem of reduced durability occurred due to weakened bonding between hydrophobic porous supports and hydrophilic ion conductors, which have different properties. The problem to be solved

[0011] The objective of the present invention is to provide a reinforced composite membrane with improved oxidation stability by increasing the residence time of an antioxidant using a crown ether-based compound containing a hydrophilic functional group.

[0012] Another objective of the present invention is to provide a reinforced composite membrane with improved mechanical and chemical stability by introducing hydrophilic functional groups to a polymer compound used as a porous support and an ion conductor, respectively, and connecting them to each other through a crown ether-based compound that is a crosslinking agent.

[0013] Another objective of the present invention is to provide a membrane-electrode assembly comprising the reinforced composite membrane.

[0014] Another objective of the present invention is to provide a fuel cell comprising the membrane-electrode assembly.

[0015] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims. means of solving the problem

[0016] One embodiment of the present invention for achieving the above objective provides a reinforced composite membrane in which an ion conductor dispersion is impregnated into a porous support comprising a polymer compound containing a first hydrophilic functional group, wherein the ion conductor dispersion comprises a first ion conductor containing a second hydrophilic functional group in a side chain and a crown ether-based compound containing a third hydrophilic functional group in a side chain.

[0017] Another embodiment of the present invention for achieving the above objective may provide a membrane-electrode assembly comprising the reinforcing composite membrane, wherein the membrane-electrode assembly comprises an anode electrode and a cathode electrode positioned opposite each other, and the reinforcing composite membrane positioned between the anode electrode and the cathode electrode.

[0018] Another embodiment of the present invention for achieving the above objective may provide a fuel cell comprising the membrane-electrode assembly. Effects of the invention

[0019] According to the present invention, a reinforced composite membrane with improved oxidation stability can be provided by increasing the residence time of an antioxidant within the reinforced composite membrane. In addition, according to the present invention, a reinforced composite membrane with improved mechanical and chemical stability can be provided.

[0020] In addition to the effects described above, the specific effects of the present invention are described together with the following explanation of the specific details for implementing the invention. Brief explanation of the drawing

[0021] FIG. 1 is a cross-sectional view showing a reinforced composite membrane according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a membrane-electrode assembly according to one embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a fuel cell according to one embodiment of the present invention. Specific details for implementing the invention

[0022] Hereinafter, each component of the present invention is described in more detail so that a person skilled in the art to which the present invention pertains can easily implement it; however, this is merely an example, and the scope of the rights of the present invention is not limited by the following.

[0023] One embodiment of the present invention is a reinforced composite membrane in which an ion conductor dispersion is impregnated into a porous support comprising a polymer compound containing a first hydrophilic functional group, wherein the ion conductor dispersion comprises a first ion conductor containing a second hydrophilic functional group in a side chain and a crown ether-based compound containing a third hydrophilic functional group in a side chain.

[0024] Hereinafter, the configuration of the present invention will be described in more detail with reference to the drawings.

[0025] 1. Reinforced composite membrane (50)

[0026] FIG. 1 is a cross-sectional view showing a reinforced composite membrane according to one embodiment of the present invention.

[0027] Referring to FIG. 1, the reinforced composite membrane (50) according to the present invention may include a porous support (52) comprising a polymer compound containing a first hydrophilic functional group.

[0028] The first hydrophilic functional group may be any one selected from the group consisting of a hydroxyl group, a carboxyl group, and an amine group.

[0029] As a method for introducing the first hydrophilic functional group into the above polymer compound, a polymerization reaction of a monomer containing a hydrophilic functional group may be used. By introducing the first hydrophilic functional group into the polymer compound used to form the porous support according to the present invention, a cross-linking bond can be formed with the first ion conductor through the crown ether-based compound described later. Accordingly, the problem of reduced mechanical durability caused by the separation of the hydrophobic porous support and the hydrophilic first ion conductor can be solved.

[0030] The porous support (52) according to the present invention may be a fluorine-based support or a nanoweb support.

[0031] The above-mentioned fluorine-based support may correspond, for example, to expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are connected to each other by fibrils. Additionally, a film having a microstructure of polymer fibrils in which nodes are not present may also be used as the above-mentioned porous support (52).

[0032] The above fluorine-based support may include a perfluorinated polymer. The porous support (52) may correspond to a more porous and stronger porous support by extruding dispersed polymerized PTFE onto a tape in the presence of a lubricant and stretching the material obtained thereby.

[0033] In addition, the amorphous content of the PTFE may be increased by heat-treating the e-PTFE at a temperature exceeding the melting point (approx. 342°C) of the PTFE. The e-PTFE film produced by the above method may have micropores of various diameters and porosity. The e-PTFE film produced by the above method may have at least 35% porosity, and the diameter of the micropores may be approximately 0.01 to 1 μm (micrometer).

[0034] A nano web support according to one embodiment of the present invention may be a non-woven fibrous web composed of a plurality of randomly oriented fibers. The non-woven fibrous web refers to a sheet having the structure of individual fibers or filaments that are interlaid but not in the same manner as a woven fabric. The non-woven fibrous web may be manufactured by any one method selected from the group consisting of carding, garneting, air-laying, wet-laying, melt blowing, spun bonding, and stitch bonding.

[0035] The above fiber may comprise one or more polymer materials, and any material generally used as a fiber-forming polymer material may be used; specifically, hydrocarbon-based fiber-forming polymer materials may be used. For example, the fiber-forming polymer material may comprise any one selected from the group consisting of polyolefins, e.g., polybutylene, polypropylene, and polyethylene; polyesters, e.g., polyethylene terephthalate and polybutylene terephthalate; polyamides (Nylon-6 and Nylon-6,6); polyurethanes, polybutene; polylactic acid; polyvinyl alcohol; polyphenylene sulfide; polysulfone; fluid crystalline polymers; polyethylene-co-vinyl acetate; polyacrylonitrile; cyclic polyolefins; polyoxymethylene; polyolefin-based thermoplastic elastomers; and combinations thereof. However, the technical concept of the present invention is not limited thereto.

[0036] A nano web support according to one embodiment of the present invention may be a support in which nanofibers are integrated in the form of a nonwoven fabric having a plurality of pores.

[0037] The above nanofibers may preferably be hydrocarbon-based polymers that exhibit excellent chemical resistance and hydrophobicity, so there is no concern about shape deformation due to moisture in high-humidity environments. Specifically, the above hydrocarbon-based polymers may be selected from the group consisting of nylon, polyimide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyphenylene sulfide, polyethylene, polypropylene, copolymers thereof, and mixtures thereof, and among these, polyimide, which has superior heat resistance, chemical resistance, and shape stability, may preferably be used.

[0038] The above nanoweb support is an aggregate of nanofibers in which nanofibers manufactured by electrospinning are randomly arranged. In this case, considering the porosity and thickness of the nanoweb, it is preferable that the nanofibers have an average diameter of 40 to 5000 nm (nanometers) when 50 fiber diameters are measured using a scanning electron microscope (JSM6700F, JEOL) and calculated from the average.

[0039] If the average diameter of the nanofiber is less than the above numerical range, the mechanical strength of the porous support may be reduced, and if the average diameter of the nanofiber exceeds the above numerical range, the porosity may be significantly reduced and the thickness may be increased.

[0040] The thickness of the nonwoven fiber web may be 10 to 50 μm (micrometers), specifically 15 to 43 μm (micrometers). If the thickness of the nonwoven fiber web is less than the above numerical range, the mechanical strength may decrease, and if it exceeds the above numerical range, the resistance loss increases, and the lightweighting and integration may decrease.

[0041] The above nonwoven fibrous web has a basic weight of 5 to 30 mg / cm² 2 It may be. If the basis weight of the above nonwoven fibrous web is less than the above numerical range, visible pores may be formed, making it difficult to function as a porous support, and if it exceeds the above numerical range, it may be manufactured in the form of paper or fabric in which pores are hardly formed.

[0042] The above porosity can be calculated by the ratio of the volume of air within the porous support to the total volume of the porous support according to the following mathematical formula 1. At this time, the total volume is calculated by manufacturing a rectangular sample and measuring its width, length, and thickness, and the volume of air can be obtained by measuring the mass of the sample and subtracting the volume of the polymer, which is inversely calculated from the density, from the total volume.

[0043] [Mathematical Formula 1]

[0044] Porosity (%) = (Volume of air in porous support / Total volume of porous support) X 100

[0045] The porosity of the porous support (52) according to the present invention may be 30 to 90%, and preferably 60 to 85%. If the porosity of the porous support (52) is less than the above numerical range, a problem of reduced impregnation of the ion conductor may occur, and if it exceeds the above numerical range, shape stability may be reduced, which may prevent the subsequent process from proceeding smoothly.

[0046] The ion conductor dispersion according to the present invention may include a first ion conductor having a second hydrophilic functional group as a side chain. Specifically, the second hydrophilic functional group may be any one selected from the group consisting of a hydroxyl group, a carboxyl group, and an amine group.

[0047] A polymerization reaction of a monomer containing a hydrophilic functional group can be used as a method to introduce a second hydrophilic functional group into the side chain of the first ion conductor.

[0048] By including the second hydrophilic functional group in the first ion conductor according to the present invention, it can form a cross-link with a polymer compound used as a porous support through a crown ether-based compound to be described later. Accordingly, the problem of reduced mechanical durability caused by the separation of the hydrophobic porous support and the hydrophilic first ion conductor can be solved.

[0049] The first ion conductor according to the present invention may contain the second hydrophilic functional group as a side chain in any one of the ion conductors selected from the group consisting of fluorine-based ion conductors, partially fluorine-based ion conductors, and hydrocarbon-based ion conductors.

[0050] The above fluorine-based ion conductor may be any one selected from the group consisting of, for example, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, and mixtures thereof, as fluorine-based polymers containing fluorine in the main chain.

[0051] The above-mentioned partially fluorinated ion conductor is, for example, a polystyrene-graft-ethylene tetrafluoroethylene copolymer, or a polystyrene-graft-polytetrafluoroethylene copolymer

[0052] The above hydrocarbon-based ion conductor is, for example, sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (S-PEEK), sulfonated polybenzimidazole (S-PBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyethersulfone, sulfonated Sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile,It may be any one selected from the group consisting of sulfonated polyarylene ether sulfone ketones and mixtures thereof.

[0053] The ion conductor dispersion according to the present invention may include a crown ether-based compound. Specifically, the crown ether-based compound may contain a third hydrophilic functional group as a side chain.

[0054] The third hydrophilic functional group may be any one selected from the group consisting of hydroxyl groups, carboxyl groups, and amine groups. By containing the third hydrophilic functional group, the crown ether compound can connect a polymer compound containing a first hydrophilic functional group and a first ion conductor containing a second hydrophilic functional group as a side chain. That is, the crown ether compound can be used as a crosslinking agent to connect them.

[0055] The main chain of the above crown ether compound may contain a molecular structure represented by the following general formula 1.

[0056] [General Formula 1]

[0057] 3n-crown-n

[0058] In the above general formula 1, n is a positive integer from 4 to 8.

[0059] The above crown ether-based compound may be any one selected from the group consisting of, for example, (18-Crown-6)-2,3,11,12-tetracarboxylic acid, 2-Aminomethyl-18-crown-6, 4'-Aminobenzo-18-crown-6, and 2-Hydroxymethyl-18-crown-6. However, the technical concept of the present invention is not limited thereto, and any material capable of capturing a metal material used as an antioxidant that is a crown ether-based compound containing a hydrophilic functional group may be applied.

[0060] According to one embodiment of the present invention, the weight ratio of the first ion conductor to the crown ether-based compound (first ion conductor:crown ether-based compound) may be 100:0.5 to 100:5, preferably 100:1 to 100:5, and more preferably 100:1 to 100:3. If the weight ratio of the first ion conductor to the crown ether-based compound falls outside the above numerical range, a problem may arise in which the ion conductivity decreases.

[0061] An ion conductor dispersion according to another embodiment of the present invention may further include an antioxidant.

[0062] Specifically, the antioxidant may include a metal-based peroxide decomposition promoter.

[0063] The above-mentioned metal-based peroxide decomposition promoter may include at least one selected from the group consisting of cerium ions, nickel ions, tungsten ions, cobalt ions, chromium ions, zirconium ions, yttrium ions, manganese ions, iron ions, titanium ions, vanadium ions, molybdenum ions, lanthanum ions, neodymium ions, silver ions, platinum ions, ruthenium ions, palladium ions, and rhodium ions.

[0064] According to the present invention, the crown ether-based compound can form a complex with the metal-based peroxide decomposition promoter. Accordingly, the problem of the metal-based peroxide decomposition promoter leaking out of the reinforced composite membrane can be minimized.

[0065] In addition, since the crown ether-based compound forms a bond with the polymer compound constituting the porous support, the metal-based peroxide decomposition promoter can be fixed inside the reinforced composite membrane. Accordingly, the residence time of the metal-based peroxide decomposition promoter is increased, and the oxidation stability of the reinforced composite membrane can be improved.

[0066] The above ion conductor dispersion may comprise 0.1 to 5 parts by weight of the crown ether-based compound and 0.05 to 5 parts by weight of the antioxidant, based on 100 parts by weight of the first ion conductor; preferably, it may comprise 0.5 to 3 parts by weight of the crown ether-based compound and 0.1 to 3 parts by weight of the antioxidant; and more preferably, it may comprise 1 to 3 parts by weight of the crown ether-based compound and 0.5 to 2 parts by weight of the antioxidant. If the content of the crown ether-based compound and the antioxidant falls outside the above numerical range, chemical stability may not be improved.

[0067] Referring to FIG. 1, the reinforced composite membrane (50) according to the present invention may include a first resin layer (54) and a second resin layer (56) facing the first resin layer (54). Specifically, the first resin layer (54) may be disposed on a first surface (52a) of the porous support (52), and the second resin layer (56) may be disposed on a second surface (52b) facing the first surface (52a). Accordingly, the ion conductor layer (55) may be formed on the surface of the porous support (52).

[0068] 2. Membrane-electrode assembly (100)

[0069] FIG. 2 is a cross-sectional view showing a membrane-electrode assembly according to one embodiment of the present invention. The above-mentioned parts and repeated descriptions are briefly described or omitted.

[0070] Referring to FIG. 2, the membrane-electrode assembly (100) according to the present invention is a membrane-electrode assembly comprising the reinforcing composite membrane (50), and comprises an anode electrode (20) and a cathode electrode (20') positioned opposite each other, and the reinforcing composite membrane (50) positioned between the anode electrode (20) and the cathode electrode (20').

[0071] The anode and cathode electrodes (20, 20') include an electrode substrate (40, 40') and a catalyst layer (30, 30') formed on the surface of the electrode substrate (40, 40'), and may further include a microporous layer (not shown) containing conductive fine particles such as carbon powder or carbon black between the electrode substrate (40, 40') and the catalyst layer (30, 30') to facilitate material diffusion from the electrode substrate (40, 40').

[0072] The catalyst layer (30, 30') of the anode and cathode electrodes (20, 20') comprises a catalyst. Any catalyst that participates in the reaction of the cell and can be used as a catalyst for a fuel cell can be used. Preferably, a platinum-based metal can be used.

[0073] The above platinum-based metal may include one selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloys, non-platinum alloys, and combinations thereof, and more preferably, a combination of two or more metals selected from the group of platinum-based catalyst metals may be used, but is not limited thereto, and any platinum-based catalyst metal available in the field of the present technology may be used without limitation.

[0074] The above M may correspond to 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). Specifically, the platinum alloy mentioned above may be used alone or in a mixture 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.

[0075] In addition, the above-mentioned non-platinum alloy may be used alone or in a mixture 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-Os, Rh-Ru-Fe, Rh-Ru-Os, and combinations thereof.

[0076] The above catalyst may be used as the catalyst itself (black) or supported on a carrier.

[0077] 3. Fuel cell

[0078] FIG. 3 is a schematic diagram illustrating a fuel cell according to one embodiment of the present invention.

[0079] Another embodiment of the present invention corresponds to a fuel cell comprising the membrane-electrode assembly.

[0080] Referring to FIG. 3, the fuel cell (200) according to the present invention may include a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reforming unit (220) that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack (230) that generates electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizing agent supply unit (240) that supplies an oxidizing agent to the reforming unit (220) and the stack (230).

[0081] The stack (230) may be equipped with a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction between a reforming gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizing agent supplied from the oxidizing agent supply unit (240).

[0082] Each unit cell refers to a unit cell that generates electricity and may include a membrane-electrode assembly that oxidizes / reduces oxygen in an oxidant and a reforming gas containing hydrogen gas, and a separator (also called a bipolar plate, hereinafter referred to as a 'separator') for supplying the reforming gas containing hydrogen gas and the oxidant to the membrane-electrode assembly. The separator is positioned on both sides of the membrane-electrode assembly with the membrane-electrode assembly at the center. At this time, the separator located at the outermost side of the stack is specifically referred to as an end plate.

[0083] Among the above separator plates, the end plate is provided with a pipe-shaped first supply pipe (231) for injecting a reforming gas containing hydrogen gas supplied from the reforming unit (220) and a pipe-shaped second supply pipe (232) for injecting oxygen gas, and the other end plate may be provided with a first discharge pipe (233) for discharging to the outside a reforming gas containing hydrogen gas that is finally unreacted and remaining in a plurality of unit cells and a second discharge pipe (234) for discharging to the outside an oxidizing agent that is finally unreacted and remaining in the above unit cells.

[0084] In the above fuel cell, the separator, fuel supply unit, and oxidant supply unit constituting the electricity generation unit are used in conventional fuel cells, so a detailed description is omitted in this specification.

[0085] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the present invention; however, this is merely an example, and the scope of the present invention is not limited by the following.

[0086] [Preparation Example 1-1: Preparation of a porous support comprising a polymer compound containing hydroxyl groups]

[0087] A mixture of para-diiodobenzene (p-diiodobenzene; pDIB, 265.0 g), sulfur (32.0 g), and 2,5-diiodophenol (2,5-diiodophenol; 89.5 g; 20 mol%) was heated from 230°C to 300°C and the pressure was gradually reduced from 170 torr to 1 torr or less, and the polymerization reaction was carried out for a total of 8 hours to synthesize a PPS (polyphenylene sulfide) copolymer (Mw = 30,000 to 50,000 g / mol) containing 20 mol% of repeating units derived from 2,5-diiodophenol. Fibers were obtained by spinning a polymer solution in which the PPS copolymer and a solvent (DMAc) were mixed in a weight ratio of 10:90 to 40:60 in a melt spinning device under conditions of 90 to 150°C, voltage 10 to 100 kV, spinning distance 5 to 30 cm, and needle diameter 12 to 28 gauge, and were chopped to a length of about 5 mm. The chopped fibers were dispersed at high speed in water, and then a nonwoven fabric was manufactured using a sheet former. The manufactured nonwoven fabric was dried and then calendered to produce a nonwoven web made of a PPS copolymer containing hydroxyl groups with a thickness of about 10 μm.

[0089] [Preparation Example 1-2: Preparation of a porous support comprising a polymer compound containing carboxyl groups]

[0090] A mixture of para-diiodobenzene (p-diiodobenzene; pDIB, 265.0 g), sulfur (32.0 g), and 2,6-dichlorobenzoic acid (2,6-Dichlorobenzoic acid; 51.8 g; 20 mol%) was heated from 230°C to 300°C and the pressure was gradually reduced from 170 torr to 1 torr or less, and the polymerization reaction was carried out for a total of 8 hours to produce a PPS copolymer (Mw = 30,000 to 50,000 g / mol) containing 20 mol% of repeating units derived from 2,6-dichlorobenzoic acid. Fibers were obtained by spinning a polymer solution in which the PPS copolymer and a solvent (DMAc) were mixed in a weight ratio of 10:90 to 40:60 in a melt spinning device under conditions of 90 to 150°C, voltage 10 to 40kV, spinning distance 5 to 30cm, and needle diameter 12 to 28 gauge, and were chopped to a length of about 5mm. The chopped fibers were dispersed at high speed in water, and then a nonwoven fabric was manufactured using a sheet former. The manufactured nonwoven fabric was dried, and then calendered to produce a nonwoven web made of the PPS copolymer with a thickness of about 12㎛.

[0092] [Preparation Example 2-1: Synthesis of a first ion conductor containing a hydroxyl group]

[0093] To maintain the structure of the main chain and control the degree of sulfonation, sulfonated 4,4'-difluorobenzophenone (SDFBP) and 4,4'-difluorobenzophenone were used at concentrations of 0.006 mol and 0.004 mol, respectively; additionally, to control and introduce the amount of carboxyl groups into the polymer, 2,2-bis(4-hydroxyphenyl)-1-propanol and 4,4'-difluorobenzophenone were used at concentrations of 0.0005 mol and 0.0095 mol, respectively. The four aforementioned substances were added together to 50 mL of methyl sulfonic acid and dissolved at room temperature. 98% sulfuric acid was added to this solution, the temperature was raised to 120°C, and the reaction was carried out for an additional 24 hours. After the reaction was completed, the solution was cooled to 0°C and placed into distilled water at room temperature to obtain a polymer precipitate. The obtained polymer was washed with a solution of distilled water and methanol mixed in a 1:1 (v / v) ratio, dried in an oven three times, and then vacuum dried to obtain the polymer.

[0094] By the above method, a first ion conductor was synthesized having 5 mol% hydroxyl groups, a degree of sulfonation of 60%, and a sulfonated main chain of poly(arylene ether ketone) (S-PAEK).

[0096] [Preparation Example 2-2: Synthesis of a Second Ionic Conductor Containing a Carboxyl Group]

[0097] To maintain the structure of the main chain and control the degree of sulfonation, sulfonated 4,4'-difluorobenzophenone and 4,4'-difluorobenzophenone were used at concentrations of 0.006 mol and 0.004 mol, respectively; additionally, to control and introduce the amount of carboxyl groups into the polymer, 4,4'-bis(4-hydroxyphenyl)valeric acid and 4,4'-difluorobenzophenone were used at concentrations of 0.0005 mol and 0.0095 mol, respectively. The four aforementioned substances were added together to 50 mL of methyl sulfonic acid and dissolved at room temperature. 98% sulfuric acid was added to this solution, the temperature was raised to 120°C, and the reaction was carried out for an additional 24 hours. After the reaction was completed, the solution was cooled to 0°C and placed into distilled water at room temperature to obtain a polymer precipitate. The obtained polymer was washed with a solution of distilled water and methanol mixed in a 1:1 ratio, dried in an oven three times, and then vacuum dried to obtain the polymer.

[0098] By the above method, a second ion conductor was synthesized having 5 mol% carboxyl groups, a degree of sulfonation of 60%, and a sulfonated main chain of poly(arylene ether ketone) (S-PAEK).

[0100] [Preparation Example 3: Preparation of Ion Conductor Dispersion]

[0101] An ion conductor dispersion was prepared with the composition shown in Table 1 below. N,N'-dimethylacetamide (DMAc) was used as the solvent for the ion conductor dispersion.

[0102] Unit: parts by weight Comparison Preparation Example 1 Comparison Preparation Example 2 Comparison Preparation Example 3 Preparation for Implementation Example 1 Preparation for Implementation Example 2 Preparation for Implementation Example 3 Preparation for Implementation Example 4 First ion conductor 1) - 100 - 100 - - - Second ion conductor 2) - - 100 - 100 100 100 Third ion conductor 3) 100 - - - - - - (18-Crown-6)-2,3,11,12-tetracarboxylic acid - - 2 - - - 2-aminomethyl-18-crown-6 - - - - 2 - - 4′-aminobenzo-18-crown-6 - - - - - 2 - 2-hydroxymethyl-18-crown-6 - - - - - - 2 cerium oxide - 3 3 3 3 3 3 1) An ion conductor containing a hydroxyl group according to Preparation Example 2-1 above 2) An ion conductor containing a carboxyl group according to Preparation Example 2-2 above 3) Sulfonated poly(arylene ether ketone) (S-PAEK) having a degree of sulfonation of 60%

[0104] [Preparation Example: Preparation of Reinforced Composite Membrane]

[0105] A reinforced composite membrane was manufactured according to the following manufacturing example.

[0106] <Comparative Example 1>

[0107] A PPS (poly(phenylene sulfide)) support having an average pore size of 0.2 μm (micrometers) and a thickness of 10 μm (micrometers) was placed in a reaction vessel containing isopropyl alcohol at room temperature and pretreated for 5 minutes, after which the pretreated porous support was obtained. An ion conductor dispersion according to Comparative Preparation Example 1 was impregnated into the pretreated porous support, and a reinforced composite membrane was prepared through a drying process.

[0109] <Comparative Example 2>

[0110] A reinforced composite membrane was prepared in the same manner as in Comparative Example 1, but the ion conductor dispersion according to Comparative Preparation Example 2 was used instead of the ion conductor dispersion according to Comparative Preparation Example 1, and the porous support according to Preparation Example 1-1 was used instead of the porous support according to Comparative Example 1.

[0112] <Comparative Example 3>

[0113] A reinforced composite membrane was prepared in the same manner as in Comparative Example 1, but the ion conductor dispersion according to Comparative Preparation Example 3 was used instead of the ion conductor dispersion according to Comparative Preparation Example 1, and the porous support according to Preparation Example 1-2 was used instead of the porous support according to Comparative Example 1.

[0115] <Example 1>

[0116] A reinforced composite membrane was prepared in the same manner as in Comparative Example 2, but the ion conductor dispersion according to Example 1 was used instead of the ion conductor dispersion according to Comparative Example 2.

[0118] <Example 2>

[0119] A reinforced composite membrane was prepared in the same manner as Comparative Example 3, but instead of the ion conductor dispersion according to Comparative Example 3, the ion conductor dispersion according to Example 2 was used.

[0121] <Example 3>

[0122] A reinforced composite membrane was prepared in the same manner as Comparative Example 3, but instead of the ion conductor dispersion according to Comparative Example 3, the ion conductor dispersion according to Example 3 was used.

[0124] <Example 4>

[0125] A reinforced composite membrane was prepared in the same manner as Comparative Example 3, but instead of the ion conductor dispersion according to Comparative Example 3, the ion conductor dispersion according to Example 4 was used.

[0127] [Experimental Example 1: Oxidation Stability Evaluation Experiment of Reinforced Composite Membrane]

[0128] A hydrogen peroxide exposure test was performed on the reinforced composite membrane according to the above manufacturing example. Specifically, the reinforced composite membrane according to the above manufacturing example was 5 x 5 cm 2 The membrane was cut and exposed to 10% hydrogen peroxide vapor for 36 hours under constant temperature and humidity conditions of 80°C and 20% RH or less. Afterward, the membrane was immersed in distilled water at 80°C for 24 hours and then dried at 80°C for 24 hours. To compare the oxidation stability of the reinforced composite membrane according to the above preparation example, the change in swelling degree (%) and ionic conductivity (S / cm) before and after the hydrogen peroxide exposure experiment were measured.

[0129] 1) Swelling degree (%)

[0130] The degree of swelling was determined by measuring the weight of the prepared reinforced composite membrane (PEM) after drying it at 80°C for 24 hours, and then measuring the weight of the reinforced composite membrane (PEM) after swelling it by immersing it in distilled water at room temperature (25°C) for 24 hours. Based on these results, the degree of swelling was calculated using Equation 1 below.

[0131] [Equation 1]

[0132]

[0133] W in Equation 1 above dry is the weight of the dried reinforced composite membrane (PEM), and W wet is the weight of the reinforced composite membrane (PEM) after swelling.

[0134] 2) Hydrogen ion conductivity (S / cm)

[0135] For a membrane-electrode assembly including a reinforced composite membrane according to the above manufacturing example, the ionic conductivity was measured at a measurement temperature of 80°C using a measuring instrument (Solatron-1280 Impedance / Gain-Phase analyzer from Solartron). Specifically, after measuring the ohmic resistance or bulk resistance using the four-point probe AC ​​impedance spectroscopic method, the ionic conductivity was calculated according to Equation 2 below.

[0136] [Equation 2]

[0137]

[0138] In Equation 2 above, σ is the ionic conductivity (S / cm), R is the ohmic resistance of the electrolyte membrane (Ω), L is the distance between electrodes (cm), and S is the area within the electrolyte through which a constant current flows (cm²). 2 It corresponds to ).

[0139] Hydrogen peroxide exposure Swelling degree (%) Hydrogen ion conductivity (S / cm) jeon after jeon after Comparative Example 1 20 10 0.029 0.015 Comparative Example 2 20 12 0.026 0.018 Comparative Example 3 20 12 0.026 0.017 Example 1 20 16 0.026 0.021 Example 2 20 17 0.026 0.022 Example 3 20 16 0.025 0.021 Example 4 20 16 0.025 0.022

[0140] Referring to Table 2 above, it can be confirmed that the example shows a relatively smaller decrease in swelling degree and hydrogen ion conductivity compared to the comparative example even when exposed to hydrogen peroxide vapor for a long time. Considering the experimental results comprehensively, it can be inferred that the crown ether-based compound increases the residence time of the antioxidant in the reinforced composite membrane, thereby providing a reinforced composite membrane with improved oxidation stability.

[0142] [Experimental Example 2: Evaluation of Mechanical Durability of Reinforced Composite Membrane]

[0143] For the polymer electrolyte membrane prepared according to the above Preparation Example, the puncture resistance of two membranes—one that was not evaluated for oxidation stability and another that was evaluated for oxidation stability according to Experimental Example 1—was measured using a Universal Testing Machine (UTM; Instron 5966). As an accessory for performing repeated punctures, a puncture test jig (sample holder and probe) provided by Instron in accordance with ASTM F1342 was used. Specifically, the specimen size was 5 x 5 cm 2 The sample was fixed to a holder (distance from base level to the sample: 100 mm) and repeated thrusts (load: 10 N) were performed with a probe under the following conditions, and the decrease in the distance [i.e., 'displacement'] for each thrust was measured. At this time, the displacement when a load of 0.2 N was applied was considered to be the zero point.

[0144] - Temperature: 23±2 ℃

[0145] - Relative humidity: 50±5 %

[0146] - Mode: Compression Mode

[0147] - Cyclic Period: 20 times

[0148] - Test Speed: 100 mm / min

[0149] The strain when the probe was subjected to piercing (load: 10 N) twice (i.e., "initial piercing strain") and the strain when it was subjected to piercing 20 times (i.e., "final piercing strain") were calculated, respectively, by the following Equations 3 and 4.

[0150] [Equation 3]

[0151] IS(%) = [(D2 - D1) / D1] × 100

[0152] [Equation 4]

[0153] FS(%) = [(D20 - D1) / D1] × 100

[0154] Here, IS is the initial strain of the piercing, FS is the final strain of the piercing, D1 is the displacement (mm) caused by the first piercing, D2 is the displacement (mm) caused by the second piercing, and D20 is the displacement (mm) caused by the 20th piercing.

[0155] The IS / FS ratio was calculated by dividing the above IS by the above FS, thereby simultaneously indicating the strength and flexibility of the polymer electrolyte membrane.

[0156] Sample IS / FS ratio before oxidation stability evaluation IS / FS ratio after oxidation stability evaluation Comparative Example 1 0.2 0.05 Comparative Example 2 0.2 0.10 Comparative Example 3 0.2 0.10 Example 1 0.23 0.18 Example 2 0.25 0.22 Example 3 0.25 0.21 Example 4 0.25 0.21

[0157] Referring to Table 3 above, it can be inferred that Examples 1 to 4 have improved overall mechanical durability compared to Comparative Examples 1 to 3.

[0158] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention. Explanation of the symbols

[0159] 50: Reinforced composite membrane 52: Porous support 52a: 1st side 52b: 2nd side 54: First resin layer 56: Second resin layer

Claims

Claim 1 A reinforced composite membrane comprising a porous support impregnated with an ion conductor dispersion, wherein the ion conductor dispersion comprises a first ion conductor having a second hydrophilic functional group as a side chain and a crown ether-based compound having a third hydrophilic functional group as a side chain, wherein the first ion conductor is cross-linked with the polymer compound through the crown ether-based compound. Claim 2 In claim 1, the first hydrophilic functional group is a reinforced composite membrane selected from the group consisting of a hydroxyl group, a carboxyl group, and an amine group. Claim 3 In claim 1, the porous support is a reinforced composite membrane that is a fluorine-based support or a nanoweb support. Claim 4 In claim 1, the second hydrophilic functional group is a reinforced composite membrane selected from the group consisting of a hydroxyl group, a carboxyl group, and an amine group. Claim 5 A reinforced composite membrane according to claim 1, wherein the first ion conductor is one of the ion conductors selected from the group consisting of fluorine-based ion conductors, partially fluorine-based ion conductors, and hydrocarbon-based ion conductors, and contains the second hydrophilic functional group as a side chain. Claim 6 In claim 1, the third hydrophilic functional group is a reinforced composite membrane selected from the group consisting of a hydroxyl group, a carboxyl group, and an amine group. Claim 7 In claim 1, the main chain of the crown ether-based compound is a reinforced composite membrane containing a molecular structure represented by the following general formula 1: [General Formula 1] 3n-crown-n, where n is a positive integer from 4 to 8. Claim 8 A reinforced composite membrane according to claim 1, wherein the weight ratio of the first ion conductor to the crown ether-based compound is 100:0.5 to 100:

5. Claim 9 In claim 1, the ion conductor dispersion is a reinforced composite membrane further comprising an antioxidant. Claim 10 In claim 9, the antioxidant is a reinforced composite membrane comprising a metal-based peroxide decomposition promoter. Claim 11 In claim 10, the metal-based peroxide decomposition promoter comprises at least one selected from the group consisting of cerium ions, nickel ions, tungsten ions, cobalt ions, chromium ions, zirconium ions, yttrium ions, manganese ions, iron ions, titanium ions, vanadium ions, molybdenum ions, lanthanum ions, neodymium ions, silver ions, platinum ions, ruthenium ions, palladium ions, and rhodium ions, forming a reinforced composite membrane. Claim 12 In claim 9, the ion conductor dispersion comprises 0.1 to 5 parts by weight of the crown ether-based compound and 0.05 to 5 parts by weight of the antioxidant, based on 100 parts by weight of the first ion conductor, forming a reinforced composite membrane. Claim 13 A membrane-electrode assembly comprising a reinforced composite membrane according to claim 1, wherein the anode electrode and a cathode electrode are positioned opposite each other, and the reinforced composite membrane is positioned between the anode electrode and the cathode electrode. Claim 14 A fuel cell comprising a membrane-electrode assembly according to paragraph 13.

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