Ion conductor dispersion, polymer electrolyte membrane produced therefrom, membrane-electrode assembly and fuel cell

Abstract

An ion conductor dispersion is provided that can improve the chemical and mechanical durability of polymer electrolyte membranes. [Solution] The ionic conductor dispersion according to the present invention contains an ionic conductor, a crosslinking agent, and a solvent, and has a contact angle of 135° or less with a PTFE (Polytetrafluoroethylene) porous membrane, where the contact angle is measured one second after the ionic conductor composition is dropped onto the PTFE (Polytetrafluoroethylene) porous membrane under conditions of 25°C and 60% relative humidity.

Description

[Technical Field]

[0001] The present invention relates to an ion conductor dispersion, a polymer electrolyte membrane, a membrane-electrode assembly, and a fuel cell produced therefrom, and more particularly to an ion conductor dispersion that improves the mechanical and chemical durability of a polymer electrolyte membrane, a polymer electrolyte membrane, a membrane-electrode assembly, and a fuel cell produced therefrom. [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 between hydrogen and oxygen contained in hydrocarbon fuel materials such as methanol, ethanol, and natural gas, into electrical energy. Due to their environmentally friendly characteristics of high energy efficiency and low pollutant emissions, fuel cells are attracting attention as a next-generation clean energy source that can replace fossil energy.

[0003] Fuel cells have the advantage of being able to produce a wide range of output power thanks to their stacked structure made up of stacked unit cells, and they are attracting attention as a small and portable power source because they have an energy density that is 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 several 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 electrode (also called a fuel electrode) and a cathode electrode (also called a air electrode) are formed on either side of an electrolyte membrane.

[0005] Fuel cells are divided into alkaline electrolyte membrane fuel cells, polymer electrolyte membrane fuel cells (PEMFC), etc. depending on the state and type of electrolyte. Among them, polymer electrolyte membrane fuel cells are attracting attention as portable, vehicular, and home power sources 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), which use hydrogen gas as fuel, and direct methanol fuel cells (DMFCs), which use liquid methanol as fuel.

[0007] To summarize the reactions that occur in a polymer electrolyte membrane fuel cell, first, when fuel such as hydrogen gas is supplied to the oxidizing electrode, the hydrogen gas is oxidized at the oxidizing electrode to produce hydrogen ions (H + ) and electrons (e - The hydrogen ions produced are transferred to the reducing electrode through the polymer electrolyte membrane, and the electrons produced are transferred to the reducing electrode through an external circuit. Oxygen gas is supplied to the reducing electrode, and the oxygen combines with the hydrogen ions and electrons to produce water through the oxygen reduction reaction.

[0008] However, there are still many technical hurdles to overcome before polymer electrolyte membrane fuel cells can be commercialized, and essential improvements are required to achieve high performance, long life, and low cost. The component that has the greatest impact on these is the membrane-electrode assembly, and the polymer electrolyte membrane is one of the key elements that has the greatest impact on the performance and cost of the MEA.

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

[0010] In the conventional process for producing ion conductor dispersions for polymer electrolyte membranes, a crosslinker was not added, resulting in problems with reduced chemical and mechanical durability of the polymer electrolyte membrane during fuel cell operation. Even when a crosslinker was added, crosslinkers such as hexamethylenediamine and oxydianiline did not mix well with the PFSA polymer. In particular, under high temperature and low humidity conditions, perfluorinated sulfonic acid polymers such as PFSA tend to change into rubber-like properties at high temperatures, and their proton conductivity drops sharply at low relative humidity. Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide an ion conductor dispersion that improves the chemical and mechanical durability of polymer electrolyte membranes.

[0012] Another object of the present invention is to provide a polymer electrolyte membrane prepared from the ion conductor dispersion.

[0013] It is yet another object of the present invention to provide a membrane-electrode assembly comprising said polymer electrolyte membrane which has improved chemical and mechanical durability under high temperature and low humidity conditions.

[0014] It is yet another object of the present invention to provide a fuel cell comprising said membrane-electrode assembly.

[0015] The objects of the present invention are not limited to those mentioned above, and other objects and advantages of the present invention not mentioned above will be understood from the following description and will become more clearly understood by the examples of the present invention. Furthermore, it will be easily understood that the objects and advantages of the present invention can be realized by the means and combinations thereof as claimed. [Means for solving the problem]

[0016] To achieve the above object, according to a first aspect of the present invention, there is provided an ion conductor dispersion comprising an ion conductor, a crosslinking agent, and a solvent, the ion conductor dispersion having a contact angle of 135° or less with a PTFE (Polytetrafluoroethylene) porous membrane, the contact angle being measured one second after the ion conductor composition is dropped onto the PTFE (Polytetrafluoroethylene) porous membrane under conditions of 25°C and 60% relative humidity.

[0017] According to a second aspect of the present invention, in the first aspect, the ionic conductor may be any one selected from the group consisting of a fluorine-based ionic conductor, a partially fluorinated ionic conductor, a hydrocarbon-based ionic conductor, and a mixture thereof.

[0018] According to a third aspect of the present invention, in the first or second aspect, the crosslinking agent may include any one selected from the group consisting of salicylic acid compounds, coumaric acid compounds, terephthalic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and combinations thereof.

[0019] According to a fourth aspect of the present invention, in the third aspect, the salicylic acid compound may include any one selected from the group consisting of salicylsalicylic acid, acetylsalicylic acid, and combinations thereof.

[0020] According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the crosslinking agent may be contained in an amount of 0.05 to 20 parts by weight based on 100 parts by weight of the ion conductor.

[0021] According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the solvent may be any one selected from the group consisting of polar solvents, non-polar solvents, and mixtures thereof.

[0022] According to a seventh aspect of the present invention, in the sixth aspect, the polar solvent may be any one selected from the group consisting of distilled water, alcohol solvents, tetrahydrofuran, 1,4-dioxane, dimethylacetamide, dimethylformamide, dimethylsulfoxide, methylene chloride, and mixtures thereof.

[0023] According to an eighth aspect of the present invention, in the sixth aspect, the non-polar solvent may be any one selected from the group consisting of n-hexane, 1,1,2,2-tetrachloroethane, 1,2-dichloroethane, chloroform, and mixtures thereof.

[0024] According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the solubility of the crosslinking agent in the solvent may be 0.5 to 400 g / L under conditions of 20 to 30°C and a relative humidity of 50 to 70%.

[0025] According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the solvent may have a dielectric constant of 48 or less.

[0026] According to an eleventh aspect of the present invention, in any one of the first to tenth aspects, the contact angle of the ion conductor dispersion with the PTFE porous membrane may be 10 to 130°.

[0027] According to a twelfth aspect of the present invention, there can be provided a polymer electrolyte membrane produced from the ion conductor dispersion liquid according to any one of the first to eleventh aspects.

[0028] According to a thirteenth aspect of the present invention, in the twelfth aspect, the polymer electrolyte membrane may include a porous support, and the porous support may be impregnated with the ion conductor dispersion.

[0029] According to a fourteenth aspect of the present invention, there can be provided a membrane-electrode assembly including the polymer electrolyte membrane according to the twelfth or thirteenth aspect, and a catalyst layer disposed on at least one surface of the polymer electrolyte membrane.

[0030] According to a fifteenth aspect of the present invention, there is provided a fuel cell including the membrane-electrode assembly according to the fourteenth aspect. [Effects of the Invention]

[0031] According to one embodiment of the present invention, it is possible to improve the chemical and mechanical durability of a polymer electrolyte membrane, and also to easily apply the method to a polymer electrolyte membrane manufacturing process, thereby improving process efficiency and economy. In particular, according to one embodiment of the present invention, it is possible to provide a polymer electrolyte membrane having improved durability under high temperature and low humidity conditions.

[0032] In addition to the above-mentioned effects, specific effects of the present invention will be described below while explaining specific details for carrying out the invention. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a cross-sectional view showing a polymer electrolyte membrane according to an embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view showing a membrane-electrode assembly according to an embodiment of the present invention. [Figure 3] 1 is a schematic diagram illustrating a fuel cell according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, each component of the present invention will be described in more detail so that a person having ordinary skill in the art to which the present invention pertains 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 content.

[0035] An ionic conductor dispersion according to an embodiment of the present invention may include an ionic conductor, a crosslinking agent, and a solvent, and may have a contact angle of 135° or less with respect to a PTFE (Polytetrafluoroethylene) porous membrane. The contact angle of the ionic conductor dispersion with the PTFE porous membrane is measured one second after the ionic conductor dispersion is dropped onto the PTFE porous membrane under conditions of 25°C and 60% relative humidity.

[0036] The configuration of the present invention will be described in more detail below.

[0037] 1. Ionic conductor dispersion The ionic conductor dispersion according to the present invention contains an ionic conductor, a crosslinking agent, and a solvent.

[0038] The ionic conductor according to the present invention may be any one selected from the group consisting of fluorine-based ionic conductors, partially fluorinated ionic conductors, hydrocarbon-based ionic conductors, and mixtures thereof.

[0039] The fluorine-based ion conductor may be, for example, any one selected from the group consisting of a fluorine-based polymer containing fluorine in its main chain, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, and a mixture thereof.

[0040] The partially fluorinated ionic conductor may be, for example, a polystyrene-graft-ethylene tetrafluoroethylene copolymer or a polystyrene-graft-polytetrafluoroethylene copolymer.

[0041] Examples of the hydrocarbon ion conductor include 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, and sulfonated polyethersulfone. sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrilenitrile), sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and mixtures thereof.

[0042] The crosslinking agent according to the present invention may include any one selected from the group consisting of salicylic acid compounds, coumaric acid compounds, terephthalic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and combinations thereof. Specifically, the salicylic acid compounds may include any one selected from the group consisting of salicylsalicylic acid, acetylsalicylic acid, and combinations thereof. The coumaric acid compounds may include any one selected from the group consisting of ortho-coumaric acid, meta-coumaric acid, para-coumaric acid, and combinations thereof.

[0043] In conventional ion conductor dispersion preparation processes, salicylic acid-based compounds are not used as crosslinkers, resulting in reduced chemical and mechanical durability of polymer electrolyte membranes prepared using the ion conductor dispersions. Even when crosslinkers are added to the ion conductor dispersions, crosslinkers such as hexamethylenediamine and oxydianiline are incompatible with the PFSA polymer. In particular, perfluorinated sulfonic acid polymers such as PFSA tend to change their physical properties to a rubber-like state at high temperatures and experience a rapid decrease in proton conductivity at low relative humidity. According to one embodiment of the present invention, the use of a salicylic acid-based crosslinker provides a unique advantage of not only being highly soluble in solvents but also in the PFSA polymer. This facilitates crosslinking between ion conductor compounds, minimizing the decrease in proton conductivity and improving the mechanical durability of polymer electrolyte membranes. In addition to the salicylic acid compounds, coumaric acid compounds, terephthalic acid, 3-hydroxybenzoic acid, and 4-hydroxybenzoic acid compounds can also perform the same function as the salicylic acid compounds.

[0044] The crosslinking agent according to the present invention may be included in an amount of 0.05 to 20 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the ion conductor. If the content of the crosslinking agent is less than the above range, the chemical and mechanical durability of the polymer electrolyte membrane may not be sufficiently improved. If the content of the crosslinking agent is more than the above range, the hydrogen ion conductivity may be excessively low, and some of the crosslinking agent may precipitate and act as foreign matter.

[0045] The solvent according to the present invention may be any one selected from the group consisting of polar solvents, non-polar solvents, and mixtures thereof.

[0046] The polar solvent may be any one selected from the group consisting of distilled water, alcohol solvents, tetrahydrofuran, 1,4-dioxane, dimethylacetamide, dimethylformamide, dimethylsulfoxide, methylene chloride, and mixtures thereof.

[0047] The alcohol solvent may be, for example, any one selected from the group consisting of methanol, ethanol, propanol, and butanol.

[0048] The non-polar solvent may be any one selected from the group consisting of n-hexane, 1,1,2,2-tetrachloroethane, 1,2-dichloroethane, chloroform, and mixtures thereof.

[0049] The solubility of the crosslinking agent in the solvent may be 0.5 to 400 g / L, preferably 1 to 300 g / L, and more preferably 2 to 150 g / L, under conditions of 20 to 30°C and a relative humidity (RH) of 50 to 70%. If the solubility of the crosslinking agent in the solvent is below the above range, it may precipitate when introduced into the polymer electrolyte membrane and not function as a crosslinking agent. If the solubility exceeds the above range, it may be washed away during operation of the fuel cell, resulting in a lower degree of crosslinking than intended.

[0050] In other words, the dielectric constant of the solvent may be, for example, 48 or less, specifically 1 to 48, and more specifically 5 to 48 at 20 to 25°C.

[0051] The contact angle of the ionic conductor dispersion with the PTFE (Polytetrafluoroethylene) porous membrane of the present invention may be 135° or less, preferably 10 to 130°, more preferably 20 to 125°, 80 to 120°, or 86 to 118°. The contact angle of the ionic conductor dispersion with the PTFE porous membrane may be measured 0.001 to 120 seconds, preferably 0.005 to 60 seconds, more preferably 0.01 to 20 seconds, after the ionic conductor dispersion is dropped onto the PTFE porous membrane at 20 to 30°C and a relative humidity of 30 to 70%. Specifically, the contact angle may be measured 1 second after the ionic conductor dispersion is dropped onto the PTFE porous membrane at 25°C and a relative humidity of 60%. For example, the contact angle of the ionic conductor dispersion may be affected comprehensively by the type of ionic conductor and solvent, the presence or absence of a crosslinking agent, and the amount of the crosslinking agent. Therefore, by appropriately adjusting the composition and content of the ion conductor, solvent, and crosslinker, it is possible to derive a contact angle of the ion conductor dispersion that improves the mechanical properties of the polymer electrolyte membrane and simultaneously improves the chemical durability of the membrane-electrode assembly.

[0052] The PTFE porous membrane may correspond to, for example, a Teflon® porous membrane. When the contact angle of the ion conductor dispersion with the PTFE porous membrane satisfies the above range, the crosslinking reaction can be carried out efficiently.

[0053] 2.Polymer electrolyte membrane Another embodiment of the present invention is a polymer electrolyte membrane manufactured using the ion conductor dispersion liquid. Here, the polymer electrolyte membrane manufactured using the ion conductor dispersion liquid may be a membrane in which a crosslinked matrix is ​​formed between the ion conductor and the crosslinker by drying the ion conductor dispersion liquid to remove the solvent and then proceeding with a crosslinking reaction. According to another aspect of the present invention, the polymer electrolyte membrane may include repeating units derived from the ion conductor and repeating units derived from the crosslinker. For example, the crosslinked matrix may include a first ion conductor chain, a second ion conductor chain different from the first ion conductor chain, and a molecular structure derived from a crosslinker that crosslinks the first and second ion conductor chains. Here, the first and second ion conductor chains can be connected to each other via the molecular structure derived from the crosslinker. For example, a method for analyzing the polymer electrolyte membrane may include: 1 H-NMR, 13 Various known analytical methods such as C-NMR and FT-IR can be used.

[0054] Meanwhile, the first and second ion conductor chains may include crosslinking reactive functional groups at their side chains that can crosslink with a crosslinking agent. Here, the crosslinking reactive functional groups may react with the crosslinking agent. For example, the crosslinking reactive functional groups may include —SO—OH.

[0055] According to yet another embodiment of the present invention, the polymer electrolyte membrane may be a single membrane type polymer electrolyte membrane.

[0056] A polymer electrolyte membrane according to another embodiment of the present invention may include a porous support, and the porous support may be impregnated with the ion conductor dispersion. The polymer electrolyte membrane may be a reinforced composite membrane in the form of a composite membrane. In this specification, "impregnated" is defined as the ion conductor dispersion permeating the internal pores of the porous support. Hereinafter, the configuration of the present invention will be described in detail with reference to FIG. 1.

[0057] FIG. 1 is a cross-sectional view showing a polymer electrolyte membrane according to an embodiment of the present invention.

[0058] Referring to FIG. 1, the porous support 52 according to the present invention may be a fluorine-based support or a nanoweb support.

[0059] The fluorine-based support may be, for example, expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are connected to each other by fibrils. Also, a film having a microstructure of polymer fibrils without nodes may be used as the porous support 52.

[0060] The fluoro-based support can include a perfluorinated polymer. The porous support 52 can be formed by extruding dispersion-polymerized PTFE into a tape in the presence of a lubricant and then expanding the resulting material to form a more porous and stronger porous support.

[0061] The amorphous content of PTFE can also be increased by heat-treating the e-PTFE at a temperature above the melting point of PTFE (approximately 342°C). The e-PTFE film produced by this method can have micropores with various diameters and porosity. The e-PTFE film produced by this method can have at least 35% pores, and the diameter of the micropores can be approximately 0.01 to 1 μm (micrometer).

[0062] The nanoweb substrate according to one embodiment of the present invention may be a nonwoven fibrous web made of randomly oriented fibers. The nonwoven fibrous web refers to a sheet having a structure of individual fibers or filaments that are interlaid but not in the same manner as a woven fabric. The nonwoven fibrous web may be manufactured by any one method selected from the group consisting of carding, garnetting, air-laying, wet-laying, meltblowing, spunbonding, and stitchbonding.

[0063] The fibers may comprise one or more polymeric materials. Any of the materials commonly used as fiber-forming polymeric materials can be used, particularly hydrocarbon-based fiber-forming polymeric materials. For example, the fiber-forming polymeric material may be any one selected from the group consisting of polyolefins, such as polybutylene, polypropylene, and polyethylene; polyesters, such as polyethylene terephthalate and polybutylene terephthalate; polyamides (nylon-6 and nylon-6,6); polyurethanes, polybutenes, polylactic acids, polyvinyl alcohols, polyphenylene sulfides, polysulfones, fluid crystalline polymers, polyethylene-co-vinyl acetate, polyacrylonitriles, cyclic polyolefins, polyoxymethylenes, polyolefin-based thermoplastic elastomers, and combinations thereof. However, the technical concept of the present invention is not limited thereto.

[0064] The nanoweb substrate according to an embodiment of the present invention may be a substrate in which nanofibers are accumulated in the form of a nonwoven fabric containing a large number of pores.

[0065] The nanofibers are preferably made of hydrocarbon-based polymers that exhibit excellent chemical resistance, hydrophobicity, and are not susceptible to deformation due to moisture in a humid environment. Specifically, the hydrocarbon-based polymer 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, polyamide imide, polyethylene terephthalate, polyphenylene sulfide, polyethylene, polypropylene, copolymers thereof, and mixtures thereof.

[0066] The nanoweb substrate is an aggregate of nanofibers produced by electrospinning and arranged randomly. The nanofibers preferably have an average diameter of 40 to 5,000 nm (nanometers) when calculated from the average of 50 fiber diameters measured using a scanning electron microscope (JSM6700F, JEOL) taking into account the porosity and thickness of the nanoweb.

[0067] If the average diameter of the nanofibers is less than the above range, the mechanical strength of the porous support may be reduced, and if the average diameter of the nanofibers is more than the above range, the porosity may be significantly reduced and the thickness may be increased.

[0068] The thickness of the nonwoven fibrous web may be 10 to 50 μm (micrometers), specifically 15 to 43 μm (micrometers). If the thickness of the nonwoven fibrous web is less than the above range, the mechanical strength may decrease, and if the thickness exceeds the above range, the resistance loss may increase, and the weight reduction and integration may decrease.

[0069] The nonwoven fibrous web has a basic weight of 5 to 30 mg / cm 2 If the basis weight of the nonwoven fibrous web is less than the above range, visible pores may be formed and the web may not function as a porous support, whereas if the basis weight is greater than the above range, the web may be manufactured in the form of paper or fabric with almost no pores.

[0070] The porosity can be calculated as the ratio of the air volume in the porous support to the total volume of the porous support according to the following Equation 1. Here, the total volume is calculated by preparing a rectangular sample and measuring its width, length, and thickness, and the air volume can be obtained by measuring the mass of the sample and then subtracting the polymer volume, which is calculated back from the density, from the total volume.

[0071] [Number 1] Porosity (%) = (air volume in the porous support / total volume of the porous support) × 100

[0072] The porosity of the porous support 52 according to the present invention is preferably 30 to 90%, and more preferably 60 to 85%. If the porosity of the porous support 52 is less than the above range, the impregnation of the ion conductor may be impaired, whereas if the porosity exceeds the above range, the shape stability may be reduced, which may hinder smooth subsequent processes.

[0073] The polymer electrolyte 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 the second surface 52b facing the first surface 52a. Therefore, the ion conductor layer 55 may be formed on the surface of the porous support 52 and may include the ion conductor described above.

[0074] According to one embodiment of the present invention, the tensile strength of the polymer electrolyte membrane 50 may be 25 to 90 MPa, 30 to 85 MPa, 35 to 82 MPa, 40 to 82 MPa, or 50 to 82 MPa. For example, the tensile strength of the polymer electrolyte membrane may be measured using a universal testing machine (SHM-C-500, Shamhan Tech, Korea) according to ASTM D882. Specifically, the means for achieving the tensile strength of the polymer electrolyte membrane may vary depending on the composition of the ion conductor dispersion.

[0075] 3. Membrane-electrode Assembly 2 is a cross-sectional view of a membrane-electrode assembly according to an embodiment of the present invention. The same or similar parts will be briefly described or omitted.

[0076] Referring to FIG. 2, the membrane-electrode assembly 100 according to the present invention is a membrane-electrode assembly including the polymer electrolyte membrane 50, and includes an anode electrode 20 and a cathode electrode 20′ positioned opposite each other, and the polymer electrolyte membrane 50 positioned between the anode electrode 20 and the cathode electrode 20′.

[0077] The anode and cathode electrodes 20, 20′ include electrode substrates 40, 40′ and catalyst layers 30, 30′ formed on the surfaces of the electrode substrates 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 substrates 40, 40′ and the catalyst layers 30, 30′ to facilitate material diffusion in the electrode substrates 40, 40′.

[0078] The catalyst layers 30, 30' of the anode and cathode electrodes 20, 20' contain a catalyst. Any catalyst that participates in the cell reaction and is generally usable as a catalyst in a fuel cell can be used. Preferably, a platinum-based metal can be used.

[0079] The 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. More preferably, a combination of two or more metals selected from the group of platinum-based catalytic metals may be used, but is not limited thereto, and any platinum-based catalytic metal that can be used in this technical field may be used without limitation.

[0080] The M may represent 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 may be 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, and may be used alone or in combination of two or more.

[0081] Furthermore, the non-platinum alloy may be 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, and may be used alone or in combination of two or more.

[0082] The catalyst may be used as a catalyst itself (black) or may be supported on a carrier.

[0083] 4.Fuel cell FIG. 3 is a schematic diagram illustrating a fuel cell according to an embodiment of the present invention.

[0084] Yet another embodiment of the present invention is a fuel cell comprising the membrane-electrode assembly described above.

[0085] Referring to FIG. 3, a fuel cell 200 according to the present invention may include a fuel supply unit 210 for supplying a mixed fuel obtained by mixing fuel and water, a reforming unit 220 for reforming the mixed fuel to generate a reformed gas containing hydrogen gas, a stack 230 for generating electrical energy by electrochemically reacting the reformed gas containing hydrogen gas supplied from the reforming unit 220 with an oxidant, and an oxidant supply unit 240 for supplying an oxidant to the reforming unit 220 and the stack 230.

[0086] The stack 230 may include a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction between the reformed gas containing hydrogen gas supplied from the reforming unit 220 and the oxidant supplied from the oxidant supplying unit 240.

[0087] Each unit cell refers to a unit cell that generates electricity and includes the membrane-electrode assembly that oxidizes / reduces the reformed gas containing hydrogen gas and oxygen in the oxidant, and a separator plate (also called a bipolar plate, hereinafter referred to as "separator plate") that supplies the reformed gas containing hydrogen gas and the oxidant to the membrane-electrode assembly. The separator plates are disposed on both sides of the membrane-electrode assembly at the center. In this case, the separator plates located at the outermost positions of the stack are sometimes referred to as end plates.

[0088] The end plate of the separation plate may be provided with a pipe-shaped first supply pipe 231 for injecting the reformed gas containing hydrogen gas supplied from the reforming section 220 and a pipe-shaped second supply pipe 232 for injecting oxygen gas, and the other end plate may be provided with a first exhaust pipe 233 for discharging the reformed gas containing hydrogen gas that ultimately remains unreacted in the plurality of unit cells to the outside and a second exhaust pipe 234 for discharging the oxidant that ultimately remains unreacted in the unit cells to the outside.

[0089] In the fuel cell, the separator, fuel supply section, and oxidant supply section that constitute the electricity generating section are the same as those used in ordinary fuel cells, and therefore detailed description thereof will be omitted in this specification.

[0090] Hereinafter, the embodiments of the present invention will be described in detail so that a person having ordinary skill in the art to which the present invention pertains 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 content.

[0091] [Production Example 1: Production of ionic conductor dispersion] An ionic conductor dispersion liquid as shown in Table 1 below was prepared.

[0092] [Table 1]

[0093] [Experimental Example 1: Contact angle on PTFE (Polytetrafluoroethylene) porous film] The contact angle of the ionic conductor dispersion liquid of Production Example 1 with a PTFE (Polytetrafluoroethylene) porous membrane (trade name: PTFE substrate of Teflon) was measured.

[0094] With the temperature maintained at 25°C and RH 60%, the ionic conductor dispersion liquid obtained in Preparation Example 1 was filled into a syringe, and a 5 μl droplet was dropped onto the PTFE porous membrane. After waiting for 1 second for the droplet to spread, the contact angle between the PTFE porous membrane and the droplet was measured using a contact angle measuring device (Model 190, manufactured by Technox Corporation).

[0095] [Table 2]

[0096] [Production Example 2: Production of polymer electrolyte membrane] The following polymer electrolyte membranes were prepared using the ion conductor dispersion liquid obtained in Preparation Example 1. In the following comparative examples and examples, drying and crosslinking were carried out simultaneously.

[0097] <Comparative Example 1> In Table 1, the ion conductor dispersion liquid obtained in Comparative Production Example 1 was formed into a film on a glass substrate, and then dried at 90° C. for 12 hours to produce a polymer electrolyte membrane.

[0098] <Comparative Example 2> The ion conductor dispersion liquid obtained in Comparative Production Example 2 was formed into a film on a glass substrate, and then dried at 90° C. for 24 hours to produce a polymer electrolyte membrane.

[0099] <Comparative Example 3> The ionic conductor dispersion according to Preparation Comparative Example 1 was impregnated into an e-PTFE (expanded-polytetrafluoroethylene) support having an average pore size of 0.2 μm and a porosity of 75%, and the impregnated PTFE (polytetrafluoroethylene) support was dried at 90°C for 12 hours to prepare a polymer electrolyte membrane (or reinforced composite membrane).

[0100] <Comparative Example 4> The ionic conductor dispersion according to Preparation Comparative Example 2 was impregnated into a PPS (polyphenylene sulfide) support having an average pore size of 0.2 μm and a porosity of 70%, and the impregnated resultant was dried at 90° C. for 24 hours to prepare a polymer electrolyte membrane (or reinforced composite membrane).

[0101] <Examples 1 and 2> The ion conductor dispersions obtained in Production Examples 1 and 2 were each formed into a film on a glass substrate, and then dried at 90° C. for 12 hours to produce a polymer electrolyte membrane.

[0102] <Examples 3 and 4> The ion conductor dispersions obtained in Production Examples 3 and 4 were each formed into a film on a glass substrate, and then dried at 90° C. for 24 hours to produce a polymer electrolyte membrane.

[0103] <Example 5> A polymer electrolyte membrane (or reinforced composite membrane) was produced in the same manner as in Comparative Example 3, except that the ion conductor dispersion liquid of Production Example 1 was used instead of the ion conductor dispersion liquid of Production Comparative Example 1.

[0104] Example 6 A polymer electrolyte membrane (or reinforced composite membrane) was produced in the same manner as in Comparative Example 3, except that the ion conductor dispersion liquid of Production Example 2 was used instead of the ion conductor dispersion liquid of Production Comparative Example 1.

[0105] Example 7 A polymer electrolyte membrane (or reinforced composite membrane) was produced in the same manner as in Comparative Example 4, except that the ion conductor dispersion liquid of Production Example 3 was used instead of the ion conductor dispersion liquid of Production Comparative Example 2.

[0106] Example 8 A polymer electrolyte membrane (or reinforced composite membrane) was produced in the same manner as in Comparative Example 4, except that the ion conductor dispersion liquid of Production Example 4 was used instead of the ion conductor dispersion liquid of Production Comparative Example 2.

[0107] [Experimental Example 2: Evaluation of tensile strength of polymer electrolyte membrane] The tensile strength of the polymer electrolyte membrane of Preparation Example 2 was measured according to the ASTM D882 method using a universal testing machine (SHM-C-500, Shamhan Tech, Korea).

[0108] [Table 3]

[0109] Referring to Table 3, it can be seen that the tensile strength of the Examples was significantly improved compared to the Comparative Examples, suggesting that the introduction of a crosslinking agent significantly improved the mechanical durability of the polymer electrolyte membrane or reinforced composite membrane.

[0110] [Experimental Example 3: OCV Reduction Rate as a Result of DOE Chemical Durability Evaluation of Membrane-Electrode Assembly] Electrodes prepared by the decal method were attached to both sides of the polymer electrolyte membrane (or reinforced composite membrane) according to Preparation Example 2, and electrode slurry (catalyst: Pt / C, Pt loading content: 0.4 mg / cm) was applied. 2 ) was directly coated onto the membrane-electrode assembly to prepare a membrane-electrode assembly. The chemical durability of the membrane-electrode assembly was evaluated based on the durability evaluation protocol of the U.S. Department of Energy (DOE). Specifically, the voltage loss was measured after 500 hours of OCV hold at 120°C and 20% RH. The measured values ​​are shown in Table 4 below.

[0111] [Table 4]

[0112] Referring to Table 4, it can be inferred that the OCV voltage loss of the Examples is relatively small compared to the Comparative Examples, and that the chemical durability is generally improved.

[0113] Although the 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 made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. an ionic conductor; a cross-linking agent; a solvent; and an ion conductor dispersion comprising: The ionic conductor dispersion is dropped onto a PTFE (Polytetrafluoroethylene) porous membrane under conditions of 25°C and 60% relative humidity, and the contact angle measured after 1 second is 135° or less. Ionic conductor dispersion.

2. The ionic conductor is The ion conductor is any one selected from the group consisting of a fluorine-based ion conductor, a partially fluorinated ion conductor, a hydrocarbon-based ion conductor, and a mixture thereof. The ionic conductor dispersion according to claim 1 .

3. The crosslinking agent is The compound includes any one selected from the group consisting of salicylic acid compounds, coumaric acid compounds, terephthalic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and combinations thereof. The ionic conductor dispersion according to claim 1 .

4. The salicylic acid compound is Any one selected from the group consisting of salicylsalicylic acid, acetylsalicylic acid, and combinations thereof, The ionic conductor dispersion according to claim 3 .

5. The crosslinking agent is The amount is 0.05 to 20 parts by weight based on 100 parts by weight of the ionic conductor. The ionic conductor dispersion according to claim 1 .

6. The solvent is any one selected from the group consisting of polar solvents, non-polar solvents, and mixtures thereof; The ionic conductor dispersion according to claim 1 .

7. The polar solvent is any one selected from the group consisting of distilled water, alcohol solvents, tetrahydrofuran, 1,4-dioxane, dimethylacetamide, dimethylformamide, dimethylsulfoxide, methylene chloride, and mixtures thereof; The ionic conductor dispersion according to claim 6 .

8. The non-polar solvent is any one selected from the group consisting of n-hexane, 1,1,2,2-tetrachloroethane, 1,2-dichloroethane, chloroform, and mixtures thereof; The ionic conductor dispersion according to claim 6 .

9. the solubility of the crosslinking agent in the solvent is 0.5 to 400 g / L under conditions of 20 to 30°C and a relative humidity of 50 to 70%; The ionic conductor dispersion according to claim 1 .

10. The solvent has a dielectric constant of 48 or less. The ionic conductor dispersion according to claim 1 .

11. A polymer electrolyte membrane produced from the ion conductor dispersion liquid according to claim 1.

12. The polymer electrolyte membrane is a porous support; the porous support is impregnated with the ion conductor dispersion; The polymer electrolyte membrane according to claim 11.

13. The polymer electrolyte membrane according to claim 11; a catalyst layer disposed on at least one surface of the polymer electrolyte membrane.

14. A fuel cell comprising the membrane-electrode assembly of claim 13.

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