Polymer electrolyte membrane, its manufacturing method and electrochemical device including the same

Abstract

The present invention relates to a polymer electrolyte membrane, a membrane-electrode assembly including the same, and an electrochemical device. The polymer electrolyte membrane includes a porous support and an ion conductor filling the pores of the porous support, and the porous support is a polymer electrolyte that is a metal porous support. The present invention provides a polymer electrolyte membrane that exhibits improved chemical and mechanical durability and good battery performance.

Description

[Technical Field]

[0001] The present invention relates to a polymer electrolyte membrane, which is a reinforced composite membrane including a porous support and an ion conductor filling the pores of the porous support, and which includes a metallic porous support made of a metal material used as a metallic antioxidant, and which has improved chemical durability and mechanical durability, and an electrochemical device including the same. [Background technology]

[0002] Fuel cells are cells that directly convert chemical energy generated by the oxidation of fuel into electrical energy, and are attracting attention as a next-generation energy source due to their high energy efficiency and environmentally friendly characteristics such as low pollutant emissions.

[0003] A fuel cell generally has a structure in which an anode and a cathode are formed on either side of an electrolyte membrane, and this structure is called a membrane electrode assembly (MEA).

[0004] Fuel cells are divided into alkaline electrolyte fuel cells, polymer electrolyte membrane fuel cells (PEMFC), etc. depending on the type of electrolyte membrane. Among them, polymer electrolyte membrane fuel cells are attracting attention as portable, vehicular, and home power sources due to their advantages such as low operating temperature of less than 100°C, fast start-up and response characteristics, and excellent durability.

[0005] A typical example of such a polymer electrolyte membrane fuel cell is a proton exchange membrane fuel cell (PEMFC), which uses hydrogen gas as fuel.

[0006] 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, hydrogen is oxidized at the oxidizing electrode to produce hydrogen ions (H+ ) and electrons (e - ) is generated. The generated hydrogen ions (H + ) is transferred to the reducing electrode through the polymer electrolyte membrane, and the generated electrons (e - ) is transferred to the reducing electrode through an external circuit. At the reducing electrode, oxygen is supplied and converted into hydrogen ions (H + ) and electrons (e - ) and produces water by oxygen reduction reaction.

[0007] The polymer electrolyte membrane absorbs hydrogen ions (H + ) is the pathway through which hydrogen ions (H + In addition, the polymer electrolyte membrane must have excellent separation ability between hydrogen gas supplied to the oxidizing electrode and oxygen supplied to the reducing electrode, and other required properties include excellent mechanical strength, dimensional stability, and chemical resistance, as well as low ohmic loss at high current densities.

[0008] The requirements for a polymer electrolyte membrane necessary for the operation of the polymer electrolyte membrane fuel cell include high proton conductivity, chemical stability, low fuel permeability, high mechanical strength, low water content, and excellent dimensional stability. Conventional polymer electrolyte membranes tend to have difficulty achieving high performance under certain temperature and relative humidity conditions, particularly high temperature / low humidity conditions. This limits the range of use of polymer electrolyte membrane fuel cells using conventional polymer electrolyte membranes.

[0009] The lifespan of a polymer electrolyte membrane is shortened due to electrochemical and physical degradation during operation. The main cause of electrochemical degradation is the generation of radicals on the platinum electrode catalyst as hydrogen and oxygen cross over the polymer electrolyte membrane.

[0010] The radicals formed on the platinum electrode catalyst react with the ion conductor in the polymer electrolyte membrane, causing degradation of the polymer electrolyte membrane through reactions such as breaking the ion conductor chains.

[0011] Therefore, there is a current demand for technological development that can improve the mechanical durability of polymer electrolyte membranes while preventing electrochemical degradation of the membranes. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Korean Patent No. 0699450 (2007.03.28) [Patent Document 2] Korean Patent Publication No. 2011-0032298 (2011.03.30) [Patent Document 3] Korean Patent No. 1093708 (2011.12.15) Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to provide a polymer electrolyte membrane that can improve both the mechanical durability and the chemical durability of the polymer electrolyte membrane.

[0014] Another object of the present invention is to provide a polymer electrolyte membrane that maintains the same level of performance of a fuel cell including the same even when it includes a porous metal support.

[0015] Another object of the present invention is to provide a polymer electrolyte membrane in which the metal-based antioxidant is not washed away and the antioxidant effect is maintained for a long period of time, thereby improving the life of a fuel cell. [Means for solving the problem]

[0016] According to one aspect of the present invention, there is provided a polymer electrolyte membrane comprising a porous support and an ion conductor filling pores of the porous support, wherein the porous support is a metal porous support.

[0017] According to one embodiment of the present invention, the metal porous support may be a metal fiber structure sheet or a metal fiber nanoweb formed of metal fibers.

[0018] According to one embodiment of the present invention, the metal porous support may include at least one selected from the group consisting of Ce, Mn, Cu, Fe, W, Ti, Ir, Pt, and alloys thereof.

[0019] According to one embodiment of the present invention, the metal fibers may have an average diameter of more than 0.005 μm and less than or equal to 5 μm.

[0020] According to one embodiment of the present invention, the metal fiber structure sheet may have pores with a diameter of 0.01 μm to 30 μm.

[0021] According to one embodiment of the present invention, the metal fiber nanoweb has a basic weight of 1 to 100 g / m 2 may be.

[0022] According to an embodiment of the present invention, the ionic conductor may be one or more selected from the group consisting of a hydrocarbon-based ionic conductor, a fluorine-based ionic conductor, and an anionic ionic conductor.

[0023] According to an embodiment of the present invention, the thickness of the metal porous support may be 15 to 60% of the total thickness of the polymer electrolyte membrane.

[0024] According to another aspect of the present invention, there is provided a membrane-electrode assembly including the above-mentioned polymer electrolyte membrane, the membrane-electrode assembly including an anode electrode and a cathode electrode positioned opposite each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode.

[0025] According to yet another aspect of the present invention, there is provided an electrochemical device comprising a membrane-electrode assembly including the polymer electrolyte membrane described above. [Effects of the Invention]

[0026] The polymer electrolyte membrane according to the present invention has a mesh-like structure made of a metal used for oxidation prevention instead of a metal-based antioxidant, and is used as a support for a reinforced composite polymer electrolyte membrane, thereby improving both chemical durability and mechanical durability and providing good battery performance.

[0027] The polymer electrolyte membrane according to the present invention has an effect of maintaining an anti-oxidation effect for a long period of time, thereby improving the life of a fuel cell.

[0028] The polymer electrolyte membrane according to the present invention includes a metal porous support that functions to remove oxidation-inducing radicals, thereby allowing the radical scavenger to be uniformly dispersed over the entire surface of the polymer electrolyte membrane, thereby preventing electrochemical degradation over the entire surface of the polymer electrolyte membrane. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a vertical cross-sectional view of a polymer electrolyte membrane according to the present invention. [Figure 2] 1 is a vertical cross-sectional view of a membrane-electrode assembly including a polymer electrolyte membrane according to the present invention. [Figure 3] 1 is a schematic diagram showing the overall configuration of a fuel cell according to an embodiment of the present invention; [Figure 4] 1 is an enlarged view of a reinforced composite membrane of a polymer electrolyte membrane according to an embodiment of the present invention. [Figure 5] FIG. 2 is an enlarged view of a polymer electrolyte membrane according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] 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.

[0031] The terms "preferred" or "preferably" used herein refer to embodiments of the present invention that have certain advantages under certain conditions. However, other embodiments may also be preferred under the same or different conditions. Furthermore, the presence of one or more preferred embodiments does not imply that other embodiments are not useful, nor does it exclude other embodiments within the scope of the present invention.

[0032] As used herein, the term "comprising" is used to list materials, compositions, devices, and methods useful in the present invention, but is not limited to the listed examples.

[0033] A polymer electrolyte membrane according to one embodiment of the present invention includes a porous support and an ion conductor filled in pores of the porous support, wherein the porous support is a metal porous support.

[0034] Polymer electrolyte membranes include a single membrane formed by casting an ion conductor having ion conductivity in a mold, and a reinforced composite membrane containing a composite material produced by immersing a porous support in a dispersion liquid in which an ion conductor is dispersed.

[0035] The reinforced composite membrane comprises a porous support and an ion conductor filling the pores of the porous support, and has the effect of improving dimensional stability and physical and mechanical properties. Even if the resistance of the polymer electrolyte membrane itself increases slightly, the performance of the cell is prevented from deteriorating, and therefore the performance and lifespan of the fuel cell itself are maintained excellently.

[0036] The porous support constituting the reinforced composite membrane is generally made of a polymer material such as a perfluorinated polymer sheet containing numerous voids due to the microstructure of polymer fibrils, or a nanoweb in which nanofibers are accumulated in the form of a nonwoven fabric containing numerous voids.

[0037] As mentioned above, the present invention generally relates to reinforced composite membranes that utilize a metallic porous support instead of a polymeric porous support.

[0038] The metal porous support may contain one or more selected from the group consisting of Ce, Mn, Cu, Fe, W, Ti, Ir, Pt, and alloys thereof, and more preferably contains one or more selected from the group consisting of Ce, Ti, and alloys thereof.

[0039] The metal constituting the metal porous support can prevent chemical degradation of the electrolyte membrane by scavenging active radicals formed during battery operation. By functioning as a porous support, the metal can function as a physical support that improves the mechanical properties and dimensional stability of the polymer electrolyte membrane, while also functioning as an additive such as a radical scavenger.

[0040] The metal porous support according to the present invention may be configured in the form of a sheet having a number of voids due to the microstructure of fibrils of a metal material, instead of polymer fibrils in a polymeric porous support, or may have the form of a nanoweb in which a number of voids are accumulated in the form of a nonwoven fabric of a metal material.

[0041] More specifically, a sheet-shaped porous support having a large number of voids due to the microstructure of fibrils of a metal material can have a large number of voids due to the microstructure consisting of nodes interconnected by fibrils of a metal material.

[0042] The microstructure may have any shape as long as it contains channel-shaped voids in which the ion conductor can form ion clusters, and may have various shapes, such as a microstructure containing voids of a regular shape, such as a grid type, a net type, or a foam type, or an irregular shape, such as a net type or a coil type.

[0043] Meanwhile, the nanoweb may be a nanoweb in which nanofibers are accumulated in the form of a nonwoven fabric containing a large number of voids. The nanoweb may be formed from a metal porous support in a form similar to that of a nonwoven fabric formed by electrospinning in a manner similar to that of an existing polymeric porous support. For example, the nanoweb may be manufactured by a method in which metal nanofibers are softened by heat and then accumulated to form a nanoweb.

[0044] The nanoweb has a basic weight of 1 g / m 2 ~100g / m 2 , preferably 5 to 50 g / m 2 Although there are differences depending on the metal configuration, the nanoweb may have a basis weight of 1 g / m 2 If the thickness is less than 100 g / m, visible pores may be formed and the material may not function as a porous support. 2 If the temperature exceeds 100°C, the product may be manufactured in the form of paper or fabric with few pores.

[0045] The porosity of the metal porous support may be 45% or more, specifically 60% or more. Meanwhile, the porous support preferably has a porosity of 90% or less. If the porosity of the metal porous support exceeds 90%, the dimensional stability may be reduced, which may hinder smooth subsequent processing. The porosity can be calculated as the ratio of the air volume to the total volume of the metal porous support using the following equation (1):

[0046] In this case, 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.

[0047]

number

[0048] The polymer electrolyte membrane may be a reinforced composite membrane in which pores in the metal porous support are filled with an ion conductor, and may include a first ion conductor layer located on one side of the metal porous support and a second ion conductor layer located on the other side of the metal porous support. The first ion conductor layer and the second ion conductor layer may be formed by forming a thin film on the surface of the metal porous support with the ion conductor remaining after filling the pores in the metal porous support.

[0049] Preferably, the metal porous support according to the present invention functions as a radical scavenger by directly reacting with radicals, and therefore may be configured adjacent to an electrode where radicals are formed, or may be configured such that the thickness between the electrode and the metal porous support is thinner than that of a typical polymer electrolyte membrane, although this is merely an example and is not limiting.

[0050] The metal porous support is composed of an aggregate of nanofibers that are three-dimensionally irregularly and discontinuously connected, thereby containing a large number of uniformly distributed pores. The porous support, which is composed of a large number of uniformly distributed pores, has excellent porosity and properties (e.g., dimensional stability) that can complement the physical properties of ion conductors.

[0051] The diameter of the pores formed in the metal porous support may be in the range of 0.01 to 30 μm. If the diameter is less than 0.01 μm, the ionic conductivity of the polymer electrolyte may decrease, and if the diameter is more than 30 μm, the mechanical strength of the polymer electrolyte may decrease.

[0052] The metal porous support may be composed of an aggregate of nanofibers in which the metal nanofibers are three-dimensionally irregularly and discontinuously connected, and the average diameter of the metal nanofibers may be in the range of more than 0.005 μm and not more than 5 μm. If the average diameter of the metal nanofibers is 0.005 μm or less, the mechanical strength of the porous support may be reduced and the support may be damaged, such as by the tendency for pores to collapse at high temperatures. If the average diameter of the metal nanofibers is more than 5 μm, it may be difficult to adjust the porosity of the porous support.

[0053] The metal porous support may have a thickness ratio of 15 to 60% of the total thickness of the polymer electrolyte membrane, preferably 18 to 55%, and most preferably 20 to 50%.

[0054] If the thickness ratio of the metal porous support is lower than the above range, the mechanical strength and dimensional stability of the polymer electrolyte membrane may be reduced, and the radical scavenging effect may be reduced.If the thickness ratio of the metal porous support is higher than the above range, the resistance loss of the polymer electrolyte may be increased.

[0055] The ionic conductors may each independently be cation conductors having cation exchange groups such as protons, or anion conductors having anion exchange groups such as hydroxy ions, carbonates, or bicarbonates.

[0056] The cation exchange group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and combinations thereof, and generally may be a sulfonic acid group or a carboxyl group.

[0057] Examples of the cation conductor include a fluorine-based polymer containing the cation exchange group and fluorine in the main chain; a hydrocarbon polymer such as benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene, or polyphenylquinoxaline; a partially fluorinated polymer such as polystyrene-graft-ethylenetetrafluoroethylene copolymer or polystyrene-graft-polytetrafluoroethylene copolymer; and sulfonimide.

[0058] More specifically, when the cation conductor is a hydrogen ion cation conductor, the polymer may have a cation exchange group in a side chain selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, and derivatives thereof. Specific examples thereof include fluorine-based polymers including poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, defluorinated sulfurized polyether ketone, or a mixture thereof; sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfidesulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and mixtures thereof.

[0059] The anion conductor is a polymer capable of transporting anions such as hydroxide ions, carbonate ions, or bicarbonate ions. Anion conductors are commercially available in hydroxide or halide (generally chloride) forms, and can be used in industrial water purification, metal separation, or catalytic processes.

[0060] The anion conductor may generally be a polymer doped with a metal hydroxide. Specifically, metal hydroxide-doped poly(ether sulfone), polystyrene, vinyl polymer, poly(vinyl chloride), poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(benzimidazole), or poly(ethylene glycol) may be used.

[0061] Among the ion conductors, fluorine-based polymers can be used. The fluorine-based polymers can be, for example, perfluorosulfonic acid (PFSA)-based polymers or perfluorocarboxylic acid (PFCA)-based polymers, but are not limited thereto. Nafion (Dupont) can be used as the perfluorosulfonic acid-based polymer, and Flemion (Asahi Glass) can be used as the perfluorocarboxylic acid-based polymer.

[0062] The weight average molecular weight of the ionic conductor may be 240 g / mol to 200,000 g / mol, specifically 240 g / mol to 10,000 g / mol.

[0063] The present invention will be described in more detail below with reference to the drawings.

[0064] However, this is merely an example for explaining the present invention, and the scope of the present invention is not limited by the following description.

[0065] FIG. 1 is a vertical cross-sectional view of a polymer electrolyte membrane according to the present invention.

[0066] Referring to FIG. 1, a polymer electrolyte membrane according to one embodiment of the present invention is a vertical cross-sectional view of a reinforced composite membrane including a metal porous support 21 having a plurality of voids and an ion conductor (not shown) impregnated into the voids of the metal porous support, and may further include ion conductor layers 31 and 32 on one and the other sides of the metal porous support impregnated with the ion conductor.

[0067] As described above, the ion conductor layers 31 and 32 located on one side and the other side of the metal porous support may be configured to be thin so that the ion conductor layers located on the surface of the metal porous support are adjacent to the electrode where radicals are generated, in order to configure the metal porous support to function better as a radical scavenger.

[0068] 2 is a cross-sectional view schematically illustrating a membrane-electrode assembly including a polymer electrolyte membrane according to the present invention. Referring to FIG. 2, the membrane-electrode assembly 100 includes the polymer electrolyte membrane 50 and electrodes 20, 20' disposed on both sides of the polymer electrolyte membrane 50. The electrodes 20, 20' include electrode substrates 40, 40' and catalyst layers 30, 30' formed on the surfaces of the electrode substrates 40, 40'. A microporous layer (not shown) containing conductive fine particles such as carbon powder or carbon black may be further included between the electrode substrates 40, 40' and the catalyst layers 30, 30' to facilitate material diffusion within the electrode substrates 40, 40'.

[0069] In the membrane-electrode assembly 100, the electrode 20 disposed on one side of the polymer electrolyte membrane 50 and performing an oxidation reaction to generate hydrogen ions and electrons from the fuel delivered to the catalyst layer 30 via the electrode substrate 40 is referred to as the anode electrode, and the electrode 20′ disposed on the other side of the polymer electrolyte membrane 50 and performing a reduction reaction to generate water from the hydrogen ions supplied through the polymer electrolyte membrane 50 and the oxidant delivered to the catalyst layer 30′ via the electrode substrate 40′ is referred to as the cathode electrode.

[0070] The electrode substrates 40 and 40' may be porous conductive substrates to ensure smooth supply of hydrogen or oxygen. Representative examples include, but are not limited to, carbon paper, carbon cloth, carbon felt, and metal cloth (a porous film made of fibrous metal cloth or a metal film formed on the surface of a polymer fiber cloth). Furthermore, the electrode substrates 40 and 40' are preferably treated with a fluorine-based resin for water repellency, which can prevent a decrease in the diffusion efficiency of reactants due to water generated during fuel cell operation. Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, and copolymers thereof.

[0071] A fuel cell according to an embodiment of the present invention includes the membrane-electrode assembly and may be, for example, a fuel cell that uses hydrogen gas as fuel.

[0072] FIG. 3 is a schematic diagram showing the overall configuration of the fuel cell.

[0073] Referring to FIG. 3, the fuel cell 200 includes a fuel supply unit 210 that supplies a mixed fuel obtained by mixing fuel and water, 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 electrochemically reacting the reformed gas containing hydrogen gas supplied from the reforming unit 220 with an oxidant, and an oxidant supply unit 240 that supplies an oxidant to the reforming unit 220 and the stack 230.

[0074] The stack 230 includes 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.

[0075] 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.

[0076] The end plate of the separator is provided with a first pipe-shaped supply pipe 231 for injecting the reformed gas containing hydrogen gas supplied from the reforming section 220 and a second pipe-shaped supply pipe 232 for injecting oxygen gas, and the other end plate is 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.

[0077] FIG. 4 is an enlarged view of a polymer electrolyte membrane according to one embodiment of the present invention, and FIG. 5 is an enlarged view of a polymer electrolyte membrane according to another embodiment of the present invention.

[0078] 4 and 5, a reinforced composite membrane using a metal porous support similar in shape to a metal foam is shown. An ion conductor (not shown) is located in the pores formed in the metal porous support, and each pore is connected to another pore in a channel-like shape. Ion clusters are formed while the ion conductor is impregnated in the pores of the metal porous support, resulting in proton conductivity.

[0079] In this case, the metal porous support reacts with radicals generated at the electrode to remove the radicals, and also functions as a porous support. This provides excellent durability and dimensional stability of the polymer electrolyte membrane, as well as excellent chemical durability.

[0080] As in the present invention, since the metal porous support is positioned over the entire surface of the polymer electrolyte membrane, it has the same effect as when a radical scavenger is uniformly distributed over the polymer electrolyte membrane, and therefore has the advantage of excellent chemical durability over the entire surface of the polymer electrolyte membrane.

[0081] The present invention will be described in more detail below based on examples, but this is merely an illustrative description for understanding the present invention, and the scope of the present invention is not limited or restricted to the following examples.

[0082] [Manufacturing example]

[0083] <Comparative Example 1> - Electrospun porous support, Nafion reinforced composite membrane

[0084] PVP polymer porous supports were fabricated by electrospinning PVP mixed with small amounts of titanium propoxide and cerium nitrate at 15 kW.

[0085] A porous support was immersed in a 20 wt% Nafion dispersion to prepare a reinforced composite membrane with a thickness of 20 μm. The porous support was configured so that an ion conductor layer could be formed spontaneously on one side and the other side.

[0086] Comparative Example 2 - Nafion Single Membrane

[0087] A 20 wt % dispersion of Nafion was formed on a glass substrate to produce a single membrane with a thickness of 20 μm.

[0088] Comparative Example 3: Hydrocarbon-based ionic conductor single membrane

[0089] A dispersion of sulfonated poly(ether sulfone) (SPES) dissolved in DMAc (dimethylacetamide) at 15 wt% was formed on a glass substrate to produce a single membrane with a thickness of 20 μm.

[0090] Example 1

[0091] A polymer electrolyte membrane was prepared by coating the center with a Ce / Ti mesh layer (metallic yarn spun with a diameter of 1 μm, porosity 70%) with a thickness ratio of 20, assuming the thickness of the membrane of Comparative Example 2 to be 100.

[0092] <Example 2>

[0093] A polymer electrolyte membrane was prepared by coating the center with a Ce / Ti mesh layer (metallic yarn spun with a diameter of 1 μm, porosity 70%) having a thickness ratio of 33, assuming the thickness of the membrane of Comparative Example 2 to be 100.

[0094] Example 3

[0095] A polymer electrolyte membrane was prepared by coating the center with a Ce / Ti mesh layer (metallic yarn spun with a diameter of 1 μm, porosity 70%) with a thickness ratio of 50, assuming the thickness of the membrane of Comparative Example 2 to be 100.

[0096] Example 4

[0097] A polymer electrolyte membrane was prepared by coating the center with a Ce / Ti mesh layer (metal nanoweb, porosity 70%) having a thickness ratio of 20, assuming the thickness of the membrane of Comparative Example 3 to be 100.

[0098] <Example 5>

[0099] A polymer electrolyte membrane was prepared by coating the center with a Ce / Ti mesh layer (metal nanoweb, porosity 70%) having a thickness ratio of 33, assuming the thickness of the membrane of Comparative Example 3 to be 100.

[0100] Example 6

[0101] A polymer electrolyte membrane was prepared by coating the center with a Ce / Ti mesh layer (metal nanoweb, porosity 70%) having a thickness ratio of 50, assuming the thickness of the membrane of Comparative Example 3 to be 100.

[0102] <Comparative Example 4>

[0103] A polymer electrolyte membrane was prepared in the same manner as in Example 1, except that the diameter of the metal threads was 6 μm, as compared to the metal threads of the metal porous support.

[0104] <Comparative Example 5>

[0105] A polymer electrolyte membrane was prepared in the same manner as in Example 1, except that the diameter of the metal threads was 0.005 μm compared to the metal threads of the metal porous support.

[0106] [Evaluation example]

[0107] 1) Battery performance evaluation:

[0108] A cathode and anode were formed using a Pt / C catalyst by the decal transfer method, and then bonded to a polymer electrolyte membrane to fabricate and evaluate a membrane-electrode assembly. The output performance was evaluated by IV measurement of the membrane-electrode assembly. Specifically, to confirm the output performance under actual fuel cell operating conditions, the membrane-electrode assembly was attached to a fuel cell unit cell evaluation device and the temperature was maintained at 65°C. Hydrogen (100% RH) and air (100% RH) were supplied to the anode and cathode, respectively, in amounts consistent with stoichiometry 1.2 / 2.0. The current density at 0.6 V was measured, and a higher value indicates better output performance.

[0109] 2) Dimensional stability evaluation:

[0110] The polymer electrolyte membrane was dried in a vacuum oven at 80°C for 12 hours, and its dimensions were measured. It was then immersed in distilled water at room temperature for 24 hours, and its dimensions were measured again. The dimensional ratios before and after water absorption were compared. The lower the dimensional change rate, the higher the stability.

[0111] 3) Chemical durability evaluation:

[0112] The cell voltage of the evaluation cell was measured at regular intervals in the OCV state, and the rate of decrease compared to the initial OCV was calculated. Measurements were made using a Scribner 850 fuel cell test system (evaluation conditions: 90°C, 30% RH, 50 kPa). Specifically, the OCV (V) / initial OCV (V) was measured over time (hr) every 24 hours. When this ratio was 0.8 or less, the evaluation was terminated, and the measurement time was used as the durability criterion.

[0113] Membrane-electrode assemblies were manufactured using the polymer electrolyte membranes of the Examples and Comparative Examples, and the battery performance, dimensional stability, chemical durability, and battery life were evaluated. The results are shown in Table 1 below.

[0114] [Table 1]

[0115] Referring to Table 1, it can be seen that the examples using a metal support showed improved dimensional change and chemical durability compared to the reinforced composite membrane of electrospun support and Nafion (Comparative Example 1), the Nafion monolayer membrane (Comparative Example 2), and the hydrocarbon-based ion conductor monolayer membrane (Comparative Example 3).

[0116] Furthermore, looking at Table 1 for Examples 1 to 3 and Examples 4 to 6, it can be seen that as the thickness ratio of the metal support to the total polymer electrolyte membrane increases, durability and dimensional stability improve, but performance also decreases. When the thickness of the metal mesh is thicker than the appropriate range, or when the diameter of the metal threads constituting the metal support is excessively large (Comparative Example 4), durability and dimensional stability can be improved, but performance is significantly reduced, making practical implementation difficult. In contrast, when the thickness of the metal mesh is thinner than the appropriate range, or when the diameter of the metal threads is excessively small (Comparative Example 5), the effect of the support is significantly reduced.

Claims

1. A polymer electrolyte membrane comprising a porous support and an ion conductor filled in the pores of the porous support, The polymer electrolyte membrane wherein the porous support is a metal porous support.

2. The polymer electrolyte membrane according to claim 1 , wherein the metal porous support is a metal fiber structure sheet or a metal fiber nanoweb formed of metal fibers.

3. 2. The polymer electrolyte membrane according to claim 1, wherein the metal porous support comprises at least one selected from the group consisting of Ce, Mn, Cu, Fe, W, Ti, Ir, Pt, and alloys thereof.

4. 3. The polymer electrolyte membrane according to claim 2, wherein the metal fibers have an average diameter of more than 0.005 μm and not more than 5 μm.

5. The polymer electrolyte membrane according to claim 2, wherein the metal fiber structure sheet has pores with a diameter of 0.01 μm to 30 μm.

6. The metal fiber nanoweb has a basic weight of 1 to 100 g / m ２ The polymer electrolyte membrane according to claim 2, wherein

7. 2. The polymer electrolyte membrane according to claim 1, wherein the ion conductor is at least one selected from the group consisting of a hydrocarbon-based ion conductor, a fluorine-based ion conductor, and an anionic ion conductor.

8. 2. The polymer electrolyte membrane according to claim 1, wherein the thickness of the porous metal support is 15 to 60% of the total thickness of the polymer electrolyte membrane.

9. A membrane-electrode assembly comprising the polymer electrolyte membrane of claim 1, an anode electrode and a cathode electrode positioned opposite each other; a membrane-electrode assembly including a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode;

10. An electrochemical device comprising the membrane-electrode assembly of claim 9.

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