Metal diaphragm and manufacturing method thereof

Abstract

The invention relates to a metal diaphragm and a manufacturing method thereof. According to the metal separator and the manufacturing method thereof, conductivity and corrosion resistance can be excellent at the same time.

Description

Technical Field

[0001] This application relates to a metal diaphragm and a method for manufacturing the same. Background Technology

[0002] In response to global warming, powertrain technology is shifting from internal combustion engines (ICE) to electric vehicles (EVs) or hydrogen fuel cell electric vehicles (FCEVs). The fuel cells used in FCEVs provide power for industrial, residential, and automotive applications, as well as for small electronic devices such as portable devices. As an energy-efficient and environmentally friendly clean energy source, its application is gradually expanding.

[0003] A fuel cell is a power generation device that converts the chemical energy of fuel into electrical energy through electrochemical reactions within a fuel stack, utilizing the energy generated during the hydrogen-oxygen combination reaction. Specifically, a fuel cell can use hydrogen as fuel, and the oxidation of hydrogen produces protons and electrons. These protons and electrons then react electrochemically with oxygen in the air to produce water, while simultaneously generating electrical energy through the flow of electrons.

[0004] This hydrogen fuel cell consists of a membrane, a gas diffusion layer (GDL), and a membrane electrode assembly coated with catalyst powder. Theoretically, a hydrogen fuel cell can generate a voltage of 1.229 V, but due to the inherent characteristics of the aforementioned components and various limitations between them, its operating voltage is between 0.6 V and 0.8 V.

[0005] Among these components, the membrane is a key component in a hydrogen fuel cell that separates and distributes hydrogen and oxygen separately, and transmits the current generated by the electrochemical reaction.

[0006] As the separator, metal membranes based on materials such as stainless steel or titanium are primarily used. Stainless steel or titanium-based membranes typically have high conductivity, but a drawback is their susceptibility to corrosion in the high-temperature, high-humidity, and / or acidic environments within the fuel cell stack. As corrosion progresses, oxides form on the corroded surface. These metal oxides act as insulators, reducing the conductivity of the metal membrane and thus degrading the performance of the hydrogen fuel cell.

[0007] To prevent corrosion from degrading the performance of metal diaphragms, coatings are required. Such coatings should not reduce the conductivity of the metal diaphragm, but rather increase its corrosion resistance. Furthermore, it is difficult to expect a single material in a coating to possess both high conductivity and chemical stability and high corrosion resistance simultaneously. Therefore, there is a need for a metal diaphragm and its manufacturing method that can simultaneously ensure high conductivity and corrosion resistance by separately coating the metal diaphragm material with materials responsible for corrosion resistance and conductivity. Summary of the Invention

[0008] Technical issues The purpose of this application is to provide a metal diaphragm with both excellent conductivity and corrosion resistance, and a method for manufacturing the same.

[0009] Technical solution To achieve the above objectives, the metal diaphragm of this application comprises: a metal substrate and a coating, the coating being formed on the surface of the metal substrate and comprising conductive filler and inorganic polymer, wherein the conductive filler is contained in the coating at an area ratio of 5% to 95%.

[0010] The conductive filler may include at least one selected from carbon black, carbon nanotubes, graphene and carbon fiber.

[0011] In addition, the particle size of the conductive filler can be from 10 nm to 100 nm.

[0012] In addition, inorganic polymers can be polymers containing bonds between group IVB transition metal elements and oxygen atoms.

[0013] In addition, the metal substrate can be made of titanium or stainless steel.

[0014] In addition, the thickness of the coating can be from 10 nm to 100 nm.

[0015] Furthermore, the contact resistance of the coating can be 1 mΩ·cm. 2 Up to 20 mΩ·cm 2 .

[0016] Furthermore, the current density of the coating can be 0.5 μA / cm. 2 Up to 30 μA / cm 2 .

[0017] Furthermore, this application relates to a method for manufacturing a metal diaphragm, wherein the metal diaphragm comprises a metal substrate and a coating, the coating being formed on the surface of the metal substrate and comprising a conductive filler and an inorganic polymer, wherein the conductive filler is contained in the coating at an area ratio of 5% to 95%, the method comprising: a first coating step of coating a coating mixture containing the conductive filler and water onto the surface of the metal substrate and then drying it to form a coating; and a second coating step of coating a liquid metal-based organic material onto the dried coating and then heat-treating it to gel the liquid metal-based organic material into an inorganic polymer.

[0018] In addition, conductive fillers can be included in the coating mixture in an amount of 0.3 to 5 parts by weight per 100 parts by weight of water.

[0019] In addition, drying can be carried out in an air atmosphere at a temperature of 100°C or higher but less than 400°C for 30 seconds to 10 minutes.

[0020] Furthermore, liquid metal-based organic substances can exist in a state in which the metal-based organic substance represented by the following chemical formula 1 is dispersed in a liquid dispersion medium: [Chemical Formula 1] M(OR)4 Where M is a group IVB transition metal element, and R is a straight-chain alkyl or branched alkyl with 1 to 6 carbon atoms.

[0021] Furthermore, the coating of liquid metal-based organic substances onto a dried coating can be carried out by immersing a metal substrate having a dried coating formed thereon into the liquid metal-based organic substance, thereby allowing the liquid metal-based organic substance to penetrate into the water-removed coating area.

[0022] In addition, heat treatment can be performed by one or more steps selected from a first heat treatment step performed in an air atmosphere at a temperature of 100°C to 380°C and a second heat treatment step performed in a vacuum atmosphere at a temperature of 450°C to 600°C.

[0023] Beneficial effects According to the metal diaphragm and its manufacturing method of this application, both electrical conductivity and corrosion resistance can be excellent simultaneously. Attached Figure Description

[0024] Figure 1 A diagram illustrating a metal diaphragm according to one embodiment of this application is provided as an example.

[0025] Figure 2 The diagram illustrates, for example, a metal diaphragm obtained by coating a coating mixture onto the surface of a metal substrate and then drying it, to explain the first coating step according to one embodiment of this application.

[0026] Figure 3 The diagram illustrates a metal substrate on which an oxide film has been formed prior to pickling, and is used to explain the pickling process according to one embodiment of this application.

[0027] Figure 4 The diagram illustrates, for example, a metal substrate on which the oxide film on the surface has been removed after pickling, and is used to explain the pickling process according to one embodiment of this application.

[0028] Figure 5 This is a 1000x magnified image obtained by taking a scanning electron microscope of the surface of the metal diaphragm after the first coating step in Example 1.

[0029] Figure 6 This is a 20,000x magnified image obtained by taking a scanning electron microscope of the surface of the metal diaphragm after the first coating step in Example 1.

[0030] Figure 7 This is a 50,000x magnified image obtained by taking a scanning electron microscope of the surface of the metal diaphragm after the first coating step in Example 1.

[0031] Figure 8 This is a 50,000x magnified image obtained by taking a scanning electron microscope of the surface of the metal diaphragm after the second coating step in Example 1. Detailed Implementation

[0032] The metal diaphragm of this application will now be described with reference to the accompanying drawings, which are exemplary and the metal diaphragm of this application is not limited to the accompanying drawings.

[0033] Figure 1 A diagram illustrating a metal diaphragm according to one embodiment of this application is shown as an example. Figure 1 As shown, the metal diaphragm 100 of this application includes a metal substrate 110 and a coating 120. According to the metal diaphragm 100 of this application, both conductivity and corrosion resistance can be excellent simultaneously.

[0034] The metal substrate 110 is a metallic material used in the metal membrane for fuel cells. There are no particular limitations on the type of metal substrate 110; any metal substrate used in the metal membrane for fuel cells can be used without restriction. For example, a substrate made of titanium or stainless steel can be used as the metal substrate 110. Specifically, stainless steel such as SUS 316L, SUS443CT, or SUS 470FC can be used as the metal substrate 110. By including the aforementioned metal substrate 110, the metal membrane 100 can exhibit excellent electrical conductivity.

[0035] Coating 120 is a layer applied to the surface of the metal substrate 110, formed on the surface of the metal substrate 110, and includes conductive filler 121 and inorganic polymer 122. Forming coating 120 on the surface of the metal substrate 110 not only improves the conductivity of the metal substrate 110 but also enhances its corrosion resistance. In this specification, the term "surface" refers to the outer surface located on one, both, or all sides of the metal substrate.

[0036] The conductive filler 121 is a conductive material. For example, the conductive filler 121 may include at least one selected from carbon black, carbon nanotubes, graphene, and carbon fibers. In one embodiment, the conductive filler 121 may be carbon black. By including the conductive filler 121 in the coating 120, the conductivity of the metal membrane 100 can be improved.

[0037] In one embodiment, the particle size of the conductive filler 121 can be from 10 nm to 100 nm. Specifically, the particle size of the conductive filler 121 can have a lower limit of 20 nm or greater, 30 nm or greater, 40 nm or greater, or 50 nm or greater, and an upper limit of 90 nm or less, or 80 nm or less. The conductivity of the conductive filler 121 can be improved by having the above-described particle size.

[0038] Furthermore, the conductive filler 121 can be included in the coating 120 at an area ratio of 5% to 95%. Specifically, the conductive filler 121 can be included in the coating 120 at an area ratio of 5% to 95%, 10% to 95%, 15% to 95%, 20% to 95%, or 25% to 95%. Here, the area ratio of the conductive filler 121 can be measured on an image obtained by taking a picture of the surface of the coating 120 formed on the metal diaphragm 100 using a scanning electron microscope. The conductivity of the conductive filler 121 can be improved by including it in the coating 120 at the above-mentioned area ratio. In contrast, when the conductive filler 121 is included in the coating 120 at an area ratio less than the above-mentioned area ratio, it may be insufficient to ensure conductivity. Furthermore, when the conductive filler 121 is included in the coating 120 at an area ratio greater than the above-mentioned area ratio, the amount of highly corrosion-resistant material (specifically inorganic polymer 122) formed on the surface of the metal substrate 110 is insufficient, and therefore it may be difficult to ensure the adhesion between the conductive filler 121 and the metal substrate 110.

[0039] Inorganic polymer 122 is a polymer whose backbone is composed of inorganic substances other than carbon, and it is a highly corrosion-resistant material. For example, inorganic polymer 122 can be a polymer containing bonds between group IVB transition metal elements and oxygen atoms. Specifically, the group IVB transition metal elements can be titanium (Ti), zirconium (Zr), hafnium (Hf), or... (Rf) element. That is, the inorganic polymer 122 can be titanium sol-gel, zirconium sol-gel, hafnium sol-gel, or... Sol-gel. The corrosion resistance of the metal diaphragm 100 can be improved by including inorganic polymer 122 in the coating 120.

[0040] In one embodiment, the thickness of coating 120 can be from 10 nm to 100 nm. Specifically, the thickness of coating 120 can have a lower limit of 20 nm or greater, 30 nm or greater, 40 nm or greater, or 50 nm or greater, and an upper limit of 90 nm or less, or 80 nm or less. By having the above-mentioned thickness range, coating 120 can be stable without sacrificing conductivity. The thickness of coating 120 refers to the length from the lower surface to the upper surface of coating 120 in contact with the metal substrate 110, and specifically, may refer to the thickness of the layer formed by inorganic polymer 122, which is a corrosion-resistant material.

[0041] In another embodiment, the thickness of coating 120 (specifically, the thickness of the layer formed by inorganic polymer 122) can be equal to or 50 nm larger than the particle size of conductive filler 121. When the thickness of coating 120 is equal to or larger than the particle size of conductive filler 121 within the aforementioned range, it can be stable without loss of conductivity. In contrast, when the thickness of coating 120 is smaller than the particle size of conductive filler 121, the adhesion of coating 120 cannot be guaranteed, and coating of inorganic polymer 122 (which is a corrosion-resistant material) may be difficult. Furthermore, when the amount by which the thickness of coating 120 exceeds the particle size of conductive filler 121 exceeds the aforementioned range, conductivity may not be ensured by covering all conductive filler 121.

[0042] The contact resistance of coating 120 can be 1 mΩ·cm 2 Up to 20 mΩ·cm 2 Specifically, the upper limit of the contact resistance of coating 120 can be 18 mΩ·cm. 2 Or smaller, or 15 mΩ·cm 2 Or even smaller. The coating 120 can give the metal diaphragm 100 excellent conductivity by having the contact resistance described above.

[0043] Furthermore, the current density of coating 120 can be 0.5 μA / cm. 2 Up to 30 μA / cm 2 Specifically, the current density of coating 120 can be 0.6 μA / cm. 2 Up to 20 μA / cm 2 0.7 μA / cm 2 Up to 10 μA / cm 2 Or 0.8 μA / cm 2 Up to 5 μA / cm 2 The coating 120 can give the metal diaphragm 100 excellent corrosion resistance by having the above-mentioned current density.

[0044] This application also relates to a method for manufacturing a metal diaphragm. The method for manufacturing a metal diaphragm relates to a method for manufacturing the aforementioned metal diaphragm, and specific details regarding the metal diaphragm described below are the same as those in the description of the aforementioned metal diaphragm, and therefore will be omitted.

[0045] The method for manufacturing a metal diaphragm according to this application includes a first coating step and a second coating step. According to the method for manufacturing a metal diaphragm according to this application, both electrical conductivity and corrosion resistance can be excellent simultaneously.

[0046] Figure 2 The diagram illustrates, for example, a metal diaphragm obtained by coating a coating mixture onto the surface of a metal substrate and then drying it, to explain the first coating step according to one embodiment of this application. Figure 2 As shown, the first coating step is the step of forming a conductive filler 121 on the surface of the metal substrate 110, and is carried out by coating the surface of the metal substrate 110 with a coating mixture of conductive filler 121 and water, and then drying it. The method for manufacturing a metal diaphragm can improve the conductivity of the metal diaphragm by including the first coating step.

[0047] In one embodiment, the method for manufacturing a metal diaphragm may further include pickling before performing the first coating step. Figure 3 The diagram illustrates a metal substrate on which an oxide film has been formed prior to pickling, and is used to explain the pickling process according to one embodiment of this application. Figure 4 A diagram illustrating a metal substrate with the oxide film removed from its surface after pickling is provided to explain a pickling process according to one embodiment of this application. Figure 3 As shown, the metal substrate 110 has an oxide film 130 naturally formed on its surface. Since the oxide film 130 acts as an insulator, it may reduce the conductivity of the metal membrane, thereby reducing the performance of the hydrogen fuel cell. Therefore, the oxide film 130 formed on the surface of the metal substrate 110 can be removed by acid pickling. Therefore, as... Figure 4 As shown, the first coating step can be performed on a metal substrate 110 on which the oxide film 130 is not present. For example, the pickling treatment can be performed using one or more selected from hydrogen fluoride, ammonium fluoride, hydrochloric acid, sulfuric acid, and acetic acid. The method for manufacturing the metal diaphragm can further improve the conductivity of the metal diaphragm by further including a pickling treatment before performing the first coating step.

[0048] In the first coating step, any coating method known in the art can be used without limitation as a coating method for the coating mixture, such as bar coating, spraying, roller coating, dip coating, doctor blade coating, brush coating, etc.

[0049] Furthermore, when coating the coating mixture, the coating thickness can range from 10 nm to 100 nm. Specifically, when coating the coating mixture, the coating thickness can have a lower limit of 20 nm or greater, 30 nm or greater, 40 nm or greater, or 50 nm or greater, and an upper limit of 90 nm or less, or 80 nm or less. By keeping the coating thickness within the above range when coating the coating mixture, the conductivity of the metal separator can be improved.

[0050] In the first coating step, the conductive filler can be mixed with water and exist in a dispersed state in the water. The conductive filler can be included in the coating mixture at an amount of 0.3 to 5 parts by weight per 100 parts by weight of water. Specifically, the conductive filler can be included in the coating mixture at an amount of 0.35 to 3 parts by weight per 100 parts by weight of water. The conductive filler can improve the conductivity of the metal membrane by being included in the coating mixture at the above amounts.

[0051] Drying is performed to remove water from the coating mixture, and this can be carried out, for example, at a temperature of 100°C to 300°C or 100°C to 200°C in an air atmosphere for 1 to 10 minutes, 5 to 10 minutes, or 8 to 10 minutes. When drying is performed at temperatures below these levels, the coating mixture may not be sufficiently dried. Furthermore, when drying is performed at temperatures above these levels, the conductive filler contained in the coating mixture may be burned. Therefore, drying can be performed under the aforementioned temperature and time conditions.

[0052] like Figure 1 As shown, the second coating step is the step of forming an inorganic polymer 122 between conductive fillers 121 formed on the surface of the metal substrate 110, and is carried out by coating a liquid metal-based organic material (not shown) onto the coating dried in the first coating step, followed by heat treatment to gel the liquid metal-based organic material into an inorganic polymer. By including the second coating step, the method for manufacturing a metal diaphragm can further improve the corrosion resistance and conductivity of the metal diaphragm.

[0053] Liquid metal-based organic substances can exist in a state in which the metal-based organic substance represented by the following chemical formula 1 is dispersed in a liquid dispersion medium: [Chemical Formula 1] M(OR)4 Where M is a group IVB transition metal element, and R is a straight-chain alkyl or branched alkyl with 1 to 6 carbon atoms.

[0054] Specifically, the transition metal elements in Group IVB can be titanium (Ti), zirconium (Zr), hafnium (Hf), or... (Rf) element. By including the above-mentioned group IVB transition metal elements in the liquid metal-based organic material, the conductivity of the metal membrane 100 can be excellent.

[0055] Furthermore, R can be a straight-chain alkyl or branched alkyl having 1 to 6 carbon atoms, specifically, it can be a straight-chain alkyl or branched alkyl having 1 to 5 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms. Specific examples of R include straight-chain alkyl consisting of ethyl, methyl, propyl, butyl, pentyl, or hexyl, or branched alkyl consisting of n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 1-methylbutyl, 1-ethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, or 4-methyl-2-pentyl.

[0056] For example, the metal-based organic substance represented by the above chemical formula 1 can be tetraisopropoxytitanium (Ti(OCH(CH3)2)4), tetraisopropoxyzirconium (Zr(OCH(CH3)2)4), tetraethoxytitanium (Ti(OC2H5)4) or tetraethoxyzirconium (Zr(OC2H5)4).

[0057] In another embodiment, the metal-based organic material may contain an inorganic acid. For example, the inorganic acid may be nitric acid (HNO3), sulfuric acid (H2SO4), hydrochloric acid (HCl), phosphoric acid (H3PO4), perchloric acid (HClO4), hypochlorous acid (HClO), hydrofluoric acid (HF), acetic acid (CH3COOH), etc. By incorporating the aforementioned inorganic acid into the metal-based organic material, the metal contained within the material can be stabilized.

[0058] Regarding the type of dispersion medium, any dispersion medium known in the art can be used without particular limitation. Inorganic oligomers can be formed by dispersing the metal-based organic substance represented by the above chemical formula 1 in a liquid dispersion medium.

[0059] The concentration of liquid metal-based organic substances can range from 0.05 mol to 1 mol. By utilizing these concentration ranges, liquid metal-based organic substances can improve the corrosion resistance of metal diaphragms.

[0060] In one embodiment, the coating of a liquid metal-based organic substance onto a dried coating can be performed by immersing a metal substrate having a dried coating formed thereon into the liquid metal-based organic substance, allowing the liquid metal-based organic substance to penetrate into the water-removed coating areas. Here, immersion can be performed from 1 second to 10 minutes. Specifically, immersion can be performed from 1 second to 8 minutes, or from 1 second to 5 minutes. By performing immersion for the aforementioned durations, the liquid metal-based organic substance can penetrate into all water-removed coating areas.

[0061] Furthermore, the heat treatment can be performed through one or more steps selected from the first heat treatment step and the second heat treatment step. In one embodiment, the heat treatment includes both the first and second heat treatment steps. For example, the first heat treatment step can be performed at a temperature of 100°C to 380°C in an air atmosphere for 30 seconds to 40 minutes. Specifically, the first heat treatment step can be performed at a temperature of 150°C to 380°C, 200°C to 380°C, 250°C to 380°C, 300°C to 380°C, or 350°C to 380°C in an air atmosphere for 1 minute to 30 minutes or 5 minutes to 20 minutes. Furthermore, the second heat treatment step can be performed at a temperature of 450°C to 600°C in a vacuum atmosphere for 10 minutes to 60 minutes. Specifically, the second heat treatment step can be performed at a temperature of 450°C to 550°C or 450°C to 500°C in a vacuum atmosphere for 10 minutes to 40 minutes or 10 minutes to 20 minutes. By performing heat treatment under the above conditions, the liquid metal-based organic material that has penetrated into the water-removed coating area can gel into an inorganic polymer 122. In this specification, the term "air atmosphere" refers to an operating environment with an atmospheric state. In this specification, the term "vacuum atmosphere" refers to an operating environment with a vacuum state. For example, the pressure of a vacuum atmosphere can be from 0.0001 Pa to 0.01 Pa. By performing heat treatment under each of the above atmospheres, the liquid metal-based organic material can gel into an inorganic polymer 122, and the lattice of the titanium dioxide oxide film that may be generated during the gelation process can be distorted to improve conductivity.

[0062] The present application will now be described in more detail by way of embodiments thereof and comparative examples not thereof, but the scope of the present application is not limited to the embodiments shown below.

[0063] Example 1 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared. A coating mixture containing 0.96 wt% carbon black (as a conductive filler with a particle size of 50 nm) and 99.04 wt% water was applied to the surface of the titanium metal substrate to form a coating with a conductive filler area ratio of 50% and a thickness of 60 nm. The metal substrate coated with the coating mixture was then dried in air at 100°C for 10 minutes to form a coating made of conductive filler on the surface of the metal substrate. The surface of the metal substrate with the dried coating was imaged using a scanning electron microscope, and the results are shown below. Figures 5 to 7 .like Figures 5 to 7 As shown, it was confirmed that the coating formed on the surface of the metal substrate has a conductive filler with an area ratio of 50%.

[0064] Then, a 0.1 mol concentration of liquid metal-based organic material (obtained by dispersing tetraisopropoxy titanium (TTIP) in a dispersion medium) was rod-coated onto a metal substrate with a dried coating, thereby infiltrating the liquid metal-based organic material into the water-removed area. The metal substrate with the liquid metal-based organic material-infiltrated coating was then heat-treated at 380°C in air for 10 minutes, followed by heat-treated at 450°C under a vacuum of 0.01 Pa for 10 minutes, causing the liquid metal-based organic material to gel into a titanium sol-gel, which is an inorganic polymer, thus fabricating a metal membrane with a 60 nm thick coating formed on its surface. The coating formed on the surface of the metal substrate of the metal membrane was photographed, and the results are shown below. Figure 8 .like Figure 8 As shown, it was confirmed that the coating formed on the surface of the metal substrate has a conductive filler with an area ratio of 50%.

[0065] Example 2 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared, and a metal diaphragm was manufactured in the same manner as in Example 1, except that a coating mixture containing 0.38 wt% carbon black (as a conductive filler with a particle size of 50 nm) and 99.62 wt% water was applied to the surface of the titanium metal substrate to form a coating with a conductive filler area ratio of 25% and a thickness of 60 nm on the surface of the titanium metal substrate.

[0066] Example 3 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared, and a metal diaphragm was manufactured in the same manner as in Example 1, except that a coating mixture containing 1.54 wt% carbon black (as a conductive filler with a particle size of 50 nm) and 98.46 wt% water was applied to the surface of the titanium metal substrate to form a coating with a conductive filler area ratio of 70% and a thickness of 80 nm on the surface of the titanium metal substrate.

[0067] Comparative Example 1 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared, and a coating mixture containing 0.96 wt% carbon black (as a conductive filler with a particle size of 50 nm) and 99.04 wt% water was applied to the surface of the titanium metal substrate to form a coating with a conductive filler area ratio of 50% and a thickness of 60 nm. The metal substrate coated with the coating mixture was then dried in air at 100°C for 10 minutes to form a coating, thereby manufacturing a metal diaphragm.

[0068] Comparative Example 2 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared, and a metal diaphragm was manufactured in the same manner as in Example 1, except that a coating mixture containing 0.24 wt% carbon black (as a conductive filler with a particle size of 50 nm) and 99.76 wt% water was applied to the surface of the titanium metal substrate to form a coating with a conductive filler area ratio of 3% and a thickness of 40 nm on the surface of the titanium metal substrate.

[0069] Comparative Example 3 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared, and a metal diaphragm was manufactured in the same manner as in Example 1, except that a coating mixture containing 30% by weight of carbon black (as a conductive filler with a particle size of 50 nm) and 70% by weight of water was applied to the surface of the titanium metal substrate to form a coating with a conductive filler area ratio of 100% and a thickness of 200 nm on the surface of the titanium metal substrate.

[0070] Comparative Example 4 Manufacturing of metal diaphragms A metal diaphragm made of a titanium metal substrate (1 pole) is prepared without forming a coating on the surface.

[0071] Comparative Example 5 Manufacturing of metal diaphragms A titanium metal substrate (Grade 1) was prepared by rod-coating the surface of the titanium metal substrate with a 0.1 mol concentration of liquid metal-based organic material (obtained by dispersing titanium tetraisopropoxy (TTIP) in a dispersion medium). The substrate coated with the liquid metal-based organic material was then heat-treated at 380 °C in air for 10 minutes, followed by heat-treatment at 450 °C under a vacuum of 0.01 Pa for 10 minutes, causing the liquid metal-based organic material to gel into a titanium sol-gel, which is an inorganic polymer. This process created a metal membrane with a 50 nm thick coating formed on the surface.

[0072] Experimental Example 1. Evaluation of Contact Resistance For each metal diaphragm manufactured in the examples and comparative examples, the contact resistance was measured using a four-wire current-voltage measurement principle with a Zahner IM6 device, and the results are shown in Table 1 below. Specifically, the contact resistance measurement was performed in a constant current mode from 10 kHz to 10 mHz, with a DC current of 5 A and an amplitude of 0.5 A, and an electrode area of ​​25 cm² in the measurement region. 2 .

[0073] Experimental Example 2. Evaluation of Current Density In a simulated polymer electrolyte fuel cell (PEFC) environment, the current density of each metal membrane fabricated in the examples and comparative examples was measured using an EG&G 273A measuring instrument, and the results are shown in Table 1 below. Specifically, each metal membrane fabricated in the examples and comparative examples was placed in a 0.1 N H2SO4 + 2 ppm HF solution at 80 °C and bubbled with nitrogen (N2) for 1 hour, with an open circuit potential (OCP) of -0.25 V. SCE Up to 1.2 V SCE Measure current density within the range.

[0074] [Table 1] As shown in Table 1 above, it was confirmed that, unlike each metal diaphragm manufactured in Comparative Examples 1 to 5, each metal diaphragm manufactured in Examples 1 to 3 simultaneously has low contact resistance and current density, thus exhibiting excellent conductivity and corrosion resistance.

[0075] [Explanation of reference numerals in the attached image] 100: Metal diaphragm 110: Metal substrate 120: Coating 121: Conductive filler 122: Inorganic polymers 130: Oxide film

Claims

1. A metal diaphragm, comprising: Metal substrate: and A coating formed on the surface of a metal substrate and comprising conductive fillers and inorganic polymers. The conductive filler is included in the coating at an area ratio of 5% to 95%.

2. The metal diaphragm according to claim 1, wherein, The conductive filler includes at least one selected from carbon black, carbon nanotubes, graphene, and carbon fiber.

3. The metal diaphragm according to claim 1, wherein, The particle size of the conductive filler is from 10 nm to 100 nm.

4. The metal diaphragm according to claim 1, wherein, The inorganic polymer is a polymer containing bonds between group IVB transition metal elements and oxygen atoms.

5. The metal diaphragm according to claim 1, wherein, The metal substrate is made of titanium or stainless steel.

6. The metal diaphragm according to claim 1, wherein, The thickness of the coating is 10 nm to 100 nm.

7. The metal diaphragm according to claim 1, wherein, The contact resistance of the coating is 1 mΩ·cm 2 Up to 20 mΩ·cm 2 .

8. The metal diaphragm according to claim 1, wherein, The current density of the coating is 0.5 μA / cm. 2 Up to 30 μA / cm 2 .

9. A method for manufacturing a metal diaphragm, wherein, The metal diaphragm comprises: a metal substrate and a coating, the coating being formed on the surface of the metal substrate and comprising a conductive filler and an inorganic polymer, wherein the conductive filler is contained in the coating at an area ratio of 5% to 95%, and the method comprises: The first coating step involves applying a coating mixture containing conductive filler and water to the surface of a metal substrate, followed by drying to form a coating; and The second coating step involves coating a liquid metal-based organic substance onto a dried coating layer, followed by heat treatment to gel the liquid metal-based organic substance into an inorganic polymer.

10. The method according to claim 9, wherein, The conductive filler is included in the coating mixture in an amount of 0.3 to 5 parts by weight per 100 parts by weight of water.

11. The method according to claim 9, wherein, Drying is carried out in air at a temperature of 100°C or higher but less than 400°C for 30 seconds to 10 minutes.

12. The method according to claim 9, wherein, Liquid metal-based organic substances exist in a state in which the metal-based organic substance represented by the following chemical formula 1 is dispersed in a liquid dispersion medium: [Chemical Formula 1] M(OR)4 Where M is a group IVB transition metal element, and R is a straight-chain alkyl or branched alkyl with 1 to 6 carbon atoms.

13. The method according to claim 9, wherein, The coating of a liquid metal-based organic substance onto a dried coating is carried out by immersing a metal substrate having a dried coating formed thereon into the liquid metal-based organic substance, such that the liquid metal-based organic substance penetrates into the water-removed coating area.

14. The method according to claim 9, wherein, The heat treatment is performed by one or more steps selected from a first heat treatment step performed in an air atmosphere at a temperature of 100°C to 380°C and a second heat treatment step performed in a vacuum atmosphere at a temperature of 450°C to 600°C.

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