Metal separator and method for manufacturing same

Abstract

The present application relates to a metal separator and a method for manufacturing same. According to the metal separator and the manufacturing method therefor of the present application, electrical conductivity and corrosion resistance can be excellent at the same time.

Description

Metal separator and manufacturing method thereof

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

[0002] Recently, to address global warming, powertrains are shifting from internal combustion engines (ICEs) to electric vehicles (EVs) and hydrogen fuel cell vehicles (FCEVs). Fuel cells used in FCEVs not only power industrial, household, and vehicular applications, but also power small electronic devices such as portable devices. Their applications are expanding as a highly efficient, clean energy source, contributing to both energy conservation and environmental protection.

[0003] A fuel cell is a type of power generation device that converts the chemical energy of fuel into electrical energy through an electrochemical reaction within a stack. It generates power by utilizing the energy generated during the reaction between hydrogen and oxygen. Specifically, a fuel cell can use hydrogen gas as fuel, and the oxidation of hydrogen gas produces hydrogen ions (protons) and electrons. These hydrogen ions and electrons then undergo an electrochemical reaction with oxygen in the air, producing water and generating electrical energy from the electron flow.

[0004] These hydrogen fuel cells consist of a separator, a gas diffusion layer (GDL), and a membrane electrode assembly coated with catalyst powder. While hydrogen fuel cells can theoretically generate a voltage of 1.229 V, their operating voltage is typically between 0.6 V and 0.8 V due to various limitations, including inherent characteristics of the components and the characteristics of each component.

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

[0006] Metallic bipolar plates, typically made of materials like stainless steel or titanium, are used as separators. While stainless steel or titanium-based bipolar plates typically exhibit high conductivity, they are prone to corrosion in the high-temperature, high-humidity, and / or acidic environments within the stack. As corrosion progresses, oxides form on the corroded surface. These metal oxides act as insulators, reducing the electrical conductivity of the metal bipolar plates and, therefore, the performance of the hydrogen fuel cell.

[0007] To prevent corrosion, which can degrade the performance of metal bipolar plates, a coating is required. This coating must not lower the conductivity of the metal bipolar plate, but must also enhance its corrosion resistance. Furthermore, it is difficult to expect a single coating material to be chemically stable, offering both high corrosion resistance and high conductivity. Therefore, there is a need for a metal bipolar plate and a manufacturing method thereof that can simultaneously secure high conductivity and corrosion resistance by coating the metal bipolar plate material with separate materials responsible for corrosion resistance and conductivity.

[0008] The object of the present application is to provide a metal separator having excellent electrical conductivity and corrosion resistance and a method for manufacturing the same.

[0009] In order to solve the above problem, the metal separator of the present application includes a metal base material; and a coating layer formed on the surface of the metal base material and including a conductive filler and an inorganic polymer, wherein the conductive filler is included in the coating layer at an area ratio of 5% to 95%.

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

[0011] Additionally, the conductive filler may have a particle size of 10 nm to 100 nm.

[0012] Additionally, the inorganic polymer may be a polymer containing a bond between a Group IVB transition metal element and an oxygen atom.

[0013] Additionally, the metal base material may be a base material made of titanium or stainless steel.

[0014] Additionally, the coating layer may have a thickness of 10 nm to 100 nm.

[0015] In addition, the coating layer has a contact resistance of 1 mΩ·cm 2 Within 20 mΩ·cm 2 It could be.

[0016] In addition, the coating layer has a current density of 0.5 ㎂ / cm 2 Within 30 ㎂ / cm 2 It could be.

[0017] In addition, the method for manufacturing a metal separator of the present application comprises a metal base material, and a coating layer formed on the surface of the metal base material and containing a conductive filler and an inorganic polymer, wherein the conductive filler is included in the coating layer at an area ratio of 5% to 95%, the method comprising a first coating step of coating a coating mixture containing a conductive filler and water on the surface of the metal base material and then drying the coating mixture to form a coating layer; and a second coating step of coating a liquid metal-based organic material on the dried coating layer and then heat-treating the liquid metal-based organic material to gel the liquid metal-based organic material into an inorganic polymer.

[0018] Additionally, the conductive filler may 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] Additionally, the drying can be performed at a temperature of 100°C to less than 400°C for 30 seconds to 10 minutes in an air atmosphere.

[0020] In addition, the liquid metal-based organic material may exist in a state in which the metal-based organic material composed of the following chemical formula 1 is dispersed in a liquid dispersion medium.

[0021] [Chemical Formula 1]

[0022] M(OR)4

[0023] In the above chemical formula 1, M is a group IVB transition metal element, and R is a straight or branched alkyl group having 1 to 6 carbon atoms.

[0024] In addition, coating the liquid metal-based organic material on the dried coating layer can be performed by immersing the metal base material on which the dried coating layer has been formed in the liquid metal-based organic material, and mixing the liquid metal-based organic material into the area of ​​the coating layer from which the water has been removed.

[0025] In addition, the heat treatment may be performed through one or more steps selected from a first heat treatment step performed at a temperature of 100°C to 380°C in an air atmosphere; and a second heat treatment step performed at a temperature of 450°C to 600°C in a vacuum atmosphere.

[0026] According to the metal separator of the present application and the method for manufacturing the same, both electrical conductivity and corrosion resistance can be excellent at the same time.

[0027] FIG. 1 is a drawing illustrating a metal separator according to one embodiment of the present application.

[0028] FIG. 2 is a drawing showing an example of a metal separator that has been dried after coating a coating mixture on the surface of a metal base material to explain a first coating step according to one embodiment of the present application.

[0029] FIG. 3 is a drawing showing a metal base material having an oxide film formed on the surface before pickling to explain the pickling treatment according to one embodiment of the present application.

[0030] FIG. 4 is a drawing showing a metal base material with an oxide film removed from the surface after pickling treatment to explain the pickling treatment according to one embodiment of the present application.

[0031] Figure 5 is a 1000x magnification image of the surface of a metal separator that has undergone the first coating step in Example 1, taken using a scanning electron microscope.

[0032] Figure 6 is a 20,000x magnification image of the surface of a metal separator that has undergone the first coating step in Example 1, taken using a scanning electron microscope.

[0033] Figure 7 is a 50,000x magnification image of the surface of a metal separator that has undergone the first coating step in Example 1, taken using a scanning electron microscope.

[0034] Figure 8 is a 50,000x magnification image of the surface of a metal separator that has undergone a second coating step in Example 1, taken using a scanning electron microscope.

[0035] Hereinafter, the metal separator of the present application will be described with reference to the attached drawings. The attached drawings are exemplary, and the metal separator of the present application is not limited to the attached drawings.

[0036] FIG. 1 is a drawing exemplarily showing a metal separator according to one embodiment of the present application. As shown in FIG. 1, the metal separator (100) of the present application includes a metal base material (110) and a coating layer (120). According to the metal separator (100) of the present application, both electrical conductivity and corrosion resistance can be excellent.

[0037] The above metal base material (110) is a metal material used in a metal separator for a fuel cell. The type of the metal base material (110) is not particularly limited, and any metal base material used in a metal separator for a fuel cell can be used without limitation. For example, a base material made of titanium or stainless steel can be used as the metal base material (110). Specifically, stainless steel such as SUS 316L, SUS 443CT, or SUS 470FC can be used as the metal base material (110). The metal separator (100) can have excellent electrical conductivity by including the above-described metal base material (110).

[0038] The above coating layer (120) is a layer coated on the surface of the metal base material (110), is formed on the surface of the metal base material (110), and includes a conductive filler (121) and an inorganic polymer (122). The coating layer (120) is formed on the surface of the metal base material (110), thereby improving not only the electrical conductivity of the metal base material (110) but also the corrosion resistance thereof. In this specification, the term “surface” means an outer surface located on one side, both sides, or all sides of the metal base material.

[0039] The conductive filler (121) is a material having electrical conductivity. For example, the conductive filler (121) may include one or more selected from carbon black, carbon nanotubes, graphene, and carbon fiber. In one embodiment, the conductive filler (121) may be carbon black. By including the conductive filler (121) in the coating layer (120), the electrical conductivity of the metal separator (100) can be improved.

[0040] In one example, the conductive filler (121) may have a particle size of 10 nm to 100 nm. Specifically, the particle size of the conductive filler (121) may have a lower limit of 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more, and an upper limit of 90 nm or less or 80 nm or less. The conductive filler (121) may have the above-described particle size, thereby improving electrical conductivity.

[0041] In addition, the conductive filler (121) may be included in the coating layer (120) at an area ratio of 5% to 95%. Specifically, the conductive filler (121) may be included in the coating layer (120) at an area ratio of 5% to 95%, 10% to 95%, 15% to 95%, 20% to 95%, or 25% to 95%. At this time, the area ratio of the conductive filler (121) may be measured on an image taken by a scanning electron microscope of the surface of the coating layer (120) formed on the metal separator (100). The conductive filler (121) may be included in the coating layer (120) at the above-described area ratio, thereby improving electrical conductivity. In contrast, if the conductive filler (121) is included in the coating layer (120) in an area ratio less than the aforementioned ratio, it may not be sufficient to secure electrical conductivity. In addition, if the conductive filler (121) is included in the coating layer (120) in an area ratio greater than the aforementioned ratio, the amount of the highly corrosion-resistant material, specifically, the inorganic polymer (122), formed on the surface of the metal base material (110) is not sufficient, so it may not be easy to secure adhesion between the conductive filler (121) and the metal base material (110).

[0042] The inorganic polymer (122) is a polymer having an inorganic substance other than carbon as a backbone and is a highly corrosion-resistant material. For example, the inorganic polymer (122) may be a polymer containing a bond between a Group IVB transition metal element and an oxygen atom. Specifically, the Group IVB transition metal element may be a titanium (Ti) element, a zirconium (Zr) element, a hafnium (Hf) element, or a rutherfordium (Rf) element. That is, the inorganic polymer (122) may be a titanium sol-gel, a zirconium sol-gel, a hafnium sol-gel, or a rutherfordium sol-gel. By including the inorganic polymer (122) in the coating layer (120), the corrosion resistance of the metal separator (100) can be improved.

[0043] In one example, the coating layer (120) may have a thickness of 10 nm to 100 nm. Specifically, the thickness of the coating layer (120) may have a lower limit of 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more, and an upper limit of 90 nm or less or 80 nm or less. By having the above-described thickness range, the coating layer (120) may be stabilized without loss of electrical conductivity. The thickness of the coating layer (120) refers to the length from the lower surface of the coating layer (120) in contact with the metal base material (110) to the upper surface, and specifically, may refer to the thickness of a layer formed by an inorganic polymer (122) which is a corrosion-resistant material.

[0044] In another example, the thickness of the coating layer (120), specifically, the thickness of the layer formed by the inorganic polymer (122), may be the same as the particle size of the conductive filler (121), or may be 50 nm or less larger than the particle size of the conductive filler (121). When the thickness of the coating layer (120) is the same as the particle size of the conductive filler (121), or is larger than the particle size of the conductive filler (121) by the aforementioned range, it can be stabilized without loss of electrical conductivity. In contrast, when the thickness of the coating layer (120) is smaller than the particle size of the conductive filler (121), it is impossible to secure the adhesion of the coating layer (120), and coating of the inorganic polymer (122), which is a corrosion-resistant material, may be difficult. In addition, if the thickness of the coating layer (120) is greater than the particle size of the conductive filler (121) by an amount exceeding the aforementioned range, it may be impossible to secure conductivity by covering all of the conductive filler (121).

[0045] The above coating layer (120) has a contact resistance of 1 mΩ·cm 2 Within 20 mΩ·cm 2 It can be. Specifically, the upper limit of the contact resistance of the coating layer (120) is 18 mΩ·cm. 2 Less than or equal to 15 mΩ·cm 2It may be as follows. Since the above coating layer (120) has the above-described contact resistance, the electrical conductivity of the metal separator (100) may be excellent.

[0046] In addition, the coating layer (120) has a current density of 0.5 ㎂ / cm 2 Within 30 ㎂ / cm 2 It can be. Specifically, the current density of the coating layer (120) is 0.6 ㎂ / cm 2 Within 20 ㎂ / cm 2 , 0.7 ㎂ / cm 2 Within 10 ㎂ / cm 2 or 0.8 ㎂ / cm 2 5 ㎂ / cm 2 It can be. Since the coating layer (120) has the above-mentioned current density, the corrosion resistance of the metal separator (100) can be excellent.

[0047] The present application also relates to a method for manufacturing a metal separator. The method for manufacturing the metal separator relates to a method for manufacturing the aforementioned metal separator. Since the specific details of the metal separator described below are equally applicable to the metal separator described above, they will be omitted.

[0048] The method for manufacturing a metal separator of the present application comprises a first coating step and a second coating step. According to the method for manufacturing a metal separator of the present application, both excellent electrical conductivity and corrosion resistance can be achieved simultaneously.

[0049] FIG. 2 is a drawing showing an example of a metal separator that has been dried after coating a coating mixture on the surface of a metal base material to explain a first coating step according to one embodiment of the present application. As shown in FIG. 2, the first coating step is a step of forming a conductive filler (121) on the surface of a metal base material (110), and is performed by coating a coating mixture of the conductive filler (121) and water on the surface of the metal base material (110) and then drying it. The method for manufacturing the metal separator can improve the electrical conductivity of the metal separator by including the first coating step.

[0050] In one example, the method for manufacturing the metal separator may further include a pickling treatment before performing the first coating step. FIG. 3 is a drawing exemplarily showing a metal base material having an oxide film formed on the surface before the pickling treatment to explain the pickling treatment according to one embodiment of the present application. FIG. 4 is a drawing exemplarily showing a metal base material from which the oxide film has been removed on the surface after the pickling treatment to explain the pickling treatment according to one embodiment of the present application. As shown in FIG. 3, the metal base material (110) has an oxide film (130) naturally formed on the surface. Since the oxide film (130) acts as an insulator, it may reduce the electrical conductivity of the metal separator, thereby reducing the performance of the hydrogen fuel cell. Therefore, the oxide film (130) formed on the surface of the metal base material (110) can be removed by the pickling treatment. Accordingly, as shown in Fig. 4, the first coating step can be performed on a metal base material (110) having no oxide film (130) on the surface. 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 separator can further improve the electrical conductivity of the metal separator by further including a pickling treatment before performing the first coating step.

[0051] 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, and for example, bar coating, spray coating, roll coating, dip coating, blade coating, or brushing coating can be used.

[0052] In addition, when coating the coating mixture, the coating thickness may be 10 nm to 100 nm. Specifically, when coating the coating mixture, the lower limit of the coating thickness may be 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more, and the upper limit may be 90 nm or less or 80 nm or less. When coating the coating mixture, the coating thickness has the above-mentioned range, so that the electrical conductivity of the metal separator can be improved.

[0053] In the first coating step, the conductive filler may be mixed with the water and present in a dispersed state within the water. The conductive filler may be included in the coating mixture in an amount of 0.3 to 5 parts by weight relative to 100 parts by weight of the water. Specifically, the conductive filler may be included in the coating mixture in an amount of 0.35 to 3 parts by weight relative to 100 parts by weight of the water. By including the conductive filler in the coating mixture in the aforementioned amount, the electrical conductivity of the metal separator may be improved.

[0054] The drying is performed to remove water contained in the coating mixture, and may be performed, 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. If the drying is performed below the temperature described above, the coating mixture may not be sufficiently dried. In addition, if the drying is performed above the temperature described above, the conductive filler contained in the coating mixture may be burned. Therefore, the drying may be performed under the temperature and time conditions described above.

[0055] The above-described secondary coating step, as shown in Fig. 1, is a step of forming an inorganic polymer (122) between the conductive filler (121) formed on the surface of the metal base material (110), and is performed by coating a liquid metal-based organic substance (not shown) on the coating layer dried in the first coating step, and then heat-treating to gel the liquid metal-based organic substance into an inorganic polymer. The method for manufacturing the metal separator can further improve the corrosion resistance of the metal separator with improved electrical conductivity by including the secondary coating step.

[0056] The above liquid metal-based organic material may exist in a state in which the metal-based organic material composed of the following chemical formula 1 is dispersed in a liquid dispersion medium.

[0057] [Chemical Formula 1]

[0058] M(OR)4

[0059] In the above chemical formula 1, M is a group IVB transition metal element, and R is a straight or branched alkyl group having 1 to 6 carbon atoms.

[0060] Specifically, the IVB group transition metal element may be a titanium (Ti) element, a zirconium (Zr) element, a hafnium (Hf) element, or a rutherfordium (Rf) element. By including the IVB group transition metal element described above in the liquid metal-based organic material, the electrical conductivity of the metal separator (200) may be excellent.

[0061] In addition, the R may be a straight-chain or branched-chain alkyl group having 1 to 6 carbon atoms, and specifically, a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms. Specific examples of the R include a straight-chain alkyl group composed of ethyl, methyl, propyl, butyl, pentyl, or hexyl, or a branched-chain alkyl group composed of n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 1-methyl-butyl, 1-ethyl-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, or 4-methyl-2-pentyl.

[0062] For example, the metal-based organic material composed of the above chemical formula 1 may be titanium tetraisopropoxide (Ti(OCH(CH3)2)4), zirconium tetraisopropoxide (Zr(OCH(CH3)2)4), titanium tetraethoxide (Ti(OC2H5)4), or zirconium tetraethoxide (Zr(OC2H5)4).

[0063] In another example, the metal-based organic material can be charged with an inorganic acid. For example, the inorganic acid may include nitric acid (HNO3), sulfuric acid (H2SO4), hydrochloric acid (HCl), phosphoric acid (H3PO4), perchloric acid (HClO4), hypochlorous acid (HClO), hydrofluoric acid (HF), or acetic acid (CH3COOH). By charging the metal-based organic material with the aforementioned inorganic acid, the metal contained in the metal-based organic material can be stabilized.

[0064] Any dispersion medium known in the art can be used without any particular limitation as the type of the above dispersion medium. By dispersing the metal-based organic material composed of the above chemical formula 1 in the liquid dispersion medium, an inorganic oligomer can be formed.

[0065] The concentration of the liquid metal-based organic material may be 0.05 mol to 1 mol. The liquid metal-based organic material having the above-described concentration range can improve the corrosion resistance of the metal separator.

[0066] In one example, coating the liquid metal-based organic material on the dried coating layer can be performed by immersing the metal base material on which the dried coating layer is formed into the liquid metal-based organic material, so that the liquid metal-based organic material is mixed into the area of ​​the coating layer from which the water has been removed. At this time, the immersion can be performed for 1 second to 10 minutes. Specifically, the immersion can be performed for 1 second to 8 minutes or 1 second to 5 minutes. By performing the immersion for the aforementioned time, the liquid metal-based organic material can be mixed into all areas of the coating layer from which the water has been removed.

[0067] In addition, the heat treatment may be performed through one or more steps selected from a first heat treatment step and a second heat treatment step. In one embodiment, the heat treatment is performed by both the first heat treatment step and the second heat treatment step. For example, the first heat treatment step may be performed in an air atmosphere at a temperature of 100°C to 380°C for 30 seconds to 40 minutes. Specifically, the first heat treatment step may be performed in an air atmosphere 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 for 1 minute to 30 minutes or 5 minutes to 20 minutes. In addition, the second heat treatment step may be performed in a vacuum atmosphere at a temperature of 450°C to 600°C for 10 minutes to 60 minutes. Specifically, the second heat treatment step may be performed under a vacuum atmosphere at a temperature of 450°C to 550°C or 450°C to 500°C for 10 to 40 minutes or 10 to 20 minutes. By performing the heat treatment under the conditions described above, the liquid metal-based organic material mixed in the area of ​​the coating layer from which the water has been removed can be gelled into an inorganic polymer (122). As used herein, the term “atmospheric atmosphere” means a working environment having an atmospheric state. As used herein, the term “vacuum atmosphere” means a working environment having a vacuum state. For example, the pressure of the vacuum atmosphere may be 0.0001 Pa to 0.01 Pa. By performing the heat treatment under each of the atmospheres described above, the liquid metal-based organic material can be gelled into an inorganic polymer (122), and the lattice of the titanium dioxide oxide film that may be generated during the gelling process can be distorted to improve electrical conductivity.

[0068]

[0069] Hereinafter, the present application will be described in more detail through examples according to the present application and comparative examples not according to the present application, but the scope of the present application is not limited by the examples presented below.

[0070]

[0071] Example 1

[0072] Manufacturing of metal separators

[0073] A titanium metal base material (Grade 1) was prepared, and a coating mixture containing 0.96 wt% of carbon black with a particle size of 50 nm and 99.04 wt% of water as a conductive filler was bar-coated on the surface of the titanium metal base material, so that the conductive filler had an area ratio of 50% and a coating layer had a thickness of 60 nm. Thereafter, the metal base material coated with the coating mixture was dried at a temperature of 100°C for 10 minutes in an air atmosphere, so that a coating layer made of the conductive filler was formed on the surface of the metal base material. At this time, the surface of the metal base material with the dried coating layer formed was photographed using a scanning electron microscope, and the results are shown in FIGS. 5 to 7. As shown in FIGS. 5 to 7, it was confirmed that the coating layer formed on the surface of the metal base material was made of the conductive filler at an area ratio of 50%.

[0074] Afterwards, the metal base material on which the above-described coating layer was formed was bar-coated with a liquid metal-based organic substance having a concentration of 0.1 mol, in which titanium tetraisopropoxide (TTIP) was dispersed in a dispersion medium, so that the liquid metal-based organic substance was mixed into the area where the water had been removed. Afterwards, the metal base material on which the coating layer with the liquid metal-based organic substance mixed was formed was heat-treated at 380°C for 10 minutes in an air atmosphere, and then heat-treated at 450°C for 10 minutes in a vacuum atmosphere of 0.01 Pa so that the liquid metal-based organic substance gelled into a titanium sol-gel, which is an inorganic polymer, thereby manufacturing a metal separator on which a 60 nm thick coating layer was formed. At this time, the coating layer formed on the surface of the metal base material of the metal separator was photographed, and the results are shown in FIG. 8. As shown in FIG. 8, it was confirmed that the coating layer formed on the surface of the metal base material consisted of the conductive filler at an area ratio of 50%.

[0075]

[0076] Example 2

[0077] Manufacturing of metal separators

[0078] A titanium metal base material (Grade 1) was prepared, and the surface of the titanium metal base material was bar-coated with a coating mixture containing 0.38 wt% of carbon black with a particle size of 50 nm and 99.62 wt% of water as a conductive filler, thereby forming a coating layer having an area ratio of 25% and a thickness of 60 nm on the surface of the titanium metal base material, and a metal separator was manufactured in the same manner as in Example 1, except that the conductive filler was applied to the surface of the titanium metal base material.

[0079]

[0080] Example 3

[0081] Manufacturing of metal separators

[0082] A titanium metal base material (Grade 1) was prepared, and the surface of the titanium metal base material was bar-coated with a coating mixture containing 1.54 wt% of carbon black with a particle size of 50 nm and 98.46 wt% of water as a conductive filler, thereby forming a coating layer having an area ratio of 70% and a thickness of 80 nm on the surface of the titanium metal base material, and a metal separator was manufactured in the same manner as in Example 1, except that the conductive filler was applied to the surface of the titanium metal base material.

[0083]

[0084] Comparative Example 1

[0085] Manufacturing of metal separators

[0086] A titanium metal substrate (Grade 1) was prepared, and the surface of the titanium metal substrate was bar-coated with a coating mixture containing 0.96 wt% of carbon black with a particle size of 50 nm and 99.04 wt% of water as a conductive filler, thereby forming a coating layer having an area ratio of 50% and a thickness of 60 nm. Thereafter, the metal substrate coated with the coating mixture was dried at a temperature of 100°C for 10 minutes in an air atmosphere to form a coating layer, thereby manufacturing a metal separator.

[0087]

[0088] Comparative Example 2

[0089] Manufacturing of metal separators

[0090] A titanium metal base material (Grade 1) was prepared, and the surface of the titanium metal base material was bar-coated with a coating mixture containing 0.24 wt% of carbon black with a particle size of 50 nm and 99.76 wt% of water as a conductive filler, thereby forming a coating layer having an area ratio of 3% and a thickness of 40 nm on the surface of the titanium metal base material, and a metal separator was manufactured in the same manner as in Example 1, except that the conductive filler was applied to the surface of the titanium metal base material.

[0091]

[0092] Comparative Example 3

[0093] Manufacturing of metal separators

[0094] A titanium metal base material (Grade 1) was prepared, and the surface of the titanium metal base material was bar-coated with a coating mixture containing 30 wt% of carbon black with a particle size of 50 nm and 70 wt% of water as a conductive filler, thereby forming a coating layer having a thickness of 200 nm and an area ratio of 100% of the conductive filler on the surface of the titanium metal base material, and a metal separator was manufactured in the same manner as in Example 1, except that the coating layer was formed.

[0095]

[0096] Comparative Example 4

[0097] Manufacturing of metal separators

[0098] A metal separator made of titanium metal base material (Grade 1) was prepared without forming a coating layer on the surface.

[0099]

[0100] Comparative Example 5

[0101] Manufacturing of metal separators

[0102] A titanium metal substrate (Grade 1) was prepared, and the surface of the titanium metal substrate was bar-coated with a liquid metal-based organic substance having a concentration of 0.1 mol and titanium tetraisopropoxide (TTIP) dispersed in a dispersion medium, thereby coating the surface of the metal substrate with the liquid metal-based organic substance. Thereafter, the metal substrate coated with the liquid metal-based organic substance was heat-treated at 380°C for 10 minutes in an air atmosphere, and then heat-treated at 450°C for 10 minutes in a vacuum atmosphere of 0.01 Pa, so that the liquid metal-based organic substance gelled into a titanium sol-gel, which is an inorganic polymer, thereby manufacturing a metal separator having a 50 nm thick coating layer formed on the surface.

[0103]

[0104] Experimental Example 1. Contact Resistance Evaluation

[0105] For each of the metal separators manufactured in the examples and comparative examples, the contact resistance was measured using the IM6 equipment of Zahner using the four-wire current-voltage measurement principle, and the results are shown in Table 1 below. Specifically, the contact resistance measurement method was performed in constant current mode with an amplitude of 0.5 A and a measurement area of ​​25 cm. 2 The experiment was performed in the range from 10 kHz to 10 mHz with a DC current of 5 A having an electrode area of ​​.

[0106]

[0107] Experimental Example 2. Current Density Evaluation

[0108] The current density for the metal separators manufactured in each of the examples and comparative examples was measured under a simulated environment of a PEFC (Polymer Electrolyte Fuel Cell) using an EG&G 273A measuring device, and the results are shown in Table 1 below. Specifically, the current density was measured by placing the metal separators manufactured in each of the examples and comparative examples in a 0.1 N H2SO4 + 2 ppm HF solution at 80°C, bubbling with nitrogen (N2) for 1 hour, and then measuring the OCP (Open circuit potential) at -0.25 V. SCE 1.2 V SCE Measured in the range.

[0109] Contact resistance (mΩ·cm) 2 )Current density (㎂ / cm 2 ) Example 1150.8 Example 2200.8 Example 3142.6 Comparative Example 1870 Comparative Example 21470 Comparative Example 3870 Comparative Example 41770 Comparative Example 52570.8

[0110] As shown in Table 1 above, the metal separators manufactured in each of Examples 1 to 3 were confirmed to have lower contact resistance and current density simultaneously, unlike the metal separators manufactured in each of Comparative Examples 1 to 5, and thus, it was confirmed that both electrical conductivity and corrosion resistance were excellent simultaneously.

[0111] <Explanation of symbols>

[0112] 100: Metal separator

[0113] 110: Metal base material

[0114] 120: Coating layer

[0115] 121: Conductive filler

[0116] 122: Inorganic polymer

[0117] 130: Oxide film

Claims

1. Metal base material; and A coating layer formed on the surface of the above metal substrate and including a conductive filler and an inorganic polymer, A metal separator in which the conductive filler is included in the coating layer at an area ratio of 5% to 95%.

2. In paragraph 1, A metal separator comprising the conductive filler at least one selected from carbon black, carbon nanotubes, graphene, and carbon fiber.

3. In paragraph 1, The above conductive filler is a metal separator having a particle size of 10 nm to 100 nm.

4. In paragraph 1, The above inorganic polymer is a metal separator which is a polymer containing a bond between a group IVB transition metal element and an oxygen atom.

5. In paragraph 1, The above metal base material is a metal separator made of titanium or stainless steel.

6. In paragraph 1, The above coating layer is a metal separator having a thickness of 10 nm to 100 nm.

7. In paragraph 1, The above coating layer has a contact resistance of 1 mΩ·cm 2 Within 20 mΩ cm 2 Metal separator plate.

8. In paragraph 1, The above coating layer has a current density of 0.5 ㎂ / cm 2 Within 30 ㎂ / cm 2 Metal separator plate.

9. A method for manufacturing a metal separator, comprising: a metal substrate; and a coating layer formed on the surface of the metal substrate and containing a conductive filler and an inorganic polymer, wherein the conductive filler is included in the coating layer at an area ratio of 5% to 95%; A first coating step of coating a coating mixture containing a conductive filler and water on the surface of a metal substrate and then drying it to form a coating layer; and A method for manufacturing a metal separator, comprising a second coating step of coating a liquid metal-based organic substance on the dried coating layer and then gelling the liquid metal-based organic substance into an inorganic polymer by heat treatment.

10. In paragraph 9, A method for manufacturing a metal separator, wherein the conductive filler is included in the coating mixture in an amount of 0.3 to 5 parts by weight relative to 100 parts by weight of water.

11. In paragraph 9, A method for manufacturing a metal separator, wherein the above drying is performed at a temperature of less than 100°C to 400°C for 30 seconds to 10 minutes in an air atmosphere.

12. In paragraph 9, The above liquid metal-based organic material is a method for manufacturing a metal separator in which the metal-based organic material having the following chemical formula 1 is dispersed in a liquid dispersion medium: [Chemical Formula 1] M(OR) 4 In the above chemical formula 1, M is a group IVB transition metal element, and R is a straight or branched chain alkyl group having 1 to 6 carbon atoms.

13. In paragraph 9, A method for manufacturing a metal separator, wherein coating the liquid metal-based organic material on the dried coating layer is performed by immersing a metal base material on which a dried coating layer has been formed in a liquid metal-based organic material and mixing the liquid metal-based organic material into an area of ​​the coating layer from which water has been removed.

14. In paragraph 9, The above heat treatment is a first heat treatment step performed at a temperature of 100°C to 380°C in an air atmosphere; and A method for manufacturing a metal separator, the method comprising performing at least one step selected from a second heat treatment step performed at a temperature of 450°C to 600°C in a vacuum atmosphere.

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