Metal separator and method for manufacturing same

Abstract

The present application relates to a metal separator and a method of manufacturing the same, the metal separator comprising a first substrate comprising a first manifold portion, a second manifold portion, and a reaction portion disposed between the first manifold portion and the second manifold portion, the first manifold portion and the second manifold portion each have a plurality of openings and a surface portion present between the plurality of openings, an upper surface of the surface portion and an inner surface of the openings each having a surface modification layer. According to the metal separator and the method for manufacturing the same, not only excellent conductivity but also excellent corrosion resistance can be achieved.

Description

Technical Field

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

[0002] In recent years, in response to global warming, powertrain systems have shifted from internal combustion engines (ICE) to electric vehicles (EVs) or hydrogen fuel cell electric vehicles (FCEVs). The fuel cells used in FCEVs not only power industrial and residential applications and driving vehicles, but also small electronic devices such as portable devices. As a highly efficient and clean energy source for energy conservation and environmental protection, its application is gradually expanding.

[0003] A fuel cell is an electrical power generation device that converts the chemical energy of fuel into electrical energy through an electrochemical reaction within a fuel stack. It generates electricity by utilizing the energy produced in the reaction between hydrogen and oxygen. Specifically, a fuel cell can use hydrogen or a substance capable of producing hydrogen as fuel. The fuel undergoes an oxidation reaction, producing hydrogen ions (protons) and electrons. These hydrogen ions and electrons then trigger an electrochemical reaction with oxygen in the air, producing water, while the electron flow generates electrical energy.

[0004] These hydrogen fuel cells consist of membrane electrode assemblies, gas diffusion layers (GDL), and metal separators.

[0005] In these components, metal separators must isolate hydrogen, oxygen, and cooling water separately and distribute and supply them evenly across the entire surface of the membrane electrode assembly to ensure stable electrochemical reactions within the assembly. Therefore, in addition to low cost, the required properties of metal separator materials include excellent processability, excellent mechanical strength, high electrical conductivity, low permeability, thermal conductivity, and chemical stability.

[0006] The shape of the metal partition can be roughly divided into two parts, such as a reaction section formed in the central part and manifold-like sections formed on both sides of the reaction section.

[0007] The manifold section has inlets and outlets for supplying hydrogen, air, etc., to enable electrochemical reactions, and also has inlets and outlets for cooling water that regulates the operating temperature of the battery stack. In this case, the manifold section is perforated to form the manifold section within the metal separator.

[0008] Alternatively, the metal partition can be surface-modified to improve corrosion resistance and conductivity, followed by perforation of the manifold portion. However, this may introduce the following problem: exposed portions may appear in the manifold portion of the metal partition, thus compromising corrosion resistance.

[0009] Therefore, in order to solve this problem, there is a need for a metal separator that not only has excellent electrical conductivity but also excellent corrosion resistance, as well as a method for manufacturing it. Summary of the Invention

[0010] Technical Purpose

[0011] The purpose of this application is to provide a metal separator that not only has excellent electrical conductivity but also excellent corrosion resistance, and a method for manufacturing the same.

[0012] Technical solution

[0013] To achieve the above objectives, the metal partition of this application includes a first substrate, the first substrate including a first manifold portion, a second manifold portion and a reaction portion disposed between the first manifold portion and the second manifold portion, wherein the first manifold portion and the second manifold portion each have a plurality of openings and a surface layer portion between the plurality of openings, and a surface modification layer is formed on the upper surface of the surface layer portion and the inner surface of the openings respectively.

[0014] The first substrate may contain 28,000% to 33,000% by weight of chromium, 0.010% by weight or less of carbon, 0.200% by weight or less of silicon, 0.300% by weight or less of manganese, 0.300% by weight or less of titanium, the balance of iron and other unavoidable impurities.

[0015] Furthermore, the surface modification layer formed on the upper surface of the surface layer portion may contain 20 atomic% to 28 atomic% of chromium in a region from the exposed external surface to a depth of 1.0 nm, and may contain 15 atomic% to 25 atomic% of iron in the region from the exposed external surface to a depth of 1.0 nm.

[0016] Furthermore, the surface modification layers formed on the upper surface of the surface layer portion and the inner surface of the opening may have been heat-treated at 100°C to 300°C for 10 to 300 seconds.

[0017] Furthermore, the first substrate can have a strength of 14 mΩ·cm at a contact pressure of 1.0 MPa. 2 Or even lower contact resistance and at 0.6V vs SCE At the potential, it is 4 μA / cm 2 Or even lower current density.

[0018] Furthermore, the metal partition can be further comprised of porous bodies stacked on the upper surface of the reaction section.

[0019] In addition, the fuel cell of this application includes a metal separator.

[0020] Furthermore, the method for manufacturing a metal partition according to this application includes: a preparation step of preparing a first substrate; a perforation step of forming a manifold portion of a first manifold portion and a second manifold portion by drilling holes on both sides of a surface of the first substrate, wherein the first manifold portion and the second manifold portion each have a plurality of openings and a surface layer portion between the plurality of openings; a surface modification layer forming step of forming a surface modification layer on the exposed surface of the first substrate by modifying the exposed surface of the first substrate on which the first manifold portion and the second manifold portion are formed; and a heat treatment step of heat treating the first substrate on which the surface modification layer is formed, wherein the surface modification layer is formed on the upper surface of the surface layer portion and the inner surface of the opening in each of the first manifold portion and the second manifold portion.

[0021] In addition, the first substrate may contain 28,000% to 33,000% by weight of chromium, 0.010% by weight or less of carbon, 0.200% by weight or less of silicon, 0.300% by weight or less of manganese, 0.300% by weight or less of titanium, the balance of iron and other unavoidable impurities.

[0022] Furthermore, the surface modification layer forming step may include: a first modification step of preparing a solution and immersing the surface of a first substrate in the solution, said solution being a solution in which one or more selected from fluorine, hydrochloric acid and phosphoric acid are added to a sulfuric acid solution; and a second modification step of immersing the first substrate, after the first modification step, in a solution containing hydrogen peroxide and fluorine.

[0023] In addition, the heat treatment step can be carried out at 100°C to 300°C for 10 to 300 seconds.

[0024] Furthermore, a second substrate can be prepared in the preparation step, and the method for manufacturing the metal partition can further include a porous perforation step of punching holes in the prepared second substrate and forming the second substrate into a porous body with multiple pores.

[0025] Furthermore, the method of manufacturing the metal partition may further include a laminate forming step, which involves stacking and bonding porous materials to the central portion of a first substrate after performing a heat treatment step and a porous perforation step, to form a laminate.

[0026] Furthermore, the surface modification layer forming step may further include forming a surface modification layer by modifying the exposed surface of the second substrate or porous body on the exposed surface of the second substrate or porous body before or after the porous body perforation step, and the heat treatment step may further include heat treating the second substrate or porous body on which the surface modification layer is formed.

[0027] Furthermore, the method for manufacturing the metal partition may further include a cutting step of cutting the widths of the first substrate and the second substrate respectively before performing the manifold-type partial perforation step and the porous body perforation step.

[0028] Effects of the present invention

[0029] The metal separator and its manufacturing method according to this application can not only achieve excellent electrical conductivity, but also excellent corrosion resistance. Attached Figure Description

[0030] Figure 1 A top view of a metal partition (as an example) according to one embodiment of this application is shown;

[0031] Figure 2 A side view (by sectioning in the width direction) of a manifold-like portion (as an example) formed in a first substrate of a metal partition according to one embodiment of this application is shown; and

[0032] Figure 3 A top view of a metal partition (as an example) according to another embodiment of this application is shown.

[0033] <Explanation of reference numerals in the attached figures>

[0034] 1100: First substrate

[0035] 1110: First manifold section

[0036] 1120: Second manifold section

[0037] 1130: Reaction Section

[0038] 1101: Opening

[0039] 1102: Surface layer portion

[0040] 1103: A surface-modified layer formed on the upper surface of the surface layer portion.

[0041] 1104: Surface-modified layer formed on the inner surface of the opening.

[0042] 1200: Porous body. Detailed Implementation

[0043] In the following description, the metal partition of this application will be described with reference to the accompanying drawings, which are illustrative and the metal partition of this application is not limited to the drawings.

[0044] Figure 1 A top view of a metal partition (as an example) according to one embodiment of this application is shown. Figure 1As shown, the metal separator of this application includes a first substrate 1100. The metal separator according to this application not only exhibits excellent electrical conductivity but also excellent corrosion resistance.

[0045] The first substrate 1100 is a material for a metal separator in a fuel cell, and includes a first manifold portion 1110, a second manifold portion 1120, and a reaction portion 1130 disposed between the first manifold portion 1110 and the second manifold portion 1120.

[0046] Figure 2 A side view (by sectioning in the width direction) is shown of a manifold-like portion (as an example) formed in a first substrate of a metal partition according to one embodiment of this application. Figure 1 and Figure 2 As shown, the first manifold portion 1110 and the second manifold portion 1120 are portions that supply hydrogen and air to the first substrate 1100 respectively so that an electrochemical reaction can occur in the partition, and each has a plurality of openings 1101 and a surface layer portion 1102 between the plurality of openings 1101; a surface modification layer 1103 and 1104 are formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120. Specifically, in the first manifold portion 1110 and the second manifold portion 1120, hydrogen inlet and outlet and air inlet and outlet can be formed for supplying and discharging hydrogen and air respectively, cooling water inlet and outlet for regulating the operating temperature can be formed, and each surface layer portion 1102 between each inlet and outlet can be provided. In one embodiment, a first manifold portion 1110 may be formed at one end relative to the longitudinal direction of the first substrate 1100, and a hydrogen inlet, a cooling water outlet, and an air outlet may be formed along a width direction perpendicular to the longitudinal direction of the first substrate 1100, with each surface layer portion 1102 existing between the hydrogen inlet, the cooling water outlet, and the air outlet. Furthermore, a second manifold portion 1120 may be formed at the other end relative to the longitudinal direction of the first substrate 1100, and an air inlet, a cooling water inlet, and a hydrogen outlet may be formed along a width direction perpendicular to the longitudinal direction of the first substrate 1100, with each surface layer portion 1102 existing between the air inlet, the cooling water inlet, and the hydrogen outlet. In this case, since there is no particular limitation on the number of openings, as long as there are two or more, there is no particular upper limit. In this specification, the term "manifold portion" is used to refer to both the first manifold portion and the second manifold portion. Furthermore, the longitudinal direction refers to the direction from one end of the first substrate 1100 toward the other end. Furthermore, the width direction refers to the direction perpendicular to the longitudinal direction.

[0047] In one embodiment, the first substrate 1100 may contain 28,000 wt% to 33,000 wt% chromium, 0.010 wt% or less carbon, 0.200 wt% or less silicon, 0.300 wt% or less manganese, 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. In one embodiment, the first substrate 1100 may contain about 28,000 wt% to about 33,000 wt% chromium, about 0.010 wt% or less carbon, about 0.200 wt% or less silicon, about 0.300 wt% or less manganese, about 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. Specifically, the first substrate 1100 may have an upper limit of chromium content of about 32,000 wt% or less or about 31,000 wt% and a lower limit of chromium content of about 29,000 wt%. Furthermore, the first substrate 1100 may have a lower limit of carbon content of about 0.001% by weight or more, a lower limit of silicon content of about 0.100% by weight or more, a lower limit of manganese content of about 0.100% by weight or more, and a lower limit of titanium content of about 0.100% by weight or more. By including the above-mentioned components, the first substrate 1100 can be excellent not only in terms of electrical conductivity but also in terms of corrosion resistance. In this case, since the physical properties of each component included in the first substrate 1100 are known in the art, these physical properties are omitted.

[0048] Furthermore, the first substrate 1100 may further comprise one or more selected from 0.030 wt% or less of phosphorus, 0.002 wt% or less of sulfur, and 0.300 wt% or less of niobium. The first substrate 1100 may further comprise one or more selected from about 0.030 wt% or less of phosphorus, about 0.002 wt% or less of sulfur, and about 0.300 wt% or less of niobium. There are no particular limitations on the lower limits of phosphorus, sulfur, and niobium; for example, they may each be about 0 wt% or more.

[0049] In one embodiment, the surface-modified layer 1103 formed on the upper surface of the surface layer portion 1102 provided in each of the first manifold portion 1110 and the second manifold portion 1120 may contain 20 atomic% to 28 atomic% of chromium in a region from the exposed surface to a depth of 1.0 nm, and in one embodiment may contain about 20 atomic% to about 28 atomic%, specifically about 22 atomic% to about 27 atomic% or about 24 atomic% to about 26 atomic%. When the surface-modified layer 1103 formed on the upper surface of the surface layer portion 1102 provided in each of the first manifold portion 1110 and the second manifold portion 1120 contains the above-mentioned amount of chromium in a region from the exposed surface to a depth of 1.0 nm, excellent conductivity and corrosion resistance can be achieved. In this case, the chromium content of the surface-modified layer 1103 can be measured using an EDAX instrument.

[0050] In another embodiment, the surface-modified layer 1103 formed on the upper surface of the surface layer portion 1102 provided in each of the first manifold portion 1110 and the second manifold portion 1120 may contain 15 atomic% to 25 atomic% iron in a region from the exposed surface to a depth of 1.0 nm, and in one embodiment may contain about 15 atomic% to about 25 atomic%, specifically about 17 atomic% to about 23 atomic% or about 19 atomic% to about 21 atomic%. When the surface-modified layer 1103 formed on the upper surface of the surface layer portion 1102 provided in each of the first manifold portion 1110 and the second manifold portion 1120 contains the above-mentioned amount of iron in a region from the exposed surface to a depth of 1.0 nm, excellent electrical conductivity and corrosion resistance can be achieved. In this case, the iron content of the surface-modified layer 1103 can be measured using an EDAX instrument.

[0051] The surface modification layer 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 may have a thickness of 5 nm or less. Specifically, the thickness of the surface modification layer 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 may be about 4 nm or less, or about 3 nm or less. Furthermore, the lower limit of the thickness of the surface modification layer 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 may be about 1 nm or more. When the surface modification layer 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 has the above-mentioned thickness, not only can the conductivity be excellent, but the corrosion resistance can also be excellent.

[0052] Furthermore, the surface modification layers 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 may have been heat-treated at 100°C to 300°C for 10 to 300 seconds. In one embodiment, the surface modification layers 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 may have been heat-treated at approximately 100°C to approximately 300°C for approximately 10 to approximately 300 seconds. Specifically, the surface modification layers 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 can be heat-treated at approximately 120°C to approximately 260°C, approximately 140°C to approximately 220°C, or approximately 160°C to approximately 180°C for approximately 30 seconds to approximately 250 seconds, approximately 50 seconds to approximately 200 seconds, approximately 70 seconds to approximately 150 seconds, or approximately 90 seconds to approximately 100 seconds. When the surface modification layers 1103 formed on the upper surface of the surface layer portion 1102 and the inner surface of the opening 1101 in each of the first manifold portion 1110 and the second manifold portion 1120 are heat-treated under the above conditions, corrosion resistance can be improved.

[0053] The reaction section 1130 is a section in which hydrogen and air supplied and discharged through the first manifold section 1110 and the second manifold section 1120 respectively undergo an electrochemical reaction.

[0054] For example, flow paths (not shown) may be formed on the upper surface of the reaction section 1130, and porous bodies (not shown) as described below may also be stacked thereon. The method for forming flow paths on the upper surface of the reaction section 1130 can be any method known in the art, and therefore there is no particular limitation thereto. Furthermore, if porous bodies are to be stacked on the reaction section 1130, the reaction section 1130 may have a plate-like form. By stacking porous bodies 1200 on the plate-like reaction section 1130, it is not necessary to form separate flow paths.

[0055] In one embodiment, the thickness of the first substrate 1100 can be from 0.05 mm to 1 mm, and in another embodiment, it can be from about 0.05 mm to about 1 mm. By keeping the thickness within the above range, the first substrate 110 can achieve excellent mechanical strength and breathability.

[0056] In another embodiment, the first substrate 1100 may have a strength of 14 mΩ·cm at a contact pressure of 1.0 MPa. 2 Or even lower contact resistance. In one embodiment, the first substrate 1100 may have a contact resistance of approximately 14 mΩ·cm at a contact pressure of 1.0 MPa. 2 Or even lower contact resistance. When the contact resistance measured under the above-mentioned contact pressure is within the above-mentioned range, the first substrate 1100 can have excellent conductivity. Furthermore, from the perspective that the lower the contact resistance of the first substrate 1100 measured under the above-mentioned contact pressure, the better the conductivity, there is no particular limitation on the lower limit, but it can be, for example, about 1 mΩ·cm. 2 The above is approximately 3 mΩ·cm. 2 Above, approximately 5 mΩ·cm 2 Above, approximately 10 mΩ·cm 2 Above or approximately 12 mΩ·cm 2 above.

[0057] Furthermore, in one embodiment, the first substrate 1100 may have a voltage of 0.6V. vs SCE At the potential, it is 4 μA / cm 2 Or even lower current density. In one embodiment, the first substrate 1100 may have a current density of 0.6V. vs SCE At the potential, it is approximately 4 μA / cm 2 Or even lower current densities. When the current density measured at the above potential is within the above range, the first substrate 1100 can exhibit excellent corrosion resistance. Furthermore, from the perspective that the lower the current density of the first substrate 1100 measured at the above potential, the better the conductivity, there is no particular limitation on the lower limit, but it can be, for example, about 1 μA / cm. 2Specifically, approximately 3 μA / cm 2 above.

[0058] Figure 3 A top view of a metal partition (as an example) according to another embodiment of this application is shown. Figure 3 As shown, the metal separator may further include a porous body 1200 stacked on the upper surface of the first substrate 1100 (specifically, on the upper surface of the reaction portion 1130), and the porous body 1200 may include a plurality of pores (not shown) and surface layer portions (not shown) formed between the plurality of pores. In this case, since there is no particular limitation on the number of pores, as long as there are two or more, there is no particular upper limit.

[0059] The porous body 1200 is the flow path for the aforementioned electrochemical reaction and has a microporous structure with a porous shape. In this case, the porous body 1200 may have a region corresponding to the reaction portion 1130 of the first substrate 1100. In this specification, the term "corresponding region" refers to the same region. By stacking on the upper surface of the reaction portion 1130 of the first substrate 1100, the porous body 1200 can improve the effect of the hydrogen or air flow path.

[0060] In one embodiment, a surface modification layer or a passivation film may be formed on the upper surface of the surface layer portion of the porous body 1200 and the inner surface of the pores, respectively. When a surface modification layer is formed on the upper surface of the surface layer portion of the porous body 1200 and / or the inner surface of the pores, excellent corrosion resistance and electrical conductivity of the porous body can be ensured. Furthermore, when a passivation film is formed on the upper surface of the surface layer portion of the porous body 1200 and / or the inner surface of the pores, oxygen penetration into the interior of the porous body 1200 can be prevented, thereby preventing rust.

[0061] The porous body 1200 may contain 28,000 wt% to 33,000 wt% chromium, 0.010 wt% or less carbon, 0.200 wt% or less silicon, 0.300 wt% or less manganese, 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. In one embodiment, the porous body 1200 may contain about 28,000 wt% to about 33,000 wt% chromium, about 0.010 wt% or less carbon, about 0.200 wt% or less silicon, about 0.300 wt% or less manganese, about 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. Specifically, the porous body 1200 may have an upper limit of chromium content of about 32,000 wt% or less or about 31,000 wt% and a lower limit of chromium content of about 29,000 wt%. Furthermore, the porous body 1200 may have a lower limit of carbon content of about 0.001% by weight or more, a lower limit of silicon content of about 0.100% by weight or more, a lower limit of manganese content of about 0.100% by weight or more, and a lower limit of titanium content of about 0.100% by weight or more. Since the porous body 1200 is made of stainless steel containing the aforementioned amounts of chromium, a very thin Cr2O3 passivation film with a thickness of 1 nm to 5 nm (about 1 nm to about 5 nm in one embodiment) can naturally form on the surface when exposed to the outside, and modification of the passivation film can form a surface modification layer. In this case, since the physical properties of each component contained in the porous body 1200 are known in the art, these physical properties are omitted.

[0062] In one embodiment, the porous body 1200 may further comprise one or more selected from 0.030 wt% or less of phosphorus, 0.002 wt% or less of sulfur, and 0.300 wt% or less of niobium. The porous body 1200 may further comprise one or more selected from about 0.030 wt% or less of phosphorus, about 0.002 wt% or less of sulfur, and about 0.300 wt% or less of niobium. There are no particular limitations on the lower limits of phosphorus, sulfur, and niobium; for example, they may each be about 0 wt% or more.

[0063] Multiple orifices can have a minor axis length formed in a direction parallel to the airflow direction and a major axis length formed in a direction perpendicular to the airflow direction. For example, the minor axis length can be from 0.3 mm to 1.0 mm, and in one embodiment, it is from about 0.3 mm to 1.0 mm. Multiple orifices can improve the hydrogen or airflow path when their respective lengths are as described above.

[0064] This application also relates to a fuel cell. The fuel cell relates to a fuel cell comprising the aforementioned metal separator; since the contents described above regarding the metal separator can be applied in the same manner, specific details of the metal separator described below will be omitted.

[0065] The fuel cell includes the aforementioned metal separator. By including the aforementioned metal separator, the fuel cell can undergo a smooth electrochemical reaction in the membrane electrode assembly and seamlessly perform its function as a circuit.

[0066] A fuel cell may include two metal separators as described above, and a first gas diffusion layer, a membrane electrode assembly, and a second gas diffusion layer may be disposed between the two metal separators. In this case, any type known in the art can be used without limitation as the first gas diffusion layer, the membrane electrode assembly, and the second gas diffusion layer, and there are no particular restrictions on them.

[0067] This application further relates to a method for manufacturing a metal partition. The method for manufacturing the metal partition relates to the method for manufacturing the aforementioned metal partition; since the content described in the above description of the metal partition can be applied in the same manner, the specific details of the metal partition described below will be omitted.

[0068] The method for manufacturing a metal separator according to this application includes a preparation step, a manifold-type partial perforation step, a surface modification layer formation step, and a heat treatment step. According to the method for manufacturing a metal separator of this application, a metal separator with excellent electrical conductivity and corrosion resistance can be manufactured.

[0069] The preparation step is the step of preparing the first substrate.

[0070] For example, the first substrate may contain 28,000 wt% to 33,000 wt% chromium, 0.010 wt% or less carbon, 0.200 wt% or less silicon, 0.300 wt% or less manganese, 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. In one embodiment, the first substrate may contain about 28,000 wt% to about 33,000 wt% chromium, about 0.010 wt% or less carbon, about 0.200 wt% or less silicon, about 0.300 wt% or less manganese, about 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. Specifically, the first substrate may have an upper limit of chromium content of about 32,000 wt% or less or about 31,000 wt% and a lower limit of chromium content of about 29,000 wt%. Furthermore, the first substrate may have a lower limit of carbon content of about 0.001% by weight or more, a lower limit of silicon content of about 0.100% by weight or more, a lower limit of manganese content of about 0.100% by weight or more, and a lower limit of titanium content of about 0.100% by weight or more. When the first substrate contains the above-mentioned components, a very thin Cr2O3 passivation film with a thickness of 1 nm to 5 nm (about 1 nm to about 5 nm in one embodiment) can be naturally formed on the surface.

[0071] Furthermore, the first substrate may further comprise one or more selected from 0.030 wt% or less of phosphorus, 0.002 wt% or less of sulfur, and 0.300 wt% or less of niobium. In one embodiment, the first substrate may further comprise one or more selected from about 0.030 wt% or less of phosphorus, about 0.002 wt% or less of sulfur, and about 0.300 wt% or less of niobium. There are no particular limitations on the lower limits of phosphorus, sulfur, and niobium; for example, they may each be about 0 wt% or more.

[0072] In one embodiment, the method of manufacturing a metal separator may further include a cold rolling step. Specifically, the cold rolling step is a step of forming the first substrate prepared in the preparation step and the second substrate described below, and can be carried out in the preparation step by passing the first substrate and the second substrate respectively between two rotating rolls at a recrystallization temperature or lower. By further including the cold rolling step, the method of manufacturing a metal separator can improve the dimensional accuracy and mechanical properties of the first substrate and the second substrate described below. In this case, when each step of the method of manufacturing a metal separator is performed, if the first substrate and / or the second substrate are exposed to the outside, a passivation film can be formed on the surface of each of the first substrate and / or the second substrate by natural oxidation. Specifically, since each of the first substrate and the second substrate is made of stainless steel containing the aforementioned amount of chromium, a very thin Cr2O3 passivation film with a thickness of 1 nm to 5 nm (about 1 nm to about 5 nm in one embodiment) can be formed naturally.

[0073] The manifold-type perforation step involves forming a first manifold-type portion and a second manifold-type portion in a first substrate, respectively, by drilling holes on both sides of one surface of the first substrate. Each of the first and second manifold-type portions has multiple openings and a surface layer portion between the openings. In this case, when performing each step of the method for manufacturing the metal separator, if the first and / or second substrates are exposed to the outside, a passivation film can be formed on the surface of each of the first and / or second substrates by natural oxidation.

[0074] The surface modification layer forming step is a step of forming a surface modification layer on the exposed surface of the first substrate that has undergone the manifold portion perforation step, and is carried out by modifying the exposed external surface of the first substrate (specifically, a passivation film formed on the surface of the first substrate) on which the first manifold portion and the second manifold portion have been formed, wherein the surface modification layer is formed on each of the upper surface of the surface layer portion and the inner surface of the opening.

[0075] Even if the first substrate contains the above-mentioned components, the method of manufacturing the metal separator can produce a metal separator that not only has excellent conductivity but also excellent corrosion resistance by performing a surface modification layer formation step after the manifold partial perforation step.

[0076] In one embodiment, the surface modification layer forming step may include a first modification step and a second modification step.

[0077] The first modification step is a step of removing the passivation film formed on the surface of the first substrate and reconstructing the chemical composition, and can be carried out by preparing a solution and immersing the surface of the first substrate in the solution, said solution being a solution in which one or more selected from fluorine, hydrochloric acid, and phosphoric acid are added to a sulfuric acid solution. Specifically, the first modification step can be carried out by preparing a solution by adding one or more selected from 1.0 mol to 5.0 mol of fluorine, 0.3 mol to 1.0 mol of hydrochloric acid, and 0.3 mol to 1.0 mmol of phosphoric acid to a sulfuric acid solution with a concentration of 350 g / L or greater, and then immersing the surface of the first substrate (specifically the passivation film formed on the surface of the first substrate) in the solution at 40°C to 80°C for 10 seconds to 180 seconds. In one embodiment, the first modification step can be performed by adding one or more of the following to a sulfuric acid solution with a concentration of about 350 g / L or greater: about 1.0 mol to about 5.0 mol of fluorine, about 0.3 mol to about 1.0 mol of hydrochloric acid, and about 0.3 mol to about 1.0 mmol of phosphoric acid. Then, the surface of the first substrate (specifically, the passivation film formed on the surface of the first substrate) is immersed in the solution at about 40°C to about 80°C for about 10 seconds to about 180 seconds. When the method for manufacturing the metal separator includes the first modification step, the amount of chromium hydroxide generated in the surface-modified layer can be improved, thus enabling the manufacture of a metal separator with improved corrosion resistance and conductivity. In this case, the proportion of components contained in the surface-modified layer can be adjusted according to the component ratio of the solution used in the first modification step and the immersion conditions.

[0078] The second modification step is a step to remove contaminants (which are byproducts that may be generated by the first modification step). This step can be performed continuously after the first modification step and can be carried out by immersing the first substrate, which has undergone the first modification step, in a solution containing hydrogen peroxide and fluorine. Specifically, the second modification step can be performed by immersing the first substrate, which has undergone the first modification step, in a solution at a temperature between 40°C and 80°C for 10 to 180 seconds: a solution containing 1.0 mol to 5.0 mol of hydrogen peroxide and 1.0 mol to 5.0 mol of fluorine. In one embodiment, the second modification step can be performed by immersing the first substrate, which has undergone the first modification step, in a solution at a temperature between about 40°C and about 80°C for about 10 to about 180 seconds: a solution containing about 1.0 mol to about 5.0 mol of hydrogen peroxide and about 1.0 mol to about 5.0 mol of fluorine. By including the second modification step, the surface modification layer formation step can ensure the surface cleanliness of the surface modification layer.

[0079] The heat treatment step is a step of strengthening the surface-modified layer formed on the first substrate, and is performed by heat treating the first substrate on which the surface-modified layer has been formed via the surface-modified layer formation step. For example, the heat treatment step may be performed at 100°C to 300°C for 10 to 300 seconds. In one embodiment, the heat treatment step may be performed at about 100°C to about 300°C for about 10 to about 300 seconds. By including the heat treatment step, the method of manufacturing a metal separator can induce dehydration and convert the ferric hydroxide contained in the surface-modified layer into ferric oxide, thereby producing a metal separator with improved corrosion resistance.

[0080] In one embodiment, the method of manufacturing the metal partition may further include preparing a second substrate in a preparation step, and may further include a porous perforation step for the resulting second substrate.

[0081] The second substrate prepared in the preparation step may contain 28,000 wt% to 33,000 wt% chromium, 0.010 wt% or less carbon, 0.200 wt% or less silicon, 0.300 wt% or less manganese, 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. In one embodiment, the second substrate may contain about 28,000 wt% to about 33,000 wt% chromium, about 0.010 wt% or less carbon, about 0.200 wt% or less silicon, about 0.300 wt% or less manganese, about 0.300 wt% or less titanium, the balance iron, and other unavoidable impurities. Specifically, the second substrate may have an upper limit of chromium content of about 32,000 wt% or less or about 31,000 wt% and a lower limit of chromium content of about 29,000 wt%. Furthermore, the second substrate may have a lower limit of carbon content of about 0.001 wt% or more, a lower limit of silicon content of about 0.100 wt% or more, a lower limit of manganese content of about 0.100 wt% or more, and a lower limit of titanium content of about 0.100 wt% or more. When the second substrate contains the above components, a very thin Cr2O3 passivation film with a thickness of 1 nm to 5 nm (about 1 nm to about 5 nm in one embodiment) can be naturally formed on the surface. Furthermore, the second substrate may further contain one or more selected from 0.030 wt% or less phosphorus, 0.002 wt% or less sulfur, and 0.300 wt% or less niobium. In one embodiment, the second substrate may further contain one or more selected from 0.030 wt% or less phosphorus, about 0.002 wt% or less sulfur, and about 0.300 wt% or less niobium. There are no particular limitations on the lower limits of phosphorus, sulfur, and niobium; for example, they may each be about 0 wt% or more.

[0082] The porous body perforation step is a step of forming a second substrate, which has not yet formed a surface-modified layer, into a porous body with multiple pores before the surface-modified layer formation step, and can be performed by perforating the second substrate before the surface-modified layer is formed. By including the porous body perforation step, the method of manufacturing metal separators can improve the effect of hydrogen or air flow paths.

[0083] In one embodiment, the method of manufacturing a metal partition may further include a three-dimensional forming step. The three-dimensional forming step is used to form airflow paths within the porous body and can be performed by shaping the porous body, which has already undergone a perforation step, using a press. By further including the three-dimensional forming step, the method of manufacturing a metal partition ensures airflow paths within the porous body that has already undergone the three-dimensional forming step, representing a three-dimensional structure.

[0084] In another embodiment, the method of manufacturing a metal separator may further include a laminate forming step. The laminate forming step is a step of forming a laminate by stacking porous bodies on a first substrate, and can be performed after a heat treatment step and a porous body perforation step by stacking and bonding the porous bodies to a central portion of the first substrate, the first substrate including first and second manifold portions having the aforementioned surface layer portion and openings. For example, the bonding method can use a bonding method employing laser welding or microspot welding. By including the laminate forming step, the method of manufacturing a metal separator can produce a two-layer structure of a metal separator in which porous bodies are stacked on a first substrate, the first substrate including first and second manifold portions having the aforementioned surface layer portion and openings.

[0085] In one embodiment, the surface modification layer forming step may further include forming a surface modification layer on the exposed surface of the second substrate or porous body by modifying the surface of the second substrate or porous body exposed to the outside before or after the porous body perforation step, and the heat treatment step may further include heat treating the second substrate or porous body on which the surface modification layer has been formed. Specifically, the surface modification layer forming step for the second substrate may be performed before the porous body perforation step, and after the surface-modified second substrate has undergone the porous body perforation step, a surface modification layer may be formed on the upper surface of each of its surface layer portions, and a passivation film may be formed on the inner surface of the pore. Furthermore, the surface modification layer forming step for the porous body may be performed after the porous body perforation step, and after the porous body has undergone the surface modification layer forming step, a surface modification layer may be formed on the upper surface of each of its surface layer portions and on the inner surface of the pore.

[0086] Furthermore, in one embodiment, the method of manufacturing the metal partition may further include a cutting step. Specifically, the cutting step is a step of cutting each of the first and second substrates, to a width applicable to the metal partition, before performing the manifold partial perforation step and the porous body perforation step. For example, the cutting step can divide each of the first and second substrates, to a width of 1 / 4, before the surface modification layer is formed.

[0087] The present application will be described in more detail below by way of embodiments based on the present application and comparative examples not based on the present application, but the scope of the present application is not limited to the embodiments shown below.

[0088] Implementation Plan 1

[0089] Manufacturing of metal partitions

[0090] A first substrate with a thickness of 0.1 mm and a second substrate with a thickness of 0.08 mm are prepared. Each substrate is composed of 30,000 wt% chromium, 0.006 wt% carbon, 0.144 wt% silicon, 0.200 wt% manganese, 0.016 wt% phosphorus, 0.001 wt% sulfur, 0.200 wt% titanium, 0.200 wt% niobium, with the balance being iron and other unavoidable impurities. Each of the first and second substrates is cold-rolled by passing it between two rotating rolls. During this process, a very thin Cr2O3 passivation film of 1 nm to 5 nm thickness is naturally formed on the surface of each substrate through natural oxidation.

[0091] Then, the width of each of the first and second substrates is divided into 120mm widths by cutting from 500nm to 1 / 4.

[0092] Then, the second substrate is perforated by drilling, and then it is three-dimensionally shaped using a press to form a porous body with multiple holes and a surface layer portion between the multiple holes. At this time, the excess outer edge portion of the porous body is removed during the three-dimensional forming process.

[0093] Then, a first manifold portion and a second manifold portion are formed in the first substrate by drilling holes on both sides of one surface of the first substrate, the first manifold portion and the second manifold portion including a plurality of openings and a surface layer portion between the plurality of openings.

[0094] Then, 3.0 mol of fluorine was added to a sulfuric acid solution with a concentration of 400 g / L to prepare a solution for surface modification as follows: a first modification treatment was performed by immersing the surface of each of the first substrate and the porous body in a solution at a temperature of 60°C for 30 seconds, followed by a second modification treatment by immersing the surface of each of the first substrate and the porous body in a solution at a temperature of 60°C for 60 seconds. A surface modification layer was formed on the surface of each of the first substrate and the porous body, thus forming a surface modification layer with a thickness of 2 nm on the upper surface of the surface layer portion and the inner surface of the opening or pore.

[0095] Then, each of the first substrate with the surface-modified layer and the porous body is heat-treated at 160°C for 90 seconds.

[0096] The porous bodies are then stacked on the central portion of a heat-treated first substrate and laser-bonded to create a metal partition with the porous bodies stacked on the first substrate.

[0097] Comparative Example 1

[0098] Manufacturing of metal partitions

[0099] A first substrate with a thickness of 0.1 mm and a second substrate with a thickness of 0.08 mm are prepared. Each substrate is composed of 30,000 wt% chromium, 0.006 wt% carbon, 0.144 wt% silicon, 0.200 wt% manganese, 0.016 wt% phosphorus, 0.001 wt% sulfur, 0.200 wt% titanium, 0.200 wt% niobium, with the balance being iron and other unavoidable impurities. The substrates are cold-rolled by passing each of the first and second substrates between two rotating rolls. During this process, a very thin Cr₂O₃ passivation film of 1 nm to 5 nm thickness is naturally formed on the surface of each substrate through natural oxidation.

[0100] Then, 3.0 mol of fluorine was added to a sulfuric acid solution with a concentration of 400 g / L to prepare a solution for surface modification as follows: a first modification treatment was performed by immersing the surface of each of the first and second substrates in a solution at a temperature of 60°C for 30 seconds, followed by a second modification treatment by immersing them in a solution containing 3.5 mol of hydrogen peroxide and 2.5 mol of fluorine at a temperature of 60°C for 60 seconds, thereby forming a surface modification layer with a thickness of 2 nm on the surface of each of the first and second substrates.

[0101] Then, each of the first and second substrates with the surface-modified layer formed is heat-treated at 160°C for 90 seconds.

[0102] Then, the width of each of the heat-treated first and second substrates is divided into 120mm widths by cutting from 500mm to 1 / 4.

[0103] Then, the heat-treated second substrate is perforated by drilling, and then it is three-dimensionally shaped using a press to form a porous body with multiple holes. At this time, the excess outer edge portion of the porous body is removed during the three-dimensional forming process.

[0104] Then, a first manifold portion and a second manifold portion are formed in the heat-treated first substrate by drilling holes on both sides of one surface of the first substrate. The first manifold portion and the second manifold portion include a plurality of openings and surface layer portions formed between the plurality of openings. At this time, a surface modification layer is formed on the upper surface of the surface layer portion formed in each of the first manifold portion and the second manifold portion, but no surface modification layer is formed on the inner surface of the opening, where a very thin Cr2O3 passivation film with a thickness of 1 nm to 5 nm is naturally formed.

[0105] Then, the porous bodies are stacked on the central portion of the first substrate and then laser bonded to create a metal partition having porous bodies stacked on the first substrate.

[0106] Comparative Example 2

[0107] Manufacturing of metal partitions

[0108] The metal partition is manufactured in the same manner as in Embodiment 1 above, except that the first modification treatment, the second modification treatment, and the heat treatment are not performed. In this case, a very thin Cr2O3 passivation film with a thickness of 1 nm to 5 nm is naturally formed on the upper surface of the surface layer portion of the first manifold portion and the second manifold portion, and on the inner surface of the opening, respectively, in the manufactured metal partition.

[0109] Comparative Example 3

[0110] Manufacturing of metal partitions

[0111] The metal partition is manufactured in the same manner as in Scheme 1 above, except that no heat treatment is performed.

[0112] Experimental Example 1. Analysis and Evaluation of the Composition of Surface Modification Layer and Passivation Film

[0113] By using energy-dispersive spectroscopy (EDS), the composition of the surface-modified layer or passivation film formed on the upper surface of the surface layer portion of the first substrate of the metal separator prepared in the embodiments and comparative examples was analyzed using an EDAX instrument, from the exposed surface to a depth of 1.0 nm. The results are shown in Table 1 below.

[0114] Experimental Example 2. Evaluation of Contact Resistance

[0115] The metal separators prepared in the embodiments and comparative examples were inserted between the gas diffusion layers (carbon paper type of SGL Co.), and the contact resistance of the first manifold portion of the metal separators prepared in the embodiments and comparative examples was measured using the method of measuring current at a contact pressure of 1.0 MPa. The results are shown in Table 1 below.

[0116] Experimental Example 3. Evaluation of Current Density

[0117] The current density of the first and second manifold portions of the metal separators prepared in the embodiments and comparative examples was evaluated using the Tafel slope of a potentiostat. The electrokinetic potential was evaluated in a mixture of 0.1N sulfuric acid and 2ppm hydrofluoric acid heated to 80°C under an applied voltage of 0.6V. SCE The voltage was measured, and the results are shown in Table 1 below.

[0118] [Table 1]

[0119]

[0120] As shown in Table 1 above, it has been confirmed that the metal separator prepared in Embodiment 1 has a lower contact resistance and current density compared with the metal separators prepared in Comparative Examples 1 and 2, and therefore has excellent conductivity and corrosion resistance.

[0121] Furthermore, it has been confirmed that the metal partition prepared in Embodiment 1 above has a similar contact resistance to the metal partition prepared in Comparative Example 3, and therefore has similar conductivity, but has a relatively low current density, thus its manifold portion has excellent corrosion resistance.

Claims

1. A metal partition, comprising: A first substrate, comprising a first manifold portion, a second manifold portion, and a reaction portion disposed between the first manifold portion and the second manifold portion. The first manifold portion and the second manifold portion each have multiple openings and a surface layer portion existing between the multiple openings. A surface modification layer is formed on the upper surface of the surface layer portion and on the inner surface of the opening, respectively.

2. The metal partition according to claim 1, wherein, The first substrate contains 28,000% to 33,000% by weight of chromium, 0.010% by weight or less of carbon, 0.200% by weight or less of silicon, 0.300% by weight or less of manganese, 0.300% by weight or less of titanium, and the balance of iron and other unavoidable impurities.

3. The metal partition according to claim 1, wherein, The surface-modified layer formed on the upper surface of the surface layer portion contains 20 atomic% to 28 atomic% chromium in a region from the exposed external surface to a depth of 1.0 nm, and 15 atomic% to 25 atomic% iron in the same region.

4. The metal partition according to claim 1, wherein, The surface modification layers formed on the upper surface of the surface layer portion and the inner surface of the opening have been heat-treated at 100°C to 300°C for 10 to 300 seconds.

5. The metal partition according to claim 1, wherein, The first substrate has a strength of 14 mΩ·cm at a contact pressure of 1.0 MPa. 2 Or even lower contact resistance and at 0.6V vsSCE At the potential, it is 4 μA / cm 2 Or even lower current density.

6. The metal partition according to claim 1, further comprising: Porous bodies stacked on the upper surface of the reaction section.

7. A fuel cell comprising a metal separator according to any one of claims 1 to 6.

8. A method for manufacturing a metal partition, comprising: Preparation steps for the first substrate; A manifold portion perforation step is performed in a first substrate to form a first manifold portion and a second manifold portion by drilling holes on both sides of a surface of the first substrate, wherein the first manifold portion and the second manifold portion each have multiple openings and a surface layer portion between the multiple openings. A surface modification layer forming step involves modifying the exposed surface of the first substrate, on the exposed surface of the first substrate having a first manifold portion and a second manifold portion, to form a surface modification layer. as well as A heat treatment step involving heat treatment of the first substrate on which the surface modification layer is formed. A surface modification layer is formed on the upper surface of the surface layer portion and the inner surface of the opening in each of the first manifold portion and the second manifold portion.

9. The method according to claim 8, wherein, The first substrate contains 28,000% to 33,000% by weight of chromium, 0.010% by weight or less of carbon, 0.200% by weight or less of silicon, 0.300% by weight or less of manganese, 0.300% by weight or less of titanium, and the balance of iron and other unavoidable impurities.

10. The method according to claim 8, wherein, The steps for forming the surface modification layer include: A first modification step of preparing a solution and immersing the surface of a first substrate in the solution, wherein the solution is a solution in which one or more selected from fluorine, hydrochloric acid, and phosphoric acid are added to a sulfuric acid solution; and A second modification step involves immersing the first substrate, which has undergone the first modification step, in a solution containing hydrogen peroxide and fluorine.

11. The method according to claim 8, wherein, The heat treatment process is carried out at 100°C to 300°C for 10 to 300 seconds.

12. The method according to claim 8, wherein, The second substrate is prepared in the preparation step. The method further includes: The step of perforating the obtained second substrate and forming the second substrate into a porous body with multiple pores.

13. The method of claim 12, further comprising: A lamination forming step that forms a laminate by stacking and bonding porous materials to the central portion of a first substrate after performing heat treatment and porous perforation steps.

14. The method according to claim 12, wherein, The surface modification layer forming step further includes forming a surface modification layer by modifying the exposed surface of the second substrate or porous body on the exposed surface of the second substrate or porous body before or after the porous body perforation step. The heat treatment step further includes heat treating the second substrate or porous body on which the surface-modified layer is formed.

15. The method of claim 12, further comprising: A cutting step that cuts the widths of the first substrate and the second substrate before performing the manifold-type partial perforation step and the porous body perforation step.

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