KR101413144B1 - Method of manufacturing protective layers on metallic bipolar plate for polymer electrolyte membrane fuel cell - Google Patents

Abstract

Disclosed is a metal separator for a fuel cell and a deposition method. The metal separator plate for a fuel cell according to the present invention is a metal separator plate for a fuel cell, wherein the metal separator plate for a fuel cell includes a coating layer provided in a plurality of layers on a base material for a metal separator plate, wherein the coating layer is made of chromium (Cr), titanium (Ti), zirconium ), Tungsten (W), nickel (Ni), and tantalum (Ta) as a material; And a second coating layer provided on the first coating layer using any one of nitrogen (N ₂ ), ammonia (NH ₃ ), oxygen (O ₂ ), boron (B) and methane (CH ₄ ) as reaction gases.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of depositing a metal separator for a fuel cell having a multi-

The present invention relates to a metal separator for a fuel cell and a deposition method for depositing a multilayer protective film for improving corrosion resistance and durability. More particularly, the present invention relates to a metal separator for a fuel cell comprising a metal layer for a fuel cell A separation plate and a deposition method.

The basic structure of a fuel cell is an electrolyte-electrode composite composed of an electrode, a catalyst layer, and a gas diffusion layer, and a separator plate alternately laminated repeatedly.

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a power generation device that produces electricity directly by electrochemical reaction between hydrogen and oxygen.

In a polymer solid electrolyte fuel cell, hydrogen is supplied through the anode and oxygen is supplied to the cathode. The hydrogen supplied to the anode is separated into hydrogen ions and electrons by the electrode layer formed on both sides of the electrolyte. Hydrogen ions are transmitted to the cathode through the electrolyte membrane. In the case of electrons, the hydrogen ions are collected through the outer conductor through the separator, Respectively. The hydrogen ions transferred to the cathode meet with oxygen in the supplied air to form water.

The separation plate is a structure for collecting and delivering the generated current, preventing the danger of explosion and combustion by preventing direct contact between hydrogen and oxygen, transporting reaction gas and product, transferring heat of reaction, bonding of each electrode and catalyst, It plays a role.

Accordingly, the separator, which is a core component of the fuel cell, requires low gas permeability, electrical conductivity, thermal conductivity, and chemical stability.

Currently used separator plates are made by extruding, molding and processing after mixing graphite particles and resin. However, the graphite separator is mechanically brittle and hermetically sealed, so that it must be manufactured to a certain thickness or more, and the manufacturing procedure is complicated and the mass production is low.

Also, the size and weight of the entire stack of fuel cell stacks stacked with the graphite separator are increased, the fuel cells are vulnerable to external impact, and the production cost is increased.

In recent years, studies have been actively conducted to replace a graphite separator with a metal separator. The thickness of the separator plate can be reduced to 1/30 or less when the metal separator plate is applied, and it is advantageous in terms of cost, productivity, and mechanical strength.

However, when a metal separator is applied to a polymer solid electrolyte fuel cell, a sulfonic acid functional group having a cation exchange ability exists in the polymer constituting the electrolyte and a gas diffusion layer. The sulfonic acid functional group acts as sulfuric acid at a concentration of about 1M during operation of the fuel cell Thereby promoting corrosion of the metal.

The metal oxide due to corrosion acts as an electrical insulator, and dissociated metal cations pollute the polymer electrolyte in the catalyst layer, thereby reducing the performance of the fuel cell.

Japanese Patent Application Laid-Open Nos. 11-162478, 10-228914, USP 6372376, 6967065 and European Patent No. 1,5111,105 disclose a method in which a surface is plated with a noble metal such as gold or an oxide of a platinum group metal A method of securing corrosion resistance and electrical conductivity by coating is disclosed. However, it is expensive to manufacture, and defects such as pin holes (minute pores or small holes) are generated, so that there is a limit to reach a practical stage.

Japanese Unexamined Patent Publication Nos. 2003-276249 and 2003-272653 disclose a method of lowering the processing cost by performing ultra thin gold plating. However, since the hardness of the gold plating is low, there is a possibility of damage to the gold thin film layer It is high, and corrosion through this part is easy.

U.S. Patent No. 6649031 discloses a method of coating a composite membrane of graphite and metal by coating a graphite emulsion with aluminum or titanium oxide in multiple layers. However, this method has a complicated process and has a problem that the composite material is peeled off due to physical shock or vibration.

Korean Patent Laid-Open Publication No. 2008-0114113 discloses a method of forming a nitride through a nitriding treatment of a chromium coating layer after chromium coating the surface of a metal separator base material together with a nickel intermediate layer.

The chromium layer and the chromium nitride layer are susceptible to surface corrosion such as protective coatings and pinholes, which are excellent in corrosion resistance, and are susceptible to the corrosion reaction. In addition, when corrosion occurs to the inner base material, peeling between the base metal and the chromium layer is likely to occur.

Due to the characteristics of the fuel cell, even if only one of the laminated plates fails, the characteristics of the entire fuel cell deteriorate, so that if the internal property of the separating plate is lowered, the lifetime of the fuel cell is shortened.

Therefore, it is necessary to improve the durability of the inner coating layer of the metal separator, and there is a need to compensate for a single combination of chromium and nitride layers.

Particularly, in the case of chromium or other metal thin films deposited by physical vapor deposition (hereinafter referred to as PVD), as shown in FIG. 1, due to the physical properties of the deposition conditions, Growth.

In this case, it is possible to penetrate the corrosion boundary along the grain boundary in the columnar structure, thereby accelerating the corrosion. Therefore, it is necessary to prevent the formation of the main phase structure of the thin film when the protective film is formed using the PVD method, which is highly mass-produced.

Korean Patent Registration No. 10-0802683 (Hyundai Motor Co., Ltd.) 2008. 02. 01.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fuel cell system in which a plurality of coating films are provided on a surface of a base material for a metal separator of a fuel cell to prevent the growth of the main phase structure of the thin film and to prevent the secondary corrosion from occurring even if corrosion occurs in the single thin film layer. To provide a metal separator for a fuel cell and a deposition method which are improved in corrosion resistance and durability.

According to an aspect of the present invention, there is provided a metal separator for a fuel cell, comprising a coating layer provided in a plurality of layers on a base material for a metal separator, wherein the coating layer is made of chromium (Cr), titanium (Ti), zirconium (Zr) , Tungsten (W), nickel (Ni), and tantalum (Ta) as a material; And nitrogen (N _2), ammonia (NH _3), oxygen (O _2), boron (B) and methane (CH ₄₎ to the one with the reaction gas in a second coating layer provided on the first coating layer A metal separator plate for a fuel cell may be provided.

The thickness of the first coating layer may be 700 to 800 nm.

The thickness of the second coating layer may be 700-800 nm.

According to another aspect of the present invention, any one of chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W), nickel (Ni), and tantalum (Ta) A first coating layer providing step of providing a first coating layer; And nitrogen (N ₂₎ to a surface of the first coating layer, an ammonia (NH _3), oxygen (O _2), to any one of boron (B) and methane (CH ₄₎ as a reaction gas to provide a second coating layer A second coating layer providing step, and a second coating layer providing step, wherein the first coating layer preparing step and the second coating layer preparing step are sequentially performed in plural.

The first coating layer may be provided by an evaporation method.

The chromium is coated on the base material by a thermal evaporation method, and the tungsten, tantalum, titanium and zirconium can be coated on the base material by an electron beam evaporation method.

The second coating layer may be provided by a plasma ion plating method in which the reactive gas is ionized by glow discharge and then the reactive gas ions are collided with the first coating layer.

According to still another aspect of the present invention, there is provided a metal separator for a fuel cell, comprising a coating layer provided in a plurality of layers on a base material for a metal separator, the coating layer being made of chromium (Cr), titanium (Ti), zirconium Zr), tungsten (W), nickel (Ni), and tantalum (Ta) as a material; And at least one of chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W), nickel (Ni), and tantalum (Ta) is coated on the first coating layer A metal separating plate for a fuel cell including a second coating layer coated with a different material may be provided.

Embodiments of the present invention can use a PVD method with high mass productivity by providing a plurality of coating films on the surface of a base material for a metal separator of a fuel cell to prevent the growth of the main phase structure of the thin film, and when corrosion occurs in a single thin film layer It is possible to prevent secondary corrosion and improve corrosion resistance and durability.

FIG. 1 is an electron microscope image representative of a columnar structure as a cross section of a chromium nitride (CrN) film formed by a general PVD method.
FIG. 2 is a cross-sectional view schematically showing a state in which a primary coating layer and a secondary coating layer are provided on a surface of a base material for a metal separator according to the present embodiment in a plurality of layers.
FIG. 3 is a graph showing the relationship between chromium and nitridation of a film formed by repeating the process of providing a primary coating layer with chromium by ion plating method and nitriding the surface of the primary coating layer with an ammonia (NH ₃ ) plasma according to an embodiment of the present invention. Section electron microscope image of the multilayer coating film of chromium.
FIG. 4 is a graph showing the result of analyzing the element ratio in the depth direction of the coating film of the multilayer coating layer shown in FIG. 3. FIG.
FIG. 5 is a schematic view of an ion plating apparatus in which an RF antenna for generating a plasma is installed and a source of heat generation and electron beam evaporation is installed.
FIG. 6 is a view schematically showing a mass-production inline system capable of performing a continuous process by separating a space in which the deposition of the primary coating layer is performed and a space in which the surface treatment of the secondary coating layer is performed in this embodiment.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

FIG. 2 is a cross-sectional view schematically showing a state in which a primary coating layer and a secondary coating layer are provided in a plurality of layers on a surface of a base material for a metal separator according to an embodiment of the present invention. FIG. 3 is a cross- Sectional electron microscope image of a thin film of a multilayer coating layer of chromium and chromium nitride formed by repeating the process of providing a primary coating layer with chromium by a deposition method and then nitriding the surface of the primary coating layer with an ammonia (NH ₃ ) plasma, FIG. 5 is a graph showing the result of analyzing the element ratio in the depth direction of the coating layer of the multilayer coating layer shown in FIG. 3, and FIG. Lt; RTI ID = 0.0 > ion plating < / RTI >

As shown in these drawings, the metal separator plate 1 for a fuel cell according to the present embodiment includes a base metal plate 10, a coating layer 20 formed of a plurality of layers on the base metal plate 10, Respectively.

The base material 10 for a metal separator is used for preventing direct contact between hydrogen and oxygen to prevent the risk of explosion and combustion and collecting and transferring the generated current. The base material 10 is made of a metal plate having cooling water flow paths and gas flow paths formed on both surfaces thereof And the joined body can be joined with the cooling water flow path facing each other.

In addition, the base material 10 for a metal separator may be constituted by a joined body of metal plates formed on both sides of the gas flow path, when the cooling water flow path is not required to be formed.

In the present embodiment, the base material 10 for a metal plate may be made of a material containing any one of commercial stainless steel, Ti or Ti alloy, Al or Al alloy, Cu or Cu alloy and low alloy steel of 0.1 to 0.2 mm .

The present embodiment can reduce the volume and weight of the stack by adopting the base material 10 for a metal separator in place of the conventional graphite separator and improve the strength of the fuel cell, Can be prevented.

As shown in FIG. 2, the coating layer 20 includes a first coating layer 21 provided on a base material 10 for a metal plate and coated on the upper surface of the base material 10 for a metal plate, And a second coating layer 23 provided on the upper side of the first coating layer 21.

Since the coating layer 20 is formed by sequentially coating a plurality of the first coating layer 21 and the second coating layer 23, it is possible to use the PVD method which is capable of preventing the growth of the columnar crystal structure of the thin film, , It is advantageous in that corrosion resistance and durability can be improved by preventing occurrence of secondary corrosion even if corrosion occurs in a single thin film layer.

The first coating layer 21 of the coating layer 20 is formed by metal separation using any one of chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W), nickel (Ni) and tantalum The base material 10 may be coated by an evaporation method.

Specifically, chromium (Cr), which is a material having a property of sublimating at low pressure, can be coated on the base material 10 for a metal plate by a thermal evaporation method, and titanium (Ti), zirconium (Zr), tungsten (W), tantalum (Ta), or the like, the element may be vaporized using the E-beam evaporation method to deposit on the base material 10 for the metal separator.

In this embodiment, the first coating layer 21 has a thickness of 700 to 800 nm in order to minimize the covering property of the coating layer and the peeling of the first coating layer 21 during the operation of the second coating layer 23 can do.

The second coating layer 23 of the coating layer 20 is formed by selectively nitriding, oxidizing, boriding, or carbonizing an element by exciting the atmosphere in the vessel vaporized by the evaporation method described above with a nitrogen plasma, an oxygen plasma, a boron plasma, or a carbon plasma Can be prepared by chemical reaction.

I.e. even if any one of the second coating layer 23 is nitrogen (N _2), ammonia (NH _3), oxygen (O _2), boron (B) and methane (CH ₄₎ in this embodiment as a reaction gas 5 The surface of the first coating layer 21 can be surface-treated by the plasma ion plating method in the ion plating apparatus A shown in FIG. Here, GD denotes a gas distributor, TE denotes a thermal evaporator, EE denotes an E-beam evaporator, and P denotes an inductively coupled plasma antenna.

In this embodiment, the thickness of the second coating layer 23 may be set in the range of 700 to 800 nm in order to minimize the covering property and peeling of the coating layer.

Hereinafter, a method of providing the coating layer 20 on the base material 10 for a metal plate in this embodiment will be briefly described.

In the method of depositing a metal separator for a fuel cell according to this embodiment, a first coating layer 21 is formed by coating a surface of a base material 10 for a metal separator with an element including chromium (Cr), and a first coating layer 21 The first coating layer 21 is treated with a nitriding treatment or the like to provide a second coating layer 23 via a reaction gas containing nitrogen or ammonia on the surface of the first coating layer 21 and the second coating layer 23, (23) is repeated.

FIG. 4 is a graph showing the results of the nitriding treatment of the chromium surface with the plasma generated by controlling the flow rate of ammonia and argon at a ratio of 4: 1 after providing the first coating layer 21 with chromium (Cr) FIG. 5 is a graph showing the results of analyzing the element ratio in the depth direction of the coating film. FIG.

The process conditions are as follows. The evaporation conditions of chromium were resistance heating with a current of 200 A and a voltage of 10 V. In the case of combination of gases, Ar was set to 7 sccm for chromium deposition, 7 sccm for Ar, and 25 sccm for NH ₃ for deposition of chromium nitride .

The process pressure is 30 mTorr and the power supplied to the inductively coupled plasma antenna is 300 W. The deposition time is 60 seconds for chromium deposition and 60 seconds for chromium nitride deposition.

Finally, the deposition thicknesses of chromium and chromium nitride are 700 to 800 nm, respectively, as described above.

6, a space in which the deposition of the first coating layer 21 is performed by the thermal evaporator TE and a space in which the deposition of the second coating layer 23 is performed by the inductively coupled plasma antenna P, The space in which the surface treatment is performed can be separated to enable a continuous process.

In addition, the present embodiment is not limited to a method of providing the coating layer 20 with a raw material and a compound, and a coating layer of binary materials may be provided.

That is, in this embodiment, the coating layer provided on the base material 10 for the metal plate as a plurality of layers is made of Cr, Ti, Zr, W, Ni, (Ti), zirconium (Zr), tungsten (W), nickel (Ni), and tantalum (Ta) as a material for the metal plate And a second coating layer coated on the first coating layer with a material different from that of the first coating layer.

As described above, according to the present embodiment, the corrosion resistance and durability of the metal separator of the fuel cell can be improved and the graphite material can be replaced with a metal material. Further, a plurality of coating films are provided on the surface of the metal separator plate of the fuel cell, It is possible to use the PVD method which is highly mass-producible by preventing the growth of the columnar structure, and it is possible to prevent the secondary corrosion even when the single thin film layer is corroded, thereby improving the corrosion resistance and the durability.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Accordingly, such modifications or variations are intended to fall within the scope of the appended claims.

1: Metal separator for fuel cell 10: Base metal for separator
20: Coating layer 21: First coating layer
23: Second coating layer A: Ion plating device
EE: Electron beam evaporator GD: Gas distributor
P: Inductively coupled plasma antenna TE: Thermal evaporator

Claims (8)

A first coating layer is formed by coating any one of chromium (Cr), titanium (Ti), zirconium (Zr), tungsten (W), nickel (Ni) and tantalum (Ta) Preparing a coating layer; And
Wherein at least one of nitrogen (N ₂ ), argon (Ar), ammonia (NH ₃ ), oxygen (O ₂ ), boron (B), and methane (CH ₄ ) is used as a reactive gas on the surface of the first coating layer And a second coating layer providing step of providing a coating layer,
The first coating layer preparing step and the second coating layer preparing step are sequentially performed in plural,
The second coating layer is formed by treating the chromium surface with a plasma generated by controlling the flow rate of ammonia and argon at a ratio of 4: 1,
Wherein a space in which the deposition of the first coating layer is performed by the thermal evaporator and a space in which the surface treatment of the second coating layer is performed by the inductively coupled plasma antenna can be separated and a continuous process can be performed . The method according to claim 1,
Wherein the first coating layer has a thickness of 700 to 800 nm. The method according to claim 1,
Wherein the thickness of the second coating layer is 700-800 nm. delete delete The method according to claim 1,
The chromium is coated on the base material by a thermal evaporation method,
Wherein the tungsten, tantalum, titanium and zirconium are coated on the base material by an electron beam evaporation method. delete delete

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