Component for solid oxide electrochemical devices, comprising a metal substrate coated with a ceramic layer

Abstract

The present invention relates to: a component for solid oxide electrochemical devices, comprising a metal substrate and at least one ceramic layer coating at least a portion of the metal substrate; a method for manufacturing said component; the use thereof in a solid oxide electrochemical device, preferably in a fuel cell or an electrolyzer; and a single repeat unit (SRU) for solid oxide electrochemical devices comprising said component.

Description

component for solid oxide electrochemical devices comprising a metallic substrate coated with a ceramic layer

[0001] The present invention relates to a component for solid oxide electrochemical devices comprising a metallic substrate and at least one ceramic coating layer of at least a portion of said metallic substrate, its manufacturing process, its use in a solid oxide electrochemical device, preferably in a fuel cell or electrolyzer, and a single repeating unit (SRU) for solid oxide electrochemical devices comprising said component.

[0002] The field of the invention is the field of electrochemical devices, preferably at high temperature, and in particular of solid oxide electrochemical devices such as solid oxide electrolyzers, also known by the anglicism "Solid Oxide ElectrolyserCell" (corresponding abbreviation "SOEC"), "HighTemperatureElectrolysis" (corresponding abbreviation "HTE"), or "HighTemperatureSteamElectrolysis" (corresponding abbreviation "HTSE") or solid oxide fuel cells, also known by the anglicism "Solid Oxide FuelCell" (corresponding abbreviation "SOFC"). State of the art

[0003] An electrolyzer generally comprises at least one cell containing two electrodes: an anode and a cathode, and an electrolyte interposed between the electrodes. It also includes at least one first and one second metallic interconnectors (also called interconnecting plates or bipolar plates) arranged on either side of the cell. The electrolyzer further comprises a cathodic compartment, defined by the volume between the first interconnector and the adjacent cathode, and an anodic compartment, defined by the volume between the second interconnector and the adjacent anode. During the electrolysis of water, an electrolytic reaction decomposes water (H₂O) into oxygen (O₂) and hydrogen gas (H₂) using an electric current.In particular, in the cathode compartment, electrons from a voltage source are supplied to the cathode (or hydrogen electrode) and allow the water vapor (H2O) distributed to the cathode to be reduced to dihydrogen (H2) and recovered. The O ions. 2- which result migrate through the electrolyte, which ensures the conduction of oxygen ions O 2- between the cathode and the anode at high temperatures of approximately 700°C. In the anodic compartment, oxygen ions O 2- are oxidized at the anode (or air electrode or oxygen electrode) into dioxygen molecules (O2), and the dioxygen produced is recovered, possibly with the help of a carrier gas such as dinitrogen or air.

[0004] Currently, the most commonly used electrolysis cells contain an electrolyte composed of solid oxide(s). These are called solid oxide electrolysis cells. In particular, electrolysis cells include an electrolyte based on yttrium-stabilized zirconium dioxide (YSZ); a porous cathode comprising yttrium-stabilized zirconium dioxide (YSZ), a mixture of nickel and yttrium-stabilized zirconium dioxide (YSZ), or a mixture of nickel and gadolinium-doped cerium dioxide (GDC); and a porous anode (oxygen electrode or air electrode) comprising a lanthanum-based oxide, such as lanthanum-strontium-cobalt ferrite (LSCF) or lanthanum-strontium-cobalt (LSC), possibly mixed with gadolinium-doped cerium dioxide (GDC). The interconnectors can be made of metal or metal alloy.

[0005] In a fuel cell, the operation is reversed to produce an electric current and heat, using either gaseous hydrogen (H2) or natural gas (e.g., methane, CH4) and gaseous oxygen (O2) or air. The electrode designations are also reversed, with the hydrogen electrode being called the anode and the oxygen electrode the cathode.

[0006] In an electrolyzer or fuel cell, several elementary electrochemical cells are typically connected in series using interconnectors to form a stack of multiple cell-interconnect assembly units, also known as single repeating units (SRUs). The primary function of the interconnectors is to ensure the passage of electric current between the cells, and they are therefore electrically conductive metallic elements. Interconnectors also facilitate gas circulation in the vicinity of each cell and separate the anodic and cathodic compartments of two adjacent cells, which are the gas circulation compartments on the anode and cathode sides of the cells, respectively. Various interconnector architectures are known.For example, interconnectors can be in the form of a stamped metal plate or sheet, or several strips, sheets, or metal plates assembled and welded together. In the electrochemical device, a peripheral part, called the "non-active zone," is distinguished, corresponding to the area of ​​the stack that does not contain the cells, from a central part, called the "active zone," in which the cells are located. The peripheral part extends around the central part. In the central part of the SRU (Selective Unit Reconnector), the interconnector makes contact with the cell.Furthermore, depending on the interconnector's architecture, in its peripheral section, the interconnector makes contact with an interconnector of an adjacent SRU, or the SRU may also include a metallic frame, generally of the same metallic nature as the interconnector, to form a cell-frame-interconnection SRU. The frame makes contact with an interconnector of an adjacent SRU. The frame has an opening in a central section configured to receive the cell during assembly. Thus, in a connecting section between the peripheral and central sections of the SRU, the frame makes contact with the edges of the cell. An electrical path passes through the central section of the stack or electrochemical device and must be as conductive as possible, while a leakage path passes through the peripheral section of the stack or electrochemical device and must have the highest possible electrical resistance.Currently, a removable mica and / or glass piece is placed between two interconnectors or between a frame and an interconnector in the inactive zone of the electrochemical device. This isolates the peripheral parts from the high operating temperatures of the electrochemical device (e.g., approximately 700-850°C). However, this solution is not entirely satisfactory due to the fragility of the materials used and / or the complexity of manufacturing such a piece. Furthermore, leakage currents are still observed despite the use of this piece.

[0007] The aim of the present invention is therefore to replace this mica and / or glass part with a component that is equally efficient, or even more efficient, in terms of eliminating leakage currents, which is easier and simpler to manufacture, and which can withstand the high temperatures used in solid oxide electrochemical devices.

[0008] The invention relates first to a component for solid oxide electrochemical devices, said component comprising a metallic substrate and at least one coating layer of at least a portion of said metallic substrate, characterized in that: - the metallic substrate comprises at least iron, - the coating layer is a ceramic layer having a specific surface resistance of at least 3 kΩ.cm 2 , and preferably of at least 100 kΩ.cm 2, and- the metallic substrate has a coefficient of thermal expansion CTE1 and the coating layer has a coefficient of thermal expansion CTE2, so that |CTE1-CTE2| ≤ 5 µm / mK at 850°C, and preferably |CTE1-CTE2| ≤ 2 µm / mK at 850°C.

[0009] The electrically insulating coating layer can be easily deposited on at least part of a metallic substrate to form a component according to the invention, which can then be easily integrated into an electrochemical device as an interconnector or frame that is at least partially electrically insulated in the peripheral part of said device, i.e., in the inactive zone of said electrochemical device. This makes it possible to electrically separate the different stages of the electrochemical device while ensuring sufficient conductivity in the central part, i.e., in the active zone of the electrochemical device. The current distribution within the cell is therefore improved and / or leakage currents passing through the periphery of the electrochemical device are consequently reduced, or even eliminated, while the central part exhibits optimal conductivity.Such a coating is easy to manufacture and simply withstands the high operating temperatures of such electrochemical devices, and remains permeable to gases to ensure good gas distribution without leaks.

[0010] The metallic substrate

[0011] The metallic substrate includes at least iron.

[0012] The metallic substrate preferably comprises at least about 50% by mass of iron, particularly preferably at least about 60% by mass of iron, and more particularly preferably at least about 70% by mass of iron, relative to the total mass of the metallic substrate.

[0013] The metallic substrate preferably comprises at most about 95% by mass of iron, particularly preferably at most about 90% by mass of iron, and more particularly preferably at most about 85% by mass of iron, relative to the total mass of the metallic substrate.

[0014] According to a preferred embodiment, the metallic substrate comprises steel, particularly preferably stainless steel, and more particularly preferably ferritic stainless steel.

[0015] According to an even more preferred embodiment, the metallic substrate is made of steel, particularly preferably of stainless steel, and even more particularly preferred of ferritic stainless steel.

[0016] Stainless steel preferably comprises a chromium content of 10.5 to 35%, and even more preferably of 12.5 to 25% by mass approximately, relative to the total mass of stainless steel.

[0017] Ferritic stainless steel is distinguished from stainless steel by a low carbon content, preferably less than 0.1% by mass, relative to the total mass of ferritic stainless steel.

[0018] Examples of suitable materials for the metallic substrate include those marketed under the reference "CROFER 22 APU", "CROFER 22 H", or "K41 (AISI 441)".

[0019] The metallic substrate can be formed from one or more metal plates.

[0020] The metallic substrate can have a thickness ranging from approximately 0.3 to 3 mm, and preferably from approximately 0.6 to 1 mm.

[0021] When the metallic substrate is formed of several metal plates, each of the metal plates can have a thickness ranging from approximately 0.1 to 1 mm, and preferably ranging from approximately 0.2 to 0.5 mm.

[0022] In the component of the invention, the metallic substrate is an electrically conductive substrate. In other words, it can have a specific surface resistance of at most 50 mΩ·cm 2 , preferably of no more than 20 mΩ.cm 2, and in a particularly preferred manner of at most 10 mΩ.cm 2 . Good morning,

[0023] In the invention, the specific surface resistance represents the through electrical resistance weighted by the contact surface (also well known by the anglicism "Area-Specific Resistance" or the acronym ASR).

[0024] In the invention, the specific surface resistance (ASR) of the metallic substrate is preferably determined by measuring a potential drop across a material subjected to an applied current and a fixed temperature. Since the electrical contact area is known, the measured electrical resistance value is weighted by this area to obtain an ASR value.

[0025] In a preferred embodiment of the invention, the coating layer is in direct physical contact with the metallic substrate.

[0026] In the present invention, the expression "in direct physical contact" means that no layer of any kind is interposed between said metallic substrate and said coating layer. The component does not include any intermediate layer(s) between said metallic substrate and said coating layer.

[0027] In another embodiment, a metallic coating underlayer (e.g., metallic coating, also called an accommodation underlayer or bonding underlayer) can be interposed between the metallic substrate and the coating layer. This underlayer serves as an anchor for the ceramic coating layer. It may contain nickel and / or chromium. In particular, it eliminates the need for sandblasting the metallic substrate before applying the coating layer.

[0028] The metal plate(s) forming said metallic substrate are preferably metal plates elongated along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other.

[0029] The component of the invention comprises at least one coating layer on at least a portion of said metallic substrate. In other words, the coating layer is applied to at least a portion of the metallic substrate.

[0030] In one embodiment of the invention, the component of the invention comprises at least one coating layer on at least a portion of at least one main face of said metallic substrate. The coating layer is then applied to at least a portion of at least one main face of said metallic substrate.

[0031] The metallic substrate (formed of one or more metallic plates) preferentially has two main faces, and particularly preferably two opposite main faces.

[0032] Also, when the metallic substrate is formed of several metallic plates, and for example includes a first end metallic plate, a second end metallic plate, and one or more intermediate plate(s) intercalated between the first and second end metallic plates, each of the first and second end plates has an external principal face, (the outermost one) which corresponds to one of the principal faces of the metallic substrate.

[0033] The coating layer can then be applied to at least part of one of the two main faces of said metallic substrate.

[0034] In a preferred embodiment of the invention, the component comprises a first coating layer covering at least a portion of one of the two opposing principal faces of said metallic substrate and a second coating layer covering at least a portion of another of the two opposing principal faces of said metallic substrate. In other words, a first coating layer is applied to at least a portion of one principal face of said metallic substrate, and a second coating layer is applied to at least a portion of another principal face of said metallic substrate. The metallic substrate is thus interposed between the first and second coating layers. This improves the electrical insulation of the electrochemical device.

[0035] In a preferred embodiment of the invention, the first coating layer is in direct physical contact with the metallic substrate and the second coating layer is in direct physical contact with the metallic substrate.

[0036] The coating layer

[0037] The coating layer has electrical insulation properties. It therefore exhibits a specific surface resistance of at least 3 kΩ·cm 2 approximately, preferably at least 100 kΩ.cm 2 approximately, and particularly preferably at least 200 kΩ.cm 2 approximately. This allows for a leakage current of less than 200 mA at a voltage of 2V, for a contact area of ​​350 cm². 2 approximately.

[0038] Since the coating layer is an electrically insulating layer, it generally does not include conductive metal particles in the zero oxidation state and / or conductive charges.

[0039] The coating layer is a ceramic layer. This provides good electrical resistance at high temperatures, for example, around 750-850°C. The ceramic layer of the invention also limits the diffusion of any chromium that may be present in the metallic substrate.

[0040] In the invention, the specific surface resistance or ASR of the coating layer is preferably determined by measuring the current through a material subjected to an imposed voltage.

[0041] In the invention, a ceramic layer is defined as a layer comprising at least approximately 80% by mass of ceramic compound(s), preferably at least approximately 90% by mass of ceramic compound(s), and most preferably at least approximately 95% by mass of ceramic compound(s), relative to the total mass of the ceramic layer, and most preferably a layer made entirely of ceramic compound(s). The ceramic compounds are non-metallic mineral compounds, also known as technical ceramics. Such ceramic compounds may be oxides or nitrides of metals or metalloids (such as Al, Zr, Ti, Si), ultra-refractory ceramics such as borides, carbides, or nitrides of refractory metals (Nb, Mo, Ta, W, Re), or one of the aforementioned compounds reinforced with silicon and / or magnesium.

[0042] According to a preferred embodiment of the invention, the coating layer comprises at least one oxide or nitride of a metal or metalloid (as a ceramic compound), and particularly preferably at least one metal oxide. This allows for improved stability and / or adhesion of the coating layer to the metallic substrate.

[0043] According to a particularly preferred embodiment of the invention, the metal oxide is among the oxides of titanium, zirconium, and aluminum. Alumina or zirconia is preferred.

[0044] The coating layer may further comprise another metal oxide. Preferably, the coating layer comprises a mixture of alumina and zirconia or a mixture of alumina and titanium dioxide.

[0045] The coating layer is preferably a non-porous layer. In other words, it has a surface porosity of less than 10% on the surface, and preferably less than or equal to 5% on the surface, relative to the total surface area of ​​the coating layer.

[0046] In the invention, the (closed) porosity of the coating layer is measured on cross-sectional microscope images of the coating layer. For this reason, the closed porosity is expressed as surface %.

[0047] The coating layer has the advantage of being stable at the operating temperature of an electrolyzer or fuel cell (700-850°C), and in environments such as air, dry water vapor, dihydrogen, etc.

[0048] In a preferred embodiment, the coating layer has a thickness ranging from approximately 100 nm to 200 µm, and particularly preferred from approximately 40 µm to 80 µm. This provides good electrical insulation while ensuring a small footprint. In particular, the coating layer must not be too thick to avoid excessive stacking within the electrochemical device.

[0049] The component

[0050] The component of the invention comprises a metallic substrate and at least one coating layer of at least a portion of said metallic substrate. The metallic substrate has a coefficient of thermal expansion CTE1 and the coating layer has a coefficient of thermal expansion CTE2, such that |CTE1-CTE2| ≤ 5 µm / mK at 850°C, and preferably |CTE1-CTE2| ≤ 2 µm / mK at 850°C. In other words, the metallic substrate and the coating layer have similar coefficients of thermal expansion, particularly at the operating temperatures of the solid oxide electrochemical device, e.g., at temperatures ranging from 700 to 850°C, and more particularly at 850°C. This ensures good adhesion and / or stability of the coating layer to the metallic substrate.

[0051] The metallic substrate can exhibit a coefficient of thermal expansion CTE1 ranging from 5 to 15 µm / mK at approximately 850°C, and preferably ranging from 7 to 13 µm / mK at approximately 850°C.

[0052] The coating layer can have a coefficient of thermal expansion CTE2 ranging from 5 to 15 µm / mK at approximately 850°C, and preferably ranging from 7 to 13 µm / mK at approximately 850°C.

[0053] In the invention, the coefficient of thermal expansion is determined according to a dilatometry measurement on the material alone.

[0054] The component can have a total thickness of at most about 0.8 mm, and preferably of at most about 0.6 mm.

[0055] The component preferably has a flatness of less than about 0.2 mm, and preferably less than about 0.1 mm.

[0056] In the invention, flatness is determined according to a difference in heights measured at several points using a confocal laser.

[0057] The coating layer(s) of the metallic substrate within the component do not delaminate from the metallic substrate, flake or crack at temperatures ranging from 20 to 850°C.

[0058] The coating layer is preferably applied to a peripheral portion of said metallic substrate (corresponding to a "non-active" portion of the SRU), and in particular to a peripheral portion of at least one main face of said metallic substrate. In other words, said component preferably comprises a metallic substrate and at least one coating layer of a peripheral portion of said metallic substrate, and in particular of a peripheral portion of at least one main face of said metallic substrate.

[0059] When the metallic substrate is intended for use as an interconnector in an SRU, the interconnector is preferably electrically insulated on one peripheral portion, or electrically insulated on the peripheral portion of at least one main face of said interconnector. The interconnector further comprises a solid or solid central portion (corresponding to an "active" portion of the SRU) which is preferably free of a coating layer.

[0060] When the metallic substrate is intended for use as the frame of an SRU, the preferred result is a frame that is electrically insulated on one peripheral portion, or a frame that is electrically insulated on the peripheral portion of at least one main face of the frame. The frame generally includes an opening in a central portion (corresponding to an "active" part of the SRU) configured to receive the cell during assembly. Therefore, the central portion is hollow (not solid).

[0061] The second object of the invention is a method for manufacturing a component in accordance with the first object of the invention, characterized in that it comprises at least one step of depositing a coating layer on at least a part of a metallic substrate, by physical vapor phase deposition or by thermal spraying.

[0062] Physical vapor deposition is well known by the anglicism "physical vapor deposition" or PVD deposition.

[0063] PVD deposition is preferentially carried out by magnetron sputtering.

[0064] Thermal spray deposition is preferably carried out using a gun or torch, ideally supplied with ceramic powder(s) and gas (such as air, argon, or helium). The gun raises the temperature of the powders to approximately 1000 to 5000°C using a flame or plasma.

[0065] Plasma projection is preferred.

[0066] When the deposition is carried out by thermal spraying, the process may also include, prior to the deposition step, a sandblasting step, or a step to create surface roughness.

[0067] The coating layer and the metallic substrate are as defined in the first object of the invention.

[0068] The process may in particular include a step of depositing a coating layer on at least part of a main face of a metallic substrate, by PVD or by thermal spraying.

[0069] The process may advantageously include a step of depositing a first coating layer on at least a part of a main face of a metallic substrate, by PVD or by thermal spraying; and a step of depositing a second coating layer on at least a part of another main face of said metallic substrate, by PVD or by thermal spraying.

[0070] The first and second coating layers and the metallic substrate are as defined in the first object of the invention.

[0071] The metallic substrate used for the deposition step in the process of the invention may have been previously machined, in particular to form channels configured for gas circulation; and / or to form through orifices configured for the assembly of the component in the SRU and / or the electrochemical device and / or for the circulation of gas, via channels, through said component.

[0072] Alternatively, machining can take place after the deposition stage.

[0073] The process may further include, prior to the deposition step, a degreasing step of the metallic substrate. Such a degreasing step can be carried out by immersion in acetone in an ultrasonic bath.

[0074] The third object of the invention is the use of a component conforming to the first object of the invention or obtained according to a process conforming to the second object of the invention, in a solid oxide electrochemical device, preferably in a fuel cell or an electrolyzer.

[0075] Due to its resistance to high temperatures, and its conductive (metallic substrate) and insulating (coating layer) nature, the component can be used in a solid oxide electrochemical device, preferably in a fuel cell or electrolyzer, as an insulated interconnector in a peripheral part or as an insulated frame.

[0076] This allows for improved current distribution within the cells (central part or "active" zone) of the solid oxide electrochemical device.

[0077] The invention has as its fourth object a single repeating unit (SRU) for solid oxide electrochemical devices, comprising: - a cell including an anode, a cathode, and an electrolyte, and - an interconnector, characterized in that: * the interconnector is an electrically isolated interconnector and corresponds to a component conforming to the first object of the invention or obtained according to a process conforming to the second object of the invention, or * said SRU further comprises an electrically isolated frame corresponding to a component conforming to the first object of the invention or obtained according to a process conforming to the second object of the invention.

[0078] In other words, the metallic substrate of said component of the invention can be an interconnector or a frame of the SRU, so as to form an electrically insulated interconnector or frame. The electrically insulated interconnector (respectively, frame) is an interconnector (respectively, frame) coated with at least one coating layer as defined in the invention.

[0079] When the metallic substrate of said component is an interconnector, the coating layer is preferably applied to a peripheral portion of said metallic substrate (corresponding to a "non-active" portion of the SRU), and in particular to a peripheral portion of at least one main face of said metallic substrate. The interconnector is therefore either electrically insulated on a peripheral portion, or electrically insulated on a peripheral portion of at least one main face. The interconnector further comprises a solid or solid central portion (corresponding to an "active" portion of the SRU) which is preferably free of a coating layer (i.e., the non-electrically insulated portion).

[0080] This embodiment is particularly suitable when the metallic substrate is formed of several flat metal plates.

[0081] When the metallic substrate of said component is a frame, the coating layer is preferentially applied to a peripheral portion of said metallic substrate (corresponding to a "non-active" portion of the SRU), and in particular to a peripheral portion of at least one main face of said metallic substrate. The frame is therefore either electrically insulated on a peripheral portion or electrically insulated on a peripheral portion of at least one main face. The frame further includes an empty central portion (corresponding to an "active" portion of the SRU) in the form of an opening configured to receive the cell during assembly.

[0082] This embodiment is particularly suitable when the metallic substrate is formed from a stamped metal plate.

[0083] In this embodiment (presence of an electrically insulated frame), the interconnector does not require electrical insulation and / or a coating layer. However, the interconnector may be an electrically insulated interconnector corresponding to a component conforming to the first object of the invention or obtained according to a process conforming to the second object of the invention. This further improves the electrical insulation of the SRU.

[0084] The interconnector is preferably intercalated between the cell and the frame as a component according to the invention.

[0085] Fluid sealing within the electrochemical device is generally ensured by seals (e.g., glass seals) placed between the interconnectors and the cells, or between the frames and the cells, in a connecting section between the peripheral and central parts. Furthermore, seals are preferentially located in the peripheral part and interposed between the interconnectors or between the frames and the interconnectors.

[0086] In the invention, the electrochemical device is preferably a high-temperature solid oxide electrochemical device, particularly preferably a fuel cell or a solid oxide electrolyzer, and more particularly preferably a solid oxide electrolyzer.

[0087] The cathode, electrolyte and anode form a cell in the SRU, also called an elementary electrochemical cell.

[0088] In the cell, the electrolyte is usually intercalated between the cathode and the anode.

[0089] In the central part of the SRU (the "active" zone), the interconnector is preferably "bare," i.e., without a coating layer. The interconnector preferably makes contact with the cell plane in the central part. For example, one of the two main faces of the central part of the interconnector is in mechanical contact with the plane of the cathode (or anode), and the other of the two main faces of the central part of the interconnector is preferably intended to make mechanical contact with the plane of an anode (or cathode) of an adjacent cell (i.e., of an adjacent SRU).

[0090] The anode is preferably a porous anode. In an electrolyzer, the anode corresponds to the oxygen electrode or air electrode. It may comprise a lanthanum-based oxide, such as lanthanum-strontium-cobalt ferrite (LSCF) or lanthanum-strontium-cobalt (LSC), possibly mixed with gadolinium-doped cerium dioxide (GDC).

[0091] The cathode is preferably a porous cathode. In an electrolyzer, the cathode corresponds to the hydrogen electrode. It can comprise yttrium-stabilized zirconium dioxide (YSZ), a mixture of nickel and yttrium-stabilized zirconium dioxide (YSZ), or a mixture of nickel and gadolinium-doped cerium dioxide (GDC).

[0092] In the invention, the electrolyte is preferably a solid electrolyte.

[0093] The electrolyte preferably comprises zirconium, and particularly preferably comprises yttrium-stabilized zirconium dioxide (YSZ).

[0094] The interconnector or the metal plate(s) forming the interconnector may include through openings or ports, intended to allow assembly of the interconnector in the SRU and / or the electrochemical device; and / or intended to allow the transport of gas, via channels, through the interconnector.

[0095] The invention also relates to a solid oxide electrochemical device comprising a stack of at least two SRUs conforming to the fourth object of the invention.

[0096] The invention also relates to a method for manufacturing an electrochemical device as defined in the invention comprising the assembly of at least two SRUs conforming to the fourth object of the invention.

[0097] The invention also relates to the use of a coating layer as defined in the invention to electrically insulate at high temperatures (700-850°C) a peripheral part of a solid oxide electrochemical device such as an electrolyzer or a fuel cell. Brief description of the figures

[0098] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings on which: a is a schematic representation of two non-limiting examples of an SRU conforming to the fourth object of the invention; a is a schematic representation of one non-limiting example of an SRU conforming to the fourth object of the invention.

[0099] It is understood that the embodiments described below are by no means exhaustive. In particular, variants of the invention may be conceived comprising only a selection of the features described below, isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one preferably functional feature without structural details, or with only a portion of the structural details if this portion is sufficient solely to confer a technical advantage or to differentiate the invention from the prior art.

[0100] In the figures, elements common to several figures retain the same reference.

[0101] Lare represents in the plane formed by the directions DX and DZ a single repeating unit (SRU)1 for a solid oxide electrochemical device such as a solid oxide electrolyzer, according to the invention, comprising:- at least one elementary electrochemical cell2 containing a porous anode (oxygen electrode or air electrode) comprising for example a lanthanum-based oxide, such as lanthanum-strontium-cobalt ferrite (LSCF) or lanthanum-strontium-cobalt (LSC), optionally in a mixture with gadolinium-doped cerium dioxide (GDC); a porous cathode comprising for example yttrium-stabilized zirconium dioxide (YSZ), a mixture of nickel and yttrium-stabilized zirconium dioxide (YSZ), or a mixture of nickel and gadolinium-doped cerium dioxide (GDC); and an electrolyte for example based on yttrium-stabilized zirconium dioxide (YSZ).The said electrolyte is in particular interposed between the anode and the cathode; and an interconnector3 forming contact with the plane of the elementary electrochemical cell2.

[0102] The interconnector 3 according to the invention has two principal faces (31, 32) and is formed of one or more elongated metal plate(s) along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other (axes of symmetry not shown). The first axis of symmetry (X) has the direction DX and the second axis of symmetry (Y) has the direction DY. At least one of the two principal faces (31, 32) of said interconnector 3, as a metallic substrate, is coated in a peripheral portion with a coating layer 4 according to the invention to form a component according to the invention, which is an electrically insulated interconnector (3, 4) in the peripheral portion or "non-active" zone of the SRU.

[0103] On the A), the electrically insulated interconnector (3,4) makes contact with the plane of the anode of the elementary electrochemical cell2. The coating layer4 is applied to a peripheral part of one of the two main faces (31) of said interconnector3. The peripheral part corresponds to the non-active area of ​​the SRU, i.e. not including the cell.

[0104] On the B), the electrically insulated interconnector (3,4) makes contact with the cathode plane of the elementary electrochemical cell2. The coating layer4 is applied to a peripheral part of each of the two main faces (31, 32) of said interconnector3. The peripheral part corresponds to the non-active area of ​​the SRU, i.e. not including the cell.

[0105] Lare represents the assembly within a single repeating unit (SRU)1 for a solid oxide electrochemical device such as a solid oxide electrolyzer, according to the invention: - of at least one elementary electrochemical cell2 which may be such as defined for the ; - an interconnector3 forming contact with the plane of the elementary electrochemical cell2 ; and - a frame5.

[0106] The interconnector 3 according to the invention is formed of one or more elongated metal plate(s) along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other. The first axis of symmetry (X) has the direction DX and the second axis of symmetry (Y) has the direction DY. The frame 5 according to the invention has two principal faces (51, 52) and is placed on the peripheral part of the SRU. At least one of the two principal faces (51, 52), and preferably both principal faces (51, 52), of said frame 5, as a metallic substrate, are coated with a layer of coating 4 according to the invention to form a component according to the invention, which is an electrically insulated frame.

Claims

A component for solid oxide electrochemical devices, said component comprising a metallic substrate (3) and at least one coating layer (4) of at least a portion of said metallic substrate (3), characterized in that: - the metallic substrate (3) comprises at least iron, - the coating layer (4) is a ceramic layer having a specific surface resistance of at least 3 kΩ.cm 2 , and preferably of at least 100 kΩ.cm 2 - the metallic substrate (3) has a coefficient of thermal expansion CTE1 and the coating layer (4) has a coefficient of thermal expansion CTE2, so that |CTE1-CTE2| ≤ 5 µm / mK at 850°C, and preferably |CTE1-CTE2| ≤ 2 µm / mK at 850°C. Component according to claim 1, characterized in that the metallic substrate (3) comprises steel, and preferably ferritic stainless steel. Component according to claim 1 or 2, characterized in that the metallic substrate (3) has a coefficient of thermal expansion CTE1 ranging from 5 to 15 µm / mK at 850°C. Component according to any one of the preceding claims, characterized in that the coating layer (4) has a thickness ranging from 100 nm to 200 µm, and preferably from 40 to 80 µm. Component according to any one of the preceding claims, characterized in that the coating layer (4) comprises at least one metal oxide, preferably selected from titanium, zirconium, and aluminum oxides. Component according to any one of the preceding claims, characterized in that said metallic substrate (3) is formed of one or more metallic plates. Component according to any one of the preceding claims, characterized in that the metallic substrate (3) comprises two opposing principal faces (31, 32) and in that the component comprises a first coating layer (4) of at least a part of one of the two opposing principal faces (31, 32) of said metallic substrate (3) and a second coating layer (4) of at least a part of another of the two opposing principal faces (31, 32) of said metallic substrate (3). A method for manufacturing a component as defined in any one of the preceding claims, characterized in that it comprises at least one step of depositing a coating layer (4) on at least a part of a metallic substrate (3), by physical vapor phase deposition or by thermal spraying. Use of a component as defined in any one of claims 1 to 7, in a solid oxide electrochemical device, preferably in a fuel cell or electrolyzer. Single Repeating Unit (SRU) for solid oxide electrochemical devices comprising: - a cell (2) comprising an anode, a cathode, and an electrolyte, and - an interconnector (3), characterized in that: * the interconnector is an electrically isolated interconnector (3, 4) and corresponds to a component as defined in any one of claims 1 to 7, or * said SRU further comprises an electrically isolated frame (5, 4) corresponding to a component as defined in any one of claims 1 to 7.

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