Method for manufacturing an interconnector for solid oxide electrochemical devices

Abstract

The present invention relates to a method for manufacturing at least one interconnector for solid oxide electrochemical devices, said interconnector comprising at least one metal plate micro-machined by chemical etching or laser etching, said micro-machined metal plate optionally being coated with an electrical contact layer; an interconnector obtained according to said method; 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 interconnector.

Description

Title of the invention: Method for manufacturing an interconnector for solid oxide electrochemical devices. Technical field

[0001] The present invention relates to a method for manufacturing at least one interconnector for solid oxide electrochemical devices, said interconnector comprising at least one metal plate micro-machined by chemical etching or laser etching, said micro-machined metal plate optionally being at least partially coated with an electrical contact layer; an interconnector obtained according to said method; its use in a solid oxide electrochemical device, preferably in a fuel cell or an electrolyzer; and a single repeating unit (SRU) for solid oxide electrochemical devices comprising said interconnector.

[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 Electrolyser Cell" (corresponding abbreviation "SOEC"), "High Temperature Electrolysis" (corresponding abbreviation "HTE"), or "High Temperature Steam Electrolysis" (corresponding abbreviation "HTSE") or solid oxide fuel cells, also known by the anglicism "Solid Oxide Fuel Cell" (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, and 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 so-called cathodic compartment defined by the volume between the first interconnector and the adjacent cathode, and an so-called 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 dioxygen (O2) and dihydrogen gas (H2) using an electric current.Specifically, in the cathode compartment, electrons from a voltage source are supplied to the cathode (or hydrogen electrode), reducing the water vapor (H2O) supplied to the cathode to dihydrogen (H2) and recovering it. The resulting O2 ions migrate through the electrolyte, which conducts oxygen ions (O2) between the cathode and the electrode. the anode at high temperatures of about 700°C. In the anodic compartment, oxygen ions O2 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 include 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 may be made of a chromium-containing metal alloy.

[0005] In a fuel cell, the operation is reversed to produce an electric current and heat, when supplied with gaseous dihydrogen (H2) or natural gas (e.g., methane CH4), and gaseous dioxygen (O2) or air. The electrode notation is also reversed, with the dihydrogen electrode being designated the anode and the dioxygen electrode the cathode.

[0006] In an electrolyzer or fuel cell, several cells are generally assembled in series using interconnectors to form a stack of several cell-interconnect assembly units, also called single repeating units (SRUs). The main function of the interconnectors is to ensure the passage of electric current between the cells and the circulation of gases in the vicinity of each cell. The interconnectors also ensure the separation of 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.

[0007] It is known in the prior art to use interconnectors in the form of three assembled plates: a first end plate, a central plate, and a second end plate, the central plate being interposed between the first and second end plates. The central plate is conventionally laser-cut to form channels or conduits for the distribution and / or circulation of gases from the interconnector to the cell and vice versa. Then, the first end plate, the laser-cut central plate, and the second end plate are welded together by welding (laser or diffusion) or by brazing. Such a cut However, laser technology has the disadvantages of being long and complex, making subsequent assembly of the plates difficult, and the quality of the channels formed is not always satisfactory (lack of precision and / or fineness and / or rigidity).

[0008] Furthermore, it is known to add coating layers and form channels on the principal external faces of an interconnector to ensure electrical and mechanical contact of the interconnector with a cathode of an elementary electrochemical cell and an anode of an adjacent elementary electrochemical cell. In particular, in an electrolyzer, a nickel or nickel alloy grid can be disposed on one of the principal external faces of an interconnector and forms a contact layer with the cathode. This grid, by virtue of its grid structure, forms channels ensuring the distribution and circulation of gases from said grid to the cell and vice versa. On the anode side, a layer of strontium-doped lanthanum manganite (LSM) can be deposited on the other principal external face of the interconnector and forms a contact layer with the anode.This LSM layer is typically manufactured from a slurry of LSM ceramic powder cast in a strip. The channels are then formed by laser machining, removing material directly from the formed ceramic layer (laser ablation). The fabrication of the coating layers and channels is lengthy and complex, and the channel geometry is not adjustable. Furthermore, machining the ceramic layer produces channels of inconsistent quality and generates significant amounts of dust and material waste, resulting in additional production costs.

[0009] The object of the present invention is therefore to provide a method for manufacturing an interconnector for solid oxide electrochemical devices such as electrolyzers or fuel cells that is simple, economical, and that improves gas circulation within the interconnector and within the solid oxide electrochemical devices; and thus improves their performance. Description of the invention

[0010] The invention has as its first object a method for manufacturing at least one interconnector for solid oxide electrochemical devices, said interconnector having two main external faces and being 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, characterized in that said method comprises at least one step i) of micromachining chosen from chemical etching and laser etching, of at least a part of at least one main face of one or more metal plate(s), to form channels or conduits for the circulation of gas.

[0011] Step i)

[0012] Thanks to this step i) of micromachining at least a portion of at least one main face of one or more metal plate(s), the performance of the electrochemical device is improved. In particular, chemical etching or laser etching makes it possible to precisely form channels or conduits and to optimize the distribution and / or collection of gases during the operation of the electrochemical device, resulting in better electrochemical performance. The process also reduces the production cost of such an interconnector and facilitates its integration into an electrochemical device.

[0013] Said interconnector has two main external faces. According to the invention, one of the main external faces is in contact with the outside and the other of the main external faces is in contact with the outside.

[0014] Furthermore, one of the two main external faces of said interconnector corresponds to one of the main faces of said 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 intended to form said interconnector; and the other of the two main external faces corresponds to one of the main faces of said 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 intended to form said interconnector.

[0015] One of said two main external faces of the interconnector is preferably intended to come into mechanical contact with the plane of a cathode of an elementary electrochemical cell and the other of said two main external faces is preferably intended to come into mechanical contact with the plane of an anode of an adjacent elementary electrochemical cell.

[0016] Channels / conduits

[0017] The channels are suitable for the distribution and / or collection of gases, such as water vapor, dihydrogen, dioxygen, air, etc.

[0018] Channels or conduits can be defined as furrows, grooves, or trenches.

[0019] When channels are formed on at least a portion of at least one main face of one or more metal plate(s) of the interconnector during step i), said portion obtained is then a micro-machined, engraved, grooved, or channeled portion. In other words, at the end of step i), said interconnector obtained comprises at least one metal plate having at least one main face that is partially micro-machined, engraved, grooved, or channeled.

[0020] According to a preferred embodiment of the invention, the channels have a depth ranging from 0.1 to 1 mm, and preferably from 0.3 to 0.5 mm.

[0021] The channels have a depth strictly less than the thickness of the micro-machined metal plate according to step i).

[0022] The channels may be intended to ensure the circulation of gases (distribution and / or collection) from outside the electrochemical device to the interconnector and vice versa, or to ensure the circulation of gases (distribution and / or collection) from the interconnector to the adjacent cell and vice versa. The positioning of the channels etched according to step i) within one or more metal plates forming the interconnector will depend on their purpose / role.

[0023] In particular, channels formed during step i) on a central part (or "active zone") of said at least one main face of one or more metal plate(s) promote the circulation of gases (distribution and / or collection) from the interconnector to the adjacent cell and vice versa; and channels formed during step i) on a peripheral part (or "non-active zone") of said at least one main face of one or more metal plate(s) promote the circulation of gases (distribution and / or collection) from outside the electrochemical device to the interconnector and vice versa.

[0024] Step i) is preferably carried out on at least a part of a main flat face of one or more metal plate(s).

[0025] Metal plates

[0026] Each of the metal plates forming the interconnector may comprise chromium and / or iron, preferably comprises stainless steel, and particularly preferably comprises ferritic stainless steel (e.g. low carbon content < 0.1% by mass, and chromium content ranging from approximately 12 to 25% by mass).

[0027] As examples of suitable materials for each of the metal plates of the interconnector, we can cite those marketed under the reference “CROFER 22 APU”, “CROFER 22 H”, or “K41 (AISI 441)”.

[0028] Each of the metal plates forming the interconnector can have a thickness ranging from 0.1 to 1.0 mm, and preferably from 0.5 to 0.8 mm.

[0029] Step i) can be conducted on a central part (intended to form an "active zone" of the cell) and / or on a peripheral part (intended to form a "non-active zone" of the cell) of said at least one main face of one or more metal plate(s).

[0030] Step i) is preferably carried out on at least a part of each of the two main external faces of said interconnector.

[0031] When the interconnector is formed of a metal plate, said main face of the metal plate intended to be micro-machined according to step i) corresponds to one of the two external main faces of said interconnector.

[0032] In a preferred embodiment, the interconnector is formed of several metal plates, and particularly preferably of at least three metal plates. The micromachining step i) then further optimizes the interfaces between the different metal plates forming the interconnector.

[0033] When the interconnector is formed of several metal plates, step i) can include several substeps ix) [eg i-1), i-2), ...ix), 1 < x < n, for n metal plates, n > 1], each of said substeps implementing micromachining by chemical etching or laser etching of each of said several metal plates, x will depend on the number of metal plates to be micromachined among the n metal plates forming the interconnector.

[0034] According to a first variant, said interconnector comprises a first metal end plate, a central metal plate, and a second metal end plate, the central plate being intercalated between the first and second metal end plates.

[0035] Each of the first end metal plate, central metal plate, and second end metal plate is preferably elongated along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other.

[0036] Step i) consists of carrying out micromachining chosen from chemical etching and laser etching of at least a part of at least one main face of the central metal plate, of at least a part of at least one main face of the first end metal plate, and / or of at least a part of at least one main face of the second end metal plate.

[0037] According to this first variant, the first end metal plate, central metal plate, and second end metal plate preferably have a substantially identical length along the first axis of symmetry (X).

[0038] According to a second variant, said interconnector comprises a first end metal plate, a first intermediate metal plate, a central metal plate, a second intermediate metal plate, and a second end metal plate, the first intermediate metal plate being interposed between the central metal plate and the first end metal plate, the central metal plate being interposed between the first and second intermediate metal plates, and the second intermediate metal plate being interposed between the central metal plate and the second end metal plate.

[0039] Each of the first end metal plate, first intermediate metal plate, central metal plate, second intermediate metal plate, and second end metal plate is preferably elongated along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other.

[0040] According to this second variant, the interconnector gains in robustness and / or rigidity.

[0041] According to this second variant, the first intermediate metal plate, central metal plate, and second intermediate metal plate preferably have a substantially identical length along the first axis of symmetry (X).

[0042] According to this second variant, the first end metal plate and the second end metal plate preferably have a substantially identical length along the first axis of symmetry (X).

[0043] According to this second variant and in a particularly preferred manner, the first end metal plate and second end metal plate have a shorter length than the first intermediate metal plate, central metal plate, and second intermediate metal plate, along the first axis of symmetry (X).

[0044] According to this second variant, the first intermediate metal plate may include two through slots arranged symmetrically on either side of the second axis of symmetry (Y). They are preferably elongated over a length corresponding substantially to a length of said first intermediate metal plate along the second axis of symmetry (Y).

[0045] According to this second variant, the second intermediate metal plate may include two through slots arranged symmetrically on either side of the second axis of symmetry (Y). They are preferably elongated over a length corresponding substantially to a length of said second intermediate metal plate along the second axis of symmetry (Y).

[0046] In the invention, one of the first or second metal end plates (first variant and second variant) is preferably intended to come into mechanical contact with the plane of a cathode of an elementary electrochemical cell, and the other of the first or second metal end plates (first variant and second variant) is preferably intended to come into mechanical contact with the plane of an anode of an adjacent elementary electrochemical cell. In other words, one of the main external faces of said interconnector may correspond to a main face of one of the first or second end plates, and the other of the main external faces of said interconnector may correspond to a main face of the other of the first or second end plates.

[0047] An elementary electrochemical cell classically comprises a cathode, an anode, and an electrolyte intercalated between the cathode and the anode.

[0048] One or more metal plates forming the interconnector may include through-holes or openings intended to allow assembly of the interconnector in the SRU and / or the electrochemical device such as the electrolyzer; and / or intended to allow the transport of gas, via the channels, through the interconnector.

[0049] In the invention, "through holes" of a metal plate are understood to mean holes opening on both sides of said metal plate.

[0050] These through holes are preferably drilled in the peripheral part (intended to form a "non-active zone" of the cell) of the metal plate.

[0051] In particular, one or more metal plates comprise four through holes. A first and a second through hole may be arranged on either side of the first axis of symmetry X and on the same first side with respect to the second axis of symmetry Y, the third and fourth through holes may be arranged on either side of the first axis of symmetry X and on the same second side with respect to the second axis of symmetry Y opposite to said same first side.

[0052] According to a preferred embodiment, the central metal plate, said first end metal plate and said second end metal plate of the first variant include through holes as defined in the invention.

[0053] According to a preferred embodiment, the central metal plate, said first intermediate metal plate and said second intermediate metal plate of the second variant include through holes as defined in the invention.

[0054] In the invention, step i) is a micromachining step selected from chemical etching and laser etching.

[0055] Chemical etching

[0056] Chemical etching, well known under the anglicism "Chemical etching", is generally implemented by immersing a substrate to be etched in a solution which will chemically attack the surface of at least a part of the surface of said substrate, the other part being protected by a protective layer.

[0057] In the invention, step i) of chemical etching is preferably carried out by immersing at least one of the metal plates of the interconnector in an etching solution comprising a chemical etching agent.

[0058] The chemical etching agent may be an acid or a precursor of an acid such as ferric chloride, hydrofluoric acid, hydrochloric acid, nitric acid, phosphoric acid, or a mixture thereof, and preferably ferric chloride possibly in a mixture with nitric acid.

[0059] Chemical etching makes it possible to selectively, rapidly and precisely form gas channels or conduits on at least a part of at least one main face (preferably flat) of one or more metal plates, and in particular on the central plate, the first end plate, and / or the second plate end. It also has the advantage of being isotropic, meaning that the etching agent will attack the metal plate(s) in all directions, giving an almost semi-spherical etching profile, promoting the circulation and / or collection of gas.

[0060] The chemical etching agent may represent at most about 40% by mass, relative to the total mass of the etching solution (density of about 1.42 g / cm3). An example of an etching solution may be a solution comprising nitric acid (e.g. 2.5 to 3.5 mol / L of nitrate ions), hydrochloric acid (e.g. 50% by volume of 36% hydrochloric acid), phosphoric acid (e.g. 0.5 to 1.5 mol / L), and dissolved iron (e.g. 70 to 140 g / L of iron(III)).

[0061] Step i) by chemical etching can be carried out with an etching speed of approximately 1 to 20 pm / min, and preferably of approximately 5 to 15 pm / min.

[0062] Before step i), the process may further include a step i0) of applying a protective coating to at least one portion of at least one main face of one or more metal plates, and in particular to the center plate, the first end plate, and / or the second end plate, which is not intended to be etched or micro-machined. Step i0) allows for the selective formation of channels without degradation of the portions of the main face that are not intended to be etched or micro-machined.

[0063] The protective layer can be a layer based on polyvinyl alcohol, phenolformaldehyde, polyvinyl cinnamate, polyvinyl acrylate or polyacrylic.

[0064] Laser engraving

[0065] In one embodiment, laser engraving is carried out by irradiation with a laser beam of at least a part of at least one main face (preferably flat) of one or more metal plates, and in particular of the central plate, the first end plate, and / or the second end plate.

[0066] The laser beam is preferentially pulsed.

[0067] The laser engraving step is preferably a femtosecond laser engraving step. It can then be carried out with pulses having a duration ranging from approximately 10 to 350 fs, and preferably around 150 fs. This improves the precision and speed of engraving.

[0068] In one embodiment, the laser beam is mobile. This allows it to move relative to the metal plate to be micro-machined along a reference trajectory.

[0069] The laser beam can have a pulse frequency ranging from approximately 1 kHz to 40 MHz, and preferably from approximately 20 kHz to 10 MHz.

[0070] The laser beam can have a scanning speed ranging from approximately 100 mm / s to 2000 mm / s, and preferably ranging from approximately 500 mm / s to 1000 mm / s.

[0071] The laser beam can be an infrared laser beam (wavelength from approximately 800 to 1100 nm), green (wavelength from approximately 500 to 540 nm) and / or ultraviolet (wavelength less than approximately 400 nm), and preferably a laser beam having a wavelength of 343 nm, 515 nm, and / or 1030 nm.

[0072] Step ii)

[0073] When the interconnector is formed of several metal plates, the method preferably further comprises a step ii) of assembling the metal plates. This assembly step ii) is facilitated by the implementation of the micromachining step i) of the invention compared to the prior art channel formation methods.

[0074] According to the first variant of the invention, said method preferably comprises after step i), a step ii) of assembling the first end metal plate, the central metal plate, and the second end metal plate.

[0075] According to the second variant of the invention, said method preferably comprises after step i), a step ii) of assembling the first end metal plate, the first intermediate metal plate, the central metal plate, the second intermediate metal plate, and the second end metal plate.

[0076] Step ii) of the invention is preferably carried out by welding (e.g. laser welding or diffusion welding), or brazing.

[0077] Diffusion welding preferably includes the compression and heating of the stack of metal plates or sheets forming the interconnector of the invention.

[0078] Depending on the number of metal plates forming the interconnector and / or the role / destination of the micro-etched channels formed, step i) may include the micromachining of at least a part of a first main face of a metal plate and at least a part of a second main face of said metal plate, preferably opposite to the first main face with respect to the plane formed by the first and second axes of symmetry (X, Y respectively); or the micromachining of at least a part of a single main face of a metal plate.

[0079] Substep i-1)

[0080] According to a preferred embodiment of the invention (first and second variants of the invention), step i) comprises a substep i-1) of micromachining, selected from chemical etching and laser etching (preferably femtosecond laser etching), of at least a portion of a first main face of the central metal plate and at least part of a second main face of the central metal plate, in a particularly preferred manner opposite to the first main face with respect to the plane formed by the first and second axes of symmetry (X, Y respectively).

[0081] According to this embodiment, step ii) being carried out so that the central plate is intercalated between the first and second end metal plates or between the first and second intermediate metal plates, an interconnector is obtained comprising a central metal plate micro-machined at least in part on two opposite main faces.

[0082] The central metal plate may include on each of the first and second main faces a central part (intended to form an "active zone" of the cell) and a peripheral part (intended to form a "non-active zone" of the cell).

[0083] According to a preferred embodiment, substep i-1) is conducted on a peripheral part of each of the first and second main faces of the central plate.

[0084] Advantageously, substep i-1) is carried out on a first zone of the peripheral part of each of the first and second main faces, and on a second zone of the peripheral part of each of the first and second main faces, said first and second zones being arranged on either side of the second axis of symmetry (Y).

[0085] At the end of substep i-1), a first main face of the central plate is obtained comprising at the periphery a first and a second micro-machined zones arranged on either side of the second axis of symmetry (Y) and a second main face of the central metal plate comprising at the periphery a first and a second micro-machined zones arranged on either side of the second axis of symmetry (Y).

[0086] The first and second micro-machined zones of the first main face (respectively of the second main face) can extend over a length corresponding substantially to a length of the central plate along the second axis of symmetry (Y).

[0087] In a preferred embodiment, the first and second micro-machined areas of the first main face (respectively of the second main face) of the central metal plate are symmetrical with respect to the central point (center) of the central metal plate.

[0088] The first (respectively the second) micro-machined zone of the first main face can extend around the first through orifice (respectively the fourth through orifice).

[0089] The first (respectively the second) micro-machined area of ​​the second main face can extend around the second through orifice (respectively the third through orifice).

[0090] Substep i-2)

[0091] According to one embodiment of the invention (first and second variants of the invention), step i) comprises a substep i-2) of micromachining selected from chemical etching and laser etching (preferably femtosecond laser etching), of at least a part of a main face of the first end metal plate.

[0092] According to this embodiment, the main face of the first metal plate is preferably an external main face of said interconnector. Thus, step ii) is preferably carried out such that the main face of the first end metal plate, which is partially micro-machined, is an external main face of said interconnector (i.e., after assembly).

[0093] At the end of step ii), an interconnector is obtained comprising a first end metal plate micro-machined at least in part on a main face which is one of the two main external faces of said interconnector.

[0094] The first metal end plate may include on the main face a central part (intended to form an "active zone" of the cell) and a peripheral part (intended to form a "non-active zone" of the cell).

[0095] According to a preferred embodiment, substep i-2) is carried out on the central part of the main face of the first end metal plate. This makes it possible to obtain a micro-machined central part on the main face of the first end metal plate.

[0096] In step ii), the metal plates are assembled so that the main face of the first end metal plate is an external main face of said interconnector. In other words, after assembly, the main face of the first end metal plate is intended to make contact with an elementary electrochemical cell. At the end of step ii), the main face of the first end metal plate, which is partially micro-machined, is therefore in contact with the outside.

[0097] Substep i-3)

[0098] According to one embodiment of the invention (first and second variants of the invention), step i) comprises a substep i-3) of micromachining selected from chemical etching and laser etching (preferably femtosecond laser etching), of at least a part of a main face of the second end metal plate.

[0099] According to this embodiment, the main face of the second metal plate is preferably an external main face of said interconnector. Thus, step ii) is preferably carried out such that the main face of the second end plate, which is partially micro-machined, is an external main face of said interconnector (i.e., after assembly).

[0100] At the end of step ii), an interconnector is obtained comprising a second end metal plate micro-machined at least in part on a main face which is one of the two external main faces of said interconnector.

[0101] The second metal end plate may include on the main face a central part (intended to form an "active zone" of the cell) and a peripheral part (intended to form a "non-active zone" of the cell).

[0102] According to a preferred embodiment, substep i-3) is carried out on the central part of the main face of the second end metal plate. This makes it possible to obtain a micro-machined central part on the main face of the second end metal plate.

[0103] In step ii), the metal plates are assembled so that the main face of the second end metal plate is an external main face of said interconnector. In other words, after assembly, the main face of the second end metal plate is intended to make contact with an elementary electrochemical cell. At the end of step ii), the main face of the second end metal plate, which is partially micro-machined, is therefore in contact with the outside or the air.

[0104] Step iii)

[0105] The process preferably further comprises a step iii) of depositing a metallic layer on at least a portion of one of the main external faces of said interconnector by screen printing, spraying, or electrochemical deposition, to obtain a main external face at least partially coated with a metallic layer. Step iii) may be repeated several times.

[0106] Said metallic layer is an electrical contact layer, in particular intended to form contact with an elementary electrochemical cell, for example with a cathode in the case of an electrolyzer.

[0107] During the implementation of step iii), the part of one of the main external faces of said interconnector to be coated may have been previously engraved or micro-machined according to step i).

[0108] According to a preferred embodiment, the part of one of the main external faces coated with a metallic layer is a central part, and particularly preferably corresponding to a central part engraved or micro-machined according to step i). In other words, steps i) and iii) or substep i-2) and üi) are performed on the same central part (intended to form an "active zone" of the cell).

[0109] Step iii) is preferably carried out after step i) of micromachining said at least a part of one of the main external faces of said interconnector.

[0110] The metallic layer is preferably deposited by screen printing. Screen printing, compared to spraying or electrochemical deposition, has the advantages of being able to modulate the thickness of the deposited metallic layer (from 10 µm to 300 µm); and of accommodating defects during the shaping of the stack of the electrochemical device at high temperature.

[0111] When the process includes step ii) of assembly, step iii) is preferably carried out after said step ii).

[0112] According to the first and second embodiments of the invention, said at least a portion of one of the external principal faces of said interconnector preferably corresponds to said at least a portion of the principal face of the first metal end plate. Then, step iii) of depositing a metallic layer is preferably carried out on at least a portion of the principal face of the first metal end plate, to obtain the principal face of the first metal end plate at least partially coated with a metallic layer.

[0113] According to the first and second variants, and in a particularly preferred embodiment, step iii) is carried out after the sequence substep i-2) and step ii). In other words, the portion of one of the main external faces of said interconnector corresponding to a portion of the main face of the first end metal plate is etched or micro-machined according to substep i-2), then the first end metal plate is assembled according to step ii) with the other metal plates forming the interconnector, and then said portion of the main face of the first end metal plate is at least partially coated with a metallic layer according to step iii). Preferably, this portion is a central portion.

[0114] The metallic layer

[0115] The metallic layer may comprise nickel or a nickel alloy.

[0116] According to a preferred embodiment, the metallic layer comprises or is made of nickel oxide.

[0117] The metallic layer preferably has a thickness ranging from approximately 10 pm to 150 pm, and particularly preferably from approximately 20 pm to 100 pm.

[0118] Step iv)

[0119] The method preferably further comprises a step iv) of depositing a ceramic layer on at least a portion of one of the main external faces of said interconnector by screen printing or spraying, to obtain a main face external at least partially coated with a ceramic layer. Step iv) can be repeated several times.

[0120] Said ceramic layer is an electrical contact layer, in particular intended to form contact with an elementary electrochemical cell, for example with an anode in the case of an electrolyzer.

[0121] During the implementation of step iv), the part of one of the main external faces of said interconnector to be coated may have been previously engraved or micro-machined according to step i).

[0122] According to a preferred embodiment, the part of one of the main external faces coated with a ceramic layer is a central part, and particularly preferably corresponding to a central part engraved or micro-machined according to step i). In other words, steps i) and iv) or substep i-3) and iv) are carried out on the same central part (intended to form an "active zone" of the cell).

[0123] Step iv) is preferably carried out after step i) of micromachining said at least a part of one of the main external faces of said interconnector.

[0124] The ceramic layer is preferably deposited by screen printing. Screen printing, compared to spraying, has the advantages of being able to modulate the thickness of the deposited ceramic layer (from 10 µm to 300 µm); and of accommodating defects during the shaping of the stack at high temperature.

[0125] When the process includes step ii) of assembly, step iv) is preferably carried out after said step ii).

[0126] According to the first and second embodiments of the invention, at least a portion of one of the external principal faces of said interconnector preferably corresponds to at least a portion of the principal face of the second end metal plate. Then, step iv) of depositing a ceramic layer is preferably carried out on at least a portion of the principal face of the second end metal plate, to obtain the principal face of the second end metal plate at least partially coated with a ceramic layer.

[0127] According to the first and second variants, and in a particularly preferred embodiment, step iv) is carried out after the sequence substep i-3) and step ii). In other words, the portion of one of the external main faces of said interconnector corresponding to a portion of the main face of the second end metal plate is etched or micro-machined according to substep i-3), then the second end metal plate is assembled according to step ii) with the other metal plates forming the interconnector, and then said portion of the main face of the second end metal plate is at least partially coated with a ceramic layer according to step iv). Preferably, this portion is a central portion.

[0128] The ceramic layer

[0129] The ceramic layer may comprise at least one ceramic material, preferably selected from strontium-doped lanthanum manganite (also known by the acronym LSM), one of its derivatives, a lamellar structure material, and an electrically conductive perovskite oxide.

[0130] As an example of strontium-doped lanthanum manganite or one of its derivatives, we may cite the compounds of formula Lai xSrxMO3, in which M is a transition metal chosen from nickel, iron, cobalt, manganese, chromium, and one of their mixtures.

[0131] As an example of a lamellar structure material, one can cite the lanthanide nickelates of formula Ln2NiO4, in which Ln is a lanthanide selected from lanthanum, neodymium, praseodymium and one of their mixtures.

[0132] According to a preferred embodiment, the ceramic layer comprises or is made of strontium-doped lanthanum manganite.

[0133] The ceramic layer preferably has a thickness ranging from approximately 10 pm to 150 pm, and particularly preferably from 20 pm to 100 pm.

[0134] 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.

[0135] According to a preferred embodiment of the method of the invention, said method comprises the following steps: one or more steps i) (or substeps i)), and preferably several steps i) (or substeps i)), then step ii), then steps iii) and iv) in any order, said interconnector being formed of several metal plates.

[0136] According to a particularly preferred embodiment of the method of the invention, said method comprises the following steps: step i) comprising substeps i-1), i-2), and i-3) in any order, then step ii), then steps iii) and iv) in any order, said interconnector being defined according to the first or second variant of the invention.

[0137] The invention has as its second object an interconnector for solid oxide electrochemical devices, characterized in that it is obtained according to a process in accordance with the first object of the invention.

[0138] Said interconnector is formed of one or more metal plates, at least one metal plate being a metal plate having a part of a main face micro-machined by chemical etching or laser etching (preferably femtosecond laser etching).

[0139] According to a preferred embodiment of the invention, said interconnector obtained has two main external faces and is formed of several metal plates elongated along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other, and comprises a first metal end plate, a central metal plate, and a second metal end plate, the central plate being interposed between the first and second metal end plates, and: - a peripheral part of a first main face of the central metal plate is a micro-machined part forming channels or conduits for gas circulation, a peripheral part of a second main face of the central metal plate is a micro-machined part forming channels or conduits for gas circulation (the second main face of the central metal plate being opposite the first main face of the central metal plate), - a central portion of a main face of the first end metal plate corresponding to one of the two external main faces of said interconnector is a micro-machined portion forming channels or conduits for gas circulation, and at least partially coated with a metallic layer, and - a central part of a main face of the second metal end plate corresponding to the other of the two external main faces of said interconnector is a micro-machined part forming channels or conduits for the circulation of gas, and at least partly coated with a ceramic layer.

[0140] According to a particularly preferred embodiment of the invention, said interconnector obtained has two main external faces, is formed of several elongated metal plates along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other, and comprises a first end metal plate, a first intermediate metal plate, a central metal plate, a second intermediate metal plate, and a second end metal plate, the first intermediate metal plate being interposed between the central metal plate and the first end metal plate, the central metal plate being interposed between the first and second intermediate metal plates, and the second intermediate metal plate being interposed between the central metal plate and the second end metal plate, and: - a peripheral part of a first main face of the central metal plate is a micro-machined part forming channels or conduits for gas circulation, a peripheral part of a second main face of the central metal plate is a micro-machined part forming channels or conduits for gas circulation (the second main face of the central metal plate being opposite the first main face of the central metal plate), - a central portion of a main face of the first end metal plate corresponding to one of the two external main faces of said interconnector is a micro-machined portion forming channels or conduits for gas circulation, and at least partially coated with a metallic layer, and - a central part of a main face of the second metal end plate corresponding to the other of the two external main faces of said interconnector is a micro-machined part forming channels or conduits for the circulation of gas, and at least partly coated with a ceramic layer.

[0141] The invention has as its third object the use of an interconnector obtained according to a process in accordance with the first object of the invention, or in accordance with the second object of the invention, in a solid oxide electrochemical device, preferably in a fuel cell or an electrolyzer.

[0142] The invention relates as a fourth object a single repeating unit (SRU) for solid oxide electrochemical devices comprising: - an interconnector obtained according to a process conforming to the first object of the invention, or conforming to the second object of the invention, - an anode, - a cathode, and - an electrolyte.

[0143] The cathode, the electrolyte and the anode form an elementary electrochemical cell.

[0144] According to one embodiment of the invention, said electrochemical device is an electrolyzer and one of said two main external faces of said interconnector, corresponding to the main face of the first (respectively second) metal end plate, is in mechanical contact with the plane of said cathode (respectively with the plane of said anode) of an elementary electrochemical cell and is coated with a metallic layer as defined in the invention (respectively with a ceramic layer as defined in the invention).

[0145] In this embodiment of the invention, the other of said two main external faces of said interconnector, corresponding to the main face of the second (respectively first) metal end plate, is preferably intended to form mechanical contact with the plane of an anode (respectively of a cathode) of an adjacent elementary electrochemical cell and is coated with a ceramic layer as defined in the invention (respectively of a metallic layer as defined in the invention).

[0146] 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).

[0147] The cathode is preferably a porous cathode. In an electrolyzer, the cathode corresponds to the hydrogen electrode. It may 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).

[0148] In the invention, the electrolyte is preferably a solid electrolyte.

[0149] The electrolyte preferably comprises zirconium, and particularly preferably comprises yttrium-stabilized zirconium dioxide (YSZ).

[0150] Said electrolyte is in particular interposed between the anode and the cathode.

[0151] The invention also relates to a method for manufacturing an SRU according to the fourth object of the invention, said method comprising at least: - a method for manufacturing an interconnector according to a method conforming to the first object of the invention, or conforming to the second object of the invention, and - at least one assembly step of said interconnector with at least one elementary electrochemical cell.

[0152] The elementary electrochemical cell preferably comprises an anode, a cathode and an electrolyte as defined in the invention.

[0153] 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.

[0154] 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 or obtained according to a method as defined in the invention. Brief description of the FIGURES

[0155] 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 in which: [Fig.1] [Fig.1] is a schematic representation of several non-limiting examples of an SRU conforming to the fourth object of the invention; [Fig.2] is a schematic representation of several non-limiting examples of an interconnector manufactured according to a process conforming to the first object of the invention or conforming to the second object of the invention. [Fig.3] [Fig.3] is a schematic representation of a non-limiting example embodiment of an interconnector manufactured according to a process conforming to the first object of the invention or conforming to the second object of the invention. [Fig.4] [Fig.4] is a schematic representation of a non-limiting example of an embodiment of a process conforming to the first object of the invention.

[0156] It is understood that the embodiments described below are in no way limiting. 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.

[0157] In the figures, the elements common to several figures retain the same reference.

[0158] Fig. 1 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 cell 2 containing a porous anode 3 (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 mixed with gadolinium-doped cerium dioxide (GDC); a porous cathode 4 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 5 for example based on yttrium-stabilized zirconium dioxide (YSZ).The said electrolyte is in particular interposed between the anode and the cathode; and . - an interconnector 6 forming contact with the plane of the elementary electrochemical cell 2.

[0159] The interconnector 6 according to the invention has two main external faces (F1, F2) 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. The interconnector 6 according to the invention is formed of one or more metal plates, at least one metal plate being a metal plate having a part of a main face micro-machined by chemical etching or laser etching forming gas circulation channels.

[0160] On [Fig. 1] A), the interconnector 6 makes contact with the plane of the anode 3 of the elementary electrochemical cell 2.

[0161] On [Fig. 1] B), the interconnector 6 makes contact with the plane of the cathode 4 of the elementary electrochemical cell 2.

[0162] Figure 2 more specifically represents the structure of interconnector 6 of the [Fig.1] in the plane formed by the directions DX and DZ. The interconnector 6 has two main external faces (F1, F2) and is formed of a metal plate 60 - FIGURES 2 A), 2 B) - or several metal plate(s) (61, 62, 63) - FIGURES 2 C), 2 D) - elongated(s) along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other, at least a part of at least one main face (61a, 62a, 62b, 63a, Fl, F2) of one or more metal plate(s) (60, 61, 62, 63), is a part micro-machined by chemical etching or laser etching forming gas circulation channels 7. In particular, to allow the circulation of gases within the SRU and the electrochemical device, gas circulation channels 7 are micro-machined according to said step i) of the process of the invention on at least a part of at least one main face (61a, 62a, 62b, 63a, Fl, F2) of one or more metal plate(s) 60, 61, 62 and / or 63.

[0163] On [Fig.2] A), the interconnector 6 is formed of a metal plate 60 having a peripheral part of a first main face (which corresponds to the external main face Fl of said interconnector) micro-machined by chemical etching or laser etching forming gas circulation channels 7 and a peripheral part of a second main face (which corresponds to the external main face F2 of said interconnector) micro-machined by chemical etching or laser etching forming gas circulation channels 7.

[0164] In [Fig. 2] B), the interconnector 6 is formed of a metal plate 60 having a peripheral portion of a first main face (which corresponds to the external main face Fl of said interconnector) micro-machined by chemical etching or laser etching forming gas flow channels 7 and a peripheral portion of a second main face (which corresponds to the external main face F2 of said interconnector) micro-machined by chemical etching or laser etching forming gas flow channels 7. Furthermore, the interconnector 6 has a central portion of one of the external main faces Fl coated with a metallic layer 8 by screen printing, spraying, or electrochemical deposition, and a central portion of the other external main face F2 coated with a ceramic layer 9 by screen printing or spraying.

[0165] In [Fig.2] C), the interconnector 6 is formed of three metal plates, a The interconnector 6 consists of a first metal end plate 61, a central metal plate 62, and a second metal end plate 63. A central portion of a main face 61a of the first metal end plate 61, corresponding to the outer main face Fl of the interconnector 6, is micro-machined by chemical etching or laser etching to form channels 7, and a central portion of a main face 63a of the second metal end plate 63, corresponding to the outer main face F2 of the interconnector 6, is micro-machined by chemical etching or laser etching to form channels 7. The central portion of the outer main face Fl of the interconnector 6 is coated with a metallic layer 8 by screen printing, spraying, or electrochemical deposition. The central portion of the other outer main face F2 of the interconnector 6 is coated with a ceramic layer 9 by screen printing or spraying.

[0166] In [Fig.2] D), the interconnector 6 is formed of three metal plates, a The interconnector 6 consists of a first metal end plate 61, a central metal plate 62, and a second metal end plate 63. A central portion of a main face 61a of the first metal end plate 61, corresponding to the outer main face Fl of the interconnector 6, is micro-machined by chemical etching or laser etching to form channels 7, and a central portion of a main face 63a of the second metal end plate 63, corresponding to the outer main face F2 of the interconnector 6, is micro-machined by chemical etching or laser etching to form channels 7. The central portion of the outer main face Fl of the interconnector 6 is coated with a metallic layer 8 by screen printing, spraying, or electrochemical deposition. The central portion of the other outer main face F2 of the interconnector 6 is coated with a ceramic layer 9 by screen printing or spraying.In addition, a peripheral part of a first main face 62a of the central metal plate 62 and a peripheral part of a second main face 62b of the central metal plate 62 are micro-machined by chemical etching or laser etching forming channels 7.

[0167] Figure 3 represents an interconnector 6 according to the invention formed of five plates metallic plates, a first end metal plate 61, a first intermediate metal plate 64, a central metal plate 62, a second intermediate metal plate 65, and a second end metal plate 63. The metal plates are elongated along a first axis of symmetry X (parallel to the direction DX) and a second axis of symmetry Y (parallel to the direction DY). Channels 7 are obtained by chemical etching or laser etching: - according to substep i-1) of a peripheral part of a first main face 62a of the central metal plate 62 and of a peripheral part of a second main face 62b of the central metal plate 62; - according to substep i-2) of a central part of a main face 61a of the first end metal plate 61 which corresponds to the external main face Fl of said interconnector 6; and - according to substep i-3) of a central part of a main face 63a of the second end metal plate 63 which corresponds to the external main face F2 of said interconnector 6.

[0168] The metal plates (61, 64, 62, 65, 63) are then assembled and on the central part of the external main face Fl or 61a of said interconnector 6 a metallic layer 8 can be deposited according to step iii) by screen printing, by spraying, or by electrochemical deposition, to obtain the external main face Fl or 61a coated with a metallic layer 8. On a central part of the other external main face F2 or 63a of said interconnector 6 a ceramic layer 9 can be deposited according to step iv) by screen printing or by spraying, to obtain an external main face F2 or 63a coated with a ceramic layer 9.

[0169] Figure 4 illustrates the method of the invention for an interconnector comprising n metal plate(s) (n > 1) comprising: - a micromachining step (i) chosen from chemical etching and laser etching of at least a part of a main face of x metal plate(s) with 1 < x < n, - when n > 1, a step ii) of assembling the n metal plates, - optionally a step iii) of depositing a metallic layer on at least part of one of the main external faces of the interconnector, and - optionally a step iv) of depositing a ceramic layer on at least part of one of the main external faces of the interconnector.

Claims

Demands

1. A method for manufacturing at least one interconnector (6) for solid oxide electrochemical devices, said interconnector (6) having two main external faces (F1, F2) and being formed of one or more metal plate(s) (60, 61, 62, 63) elongated along a first axis of symmetry (X) and a second axis of symmetry (Y) orthogonal to each other, characterized in that said method comprises at least one step i) of micromachining selected from chemical etching and laser etching, of at least a part of at least one main face (F1, F2, 61a, 63a, 62a, 62b), of one or more metal plate(s) (60, 61, 62, 63), to form channels or conduits (7) for the circulation of gas.

2. Method according to claim 1, characterized in that said interconnector (6) is formed of several metal plates (61, 62, 63) and it further comprises a step ii) of assembling the metal plates (61, 62, 63).

3. Method according to claim 1 or 2, characterized in that said interconnector (6) comprises a first metal end plate (61), a central metal plate (62), and a second metal end plate (63), the central plate (62) being intercalated between the first and second metal end plates (61, 63).

4. A method according to any one of the preceding claims, characterized in that the channels (7) have a depth ranging from 0.1 to 1 mm, and preferably from 0.3 to 0.5 mm.

5. A method according to any one of the preceding claims, characterized in that it further comprises a step iii) of depositing a metallic layer (8) on at least a part of one of the main external faces (Fl, 61a) of said interconnector (6) by screen printing, spraying, or electrochemical deposition, to obtain a main external face (Fl, 61a) at least partly coated with a metallic layer (8).

6. A method according to any one of the preceding claims, characterized in that it further comprises a step iv) of deposition of a ceramic layer (9) on at least a portion of one of the principal external faces (F2, 63a) of said interconnector by screen printing or spraying, to obtain an external main face (F2, 63a) at least partly coated with a ceramic layer (9).

7. A method according to claim 5, characterized in that the metallic layer (8) has a thickness ranging from 10 pm to 150 pm, and preferably from 20 pm to 100 pm.

8. A method according to any one of the preceding claims, characterized in that said interconnector (6) comprises a first metal end plate (61), a central metal plate (62), and a second metal end plate (63), the central plate (62) being intercalated between the first and second metal end plates (61, 63) and step i) comprises a substep i-1) of micromachining selected from chemical etching and laser etching, of at least a portion of a first main face (62a) of the central metal plate (62) and at least a portion of a second main face (62b) of the central metal plate (62).

9. A method according to any one of the preceding claims, characterized in that said interconnector (6) comprises a first metal end plate (61), a central metal plate (62), and a second metal end plate (63), the central plate (62) being intercalated between the first and second metal end plates (61, 63) and step i) comprises a substep i-2) of micromachining selected from chemical etching and laser etching, of at least a portion of a principal face (61a) of the first metal end plate (61) and in that the principal face (61a) of the first metal end plate (61) is an external principal face (Fl) of said interconnector (6).

10. A method according to any one of the preceding claims, characterized in that said interconnector (6) comprises a first metal end plate (61), a central metal plate (62), and a second metal end plate (63), the central plate (62) being intercalated between the first and second metal end plates (61, 63) and step i) comprises a substep i-3) of micromachining selected from chemical etching and laser etching, of at least a portion of a principal face (63a) of the second end plate (63) and in that the principal face (63a) of the second end plate (63) is an external principal face (F2) of said interconnector (6).

11. A method according to claim 5, characterized in that said interconnector (6) comprises a first metal end plate (61), a central metal plate (62), and a second metal end plate (63), the central plate (62) being intercalated between the first and second metal end plates (61, 63) and step iii) of depositing a metallic layer (8) is carried out on at least a part of a main face (61a) of the first end plate (61), to obtain the main face (61a) of the first end plate (61) at least partly coated with a metallic layer (106).

12. A method according to claim 6, characterized in that said interconnector (6) comprises a first metal end plate (61), a central metal plate (62), and a second metal end plate (63), the central plate (62) being intercalated between the first and second metal end plates (61, 63) and step iv) of depositing a ceramic layer (9) is carried out on at least a part of a main face (63a) of the second end plate (63), to obtain the main face (63a) of the second end plate (63) at least partly coated with a ceramic layer (9).

13. Interconnector (6) for solid oxide electrochemical devices, characterized in that it is obtained according to a process as defined in any one of the preceding claims.

14. Use of an interconnector (6) obtained according to a process as defined in any one of claims 1 to 12, or according to claim 13, in a solid oxide electrochemical device, preferably in a fuel cell or electrolyzer.

15. Single Repeating Unit (SRU) (1) for solid oxide electrochemical devices comprising: - an interconnector (6) obtained by a process as defined in any one of claims 1 to 12, or according to claim 13, - an anode (3), - a cathode (4), and - an electrolyte (5).

Images