Method for manufacturing interconnectors for solid oxide electrochemical devices and interconnector for solid oxide electrochemical devices

Abstract

The invention relates to a method for manufacturing at least one interconnector (1) for solid oxide electrochemical devices, referred to as ISO (1), referred to as the method. The method includes: compressing (7) a stack (2) comprising at least two machined metal sheets (3) in contact with one another; and, at the same time as the pressure is applied, heating the stack to a temperature of between 700°C and 1200°C. The compressing includes applying a pressure greater than or equal to 4 bar. The at least two metal sheets are machined and arranged such that, after manufacture, the ISO is formed. The pressure is applied perpendicularly to the at least two sheets.

Description

Method for manufacturing interconnectors for solid oxide electrochemical devices and interconnector for solid oxide electrochemical devices

[0001] The present invention relates to a method for manufacturing interconnectors for solid oxide electrochemical devices.

[0002] The invention also relates to interconnectors for solid oxide electrochemical devices.

[0003] The invention belongs, in particular, to the field of interconnectors for electrolyzers and solid oxide fuel cells.

[0004] The invention relates, more particularly, to the field of interconnectors for stacks of planar single repeating units (SRU). State of the art

[0005] The stack of individual high-temperature solid oxide electrolysis cells (SOEC) and the stack of solid oxide fuel cells (SOFC) are an essential component of current electrolyzers and fuel cells.

[0006] For both applications, the stack is a series assembly of single repeating units (SRUs) within each of which the electrochemical reaction takes place.

[0007] The main function of the SRU stack is to: distribute and recover gas, and / or distribute / collect current through each cell, and / or isolate (electrically) each SRU.

[0008] In the case of solid oxide technologies, the packaging of the SRU stack (or the “stack”) must withstand a high temperature environment, for example temperatures of 850°C) and a pressurized gaseous environment (e.g. 500 mbars).

[0009] Several SRU stack architectures have been developed: tubular, microtubular and planar architectures.

[0010] In planar architectures, the SRU assembly consists of an electrochemical cell, current collectors, a sealing gasket, and an interconnector. The interconnector connects two SRUs in series. The interconnector provides mechanical support for the subassembly and separates the two gas chambers.

[0011] In the prior art, ceramic interconnecting parts are known. Metal alloy interconnecting parts are also known.

[0012] The interconnectors must withstand the high-temperature oxidizing environment of SOEC / SOFC and exhibit low permeability to reactive gases.

[0013] Depending on the design, the interconnector can also perform the functions of gas flow distribution and electrical current collection.

[0014] The prior art includes processes for assembling or manufacturing interconnectors. Sheet metal brazing, sheet metal stamping, and powder metallurgy are well-known manufacturing processes for the mass production of interconnectors.

[0015] One object of the invention is to propose a manufacturing process for interconnectors for solid oxide electrochemical devices and interconnector for solid oxide electrochemical devices: offering good reproducibility and / or superior reproducibility to the manufacturing processes of interconnectors of the prior art, and / or ensuring the manufacture of several dozen, preferably several hundred, of interconnectors in parallel, and / or allowing the assembly of the sheets / plates, intended to form the interconnector, in a single step, and / or reducing manufacturing costs.

[0016] To this end, the invention is proposed a method for manufacturing at least one interconnector for solid oxide electrochemical devices, called ISO, called method.

[0017] The process includes compressing a stack comprising, preferably consisting of, at least two metallic sheets.

[0018] Compression involves applying a pressure greater than or equal to 4 bars.

[0019] Preferably, the pressure is greater than or equal to 4 bars, preferably even more so to 5 bars and most preferably to 6 bars and / or less than or equal to 15 bars, preferably even more so to 14 bars, most preferably to 13 bars, most preferably to 12 bars, most preferably to 11 bars, most advantageously to 10 bars, most advantageously to 9 bars, most advantageously to 8 bars and most preferably to 7 bars.

[0020] The pressure is applied perpendicularly to at least two metal sheets.

[0021] The process also includes heating, preferably under vacuum, concurrent with the application of pressure, of the stacking at a temperature between 700 and 1200°C.

[0022] Preferably, the heating is implemented at a temperature greater than or equal to 700°C, preferably even more at 750°C, preferably at 800°C, more preferably at 850°C, even more preferably at 900°C, advantageously at 950°C and particularly advantageously at 1000°C and / or at a temperature less than or equal to 1200°C, preferably even more at 1150°C and preferably at 1100°C.

[0023] Preferably, at least two sheets are, preferably each one, machined.

[0024] Preferably, at least two sheets should be in contact with each other.

[0025] Preferably, the at least two metal sheets are machined and / or arranged to form, after manufacture, the ISO.

[0026] Preferably, the stack consists of or is formed by or is composed of at least two metallic sheets.

[0027] Preferably, the stack comprises only, preferably is made up, formed or composed solely, of at least two metal sheets.

[0028] Preferably, the compression and heating of the stack constitute a single and / or the same and / or single step, or are implemented in a single or the same and / or single step.

[0029] Preferably, it is understood to mean at least one interconnector: one interconnector, preferably several interconnectors, and particularly advantageously a set of interconnectors.

[0030] Preferably, the process according to the invention is a process for manufacturing several interconnectors during a manufacturing step, preferably during the same and / or a single manufacturing step.

[0031] Preferably, the process according to the invention is a process for manufacturing several interconnectors during the manufacturing step comprising or consisting of compressing and heating the stack of at least two sheets.

[0032] Preferably, the compression and heating of the stack of at least two metal sheets are carried out simultaneously.

[0033] Preferably, the electrochemical devices are solid oxide electrolyzers or solid oxide fuel cells.

[0034] A metallic sheet can be understood to be a sheet made of a metallic alloy.

[0035] It can be understood by machined: comprising openings, which may be through or non-through, and / or channels and / or grooves and / or any other pattern, which may be through or non-through.

[0036] Preferably, the at least two metal sheets are arranged, individually and / or in relation to each other or relative to each other and / or within the stack, to form, after manufacture, the ISO.

[0037] Preferably, each stack is designed and / or arranged to form, after manufacture, an individual ISO. Preferably, at least two metal sheets in a stack, or even more preferably each metal sheet in each stack, are arranged to form, after manufacture, an individual ISO.

[0038] Preferably, each sheet and / or separator can be defined as having one dimension, for example its thickness, less than its other two dimensions, for example its width and length. It can also be defined that the length of each sheet and / or separator is greater than or equal to its width. Preferably, "applying pressure perpendicular to the sheets and / or separators" means applying pressure parallel to the thickness of each sheet and / or separator.

[0039] Preferably, each sheet and / or each separator can be defined as extending, preferably as extending primarily, along a plane comprising or parallel to the width and length. Preferably, "applying pressure perpendicular to the sheets and / or separators" means applying pressure perpendicular to the plane along which each sheet and / or separator extends.

[0040] The process can be defined as a welding process or a diffusion welding process.

[0041] Preferably, the process according to the invention is a process for manufacturing an interconnector by diffusion welding.

[0042] Preferably, the method according to the invention is a method for manufacturing an interconnector comprising diffusion welding of the stack of at least two metal sheets. Preferably, the diffusion welding of the stack of at least two metal sheets constitutes a single step.

[0043] Preferably, the process according to the invention is a process for manufacturing an interconnector by diffusion welding comprising the compression and heating of the stack of at least two metal sheets.

[0044] Preferably, compression and / or heating are carried out for a period of between 1 and 10 hours.

[0045] Preferably, the heating is operated for a period of 1 hour or more, preferably 2 hours or more, and preferably 3 hours and / or for a period of 10 hours or less, preferably 9 hours or more, preferably 8 hours or more, preferably 7 hours or more, and preferably 6 hours or more.

[0046] Preferably, each metal sheet has a thickness between 0.1 and 7 mm.

[0047] Preferably, a metallic foil, preferably each metallic foil, has a thickness greater than or equal to 0.1 mm, preferably also 0.5 mm, preferably 1 mm, more preferably 1.25 mm, even more preferably 1.5 mm, advantageously 1.75 mm, particularly advantageously 2 mm, very particularly advantageously 2.25 mm and most preferably 2.5 mm and / or less than or equal to 7 mm, preferably also 6.5 mm, preferably 6 mm, more preferably 5.75 mm, even more preferably 5.5 mm, advantageously 5.25 mm, particularly advantageously 5 mm, very particularly advantageously 4.75 mm and most preferably 4.5 mm.

[0048] Preferably, each sheet is made of the same material.

[0049] Preferably, each sheet is made of a material with the same composition and / or the same crystalline structure.

[0050] Preferably, for a given stack, preferably for each stack, at least one sheet, preferably each sheet, comprises: trenches or grooves intended and / or arranged to form channels or conduits for ISO gas, and / or at least one through-hole intended to permit: the assembly or mounting of the ISO, and / or the transport of gas, via the trenches, through the ISO.

[0051] Preferably, compression and heating are applied simultaneously to a set of stacks.

[0052] Preferably, a separator is inserted between two stacks and in contact with said two stacks.

[0053] Preferably, the stacks, of the set of stacks, to which compression and heating are applied are superimposed, preferably in the direction in which the pressure is applied.

[0054] Preferably, the stacking set includes at least two stacks.

[0055] Preferably, the pressure is applied perpendicularly to each separator.

[0056] Preferably, the separator(s) allow the stacks to be isolated or separated from each other.

[0057] Preferably, the separator or each separator is in physical or direct contact with the two stacks between which it is inserted.

[0058] Preferably, the separator or separators are in contact with the entire contact surface of the two sheets of the two stacks between which the separator is intercalated.

[0059] Preferably, the separator constitutes, or is arranged to constitute, a diffusion barrier to the atoms of the sheets, in particular to the metallic atoms of the sheets.

[0060] Preferably, the separator prevents welding between said separator and each of the two stacks with which it is in contact.

[0061] Preferably, the separator prevents welding between the two stacks with which it is in contact.

[0062] Preferably, the separator(s) are made of molybdenum alloy or ceramic, preferably alumina.

[0063] Preferably, at least two sheets or each sheet are made of ferritic stainless steel.

[0064] According to the invention, an interconnector for a solid oxide electrolyzer or solid oxide fuel cell, called ISO, is also proposed, which can be obtained by implementing the process according to the invention.

[0065] According to the invention, an interconnector for a solid oxide electrolyzer or solid oxide fuel cell, called ISO, is also proposed, comprising, preferably being made of, a single material.

[0066] Preferably, the ISO does not include, preferably within the volume (or "bulk") of the ISO, any interface(s) and / or discontinuity(ies) and / or pore(s).

[0067] Preferably, the ISO does not include an interface between two different materials, in particular between two materials whose composition is different and / or whose crystalline structure is different.

[0068] In particular, ISO does not include layer(s), line(s) or point(s) of electrical contact made between two sheets of the same stack.

[0069] Preferably, the ISO comprises, or is made up of, a single and / or the same and / or a single layer.

[0070] Preferably, ISO comprises or consists of a continuous layer.

[0071] Preferably, the ISO comprises, preferably is made up of, a single and / or the same and / or a single crystal lattice.

[0072] Preferably, the ISO comprises, preferably is made of, a continuous crystalline lattice.

[0073] According to the invention, a single repeating unit (SRU) for a solid oxide electrolyzer or solid oxide fuel cell is also proposed, comprising: the ISO according to the invention, a cathode, an anode, current collectors, and a sealing gasket.

[0074] Preferably, the manufacturing process according to the invention is suitable, preferably still is particularly suitable, more preferably is designed and particularly advantageously is specially designed, to implement the ISO according to the invention.

[0075] Therefore, any characteristic of the manufacturing process according to the invention is directly transposable to the ISO according to the invention, and vice versa. Brief description of the FIGURES

[0076] 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: the first is a schematic representation of a non-limiting example embodiment of the process for manufacturing interconnectors for solid oxide electrochemical devices; the second comprises, on the left, a schematic representation of a non-limiting example of a device used for implementing the process for manufacturing interconnectors for solid oxide electrochemical devices and, on the right, a schematic representation of interconnectors for solid oxide electrochemical devices obtained according to the invention;This is a schematic representation of a non-limiting example of a stack of metal sheets used for implementing the manufacturing process and for obtaining an interconnector for solid oxide electrochemical devices according to the invention.

[0077] 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 alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0078] In particular, all the variants and embodiments described can be combined with each other if there are no technical obstacles to this combination. Detailed description of the FIGURES

[0079] Figures 1 and 2 illustrate a non-limiting embodiment of the manufacturing process for interconnectors 1 for solid oxide electrochemical devices, referred to as ISO 1.

[0080] According to the non-limiting embodiment, ISO 1 is an interconnector for electrolyzer or in solid oxide fuel cell.

[0081] The process comprises diffusion welding of at least two metallic sheets 3. Diffusion welding according to the process is carried out by simultaneously compressing 7 a stack 2 made up of at least two metallic sheets 3 and heating the stack 2.

[0082] According to the non-limiting embodiment, the 3 metal sheets have a 2B finish according to EN 10088-4. Control of the surface roughness of the 3 metal sheets is optional.

[0083] Compression step 7 is implemented by applying a pressure advantageously greater than or equal to 4 bars. The pressure applied is between 6 and 7 bars depending on the non-limiting embodiment.

[0084] The heating is implemented at a temperature between 1000 and 1100°C according to the non-limiting embodiment.

[0085] Depending on the embodiment, the heating is carried out under vacuum. In particular, the heating is carried out under a pressure less than or equal to 1.10 -5 mbars, preferably at 1.10 -6 mbars.

[0086] Typically, the temperature applied during heating can be between 40 and 80% of the melting temperature of the 3 layers.

[0087] Heating and compression are applied for a period of between 3 and 6 hours according to the non-limiting embodiment.

[0088] Compression 7 consists of applying pressure perpendicular to at least two sheets 3. Each sheet 3 of the stack 2 forms a plate 3. Compression 7 is applied perpendicular to the plate formed by each sheet 3.

[0089] The at least two sheets 3 of the same stack 2 are in contact with each other before implementation of the process. The at least two metal sheets 3 are machined, arranged and positioned relative to each other to form, after fabrication, the ISO 1.

[0090] It is advantageous for each layer 3 to have a low and constant specific surface resistance (i.e., high electronic conductivity). Preferably, the specific resistivity of the layers 3 is less than or equal to 9000 S / cm, and even more preferably 8000 S / cm. It is also advantageous for the coefficient of thermal expansion (CTE) of each layer 3 to be compatible with the electrochemical cell (i.e., typically on the order of 10 x 10⁻¹⁰). −6 °C −1 (from 25 to 1000 °C).

[0091] The invention enables the production of several ISO1 units during the same manufacturing step. Indeed, the compression 7 and heating 2 applied simultaneously to one or more stacks allow for the simultaneous production of several ISO1 units in parallel. To achieve this, a separator 6 is inserted between two consecutive stacks 2. Each separator 6 is in contact with the two stacks 2 between which it is inserted.

[0092] Each separator 6 constitutes a diffusion barrier to the atoms of the sheets 3 with which the separator is in contact. Each separator 6 prevents bonding between said separator and the two stacks with which it is in contact.

[0093] The separators 6 are made of a different material from the material constituting the sheets 3. The separators 6 are made of alumina according to the non-limiting embodiment presented.

[0094] According to the non-limiting embodiment illustrated in FIGURES 1 and 2, the process is implemented for five stacks 2. Each stack 2 consists of four sheets 3. Five ISO 1s are thus obtained.

[0095] The process is implemented using a press comprising two jaws 8. Pressure is applied between the two jaws 8 by moving one jaw, for example by means of a piston, the other remaining stationary according to the embodiment. The stacks 2 and the separators 6 are arranged between the two jaws 8 so as to compress them during the relative movement of the jaws with respect to each other.

[0096] Following the implementation of the diffusion welding process, the manufactured separators 6 and ISO 1 are recovered.

[0097] As with state-of-the-art interconnector manufacturing techniques, the 3 sheets are machined, prior to their assembly, to form, after manufacturing, the ISO 1. The 3 sheets are individually machined so that the ISO 1, i.e. the assembled 3 sheets, distributes and recovers the gas (air, H2O, O2, H2) and distributes / collects the current through each cell and electrically isolates the single repeating units (SRU) from each other.

[0098] The metal sheets 3 can be machined by any known machining process, such as, for example, cutting, in particular laser cutting, drilling and / or milling and / or engraving (chemical or plasma).

[0099] By way of non-limiting example, with reference to the illustration, a stack 2 of metal sheets 3 used for manufacturing an ISO 1 according to the embodiment is shown. Trenches or grooves 4 formed in some of the sheets 3 are intended to form gas channels or conduits for the ISO 1. The channels allow the circulation of gases (air, H2O, H2, O2) from one SRU to another. Through holes 5 formed in the sheets 3 are intended to allow the assembly or mounting of the ISO 1 in the SRU and / or in the electrolyzer or in the fuel cell. According to the non-limiting embodiment, the holes 5 are also arranged to ensure the transport of gas, via the trenches 4, through the ISO 1.

[0100] The metal sheets 3 in each stack 2 have a thickness between 0.1 and 7 mm. The metal sheets 3 have a thickness between 2 and 5 mm depending on the embodiment.

[0101] Advantageously, each layer 3 of each stack 2 is made of the same material. The layers 3 are made of ferritic stainless steel, depending on the embodiment. By way of non-limiting example, the layers 3 are made of K41 or Crofer, depending on the embodiment.

[0102] The use of metal alloys reduces the manufacturing costs of ISO 1 compared to state-of-the-art ceramic interconnectors.

[0103] The diffusion welding process according to the invention ensures optimal welding between the layers 3 (and therefore optimal ISO 1). No brazing or any layer, line, bead, or point of contact is required to ensure welding and / or electrical contact for the manufacture of ISO 1 according to the invention.

[0104] Indeed, during the diffusion welding process, plastic deformation and interconnection occur initially between the two contacting surfaces of two layers 3. Subsequently, controlled diffusion of atoms from the layers takes place at the interconnection point; spaces, pores, and irregularities at this interconnection are reduced and eliminated by grain migration / grain boundaries. Thirdly, atoms migrate between the two layers 3 by diffusion, resulting in the disappearance of the interface between them through the formation of bonds. Thus, the diffusion welding process yields a continuous material without interfaces, irregularities, or defects within its volume. Furthermore, the part produced by diffusion welding exhibits a continuous crystalline lattice without breaks or discontinuities within its volume.

[0105] The use of sheets 3 made of the same material ensures optimal bonding between sheets 3 (and therefore optimal ISO 1) by allowing the migration of atoms and the formation of a continuous crystal lattice between sheets 3 of each stack 2. In this case, the lattice matching between sheets 3 and / or the identical composition between sheets 3 ensures the obtaining of ISO 1 with a single continuous crystal lattice.

[0106] Thus, with reference to the, a set of five ISO 1s obtained by the process according to the invention is illustrated.

[0107] Each ISO 1 obtained does not include interface(s) and / or discontinuity(ies) and / or pore(s) within its volume (or bulk).

[0108] Each ISO 1 obtained consists of a single continuous layer.

[0109] As previously indicated, the use of sheets 3, within a stack, preferably within each stack 2, consisting of the same material, makes it possible to obtain an ISO 1 made of a single material.

[0110] Each ISO 1 obtained comprises a single and / or the same and / or a unique crystal lattice.

[0111] Each ISO 1 obtained does not include discontinuities or breaks within its crystal lattice.

[0112] According to the invention, a single repeating unit (SRU) for a solid oxide electrolyzer or solid oxide fuel cell is also proposed. The SRU comprises: the ISO 1 according to the invention, a cathode, an anode, current collectors, and a sealing gasket.

[0113] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0114] Thus, in combinable variants of the previously described embodiments: an ISO1 1 is proposed that can be obtained, obtained or directly obtained by the process according to the invention.

[0115] Furthermore, the different features, forms, variants and embodiments of the invention can be associated with each other in various combinations insofar as they are not incompatible or mutually exclusive.

Claims

A method for manufacturing at least one interconnector (1) for solid oxide electrochemical devices, referred to as ISO (1), said method, comprising: a compression (7) of a stack (2) comprising at least two machined metallic sheets (3) in contact with each other, said compression comprising the application of a pressure greater than or equal to 4 bars; said at least two metallic sheets being machined and arranged to form, after manufacture, the ISO; said pressure being applied perpendicular to the at least two sheets, a heating, concomitant with the application of the pressure, of the stack to a temperature between 700 and 1200°C. A method according to claim 1, wherein compression (7) and / or heating are carried out for a period of between 1 and 10 hours. A method according to claim 1 or 2, wherein each metallic sheet (3) has a thickness between 0.1 and 7 mm. A method according to any one of the preceding claims, wherein each sheet (3) is made of the same material. A method according to any one of the preceding claims, wherein, for a given stack (2), at least one sheet (3) comprises: trenches or grooves (4) intended to form channels or conduits for the ISO gas (1), and / or at least one through orifice (5) intended to permit: the assembly or mounting of the ISO, and / or the transport of gas, via the trenches, through the ISO. A method according to claim 1 or 2, wherein compression (7) and heating are applied simultaneously to a set of stacks (2); a separator (6) being interposed between two stacks and in contact with said two stacks. A method according to the preceding claim, wherein the separator (6) constitutes a diffusion barrier to the atoms of the sheets (3) preventing the bonding between the two stacks with which it is in contact and / or between said separator and each of the stacks with which it is in contact. Method according to claim 6 or 7, wherein the separator(s) (6) are made of molybdenum alloy or ceramic. A method according to any one of the preceding claims, wherein the at least two sheets (3) are made of ferritic stainless steel. Interconnector (1) for solid oxide electrolyzer or solid oxide fuel cell, referred to as ISO (1), directly obtained by implementing the process according to any one of claims 1 to 9. Interconnector (1) for solid oxide electrolyzer or solid oxide fuel cell, referred to as ISO (1), comprising a single material. ISO (1) according to the preceding claim, not comprising interface(s) and / or discontinuity(ies) and / or pore(s). ISO (1) according to claim 11 or 12, comprising a single and / or the same and / or a single layer. ISO (1) according to any one of claims 11 to 13, comprising a single and / or the same and / or a single crystal lattice. Single repeating unit (SRU) for solid oxide electrolyzer or solid oxide fuel cell, comprising: ISO (1) according to any one of claims 10 to 14, a cathode, an anode, current collectors, and a sealing gasket.

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