Electrolysis or co-electrolysis reactor (SOEC) or fuel cell (SOFC) with stacking of electrochemical cells in pre-assembled modules with the interposition of a removable intermediate plate dedicated to the passage of gases and the electrical connection, Associated production method.

Abstract

Electrolysis or co-electrolysis reactor (SOEC) or fuel cell (SOFC) with stack of electrochemical cells by pre-assembled modules with interposition of a removable interposed plate dedicated to the passage of gases and the electrical connection, Associated production method. The invention relates to an electrochemical device formed by assembly by stacking of pre-assembled modules, each of these modules being produced like a usual stack of electrochemical cells, as according to patent application EP3955353A1. An interposed plate which supports the contact elements and sealing joints, as mounted in a removable manner between stiffening plates of two adjacent modules always allows good circulation of gases and ensures good sealing, and also ensures good electrical contact, while guaranteeing faster and easier installation. Figure for the abstract: fig.6

Description

Title of the invention: Electrolysis or co-electrolysis reactor (SOEC) or fuel cell (SOFC) with stacking of electrochemical cells by pre-assembled modules with interposition of a removable intermediate plate dedicated to the passage of gases and the electrical connection, Associated production method. Technical field

[0001] The present invention relates to the field of solid oxide fuel cells (SOFC, English acronym for "Solid Oxide Fuel Cell"), that of high temperature water electrolysis (EHT, or EVHT for high temperature water vapor electrolysis, or HTE English acronym for High Temperature Electrolysis, or HTSE English acronym for High Temperature Steam Electrolysis) also with solid oxides (SOEC, English acronym for "Solid Oxide Electrolyser Cell"), and that of high temperature co-electrolysis of water and another gas chosen from carbon dioxide CO2 and nitrogen dioxide NO2.

[0002] The invention relates more particularly to the production of an electrochemical device constituting a high-temperature water electrolysis or co-electrolysis (HTE) reactor of the SOEC type, or a fuel cell of the SOFC type, with a stack of elementary electrochemical cells.

[0003] The present invention aims firstly to improve the assembly of such a device and also its operation.

[0004] Although described with reference mainly to the application of high temperature water electrolysis, the invention applies equally well to co-electrolysis of water and another gas chosen from carbon dioxide CO2, as to a SOFC fuel cell.

[0005] The invention applies to a SOFC fuel cell using as fuel either hydrogen or a hydrocarbon, for example methane CH4, or any other fuel such as NH3. Prior art

[0006] A SOFC fuel cell or an EHT electrolyser is an electrochemical device consisting of a stack of elementary patterns each comprising a solid oxide electrochemical cell, consisting of three layers superimposed on each other anode / electrolyte / cathode, and interconnection plates made of metal alloys also called bipolar plates, or interconnectors. The function of the interconnectors is to ensure both the passage of the electric current and the circulation of gases in the vicinity of each cell (injected water vapor, hydrogen and oxygen produced in an EHT electrolyzer; injected air and hydrogen and water produced in an SOFC stack) and to separate the anode and cathode compartments which are the gas circulation compartments on the side of the anodes and cathodes of the cells respectively.

[0007] To carry out the electrolysis of water vapor at high temperature EHT, typically between 600 and 950°C, water vapor H2O is injected into the cathode compartment. Under the effect of the current applied to the cell, the dissociation of water molecules in vapor form is carried out at the interface between the hydrogen electrode (cathode) and the electrolyte: this dissociation produces dihydrogen gas H2 and oxygen ions. The dihydrogen is collected and evacuated at the outlet of the hydrogen compartment. The oxygen ions O2- migrate through the electrolyte and recombine into dioxygen at the interface between the electrolyte and the oxygen electrode (anode).

[0008] To ensure the operation of a SOFC fuel cell, air (oxygen) is injected into the cathode compartment and hydrogen into the anode compartment. The hydrogen H2 will transform into H+ ions and release electrons which are captured by the anode. The H+ ions arrive at the cathode where they combine with O2- ions formed from the oxygen in the air, to form water. The transfer of H+ ions and electrons to the cathode will produce a direct electric current from the hydrogen.

[0009] To increase the flow rates of hydrogen and oxygen produced in the case of EHT electrolysis or to increase the electrical power supplied in the case of a SOFC fuel cell, it is known to stack several elementary electrochemical cells on top of each other by separating them by the interconnectors. The assembly is positioned between two end connection plates which support the electrical power supplies and the gas supplies / collection of an electrolyzer (electrolysis reactor) or of a SOFC fuel cell.

[0010] Furthermore, to improve the quality of the electrical contacts established between the interconnectors and the electrodes, and therefore the performance of the aforementioned electrochemical devices, electrical contact elements are individually intercalated and arranged on the electrodes. In an electrochemical device, a nickel grid is conventionally used for contact with the hydrogen electrode (cathode in an EHT reactor, anode in an SOFC cell), because it gives satisfactory results at low cost.

[0011] In general, to date, stacks have a limited number of electrochemical cells. Typically, the applicant implements stacks of a number of 25 electrochemical cells.

[0012] Before the operation of an aforementioned electrochemical device, it is necessary to subject its stack to at least one heat treatment step called reduction, in order to put the electrochemical cells in their reduced form, and not oxidized as they are initially.

[0013] This reduction step can be a thermomechanical cycle under gas, a reducing gas for the hydrogen electrode and air or neutral gas for the oxygen electrode.

[0014] A particular heat treatment step has been described in patent EP2870650B1.

[0015] The stacks implemented to date generally use, at each of their stages, joints which must guarantee the seal between two distinct adjacent gas circulation compartments, i.e. an anode compartment and a cathode compartment. Advantageous joints have been described in patent EP3078071B1. These joints have the particularity of requiring thermal conditioning during which they are crushed.

[0016] Contact elements, such as the layers described in patent application EP2900846A1 or nickel grids, also collapse during thermal conditioning and during operation of the electrochemical device, which ensures their proper placement. Elements that serve as contact elements in the hydrogen chamber also collapse. In other words, during the thermal conditioning step, a stack of an aforementioned electrochemical device collapses, typically by several centimeters. To date, given the relatively small number of stacked cells, the collapse is taking place correctly.

[0017] To obtain stacking embodiments with a greater number of electrochemical cells than usual devices, typically beyond 25 cells, while avoiding, when tightening the stack, mechanical problems of blocking of the arching type on the guide rods, which could harm the electrochemical operation of the devices, patent application EP3955353A1 proposed an electrochemical device which is formed by assembly by stacking previously assembled modules, each of these modules being produced like a usual stack of electrochemical cells.

[0018] [Fig.l] shows an electrochemical device 1 according to EP3955353A1 which can operate reversibly as a high-temperature electrolyser or SOFC fuel cell.

[0019] This device 1 comprises a stack of three pre-assembled modules M1, M2, M3.

[0020] Each of the modules M1, M2, M3 comprises a stack respectively 2.1, 2.2, 2.3 of electrochemical cells based on solid oxides of the SOEC / SOFC type.

[0021] Within each stack 2.1, 2.2, 2.3, a plurality of electrical and fluidic interconnectors, not shown, is arranged individually on either side of each of the electrochemical cells. Each interconnector consists of at least one component made of electronically conductive and gas-tight material for bringing or collecting the electrical current to the cells and for bringing, collecting and circulating gases on each electrode of each electrochemical cell.

[0022] Similarly, within each stack 2.1, 2.2, 2.3, a plurality of contact elements and sealing gaskets around each gas inlet / outlet are arranged individually on each electrochemical cell electrode.

[0023] In other words, each module M1, M2, M3 comprises a stack of cells with individual intercalation of interconnectors, contact elements and sealing joints as done according to the state of the art for a complete electrochemical device.

[0024] Each module M1, M2, M3 further comprises two stiffening plates respectively 3.1, 4.1; 3.2, 4.2 and 3.3, 4.3 between which the stack of cells 2.1, 2.2, 2.3 is arranged.

[0025] In the stack of modules, the stiffening plates 4.1, 3.2, 4.2, 3.3 within the stack of modules, form electrical and fluidic interconnectors between modules.

[0026] The two stiffening plates 3.1, 4.3, arranged at the ends of the stack of modules, form electrical and fluidic connectors for bringing or collecting the electric current from the electrochemical device to the outside and for bringing, collecting and circulating the gases from the electrochemical device to the outside.

[0027] An electrical contact element 5.1 is arranged between the two adjacent modules M1, M2 with contact between their stiffening plates 4.1 and 3.2.

[0028] A seal 6.1 is arranged between the two adjacent modules M1, M2 to ensure sealing around each gas inlet / outlet from one module M1 to the other M2.

[0029] An electrical contact element 5.2 is arranged between the two adjacent modules M2, M3 with contact between their stiffening plates 4.2 and 3.3.

[0030] A seal 6.2 is arranged between the two adjacent modules M2, M3 to ensure sealing around each gas inlet / outlet from one module M2 to the other M3.

[0031] Two electrical connection rods 7, 8, usually called current rods, are each screwed into a thread on the edge of one of the two stiffening plates 3.1, 4.3 which are at the ends of the stack of modules. Thus, the electric current can be brought in by one of the rods 7 and exit the stack of modules by the other rod 8. The current rods 7, 8 can advantageously each be made up of a rod made of a first metallic material and a sheath entirely covering and welded to the rod and made of a second metallic material, stainless steel, with electrical resistivity greater than the electrical resistivity of the first metallic material. The rod and the sheath are preferably welded to each other by hot isostatic pressing, as described in patent EP3098889B1.

[0032] For example, the rod is made of copper and is covered with a stainless steel sheath.

[0033] Each module is pre-assembled by initially making tappings. 9 at the four corners of each of the stiffening plates, threaded hole into which a fixing lug 10 is screwed ([Fig.2]). Also, each stiffening plate is pierced with through-holes 30 or 40 for the passage of gases.

[0034] At room temperature, a system of tightening bolts is put in place, each consisting of a threaded rod 11 and nuts 12 at the four corners of each module, as illustrated in [Fig.3] with module M1. Each of the rods 11 is inserted into the hole of a fixing lug 10. These fixing lugs can also be machined from the mass of the plate ([Fig.4]).

[0035] For each module M1 to M3, a tightening force is then applied by the bolt system 10, 11, 12 between its two stiffening plates so as to obtain a pre-assembly of each module allowing it to be transported ([Fig.3]).

[0036] Thus, the electrochemical device 1 according to EP3955353A1 is a superposition of preassembled modules M1 to M3 through which the gases of the electrochemical reaction and the electric currents circulate, each of the modules M1 to M3 comprising a stack of electrochemical cells alternating with interconnectors, contact elements and sealing joints.

[0037] This solution is completely satisfactory from the point of view of the expected performances. That being said, the assembly of such a device with pre-assembled modules has drawbacks, more particularly in the event of desired disassembly of one and / or the other of the modules, in the event of failure and / or maintenance to be carried out.

[0038] Indeed, the installation of the contact element 5.1, 5.2 and that of the sealing joints 6.1, 6.2 between two adjacent modules within the device can be delicate due to the precision to be obtained and it may not be suitable for all situations of deformation of the stiffening plates 4.1, 3.2; 4.2, 3.3 which may occur during operation of the device.

[0039] Concretely, as shown in [Fig.4], once a module M2 is in position, we first proceed to install an electrical contact element 5.1, in the form of a single sheet, directly in contact with the upper stiffening plate 3.2.

[0040] Then, as shown in [Fig.5], an electrically insulating support 60.1 is positioned, generally in the form of a mica sheet, pierced with through openings, placing the latter opposite the openings 30 of the plate of stiffening 3.2, sealing gaskets in the form of cords having been previously deposited individually around each through opening of the support.

[0041] There is therefore a need to further improve electrochemical devices with a stack of modules themselves with a stack of electrochemical cells, forming an SOEC type electrolysis reactor or a SOFC type fuel cell, as according to patent application EP3955353A1, in particular by facilitating the production of contact elements and sealing joints at the interface between two adjacent modules. Statement of the invention

[0042] To do this, the invention firstly relates to an electrochemical device, constituting an SOEC electrolysis or co-electrolysis reactor or an SOFC fuel cell, intended to operate at high temperature, comprising: - a stack of at least two pre-assembled modules, in which each pre-assembled module comprises:

[0043] a stack of electrochemical cells based on solid oxides of the SOEC / SOFC type;

[0044] a plurality of electrical and fluidic interconnectors, each comprising a component made of electronically conductive and gas-tight material for supplying or collecting electrical current to the cells and for supplying, collecting and circulating gases on each electrode of each electrochemical cell; the interconnectors being arranged individually on either side of each of the electrochemical cells;

[0045] two stiffening plates between which the stack is arranged; the stiffening plates, arranged within the stack of modules, form electrical and fluidic interconnectors between modules, while the two stiffening plates, arranged at the ends of the stack of modules, form electrical and fluidic connectors for bringing or collecting the electric current between the electrochemical device and the exterior and for bringing, collecting and circulating the gases between the electrochemical device and the exterior; - at least one intermediate plate with at least one electrically conductive sheet having two substantially parallel flat faces, removably mounted between two adjacent modules, the plate being provided with through openings from one face to the other to circulate the gases between the two modules, each of the two faces of the plate supporting at least one electrical contact element arranged with contact with one of the stiffening plates of one of the two modules and at least one sealing gasket arranged around each of the through openings to ensure sealing around each gas inlet / outlet from one module to the other.

[0046] The sheet material of the interlayer plate is preferably steel, more preferably ferritic steel with about 20% chromium.

[0047] The thickness of the sheet metal is advantageously between 0.2 and 10 mm, preferably between 0.5 and 1 mm.

[0048] According to a first advantageous variant embodiment, the electrical contact element(s) supported by each of the two faces of the intermediate plate comprise(s) at least one layer of a conductive ceramic material.

[0049] According to this first variant, the conductive ceramic material is advantageously chosen from the group consisting of:

[0050] - Lao,6Sro,4Coo,8Feo,203 (LSCF); - Lao,8Sro,2Cuo,9Feo,16)2.5 (LSCuF); - La0j7Sr0j3CoO3 (LSC); - Sm0.5Sr0.5CoO3 (SSC); - SmBa0j5Sroj5Co205 (SBSC); - GdSrCo2O5 (GSC); - La0.65Sr0.3MnO3 (LSM); - LaBaCo2O5 (LBC); - YBaCo2O5 (YBC); - Ndlj8Ce0j2CuO4 (NCC); ■ Lao,8Sroj2Cooj3 Mn03 Fe0.6O3 (LSCMF); - Lao,98Nio,6Feoj403 (LNF); - La1>2Sr0j8NiO4 (LSN); - La0.7Sr0.3FeO3 (LSF); - La2Nio,6Cu0,404 (LNC).

[0051] Advantageously, the conductive ceramic material is chosen from the group consisting of LSM, LSC, LNF, and LSCF.

[0052] Preferably, the layer of conductive ceramic material is hollowed out over at least part of its thickness. The hollowing may consist of grooves, holes or any other shape. Hollowing out, in particular grooving the contact layer, allows for the same crushing force to increase the stress and therefore to crush the layer more and thereby better correct the surface defects. In other words, by grooving a contact layer, its crushing capacity is improved. Conversely, a solid contact layer promotes electrical contact due to a larger current flow surface.

[0053] Advantageously, the layer of conductive ceramic material is bonded, preferably by heat pressing or by means of an adhesive or by heat pressing by the sheet metal previously heated by the Joule effect by the passage of current or inductively. may refer to the advantageous heat-pressing methods described in patent EP2900846B1 or residue-free bonding described in patent application WO2022 / 234214. Inductive heat-pressing consists of heating the sheet by Joule effect and then directly applying the layer of ceramic material to the desired location.

[0054] Advantageously, the thickness of the layer of conductive ceramic material on each face of the sheet is between 100 μm and 5 mm.

[0055] Care is also taken to ensure that the surface area of ​​a ceramic material layer is minimized so as to increase the local clamping stresses applied to the stack. Indeed, the clamping force applied is constant. Also, by reducing the surface area of ​​the contact layer the stress (F / S) will be increased. For example, with the same force and a ceramic material layer whose surface area is half as small, the stress is twice as high.

[0056] According to a second variant, the electrical contact element(s) supported by each of the two faces of the intermediate plate comprise(s) at least one electrically conductive grid, preferably made of gold.

[0057] A gold grid can have a surface area between 0.5 and 5cm2, preferably of the order of 2cm2 with a number of meshes of 100 to 3600 meshes / cm2. A nickel grid can also be considered. In this case, care should be taken to create a seal around the grid to prevent it from oxidizing. A copper grid can also be considered. A conductive ceramic grid can also be considered. Ferritic steel grids, preferably ferritic steel with approximately 20% chromium, preferably CROFER® or K41 (441 steel) can work if they are in the form of a grid. Indeed, these steels with a high Cr content are highly resistant to corrosion and are good electrical conductors.

[0058] Precious metal grids, such as platinum, may also be considered.

[0059] The number of grids supported per face of the interposed plate may be between 1 and 10, preferably equal to 5. With a single grid, the quantity of material is limited but the mechanical balance of the modules and their interposed plates may not be optimal. With a number of 10 grids, the mechanical balance is ensured but the quantity of material used may be significant.

[0060] Preferably, the surface area of ​​a grid is between 0.5 and 5cm2, preferably of the order of 2cm2, for a sheet metal surface area of ​​the order of 500 cm2.

[0061] More preferably, the grid(s) is(are) welded directly to each of the two faces of the sheet. The welding may be by spots.

[0062] According to a preferred arrangement, the grid(s) supported by one of the two faces is / are offset from the grid(s) supported by the other of the two faces, by at most 10% of the length and / or width of the grid(s). This makes it possible to minimize the path of the electric current in the thickness of the sheet and therefore not to introduce too much electrical resistance into the stack of the device.

[0063] According to an advantageous embodiment, a number of five grids are provided, supported by each of the two faces, distributed in a square with one of them in the center of the square.

[0064] Advantageously, the thickness of each of the stiffening plates is between 1 and 10 mm.

[0065] According to an advantageous embodiment, the device comprises two additional end plates, called terminal plates, distinct from the stiffening plates between which the stack of modules is arranged. Arranging end plates in addition to the stiffening plates at the ends of the stack of modules can allow a simpler fluid connection with the surrounding fluid management system, in particular due to the changes in dimensions between the fluid distributions of the stack of modules and the fluid management system.

[0066] Preferably, the thickness of each of the end plates is greater than 5 mm.

[0067] According to another advantageous embodiment, the device comprises at least one electrical connection rod fixed to each of the two stiffening plates or, where appropriate, to each of the two terminal plates, arranged at the ends of the stack of modules.

[0068] Preferably, each of the electrical connection rods is screwed into a thread on the edge of one of the two stiffening plates or, where appropriate, one of the two end plates.

[0069] More preferably, four connecting rods may be provided, fixed individually to the corners of each of the two stiffening plates or, where appropriate, to each of the two end plates, arranged at the ends of the stack of modules. This makes it possible to improve the homogeneity of the surface distribution of the electric current and thereby to have thinner plates.

[0070] The invention also relates to a method for producing an electrochemical device, forming an SOEC electrolysis or co-electrolysis reactor or an SOFC fuel cell, intended to operate at high temperature, comprising the following steps:

[0071] a / production of at least two modules, each module comprising:

[0072] - a stack of electrochemical cells based on solid oxides of the SOEC type / SOFC;

[0073] - a plurality of electrical and fluidic interconnectors, each comprising a component made of electronically conductive and gas-tight material for bringing or collecting electric current to cells and for bringing, collecting and circulating gas on each electrode of each electrochemical cell; the interconnectors being arranged on either side of each of the electrochemical cells;

[0074] - two stiffening plates between which the stack is arranged;

[0075] b / application of a clamping force to each module by a system of bolts between its two stiffening plates so as to obtain a pre-assembly of each module allowing it to be transported;

[0076] c / stacking on top of each other the modules preassembled according to step b / , with intercalation between two adjacent modules of a removable intermediate plate with at least one electrically conductive sheet having two substantially parallel flat faces, the plate being provided with through openings from one face to the other to circulate the gases between the two modules, each of the two faces of the plate supporting at least one electrical contact element arranged with contact with one of the stiffening plates of one of the two modules and at least one sealing gasket arranged around each of the through openings to ensure sealing around each gas inlet / outlet from one module to the other;

[0077] d / application of a clamping force to the stack of modules by a clamping system, independent of the bolt systems of the modules, between the two end stiffening plates so as to obtain an assembly;

[0078] e / removal of the bolt systems from the assembly while maintaining independent tightening;

[0079] f / application of a thermomechanical treatment to the assembly so as to finalize at least the installation of the electrical contact elements and the sealing joints between stiffening plates and thus obtain the final assembly;

[0080] the method comprising a step of reducing all the electrochemical cells.

[0081] To apply the tightening of step b / , it is also possible to use the device described in patent application WO2023 / 285751.

[0082] According to an advantageous embodiment variant, step a / comprises a step al / of applying a thermomechanical treatment to each module produced, so as to finalize at least the installation of electrical contact elements and sealing joints within each module.

[0083] The modules must be reduced. The step of reducing the electrochemical cells can be carried out during step a1 / for each module or during step f / for the assembly of modules. The reduction can therefore be carried out during the initial temperature setting of each of the modules, or later once the stacking of the modules has been carried out.

[0084] The reduction of electrochemical cells can be carried out from 650°C or advantageously at 800°C for a period of one hour to several days depending on the hydrogen flow rates sent.

[0085] A certain volume of hydrogen is necessary to completely reduce an electrochemical cell, and it is preferably necessary to send small quantities of hydrogen at a time to avoid too abrupt a reduction so as not to risk deformation of the cells, or even their breakage. Once reduced, the cells and therefore the electrochemical device can operate normally, that is to say implement an EHT electrolysis reaction or produce electricity.

[0086] According to another advantageous variant, when the step of reducing the electrochemical cells is carried out during step a1 / for each module, a step a2 / of measuring the total electrical voltage of each module is advantageously carried out at the end of the latter.

[0087] According to another advantageous variant, the method comprises a step a3 / of testing the tightness of each module.

[0088] Thus, the invention essentially consists of an electrochemical device formed by assembly by stacking previously assembled modules, each of these modules being produced like a usual stack of electrochemical cells, as according to patent application EP3955353A1.

[0089] An intermediate plate which supports the contact elements and sealing joints, such as removably mounted between stiffening plates of two adjacent modules, always makes it possible to obtain good circulation of gases and to ensure good sealing, and also to ensure good electrical contact, while guaranteeing faster and easier installation.

[0090] Furthermore, in the event of replacement of a module if it is defective and / or in the event of maintenance, the intermediate plate can also be easily removed from the stack and, if necessary, also be replaced with the defective module.

[0091] In addition, the prior positioning of the contact elements is facilitated on the removable plate and the fact that they are present on each of the faces of this plate makes it possible to better compensate for the deformations of the stiffening plates at the ends of the modules on either side.

[0092] Ultimately, the invention retains the same advantages as those of the device according to patent application EP3955353A1, which can be summarized as follows: - due to the manufacture of pre-assembled modules then stacked, production of electrochemical devices with a large number of electrochemical cells, without the problems of bracing present and excessively large crushing strokes encountered in stacks of cells according to the state of the art, i.e. in a single block; - obtaining an electrochemical device whose voltage level, total power or size can be easily modulated. It is thus possible to provide electrical voltages between 10 and 1000 V using a single electrochemical device, by modulating the total number of cells per module and the number of stacked modules.

[0093] Other advantages and characteristics will become more apparent upon reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures. Brief description of the drawings

[0094] [Fig-1] [Fig.l] is a schematic side view of an example of a device electrochemical with pre-assembled modules according to patent application EP3955353A1.

[0095] [Fig.2] [Fig.2] is a schematic top view of an example of a stiffening plate with its holes for the circulation of gases and its means for attaching a threaded bolt clamping system for the transport and handling of a pre-assembled module according to EP3955353A1.

[0096] [Fig.3] [Fig.3] is a schematic side view of an example of an electrochemical cell stack module equipped with its bolt clamping system according to EP3955353A1.

[0097] [Fig.4] [Fig.4] is a photographic reproduction showing a contact grid placed on a stiffening plate of a module according to EP3955353A1, as well as fixing lugs machined directly into the part.

[0098] [Fig.5] [Fig.5] is a photographic reproduction showing a mica sheet supporting sealing gaskets, placed on a stiffening plate of a module according to EP3955353A1

[0099] [Fig.6], [Fig.6A] Figures 6 and 6A are schematic views respectively from above and in longitudinal section of a removable interposed plate of an electrochemical device according to the invention.

[0100] [Fig.7] [Fig.7] is a photographic reproduction of a removable interposed plate according to the invention and according to a first variant embodiment of an electrical contact element supported by the sheet metal of the plate.

[0101] [Fig.8A], [Fig.8B] Figures 8A and 8B are schematic sectional views longitudinal view of a removable interposed plate of an electrochemical device according to the invention showing two possible arrangements of electrical contact grids.

[0102] [Fig.9] [Fig.9] is a photographic reproduction of a removable interposed plate according to the invention and according to a second variant embodiment of an electrical contact element supported by the sheet metal of the plate.

[0103] [Fig. 10] [Fig. 10] is a photographic reproduction of a removable interposed plate according to the invention and according to the second variant embodiment of an electrical contact element supported by the sheet metal of the plate and with the presence of sealing gaskets.

[0104] [Fig. 11 A], [Fig.llB], [Fig.llC] Figures 11A, 11B and 11C are reproductions photographs showing steps in producing an electrochemical device according to the invention, including the step of inserting a removable plate supporting the electrical contact elements and sealing joints. Detailed description

[0105] For the sake of clarity, the same elements of an electrochemical device according to the state of the art and of an electrochemical device according to the invention are designated by the same numerical references.

[0106] Throughout the present application, the terms “lower”, “upper”, “above”, “below”, “inner”, “outer”, “internal” “external” are to be understood with reference to an electrochemical device according to the invention in operating configuration, i.e. the modules being stacked vertically.

[0107] It is also specified that the electrolysers or fuel cells described are of the solid oxide type (SOEC, English acronym for “Solid Oxide Electrolyte Cell” or SOFC, English acronym for “Solid Oxide Fuel Cell”) operating at high temperature.

[0108] Thus, all the constituents (anode / electrolyte / cathode) of an electrolysis cell or battery are ceramics.

[0109] The high operating temperature of an electrolyser (electrolysis reactor) or a battery is typically between 600°C and 1000°C.

[0110] Typically, the characteristics of a SOEC electrolysis cell suitable for the invention, of the cathode support type (CSC), may be those indicated as follows in Table 1 below. [YES] [Tables 1] Electrolysis cell Unit Value Cathode Constituent material Ni-YSZ Thickness pm 400 Thermal conductivity W m *K1 13.1 Electrical conductivity Q 1 m 1 105 Porosity 0.37 Permeability m2 1013 Tortuosity 4 Current density A.m2 5300 Anode Constituent material LSM, LSC Thickness pm between 10 and 50 Thermal conductivity W m *K1 9.6 Electrical conductivity Q 1 m 1 1 104 Porosity 0.37 Permeability m2 1013 Tortuosity 4 Current density A.m2 2000 Electrolyte Constituent material YSZ Thickness pm <10 Resistivity Q m 0.42

[0112] Figures 1 to 5 relating to an electrochemical device 1 according to patent application EP3955353A1 have been described in the preamble. They are therefore not commented on below.

[0113] The inventors thought of improving the production of such a device by simplifying and making more reliable the installation of the electrical contact elements and sealing joints between the stiffening plates of adjacent modules within a stack.

[0114] Thus, they produced an intermediate plate 100 as shown in Figures 6 and 6A, which is intended to be mounted in a removable manner, directly between two adjacent modules.

[0115] This intermediate plate 100 comprises a metal sheet 110 with two opposite flat and parallel faces 111, 112. The sheet 110 is provided with through openings 113 from one face to the other to circulate the gases between two adjacent modules within the stack.

[0116] Each of the two faces 110, 111 supports at least one electrical contact element 114, intended to be arranged with contact with one of the stiffening plates of one of the two adjacent modules and at least one sealing gasket 115 arranged around each of the through openings 113 to ensure sealing around each gas inlet / outlet from one module to the other.

[0117] This intermediate plate 100 thus constitutes a single-piece assembly ready to be inserted directly between two adjacent pre-assembled modules M1 to M3 as according to EP3955353A1.

[0118] The contact element 114 may be in the form of a single conductive ceramic layer arranged in the central portion of each of the faces 111, 112 as shown in [Fig.7]. This layer 114 may be a bonded strontium-doped lanthanum manganite (LSM) strip, which has been previously cut. The bonding may be carried out without residue as described in patent application WO2022 / 234214. The LSM strip 114 may also be secured by heat pressing to one face 111, 112 of the sheet, as described in EP2900846B1.

[0119] It is possible to simultaneously secure the layers 114 on the two opposite faces 111, 112 by clamping said layers and heating the sheet 110 by Joule effect by circulating an electric current therein. Such a heat-pressing process, called current flow or inductive, makes it possible to keep the face of the layer 114 which is towards the outside cold while the one in direct contact with the sheet 110 adheres to it.

[0120] Instead of a single conductive ceramic layer, one or more electrically conductive grids, in particular made of gold, can be secured to each of the two faces 111, 112 of the sheet 110.

[0121] Preferably, the grid surfaces 114 which are on the opposite faces 111, 112 must be as opposite each other as possible, that is to say as little offset from each other as possible, in order to minimize the path of the current in the thickness of the sheet 110. In other words, the offset between the grid surfaces 114 on the opposite faces 110, 111 must not be too large. This offset must be between 0 and 100% of the width of a grid of square or rectangular section, with a maximum of 10% as a preferred value.

[0122] Figures 8A and 8B highlight the advantage of minimizing the offset between grids 114 on either side of a sheet 110.

[0123] In the configuration of [Fig.8A], a grid 114 of thickness El present on the face 110 is offset by a distance approximately equal to L1 from the grid 114 of the same thickness El present on the other face 111. In this configuration, the electric current must pass through a long length since it is equal to L1 + 2xEl+E, E being the thickness of the sheet 110. This configuration is not optimal because the crossing by the current of the long length L1 adds a significant electrical resistance and therefore a voltage drop, which is not desirable for the operation of an electrochemical device 1.

[0124] In the configuration of [Fig.8B], a grid 114 of thickness El present on the face 110 is arranged opposite the grid 114 of the same thickness El present on the other face 111. Here, the electric current must cross a distance E2 equal to 2xEl+E, E being the thickness of the sheet 110. This distance E2 is therefore small and does not generate significant electrical resistance.

[0125] Furthermore, a number of contact surfaces 114 greater than 1 makes it possible to obtain a good compromise between mechanical balance between modules and the plate 110 and the quantity of material to be used to obtain good electrical contact between them.

[0126] [Fig.9] shows a plate 100 with a single metal sheet 110 and which comprises a number of five gold grids, distributed in a square with one in the center of the square. This plate has been successfully tested and the associated electrical resistance is less than 0.1V for a current of 200 A. The grid used had a thickness of 0.5 mm. The metal sheet is made of Crofer® and had a thickness of 0.5 mm.

[0127] [Fig. 10] reproduces the successfully tested variant of [Fig. 9] with the presence of sealing gaskets around each through opening 113 dedicated to the passage of gases in a device 1.

[0128] A method of producing an electrochemical device 1 according to the invention is now described with reference to FIGS. 1 1A to 1 1C.

[0129] Step a / : each of the modules M1 to M3 is produced with a stack of cells 2.1, 2.2, 2.3 between two stiffening plates 3.1, 3.2, 3.3 and 4.1, 4.2, 4.3. An example of a module M1 produced is as according to EP3955353A1.

[0130] Each of the stiffening plates 3.1, 3.2, 3.3 is preferably made up of a thick metal plate, and on one of its faces on which the gases must circulate, of two thin metal sheets. In other words, it is the thickness of the metal plate which provides the stiffening, the thin sheets allowing the circulation of the gases and the electrical continuity.

[0131] The thick metal plate is preferably made of ferritic steel, in particular of the Crofer®, AISI 441 and / or AISI 430 type. The thickness of the thick metal plate is preferably greater than 1 mm. The thickness of each thin sheet is preferably between 0.1 and 0.5 mm, preferably equal to 0.2 mm. The total thickness of a stiffening plate 3.1, 3.2, 3.3 is preferably between 1 and 10 mm.

[0132] A thermomechanical treatment is applied to each module produced so as to finalize at least the installation of electrical contact elements and sealing joints within each module. This thermomechanical treatment may also include the reduction of the electrochemical cells.

[0133] The temperatures are determined by the temperatures required for the installation of the seals, typically made of glass or glass-ceramic. Depending on the seal used, this temperature may vary. It may be, for example, 920°C for 1 hour as described in patent EP2870650B1. The temperature rise may be up to 10°C / min for a given module.

[0134] The reduction of electrochemical cells can be done from 650°C or advantageously at 800°C for a period of one hour to several days depending on the hydrogen flow rates sent.

[0135] Then the total electrical voltage of each module is measured, which allows the correct electrical operation of each module to be validated.

[0136] The heating of the thermomechanical treatment is stopped and the temperature will return to 20°C naturally. It is possible to cool more quickly by sending cold air to increase the cooling speeds.

[0137] A leak test of each module is then carried out.

[0138] Step b / : As illustrated in [Fig.2] in relation to a stiffening plate 3.1 or 4.1, each of the stiffening plates of the modules M1 to M3 is pierced on its edge and at its four corners with a thread 9 in which a fixing lug 10 is screwed. Also, each stiffening plate is pierced with through-holes 30 or 40 for the passage of gases. The fixing lug can also be machined directly in the part as shown in [Fig.4].

[0139] At room temperature, a system of tightening bolts is put in place, each consisting of a threaded rod 11 and nuts 12 at the four corners of each module, as illustrated in [Fig.3] with module M1. Each of the rods 11 is inserted into the hole of a fixing lug 10. It is also possible to use the device described in patent application WO2023 / 285751.

[0140] It is specified that the location of the threads 9 and the fixing lugs 10 which are screwed is offset from one module M1 to another M2 which will be stacked on the module M1. Indeed, as explained below, the bolting system of each module M1 to M3 having to be removed subsequently, there must be no physical interference when removing the threaded rods 11.

[0141] For each module M1 to M3, a tightening force is then applied by the bolt system 10, 11, 12 between its two stiffening plates so as to obtain a pre-assembly of each module allowing it to be transported ([Fig.3]).

[0142] Step c / : the pre-assembled modules M1 to M3 are then transported and then stacked on top of each other according to step b / , with the interposition between two adjacent modules of a removable interposed plate 100 as described previously.

[0143] More precisely,

[0144] - a lower module M3 is positioned ([Fig.l IA]);

[0145] - the intermediate plate 100 is positioned on the lower module M3 by placing opposite the through openings 113 of the plate 100 with that of the upper stiffening plate 3.3 of the module M3 ([Fig.llC]);

[0146] - the upper module M2 is positioned directly on the intermediate plate 100 in placing the through openings 113 of the plate 100 opposite that of the lower stiffening plate 4.2 of the upper module M2 ([Fig.llC]);.

[0147] Step d / : a clamping force is then applied to the stack of modules M1 to M3 by a clamping system, independent of the bolt systems of the modules, between the two end stiffening plates 3.1 and 4.3 so as to obtain an assembly.

[0148] Step e / : Once the assembly has been carried out with the loading of the entire stack according to step d / , the bolt systems are removed. The offsetting of the location of the threads 9 and fixing lugs 10 from one module M1 or M2 to another adjacent one in the stack M2 or M3 makes it possible to easily release the threaded rods 11 from the bolting systems.

[0149] Step f / a thermomechanical treatment is then applied to the assembly so as to finalize at least the installation of the electrical contact elements 114 and the sealing joints 115 of the intermediate plates 100. The formation of the sealing joints can be done under neutral gas which has the function of preventing oxidation. This can be nitrogen, argon, helium or neon.

[0150] The final assembly is thus obtained.

[0151] One of the advantages of an electrochemical device 1 by stacking pre-assembled modules M1 to M3 such as has just been described is to be able to easily replace a faulty module without needing to replace the complete device.

[0152] To do this, we can proceed as follows:

[0153] - stopping of electrochemical operation with electrical disconnection and return to ambient temperature of device 1 under clamping load;

[0154] - for each module Ml to M3, replacement of its clamping system by bolts 10, 11, 12;

[0155] - removal of the overall clamping system of the device, independent of the systems by bolts;

[0156] - removal of the defective module;

[0157] - removal of the intermediate plate 100;

[0158] - replacement of the intermediate plate 100 and the defective module respectively by a new 100 insert plate and module;

[0159] - reloading by the overall tightening system of the device;

[0160] - removal of all bolt clamping systems 10, 11, 12;

[0161] - application of a thermomechanical treatment to replace the elements contact 114 and the seals 115 of the new intermediate plate 100.

[0162] The invention is not limited to the examples which have just been described; it is possible in particular to combine characteristics of the examples illustrated within non-illustrated variants.

[0163] Other variants and improvements may be envisaged without departing from the scope of the invention.

Claims

1. Claims Electrochemical device (1) intended to operate at high temperature, comprising: - a stack of at least two pre-assembled modules (M1, M2, M3), in which each pre-assembled module comprises: a stack (2.1, 2.2, 2.3) of electrochemical cells based on solid oxides of the SOEC / SOFC type; a plurality of electrical and fluidic interconnectors, each comprising a component made of electronically conductive and gas-tight material for supplying or collecting electrical current to the cells and for supplying, collecting and circulating gases on each electrode of each electrochemical cell; the interconnectors being arranged individually on either side of each of the electrochemical cells; two stiffening plates (3.1, 4.1; 3.2, 4.2; 3.3, 4.3) between which the stack is arranged; the stiffening plates (4.1; 3.2, 4.2; 3.3), arranged within the stack of modules, form electrical and fluidic interconnectors between modules, while the two stiffening plates (3.1; 4.3), arranged at the ends of the stack of modules, form electrical and fluidic connectors for bringing or collecting the electric current between the electrochemical device and the exterior and for bringing, collecting and circulating the gases between the electrochemical device and the exterior; - at least one intermediate plate (100) with at least one electrically conductive sheet (110) having two substantially parallel flat faces (111, 112), removably mounted between two adjacent modules, the plate being provided with through openings (113) from one face to the other to circulate the gases between the two modules, each of the two faces of the plate supporting at least one electrical contact element (114) arranged with contact with one of the stiffening plates of one of the two modules and at least one sealing gasket (115) arranged around each through openings to ensure sealing around each gas inlet / outlet from one module to another.

2. Electrochemical device according to claim 1, the material of the sheet of the interlayer plate being steel, more preferably ferritic steel with approximately 20% chromium.

3. Electrochemical device according to one of claims 1 or 2, the thickness of the sheet being between 0.2 and 10 mm, preferably between 0.5 and 1 mm.

4. Electrochemical device according to one of the preceding claims, the electrical contact element(s) supported by each of the two faces of the intermediate plate comprising at least one layer of a conductive ceramic material.

5. Electrochemical device according to claim 4, the conductive ceramic material being selected from the group consisting of: - Lao,6Sro,4Coo,8Feo,203 (LSCF); ■ Lao,8Sro,2Cuo,9Feo,i02,5 (LSCuF); - La0,7Sr0,3CoO3 (LSC); - Smo,5Sro,5Co03 (SSC); - SmBaoj5Sr0j5Co205 (SBSC); - GdSrCo2O5 (GSC); - La0j65Sr0j3MnO3 (LSM); - LaBaCo2O5 (LBC); - YBaCo2O5 (YBC); - Ndlj8Ce0j2CuO4 (NCC); - Lao,8Sro,2Coo,3 Mnoj Feo6G3 (LSCMF); ■ Laoj98Nioj6Feo>403 (LNF); - Lalj2Sr0.8NiO4 (LSN); - La0j7Sr0j3FeO3 (LSF); - La2Nio.6Cu0.404 (LNC).

6. Electrochemical device according to one of claims 4 or 5, the layer of conductive ceramic material being hollowed out over at least part of its thickness.

7. Electrochemical device according to one of claims 4 to 6, the layer of conductive ceramic material being bonded, preferably by heat pressing or by means of an adhesive or by heat pressing by the sheet metal previously heated by Joule effect by passage of current or inductively.

8. Electrochemical device according to one of claims 4 to 7, the thickness of the layer of conductive ceramic material on each face of the sheet being between 100 pm and 5 mm.

9. Electrochemical device according to one of claims 1 to 3, the electrical contact element(s) supported by each of the two faces of the intermediate plate comprising at least one electrically conductive grid, preferably made of gold.

10. Electrochemical device according to claim 9, the number of grids supported per face of the interposed plate being between 1 and 10, preferably equal to 5.

11. Electrochemical device according to claim 9 or 10, the surface area of a grid being between 0.5 and 5cm2, preferably of the order of 2cm2.

12. Electrochemical device according to claim 9 to 11, the grid(s) being welded directly to each of the two faces of the sheet.

13. Electrochemical device according to claim 9 to 12, the grid(s) supported by one of the two faces being offset from the grid(s) supported by the other of the two faces, by at most 10% of the length and / or width of the grid(s).

14. An electrochemical device according to claim 10 to 13, comprising a number of five grids supported by each of the two faces, distributed in a square with one of them in the center of the square.

15. Method for producing an electrochemical device, forming a SOEC electrolysis or co-electrolysis reactor or a SOFC fuel cell, intended to operate at high temperature, comprising the following steps: a / producing at least two modules, each module comprising: - a stack of electrochemical cells based on solid oxides of the SOEC / SOFC type; - a plurality of electrical and fluidic interconnectors, each comprising a component made of electronically conductive and gas-tight material for supplying or collecting the electric current to the cells and for supplying, collecting and circulating gases on each electrode of each electrochemical cell; the interconnectors being arranged on either side of each of the electrochemical cells; - two stiffening plates between which the stack is arranged; b / application of a clamping force to each module by a system of bolts between its two stiffening plates so as to obtain a pre-assembly of each module allowing it to be transported;c / stacking on top of each other the modules preassembled according to step b / , with intercalation between two adjacent modules of a removable intermediate plate (100) with at least one electrically conductive sheet (110) having two substantially parallel flat faces (111, 112), the plate being provided with through openings (113) from one face to the other to circulate the gases between the two modules, each of the two faces of the plate supporting at least one electrical contact element (114) arranged with contact with one of the stiffening plates of one of the two modules and at least one seal (115) arranged around each of the through openings to ensure sealing around each gas inlet / outlet from one module to the other; d / application of a clamping force to the stack of modules by a clamping system, independent of the bolt systems of the modules, between the two end stiffening plates so as to obtain an assembly;e / removing the bolt systems from the assembly while maintaining independent tightening; f / applying a thermomechanical treatment to the assembly so as to finalize at least the installation of the electrical contact elements and the sealing gaskets of each intermediate plate between stiffening plates and thus the final assembly; the method comprising a step of reducing all the electrochemical cells.;

16. Method according to claim 15, step a / comprising a step al / of applying a thermomechanical treatment to each module produced so as to finalize at least the installation of electrical contact elements and sealing joints within each module.

17. Method according to claim 15 or 16, the step of reducing the electrochemical cells being carried out during step a1 / for each module or during step f / for the assembly of modules, preferably,

18. when the step of reducing the electrochemical cells is carried out during step al / for each module, a step a2 / of measuring the total electrical voltage of each module is carried out at the end of the latter. Method according to one of claims 15 to 17, comprising a step a3 / of testing the tightness of each module.

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