Interconnectors with optimized tab shapes for SOEC / SOFC type solid oxide cell stacks

Abstract

The main subject of the present invention is an interconnect for a solid oxide battery stack of the SOEC / SOFC type, intended to be placed between two adjacent electrochemical cells, the interconnect (5) being formed by the assembly of at least three plates extending along a first and a second axis of symmetry, the main plates comprising holes, each hole comprising tabs (710) spaced apart to form a comb and a slot (711) defined between the edge of the hole (71) and the tab (710) or between two consecutive tabs (711), the width (le) of each tab (710) of at least one hole (71) being between 0.1 mm and 3 mm.

Description

[Technical field]

[0001] The present invention relates to the general field of high temperature electrolysis (HTE), in particular high temperature steam electrolysis (HTSE), carbon dioxide (CO2) electrolysis and also high temperature steam and carbon dioxide (CO2) co-electrolysis.

[0002] More specifically, the invention relates to the field of high-temperature solid oxide electrolysis devices, known by the acronym SOEC (Solid Oxide Electrolysis Cell).

[0003] It also relates to the field of high-temperature solid oxide fuel cells, known by the acronym SOFC (Solid Oxide Fuel Cell).

[0004] More generally, the invention therefore relates to the field of solid oxide cell stacks of the SOEC / SOFC type operating at high temperatures.

[0005] More specifically, the present invention relates to an interconnect for a solid oxide cell stack of the SOEC / SOFC type having an optimized shaped tab in a hole in a central plate constituting the interconnect, and to a solid oxide cell stack of the SOEC / SOFC type including a plurality of such interconnects. [Background technology]

[0006] High-temperature solid oxide electrolyzers of the SOEC type convert water vapor (H2O) into hydrogen (H2) or other fuels, such as methane (CH4), natural gas or biogas, and oxygen (O2) by electric current in a single electrochemical device, and / or convert carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2). In high-temperature solid oxide fuel cells of the SOFC type, the operation is reversed to produce electric current and heat by consuming hydrogen (H2) and oxygen (O2), typically air and natural gas, i.e. methane (CH4). For simplicity, the following description focuses on the operation of high-temperature solid oxide electrolyzers of the SOEC type performing water vapor electrolysis. However, this operation is applicable to carbon dioxide (CO2) electrolysis and even to high-temperature (HTE) water vapor and carbon dioxide (CO2) co-electrolysis. Moreover, this operation is applicable when using high-temperature solid oxide fuel cells of the SOFC type.

[0007] Water electrolysis is advantageously carried out at high temperatures, typically between 600 and 1000 °C, because it is more advantageous to electrolyze water vapor than liquid water, and some of the energy required for the reaction can be provided by heat, which is cheaper than electricity.

[0008] To perform high-temperature steam electrolysis (HTSE), a high-temperature solid oxide electrolyzer of the SOEC type consists of a stack of several basic units, each of which has a solid oxide electrolysis or electrochemical cell with anode / electrolyte / cathode triplet and an interconnecting plate (also called bipolar plate or interconnector), often made of a metal alloy. Each electrochemical cell is sandwiched between two interconnecting plates. Thus, a high-temperature solid oxide electrolyzer of the SOEC type is a stack of alternating electrochemical cells and interconnectors. A high-temperature solid oxide fuel cell of the SOFC type consists of a stack of the same type of basic units. This high-temperature technology is reversible, so the same stack can function either in electrolysis mode, producing hydrogen and oxygen from water and electricity, or in fuel cell mode, producing electricity from hydrogen and oxygen.

[0009] Each electrochemical cell corresponds to an electrolyte / electrode assembly, which is typically a multi-layer ceramic assembly, in which the electrolyte is formed by a central ion-conducting layer, which is solid, dense and sealed, sandwiched between two porous layers that form the electrodes. It should be noted that additional layers may be present, but only serve to improve one or more of the aforementioned layers.

[0010] The electrical and fluidic interconnect device is an electronic conductor; electrically, it connects the electrochemical cells of the basic units in a stack of basic units, ensuring electrical contact between one face and the cathode of one cell and between the other face and the anode of the next cell, and fluidically, it provides the supply of reagents to each cell and the removal of products. The interconnect thus performs the functions of supplying and collecting electrical current and delimiting gas flow compartments for distribution and / or collection. More specifically, the main function of the interconnector is to ensure the passage of electric current and the flow of gases in the vicinity of each cell (i.e., injected water vapor, extracted hydrogen and oxygen for HTE electrolysis, and air and fuel (including injected hydrogen and extracted water vapor) for SOFC) and to separate the anode and cathode compartments of two adjacent cells, which are the gas flow compartments on the anode and cathode sides of the cells, respectively.

[0011] In particular, in a high-temperature solid oxide electrolyser of the SOEC type, the cathode compartment contains water vapor and hydrogen, which is a product of the electrochemical reaction, and the anode compartment contains drain gas, if present, and oxygen, which is another product of the electrochemical reaction. In a high-temperature solid oxide fuel cell of the SOFC type, the anode compartment contains the fuel and the cathode compartment contains the oxidant.

[0012] To perform high temperature steam electrolysis (HTSE), water vapor (HO) is injected into the cathode compartment. Under the influence of an electric current applied to the cell, water molecules in the form of water vapor are dissociated at the interface between the hydrogen electrode (cathode) and the electrolyte. This dissociation produces hydrogen gas (H2) and oxygen ions (O 2-) is produced. Hydrogen (H2) is collected and pumped out of the hydrogen compartment. Oxygen ions (O 2- ) migrates through the electrolyte and recombines into oxygen (O2) at the interface between the electrolyte and the oxygen electrode (anode). A drain gas (such as air) flows past the anode so that the oxygen produced in gaseous form at the anode can be collected.

[0013] To use a solid oxide fuel cell (SOFC), air (oxygen) is injected into the cathode compartment of the cell and hydrogen is injected into the anode compartment. The oxygen in the air is converted to O 2- The hydrogen is dissociated into ions. These ions migrate in the electrolyte from the cathode to the anode to oxidize the hydrogen to form water and simultaneously generate electricity. In SOFCs, water vapor is present in the hydrogen (H2) compartment, just as in SOEC electrolysis; the polarity is simply reversed.

[0014] As an example, the operating principle of a high-temperature solid oxide electrolyzer of the SOEC type is shown in Figure 1. The function of such an electrolyzer is to convert water vapor into hydrogen and oxygen according to the following electrochemical reactions: 2H2O → 2H2+ O2

[0015] This reaction takes place electrochemically in the cells of an electrolyser. As shown diagrammatically in FIG. 1, each elementary electrolysis cell 1 consists of a cathode 2 and an anode 4 arranged on either side of a solid electrolyte 3. The two electrodes (cathode and anode) 2 and 4 are conductors of electrons and / or ions made of porous materials, while the electrolyte 3 is gas-tight, electronically insulating and ionically conducting. The electrolyte 3 is in particular an anion conductor, more specifically O 2- The electrolyser can be an anion conductor for protons (H + ) In contrast to electrolytes, they are called anion electrolysers.

[0016] An electrochemical reaction occurs at the interface between each electronic conductor and ionic conductor.

[0017] At cathode 2, the half-reactions are: 2H2O + 4e -→ 2H2+ 2O 2-

[0018] At the anode 4, the half-reactions are: 2O 2- → O2+ 4e -

[0019] The electrolyte 3 inserted between the two electrodes 2 and 4 converts O 2- This is where ions move.

[0020] As shown in brackets in Figure 1, the water vapor at the cathode inlet can be accompanied by hydrogen H2, and the hydrogen produced and collected at the outlet can be accompanied by water vapor. Similarly, drain gas (such as air) can be injected into the anode inlet to remove the oxygen produced, as shown by the dashed line in the figure. Injecting the drain gas has the additional function of acting as a thermal regulator.

[0021] As mentioned above, a basic electrolysis device or reactor is constructed, consisting of a basic cell having a cathode 2, an electrolyte 3 and an anode 4, and two interconnects performing the functions of electrical and fluid distribution.

[0022] To increase the flow rate of hydrogen and oxygen produced, it is known to stack several elementary electrolysis cells, separated from each other by an interconnector, the assembly being located between two end interconnect plates carrying the power supply and the gas supply to the electrolyser (electrolysis reactor).

[0023] A high-temperature solid oxide electrolyser of the SOEC type is therefore constructed by at least one, and generally several, electrolytic cells stacked on top of each other, each elementary cell consisting of an electrolyte, a cathode and an anode, the electrolyte being inserted between the anode and the cathode.

[0024] As mentioned above, fluidic and electrical interconnection devices in electrical contact with one or more electrodes generally function to source and collect electrical current and define one or more gas flow compartments.

[0025] The function of the cathode compartment is therefore to distribute electrical current and water vapor and to recover hydrogen from the cathode contact.

[0026] The function of the anode compartment is to distribute the current and to recover the oxygen produced at the contacted anode, optionally using a drain gas.

[0027] Figure 2 shows an exploded view of a basic unit of a high-temperature solid oxide electrolyser of the SOEC type according to the prior art. The electrolyser comprises a number of basic electrolysis cells C1, C2 of the solid oxide cell (SOEC) type, stacked alternately with interconnects 5. Each cell C1, C2 consists of a cathode 2.1, 2.2 and an anode (only the anode 4.2 of cell C2 is shown), between which an electrolyte is placed (only the electrolyte 3.2 of cell C2 is shown).

[0028] The interconnector 5, typically a metal alloy part, provides the separation between the cathode compartment 50 and the anode compartment 51, defined by the volume contained between the interconnector 5 and the adjacent cathode 2.1 and between the interconnector 5 and the adjacent anode 4.2, respectively. It also ensures that the gas is distributed to the cells. Water vapor is injected into each elementary unit of the cathode compartment 50. The hydrogen and residual water vapor produced in the cathodes 2.1, 2.2 are collected in the cathode compartment 50 downstream of the cells C1, C2 after dissociation of the water vapor by the cells C1, C2. The oxygen produced in the anode 4.2 is collected in the anode compartment 51 downstream of the cells C1, C2 after dissociation of the water vapor by the cells C1, C2. The interconnector 5 ensures the passage of the electric current between the cells C1 and C2 by direct contact of the adjacent electrodes, i.e. the anode 4.2 and the cathode 2.1.

[0029] The operating conditions of high temperature solid oxide electrolysers (SOECs) are very similar to those of solid oxide fuel cells (SOFCs), and therefore the same technological constraints apply.

[0030] Therefore, for smooth operation of a solid oxide battery stack of the SOEC / SOFC type operating at high temperatures, the following main points must be observed:

[0031] First of all, electrical insulation between two consecutive interconnects is necessary to avoid short-circuiting the electrochemical cell, good electrical contact and adequate contact area between the cell and the interconnect are required, and a minimum ohmic resistance between the cell and the interconnect is required.

[0032] Furthermore, the anode and cathode compartments must be sealed from each other to avoid recombination of the product gases, which would lead to a loss of efficiency and in particular to the appearance of hot spots which could damage the stack.

[0033] Finally, good gas distribution, both at the inlet and at the product recovery stage, is essential to avoid yield losses, pressure and temperature fluctuations in the various basic units and even irreparable damage to the electrochemical cell.

[0034] To improve the production efficiency and achieve good operational consistency of SOEC / SOFC type solid oxide cell stacks operating at high temperatures, the role of the interconnect is important, especially in obtaining good electrical contact between the various parts of the stack and allowing a proper gas distribution within the electrochemical cells. The interconnect can be made of metal and consist of three thin plates, as described in US Pat. No. 5,399,363.

[0035] FIG. 3 shows an exploded view of an exemplary prior art interconnect 5 formed from an assembly of three assembled and stacked thin metal sheets 21-23.

[0036] The three sheets 21, 22, 23 extend along two mutually perpendicular axes of symmetry X and Y, the sheets are laminated and assembled by welding. The central sheet 22 is inserted between the first end sheet 21 and the second end sheet 23.

[0037] Central sheet 22 includes an embossed central portion 70 that defines raised or embossed elements 10 and has four holes 71, 72, 73, 74 drilled around the periphery of central portion 70. The "holes" refer to holes that open onto both sides of the metal sheet.

[0038] One of the flat end sheets 21 includes a flat central portion 69 having four holes 61, 62, 63, 64 drilled around the periphery of the central portion 69. The first end sheet 21 also includes two slots 67, 68, which are symmetrically disposed on either side of the Y axis and extend over a length that substantially corresponds to the length of the central portion 69 along the Y axis.

[0039] The other flat end sheet 23 includes a hollow central portion 89 having four holes 81, 82, 83, 84 drilled around the periphery of the central portion 89.

[0040] The holes 61, 71, 81, 63, 73, 83 in each sheet extend over a length substantially corresponding to the length of the central portions 69, 70, 89 along the X-axis, while the holes 62, 72, 82, 64, 74, 84 in each sheet extend over a length substantially corresponding to the length of the central portions 69, 70, 89 along the Y-axis.

[0041] Holes 71 to 74 in central sheet 22 are enlarged relative to holes 61, 81, 62, 82, 63, 83, 64, 84, respectively, and are provided with comb-like spaced apart sheet tabs 710, 720, 730, 740. Each slot 711 defined between the edge of enlarged hole 71 and a tab 710, or between two consecutive tabs 710, opens into a channel 11 defined by raised or embossed portion 10. The same is true for the slots at the sides of holes 72, 73, 74.

[0042] The sheets 21, 22, 23 are typically made of ferritic steel with about 20% chromium, preferably CROFER® 22APU or FT18TNb, with a nickel base of the Inconel® 600 or Haynes® type, and their thickness typically ranges from 0.1 to 1 mm.

[0043] These interconnectors may be as described in the patent application WO 2005 / 023363. In this application, the interconnector corresponds to a component having a metal alloy substrate based on iron (Fe) or nickel (Ni), coated on one of its main faces with a thick layer of metal or ceramic grooved to delimit channels suitable for distributing and / or collecting gases such as water vapor H2O, H2, O2, drain gases, etc. In particular, a thick ceramic contact layer comprising lanthanum manganite doped with strontium can be provided on the oxygen electrode side (anode in HTE, cathode in SOFC). By "thick layer" we mean a layer thicker than those obtained with the so-called "thin film" technology, typically in the range of 2 to 15 μm. Thus, a good performance level and a good consistency level of solid oxide cell stacks of the SOFC / SOEC type are achieved at low production costs.

[0044] Nevertheless, there remains a need to optimize such interconnects, especially from a fluidic and mechanical point of view, and in particular to reduce the pressure losses occurring during gas flow. [Prior art documents] [Patent documents]

[0045] [Patent Document 1] French Patent No. 3024985 [Patent Document 2] French Patent No. 2996065 [Patent Document 3] French Patent No. 3045215 Summary of the Invention [Problem to be solved by the invention]

[0046] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to at least partially fulfill the aforementioned needs and overcome the shortcomings of the prior art. [Means for solving the problem]

[0047] In particular, the aim is to create an optimized design of an interconnect for solid oxide cell stacks of the SOEC / SOFC type by modifying the comb-tooth tabs and possibly machining the contact layers of the interconnect in a specific way, which allows to obtain high electrical conductivity and good mechanical and electrical contact of the interconnect for a given clamping force, while at the same time reducing the pressure loss for the gas flow.

[0048] Thus, according to one aspect of the invention, there is provided an interconnect for a stack of solid oxide batteries of the SOEC / SOFC type operating at high temperature, intended to be placed between two adjacent electrochemical cells in said stack, each electrochemical cell consisting of a cathode, an anode and an electrolyte inserted between said cathode and said anode, said interconnect being formed by an assembly of at least three plates extending along mutually perpendicular first and second axes of symmetry, a central plate sandwiched between a first end plate and a second end plate, said central plate comprising a central part and, at its periphery, at least two holes extending over a length substantially corresponding to the length of said central part along the first axis of symmetry and two holes extending over a length substantially corresponding to the length of said central part along the second axis of symmetry, each hole comprising tabs spaced apart so as to form a comb and slots defined between the edge of the hole and the tab or between two successive tabs, The interconnect is characterized in that the width of each tab of the at least one hole is between 0.1 mm and 3 mm, in particular about 1 mm.

[0049] An interconnect according to the invention may have one or more of the following features, either individually or in any technically feasible combination:

[0050] The width of each slot of the at least one hole may be between 3 and 5 mm, in particular about 4.9 mm.

[0051] Furthermore, the height of each tab of the at least one hole may be from 0.25 to 1 mm, in particular about 0.3 mm.

[0052] Furthermore, according to one aspect of the invention, the interconnect, in particular the central portion of the central plate, has a flat surface on which at least one first group of first identical elements raised relative to the flat surface and one second group of second identical elements raised relative to the flat surface are formed, the first raised element has different geometric characteristics than the second raised element; a height of each of the first raised elements measured as a maximum perpendicular dimension of the first raised element relative to the flat surface differs from a height of each of the second raised elements measured as a maximum perpendicular dimension of the second raised element; The contact width of each of the first raised elements, measured as the maximum horizontal dimension of the outer contact end of each of the first raised elements relative to the flat surface, is opposite the inner end contacting the flat surface and intended to contact an electrochemical cell, and the contact width of each of the second raised elements, measured as the maximum horizontal dimension of the outer contact end of each of the second raised elements, relative to the flat surface, is opposite the inner end contacting the flat surface and intended to contact an electrochemical cell, and the contact width of each of the first raised elements is different from the contact width of each of the second raised elements.

[0053] Further, the first raised element may have a contact width greater than the contact width of the second raised element, the first raised element being disposed along a tab of at least one hole, and the second raised element may be disposed along a slot of the at least one hole.

[0054] Furthermore, it is preferred that said contact width of said first raised element is equal to the width of a tab of said at least one hole.

[0055] The contact width of each of the first raised elements is in the range of 0.5 to 5 mm, preferably equal to 1 mm.

[0056] Said contact width of each said second raised element is in the range of 0.005 mm to 0.5 mm, preferably equal to 100 μm.

[0057] Said height of each said first raised element is in the range of 200 μm to 1000 μm, preferably equal to 350 μm.

[0058] Said height of each said second raised element is in the range of 250 μm to 1050 μm, preferably equal to 400 μm.

[0059] The difference between the height of each said second raised element and the height of each said first raised element is in the range of 5 μm to 500 μm, preferably about 50 μm.

[0060] Further, the interconnect comprises N groups of raised elements formed on the flat surface, where N is an integer equal to or greater than 2, preferably in the range of 2 to 50, and more preferably equal to 5, and all the raised elements of the same group are identical, and the raised elements of different groups have different geometric characteristics, i.e. different heights and different contact widths.

[0061] The raised elements may be in the form of teeth or grooves and arranged parallel to one another, with spaces between the raised elements forming gas flow paths.

[0062] The raised elements may also be in the form of studs, in particular cylindrical studs, the spaces between which form a single tortuous gas flow path. Other shapes are also possible, for example parallelepiped shapes.

[0063] Furthermore, said raised elements may be evenly distributed on said flat surface, in particular spaced apart by equal distances along at least one horizontal direction on said flat surface, in the range of 50 μm to 5 mm, preferably equal to 750 μm.

[0064] At least one region of said flat surface, in particular the central region, may be free of raised elements.

[0065] Additionally, the raised element having the greatest width may be located at the periphery of the planar surface and away from the gas flow passage or passages formed by other raised elements and spaces between those raised elements.

[0066] The interconnector comprises a metal alloy substrate, in particular of the chromium-forming type, in particular a ferritic steel based on iron or nickel, in particular of the Uginox® K41 type or VDM® Crofer type, and has two main planes, one of which comprises a first coating layer forming a first contact layer with the electrochemical cell and the other of which comprises a second coating layer forming a second contact layer with the electrochemical cell, the first coating layer and / or the second coating layer comprising a flat surface and raised elements thereon, in particular formed by machining.

[0067] The first coating layer may be a porous or non-porous thick ceramic coating layer, the ceramic material being in particular nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr), M (transition metals), either alone or as a mixture, La 1-x Sr x The material may be selected from lanthanum manganites such as MO3, or from materials with layered structures, such as lanthanide nickel oxides such as Ln2NiO4 (Ln=lanthanum (La), neodymium (Nd), praseodymium (Pr)), or other electrically conductive perovskite oxides.

[0068] The second coating layer may be a thick metallic coating layer, in particular of the grid or dense material type, the metallic material being in particular selected from nickel (Ni) and its alloys or chromium-forming alloys, the base element of which is iron (Fe), in particular a ferritic steel of the Uginox® K41 or VDM® Crofer type.

[0069] Furthermore, according to another aspect of the present invention, there is provided a solid oxide battery stack of the SOEC / SOFC type operating at high temperature, comprising a plurality of electrochemical cells, each of which consists of a cathode, an anode and an electrolyte sandwiched between said cathode and said anode, and a plurality of interconnects as defined above, each of said interconnects being disposed between two adjacent electrochemical cells.

[0070] The invention will be better understood with reference to the detailed description of non-limiting exemplary embodiments, as well as the schematic and partial drawings, of the accompanying drawings, in which: [Brief description of the drawings]

[0071] [Figure 1] FIG. 1 is a schematic diagram illustrating the operating principle of a high temperature solid oxide electrolyzer (SOEC). [Diagram 2] FIG. 2 is an exploded schematic diagram of a portion of a high temperature solid oxide electrolyzer (SOEC) including an interconnect according to the prior art. [Diagram 3] FIG. 3 is an exploded view of an interconnect for a high temperature SOEC / SOFC type solid oxide cell stack, corresponding to an assembly of three thin sheets or plates. [Figure 4] FIG. 4 is a partial cross-sectional view of a prior art interconnect 5 made of three thin sheets or plates with a central sheet containing a tab. [Diagram 5] FIG. 5 is a schematic front view of a prior art interconnect for a high temperature electrolysis (SOEC) or fuel cell (SOFC) stack operating at high temperatures. [Figure 5A]FIG. 5A is a cross-sectional detail view of the interconnect of FIG. [Figure 5B] FIG. 5B is a view similar to FIG. 5 showing current lines passing through the interconnect. [Figure 6] FIG. 6 is a partial perspective view of an interconnect according to the present invention including optimized shaped tabs and raised elements. [Figure 7] FIG. 7 is a graph showing interconnect tooth height (mm) as a function of length (mm) for pre-clamped and post-clamped designs of a high temperature electrolysis (SOEC) or high temperature fuel cell (SOFC) stack. [Figure 8] FIG. 8 is a graph showing the polarization curves of three different designs, having two different tooth geometries and two different clamping forces. [Figure 9] FIG. 9 is a cross-sectional view of two teeth and one channel of a conventional interconnect for a high temperature SOEC / SOFC type solid oxide cell stack. [Figure 10] FIG. 10 is a cross-sectional view of five teeth and four channels of an interconnect for a high temperature SOEC / SOFC type solid oxide cell stack before clamping. [Figure 11] FIG. 11 is a cross-sectional view of the design of FIG. 9 after clamping. [Figure 12] FIG. 12 is a plan view of the design of FIGS. [Figure 13] FIG. 13 is a partial perspective view of an interconnect according to the present invention including an optimized positional relationship between an optimized shaped tab and a raised element. [Figure 14] FIG. 14 is an alternative embodiment of the design of FIG. [Figure 15] FIG. 15 is a plan view of the design of FIG. [Figure 16] FIG. 16 is an alternative embodiment of the design of FIG. [Figure 17] FIG. 17 is another geometric embodiment of the design of FIG. [Figure 18] FIG. 18 is an alternative embodiment of the design of FIG. [Figure 19] FIG. 19 shows a perspective view and a top view of an assembly including a stack of solid oxide cells of the SOEC / SOFC type with an interconnect according to the invention and a clamping system for the stack.

[0072] Throughout the figures, the same reference numbers are used to designate the same or similar elements.

[0073] Furthermore, the various parts shown in the figures are not necessarily drawn to uniform scale, in order to make the figures easier to read. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0074] Figures 1 to 3 have already been described in the sections on the prior art and the technical background of the invention. It should be noted that in Figures 1 and 2, for the sake of clarity and precision, symbols and arrows for the supply of water vapor H2O, hydrogen H2, oxygen O2, air, and the distribution and recovery of electric current are shown to explain the operation of the device shown.

[0075] Also, note that all components (anode / electrolyte / cathode) of a given electrochemical cell are preferably ceramic. Operating temperatures for high temperature SOEC / SOFC type stacks are typically in the range of 600 to 1000°C.

[0076] Furthermore, the terms "top" and "bottom" herein should be understood to refer to the normal orientation of an SOEC / SOFC type stack in its configuration of use.

[0077] An interconnector 5 according to the prior art has already been described above with reference to figure 3. Similar elements will not be described again but remain within the scope of the present invention.

[0078] 4 is a partial cross-sectional view of interconnect 5 including three sheets 21, 22 and 23, partially cut away at tab 710 and slot 711 of hole 71 to show their dimensions, and of course similarly for holes 72, 73 and 74.

[0079] Thus, in a standard configuration, the width le of tab 710 measured along the X-axis is approximately 4 mm. Additionally, the width lf of slot 711 measured along the X-axis is approximately 6.4 mm. The height he of each tab 710 measured perpendicular to the X-axis is approximately 0.2 mm. Additionally, the total width of hole 71 is approximately 100 mm, but may be greater.

[0080] Approximately 12Nl / min / cell / cm 2 For an air flow rate of 100 psi, the pressure loss through the tab 710 is approximately 50 mbar. In this configuration, the pressure loss comes from both the limited flow rate and the tendency of the channels 11 to compress. This compression occurs as the plates 23 or sheets deform and move closer to the central plate 22.

[0081] According to the present invention, in order to optimize the shape of the tabs 710 and the slots 711, the width le of the tabs 710 is in the range of 0.1 mm to 3 mm. In this way, the width le of each tab 710 is reduced to increase the volume of the channel 11. The width le of the tabs 710 is preferably about 1 mm, which is an optimal balance between design difficulty and increased gas flow rate.

[0082] Furthermore, according to the present invention, the width lf of each slot 711 is in the range of 3 to 5 mm, preferably about 4.9 mm, which is the optimum value for reducing compression without significantly reducing the volume of the gas channel 11.

[0083] Furthermore, according to the invention, the height he of each tab 710 is increased by using a central sheet 22 with a height higher than the standard height of 0.2 mm. In this way, the height he of each tab 710 is in the range of 0.25 to 1 mm, preferably with a value of 0.3 mm, which is the optimum value that increases the volume of the channel 11 for the gas flow while significantly reducing the pressure losses, limiting the amount of metal used and the total height of the interconnect 5.

[0084] These modifications according to the invention therefore allow a reduction in pressure loss of at least 25% and up to about 80%.

[0085] Furthermore, the interconnector 5 can have a particular shape, in particular with grooves, in which the teeth and channels are present. For example, as described in US Pat. No. 5,999,366, the interconnector 5 consists of a component comprising a metal alloy substrate, in particular of the chromium-forming type, the base element of which is iron or nickel, in particular a ferritic steel of the Uginox® K41 type or VDM® Crofer type, this substrate having two main planes, one of which is covered with a coating comprising a thick ceramic layer, porous or non-porous, in which grooves are formed so as to separate the teeth from the channels for distributing and / or collecting gases, this layer also being called the "contact layer". In this way, the teeth and channels can be formed on the contact layer. Furthermore, in the following description, it is to be understood that the teeth and channels of the interconnector 5, or more generally the ridges, can be formed on the contact layer of this interconnector 5.

[0086] Figures 5, 5A and 5B show an interconnector 5, widely used in high temperature SOEC / SOFC type stacks. The current is supplied to or collected from the electrodes by raised elements in the form of teeth 10 or ribs, which are in direct mechanical contact with the subject electrodes. In the electrolyser of the HTE, the supply of water vapor to the cathode or drain gas to the anode, and in the SOFC, the supply of oxygen to the cathode or hydrogen to the anode, are indicated by arrows F1 in Figure 5.

[0087] The hydrogen produced at the cathode or the oxygen produced at the anode in the electrolyser of the HTE, and the water produced at the cathode or the excess hydrogen produced at the anode in the SOFC, are collected by channels 11 that open into a fluid connection (commonly called a manifold) shared by the stack of cells. The structure of these interconnects 5 is designed to balance the two functions of supply and collection (gas / current).

[0088] 6 is a partial perspective view of the tooth 10 and the channel 11, also showing the tabs 710 and the slots 711. According to the present invention, the width le of the tabs 710 is in the range of 0.1 mm to 3 mm, preferably about 1 mm. Furthermore, the width lf of each slot 711 is in the range of 3 to 5 mm, preferably about 4.9 mm. Similarly, the height he of each tab 710 is in the range of 0.25 to 1 mm, preferably about 0.3 mm.

[0089] To obtain good electrical conductivity between the interconnect 5, and in particular the contact layer, and the electrochemical cell, it is necessary to have the teeth 10 close to each other, however this tends to result in a reduction in the gas flow area, which can cause large pressure losses during operation.

[0090] Furthermore, the interconnect 5 must allow the gas to flow properly and have low pressure loss by using wide channels 11. However, this leads to spacing of the teeth 10, reducing electrical conductivity.

[0091] Furthermore, the shape of the teeth 10 and channels 11 must be able to adapt, especially to surface imperfections of the cells and the interconnects 5. For this, they must be easily collapsible. This can be achieved, for example, by designing the teeth 10 with a small width. However, if the teeth 10 are compressed too much, the height of the channels 11 will be greatly reduced, which will reduce the gas flow area and therefore lead to high pressure losses. As an example, Figure 7 shows a graph of the height H (mm) of the teeth 10 as a function of the length L (mm) for the pre-clamped design C1 and the post-clamped design C2.

[0092] The force applied to a stack of solid oxide cells of the SOEC / SOFC type is used to calculate the local clamp stress. For example, if the force F is 1000 N and the support area S is 100 cm 2 , the stress F / S amounts to 0.2 MPa. If the contact is made using the interconnect 5, the tooth 10, and in particular its contact layer, which represents half the surface area, the local stress amounts to 0.4 MPa.

[0093] Surface area 100cm 2 Three real experiments (E1, E2, E3) for hydrogen production from a five-cell SOEC type stack were carried out with two different interconnect geometries (tooth A and tooth B) and two different clamping forces (force A and force B). The total flow rate of the water vapor / hydrogen mixture was 12 Nml / min / cell / cm. 2 The H2O / H2 mixture was 90% H2O and 10% H2. The stack temperature was 800 °C.

[0094] The polarization curves (E1 is tooth A, force A, E2 is tooth B, force A, E3 is tooth B, force B) are plotted against the current i (A / cm 2 ) and measuring the voltage E (V) of the associated cell each time. These curves are used to measure the maximum utilization t of water vapor, as well as the area specific resistance (ASR) from cells, interconnects, interfaces, connection systems, etc.

[0095] The nominal geometry of the interconnect includes an interconnect having teeth 10 of width A (tooth A), particularly at the contact layer. A second interconnect geometry was made with teeth 10 of width B (tooth B) that is three times smaller than width A. The applied force can be nominal force A (force A) or force B that is three times smaller than force A.

[0096] Figure 8 is a graph showing the polarization curves E1, E2, E3 obtained for three stacks with two different interconnect geometries (tooth A, tooth B) and two different forces (force A, force B). Additionally, Table 1 shows the relative pressure losses obtained from the O2 chamber. [Table 1]

[0097] Thus, if the teeth are thinner (tooth B) while maintaining the same clamping force (Force A), performance improves due to lower ASR, but pressure drop increases. Tooth fracture has reduced the gas flow area. If the teeth are thinner (tooth B) but force is reduced (Force B), performance decreases (higher ASR, reduced maximum duty cycle), but pressure drop is significantly reduced.

[0098] Particular aspects of the invention described with reference to Figures 9 to 18 provide in particular a particular shape of the tooth raised elements 10 in addition to an optimized shape of the tabs 711, with the aim of optimizing these aspects, in particular the interconnect design of the contact layer, allowing both good compression of the teeth 10 and maintaining a large volume of gas flow channel 11.

[0099] The interconnector 5 of a solid oxide battery stack of the SOEC / SOFC type operating at high temperatures is intended to be placed between two adjacent electrochemical cells 1 in the stack, each cell consisting of a cathode, an anode and an electrolyte inserted between the cathode and the anode, and usually having a regular shape. In particular, the contact layer forming a coating on one side of the metal alloy substrate of the interconnector 5 conventionally comprises teeth 10 and channels 11 of regular shape. In this way, all the teeth 10 have the same dimensions (height and width) and all the channels 11 have the same width. The main characteristics of the teeth 10 and the channels 11 are shown in detail in the cross-sectional view of FIG. 9. In this way, the contact width of the teeth 10 is denoted D, the width of the top of the channels 11 is denoted Ch, the width of the bottom of the channels 11 is denoted Cb and the height of the teeth 10 is denoted H.

[0100] According to one aspect of the invention, the geometry of the interconnect 5, in particular the contact layer, is modified in order to obtain irregularities that provide both an optimal electrical contact and a gas distribution with low resistance to gas flow. In particular, machining of the irregularities is performed in order to obtain teeth and channels with different properties on the same interconnect 5, in particular on the same contact layer of this interconnect 5.

[0101] In this way, the interconnect 5 comprises a flat surface P on which at least one first group of first identical raised elements 10a and a second group of second identical raised elements 10b are formed, the first raised elements 10a and the second raised elements 10b having different geometric characteristics.

[0102] 10 and 11 show exemplary embodiments of two types of machined shapes, before and after compression, however, within the scope of the present invention, the interconnect 5 can be provided with a number of different shapes.

[0103] In this way, the height H1 of each first raised element 10a, measured as the maximum vertical dimension of the first raised element 10a relative to the flat surface P, is different from the height H2 of each second raised element 10b, measured as the maximum vertical dimension of the second raised element 10b. Similarly, the contact width D1 of each first raised element 10a, measured as the maximum horizontal dimension of the outer contact end 10ae of each first raised element 10a relative to the flat surface P, is opposite the inner end 10ai that contacts the flat surface P and is intended to contact the electrochemical cell 1, and the contact width D2 of each second raised element 10b, measured as the maximum horizontal dimension of the outer contact end 10be of each second raised element 10b relative to the flat surface P, is opposite the inner end 10bi that contacts the flat surface P and is intended to contact the electrochemical cell 1, and the contact width D1 of each first raised element 10a is different from the contact width D2 of each second raised element 10b.

[0104] In particular, the contact width D1 of each first raised element 10a is in the range of 0.5 to 5 mm, preferably equal to 1 mm, this large width being meant to withstand clamping stresses and act as a compression limiter.

[0105] The contact width D2 of each second raised element 10b is in the range of 0.005 mm to 0.5 mm and is preferably equal to 100 μm. This small width means that the contact points can be evenly distributed over the entire contact surface of the electrochemical cell 1 without impeding the flow of fluids. Moreover, the height H1 of each first raised element 10a is smaller than the height H2 of each second raised element 10b, for example 350 μm and 400 μm, respectively. In this way, the raised elements 10b with a small width D2 ensure electrical contact.

[0106] It should be noted that in the example shown in Figures 10 and 11, the raised elements 10a, 10b, 10c are in the shape of teeth or grooves and are arranged parallel to each other. However, the raised elements can take any shape to ensure electrical contact and gas flow. In this way, the spaces between the raised elements 10a, 10b, 10c form the gas flow channels 11.

[0107] Moreover, the raised elements 10a, 10b are here uniformly distributed on the flat surface P. In particular, they are spaced apart by the same distance Cb along at least one horizontal direction DH on the flat surface P, in particular within the range of 50 μm to 5 mm, preferably equal to 750 μm. The spacing of the raised elements 10a, 10b is therefore constant, allowing a uniform distribution of the current in the electrodes of the electrochemical cell 1. The value of the spacing may depend on the electrochemical cell 1 used.

[0108] During clamping, the raised elements 10b are compressed first due to their greater height, and then due to their smaller contact width D2, the compression becomes greater, which allows geometrical imperfections to be accommodated.

[0109] This compression continues until the height H2 of the raised element 10b reaches the height H1 of the raised element 10a. Thus, the contact area increases rapidly and the compression stops. This cessation of compression preserves a large space for the gas flow channel 11. In this way, the pressure loss can be kept low. Moreover, the rather low spacing Cb between the raised elements 10a, 10b results in good electrical conductivity.

[0110] Advantageously, the present invention does not require fine adjustment of the clamping force to stop compression, in fact, the significant increase in surface area upon contact with raised elements 10a can limit the effect of the initial force and greatly reduce stress.

[0111] FIG. 12 shows a regular distribution of the first raised elements 10a and the second raised elements 10b of the example shown in FIGS.

[0112] According to the present invention, the tabs 710 are aligned with the teeth 10 of the interconnect 5 as shown in FIG.

[0113] In this way, the teeth 10a with width D1 are arranged in line with the tabs 710, whereas the narrow teeth 10b with width D2 are arranged oppositely in the slots 711. This optimizes the fluidics of the interconnect 5, in particular the contact layers.

[0114] The width D1 of the tooth 10a is advantageously equal to the width le of the tab 710.

[0115] Width D1 advantageously does not create any particular excess pressure since it corresponds to the width of tab 710. Furthermore, the fluidics of distribution are improved since the gas flows in a straight line without flow disturbances.

[0116] Furthermore, because manufacturing of the interconnect 5 and electrochemical cell 1 is not consistent, it may also be advantageous to have an interconnect 5 whose compression can be modulated during operation, particularly a contact layer of the interconnect 5 that includes raised elements.

[0117] In this way, by creating N different shapes, it is possible to obtain a compression stage that is easily accessible even during testing. In other words, the interconnect may more generally comprise a group of N raised elements formed on a flat surface P, where N is an integer equal to or greater than 2, preferably in the range of 2 to 50, and even more preferably equal to 5, and where the raised elements of the same group are all identical and the raised elements of different groups have different geometrical characteristics, i.e. different heights and different contact widths.

[0118] 14 and 15 show the case where N=3, which is merely an illustrative and non-limiting example of the present invention. Thus, the interconnect 5 includes a first raised element 10a having a contact width D1 and a height H1, a second raised element 10b having a contact width D2 and a height H2, and a third raised element 10c having a contact width D3 and a height H3. The selected values ​​are such that D3>D1>D2 and H2>H1>H3.

[0119] This results in several possible compression levels. In this way, a compression with force 1 is possible, which only compresses raised element 10b. If this is insufficient due to large geometric defects to be compensated, it is possible to go to force 2, which is greater than force 1, and compress raised element 10a to height H3 of raised element 10c. In this way, the compression and contact can be adjusted as required.

[0120] It is therefore possible to have N different shapes with increasing contact widths, if desired. By successively increasing the clamping force, the raised elements can be compressed stepwise and stopped as soon as the contact is good and optimal compression is obtained. This results in an interconnect 5, or its contact layer, that fits all shapes.

[0121] FIG. 16 shows the option where the raised element 10c having the maximum contact width D3 is located at the periphery Pi of the flat surface P, away from the other raised elements 10a, 10b and the gas flow channel 11.

[0122] These raised elements 10c form compression limiters since they have a maximum contact width D3. They can be placed outside the active area. In this way, a maximum surface area is ensured for gas flow.

[0123] Furthermore, the raised elements 10a, 10b, 10c can be of any shape, they do not have to be in the shape of teeth as described above.

[0124] Thus, figures 17 and 18 show the option of making the raised elements 10a, 10b in the form of studs, in particular cylindrical studs. Other shapes are also possible, for example parallelepiped shapes. The spaces between the raised elements 10a, 10b form a single serpentine gas flow channel 11.

[0125] This allows the stress to be adjusted as precisely as possible through suitable surfaces and optimized gas flows.

[0126] Furthermore, Fig. 18 shows the option that at least one region Z of the flat surface P, in this case the central region Z, does not contain raised elements. Indeed, the heat generated by an excessively large surface area of ​​the electrochemical cell 1 may cause overheating problems, especially in the center of the cell 1, where it is difficult to remove the heat. In this way, it is possible to intentionally limit the reaction in the center of the cell 1 by intentionally reducing the electrical conductivity of a certain central region Z, excluding the electrical contacts. Advantageously, it should be noted that the interconnector 5 according to the invention may comprise a metal alloy substrate, in particular of the chromium-forming type, whose basic elements are iron (Fe) or nickel (Ni), in particular a ferritic steel of the Uginox® K41 type or VDM® Crofer type, as described in US Pat. No. 5,399,323, and which has two main planes.

[0127] One of the major planes comprises a first coating layer forming a first contact layer with the electrochemical cell 1 and the other of the major planes comprises a second coating layer forming a second contact layer with the electrochemical cell 1 .

[0128] The first coating layer and / or the second coating layer may comprise a flat surface P and raised elements 10a, 10b, 10c thereon, in particular formed by machining as described above.

[0129] These raised elements do not have to be identical on the first and second coating layers, and if these two coating layers have such raised elements, their distribution does not have to be identical on the first and second coating layers.

[0130] The first covering layer may in particular be a porous or non-porous first thick ceramic contact layer, in particular comprising strontium-doped lanthanum manganite, which may be provided on the oxygen electrode side.

[0131] The second coating layer may be a second thick metal contact layer, in particular comprising nickel, which may be provided on the hydrogen electrode side.

[0132] This second layer may in particular contain at least two different types of nickel grids. In these grids, cm 2 The number of meshes per grid and the wire diameter can be modulated: for example, a grid A with height Ha and with a large number of meshes Na forming raised elements can be used to compress it heavily, and a second grid B with height Hb less than height Ha and with meshes Nb forming fewer raised elements than meshes Na can be used to act as a compression limiter.

[0133] Furthermore, FIG. 19 shows a stack 20 of solid oxide cells of the SOEC / SOFC type operating at high temperature according to the present invention.

[0134] More specifically, FIG. 19 shows an assembly 80 including a stack 20 of solid oxide cells of the SOEC / SOFC type and a clamping system 60 .

[0135] This assembly 80 has a structure similar to that described in US Pat. No. 5,399,633.

[0136] The stack 20 comprises a plurality of electrochemical cells 1, each consisting of a cathode, an anode and an electrolyte inserted between the cathode and the anode, and a plurality of interconnects 5 according to the invention, each interconnect being placed between two adjacent electrochemical cells 1. This assembly of electrochemical cells 1 and interconnects 5 can also be called a "stack".

[0137] Further, the stack 20 includes an upper end plate 43 and a lower end plate 44, also referred to as the upper stack end plate 43 and the lower stack end plate 44, respectively, between which the plurality of electrochemical cells 1 and the plurality of interconnects 5 are clamped, i.e., between which the stack is located.

[0138] Furthermore, the assembly 80 also includes a clamping system 60 for the stack 20 of SOEC / SOFC type solid oxide cells, comprising an upper clamping plate 45 and a lower clamping plate 46 between which the stack 20 of SOEC / SOFC type solid oxide cells is clamped.

[0139] Each clamp plate 45, 46 of the clamp system 60 includes four clamp holes 54. Furthermore, the clamp system 60 also includes four clamp rods 55, or tie rods, extending through the clamp holes 54 of the upper clamp plate 45 and through corresponding clamp holes 54 of the lower clamp plate 46, making it possible to couple the upper clamp plate 45 and the lower clamp plate 46 together. The clamp system 60 also includes, in each clamp hole 54 of the upper 45 and lower 46 clamp plates, clamping means 56, 57, 58, which cooperate with the clamp rods 55 and make it possible to couple the upper clamp plate 45 and the lower clamp plate 46 together. More specifically, the clamping means includes, in each clamp hole 54 of the upper clamp plate 45, a first clamp nut 56 which cooperates with a corresponding clamp rod 55 inserted in the clamp hole 54. Additionally, the clamping means includes, in each clamping hole 54 of the lower clamping plate 46, a clamping washer 58 and an associated second clamping nut 57 which cooperate with a corresponding clamping rod 55 inserted in the clamping hole 54. The clamping washer 58 is located between the second clamping nut 57 and the lower clamping plate 46.

[0140] Of course, the invention is not limited to the exemplary embodiments described above, as various modifications are possible to those skilled in the art. [Explanation of symbols]

[0141] 1 cell 2 cathode 3 Electrolytes 4 Anode 5 Interconnector 10,10a,10b,10c Raised element 10ae,10be outer contact end 10ai,10bi inner edge 11 Channels 20 Stack 21, 22, 23 sheets 43 Upper end plate 44 Lower end plate 45 Upper clamp plate 46 Lower clamp plate 50 Cathode compartment 51 Anode compartment 54 Clamp hole 55 Clamp rod 56, 57, 58 Clamping means 60 Clamp System 61,62,63,64,71,72,73,74,81,82,83,84 holes 67,68,711 Slots 69,70,89 central part 80 Assembly 710,720,730,740 Sheet Tabs

Claims

1. An interconnector (5) for a solid oxide cell stack (20) of the SOEC / SOFC type operating at high temperatures, comprising: It is intended to be placed between two adjacent electrochemical cells (1) in the stack (20), each of the electrochemical cells (1) consisting of a cathode, an anode and an electrolyte inserted between the cathode and the anode; The interconnector (5) is formed by an assembly of at least three plates (21, 22, 23) extending along mutually orthogonal first and second axes of symmetry (X, Y), with a central plate (22) sandwiched between a first end plate (21) and a second end plate (23); the central plate (22) comprises a central portion (70) and, at its periphery, at least two holes (71, 73) extending over a length substantially corresponding to the length of the central portion (70) along the first axis of symmetry (X) and two holes (72, 74) extending over a length substantially corresponding to the length of the central portion (70) along the second axis of symmetry (Y); Each of said holes (71, 72, 73, 74) includes tabs (710, 720, 730, 740) spaced apart to form a comb, and a slot (711) defined between the edge of the hole (71) and a tab (710) or between two consecutive tabs (711); characterized in that the width (le) of each tab (710) of the at least one hole (71) is between 0.1 mm and 3 mm, in particular about 1 mm; The interconnector (5) comprises a metal alloy substrate having two main surfaces, one of which comprises a first coating layer forming a first contact layer with the electrochemical cell (1), and the other of which comprises a second coating layer forming a second contact layer with the electrochemical cell (1); The first coating layer and / or the second coating layer comprises a flat surface (P) and raised elements (10a, 10b, 10c) formed thereon; Interconnector.

2. 2. An interconnector according to claim 1, characterized in that the width (lf) of each slot (711) of the at least one hole (71) is between 3 and 5 mm, in particular about 4.9 mm.

3. 2. An interconnector according to claim 1, characterized in that the height (he) of each tab (710) of the at least one hole (71) is between 0.25 and 1 mm, in particular about 0.3 mm.

4. The interconnector (5), in particular the central part (70) of the central plate (22), comprises a flat surface (P) on which at least one first group of identical first elements (10a) raised relative to the flat surface (P) and one second group of identical second elements (10b) raised relative to the flat surface (P) are formed; the first raised element (10a) has different geometric characteristics than the second raised element (10b); a height (H1) of each of the first raised elements (10a), measured as the maximum perpendicular dimension of the first raised element (10a) relative to the flat surface (P), is different from a height (H2) of each of the second raised elements (10b), measured as the maximum perpendicular dimension of the second raised element (10b); 2. The interconnector according to claim 1, wherein a contact width (D1) of each of the first raised elements (10a), measured as the maximum horizontal dimension of an outer contact end (10ae) of each of the first raised elements (10a) relative to the flat surface (P), is opposite an inner end (10ai) contacting the flat surface (P) and intended to contact an electrochemical cell (1); and a contact width (D2) of each of the second raised elements (10b), measured as the maximum horizontal dimension of an outer contact end (10be) of each of the second raised elements (10b) relative to the flat surface (P), is opposite an inner end (10bi) contacting the flat surface (P), and intended to contact an electrochemical cell (1); and wherein the contact width (D1) of each of the first raised elements (10a) is different from the contact width (D2) of each of the second raised elements (10b).

5. 5. The interconnector of claim 4, wherein the first raised element (10a) has a contact width (D1) greater than the contact width (D2) of the second raised element (10b), the first raised element (10a) is arranged along a tab (710) of at least one hole (71), and the second raised element (10b) is arranged along a slot (711) of the at least one hole (71).

6. 6. The interconnector according to claim 5, characterized in that the contact width (D1) of the first raised element (10a) is equal to the width (le) of the tab (710) of the at least one hole (71).

7. 5. The interconnector according to claim 4, characterized in that the contact width (D1) of each first raised element (10a) is in the range of 0.5 to 5 mm, preferably equal to 1 mm, the contact width (D2) of each second raised element (10b) is in the range of 0.005 mm to 0.5 mm, preferably equal to 100 μm, the height (H1) of each first raised element (10a) is in the range of 200 μm to 1000 μm, preferably equal to 350 μm, and the height (H2) of each second raised element (10b) is in the range of 250 μm to 1050 μm, preferably equal to 400 μm.

8. 5. The interconnector of claim 4, wherein the difference between the height (H2) of each second raised element (10b) and the height (H1) of each first raised element (10a) is in the range of 5 μm to 500 μm, in particular about 50 μm.

9. 5. The interconnector according to claim 4, characterized in that it comprises N groups of raised elements (10a, 10b, 10c) formed on the flat surface (P), N being an integer equal to or greater than 2, preferably in the range of 2 to 50, and more preferably equal to 5, the raised elements (10a, 10b, 10c) of the same group are all identical, and the raised elements (10a, 10b, 10c) of different groups have different geometrical characteristics, i.e. different heights (H1, H2, H3) and different contact widths (D1, D2, D3).

10. 5. The interconnector of claim 4, wherein the raised elements (10a, 10b, 10c) are in the form of teeth or grooves and are arranged parallel to one another, and the spaces between the raised elements (10a, 10b, 10c) form gas flow channels (11).

11. 5. The interconnector of claim 4, wherein the raised elements (10a, 10b, 10c) are in the form of studs, in particular cylindrical studs, and the spaces between the raised elements (10a, 10b, 10c) form a single serpentine gas flow channel (11).

12. 5. The interconnector of claim 4, wherein the raised element (10c) having the maximum width (D3) is located at the periphery (Pi) of the flat surface (P) and is located away from the other raised elements (10a, 10b) and the gas flow channel (11) formed by the spaces between those raised elements (10a, 10b).

13. 2. The interconnector according to claim 1, characterized in that the metal alloy substrate is of the chromium-forming type, the base element of which is iron (Fe) or nickel (Ni), and the raised elements (10a, 10b, 10c) formed on the flat surface (P) are formed by machining.

14. The first coating layer is a porous or non-porous thick ceramic coating layer, the ceramic material being in particular nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr), M (transition metals), either alone or in mixtures, La １－ｘ Sr ｘ MO ３ or a material having a layer structure, such as Ln ２ NiO ４ 2. The interconnector according to claim 1, characterized in that it is selected from lanthanide nickel oxides (Ln = lanthanum (La), neodymium (Nd), praseodymium (Pr)) or other electrically conductive perovskite oxides.

15. 2. The interconnector according to claim 1, characterized in that the second coating layer is a thick metallic coating layer, the metallic material being selected in particular from nickel (Ni) and its alloys or chromium-forming alloys, the base element of which is iron (Fe).

16. A solid oxide cell stack (20) of the SOEC / SOFC type operating at high temperatures, comprising: A plurality of electrochemical cells (1) each consisting of a cathode, an anode, and an electrolyte inserted between the cathode and the anode; a plurality of interconnectors (5) according to any one of claims 1 to 15, A stack, wherein each said interconnector is disposed between two adjacent electrochemical cells (1).

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