Method for manufacturing SOEC / SOFC type solid oxide stacks and related stacks

Abstract

The present invention mainly relates to a method for making a SOEC / SOFC type solid oxide stack operating at high temperatures, comprising a number of electrochemical cells each formed by a cathode, an anode and an electrolyte inserted between the cathode and the anode, and a number of metallic interconnects each arranged between two adjacent electrochemical cells, each interconnect having two main planes, a first of which (P1) comprises a metallization layer (GN) in the form of a grid forming a contact layer with the electrochemical cells, the method comprising a step of spot welding (S) the metallization layer (GN) to the first plane (P1) of the interconnect to enable its attachment.

Description

[Technical Field]

[0001] This invention relates to the general field of high-temperature electrolysis (HTE) of water, particularly high-temperature steam electrolysis (HTSE), electrolysis of carbon dioxide (CO2), and high-temperature co-electrolysis (HTE) of water and carbon dioxide (CO2).

[0002] More specifically, the present invention relates to the field of high-temperature solid oxide electrolyzers, which are commonly referred to by the acronym SOEC (an abbreviation for "Solid-Oxide Electrolyser Cell").

[0003] Furthermore, in the field of high-temperature solid oxide fuel cells, solid oxide fuel cells are commonly referred to by the acronym SOFC (an abbreviation for "Solid-Oxide Fuel Cells").

[0004] Therefore, more generally, the present invention relates to the field of SOEC / SOFC type solid oxide stacks that operate at high temperatures.

[0005] More specifically, the present invention relates to a method for manufacturing or assembling an SOEC / SOFC type solid oxide stack, and an associated stack, which includes the step of spot welding a contact layer to the surface of each interconnector of the stack to fix the contact layer. [Background technology]

[0006] In the context of high-temperature SOEC solid oxide electrolytic cells, the process consists of converting water vapor (H2O) to dihydrogen (H2) and dioxygen (O2) and / or carbon dioxide (CO2) to carbon monoxide (CO) and dioxygen (O2) by electric current within the same electrochemical apparatus. In the context of high-temperature SOFC solid oxide fuel cells, the operation is reversed, with electric current and heat generated by supplying dihydrogen (H2) and dioxygen (O2), typically air and natural gas, i.e., methane (CH4). For brevity, the following description will prioritize the operation of a high-temperature SOEC solid oxide electrolytic cell performing the electrolysis of water. However, this operation can be applied to the electrolysis of carbon dioxide (CO2), or to the high-temperature co-electrolysis (HTE) of water and carbon dioxide (CO2). Furthermore, this operation can be substituted for the case of a high-temperature SOFC solid oxide fuel cell.

[0007] Electrolysis of water is advantageous at high temperatures, typically 600-1000°C. This is because electrolyzing water vapor is more advantageous than electrolyzing liquid water, and some of the energy required for the reaction can be supplied by heat, which is cheaper than electricity.

[0008] To perform high-temperature electrolysis (HTE) of water, a high-temperature solid oxide electrolytic cell (SOEC) consists of a stack of solid oxide electrolytic cells, or electrochemical cells, each consisting of three layers of anode / electrolyte / cathode, stacked on top of each other, and interconnecting plates, often made of metal alloy, also called bipolar plates or interconnectors. Each electrochemical cell is sandwiched between two interconnecting plates. A high-temperature SOEC solid oxide electrolytic cell is an alternating stack of electrochemical cells and interconnectors. A high-temperature solid oxide fuel cell (SOFC) consists of a stack of the same type of basic pattern. Because this high-temperature technology is reversible, the same stack can operate in an electrolytic mode to produce hydrogen and oxygen from water and electricity, or in a fuel cell mode to produce electricity from hydrogen and oxygen.

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

[0010] The electrical and fluid interconnectors consist of electron conductors that, from an electrical standpoint, ensure the connection between each electrochemical cell and the basic pattern in the stack of basic patterns, ensuring electrical contact between one face and the cathode of the cell, and between the other face and the anode of the next cell, and from a fluid standpoint, thereby combining the respective generation of the cells. Thus, the interconnectors ensure the function of supplying and collecting current and partitioning gas circulation compartments for distribution and / or collection.

[0011] More specifically, the primary function of the interconnector is to ensure the passage of current and the circulation of gases in the vicinity of each cell (i.e., in the case of HTE electrolysis, injected water vapor, extracted hydrogen, and oxygen; in the case of SOFC cells, air and fuel containing injected hydrogen and extracted water), and to separate the anode and cathode compartments of two adjacent cells, which are the gas circulation compartments on the anode and cathode sides of the cells, respectively.

[0012] In particular, in the case of a high-temperature SOEC type solid oxide electrolytic cell, the cathode compartment contains water vapor and hydrogen produced from the electrochemical reaction, while the anode compartment contains exhaust gas, if present, and oxygen, which is another product of the electrochemical reaction. In the case of a high-temperature SOFC type solid oxide fuel cell, the anode compartment contains fuel, while the cathode compartment contains an oxidizer.

[0013] To perform high-temperature steam electrolysis (HTE), water vapor (H2O) is injected into the cathode compartment. Under the action of the current applied to the cell, the dissociation of water molecules in the form of water vapor occurs at the interface between the hydrogen electrode (cathode) and the electrolyte: this dissociation produces dihydrogen gas (H2) and oxygen ions (O2).2- ) is generated. Dihydrogen (H2) is collected and released at the hydrogen compartment outlet. Oxygen ions (O 2- The oxygen moves through the electrolyte and recombines with dioxygen (O2) at the interface between the electrolyte and the oxygen electrode (anode). Exhaust gases such as air circulate at the anode, and as a result, the oxygen produced at the anode can be collected in gaseous form.

[0014] To ensure the operation of a solid oxide fuel cell (SOFC), air (oxygen) is injected into the cathode section of the cell and hydrogen is injected into the anode section. Oxygen in the air is O 2- It dissociates into ions. These ions move through the cathode electrolyte towards the anode, oxidizing hydrogen to form water and simultaneously generating electricity. In an SOFC cell, as in SOEC electrolysis, water vapor is in the dihydrogen compartment (H2). Only the polarity is reversed.

[0015] For illustrative purposes, Figure 1 shows a schematic diagram illustrating the operating principle of a high-temperature SOEC-type solid oxide electrolytic cell. The function of such an electrolytic cell is to convert water vapor into hydrogen and oxygen according to the following electrochemical reaction: 2H2O → 2H2 + O2.

[0016] This reaction is carried out electrochemically in the cells of an electrolytic cell. As illustrated in Figure 1, each basic electrolytic cell 1 is formed by a cathode 2 and an anode 4 positioned on either side of a solid electrolyte 3. The two electrodes (cathode and anode) 2 and 4 are electron conductors and / or ionic conductors made of porous material, and the electrolyte 3 is an electronic insulator and ionic conductor with an airtight structure. In particular, the electrolyte 3 is an anionic conductor, more specifically, O 2- In some cases, the ion may be an anion conductor, in which case the electrolytic cell will contain a proton electrolyte (H + In contrast to the case of an anion electrolytic cell, this is called an anion electrolytic cell.

[0017] Electrochemical reactions occur at the interface between each electron conductor and an ionic conductor.

[0018] At the cathode 2, the half-reaction is as follows: 2H2O + 4e - → 2H2+ 2O 2- .

[0019] At the anode 4, the half-reaction is as follows: 2O 2- → O2+ 4e - .

[0020] The electrolyte 3 inserted between the two electrodes 2 and 4 is the place where the ion O 2- moves under the action of the electric field created by the potential difference imposed between the anode 4 and the cathode 2.

[0021] As shown in the brackets in Figure 1, the water vapor at the cathode inlet may be accompanied by hydrogen H2, and the hydrogen generated and recovered at the outlet may be accompanied by water vapor. Similarly, as shown by the dotted line, exhaust gas such as air can be injected at the inlet to release the generated oxygen. The injection of the exhaust gas has an additional function acting as heat control.

[0022] The basic electrolytic cell or electrolytic reactor consists of the above-described basic cell including the cathode 2, the electrolyte 3, and the anode 4, and two interconnects that ensure the electrical, hydraulic, and thermal distribution functions.

[0023] To increase the flow rates of the generated hydrogen and oxygen, it is known to stack several basic electrolytic cells while separating them by interconnects. The assembly is placed between two end interconnect plates that support the power supply and gas supply of the electrolytic cell (electrolytic reactor).

[0024] Thus, the high-temperature SOEC type solid oxide electrolytic cell includes at least one, generally a plurality of electrolytic cells stacked on each other. Each basic cell is formed of an electrolyte, a cathode, and an anode, and the electrolyte is inserted between the anode and the cathode.

[0025] As shown above, a fluidic and electrical interconnect device in electrical contact with one or more electrodes generally ensures the functions of supplying and collecting current and delimits one or more gas circulation compartments.

[0026] Thus, the function of the so-called cathode compartment is the distribution of current and water vapor, and the recovery of hydrogen at the contacting cathode.

[0027] The function of the so-called anode compartment consists of the distribution of current and the recovery of oxygen generated at the contacting anode, optionally using the exhaust gas.

[0028] FIG. 2 shows an exploded view of the basic pattern of a high-temperature SOEC-type solid oxide electrolyzer according to the prior art. This electrolyzer includes a plurality of basic electrolysis cells C1, C2 of the solid oxide type (SOEC) stacked alternately with an interconnector 5. Each cell C1, C2 consists of cathodes 2.1, 2.2 and an anode (only the anode 4.2 of cell C2 is shown), and there is an electrolyte (only the electrolyte 3.2 of cell C2 is shown) between them.

[0029] The interconnector 5 is typically a component made of a metal alloy and ensures the separation between the cathode 50 and anode 51 compartments defined by the volumes respectively included between the interconnector 5 and the adjacent cathode 2.1 and between the interconnector 5 and the adjacent anode 4.2. It also ensures the distribution of gas to the cells. The injection of water vapor into each basic pattern is carried out in the cathode compartment 50. The collection of the generated hydrogen and the residual water vapor at the cathodes 2.1, 2.2 is carried out in the cathode compartment 50 downstream of the cells C1, C2, after the dissociation of water vapor by the latter. The collection of the oxygen generated at the anode 4.2 is carried out in the anode compartment 51 downstream of the cells C1, C2, after the dissociation of water vapor by the latter. The interconnector 5 ensures the passage of current between cells C1 and C2 by direct contact between the adjacent electrodes, i.e., the anode 4.2 and the cathode 2.1.

[0030] Because the operating conditions of high-temperature solid oxide electrolytic cells (SOECs) are very similar to those of solid oxide fuel cells (SOFCs), the same technical constraints are observed.

[0031] Therefore, proper operation of the SOEC / SOFC type solid oxide stack operating at high temperatures requires addressing the points clearly outlined below.

[0032] In particular, electrical insulation is required between the two consecutive interconnectors; otherwise, a short circuit will occur in the electrochemical cell. Good electrical contact and sufficient contact surface are also necessary between the cell and the interconnector. The ohmic resistance between the cell and the interconnector should be as low as possible.

[0033] Furthermore, the space between the anode and cathode compartments must be sealed; otherwise, recombination of the generated gases will occur, leading to a decrease in yield and, above all, the appearance of hot spots that damage the stack.

[0034] Finally, good gas distribution is necessary at both the inlet and product recovery; otherwise, it will lead to reduced yield, pressure and temperature heterogeneity within different basic patterns, and potentially significant degradation of the electrochemical cell.

[0035] Interconnectors play an essential role in achieving improved production efficiency and good operational homogeneity of SOEC / SOFC type solid oxide stacks operating at high temperatures, particularly for ensuring good electrical contact between different parts of the stack and enabling good gas distribution within the electrochemical cell. Interconnectors may consist of three thin plates, also called sheet metal or strips, made of metal and welded to each other, as described in French patent application FR 3 024 985 A1.

[0036] Therefore, Figure 3 shows an exploded view of an example of an interconnector 5 formed from an assembly of three thin sheet metals 21-23 that are assembled and laminated.

[0037] Three sheet metals 21, 22, and 23 are stretched along two mutually orthogonal axes of symmetry X and Y, and the sheet metals are laminated and assembled together by welding. The central sheet metal 22 is inserted between the first end sheet metal 21 and the second end sheet metal 23.

[0038] In this specification, the central sheet metal 22 includes a stamped central portion 70 that defines the raised or stamped elements 10. Alternatively, the central sheet metal 22, and therefore the central portion 70, may be smooth. Furthermore, four openings 71, 72, 73, and 74 are provided on the outer edge of the central portion 70. The “openings” should be understood as holes on both sides of the sheet metal.

[0039] One of the end-sheet metal pieces 21 includes a planar central section 69, with four openings 61, 62, 63, and 64 at its outer edge. The first end-sheet metal piece 21 further includes two grooves 67 and 68, which are openings symmetrically arranged on either side of the axis Y. These extend along the axis Y for a length substantially corresponding to the length of the central section 69.

[0040] One of the end-flat sheet metals 23 includes a recessed and perforated central portion 89, and has four openings 81, 82, 83, and 84 on the outer edge of the central portion 89.

[0041] The openings 61, 71, 81, 63, 73, and 83 of each sheet metal are elongated along axis X for a length substantially corresponding to the length of the central section 69, 70, and 89, while the openings 62, 72, 82, 64, 74, and 84 of each sheet metal extend along axis Y for a length substantially corresponding to the length of the central section 69, 70, and 89.

[0042] The openings 71-74 of the central sheet metal 22 widen to openings 61, 81, 62, 82, 63, 83, 64, and 84, respectively, and these widened portions include spaced sheet metal tabs 710, 720, 730, and 740 that form a comb. Each of the grooves 711 defined between the end of the widened opening 71 and the tab 710, or between two consecutive tabs 710, opens into the relief 10 or the channel 11 defined by the stamping. The grooves created on the sides of openings 72, 73, and 74 are similar.

[0043] The sheet metals 21, 22, and 23 are typically made of ferritic steel with about 20% chromium, preferably Inconel® 600 or Haynes® type nickel-based CROFER® 22 (APU or H), or K41 (ASI 441), or FT18TNb, and are typically thicknesses ranging from 0.1 to 1 mm.

[0044] These interconnectors may also be described in French patent application FR 2 996 065 A1. In this application, the interconnector corresponds to a component having a substrate made of a metal alloy whose basic element is iron (Fe) or nickel (Ni), wherein one of the main planes is covered with a thick ceramic layer, with grooves formed therein, separating channels suitable for the distribution and / or recovery of gases such as water vapor (H2O), H2, and air, and the other of the main planes is covered with a thick metal layer, with grooves formed therein, separating channels suitable for the distribution and / or recovery of gases such as water vapor (H2O), H2, O2, and exhaust gases. In particular, a thick ceramic contact layer based on strontium-doped lanthanum manganite may be provided on the oxygen electrode (EHT anode, cathode of the SOFC cell) side on the end sheet metal 23 which has been hot-pressed according to the principle of FR 2 996 065 A1, and a thick nickel-based metal contact layer may be provided on the hydrogen electrode (HTE cathode, anode of the SOFC cell) side on the end sheet metal 21, and may be in the form of a nickel grid in particular.

[0045] A "thick layer" should be understood as a layer whose thickness is greater than that of a layer obtained using the so-called "thin layer" technique, and is typically between 2 and 15 μm. In this way, SOFC / SOEC type solid oxide stacks can be manufactured at low cost, with good performance and good homogeneity.

[0046] The entire production and assembly of the stack, i.e., the electrochemical cell 1 and interconnector 5, is carried out in a specific manner, taking into account the shape of the plates and the technical design choices made. In particular, the continuous layer stack is made in the following order: interconnector, then ceramic contact layer, then electrochemical cell, then metal contact layer, then interconnector, etc.

[0047] Furthermore, in order to form a stack, it is still necessary to optimize the stacking of such consecutive layers, and in particular, to obtain a fixed assembly in order to enable the production of the stack while avoiding movement during the assembly and stacking stages. [Prior art documents] [Patent Documents]

[0048] [Patent Document 1] French Patent Application FR 3 024 985 A1 [Patent Document 2] French Patent Application FR 2 996 065 A1 [Patent Document 3] French Patent Application FR 3 056 337 A1 [Patent Document 4] French Patent Application FR 3 045 215 A1 [Overview of the project] [Problems that the invention aims to solve]

[0049] The present invention aims to address, at least partially, the aforementioned needs and the drawbacks associated with the embodiments of the prior art.

[0050] In particular, the present invention aims to manufacture stable and fixed interconnectors / contact layers / electrochemical cell assemblies for SOEC / SOFC type solid oxide stacks in order to facilitate stack production. [Means for solving the problem]

[0051] Accordingly, the object of the present invention is a method for manufacturing a SOEC / SOFC type solid oxide stack that operates at high temperatures, comprising a plurality of electrochemical cells formed by a cathode, an anode, and an electrolyte inserted between the cathode and the anode, and a plurality of metal interconnectors disposed between two adjacent electrochemical cells, each interconnector having two main planes, the first of the two main planes comprising a metal coating layer in the form of a grid that forms a contact layer with the electrochemical cells, The method includes a step of spot welding a metal coating layer to the first surface of an interconnect to enable its fixation.

[0052] The manufacturing method according to the present invention may further include one or more of the following features, which are considered separately or in any combination that is technically feasible:

[0053] The metallic material of the coating layer can be selected from nickel and its alloys, and the coating layer is in the form of a nickel grid, or a chromia-forming alloy in which the basic element is iron.

[0054] Furthermore, by distributing several welding spots evenly along the outer edge of the coating layer, particularly at the corners of the coating layer, at least four, and possibly at least eight, welding spots can be formed.

[0055] Furthermore, the manufacturing method may, advantageously, include a step of depositing an adhesive onto a coating layer with the intention of fixing an electrochemical cell. Advantageously, the adhesive may contain 5% to 50% by mass of polyvinyl butyral (PVB), 5% to 50% by mass of terpineol, and 5% to 95% by mass of ethanol.

[0056] The adhesive can be deposited on the outer edge of the coating layer, particularly in a location that is outside the active region and away from the gas supply.

[0057] Furthermore, this manufacturing method may include a step of depositing a glass layer on the coating layer before the adhesive deposition step.

[0058] Furthermore, each interconnector has two main planes, and the second surface of the main plane may include a thick ceramic coating layer that forms a contact layer with the electrochemical cell, the ceramic material being, in particular, of the formula La, either alone or in mixtures. 1-x Sr x The material is selected from lanthanum-doped lanthanum manganite of the formula MO3 (M (transition metal) = nickel, iron, cobalt, manganese, chromium), or a material having a lamellar structure such as lanthanide nickelate of the formula Ln2NiO4 (Ln = lanthanum, neodymium, praseodymium), or another conductive perovskite oxide.

[0059] Furthermore, each interconnector may be formed from an assembly of at least three plates stretched along mutually orthogonal first and second axes of symmetry, with a central plate inserted between the first and second end plates.

[0060] Furthermore, another object of the present invention, according to another aspect thereof, is a high-temperature operating SOEC / SOFC type solid oxide stack obtained using the manufacturing method previously defined, comprising a plurality of electrochemical cells formed by a cathode, an anode, and an electrolyte inserted between the cathode and the anode, and a plurality of metal interconnectors positioned between two adjacent electrochemical cells.

[0061] The present invention will be better understood when reading the detailed description of its non-limiting embodiments below and when examining the schematic and partial drawings of the accompanying drawings. [Brief explanation of the drawing]

[0062] [Figure 1] This is a schematic diagram illustrating the operating principle of a high-temperature solid oxide electrolytic cell (SOEC). [Figure 2] This is a schematic diagram of a portion of a high-temperature solid oxide electrolytic cell (SOEC) including an interconnector, based on conventional technology. [Figure 3] This is an exploded view of an interconnector for high-temperature SOEC / SOFC type solid oxide stacks, which corresponds to an assembly of three thin sheet metals or plates. [Figure 4] This is a partial front view of an interconnect sheet metal for high-temperature SOEC / SOFC type solid oxide stacks, illustrating the spot welding process of the manufacturing method according to the present invention. [Figure 5] This figure shows a graph of thermogravimetric analysis (TGA) results of the adhesive manufactured according to the present invention under different atmospheric conditions. [Figure 6] Figure 4 is a partial front view of the interconnect sheet metal, illustrating the adhesive deposition process of the manufacturing method according to the present invention. [Figure 7] Figure 4 is a partial front view of the interconnect sheet metal, illustrating the adhesive deposition process of the manufacturing method according to the present invention. [Figure 8] Figures 6 and 7 show a partial front view of the sheet metal of the interconnect shown in Figure 4, illustrating the process of bonding the electrochemical cells after the deposition of the adhesive. [Figure 9] This figure shows a set, obtained by the manufacturing method according to the present invention, including an SOEC / SOFC type solid oxide stack having an electrochemical cell stack and an interconnector stack, and a system for clamping the stack, as shown by perspective and observation from above. [Modes for carrying out the invention]

[0063] In all of these figures, the same reference numeral may indicate the same or similar elements.

[0064] Furthermore, to make the diagram easier to understand, the different parts shown in the diagram are not necessarily drawn to a uniform scale.

[0065] Figures 1 to 3 have already been described in parts relevant to the prior art and the technical context of the present invention. With respect to Figures 1 and 2, it should be noted that the symbols and arrows for water vapor (H2O) supply, dihydrogen (H2), oxygen (O2), air distribution and recovery, and electric current are shown for clarity and accuracy to illustrate the operation of the shown apparatus.

[0066] Furthermore, it should be noted that all components of a given electrochemical cell (anode / electrolyte / cathode) are preferably ceramic. Additionally, the operating temperature of high-temperature SOEC / SOFC type stacks is typically between 600 and 1,000°C.

[0067] Furthermore, the possible terms “upper side” and “lower side” should be understood herein according to their usual orientation when an SOEC / SOFC type stack is in use.

[0068] Figure 3, described earlier, relates to an interconnector 5 formed from an assembly of three thin sheet metals 21-23.

[0069] The manufacturing method according to the present invention will be described with reference to Figures 4 to 8, where Figures 4 and 6 to 8 partially show the sheet metal 21 of the interconnector 5 in Figure 3. Furthermore, elements that have already been described will not be described again.

[0070] It should be noted that interconnector 5 may include a substrate having two main planes P1 and P2, made of a metal alloy whose basic element is iron (Fe) or nickel (Ni), particularly a chromia-forming metal alloy, as also described in French patent application FR 2 996 065 A1.

[0071] Therefore, as shown in Figure 3, the interconnector 5 has two main planes P1 and P2. The first main plane P1 is intended to be covered by a metal coating layer GN provided in particular on the hydrogen electrode side, forming a contact layer with the electrochemical cell 1, as seen in Figure 4. Preferably, the material of this metal coating layer GN is selected from nickel and its alloys, or chromia-forming alloys whose basic element is iron Fe. In particular, this metal coating layer GN is in the form of a nickel grid, as shown in Figures 4, 6, and 7.

[0072] The manufacturing method according to the present invention aims to enable optimal assembly between the interconnector 5 and the electrochemical cell 1, particularly between the end sheet metal 21 and the nickel grid GN.

[0073] Therefore, this method includes a step of spot welding S a metal coating layer GN to the first surface PI of the interconnector 5 to enable its fixation. As shown in Figure 4, this welding is carried out using a welding tool OS, in particular a spot welding apparatus.

[0074] The nickel grid GN is placed on the central portion 69 of the end sheet metal 21, with its openings 62 and 63 visible in Figure 4, and welding spots S are formed all over the outer edge of the nickel grid GN, allowing it to be fixed to the first main plane P1.

[0075] In this specification, eight welding spots S are formed in the outer edge region of the nickel grid GN, specifically four welding spots S at the four corners of the nickel grid GN and four spots in the middle on both sides of the nickel grid GN. These welding spots S are spaced evenly apart along the outer edge of the nickel grid GN. It is possible to increase the number of welding spots S, but doing so would lengthen the duration of this step in the manufacturing method.

[0076] Advantageously, unlike conventional solutions that do not provide a means for fixing the nickel grid GN to the end sheet metal 21, this spot welding method allows the nickel grid GN to be held in place without deformation of the nickel grid GN and without supplying filler elements to limit contamination.

[0077] Furthermore, as shown in Figures 6 and 7, the manufacturing method according to the present invention includes the step of depositing adhesive C onto nickel grid GN to prepare the nickel grid GN to receive the electrochemical cell 1, and enabling optimal fixation of the electrochemical cell 1 onto interconnector 5 via the contact layer formed by the nickel grid GN.

[0078] The adhesive C or tack used contains a highly precise composition to enable optimized fixation to the nickel grid GN and to leave no residue during the transition to high temperatures.

[0079] In particular, adhesive C contains 5% to 50% by mass of polyvinyl butyral (PVB), 5% to 50% by mass of terpineol, and 5% to 95% by mass of ethanol. Preferably, adhesive C contains 17% by mass of polyvinyl butyral (PVB), 28% by mass of terpineol, and 55% by mass of ethanol. Therefore, although the composition of adhesive C may vary, the viscosity of adhesive C will vary depending on the mixing ratio.

[0080] The advantage of this bonding process is that it avoids the movement of the electrochemical cell 1 during the next stage of stack or assembly manufacturing, but also to flatten it again, as the electrochemical cell 1 is often curved. Furthermore, the specific composition of the proposed adhesive C makes it possible to avoid the drawbacks of conventional adhesives, which leave residue after heating, thereby causing contamination that is detrimental to the durability of the SOFC / SOEC stack.

[0081] Figure 7 is a graph showing the change in mass loss PM as a percentage (%) as a function of temperature T, expressed in degrees Celsius (°C). Therefore, this is derived from the thermogravimetric analysis (TGA) of adhesive C. Three curves C1, C2, and C3 are shown, corresponding to three different atmospheres. Thus, it can be seen that, regardless of the atmosphere, no mass residue is obtained above 500°C. In this way, adhesive C used, having a specific composition, enables the absence of residue after heating.

[0082] Advantageously, the adhesive C is deposited on the outer edge of the nickel grid GN, away from the active region and the gas supply. Therefore, as shown in Figures 6 and 7, the adhesive C is placed in the outer edge adhesive deposition region ZC using the adhesive deposition tool OC to avoid clogging of the gas circulation.

[0083] Once the adhesive C is deposited, the electrochemical cell 1 is placed in its designated position as shown in Figure 8, and a load is applied for several hours to allow the adhesive C to dry and to maintain the electrochemical cell 1 even if it is initially deformed.

[0084] However, prior to the deposition of adhesive C, the manufacturing method according to the present invention may include a step of depositing the glass layer V, as shown in Figure 8, onto the nickel grid GN. The deposition of glass V allows for increased fluid distribution, as also described in French patent application FR 3 056 337 A1. Furthermore, by performing bonding after the deposition of glass V, it is possible to obtain a more flexible glass layer V because it is not completely dry.

[0085] As shown in Figure 3, it should also be noted that the interconnector 5 has a second surface P2, which includes a thick ceramic coating layer, provided particularly on the oxygen electrode side and forming a contact layer with the electrochemical cell 1. The ceramic material is of the formula La, either alone or as a mixture. 1-x Sr x The material can be selected from strontium-doped lanthanum manganite of the formula MO3 (M (transition metal) = nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr)), or a material having a lamellar structure such as lanthanide nickelate of the formula Ln2NiO4 (Ln = lanthanum (La), neodymium (Nd), praseodymium (Pr)), or another conductive perovskite oxide.

[0086] The different steps of the manufacturing method according to the present invention are repeated for all interconnectors 5 and electrochemical cells 1 to obtain a SOEC / SOFC type solid oxide stack 20 that operates at high temperatures.

[0087] Figure 9 shows the SOEC / SOFC type solid oxide stack 20 operating at high temperatures according to the present invention.

[0088] More specifically, Figure 9 shows a set 80 including an SOEC / SOFC type solid oxide stack 20 and a clamping system 60.

[0089] This set 80 has a structure similar to that of the assembly described in French patent application FR 3 045 215 A1.

[0090] The stack 20 includes a plurality of electrochemical cells 1, each formed by a cathode, an anode, and an electrolyte inserted between the cathode and the anode, and a plurality of metal interconnectors 5, each positioned between two adjacent electrochemical cells 1. This set of electrochemical cells 1 and interconnectors 5 is called a “stack” and is obtained by the manufacturing method previously described in accordance with the present invention.

[0091] Furthermore, the stack 20 includes an upper end plate 43 and a lower end plate 44, also called the upper stack end plate 43 and the lower stack end plate 44, between which multiple electrochemical cells 1 and multiple interconnectors 5 are clamped, or between which the stack is positioned.

[0092] Furthermore, set 80 also includes a system 60 for clamping the SOEC / SOFC type solid oxide stack 20, which includes an upper clamp plate 45 and a lower clamp plate 46 between which the SOEC / SOFC type solid oxide stack 20 is clamped.

[0093] Each clamp plate 45, 46 of the clamping system 60 includes four clamp orifices 54. Furthermore, the clamping system 60 further includes four clamp rods 55 or tie rods that extend through the entire clamp orifice 54 of the upper clamp plate 45 and through the entire corresponding clamp orifice 54 of the lower clamp plate 46, enabling assembly of the upper 45 clamp plate and the lower 46 clamp plate. Furthermore, the clamping system 60 includes clamping means 56, 57, 58 in each clamp orifice 54 of the upper 45 clamp plate and the lower 46 clamp plate, which cooperate with the clamp rods 55 to enable assembly of the upper 45 clamp plate and the lower 46 clamp plate. More specifically, the clamping means include a first clamp nut 56 in each clamp orifice 54 of the upper clamp plate 45 that cooperates with the corresponding clamp rod 55 inserted through the entire clamp orifice 54. Furthermore, the clamping mechanism includes a second clamp nut 57 associated with a clamp washer 58 at each clamp orifice 54 of the lower clamp plate 46, which cooperates with a corresponding clamp rod 55 inserted through the entire clamp orifice 54. The clamp washer 58 is positioned between the second clamp nut 57 and the lower clamp plate 46.

[0094] Naturally, the present invention is not limited to the embodiments described above. Various modifications can be made thereto by those skilled in the art. [Explanation of Symbols]

[0095] 1. Basic electrolytic cell 1. Electrochemical cell 2 Cathodes 2 electrodes 2.1 Cathode 2.2 Cathode 3 Electrolytes 3.2 Electrolytes 4 Anodes 4 electrodes 4.2 Anode 5 Interconnectors 10 Reliefs 11 channels 21 First end sheet metal 21 End sheet metal 21 Sheet Metal 22 Central sheet metal 22 Sheet Metal 23 Second end sheet metal 23 End sheet metal 23 Sheet Metal 50 Cathode Sections 51 Anode Sections 60 Clamp System 61 Opening 62 Opening 63 Opening 64 openings 67 Groove 68 Groove 69 Central part 70 Central part 71 Opening 72 Opening 73 Opening 74 openings 80 sets 81 Opening 82 Opening 83 Opening 84 Opening 89 Central part 710 Sheet Metal Tabs 720 Sheet Metal Tabs 730 Sheet Metal Tabs 740 Sheet Metal Tabs C Adhesive C1 Basic Electrolytic Cell Cell C1 C2 Basic Electrolytic Cell Cell C2 GN metal coating layer GN coating layer GN Nickel Grid OC Adhesive Deposition Tool OS Welding Tools P1 principal plane P1 First main plane P1 First side P2 principal plane P2 Second side S spot welding S welding spot V glass layer V Glass ZC adhesive deposition area

Claims

1. A method for producing a high-temperature operating SOEC / SOFC type solid oxide stack (20) comprising a plurality of electrochemical cells (1) each formed of a cathode, an anode, and an electrolyte inserted between the cathode and the anode, and a plurality of metal interconnectors (5) each positioned between two adjacent electrochemical cells (1), wherein each interconnector (5) has two main planes, and the first of the two main planes (P1) includes a grid-like metal coating layer (GN) that forms a contact layer with the electrochemical cells (1), the method being: A step of spot welding (S) a metal coating layer (GN) to the first surface (P1) of the interconnect (5) to enable its fixation, A method comprising the step of depositing an adhesive at the outer edge of the coating layer (GN), away from the active region and away from the gas supply, with the intention of fixing an electrochemical cell (1), wherein the adhesive comprises 5% to 50% by mass of polyvinyl butyral (PVB), 5% to 50% by mass of terpineol, and 5% to 95% by mass of ethanol.

2. The method according to claim 1, characterized in that the metallic material of the coating layer (GN) is selected from nickel (Ni) and its alloys, or chromia-forming alloys whose basic element is iron (Fe).

3. The method according to claim 2, characterized in that the coating layer (GN) is in the form of a nickel grid (GN).

4. The method according to any one of claims 1 to 3, characterized in that at least four welding spots (S) are formed by evenly distributing several welding spots (S) on the outer edge of the coating layer (GN).

5. The method according to any one of claims 1 to 3, characterized by including a step of depositing a glass layer (V) on a coating layer (GN) before the adhesive deposition step.

6. The method according to any one of claims 1 to 3, characterized in that each interconnector (5) has two main planes, and the second surface (P2) of the main planes includes a thick ceramic coating layer that forms a contact layer with the electrochemical cell (1).

7. The method according to claim 6, characterized in that the ceramic material is selected from strontium-doped lanthanum oxide of the formula La 1-x Sr x MO 3 (M (transition metal) = nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr)) as a single or mixed material, or a lamellar structure material containing lanthanide nickelate of the formula Ln 2 NiO 4 (Ln = lanthanum (La), neodymium (Nd), praseodymium (Pr)), or another conductive perovskite oxide.

8. The method according to any one of claims 1 to 3, characterized in that each interconnector (5) is formed by an assembly of at least three plates (21, 22, 23) stretched along mutually orthogonal first and second axes of symmetry (X and Y), and a central plate (22) is inserted between the first end plate (21) and the second end plate (23).

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