SOEC / SOFC solid oxide cells with inner guide elements.

Abstract

The main subject of the invention is a stack of SOEC / SOFC solid oxide cells, said stack consisting of a number of stacked plates (P) and including two guide elements (11, 12) ensuring that the vertical stacking of at least some of the plates (P) is guided, each plate (P) having two guide openings (O1, O2), characterized in that in the stack, seen in cross section, the guide openings are spaced apart by a minimum inter-opening distance (Do1) next to each other in a first horizontal direction (X) and the guide elements (11, 12) are spaced apart by a larger minimum inter-element distance (Dt1), the difference of which corresponds to an identical inner gap (Jm1) for the two guide openings, and that the guide openings (O1, O2) are spaced apart by a maximum inter-opening distance (Do2) and the guide elements (11, 12) are spaced apart by a smaller maximum inter-element distance (Dt2), the difference of which corresponds to an outer gap (Jm2) that is larger than the inner gap (Jm1).

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 or high-temperature co-electrolysis of water steam and carbon dioxide (CO2), known by the English names "High-Temperature Electrolysis" (HTE) and "High-Temperature Steam Electrolysis" (HTSE), respectively.

[0002] More particularly, the invention relates to the field of high-temperature solid oxide electrolysis devices, commonly referred to by the acronym SOEC, which stands for "Solid-Oxide Electrolysis Cell" in English.

[0003] This also relates to the field of high-temperature solid oxide fuel cells, usually referred to by the acronym SOFC, which stands for "Solid-Oxide Fuel Cells" in English.

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

[0005] More particularly, the present invention relates to a SOEC / SOFC type solid oxide cell stack including an inner guide element, as well as an associated conditioning process. [Background technology]

[0006] In the context of a SOEC-type high-temperature solid oxide electrolyzer, water vapor (H2O) is converted to dihydrogen (H2) and dioxygen (O2) and / or carbon dioxide (CO2) is converted to carbon monoxide (CO) and dioxygen (O2) by an electric current in the same electrochemical device. In the context of a SOFC-type high-temperature solid oxide fuel cell, the operation is reversed to generate electric current and heat by feeding dihydrogen (H2) or other fuels such as methane (CH4), natural gas, biogas, and dioxygen (O2), for example the dioxygen contained in air. For simplicity, the following description gives priority to the operation of a SOEC-type high-temperature solid oxide electrolyzer performing electrolysis of water vapor. Nevertheless, this operation is applicable to the electrolysis of carbon dioxide (CO2) or to the co-electrolysis of water vapor and carbon dioxide (CO2) at high temperatures. In addition, this operation can be transposed to the case of a SOFC-type high-temperature solid oxide fuel cell.

[0007] To perform water electrolysis, it is advantageous to do this at high temperatures, usually between 600 and 1000 °C, because it is more advantageous to electrolyze water vapor than liquid water, and because part 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), the SOEC-type high-temperature solid oxide electrolyzer consists of a stack of basic units, each of which contains a solid oxide electrolysis cell, or electrochemical cell, consisting of three anode / electrolyte / cathode layers stacked on top of each other, and an interconnect plate, also called a bipolar plate or interconnector, made of a metal alloy. Each electrochemical cell is sandwiched between two interconnect plates. The SOEC-type high-temperature solid oxide electrolyzer is then an alternating stack of electrochemical cells and interconnectors. The SOFC-type high-temperature solid oxide fuel cell consists of a stack of the same type of basic units. This high-temperature technology is reversible, so the same stack can operate in electrolysis mode to produce hydrogen and oxygen from water and electricity, or in fuel cell mode to produce electricity from hydrogen and oxygen.

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

[0010] The electrical and fluidic interconnection device is an electronic conductor that ensures, from an electrical point of view, the connection of the electrochemical cells of each basic unit in the stack of basic units, the electrical contact between one face of the cell and the cathode and between the other face of the next cell and the anode, and, from a fluidic point of view, the supply of reagents and the discharge of products for each of the cells. The interconnect thus ensures the function of supplying and collecting electric current and separates the gas circulation chambers for distribution and / or collection.

[0011] More specifically, the main function of the interconnector is to ensure not only the passage of electric current but also the circulation of gases (i.e., injected steam, extracted hydrogen and oxygen for HTE electrolysis, air and fuel with injected hydrogen and extracted water for SOFC cells) near each cell, as well as to separate the anode and cathode chambers of two adjacent cells, which are the gas circulation chambers on the anode and cathode sides of the cells, respectively.

[0012] In particular, in a SOEC type high temperature solid oxide electrolyser, the cathode chamber contains water vapor and hydrogen produced from the electrochemical reaction, while the anode chamber contains exhaust gases, if present, and oxygen, another product of the electrochemical reaction. In a SOFC type high temperature solid oxide fuel cell, the anode chamber contains the fuel, while the cathode chamber contains the fuel.

[0013] To perform high temperature steam electrolysis (HTE), water vapor (HO) is injected into the cathode chamber. Under the effect of an electric current applied to the cell, dissociation of water molecules in the form of water vapor takes place at the interface between the hydrogen electrode (cathode) and the electrolyte, which dissociates into dihydrogen gas (H2) and oxygen ions (O2- ) is produced. Dihydrogen (H2) is collected and discharged at the exit of the hydrogen chamber. Oxygen ions (O 2- ) migrates through the electrolyte and recombines into dioxygen (O2) at the interface between the electrolyte and the oxygen electrode (anode). The oxygen produced in gas form can be collected at the anode, as an exhaust gas, such as air, circulates at the anode.

[0014] To ensure the operation of a solid oxide fuel cell (SOFC), air (oxygen) is injected into the cathode chamber of the cell and hydrogen into the anode chamber. The oxygen in the air is O 2- The hydrogen dissociates into hydrogen ions. These ions move through the electrolyte from the cathode to the anode and oxidize the hydrogen, forming water and simultaneously producing electricity. In a SOFC cell, the water vapor is in the dihydrogen compartment (H2), just like in a SOEC electrolysis. Only the polarity is reversed.

[0015] For illustrative purposes, a schematic diagram illustrating the working principle of an SOEC type high temperature solid oxide electrolyser is shown in Figure 1. The function of such an electrolyser 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 electrolyser. As shown diagrammatically in FIG. 1, each elementary electrolysis cell 1 is formed 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 electronic and / or ionic conductors, made of porous materials, and the electrolyte 3 is gas-tight, an electronic insulator and an ionic conductor. In particular, the electrolyte 3 is an anion conductor, more specifically O 2- The electrolysis device can then be a proton electrolyte (H + ) are called anion electrolysis devices.

[0017] The electrochemical reactions take place at the interfaces between each of the electronic conductors and the ionic conductor.

[0018] At cathode 2 the half-reactions are: 2H2O + 4e - → 2H2+ 2O 2-

[0019] At anode 4, the half-reactions are: 2O 2- → O2+ 4e -

[0020] The electrolyte 3 interposed between the two electrodes 2 and 4 converts O 2- This is the site where ions move.

[0021] Water vapor can accompany the hydrogen H2 at the cathode inlet and water vapor can accompany the hydrogen produced and collected at the outlet, as shown in brackets in Figure 1. Similarly, an exhaust gas such as air can be injected at the anode side inlet to evacuate the produced oxygen, as shown by the dotted line. An additional function of the injection of the exhaust gas is to act as a thermal moderator.

[0022] The basic electrolysis device, or electrolysis reactor, consists of a basic cell as described above, with a cathode 2, an electrolyte 3 and an anode 4, as well as two interconnects ensuring the functions of electrical and fluid distribution.

[0023] To increase the flow rate of hydrogen and oxygen produced, it is known to stack several elementary electrolysis cells one on top of the other, separated by an interconnector, and this assembly is placed between two end interconnect plates that support the power supply and the gas supply of the electrolyzer (electrolysis reactor).

[0024] Thus, a high-temperature solid oxide electrolyser of the SOEC type comprises at least one, and usually several, electrolysis cells stacked one on top of the other, each elementary cell being formed by an electrolyte, a cathode and an anode, the electrolyte being interposed between the anode and the cathode.

[0025] As previously indicated, a fluidic and electrical interconnect device in electrical contact with one or more electrodes generally provides current supply and collection functions and defines one or more gas circulation chambers.

[0026] The function of the so-called cathode compartment is therefore the distribution of electric current and of water vapor, as well as the recovery of hydrogen in contact with the cathode.

[0027] The function of the so-called anode chamber is the distribution of the electric current as well as the recovery of the oxygen produced at the adjacent anode, possibly with the aid of exhaust gases.

[0028] 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 elementary electrolysis cells C1, C2 of the solid oxide cell (SOEC) type, stacked one on top of the other 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 arranged (only the electrolyte 3.2 of cell C2 is shown).

[0029] The interconnector 5 is a part made of a metal alloy that ensures the separation between the cathode chamber 50 and the anode chamber 51, defined by the volumes 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 the distribution of gas to the cells. The injection of water vapor to each basic unit is carried out in the cathode chamber 50. The collection of the hydrogen produced in the cathodes 2.1, 2.2 and of the residual vapor is carried out in the cathode chamber 50 downstream of this, after the dissociation of the water vapor by the cells C1, C2. The collection of the oxygen produced in the anode 4.2 is carried out in the anode chamber 51 downstream of this, after the dissociation of the water vapor by the cells C1, C2. The interconnector 5 ensures the passage of electric current between the cells C1 and C2 by direct contact between the adjacent electrodes, i.e. the anode 4.2 and the cathode 2.1.

[0030] To ensure good electrical contact between all of the interconnects, the electrochemical cells and the interconnects are sandwiched between two rigid plates, the so-called upper and lower end plates, which are electrically insulated from the interconnects. The sandwich thus formed is the so-called "stack" and therefore corresponds to an assembly comprising upper and lower end plates, the electrochemical cells and the interconnects. This stack should be kept under compressive force to ensure good electrical continuity of the contact surfaces between the plates.

[0031] During the first stage of stack fabrication, the formation of the glass-ceramic seal is facilitated by subjecting the stack to a thermal cycle, called the conditioning cycle, while a controlled compressive force is applied to the stack.

[0032] In fact, the various seals between the circuits are ensured by seals made of molten glass. This molten glass is obtained by depositing a slip, a precursor of glass. The slip is deposited in the form of beads sandwiched between the interconnect plates (or interconnectors). This slip is then dried in place to create beads of glass powder supplemented with an organic binder. Thus, when cold, the interconnect plates are separated by dry slip beads, before the temperature increase cycle that will form the glass. These beads will melt during the heating cycle, establishing contacts in the aforementioned reaction zones. As a result of the melting of the beads, the thickness of the slip beads can be reduced by more than 50%. These beads can also be made of already dense glass sandwiched between two successive interconnectors of the stack. Just as during the conditioning cycle with the dry slip beads, the melting of the glass seal will cause the space between the interconnectors to shrink, but to a lesser extent than the slip.

[0033] In both cases, it is important to ensure guidance according to a direction perpendicular to the plane of the interconnects or collinear with the direction of the compressive forces of the interconnection plates and of the end plates. Such guidance makes it possible to ensure that the components of the stack (especially the interconnects, the insulating plates, the end plates) remain correctly aligned relative to one another during the shrinkage of the stack, which occurs during the forming of the glass. During this stage, the height of the stack is effectively reduced by 50%, which results in a significant vertical movement of the stack.

[0034] The development of industrial systems incorporating high-temperature electrolysers entails an increase in the volume of gas to be processed (in SOEC or SOFC). To do so, an increase in the surface area, the number of cells and of interconnects is necessary. However, a significant increase in the number of plates and therefore in the height of the stack creates many technical difficulties, especially during the manufacturing phase. Indeed, the greater the stack height, the greater the amplitude of shrinkage during the conditioning phase, making the control of the guidance more critical.

[0035] In the current design, this guidance is ensured by cylindrical columns placed inside the stack structure passing through different plates, in which cylindrical or rectangular holes are machined that closely match the diameter of the columns, the bases of these columns being mechanically blocked in the lower end plate.

[0036] This type of device has various limitations related to the small diameter of the guide posts imposed by the internal structure of the interconnector. Obtaining a satisfactory guiding of a large number of thin plates over a large height by this type of post involves a fine control of the relative gap between the posts and the diameter of the through holes. With the small gap, this type of assembly is exposed to the risk of mis-centering during rotation, which may occur during the cycle of formation of the sealing glass ceramic, during which the stack undergoes a significant contraction of its height. It should be noted that the forces applied to ensure the contact of the different plates are not very large, so that any inadvertent jamming of a plate against its guiding elements becomes problematic.

[0037] For the sake of illustration, Figures 3A and 3B show a current guiding solution. Two pillars 11 and 12 are used to guide the plates P of the stack 20 (shown here very diagrammatically) during their descent. The plates P can consist of interconnecting plates, insulating plates or lower and upper end plates. In this case, in Figure 3B, for example, two interconnecting plates P are considered, other possible interconnecting and insulating plates as well as lower and upper end plates are therefore not shown.

[0038] On one side, openings O1 of circular cross section are used, with a very fine adjustment between the plates P and the columns 11, for example the gap J1 being in the range of 0.1 mm. On the other side, openings O2 in the plates P have a rectangular cross section, leaving a larger gap J2. Then, as the glass-ceramic seal melts, a slight bending of these plates P is caused by lowering them by pressing in the middle, as per the arrow F, which may cause a misalignment blockage, represented by AC in FIG. 3B, at the columns 11 with a tight adjustment. In fact, to avoid the risk of misalignment of AC, the gap J1 around the guiding columns 11 can be increased considerably, but this is not desirable, as it would then radically reduce the guiding function.

[0039] There is therefore a need to propose an effective guiding solution that makes it possible to avoid this decentering problem while maintaining the guiding accuracy during shrinkage of the stack of plates. Summary of the Invention [Problem to be solved by the invention]

[0040] The present invention aims to at least partially address the above-mentioned needs and shortcomings associated with prior art embodiments. [Means for solving the problem]

[0041] The object of the present invention is therefore, according to one of its aspects, a stack of solid oxide cells of the SOEC / SOFC type operating at high temperatures, consisting of a plurality of plates stacked one on top of the other according to a vertical direction substantially perpendicular to the horizontal extent of each plate, said plurality of plates having at least: a plurality of electrochemical cells each formed of a cathode, an anode, and an electrolyte interposed between the cathode and the anode, and a plurality of interconnectors each disposed between two adjacent electrochemical cells; an upper end plate and a lower end plate having a plurality of electrochemical cells and a plurality of interconnects sandwiched therebetween; Including, the stack further comprises at least two guiding elements ensuring guiding of at least some of the plates into a vertical stack, each plate of said at least a portion of the plates includes at least two guide openings opening onto the upper and lower faces of each plate respectively and allowing the passage of said at least two guide elements; In the stack: when observed in cross section in the horizontal extent of each plate of said at least some of the plates, said at least two guide openings are aligned according to a first horizontal direction and spaced apart by a minimum inter-opening distance, and said at least two guide elements are spaced apart by a minimum inter-element distance that is greater than said minimum inter-opening distance, the difference between the minimum inter-element distance and the minimum inter-opening distance corresponding to an inner gap and being the same for said at least two guide openings and for said at least two guide elements, According to a first horizontal direction, the at least two guide openings are spaced apart by a maximum inter-opening distance, and the at least two guide elements are spaced apart by a maximum inter-element distance that is smaller than the maximum inter-opening distance, the difference between the maximum inter-opening distance and the maximum inter-element distance corresponding to an outer gap; and The outer gap is characterized by being larger than the inner gap.

[0042] The stack according to the invention may further comprise one or more of the following features, considered separately or according to any technically possible combination:

[0043] Advantageously, the inner gap is greater than 0, in particular greater than 0.6 μm, in particular comprised between 1 μm and 100 μm.

[0044] Advantageously, the outer gap is larger than the inner gap, in particular being comprised between 0.5 mm and 3 mm.

[0045] The ratio between the outer gap and the inner gap is greater than 30 and may in particular be comprised between 30 and 500.

[0046] The value of the inner and / or outer gap may depend on the thickness of the plates and also on their possible or permitted inclination due to local solid movements or due to deformations, especially during bending. The determination of this value also depends on the level of the pressing force and the stiffness of the plates.

[0047] In addition, the outer gap may be the same for said at least two guide openings and said at least two guide elements.

[0048] The at least two guide openings may have the same shape and the same dimensions.

[0049] Furthermore, the at least two guide openings have an elongated or circular or polygonal cross section, in particular a square or rectangular cross section, and in particular form an angle different from 90°, in particular greater than 90°, at least closest to the center of the plate.

[0050] Furthermore, each plate of said at least some of the plates may be square or rectangular.The at least two guide openings may be diagonally opposite each other.

[0051] The at least two guide elements may consist of guide rods having a cylindrical shape, in particular a circular cross section.

[0052] Furthermore, when observed in cross section in the horizontal extent of each plate of at least a portion of the plates, the maximum guide opening dimension of each guide opening according to a second horizontal direction perpendicular to the first horizontal direction can be greater than the maximum guide element dimension of each guide element measured according to the second horizontal direction.

[0053] In addition, the ratio between the maximum guide opening dimension and the maximum guide element dimension, measured according to the second horizontal direction, can be comprised between 1 and 3. This ratio can be determined according to various parameters such as, inter alia, the plate thickness, the plate stiffness, the possible plate inclination. This determination is carried out by mechanical calculations with geometric criteria that ensure the existence of a functional gap, taking into account the solid movements of the mechanical element as well as any deformations thereof.

[0054] Furthermore, another object of the invention, according to another of its aspects, is a method for packaging a stack of solid oxide cells of the SOEC / SOFC type operating at high temperatures as defined previously, characterized in that it comprises a step of guiding at least some of the plates constituting the stack into a vertical stack by means of said at least two guiding elements.

[0055] The guiding step may be performed while keeping a gap between the at least two guiding elements and the at least two guiding openings substantially constant.

[0056] Additionally, the at least two guiding elements are fixed in a packaging base, and the method can include using the same thermal expansion coefficient for the material of the plate and of the adjustment base.

[0057] In particular, the materials used for the plate and the packaging base may be the same so as to have the same thermal expansion coefficient, or may be different but have the same thermal expansion coefficient.

[0058] The invention can be better understood on reading the following detailed description of non-limiting examples of its implementation and on examining the accompanying schematic and partial figures. [Brief description of the drawings]

[0059] [Figure 1] FIG. 1 is a schematic diagram showing the operating principle of a high temperature solid oxide electrolyzer (SOEC). [Diagram 2] FIG. 1 is an exploded schematic view of a portion of a high temperature solid oxide electrolyzer (SOEC) including an interconnect according to the prior art. [Figure 3A] 1 shows, according to a top view, a schematic and partial representation of a prior art principle for guiding the plates of a high-temperature stack of the SOEC / SOFC type; [Figure 3B] 1 shows, according to a side view, a schematic and partial representation of a prior art principle for guiding the plates of a high-temperature stack of the SOEC / SOFC type; [Figure 4A] 1 shows, according to a top view, a schematic and partial representation of an example according to the invention for guiding the plates of a high-temperature stack of the SOEC / SOFC type; [Figure 4B] 1 shows, according to a side view, a schematic and partial representation of an example according to the invention for guiding the plates of a high-temperature stack of the SOEC / SOFC type; [Figure 4C] FIG. 4B is an enlarged view of C in FIG. 4A. [Figure 4D] FIG. 4B is an enlarged view of D in FIG. 4A. [Figure 5A] FIG. 2 shows, according to a top view, a schematic and partial view of another example according to the invention for guiding the plates of a high-temperature stack of the SOEC / SOFC type. [Figure 5B] FIG. 5B is an enlarged view of B1 in FIG. 5A. [Figure 6A] 3 shows, according to a top view, a schematic and partial view of yet another example according to the invention for guiding the plates of a high-temperature stack of the SOEC / SOFC type; [Figure 6B] FIG. 6B is an enlarged view of B2 in FIG. 6A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] In all these figures, the same reference numbers may indicate the same or similar elements.

[0061] In addition, in order to make the figures more readable, the different parts shown in the figures are not necessarily plotted according to uniform scale.

[0062] Figures 1 to 3 have already been described above in the prior art and in the section relating to the technical context of the present invention. It is clearly indicated that in Figures 1 and 2, symbols and arrows for the steam supply H2O, for the distribution and recovery of dihydrogen H2, oxygen O2, air and electric current are shown for the purposes of clarity and precision to explain the operation of the illustrated device.

[0063] Furthermore, it should be noted that all of the components (anode / electrolyte / cathode) of a given electrochemical cell are preferably ceramic, and the operating temperatures of SOEC / SOFC type high temperature stacks are usually comprised between 600 and 1000° C.

[0064] Additionally, any of the terms "upper", "lower", "horizontal" and "vertical" used herein should be understood according to the conventional direction of orientation of the SOEC / SOFC type stack when in its configuration of use.

[0065] 4A to 6B make it possible to illustrate the guidance principle according to the invention.

[0066] First, Figures 4A to 4D show a first possibility for guiding the plates P of a stack 20 of SOEC / SOFC type high-temperature solid oxide cells into the stack, in which the plates P are arranged one on top of the other according to a vertical direction substantially perpendicular to the extent of each horizontal surface of each plate P.

[0067] It should be noted that in all of the examples described herein, the plate P may in particular correspond to an electrochemical cell C1, C2, an interconnector 5, an upper or lower end plate, or an insulating plate. Preferably, the plate P will usually be the interconnector 5.

[0068] Guidance to vertical stacking is here performed using two guide elements 11 and 12 in the form of guide rods or pillars, which are here spaced diagonally apart on each square plate P, although this choice is not limiting.

[0069] In addition, each plate P includes two guide openings O1 and O2 opening respectively onto the upper face FS and the lower face FI of each plate P. These guide openings O1, O2 allow the passage of guide posts 11, 12, which are also here spaced diagonally apart on each plate P, although this choice is not limiting.

[0070] When packaging the stack 20, a vertical compressive force is applied thereto. This force is usually located between the guide posts 11, 12, which may cause bending of the stacked plates P, as shown by the arrow F in Fig. 3B and here in Fig. 4B. If the plates P come into contact with the posts 11, 12, as previously shown in Fig. 3B, the undesirable off-centering phenomenon of AC may occur.

[0071] 4A to 4D, the configuration proposed according to the invention, when viewed in cross section in the horizontal extent of each plate P, has guide openings O1, O2 aligned along a first horizontal direction X and spaced apart by a minimum inter-opening distance Do1. In addition, the guide pillars 11, 12 are spaced apart by a minimum inter-element distance Dt1 that is greater than the minimum inter-opening distance Do1.

[0072] The difference between the minimum inter-element distance Dt1 and the minimum inter-opening distance Do1 corresponds to the inner gap Jm1, which is the same at the level of each pair of guide opening and guide post O1,11 and O2,12.

[0073] Further, in accordance with the first horizontal direction X, the guide openings O1, O2 are spaced apart by a maximum inter-opening distance Do2, and the guide pillars 11, 12 are spaced apart by a maximum inter-element distance Dt2 that is smaller than the maximum inter-opening distance Do2.

[0074] The difference between the maximum inter-opening distance Do2 and the maximum inter-element distance Dt2 corresponds to the outer gap Jm2, which is advantageously larger than the inner gap Jm1.

[0075] As a result, the bending of the plate P, as shown by the arrow F in Fig. 4B, will be in a direction facilitating its vertical descent here. Indeed, during bending, the minimum inter-opening distance Do1 measured according to the first horizontal direction X, i.e. the distance between the points A1 and A1', will decrease due to the bending of the plate P, which will tend to free the vertical movement of the plate P, since the minimum inter-element distance Dt1, measured according to the first horizontal distance X always between the two pillars 11 and 12, remains constant. The resulting inner gap Jm1' (see Fig. 4B) will therefore increase compared to the gap Jm1.

[0076] Similarly, the maximum inter-opening distance Do2, i.e. the distance between points A2 and A2', will also decrease upon bending as shown in Fig. 4B. However, due to the presence of the outer gap Jm2, which is much larger than the inner gap Jm1, and because the maximum inter-element distance Dt2 does not change, there is no contact between the plate P and the columns 11, 12 and therefore no jamming or off-centering phenomenon.

[0077] To avoid any interruption of the plate P on the pillars 11, 12, the inner gap Jm1 may be comprised between 1 μm and 100 μm.

[0078] Similarly, the outer gap Jm2 may be comprised between 0.5 mm and 3 mm.

[0079] In particular, with a minimum inter-opening distance Do1 in the range of 300 mm and a plate height H in the range of 0.6 mm, the gap Jm1 can be made larger than 0.6 μm so as to avoid any blockage in the local solid movement of the plate P. This corresponds to a very small gap value and therefore allows a very accurate guiding and thus positioning of the plate P relative to the guide posts 11, 12.

[0080] It should also be noted that, advantageously, the outer gap Jm2 is identical for the two guide openings O1, O2 and the two guide posts 11, 12.

[0081] Also, in this example of Figures 4A-4B, each of the guide openings O1, O2 has an oval cross section. In this case, the dimensional ratio between the maximum guide opening dimension do2 of each guide opening O1, O2 according to a second horizontal direction Y perpendicular to the first horizontal direction X, i.e. the distance between points B1 and B2 or between points B1' and B2' in the examples of Figures 4C and 4D, and the maximum guide element dimension dt2 of each guide element 11, 12 measured according to the second horizontal direction Y, i.e. the diameter passing through the center O of the pillars 11, 12, as shown here, for example, in Figures 5B and 6B, may be too close to 1. In other words, the distances B1B2 and B1'B2' may be substantially equal to the diameter of the pillars 11, 12.

[0082] Then, there may be a center shift at the oval points B1, B1', B2 and B2' (see Figures 4C and 4D) if the plate P rotates according to the first horizontal direction X. To avoid this phenomenon, another configuration according to the invention can be proposed.

[0083] 5A and 5B, the guide openings O1, O2 thus correspond to a cylinder whose circular cross section is larger than that of the posts 11, 12. In other words, the diameter of each guide opening O1, O2 is larger than the diameter of each guide post 11, 12. The guide openings O1, O2 are eccentric with respect to the guide posts 11, 12.

[0084] At points A1 and A1' a tight fit is maintained, but at points B1, B2, B1' and B2' there is a larger gap.

[0085] In particular, the maximum guide opening dimension do2 of each guide opening O1, O2 according to a second horizontal direction Y, which in the example of Figures 5A and 5B is different at a distance B1B2 or B1'B2' in this specification, is greater than the maximum guide element dimension dt2 of each guide pillar 11, 12, i.e. its diameter passing through the centre O in this specification.

[0086] Advantageously, the ratio between the maximum guide opening dimension do2 and the maximum guide element dimension dt2, measured according to the second horizontal direction Y, is comprised between 1 and 3.

[0087] A third possible configuration of the invention, shown in FIGS. 6A and 6B, consists in using larger, substantially square-shaped guide openings O1, O2 that are eccentric with respect to the position of the posts 11, 12.

[0088] This configuration illustrates a similar principle to Figures 5A and 5B, however, here we use "V" shaped contacts (A1, O, A2) as shown in Figure 6B.

[0089] This configuration prevents rotation according to the third vertical direction Z, and still retains the advantage of avoiding any contact between the plate P and the columns 11, 12 during stacking vertically downwards during the process of packaging the stack 20, due to the shortening of the distances A1A1' or A2A2'. Any off-centering problems are thus avoided. The angle α closest to the center of the plate P, i.e. the angle α of the two contact surfaces, can be variable. Advantageously, it is chosen to be different from 90°, in particular greater than this value, so as to allow a little more possibility of rotation according to the directions X and Z.

[0090] During the process of packaging such a stack 20, in particular during the temperature rise, a substantially constant difference should be kept between the guide posts 11, 12 and the guide openings O1, O2. This difference should be able to remain greater than 0. To ensure this, the thermal expansions governing both the size of the posts 11, 12 and the size of the plate P should be balanced, in particular by a careful choice of the thermal expansion coefficients of the materials used and by a temperature field that is as homogeneous as possible throughout the assembly.

[0091] Advantageously, the guide posts 11, 12 will be fixed in the packaging base, and one or more of the same materials will be used for the plate P and for the adjustment base in order to obtain the same thermal expansion coefficient.

[0092] The present invention finds its main application in the assembly of high temperature stacks, mainly of the SOEC / SOFC type, and in particular is applicable during the conditioning phase, during which the size of the stack is significantly reduced due to the melting of the glass joints of the assembly, as previously described in the prior art and in the section relating to the technical context of the invention.

[0093] Of course, the invention is not limited to the embodiment just described, as various modifications thereto can be made by those skilled in the art. [Explanation of symbols]

[0094] 20 Stack 11, 12 Guidepost 5 Interconnector P-Plate C1, C2 electrochemical cells O1, O2 guide opening FS top surface FI bottom Do1 Minimum opening distance Dt1 Minimum element distance Do2 Maximum distance between openings Dt2 Maximum element distance Jm1, Jm1' inner gap Jm2 Outer gap do2 Maximum guide opening size dt2 Maximum guide element size

Claims

1. A stack (20) of solid oxide cells of the SOEC / SOFC type operating at high temperatures, comprising a plurality of plates (P) stacked one on top of the other according to a vertical direction substantially perpendicular to the extent of each horizontal surface of each plate (P), said plurality of plates (P) having at least: A plurality of electrochemical cells (C1, C2), each formed of a cathode, an anode, and an electrolyte interposed between the cathode and the anode, and a plurality of interconnectors (5) respectively disposed between two adjacent electrochemical cells (C1, C2); an upper end plate (P) and a lower end plate (P) between which the electrochemical cells (C1, C2) and the interconnectors (5) are sandwiched; Including, said stack (20) further comprises at least two guiding elements (11, 12) ensuring the guiding of at least some of said plates (P) into a vertical stack, each plate (P) of said at least part of said plates (P) comprises at least two guide openings (O1, O2) opening respectively on the upper face (FS) and on the lower face (FI) of each plate (P) and allowing the passage of said at least two guide elements (11, 12); In the stack (20), when observed in cross section in the horizontal extent of each plate (P) of said at least some of said plates (P), said at least two guide openings (O1, O2) are arranged side by side according to a first horizontal direction (X) and spaced apart by a minimum inter-opening distance (Do1), and said at least two guide elements (11, 12) are spaced apart by a minimum inter-element distance (Dt1) that is greater than said minimum inter-opening distance (Do1), the difference between said minimum inter-element distance (Dt1) and said minimum inter-opening distance (Do1) corresponding to an inner gap (Jm1) and being identical for said at least two guide openings (O1, O2) and for said at least two guide elements (11, 12), According to the first horizontal direction (X), the at least two guide openings (O1, O2) are spaced apart by a maximum inter-opening distance (Do2), and the at least two guide elements (11, 12) are spaced apart by a maximum inter-element distance (Dt2) that is smaller than the maximum inter-opening distance (Do2), the difference between the maximum inter-opening distance (Do2) and the maximum inter-element distance (Dt2) corresponding to an outer gap (Jm2); The outer gap (Jm2) is larger than the inner gap (Jm1), Stack(20).

2. Stack according to claim 1, characterized in that said inner gap (Jm1) is comprised between 1 μm and 100 μm.

3. Stack according to claim 1 or 2, characterized in that the outer gap (Jm2) is comprised between 0.5 mm and 3 mm.

4. 4. A stack according to claim 1, characterized in that the outer gap (Jm2) is identical for the at least two guiding openings (O1, O2) and for the at least two guiding elements (11, 12).

5. 5. A stack according to claim 1, characterized in that the at least two guiding openings (O1, O2) have the same shape and the same dimensions.

6. 6. A stack according to claim 5, characterized in that said at least two guiding openings (O1, O2) are elongated in cross section.

7. 7. A stack according to claim 6, characterized in that said at least two guiding openings (O1, O2) are circular in cross section.

8. 7. The stack according to claim 6, characterized in that the at least two guiding openings (O1, O2) are polygonal in cross section, in particular square or rectangular, and in particular at least the angle (α) closest to the centre of the plate (P) forms an angle different from 90°, in particular greater than 90°.

9. 9. A stack according to claim 1, characterized in that each plate (P) of at least a portion of the plates (P) is square or rectangular and that the at least two guiding openings (O1, O2) are diagonally opposite each other.

10. 10. A stack according to any one of the preceding claims, characterized in that the at least two guide elements (11, 12) are guide rods (11, 12) having a cylindrical shape, in particular a circular cross section.

11. 11. A stack according to claim 1, characterized in that, when observed in cross section in the horizontal extent of each plate (P) of at least a portion of said plates (P), the maximum guide opening dimension (do2) of each guide opening (O1, O2) according to a second horizontal direction (Y) perpendicular to said first horizontal direction (X) is greater than the maximum guide element dimension (dt2) of each guide element (11, 12) measured according to said second horizontal direction (Y).

12. Stack according to claim 11, characterized in that the ratio between the maximum guide opening dimension (do2) and the maximum guide element dimension (dt2), measured according to the second horizontal direction (Y), is comprised between 1 and 3.

13. 13. A method for packaging a stack (20) of solid oxide cells of the SOEC / SOFC type operating at high temperatures according to any one of claims 1 to 12, characterized in that it comprises a step of guiding at least a part of the plates (P) constituting the stack (20) into a vertical stack by means of the at least two guiding elements (11, 12).

14. 14. Method according to claim 13, characterized in that the guiding step is performed while keeping a gap between the at least two guiding elements (11, 12) and the at least two guiding openings (O1, O2) substantially constant.

15. 15. The method according to claim 13 or 14, characterized in that the at least two guiding elements (11, 12) are fixed in a packaging base, the method comprising the step of using the same thermal expansion coefficient for the material of the plate (P) and of the adjustment base.

Images