Electrochemical cell with structured support electrode

Abstract

The invention relates to an electrochemical cell unit comprising, in the following order in the direction of the thickness thereof: - a support hydrogen electrode comprising a first surface and a second surface opposite one another; - a solid electrolyte comprising a first surface and a second surface opposite one another, the first surface of the solid electrolyte facing the second surface of the hydrogen electrode; and - an oxygen electrode comprising a first surface and a second surface opposite one another, the first surface of the oxygen electrode facing the second surface of the solid electrolyte, wherein the support hydrogen electrode comprises at least one gas circulation channel formed as a recess that opens onto the first surface of the hydrogen electrode without opening onto the second surface of the hydrogen electrode. The invention relates to the optimisation of a solid oxide cell, including solid oxide fuel cells and solid oxide electrolyser cells.

Description

[0001] “Electrochemical cell with structured support electrode”

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the optimization of a solid oxide cell called SOC for Solid Oxide Cell in English and in particular of the support electrode by its structuring. This type of cell is used in systems for producing electricity from hydrogen and oxygen (solid oxide fuel cell or cell called SOFC for Solid Oxide Fuel Cell) or hydrogen and oxygen from water vapor (solid oxide electrolyzer cell called SOEC for Solid Oxide Electrolysiser Cells).

[0004] STATE OF THE ART

[0005] An SOC electrochemical cell is schematically represented by 3 layers, i.e. 2 electrodes separated by an electrolyte. The electrodes are the site of electrochemical reactions, and are electronically conductive, or even mixed electronic / ionic, while the electrolyte is only ionically conductive.

[0006] SOFC fuel cells are electrochemical cells that produce electrical and thermal energy and use the chemical energy generated by the reaction of water formation from hydrogen and oxygen. The operating principle of a SOFC cell is based on the following mechanism: oxygen from the air, which is supplied to the cathode, is dissociated to give O2- anions. The anions thus formed migrate through the electrolyte until they reach the anode where they oxidize the hydrogen atoms that are supplied by the fuel. This reaction releases electrons and water.

[0007] A cell operating as a SOEC (Solid Oxide Electrolysiser Cells) is a hydrogen-producing electrochemical cell whose operating principle is strictly the opposite of that of SOFCs. In fact, in the case of a SOEC cell, water vapor is supplied to the cathode and the water molecules are dissociated into hydrogen and O2 anions. The anions thus formed diffuse through the electrolyte to recombine in the form of oxygen at the anode while the hydrogen remains, with the water vapor, at the cathode. This hydrogen can then be recovered for use as fuel in other applications.

[0008] Hydrogen is thus produced with high efficiency, which makes this technology very relevant in the current energy context. Indeed, the increasing use of renewable energies, often intermittent, requires an efficient means of storage, and the hydrogen vector then takes on its full meaning.

[0009] Developments in the materials and shaping processes used to produce electrochemical cells over the past fifteen years have made it possible to achieve high levels of performance. These make high-temperature technology compatible with hydrogen cost targets. However, certain aging mechanisms, linked to the high operating temperature or specific to the high-temperature electrolysis (HTE) operating mode, actually temper the appeal of this new technology. These mechanisms are often relatively difficult to identify and depend on the test conditions (current density, percentage of vapor in the electrolyzed H2O / H2 mixture, conversion rate, temperature, etc.).

[0010] Initially, SOCs were optimized for operation in SOFC fuel cell mode. The reversibility of these electrochemical systems allows them to also operate in SOEC mode, which can also be called EHT, but different reaction mechanisms for these two operating modes result in different polarization or concentration overvoltages. This may also require different architectures and microstructures to supply / remove reactants / reaction products. Regarding the degradation mechanisms, some are identical for these two operating modes, and others are specific to electrolysis. Several steps constituting the reaction mechanism take place within the electrodes and are not always clearly established.A proposed mechanism is as follows: first, water vapor diffuses into the electrode porosity to the nickel sites, triple points (ceramic oxide, nickel, porosity) where the dissociative adsorption of H2O occurs. The produced hydrogen diffuses from the reaction sites to the electrode surface through the electrode porosity. The oxygen adsorbed on the surface of the nickel particles diffuses to the nickel / ionic conductor interface (YSZ). Then, the charge transfer reaction takes place between the adsorbed oxygen and the electronic charges conducted by the nickel.

[0011] Electrodes are highly heterogeneous porous media, the sites of local mechanisms, which explain the macroscopic behavior of electrolysis cells. The microstructure of the electrodes thus plays a key role in the electrochemical performance of the cells. For example, the diffusion of gases through the thick substrate formed by the electrode of a cell induces strong concentration overvoltages which can limit the efficiency of the cell at high current. Furthermore, electrochemical degradations or mechanical damages, which appear during operation under current or during thermal or 'redox' cycles, are often linked to microstructural changes in porous electrodes.

[0012] Therefore, optimizing the microstructure of the electrodes is an essential step towards obtaining high-performance, robust and durable cells.

[0013] SUMMARY OF THE INVENTION

[0014] To achieve this objective, according to one embodiment, an electrochemical cell unit is provided comprising, in the order according to its thickness: - a supporting hydrogen electrode comprising a first surface and a second surface, opposite each other, - a solid oxide electrolyte comprising a first surface and a second surface, opposite each other, the first surface of the solid oxide electrolyte facing the second surface of the supporting hydrogen electrode, and - an oxygen electrode comprising a first surface and a second surface, opposite each other, the first surface of the oxygen electrode facing the second surface of the solid oxide electrolyte, the supporting hydrogen electrode comprising at least one channel for circulating at least one gas,formed in a hollow and opening at the first surface of the supporting hydrogen electrode and without opening at the second surface of the supporting hydrogen electrode.,

[0015] This arrangement has the advantage of allowing a better supply of gas to the electrode and in particular to the hydrogen electrode acting as a support electrode. This structure of the hydrogen support electrode also allows a simplification of the interconnection plates in the cell stack. The presence of this at least one circulation channel, advantageously of a gas such as hydrogen or water vapor, makes it possible to limit the overvoltages linked to the diffusion of hydrogen and water vapor in the support electrode of the cell unit.The distance to be traveled in the support electrode for the gases is reduced, the thickness of the support electrode being reduced at the level of the at least one circulation channel allowing the gases to more easily reach the electrochemical reaction sites which are preferably located in a thickness of 20 μm from the second surface of the support hydrogen electrode advantageously interfacing with the solid oxide electrolyte.

[0016] According to another aspect, the invention relates to a stack comprising at least one electrochemical cell unit as described above, the stack comprises a first interconnector intended to be arranged facing the first surface of the supporting hydrogen electrode and / or a second interconnector intended to be arranged facing the second surface of the oxygen electrode, the first interconnector comprises a first planar surface intended to be facing the first surface of the supporting hydrogen electrode. The configuration of the cell unit makes it possible to provide a stack that does away with diffusion channels in the interconnectors. The interconnectors connecting the different cell units in a stack advantageously have planar surfaces contributing to facilitating their manufacture and limiting their cost.

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0019] Figure 1 shows a cross-sectional view, along the thickness, of a cell unit according to one embodiment of the invention.

[0020] Figure 2 shows a cross-sectional view, along the thickness, of a cell unit according to another embodiment.

[0021] Figure 3 shows a cross-sectional view, along the thickness, of a stack comprising the cell unit according to Figure 1.

[0022] Figure 4 shows a cross-sectional view, along the thickness, of the stack according to a variant of Figure 3.

[0023] Figure 5 represents a front view of the first surface of the hydrogen electrode according to one embodiment. Figure 6 represents a detail view according to Figure 5.

[0024] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, the thicknesses of the layers are not representative of reality.

[0025] DETAILED DESCRIPTION OF THE INVENTION

[0026] Before commencing a detailed review of embodiments of the invention, optional features which may optionally be used in combination or alternatively are set out below:

[0027] - According to one example, the at least one circulation channel 100 has a depth P extending along the thickness Ep of the electrochemical cell unit 1, a width I extending transversely to the thickness Ep and a length L extending transversely to the thickness Ep and to the width I, the at least one circulation channel 100 opening over its entire length L and its width I;

[0028] - According to one example, the at least one circulation channel 100 has a variation in its depth P;

[0029] - According to one example, the at least one circulation channel 100 is arranged in the form of a spiral extending in a plane parallel to the second surface 202 of the support hydrogen electrode 200;

[0030] - According to one example, the electrochemical cell unit 1 comprises a gas inlet arranged at the center 1002 of the spiral;

[0031] - According to one example, the depth P of the circulation channel 100 increases from the center 1002 of the spiral, preferably continuous;

[0032] - According to one example, the at least one circulation channel 100 is formed of grooves arranged parallel to each other and extending in a longitudinal direction perpendicular to the thickness Ep of the electrochemical cell unit 1;

[0033] - According to one example, the grooves have between them a depth P decreasing towards the center 1000 of the electrochemical cell unit;

[0034] - According to one example, the electrochemical cell unit 1 has a density gradient of the grooves, preferably between the center 1000 of the cell unit and its edges 1001, the use of a depth gradient of the at least one circulation channel and a density gradient of the grooves makes it possible to manage the loss of charge within the cell unit and thus to be able to supply certain parts of the cell unit differently in order to have a homogeneous operation of the cell unit in terms of current density;

[0035] - According to one example, the at least one circulation channel 100 has a maximum depth P of 80% of the thickness 10 of the support hydrogen electrode 200, preferably 2 / 3 of the thickness (6) of the support hydrogen electrode 200;

[0036] - According to one example, the at least one circulation channel 100 represents a maximum of 50% of the first surface 201 of the supporting hydrogen electrode 200;

[0037] - According to one example, the electrochemical cell unit opening 1 comprises an interface element arranged facing the first surface 201 of the support hydrogen electrode 200 comprising communicating passages arranged facing said first surface 200;

[0038] - According to one example, the interface element is a contact grid 700 arranged on the first surface 200 of the support hydrogen electrode 200 and advantageously intended to come into contact with an interconnector;

[0039] - According to one example, the interface element is a contact layer 6 comprising at least one complementary channel 603 to the at least one circulation channel 100 of the support hydrogen electrode 200 arranged opposite the first surface 201 of the support hydrogen electrode 200 and advantageously intended to come into contact with an interconnector. With this configuration, the contact between the support hydrogen electrode and the interconnector is sufficient.

[0040] For the remainder of the description, 'top' and 'bottom', or their derivatives, are understood to mean a quality of relative positioning of a cell unit element or of the stack as shown in the figures, the 'top' being oriented away from the ground and the 'bottom' 1 being oriented towards the ground. The upper end is at the top and the lower end is at the bottom.

[0041] Vertical means that which is directed according to the thickness of the stack or cell unit, that is to say according to the main direction of extension of the stack or cell unit, and horizontal means that which is perpendicular to the vertical. The top and the bottom are vertically opposed.

[0042] Transverse means a direction perpendicular to a longitudinal direction. The longitudinal direction means a direction perpendicular to the thickness of the stack or cell unit. A transverse section is a section perpendicular to the longitudinal axis. A transverse section is a section along the thickness of the stack or cell unit. A longitudinal section is a section perpendicular to the thickness of the stack or cell unit.

[0043] A parameter "substantially equal / greater / less than" or "of the order of" a given value means that this parameter is equal / greater / less than the given value, to within plus or minus 10%, or even plus or minus 5%, of this value.

[0044] For the purposes of this disclosure, the expression "A and / or B" means (A), (B) or (A and B). For the purposes of this disclosure, the expression "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0045] The terms "first," "second," and "third," "additional," etc., are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0046] The term "upper" used in particular to describe a face of a layer is here only used to designate the first of the two faces of a layer (the other being the lower face), without making any assumptions about the relative position of the faces, in a vertical direction. The upper face could thus also have been called the front face, as opposed to a rear face.

[0047] The shapes or dimensions given for certain components of the present invention are always only indicative and are understood as including substantially equivalent shapes and dimensions.

[0048] It is specified that in the context of the present invention, the term "on", "overcomes", "covers", "above" or "underlying" or "below" or their equivalents do not necessarily mean "in contact with". For example, the deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but it does mean that the first layer at least partially covers the second layer either by being directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0049] The present invention relates to an electrochemical cell unit 1. The electrochemical cell unit is intended to be used for forming SOFC type solid oxide fuel cells and SOEC solid oxide electrolysers.

[0050] The cell unit 1 comprises a superposition of layers including an anode, a cathode and a solid oxide electrolyte 300 arranged between the anode and the cathode.

[0051] The hydrogen electrode 200 is advantageously the seat of the water reduction reactions or alternatively the hydrogen oxidation reactions. The hydrogen electrode is the electrode near which hydrogen and water vapor circulate.

[0052] According to a preferred possibility, the electrochemical cell unit 1 is of the support electrode type. The term support electrode is understood to mean an electrode which ensures the mechanical support of the cell unit. More precisely, according to the invention it is the hydrogen electrode 200 which preferentially ensures the mechanical support of the cell unit 1. The term support is understood to mean the electrode on which the weight of the rest of the cell unit is exerted. Preferably, the support electrode is the lower electrode of the cell unit. According to this possibility, the hydrogen electrode 200 is a layer with a minimum thickness of the order of 400 μm and for example of the order of 500 μm. Advantageously, the electronic conductivity of the support electrode is greater than 1000 S / cm. The cell unit with support electrode makes it possible to reduce the operating temperature while maintaining an acceptable ohmic drop.Support electrode cells generally operate between 600° and 800°C, greatly limiting degradation problems while allowing the consideration of cheaper metal alloy interconnection plates.

[0053] In the remainder of the description, the terms hydrogen electrode, support electrode or hydrogen support electrode are used interchangeably.

[0054] For example, the hydrogen electrode 200 is a cermet. For example, the hydrogen electrode 200 is composed of a mixture of ionically conductive oxide and a catalyst metal, most often nickel. This metal has a high catalytic activity with respect to the reduction of water and therefore the production of hydrogen. In addition, thanks to its high electronic conductivity (4.5, 10 3S.cm-1 at 800°C), nickel ensures electronic continuity in the electrode. The ceramic network accommodates thermomechanical constraints linked to a difference in coefficient of thermal expansion (CTE) between that of nickel (16.5, 10' 6 K-1) and that of the electrolyte (10.5, 10' 6 K-1 for 8YSZ). For example, a 40% vol Ni - 60% vol 8YSZ cermet has a CET of approximately 13.10' 6 K-1. Finally, thanks to its high ionic conductivity, this ceramic network allows the electrochemical reaction to be delocalized in a volume close to the interface with the solid electrolyte 300.

[0055] The hydrogen electrode 200 comprises a first surface 201 and a second surface 202, opposite each other and preferably parallel. The first surface

[0056] 201 and the second surface 202 extend along a longitudinal plane, perpendicular to the thickness of the cell unit 1. Preferably, the first surface 201 and the second surface 202 are of identical dimensions. Preferably, the second surface

[0057] 202 is flat.

[0058] As a non-limiting example, the hydrogen electrode is made up of a mixture of nickel oxide NiO, and doped zirconium oxide (typically doped with yttrium oxide at a rate of 8 mol%). The mixtures conventionally used have a content of approximately 50 to 70% by mass of NiO.

[0059] According to the invention, the cell unit 1 is characterized in that it comprises a structure formed in its thickness. Advantageously, it is the hydrogen electrode 200 which comprises a structure.

[0060] The structure of the hydrogen electrode 200 is intended to allow a better supply of gas to the electrode, despite its support electrode thickness.

[0061] According to the invention, the cell unit 1 comprises at the level of the hydrogen electrode 200, called the support electrode, at least one circulation channel 100.

[0062] In the remainder of the description, reference is made to a circulation channel 100 without being limiting. The hydrogen electrode 200, called the support electrode, may comprise several circulation channels 100.

[0063] The circulation channel 100 is advantageously intended to allow the circulation of a gas or a mixture of gases such as water vapor and / or dihydrogen.

[0064] The circulation channel 100 is formed in a hollow from the first surface 201 of the hydrogen electrode 200. The circulation channel 100 opens out at the first surface 201 of the hydrogen electrode 200. Advantageously, the circulation channel 100 does not open out at the second surface 202 of the hydrogen electrode 200. The circulation channel 100 is formed in the thickness of the hydrogen electrode 200, preferably in only one part, so as to maintain a thickness 11 of the hydrogen electrode 200 directly above the circulation channel 100. Preferably, the minimum thickness 11 of the hydrogen electrode 200 is of the order of 20 μm.

[0065] The circulation channel 100 has a depth P extending along the thickness Ep of the cell unit, a width I extending transversely to the thickness Ep and a length L extending transversely to the thickness Ep and to the width I.

[0066] According to a preferred embodiment, the circulation channel 100 opens over its entire surface into a plane parallel to the plane of the first surface 201 of the hydrogen electrode 200. The circulation channel is said to be surface-like and has the shape of a gutter, that is to say an elongated recess.

[0067] According to one possibility, the circulation channel 100 has a depth P representing a maximum of 80% of the thickness 10 of the hydrogen electrode 200. Preferably, the circulation channel 100 has a depth P representing a minimum of 1 / 3 of the thickness 10 of the hydrogen electrode 200. This dimension of the circulation channel 100 makes it possible to improve the gas diffusion without weakening the cell unit by getting too close to the solid electrolyte 300.

[0068] Preferably, the circulation channel 100 has a width I of between 25 μm and 150 μm. Advantageously, the surface area of ​​the circulation channel 100 taken transversely to the thickness Ep is less than or equal to 50% of the surface area of ​​the second surface 202 of the hydrogen electrode 200. This selection of the minimum remaining surface area of ​​the first surface 201 of the hydrogen electrode 200 makes it possible to ensure electrical contact with the interconnector 900 configured to come opposite this first surface of 101.

[0069] The geometry of the circulation channel 100 is for example in cross-section as illustrated in FIGS. 1 to 4 of a parallelepiped or triangular shape, one of the vertices being oriented towards the second surface 202 of the hydrogen electrode 200.

[0070] According to one embodiment, the circulation channel 100 is arranged in the form of a spiral extending in a longitudinal plane perpendicular to the thickness 10 of the hydrogen electrode 200.

[0071] Preferably, the turns forming the spiral are regularly spaced, corresponding for example to an Archimedean spiral.

[0072] Alternatively, the turns have an increasing spacing from the center 1002 of the spiral towards its circumference 1003 of the spiral, corresponding for example to a logarithmic spiral.

[0073] According to yet another alternative, the turns have a decreasing spacing from the center 1002 of the spiral towards its circumference 1003, the spiral corresponding for example to an algebraic spiral.

[0074] The last two alternatives allow the turn density to be varied to allow homogeneous operation of the cell unit in terms of current density.

[0075] According to one embodiment, the circulation channel 100 has a variable depth P. According to a first possibility, the depth P of the circulation channel 100 increases from the center 1002 of the spiral towards its circumference 1003. The increase in the depth P is preferably continuous and progressive along the circulation channel 100. The depth P thus increases progressively from the center 1002 of the spiral along the turns thereof. This arrangement makes it possible to have a pressure drop decreasing between the inlet and the outlet. This allows a potentially more homogeneous supply across the entire cell.

[0076] Advantageously, the circulation channel 100 in the form of a spiral is supplied with gas at its center 1002 by a gas inlet external to the cell unit and is advantageously formed at the level of the interconnector 900 for example by an opening of 5 to 10 mm in diameter.

[0077] According to another embodiment, the circulation channel 100 comprises grooves. Advantageously, the grooves are arranged parallel to each other. The grooves advantageously extend in a longitudinal direction perpendicular to the thickness Ep of the cell unit 1.

[0078] According to one possibility, at at least one of their ends the grooves are in fluid communication allowing the circulation of gas between them. The grooves thus form a circulation channel 100. This arrangement allows gas to arrive through one side of the cell and gas to leave through the opposite side, preferably via supply and recovery channels.

[0079] Alternatively, the grooves are not in fluid communication with each other.

[0080] According to one embodiment, the grooves have a variable depth P. Preferably, the depth P of successive grooves decreases towards the center 1000 of the cell unit 1.

[0081] According to one embodiment, the spacing between the grooves is constant as illustrated in Figure 1.

[0082] According to another embodiment, the grooves have a variable spacing between them. According to a preferred possibility, the spacing between the grooves is decreasing from the center 1000 towards the edges 1001 of the cell unit 1 as illustrated in FIG. 2. According to another possibility, the spacing between the grooves is increasing from the center 1000 towards the edges 1001 of the cell unit 1. The density of the grooves is thus variable at the first surface 201 of the support hydrogen electrode 200. Advantageously, this possibility makes it possible to supply certain areas of the cell differently, which can make it possible to homogenize the current densities across the entire cell, and therefore potentially limit the aging of the cell.

[0083] The superposition of the layers of the cell unit 1 is done according to the thickness 10 of the hydrogen electrode layer 200. The thickness 10 of the hydrogen electrode layer 200 is parallel to the thickness EP of the cell unit 1.

[0084] The cell unit 1 comprises, opposite the first surface 201 of the hydrogen electrode 200, a solid electrolyte 300. The solid electrolyte 300 is a layer comprising a first surface 301 and a second surface 302, opposite each other and preferably parallel. The first surface 301 and the second surface 302 extend along a longitudinal plane, perpendicular to the thickness E1 of the cell unit 1. Preferably, the first surface 301 and the second surface 302 are flat. Preferably, the first surface 301 and the second surface 302 are of identical dimensions. Preferably, the first surface 301 and the second surface 302 of the solid electrolyte 300 are of dimensions substantially equivalent to the second surface 202 of the hydrogen electrode 200. The solid electrolyte 300 is an electrolytic membrane which constitutes the separation between the two compartments of a battery.As such, it must be perfectly dense to be impermeable to gas. Advantageously, the second surface 202 of the hydrogen electrode 200 is arranged in contact with the first surface 301 of the solid electrolyte 300. By way of non-limiting example, conventional electrolyte materials are zirconium oxides, doped with yttrium or scandium oxides at a level of 3 to 10 mol%.

[0085] The cell unit 1 comprises, opposite the second surface 302 of the solid electrolyte 300, an oxygen electrode 400. The oxygen electrode 400 has a first surface 401 and a second surface 402, opposite each other and preferably parallel. The first surface 401 and the second surface 402 extend along a longitudinal plane perpendicular to the thickness Ep of the cell unit 1. Preferably, the first surface 401 and the second surface 402 are of identical dimensions. Preferably, the first surface 401 and the second surface 402 of the oxygen electrode 400 are of smaller dimensions than those of the second surface 302 of the solid electrolyte 300. Preferably, the first surface 401 and the second surface 402 of the oxygen electrode 400 are flat. The oxygen electrode corresponds to the electrode where the circulation of air and therefore oxygen takes place.As a non-limiting example, oxygen electrode materials are typically of perovskite structure (ABO3). One of the materials currently most used is the material (LaSr)(CoFe)03.

[0086] Preferably, the oxygen electrode 400 is configured so as not to cover the entire second surface 302 of the solid electrolyte 300. Preferably, the oxygen electrode 400 leaves the edge of the second surface 302 of the solid electrolyte 300 free so as to form a frame devoid of oxygen electrode 400. For example, 5 to 10% of the surface of the solid electrolyte 300 is left free in order to position the sealing zone at this location to allow direct contact between the sealing solution and a dense material such as the solid electrolyte.

[0087] According to one possibility, the cell unit 1 comprises a barrier layer 500 arranged between the solid electrolyte 300 and the oxygen electrode 400. More precisely, the barrier layer 500 is arranged between the second surface 302 of the solid electrolyte 300 and the first surface 401 of the oxygen electrode 400. The barrier layer 500 has a first surface 501 and a second surface 502 opposite each other and preferably parallel. The first surface 501 and the second surface 502 extend along a longitudinal plane perpendicular to the thickness Ep of the cell unit 1. Preferably, the first surface 501 and the second surface 502 are planar. Preferably, the first surface 501 and the second surface 502 are of identical dimensions. Preferably, the first surface 501 and the second surface 502 of the barrier layer 500 are of identical dimensions to the second surface 402 of the oxygen electrode 400.The barrier layer 500 is intended to limit the diffusion of elements and reactivity between the oxygen electrode and the electrolyte material (typically strontium and lanthanum). Indeed, without this barrier layer insulating phases can form during the manufacture of the cell or its operation and harm the initial performance and durability.

[0088] According to one possibility, the cell unit 1 comprises at least one interface element arranged facing the first surface 201 of the support hydrogen electrode 200. The interface element is intended to optimize the circulation and diffusion of gas towards the hydrogen electrode 200. Preferably, the interface element comprises communicating passages arranged facing said first face and advantageously configured to ensure the circulation of gas towards the first surface 201 of the support hydrogen electrode 200.

[0089] According to a first possibility, the interface element is a first contact layer 600.

[0090] For example, the cell unit 1 comprises a first contact layer 600 arranged opposite the first surface 201 of the hydrogen electrode 200.

[0091] The first contact layer 600 has a first surface 601 and a second surface 602, opposite each other and preferably parallel. The first surface 601 and the second surface 602 extend along a longitudinal plane perpendicular to the thickness Ep of the cell unit 1. Preferably, the first surface 601 and the second surface 602 are of identical dimensions. Preferably, the first surface 601 and the second surface 602 of the first contact layer 600 are of dimensions identical to those of the hydrogen electrode 200. Preferably, the first surface 601 and the second surface 602 of the first contact layer 600 are discontinuous. According to one embodiment, the first contact layer 600 comprises at least one complementary channel 603 arranged opposite the circulation channel 100.The first contact layer 600 is formed by alternating hollows and pads 604 arranged to form a complementary channel 603 to the circulation channel 100 of the hydrogen electrode 200. Advantageously, the second surface 602 of the first contact layer 600 is arranged in contact with the first surface 201 of the hydrogen electrode 200. The contact layer makes it possible to reduce the contact resistances with the interconnectors. The contact layer 600 advantageously has better electronic conductivity of the hydrogen electrode, for example because it is made of pure nickel.

[0092] For example, the cell unit 1 comprises a second contact layer 800 arranged opposite the second surface 402 of the oxygen electrode 400.

[0093] The first contact layer 800 has a first surface 801 and a second surface 802, opposite each other and preferably parallel. The first surface 801 and the second surface 802 extend along a longitudinal plane perpendicular to the thickness Ep of the cell unit 1. Preferably, the first surface 801 and the second surface 802 are of identical dimensions. Preferably, the first surface 801 and the second surface 802 of the second contact layer 800 are of smaller dimensions than those of the second surface 302 of the solid electrolyte 300. Preferably, the second contact layer 800 has a surface identical to that of the oxygen electrode 400. The contact layer 800 is intended to ensure the lowest possible contact resistance between the interconnector and the oxygen electrode.The contact layer 800 advantageously has better electronic conductivity than the oxygen electrode, for example because it is made of pure nickel. According to a second possibility, the interface element is a contact grid 700 arranged opposite the first surface 201 of the hydrogen electrode 200. The contact grid 700 has a first surface 701 and a second surface 702, opposite each other and preferably parallel. The first surface 701 and the second surface 702 extend along a longitudinal plane perpendicular to the thickness Ep of the cell unit 1. Preferably, the first surface 701 and the second surface 702 are of identical dimensions. Preferably, the first surface 701 and the second surface 702 of the contact grid 700 are of dimensions identical to that of the hydrogen electrode 200.Preferably, the first surface 701 and the second surface 702 of the contact grid 700 are flat. According to one embodiment, the contact grid 700 is porous and comprises passages allowing the preferential circulation of gas such as dihydrogen and water vapor between the first surface 701 and the second surface 702. The contact grid 700 advantageously has a dual role of improving the contact resistance as for the contact layers 600, 800 and gas diffuser.

[0094] According to another aspect, the invention relates to a stack comprising a cell unit 1 as described above and a first interconnector 900 arranged facing the first surface 201 of the hydrogen electrode 200. Preferably, the interconnector 900 has a surface facing the hydrogen electrode 200 which is greater than the first surface 201 of the hydrogen electrode 200 and / or greater than the first surface 301 of the solid electrolyte 300. According to one possibility, the stack comprises a second interconnector, not illustrated, arranged facing the second surface 402 of the oxygen electrode 400. Preferably, the second interconnector is arranged at the second surface 802 of the contact layer 800.

[0095] Advantageously, the cell unit one according to the invention makes it possible to use in the stack a first interconnector 900 comprising a first surface 901 and a second surface 902, opposite one another, the second surface 902 of which is flat and intended to be opposite the first surface 201 of the hydrogen electrode 200. The second surface 902 of the interconnector 900 advantageously does not comprise a relief intended for gas distribution.

[0096] According to one aspect, the invention relates to a method of manufacturing a cell unit 1 as described above.

[0097] The manufacture of the cell unit 1 and more particularly the superposition of the different layers is carried out by the different techniques known to a person skilled in the art.

[0098] As regards the formation of the at least one circulation channel 100 formed in a hollow and opening onto the first surface of the hydrogen electrode 200, it is to be carried out by strip casting, calendering, micromachining. Preferably, the formation of the at least one circulation channel 100 is carried out by laser micromachining. The formation of the circulation channel 100 by the earth makes it possible to control the energy supplied in order to structure the supporting hydrogen electrode significantly without harming the quality of the solid electrolyte 300, the quality of which is essential for the performance and durability of the cell unit.

[0099] For example, a cell unit according to the invention is produced by an IN-NOSLAB laser of the Edgewave brand (model BX60). This is a Nd-YAG laser with a power of 30W.

[0100] The following parameters were used:

[0101] - Laser power = 100% or 30W

[0102] - Laser speed on = 1495 mm / s

[0103] - Laser speed off (jump) = 3000 mm / s

[0104] The laser beam before the lens is directed by two galvanometric mirrors, which imposes physical constraints on the beam displacement. Each marking vector is divided into micro-vectors, and the length of these micro-vectors is configurable as well as their duration. It is from these two parameters that the marking speed is adjusted. The duration of a micro-vector is given in ps and its length in LSB, equivalent to one mm per byte. With a 220*220mm field lens as used, one LSB is equivalent to 3.74pm.

[0105] The step size is set to 20 LSB, and the step interval to 50 ps.

[0106] The parameters chosen are the following to obtain the adequate definition of the structuring:

[0107] - ON delay = 100 ps

[0108] - OFF delay = 100 ps

[0109] Regarding the laser beam,

[0110] - The width of the draw is fixed at 9ps

[0111] - The pulse frequency is set to 100kHz

[0112] - The number of repetitions is set to 500.

[0113] A spiral-shaped support structure (50mm diameter) was thus created. The pitch between the turns is 445pm, as shown in Figures 5 and 6.

[0114] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

[0115] LIST OF REFERENCES

[0116] I. Electrochemical cell unit

[0117] 10. Thickness of the hydrogen electrode support

[0118] II. Thickness of the hydrogen electrode support at the level of a circulation channel

[0119] 100. Traffic channel

[0120] 200. Hydrogen electrode

[0121] 201. First surface

[0122] 202. Second surface

[0123] 300. Solid electrolyte

[0124] 301. First surface

[0125] 302. Second surface

[0126] 400. Oxygen electrode

[0127] 401. First surface 02. Second surface 00. Barrier layer 01. First surface 02. Second surface 00. First contact layer 01. First surface 02. Second surface 03. Complementary channel 04. Pad 00. Contact grid

[0128] 701. First surface

[0129] 702. Second surface

[0130] 800. Second contact layer

[0131] 801. First surface

[0132] 802. Second surface

[0133] 900. First interconnector

[0134] 901. First surface

[0135] 902. Second surface

[0136] 1000. Center of the cell unit

[0137] 1001. Edges of the cell unit

[0138] 1002: center of the spiral

[0139] 1003. Circumference of the spiral Ep. Thickness of the cell unit P. Depth of the circulation channel I. Width of the circulation channel L. Length of the circulation channel

Claims

CLAIMS 1. Electrochemical cell unit (1) comprising in order according to its thickness: - a supporting hydrogen electrode (200) comprising a first surface (201) and a second surface (202), opposite each other, - a solid oxide electrolyte (300) comprising a first surface (301) and a second surface (302), opposite each other, the first surface (301) of the solid oxide electrolyte (300) facing the second surface (202) of the supporting hydrogen electrode (200), and - an oxygen electrode (400) comprising a first surface (401) and a second surface (402), opposite each other, the first surface (401) of the oxygen electrode (400) facing the second surface (302) of the solid oxide electrolyte (300), characterized in that the supporting hydrogen electrode (200) comprises at least one circulation channel (100) of at least one gas, formed hollow and opening, at the first surface (201) of the supporting hydrogen electrode (200) and without opening at the second surface (202) of the supporting hydrogen electrode (200) and that the at least one circulation channel (100) has a depth (P) extending along the thickness (Ep) of the electrochemical cell unit (1), a width (I) extending transversely to the thickness (Ep) and a length (L) extending transversely to the thickness (Ep) and to the width (I),the at least one circulation channel (100) opening over its entire length (L) and its width (I) at the level of the first surface (201)., 2. Electrochemical cell unit (1) according to any one of the preceding claims wherein the at least one circulation channel (100) has a variation in depth (P).

3. Electrochemical cell unit (1) according to any one of the preceding claims wherein the at least one circulation channel (100) is arranged in the form of a spiral extending in a plane parallel to the second surface (202) of the supporting hydrogen electrode (200).

4. Electrochemical cell unit (1) according to the preceding claim comprising a gas inlet arranged at the center (1002) of the spiral.

5. Electrochemical cell unit (1) according to any one of the two preceding claims in combination with claim 2 wherein, the depth (P) of the circulation channel (100) is increasing from the center (1002) of the spiral.

6. Electrochemical cell unit (1) according to any one of claims 1 to 2 wherein the at least one circulation channel (100) is formed of grooves arranged parallel to each other and extending in a longitudinal direction perpendicular to the thickness (Ep) of the electrochemical cell unit (1).

7. Electrochemical cell unit (1) according to the preceding claim in which the grooves have between them a depth (P) decreasing towards the center (1000) of the electrochemical cell unit.

8. Electrochemical cell unit (1) according to either of the two preceding claims having a density gradient of the grooves, preferably between the center (1000) of the cell unit and its edges (1001).

9. Electrochemical cell unit (1) according to any one of the preceding claims in which the at least one circulation channel (100) has a maximum depth (P) of 80% of the thickness (10) of the supporting hydrogen electrode (200), preferably 2 / 3 of the thickness (6) of the supporting hydrogen electrode (200).

10. Electrochemical cell unit (1) according to any one of the preceding claims wherein the at least one circulation channel (100) represents a maximum of 50% of the first surface (201) of the supporting hydrogen electrode (200).

11. An electrochemical cell unit opening (1) according to any one of the preceding claims comprising an interface element arranged facing the first surface (201) of the supporting hydrogen electrode (200) comprising communicating passages arranged facing said first surface (200).

12. Electrochemical cell unit (1) according to the preceding claim wherein the interface element is a contact grid (700) arranged on the first surface (200) of the supporting hydrogen electrode (200).

13. Electrochemical cell unit (1) according to claim 11 wherein the interface element is a contact layer (6) comprising at least one complementary channel (603) to the at least one circulation channel (100) of the support hydrogen electrode (200) arranged facing the first surface (201) of the support hydrogen electrode (200).

14. Stack comprising at least one electrochemical cell unit (1) according to any one of the preceding claims, characterized in that it comprises a first interconnector (900) intended to be arranged facing the first surface (201) of the supporting hydrogen electrode (200) and / or a second interconnector intended to be arranged facing the second surface (402) of the oxygen electrode (400), the first interconnector (900) comprises a first planar surface (901) intended to be facing the first surface (201) of the supporting hydrogen electrode (200).

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