electrochemical cell

Abstract

An electrochemical cell is disclosed that includes a porous metal support, at least one layer of a first electrode on the porous metal support, a first electron-blocking electrolyte layer made of rare-earth-doped zirconia on the at least one layer of the first electrode, and a second bulk electrolyte layer made of rare-earth-doped ceria on the first electron-blocking electrolyte layer. The thickness of the first electron-blocking electrolyte layer made of rare-earth-doped zirconia can be 0.5 μm or more, and the thickness of the second bulk electrolyte layer made of rare-earth-doped ceria can be 4 μm or more.

Description

[Technical Field]

[0001] The present invention relates to electrochemical cells, stacks of electrochemical cells, and methods of manufacturing such electrochemical cells, as well as to electrolysis systems including such electrochemical cells and methods of operating such electrochemical cells in an electrolysis mode. [Background technology]

[0002] Electrochemical cells formed from oxide layers, often known as solid oxide cells (SOC), can be used as fuel cells or electrolyzer / electrolysis cells.

[0003] SOC fuel cell units generate electricity by using an electrochemical conversion process to oxidize fuel. SOC cell units can additionally or alternatively operate as regenerative fuel cell (or reverse fuel cell) units, often known as solid oxide electrolysis fuel cell units, for example, to separate hydrogen and oxygen from water or carbon monoxide and oxygen from carbon dioxide.

[0004] SOC units are typically ceramic-based and use an oxygen-ion-conducting metal oxide-containing ceramic as the electrolyte. SOCs tend to operate at high temperatures because many ceramic oxygen-ion conductors (e.g., doped zirconium oxide or doped cerium oxide) have useful ionic conductivity at temperatures above 500°C (for cerium oxide-based electrolytes) or 650°C (for zirconium oxide-based ceramics).

[0005] Solid oxide fuel cells (SOFCs) generate electrical energy through the electrochemical oxidation of a fuel gas (usually hydrogen-based). During operation, the electrolyte of a SOFC conducts oxygen ions from the cathode to the anode, located on either side of the electrolyte. The fuel, e.g., a fuel derived from the reforming of hydrocarbons or alcohols, is in contact with the anode (commonly known as the "fuel electrode"), and an oxidant, e.g., air or an oxygen-rich fluid, is in contact with the cathode (commonly known as the "air electrode").

[0006] A solid oxide electrolysis cell (SOEC) may have the same structure as a SOFC, but is actually a SOFC operated in reverse or regenerative mode to achieve the electrolysis of water and / or carbon dioxide.

[0007] Conventional ceramic-supported (e.g., anode-supported) SOCs have low mechanical strength and are prone to breakage. Therefore, metal-supported SOFCs, which have active fuel cell component layers supported on a metal substrate, have recently been developed. In these cells, the ceramic layers perform only electrochemical functions and can be very thin; that is, they are not self-supporting but rather a thin coating / film laid on and supported by a metal substrate. Such metal-supported SOC stacks are more robust and lower cost than ceramic-supported SOCs, have superior thermal properties, and can be sealed using conventional metal welding techniques.

[0008] The applicant's earlier patent application WO-A-2015 / 136295 discloses a metal-supported SOFC, in which electrochemically active layers (or active fuel cell component layers) include an anode layer, an electrolyte layer, and a cathode layer, each of which is deposited (e.g., as a thin coating / film) on and supported by a metal support plate (e.g., foil). The metal support plate has porous regions surrounded by non-porous regions, and the active layers are deposited on the porous regions, allowing gas to pass through the holes from one side of the metal support plate to the other to access the active layers coated thereon. The porous regions include individual openings (holes drilled in the metal foil substrate) extending through the support plate, which are located above the anode (or cathode, depending on the orientation of the electrochemically active layers). The applicant's earlier patent application GB-A-2456445 discloses depositing a layer of metal oxide crystalline ceramic on a substrate.

[0009] US-A-2019 / 0330751 discloses an SOEC system with a heating function. WO-A-2021 / 201195 discloses a metal-supported SOFC constructed by providing an anode electrode layer, an electrolyte layer, and a cathode electrode layer on the surface of a metal support. US-A-2007 / 269701 discloses an SOFC equipped with a metal support. EP-A-1306920 discloses a unit cell for a fuel cell and a solid oxide fuel cell. CN-A-113764710 and CN-A-113782799 disclose metal-supported SOECs. US-A-2011 / 076594 discloses a ceria-based bulk electrolyte layer in an SOFC. JP-A-2011 181262 and KR-A-20120137917 disclose SOFCs constructed of electrodes and electrolytes without a metal support. US-A-2020 / 0014051 discloses a method for manufacturing a metal-supported electrochemical element.

[0010] Attempts are being made to reduce manufacturing costs, improve reliability, and increase efficiency for SOFCs and SOECs. Unfortunately, materials that offer better performance at low temperatures may be less stable than currently used materials. In particular, some electrolyte materials can be partially reduced when exposed to the fuel atmosphere, exhibiting mixed ionic and electronic conductivity, which can reduce operational efficiency.

[0011] Therefore, there is a need to provide electrochemical cells with improved electrolyte systems, and the present invention is directed to addressing that need. Summary of the Invention

[0012] Accordingly, in a first aspect, the present invention provides an electrochemical cell comprising a porous metal support, at least one layer of a first electrode on the porous metal support, a first electron-blocking electrolyte layer comprising rare earth-doped zirconia on the at least one layer of the first electrode, and a second bulk electrolyte layer comprising rare earth-doped ceria on the first electrolyte layer.

[0013] The first electron-blocking electrolyte layer made of rare earth-doped zirconia may have a thickness of 0.5 μm or more.

[0014] The thickness of the second bulk electrolyte layer of rare earth doped ceria can be 4 μm or greater.

[0015] This is advantageous because the second bulk electrolyte layer, made of doped ceria, may be less susceptible to reduction during use. Reduction of the doped ceria may result in higher electronic conductivity in the second bulk electrolyte layer, causing the doped ceria layer to expand. Mixed electronic / ionic conductivity of the electrolyte may result in reduced efficiency. Expansion of the doped ceria layer may shorten the life of the electrochemical cell.

[0016] The thickness of the first electron-blocking electrolyte layer of rare earth-doped zirconia can be 1 μm or more, optionally 2 μm or more.

[0017] The thickness of the first electron-blocking electrolyte layer of rare earth-doped zirconia can be 5 μm or less. Optionally, the thickness of the first electron-blocking electrolyte layer of rare earth-doped zirconia can be 4 μm or less or 3 μm or less.

[0018] Therefore, the thickness of the first electron-blocking electrolyte layer made of rare-earth-doped zirconia can be in the range of 0.5 μm to 5 μm, in the range of 1 μm to 4 μm, or in the range of 2 μm to 3 μm.

[0019] Generally, it is advantageous for the thickness of the first electron-blocking electrolyte layer to be within these ranges, since the first and second electrolyte layers together have low electronic conductivity or are electronically insulating. The optimal thickness is a trade-off between electronic leakage (which can begin to occur when the layer is thin) and ionic resistance (which tends to increase when the layer is thick).

[0020] The rare-earth-doped zirconia first electron-blocking electrolyte layer can advantageously act to block electronic leakage current by being a pure oxide ion conductor, and can also provide sufficiently low gas permeability to prevent the doped ceria second bulk electrolyte layer from being significantly reduced (and thus becoming electronically conductive) during use.

[0021] The first electron-blocking electrolyte layer is preferably dense enough to inhibit the diffusion of reducing fuel gas (e.g., hydrogen) into the second bulk electrolyte layer. Therefore, the first electron-blocking electrolyte layer preferably has low porosity or is substantially non-porous (although it may have some closed porosity). Providing a dense layer (and reducing porosity) can be achieved by carefully selecting particle size, sintering aids, and temperature profile.

[0022] The second bulk electrolyte layer of rare earth-doped ceria can have a thickness of 17 μm or less. Optionally, the second bulk electrolyte layer of rare earth-doped ceria can have a thickness of 15 μm or less, optionally 12 μm or less.

[0023] The thickness of the second bulk electrolyte layer of rare earth-doped ceria can be 4 μm or more. Optionally, the thickness of the second bulk electrolyte layer of rare earth-doped ceria can be 5 μm or more, 6 μm or more, or 7 μm or more.

[0024] Therefore, the thickness of the second bulk electrolyte layer made of rare earth-doped ceria can be in the range of 4 μm to 17 μm, in the range of 5 μm to 15 μm, or in the range of 6 μm to 12 μm.

[0025] The second bulk electrolyte layer, consisting of rare-earth doped ceria, has the primary purpose of facilitating oxygen ion diffusion from one electrode to the other, and may advantageously provide a mechanically stable layer with very low or no gas permeability and the lowest possible ionic resistance.

[0026] A second bulk electrolyte layer can be advantageous because it provides a more gas-tight and mechanically robust layer, although the optimal thickness is a trade-off between gas leakage (more likely when the layer is thin) and ionic resistance (which tends to increase with thickness).

[0027] Optionally, the second bulk electrolyte layer of rare earth doped ceria may be thicker than the first bulk electrolyte layer of rare earth doped zirconia.

[0028] The electrochemical cell may include a solid oxide electrochemical cell.

[0029] The electrochemical cell may be a fuel cell or an electrolysis cell (also referred to as an electrolyzer). In the fuel cell mode, since the fuel contacts the anode (fuel electrode) and an oxidant such as air or a fluid rich in oxygen contacts the cathode (air electrode), the air electrode becomes the cathode during operation in the fuel cell mode. A solid oxide electrolysis cell (SOEC) may have the same structure as an SOFC, but essentially operates the SOFC in the reverse or regenerative mode to achieve the electrolysis of reactants (e.g., generating hydrogen gas and / or carbon monoxide and oxygen from water and / or carbon dioxide).

[0030] The advantages of the present disclosure are particularly advantageous when a voltage is applied to the electrochemical cell. Therefore, the electrochemical cell may be an electrolysis cell during use.

[0031] Alternatively, the electrochemical cell may be a fuel cell or a reversible fuel cell during use.

[0032] As a further alternative, the electrochemical cell may be an oxygen separator or a sensor during use.

[0033] The rare earth doped zirconia may include zirconia doped with at least one rare earth element selected from Y, Sc, or a lanthanoid (Ln). An example of Ln is Yb.

[0034] The rare earth doped zirconia may be selected from scandia stabilized zirconia (ScSZ), yttria stabilized zirconia (YSZ), scandia ceria co-stabilized zirconia (ScCeSZ), ytterbia stabilized zirconia (YbSZ), scandia yttria co-stabilized zirconia (ScYSZ), and mixtures thereof. The doped zirconia may be a solid solution represented by the following formula, Zr (1-x) M x O (2-0.5x-δ) where 0 < x ≦ 0.2 and M is a rare earth element (M = Sc, Y, Ln, or a mixture thereof).

[0035] The dopant concentration in zirconia may range from 5 to 15 atomic %, and optionally from 6 to 12 atomic %.

[0036] When the dopant is Y, the dopant concentration of Y in zirconia may range from 5 to 15 atomic %, and optionally may be about 8 atomic %. When the dopant is Sc, the dopant concentration of Sc in zirconia may range from 5 to 15 atomic %, and optionally may be about 10 atomic %.

[0037] The rare earth doped ceria may include ceria doped with at least one rare earth element selected from Y, Sc, or a lanthanoid (Ln).

[0038] The rare earth doped ceria is selected from samarium doped ceria (SDC), gadolinium doped ceria (GDC), samaria gadolinia doped ceria (SGDC), and mixtures thereof. Gd and Sm are advantageous as higher ionic conductivity may be obtained. The doped ceria may have the following formula, Ce (1-x) M x O (2-0.5x-δ) and may be a solid solution having the formula, where 0 < x ≦ 0.5, (M = Sc, Y, Ln, or a mixture thereof).

[0039] The dopant concentration in ceria may range from 3 to 45 atomic %, optionally from 5 to 40 atomic %, and optionally from 10 to 20 atomic %.

[0040] The layer of the first electrode may include doped ceria or doped zirconia. Preferably, the layer of the first electrode may include ceria gadolinium oxide (CGO).

[0041] The layer of the first electrode may include a source of nickel and optionally nickel oxide. The layer of the first electrode may include a nickel CGO cermet.

[0042] The thickness of the first electrode layer may be 3 μm or more, optionally 5 μm or more, optionally 10 μm or more, optionally 15 μm or more. The thickness of the first electrode layer may be 60 μm or less, 50 μm or less, optionally 45 μm or less, optionally 40 μm or less, optionally 35 μm or less. Thus, the thickness of the first electrode layer may be in the range of 3 μm to 60 μm, in the range of 5 μm to 50 μm, optionally in the range of 15 μm to 25 μm.

[0043] The first electrode may have one or more layers, and thus a layer of the first electrode may be the only layer of the first electrode or the first layer of the first electrode.

[0044] The first electrode can be the fuel electrode, which is particularly advantageous because it reduces the likelihood of increased electronic conductivity of the doped ceria that can occur in a reducing atmosphere, and also reduces the likelihood of cracking of the second bulk electrolyte layer due to expansion that can occur during reduction.

[0045] By placing a first electron-blocking electrolyte layer on the fuel side of the cell, the doped ceria layer is at least partially shielded from more reducing (low-oxygen chemical) potentials that could affect it. This is advantageous because doped ceria has reduced electronic conductivity in more oxidizing atmospheres. Furthermore, in more reducing atmospheres (at typical SOC operating temperatures), the doped ceria can be chemically reduced and expand, especially when a voltage is applied (e.g., in SOEC mode). As a result, at a critical voltage (a function of temperature), cell failure can occur under compressive stress. Additionally, there may be creep mechanisms that affect the layer after a period of time at operating temperature, during temperature cycling, and under applied voltage.

[0046] The electrochemical cell may further include a second electrode on the electrolyte layer. The second electrode may be an air electrode. The second electrode may include one or more layers. For example, the second electrode may include an active second electrode layer (disposed adjacent to the electrolyte) and a bulk second electrode layer. The active second electrode layer and the bulk second electrode layer may include suitable materials, and the bulk layer material may be, for example, lanthanum cobaltate, lanthanum ferrite, lanthanum nickel ferrite, La 0.99 Co 0.4 Ni 0.6 O (3-δ) (LCN60), and mixtures thereof.

[0047] The metal support may comprise an apertured metal foil (i.e., solid metal), which has the advantage that the porosity can be tailored and positioned in specific areas of the support. Alternatively, or in addition, the metal substrate may have inherent porosity (e.g., isotropic porosity) formed, for example, as a tape cast by depositing a powder to form a film, which is then sintered to form a porous substrate. References herein to a metal support or porous steel plate may refer to either of these.

[0048] The porous metal support may comprise steel, preferably stainless steel. Typically, the porous metal support may comprise a perforated metal support, optionally a laser-drilled metal support.

[0049] In some situations (for example, when it is desired to further protect the metal support from corrosion), the porous metal support may be provided with a barrier layer on its surface, and the electrode layer may be provided on the barrier layer.

[0050] The electrochemical cell may comprise other layers.

[0051] Optionally, the electrochemical cell does not include a second layer of rare earth doped zirconia.

[0052] The electrochemical cell according to the first aspect may be arranged as a stack of electrochemical cell units electrically connected in series.

[0053] Thus, in a second aspect, there is provided a stack of electrochemical cells, each electrochemical cell being as described above.

[0054] The first electrode layer, the first electrolyte layer and the second electrolyte layer may be deposited sequentially on the metal support by any suitable method.

[0055] In a third aspect, there is provided a method of manufacturing an electrochemical cell, the method comprising: providing a porous metal substrate having at least one layer of a first electrode on a surface thereof; providing a first ink comprising a precursor of a first electron-blocking electrolyte layer comprised of rare earth-doped zirconia; applying the first ink onto the at least one layer of the first electrode to form the first electron-blocking electrolyte layer comprised of rare earth-doped zirconia, optionally drying and optionally sintering; providing a second ink comprising a precursor of a second bulk electrolyte layer comprised of rare earth-doped ceria; applying the second ink onto the first electron-blocking electrolyte layer to form the second bulk electrolyte layer comprised of rare earth-doped ceria, optionally drying and optionally sintering.

[0056] The first and / or second ink may be applied by spraying (eg, atomized spraying) or by printing, optionally by roller printing, jet printing, or screen printing.

[0057] Alternatively, the electron blocking layer may be applied and / or deposited using physical vapor deposition (PVD).

[0058] The optional sintering can be carried out at a temperature in the range of 750° C. to 1100° C., preferably in the range of 800° C. to 970° C. The sintering can be carried out in an air atmosphere.

[0059] Thus, in a fourth aspect, there is provided an electrochemical cell obtainable by the method according to the third aspect.

[0060] Thus, in a fifth aspect, there is provided an electrolysis system comprising an electrochemical cell according to the first aspect.

[0061] Accordingly, in a sixth aspect, there is provided a method of operating an electrochemical cell in an electrolysis mode, the method comprising providing an electrochemical cell according to the first aspect, contacting the electrochemical cell with reactants, and applying an electric potential to the electrochemical cell.

[0062] The reactants may be, for example, water and / or carbon dioxide to produce hydrogen gas and / or carbon monoxide and oxygen, respectively. definition

[0063] As used herein, the term "rare earth metal" or "rare earth element" refers to a metal selected from Y, Sc, and the lanthanides.

[0064] "Lanthanoid," "lanthanide," and "Ln" are used interchangeably to refer to metallic chemical elements with atomic numbers 57-71.

[0065] As used herein, the term "dopant" is not limited to a maximum content of an element, ion, or compound added to a chemical structure. Similarly, the term "doping" refers to the addition of an amount of an element, ion, or compound to a material. It is not limited to a maximum amount of material beyond which the addition of material no longer constitutes doping.

[0066] The term "perovskite structure" as used herein generally refers to a single network of chemically bonded crystalline structures having a perovskite (ABX3) structure. This does not mean that this single network has a single uniform crystalline structure throughout the entire structure. However, when different crystalline structures exist between different regions of the network, these regions often have complementary structures, and chemical bonds are easily formed between them.

[0067] The term "solid oxide cell (SOC)" is intended to encompass both solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs).

[0068] The term "source of" an element, compound, or other material refers to a material that includes the element, compound, or other material, whether or not it is chemically bonded in the source. The source of the element, compound, or other material may be an elemental source (e.g., Ln, Ni, or O), or may be in the form of a compound or mixture that includes elements, compounds, or other materials, such as one or more of these elements, compounds, or other materials.

[0069] References herein to electrochemical cells, SOCs, SOFCs, and SOECs may refer to tubular or planar cells. Electrochemical cell units may be tubular or planar in configuration. Planar fuel cell units may be arranged on top of each other in a stacked configuration, e.g., a stack of 100-200 fuel cell units, and individual fuel cell units may be arranged electrically in series. Thus, references to a "stack of electrochemical cells" refer to multiple electrochemical cell units arranged electrically in series.

[0070] An electrochemical cell may be a fuel cell, a reversible fuel cell, or an electrolysis cell. Generally, these cells may have similar construction, and reference to an "electrochemical cell" (unless the context dictates otherwise) may refer to any of these types of cells.

[0071] The terms "oxidant electrode" or "air electrode" and "fuel electrode" are sometimes used interchangeably herein to refer to the cathode and anode, respectively, in a SOFC to avoid confusion between fuel cells and electrolysis / electrolysis cells.

[0072] An electrochemical cell encompassed by the present invention may comprise: a) two flat components (e.g., a substrate with an electrochemical layer, an interconnector (another plate)) welded with a fluid space between them, b) Three planar components welded together with a fluid space between them (e.g., a substrate with an electrochemical layer, an interconnector (another plate), and a spacer forming a fluid space).

[0073] As will be understood by those skilled in the art, the various features of the aspects of the present disclosure described herein may be used in combination with any other feature of the same or other aspects of the present disclosure, with appropriate modifications as necessary.

[0074] Furthermore, it is specifically contemplated that all aspects of the present invention or disclosure preferably "comprise" the features described in connection with that aspect, but may also particularly "consist" or "consist essentially" of the features outlined in the claims.

[0075] The present invention will now be described with reference to the accompanying drawings and examples. [Brief explanation of the drawings]

[0076] [Figure 1] 1 shows a cross section of an electrochemical cell unit. [Figure 2] 1 shows a scanning electron micrograph (SEM) of a cross section through a portion of an electrochemical cell unit. [Figure 3] 10 shows a graph of cell voltage as a function of normalized current density for a cell at 550° C., 50%:50% H 2 :H 2 O according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0077] FIG. 1 shows a schematic cross-section of an electrochemical cell unit 2, which may be an SOFC or SOEC, and is not drawn to scale (for clarity). A ferritic stainless steel metal support 4 has a peripheral non-porous portion 6 and a central porous region 8, which is perforated with holes extending through the metal support 4. A barrier layer (not shown) to reduce corrosion is disposed on the surface of the metal support 4. A fuel electrode layer 10 made of Ni:CGO having a thickness of 15 μm to 35 μm is disposed on the porous portion 8 of the metal support 4. A first electrolyte layer 12 made of rare earth (RE)-stabilized zirconia (RE=Y, Sc, or any Ln, e.g., Yb) having a thickness of 0.5 μm or more (e.g., 1 μm to 4 μm) is disposed on the fuel electrode layer 10. A second electrolyte layer 14 made of rare earth doped ceria (RE=Y, Sc, or any Ln) with a thickness of 4 μm or more (optionally 6 μm-12 μm) is disposed on the first electrolyte layer 12. The second electrolyte layer 14 surrounds the fuel electrode layer 10 and prevents gas flow through the fuel electrode layer 10 from the fuel side 20 to the air (oxidant) side 18, or vice versa. The cell unit is completed by a second (air) electrode assembly 16 disposed on the second 14 electrolyte layer. The second electrode 16 may be formed from a bulk air electrode layer and an active air electrode layer made of LCN 60.

[0078] FIG. 2 shows an SEM of a portion of a cell showing the fuel electrode layer 10, the first electrolyte layer 12 made of rare earth (RE) stabilized zirconia (8YZ, i.e., zirconia doped with 8 atomic % Y), and the second electrolyte layer 14 made of rare earth doped ceria (RE=Y, Sc, or any Ln).

[0079] At the operating temperatures of electrochemical cells according to the present disclosure (e.g., 550°C to 625°C), ceria can be chemically reduced and expand as the voltage increases (this occurs especially in the SOEC mode). This is not the case for YSZ. As a result, cell failure occurs under compressive stress at a critical voltage (temperature dependent). Temperature cycling and voltage application at operating temperatures can also result in creep effects under stress, potentially shortening the cell's lifespan.

[0080] To address this issue, embodiments of the electrochemical cell of the present disclosure may be constructed with a bilayer electrolyte containing a first layer of rare-earth (RE)-stabilized zirconia (RE = Y, Sc, or any Ln, e.g., Yb), with a dopant concentration ranging from 6 to 12% (e.g., % is the atomic percent of the metal), with the optimum concentration depending on the RE (e.g., about 8% for Y and about 10% for Sc). The function of this layer is to be a pure oxide-ion conductor, thereby blocking electronic leakage current, and to provide a structure with low or virtually no gas permeability, thereby preventing significant reduction (and electronic conductivity) of the second layer of doped ceria. The thickness may be in the range of 1 to 4 μm or 2 to 3 μm. The thickness of such YSZ or ScSZ is believed to provide sufficient electronic shielding, a trade-off between electronic leakage (which can occur with thinner layers) and ionic resistance (which tends to increase with thicker layers). The layer is dense enough to prevent H2 gas from permeating through to the CGO electrolyte layer. This density can be achieved by careful selection of particle size, sintering aids, and temperature profile.

[0081] The second layer of rare-earth doped ceria (RE = Y, Sc, or any Ln) may have a dopant concentration ranging from 5 to 40%, with an optimal concentration of 10 to 20%. Its primary function is mechanical stability and very low or no gas permeability. The primary performance indicator is ionic resistance, which should be as low as possible. Its thickness may range from 5 to 15 μm or 6 to 10 μm. The thicker CGO layer provides a more gas-tight and mechanically robust electrolyte.

[0082] FIG. 3 shows the IV curve of a cell in a 50%:50% H:H O atmosphere at 550° C., according to the present disclosure, showing that the cell voltage can be up to 1.45 V at a normalized current density of 1.

[0083] The electrochemical cell of the present disclosure significantly reduces the electronic conductivity of CGO by reducing or eliminating the thermodynamic conditions (i.e., reducing atmospheres) that cause the reduction of ceria, and for the same reason, reduces electrolyte cracking due to chemical expansion that occurs during the reduction of ceria.

[0084] All publications mentioned in the above specification are incorporated herein by reference. Although exemplary embodiments of the present invention are disclosed in detail herein with reference to the accompanying drawings, it is understood that the present invention is not limited to the precise embodiments, and that various changes and modifications can be made by those skilled in the art without departing from the scope of the present invention as defined by the appended claims and their equivalents. [Explanation of symbols]

[0085] 2. Electrochemical Cell 4 Metal support 6. Non-porous part of metal support 8. Porous portion of metal support 10 Fuel electrode layer 12 First electrolyte layer 14 Second electrolyte layer 16 Second (air) electrode assembly 18 Oxidant (air) side 20 Fuel side

Claims

1. A porous metal support, At least one layer of the first electrode on the porous metal support, A first electron shielding electrolyte layer made of rare earth-doped zirconia on at least one layer of the first electrode, A second bulk electrolyte layer consisting of rare earth-doped ceria on the first electron-shielding electrolyte layer and An electrochemical cell equipped with the following features.

2. The electrochemical cell according to claim 1, wherein the thickness of the first electron-shielding electrolyte layer made of rare-earth doped zirconia is 0.5 μm or more.

3. The electrochemical cell according to claim 1, wherein the thickness of the second bulk electrolyte layer, which consists of rare earth doped ceria, is 4 μm or more.

4. The electrochemical cell according to claim 1, wherein the thickness of the first electron-shielding electrolyte layer, which is made of rare-earth doped zirconia, is 5 μm or less.

5. The electrochemical cell according to claim 1, wherein the thickness of the second bulk electrolyte layer, which is made of rare earth doped ceria, is 17 μm or less.

6. The electrochemical cell according to claim 1, wherein it is a solid oxide cell.

7. The electrochemical cell according to claim 1, wherein the rare earth-doped zirconia comprises zirconia doped with at least one rare earth element selected from Y, Sc, or lanthanides (Ln).

8. The electrochemical cell according to claim 1, wherein the rare earth-doped ceria comprises ceria doped with at least one rare earth element selected from Y, Sc, or lanthanides (Ln).

9. The electrochemical cell according to claim 8, wherein the rare earth doped ceria is selected from samarium doped ceria (SDC), gadolinium doped ceria (GDC), samariagadolinia doped ceria (SGDC), and mixtures thereof.

10. The electrochemical cell according to claim 1, wherein the layer of the first electrode contains doped ceria, and optionally contains doped ceria gadolinium oxide (CGO).

11. The electrochemical cell according to claim 1, wherein the layer of the first electrode comprises a nickel source and optionally comprises nickel oxide.

12. The electrochemical cell according to claim 1, wherein the layer of the first electrode comprises a nickel CGO cermet.

13. The electrochemical cell according to claim 1, wherein the thickness of the layer of the first electrode is 3 μm or more, optionally 5 μm or more, optionally 10 μm or more, or optionally 15 μm or more.

14. The electrochemical cell according to claim 1, wherein the thickness of the layer of the first electrode is 50 μm or less, and optionally 45 μm or less, optionally 40 μm or less, and optionally 35 μm or less.

15. The electrochemical cell according to claim 1, wherein the first electrode is a fuel electrode.

16. The electrochemical cell according to claim 1, further comprising a second electrode on the second electrolyte layer, wherein the second electrode is optionally an air electrode.

17. The electrochemical cell according to claim 1, wherein the porous metal substrate includes a steel substrate, preferably a stainless steel substrate.

18. The electrochemical cell according to claim 1, wherein the porous metal substrate includes a perforated metal substrate, and optionally a laser-perforated metal substrate.

19. The electrochemical cell according to claim 1, wherein the porous metal substrate has a barrier layer on its surface, and the layer of the first electrode is located on the barrier layer.

20. A stack of electrochemical cells, each of which is an electrochemical cell as described in claim 1.

21. To provide a porous metal substrate having at least one layer of a first electrode on its surface, To provide a first ink comprising a precursor of a first electron-shielding electrolyte layer made of rare-earth doped zirconia, To form the first electron-shielding electrolyte layer made of rare-earth doped zirconia, the first ink is applied to at least one layer of the first electrode, Optional drying, The option to perform sintering, To provide a second ink containing a precursor for a second bulk electrolyte layer made of rare earth doped ceria, To form the second bulk electrolyte layer consisting of rare earth doped ceria, the second ink is applied to the first electron-shielding electrolyte layer, Optional drying, Optional sintering A method for manufacturing an electrochemical cell, including [a specific component].

22. The method according to claim 21, wherein the first ink and / or the second ink are applied by printing, optionally by screen printing.

23. An electrochemical cell obtainable by the method described in claim 21.

24. An electrolysis system comprising an electrochemical cell according to any one of claims 1 to 20.

25. A method for operating an electrochemical cell in an electrolysis mode, the method comprising: providing an electrochemical cell according to any one of claims 1 to 20; bringing the electrochemical cell into contact with a reactant to be subjected to electrolysis; and applying an electric potential to the electrochemical cell.

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