Electrochemical cell

Abstract

Disclosed is an electrochemical cell having: a porous metal support; at least one layer of a first electrode on the porous metal support; a first electron blocking electrolyte layer of rare earth doped zirconia on the at least one layer of the first electrode; and a second bulk electrolyte layer of rare earth doped cerium oxide on the first electron blocking electrolyte layer. The first electron blocking electrolyte layer of rare earth doped zirconia may have a thickness of 0.5 [mu] m or more, and the second bulk electrolyte layer of rare earth doped ceria may have a thickness of 4 [mu] m or more.

Description

Technical Field

[0001] The present invention relates to an electrochemical cell, a stack of electrochemical cells and a method of making such an electrochemical cell. The present invention also relates to an electrolysis system comprising such an electrochemical cell and a method of operating such an electrochemical cell in an electrolysis mode. Background Art

[0002] Electrochemical cells formed from oxide layers (often referred to as solid oxide cells: SOCs) can be used as fuel cells or electrolyzers / electrolysis cells.

[0003] The SOC fuel cell unit uses an electrochemical conversion process of an oxidized fuel to generate electricity. The SOC cell unit may also or alternatively operate as a regenerative fuel cell (or reverse fuel cell) unit, which is generally referred to as a solid oxide electrolyzer fuel cell unit, for example to separate hydrogen and oxygen from water or to separate carbon monoxide and oxygen from carbon dioxide.

[0004] SOC cells are typically ceramic based, using oxygen ion conducting metal oxide containing ceramics as electrolytes. Many ceramic oxygen ion conductors (e.g., doped zirconia or doped ceria) have usable ionic conductivity at temperatures exceeding 500°C (for ceria based electrolytes) or 650°C (for zirconia based ceramics), so SOCs are intended to operate at high temperatures.

[0005] Solid oxide fuel cells (SOFCs) generate electricity by electrochemically oxidizing a fuel gas (usually hydrogen-based). In operation, the electrolyte of the SOFC conducts oxygen ions from the cathode to the anode, which are arranged on opposite sides of the electrolyte. The fuel (e.g., a fuel from a recombinant hydrocarbon or alcohol) contacts the anode (commonly referred to as the "fuel electrode") and the oxidant (e.g., air or an oxygen-rich fluid) contacts the cathode (commonly referred to as the "air electrode").

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

[0007] Conventional ceramic supported (e.g. anode supported) SOCs have low mechanical strength and break easily. Therefore, metal supported SOCs with layers of active fuel cell components supported on a metal substrate have recently been developed. In these cells, the ceramic layers can be very thin since they only perform electrochemical functions: in other words, such ceramic layers are not self-supporting but thin coatings / films covering and supported by a metal substrate. Compared to ceramic supported SOCs, such metal supported SOC stacks are stronger, lower cost, have better thermal properties and can be sealed using conventional metal welding techniques.

[0008] The applicant's previous patent application WO-A-2015 / 136295 discloses a metal supported SOFC, wherein such electrochemically active layer (or active fuel cell component layer) comprises anode, electrolyte and cathode layers deposited (e.g. as thin coatings / films) separately on and supported by a metal support plate (e.g. foil). The metal support plate has a porous region surrounded by a non-porous region, and such active layer is deposited on the porous region so that gas can pass through such pores from one side of the metal support plate to the other side to reach the active layer coated thereon. The porous region comprises a plurality of separate small holes (holes drilled through the metal foil substrate) extending through the support plate overlapping the anode (or cathode, depending on the orientation of the electrochemically active layer). The applicant's previous patent application GB-A-2456445 discloses depositing a layer of metal oxide crystalline ceramic on a substrate.

[0009] US-A-2019 / 0330751 discloses a SOEC system with heating capability. WO-A-2021 / 201195 discloses a metal-supported SOFC configured 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 a SOFC 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 SOEC. US-A-2011 / 076594 discloses a main electrolyte layer based on cerium oxide in a SOFC. JP-A-2011181262 and KR-A-20120137917 disclose a SOFC consisting of an electrode and an electrolyte and having no metal support. US-A-2020 / 0014051 discloses a method for manufacturing a metal-supported electrochemical component.

[0010] Attempts have been made to reduce manufacturing costs, increase reliability, and increase the efficiency of SOFCs and SOECs. Unfortunately, materials that have higher performance at lower temperatures are less stable than currently used materials. Specifically, when exposed to a fuel environment, some electrolyte materials are partially reduced to exhibit mixed ionic / electronic conductivity, thereby reducing operating efficiency.

[0011] Therefore, there is a need to provide electrochemical cells with improved electrolyte systems. The present invention aims to address this need. Summary of the invention

[0012] The present invention therefore provides, in a first aspect, an electrochemical cell comprising: a porous metal support; at least one layer of a first electrode, which is located on the porous metal support; a first electron blocking electrolyte layer of rare earth-doped zirconium oxide, which is located on the at least one layer of the first electrode; and a second main electrolyte layer of rare earth-doped cerium oxide, which is located on the first electrolyte layer.

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

[0014] The second host electrolyte layer of rare earth doped cerium oxide may have a thickness of 4 μm or more.

[0015] This is advantageous because it results in less reduction of the second bulk electrolyte layer of doped ceria. Reduction of doped ceria results in higher electronic conductivity of the second bulk electrolyte layer and can lead to expansion of the doped ceria layer. The mixed electronic / ionic conductivity of the electrolyte can lead to reduced efficiency. Expansion of the doped ceria layer can reduce the life of the electrochemical cell.

[0016] The first electron blocking electrolyte layer of rare earth doped zirconia may have a thickness of 1 μm or more, optionally 2 μm or more.

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

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

[0019] Generally, thicknesses of the first electron blocking electrolyte layer within these ranges are advantageous because they make such first and second electrolyte layers together have low electronic conductivity or electronic insulation. The optimal thickness is a compromise between electron leakage (which can begin to occur when the layer is thinner) and ionic resistance (which increases when the layer is thicker).

[0020] The first electron blocking electrolyte layer of rare earth doped zirconia can be advantageously used to block electron leakage current because it is a pure oxide ion conductor. In addition, the first electron blocking electrolyte layer can provide sufficiently low gas permeability so that the second bulk electrolyte layer doped with cerium oxide will not be significantly reduced (making it electronically conductive) during use.

[0021] The first electron blocking electrolyte layer is preferably dense enough to reduce the diffusion of reducing fuel gas (e.g., hydrogen) to the second bulk electrolyte layer. Therefore, the first electron blocking electrolyte layer preferably has low porosity or is not substantially porous (although it may have some closed pores). 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 may have a thickness of 17 μm or less. Optionally, the second bulk electrolyte layer of rare earth doped ceria may have a thickness of 15 μm or less, optionally 12 μm or less.

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

[0024] Therefore, the second body electrolyte layer of rare earth doped cerium oxide has a thickness in the range of 4 μm to 17 μm, a thickness in the range of 5 μm to 15 μm, or a thickness in the range of 6 μm to 12 μm.

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

[0026] The second bulk electrolyte layer may be advantageous because it provides a more gas-tight and mechanically strong layer. However, the optimum thickness is a compromise between gas leakage (which is more likely to occur when the layer is thinner) and ionic resistance (which increases 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 comprise a solid oxide electrochemical cell.

[0029] The electrochemical cell may be a fuel cell or an electrolysis (also known as an electrolyzer) cell. In the fuel cell mode, the fuel contacts the anode (fuel electrode) and the oxidant, such as air or an oxygen-rich fluid, contacts the cathode (air electrode), so that in the fuel cell mode of operation, the air electrode will act as the cathode. A solid oxide electrolyzer cell (SOEC) may have the same structure as a SOFC, but is essentially a SOFC operated in reverse or in a regenerative mode to achieve electrolysis of reagents (e.g., electrolysis of water and / or carbon dioxide to produce hydrogen and / or carbon monoxide and oxygen).

[0030] The advantages of the present disclosure are particularly advantageous when an electrochemical cell has an applied voltage. Thus, the electrochemical cell can be an electrolytic cell when in use.

[0031] Alternatively, the electrochemical cell can be a fuel cell or a reversible fuel cell when in use.

[0032] Other alternative examples are that the electrochemical cell can be an oxygen separator or a sensor when in use.

[0033] The rare earth doped zirconia can comprise zirconia doped with at least one rare earth element selected from Y, Sc, or lanthanide elements (Ln). An example of Ln can be Yb.

[0034] The rare earth doped zirconia can 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 can be a solid solution that can have the chemical 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).

[0035] The dopant concentration in the zirconia can be in the range of 5 to 15 atomic %, optionally in the range of 6 to 12 atomic %.

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

[0037] The rare earth doped ceria comprises ceria doped with at least one rare earth element selected from Y, Sc, or lanthanide elements (Ln).

[0038] The rare earth doped ceria can be selected from samarium doped ceria (SDC), gadolinium doped ceria (GDC), samarium-gadolinium doped ceria (SGDC), and mixtures thereof. Gd and Sm are advantageous and can result in higher ionic conductivity. The doped ceria can be a solid solution that can have the chemical formula Ce (1-x) M x O (2-0.5x-δ) where 0 < x ≤ 0.5, (M = Sc, Y, Ln, or a mixture).

[0039] The dopant concentration in the ceria can be in the range of 3 to 45 atomic %, optionally in the range of 5 to 40 atomic %, optionally in the range of 10 to 20 atomic %.

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

[0041] The layer of the first electrode may comprise a nickel source, which is optionally nickel oxide.The layer of the first electrode may comprise nickel CGO ceramic.

[0042] The layer of the first electrode may have a thickness of 3 μm or more, optionally 5 μm or more, optionally 10 μm or more, optionally 15 μm or more. The layer of the first electrode may have a thickness of 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 layer of the first electrode may have a thickness in the range of 3 μm to 60 μm, 5 μm to 50 μm, optionally 15 μm to 25 μm.

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

[0044] The first electrode may be a fuel electrode. This is particularly advantageous because it reduces the likelihood of increased electronic conductivity of the doped cerium oxide that may occur in a reducing environment. This also reduces the chance of rupture of the second bulk electrolyte layer due to expansion that occurs upon reduction.

[0045] The placement of the first electron blocking electrolyte layer on the fuel side of the cell at least partially blocks the doped ceria layer from being affected by a more reducing (low oxygen chemical) potential that would otherwise affect it. This is advantageous because the doped ceria becomes less electronically conductive in a more oxidizing environment. In addition, the doped ceria will chemically reduce and expand in a more reducing environment (at typical operating temperatures of the SOC), particularly in the presence of an applied voltage (as in the SOEC mode). The result may be failure of the cell under compressive stress at a certain critical voltage (which varies depending on temperature). In addition, there may be creep mechanisms that affect the layer after a period of time at this operating temperature, during temperature cycling, and under applied voltage.

[0046] The electrochemical cell may also 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 activated second electrode layer (disposed closer to the electrolyte) and a bulk second electrode layer. The activated second electrode layer and the bulk second electrode layer may include suitable materials, such as lanthanum cobalt oxide, 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 a metal foil (i.e. a solid metal) provided with a plurality of holes. This has the advantage that the porosity can be adjusted and positioned in specific areas of the substrate. Alternatively or additionally, the metal substrate may have inherent porosity (isotropic porosity), formed as a strip cast, for example, by depositing a thin film from a powder and then sintering the film to form a porous substrate. Reference herein to a metal support or porous steel sheet may refer to either of these situations.

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

[0049] In certain cases (eg, when further protection of the metal support from corrosion is desired), the porous metal support may include a barrier layer on its surface and the electrode layer may be located on the barrier layer.

[0050] The electrochemical cell may contain other layers.

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

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

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

[0054] The layers of the first electrode, 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, a method for manufacturing an electrochemical cell is provided, the method comprising: providing a porous metal substrate having at least one layer of a first electrode on a surface of the porous metal substrate; providing a first ink, the first ink comprising a precursor for a first electron blocking electrolyte layer of rare earth-doped zirconia; applying the first ink to the at least one layer of the first electrode to form the first electron blocking electrolyte layer of rare earth-doped zirconia; optionally drying; optionally sintering; providing a second ink, the second ink comprising a precursor for a second main electrolyte layer of rare earth-doped cerium oxide; applying the second ink to the first electron blocking electrolyte layer to form the second main electrolyte layer of rare earth-doped cerium oxide; optionally drying; and optionally sintering.

[0056] Such first and / or second ink may be applied by spraying, for example atomized spraying, or by printing, optionally 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 may be performed at a temperature in the range of 750° C. to 1100° C., preferably 800° C. to 970° C. The sintering may be performed in an air environment.

[0059] In a fourth aspect, there is therefore provided an electrochemical cell obtainable by the method as described in the third aspect.

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

[0061] In a sixth aspect there is therefore 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 a reagent; and applying an electrical potential to the electrochemical cell.

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

[0063] definition

[0064] In this specification, the term "rare earth metal" or "rare earth element" refers to a metal selected from Y, Sc and "lanthanide elements".

[0065] The term "dopant" as used herein is not intended to be limited to a maximum percentage of an element, ion, or compound added to a chemical structure. Similarly, the term "doping" is intended to mean adding a certain amount of an element, ion, or compound to a material. It is not limited to a maximum amount of material after which the addition of the material no longer constitutes doping.

[0066] The term "perovskite structure" as used herein refers to a chemically connected crystalline structure having a single network structure of a general perovskite (ABX3) structure. This does not mean that the single network structure needs to have a single, uniform crystalline structure throughout the structure. However, when different crystalline structures are produced between different regions of the network structure, it is often the case that these regions have complementary structures that allow chemical bonds to form more easily between them.

[0067] The term "solid oxide cell" (SOC) is intended to encompass 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 contains the element, compound, or other material, whether or not chemically linked in the source. The source of the element, compound, or other material may be an elemental source (e.g., Ln, Ni, or O2) or may be in the form of a compound or mixture that contains the element, compound, or other material and includes one or more of these elements, compounds, or materials.

[0069] In this specification, the electrochemical cells, SOC, SOFC and SOEC referred to may be tubular or planar cells. The electrochemical cell units may be tubular or planar structures. Planar fuel cell units may be arranged to overlap each other in a stack configuration, for example 100 to 200 fuel cell units in a stack, and such individual fuel cell units are arranged electrically in series. Therefore, the so-called "stack of electrochemical cells" refers to a plurality of electrochemical cells arranged electrically in series.

[0070] The electrochemical cell may be a fuel cell, a reversible fuel cell, or an electrolyzer cell. In general, these cells may have the same structure and reference to an electrochemical cell may refer (unless the context suggests otherwise) to any of these types of cells.

[0071] Because of possible confusion between a fuel cell or an electrolyzer / electrolysis cell, "oxidant electrode" or "air electrode" and "fuel electrode" are used herein and interchangeably to refer to the cathode and anode, respectively, of a SOFC.

[0072] The electrochemical cells encompassed by the present invention may comprise:

[0073] a) Two planar components welded together with a fluid volume between them (e.g. a substrate with an electrochemical layer and an interconnect (separating plates));

[0074] b) Three planar components welded together with a fluid volume between them (eg a substrate with electrochemical layers and interconnects (separating plates) and separators providing the fluid volume).

[0075] It will be appreciated by those skilled in the art that the various features of aspects of the disclosure described herein may be combined with any other features of the same or other aspects of the disclosure with appropriate modification, if desired.

[0076] Furthermore, while all aspects of the invention or disclosure preferably "comprise" the features described in connection with that aspect, it is specifically contemplated that they may "consist of" or "consist essentially of" those features set out in the claims.

[0077] The present invention is described below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1A cross-sectional view of an electrochemical cell is shown.

[0079] Figure 2 A scanning electron micrograph (SEM) of a cross-section of a portion of an electrochemical cell is shown.

[0080] Figure 3 A graph showing the change in cell voltage as a function of the normalized current density of the cell at 550° C.; 50%:50% H 2 :H 2 O according to the present disclosure is shown. DETAILED DESCRIPTION

[0081] Figure 1 A cross-sectional view of an electrochemical cell unit 2, which may be a SOFC or SOEC, is shown schematically and not to scale (for clarity). A ferrite stainless steel metal support 4 has a peripheral non-porous portion 6 and a central porous portion 8 through which a plurality of holes have been drilled. A barrier layer (not shown) for reducing corrosion is disposed on the surface of the metal support 4. A fuel electrode layer 10 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 of rare earth (RE) stabilized zirconia (RE = Y, Sc or any Ln, such as 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 of rare earth doped cerium oxide (RE = Y, Sc or any Ln) having a thickness of 4 μm or more (optionally 6 μm to 12 μm) is disposed on the first electrolyte layer 12. The second electrolyte layer 14 surrounds the fuel electrode 10 to prevent gas from flowing from the fuel side 20 through the fuel electrode layer 10 to the air (oxidant) side 18, or vice versa. The cell ends with a second (air) electrode assembly 16 disposed on the second electrolyte layer 14. The second electrode 16 can be formed by an activated air electrode layer and a bulk air electrode layer of the LCN 60.

[0082] Figure 2 A SEM of a portion of a cell is shown, showing a fuel electrode layer 10, a first electrolyte layer 12 of rare earth (RE) stabilized zirconia (8YZ, i.e. 8 atomic % Y-doped zirconia) and a second electrolyte layer 14 of rare earth doped cerium oxide (RE = Y, Sc or any Ln).

[0083] At operating temperatures of electrochemical cells according to the present disclosure (e.g., 550° C. to 625° C.), cerium oxide can chemically reduce and expand when voltage is increased (this occurs particularly in SOEC mode). This is not true for YSZ. The result is that the cell fails at a certain critical voltage (depending on temperature) under compressive stress. When temperature is cycled and voltage is applied at operating temperatures, creep mechanisms may also occur under stress, reducing the life of the cell.

[0084] To address this problem, embodiments of the disclosed electrochemical cells may be constructed with a double layer electrolyte comprising a first layer of rare earth (RE) stabilized zirconia (RE = Y, Sc or any Ln, such as Yb) with a dopant concentration in the range of 6 to 12% (e.g., where % is atomic % of the metal), where the optimum concentration depends on the RE (e.g., about 8% for Y and about 10% for Sc). As a pure oxide ion conductor, the function of this layer is to block leakage current and provide low or no gas permeability so that the second layer of doped cerium oxide is not significantly reduced (which makes it electronically conductive). The thickness may be in the range of 1 to 4 μm thick or 2 to 3 μm. It is believed that this YSZ or ScSZ thickness provides sufficient electron blocking functionality: the thickness is a compromise between electron leakage (which can occur in thinner layers) and ionic resistance (which increases with thickness). The layer is dense enough to prevent H2 gas from passing through and reaching the CGO electrolyte layer. The density can be achieved by careful selection of particle size, sintering aids, and temperature profile.

[0085] The second layer of rare earth doped cerium oxide (RE = Y, Sc or any Ln) can have a dopant concentration in the range of 5 to 40%, with an optimum concentration of 10 to 20%. The main function is to provide mechanical stability with very low or no gas permeability. An important performance metric is ionic impedance, which should be as low as possible. The thickness can be in the range of 5 to 15 μm or 6 to 10 μm. The thicker CGO layer provides a gas-tight and mechanically strong electrolyte.

[0086] Figure 3 An IV curve of a battery according to the present disclosure at 550° C. with a 50%:50% H 2 :H 2 O environment is shown, which shows that the battery voltage can reach 1.45V at a normalized current density of 1.

[0087] The electrochemical cell according to the present disclosure substantially reduces the electronic conductivity of CGO by reducing or eliminating the thermal conditions (ie, reducing environment) that lead to the reduction of ceria. For the same reason, it can also reduce electrolyte cracking due to chemical expansion of ceria reduction.

[0088] Reference numerals

[0089] 2 Electrochemical Cells

[0090] 4Metal support parts

[0091] 6 Non-porous part of metal support

[0092] 8Porous part of the metal support

[0093] 10Fuel electrode layer

[0094] 12. First electrolyte layer

[0095] 14 Second electrolyte layer

[0096] 16 Second (air) electrode assembly

[0097] 18 Oxidant (air) side

[0098] 20 Fuel side

[0099] All publications mentioned in the above specification are incorporated herein by reference. Although exemplary embodiments of the present invention have been disclosed herein in detail with reference to the accompanying drawings, it is to be understood that the present invention is not limited to the precise embodiments and that various changes and modifications may be made by those skilled in the art in the precise embodiments without departing from the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. An electrochemical cell comprising: A porous metal support; at least one layer of a first electrode disposed on said porous metal support; a first electron blocking electrolyte layer of rare earth doped zirconium oxide on the at least one layer of the first electrode; and A second main electrolyte layer of rare earth doped cerium oxide is located on the first electron blocking electrolyte layer. 2 . The electrochemical cell according to claim 1 , wherein the first electron blocking electrolyte layer of rare earth doped zirconia has a thickness of 0.5 μm or more.

3. The electrochemical cell according to claim 1 or 2, wherein the second bulk electrolyte layer of rare earth doped cerium oxide has a thickness of 4 μm or more.

4. The electrochemical cell according to any one of the preceding claims, wherein the first electron blocking electrolyte layer of rare earth doped zirconium oxide has a thickness of 5 μm or less.

5. The electrochemical cell according to any one of the preceding claims, wherein the second bulk electrolyte layer of rare earth doped ceria has a thickness of 17 μm or less.

6. The electrochemical cell according to any one of the preceding claims, wherein the electrochemical cell is a solid oxide cell.

7. The electrochemical cell according to any one of the preceding claims, wherein the rare earth doped zirconium oxide comprises zirconium oxide doped with at least one rare earth element selected from Y, Sc or a lanthanum element (Ln).

8. The electrochemical cell according to any one of the preceding claims, wherein the rare earth doped cerium oxide comprises cerium oxide doped with at least one rare earth element selected from Y, Sc or a lanthanum element (Ln).

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

10. The electrochemical cell of any one of the preceding claims, wherein the layer of the first electrode comprises doped ceria, optionally wherein the layer of the first electrode comprises doped ceria gadolinium oxide (CGO).

11. The electrochemical cell of any preceding claim, wherein the layer of the first electrode comprises a source of nickel, optionally nickel oxide.

12. The electrochemical cell of any preceding claim, wherein the layer of the first electrode comprises nickel CGO ceramic.

13. The electrochemical cell of any preceding claim, wherein the layer of the first electrode has a thickness of 3 μm or more, optionally 5 μm or more, optionally 10 μm or more, optionally 15 μm or more.

14. The electrochemical cell of any one of the preceding claims, wherein the layer of the first electrode has a thickness of 50 μm or less, optionally equal to or less than 45 μm or less, optionally 40 μm or less, optionally 35 μm or less.

15. The electrochemical cell of any preceding claim, wherein the first electrode is a fuel electrode.

16. The electrochemical cell of any preceding claim, further comprising a second electrode located on the second electrolyte layer, optionally wherein the second electrode is an air electrode.

17. The electrochemical cell according to any one of the preceding claims, wherein the porous metal substrate comprises a steel substrate, preferably a stainless steel substrate.

18. The electrochemical cell of any one of the preceding claims, wherein the porous metal substrate comprises a drilled metal substrate, which is optionally a laser drilled metal substrate.

19. The electrochemical cell of any preceding claim, wherein the porous metal substrate comprises a barrier layer on a surface thereof, and the layer of the first electrode is located on the barrier layer.

20. A stack of electrochemical cells, wherein each electrochemical cell is an electrochemical cell according to any one of the preceding claims.

21. A method for manufacturing an electrochemical cell, the method comprising: providing a porous metal substrate having at least one layer of a first electrode on a surface of the porous metal substrate; providing a first ink comprising a precursor for a first electron blocking electrolyte layer of rare earth doped zirconium oxide; applying the first ink to the at least one layer of the first electrode to form a first electron blocking electrolyte layer of the rare earth doped zirconia; optionally drying; optionally sintering; providing a second ink comprising a precursor for a second bulk electrolyte layer of rare earth doped ceria; applying the second ink to the first electron blocking electrolyte layer to form the second electrolyte layer of the rare earth doped cerium oxide; optionally drying; as well as Optionally sintered.

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

23. An electrochemical cell obtainable by the method according to claim 21 or 22.

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

25. A method of operating an electrochemical cell in an electrolysis mode, the method comprising: Providing an electrochemical cell according to any one of claims 1 to 20; contacting the electrochemical cell with a reagent to be electrolyzed; and applying an electrical potential to the electrochemical cell.

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