Method for manufacturing an electrochemical cell, electrochemical cell, electrochemical cell device

Abstract

The invention relates to a method (10) for producing an electrochemical cell (12), in particular an electrolysis cell (14), comprising a cell substrate (16), a first electrode layer (26), a second electrode layer (32), an electrolyte layer (28) arranged between the first electrode layer (26) and the second electrode layer (32), and a first barrier layer (22) arranged between the cell substrate (16) and the first electrode layer (26), wherein the first barrier layer (22) is deposited onto the cell substrate (16) by means of a physical vapor deposition (PVD) process, and wherein the first barrier layer (22) comprises a cerium oxide which has a first doping with a rare earth element. It is proposed that the cerium oxide has a second doping with a transition metal from the fifth or sixth subgroup.

Description

[0001] The invention relates to a method for manufacturing an electrochemical cell according to the preamble of the independent claim. The invention further relates to an electrochemical cell and an electrochemical cell device. State of the art

[0002] Solid oxide electrolyzer cells (SOECs) are promising electrochemical energy converters that enable the efficient conversion of electrical energy into chemical energy in the form of hydrogen. SOECs with metallic substrates, in particular, offer advantages in terms of mechanical stability, thermal conductivity, and lower manufacturing costs.

[0003] A known problem with SOECs using metallic substrates, especially at high operating temperatures, is the formation of an undesirable oxide layer, the so-called thermally grown oxide (TGO) layer, at the interface between the metallic substrate and the electrochemically active layers. The TGO layer, usually consisting of chromium oxide (Cr₂O₃), forms through the reaction of the chromium contained in the steel with oxygen or water vapor during operation.

[0004] However, this TGO layer poses a barrier to the performance and longevity of the SOEC. Its high electrical resistance leads to significant ohmic losses within the cell, thus reducing the energy efficiency of the electrolysis process. Furthermore, the continuous growth of the TGO layer during operation induces mechanical stresses at the interface between the layers. These stresses can compromise the cell's integrity and, over time, lead to cracking, delamination, and ultimately, SOEC failure. Disclosure of the invention Advantages

[0005] The present invention describes a method for producing an electrochemical cell, in particular an electrolysis cell, comprising a cell substrate, a first electrode layer, a second electrode layer, an electrolyte layer arranged between the first and second electrode layers, and a first barrier layer arranged between the cell substrate and the first electrode layer, wherein the first barrier layer is deposited onto the cell substrate by means of a physical vapor deposition (PVD) process, wherein the first barrier layer comprises a cerium oxide which has a first doping with a rare earth element. According to the invention, the cerium oxide has a second doping with a transition metal from group 5 or group 6.

[0006] The advantage of this process lies in the production of an electrochemical cell with improved performance and stability. Doping the cerium oxide in the first barrier layer with a transition metal from the fifth or sixth subgroup increases the layer's conductivity while simultaneously reducing oxygen conductivity. This leads to a reduction in ohmic losses within the cell and improves overall efficiency. In particular, the reduced oxygen conductivity prevents the formation of a thermally grown oxide layer (TGO layer) on the cell substrate. A TGO layer typically consists of chromium oxide (Cr₂O₃) and forms in state-of-the-art cells through the reaction of chromium contained in the steel of the cell substrate with oxygen or water vapor during cell operation. Using the PVD process, the first barrier layer can be produced very thinly and uniformly.

[0007] An electrochemical cell is understood to be, in particular, an arrangement that provides usable electrical energy through chemical reactions or is intended for the chemical production or conversion of substances by applying a voltage. An electrochemical cell has at least two or more functional layers. The functional layers comprise at least two electrode layers and a separating layer or electrolyte layer. The electrode layers each function as an electron conductor and are conductively connected to the separating layer or electrolyte layer. Also important for the electrode layers is ion transport and catalytic activity or oxygen exchange capacity between the electrode layer and the gas phase. The separating layer or electrolyte layer functions, in particular, as an ion conductor, especially for oxygen ions. Furthermore, the separating layer or electrolyte layer...Electrolyte layer provided for the separation of the two gas compartments, for example the separation between air and fuel gas in a fuel cell.

[0008] In particular, the term "electrochemical cell" shall be understood to mean a fuel cell or an electrolysis cell. In this context, the terms "fuel cell" and "electrolysis cell" shall be understood to mean, in particular, at least a part, especially a subassembly, of a fuel cell system, in particular a solid oxide fuel cell system, and / or an electrolysis cell device, in particular a high-temperature electrolyzer. In particular, the electrochemical cell may also comprise the entire fuel cell, in particular the entire solid oxide fuel cell, the entire electrolyzer, in particular the entire high-temperature electrolyzer, a stack of several stacked fuel cells and / or electrolysis cells, and / or a combination of several stacks of fuel cells and / or electrolysis cells.

[0009] Preferably, the electrochemical cell is designed to convert a fuel into electrical energy in an electrochemical combustion process by supplying an oxidant. Alternatively or additionally, the electrochemical cell is designed to separate a fluid into at least two components in a separation process by supplying electrical energy. "Designed" is understood to mean, in particular, specially configured, specially designed, and / or specially equipped. The phrase "designed" means, in particular, that an object fulfills and / or performs this specific function in at least one application and / or operating state.

[0010] Preferably, the electrochemical cell comprises at least three functional layers. A functional layer is preferably understood to be a layer that is directly involved in the electrochemical reaction process and / or the separation process carried out by means of the electrochemical cell. In particular, two of the functional layers are preferably configured as electrode layers, especially for use as the cathode and / or anode. Preferably, at least one electrode layer is configured as an oxidant electrode or air electrode, especially for contact with the oxidant and / or a fission product. Preferably, at least one electrode layer is configured as a fuel electrode, especially for contact with the fuel and / or another fission product. Preferably, at least one functional layer is configured as an electrolyte layer.Preferably, at least one separating layer is arranged on at least one electrode layer, in particular between two electrode layers.

[0011] A cell substrate can, in particular, comprise a sintered or unsintered ceramic or metal-ceramic substrate. It is also possible for the cell substrate to comprise a sintered or unsintered powdered metallic substrate. It is also conceivable that the cell substrate comprises at least a portion of a metal; for example, the cell substrate can comprise a sheet with drilled, etched, and / or punched holes, and / or expanded metal, foam, mesh / fabric, or the like. In particular, the cell substrate can be highly porous or have large pores and / or openings; for example, the cell substrate can have meshes, drilled or etched holes, or the like. Advantageously, the cell substrate is made entirely of metal.

[0012] Advantageously, the first electrode layer is a fuel gas electrode layer. Preferably, the first electrode layer comprises a mixture of Ni or NiO with doped cerium oxide, e.g., Gd-doped cerium oxide (CGO) or Sm-doped cerium oxide (SDC). It is also conceivable that the first electrode layer comprises a mixture of Ni or NiO with stabilized zirconium oxide, in particular zirconium oxide stabilized with Sc, Y, and / or Ce, for example, scandium-stabilized zirconium oxide (ScSZ), yttrium-stabilized zirconium oxide (YSZ), scandium / yttrium-stabilized zirconium oxide (ScYSZ), scandium / cerium-stabilized zirconium oxide (ScCeSZ), or the like. It is also possible that the first electrode layer has oxides with a perovskite structure, for example La(Sr)Ga(Mg)O3-δ, SrCe(Yb)O3-δ or La-Ca-Cr oxide, optionally mixed with doped cerium oxide or stabilized zirconium oxide.

[0013] Niobium (Nb), tungsten (W), vanadium (V), molybdenum (Mo) and / or tantalum (Ta) have proven to be particularly advantageous elements for the second doping with at least one transition metal from the fifth or sixth subgroup of the periodic table.

[0014] The cell substrate is first coated with the first barrier layer, and then the first electrode layer is applied to the first barrier layer. In particular, the first electrode layer can be a suspension-based layer. This allows for the easy and reliable achievement of advantageous layer thicknesses. For example, the first electrode layer can be deposited using screen printing. However, other processes such as gravure printing, flexographic printing, pad printing, spraying, film casting, or slot-die coating are also conceivable for applying the first electrode layer.

[0015] By placing the first barrier layer between the first electrode layer and the cell substrate, reactions of the cell substrate with the first electrode layer can be prevented, especially in the further manufacturing process.

[0016] The electrolyte layer advantageously comprises zirconium oxide stabilized at least with scandium (Sc). The electrolyte layer can be deposited by a sputtering process or another thin-film method; however, it is also conceivable that the electrolyte layer could be applied by screen printing. Other processes, such as gravure printing, flexographic printing, pad printing, spraying, foil casting, or slot-die coating, are also possible.

[0017] An example of thin-film deposition methods is PVD, or physical vapor deposition, such as magnetron sputtering or reactive magnetron sputtering, high-power impulse magnetron sputtering (HiPIMS), gas flow sputtering, or (plasma-enhanced) electron beam evaporation. Another example of thin-film deposition methods is CVD, or chemical vapor deposition, such as metal-organic CVD, plasma-enhanced CVD, or laser-enhanced CVD. Atomic layer deposition (ALD), which can potentially produce very thin, dense layers via multi-stage chemical deposition, also falls into this category. Further examples of thin-film deposition methods include particle-based (vacuum) spraying processes such as aerosol deposition, or novel methods of plasma spraying or thermal plasma spraying.

[0018] Advantageously, in this process, the cell substrate is first coated with the first barrier layer, the first electrode layer, and optionally a transition layer. Before applying the electrolyte layer—particularly by a sputtering process or another thin-film method—the composite of the cell substrate with the first electrode layer and, if applicable, the transition layer is advantageously sintered in a first sintering step. However, it is also conceivable that the first barrier layer, the first electrode layer—optionally a transition layer—and the electrolyte layer are applied—particularly by a printing process—and this composite layer is sintered together. Sintering is preferably carried out at a temperature between 900°C and 1200°C, and particularly preferably between 1000°C and 1100°C.Preferably, the layered structure on the cell substrate is sintered in air, for example, for a time between 0.1 and 10.0 hours, preferably between 0.5 and 5.0 hours, and particularly preferably between 1.0 and 3.0 hours. This reduces energy consumption and increases the process speed. Alternatively, sintering at higher temperatures and / or in atmospheres other than air is possible, for example, in forming gas or in an inert gas such as nitrogen or argon.

[0019] In the sintering process step, the suspension-based functional layers, in particular the first electrode layer, sinter to their respective desired microstructure; in particular, a suspension-based transition layer sinters to an advantageously pore-free or finely porous microstructure, especially with low roughness.

[0020] In advantageous embodiments, a second barrier layer can be deposited on the electrolyte layer. In particular, the second barrier layer is designed as a chemical barrier. For example, an electrolyte layer comprising stabilized zirconium oxide can be protected by a thin second barrier layer comprising doped cerium oxide, which protects the zirconium oxide, for example, against a reaction with a second electrode layer containing sr adjacent to the cell structure. Advantageously, the second barrier layer has a thickness between 0.05 µm and 5.0 µm, preferably between 0.1 µm and 2.0 µm, and most preferably between 0.5 µm and 1.0 µm. The second barrier layer is particularly advantageously applied using a thin-film method.

[0021] The second electrode layer is advantageously the air electrode. Advantageously, the second electrode layer is deposited using a suspension-based process, particularly a printing process such as screen printing. The second electrode layer can, for example, consist of oxides with a perovskite structure, such as La-Sr-Co oxide (LSC), La-Sr-Co-Fe oxide (LSCF), or La-Sr-Mn oxide (LSM). The second electrode layer can also consist of oxides with a perovskite structure combined or mixed with doped cerium oxide—for example, CGO or SDC—and / or combined or mixed with stabilized zirconium oxide, such as YSZ, ScSZ, ScYSZ, ScCeSZ, and the like.

[0022] It is advantageous to have a current collector layer or contact layer arranged on the second electrode layer. Preferably, the current collector layer or contact layer is deposited on the second electrode layer using a suspension-based process. The current collector layer or contact layer can, for example, have a liquid contact coating (LSC). Advantageously, the current collector layer or contact layer is applied by screen printing. However, other processes, such as gravure printing, flexographic printing, pad printing, spraying, film casting, or slot-die coating, are also conceivable for applying the current collector layer or contact layer.

[0023] Optionally, after applying the second electrode layer or a current collector layer or contact layer, a second sintering step is carried out, preferably at a temperature below 1100 °C, and particularly preferably below 1000 °C. Advantageously, a temperature is chosen that is below the temperatures typically used for sintering fuel gas electrodes and, if applicable, electrolytes. Advantageously, the second sintering step is carried out at a lower temperature than the first. In particular, it is advantageous for the second sintering step to be carried out at a temperature between 800 °C and 1100 °C, and particularly preferably between 900 °C and 1000 °C.

[0024] Advantageous further developments of the method are possible due to the features listed in the dependent claims.

[0025] The process is further improved by using a sputtering process in the PVD process and employing a target containing between 0.2 and 10.0 atomic percent of the transition metal from the fifth or sixth subgroup relative to the metals in the target, preferably between 0.5 and 5.0 at.%, and particularly preferably between 1.0 and 2.0 at.%. The use of a sputtering process with a defined target material allows for precise control of the doping concentration in the first barrier layer. The parameter range for the proportion of the transition metal from the fifth or sixth subgroup has proven particularly advantageous for producing a first barrier layer with optimal second doping for high conductivity and low oxygen conductivity.

[0026] The target can be a metallic target and / or contain metal compounds, such as metal oxides and / or metal nitrides. It is important that the proportion of at least 10 at% Sc in the target refers only to the metallic atoms in the target. If, for example, the target contains gadolinium oxide (Gd₂O₃), cerium oxide (CeO₂), and niobium oxide (Nb₂O₅), the oxygen atoms of both compounds are disregarded when determining the at% proportion of Nb with respect to the metals Gd, Ce, and Nb. In particular, oxygen and nitrogen are not metals.

[0027] For example, the target could have the metal composition Me X Gd Y Ce 1-X-Yhaving, wherein Me is a transition metal from the fifth subgroup or sixth subgroup and X has a value between 0.002 and 0.1, preferably between 0.005 and 0.05, particularly preferably between 0.01 and 0.02 and Y has a value between 0.005 and 0.3, preferably between 0.01 and 0.2, particularly preferably between 0.05 and 0.1.

[0028] It is conceivable that the target could be designed as a planar target, for example. A tube target, particularly a rotating tube target, is advantageous. Argon is typically used as the process gas, but the use of other noble gases such as helium, neon, and / or krypton is also possible.

[0029] It is also advantageous if the PVD process is a reactive sputtering process using oxygen as the reactive gas. In particular, a reactive magnetron sputtering process with oxygen as the reactive gas is conceivable. By using a reactive sputtering process with oxygen, it is possible to form the desired oxides on the first barrier layer when the target contains metallic components, such as metallic Gd and / or Ce. Even if the metals in the target are present as compounds with other elements, such as nitrogen, the desired oxide compounds can be produced in this way. Furthermore, the oxygen stoichiometry of the first barrier layer can be controlled during the deposition process. This enables the production of a dense and well-adhering layer with optimal properties.

[0030] Oxygen is added to the process gas, such as argon, as a reactive gas. Advantageously, the oxygen content in the plasma during the sputtering process is controlled within a preset, optimal range. The oxygen content must not be too high, as this can lead to the formation of oxide layers on the target, a process known as target poisoning. Conversely, the oxygen content must not be too low, as this would prevent the desired oxygen compounds from being deposited at a high deposition rate. The optimal range for the oxygen content in the plasma depends on the process parameters and the tools used, particularly the dimensions of the sputtering chamber, the target, and the cell substrate, the precise material compositions, the heating power, the plasma heating temperatures, and the specific heating methods, among other factors.The oxygen content can either be set at a fixed level or controlled by a suitable process control system, in particular by control based on a process parameter or a measured value, such as a measurement of the cathode voltage and / or a measurement of the plasma composition by optical emission spectrometry (OES) and / or by a lambda probe. For example, the control system can be designed to keep the cathode voltage constant by appropriately varying the oxygen flow supplied to the plasma.

[0031] The present invention further describes an electrochemical cell, in particular an electrolysis cell, comprising a cell substrate, a first electrode layer, a second electrode layer, an electrolyte layer arranged between the first and second electrode layers, and a first barrier layer arranged between the cell substrate and the first electrode layer, wherein the first barrier layer comprises a cerium oxide which is first doped with a rare-earth element. According to the invention, the cerium oxide is secondly doped with a transition metal from group 5 or 6. This provides the advantages of an improved electrochemical cell described above. The second doping with a transition metal increases the conductivity and reduces the oxygen conductivity, leading to improved performance and stability of the electrochemical cell.

[0032] The electrochemical cell is further improved by having the first barrier layer contain between 0.2 and 10.0 atomic percent of the second doping with respect to the metals of the first barrier layer, preferably between 0.5 and 5.0 at.%, and particularly preferably between 1.0 and 2.0 at.%. This parameter range for the proportion of the second doping ensures that the first barrier layer exhibits the desired properties. Excessive doping can impair conductivity, while insufficient doping does not adequately reduce oxygen conductivity.

[0033] It has proven advantageous if the second doping of the first barrier layer contains niobium and / or tungsten as a transition metal from the fifth or sixth transition group.

[0034] The electrochemical cell is further improved if the first doping of the first barrier layer consists of gadolinium, samarium, lanthanum, yttrium, and / or neodymium as rare earth elements. Gadolinium is particularly advantageous when used as the first dopant of the cerium oxide, resulting in a Gd-doped cerium oxide, or CGO or GDC for short.

[0035] The electrochemical cell is further improved by providing the first barrier layer with a thickness between 0.3 and 5.0 µm, preferably between 0.5 and 3.0 µm, and most preferably between 1.0 and 2.0 µm. The thickness of the first barrier layer plays a crucial role in the cell's performance and stability. A layer that is too thin can lead to insufficient protection of the first electrode layer from the substrate, while a layer that is too thick can increase the cell's resistance. The parameter range found here ensures an optimal compromise between protection and resistance.

[0036] It is also advantageous if the cerium oxide of the first barrier layer exhibits a substoichiometry with respect to oxygen between 1% and 10%, advantageously between 3% and 8%, and particularly advantageous between 5% and 6%. The resulting layer is not completely oxidized and thus grows substoichiometrically. This allows for a denser second barrier layer with improved oxidation protection. This can be achieved, in particular, in a sputtering process for producing the first barrier layer through appropriate process control, especially with feedback control of the process parameters. For example, the oxygen flow, pulse duration, and / or plasma power can be adjusted to a measured variable such as cathode voltage, plasma emission, and / or oxygen concentration.In particular, when producing the first barrier layer using a reactive sputtering process with oxygen as the reactive gas, the oxygen content in the process gas can be adjusted so that the desired substoichiometry with respect to oxygen in the cerium oxide is achieved.

[0037] If the cerium oxide of the first barrier layer has a substoichiometry with respect to oxygen of x%, this means that the oxygen concentration in the cerium oxide is (100 - x)% of the concentration that would be present in the corresponding stoichiometric oxide. For example, if the oxygen concentration in the cerium oxide of the first barrier layer has a substoichiometry of 5%, this means that the oxygen concentration in the cerium oxide is 95% of the concentration of the stoichiometric cerium oxide.

[0038] The present invention further describes an electrochemical cell device comprising an electrochemical cell unit with at least one electrochemical cell according to the present invention. The electrochemical cell device benefits from the advantages of the improved electrochemical cell. The improved performance, stability, and efficiency of the individual cell contribute to the overall performance and service life of the cell device. Drawings

[0039] The drawings illustrate exemplary embodiments of the method for manufacturing an electrochemical cell, the electrochemical cell itself, and electrochemical cell devices, and are explained in more detail in the following description. They show Fig. 1 the electrochemical cell according to the present invention produced by the method according to the present invention, Fig. 2 a schematic representation of the process for manufacturing the electrochemical cell, Fig. 3 a schematic representation of an electrolysis cell device with an electrochemical cell according to the present invention as well as Fig. 4 a schematic representation of a fuel cell device with an electrochemical cell according to the present invention. Description

[0040] In the different versions, identical parts receive the same reference numbers.

[0041] Fig. Figure 1 shows an electrochemical cell 12, which is exemplified as an electrolysis cell 14, in Fig. 2 a schematic overview of the sequence of process steps S1 to S6 of a process 10 for the production of this electrochemical cell 12.

[0042] In a first step S1, a cell substrate 16 is coated with a first barrier layer 22 (sub-step S1a), and a transfer substrate is coated with a first electrode layer 26 (sub-step S1b). For example, the cell substrate 16 is a metallic cell substrate, manufactured as a sheet with a plurality of through openings 20. The openings 20 can be etched, punched, drilled, or formed using an expanded metal process.

[0043] The process uses a transfer lamination process as an example, in which layers are first applied to a transfer substrate, then these layers are laminated onto the cell substrate with the transfer substrate, and in a subsequent step the transfer substrate is removed - the transfer substrate is therefore not part of the finished electrochemical cell.

[0044] This has the advantage that very thin and smooth layers can be applied using the transfer substrate, since the transfer substrate – unlike the cell substrate, if applicable – can be very flat and smooth. This is possible because the transfer substrate is only used for the manufacturing process and is not part of the electrochemical cell. After the transfer substrate is removed, the surface of the first layer – the former contact surface of the transition layer to the transfer substrate – exhibits high flatness and low roughness, which is advantageous for the subsequent application of a thin, dense functional layer, particularly a separating layer or electrolyte layer, in a later process step. In this way, the risk of defects forming in the functional layer, especially the separating layer or electrolyte layer, due to pores, defects, or "high spots" in the transition layer can be reduced.

[0045] However, transfer lamination is not essential for the present invention; it is also possible that the layers are deposited or applied directly onto the cell substrate 16, in particular the functional layers, especially electrode layers.

[0046] In the exemplary embodiment, in step S1a, the metallic cell substrate 16 is coated with a metal oxide as a first barrier layer 22. The first barrier layer 22 serves as a chemical barrier to the first electrode layer 26 produced in step S1b. The metal oxide of the first barrier layer 22 is a niobium-doped CGO. In the exemplary embodiment, the niobium doping is 0.7 at.%.

[0047] The coating of the first barrier layer 22 is carried out using a PVD process, in this example a reactive sputtering process with oxygen as the reactive gas. In the exemplary embodiment, a target comprising Nb is used for this purpose. 0,007 Gd0,1 Ce 0,893 used. For example, the thickness of the first barrier layer is 22 1.5 µm.

[0048] As an example, argon with a varying proportion of oxygen is used as the process gas. The oxygen content is controlled according to the cathode voltage. The oxygen content is adjusted such that the cerium oxide of the first barrier layer 22 exhibits a substoichiometry with respect to oxygen of 4%.

[0049] In a variant, it is conceivable that before the first barrier layer 22 the metallic cell substrate 16 is coated with an intermediate layer, preferably by means of a PVD process, and then the first barrier layer 22 is applied to the intermediate layer.

[0050] In an optional sub-process of step S1b, a thin suspension-based transition layer 24 is first applied to the transfer substrate. For example, the transfer substrate is a polymer film. In this embodiment, the transition layer is applied with a wet film thickness of 4.0 µm. In the dried and sintered state, the dry film thickness of the transition layer is 2.0 µm. For example, the transition layer 24 is applied by gravure printing; however, other processes such as screen printing, flexographic printing, or spray coating are conceivable. The transition layer 24 is then dried. For example, the transition layer 24 consists of NiO-CGO in a suspension. The particle sizes, mixing ratios, and additives are selected to achieve a microstructure with as few pores as possible and / or a fine pore structure after subsequent sintering at temperatures below 1100 °C (step S4).In the exemplary embodiment, a particle size distribution is used for the powders of the transition layer 24 in which 50% of the particles have a particle size of less than 0.1 µm, 97% of the particles have a particle size of less than 1.0 µm, and no particles are larger than 10.0 µm.

[0051] After drying, in the main part of sub-step S1b, a suspension-based first electrode layer 26 is applied to the transition layer 24. In other variants, the first electrode layer 26 is applied directly to the transfer substrate in sub-step S1b. For example, the first electrode layer 26 is a fuel gas electrode layer. In this embodiment, the wet film thickness of the first electrode layer 26 is 40 µm. In the dried and sintered state, the dry film thickness of the first electrode layer 26 is approximately 20 µm. In various embodiments, the wet film thickness of the first electrode layer 26 is preferably between 1.0 µm and 100.0 µm, particularly preferably between 10 µm and 50 µm, resulting in a preferred dry film thickness in the dried and sintered state of between 0.5 µm and 50 µm, particularly preferably between 5 µm and 25 µm. By way of example, the first electrode layer 26 is applied by screen printing.The first electrode layer 26 is then completely dried, or alternatively, at least partially dried. In the exemplary embodiment, the first electrode layer 26, or its suspension, comprises NiO-CGO. The particle sizes, mixing ratios, and additives are selected such that, after subsequent sintering at below 1100°C (see S4), the first electrode layer 26 achieves the most efficient and sufficiently age-resistant microstructure possible.

[0052] In an optional subsequent step S2, the transition layer 24 and the first electrode layer 26 are laminated from the transfer substrate 18 onto the metallic cell substrate 16 coated with the first barrier layer 22. In the exemplary embodiment, lamination is carried out by pressing at 80°C and with a pressure of 30 MPa. In variants, lamination is carried out by pressing at temperatures between 50°C and 100°C, and at pressures between 5 MPa and 50 MPa. After lamination, the first electrode layer 26 is arranged between the transition layer 24 and the cell substrate 16. By way of example, the first barrier layer 22 is arranged between the cell substrate 16 and the first electrode layer 26.

[0053] In an optional subsequent step S3, the transfer substrate is removed by peeling. The layered assembly consisting of cell substrate 16, first electrode layer 26, and transition layer 24 is then sintered in a single step S4. This sintering is carried out, for example, at 1050 °C in air for a period of 2 hours.

[0054] Subsequently, in an optional step S5, an electrolyte layer 28 is deposited onto the sintered transition layer 24 by a sputtering process. In the exemplary embodiment, the second electrolyte layer 28 has a thickness of 2 µm. In variants, the thickness of the second electrolyte layer 28 is between 1 µm and 3 µm. As an example, the second electrolyte layer 28 is applied by reactive magnetron sputtering. For this purpose, a target with a metallic alloy of 80 at.% Zr, 18 at.% Sc, and 2 at.% Y is used. Sc and Y are additive metals intended to stabilize or dope the zirconium oxide in the electrolyte layer 28. The amount of additive metals in the target is therefore 20 at.% relative to the metals in the target.

[0055] For example, argon with a varying oxygen content between 2 mol% and 4 mol% is used as the process gas. The oxygen content is regulated according to the cathode voltage. For example, the cathode voltage is maintained in a range between 415 V and 435 V by gradually increasing the oxygen content between 2.5 mol% and 3.7 mol% during the sputtering process. For example, the coating process takes approximately 25 minutes.

[0056] The process gas is, for example, at a pressure of 8 µbar, and sputtering is carried out with a power of 500 W. In this embodiment, the electrolyte layer 28 has ScYSZ as the electrolyte material; alternative materials such as ScSZ, ScYAlSz, or ScCeSZ are conceivable.

[0057] Advantageously, a second barrier layer 30 is subsequently deposited onto the electrolyte layer 28. For example, the thickness of the second barrier layer 30 is 3.0 µm. In this embodiment, the second barrier layer is also deposited by PVD, advantageously by magnetron sputtering. Preferably, the second barrier layer 30 comprises doped cerium oxide, in this embodiment CGO; in one variant, SDC is possible. In this embodiment, the second barrier layer 30 advantageously serves as a chemical barrier against sr-containing perovskites in a second electrode layer 32.

[0058] In an optional subsequent step S6, the second electrode layer 32 is applied to the second barrier layer 30. In the exemplary embodiment, the second electrode layer 32 has an air electrode. Advantageously, a current collector layer or contact layer 34 is applied to the second electrode layer 32. For example, both the second electrode layer 32 and the contact layer 34 are applied using a suspension-based process, e.g., screen printing. The second electrode layer 32 has, for example, LSC-CGO. The contact layer 34 has, for example, LSC. Optionally, a further sintering step can follow, in which the sintering takes place at a temperature below the temperature used for the sintering S4 of the first electrode layer 26 and the transition layer 24.

[0059] Fig. Figure 3 shows, as an example of an electrochemical cell device, an electrolysis cell device 36 for producing hydrogen from electricity and water. The electrolysis cell device 36 has an electrolysis cell stack 38, which in turn comprises a plurality of stacked electrolysis cells 14. The electrolysis cell stack 38 is an electrochemical cell unit, and an electrolysis cell 14 is an electrochemical cell. For example, the electrolysis cells 14 are configured as high-temperature SOECs. The electrolysis cell stack 38 is supplied with water via a water supply 40 and with electricity via power electronics 42.

[0060] Fig.Figure 4 shows another example of an electrochemical cell device, a fuel cell device 44 for generating electricity from hydrogen and air. The fuel cell device 44 includes, by way of example, a fuel cell stack 46, which comprises a plurality of stacked electrochemical cells 12, configured as fuel cells 48. The fuel cell stack 46 is an electrochemical cell unit. The fuel cells 48 are, by way of example, configured as high-temperature SOFCs. The fuel cell stack 46 is supplied with hydrogen via a fuel supply 50 and with air via an air supply 52. ​​The hydrogen and air are metered by means of control electronics 54, which actuate corresponding valves and fans. The voltage drawn from the fuel cell stack 46 is converted as required by power electronics 42.

Claims

[1] Method (10) for producing an electrochemical cell (12), in particular an electrolysis cell (14), comprising a cell substrate (16), a first electrode layer (26), a second electrode layer (32), an electrolyte layer (28) arranged between the first electrode layer (26) and the second electrode layer (32), and a first barrier layer (22) arranged between the cell substrate (16) and the first electrode layer (26), wherein the first barrier layer (22) is deposited onto the cell substrate (16) by means of a physical vapor deposition (PVD) process, wherein the first barrier layer (22) comprises a cerium oxide which has a first doping with a rare earth element, characterized by that the cerium oxide has a second doping with a transition metal from the fifth or sixth transition group. [2] Method (10) according to claim 1, characterized bythat the PVD process is a sputtering process and a target is used which has between 0.2 and 10.0 atomic percent (At%) of the transition metal from the fifth subgroup or sixth subgroup with respect to the metals of the target, preferably between 0.5 and 5.0 At%, particularly preferably between 1.0 and 2.0 At%. [3] Method (10) according to any of the preceding claims, characterized by that the PVD process is a reactive sputtering process using oxygen as the reactive gas. [4] Electrochemical cell (12), in particular electrolysis cell (14), comprising a cell substrate (16), a first electrode layer (26), a second electrode layer (32), an electrolyte layer (28) arranged between the first electrode layer (26) and the second electrode layer (32), and a first barrier layer (22) arranged between the cell substrate (16) and the first electrode layer (26), wherein the first barrier layer (22) comprises a cerium oxide which has a first doping with a rare earth element, characterized by that the cerium oxide has a second doping with a transition metal from the fifth or sixth transition group. [5] Electrochemical cell (12) according to claim 4, characterized by, that the first barrier layer (22) has between 0.2 and 10.0 atomic percent (At%) of the second doping with respect to the metals of the first barrier layer (22), preferably between 0.5 and 5.0 At%, particularly preferably between 1.0 and 2.0 At%. [6] Electrochemical cell (12) according to one of claims 4 to 5, characterized by , that the second doping of the first barrier layer (22) contains niobium (Nb) and / or tungsten (W). [7] Electrochemical cell (12) according to any one of claims 4 to 6, characterized by , that the first doping of the first barrier layer (22) contains gadolinium (Gd), samarium (Sm), lanthanum (La), yttrium (Y) and / or neodymium (Nd). [8] Electrochemical cell (12) according to any one of claims 4 to 7, characterized by , that the first barrier layer (22) has a layer thickness between 0.3 and 5.0 µm, preferably between 0.5 and 3.0 µm, particularly preferably between 1.0 and 2.0 µm. [9] Electrochemical cell (12) according to any one of claims 4 to 8, characterized by , that the cerium oxide of the first barrier layer (22) has a substoichiometry with respect to oxygen between 1% and 10%, advantageously between 3% and 8%, particularly advantageously between 5% and 6%. [10] Electrochemical cell device (36, 44) comprising an electrochemical cell unit (38, 46) comprising at least one electrochemical cell (12, 14, 48) according to any one of claims 4 to 9.

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