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

Abstract

The invention relates to a method (100) for producing an electrochemical cell element (10), comprising an electrochemical cell (14), in particular an electrolysis cell (14), and an interconnector (24), wherein the electrolysis cell (14) has at least three functional layers (26) and a metallic cell substrate (22), and wherein the interconnector (24) has protrusions (16). It is proposed that the interconnector (24) be connected to the cell substrate (22) by a plurality of micro-welds (34), wherein each micro-weld (34) is arranged on a protrusion (16).

Description

[0001] The invention relates to a method (100) for producing an electrochemical cell element according to the preamble of the independent claim. The invention further relates to such an electrochemical cell element and to an electrochemical cell device comprising such an electrochemical cell element. State of the art

[0002] Metal-supported solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are considered promising technologies for efficient and clean energy conversion. A key element of these cells are the interconnectors, which establish the electrical contact between the individual cells and simultaneously serve as mechanical support.

[0003] Conventional interconnects are often made of metallic materials and connected to the cells using various methods, typically press fits. However, these methods have several disadvantages. The high operating temperatures of the cells and the differing coefficients of thermal expansion of the materials often lead to mechanical stress and degradation of the contact points. Oxidation at the contact points, in particular, results in increased electrical resistance; this type of connection ultimately leads to a deterioration in cell performance and lifespan.

[0004] Another disadvantage of conventional connection technologies is the relatively large area required for the contact points. This limits the miniaturization of the cells and the increase in the power density of fuel cell and electrolysis stacks. Disclosure of the invention Advantages

[0005] The present invention describes a method for manufacturing an electrochemical cell element comprising an electrochemical cell, in particular an electrolysis cell, and an interconnector. The electrolysis cell has at least three functional layers and a metallic cell substrate. The interconnector has protrusions. According to the invention, the interconnector is connected to the cell substrate by a plurality of micro-welds, with each micro-weld being arranged on a protrusion.

[0006] The advantage of this method lies in the creation of a strong, metallurgical, and therefore permanent connection between the interconnector and the cell substrate. The micro-welds on the raised areas achieve a defined contact, ensuring low electrical resistance while simultaneously not negatively impacting the electrochemically active surfaces of the cell.

[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 metallic 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] The electrochemical cell element, consisting of an electrochemical cell and an interconnector, is the smallest unit from which electrochemical cell units—or electrochemical stacks for short—are assembled. This is achieved by stacking a large number of electrochemical cell elements on top of each other. The electrochemical cell element is therefore sometimes also referred to as a repeating unit.

[0013] In this context, an electrochemical cell unit, or stack for short, refers specifically to a unit comprising multiple electrochemical cell elements. Typically, these elements are stacked on top of each other. Each electrochemical cell element, as the electrochemical cell, typically comprises a plate-shaped cell substrate—sometimes also called a support—on which the functional layers are arranged, and a plate-shaped interconnect with raised sections. Within the stack, the interconnect is positioned between the cell substrate and the substrate of the adjacent cell element. The interconnect establishes an electrical connection with the neighboring cell element via these raised sections.Furthermore, the interconnect creates a gap between the cell substrate of one cell element and the cell substrate of an adjacent cell element, thus increasing the available flow space. This enables the supply of fluids to the electrochemical cells and the functional layers arranged on them. Advantageously, the cell elements are electrically connected in series. It is also conceivable that the cell units are electrically connected in parallel. The cells in the stack can advantageously be arranged on a common chassis or support, or in a common housing. Examples of stacks include fuel cell units and electrolysis cell units.

[0014] Electrochemical cells are typically planar. The stack is advantageously designed so that the fluids necessary for the electrochemical reaction can flow between the individual cells. Advantageously, the protrusions of a cell element are arranged such that a flowable space or region is formed between them. In particular, the protrusions can be arranged on the interconnect such that, in a mounted state where the protrusions contact an adjacent cell element, a first flowable space or region exists between the interconnect and the cell substrate of a cell element.

[0015] A second, flowable space is formed between the interconnector and the cell substrate of the adjacent cell element. The interconnector fluidically separates the first space from the second. In this way, the electrochemical cells of the electrochemical cell unit can be supplied with different fluids, and in particular, the two different electrode layers can be supplied with different fluids. For example, it is conceivable that the interconnect faces a fuel electrode of its own cell element on the side of the first space and the air electrode of the adjacent cell element on the side of the second space. Specifically, the first space can be used for the fuel supply and the second space for the air supply.

[0016] Advantageously, the elevations on a cell are arranged in a regular distribution, particularly in repeating sections or segments. For example, it is conceivable that the elevations on a cell are arranged at the grid points of an imaginary regular grid.

[0017] In the context of the present invention, a microweld is understood to be, in particular, a metallurgically bonded, electrically conductive connection between the cell substrate of an electrochemical cell and an interconnector, which is produced by a local welding process with microscopic dimensions. The microweld is characterized by a small diameter compared to the thickness of the cell substrate, typically in the range of 10 µm to 300 µm, and is formed by the local melting of the material at the connection point between the cell substrate and the interconnector. In contrast to large-area welds, which are common, for example, in the production of bipolar plates, the microweld enables precise contact at defined locations while simultaneously minimizing the impairment of the electrochemically active areas of the cell.

[0018] Advantageous further developments of the method are possible due to the features listed in the dependent claims.

[0019] The process is further improved by ensuring that the micro-weld has a diameter between 2% and 40% of the thickness of the cell substrate, preferably between 4% and 20%, and particularly preferably between 6% and 10%. This limitation of the micro-weld diameter relative to the thickness of the cell substrate ensures that the welds are small enough not to unduly impair the electrochemically active areas of the cell. At the same time, selecting a minimum diameter guarantees sufficient mechanical stability and electrical conductivity of the connection.

[0020] It is also advantageous if the micro-welds have a diameter between 10 µm and 300 µm, preferably between 20 µm and 200 µm, and particularly preferably between 50 µm and 100 µm. Maintaining this range for the diameter of the micro-welds ensures that they are small enough not to affect the electrochemically active areas of the cell, but at the same time large enough to guarantee sufficient mechanical stability and electrical conductivity.

[0021] It remains advantageous to produce the micro-welded joints using resistance welding. Resistance welding is a reliable and cost-effective method suitable for creating micro-welded joints. It allows for precise control of the welding parameters and results in robust connections. The use of ultrasonic and laser welding is also conceivable in variations. With resistance or ultrasonic welding, weld nuggets of approximately 10 µm to 100 µm are typically created in both sheets. With laser welding, the interconnect is welded through, and the cell substrate is melted with a weld nugget of approximately 50 µm to 200 µm.

[0022] It is also advantageous if the micro-welds are arranged at a distance of 1 mm to 15 mm from each other, preferably between 2 mm and 10 mm, and particularly preferably between 3 mm and 5 mm. By selecting a suitable distance between the micro-welds, a compromise is achieved between manufacturing effort and a sufficiently low ohmic resistance and mechanical stability of the cell element.

[0023] It remains advantageous for the micro-welds to be linear. Compared to spot connections, linear micro-welds offer the advantage of a larger contact area for the same diameter. This results in lower contact resistance and improves current transfer between the interconnect and the cell substrate.

[0024] It is also advantageous if the protrusions are channel-shaped. Channel-shaped protrusions offer the benefit of an increased surface area, which improves the connection of the interconnect to the cell substrate and simultaneously reduces the flow resistance for the reactants. Channel-shaped protrusions can be advantageously combined with linear micro-welds extending along the channel-shaped protrusion.

[0025] In the context of the present invention, a channel-shaped elevation is understood to be, in particular, a three-dimensional surface structure on an interconnector, having an elongated, trough-like shape and bounded by two opposing, raised edges. In contrast to a simple, point-shaped elevation, the channel-shaped elevation offers an increased contact area with the cell substrate, thus enabling a more stable and larger-area connection between the interconnector and the cell. The elongated shape of the elevation also reduces the flow resistance for the reactants in the electrochemical cell, which has a positive effect on the cell's performance and efficiency. The channel-shaped elevation can, in particular, extend linearly.

[0026] It is also advantageous if the cell substrate and / or the interconnect have protrusions that serve as defined contact points for creating the micro-welds. Using protrusions as defined contact points simplifies the positioning of the micro-welds and ensures uniform contact with the cell substrate. This contributes to improved electrical conductivity and mechanical stability.

[0027] In the context of the present invention, a protrusion is understood to be, in particular, a locally confined elevation on the surface of the cell substrate or the interconnect, which serves as a defined contact point for the production of the micro-welds. These protrusions are characterized by a greater height compared to the surrounding surface and can be distributed across the surface in either a regular or irregular geometric pattern. The targeted placement of protrusions on the cell substrate and / or the interconnect facilitates the positioning of the micro-welds during the joining process and ensures uniform contact between the two components. The shape of the protrusions can be adapted to the specific geometry of the interconnect and the requirements for current transmission.In the context of the present invention, small, point-like projections arranged on the ridges of the interconnect, sometimes also referred to as dimples, are particularly suitable. Especially in combination with resistance welding, these projections offer the advantage of creating a defined electrical contact point between the cell substrate and the interconnect during the manufacturing of the cell unit, at which the micro-weld is formed during resistance welding.

[0028] The present invention further describes an electrochemical cell element comprising an electrochemical cell, in particular an electrolysis cell, and an interconnector. The electrolysis cell has at least three functional layers and a metallic cell substrate. The interconnector has protrusions. According to the invention, the interconnector is connected to the cell substrate by a plurality of micro-welds, with each micro-weld being arranged on a protrusion. Advantageously, the electrochemical cell element is manufactured using the method according to the invention.

[0029] The electrochemical connection is characterized by a reliable and durable bond between the interconnect and the cell substrate. The micro-welded connections ensure low electrical resistance and thus efficient current transmission.

[0030] The present invention further describes an electrochemical cell device with an electrochemical cell unit comprising at least one electrochemical cell element according to the present invention.

[0031] The electrochemical cell device benefits from the advantages of the cell elements according to the invention and is characterized by improved performance, efficiency, and service life. The reliable contacting of the cell elements using micro-welded connections contributes significantly to these improvements.

[0032] A cell device is understood to be, in particular, a device designed for the electrochemical reaction of at least two fluids. The cell device comprises a cell unit that electrochemically reacts the two fluids, components that supply the cell unit with electrical energy (i.e., supply and / or remove electrical energy), and components that supply the cell unit with the two fluids. This supply can be active—for example, via supply lines, pumps, fluid reservoirs, etc.—or passive—for example, using ambient air as the fluid—without active transport. Advantageously, the cell device also includes components for the removal and / or recycling of the reacted fluids. Advantageously, the cell device also includes components for heat transfer, in particular for temperature control of the cell unit, for example, for the utilization of waste heat.Examples of cell devices include fuel cell devices or electrolysis devices.

[0033] An electrolysis cell device for producing fuel from at least one feedstock and electric current – ​​in particular hydrogen from electric current and water – is also advantageous, comprising at least one electrolysis cell stack, a feedstock supply – in particular a water supply – further comprising an anode exhaust gas guide and a cathode exhaust gas guide, as well as control electronics and power electronics, wherein the electrolysis cell stack is designed as an electrochemical stack with electrochemical cell units according to the present invention or comprises electrochemical cell units manufactured by a method according to the present invention. Due to the use of such an electrolysis cell stack with its aforementioned advantages, it can be operated with high reliability and performance. This enables efficient operation of the electrolysis cell device.Additionally, the advantageous properties of the electrolysis cells allow for particularly safe and reliable operation.

[0034] An electrolysis cell device is understood to be, in particular, a device designed for the production of fuel from at least one feedstock and electricity—especially hydrogen from electricity and water—by electrolysis. The electrolysis cell device comprises an electrolysis unit, which includes at least one electrolysis stack. The electrolysis unit is supplied with a medium as the feedstock—for example, water—and advantageously with an auxiliary medium. Within the electrolysis unit, the medium is reduced in a redox reaction under the input of electrical energy, producing oxygen. Specifically, the electrolysis unit generates a product gas containing the reduced medium and an exhaust gas containing oxygen. The reduced medium is discharged from the electrolysis unit and constitutes the fuel, for example, hydrogen.Accordingly, the electrolysis cell device includes components and lines to supply the electrolysis unit with the medium and fuel, to provide electrical energy, and to remove and, if necessary, store the reduced medium and exhaust gas from the electrolysis unit. Furthermore, the electrolysis cell device includes components and lines to bring the respective fluids to the temperatures required for electrolysis and / or to process the waste heat generated in the electrolysis unit. An auxiliary medium is understood to be, in particular, a sufficiently inert gas intended to drive the oxygen out of the electrolysis unit. Advantageously, the auxiliary medium is also intended to heat or cool the electrolysis unit. Possible auxiliary media include, for example, air, CO2, or N2; air is typically used.

[0035] A fuel cell device for generating electricity from a fuel, in particular hydrogen and / or natural gas, and air is also advantageous, comprising at least one fuel cell stack, a fuel supply, an air supply, an anode exhaust guide and cathode exhaust guide, as well as control electronics and power electronics, wherein the fuel cell stack comprises electrochemical cell units according to the present invention or electrochemical cell units manufactured by a method according to the present invention. Due to the use of a fuel cell stack according to the invention with its aforementioned advantages, it can be operated with high reliability and performance. Furthermore, due to its high load capacity, a wide modulation range of the delivered power is possible. This enables flexible operation that can reliably meet changing power requirements.Additionally, the advantageous properties of fuel cells allow for particularly safe operation.

[0036] A fuel cell device is understood to be, in particular, a device that forms a component, especially a functional one, particularly a structural and / or functional component, of a fuel cell system, or the entire fuel cell system. In this context, a fuel cell system is understood to be, in particular, a system for the stationary and / or mobile generation of, in particular, electrical and / or thermal energy using at least one fuel cell unit.

[0037] A fuel cell system comprises one or more fuel cell stacks. Typically, a fuel cell system includes components and lines for supplying fuel and air to the fuel cell stack. Furthermore, a fuel cell system includes components and lines for removing exhaust gases from the fuel cell stack. Advantageously, fuel cell systems include a recirculation circuit comprising components and lines for returning unreacted fuel and / or unreacted air to the fuel cell stack. Overall, a fuel cell system includes at least one or more fans for conveying a fluid, in particular a gaseous fluid. The fluid can be, in particular, fuel, air, exhaust gas, or a combination thereof.The blowers can be, in particular, air supply blowers, fuel supply blowers, exhaust gas exhaust blowers, and / or recirculation blowers. Advantageously, the fuel cell system includes one or more heat exchangers, especially to recover heat from the exhaust gas, or more specifically, the anode and cathode exhaust gases, and to transfer this heat back to the fluids supplied to the fuel cell unit—especially air, fuel, and / or recirculated fluid. The terms heat exchanger and heat transfer unit are used synonymously here. Drawings

[0038] The drawings illustrate exemplary embodiments of the method for producing an electrochemical cell element according to the present invention, the electrochemical cell element according to the present invention, an electrochemical cell unit according to the present invention, and electrochemical cell devices according to the present invention, and are explained in more detail in the following description. They show Fig. 1 a schematic cross-sectional view of an electrolysis cell stack with several electrochemical cell elements, Fig. 2A an exploded view of an electrochemical cell element with interconnect, cell substrate and functional layers, Fig. 2B an enlarged representation of the surveys of the interconnector from Fig. 2A, Fig. 3 a detailed view of an elevation of the interconnector and its contacting with the cell substrate and the functional layers of an adjacent cell element, Fig. 4 a schematic sectional view of an electrochemical cell element with a detailed representation of the layering of the functional layers, Fig. 5A a section through an interconnect with channel-shaped elevations and projections for contacting the cell substrate, Fig. 5B another cut through the interconnect from Fig. 5A along a rise, Fig. 6 the process steps for the production of an electrochemical cell element, Fig. 7 a schematic representation of an electrolysis cell device for hydrogen production and Fig. 8 A schematic representation of a fuel cell device for generating electricity. Description

[0039] In the different versions, identical parts receive the same reference numbers.

[0040] Fig. Figure 1 shows a schematic sectional view of an electrochemical cell unit 56, which is exemplified as an electrolysis cell stack 54. A plurality of electrochemical cell elements 10 are compressed between a first end plate 12a and a second end plate 12b. Each electrochemical cell element 10 has an electrochemical cell 14, exemplified as an electrolysis cell 14, and an interconnector 24. Each electrochemical cell element 10 has a plurality of protrusions 16 on its interconnector 24. For example, the protrusions 16 extend in Fig. 1 each point downwards and contact the electrochemical cell element 10 arranged below it or the electrochemical cell 14 of the electrochemical cell element 10 arranged below it. Furthermore, the interconnector 24 contacts with in Fig. 1 invisible elevations 16 also the electrochemical cell 14 of its own electrochemical cell element 10, see Fig. 3.

[0041] In the sectional view shown, seals 18 are assigned to the left and right sides of each electrochemical cell element 10. These seals form fluid channels along the stacking direction of the electrochemical cell elements 10, through which water, oxygen, and hydrogen can flow. The projections 16 of the interconnector 24 create two flowable spaces 20 between two adjacent electrochemical cells 14. The two spaces 20 are located in the Fig. 3 and Fig. Figure 4 shows a more detailed illustration. These spaces 20 are fluidically connected to the fluid channels. In this way, the electrochemical cells 14 of the electrochemical cell elements 10 can be supplied with water and optionally air, and after their reaction, hydrogen and air can be discharged from the cell elements 10.

[0042] Fig. Figure 2 illustrates the structure of an electrochemical cell element. Fig. Figure 2A shows an exploded view of a first electrochemical cell element 10. The electrochemical cell element 10 comprises an electrochemical cell 14 and an interconnector 24, which are, for example, made of stainless steel. The electrochemical cell 14 has a metallic cell substrate 22, which is, for example, made of stainless steel. The cell substrate 22 and the interconnector 24 are each formed as flat surfaces and are welded together in the finished state. The functional layers 26 of the electrochemical cell 14 are arranged on the side of the cell substrate 22 facing away from the interconnector 24. In the electrochemical cell 14, the functional layers 26 are applied to the cell substrate 22 by a coating process, for example, printing and / or vapor deposition. The functional layers 26 comprise, in particular, a cathode layer, an anode layer, and a separating layer arranged between them.For example, the functional layers 26 are configured as layers of a SOEC. On the side of the interconnector 24 facing away from the cell substrate 22, second functional layers 26a of a second electrochemical cell 14a of an adjacent second electrochemical cell element are arranged. In the assembled state, the projections 16 of the first electrochemical cell element 10 or its interconnector 24 contact the functional layers 26a of the second electrochemical cell element 10a.

[0043] Furthermore, on the side of the cell substrate 22 facing away from the interconnector 24, a seal 18 is arranged on each of the two end faces of the first electrochemical cell element 10. The cell substrate 22 and the interconnector 24 have corresponding openings or holes, so that in the assembled electrochemical cell unit 56 with the stacked electrochemical cell elements 10, a channel extending in the stacking direction is formed on each end face for guiding a fluid. The seals 18 can each have channels extending in the plane of the cell, which can guide a portion of the fluid into the plane of the cell or onto the side of the cell substrate 22 facing away from the interconnector 24, or drain it away from this side.

[0044] Fig. Figure 2B illustrates the elevations 16 of the first electrochemical cell element 10. Fig. 2B is an enlargement of the in Fig. 2A, section B of the exploded view. As can be clearly seen, the interconnector 24 has a multitude of protrusions 16 in a section or area congruent with or covered by the functional layers 26, 26a. By way of example, the protrusions 16 are arranged at the corners of an imaginary square grid, the imaginary grid lines of which are aligned along a longitudinal direction of the electrochemical cell element 10. The protrusions 16 extend from the cell plane or from the plane of the interconnector 24 in the direction of the functional layers 26a of the adjacent second electrochemical cell 14a.

[0045] For example, the cell substrate 22 has a multitude of openings or perforations 28. The perforations 28 are specifically designed to connect a fluid flowing between the interconnector 24 and the cell substrate 22 to the functional layers 26 of the first electrochemical cell 14. In particular, this allows the electrode layer of the functional layers 24 facing the cell substrate 22 to be supplied with fluids and exhaust gases to be removed. For example, the perforations 28 are arranged at the corners of an imaginary square grid, with the imaginary grid lines of the imaginary grid being aligned along a longitudinal direction of the electrochemical cell 14.

[0046] Fig. Figure 3 shows a detailed view of a section through a variant of a projection 16a. The projection 16a extends from the electrochemical cell element 10 or the interconnector 24 towards the adjacent functional layers 26a of the neighboring electrochemical cell 14a and, for example, has the form of a flattened dome, with a flattened section 16c of the projection 16a contacting the adjacent functional layers 26a of the neighboring electrochemical cell 14a. For example, a first space 20a is formed between the interconnector 24 and the adjacent functional layers 26a of the neighboring electrochemical cell 14a, through which a first fluid can flow. A second space 20b is formed between the interconnector 24 and the cell substrate, through which a second fluid can flow. The interconnector 24 fluidically separates the first space 20a from the second space 20b.

[0047] For example, the interconnector 24 between the protrusions 16a in the direction of the adjacent electrochemical cell element also has protrusions 16b, which extend from the interconnector 24 towards the cell substrate 22 of the electrochemical cell element and contact it with a circular, flat section. The interconnector 24 is welded to the cell substrate at the protrusions 16b by micro-welds 34. For example, the protrusions 16b are arranged on the diagonals of the imaginary grid at whose corners the protrusions 16a are arranged, in particular at the midpoints between two protrusions 16a adjacent on the diagonal. In this way, each protrusion 16a is directly surrounded by four protrusions 16b and conversely, each protrusion 16b is directly surrounded by four protrusions 16a. In the Fig. The block-shaped section shown in Figure 3, centered on a protrusion 16a, therefore contains one quarter of each of the four adjacent depressions 16b. In the cross-sectional view through half of the block in Fig. Therefore, two of the quartered elevations 16b are visible in Figure 3. By way of example, the elevations 16a, or the dome-shaped sections, on the side adjacent to the functional layer 26a of the neighboring electrochemical cell 14a, have a first coating 32. The first coating 32 is, by way of example, made of a porous material.

[0048] Fig. Figure 4 shows a schematic cross-sectional view through another variant of an electrochemical cell element 10. The cell element 10 shown is produced by a method 100 according to the present invention, and the cell substrate 22 is attached to the interconnector 24 by micro-welds 34. The functional layers 26 comprise a first electrode layer 36, an electrolyte layer 38, and a second electrode layer 40. By way of example, the first electrode layer 36 is arranged on the cell substrate 22. Advantageously, the first electrode layer 36 is a fuel gas electrode layer. Preferably, the first electrode layer 36 comprises a mixture of Ni or NiO with doped cerium oxide, e.g., Gd-doped cerium oxide (CGO) or Sm-doped cerium oxide (SDC). Advantageously, the first electrode layer comprises a cerium-nickel cermet. In particular, the first electrode layer 36 can be a suspension-based layer.In this way, advantageous layer thicknesses can be achieved particularly easily and reliably. For example, the first electrode layer 36 can be deposited 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 first electrode layer.

[0049] For example, the electrolyte layer 38 covers the first electrode layer 36. For example, the electrolyte layer 38 exhibits CGO. 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, a spraying process, film casting, or slot-die coating, are also conceivable.

[0050] The second electrode layer 40 is arranged on the electrolyte layer 38 as an example. Advantageously, the second electrode layer 40 is the air electrode. Advantageously, the second electrode layer 40 is deposited using a suspension-based process, in particular a printing process, for example, screen printing. The second electrode layer 40 can, for example, have oxides with a perovskite structure, such as La-Sr-Co oxide (LSC), La-Sr-Co-Fe oxide (LSCF), or La-Sr-Mn oxide (LSM).

[0051] The cell substrate 22 is exemplarily made of stainless steel and has perforations 28 which were produced exemplarily by laser drilling.

[0052] The interconnector 24 is, by way of example, made of stainless steel. The interconnector 24 has protrusions 16, which are, by way of example, channel-shaped. In the Fig. In the cross-section shown in Figure 4, it is clearly evident that the channel-shaped protrusions 16 have a largely triangular cross-section. The channel-shaped protrusions 16 extend into and out of the plane of the image, and their cross-section remains largely unchanged along their longitudinal direction. As can be clearly seen, the protrusions 16 form the second interspace 20b between the interconnector 24 and the cell substrate 22.

[0053] As an example, the interconnector 24 has a second coating 42 on its side facing the cell substrate 22. The second coating 42 is intended for contacting the cell substrate 22. It is conceivable that the second coating 42 is designed to protect the interconnector 24 or its metallic core from the influence of fluids flowing through the second space 20b during operation.

[0054] As an example, the interconnector 24 has the first coating 32 on its side facing away from the cell substrate 22. The first coating 32 is intended for contacting the functional layers 26 of the adjacent cell element 10, in the illustrated variant for contacting the second electrode layer 40 of the adjacent cell element 10. The first coating 32 is advantageously designed such that good electrical contact with the second electrode layer 40 can be established. Advantageously, the first coating 32 is chemically compatible with the second electrode layer 40 in the sense that no chemical reactions occur.

[0055] Interactions occur between the first coating 32 and the second electrode layer 40. It is also conceivable that the first coating 32 is designed to protect the interconnector 24 or its metallic core from the influence of fluids flowing through the first gap 20a during operation.

[0056] It is also conceivable that the first coating 32 and / or the second coating 42 are intended to reduce contact resistance and / or to prevent or reduce the evaporation of chromium. In particular, it is conceivable that the first coating 32 and / or the second coating 42 comprise a chromium getter material. A chromium getter material is understood to be, in particular, a material that reacts with volatile chromium compounds to form stable chromium compounds, for example, barium or strontium. The chromium is fixed by its bonding to the chromium getter materials.

[0057] Fig. Figure 5 shows another variant of the interconnect before connecting to the cell substrate 22. Fig. Figure 5A shows a section through the interconnector 24 along the elevations 16; three elevations 16 are shown as examples. Fig. Figure 5B shows a section through the interconnector 24 along one of the elevations 16. As can be clearly seen, the elevations 16 are channel-shaped here. The elevation 16 extends along the image plane of Fig. 5 B. In Fig. 5 A the elevations extend into or out of the image plane.

[0058] As can be clearly seen, each of the elevations 16 has a plurality of central projections 44, which are distributed regularly along the longitudinal extent of the respective elevation. For example, the projections 44 closest to each other on an elevation 16 have a diameter of 7 mm.

[0059] The projections 44 protrude from the elevation 16. The projections 44 are designed to establish a defined electrical contact between the cell substrate 22 and the interconnector 24 during process 100. For this purpose, the cell substrate 22 and the interconnector 24 are brought into contact with each other so that the projections 44 make contact with the cell substrate 22. In this way, an electrical contact is established via the projections 44. During resistance welding, a current flows through the projections 44, and the micro-welds are formed at the location of the projections.

[0060] Fig. Figure 6 shows a process 100 for manufacturing the electrochemical cell element 10. In a first step S1, an electrolysis cell 14 is produced using standard SOC manufacturing methods. For this purpose, a stainless steel cell substrate 22 is first provided, and through-holes or perforations 28 are drilled into the cell substrate using laser drilling. Subsequently, the functional layers 26 are applied to the cell substrate 22, for example, as a slick using a printing process, and then the composite of cell substrate 22 and functional layers 26 is sintered.

[0061] In a further step S2, the interconnector 24 is manufactured from a stainless steel sheet. The raised areas 16 are stamped on together with the projections 44 using a die.

[0062] In step S3, the interconnector 24 and the cell substrate 22 are welded together. For this purpose, the interconnector 24, with its raised sections 16, is brought into contact with the cell substrate 22 on the side of the cell substrate 22 that does not have the functional layers 26, so that the raised sections 16 and the projections 44 make contact with the cell substrate 22. Subsequently, the interconnector 24 and the cell substrate 22 are joined together by resistance welding. The current flowing through the raised sections 16 and projections 44 melts the steel of the cell substrate 22 and the interconnector 24 at the contact points, forming weld nuggets with a diameter of approximately 30 µm to 40 µm in the cell substrate 22 and in the interconnector 24, which constitute the micro-welds 34.

[0063] Fig. Figure 7 shows, as an example of an electrochemical cell device 50, an electrolysis cell device 52 for producing hydrogen from electricity and water. The electrolysis cell device 52 has an electrolysis cell stack 54, which in turn has a plurality of stacked electrochemical cell elements 10. Each electrochemical cell element 10 has an electrolysis cell 14 as its electrochemical cell 14. The electrolysis cell stack 54 is an example of an electrochemical cell unit 56. The electrolysis cells 14 are designed as high-temperature SOECs (solid-state electrochemical units). The electrolysis cell stack 54 is supplied with water via a water supply 58 and with electricity via power electronics 60.

[0064] Fig.Figure 8 shows another example of an electrochemical cell device 50, a fuel cell device 62 for generating electricity from hydrogen and air. The fuel cell device 62 includes, by way of example, a fuel cell stack 64, which comprises a plurality of stacked electrochemical cell elements 10. Each electrochemical cell element 10 contains a fuel cell as an electrochemical cell 14. The fuel cell stack 64 is another example of an electrochemical cell unit 56. The fuel cells are, by way of example, designed as high-temperature SOFCs. The fuel cell stack 64 is supplied with hydrogen via a fuel supply 66 and with air via an air supply 68. The hydrogen and air are metered by means of control electronics 70, which actuates corresponding valves and fans.The voltage tapped from the fuel cell stack 64 is converted according to demand via a power electronics unit 60.

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