Method for producing an electrolysis assembly

Abstract

The invention relates to a method for producing an electrolysis assembly comprising at least one housing with an interior, and with at least one stack assembly disposed in the interior of the housing, the stack assembly comprising a plurality of electrolytic cells stacked in a stacking direction, at least some of the electrolytic cells each comprising a membrane electrode assembly and an interconnector, and the membrane electrode assembly and the interconnector each having an oxygen side and a hydrogen side, wherein, in a preparation step for producing membrane electrode assemblies, at least one pasty layer is applied to each of the two surfaces of an electrolyte membrane, at least one of the layers on one surface being used to form a first electrode formed on the hydrogen side of the membrane electrode assemblies and at least one of the layers on the other surface being used to form a second electrode formed on the oxygen side of the membrane electrode assemblies, in a preparation step a seal material comprising glass and / or glass-ceramic is applied to the interconnectors, in an assembling step the prepared interconnectors and membrane electrode assemblies are stacked in alternation to form a stack, and in an assembling step the stack is joined under the action of thermal energy and of a mechanical clamping force which is applied to the stack inwardly in the stacking direction.

Description

[0001] DESCRIPTION

[0002] Method for producing an electrolysis arrangement

[0003] The invention relates to a method for producing an electrolysis arrangement which can be used in electrolysis plants such as high-temperature electrolysis plants or fuel cell plants.

[0004] The electrolysis arrangement according to the invention is particularly suitable for use in solid oxide electrolysis cell systems (SOEC) and in reversible solid oxide cell systems (rSOC) in electrolysis mode. Such systems are primarily used for high-temperature electrolysis (HTE).

[0005] A solid oxide electrolyzer (SOEC) comprises at least one electrolysis cell that uses electrical energy to split water (H2O) into its components, hydrogen (H2) and oxygen (O2). The structure and function of a solid oxide electrolysis cell are similar to those of a solid oxide fuel cell (SOFC), as they are based on the same technology. A key difference is that electrolysis uses water vapor (H2O(g)) as the input medium (reactant gas), whereas a fuel cell uses oxygen and fuel gas (e.g., hydrogen) as the input media.

[0006] A solid oxide electrolyzer utilizes high-temperature operation (typically 650-1000°C) because its efficiency is significantly higher than that of other electrolysis technologies. This technology takes advantage of the fact that at these temperatures, the ceramic materials used in the electrolytes become ionically conductive. A solid oxide electrolyzer consists of several components, each performing a different function. The essential components of a solid oxide electrolyzer include a stack with numerous cells, each cell comprising, among other components, an anode, an electrolyte layer, and a cathode. The cathode often contains a mixture of nickel and electrolyte materials. Water, in the form of steam in high-temperature electrolysis, is fed to the cathode.The electrolysis process works as follows: when an electrical voltage is applied to the cell that is above the open-circuit voltage (OCV), the water diffuses into the cathode, where the electrochemical conversion (redox reaction) of the water vapor takes place by absorbing electrons, producing hydrogen and oxygen ions. The electrolyte layer consists of a solid electrolyte material, such as yttrium-stabilized zirconia (YSZ). This electrolyte layer enables the transport of oxygen ions (O). 2 ) from the cathode to the anode. The anode consists of anode materials such as lanthanum manganese cobaltite or lanthanum ferrite. At the anode, the oxygen ions (O 2 ) molecular oxygen (O2) is produced by releasing electrons.

[0007] Solid oxide electrolysis cells are efficient due to their high operating temperatures and can produce clean hydrogen. They are used in hydrogen production, energy storage, and other industrial processes.

[0008] High-temperature electrolysis (HTE) is an electrolysis process for producing hydrogen from water at high temperatures using electrical energy. In contrast to low-temperature electrolysis (LTE), which operates at temperatures below 100 degrees Celsius, high-temperature electrolysis takes place at much higher temperatures, typically in the range of 500 to 1000 degrees Celsius. In low-temperature electrolysis, a polymer electrolyte membrane (PEM) is usually used as the electrolyte and is therefore often referred to as a PEM electrolysis process. The PEM is a thin polymer membrane that allows protons to pass through while blocking electrons and gases. A perfluorosulfonated polymer, such as Nafion, is often used as the material for the PEM. PEM electrolysis is frequently used in applications where fast response time and flexibility are required.These include, for example, hydrogen production for fuel cell vehicles, the integration of renewable energies through electrolysis and decentralized hydrogen production.

[0009] In a generic electrolysis arrangement, several, often a large number, of membrane electrode assemblies (MEAs) are arranged in a stack. Such stacks are also called electrolysis cell stacks or fuel cell stacks. Such stacks generally have a large number of levels, with each MEA of a stack being considered a single level. Interconnectors (also known as bipolar plates) are arranged between these levels. In a stack, a large number of these MEAs and interconnectors are stacked as repeating units. The finished stack is also referred to as a stack. Such stacks can have several hundred levels, in particular more than 800 or more than 900 levels.

[0010] For the electrolysis process, gas streams are fed into and removed from the MEA. The supplied gas is typically guided through channels arranged on the surface of the MEA.

[0011] EP 3360187 A1 discloses a system for regulating the pressure of a reactor for high-temperature electrolysis or co-electrolysis (HTE) or for a pressurized SOFC fuel cell stack. The operation of the system includes: regulating the volume flow of a moisture-containing gas upstream of one of the chambers to ensure electrochemical stability at a preset operating point; and pressure control using valves located downstream of the stack to regulate gases, including the moisture-containing gas, which are generally hot.

[0012] From US 2008118803 A1 a fuel cell unit is known, consisting of an electrolyte with an anode on one side and a cathode on the other side, each provided with a flow / gas distribution grid with gas supply / discharge, wherein each grid is adjacent to a separator plate and a seal acting on the separator plate.

[0013] Research into conventional electrolysis systems has shown that the structural designs of known systems allow for optimization of electrolysis with high efficiency during continuous operation. The object of the present invention is to provide a method for producing an electrolysis system that enables high efficiency even during continuous operation.

[0014] The object is achieved by the method specified in claim 1. Advantageous embodiments are the subject of the subclaims.

[0015] According to the invention, a method for producing an electrolysis arrangement comprising at least one housing with an interior space and at least one stack arrangement arranged in the interior space of the housing, wherein the stack arrangement comprises a plurality of electrolysis cells stacked in a stacking direction, wherein at least some of the electrolysis cells each comprise a membrane electrode assembly (MEA) and an interconnector, and wherein the membrane electrode assembly and the interconnector each have an oxygen side and a hydrogen side. The method is characterized in that, in a preparatory step for producing a membrane electrode assembly, at least one pasty layer is applied to each of the two surfaces of an electrolyte membrane,wherein at least one of the layers on each surface serves to form a first electrode formed on the hydrogen side of the membrane-electrode assemblies and a second electrode formed on the oxygen side of the membrane-electrode assemblies, in a preparation step, a sealing material comprising glass and / or glass ceramic is applied to the interconnectors, in an assembly step, the prepared interconnectors and membrane-electrode assemblies are alternately stacked to form a stacked assembly, and in an assembly step, the stacked assembly is joined under the action of thermal energy and a mechanical clamping force directed inwardly on the stacked assembly in the stacking direction.

[0016] The pasty layer is at least one paste applied to the electrolyte membrane. At least one of the layers is made of a nickel oxide paste. The pasty layer is applied wet and dried before joining. It may be provided that one or more of the pasty layers are sintered before or during joining. Sintering before the joining step can be particularly advantageous if a stable layer must already be present for the joining step, in which the stack arrangement is subjected to thermal conditioning and high compressive forces are exerted on the stack assembly.

[0017] For joining, the stacked assembly is subjected to a specified temperature profile. Thermal conditioning is carried out over a specified period until all components have reached a joining temperature. During this process, the components bond together in a fluidic seal. Amorphous or semi-crystalline materials, such as a sealing material designed as glass gaskets, become viscous and adhere to the interconnectors, forming a fluidic seal and electrically insulating them.

[0018] The sealing material is preferably band-shaped and is applied to the interconnector with a geometrically recurring structure. The geometrically recurring structure of the sealing material is envisaged to be applied in a zigzag, tab-shaped, meandering, or in the form of consecutive semicircles. In particular, the sealing material on the hydrogen side of the interconnector completely surrounds the edge area of ​​the latter. On the oxygen side of the interconnector, the sealing material is arranged around the manifold openings incorporated in the interconnector, completely surrounding their opening edges.

[0019] Applying the layer with a geometrically repeating structure increases the length of the ribbon-shaped glass seal compared to a linear guide. This allows a larger surface area of ​​the sealant to be provided with the same amount of sealant compared to a linear guide, which allows for better degassing of the sealant during the subsequent sintering process. Alternatively, the same area can be sealed with less sealant.

[0020] It is conceivable that the sealing arrangements in at least two electrolysis cells of the stack arrangement differ with regard to the pattern, number, thickness and / or material composition of the sealing material. According to one embodiment, the sealing material (44, 46) is applied with different thicknesses. The thickness of the sealing material differs along its applied length. In this case, it can be provided that the sealing material, preferably applied in strip form, is applied more thickly in the edge region of the manifold openings of the interconnectors. In the region of the manifold openings, there is a greater risk of bending of the interconnectors during later clamping and / or joining of the stack arrangement if the MEA is arranged approximately centrally on the interconnectors, thus creating a free space in the edge region.In particular, the application of the sealing material with different thicknesses applies to the seal that completely surrounds the edge area of ​​the interconnector.

[0021] For the design of the interconnectors, a first variant envisages that the interconnectors are free of gas-conducting structures on the oxygen side and / or on the hydrogen side. Preferably, at least some interconnectors are designed as flat, in particular plate-shaped components that are free of gas-conducting structures on the hydrogen side and / or on the oxygen side, wherein these interconnectors are preferably designed as flat steel sheets. The interconnectors may have coatings which, however, do not have a gas-conducting function. For example, an oxygen-impermeable coating may be arranged on the oxygen side of the interconnectors, which prevents oxygen from passing through to the metallic material of the interconnector in order to reduce or prevent oxidation of the metallic material.

[0022] To facilitate the manufacture of the stack arrangement, it can be provided that at least some components of the stack arrangement, such as membrane electrode assemblies, interconnectors, connector plates, top plate and / or base plate, each have an orientation feature by means of which the components are oriented in the stack assembly for the manufacture of the stack arrangement, in particular according to the Poka-Yoke principle.

[0023] In particular, with an orientation feature on the interconnectors, these can be advantageously oriented and arranged manually, mechanically, or with machine assistance, in particular using the poka-yoke principle, to create the stacked assembly of the stacked arrangement, in such a way that a specific alignment pattern is achieved within the stacked arrangement. The orientation features facilitate the identification of the orientation of the components, thus reducing or completely avoiding errors.

[0024] According to a preferred embodiment, at least one of the pasty layers can define a structure that, when the stack arrangement is assembled, forms a gas-conducting structure on the surface of the MEA. This structure can be designed in the form of ribs or channels, or the structure can be a gas-permeable layer, such as a porous ceramic.

[0025] In particular, this gas-conducting structure can be an oxygen-permeable structure on the oxygen side of the membrane-electrode assembly, which serves to discharge oxygen produced on the oxygen side of the membrane-electrode assembly into the interior of the housing. For this purpose, according to a preferred embodiment, the oxygen-permeable structure is designed to be open in the region of at least one side surface of the stack assembly to discharge the oxygen into the interior of the housing. It is conceivable that the oxygen-permeable structure is designed as a channel structure, preferably a channel structure oriented in a substantially perpendicular direction with respect to the direction of a reactant gas channel structure. The channels can, in particular, be designed in the manner of ribs.The channels can be limited laterally by channel bridges, downwards by the body of the MEA and upwards the channels can be open so that oxygen generated between the MEA and the interconnector arranged above it can be discharged in a directed manner.

[0026] Oxygen can also be conveyed into the interior if the oxygen-conducting structure is made of a gas-permeable material, such as porous ceramic or the like. Oxygen transport can be achieved, in particular, by means of a pressure gradient between the interior of the housing of the electrode assembly and the gas-conducting space between the oxygen sides of two membrane-electrode assemblies and interconnectors arranged directly above one another. According to a further embodiment, support elements can be arranged between the membrane-electrode assembly and the interconnector in at least some electrolysis cells.

[0027] The support elements primarily serve to adjust and secure the MEA relative to the interconnector. A load flow directed in the stacking direction of the stack assembly due to tension between the components of the stack assembly can also be at least partially compensated by the support elements, thus reducing the risk of damage to the MEA. These tension states within the stack assembly are, for example, the result of different material expansion of the components of the stack assembly during temperature changes due to different thermal expansion coefficients.

[0028] The support elements are preferably separate elements that are placed between the MEA and the interconnectors to create the stack arrangement. The material of the support elements is selected, for example, so that they are viscous when the electrolysis arrangement is in operation. This ensures good contact between the support elements on the MEA on the one hand and the interconnector on the other. The support elements are preferably arranged between the oxygen sides of the MEA and the interconnector. The transition between a viscous state and a solid state of the support elements occurs, for example, at the glass transition temperature. When the electrolysis arrangement is in operation, the support elements assume a temperature of over 900°C, in particular 950°C. When the electrolysis arrangement is in the idle state, the electrolysis process is stopped and the temperature of the arrangement is below the glass transition temperature of the support elements.

[0029] A design with support elements with a height of approximately 200 to 400 pm has proven technically successful. The support elements are preferably made of glass or glass ceramic.

[0030] Regarding the placement of the support elements on the MEA, it is envisaged that they are arranged in recesses in an outer layer of the MEA. For this purpose, at least one pasty layer, used for the production of the membrane electrode assemblies of the electrolysis cells equipped with support elements, is applied to the electrolyte membrane, incorporating cutouts to create recesses for accommodating the support elements.

[0031] According to one embodiment of the manufacturing method, it is contemplated that in a preparatory step a coating is applied to at least some interconnectors by means of printing, in particular by means of screen printing.

[0032] It is preferably provided that the coating of the interconnectors comprises a semiconducting oxide ceramic, in particular a ceramic comprising lanthanum (La), strontium (Sr), manganese (Mn) and / or cobalt (Co), preferably lanthanum-strontium-manganese-cobalt (LSMC), manganese cobalt iron oxide (MCF), lanthanum strontium manganese (LSM), lanthanum-strontium-cobalt iron oxide (LSCF), or lanthanum-manganese-cobalt (LMC).

[0033] Furthermore, it is contemplated that in a preparatory step, interconnectors are provided which each have two manifold openings, and wherein the interconnectors are stacked for the production of the stack arrangement in such a way that a reactant gas manifold structure and a product gas manifold structure are formed within the stack arrangement by means of the manifold openings.

[0034] A particularly efficient and well-distributed supply and removal of reactant and product gas over the height of the stack arrangement can be supported by the reactant gas manifold openings incorporated into the interconnectors and / or the product gas manifold openings between one interconnector and a next interconnector being of different sizes, and wherein the sizes of the manifold openings are selected and the interconnectors are stacked for the production of the stack arrangement in such a way that an reactant gas manifold structure tapering in the stacking direction of the stack arrangement and / or a tapering product gas manifold structure is produced.

[0035] For example, a tapered cross-section can be achieved by appropriately modifying the cross-section of the manifold openings in the interconnectors. The shape of the gas-carrying volume within the manifold structures can take on a desired shape by stacking the numerous interconnectors. Alternatively or additionally, the shape of the manifold structures can be predetermined by inserts inserted into the manifold structures.

[0036] For the effective guidance of reactant gas and product gas, it can be provided, in particular, that the reactant gas manifold structure and / or the product gas manifold structure is at least partially wedge-shaped, prism-shaped, truncated prism-shaped, pyramid-shaped, truncated pyramid-shaped, conical, or truncated cone-shaped, and / or that at least one wall surface of the reactant gas manifold structure and / or the product gas manifold structure is curved, at least partially, in the stacking direction. To avoid a multitude of differently equipped interconnectors, which would increase the manufacturing effort and the effort for assembling the stack arrangement, it can be provided to use insert bodies that can be arranged in the manifold structures for shaping.

[0037] According to one embodiment, at least some of the electrolysis cells may comprise a mesh-like metal mesh, preferably comprising nickel, in particular an iron-nickel alloy, which is arranged between the membrane electrode assembly and the interconnector. The ratio of iron to nickel in the metal mesh may, for example, be 50:50. The use of an iron-chromium alloy is also conceivable, preferably the material known as Crofer 22, for example, material 1.4760 XlCrTiLa22 or 1.4755 XlCrWNbTiLa22-2. The metal mesh can serve, in particular, to support the MEA above the hydrogen side of the adjacent interconnector.

[0038] To fix the metal braid, it can be provided that the metal braid is attached to the hydrogen side of an interconnector by welding, in particular by spot welding.

[0039] The joining process for producing the stack arrangement can be supported in that the joining comprises a joining step in which at least some interconnectors (22) are subjected to an electric current and are heated by means of the current conducted through the interconnector (22). For this purpose, individual interconnectors or a subset, in particular all of the interconnectors, on one side of the stack arrangement are preferably subjected to a first voltage potential transversely to the stacking direction and to a second, different voltage potential on the opposite side of the stack arrangement, such that a current flow is generated between the potentials. The current flow leads to a controlled heating of the interconnectors. The current flow is dimensioned such that the interconnectors reach a desired joining temperature.

[0040] For an enclosure of the stack arrangement that allows the application of high compressive forces to the stack composite of the stack arrangement, it is intended that for the production of the stack arrangement a top plate is arranged that limits the stack arrangement upwards in the stacking direction and a base plate is arranged that limits the stack arrangement downwards in the stacking direction.

[0041] As a transition between a base plate and the first electrolysis cell of the stack arrangement in the stacking direction or between the last electrolysis cell in the stacking direction and a top plate of the stack arrangement, according to one embodiment it is conceivable that a connector plate is arranged between the top plate and the last membrane electrode arrangement in the stacking direction, arranged below the top plate, and / or that a connector plate is arranged between the base plate and the first membrane electrode arrangement in the stacking direction, arranged above the base plate, wherein a coating is preferably applied to the connector plate, in particular such that several spaced-apart surface areas of the connector plate are coated, preferably in the form of a checkerboard pattern.

[0042] The coating of the connector plate can comprise a semiconducting oxide ceramic, in particular a ceramic comprising lanthanum (La), strontium (Sr), manganese (Mn) and / or cobalt (Co), preferably lanthanum-strontium-manganese-cobalt (LSMC), manganese-cobalt-iron oxide (MCF), lanthanum-strontium-manganite (LSM), lanthanum-strontium-cobalt-iron oxide (LSCF) or lanthanum-manganese-cobalt (LMC). The top plate, the base plate and / or the interconnectors can also be provided with such a coating. With regard to the coating of the connector plate, it is contemplated that the connector plate has a coating at least in some areas on at least one side, in particular such that several spaced-apart surface areas of the connector plate are coated, preferably in the form of a checkerboard pattern.The free spaces between the coating zones can help to allow a high binder content in the coating to escape during curing, for example, during a joining process during the production of the stack assembly. Without sufficient opportunity for the binder content to escape, for example, via the free spaces between the coating zones, pore formation or undesirable height differences on the connector plate can occur after the coating has cured.

[0043] Finally, during the production of the stacked assembly forming the stack arrangement, the components, such as interconnectors, can be arranged, in particular stacked, according to the poka-yoke principle. In particular, it can be provided that some components are sorted in a preparation step according to certain criteria, such as bending, size of the manifold openings, or the like.

[0044] The following should be noted regarding the definition: In the context of this application, the term "interconnector" refers to both an interconnector and a bipolar plate. The statements regarding interconnectors contained in this application also apply accordingly to bipolar plates. High-temperature electrolysis, in the context of this application, refers to electrolysis in the temperature range between 600°C and 1000°C, in particular 800°C and 950°C. However, high-temperature analysis is not limited to this temperature range; it can also be carried out at higher temperatures, for example, up to 1400°C.

[0045] The present invention is explained in more detail with reference to the following drawings. They show:

[0046] Fig. 1 is a highly schematic representation of an inventive

[0047] Electrolysis arrangement, Fig. 2 a simplified exploded view of a preferred variant of

[0048] MEA, interconnectors and glass seals of an electrolysis arrangement according to the invention,

[0049] Fig. 3 is a simplified exploded view of a general structure of a

[0050] Stack arrangement of an electrolysis arrangement according to the invention,

[0051] Fig. 4a, 4b, 4c a simplified sectional view of a stack arrangement halved lengthwise with a tapered manifold structure,

[0052] Fig. 5 a simplified exploded view of stacked interconnectors,

[0053] Fig. 6a, 6b a detailed view of glass seals on an interconnector,

[0054] Fig. 7 a connector plate, and

[0055] Fig. 8 is a highly schematic sectional view of channel cross-sections on an interconnector.

[0056] Figure 1 shows a highly schematic representation of an electrolysis arrangement 10 according to the invention with a housing 12 and a stack arrangement 16 arranged in the interior 14 of the housing 12. The stack arrangement 16 comprises a plurality of electrolysis cells 18, which in the present example are enclosed in the stacking direction S at the bottom by a base plate 42 and at the top by a top plate 40. A reactant gas manifold structure 66 and a product gas manifold structure 68 are indicated by dashed lines. Within the reactant gas manifold structure 66, a reactant gas, such as water vapor (H2O(g)), is fed into the stack arrangement 16 and guided to the electrolysis cells 18. In the product gas manifold structure 68, a product gas, such as hydrogen (FE), is guided away from the electrolysis cells 18 and out of the stack arrangement 16.

[0057] Figure 2 shows an exploded view of a preferred variant of an electrolysis cell, consisting of a membrane electrode assembly (MEA) 20, an interconnector 22, a glass seal 46 arranged above the interconnector 22, and two glass seals 44 arranged below the interconnector 22. The plate-shaped MEA 20 has a hydrogen side (bottom side not shown) and an oxygen side (top side shown). The interconnector 22, which is also approximately plate-shaped, also has a hydrogen side (top side shown) and an oxygen side (bottom side not shown). The oxygen side of the interconnector 22 lies on the oxygen side of the MEA 20 when the electrolysis cell is assembled. To form a stack arrangement 16 (cf. Fig. 1 or Fig. 3), a plurality of electrolysis cells 18 are stacked one above the other in a stacking direction S.Accordingly, an MEA 20 is connected to the hydrogen side of the interconnector 22. The adjoining MEA 20 of an electrolysis cell 18 arranged immediately above in the stacking direction S lies with its hydrogen side on the hydrogen side of the interconnector 22 of the electrolysis cell 18 arranged directly below.

[0058] The interconnector 22 has two manifold openings 28, 30, a first manifold opening 28 serving for the conduction of reactant gas and a second manifold opening 30 serving for the conduction of product gas. On the oxygen side of the interconnector 22, two glass seals 44 are arranged around the opening edge of the manifold openings 28, 30. The glass seals 44 seal the manifold openings 28, 30 of two stacked electrolysis cells 18 in such a way that a reactant gas stream or the product gas stream is respectively guided through a reactant gas manifold structure 66 or product gas manifold structure 68 formed by the manifold openings 28, 30 of stacked electrolysis cells 18. The individual electrolysis cells 18 are furthermore designed such that a reactant gas flow guided in a reactant gas manifold structure 66 can be guided from there to the hydrogen side of the interconnector 22.On the hydrogen side of the interconnector 22, the reactant gas stream for the electrolysis process comes into contact with the hydrogen side of an MEA 20 located on the hydrogen side of the interconnector 22. During the electrolysis process, the reactant gas is converted into product gas between the hydrogen side of the interconnector 22 and the hydrogen side of the MEA 20. The resulting product gas is further conducted on the hydrogen side of the interconnector 22 into the manifold opening 30 of the interconnector 22, which is provided for the conduction of product gas.

[0059] To guide reactant gas from the manifold opening 28 of the interconnector 22, which carries the reactant gas, an reactant gas line structure 32 can be formed on the hydrogen side of the interconnector 22—as in the example shown. The channel structure on the interconnector 22 can have 60 to 100 channels to achieve a fine, laminar flow. As also indicated in Fig. 2, an oxygen-permeable structure 34 designed as a channel structure can be formed on the oxygen side of the MEA 20 to guide the oxygen generated there. The oxygen-permeable structure 34 can be designed and configured such that the oxygen is discharged in a lateral direction, transverse to the orientation of the reactant gas line structure 32.The electrolysis cell 18 is designed such that in a stacked arrangement of several electrolysis cells 18 to form a stack arrangement 16, the oxygen is released from the stack arrangement 16 into the interior 14 of the housing 12.

[0060] Glass seals 44, 46 on the hydrogen side and on the oxygen side of the interconnector 22 ensure a gas-tight seal between electrolysis cells 18 stacked in a stack arrangement 16, in particular between the interconnectors 22 of directly adjacent electrolysis cells 18, such that the reactant gas manifold structure 66 and the product gas manifold structure 68 are fluidically separated from one another with respect to the interior 14 of the housing 12. The glass seal 46 on the hydrogen side of the interconnector 22 is arranged such that it completely surrounds the interconnector 22 in the edge region of its hydrogen side. In the assembled state of the stack arrangement 16, the glass seal 44 seals a first interconnector 22, in the stacking direction S, on its hydrogen side, from a second interconnector 22, arranged adjacently in the stacking direction S, on its oxygen side.The glass seals 44, 46 interact with the interconnectors 22 of stacked electrolysis cells 18 in such a way that, on the one hand, a fluidically conductive connection is formed between the hydrogen sides of the directly stacked MEA 20 and interconnector 22, the reactant gas manifold structure 66 for the reactant gas, and the product gas manifold structure 68 for the product gas. Furthermore, the glass seals 44, 46 interact with the interconnectors 22 of stacked electrolysis cells 18 in such a way that the space between the oxygen sides of the directly stacked MEA 20 and interconnector 22 is fluidically connected to the interior 14 of the housing 12 of an electrolysis arrangement 10.

[0061] On the oxygen side of the MEA 20, as shown in Fig. 2, support elements 48 can be provided between the MEA 20 and the interconnector 22. These support elements serve to compensate for mechanical stresses between the MEA 20 and the interconnector 22, in particular caused by temperature differences. The support elements 48 are preferably made of glass or a glass ceramic and are therefore also called glass pins. When the electrolysis cell 18 heats up, mechanical stresses arise due to the different thermal expansion coefficients of the different materials of the various components of the electrolysis cell 18. With a thickness of well under one millimeter, for example, 80 μm, preferably 30 μm, the MEA 20 is a fragile structure that can crack or break under mechanical stress. In particular, localized compressive loads lead to fractures in the MEA 20.The support elements 48, together with the seals 44, 46, ensure that the MEA 20 does not warp when the electrolytic cell 18 heats up. The support elements 48 can be arranged at least partially in recesses 64 of the MEA 20, wherein the recesses 64 are preferably incorporated into the MEA 20 in a non-penetrating manner. The recesses 64 are preferably incorporated into a first layer of the MEA 20. Alternatively, the recesses 64 are formed by applying multiple layers to the MEA 20, with certain layers not being applied in certain regions.

[0062] Figure 3 shows a simplified exploded diagram in schematic form of the general structure of a stack arrangement 16. In the example shown in Figure 3, the stack arrangement 16 has three MEAs 20, i.e., three levels. The stack arrangement 16 according to the invention can alternatively comprise fewer or more MEAs 20 and thus correspondingly more levels. The number of levels depends on the desired performance of the electrolysis arrangement 10. On the ceiling side, above the last MEA 20 in the stacking direction S, the stack arrangement 16 terminates with a top plate 40. On the bottom side, below the first MEA 20 in the stacking direction, the stack arrangement 16 terminates with a base plate 42.

[0063] Three electrolysis cells 18 are arranged above the base plate 42. In the example shown, the electrolysis cells 18 each comprise a mesh-like metal mesh 38, preferably made of nickel mesh, an MEA 20, two glass seals 44 provided for sealing the manifold openings 28, 30 of the interconnectors 22, an interconnector 22, and another glass seal 46 provided for sealing the edge region of the interconnectors 22. The mesh-like metal mesh 38 is optional. The mesh-like metal mesh 38 can form a gas-conducting structure and can also serve to mechanically support the MEA 20 on the interconnector 22. The base plate 42 is in this case designed on its upper side analogously to a hydrogen side of an interconnector 22 and is sealed with a glass seal 46 arranged on the upper side relative to the interconnector 22 of the first electrolysis cell 18 in the stacking direction S.The third and final electrolysis cell 18 in the stacking direction S has, instead of an interconnector 22, a top plate 40, which is configured on its underside analogously to the oxygen side of an interconnector 22. Unlike the interconnectors 22, the top plate does not have manifold openings 28, 30. The top plate 40 closes the stack arrangement 16 at the top in the stacking direction S and seals the reactant gas and product gas manifold structures 66, 68 formed in the stack arrangement 16.

[0064] The stack arrangements 16 according to the invention can have a few, for example, 30 or 60, or many, for example, 400 to approximately 900 levels. Stack arrangements 16 with more than 900 levels are also conceivable in principle, although it should be noted that the requirements for the mechanical stability of the arrangement increase with the number of levels.

[0065] Directly below the top plate 40 of the stack arrangements 16, a further interconnector 22 (not shown) or a connector plate (not shown) can be inserted between the uppermost MEA 20 and the top plate 40. The connector plate is preferably electrically conductive in order to realize an electrical connection between the stack and the top or bottom plate, and further preferably has a non-stick coating. The non-stick coating serves to mechanically decouple the stack from the top or bottom plate. The connector plate can additionally have a structure designed such that, when the temperature changes, the different thermal expansions of the different materials can be mechanically compensated, in particular transversely to the stacking direction.

[0066] Figures 4a, 4b, and 4c show three schematic partial sections of the cross-section of a stack arrangement 16 with a tapered cross-section of a manifold structure 66, 68. In particular, Figures 4a-c each show a tapered manifold structure 66, 68, in which the taper extends from the base plate 42 across the electrolysis cells 18 stacked one above the other in the stacking direction S to the top plate 40 sealingly closing the manifold structure 66, 68. The taper can be provided in the reactant gas manifold structure 66 and / or in the product gas manifold structure 68.

[0067] In the example according to Figure 4a, the tapering of the manifold structure 66, 68 is implemented by means of the manifold openings 28, 30 incorporated into the interconnectors 22. As schematically indicated, the interconnectors 22 have manifold openings 28, 30 of different sizes for this purpose, with the interconnectors 22 of individual electrolysis cells being selected and the electrolysis cells 18 being stacked in such a way that a tapered structure results in the stack arrangement 16. As shown, this can in particular produce an approximately wedge-shaped structure. A wedge shape is achieved, for example, if the manifold openings 28, 30 of the interconnectors 22 are each approximately rectangular with two side lengths and the manifold openings 28, 30 narrow upwards along one side length in the stacking direction S. Alternatively, the tapered structure can also be approximately conical in shape.A pyramid shape or truncated pyramid shape is achieved, for example, if the manifold openings 28, 30 of the interconnectors 22 are each approximately rectangular with two side lengths and the manifold openings 28, 30 narrow upwards in the stacking direction S along both side lengths.

[0068] Figure 4b shows a tapered manifold structure 66, 68, in which the taper is implemented by means of an insert body 50 inserted into the manifold structure 66, 68. The interconnectors 22 of the individual electrolysis cells 18 each have manifold openings 28, 30 of the same size. This allows identical interconnectors 22 to be used to provide the individual electrolysis cells 18 of a stack arrangement 16, which significantly reduces manufacturing costs. To form the taper, the insert body 50 is inserted into the manifold structure 66, 68 formed by the manifold openings 28, 30. The insert body 50 can—as shown—have an approximately triangular cross-section in the stacking direction S, so that a wedge-shaped tapered structure is realized. Figure 4c shows a special form of a taper of the manifold structure 66, 68 produced by means of an insert body 50. As in the embodiment according to Fig.4b, the interconnectors 22 of the individual electrolysis cells 18 each have manifold openings 28, 30 of equal size. In contrast to the design in Fig. 4b, the insert body 50 does not have a straight tapered surface, but rather a curved one. This creates a curved, tapered manifold structure 66, 68, which enables a particularly laminar flow of the reactant gas or product gas into or out of the electrolysis cells 18.

[0069] Figure 5 shows a stack arrangement 16 in which, to illustrate details, only the interconnectors 22 of individual electrolysis cells 18 are shown. The interconnectors 22 each have at least one orientation feature 60, in the example shown here, a reactant gas line structure 32 formed with guide channels, two manifold openings 28, 30, and on two opposite sides at the edge, in each case, a contact device 52 - in the example shown as an elongated hole - for establishing an electrically conductive contact with the interconnector 22. In addition to the contact device 52 designed as an elongated hole, a recess 54 is incorporated into the edge region of the interconnector 22 on each of the two opposite side edges of the interconnector 22.The contact device 52, which in the example shown is designed as an elongated hole, can be used to connect measuring devices for testing the stack arrangement, for example to identify defective electrolysis cells.

[0070] In this embodiment, the interconnectors 22 are stacked one on top of the other, each rotated by 180°, so that the contact devices 52, designed as elongated holes, and the recesses 54 are arranged alternately one above the other in the stack. The orientation feature 60 serves to avoid errors during stacking and to enable immediate or early error detection and prevention through technical precautions or devices. The idea for this originates from the poka-yoke principle. If a stacked stack arrangement 16 is only joined after stacking, an error in the stack can no longer be corrected. As long as the stack arrangement 16 is not yet joined, a stacking fault can still be corrected. Figures 6a and 6b each show an interconnector 22 with a glass seal 46 arranged on the hydrogen side of the interconnector 22.As shown in a detailed view of Figures 6a and 6b, the glass seals 46 can be applied to the interconnector 22 in a special shape. In the present case, Fig. 6a shows a meandering pattern and Fig. 6a a zigzag pattern of the glass seal 46 applied to the interconnector 22. Other patterns are also conceivable. This special application pattern increases the length of the band-shaped glass seal compared to a straight path. This allows a larger surface area of ​​the sealing material to be provided with the same amount of sealing material compared to a straight path, which enables better degassing of the sealing material during a subsequent sintering process. This better degassing can accelerate the sintering process. Alternatively, the same area can be sealed with a smaller amount of sealing material.This saves sealing material because less material is applied, the sealing performance is not impaired and superfluous sealing material that can escape from the stack during sintering is avoided.

[0071] Figure 7 schematically shows a connector plate 36, which can be arranged, for example, below a top plate 40 or above a base plate 42. The connector plate 62 has a coating 62 on at least one side. The coating 62 can be arranged—as in the example shown—in a checkerboard pattern on the surface of the connector plate 36. A coating can also be present on the side of the connector plate 36 not shown.

[0072] Figure 8 shows, very schematically, examples of channel cross-sectional shapes of a reactant gas line structure 32 designed as a channel structure on the hydrogen side of an interconnector 22. The channel structure shown is shown in a sectional view. As the figure shows, the channels 70 can be separated from one another by two adjacent channel webs 72. The example shown illustrates conceivable cross-sectional shapes of the channel webs 72 or the cross-sectional shapes of the channels 70 formed thereby. An MEA 20 (not shown) is arranged above the channel webs 72 in the stack arrangement 16. The channels 70 are bounded at the bottom by the body of the interconnector 22 or a coating present on the interconnector 22. At the top, the channels 70 are open towards an MEA 20 (not shown) arranged above them.For the electrolysis process, the reactant gas guided in the channels 70 comes into contact with the MEA 20 at the open upper sides of the channels 70. To ensure that a sufficient amount of reactant gas is available for contact with the MEA 20 even in the edge region of the channels 70, the flank steepness F of the side walls of the channel webs 72 is greater than or equal to 85°. The flank steepness is referred to as a median relative to the plane defined by the plate-shaped interconnector 22.

[0073] LIST OF REFERENCE SYMBOLS

[0074] 10 E1 electrolysis arrangement 50 insert body

[0075] 12 Housing 52 Contact device

[0076] 14 Interior 54 Recess

[0077] 16 stack arrangement 56 meandering structure

[0078] 18 electrolysis cells 58 zigzag structure

[0079] 20 Membrane electrode arrangement 60 Orientation feature

[0080] 22 Interconnector 62 Coating

[0081] 24 reactant gas openings 64 recesses

[0082] 26 Product gas opening 66 Educt gas manifold structure

[0083] 28 Manifold opening 68 Product gas manifold structure

[0084] 30 manifold opening 70 channels

[0085] 32 Educt gas line structure 72 channel webs

[0086] 34 oxygen-permeable structure

[0087] 36 Connector plate S stacking direction

[0088] 38 net-like metal mesh F flank steepness

[0089] 40 top plate

[0090] 42 base plate

[0091] 44 Glass seal

[0092] 46 Glass seal

[0093] 48 support elements

Claims

CLAIMS 1. A method for producing an electrolysis arrangement (10) comprising at least one housing (12) with an interior space (14), and at least one stack arrangement (16) arranged in the interior space (14) of the housing (12), wherein the stack arrangement (16) comprises a plurality of electrolysis cells (18) stacked in a stacking direction (S), wherein at least some of the electrolysis cells (18) each comprise a membrane electrode assembly (MEA) (20) and an interconnector (22), and wherein the membrane electrode assembly (20) and the interconnector (22) each have an oxygen side and a hydrogen side, characterized in that in a preparatory step for producing a membrane electrode assembly (20), at least one pasty layer is applied to each of the two surfaces of an electrolyte membrane,wherein at least one of the layers on each surface serves to form a first electrode formed on the hydrogen side of the membrane electrode assemblies (20) and a second electrode formed on the oxygen side of the membrane electrode assemblies (20), in a preparation step, a sealing material (44, 46) comprising glass and / or glass ceramic is applied to the interconnectors (22), in an assembly step, the prepared interconnectors (22) and membrane electrode assemblies (20) are alternately stacked to form a stacked assembly, and in an assembly step, the stacked assembly is joined under the action of thermal energy and a mechanical clamping force directed inward onto the stacked assembly in the stacking direction (S).

2. Method according to claim 1, characterized in that the sealing material (44, 46) with a geometrically recurring structure (56, 58) is applied to the interconnectors (22).

3. Method according to claim 1 or 2, characterized in that the geometrically recurring structure (56, 58) of the sealing material (44, 46) is applied in a zigzag shape, a tab shape, a meander shape or in the form of semicircles arranged in a row.

4. Method according to at least one of the preceding claims, characterized in that the sealing material (44, 46) is applied with different thicknesses.

5. Method according to at least one of the preceding claims, characterized in that the interconnectors (22) on the oxygen side and / or on the hydrogen side are free of gas-conducting structures.

6. Method according to at least one of the preceding claims, characterized in that at least some components of the stack arrangement (16), such as membrane electrode arrangements (20), interconnectors (22), connector plates (36), top plate (40) and / or bottom plate (42) each have an orientation feature (60) by means of which the components are oriented in the stack assembly for producing the stack arrangement (16), in particular according to the poka-yoke principle.

7. Method according to at least one of the preceding claims, characterized in that at least one of the pasty layers defines a structure which, in the joined state of the stack arrangement, forms a gas-conducting structure on the surface of the MEA.

8. Method according to at least one of the preceding claims, characterized in that at least in some electrolysis cells (18) support elements (48) are arranged between the membrane-electrode arrangement (20) and the interconnector (22).

9. The method according to claim 8, characterized in that at least one pasty layer applied to the electrolyte membrane for the production of the membrane electrode assemblies (20) of the electrolysis cells (18) equipped with support elements (48) is applied with the incorporation of omissions for producing recesses (64) for receiving the support elements (48).

10. Method according to at least one of the preceding claims, characterized in that in a preparatory step, a coating is applied to at least some of the interconnectors (22) by means of printing, in particular by means of screen printing.

11. The method according to claim 10, characterized in that the coating of the interconnectors (22) comprises a semiconducting oxide ceramic, in particular a ceramic comprising lanthanum (La), strontium (Sr), manganese (Mn) and / or cobalt (Co), preferably lanthanum-strontium-manganese-cobalt (LSMC), manganese cobalt iron oxide (MCF), lanthanum strontium manganese (LSM), lanthanum-strontium-cobalt iron oxide (LSCF), or lanthanum-manganese-cobalt (LMC).

12. Method according to at least one of the preceding claims, characterized in that in a preparatory step interconnectors (22) are provided, each having two manifold openings (28, 30), and wherein the interconnectors (22) are stacked for the production of the stack arrangement (16) in such a way that an educt gas manifold structure (66) and a product gas manifold structure (68) are formed within the stack arrangement (16) by means of the manifold openings (28, 30).

13. The method according to claim 12, characterized in that the reactant gas manifold openings (28) and / or the product gas manifold openings (30) incorporated in the interconnectors (22) between one interconnector (22) and a next interconnector (22) are of different sizes, and wherein the sizes of the manifold openings (28, 30) are selected and the interconnectors (22) are stacked for the production of the stack arrangement (16) in such a way that a stacking direction (S) the stack arrangement (16) is produced with a tapered educt gas manifold structure (66) and / or a tapered product gas manifold structure (68).

14. Method according to at least one of the preceding claims, characterized in that at least some of the electrolysis cells (18) comprise a net-like metal mesh (38), preferably comprising nickel, in particular an iron-nickel alloy, which is arranged between the membrane electrode arrangement (20) and the interconnector (22).

15. The method according to claim 14, characterized in that the metal mesh (38) is attached to the hydrogen side of an interconnector (22) by welding, in particular by spot welding.

16. Method according to at least one of the preceding claims, characterized in that the joining comprises a joining step in which at least some interconnectors (22) are subjected to an electric current and are heated by means of the current conducted through the interconnector (22).

17. Method according to at least one of the preceding claims, characterized in that for the production of the stack arrangement (16) a top plate (40) is arranged at the top in the stacking direction (S) which delimits the stack arrangement (16) upwards and a bottom plate (42) is arranged at the bottom in the stacking direction (S) which delimits the stack arrangement (16) downwards.

18. Method according to at least claim 17, characterized in that a connector plate (36) is arranged between the top plate (40) and the last membrane electrode arrangement (20) in the stacking direction (S) arranged below the top plate (40) and / or that a connector plate (36) is arranged between the bottom plate (42) and the first membrane electrode arrangement (20) in the stacking direction (S) arranged above the bottom plate (40), wherein preferably a coating (62) is applied to the connector plate (36), in particular in such a way that several mutually spaced surface areas of the connector plate (36) are coated, preferably in the form of a checkerboard pattern.

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