EP4575037A1 - Electrolysis arrangement - Google Patents

Abstract

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 arrangement and an interconnector, and wherein the membrane electrode arrangement and the interconnector each have an oxygen side and a hydrogen side, wherein at least some electrolysis cells have support elements between the membrane electrode arrangement and the interconnector, and wherein the support elements are designed and configured such that they are viscous in an operating state of the electrolysis arrangement and solid in a rest state of the electrolysis arrangement.

Description

The invention relates to an electrolysis arrangement which can be used in electrolysis plants such as high-temperature electrolysis plants or fuel cell plants.

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

A solid oxide electrolyzer (SOEC) comprises at least one electrolysis cell which 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.

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 utilizes 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 fulfilling a different function. The essential components of a solid oxide electrolyzer include a stack with numerous cells, each cell comprising, among other things, 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: if an electrical voltage above the open circuit voltage (OCV) is applied to the cell, the water diffuses into the cathode, where the electrochemical conversion (redox reaction) of the water vapor takes place by absorbing electrons and hydrogen and oxygen ions are produced. 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, molecular oxygen (O ² ) is produced from the oxygen ions (O _2- ) by releasing electrons.

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.

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 requiring fast response times and flexibility. These include, for example, hydrogen production for fuel cell vehicles, the integration of renewable energies through electrolysis, and decentralized hydrogen production.

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 usually have a large number of Layers, with each MEA of a stack being considered a layer. Interconnectors (also known as bipolar plates) are arranged between these layers. 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 layers, in particular more than 800 or more than 900 layers.

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.

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

Out of 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, each grid being adjacent to a separator plate and a seal acting on the separator plate.

Research into conventional electrolysis systems has shown that the structural designs of known systems leave room for optimizing electrolysis with high efficiency during continuous operation.

The object of the present invention is to provide an electrolysis arrangement which enables a high degree of efficiency even during continuous operation.

This object is achieved by the electrolysis arrangement specified in the claims. Advantageous embodiments are the subject of the dependent claims.

According to the invention, an electrolysis arrangement comprises 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 electrolysis arrangement is characterized in that at least some electrolysis cells have support elements between the membrane electrode assembly and the interconnector, and wherein the support elements are designed and configured such that they are viscous in an operating state of the electrolysis arrangement and solid in a rest state of the electrolysis arrangement.

The support elements according to the invention primarily serve to adjust and fix the MEA relative to the interconnector. A load flow pointing in the stacking direction of the stack arrangement due to tension between the components of the stack arrangement 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 arrangement are, for example, the result of different material expansion of the components of the stack arrangement during temperature changes due to different thermal expansion coefficients.

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 so that they are viscous in the operating state of the electrolysis arrangement. This ensures good contact between the support elements on the MEA on the one hand and on 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 takes place, for example, at the glass transition temperature. In the operating state of the In an electrolysis arrangement, the support elements, for example, assume a temperature of over 900°C, especially 950°C. When the electrolysis arrangement is at rest, the electrolysis process is stopped, and the temperature of the arrangement is below the glass transition temperature of the support elements.

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

In a preferred variant, the interconnector of a stack arrangement according to the invention is a flat metal component. The component can be made, for example, of the material known under the designation Crofer 22, such as the materials 1.4760 X1CrTiLa22 or 1.4755 - X1CrWNbTiLa22-2. For rapid and cost-effective production of a large number of interconnectors, the interconnector can be a punched sheet. In principle, it is conceivable that the shape of the plate-shaped interconnectors can be freely selected, i.e., in particular, round, circular, oval, square, triangular, or the like. However, it has been shown that the production of a stack arrangement according to the invention is facilitated when the interconnectors are rectangular. The plate-shaped interconnector can thus be stacked quickly and easily orientated.

The interconnector and the membrane electrode assembly are plate-shaped elements whose flat surfaces each define a hydrogen and oxygen side. Within the stack arrangement, the hydrogen sides of directly successive membrane electrode assemblies and interconnectors face each other. Likewise, the oxygen sides of directly successive membrane electrode assemblies and interconnectors face each other, as do the hydrogen sides. During electrolysis, oxygen is produced on the oxygen side of the membrane electrode assembly, which is transported away through the space formed between the oxygen side of the membrane electrode assembly and the oxygen side of the interconnector. A reactant gas, in this case water vapor, guided between the hydrogen side of a membrane electrode assembly and an interconnector is on the hydrogen side of the membrane electrode assembly into product gas, in this case hydrogen.

The space between the oxygen sides of the interconnectors and membrane electrode assemblies is fluidically separated from the space between the hydrogen sides of the interconnectors and membrane electrode assemblies to prevent mixing of hydrogen and oxygen. For this purpose, seals are planned to be provided on the hydrogen side and the oxygen side between the interconnectors and the membrane electrode assemblies.

In a preferred embodiment, it is envisaged that on the oxygen side of at least some membrane electrode assemblies there is at least one layer which has recesses for receiving the support elements, and wherein the layer having the recesses is preferably an oxygen-permeable structure by means of which oxygen released on the oxygen side of the membrane electrode assembly can be diverted to a side edge of the membrane electrode assembly.

The oxygen-permeable structure on the oxygen side of the membrane-electrode assembly 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 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 essentially perpendicular to the direction of a reactant gas channel structure. The channels can in particular be rib-like. The channels can be delimited laterally by channel webs, downwards by the body of the MEA, and upwards the channels can be open, so that oxygen produced between the MEA and the interconnector arranged above it can be discharged in a directed manner.

Oxygen conduction into the interior is also possible if the oxygen-conducting structure is designed as a gas-permeable material, for example as a porous ceramic or the like. In particular, the oxygen-conducting structure can be a layer or one or more coatings of the membrane electrode assembly. 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 one embodiment, the support elements and/or the recesses have a contour shape selected from the group consisting of circular, circular segment-shaped, square, rectangular, quadrangular, triangular, or diamond-shaped. The contour shapes of the support elements, i.e., the outer contour of the support elements in a plane parallel to the plane of the MEA, do not have to be identical to the contour of the recesses. Preferably, the support elements are arranged between the oxygen sides of the MEA and the interconnector. It must be ensured that oxygen can be discharged laterally between the oxygen sides of the MEA and the interconnector.

A design that has proven technically successful is one in which the surface area of the projection area of a support element is approximately 5-15% of the surface area of the membrane electrode assemblies of the electrolysis cell that can be exposed to reactant gas. The projection area of a support element is defined as the area projected by orthogonal projection into the plane of the membrane electrode assemblies or the interconnector of the electrolysis cell.

Preferably, the surface area of the projection surface of the support elements can be smaller than the surface area of the recesses for accommodating the support elements. This allows for the creation of free space around the support surfaces between the oxygen sides of the MEA and the interconnector, even when support elements are closely arranged in the edge region of the MEA, which serves to dissipate oxygen.

For the design of the interconnectors, it is envisaged in a first variant that at least some interconnectors are designed as a flat, in particular plate-shaped component, which is free of gas-conducting structures, 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.

The interconnectors preferably each have two manifold openings, by means of which a reactant gas manifold structure and a product gas manifold structure are formed within the stack arrangement. The manifold openings of the interconnectors that delimit the manifold structures within the stack arrangement are preferably completely open, i.e., are formed without webs within their outer opening edge. Each interconnector preferably has exactly one manifold opening for forming the reactant gas manifold structure and exactly one manifold opening for forming the product gas manifold structure.

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, 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, preferably the material known as Crofer 22, for example, material 1.4760 X1CrTiLa22 or 1.4755 - X1CrWNbTiLa22-2, is also conceivable.

The production of a stack arrangement can be facilitated in 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 can be aligned in the stack assembly in order to produce the stack arrangement, in particular according to the poka-yoke principle.

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

In particular, it can be provided that at least some interconnectors in the stack arrangement are stacked alternately rotated by 180° based on orientation features arranged on the interconnectors. The 180° rotation can occur about the axis running in the stacking direction. This rotation can occur, for example, in order to arrange the interconnectors in the stack assembly of the stack arrangement on one side at one edge or mirror-symmetrically at two opposite edges with alternating placement. For example, contact devices for connecting electrical connection bodies can be placed alternately in the stack arrangement in such a way that they are more easily accessible for later contacting, for example for testing the functionality of the stack arrangement after joining.

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 the stack arrangement has a top plate that limits the stack arrangement upwards in the stacking direction and a bottom plate that limits the stack arrangement downwards in the stacking direction.

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 envisaged 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.

According to a preferred embodiment, it is provided that the connector plate is designed as a plate-shaped sheet, wherein the outer contour shape of the connector plate corresponds at least substantially to the contour shape of the interconnector arranged adjacent to the connector plate in the stacking direction, and wherein the connector plate is preferably free of gas-conducting structures.

Such a connector plate, which preferably has a contour shape corresponding to the interconnectors, can fulfill various functions. On the one hand, the connector plate can establish an electrically conductive connection between the base plate or top plate and the first or last electrolysis cell. Furthermore, the connector plate can be designed and configured to absorb and compensate for mechanical stresses in the stack arrangement, particularly those directed in the stacking direction. This can reduce the risk of stress cracks in the electrolysis cells of the stack arrangement and in particular in the membrane-electrode assemblies of the electrolysis cells. In particular, the connector plate can serve to compensate for unevenness of the electrolysis cells arranged one above the other, which can reduce electrical contact with the top or base plate. These unevennesses can arise, for example, from joining the stack arrangement during its assembly. Due to its flexibility compared to the top or base plate, the connector plate establishes a flat contact with the stack of electrolysis cells, whereby the connector plate, in turn, is in electrical contact with the top or base plate.

A connector plate arranged between the base plate and the first electrolysis cell above the base plate in the stacking direction preferably has manifold openings if it covers the reactant gas opening or the product gas opening of the base plate. In principle, the connector plate can have the same external dimensions, in particular the same thickness, as an interconnector. However, it can also be thicker or thinner than the interconnector. Interconnectors and connector plates are preferably made of the same material. A connector plate is preferably electrically conductive, such that an electrical contact is established between the connector plate and the base plate or top plate.

The connector plate can serve, among other things, to compensate for mechanical compressive forces that vary across the cross-sectional area of the stack arrangement perpendicular to the stacking direction. For example, due to an MEA positioned approximately centrally to an interconnector, higher compressive forces can occur in the center of the stack arrangement than in the edge region of the stack arrangement. Accordingly, the connector plate can be designed to be thicker in its edge region than in its center region.

According to one embodiment, it is provided that the connector plate, and/or the top plate and/or the base plate has a coating, wherein the coating 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).

With regard to the coating of the connector plate, it is envisaged that the connector plate has a coating on at least one side, at least in some areas, 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 areas between the coating zones can help to allow a high binder content in the coating to escape during the curing of the layer, for example, in a joining process during the production of the stack arrangement. Without sufficient opportunity for the binder content to escape, for example via the free areas between the coating zones, pore formation or undesirable height differences on the connector plate can occur after the coating has cured.

To support a joining process during the production of the stack arrangement according to the invention and to maintain a clamping force between the base plate and the top plate of the stack arrangement, it can be provided that the top plate and the base plate each have clamping devices, in particular in the form of holding elements projecting outwards at the edge region of the top plate and the base plate, such that clamping means can be arranged on the outside of the stack arrangement at a distance from the stack arrangement between the clamping devices of the top plate and the base plate, by means of which a tensile force acting between the top plate and the base plate along the stacking direction axis can be applied.

The clamping devices can in particular be arranged such that the holding elements are aligned at the top and bottom in the stacking direction. This makes it easy to attach a clamping device running parallel to the stacking axis to the holding elements, with which a tensile force running parallel to the stacking direction axis can be applied between the top plate and the base plate. It is conceivable that the holding elements of the base plate and/or the top plate have holes for receiving or attaching clamping devices. The clamping device can be, for example, a rod(s) or a belt that is connected to the holding elements of the top plate and the base plate. When arranging clamping devices between the top plate and the base plate, care must be taken to ensure that the clamping devices do not create a potential equalization between the top plate and the base plate or with interconnectors arranged in the stack arrangement. The clamping devices should therefore be electrically insulated or non-conductive, at least in the contact area of the clamping devices on the top plate and/or the base plate.

For the electrical contacting of the top plate and/or the base plate, in particular for supplying the electrical energy required for the electrolysis process to the stack arrangement, it is envisaged that the top plate and/or the base plate have contact devices for electrically contacting the top plate and/or the base plate. In a particularly advantageous embodiment, the contact devices are formed by means of the clamping devices.

For electrical contacting of the interconnectors, for example for measuring the electrical potential of an electrolysis cell, it can be provided that at least some of the interconnectors have at least one contact device in their edge region, which is electrically conductively connected to the interconnector.

In principle, various designs are conceivable for the design of the contact devices of the interconnectors. Preferably, the contact devices are designed and constructed in such a way that even in a narrow stacked stack assembly of the stack arrangement, measuring equipment is made possible easily and with little risk of electrical bridging of stacked interconnectors. According to a first variant, it can be provided that the contact device comprises a hole, in particular an elongated hole, machined into the edge region of the interconnector. With a hole or elongated hole, in particular through the interconnector as seen in the stacking direction, suitable measuring equipment can be connected to the interconnector quickly and easily, in particular in a force-fitting and/or form-fitting manner. The contact devices can protrude laterally outwards at the side edge of the stack arrangement in order to support easy contacting. Preferably, however, the contact devices can be arranged such that they are arranged within the side edge of the stack arrangement. The side contour of the stack arrangement between the top plate and the base plate is, for example, approximately rectangular with four straight side edges in its orthogonal projection onto a plane perpendicular to the stacking direction.

In order to enable rapid contacting and to reduce the risk of unwanted electrical bridging of interconnectors stacked on top of one another, it is envisaged that the interconnectors, each having at least one contact device, are designed and/or arranged within the stack arrangement in such a way that the contact devices of the interconnectors of two electrolysis cells stacked on top of one another are arranged offset from one another transversely to the stacking direction.

To further improve fast and reliable contacting of the interconnectors, the interconnectors can be provided with recesses in their edge regions, which are aligned in the stacking direction of the stack arrangement with the contact device of an interconnector arranged directly above and below. Thus, the contact device of an interconnector is prominent compared to the contact devices of its immediate neighbors in the stack assembly, supporting accurate contacting.

Regarding the definition, the following should be noted: 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 apply This also applies to bipolar plates. For the purposes of this application, high-temperature electrolysis refers to electrolysis in the temperature range between 600°C and 1000°C, in particular between 800°C and 950°C. However, high-temperature analysis is not limited to this temperature range, but can also be carried out at higher temperatures, for example, up to 1400°C.

Fig. 1

eine stark schematisierte Darstellung einer erfindungsgemäßen Elektrolyseanordnung,

Fig. 2

eine vereinfachte Explosionsdarstellung einer bevorzugten Variante von MEA, Interkonnektoren und Glasdichtungen einer erfindungsgemäßen Elektrolyseanordnung,

Fig. 3

eine vereinfachte Explosionsdarstellung eines generellen Aufbaus einer Stackanordnung einer erfindungsgemäßen Elektrolyseanordnung,

Fig. 4a, 4b, 4c

eine vereinfachte Schnittdarstellung einer der Länge nach halbierten Stackanordnung mit sich verjüngender Manifoldstruktur,

Fig. 5

eine vereinfachte Explosionsdarstellung von gestapelten Interkonnektoren,

Fig. 6a, 6b

eine Detailansicht von Glasdichtungen auf einem Interkonnektor,

Fig. 7

eine Konnektorplatte, und

Fig. 8

eine stark schematisierte Schnittdarstellung von Kanalquerschnitten auf einem Interkonnektor.

The present invention is explained in more detail with reference to the following drawings.

Fig. 1

a highly schematic representation of an electrolysis arrangement according to the invention,

Fig. 2

a simplified exploded view of a preferred variant of MEA, interconnectors and glass seals of an electrolysis arrangement according to the invention,

Fig. 3

a simplified exploded view of a general structure of a stack arrangement of an electrolysis arrangement according to the invention,

Fig. 4a, 4b, 4c

a simplified sectional view of a stack arrangement halved lengthwise with a tapered manifold structure,

Fig. 5

a simplified exploded view of stacked interconnectors,

Fig. 6a, 6b

a detailed view of glass seals on an interconnector,

Fig. 7

a connector plate, and

Fig. 8

a highly schematic sectional view of channel cross-sections on an interconnector.

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 (H ₂ O(g)), is introduced into the stack arrangement 16 and fed to the electrolysis cells 18. In the product gas manifold structure 68, a product gas, such as hydrogen (H ₂ ), is led away from the electrolysis cells 18 and out of the stack arrangement 16.

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 in the assembled state of the electrolysis cell. To form a stack arrangement 16 (cf. Fig. 1 or Fig. 3 ), several 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 subsequent 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.

The interconnector 22 has two manifold openings 28, 30, a first manifold opening 28 serving to guide reactant gas and a second manifold opening 30 serving to guide 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 flow for the electrolysis process comes into contact with the hydrogen side of a manifold structure 66 arranged 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.

To guide reactant gas from the manifold opening 28 of the interconnector 22, 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 in Fig. 2 As also indicated, an oxygen-permeable structure 34 designed as a channel structure for guiding the oxygen generated there can be formed on the oxygen side of the MEA 20. 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 configured 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.

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 stacked electrolysis cells 18 such 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 such that the intermediate space between the oxygen sides of the directly stacked MEA 20 and interconnector 22 is fluidically conductively connected to the interior 14 of the housing 12 of an electrolysis arrangement 10.

On the oxygen side of the MEA 20, as in Fig. 2 shown - between the MEA 20 and the interconnector 22, support elements 48 can be provided, which serve to mechanically equalize 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 tear or break under mechanical stress; in particular, point pressure loads lead to fractures in the MEA 20. The support elements 48, together with the seals 44, 46, ensure that any warping of the MEA 20 when the electrolysis cell 18 heats up. The support elements 48 can be arranged at least in regions in recesses 64 of the MEA 20, wherein the recesses 64 are preferably incorporated non-penetratively into the MEA 20. 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.

Figure 3 shows a simplified exploded view in schematic form of the general structure of a stack arrangement 16. In the Figure 3 In the example shown, the stack arrangement 16 has three MEAs 20, i.e. three levels. The stack arrangement 16 according to the invention can alternatively also have fewer or more MEAs 20 and thus correspondingly comprise 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 floor side, below the first MEA 20 in the stacking direction S, the stack arrangement 16 terminates with a base plate 42.

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. In this case, the top side of the base plate 42 is configured analogously to a hydrogen side of an interconnector 22 and is sealed with a glass seal 46 arranged on the top side relative to the interconnector 22 of the first electrolysis cell 18 in the stacking direction S. Instead of an interconnector 22, the third and final electrolysis cell 18 in the stacking direction S has a top plate 40, which is configured analogously to an oxygen side of an interconnector 22 on its underside. Unlike the interconnectors 22, the top plate does not have manifold openings 28, 30. The top plate 40 closes off the stack arrangement 16 at the top in the stacking direction S and closes the reactant gas and product gas manifold structures 66, 68 formed in the stack arrangement 16.

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.

Directly below the top plate 40 of the stack arrangements 16, between the uppermost MEA 20 and the top plate 40, a further interconnector 22 (not shown) or a connector plate (not shown). The connector plate is preferably electrically conductive in order to establish 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.

The Figures 4a , 4b , 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, the Figures 4a-c each having a tapered manifold structure 66, 68, in which the taper extends from the base plate 42 over 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.

In the example after 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, wherein the interconnectors 22 of individual electrolysis cells are selected and the electrolysis cells 18 are 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, when 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.

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 the same size. The insert body 50 has, in contrast to the design in Fig. 4b not a straight-line tapered surface, but 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.

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, 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 designed as an elongated hole in the example shown can be used to connect measuring devices for testing the stack arrangement, for example to identify defective electrolysis cells.

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 stems 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 error can still be corrected.

The Figures 6a, 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 the Figures 6a and 6b As shown, the glass seals 46 can be applied in a special form to the interconnector 22. In the present case, Fig. 6a a meandering course and in Fig. 6a A zigzag-shaped course of the glass seal 46 applied to the interconnector 22 is shown. Other course shapes are also conceivable. This special application form increases the length of the band-shaped glass seal in contrast to a straight guide. This allows a larger surface area of the sealing material to be provided with the same amount of sealing material compared to a straight guide, 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 less 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.

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 in a checkerboard pattern on the surface of the connector plate 36, as in the example shown. A coating can also be present on the side of the connector plate 36 not shown.

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 means of 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 delimited 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. In order to provide a sufficient amount of reactant gas 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.

LIST OF REFERENCE SYMBOLS

10 Electrolysis arrangement 50 Insert body 12 Housing 52 Contact device 14 Interior 54 recess 16 Stack arrangement 56 meandering structure 18 Electrolysis cells 58 zigzag structure 20 Membrane electrode assembly 60 Orientation feature 22 Interconnector 62 Coating 24 Educt gas opening 64 recesses 26 Product gas opening 66 Educt gas manifold structure 28 Manifold opening 68 Product gas manifold structure 30 Manifold opening 70 Channels 32 Educt gas pipeline structure 72 Canal bridges 34 oxygen-permeable structure 36 connector plate S Stacking direction 38 net-like metal mesh F Slope 40 Top plate 42 base plate 44 Glass seal 46 Glass seal 48 Support elements

Claims (19)

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 (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 at least some electrolysis cells (18) have support elements (48) between the membrane electrode assembly (20) and the interconnector (22), and wherein the support elements (48) are designed and arranged such that they are viscous in an operating state of the electrolysis arrangement (10) and solid in a rest state of the electrolysis arrangement (10). Electrolysis arrangement (10) according to claim 1, characterized in that on the oxygen side of at least some membrane electrode arrangements (20) there is at least one layer which has recesses (64) for receiving the support elements (48), and wherein the layer having the recesses (64) is preferably an oxygen-permeable structure (34) by means of which oxygen released on the oxygen side of the membrane electrode arrangement (20) can be diverted to a side edge of the membrane electrode arrangement (20). Electrolysis arrangement (10) according to claim 1 or 2, characterized in that the support elements (48) and/or the recesses (64) have a contour shape selected from the group consisting of circular, circular segment-shaped, square, rectangular, quadrangular, triangular or diamond-shaped. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that the surface area of the projection surface of a support element (48) is approximately 5-15% of the surface area of the membrane electrode arrangements (20) of the electrolysis cell (18) to which reactant gas can flow. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that the surface size of the projection surface of the support elements (48) is smaller than the surface area of the recesses (64) for receiving the support elements (48). Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some interconnectors (22) are designed as a flat, in particular plate-shaped component which is free of gas-conducting structures on the hydrogen side and/or on the oxygen side, wherein these interconnectors (22) are preferably designed as a flat steel sheet. Electrolysis arrangement (10) 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). Electrolysis arrangement (10) 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 can be aligned in the stack assembly in order to produce the stack arrangement (16), in particular according to the poka-yoke principle. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some interconnectors (22) in the stack arrangement (16) are stacked alternately rotated by 180° using orientation features (60) arranged on the interconnectors (22). Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that the stack arrangement (16) has a top plate (40) delimiting the stack arrangement (16) upwards in the stacking direction (S) at the top and a bottom plate (42) delimiting the stack arrangement (16) downwards in the stacking direction (S) at the bottom. Electrolysis arrangement (10) according to claim 10, characterized in that the coating of the top plate (40) and/or the bottom plate (42) 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). Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that the top plate (40) and the base plate (42) each have clamping devices, in particular in the form of holding elements projecting outwards at the edge region of the top plate (40) and the base plate (42), such that clamping means can be arranged on the outside of the stack arrangement at a distance from the stack arrangement between the clamping devices of the top plate (40) and the base plate (42), by means of which clamping means a tensile force acting between the top plate (40) and the base plate (42) along the stack direction axis can be applied. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some of the interconnectors (22) have at least one contact device (52) in their edge region, which is electrically conductively connected to the interconnector (22). Electrolysis arrangement (10) according to claim 13, characterized in that the contact device (52) comprises a hole, in particular an elongated hole (52), machined into the edge region of the interconnector (22). Electrolysis arrangement (10) according to claim 13 or 14, characterized in that the interconnectors (22) each having at least one contact device (52) are designed and/or arranged within the stack arrangement (16) in such a way that the contact devices (52) of the interconnectors (22) of two electrolysis cells (18) stacked one above the other are arranged offset from one another transversely to the stacking direction (S). Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that the stack arrangement (16) has a top plate (40) delimiting the stack arrangement (16) upwards in the stacking direction (S) at the top and a bottom plate (42) delimiting the stack arrangement (16) downwards in the stacking direction (S) at the bottom. Electrolysis arrangement according to claim 16, 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) and 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) and arranged above the bottom plate (40). Electrolysis arrangement according to claim 17, characterized in that the connector plate (36) is designed as a plate-shaped sheet, wherein the outer contour shape of the connector plate (36) corresponds at least substantially to the contour shape of the interconnector (22) arranged adjacent to the connector plate (36) in the stacking direction (S), and wherein the connector plate (36) is preferably free of gas-conducting structures. Electrolysis arrangement according to claim 17 or 18, characterized in that the connector plate (36) has a coating (62) at least on one side at least in some areas, in particular such that several spaced-apart surface areas of the connector plate (36) are coated, preferably in the form of a checkerboard pattern.

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