Electrolysis assembly

Abstract

The invention relates to an electrolysis assembly comprising a stack assembly. At least some of the interconnectors are designed in the form of substantially rectangular single-layer sheet-metal structures, the first face of which defines the hydrogen side of the interconnector and the second face of which defines the oxygen side of the interconnector, wherein the thickness of the interconnectors in the form of sheet-metal structures ranges from 0.3 to 0.8 mm, and at least some of the interconnectors have a reactant gas manifold opening in a first edge region in order to conduct reactant gas and a product gas manifold opening in a second edge region lying opposite the first edge region in order to conduct product gas. Between the membrane electrode assembly and the interconnector of at least some of the electrolysis cells is a reactant gas line structure designed to conduct reactant gas out of the reactant gas manifold structure along the hydrogen side of the membrane electrode assemblies and to the product gas manifold structure, and the reactant gas line structure has a plurality of flow channels, each of which is laterally delimited by means of two mutually spaced channel webs, at least some of the channel webs having, on average, an edge steepness of >= 85° at at least one surface which delimits a flow channel.

Description

[0001] DESCRIPTION

[0002] Electrolysis arrangement

[0003] The invention relates to 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 leave room for optimizing electrolysis with high efficiency during continuous operation.

[0014] The object of the present invention is to provide an electrolysis system that enables high efficiency even during continuous operation. This object is achieved by the electrolysis system specified in the claims. Advantageous embodiments are the subject of the subclaims.

[0015] 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 of the interconnectors are designed in the form of a single-layer, substantially rectangular sheet metal structure, the first surface of which defines the hydrogen side of the interconnector and the second surface of which defines the oxygen side of the interconnector, the thickness of the interconnectors designed as a sheet metal structure being in the range from 0.3 to 0.8 mm.At least some of the interconnectors have an educt gas manifold opening in a first edge region for guiding educt gas and a product gas manifold opening in a second edge region opposite the first edge region for guiding product gas, wherein an educt gas line structure designed to guide educt gas out of the educt gas manifold structure along the hydrogen side of the membrane electrode assemblies and towards the product gas manifold structure is arranged between the membrane electrode assembly and the interconnector of at least some electrolysis cells, and wherein the educt gas line structure comprises a plurality of flow channels, each of which is laterally delimited by two spaced-apart channel webs, wherein at least some of the channel webs have an average flank steepness of 85° or more than 85° on at least one surface delimiting a flow channel.

[0016] 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 XlCrTiLa22 or 1.4755 - XlCrWNbTiLa22-2. 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.

[0017] 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 adjacent membrane-electrode assemblies and interconnectors face each other. Likewise, the oxygen sides of directly adjacent 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, which is conducted between the hydrogen side of a membrane electrode assembly and an interconnector, is converted into product gas, in this case hydrogen, during electrolysis on the hydrogen side of the membrane electrode assembly.

[0018] The interconnects are very thin, with a height in the range of 300 pm to 800 pm. Technically, a thickness range of the interconnects in the range of 600 pm to 800 pm has proven to be particularly effective for optimizing the overall height of a stack arrangement according to the invention, taking into account the function and stability of the interconnectors.

[0019] The reactant gas line structure is provided in the area covered by a membrane electrode assembly, between the membrane electrode assembly and the interconnector. The reactant gas line structure is preferably designed as a channel structure having multiple channels, wherein the channels guide the reactant gas from the reactant gas manifold structure along the hydrogen side of the membrane electrode assembly and the product gas produced on the hydrogen side of the membrane electrode assembly during electrolysis into the product gas manifold structure. The channel structure can in particular be formed from straight channels separated from one another by channel webs. The membrane electrode assembly can rest on the channel webs with its hydrogen side. The channels of such a channel structure advantageously have a guide direction oriented perpendicular to the stacking direction.To support a fine and laminar flow, the channel structure can have a large number of channels, for example 60 or more than 60 channels, in particular up to 100 channels.

[0020] An MEA is arranged in the stack arrangement above the channel webs of a reactant gas line structure implemented using channels. The channels are limited at the bottom by the body of the interconnector. At the top, the channels are open towards the MEA arranged above. For the electrolysis process, the reactant gas guided in the channels comes into contact with the hydrogen side of the MEA at the open upper sides of the channels to initiate the electrolysis process there. To ensure that a sufficient amount of reactant gas is also provided in the edge region of the channels for contact with the MEA, the mean value of the flank steepness of the side walls of the channel webs is greater than or equal to 85° relative to the plane spanned by the interconnector.

[0021] In one embodiment, it is provided that exactly one reactant gas manifold structure for providing reactant gas to the electrolysis cells and exactly one product gas manifold structure for discharging product gas from the electrolysis cells are formed in the stack arrangement.

[0022] Preferably, the reactant gas manifold structure and / or the product gas manifold structure are designed as a blind hole within the stack arrangement. The inlet and outlet openings of the two manifold structures are preferably formed in a base plate of the stack arrangement. It is also conceivable in principle to design the reactant gas manifold structure and / or the product gas manifold structure as a through-opening in the stack arrangement. In a blind hole-like design, which has proven technically successful in the electrolysis arrangement according to the invention, only one opening is provided for each manifold structure in the stack arrangement, preferably in the base plate. The manifold structures extend from the base plate in the stack direction to the last electrolysis cell to be supplied with reactant gas in the stack direction, preferably to a top plate.

[0023] The interconnector manifold openings that define the manifold structures within the stack arrangement are preferably completely open, i.e., free of webs within their outer opening edge. Each interconnector preferably has exactly one manifold opening for the formation of the reactant gas manifold structure and exactly one manifold opening for the formation of the product gas manifold structure.

[0024] Preferably, the interconnectors and the membrane electrode assemblies are arranged within the stack arrangement such that the membrane electrode assemblies are aligned approximately centrally with respect to the stacked interconnectors. The membrane electrode assemblies typically have a smaller surface area than the interconnector, so that the edge regions of the interconnectors remain free, i.e., uncovered by the membrane electrode assemblies. The manifold openings for the manifold structures are arranged in the free edge regions of the interconnectors. Furthermore, seals can be provided in the free edge regions to separate stacked interconnectors from one another in a fluidically sealed and / or electrically insulating manner.

[0025] To ensure a favorable gas supply to the electrolysis cells, the dimensioning of the manifold openings should ensure that the cross-sectional area of ​​the manifold openings of an interconnector of at least some electrolysis cells is in the range of 9% to 22% or in the range of 12% to 21% or in the range of 13% to 18% of the surface area of ​​the membrane electrode assemblies of the electrolysis cell to which reactant gas can flow.

[0026] With regard to the reactant gas conduit structure implemented using channels, it is envisaged that at least some of the channel webs have a triangular, rectangular, or semi-elliptical cross-section, in particular such that the flow channels defined by the channel webs have a substantially triangular, trapezoidal, rectangular, or semi-hyperbolic cross-section. This promotes the creation of a very homogeneous and laminar flow field along the MEA, which is particularly important for co-electrolysis.

[0027] According to one embodiment, a coating can be provided on the oxygen side of the interconnector, in particular a coating that inhibits the passage of oxygen. This coating is essentially an oxygen-impermeable layer; depending on the selection of the coating material, it can be provided that the oxygen impermeability is established or increases with increasing oxidation of the coating components.

[0028] With regard to the coating, it is envisaged that the coating of the interconnector 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 cobalt iron oxide (LSCF), or lanthanum strontium manganese (LSM) or lanthanum manganese cobalt (LMC).

[0029] According to a preferred embodiment, it is contemplated that at least some electrolysis cells have support elements between the membrane electrode assembly and the interconnector.

[0030] 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.

[0031] 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 when the electrolysis arrangement is in operation. 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 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.

[0032] 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.

[0033] For the arrangement of the support elements on the MEA, it can be provided that on the oxygen side of at least some membrane electrode assemblies at least one layer is present 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.

[0034] The oxygen-permeable structure on the oxygen side of the membrane-electrode assembly serves to dissipate oxygen generated 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 dissipate 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 substantially perpendicular to the direction of a reactant gas channel structure. The channels can, in particular, be designed as 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.

[0035] Oxygen can also be conveyed into the interior 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.

[0036] 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.

[0037] With regard to the material of the support elements, it is considered that the support elements consist of glass, preferably a glass ceramic.

[0038] According to one embodiment of the electrode arrangement, it is provided that a channel structure is formed on the oxygen side of at least some interconnectors for guiding oxygen released on the oxygen side of a membrane electrode arrangement.

[0039] The channel structure on the oxygen side of the interconnectors 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 channel 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. The channel structure is preferably designed as 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 rib-like. The channels can be delimited laterally by channel webs; at the channel base, the channels can be defined by the body of the interconnector, and on the opposite side, 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.

[0040] The channels can therefore be arranged on the oxygen side of the interconnector from one edge to an edge of the interconnector opposite this edge, wherein the channel structure on the oxygen side preferably runs orthogonally to channels designed for the guidance of reactant and product gas on the hydrogen side of the interconnector.

[0041] Regarding the choice of material for the interconnector, it is intended that at least some of the interconnectors be made of a ferritic high-temperature stainless steel, particularly an iron-chromium alloy. The use of the material known as Crofer 22 is conceivable, for example, material 1.4760 XlCrTiLa22 or 1.4755 - XlCrWNbTiLa22-2

[0042] 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.

[0043] In principle, various designs are conceivable for the design of the contact devices of the interconnectors. Preferably, in any case, it is contemplated that the contact devices are configured and designed in such a way that, even in a closely stacked stack of the stack arrangement, measuring equipment can be easily inserted 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 with a force-fitting and / or form-fitting connection. The contact devices can protrude laterally outwards at the side edge of the stack arrangement to support easy contacting.Preferably, however, the contact devices can be arranged such that they are located within the side edge of the stacking arrangement. The side contour of the stacking arrangement between the top plate and the bottom plate is, for example, approximately rectangular in shape with four straight side edges when projected orthogonally onto a plane perpendicular to the stacking direction.

[0044] 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 contemplated 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.

[0045] To further improve fast and reliable contacting of the interconnectors, the interconnectors can be provided with recesses in their edge areas, which are aligned in the stacking direction of the stack arrangement with the contact device of an interconnector arranged directly above and below. This places the contact device of an interconnector prominently above the contact devices of its immediate neighbors in the stack, supporting accurate contacting.

[0046] The production of a stack arrangement can be facilitated by at least some components of the stack arrangement, such as membrane electrode assemblies, interconnectors, connector plates, top plate and / or base plate, each having an orientation feature by means of which the components can be oriented in the stack assembly for producing 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 support, in particular using the poka-yoke principle, in order to produce the stack 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 in order to reduce or completely avoid errors.

[0047] For the identifiability and traceability of individual components of an electrolysis system, it can be provided that at least some components of the electrolysis arrangement, such as the housing, stack arrangement, electrolysis cell, membrane electrode arrangements, interconnectors, connector plate, top plate and / or base plate, have a machine-readable and / or human-readable identifier.

[0048] In particular, it can be provided that the identifier comprises a DataMatrix code (DMC), a QR code, a barcode and / or an alphanumeric code.

[0049] To separate the hydrogen- and oxygen-carrying spaces in the stack arrangement, at least one glass seal is applied to the interconnectors to seal stacked electrolysis cells from each other. These glass seals are made of glass or glass ceramic and seal the hydrogen spaces from the oxygen spaces of the electrolysis arrangement. Furthermore, the glass seals can be used to achieve electrical insulation between stacked interconnectors.

[0050] With regard to the arrangement of the seals on the interconnector, one embodiment envisages the glass seal being applied in a meandering or zigzag pattern. This application form increases the length of the band-shaped glass seal compared to a straight path. Thus, with the same amount of sealing material, a larger surface area of ​​the sealing material can be provided compared to a straight path, which enables better degassing of the sealing material during a subsequent sintering process. Alternatively, the same area can be sealed with less sealing material. In a further embodiment, the interconnector has an elongated groove-like recess in its edge region on the oxygen side and / or on the hydrogen side between the side edge and the reactant gas manifold opening and / or between the side edge and the product gas manifold opening.This elongated recess can be arranged, in particular, between the side edge of the interconnector and the glass seal applied in the edge region. The recess acts like a groove at the edge of the interconnector, accommodating the glass material of the glass seals that swells toward the edge region during the joining process, in which the glass seals arranged near the recess become viscous under the influence of high compressive forces and the input of high thermal energy. The recess can completely surround the interconnector in its edge region. Preferably, the recesses are arranged only on two opposite edges of the interconnector.

[0051] 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.

[0052] The present invention is explained in more detail with reference to the following drawings. They show:

[0053] Fig. 1 is a highly schematic representation of an inventive

[0054] Electrolysis arrangement,

[0055] Fig. 2 is a simplified exploded view of a preferred variant of

[0056] MEA, interconnectors and glass seals of an electrolysis arrangement according to the invention,

[0057] Fig. 3 is a simplified exploded view of a general structure of a

[0058] Stack arrangement of an electrolysis arrangement according to the invention, Fig. 4a, 4b, 4c a simplified sectional view of a halved lengthwise

[0059] Stack arrangement with tapered manifold structure,

[0060] Fig. 5 a simplified exploded view of stacked interconnectors,

[0061] Fig. 6a, 6b a detailed view of glass seals on an interconnector,

[0062] Fig. 7 a connector plate, and

[0063] Fig. 8 is a highly schematic sectional view of channel cross-sections on an interconnector.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] To guide reactant gas from the manifold opening 28 of the interconnector 22, a 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.

[0068] 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 for guiding 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 conduit 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 at the top. The taper can be provided in the reactant gas manifold structure 66 and / or in the product gas manifold structure 68. In the example according to Figure 4a, the taper of the manifold structure 66, 68 is implemented by means of the manifold openings 28, 30 incorporated in 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.

[0076] 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.

[0077] Figure 4c shows a special form of a tapered 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. In contrast to the embodiment in Fig. 4b, the insert body 50 does not have a straight-line 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.

[0078] 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.

[0079] 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 prevent stacking errors 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.

[0080] 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 shows 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 pattern. This allows a larger surface area of ​​the sealing material to be provided with the same amount of sealing material compared to a straight pattern, which enables better degassing of the sealing material during a subsequent sintering process. This improved degassing can accelerate the sintering process.Alternatively, the same area can be sealed using less sealing material. This saves sealing material because less material is applied, the sealing performance is not compromised, and excess sealing material that can escape from the stack during sintering is avoided.

[0081] 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.

[0082] 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.

[0083] LIST OF REFERENCE SYMBOLS

[0084] 10 Electrolysis arrangement 50 Insert body

[0085] 12 Housing 52 Contact device

[0086] 14 Interior 54 Recess

[0087] 16 stack arrangement 56 meandering structure

[0088] 18 electrolysis cells 58 zigzag structure

[0089] 20 Membrane electrode assembly 60 Orientation feature

[0090] 22 Interconnector 62 Coating

[0091] 24 reactant gas openings 64 recesses

[0092] 26 Product gas opening 66 Educt gas manifold structure

[0093] 28 Manifold opening 68 Product gas manifold structure

[0094] 30 manifold opening 70 channels

[0095] 32 Educt gas line structure 72 channel webs

[0096] 34 oxygen-permeable structure

[0097] 36 Connector plate S stacking direction

[0098] 38 net-like metal mesh F flank steepness

[0099] 40 top plate

[0100] 42 base plate

[0101] 44 Glass seal

[0102] 46 Glass seal

[0103] 48 support elements

Claims

CLAIMS 1. 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 at least some of the interconnectors (22) are designed in the form of a single-layer, substantially rectangular sheet metal structure, the first surface of which defines the hydrogen side of the interconnector (22) and the second surface of which defines the oxygen side of the interconnector (22), wherein the thickness of the interconnectors (22) designed as a sheet metal structure is in the range of 0.3 to 0.8 mm, at least some of the interconnectors (22) have an educt gas manifold opening (28) for guiding educt gas in a first edge region and a product gas manifold opening (30) for guiding product gas in a second edge region opposite the first edge region, wherein an educt gas line structure (32) designed to guide educt gas out of the educt gas manifold structure (66) along the hydrogen side of the membrane electrode assemblies (20) and towards the product gas manifold structure (68) is arranged between the membrane electrode assembly (20) and the interconnector (22) of at least some electrolysis cells (18), and wherein the educt gas line structure (32) comprises a plurality of flow channels (70) which are each laterally delimited by two spaced-apart channel webs (72), wherein at least some of the channel webs (72) are connected to at least one,a surface bounding a flow channel (70) have an average flank steepness (F) of >= 85°., 2. Electrolysis arrangement (10) according to claim 1, characterized in that in the stack arrangement (16) exactly one reactant gas manifold structure (66) for providing reactant gas to the electrolysis cells (18) and exactly one product gas manifold structure (68) for discharging product gas from the electrolysis cells (18) are formed.

3. Electrolysis arrangement (10) according to claim 1 or 2, characterized in that the cross-sectional area of ​​the manifold openings (28, 30) of an interconnector (22) of at least some electrolysis cells (18) is in each case in the range from 9% to 22% or in the range from 12% to 21% or in the range from 13% to 18% of the surface area of ​​the membrane electrode arrangements (20) of the electrolysis cell (18) against which reactant gas can flow.

4. Electrolysis arrangement (10) according to one of the preceding claims, characterized in that at least some of the channel webs (72) have a triangular, rectangular or semi-elliptical cross-section, in particular such that the flow channels (70) delimited by the channel webs (72) have a substantially triangular, trapezoidal, rectangular, semi-hyperbolic cross-section.

5. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that a coating is present on the oxygen side of the interconnector (22), in particular a coating which inhibits the passage of oxygen.

6. Electrolysis arrangement (10) according to claim 5, characterized in that the coating of the interconnector (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-cobalt-iron oxide (LSCF), or lanthanum strontium manganese (LSM) or lanthanum-manganese-cobalt (LMC).

7. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some electrolysis cells (18) have support elements (48) between the membrane electrode assembly (20) and the interconnector (22).

8. Electrolysis arrangement (10) according to claim 7, 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).

9. Electrolysis arrangement (10) according to claim 7 or 8, 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.

10. Electrolysis arrangement (10) according to one of claims 7 to 9, characterized in that the support elements comprise glass, preferably a glass ceramic.

11. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that a channel structure for guiding oxygen released on the oxygen side of a membrane electrode arrangement (20) is formed on the oxygen side of at least some interconnectors (22).

12. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some of the interconnectors (22) consist of a ferritic high-temperature stainless steel, in particular of an iron-chromium alloy.

13. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some of the interconnectors (22) in their edge region have at least one contact device (52) which is electrically conductively connected to the interconnector (22).

14. 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).

15. 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 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).

16. 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.

17. Electrolysis arrangement (10) according to at least one of the preceding claims, characterized in that at least some components of the electrolysis arrangement (10), such as housing (12), stack arrangement (16), electrolysis cell (18), membrane electrode arrangements (20), interconnectors (22), connector plate (36), top plate (40) and / or base plate (42) have a machine-readable and / or human-readable identifier.

18. Electrolysis arrangement (10) according to claim 17, characterized in that the identifier comprises a DataMatrix code (DMC), a QR code, a barcode and / or an alphanumeric code.

19. Electrolysis arrangement (10) according to one of the preceding claims, characterized in that at least one glass seal (44, 46) is applied to the interconnector (22) for sealing stacked electrolysis cells (18) from one another.

20. Electrolysis arrangement (10) according to claim 19, characterized in that the glass seal is applied in a meandering or zigzag shape.

21. Electrolysis arrangement (10) according to one of the preceding claims, characterized in that the interconnector (22) has an elongated depression in the manner of a groove in its edge region on the oxygen side and / or on the hydrogen side between the side edge and the reactant gas manifold opening (28) and / or between the side edge and the product gas manifold opening (30).

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