Method for producing a plate assembly, plate assembly and electrochemical cell

Abstract

The invention relates to a method for producing a plate assembly (2) of a stack (1) of electrochemical cells (3), wherein the plate assembly (2) is generated in one piece comprising a plurality of plates additively in a 3D printing method, wherein the plate assembly (2) is formed with an anode side (2a) and a cathode side (2b), wherein plates arranged parallel to one another in production planes oriented perpendicularly to the plates are generated additively. At least two cooling planes (KE) arranged parallel to one another are formed within a cooling plate (4) of the plate assembly (2) and parallel to the anode side (2a) and the cathode side (2b), in which cooling channels (15, 15') running separately from one another are formed for the parallel-connected passage of coolant (KW). A fluid-permeable plate in the form of an openly porous, multi-layer transport ply (7, 11) is generated adjacent to at least one side of the cooling plate (4), and the layers (8, 9; 12, 13) of the openly porous transport ply (7, 11) are formed differently from one another in terms of at least one of the parameters of layer thickness and porosity. The invention additionally relates to a plate assembly (2) produced accordingly and to an electrochemical cell (3).

Description

[0001] Method for manufacturing a plate arrangement, plate assembly and electrochemical cell

[0002] The invention relates to a method for manufacturing a plate arrangement of a stack of electrochemical cells using additive manufacturing methods. Furthermore, the invention relates to a plate arrangement for an electrochemical system comprising additively manufactured components. Finally, the invention relates to an electrochemical cell, in particular an electrolyzer.

[0003] The additive manufacturing of components for a fuel cell stack or electrolyzer is known in principle, for example, from DE 10 2013 108 413 A1. Laser, electron beam, and steam jet sintering are mentioned therein as manufacturing technologies. Additive manufacturing processes are also said to be suitable for joining components of a cell stack.

[0004] WO 2023 / 021217 A1 discloses an integrated process, based on a single 3D printing system, for the production of a monolithic solid oxide cell (SOC) stack. The process according to WO 2023 / 021217 A1 includes the production of various electrodes as well as electrolyte and intermediate layers. Housing components containing insulating ceramic material are also said to be additively manufactured.

[0005] US Patent 2015 / 0290860 A1 addresses the geometry of nozzles intended for the additive manufacturing of components for electrochemical systems. A nozzle geometry deviating from a circular shape is proposed. This is intended to enable the fabrication of composite components with various planar surfaces, including channels for the passage of fuel or air.

[0006] The additive manufacturing of fuel cell components is also addressed in US 2008 / 0008826 A1. Here, powder layers are solidified by laser sintering, with the aim of producing areas with different porosities. At least two layers of the arrangement described in US 2008 / 0008826 A1 have different compositions and different thicknesses.

[0007] A method for manufacturing an electrochemical cell device, described in DE 10 2018 100 772 A1, involves producing a functional layer on a cell support by direct material application. The cell support is a cell separator that forms the outer boundary of an electrochemical cell. The cell support can be made of stainless steel and have a corrosion protection layer. Functional layers to be built up successively on the cell support are designed, in particular, as a gas distribution layer and a catalyst layer. According to DE 10 2018 100 772 A1, it is also possible to produce an electrochemical functional layer with a gradient, wherein the gradient relates to the geometric design and / or materials, and wherein the gradient is produced in the stacking direction and / or transversely to the stacking direction.

[0008] According to DE 10 2014 226 567 A1, at least a portion of a bipolar plate of a fuel cell system is to be manufactured using additive manufacturing. To create a flow field, material is to be selectively applied only to projections of a specific topology on the base plate of the bipolar plate. In this way, contacts, for example made of titanium, nickel, or chromium, are to be created.

[0009] US patent 2005 / 0221150 A1 deals with the additive manufacturing of honeycomb structures for electrochemical cells. The process involves solidifying a metal powder containing nickel and chromium through laser sintering. Additionally, the metallic layers may contain bronze as a binder.

[0010] The publication “Fully printed and integrated electrolyzer cell with additive manufacturing for high efficiency water splitting”, Gaoqiang Yang et al., Applied Energy 215 (2018), pages 202 to 210, describes the integration of a fluid diffusion layer, a bipolar plate, a seal and a current distributor into an additively manufactured plate of a proton exchange membrane electrolysis cell.

[0011] The invention is based on the objective of further developing the production of layered cells of electrochemical systems compared to the aforementioned prior art, whereby more effective cooling of the cell components should be possible.

[0012] This problem is solved according to the invention by a method for producing a plate arrangement of a stack of electrochemical cells, in particular electrolysis cells or fuel cells, according to claim 1. Likewise, the problem is solved by a plate arrangement having the features of claim 7 and an electrochemical cell having the features of claim 10.

[0013] The embodiments and advantages of the invention explained below in connection with the plate arrangement or the entire electrochemical system also apply analogously to the manufacturing process according to the invention and vice versa.

[0014] The process for manufacturing a one-piece plate arrangement of a stack of electrochemical cells is characterized by the additive production and metallurgical bonding of plates arranged parallel to each other in planes which are oriented perpendicular to the plates.

[0015] This is – to put it simply – equivalent to each individual plate of the plate assembly being built, and especially printed, standing upright on one of its narrow edges. Nevertheless, a solid connection is created between the plates, resulting in a plate assembly formed from a single piece. Plates of cell stacks or other stacks produced using conventional 3D printing methods are typically formed lying flat on one of their large surface areas.

[0016] The inventive method for manufacturing a plate arrangement of a stack of electrochemical cells is thus designed to additively produce the plate arrangement in one piece, comprising several plates. The plate arrangement is formed with an anode side and a cathode side, with plates arranged parallel to each other being additively produced in manufacturing planes that are oriented perpendicular to the plates. At least two cooling planes arranged parallel to each other are formed within a cooling plate of the plate arrangement and parallel to the anode side and the cathode side, in which cooling channels running separately from each other are formed for the parallel passage of coolant.In addition, a fluid-permeable plate in the form of an open-porous, multi-layered transport layer is created adjacent to at least one side of the cooling plate, wherein the layers of the open-porous transport layer are designed differently from each other with respect to at least one of the parameters layer thickness and porosity.

[0017] The cooling plate is permeable to coolant flow in the direction of the cooling channels, which terminate at opposite narrow edges of the cooling plate or converge there to form at least one cooling channel. Due to the fluidically separated cooling levels, the coolant can flow through these channels in either co-current or counter-current flow. The cooling channels are therefore designed to allow flow in or against the pressure direction of the cooling plate. The two large side surfaces of the cooling plate, which are aligned parallel to the anode and cathode sides of the plate assembly, are flat and, perpendicular to these, impermeable to fluid.For example, in an electrolysis cell, the coolant cannot come into contact with process water used in the electrolysis process for hydrogen production, which can flow unhindered through a fluid-permeable, open-porous transport layer adjacent to the cooling plate on at least one side, perpendicular to the anode or cathode side of the plate arrangement.

[0018] The vertical additive manufacturing of the plates, where each plate is built upright on a 3D printing platform starting from one of its narrow edges, allows for the creation of particularly intricate and complex structures that would be impossible to produce on a 3D printing platform starting from a single, horizontally oriented large edge. For example, recesses for creating overhangs in 3D printing can only be produced with low quality if the plates are built up sequentially, i.e., horizontally. This is because when a powdered material is melted by a laser, the laser beam penetrates to an undesirable depth, forming a structure similar to a cave ceiling above the recess. The greater the desired overhang length and the shallower the angle of inclination of the resulting solidified structure, the lower the print quality.

[0019] If the plates of the plate assembly were generated lying flat on top of each other, the entire underside would form a 90° overhang towards the printing surface. This overhang would require support structures, which would then have to be mechanically removed after 3D printing. The surface with the remnants of these support structures would be unsuitable as a contact surface for the membrane of an electrochemical cell. Furthermore, the thermal stresses generated during 3D printing would be so high across the surface that such support structures would not be mechanically stable.

[0020] Simultaneously with reduced print quality, the load-bearing capacity of a 3D-printed structure under pressure deteriorates in the area of ​​the recesses. This is unacceptable, particularly for electrochemical cells operated at high pressures, such as electrolyzers, also for safety reasons. Such problems can be avoided by constructing a plate arrangement according to the inventive method, and a wide range of high-quality 3D-printed structures can be produced.

[0021] Furthermore, a horizontal positioning is uneconomical when 3D printing the plate arrangement because, based on an identically dimensioned printing surface, far fewer or even only one plate arrangement can be printed simultaneously due to space constraints, in contrast to the upright printing process.

[0022] The plate assembly is formed in one piece from the parallel plates to reduce assembly effort during the construction of an electrochemical cell and to lower contact resistance. Furthermore, heat dissipation from the anode and cathode sides of the plate assembly towards the solid cooling plate is improved.

[0023] The provision of at least two cooling levels in the cooling plate of a plate arrangement is easily possible thanks to the method according to the invention and significantly improves heat dissipation from an electrochemical cell. This is particularly advantageous at high currents, such as those required in the operation of electrolyzers on an industrial scale.

[0024] It has proven effective to simultaneously build several identical, parallel plate arrangements on a 3D printing platform, each comprising multiple different plates positioned perpendicular to the platform with their edges aligned vertically. This increases the number of parts produced in a single print run and reduces manufacturing costs.

[0025] The preferred method involves the additive manufacturing of different plates made from various materials on the 3D printing platform, all applied in the same 3D printing layer. Plates made of, for example, steel can be combined with plates made of, for example, titanium, and bonded together to form a solid, continuous surface.

[0026] At least one of the plates is produced as a fluid-permeable, open-porous, multilayer transport layer, wherein the different layers of the open-porous transport layer differ from each other with respect to at least one of the parameters layer thickness and porosity. Such open-porous transport layers are used in electrochemical cells as diffusion layers in fuel cells or as open-porous transport layers (PTLs) in electrolyzers, which are in direct or indirect contact with a membrane or a membrane electrode assembly.

[0027] Openings can be subsequently introduced into the at least one open-porous transport layer via the anode or cathode side, depending on which side the transport layer is located on and where it forms a free surface of the plate assembly. This can be done locally or across the entire plate or transport layer, with the number of subsequently created openings varying locally. Suitable methods include, for example, laser drilling, plasma drilling, or etching.

[0028] The additive manufacturing process according to the invention can be designed to be particularly efficient by simultaneously building several identical, parallel plate groups on a 3D printing platform. Each plate group comprises a plurality of different plates and is positioned perpendicular to the 3D printing platform. The individual plate groups, which are produced together in a single print batch, can be either integrated into a single cell stack or distributed across multiple cell stacks after additive manufacturing. Each plate assembly is also referred to as a sandwich and can be depowdered after separation from the build platform, i.e., the 3D printing platform, provided a powdered printing material is used.

[0029] This can be followed by heat treatment. Optionally, the outer surfaces of the plate assembly are processed by grinding. An additional straightening process can also be performed. Likewise, an electrically conductive coating, for example made of a precious metal such as platinum, can be applied, at least to a portion of one or both sides of the plate assembly. This allows for the coating of the outer side of the open-porous transport layer, the side facing away from the cooling plate. The coating is preferably applied using a PVD or PACVD process. Optionally, plasma etching of the surfaces to be coated can be performed prior to the coating process to remove existing oxide layers and thus ensure good adhesion and electrical contact of the coating to the plate assembly.By applying a coating, including prior plasma etching of existing oxide layers, an electrical resistance of the entire plate arrangement, i.e., from polymer electrolyte membrane to polymer electrolyte membrane, can be achieved as if it were made entirely of gold.

[0030] The plate arrangement according to the invention is formed in one piece and comprises a plurality of additively manufactured, parallel, but not necessarily identical plates, wherein 3D-printed layers are oriented orthogonally to the plates, and wherein at least two cooling planes arranged parallel to each other are formed within a cooling plate of the plate arrangement and parallel to the anode side and the cathode side, wherein cooling channels running separately from each other are provided in the cooling planes for the parallel flow of coolant through the plate arrangement. Adjacent to at least one side of the cooling plate is a fluid-permeable plate in the form of an open-porous, multi-layered transport layer, wherein the layers of the open-porous transport layer differ from each other with respect to at least one of the parameters layer thickness and porosity.

[0031] The cooling plate essentially functions like a conventional bipolar plate. A particular advantage of this plate arrangement is the close material bond between the plates, eliminating electrical losses unlike the contact points where plates are merely pressed together in conventional electrochemical cells. This results in highly efficient operation of an electrochemical cell constructed in this way, and the multiple cooling layers provide excellent cooling capabilities.

[0032] The entire plate assembly is electrically conductive and made of metallic materials. During the additive manufacturing of at least one multi-layered, open-porous transport layer, the different layers appear as adjacent strips within the layer currently being built up by 3D printing.

[0033] According to various possible configurations, several plates belonging to the plate assembly are designed as open-porous transport layers of the sandwich-like plate assembly. These open-porous transport layers are multilayered, cathode-side and anode-side open-porous transport layers of the subsequent electrochemical cells. In particular, a fluid-permeable plate in the form of an open-porous, multilayered transport layer is arranged adjacent to both sides of the cooling plate. The open-porous transport layers preferably enclose a cooling plate between them and each preferably form a free surface of the plate assembly on the cathode side and the anode side, respectively.In this arrangement, the first layer of each open-porous transport layer is preferably coarsely porous, whereas the second layer of each open-porous transport layer is preferably comparatively thin and finely porous. This second layer of each open-porous transport layer preferably forms, at least in a partial region of the plate arrangement, an outer surface of the plate arrangement on its cathode or anode side. The pores of the finely porous second layer preferably have a pore diameter of < 80 pm, particularly in the range of 60 to 80 pm, while the pores or channels in a coarsely porous first layer preferably have a pore diameter > 0.2 mm, particularly > 1 mm.

[0034] In this process, fine-pored second layers of each open-porous transport layer preferably have layer thicknesses of < 0.2 mm and coarse-pored first layers of each open-porous transport layer preferably have layer thicknesses of > 0.5 mm.

[0035] Openings representing the pores of the open-porous transport layer, particularly its outer, fine-pored second layer, are introduced during additive manufacturing, and optionally subsequently. In the latter case, additional fine porosity can be created, for example, by plasma drilling, laser drilling, or etching. Fundamentally, pores in open-porous transport layers can have either a geometrically defined shape or geometrically undefined shapes with a stochastic size distribution, whereby in each case there is permeability, i.e., open porosity, between the coarse-pored first layer and the fine-pored second layer.

[0036] In the case of the coarse-pored first layer, a defined geometry, for example in the form of a grid, is particularly suitable. During operation of the electrochemical cell, this grid transmits forces between adjacent cell components and simultaneously provides free flow cross-sections for operating fluids. The same applies to the fine-pored second layer, which borders the grid and, in particular, provides a flat contact surface for a component adjacent to the electrochemical cell, such as a proton-permeable polymer electrolyte membrane or a gas diffusion layer made of carbon paper or carbon fleece. Due to the 3D printing process, the flat contact surface exhibits a roughness that increases its surface area. Roughness values ​​in the range of Rz16 have proven effective here.

[0037] In contrast to the open-porous transport layers of the plate arrangement, the cooling plate, also part of the plate arrangement and in the form of a bipolar plate, forms channels for a cooling medium, which is preferably kept separate from the operating fluids of the electrochemical system. The cooling medium is primarily water, but other coolants can also be used. Preferably, at least one of the plates is designed as such a bipolar plate, with opposing sides of the bipolar plate enclosing channels for the passage of a fluid, in this case the coolant, on several separate levels between them.

[0038] Unlike the cooling medium, deionized water is used as the process water in an electrolyzer, where it is split into hydrogen and oxygen through electrolysis. Therefore, the expensive process water is preferably kept separate from a less expensive cooling medium in the electrolyzer to save costs.

[0039] In any type of plate assembly for electrochemical cells, a frame can be integrally bonded to the plates, which is also manufactured together with them using additive manufacturing. The plate assembly thus comprises the plates and preferably also a frame encompassing the plates at their edges, wherein the frame comprises a lattice structure and at least one reinforcement. The frame is bonded to the plates and is an integral part of the one-piece plate assembly. The lattice structure serves to relieve residual stresses in the 3D printing process, thus ensuring printability. This means that without such a frame, cracks and distortions can occur in the plate assembly, which can impair or even destroy its functionality.Furthermore, the grid structure serves to reduce the plate arrangement weight and to counteract internal pressure in the electrochemically active area of ​​an electrochemical cell, similar to a pressure vessel.

[0040] Openings for the operating media and coolant, as well as openings for mounting a cell stack, can also be located in this frame. The frame preferably has reinforcement around its circumference and surrounding each of the multiple openings. This reinforcement is a solid and fluid-tight accumulation of material made from the same material as the grid structure. The reinforcement in the area of ​​the openings serves to channel the coolant and operating media and to withstand pressure. The reinforcement around the perimeter of the plate assembly serves to provide a fluid-tight and pressure-resistant shell around the plate assembly when the electrochemical cell is assembled. This reinforcement is a 3D-printed component of the 3D-printed frame and thus also a component of the one-piece 3D-printed plate assembly.

[0041] Regardless of the external shape of the cooling plate, whether a simple flat surface or a more complex bipolar plate, it can be constructed from several different materials. In particular, titanium can be used on the anode side and stainless steel on the cathode side. Alternatively, the entire cooling plate, or even all additively manufactured components of the electrochemical cell, can be made from the same material, for example, a light metal, especially titanium. The titanium alloy Ti6Al4V is preferred, as it is heat-treatable and forms a dense oxide layer. This increases the impact strength, which is an important factor in pressurized systems, and reduces hydrogen embrittlement.

[0042] The open-porous transport layers, which border the cooling plate on both sides, can be made of the same material as the cooling plate's surface. This means, in particular, that all layers of the anode-side open-porous transport layer can be made of titanium and all layers of the cathode-side open-porous transport layer can be made of stainless steel. Alternatively, for example, the coarse-porous, inner layers of the open-porous transport layers bordering the cooling plate can be made of copper. This improves heat dissipation towards the cooling plate.

[0043] One advantage of the one-piece plate assembly, aside from the efficient, reliable manufacturing methods and the resulting low electrical resistance, lies particularly in the fact that the special additive manufacturing process eliminates the need for seals between individual half-cells of electrochemical cells, especially electrolysis, redox flow, or fuel cells. Furthermore, the prefabrication of the complete, materially diverse, sandwich-like plate assemblies facilitates highly efficient, geometrically precise, and reliable assembly of the entire cell stack and offers the possibility of optimizing heat dissipation from the cell stack.

[0044] An electrochemical cell according to the invention, in particular an electrochemical system such as an electrolyzer, comprises at least one cell stack with two end plates, between which at least one plate arrangement according to the invention and at least two polymer electrolyte membranes are arranged. Due to the small number of individual parts, such a cell exhibits a high degree of tightness with respect to the operating media and the coolant and can be manufactured quickly and efficiently.

[0045] The membrane of an electrochemical cell is applied to the plate assembly either before or during the assembly of the entire electrochemical cell stack. The finely porous second layer of the plate assembly, which, unlike the membrane, is additively manufactured, is specifically designed with regard to its electrical and corrosion properties to suit the operating conditions of the electrochemical cells and the properties of the membrane. Within the cell stack, the membrane is positioned in a plane that perpendicularly intersects the successive 3D-printed planes created during additive manufacturing. Specifically, the membrane, or a membrane coated with electrodes on both sides, is directly adjacent to the cathode or anode side of the plate assembly.

[0046] In particular, each end plate is formed in one piece and comprises a plurality of additively manufactured, parallel plates, wherein 3D-printed layers are oriented orthogonally to the plates and wherein each end plate has an electrical contact arrangement. Instead of a bipolar plate as provided in a plate arrangement, each end plate has a carrier plate which has an open-porous, multi-layered transport layer only on one side. The carrier plate can also be designed with cooling channels. In principle, however, an end plate is thus constructed in the same way as a plate arrangement that does not have an open-porous transport layer(s) on the side facing away from the electrochemical cells. An end plate can also preferably be designed with a frame consisting of a grid structure, openings, and reinforcement, just like a plate arrangement, and thus be adapted to the shape and design of a plate arrangement.

[0047] A schematic process for the production of an electrochemical system can be outlined as follows.

[0048] In a first step, the plate assembly is manufactured using a 3D printing process, particularly laser 3D printing. The one-piece plate assembly is preferably produced with a frame thickness in the range of 7 to 12 mm, particularly 9 mm. The layer thicknesses of the coarse-pored first inner layers of the open-porous transport layers are selected to be greater than 0.5 mm. The coarse-pored structure of the first inner layers of the open-porous transport layers is formed using the 3D printing process. These first inner layers exhibit a delicate rod structure, forming an elongated honeycomb pattern. Due to the long overhangs of this rod structure, the plate build-up direction, starting from the narrow edge of the plate, is essential for its feasibility.

[0049] The layer thicknesses of the second outer layers of the open-porous transport layers are specifically selected to be < 0.2 mm. The fine-pored structure of the second outer layers of the open-porous transport layers is formed using 3D printing, optionally further enhanced by subsequent processing such as laser drilling. The second outer layers of the open-porous transport layers are preferably created with a regular three-dimensional pyramid structure on the respective first inner layer.

[0050] The reinforcement in the area of ​​the frame's perimeter or in the area of ​​the channels for operating media has a thickness of at least 0.5 mm in particular, in order to be reliably fluid-tight and pressure-resistant.

[0051] In a second step, the plate assembly is ground on both sides. The grinding process optionally includes grinding the surfaces of the outer second layers of the open-porous transport layers.

[0052] Optionally, a third step involves laser drilling to optionally create further pores in the outer second layers of the open-porous transport layers.

[0053] The fourth step involves a subsequent cleaning of the plate arrangement.

[0054] In a fifth, optional step, one or both of the outer second layers of the open-porous transport layers can be coated. A PVD process, for example, can be used for this purpose. Catalytically active precious metals or precious metal alloys, such as platinum and / or indium, have proven effective as coating materials.

[0055] In a sixth step, seals are inserted into grooves around the channels for the operating media and the outer second layers of the open-porous transport layers. This can be done by inserting O-rings or using an injection molding process.

[0056] In a seventh step, the cell stack or electrochemical system is built up, whereby several electrochemical cells are stacked between two clamping plates and electrically separated from them, and clamped together.

[0057] Various embodiments of the invention are explained in more detail below with reference to the drawings. These show:

[0058] Figure 1 shows a schematic three-dimensional view of a plate arrangement, Figure 2 shows a partial and schematic representation of a production plant for the simultaneous production of several plate arrangements according to Fig. 1, Figure 3 shows a side view of a plate arrangement.

[0059] Figure 4 shows the flow pattern of the fluids within the plate arrangement according to Figure 3,

[0060] Figure 5 shows an enlarged view of the plate arrangement according to Figure 3 in the area of ​​the coolant supply surrounded by a dashed line.

[0061] Figure 6 shows section AA through the plate arrangement according to Figure 3,

[0062] Figure 7 shows section BB through the plate arrangement according to Figure 3,

[0063] Figure 8 shows an enlarged view of the plate arrangement according to Figure 7 in the area surrounded by a dashed line.

[0064] Figure 9 shows a section through the plate arrangement according to Figure 3 parallel to one of the two cooling planes,

[0065] Figure 10 schematically shows an electrochemical system in the form of an electrolysis system.

[0066] Figure 11 shows an enlarged view of the inner layer of the two transport layers,

[0067] Figure 12 shows an enlarged view of the plate arrangement according to Figure 3 on the anode side,

[0068] Figure 13 shows an enlarged representation of the plate arrangement according to Figure 3 on the cathode side,

[0069] Figure 14 shows a schematic flowchart for the production of a plate arrangement, and

[0070] Figure 15 shows the structure of an electrolysis system.

[0071] Figure 1 shows a plate arrangement 2 for a stack of electrochemical cells 3 (compare Figure 10). The plate arrangement 2 is formed in one piece and comprises a plurality of additively manufactured, parallel plates 4, 7, 11, with 3D-printed layers oriented orthogonally to the plates 4, 7, 11. Starting from the cooling plate 4, which is in the form of a bipolar plate and has two parallel cooling planes KE within the plate arrangement 2, in which separately running cooling channels 15, 15' are formed for the parallel flow of coolant, the anode side 2a and the cathode side 2b are formed parallel to it. Open-porous transport layers 7, 11 are present on both sides of the cooling plate 4. Each cooling plate 4 is bordered on one side by an anode-side open-porous transport layer 7 and on the other side by an open-porous transport layer 11 on the cathode side. Each open-porous transport layer 7, 11 is, as shown in the Fig.The structure shown in Figures 1 to 2 is two-layered. The open-porous transport layer 7 on the future anode side 2a of an electrochemical cell 3 has a coarse-pored first, inner layer 8, which is connected to the cooling plate 4 in the form of the bipolar plate. On top of this is a finer-pored second outer layer 8, which is connected to the first inner layer 8 and whose surface 22' in the future electrochemical cell 3 faces the anode side of a polymer electrolyte membrane 34, 34' (see Figure 10). The open-porous transport layer 11 on the future cathode side 2b of an electrochemical cell 3 has a coarse-pored first, inner layer 12, which is connected to the cooling plate 4. On top of this is a finer-pored second outer layer 13, which is connected to the first inner layer 12 and whose surface 22 in the later electrochemical cell 3 faces the cathode side of a polymer electrolyte membrane 34, 34' (compare figure 10).Fine pores 14, 14' are visible in the second outer layers 9, 13 of the open-porous transport layers 7, 11. In the exemplary embodiment, the diameter of the pores 14, 14' is approximately 60 pm. The pores 14, 14' are not necessarily arranged in the regular pattern shown in Figures 1 and 2. Rather, the pores 14, 14' can be arranged and shaped stochastically. The two cathode-side layers 12, 13 of the open-porous transport layer 11 are made of stainless steel. In this case, the two anode-side layers 8, 9 of the open-porous transport layer 7 are made of titanium. The cooling plate 4 is made of titanium on the anode side and stainless steel on the cathode side.

[0072] Figure 2 shows a section of a manufacturing system 23 for the simultaneous production of several plate assemblies 2 according to Fig. 1 using additive manufacturing in one build direction AR. The plates 4, 7, 11, arranged parallel to each other, are additively produced in build planes that are oriented perpendicular to the plates 4, 7, 11. The first build plane is formed by the top of the 3D printing platform 21. The stacking direction ST indicates how the plate assemblies 2 are stacked in a subsequent electrochemical system 10, with at least one polymer electrolyte membrane 34, 34' being inserted between two plate assemblies 2 (see Figure 10). In the example according to Fig. 2, five plate assemblies 2 are generated simultaneously. Among other things, the channels 15, 15' for a cooling medium KW and channels 16, 17, 18 for operating media of the electrochemical system 10 are formed.The operating media in this case are an oxygen-containing gas O2, a hydrogen-containing gas H2, and process water PW (see Figure 4).

[0073] The assembly direction AR forms a right angle with the stacking direction ST of the plate assemblies 2. After the plate assemblies 2 have been removed from the production plant 23, which is only partially shown in Fig. 2, mechanical finishing of the plate assemblies 2 can be carried out.

[0074] Figure 3 shows a side view of a plate assembly 2. The channels 15, 15', 16, 17, and 18 mentioned above are integrated into a frame 19, which is also produced using additive manufacturing. The frame 19 comprises a lattice structure 20 and at least one reinforcement 24. The lattice structure 20 serves to relieve residual stresses in the 3D printing process, thus ensuring printability. Furthermore, the lattice structure 20 serves to reduce the weight of the plate assembly and to counteract internal pressure in the electrochemically active area of ​​an electrochemical cell 3, acting like a pressure vessel. The reinforcement 24 encloses a circumference around the frame 19 and several openings in the form of the channels 15, 15', 16, 17, and 18. The reinforcement 24 thus forms a pressure-resistant barrier for the operating media.

[0075] The cathode-side open-porous transport layer 11, not visible in Figure 2, and the adjacent side of the cooling plate 4 in the form of a bipolar plate, are assigned to a half-cell of a subsequent electrochemical cell 3. The anode-side open-porous transport layer 7, visible in Figure 2, and the adjacent side of the cooling plate 4 in the form of a bipolar plate are also assigned to a half-cell of a subsequent electrochemical cell 3. The operating media are guided through the channels 15, 15', 16, 17, 18 within the frame 19 of each plate arrangement 2, with coolant being guided to and through the cooling plate 4 via channels 15 and 15'. In the case of an electrolyzer, channels 16 supply the process water PW, and channels 17 and 18 remove the reaction products (H2, O2) formed from the process water. Figure 4 shows this fluid flow pattern within the plate arrangement 2 according to Figure 3.

[0076] Figure 5 shows an enlarged view of the plate arrangement 2 according to Figure 3 in the area of ​​one of the channels 15, 15' surrounded by a dashed line, or the two existing cooling levels KE. The frame 19 of the plate arrangement 2 has a frame thickness d that corresponds to the total thickness of the plates, comprising the cooling plate 4 and the open-porous transport layers 7, 11 (see Figure 1).

[0077] Figure 6 shows the section AA through the plate arrangement according to Figure 3. The process water PW is directed to the anode side 2a of the plate arrangement 2.

[0078] Figure 7 shows the section BB through the plate arrangement 2 according to Figure 3. Hydrogen-containing gas H2 is discharged on the cathode side 2b via the channels 18.

[0079] Figure 8 shows an enlarged view of the plate arrangement 2 according to Figure 7 in the area surrounded by a dashed line. The cooling planes KE with the cooling channels 15, 15' in the two separate cooling planes KE are now visible.

[0080] Figure 9 shows a section through the plate arrangement 2 according to Figure 3, parallel to one of the cooling levels KE. The same reference numerals as in the preceding figures denote identical elements. Two separate flow fields 5, 6 for the coolant KW are visible. The coolant KW is supplied via two corners of the plate arrangement 2 and deflected in a direction parallel to one side of the plate arrangement 2. It is then deflected by 90° towards the opposite side of the plate arrangement 2 and introduced into the respective flow field 5, 6. Upon exiting the flow fields 5, 6, the coolant KW is deflected again by 90° in a direction parallel to the opposite side of the plate arrangement 2. Finally, the heated coolant KW is deflected towards the corners of the plate arrangement 2 and discharged. This process occurs simultaneously in both cooling levels DE.Further fluid flow structures extending from channels 16 and 18 are also visible in this view. Figure 10 schematically shows an electrochemical system, designated 10, in the form of an electrolysis system for the production of hydrogen from process water PW, in an exploded view. The core component of the electrolysis system is a cell stack 1 comprising at least two electrochemical cells 3. These are arranged in sequence: a first electrochemical cell 3 comprising the end plate 28, the polymer electrolyte membrane 34', and the plate arrangement 2 (one half); and a second electrochemical cell 3 comprising the plate arrangement 2 (the other half), the polymer electrolyte membrane 34', and the end plate 29.

[0081] Figure 11 shows an enlarged view of the first inner layer 8 of the anode-side open-porous transport layer 7 and the first inner layer 12 of the cathode-side open-porous transport layer 11. The first inner layers 8 and 12 each have a delicate rod structure that forms an elongated honeycomb pattern.

[0082] Figure 12 shows a further enlarged representation of the plate arrangement 2 according to Figure 3 on the anode side with a piece of the frame 19 and the outer second layer 9 in pyramid structure on the first inner layer 8 (indicated here, but not actually visible), which has the delicate rod structure that forms an elongated honeycomb pattern.

[0083] Figure 13 shows an enlarged view of the plate arrangement 2 according to Figure 3 on the cathode side and thus the back of the plate arrangement 2 shown in Figure 3, with a piece of the frame 19 and the outer layer 13, which also has a pyramid structure and is arranged on a first inner layer 12 (indicated here, but not actually visible) in the form of a delicate rod structure, which forms an elongated honeycomb pattern.

[0084] Fig. 14 shows a schematic flowchart for the production of an electrochemical system 10. In a first step 40, the plate assembly 2 is manufactured in one piece using a 3D printing process. In a second step 41, the plate assembly 2 is ground on both sides. The grinding process optionally includes grinding the surfaces 22, 22' of the outer layers 9, 13 of the open-porous transport layers 7, 11. Optionally, in a third step 42, laser drilling is performed to create additional pores in the outer second layers 9, 13 of the open-porous transport layers 7, 11. The fourth step 43 comprises subsequent cleaning of the plate assembly 2. In a fifth, optional step 44, the outer second layers 9, 13 of the open-porous transport layers 7, 11 can be coated.For example, a PVD process with upstream plasma etching of the surface to be coated can be used. Platinum has proven particularly effective as a coating material. In a sixth step 45, seals are inserted into existing grooves. In a seventh step 46, the cell stack 1 or the electrochemical system 10 is then assembled.

[0085] Figure 15 shows the structure of an electrolysis system 10 consisting of a plurality of electrochemical cells 3 (see Figure 10). Several plate arrangements 2, shown here only schematically, are stacked alternately with polymer electrolyte membranes 34 or membrane electrode units on an end plate 28. The end plate 28 has an electrical connection contact 25 and is arranged on an insulating plate 36, which in turn is arranged on a clamping plate 35. Dowel pins 26 and sleeves 27 serve as aids for positioning the stacked layers. After completion of the electrolysis system 10 and placement of another end plate 29 (see Figure 10) and another clamping plate, the positioning aids are removed and the layers are clamped together. Screws or hydraulic systems can be used for this purpose.

[0086] List of reference signs

[0087] Cell stacks, stacks of electrochemical cells

[0088] Plate arrangement a anode side b cathode side electrochemical cell

[0089] Cooling plate, bipolar plate

[0090] River field

[0091] Flow field open-porous transport layer, anode-side first, inner layer of the anode-side open-porous transport layer second, outer layer of the anode-side open-porous transport layer 0 electrochemical system, electrolysis system 1 open-porous transport layer, cathode-side 2 first, inner layer of the cathode-side open-porous transport layer 3 second, outer layer of the cathode-side open-porous transport layer 4, 14' Opening, pore 5, 15' Channel for a cooling medium 6 Channel for a working medium (process water) 7 Channel for a working medium (oxygen) 8 Channel for a working medium (hydrogen) 9, 19' Frame 0 Lattice structure 1 3D printing platform 2, 22' Surface of the outer layer of the open-porous transport layer 3 Manufacturing plant 4 Reinforcement 5 Electrical connection contact 6 Dowel pin 7 Sleeve 8 End plate 9 End plate 34, 34' Polymer electrolyte membrane

[0092] 35 clamping plate

[0093] 36 Insulation board

[0094] 40 First step: 3D printing

[0095] 41 Second step: Grinding process

[0096] 42 Optional third step: Laser drilling

[0097] 43 Fourth step: Cleaning

[0098] 44 Optional fifth step: Coating

[0099] 45 sixth step: Attaching seals

[0100] 46 seventh step: Stacking

[0101] AR construction direction

[0102] ST stacking direction d frame thickness

[0103] KE cooling level

[0104] Coolant, cooling water

[0105] PW process water

[0106] H2 Hydrogen-containing gas

[0107] O2 Oxygen-containing gas

Claims

Patent claims 1. Method for manufacturing a plate arrangement (2) of a stack (1) of electrochemical cells (3), wherein the plate arrangement (2) is additively manufactured in a 3D printing process as a single unit comprising several plates, wherein the plate arrangement (2) is formed with an anode side (2a) and a cathode side (2b), wherein plates arranged parallel to each other are additively manufactured in manufacturing planes which are oriented perpendicular to the plates, wherein at least two cooling planes (KE) arranged parallel to each other are formed within a cooling plate (4) of the plate arrangement (2) and parallel to the anode side (2a) and the cathode side (2b), in which cooling channels (15, 15') extending separately from each other are formed for the parallel passage of coolant (KW), and wherein a fluid-permeable plate in the form of an open-porous, multi-layered transport layer (7, 11) is produced adjacent to at least one side of the cooling plate (4),wherein the layers (8, 9; 12, 13) of the open-porous transport layer (7, 11) differ from each other with respect to at least one of the parameters layer thickness and porosity.

2. Method according to claim 1, wherein several similar, mutually parallel plate arrangements (2) are built simultaneously on a 3D printing platform (21), each comprising a plurality of different plates that stand perpendicular with their plate edges on the 3D printing platform (21).

3. Method according to claim 2, wherein different additively produced plates made of different materials are created on the 3D printing platform (21) and applied in the same 3D printing layer.

4. Method according to one of claims 1 to 3, wherein openings (14) are subsequently introduced in the at least one transport position (7, 11) to create additional porosity.

5. Method according to one of claims 1 to 4, wherein an open-porous, multi-layered transport layer (7, 11) is produced adjacent to both sides of the cooling plate (4).

6. Method according to any one of claims 1 to 5, wherein the plate arrangement is produced with a frame (19) comprising the plates at their plate edges, wherein the frame (19) is formed comprising a grid structure (20) and at least one reinforcement (24).

7. Plate arrangement (2) for an electrochemical system (10), manufactured according to one of claims 1 to 6, which is formed in one piece and comprises a plurality of additively manufactured, mutually parallel plates, wherein 3D printed layers are aligned orthogonally to the plates and wherein at least two cooling planes (KE) arranged parallel to each other are formed within the plate arrangement (2) and parallel to the anode side (2a) and the cathode side (2b), wherein cooling channels (15, 15') running separately from each other are provided in the cooling planes (KE) for the parallel passage of coolant (KW) through the plate arrangement (2), and wherein a fluid-permeable plate in the form of an open-porous, multi-layered transport layer (7, 11) is arranged adjacent to at least one side of the cooling plate (4), wherein the layers (8, 9;12, 13) of the open-porous transport layer (7, 11) are different from each other with respect to at least one of the parameters layer thickness and porosity.; 8. Plate arrangement (2) according to claim 7, wherein the plate arrangement comprises the plates and a frame (19) encompassing the plates at their plate edges, wherein the frame (19) comprises a grid structure (20) and at least one reinforcement (24).

9. Plate arrangement (2) according to claim 8, wherein the frame (19) has a circumference and several openings, wherein a reinforcement (24) is arranged on the circumference and surrounding the openings.

10. Electrochemical cell (3), in particular an electrochemical system in the form of an electrolyzer, with a cell stack (1) comprising two end plates (28, 29) between which at least one plate arrangement (2) according to one of claims 7 to 9 and at least two polymer electrolyte membranes (34, 34') are arranged.

11. Electrochemical cell (3) according to claim 10, wherein each end plate (28, 29) is formed in one piece and comprises a plurality of additively manufactured, mutually parallel plates, wherein 3D printed layers are oriented orthogonally to the plates, and wherein each end plate (28, 29) has an electrical contact arrangement.

12. Electrochemical cell (3) according to claim 10 or 11, wherein each end plate (28, 29) comprises a carrier plate which has an open-porous, multi-layered transport layer (7, 11) only on one side.

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