WO2024255952A2 - Method for producing a plate assembly, plate assembly and electrochemical cell - Google Patents

Abstract

The invention relates to production of a plate assembly (2) of a stack (1) of electrochemical cells (3), wherein plates arranged parallel to one another are additively manufactured in planes oriented perpendicularly to the plates. The invention also relates to an 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 such plate assembly (2) and at least two polymer electrolyte membranes (34, 34') are arranged.

Description

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

The invention relates to a method for producing a plate arrangement of a stack of electrochemical cells using generative manufacturing methods. The invention also relates to a plate arrangement for an electrochemical system, which comprises generatively manufactured components. Finally, the invention relates to an electrochemical cell, in particular an electrolyzer.

The generative production of components of a fuel cell stack or electrolyzer is basically known, for example, from DE 10 2013 108 413 A1. Laser, electron beam and water vapor jet sintering are mentioned as production technologies. Generative processes should also be suitable for joining components of a cell stack together.

WO 2023/021217 A1 discloses an integrated method for producing a monolithic solid oxide cell (SOC) stack based on a single 3D printing system. The method 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 should also be able to be produced additively.

US 2015/0290860 A1 deals with the geometry of nozzles intended for the additive manufacturing of components of electrochemical systems. A nozzle geometry that deviates from a circular shape is proposed. This should make it possible to build a composite of various flat components that, among other things, has channels for the passage of fuel or air.

US 2008/0008826 A1 also deals with the additive manufacturing of fuel cell components. Powder layers are solidified by laser sintering, whereby areas with different porosities are to be produced. At least two layers of the arrangement described in US 2008/0008826 A1 have a different composition and a different thickness.

A method for producing an electrochemical cell device described in DE 10 2018 100 772 A1 provides that a functional layer is produced on a cell carrier by direct material application. The cell carrier is a cell separator which forms an outer boundary of an electrochemical cell. The cell carrier can be made of stainless steel and have a corrosion protection layer. Functional layers to be built up one after the other on the cell carrier are designed in particular as a gas distribution layer and a catalyst layer. According to DE 10 2018 100 772 A1, it should also be possible to produce an electrochemical functional layer with a gradation, wherein the gradation takes place with respect to the geometric design and/or materials, and wherein a gradation is produced in the stacking direction and/or transversely to the stacking direction.

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 a generative layer construction process. In order to form a flow field, material is to be selectively applied only to projections of a topology of a base plate of the bipolar plate. In this way, contacts, for example made of titanium, nickel or chromium, are to be created.

US 2005/0221150 A1 deals with the generative production of honeycomb structures for electrochemical cells. A metal powder containing the elements nickel and chromium is to be solidified by laser sintering. In addition, metallic layers can contain bronze as a binder.

The invention is based on the object of improving the production of layered cells of electrochemical systems compared to the prior art to be further developed, whereby in particular the simultaneous production of several cell components should be possible.

This object is achieved 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. The object is also achieved by a plate arrangement with the features of claim 7 and an electrochemical cell with the features of claim 14. The embodiments and advantages of the invention explained below in connection with the plate arrangement or the entire electrochemical system also apply mutatis mutandis to the production method according to the application and vice versa.

The method for producing a plate arrangement of a stack of electrochemical cells is characterized in that plates arranged parallel to each other are additively produced in planes which are aligned perpendicular to the plates.

To put it figuratively, this means that each individual panel in the panel arrangement resembles a slice sawn from a tree that is cut across the grain. Panels made from cell stacks or other stacks produced using conventional 3D printing processes, on the other hand, resemble - to stay with the image - normal boards that have been sawn lengthways along the tree trunk.

The vertical additive manufacturing of the plates, whereby each of the plates is built upright on a 3D printing platform starting from a narrow edge of the plate, makes it possible to create particularly delicate and complex structures that would not be possible if the plates were manufactured on a 3D printing platform starting from a large, lying plate side. For example, recesses for the formation of overhangs can only be created with low quality in 3D printing if the plates are built up one after the other, i.e. lying down, because when the powdered material is melted using a laser, the laser beam reaches to an undesirable depth and a structure similar to a stalactite cave ceiling is created above the formed recess is formed. The larger the desired overhang length and the smaller the rise angle of the solidified structure formed, the lower the print quality.

If the plates of the plate arrangement were generated lying on top of each other, the entire underside would form a 90° overhang in the direction of the printing base. This would have to be supported with support structures, which would have to be mechanically removed after 3D printing. The surface with the remains of the support structures would be unsuitable as a contact surface for a membrane of an electrochemical cell. In addition, the thermal residual stresses in the surface during 3D printing would be so great that such support structures would not hold mechanically.

At the same time as the print quality is lower, the load-bearing capacity of a 3D-printed structure under pressure deteriorates in the area of the recesses, which is unacceptable for safety reasons, particularly in the case of electrochemical cells that are operated under high operating pressure, such as electrolyzers. Such problems can be avoided when constructing a plate arrangement according to the method according to the invention and a wide range of 3D-printed structures can be produced in high quality.

In addition, a horizontal positioning of the plate arrangement is uneconomical when 3D printing, because, in contrast to the vertical printing process, far fewer or even only one plate arrangement can be printed at the same time due to space constraints based on an identically dimensioned printing base.

It has proven particularly effective if the plate arrangement is formed as a single piece from the plates arranged parallel to one another. However, at least two plates should be formed as a single piece in order to save assembly effort when assembling an electrochemical cell and to reduce the contact resistance. The plate arrangement according to the invention is formed in one piece and comprises a plurality of additively manufactured, parallel, not necessarily identical plates, with 3D printing layers aligned orthogonally to these plates. A particular advantage of the plate arrangement is that within it there is an intimate material bond between the plates and no electrical losses occur, as is the case in the area of contact points of plates that are merely pressed against one another in conventional electrochemical cells. This means that an electrochemical cell can be operated highly efficiently.

For example, a first type of plate can be designed as a bipolar plate. The term "bipolar plate" is used here in analogy to a structure in conventional electrochemical cells. However, the complete plate arrangement can provide the electrical properties of such a bipolar plate, since it is electrically conductive overall and is made of metallic materials.

Plates constructed in this way as 3D printed objects can also function as porous transport layers in electrochemical cells. In such a case, it is particularly possible to construct the transport layers in multiple layers, with the individual layers having different porosities and/or thicknesses. During the generative production of the porous transport layers, the various layers for constructing the plates of a plate arrangement appear as adjacently arranged strips within the layer currently constructed by 3D printing.

The additive manufacturing process according to the invention can be designed particularly efficiently by simultaneously building up several identical, parallel plate groups on a 3D printing platform, each of which comprises a plurality of different plates and is perpendicular to the 3D printing platform. The individual plate groups, which are produced together in a print batch, can be installed in a single cell stack after additive manufacturing or distributed across several cell stacks. Each of the plate assemblies is also referred to as a sandwich and can be depowdered after being separated from the construction platform, i.e. the 3D printing platform. This can be followed by heat treatment. Optionally, the outer surfaces of the plate assembly can be processed by grinding. An additional straightening process can also be carried out. A An electrically conductive coating, for example made of a precious metal such as platinum, can be applied to at least one partial area on one or both sides of the plate arrangement. This allows the outer second layers of the porous transport layers to be coated. The coating is preferably applied using a PVD or PACVD process. Before the coating process, the surfaces to be coated can optionally be plasma etched in order to remove existing oxide layers and thus ensure good adhesion and electrical contact between the coating and the plate arrangement. By providing 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.

According to various possible embodiments, several plates which are to be assigned to the plate assembly are designed as porous layers of the sandwich-like plate assembly. In particular, the porous layers can be multilayered, cathode-side or anode-side porous transport layers of the later electrochemical cells. In this case, a first layer of each porous transport layer is constructed in particular with large pores, whereas a second layer of each porous transport layer is preferably constructed comparatively thin and with fine pores. The latter second layer of each porous transport layer preferably forms an outer surface of the plate arrangement, at least in a partial area of the plate arrangement. The pores of the fine-pored second layer preferably have a pore diameter <80 pm, in particular in the range from 60 to 80 pm, while the pores or channels in a coarse-pored first layer preferably have a pore diameter >0.2 mm, in particular >1 mm.

Fine-pored second layers of each porous transport layer preferably have layer thicknesses of < 0.2 mm and coarse-pored first layers of each porous transport layer preferably have layer thicknesses of > 0.5 mm. Openings representing the pores of the relevant second layer are introduced into the porous transport layer, particularly into its outer, fine-pored second layer, during additive manufacturing, optionally also subsequently. In the latter case, additional fine porosity can be created, for example, by plasma drilling, laser drilling or etching. In principle, pores in porous transport layers can have either a geometrically defined shape or geometrically undefined shapes with stochastic size distribution, whereby in each case there is permeability, i.e. open porosity, of the coarse-pored first layer and the fine-pored second layer.

In the case of the first, coarse-pored layer, a defined geometry, for example in the form of a grid, is particularly suitable. This grid transfers forces between adjacent cell components during operation of the electrochemical cell and at the same time provides free flow cross-sections for operating media. The same applies to the fine-pored second layer, which borders on the grid and in particular provides a flat support surface for a component adjacent to an electrochemical cell, such as a proton-permeable polymer electrolyte membrane or a gas diffusion layer made of carbon paper or carbon fleece of the electrochemical cell. Due to the 3D printing, the flat support surface has a roughness that enlarges the surface area of this support surface. Roughnesses in the range of Rz16 have proven to be effective here.

The membrane is subsequently applied to the plate arrangement before assembly or during assembly of the entire electrochemical cell stack. The finely porous second layer of the plate arrangement, which is additively manufactured in contrast to the membrane, is tailored to the conditions prevailing during operation of the electrochemical cells and to the properties of the membrane in terms of its electrical properties and corrosion properties. The membrane is arranged within the cell stack in a plane that vertically intersects the 3D printing planes that are gradually created during additive manufacturing. In contrast to the porous transport layers of the plate arrangement, the bipolar plate, which is also part of the plate arrangement, can form a channel for a cooling medium that is separated from the operating media of the electrochemical system. The cooling medium is in particular water. Preferably, at least one of the plates is therefore designed as a bipolar plate, with opposite sides of the bipolar plate enclosing at least one channel for the passage of a fluid, in this case the coolant, between them.

In contrast to the cooling medium, deionized water is used as process water, which is split into hydrogen and oxygen through electrolysis. The process water is therefore fed into an electrolyzer separately from the cooling medium.

For any type of electrochemical cell, a frame can be connected in one piece to the plates, which is also produced in the course of additive manufacturing. The plate arrangement therefore comprises the plates and preferably also a frame that encompasses the plates, the frame being formed to include a lattice structure and at least one reinforcement. The lattice structure serves to reduce residual stresses in 3D printing and thus to make it printable. The lattice structure also serves to reduce the weight of the plate arrangement and to counteract internal pressure in the electrochemically active area of an electrochemical cell such as a pressure vessel.

This frame can also contain openings for the operating media and the coolant, as well as openings for mounting a cell stack. The frame preferably has reinforcement around its periphery and around the multiple openings. Such reinforcement is a solid and fluid-tight collection of materials made of the same material from which the grid structure is formed. The reinforcement in the area of the openings serves to channel the coolant and the operating media and to withstand pressure.

The reinforcement in the area of the perimeter of the plate arrangement serves to assembled state of the electrochemical cell to provide a fluid-tight and pressure-resistant jacket around the plate assembly.

Regardless of the external shape of the bipolar plate, which can be either purely flat or more complex, it can be made of several different materials. In particular, this can be titanium on the anode side and stainless steel on the cathode side. Alternatively, the entire bipolar plate or even all of the additively manufactured components of the electrochemical cell can be made of the same material, for example a light metal, in particular titanium. The titanium alloy Ti6AI4V is preferred here, as it is heat-treatable and forms a dense oxide layer. This increases the notch impact strength, which is an important factor in pressurized systems, and reduces material embrittlement due to hydrogen.

The porous transport layers, which border the bipolar plate on both sides, can be made of the same material from which the relevant surface of the bipolar plate is made. This means in particular that all layers of the anode-side porous transport layers can be made of titanium and all layers of the cathode-side porous transport layers can be made of stainless steel using additive manufacturing. Alternatively, it is possible, for example, to manufacture the coarsely porous, inner layers of the porous transport layers bordering the bipolar plate from copper. This improves heat dissipation from the bipolar plate in particular.

One advantage of the one-piece plate arrangement, apart from the efficient, process-reliable manufacturing methods and the low electrical resistances that can be achieved as a result, is that the special type of additive manufacturing means that seals between individual half-cells of the electrochemical cells, in particular electrolysis, redox flow or fuel cells, can be dispensed with. In addition, the prefabrication of the complete, non-uniformly constructed sandwich-like plate arrangements facilitates a very efficient, geometrically precise, process-reliable assembly of the entire cell stack. 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 few individual parts, such a cell has a high degree of impermeability to the operating media and the coolant and can be produced quickly and efficiently.

In particular, each end plate is formed in one piece and comprises a plurality of additively manufactured plates that are parallel to one another, with 3D printing layers being aligned orthogonally to the plates and with each end plate having an electrical contact arrangement. Instead of a bipolar plate provided in a plate arrangement, a carrier plate is provided in each end plate that has a porous, multi-layer transport layer on only one side. The carrier plate can also be designed with cooling channels running through it. In principle, however, an end plate is constructed in the same way as a plate arrangement that does not have a porous transport layer(s) on one side. An end plate can also preferably be designed like a plate arrangement with regard to a frame made of a lattice structure, openings and reinforcement, and can thus be adapted to the shape and design of a plate arrangement.

A schematic process for the fabrication of an electrochemical system can be outlined as follows.

In a first step, the plate arrangement is produced using a 3D printing process, in particular a laser 3D printing process. The one-piece plate arrangement is preferably produced with a frame thickness in the range of 7 to 12 mm, in particular 9 mm. The layer thicknesses of the coarse-pored first inner layers of the porous transport layers are selected in particular to be > 0.5 mm. The coarse-pored structure of the first inner layers of the porous transport layers are formed using the 3D printing process. The first inner layers in particular have a filigree rod structure, which forms an elongated honeycomb pattern. Due to the long overhangs of this rod structure, the construction direction of the plates starting from the narrow edge of the plate ensures technical manufacturability. The layer thicknesses of the second outer layers of the porous transport layers are selected to be < 0.2 mm. The fine-pored structure of the second outer layers of the porous transport layers is formed using a 3D printing process, optionally by subsequent processing such as laser drilling. The second outer layers of the porous transport layers are preferably created with a regular three-dimensional pyramid structure on the respective first inner layer.

The reinforcement in the area of the circumference of the frame or in the area of the channels for operating media has a thickness of at least 0.5 mm in order to be able to be reliably fluid-tight and pressure-resistant.

In a second step, the plate assembly is subjected to grinding on both sides. The grinding process optionally includes grinding of the surfaces of the outer second layers of the porous transport layers.

Optionally, laser drilling follows in a third step to optionally form additional pores in the outer second layers of the porous transport layers.

The fourth step involves subsequent cleaning of the plate assembly.

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

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

In a seventh step, the cell stack or the electrochemical system is constructed, whereby several electrochemical cells are stacked and clamped together between two clamping plates and electrically separated from them. Various embodiments of the invention are explained in more detail below with reference to drawings.

Fig. 1 a plate arrangement of a stack of electrochemical cells,

Fig. 2 shows a detail of a production plant for the simultaneous production of several plate arrangements according to Fig. 1,

Fig. 3 a plate arrangement with a schematically shown media distribution structure,

Fig. 4 a plate arrangement with a frame,

Fig. 5 is a three-dimensional representation of the plate arrangement according to Figure 4 in partial section,

Fig. 6 another plate arrangement in three-dimensional representation in partial section with a detail enlargement,

Fig. 7 is a further enlarged view of the plate arrangement according to Figure 6 on the anode side,

Fig. 8 is an enlarged view of the plate arrangement according to Figure 6 on the cathode side,

Fig. 9 is a further enlarged view of the plate arrangement according to Figure 6 on the anode side,

Fig. 10 is a further enlarged view of the plate arrangement according to Figure 9 on the anode side,

Fig. 11 is a further enlarged view of the plate arrangement according to Figure 6 on the anode side,

Fig. 12 is a further enlarged view of the plate arrangement according to Figure 6 on the anode side,

Fig. 13a - 13k the steps in the construction of an electrochemical cell,

Fig. 14 schematically shows the structure of an electrolyzer comprising two electrochemical cells, and Fig. 15 is a schematic flow diagram for the production of a plate assembly.

The same reference symbols used in the figures indicate identical components throughout.

Figure 1 shows a plate arrangement 2 for a stack of electrochemical cells 3 (see Figure 14). The plate arrangement 2 is formed in one piece and comprises a plurality of additively manufactured, mutually parallel plates 4, 7, 11, with 3D printing layers being aligned orthogonally to the plates 4, 7, 11. Starting from a bipolar plate 4, which has channels 15 for a cooling medium, porous transport layers 7, 11 are present on both sides. Each bipolar plate 4 is bordered on the one hand by an anode-side porous transport layer 7 and on the other hand by a cathode-side porous transport layer 11. Each porous transport layer 7, 11 is constructed in two layers, as can be seen from Figures 1 to 3. The porous transport layer 7 on the later anode side of an electrochemical cell 3 has a coarse-pored first, inner layer 8, which is connected to the bipolar plate 4. On top of this there is a finer-pored second outer layer 8 which is connected to the first inner layer 8 and whose surface 22' in the later electrochemical cell 3 faces the anode side of a polymer electrolyte membrane 34, 34' (see Figure 14). The porous transport layer 11 on the later cathode side of an electrochemical cell 3 has a coarse-pored first, inner layer 12 which is connected to the bipolar plate 4. On top of this there 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' (see Figure 14). Fine pores 14, 14' can be seen in the second outer layers 9, 13 of the 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 that can be seen in Figures 1 to 3. Rather, the pores 14, 14' can be arranged and shaped stochastically. The two cathode-side layers 12, 13 of the porous transport layer 11 are made of stainless steel here. In the present case, the two anode-side layers 8, 9 of the porous transport layer 7 are made of titanium. The bipolar plate 4 is made of titanium on the anode side and of stainless steel on the cathode side. Figure 2 shows a detail of a production system for the simultaneous production of several plate arrangements 2 according to Fig. 1 by means of additive manufacturing. The plates 4, 7, 11 arranged parallel to one another are additively produced in planes which are aligned perpendicular to the plates 4, 7, 11.

This is based on a 3D printing platform 21 on which several plate arrangements 2 are built simultaneously in a construction direction AR. For this purpose, a 3D printing device is used which can apply different materials in one and the same layer and solidify them by laser. These layers are generally referred to as 3D printing layers and are parallel to the surface of the 3D printing platform 21 and thus orthogonal to the plate-shaped components 4, 7,

11 of the plate arrangements 2. Accordingly, each plate 4, 7, 11 of the plate arrangement 2 is built up starting from a narrow plate edge in the construction direction AR. The coarse-pored first layers 8,

12 of the porous transport layers 7, 11 can be produced in high quality, which would not be possible if the plates 4, 7, 11 were constructed horizontally, i.e. if one plate was constructed after the other in the construction direction AR.

In the example according to Fig. 2, five plate arrangements 2 are generated simultaneously. Among other things, channels 15 for a cooling medium and channels 16, 17, 18 for operating media of the electrochemical system 10 are formed. In this case, the operating media are an oxygen-containing gas, a hydrogen-containing gas, and process water.

The assembly direction AR forms a right angle with a stacking direction ST of the plate arrangements 2. After the plate arrangements 2 have been removed from the production plant designated overall by 23, which is only partially shown in Fig. 2, the plate arrangements 2 can be mechanically finished. The aforementioned channels 15, 16, 17, 18 pass through, among other things, a frame 19, which is only shown schematically in Figure 3 and is also created during generative manufacturing. The porous transport layer 11 on the cathode side and the side of the bipolar plate 4 adjacent to it are assigned to a half-cell 5 of a later electrochemical cell 3. The porous transport layer 7 on the anode side and the side of the bipolar plate 4 adjacent to it are assigned to a half-cell 6 of a later electrochemical cell 3. The operating media are supplied through the channels 15, 16, 17, 18 in the frame 19 of each plate arrangement 2, with coolant being supplied to the bipolar plate 4 through the channels 15, in the case of an electrolyzer the channels 16 supply the process water, and the channels 17, 18 discharge the reaction products formed from the process water.

Figure 4 now shows a plate arrangement 2 with a frame 19 in a top view of the side on which the second outer layer 9 of the porous transport layer 7 is located. The frame 19 comprises a lattice structure 20 and at least one reinforcement 24. The lattice structure 20 serves to reduce residual stresses in 3D printing and thus to create printability. Furthermore, the lattice structure serves to reduce the weight of the plate arrangement and to counteract internal pressure in the electrochemically active area of an electrochemical cell 3 like a pressure vessel. The reinforcement 24 encloses a circumference and several openings in the form of the channels 15, 16, 17, 18 and guide openings 26 in the frame 19. The reinforcement 24 thus forms a pressure-resistant barrier for the operating media and, in the area of the guide openings 26, a smooth guide for bolts 33, which are used to clamp the components of an electrochemical cell 3, compare Figures 13a - 13k. Furthermore, a sensor receiving space 25 is present, which can be used in an electrochemical cell 3 to accommodate measuring arrangements or electrical lines for connecting such measuring arrangements. The channels 15, 16, 17, 18 as well as the porous transport layer 7 are each surrounded by a groove 27 created during 3D printing, which is intended to accommodate elastomer seals 30 (compare Figure 5). Figure 5 shows a three-dimensional representation of the one-piece plate arrangement 2 according to Figure 4 in partial section and thus illustrates its internal structure. Here, the bipolar plate 4 with the cooling channels 15 for coolant, the first inner layer 12 and the second outer layer 13 of the cathode-side porous transport layer 11 can be seen. Furthermore, the first inner layer 8 and the second outer layer 9 of the anode-side porous transport layer 7 and the structure of the second outer layer 9 can be seen.

Figure 6 shows a further plate arrangement 2 in a three-dimensional representation in partial section in the plane of the channels 15 in the bipolar plate 4. In the enlarged detail shown on the right, part of the anode-side porous transport layer 7 can be seen. Its first inner layer 8 (indicated here, but not actually visible) has a filigree rod structure that forms an elongated honeycomb pattern. The second outer layer 9 formed on top of this has a pyramid structure.

Figure 7 shows a further enlarged view of the plate arrangement 2 according to Figure 6 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 visible in reality), which has the filigree rod structure which forms an elongated honeycomb pattern.

Fig. 8 shows an enlarged view of the plate arrangement 2 according to Figure 6 on the cathode side and thus the back of the plate arrangement 2 shown in Figure 6, 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 visible in reality) in the form of a filigree rod structure, which forms an elongated honeycomb pattern.

Figures 9 and 10 show an enlarged view of the plate arrangement 2 according to Figure 6 on the anode side without a second outer layer 9, that is, with View of the first inner layer 8 in a real view of the permeable honeycomb structure formed by 3D printing.

Figures 11 and 12 show a further enlarged view of the plate arrangement 2 according to Figure 6 on the cathode side without the second outer layer 13, that is, with a view of the first inner layer 12 in a real view of the permeable honeycomb structure formed in the 3D printing process.

Figures 13a to 13k show the steps in the construction of two electrochemical cells 3 using the plate arrangement 2 according to Figures 4 and 5. Of course, any number of electrochemical cells 3 can be installed here.

According to Figure 13a, a bracing plate 31 is provided and fitted with bolt screws 33. The bolt screws 33 are coated with an electrically insulating coating, in particular made of plastic. According to Figure 13b, an insulating plate 32, preferably made of an electrically non-conductive plastic, is then pushed onto the bolt screws 33 and brought into contact with the bracing plate 31.

Now, according to Figure 13c, an end plate 28 follows, which is formed in one piece and comprises additively manufactured plates that are parallel to one another, with 3D printing layers aligned orthogonally to these plates. The plates of the end plate 28 are designed in the form of a carrier plate 4' and a porous transport layer 7 (two-layered). The end plate 28 also has an electrical connection contact 28'. The carrier plate 4' is made of stainless steel, while the porous transport layer 7 is made of titanium.

According to Figure 13d, a gas diffusion layer 36 is applied or placed on the porous transport layer 7, which is made of a fluid-permeable, compressible carbon paper or carbon fleece. This is optionally present and serves to compensate for tolerances when screwing the cell components together.

According to Figure 13e, a polymer electrolyte membrane 34 follows and according to Figure 13f, a plate arrangement 2. The anode side of the plate arrangement 2 facing away from the polymer electrolyte membrane 34 is, according to Figure 13g, in the region of the second outer Layer 9 of the porous transport layer 7 is covered with a gas diffusion layer 36' and a further polymer electrolyte membrane 34' is applied as shown in Figure 13h.

To construct any number of electrochemical cells 3 in succession, additional plate arrangements 2, gas diffusion layers 36 and polymer electrolyte membranes 34 can now optionally be installed.

According to Figure 13i, there follows a further end plate 29, which is formed in one piece and comprises additively manufactured plates that are parallel to one another, with 3D printing layers aligned orthogonally to these plates. The plates of the end plate 29 are designed in the form of a further carrier plate 4' and a porous transport layer 11 that is not visible here. The end plate 29 also has an electrical connection contact 29'. The carrier plate 4' and the porous transport layer 11 are made of stainless steel.

At this point, it should be added that the end plates 28, 29 each correspond, for example, to half a plate arrangement 2, with the carrier plate 4' being provided instead of the bipolar plate 4, which can also be traversed by channels 15 for coolant. The end plates 28, 29 can also each have a frame 19 which has the grid structure 20, the openings for the channels 15, 16, 17, 18 for the supply and removal of fluids, the guide openings 26 and the reinforcements 24.

Now, according to Figure 13k, another insulating plate 32' and another bracing plate 31' are attached and the screw nuts 35 are fastened to the bolts 33. The components of the cell stack 1 formed are braced together using the bolts 33 so that good mechanical and, where necessary, electrical contact between the components is formed. Fluid connections 37 for supplying and removing operating media to the electrochemical cells 3 or reaction products from the electrochemical cells 3 are also attached to the ends of the bracing plates 31, 31'. The cell stack 1 here therefore comprises two electrochemical cells 3, see Figure 14.

Figure 14 shows an electrochemical system designated 10 in the form of an electrolysis system for producing hydrogen from water in an exploded view. The core component of the electrolysis system is the cell stack 1 according to Figure 13k, that is to say a stack comprising at least two electrochemical cells 3. The following follow in order: a first electrochemical cell 3 comprising the end plate 29, the polymer electrolyte membrane 34', the gas diffusion layer 36', the plate arrangement 2 (anode-side half cell 6); and a second electrochemical cell 3 comprising the plate arrangement 2 (cathode-side half cell 5), the polymer electrolyte membrane 34, the gas diffusion layer 36, the end plate 28.

The frame 19 of the plate arrangement 2 has a frame thickness d which corresponds to the total thickness of the plates, comprising the bipolar plate 4 and the porous transport layers 7, 11, see Figure 1.

Fig. 15 shows a schematic flow diagram for the production of an electrochemical system 10. In a first step 40, the plate arrangement 2 is produced in one piece using a 3D printing process. In a second step 41, the plate arrangement 2 is subjected to grinding on both sides. The grinding process optionally includes grinding the surfaces of the outer layers 9, 13 of the porous transport layers 7, 11, designated 22, 22'. Optionally, a third step 42 is followed by laser drilling to form further pores in the outer second layers 9, 13 of the porous transport layers 7, 11. The fourth step 43 comprises subsequent cleaning of the plate arrangement 2. In a fifth optional step 44, the outer second layers 9, 13 of the 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 to be particularly suitable as a coating material. In a sixth step 45, the seals 30 are introduced into the grooves 27. In a seventh step 46, the cell stack 1 or the electrochemical system 10 is then constructed, with the stack formation process being carried out, for example, according to Figures 13a to 13k. list of reference symbols

cell stack, stack of electrochemical cells

plate arrangement electrochemical cell

bipolar plate ' carrier plate

half-cell

Half cell porous transport layer, anode side first, inner layer of the anode side porous transport layer second, outer layer of the anode side porous transport layer0 electrochemical system, electrolysis system 1 porous transport layer, cathode side first, inner layer of the cathode side porous transport layer3 second, outer layer of the cathode side porous transport layer , 14' opening, pore 5 channel for a cooling medium

Channel for an operating medium 7 Channel for an operating medium 8 Channel for an operating medium 9, 19' Frame 0 Grid structure 1 3D printing platform , 22' Surface of the outer layer of the porous transport layer 3 Manufacturing plant

Armature 5 Sensory Recording Room

Guide opening 7 Groove 8 End plate 8' electrical connection contact 9 End plate 29' electrical connection contact 30 seal

31 , 31 ' bracing plate

32, 32' insulation plate

33 Bolt screw (with electrically insulating coating)

34, 34' polymer electrolyte membrane

35 screw nut

36, 36' gas diffusion layer

37 fluid connection

40 first step: 3D printing

41 second step: grinding

42 optional third step: laser drilling

43 fourth step: cleaning

44 optional fifth step: coating

45 sixth step: attaching the seals 30

46 seventh step: stacking

AR construction direction

ST stacking direction d frame thickness

Claims

patent claims 1. Method for producing a plate arrangement (2) of a stack (1) of electrochemical cells (3), wherein plates arranged parallel to one another are additively produced in planes which are aligned perpendicular to the plates. 2. Method according to claim 1, characterized in that a plurality of identical, mutually parallel plate arrangements (2), each comprising a plurality of different plates and standing perpendicular to the 3D printing platform (21), are constructed on a 3D printing platform (21). 3. Method according to claim 2, characterized in that different plates made of different materials, which are additively produced on the 3D printing platform (21), are produced and applied in the same 3D printing layer. 4. Method according to one of claims 1 to 3, characterized in that at least one of the plates is produced as a porous, multi-layer layer (7, 11), wherein the different layers (8, 9, 12, 13) of the porous layer (7, 11) differ from one another with respect to at least one of the parameters layer thickness and porosity. 5. Method according to claim 4, characterized in that openings (14) are subsequently introduced into at least one of the plates in order to produce porosity. 6. Method according to one of claims 1 to 5, characterized in that the plate arrangement (2) is formed in one piece from the plates arranged parallel to one another. 7. Plate arrangement (2) for an electrochemical system (10), which is formed in one piece and comprises a plurality of additively manufactured plates parallel to one another, wherein 3D printing layers are aligned orthogonal to the plates. 8. Plate arrangement (2) according to claim 7, characterized in that it comprises the plates and a frame (19) comprising the plates, wherein the frame (19) is formed comprising a grid structure (20) and at least one reinforcement (24). 9. Plate arrangement (2) according to claim 7 or 8, characterized in that at least one of the plates is designed as a bipolar plate (4), wherein opposite sides of the bipolar plate (4) enclose at least one channel (15) for the passage of a fluid between them. 10. Plate arrangement (2) according to claim 9, characterized in that the opposite sides of the bipolar plate (4) are made of different materials. 11. Plate arrangement (2) according to claim 9 or 10, characterized in that plates bordering the bipolar plate (4) are each designed as porous, multi-layer transport layers (7, 11), wherein the individual layers (8, 9, 12, 13) of each transport layer (7, 11) differ from one another both in terms of layer thickness and in terms of porosity. 12. Plate arrangement (2) according to claim 11, characterized in that the bipolar plate (4) is bordered on the one hand by a porous transport layer (11) made of steel and on the other hand by a porous transport layer (7) made of titanium. 13. Plate arrangement (2) according to one of claims 8 to 12, characterized in that the frame (19) has a circumference and a plurality of openings, wherein a reinforcement (24) is arranged on the circumference and enclosing the openings. 14. Electrochemical cell (3), in particular 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 13 and at least two polymer electrolyte membranes (34, 34') are arranged. 15. Electrochemical cell (3) according to claim 14, 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 aligned orthogonal to the plates, and wherein each end plate (28, 29) has an electrical contact arrangement (28', 29'). 16. Electrochemical cell (3) according to claim 14 or 15, wherein each end plate (31, 31') comprises a carrier plate (4') which has a porous, multi-layer transport layer (7, 11) on only one side.