Method for producing a cell layer, and electrode-coated cell layer

Abstract

The invention relates to a method for producing an electrode-coated cell layer (100) for an electrochemical cell stack, in particular a fuel cell stack or an electrolysis cell stack, and at least one catalyst-containing electrode (120, 130), in particular an anode electrode (120) and / or a cathode electrode (130), for the cell stack, is applied to a cell stack substrate (110), wherein an electrode coating material is printed, by means of a screen printing method, onto a large-area outer side of the cell stack substrate (110), said electrode coating material being printed as a screen-printed electrode (120, 130) which has a planar pattern in two length dimensions and is structured in its thickness dimension (D).

Description

[0001] Description

[0002] title

[0003] Methods for producing a cell layer as well as electrode-coated cell layers

[0004] The invention relates to a method for producing an electrode-coated cell layer for an electrochemical cell stack, as well as a cell layer for an electrochemical cell stack. Furthermore, the invention relates to an electrochemical cell stack, an electrochemical unit, and an electrochemical system.

[0005] State of the art

[0006] In an electrolyzer of an electrolyzer unit (stationary or mobile), e.g., an electrolyzer system, water is electrochemically converted into hydrogen and oxygen using electrical energy, generating heat in the process. In a low-temperature polymer electrolyte fuel cell of a fuel cell unit (mobile or stationary), e.g., a fuel cell system in a fuel cell vehicle, two reactants of two operating media are electrochemically converted into electrical energy and heat.

[0007] The assembly in question can comprise at least one membrane electrode assembly, for example, a membrane electrode assembly (MEA) with a proton exchange membrane (PEM) or an anion exchange membrane (AEM). Alternatively to the MEA, at least one electrode of a membrane electrode assembly can be located away from and directly opposite the membrane on a fluid transport structure of the membrane electrode assembly. The assembly can be configured with a plurality of membrane electrode assemblies or analogues arranged in a stack and bipolar plates arranged between them, forming an electrochemical cell stack with a plurality of individual cells.

[0008] Task

[0009] There are ongoing efforts to improve electrolyzer and fuel cell systems and to design them to be cost-effective with regard to their materials, manufacturing costs, and / or maintenance costs. It is an object of the invention to provide an improved, and in particular cost-effective, cell arrangement for an electrochemical cell stack, especially an electrolysis cell stack or a fuel cell stack.

[0010] Disclosure of the invention

[0011] The object of the invention is achieved by a method for producing an electrode-coated cell layer for an electrochemical cell stack, by means of a cell layer for an electrochemical cell stack, by means of an electrochemical cell stack for an electrochemical unit, as well as by means of an electrochemical unit and an electrochemical system. Advantageous further developments, additional features and / or advantages of the invention will become apparent from the dependent claims and the following description.

[0012] In the inventive method for producing an electrode-coated cell layer for an electrochemical cell stack, at least one catalyst-containing electrode, in particular an anode electrode and / or a cathode electrode, for the cell stack is applied to a cell stack substrate, wherein a (viscous) liquid electrode coating material is printed onto a large-area outer surface of the cell stack substrate by a screen printing process as a screen-printed electrode patterned in two length dimensions and preferably structured in its thickness dimension. The screen printing process can be, for example, a rotary screen printing process or a flatbed screen printing process. That is, the electrode of the cell layer is preferably a screen-printed electrode with at least two-dimensional patterns (2D screen-printed electrode, see Fig. 2) or a three-dimensionally patterned and structured screen-printed electrode (3D screen-printed electrode, see Fig. 3).3 and 4) on the cell stack substrate. - A two-dimensionally patterned screen-printed electrode is understood to be an electrode that is substantially patterned in two length dimensions. The patterned (structural and / or geometric, etc.) screen-printed electrode can, for example, exhibit a regular (stripes, checkerboard, regular or irregular n-gons, ellipses, dots, areas, etc.) or irregular (fractal-like, picture-like, etc.) pattern.

[0013] Preferably, depending on the screen printing process, the screen-printed electrode of the pattern has a certain height in the thickness dimension as the third length dimension, which is small compared to the overall surface area of ​​the screen-printed electrode. Through the screen printing process, an intentional structure (geometry and / or different surface roughness, etc.) can be introduced into the electrode layers (porosity, concentration differences (catalyst or other substance) and / or different electrode materials, etc.) and / or into the side edges of the pattern extending into the thickness dimension.

[0014] In a screen printing process, at least one (viscous) liquid electrode coating material is printed onto the outer surface of the cell stack substrate to be printed, using a squeegee or an analogue, through a fine-mesh fabric or analogue. At those points where no electrode material (negative areas in the pattern) is to be printed according to a printed image (positive pattern) of the screen-printed electrode, the openings in the fabric or analogue are impermeable to liquid.

[0015] The electrode coating material can be applied (printed) directly using a screen printing process, thus avoiding overspray. The electrode coating material is applied to the cell stack substrate with virtually 100% coverage, resulting in an effective reduction in catalyst use. Furthermore, the process yields sharper edges because screen printing eliminates shadowing effects (more homogeneous coating). The complex mask manufacturing process required for spray coating is eliminated (screens for screen printing are standard components).

[0016] When structuring the screen-printed electrode, multiple electrode layers can be printed into the thickness dimension, whereby essentially the same electrode coating material or substantially different electrode coating materials are printed onto at least two or all electrode layers using the screen-printing process. Furthermore, the side edges of the pattern on the screen-printed electrode can be structured into the thickness dimension using the screen-printing process. In this process, a screen-printed electrode with a specific porosity of the electrode layers can be created within the thickness dimension. This can, of course, be done selectively or essentially globally with respect to the surface-patterned screen-printed electrode.

[0017] In this process, an upper electrode layer can be printed onto the lower electrode layer, being essentially smaller, the same size, or even slightly larger than the corresponding lower electrode layer. This allows for precise control over the thickness dimension, for example, by adjusting the geometry of the side edges. The side edges can be designed to be, for example, stepped, angled, convex, concave, etc. Furthermore, directly adjacent side edges can be aligned to create complementary, symmetrical (partially concave and partially concave), or otherwise aligned side edges.

[0018] Furthermore, at least two electrode layers made of the same electrode coating material can be printed on. Alternatively, at least two electrode layers made of different electrode coating materials can be printed on. This allows for the targeted adjustment of properties such as porosity (material properties), concentration differences, electrical, thermal, and / or material conductivity or resistance, etc., in the screen-printed electrode. In particular, this allows for the targeted adjustment of different surface roughnesses at the edges. The porosity of the electrode layers can be adjusted by means of volatile additives in the electrode coating material, whereby the additives are selected such that they evaporate during subsequent operation of the electrochemical cell stack. Such volatile additives include, for example, granules, particles, etc.of salts or carbon, which have a size analogous to the desired porosity. - The cell layer produced according to the invention can be structured like a cell layer described below.

[0019] The cell layer according to the invention comprises at least one cell stack substrate on which a catalyst-containing electrode, in particular an anode electrode and / or a cathode electrode, is applied, wherein the electrode is printed as a screen-printed electrode that is patterned in two length dimensions and preferably structured in its thickness dimension. The screen-printed electrode is, of course, printed onto a large outer surface of the cell stack substrate by a screen-printing process. Such an electrode printed by a screen-printing process can be easily identified by its edges and by the absence of shadow areas, such as those that occur in the spray-coating process.

[0020] The screen-printed electrode of the cell layer can have multiple printed electrode layers in terms of thickness. A sufficiently large volume element of solid material in at least two or all electrode layers can exhibit essentially the same properties. Furthermore, a sufficiently large volume element of solid material in at least two or all electrode layers can exhibit different physical and / or chemical properties. Additionally, at least two or all electrode layers, regardless of their position within the cell layer, can exhibit different geometric, material, electrical, and / or thermal properties.

[0021] The edges of the pattern on the screen-printed electrode can be structured according to their thickness. This means the electrode layers are printed in such a way that a defined geometry (see above) is formed at the edges of the pattern. Furthermore, at least two or all electrode layers can have different porosities. The bottom electrode layer can have the lowest porosity, and the top electrode layer the highest (pore volume per unit volume of material in a standardized volume element). This can, of course, also be reversed. This can, again, be implemented partially or entirely with respect to the surface-patterned screen-printed electrode.

[0022] The cell layer can comprise a membrane and at least one or exactly two fluid transport structures as cell stack substrates. Furthermore, the cell layer, consisting of the membrane and at least one or exactly two fluid transport structures, can have exactly one printed screen-printed electrode. In addition, at least one screen-printed electrode can be printed onto the membrane and / or the fluid transport structure. The cell layer can also include a cell frame and / or a sealing sleeve. Finally, the cell layer can be part of a membrane-electrode assembly.

[0023] The manufacturing process or cell layer can determine the edge length density of the screen printing electrode in m / m². 2 greater than: 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,500, 4,000, 3,500, 3,000, 2,500, 2,000, 1,750, 1,500, 1,250, 1,000, 900, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 225, 200, 175, 150, 125, 100, 90, 80, 75, 70, 65, 60, 55, 50 It could be 45, 40, 35, 30, 20 or 10.

[0024] Edge length density is defined as the summed edge length (in meters, m) per area (in square meters) of the screen printing electrode, where the edge length can be determined along a line on the cell stack substrate that is essentially visible to the naked eye or with a magnifying glass. This means that the (mean) surface roughness of the edge length is not included in the edge length of the screen printing electrode. Including surface roughness would result in significantly higher values ​​than those specified, depending on the measurement method. For a three-dimensionally patterned screen printing electrode, the edge length is the mean edge length of the side edges of the multi-layered screen printing electrode.

[0025] The cathode electrode can be designed as a substantially solid electrode, and the anode electrode as the patterned screen-printed electrode. The global outer circumference of the cathode electrode can be smaller, essentially equal to, or larger than the global outer circumference of the anode electrode. The same principles apply to the global outer circumference as described for the edge length, except that it does not follow any pattern but is simply a closed perimeter, e.g., rectangular, square, elliptical, circular, etc. Within the cell layer, the actual anode electrode can cover a smaller area than the actual cathode electrode.

[0026] The negative areas of the patterned, screen-printed electrode are naturally not part of the actual electrode surface. That is, analogous to the prior art, the physical surface area of ​​the anode electrode can be smaller than that of the cathode electrode, or, according to the invention, even smaller due to the patterning of the anode electrode, while the electrically active anode surface can be increased. The anode electrode and the cathode electrode do not necessarily have to be located on the same component, i.e., the membrane, but can also be distributed across the membrane and a fluid transport structure, or, bypassing the membrane, across both fluid transport structures.

[0027] The invention enables a reduction in the use of precious metal-based catalysts through a new electrode design, without compromising the performance of the electrode, and in fact, may even increase it. This is achieved through a screen-printed patterned electrode surface, preferably with two corresponding electrodes of different sizes. The electrode pattern allows for an increase in the electrochemically active area (sum of the structure's edge length) while reducing the coated area, thus enabling a smaller coating area for the anode in particular.

[0028] This effect can be enhanced by a 3D multilayer design of the electrode. Advantages of the 3D multilayer design include further improved utilization of the active catalyst material and / or improved contact with the fluid transport structure due to, for example, a stepped design of the electrode. Overall, the catalyst usage is reduced, and the costs of the CCM or an electrode-coated fluid transport structure are significantly lowered. The cell layer according to the invention can be produced by a manufacturing process described above. The electrochemical cell stack according to the invention comprises a plurality of electrochemical individual cells, wherein cell layers of the cell stack are produced by a manufacturing process according to the invention, and / or cell layers of the cell stack are designed according to the invention. Within the cell stack, or...A membrane and / or a fluid transport structure can be configured as a cell-stacked substrate with a patterned screen-printed electrode. The patterned screen-printed electrode can be pressed into or penetrated by its end faces or surfaces into the surface of a fluid transport structure. That is, the patterned screen-printed electrode penetrates the fluid transport structure to a certain degree. Furthermore, two bipolar plates can clamp together a membrane and fluid transport structures positioned on either side of it.

[0029] The electrochemical unit or system according to the invention comprises at least one electrochemical cell stack and a control unit for controlling and / or regulating the operation of the cell stack, wherein cell layers of the cell stack are manufactured by a manufacturing process according to the invention, cell layers of the cell stack are designed according to the invention, and / or the cell stack itself is designed according to the invention. Overall, the invention results in an increase in the active surface area of ​​the cell stack substrate exposed to flow during operation of the cell stack, which increases the electrochemical performance of the cell stack. Furthermore, it results in a significant saving of the rare catalyst materials, in particular iridium dioxide, platinum, etc., thereby achieving a considerable cost reduction of the most expensive component of the cell stack.

[0030] Brief description of the characters

[0031] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying schematic drawing, which is not to scale. In the invention, a feature can be positive (i.e., present) or negative (i.e., absent). In this specification, a negative feature is not explicitly defined as a feature unless the invention specifically emphasizes its absence. That is, the actual invention, rather than one constructed by the prior art, consists of omitting this feature. The absence of a feature (negative feature) in an exemplary embodiment indicates that the feature may be optional (to a person skilled in the art). The figures (Fig.) in the drawing, which are merely exemplary and schematic, show:

[0032] Fig. 1 shows a simplified block diagram of an embodiment of a fuel cell unit with an electrochemical fuel cell stack for a fuel cell system of a fuel cell vehicle, Fig. 2 shows a simplified block diagram of an embodiment of an electrolyzer unit with an electrochemical electrolysis cell stack for an electrolyzer system, e.g., an electrolyzer plant, and Figs. 3 to 5 show a cutaway side view of an electrode-coated cell layer, wherein the electrode is printed as a surface-patterned and preferably structured screen-printed electrode.

[0033] Embodiments of the invention

[0034] The invention is explained in more detail with reference to an electrode-coated cell layer 100 (see Figs. 3 to 5) for an electrochemical cell stack 10, 60 of an electrochemical unit 1, 51. The unit 1, 51 can be configured as a fuel cell unit 1 (see Fig. 1) for a mobile or stationary fuel cell system, or as a stationary or mobile electrolyzer unit 51 (see Fig. 2) for an electrolyzer system.

[0035] The drawing shows only those sections of the fuel cell system or electrolyzer system that are necessary for understanding the invention. Although the invention is described and illustrated in detail by preferred embodiments, the invention is not limited by the disclosed embodiments. Other variations can be derived from them without departing from the scope of protection of the invention.

[0036] Figures 1 and 2 each show an electrochemical unit 1, 51 (Fig. 1: fuel cell unit 1, Fig. 2: electrolyzer unit 51) according to a general embodiment, with at least one, in particular a plurality of, electrochemical individual cells 11, 61 (Fig. 1: individual fuel cells 11, Fig. 2: individual electrolysis cells 61) bundled to form an electrochemical cell stack 10, 60 or a stack 10, 60 (Fig. 1: fuel cell stack 10, Fig. 2: electrolysis cell stack 60), which are housed in a preferably fluid-tight stack housing 16, 66.

[0037] Each individual cell 11, 61 comprises an electrode compartment 12, 62 configured as an anode compartment 12, 62 and an electrode compartment 13, 63 configured as a cathode compartment 13, 63, which are spatially and electrically separated from each other by a membrane 110 or a membrane 110 of an MEA or a CCM (catalyst-coated membrane). An electrically conductive fluid transport structure 150 is provided in each electrode compartment 12, 13; 62, 63, which is in fluid communication with a bipolar plate 17, 67. Alternatively, or in addition to an MEA or a CCM with only one electrode, at least one electrode can also be provided away from the membrane 131 on at least one fluid transport structure 150.

[0038] A membrane electrode assembly 15, 65 of the cell stack 10, 60 comprises a membrane 110 or a membrane 110 of an MEA or a CCM, and fluid transport structures 110, 150 on its large-area sides (see also Figures 3 and 4). A single fluid transport structure 110, 150 can comprise a transport layer, a transport layer, a porous transport layer (PTL), a gas diffusion layer (GDL), a sintered metal element, a sintered metal paper element, a fiber element, a carbon layer, a carbon paper element, a flow structure, and / or a flow field, etc. The fluid transport structures 110, 150, which are not explicitly shown in Figures 1 and 2, are arranged in the anode compartments 12 and the cathode compartments 13 of the cell stack 10, 60.

[0039] A bipolar plate 17, 67 is arranged between two directly adjacent membrane electrode arrangements 15, 15; 65, 65 including a corresponding anode compartment 12, 62 and a respective cathode compartment 13, 63, which serves, among other things, to supply / discharge media 3 / 4, 5 / 6, 7 / 8; 53 / 54, 56 to an anode compartment 12, 62 of a first single cell 11, 61 or a cathode compartment 13, 63 of a directly adjacent second single cell 11, 61 and also provides an electrically conductive connection between these single cells 11, 11; 61, 61. - The cathode spaces 13, 63 and, if applicable, their common inflow area or their actual electrodes form a cathode 39, 89, and the anode spaces 12, 62 and, if applicable, their common inflow area or their actual electrodes form an anode 29, 79 of the cell stack 10, 60.

[0040] In principle, the membranes of the cell stack can comprise 10 or 60 PEMs (proton exchange membranes) or AEMs (anion exchange membranes). Preferably, a fuel cell stack comprises 10 PEMs and an electrolysis cell stack comprises 60 AEMs or PEMs. The fuel cell system or electrolyzer system comprises, in addition to the fuel cell unit 1 or the electrolyzer unit 51, peripheral system components, such as a control unit, which can be one of the fuel cell system or the electrolyzer system itself, etc.

[0041] The following explanations relate only to the electrochemical unit 1 as fuel cell unit 1, e.g., according to Fig. 1. - To supply the electrochemical cell stack 10 as fuel cell stack 10 with its actual operating media 3 (anode operating medium, actual fuel), 5 (cathode operating medium, usually air), the fuel cell unit 1 has an anode supply 20 and a cathode supply 30.

[0042] The anode supply 20 preferably comprises: a fuel storage 23 for the anode operating medium 3 (flowing in); an anode supply path 21 (medium path 21) with a pressure reducer, a shut-off valve and / or a metering valve 27 (by way of example), as well as a jet pump 24 (jet pump 24, e-ejector 24); an anode exhaust path 22 (medium path 22) for an anode exhaust medium 4 (flowing out, usually into the environment 2); a fuel recirculation path 25 with a fluid conveying device 26 located therein; optionally a water separator with preferably a water tank.

[0043] The cathode supply 30 preferably comprises: a cathode supply path 31 (medium path 31) for the cathode operating medium 5 (flowing in, usually from the environment 2), with a fluid conveying device 33; a cathode exhaust path 32 (medium path 32) for a cathode exhaust medium 6 (flowing out, usually into the environment 2), with preferably a turbine 34, in particular for the fluid conveying device 33; a moisture exchanger 36, in particular a gas-to-gas humidifier 36; optionally a cathode-side stack bypass 35 (wastegate 35) between the cathode supply path 31 and the cathode exhaust path 32, with a bypass valve 37; optionally a water separator with preferably a water tank.

[0044] The fuel cell assembly 1 further comprises, in particular, a cooling medium supply 40 of a thermal system, through which the fuel cell stack 10 can preferably be integrated into a cooling circuit for temperature control by means of its bipolar plates 17 (cooling medium paths 43). The cooling medium supply 40 comprises a cooling medium inlet path 41 and a cooling medium outlet path 42. The cooling medium 7 (inflow), 8 (outflow) circulating in the cooling medium supply 40 is preferably conveyed by means of at least one cooling medium conveying device 44.

[0045] The following descriptions pertain solely to the electrochemical unit 51 as an electrolyzer unit 51, e.g., according to Fig. 2. To supply the electrochemical cell stack 60 as an electrolysis cell stack 60 with, e.g., mildly alkaline water 53 as a supply medium 53, the electrolyzer unit 51 has a medium supply 70. And to extract the media 54, 56 from the cell stack 60, the electrolyzer unit 51 has a medium extraction port 80.

[0046] The medium supply 70 preferably comprises: a medium reservoir 73 for the supply medium 53 (flowing in), a supply path 71 (medium path 71), and a conveying device 76 on / in the supply path 71. The medium discharge 80 has at least one disposal path 81 (medium path 81) for a disposal medium 54 or a disposal medium 54 with oxygen back into the medium reservoir 73, optionally with a gas separator for oxygen, and / or in another direction (shown with dashed lines), e.g., into the environment 2. A product medium 56 of the electrolyzer unit 51, i.e., the produced hydrogen 56, is transported away through a product medium path 82 of the medium discharge 80. In this case, a gas / liquid separator 83 with a valve 84 can be used in the product medium path 82 to separate the disposal medium 54 in the product medium path 82.The waste medium 54 separated in the gas / liquid separator 83 can be returned to the medium reservoir 73 or conveyed in another direction, e.g., to the surrounding environment 2, possibly by gravity. The produced hydrogen 56 can be stored, for example, in a hydrogen storage tank 90, with the product medium path 82 potentially leading directly into the hydrogen storage tank 90. ​​Of course, other methods of transporting the hydrogen 56 are also possible.

[0047] Depending on the embodiment of the electrolyzer unit 51, the media flow within the cell stack 60 can be configured differently. It is possible to provide a temperature control system that differs from the electrochemical function of the cell stack 60, in particular water cooling, or to implement the temperature control system together with the electrochemical function of the cell stack 60.

[0048] In membrane electrode devices 65 with AEMs, it is possible to configure, in addition to anode-side and cathode-side supply, a supply of the supply medium 53 that is optionally exclusively anode-side (dotted arrow at the anode 79), possibly also serving as a cooling medium. Furthermore, in membrane electrode devices 65 with PEMs, it is possible to configure, in addition to an exclusively anode-side supply, a supply of the supply medium 53 that is optionally exclusively cathode-side 89, possibly also serving as a cooling medium (dotted arrow at the cathode 89).

[0049] The production of a membrane coated with a catalyst-containing electrode is achieved in the prior art using a slurry-based coating process, i.e., a process for coating with suspensions. A liquid electrode coating material is applied directly to the membrane over its entire surface using a spray coating process, whereby achieving a perfectly overlapping coating on both sides of the membrane is challenging. After coating, the membrane is dried using convection dryers. Spray coating processes have disadvantages, particularly when using a mask.

[0050] When using a mask in the spray-coating process, a large proportion of the liquid electrode coating material ends up on the mask itself, not on the membrane. The coating of the membrane is uneven due to the mask's placement (the mask leaves a shadow where no catalyst is applied). This process is generally complex due to the mask's manufacturing, positioning, cleaning, etc. The spray-coating process is always problematic because of overspray and inefficient use of the liquid electrode coating material.

[0051] The invention teaches a significant reduction in precious metal-based catalysts in electrodes through electrode design, without reducing the performance of the electrochemical individual cells 11, 61, or even potentially increasing it. For this to be achieved, it is necessary to utilize as much catalyst material as possible effectively, since, for example, with a conventional, full-surface electrode design, only about 51-55% of the precious metal input is utilized during the electrochemical reactions.

[0052] Within the scope of the invention – see also Figures 3 to 5 – it has been shown that strip-shaped or otherwise 2D-structured electrodes (hereinafter: planar patterned electrode 120, 130) can contribute to significant increases in performance and reductions in material consumption. This means that, in particular, a physical electrode surface (in the top view), especially an anode surface, can be made smaller, while an electrochemically active electrode surface is enlarged, thereby at least maintaining or even increasing the performance of the respective individual cell 11, 61.

[0053] Furthermore, experiments on the invention have shown that an electrical connection of a fluid transport structure 150 to a catalyst-containing electrode 120, 130 can be crucial for achieving improved performance of a fuel cell stack 10 and / or an electrolysis cell stack 60. However, with a surface-patterned electrode 120, 130 (positive patterning), continuous electrical contact between the electrode 120, 130 and the fluid transport structure 150, in particular a PTL or a GDL, is no longer guaranteed due to an exposed area (negative patterning of the electrode 120, 130).

[0054] The invention, which is explained in more detail below with reference to exemplary embodiments, comprises a cell stack substrate 110, which is formed, or is formed, by an electrode coating to form a cell layer 100 for an electrochemical cell stack 10, 60. The cell stack substrate 110 can be configured as a membrane 110 and / or a fluid transport structure 110. That is, the electrode-coated cell layer 100 can be configured as an electrode-coated membrane 110 and / or an electrode-coated fluid transport structure 110. Furthermore, the cell layer 100 can have at least one non-electrode-coated fluid transport structure 150 (see Fig. 4).

[0055] The invention overcomes the main problem of the spray-coating process by printing at least one catalyst-containing electrode 120, 130, in particular an anode electrode 120, onto the cell stack substrate 110 using a screen-printing process. The catalyst-containing electrode 120, 130 can be printed onto the cell stack substrate 110 using a 2D screen-printing process or a 3D screen-printing process. The other catalyst-containing electrode 130, 120, in particular a cathode electrode 130, 120, can be manufactured in a conventional manner. A manufacturing process according to the invention for this electrode 130, 120 is, of course, applicable.

[0056] Furthermore, the invention overcomes the problem of the high precious metal usage by designing the electrode 120, 130 as a surface-patterned electrode 120, 130 (screen-printed electrode as a 2D screen-printed electrode). In addition, the invention can overcome the problem of the electrical connection of the fluid transport structure 150 to the catalyst-containing electrode 120, 130 by printing the surface-patterned screen-printed electrode 120, 130 with a structured pattern in its thickness dimension D (screen-printed electrode as a 3D screen-printed electrode). At least one surface-patterned 2D screen-printed electrode 120, 130 is realized (Fig. 3). Furthermore, a surface-patterned 3D screen-printed electrode 120, 130 with a structured pattern in its thickness dimension D can also be realized (Figs. 4 and 5).The thickness dimension D (third length dimension D) is not only the thickness dimension D of the screen printing electrode 120, 130 but also one of the cell stack substrate 110, the cell layer 100, the fluid transport structure 150 etc. or an axial direction of the cell stack 10, 60.

[0057] The screen-printed electrode 120, 130 can be printed in a single layer (Fig. 3) or in multiple layers (Figs. 4 and 5; electrode layers 141 (bottom or inner), 142 (middle), 142 (top or outer)). A multi-layered screen-printed electrode 120, 130 can be designed, in particular, as having two, three, or four layers, with more than four layers being applicable. Such a single layer is, of course, a screen-printed layer of the catalyst-containing screen-printed electrode 120, 130.

[0058] Here, a single-layer screen-printed electrode 120, 130 is patterned across two length dimensions. A multi-layer screen-printed electrode 120, 130 is also patterned across two length dimensions and structured in the thickness dimension D. The structuring in the thickness dimension D can be achieved through a variety of methods. For example, the electrode layers 141, 142, 143, ... can be printed with the same pattern (not shown), similar patterns (see Figures 4 and 5), and / or at least two other patterns (not shown). Furthermore, the electrode layers 141, 142, 143, ... can be printed with the same electrode coating material or with different electrode coating materials.

[0059] If, in the case of a single-layer screen-printed electrode 120, 130, the fluid flow around the fuel cell stack 10 or the electrolysis cell stack 60 is essentially directed in two dimensions, the 3D structure of the screen-printed electrode 120, 130 achieves a significantly larger surface area (side edge 140 in the thickness dimension D or axial D side edge 140) and therefore significantly improves catalyst utilization through a fluid flow directed essentially in three dimensions. The side edge 140 (see also above) of the screen-printed electrode 120, 130 can, in principle, be of any shape, whereby a single, multiple, or a multitude of different side edge shapes 140 can be used for each screen-printed electrode 120, 130. Depending on the thickness of the electrode layers 141, 142, 143, ..., a sloping or stepped design of the side edge 140 is preferred, wherein an upper electrode layer 142, 143, ...in a top view in a relevant area smaller than the lower electrode layer 141 , 142, ... is formed.

[0060] Furthermore, the 3D structure of the screen-printed electrode 120, 130, due to a statistical distribution of the fibers, particularly the GDL or PTL, ensures electrical contact even for smaller or larger GDL or PTL fibers. This is especially true when a cross-section of at least one section of the pattern(s) of the screen-printed electrode 120, 130 tapers outwards from the cell stack substrate 110, in this case the membrane 110, to a thickness dimension D (see Fig. 4, where the pattern of the screen-printed electrode 120, 130 penetrates a surface of the fluid transport structure 150 and may even pierce it). Such a tapering or reduction of cross-sections of the pattern of the screen-printed electrode 120, 130 is, of course, also applicable in other embodiments.

[0061] Furthermore, the multilayer screen-printed electrode 120, 130 leads to a significant reduction in the required electrode volume, particularly the anode volume, while simultaneously significantly increasing the electrode surface area (side edge 140) and thus the catalytically active surface area exposed to the flow. Different structures of the screen-printed electrodes 120, 130 are possible to improve the effectiveness of the resulting electrochemically active surface (see above).

[0062] One advantage of a multilayer screen-printed electrode 120, 130 is that a graded coating can be established, allowing for adjustment of the porosity (see Fig. 5) of the upper layers relative to the lower layers, or vice versa, resulting in improved performance due to enhanced diffusion processes and / or reduced mass transport losses. The varying porosity of a multilayer screen-printed electrode 120, 130 can be achieved through volatile substances such as salts, but also through the incorporation of carbon particles of varying sizes. Since carbon is completely corroded and converted to carbon dioxide at the electrical potentials used, for example, in an electrolyzer, it does not remain in the screen-printed electrode 120, 130, thus eliminating the risk of catalyst contamination within the electrode.

[0063] The invention leads to a significant saving of limited precious metals for catalysts, which significantly reduces the cost of the core element of the fuel cell and electrolyzer, in particular the COM.

Claims

Claims 1. Method for producing an electrode-coated cell layer (100) for an electrochemical cell stack (10, 60), in particular a fuel cell stack (10) or an electrolysis cell stack (60), wherein at least one catalyst-containing electrode (120, 130), in particular an anode electrode (120) and / or a cathode electrode (130), for the cell stack (10, 60), is applied to a cell stack substrate (110), characterized in that an electrode coating material is printed onto a large-area outer surface of the cell stack substrate (110) by a screen printing process as a screen-printed electrode (120, 130) patterned in two length dimensions and structured in its thickness dimension (D).

2. Manufacturing method according to the preceding claim, characterized in that, during the structuring of the screen-printed electrode (120, 130), a plurality of electrode layers (141 , 142, 143, ...) are printed into the thickness dimension (D), wherein for at least two or all electrode layers (141 , 142, 143, ...) substantially the same electrode coating material or substantially different electrode coating materials are printed by the screen-printing process.

3. Manufacturing method according to one of the preceding claims, characterized in that by the screen printing process side edges (140) of the pattern of the screen printing electrode (120, 130) are structured into the thickness dimension (D), and / or a screen printing electrode (120, 130) graded in particular with respect to a porosity of the electrode layers (141 , 142, 143, ...) is set into the thickness dimension (D).

4. Manufacturing method according to one of the preceding claims, characterized in that a porosity of the electrode layers (141 , 142, 143, ...) is adjusted by means of volatile additives in the electrode coating material, wherein the additives are selected such that they evaporate during a subsequent operation of the electrochemical cell stack (10, 60).

5. Cell layer (100) for an electrochemical cell stack (10, 60), in particular a fuel cell stack (10) or an electrolysis cell stack (60), wherein the cell layer (100) comprises at least one cell stack substrate (110) on which a catalyst-containing electrode (120, 130), in particular an anode electrode (120) and / or a cathode electrode (130), is applied, characterized in that the electrode (120, 130) is printed as a screen-printed electrode (120, 130) which is patterned in two length dimensions and structured in its thickness dimension (D).

6. Cell layer (100) according to the preceding claim, characterized in that the screen-printed electrode (120, 130) has a plurality of printed electrode layers (141 , 142, 143, ...) in thickness dimension (D), wherein: • each a sufficiently large volume element of a solid material of at least two or all electrode layers (141 , 142, 143, ...) exhibit essentially the same properties, • each sufficiently large volume element of a solid material of at least two or all electrode layers (141 , 142, 143, ...) exhibits different physical and / or different chemical properties, and / or • at least two or all electrode layers (141 , 142, 143, ...), regardless of their position in the cell layer (100), exhibit different geometric, material, electrical and / or thermal properties.

7. Cell layer (100) according to one of the preceding claims, characterized in that the screen printing electrode (120, 130) has a thickness dimension (D) has a plurality of printed electrode layers (141 , 142, 143, ...) wherein The side edges (140) of the pattern of the screen printing electrode (120, 130) are structured into the thickness dimension (D), and / or at least two or all electrode layers (141 , 142, 143, ...) have a different porosity.

8. Cell layer (100) according to one of the preceding claims, characterized in that: • the cell layer (100) as cell stack substrates (110, 150) comprises a membrane (110) and at least one (110 / 150) or exactly two fluid transport structures (110, 150; 150, 150), • the cell layer (100) consists of the membrane (110) and at least one (110 / 150) or exactly two fluid transport structures (110, 150; 150, 150) and exactly one printed screen-printed electrode (120, 130), and / or • at least one screen-printed electrode (120, 130) is printed onto the membrane (110) and / or the fluid transport structure (110; 150; 150, 150).

9. Manufacturing method or cell layer (100) according to one of the preceding claims, characterized in that an edge length density of the screen printing electrode (120, 130) in m / m 2 greater than: 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,500, 4,000, 3,500, 3,000, 2,500, 2,000, 1,750, 1,500, 1,250, 1,000, 900, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 225, 200, 175, 150, 125, 100, 90, 80, 75, 70, 65, 60, 55, 50 45, 40, 35, 30, 20 or 10.

10. Manufacturing method or cell layer (100) according to one of the preceding claims, characterized in that: • the cathode electrode (130) is designed as an essentially full-surface electrode (130) and the anode electrode (120) is designed as the patterned screen-printed electrode (120), • a global outer circumference of the cathode electrode (130) is smaller, substantially equal to or larger than a global outer circumference of the anode electrode (120), and / or within the cell layer (100) the actual anode electrode (120) covers a smaller area than the actual cathode electrode (130).

11. Electrochemical cell stack (10, 60), in particular fuel cell stack (10) or electrolysis cell stack (60), for an electrochemical unit (1, 51), in particular a fuel cell unit (1) or an electrolyzer unit (51), with a plurality of electrochemical individual cells (11, 51), characterized in that cell layers (100) of the cell stack (10, 60) are produced by a manufacturing process according to one of the preceding claims, and / or cell layers (100) of the cell stack (10, 60) are formed according to one of the preceding claims.

12. Electrochemical cell stack (10, 60) according to the preceding claim, characterized in that the cell stack (10, 60) contains: • a membrane (110) and / or a fluid transport structure (110) is / are designed as a cell stack substrate (100) with a patterned screen-printed electrode (120, 130), • a patterned screen-printed electrode (120, 130) with its end-face edges or surfaces is pressed into or penetrated a surface of a fluid transport structure (150), and / or • each pair of bipolar plates (17, 17; 67, 67) clamps together a membrane (110) and fluid transport structures (150, 150; 110, 150) arranged on both sides of it.

13. Electrochemical unit (1, 51), in particular fuel cell unit (1) or electrolyzer unit (51), or electrochemical system, in particular fuel cell system or electrolyzer system, with at least one electrochemical cell stack (10, 60) and a control unit for controlling and / or regulating the operation of the cell stack (10, 60), characterized in that Cell layers (100) of the cell stack (10, 60) are produced by a manufacturing process according to one of the preceding claims, cell layers (100) of the cell stack (10, 60) according to one of the preceding claims che are formed, and / or the cell stack (10, 60) is formed according to one of the preceding claims.

Images