Assembly composed of a grooved polymer electrolyte membrane and a bipolar plate for an electrochemical system, and method of manufacturing the plate assembly

Abstract

The invention provides a plate assembly (1) for an electrochemical system, for example a fuel cell system or electrolysis system, comprising a bipolar plate (3) that forms mutually parallel channels (4). The plate assembly (1) further comprises a proton-permeable membrane (13) which is spaced apart from and parallel to the bipolar plate (3) and in which there are grooves (9) that correspond to said channels (4) and are filled with a catalytic coating (8).

Description

[0001] ARRANGEMENT OF A GROOVED POLYMER ELECTROLYTE MEMBRANE AND A BIPOLAR PLATE FOR AN ELECTROCHEMICAL SYSTEM, AND METHOD FOR PRODUCEING THE PLATE ARRANGEMENT

[0002] The invention relates to a plate arrangement intended for use in an electrochemical system. The invention further relates to a method for manufacturing such a plate arrangement.

[0003] DE 10 2022 110 834 A1 discloses a fuel cell system and a method for manufacturing a plate arrangement for a fuel cell stack. In particular, DE 10 2022 110 834 A1 addresses sealing arrangements within a cell stack.

[0004] German patent application DE 10 2005 051 162 A1 relates to an ion-conducting polymer electrolyte membrane intended for use in an electrolysis cell. The polymer electrolyte membrane is composed of several polymer electrolyte membrane materials and has a three-dimensional structure. The polymer electrolyte membrane materials contain an ionomer that has sulfonic acid, carboxylic acid, and / or phosphonic acid groups.

[0005] US 2007 / 0026291 A1 proposes creating ribbed surface structures on membranes using tools with corresponding counter-contours. US 2005 / 0181252 A1 states that the surface area of ​​a membrane for an electrochemical system can be increased using chemical or physical deposition processes. EP 1 171 924 B1 mentions, among other things, roughening a membrane as a possible processing step before applying a catalyst layer.

[0006] Various membranes designed for electrochemical systems, which

[0007] Microstructuring, for example in the form of microholes, is evident from documents JP 2005-174565 A, WO 2004 / 001876 A2 and US 2023 / 0253595 A1.

[0008] US patent 2018 / 0331380 A1 discloses a device and a method for manufacturing membrane electrode assemblies for fuel cells. In this method, web-shaped material is unwound from a roll and passed through various processing stations.

[0009] WO 2006 / 065618 A2 describes an electrolyte plate with a striped pattern. The electrolyte plate is made of a polycrystalline ceramic. The possible thickness of the electrolyte plate is specified as ranging from 5 micrometers to 100 micrometers.

[0010] The invention is based on the objective of further developing plate arrangements for electrochemical systems compared to the aforementioned prior art, whereby a particularly good utilization of the available installation space for the desired electrochemical reactions as well as economical material use is sought.

[0011] This problem is solved according to the invention by a plate arrangement having the features of claim 1. Likewise, the problem is solved by a method designed according to claim 7 for manufacturing a plate arrangement for an electrochemical system.

[0012] The plate arrangement is designed, for example, for use in a fuel cell system or an electrolysis system and comprises a bipolar plate through which parallel channels are formed. Cooling and / or operating media of the electrochemical system can flow through these channels. Furthermore, the plate arrangement according to the application comprises a proton-permeable membrane spaced parallel to the bipolar plate, in which grooves are located that are congruent with the aforementioned channels and are filled with a catalytic coating.

[0013] The medium flowing in the channels formed by the bipolar plate flows parallel to the strip-shaped, catalytically active areas. Each channel can have a cross-section open towards the catalytic coating of the membrane. Thus, the catalytically coated membrane covers one side of the channel's cross-section, while the remaining channel cross-section is defined by the bipolar plate. Optionally, a permeable material layer is inserted between the channel and the catalytically active surface of the membrane. This material layer can be a gas diffusion layer and / or a porous transport layer. In any case, the strip shape of the catalytic coating, adapted to the channels, ensures efficient use of the coating material. The membrane surface facing the bipolar plate, including the catalytic coating, can be completely flat.

[0014] Optionally, the catalytic coating can also cover the membrane surface areas located between the grooves. The catalytic coating can form a closed, flat surface, meaning that the coating has a certain thickness within the grooves, while the same coating is present in a comparatively thinner layer outside the grooves. This is particularly useful in cases where, as mentioned earlier, a fluid-permeable material layer (i.e., liquids and / or gases) is located between the membrane and the bipolar plate. In such cases, the fluid flowing through the channel can also reach areas of the coating located laterally to the channel via the permeable material layer.In comparison to the catalytically coated area located directly on the side of the permeable material layer opposite the channel, i.e., in the groove area, the coating areas located laterally next to the channel are exposed to relatively little fluid. Thus, the thickness of the catalytic coating is adapted to the fluid flow reaching the membrane. For example, the maximum thickness of the catalytic coating within the grooves is at least twice and at most five times the minimum thickness of the catalytic coating outside the grooves.Regardless of the presence of a permeable material layer inserted between the membrane and the bipolar plate, both the membrane – which is considered here without a coating – and the bipolar plate can describe a ribbed shape, with ribs being formed by strip-shaped elevations between the grooves or between the channels.

[0015] The height of the channel, measured in the stacking direction of the plate arrangement, i.e. in the normal direction to the mutually parallel planes in which the bipolar plate and the membrane lie, deviates from the sum of the thickness of the permeable material layer and the maximum thickness of the catalytic coating, for example, by no more than 30%.

[0016] The patented method for manufacturing a plate arrangement for an electrochemical system is characterized by the fact that grooves are formed in a membrane and the surface of the membrane, including the grooves, is provided with a catalytic coating such that a flat surface is created. Subsequently, a permeable material layer is applied to this catalytically active surface. Finally, a bipolar plate provided with channels is placed on the permeable material layer such that the channels, which are open towards the permeable material layer, are aligned with the grooves in the membrane.

[0017] The grooves in the membrane can be created, for example, by plasma etching. Plasma etching, also known as plasma-assisted ion etching, involves material removal through the impact of ions on a surface. For technical background information, see, for example, documents EP 1 255 690 B1 and DE 102007 018 010 A1. Similarly, grooves can be created in the membrane surface using photochemical processes. Such processes are described, for example, in documents DE 10 2016 219 732 A1 and DE 10 2016 219 733 A1. Grooves can also be created by mechanical processing.

[0018] Regarding the formation of the channels in the bipolar plate, established technologies can be used, including forming processes and additive manufacturing. In this context, reference is made to documents WO 2022 / 268256 A1 and WO 2024 / 041685 A1 as examples.

[0019] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows:

[0020] Fig. 1 shows a plate arrangement of an electrochemical system in a sectional view.

[0021] Fig. 2 shows a section of the arrangement according to Fig. 1 ,

[0022] Fig. 3 shows in a diagram the spatial dependence of the concentration of different substances within the plate arrangement according to Fig. 1.

[0023] A plate arrangement, designated as a whole by reference numeral 1, is intended for use in an electrochemical system not shown, for example in a fuel cell system or in an electrolyzer for producing hydrogen from water.

[0024] The plate arrangement 1 is used in a stacked arrangement of electrochemical cells 2, referred to as a stack 10, i.e., in a cell stack 10, and comprises a bipolar plate 3 which separates a half-cell of a first electrochemical cell 2 from a half-cell of another, identical electrochemical cell 2. The cell stack 10 comprises a plurality of cells 2, although means for clamping the cells 2 are not shown.

[0025] As shown in Figures 1 and 2, the bipolar plate 3 forms several channels 4, which in this case have a trapezoidal cross-section. The parallel channels 4, open downwards in the arrangement shown in Figures 1 and 2, allow the flow of operating and / or cooling media of the electrochemical system to which the plate arrangement 1 belongs. Any geometric terms such as "bottom" or "top" used in this text refer only to the arrangements illustrated in the figures and do not imply any statement about the actual orientation of the components of the plate arrangement 1 in space. For example, plate-shaped components, such as the bipolar plate 3, can be oriented vertically.

[0026] The channels 4 are formed by a structuring 5 of the bipolar plate 3. The structuring 5 can be produced, in particular, by forming processes, whereby the bipolar plate 3 can be constructed in one or more parts. The channel width is specified as B4, and the channel height as H4. The channels 4 are separated from each other by ribs 6 of the bipolar plate 3, which are also formed by the structuring 5. The undersides of the ribs 6 lie in a common plane that is tangent to a surface of a permeable material layer 7. The permeable material layer 7 can be composed of a single or multiple material and may include a gas diffusion layer and / or a porous transport layer.

[0027] Between the half-cells of the same electrochemical cell 2 is a proton-permeable membrane 13, which is provided with a catalytic coating 8. The permeable material layer 7, whose thickness is specified as H7, rests on the membrane 13. Grooves 9 are formed in the membrane 13, the width B9 of which, in the exemplary embodiment, corresponds to the width B4 of a channel 4 above it. Each groove 9 runs parallel below a channel 4, so that the channels 4 and grooves 9 are perfectly aligned. The catalytic coating 8 fills both the grooves 9 and the surface areas of the membrane 13 between the grooves 9 such that the coating 8 has a completely flat surface. The permeable material layer 7 rests fully on the coating 8.

[0028] The maximum thickness of the coating 8, designated H8max, is found in the groove 9. H8min denotes the minimum thickness of the coating 8, measured between adjacent grooves 9. In the embodiment shown in Figures 1 to 3, the maximum thickness H8max is at least twice and at most five times the minimum thickness H8min of the catalytic coating 8. At the same time, the maximum thickness H8max is less than half the total thickness of the membrane 13, including the coating 8. Areas of the coating 8 that fill the groove 9 are to be understood as areas 12 of high catalyst concentration CC. In contrast, the strip-shaped areas of the coating 8 located between each pair of grooves 9, which have the minimum thickness H8min, represent areas 11 of low catalyst concentration CC.

[0029] The height H4 of channel 4, measured in the stacking direction of the plate arrangement (in this case, vertically), deviates from the sum of the thickness H7 of the permeable material layer 7 and the maximum thickness H8max of the catalytic coating 8 by no more than 30%. Channel 4, like groove 9, has a trapezoidal cross-section. The flanks of channel 4 are designated 14, and the flanks of groove 9 are designated 15.

[0030] The trapezoidal shape of groove 3 is also reflected in the diagram in Fig. 3, which shows, among other things, the spatially dependent concentration profile VC of the catalyst. The x-axis is oriented orthogonally to groove 9 and channel 4, lying in the same plane as membrane 13. In addition to the concentration profile VC, which relates to the catalyst contained in the coating 8, Fig. 3 also shows an idealized concentration profile VR, which relates to a reactant located in the electrochemical cell 2. The concentration profile VR reaches a maximum in the center of the section of the plate arrangement 1 shown in Figures 2 and 3, i.e., in the central region of channel 4 and the underlying permeable material layer 7. As indicated in Fig. 3, reactant is distributed throughout cell 2 via the permeable material layer 7, including laterally adjacent to channel 4.

[0031] This ensures that the reactant reaches the entire surface of the coating 8, but not in a uniform distribution. Rather, the concentration of the reactant, generally denoted as CR, decreases from an area located centrally beneath the channel 4 to the areas to the sides of the channel 4. This results in a concentration profile, which is expressed as the curved curve VR of the reactant concentration. As can be clearly seen in Fig. 3, the concentration profile VC of the catalyst approximately reflects the concentration profile VR of the reactant. The catalyst, which enables or accelerates the electrochemical reactions taking place in the cells 2 of the stack 10, is thus distributed within the coating 8 as required.

[0032] List of reference signs

[0033] 1. Plate arrangement

[0034] 2 electrochemical cells

[0035] 3 Bipolar plate

[0036] 4-channel

[0037] 5. Structuring

[0038] 6th rib

[0039] 7 permeable material layer

[0040] 8 catalytic coating

[0041] 9 grooves in the membrane

[0042] 10 cell stacks, Stack

[0043] 11. Low catalyst concentration range

[0044] 12 Area of ​​high catalyst concentration

[0045] 13 Membran

[0046] 14. Flank of the canal

[0047] 15 Flank of the groove

[0048] B4 Channel width

[0049] B9 Width of the groove

[0050] CC concentration of a catalyst

[0051] CR concentration of a reactant

[0052] H4 Height of the canal

[0053] H7 Material layer thickness

[0054] H8min minimum coating thickness

[0055] H8max maximum coating thickness x x-direction, perpendicular to the channel

[0056] VC concentration profile catalyst

[0057] VR concentration profile reactant

Claims

Patent claims 1. Plate arrangement (1) for an electrochemical system comprising a bipolar plate (3) through which parallel channels (4) are formed, and a proton-permeable membrane (13) spaced parallel to the bipolar plate (3), in which grooves (9) corresponding to the said channels (4) are located and which are filled with a catalytic coating (8).

2. Plate arrangement (1 ) according to claim 1 , characterized in that the catalytic coating (8) also covers the surface areas of the membrane (13) located between the grooves (9).

3. Plate arrangement (1 ) according to claim 2, characterized in that the catalytic coating (8) has a flat surface.

4. Plate arrangement (1 ) according to claim 3, characterized in that the maximum thickness (H8max) of the catalytic coating (8) given in the grooves (9) is at least twice and at most five times the minimum thickness (H8min) of the catalytic coating (8) given outside the grooves (9).

5. Plate arrangement (1 ) according to one of claims 1 to 4, characterized by a permeable material layer (7) located between the membrane (13) and the bipolar plate (3).

6. Plate arrangement (1 ) according to one of claims 1 to 5, characterized in that the height (H4) of the channel (4) to be measured in the stacking direction of the plate arrangement (1 ) does not deviate from the sum of the thickness (H7) of the permeable material layer (7) and the maximum thickness (H8max) of the catalytic coating (8) by more than 30%.

7. Method for producing a plate arrangement (1) for an electrochemical system, wherein grooves (9) are provided in a membrane (13), the surface of the membrane (13) including the grooves (9) is provided with a catalytic coating (8) such that a flat surface is formed, a permeable material layer (7) is applied to this surface, and a channeled plate (4) is placed on said material layer (7). The bipolar plate (3) is positioned such that the channels (4) run in a congruent arrangement with the grooves (9) located in the membrane (13).

8. The method of claim 7, characterized in that the grooves (9) are produced by plasma etching.

9. The method of claim 7, characterized in that the grooves (9) are produced by photochemical processing.

10. Method according to claim 7, characterized in that the grooves (9) are produced by mechanical processing.

Images