Bipolar plate, plate arrangement and electrolyzer

Abstract

A bipolar plate (1) of an electrochemical system (10), in particular an electrolysis system, separates an anode side of the electrochemical system (10) from a cathode side of the electrochemical system, wherein a reference plane (EE) is defined by a boundary region (6) of the bipolar plate (1) and ports (7, 8) for supplying and draining media to and from an active field (9) of the electrochemical system (10) and from the active field (9) are located in the boundary region (6), and wherein a structuring (12) of the bipolar plate (1) is formed in the active field (9) such that an active field base plane (EA) formed by planar material of the bipolar plate (1) is spaced parallel to the reference plane (EE), namely offset towards the cathode side, and individual embossing elements (13, 22) project from the active field base plane (EA) towards the anode side.

Description

[0001] The invention relates to a bipolar plate intended for use in an electrochemical system. The invention further relates to a plate arrangement including a bipolar plate and an electrolyzer.

[0002] A possible design for a bipolar plate and an electrochemical cell is described, for example, in DE 10 2022 122 717 B3. The bipolar plate according to DE 10 2022 122 717 B3 consists of two half-sheets that are firmly joined together, with fluid inlet and outlet openings formed by the bipolar plate. Furthermore, distribution fields and an active field are formed. Seals are located on both sides of the bipolar plate, arranged congruently one above the other and reinforced by embossed structures. The electrochemical cell according to DE 10 2022 122 717 B3 can, in particular, be an electrolysis cell for the electrolysis of water.

[0003] DE 10 2021 206 090 A1 discloses a fuel cell system comprising several distributor plates. Flow channels for a reactant are formed through the first side of a distributor plate, while flow channels for a coolant are formed through the second side of the distributor plate.

[0004] Another bipolar plate designed for use in a fuel cell stack is described in DE 10 2006 059 857 A1. In this case, flow fields in the form of a positive and a negative structure are provided by a component generally referred to as a disk part, whereby channel-shaped structures in the inflow and outflow regions may exhibit a meandering structure.

[0005] The invention is based on the objective of further developing stacked electrochemical systems compared to the aforementioned prior art, whereby a high power density in relation to the stack height is sought in a manufacturing-friendly, robust design.

[0006] This problem is solved according to the invention by a bipolar plate designed as a component of an electrochemical system, having the features of claim 1. The bipolar plate is suitable for use in a plate arrangement according to claim 7. The plate arrangement, in turn, is suitable for use in an electrochemical system, in particular in an electrolyzer according to claim 10.

[0007] The bipolar plate according to the patent application, when installed in an electrochemical system, separates an anode side of the electrochemical system from a cathode side of the same system. A reference plane is defined by a boundary region of the bipolar plate. Ports for supplying media to an active field of the electrochemical system or for discharging media from the active field are located in this boundary region. Within the active field, the bipolar plate is structured such that an active field base plane, formed by planar material, in particular undeformed material, of the bipolar plate, is spaced parallel to the reference plane. This active field base plane is offset towards the cathode side. Simultaneously, individual embossed elements project from the active field base plane towards the anode side.

[0008] Both sides of the bipolar plate, which is structured three-dimensionally at least in the area of ​​the active field, can represent flow-guiding structures, with the structuring simultaneously contributing significantly to the mechanical stability of the bipolar plate. If the offset of the active field base plane relative to the reference plane is considered a deformation in a first direction, then the numerous embossed elements that protrude from the active field base plane are to be considered elements deformed in the opposite direction. This makes no statement about simultaneous or sequential forming steps. In particular, it is possible to produce the structuring in a single forming process.

[0009] According to various possible configurations, the embossing elements emanating from the active field ground plane are located – viewed from the reference plane – on the cathode side for at least 60% of their height, and in particular for at least 80% of their height. A complete arrangement of the embossing elements on the cathode side occurs in cases where the embossing elements are tangent to the reference plane.

[0010] An intermediate region of the bipolar plate can be formed between its edge and the structure defined by the active field. Within this intermediate region, a plate-like intermediate plane formed by planar material, particularly undeformed material, is arranged parallel to the reference plane and the active field base plane. Supporting embossing elements project from this intermediate plate plane towards the anode side, maintaining unobstructed flow cross-sections. The term "supporting embossing elements" is intended to clarify that these elements, in addition to a fluid-related function (which will be discussed in more detail later), also provide structural support. This does not mean that other embossing elements formed by the bipolar plate lack such a mechanical function. Rather, the term "supporting embossing elements" was chosen to distinguish them from other embossing elements.

[0011] One possible further development involves arranging several embossing elements formed in the active field parallel to each other, each with an elongated shape. Cross-flow paths are created by recesses formed within the embossing elements. These recesses are arranged such that a series of recesses formed by a plurality of embossing elements is oriented perpendicular to the longitudinal direction of the embossing elements.

[0012] Similarly, variations of the bipolar plate are possible in which a herringbone pattern is formed by its structuring. Such a herringbone pattern is composed of numerous embossed elements with an elongated rectangular base shape. Furthermore, embossed elements with a different shape, particularly a triangular base shape, can be located at at least one edge of the herringbone pattern.

[0013] With various designs of the embossed structure, the free flow cross-sections formed by the structuring on the anode side can be larger than those formed on the cathode side. At least a subset of the embossed elements can be knob-shaped, allowing flow around them on the anode side. Viewed from the cathode side, however, these same embossed elements represent blind-hole-like depressions, i.e., spaces unsuitable for the straight passage of a fluid.

[0014] The plate arrangement according to the application comprises, in addition to at least one bipolar plate configured according to claim 1, several frames between which the bipolar plate is inserted. Furthermore, the plate arrangement comprises various porous transport layers, namely an anode-side transport layer and a cathode-side transport layer, between which the bipolar plate is located. Porous transport layers are generally flow-permeable and electrically conductive materials. The porous transport layers of the plate arrangement according to the application are also capable of absorbing forces acting in the active field that act in the stacking direction of the electrochemical system.

[0015] If the electrochemical system is configured as an electrolyzer for hydrogen production, process water flows in the porous transport layer on the anode side. This process water contains hydrogen atoms that, after donating an electron as protons, penetrate the membrane of the electrochemical cell to form gaseous hydrogen on the cathode side, together with electrons. Cooling water, kept separate from the process water, can be used to dissipate the heat generated during electrolysis. Alternatively or additionally, the process water can be used for cooling.

[0016] One possible embodiment of the plate arrangement provides that the active field is framed by a seal which contacts a proton-permeable, catalytically coated membrane, wherein the anode-side porous transport layer rests on the membrane on the side facing away from the seal and has a larger area than the cathode-side porous transport layer, and wherein the seal lies in a common plane with the cathode-side porous transport layer.

[0017] The previously mentioned support embossing elements can be combined with this design by forming media channels between the anode-side porous transport layer and one of the ports. These channels connect to the flow cross-sections maintained between the support embossing elements, facing the active field. The media channels can be formed, for example, by a frame or by an insert part integrated into a frame. The frame, as well as the optional insert part, can be made of plastic – even in other configurations of the plate arrangement.

[0018] In various configurations of the plate arrangement, the three-dimensional structuring of the bipolar plate, which separates a half-cell of a first electrochemical cell from a half-cell of a second electrochemical cell, can be designed such that one of the two half-cells, namely an anode-side half-cell, has a greater height in the stacking direction of the layered system compared to the second half-cell, i.e., a cathode-side half-cell. This design allows, in particular, the provision of a larger flow cross-section on the anode side than on the cathode side.

[0019] If one considers only the flow cross-sections at the level of the bipolar plate, a defined flow cross-section on the anode side of the bipolar plate can even be contrasted with a non-existent flow cross-section on the cathode side. This applies, for example, to cases in which the embossing elements of the bipolar plate appear on the cathode side exclusively as island-shaped, approximately point-like depressions. In such cases, the individual embossing elements present as depressions on the cathode side may primarily serve to absorb the tensile forces of the entire stacked electrochemical system, particularly an electrolysis system. The same embossing elements that appear as depressions on the cathode side appear as knob-shaped embossing elements on the anode side, assuming an at least approximately circular shape.These embossing elements can be surrounded by flow on the anode side and can be combined with other, for example elongated, embossing elements.

[0020] Several embodiments of the invention are explained in more detail below with reference to a drawing. These drawings show, in some cases simplified form: Fig. 1. Partially an electrochemical system, namely an electrolyzer for the production of hydrogen, Fig. 2 a bipolar plate of the electrolyzer after Fig. 1 in top view, Fig. 3 several elongated embossing elements of the bipolar plate according to Fig. 2 in perspective view, Fig. 4 and Fig. 5 one of the embossing elements according to Fig. 3 in side view or in cutaway view, Fig. 6 differently shaped embossing elements of a bipolar plate in an analogous representation Fig. 3, Fig. 7 and Fig. 8 Flow possibilities for operating and cooling media of an electrochemical system given by three-dimensional structuring of bipolar plates in representations similar to Fig. 4 and Fig. 5, Fig. 9 one compared to the variant after Fig. 6 modified three-dimensional structuring of a bipolar plate, Fig. 10 a three-dimensionally structured bipolar plate providing longitudinal and transverse flow paths in a Fig. 3 based on a representation, Fig. 11 another design of a three-dimensionally structured bipolar plate for an electrochemical system, Fig. 12. Partially a herringbone pattern of the bipolar plate according to Fig. 11.

[0021] Unless otherwise stated, the following explanations apply to all embodiments. Corresponding or essentially equivalent parts are marked with the same reference numerals in all figures.

[0022] Bipolar plates 1 belong to an electrochemical system 10, which in the present case is an electrolyzer for producing hydrogen from water. The parallel bipolar plates 1 are part of a plate arrangement 11, also referred to as a stack, which constitutes the core component of the electrochemical system 10. Other components, such as containers for feedstocks, end products, and coolant, pumps, as well as measuring and control devices, are not shown. For the basic structure and function of the electrolyzer 10, reference is made to the prior art cited above.

[0023] The stack 11 comprises a plurality of electrochemical cells 2, that is, electrolysis cells. Each electrolysis cell 2 comprises two half-cells 3, 4, namely an anode-side half-cell 3 and a cathode-side half-cell 4, which are separated from each other by a catalytically coated, proton-permeable membrane 5. The bipolar plate 1 is arranged between a half-cell 3 of a first electrochemical cell 2 and a half-cell 4 of another electrochemical cell 2.

[0024] In a peripheral region 6 of the bipolar plate 1, various ports 7, 8 are located for the passage of operating and cooling media. An active field, in which the desired electrochemical reactions take place, is designated 9. In all embodiments, a structuring 12 of the bipolar plate 1 is present in the active field 9. In each case, the structuring 12 comprises rib-shaped embossed elements 13. Optional knob-shaped embossed elements are designated 22. Viewed from the cathode side of the bipolar plate 1, the embossed elements 13, 22 represent elongated or point-like depressions, respectively. This is equivalent to the fact that the embossed elements 13, 22 project from an active field base plane EA in the direction of the anode side.

[0025] The active field ground plane EA is parallel to and spaced apart from a reference plane EE, which is defined by the position of the boundary region 6. The distance between the reference plane EE and the active field ground plane EA is denoted by dEA. In the cases of Fig. For 1 to 8 and 10, the distance dEA is identical to an embossing depth PT, which is also generally referred to as the height of the embossing elements 13, 22 or as the forming height. In these cases, the area of ​​maximum indentation designated 14, which is also referred to as the embossing roof, lies on the reference plane EE.

[0026] The bipolar plate 1 is arranged in a sandwich-like manner between an anode-side porous transport layer 15 and a cathode-side porous transport layer 16. As shown from Fig. As can be seen from Figure 1, the area of ​​the anode-side porous transport layer 15 is larger than the area of ​​the cathode-side porous transport layer 16. Furthermore, the thickness of the anode-side porous transport layer 15, denoted by dPa, is greater than the thickness of the cathode-side porous transport layer 16, denoted by dPk.

[0027] Support embossing elements 19 are located on the anode-side porous transport layer 15, extending beyond the active field 9 and the cathode-side porous transport layer 16. These elements project from a planar intermediate area 18 of the bipolar plate 1 towards the anode side. The planar intermediate area 18 lies in a plate intermediate plane PZ, which is arranged parallel between the reference plane EE and the active field base plane EA. The support embossing elements 19, as well as the embossing elements 13 and 22, are tangent to the reference plane EE. A plastic frame 23 rests on the side of the planar intermediate area 18 facing away from the support embossing elements 19. An active surface seal 17 rests on an inner rib 24 of the frame 23, which borders the active field 9 and is located at the level of the cathode-side porous transport layer 16.

[0028] Where geometric terms such as "resting on" or "at the height of" are used in this text, these terms refer only to the areas described in the text. Fig. The arrangements shown in Figures 1 to 10 do not imply any statement about the actual orientation of the components of the electrochemical system 10 in space. In particular, the bipolar plates 1, as well as the frames 23 and the membranes 5, can be vertically oriented.

[0029] Seals arranged in the edge region 6, located, among other places, between the ports 7 and the flat intermediate region 18, are generally designated as 20. Unlike the active surface seal 17, the seals 20 contact not only the frame 23 but also the bipolar plate 1. On its side facing away from the seal 20, the frame 23 contacts an insert 21, which is optionally designed as an integral part of the frame 23, laterally adjacent to the active surface seal 17. The insert 21 forms media channels MK, which extend from the ports 7 towards the active field 9. Free flow areas connecting the media channels MK to the active field 9 are kept open between the support embossed elements 19.

[0030] Details of the three-dimensional structuring 12, as shown in the embodiment according to Fig. Given 1, it follows from the Fig. 3 to 5 stand out. Then, flow zones S are defined by the strip-shaped, parallel embossing elements 13 on the cathode side of the bipolar plate 1. in formed, which are located in the embossed elements 13 designed as depressions. These are to be distinguished from external flow regions S out on the anode side of the bipolar plate 1. The outer flow regions S out are located between the outer surfaces of the strip-shaped embossing elements 13. Overall, the flow cross-section on the anode side is larger than on the cathode side.

[0031] The Fig. Figures 6 to 8 illustrate an embodiment of a bipolar plate 1, which, in addition to strip-shaped embossed elements 13, has several stud-shaped embossed elements 22. On the anode side, the stud-shaped embossed elements 22 are open to flow. In contrast, on the cathode side, the stud-shaped embossed elements 22 have the form of blind holes, which do not allow flow through them. In this case, the static function of the stud-shaped embossed elements 22 is paramount.

[0032] In the exemplary embodiment according to Fig. 9. The embossing elements 13, 22 project beyond the reference plane EE from the active field ground plane EA. The section projecting beyond the reference plane EE results in an embossing overhang PUE. Nevertheless, even in this case, viewed from the reference plane EE, the predominant height PT of the embossing elements 13, 22 is located on the anode side.

[0033] The exemplary embodiment according to Fig. 10 differs from the embodiment according to the Fig. 1 to 5 are characterized by the fact that each of the strip-shaped embossing elements 13 contains several recesses 25, in this case two per embossing element 13. Within the recesses 25, the material of the bipolar plate 1 is located at least approximately at the level of the plate intermediate plane PZ, that is, between the active field ground plane EA and the reference plane EE. The recesses 25 create cross-flow paths S oriented orthogonally to the embossing elements 13. qu formed on the anode side of bipolar plate 1.

[0034] In the exemplary embodiment according to the Fig. 11 and Fig. The structure 12 is a herringbone pattern 26. This pattern 26 comprises a large number of embossed elements 27 with a rectangular base shape. In addition, there are individual embossed elements 28 with a triangular base shape at the edge of the herringbone pattern 26. Reference symbol list 1 Bipolar plate 2 electrochemical cell, electrolysis cell 3 half-cells, anode side 4 half-cell, cathode-side 5 membrane, catalytically coated 6 Edge area 7 Port 8 Port 9 Active field 10 electrochemical system, electrolyzer 11. Plate arrangement, stack 12. Structuring 13 Embossing element, strip-shaped 14 Area of ​​maximum impression, embossing roof 15 porous transport layer, anode side 16 porous transport layer, cathode side 17 Active surface sealing 18 area intermediate zone 19 Support embossing element 20 Seal 21 insert 22 Embossing element, studded 23 frames 24 inner strip 25. Withdrawal 26 herringbone patterns 27 Embossing element with rectangular base shape 28 embossing element with triangular base shape dPa thickness of the anode-side porous transport layer dPk Thickness of the cathode-side porous transport layer dEA Distance between the reference plane and the active field ground plane EA Active Field Basic Level EE Reference Level MK Media Channel PT Embossing depth, height of the embossing elements, forming height PUE embossing overhang PZ plate intermediate level S in Flow area in the embossing element S out Flow area between embossing elements S qu Crossflow path QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 122 717 B3

[0002] DE 10 2021 206 090 A1

[0003] DE 10 2006 059 857 A1

[0004]

Claims

[1] Bipolar plate (1) of an electrochemical system (10), separating an anode side of the electrochemical system (10) from a cathode side of the electrochemical system, wherein a reference plane (EE) is defined by a boundary region (6) of the bipolar plate (1) and ports (7, 8) for supplying and draining media to and from an active field (9) of the electrochemical system (10) and from the active field (9) are located in the boundary region (6), and wherein a structuring (12) of the bipolar plate (1) is formed in the active field (9) such that an active field basic plane (EA) formed by planar material of the bipolar plate (1) is spaced parallel to the reference plane (EE), namely offset towards the cathode side, and individual embossing elements (13, 22) project from the active field basic plane (EA) towards the anode side. [2] Bipolar plate (1) according to claim 1, characterized by, that the embossing elements (13, 22) - viewed from the reference plane (EE) - are located on the cathode side to at least 60% of their height (PT). [3] Bipolar plate (1) according to claim 1 or 2, characterized by , that between the boundary region (6) and the structuring (12) given in the active field (9) an intermediate region (18) of the bipolar plate (1) is formed, in which a plate intermediate plane (PZ) formed by planar material is arranged parallel between the reference plane (EE) and the active field base plane (EA), wherein support embossing elements (19) project out from the plate intermediate plane (PZ) in the direction towards the anode side while keeping flow cross-sections clear. [4] Bipolar plate (1) according to any one of claims 1 to 3, characterized by , that several embossing elements (13) formed in the active field (9) are arranged parallel to each other and each has an elongated shape, with cross-flow paths (S qu) are formed by recesses (25) formed within the embossing elements (13), which are arranged such that a series of recesses (25) formed by a plurality of embossing elements (13) is oriented perpendicular to the longitudinal direction of the embossing elements (13). [5] Bipolar plate (1) according to any one of claims 1 to 4, characterized by , that the free flow cross-sections formed on the anode side by the structuring (12) are larger than the free flow cross-sections formed on the cathode side, wherein at least a subset of the embossing elements (22) is knob-shaped, so that the embossing elements (22) in question are open to flow on the anode side. [6] Bipolar plate (1) according to any one of claims 1 to 3, characterized by , that the structuring (12) forms a herringbone pattern (26). [7] Plate arrangement (11) for an electrochemical system (10), comprising a bipolar plate (1) designed according to claim 1, and a frame (23) between which the bipolar plate (1) is inserted, wherein the bipolar plate (1) is located between an anode-side porous transport layer (15) and a cathode-side porous transport layer (16). [8] Plate arrangement (11) according to claim 7, characterized by , that the active field (9) is framed by a seal (17) which contacts a proton-permeable, catalytically coated membrane (5), wherein the anode-side porous transport layer (15) rests on the membrane (5) on the side facing away from the seal (17) and has a larger area than the cathode-side porous transport layer (16), and wherein the seal (17) lies in a common plane with the cathode-side porous transport layer (16). [9] Plate arrangement (11) according to claims 4 and 8, characterized by, that between the anode-side porous transport layer (15) and at least one of the ports (7) media channels (MK) are formed, which connect to the flow cross-sections kept free between the support embossing elements (19) towards the active field (9). [10] Electrolyzer (10) comprising at least one plate arrangement (11) according to claim 7.

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