Stack of electrochemical cells and plate-shaped element of a cell stack

Abstract

A plate-shaped element (10) of a cell stack (2) of an electrochemical system (1) has a plurality of perforations (13, 21, 22, 23, 25) and a structuring (14) on at least one side. The structuring (14) comprises a coolant guide structure (15, 16) through which a first coolant path (15) and a second coolant path (16) are formed, each of which has an inlet section (17), a central section (18) extending from the inlet section (17) and fanning out, describing at least one meander arc (19), and an outlet section (20) adjoining the central section (18) that is narrower than the central section (18).

Description

[0001] The invention relates to a stack of electrochemical cells, for example fuel cells, electrolysis cells, or redox flow cells. Furthermore, the invention relates to a plate-shaped element suitable for use in such a cell stack.

[0002] A plate-shaped element, namely an electrode plate, for an electrolysis system is known, for example, from DE 10 2022 112 583 A1. The known electrode plate comprises an active field and a frame region surrounding it. While the frame region is formed from undeformed sheet metal lying in a base plane, the active field has an embossed structure with raised and recessed embossed elements.

[0003] The documents US 2020 / 0144647 A1 and US 2020 / 0176803 A1, which belong to the same patent family, deal with the production of fuel cell components using additive processes. Among other things, a barrier layer and a catalytic layer are to be additively constructed. In one embodiment, a fuel cell can be manufactured using only an additive manufacturing machine.

[0004] US Pat. No. 6,838,203 B2 disclosed a monolithic fuel cell. Suitable manufacturing processes include stereolithography, selective laser sintering, and LOM (laminated object manufacturing). Starting materials for additive manufacturing can be in the form of pastes, for example.

[0005] EP 2 107 628 B1 deals, among other things, with connections between metallic and non-metallic components in the production of a fuel cell module. Specifically, it proposes to crosslink a pre-crosslinked compound made of solid rubber both with a porous layer and with a separator.

[0006] The invention is based on the object of achieving progress in the production of electrochemical cell stacks and their components compared to the cited prior art, particularly with regard to manufacturing technology.

[0007] This object is achieved according to the invention by a plate-shaped element having the features of claim 1. The plate-shaped element is suitable for installation in a cell stack of an electrochemical system according to claim 9. The cell stack is, for example, an electrolysis cell stack. Alternatively, the cell stack can be designed, for example, as a stack of fuel cells or redox flow cells.

[0008] The plate-shaped element according to the application has a plurality of perforations and a structuring on at least one side. The structuring of the plate-shaped element comprises a coolant guide structure, which forms two coolant paths, each comprising an inflow section, a central section extending from the inflow section, fanning out and describing at least one meandering arc, and an outflow section adjoining the central section and narrowing compared to the central section according to the dimensions of the inflow section. In particular, the width of the inflow section corresponds to the width of the outflow section. Alternatively, the inflow and outflow sections can have different widths.

[0009] In addition to the coolant conducting structure, the plate-shaped element can be provided with additional structures in a variety of ways, each of which serves a function within the cell stack, i.e., the stack of electrochemical cells. The features of the coolant conducting structure defined in claim 1 provide a basis for large-area, low-resistance cooling, while at the same time leaving sufficient space for the placement of additional structures separated from the coolant flow.

[0010] The invention is based on the idea that cell stacks of electrochemical systems are constructed from a multitude of flat individual components. Depending on the degree of integration of the individual components, technical and logistical challenges can arise at various points in the manufacturing process. If individual components are used, each of which is constructed from the same material and has a simple shape, not only does the handling of a multitude of different individual parts become necessary, but the issue of very long tolerance chains must also be considered when assembling the cell stack. Especially for systems that carry hydrogen, very high requirements must be met with regard to tightness, whereby geometric deviations from target values ​​can add up within the cell stack.However, if larger pre-assembled assemblies are assembled to form the final product, i.e., cell stacks, in addition to a one-time inspection of the final product, many individual testing steps, including leak testing, must be performed in upstream production processes. In addition, the assembly of geometrically complex pre-products with non-uniform material construction is more complex than the assembly of simpler, flat, metallic base products.

[0011] Based on these considerations, the plate-shaped element according to the application provides a component of a cell stack constructed from a single material. In addition to its function as a cooling element with a suitable coolant conduction structure, for example, including cooling fins, it also provides additional functions that can be combined in a variety of ways. When used in an electrolysis cell stack, the plate-shaped element can, for example, realize the following functions: - Pole plate of the electrochemical cell, - Cell frame, enclosing an active field, - Distribution panel for process water and / or other operating media, - collector fields, especially for oxygen, hydrogen and water, - Mountings for seals.

[0012] The seals to be inserted into the receptacles provided by the plate-shaped element can be, for example, cord-shaped seals, particularly O-ring seals. In-situ formed seals in the form of injection-molded or pressed seals can also be provided. The installation of polymer- or metal-based flat seals on the plate-shaped element is also possible.

[0013] Regardless of the type of electrochemical system, a mirror symmetry exists between the two coolant paths within the plate-shaped element. For example, each coolant path contains two or more meandering arcs connected in series.

[0014] The inflow and outflow sections of the coolant paths can be aligned in particular along the diagonals of the plate-shaped element, assuming a rectangular or square basic shape of the said element intended for installation in a plate stack.

[0015] According to this design, there are a total of four straight inlet and outlet sections, with a V-shaped arrangement with two separate V-shaped limbs on each of the four sides of the plate-shaped element. Each V-shaped limb is formed by one of the inlet or outlet sections.

[0016] A pair of slot-shaped openings for media passage can be arranged between the two inflow sections, positioned along a common straight line. Similarly, two slot-shaped openings for media passage can be integrated into the plate-shaped element between the two outflow sections, positioned along a common straight line, with the two aforementioned straight lines being parallel to each other.

[0017] Two additional parallel straight lines can be drawn through the center of an opening in the plate-shaped element, to which one of the inflow sections is connected, and through the center of the opening to which the corresponding outflow section is connected. The entire set of slot-shaped openings for media passage can be arranged between the latter two straight lines.

[0018] Optionally, a linear channel structure attributable to the structuring of the plate-shaped element, directed in a star shape toward the center of the plate-shaped element and located outside the meandering curves, extends from individual or all of the slot-shaped openings serving as media feedthroughs. All pairs of slot-shaped openings can be arranged within a rectangular area, the corners of which are formed by the centers of the openings, each of which is connected to an inlet or outlet section.

[0019] Various designs of the plate-shaped element are characterized by being structured on exactly one side, while the other side is flat. Alternatively, both sides of the plate-shaped element can be three-dimensionally structured. In this case, water and gas, for example, can be channeled and distributed on one of the two structured sides.

[0020] Within the fully assembled cell stack, the plate-shaped element can contact another plate-shaped element of the same shape and / or at least one other metallic or non-metallic element.

[0021] An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. The drawings show, in simplified form: Fig. 1 a cell stack of an electrochemical system in a schematic, incomplete representation, Fig. 2 a plate-shaped element of the cell stack made of sheet metal and having a structure according to Fig. 1.

[0022] An electrochemical system, designated 1 overall, is designed in this case as an electrolyzer for producing hydrogen from water. The core component of the electrolyzer 1 is a cell stack 2, also referred to as a stack for short, which comprises a plurality of electrochemical cells 3, i.e., electrolysis cells.

[0023] Each electrolysis cell 3 is constructed from two half-cells 4, 5, with a membrane 6 separating the two half-cells 4, 5 from each other. Gas-permeable material within the half-cells 4, 5 is designated 7. Two end plates 8, 9 define the entire stack 2. The end plates 8, 9 contain openings 11 for the passage of coolant, as well as openings 12 for the passage of operating media of the electrochemical system 1. The entire stack 2 is braced by tie rods (not shown). The tie rods are inserted through openings (not shown) in the end plates 8, 9, which are aligned with openings 13 located in numerous plate-shaped elements 10 of the cell stack 2.

[0024] The plate-shaped elements 10 are sheet metal parts with a one-sided structuring 14. The structuring 14 comprises a first coolant path 15 and a second coolant path 16, which are collectively referred to as a coolant conduction structure 15, 16. Each coolant path 15, 16 is formed by an inflow section 17, a central section 18, and an outflow section 20. Within each coolant path 15, 16, the central section 18 is formed by two meandering bends 19 arranged one behind the other. The inflow section 17 adjoins a circular opening 21 in the present case, through which a fluid-conducting connection is established with one of the openings 11. In a similar manner, an opening 22 adjoining the outflow section 20, which is also circular and allows the discharge of coolant, is connected to one of the further openings 11 in the end plates 8, 9.

[0025] The inlet and outlet sections 17, 20 lie on the two diagonals of the approximately square plate 10. The coolant paths 15, 16, which are formed by the structuring 14 of the plate 10, i.e., the plate-shaped element, each comprise a plurality of coolant channels 26 running parallel to one another. Directly adjacent to the openings 21, 22, i.e., within the inlet and outlet sections 17, 20, the individual coolant channels 26 lie close to one another. As soon as the coolant path 15, 16 merges into the central section 18, i.e., the meandering curves 19, the bundle of coolant channels 26 expands, which is equivalent to a widening of the coolant paths 15, 16.

[0026] Overall, the four inlet and outlet sections 17, 20 roughly describe an X-shape, with the four meandering curves 19 located in the center of this X-shaped structure in a central rectangular area of ​​the plate-shaped element 10. Two adjacent inlet and outlet sections 17, 20 can also be considered incompletely formed, spaced-apart V-shaped legs. Between each of the two inlet-side V-shaped legs and between each of the two outlet-side V-shaped legs, there are two slot-shaped openings 23 arranged along a common straight line for the passage of operating media of the stack 2.

[0027] Both the side of the plate-shaped element 10 provided with the structuring 14 and the opposite flat plate side, designated 27, exhibit multiple symmetries. Firstly, there is a symmetry with respect to a mirror plane that intersects the plate-shaped element 10 centrally and lies between the first coolant path 15 and the second coolant path 16. Secondly, there is a mirror symmetry with respect to another mirror plane that intersects the first mirror plane orthogonally and lies centrally between the openings 21 on the one hand and the openings 22 on the other. As shown in Fig.As indicated in Figure 1, closed flow cross-sections of the coolant channels 26 can be formed by two plate-shaped elements 10 with their structures 14 lying on top of one another, with seals not shown. Alternatively, each plate-shaped element 10 of the stack 2 can contact a flat plate in a sealed manner. Electrical connections of the stack 2 and fluid-carrying lines connected to the stack 2 are not shown in the figures. The entire electrochemical system 1 can comprise a plurality of similar or different stacks 2. List of reference symbols 1 Electrochemical system, electrolyzer 2 cell stacks, stack 3 Electrochemical cell, electrolysis cell 4 half-cell 5 half-cell 6 Membran 7 gas-permeable material 8 End plate 9 End plate 10 plate-shaped element 11 Opening for the passage of coolant 12 Opening for the passage of operating media 13 Opening for inserting a tension rod 14 Structuring of the plate-shaped element 15 first coolant path 16 second coolant path 17 Inflow section 18 Middle section 19 meander arch 20 outflow section 21 Opening for the introduction of coolant 22 Opening for the discharge of coolant 23 slot-shaped opening for operating media 24 - 25 - 26 Coolant channel 27 flat plate side QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2022 112 583 A1

[0002] US 2020 / 0144647 A1

[0003] US 2020 / 0176803 A1

[0003] US 6,838,203 B2

[0004] EP 2 107 628 B1

[0005]

Claims

[1] Plate-shaped element (10) of a cell stack (2) of an electrochemical system (1), having a plurality of openings (13, 21, 22, 23) and an at least one-sided structuring (14) which comprises a coolant conducting structure (15, 16), wherein a first coolant path (15) and a second coolant path (16) are formed by the coolant conducting structure (15, 16), which each have an inflow section (17), a central section (18) extending from the inflow section (17), fanning out and describing at least one meandering arc (19), and an outflow section (20) adjoining the central section (18) and narrower than the central section (18). [2] Plate-shaped element (10) according to claim 1, characterized by a mirror symmetry between both coolant paths (15, 16). [3] Plate-shaped element (10) according to claim 1 or 2, characterized bythat at least two meander bends (19) exist per coolant path (15, 16). [4] Plate-shaped element (10) according to one of claims 1 to 3, characterized by that the inflow and outflow sections (17, 20) are aligned along the diagonals of the plate-shaped element (10). [5] Plate-shaped element (10) according to claim 4, characterized by that between two inflow sections (17) and between two outflow sections (20) a pair of slot-shaped openings (23) for media passage, each placed along a common straight line, is arranged. [6] Plate-shaped element (10) according to claim 5, characterized bythat all pairs of slot-shaped openings (23) are arranged between two mutually parallel straight lines, which are each determined by the position of the center point of an opening (21) to which an inflow section (17) adjoins, and by the position of the center point of an opening (22) to which an outflow section (20) adjoins. [7] Plate-shaped element (10) according to one of claims 1 to 6, characterized by that it has a square basic shape. [8] Plate-shaped element (10) according to one of claims 1 to 7, characterized by that it is structured on exactly one side, whereas the other side is flat. [9] Cell stack (2) of an electrochemical system (1), comprising a plurality of plate-shaped, mutually parallel elements (10), each formed according to one of claims 1 to 8. [10] Cell stack (2) according to claim 9, characterized bythat it is designed as an electrolysis cell stack for hydrogen production.

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