Plate-like element of a cell stack, and cell stack

Abstract

The invention relates to a plate-like element (10) of a cell stack (2) of an electrochemical system (1), having a first plate side (26), a second plate side (27), a plurality of openings (13, 21, 22, 23, 23') and a first structure (14) for forming a flow field for coolant and several further structures (14') for forming distributors for operating media on the first plate side (26). The structure (14) comprises a coolant conducting structure (15, 16) through which a first coolant path (15) and a second coolant path (16) arranged mirror-symmetrically thereto are formed, each of which have, starting from one of the openings (21), an elongate inflow portion (17), a centre portion (18) which starts from the inflow portion (17), fans out and describes at least one meandering bend (19), and an elongate outflow portion (20) which adjoins the centre potion (18) and is narrower than the centre portion (18). A longitudinal axis (30) of the inflow portion (17) of the first coolant path (15) matches a longitudinal axis (30) of the outflow portion (20) of the second coolant path (16), and a longitudinal axis (30') of the inflow portion (17) of the second coolant path (16) matches a longitudinal axis (30') of the outflow portion (20) of the first coolant path (15). The invention also relates to a cell stack (2) comprising a plurality of such plate-like elements (10) which are parallel to one another.

Description

[0001] Plate-shaped element of a cell stack and cell stack

[0002] The invention relates to a plate-shaped element of a cell stack of an electrochemical system comprising electrochemical cells, for example fuel cells, electrolysis cells, or redox flow cells. Furthermore, the invention relates to such a cell stack.

[0003] A plate-shaped element, namely an electrode plate, for an electrolysis system is known, for example, from DE 10 2022 110 122 A1. This electrolysis system features a coolant circuit that runs hermetically separated from the process water used to produce hydrogen. It includes an anode plate and a spaced-apart cathode plate, with the anode plate acting as a heat exchanger plate integrated into the coolant circuit. The anode plate and the cathode plate are formed from two half-sheets that together form a bipolar plate and have different surface areas and wall thicknesses.

[0004] 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, in particular with regard to manufacturing aspects and the achievable cooling performance.

[0005] 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 10.

[0006] 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. The plate-shaped element according to the invention has a first plate side, a second plate side, and a plurality of openings, as well as a first structure for forming a flow field for coolant and several further structures for forming distributors for operating media on the first plate side.The first structuring of the plate-shaped element comprises a coolant guide structure, which forms a first coolant path and a second coolant path arranged mirror-symmetrically thereto, each of which has an elongated inflow section starting from one of the openings, a central section fanning out from the inflow section and describing at least one meandering arc, and an elongated outflow section adjoining the central section and narrowing compared to the central section in accordance with the dimensions of the inflow section. A longitudinal axis of the inflow section of the first coolant path coincides with a longitudinal axis of the outflow section of the second coolant path, and a longitudinal axis of the inflow section of the second coolant path coincides with a longitudinal axis of the outflow section of the first coolant path.

[0007] The plate-shaped element is constructed in one or two parts in order to minimize the number of components in an electrochemical system. The plate-shaped element is preferably formed from one or two solid components, the structuring of which is carried out by milling or etching from a solid material, in particular steel. In particular if the plate-shaped element is used in high-pressure electrolysis, plate thicknesses in the millimeter range, preferably in the range of 1 to 10 mm, are required in order to ensure corresponding stability. If it is constructed in two parts, the plate-shaped element preferably has the first structuring for forming the flow field for coolant on a flow field insert element, which can be inserted in a form-fitting manner into a recess on the first side of the plate.

[0008] 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. In particular, there is also a mirror symmetry between the inflow section and the outflow section of the respective coolant path, i.e., the first coolant path and the second coolant path.

[0009] In addition to the coolant conduction structure, the plate-shaped element can be provided with a variety of additional structures that serve a function within the cell stack, i.e., the stack of electrochemical cells. The features of the coolant conduction 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. Due to the special arrangement of the inlet and outlet sections on the first plate side, the corner areas in a cell stack, which are often affected by heat buildup, can also be exposed to coolant over a larger area, thus significantly increasing the cooling performance.

[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 regarding leak tightness must be met, 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, non-uniformly constructed pre-products is more complex than the assembly of simpler, flat, metallic 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:

[0012] - Pole plate of the electrochemical cell,

[0013] - Cell frame, enclosing an active field,

[0014] - Distribution panel for process water and / or other operating media,

[0015] - collector fields, especially for oxygen, hydrogen and water,

[0016] - Mountings for seals.

[0017] 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.

[0018] 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 may have two or more meandering curves connected in series. The longitudinal axes of the inlet and outlet sections are aligned along the diagonals of the plate-shaped element, assuming a rectangular or square basic shape for the aforementioned plate-shaped element intended for installation in a plate stack.

[0019] According to this embodiment, there are a total of four elongated inlet and outlet sections, each of which is straight and preferably rectangular or approximately rectangular in plan view. A V-shaped arrangement with two separate V-shaped limbs is defined on each of the four sides of the plate-shaped element. Due to the selected shape of the periphery of the openings for the inlet and outlet of coolant, the inlet and outlet sections may only have an approximately rectangular shape in plan view. Each V-shaped limb is formed by one of the inlet or outlet sections.

[0020] At least one pair of slot-shaped openings, positioned along a common straight line, for the passage of operating media can be arranged between the two inflow sections. Similarly, at least two slot-shaped openings, positioned along a common straight line, for the passage of operating media can be integrated into the plate-shaped element between the two outflow sections, wherein the two said straight lines are parallel to each other. Optionally, a further pair of slot-shaped openings, positioned along a common straight line, for the passage of operating media can be arranged between an inflow section and an outflow section along the respective coolant path.

[0021] Two additional parallel straight lines can be laid 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. All of the slot-shaped openings for the passage of operating media can be arranged between the last two straight lines. Optionally, a linear channel structure attributable to the structuring of the plate-shaped element, directed overall in a star shape toward the center of the plate-shaped element and located outside the meandering curves, emanates from individual or all of the slot-shaped openings serving as the passage of operating media.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, to which an inflow or outflow section is connected.

[0022] Various designs of the plate-shaped element can be characterized by being structured on precisely the first plate side, in this case the coolant side, while the second plate side of the plate-shaped element is flat. Alternatively, both sides of the plate-shaped element can be three-dimensionally structured. In this case, operating media, such as process water and gas in the case of an electrolyzer, can be conducted and distributed on the second plate side.

[0023] The one- or two-part plate-shaped element preferably has a rectangular recess on the second side of the plate for accommodating an open-porous material in the form of one or more porous transport layers. The recess facilitates the correct positioning of the transport layer(s).

[0024] The term "porous transport layer" is particularly familiar in electrolyzers, while in the field of fuel cells, the term "gas diffusion layer" is analogous. Such a transport layer can also consist of two or more different open-pore layers, with the pore diameters typically decreasing toward the membrane in the cell stack. Such a transport layer can also comprise layers of different materials.

[0025] In the case that it is formed in two parts, the plate-shaped element preferably has the first structuring for forming the flow field for coolant on a flow field insert element, which can be inserted in a form-fitting manner into a recess on the first plate side.

[0026] A circumferential seal is preferably arranged on the circumference of the flow field insert element, which seal is injection-molded onto the flow field insert element and ensures a play-free and form-fitting insertion into the recess on the first plate side.

[0027] The plate-shaped element itself can furthermore have a circumferential, molded-on seal on its circumference, which can serve to seal against other components in a cell stack.

[0028] 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. Two plate-shaped elements are preferably combined in such a way that the first plate sides lie on top of each other, allowing the coolant to flow between them.

[0029] In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawings. In each case, simplified:

[0030] Fig. 1 shows a cell stack of an electrochemical system in a schematic representation,

[0031] Fig. 2 shows a one-piece plate-shaped element on the first plate side according to Fig. 1,

[0032] Fig. 3 is a three-dimensional view of another one-piece plate-shaped element on the first plate side,

[0033] Fig. 4 is a three-dimensional view of the further one-piece plate-shaped element according to Fig. 3 on the second plate side, Fig. 5 is a flow field insert element for forming a two-piece plate-shaped element in a three-dimensional view, and

[0034] Fig. 6 shows a plate in three-dimensional view for inserting the flow field insert element according to Figure 5 to form a two-part plate-shaped element.

[0035] An electrochemical system, designated 1 in Figure 1, is designed in this case as an electrolyzer for producing hydrogen from water or process water. The core component of the electrolyzer 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.

[0036] 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. Open-porous material in the form of at least one porous transport layer within the half-cells 4, 5 is designated 7, 7'. Two end plates 8, 9 delimit the entire stack or cell stack 2. In the end plates 8, 9 there are openings 11, 11' for the passage of coolant, in particular cooling water, as well as openings 12, 12' for the passage of operating media, in particular process water and reaction products such as oxygen and hydrogen, of the electrochemical system 1. The entire stack or cell 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.

[0037] The plate-shaped elements 10 (see Figure 2) are solid milled and / or etched metal parts with a first plate side 26, which have a first structure 14 for forming a flow field for coolant and several further structures 14' for forming distributors for operating media. The first structure 14 comprises a first coolant path 15 and a second coolant path 16, which are collectively referred to as a coolant guide 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 to one of the openings 11, 11' is established.In a similar manner, an opening 22, which is also circular and adjoins the outflow section 20 and allows the discharge of coolant, is connected to one of the further openings 11, 11' in the end plates 8, 9. Due to the selected shape of the circumference of the openings 21, 22, here circular, for the inlet and outlet of coolant, the inlet and outlet sections 17, 20 have only an approximately rectangular shape in the plan view of the first plate side 26. Overall, however, the inlet and outlet sections 17, 20 on the first plate side 26 form elongated sections that are attached at an angle to the corners of the first structuring 14.

[0038] The inflow and outflow sections 17, 20 lie on the two diagonals of the approximately square plate 10. The diagonals correspond to the longitudinal axes 30, 30' of the inflow sections 17 and outflow sections 20. The longitudinal axis 30 of the inflow section 17 of the first coolant path 15 coincides with the longitudinal axis 30 of the outflow section 20 of the second coolant path 16. The longitudinal axis 30' of the inflow section 17 of the second coolant path 16 coincides with the longitudinal axis 30' of the outflow section 20 of the first coolant path 15. The coolant paths 15, 16, which are formed by the structuring 14, 14' of the one-piece plate-shaped element 10, each comprise a plurality of coolant channels 28 running parallel to one another; see Figure 3 for details.Directly adjacent to the openings 21, 22, i.e., within the inlet and outlet sections 17, 20, the individual coolant channels 28 are located close to one another. As soon as the coolant path 15, 16 merges into the central section 18, i.e., into the meandering bends 19, the bundle of coolant channels 28 expands, which is equivalent to a widening of the coolant paths 15, 16. Overall, the four inlet and outlet sections 17, 20 roughly describe an X-shape, with the four meandering bends 19 located in the center of this X-shaped structure in a central rectangular area of ​​the plate-shaped element 10. Two inlet and outlet sections 17, 20 arranged next to one another can also be understood as incompletely formed, spaced-apart V-legs.Between each of the two inflow-side V-legs and between each of the two outflow-side V-legs there are two slot-shaped openings 23, 23' (see also Figure 4) arranged along a common straight line for the passage of operating media of the stack or cell stack 2.

[0039] Both the first plate side 26 of the plate-shaped element 10, provided with the structuring 14, 14', and the opposite, flat second plate side, designated 27, exhibit multiple symmetries. Firstly, there is 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 mirror symmetry with respect to a further 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 indicated in Figure 1, closed flow cross-sections of the coolant channels 28 can be formed by placing two plate-shaped elements 10 with their structurings 14, 14' on top of one another, although seals are not shown here.Alternatively, each plate-shaped element 10 of the stack or cell stack 2 can contact a flat plate in a sealed manner. Electrical connections of the stack or cell stack 2 and fluid-carrying lines connected thereto are not shown in the figures. The entire electrochemical system 1 can comprise a plurality of similar or different stacks or cell stacks 2.

[0040] Fig. 3 shows a three-dimensional view of another one-piece plate-shaped element 10 on the first plate side 26. The same reference numerals as in Figures 1 and 2 indicate the same elements. Fig. 4 shows a three-dimensional view of the other one-piece plate-shaped element 10 according to Figure 3 on the second plate side 27. The same reference numerals as in Figure 3 indicate the same parts. The second plate side 27 here has a recess 29 for receiving an open-porous material in the form of at least one porous transport layer 7, 7'.

[0041] Fig. 5 shows a three-dimensional view of a flow field insert element 24. The same reference numerals as in Figure 3 indicate the same elements. The flow field insert element 24 has openings 21 and 22' for the inlet and outlet of coolant. A sealing element 25' is molded onto the circumference of the flow field insert element 24.

[0042] Fig. 6 shows a three-dimensional view of a plate for inserting the flow field insert element 24 according to Figure 5 into a recess 29', forming a two-part plate-shaped element 10 with a view of the first plate side 26. The sealing element 25' of the flow field insert element 24 enables play-free and form-fitting insertion. The same reference numerals as in Figure 3 indicate the same parts. The openings 21', 22' of the flow field insert element 24 lie over the openings 21, 22 in the plate. A sealing element 25 is injection-molded onto the circumference of the plate to accommodate the flow field insert element 24.

[0043] List of reference symbols

[0044] Electrochemical system, electrolyzer

[0045] cell stack, stack

[0046] Electrochemical cell, electrolysis cell

[0047] Half-cell

[0048] Half-cell

[0049] Membrane, 7' open-porous material, porous transport layer

[0050] End plate

[0051] End plate 0 plate-shaped element 1, 11 ' Opening for the passage of coolant2, 12' Opening for the passage of operating media3 Opening for the insertion of a tie rod4 Structuring of the plate-shaped element - Flow field for coolant distribution4' Structuring of the plate-shaped element -

[0052] Distributor for operating medium distribution 5 First coolant path 6 Second coolant path 7 Inflow section 8 Middle section 9 Meander bend 0 Outflow section 1 Opening for the introduction of coolant 2 Opening for the discharge of coolant 3, 23' Slot-shaped opening for operating media 4 Flow field insert element 5, 25' Sealing element 6 First plate side Second plate side

[0053] Coolant channel, 29' recess, 30' longitudinal axis

Claims

Patent claims 1 . Plate-shaped element (10) of a cell stack (2) of an electrochemical system (1), comprising a first plate side (26), a second plate side (27) and a plurality of openings (13, 21, 22, 23, 23'), as well as a first structuring (14) for forming a flow field for coolant and a plurality of further structurings (14') for forming distributors for operating media on the first plate side (26), wherein the first structuring (14) comprises a coolant conducting structure (15, 16), wherein a first coolant path (15) and a second coolant path (16) arranged mirror-symmetrically thereto are formed by the coolant conducting structure (15, 16), which each comprise, starting from one of the openings (21), an elongated inflow section (17), a central section (18) starting from the inflow section (17), fanning out and describing at least one meandering arc (19), and one adjoining the central section (18),have an elongated outflow section (20) that is narrower than the central section (18), wherein a longitudinal axis (30) of the inflow section (17) of the first coolant path (15) coincides with a longitudinal axis (30) of the outflow section (20) of the second coolant path (16) and a longitudinal axis (30') of the inflow section (17) of the second coolant path (16) coincides with a longitudinal axis (30') of the outflow section (20) of the first coolant path (15).

2. Plate-shaped element (10) according to claim 1, characterized by a mirror symmetry between the inflow section (17) and the outflow section (20) of each coolant path (15, 16).

3. Plate-shaped element (10) according to claim 1 or 2, characterized in that at least two meandering bends (19) exist per coolant path (15, 16).

4. Plate-shaped element (10) according to one of claims 1 to 3, characterized in that the longitudinal axes (30, 30') are aligned along the diagonals of the plate-shaped element (10).

5. Plate-shaped element (10) according to claim 4, characterized in that between two inflow sections (17) and between two outflow sections (20) at least one pair of slot-shaped openings (23), each placed along a common straight line, is arranged for the passage of operating media, and that optionally furthermore between an inflow section (17) and an outflow section (20) a further pair of slot-shaped openings (23), each placed along a common straight line, is arranged for the passage of operating media along the respective coolant path (15, 16).

6. Plate-shaped element (10) according to claim 5, characterized in that all pairs of slot-shaped openings (23) are arranged between two mutually parallel straight lines, which are each given 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 in that it has a square basic shape.

8. Plate-shaped element (10) according to one of claims 1 to 7, characterized in that it is formed in one part or in two parts and optionally has a rectangular recess (29) on the second plate side (27) for receiving a porous transport layer (7, 7').

9. Plate-shaped element (10) according to one of claims 1 to 7, characterized in that it is formed in two parts, in that the first structuring (14) for forming the flow field for coolant is on a flow field An insert element (24) is arranged which can be inserted in a form-fitting manner into a recess (29') on the first plate side (26), and wherein a rectangular recess (29) for receiving a porous transport layer (7, 7') is optionally formed on the second plate side (27).

10. 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 9.

11. Cell stack (2) according to claim 10, characterized in that it is designed as Electrolysis cell stack designed for hydrogen production.

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