Cell frame for an electrochemical cell, electrolyzer with a stack of electrochemical cells, and method for producing a cell frame

Abstract

Cell frame (1) for an electrochemical cell, comprising a plurality of inlet openings (6) and a plurality of outlet openings (7) for a fluid, which are each arranged side by side along a periphery of the cell frame (1), wherein the cell frame (1) is formed from a fiber-reinforced plastic.

Description

[0001] 24028PW001

[0002] Schaeffler Technologies AG & Co. KG

[0003] 91074 Herzogenaurach (DE)

[0004] Sunfire SE

[0005] 01237 Dresden (DE)

[0006] Fiber-Tech Construction GmbH

[0007] 09116 Chemnitz (DE)

[0008] Sengicon GmbH

[0009] 09116 Chemnitz (DE)

[0010] Cell frame for an electrochemical cell, electrolyzer with a stack of electrochemical cells and method for manufacturing a cell frame

[0011] Description:

[0012] The present invention relates to a cell frame for an electrochemical cell and to an electrolyzer with a stack of electrochemical cells, in particular an alkaline electrolyzer. It further relates to a method for manufacturing a cell frame.

[0013] With the increasing use of renewable energies, technologies for storing the generated electrical energy are gaining in importance. One possibility is storage in the form of hydrogen, which is produced using an electrolyzer. Depending on their design, such electrolyzers can consist of stacks of electrochemical cells. Typical cells, for example, each have a steel cell frame, which can be circular or rectangular, surrounding the electrochemical cell and holding a bipolar separator plate, which can also be made of steel or ceramic and separates adjacent cells.

[0014] Typically, each cell has an inlet and an outlet for a fluid, such as an electrolyte. The placement of these openings influences the flow field within the electrochemical cell and thus local process parameters.

[0015] Similar electrochemical cells can also be used for liquid batteries, e.g. (redox) flow batteries, electrochemical water treatment systems or fuel cells.

[0016] It is an object of the present invention to provide a cell frame for an electrochemical cell which is particularly easy to manufacture and also enables particularly efficient operation.

[0017] This problem is solved by the subject matter of the independent patent claim. Advantageous embodiments and further developments are the subject matter of the dependent claims.

[0018] According to one aspect of the invention, a cell frame for an electrochemical cell is provided, comprising a plurality of inlet openings and a plurality of outlet openings for a fluid, each arranged side by side along a circumference of the cell frame. The cell frame is made of a fiber-reinforced plastic.

[0019] In particular, all inlet openings are arranged side by side on one side of the cell frame and all outlet openings on an opposite side of the cell frame.

[0020] The fluid can contain liquid and / or gaseous components. For example, the fluid contains an electrolyte, water, and / or a carrier gas. In particular, the fluid can contain gases formed when it flows out through the drain openings in the cell. The cell frame according to the invention can be used for various types of electrochemical cells. A preferred application is in the electrochemical cells of an electrolyzer, i.e., in an electrolyzer with a stack of electrochemical cells. Alternative applications of the cell frame according to the invention include, for example, electrochemical cells in liquid batteries, e.g., (redox) flow batteries, electrochemical water treatment systems, or fuel cells.

[0021] The cell frame offers the advantage that the numerous inlet and outlet openings arranged side by side allow for a relatively uniform flow field within the electrochemical cell. This enables the optimization of local process parameters towards a desired operating point, which, despite increased current density, ensures the reliable removal of the media (fluid, electrolyte, generated gases) and waste heat. The resulting high current density is crucial for the electrolyzer's high efficiency. The cell frame thus facilitates particularly efficient electrolyzer operation.

[0022] The cell frame is made of a fiber-reinforced, specifically glass fiber-reinforced, plastic. Using a plastic allows for particularly simple shaping and mass production, as the cell frame can be manufactured using a casting or lamination process, or a combination thereof. This also makes it possible to incorporate inlet and outlet openings into the cell frame with reasonable effort. While the use of unreinforced plastic typically does not provide sufficient stability for the cell frame, it has been shown that fiber-reinforced plastics can withstand the pressures exerted during electrolysis.

[0023] When inserting the fibers into the cell frame, the fibers can be positioned at particularly stressed points, such as corners of the cell frame, depending on the method used, in such a way as to absorb maximum load. The plastic can be a thermoset, but a thermoplastic can also be used.

[0024] According to one embodiment, a channel structure is formed within the cell frame, which is in flow communication with the inlet and outlet openings. In this embodiment, the inlet and outlet are integrated into the cell frame, thus eliminating the need to lay additional pipes, including their seals, when passing through the cell frame.

[0025] In the case of a cell frame made of fiber-reinforced plastic, this embodiment also has the advantage that the channel structure can be molded into the cell frame during its manufacture, thus saving process steps for the production of the cell frame.

[0026] The channel structure can, in particular, have at least one central distribution channel which has a plurality of openings that are in flow connection with the inlet openings and the outlet openings.

[0027] The central distribution channel can be formed in particular by a pipe made of fiber-reinforced plastic and having bores as openings.

[0028] This embodiment has the advantage that the central distribution channel can be manufactured particularly easily. In particular, the pipe can be prefabricated and integrated into the cell frame during its production. For this purpose, the pipe (preferably without openings) can be placed in a mold in which the cell frame is manufactured. In this case, the cell frame can be manufactured using a casting process and / or a lamination process. The fiber-reinforced plastic is then introduced into the mold. In a lamination process, for example, one or more layers of fibers are placed in the mold together with the plastic. The pipe is thus surrounded by the glass fiber-reinforced plastic and firmly integrated into the cell frame. The openings in the distribution channel can expediently be added subsequently, with the inlet and outlet openings being simultaneously incorporated into the cell frame.

[0029] According to an alternative embodiment, each inlet and / or outlet opening has a separate distribution channel in the cell frame. These separate distribution channels can, for example, extend orthogonally to the cell plane in the stacking direction through the cell frame and thus supply several successive cells in the stack.

[0030] These individual distribution channels and the inlet and outlet openings can then be formed relatively easily in the cell frame by drilling, cutting, or milling. In this variant, a central distribution channel running in the plane of the cell frame is eliminated, thus making it unnecessary to insert a pipe during the cell frame's formation. When such cells are arranged in a stack, the distribution channels of adjacent cells are preferably aligned with each other so that they form distribution channels extending in the stack direction.

[0031] According to one embodiment, the electrochemical cells have a substantially rectangular cross-section, and the inlet openings are arranged equidistantly over one side of the rectangle, and the outlet openings are arranged equidistantly over the opposite side of the rectangle.

[0032] When manufacturing the cell frame from glass fiber reinforced plastic, many different geometries of the frame and the enclosed cells can be achieved, for example, a rectangular cross-section. In this case, the inlet and outlet openings are evenly distributed on opposite sides of the rectangle to create a uniform flow field. "Substantially rectangular" here means that minor deviations from a perfect rectangle are included. In particular, a substantially rectangular cell frame can, for example, also have rounded corners.

[0033] According to an alternative embodiment, the electrochemical cells have a circular cross-section. The inlet openings are distributed across a first circular segment in one half of the circle, and the outlet openings are distributed across a second circular segment opposite the first segment in the other half of the circle. The inlet and outlet openings can have different distances between them and / or different diameters.

[0034] In particular, the distances to adjacent inlet or outlet openings can be relatively small and / or the diameter of the inlet or outlet openings can be relatively large for those inlet or outlet openings whose distance from opposite outlet or inlet openings is relatively large.

[0035] In this embodiment, it is taken into account that for a uniform flow field in the case of a circular cross-section of the cells, the inflow or outflow of fluid should not be the same at all openings, because the flow path is shorter in the boundary regions of the flow field and therefore the volume of space flowed through is not the same everywhere.

[0036] The use of fiber-reinforced plastic as the material for the cell frames advantageously allows for various manufacturing processes. Such processes can include, for example, the following steps: manufacturing or providing a mold, introducing and / or arranging the fibers (e.g., by lamination), introducing / infusing a thermoplastic or thermosetting plastic (e.g., by lamination, casting, or infusion), and / or a curing step. Various combinations of these steps are possible, or individual steps can be omitted. In particular, the introduction and / or arranging of the fibers can be carried out simultaneously with the introduction of the plastic (e.g., by lamination or prepreg processes). This also applies to casting processes when using short fibers.For the purposes of this application, the term "casting process" is intended to encompass all casting processes, with or without pressure, as well as with vacuum infusion, and in particular injection molding, casting, or vacuum infusion. The curing step can also be achieved by cooling, especially when using a thermoplastic.

[0037] According to one aspect of the invention, a method for manufacturing the described cell frame is specified, wherein the cell frame is manufactured in a casting process and / or a lamination process.

[0038] The use of a casting process and / or a lamination process using a fiber-reinforced plastic as the material for the cell frames allows for a particularly simple formation of inlet and outlet structures in the cell frame in order to achieve a uniform flow field.

[0039] In particular, a semi-finished product in the form of a tube can be inserted into the mold for the cell frame during or before casting or laminating to form a central distribution channel. Otherwise, creating a central distribution channel in a casting or laminating process would be extremely difficult. Using a semi-finished product significantly simplifies the production of the cell frame.

[0040] After casting and / or laminating, the inlet and / or outlet openings can be formed in the cell frame, simultaneously creating the openings in the tube that are in flow connection with them. This can be done, for example, by drilling, sawing, cutting, or milling. To prevent glass fibers from being exposed on the surface of these bores or openings, the edges of the bores, especially their inner surfaces, can subsequently be sealed with a plastic. This increases the cell frame's resistance to alkaline electrolytes. Exemplary embodiments of the invention are described below with reference to schematic drawings.

[0041] Figure 1 shows a cross-section through a cell frame for an electrochemical cell according to an embodiment of the invention,

[0042] Figure 2 shows a cross-section through a cell frame for an electrochemical cell according to an alternative embodiment of the invention,

[0043] Figure 3 schematically shows the relationship between the placement of the inlet and outlet openings and the flow field for a rectangular cell frame according to one embodiment of the invention and

[0044] Figure 4 schematically shows the relationship between the placement of the inlet and outlet openings and the flow field for a round cell frame according to one embodiment of the invention.

[0045] Figure 1 shows a cross-sectional view of a cell frame 1 for an electrochemical cell. This could be, for example, an electrochemical cell of an electrolyzer, a fuel cell, a liquid battery, or an electrochemical water treatment system. The cell frame 1 is made of glass fiber reinforced plastic and has a rectangular cross-section. A frame body 2 surrounds a rectangular interior 3 in which the electrodes (not shown) are arranged and which is traversed by a fluid during operation.

[0046] Channel structures for guiding the fluid are integrated into the cell frames 1. On a first side 4 of the rectangular cell frame 1, a plurality of inlet openings 6 are arranged, which are in flow communication with a central distribution channel 8. On the opposite second side 5, a plurality of outlet openings 7 are arranged, which are also in flow communication with a central distribution channel 9. Both distribution channels 8, 9 are connected to supply channels 12, each of which extends through the entire stack of cell frames 1 perpendicular to the plane spanned by the cell frames 1. In an alternative embodiment, the supply channels 12 are formed outside the cell frame 1.

[0047] The inlet openings 6 and the outlet openings 7 are formed by inlet channels 10 and outlet channels 11, which are designed, for example, as bores and which connect the distribution channels 8, 9 with the interior 3.

[0048] In the production of the cell frame 1, the distribution channels 8, 9 are inserted as a semi-finished product in the form of a tube into a mold in which the cell frame 1 is formed from a plastic and glass fibers, for example in the form of tapes or mats, using a casting and / or lamination process. In a suitable lamination process, the reinforcing fibers are, for example, impregnated with plastic and fixed in a tool until the plastic has been absorbed.

[0049] Once the cell frame 1 has cured, the inlet channels 10 and outlet channels 11 are inserted from the interior 3 into the frame body 2 to establish the flow connection between the distribution channels 8, 9 and the interior 3. Glass fibers may then be exposed on the inner walls of the inlet channels 10 and outlet channels 11. To make the cell frame 1 more durable, the inner walls of the inlet channels 10 and outlet channels 11 can subsequently be sealed with a plastic material, so that a thin layer of plastic lines the inner walls of the inlet channels 10 and outlet channels 11 and prevents direct contact between the glass fibers and the fluid.

[0050] Figure 2 shows a cross-sectional view of a cell frame 1 for an electrochemical cell according to an alternative embodiment. This embodiment, like the one described above, can be used, for example, in an electrolyzer, a fuel cell, a liquid battery, or an electrochemical water treatment system. This embodiment differs from the one shown in Figure 1 in that the distribution channels 14 and 15, which are in flow communication with the inlet channels 10 and the outlet channels 11 respectively, run perpendicular to the plane of the drawing and thus do not extend within a single cell frame 1, but rather through several cell frames 1 stacked consecutively.

[0051] Figure 3 also shows a cross-section through a rectangular cell frame 1 according to an embodiment of the invention. In this figure, however, the cell frame 1 is shown only schematically, and the inlet openings 6 and outlet openings 7 are also shown only schematically to indicate their positions and diameters on sides 4 and 5 of the frame body 2. The round cross-sections 6 and 7 shown in drawings 3 and 4 are not to be interpreted as actual round openings in the depicted section plane.

[0052] In the embodiment shown in Figure 3, the inlet openings 6 are distributed equidistantly along the first side 4 of the cell frame 1, while the outlet openings 7 are distributed equidistantly along the opposite second side 5. Adjacent inlet openings 6 and outlet openings 7 are each spaced a uniform distance a apart.

[0053] With such an arrangement of the inlet openings 6 and outlet openings 7, the flow field indicated by arrows 13 results during operation, i.e., a uniform flow from the first side 4 to the opposite second side 5 of the cell frame 1. In the embodiment shown in Figure 3, the inlet openings 6 and the outlet openings 7 all have the same diameter d.

[0054] The uniform flow field ensures uniform reaction conditions at the electrodes, which can be precisely adjusted by the inflow.

[0055] Figure 4 shows an alternative embodiment of the cell frame 1 only schematically, this embodiment differing from that shown in Figure 3 in that the cell frame 1 has a round cross-section. With such a geometry, an even more reduced flow rate is required in the edge regions of sides 4 and 5. For this purpose, the outer inlet openings 6 and outlet openings 7 have a significantly smaller diameter d than the central inlet openings 6 and outlet openings 7, with the diameter d decreasing with increasing distance from the center of sides 4 and 5.

[0056] In the embodiment shown in Figure 4, the inlet openings 6 and the outlet openings 7 are equidistantly distributed. Alternatively or in addition to varying the diameters d, the distances a could also be varied to achieve a uniform flow field. Reference numerals:

[0057] 1 cell frame

[0058] 2 Frame body 3 Interior

[0059] Page 4

[0060] Page 5

[0061] 6 Inlet opening

[0062] 7 Drainage opening

[0063] 8 distribution channel

[0064] 9 Distribution channel 10 Inlet channel

[0065] 11 Drainage channel

[0066] 12 Supply channel 13 Arrow

[0067] 14 distribution channel

[0068] 15 distribution channel

[0069] a, a' distance

[0070] d diameter

Claims

24028PW001 Patent claims:

1. Cell frame (1) for an electrochemical cell, comprising a plurality of inlet openings (6) and a plurality of outlet openings (7) for a fluid, each arranged side by side along a circumference of the cell frame (1), wherein the cell frame (1) is made of a fiber-reinforced plastic.

2. Cell frame (1) according to claim 1 , the plastic is either a thermoset or a thermoplastic.

3. Cell frame (1) according to claim 1 or 2, wherein a channel structure is formed in the cell frame (1) which is in flow connection with the inlet openings (6) and the outlet openings (7).

4. Cell frame (1) according to claim 3, wherein the channel structure has at least one central distribution channel (8, 9) which has a plurality of openings which are in flow connection with the inlet openings (6) and the outlet openings (7).

5. Cell frame (1) according to claim 4, wherein the central distribution channel (8, 9) is formed by a pipe made of fiber-reinforced plastic and having inlet and / or outlet channels (10, 11).

6. Cell frame (1) according to claim 3, wherein the channel structure comprises distribution channels (14, 15) extending perpendicular to the plane of the cell frame (1) and which are in flow communication with the inlet openings (6) and the outlet openings (7).

7. Cell frame (1) according to any one of claims 1 to 6, wherein the electrochemical cell has a substantially rectangular cross-section and the inlet openings (6) are arranged equidistantly over one side (4, 5) of the rectangle and the outlet openings (7) are arranged equidistantly over the opposite side (4, 5) of the rectangle.

8. Cell frame (1) according to any one of claims 1 to 6, wherein the electrochemical cell has a substantially circular cross-section and the inlet openings (6) are arranged distributed over a first circular segment in one half of the circle and the outlet openings (7) are arranged distributed over a second circular segment opposite the first circular segment in the other half of the circle, wherein the inlet openings (6) and the outlet openings (7) have different distances from each other and / or diameters.

9. Cell frame (1) according to any one of claims 1 to 8, where distances (a, a') to adjacent inlet or outlet openings (7) are relatively small and / or a diameter (d) of the inlet or outlet openings (7) is relatively large for those inlet or outlet openings (7) whose distance (a, a') from opposite outlet or inlet openings (6) is relatively large.

10. Electrolyzer with a stack of electrochemical cells, each surrounded by a cell frame (1) according to any one of claims 1 to 9 and through which a fluid flows.

11. Method for producing a cell frame (1) according to any one of claims 1 to 9, comprising the steps: - Providing a form, - Introducing fibers into the mold, - Introducing plastic into the mold, - Curing of the plastic.

12. Method for producing a cell frame (1) according to any one of claims 1 to 9, wherein the cell frame (1) is manufactured using a casting process and / or a lamination process.

13. Method according to claim 12, wherein a semi-finished product in the form of a tube is inserted into the mold for the cell frame (1) to form a central distribution channel (8, 9) before casting or during lamination.

14. Method according to claim one of claims 11 to 13, wherein, after casting or laminating or after curing, inlet and / or outlet channels (10, 11) and inlet and / or outlet openings (6, 7) are introduced into the cell frame and, if necessary, into the pipe.

15. Method according to claim 14, wherein the inner surfaces and / or edge areas of the inlet and / or outlet channels (10, 11) and / or the inlet and / or outlet openings (6, 7) are subsequently sealed with a plastic.

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