Stack formation of an electrolyzer or of a fuel cell

Abstract

The invention relates to a stack formation (20) of an electrolyzer (10) or of a fuel cell (10). The stack formation (20) comprises a multiplicity of individual cells (12) stacked vertically one on top of the other. The individual cells (12) comprise at least a cathode frame (22), an anode frame (24), at least one bipolar plate (26), at least one gas-diffusion layer (28), at least one porous transport layer (30) (PTL) and at least one membrane (38), wherein the stack formation (20) has a first end plate (14) and a second end plate (16), which by means of a number of clamping elements (18) clamp together the individual cells (12) arranged between the end plates (14, 16). Formed in the anode and / or cathode frame (24, 22) of the individual cells (12) there is a least one peripheral depression (40), which is connected to a drainage opening (42). The invention also relates to the use of the stack formation (20) in an electrolyzer (10) or in a fuel cell (10).

Description

[0001] Description

[0002] title

[0003] Stack structure of an electrolyzer or a fuel cell

[0004] Technical area

[0005] The invention relates to a stacked structure of an electrolyzer or a fuel cell comprising a plurality of individual cells arranged vertically stacked one above the other, each having at least one cathode frame, at least one anode frame, at least one bipolar plate, at least one gas diffusion layer, at least one porous transport layer, and at least one membrane. The stacked structure comprises a first and a second end plate that clamps the individual cells arranged between the end plates against one another using a number of clamping elements. Furthermore, the invention relates to the use of the stacked structure in an electrolyzer or in a fuel cell.

[0006] State of the art

[0007] For example, electrolyzers are used in PEM electrolysis, which can produce impure hydrogen from the raw material water, with only oxygen as a byproduct. PEM electrolyzers use so-called PEM membranes (proton exchange membranes) surrounded by water. When an electrical voltage is applied to such a membrane, protons diffuse from the anode through the membrane to the cathode. Oxygen is produced at the anode, and hydrogen at the cathode, with the two gases physically separated from each other by the membrane. The gaseous hydrogen is discharged to the cathode side, dried, and can be stored.Typically, an electrolyzer uses several individual cells, each comprising a cathode frame, a gas diffusion layer, a membrane, optionally with a catalyst, an anode frame, a porous transport layer and at least one bipolar plate, each of which is stacked on top of each other.

[0008] In each individual cell, a medium, usually water, is transported to the membrane containing the catalyst, and corresponding reaction products, such as oxygen, hydrogen, and residual water, are removed. This transport of media places high demands on the tightness of the individual cells stacked vertically. Sealing the individual cells is complicated by the fact that such electrolysis is typically carried out at elevated pressures (on the order of 40 bar), and tightness must be ensured over the entire service life of a stack suitable for electrolysis. The service life is currently approximately 40,000 hours.

[0009] Disclosure of the invention

[0010] According to the invention, a stacked structure of an electrolyzer or a fuel cell is proposed, comprising a plurality of individual cells arranged vertically one above the other, each comprising at least one cathode frame, at least one anode frame, at least one bipolar plate, at least one gas diffusion layer, at least one porous transport layer, and at least one membrane. The stacked structure has a first end plate and a second end plate, which clamp the individual cells arranged between the end plates against one another using a number of clamping elements. At least one circumferential recess is formed in the anode and / or cathode frame of the individual cells, which is connected to at least one discharge opening.

[0011] The solution proposed according to the invention makes it possible to collect and selectively drain gaseous or liquid media, water or water-containing media, in each individual cell within the stack structure. This makes it possible to safely operate such a stack structure with a certain permissible level of leakage. In an advantageous development of the stack structure proposed according to the invention, the anode and / or cathode frames are vulcanized.

[0012] In a further advantageous embodiment of the stack structure proposed according to the invention, the at least one circumferential recess in the individual cells is designed as a channel or as a groove.

[0013] In a further advantageous embodiment of the stack structure proposed according to the invention, gaseous or liquid media, water or water-containing media are collected in the at least one circumferential recess.

[0014] In the stack structure proposed according to the invention, the at least one discharge opening is advantageously arranged in a corner region of the anode and / or cathode frame.

[0015] The stack structure proposed according to the invention is advantageously designed such that, when the individual cells are stacked one above the other, discharge openings arranged one above the other form at least one drainage channel.

[0016] Furthermore, the invention relates to a method for operating a stack structure, wherein the following method steps are carried out: a) collecting liquid and / or gaseous media, water or water-containing media, in the at least one circumferential recess of the individual cells, b) selectively draining the media collected according to method step a) into a drainage channel, c) determining the quantity of drained media and d) evaluating the condition of the stack structure to detect emerging aging effects.

[0017] Finally, the invention relates to the use of the stack structure in an electrolyzer for producing gaseous hydrogen or in a fuel cell or in a fuel cell assembly for powering a vehicle. Advantages of the invention

[0018] The solution proposed by the invention advantageously makes it possible to collect and specifically divert any leaks that occur with a slight modification of the individual cells arranged in the individual structure. This opens up the possibility of safely operating a PEM electrolysis stack structure, in particular with a certain degree of leakage. Because leaks can be permitted that can be safely and specifically diverted, higher tolerances for the stacked individual cells can be permitted. Furthermore, the requirements for tightness can be somewhat reduced, since higher tolerances can be permitted and reliable removal of leakage quantities is ensured by the solution proposed by the invention. In a particularly advantageous manner, the at least one circumferential recess in the individual cells can be designed as a groove, a channel, a trough, or the like.In particular, it is possible to connect the at least one circumferential recess to a discharge opening, which can be formed in particular in the corner region of the surface of the individual cells. In addition to the additional media channels for transporting oxygen and hydrogen or water, the discharge channel is formed by aligning the discharge openings arranged in a corner region of individual cells stacked vertically one above the other and forming a continuous channel within the stack structure proposed by the invention, which channel extends through it essentially from the first, upper end plate to the second, lower end plate.

[0019] The method proposed according to the invention allows conclusions to be drawn about the aging state of individual cells within the stack and / or the entire stack from the quantity of leaks derived from the stack structure. This allows emerging aging effects to be detected early, so that remedial measures can be initiated in a timely manner. Furthermore, a chemical analysis of the leaks that have occurred, for example, elemental analysis using ICP-MS, allows conclusions to be drawn about their causes, such as membrane degradation and corrosion. Insights into these phenomena are extremely helpful, particularly during the development phase, as well as in defining remedial measures or in risk analysis. Brief description of the drawings

[0020] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0021] They show:

[0022] Figure 1 is a perspective view of an electrolyzer,

[0023] Figure 2 is a schematic representation of a single cell within the stack structure according to Figure 1 and

[0024] Figure 3 is a schematic representation of a cathode or anode frame with a circumferential recess for collecting leaks including a discharge opening.

[0025] Embodiments of the invention

[0026] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0027] Figure 1 shows a schematic representation of an electrolyzer in perspective.

[0028] The electrolyzer 10 shown in Figure 1 comprises a plurality of individual cells 12 stacked vertically one above the other. The plurality of individual cells 12 of the stack structure 20 shown in Figure 1 is enclosed by a first, upper end plate 14 and a second, lower end plate 16. The two end plates 14, 16 are clamped against one another by a number of clamping elements 18, which are arranged evenly distributed along the circumference of the first and second end plates 14, 16 and are designed here as screws. The clamping elements 18 could also be designed as tensioning belts or the like. A prestressing force is introduced into the stack structure 20 via the clamping elements 18 as shown in Figure 1, so that the individual cells 12, which are arranged vertically one above the other, bear against one another in a sealed manner.

[0029] Figure 2 shows a schematic representation of individual cells 12, as they are arranged vertically stacked one above the other in an electrolyzer 10 as shown in Figure 1. Instead of the electrolyzer 10 as shown in Figure 1, the stack structure 20 as shown in Figure 1 could also be that of a fuel cell for generating electrical current to drive an electric drive of a vehicle.

[0030] Figure 2 shows that the single cell 12 typically comprises a cathode frame 22 and an anode frame 24. Both the cathode frame 22 and the anode frame 24 can be vulcanized. Furthermore, according to the schematic representation in Figure 1, the single cell 12 comprises at least one bipolar plate 26, at least one gas diffusion layer 28 (GDL), and at least one porous transport layer 30 (PTL).

[0031] Between the cathode frame 22 and the anode frame 24 is a membrane 38, preferably designed as a proton exchange membrane (PEM), which is surrounded by water. When an electrical voltage is applied to the membrane 38, protons diffuse from the anode side to the cathode side. Oxygen is produced at the anode and hydrogen at the cathode, which remain physically separated from each other by the membrane 38. The hydrogen is removed from the cathode side, dried, and can be stored.

[0032] The illustration in Figure 2 further shows that the individual cell 12 shown there is supplied with water, which is done via the media supply 32. Reaction products, such as oxygen and hydrogen, are removed via corresponding outlets 34, 36, as are water residues. This transport of media into and out of the cell places very high demands on the tightness of the stacked individual cells 12 within the stack structure 20 shown in Figure 1.

[0033] The illustration in Figure 2 further shows that circumferential recesses 40 can be formed in the cathode frame 22, which is particularly vulcanized, and / or the anode frame 24, which can also be vulcanized. These recesses run perpendicular to the plane of the drawing according to the sectional view of the individual cell 12 in Figure 2.

[0034] Figure 3 shows a schematic representation of a cathode frame 22 or an anode frame 24, which is provided with at least one circumferential recess 40.

[0035] From the illustration in Figure 3, it can be seen that the circumferential recess 40 extends in a surface 46 of the cathode frame 22 and / or the anode frame 24. This recess can be formed as a channel-shaped recess, a groove, or even a channel and preferably runs along the edge region of the vulcanized cathode frame 22 or the vulcanized anode frame 24.

[0036] The at least one circumferential recess 40, which is formed in the surface 46, comprises, within a corner region 48, a discharge opening 42, which is here, for example, circular in shape. The discharge opening 42 is integrated into the circumferential recess 40, which runs in the surface 46. The circumferential recess 40, which is provided as a groove, a channel, or with a rounded collar, has, for example, a slight gradient, thus ensuring that gas or liquid media, water, or water-containing media can flow to the discharge opening 42.

[0037] Due to the individual cells 12 being arranged vertically one above the other within the stack structure 20 as shown in Figure 1, the individual discharge openings 42 in the stack structure 20 lie one above the other. As a result, the discharge openings 42 located within the corner region 48 are vertically aligned with one another, so that the plurality of individual cells 12 and thus the plurality of aligned discharge openings 42 form a discharge channel 50 extending from the first, upper end plate 14 to the second, lower end plate 16. This preferably runs in a corner region 48 of the stack structure 20 as shown in Figure 1. This allows leaks to be collected in each individual cell 12 and specifically transported away via the discharge channel 50 formed by the discharge openings 42 lying one above the other.Furthermore, the method proposed according to the invention according to method step a) can collect liquid and / or gaseous media, water, or water-containing media in the at least one circumferential recess 40 of the surface 46 of a respective individual cell 12. According to method step b), the media collected according to method step a) are specifically drained into the drainage channel 50, which is formed by the superimposed drainage openings 42 in the stacked arrangement of the individual cells 12 within the stack structure 20. According to method step c), the quantity of drained media is determined, and from this, according to method step d), an assessment of the condition of the stack structure 20 is carried out. This allows aging effects to be detected early and appropriate remedial measures to be taken.

[0038] The stack structure 20 proposed according to the invention is advantageously used in an electrolyzer 10 for generating gaseous hydrogen or can be used in a fuel cell that generates electricity to power an electrically powered vehicle. Furthermore, the invention can be used not only in PEM electrolysis or a PEM electrolyzer, but also in AEM electrolysis. AEM electrolysis uses a membrane type that differs from PEM electrolysis.

[0039] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

Claims

Claims 1. A stack structure (20) of an electrolyzer (10) or a fuel cell (10) with a plurality of individual cells (12) arranged vertically one above the other, each comprising a cathode frame (22), an anode frame (24), at least one bipolar plate (26), at least one gas diffusion layer (28), at least one porous transport layer (30) and a membrane (38), wherein the stack structure (20) has a first end plate (14) and a second end plate (16) which, with a number of clamping elements (18), clamp the individual cells (12) arranged between the end plates (14, 16) against one another, characterized in that at least one circumferential recess (40) is formed in the anode and / or cathode frame (22, 24) of the individual cells (12), which recess is connected to at least one discharge opening (42).

2. Stack structure (20) according to claim 1, characterized in that the anode and / or cathode frame (24, 22) is vulcanized 3. Stack structure (20) according to claims 1 and 2, characterized in that the at least one circumferential recess (40) is designed as a channel (44) or as a groove (44).

4. Stack structure (20) according to claims 1 to 3, characterized in that gaseous or liquid media, water or water-containing media are collected in the at least one circumferential recess (40).

5. Stack structure (20) according to claims 1 to 4, characterized in that in the anode and / or cathode frame (24, 22) the at least one discharge opening (42) is arranged in a corner region (48) of the anode and / or cathode frame (24, 22).

6. Stack structure (20) according to claims 1 to 5, characterized in that in the stacked state of the individual cells (12), discharge openings (42) lying one above the other form at least one discharge channel (50).

7. Method for operating a stack structure (20) according to one of claims 1 to 6 with the following method steps: a) collecting liquid and / or gaseous media, water or water-containing media in the at least one circumferential recess (40) of the individual cells (12), b) selectively draining the media collected according to method step a) into at least one drainage channel (50), c) determining the quantity of drained media and d) evaluating the condition of the stack structure (20) to detect any aging effects that may occur.

8. Use of the stack structure (20) according to one of claims 1 to 6 in an electrolyzer (10) for producing gaseous hydrogen.

9. Use of the stack structure (20) according to one of claims 1 to 6 in a fuel cell (10) for driving a vehicle.

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