Electrochemical cell and method for assembling an electrochemical cell

Abstract

The present invention relates to an electrochemical cell (1), in particular a PEM electrolysis cell. The electrochemical cell (1) comprises a catalyst-coated membrane (100) and at least one diffusion layer (5, 6) arranged thereon. The electrochemical cell (1) further comprises a seal (40), wherein the seal (40) surrounds the diffusion layer (5, 6). The seal (40) has a fixing geometry (50, 51, 52), wherein the diffusion layer (5, 6) is clamped within the seal (40) by means of the fixing geometry (50, 51, 52).

Description

The present invention relates to an electrochemical cell and a method for assembling such an electrochemical cell.Prior ArtElectrochemical cells, for example fuel cells, having membrane electrode arrangements and bipolar plates arranged on both sides are known from the prior art. The membrane electrode arrangements in turn comprise a catalyst-coated membrane and diffusion layers arranged on both sides. It is known from DE1020201312 A1 that the diffusion layers can have channel structures facing the bipolar plates for more homogeneous distribution of the reaction media to the catalyst-coated membrane. Electrolysis cells can have a similar structure; this applies both to water electrolysis and to CO2 electrolysis. By way of example, DE102019127037 A1 can be used to find a process for CO2 elektrolyse.Effective fluid management is an important aspect in electrochemical cell development. The diffusion layers are of important importance in this respect. The stacking of individual electrochemical cells to form a cell stack is subject to continuous optimizations. The handling of individual cells plays an important role in this connection. The present invention is intended to improve the handling of the single cell.Disclosure of the InventionFor this purpose, the electrochemical cell comprises a catalyst-coated membrane and at least one diffusion layer arranged thereon. The electrochemical cell further includes a seal, the seal enclosing the diffusion layer. The seal has at least one fixing geometry, wherein the diffusion layer is braced within the seal by means of the fixing geometry.As a result, the electrochemical cell can be handled better during production, for example even rotated. The diffusion layer is fixed by means of the fixing geometry and cannot fall out of the seal. Also during operation of the electrochemical cell, the diffusion layer is better secured against displacements within the seal. Advantageously, the diffusion layer is fixed within the seal by a plurality of fixing geometries.In advantageous embodiments, the electrochemical cell is an electrolysis cell, particularly preferably a PEM electrolysis cell. Moisture management plays an important role for electrochemical cells with a PEM membrane (proton exchange membrane), regardless of whether the fuel cell or electrolysis cell. The membrane must not be dry, but also not flooded; the diffusion layers regulate the supply and discharge of water to the catalyst-coated membrane. An exact positioning of the diffusion layer that is stable over the service life thus also makes the moisture management of the membrane, in particular of the PEM membrane, more stable. In electrolysis cells, the diffusion layers are usually thicker than in PEM fuel cells, so that the diffusion layer has a sufficient thickness and thus also a sufficient rigidity to be able to be well fixed in the seal with the aid of the fixing geometries.In advantageous refinements, the electrochemical cell has a cathode-side diffusion layer and an anode-side diffusion layer. Both diffusion layers are braced within the seal by means of at least one fixing geometry each. The two diffusion layers can also be configured quite differently, for example as expanded metal grids or porous sintered metal.The seal is preferably designed as a one-piece seal. Particularly preferably, both diffusion layers are braced in the one-piece seal by means of the fixing geometries. The one-piece seal is then virtually an integral frame for the catalyst-coated membrane and the two diffusion layers. The handling for stacking a cell stack is then particularly simple.In advantageous embodiments, the seal has a step. The catalyst-coated membrane then rests on this stage and is accordingly fixed in the height direction (stacking direction) by the stage. Particularly preferably, the seal encloses the catalyst-coated membrane, i.e. it completely surrounds it. This ensures very good sealing of the electrochemical cell from the outside to the environment.In advantageous embodiments, the fixing geometry has a convex geometry with respect to the diffusion layer to be positioned. As a result, the force-fit connection between the fixing geometry and the diffusion layer can be produced most easily.In advantageous refinements, at least six fixing geometries are arranged on the seal over a circumference of the seal. As a result, the diffusion layer is fixed sufficiently homogeneously within the seal.The invention further comprises a method for assembling an electrochemical cell according to any of the above statements. The electrochemical cell includes a cathode-side diffusion layer, an anode-side diffusion layer, a catalyst coated membrane, and a one-piece gasket. Both diffusion layers are braced within the seal by means of at least one fixing geometry each. The method comprises the following method steps:providing the seal,clamping the anode-side diffusion layer on at least one anode-side fixing geometry,inserting the catalyst-coated membrane,clamping the cathode-side diffusion layer on at least one cathode-side fixing geometry.As a result, both diffusion layers are fixed within the seal. The catalyst-coated membrane is braced between the two diffusion layers. The assembly of the seal, diffusion layers and catalyst-coated membrane, also referred to as membrane electrode unit, can thereby be handled, in particular rotated, as desired without a diffusion layer falling out of the seal.Exemplary embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. The following are shown: FIG. 1 schematically shows an electrochemical cell from the prior art, only the essential regions being shown. FIG. 2 schematically shows an electrochemical cell according to the invention in a cross section, only the essential regions being shown. FIG. 3 shows the marked detail in FIG. 2 of variants of a fixing geometry arranged on a seal. FIG. 4 schematically shows a seal of an electrochemical cell according to the invention in plan view, only the essential regions being shown.FIG. 1 schematically shows an electrochemical cell 1 known from the prior art in the form of an electrolysis cell, only the essential regions being shown. The electrolysis cell 1 has an electrolyte 2, for example a membrane, in particular a polymer electrolyte membrane, so that the electrolysis cell 1 is designed as a PEM electrolysis cell. Viewed in the stacking direction z, a cathode space 1 ais formed on one side of the membrane 2, and an anode space 1 bis formed on the other side.In the cathode chamber 1a, an electrode layer 3, a diffusion layer 5 and a distributor plate 7 are arranged facing outwards from the membrane 2, i.e. in the normal direction z. Similarly, in the anode compartment 1b, an electrode layer 4, a diffusion layer 6 and a distributor plate 8 are arranged facing outward from the membrane 2.The composite of the membrane 2 and the two electrode layers 3, 4 represents a catalyst-coated membrane 100. The catalyst-coated membrane 100 and the two diffusion layers 5, 6 form a membrane-electrode unit 10.The distributor plates 7, 8 have channels 11 for the medium supply and discharge-for example hydrogen in the cathode space 1a and water in the anode space 1b-to the diffusion layers 5, 6. The diffusion layers 5, 6 can consist, for example, of nonwoven fabrics and / or porous metal layers and / or wire mesh.The distributor plates 7, 8 have webs 12 which delimit the channels 11 and thus implicitly also the channels 11. The undersides of these webs 12 consequently form a contact surface 7 a, 8 aof the respective distributor plate 7, 8 with respect to the corresponding contact surface 5 a, 6 aof the diffusion layer 5, 6 lying thereunder.The cathode-side distributor plate 7 of an electrochemical cell 1 and the anode-side distributor plate 8 of the electrochemical cell adjacent thereto can be firmly connected in their connecting surfaces 20 b, for example by welded connections, and thus be combined to form a bipolar plate 20. The distributor plates 7, 8 can also be embodied as one piece, so that the second distributor plate 8 is omitted. The distributor plate 7 can also be designed without channels 11 in particular for the last case; the bipolar plate 20 would thus be a distributor plate 7 designed as a flat sheet metal; the actual media distribution would then take place completely in the diffusion layers 5, 6.The schematic view of FIG. 1 shows the electrochemical cell 1 in an active region. FIG. 2 shows a section of an electrochemical cell 1 according to the invention in a part of the active region 31 and the sealing region 32. the active region 31 comprises the catalyst-coated membrane 100 with the diffusion layers 5, 6 arranged on both sides and distributor plates 7, 8. In the sealing region 32, a seal 40 encloses at least the two diffusion layers 5, 6 on their periphery. The seal 40 can be embodied in one part or in two parts with a cathode seal 41 and an anode seal 42. In the case of a two-part seal 41, 42, the catalyst coated membrane 100 may be pinched between the cathode seal 41 and the anode seal 42 as indicated by the black dashed line. Preferably, however, the seal 40 is embodied in one piece, and the catalyst-coated membrane 100 ends almost flush with the seal 40 at the end face. Particularly preferably, the seal 40 has a step 43 on which the catalyst-coated membrane 100 rests as it were. In this case, the cathode-side diffusion layer 5 advantageously comprises a smaller area than the anode-side diffusion layer 6.Until now, the positioning of the diffusion layers 5, 6 within the seal 40 has been effected initially only by stacking a plurality of electrochemical cells 1 in the loose composite. Fixing also in the xy plane is then effected by means of the bracing of the cell stack constructed in this way in the z direction. According to the invention, at least one fixing geometry 50, 51, 52 for positioning at least one of the two diffusion layers 5, 6 within the seal 40 is now arranged on the seal 40. The fixing geometry 50, 51, 52 clamps the diffusion layer 5, 6 interacting with it in the xy plane, i.e. orthogonally to a later clamping of the cell stack by means of clamping elements such as screw connections or clamping bands.Preferably, both the cathode-side diffusion layer 5 and the anode-side diffusion layer 6 are fastened within the seal by means of fixing geometries 50, 51, 52. By placing a plurality of fixing geometries 50, 51, 52 in the recesses of the seal 40 for fixing the two diffusion layers 5, 6, individual electrochemical cells 1 can be pre-assembled and thus handled and stacked more easily. Furthermore, quality preliminary tests on the electrochemical cells 1 pre-assembled in this way can be simplified and made flexible.The fixing geometries 50, 51, 52 represent punctiform interference fits between the seal 40, 41, 42 and the diffusion layers 5, 6. The fixing geometries 50, 51, 52 are preferably in fixed connection with the seal 40, 41, 42. Advantageously, the seal 40 is designed as a one-piece frame, i.e. seals both the cathode space 1 aand the anode space 1 bof the electrochemical cell 1FIG. 3 shows the detail characterized in FIG. 2 with four possible configurations of the fixing geometry 50, 51, 52 arranged on the seal 40, 41, 42. FIG. 3 ashows a fixing geometry 50, 51, 52, which is rectangular in cross section, FIG. 3 bshows a fixing geometry 50, 51, 52, which is triangular in cross section, FIG. 3 cshows a fixing geometry 50, 51, 52, which is substantially circular in cross section, and FIG. 3 dshows a fixing geometry 50, 51, 52, which is trapezoidal in cross section. The fixing geometries 50, 51, 52 can therefore be configured, for example, in the form of a wedge, a ball, a cylinder, a rectangular or a polygon. For the best possible fixing or mounting of the diffusion layers 5, 6 within the seal 40, 41, 42, the fixing geometries 50, 51, 52 have a convex geometry with respect to the diffusion layer 5, 6 to be positioned, as for example in the embodiments of FIGS. 3 cand 3 d. The process of bracing the diffusion layer 5, 6 within the seal 5, 6 can thus be carried out most easily. The fixing geometries 50, 51, 52 can be embodied at any desired height or over the entire height (i.e. in the z direction) of the seal 40, 41, 42.FIG. 4 shows a plan view of a rectangular seal 40, 41, 42 which comprises a recess for the active region 31 of the electrochemical cell 1. The seal 40, 41, 42 has ten fixing geometries 50, 51, 52, distributed over its circumference, for bracing the diffusion layers 5, 6.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 102020201312 A1

[0002] DE 102019127037 A1

[0002]

Claims

Electrochemical cell (1) having a catalyst-coated membrane (100) and at least one diffusion layer (5, 6) arranged thereon and a seal (40, 41, 42), wherein the seal (40, 41, 42) encloses the diffusion layer (5, 6), characterized in that the seal (40, 41, 42) has a fixing geometry (50, 51, 52), wherein the diffusion layer (5, 6) is braced within the seal (40, 41, 42) by means of the fixing geometry (50, 51, 52).Electrochemical cell (1) according to Claim 1da characterized in that the electrochemical cell (1) has a cathode-side diffusion layer (5) and an anode-side diffusion layer (6), the two diffusion layers (5, 6) being braced within the seal (40, 41, 42) by means of in each case at least one fixing geometry (50, 51, 52).Electrochemical cell (1) according to Claim 1 or 2, characterized in that the seal (40, 41, 42) is designed as a one-piece seal (40).Electrochemical cell (1) according to one of the preceding claims, characterized in that the seal (40, 41, 42) has a step (43).The electrochemical cell (1) of claim 4 characterized in that the seal (40, 41, 42) encloses the catalyst coated membrane (100).Electrochemical cell (1) according to one of the preceding claims, characterized in that the fixing geometry (50, 51, 52) has a convex geometry with respect to the diffusion layer (5, 6) to be positioned.Electrochemical cell (1) according to one of the preceding claims, characterized in that at least six fixing geometries (50, 51, 52) are arranged on the seal (40, 41, 42) over a circumference of the seal (40, 41, 42).Electrochemical cell (1) according to one of the preceding claims, characterized in that the electrochemical cell (1) is an electrolysis cell (1), in particular a PEM electrolysis cell.Method for assembling an electrochemical cell (1) according to one of the preceding claims, wherein the electrochemical cell (1) has a cathode-side diffusion layer (5), an anode-side diffusion layer (6), a catalyst-coated membrane (100) and a one-piece seal (40), wherein the two diffusion layers (5, 6) are braced within the seal (40) by means of in each case at least one fixing geometry (50, 51, 52), having the following method steps: - providing the seal (40), - bracing the anode-side diffusion layer (6) on at least one anode-side fixing geometry (52), - inserting the catalyst-coated membrane (100), - bracing the cathode-side diffusion layer (5) on at least one cathode-side fixing geometry (51).

Images